Sample records for niobium-doped strontium titanates

  1. Electrical characterization of doped strontium titanate thin films for semiconductor memories

    NASA Astrophysics Data System (ADS)

    Han, Jeong Hee

    2002-08-01

    Doped strontium titanate (ST) thin films were investigated for high-density memory applications. ST has become a promising candidate to replace conventional silicon oxide due to its high inherent dielectric constant, superior leakage characteristics, and good chemical stability. However, oxygen vacancies and the problems that arise as a result are one of the main drawbacks against this material. Resistance degradation is a serious reliability issue in perovskite titanate films and may be a result of oxygen vacancies. In this dissertation, an attempt to reduce the resistance degradation was made by doping the ST films with both niobium and lanthanum. Niobium is a B-site donor in the perovskite, whereas lanthanum is an A-site donor. Both have an extra valence charge than the atom which it replaces in the crystal structure. With a higher valence charge, the number of oxygen vacancies is hoped to be reduced and result in better electrical performance. Experimental results showed that the degradation rate is reduced by doping with either niobium or lanthanum. A bi-layer study was also performed to optimize the dielectric with the strengths of both doped and undoped strontium titanate and to distinguish the source of the oxygen vacancies. A study on the conduction mechanisms and dielectric dispersion was also performed. An additional study was made on the effect of iridium as a possible gate electrode for a MOS capacitor. Hafnium oxide was used as the high-permittivity oxide. The results observed showed that the capacitance was higher for iridium electrodes than those for platinum electrodes. However, both electrodes showed unacceptable frequency dispersion which may be caused by crude patterning techniques. A hysteresis review was also done for hafnium and zirconium oxides. It was observed that the hysteresis measured in the high-permittivity oxides are dependent on the accumulation sweep voltage due to the trapping and de-trapping of charge at the dielectric

  2. Composite solid oxide fuel cell anode based on ceria and strontium titanate

    DOEpatents

    Marina, Olga A.; Pederson, Larry R.

    2008-12-23

    An anode and method of making the same wherein the anode consists of two separate phases, one consisting of a doped strontium titanate phase and one consisting of a doped cerium oxide phase. The strontium titanate phase consists of Sr.sub.1-xM.sub.xTiO.sub.3-.delta., where M is either yttrium (Y), scandium (Sc), or lanthanum (La), where "x" may vary typically from about 0.01 to about 0.5, and where .delta. is indicative of some degree of oxygen non-stoichiometry. A small quantity of cerium may also substitute for titanium in the strontium titanate lattice. The cerium oxide consists of N.sub.yCe.sub.1-yO.sub.2-.delta., where N is either niobium (Nb), vanadium (V), antimony (Sb) or tantalum (Ta) and where "y" may vary typically from about 0.001 to about 0.1 and wherein the ratio of Ti in said first phase to the sum of Ce and N in the second phase is between about 0.2 to about 0.75. Small quantities of strontium, yttrium, and/or lanthanum may additionally substitute into the cerium oxide lattice. The combination of these two phases results in better performance than either phase used separately as an anode for solid oxide fuel cell or other electrochemical device.

  3. Fabrication of barium titanate doped strontium using co-precipitation method

    NASA Astrophysics Data System (ADS)

    Iriani, Y.; Yasin, M. A.; Suryana, R.

    2018-03-01

    Fabrication of barium titanate (BaTiO3/BT) doped strontium (Sr) using co-precipitation method has been successfully conducted. The research aim is to get the best of mole variation of Sr doping to ferroelectric material properties. Doping Sr was varied at 1%, 2%, 3%, 4% and 5% in BaTiO3. Each sample was sintered at temperature of 1100°C with holding time for 6 h and temperature rate at 10°C/min. They were then characterized by XRD instrument to investigate the crystal structure, LCR meter to measure the dielectric constant, and Sawyer Tower circuit to reveal the hysteresis curve. The peaks of XRD shift towards larger angle when mole doping Sr increase. The crystallinity of all samples is above 90% and the crystallite size is in the range of 27 nm to 34 nm. Hysteresis curve from Sawyer Tower testing confirms that all samples are ferroelectric material. The RLC measurement results reveal that the less frequency leads to the higher dielectric constant while the highest dielectric constant belongs to the BT doped 3% of Sr. Therefore, it is the best variation obtained in this research.

  4. Cerium-modified doped strontium titanate compositions for solid oxide fuel cell anodes and electrodes for other electrochemical devices

    DOEpatents

    Marina, Olga A [Richland, WA; Stevenson, Jeffry W [Richland, WA

    2010-03-02

    The present invention provides novel compositions that find advantageous use in making electrodes for electrochemical cells and electrochemical devices such as solid oxide fuel cells, electrolyzers, sensors, pumps and the like, the compositions comprising cerium-modified doped strontium titanate. The invention also provides novel methods for making and using anode material compositions and solid oxide fuel cells and solid oxide fuel cell assemblies having anodes comprising the compositions.

  5. Cerium-modified doped strontium titanate compositions for solid oxide fuel cell anodes and electrodes for other electrochemical devices

    DOEpatents

    Marina, Olga A [Richland, WA; Stevenson, Jeffry W [Richland, WA

    2010-11-23

    The present invention provides novel compositions that find advantageous use in making electrodes for electrochemical cells and electrochemical devices such as solid oxide fuel cells, electrolyzers, sensors, pumps and the like, the compositions comprising cerium-modified doped strontium titanate. The invention also provides novel methods for making and using anode material compositions and solid oxide fuel cells and solid oxide fuel cell assemblies having anodes comprising the compositions.

  6. Effect of crystal size distribution on thermoelectric performance for Lanthanum-doped strontium titanate bulk material

    NASA Astrophysics Data System (ADS)

    Zhang, Boyu; Wang, Jun; Yaer, Xinba; Huo, Zhenzhen; Wu, Yin; Li, Yan; Miao, Lei; Liu, Chengyan; Zou, Tao; Ma, Wen

    2015-07-01

    Effect of crystal size distribution on thermoelectric performance of Lanthanum-doped strontium titanate (La-SrTiO3) ceramics are investigated in this study. Thermoelectric performance measurement, coupled with microstructure studies, shows that the electrical conductivity strongly depends on the crystal size, potential barrier on the grain boundary and porosity. Meantime, because the average potential barriers height are increased along with the reduction of crystal size, the Seebeck coefficients are increased by energy filtering effect at the large number of grain boundaries. As a result, by controlling of crystal size distribution, ZT value of La-SrTiO3 is improved.

  7. Barium strontium titanate thin film growth with variation of lanthanum dopant compatibility as sensor prototype in the satellite technology

    NASA Astrophysics Data System (ADS)

    Mulyadi; Wahyuni, Rika; Hardhienata, Hendradi; Irzaman

    2018-05-01

    Electrical properties of barium strontium titanate thin films were investigated. Three layers of barium strontium titanate thin films have been prepared by chemical solution deposition method and spin coating technique at 8000 rpm rotational speed for 30 seconds and temperature of annealing at 850°C for eight hours with temperature increment of 1.67°C/minute. Materials produced by the process of lanthanum dopant with doping variations of 2%, 4% and 6% above type-p silicon (100) substrates. Film obtained was then carried out the characterization using USB 2000 VIS-NIR and tauc plot method. As a result, the barium strontium titanate thin film has the value of band gap energy of 1.58 eV, 1.92 eV and 2.24 eV respectively. The characterization of electrical properties shows that the band gap value of barium strontium titanate thin film with lanthanum dopant was in the range of semiconductor value. Barium strontium titanate thin films with lanthanum dopant are sensitive to temperature changes, so it potentially to be applied to temperature monitoring on satellite technology.

  8. Tuned sensitivity towards H{sub 2}S and NH{sub 3} with Cu doped barium strontium titanate materials

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Simion, C. E., E-mail: simion@infim.ro; Teodorescu, V. S.; Stănoiu, A.

    2014-11-05

    The different amount of Cu-doped Barium Strontium Titanate (BST) thick film materials have been tested for their gas-sensing performances towards NH{sub 3} and H{sub 2}S under dry and 50% relative humidity (RH) background conditions. The optimum NH{sub 3} sensitivity was attained with 0.1mol% Cu-doped BST whereas the selective detection of H{sub 2}S was highlighted using 5mol% Cu-doped BST material. No cross-sensitivity effects to CO, NO{sub 2}, CH{sub 4} and SO{sub 2} were observed for all tested materials operated at their optimum temperature (200°C) under humid conditions (50% RH). The presence of humidity clearly enhances the gas sensitivity to NH{sub 3}more » and H{sub 2}S detection.« less

  9. Magnetic phase composition of strontium titanate implanted with iron ions

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Dulov, E.N., E-mail: evgeny.dulov@ksu.ru; Ivoilov, N.G.; Strebkov, O.A.

    2011-12-15

    Highlights: Black-Right-Pointing-Pointer The origin of RT-ferromagnetism in iron implanted strontium titanate. Black-Right-Pointing-Pointer Metallic iron nanoclusters form during implantation and define magnetic behaviour. Black-Right-Pointing-Pointer Paramagnetic at room temperature iron-substituted strontium titanate identified. -- Abstract: Thin magnetic films were synthesized by means of implantation of iron ions into single-crystalline (1 0 0) substrates of strontium titanate. Depth-selective conversion electron Moessbauer spectroscopy (DCEMS) indicates that origin of the samples magnetism is {alpha}-Fe nanoparticles. Iron-substituted strontium titanate was also identified but with paramagnetic behaviour at room temperature. Surface magneto-optical Kerr effect (SMOKE) confirms that the films reveal superparamagnetism (the low-fluence sample) or ferromagnetism (themore » high-fluence sample), and demonstrate absence of magnetic in-plane anisotropy. These findings highlight iron implanted strontium titanate as a promising candidate for composite multiferroic material and also for gas sensing applications.« less

  10. XANES study of Fe-implanted strontium titanate

    NASA Astrophysics Data System (ADS)

    Lobacheva, O.; Goncharova, L. V.; Chavarha, M.; Sham, T. K.

    2014-03-01

    Properties of strontium titanate SrTiO3 (STO) depend to a great extent on the substitutional dopants and defects of crystal structure. The ion beam implantation method was used for doping STO (001) crystals with Fe at different doses. Implanted samples were then annealed at 350°C in oxygen to induce recrystallization and remove oxygen vacancies produced during ion implantation process. The effect of Fe doping and post-implantation annealing was studied by X-ray Absorption Near Edge Spectroscopy (XANES) method and Superconducting Quantum Interference Device (SQUID). XANES allowed to monitor the change in structure of STO crystals and in the local environment of Fe following the implantation and annealing steps. SQUID measurements revealed correlation between magnetic moment and Fe implantation dose. Ferromagnetic hysteresis was observed on selected Fe-implanted STO at 5 K. The observed magnetic properties can be correlated with the several Fe oxide phases in addition to the presence of O/Ti vacancies.

  11. Hydrothermal synthesis of barium strontium titanate and bismuth titanate materials

    NASA Astrophysics Data System (ADS)

    Xu, Huiwen

    Hydrothermal processing facilitates the synthesis of crystalline ceramic materials of varying composition or complex crystal structure. The present work can be divided into two parts. First is to study the low temperature hydrothermal synthesis of bismuth titanate. Second is to study both thermodynamic and kinetic aspects of the hydrothermally synthesized barium strontium titanate. A chelating agent was used to form a Bi-Ti gel precursor. By hydrothermally treating the Bi-Ti gel, crystalline bismuth titanate has been synthesized at 160°C for the first time. Microstructural evolution during the low temperature synthesis of bismuth titanate can be divided into two stages, including condensation of Bi-Ti gel particles and crystallization of bismuth titanate. Crystallization of bismuth titanate occurred by an in situ transformation mechanism at an early stage followed by a dissolution-reprecipitation mechanism. Phase separation was observed in hydrothermally synthesized barium strontium titanate (BST). By hydrothermally treating BST powders between 250°C--300°C, an asymmetrical miscibility gap was found in the BaTiO3-SrTiO 3 system at low temperatures (T ≤ 320°C). A subregular solid solution model was applied to calculate the equilibrium compositions and the Gibbs free energy of formation of BST solid solution at low temperatures (T ≤ 320°C). The Gibbs free energy of formation of Sr-rich BST phase is larger than that of Ba-rich BST phase. Kinetic studies of single phase BST solid solution at 80°C show that, compared to the BaTiO3 or Ba-rich BST, SrTiO3 and Sr-rich BST powders form at lower reaction rates.

  12. Multicomponent doped barium strontium titanate thin films for tunable microwave applications

    NASA Astrophysics Data System (ADS)

    Alema, Fikadu Legesse

    In recent years there has been enormous progress in the development of barium strontium titanate (BST) films for tunable microwave applications. However, the properties of BST films still remain inferior compared to bulk materials, limiting their use for microwave technology. Understanding the film/substrate mismatch, microstructure, and stoichiometry of BST films and finding the necessary remedies are vital. In this work, BST films were deposited via radio frequency magnetron sputtering method and characterized both analytically and electrically with the aim of optimizing their properties. The stoichiometry, crystal structure, and phase purity of the films were studied by varying the oxygen partial pressure (OPP) and total gas pressure (TGP) in the chamber. A better stoichiometric match between film and target was achieved when the TGP is high (> 30 mTorr). However, the O2/Ar ratio should be adjusted as exceeding a threshold of 2 mTorr in OPP facilitates the formation of secondary phases. The growth of crystalline film on platinized substrates was achieved only with a lower temperature grown buffer layer, which acts as a seed layer by crystallizing when the temperature increases. Concurrent Mg/Nb doping has significantly improved the properties of BST thin films. The doped film has shown an average tunability of 53%, which is only ˜8 % lower than the value for the undoped film. This drop is associated with the Mg ions whose detrimental effects are partially compensated by Nb ions. Conversely, the doping has reduced the dielectric loss by ˜40 % leading to a higher figure of merit. Moreover, the two dopants ensure a charge neutrality condition which resulted in significant leakage current reduction. The presence of large amounts of empty shallow traps related to Nb Ti localize the free carriers injected from the contacts; thus increase the device control voltage substantially (>10 V). A combinatorial thin film synthesis method based on co-sputtering of two BST

  13. In vitro dissolution of strontium titanate to estimate clearance rates in human lungs

    NASA Astrophysics Data System (ADS)

    Anderson, Jeri Lynn

    At the In-Tank Precipitation facility (ITP) of the Savannah River Site, strontium and other radionuclides are removed from high-level radioactive waste and sent to the Defense Waste Processing Facility (DWPF). Strontium removal is accomplished by ion-exchange using monosodium titanate slurry which creates a form of strontium titanate with unknown solubility characteristics. In the case of accidental inhalation of a compound containing radioactive strontium, the ICRP, in Publication 66, recommends using default values for rates of absorption into body fluids at the lungs in the absence of reliable human or animal data. The default value depends on whether the absorption is considered to be fast, moderate, or slow (Type F, M, or S). Current dose assessment for an individual upon inadvertent exposure to airborne radioactive strontium assumes that all strontium compounds are Type F (soluble) or Type S (insoluble). Pure high-fired strontium titanate (SrTiOsb3) is considered Type S. The purpose of this project was to determine the solubility of strontium titanate in the form created at the ITP facility. An in vitro dissolution study was done with a precipitate simulant and with several types of strontium titanate and the results were compared. An in vivo study was also performed with high-fired SrTiOsb3 in rats. The data from both studies were used independently to assign the compounds to absorption type based on criteria specified in ICRP 71. Results of the in vitro studies showed that the DWPF simulant should be assigned to Type M and the strontium titanate should be assigned to Type S. It is possible the difference in the DWPF simulant is due to the other chemicals present. Results of the in vivo study verified that SrTiOsb3 should be assigned to Type S. Lung clearance data of SrTiOsb3 from rats showed that 85% cleared within the first 24 hours and the remaining 15% with a half-time of 130 days. The initial rapid clearance is attributed to deposition in airways as

  14. High temperature dielectric relaxation anomaly of Y³⁺ and Mn²⁺ doped barium strontium titanate ceramics

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Yan, Shiguang; Mao, Chaoliang, E-mail: maochaoliang@mail.sic.ac.cn, E-mail: xldong@mail.sic.ac.cn; Wang, Genshui

    2014-10-14

    Relaxation like dielectric anomaly is observed in Y³⁺ and Mn²⁺ doped barium strontium titanate ceramics when the temperature is over 450 K. Apart from the conventional dielectric relaxation analysis method with Debye or modified Debye equations, which is hard to give exact temperature dependence of the relaxation process, dielectric response in the form of complex impedance, assisted with Cole-Cole impedance model corrected equivalent circuits, is adopted to solve this problem and chase the polarization mechanism in this paper. Through this method, an excellent description to temperature dependence of the dielectric relaxation anomaly and its dominated factors are achieved. Further analysismore » reveals that the exponential decay of the Cole distribution parameter n with temperature is confirmed to be induced by the microscopic lattice distortion due to ions doping and the interaction between the defects. At last, a clear sight to polarization mechanism containing both the intrinsic dipolar polarization and extrinsic distributed oxygen vacancies hopping response under different temperature is obtained.« less

  15. Phase transition studies in barium and strontium titanates at microwave frequencies

    NASA Technical Reports Server (NTRS)

    Dahiya, Jai N.

    1993-01-01

    The objectives were the following: to understand the phase transformations in barium and strontium titanates as the crystals go from one temperature to the other; and to study the dielectric behavior of barium and strontium titanate crystals at a microwave frequency of 9.12 GHz and as a function of temperature. Phase transition studies in barium and strontium titanate are conducted using a cylindrical microwave resonant cavity as a probe. The cavity technique is quite successful in establishing the phase changes in these crystals. It appears that dipole relaxation plays an important role in the behavior of the dielectric response of the medium loading the cavity as phase change takes place within the sample. The method of a loaded resonant microwave cavity as applied in this work has proven to be sensitive enough to monitor small phase changes of the cavity medium.

  16. SELECTIVE REMOVAL OF STRONTIUM AND CESIUM FROM SIMULATED WASTE SOLUTION WITH TITANATE ION-EXCHANGERS IN A FILTER CARTRIDGE CONFIGURATIONS-12092

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Oji, L.; Martin, K.; Hobbs, D.

    2012-01-03

    Experimental results for the selective removal of strontium and cesium from simulated waste solutions with monosodium titanate and crystalline silicotitanate laden filter cartridges are presented. In these proof-of-principle tests, effective uptake of both strontium-85 and cesium-137 were observed using ion-exchangers in this filter cartridge configuration. At low salt simulant conditions, the instantaneous decontamination factor for strontium-85 with monosodium titanate impregnated filter membrane cartridges measured 26, representing 96% strontium-85 removal efficiency. On the other hand, the strontium-85 instantaneous decontamination factor with co-sintered active monosodium titanate cartridges measured 40 or 98% Sr-85 removal efficiency. Strontium-85 removal with the monosodium titanate impregnated membranemore » cartridges and crystalline silicotitanate impregnated membrane cartridges, placed in series arrangement, produced an instantaneous decontamination factor of 41 compared to an instantaneous decontamination factor of 368 for strontium-85 with co-sintered active monosodium titanate cartridges and co-sintered active crystalline silicotitanate cartridges placed in series. Overall, polyethylene co-sintered active titanates cartridges performed as well as titanate impregnated filter membrane cartridges in the uptake of strontium. At low ionic strength conditions, there was a significant uptake of cesium-137 with co-sintered crystalline silicotitanate cartridges. Tests results with crystalline silicotitanate impregnated membrane cartridges for cesium-137 decontamination are currently being re-evaluated. Based on these preliminary findings we conclude that incorporating monosodium titanate and crystalline silicotitanate sorbents into membranes represent a promising method for the semicontinuous removal of radioisotopes of strontium and cesium from nuclear waste solutions.« less

  17. Radiation damage and nanocrystal formation in uranium-niobium titanates

    NASA Astrophysics Data System (ADS)

    Lian, J.; Wang, S. X.; Wang, L. M.; Ewing, R. C.

    2001-07-01

    Two uranium-niobium titanates, U 2.25Nb 1.90Ti 0.32O 9.8 and Nb 2.75U 1.20Ti 0.36O 10, formed during the synthesis of brannnerite (UTi 2O 6), a minor phase in titanate-based ceramics investigated for plutonium immobilization. These uranium titanates were subjected to 800 keV Kr 2+ irradiation from 30 to 973 K. The critical amorphization dose of the U-rich and Nb-rich titanates at room temperature were 4.72×10 17 and 5×10 17 ions/ m2, respectively. At elevated temperature, the critical amorphization dose increases due to dynamic thermal annealing. The critical amorphization temperature for both Nb-rich and U-rich titanates is ˜933 K under a 800 keV Kr 2+ irradiation. Above the critical amorphization temperature, nanocrystals with an average size of ˜15 nm were observed. The formation of nanocrystals is due to epitaxial recrystallization. At higher temperatures, an ion irradiation-induced nucleation-growth mechanism also contributes to the formation of nanocrystals.

  18. P-type conductivity in annealed strontium titanate

    DOE PAGES

    Poole, Violet M.; Corolewski, Caleb D.; McCluskey, Matthew D.

    2015-12-17

    In this study, Hall-effect measurements indicate p-type conductivity in bulk, single-crystal strontium titanate (SrTiO 3, or STO) samples that were annealed at 1200°C. Room temperature mobilities above 100 cm 2/Vs were measured, an order of magnitude higher than those for electrons (5-10 cm 2/Vs). Average hole densities were in the 10 9-10 10 cm -3 range, consistent with a deep acceptor.

  19. Variation in superconducting transition temperature due to tetragonal domains in two-dimensionally doped SrTiO 3

    DOE PAGES

    Noad, Hilary; Spanton, Eric M.; Nowack, Katja C.; ...

    2016-11-28

    Strontium titanate is a low-temperature, non–Bardeen-Cooper-Schrieffer superconductor that superconducts to carrier concentrations lower than in any other system and exhibits avoided ferroelectricity at low temperatures. Neither the mechanism of superconductivity in strontium titanate nor the importance of the structure and dielectric properties for the superconductivity are well understood. We studied the effects of twin structure on superconductivity in a 5.5-nm-thick layer of niobium-doped SrTiO 3 embedded in undoped SrTiO 3. We used a scanning superconducting quantum interference device susceptometer to image the local diamagnetic response of the sample as a function of temperature. We observed regions that exhibited a superconductingmore » transition temperature T c ≳ 10% higher than the temperature at which the sample was fully superconducting. The pattern of these regions varied spatially in a manner characteristic of structural twin domains. Some regions are too wide to originate on twin boundaries; therefore, we propose that the orientation of the tetragonal unit cell with respect to the doped plane affects T c. Finally, our results suggest that the anisotropic dielectric properties of SrTiO 3 are important for its superconductivity and need to be considered in any theory of the mechanism of the superconductivity.« less

  20. Physicochemical Properties and Cellular Responses of Strontium-Doped Gypsum Biomaterials

    PubMed Central

    Pouria, Amir; Bandegani, Hadis; Pourbaghi-Masouleh, Milad; Hesaraki, Saeed; Alizadeh, Masoud

    2012-01-01

    This paper describes some physical, structural, and biological properties of gypsum bioceramics doped with various amounts of strontium ions (0.19–2.23 wt%) and compares these properties with those of a pure gypsum as control. Strontium-doped gypsum (gypsum:Sr) was obtained by mixing calcium sulfate hemihydrate powder and solutions of strontium nitrate followed by washing the specimens with distilled water to remove residual salts. Gypsum was the only phase found in the composition of both pure and gypsum:Sr, meanwhile a shift into lower diffraction angles was observed in the X-ray diffraction patterns of doped specimens. Microstructure of all gypsum specimens consisted of many rod-like small crystals entangled to each other with more elongation and higher thickness in the case of gypsum:Sr. The Sr-doped sample exhibited higher compressive strength and lower solubility than pure gypsum. A continuous release of strontium ions was observed from the gypsum:Sr during soaking it in simulated body fluid for 14 days. Compared to pure gypsum, the osteoblasts cultured on strontium-doped samples showed better proliferation rate and higher alkaline phosphatase activity, depending on Sr concentration. These observations can predict better in vivo behavior of strontium-doped gypsum compared to pure one. PMID:22719270

  1. Electronic structure of barium strontium titanate by soft-x-ray absorption spectroscopy

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Uehara, Y.; Underwood, J.H.; Gullikson, E.M.

    1997-04-01

    Perovskite-type titanates, such as Strontium Titanate (STO), Barium Titanate (BTO), and Lead Titanate (PTO) have been widely studied because they show good electric and optical properties. In recent years, thin films of Barium Strontium Titanate (BST) have been paid much attention as dielectrics of dynamic random access memory (DRAM) capacitors. BST is a better insulator with a higher dielectric constant than STO and can be controlled in a paraelectric phase with an appropriate ratio of Ba/Sr composition, however, few studies have been done on the electronic structure of the material. Studies of the electronic structure of such materials can bemore » beneficial, both for fundamental physics research and for improving technological applications. BTO is a famous ferroelectric material with a tetragonal structure, in which Ti and Ba atoms are slightly displaced from the lattice points. On the other hand, BST keeps a paraelectric phase, which means that the atoms are still at the cubic lattice points. It should be of great interest to see how this difference of the local structure around Ti atoms between BTO and BST effects the electronic structure of these two materials. In this report, the authors present the Ti L{sub 2,3} absorption spectra of STO, BTO, and BST measured with very high accuracy in energy of the absorption features.« less

  2. Superfluid density and carrier concentration across a superconducting dome: The case of strontium titanate

    NASA Astrophysics Data System (ADS)

    Collignon, Clément; Fauqué, Benoît; Cavanna, Antonella; Gennser, Ulf; Mailly, Dominique; Behnia, Kamran

    2017-12-01

    We present a study of the lower critical field, Hc 1, of SrTi1 -xNbxO3 as a function of carrier concentration with the aim of quantifying the superfluid density. At low carrier concentration (i.e., the underdoped side), superfluid density and the carrier concentration in the normal state are equal within experimental margin. A significant deviation between the two numbers starts at optimal doping and gradually increases with doping. The inverse of the penetration depth and the critical temperature follow parallel evolutions as in the case of cuprate superconductors. In the overdoped regime, the zero-temperature superfluid density becomes much lower than the normal-state carrier density before vanishing all together. We show that the density mismatch and the clean-to-dirty crossover are concomitant. Our results imply that the discrepancy between normal and superconducting densities is expected whenever the superconducting gap becomes small enough to put the system in the dirty limit. A quantitative test of the dirty BCS theory is not straightforward, due to the multiplicity of the bands in superconducting strontium titanate.

  3. 40 CFR 721.10423 - Complex strontium aluminate, rare earth doped (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... earth doped (generic). 721.10423 Section 721.10423 Protection of Environment ENVIRONMENTAL PROTECTION... New Uses for Specific Chemical Substances § 721.10423 Complex strontium aluminate, rare earth doped... substances identified generically as complex strontium aluminate, rare earth doped (PMNs P-12-22, P-12-23, P...

  4. Influence of oxygen partial pressure on the composition and orientation of strontium-doped lead zirconate titanate thin films.

    PubMed

    Sriram, S; Bhaskaran, M; du Plessis, J; Short, K T; Sivan, V P; Holland, A S

    2009-01-01

    The influence of oxygen partial pressure during the deposition of piezoelectric strontium-doped lead zirconate titanate thin films is reported. The thin films have been deposited by RF magnetron sputtering in an atmosphere of high purity argon and oxygen (in the ratio of 9:1), on platinum-coated silicon substrates (heated to 650 degrees C). The influence of oxygen partial pressure is studied to understand the manner in which the stoichiometry of the thin films is modified, and to understand the influence of stoichiometry on the perovskite orientation. This article reports on the results obtained from films deposited at oxygen partial pressures of 1-5 mTorr. The thin films have been studied using a combination of X-ray photoelectron spectroscopy (XPS), glancing angle X-ray diffraction (GA-XRD), and atomic force microscopy (AFM). XPS analysis highlights the marked influence of variations in oxygen pressure during sputtering, observed by variations in oxygen concentration in the thin films, and in some cases by the undesirable decrease in lead concentration in the thin films. GA-XRD is used to study the relative variations in perovskite peak intensities, and has been used to determine the deposition conditions to attain the optimal combination of stoichiometry and orientation. AFM scans show the marked influence of the oxygen partial pressure on the film morphology.

  5. Spatially inhomogeneous electron state deep in the extreme quantum limit of strontium titanate

    DOE PAGES

    Bhattacharya, Anand; Skinner, Brian; Khalsa, Guru; ...

    2016-09-29

    When an electronic system is subjected to a sufficiently strong magnetic field that the cyclotron energy is much larger than the Fermi energy, the system enters the extreme quantum limit (EQL) and becomes susceptible to a number of instabilities. Bringing a three-dimensional electronic system deeply into the EQL can be difficult however, since it requires a small Fermi energy, large magnetic field, and low disorder. Here we present an experimental study of the EQL in lightly-doped single crystals of strontium titanate. Our experiments probe deeply into the regime where theory has long predicted an interaction-driven charge density wave or Wignermore » crystal state. A number of interesting features arise in the transport in this regime, including a striking re-entrant nonlinearity in the current-voltage characteristics. As a result, we discuss these features in the context of possible correlated electron states, and present an alternative picture based on magnetic-field induced puddling of electrons.« less

  6. Hydrogen generation from water/methanol under visible light using aerogel prepared strontium titanate (SrTiO3) nanomaterials doped with ruthenium and rhodium metals

    NASA Astrophysics Data System (ADS)

    Kuo, Yenting; Klabunde, Kenneth J.

    2012-07-01

    Nanostructured strontium titanate visible-light-driven photocatalysts containing rhodium and ruthenium were synthesized by a modified aerogel synthesis using ruthenium chloride and rhodium nitrate as dopant precursors, and titanium isopropoxide and strontium metal as the metal sources. The well-defined crystalline SrTiO3 structure was confirmed by means of x-ray diffraction. After calcination at 500 °C, diffuse reflectance spectroscopy shows an increase in light absorption at 370 nm due to the presence of Rh3 + ; however an increase of the calcination temperature to 600 °C led to a decrease in intensity, probably due to a loss of surface area. An increase in the rhodium doping level also led to an increase in absorption at 370 nm however, the higher amounts of dopant lowered the photocatalytic activity. The modified aerogel synthesis allows greatly enhanced H2 production performance from an aqueous methanol solution under visible light irradiation compared with lower surface area conventional materials. We believe that this enhanced activity is due to the higher surface areas while high quality nanocrystalline materials are still obtained. Furthermore, the surface properties of these nanocrystalline aerogel materials are different, as exhibited by the higher activities in alkaline solutions, while conventional materials (obtained via high temperature solid-state synthesis methods) only exhibit reasonable hydrogen production in acidic solutions. Moreover, an aerogel synthesis approach gives the possibility of thin-film formation and ease of incorporation into practical solar devices.

  7. Low temperature detection of phase transitions and relaxation processes in strontium titanate by means of cathodoluminescence

    NASA Astrophysics Data System (ADS)

    Yang, B.; Townsend, P. D.; Fromknecht, R.

    2004-11-01

    Cathodoluminescence is an effective tool for investigating phase changes and relaxation processes in insulators and data are presented for strontium titanate. The results demonstrate considerable sensitivity to the origin of the samples as the detailed spectra and intensity changes with temperature are strongly dependent on the growth conditions, trace impurities and radiation induced defects. It is of particular note that in the defective surface layer the normal second-order phase transition cited near 105 K transforms into a sharply defined first-order transition because of the relaxation of the near surface layer in doped crystals. Detection of the other main relaxation stages is also straightforward via intensity and spectral changes. Secondary effects of phase changes incorporated within the surface layers are clearly evident, particularly for the 197 K sublimation of CO2 nanoparticle inclusions.

  8. Lanthanide doped strontium-barium cesium halide scintillators

    DOEpatents

    Bizarri, Gregory; Bourret-Courchesne, Edith; Derenzo, Stephen E.; Borade, Ramesh B.; Gundiah, Gautam; Yan, Zewu; Hanrahan, Stephen M.; Chaudhry, Anurag; Canning, Andrew

    2015-06-09

    The present invention provides for a composition comprising an inorganic scintillator comprising an optionally lanthanide-doped strontium-barium, optionally cesium, halide, useful for detecting nuclear material.

  9. Degradation and recovery of iron doped barium titanate single crystals via modulus spectroscopy and thermally stimulated depolarization current

    NASA Astrophysics Data System (ADS)

    Carter, J. J.; Bayer, T. J. M.; Randall, C. A.

    2017-04-01

    Understanding resistance degradation during the application of DC bias and recovery after removing the DC bias provides insight into failure mechanisms and defects in dielectric materials. In this experiment, modulus spectroscopy and thermally stimulated depolarization current (TSDC) techniques were used to characterize the degradation and recovery of iron-doped barium titanate single crystals. Modulus spectroscopy is a very powerful analytical tool applied during degradation and recovery to observe changes in the local conductivity distribution. During degradation, oxygen vacancies migrate to the cathode region, and a counter flow of oxygen anions migrates towards the anode. With increasing time during degradation, the distribution of conductivity broadens only slightly exhibiting crucial differences to iron doped strontium titanate. After removing the DC bias, the recovery shows that a second previously unobserved and distinct conductivity maximum arises in the modulus data. This characteristic with two maxima related to different conductivities in the anode and cathode region is what can be expected from the published defect chemistry. It will be concluded that only the absence of an external electric field during recovery measurements permits the observation of local conductivity measurements without the presence of non-equilibrium conditions such as charge injection. Equilibrium conductivity as a function of oxygen vacancy concentration is described schematically. Oxygen vacancy migration during degradation and recovery is verified by TSDC analysis. We establish a self-consistent rationale of the transient changes in the modulus and TSDC for the iron doped barium titanate single crystal system including electron, hole and oxygen vacancy conductivity. During degradation, the sample fractured.

  10. Cavity resonator for dielectric measurements of high-ɛ, low loss materials, demonstrated with barium strontium zirconium titanate ceramics

    NASA Astrophysics Data System (ADS)

    Marksteiner, Quinn R.; Treiman, Michael B.; Chen, Ching-Fong; Haynes, William B.; Reiten, M. T.; Dalmas, Dale; Pulliam, Elias

    2017-06-01

    A resonant cavity method is presented which can measure loss tangents and dielectric constants for materials with dielectric constant from 150 to 10 000 and above. This practical and accurate technique is demonstrated by measuring barium strontium zirconium titanate bulk ferroelectric ceramic blocks. Above the Curie temperature, in the paraelectric state, barium strontium zirconium titanate has a sufficiently low loss that a series of resonant modes are supported in the cavity. At each mode frequency, the dielectric constant and loss tangent are obtained. The results are consistent with low frequency measurements and computer simulations. A quick method of analyzing the raw data using the 2D static electromagnetic modeling code SuperFish and an estimate of uncertainties are presented.

  11. High temperature thermoelectric properties of strontium titanate thin films with oxygen vacancy and niobium doping.

    PubMed

    Kumar, S R Sarath; Barasheed, Abeer Z; Alshareef, H N

    2013-08-14

    We report the evolution of high temperature thermoelectric properties of SrTiO3 thin films doped with Nb and oxygen vacancies. Structure-property relations in this important thermoelectric oxide are elucidated and the variation of transport properties with dopant concentrations is discussed. Oxygen vacancies are incorporated during growth or annealing in Ar/H2 above 800 K. An increase in lattice constant due to the inclusion of Nb and oxygen vacancies is found to result in an increase in carrier density and electrical conductivity with simultaneous decrease in carrier effective mass and Seebeck coefficient. The lattice thermal conductivity at 300 K is found to be 2.22 W m(-1) K(-1), and the estimated figure of merit is 0.29 at 1000 K.

  12. Integration of PLZT and BST family oxides with GaN[Lead Lanthanum Zirconate Titanate, Barium Strontium Titanate

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Osinsky, A.V.; Fuflyigin, V.N.; Wang, F.

    2000-07-01

    Recent advances in the processing of complex-oxide materials has allowed the authors to monolithically grow ferroelectrics of lead lanthanum zirconate titanate (PLZT) and barium strontium titanate (BST) systems on a GaN/sapphire structure. High quality films of PLZT and BST were grown on GaN/c-Al{sub 2}O{sub 3} in a thickness range of 0.3--5 {micro}m by a sol-gel technique. Field-induced birefringence, as large as 0.02, was measured from a PLZT layer grown on a buffered GaN/sapphire structure. UV illumination was found to result in more symmetrical electrooptic hysteresis loop. BST films on GaN demonstrated a low frequency dielectric constant of up to 800more » with leakage current density as low as 5.5 {center_dot} 10{sup {minus}8} A/cm{sup 2}.« less

  13. Multisite occupation of divalent dopants in barium and strontium titanates

    NASA Astrophysics Data System (ADS)

    Zulueta, Yohandys A.; Nguyen, Minh Tho

    2018-10-01

    Based on recent experimental and theoretical proofs of calcium multisite occupation in barium titanate, we investigated a mixed incorporation mechanism for divalent dopants in barium and strontium titanates (BaTiO3 and SrTiO3). Our present theoretical results demonstrated the multisite occupation of divalent dopants in both perovskite structures. We determined the dependences of the solution, binding energies, and final solution energies with respect to the ionic radii of the dopants. Calculated results obtained based on classical simulations showed that the divalent dopants can occupy both A- and Ti- cation sites in ATiO3 perovskite structures. Such a multisite occupation has direct implications for other experimental findings regarding BaTiO3, such as non-stabilization of the tetragonal phase, shifts in the Curie temperature, intensification of the diffuse phase transition, and shifts in the absorption of ultraviolet light to the visible range in photocatalytic applications related to solar cells for producing energy.

  14. Strain engineered barium strontium titanate for tunable thin film resonators

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Khassaf, H.; Khakpash, N.; Sun, F.

    2014-05-19

    Piezoelectric properties of epitaxial (001) barium strontium titanate (BST) films are computed as functions of composition, misfit strain, and temperature using a non-linear thermodynamic model. Results show that through adjusting in-plane strains, a highly adaptive rhombohedral ferroelectric phase can be stabilized at room temperature with outstanding piezoelectric response exceeding those of lead based piezoceramics. Furthermore, by adjusting the composition and the in-plane misfit, an electrically tunable piezoelectric response can be obtained in the paraelectric state. These findings indicate that strain engineered BST films can be utilized in the development of electrically tunable and switchable surface and bulk acoustic wave resonators.

  15. Synthesis and Characterization of Iron Doped Nano Barium Titanate Through Mechanochemical Route

    NASA Astrophysics Data System (ADS)

    Mukherjee, Soumya; Ghosh, S.; Ghosh, C.; Mitra, M. K.

    2013-04-01

    Mechanochemical activation was used to prepare Fe doped barium titanate with intense milling in high energy planetary ball mill. Calcination was done at 1250°C for 30 min to obtain BaO, followed by milling with titania, at 400 rpm for 3 and 6 h. Ferric oxide was used for Fe doping. Annealing was done on the milled sample at 650, 750 and 850 °C for 3 and 6 h to generate stoichiometric compound of barium titanate phase. Fe doped barium titanate results in dense cluster of irregular polygonal shape morphology while morphology was spherical in nature for undoped sample. UV-VIS spectra analysis was carried out to determine bandgap (3.93 eV for undoped BT and 3.88 eV for Fe doped BT) followed by emission-excitation of the sample by fluorometric analysis.

  16. Fabrication and characterization of cerium-doped barium titanate inverse opal by sol-gel method

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Jin Yi; Zhu Yihua; Yang Xiaoling

    Cerium-doped barium titanate inverted opal was synthesized from barium acetate contained cerous acetate and tetrabutyl titanate in the interstitial spaces of a polystyrene (PS) opal. This procedure involves infiltration of precursors into the interstices of the PS opal template followed by hydrolytic polycondensation of the precursors to amorphous barium titanate and removal of the PS opal by calcination. The morphologies of opal and inverse opal were characterized by scanning electron microscope (SEM). The pores were characterized by mercury intrusion porosimetry (MIP). X-ray photoelectron spectroscopy (XPS) investigation showed the doping structure of cerium, barium and titanium. And powder X-ray diffraction allowsmore » one to observe the influence of doping degree on the grain size. The lattice parameters, crystal size and lattice strain were calculated by the Rietveld refinement method. The synthesis of cerium-doped barium titanate inverted opals provides an opportunity to electrically and optically engineer the photonic band structure and the possibility of developing tunable three-dimensional photonic crystal devices. - Graphical abstract: Cerium-doped barium titanate inverted opal was synthesized from barium acetate acid contained cerous acetate and tetrabutyl titanate in the interstitial spaces of a PS opal, which involves infiltration of precursors into the interstices of the PS opal template and removal of the PS opal by calcination.« less

  17. Properties and mechanisms of surface doped barium titanate sintered in reducing atmospheres

    NASA Astrophysics Data System (ADS)

    Spang, David Irwin

    2001-07-01

    Barium titanate-based dielectric compositions for Multilayer Ceramic Capacitor (MLCC) applications that are properly formulated can maintain acceptable dielectric properties after firing in a reducing atmosphere. The data to be presented relates to the application of an experimental scheme to probe the fundamental nature of doped BaTiO3-based dielectrics exposed to low pO2 sintering atmospheres. Specifically, the effect of Y and Rare Earth dopants Nd, Dy, Ho, and Er and donor dopants Nb, and V have been studied for compositions in the system BaTi(Mn)O3 + SiO2. All dopants were applied to high purity barium titanate as chemical surface coatings. Each coated formulation was evaluated after firing under three different atmospheric conditions. These conditions were comprised of firing in air at 1250°C for 2 hours, firing at 10-10 atm pO2 at 1250°C for 2 hours, and firing at 10-10 atm pO2 at 1250°C for 2 hours with an anneal at 10 -9 atm pO2 at 1000°C for 1 hour. This testing method was useful in gaining insight into the mechanism of the dopant interaction and/or the compensation of the oxygen vacancy concentration. As a donor addition, vanadium was observed to produce the highest dissipation factor when sintered under oxidizing conditions and the lowest dissipation factor when sintered under reducing conditions. The V-doped formulations exhibited satisfactory basic MLCC electrical properties when sintered under reducing conditions. Niobium was observed to impart strong donor character to the dielectric formulations sintered under reducing conditions suggesting that it was unlikely that compensatory A-site cation vacancies were induced. For Y and Rare Earth doped formulations there was an observed shifting and suppression of the Curie Peak that seemed to be attributable to electrostrain effects, related to the ionic radius of the dopants. The observed difference in the TCC behavior of the Nd-doped formulations illustrated two possible effects of Nd doping. One is

  18. Thermostable ferroelectric capacitors based on graded films of barium strontium titanate

    NASA Astrophysics Data System (ADS)

    Tumarkin, A. V.; Razumov, S. V.; Volpyas, V. A.; Gagarin, A. G.; Odinets, A. A.; Zlygostov, M. V.; Sapego, E. N.

    2017-10-01

    The influence of the pressure of working gas during the ion-plasma sputtering on properties of deposited ferroelectric barium strontium titanate coatings has been experimentally studied. Variations in the of pressure of the working gas during deposition allows the component composition of the deposited layer to be changed, which leads to the diffusion of the phase transition and the improvement of temperature stability of properties of ferroelectric film. The gradation of layers has an impact on the temperature of the dielectric permittivity maximum, the shape of the dependence of the capacity on temperature, and the capacitance-voltage characteristics of the capacitor structures.

  19. Concurrent atomistic and continuum simulation of bi-crystal strontium titanate with tilt grain boundary

    PubMed Central

    Yang, Shengfeng; Chen, Youping

    2015-01-01

    In this paper, we present the development of a concurrent atomistic–continuum (CAC) methodology for simulation of the grain boundary (GB) structures and their interaction with other defects in ionic materials. Simulation results show that the CAC simulation allows a smooth passage of cracks through the atomistic–continuum interface without the need for additional constitutive rules or special numerical treatment; both the atomic-scale structures and the energies of the four different [001] tilt GBs in bi-crystal strontium titanate obtained by CAC compare well with those obtained by existing experiments and density function theory calculations. Although 98.4% of the degrees of freedom of the simulated atomistic system have been eliminated in a coarsely meshed finite-element region, the CAC results, including the stress–strain responses, the GB–crack interaction mechanisms and the effect of the interaction on the fracture strength, are comparable with that of all-atom molecular dynamics simulation results. In addition, CAC simulation results show that the GB–crack interaction has a significant effect on the fracture behaviour of bi-crystal strontium titanate; not only the misorientation angle but also the atomic-level details of the GB structure influence the effect of the GB on impeding crack propagation. PMID:25792957

  20. Concurrent atomistic and continuum simulation of bi-crystal strontium titanate with tilt grain boundary.

    PubMed

    Yang, Shengfeng; Chen, Youping

    2015-03-08

    In this paper, we present the development of a concurrent atomistic-continuum (CAC) methodology for simulation of the grain boundary (GB) structures and their interaction with other defects in ionic materials. Simulation results show that the CAC simulation allows a smooth passage of cracks through the atomistic-continuum interface without the need for additional constitutive rules or special numerical treatment; both the atomic-scale structures and the energies of the four different [001] tilt GBs in bi-crystal strontium titanate obtained by CAC compare well with those obtained by existing experiments and density function theory calculations. Although 98.4% of the degrees of freedom of the simulated atomistic system have been eliminated in a coarsely meshed finite-element region, the CAC results, including the stress-strain responses, the GB-crack interaction mechanisms and the effect of the interaction on the fracture strength, are comparable with that of all-atom molecular dynamics simulation results. In addition, CAC simulation results show that the GB-crack interaction has a significant effect on the fracture behaviour of bi-crystal strontium titanate; not only the misorientation angle but also the atomic-level details of the GB structure influence the effect of the GB on impeding crack propagation.

  1. Off Axis Growth of Strontium Titanate Films with High Dielectric Constant Tuning and Low Loss

    DTIC Science & Technology

    2003-04-03

    80309, U.S.A. ABSTRACT We have measured the nonlinear dielectric properties of strontium titanate (STO) thin films grown on neodymium gallate (NGO...and lanthanum aluminate (LAO) substrates. The films prepared by off-axis pulsed laser deposition were characterized by their dielectric constant and...performed on the films prepared with the off axis growth. EXPERIMENTAL Pulsed laser deposition (PLD) was used to deposit STO films on lanthanum

  2. Synthesis of Silver-Strontium Titanate Hybrid Nanoparticles by Sol-Gel-Hydrothermal Method.

    PubMed

    Ueno, Shintaro; Nakashima, Kouichi; Sakamoto, Yasunao; Wada, Satoshi

    2015-03-24

    Silver (Ag) nanoparticle-loaded strontium titanate (SrTiO₃) nanoparticles were attempted to be synthesized by a sol-gel-hydrothermal method. We prepared the titanium oxide precursor gels incorporated with Ag⁺ and Sr 2+ ions with various molar ratios, and they were successfully converted into the Ag-SrTiO₃ hybrid nanoparticles by the hydrothermal treatment at 230 °C in strontium hydroxide aqueous solutions. The morphology of the SrTiO₃ nanoparticles is dendritic in the presence and absence of Ag⁺ ions. The precursor gels, which act as the high reactive precursor, give rise to high nucleation and growth rates under the hydrothermal conditions, and the resultant diffusion-limited aggregation phenomena facilitate the dendritic growth of SrTiO₃. From the field-emission transmission electron microscope observation of these Ag-SrTiO₃ hybrid nanoparticles, the Ag nanoparticles with a size of a few tens of nanometers are distributed without severe agglomeration, owing to the competitive formation reactions of Ag and SrTiO₃.

  3. Morphology, Composition, and Bioactivity of Strontium-Doped Brushite Coatings Deposited on Titanium Implants via Electrochemical Deposition

    PubMed Central

    Liang, Yongqiang; Li, Haoyan; Xu, Jiang; Li, Xin; Qi, Mengchun; Hu, Min

    2014-01-01

    Surface modification techniques have been applied to generate titanium implant surfaces that promote osseointegration for use in dental applications. In this study, strontium-doped brushite coatings were deposited on titanium by electrochemical deposition. The phase composition of the coating was investigated by energy dispersive X-ray spectroscopy and X-ray diffraction. The surface morphologies of the coatings were studied through scanning electron microscopy, and the cytocompatibility and bioactivity of the strontium-doped brushite coatings were evaluated using cultured osteoblasts. Osteoblast proliferation was enhanced by the addition of strontium, suggesting a possible mechanism by which strontium incorporation in brushite coatings increased bone formation surrounding the implants. Cell growth was also strongly influenced by the composition of the deposited coatings, with a 10% Sr-doped brushite coating inducing the greatest amount of bone formation among the tested materials. PMID:24901526

  4. Supercritical fluid route for synthesizing crystalline Barium Strontium Titanate nanoparticles.

    PubMed

    Reverón, H; Elissalde, C; Aymonier, C; Bidault, O; Maglione, M; Cansell, F

    2005-10-01

    Pure and well-crystallized Barium Strontium Titanate (BST) nanoparticles with controlled Ba/Sr ratio have been successfully synthesized under supercritical conditions using a continuous-flow reactor in the temperature range of 150-380 degrees C at 26 MPa. To synthesize the Ba0.6Sr0.4TiO3 composition, alkoxides, ethanol and water were used. The resulting nanopowder consists of fine particles with an average particle size of 23 nm. The results show that the Ba/Sr ratio of this powder can be accurately controlled from the composition of precursor. The characterization of the as-synthesized Ba0.6Sr0.4TiO3 solid-solution and the dielectric properties of the sintered ceramics are here reported.

  5. Barium-strontium-titanate etching characteristics in chlorinated discharges

    NASA Astrophysics Data System (ADS)

    Stafford, Luc; Margot, Joëlle; Langlois, Olivier; Chaker, Mohamed

    2003-07-01

    The etching characteristics of barium-strontium-titanate (BST) were investigated using a high-density plasma sustained by surface waves at 190 MHz in Ar/Cl2 gas mixtures. The etch rate was examined as a function of both the total gas pressure and the Cl2 fraction in Ar/Cl2 using a wafer temperature of 10 °C. The results were correlated to positive ion density and plasma composition obtained from Langmuir probes and mass spectrometry. The BST etch rate was found to increase linearly with the positive ion density and to decrease with increasing chlorine atom concentration. This result indicates that for the temperature conditions used, the interaction between chlorine and BST yields compounds having a volatility that is lower than the original material. As a consequence, the contribution of neutral atomic Cl atoms to the etch mechanism is detrimental, thereby reducing the etch rate. As the wafer temperature increases, the role of chemistry in the etching process is enhanced.

  6. Processing/structure/property Relationships of Barium Strontium Titanate Thin Films for Dynamic Random Access Memory Application.

    NASA Astrophysics Data System (ADS)

    Peng, Cheng-Jien

    The purpose of this study is to see the application feasibility of barium strontium titanate (BST) thin films on ultra large scale integration (ULSI) dynamic random access memory (DRAM) capacitors through the understanding of the relationships among processing, structure and electrical properties. Thin films of BST were deposited by multi-ion -beam reactive sputtering (MIBERS) technique and metallo -organic decomposition (MOD) method. The processing parameters such as Ba/Sr ratio, substrate temperature, annealing temperature and time, film thickness and doping concentration were correlated with the structure and electric properties of the films. Some effects of secondary low-energy oxygen ion bombardment were also examined. Microstructures of BST thin films could be classified into two types: (a) Type I structures, with multi-grains through the film thickness, for amorphous as-grown films after high temperature annealing, and (b) columnar structure (Type II) which remained even after high temperature annealing, for well-crystallized films deposited at high substrate temperatures. Type I films showed Curie-von Schweidler response, while Type II films showed Debted type behavior. Type I behavior may be attributed to the presence of a high density of disordered grain boundaries. Two types of current -voltage characteristics could be seen in non-bombarded films depending on the chemistry of the films (doped or undoped) and substrate temperature during deposition. Only the MIBERS films doped with high donor concentration and deposited at high substrate temperature showed space-charge -limited conduction (SCLC) with discrete shallow traps embedded in trap-distributed background at high electric field. All other non-bombarded films, including MOD films, showed trap-distributed SCLC behavior with a slope of {~}7.5-10 due to the presence of grain boundaries through film thickness or traps induced by unavoidable acceptor impurities in the films. Donor-doping could

  7. XPS studies of nitrogen doping niobium used for accelerator applications

    NASA Astrophysics Data System (ADS)

    Yang, Ziqin; Lu, Xiangyang; Tan, Weiwei; Zhao, Jifei; Yang, Deyu; Yang, Yujia; He, Yuan; Zhou, Kui

    2018-05-01

    Nitrogen doping study on niobium (Nb) samples used for the fabrication of superconducting radio frequency (SRF) cavities was carried out. The samples' surface treatment was attempted to replicate that of the Nb SRF cavities, which includes heavy electropolishing (EP), nitrogen doping and the subsequent EP with different amounts of material removal. The surface chemical composition of Nb samples with different post treatments has been studied by XPS. The chemical composition of Nb, O, C and N was presented before and after Gas Cluster Ion Beam (GCIB) etching. No signals of poorly superconducting nitrides NbNx was found on the surface of any doped Nb sample with the 2/6 recipe before GCIB etching. However, in the depth range greater than 30 nm, the content of N element is below the XPS detection precision scope even for the Nb sample directly after nitrogen doping treatment with the 2/6 recipe.

  8. Properties of barium strontium titanate and niobate nanoparticles produced in gas discharge

    NASA Astrophysics Data System (ADS)

    Plyaka, Pavel; Kazaryan, Mishik; Pavlenko, Anatoly

    2018-03-01

    Dust particles produced in the gas-discharge plasma by barium-strontium titanate and niobate targets sputtering have been investigated in the paper. Particles shape, size and chemical composition were identified. It have been established by Raman scattering investigation and X-ray structure analysis that a part of the collected dust particles retained original crystal structure of the sputtering target. For electro-physical investigations two discs were formed by pressuring from produced particles, and electrodes were deposited on disc flat surface. Capacitance and dielectric loss temperature dependences measurement resulted in the frequency range proving the ferroelectric properties of assembled nanoparticles, similar to the sputtered material.

  9. The fundamental science of nitrogen-doping of niobium superconducting cavities

    NASA Astrophysics Data System (ADS)

    Gonnella, Daniel Alfred

    Doping of niobium superconducting RF cavities with impurities has been demonstrated to have the ability to significantly improve the cryogenic efficiency of the accelerating structures. Doping SRF cavities with nitrogen is a relatively simple additional step to cavity preparation that can make drastic improvements in a cavity's intrinsic quality factor, Q0. Nitrogen-doping consists of treating SRF cavities at high temperatures in a low nitrogen-atmosphere. This leads to two important effects: an improvement in Q0 at low fields, and the presence of an "anti-Q slope" in which the cryogenic efficiency of doped cavities actually improves at higher fields. After its initial discovery, nitrogen-doping showed real promise but many fundamental scientific questions remained about the process. Nitrogen-doped cavities consistently quenched at lower fields than un-doped cavities, cooling the cavities through their critical temperature slowly led to poor performance, and the mechanism behind the Q0 improvement was not well understood. This dissertation focuses on addressing these issues. Single-cell 1.3 GHz cavities were prepared with different nitrogen-dopings and their effects studied systematically. It was found that nitrogen-doping drastically lowers the mean free path of the RF penetration layer of the niobium, leading to a lowering of the temperature-dependent BCS resistance, RBCS, at low fields. Theoretical work to predict the anti-Q slope was compared with experimental results to more fundamentally understand the nature of the field dependence of RBCS. Nitrogen-doped cavities were found to have a much larger sensitivity of residual resistance from trapped magnetic flux than un-doped cavities. Fast cool downs with large spatial temperature gradients through Tc were found to more efficiently expel magnetic flux. The full dependence of this sensitivity to trapped magnetic flux was studied as a function of changing mean free path and found to be in good agreement with

  10. Properties of barium strontium titanate at millimeter wave frequencies

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Osman, Nurul; Free, Charles

    2015-04-24

    The trend towards using higher millimetre-wave frequencies for communication systems has created a need for accurate characterization of materials to be used at these frequencies. Barium Strontium Titanate (BST) is a ferroelectric material whose permittivity is known to change as a function of applied electric field and have found varieties of application in electronic and communication field. In this work, new data on the properties of BST characterize using the free space technique at frequencies between 145 GHz and 155 GHz for both thick film and bulk samples are presented. The measurement data provided useful information on effective permittivity and loss tangentmore » for all the BST samples. Data on the material transmission, reflection properties as well as loss will also be presented. The outcome of the work shows through practical measurement, that BST has a high permittivity with moderate losses and the results also shows that BST has suitable properties to be used as RAM for high frequency application.« less

  11. Electrical Properties of Heavily Doped Niobium Pentoxide

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Valletta, R.

    An analysis of the resistivity and thermoelectric power of heavily doped Nb 2O 5 [over-all composition (Nb 1-xW x) 2O 5 where x varies from 0.0025 to 0.15] shows that mixed valence semiconduction has been observed. The major factor determining the value of the thermoelectric power at high temperatures appears to be an entropy of mixing term. In samples with x > 0.10, it is concluded that the electrons can be trapped on tungsten ions as well as niobium ions. The low-temperature resistivity data indicate that the conduction mechanism is not simply described at temperatures where the tungsten impurity ionsmore » are incompletely ionized.« less

  12. Controlling the strontium-doping in calcium phosphate microcapsules through yeast-regulated biomimetic mineralization.

    PubMed

    Huang, Miaojun; Li, Tianjie; Pan, Ting; Zhao, Naru; Yao, Yongchang; Zhai, Zhichen; Zhou, Jiaan; Du, Chang; Wang, Yingjun

    2016-10-01

    Yeast cells have controllable biosorption on metallic ions during metabolism. However, few studies were dedicated to using yeast-regulated biomimetic mineralization process to control the strontium-doped positions in calcium phosphate microcapsules. In this study, the yeast cells were allowed to pre-adsorb strontium ions metabolically and then served as sacrificing template for the precipitation and calcination of mineral shell. The pre-adsorption enabled the microorganism to enrich of strontium ions into the inner part of the microcapsules, which ensured a slow-release profile of the trace element from the microcapsule. The co-culture with human marrow stromal cells showed that gene expressions of alkaline phosphatase and Collagen-I were promoted. The promotion of osteogenic differentiation was further confirmed in the 3D culture of cell-material complexes. The strategy using living microorganism as 'smart doping apparatus' to control incorporation of trace element into calcium phosphate paved a pathway to new functional materials for hard tissue regeneration.

  13. Variation of Strontium (Sr) in the Ferroelectric Material Barium Strontium Titanate (Ba1-xSrxTiO3) by Co precipitation Method

    NASA Astrophysics Data System (ADS)

    Subarwanti, Y.; Safitri, R. D.; Supriyanto, A.; Iriani, Y.; Jamaludin, A.

    2017-02-01

    Barium Strontium Titanate (BST) have been made with variation strontium (Sr) 10%, 30% and 50% by co-precipitation method. This study aims to determine influence addition Sr against the crystal structure, crystallite size, lattice parameter, grain size and dielectric constant. Samples have been made by co-precipitation method and then the samples were sintered by furnace at 1100°C with holding time 4 hours. Characterization of BST use X-Ray Diffraction instrument, Scanning Electron Microscopy and Resistance Capacitance Inductance (RCL meter). Based on result obtained, the larger Sr content cause the diffraction angle shift to the right (the greater) and crystallinity increasing. But, the value of dielectric constant, crystallite size and grain size decreasing with additional Sr content. Measurement of dielectric constant (K) performed in the frequency range 1 kHz to 100 kHz and the highest value at Sr content 0.1 i.e. 258.35. The addition of Sr content 30% and 50% change the crystal structure from tetragonal to cubic which has paraelectric phase.

  14. Effect of nitrogen doping on the microstructure and visible light photocatalysis of titanate nanotubes by a facile cohydrothermal synthesis via urea treatment

    NASA Astrophysics Data System (ADS)

    Hu, Cheng-Ching; Hsu, Tzu-Chien; Lu, Shan-Yu

    2013-09-01

    A facile one-step cohydrothermal synthesis via urea treatment has been adopted to prepare a series of nitrogen-doped titanate nanotubes with highly efficient visible light photocatalysis of rhodamine B, in an effect to identify the effect of nitrogen doping on the photodegradation efficiency. The morphology and microstructure of the thus-prepared N-doped titanates were characterized by nitrogen adsorption/desorption isotherms, transmission electron microscopy, and scanning electron microscopy. With increasing urea loadings, the N-doped titanates change from a porous multi-layer and nanotube-shaped to a dense and aggregated particle-shaped structure, accompanied with reduced specific surface area and pore volume and enhanced pore diameter. Interstitial linkage to titanate via Tisbnd Osbnd N and Tisbnd Nsbnd O is confirmed by X-ray photoelectron spectroscopy. Factors governing the photocatalytic degradation such as the specific surface area of the catalyst and the degradation pathway are analyzed, a mechanistic illustration on the photodegradation is provided, and a 3-stage degradation mechanism is identified. The synergistic contribution due to the enhanced deethylation and chromophore cleavage on rhodamine B molecules and the reduced band gap on the catalyst TiO2 by interstitial nitrogen-doping has been accounted for the high photodegradation efficiency of the N-doped titanate nanotubes.

  15. Structure, Raman, dielectric behavior and electrical conduction mechanism of strontium titanate

    NASA Astrophysics Data System (ADS)

    Trabelsi, H.; Bejar, M.; Dhahri, E.; Graça, M. P. F.; Valente, M. A.; Khirouni, K.

    2018-05-01

    Strontium titanate was prepared by solid-state reaction method. According to the XRD, it was single phase and has a cubic perovskite structure. The Raman spectroscopic investigation was carried out at room-temperature, and the second-order Raman modes were observed. By employing impedance spectroscopy, the dielectric relaxation and electrical properties were investigated over the temperature range of 500-700 K at various frequencies. The activation energies evaluated from dielectric and modulus studies are in good agreement and these values are attributed to the bulk relaxation. The impedance data were well fitted to an (R1//C1)-(R2//CPE1) equivalent electrical circuit. It could be concluded that the grain boundaries are more resistive and capacitive than the grains. The ac conductivity was found to follow the Jonscher's universal dynamic law ωS and the correlated barrier hopping model (CBH) has been proposed to describe the conduction mechanism.

  16. Niobium Doped Lanthanum Strontium Ferrite as A Redox-Stable and Sulfur-Tolerant Anode for Solid Oxide Fuel Cells.

    PubMed

    Li, Jingwei; Wei, Bo; Cao, Zhiqun; Yue, Xing; Zhang, Yaxin; Lü, Zhe

    2018-01-10

    The Nb-doped lanthanum strontium ferrite perovskite oxide La 0.8 Sr 0.2 Fe 0.9 Nb 0.1 O 3-δ (LSFNb) is evaluated as an anode material in a solid oxide fuel cell (SOFC). The effects of Nb partial substitution in the crystal structure, the electrical conductivity, and the valence of Fe ions are studied. LSFNb exhibits good structural stability in a severe reducing atmosphere at 800 °C, suggesting that high-valent Nb can effectively promote the stability of the lattice structure. The concentration of Fe 2+ increases after Nb doping, as confirmed by X-ray photoelectron spectroscopy. The maximum power density of a thick Sc-stabilized zirconia (ScSZ) electrolyte-supported single cell reached 241.6 mW cm -2 at 800 °C with H 2 as fuel. The cell exhibited excellent stability for 100 h continuous operation without detectable degeneration. Scanning electron microscopy clearly revealed exsolution on the LSFNb surface after operation. Meanwhile, LSFNb particles agglomerated significantly during long-term stability testing. Impedance spectra suggested that both the LSFNb anode and the (La 0.75 Sr 0.25 ) 0.95 MnO 3-δ /ScSZ cathode underwent an activation process during long-term testing, through which the charge transfer ability increased significantly. Meanwhile, low-frequency resistance (R L ) mainly attributed to the anode (80 %) significantly increased, probably due to the agglomeration of LSFNb particles. The LSFNb anode exhibits excellent anti-sulfuring poisoning ability and redox stability. These results demonstrate that LSFNb is a promising anode material for SOFCs. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Comparison study of biomimetic strontium-doped calcium phosphate coatings by electrochemical deposition and air plasma spray: morphology, composition and bioactive performance.

    PubMed

    Li, Ling; Lu, Xia; Meng, Yizhi; Weyant, Christopher M

    2012-10-01

    In this study, strontium-doped calcium phosphate coatings were deposited by electrochemical deposition and plasma spray under different process parameters to achieve various coating morphologies. The coating composition was investigated by energy dispersive X-ray spectroscopy and X-ray diffraction. The surface morphologies of the coatings were studied through scanning electron microscopy while the cytocompatibility and bioactivity of the strontium-doped calcium phosphate coatings were evaluated using bone cell culture using MC3T3-E1 osteoblast-like cells. The addition of strontium leads to enhanced proliferation suggesting the possible benefits of strontium incorporation in calcium phosphate coatings. The morphology and composition of deposited coatings showed a strong influence on the growth of cells.

  18. Dielectric properties of calicum and barium-doped strontium titanate

    NASA Astrophysics Data System (ADS)

    Tung, Li-Chun

    Dielectric properties of high quality polycrystalline Ca- and Ba-doped SrTiO3 perovskites are studied by means of dielectric constant, dielectric loss and ferroelectric hysteresis measurements. Low frequency dispersion of the dielectric constant is found to be very small and a simple relaxor model may not be able to explain its dielectric behavior. Relaxation modes are found in these samples, and they are all interpreted as thermally activated Bipolar re-orientation across energy barriers. In Sr1- xCaxTiO3 (x = 0--0.3), two modes are found associated with different relaxation processes, and the concentration dependence implies a competition between these processes. In Sr1-xBa xTiO3 (x = 0--0.25), relaxation modes are found to be related to the structural transitions, and the relaxation modes persist at low doping levels (x < 0.1), where structural ordering is not observed by previous neutron scattering studies. The validity of well-accepted Barret formula is discussed and two of the well-accepted models, anharmonic oscillator model and transverse Ising model, are found to be equivalent. Both of the Ca and Ba systems can be understood qualitatively within the concept of transverse Ising model.

  19. Review on dielectric properties of rare earth doped barium titanate

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ismail, Fatin Adila, E-mail: fatinadilaismail@gmail.com; Osman, Rozana Aina Maulat, E-mail: rozana@unimap.edu.my; Frontier Materials Research, Seriab, 01000 Kangar, Perlis

    2016-07-19

    Rare earth doped Barium Titanate (BaTiO{sub 3}) were studied due to high permittivity, excellent electrical properties and have wide usage in various applications. This paper reviewed on the electrical properties of RE doped BaTiO{sub 3} (RE: Lanthanum (La), Erbium (Er), Samarium (Sm), Neodymium (Nd), Cerium (Ce)), processing method, phase transition occurred and solid solution range for complete study. Most of the RE doped BaTiO{sub 3} downshifted the Curie temperature (T{sub C}). Transition temperature also known as Curie temperature, T{sub C} where the ceramics had a transition from ferroelectric to a paraelectric phase. In this review, the dielectric constant of La-dopedmore » BaTiO{sub 3}, Er-doped BaTiO{sub 3}, Sm-doped BaTiO{sub 3}, Nd-doped BaTiO{sub 3} and Ce-doped BaTiO{sub 3} had been proved to increase and the transition temperature or also known as T{sub C} also lowered down to room temperature as for all the RE doped BaTiO{sub 3} except for Er-doped BaTiO{sub 3}.« less

  20. Study of a Flexible Low Profile Tunable Dipole Antenna Using Barium Strontium Titanate Varactors

    NASA Technical Reports Server (NTRS)

    Cure, David; Weller, Thomas; Miranda, Felix A.

    2014-01-01

    In this paper a flexible low profile dipole antenna using a frequency selective surface (FSS) with interdigital barium strontium titanate (BST) varactor-tuned unit cells is presented. The varactor chips were placed only along one dimension of the FSS to avoid the use of vias and simplify the DC bias network. The antenna uses overlapping metallic plates that resemble fish scales as a ground plane to improve the flexibility of the multi-material stack structure. The measured data of the antenna demonstrate tunability from 2.42 GHz to 2.66 GHz and 1.3 dB gain drop when using overlapping metallic plates instead of continuous ground plane. The total antenna thickness is approximately lambda/24.

  1. Electrical properties of zinc-oxide-based thin-film transistors using strontium-oxide-doped semiconductors

    NASA Astrophysics Data System (ADS)

    Wu, Shao-Hang; Zhang, Nan; Hu, Yong-Sheng; Chen, Hong; Jiang, Da-Peng; Liu, Xing-Yuan

    2015-10-01

    Strontium-zinc-oxide (SrZnO) films forming the semiconductor layers of thin-film transistors (TFTs) are deposited by using ion-assisted electron beam evaporation. Using strontium-oxide-doped semiconductors, the off-state current can be dramatically reduced by three orders of magnitude. This dramatic improvement is attributed to the incorporation of strontium, which suppresses carrier generation, thereby improving the TFT. Additionally, the presence of strontium inhibits the formation of zinc oxide (ZnO) with the hexagonal wurtzite phase and permits the formation of an unusual phase of ZnO, thus significantly changing the surface morphology of ZnO and effectively reducing the trap density of the channel. Project supported by the National Natural Science Foundation of China (Grant No. 6140031454) and the Innovation Program of Chinese Academy of Sciences and State Key Laboratory of Luminescence and Applications.

  2. Sorption Modeling of Strontium, Plutonium, Uranium and Neptunium Adsorption on Monosodium Titanate

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Fondeur, F.F.

    2003-10-30

    We examined the ability of various equilibrium isotherms to replicate the available data for the adsorption of strontium (Sr), plutonium (Pu), uranium (U) and neptunium (Np) on monosodium titanate (MST) during the treatment of simulated and actual Savannah River Site high-level waste. The analysis considered 29 isotherm models from the literature. As part of this study, we developed a general method for selecting the best isotherm models. The selection criteria for rating the isotherms considered the relative error in predicting the experimental data, the complexity of the mathematical expressions, the thermodynamic validity of the expressions, and statistical significance for themore » expressions. The Fowler Guggenheim-Jovanovic Freundlich (FG-JF), the Fowler Guggenheim-Langmuir Freundlich (FG-LF) and the Dubinin-Astashov (DA) models each reliably predicted the actinide and strontium adsorption on MST. The first two models describe the adsorption process by single layer formation and later al interactions between adsorbed sorbates while the Dubinin-Astashov model assumes volume filling of micropores (by osmotic pressure difference). These two mechanisms include mutually exclusive assumptions. However, we can not determine which model best represents the various adsorption mechanisms on MST. Based on our analysis, the DA model predicted the data well. The DA model assumes that an initial sorption layer forms after which networking begins in the pore spaces, filling the volume by a second mechanism. If this mechanism occurs in MST, as the experimental data suggests, then we expect all the empty and closed spaces of MST to contain actinides and strontium when saturated. Prior microstructure analyses determined that the MST surface is best described as heterogeneous (i.e., a semi-crystalline outer layer on an amorphous core) or composite material for adsorption. Therefore, we expect the empty spaces (of nanometer size) between the crystalline units in the fibrous

  3. Accurate X-ray diffraction studies of KTiOPO{sub 4} single crystals doped with niobium

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Novikova, N. E., E-mail: natnov@ns.crys.ras.ru; Sorokina, N. I.; Alekseeva, O. A.

