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Sample records for cerium tellurides

  1. Mercury Telluride and Cadmium Telluride

    NASA Technical Reports Server (NTRS)

    2004-01-01

    A semiconductor's usefulness is determined by how atoms are ordered within the crystal's underlying three-dimensional structure. While this mercury telluride and cadmium telluride alloy sample mixes completely in Earth -based laboratories, convective flows prevent them from mixing uniformly.

  2. Mercury Telluride and Cadmium Telluride

    NASA Technical Reports Server (NTRS)

    2004-01-01

    A semiconductor's usefulness is determined by how atoms are ordered within the crystal's underlying three-dimensional structure. While this mercury telluride and cadmium telluride alloy sample mixes completely in Earth -based laboratories, convective flows prevent them from mixing uniformly. In space, the ingredients mix more homogenously, resulting in a superior product.

  3. Cerium Oxide and Cerium Compounds

    Integrated Risk Information System (IRIS)

    EPA / 635 / R - 08 / 002F www.epa.gov / iris TOXICOLOGICAL REVIEW OF Cerium Oxide and Cerium Compounds ( CAS No . 1306 - 38 - 3 ) In Support of Summary Information on the Integrated Risk Information System ( IRIS ) September 2009 U.S . Environmental Protection Agency Washington , DC ii DISCLAIMER Th

  4. PLUTONIUM-CERIUM ALLOY

    DOEpatents

    Coffinberry, A.S.

    1959-01-01

    An alloy is presented for use as a reactor fuel. The binary alloy consists essentially of from about 5 to 90 atomic per cent cerium and the balance being plutonium. A complete phase diagram for the cerium--plutonium system is given.

  5. Cadmium telluride photovoltaic radiation detector

    DOEpatents

    Agouridis, D.C.; Fox, R.J.

    A dosimetry-type radiation detector is provided which employs a polycrystalline, chlorine-compensated cadmium telluride wafer fabricated to operate as a photovoltaic current generator used as the basic detecting element. A photovoltaic junction is formed in the wafer by painting one face of the cadmium telluride wafer with an n-type semi-conductive material. The opposite face of the wafer is painted with an electrically conductive material to serve as a current collector. The detector is mounted in a hermetically sealed vacuum containment. The detector is operated in a photovoltaic mode (zero bias) while DC coupled to a symmetrical differential current amplifier having a very low input impedance. The amplifier converts the current signal generated by radiation impinging upon the barrier surface face of the wafer to a voltage which is supplied to a voltmeter calibrated to read quantitatively the level of radiation incident upon the detecting wafer.

  6. Cadmium telluride photovoltaic radiation detector

    DOEpatents

    Agouridis, Dimitrios C.; Fox, Richard J.

    1981-01-01

    A dosimetry-type radiation detector is provided which employs a polycrystalline, chlorine-compensated cadmium telluride wafer fabricated to operate as a photovoltaic current generator used as the basic detecting element. A photovoltaic junction is formed in the wafer by painting one face of the cadmium telluride wafer with an n-type semiconductive material. The opposite face of the wafer is painted with an electrically conductive material to serve as a current collector. The detector is mounted in a hermetically sealed vacuum containment. The detector is operated in a photovoltaic mode (zero bias) while DC coupled to a symmetrical differential current amplifier having a very low input impedance. The amplifier converts the current signal generated by radiation impinging upon the barrier surface face of the wafer to a voltage which is supplied to a voltmeter calibrated to read quantitatively the level of radiation incident upon the detecting wafer.

  7. Phonon dynamics of americium telluride

    NASA Astrophysics Data System (ADS)

    Arya, B. S.; Aynyas, Mahendra; Ahirwar, Ashok K.; Sanyal, S. P.

    2013-06-01

    We report for the first time the complete phonon dispersion curves for Americium telluride (AmTe) using a breathing shell models (BSM) to establish their predominant ionic nature. The results obtained in the present study show the general features of the phonon spectrum. We could not compare our results with the experimental measurements as they are not available so far. We emphasize the need of neutron scattering measurements to compare our results. We also report, for the first time specific heat for this compound.

  8. Process for producing large grain cadmium telluride

    DOEpatents

    Hasoon, F.S.; Nelson, A.J.