    2017-01-15

    Single crystals of potassium titanyl phosphate doped with 4% of niobium (КТР:4%Nb) and 6% of niobium (KTP:6%Nb) are studied by accurate X-ray diffraction at room temperature. The niobium atoms are localized near the Ti1 and Ti2 atomic positions, and their positions are for the first time refined independent of the titanium atomic positions. Maps of difference electron density in the vicinity of K1 and K2 atomic positions are analyzed. It is found that in the structure of crystal КТР:4%Nb, additional positions of K atoms are located farther from the main positions and from each other than in КТР and KTP:6%Nbmore » crystals. The nonuniform distribution of electron density found in the channels of the КТР:4%Nb structure is responsible for ~20% increase in the signal of second harmonic generation.« less

  4. Strontium-doped calcium silicate bioceramic with enhanced in vitro osteogenic properties.

    PubMed

    No, Young Jung; Roohaniesfahani, Seyediman; Lu, Zufu; Shi, Jeffrey; Zreiqat, Hala

    2017-06-05

    Gehlenite (GLN, Ca 2 SiAl 2 O 7 ) is a bioceramic that has been recently shown to possess excellent mechanical strength and in vitro osteogenic properties for bone regeneration. Substitutional incorporation of strontium in place of calcium is an effective way to further enhance biological properties of calcium-based bioceramics and glasses. However, such strategy has the potential to affect other important physicochemical parameters such as strength and degradation due to differences in the ionic radius of strontium and calcium. This study is the first to investigate the effect of a range of concentrations of strontium substitution of calcium at 1, 2, 5, 10 mol% (S1-GLN, S2-GLN, S5-GLN and S10-GLN) on the physicochemical and biological properties of GLN. We showed that up to 2 mol% strontium ion substitution retains the monophasic GLN structure when sintered at 1450 °C, whereas higher concentrations resulted in presence of calcium silicate impurities. Increased strontium incorporation resulted in changes in grain morphology and reduced densification when the ceramics were sintered at 1450 °C. Porous GLN, S1-GLN and S2-GLN scaffolds (∼80% porosity) showed compressive strengths of 2.05 ± 0.46 MPa, 1.76 ± 0.79 MPa and 1.57 ± 0.52 MPa respectively. S1-GLN and S2-GLN immersed in simulated body fluid showed increased strontium ion release but reduced calcium and silicon ion release compared to GLN without affecting overall weight loss and pH over a 21 d period. The bioactivity of the S2-GLN ceramics was significantly improved as reflected in the significant upregulation of HOB proliferation and differentiation compared to GLN. Overall, these results suggest that increased incorporation of strontium presents a trade-off between bioactivity and mechanical strength for GLN bioceramics. This is an important consideration in the development of strontium-doped bioceramics.

  5. Ion beam irradiation of lanthanum and thorium-doped yttrium titanates

    NASA Astrophysics Data System (ADS)

    Lian, J.; Zhang, F. X.; Peters, M. T.; Wang, L. M.; Ewing, R. C.

    2007-05-01

    Y2Ti2O7 pyrochlores doped with La have been sintered at 1373 K for 12 h with the designed compositions of the (LaxY1-x)2Ti2O7 system (x = 0, 0.08, 0.5, and 1), and the phase compositions were analyzed by X-ray diffraction. Limited amounts of La were incorporated into yttrium titanate pyrochlore structure for La-doped samples; while, the end member composition of La2Ti2O7 formed a layered perovskite structure. Ion beam-induced amorphization occurred for all compositions in the (LaxY1-x)2Ti2O7 binary under 1 MeV Kr2+ irradiation at room temperature, and the critical amorphization dose decreased with increasing amounts of La3+. The critical amorphization temperatures for Y2Ti2O7, (La0.162Y0.838)2Ti2O7 and La2Ti2O7 were determined to be ∼780, 890 and 920 K, respectively. Th4+ and Fe3+-doped yttrium titanate pyrochlores were synthesized at 1373 K by sintering Y2Ti2O7 with (ThO2 + Fe2O3). Pyrochlore structures and the chemical compositions were primarily identified by the X-ray diffraction and energy dispersive X-ray (EDX) measurements. The lattice parameter and the critical amorphization dose (1 MeV Kr2+ at room temperature) increase for yttrium titanate pyrochlores with the addition of Th. The increasing 'resistance' to amorphization with less La and greater Th and Fe contents for (Y1-xLax)2Ti2O7 and Y2Ti2O7-Fe2O3-ThO2 systems, respectively, are consistent with the changes in the average ionic radius ratio at the A-sites and B-sites. These results suggest that the addition of lanthanides and actinides (e.g., Th, U, or Pu) will affect the structural stability, as well as the radiation response behavior of the pyrochlore structure-type.

  6. First-principles many-body investigation of δ-doped titanates

    NASA Astrophysics Data System (ADS)

    Lechermann, Frank; Obermeyer, Michael

    2015-03-01

    Studying oxide heterostructures provides the possibility for exploring novel composite materials beyond nature's original conception. In this respect, the doping of Mott-insulating distorted-perovskite titanates such as LaTiO3 and GdTiO3 with a single SrO layer gives rise to a very rich correlated electronic structure. A realistic superlattice survey by means of the charge self-consistent combination of density functional theory (DFT) with dynamical mean-field theory (DMFT) reveals layer- and temperature-dependent multi-orbital metal-insulator transitions. In [001] stacking, an orbital-selective metallic layer at the interface dissolves via an orbital-polarized doped-Mott state into an orbital-ordered insulating regime beyond the two conducting TiO2 layers. We find large differences in the scattering behavior within the latter. Breaking the spin symmetry in δ-doped GdTiO3 results in blocks of ferromagnetic itinerant and ferromagnetic Mott-insulating layers which are coupled antiferromagnetically. Support from the DFG-FOR1346 is acknowledged.

  7. Dielectric function for doped graphene layer with barium titanate

    NASA Astrophysics Data System (ADS)

    Martinez Ramos, Manuel; Garces Garcia, Eric; Magana, Fernado; Vazquez Fonseca, Gerardo Jorge

    2015-03-01

    The aim of our study is to calculate the dielectric function for a system formed with a graphene layer doped with barium titanate. Density functional theory, within the local density approximation, plane-waves and pseudopotentials scheme as implemented in Quantum Espresso suite of programs was used. We considered 128 carbon atoms with a barium titanate cluster of 11 molecules as unit cell with periodic conditions. The geometry optimization is achieved. Optimization of structural configuration is performed by relaxation of all atomic positions to minimize their total energies. Band structure, density of states and linear optical response (the imaginary part of dielectric tensor) were calculated. We thank Dirección General de Asuntos del Personal Académico de la Universidad Nacional Autónoma de México, partial financial support by Grant IN-106514 and we also thank Miztli Super-Computing center the technical assistance.

  8. Probing the thermal Hall effect using miniature capacitive strontium titanate thermometry

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Tinsman, Colin; Li, Gang; Asaba, Tomoya

    2016-06-27

    The thermal Hall effect is the thermal analog of the electrical Hall effect. Rarely observed in normal metals, thermal Hall signals have been argued to be a key property for a number of strongly correlated materials, such as high temperature superconductors, correlated topological insulators, and quantum magnets. The observation of the thermal Hall effect requires precise measurement of temperature in intense magnetic fields. Particularly at low temperature, resistive thermometers have a strong dependence on field, which makes them unsuitable for this purpose. We have created capacitive thermometers which instead measure the dielectric constant of strontium titanate (SrTiO{sub 3}). SrTiO{sub 3}more » approaches a ferroelectric transition, causing its dielectric constant to increase by a few orders of magnitude at low temperature. As a result, these thermometers are very sensitive at low temperature while having very little dependence on the applied magnetic field, making them ideal for thermal Hall measurements. We demonstrate this method by making measurements of the thermal Hall effect in Bismuth in magnetic fields of up to 10 T.« less

  9. Dielectric loss of strontium titanate thin films

    NASA Astrophysics Data System (ADS)

    Dalberth, Mark Joseph

    1999-12-01

    Interest in strontium titanate (STO) thin films for microwave device applications continues to grow, fueled by the telecommunications industry's interest in phase shifters and tunable filters. The optimization of these devices depends upon increasing the phase or frequency tuning and decreasing the losses in the films. Currently, the dielectric response of thin film STO is poorly understood through lack of data and a theory to describe it. We have studied the growth of STO using pulsed laser deposition and single crystal substrates like lanthanum aluminate and neodymium gallate. We have researched ways to use ring resonators to accurately measure the dielectric response as a function of temperature, electric field, and frequency from low radio frequencies to a few gigahertz. Our films grown on lanthanum aluminate show marked frequency dispersion in the real part of the dielectric constant and hints of thermally activated loss behavior. We also found that films grown with conditions that optimized the dielectric constant showed increased losses. In an attempt to simplify the system, we developed a technique called epitaxial lift off, which has allowed us to study films removed from their growth substrates. These free standing films have low losses and show obvious thermally activated behavior. The "amount of tuning," as measured by a figure of merit, KE, is greater in these films than in the films still attached to their growth substrates. We have developed a theory that describes the real and imaginary parts of the dielectric constant. The theory models the real part using a mean field description of the ionic motion in the crystal and includes the loss by incorporating the motion of charged defects in the films.

  10. Microstructural, dielectric and magnetic properties of multiferroic composite system barium strontium titanate – nickel cobalt ferrite

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Pahuja, Poonam, E-mail: poonampahuja123@gmail.com; Tandon, R. P., E-mail: ram-tandon@hotmail.com

    2015-05-15

    Multiferroic composites (1-x) Ba{sub 0.95}Sr{sub 0.05}TiO{sub 3} + (x) Ni{sub 0.8}Co{sub 0.2}Fe{sub 2}O{sub 4} (where x = 0.1, 0.2, 0.3, 0.4) has been prepared by solid state reaction method. X-ray diffraction analysis of the composite samples confirmed the presence of both barium strontium titanate (BST) and nickel cobalt ferrite (NCF) phases. FESEM images indicated the well dispersion of NCF grains among BST grains. Dielectric constant and loss of the composite samples decreases with increase in frequency following Maxwell-Wagner relaxation mechanism. Composite sample with highest ferrite content possesses highest values of remanent and saturation magnetization.

  11. Model for interface formation and the resulting electrical properties for barium-strontium-titanate films on silicon

    NASA Astrophysics Data System (ADS)

    Mueller, A. H.; Suvorova, N. A.; Irene, E. A.; Auciello, O.; Schultz, J. A.

    2003-04-01

    The interface formation between sputtered barium strontium titanate (BST) films and both Si and SiO2 substrate surfaces has been followed using real-time spectroscopic ellipsometry and the mass spectrometry of recoiled ions. In both substrates an intermixed interface layer was observed and subcutaneous Si oxidation occurred. A model for the interface formation is proposed in which the interface includes an SiO2 film on Si, and an intermixed film on which is pure BST. During the deposition of BST the interfaces films were observed to change in time. Electrical characterization of the resulting metal-BST interface capacitors indicates that those samples with SiO2 on the Si surface had the best electrical characteristics.

  12. Macro- and microscopic properties of strontium doped indium oxide

    NASA Astrophysics Data System (ADS)

    Nikolaenko, Y. M.; Kuzovlev, Y. E.; Medvedev, Y. V.; Mezin, N. I.; Fasel, C.; Gurlo, A.; Schlicker, L.; Bayer, T. J. M.; Genenko, Y. A.

    2014-07-01

    Solid state synthesis and physical mechanisms of electrical conductivity variation in polycrystalline, strontium doped indium oxide In2O3:(SrO)x were investigated for materials with different doping levels at different temperatures (T = 20-300 °C) and ambient atmosphere content including humidity and low pressure. Gas sensing ability of these compounds as well as the sample resistance appeared to increase by 4 and 8 orders of the magnitude, respectively, with the doping level increase from zero up to x = 10%. The conductance variation due to doping is explained by two mechanisms: acceptor-like electrical activity of Sr as a point defect and appearance of an additional phase of SrIn2O4. An unusual property of high level (x = 10%) doped samples is a possibility of extraordinarily large and fast oxygen exchange with ambient atmosphere at not very high temperatures (100-200 °C). This peculiarity is explained by friable structure of crystallite surface. Friable structure provides relatively fast transition of samples from high to low resistive state at the expense of high conductance of the near surface layer of the grains. Microscopic study of the electro-diffusion process at the surface of oxygen deficient samples allowed estimation of the diffusion coefficient of oxygen vacancies in the friable surface layer at room temperature as 3 × 10-13 cm2/s, which is by one order of the magnitude smaller than that known for amorphous indium oxide films.

  13. Recovery of niobium from irradiated targets

    DOEpatents

    Phillips, Dennis R.; Jamriska, Sr., David J.; Hamilton, Virginia T.

    1994-01-01

    A process for selective separation of niobium from proton irradiated molybdenum targets is provided and includes dissolving the molybdenum target in a hydrogen peroxide solution to form a first ion-containing solution, contacting the first ion-containing solution with a cationic resin whereby ions selected form the group consisting of molybdenum, biobium, technetium, selenium, vanadium, arsenic, germanium, zirconium and rubidium remain in a second ion-containing solution while ions selected from the group consisting of rubidium, zinc, beryllium, cobalt, iron, manganese, chromium, strontium, yttrium and zirconium are selectively adsorbed by the cationic resin; adjusting the pH of the second ion-containing solution to within a range of from about 5.0 to about 6.0; contacting the pH adjusting second ion-containing solution with a dextran-based material for a time to selectively separate niobium from the solution and recovering the niobium from the dextran-based material.

  14. Enhancement of thermoelectric performance in strontium titanate by praseodymium substitution

    NASA Astrophysics Data System (ADS)

    Kovalevsky, A. V.; Yaremchenko, A. A.; Populoh, S.; Weidenkaff, A.; Frade, J. R.

    2013-02-01

    In order to identify the effects of Pr additions on thermoelectric properties of strontium titanate, crystal structure, electrical and thermal conductivity, and Seebeck coefficient of Sr1-xPrxTiO3 (x = 0.02-0.30) materials were studied at 400 < T < 1180 K under highly reducing atmosphere. The mechanism of electronic transport was found to be similar up to 10% of praseodymium content, where generation of the charge carriers upon substitution resulted in significant increase of the electrical conductivity, moderate decrease in Seebeck coefficient, and general improvement of the power factor. Formation of point defects in the course of substitution led to suppression of the lattice thermal conductivity, whilst the contribution from electronic component was increasing with carrier concentration. Possible formation of layered structures and growing distortion of the perovskite lattice resulted in relatively low thermoelectric performance for Sr0.80Pr0.20TiO3 and Sr0.70Pr0.30TiO3. The maximum dimensionless figure of merit was observed for Sr0.90Pr0.10TiO3 and amounted to ˜0.23 at 670 K and ˜0.34 at 1170 K, close to the values, obtained in similar conditions for the best bulk thermoelectrics, based on rare-earth substituted SrTiO3.

  15. Crystallization dynamics and interface stability of strontium titanate thin films on silicon.

    PubMed

    Hanzig, Florian; Hanzig, Juliane; Mehner, Erik; Richter, Carsten; Veselý, Jozef; Stöcker, Hartmut; Abendroth, Barbara; Motylenko, Mykhaylo; Klemm, Volker; Novikov, Dmitri; Meyer, Dirk C

    2015-04-01

    Different physical vapor deposition methods have been used to fabricate strontium titanate thin films. Within the binary phase diagram of SrO and TiO 2 the stoichiometry ranges from Ti rich to Sr rich, respectively. The crystallization of these amorphous SrTiO 3 layers is investigated by in situ grazing-incidence X-ray diffraction using synchrotron radiation. The crystallization dynamics and evolution of the lattice constants as well as crystallite sizes of the SrTiO 3 layers were determined for temperatures up to 1223 K under atmospheric conditions applying different heating rates. At approximately 473 K, crystallization of perovskite-type SrTiO 3 is initiated for Sr-rich electron beam evaporated layers, whereas Sr-depleted sputter-deposited thin films crystallize at 739 K. During annealing, a significant diffusion of Si from the substrate into the SrTiO 3 layers occurs in the case of Sr-rich composition. This leads to the formation of secondary silicate phases which are observed by X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy.

  16. Influence of processing parameters on the structure and properties of barium strontium titanate ceramics

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Yun Sining; Department of Materials Physics, School of Science, Xi'an Jiaotong University, Xi'an 710049; Wang Xiaoli

    2008-08-04

    Barium strontium titanate (BST) with the molar formula (Ba{sub 0.8}Sr{sub 0.2}TiO{sub 3}) has been prepared by two different processing methods: mixed-oxide (BST-MO) and reaction-sintering (BST-RS). X-ray powder diffraction study shows differences in grain size and crystal symmetry for both these ceramics. The former shows a tetragonal symmetry while the latter presents a cubic symmetry. The occurrence of polar micro-regions associated with the higher chemical non-homogeneous distribution of ion defects from the influence of the processing parameters is the main reason for the higher peak dielectric constant (K{sub m}), the higher remanent polarization (P{sub r}), the higher coercive field (E{sub c}),more » the higher peak current density (J{sub m}), and the lower temperature of peak dielectric constant (T{sub m}) in BST-MO ceramics.« less

  17. New Insights into Sensitization Mechanism of the Doped Ce (IV) into Strontium Titanate

    PubMed Central

    Wang, Yuan; Liu, Chenglun; Xu, Longjun

    2018-01-01

    SrTiO3 and Ce4+ doped SrTiO3 were synthesized by a modified sol–gel process. The optimization synthesis parameters were obtained by a series of single factor experiments. Interesting phenomena are observable in Ce4+ doped SrTiO3 systems. Sr2+ in SrTiO3 system was replaced by Ce4+, which reduced the surface segregation of Ti4+, ameliorated agglomeration, increased specific surface area more than four times compared with pure SrTiO3, and enhanced quantum efficiency for SrTiO3. Results showed that Ce4+ doping increased the physical adsorption of H2O and adsorbed oxygen on the surface of SrTiO3, which produced additional catalytic active centers. Electrons on the 4f energy level for Ce4+ produced new energy states in the band gap of SrTiO3, which not only realized the use of visible light but also led to an easier separation between the photogenerated electrons and holes. Ce4+ repeatedly captured photoelectrons to produce Ce3+, which inhibited the recombination between photogenerated electrons and holes as well as prolonged their lifetime; it also enhanced quantum efficiency for SrTiO3. The methylene blue (MB) degradation efficiency reached 98.7% using 3 mol % Ce4+ doped SrTiO3 as a photocatalyst, indicating highly photocatalytic activity. PMID:29690605

  18. Characterization of barium strontium titanate thin films on sapphire substrate prepared via RF magnetron sputtering system

    NASA Astrophysics Data System (ADS)

    Jamaluddin, F. W.; Khalid, M. F. Abdul; Mamat, M. H.; Zoolfakar, A. S.; Zulkefle, M. A.; Rusop, M.; Awang, Z.

    2018-05-01

    Barium Strontium Titanate (Ba0.5Sr0.5TiO3) is known to have a high dielectric constant and low loss at microwave frequencies. These unique features are useful for many electronic applications. This paper focuses on material characterization of BST thin films deposited on sapphire substrate by RF magnetron sputtering system. The sample was then annealed at 900 °C for two hours. Several methods were used to characterize the structural properties of the material such as X-ray diffraction (XRD) and atomic force microscopy (AFM). Field emission scanning electron microscopy (FESEM) was used to analyze the surface morphology of the thin film. From the results obtained, it can be shown that the annealed sample had a rougher surface and better crystallinity as compared to as-deposited sample.

  19. Tungsten-doped thin film materials

    DOEpatents

    Xiang, Xiao-Dong; Chang, Hauyee; Gao, Chen; Takeuchi, Ichiro; Schultz, Peter G.

    2003-12-09

    A dielectric thin film material for high frequency use, including use as a capacitor, and having a low dielectric loss factor is provided, the film comprising a composition of tungsten-doped barium strontium titanate of the general formula (Ba.sub.x Sr.sub.1-x)TiO.sub.3, where X is between about 0.5 and about 1.0. Also provided is a method for making a dielectric thin film of the general formula (Ba.sub.x Sr.sub.1-x)TiO.sub.3 and doped with W, where X is between about 0.5 and about 1.0, a substrate is provided, TiO.sub.2, the W dopant, Ba, and optionally Sr are deposited on the substrate, and the substrate containing TiO.sub.2, the W dopant, Ba, and optionally Sr is heated to form a low loss dielectric thin film.

  20. All-alkoxide synthesis of strontium-containing metal oxides

    DOEpatents

    Boyle, Timothy J.

    2001-01-01

    A method for making strontium-containing metal-oxide ceramic thin films from a precursor liquid by mixing a strontium neo-pentoxide dissolved in an amine solvent and at least one metal alkoxide dissolved in a solvent, said at least one metal alkoxide selected from the group consisting of alkoxides of calcium, barium, bismuth, cadmium, lead, titanium, tantalum, hafnium, tungsten, niobium, zirconium, yttrium, lanthanum, antimony, chromium and thallium, depositing a thin film of the precursor liquid on a substrate, and heating the thin film in the presence of oxygen at between 550 and 700.degree. C.

  1. Modified cermet fuel electrodes for solid oxide electrochemical cells

    DOEpatents

    Ruka, Roswell J.; Spengler, Charles J.

    1991-01-01

    An exterior porous electrode (10), bonded to a solid oxygen ion conducting electrolyte (13) which is in contact with an interior electrode (14), contains coarse metal particles (12) of nickel and/or cobalt, having diameters from 3 micrometers to 35 micrometers, where the coarse particles are coated with a separate, porous, multiphase layer (17) containing fine metal particles of nickel and/or cobalt (18), having diameters from 0.05 micrometers to 1.75 micrometers and conductive oxide (19) selected from cerium oxide, doped cerium oxide, strontium titanate, doped strontium titanate and mixtures thereof.

  2. Structure and properties of strontium-doped phosphate-based glasses

    PubMed Central

    Abou Neel, Ensanya A.; Chrzanowski, Wojciech; Pickup, David M.; O'Dell, Luke A.; Mordan, Nicola J.; Newport, Robert J.; Smith, Mark E.; Knowles, Jonathan C.

    2008-01-01

    Owing to similarity in both ionic size and polarity, strontium (Sr2+) is known to behave in a comparable way to calcium (Ca2+), and its role in bone metabolism has been well documented as both anti-resorptive and bone forming. In this study, novel quaternary strontium-doped phosphate-based glasses, containing 1, 3 and 5 mol% SrO, were synthesized and characterized. 31P magic angle spinning (MAS) nuclear magnetic resonance results showed that, as the Sr2+ content is increased in the glasses, there is a slight increase in disproportionation of Q2 phosphorus environments into Q1 and Q3 environments. Moreover, shortening and strengthening of the phosphorus to bridging oxygen distance occurred as obtained from FTIR. The general broadening of the spectral features with Sr2+ content is most probably due to the increased variation of the phosphate–cation bonding interactions caused by the introduction of the third cation. This increased disorder may be the cause of the increased degradation of the Sr-containing glasses relative to the Sr-free glass. As confirmed from elemental analysis, all Sr-containing glasses showed higher Na2O than expected and this also could be accounted for by the higher degradation of these glasses compared with Sr-free glasses. Measurements of surface free energy (SFE) showed that incorporation of strontium had no effect on SFE, and samples had relatively higher fractional polarity, which is not expected to promote high cell activity. From viability studies, however, the incorporation of Sr2+ showed better cellular response than Sr2+-free glasses, but still lower than the positive control. This unfavourable cellular response could be due to the high degradation nature of these glasses and not due to the presence of Sr2+. PMID:18826914

  3. Barium Strontium Titanate Thin Film Growth with rotational speed variation as a satellite temperature sensor prototype

    NASA Astrophysics Data System (ADS)

    Mulyadi; Rika, W.; Sulidah; Irzaman; Hardhienata, Hendradi

    2017-01-01

    Barium Strontium Titanate(BST) is a promising material for sensor devices such as temperature and infrared sensor. BaxSr1-xTiO3 thin films with affordable Si substrate were prepared by chemical solution deposition method and spin coating technique for 30 seconds with variation in rotation speed (3000 rpm, 5500 rpm and 8000 rpm). A high baking temperature at 8500C has been used for 15 hours during the annealing process. The thickness of BST film was calculated via gravimetric calculation. USB 2000 VIS-NIR was used to characterize the optical properties of BST thin film. The obtained reflectance curve showed that the most reflected wavelengths were in the range of 408-452 nm respectively. The result of the optical film characterization is very important for further development as a sensor in satellite technology.

  4. Effect of crystal structure on strontium titanate thin films and their dielectric properties

    NASA Astrophysics Data System (ADS)

    Kampangkeaw, Satreerat

    Strontium titanate (SrTiO3 or STO) has application in radio and microwave-frequency tunable capacitor devices particularly at low temperatures due to its high dielectric constant, low loss and the electric field tunability of its dielectric constant. The main goal of improving the performance in these devices is to increase the tunability and decrease the dielectric loss at the same time, especially at microwave frequencies. Thin films of STO however, show dramatic differences compared to the bulk. The dielectric constant of bulk STO increases nonlinearly from 300 at room temperature to 30000 at 4 K and the loss range is 10-3--10 -4. On the other hand. STO thin films, while showing a dielectric constant close to 300 at room temperature, typically reach a maximum between 1000 and 10000 in the 30 K to 100 K range before decreasing, and the high-loss range is 10-2--10-3. We have grown strontium titanate thin films using a pulsed laser deposition technique on substrates selected to have a small lattice mismatch between the film and substrate. Neodymium gallate (NdGaO3 or NGO) and lanthanum aluminate (LaAlO3 or LAO) substrates were good candidates due to only 1--2% mismatching. Film capacitor devices were fabricated with 25 micron gap separation. 1.5 mm total gap length and an overall 1 x 2 mm dimension using standard lithography and gold metal evaporative techniques. Their nonlinear dielectric constant and loss tangent were measured at low frequencies and also at 2 GHz, and from room temperature down to 4 K. The resulting films show significant variations of dielectric properties with position on the substrates with respect to the deposition plume axis. In the presence of DC electric fields up to +/-4 V/mum, STO films show improved dielectric tunability and low loss in regions far from the plume axis. We found that the films grown on NCO have lower dielectric loss than those on LAO due to a closer match of the NCO lattice to that of STO. We investigated the possible

  5. Water as probe molecule for midgap states in nanocrystalline strontium titanate by conventional and synchronous luminescence spectroscopy under ambient conditions

    NASA Astrophysics Data System (ADS)

    Taylor, Sean; Samokhvalov, Alexander

    2017-03-01

    Alkaline earth metal titanates are broad bandgap semiconductors with applications in electronic devices, as catalysts, photocatalysts, sorbents, and sensors. Strontium titanate SrTiO3 is of interest in electronic devices, sensors, in the photocatalytic hydrogen generation, as catalyst and sorbent. Both photocatalysis and operation of electronic devices rely upon the pathways of relaxation of excited charge in the semiconductor, including relaxation through the midgap states. We report characterization of nanocrystalline SrTiO3 at room temperature by "conventional" vs. synchronous luminescence spectroscopy and complementary methods. We determined energies of radiative transitions in the visible range through the two midgap states in the nanocrystalline SrTiO3. Further, adsorption and desorption of vapor of water as "probe molecule" for midgap states in the nanocrystalline SrTiO3 was studied, for the first time, by luminescence spectroscopy under ambient conditions. Emission of visible light from the nanocrystalline SrTiO3 is significantly increased upon desorption of water and decreased (quenched) upon adsorption of water vapor, due to interactions with the surface midgap states.

  6. Transport Properties of La- doped SrTiO3 Ceramics Prepared Using Spark Plasma Sintering

    NASA Astrophysics Data System (ADS)

    Mehdizadeh Dehkordi, Arash; Bhattacharya, Sriparna; Tritt, Terry M.; Alshareef, Husam N.

    2012-02-01

    In this work, thermoelectric transport properties of La-doped SrTiO3 ceramics prepared using conventional solid state reaction and spark plasma sintering have been investigated. Room temperature power factor of single crystal strontium titanate (SrTiO3), comparable to that of Bi2Te3, has brought new attention to this perovskite-type transition metal-oxide as a potential n-type thermoelectric for high temperature applications. Electronic properties of this model complex oxide, SrTiO3 (ABO3), can be tuned in a wide range through different doping mechanisms. In addition to A site (La-doped) or B site (Nb-doped) substitutional doping, introducing oxygen vacancies plays an important role in electrical and thermal properties of these structures. Having multiple doping mechanisms makes the transport properties of these perovskites more dependent on preparation parameters. The effect of these synthesis parameters and consolidation conditions on the transport properties of these materials has been studied.

  7. Calcium-doped ceria/titanate tabular functional nanocomposite by layer-by-layer coating method

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Liu, Xiang W., E-mail: lxwluck@gmail.co; Devaraju, M.K.; Yin, Shu

    2010-07-15

    Ca-doped ceria (CDC)/tabular titanate (K{sub 0.8}Li{sub 0.27}Ti{sub 1.73}O{sub 4}, TT) UV-shielding functional nanocomposite with fairly uniform CDC coating layers was prepared through a polyelectrolyte-associated layer-by-layer (LbL) coating method. TT with lepidocrocite-like layered structure was used as the substrate, poly (diallyldimethylammonium chloride) (PDDA) was used as a coupling agent, CDC nanoparticles were used as the main UV-shielding component. CDC/TT nanocomposites with various coating layers of CDC were obtained through a multistep coating process. The phases were studied by X-ray diffraction. The morphology and coating quality were studied by scanning electron microscopy and element mapping of energy dispersive X-ray analysis. The oxidationmore » catalytic activity, UV-shielding ability and using comfort were characterized by Rancimat test, UV-vis spectra and dynamic friction test, respectively. CDC/TT nanocomposites with low oxidation catalytic activity, high UV-shielding ability and good using comfort were finally obtained. - Graphical abstract: Through the control of surface charge of particles calcium-doped ceria/titanate composites with low oxidation catalytic activity, higher UV-shielding ability and excellent comfort was obtained by a facile layer-by-layer coating method.« less

  8. Influence of niobium doping in hierarchically organized titania nanostructure on performance of dye-sensitized solar cells.

    PubMed

    Park, Jong Hoon; Noh, Jun Hong; Han, Byung Suh; Shin, Seong Sik; Park, Ik Jae; Kim, Dong Hoe; Hong, Kug Sun

    2012-06-01

    Niobium doped hierarchically organized TiO2 nanostructures composed of 20 nm size anatase nanocrystals were synthesized using pulsed laser deposition (PLD). The Nb doping concentration could be facilely controlled by adjusting the concentration of Nb in target materials. We could investigate the influence of Nb doping in the TiO2 photoelectrode on the cell performance of dye-sensitized solar cells (DSSCs) by the exclusion of morphological effects using the prepared Nb-doped TiO2 anostructures. We found no significant change in short circuit current density (Jsc) as a function of Nb doping concentration. However, open circuit voltage (Voc) and fill factor (FF) monotonously decrease with increasing Nb concentration. Dark current characteristics of the DSSCs reveal that the decrease in Voc and FF is attributed to the decrease in shunt resistance due to the increase in conductivity TiO2 by Nb doping. However, electrochemical impedance spectra (EIS) analysis at open circuit condition under illumination showed that the resistance at the TiO2/dye/electrolyte interface increases with Nb concentration, revealing that Nb doping suppress the charge recombination at the interface. In addition, electron life time obtained using characteristic frequency in Bode plot increases from 14 msec to 56 msec with increasing Nb concentration from 0 to 1.2 at%. This implies that the improved light harvesting can be achieved by increasing diffusion length through Nb-doping in the conventional TiO2 photoelectrode.

  9. Growth and micro structural studies on Yittria Stabilized Zirconia (YSZ) and Strontium Titanate (STO) buffer layers

    NASA Technical Reports Server (NTRS)

    Srinivas, S.; Pinto, R.; Pai, S. P.; Dsousa, D. P.; Apte, P. R.; Kumar, D.; Purandare, S. C.; Bhatnagar, A. K.

    1995-01-01

    Microstructure of Yittria Stabilized Zirconia (YSZ) and Strontium Titanate (STO) of radio frequency magnetron sputtered buffer layers was studied at various sputtering conditions on Si (100), Sapphire and LaAlO3 (100) substrates. The effect of substrate temperatures up to 800 C and sputtering gas pressures in the range of 50 mTorr. of growth conditions was studied. The buffer layers of YSZ and STO showed a strong tendency for columnar growth was observed above 15 mTorr sputtering gas pressure and at high substrate temperatures. Post annealing of these films in oxygen atmosphere reduced the oxygen deficiency and strain generated during growth of the films. Strong c-axis oriented superconducting YBa2Cu3O7-x (YBCO) thin films were obtained on these buffer layers using pulsed laser ablation technique. YBCO films deposited on multilayers of YSZ and STO were shown to have better superconducting properties.

  10. Strontium-doped hydroxyapatite polysaccharide materials effect on ectopic bone formation

    PubMed Central

    Aid-Launais, R.; Sagardoy, T.; Siadous, R.; Bareille, R.; Rey, S.; Pechev, S.; Etienne, L.; Kalisky, J.; de Mones, E.; Letourneur, D.; Amedee Vilamitjana, J.

    2017-01-01

    Previous studies performed using polysaccharide-based matrices supplemented with hydroxyapatite (HA) particles showed their ability to form in subcutaneous and intramuscular sites a mineralized and osteoid tissue. Our objectives are to optimize the HA content in the matrix and to test the combination of HA with strontium (Sr-HA) to increase the matrix bioactivity. First, non-doped Sr-HA powders were combined to the matrix at three different ratios and were implanted subcutaneously for 2 and 4 weeks. Interestingly, matrices showed radiolucent properties before implantation. Quantitative analysis of micro-CT data evidenced a significant increase of mineralized tissue formed ectopically with time of implantation and allowed us to select the best ratio of HA to polysaccharides of 30% (w/w). Then, two Sr-substitution of 8% and 50% were incorporated in the HA powders (8Sr-HA and 50Sr-HA). Both Sr-HA were chemically characterized and dispersed in matrices. In vitro studies performed with human mesenchymal stem cells (MSCs) demonstrated the absence of cytotoxicity of the Sr-doped matrices whatever the amount of incorporated Sr. They also supported osteoblastic differentiation and activated the expression of one late osteoblastic marker involved in the mineralization process i.e. osteopontin. In vivo, subcutaneous implantation of these Sr-doped matrices induced osteoid tissue and blood vessels formation. PMID:28910401

  11. Frequency and Temperature Dependent Dielectric Properties of Free-standing Strontium Titanate Thin Films.

    NASA Astrophysics Data System (ADS)

    Dalberth, Mark J.; Stauber, Renaud E.; Anderson, Britt; Price, John C.; Rogers, Charles T.

    1998-03-01

    We will report on the frequency and temperature dependence of the complex dielectric function of free-standing strontium titanate (STO) films. STO is an incipient ferroelectric with electric-field tunable dielectric properties of utility in microwave electronics. The films are grown epitaxially via pulsed laser deposition on a variety of substrates, including lanthanum aluminate (LAO), neodymium gallate (NGO), and STO. An initial film of yttrium barium cuprate (YBCO) is grown on the substrate, followed by deposition of the STO layer. Following deposition, the sacrificial YBCO layer is chemically etched away in dilute nitric acid, leaving the substrate and a released, free-standing STO film. Coplanar capacitor structures fabricated on the released films allow us to measure the dielectric response. We observe a peak dielectric function in excess of 5000 at 35K, change in dielectric constant of over a factor of 8 for 10Volt/micron electric fields, and temperature dependence above 50K that is very similar to bulk material. The dielectric loss shows two peaks, each with a thermally activated behavior, apparently arising from two types of polar defects. We will discuss the correlation between dielectric properties, growth conditions, and strain in the free-standing STO films.

  12. Process for strontium-82 separation

    DOEpatents

    Heaton, Richard C.; Jamriska, Sr., David J.; Taylor, Wayne A.

    1992-01-01

    A process for selective separation of strontium-82 and strontium-85 from proton irradiated molybdenum targets comprises dissolving the molybdenum target in a hydrogen peroxide solution to form a first solution containing ions selected from a group consisting of molybdenum, niobium, technetium, selenium, vanadium, arsenic, germanium, zirconium, rubidium, zinc, beryllium, cobalt, iron, manganese, chromium, strontium, and yttrium; passing the solution through a first cationic resin whereby ions selected from a group consisting of zinc, beryllium, cobalt, iron, manganese, chromium, strontium, yttrium a portion of zirconium and a portion of rubidium are selectively absorbed by the first resin; contacting the first resin with an acid solution to strip and remove the absorbed ions from the first cationic exchange resin to form a second solution; evaporating the second solution for a time sufficient to remove substantially all of the acid and water from the solution whereby a residue remains; dissolving the residue in a dilute acid to form a third solution; passing the third solution through a second cationic resin whereby the ions are absorbed by the second resin; contacting the second resin with a dilute sulfuric acid solution whereby the absorbed ions selected from the group consisting of rubidium, zinc, beryllium, cobalt, iron, manganese, chromium and zirconium are selectively removed from the second resin; and contacting the second resin with a dilute acid solution whereby the absorbed strontium ions are selectively removed.

  13. The Effect of Acceptor and Donor Doping on Oxygen Vacancy Concentrations in Lead Zirconate Titanate (PZT).

    PubMed

    Slouka, Christoph; Kainz, Theresa; Navickas, Edvinas; Walch, Gregor; Hutter, Herbert; Reichmann, Klaus; Fleig, Jürgen

    2016-11-22

    The different properties of acceptor-doped (hard) and donor-doped (soft) lead zirconate titanate (PZT) ceramics are often attributed to different amounts of oxygen vacancies introduced by the dopant. Acceptor doping is believed to cause high oxygen vacancy concentrations, while donors are expected to strongly suppress their amount. In this study, La 3+ donor-doped, Fe 3+ acceptor-doped and La 3+ /Fe 3+ -co-doped PZT samples were investigated by oxygen tracer exchange and electrochemical impedance spectroscopy in order to analyse the effect of doping on oxygen vacancy concentrations. Relative changes in the tracer diffusion coefficients for different doping and quantitative relations between defect concentrations allowed estimates of oxygen vacancy concentrations. Donor doping does not completely suppress the formation of oxygen vacancies; rather, it concentrates them in the grain boundary region. Acceptor doping enhances the amount of oxygen vacancies but estimates suggest that bulk concentrations are still in the ppm range, even for 1% acceptor doping. Trapped holes might thus considerably contribute to the charge balancing of the acceptor dopants. This could also be of relevance in understanding the properties of hard and soft PZT.

  14. The Effect of Acceptor and Donor Doping on Oxygen Vacancy Concentrations in Lead Zirconate Titanate (PZT)

    PubMed Central

    Slouka, Christoph; Kainz, Theresa; Navickas, Edvinas; Walch, Gregor; Hutter, Herbert; Reichmann, Klaus; Fleig, Jürgen

    2016-01-01

    The different properties of acceptor-doped (hard) and donor-doped (soft) lead zirconate titanate (PZT) ceramics are often attributed to different amounts of oxygen vacancies introduced by the dopant. Acceptor doping is believed to cause high oxygen vacancy concentrations, while donors are expected to strongly suppress their amount. In this study, La3+ donor-doped, Fe3+ acceptor-doped and La3+/Fe3+-co-doped PZT samples were investigated by oxygen tracer exchange and electrochemical impedance spectroscopy in order to analyse the effect of doping on oxygen vacancy concentrations. Relative changes in the tracer diffusion coefficients for different doping and quantitative relations between defect concentrations allowed estimates of oxygen vacancy concentrations. Donor doping does not completely suppress the formation of oxygen vacancies; rather, it concentrates them in the grain boundary region. Acceptor doping enhances the amount of oxygen vacancies but estimates suggest that bulk concentrations are still in the ppm range, even for 1% acceptor doping. Trapped holes might thus considerably contribute to the charge balancing of the acceptor dopants. This could also be of relevance in understanding the properties of hard and soft PZT. PMID:28774067

  15. An Experimental Investigation towards Improvement of Thermoelectric Properties of Strontium Titanate Ceramics

    NASA Astrophysics Data System (ADS)

    Mehdizadeh Dehkordi, Arash

    The direct energy conversion between heat and electricity based on thermoelectric effects is a topic of long-standing interest in condensed matter materials science. Experimental and theoretical investigations in order to understand the mechanisms involved and to improve the materials properties and conversion efficiency have been ongoing for more than half a century. While significant achievements have been accomplished in improving the properties of conventional heavy element based materials (such as Bi2Te 3 and PbTe) as well as the discovery of new materials systems for the close-to-room temperature and intermediate temperatures, high-temperature applications of thermoelectrics is still limited to one materials system, namely SiGe. Recently, oxides have exhibited great potential to be investigated for high-temperature thermoelectric power generation. The objective of this dissertation is to synthesize and investigate both electronic and thermal transport in strontium titanate (SrTiO3) ceramics in order to experimentally realize its potential and to ultimately investigate the possibility of further improvement of the thermoelectric performance of this perovskite oxide for mid- to high temperature applications. Developing a synthesis strategy and tuning various synthesis parameters to benefit the thermoelectric transport form the foundation of this study. It is worth mentioning that the results of this study has been employed to prepare targets for pulsed-laser deposition (PLD) to study the thermoelectric properties of corresponding thin films and superlattice structures at Dr. Husam Alshareef's group at King Abdullah University of Science and Technology (KAUST), Saudi Arabia. Considering the broad range of functionality of SrTiO3, the findings of this work will surely benefit other fields of research and application of this functional oxide such as photoluminescence, ferroelectricity or mixed-ionic electronic conductivity. This dissertation will ultimately

  16. Nd and Ru co-doped bismuth titanate polycrystalline thin films with improved ferroelectric properties

    NASA Astrophysics Data System (ADS)

    Sahoo, Kishor Kumar; Singh Rajput, Shailendra; Gupta, Rajeev; Roy, Amritendu; Garg, Ashish

    2018-02-01

    We report the ferroelectric properties of pulsed laser deposited thin films of Nd and Ru co-doped bismuth titanate (Bi4-x Nd x Ti3-y Ru y O12). Structural analysis of the as-grown films, using x-ray diffraction, showed a single-phase formation with a polycrystalline structure. In comparison to un-doped and Nd-doped films, ferroelectric measurements on co-doped films demonstrated improved properties with remnant polarization (P r) ~ 12.5 µC cm-2 and an enhanced electrical fatigue life for Bi3.25Nd0.75Ti2.8Ru0.20O12 films. The enhancement in remanent polarization is attributed to microscopic changes, such as local structural distortion and the modification of the dynamical/effective charges on constituent ions due to chemical strain upon simultaneous Bi- (A) and Ti- (B) site doping with Nd and Ru, which has a far stronger effect than only A-site doping with Nd. Piezoresponse force microscopy further confirmed the polar structure and domain switching at nanoscale. The films exhibit small yet finite magnetization at 10 K resulting from strain.

  17. Three dimensional X-ray Diffraction Contrast Tomography Reconstruction of Polycrystalline Strontium Titanate during Sintering and Electron Backscatter Diffraction Validation

    NASA Astrophysics Data System (ADS)

    Syha, M.; Rheinheimer, W.; Loedermann, B.; Graff, A.; Trenkle, A.; Baeurer, M.; Weygand, D.; Ludwig, W.; Gumbsch, P.

    The microstructural evolution of polycrystalline strontium titanate was investigated in three dimensions (3D) using X-ray diffraction contrast tomography (DCT) before and after ex-situ annealing at 1600°C. Post-annealing, the specimen was additionally subjected to phase contrast tomography (PCT) in order to finely resolve the porosities. The resulting microstructure reconstructions were studied with special emphasis on morphology and interface orientation during microstructure evolution. Subsequently, cross-sections of the specimen were studied using electron backscatter diffraction (EBSD). Corresponding cross-sections through the 3D reconstruction were identified and the quality of the reconstruction is validated with special emphasis on the spatial resolution at the grain boundaries, the size and location of pores contained in the material and the accuracy of the orientation determination.

  18. 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.

  19. 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

  20. Thermoluminescent properties of rare earth doped lithium strontium borate phosphors

    NASA Astrophysics Data System (ADS)

    Jakathamani, S.; Annalakshmi, O.; Jose, M. T.

    2018-04-01

    Thermoluminescence (TL) of borates is remarkable in the field of radiation dosimetry because they can detect both neutron and gamma radiations. Usually, the TL efficiency of pure borates is low and hence dopants have to be added to increase their TL output. Their sensitivity and thermal stability vary widely and depend strongly on the preparation method. In this study polycrystalline powders of different rare earth doped thermoluminescent phosphors of Lithium Strontium borate (LSB) were synthesized by solid state sintering technique. Among the different rare earth dopants, the phosphor doped with cerium was found to have a simple glow curve structure with a dosimetric peak at around 265°C for a heating rate of 5°C/s. In order to study the effect of dopant on the TL characteristics, LSB phosphor with different concentrations of Ce dopant was synthesized and the TL intensity was found to be maximum for a dopant concentration of 0.7 mol%. All other important dosimetric characteristics like dose response and fading were carried out for the LSB:Ce (0.7 mol%) phosphor. Kinetic parameters like trap depth and frequency factor were determined using Peak shape method from Chen's equation.

  1. Impact of nitrogen doping of niobium superconducting cavities on the sensitivity of surface resistance to trapped magnetic flux

    NASA Astrophysics Data System (ADS)

    Gonnella, Dan; Kaufman, John; Liepe, Matthias

    2016-02-01

    Future particle accelerators such as the SLAC "Linac Coherent Light Source-II" (LCLS-II) and the proposed Cornell Energy Recovery Linac require hundreds of superconducting radio-frequency (SRF) niobium cavities operating in continuous wave mode. In order to achieve economic feasibility of projects such as these, the cavities must achieve a very high intrinsic quality factor (Q0) to keep cryogenic losses within feasible limits. To reach these high Q0's in the case of LCLS-II, nitrogen-doping of niobium cavities has been selected as the cavity preparation technique. When dealing with Q0's greater than 1 × 1010, the effects of ambient magnetic field on Q0 become significant. Here, we show that the sensitivity to RF losses from trapped magnetic field in a cavity's walls is strongly dependent on the cavity preparation. Specifically, standard electropolished and 120 °C baked cavities show a sensitivity of residual resistance from trapped magnetic flux of ˜0.6 and ˜0.8 nΩ/mG trapped, respectively, while nitrogen-doped cavities show a higher sensitivity of residual resistance from trapped magnetic flux of ˜1 to 5 nΩ/mG trapped. We show that this difference in sensitivities is directly related to the mean free path of the RF surface layer of the niobium: shorter mean free paths lead to less sensitivity of residual resistance to trapped magnetic flux in the dirty limit (ℓ ≪ ξ0), while longer mean free paths lead to lower sensitivity of residual resistance to trapped magnetic flux in the clean limit (ℓ ≫ ξ0). These experimental results are also shown to have good agreement with recent theoretical predictions for pinned vortex lines oscillating in RF fields.

  2. Optically-Induced Persistent Magnetization in Oxygen Deficient Strontium Titanate

    NASA Astrophysics Data System (ADS)

    Crooker, Scott

    2015-03-01

    Interest in electronics and spintronics based on complex oxide materials has exploded in recent years, fueled by the ability to grow atomically-precise heterostructures of various oxides 1. A foundational material in this burgeoning field is strontium titanate, a (nominally) non-magnetic wide-bandgap semiconductor. Owing to its ubiquity in oxide materials science, studies of SrTiO3's interesting dielectric, lattice, and optical properties represent mature research areas. However, renewed interest in SrTiO3 was recently sparked by observations of unexpected spin and magnetization phenomena at interfaces between SrTiO3 and other nonmagnetic oxides 1. The formation and distribution of oxygen vacancies (VO) in SrTiO3 are widely thought to play an essential but as-yet-incompletely understood role in these emergent phenomena. Here we demonstrate a surprising new aspect to the phenomenology of magnetism in SrTiO3 by reporting the observation of an optically-induced and persistent magnetization in slightly oxygen-deficient SrTiO3-δ bulk crystals, using magnetic circular dichroism spectroscopy and optically-coupled SQUID studies 2. This magnetization appears below 18K, persists for hours below 10K, and is tunable via the polarization and wavelength of sub-bandgap (400-500 nm) light. As such, magnetic patterns can be ``written'' into SrTiO3-δ, and subsequently read out, using light alone. This magnetism occurs only in crystals containing VO, and is consistent with a metastable spin polarization of VO-related defect complexes. These data reveal a detailed interplay between magnetism, lattice defects, and light in an archetypal complex oxide material, which may yield new insights into the recent exciting spin physics observed at oxide interfaces.

  3. Osteoclastogenesis and Osteoclastic Resorption of Tricalcium Phosphate: Effect of Strontium and Magnesium Doping

    PubMed Central

    Roy, Mangal; Bose, Susmita

    2012-01-01

    Bone substitute materials are required to support the remodeling process, which consists of osteoclastic resorption and osteoblastic synthesis. Osteoclasts, the bone resorbing cells, generate from differentiation of hemopoietic mononuclear cells. In the present study we have evaluated the effects of 1.0 wt% strontium (Sr) and 1.0 wt% magnesium (Mg) doping in beta-tricalcium phosphate (β-TCP) on the differentiation of mononuclear cells into osteoclast-like cells and its resorptive activity. In vitro osteoclast-like cell formation, adhesion, and resorption were studied using osteoclast precursor RAW 264.7 cell, supplemented with receptor activator of nuclear factor κβ ligand (RANKL). Osteoclast-like cell formation was noticed on pure and Sr doped β-TCP samples at day 8 which was absent on Mg doped β-TCP samples indicating decrease in initial osteoclast differentiation due to Mg doping. After 21 days of culture, osteoclast-like cell formation was evident on all samples with osteoclastic markers such as actin ring, multiple nuclei, and presence of vitronectin receptor αvβ3 integrin. After osteoclast differentiation, all substrates showed osteoclast-like cell mediated degradation, however; significantly restricted for Mg doped β-TCP samples. Our present results indicated substrate chemistry controlled osteoclast differentiation and resorptive activity which can be used in designing TCP based resorbable bone substitutes with controlled degradation properties. PMID:22566212

  4. Osteoclastogenesis and osteoclastic resorption of tricalcium phosphate: effect of strontium and magnesium doping.

    PubMed

    Roy, Mangal; Bose, Susmita

    2012-09-01

    Bone substitute materials are required to support the remodeling process, which consists of osteoclastic resorption and osteoblastic synthesis. Osteoclasts, the bone-resorbing cells, generate from differentiation of hemopoietic mononuclear cells. In the present study, we have evaluated the effects of 1.0 wt % strontium (Sr) and 1.0 wt % magnesium (Mg) doping in beta-tricalcium phosphate (β-TCP) on the differentiation of mononuclear cells into osteoclast-like cells and its resorptive activity. In vitro osteoclast-like cell formation, adhesion, and resorption were studied using osteoclast precursor RAW 264.7 cell, supplemented with receptor activator of nuclear factor κβ ligand (RANKL). Osteoclast-like cell formation was noticed on pure and Sr-doped β-TCP samples at day 8, which was absent on Mg-doped β-TCP samples indicating decrease in initial osteoclast differentiation due to Mg doping. After 21 days of culture, osteoclast-like cell formation was evident on all samples with osteoclastic markers such as actin ring, multiple nuclei, and presence of vitronectin receptor α(v)β(3) integrin. After osteoclast differentiation, all substrates showed osteoclast-like cell-mediated degradation, however, significantly restricted for Mg-doped β-TCP samples. Our present results indicated that substrate chemistry controlled osteoclast differentiation and resorptive activity, which can be used in designing TCP-based resorbable bone substitutes with controlled degradation properties. Copyright © 2012 Wiley Periodicals, Inc.

  5. P-doped strontium titanate grown using two target pulsed laser deposition for thin film solar cells

    NASA Astrophysics Data System (ADS)

    Man, Hamdi

    Thin-film solar cells made of Mg-doped SrTiO3 p-type absorbers are promising candidates for clean energy generation. This material shows p-type conductivity and also demonstrates reasonable absorption of light. In addition, p-type SrTiO3 can be deposited as thin films so that the cost can be lower than the competing methods. In this work, Mg-doped SrTiO3 (STO) thin-films were synthesized and analyzed in order to observe their potential to be employed as the base semiconductor in photovoltaic applications. Mg-doped STO thin-films were grown by using pulsed laser deposition (PLD) using a frequency quadrupled Yttrium Aluminum Garnet (YAG) laser and with a substrate that was heated by back surface absorption of infrared (IR) laser light. The samples were characterized using X-ray photoelectron spectroscopy (XPS) and it was observed that Mg atoms were doped successfully in the stoichiometry. Reflection high energy electron diffraction (RHEED) spectroscopy proved that the thin films were polycrystalline. Kelvin Probe work function measurements indicated that the work function of the films were 4.167 eV after annealing. UV/Vis Reflection spectroscopy showed that Mg-doped STO thin-films do not reflect significantly except in the ultraviolet region of the spectrum where the reflection percentage increased up to 80%. Self-doped STO thin-films, Indium Tin Oxide (ITO) thin films and stainless steel foil (SSF) were studied in order to observe their characteristics before employing them in Mg-doped STO based solar cells. Self-doped STO thin films were grown using PLD and the results showed that they are capable of serving as the n-type semiconductor in solar cell applications with oxygen vacancies in their structure and low reflectivity. Indium Tin Oxide thin-films grown by PLD system showed low 25-50 ?/square sheet resistance and very low reflection features. Finally, commercially available stainless steel foil substrates were excellent substrates for the inexpensive growth of

  6. Fluorescence properties and white light generation from Dy3+-doped niobium phosphate glasses

    NASA Astrophysics Data System (ADS)

    Srihari, T.; Jayasankar, C. K.

    2017-07-01

    Niobium phosphate glasses (P2O5+Nb2O5+K2O + Al2O3+Dy2O3) doped with different concentrations of Dy3+ ions have been synthesized by melt quenching technique and characterized through structural and optical measurements to evaluate the fluorescence properties and find their suitability for white light emitting diodes (LEDs). Phonon energy and vibrational groups of the host matrix have been analyzed from Raman spectra. Judd-Ofelt analysis has been applied for 1.0 mol% Dy2O3-doped glass and inturn radiative properties have been evaluated for excited states of the Dy3+ ion. The higher value of stimulated emission cross-section (σe = 6.4 × 10-21 cm2) for the 4F9/2 → 6H13/2 level confirms its potentiality to be used as yellow laser. The decay curves exhibit non-exponential nature at higher concentrations (≥1 mol %) of Dy3+ ion. From the decay curve analysis, the quantum efficiency for the 4F9/2 level of 1.0 mol % Dy3+-doped glass is found to be 92%. The yellow to blue intensity ratios and chromaticity color co-ordinates are found to vary with Dy3+ ion concentrations/excitation wavelengths and are within the white light region.

  7. Process for strontium-82 separation

    DOEpatents

    Heaton, R.C.; Jamriska, D.J. Sr.; Taylor, W.A.

    1992-12-01

    A process for selective separation of strontium-82 and strontium-85 from proton irradiated molybdenum targets comprises dissolving the molybdenum target in a hydrogen peroxide solution to form a first solution containing ions selected from a group consisting of molybdenum, niobium, technetium, selenium, vanadium, arsenic, germanium, zirconium, rubidium, zinc, beryllium, cobalt, iron, manganese, chromium, strontium, and yttrium; passing the solution through a first cationic resin whereby ions selected from a group consisting of zinc, beryllium, cobalt, iron, manganese, chromium, strontium, yttrium a portion of zirconium and a portion of rubidium are selectively absorbed by the first resin; contacting the first resin with an acid solution to strip and remove the absorbed ions from the first cationic exchange resin to form a second solution; evaporating the second solution for a time sufficient to remove substantially all of the acid and water from the solution whereby a residue remains; dissolving the residue in a dilute acid to form a third solution; passing the third solution through a second cationic resin whereby the ions are absorbed by the second resin; contacting the second resin with a dilute sulfuric acid solution whereby the absorbed ions selected from the group consisting of rubidium, zinc, beryllium, cobalt, iron, manganese, chromium and zirconium are selectively removed from the second resin; and contacting the second resin with a dilute acid solution whereby the absorbed strontium ions are selectively removed. 1 fig.

  8. SELECTIVE REMOVAL OF STRONTIUM AND CESIUM FROM SIMULATED WASTE SOLUTION WITH TITANATE ION EXCHANGERS IN A FILTER CARTRIDGE CONFIGURATION

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Oji, L.; Martin, K.; Hobbs, D.

    2011-05-26

    This report describes experimental results for the selective removal of strontium and cesium from simulated waste solutions using monosodium titanate (MST) and crystalline silicotitanate (CST)-laden filter cartridges. Four types of ion exchange cartridge media (CST and MST designed by both 3M and POROX{reg_sign}) were evaluated. In these proof-of-principle tests effective uptake of both Sr-85 and Cs-137 was observed. However, the experiments were not performed long enough to determine the saturation levels or breakthrough curve for each filter cartridge. POREX{reg_sign} MST cartridges, which by design were based on co-sintering of the active titanates with polyethylene particles, seem to perform as wellmore » as the 3M-designed MST cartridges (impregnated filter membrane design) in the uptake of strontium. At low salt simulant conditions (0.29 M Na{sup +}), the instantaneous decontamination factor (D{sub F}) for Sr-85 with the 3M-design MST cartridge measured 26, representing the removal of 96% of the Sr-85. On the other hand, the Sr-85 instantaneous D{sub F} with the POREX{reg_sign} design MST cartridge measured 40 or 98% removal of the Sr-85. Strontium removal with the 3M-design MST and CST cartridges placed in series filter arrangement produced an instantaneous decontamination factor of 41 or 97.6% removal compared to an instantaneous decontamination factor of 368 or 99.7% removal of the strontium with the POREX{reg_sign} MST and CST cartridge design placed in series. At high salt simulant conditions (5.6 M Na{sup +}), strontium removal with 3M-designed MST cartridge only and with 3M-designed MST and CST cartridges operated in a series configuration were identical. The instantaneous decontamination factor and the strontium removal efficiency, under the above configuration, averaged 8.6 and 88%, respectively. There were no POREX{reg_sign} cartridge experiments using the higher ionic strength simulant solution. At low salt simulant conditions, the uptake of Cs

  9. Thermoluminescence (TL) dosimeter of dysprosium doped strontium borate glass for different glass modifiers (Na, Li, Ca) subjected from 1 to 9 Gy doses

    NASA Astrophysics Data System (ADS)

    Hamzah, S. A.; Saeed, M. A.; Wagiran, H.; Hashim, I. H.

    2017-10-01

    This article reports TL response for different glass modifier and doping concentration. Alkali oxides (Na2O and Li2O) and alkali earth oxide (CaO) will be used as a glass modifier for strontium borate based glass. The samples were prepared by melt quenching technique. Dy2O3 concentrations ranging from 0.00 to 0.70 mol% and exposure doses of 1 to 9 Gy will be varied. All glass samples exhibit the prominent peak temperature positioned at 186 oC to 232 oC. From all the samples, one of the samples shows an excellent linearity dose response, higher TL and show good reproducibility after 5 cycles exposure which is sodium strontium borate doped with 0.1 mol% Dy2O3 (optimum concentration).

  10. Key to enhance thermoelectric performance by controlling crystal size of strontium titanate

    NASA Astrophysics Data System (ADS)

    Wang, Jun; Ye, Xinxin; Yaer, Xinba; Wu, Yin; Zhang, Boyu; Miao, Lei

    2015-09-01

    One-step molten salt synthesis process was introduced to fabricate nano to micrometer sized SrTiO3 powders in which effects of synthesis temperature, oxide-to-flux ratios and raw materials on the generation of SrTiO3 powders were examined. 100 nm or above sized pure SrTiO3 particles were obtained at relatively lower temperature of 900∘C. Micro-sized rhombohedral crystals with a maximum size of approximately 12 μm were obtained from SrCO3 or Sr(NO3)2 strontium source with 1:1 O/S ratio. Controlled crystal size and morphology of Nb-doped SrTiO3 particles are prepared by using this method to confirm the performance of thermoelectric properties. The Seebeck coefficient obtained is significantly high when compared with the reported data, and the high ratio of nano particles in the sample has a positive effect on the increase of Seebeck coefficient too, which is likely due to the energy filtering effect at large numbers of grain boundaries resulting from largely distributed structure.

  11. Effects of strontium-doped bioactive glass on the differentiation of cultured osteogenic cells.

    PubMed

    Isaac, J; Nohra, J; Lao, J; Jallot, E; Nedelec, J M; Berdal, A; Sautier, J M

    2011-02-08

    There is accumulating evidence that strontium-containing biomaterials have positive effects on bone tissue repair. We investigated the in vitro effect of a new Sr-doped bioactive glass manufactured by the sol-gel method on osteoblast viability and differentiation. Osteoblasts isolated from foetal mouse calvaria were cultured in the presence of bioactive glass particles; particles were undoped (B75) or Sr-doped with 1 wt.% (B75-Sr1) and 5 wt.% (B75-Sr5). Morphological analysis was carried out by contrast-phase microscopy and scanning electron microscopy (SEM). Cell viability was evaluated by the MTS assay at 24 h, 48 h and 72 h. At 24 h, day 6 and day 12, osteoblast differentiation was evaluated by assaying alkaline phosphatase (ALP) activity, osteocalcin (OC) secretion and gene expression of various bone markers, using Real-Time-PCR. Alizarin Red staining and ALP histoenzymatic localisation were performed on day 12. Microscopic observations and MTS showed an absence of cytotoxicity in the three investigated bioactive glasses. B75-Sr5 particles in cell cultures, in comparison with those of B75 and B75-Sr1, resulted in a significant up-regulation of Runx2, Osterix, Dlx5, collagen I, ALP, bone sialoprotein (BSP) and OC mRNA levels on day 12, which was associated with an increase of ALP activity on day 6 and OC secretion on day 12. In conclusion, osteoblast differentiation of foetal mouse calvarial cells was enhanced in the presence of bioactive glass particles containing 5 wt.% strontium. Thus, B75-Sr5 may represent a promising bone-grafting material for bone regeneration procedures.

  12. Off Axis Growth of Strontium Titanate Films with High Dielectric Constant Tuning and Low Loss

    NASA Astrophysics Data System (ADS)

    Kampangkeaw, Satreerat

    2002-03-01

    Using off-axis pulsed laser deposition, we have grown strontium titanate (STO) films on neodymium gallate (NGO) and lanthanum aluminate (LAO) substrates. We measured the film dielectric constant and loss tangent as a function of temperature in the 10kHz to 1 MHz frequency range. We found that the loss is less than 0.01 We also obtained a figure of merit from the relative variation of the dielectric constant divided by the loss tangent. The obtained figured of merit at 35K and 1MHz is about 1000 comparable to bulk values. The dielectric constant of these films can be changed by a factor of 4-8 in the presence of a DC electric field up to 5V/μm. The films show significant variations of dielectric properties grown on different substrates at different locations respect to the axis of the plume. The STO films on LAO having high dielectric constant and dielectric tuning were grown in region near the center of the plume. On the other hand, STO on NGO shows this effect only on the films grown far from the plume axis.

  13. Synthesis and characterization of UV-treated Fe-doped bismuth lanthanum titanate-doped TiO2 layers in dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Song, Myoung Geun; Bark, Chung Wung

    2016-06-01

    Dye-sensitized solar cells (DSSCs) based on titanium dioxide (TiO2) have been extensively studied because they constitute promising low-cost alternatives to their conventional semiconductor-based counterparts. However, much of the effort aimed at achieving high conversion efficiencies has focused on dye and liquid electrolytes. In this work, we report the photovoltaic characteristics of DSSCs fabricated by mixing TiO2 with Fe-doped bismuth lanthanum titanate (Fe-BLT). These nanosized Fe-BLT powders were prepared by using a high-energy ball-milling process. In addition, we used a UV radiation-ozone (UV-O3) treatment to change the surface wettability of TiO2 from hydrophobic to hydrophilic and thereby prevented the easy separation of the Fe-BLT-mixed TiO2 from the fluorine-doped tin-oxide (FTO) coating glass.

  14. Structural, topographical and electrical properties of cerium doped strontium barium niobate (Ce:SBN60) ceramics

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Raj, S. Gokul; Mathivanan, V.; Mohan, R.

    2016-05-06

    Tungsten bronze type cerium doped strontium barium niobate (Ce:SBN - Sr{sub 0.6}B{sub 0.4}Nb{sub 2}O{sub 6}) ceramics were synthesized by solid state process. Cerium was used as dopant to improve its electrical properties. Influence of Ce{sup +} ions on the photoluminescence properties was investigated in detail. The grain size topographical behavior of SBN powders and their associated abnormal grain growth (AGG) were completely analyzed through SEM studies. Finally dielectric, measurement discusses about the broad phase transition observed due to cerium dopant The results were discussed in detail.

  15. Hierarchically 3D assembled strontium titanate nanomaterials for water splitting application

    NASA Astrophysics Data System (ADS)

    Moniruddin, Md; Afroz, Khurshida; Shabdan, Yerkin; Bizri, Baraa; Nuraje, Nurxat

    2017-10-01

    Water splitting is an important technique to store solar energy in the simple form of chemical energy, such as hydrogen. Strontium titanate (SrTiO3) is one of the most promising photocatalysts to produce hydrogen gas from water splitting. In this research, an electrospinning technique in combination with sol-gel method was developed to synthesize 3D porous SrTiO3 nanostructures. Different crystallite sizes of SrTiO3-nanofibers (STO-NFs) were produced by varying the synthesis parameters including precursor concentration and calcination temperature. The synthesized nanofibers were characterized using DSC, TGA, XRD, SEM, and TEM. The crystallite size of STO-NFs decreases with increasing precursor concentration (3.03-15.78 vol.%) and gradually increases as the calcination temperature increases within the range of 600-800 °C. The photocatalytic activity of different STO-NFs (based on crystallite size) was also evaluated by the amount of H2 production from water splitting under UV irradiation. The H2 evolution study demonstrated that the photocatalytic activity of the STO-NFs strongly depends on the crystallite size of the nanofibers, precursor concentration, and calcination temperature. The H2 production rate increases with increasing crystallite size and temperature, whereas it decreases with increasing precursor concentration. The photocatalytic performance of the STO-NFs was also compared with the commercial SrTiO3 nanoparticles (STO-NPs) after Pt addition as a cocatalyst, where the synthesized nanofibers showed 2 times higher H2 production rate (1.14 mmol/g-h) than that of the nanoparticles. This synthesis technique provides a good example to produce other inorganic photocatalytic 3D porous structure materials.

  16. Facile synthesis and enhanced visible light photocatalytic activity of N and Zr co-doped TiO2 nanostructures from nanotubular titanic acid precursors

    NASA Astrophysics Data System (ADS)

    Zhang, Min; Yu, Xinluan; Lu, Dandan; Yang, Jianjun

    2013-12-01

    Zr/N co-doped TiO2 nanostructures were successfully synthesized using nanotubular titanic acid (NTA) as precursors by a facile wet chemical route and subsequent calcination. These Zr/N-doped TiO2 nanostructures made by NTA precursors show significantly enhanced visible light absorption and much higher photocatalytic performance than the Zr/N-doped P25 TiO2 nanoparticles. Impacts of Zr/N co-doping on the morphologies, optical properties, and photocatalytic activities of the NTA precursor-based TiO2 were thoroughly investigated. The origin of the enhanced visible light photocatalytic activity is discussed in detail.

  17. Facile synthesis and enhanced visible light photocatalytic activity of N and Zr co-doped TiO2 nanostructures from nanotubular titanic acid precursors

    PubMed Central

    2013-01-01

    Zr/N co-doped TiO2 nanostructures were successfully synthesized using nanotubular titanic acid (NTA) as precursors by a facile wet chemical route and subsequent calcination. These Zr/N-doped TiO2 nanostructures made by NTA precursors show significantly enhanced visible light absorption and much higher photocatalytic performance than the Zr/N-doped P25 TiO2 nanoparticles. Impacts of Zr/N co-doping on the morphologies, optical properties, and photocatalytic activities of the NTA precursor-based TiO2 were thoroughly investigated. The origin of the enhanced visible light photocatalytic activity is discussed in detail. PMID:24369051

  18. Facile synthesis and enhanced visible light photocatalytic activity of N and Zr co-doped TiO2 nanostructures from nanotubular titanic acid precursors.

    PubMed

    Zhang, Min; Yu, Xinluan; Lu, Dandan; Yang, Jianjun

    2013-12-26

    Zr/N co-doped TiO2 nanostructures were successfully synthesized using nanotubular titanic acid (NTA) as precursors by a facile wet chemical route and subsequent calcination. These Zr/N-doped TiO2 nanostructures made by NTA precursors show significantly enhanced visible light absorption and much higher photocatalytic performance than the Zr/N-doped P25 TiO2 nanoparticles. Impacts of Zr/N co-doping on the morphologies, optical properties, and photocatalytic activities of the NTA precursor-based TiO2 were thoroughly investigated. The origin of the enhanced visible light photocatalytic activity is discussed in detail.

  19. Photoemission and Photoabsorption Investigation of the Electronic Structure of Ytterbium Doped Strontium Fluoroapatite

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Nelson, A J; van Buuren, T; Bostedt, C

    X-ray photoemission and x-ray photoabsorption were used to study the composition and the electronic structure of ytterbium doped strontium fluoroapatite (Yb:S-FAP). High resolution photoemission measurements on the valence band electronic structure was used to evaluate the density of occupied states of this fluoroapatite. Element specific density of unoccupied electronic states in Yb:S-FAP were probed by x-ray absorption spectroscopy (XAS) at the Yb 4d (N{sub 4,5}-edge), Sr 3d (M{sub 4,5}-edge), P 2p (L{sub 2,3}-edge), F 1s and O 1s (K-edges) absorption edges. These results provide the first measurements of the electronic structure and surface chemistry of this material.

  20. Colossal Room-Temperature Electrocaloric Effect in Ferroelectric Polymer Nanocomposites Using Nanostructured Barium Strontium Titanates.

    PubMed

    Zhang, Guangzu; Zhang, Xiaoshan; Yang, Tiannan; Li, Qi; Chen, Long-Qing; Jiang, Shenglin; Wang, Qing

    2015-07-28

    The electrocaloric effect (ECE) refers to conversion of thermal to electrical energy of polarizable materials and could form the basis for the next-generation refrigeration and power technologies that are highly efficient and environmentally friendly. Ferroelectric materials such as ceramic and polymer films exhibit large ECEs, but each of these monolithic materials has its own limitations for practical cooling applications. In this work, nanosized barium strontium titanates with systematically varied morphologies have been prepared to form polymer nanocomposites with the ferroelectric polymer matrix. The solution-processed polymer nanocomposites exhibit an extraordinary room-temperature ECE via the synergistic combination of the high breakdown strength of a ferroelectric polymer matrix and the large change of polarization with temperature of ceramic nanofillers. It is found that a sizable ECE can be generated under both modest and high electric fields, and further enhanced greatly by tailoring the morphology of the ferroelectric nanofillers such as increasing the aspect ratio of the nanoinclusions. The effect of the geometry of the nanofillers on the dielectric permittivity, polarization, breakdown strength, ECE and crystallinity of the ferroelectric polymer has been systematically investigated. Simulations based on the phase-field model have been carried out to substantiate the experimental results. With the remarkable cooling energy density and refrigerant capacity, the polymer nanocomposites are promising for solid-state cooling applications.

  1. Low leakage Ru-strontium titanate-Ru metal-insulator-metal capacitors for sub-20 nm technology node in dynamic random access memory

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Popovici, M., E-mail: Mihaela.Ioana.Popovici@imec.be; Swerts, J.; Redolfi, A.

    2014-02-24

    Improved metal-insulator-metal capacitor (MIMCAP) stacks with strontium titanate (STO) as dielectric sandwiched between Ru as top and bottom electrode are shown. The Ru/STO/Ru stack demonstrates clearly its potential to reach sub-20 nm technology nodes for dynamic random access memory. Downscaling of the equivalent oxide thickness, leakage current density (J{sub g}) of the MIMCAPs, and physical thickness of the STO have been realized by control of the Sr/Ti ratio and grain size using a heterogeneous TiO{sub 2}/STO based nanolaminate stack deposition and a two-step crystallization anneal. Replacement of TiN with Ru as both top and bottom electrodes reduces the amount of electricallymore » active defects and is essential to achieve a low leakage current in the MIM capacitor.« less

  2. Synthesis, microstructure and dielectric properties of zirconium doped barium titanate

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kumar, Rohtash; School of Physical Sciences, Jawaharlal Nehru University, New Delhi; Asokan, K.

    2016-05-23

    We report on synthesis, microstructural and relaxor ferroelectric properties of Zirconium(Zr) doped Barium Titanate (BT) samples with general formula Ba(Ti{sub 1-x}Zr{sub x})O{sub 3} (x=0.20, 0.35). These lead-free ceramics were prepared by solid state reaction route. The phase transition behavior and temperature dependent dielectric properties and composition dependent ferroelectric properties were investigated. XRD analysis at room temperature confirms phase purity of the samples. SEM observations revealed retarded grain growth with increasing Zr mole fraction. Dielectric properties of BZT ceramics is influenced significantly by small addition of Zr mole fraction. With increasing Zr mole fraction, dielectric constant decreases while FWHM and frequencymore » dispersion increases. Polarization vs electric field hysteresis measurements reveal ferroelectric relaxor phase at room temperature. The advantages of such substitution maneuvering towards optimizing ferroelectric properties of BaTiO{sub 3} are discussed.« less

  3. Electronic Structure of Ytterbium-Doped Strontium Fluoroapatite: Photoemission and Photoabsorption Investigation

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Nelson, Art J.; Van Buuren, Tony W.; Bostedt, C

    X-ray photoemission and x-ray photoabsorption were used to study the composition and the electronic structure of ytterbium-doped strontium fluoroapatite (Yb:S-FAP). High resolution photoemission measurements on the valence band electronic structure and Sr 3d, P 2p and 2s, Yb 4d and 4p, F 1s and O 1s core lines were used to evaluate the surface and near surface chemistry of this fluoroapatite. Element specific density of unoccupied electronic states in Yb:S-FAP were probed by x-ray absorption spectroscopy (XAS) at the Yb 4d (N4,5-edge), Sr 3d (M4,5-edge), P 2p (L2,3-edge), F 1s and O 1s (K-edges) absorption edges. These results provide themore » first measurements of the electronic structure and surface chemistry of this material.« less

  4. 40 CFR 721.9511 - Silicic acid (H6SiO2O7), magnesium, strontium salt(1:1:2), dysprosium and europium-doped.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) TOXIC SUBSTANCES CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.9511 Silicic acid (H6SiO2O7), magnesium, strontium salt(1:1:2), dysprosium and europium-doped. (a) Chemical substance and significant new...

  5. Novel strontium-doped bioactive glass nanoparticles enhance proliferation and osteogenic differentiation of human bone marrow stromal cells

    NASA Astrophysics Data System (ADS)

    Strobel, L. A.; Hild, N.; Mohn, D.; Stark, W. J.; Hoppe, A.; Gbureck, U.; Horch, R. E.; Kneser, U.; Boccaccini, A. R.

    2013-07-01

    The present study investigates a new family of bioactive glass nanoparticles with and without Sr-doping focusing on the influence of the nanoparticles on human bone marrow stromal cells (hBMSCs) in vitro. The bioactive glass nanoparticles were fabricated by flame spray synthesis and a particle diameter of 30-35 nm was achieved. Glass nanoparticles were undoped (BG 13-93-0Sr) or doped with 5 wt% strontium (Sr) (BG 13-93-5Sr) and used at concentrations of 10 and 100 μg/cm² (particles per culture plate area), respectively. Cells were cultured for 14 days after which the samples were analysed regarding metabolic activity and expression of various bone-specific genes. Cell growth and morphology indicated the high cytocompatibility of the nanoparticulate bioactive glass. The presence of the nanoparticles enhanced cell growth compared to the plain polystyrene control group. At a concentration of 100 μg/cm², Sr-doped particles led to significantly enhanced gene expression of osteocalcin, collagen type 1 and vascular endothelial growth factor. Thus, Sr-doped nanoparticles showing a dose-dependent increase of osteogenic differentiation in hBMSCs are a promising biomaterial for bone regeneration purposes.

  6. Dielectric relaxation of barium strontium titanate and application to thin films for DRAM capacitors

    NASA Astrophysics Data System (ADS)

    Baniecki, John David

    This thesis examines the issues associated with incorporating the high dielectric constant material Barium Strontium Titanate (BSTO) in to the storage capacitor of a dynamic random access memory (DRAM). The research is focused on two areas: characterizing and understanding the factors that control charge retention in BSTO thin films and modifying the electrical properties using ion implantation. The dielectric relaxation of BSTO thin films deposited by metal-organic chemical vapor deposition (MOCVD) is investigated in the time and frequency domains. It is shown that the frequency dispersion of the complex capacitance of BSTO thin films can be understood in terms of a power-law frequency dependence from 1mHz to 20GHz. From the correspondence between the time and frequency domain measurements, it is concluded that the power-law relaxation currents extend back to the nano second regime of DRAM operation. The temperature, field, and annealing dependence of the dielectric relaxation currents are also investigated and mechanisms for the observed power law relaxation are explored. An equivalent circuit model of a high dielectric constant thin film capacitor is developed based on the electrical measurements and implemented in PSPICE. Excellent agreement is found between the experimental and simulated electrical characteristics showing the utility of the equivalent circuit model in simulating the electrical properties of high dielectric constant thin films. Using the equivalent circuit model, it is shown that the greatest charge loss due to dielectric relaxation occurs during the first read after a refresh time following a write to the opposite logic state for a capacitor that has been written to the same logic state for a long time (opposite state write charge loss). A theoretical closed form expression that is a function of three material parameters is developed which estimates the opposite state write charge loss due to dielectric relaxation. Using the closed form

  7. CHARACTERIZATION REPORT FOR STRONTIUM TITANATE IN SWSA 7 AND ADJACENT PARCELS IN SUPPORT OF THE NATIONAL PRIORITIES LIST SITE BOUNDARY DEFINITION PROGRAM OAK RIDGE, TENNESSEE

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    David A. King

    2011-10-10

    The U.S. Department of Energy (DOE) Oak Ridge Office requested support from the Oak Ridge Institute for Science and Education (ORISE) contract to delineate the extent of strontium titanate (SrTiO3) contamination in and around Solid Waste Storage Area (SWSA) 7 as part of the Oak Ridge National Priorities List Site boundary definition program. The study area is presented in Fig. 1.1 relative to the Oak Ridge Reservation (ORR). The investigation was executed according to Sampling and Analysis Plan/Quality Assurance Project Plan (SAP/QAPP) (DOE 2011) to supplement previous investigations noted below and to determine what areas, if any, have been adverselymore » impacted by site operations.« less

  8. Process for recovering niobium from uranium-niobium alloys

    DOEpatents

    Wallace, Steven A.; Creech, Edward T.; Northcutt, Walter G.

    1983-01-01

    Niobium is recovered from scrap uranium-niobium alloy by melting the scrap with tin, solidifying the billet thus formed, heating the billet to combine niobium with tin therein, placing the billet in hydrochloric acid to dissolve the uranium and leave an insoluble residue of niobium stannide, then separating the niobium stannide from the acid.

  9. Pressure, temperature, and electric field dependence of phase transformations in niobium modified 95/5 lead zirconate titanate

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Dong, Wen D.; Carlos Valadez, J.; Gallagher, John A.

    2015-06-28

    Ceramic niobium modified 95/5 lead zirconate-lead titanate (PZT) undergoes a pressure induced ferroelectric to antiferroelectric phase transformation accompanied by an elimination of polarization and a volume reduction. Electric field and temperature drive the reverse transformation from the antiferroelectric to ferroelectric phase. The phase transformation was monitored under pressure, temperature, and electric field loading. Pressures and temperatures were varied in discrete steps from 0 MPa to 500 MPa and 25 °C to 125 °C, respectively. Cyclic bipolar electric fields were applied with peak amplitudes of up to 6 MV m{sup −1} at each pressure and temperature combination. The resulting electric displacement–electric field hysteresis loops weremore » open “D” shaped at low pressure, characteristic of soft ferroelectric PZT. Just below the phase transformation pressure, the hysteresis loops took on an “S” shape, which split into a double hysteresis loop just above the phase transformation pressure. Far above the phase transformation pressure, when the applied electric field is insufficient to drive an antiferroelectric to ferroelectric phase transformation, the hysteresis loops collapse to linear dielectric behavior. Phase stability maps were generated from the experimental data at each of the temperature steps and used to form a three dimensional pressure–temperature–electric field phase diagram.« less

  10. Development, characterization and comparison of two strontium doped nano hydroxyapatite molecules for enamel repair/regeneration.

    PubMed

    Krishnan, Vinod; Bhatia, Ankit; Varma, Harikrishna

    2016-05-01

    Enamel damage resulting or arising from/associated with orthodontic treatment such as white spot lesions and surface deterioration after debonding brackets along with incipient carious lesions are considered problems not amenable for routine restorations due to its invasive nature. The present study was aimed at synthesizing and characterizing nHAp and 25 and 50 mol% strontium nHAp as a surface application modality for dental enamel remineralization/repair. 25 and 50 mol% Sr nHAp was synthesized and characterized in comparison with custom made pure nHAp initially with the help of transmission and scanning electron microscopy as well as toxicological assessment. Further, comparative evaluation of these novel synthesized strontium substituted particles was assessed for its efficacy in repairing damaged enamel with the help of atomic force microscopy, scanning electron microscopy and micro indentation testing. There is increase in crystallinity and reduced particle size favoring dissolution and re-precipitation through small incipient carious lesions and soft white spot areas with 25% Sr-nHAp. Sr doped specimens showed more cell viability in comparison with pure nHAP make it less cytotoxic and hence a biologically friendly material which can be safely applied in patient's mouth. AFM images obtained from 25% and 50% Sr nHAp treated specimens clearly indicated increased roughness in surface topography and performed well with micro indentation test. The novel synthesized Sr doped nHAp forms an improved treatment modality to tackle the long standing quest for solving the problem of enamel loss with incipient carious lesions and WSL from orthodontic procedures. Copyright © 2016 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  11. Investigation of the effect of temperature on aging behavior of Fe-doped lead zirconate titanate

    NASA Astrophysics Data System (ADS)

    Promsawat, Napatporn; Promsawat, Methee; Janphuang, Pattanaphong; Marungsri, Boonruang; Luo, Zhenhua; Pojprapai, Soodkhet

    The aging degradation behavior of Fe-doped Lead zirconate titanate (PZT) subjected to different heat-treated temperatures was investigated over 1000h. The aging degradation in the piezoelectric properties of PZT was indicated by the decrease in piezoelectric charge coefficient, electric field-induced strain and remanent polarization. It was found that the aging degradation became more pronounced at temperature above 50% of the PZT’s Curie temperature. A mathematical model based on the linear logarithmic stretched exponential function was applied to explain the aging behavior. A qualitative aging model based on polar macrodomain switchability was proposed.

  12. Glass-Like Thermal Conductivity of (010)-Textured Lanthanum-Doped Strontium Niobate Synthesized with Wet Chemical Deposition

    DOE PAGES

    Foley, Brian M.; Brown-Shaklee, Harlan J.; Campion, Michael J.; ...

    2014-11-08

    We have measured the cross-plane thermal conductivity (κ) of (010)-textured, undoped, and lanthanum-doped strontium niobate (Sr 2-xLa xNb 2O 7-δ) thin films via time-domain thermoreflectance. Then the thin films were deposited on (001)-oriented SrTiO 3 substrates via the highly-scalable technique of chemical solution deposition. We find that both film thickness and lanthanum doping have little effect on κ, suggesting that there is a more dominant phonon scattering mechanism present in the system; namely the weak interlayer-bonding along the b-axis in the Sr 2Nb 2O 7 parent structure. We also compare our experimental results with two variations of the minimum-limit modelmore » for κ and discuss the nature of transport in material systems with weakly-bonded layers. The low cross-plane κ of these scalably-fabricated films is comparable to that of similarly layered niobate structures grown epitaxially.« less

  13. Studies of ferroelectric and dielectric properties of pure and doped barium titanate prepared by sol-gel method

    NASA Astrophysics Data System (ADS)

    Bisen, Supriya; Mishra, Ashutosh; Jarabana, Kanaka M.

    2016-05-01

    In this work, Barium Titanate (BaTiO3) powders were synthesized via Sol-Gel auto combustion method using citric acid as a chelating agent. We study the behavior of ferroelectric and dielectric properties of pure and doped BaTiO3 on different concentration. To understand the phase and structure of the powder calcined at 900°C were characterized by X-ray Diffraction shows that tetragonal phase is dominant for pure and doped BTO and data fitted by Rietveld Refinement. Electric and Dielectric properties were characterized by P-E Hysteresis and Dielectric measurement. In P-E measurement ferroelectric loop tracer applied for different voltage. The temperature dependant dielectric constant behavior was observed as a function of frequency recorded on hp-Hewlett Packard 4192A, LF impedance, 5Hz-13Hz analyzer.

  14. Local environments and transport properties of heavily doped strontium barium niobates Sr0.5Ba0.5Nb2O6

    NASA Astrophysics Data System (ADS)

    Ottini, Riccardo; Tealdi, Cristina; Tomasi, Corrado; Tredici, Ilenia G.; Soffientini, Alessandro; Burriel, Ramón; Palacios, Elías; Castro, Miguel; Anselmi-Tamburini, Umberto; Ghigna, Paolo; Spinolo, Giorgio

    2018-02-01

    Undoped as well as K-doped (40%), Y-doped (40%), Zr-doped (10%), and Mo-doped (12.5%) strontium barium niobate Sr0.5Ba0.5Nb2O6 (SBN50) materials have been investigated to explore the effect of heavy doping on the structural and functional properties (thermo-power, thermal and electrical conductivities) both in the as prepared (oxidized) and reduced states. For all materials, the EXAFS spectra at the Nb - K edge can be consistently analyzed with the same model of six shells around the Nb sites. Doping mostly gives a simple size effect on the structural parameters, but doping on the Nb sites weakens the Nb-O bond regardless of dopant size and charge. Shell sizes and Debye-Waller factors are almost unaffected by temperature and oxidation state, and the disorder is of static nature. The functional effects of heavy doping do not agree with a simple model of hole or electron injection by aliovalent substitutions on a large band gap semiconductor. With respect to the undoped samples, doping with Mo depresses the thermal conductivity by 30%, Y doping enhances the electrical conductivity by an order of magnitude, while Zr doping increases the Seebeck coefficient by a factor of 2-3. Globally, the ZT efficiency factor of the K-, Y-, and Zr-doped samples is enhanced at least by one order of magnitude with respect to the undoped or Mo-doped materials.

  15. Process for recovering niobium from uranium-niobium alloys

    DOEpatents

    Wallace, S.A.; Creech, E.T.; Northcutt, W.G.

    1982-09-27

    Niobium is recovered from scrap uranium-niobium alloy by melting the scrap with tin, solidifying the billet thus formed, heating the billet to combine niobium with tin therein, placing the billet in hydrochloric acid to dissolve the uranium and form a precipitate of niobium stannide, then separating the precipitate from the acid.

  16. Surface processing for bulk niobium superconducting radio frequency cavities

    DOE PAGES

    Kelly, M. P.; Reid, T.

    2017-02-21

    The majority of niobium cavities for superconducting particle accelerators continue to be fabricated from thin-walled (2-4mm) polycrystalline niobium sheet and, as a final step, require material removal from the radio frequency (RF) surface in order to achieve performance needed for use as practical accelerator devices. More recently bulk niobium in the form of, single-or large-grain slices cut from an ingot has become a viable alternative for some cavity types. In both cases the so-called damaged layer must be chemically etched or electrochemically polished away. The methods for doing this date back at least four decades, however, vigorous empirical studies onmore » real cavities and more fundamental studies on niobium samples at laboratories worldwide have led to seemingly modest improvements that, when taken together, constitute a substantial advance in the reproducibility for surface processing techniques and overall cavity performance. This article reviews the development of niobium cavity surface processing, and summarizes results of recent studies. We place some emphasis on practical details for real cavity processing systems which are difficult to find in the literature but are, nonetheless, crucial for achieving the good and reproducible cavity performance. New approaches for bulk niobium surface treatment which aim to reduce cost or increase performance, including alternate chemical recipes, barrel polishing and 'nitrogen doping' of the RF surface, continue to be pursued and are closely linked to the requirements for surface processing.« less

  17. Surface processing for bulk niobium superconducting radio frequency cavities

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kelly, M. P.; Reid, T.

    The majority of niobium cavities for superconducting particle accelerators continue to be fabricated from thin-walled (2-4mm) polycrystalline niobium sheet and, as a final step, require material removal from the radio frequency (RF) surface in order to achieve performance needed for use as practical accelerator devices. More recently bulk niobium in the form of, single-or large-grain slices cut from an ingot has become a viable alternative for some cavity types. In both cases the so-called damaged layer must be chemically etched or electrochemically polished away. The methods for doing this date back at least four decades, however, vigorous empirical studies onmore » real cavities and more fundamental studies on niobium samples at laboratories worldwide have led to seemingly modest improvements that, when taken together, constitute a substantial advance in the reproducibility for surface processing techniques and overall cavity performance. This article reviews the development of niobium cavity surface processing, and summarizes results of recent studies. We place some emphasis on practical details for real cavity processing systems which are difficult to find in the literature but are, nonetheless, crucial for achieving the good and reproducible cavity performance. New approaches for bulk niobium surface treatment which aim to reduce cost or increase performance, including alternate chemical recipes, barrel polishing and 'nitrogen doping' of the RF surface, continue to be pursued and are closely linked to the requirements for surface processing.« less

  18. 40 CFR 721.9511 - Silicic acid (H6SiO2O7), magnesium, strontium salt(1:1:2), dysprosium and europium-doped.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Silicic acid (H6SiO2O7), magnesium...), magnesium, strontium salt(1:1:2), dysprosium and europium-doped. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as silicic acid (H6SiO2O7) magnesium...

  19. 40 CFR 721.9511 - Silicic acid (H6SiO2O7), magnesium, strontium salt(1:1:2), dysprosium and europium-doped.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Silicic acid (H6SiO2O7), magnesium...), magnesium, strontium salt(1:1:2), dysprosium and europium-doped. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as silicic acid (H6SiO2O7) magnesium...

  20. 40 CFR 721.9511 - Silicic acid (H6SiO2O7), magnesium, strontium salt(1:1:2), dysprosium and europium-doped.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Silicic acid (H6SiO2O7), magnesium...), magnesium, strontium salt(1:1:2), dysprosium and europium-doped. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as silicic acid (H6SiO2O7) magnesium...

  1. 40 CFR 721.9511 - Silicic acid (H6SiO2O7), magnesium, strontium salt(1:1:2), dysprosium and europium-doped.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Silicic acid (H6SiO2O7), magnesium...), magnesium, strontium salt(1:1:2), dysprosium and europium-doped. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as silicic acid (H6SiO2O7) magnesium...

  2. Tunable dielectric properties of Barium Magnesium Niobate (BMN) doped Barium Strontium Titanate (BST) thin films by magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Alema, Fikadu; Reinholz, Aaron; Pokhodnya, Konstantin

    2013-03-01

    We report on the tunable dielectric properties of Mg and Nb co-doped Ba0.45Sr0.55TiO3 (BST) thin film prepared by the magnetron sputtering using BST target (pure and doped with BaMg0.33Nb0.67O3 (BMN)) on Pt/TiO2/SiO2/Al2O3 4'' wafers at 700 °C under oxygen atmosphere. The electrical measurements are conducted on 2432 metal-ferroelectric-metal capacitors using Pt as the top and bottom electrode. The crystalline structure, microstructure, and surface morphology of the films are analyzed and correlated to the films dielectric properties. The BMN doped and undoped BST films have shown tunabilities of 48% and 52%; and leakage current densities of 2.2x10-6 A/cm2 and 3.7x10-5 A/cm2, respectively at 0.5 MV/cm bias field. The results indicate that the BMN doped film exhibits a lower leakage current with no significant decrease in tunability. Due to similar electronegativity and ionic radii, it was suggested that both Mg2+ (accepter-type) and Nb5+ (donor-type) dopants substitutTi4+ ion in BST. The improvement in the film dielectric losses and leakage current with insignificant loss of tunability is attributed to the adversary effects of Mg2+ and Nb5+ in BST.

  3. Spectroscopic investigations on Pr³+ and Nd³+ doped strontium-lithium-bismuth borate glasses.

    PubMed

    Rajesh, D; Balakrishna, A; Seshadri, M; Ratnakaram, Y C

    2012-11-01

    Spectroscopic investigations on different concentrations (0.1, 0.5, 1.0, 1.5 and 2.0mol%) of Pr(3+) and Nd(3+) doped strontium lithium bismuth borate glasses have been done. X-ray diffraction, SEM with EDS, absorption and luminescence spectra were recorded for all the glass matrices and analyzed. X-ray diffraction profiles and SEM images conformed amorphous nature of investigated glass samples. EDS spectra of host glass and Pr(3+)doped glass matrices gave information about the chemical composition of glass samples. From the absorption spectra of Pr(3+) and Nd(3+) ions, Judd-Ofelt (J-O) intensity parameters (Ω(λ),λ=2, 4 and 6) have been calculated and compared with other glass matrices. The emission characteristics such as radiative lifetimes (τ(R)), measured and calculated branching ratios (β) and stimulated emission cross-sections (σ(P)) have been obtained for the observed emission transitions of Pr(3+) and Nd(3+) ions in the above glass matrix for all the concentrations. From the emission spectra of Pr(3+) and Nd(3+) doped glass matrices, the effect of concentration on the quenching of intensity of (1)D(2)→(3)H(4) transition of Pr(3+) ion and (4)F(3/2)→(4)I(9/2), (4)I(11/2) and (4)I(13/2) transitions of Nd(3+) have been studied and discussed. Copyright © 2012 Elsevier B.V. All rights reserved.

  4. Studies of ferroelectric and dielectric properties of pure and doped barium titanate prepared by sol-gel method

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Bisen, Supriya; Mishra, Ashutosh; Jarabana, Kanaka M.

    2016-05-23

    In this work, Barium Titanate (BaTiO{sub 3}) powders were synthesized via Sol-Gel auto combustion method using citric acid as a chelating agent. We study the behavior of ferroelectric and dielectric properties of pure and doped BaTiO{sub 3} on different concentration. To understand the phase and structure of the powder calcined at 900°C were characterized by X-ray Diffraction shows that tetragonal phase is dominant for pure and doped BTO and data fitted by Rietveld Refinement. Electric and Dielectric properties were characterized by P-E Hysteresis and Dielectric measurement. In P-E measurement ferroelectric loop tracer applied for different voltage. The temperature dependant dielectricmore » constant behavior was observed as a function of frequency recorded on hp-Hewlett Packard 4192A, LF impedance, 5Hz-13Hz analyzer.« less

  5. Study on the Key Technology of High Purity Strontium Titanate Powder Synthesized from Oxalic Acid Co-sediment Precipitation

    NASA Astrophysics Data System (ADS)

    Bi, Xiaoguo; Dong, Yingnan; Li, Yingjie; Niu, Wei; Tang, Jian; Ding, Shuang; Li, Meiyang

    2017-09-01

    Oxalate coprecipitation is applied in this paper, high purity titanium tetrachloride, and after the purification of strontium chloride, match with a certain concentration of solution, oxalate and strontium chloride and titanium tetrachloride in 1.005:1.000 make strontium titanium mixture ratio, slowly under 60°C to join in oxalic acid solution, aging around 4 h, get oxygen titanium strontium oxalate (SrTiO(C2O4)2 • 4H2 ) precipitation, after washing, drying and other process made oxygen titanium strontium oxalate powder.

  6. Comparison of the Thermal Degradation of Heavily Nb-Doped and Normal PZT Thin Films.

    PubMed

    Yang, Jeong-Suong; Kang, YunSung; Kang, Inyoung; Lim, SeungMo; Shin, Seung-Joo; Lee, JungWon; Hur, Kang Heon

    2017-03-01

    The degradation of niobium-doped lead zirconate titanate (PZT) and two types of PZT thin films were investigated. Undoped PZT, two-step PZT, and heavily Nb-doped PZT (PNZT) around the morphotropic phase boundary were in situ deposited under optimum condition by RF-magnetron sputtering. All 2- [Formula: see text]-thick films had dense perovskite columnar grain structure and self-polarized (100) dominant orientation. PZT thin films were deposited on Pt/TiO x bottom electrode on Si wafer, and PNZT thin film was on Ir/TiW electrode with the help of orientation control. Sputtered PZT films formed on microelectromechanical system (MEMS) gyroscope and the degradation rates were compared at different temperatures. PNZT showed the best resistance to the thermal degradation, followed by two-step PZT. To clarify the effect of oxygen vacancies on the degradation of the film at high temperature, photoluminescence measurement was conducted, which confirmed that oxygen vacancy rate was the lowest in heavy PNZT. Nb-doping PZT thin films suppressed the oxygen deficit and made high imprint with self-polarization. This defect distribution and high internal field allowed PNZT thin film to make the piezoelectric sensors more stable and reliable at high temperature, such as reflow process of MEMS packaging.

  7. Influence of single and binary doping of strontium and lithium on in vivo biological properties of bioactive glass scaffolds

    NASA Astrophysics Data System (ADS)

    Khan, Pintu Kumar; Mahato, Arnab; Kundu, Biswanath; Nandi, Samit K.; Mukherjee, Prasenjit; Datta, Someswar; Sarkar, Soumya; Mukherjee, Jayanta; Nath, Shalini; Balla, Vamsi K.; Mandal, Chitra

    2016-09-01

    Effects of strontium and lithium ion doping on the biological properties of bioactive glass (BAG) porous scaffolds have been checked in vitro and in vivo. BAG scaffolds were prepared by conventional glass melting route and subsequently, scaffolds were produced by evaporation of fugitive pore formers. After thorough physico-chemical and in vitro cell characterization, scaffolds were used for pre-clinical study. Soft and hard tissue formation in a rabbit femoral defect model after 2 and 4 months, were assessed using different tools. Histological observations showed excellent osseous tissue formation in Sr and Li + Sr scaffolds and moderate bone regeneration in Li scaffolds. Fluorochrome labeling studies showed wide regions of new bone formation in Sr and Li + Sr doped samples as compared to Li doped samples. SEM revealed abundant collagenous network and minimal or no interfacial gap between bone and implant in Sr and Li + Sr doped samples compared to Li doped samples. Micro CT of Li + Sr samples showed highest degree of peripheral cancellous tissue formation on periphery and cortical tissues inside implanted samples and vascularity among four compositions. Our findings suggest that addition of Sr and/or Li alters physico-chemical properties of BAG and promotes early stage in vivo osseointegration and bone remodeling that may offer new insight in bone tissue engineering.

  8. Influence of single and binary doping of strontium and lithium on in vivo biological properties of bioactive glass scaffolds

    PubMed Central

    Khan, Pintu Kumar; Mahato, Arnab; Kundu, Biswanath; Nandi, Samit K.; Mukherjee, Prasenjit; Datta, Someswar; Sarkar, Soumya; Mukherjee, Jayanta; Nath, Shalini; Balla, Vamsi K.; Mandal, Chitra

    2016-01-01

    Effects of strontium and lithium ion doping on the biological properties of bioactive glass (BAG) porous scaffolds have been checked in vitro and in vivo. BAG scaffolds were prepared by conventional glass melting route and subsequently, scaffolds were produced by evaporation of fugitive pore formers. After thorough physico-chemical and in vitro cell characterization, scaffolds were used for pre-clinical study. Soft and hard tissue formation in a rabbit femoral defect model after 2 and 4 months, were assessed using different tools. Histological observations showed excellent osseous tissue formation in Sr and Li + Sr scaffolds and moderate bone regeneration in Li scaffolds. Fluorochrome labeling studies showed wide regions of new bone formation in Sr and Li + Sr doped samples as compared to Li doped samples. SEM revealed abundant collagenous network and minimal or no interfacial gap between bone and implant in Sr and Li + Sr doped samples compared to Li doped samples. Micro CT of Li + Sr samples showed highest degree of peripheral cancellous tissue formation on periphery and cortical tissues inside implanted samples and vascularity among four compositions. Our findings suggest that addition of Sr and/or Li alters physico-chemical properties of BAG and promotes early stage in vivo osseointegration and bone remodeling that may offer new insight in bone tissue engineering. PMID:27604654

  9. Dual-step synthesis of 3-dimensional niobium oxide - Zinc oxide

    NASA Astrophysics Data System (ADS)

    Rani, Rozina Abdul; Zoolfakar, Ahmad Sabirin; Rusop, M.

    2018-05-01

    A facile fabrication process for constructing 3-dimensional (3D) structure of Niobium oxide - Zinc oxide (Nb2O5-ZnO) consisting of branched ZnO microrods on top of nanoporous Nb2O5 films was developed based on dual-step synthesis approach. The preliminary procedure was anodization of sputtered niobium metal on Fluorine doped Tin Oxide (FTO) to produce nanoporous Nb2O5, and continued with the growth of branched microrods of ZnO by hydrothermal process. This approach offers insight knowledge on the development of novel 3D metal oxide films via dual-step synthesis process, which might potentially use for multi-functional applications ranging from sensing to photoconversion.

  10. Passivated niobium cavities

    DOEpatents

    Myneni, Ganapati Rao [Yorktown, VA; Hjorvarsson, Bjorgvin [Lagga Arby, SE; Ciovati, Gianluigi [Newport News, VA

    2006-12-19

    A niobium cavity exhibiting high quality factors at high gradients is provided by treating a niobium cavity through a process comprising: 1) removing surface oxides by plasma etching or a similar process; 2) removing hydrogen or other gases absorbed in the bulk niobium by high temperature treatment of the cavity under ultra high vacuum to achieve hydrogen outgassing; and 3) assuring the long term chemical stability of the niobium cavity by applying a passivating layer of a superconducting material having a superconducting transition temperature higher than niobium thereby reducing losses from electron (cooper pair) scattering in the near surface region of the interior of the niobium cavity. According to a preferred embodiment, the passivating layer comprises niobium nitride (NbN) applied by reactive sputtering.

  11. The role of nanoscale seed layers on the enhanced performance of niobium doped TiO 2 thin films on glass

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Nikodemski, Stefan; Dameron, Arrelaine A.; Perkins, John D.

    Transparent conducting oxide (TCO) coatings with decreased cost and greater process or performance versatility are needed for a variety of optoelectronic applications. Among potential new TCO candidates, doped titanium dioxide is receiving particular interest. In this study, niobium-doped titania bilayer structures consisting of a nanoscale seed layer (deposited by atomic layer deposition or RF magnetron sputtering) followed by a thick bulk-like layer were grown directly on glass in order to examine the effects of the seed layer processing on the subsequent crystallization and electrical properties of these heterostructures. Observations from Raman spectroscopy suggest that higher oxygen content in the seedmore » layer suppresses the formation of detrimental titania polymorph phases, found in films produced by annealing directly after synthesis without any exposure to oxygen. Here, our results indicate that the generation of excellent Nb:TiO 2 conductors on glass (without breaking vacuum) only occurs within a narrow processing range and that the sequential deposition of oxygen-poor layers on oxygen-rich layers is a critical step towards achieving films with low resistivity.« less

  12. The role of nanoscale seed layers on the enhanced performance of niobium doped TiO 2 thin films on glass

    DOE PAGES

    Nikodemski, Stefan; Dameron, Arrelaine A.; Perkins, John D.; ...

    2016-09-09

    Transparent conducting oxide (TCO) coatings with decreased cost and greater process or performance versatility are needed for a variety of optoelectronic applications. Among potential new TCO candidates, doped titanium dioxide is receiving particular interest. In this study, niobium-doped titania bilayer structures consisting of a nanoscale seed layer (deposited by atomic layer deposition or RF magnetron sputtering) followed by a thick bulk-like layer were grown directly on glass in order to examine the effects of the seed layer processing on the subsequent crystallization and electrical properties of these heterostructures. Observations from Raman spectroscopy suggest that higher oxygen content in the seedmore » layer suppresses the formation of detrimental titania polymorph phases, found in films produced by annealing directly after synthesis without any exposure to oxygen. Here, our results indicate that the generation of excellent Nb:TiO 2 conductors on glass (without breaking vacuum) only occurs within a narrow processing range and that the sequential deposition of oxygen-poor layers on oxygen-rich layers is a critical step towards achieving films with low resistivity.« less

  13. Mesostructured niobium-doped titanium oxide-carbon (Nb-TiO2-C) composite as an anode for high-performance lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Hwang, Keebum; Sohn, Hiesang; Yoon, Songhun

    2018-02-01

    Mesostructured niobium (Nb)-doped TiO2-carbon (Nb-TiO2-C) composites are synthesized by a hydrothermal process for application as anode materials in Li-ion batteries. The composites have a hierarchical porous structure with the Nb-TiO2 nanoparticles homogenously distributed throughout the porous carbon matrix. The Nb content is controlled (0-10 wt%) to investigate its effect on the physico-chemical properties and electrochemical performance of the composite. While the crystalline/surface structure varied with the addition of Nb (d-spacing of TiO2: 0.34-0.36 nm), the morphology of the composite remained unaffected. The electrochemical performance (cycle stability and rate capability) of the Nb-TiO2-C composite anode with 1 wt% Nb doping improved significantly. First, a full cut-off potential (0-2.5 V vs. Li/Li+) of Nb-doped composite anode (1 wt%) provides a higher energy utilization than that of the un-doped TiO2-C anode. Second, Nb-TiO2-C composite anode (1 wt%) exhibits an excellent long-term cycle stability (100% capacity retention, 297 mAh/g at 0.5 C after 100 cycles and 221 mAh/g at 2 C after 500 cycles) and improved rate-capability (192 mAh/g at 5 C), respectively (1 C: 150 mA/g). The superior electrochemical performance of Nb-TiO2-C (1 wt%) could be attributed to the synergistic effect of improved electronic conductivity induced by optimal Nb doping (1 wt%) and lithium-ion penetration (high diffusion kinetics) through unique pore structures.

  14. A comparison study of rhodamine B photodegradation over nitrogen-doped lamellar niobic acid and titanic acid under visible-light irradiation.

    PubMed

    Li, Xiukai; Kikugawa, Naoki; Ye, Jinhua

    2009-01-01

    A solid-state reaction method with urea as a nitrogen precursor was used to prepare nitrogen-doped lamellar niobic and titanic solid acids (i.e., HNb(3)O(8) and H(2)Ti(4)O(9)) with different acidities for visible-light photocatalysis. The photocatalytic activities of the nitrogen-doped solid acids were evaluated for rhodamine B (RhB) degradation and the results were compared with those obtained over the corresponding nitrogen-doped potassium salts. Techniques such as XRD, BET, SEM, X-ray photoelectron spectroscopy, and UV-visible diffuse reflectance spectroscopy were adopted to explore the nature of the materials as well as the characteristics of the doped nitrogen species. It was found that the intercalation of the urea precursor helped to stabilize the layered structures of both lamellar solid acids and enabled easier nitrogen doping. The effects of urea intercalation were more significant for the more acidic HNb(3)O(8) sample than for the less acidic H(2)Ti(4)O(9). Compared with the nitrogen-doped KNb(3)O(8) and K(2)Ti(4)O(9) samples, the nitrogen-doped HNb(3)O(8) and H(2)Ti(4)O(9) solid acids absorb more visible light and exhibit a superior activity for RhB photodegradation under visible-light irradiation. The nitrogen-doped HNb(3)O(8) sample performed the best among all the samples. The results of the current study suggest that the protonic acidity of the lamellar solid-acid sample is a key factor that influences nitrogen doping and the resultant visible-light photocatalysis.

  15. Strontium-Doped Hematite as a Possible Humidity Sensing Material for Soil Water Content Determination

    PubMed Central

    Tulliani, Jean-Marc; Baroni, Chiara; Zavattaro, Laura; Grignani, Carlo

    2013-01-01

    The aim of this work is to study the sensing behavior of Sr-doped hematite for soil water content measurement. The material was prepared by solid state reaction from commercial hematite and strontium carbonate heat treated at 900 °C. X-Ray diffraction, scanning electron microscopy and mercury intrusion porosimetry were used for microstructural characterization of the synthesized powder. Sensors were then prepared by uniaxially pressing and by screen-printing, on an alumina substrate, the prepared powder and subsequent firing in the 800–1,000 °C range. These sensors were first tested in a laboratory apparatus under humid air and then in an homogenized soil and finally in field. The results evidenced that the screen printed film was able to give a response for a soil matric potential from about 570 kPa, that is to say well below the wilting point in the used soil. PMID:24025555

  16. Enhanced magnetic separation and photocatalytic activity of nitrogen doped titania photocatalyst supported on strontium ferrite.

    PubMed

    Abd Aziz, Azrina; Yong, Kok Soon; Ibrahim, Shaliza; Pichiah, Saravanan

    2012-01-15

    An enhanced ferromagnetic property, visible light active TiO(2) photocatalyst was successfully synthesized by supporting strontium ferrite (SrFe(12)O(19)) onto TiO(2) doped with nitrogen (N) and compared with N-doped TiO(2). The synthesized catalysts were further characterized with X-ray diffraction (XRD), transmission electron microscope (TEM), energy dispersive X-ray spectroscopy (EDS), BET surface area analysis, vibrating sample magnetometer (VSM), X-ray photon spectroscopy (XPS) and visible light spectroscopy analysis for their respective properties. The XRD and EDS revealed the structural and inorganic composition of N-TiO(2) supported on SrFe(12)O(19). The supported N-TiO(2) exhibited a strong ferromagnetic property with tremendous stability against magnetic property losses. It also resulted in reduced band gap (2.8 eV) and better visible light absorption between 400 and 800 nm compared to N-doped TiO(2). The photocatalytic activity was investigated with a recalcitrant phenolic compound namely 2,4-dichlorophenol (2,4-DCP) as a model pollutant under direct bright and diffuse sunlight exposure. A complete degradation of 2,4-DCP was achieved with an initial concentration of 50mg/L for both photocatalysts in 180 min and 270 min respectively under bright sunlight. Similarly the diffuse sunlight study resulted in complete degradation for supported N-TiO(2) and >85% degradation N-TiO(2), respectively. Finally the supported photocatalyst was separated under permanent magnetic field with a mass recovery ≈ 98% for further reuse. Copyright © 2011 Elsevier B.V. All rights reserved.

  17. Unexpectedly high piezoelectricity of Sm-doped lead zirconate titanate in the Curie point region.

    PubMed

    Seshadri, Shruti B; Nolan, Michelle M; Tutuncu, Goknur; Forrester, Jennifer S; Sapper, Eva; Esteves, Giovanni; Granzow, Torsten; Thomas, Pam A; Nino, Juan C; Rojac, Tadej; Jones, Jacob L

    2018-03-07

    Large piezoelectric coefficients in polycrystalline lead zirconate titanate (PZT) are traditionally achieved through compositional design using a combination of chemical substitution with a donor dopant and adjustment of the zirconium to titanium compositional ratio to meet the morphotropic phase boundary (MPB). In this work, a different route to large piezoelectricity is demonstrated. Results reveal unexpectedly high piezoelectric coefficients at elevated temperatures and compositions far from the MPB. At temperatures near the Curie point, doping with 2 at% Sm results in exceptionally large piezoelectric coefficients of up to 915 pm/V. This value is approximately twice those of other donor dopants (e.g., 477 pm/V for Nb and 435 pm/V for La). Structural changes during the phase transitions of Sm-doped PZT show a pseudo-cubic phase forming ≈50 °C below the Curie temperature. Possible origins of these effects are discussed and the high piezoelectricity is posited to be due to extrinsic effects. The enhancement of the mechanism at elevated temperatures is attributed to the coexistence of tetragonal and pseudo-cubic phases, which enables strain accommodation during electromechanical deformation and interphase boundary motion. This work provides insight into possible routes for designing high performance piezoelectrics which are alternatives to traditional methods relying on MPB compositions.

  18. Effects of synthesis techniques on chemical composition, microstructure and dielectric properties of Mg-doped calcium titanate

    NASA Astrophysics Data System (ADS)

    Jongprateep, Oratai; Sato, Nicha

    2018-04-01

    Calcium titanate (CaTiO3) has been recognized as a material for fabrication of dielectric components, owing to its moderate dielectric constant and excellent microwave response. Enhancement of dielectric properties of the material can be achieved through doping, compositional and microstructural control. This study, therefore, aimed at investigating effects of powder synthesis techniques on compositions, microstructure, and dielectric properties of Mg-doped CaTiO3. Solution combustion and solid-state reaction were powder synthesis techniques employed in preparation of undoped CaTiO3 and CaTiO3 doped with 5-20 at% Mg. Compositional analysis revealed that powder synthesis techniques did not exhibit a significant effect on formation of secondary phases. When Mg concentration did not exceed 5 at%, the powders prepared by both techniques contained only a single phase. An increase of MgO secondary phase was observed as Mg concentrations increased from 10 to 20 at%. Experimental results, on the contrary, revealed that powder synthesis techniques contributed to significant differences in microstructure. Solution combustion technique produced powders with finer particle sizes, which consequently led to finer grain sizes and density enhancement. High-density specimens with fine microstructure generally exhibit improved dielectric properties. Dielectric measurements revealed that dielectric constants of all samples ranged between 231 and 327 at 1 MHz, and that superior dielectric constants were observed in samples prepared by the solution combustion technique.

  19. Investigation of niobium surface structure and composition for improvement of superconducting radio-frequency cavities

    NASA Astrophysics Data System (ADS)

    Trenikhina, Yulia

    Nano-scale investigation of intrinsic properties of niobium near-surface is a key to control performance of niobium superconducting radio-frequency cavities. Mechanisms responsible for the performance limitations and their empirical remedies needs to be justified in order to reproducibly control fabrication of SRF cavities with desired characteristics. The high field Q-slope and mechanism behind its cure (120°C mild bake) were investigated by comparison of the samples cut out of the cavities with high and low dissipation regions. Material evolution during mild field Q-slope nitrogen treatment was characterized using the coupon samples as well as samples cut out of nitrogen treated cavity. Evaluation of niobium near-surface state after some typical and novel cavity treatments was accomplished. Various TEM techniques, SEM, XPS, AES, XRD were used for the structural and chemical characterization of niobium near-surface. Combination of thermometry and structural temperature-dependent comparison of the cavity cutouts with different dissipation characteristics revealed precipitation of niobium hydrides to be the reason for medium and high field Q-slopes. Step-by-step effect of the nitrogen treatment processing on niobium surface was studied by analytical and structural characterization of the cavity cutout and niobium samples, which were subject to the treatment. Low concentration nitrogen doping is proposed to explain the benefit of nitrogen treatment. Chemical characterization of niobium samples before and after various surface processing (Electropolishing (EP), 800°C bake, hydrofluoric acid (HF) rinsing) showed the differences that can help to reveal the microscopic effects behind these treatments as well as possible sources of surface contamination.

  20. Growth temperature-dependent metal–insulator transition of vanadium dioxide epitaxial films on perovskite strontium titanate (111) single crystals

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wang, Liangxin; Zhao, Jiangtao; Hong, Bin

    2016-04-14

    Vanadium dioxide (VO{sub 2}) epitaxial films were grown on perovskite single-crystal strontium titanate (SrTiO{sub 3}) substrates by reactive radio-frequency magnetron sputtering. The growth temperature-dependent metal–insulator transition (MIT) behavior of the VO{sub 2} epitaxial films was then investigated. We found that the order of magnitude of resistance change across the MIT increased from 10{sup 2} to 10{sup 4} with increasing growth temperature. In contrast, the temperature of the MIT does not strongly depend on the growth temperature and is fairly stable at about 345 K. On one hand, the increasing magnitude of the MIT is attributed to the better crystallinity and thusmore » larger grain size in the (010)-VO{sub 2}/(111)-SrTiO{sub 3} epitaxial films at elevated temperature. On the other hand, the strain states do not change in the VO{sub 2} films deposited at various temperatures, resulting in stable V-V chains and V-O bonds in the VO{sub 2} epitaxial films. The accompanied orbital occupancy near the Fermi level is also constant and thus the MIT temperatures of VO{sub 2} films deposited at various temperatures are nearly the same. This work demonstrates that high-quality VO{sub 2} can be grown on perovskite substrates, showing potential for integration into oxide heterostructures and superlattices.« less

  1. Microstructure evolution and electrical characterization of Lanthanum doped Barium Titanate (BaTiO{sub 3}) ceramics

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Billah, Masum, E-mail: masum.buet09@gmail.com; Ahmed, A., E-mail: jhinukbuetmme@gmail.com; Rahman, Md. Miftaur, E-mail: miftaurrahman@mme.buet.ac.bd

    2016-07-12

    In the current work, we investigated the structural and dielectric properties of Lanthanum oxide (La{sub 2}O{sub 3}) doped Barium Titanate (BaTiO{sub 3}) ceramics and established a correlation between them. Solid state sintering method was used to dope BaTiO{sub 3} with 0.3, 0.5 and 0.7 mole% La{sub 2}O{sub 3} under different sintering parameters. The raw materials used were La{sub 2}O{sub 3} nano powder of ~80 nm grain size and 99.995% purity and BaTiO{sub 3} nano powder of 100 nm grain size and 99.99% purity. Grain size distribution and morphology of fracture surface of sintered pellets were examined by Field Emission Scanningmore » Electron Microscope and X-Ray Diffraction analysis was conducted to confirm the formation of desired crystal structure. The research result reveal that grain size and electrical properties of BaTiO{sub 3} ceramic significantly enhanced for small amount of doping (up to 0.5 mole% La{sub 2}O{sub 3}) and then decreased with increasing doping concentration. Desired grain growth (0.80-1.3 µm) and high densification (<90% theoretical density) were found by proper combination of temperature, sintering parameters and doping concentration. We found the resultant stable value of dielectric constant was 10000-12000 at 100-300 Hz in the temperature range of 30°-50° C for 0.5 mole% La{sub 2}O{sub 3} with corresponding shift of curie temperature around 30° C. So overall this research showed that proper La{sup 3+} concentration can control the grain size, increase density, lower curie temperature and hence significantly improve the electrical properties of BaTiO{sub 3} ceramics.« less

  2. Improved Ceramic Anodes for Corrosion Protection.

    DTIC Science & Technology

    1984-11-01

    34 . 4 UNCLASSIFIED SECURITY CLASSIFICATION OF THIS PAGE(Whi Data Entered) BLOCK 20 (Continued) ferrite over niobium over Ni- Cr -AI-Y...plasma-sprayed lithium ferrite on a valve metal substrate. Donor doped and reduced solid sintered titanate compounds yielded electrically conductive...Traditionally. impressed current systems have used tion (CEGS) 2310. antides that are either inexpensive and very large (high silicon, chromium

  3. Strontium

    USGS Publications Warehouse

    Ober, J.A.

    1996-01-01

    Part of the Annual Commodities Review 1995. In 1995, U.S. strontium imports and consumption increased nearly 30 percent due to increased domestic production of color television picture tube glass. However, strontium compound exports fell during 1995. Strontium is also used in the production of permanent ceramic ferrite magnets. Strontium nitrate, strontium chromate, and strontium chloride are also commonly used materials. Although the development of an affordable flatscreen display could eliminate the need for strontium in television production, this technology is not expected to be perfected in the immediate future.

  4. Chromium–niobium co-doped vanadium dioxide films: Large temperature coefficient of resistance and practically no thermal hysteresis of the metal–insulator transition

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Miyazaki, Kenichi, E-mail: kenichi-miyazaki@denso.co.jp, E-mail: k.shibuya@aist.go.jp; University of Tsukuba, Tsukuba 305-8571; Shibuya, Keisuke, E-mail: kenichi-miyazaki@denso.co.jp, E-mail: k.shibuya@aist.go.jp

    We investigated the effects of chromium (Cr) and niobium (Nb) co-doping on the temperature coefficient of resistance (TCR) and the thermal hysteresis of the metal–insulator transition of vanadium dioxide (VO{sub 2}) films. We determined the TCR and thermal-hysteresis-width diagram of the V{sub 1−x−y}Cr{sub x}Nb{sub y}O{sub 2} films by electrical-transport measurements and we found that the doping conditions x ≳ y and x + y ≥ 0.1 are appropriate for simultaneously realizing a large TCR value and an absence of thermal hysteresis in the films. By using these findings, we developed a V{sub 0.90}Cr{sub 0.06}Nb{sub 0.04}O{sub 2} film grown on amore » TiO{sub 2}-buffered SiO{sub 2}/Si substrate that showed practically no thermal hysteresis while retaining a large TCR of 11.9%/K. This study has potential applications in the development of VO{sub 2}-based uncooled bolometers.« less

  5. Barium iodide and strontium iodide crystals andd scintillators implementing the same

    DOEpatents

    Payne, Stephen A; Cherepy, Nerine J; Hull, Giulia E; Drobshoff, Alexander D; Burger, Arnold

    2013-11-12

    In one embodiment, a material comprises a crystal comprising strontium iodide providing at least 50,000 photons per MeV. A scintillator radiation detector according to another embodiment includes a scintillator optic comprising europium-doped strontium iodide providing at least 50,000 photons per MeV. A scintillator radiation detector in yet another embodiment includes a scintillator optic comprising SrI.sub.2 and BaI.sub.2, wherein a ratio of SrI.sub.2 to BaI.sub.2 is in a range of between 0:1 A method for manufacturing a crystal suitable for use in a scintillator includes mixing strontium iodide-containing crystals with a source of Eu.sup.2+, heating the mixture above a melting point of the strontium iodide-containing crystals, and cooling the heated mixture near the seed crystal for growing a crystal. Additional materials, systems, and methods are presented.

  6. Improved dielectric and ferroelectric properties of Mn doped barium zirconium titanate (BZT) ceramics for energy storage applications

    NASA Astrophysics Data System (ADS)

    Sangwan, Kanta Maan; Ahlawat, Neetu; Kundu, R. S.; Rani, Suman; Rani, Sunita; Ahlawat, Navneet; Murugavel, Sevi

    2018-06-01

    Lead free Mn doped barium zirconium titanate ceramic of composition BaZr0.045 (MnxTi1-x)0.955O3 (x = 0.00, 0.01, 0.02) were prepared by solid state reaction method. Tetragonal perovskite structure was confirmed by Rietveld refinement of X-ray diffraction pattern. Analysis of Scanning electron microscope (SEM) micrographs revealed that addition of Mn up to a certain limit accelerates grain growth of BZT ceramic. Static dielectric constant was successfully extended up to high frequencies with an appreciable decrease in dielectric loss about 70% for Mn doped BZT ceramics. The experimental data fitted with Curie Weiss Law and Power Law confirmed first order transition and diffusive behavior of the investigated system. The shifting of Curie temperature (Tc) from 387 K to 402 K indicated tendency for sustained ferroelectricity in doped BZMT ceramics. High value of percentage temperature coefficient of capacitance TCC >10% near Tc was observed for all the compositions and increases with Mn content in pure BZT. At room temperature, BZT modified ceramic corresponding to x = 0.01 composition shows better values of remnant polarization (Pr = 5.718 μC/cm2), saturation polarization (Ps = 14.410 μC/cm2), low coercive field (Ec = 0.612 kV/cm), and highest value of Pr/Ps = 0.396.

  7. Visible-light induced photocatalysis of AgCl@Ag/titanate nanotubes/nitrogen-doped reduced graphite oxide composites

    NASA Astrophysics Data System (ADS)

    Pan, Hongfei; Zhao, Xiaona; Fu, Zhanming; Tu, Wenmao; Fang, Pengfei; Zhang, Haining

    2018-06-01

    High recombination rate of photogenerated electron-hole pairs and relatively narrow photoresponsive range of TiO2-based photocatalysts are the remaining challenges for their practical applications. To address such challenges, photocatalysts consisting of AgCl covered Ag nanoparticles (AgCl@Ag), titanate nanotubes (TiNT), and nitrogen-doped reduced graphite oxide (rGON) are fabricated through alkaline hydrothermal process, followed by deposition and in situ surface-oxidation of silver nanoparticles. In the synthesized photocatalysts, the titanate nanotubes have average length of about 100 nm with inner diameters of about 5 nm and the size of the formed silver nanoparticles is in the range of 50-100 nm. The synthesized photocatalyst degrades almost all the model organic pollutant Rhodamine B in 35 min and remains 90% of photocatalytic efficiency after 5 degradation cycles under visible light irradiation. Since the oxidant FeCl3 applied for oxidation of surface Ag to AgCl is difficult to be completely removed due to the high adsorption capacity of TiNT and rGON, the effect of reside Fe atoms on photocatalytic activity is evaluated and the results reveal that the residue Fe atom only affect the initial photodegradation performance. Nevertheless, the results demonstrate that the formed composite catalyst is a promising candidate for antibiosis and remediation in aquatic environmental contamination.

  8. Low-temperature sintering and electrical properties of strontium- and magnesium-doped lanthanum gallate with V2O5 additive

    NASA Astrophysics Data System (ADS)

    Ha, Sang Bu; Cho, Yoon Ho; Ji, Ho-Il; Lee, Jong-Ho; Kang, Yun Chan; Lee, Jong-Heun

    2011-03-01

    The effects of a V2O5 additive on the low-temperature sintering and ionic conductivity of strontium- and magnesium-doped lanthanum gallate (LSGM: La0.8Sr0.2Ga0.8Mg0.2O2.8) are studied. The LSGM powders prepared by the glycine nitrate method are mixed with 0.5-2 at.% of VO5/2 and then sintered at 1100-1400 °C in air for 4 h. The apparent density and phase purity of the LSGM specimens are increased with increasing sintering temperature and VO5/2 concentration due to the enhanced sintering and mass transfer via the intergranular liquid phase. The 1 at.% VO5/2-doped LSGM specimen sintered at 1300 °C exhibits a high oxide ion conductivity of ∼0.027 S cm-1 at 700 °C over a wide range of oxygen partial pressure (PO2 =10-27 - 1 atm), thereby demonstrating its potential as a useful electrolyte for anode-supported solid oxide fuel cells (SOFCs) without the requirement for any buffer layer between the electrolyte and anode.

  9. Insight into the Selectivity of Isopropanol Conversion at Strontium Titanate (100) Surfaces: A Combination Kinetic and Spectroscopic Study

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Tan, Shuai; Grey, Matthew B.; Kidder, Michelle

    This work aims to better understand the role of interfacial molecular structure that governs selectivity and activity in heterogeneous catalytic reactions. To address this, a comprehensive study of isopropanol conversion over an archetypal perovskite material, strontium titanate (SrTiO 3 or STO), was performed with an array of techniques sensitive to orthogonal aspects of the ensuing chemistry. Cubic-shape STO nanoparticles with only the (100) facet exposed were synthesized and used to study the ensemble kinetic conversion of isopropanol over the surfaces, which showed a remarkable selectivity to form acetone, with minor propylene products appearing at elevated temperatures. These results in combinationmore » with inelastic neutron scattering measurements provide not only new insight into the selectivity and overall activity of the catalysts but also low frequency vibrational signatures of the adsorbed and reacted species. To compliment these measurements, pristine thin films of STO (100) were synthesized and used in combination with vibrational sum frequency generation spectroscopy to extract the absolute molecular orientation of the adsorbed molecules at the interface. It was found that the isopropanol assumes an orientation where the -CH group points towards the STO surface; this pre-reaction geometry offers an obvious pathway to produce acetone by abstracting the alpha-proton and, thus, provides a mechanistic explanation of selectivity at STO (100) surfaces. This new insight opens up pathways to explore and modify surfaces to tune the activity/selectivity though a molecular level understanding of the reactions at the surface.« less

  10. Insight into the Selectivity of Isopropanol Conversion at Strontium Titanate (100) Surfaces: A Combination Kinetic and Spectroscopic Study

    DOE PAGES

    Tan, Shuai; Grey, Matthew B.; Kidder, Michelle; ...

    2017-10-13

    This work aims to better understand the role of interfacial molecular structure that governs selectivity and activity in heterogeneous catalytic reactions. To address this, a comprehensive study of isopropanol conversion over an archetypal perovskite material, strontium titanate (SrTiO 3 or STO), was performed with an array of techniques sensitive to orthogonal aspects of the ensuing chemistry. Cubic-shape STO nanoparticles with only the (100) facet exposed were synthesized and used to study the ensemble kinetic conversion of isopropanol over the surfaces, which showed a remarkable selectivity to form acetone, with minor propylene products appearing at elevated temperatures. These results in combinationmore » with inelastic neutron scattering measurements provide not only new insight into the selectivity and overall activity of the catalysts but also low frequency vibrational signatures of the adsorbed and reacted species. To compliment these measurements, pristine thin films of STO (100) were synthesized and used in combination with vibrational sum frequency generation spectroscopy to extract the absolute molecular orientation of the adsorbed molecules at the interface. It was found that the isopropanol assumes an orientation where the -CH group points towards the STO surface; this pre-reaction geometry offers an obvious pathway to produce acetone by abstracting the alpha-proton and, thus, provides a mechanistic explanation of selectivity at STO (100) surfaces. This new insight opens up pathways to explore and modify surfaces to tune the activity/selectivity though a molecular level understanding of the reactions at the surface.« less

  11. Strontium

    USGS Publications Warehouse

    Ober, J.A.

    1994-01-01

    Production figures are not published for stronium carbonate because there is only one company producing strontium carbonate domestically. Strontium carbonate is produced in the U.S. from imported celestite. Consumption can be estimated from trade data published by the U.S. Bureau of the Census. Consumption is estimated at approximately 24.5 kt of strontium. The largest end-use of strontium carbonate is in the production of faceplate glass for color television picturetubes. Other applications and markets for strontium are discussed.

  12. Influence of strontium on the synthesis and surface properties of biphasic calcium phosphate (BCP) bioceramics.

    PubMed

    Kanchana, Ponnusamy; Sekar, Chinnathambi

    2010-01-01

    Biphasic calcium phosphate (BCP) ceramics are suitable for synthetic bone applications. The strontium substituted calcium phosphate ceramics have potential for use in orthopedic surgeries. Aim of the present work is to introduce strontium into BCP (composed of hydroxyapatite and tricalcium phosphate) ceramics and to study their bioactivity and mechanical properties. BCP ceramics have been synthesized at room temperature under the physiological pH of 7.4 by gel method in the presence of strontium (5, 10 M %). The appropriate choice of anhydrous CaCl₂ as precursor solution has promoted the formation of BCP instead of pure HA for CaCl₂.2H₂O. Powder X-ray diffraction analysis confirmed the formation of BCP with different HA and ß -TCP ratios depending upon the Sr content. The presence of Sr has reduced the nucleation and growth rate of BCP when compared to pure system. The SEM micrographs showed that the microstructural morphology of BCP changes from fibrous to platelet. Nanoindentation studies indicate a significant decrease in the hardness and elastic modulus values of BCP ceramics due to Sr doping. In vitro bioactivity study has revealed the formation of apatite layer on the Sr doped BCP samples and the doping enhanced its bioactivity.

  13. Crystal growth and characterization of europium doped lithium strontium iodide scintillator as an ionizing radiation detector

    NASA Astrophysics Data System (ADS)

    Uba, Samuel

    High performance detectors used in the detection of ionizing radiation is critical to nuclear nonproliferation applications and other radiation detectors applications. In this research we grew and tested Europium doped Lithium Strontium Iodide compound. A mixture of lithium iodide, strontium iodide and europium iodide was used as the starting materials for this research. Congruent melting and freezing temperature of the synthesized compound was determined by differential scanning calorimetry (DSC) using a Setaram Labsys Evo DSC-DTA instrument. The melting temperatures were recorded at 390.35°C, 407.59°C and freezing temperature was recorded at 322.84°C from a graph of heat flow plotted against temperature. The synthesized material was used as the charge for the vertical Bridgeman growth, and a 6.5 cm and 7.7cm length boule were grown in a multi-zone transparent Mullen furnace. A scintillating detector of thickness 2.53mm was fabricated by mechanical lapping in mineral oil, and scintillating response and timing were obtained to a cesium source using CS-137 isotope. An energy resolution (FWHM over peak position) of 12.1% was observed for the 662keV full absorption peak. Optical absorption in the UV-Vis wavelength range was recorded for the grown crystal using a U-2900 UV/VIS Spectrophotometer. Absorption peaks were recorded at 194nm, 273nm, and 344nm from the absorbance spectrum, various optical parameters such as absorption coefficient, extinction coefficient, refractive index, and optical loss were derived. The optical band gap energy was calculated using Tauc relation expression at 1.79eV.

  14. Buffer layer for thin film structures

    DOEpatents

    Foltyn, Stephen R.; Jia, Quanxi; Arendt, Paul N.; Wang, Haiyan

    2006-10-31

    A composite structure including a base substrate and a layer of a mixture of strontium titanate and strontium ruthenate is provided. A superconducting article can include a composite structure including an outermost layer of magnesium oxide, a buffer layer of strontium titanate or a mixture of strontium titanate and strontium ruthenate and a top-layer of a superconducting material such as YBCO upon the buffer layer.

  15. Buffer layer for thin film structures

    DOEpatents

    Foltyn, Stephen R.; Jia, Quanxi; Arendt, Paul N.; Wang, Haiyan

    2010-06-15

    A composite structure including a base substrate and a layer of a mixture of strontium titanate and strontium ruthenate is provided. A superconducting article can include a composite structure including an outermost layer of magnesium oxide, a buffer layer of strontium titanate or a mixture of strontium titanate and strontium ruthenate and a top-layer of a superconducting material such as YBCO upon the buffer layer.

  16. Strontium

    USGS Publications Warehouse

    Ober, J.A.

    2000-01-01

    Mexico is the leading producer of celestite, the most common strontium ore. Chemical Products is the only major US maker of strontium compounds. It produces all of its strontium carbonate from imported Mexican celestite. Mexico is also a large producer of strontium carbonate, as are China, Germany, Japan and the Republic of Korea. There has been no celestite production in the United States since 1959.

  17. METHOD OF PRODUCING NIOBIUM METAL

    DOEpatents

    Wilhelm, H.A.; Stevens, E.R.

    1960-05-24

    A process is given for preparing ductile niobium metal by the reduction of niobium pentoxide with carbon. The invention resides in the addition, to the reaction mass, of from 0.05 to 0.4 atom of titanium (in the form of metallic titanium, titanium carbide, and/or titanium oxide) per one mole of niobium pentoxide. The mixture is heated under subatmospheric pressure to above 1300 deg C but below the melting point of niobium, and the carbon- and oxygen-free niobium sponge obtained is cooled under reduced pressure.

  18. Synthesis and structural properties of (Y, Sr)(Ti, Fe, Nb)O3-δ perovskite nanoparticles fabricated by modified polymer precursor method

    NASA Astrophysics Data System (ADS)

    Miruszewski, T.; Gdaniec, P.; Karczewski, J.; Bochentyn, B.; Szaniawska, K.; Kupracz, P.; Prześniak-Welenc, M.; Kusz, B.

    2016-09-01

    The yttrium, iron and niobium doped-SrTiO3 powders have been successfully fabricated by a modified low-temperature synthesis method from a polymer complex. The usage of strontium hydroxide precursor instead of conventional strontium nitrate or strontium carbonate provides to the possibility of significant decrease of annealing temperature. It allows to prepare a material with sphere-shape grains of nanometric size (15-70 nm). The results of thermal analysis indicate that the crystallization of precursor takes place at different stages. The product after heat treatment at 600 °C for 3 h in air was also characterized by X-Ray diffraction method (XRD) and Fourier transform - infrared spectroscopy (FT-IR). After the crystallization and the impurity removal process, a single-phase material was obtained in case of all analyzed samples. The morphology of obtained nano-powders was also studied by a scanning electron microscopy (SEM). It can be concluded, that this method allows obtaining a perovskite phase of a metal doped SrTiO3 with nanometric particles.

  19. Niobium and tantalum

    USGS Publications Warehouse

    Schulz, Klaus J.; Piatak, Nadine M.; Papp, John F.; Schulz, Klaus J.; DeYoung,, John H.; Seal, Robert R.; Bradley, Dwight C.

    2017-12-19

    Niobium and tantalum are transition metals that are almost always found together in nature because they have very similar physical and chemical properties. Their properties of hardness, conductivity, and resistance to corrosion largely determine their primary uses today. The leading use of niobium (about 75 percent) is in the production of high-strength steel alloys used in pipelines, transportation infrastructure, and structural applications. Electronic capacitors are the leading use of tantalum for high-end applications, including cell phones, computer hard drives, and such implantable medical devices as pacemakers. Niobium and tantalum are considered critical and strategic metals based on the potential risks to their supply (because current production is restricted to only a few countries) and the significant effects that a restriction in supply would have on the defense, energy, high-tech industrial, and medical sectors.The average abundance of niobium and tantalum in bulk continental crust is relatively low—8.0 parts per million (ppm) niobium and 0.7 ppm tantalum. Their chemical characteristics, such as small ionic size and high electronic field strength, significantly reduce the potential for these elements to substitute for more common elements in rock-forming minerals and make niobium and tantalum essentially immobile in most aqueous solutions. Niobium and tantalum do not occur naturally as pure metals but are concentrated in a variety of relatively rare oxide and hydroxide minerals, as well as in a few rare silicate minerals. Niobium is primarily derived from the complex oxide minerals of the pyrochlore group ((Na,Ca,Ce)2(Nb,Ti,Ta)2(O,OH,F)7), which are found in some alkaline granite-syenite complexes (that is, igneous rocks containing sodium- or potassium-rich minerals and little or no quartz) and carbonatites (that is, igneous rocks that are more than 50 percent composed of primary carbonate minerals, by volume). Tantalum is derived mostly from the

  20. Judd-Ofelt analysis and spectral properties of Dy3+ ions doped niobium containing tellurium calcium zinc borate glasses

    NASA Astrophysics Data System (ADS)

    Ravi, O.; Reddy, C. Madhukar; Reddy, B. Sudhakar; Deva Prasad Raju, B.

    2014-02-01

    Niobium containing tellurium calcium zinc borate (TCZNB) glasses doped with different concentrations of Dy3+ ions were prepared by the melt quenching method and their optical properties have been studied. The Judd-Ofelt (J-O) intensity parameters Ωt (t=2, 4 and 6) were calculated using the least square fit method. Based on the magnitude of Ω2 parameter the hypersensitivity of 6H15/2→6F11/2 has also been discussed. From the evaluated J-O intensity parameters as well as from the emission and lifetime measurements, radiative transition properties such as radiative transition probability rates and branching ratios were calculated for 4F9/2 excited level. It is found that for Dy3+ ion, the transition 4F9/2→6H13/2 shows highest emission cross-section at 1.0 mol% TCZNB glass matrix. From the visible luminescence spectra, yellow to blue (Y/B) intensity ratios and chromaticity color coordinates were also estimated. The TCZNB glasses exhibit good luminescence properties and are suitable for generation of white light.

  1. Ho3+-doped strontium-aluminium-bismuth-borate glasses for green light emission.

    PubMed

    Rajesh, D; Dhamodhara Naidu, M; Ratnakaram, Y C; Balakrishna, A

    2014-11-01

    Strontium-aluminium-bismuth-borate glasses (SAlBiB) doped with different concentrations of Ho(3+) were prepared using conventional melt quenching technique and their structural and optical properties investigated. X-ray diffraction and scanning electron microscopy analysis were used to study the structural properties. Optical properties were studied by measuring the optical absorption and visible luminescence spectra. The Judd-Ofelt (J-O) theory was applied to evaluate J-O intensity parameters, Ω(λ) (λ = 2, 4 and 6). Using J-O intensity parameters, radiative properties such as spontaneous transition probabilities (A(R)), branching ratios (β(R)) and radiative lifetimes (τ(R)) were determined. From the emission spectra, a strong green emission nearly at 549 nm corresponding to the transition, (5)S2 ((5)F4)→(5)I(8) was observed. Emission peak positions (λ(P)), effective bandwidths (Δλ(eff)) and stimulated emission cross-sections (σ(p)) were calculated for the observed emission transitions, (5)F3 →(5)I(8), (5)S2((5)F4)→(5)I(8) and (5)F5 →(5)I(8) of Ho(3+) in all the glass matrices. Chromaticity color coordinates were calculated using the emission spectra. The experimental results suggest that SAlBiB glass matrix with 1.5 mol% of Ho(3+) has better emission properties. Copyright © 2014 John Wiley & Sons, Ltd.

  2. Recovery of strontium activity from a strontium-82/rubidium-82 generator

    DOEpatents

    Taylor, Wayne A.; Phillips, Dennis R.; Sosnowski, Kenneth M.

    1999-10-12

    Strontium-82 is recovered from spent strontium-82/rubidium-82 generators to provide a source of strontium-82 for additional strontium-82/rubidium-82 generators. The process involves stripping of the strontium-82 from used strontium-82/rubidium-82 generators followed by purification of the strontium-82 material to remove additional metal contaminants to desired levels.

  3. Simultaneous removal of Cr(VI) and 4-chlorophenol through photocatalysis by a novel anatase/titanate nanosheet composite: Synergetic promotion effect and autosynchronous doping.

    PubMed

    Liu, Wen; Sun, Weiling; Borthwick, Alistair G L; Wang, Ting; Li, Fan; Guan, Yidong

    2016-11-05

    Clean-up of wastewaters with coexisting heavy metals and organic contaminants is a huge issue worldwide. In this study, a novel anatase/titanate nanosheet composite material (labeled as TNS) synthesized through a one-step hydrothermal reaction was demonstrated to achieve the goal of simultaneous removal of Cr(VI) and 4-cholophenol (4-CP) from water. TEM and XRD analyses indicated the TNS was a nano-composite of anatase and titanate, with anatase acting as the primary photocatalysis center and titanate as the main adsorption site. Enhanced photocatalytic removal of co-existent Cr(VI) and 4-CP was observed in binary systems, with apparent rate constants (k1) for photocatalytic reactions of Cr(VI) and 4-CP about 3.1 and 2.6 times of that for single systems. In addition, over 99% of Cr(VI) and 4-CP was removed within 120min through photocatalysis by TNS at pH 7 in the binary system. Mechanisms for enhanced photocatalytic efficiency in the binary system are identified as: (1) a synergetic effect on the photo-reduction of Cr(VI) and photo-oxidation of 4-CP due to efficient separation of electron-hole pairs, and (2) autosynchronous doping because of reduced Cr(III) adsorption onto TNS. Furthermore, TNS could be efficiently reused after a simple acid-base treatment. Copyright © 2016 Elsevier B.V. All rights reserved.