    1996-01-16

    A process is described for producing a cadmium telluride polycrystalline film having grain sizes greater than about 20 {micro}m. The process comprises providing a substrate upon which cadmium telluride can be deposited and placing that substrate within a vacuum chamber containing a cadmium telluride effusion cell. A polycrystalline film is then deposited on the substrate through the steps of evacuating the vacuum chamber to a pressure of at least 10{sup {minus}6} torr.; heating the effusion cell to a temperature whereat the cell releases stoichiometric amounts of cadmium telluride usable as a molecular beam source for growth of grains on the substrate; heating the substrate to a temperature whereat a stoichiometric film of cadmium telluride can be deposited; and releasing cadmium telluride from the effusion cell for deposition as a film on the substrate. The substrate then is placed in a furnace having an inert gas atmosphere and heated for a sufficient period of time at an annealing temperature whereat cadmium telluride grains on the substrate grow to sizes greater than about 20 {micro}m.

  9. Process for producing large grain cadmium telluride

    DOEpatents

    Hasoon, Falah S.; Nelson, Art J.

    1996-01-01

    A process for producing a cadmium telluride polycrystalline film having grain sizes greater than about 20 .mu.m. The process comprises providing a substrate upon which cadmium telluride can be deposited and placing that substrate within a vacuum chamber containing a cadmium telluride effusion cell. A polycrystalline film is then deposited on the substrate through the steps of evacuating the vacuum chamber to a pressure of at least 10.sup.-6 torr.; heating the effusion cell to a temperature whereat the cell releases stoichiometric amounts of cadmium telluride usable as a molecular beam source for growth of grains on the substrate; heating the substrate to a temperature whereat a stoichiometric film of cadmium telluride can be deposited; and releasing cadmium telluride from the effusion cell for deposition as a film on the substrate. The substrate then is placed in a furnace having an inert gas atmosphere and heated for a sufficient period of time at an annealing temperature whereat cadmium telluride grains on the substrate grow to sizes greater than about 20 .mu.m.

  10. Thin film cadmium telluride, zinc telluride, and mercury zinc telluride solar cells

    SciTech Connect

    Chu, T.L. )

    1992-04-01

    This report describes research to demonstrate (1) thin film cadmium telluride solar cells with a quantum efficiency of 75% or higher at 0. 44 {mu}m and a photovoltaic efficiency of 11.5% or greater, and (2) thin film zinc telluride and mercury zinc telluride solar cells with a transparency to sub-band-gap radiation of 65% and a photovoltaic conversion efficiency of 5% and 8%, respectively. Work was directed at (1) depositing transparent conducting semiconductor films by solution growth and metal-organic chemical vapor deposition (MOCVD) technique, (2) depositing CdTe films by close-spaced sublimation (CSS) and MOCVD techniques, (3) preparing and evaluating thin film CdTe solar cells, and (4) preparing and characterizing thin film ZnTe, CD{sub 1-x}Zn{sub 1-x}Te, and Hg{sub 1-x}Zn{sub x}Te solar cells. The deposition of CdS films from aqueous solutions was investigated in detail, and their crystallographic, optical, and electrical properties were characterized. CdTe films were deposited from DMCd and DIPTe at 400{degrees}C using TEGa and AsH{sub 3} as dopants. CdTe films deposited by CSS had significantly better microstructures than those deposited by MOCVD. Deep energy states in CdTe films deposited by CSS and MOCVD were investigated. Thin films of ZnTe, Cd{sub 1- x}Zn{sub x}Te, and Hg{sub 1-x}Zn{sub x}Te were deposited by MOCVD, and their crystallographic, optical, and electrical properties were characterized. 67 refs.

  11. Research support for cadmium telluride crystal growth

    NASA Technical Reports Server (NTRS)

    Rosenberger, Franz; Banish, Michael

    1993-01-01

    Work performed during the period 11 Feb. 1992 to 10 Aug. 1993 on research support for cadmium telluride crystal growth is reported. Work on chemical impurity characterization and mass spectroscopy is described.

  12. Reaction of mercury telluride with lead

    SciTech Connect

    Tomashik, V.N.; Kurbanov, K.R.; Mizetskaya, I.B.; Vengel P.F.

    1986-07-01

    This paper studies the reaction of mercury telluride with lead by physicochemical methods of analysis. Differential thermal analysis was carried out on a microcalorimeter, with a battery of 64 thermocouples serving as the differential thermocouple unit. The microstructure of mechanically polished samples was studied on an MIM-7 metallograph. All the phases present show good contrast. It is shown that mercury telluride reacts with lead to form lead telluride and free mercury. The exchange reaction begins right after the lead melts but the lead telluride formed as an interlayer slows down the process. The interlayer is removed at 558 C by the eutectic melting at the HgTe/PbTe interface allowing complete chemical reaction of the components with a consequent large exothermic effect shown on the heating thermograms.

  13. Cerium compounds as scintillators

    SciTech Connect

    Wojtowicz, A.J.; Berman, E.; Koepke, C.; Lempicki, A.

    1991-01-01

    Stoichiometric Ce-materials with negligible Ce-Ce interactions should have superior scintillator properties. We present two materials: CeF{sub 3} and Ce{sub x}La{sub 1-x}P{sub 5}O{sub 14}. While cerium trifluoride is a known scintillator, pentaphosphate is of a limited usefulness, except as a remarkable model material. We show that quenching in fluoride is responsible for loss of 50% of the light output and is the cause of the, so-called, ultra fast component (2 ns). Light output of fluoride (about 50% of BGO) could be significantly improved. Deeper understanding of Ce-systems is needed to fully exploit their potentials. 10 figs., 6 refs.

  14. Cerium compounds as scintillators

    SciTech Connect

    Wojtowicz, A.J.; Berman, E.; Koepke, C.; Lempicki, A.

    1991-12-31

    Stoichiometric Ce-materials with negligible Ce-Ce interactions should have superior scintillator properties. We present two materials: CeF{sub 3} and Ce{sub x}La{sub 1-x}P{sub 5}O{sub 14}. While cerium trifluoride is a known scintillator, pentaphosphate is of a limited usefulness, except as a remarkable model material. We show that quenching in fluoride is responsible for loss of 50% of the light output and is the cause of the, so-called, ultra fast component (2 ns). Light output of fluoride (about 50% of BGO) could be significantly improved. Deeper understanding of Ce-systems is needed to fully exploit their potentials. 10 figs., 6 refs.

  15. Process for producing cadmium sulfide on a cadmium telluride surface

    DOEpatents

    Levi, Dean H.; Nelson, Art J.; Ahrenkiel, Richard K.

    1996-01-01

    A process for producing a layer of cadmium sulfide on a cadmium telluride surface to be employed in a photovoltaic device. The process comprises providing a cadmium telluride surface which is exposed to a hydrogen sulfide plasma at an exposure flow rate, an exposure time and an exposure temperature sufficient to permit reaction between the hydrogen sulfide and cadmium telluride to thereby form a cadmium sulfide layer on the cadmium telluride surface and accomplish passivation. In addition to passivation, a heterojunction at the interface of the cadmium sulfide and the cadmium telluride can be formed when the layer of cadmium sulfide formed on the cadmium telluride is of sufficient thickness.

  16. Preparation of cerium halide solvate complexes

    DOEpatents

    Vasudevan, Kalyan V; Smith, Nickolaus A; Gordon, John C; McKigney, Edward A; Muenchaussen, Ross E

    2013-08-06

    Crystals of a solvated cerium(III) halide solvate complex resulted from a process of forming a paste of a cerium(III) halide in an ionic liquid, adding a solvent to the paste, removing any undissolved solid, and then cooling the liquid phase. Diffusing a solvent vapor into the liquid phase also resulted in crystals of a solvated cerium(III) halide complex.

  17. PLUTONIUM-CERIUM-COBALT AND PLUTONIUM-CERIUM-NICKEL ALLOYS

    DOEpatents

    Coffinberry, A.S.