  4. Synthesis of praseodymium-ion-doped perovskite nanophosphor in supercritical water

    NASA Astrophysics Data System (ADS)

    Hakuta, Yukiya; Sue, Kiwamu; Takashima, Hiroshi

    2018-05-01

    We report the synthesis of praseodymium-doped calcium strontium titanate nanoparticles, (Ca0.6Sr0.4)0.997Pr0.002TiO3 (PCSTO), using hydrothermal synthesis under supercritical water conditions and the production of red luminescence. Starting solutions were prepared by dissolving calcium nitrate, strontium nitrate, titanium hydroxide sols, and praseodymium nitrate in distilled water. We investigated the effect of the reaction temperature, concentration, and pH of the starting solution on the luminescence properties. Synthesis was conducted at temperatures of 200 °C–400 °C, a reaction pressure of 30 MPa, and for reaction times of 4–20 s. The Pr concentration was set to 0.2 mol% relative to the (Ca0.6Sr0.4) ions. We also investigated the effect of high temperature annealing on the luminescence properties of the PCSTO nanoparticles. Particle characteristics were evaluated using x-ray diffraction, a scanning transmission electron microscope (STEM) equipped with an energy-dispersive x-ray spectrometer, and a fluorometer. Single-phase perovskite particles were obtained at hydrothermal reaction temperatures of over 300 °C even for a reaction time of several seconds. STEM images showed that the particles had cubic-like shapes with diameters of 8–13 nm and that they were chemically homogeneous. The PCSTO nanoparticles exhibited sharp red luminescence at 612 nm corresponding to the f–f transition of Pr3+ ions. Moreover, annealing at 1000 °C led to particle growth, achieving diameters of 40 nm and an increase in the quantum efficiency to around 12.0%.

  5. Strontium

    USGS Publications Warehouse

    Ober, J.A.

    2006-01-01

    China, Mexico, Spain and Turkey are the world's leading producers of celestite (strontium sulphate). These countries accounted for 98% of the total world production in 2005. For the same period, US apparent consumption of strontium decreased to 12.3 kt. Imports were 21.2 kt, of which 84% came from Mexico. Imports of celestite and strontium carbonate decreased 71% and 24% respectively.

  6. Strontium

    USGS Publications Warehouse

    Angulo, M.A.

    2010-01-01

    In 2009, U.S. apparent consumption of strontium (contained in celestite and manufactured strontium compounds) increased to 16 kt (17,600 st) from 10.6 kt (11,700 st) in 2008, an increase of 52 percent. This increase was attributed primarily to an increase in imported celestite. Gross weight of imports totaled 25.3 kt (27,900 st), of which 91 percent came from Mexico. Imports in 2009 were 18 percent more than in 2008. Exports of strontium compounds in 2009 decreased 15 percent to 9.3 kt (10,250 st) from 10.9 kt (12,000 st) in 2008. In 2009, the U.S. Customs value of imported strontium carbonate was 65 cents/kg (29 cents/lb); for strontium nitrate, the unit value was $ 1/kg (45 cents/lb). The unit value of imported celestite, all of which was from Mexico, was about $47/t ($43/st).

  7. Advancement in the Understanding of the Field and Frequency Dependent Microwave Surface Resistance of Niobium

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Martinello, M.; Aderhold, S.; Chandrasekaran, S. K.

    The radio-frequency surface resistance of niobium resonators is incredibly reduced when nitrogen impurities are dissolved as interstitial in the material, conferring ultra-high Q-factors at medium values of accelerating field. This effect has been observed in both high and low temperature nitrogen treatments. As a matter of fact, the peculiar anti Q-slope observed in nitrogen doped cavities, i.e. the decreasing of the Q-factor with the increasing of the radio-frequency field, come from the decreasing of the BCS surface resistance component as a function of the field. Such peculiar behavior has been considered consequence of the interstitial nitrogen present in the niobiummore » lattice after the doping treatment. The study here presented show the field dependence of the BCS surface resistance of cavities with different resonant frequencies, such as: 650 MHz, 1.3 GHz, 2.6 GHz and 3.9 GHz, and processed with different state-of-the-art surface treatments. These findings show for the first time that the anti Q-slope might be seen at high frequency even for clean Niobium cavities, revealing useful suggestion on the physics underneath the anti Q-slope effect.« less

  8. Proton in SRF Niobium

    NASA Astrophysics Data System (ADS)

    Wallace, John Paul

    2011-03-01

    Hydrogen is a difficult impurity to physically deal with in superconducting radio frequency (SRF) niobium, therefore, its properties in the metals should be well understood to allow the metal's superconducting properties to be optimized for minimum loss in the construction of resonant accelerator cavities. It is known that hydrogen is a paramagnetic impurity in niobium from NMR studies. This paramagnetism and its effect on superconducting properties are important to understand. To that end analytical induction measurements aimed at isolating the magnetic properties of hydrogen in SRF niobium are introduced along with optical reflection spectroscopy which is also sensitive to the presence of hydrogen. From the variety, magnitude and rapid kinetics found in the optical and magnetic properties of niobium contaminated with hydrogen forced a search for an atomic model. This yielded quantum mechanical description that correctly generates the activation energy for diffusion of the proton and its isotopes not only in niobium but the remaining metals for which data is available. This interpretation provides a frame work for understanding the individual and collective behavior of protons in metals.

  9. Magnetoelectric coupling of multiferroic chromium doped barium titanate thin film probed by magneto-impedance spectroscopy

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Shah, Jyoti, E-mail: shah.jyoti1@gmail.com; Kotnala, Ravinder K., E-mail: rkkotnala@nplindia.org, E-mail: rkkotnala@gmail.com

    2014-04-07

    Thin film of BaTiO{sub 3} doped with 0.1 at. % Cr (Cr:BTO) has been prepared by pulsed laser deposition technique. Film was deposited on Pt/SrTiO{sub 3} substrate at 500 °C in 50 mTorr Oxygen gas pressure using KrF (298 nm) laser. Polycrystalline growth of single phase Cr:BTO thin film has been confirmed by grazing angle X-ray diffraction. Cr:BTO film exhibited remnant polarization 6.4 μC/cm{sup 2} and 0.79 MV/cm coercivity. Magnetization measurement of Cr:BTO film showed magnetic moment 12 emu/cc. Formation of weakly magnetic domains has been captured by magnetic force microscopy. Theoretical impedance equation fitted to experimental data in Cole-Cole plot for thin film inmore » presence of transverse magnetic field resolved the increase in grain capacitance from 4.58 × 10{sup −12} to 5.4 × 10{sup −11} F. Film exhibited high value 137 mV/cm-Oe magneto-electric (ME) coupling coefficient at room temperature. The high value of ME coupling obtained can reduce the typical processing steps involved in multilayer deposition to obtain multiferrocity in thin film. Barium titanate being best ferroelectric material has been tailored to be multiferroic by non ferromagnetic element, Cr, doping in thin film form opens an avenue for more stable and reliable spintronic material for low power magnetoelectric random excess memory applications.« less

  10. Method of surface preparation of niobium

    DOEpatents

    Srinivasan-Rao, Triveni; Schill, John F.

    2003-01-01

    The present invention is for a method of preparing a surface of niobium. The preparation method includes polishing, cleaning, baking and irradiating the niobium surface whereby the resulting niobium surface has a high quantum efficiency.

  11. Processing and optical characterization of lead calcium titanate borosilicate glass doped with germanium

    NASA Astrophysics Data System (ADS)

    Gautam, C. R.; Das, Sangeeta; Gautam, S. S.; Madheshiya, Abhishek; Singh, Anod Kumar

    2018-04-01

    In this study, various compositions of lead calcium titanate borosilicate glass doped with a fixed amount of germanium were synthesized using the rapid melt quench technique. The amorphous nature of the synthesized glass was confirmed by X-ray diffraction and scanning electron microscopy analyses. The structural and optical properties were deduced using Raman, Fourier transform infrared (FTIR), and ultraviolet-visible (UV-Vis) spectroscopy. FTIR spectroscopy confirmed the presence of borate groups in triangular and tetrahedral coordination. Infrared and Raman analyses detected the vibrational bonds of Gesbnd Osbnd Ge, Bsbnd Osbnd Ge, Sisbnd Osbnd Ge, Sisbnd Osbnd Si, and Pbsbnd Osbnd Ge. The energy band gaps were evaluated for the prepared glass samples based on Tauc plots of the UV-Vis spectra. The calculated values of the optical band gap decreased from 2.91 to 2.85 eV as the PbO content increased from x = 0.0 to x = 0.7. Furthermore, the Urbach energy was studied based on the UV-Vis results to confirm the disordered structure of the glass. The calculated densities of the glass samples (1.5835 g/cm3 to 3.9184 g/cm3) increased as the concentration of PbO increased, whereas they decreased with the molar volume.

  12. Niobium powder synthesized by calciothermic reduction of niobium hydroxide for use in capacitors

    NASA Astrophysics Data System (ADS)

    Baba, Masahiko; Kikuchi, Tatsuya; Suzuki, Ryosuke O.

    2015-03-01

    Metallic niobium powder was produced for applications in electric capacitors via calciothermic reduction of niobium hydroxide in molten CaCl2. Sub-micrometer spherical metallic particles with coral-like morphologies reflected the particle size of the starting oxide powder. A fine powder was obtained from the mixtures of niobium hydroxide and CaO or Ca(OH)2, respectively. Sintered pellets of the metallic powder showed a higher capacitance (CV) than those of the simply reduced powder without pre-treatment, because the shrinkage during sintering was smaller. The CV was as large as that of commercially sintered pellets for tantalum capacitors. Therefore, this niobium powder would act as a higher-voltage capacitor by applying chemical anodic treatment at higher voltages, and lower oxygen content in the reduced power could realize a lower leak current.

  13. An experimental analysis of strontium titanate ceramic substrates polished by magnetorheological finishing with dynamic magnetic fields formed by rotating magnetic poles

    NASA Astrophysics Data System (ADS)

    Pan, Jisheng; Yu, Peng; Yan, Qiusheng; Li, Weihua

    2017-05-01

    Strontium titanate (SrTiO3, STO) ceramic substrate is an incipient ferroelectric material with a perovskite structure and which has a wide range of applications in the fields of microwave, millimetre wave, and optic fibre. This paper reports on a system of experiments carried out on STO substrates using a new magnetorheological (MR) finishing process where dynamic magnetic fields are formed by magnetic poles rotate. The results show that a circular ring shaped polishing belt with a stability evaluation zone appears on the surface after being polished by MR finishing with a single-point dynamic magnetic field. The dynamic magnetic fields are stronger when the revolutions of magnetic pole increase and eccentricity of pole enlarge, with the surface finish is smoother and more material is removed. The optimum machining times, machining gap, oscillation distance, eccentricity of pole, revolutions of the workpiece and magnetic pole are 60 min, 0.8 mm, 0 mm, 7 mm, and 350 r min-1 and 90 r min-1, respectively, and the best MR fluid consists of 6 wt% of diamond abrasives in W1 particle size and 18 wt% of carbonyl iron powder in W3.5 particle size. A surface roughness of Ra and a material removal rate of 8 nm and 0.154 μm min-1 can be obtained in these optimum process conditions. Finally, the polishing mechanism for dynamic magnetic fields and the mechanism for removing material from STO ceramic substrates are discussed in detail.

  14. Niobium and tantalum: indispensable twins

    USGS Publications Warehouse

    Schulz, Klaus; Papp, John

    2014-01-01

    Niobium and tantalum are transition metals almost always paired together in nature. These “twins” are difficult to separate because of their shared physical and chemical properties. In 1801, English chemist Charles Hatchett uncovered an unknown element in a mineral sample of columbite; John Winthrop found the sample in a Massachusetts mine and sent it to the British Museum in London in 1734. The name columbium, which Hatchet named the new element, came from the poetic name for North America—Columbia—and was used interchangeably for niobium until 1949, when the name niobium became official. Swedish scientist Anders Ekberg discovered tantalum in 1802, but it was confused with niobium, because of their twinned properties, until 1864, when it was recognized as a separate element. Niobium is a lustrous, gray, ductile metal with a high melting point, relatively low density, and superconductor properties. Tantalum is a dark blue-gray, dense, ductile, very hard, and easily fabricated metal. It is highly conductive to heat and electricity and renowned for its resistance to acidic corrosion. These special properties determine their primary uses and make niobium and tantalum indispensable.

  15. METHOD FOR COATING GRAPHITE WITH NIOBIUM CARBIDE

    DOEpatents

    Kane, J.S.; Carpenter, J.H.; Krikorian, O.H.

    1962-01-16

    A method is given for coating graphite with a hard, tenacious layer of niobium carbide up to 30 mils or more thick. The method makes use of the discovery that niobium metal, if degassed and heated rapidly below the carburization temperature in contact with graphite, spreads, wets, and penetrates the graphite without carburization. The method includes the obvious steps of physically contacting niobium powders or other physical forms of niobium with graphite, degassing the assembly below the niobium melting point, e.g., 1400 deg C, heating to about 2200 to 2400 deg C within about 15 minutes while outgassing at a high volume throughput, and thereafter carburizing the niobium. (AEC)

  16. Built-in Electric Field Induced Mechanical Property Change at the Lanthanum Nickelate/Nb-doped Strontium Titanate Interfaces

    DOE PAGES

    Chien, TeYu; Liu, Jian; Yost, Andrew J.; ...

    2016-01-08

    The interactions between electric field and the mechanical properties of materials are important for the applications of microelectromechanical and nanoelectromechanical systems, but relatively unexplored for nanoscale materials. Here, we observe an apparent correlation between the change of the fractured topography of Nb-doped SrTiO 3 (Nb:STO) within the presence of a built-in electric field resulting from the Schottky contact at the interface of a metallic LaNiO 3 thin film utilizing cross-sectional scanning tunneling microscopy and spectroscopy. The change of the inter-atomic bond length mechanism is argued to be the most plausible origin. This picture is supported by the strong-electric-field-dependent permittivity inmore » STO and the existence of the dielectric dead layer at the interfaces of STO with metallic films. Finally, these results provided direct evidence and a possible mechanism for the interplay between the electric field and the mechanical properties on the nanoscale for perovskite materials.« less

  17. Preparation and Characterization of Niobium Doped Lead-Telluride Glass Ceramics

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Sathish, M.; Eraiah, B.; Anavekar, R. V.

    2011-07-15

    Niobium-lead-telluride glass ceramics of composition xNb{sub 2}O{sub 5}-(20-x) pbO-80TeO{sub 2}(where x = 0.1 mol% to 0.5 mol%) were prepared by using conventional melt quenching method. The prepared glass samples were initially amorphous in nature after annealed at 400 deg. c all samples were crystallized. This was confined by X-ray diffraction and scanning electron microscopy. The particle size of these glass ceramics have been calculated by using Debye-Scherer formula and the particle size is in the order of 15 nm to 60 nm. The scanning electron microscopy (SEM) photograph shows the presence of needle-like crystals in these samples.

  18. Large grain cavities from pure niobium ingot

    DOEpatents

    Myneni, Ganapati Rao [Yorktown, VA; Kneisel, Peter [Williamsburg, VA; Cameiro, Tadeu [McMurray, PA

    2012-03-06

    Niobium cavities are fabricated by the drawing and ironing of as cast niobium ingot slices rather than from cold rolled niobium sheet. This method results in the production of niobium cavities having a minimum of grain boundaries at a significantly reduced cost as compared to the production of such structures from cold rolled sheet.

  19. Hybrid Molecular Beam Epitaxy for High Quality Strontium Titanate

    NASA Astrophysics Data System (ADS)

    Jalan, Bharat

    2011-12-01

    Advancement in thin film growth techniques drives new physics and technologies. Thin film growth approaches and characterization techniques have become more crucial than ever to design and evaluate many emerging materials systems, such as complex oxides. Complex oxides with the perovskite and related structures are fundamentally different from conventional semiconductors and exhibit much richer phenomena as diverse as ferroelectricity, superconductivity, and strongly-correlated Mott-Hubbard-type insulator characteristics. The structural quality of oxide films grown by molecular beam epitaxy (MBE) now matches that of epitaxial semiconductors. Stoichiometry control, however, remains a major challenge. The presence of large (˜tens of ppm) amounts of point defects and impurities, which are commonly present in thin films, has often made the realization and interpretation of intrinsic phenomena difficult. In this dissertation we first describe our work in the development of a hybrid MBE approach for the growth of high quality insulating SrTiO 3 films. The approach uses a combination of solid and metal-organic sources to supply the metals. Films grow in layer-by-layer and step-flow growth modes, with atomically smooth surfaces and an excellent structural quality that is only limited by those of the substrates. A major as- pect of this MBE technique is that it provides a route to stoichiometric SrTiO3. This is achieved by growing films within a "MBE growth window", in which the stoichiome- try is self-regulating, independent of the precise metal flux ratios. Despite the use of a chemical precursor that supply Ti, the carbon incorporation in the films remains below or in the low ppm range. This was achieved by growing films at relatively high temper- atures. We will discuss the transport properties of MBE grown SrTiO3 film. We show that excellent stoichiometry control and low intrinsic defect concentrations, afforded by MBE, allow for the high electron mobility in n-doped

  20. Orientation dependent ferroelectric properties in samarium doped bismuth titanate thin films grown by the pulsed-laser-ablation method

    NASA Astrophysics Data System (ADS)

    Cheng, Zhenxiang; Kannan, Chinna Venkatasamy; Ozawa, Kiyoshi; Kimura, Hideo; Wang, Xiaolin

    2006-07-01

    Samarium doped bismuth titanate thin films with the composition of Bi3.25Sm0.75Ti3O12 and with strong preferred orientations along the c axis and the (117) direction were fabricated on Pt /TiO2/SiO2/Si substrate by pulsed laser ablation. Measurements on Pt /BSmT/Pt capacitors showed that the c-axis oriented film had a small remanent polarization (2Pr) of 5μC/cm2, while the highly (117) oriented film showed a 2Pr value of 54μC/cm2 at an electrical field of 268kV/cm and a coercive field Ec of 89kV/cm. This is different from the sol-gel derived c-axis oriented Bi3.15Sm0.85Ti3O12 film showing a 2Pr value of 49μC/cm2.

  1. Vapor deposition of hardened niobium

    DOEpatents

    Blocher, Jr., John M.; Veigel, Neil D.; Landrigan, Richard B.

    1983-04-19

    A method of coating ceramic nuclear fuel particles containing a major amount of an actinide ceramic in which the particles are placed in a fluidized bed maintained at ca. 800.degree. to ca. 900.degree. C., and niobium pentachloride vapor and carbon tetrachloride vapor are led into the bed, whereby niobium metal is deposited on the particles and carbon is deposited interstitially within the niobium. Coating apparatus used in the method is also disclosed.

  2. Process for alloying uranium and niobium

    DOEpatents

    Holcombe, Cressie E.; Northcutt, Jr., Walter G.; Masters, David R.; Chapman, Lloyd R.

    1991-01-01

    Alloys such as U-6Nb are prepared by forming a stacked sandwich array of uraniun sheets and niobium powder disposed in layers between the sheets, heating the array in a vacuum induction melting furnace to a temperature such as to melt the uranium, holding the resulting mixture at a temperature above the melting point of uranium until the niobium dissolves in the uranium, and casting the uranium-niobium solution. Compositional uniformity in the alloy product is enabled by use of the sandwich structure of uranium sheets and niobium powder.

  3. Barium iodide and strontium iodide crystals and scintillators implementing the same

    DOEpatents

    Payne, Stephen A.; Cherepy, Nerine J.; Hull, Giulia E.; Drobshoff, Alexander D.; Burger, Arnold

    2016-11-29

    In one embodiment, a material comprises a crystal comprising strontium iodide providing at least 50,000 photons per MeV, where the strontium iodide material is characterized by a volume not less than 1 cm.sup.3. In another embodiment, a scintillator optic includes europium-doped strontium iodide providing at least 50,000 photons per MeV, where the europium in the crystal is primarily Eu.sup.2+, and the europium is present in an amount greater than about 1.6%. A scintillator radiation detector in yet another embodiment includes a scintillator optic comprising SrI.sub.2 and BaI.sub.2, where a ratio of SrI.sub.2 to BaI.sub.2 is in a range of between 0:1 and 1.0, the scintillator optic is a crystal that provides at least 50,000 scintillation photons per MeV and energy resolution of less than about 5% at 662 keV, and the crystal has a volume of 1 cm.sup.3 or more; the scintillator optic contains more than about 2% europium.

  4. [Strontium and calcium metabolism. Interaction of strontium and vitamin D].

    PubMed

    Rousselet, F; El Solh, N; Maurat, J P; Gruson, M; Girard, M L

    1975-01-01

    Oral administration of strontium to calcium wellfed rats blocks the intestinal absorption of calcium. When high doses of vitamine D are given over long period, the inhibition of calcium intestinal absorption disapears. Under these conditions the absorption of strontium is increased. It is suggested that there is only one absorption mechanism for these two cations. An overdose of the vitamine D increases the renal elimination of strontium but under these conditions the plasma concentration of the strontium is unchanged. Vitamine D brings about the some action on the bone fixation of the strontium as it does on the bone fixation of calcium. The bone fixation is increased with low dosages. The bone fixation is decreased with high dosages.

  5. Method of nitriding niobium to form a superconducting surface

    DOEpatents

    Kelley, Michael J.; Klopf, John Michael; Singaravelu, Senthilaraja

    2014-08-19

    A method of forming a delta niobium nitride .delta.-NbN layer on the surface of a niobium object including cleaning the surface of the niobium object; providing a treatment chamber; placing the niobium object in the treatment chamber; evacuating the chamber; passing pure nitrogen into the treatment chamber; focusing a laser spot on the niobium object; delivering laser fluences at the laser spot until the surface of the niobium object reaches above its boiling temperature; and rastering the laser spot over the surface of the niobium object.

  6. STRONTIUM PRECIPITATION

    DOEpatents

    McKenzie, T.R.

    1960-09-13

    A process is given for improving the precipitation of strontium from an aqueous phosphoric-acid-containing solution with nickel or cobalt ferrocyanide by simultaneously precipitating strontium or calcium phosphate. This is accomplished by adding to the ferrocyanide-containing solution calcium or strontium nitrate in a quantity to yield a concentration of from 0.004 to 0.03 and adjusting the pH of the solution to a value of above 8.

  7. One hundred angstrom niobium wire

    NASA Technical Reports Server (NTRS)

    Cline, H. E.; Rose, R. M.; Wulff, J.

    1968-01-01

    Composite of fine niobium wires in copper is used to study the size and proximity effects of a superconductor in a normal matrix. The niobium rod was drawn to a 100 angstrom diameter wire on a copper tubing.

  8. Titan!

    NASA Astrophysics Data System (ADS)

    Matson, Dennis L.

    2010-05-01

    Cassini-Huygens achieved Saturnian orbit on July 1, 2004. The first order of business was the safe delivery of the Huygens atmospheric probe to Titan that took place on January 14, 2005. Huygens descended under parachute obtaining observations all the way down to a safe landing. It revealed Titan for the first time. Stunning are the similarities between Titan and the Earth. Viewing the lakes and seas, the fluvial terrain, the sand dunes and other features through the hazy, nitrogen atmosphere, brings to mind the geological processes that created analogous features on the Earth. On Titan frozen water plays the geological role of rock; liquid methane takes the role of terrestrial water. The atmospheres of both Earth and Titan are predominately nitrogen gas. Titan's atmosphere contains 1.5% methane and no oxygen. The surface pressure on Titan is 1.5 times the Earth's. There are aerosol layers and clouds that come and go. Now, as Saturn proceeds along its solar orbit, the seasons are changing. The effects upon the transport of methane are starting to be seen. A large lake in the South Polar Region seems to be filling more as winter onsets. Will the size and number of the lakes in the South grow during winter? Will the northern lakes and seas diminish or dry up as northern summer progresses? How will the atmospheric circulation change? Much work remains not only for Cassini but also for future missions. Titan has many different environments to explore. These require more capable instruments and in situ probes. This work was conducted at the Jet Propulsion Laboratory, California Institute of Technology under contract with the National Aeronautics and Space Administration.

  9. Strontium

    USGS Publications Warehouse

    Ober, J.A.

    2013-01-01

    In 2012, U.S. apparent consumption of strontium (contained in celestite and manufactured strontium compounds) decreased to 16.7 kt (18,400 st) from 17.3 kt (19,100 st) in 2011. Gross weight of imports was 34.3 kt (37,800 st), 86 percent of which originated in Mexico.

  10. Strontium

    USGS Publications Warehouse

    ,

    2012-01-01

    In 2011, U.S. apparent consumption of strontium (contained in celestite and manufactured strontium compounds) increased markedly to 18.4 kt (20,300 st) from 10.4 kt (11,500 st) in 2010. Gross weight of imports was 34.4 kt (38,000 st), of which 76 percent originated from Mexico.

  11. The growth of strontium titanate and lutetium ferrite thin films by molecular-beam epitaxy

    NASA Astrophysics Data System (ADS)

    Brooks, Charles M.

    Included in this work is a range of studies on films of homoeptaxial and heteroepitaxial films of SrTiO3 and the first reported phase-pure films of LuFe2O4. We report the structural properties of homoepitaxial (100) SrTiO3 films grown by reactive molecular-beam epitaxy (MBE). The lattice spacing and x-ray diffraction (XRD) rocking curves of stoichiometric MBEgrown SrTiO3 films are indistinguishable from the underlying SrTiO3 substrates. The effect of off-stoichiometry for both strontium-rich and strontium-poor compositions results in lattice expansion with significant changes to the shuttered reflection high-energy electron diffraction oscillations, XRD, film microstructure, and thermal conductivity. Up to an 80% reduction in Sr(1+x)TiO3 film thermal conductivity is measured for x = -0.1 to 0.5. Significant reduction, from 11.5 to ˜2 W˙m-1K-1, occurs through the formation of Ruddlesden-Popper planar faults. The ability to deposit films with a reduction in thermal conductivity is applicable to thermal barrier coatings and thermoelectrics. Scanning transmission electron microscopy is used to examine the formation of Ruddlesden-Popper planar faults in films with strontium excess. We also show that the band gap of SrTiO3 can be altered by >10% (0.3 eV) by using experimentally realizable biaxial strains providing a new means to accomplish band gap engineering of SrTiO3 and related perovskites. Such band gap manipulation is relevant to applications in solar cells water splitting, transparent conducting oxides, superconductivity, two-dimensional electron liquids, and other emerging oxide electronics. This work also presents the adsorption-controlled growth of single-phase (0001)-oriented epitaxial films of charge ordered multiferroic, LuFe2O4, on (111) MgAl2O4, (111) MgO, and (0001) 6H-SiC substrates in an iron-rich environment at pressures and temperatures where excess iron desorbs from the film surface during growth. Scanning transmission electron microscopy reveals

  12. Er{sup 3+}-doped strontium lithium bismuth borate glasses for broadband 1.5 {mu}m emission - optical properties

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Rajesh, D.; Balakrishna, A.; Ratnakaram, Y. C.

    2013-02-05

    Strontium lithium bismuth borate glasses (SLBiB) doped with various concentrations of Er{sup 3+} were prepared using conventional melt quench technique and investigated their optical properties. The amorphous nature of the prepared glass samples was confirmed by X-ray diffraction and SEM analysis. Optical properties were studied by measuring the optical absorption and near infrared luminescence spectra at room temperature. Judd-Ofelt (J-O) theory has been applied for the f.f transitions of Er{sup 3+} ions to evaluate J-O intensity parameters, {Omega}{lambda} ({lambda} = 2, 4 and 6). Using the J-O intensity parameters, radiative properties such as transition probabilities (A{sub R}), branching ratios ({beta})more » and radiative lifetimes ({tau}) are estimated for certain transitions. From the emission spectra, peak emission-cross sections ({sigma}{sub p}) and products of stimulated emission cross-section and full width at half maximum ({sigma}{sub p} Multiplication-Sign FWHM) were calculated for the observed emission transition, {sup 4}I{sub 13/2}{yields}{sup 4}I{sub 15/2}.« less

  13. Strontium

    USGS Publications Warehouse

    Angulo, M.A.

    2011-01-01

    In 2010, U.S. apparent consumption of strontium (contained in celestite and manufactured strontium compounds) decreased by 11 percent to 10.4 kt (11,460 st) from 11.8 kt (13,000 st) in 2009. Gross weight of imports totaled 20.9 kt (23,000 st), of which 65 percent originated from Mexico.

  14. Platinum-doped titanate nanotubes/reduced graphene oxide: photocatalytic activity and flame retardancy

    NASA Astrophysics Data System (ADS)

    Liu, Guangya; Sang, Bin; Zhou, Zhiqi; Li, Zhiwei

    2018-01-01

    The ‘white pollution’ produced by wasted flexible polyvinyl chloride (PVC) with poor degradation ability and the potential fire hazard of PVC with high flammability not only restrict their application but also cause serious environmental problem. Thus platinum-doped titanate nanotubes/reduced graphene oxide (denoted as Pt-TNTs/rGO) nanocomposites were prepared by a facile method in order to improve the visible photodegradation and get rid of the ‘white pollution’ as well as flame retardancy of PVC. The photodegradation activity and flame retardancy effect of the as-prepared Pt-TNTs/rGO nanocomposites were investigated by ultraviolet and visible light irradiation as well as cone calorimetry. Results show that the Pt-TNTs/rGO-PVC nanocomposites exhibit enhanced visible light photodegradation performance (with mass loss being 6.5%) during 15 day exposure to solar irradiation, and good flame retardancy (providing a 44% reduction of total smoke release as compared with that of PVC matrix). Besides, Pt-TNTs/rGO-PVC nanocomposites show suppressed smoke and reduced CO production as compared with the PVC matrix. These results demonstrate that Pt-TNTs/rGO not only get rid of the ‘white pollution’ as the photocatalyst but also improve the fire safety of PVC as the flame retardant. This could be ascribed to the combination effect between Pt-TNTs and rGO. The present research, hopefully, is to pave a potential pathway to constructing polymer-matrix composites with desired photodegradation activity and flame retardancy, thereby shedding light on simultaneously dealing with the ‘white pollution’ and high flammability of polymer matrix like PVC.

  15. History and current status of strontium iodide scintillators

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Cherepy, Nerine J.; Beck, Patrick R.; Payne, Stephen A.

    Eu-doped strontium iodide single crystal growth has reached maturity and prototype SrI 2(Eu)-based gamma ray spectrometers provide detection performance advantages over standard detectors. SrI 2(Eu) offers a high, proportional light yield of >80,000 photons/MeV. Energy resolution of <3% at 662 keV with 1.5” x 1.5” SrI2(Eu) crystals is routinely achieved, by employing either a small taper at the top of the crystal or a digital readout technique. These methods overcome light-trapping, in which scintillation light is re-absorbed and re-emitted in Eu 2+-doped crystals. As a result, its excellent energy resolution, lack of intrinsic radioactivity or toxicity, and commercial availability makemore » SrI 2(Eu) the ideal scintillator for use in handheld radioisotope identification devices. A 6-lb SrI 2(Eu) radioisotope identifier is described.« less

  16. History and current status of strontium iodide scintillators

    DOE PAGES

    Cherepy, Nerine J.; Beck, Patrick R.; Payne, Stephen A.; ...

    2017-09-15

    Eu-doped strontium iodide single crystal growth has reached maturity and prototype SrI 2(Eu)-based gamma ray spectrometers provide detection performance advantages over standard detectors. SrI 2(Eu) offers a high, proportional light yield of >80,000 photons/MeV. Energy resolution of <3% at 662 keV with 1.5” x 1.5” SrI2(Eu) crystals is routinely achieved, by employing either a small taper at the top of the crystal or a digital readout technique. These methods overcome light-trapping, in which scintillation light is re-absorbed and re-emitted in Eu 2+-doped crystals. As a result, its excellent energy resolution, lack of intrinsic radioactivity or toxicity, and commercial availability makemore » SrI 2(Eu) the ideal scintillator for use in handheld radioisotope identification devices. A 6-lb SrI 2(Eu) radioisotope identifier is described.« less

  17. Strontium

    USGS Publications Warehouse

    Ober, J.A.

    1993-01-01

    Part of a special section reviewing the market performance of industrial minerals in 1992. Imports of celestite (strontium ore) reached nearly 45 kt, which represents an increase of 35 percent over 1991. Mexico supplied almost all of the celestite. Nearly 70 percent of the strontium consumed in the U.S. is used in television picture tube faceplate glass to block X-ray emissions.

  18. Presynaptic strontium dynamics and synaptic transmission.

    PubMed Central

    Xu-Friedman, M A; Regehr, W G

    1999-01-01

    Strontium can replace calcium in triggering neurotransmitter release, although peak release is reduced and the duration of release is prolonged. Strontium has therefore become useful in probing release, but its mechanism of action is not well understood. Here we study the action of strontium at the granule cell to Purkinje cell synapse in mouse cerebellar slices. Presynaptic residual strontium levels were monitored with fluorescent indicators, which all responded to strontium (fura-2, calcium orange, fura-2FF, magnesium green, and mag-fura-5). When calcium was replaced by equimolar concentrations of strontium in the external bath, strontium and calcium both entered presynaptic terminals. Contaminating calcium was eliminated by including EGTA in the extracellular bath, or by loading parallel fibers with EGTA, enabling the actions of strontium to be studied in isolation. After a single stimulus, strontium reached higher peak free levels than did calcium (approximately 1.7 times greater), and decayed more slowly (half-decay time 189 ms for strontium and 32 ms for calcium). These differences in calcium and strontium dynamics are likely a consequence of greater strontium permeability through calcium channels, lower affinity of the endogenous buffer for strontium, and less efficient extrusion of strontium. Measurements of presynaptic divalent levels help to explain properties of release evoked by strontium. Parallel fiber synaptic currents triggered by strontium are smaller in amplitude and longer in duration than those triggered by calcium. In both calcium and strontium, release consists of two components, one more steeply dependent on divalent levels than the other. Strontium drives both components less effectively than does calcium, suggesting that the affinities of the sensors involved in both phases of release are lower for strontium than for calcium. Thus, the larger and slower strontium transients account for the prominent slow component of release triggered by

  19. Citrate gel synthesis of aluminum-doped lithium lanthanum titanate solid electrolyte for application in organic-type lithium-oxygen batteries

    NASA Astrophysics Data System (ADS)

    Le, Hang T. T.; Kalubarme, Ramchandra S.; Ngo, Duc Tung; Jang, Seong-Yong; Jung, Kyu-Nam; Shin, Kyoung-Hee; Park, Chan-Jin

    2015-01-01

    Aluminium doped lithium lanthanum titanate (A-LLTO) powders with various excess Li2O content are synthesized using a simple citrate gel method. The obtained A-LLTO powders show an agglomerated form, composed of nano-sized particles of 20-50 nm. The morphology and conductivity of the A-LLTO ceramics are largely affected by the content of excess Li2O. The highest total ionic conductivity of 3.17 × 10-4 S cm-1 is achieved for the A-LLTO sample containing 20% excess Li2O, exhibiting a vacancy content of 6%, and a total activation energy of 0.358 eV. The A-LLTO can act as a membrane to protect lithium metal from oxygen and other contaminants diffused through the oxygen electrode part. The Li-O2 cell employing the A-LLTO solid electrolyte shows a good cycle life of longer than 100 discharge-charge cycles, under the constant capacity mode of 300 mAh g-1.

  20. All-optical tunable dual Fano resonance in nonlinear metamaterials in optical communication range

    NASA Astrophysics Data System (ADS)

    Zhou, Yi; Hu, Xiaoyong; Li, Chong; Yang, Hong; Gong, Qihuang

    2018-01-01

    Low-power, ultra-fast all-optical tunable dual Fano resonance was realized in a metamaterial coated with a non-linear nanocomposite layer composed of gold nanoparticle-doped polycrystalline barium strontium titanate and multilayer tungsten disulphide microsheets. A high non-linear refractive index of -2.148 × 10-11 m2/W was achieved in the nanocomposite material that originated in the non-linearity enhancement associated with the quantum confinement effect, the local-field enhancement effect, and reinforced interactions between photons and the multilayer tungsten disulphide microsheets. An ultra-low threshold pump intensity of 600 kW/cm2 was obtained. An ultra-fast response time of 25.4 ps was maintained because of the fast relaxation dynamics of the bound electrons in the nanoscale polycrystalline barium strontium titanate grains. The large third-order non-linear responses of the metamaterial were confirmed with a high third harmonic generation conversion efficiency of 5.4 × 10-5. This work may help to pave the way towards realization of ultra-high-speed information processing chips and multifunctional integrated photonic devices based on metamaterials.

  1. Strain-Enhanced p Doping in Monolayer MoS2

    NASA Astrophysics Data System (ADS)

    Choi, Minseok

    2018-02-01

    Achievement of desired p -type electrical properties in MoS2 remains a challenge. Here, we demonstrate that p doping in monolayer MoS2 can be enhanced in terms of strain manipulation, through first-principles hybrid functional calculations. Biaxial tensile strain and shear strain with smaller in-plane angles induce the dramatic reduction in formation energy of p dopants such as niobium and tantalum, providing the moderate doping contents required for applications. In addition, the formation of sulfur vacancies which are potential compensators of holes released from the dopants is suppressed by the strains. Our calculations pave an alternative strategy to overcome in the realization of p doping in monolayer MoS2 .

  2. PROCESS OF COATING GRAPHITE WITH NIOBIUM-TITANIUM CARBIDE

    DOEpatents

    Halden, F.A.; Smiley, W.D.; Hruz, F.M.

    1961-07-01

    A process of coating graphite with niobium - titanium carbide is described. It is found that the addition of more than ten percent by weight of titanium to niobium results in much greater wetting of the graphite by the niobium and a much more adherent coating. The preferred embodiment comprises contacting the graphite with a powdered alloy or mixture, degassing simultaneously the powder and the graphite, and then heating them to a high temperature to cause melting, wetting, spreading, and carburization of the niobium-titanium powder.

  3. Ferroelectric properties of substituted barium titanate ceramics

    NASA Astrophysics Data System (ADS)

    Kumar, Parveen; Singh, Sangeeta; Juneja, J. K.; Prakash, Chandra; Raina, K. K.

    2009-06-01

    Barium titanate (BT) is among the most studied ferroelectric material which has been used in various forms, e.g. bulk, thin and thick film, powder, in a number of applications. In order to achieve a material with desired properties, it is modified with a variety of substituents. Most common substituents have been strontium, calcium and zirconium. Here we report studies on lead and zirconium substituted BT. The material series with compositional formula Ba 0.80Pb 0.20Ti 1-xZr xO 3 with, 0< x<0.1 was chosen for investigations. The material was synthesized by solid state reaction method. Reacted powder compacted in form of circular discs were sintered in the range of 1300 °C. All the samples were subjected to X-ray analysis and found to be single phase. Ferroelectric properties were studied as a function of composition and temperature. Pr/ Ps ratio was determined. It was found to decrease with increase in x.

  4. Specific activity and isotope abundances of strontium in purified strontium-82

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Fitzsimmons, J. M.; Medvedev, D. G.; Mausner, L. F.

    2015-11-12

    A linear accelerator was used to irradiate a rubidium chloride target with protons to produce strontium-82 (Sr-82), and the Sr-82 was purified by ion exchange chromatography. The amount of strontium associated with the purified Sr-82 was determined by either: ICP-OES or method B which consisted of a summation of strontium quantified by gamma spectroscopy and ICP-MS. The summation method agreed within 10% to the ICP-OES for the total mass of strontium and the subsequent specific activities were determined to be 0.25–0.52 TBq mg -1. Method B was used to determine the isotope abundances by weight% of the purified Sr-82, andmore » the abundances were: Sr-82 (10–20.7%), Sr-83 (0–0.05%), Sr-84 (35–48.5%), Sr-85 (16–25%), Sr-86 (12.5–23%), Sr-87 (0%), and Sr-88 (0–10%). The purified strontium contained mass amounts of Sr-82, Sr-84, Sr-85, Sr-86, and Sr-88 in abundances not associated with natural abundance, and 90% of the strontium was produced by the proton irradiation. A comparison of ICP-OES and method B for the analysis of Sr-82 indicated analysis by ICP-OES would be easier to determine total mass of strontium and comply with regulatory requirements. An ICP-OES analytical method for Sr-82 analysis was established and validated according to regulatory guidelines.« less

  5. From Titan's chemistry and exobiology to Titan's astrobiology

    NASA Astrophysics Data System (ADS)

    Raulin, François

    2015-04-01

    When the IDS proposal « Titan's chemistry and exobiology » was submitted to ESA 25 years ago, in the frame of what will become the Cassini-Huygens mission, Titan was already seen as a quite interesting planetary object in the solar system for Exobiology. Several organic compounds of prebiotic interest were identified in its atmosphere, which was thus was expected to be chemically very active, especially in term of organic processes. Atmospheric aerosols seemed to play a key role in this chemistry. Moreover, the presence of an internal aqueous ocean, compatible with life was suspected. A few years later, when astrobiology was (re)invented, Titan became one of the most interesting planetary target for this new (but very similar to exobiology) field. With the Cassini-Huygens mission, the exo/astrobiological interest of Titan has become more and more important. However, the mission has been providing a vision of Titan quite different from what it was supposed. Its atmospheric organic chemistry is very complex and starts in much higher zones than it was believed before, involving high molecular weight species in the ionosphere. Titan's surface appears to be far from homogeneous: instead of been covered by a global methane-ethane ocean, it is very diversified, with dunes, lakes, bright and dark areas, impact and volcanic craters with potential cryovolcanic activity. These various geological areas are continuously feeded by atmospheric aerosols, which represent an important step in the complexity of Titan's organic chemistry, but probably not the final one. Indeed, after being deposited on the surface, in the potential cryovolvanic zones, these particles may react with water ice and form compounds of exo/astrobiological interest, such as amino acids, purine and pyrimidine bases. Moreover, The Cassini-Huygens data strongly support the potential presence of an internal water ocean, which becomes less and less hypothetical and of great interest for exobiology. These

  6. Simulating the Transfer of Strontium-90 from Soil to Leafy Vegetables by Using Strontium-88.

    PubMed

    Kuke, Ding; Shujuan, Liu; Yingxue, He; Dong, Yan; Fengshou, Zhang; Shuifeng, Wang; Jinghua, Guo; Wei, Zhang; Xin, Wang; Xiaoyan, Jiang

    The transfer, from soil to Chinese cabbage and spinach, of radioactive strontium-90 released as a result of accidents in nuclear power stations was studied using a stable isotope of strontium, namely nuclide strontium-88 ( 88 Sr). The study led to an experimental model for assessing the hazard of radionuclide strontium-90 ( 90 Sr) entering the food chain and for predicting the risk to food safety. Chinese cabbage and spinach were grown in pots in a greenhouse and irrigated with deionized water containing known quantities of strontium. Based on the strontium content of that water, the plants were divided into five groups (treatments) and strontium content of the soil, and 30-day-old plants were determined by inductively coupled plasma atomic emission spectroscopy instrument (ICP-AES). Data on the strontium content of soil and plants enabled the development of a model using MATLAB, a mathematical software package, which included curve fitting and problem solving using regression equations and differential equations. Although strontium curves for leaves, stems, and roots of Chinese cabbage were not exactly the same, all showed a non-linear increase when compared with the increase in the content of strontium in soil. Strontium curves for leaves, stems, and roots of spinach were very similar and showed an initial increase followed by a decrease. Strontium concentrations in both Chinese cabbage and spinach were initially related to the concentrations of sodium and sulfur, the next two relevant nuclides being calcium and magnesium. The relationship between calcium and strontium in Chinese cabbage was different from that in spinach. By using 88 Sr to simulate the transfer of radionuclide 90 Sr from soil to a crop, the relevant data required to deal with accidental release of strontium can be obtained using a fitting curve and regression equations, thereby providing some experimental basis for evaluating the potential hazards posed by such accidents to the food chain.

  7. The effect of carrier strontium on the absorption of oral doses of radioactive strontium in rats

    PubMed Central

    Harrison, G. E.; Jones, H. G.; Sutton, A.

    1957-01-01

    Carrier strontium had relatively little effect on the retention of an oral dose of radioactive strontium by the rat when it was administered immediately after the radioactive dose. The proportion of the radioactive dose which was excreted in the urine, on the other hand, increased progressively with the carrier dose. There was a decreased uptake of radioactive strontium in rats fed on a special low strontium diet. The effects of dietary strontium are discussed. Evidence was found of a discrimination by the rat against strontium in favour of calcium which was accounted for, at least in part, by a preferential urinary excretion of strontium. PMID:13460240

  8. Titan Accent Mark

    NASA Image and Video Library

    2015-10-05

    A coincidence of viewing angle makes Pandora appear to be hovering over Titan, almost like an accent mark. Little Pandora is much closer to Cassini than hazy Titan in this view. (Titan is nearly three times farther away.) Even so, Titan (3,200 miles or 5,150 kilometers across) dwarfs Pandora (50 miles or 81 kilometers across). This gives us some sense of the diversity in sizes, and shapes, of Saturn's many moons. North on Titan is up and rotated 19 degrees to the right. The image was taken in visible green light with the Cassini spacecraft narrow-angle camera on July 4, 2015. The view was acquired at a distance of approximately 1.2 million miles (1.9 million kilometers) from Titan. Image scale is 7 miles (12 kilometers) per pixel on Titan. Pandora is at a distance of 436,000 miles (698,000 kilometers) away from the spacecraft. The scale on Pandora is about 3 miles (4 kilometers) per pixel. http://photojournal.jpl.nasa.gov/catalog/PIA18338

  9. Integration and High-Temperature Characterization of Ferroelectric Vanadium-Doped Bismuth Titanate Thin Films on Silicon Carbide

    NASA Astrophysics Data System (ADS)

    Ekström, Mattias; Khartsev, Sergiy; Östling, Mikael; Zetterling, Carl-Mikael

    2017-07-01

    4H-SiC electronics can operate at high temperature (HT), e.g., 300°C to 500°C, for extended times. Systems using sensors and amplifiers that operate at HT would benefit from microcontrollers which can also operate at HT. Microcontrollers require nonvolatile memory (NVM) for computer programs. In this work, we demonstrate the possibility of integrating ferroelectric vanadium-doped bismuth titanate (BiTV) thin films on 4H-SiC for HT memory applications, with BiTV ferroelectric capacitors providing memory functionality. Film deposition was achieved by laser ablation on Pt (111)/TiO2/4H-SiC substrates, with magnetron-sputtered Pt used as bottom electrode and thermally evaporated Au as upper contacts. Film characterization by x-ray diffraction analysis revealed predominately (117) orientation. P- E hysteresis loops measured at room temperature showed maximum 2 P r of 48 μC/cm2, large enough for wide read margins. P- E loops were measurable up to 450°C, with losses limiting measurements above 450°C. The phase-transition temperature was determined to be about 660°C from the discontinuity in dielectric permittivity, close to what is achieved for ceramics. These BiTV ferroelectric capacitors demonstrate potential for use in HT NVM applications for SiC digital electronics.

  10. A promising lightweight multicomponent microwave absorber based on doped barium hexaferrite/calcium titanate/multiwalled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Afghahi, Seyyed Salman Seyyed; Jafarian, Mojtaba; Atassi, Yomen

    2016-07-01

    We present the design of a microwave absorber in the X band based on ternary nanocomposite of doped barium hexaferrite (Ba-M)/calcium titanate (CTO)/multiwall carbon nanotubes (MWCNTs) in epoxy matrix. The hydrothermal method has been used to synthesize Ba-M and CTO nanopowder. The phase identification has been investigated using XRD patterns. Scanning electron microscope, transmission electron microscope, vibrating sample magnetometer, and vector network analyzer are used to analyze the morphology of the different components and the magnetic, electromagnetic, and microwave absorption properties of the final composite absorbers, respectively. As far as we know, the design of this type of multicomponent microwave absorber has not been investigated before. The results reveal that the combination of these three components with their different loss mechanisms has a synergistic effect that enhances the attenuation properties of the final composite. The absorber of only 2.5-mm thickness and 35 wt% of loading ratio exhibits a minimum reflection loss of -43 dB at 10.2 GHz with a bandwidth of 3.6 GHz, while the corresponding absorber based on pure (Ba-M) shows a minimum reflection loss of -34 dB at 9.8 GHz with a bandwidth of 0.256 GHz and a thickness of 4 mm.

  11. Future Exploration of Titan

    NASA Astrophysics Data System (ADS)

    Lorenz, R. D.; Titan Decadal Panel Collaboration

    2001-11-01

    Titan promises to be the Mars of the Outer Solar System - the focus of not only the broadest range of investigations in planetary science but also the focus of public attention. The reasons for exploring Titan are threefold: 1. Titan and Astrobiology : Titan ranks with Mars and Europa as a prime body for astrobiological study due to its abundant organics. Like Europa, it may well have a liquid water interior. 2. Titan - A world in its own right. Titan deserves study even only to put other satellites (its remarkably smaller Saturnian siblings, and its same-sized but volatile-poor Jovian counterparts) in context. The added dimension of an atmosphere makes Titan's origin and evolution particularly interesting. 3. Titan - an environmental laboratory for Earth. Titan will be an unrivalled place to investigate meteorological, oceanographical and other processes. Many of these (e.g. wave generation by wind) are only empirically parameterized - the very different physical parameters of the Titan environment will bring new insights to these phenomena. While Cassini-Huygens will dramatically boost our knowledge of Titan, it will likely only whet our appetite for more. The potential for prebiotic materials at various locations (in particular where liquid water has interacted with photochemical deposits) and the need to monitor Titan's meteorology favor future missions that may exploit Titan's unique thick-atmosphere, low-gravity environment - a mobile platform like an airship or helicopter, able to explore on global scales, but access the surface for in-situ chemical analysis and probe the interior by electromagnetic and seismic means. Such missions have dramatic potential to capture the public's imagination, on both sides of the Atlantic.

  12. Influence of dehydrated nanotubed titanic acid on charge transport and luminescent properties of polymer light-emitting diodes with fluorescent dye

    NASA Astrophysics Data System (ADS)

    Qian, Lei; Bera, Debasis; Jin, Zhen-Sheng; Du, Zu-Liang; Xu, Zheng; Teng, Feng; Liu, Wei

    2007-09-01

    In this paper, we discuss the influence of dehydrated nanotubed titanic acid (DNTA) on charge transport and luminescent properties of polymer light-emitting diodes (PLEDs) doped with fluorescent dye. Photoluminescence results confirm the efficient energy transfer from PVK to 4-(dicyanom-ethylene)-2- t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) and tris-(8-hydroxtquinoline) aluminum (Alq 3) in a DNTA-doped device. The device showed lower turn-on voltages and higher charge current by doping with DNTA, which also caused a shift in the exciton's recombination region.

  13. Strontium-90 in hair.

    PubMed

    HOPKINS, B J; TUTTLE, L W; PORIES, W J; STRAIN, W H

    1963-03-15

    The hair of rats injected with strontium-90 retains a significant amount of the radionuclide. Although the strontium-90 content of hair is variable in these rats and appears to be subject to a variety of influences, determination of the radionuclide content of hair may offer a nondestructive method of estimating strontium-90 in bone.

  14. Titan's Exotic Weather

    NASA Astrophysics Data System (ADS)

    Griffith, Caitlin A.

    2006-09-01

    Images of Titan, taken during the joint NASA and European Space Agency Cassini-Huygens mission, invoke a feeling of familiarity: washes wind downhill to damp lakebeds; massive cumuli form and quickly dissipate, suggestive of rain; and dark oval regions resemble lakes. These features arise from Titan's unique similarity with Earth: both cycle liquid between their surfaces and atmospheres, but in Titan's cool atmosphere it is methane that exists as a gas, liquid, and ice. While Titan enticingly resembles Earth, its atmosphere is 10 times thicker, so that its radiative time constant near the surface exceeds a Titan year, and prohibits large thermal gradients and seasonal surface temperature variations exceeding 3K. Titan also lacks oceans - central to Earth's climate - and instead stores much of its condensible in its atmosphere. As a result, Titan's weather differs remarkably from Earth's. Evidence for this difference appears in the location of Titan's large clouds, which frequent a narrow band at 40S latitude and a region within 30 latitude of the S. Pole. Ground-based and Cassini observations, combined with thermodynamic considerations, indicate that we are seeing large convective cloud systems. Detailed cloud models and general circulation models further suggest that these are severe rain storms, which will migrate with the change in season. Outside these migrating "gypsy" cloud bands, the atmosphere appears to be calm, humid and thus frequented by thin stratiform clouds. An intriguingly alien environment is predicted. Yet, the combined effects of Titan's patchy wet surface, atmospheric tides, possible ice volcanoes, and detailed seasonal variations remain unclear as we have witnessed only one season so far. This talk will review observations of Titan's lower atmosphere and modeling efforts to explain the observations, and explore the questions that still elude us.

  15. High-resolution stratigraphy with strontium isotopes.

    PubMed

    Depaolo, D J; Ingram, B L

    1985-02-22

    The isotopic ratio of strontium-87 to strontium-86 shows no detectable variation in present-day ocean water but changes slowly over millions of years. The strontium contained in carbonate shells of marine organisms records the ratio of strontium-87 to strontium-86 of the oceans at the time that the shells form. Sedimentary rocks composed of accumulated fossil carbonate shells can be dated and correlated with the use of high precision measurements of the ratio of strontium-87 to strontium-86 with a resolution that is similar to that of other techniques used in age correlation. This method may prove valuable for many geological, paleontological, paleooceanographic, and geochemical problems.

  16. Efficient degradation of Methylene Blue dye over highly reactive Cu doped strontium titanate (SrTiO3) nanoparticles photocatalyst under visible light.

    PubMed

    Rahman, Qazi Inamur; Ahmad, Musheer; Misra, Sunil Kumar; Lohani, Minaxi

    2012-09-01

    Visible light induced photocatalysts of Cu doped SrTiO3 (Cu/SrTiO3) nanoparticles with the size -60-75 nm were prepared via facile sol-gel method. The morphological, optical, crystalline properties and compositions of synthesized Cu/SrTiO3 nanoparticles were thoroughly characterized by field emission scanning electron microscopy (FE-SEM), powder X-ray diffraction (XRD), ultra violet-visible spectroscopy (UV-Vis) and energy dispersive X-ray (EDX). A significant red shift in the UV-diffused reflectance spectrum was observed and the absorption edge shifted to visible region by the Cu doping. Surprisingly, the band gap of SrTiO3 was changed from 3.2 eV drop to 2.96 eV. The photocatalytic activity of the synthesized Cu/SrTiO3 nanoparticles was demonstrated for the degradation of Methylene Blue dye under visible light irradiation. The formation of new acceptor region in Cu/SrTiO3 was responsible for high photocatalytic activity of Cu/SrTiO3 nanoparticles. The results showed that the Methylene Blue dye was degraded by -66% within time span of 2 h over the Cu/SrTiO3 nanoparticles. This dye degradation reaction followed the Langmuir-Hinshelwood kinetics and also exhibited first order reaction rate. The calculated rate constant for the degradation reaction following first order kinetics was k = 0.0016 min(-1).

  17. Determination of niobium in the parts per million range in rocks

    USGS Publications Warehouse

    Grimaldi, F.S.

    1960-01-01

    A modified niobium thiocyanate spectrophotometric procedure relatively insensitive to titanium interference is presented. Elements such as tungsten, molybdenum, vanadium, and rhenium, which seriously interfere in the spectrophotometric determination of niobium, are separated by simple sodium hydroxide fusion and leach; iron and magnesium are used as carriers for the niobium. Tolerance limits are given for 28 elements in the spectrophotometric method. Specific application is made to the determination of niobium in the parts per million range in rocks. The granite G-1 contains 0.0022% niobium and the diabase W-1 0.00096% niobium.

  18. The effect of ionic Co presence on the structural, optical and photocatalytic properties of modified cobalt-titanate nanotubes.

    PubMed

    Barrocas, B; Silvestre, A J; Rolo, A G; Monteiro, O C

    2016-07-21

    With the aim of producing materials with enhanced optical and photocatalytic properties, titanate nanotubes (TNTs) modified by cobalt doping (Co-TNT) and by Na(+)→ Co ion-exchange (TNT/Co) were successfully prepared by a hydrothermal method. The influence of the doping level and of the cobalt position in the TNT crystalline structure was studied. Although no perceptible influence of the cobalt ion position on the morphology of the prepared titanate nanotubes was observed, the optical behaviour of the cobalt modified samples is clearly dependent on the cobalt ions either substituting the Ti(4+) ions in the TiO6 octahedra building blocks of the TNT structure (doped samples) or replacing the Na(+) ions between the TiO6 interlayers (ion-exchange samples). The catalytic ability of these materials on pollutant photodegradation was investigated. First, the evaluation of hydroxyl radical formation using the terephthalic acid as a probe was performed. Afterwards, phenol, naphthol yellow S and brilliant green were used as model pollutants. Anticipating real world situations, photocatalytic experiments were performed using solutions combining these pollutants. The results show that the Co modified TNT materials (Co-TNT and TNT/Co) are good catalysts, the photocatalytic performance being dependent on the Co/Ti ratio and on the structural metal location. The Co(1%)-TNT doped sample was the best photocatalyst for all the degradation processes studied.

  19. Antibacterial and biological characteristics of plasma sprayed silver and strontium doped hydroxyapatite coatings

    PubMed Central

    Fielding, Gary A.; Roy, Mangal; Bandyopadhyay, Amit

    2012-01-01

    Infection in primary total joint prostheses is estimated to occur in up to 3% of all surgeries. As a measure to improve the antimicrobial properties of implant materials, silver (Ag) was incorporated into plasma sprayed hydroxyapatite (HA) coatings. To offset potential cytotoxic effects of Ag in the coatings, strontium (Sr) was also added as a binary dopant. HA powder were doped with 2.0 wt% Ag2O, 1.0 wt% SrO and the powder was then heat treated at 800° C. Titanium substrates were coated using a 30 kW plasma spray system equipped with a supersonic nozzle. X-ray diffraction (XRD) confirmed the phase purity and high crystallinity of the coatings. Samples were evaluated for mechanical stability by adhesive bond strength testing. Results show that the addition of dopants did not affect the overall bond strength of the coatings. The antibacterial efficacies of the coatings were tested against Pseudomonas aeruginosa. Samples that contained the Ag2O dopant were found to be highly effective against the bacterial colonization. In vitro cell-material interactions using human fetal osteoblast (hFOB) cells were characterized by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay for cell viability, field emission scanning electron microscopy (FESEM) for cell morphology and confocal imaging for the important differentiation marker alkaline phosphatase (ALP). Our results showed evidence of cytotoxic effects in the Ag-HA coatings, characterized by poor cellular morphology and cell death and nearly complete impediment of functional ALP activity. The addition of SrO to Ag-HA coatings was able to effectively offset these negative effects and improve the performance when compared to pure HA coated samples. PMID:22487928

  20. Niobium oxide compositions and methods for using same

    DOEpatents

    Goodenough, John B; Han, Jian-Tao

    2014-02-11

    The disclosure relates a niobium oxide useful in anodes of secondary lithium ion batteries. Such niobium oxide has formula Li.sub.xM.sub.1-yNb.sub.yNb.sub.2O.sub.7, wherein 0.ltoreq.x.ltoreq.3, 0.ltoreq.y.ltoreq.1, and M represents Ti or Zr. The niobium oxide may be in the form of particles, which may be carbon coated. The disclosure also relates to an electrode composition containing at least one or more niobium oxides of formula Li.sub.xM.sub.1-yNb.sub.yNb.sub.2O.sub.7. The disclosure further relates to electrodes, such as anodes, and batteries containing at least one or more niobium oxides of formula Li.sub.xM.sub.1-yNb.sub.yNb.sub.2O.sub.7. Furthermore, the disclosure relates to methods of forming the above.

  1. Role of orbital filling on nonlinear ionic Raman scattering in perovskite titanates

    NASA Astrophysics Data System (ADS)

    Gu, Mingqiang; Rondinelli, James M.

    2017-01-01

    The linear and nonlinear phononic interactions between an optically excited infrared (IR) or hyper-Raman mode and a driven Raman mode are computed for the d0 (CaTiO3) and d1 (LaTiO3) titanates within a first-principles density functional framework. We calculate the potential energy surface expanded in terms of the Ag or B1 g mode amplitudes coupled to the Au or the B3 u mode and determine the coupling coefficients for these multimode interactions. We find that the linear-quadratic coupling dominates the anharmonicities over the quadratic-quadratic interaction in the perovskite titanates. The IR and Raman modes both modify the electronic structure with the former being more significant but occurring on a different time scale; furthermore, the coupled-mode interactions lead to sizable perturbations to the valence bandwidth (˜100 meV ) and band gap (˜50 meV). By comparing the coupling coefficients of undoped CaTiO3 and LaTiO3 to those for electron-doped (CaTiO3) and hole-doped (LaTiO3) titanates, we isolate the role of orbital filling in the nonlinear coupling process. We find that with increasing occupancy of the d manifold, the linear-quadratic interaction decreases by approximately 30% with minor changes induced by the cation chemistry (that mainly affect the phonon mode frequencies) or by electron correlation. We identify the importance of the Ti-O bond stiffness, which depends on the orbital filling, in governing the lattice anharmonicitiy. This microscopic understanding can be used to increase the nonlinear coupling coefficient to facilitate more facile access of nonequilibrium structures and properties through ionic Raman scattering processes.

  2. Niobium-bearing arsenides and germanides from elemental mixtures not involving niobium: a new twist to an old problem in solid-state synthesis.

    PubMed

    Baranets, Sviatoslav; He, Hua; Bobev, Svilen

    2018-05-01

    Three isostructural transition-metal arsenides and germanides, namely niobium nickel arsenide, Nb 0.92(1) NiAs, niobium cobalt arsenide, NbCoAs, and niobium nickel germanide, NbNiGe, were obtained as inadvertent side products of high-temperature reactions in sealed niobium containers. In addition to reporting for the very first time the structures of the title compounds, refined from single-crystal X-ray diffraction data, this article also serves as a reminder that niobium containers may not be suitable for the synthesis of ternary arsenides and germanides by traditional high-temperature reactions. Synthetic work involving alkali or alkaline-earth metals, transition or early post-transition metals, and elements from groups 14 or 15 under such conditions may yield Nb-containing products, which at times could be the major products of such reactions.

  3. GIANT DIELECTRIC TUNABLE BEHAVIOR OF Pr-DOPED SrTiO3 AT LOW TEMPERATURE

    NASA Astrophysics Data System (ADS)

    Wei, T.; Song, Q. G.; Zhou, Q. J.; Li, Z. P.; Chen, Y. F.; Qi, X. L.; Guo, S. Q.; Liu, J.-M.

    2012-03-01

    Contrast with conventional dielectric tunable materials such as barium strontium titanate (BST), here, we report one new dielectric tunable behavior for Sr1-xPrxTiO3 system at low temperature. Giant dielectric tunability is confirmed in this system. More importantly, the efficient dielectric tunability can be realized just using small bias field. In addition, critical threshold electric field is also confirmed. This phenomenon may be related with the competition interaction of polar state with quantum fluctuations.

  4. Titan Submarines!

    NASA Astrophysics Data System (ADS)

    Oleson, S. R.; Lorenz, R. D.; Paul, M. V.; Hartwig, J. W.; Walsh, J. M.

    2017-02-01

    A NIAC Phase II submarine concept, dubbed 'Titan Turtle' for Saturn's moon Titan's northern sea, Ligea Mare. A design concept including science and operations is described for this -180°C liquid methane sea.

  5. Not So Titanic

    NASA Image and Video Library

    2015-07-13

    Titan may be a "large" moon -- its name even implies it! -- but it is still dwarfed by its parent planet, Saturn. As it turns out, this is perfectly normal. Although Titan (3200 miles or 5150 kilometers across) is the second-largest moon in the solar system, Saturn is still much bigger, with a diameter almost 23 times larger than Titan's. This disparity between planet and moon is the norm in the solar system. Earth's diameter is "only" 3.7 times our moon's diameter, making our natural satellite something of an oddity. (Another exception to the rule: dwarf planet Pluto's diameter is just under two times that of its moon.) So the question isn't why is Titan so small (relatively speaking), but why is Earth's moon so big? This view looks toward the anti-Saturn hemisphere of Titan. North on Titan is up. The image was taken with the Cassini spacecraft wide-angle camera on April 18, 2015 using a near-infrared spectral filter with a passband centered at 752 nanometers. The view was acquired at a distance of approximately 930,000 miles (1.5 million kilometers) from Titan. Image scale is 56 miles (90 kilometers) per pixel. http://photojournal.jpl.nasa.gov/catalog/PIA18326

  6. Could binary mixture of Nd-Ni ions control the electrical behavior of strontium-barium M-type hexaferrite nanoparticles?

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Iqbal, Muhammad Javed, E-mail: mjiqauchem@yahoo.com; Farooq, Saima

    2011-05-15

    Research highlights: {yields} Strontium-barium hexaferrites (Sr{sub 0.5}Ba{sub 0.5}Fe{sub 12}O{sub 19}) in single magnetoplumbite phase solid structure are synthesized by the co-precipitation method. {yields} Structural and electrical properties of Nd-Ni substituted ferrites are investigated. {yields} These ferrite materials possess high electrical resistivity (108 {Omega} cm) that is essential to curb the eddy current loss, which is pre-requisite for surface mount devices. -- Abstract: Cationic substitution in M-type hexaferrites is considered to be an important tool for modification of their electrical properties. This work is part of our comprehensive study on the synthesis and characterization of Nd-Ni doped strontium-barium hexaferrite nanomaterials ofmore » nominal composition Sr{sub 0.5}Ba{sub 0.5-x}Nd{sub x}Fe{sub 12-y}Ni{sub y}O{sub 19} (x = 0.00-0.10; y = 0.00-1.00). Doping with this binary mixture modulates the physical and electrical properties of strontium-barium hexaferrite nanoparticles. Structural and electrical properties of the co-precipitated ferrites are investigated using state-of-the-art techniques. The results of X-ray diffraction analysis reveal that the lattice parameters and cell volume are inversely related to the dopant content. Temperature dependent DC-electrical resistivity measurements infer that resistivity of strontium-barium hexaferrites decreases from 1.8 x 10{sup 10} to 2.0 x 10{sup 8} {Omega} cm whereas the drift mobility, dielectric constant and dielectric loss tangent are directly related to the Nd-Ni content. The results of the study demonstrate a relationship between the modulation of electrical properties of substituted ferrites and nature of cations and their lattice site occupancy.« less

  7. Towards Mott design by δ-doping of strongly correlated titanates

    NASA Astrophysics Data System (ADS)

    Lechermann, Frank; Obermeyer, Michael

    2015-04-01

    Doping the distorted-perovskite Mott insulators LaTiO3 and GdTiO3 with a single SrO layer along the [001] direction gives rise to a rich correlated electronic structure. A realistic superlattice study by means of the charge self-consistent combination of density functional theory with dynamical mean-field theory reveals layer- and temperature-dependent multi-orbital metal-insulator transitions. An orbital-selective metallic layer at the interface dissolves via an orbital-polarized doped-Mott state into an orbital-ordered insulating regime beyond the two conducting TiO2 layers. We find large differences in the scattering behavior within the latter. Breaking the spin symmetry in δ-doped GdTiO3 results in blocks of ferromagnetic itinerant and ferromagnetic Mott-insulating layers that are coupled antiferromagnetically.

  8. Titan's Radioactive Haze : Production and Fate of Radiocarbon On Titan

    NASA Astrophysics Data System (ADS)

    Lorenz, R. D.; Jull, A. J. T.; Swindle, T. D.; Lunine, J. I.

    Just as cosmic rays interact with nitrogen atoms in the atmosphere of Earth to gener- ate radiocarbon (14C), the same process should occur in Titan`s nitrogen-rich atmo- sphere. Titan`s atmosphere is thick enough that cosmic ray flux, rather than nitrogen column depth, limits the production of 14 C. Absence of a strong magnetic field and the increased distance from the sun suggest production rates of 9 atom/cm2/s, approx- imately 4 times higher than Earth. On Earth the carbon is rapidly oxidised into CO2. The fate and detectability of 14C on Titan depends on the chemical species into which it is incorporated in Titan's reducing atmosphere : as methane it would be hopelessly diluted even in only the atmosphere (ignoring the other, much more massive carbon reservoirs likely to be present on Titan, like hydrocarbon lakes.) However, in the more likely case that the 14C attaches to the haze that rains out onto the surface (as tholin, HCN or acetylene and their polymers - a much smaller carbon reservoir) , haze in the atmosphere or recently deposited on the surface would therefore be quite intrinsically radioactive. Such activity may modify the haze electrical charging and hence its coag- ulation. Measurements with compact instrumentation on future in-situ missions could place useful constraints on the mass deposition rates of photochemical material on the surface and identify locations where surface deposits of such material are `freshest`.

  9. Strontium-89 and Strontium-90 Levels in Breast Milk and in Mineral-Supplement Preparations

    PubMed Central

    Jarvis, Anita A.; Brown, John R.; Tiefenbach, Bella

    1963-01-01

    Strontium-90, strontium-89 and S.U. values were determined in human milk before and after the resumption of atmospheric nuclear testings in 1961, and the levels were compared to cows' milk values reported during the same time. S.U.90 levels in human milk were approximately one-fifth of those found in cows' milk. Assuming an average dietary intake of 11-13 S.U.90 during the period tested, the mean strontium/calcium ratio of 1.78 found in human milk represents an Observed Ratio milk-diet of approximately 0.14-0.16. Although strontium-89 was present in cows' milk already in September 1961, it did not appear in human milk until November 1961. It seems, therefore, that there was a two-month lag period between the appearance of fresh fallout in cows' milk and human milk. Calcium-supplement mineral preparations used by pregnant and lactating women were tested to find their strontium-89, strontium-90 and S.U. levels, because strontium isotopes, if present in these products, will be transferred to the fetus and to breast-fed infants. The compounds tested had S.U.90 levels of 0.13-2.62; in none of the preparations was Sr89 present. PMID:14041888

  10. Strontium-89 and strontium-90 levels in breast milk and in mineral-suplement preparations.

    PubMed

    JARVIS, A A; BROWN, J R; TIEFENBACH, B

    1963-01-19

    Strontium-90, strontium-89 and S.U. values were determined in human milk before and after the resumption of atmospheric nuclear testings in 1961, and the levels were compared to cows' milk values reported during the same time. S.U.(90) levels in human milk were approximately one-fifth of those found in cows' milk. Assuming an average dietary intake of 11-13 S.U.(90) during the period tested, the mean strontium/calcium ratio of 1.78 found in human milk represents an Observed Ratio milk-diet of approximately 0.14-0.16. Although strontium-89 was present in cows' milk already in September 1961, it did not appear in human milk until November 1961. It seems, therefore, that there was a two-month lag period between the appearance of fresh fallout in cows' milk and human milk. Calcium-supplement mineral preparations used by pregnant and lactating women were tested to find their strontium-89, strontium-90 and S.U. levels, because strontium isotopes, if present in these products, will be transferred to the fetus and to breast-fed infants. The compounds tested had S.U.(90) levels of 0.13-2.62; in none of the preparations was Sr(89) present.