    1959-08-25

    >New plutonium-base teroary alloys useful as liquid reactor fuels are described. The alloys consist of 10 to 20 atomic percent cobalt with the remainder plutonium and cerium in any desired proportion, with the plutonium not in excess of 88 atomic percent; or, of from 10 to 25 atomic percent nickel (or mixture of nickel and cobalt) with the remainder plutonium and cerium in any desired proportion, with the plutonium not in excess of 86 atomic percent. The stated advantages of these alloys over unalloyed plutonium for reactor fuel use are a lower melting point and a wide range of permissible plutonium dilution.

  18. Cerium ion conducting solid electrolyte

    NASA Astrophysics Data System (ADS)

    Hasegawa, Yasunori; Imanaka, Nobuhito; Adachi, Gin-ya

    2003-02-01

    A cerium ion conducting solid electrolyte, (Ce xZr 1- x) 4/4- xNb(PO 4) 3, was successfully realized with the NASICON-type structure which possesses a three-dimensional network, especially suitable for bulky ion migration. The cerium ion conductivity exceeds approximately one order of magnitude in comparison to that of the rare-earth ion conducting R2(WO 4) 3 and R1/3Zr 2(PO 4) 3 ( R=Sc, Y, Eu-Lu) series and the value is in the range between typical oxide anion conductors of yttria stabilized zirconia (YSZ) and calcia stabilized zirconia (CSZ). Since cerium ion has been demonstrated to be another migrating ion species in solid electrolyte field, a promising application for various functional materials is greatly expected.

  19. Floating zone melting of cadmium telluride

    NASA Technical Reports Server (NTRS)

    Chang, Wen-Ming; Regel, L. L.; Wilcox, W. R.

    1992-01-01

    To produce superior crystals of cadmium telluride, floating zone melting in space has been proposed. Techniques required for floating zone melting of cadmium telluride are being developed. We have successfully float-zoned cadmium telluride on earth using square rods. A resistance heater was constructed for forming the molten zone. Evaporation of the molten zone was controlled by adding excess cadmium to the growth ampoule combined with heating of the entire ampoule. An effective method to hold the feed rod was developed. Slow rotation of the growth ampoule was proven experimentally to be necessary to achieve a complete symmetric molten zone. Most of the resultant cylindrical rods were single crystals with twins. Still needed is a suitable automatic method to control the zone length. We tried a fiber optical technique to control the zone length, but experiments showed that application of this technique to automate zone length control is unlikely to be successful.

  20. Electrodeposition and Characterization of Bismuth Telluride Nanowires

    NASA Astrophysics Data System (ADS)

    Frantz, C.; Stein, N.; Gravier, L.; Granville, S.; Boulanger, C.

    2010-09-01

    In this work, we report thermoelectric measurements on electroplated bismuth telluride nanowires. Porous polycarbonate membranes, obtained by ion-track irradiation lithography, were chosen as electroplating templates. Bismuth telluride nanowires were achieved in acidic media under potentiostatic conditions at -100 mV versus saturated silver chloride electrode. The filling ratio of the pores was increased to 80% by adding dimethyl sulfoxide to the electrolyte. Whatever the experimental conditions, the nanowires were polycrystalline in the rhombohedral phase of Bi2Te3. Finally, the power output of arrays of bismuth telluride nanowires was analyzed as a function of load resistance. The results were strongly dependent on the internal resistance, which can be significantly reduced by the presence of dimethyl sulfoxide during electroplating.

  1. Cancer diagnosis using a conventional x-ray fluorescence camera with a cadmium-telluride detector

    NASA Astrophysics Data System (ADS)

    Sato, Eiichi; Enomoto, Toshiyuki; Hagiwara, Osahiko; Abudurexiti, Abulajiang; Sato, Koetsu; Sato, Shigehiro; Ogawa, Akira; Onagawa, Jun

    2011-10-01

    X-ray fluorescence (XRF) analysis is useful for mapping various atoms in objects. Bremsstrahlung X-rays are selected using a 3.0 mm-thick aluminum filter, and these rays are absorbed by indium, cerium and gadolinium atoms in objects. Then XRF is produced from the objects, and photons are detected by a cadmium-telluride detector. The Kα photons are discriminated using a multichannel analyzer, and the number of photons is counted by a counter card. The objects are moved and scanned by an x-y stage in conjunction with a two-stage controller, and X-ray images obtained by atomic mapping are shown on a personal computer monitor. The scan steps of the x and y axes were both 2.5 mm, and the photon-counting time per mapping point was 0.5 s. We carried out atomic mapping using the X-ray camera, and Kα photons from cerium and gadolinium atoms were produced from cancerous regions in nude mice.