  11. Field determination of microgram quantities of niobium in rocks

    USGS Publications Warehouse

    Ward, F.N.; Marranzino, A.P.

    1955-01-01

    A rapid, simple, and moderately accurate method was needed for the determination of traces of niobium in rocks. The method developed is based on the reaction of niobium(V) with thiocyanate ion in a 4M hydrochloric acid and 0.5M tartaric acid medium, after which the complex is extracted with ethyl ether. The proposed procedure is applicable to rocks containing from 50 to 2000 p.p.m. of niobium, and, with modifications, can be used on rocks containing larger amounts. Five determinations on two rocks containing 100 p.p.m. or less of niobium agree within 5 p.p.m. of the mean, and the confidence limits at the 95% level are, respectively, ??6 and ??4 p.p.m. The addition of acetone to the ether extract of the niobium thiocyanate inhibits the polymerization of the thiocyanate ion and stabilizes the solution for at least 20 hours. The proposed procedure permits the determination of 20 ?? of niobium in the presence of 1000 ?? of iron, titanium, or uranium; 500 ?? of vanadium; or 100 ?? of tungsten or molybdenum or both.

  12. Intensive Titan exploration begins.

    PubMed

    Mahaffy, Paul R

    2005-05-13

    The Cassini Orbiter spacecraft first skimmed through the tenuous upper atmosphere of Titan on 26 October 2004. This moon of Saturn is unique in our solar system, with a dense nitrogen atmosphere that is cold enough in places to rain methane, the feedstock for the atmospheric chemistry that produces hydrocarbons, nitrile compounds, and Titan's orange haze. The data returned from this flyby supply new information on the magnetic field and plasma environment around Titan, expose new facets of the dynamics and chemistry of Titan's atmosphere, and provide the first glimpses of what appears to be a complex, fluid-processed, geologically young Titan surface.

  13. Ferroelectric relaxor behaviour and impedance spectroscopy of Bi2O3-doped barium zirconium titanate ceramics

    NASA Astrophysics Data System (ADS)

    Mahajan, Sandeep; Thakur, O P; Bhattacharya, D K; Sreenivas, K

    2009-03-01

    Bi2O3-doped barium zirconate titanate ceramics, Ba1-xBix(Zr0.05Ti0.95)O3, have been prepared by the conventional solid-state reaction method. The ferroelectric relaxor behaviour and dielectric properties have been investigated in detail. By XRD analysis, it is suggested that up to x = 0.04, Bi3+ substitutes A-site ion, and thereafter with higher Bi3+ content, it enters the B-site sub lattice. Substitution of Bi3+ ions induces ferroelectric relaxor behaviour and the degree of relaxation behaviour increases with bismuth concentration. The remanent polarization and strain behaviour show a slight increase with the substitution level. The degree of hysteresis (strain versus electric field) also reduces from 21.4% to 4.6% with bismuth substitution. Impedance measurements were made on the prepared sample over a wide range of temperatures (300-723 K) and frequencies (40 Hz-1 MHz), which show the presence of both bulk and grain boundary effects in the material. The bulk and grain boundary conductivities determined from impedance study indicate the Arrhenius-type thermally activated process. Impedance spectroscopy is shown to be an efficient method capable of detecting the contributions of the resistances of grains and grain boundaries to the complex impedance of a ceramic system, accurately estimating its electrical conductivity as well as its corresponding activation energies and drawing conclusions on its structural properties.

  14. Titan Casts Revealing Shadow

    NASA Astrophysics Data System (ADS)

    2004-05-01

    A rare celestial event was captured by NASA's Chandra X-ray Observatory as Titan -- Saturn's largest moon and the only moon in the Solar System with a thick atmosphere -- crossed in front of the X-ray bright Crab Nebula. The X-ray shadow cast by Titan allowed astronomers to make the first X-ray measurement of the extent of its atmosphere. On January 5, 2003, Titan transited the Crab Nebula, the remnant of a supernova explosion that was observed to occur in the year 1054. Although Saturn and Titan pass within a few degrees of the Crab Nebula every 30 years, they rarely pass directly in front of it. "This may have been the first transit of the Crab Nebula by Titan since the birth of the Crab Nebula," said Koji Mori of Pennsylvania State University in University Park, and lead author on an Astrophysical Journal paper describing these results. "The next similar conjunction will take place in the year 2267, so this was truly a once in a lifetime event." Animation of Titan's Shadow on Crab Nebula Animation of Titan's Shadow on Crab Nebula Chandra's observation revealed that the diameter of the X-ray shadow cast by Titan was larger than the diameter of its solid surface. The difference in diameters gives a measurement of about 550 miles (880 kilometers) for the height of the X-ray absorbing region of Titan's atmosphere. The extent of the upper atmosphere is consistent with, or slightly (10-15%) larger, than that implied by Voyager I observations made at radio, infrared, and ultraviolet wavelengths in 1980. "Saturn was about 5% closer to the Sun in 2003, so increased solar heating of Titan may account for some of this atmospheric expansion," said Hiroshi Tsunemi of Osaka University in Japan, one of the coauthors on the paper. The X-ray brightness and extent of the Crab Nebula made it possible to study the tiny X-ray shadow cast by Titan during its transit. By using Chandra to precisely track Titan's position, astronomers were able to measure a shadow one arcsecond in

  15. Pure Niobium as a Pressure Vessel Material

    NASA Astrophysics Data System (ADS)

    Peterson, T. J.; Carter, H. F.; Foley, M. H.; Klebaner, A. L.; Nicol, T. H.; Page, T. M.; Theilacker, J. C.; Wands, R. H.; Wong-Squires, M. L.; Wu, G.

    2010-04-01

    Physics laboratories around the world are developing niobium superconducting radio frequency (SRF) cavities for use in particle accelerators. These SRF cavities are typically cooled to low temperatures by direct contact with a liquid helium bath, resulting in at least part of the helium container being made from pure niobium. In the U.S., the Code of Federal Regulations allows national laboratories to follow national consensus pressure vessel rules or use of alternative rules which provide a level of safety greater than or equal to that afforded by ASME Boiler and Pressure Vessel Code. Thus, while used for its superconducting properties, niobium ends up also being treated as a material for pressure vessels. This report summarizes what we have learned about the use of niobium as a pressure vessel material, with a focus on issues for compliance with pressure vessel codes. We present results of a literature search for mechanical properties and tests results, as well as a review of ASME pressure vessel code requirements and issues.

  16. Effects of oral supplementation with stable strontium

    PubMed Central

    Skoryna, Stanley C.

    1981-01-01

    The biologic effects of stable strontium, a naturally occurring trace element in the diet and the body, have been little investigated. This paper discusses the effects of oral supplementation with stable strontium in laboratory studies and clinical investigations. The extent of intestinal absorption of various doses of orally administered strontium was estimated by determining serum and tissue levels with atomic absorption spectrophotometry. The central observation is that increased oral intake produces a direct increase in serum levels and intracellular uptake of strontium. The results of these studies, as well as those of other investigators, demonstrate that a moderate dosage of stable strontium does not adversely affect the level of calcium either in the serum or in soft tissues. In studies of patients receiving 1 to 1.5 g/d of strontium gluconate, a sustained increase in the serum level of strontium produced a 100-fold increase in the strontium:calcium ratio. In rats, studies indicate that an increase in intracellular strontium content following supplementation may exert a protective effect on mitochondrial structure, probably by means of a stabilizing effect of strontium on membranes. The strontium:calcium ratio in animals receiving a standard diet is higher in the cell than in the extracellular fluid; this may be of physiologic significance. An increase in density that corresponded to the deposition of stable strontium was observed in areas of bone lesions due to metastatic cancer in patients receiving stable strontium supplementation. This suggests the possibility of using strontium to mineralize osteophenic areas and to relieve bone pain. Also, because of reports of an inverse relation between the incidence of dental caries and a high strontium content in drinking water, the use of natural water containing relatively high levels of stable strontium should be considered. In each of these instances it is important to maintain a normal dietary intake of

  17. Titan's Variable Plasma Interaction

    NASA Astrophysics Data System (ADS)

    Ledvina, S. A.; Brecht, S. H.

    2015-12-01

    Cassini observations have found that the plasma and magnetic field conditions upstream of Titan are far more complex than they were thought to be after the Voyager encounter. Rymer et al., (2009) used the Cassini Plasma Spectrometer (CAPS) electron observations to classify the plasma conditions along Titan's orbit into 5 types (Plasma Sheet, Lobe, Mixed, Magnetosheath and Misc.). Nemeth et al., (2011) found that the CAPS ion observations could also be separated into the same plasma regions as defined by Rymer et al. Additionally the T-96 encounter found Titan in the solar wind adding a sixth classification. Understanding the effects of the variable upstream plasma conditions on Titan's plasma interaction and the evolution of Titan's ionosphere/atmosphere is one of the main objectives of the Cassini mission. To compliment the mission we perform hybrid simulations of Titan's plasma interaction to examine the effects of the incident plasma distribution function and the flow velocity. We closely examine the results on Titan's induced magnetosphere and the resulting pickup ion properties.

  18. The astrobiology of Titan

    NASA Astrophysics Data System (ADS)

    Raulin, F.; Coll, P.; Cabane, M.; Hebrard, E.; Israel, G.; Nguyen, M.-J.; Szopa, C.; Gpcos Team

    Largest satellite of Saturn and the only satellite in the solar system having a dense atmosphere, Titan is one of the key planetary bodies for astrobiological studies, due to several aspects: Its analogies with planet Earth, in spite of much lower temperatures, The Cassini-Huygens data have largely confirmed the many analogies between Titan and our own planet. Both have similar vertical temperature profiles, (although much colder, of course, on Titan). Both have condensable and non condensable greenhouse gases in their atmosphere. Both are geologically very active. Furthermore, the data also suggest strongly the presence of a methane cycle on Titan analogous to the water cycle on Earth. The presence of an active organic chemistry, involving several of the key compounds of prebiotic chemistry. The recent data obtained from the Huygens instruments show that the organic matter in Titan low atmosphere (stratosphere and troposphere) is mainly concentrated in the aerosol particles. Because of the vertical temperature profile in this part of the atmosphere, most of the volatile organics are probably mainly condensed on the aerosol particles. The nucleus of these particles seems to be made of complex macromolecular organic matter, well mimicked in the laboratory by the "Titan's tholins". Now, laboratory tholins are known to release many organic compounds of biological interest, such as amino acids and purine and pyrimidine bases, when they are in contact with liquid water. Such hydrolysis may have occurred on the surface of Titan, in the bodies of liquid water which episodically may form on Titan's surface from meteoritic and cometary impacts. The formation of biologically interesting compounds may also occur in the deep water ocean, from the hydrolysis of complex organic material included in the chrondritic matter accreted during the formation of Titan. The possible emergence and persistence of Life on Titan 1 All ingredients which seems necessary for Life are present on

  19. Mapping of Titan: Results from the first Titan radar passes

    USGS Publications Warehouse

    Stofan, E.R.; Lunine, J.I.; Lopes, R.; Paganelli, F.; Lorenz, R.D.; Wood, C.A.; Kirk, R.; Wall, S.; Elachi, C.; Soderblom, L.A.; Ostro, S.; Janssen, M.; Radebaugh, J.; Wye, L.; Zebker, H.; Anderson, Y.; Allison, M.; Boehmer, R.; Callahan, P.; Encrenaz, P.; Flamini, E.; Francescetti, G.; Gim, Y.; Hamilton, G.; Hensley, S.; Johnson, W.T.K.; Kelleher, K.; Muhleman, D.; Picardi, G.; Posa, F.; Roth, L.; Seu, R.; Shaffer, S.; Stiles, B.; Vetrella, S.; West, R.

    2006-01-01

    The first two swaths collected by Cassini's Titan Radar Mapper were obtained in October of 2004 (Ta) and February of 2005 (T3). The Ta swath provides evidence for cryovolcanic processes, the possible occurrence of fluvial channels and lakes, and some tectonic activity. The T3 swath has extensive areas of dunes and two large impact craters. We interpret the brightness variations in much of the swaths to result from roughness variations caused by fracturing and erosion of Titan's icy surface, with additional contributions from a combination of volume scattering and compositional variations. Despite the small amount of Titan mapped to date, the significant differences between the terrains of the two swaths suggest that Titan is geologically complex. The overall scarcity of impact craters provides evidence that the surface imaged to date is relatively young, with resurfacing by cryovolcanism, fluvial erosion, aeolian erosion, and likely atmospheric deposition of materials. Future radar swaths will help to further define the nature of and extent to which internal and external processes have shaped Titan's surface. ?? 2006 Elsevier Inc. All rights reserved.

  20. Mineral Resource of the Month: Niobium

    USGS Publications Warehouse

    Papp, John F.

    2014-01-01

    Niobium, also called columbium, is a transition metal with a very high melting point. It is in greatest demand in industrialized countries, like the United States, because of its defense-related uses in the aerospace, energy and transportation industries. Niobium is used mostly to make high-strength, low-alloy (HSLA) steel and stainless steel. HSLA steels are used in large-diameter pipes for oil and natural gas pipelines and automobile wheels.

  1. Dunelands of Titan

    NASA Image and Video Library

    2015-11-02

    Saturn's frigid moon Titan has some characteristics that are oddly similar to Earth, but still slightly alien. It has clouds, rain and lakes (made of methane and ethane), a solid surface (made of water ice), and vast dune fields (filled with hydrocarbon sands). The dark, H-shaped area seen here contains two of the dune-filled regions, Fensal (in the north) and Aztlan (to the south). Cassini's cameras have frequently monitored the surface of Titan (3200 miles or 5150 kilometers across) to look for changes in its features over the course of the mission. Any changes would help scientists better understand different phenomena like winds and dune formation on this strangely earth-like moon. For a closer view of Fensal-Aztlan, see PIA07732 . This view looks toward the leading side of Titan. North on Titan is up. The image was taken with the Cassini spacecraft narrow-angle camera on July 25, 2015 using a spectral filter sensitive to wavelengths of near-infrared light centered at 938 nanometers. The view was obtained at a distance of approximately 450,000 miles (730,000 kilometers) from Titan and at a Sun-Titan-spacecraft, or phase, angle of 32 degrees. Image scale is 3 miles (4 kilometers) per pixel. http://photojournal.jpl.nasa.gov/catalog/PIA18341

  2. Strontium and barium iodide high light yield scintillators

    NASA Astrophysics Data System (ADS)

    Cherepy, Nerine J.; Hull, Giulia; Drobshoff, Alexander D.; Payne, Stephen A.; van Loef, Edgar; Wilson, Cody M.; Shah, Kanai S.; Roy, Utpal N.; Burger, Arnold; Boatner, Lynn A.; Choong, Woon-Seng; Moses, William W.

    2008-02-01

    Europium-doped strontium and barium iodide are found to be readily growable by the Bridgman method and to produce high scintillation light yields. SrI2(Eu ) emits into the Eu2+ band, centered at 435nm, with a decay time of 1.2μs and a light yield of ˜90000photons/MeV. It offers energy resolution better than 4% full width at half maximum at 662keV, and exhibits excellent light yield proportionality. BaI2(Eu ) produces >30000photons/MeV into the Eu2+ band at 420nm (<1μs decay). An additional broad impurity-mediated recombination band is present at 550nm (>3μs decay), unless high-purity feedstock is used.

  3. Perovskite phase thin films and method of making

    DOEpatents

    Boyle, Timothy J.; Rodriguez, Mark A.

    2000-01-01

    The present invention comprises perovskite-phase thin films, of the general formula A.sub.x B.sub.y O.sub.3 on a substrate, wherein A is selected from beryllium, magnesium, calcium, strontium, and barium or a combination thereof; B is selected from niobium and tantalum or a combination thereof; and x and y are mole fractions between approximately 0.8 and 1.2. More particularly, A is strontium or barium or a combination thereof and B is niobium or tantalum or a combination thereof. Also provided is a method of making a perovskite-phase thin film, comprising combining at least one element-A-containing compound, wherein A is selected from beryllium, magnesium, calcium, strontium or barium, with at least one element-B-containing compound, wherein B niobium or tantalum, to form a solution; adding a solvent to said solution to form another solution; spin-coating the solution onto a substrate to form a thin film; and heating the film to form the perovskite-phase thin film.

  4. Niobium hyperfine structure in crystal calcium tungstate

    NASA Technical Reports Server (NTRS)

    Tseng, D. L.; Kikuchi, C.

    1972-01-01

    A study of the niobium hyperfine structure in single crystal calcium tungstate was made by the combination of the technique of electron paramagnetic resonance and electron nuclear double resonance (EPR/ENDOR). The microwave frequency was about 9.4 GHz and the radio frequency from 20MHz to 70 MHz. The rare earth ions Nd(3+), U(3+), or Tm(3+) were added as the charge compensator for Nb(5+). To create niobium paramagnetic centers, the sample was irradiated at 77 deg K with a 10 thousand curie Co-60 gamma source for 1 to 2 hours at a dose rate of 200 K rads per hour and then transferred quickly into the cavity. In a general direction of magnetic field, the spectra showed 4 sets of 10 main lines corresponding to 4 nonequivalent sites of niobium with I = 9/2. These 4 sets of lines coalesced into 2 sets of 10 in the ab-plane and into a single set of 10 along the c-axis. This symmetry suggested that the tungsten ions are substituted by the niobium ions in the crystal.

  5. Fabrication and electrochemical performance of nickel- and gadolinium-doped ceria-infiltrated La0·2Sr0·8TiO3 anodes for solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Lee, Min-Jin; Shin, Jae-Hwa; Ji, Mi-Jung; Hwang, Hae-Jin

    2018-01-01

    In this work, nickel and gadolinium-doped ceria (GDC)-infiltrated lanthanum strontium titanate (LST) anodes are fabricated, and their electrode performances under a hydrogen atmosphere is investigated in terms of the Ni:GDC ratios and cell operating temperature. The Ni/GDC-infiltrated LST anode exhibits excellent electrode performance in comparison with the Ni- or GDC-infiltrated anodes, which is attributed to the synergistic effect of an extended triple-phase boundary length by GDC and good catalytic activity for hydrogen oxidation because of the Ni particles. The polarization resistances (Rp) of Ni/GDC-infiltrated LST are 0.07, 0.08, and 0.12 Ω cm2 at 800, 750, and 700 °C, respectively, which are approximately three orders of magnitude lower than that of the LST anode (68.5 Ω cm2 at 700 °C). The effect of Ni and GDC on the electrochemical performance of LST was also investigated by using electrochemical impedance spectroscopy (EIS). The anode polarization resistance (Rp) is confirmed to be dependent on the content and dispersion state (microstructure) of the Ni and GDC nanoparticles.

  6. Niobium Doping Effects on TiO2 Mesoscopic Electron Transport Layer-Based Perovskite Solar Cells.

    PubMed

    Kim, Dong Hoe; Han, Gill Sang; Seong, Won Mo; Lee, Jin-Wook; Kim, Byeong Jo; Park, Nam-Gyu; Hong, Kug Sun; Lee, Sangwook; Jung, Hyun Suk

    2015-07-20

    Perovskite solar cells (PSCs) are the most promising candidates as next-generation solar energy conversion systems. To design a highly efficient PSC, understanding electronic properties of mesoporous metal oxides is essential. Herein, we explore the effect of Nb doping of TiO2 on electronic structure and photovoltaic properties of PSCs. Light Nb doping (0.5 and 1.0 at %) increased the optical band gap slightly, but heavy doping (5.0 at %) distinctively decreased it. The relative Fermi level position of the conduction band is similar for the lightly Nb-doped TiO2 (NTO) and the undoped TiO2 whereas that of the heavy doped NTO decreased by as much as ∼0.3 eV. The lightly doped NTO-based PSCs exhibit 10 % higher efficiency than PSCs based on undoped TiO2 (from 12.2 % to 13.4 %) and 52 % higher than the PSCs utilizing heavy doped NTO (from 8.8 % to 13.4 %), which is attributed to fast electron injection/transport and preserved electron lifetime, verified by transient photocurrent decay and impedance studies. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Two Titans

    NASA Image and Video Library

    2017-08-11

    These two views of Saturn's moon Titan exemplify how NASA's Cassini spacecraft has revealed the surface of this fascinating world. Cassini carried several instruments to pierce the veil of hydrocarbon haze that enshrouds Titan. The mission's imaging cameras also have several spectral filters sensitive to specific wavelengths of infrared light that are able to make it through the haze to the surface and back into space. These "spectral windows" have enable the imaging cameras to map nearly the entire surface of Titan. In addition to Titan's surface, images from both the imaging cameras and VIMS have provided windows into the moon's ever-changing atmosphere, chronicling the appearance and movement of hazes and clouds over the years. A large, bright and feathery band of summer clouds can be seen arcing across high northern latitudes in the view at right. These views were obtained with the Cassini spacecraft narrow-angle camera on March 21, 2017. Images taken using red, green and blue spectral filters were combined to create the natural-color view at left. The false-color view at right was made by substituting an infrared image (centered at 938 nanometers) for the red color channel. The views were acquired at a distance of approximately 613,000 miles (986,000 kilometers) from Titan. Image scale is about 4 miles (6 kilometers) per pixel. https://photojournal.jpl.nasa.gov/catalog/PIA21624

  8. Preparation and properties of plate-like titanate (PLT)/calcia-doped ceria (CDC) composites by sol-gel coating method.

    PubMed

    Liu, Xiangwen; Liu, Jingxiao; Dong, Xiaoli; Yin, Shu; Sato, Tsugio

    2009-08-01

    In order to obtain UV-shielding materials with good comfort, higher safety and effective UV-shielding ability, lepidocrocite type plate-like titanate (K(0.8)Li(0.27)Ti(1.73)O(4), donated as: PLT)/calcia-doped ceria (donated as: CDC) composites were synthesized by a sol-gel method. After dissolving Ce(NO(3))(3).6H(2)O and Ca(NO(3))(2).4H(2)O into absolute ethanol at 40 degrees C, glacial acetic acid (HAc) and PLT particles dispersed into absolute ethanol were added. Then, the solution was heated at 60 degrees C to get gel-like substance. This gel was dried in a vacuum oven at 333 K for 5 h, and then, the product was collected and ground in an agate mortar followed by calcination at 1073 K for 2 h to form PLT/CDC composites. By optimization, 20 mass% of CDC was coated by one operation. PLT/CDC composites with higher CDC content were obtained by repeating the coating process. The morphology, catalytic activity for the oxidation of organic material, UV-shielding ability and dynamic friction coefficient of as-obtained PLT/CDC composites were characterized. As a result, broad-spectrum UV-shielding composite materials with good comfort and low oxidation catalytic activity were successfully synthesized.

  9. Volumetric determination of uranium using titanous sulfate as reductant before oxidimetric titration

    USGS Publications Warehouse

    Wahlberg, James S.; Skinner, Dwight L.; Rader, Lewis F.

    1956-01-01

    A new method for determining uranium in samples containing 0.05 percent or more U3O8, using titanous sulfate as reducing agent, is much shorter, faster, and has fewer interferences than conventional methods using reductor columns. The sample is dissolved with sulfuric, nitric, perchloric, and hydrofluoric acids. Elements that would otherwise form insoluble fluorides are kept in solution by complexing the fluoride ion with boric acid. A precipitation is made with cupferron to remove interfering elements. The solution is filtered to remove the precipitated cupferrates instead of extracting them with chloroform as is usually done. Filtration is preferred to extraction because any niobium that may be in solution forms an insoluble cupferrate that may be removed by filtering but is very difficult to extract with chloroform. Excess cupferron is destroyed by oxidizing with nitric and perchloric acids, and evaporating to dense fumes of sulfuric acid. The uranium is reduced to U(IV) by the addition of titanous sulfate, with cupric sulfate used as an indicator of the completeness of the reduction. Metallic copper is formed when all the uranium is reduced. The reduced copper is then reoxidized by the addition of mercuric perchlorate, an excess of ferric sulfate added, and the solution titrated immediately with standard ceric sulfate with ferroin as an indicator. Precision of the method compared favorable with methods in common use, both for uranium ores and for most types of uranium-rich materials.

  10. Hypsometry of Titan

    NASA Astrophysics Data System (ADS)

    Lorenz, Ralph D.; Turtle, Elizabeth P.; Stiles, Bryan; Le Gall, Alice; Hayes, Alexander; Aharonson, Oded; Wood, Charles A.; Stofan, Ellen; Kirk, Randy

    2011-01-01

    Cassini RADAR topography data are used to evaluate Titan's hypsometric profile, and to make comparisons with other planetary bodies. Titan's hypsogram is unimodal and strikingly narrow compared with the terrestrial planets. To investigate topographic extremes, a novel variant on the classic hypsogram is introduced, with a logarithmic abscissa to highlight mountainous terrain. In such a plot, the top of the terrestrial hypsogram is quite distinct from those of Mars and Venus due to the 'glacial buzz-saw' that clips terrestrial topography above the snowline. In contrast to the positive skew seen in other hypsograms, with a long tail of positive relief due to mountains, there is an indication (weak, given the limited data for Titan so far) that the Titan hypsogram appears slightly negatively skewed, suggesting a significant population of unfilled depressions. Limited data permit only a simplistic comparison of Titan topography with other icy satellites but we find that the standard deviation of terrain height (albeit at different scales) is similar to those of Ganymede and Europa.

  11. The impact of nitrogen doping and reduced-niobium self-doping on the photocatalytic activity of ultra-thin Nb 3 O 8 - nanosheets

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zhou, Yannan; Wen, Ting; Kong, Weiqian

    Ultra-thin [Nb 3O 8] -nanosheets with N doping, reduced-Nb doping and N/reduced-Nb codoping were fabricated by combining chemically controlled syntheses and liquid exfoliation, which enable comparative studies on the doping effect for photocatalytic H 2evolution.

  12. SRF MATERIALS OTHER THAN NIOBIUM

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Valente, Anne-Marie

    2008-02-12

    For the past three decades, bulk niobium has been the material of choice for SRF cavity applications. Alternative materials, mainly Nb compounds and A15 compounds have been investigated with moderate effort in the past. In the recent years, RF cavity performance has approached the theoretical limit for bulk niobium. For further improvement of RF cavity performance for future accelerator projects, research interest is renewed towards alternative materials to niobium. A few laboratories around the world are now investigating superconductors with higher transition temperature Tc for application to SRF cavities. This paper gives an overview of the results obtained and challengesmore » encountered for Nb compounds and A15 compounds, as well as for MgB2, for SRF cavity applications. An interesting alternative has been recently proposed by Alex Gurevich with the Superconductor-Insulator-Superconductor multilayer approach. This could potentially lead to further improvement in RF cavity performance using the benefit of the higher critical field Hc of higher-Tc superconductors without being limited with their lower Hc1.« less

  13. Combined transuranic-strontium extraction process

    DOEpatents

    Horwitz, E. Philip; Dietz, Mark L.

    1992-01-01

    The transuranic (TRU) elements neptunium, plutonium and americium can be separated together with strontium from nitric acid waste solutions in a single process. An extractant solution of a crown ether and an alkyl(phenyl)-N,N-dialkylcarbanylmethylphosphine oxide in an appropriate diluent will extract the TRU's together with strontium, uranium and technetium. The TRU's and the strontium can then be selectively stripped from the extractant for disposal.

  14. First-principles calculations of niobium hydride formation in superconducting radio-frequency cavities

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ford, Denise C.; Cooley, Lance D.; Seidman, David N.

    Niobium hydride is suspected to be a major contributor to degradation of the quality factor of niobium superconducting radio-frequency (SRF) cavities. In this study, we connect the fundamental properties of hydrogen in niobium to SRF cavity performance and processing. We modeled several of the niobium hydride phases relevant to SRF cavities and present their thermodynamic, electronic, and geometric properties determined from calculations based on density-functional theory. We find that the absorption of hydrogen from the gas phase into niobium is exothermic and hydrogen becomes somewhat anionic. The absorption of hydrogen by niobium lattice vacancies is strongly preferred over absorption intomore » interstitial sites. A single vacancy can accommodate six hydrogen atoms in the symmetrically equivalent lowest-energy sites and additional hydrogen in the nearby interstitial sites affected by the strain field: this indicates that a vacancy can serve as a nucleation center for hydride phase formation. Small hydride precipitates may then occur near lattice vacancies upon cooling. Vacancy clusters and extended defects should also be enriched in hydrogen, potentially resulting in extended hydride phase regions upon cooling. We also assess the phase changes in the niobium-hydrogen system based on charge transfer between niobium and hydrogen, the strain field associated with interstitial hydrogen, and the geometry of the hydride phases. The results of this study stress the importance of not only the hydrogen content in niobium, but also the recovery state of niobium for the performance of SRF cavities.« less

  15. Visible-light photochemical activity of heterostructured core-shell materials composed of selected ternary titanates and ferrites coated by tiO2.

    PubMed

    Li, Li; Liu, Xuan; Zhang, Yiling; Nuhfer, Noel T; Barmak, Katayun; Salvador, Paul A; Rohrer, Gregory S

    2013-06-12

    Heterostructured photocatalysts comprised of microcrystalline (mc-) cores and nanostructured (ns-) shells were prepared by the sol-gel method. The ability of titania-coated ATiO3 (A = Fe, Pb) and AFeO3 (A = Bi, La, Y) catalysts to degrade methylene blue in visible light (λ > 420 nm) was compared. The catalysts with the titanate cores had enhanced photocatalytic activities for methylene blue degradation compared to their components alone, whereas the catalysts with ferrite cores did not. The temperature at which the ns-titania shell is crystallized influences the photocatalytic dye degradation. mc-FeTiO3/ns-TiO2 annealed at 500 °C shows the highest reaction rate. Fe-doped TiO2, which absorbs visible light, did not show enhanced photocatalytic activity for methylene blue degradation. This result indicates that iron contamination is not a decisive factor in the reduced reactivity of the titania coated ferrite catalysts. The higher reactivity of materials with the titanate cores suggests that photogenerated charge carriers are more easily transported across the titanate-titanate interface than the ferrite-titanate interface and this provides guidance for materials selection in composite catalyst design.

  16. Titanic Weather Forecasting

    NASA Astrophysics Data System (ADS)

    2004-04-01

    New Detailed VLT Images of Saturn's Largest Moon Optimizing space missions Titan, the largest moon of Saturn was discovered by Dutch astronomer Christian Huygens in 1655 and certainly deserves its name. With a diameter of no less than 5,150 km, it is larger than Mercury and twice as large as Pluto. It is unique in having a hazy atmosphere of nitrogen, methane and oily hydrocarbons. Although it was explored in some detail by the NASA Voyager missions, many aspects of the atmosphere and surface still remain unknown. Thus, the existence of seasonal or diurnal phenomena, the presence of clouds, the surface composition and topography are still under debate. There have even been speculations that some kind of primitive life (now possibly extinct) may be found on Titan. Titan is the main target of the NASA/ESA Cassini/Huygens mission, launched in 1997 and scheduled to arrive at Saturn on July 1, 2004. The ESA Huygens probe is designed to enter the atmosphere of Titan, and to descend by parachute to the surface. Ground-based observations are essential to optimize the return of this space mission, because they will complement the information gained from space and add confidence to the interpretation of the data. Hence, the advent of the adaptive optics system NAOS-CONICA (NACO) [1] in combination with ESO's Very Large Telescope (VLT) at the Paranal Observatory in Chile now offers a unique opportunity to study the resolved disc of Titan with high sensitivity and increased spatial resolution. Adaptive Optics (AO) systems work by means of a computer-controlled deformable mirror that counteracts the image distortion induced by atmospheric turbulence. It is based on real-time optical corrections computed from image data obtained by a special camera at very high speed, many hundreds of times each second (see e.g. ESO Press Release 25/01 , ESO PR Photos 04a-c/02, ESO PR Photos 19a-c/02, ESO PR Photos 21a-c/02, ESO Press Release 17/02, and ESO Press Release 26/03 for earlier NACO

  17. Three-dimensional micro electromechanical system piezoelectric ultrasound transducer

    NASA Astrophysics Data System (ADS)

    Hajati, Arman; Latev, Dimitre; Gardner, Deane; Hajati, Azadeh; Imai, Darren; Torrey, Marc; Schoeppler, Martin

    2012-12-01

    Here we present the design and experimental acoustic test data for an ultrasound transducer technology based on a combination of micromachined dome-shaped piezoelectric resonators arranged in a flexible architecture. Our high performance niobium-doped lead zirconate titanate film is implemented in three-dimensional dome-shaped structures, which form the basic resonating cells. Adjustable frequency response is realized by mixing these basic cells and modifying their dimensions by lithography. Improved characteristics such as high sensitivity, adjustable wide-bandwidth frequency response, low transmit voltage compatible with ordinary integrated circuitry, low electrical impedance well matched to coaxial cabling, and intrinsic acoustic impedance match to water are demonstrated.

  18. Strontium (Sr) separation from seawater using titanate adsorbents: Effects of seawater matrix ions on Sr sorption behavior

    NASA Astrophysics Data System (ADS)

    Ryu, Jungho; Hong, Hye-jin; Ryu, Taegong; Park, In-Su

    2017-04-01

    Strontium (Sr) which has many industrial applications such as ferrite magnet, ceramic, and fire works exists in seawater with the concentration of approximately 7 mg/L. In previous report estimating economic potential on recovery of various elements from seawater in terms of their commercial values and concentrations in seawater, Sr locates upper than approximate break-even line, which implies Sr recovery from seawater can be potentially profitable. Recently, Sr separation from seawater has received great attention in the environmental aspect after Fukushima Nuclear Power Plant (NPP) accident which released much amount of radioactive Sr and Cs. Accordingly, the efficient separation of radioactive elements released to seawater has become critical as an important technological need as well as their removal from radioactive wastes. So far, it has been introduced to separate Sr from aqueous media by various methods including solvent extraction, adsorption by solid materials, and ion exchange. Among them, the adsorption technique using solid adsorbents is of great interest for selectively separating Sr from seawater with respect to low concentration level of Sr. In this study, we synthesized titanate nanotube (TiNT) by simple hydrothermal reaction, characterized its physicochemical properties, and systematically evaluated Sr sorption behavior under various reaction conditions corresponding to seawater environment. The synthesized TiNT exhibited the fibril-type nanotube structure with high specific surface area of 260 m2/g. The adsorption of Sr on TiNT rapidly occurred following pseudo-second-order kinetic model, and was in good agreement with Langmuir isotherm model, indicating maximum adsorption capacity of 97 mg/g. Based on Sr uptake and Na release with stoichiometric balance, sorption mechanism of Sr on TiNT was found to be ion-exchange between Na in TiNT lattice and Sr in solution phase, which was also confirmed by XRD and Raman analysis. Among competitive ions, Ca

  19. Combined transuranic-strontium extraction process

    DOEpatents

    Horwitz, E.P.; Dietz, M.L.

    1992-12-08

    The transuranic (TRU) elements neptunium, plutonium and americium can be separated together with strontium from nitric acid waste solutions in a single process. An extractant solution of a crown ether and an alkyl(phenyl)-N,N-dialkylcarbanylmethylphosphine oxide in an appropriate diluent will extract the TRU's together with strontium, uranium and technetium. The TRU's and the strontium can then be selectively stripped from the extractant for disposal. 3 figs.

  20. Lakes on Titan

    NASA Image and Video Library

    2006-07-24

    The Cassini spacecraft, using its radar system, has discovered very strong evidence for hydrocarbon lakes on Titan. Dark patches, which resemble terrestrial lakes, seem to be sprinkled all over the high latitudes surrounding Titan north pole

  1. A niobium oxide-tantalum oxide selector-memristor self-aligned nanostack

    NASA Astrophysics Data System (ADS)

    Diaz Leon, Juan J.; Norris, Kate J.; Yang, J. Joshua; Sevic, John F.; Kobayashi, Nobuhiko P.

    2017-03-01

    The integration of nonlinear current-voltage selectors and bi-stable memristors is a paramount step for reliable operation of crossbar arrays. In this paper, the self-aligned assembly of a single nanometer-scale device that contains both a selector and a memristor is presented. The two components (i.e., selector and memristor) are vertically assembled via a self-aligned fabrication process combined with electroforming. In designing the device, niobium oxide and tantalum oxide are chosen as materials for selector and memristor, respectively. The formation of niobium oxide is visualized by exploiting the self-limiting reaction between niobium and tantalum oxide; crystalline niobium (di)oxide forms at the interface between metallic niobium and tantalum oxide via electrothermal heating, resulting in a niobium oxide selector self-aligned to a tantalum oxide memristor. A steady-state finite element analysis is used to assess the electrothermal heating expected to occur in the device. Current-voltage measurements and structural/chemical analyses conducted for the virgin device, the electroforming process, and the functional selector-memristor device are presented. The demonstration of a self-aligned, monolithically integrated selector-memristor device would pave a practical pathway to various circuits based on memristors attainable at manufacturing scales.

  2. Cryovolcanic features on Titan's surface as revealed by the Cassini Titan Radar Mapper

    USGS Publications Warehouse

    Lopes, R.M.C.; Mitchell, K.L.; Stofan, E.R.; Lunine, J.I.; Lorenz, R.; Paganelli, F.; Kirk, R.L.; Wood, C.A.; Wall, S.D.; Robshaw, L.E.; Fortes, A.D.; Neish, Catherine D.; Radebaugh, J.; Reffet, E.; Ostro, S.J.; Elachi, C.; Allison, M.D.; Anderson, Y.; Boehmer, R.; Boubin, G.; Callahan, P.; Encrenaz, P.; Flamini, E.; Francescetti, G.; Gim, Y.; Hamilton, G.; Hensley, S.; Janssen, M.A.; Johnson, W.T.K.; Kelleher, K.; Muhleman, D.O.; Ori, G.; Orosei, R.; Picardi, G.; Posa, F.; Roth, L.E.; Seu, R.; Shaffer, S.; Soderblom, L.A.; Stiles, B.; Vetrella, S.; West, R.D.; Wye, L.; Zebker, H.A.

    2007-01-01

    The Cassini Titan Radar Mapper obtained Synthetic Aperture Radar images of Titan's surface during four fly-bys during the mission's first year. These images show that Titan's surface is very complex geologically, showing evidence of major planetary geologic processes, including cryovolcanism. This paper discusses the variety of cryovolcanic features identified from SAR images, their possible origin, and their geologic context. The features which we identify as cryovolcanic in origin include a large (180 km diameter) volcanic construct (dome or shield), several extensive flows, and three calderas which appear to be the source of flows. The composition of the cryomagma on Titan is still unknown, but constraints on rheological properties can be estimated using flow thickness. Rheological properties of one flow were estimated and appear inconsistent with ammonia-water slurries, and possibly more consistent with ammonia-water-methanol slurries. The extent of cryovolcanism on Titan is still not known, as only a small fraction of the surface has been imaged at sufficient resolution. Energetic considerations suggest that cryovolcanism may have been a dominant process in the resurfacing of Titan. ?? 2006 Elsevier Inc.

  3. The effect of strontium and barium doping on perovskite-structured energy materials for photovoltaic applications

    NASA Astrophysics Data System (ADS)

    Wu, Ming-Chung; Chen, Wei-Cheng; Chan, Shun-Hsiang; Su, Wei-Fang

    2018-01-01

    Perovskite solar cell is a novel photovoltaic technology with the superior progress in efficiency and the simple solution processes. Develop lead-free or lead-reduced perovskite materials is a significant concern for high-performance perovskite solar cell. Among the alkaline earth metals, the Sr2+ and Ba2+ are suitable for Pb2+ replacement in perovskite film due to fitting Goldschmidt's tolerance factor. In this study, we adopted Ba-doped and Sr-doped perovskite structured materials with different doping levels, including 1.0, 5.0, and 10.0 mol%, to prepare perovskite solar cells. Both Ba-doped and Sr-doped perovskite structured materials have a related tendency in absorption behavior and surface morphology. At 10.0 mol% doping level, the power conversion efficiency (PCE) of Sr-doped perovskite solar cells is only ∼0.5%, but the PCE of Ba-doped perovskite solar cells can be achieved to ∼9.7%. Ba-doped perovskite solar cells showed the acceptable photovoltaic characteristics than Sr-doped perovskite solar cells. Ba dopant can partially replace the amount of lead in the perovskite solar cells, and it could be a potential candidate in the field of lead-free or lead-reduced perovskite energy materials.

  4. Phase stability and processing of strontium and magnesium doped lanthanum gallate

    NASA Astrophysics Data System (ADS)

    Zheng, Feng

    Fuel Cells are one of the most promising energy transformers with respect to ecological and environmental issues. Solid Oxide Fuel Cells (SOFC) are all solid-state devices. One of the challenges to improve a SOFC is to lower the operating temperature while maintaining or increasing its output voltage. Undoped LaGaO3 is an insulator, doping transforms it into an oxygen-ionic conductor. Sr and Mg doped LaGaO3 (LSGM) perovskite is a new oxygen-ionic conductor with higher conductivity than yttria-stabilized zirconia (YSZ). This material is a candidate for a wide variety of electrochemical devices. In order to realize this potential, the phase stability and processing of this material needs to be investigated in detail. In this study, a systematic investigation of the LSGM materials in terms of phase stability, phase transition, sintering, microstructure and electrical conductivity as functions of temperature, doping content and A/B cation ratio has been carried out. The generalized formula of the materials investigated is (La1--xSrx)A(Ga1--yMg y)BO3--delta. Optimized processing parameters have been obtained by investigating their impact on density change and microstructure. Consequently, a suitable compositional window of the LSGM perovskite has been identified for SOFC electrolyte applications. Based on detailed diffraction analysis, it is found that the undoped LaGaO3 takes on the orthorhombic (Pbnm) symmetry at room temperature. This structure changes to rhombohedral (R3c) at 147 +/- 2°C or changes to monoclinic (I2/a) when the doping level increases from 0.1 to 0.2 moles. We have optimized the compositional window to make the single perovskite phase with high oxygen ionic conductivity (x = 0.10 to 0.20 with A/B ratio between 0.98 to 1.02). The best processing condition, starting from glycine nitrate process (GNP) combustion synthesized ultra-fine LSGM powder, is sintering in air at 1500°C for 2 hours. The doped material has higher oxygen ionic conductivity than

  5. Superconducting structure with layers of niobium nitride and aluminum nitride

    DOEpatents

    Murduck, James M.; Lepetre, Yves J.; Schuller, Ivan K.; Ketterson, John B.

    1989-01-01

    A superconducting structure is formed by depositing alternate layers of aluminum nitride and niobium nitride on a substrate. Deposition methods include dc magnetron reactive sputtering, rf magnetron reactive sputtering, thin-film diffusion, chemical vapor deposition, and ion-beam deposition. Structures have been built with layers of niobium nitride and aluminum nitride having thicknesses in a range of 20 to 350 Angstroms. Best results have been achieved with films of niobium nitride deposited to a thickness of approximately 70 Angstroms and aluminum nitride deposited to a thickness of approximately 20 Angstroms. Such films of niobium nitride separated by a single layer of aluminum nitride are useful in forming Josephson junctions. Structures of 30 or more alternating layers of niobium nitride and aluminum nitride are useful when deposited on fixed substrates or flexible strips to form bulk superconductors for carrying electric current. They are also adaptable as voltage-controlled microwave energy sources.

  6. Ferromagnetism induced by entangled charge and orbital orderings in ferroelectric titanate perovskites

    PubMed Central

    Bristowe, N. C.; Varignon, J.; Fontaine, D.; Bousquet, E.; Ghosez, Ph.

    2015-01-01

    In magnetic materials, the Pauli exclusion principle typically drives anti-alignment between electron spins on neighbouring species resulting in antiferromagnetic behaviour. Ferromagnetism exhibiting spontaneous spin alignment is a fairly rare behaviour, but once materialized is often associated with itinerant electrons in metals. Here we predict and rationalize robust ferromagnetism in an insulating oxide perovskite structure based on the popular titanate series. In half-doped layered titanates, the combination of Jahn–Teller and oxygen breathing motions opens a band gap and creates an unusual charge and orbital ordering of the Ti d electrons. It is argued that this intriguingly intricate electronic network favours the elusive inter-site ferromagnetic (FM) ordering, on the basis of intra-site Hund's rules. Finally, we find that the layered oxides are also ferroelectric with a spontaneous polarization approaching that of BaTiO3. The concepts are general and design principles of the technologically desirable FM ferroelectric multiferroics are presented. PMID:25807180

  7. Effect of vanadium doping on the properties of high Curie point ferroelectric strontium niobate ceramic

    NASA Astrophysics Data System (ADS)

    Ning, Huanpo

    2017-10-01

    Different levels of isovalent dopant vanadium were doped on the B site of Sr2Nb2O7 to explore the doping effect on its dielectric and ferroelectric properties. A second phase could be detected with above 1 mol% V2O5 doping. The grains after doping remained anisotropic and plate-like. The samples are not dense, as there are pores present at the grain boundaries. The corrected dielectric constant for 0.1 mol%, 0.2 mol%, and 0.3 mol% V doped SNO at 1 MHz is around 46, 48 and 49, respectively, which indicates the effect of V doping on the increase of dielectric constant of SNO (ɛr is about 40 at 1 MHz). The Curie point Tc increased with the increase in the V doping level. The relatively high d33 (2.3 pC/N) measured from the non-dense and untextured samples indicates the potential effect of V2O5 doping on the improvement of piezoelectricity of SNO.

  8. Titan's impact history

    NASA Astrophysics Data System (ADS)

    Zahnle, Kevin

    2010-04-01

    Impacts play a major role in the growth and evolution of planets, satellites, and other nameless things. Titan is no exception. This talk will address a subset of the following topics: (i) The modern impact rate is constrained by the population of Centaurs and the impact rate at Jupiter. (ii) Titan's thick atmosphere and volatile surface cause it to respond to major impacts in an Earth-like manner. The impact that made Menrva - the 440 km diameter impact basin sited near the current apex of Titan's motion - was big enough to raise the average global surface temperature above 273 K, which suggests that water rain was possible. This would have been followed by methane drizzles lasting for thousands of years. More modest impacts will generate crater lakes and will saturate the atmosphere with methane, the latter leading to hundreds of years of intermittent drizzle. (iii) Impact ejecta from Menrva will strike Hyperion and should saturate the latter with sesquinary craters. (iv) In any modern story of how Titan got its atmosphere, solar nebular condensates (comets) deliver the volatiles. A consequence of a cometogenic atmosphere is that the atmosphere is heavily processed by strong shocks. The high temperatures produce a wide range of chemical species that would not otherwise be abundant. Some of these will survive to mix into the atmosphere (e.g., CO) or freeze out to fall to the surface (e.g. CO2). (v) That Titan even has an atmosphere, when Callisto and Ganymede do not, is an excellent question. The leading explanation is that Titan alone was made from ammonia - and methane - rich stuff. But the competition between impact delivery and impact expulsion of volatiles can strongly favor Titan over Callisto. Stable isotopes as well as total volatile inventories provide constraints.

  9. Mechanical properties of niobium radio-frequency cavities

    DOE PAGES

    Ciovati, Gianluigi; Dhakal, Pashupati; Matalevich, Joseph R.; ...

    2015-07-02

    Radio-frequency cavities made of bulk niobium are one of the components used in modern particle accelerators. The mechanical stability is an important aspect of cavity design, which typically relies on finite-element analysis simulations using material properties from tensile tests on sample. This contribution presents the results of strain and resonant frequency measurements as a function of a uniform pressure up to 722 kPa, applied to single-cell niobium cavities with different crystallographic structure, purity and treatments. In addition, burst tests of high-purity multi-cell cavities with different crystallographic structure have been conducted up to the tensile strength of the material. Finite-element analysismore » of the single-cell cavity geometry is in good agreement with the observed behavior in the elastic regime assuming a Young's modulus value of 88.5 GPa and a Poisson's ratio of 0.4, regardless of crystallographic structure, purity or treatment. However, the measured yield strength and tensile strength depend on crystallographic structure, material purity and treatment. In particular, the results from this study show that the mechanical properties of niobium cavities with large crystals are comparable to those of cavities made of fine-grain niobium.« less

  10. Separation of strontium from fecal matter

    DOEpatents

    Kester, Dianne K.

    1995-01-01

    A method of separating strontium from a sample of biomass potentially contaminated with various radionuclides. After the sample is reduced, dissociated, and carried on a first precipitate of actinides, the first precipitate is removed to leave a supernate. Next, oxalic acid is added to the supernate to cause a second precipitate of strontium and calcium. Then, after separating the second precipitate, nitric acid is added to the second precipitate to cause a third precipitate of strontium. The calcium remains in solution and is discarded to leave essentially the precipitate of strontium.

  11. Separation of strontium from fecal matter

    DOEpatents

    Kester, D.K.

    1995-01-03

    A method is presented of separating strontium from a sample of biomass potentially contaminated with various radionuclides. After the sample is reduced, dissociated, and carried on a first precipitate of actinides, the first precipitate is removed to leave a supernate. Next, oxalic acid is added to the supernate to cause a second precipitate of strontium and calcium. Then, after separating the second precipitate, nitric acid is added to the second precipitate to cause a third precipitate of strontium. The calcium remains in solution and is discarded to leave essentially the precipitate of strontium.

  12. Strontium doping promotes bioactivity of rhBMP-2 upon calcium phosphate cement via elevated recognition and expression of BMPR-IA.

    PubMed

    Huang, Baolin; Tian, Yu; Zhang, Wenjing; Ma, Yifan; Yuan, Yuan; Liu, Changsheng

    2017-11-01

    Preserving and improving osteogenic activity of bone morphogenetic protein-2 (BMP-2) upon implants remains one of the key limitations in bone regeneration. With calcium phosphate cement (CPC) as model, we have developed a series of strontium (Sr)-doped CPC (SCPC) to address this issue. The effects of fixed Sr on the bioactivity of recombinant human BMP-2 (rhBMP-2) as well as the underlying mechanism were investigated. The results suggested that the rhBMP-2-induced osteogenic activity was significantly promoted upon SCPCs, especially with a low amount of fixed Sr (SrCO 3 content <10wt%). Further studies demonstrated that the Sr-induced enhancement of bioactivity of rhBMP-2 was related to an elevated recognition of bone morphogenetic protein receptor-IA (BMPR-IA) to rhBMP-2 and an increased expression of BMPR-IA in C2C12 model cells. As a result, the activations of BMP-induced signaling pathways were different in C2C12 cells incubated upon CPC/rhBMP-2 and SCPCs/rhBMP-2. These findings explicitly decipher the mechanism of SCPCs promoting osteogenic bioactivity of rhBMP-2 and signify the promising application of the SCPCs/rhBMP-2 matrix in bone regeneration implants. Copyright © 2017 Elsevier B.V. All rights reserved.

  13. Superconducting structure with layers of niobium nitride and aluminum nitride

    DOEpatents

    Murduck, J.M.; Lepetre, Y.J.; Schuller, I.K.; Ketterson, J.B.

    1989-07-04

    A superconducting structure is formed by depositing alternate layers of aluminum nitride and niobium nitride on a substrate. Deposition methods include dc magnetron reactive sputtering, rf magnetron reactive sputtering, thin-film diffusion, chemical vapor deposition, and ion-beam deposition. Structures have been built with layers of niobium nitride and aluminum nitride having thicknesses in a range of 20 to 350 Angstroms. Best results have been achieved with films of niobium nitride deposited to a thickness of approximately 70 Angstroms and aluminum nitride deposited to a thickness of approximately 20 Angstroms. Such films of niobium nitride separated by a single layer of aluminum nitride are useful in forming Josephson junctions. Structures of 30 or more alternating layers of niobium nitride and aluminum nitride are useful when deposited on fixed substrates or flexible strips to form bulk superconductors for carrying electric current. They are also adaptable as voltage-controlled microwave energy sources. 8 figs.

  14. International strategic minerals inventory summary report; niobium (columbium) and tantalum

    USGS Publications Warehouse

    Crockett, R.N.; Sutphin, D.M.

    1993-01-01

    Major world resources of niobium and tantalum are described in this summary report of information in the International Strategic Minerals Inventory (ISMI). ISMI is a cooperative data-collection effort of earth-science and mineral-resource agencies in Australia, Canada, the Federal Republic of Germany, the Republic of South Africa, the United Kingdom, and the United States of America. Part I of this report presents an overview of the resources and potential supply of niobium and tantalum based on inventory information; Part II contains tables of both geologic and mineral-resource information and includes production data collected by ISMI participants. Niobium is used principally as an alloying element in special steels and superalloys, and tantalum is used mainly in electronics. Minerals in the columbite-tantalite series are principal ore minerals of niobium and tantalum. Pyrochlore is a principal source of niobium. These minerals are found in carbonatite, certain rocks in alkaline igneous complexes, pegmatite, and placer deposits. ISMI estimates show that there are over 7 million metric tons of niobium and almost 0.5 million metric tons of tantalum in known deposits, outside of China and the former Soviet Union, for which reliable estimates have been made. Brazilian deposits, followed by Canadian deposits, contain by far the largest source of niobium. Tantalum production is spread widely among several countries, and Brazil and Canada are the most significant of these producers. Brazil's position is further strengthened by potential byproduct columbite from tin mining. Present economically exploitable resources of niobium appear to be sufficient for the near future, but Brazil will continue to be the predominant world supplier of ferrocolumbium. Tantalum, a byproduct of tin production, has been captive to the fluctuations of that market, but resources in pegmatite in Canada and Australia make it likely that future increases in the present modest demand will be met.

  15. Transition from Reconstruction toward Thin Film on the (110) Surface of Strontium Titanate

    PubMed Central

    2016-01-01

    The surfaces of metal oxides often are reconstructed with a geometry and composition that is considerably different from a simple termination of the bulk. Such structures can also be viewed as ultrathin films, epitaxed on a substrate. Here, the reconstructions of the SrTiO3 (110) surface are studied combining scanning tunneling microscopy (STM), transmission electron diffraction, and X-ray absorption spectroscopy (XAS), and analyzed with density functional theory calculations. Whereas SrTiO3 (110) invariably terminates with an overlayer of titania, with increasing density its structure switches from n × 1 to 2 × n. At the same time the coordination of the Ti atoms changes from a network of corner-sharing tetrahedra to a double layer of edge-shared octahedra with bridging units of octahedrally coordinated strontium. This transition from the n × 1 to 2 × n reconstructions is a transition from a pseudomorphically stabilized tetrahedral network toward an octahedral titania thin film with stress-relief from octahedral strontia units at the surface. PMID:26954064

  16. Transition from reconstruction toward thin film on the (110) surface of strontium titanate

    DOE PAGES

    Wang, Z.; Loon, A.; Subramanian, A.; ...

    2016-03-08

    The surfaces of metal oxides often are reconstructed with a geometry and composition that is considerably different from a simple termination of the bulk. Such structures can also be viewed as ultrathin films, epitaxed on a substrate. Here, the reconstructions of the SrTiO 3 (110) surface are studied combining scanning tunneling microscopy (STM), transmission electron diffraction, and X-ray absorption spectroscopy (XAS), and analyzed with density functional theory calculations. Whereas SrTiO 3 (110) invariably terminates with an overlayer of titania, with increasing density its structure switches from n × 1 to 2 × n. At the same time the coordination ofmore » the Ti atoms changes from a network of corner-sharing tetrahedra to a double layer of edge-shared octahedra with bridging units of octahedrally coordinated strontium. Furthermore, this transition from the n × 1 to 2 × n reconstructions is a transition from a pseudomorphically stabilized tetrahedral network toward an octahedral titania thin film with stress-relief from octahedral strontia units at the surface.« less

  17. Surface processing for bulk niobium superconducting radio frequency cavities

    NASA Astrophysics Data System (ADS)

    Kelly, M. P.; Reid, T.

    2017-04-01

    The majority of niobium cavities for superconducting particle accelerators continue to be fabricated from thin-walled (2-4 mm) polycrystalline niobium sheet and, as a final step, require material removal from the radio frequency (RF) surface in order to achieve performance needed for use as practical accelerator devices. More recently bulk niobium in the form of, single- or large-grain slices cut from an ingot has become a viable alternative for some cavity types. In both cases the so-called damaged layer must be chemically etched or electrochemically polished away. The methods for doing this date back at least four decades, however, vigorous empirical studies on real cavities and more fundamental studies on niobium samples at laboratories worldwide have led to seemingly modest improvements that, when taken together, constitute a substantial advance in the reproducibility for surface processing techniques and overall cavity performance. This article reviews the development of niobium cavity surface processing, and summarizes results of recent studies. We place some emphasis on practical details for real cavity processing systems which are difficult to find in the literature but are, nonetheless, crucial for achieving the good and reproducible cavity performance. New approaches for bulk niobium surface treatment which aim to reduce cost or increase performance, including alternate chemical recipes, barrel polishing and ‘nitrogen doping’ of the RF surface, continue to be pursued and are closely linked to the requirements for surface processing.

  18. Titan's highly variable plasma environment

    NASA Astrophysics Data System (ADS)

    Wolf, D. A.; Neubauer, F. M.

    1982-02-01

    It is noted that Titan's plasma environment is variable for two reasons. The variability of the solar wind is such that Titan may be located in the outer magnetosphere, the magnetosheath, or the interplanetary medium around noon Saturnian local time. What is more, there are local time variations in Saturn's magnetosphere. The location of the stagnation point of Saturn's magnetosphere is calculated, assuming a terrestrial type magnetosphere. Characteristic plasma parameters along the orbit of Titan are shown for high solar wind pressure. During crossings of the Saturnian magnetopause or bow shock by Titan, abrupt changes in the flow direction and stagnation pressure are expected, as are rapid associated changes in Titan's uppermost atmosphere.

  19. Titan's organic chemistry

    NASA Technical Reports Server (NTRS)

    Sagan, C.; Thompson, W. R.; Khare, B. N.

    1985-01-01

    Voyager discovered nine simple organic molecules in the atmosphere of Titan. Complex organic solids, called tholins, produced by irradiation of the simulated Titanian atmosphere, are consistent with measured properties of Titan from ultraviolet to microwave frequencies and are the likely main constituents of the observed red aerosols. The tholins contain many of the organic building blocks central to life on earth. At least 100-m, and possibly kms thicknesses of complex organics have been produced on Titan during the age of the solar system, and may exist today as submarine deposits beneath an extensive ocean of simple hydrocarbons.

  20. Giant energy density and high efficiency achieved in bismuth ferrite-based film capacitors via domain engineering.

    PubMed

    Pan, Hao; Ma, Jing; Ma, Ji; Zhang, Qinghua; Liu, Xiaozhi; Guan, Bo; Gu, Lin; Zhang, Xin; Zhang, Yu-Jun; Li, Liangliang; Shen, Yang; Lin, Yuan-Hua; Nan, Ce-Wen

    2018-05-08

    Developing high-performance film dielectrics for capacitive energy storage has been a great challenge for modern electrical devices. Despite good results obtained in lead titanate-based dielectrics, lead-free alternatives are strongly desirable due to environmental concerns. Here we demonstrate that giant energy densities of ~70 J cm -3 , together with high efficiency as well as excellent cycling and thermal stability, can be achieved in lead-free bismuth ferrite-strontium titanate solid-solution films through domain engineering. It is revealed that the incorporation of strontium titanate transforms the ferroelectric micro-domains of bismuth ferrite into highly-dynamic polar nano-regions, resulting in a ferroelectric to relaxor-ferroelectric transition with concurrently improved energy density and efficiency. Additionally, the introduction of strontium titanate greatly improves the electrical insulation and breakdown strength of the films by suppressing the formation of oxygen vacancies. This work opens up a feasible and propagable route, i.e., domain engineering, to systematically develop new lead-free dielectrics for energy storage.

  1. Determination of niobium in rocks by an isotope dilution spectrophotometric method

    USGS Publications Warehouse

    Greenland, L.P.; Campbell, E.Y.

    1970-01-01

    Rocks and minerals are fused with sodium peroxide in the presence of carrierfree 95Nb. The fusion cake is leached with water and the precipitate dissolved in hydrofluoric-sulfuric acid mixture. Niobium is extracted into methyl isobutyl ketone and further purified by ion exchange. The amount of niobium is determined spectrophotometrically with 4-(2-pyridylazo)-resorcinol, and the chemical yield of the separations determined by counting 95Nb. This procedure is faster and less sensitive to interferences than previously proposed methods for determining niobium in rocks.The high purity of the separated niobium makes the method applicable to nearly all matrices. ?? 1970.

  2. STIR: Novel Electronic States by Gating Strongly Correlated Materials

    DTIC Science & Technology

    2016-03-01

    plan built on my group’s recent demonstration of electrolyte gating in Strontium Titanate, using an atomically thin hexagonal Boron Nitride barrier to...demonstration of electrolyte gating in Strontium Titanate, using an atomically thin hexagonal Boron Nitride barrier to prevent disorder and chemical...techniques and learned to apply thin hexagonal Boron Nitride to single crystals of materials expected to show some of the most exciting correlated

  3. Crystallography and Morphology of Niobium Carbide in As-Cast HP-Niobium Reformer Tubes

    NASA Astrophysics Data System (ADS)

    Buchanan, Karl G.; Kral, Milo V.

    2012-06-01

    The microstructures of two as-cast heats of niobium-modified HP stainless steels were characterized. Particular attention was paid to the interdendritic niobium-rich carbides formed during solidification of these alloys. At low magnifications, these precipitates are grouped in colonies of similar lamellae. Higher magnifications revealed that the lamellae actually obtain two distinct morphologies. The type I morphology exhibits broad planar interfaces with a smooth platelike shape. Type II lamellae have undulating interfaces and an overall reticulated shape. To provide further insight into the origin of these two different morphologies, the microstructure and crystallography of each have been studied in detail using high resolution scanning electron microscopy, transmission electron microscopy, various electron diffraction methods (electron backscatter diffraction (EBSD), selected area diffraction (SAD), and convergent beam electron diffraction (CBED)), and energy dispersive X-ray spectroscopy.

  4. Removal of Strontium from Drinking Water by Conventional ...

    EPA Pesticide Factsheets

    The United States Environmental Protection Agency Contaminant Candidate List 3 lists strontium as a contaminant for potential regulatory consideration in drinking water. There is very little data available on strontium removal from drinking water. As a result, there is an immediate need to perform treatment studies. The objective of this work is to evaluate the effectiveness of conventional and lime-soda ash softening treatments to remove strontium from surface and ground waters. Conventional drinking water treatment with aluminum and iron coagulants were able to achieve 12% and 5.9% strontium removal at best, while lime softening removed as much as 78% from natural strontium-containing ground water. Systematic fundamental experiments showed that strontium removal during the lime-soda ash softening was related to pH, calcium concentration and dissolved inorganic carbon concentration. Final strontium concentration was also directly associated with initial strontium concentration. Precipitated solids showed well-formed crystals or agglomerates of mixed solids, two polymorphs of calcium carbonate (vaterite and calcite), and strontianite, depending on initial water quality conditions. X-ray diffraction analysis suggested that strontium likely replaced calcium inside the crystal lattice and was likely mainly responsible for removal during lime softening. To inform the public.

  5. Cassini/Huygens Investigations of Titan's Methane Cycle

    NASA Astrophysics Data System (ADS)

    Griffith, C. A.; Penteado, P.

    2008-12-01

    In Titan's atmosphere, the second most abundant constituent, methane, exists as a gas, liquid and solid, and cycles between the atmosphere and surface. Similar to Earth's hydrological cycle, Titan sports clouds, rain, and lakes. Yet, Titan's cycle differs dramatically from its terrestrial counterpart, and reveals the workings of weather in an atmosphere that is ten times thicker than Earth's atmosphere, that is two orders of magnitude less illuminated, and that involves a different condensable. Measurements of Titan's troposphere, where the methane cycle plays out, are limited largely to spectral images of Titan's clouds, several temperature profiles by Voyager, Huygens and Cassini, recent Keck spectra of the surface methane humidity, and one vertical profile of Titan's methane abundance, measured on a summer afternoon in Titan's tropical atmosphere by the Huygens probe. The salient features of Titan's methane cycle are distinctly alien: clouds have predominated the northern and southern polar atmospheres; the one humidity profile precisely matches the profile (of cartoonish simplicity) used in pre-Cassini models, and surface features correlate with latitude. Data of Titan's troposphere are analyzed with thermodynamic and radiative transfer calculations, and synthesized with other studies of Titan's stratosphere and surface, to investigate the workings of Titan's methane cycle. At the end of Cassini's nominal mission, we find that Titan's weather, climate and surface-to-atmosphere exchange of volatiles vastly differs from the manifestation of these processes on Earth, largely as a result of different basic characteristics of these planetary bodies. The talk ends with a comparison between Titan and Earth's tropospheres, their fundamental properties, the energetics of their condensible cycles, their weather and climates. References: Griffith C.A. et al. Titan's Tropical Storms in an Evolving Atmosphere. Ap.J. In Press (2008). Griffith C.A. Storms, Polar Deposits, and

  6. Highlighting Titan's Hazes

    NASA Image and Video Library

    2017-08-11

    NASA's Cassini spacecraft looks toward the night side of Saturn's moon Titan in a view that highlights the extended, hazy nature of the moon's atmosphere. During its long mission at Saturn, Cassini has frequently observed Titan at viewing angles like this, where the atmosphere is backlit by the Sun, in order to make visible the structure of the hazes. Titan's high-altitude haze layer appears blue here, whereas the main atmospheric haze is orange. The difference in color could be due to particle sizes in the haze. The blue haze likely consists of smaller particles than the orange haze. Images taken using red, green and blue spectral filters were combined to create this natural-color view. The image was taken with the Cassini spacecraft narrow-angle camera on May 29, 2017. The view was acquired at a distance of approximately 1.2 million miles (2 million kilometers) from Titan. Image scale is 5 miles (9 kilometers) per pixel. https://photojournal.jpl.nasa.gov/catalog/PIA21625

  7. Nonresonant valence-to-core x-ray emission spectroscopy of niobium

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ravel, Bruce; Kropf, A. Jeremy; Yang, Dali

    The valence-to-core (V2C) portion of x-ray emission spectroscopy (XES) measures the electron states close to the Fermi level. These states are involved in bonding, thus providing a measure of the chemistry of the material. For this paper, we show the V2C XES spectra for several niobium compounds. The Kβ" peak in the V2C XES results from the transition of a ligand 2s electron into the 1s core-hole of the niobium, a transition allowed by hybridization with the niobium 4p . This location in energy of this weak peak shows a strong ligand dependence, thus providing a sensitive probe of themore » ligand environment about the niobium.« less

  8. Nonresonant valence-to-core x-ray emission spectroscopy of niobium

    DOE PAGES

    Ravel, Bruce; Kropf, A. Jeremy; Yang, Dali; ...

    2018-03-23

    The valence-to-core (V2C) portion of x-ray emission spectroscopy (XES) measures the electron states close to the Fermi level. These states are involved in bonding, thus providing a measure of the chemistry of the material. For this paper, we show the V2C XES spectra for several niobium compounds. The Kβ" peak in the V2C XES results from the transition of a ligand 2s electron into the 1s core-hole of the niobium, a transition allowed by hybridization with the niobium 4p . This location in energy of this weak peak shows a strong ligand dependence, thus providing a sensitive probe of themore » ligand environment about the niobium.« less

  9. Peering Through Titan Haze

    NASA Image and Video Library

    2015-12-04

    This composite image shows an infrared view of Saturn's moon Titan from NASA's Cassini spacecraft, acquired during the mission's "T-114" flyby on Nov. 13, 2015. The spacecraft's visual and infrared mapping spectrometer (VIMS) instrument made these observations, in which blue represents wavelengths centered at 1.3 microns, green represents 2.0 microns, and red represents 5.0 microns. A view at visible wavelengths (centered around 0.5 microns) would show only Titan's hazy atmosphere (as in PIA14909). The near-infrared wavelengths in this image allow Cassini's vision to penetrate the haze and reveal the moon's surface. During this Titan flyby, the spacecraft's closest-approach altitude was 6,200 miles (10,000 kilometers), which is considerably higher than those of typical flybys, which are around 750 miles (1,200 kilometers). The high flyby allowed VIMS to gather moderate-resolution views over wide areas (typically at a few kilometers per pixel). The view looks toward terrain that is mostly on the Saturn-facing hemisphere of Titan. The scene features the parallel, dark, dune-filled regions named Fensal (to the north) and Aztlan (to the south), which form the shape of a sideways letter "H." Several places on the image show the surface at higher resolution than elsewhere. These areas, called subframes, show more detail because they were acquired near closest approach. They have finer resolution, but cover smaller areas than data obtained when Cassini was farther away from Titan. Near the limb at left, above center, is the best VIMS view so far of Titan's largest confirmed impact crater, Menrva (first seen by the RADAR instrument in PIA07365). Similarly detailed subframes show eastern Xanadu, the basin Hotei Regio, and channels within bright terrains east of Xanadu. (For Titan maps with named features see http://planetarynames.wr.usgs.gov/Page/TITAN/target.) Due to the changing Saturnian seasons, in this late northern spring view, the illumination is significantly

  10. Anomalous behavior of B{sub 1g} mode in highly transparent anatase nano-crystalline Nb-doped Titanium Dioxide (NTO) thin films

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Gautam, Subodh K., E-mail: subodhkgtm@gmail.com, E-mail: fouran@gmail.com; Ojha, S.; Singh, Fouran, E-mail: subodhkgtm@gmail.com, E-mail: fouran@gmail.com

    2015-12-15

    The effect of Niobium doping and size of crystallites on highly transparent nano-crystalline Niobium doped Titanium Dioxide (NTO) thin films with stable anatase phase are reported. The Nb doping concentration is varied within the solubility limit in TiO{sub 2} lattice. Films were annealed in controlled environment for improving the crystallinity and size of crystallites. Elemental and thickness analysis were carried out using Rutherford backscattering spectrometry and cross sectional field emission scanning electron microscopy. Structural characteristics reveal a substitutional incorporation of Nb{sup +5} in the TiO{sub 2} lattice which inhibits the anatase crystallites growth with increasing the doping percentage. The micro-Ramanmore » (MR) spectra of films with small size crystallites shows stiffening of about 4 cm{sup −1} for the E{sub g(1)} mode and is ascribed to phonon confinement and non-stoichiometry. In contrast, B{sub 1g} mode exhibits a large anomalous softening of 20 cm{sup −1} with asymmetrical broadening; which was not reported for the case of pure TiO{sub 2} crystallites. This anomalous behaviour is explained by contraction of the apical Ti-O bonds at the surface upon substitutional Nb{sup 5+} doping induced reduction of Ti{sup 4+} ions also known as hetero-coordination effect. The proposed hypotheses is manifested through studying the electronic structure and phonon dynamics by performing the near edge x-ray absorption fine structure (NEXAFS) and temperature dependent MR down to liquid nitrogen temperature on pure and 2.5 at.% doped NTO films, respectively.« less

  11. Titan's atmosphere and climate

    NASA Astrophysics Data System (ADS)

    Hörst, S. M.

    2017-03-01

    Titan is the only moon with a substantial atmosphere, the only other thick N2 atmosphere besides Earth's, the site of extraordinarily complex atmospheric chemistry that far surpasses any other solar system atmosphere, and the only other solar system body with stable liquid currently on its surface. The connection between Titan's surface and atmosphere is also unique in our solar system; atmospheric chemistry produces materials that are deposited on the surface and subsequently altered by surface-atmosphere interactions such as aeolian and fluvial processes resulting in the formation of extensive dune fields and expansive lakes and seas. Titan's atmosphere is favorable for organic haze formation, which combined with the presence of some oxygen-bearing molecules indicates that Titan's atmosphere may produce molecules of prebiotic interest. The combination of organics and liquid, in the form of water in a subsurface ocean and methane/ethane in the surface lakes and seas, means that Titan may be the ideal place in the solar system to test ideas about habitability, prebiotic chemistry, and the ubiquity and diversity of life in the universe. The Cassini-Huygens mission to the Saturn system has provided a wealth of new information allowing for study of Titan as a complex system. Here I review our current understanding of Titan's atmosphere and climate forged from the powerful combination of Earth-based observations, remote sensing and in situ spacecraft measurements, laboratory experiments, and models. I conclude with some of our remaining unanswered questions as the incredible era of exploration with Cassini-Huygens comes to an end.

  12. Mineral resource of the month: niobium (columbium)

    USGS Publications Warehouse

    Papp, John F.

    2007-01-01

    It’s not just diamonds associated with conflict in Africa. Coltan, short for columbite-tantalite (a blend of niobium — also called columbium — and tantalum minerals), is linked with the recent conflicts in the Congo that involved several African countries. The metallic ore, which is processed to separate out niobium and the very valuable tantalum (see Geotimes, August 2004), is believed to be smuggled out and sold to help finance the armed conflicts.

  13. A niobium and tantalum co-doped perovskite cathode for solid oxide fuel cells operating below 500 °C

    PubMed Central

    Li, Mengran; Zhao, Mingwen; Li, Feng; Zhou, Wei; Peterson, Vanessa K.; Xu, Xiaoyong; Shao, Zongping; Gentle, Ian; Zhu, Zhonghua

    2017-01-01

    The slow activity of cathode materials is one of the most significant barriers to realizing the operation of solid oxide fuel cells below 500 °C. Here we report a niobium and tantalum co-substituted perovskite SrCo0.8Nb0.1Ta0.1O3−δ as a cathode, which exhibits high electroactivity. This cathode has an area-specific polarization resistance as low as ∼0.16 and ∼0.68 Ω cm2 in a symmetrical cell and peak power densities of 1.2 and 0.7 W cm−2 in a Gd0.1Ce0.9O1.95-based anode-supported fuel cell at 500 and 450 °C, respectively. The high performance is attributed to an optimal balance of oxygen vacancies, ionic mobility and surface electron transfer as promoted by the synergistic effects of the niobium and tantalum. This work also points to an effective strategy in the design of cathodes for low-temperature solid oxide fuel cells. PMID:28045088

  14. Titan's Methane Cycle is Closed

    NASA Astrophysics Data System (ADS)

    Hofgartner, J. D.; Lunine, J. I.

    2013-12-01

    Doppler tracking of the Cassini spacecraft determined a polar moment of inertia for Titan of 0.34 (Iess et al., 2010, Science, 327, 1367). Assuming hydrostatic equilibrium, one interpretation is that Titan's silicate core is partially hydrated (Castillo-Rogez and Lunine, 2010, Geophys. Res. Lett., 37, L20205). These authors point out that for the core to have avoided complete thermal dehydration to the present day, at least 30% of the potassium content of Titan must have leached into an overlying water ocean by the end of the core overturn. We calculate that for probable ammonia compositions of Titan's ocean (compositions with greater than 1% ammonia by weight), that this amount of potassium leaching is achievable via the substitution of ammonium for potassium during the hydration epoch. Formation of a hydrous core early in Titan's history by serpentinization results in the loss of one hydrogen molecule for every hydrating water molecule. We calculate that complete serpentinization of Titan's core corresponds to the release of more than enough hydrogen to reconstitute all of the methane atoms photolyzed throughout Titan's history. Insertion of molecular hydrogen by double occupancy into crustal clathrates provides a storage medium and an opportunity for ethane to be converted back to methane slowly over time--potentially completing a cycle that extends the lifetime of methane in Titan's surface atmosphere system by factors of several to an order of magnitude over the photochemically-calculated lifetime.

  15. Titan Mystery Clouds

    NASA Image and Video Library

    2016-12-21

    This comparison of two views from NASA's Cassini spacecraft, taken fairly close together in time, illustrates a peculiar mystery: Why would clouds on Saturn's moon Titan be visible in some images, but not in others? In the top view, a near-infrared image from Cassini's imaging cameras, the skies above Saturn's moon Titan look relatively cloud free. But in the bottom view, at longer infrared wavelengths, Cassini sees a large field of bright clouds. Even though these views were taken at different wavelengths, researchers would expect at least a hint of the clouds to show up in the upper image. Thus they have been trying to understand what's behind the difference. As northern summer approaches on Titan, atmospheric models have predicted that clouds will become more common at high northern latitudes, similar to what was observed at high southern latitudes during Titan's late southern summer in 2004. Cassini's Imaging Science Subsystem (ISS) and Visual and Infrared Mapping Spectrometer (VIMS) teams have been observing Titan to document changes in weather patterns as the seasons change, and there is particular interest in following the onset of clouds in the north polar region where Titan's lakes and seas are concentrated. Cassini's "T120" and "T121" flybys of Titan, on June 7 and July 25, 2016, respectively, provided views of high northern latitudes over extended time periods -- more than 24 hours during both flybys. Intriguingly, the ISS and VIMS observations appear strikingly different from each other. In the ISS observations (monochrome image at top), surface features are easily identifiable and only a few small, isolated clouds were detected. In contrast, the VIMS observations (color image at bottom) suggest widespread cloud cover during both flybys. The observations were made over the same time period, so differences in illumination geometry or changes in the clouds themselves are unlikely to be the cause for the apparent discrepancy: VIMS shows persistent

  16. A green synthesis of a layered titanate, potassium lithium titanate; lower temperature solid-state reaction and improved materials performance

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ogawa, Makoto, E-mail: waseda.ogawa@gmail.com; Department of Earth Sciences, Waseda University, 1-6-1 Nishiwaseda, Shinjuku-ku, Tokyo 169-8050; Morita, Masashi, E-mail: m-masashi@y.akane.waseda.jp

    2013-10-15

    A layered titanate, potassium lithium titanate, with the size range from 0.1 to 30 µm was prepared to show the effects of the particle size on the materials performance. The potassium lithium titanate was prepared by solid-state reaction as reported previously, where the reaction temperature was varied. The reported temperature for the titanate preparation was higher than 800 °C, though 600 °C is good enough to obtain single-phase potassium lithium titanate. The lower temperature synthesis is cost effective and the product exhibit better performance as photocatalysts due to surface reactivity. - Graphical abstract: Finite particle of a layered titanate, potassiummore » lithium titanate, was prepared by solid-state reaction at lower temperature to show modified materials performance. Display Omitted - Highlights: • Potassium lithium titanate was prepared by solid-state reaction. • Lower temperature reaction resulted in smaller sized particles of titanate. • 600 °C was good enough to obtain single phased potassium lithium titanate. • The product exhibited better performance as photocatalyst.« less

  17. Chemistry and evolution of Titan's atmosphere

    NASA Technical Reports Server (NTRS)

    Strobel, D. F.

    1982-01-01

    The chemistry and evolution of Titan's atmosphere are reviewed, in light of the scientific findings from the Voyager mission. It is argued that the present N2 atmosphere may be Titan's initial atmosphere, rather than one photochemically derived from an original NH3 atmosphere. The escape rate of hydrogen from Titan is controlled by photochemical production from hydrocarbons. CH4 is irreversibly converted to less hydrogen-rich hydrocarbons, which over geologic time accumulate on the surface to a layer thickness of about 0.5 km. Magnetospheric electrons interacting with Titan's exosphere may dissociate enough N2 into hot, escaping N atoms to remove about 0.2 of Titan's present atmosphere over geologic time. The energy dissipation of magnetospheric electrons exceeds solar EUV energy deposition in Titan's atmosphere by an order of magnitude, and is the principal driver of nitrogen photochemistry. The environmental conditions in Titan's upper atmosphere are favorable to building up complex molecules, particularly in the north polar cap region.

  18. The effect of CHA-doped Sr addition to the mechanical strength of metakaolin dental implant geopolymer composite

    NASA Astrophysics Data System (ADS)

    Sunendar, Bambang; Fathina, Afiya; Harmaji, Andrie; Mardhian, Deby Fajar; Asri, Lia; Widodo, Haris Budi

    2017-09-01

    The prospective material for implant plate required sufficient mechanical properties to maintain fracture fixation and resist physiological stress until bone healing process finished. Various problem implant plate based on metal and polymer materials when used as fixation for bone defect case induced developmental of bioceramic for implant plate materials. Materials that now has been attract a lot of attention is carbonate apatite and strontium as doping which known to have good biocompability along with biointegrity and mechanical charateristics. Other materials that have been known to have good mechanical properties are metakaolin and use of chitosan as coupling agent. Metakaolin and carbonate apatite can be produced by sol-gel methode which simpler, economical and energy-saving procedure furthermore use of chitosan which is widely found in the nature of Indonesia can be used to encourage the utilization of natural resources. The aim fo this paper is to investigated effect of CHA-doped Sr 5 (%) mol addition to the mechanical strength of metakaolin dental implant geoploymer composite. In this paper metakaolin is used as geopolymerization precursors. The test results have shown that addition of filler of apatite carbonate doped 5% mol strontium can be said to increase the value of mechnical properties but high concentration of calcium in the nanocomposite also can complicate the equilibrium of the geopolymerization process and induce alkali aggregate reactivity (AAR). The sample group of nanocomposite of metakaolin and carbonate apatite-doped 5% mol strontium (2: 1% wt) with 2% chitosan as a coupling agent based on geopolymerization for implant plate application has the best mechanical properties among all sample groups but does not qualify as an implant plate on cortical bone but can be used for the application of the implant plate on the trabecular bone specifically and potentially as a bone initiator.

  19. Titan Polar Landscape Evolution

    NASA Technical Reports Server (NTRS)

    Moore, Jeffrey M.

    2016-01-01

    With the ongoing Cassini-era observations and studies of Titan it is clear that the intensity and distribution of surface processes (particularly fluvial erosion by methane and Aeolian transport) has changed through time. Currently however, alternate hypotheses substantially differ among specific scenarios with respect to the effects of atmospheric evolution, seasonal changes, and endogenic processes. We have studied the evolution of Titan's polar region through a combination of analysis of imaging, elevation data, and geomorphic mapping, spatially explicit simulations of landform evolution, and quantitative comparison of the simulated landscapes with corresponding Titan morphology. We have quantitatively evaluated alternate scenarios for the landform evolution of Titan's polar terrain. The investigations have been guided by recent geomorphic mapping and topographic characterization of the polar regions that are used to frame hypotheses of process interactions, which have been evaluated using simulation modeling. Topographic information about Titan's polar region is be based on SAR-Topography and altimetry archived on PDS, SAR-based stereo radar-grammetry, radar-sounding lake depth measurements, and superposition relationships between geomorphologic map units, which we will use to create a generalized topographic map.

  20. Dark and Light Titan

    NASA Image and Video Library

    2010-09-08

    NASA Cassini spacecraft examines Titan dark and light seasonal hemispheric dichotomy as it images the moon with a filter sensitive to near-infrared light. This image also shows Titan north polar hood.

  1. Seasonal Change in Titan's Cloud Activity

    NASA Astrophysics Data System (ADS)

    Schaller, E. L.; Brown, M. E.; Roe, H. G.

    2006-12-01

    We have acquired whole disk spectra of Titan on nineteen nights with IRTF/SpeX over a three-month period in the spring of 2006 and will acquire data on ~50 additional nights between September and December 2006. The data encompass the spectral range of 0.8 to 2.4 microns at a resolution of 375. These disk- integrated spectra allow us to determine Titan's total fractional cloud coverage and altitudes of clouds present. We find that Titan had less than 0.15% fractional cloud coverage on all but one of the nineteen nights. The near lack of cloud activity in these spectra is in sharp contrast to nearly every spectrum taken from 1995-1999 with UKIRT by Griffith et al. (1998 &2000) who found rapidly varying clouds covering ~0.5% of Titan's disk. The differences in these two similar datasets indicate a striking seasonal change in the behavior of Titan's clouds. Observations of the latitudes, magnitudes, altitudes, and frequencies of Titan's clouds as Titan moves toward southern autumnal equinox in 2009 will help elucidate when and how Titan's methane hydrological cycle changes with season.

  2. Strontium-90 in antlers of red deer: an indicator of environmental contamination by strontium-90.

    PubMed

    Schönhofer, F; Tataruch, F; Friedrich, M

    1994-12-11

    The sampling procedures in connection with a very sensitive analytical method are described. Results from different areas in Austria are presented and an interpretion of the results is attempted. Some findings are in accordance with measurements from other substances, some are not. The differences most probably depend on several factors like soil type, precipitation, migration of strontium-90, concentration of stable strontium and calcium. No significant rise in the concentration could be found after 1986 thus in accordance with other measurements of strontium-90 contamination after the Chernobyl accident.

  3. ON THE GEOCHEMISTRY OF NIOBIUM AND TANTALUM IN CLAYS (in Russian)

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Pachadzhanov, D.N.

    1963-10-01

    With the aid of the spectral method with a preliminary enrichment in tannin, the niobium and tantalum content was determined in some humid and arid clays of the Russian platform. The investigated samples were composed of 354 specimens. The average content of niobium in humid clays is 0.0020%, of tantalum 0.00024% (the Nb/Ta ratio is 8.4) and in arid clays is respectively the content of niobium 0.00133% and the content of tantalum 0.00009% (the Nb/Ta ratio is 14.8). The average value of the content of niobium content for all studied clays is 0.00183% and of the tantalum content 0.00020%, themore » Nb/Ta ratio being 9.1. In clays an interconnection of niobium with tantalum, as well as with aluminium, titanium, zirconium, and hafnium was observed. However, on the background of this connection some separation of the named elements is noted. A tendency for the Nb/Ta ratio shift from the region of matter removal towards the center of the marine basin was observed. The study of niobium and tantalum distribution over different clay fractions showed that one part of elements is connected with zircon and titanium minerals in aleuosand fraction (0.1-- 0.01 mm). Another, approximately similar part is contained in the proper clay fraction (<0. 01 mm), the tantalum somewhat more concentrating in the aleurosand fraction and niobium in the clay fraction. (P.C.H.)« less

  4. White- and blue-light-emitting dysprosium(III) and terbium(III)-doped gadolinium titanate phosphors.

    PubMed

    Antić, Ž; Kuzman, S; Đorđević, V; Dramićanin, M D; Thundat, T

    2017-06-01

    Here we report the synthesis and structural, morphological, and photoluminescence analysis of white- and blue-light-emitting Dy 3 + - and Tm 3 + -doped Gd 2 Ti 2 O 7 nanophosphors. Single-phase cubic Gd 2 Ti 2 O 7 nanopowders consist of compact, dense aggregates of nanoparticles with an average size of ~25 nm for Dy 3 + -doped and ~50 nm for Tm 3 + -doped samples. The photoluminescence results indicated that ultraviolet (UV) light excitation of the Dy 3 + -doped sample resulted in direct generation of white light, while a dominant yellow emission was obtained under blue-light excitation. Intense blue light was obtained for Tm 3 + -doped Gd 2 Ti 2 O 7 under UV excitation suggesting that this material could be used as a blue phosphor. Copyright © 2016 John Wiley & Sons, Ltd.

  5. Investigation of Voltage-Activated BAW Devices and Filters

    DTIC Science & Technology

    2016-09-04

    strontium titanate (STO) and barium-strontium titanate (BST), with the ultimate objective of creating high- performance, reconfigurable filters and...Distribution Unlimited UU UU UU UU 04-09-2016 1-Sep-2010 31-Aug-2014 Final Report: Investigation of Voltage-Activated BAW Devices and Filters The views...2016 Investigation of Voltage-Activated BAW Devices and Filters Final Report Award Information: Contract Number: W911NF1010286 Period of Work

  6. STRONTIUM 90: ESTIMATION OF WORLDWIDE DEPOSITION.

    PubMed

    VOLCHOK, H L

    1964-09-25

    The relation between the worldwide deposition of strontium-90, as calculated by many investigators over the last decade, and that observed in rainfall in New York City has been relatively constant. On the average, for each millicurie of strontium-90 per square mile deposited in New York City, 0.055 megacurie has been deposited on the earth's total surface. Cumulative deposits of strontium-90 on the earth's surface at various intervals over the last 10 years have been computed from this ratio. From the mean quarterly fraction of the annual strontium-90 fallout in New York City for the last 9 years, the worldwide deposition of this nuclide, equal to 2.48 megacuries, is predicted for 1964.

  7. Immunization against strontium-90 induction of bone tumors with inactivated FBJ virus and irradiated syngeneic strontium-90-induced tumor cells

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Reif, A.E.; Triest, W.E.

    1981-01-01

    Three hundred six C57BL/6J female mice were subdivided into a control group left untreated and an experimental group treated intraperitoneally with 1.0 ..mu..Ci strontium-90/g of body weight at an age of 66 days. Treatments for the groups were as follows: none, 6 injections of formalin-inactivated FBJ viral preparation, 6 injections of active FBJ viral preparation, and 2 injections of 10,000 rad irradiated transplantable osteosarcoma previously induced in C57BL/6J mice by strontium-90. In addition to the above groups, two other groups were treated with respectively 0.032 and 0.10 ..mu..Ci strontium-90/g body weight in order to obtain information on the dose-response relationshipmore » between the injection of strontium-90 and the yield of bone tumors. In the groups not treated with strontium-90, only 1 bone tumor developed; this occurred in the group injected with FBJ virus. The incidence of bone tumors in the groups treated with 1.0 ..mu..Ci strontium-90 was significantly lower (18.5% or 18.2%) in the two groups that had received injections of inactivated FBJ virus or irradiated isogenic osteosarcoma when compared to the group left uninjected, which developed 43.5% tumors. In contrast, the strontium-90-treated group that also received injections of active FBJ virus developed 63.0% tumors. Only a single bone tumor developed in the groups treated solely with intermediate doses of strontium-90. The results indicate that immunization with inactivated FBJ virus or with irradiated syngeneic strontium-90-induced tumor cells can significantly decrease the development of strontium-90-induced tumors.« less

  8. STRONTIUM-90 IN THE TOTAL DIET

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    None

    Food, milk, and drinking water representative of the total diet of a hungry teen-ager were collected in 24 cities throughout the United States and one in Canada. The diets were analyzed for strontium-90 content. Results are compared with the strontium-90 levels in milk samples collected in the same cities. Results indicate that milk furnished only slightly more than half of the strontium-90 consumed in the total diet. (C.H.)

  9. First-Principles Study of Carbon and Vacancy Structures in Niobium

    DOE PAGES

    Ford, Denise C.; Zapol, Peter; Cooley, Lance D.

    2015-04-03

    The interstitial chemical impurities hydrogen, oxygen, nitrogen, and carbon are important for niobium metal production, and particularly for the optimization of niobium SRF technology. These atoms are present in refined sheets and can be absorbed into niobium during processing treatments, resulting in changes to the residual resistance and the performance of SRF cavities. A first-principles approach is taken to study the properties of carbon in niobium, and the results are compared and contrasted with the properties of the other interstitial impurities. The results indicate that C will likely form precipitates or atmospheres around defects rather than strongly bound complexes withmore » other impurities. Based on the analysis of carbon and hydrogen near niobium lattice vacancies and small vacancy chains and clusters, the formation of extended carbon chains and hydrocarbons is not likely to occur. Association of carbon with hydrogen atoms can, however, occur through the strain fields created by interstitial binding of the impurity atoms. In conclusion, calculated electronic densities of states indicate that interstitial C may have a similar effect as interstitial O on the superconducting transition temperature of Nb.« less

  10. Strontium

    USGS Publications Warehouse

    Ober, J.A.

    2003-01-01

    Mexico and Spain are the leading producers of celestite, the most common strontium ore. Those countries produced nearly 80 percent of the estimated 360 kt (397,000 st) of celestite produced worldwide during 2002. China and Turkey are other significant celestite producers.

  11. Strontium

    Integrated Risk Information System (IRIS)

    Strontium ; CASRN 7440 - 24 - 6 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinogenic Effect

  12. Synthesis, characterization, and catalytic application of ordered mesoporous carbon–niobium oxide composites

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Gao, Juan-Li; Gao, Shuang; Liu, Chun-Ling

    2014-11-15

    Graphical abstract: The ordered mesoporous carbon–niobium oxide composites have been synthesized by a multi-component co-assembly method associated with a carbonization process. - Highlights: • Ordered mesoporous carbon–niobium oxide composites were synthesized. • The content of Nb{sub 2}O{sub 5} in the composites could be tuned from 38 to 75%. • Niobium species were highly dispersed in amorphous carbon framework walls. • The composites exhibited good catalytic performance in the dehydration of fructose. - Abstract: Ordered mesoporous carbon–niobium oxide composites have been synthesized by a multi-component co-assembly method associated with a carbonization process using phenolic resol as carbon source, niobium chloride asmore » precursor and amphiphilic triblock copolymer Pluronic F127 as template. The resulting materials were characterized using a combination of techniques including differential scanning calorimetry–thermogravimetric analysis, N{sub 2} physical adsorption, X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy. The results show that with increasing the content of Nb{sub 2}O{sub 5} from 38 to 75% the specific surface area decreases from 306.4 to 124.5 m{sup 2} g{sup −1}, while the ordered mesoporous structure is remained. Niobium species is well dispersed in the amorphous carbon framework. The mesoporous carbon–niobium oxide composites exhibit high catalytic activity in the dehydration of fructose to 5-hydroxymethylfurfural. A 100% conversion of fructose and a 76.5% selectivity of 5-hydroxymethylfurfural were obtained over the carbon–niobium oxide composite containing 75% Nb{sub 2}O{sub 5} under the investigated reaction conditions.« less

  13. Nitrogen Chemistry in Titan's Upper Atmosphere

    NASA Technical Reports Server (NTRS)

    McKay, Christopher P.; Cuzzi, Jeffrey (Technical Monitor)

    1996-01-01

    In Titan's upper atmosphere N2 is dissociated to N by solar UV and high energy electrons. This flux of N provides for interesting organic chemistry in the lower atmosphere of Titan. Previously the main pathway for the loss of this N was thought to be the formation of HCN, followed by diffusion of this HCN to lower altitudes leading ultimately to condensation. However, recent laboratory simulations of organic chemistry in Titan's atmosphere suggest that formation of the organic haze may be an important sink for atmospheric N. Because estimates of the eddy diffusion profile on Titan have been based on the HCN profile, inclusion of this additional sink for N will affect estimates for all transport processes in Titan's atmosphere. This and other implications of this sink for the N balance on Titan are considered.

  14. Conserving the Giant Titans

    Science.gov Websites

    Virtual Herbarium Conserving the Giant Titans The gigantic and pungent Titan Arum or Corpse Flower Milonic.com Copyright © 2007 Virtual Herbarium - All rights reserved 11935 Old Cutler Road, Coral Gables, FL

  15. Mimas...and Titan Beyond

    NASA Image and Video Library

    2006-01-03

    Titan, Saturn largest moon and Mimas in the foreground are seen together in this view from Cassini. Titan gravity is weaker than Earth, so the moon atmosphere is quite extended -- a quality hinted at in this view

  16. Inside Titan Author Concept

    NASA Image and Video Library

    2012-06-28

    This artist concept shows a possible scenario for the internal structure of Titan, as suggested by data from NASA Cassini spacecraft. Scientists have been trying to determine what is under Titan organic-rich atmosphere and icy crust.

  17. Squeezing and Stretching Titan Author Concept

    NASA Image and Video Library

    2012-06-28

    This artist concept shows tides on Titan raised by Saturn gravity, as detected by NASA Cassini spacecraft. Saturn gravitational pull on Titan, its largest moon, varies as Titan orbits along an elliptical path around the planet every 16 days.

  18. Effects of calcium and magnesium on strontium distribution coefficients

    USGS Publications Warehouse

    Bunde, R.L.; Rosentreter, J.J.; Liszewski, M.J.; Hemming, C.H.; Welhan, J.

    1997-01-01

    The effects of calcium and magnesium on the distribution of strontium between a surficial sediment and simulated wastewater solutions were measured as part of an investigation to determine strontium transport properties of surficial sediment at the Idaho National Engineering Laboratory (INEL), Idaho. The investigation was conducted by the U.S. Geological Survey and Idaho State University, in cooperation with the U.S. Department of Energy. Batch experimental techniques were used to determine strontium linear sorption isotherms and distribution coefficients (K(d)'s) using simulated wastewater solutions prepared at pH 8.0??0.1 with variable concentrations of calcium and magnesium. Strontium linear sorption isotherm K(d)'s ranged from 12??1 to 85??3 ml/g, increasing as the concentration of calcium and magnesium decreased. The concentration of sorbed strontium and the percentage of strontium retained by the sediment were correlated to aqueous concentrations of strontium, calcium, and magnesium. The effect of these cation concentrations on strontium sorption was quantified using multivariate least-squares regression techniques. Analysis of data from these experiments indicates that increased concentrations of calcium and magnesium in wastewater discharged to waste disposal ponds at the INEL increases the availability of strontium for transport beneath the ponds by decreasing strontium sorption to the surficial sediment.

  19. Structural phase transitions in niobium oxide nanocrystals

    NASA Astrophysics Data System (ADS)

    Yuvakkumar, R.; Hong, Sun Ig

    2015-09-01

    Niobium oxide nanocrystals were successfully synthesized employing the green synthesis method. Phase formation, microstructure and compositional properties of 1, 4 and 7 days incubation treated samples after calcinations at 450 °C were examined using X-ray diffraction, Raman, photoluminescence (PL), infrared, X-ray photoelectron spectra and transmission electron microscopic characterizations. It was observed that phase formation of Nb2O5 nanocrystals was dependent upon the incubation period required to form stable metal oxides. The characteristic results clearly revealed that with increasing incubation and aging, the transformation of cubic, orthorhombic and monoclinic phases were observed. The uniform heating at room temperature (32 °C) and the ligation of niobium atoms due to higher phenolic constituents of utilized rambutan during aging processing plays a vital role in structural phase transitions in niobium oxide nanocrystals. The defects over a period of incubation and the intensities of the PL spectra changing over a period of aging were related to the amount of the defects induced by the phase transition.

  20. Large structural modulations in the relaxor ferroelectric and intermediate state of strontium rich members (x>0.6) of the Sr{sub x}Ba{sub 1−x}Nb{sub 2}O{sub 6} (sbn) solid solution series

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Graetsch, H.A., E-mail: heribert.graetsch@rub.de

    The amplitudes of the positional, occupational and adp modulations of sbn mixed crystals are strongly enhanced for high strontium contents. The increase of structural modulations is accompanied by reduced spontaneous electric polarization largely due to smaller off-center shifts of the niobium atoms. Beyond the room temperature ferroelectric – intermediate transition near x=0.77, anomal large U{sub 33} atomic displacement parameters of the niobium atoms indicate static disorder caused by loss of orientational coupling between residual shifts of Nb atoms in neighboring NbO{sub 6} octahedra. Change of satellite intensities show a reduction from two-dimensional to one-dimensional modulation which is not consistent withmore » tetragonal symmetry. The pseudo-tetragonally twinned crystal structure of sbn82 was refined in the orthorhombic super-space group A2mm(½0γ)000. The apparent tetragonal symmetry of the other investigated sbn samples also seems to be due to pseudo tetragonal twinning with equal twin volumes. The modulations mainly consist of cooperatively tilted NbO{sub 6} octahedra and wave-like ordered incomplete occupation of the largest cation sites (Me2a and b) by Ba{sup 2+} and Sr{sup 2+}. Furthermore, the atomic displacement parameters of the Me2 sites are strongly modulated. - Graphical abstract: Satellite reflections and modulation coefficients in the solid solution series Sr{sub x}Ba{sub 1−x}Nb{sub 2}O{sub 6}. - Highlights: • The modulationed structures are refined for the whole composition range of sbn32–sbn82 in tetragonal and orthorhombic setting. • The amplitudes of positional, occupational and adp modulations increase strongly with the strontium content. • Evidence is presented that the sbn crystals are pseudo tetragonally twinned. • The ferroelectric–intermediate paraelectric transition is not accompanied by a change of symmetry. • Anomal adp of intermediate (non-ferroelectric) sbn82 indicate loss of coupling between off

  1. Weather on Titan

    NASA Astrophysics Data System (ADS)

    Griffith, C. A.; Hall, J. L.; Geballe, T. R.

    2000-10-01

    Titan's atmosphere potentially sports a cycle similar to the hydrologic one on Earth with clouds, rain and seas, but with methane playing the terrestrial role of water. Over the past ten years many independent efforts indicated no strong evidence for cloudiness until some unique spectra were analyzed in 1998 (Griffith et al.). These surprising observations displayed enhanced fluxes of 14-200% on two nights at precisely the wavelengths (windows) that sense Titan's lower altitude where clouds might reside. The morphology of these enhancements in all 4 windows observed indicate that clouds covered ~6-9% of Titan's surface and existed at ~15 km altitude. Here I discuss new observations recorded in 1999 aimed to further characterize Titan's clouds. While we find no evidence for a massive cloud system similar to the one observed previously, 1%-4% fluctuations in flux occur daily. These modulations, similar in wavelength and morphology to the more pronounced ones observed earlier, suggest the presence of clouds covering <=1% of Titan's disk. The variations are too small to have been detected by most prior measurements. Repeated observations, spaced 30 minutes apart, indicate a temporal variability observable in the time scale of a couple of hours. The cloud heights hint that convection governs their evolutions. Their short lives point to the presence of rain. C. A. Griffith and J. L. Hall are supported by the NASA Planetary Astronomy Program NAG5-6790.

  2. An investigation of the Nb doping effect on structural, morphological, electrical and optical properties of spray deposited F doped SnO2 films

    NASA Astrophysics Data System (ADS)

    Turgut, G.; Keskenler, E. F.; Aydın, S.; Yılmaz, M.; Doǧan, S.; Düzgün, B.

    2013-03-01

    F and Nb + F co-doped SnO2 thin films were deposited on glass substrates by the spray pyrolysis method. The microstructural, morphological, electrical and optical properties of the 10 wt% F doped SnO2 (FTO) thin films were investigated specifically for niobium (Nb) doping in the range of 0-4 at.% with 1 at.% steps. As shown by the x-ray diffraction patterns, the films exhibited a tetragonal cassiterite structure with (200) preferential orientation. It was observed that grain sizes of the films for (200) and (301) peaks depended on the Nb doping concentration and varied in the range of 25.11-32.19 and 100.6-183.7 nm, respectively. The scanning electron microscope (SEM) micrographs showed that the FTO films were made of small pyramidal grains, while doubly doped films were made of small pyramidal grains and big polyhedron grains. From electrical studies, although 1 at.% Nb doped FTO films have the lowest sheet resistance and resistivity values, the highest figure-of-merit and optical band gap values obtained for FTO films were 16.2 × 10-2 Ω-1 and 4.21 eV, respectively. Also, infrared reflectivity values of the films were in the range of 97.39-98.98%. These results strongly suggest that these films are an attractive candidate for various optoelectronic applications and for photothermal conversion of solar energy.

  3. Processing of Niobium-Lined M240 Machine Gun Barrels

    DTIC Science & Technology

    2014-11-01

    different materials (the gun steel and the niobium liner). A large chunk of the niobium liner in barrel 2 was torn away from the end of the liner at...it to increase the frictional bond between the liner and gun steel . The barrels with liners were hammer forged by FN. FN experienced some...

  4. Enhanced airglow at Titan

    NASA Astrophysics Data System (ADS)

    Royer, Emilie; Esposito, Larry; Wahlund, Jan-Erik

    2016-06-01

    The Cassini Ultraviolet Imaging Spectrograph (UVIS) instrument made thousand of observations of Titan since its arrival in the Saturnian system in 2004, but only few of them have been analyzed yet. Using the imaging capability of UVIS combined to a big data analytics approach, we have been able to uncover an unexpected pattern in this observations: on several occasions the Titan airglow exhibits an enhanced brightness by approximately a factor of 2, generally combined with a lower altitude of the airglow emission peak. These events typically last from 10 to 30 minutes and are followed and preceded by an airglow of regular and expected level of brightness and altitude. Observations made by the Cassini Plasma Spectrometer (CAPS) instrument onboard Cassini allowed us to correlate the enhanced airglow observed on T-32 with an electron burst. The timing of the burst and the level of energetic electrons (1 keV) observed by CAPS correspond to a brighter and lower than typical airglow displayed on the UVIS data. Furthermore, during T-32 Titan was inside the Saturn's magnetosheath and thus more subject to bombardment by energetic particles. However, our analysis demonstrates that the presence of Titan inside the magnetosheath is not a necessary condition for the production of an enhanced airglow, as we detected other similar events while Titan was within Saturn's magnetosphere. The study presented here aims to a better understanding of the interactions of Titan's upper atmosphere with its direct environment.

  5. Titanic: A Statistical Exploration.

    ERIC Educational Resources Information Center

    Takis, Sandra L.

    1999-01-01

    Uses the available data about the Titanic's passengers to interest students in exploring categorical data and the chi-square distribution. Describes activities incorporated into a statistics class and gives additional resources for collecting information about the Titanic. (ASK)

  6. Magnetospheric particle precipitation at Titan

    NASA Astrophysics Data System (ADS)

    Royer, Emilie; Esposito, Larry; Crary, Frank; Wahlund, Jan-Erik

    2017-04-01

    Although solar XUV radiation is known to be the main source of ionization in Titan's upper atmosphere around 1100 km of altitude, magnetospheric particle precipitation can also account for about 10% of the ionization process. Magnetospheric particle precipitation is expected to be the most intense on the nightside of the satelllite and when Titan's orbital position around Saturn is the closest to Noon Saturn Local Time (SLT). In addition, on several occasion throughout the Cassini mission, Titan has been observed while in the magnetosheath. We are reporting here Ultraviolet (UV) observations of Titan airglow enhancements correlated to these magnetospheric changing conditions occurring while the spacecraft, and thus Titan, are known to have crossed Saturn's magnetopause and have been exposed to the magnetosheath environnment. Using Cassini-Ultraviolet Imaging Spectrograph (UVIS) observations of Titan around 12PM SLT as our primary set of data, we present evidence of Titan's upper atmosphere response to a fluctuating magnetospheric environment. Pattern recognition software based on 2D UVIS detector images has been used to retrieve observations of interest, looking for airglow enhancement of a factor of 2. A 2D UVIS detector image, created for each UVIS observation of Titan, displays the spatial dimension of the UVIS slit on the x-axis and the time on the y-axis. In addition, data from the T32 flyby and from April 17, 2005 from in-situ Cassini instruments are used. Correlations with data from simultaneous observations of in-situ Cassini instruments (CAPS, RPWS and MIMI) has been possible on few occasions and events such as electron burst and reconnections can be associated with unusual behaviors of the Titan airglow. CAPS in-situ measurements acquired during the T32 flyby are consistent with an electron burst observed at the spacecraft as the cause of the UV emission. Moreover, on April 17, 2005 the UVIS observation displays feature similar to what could be aTitan

  7. Deformation and recrystallization behavior of super high-purity niobium for SRF cavity

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Y.; Doryo, H.; Yuasa, M.; Miyamoto, H.; Yamanaka, M.

    2017-05-01

    Deformation and recyrstallization behavior of pure niobium was investigated in order to clarify the origin of its low hydro-formability despite of its high ductility comparable with pure iron. It was found that pure niobium exhibits lower strain hardening in cold rolling compared with pure iron. Furthermore, in post-deformation annealing, the hardness of niobium decreased monotonously with an increase of temperature, and the typical sharp drop by recrystallization was not evident. This softening behavior was contrasted with the high-purity iron. It is suggested that niobium exhibit the so-called in-situ recrystallization possibly because of low elastic modulus and low accumulative plastic strain energy in spite of high melting temperature. The low hydro-formability of pure niobium sheets or tubes is caused by its low strain hardening and its unique plastic anisotropy which is associated with this recovered residual rolled texture.

  8. The Titan Sky Simulator ™ - Testing Prototype Balloons in Conditions Approximating those in Titan's Atmosphere

    NASA Astrophysics Data System (ADS)

    Nott, Julian

    This paper will describe practical work flying prototype balloons in the "The Titan Sky Simulator TM " in conditions approximating those found in Titan's atmosphere. Saturn's moon, Titan, is attracting intense scientific interest. This has led to wide interest in exploring it with Aerobots, balloons or airships. Their function would be similar to the Rovers exploring Mars, but instead of moving laboriously across the rough terrain on wheels, they would float freely from location to location. To design any balloon or airship it is essential to know the temperature of the lifting gas as this influences the volume of the gas, which in turn influences the lift. To determine this temperature it is necessary to know how heat is transferred between the craft and its surroundings. Heat transfer for existing balloons is well understood. However, Titan conditions are utterly different from those in which balloons have ever been flown, so heat transfer rates cannot currently be calculated. In particular, thermal radiation accounts for most heat transfer for existing balloons but over Titan heat transfer will be dominated by convection. To be able to make these fundamental calculations, it is necessary to get fundamental experimental data. This is being obtained by flying balloons in a Simulator filled with nitrogen gas at very low temperature, about 95° K / minus 180° C, typical of Titan's temperatures. Because the gas in the Simulator is so cold, operating at atmospheric pressure the density is close to that of Titan's atmosphere. "The Titan Sky Simulator TM " has an open interior approximately 4.5 meter tall and 2.5 meters square. It has already been operated at 95° K/-180° C. By the time of the Conference it is fully expected to have data to present from actual balloons flying at this temperature. Perhaps the most important purpose of this testing is to validate numerical [computational fluid dynamics] models being developed by Tim Colonius of Caltech. These numerical

  9. Niobium-Matrix-Composite High-Temperature Turbine Blades

    NASA Technical Reports Server (NTRS)

    Kaplan, Richard B.; Tuffias, Robert H.; La Ferla, Raffaele; Heng, Sangvavann; Harding, John T.

    1995-01-01

    High-temperture composite-material turbine blades comprising mainly niobium matrices reinforced with refractory-material fibers being developed. Of refractory fibrous materials investigated, FP-AL(2)0(3), tungsten, and polymer-based SiC fibers most promising. Blade of this type hollow and formed in nearly net shape by wrapping mesh of reinforcing refractory fibers around molybdenum mandrel, then using thermal-gradient chemical-vapor infiltration (CVI) to fill interstices with niobium. CVI process controllable and repeatable, and kinetics of both deposition and infiltration well understood.

  10. The atmospheric temperature structure of Titan

    NASA Technical Reports Server (NTRS)

    Mckay, Christopher P.; Pollack, J. B.; Courtin, Regis; Lunine, Jonathan I.

    1992-01-01

    The contribution of various factors to the thermal structure of Titan's past and present atmosphere are discussed. A one dimensional model of Titan's thermal structure is summarized. The greenhouse effect of Titan's atmosphere, caused primarily by pressure induced opacity of N2, CH4, and H2, is discussed together with the antigreenhouse effect dominated by the haze which absorbs incident sunlight. The implications for the atmosphere of the presence of an ocean on Titan are also discussed.

  11. Night Side of Titan

    NASA Image and Video Library

    1999-02-23

    NASA Voyager 2 obtained this wide-angle image of the night side of Titan on Aug. 25, 1979. This is a view of Titan extended atmosphere. the bright orangish ring being caused by the atmosphere scattering of the incident sunlight.

  12. Titan Haze is Falling

    NASA Image and Video Library

    2011-05-05

    The change in Titan haze layer is illustrated in this figure, derived from data obtained by NASA Cassini spacecraft. The picture of Titan in panel a was taken on May 3, 2006, panel b was taken on April 2, 2010.

  13. Titan as the Abode of Life

    NASA Technical Reports Server (NTRS)

    Mckay, Christopher P.

    2016-01-01

    Titan is the only world we know other than Earth that has a liquid on its surface. It has a thick atmosphere composed of nitrogen and methane with a thick organic haze. There are lakes, rain, and clouds of methane and ethane. Here, we address the question of carbon-based life living in Titan liquids. Photochemically produced organics, particularly acetylene, in Titan's atmosphere could be a source of biological energy when reacted with atmospheric hydrogen. Light levels on the surface of Titan are more than adequate for photosynthesis but the biochemical limitations due to the few elements available in the environment may lead only to simple ecosystems that only consume atmospheric nutrients. Life on Titan may make use of the trace metals and other inorganic elements produced by meteorites as they ablate in the atmosphere. It is conceivable that H2O molecules on Titan could be used in a biochemistry that is rooted in hydrogen bonds in a way that metals are used in enzymes by life on Earth. Previous theoretical work has shown possible membrane structures in Titan liquids, azotosomes, composed of small organic nitrogen compounds, such as acrylonitrile. The search for a plausible information molecule for life in Titan liquids remains an open research topic - polyethers have been considered and shown to be insoluble at Titan temperatures. Possible search strategies for life on Titan include looking for unusual concentrations of certain molecules reflecting biological selection. Homochirality is a special and powerful example of such biology selection. Environmentally, a depletion of hydrogen in the lower atmosphere may be a sign of metabolism. A discovery of life in liquid methane and ethane would be our first compelling indication that the Universe is full of diverse and wondrous life forms.

  14. Titan as the Abode of Life

    NASA Astrophysics Data System (ADS)

    McKay, Christopher P.

    2016-02-01

    Titan is the only world we know, other than Earth, that has a liquid on its surface. It also has a thick atmosphere composed of nitrogen and methane with a thick organic haze. There are lakes, rain, and clouds of methane and ethane. Here, we address the question of carbon-based life living in Titan liquids. Photochemically produced organics, particularly acetylene, in Titan's atmosphere could be a source of biological energy when reacted with atmospheric hydrogen. Light levels on the surface of Titan are more than adequate for photosynthesis, but the biochemical limitations due to the few elements available in the environment may lead only to simple ecosystems that only consume atmospheric nutrients. Life on Titan may make use of the trace metals and other inorganic elements produced by meteorites as they ablate in its atmosphere. It is conceivable that H2O molecules on Titan could be used in a biochemistry that is rooted in hydrogen bonds in a way that metals are used in enzymes by life on Earth. Previous theoretical work has shown possible membrane structures, azotosomes, in Titan liquids, azotosomes, composed of small organic nitrogen compounds, such as acrylonitrile. The search for a plausible information molecule for life in Titan liquids remains an open research topic - polyethers have been considered and shown to be insoluble at Titan temperatures. Possible search strategies for life on Titan include looking for unusual concentrations of certain molecules reflecting biological selection. Homochirality is a special and powerful example of such biology selection. Environmentally, a depletion of hydrogen in the lower atmosphere may be a sign of metabolism. A discovery of life in liquid methane and ethane would be our first compelling indication that the universe is full of diverse and wondrous life forms.

  15. Titan as the Abode of Life.

    PubMed

    McKay, Christopher P

    2016-02-03

    Titan is the only world we know, other than Earth, that has a liquid on its surface. It also has a thick atmosphere composed of nitrogen and methane with a thick organic haze. There are lakes, rain, and clouds of methane and ethane. Here, we address the question of carbon-based life living in Titan liquids. Photochemically produced organics, particularly acetylene, in Titan's atmosphere could be a source of biological energy when reacted with atmospheric hydrogen. Light levels on the surface of Titan are more than adequate for photosynthesis, but the biochemical limitations due to the few elements available in the environment may lead only to simple ecosystems that only consume atmospheric nutrients. Life on Titan may make use of the trace metals and other inorganic elements produced by meteorites as they ablate in its atmosphere. It is conceivable that H₂O molecules on Titan could be used in a biochemistry that is rooted in hydrogen bonds in a way that metals are used in enzymes by life on Earth. Previous theoretical work has shown possible membrane structures, azotosomes, in Titan liquids, azotosomes, composed of small organic nitrogen compounds, such as acrylonitrile. The search for a plausible information molecule for life in Titan liquids remains an open research topic-polyethers have been considered and shown to be insoluble at Titan temperatures. Possible search strategies for life on Titan include looking for unusual concentrations of certain molecules reflecting biological selection. Homochirality is a special and powerful example of such biology selection. Environmentally, a depletion of hydrogen in the lower atmosphere may be a sign of metabolism. A discovery of life in liquid methane and ethane would be our first compelling indication that the universe is full of diverse and wondrous life forms.

  16. Titan Despeckled Montage

    NASA Image and Video Library

    2015-02-12

    This montage of Cassini Synthetic Aperture Radar (SAR) images of the surface of Titan shows four examples of how a newly developed technique for handling noise results in clearer, easier to interpret views. The top row of images was produced in the manner used since the mission arrived in the Saturn system a decade ago; the row at bottom was produced using the new technique. The three leftmost image pairs show bays and spits of land in Ligea Mare, one of Titan's large hydrocarbon seas. The rightmost pair shows a valley network along Jingpo Lacus, one of Titan's larger northern lakes. North is toward the left in these images. Each thumbnail represents an area 70 miles (112 kilometers) wide. http://photojournal.jpl.nasa.gov/catalog/PIA19053

  17. Structural contribution to the ferroelectric fatigue in lead zirconate titanate ceramics

    NASA Astrophysics Data System (ADS)

    Hinterstein, M.; Rouquette, J.; Haines, J.; Papet, Ph.; Glaum, J.; Knapp, M.; Eckert, J.; Hoffman, M.

    2014-09-01

    Many ferroelectric devices are based on doped lead zirconate titanate (PZT) ceramics with compositions near the morphotropic phase boundary (MPB), at which the relevant material's properties approach their maximum. Based on a synchrotron x-ray diffraction study of MPB PZT, bulk fatigue is unambiguously found to arise from a less effective field induced tetragonal-to-monoclinic transformation, at which the degradation of the polarization flipping is detected by a less intense and more diffuse anomaly in the atomic displacement parameter of lead. The time dependence of the ferroelectric response on a structural level down to 250 μs confirms this interpretation in the time scale of the piezolectric strain response.

  18. Titan's Lakes in a Beaker

    NASA Astrophysics Data System (ADS)

    Hodyss, R. P.

    2017-12-01

    The surface of Titan presents a complex, varied surfaced, with mountains, plains, dunes, rivers, lakes and seas, composed of a layer of organics over a water ice bedrock. Over the past 10 years, our group at JPL has developed a variety of techniques to study the chemistry of Titan's organic surface under relevant temperature and pressure conditions (90-100 K, 1.5 bar). Dissolution, precipitation, and both covalent and non-covalent chemical processes are examined using Raman and infrared spectroscopy, mass spectrometry, optical microscopy, and synchrotron X-ray powder diffraction. Despite the low temperatures, our experiments are revealing that a rich and active organic chemistry is possible on Titan's surface. Laboratory experiments like these can provide crucial insights into the geological processes occurring Titan's surface, and help explain the wealth of observational data returned by the Cassini/Huygens mission. This type of data is also critical for the development of future missions to Titan.

  19. SRF niobium characterization using SIMS and FIB-TEM

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Stevie, F. A.

    2015-12-04

    Our understanding of superconducting radio frequency (SRF) accelerator cavities has been improved by elemental analysis at high depth resolution and by high magnification microscopy. This paper summarizes the technique development and the results obtained on poly-crystalline, large grain, and single crystal SRF niobium. Focused ion beam made possible sample preparation using transmission electron microscopy and the images obtained showed a very uniform oxide layer for all samples analyzed. Secondary ion mass spectrometry indicated the presence of a high concentration of hydrogen and the hydrogen content exhibited a relationship with improvement in performance. Depth profiles of carbon, nitrogen, and oxygen didmore » not show major differences with heat treatment. Niobium oxide less than 10 nm thick was shown to be an effective hydrogen barrier. Niobium with titanium contamination showed unexpected performance improvement.« less

  20. SEPARATION OF URANIUM FROM ZIRCONIUM AND NIOBIUM BY SOLVENT EXTRACTION

    DOEpatents

    Voiland, E.E.

    1958-05-01

    A process for separation of the uranium from zirconium and/or niobium values contained in 3 to 7M aqueous nitric acid solutions is described. This is accomplished by adding phosphoric acid anions to the nitric acid solution containing the uranium, zirconium, and/or niobium in an amount sufficient to make the solution 0.05 to 0.2M in phosphate ion and contacting the solution with an organic water-immiscible solvent such as MEK, whereby the uranyl values are taken up by the extract phase while the zirconium and niobium preferentially remain in the aqueous raffinate.

  1. DEVELOPMENT OF NIOBIUM-BASE ALLOYS. Period covered January 1, 1956 to March 1, 1957

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Begley, R.T. ed.

    1957-11-01

    The flow and fracture characteristics of commercial purity powder metallurgy niobium were investigated in the range 250 to --196 deg C. Niobium was found to undergo a ductile-brittle transition in the range --125 to --196 deg C, and the transition temperature range of niobium was found to be less affected by the presence of interstitial impurities than many other body-centered cubic metals. The creeprupture properties of powder metallurgy niobium were investigated at 982 and 1O93 deg C (1800 and 2OOO deg F), and the 100-hour rupture strength of commercial niobium in vacuum was determined to be sigdicantiy greater than unalloyedmore » molybdenum. The creep-rupture results suggest that small quantities of gaseous contaminants may be responslble for the high strength of commercial niobium at elevated temperatures. The oxidation behavior of nioblum was investigated in the temperature range 350 to 7OO C. At the higher temperatures, oxidation followed a linear rate law. Between 500 and 625 deg C, the rate of oxidation was found to be nearly independent of temperature. Oxygen and nitrogen contamination of welding atmospheres was studied to determine its effect on the weld properties of niobium. Nitrogen was establlshed to be very detrimental to the mechanical properties of niobium welds. High-purity niobium, having a hardness of less than 60 VPN, was produced by cage-zone refinieg techniques. (auth)« less

  2. From Titan to the primitive Earth

    NASA Astrophysics Data System (ADS)

    Raulin, F.; Gpcos Team

    Our knowledge of the conditions prevailing in the environment of the primitive Earth is still very limited, due to the lack of geological data. Fortunately, there are a few planetary objects in the solar system which present similarities with our planet, including during its early history. Titan is one of these. With a diameter of more than 5100 km, Titan, the largest moon of Saturn, is also the only one to have a dense atmosphere. This atmosphere, clearly evidenced by the presence of haze layers, extends to approximately 1500 km. Like the Earth, Titan's atmosphere is mainly composed of dinitrogen, N2 . The other main constituents are methane, CH4 , about 1.6% to 2.0% in the stratosphere, as measured by CIRS on Cassini and GC-MS on Huygens and dihydrogen (H2 , approximate 0.1%). With surface temperatures of approximately 94 K, and an average surface pressure of 1.5 bar, Titan's atmosphere is nearly five times denser than the Earth's. Despite of these differences between Titan and the Earth there are several analogies that can be drawn between the two planetary bodies. The first resemblances concern the vertical atmospheric structure. Although Titan is much colder, with a troposphere (˜94-˜70 K), a tropopause (70.4 K) and a stratosphere (˜70-175 K) its atmosphere presents a similar complex structure to that of the Earth. These analogies are linked to the presence in both atmospheres of greenhouse gases: CH4 and H2 on Titan, equivalent respectively to terrestrial condensable H2 O and non-condensable CO2 . In addition the haze particles and clouds in Titan's atmosphere play an antigreenhouse effect similar to that of the terrestrial atmospheric aerosols and clouds. Indeed, methane on Titan seems to play the role of water on the Earth, with a complex cycle, which still has to be understood. The possibility that Titan is covered with hydrocarbon oceans is now ruled out, but it is still possible that Titan's surface include lakes of methane and ethane. Moreover, the

  3. Titan - a New Laboratory for Oceanography

    NASA Astrophysics Data System (ADS)

    Lorenz, R. D.

    2001-12-01

    Saturn's giant moon Titan has a thick (1.5 bar) nitrogen atmosphere, and quite probably large expanses of liquid hydrocarbons on its surface. The physical processes in these lakes and seas will open new vistas on oceanography and limnology. Although the Voyager-era paradigm of a deep, global ocean is ruled out by radar and infrared data showing that at least part of Titan's surface is icy, the photochemical arguments that originally led to the proposal of hydrocarbon oceans still apply. Even if the methane in the atmosphere is being resupplied by delivery from the interior, the ethane produced by photolysis would still accumulate to form large deposits on the surface. The near-infrared maps of Titan's surface from the Hubble Space Telescope and groundbased adaptive optics consistently show a number of dark (in fact, pitch-black!) regions that are strong candidates for hydrocarbon seas. These could be up to some 500km in extent. Titan promises to be a new laboratory for oceanography. Like in meteorology, many ocean processes are better parameterized than they are understood, and thus the different physical circumstances on Titan may shed new light on them. Titan has a lower gravity and its ocean fluids are of lower density, perhaps of lower viscosity (depending on solutes and suspended material) and probably rather more likely to cavitate. The ratio of atmospheric density to ocean density is much larger on Titan than on Earth, suggesting that liquid motions will be well-coupled to surface winds (although the distance from the sun is such that the energy in such winds is likely to be low.) Titan is also subject to strong tidal forces (the equilibrium tide due to Saturn's gravity is some 400x larger than that of the moon on Earth.) Although the 100m tidal bulge stays almost fixed because Titan rotates synchronously, the eccentricity of Titan's orbit leads to significant libration and variation in the tidal strength. The 500km seas allowed by the IR data may yet have a

  4. Studies of Niobium Thin Film Produced by Energetic Vacuum Deposition

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Genfa Wu; Anne-Marie Valente; H. Phillips

    2004-05-01

    An energetic vacuum deposition system has been used to study deposition energy effects on the properties of niobium thin films on copper and sapphire substrates. The absence of working gas avoids the gaseous inclusions commonly seen with sputtering deposition. A biased substrate holder controls the deposition energy. Transition temperature and residual resistivity ratio of the niobium thin films at several deposition energies are obtained together with surface morphology and crystal orientation measurements by AFM inspection, XRD and TEM analysis. The results show that niobium thin films on sapphire substrate exhibit the best cryogenic properties at deposition energy around 123 eV.more » The TEM analysis revealed that epitaxial growth of film was evident when deposition energy reaches 163 eV for sapphire substrate. Similarly, niobium thin film on copper substrate shows that film grows more oriented with higher deposition energy and grain size reaches the scale of the film thickness at the deposition energy around 153 eV.« less

  5. Process for the generation of .alpha., .beta.-unsaturated carboxylic acids and esters using niobium catalyst

    DOEpatents

    Gogate, Makarand Ratnakav; Spivey, James Jerome; Zoeller, Joseph Robert

    1999-01-01

    A process using a niobium catalyst includes the step of reacting an ester or carboxylic acid with oxygen and an alcohol in the presence a niobium catalyst to respectively produce an .alpha.,.beta.-unsaturated ester or carboxylic acid. Methanol may be used as the alcohol, and the ester or carboxylic acid may be passed over the niobium catalyst in a vapor stream containing oxygen and methanol. Alternatively, the process using a niobium catalyst may involve the step of reacting an ester and oxygen in the presence the niobium catalyst to produce an .alpha.,.beta.-unsaturated carboxylic acid. In this case the ester may be a methyl ester. In either case, niobium oxide may be used as the niobium catalyst with the niobium oxide being present on a support. The support may be an oxide selected from the group consisting of silicon oxide, aluminum oxide, titanium oxide and mixtures thereof. The catalyst may be formed by reacting niobium fluoride with the oxide serving as the support. The niobium catalyst may contain elemental niobium within the range of 1 wt % to 70 wt %, and more preferably within the range of 10 wt % to 30 wt %. The process may be operated at a temperature from 150 to 450.degree. C. and preferably from 250 to 350.degree. C. The process may be operated at a pressure from 0.1 to 15 atm. absolute and preferably from 0.5-5 atm. absolute. The flow rate of reactants may be from 10 to 10,000 L/kg.sub.(cat) /h, and preferably from 100 to 1,000 L/kg.sub.(cat) /h.

  6. Vanadium Oxide Deposited on Strontium Titanate and Related Supports: Structural, Redox, and Catalytic Properties in Oxidative Dehydrogenation Reactions

    NASA Astrophysics Data System (ADS)

    McCarthy, James A.

    The field of heterogeneous catalysis has advanced largely through the understanding of structure-function relationships, and novel support materials constitute one possible strategy to further this knowledge through the determination of support effects. To this end, the synthesis, characterization, and reactivity of a new catalytic system are reported herein. Vanadium oxide supported on SrTiO3 (VOx/STO) was prepared by atomic layer deposition, and its activity was investigated in various oxidative dehydrogenation (ODH) reactions. In cyclohexane and propane ODH experiments at 500 °C, selectivity toward COx was found to decrease with greater VOx density and minimal STO surface exposure. This indicates that the support itself is an effective total oxidation catalyst, which complicates VOx performance measurements. In the propane studies, VOx/STO achieved lower turnover frequency (TOF) and propylene yield compared to conventional supported VO x materials. The lower activity of VOx/STO catalysts was correlated with their VOx species being less easily reducible, as determined by temperature-programmed reduction (TPR). The suppressed reducibility is attributed to the stronger surface basicity of STO, which is induced by the presence of relatively electropositive Sr2+ within the perovskite lattice. Studies of cyclohexene ODH at 300 °C were conducted to minimize intrinsic conversion from the supports. The VOx/STO catalysts were mostly found to be less active than VOx/TiO2 and VOx/Al 2O3, in accordance with reducibility measurements. However, one sample containing 0.75% vanadium on STO was particularly active, achieving a TOF greater than 0.01 s-1, while maintaining almost 90% dehydrogenation selectivity. In general, VOx/STO materials were found to be more selective for 1,3-cyclohexadiene compared to traditional catalysts. Other titanates of the form A2+TiO3 were also investigated as supports, and the reducibility of VOx was found to trend with the electronegativity of the

  7. Initial Assessment of CSA Group Niobium Boron Based Coatings on 4340 Steel

    DTIC Science & Technology

    2017-07-01

    Technical Report ARWSB-TR-17026 Initial Assessment of CSA Group Niobium- Boron Based Coatings on 4340 Steel C.P. Mulligan...REPORT TYPE Technical 3. DATES COVERED (From - To) 4. TITLE AND SUBTITLE Initial Assessment of CSA Group Niobium- Boron Based Coatings on 4340...metallographic mounts reported as (1) thin and (2) thick Niobium- Boron (Nb-B) type coatings on steel. CSA Group is interested in providing coatings for potential

  8. The greenhouse of Titan.

    NASA Technical Reports Server (NTRS)

    Sagan, C.

    1973-01-01

    Analysis of non-gray radiative equilibrium and gray convective equilibrium on Titan suggests that a massive molecular-hydrogen greenhouse effect may be responsible for the disagreement between the observed IR temperatures and the equilibrium temperature of an atmosphereless Titan. Calculations of convection indicate a probable minimum optical depth of 14 which corresponds to a molecular hydrogen shell of substantial thickness with total pressures of about 0.1 bar. It is suggested that there is an equilibrium between outgassing and blow-off on the one hand and accretion from the protons trapped in a hypothetical Saturnian magnetic field on the other, in the present atmosphere of Titan. It is believed that an outgassing equivalent to the volatilization of a few kilometers of subsurface ice is required to maintain the present blow-off rate without compensation for all geological time. The presence of an extensive hydrogen corona around Titan is postulated, with surface temperatures up to 200 K.

  9. THE COLORIMETRIC DETERMINATION OF VANADIUM IN NIOBIUM-VANADIUM ALLOYS

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Articolo, O.J.

    1959-06-26

    A procedure is described for the analysis of vanadium in niobium-- vanadium alloys in the range >0.1% vanadium with an accuracy of better than 3%. The method was applied to the analysis of niobium alloys in which the nominal per cent vanadium varied between 0.3 to 4.6%. The sample is dissolved in a mixture of nitric and hydrofluoric acid and then evaporated to fumes with sulfuric acid. The niobium is hydrolyzed with sulfurous acid and separated from the vanadium by filtration. Hydrogen peroxide is added to the filtrate to form a reddish brown complex with the vanadium. The optical densitymore » of the resulting solution is obtained at 450 m mu on a model B Beckman spectrophotometer. (auth)« less

  10. The Global Energy Balance of Titan

    NASA Technical Reports Server (NTRS)

    Li, Liming; Nixon, Conor A.; Achterberg, Richard K.; Smith, Mark A.; Gorius, Nicolas J. P.; Jiang, Xun; Conrath, Barney J.; Gierasch, Peter J.; Simon-Miller, Amy A.; Flasar, F. Michael; hide

    2011-01-01

    We report the first measurement of the global emitted power of Titan. Longterm (2004-2010) observations conducted by the Composite Infrared Spectrometer (CIRS) onboard Cassini reveal that the total emitted power by Titan is (2.84 plus or minus 0.01) x 10(exp 8) watts. Together with previous measurements of the global absorbed solar power of Titan, the CIRS measurements indicate that the global energy budget of Titan is in equilibrium within measurement error. The uncertainty in the absorbed solar energy places an upper limit on the energy imbalance of 5.3%.

  11. Method for etching thin films of niboium and niobium-containing compounds for preparing superconductive circuits

    DOEpatents

    Kampwirth, R.T.; Schuller, I.K.; Falco, C.M.

    1979-11-23

    An improved method of preparing thin film superconducting electrical circuits of niobium or niobium compounds is provided in which a thin film of the niobium or niobium compound is applied to a nonconductive substrate and covered with a layer of photosensitive material. The sensitive material is in turn covered with a circuit pattern exposed and developed to form a mask of the circuit in photoresistive material on the surface of the film. The unmasked excess niobium film is removed by contacting the substrate with an aqueous etching solution of nitric acid, sulfuric acid, and hydrogen fluoride, which will rapidly etch the niobium compound without undercutting the photoresist. A modification of the etching solution will permit thin films to be lifted from the substrate without further etching.

  12. Titan Temperature Lag Maps

    NASA Image and Video Library

    2016-02-18

    This sequence of maps shows varying surface temperatures on Saturn moon Titan at two-year intervals, from 2004 to 2016. The measurements were made by the Composite Infrared Spectrometer CIRS instrument on NASA Cassini spacecraft. The maps show thermal infrared radiation (heat) coming from Titan's surface at a wavelength of 19 microns, a spectral window at which the moon's otherwise opaque atmosphere is mostly transparent. Temperatures have been averaged around the globe from east to west (longitudinally) to emphasize the seasonal variation across latitudes (from north to south). Black regions in the maps are areas for which there was no data. Titan's surface temperature changes slowly over the course of the Saturn system's long seasons, which each last seven and a half years. As on Earth, the amount of sunlight received at each latitude varies as the sun's illumination moves northward or southward over the course of the 30-year-long Saturnian year. When Cassini arrived at Saturn in 2004, Titan's southern hemisphere was in late summer and was therefore the warmest region. Shortly after the 2009 equinox, in 2010, temperatures were symmetrical across the northern and southern hemispheres, mimicking the distribution observed by Voyager 1 in 1980 (one Titan year earlier). Temperatures subsequently cooled in the south and rose in the north, as southern winter approached. While the overall trend in the temperature shift is clearly evident in these maps, there is narrow banding in several places that is an artifact of making the observations through Titan's atmosphere. The moon's dense, hazy envelope adds noise to the difficult measurement. Although it moves in latitude, the maximum measured temperature on Titan remains around -292 degrees Fahrenheit (-179.6 degrees Celsius, 93.6 Kelvin), with a minimum temperature at the winter pole only 6 degrees Fahrenheit (3.5 degrees Celsius or Kelvin) colder. This is a much smaller contrast than exists between Earth's warmest and

  13. Crystal growth and scintillation properties of potassium strontium bromide

    NASA Astrophysics Data System (ADS)

    Stand, L.; Zhuravleva, M.; Wei, H.; Melcher, C. L.

    2015-08-01

    In this work, potassium strontium bromide activated with divalent europium, (KSr2Br5:Eu) has been studied. It has a monoclinic crystal structure and a density of 3.98 g/cm3. Two single crystals of KSr2Br5 doped with 5% Eu2+, with diameters of 13 mm and 22 mm, were grown in a two zone transparent furnace via the Bridgman technique. The X-ray excited emission spectrum consisted of a single peak at ∼427 nm due to the 5d-4f transition in Eu2+. The measured light yield and energy resolution at 662 keV was 75,000 ph/MeV and 3.5%. At low energies KSr2Br5:Eu 5% also displays good energy resolution, 6.7% at 122 keV and 7.9% at 59.5 keV.

  14. Extraction spectrophotometric determination of niobium in rocks with sulfochlorophenol S

    USGS Publications Warehouse

    Childress, A.E.; Greenland, L.P.

    1980-01-01

    After acid decomposition and potassium pyrosulfate fusion, niobium (1-26 ppm) is separated from interfering elements by extraction into methyl isobutyl ketone from 6 M H2SO4-2 M HF and back-extracted into water. The niobium-sulfochloro-phenol S complex is extracted into amyl alcohol. ?? 1980.

  15. Titan AVIATR - Aerial Vehicle for In Situ and Airborne Titan Reconnaissance

    NASA Astrophysics Data System (ADS)

    Kattenhorn, Simon A.; Barnes, J. W.; McKay, C. P.; Lemke, L.; Beyer, R. A.; Radebaugh, J.; Adamkovics, M.; Atkinson, D. H.; Burr, D. M.; Colaprete, T.; Foch, R.; Le Mouélic, S.; Merrison, J.; Mitchell, J.; Rodriguez, S.; Schaller, E.

    2010-10-01

    Titan AVIATR - Aerial Vehicle for In Situ and Airborne Titan Reconnaissance - is a small (120 kg), nuclear-powered Titan airplane in the Discovery/New Frontiers class based on the concept of Lemke (2008 IPPW). The scientific goals of the mission are designed around the unique flexibility offered by an airborne platform: to explore Titan's diversity of surface landforms, processes, and compositions, as well as to study and measure the atmospheric circulation, aerosols, and humidity. AVIATR would address and surpass many of the science goals of hot-air balloons in Titan flagship studies. The strawman instrument payload is narrowly focused on the stated scientific objectives. The optical remote sensing suite comprises three instruments - an off-nadir high-resolution 2-micron camera, a horizon-looking 5-micron imager, and a 1-6 micron pushbroom near-infrared spectrometer. The in situ instruments include atmospheric structure, a methane humidity sensor, and a raindrop detector. An airplane has operational advantages over a balloon. Its piloted nature allows a go-to capability to image locations of interest in real time, thereby allowing for directed exploration of many features of primary geologic interest: Titan's sand dunes, mountains, craters, channels, and lakes. Subsequent imaging can capture changes in these features during the primary mission. AVIATR can fly predesigned routes, building up large context mosaics of areas of interest before swooping down to low altitude to acquire high-resolution images at 30-cm spatial sampling, similar to that of HiRISE at Mars. The elevation flexibility of the airplane allows us to acquire atmospheric profiles as a function of altitude at any desired location. Although limited by the direct-to-Earth downlink bandwidth, the total scientific data return from AVIATR will be >40 times that returned from Huygens. To maximize the science per bit, novel data storage and downlink techniques will be employed, including lossy compression

  16. Welding Niobium Bearing HSLA Steels 'Myths and Magic'

    NASA Astrophysics Data System (ADS)

    Kirkwood, Phil

    Niobium is not currently added to ferritic steels with the specific objective of improving weldability and is more likely to be present to harness its combined beneficial effects on strength and toughness. Nevertheless, as carbon levels in many classes of HSLA steel, are progressively reduced, there is an increasing awareness that, amongst the microalloying elements, niobium is uniquely placed to deliver the mechanical property combinations that modern specifications demand and simultaneously deliver a `bonus' by way of enhanced weldability.

  17. Titan's greenhouse and antigreenhouse effects

    NASA Technical Reports Server (NTRS)

    Mckay, Christopher P.; Pollack, James B.; Courtin, Regis

    1992-01-01

    Thermal mechanisms active in Titan's atmosphere are discussed in a brief review of data obtained during the Voyager I flyby in 1980. Particular attention is given to the greenhouse effect (GHE) produced by atmospheric H2, N2, and CH4; this GHE is stronger than that on earth, with CH4 and H2 playing roles similar to those of H2O and CO2 on earth. Also active on Titan is an antigreenhouse effect, in which dark-brown and orange organic aerosols block incoming solar light while allowing IR radiation from the Titan surface to escape. The combination of GHE and anti-GHE leads to a surface temperature about 12 C higher than it would be if Titan had no atmosphere.

  18. Titan as the Abode of Life

    PubMed Central

    McKay, Christopher P.

    2016-01-01

    Titan is the only world we know, other than Earth, that has a liquid on its surface. It also has a thick atmosphere composed of nitrogen and methane with a thick organic haze. There are lakes, rain, and clouds of methane and ethane. Here, we address the question of carbon-based life living in Titan liquids. Photochemically produced organics, particularly acetylene, in Titan’s atmosphere could be a source of biological energy when reacted with atmospheric hydrogen. Light levels on the surface of Titan are more than adequate for photosynthesis, but the biochemical limitations due to the few elements available in the environment may lead only to simple ecosystems that only consume atmospheric nutrients. Life on Titan may make use of the trace metals and other inorganic elements produced by meteorites as they ablate in its atmosphere. It is conceivable that H2O molecules on Titan could be used in a biochemistry that is rooted in hydrogen bonds in a way that metals are used in enzymes by life on Earth. Previous theoretical work has shown possible membrane structures, azotosomes, in Titan liquids, azotosomes, composed of small organic nitrogen compounds, such as acrylonitrile. The search for a plausible information molecule for life in Titan liquids remains an open research topic—polyethers have been considered and shown to be insoluble at Titan temperatures. Possible search strategies for life on Titan include looking for unusual concentrations of certain molecules reflecting biological selection. Homochirality is a special and powerful example of such biology selection. Environmentally, a depletion of hydrogen in the lower atmosphere may be a sign of metabolism. A discovery of life in liquid methane and ethane would be our first compelling indication that the universe is full of diverse and wondrous life forms. PMID:26848689

  19. Identification of Acetylene on Titan's Surface

    NASA Astrophysics Data System (ADS)

    Singh, S.; McCord, T. B.; Rodriguez, S.; Combe, J. P.; Cornet, T.; Le Mouelic, S.; Maltagliati, L.; Chevrier, V.; Clark, R. N.

    2015-12-01

    Titan's atmosphere is opaque in the near infrared due to gaseous absorptions, mainly by methane, and scattering by aerosols, except in a few "transparency windows" (e.g., Sotin et al., 2005). Thus, the composition of Titan surface remains difficult to access from space and is still poorly constrained, limited to ethane in the polar lakes (Brown et al., 2008) and a few possible organic molecules on the surface (Clark et al., 2010). Photochemical models suggest that most of the organic compounds formed in the atmosphere are heavy enough to condense and build up at the surface in liquid and solid states over geological timescale (Cordier et al., 2009, 2011). Acetylene (C2H2) is one of the most abundant organic molecules in the atmosphere and thus thought to present on the surface as well. Here we report direct evidence of solid C2H2 on Titan's surface using Cassini Visual and Infrared Mapping Spectrometer (VIMS) data. By comparing VIMS observations and laboratory measurements of solid and liquid C2H2, we identify a specific absorption at 1.55 µm that is widespread over Titan but is particularly strong in the brightest terrains. This surface variability suggests that C2H2 is mobilized by surface processes, such as surface weathering, topography, and dissolution/evaporation. The detection of C2H2 on the surface of Titan opens new paths to understand and constrain Titan's surface activity. Since C2H2 is highly soluble in Titan liquids (Singh et al. 2015), it can easily dissolve in methane/ethane and may play an important role in carving of fluvial channels and existence of karstic lakes at higher latitudes on Titan. These processes imply the existence of a dynamic surface with a continued history of erosion and deposition of C2H2 on Titan.

  20. Handling Late Changes to Titan Science

    NASA Technical Reports Server (NTRS)

    Pitesky, Jo Eliza; Steadman, Kim; Ray, Trina; Burton, Marcia

    2014-01-01

    The Cassini mission has been in orbit for eight years, returning a wealth of scientific data from Titan and the Saturnian system. The mission, a cooperative undertaking between NASA, ESA and ASI, is currently in its second extension of the prime mission. The Cassini Solstice Mission (CSM) extends the mission's lifetime until Saturn's northern summer solstice in 2017. The Titan Orbital Science Team (TOST) has the task of integrating the science observations for all 56 targeted Titan flybys in the CSM. In order to balance Titan science across the entire set of flybys during the CSM, to optimize and influence the Titan flyby altitudes, and to decrease the future workload, TOST went through a "jumpstart" process before the start of the CSM. The "jumpstart" produced Master Timelines for each flyby, identifying prime science observations and allocating control of the spacecraft attitude to specific instrument teams. Three years after completing this long-range plan, TOST now faces a new challenge: incorporating changes into the Titan Science Plan without undoing the balance achieved during the jumpstart.

  1. Strontium-90 in newborns and childhood disease.

    PubMed

    Mangano, J J; Sternglass, E J; Gould, J M; Sherman, J D; Brown, J; McDonnell, W

    2000-01-01

    Radioactive strontium-90 concentrations in baby teeth obtained from Suffolk County, New York, rose steadily during the 1980s. Recent levels of strontium-90 are similar to those reported for babies born in the late 1950s-at the height of atmospheric nuclear weapons testing in Nevada. Strontium-90 concentrations increased concomitantly with increases in cancer incidence among Suffolk children under the age of 5 y, a result that mimicked parallel trends observed in the 1950s and early 1960s. Given that effects of strontium-90 on developing cells are most pronounced during the fetal and infant periods, escalating levels should be viewed as a factor in the recent decline in various child health status measures.

  2. Energetics of magnesium, strontium, and barium doped lanthanum gallate perovskites

    NASA Astrophysics Data System (ADS)

    Cheng, Jihong; Navrotsky, Alexandra

    2004-01-01

    LaGaO 3 perovskites doped with Sr or Ba at the La site and Mg at the Ga site were prepared by solid-state reaction or sol-gel method and characterized. Enthalpies of formation from constituent oxides at 298 K were determined by high-temperature oxide melt solution calorimetry. Energetic trends are discussed in terms of defect chemistry. As oxygen deficiency increases, formation enthalpies define three trends, LaGa 1- yMg yO 3- δ (LGM), La 1- xSr xGa 1- yMg yO 3- δ (LSGM), and La 1- xBa xGa 1- yMg yO 3- δ (LBGM). They become less exothermic with increasing doping, suggesting a dominant destabilization effect from oxygen vacancies. The endothermic enthalpy of vacancy formation is 275±37, 166±18 and 138±12 kJ/mol of VO·· for LGM, LBGM and LSGM, respectively. Tolerance factor and ion size mismatch also affect enthalpies. In terms of energetics, Sr is the best dopant for the La site and Mg for the Ga site, supporting earlier studies, including oxygen ion conductivity and computer modeling.

  3. Titan Orbiter with Aerorover Mission (TOAM)

    NASA Astrophysics Data System (ADS)

    Sittler, Edward C.; Cooper, J. F.; Mahaffey, P.; Esper, J.; Fairbrother, D.; Farley, R.; Pitman, J.; Kojiro, D. R.; TOAM Team

    2006-12-01

    We propose to develop a new mission to Titan called Titan Orbiter with Aerorover Mission (TOAM). This mission is motivated by the recent discoveries of Titan, its atmosphere and its surface by the Huygens Probe, and a combination of in situ, remote sensing and radar mapping measurements of Titan by the Cassini orbiter. Titan is a body for which Astrobiology (i.e., prebiotic chemistry) will be the primary science goal of any future missions to it. TOAM is planned to use an orbiter and balloon technology (i.e., aerorover). Aerobraking will be used to put payload into orbit around Titan. The Aerorover will probably use a hot air balloon concept using the waste heat from the MMRTG 500 watts. Orbiter support for the Aerorover is unique to our approach for Titan. Our strategy to use an orbiter is contrary to some studies using just a single probe with balloon. Autonomous operation and navigation of the Aerorover around Titan will be required, which will include descent near to the surface to collect surface samples for analysis (i.e., touch and go technique). The orbiter can provide both relay station and GPS roles for the Aerorover. The Aerorover will have all the instruments needed to sample Titan’s atmosphere, surface, possible methane lakes-rivers, use multi-spectral imagers for surface reconnaissance; to take close up surface images; take core samples and deploy seismometers during landing phase. Both active and passive broadband remote sensing techniques will be used for surface topography, winds and composition measurements.

  4. Synthesis and photocatalytic activity of N-doped TiO2 produced in a solid phase reaction

    NASA Astrophysics Data System (ADS)

    Xin, Gang; Pan, Hongfei; Chen, Dan; Zhang, Zhihua; Wen, Bin

    2013-02-01

    N-doped TiO2 was synthesized by calcining a mixture of titanic acid and graphitic carbon nitride (g-C3N4) at temperatures above 500 °C. The final samples were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), electron energy loss spectroscopy (EELS), and UV-vis diffuse reflectance spectra. The photocatalytic activity of N-doped TiO2 was studied by assessing the degradation of methylene blue in an aqueous solution, under visible light and UV light irradiation. It was found that the N-doped TiO2 displayed higher photocatalytic activity than pure TiO2, under both visible and UV light.

  5. The influences of mole composition of strontium (x) on properties of barium strontium titanate (Ba{sub 1−x}Sr{sub x}TiO{sub 3}) prepared by solid state reaction method

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Sandi, Dianisa Khoirum; Supriyanto, Agus; Iriani, Yofentina, E-mail: yopen-2005@yahoo.com

    2016-02-08

    Barium Strontium Titanate (Ba{sub 1-x}Sr{sub x}TiO{sub 3}) or BST was prepared by solid state reaction method. Raw materials are BaCO{sub 3}, SrCO{sub 3}, and TiO{sub 2}. Those materials are mixed for 8 h, pressed, and sintered at temperature 1200°C for 2 h. Mole composition of Sr (x) was varied to study its influences on structural, morphological, and electrical properties of BST. Variation of (x) are x = 0; x = 0.1; and x = 0.5. XRD patterns showed a single phase of BST, which mean that mixture of raw materials was homogenous. Crystal structure was influenced by x. BaTiO{sub 3} and Ba{submore » 0.9}Ti{sub 0.1}TiO{sub 3} have tetragonal crystal structure, while Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3} is cubic. The diffraction angle shifted to right side (angle larger) as the increases of x. Crystalline size of BaTiO{sub 3}, Ba{sub 0.9}Sr{sub 0.1}TiO{sub 3}, and Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3} are 38.13 nm; 38.62 nm; and 37.13 nm, respectively. SEM images showed that there are still of pores which were influenced by x. Ba{sub 0.9}Sr{sub 0.1}TiO{sub 3} has densest surface (pores are few and small in size). Sawyer Tower circuit showed that BaTiO{sub 3} and Ba{sub 0.9}Sr{sub 0.1} TiO{sub 3} is ferroelectric, while Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3} is paraelectric. The dielectric constants of BaTiO{sub 3}, Ba{sub 0.9}Sr{sub 0.1}TiO{sub 3} and Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3} at frequency of 1 KHz are 156; 196; and 83, respectively. Ba{sub 0.9}Sr{sub 0.1}TiO{sub 3} has relatively highest dielectric constant. It is considered that Ba{sub 0.9}Sr{sub 0.1}TiO{sub 3} has densest surface.« less

  6. The bulk composition of Titan's atmosphere.

    NASA Technical Reports Server (NTRS)

    Trafton, L.

    1972-01-01

    Consideration of the physical constraints for Titan's atmosphere leads to a model which describes the bulk composition of the atmosphere in terms of observable parameters. Intermediate-resolution photometric scans of both Saturn and Titan, including scans of the Q branch of Titan's methane band, constrain these parameters in such a way that the model indicates the presence of another important atmospheric gas, namely, another bulk constituent or a significant thermal opacity. Further progress in determining the composition and state of Titan's atmosphere requires additional observations to eliminate present ambiguities. For this purpose, particular observational targets are suggested.

  7. Titan's Ammonia Feature

    NASA Technical Reports Server (NTRS)

    Smythe, W.; Nelson, R.; Boryta, M.; Choukroun, M.

    2011-01-01

    NH3 has long been considered an important component in the formation and evolution of the outer planet satellites. NH3 is particularly important for Titan, since it may serve as the reservoir for atmospheric nitrogen. A brightening seen on Titan starting in 2004 may arise from a transient low-lying fog or surface coating of ammonia. The spectral shape suggests the ammonia is anhydrous, a molecule that hydrates quickly in the presence of water.

  8. The environment of Titan, 1975

    NASA Technical Reports Server (NTRS)

    1976-01-01

    Information regarding the physical characteristics of Titan and atmospheric models necessary to support design and mission planning of spacecraft that are to orbit Titan, enter its atmosphere or land on its surface is given.

  9. Titan Extraterrestrial Land of Lakes

    NASA Image and Video Library

    2013-12-12

    A colorized flyover of Titan's hydrocarbon seas and lakes. Data was collected by the Cassini spacecraft radar instrument between 2004 and 2013 during several flybys of Titan. Heights of features are exaggerated 10 times.

  10. Thermal and Electrical Transport in Oxide Heterostructures

    NASA Astrophysics Data System (ADS)

    Ravichandran, Jayakanth

    vacancies are employed to achieve band engineering. This method was used to obtain tunable transparent conducting properties and thermoelectric properties for heavily doped strontium titanate. The second aspect investigated is the use of strongly correlated materials for thermoelectricity. The cobaltates, specifically layered cobaltates, show large thermopower even at very large carrier densities. The coupling of thermopower and electrical conductivity is shown to be weaker for a strongly correlated material such as cobaltate, which opens up possibilities of complete decoupling of all three thermoelectric coefficients. Finally, the thermal properties of complex oxides, specifically in perovskite titanates, is addressed in detail. Thermal conductivity is demonstrated to be a sensitive probe for defects in a system, where processing conditions play a significant role in modulating the crystallinity of the material. The perovskite titanate superlattice system of strontium titanate and calcium titanate is used beat alloy limit. It also shows interesting period thickness dependent thermal properties. The possible origin of this effect is briefly discussed and future directions for this research is also elaborated in detail.

  11. The Veils of Titan

    NASA Image and Video Library

    2004-05-06

    The veils of Saturn's most mysterious moon have begun to lift in Cassini's eagerly awaited first glimpse of the surface of Titan, a world where scientists believe organic matter rains from hazy skies and seas of liquid hydrocarbons dot a frigid surface. Surface features previously observed only from Earth-based telescopes are now visible in images of Titan taken in mid-April by Cassini through one of the narrow angle camera's spectral filters specifically designed to penetrate the thick atmosphere. The image scale is 230 kilometers (143 miles) per pixel, and it rivals the best Earth-based images. The two images displayed here show Titan from a vantage point 17 degrees below its equator, yielding a view from 50 degrees north latitude all the way to its south pole. The image on the left was taken four days after the image on the right. Titan rotated 90 degrees in that time. The two images combined cover a region extending halfway around the moon. The observed brightness variations suggest a diverse surface, with variations in average reflectivity on scales of a couple hundred kilometers. The images were taken through a narrow filter centered at 938 nanometers, a spectral region in which the only obstacle to light is the carbon-based, organic haze. Despite the rather long 38-second exposure times, there is no noticeable smear due to spacecraft motion. The images have been magnified 10 times and enhanced in contrast to bring out details. No further processing to remove the effects of the overlying atmosphere has been performed. The superimposed grid over the images illustrates the orientation of Titan -- north is up and rotated 25 degrees to the left -- as well as the geographical regions of the satellite that are illuminated and visible. The yellow curve marks the position of the boundary between day and night on Titan. The enhanced image contrast makes the region within 20 degrees of this day and night division darker than usual. The Sun illuminates Titan from the

  12. Study on Resistive Switching Property of Ti Doped Novel NiO Thin Films

    NASA Astrophysics Data System (ADS)

    Li, Y.; Zhao, G. Y.; Kou, Z. B.; Liu, J. C.; Zhu, R.

    2018-01-01

    Ti doped nickel oxide thin films have been fabricated by sol-gel dip-coating process using nickel acetate and tetrabutyl titanate as source materials. The effect of the amount of Ti dopant on the surface roughness, optical, chemical state and electrical properties of NiO: Ti thin films was observed by atomic force microscopy (AFM), Uv-vis spectroscopy, X-ray photoelectron spectroscopy(XPS) and I-V measurement, respectively. Results show that the Ti doping is an effective ways to improve the resistive switching behaviors and it is a convenient way to understand the mechanism of the resistive switching behaviors.

  13. Phase stabilisation of hexagonal barium titanate doped with transition metals: A computational study

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Dawson, J.A., E-mail: mtp09jd@sheffield.ac.uk; Freeman, C.L.; Harding, J.H.

    Interatomic potentials recently developed for the modelling of BaTiO{sub 3} have been used to explore the stabilisation of the hexagonal polymorph of BaTiO{sub 3} by doping with transition metals (namely Mn, Co, Fe and Ni) at the Ti-site. Classical simulations have been completed on both the cubic and hexagonal polymorphs to investigate the energetic consequences of transition metal doping on each polymorph. Ti-site charge compensation mechanisms have been used for the multi-valent transition metal ions and cluster binding energies have been considered. Simulations show a significant energetic gain when doping occurs at Ti sites in the face sharing dimers (Ti{submore » 2} sites) of the hexagonal polymorph compared with the doping of the cubic polymorph. This energetic difference between the two polymorphs is true for all transition metals tested and all charge states and in the case of tri- and tetra-valent dopants negative solution energies are found for the hexagonal polymorph suggesting actual polymorph stabilisation occurs with the incorporation of these ions as observed experimentally. Oxidation during incorporation of Ni{sup 2+} and Fe{sup 3+} ions has also been considered. - Graphical abstract: The representation of the strongest binding energy clusters for tri-valent dopants—(a) Ti{sub 2}/O{sub 1} cluster and (b) Ti{sub 2}/O{sub 2} cluster. Highlights: ► Classical simulations show a significant energetic gain when doping occurs at Ti sites in the face sharing dimers (Ti2 sites) of the hexagonal polymorph compared with the doping of the cubic polymorph. ► This energetic difference between the two polymorphs is true for all transition metals tested and all charge states. ► In the case of tri- and tetra- valent dopants negative solution energies are found for the hexagonal polymorph suggesting actual polymorph stabilisation occurs with the incorporation of these ions.« less

  14. Dilatometric shrinkage study on magnesium titanate-based ceramic systems

    NASA Astrophysics Data System (ADS)

    Ermawati, F. U.; Suasmoro, S.

    2018-03-01

    The development of dielectric materials for applications in the microwave frequencies has been increasing with rapid progress in mobile and satellite communication systems. Magnesium titanate (MgTiO3)-based ceramics have been the favourite candidates for such applications due to their excellent dielectric characteristics, i.e. a moderate level of dielectric constant together with a high-quality factor and high-temperature stability. These outstanding performance, however, can only be achieved when the ceramics are highly dense. The work reported in this paper discussed the study on the dilatometric shrinkage behaviour of pure and zinc-doped magnesium titanate (Mg1–xZn x TiO3 for x = 0–0.5) ceramic systems after the systems following the heating passage up to 1300 °C. The results were discussed based on the phase formation data recorded from powder X-ray diffraction (XRD). An additional 2 wt. % V2O5 to the MZT0.2 system has increased the shrinkage of the system, and hence the relative density. The V2O5 addition also prevented the grain growth and did not alter the structure. From 100 Hz to 20 MHz, the dielectric permittivity is constant; which varies from (15.4 – 17.0) ± 0.1 % throughout the samples, these values are therefore frequency independent.

  15. Organic chemistry on Titan: Surface interactions

    NASA Technical Reports Server (NTRS)

    Thompson, W. Reid; Sagan, Carl

    1992-01-01

    The interaction of Titan's organic sediments with the surface (solubility in nonpolar fluids) is discussed. How Titan's sediments can be exposed to an aqueous medium for short, but perhaps significant, periods of time is also discussed. Interactions with hydrocarbons and with volcanic magmas are considered. The alteration of Titan's organic sediments over geologic time by the impacts of meteorites and comets is discussed.

  16. AVIATR—Aerial Vehicle for In-situ and Airborne Titan Reconnaissance. A Titan airplane mission concept

    NASA Astrophysics Data System (ADS)

    Barnes, Jason W.; Lemke, Lawrence; Foch, Rick; McKay, Christopher P.; Beyer, Ross A.; Radebaugh, Jani; Atkinson, David H.; Lorenz, Ralph D.; Le Mouélic, Stéphane; Rodriguez, Sebastien; Gundlach, Jay; Giannini, Francesco; Bain, Sean; Flasar, F. Michael; Hurford, Terry; Anderson, Carrie M.; Merrison, Jon; Ádámkovics, Máté; Kattenhorn, Simon A.; Mitchell, Jonathan; Burr, Devon M.; Colaprete, Anthony; Schaller, Emily; Friedson, A. James; Edgett, Kenneth S.; Coradini, Angioletta; Adriani, Alberto; Sayanagi, Kunio M.; Malaska, Michael J.; Morabito, David; Reh, Kim

    2012-03-01

    We describe a mission concept for a stand-alone Titan airplane mission: Aerial Vehicle for In-situ and Airborne Titan Reconnaissance (AVIATR). With independent delivery and direct-to-Earth communications, AVIATR could contribute to Titan science either alone or as part of a sustained Titan Exploration Program. As a focused mission, AVIATR as we have envisioned it would concentrate on the science that an airplane can do best: exploration of Titan's global diversity. We focus on surface geology/hydrology and lower-atmospheric structure and dynamics. With a carefully chosen set of seven instruments—2 near-IR cameras, 1 near-IR spectrometer, a RADAR altimeter, an atmospheric structure suite, a haze sensor, and a raindrop detector—AVIATR could accomplish a significant subset of the scientific objectives of the aerial element of flagship studies. The AVIATR spacecraft stack is composed of a Space Vehicle (SV) for cruise, an Entry Vehicle (EV) for entry and descent, and the Air Vehicle (AV) to fly in Titan's atmosphere. Using an Earth-Jupiter gravity assist trajectory delivers the spacecraft to Titan in 7.5 years, after which the AVIATR AV would operate for a 1-Earth-year nominal mission. We propose a novel `gravity battery' climb-then-glide strategy to store energy for optimal use during telecommunications sessions. We would optimize our science by using the flexibility of the airplane platform, generating context data and stereo pairs by flying and banking the AV instead of using gimbaled cameras. AVIATR would climb up to 14 km altitude and descend down to 3.5 km altitude once per Earth day, allowing for repeated atmospheric structure and wind measurements all over the globe. An initial Team-X run at JPL priced the AVIATR mission at FY10 715M based on the rules stipulated in the recent Discovery announcement of opportunity. Hence we find that a standalone Titan airplane mission can achieve important science building on Cassini's discoveries and can likely do so

  17. AVIATR - Aerial Vehicle for In-situ and Airborne Titan Reconnaissance A Titan Airplane Mission Concept

    NASA Technical Reports Server (NTRS)

    Barnes, Jason W.; Lemke, Lawrence; Foch, Rick; McKay, Christopher P.; Beyer, Ross A.; Radebaugh, Jani; Atkinson, David H.; Lorenz, Ralph D.; LeMouelic, Stephane; Rodriguez, Sebastien; hide

    2011-01-01

    We describe a mission concept for a stand-alone Titan airplane mission: Aerial Vehicle for In-situ and Airborne Titan Reconnaissance (AVIATR). With independent delivery and direct-to-Earth communications, AVIATR could contribute to Titan science either alone or as part of a sustained Titan Exploration Program. As a focused mission, AVIATR as we have envisioned it would concentrate on the science that an airplane can do best: exploration of Titan's global diversity. We focus on surface geology/hydrology and lower-atmospheric structure and dynamics. With a carefully chosen set of seven instruments-2 near-IR cameras, 1 near-IR spectrometer, a RADAR altimeter, an atmospheric structure suite, a haze sensor, and a raindrop detector-AVIATR could accomplish a significant subset of the scientific objectives of the aerial element of flagship studies. The AVIATR spacecraft stack is composed of a Space Vehicle (SV) for cruise, an Entry Vehicle (EV) for entry and descent, and the Air Vehicle (AV) to fly in Titan's atmosphere. Using an Earth-Jupiter gravity assist trajectory delivers the spacecraft to Titan in 7.5 years, after which the AVIATR AV would operate for a 1-Earth-year nominal mission. We propose a novel 'gravity battery' climb-then-glide strategy to store energy for optimal use during telecommunications sessions. We would optimize our science by using the flexibility of the airplane platform, generating context data and stereo pairs by flying and banking the AV instead of using gimbaled cameras. AVIATR would climb up to 14 km altitude and descend down to 3.5 km altitude once per Earth day, allowing for repeated atmospheric structure and wind measurements all over the globe. An initial Team-X run at JPL priced the AVIATR mission at FY10 $715M based on the rules stipulated in the recent Discovery announcement of opportunity. Hence we find that a standalone Titan airplane mission can achieve important science building on Cassini's discoveries and can likely do so within

  18. TSSM: The in situ exploration of Titan

    NASA Astrophysics Data System (ADS)

    Coustenis, A.; Lunine, J. I.; Lebreton, J. P.; Matson, D.; Reh, K.; Beauchamp, P.; Erd, C.

    2008-09-01

    The Titan Saturn System Mission (TSSM) mission was born when NASA and ESA decided to collaborate on two missions independently selected by each agency: the Titan and Enceladus mission (TandEM), and Titan Explorer, a 2007 Flagship study. TandEM, the Titan and Enceladus mission, was proposed as an L-class (large) mission in response to ESA's Cosmic Vision 2015-2025 Call. The mission concept is to perform remote and in situ investigations of Titan primarily, but also of Enceladus and Saturn's magentosphere. The two satellites are tied together by location and properties, whose remarkable natures have been partly revealed by the ongoing Cassini-Huygens mission. These bodies still hold mysteries requiring a complete exploration using a variety of vehicles and instruments. TSSM will study Titan as a system, including its upper atmosphere, the interactions with the magnetosphere, the neutral atmosphere, surface, interior, origin and evolution, as well as the astrobiological potential of Titan. It is an ambitious mission because its targets are two of the most exciting and challenging bodies in the Solar System. It is designed to build on but exceed the scientific and technological accomplishments of the Cassini- Huygens mission, exploring Titan and Enceladus in ways that are not currently possible (full close-up and in situ coverage over long periods of time for Titan, several close flybys of Enceladus). One overarching goal of the TSSM mission is to explore in situ the atmosphere and surface of Titan. In the current mission architecture, TSSM consists of an orbiter (under NASA's responsibility) with a large host of instruments which would perform several Enceladus and Titan flybys before stabilizing in an orbit around Titan alone, therein delivering in situ elements (a Montgolfière, or hot air balloon, and a probe/lander). The latter are being studied by ESA. The balloon will circumnavigate Titan above the equator at an altitude of about 10 km for several months. The

  19. Impact craters on Titan

    USGS Publications Warehouse

    Wood, Charles A.; Lorenz, Ralph; Kirk, Randy; Lopes, Rosaly; Mitchell, Karl; Stofan, Ellen; ,

    2010-01-01

    Five certain impact craters and 44 additional nearly certain and probable ones have been identified on the 22% of Titan's surface imaged by Cassini's high-resolution radar through December 2007. The certain craters have morphologies similar to impact craters on rocky planets, as well as two with radar bright, jagged rims. The less certain craters often appear to be eroded versions of the certain ones. Titan's craters are modified by a variety of processes including fluvial erosion, mass wasting, burial by dunes and submergence in seas, but there is no compelling evidence of isostatic adjustments as on other icy moons, nor draping by thick atmospheric deposits. The paucity of craters implies that Titan's surface is quite young, but the modeled age depends on which published crater production rate is assumed. Using the model of Artemieva and Lunine (2005) suggests that craters with diameters smaller than about 35 km are younger than 200 million years old, and larger craters are older. Craters are not distributed uniformly; Xanadu has a crater density 2-9 times greater than the rest of Titan, and the density on equatorial dune areas is much lower than average. There is a small excess of craters on the leading hemisphere, and craters are deficient in the north polar region compared to the rest of the world. The youthful age of Titan overall, and the various erosional states of its likely impact craters, demonstrate that dynamic processes have destroyed most of the early history of the moon, and that multiple processes continue to strongly modify its surface. The existence of 24 possible impact craters with diameters less than 20 km appears consistent with the Ivanov, Basilevsky and Neukum (1997) model of the effectiveness of Titan's atmosphere in destroying most but not all small projectiles.

  20. Impact craters on Titan

    USGS Publications Warehouse

    Wood, C.A.; Lorenz, R.; Kirk, R.; Lopes, R.; Mitchell, Ken; Stofan, E.

    2010-01-01

    Five certain impact craters and 44 additional nearly certain and probable ones have been identified on the 22% of Titan's surface imaged by Cassini's high-resolution radar through December 2007. The certain craters have morphologies similar to impact craters on rocky planets, as well as two with radar bright, jagged rims. The less certain craters often appear to be eroded versions of the certain ones. Titan's craters are modified by a variety of processes including fluvial erosion, mass wasting, burial by dunes and submergence in seas, but there is no compelling evidence of isostatic adjustments as on other icy moons, nor draping by thick atmospheric deposits. The paucity of craters implies that Titan's surface is quite young, but the modeled age depends on which published crater production rate is assumed. Using the model of Artemieva and Lunine (2005) suggests that craters with diameters smaller than about 35 km are younger than 200 million years old, and larger craters are older. Craters are not distributed uniformly; Xanadu has a crater density 2-9 times greater than the rest of Titan, and the density on equatorial dune areas is much lower than average. There is a small excess of craters on the leading hemisphere, and craters are deficient in the north polar region compared to the rest of the world. The youthful age of Titan overall, and the various erosional states of its likely impact craters, demonstrate that dynamic processes have destroyed most of the early history of the moon, and that multiple processes continue to strongly modify its surface. The existence of 24 possible impact craters with diameters less than 20 km appears consistent with the Ivanov, Basilevsky and Neukum (1997) model of the effectiveness of Titan's atmosphere in destroying most but not all small projectiles. ?? 2009 Elsevier Inc.

  1. Diurnal variations of Titan

    NASA Astrophysics Data System (ADS)

    Cui, J.; Galand, M.; Yelle, R. V.; Vuitton, V.; Wahlund, J.-E.; Lavvas, P. P.; Mueller-Wodarg, I. C. F.; Kasprzak, W. T.; Waite, J. H.

    2009-04-01

    We present our analysis of the diurnal variations of Titan's ionosphere (between 1,000 and 1,400 km) based on a sample of Ion Neutral Mass Spectrometer (INMS) measurements in the Open Source Ion (OSI) mode obtained from 8 close encounters of the Cassini spacecraft with Titan. Though there is an overall ion depletion well beyond the terminator, the ion content on Titan's nightside is still appreciable, with a density plateau of ~700 cm-3 below ~1,300 km. Such a plateau is associated with the combination of distinct diurnal variations of light and heavy ions. Light ions (e.g. CH5+, HCNH+, C2H5+) show strong diurnal variation, with clear bite-outs in their nightside distributions. In contrast, heavy ions (e.g. c-C3H3+, C2H3CNH+, C6H7+) present modest diurnal variation, with significant densities observed on the nightside. We propose that the distinctions between light and heavy ions are associated with their different chemical loss pathways, with the former primarily through "fast" ion-neutral chemistry and the latter through "slow" electron dissociative recombination. The INMS data suggest day-to-night transport as an important source of ions on Titan's nightside, to be distinguished from the conventional scenario of auroral ionization by magnetospheric particles as the only ionizing source on the nightside. This is supported by the strong correlation between the observed night-to-day ion density ratios and the associated ion lifetimes. We construct a time-dependent ion chemistry model to investigate the effects of day-to-night transport on the ionospheric structures of Titan. The predicted diurnal variation has similar general characteristics to those observed, with some apparent discrepancies which could be reconciled by imposing fast horizontal thermal winds in Titan's upper atmosphere.

  2. Review of ingot niobium as a material for superconducting radiofrequency accelerating cavities

    NASA Astrophysics Data System (ADS)

    Kneisel, P.; Ciovati, G.; Dhakal, P.; Saito, K.; Singer, W.; Singer, X.; Myneni, G. R.

    2015-02-01

    As a result of collaboration between Jefferson Lab and niobium manufacturer Companhia Brasileira de Metalurgia e Mineração (CBMM), ingot niobium was explored as a possible material for superconducting radiofrequency (SRF) cavity fabrication. The first single cell cavity from large-grain high purity niobium was fabricated and successfully tested at Jefferson Lab in 2004. This work triggered research activities in other SRF laboratories around the world. Large-grain (LG) niobium became not only an interesting alternative material for cavity builders, but also material scientists and surface scientists were eager to participate in the development of this technology. Many single cell cavities made from material of different suppliers have been tested successfully and several multi-cell cavities have shown performances comparable to the best cavities made from standard fine-grain niobium. Several 9-cell cavities fabricated by Research Instruments and tested at DESY exceeded the best performing fine grain cavities with a record accelerating gradient of Eacc=45.6 MV/m. The quality factor of those cavities was also higher than that of fine-grain (FG) cavities processed with the same methods. Such performance levels push the state-of-the art of SRF technology and are of great interest for future accelerators. This contribution reviews the development of ingot niobium technology and highlights some of the differences compared to standard FG material and opportunities for further developments.

  3. Precipitation of hydrides in high purity niobium after different treatments

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Barkov, F.; Romanenko, A.; Trenikhina, Y.

    Precipitation of lossy non-superconducting niobium hydrides represents a known problem for high purity niobium in superconducting applications. Using cryogenic optical and laser confocal scanning microscopy we have directly observed surface precipitation and evolution of niobium hydrides in samples after different treatments used for superconducting RF cavities for particle acceleration. Precipitation is shown to occur throughout the sample volume, and the growth of hydrides is well described by the fast diffusion-controlled process in which almost all hydrogen is precipitated atmore » $T=140$~K within $$\\sim30$$~min. 120$$^{\\circ}$$C baking and mechanical deformation are found to affect hydride precipitation through their influence on the number of nucleation and trapping centers.« less

  4. Map of Titan - April 2011

    NASA Image and Video Library

    2011-10-26

    This global digital map of Saturn moon Titan was created using images taken by NASA Cassini spacecraft imaging science subsystem ISS. Because of the scattering of light by Titan dense atmosphere, no topographic shading is visible here.

  5. Space Art "Titan"

    NASA Image and Video Library

    2006-09-13

    Artist Daniel Zeller used the breathtaking imagery from the Cassini spacecraft as a departure point to interpret the intricate surface of Saturn’s moon Titan in this peice titled "Titan". Cassini entered Saturn's orbit in July of 2004 after a seven-year voyage. It then began a four-year mission that includes more than 70 orbits around the ringed planet and its moons. Ink on Paper, 17x21. 2006. Copyrighted: For more information contact Curator, NASA Art Program.

  6. An evaluation of strontium chloride, Rappaport and strontium selenite enrichment for the isolation of salmonellas from man, animals, meat products and abbattoir effluents

    PubMed Central

    Iveson, J. B.; Mackay-Scollay, E. M.

    1972-01-01

    Strontium chloride enrichment broth was found to be comparable to Rappaport broth for the recovery of a wide range of Salmonella serotypes from man, animals, meat products and effluents. With the exception of cloacal samples from reptiles, both procedures were superior to selenite F. The performance of strontium chloride Mand selenite F enrichment was improved when effluent samples were incubated at 43° C. Strontium chloride M and Rappaport enrichment were superior to selenite F for the isolation of Arizona species from reptiles. Strontium chloride B, strontium selenite and Rappaport broths were found suitable for the isolation of multiple Salmonella serotypes from sea water contaminated with abattoir effluents. The strontium chloride B and strontium selenite enrichment media were superior to Rappaport broth when samples were incubated at 43° C. Modified bismuth sulphite agar was found superior to Salmonella—Shigella agar as a solid subculture medium. The investigation of a food poisoning outbreak due to Salmonella typhimurium phage type 21 is reported. The significance of the choice of sampling and isolation techniques in salmonellosis in man and animals is discussed. PMID:4503874

  7. Infrared Optical Absorption in Low-spin Fe2+-doped SrTiO3

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Comes, Ryan B.; Kaspar, Tiffany C.; Heald, Steve M.

    2016-01-06

    Band gap engineering in SrTiO3 and related titanate perovskites has long been explored due to the intriguing properties of the materials for photocatalysis and photovoltaic applications. A popular approach in the materials chemistry community is to substitutionally dope aliovalent transition metal ions onto the B site in the lattice to alter the valence band. However, in such a scheme there is limited control over the dopant valence, and compensating defects often form. Here we demonstrate a novel technique to controllably synthesize Fe2+- and Fe3+-doped SrTiO3 thin films without formation of compensating defects by co-doping with La3+ ions on the Amore » site. We stabilize Fe2+-doped films by doping with two La ions for every Fe dopant, and find that the Fe ions exhibit a low-spin electronic configuration, producing optical transitions in the near infrared regime and degenerate doping. The novel electronic states observed here offer a new avenue for band gap engineering in perovskites for photocatalytic and photovoltaic applications.« less

  8. Titan Saturn System Mission Instrumentation

    NASA Astrophysics Data System (ADS)

    Coustenis, A.; Lunine, J.; Reh, K.; Lebreton, J.-P.; Erd, C.; Beauchamp, P.; Matson, D.

    2012-10-01

    The Titan Saturn System Mission (TSSM), another future mission proposed for Titan's exploration, includes an orbiter and two in situ elements: a hot-air balloon and a lake lander. The instrumentation of those two elements will be presented.

  9. Alternating current response studies on nickel ferrite-niobium composite at room temperature

    NASA Astrophysics Data System (ADS)

    Reddy, L. P. Babu; Rajprakash, H. G.; Chethan, B.; Vijayakumari, S. C.; Ravikiran, Y. T.

    2018-05-01

    In the present research NDNF -Niobium Pentaxide doped Nickel Ferrite [NiFe2O4-Nb2O5-50%] composite was prepared by Mechano-Chemical mixing of NiFe2O4 [NF] with Nb2O5. NF and the NDNF were structurally characterized by four transform infrared spectroscopy [FTIR] and X-ray diffraction [XRD] techniques. The presence of characteristic absorption bands of NF and Nb2O5 in the FTIR spectrum of NDNF with small shift confirmed interfacial interaction of NF with Nb2O5. XRD studies also confirm interfacial interaction between NF and Nb2O5 in the composite and crystalline nature with an average crystallite size of 30nm. The Alternating Current (AC) response parameters of NF and the NDNF were comparatively studied in the frequency range 100Hz-1MHz at room temperature. Increase in AC conductivity of the NDNF has compared to NF was observed and discussed based on the electron hole exchange mechanism.

  10. Indentation Behavior and Mechanical Properties of Tungsten/Chromium co-Doped Bismuth Titanate Ceramics Sintered at Different Temperatures

    PubMed Central

    Xu, Jiageng; Chen, Yu; Tan, Zhi; Nie, Rui; Wang, Qingyuan; Zhu, Jianguo

    2018-01-01

    A sort of tungsten/chromium(W/Cr) co-doped bismuth titanate (BIT) ceramics (Bi4Ti2.95W0.05O12.05 + 0.2 wt % Cr2O3, abbreviate to BTWC) are ordinarily sintered between 1050 and 1150 °C, and the indentation behavior and mechanical properties of ceramics sintered at different temperatures have been investigated by both nanoindentation and microindentation technology. Firstly, more or less Bi2Ti2O7 grains as the second phase were found in BTWC ceramics, and the grain size of ceramics increased with increase of sintering temperatures. A nanoindentation test for BTWC ceramics reveals that the testing hardness of ceramics decreased with increase of sintering temperatures, which could be explained by the Hall–Petch equation, and the true hardness could be calculated according to the pressure-state-response (PSR) model considering the indentation size effect, where the value of hardness depends on the magnitude of load. While, under the application of microsized Vickers, the sample sintered at a lower temperature (1050 °C) gained four linearly propagating cracks, however, they were observed to shorten in the sample sintered at a higher temperature (1125 °C). Moreover, both the crack deflection and the crack branching existed in the latter. The hardness and the fracture toughness of BTWC ceramics presented a contrary variational tendency with increase of sintering temperatures. A high sintering tends to get a lower hardness and a higher fracture toughness, which could be attributed to the easier plastic deformation and the stronger crack inhibition of coarse grains, respectively, as well as the toughening effect coming from the second phase. PMID:29584677

  11. Amino acidis derived from Titan tholins

    NASA Technical Reports Server (NTRS)

    Khare, Bishun N.; Sagan, Carl; Ogino, Hiroshi; Nagy, Bartholomew; Er, Cevat

    1986-01-01

    The production of amino acids by acid treatment of Titan tholin is experimentally investigated. The synthesis of Titan tholin and the derivatization of amino acids to N-trifluoroacetyl isopropyl esters are described. The gas chromatography/mass spectroscopy analysis of the Titan tholins reveals the presence of glycine, alpha and beta alainine, and aspartic acid, and the total yield of amino acids is about 0.01.

  12. Titan's Methane Hydrological Cycle: Detection of Seasonal Change

    NASA Astrophysics Data System (ADS)

    Schaller, E. L.; Brown, M. E.; Roe, H. G.

    2007-08-01

    We have acquired whole disk spectra of Titan on over 100 nights with IRTF/SpeX during the 2006-2007 Titan season. The data encompass the spectral range of 0.8 to 2.4 microns at a resolution of 375. These disk- integrated spectra allow us to determine Titan's total fractional cloud coverage and altitudes of clouds present. The near lack of tropospheric cloud activity in these spectra is in sharp contrast to nearly every spectrum taken from 1995-1999 with UKIRT by Griffith et al. (1998 & 2000) who found rapidly varying clouds covering 0.5-9% of Titan's disk. The differences in these two similar datasets indicate a striking seasonal change in the behavior of Titan's clouds. Adaptive optics observations from Keck and Gemini also show markedly decreased cloud activity in the late southern summer era compared with the period surrounding southern summer solstice (October 2002). Observations of the latitudes, magnitudes, altitudes, and frequencies of Titan's clouds as Titan moves toward southern autumnal equinox in 2009 will help elucidate when and how Titan's methane hydrological cycle changes with season.

  13. Effect of fluorine doped TiO2 on the property of perovskite solar cell

    NASA Astrophysics Data System (ADS)

    Zhang, X. Q.; Wu, Y. P.; Huang, Y.; Zhou, Z. H.; Shen, S.

    2017-03-01

    Anatase TiO2 nanoparticles with different amounts of fluorine doping were synthesized by a hydrothermal method using hydrogen titanate nanotubes as a precursor and applied as mesoporous layer for preparing perovskite solar cell. The morphology and structures were characterized by scanning electron microscope (SEM) and X-ray diffraction (XRD), meanwhile, the properties and performances were tested by photoluminescence spectrum (PL) and current density and voltage (J-V) curve. It was found that doping fluorine into TiO2 made the photoelectric conversion efficiency (PCE) of perovskite solar cell (PSC) to be improved. The best PCE of PSC based on a F-doped TiO2 was 13.06% and increased by 51% compared to an un-doped TiO2. The study provided a direction for the exploration of high performance electron transport layer of perovskite solar cell.

  14. Electrical Properties of Thin-Film Capacitors Fabricated Using High Temperature Sputtered Modified Barium Titanate.

    PubMed

    Reynolds, Glyn J; Kratzer, Martin; Dubs, Martin; Felzer, Heinz; Mamazza, Robert

    2012-04-13

    Simple thin-film capacitor stacks were fabricated from sputter-deposited doped barium titanate dielectric films with sputtered Pt and/or Ni electrodes and characterized electrically. Here, we report small signal, low frequency capacitance and parallel resistance data measured as a function of applied DC bias, polarization versus applied electric field strength and DC load/unload experiments. These capacitors exhibited significant leakage (in the range 8-210 μA/cm²) and dielectric loss. Measured breakdown strength for the sputtered doped barium titanate films was in the range 200 kV/cm -2 MV/cm. For all devices tested, we observed clear evidence for dielectric saturation at applied electric field strengths above 100 kV/cm: saturated polarization was in the range 8-15 μC/cm². When cycled under DC conditions, the maximum energy density measured for any of the capacitors tested here was ~4.7 × 10 -2 W-h/liter based on the volume of the dielectric material only. This corresponds to a specific energy of ~8 × 10 -3 W-h/kg, again calculated on a dielectric-only basis. These results are compared to those reported by other authors and a simple theoretical treatment provided that quantifies the maximum energy that can be stored in these and similar devices as a function of dielectric strength and saturation polarization. Finally, a predictive model is developed to provide guidance on how to tailor the relative permittivities of high-k dielectrics in order to optimize their energy storage capacities.

  15. Electrical Properties of Thin-Film Capacitors Fabricated Using High Temperature Sputtered Modified Barium Titanate

    PubMed Central

    Reynolds, Glyn J.; Kratzer, Martin; Dubs, Martin; Felzer, Heinz; Mamazza, Robert

    2012-01-01

    Simple thin-film capacitor stacks were fabricated from sputter-deposited doped barium titanate dielectric films with sputtered Pt and/or Ni electrodes and characterized electrically. Here, we report small signal, low frequency capacitance and parallel resistance data measured as a function of applied DC bias, polarization versus applied electric field strength and DC load/unload experiments. These capacitors exhibited significant leakage (in the range 8–210 μA/cm2) and dielectric loss. Measured breakdown strength for the sputtered doped barium titanate films was in the range 200 kV/cm −2 MV/cm. For all devices tested, we observed clear evidence for dielectric saturation at applied electric field strengths above 100 kV/cm: saturated polarization was in the range 8–15 μC/cm2. When cycled under DC conditions, the maximum energy density measured for any of the capacitors tested here was ~4.7 × 10−2 W-h/liter based on the volume of the dielectric material only. This corresponds to a specific energy of ~8 × 10−3 W-h/kg, again calculated on a dielectric-only basis. These results are compared to those reported by other authors and a simple theoretical treatment provided that quantifies the maximum energy that can be stored in these and similar devices as a function of dielectric strength and saturation polarization. Finally, a predictive model is developed to provide guidance on how to tailor the relative permittivities of high-k dielectrics in order to optimize their energy storage capacities. PMID:28817001

  16. Recent Origin of Titan's Orbital Eccentricity

    NASA Astrophysics Data System (ADS)

    Cuk, Matija

    2014-05-01

    Saturn's regular satellite system contains several dynamical mysteries, including the high tidal heating of Enceladus and undamped eccentricity of Titan. Lainey et al.(2012) proposed that the tidal evolution of the system is much faster than previously thought, which would explain heating of Enceladus and implies that some of the current satellites are less than 1 Gyr old. Cuk et al.(2014) pointed out that this fast tidal evolution could also explain the Titan-Hyperion resonance. If the inner, mid-sized Saturnian moons were re-accreted within the last Gyr, then the same event could have generated the observed eccentricity of Titan. Titan-Hyperion resonance puts strong constraints on this event, as many scenarios lead to the loss of Hyperion (usually through collision with Titan). Here I report on the ongoing study of the history of the Saturnian system, using symplectic integrators SIMPL (for stable configurations) and COMPLEX (for situations when the moons' orbits crossed). I find that the past system of icy satellites could have naturally evolved into instability, by having Dione and Rhea-like moons enter the mutual 4:3 resonance. This resonance is chaotic due to overlap with the solar evection resonance (i.e. the moons' precession rates in the mean-motion resonance overlap with Saturn's mean motion). The outcome of such resonance is a collision between the mid-sized moons, likely followed by re-accretion, with Titan being largely unaffected. I also find that close encounters between a mid-sized moon and Titan could with significant probability both excite Titan and preserve its resonance with Hyperion (cf. Hamilton 2013). I will present possible scenarios in which the previous system had an additional moon exterior to Rhea. This additional moon would have been destabilized by resonances with the inner moons and eventually absorbed by Titan, which acquired its eccentricity in the process. This research is supported by NASA's Outer Planet Research Program.

  17. Mapping products of Titan's surface

    USGS Publications Warehouse

    Stephan, Katrin; Jaumann, Ralf; Karkoschka, Erich; Barnes, Jason W.; Tomasko, Martin G.; Turtle, Elizabeth P.; Le Corre, Lucille; Langhans, Mirjam; Le Mouelic, Stephane; Lorenz, Ralf D.; Perry, Jason; Brown, Robert H.; Lebreton, Jean-Pierre

    2009-01-01

    Remote sensing instruments aboard the Cassini spacecraft have been observed the surface of Titan globally in the infrared and radar wavelength ranges as well as locally by the Huygens instruments revealing a wealth of new morphological features indicating a geologically active surface. We present a summary of mapping products of Titan's surface derived from data of the remote sensing instruments onboard the Cassini spacecraft (ISS, VIMS, RADAR) as well as the Huygens probe (DISR) that were achieved during the nominal Cassini mission including an overview of Titan's recent nomenclature.

  18. Strontium-90 deposition in New York City.

    PubMed

    Volchok, H L

    1967-06-16

    Measurements of strontium-90 deposited in New York City over the past 12 years make for broader understanding of the fallout phenomenon. The data indicate a stratospheric half-residence time of 8 to 10 months. The seasonal oscillation of strontium-90 fallout is very symmetrical and consistent from year to year and completely independent of the timing and magnitude of nuclear tests. The predicted fallout of strontium-90 in 1970 is less than 1 percent of that during the peak year 1963.

  19. Hubble Observes Surface of Titan

    NASA Technical Reports Server (NTRS)

    1994-01-01

    Scientists for the first time have made images of the surface of Saturn's giant, haze-shrouded moon, Titan. They mapped light and dark features over the surface of the satellite during nearly a complete 16-day rotation. One prominent bright area they discovered is a surface feature 2,500 miles across, about the size of the continent of Australia.

    Titan, larger than Mercury and slightly smaller than Mars, is the only body in the solar system, other than Earth, that may have oceans and rainfall on its surface, albeit oceans and rain of ethane-methane rather than water. Scientists suspect that Titan's present environment -- although colder than minus 289 degrees Fahrenheit, so cold that water ice would be as hard as granite -- might be similar to that on Earth billions of years ago, before life began pumping oxygen into the atmosphere.

    Peter H. Smith of the University of Arizona Lunar and Planetary Laboratory and his team took the images with the Hubble Space Telescope during 14 observing runs between Oct. 4 - 18. Smith announced the team's first results last week at the 26th annual meeting of the American Astronomical Society Division for Planetary Sciences in Bethesda, Md. Co-investigators on the team are Mark Lemmon, a doctoral candidate with the UA Lunar and Planetary Laboratory; John Caldwell of York University, Canada; Larry Sromovsky of the University of Wisconsin; and Michael Allison of the Goddard Institute for Space Studies, New York City.

    Titan's atmosphere, about four times as dense as Earth's atmosphere, is primarily nitrogen laced with such poisonous substances as methane and ethane. This thick, orange, hydrocarbon haze was impenetrable to cameras aboard the Pioneer and Voyager spacecraft that flew by the Saturn system in the late 1970s and early 1980s. The haze is formed as methane in the atmosphere is destroyed by sunlight. The hydrocarbons produced by this methane destruction form a smog similar to that found over large cities, but is much

  20. Niobium oxide nanocolumns formed via anodic alumina with modulated pore diameters

    NASA Astrophysics Data System (ADS)

    Pligovka, A.; Zakhlebayeva, A.; Lazavenka, A.

    2018-03-01

    Niobium oxide nanocolumns with modulated diameters were formed for the first time. An Al/Nb bilayer specimen was prepared by successive sputter-deposition of 300 nm niobium layer and 1200 nm aluminum layer onto silicon wafer. Regular anodic alumina matrix with modulated pore diameters was formed by sequential anodization of initial specimen in tartaric acid at 180 V, and in oxalic acid at 37 V. Further potentiodynamic reanodization of the specimen up to 400 V causes the simultaneous growth of 440 nm continuous niobium oxide layer beneath the alumina film and two types of an array of oxide nanocolumns (thick – with 100 nm width and 630 nm high and thin – with 25 nm width and 170 nm high), which are the filling of the alumina pores. The morphology of the formed anodic niobium oxide nanocolumns with modulated diameters was determined by field emission scanning electron microscopy. The formed nanostructures can be used for perspective devices of nano- and optoelectronics such as photonic crystals.

  1. 40 CFR 721.10598 - Lead strontium titanium zirconium oxide.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Lead strontium titanium zirconium... Specific Chemical Substances § 721.10598 Lead strontium titanium zirconium oxide. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as lead strontium...

  2. 40 CFR 721.10598 - Lead strontium titanium zirconium oxide.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Lead strontium titanium zirconium... Specific Chemical Substances § 721.10598 Lead strontium titanium zirconium oxide. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as lead strontium...

  3. The Lakes and Seas of Titan

    NASA Astrophysics Data System (ADS)

    Hayes, Alexander G.

    2016-06-01

    Analogous to Earth's water cycle, Titan's methane-based hydrologic cycle supports standing bodies of liquid and drives processes that result in common morphologic features including dunes, channels, lakes, and seas. Like lakes on Earth and early Mars, Titan's lakes and seas preserve a record of its climate and surface evolution. Unlike on Earth, the volume of liquid exposed on Titan's surface is only a small fraction of the atmospheric reservoir. The volume and bulk composition of the seas can constrain the age and nature of atmospheric methane, as well as its interaction with surface reservoirs. Similarly, the morphology of lacustrine basins chronicles the history of the polar landscape over multiple temporal and spatial scales. The distribution of trace species, such as noble gases and higher-order hydrocarbons and nitriles, can address Titan's origin and the potential for both prebiotic and biotic processes. Accordingly, Titan's lakes and seas represent a compelling target for exploration.

  4. The rotation of Titan and Ganymede

    NASA Astrophysics Data System (ADS)

    Van Hoolst, Tim; Coyette, Alexis; Baland, Rose-Marie; Trinh, Antony

    2016-10-01

    The rotation rates of Titan and Ganymede, the largest satellites of Saturn and Jupiter, are on average equal to their orbital mean motion. Here we discuss small deviations from the average rotation for both satellites and evaluate the polar motion of Titan induced by its surface fluid layers. We examine different causes at various time scales and assess possible consequences and the potential of using librations and polar motion as probes of the interior structure of the satellites.The rotation rate of Titan and Ganymede cannot be constant on the orbital time scale as a result of the gravitational torque of the central planet acting on the satellites. Titan is moreover expected to show significant polar motion and additional variations in the rotation rate due to angular momentum exchange with the atmosphere, mainly at seasonal periods. Observational evidence for deviations from the synchronous state has been reported several times for Titan but is unfortunately inconclusive. The measurements of the rotation variations are based on determinations of the shift in position of Cassini radar images taken during different flybys. The ESA JUICE (JUpiter ICy moons Explorer) mission will measure the rotation variations of Ganymede during its orbital phase around the satellite starting in 2032.We report on different theoretical aspects of the librations and polar motion. We consider the influence of the rheology of the ice shell and take into account Cassini measurements of the external gravitational field and of the topography of Titan and similar Galileo data about Ganymede. We also evaluate the librations and polar motion induced by Titan's hydrocarbon seas and use the most recent results of Titan's atmosphere dynamics. We finally evaluate the potential of rotation variations to constrain the satellite's interior structure, in particular its ice shell and ocean.

  5. Future Exploration of Titan and Enceladus

    NASA Astrophysics Data System (ADS)

    Matson, D. L.; Coustenis, A.; Lunine, J.; Lebreton, J.; Reh, K.; Beauchamp, P.

    2009-05-01

    The future exploration of Titan and Enceladus has become very important for the planetary community. The study conducted last year of the Titan Saturn System Mission (TSSM) led to an announcement in which ESA and NASA prioritized future OPF missions, stating that TSSM is planned after EJSM (for details see http://www.lpi.usra.edu/opag/). TSSM consists of a TSSM Orbiter that would carry two in situ elements: the Titan Montgolfiere hot air balloon and the Titan Lake Lander. The mission could launch in the 2023-2025 timeframe on a trajectory to arrive ~9 years later for a 4-year mission in the Saturn system. Soon after arrival at Saturn, the montgolfiere would be delivered to Titan to begin its mission of airborne, scientific observations of Titan from an altitude of about 10 km. The montgolfiere would have a Multi-Mission Radioisotope Thermoelectric Generator (MMRTG) power system and would be designed to last at least 6-12 months in Titan's atmosphere. With the predicted winds and weather, that would be sufficient to circumnavigate the globe! On a subsequent fly-by, the TSSM orbiter would release the Lake Lander on a trajectory toward Titan for a targeted entry. It would descend through the atmosphere making scientific measurements, much like Huygens did, and then land and float on one of Titan's seas. This would be its oceanographic phase, making a physical and chemical assessment of the sea. The Lake Lander would operate 8-10 hours until its batteries become depleted. Following the delivery of the in situ elements, the TSSM orbiter would explore the Saturn system via a 2-year tour that includes in situ sampling of Enceladus' plumes as well as Titan flybys. After the Saturn system tour, the TSSM orbiter would enter orbit around Titan for a global survey phase. Synergistic and coordinated observations would be carried out between the TSSM orbiter and the in situ elements. The scientific requirements were developed by the international TSSM Joint Science Definition

  6. Enhanced magnetic Purcell effect in room-temperature masers

    PubMed Central

    Breeze, Jonathan; Tan, Ke-Jie; Richards, Benjamin; Sathian, Juna; Oxborrow, Mark; Alford, Neil McN

    2015-01-01

    Recently, the world’s first room-temperature maser was demonstrated. The maser consisted of a sapphire ring housing a crystal of pentacene-doped p-terphenyl, pumped by a pulsed rhodamine-dye laser. Stimulated emission of microwaves was aided by the high quality factor and small magnetic mode volume of the maser cavity yet the peak optical pumping power was 1.4 kW. Here we report dramatic miniaturization and 2 orders of magnitude reduction in optical pumping power for a room-temperature maser by coupling a strontium titanate resonator with the spin-polarized population inversion provided by triplet states in an optically excited pentacene-doped p-terphenyl crystal. We observe maser emission in a thimble-sized resonator using a xenon flash lamp as an optical pump source with peak optical power of 70 W. This is a significant step towards the goal of continuous maser operation. PMID:25698634

  7. Rivers on Titan - numerical modelling of sedimentary structures

    NASA Astrophysics Data System (ADS)

    Misiura, Katarzyna; Czechowski, Leszek

    2016-07-01

    On Titan surface we can expect a few different geomorphological forms, e.g. fluvial valley and river channels. In our research we use numerical model of the river to determine the limits of different fluvial parameters that play important roles in evolution of the rivers on Titan and on Earth. We have found that transport of sediments as suspended load is the main way of transport for Titan [1]. We also determined the range of the river's parameters for which braided river is developed rather than meandering river. Similar, parallel simulations for rivers deltas are presented in [2]. Introduction Titan is a very special body in the Solar System. It is the only moon that has dense atmosphere and flowing liquid on its surface. The Cassini-Huygens mission has found on Titan meandering rivers, and indicated processes of erosion, transport of solid material and its sedimentation. This work is aimed to investigate the similarity and differences between these processes on Titan and the Earth. Numerical model The dynamical analysis of the considered rivers is performed using the package CCHE modified for the specific conditions on Titan. The package is based on the Navier-Stokes equations for depth-integrated two dimensional, turbulent flow and three dimensional convection-diffusion equation of sediment transport. For more information about equations see [1]. Parameters of the model We considered our model for a few different parameters of liquid and material transported by a river. For Titan we consider liquid corresponding to a Titan's rain (75% methane, 25% nitrogen), for Earth, of course, the water. Material transported in rivers on Titan is water ice, for Earth - quartz. Other parameters of our model are: inflow discharge, outflow level, grain size of sediments etc. For every calculation performed for Titan's river similar calculations are performed for terrestrial ones. Results and Conclusions The results of our simulation show the differences in behaviour of the

  8. Clash of the Titans

    ERIC Educational Resources Information Center

    Subramaniam, Karthigeyan

    2010-01-01

    WebQuests and the 5E learning cycle are titans of the science classroom. These popular inquiry-based strategies are most often used as separate entities, but the author has discovered that using a combined WebQuest and 5E learning cycle format taps into the inherent power and potential of both strategies. In the lesson, "Clash of the Titans,"…

  9. Synthesis of nanosized sodium titanates

    DOEpatents

    Hobbs, David T.; Taylor-Pashow, Kathryn M. L.; Elvington, Mark C.

    2015-09-29

    Methods directed to the synthesis and peroxide-modification of nanosized monosodium titanate are described. Methods include combination of reactants at a low concentration to a solution including a nonionic surfactant. The nanosized monosodium titanate can exhibit high selectivity for sorbing various metallic ions.

  10. Titan Topography: A Comparison Between Cassini Altimeter and SAR Imaging from Two Titan Flybys

    NASA Astrophysics Data System (ADS)

    Gim, Y.; Stiles, B.; Callahan, P. S.; Johnson, W. T.; Hensley, S.; Hamilton, G.; West, R.; Alberti, G.; Flamini, E.; Lorenz, R. D.; Zebker, H. A.; Cassini RADAR Team

    2007-12-01

    The Cassini RADAR has collected twelve altimeter data sets of Titan since the beginning of the Saturn Tour in 2004. Most of the altimeter measurements were made at high altitudes, from 4,000 km to 15,000 km, resulting in low spatial resolutions due to beam footprint sizes larger than 20 km, as well as short ground tracks less than 600 km. One flyby (T30) was dedicated to altimeter data collection from 15,000 km to the closest approach altitude of 950 km. This produced a beam footprint size of 6 km at the lowest altitude and an altimeter ground track of about 3,500 km covering Titan's surface from near the equator to high latitude areas near Titan's north pole. More importantly, the ground track is located inside the SAR swath viewed from an earlier Titan flyby (T28). This provides a rare opportunity to investigate Titan topography with a relatively high spatial resolution and compare nadir-looking altimeter data with side-looking SAR imaging. From altimeter data, we have measured the mean Titan radius of 2575.1 km +/- 0.1 km and observed rather complex topographical variations over a short distance. By comparing altimeter data and SAR images at altitudes below 2,000 km, we have found that there is a strong correlation between SAR brightness and altimeter waveform; SAR dark areas correspond to strong and sharp altimeter waveforms while SAR bright areas correspond to weak and diffused altimeter waveforms. The research described here was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.

  11. Rotational Symmetry Breaking in a Trigonal Superconductor Nb-doped Bi 2 Se 3

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Asaba, Tomoya; Lawson, B. J.; Tinsman, Colin

    2017-01-27

    The search for unconventional superconductivity has been focused on materials with strong spin-orbit coupling and unique crystal lattices. Doped bismuth selenide (Bi 2Se 3) is a strong candidate, given the topological insulator nature of the parent compound and its triangular lattice. The coupling between the physical properties in the superconducting state and its underlying crystal symmetry is a crucial test for unconventional superconductivity. In this paper, we report direct evidence that the superconducting magnetic response couples strongly to the underlying trigonal crystal symmetry in the recently discovered superconductor with trigonal crystal structure, niobium (Nb)-doped Bi 2Se 3. As a result,more » the in-plane magnetic torque signal vanishes every 60°. More importantly, the superconducting hysteresis loop amplitude is enhanced along one preferred direction, spontaneously breaking the rotational symmetry. This observation indicates the presence of nematic order in the superconducting ground state of Nb-doped Bi 2Se 3.« less

  12. Review of ingot niobium as a material for superconducting radiofrequency accelerating cavities

    DOE PAGES

    Kneisel, P.; Ciovati, G.; Dhakal, P.; ...

    2014-12-01

    As a result of collaboration between Jefferson Lab and niobium manufacturer Companhia Brasileira de Metalurgia e Mineração (CBMM), ingot niobium was explored as a possible material for superconducting radiofrequency (SRF) cavity fabrication. The first single cell cavity from large-grain high purity niobium was fabricated and successfully tested at Jefferson Lab in 2004. This work triggered research activities in other SRF laboratories around the world. The large-grain (LG) niobium became not only an interesting alternative material for cavity builders, but also material scientists and surface scientists were eager to participate in the development of this technology. Many single cell cavities mademore » from material of different suppliers have been tested successfully and several multi-cell cavities have shown performances comparable to the best cavities made from standard fine-grain niobium. Several 9-cell cavities fabricated by Research Instruments and tested at DESY exceeded the best performing fine grain cavities with a record accelerating gradient of E acc=45.6 MV/m. The quality factor of those cavities was also higher than that of fine-grain (FG) cavities processed with the same methods. Such performance levels push the state-of-the art of SRF technology and are of great interest for future accelerators. This contribution reviews the development of ingot niobium technology and highlights some of the differences compared to standard FG material and opportunities for further developments.« less

  13. Coated conductors

    DOEpatents

    Arendt, Paul N.; Foltyn, Stephen R.; Stan, Liliana; Usov, Igor O.; Wang, Haiyan

    2010-06-15

    Articles are provided including a base substrate having a layer of an IBAD oriented material thereon, and, a layer of barium-containing material selected from the group consisting of barium zirconate, barium hafnate, barium titanate, barium strontium titanate, barium dysprosium zirconate, barium neodymium zirconate and barium samarium zirconate, or a cubic metal oxide material selected from the group consisting of rare earth zirconates and rare earth hafnates upon the layer of an IBAD oriented material. Such articles can further include thin films of high temperature superconductive oxides such as YBCO upon the layer of barium-containing material selected from the group consisting of barium zirconate, barium hafnate, barium titanate, barium strontium titanate, barium dysprosium zirconate, barium neodymium zirconate and barium samarium zirconate, or a cubic metal oxide material selected from the group consisting of rare earth zirconates and rare earth hafnates.

  14. 40 CFR 721.10011 - Barium calcium manganese strontium oxide.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... manganese strontium oxide (PMN P-00-1124; CAS No. 359427-90-0) is subject to reporting under this section... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Barium calcium manganese strontium... Specific Chemical Substances § 721.10011 Barium calcium manganese strontium oxide. (a) Chemical substance...

  15. 40 CFR 721.10011 - Barium calcium manganese strontium oxide.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... manganese strontium oxide (PMN P-00-1124; CAS No. 359427-90-0) is subject to reporting under this section... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Barium calcium manganese strontium... Specific Chemical Substances § 721.10011 Barium calcium manganese strontium oxide. (a) Chemical substance...

  16. 40 CFR 721.10011 - Barium calcium manganese strontium oxide.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... manganese strontium oxide (PMN P-00-1124; CAS No. 359427-90-0) is subject to reporting under this section... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Barium calcium manganese strontium... Specific Chemical Substances § 721.10011 Barium calcium manganese strontium oxide. (a) Chemical substance...

  17. A FUSE Search for Argon on Titan

    NASA Astrophysics Data System (ADS)

    Gladstone, G. R.; Link, R.; Stern, S. A.; Festou, M.; Waite, J. H.

    2002-09-01

    The origin of Titan's thick nitrogen and methane atmosphere is a compelling enigma. One key and still missing observable concerns the abundances of noble gases in general, and argon in particular. Detection of sufficient argon could indicate that the N2 and CO now found in the atmosphere came in with ice during Titan's accretion. Alternatively, if there is very little argon, then we have to turn to models starting with frozen ammonia, methane and water ice, indicating a more important role for the Saturn sub-nebula, and requiring subsequent modification by photochemistry. Current estimates on the fraction of argon in Titan's atmosphere are crude, and based only on indirect evidence, and range up to 25%. On Sept. 21, 2000, using the Far Ultraviolet Spectroscopic Explorer (FUSE) satellite, we performed an observation of Titan to search for argon and to make a survey of Titan's dayglow in the 90--115 nm FUSE bandpass. No emissions were found in the 18 ks exposure, although only 7.4 ks were obtained when FUSE was in Earth's shadow where terrestrial airglow contamination is minimal. While no Ar, N, or N2 emissions were detected, 2-σ upper limits of 4 R (for Ar 104.8 nm) and 20 R (for N 113.4 nm) are found using the best of the FUSE data. There is a bump on the terrestrial geocorona H Lyβ emission at 102.5 nm which may be due to Titan and a Titan Torus. The signal in the bump is about 400 R. Model estimates suggest that the Lyβ brightness of Titan should be about 20 R and the Titan Torus in the 30--700 R range. For an assumed argon abundance of 5% the 104.8 nm emission is predicted to be 7 R, so the argon estimate is constraining already. The nitrogen estimate is very close to the model expectation of 15 R. An accurate determination of the abundance of argon on Titan would be useful in preparing for the arrival of the Cassini orbiter and Huygens probe at the Saturn system, so further FUSE observations of Titan are planned. We gratefully acknowledge support from NASA

  18. The effects of upstream plasma properties on Titan's ionosphere

    NASA Astrophysics Data System (ADS)

    Ledvina, S. A.; Brecht, S. H.

    2016-12-01

    Cassini observations have found that the plasma and magnetic field conditions upstream of Titan are far more complex than they were thought to be after the Voyager encounter. Rymer et al., (2009) used the Cassini Plasma Spectrometer (CAPS) electron observations to classify the plasma conditions along Titan's orbit into 5 types (Plasma Sheet, Lobe, Mixed, Magnetosheath and Misc.). Nemeth et al., (2011) found that the CAPS ion observations could also be separated into the same plasma regions as defined by Rymer et al. Additionally the T-96 encounter found Titan in the solar wind adding a sixth classification. Understanding the effects of the variable upstream plasma conditions on Titan's plasma interaction and the evolution of Titan's ionosphere/atmosphere is one of the main objectives of the Cassini mission. To compliment the mission we perform hybrid simulations of Titan's plasma interaction to examine how the properties of the incident plasma (composition, density, temperature etc…) affect Titan's ionosphere. We examine how much ionospheric plasma is lost from Titan as well as the amount of mass and energy deposited into Titan's atmosphere.

  19. Flyover of Sotra Facula, Titan

    NASA Image and Video Library

    2010-12-14

    This frame from a movie is based on data from NASA Cassini spacecraft and shows a flyover of an area of Saturn moon Titan known as Sotra Facula. Scientists believe Sotra is the best case for an ice volcano, or cryovolcano, region on Titan.

  20. Titan South Polar Cloud Burst

    NASA Image and Video Library

    2009-06-03

    This infrared image of Saturn's moon Titan shows a large burst of clouds in the moon's south polar region. These clouds form and move much like those on Earth, but in a much slower, more lingering fashion, new results from NASA's Cassini Spacecraft show. This image is a color composite, with red shown at a 5-micron wavelength, green at 2.7 microns, and blue at 2 microns. An infrared color mosaic is also used as a background image (red at 5 microns, green at 2 microns, blue at 1.3 microns). The images were taken by Cassini's visual and infrared mapping spectrometer during a flyby of Titan on March 26, 2007, known as T27. For a similar view see PIA12004. Titan's southern hemisphere still shows a very active meteorology (the cloud appears in white-reddish tones) even in 2007. According to climate models, these clouds should have faded out since 2005. Scientists have monitored Titan's atmosphere for three-and-a-half years, between July 2004 and December 2007, and observed more than 200 clouds. The way these clouds are distributed around Titan matches scientists' global circulation models. The only exception is timing—clouds are still noticeable in the southern hemisphere while fall is approaching. http://photojournal.jpl.nasa.gov/catalog/PIA12005

  1. Materials system for intermediate temperature solid oxide fuel cells based on doped lanthanum-gallate electrolyte

    NASA Astrophysics Data System (ADS)

    Gong, Wenquan

    2005-07-01

    The objective of this work was to identify a materials system for intermediate temperature solid oxide fuel cells (IT-SOFCs). Towards this goal, alternating current complex impedance spectroscopy was employed as a tool to study electrode polarization effects in symmetrical cells employing strontium and magnesium doped lanthanum gallate (LSGM) electrolyte. Several cathode materials were investigated including strontium doped lanthanum manganite (LSM), Strontium and iron doped lanthanum cobaltate (LSCF), LSM-LSGM, and LSCF-LSGM composites. Investigated Anode materials included nickel-gadolinium or lanthanum doped cerium oxide (Ni-GDC, or Ni-LDC) composites. The ohmic and the polarization resistances of the symmetrical cells were obtained as a function of temperature, time, thickness, and the composition of the electrodes. Based on these studies, the single phase LSM electrode had the highest polarization resistance among the cathode materials. The mixed-conducting LSCF electrode had polarization resistance orders of magnitude lower than that of the LSM-LSGM composite electrodes. Although incorporating LSGM in the LSCF electrode did not reduce the cell polarization resistance significantly, it could reduce the thermal expansion coefficient mismatch between the LSCF electrodes and LSGM electrolyte. Moreover, the polarization resistance of the LSCF electrode decreased asymptotically as the electrode thickness was increased thus suggesting that the electrode thickness needed not be thicker than this asymptotic limit. On the anode side of the IT-SOFC, Ni reacted with LSGM electrolyte, and lanthanum diffusion occurred from the LSGM electrolyte to the GDC barrier layer, which was between the LSGM electrolyte and the Ni-composite anode. However, LDC served as an effective barrier layer. Ni-LDC (70 v% Ni) anode had the largest polarization resistance, while all other anode materials, i.e. Ni-LDC (50 v% Ni), Ni-GDC (70 v% NO, and Ni-GDC (50 v% Ni), had similar polarization

  2. Chemical investigation of Titan and Triton tholins

    NASA Technical Reports Server (NTRS)

    Mcdonald, Gene D.; Thompson, W. R.; Heinrich, Michael; Khare, Bishun N.; Sagan, Carl

    1994-01-01

    We report chromatographic and spectroscopic analyses of both Titan and Triton tholins, organic solids made from the plasma irradiation of 0.9:0.1 and 0.999:0.001 N2/CH4 gas mixtures, respectively. The lower CH4 mixing ratio leads to a nitrogen-richer tholin (N/C greater than 1), probably including nitrogen heterocyclic compounds. Unlike Titan tholin, bulk Triton tholin is poor in nitriles. From high-pressure liquid chromatography, ultraviolet and infrared spectroscopy, and molecular weight estimation by gel filtration chromatography, we conclude that (1) several H2O-soluble fractions, each with distinct UV and IR spectral signatures, are present, (2) these fractions are not identical in the two tholins, (3) the H2O-soluble fractions of Titan tholins do not contain significant amounts of nitriles, despite the major role of nitriles in bulk Titan tholin, and (4) the H2O-soluble fractions of both tholins are mainly molcules containing about 10 to 50 (C + N) atoms. We report yields of amino acids upon hydrolysis of Titan and Triton tholins. Titan tholin is largely insoluble in the putative hydrocarbon lakes or oceans on Titan, but can yield the H2O-soluble species investigated here upon contact with transient (e.g., impact-generated) liquid water.

  3. Titan Global Map - June 2015

    NASA Image and Video Library

    2015-10-09

    This global digital map of Saturn's moon Titan was created using images taken by NASA's Cassini spacecraft's imaging science subsystem (ISS). The map was produced in June 2015 using data collected through Cassini's flyby on April 7, 2014, known as "T100." The images were taken using a filter centered at 938 nanometers, allowing researchers to examine variations in albedo (or inherent brightness) across the surface of Titan. Because of the scattering of light by Titan's dense atmosphere, no topographic shading is visible in these images. The map is an equidistant projection and has a scale of 2.5 miles (4 kilometers) per pixel. Actual resolution varies greatly across the map, with the best coverage (close to the map scale) along the equator near the center of the map at 180 degrees west longitude. The lowest resolution coverage can be seen in the northern mid-latitudes on the sub-Saturn hemisphere. Mapping coverage in the northern polar region has greatly improved since the previous version of this map in 2011 (see PIA14908). Large dark areas, now known to be liquid-hydrocarbon-filled lakes and seas, have since been documented at high latitudes. Titan's north pole was not well illuminated early in Cassini's mission, because it was winter in the northern hemisphere when the spacecraft arrived at Saturn. Cassini has been better able to observe northern latitudes in more recent years due to seasonal changes in solar illumination. This map is an update to the previous versions released in April 2011 and February 2009 (see PIA11149). Data from the past four years (the most recent data in the map is from April 2014) has completely filled in missing data in the north polar region and replaces the earlier imagery of the Xanadu region with higher quality data. A data gap of about 3 to 5 percent of Titan's surface still remains, located in the northern mid-latitudes on the sub-Saturn hemisphere of Titan. The uniform gray area in the northern hemisphere indicates a gap in the

  4. Heavy Ion Formation in Titan's Ionosphere: Magnetospheric Introduction of Free Oxygen and Source of Titan's Aerosols?

    NASA Technical Reports Server (NTRS)

    Sittler, E. C., Jr.; Hartle, R. E.; Cooper, J. F.; Johnson, R. E.; Coates, A.; dePater, imke; Strom, Daphne; Simoes, F.; Steele, A.; Robb, F.

    2007-01-01

    With the recent discovery of heavy ions, positive and negative, by the Cassini Plasma Spectrometer (CAPS) instrument in Titan's ionosphere, it reveals new possibilities for aerosol formation at Titan and the introduction of free oxygen to the aerosol chemistry from Saturn's magnetosphere with Enceladus as the primary oxygen source. One can estimate whether the heavy ions in the ionosphere are of sufficient number to account for all the aerosols, under what conditions are favorable for heavy ion formation and how they are introduced as seed particles deeper in Titan's atmosphere where the aerosols form and eventually find themselves on Titan's surface where unknown chemical processes can take place. Finally, what are the possibilities with regard to their chemistry on the surface with some free oxygen present in their seed particles?

  5. Strontium ranelate for preventing and treating postmenopausal osteoporosis.

    PubMed

    O'Donnell, S; Cranney, A; Wells, G A; Adachi, J D; Reginster, J Y

    2006-10-18

    Strontium ranelate is a new treatment for osteoporosis therefore, its benefits and harms need to be known. To determine the efficacy and safety of strontium ranelate for the treatment and prevention of postmenopausal osteoporosis. We searched MEDLINE (1996 to March 2005), EMBASE (1996 to week 9 2005), the Cochrane Library (1996 to Issue 1 2005), reference lists of relevant articles and conference proceedings from the last two years. Additional data was sought from authors. We included randomized controlled trials (RCTs) of at least one year duration comparing strontium ranelate versus placebo reporting fracture incidence, bone mineral density (BMD), health related quality of life or safety in postmenopausal women. Treatment (versus prevention) population was defined as women with prevalent vertebral fractures and/or lumbar spine BMD T score < -2.5 SD. Two reviewers independently determined study eligibility, assessed trial quality and extracted the relevant data. Disagreements were resolved by consensus. RCTs were grouped by dose of strontium ranelate and treatment duration. Where possible, meta-analysis was conducted using the random effects model. Four trials met the inclusion criteria. Three included a treatment population (0.5 to 2 g of strontium ranelate daily) and one a prevention population (0.125 g, 0.5 g and 1 g daily). A 37% reduction in vertebral fractures (RR 0.63, 95% CI 0.56, 0.71) and a 14% reduction in non-vertebral fractures (RR 0.86, 95% CI 0.75, 0.98) were demonstrated over three years with 2 g of strontium ranelate daily in a treatment population. An increase in BMD was shown at all BMD sites after two to three years in both populations. Lower doses of strontium ranelate were superior to placebo and the highest dose demonstrated the greatest reduction in vertebral fractures and increase in BMD. An increased risk of diarrhea with 2 g of strontium ranelate was found; however, adverse events did not affect the risk of discontinuing treatment nor

  6. Size and shape of Saturn's moon Titan.

    PubMed

    Zebker, Howard A; Stiles, Bryan; Hensley, Scott; Lorenz, Ralph; Kirk, Randolph L; Lunine, Jonathan

    2009-05-15

    Cassini observations show that Saturn's moon Titan is slightly oblate. A fourth-order spherical harmonic expansion yields north polar, south polar, and mean equatorial radii of 2574.32 +/- 0.05 kilometers (km), 2574.36 +/- 0.03 km, and 2574.91 +/- 0.11 km, respectively; its mean radius is 2574.73 +/- 0.09 km. Titan's shape approximates a hydrostatic, synchronously rotating triaxial ellipsoid but is best fit by such a body orbiting closer to Saturn than Titan presently does. Titan's lack of high relief implies that most--but not all--of the surface features observed with the Cassini imaging subsystem and synthetic aperture radar are uncorrelated with topography and elevation. Titan's depressed polar radii suggest that a constant geopotential hydrocarbon table could explain the confinement of the hydrocarbon lakes to high latitudes.

  7. Size and shape of Saturn's moon Titan

    USGS Publications Warehouse

    Zebker, Howard A.; Stiles, Bryan; Hensley, Scott; Lorenz, Ralph; Kirk, Randolph L.; Lunine, Jonathan

    2009-01-01

    Cassini observations show that Saturn's moon Titan is slightly oblate. A fourth-order spherical harmonic expansion yields north polar, south polar, and mean equatorial radii of 2574.32 ± 0.05 kilometers (km), 2574.36 ± 0.03 km, and 2574.91 ± 0.11 km, respectively; its mean radius is 2574.73 ± 0.09 km. Titan's shape approximates a hydrostatic, synchronously rotating triaxial ellipsoid but is best fit by such a body orbiting closer to Saturn than Titan presently does. Titan's lack of high relief implies that most—but not all—of the surface features observed with the Cassini imaging subsystem and synthetic aperture radar are uncorrelated with topography and elevation. Titan's depressed polar radii suggest that a constant geopotential hydrocarbon table could explain the confinement of the hydrocarbon lakes to high latitudes.

  8. The Exploration of Titan and the Saturnian System

    NASA Astrophysics Data System (ADS)

    Coustenis, Athena

    The exploration of the outer solar system and in particular of the giant planets and their environments is an on-going process with the Cassini spacecraft currently around Saturn, the Juno mission to Jupiter preparing to depart and two large future space missions planned to launch in the 2020-2025 time frame for the Jupiter system and its satellites (Europa and Ganymede) on the one hand, and the Saturnian system and Titan on the other hand [1,2]. Titan, Saturn's largest satellite, is the only other object in our Solar system to possess an extensive nitrogen atmosphere, host to an active organic chemistry, based on the interaction of N2 with methane (CH4). Following the Voyager flyby in 1980, Titan has been intensely studied from the ground-based large telescopes (such as the Keck or the VLT) and by artificial satellites (such as the Infrared Space Observatory and the Hubble Space Telescope) for the past three decades. Prior to Cassini-Huygens, Titan's atmospheric composition was thus known to us from the Voyager missions and also through the explorations by the ISO. Our perception of Titan had thus greatly been enhanced accordingly, but many questions remained as to the nature of the haze surrounding the satellite and the composition of the surface. The recent revelations by the Cassini-Huygens mission have managed to surprise us with many discoveries [3-8] and have yet to reveal more of the interesting aspects of the satellite. The Cassini-Huygens mission to the Saturnian system has been an extraordinary success for the planetary community since the Saturn-Orbit-Insertion (SOI) in July 2004 and again the very successful probe descent and landing of Huygens on January 14, 2005. One of its main targets was Titan. Titan was revealed to be a complex world more like the Earth than any other: it has a dense mostly nitrogen atmosphere and active climate and meteorological cycles where the working fluid, methane, behaves under Titan conditions the way that water does on

  9. Titan Lingering Clouds

    NASA Image and Video Library

    2009-06-03

    Lots of clouds are visible in this infrared image of Saturn's moon Titan. These clouds form and move much like those on Earth, but in a much slower, more lingering fashion, new results from NASA's Cassini spacecraft show. Scientists have monitored Titan's atmosphere for three-and-a-half years, between July 2004 and December 2007, and observed more than 200 clouds. The way these clouds are distributed around Titan matches scientists' global circulation models. The only exception is timing—clouds are still noticeable in the southern hemisphere while fall is approaching. Three false-color images make up this mosaic and show the clouds at 40 to 50 degrees mid-latitude. The images were taken by Cassini's visual and infrared mapping spectrometer during a close flyby of Titan on Sept. 7, 2006, known as T17. For a similar view see PIA12005. Each image is a color composite, with red shown at the 2-micron wavelength, green at 1.6 microns, and blue at 2.8 microns. An infrared color mosaic is also used as a background (red at 5 microns, green at 2 microns and blue at 1.3 microns). The characteristic elongated mid-latitude clouds, which are easily visible in bright bluish tones are still active even late into 2006-2007. According to climate models, these clouds should have faded out since 2005. http://photojournal.jpl.nasa.gov/catalog/PIA12004

  10. ISO observations of Titan with SWS/grating

    NASA Technical Reports Server (NTRS)

    Coustenis, A.; Encrenaz, T.; Salama, A.; Lellouch, E.; Gautier, D.; Kessler, M. F.; deGraauw, T.; Samuelson, R. E.; Bjoraker, G.; Orton, G.

    1997-01-01

    The observations of Titan performed by the Infrared Space Observatory (ISO) short wavelength spectrometer (SWS), in the 2 micrometer to 45 micrometer region using the grating mode, are reported on. Special attention is given to data from Titan concerning 7 micrometer to 45 micrometer spectral resolution. Future work for improving Titan's spectra investigation is suggested.

  11. Seasonal Changes in Titan's Meteorology

    NASA Technical Reports Server (NTRS)

    Turtle, E. P.; DelGenio, A. D.; Barbara, J. M.; Perry, J. E.; Schaller, E. L.; McEwen, A. S.; West, R. A.; Ray, T. L.

    2011-01-01

    The Cassini Imaging Science Subsystem has observed Titan for 1/4 Titan year, and we report here the first evidence of seasonal shifts in preferred locations of tropospheric methane clouds. South \\polar convective cloud activity, common in late southern summer, has become rare. North \\polar and northern mid \\latitude clouds appeared during the approach to the northern spring equinox in August 2009. Recent observations have shown extensive cloud systems at low latitudes. In contrast, southern mid \\latitude and subtropical clouds have appeared sporadically throughout the mission, exhibiting little seasonality to date. These differences in behavior suggest that Titan s clouds, and thus its general circulation, are influenced by both the rapid temperature response of a low \\thermal \\inertia surface and the much longer radiative timescale of Titan s cold thick troposphere. North \\polar clouds are often seen near lakes and seas, suggesting that local increases in methane concentration and/or lifting generated by surface roughness gradients may promote cloud formation. Citation

  12. Prebiotic-like chemistry on Titan.

    PubMed

    Raulin, François; Brassé, Coralie; Poch, Olivier; Coll, Patrice

    2012-08-21

    Titan, the largest satellite of Saturn, is the only one in the solar system with a dense atmosphere. Mainly composed of dinitrogen with several % of methane, this atmosphere experiences complex organic processes, both in the gas and aerosol phases, which are of prebiotic interest and within an environment of astrobiological interest. This tutorial review presents the different approaches which can be followed to study such an exotic place and its chemistry: observation, theoretical modeling and experimental simulation. It describes the Cassini-Huygens mission, as an example of observational tools, and gives the new astrobiologically oriented vision of Titan which is now available by coupling the three approaches. This includes the many analogies between Titan and the Earth, in spite of the much lower temperature in the Saturn system, the complex organic chemistry in the atmosphere, from the gas to the aerosol phases, but also the potential organic chemistry on Titan's surface, and in its possible internal water ocean.

  13. Impact Craters on Titan? Cassini RADAR View

    NASA Technical Reports Server (NTRS)

    Wood, Charles A.; Lopes, Rosaly; Stofan, Ellen R.; Paganelli, Flora; Elachi, Charles

    2005-01-01

    Titan is a planet-size (diameter of 5,150 km) satellite of Saturn that is currently being investigated by the Cassini spacecraft. Thus far only one flyby (Oct. 26, 2004; Ta) has occurred when radar images were obtained. In February, 2005, and approximately 20 more times in the next four years, additional radar swaths will be acquired. Each full swath images about 1% of Titan s surface at 13.78 GHz (Ku-band) with a maximum resolution of 400 m. The Ta radar pass [1] demonstrated that Titan has a solid surface with multiple types of landforms. However, there is no compelling detection of impact craters in this first radar swath. Dione, Tethys and other satellites of Saturn are intensely cratered, there is no way that Titan could have escaped a similar impact cratering past; thus there must be ongoing dynamic surface processes that erase impact craters (and other landforms) on Titan. The surface of Titan must be very young and the resurfacing rate must be significantly higher than the impact cratering rate.

  14. The tides of Titan.

    PubMed

    Iess, Luciano; Jacobson, Robert A; Ducci, Marco; Stevenson, David J; Lunine, Jonathan I; Armstrong, John W; Asmar, Sami W; Racioppa, Paolo; Rappaport, Nicole J; Tortora, Paolo

    2012-07-27

    We have detected in Cassini spacecraft data the signature of the periodic tidal stresses within Titan, driven by the eccentricity (e = 0.028) of its 16-day orbit around Saturn. Precise measurements of the acceleration of Cassini during six close flybys between 2006 and 2011 have revealed that Titan responds to the variable tidal field exerted by Saturn with periodic changes of its quadrupole gravity, at about 4% of the static value. Two independent determinations of the corresponding degree-2 Love number yield k(2) = 0.589 ± 0.150 and k(2) = 0.637 ± 0.224 (2σ). Such a large response to the tidal field requires that Titan's interior be deformable over time scales of the orbital period, in a way that is consistent with a global ocean at depth.

  15. Evaluation of Niobium as Candidate Electrode Material for DC High Voltage Photoelectron Guns

    NASA Technical Reports Server (NTRS)

    BastaniNejad, M.; Mohamed, Abdullah; Elmustafa, A. A.; Adderley, P.; Clark, J.; Covert, S.; Hansknecht, J.; Hernandez-Garcia, C.; Poelker, M.; Mammei, R.; hide

    2012-01-01

    The field emission characteristics of niobium electrodes were compared to those of stainless steel electrodes using a DC high voltage field emission test apparatus. A total of eight electrodes were evaluated: two 304 stainless steel electrodes polished to mirror-like finish with diamond grit and six niobium electrodes (two single-crystal, two large-grain, and two fine-grain) that were chemically polished using a buffered-chemical acid solution. Upon the first application of high voltage, the best large-grain and single-crystal niobium electrodes performed better than the best stainless steel electrodes, exhibiting less field emission at comparable voltage and field strength. In all cases, field emission from electrodes (stainless steel and/or niobium) could be significantly reduced and sometimes completely eliminated, by introducing krypton gas into the vacuum chamber while the electrode was biased at high voltage. Of all the electrodes tested, a large-grain niobium electrode performed the best, exhibiting no measurable field emission (< 10 pA) at 225 kV with 20 mm cathode/anode gap, corresponding to a field strength of 18:7 MV/m.

  16. Titan through Time: Evolution of Titan's Atmosphere and its Hydrocarbon Cycle on the Surface

    NASA Astrophysics Data System (ADS)

    Gilliam, Ashley E.

    The Introduction and Appendix i-A outline briefly the history of Titan exploration since its discovery by Christiaan Huygens in 1675 through the recent International Mission of Cassini-Huygens.. Chapter 1: This chapter discusses two possible pathways of loss of the two main gases from Titan's post-accretional atmosphere, methane (CH 4) and ammonia (NH3), by the mechanisms of thermal escape and emission from the interior coupled with thermal escape. Chapter 2: In this chapter, a simple photolysis model is created, where the second most abundant component of the present-day Titan atmosphere, methane (CH4), can either escape the atmosphere or undergo photolytic conversion to ethane (C2H6). Chapter 3: This chapter examines different fluvial features on Titan, identified by the Cassini spacecraft, and evaluates the possibilities of channel formation by two mechanisms: dissolution of ice by a concentrated solution of ammonium sulfate, and by mechanical erosion by flow of liquid ammonia and liquid ethane. Chapter 4: This chapter presents: (1) new explicit mathematical solutions of mixed 1st and 2nd order chemical reactions, represented by ordinary differential first-degree and Riccati equations; (2) the computed present-day concentrations of the three gases in Titan's scale atmosphere, treated as at near-steady state; and (3) an analysis of the reported and computed atmospheric concentrations of CH4, CH 3, and C2H6 on Titan, based on the reaction rate parameters of the species, the rate parameters taken as constants representative of their mean values. Chapter 5: This chapter examines the possible reactions of methane formation in terms of the thermodynamic relationships of the reactions that include pure carbon as graphite, the gases H2, CO2, H2 O, and serpentinization and magnetite formation from olivine fayalite. (Abstract shortened by ProQuest.).

  17. Bismuth doping effect on crystal structure and photodegradation activity of Bi-TiO2 nanoparticles

    NASA Astrophysics Data System (ADS)

    Wu, Ming-Chung; Chang, Yin-Hsuan; Lin, Ting-Han

    2017-04-01

    The bismuth precursor is adopted as dopant to synthesize bismuth doped titanium dioxide nanoparticles (Bi-TiO2 NPs) with sol-gel method following by the thermal annealing treatment. We systematically developed a series of Bi-TiO2 NPs at several calcination temperatures and discovered the corresponding crystal structure by varying the bismuth doping concentration. At a certain 650 °C calcination temperature, the crystal structure of bismuth titanate (Bi2Ti2O7) is formed when the bismuth doping concentration is as high as 10.0 mol %. The photocatalytic activity of Bi-TiO2 NPs is increased by varying the doping concentration at the particular calcination temperature. By the definition X-ray diffraction (XRD) structural identification, a phase diagram of Bi-TiO2 NPs in doping concentration versus calcination temperature is provided. It can be useful for further study in the crystal structure engineering and the development of photocatalyst.

  18. Strontium ranelate for preventing and treating postmenopausal osteoporosis.

    PubMed

    O'Donnell, S; Cranney, A; Wells, G A; Adachi, J D; Reginster, J Y

    2006-07-19

    Strontium ranelate is a new anti-osteoporosis therapy therefore, its benefits and harms need to be known. To determine the efficacy and safety of strontium ranelate for the treatment and prevention of postmenopausal osteoporosis. We searched MEDLINE (1996 to March 2005), EMBASE (1996 to week 9 2005), the Cochrane Library (1996 to Issue 1 2005), reference lists of relevant articles and conference proceedings from the last two years. Additional data was sought from authors and industry sponsors. We included randomized controlled trials (RCTs) of at least one year duration comparing strontium ranelate versus placebo reporting fracture incidence, bone mineral density (BMD), health related quality of life and/or safety outcomes in postmenopausal women. Treatment (versus prevention) population was defined as women with prevalent vertebral fractures and/or lumbar spine BMD T score < -2.5 SD. Two reviewers independently determined study eligibility, assessed trial quality and extracted the relevant data. Disagreements were resolved by consensus. RCTs were grouped by dose of strontium ranelate and treatment duration. Where possible, meta-analysis was conducted using the random effects model. A total of four trials met our inclusion criteria, three of which investigated the effects of strontium ranelate compared to placebo in a treatment population (doses ranged from 0.5 to 2 g daily) and one, in a prevention population (doses 0.125, 0.5 and 1 g daily). In osteoporotic, postmenopausal women a 37% reduction in vertebral fractures (two trials, n = 5082, RR 0.63, 95% CI 0.56 to 0.71) and a 14% reduction in non-vertebral fractures (two trials, n = 6572, RR 0.86, 95% CI 0.75 to 0.98) was demonstrated over a three year period with 2 g of strontium ranelate daily. An increase in BMD at all sites was shown with the same dose: lumbar spine BMD (two trials, n = 1614, WMD adjusted for strontium content 5.44, 95% CI 3.41 to 7.46 and WMD not adjusted 11.29, 95% CI 10.22 to 12.37 over two

  19. Titan LEAF: A Sky Rover Granting Targeted Access to Titan's Lakes and Plains

    NASA Astrophysics Data System (ADS)

    Ross, Floyd; Lee, Greg; Sokol, Daniel; Goldman, Benjamin; Bolisay, Linden

    2016-10-01

    Northrop Grumman, in collaboration with L'Garde Inc. and Global Aerospace Corporation (GAC), has been developing the Titan Lifting Entry Atmospheric Flight (T-LEAF) sky rover to roam the atmosphere and observe at close quarters the lakes and plains of Titan. T-LEAF also supports surface exploration and science by providing precision delivery of in situ instruments to the surface.T-LEAF is a maneuverable, buoyant air vehicle. Its aerodynamic shape provides its maneuverability, and its internal helium envelope reduces propulsion power requirements and also the risk of crashing. Because of these features, T-LEAF is not restricted to following prevailing wind patterns. This freedom of mobility allows it be commanded to follow the shorelines of Titan's methane lakes, for example, or to target very specific surface locations.T-LEAF utilizes a variable power propulsion system, from high power at ~200W to low power at ~50W. High power mode uses the propellers and control surfaces for additional mobility and maneuverability. It also allows the vehicle to hover over specific locations for long duration surface observations. Low power mode utilizes GAC's Titan Winged Aerobot (TWA) concept, currently being developed with NASA funding, which achieves guided flight without the use of propellers or control surfaces. Although slower than high powered flight, this mode grants increased power to science instruments while still maintaining control over direction of travel.Additionally, T-LEAF is its own entry vehicle, with its leading edges protected by flexible thermal protection system (f-TPS) materials already being tested by NASA's Hypersonic Inflatable Aerodynamic Decelerator (HIAD) group. This f-TPS technology allows T-LEAF to inflate in space, like HIAD, and then enter the atmosphere fully deployed. This approach accommodates entry velocities from as low as ~1.8 km/s if entering from Titan orbit, up to ~6 km/s if entering directly from Saturn orbit, like the Huygens probe

  20. Diurnal variations of Titan's ionosphere

    NASA Astrophysics Data System (ADS)

    Cui, J.; Galand, M.; Yelle, R. V.; Vuitton, V.; Wahlund, J.-E.; Lavvas, P. P.; Müller-Wodarg, I. C. F.; Cravens, T. E.; Kasprzak, W. T.; Waite, J. H.

    2009-06-01

    We present our analysis of the diurnal variations of Titan's ionosphere (between 1000 and 1300 km) based on a sample of Ion Neutral Mass Spectrometer (INMS) measurements in the Open Source Ion (OSI) mode obtained from eight close encounters of the Cassini spacecraft with Titan. Although there is an overall ion depletion well beyond the terminator, the ion content on Titan's nightside is still appreciable, with a density plateau of ˜700 cm-3 below ˜1300 km. Such a plateau is a combined result of significant depletion of light ions and modest depletion of heavy ones on Titan's nightside. We propose that the distinctions between the diurnal variations of light and heavy ions are associated with their different chemical loss pathways, with the former primarily through “fast” ion-neutral chemistry and the latter through “slow” electron dissociative recombination. The strong correlation between the observed night-to-day ion density ratios and the associated ion lifetimes suggests a scenario in which the ions created on Titan's dayside may survive well to the nightside. The observed asymmetry between the dawn and dusk ion density profiles also supports such an interpretation. We construct a time-dependent ion chemistry model to investigate the effect of ion survival associated with solid body rotation alone as well as superrotating horizontal winds. For long-lived ions, the predicted diurnal variations have similar general characteristics to those observed. However, for short-lived ions, the model densities on the nightside are significantly lower than the observed values. This implies that electron precipitation from Saturn's magnetosphere may be an additional and important contributor to the densities of the short-lived ions observed on Titan's nightside.

  1. Titan's atmosphere and surface in 2026: the AVIATR Titan Airplane Mission

    NASA Astrophysics Data System (ADS)

    McKay, Chris; Barnes, Jason W.; Lemke, Lawrence; Beyer, Ross A.; Radebaugh, Jani; Atkinson, David; Flasar, F. Michael

    2010-04-01

    This poster describes the scientific, engineering, and operations planning for a Discovery / New Frontiers class Titan airplane mission, AVIATR (Aerial Vehicle for In-situ and Airborne Titan Reconnaissance). The mission would focus on Titan's surface and atmospheric diversity, using high-resolution imaging, near-infrared spectroscopy, a haze spectrometer, and atmospheric structure measurements. Previous mission studies have elected to use hot-air balloons to achieve similar science goals. These hot-air balloon concepts require the waste heat from inefficient thermocouple-based Radioisotope Thermoelectric Generators (RTGs) for buoyancy. New Advanced Stirling Radioisotope Generators (ASRGs) are much more efficient than RTGs both in terms of power produced per gram of plutonium-238 and the total watts-per-kilogram of the power unit itself. However, they are so efficient that they are much less effective for use in heating a hot-air balloon. Similarly, old-style RTGs produce insufficient specific power for heavier-than-air flight, but the use of 2 ASRGs can support a 120 kg airplane for a long-duration mission at Titan. The AVIATR airplane concept has several advantages in its science capabilities relative to a balloon, including the ability to target any site of interest, remaining on the dayside, stereo and repeat coverage, and easy altitude changes. It also possesses engineering advantages over a balloon like low total mass, a more straightforward deployment sequence, direct-to-Earth communications capability, and a more robust airframe.

  2. Effect of ‘A’-site non stoichiometry in strontium doped lanthanum ferrite based solid oxide fuel cell cathodes

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Banerjee, Koyel; Mukhopadhyay, Jayanta, E-mail: jayanta_mu@cgcri.res.in; Barman, Madhurima

    2015-12-15

    Highlights: • La{sub 1−x}Sr{sub x}Co{sub y}Fe{sub 1−y}O{sub 3−δ}, x = 0.4; y = 0.2 system varying La-site (0.6–0.54) are studied. • Combustion synthesis technique is used to prepare the powder samples. • Highest electrical conductivity observed with largest A-site deficit composition. • Lowest cathode polarization is found with the same composition (0.02 Ω cm{sup 2}). • Composition with largest A-site deficiency exhibits best performance (2.84 A cm{sup −2}). - Abstract: Effect of A-site non-stoichiometry in strontium doped lanthanum cobalt ferrite (La{sub 1−x}Sr{sub x}Co{sub y}Fe{sub 1−y}O{sub 3−δ}, x = 0.4; y = 0.2) is studied in a systematic manner with variationmore » of ‘A’ site stoichiometry from 1 to 0.94. The perovskite based cathode compositions are synthesized by combustion synthesis. Powder characterizations reveal rhombohedral crystal structure with crystallite size ranging from 29 to 34 nm with minimum lattice spacing of 0.271 nm. Detailed sintering studies along with total DC electrical conductivities are evaluated in the bulk form with variation of sintering temperatures. The electrode polarizations are measured in the symmetric cell configuration by impedance spectroscopy which is found to be the lowest (0.02 Ω cm{sup 2} at 800 °C) for cathode having highest degree of ‘A’-site deficiency. The same cathode composition exhibits a current density of 2.84 A cm{sup −2} (at 0.7 V, 800 °C) in anode-supported single cell. An attempt has been made to correlate the trend of electrical behaviour with increasing ‘A’-site deficiency for such cathode compositions.« less

  3. Superconducting 500 MHz accelerating copper cavities sputter-coated with niobium films

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Benvenuti, C.; Circelli, N.; Hauer, M.

    Thermal breakdown induced either by electron loading or by local defects of enhanced RF losses limits the accelerating field of superconducting niobium cavities. Replacing niobium with a material of higher thermal conductivity would be highly desirable to increase the maximum field. Therefore, cavities made of OFHC copper were coated by D.C. bias sputtering with a thin niobium film (1.5 to 5 ..mu..). Accelerating fields up to 8.6 MVm/sup -1/ were obtained without observing any field breakdown, the limitation being due to the available rf power. The Q values achieved at 4.2 K and low field were similar to those ofmore » niobium sheet cavities (i.e. about 2 x 10/sup 9/), but a fast initial decrease of Q to about 10/sup 9/ was reproducibly experienced. Subsequent inspection of regions of enhanced rf losses revealed defects the origin of which is under study. The apparatus used for coating the cavities and the results obtained are presented and discussed.« less

  4. Investigation of strontium accumulation on ovariectomized Sprague-Dawley rat tibia by micro-PIXE

    NASA Astrophysics Data System (ADS)

    Li, X.; Li, Y.; Jin, W.; Zheng, Y.; Rong, C.; Lyu, H.; Shen, H.

    2014-08-01

    Strontium ranelate is a newly developed drug effective in osteoporosis treatment by depressing bone resorption and maintaining bone formation. Strontium accumulation and distribution are determined in bones of rat after strontium ranelate administration by using micro-PIXE. The investigated rats are divided into four groups: (A) control, (B) ovariectomized, (C) ovariectomized followed with strontium chloride, (D) ovariectomized followed with strontium ranelate. It was found that strontium ranelate would result in increasing trabecular volume and decreasing bone resorption to treat osteoporosis. There are similar contours of calcium and strontium in two-dimensional images, while the strontium is not evenly distributed in the bone. It supports the conclusion that strontium has an affinity for bone and it is capable of replacing calcium atoms as a part of the strontium mechanism in the osteoporosis treatment. The results related to biochemistry are also discussed.

  5. Strontium-Doped Calcium Phosphate and Hydroxyapatite Granules Promote Different Inflammatory and Bone Remodelling Responses in Normal and Ovariectomised Rats

    PubMed Central

    Xia, Wei; Emanuelsson, Lena; Norlindh, Birgitta; Omar, Omar; Thomsen, Peter

    2013-01-01

    The healing of bone defects may be hindered by systemic conditions such as osteoporosis. Calcium phosphates, with or without ion substitutions, may provide advantages for bone augmentation. However, the mechanism of bone formation with these materials is unclear. The aim of this study was to evaluate the healing process in bone defects implanted with hydroxyapatite (HA) or strontium-doped calcium phosphate (SCP) granules, in non-ovariectomised (non-OVX) and ovariectomised (OVX) rats. After 0 (baseline), six and 28d, bone samples were harvested for gene expression analysis, histology and histomorphometry. Tumour necrosis factor-α (TNF-α), at six days, was higher in the HA, in non-OVX and OVX, whereas interleukin-6 (IL-6), at six and 28d, was higher in SCP, but only in non-OVX. Both materials produced a similar expression of the receptor activator of nuclear factor kappa-B ligand (RANKL). Higher expression of osteoclastic markers, calcitonin receptor (CR) and cathepsin K (CatK), were detected in the HA group, irrespective of non-OVX or OVX. The overall bone formation was comparable between HA and SCP, but with topological differences. The bone area was higher in the defect centre of the HA group, mainly in the OVX, and in the defect periphery of the SCP group, in both non-OVX and OVX. It is concluded that HA and SCP granules result in comparable bone formation in trabecular bone defects. As judged by gene expression and histological analyses, the two materials induced different inflammatory and bone remodelling responses. The modulatory effects are associated with differences in the spatial distribution of the newly formed bone. PMID:24376855

  6. Titan and habitable planets around M-dwarfs.

    PubMed

    Lunine, Jonathan I

    2010-01-01

    The Cassini-Huygens mission discovered an active "hydrologic cycle" on Saturn's giant moon Titan, in which methane takes the place of water. Shrouded by a dense nitrogen-methane atmosphere, Titan's surface is blanketed in the equatorial regions by dunes composed of solid organics, sculpted by wind and fluvial erosion, and dotted at the poles with lakes and seas of liquid methane and ethane. The underlying crust is almost certainly water ice, possibly in the form of gas hydrates (clathrate hydrates) dominated by methane as the included species. The processes that work the surface of Titan resemble in their overall balance no other moon in the solar system; instead, they are most like that of the Earth. The presence of methane in place of water, however, means that in any particular planetary system, a body like Titan will always be outside the orbit of an Earth-type planet. Around M-dwarfs, planets with a Titan-like climate will sit at 1 AU--a far more stable environment than the approximately 0.1 AU where Earth-like planets sit. However, an observable Titan-like exoplanet might have to be much larger than Titan itself to be observable, increasing the ratio of heat contributed to the surface atmosphere system from internal (geologic) processes versus photons from the parent star.

  7. Titan cells confer protection from phagocytosis in Cryptococcus neoformans infections.

    PubMed

    Okagaki, Laura H; Nielsen, Kirsten

    2012-06-01

    The human fungal pathogen Cryptococcus neoformans produces an enlarged "titan" cell morphology when exposed to the host pulmonary environment. Titan cells exhibit traits that promote survival in the host. Previous studies showed that titan cells are not phagocytosed and that increased titan cell production in the lungs results in reduced phagocytosis of cryptococcal cells by host immune cells. Here, the effect of titan cell production on host-pathogen interactions during early stages of pulmonary cryptococcosis was explored. The relationship between titan cell production and phagocytosis was found to be nonlinear; moderate increases in titan cell production resulted in profound decreases in phagocytosis, with significant differences occurring within the first 24 h of the infection. Not only were titan cells themselves protected from phagocytosis, but titan cell formation also conferred protection from phagocytosis to normal-size cryptococcal cells. Large particles introduced into the lungs were not phagocytosed, suggesting the large size of titan cells protects against phagocytosis. The presence of large particles was unable to protect smaller particles from phagocytosis, revealing that titan cell size alone is not sufficient to provide the observed cross-protection of normal-size cryptococcal cells. These data suggest that titan cells play a critical role in establishment of the pulmonary infection by promoting the survival of the entire population of cryptococcal cells.

  8. Titan's geoid and hydrology: implications for Titan's geological evolution

    NASA Astrophysics Data System (ADS)

    Sotin, Christophe; Seignovert, Benoit; Lawrence, Kenneth; MacKenzie, Shannon; Barnes, Jason; Brown, Robert

    2014-05-01

    A 1x1 degree altitude map of Titan is constructed from the degree 4 gravity potential [1] and Titan's shape [2] determined by the Radio Science measurements and RADAR observations of the Cassini mission. The amplitude of the latitudinal altitude variations is equal to 300 m compared to 600 m for the amplitude of the latitudinal shape variations. The two polar caps form marked depressions with an abrupt change in topography at exactly 60 degrees at both caps. Three models are envisaged to explain the low altitude of the polar caps: (i) thinner ice crust due to higher heat flux at the poles, (ii) fossil shape acquired if Titan had higher spin rate in the past, and (iii) subsidence of the crust following the formation of a denser layer of clathrates as ethane rain reacts with the H2O ice crust [3]. The later model is favored because of the strong correlation between the location of the cloud system during the winter season and the latitude of the abrupt change in altitude. Low altitude polar caps would be the place where liquids would run to and eventually form large seas. Indeed, the large seas of Titan are found at the deepest locations at the North Pole. However, the lakes and terrains considered to be evaporite candidates due to their spectral characteristics in the infrared [4,5] seem to be perched. Lakes may have been filled during Titan's winter and then slowly evaporated leaving material on the surface. Interestingly, the largest evaporite deposits are located at the equator in a deep depression 150 m below the altitude of the northern seas. This observation seems to rule out the presence of a global subsurface hydrocarbon reservoir unless the evaporation rate at the equator is faster than the transport of fluids from the North Pole to the equator. This work has been performed at the Jet Propulsion Laboratory, California Institute of Technology, under contract to NASA. [1] Iess L. et al. (2012) Science, doi 10.1126/science.1219631. [2] Lorenz R.D. (2013

  9. Planetary science: Titan's lost seas found

    NASA Astrophysics Data System (ADS)

    Sotin, Christophe

    2007-01-01

    When the Cassini spacecraft found no methane ocean swathing Saturn's moon Titan, it was a blow to proponents of an Earth-like world. The discovery of northern lakes on Titan gives them reason for cheer.

  10. A process for the development of strontium hydroxyapatite

    NASA Astrophysics Data System (ADS)

    Zahra, N.; Fayyaz, M.; Iqbal, W.; Irfan, M.; Alam, S.

    2014-06-01

    A procedure for the preparation of Strontium Hydroxyapatite is adapted to produce high purity and better homogeneity ceramic with good Crystallinity. The strontium substituted bone cement has potential for use in orthopedic surgeries. Ionic Strontium (Sr) in humans shares the same physiological pathway as calcium and can be deposited in the mineral structure of the bone. In the present study, a novel concept of preparing Sr-contained Hydroxyapatite bone cement by using a precipitation method is proposed to get an ideal biomaterial that possesses potential degradability and more excellent pharmacological effect. Chemical analysis, Fourier Transform Infra Red analysis and Thermogravimetric/ Differential Scanning Calorimetric studies were conducted on prepared Strontium Hydroxyapatite sample to characterize the incorporation of 15% Sr2+ into the crystal lattice of Hydroxyapatite. Strontium was quantitatively incorporated into Hydroxyapatite where its substitution for calcium provoked a linear shift of the infrared absorption bands of the hydroxyl and phosphate groups. Thus, the formation of Sr-HAp was confirmed by Chemical Analysis, FT-IR and TGA/DSC results.

  11. Anomaly diffuse and dielectric relaxation in strontium doped lanthanum molybdate

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Liu, Xiao; Fan, Huiqing, E-mail: hqfan3@163.com; Shi, Jing

    2011-12-15

    Highlights: Black-Right-Pointing-Pointer The anomaly diffuse and dielectric relaxation behaviors are fitted by the Cole-Cole approach. Black-Right-Pointing-Pointer The peak in the LSMO is corresponding to different oxygen ion diffusion process. Black-Right-Pointing-Pointer We first give better explanation about the strange conductivity change caused by doping. Black-Right-Pointing-Pointer The oxygen ion diffusion is due to a combination of the dipolar relaxation and the motion of ions. -- Abstract: The dielectric properties of the La{sub 2-x}Sr{sub x}Mo{sub 2}O{sub 9-{delta}} (x = 0-0.2) ceramics were investigated in the temperature range of 300-800 K. Dielectric measurement reveals that two dielectric anomalies, associated with the oxygen ion diffusion,more » exist in frequency spectrum with x = 0.5. The broad dielectric peaks in tan {delta}({omega}) can be well fitted by a modified Cole-Cole approach. When x = 0.1, only one dielectric relaxation peak is observed, corresponding to different oxygen ion diffusion processes, as distinct from the only relaxation peak in the pure La{sub 2}Mo{sub 2}O{sub 9}. The relaxation parameters {tau}{sub 0}, the dielectric relaxation strength {Delta}, and the activation energy E{sub a} were obtained. The result of this work shows that, the conductivity change caused by doping between the two phases is due to the combination of the dipolar effects and motion of ions.« less

  12. Broad-Based Search for New and Practical Superconductors

    DTIC Science & Technology

    2014-10-31

    dielectric metamaterial has been tested in experiments with compressed mixtures of tin and barium titanate (BTO) and strontium titanate(STO) nanoparticles...work is published in Phys. Rev. B 89 , 134516 (2014). 3. New/Unexplored Directions: Search for Superconductivity in Naturally Occurring Mineral

  13. Titan

    NASA Technical Reports Server (NTRS)

    Flasar, F. M.

    1999-01-01

    With a launch in December 2001, Space Infrared Telescope Facility (SIRTF) can observe Titan in the interval after Infrared Space Observatory (ISO) but before the onset of observations by Cassini. By virtue of its broad spectral coverage in the thermal infrared, 10-180 micron, its moderately high spectral resolution, approaching lambda/delta lambda=600 over part of this wavelength range, and the very high sensitivity of its helium- cooled detectors, the Infrared Spectrometer (IRS) and MIPS on SIRTF can address several issues raised through earlier observations by the Voyager IRIS experiment and by ISO. These include, for example, a better characterization of the vertical distribution of water in Titan's middle and upper atmospheres and the discovery of new compounds, such as allene or proprionitrile. This talk will address the temperature- and composition-sounding capabilities of SIRTF, particularly in the context of how they will complement Cassini observations and aid in their planning.

  14. Strontium-90 content of deciduous human incisors.

    PubMed

    ROSENTHAL, H L; GILSTER, J E; BIRD, J T

    1963-04-12

    The concentrations of strontium-90 in deciduous incisor teeth of children born in St. Louis between 1949 to 1957 are in accord with estimated bone levels, suggesting that human deciduous teeth are useful as an index of strontium-90 accumulation during the time the teeth are formed.

  15. Interaction of Titan's ionosphere with Saturn's magnetosphere.

    PubMed

    Coates, Andrew J

    2009-02-28

    Titan is the only Moon in the Solar System with a significant permanent atmosphere. Within this nitrogen-methane atmosphere, an ionosphere forms. Titan has no significant magnetic dipole moment, and is usually located inside Saturn's magnetosphere. Atmospheric particles are ionized both by sunlight and by particles from Saturn's magnetosphere, mainly electrons, which reach the top of the atmosphere. So far, the Cassini spacecraft has made over 45 close flybys of Titan, allowing measurements in the ionosphere and the surrounding magnetosphere under different conditions. Here we review how Titan's ionosphere and Saturn's magnetosphere interact, using measurements from Cassini low-energy particle detectors. In particular, we discuss ionization processes and ionospheric photoelectrons, including their effect on ion escape from the ionosphere. We also discuss one of the unexpected discoveries in Titan's ionosphere, the existence of extremely heavy negative ions up to 10000amu at 950km altitude.

  16. PEROXOTITANATE- AND MONOSODIUM METAL-TITANATE COMPOUNDS AS INHIBITORS OF BACTERIAL GROWTH

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Hobbs, D.

    2011-01-19

    Sodium titanates are ion-exchange materials that effectively bind a variety of metal ions over a wide pH range. Sodium titanates alone have no known adverse biological effects but metal-exchanged titanates (or metal titanates) can deliver metal ions to mammalian cells to alter cell processes in vitro. In this work, we test a hypothesis that metal-titanate compounds inhibit bacterial growth; demonstration of this principle is one prerequisite to developing metal-based, titanate-delivered antibacterial agents. Focusing initially on oral diseases, we exposed five species of oral bacteria to titanates for 24 h, with or without loading of Au(III), Pd(II), Pt(II), and Pt(IV), andmore » measuring bacterial growth in planktonic assays through increases in optical density. In each experiment, bacterial growth was compared with control cultures of titanates or bacteria alone. We observed no suppression of bacterial growth by the sodium titanates alone, but significant (p < 0.05, two-sided t-tests) suppression was observed with metal-titanate compounds, particularly Au(III)-titanates, but with other metal titanates as well. Growth inhibition ranged from 15 to 100% depending on the metal ion and bacterial species involved. Furthermore, in specific cases, the titanates inhibited bacterial growth 5- to 375-fold versus metal ions alone, suggesting that titanates enhanced metal-bacteria interactions. This work supports further development of metal titanates as a novel class of antibacterials.« less

  17. A whiff of nebular gas in Titan's atmosphere - Potential implications for the conditions and timing of Titan's formation

    NASA Astrophysics Data System (ADS)

    Glein, Christopher R.

    2017-09-01

    In situ data from the GCMS instrument on the Huygens probe indicate that Titan's atmosphere contains small amounts of the primordial noble gases 36Ar and 22Ne (tentative detection), but it is unknown how they were obtained by the satellite. Based on the apparent similarity in the 22Ne/36Ar (atom) ratio between Titan's atmosphere and the solar composition, a previously neglected hypothesis for the origin of primordial noble gases in Titan's atmosphere is suggested - these species may have been acquired near the end of Titan's formation, when the moon could have gravitationally captured some nebular gas that would have been present in its formation environment (the Saturnian subnebula). These noble gases may be remnants of a primary atmosphere. This could be considered the simplest hypothesis to explain the 22Ne/36Ar ratio observed at Titan. However, the 22Ne/36Ar ratio may not be exactly solar if these species can be fractionated by external photoevaporation in the solar nebula, atmospheric escape from Titan, or sequestration on the surface of Titan. While the GCMS data are consistent with a 22Ne/36Ar ratio of 0.05 to 2.5 times solar (1σ range), simple estimates that attempt to account for some of the effects of these evolutionary processes suggest a sub-solar ratio, which may be depleted by approximately one order of magnitude. Models based on capture of nebular gas can explain why the GCMS did not detect any other primordial noble gas isotopes, as their predicted abundances are below the detection limits (especially for 84Kr and 132Xe). It is also predicted that atmospheric Xe on Titan should be dominated by radiogenic 129Xe if the source of primordial Xe is nebular gas. Of order 10-2-10-1 bar of primordial H2 may have been captured along with the noble gases from a gas-starved disk, but this H2 would have quickly escaped from the initial atmosphere. To have the opportunity to capture nebular gas, Titan should have formed within ∼10 Myr of the formation of the

  18. Coupled atmosphere-ocean models of Titan's past

    NASA Technical Reports Server (NTRS)

    Mckay, Christopher P.; Pollack, James B.; Lunine, Jonathan I.; Courtin, Regis

    1993-01-01

    The behavior and possible past evolution of fully coupled atmosphere and ocean model of Titan are investigated. It is found that Titan's surface temperature was about 20 K cooler at 4 Gyr ago and will be about 5 K warmer 0.5 Gyr in the future. The change in solar luminosity and the conversion of oceanic CH4 to C2H6 drive the evolution of the ocean and atmosphere over time. Titan appears to have experienced a frozen epoch about 3 Gyr ago independent of whether an ocean is present or not. This finding may have important implications for understanding the inventory of Titan's volatile compounds.

  19. Halving Titan

    NASA Image and Video Library

    2010-01-11

    Titan seasonal hemispheric dichotomy is chronicled in black and white, with the moon northern half appearing slightly lighter than the dark southern half in this image taken by NASA Cassini spacecraft.

  20. Surface modification of strontium-doped porous bioactive ceramic scaffolds via poly(DOPA) coating and immobilizing silk fibroin for excellent angiogenic and osteogenic properties.

    PubMed

    Wang, Xu; Gu, Zhipeng; Jiang, Bo; Li, Li; Yu, Xixun

    2016-04-01

    For bioceramic scaffolds employed in clinical applications, excellent bioactivity and tenacity were of great importance. Modifying inorganic SCPP scaffolds with biological macromolecules could obviously improve its bioactivity and eliminate its palpable brittleness. However, it was hard to execute directly due to extremely bad interfacial compatibility between them. In this research, dopamine (DOPA) was introduced onto strontium-doped calcium polyphosphate (SCPP) scaffolds, subsequently the preliminary material was successfully further modified by silk fibroin (SF). SCPP/D/SF possessed suitable biomechanical properties, ability to stimulate angiogenic factor secretion and excellent biocompatibility. Biomechanical examination demonstrated that SCPP/D/SF scaffolds yielded better compressive strength because of improved interfacial compatibility. MTT assay and CLSM observation showed that SCPP/D/SF scaffolds had good cytocompatibility and presented better inducing-cell-migration potential than pure SCPP scaffolds. Meanwhile, its ability to stimulate angiogenic factor secretion was measured through the ELISA assay and immunohistological analysis in vitro and in vivo respectively. The results revealed, superior to SCPP, SCPP/D/SF could effectively promote VEGF and bFGF expression, possibly leading to enhancing angiogenesis and osteogenesis. In a word, SCPP/D/SF could serve as a potential bone tissue engineering scaffold for comparable biomechanical properties and excellent bioactivity. It provided a novel idea for modification of inorganic materials to prepare promising bone tissue engineering scaffolds with the ability to accelerate bone regeneration and vascularization.

  1. NIOBIUM-TANTALUM SEPARATION

    DOEpatents

    Wilhelm, H.A.; Foos, R.A.

    1959-01-27

    The usual method for the separation of tantalum and niobium consists of a selective solvent extraction from an aqueous hydrofluoric acid solution of the metals. A difficulty encountered in this process is the fact that the corrosion problems associated with hydrofluoric acid are serious. It has been found that the corrosion caused by the hydrofluoric acid may be substantially reduced by adding to the acidic solution an amine, such as phenyl diethanolamine or aniline, and adjusting pH value to between 4 and 6.

  2. Age and gender specific biokinetic model for strontium in humans

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Shagina, N. B.; Tolstykh, E. I.; Degteva, M. O.

    A biokinetic model for strontium in humans is necessary for quantification of internal doses due to strontium radioisotopes. The ICRP-recommended biokinetic model for strontium has limitation for use in a population study, because it is not gender specific and does not cover all age ranges. The extensive Techa River data set on 90Sr in humans (tens of thousands of measurements) is a unique source of data on long-term strontium retention for men and women of all ages at intake. These, as well as published data, were used for evaluation of age- and gender-specific parameters for a new compartment biokinetic modelmore » for strontium (Sr-AGe model). The Sr-AGe model has similar structure as the ICRP model for the alkaline earth elements. The following parameters were mainly reevaluated: gastro-intestinal absorption and parameters related to the processes of bone formation and resorption defining calcium and strontium transfers in skeletal compartments. The Sr-AGe model satisfactorily describes available data sets on strontium retention for different kinds of intake (dietary and intravenous) at different ages (0–80 years old) and demonstrates good agreement with data sets for different ethnic groups. The Sr-AGe model can be used for dose assessment in epidemiological studies of general population exposed to ingested strontium radioisotopes.« less

  3. Laboratory simulation of photochemistry on Titan

    NASA Astrophysics Data System (ADS)

    Ferris, J.; Tran, B.; Force, M.; Briggs, R.; Vuitton, V.

    Solar UV radiation is the principal energy source driving the chemistry in Titan's atmosphere ....(Sagan and Thompson, 1984). We have investigated the photochemical reactions in Titan's atmosphere in a flow reactor using the 185 and 254 nm UV emissions from a low-pressure mercury lamp ....(Clarke, et al., 2000) .....(Tran, et al., 2003). A solid product is formed using this apparatus and its optical properties have been measured since it is an analog of the haze layer on Titan. The complex refractive index of the solid material was determined and compared with the corresponding refractive index derived from the optical data obtained from Voyager 1 .......(Tran, et al., 2003). The current research focuses on the volatile reaction products. The principal gaseous compounds that absorb 185 nm light in Titan's atmosphere (acetylene, ethylene, and cyanoacetylene) were irradiated individually and in the presence of other atmospheric constituents at their mixing ratios in the Titan atmosphere. The objectives of this study are to determine the reaction pathways and to construct a model that reproduces the experimental results. Quantum yields for the loss of reactants and the formation of products were determined from the rates measured by gas chromatographic analysis. Irradiation of a mixture of acetylene, ethylene, cyanoacetylene, methane, hydrogen and nitrogen generated over 120 compounds. The structures of about 100 of these compounds were determined by GC/MS. The structures of many of these compounds were confirmed by use of authentic samples. The similarities and difference in the products obtained photochemically and by plasma discharges will be discussed. Clarke D. W., J. C. Joseph and J. P. Ferris, 2000, The design and use of a photochemical flow reactor: A laboratory study of the atmospheric chemistry of cyanoacetylene on Titan, Icarus, 282-291. Sagan C. and W. R. Thompson, 1984, Production and condensation of organic gases in the atmosphere of Titan, Icarus, 59

  4. Evaluation of niobium as candidate electrode material for DC high voltage photoelectron guns

    DOE PAGES

    BastaniNejad, M.; Mohamed, Md. Abdullah; Elmustafa, A. A.; ...

    2012-08-17

    In this study, the field emission characteristics of niobium electrodes were compared to those of stainless steel electrodes using a DC high voltage field emission test apparatus. A total of eight electrodes were evaluated: two 304 stainless steel electrodes polished to mirror-like finish with diamond grit and six niobium electrodes (two single-crystal, two large-grain and two fine-grain) that were chemically polished using a buffered-chemical acid solution. Upon the first application of high voltage, the best large-grain and single-crystal niobium electrodes performed better than the best stainless steel electrodes, exhibiting less field emission at comparable voltage and gradient. In all cases,more » field emission from electrodes (stainless steel and/or niobium) could be significantly reduced and sometimes completely eliminated, by introducing krypton gas into the vacuum chamber while the electrode was biased at high voltage. Of all the electrodes tested, a large-grain niobium electrode performed the best, exhibiting no measurable field emission (< 10 pA) at 225 kV with 20 mm cathode/anode gap, corresponding to a gradient of 18.7 MV/m.« less

  5. Pluto's Implications for a Snowball Titan

    NASA Astrophysics Data System (ADS)

    Wong, M.; Yung, Y. L.; Gladstone, R.

    2013-12-01

    The recent Cassini-Huygens Mission to the Saturnian system provides compelling evidence that the present state of Titan's dense atmosphere is unsustainable over the age of the Solar System. Instead, for most of the time Titan's atmosphere must have existed in a collapsed snowball state, characterized by a cold surface and a thin atmosphere, much like those of present-day Pluto and Triton. We will briefly review how the present Titan atmosphere exists due to a sensitive coupling between photochemistry, radiation, and dynamics. This delicate 'house of cards' must have collapsed in the past when it ran out of CH4 or when the sun was dimmer. We will investigate how the rate of organic synthesis on Snowball Titan differs from that of contemporary Titan. The forthcoming New Horizons Mission to Pluto and the Kuiper Belt may allow us to gain insights into the fine balance and the evolutionary history of certain planetary atmospheres. In particular, the high SNR solar occultations planned for observation with the Alice UV spectrograph on New Horizons are expected to yield abundance profiles of important hydrocarbons and nitriles in Pluto's atmosphere, providing detailed constraints for photochemical models such as those considered here.

  6. The use of synthesized aqueous solutions for determining strontium sorption isotherms

    USGS Publications Warehouse

    Liszewski, M.J.; Bunde, R.L.; Hemming, C.; Rosentreter, J.; Welhan, J.

    1998-01-01

    The use of synthesized aqueous solutions for determining experimentally derived strontium sorption isotherms of sediment was investigated as part of a study accessing strontium chemical transport properties. Batch experimental techniques were used to determine strontium sorption isotherms using synthesized aqueous solutions designed to chemically represent water from a natural aquifer with respect to major ionic character and pH. A strontium sorption isotherm for a sediment derived using a synthesized aqueous solution was found to be most comparable to an isotherm derived using natural water when the synthesized aqueous solution contained similar concentrations of calcium and magnesium. However, it is difficult to match compositions exactly due to the effects of disequilibrium between the solution and the sediment. Strong linear relations between sorbed strontium and solution concentrations of calcium and magnesium confirm that these cations are important co-constituents in these synthesized aqueous solutions. Conversely, weak linear relations between sorbed strontium and solution concentrations of sodium and potassium indicate that these constituents do not affect sorption of strontium. The addition of silica to the synthesized aqueous solution does not appreciably affect the resulting strontium sorption isotherm.

  7. Titan Cells Confer Protection from Phagocytosis in Cryptococcus neoformans Infections

    PubMed Central

    Okagaki, Laura H.

    2012-01-01

    The human fungal pathogen Cryptococcus neoformans produces an enlarged “titan” cell morphology when exposed to the host pulmonary environment. Titan cells exhibit traits that promote survival in the host. Previous studies showed that titan cells are not phagocytosed and that increased titan cell production in the lungs results in reduced phagocytosis of cryptococcal cells by host immune cells. Here, the effect of titan cell production on host-pathogen interactions during early stages of pulmonary cryptococcosis was explored. The relationship between titan cell production and phagocytosis was found to be nonlinear; moderate increases in titan cell production resulted in profound decreases in phagocytosis, with significant differences occurring within the first 24 h of the infection. Not only were titan cells themselves protected from phagocytosis, but titan cell formation also conferred protection from phagocytosis to normal-size cryptococcal cells. Large particles introduced into the lungs were not phagocytosed, suggesting the large size of titan cells protects against phagocytosis. The presence of large particles was unable to protect smaller particles from phagocytosis, revealing that titan cell size alone is not sufficient to provide the observed cross-protection of normal-size cryptococcal cells. These data suggest that titan cells play a critical role in establishment of the pulmonary infection by promoting the survival of the entire population of cryptococcal cells. PMID:22544904

  8. Characterization of high-purity niobium structures fabricated using the electron beam melting process

    NASA Astrophysics Data System (ADS)

    Terrazas Najera, Cesar Adrian

    Additive Manufacturing (AM) refers to the varied set of technologies utilized for the fabrication of complex 3D components from digital data in a layer-by-layer fashion. The use of these technologies promises to revolutionize the manufacturing industry. The electron beam melting (EBM) process has been utilized for the fabrication of fully dense near-net-shape components from various metallic materials. This process, catalogued as a powder bed fusion technology, consists of the deposition of thin layers (50 - 120microm) of metallic powder particles which are fused by the use of a high energy electron beam and has been commercialized by Swedish company Arcam AB. Superconducting radio frequency (SRF) cavities are key components that are used in linear accelerators and other light sources for studies of elemental physics. Currently, cavity fabrication is done by employing different forming processes including deep-drawing and spinning. In both of the latter techniques, a feedstock high-purity niobium sheet with a thickness ranging from 3-4 mm is mechanically deformed and shaped into the desired geometry. In this manner, half cavities are formed that are later joined by electron beam welding (EBW). The welding step causes variability in the shape of the cavity and can also introduce impurities at the surface of the weld interface. The processing route and the purity of niobium are also of utmost importance since the presence of impurities such as inclusions or defects can be detrimental for the SRF properties of cavities. The focus of this research was the use of the EBM process in the manufacture of high purity niobium parts with potential SRF applications. Reactor grade niobium was plasma atomized and used as the precursor material for fabrication using EBM. An Arcam A2 system was utilized for the fabrication. The system had all internal components of the fabrication chamber replaced and was cleaned to prevent contamination of niobium powder. A mini-vat, developed at

  9. Dark Spots on Titan

    NASA Image and Video Library

    2005-05-02

    This recent image of Titan reveals more complex patterns of bright and dark regions on the surface, including a small, dark, circular feature, completely surrounded by brighter material. During the two most recent flybys of Titan, on March 31 and April 16, 2005, Cassini captured a number of images of the hemisphere of Titan that faces Saturn. The image at the left is taken from a mosaic of images obtained in March 2005 (see PIA06222) and shows the location of the more recently acquired image at the right. The new image shows intriguing details in the bright and dark patterns near an 80-kilometer-wide (50-mile) crater seen first by Cassini's synthetic aperture radar experiment during a Titan flyby in February 2005 (see PIA07368) and subsequently seen by the imaging science subsystem cameras as a dark spot (center of the image at the left). Interestingly, a smaller, roughly 20-kilometer-wide (12-mile), dark and circular feature can be seen within an irregularly-shaped, brighter ring, and is similar to the larger dark spot associated with the radar crater. However, the imaging cameras see only brightness variations, and without topographic information, the identity of this feature as an impact crater cannot be conclusively determined from this image. The visual infrared mapping spectrometer, which is sensitive to longer wavelengths where Titan's atmospheric haze is less obscuring -- observed this area simultaneously with the imaging cameras, so those data, and perhaps future observations by Cassini's radar, may help to answer the question of this feature's origin. The new image at the right consists of five images that have been added together and enhanced to bring out surface detail and to reduce noise, although some camera artifacts remain. These images were taken with the Cassini spacecraft narrow-angle camera using a filter sensitive to wavelengths of infrared light centered at 938 nanometers -- considered to be the imaging science subsystem's best spectral filter

  10. Titan Polar Maps - 2015

    NASA Image and Video Library

    2015-10-09

    The northern and southern hemispheres of Titan are seen in these polar stereographic maps, assembled in 2015 using the best-available images of the giant Saturnian moon from NASA's Cassini mission. The images were taken by Cassini's imaging cameras using a spectral filter centered at 938 nanometers, allowing researchers to examine variations in albedo (or inherent brightness) across the surface of Titan. These maps utilize imaging data collected through Cassini's flyby on April 7, 2014, known as "T100." Titan's north pole was not well illuminated early in Cassini's mission, because it was winter in the northern hemisphere when the spacecraft arrived at Saturn. Cassini has been better able to observe northern latitudes in more recent years due to seasonal changes in solar illumination. Compared to the previous version of Cassini's north polar map (see PIA11146), this map provides much more detail and fills in a large area of missing data. The imaging data in these maps complement Cassini synthetic aperture radar (SAR) mapping of Titan's north pole (see PIA17655). The uniform gray area in the northern hemisphere indicates a gap in the imaging coverage of Titan's surface, to date. The missing data will be imaged by Cassini during flybys on December 15, 2016 and March 5, 2017. Lakes are also seen in the southern hemisphere map, but they are much less common than in the north polar region. Only a lakes have been confirmed in the south. The dark, footprint-shaped feature at 180 degrees west is Ontario Lacus; a smaller lake named Crveno Lacus can be seen as a very dark spot just above Ontario. The dark-albedo area seen at the top of the southern hemisphere map (at 0 degrees west) is an area called Mezzoramia. Each map is centered on one of the poles, and surface coverage extends southward to 60 degrees latitude. Grid lines indicate latitude in 10-degree increments and longitude in 30-degree increments. The scale in the full-size versions of these maps is 4,600 feet (1

  11. Analyzing the defect structure of CuO-doped PZT and KNN piezoelectrics from electron paramagnetic resonance.

    PubMed

    Jakes, Peter; Kungl, Hans; Schierholz, Roland; Eichel, Rüdiger-A

    2014-09-01

    The defect structure for copper-doped sodium potassium niobate (KNN) ferroelectrics has been analyzed with respect to its defect structure. In particular, the interplay between the mutually compensating dimeric (Cu(Nb)'''-V(O)··) and trimeric (V(O)··-Cu(Nb)'''-V(O)··)· defect complexes with 180° and non-180° domain walls has been analyzed and compared to the effects from (Cu'' - V(O)··)(x)× dipoles in CuO-doped lead zirconate titanate (PZT). Attempts are made to relate the rearrangement of defect complexes to macroscopic electromechanical properties.

  12. Experimental simulation of aerosols evolution in Titan's ionosphere

    NASA Astrophysics Data System (ADS)

    Chatain, A.; Carrasco, N.; Guaitella, O.

    2017-09-01

    Many recent studies on Titan are concerned with aerosols. In particular, questions are asked on how these complex organic molecules are formed and evolve in Titan's atmosphere. Here for the first time we experimentally study how harsh plasma environment simulating Titan ionosphere can affect these aerosols. Titan tholins are placed in a N2-H2 plasma reactor and sample signatures are measured by infrared transmission spectroscopy. First results show an evolution of the absorption bands. Therefore, plasma conditions seem to change tholin chemical structure.

  13. Seawater strontium isotopes, acid rain, and the Cretaceous-Tertiary boundary

    NASA Technical Reports Server (NTRS)

    Macdougall, J. D.

    1988-01-01

    A large bolide impact at the end of the Cretaceous would have produced significant amounts of nitrogen oxides by shock heating of the atmosphere. The resulting acid precipitation would have increased continental weathering greatly and could be an explanation for the observed high ratio of strontium-87 to strontium-86 in seawater at about this time, due to the dissolution of large amounts of strontium from the continental crust. Spikes to high values in the seawater strontium isotope record at other times may reflect similar episodes.

  14. High-temperature superconductivity in space-charge regions of lanthanum cuprate induced by two-dimensional doping

    PubMed Central

    Baiutti, F.; Logvenov, G.; Gregori, G.; Cristiani, G.; Wang, Y.; Sigle, W.; van Aken, P. A.; Maier, J.

    2015-01-01

    The exploitation of interface effects turned out to be a powerful tool for generating exciting material properties. Such properties include magnetism, electronic and ionic transport and even superconductivity. Here, instead of using conventional homogeneous doping to enhance the hole concentration in lanthanum cuprate and achieve superconductivity, we replace single LaO planes with SrO dopant planes using atomic-layer-by-layer molecular beam epitaxy (two-dimensional doping). Electron spectroscopy and microscopy, conductivity measurements and zinc tomography reveal such negatively charged interfaces to induce layer-dependent superconductivity (Tc up to 35 K) in the space-charge zone at the side of the planes facing the substrate, where the strontium (Sr) profile is abrupt. Owing to the growth conditions, the other side exhibits instead a Sr redistribution resulting in superconductivity due to conventional doping. The present study represents a successful example of two-dimensional doping of superconducting oxide systems and demonstrates its power in this field. PMID:26481902

  15. Probing Titan's atmosphere with a stellar occultation

    NASA Technical Reports Server (NTRS)

    Hubbard, W. B.

    1991-01-01

    The 3 July, 1989 occultation of 28 Sgr by Titan is discussed. The star was readily detectable throughout the occultation, reaching a minimum normalized flux of about 0.05. The occultation probed Titan's atmosphere in a region not studied by the Voyager spacecraft. The region is important for the aerobraking of Titan entry probes, and direct information about its properties is important for the Cassini mission. Occultation data (normalized stellar flux vs universal time) is shown in chart form for NASA supported stations, along with data from a collaborating group at the Wise observatory in Israel. Strong scintillation data of the star is noticeable in the data records, and provides information on waves/turbulence in Titan's high atmosphere.

  16. A strontium-90 sequestrant for first-aid treatment of radiation emergency.

    PubMed

    Haratake, Mamoru; Hatanaka, Eisuke; Fuchigami, Takeshi; Akashi, Makoto; Nakayama, Morio

    2012-01-01

    In this study, hydrophilic porous polymer beads with phosphonic acid groups (PGMA-EGDMA-TTA-MP) were synthesized, and assessed as a radioactive strontium-90 sequestrant for the treatment of the radiation emergency. Strontium ions were rapidly absorbed into the blood from the gastrointestinal (GI) tract after oral administration to rats, and distributed to the target organ, i.e., bones. Over 40% of the administered strontium was absorbed into the blood, while the remainder was discharged in the feces within 48 h after the administration. When the PGMA-EGDMA-TTA-MP beads were administered to rats subsequent to the strontium solution, the strontium had accumulated less in the femur. Consequently, the oral administration of the PGMA-EGDMA-TTA-MP beads was effective in suppressing the absorption of strontium from the GI tract.

  17. A Numerical Study of Micrometeoroids Entering Titan's Atmosphere

    NASA Technical Reports Server (NTRS)

    Templeton, M.; Kress, M. E.

    2011-01-01

    A study using numerical integration techniques has been performed to analyze the temperature profiles of micrometeors entering the atmosphere of Saturn s moon Titan. Due to Titan's low gravity and dense atmosphere, arriving meteoroids experience a significant cushioning effect compared to those entering the Earth's atmosphere. Temperature profiles are presented as a function of time and altitude for a number of different meteoroid sizes and entry velocities, at an entry angle of 45. Titan's micrometeoroids require several minutes to reach peak heating (ranging from 200 to 1200 K), which occurs at an altitude of about 600 km. Gentle heating may allow for gradual evaporation of volatile components over a wide range of altitudes. Computer simulations have been performed using the Cassini/Huygens atmospheric data for Titan. Keywords micrometeoroid Titan atmosphere 1 Introduction On Earth, incoming micrometeoroids (100 m diameter) are slowed by collisions with air molecules in a relatively compact atmosphere, resulting in extremely rapid deceleration and a short heating pulse, often accompanied by brilliant meteor displays. On Titan, lower gravity leads to an atmospheric scale height that is much larger than on Earth. Thus, deceleration of meteors is less rapid and these particles undergo more gradual heating. This study uses techniques similar to those used for Earth meteoroid studies [1], exchanging Earth s planetary characteristics (e.g., mass and atmospheric profile) for those of Titan. Cassini/Huygens atmospheric data for Titan were obtained from the NASA Planetary Atmospheres Data Node [4]. The objectives of this study were 1) to model atmospheric heating of meteoroids for a range of micrometeor entry velocities for Titan, 2) to determine peak heating temperatures and rates for micrometeoroids entering Titan s atmosphere, and 3) to create a general simulation environment that can be extended to incorporate additional parameters and variables, including different

  18. Structure and mechanical properties of a multilayer carbide-hardened niobium composite material fabricated by diffusion welding

    NASA Astrophysics Data System (ADS)

    Korzhov, V. P.; Ershov, A. E.; Stroganova, T. S.; Prokhorov, D. V.

    2016-04-01

    The structure, the bending strength, and the fracture mechanism of an artificial niobium-based composite material, which is fabricated by high-pressure diffusion welding of multilayer stacks assembled from niobium foils with a two-sided carbon coating, are studied. The microstructure of the composite material is found to consist of alternating relatively plastic layers of the solid solution of carbon in niobium and hardening niobium carbide layers. The room-temperature proportional limit of the developed composite material is threefold that of the composite material fabricated from coating-free niobium foils using the proposed technology. The proportional limit of the developed composite material and the stress corresponding to the maximum load at 1100°C are 500 and 560 MPa, respectively. The developed material is considered as an alternative to Ni-Al superalloys.

  19. Quench-age method for the fabrication of niobium-aluminum superconductors

    DOEpatents

    Pickus, Milton R.; Ciardella, Robert L.

    1978-01-01

    A flexible Nb.sub.3 Al superconducting wire is fabricated from a niobium-aluminum composite wire by heating to form a solid solution which is retained at room temperature as a metastable solid solution by quenching. The metastable solid solution is then transformed to the stable superconducting A-15 phase by low temperature aging. The transformation induced by aging can be controlled to yield either a multifilamentary or a solid A-15 core surrounded by ductile niobium.

  20. Morphology and structure of Ti-doped diamond films prepared by microwave plasma chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Liu, Xuejie; Lu, Pengfei; Wang, Hongchao; Ren, Yuan; Tan, Xin; Sun, Shiyang; Jia, Huiling

    2018-06-01

    Ti-doped diamond films were deposited through a microwave plasma chemical vapor deposition (MPCVD) system for the first time. The effects of the addition of Ti on the morphology, microstructure and quality of diamond films were systematically investigated. Secondary ion mass spectrometry results show that Ti can be added to diamond films through the MPCVD system using tetra n-butyl titanate as precursor. The spectra from X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy and the images from scanning electron microscopy of the deposited films indicate that the diamond phase clearly exists and dominates in Ti-doped diamond films. The amount of Ti added obviously influences film morphology and the preferred orientation of the crystals. Ti doping is beneficial to the second nucleation and the growth of the (1 1 0) faceted grains.