  2. PLUTONIUM-CERIUM-COPPER ALLOYS

    DOEpatents

    Coffinberry, A.S.

    1959-05-12

    A low melting point plutonium alloy useful as fuel is a homogeneous liquid metal fueled nuclear reactor is described. Vessels of tungsten or tantalum are useful to contain the alloy which consists essentially of from 10 to 30 atomic per cent copper and the balance plutonium and cerium. with the plutontum not in excess of 50 atomic per cent.

  3. IRIS Toxicological Review of Cerium Oxide and Cerium Compounds (External Review Draft)

    EPA Science Inventory

    EPA conducted a peer review of the scientific basis supporting the human health hazard and dose-response assessment of cerium oxide and cerium compounds that will appear on the Integrated Risk Information System (IRIS) database.

  4. Nanoparticle cerium oxide and mixed cerium oxides for improved fuel cell lifetime

    NASA Astrophysics Data System (ADS)

    Stewart, Stephen Michael

    While there is a rich body of literature concerning of properties of bulk cerium oxide and cerium cations in solution, the discussion has been inappropriately applied to nanoscale cerium oxide resulting in many unexpected or unexplained results. In particular, there is very limited understanding about the properties of cerium oxide and its potential use as a radical scavenger, and how the catalytic properties of cerium oxide change as the particle size approaches the nanoscale. For example, the involvement of Ce+4 and Ce+3 cations in reactions such as hydrogen peroxide decomposition have been investigated for both cerium cations and bulk cerium oxide. However, while both are assumed to decompose hydrogen peroxide through the same mechanism, whereby Ce+4 is involved in peroxide decomposition while Ce +3 is involved in radical scavenging, there has been very little done to address how the selectivity and activity of these reactions are affected by changing the majority cation population, as cerium cations in solution are predominantly in the +3 oxidation state while cerium cations are predominantly in the +4 oxidation state in cerium oxide. This matter is further complicated in cerium oxide nanoparticles where the surface concentration of Ce +3 cations is increased due to particle curvature effects. Due to the potential of controlling the surface cerium oxidation state using particle size and using this control to change the catalytic properties, this project investigated the effect of particle size and composition and the activity and selectivity of cerium oxide nanoparticles, and has served to expand the understanding of the properties of pure and mixed nanoparticle cerium oxide. This work explains the metric developed for measuring the catalytic properties of pure and mixed cerium oxide nanoparticles, which is also good at predicting the immediate and long-term behavior of nanoparticles in hydrogen fuel cells. This work also directly demonstrates praseodymium

  5. Grain Growth in Cerium Metal

    NASA Astrophysics Data System (ADS)

    Cooley, Jason; Katz, Martha; Mielke, Charles; Montalvo, Joel

    We report on grain growth in forged and rolled cerium plate for temperatures from 350 to 700 degrees C and times from 30 to 120 minutes. The cerium was made by arc-melting into a 25 mm deep by 80 mm diameter copper mold. The resulting disk was forged at room temperature to a 25% reduction of thickness four times with a 350 degree C strain relief heat treatment for 60 minutes between forging steps. The resulting 8 mm thick plate was clock rolled at room temperature to a 25% reduction of thickness three times with a 350 C strain relief heat treatment between steps resulting in a plate approximately 3 mm thick. 5 x 10 mm coupons were cut from the plate for the grain growth study.

  6. Process for producing cadmium sulfide on a cadmium telluride surface

    DOEpatents

    Levi, D.H.; Nelson, A.J.; Ahrenkiel, R.K.

    1996-07-30

    A process is described for producing a layer of cadmium sulfide on a cadmium telluride surface to be employed in a photovoltaic device. The process comprises providing a cadmium telluride surface which is exposed to a hydrogen sulfide plasma at an exposure flow rate, an exposure time and an exposure temperature sufficient to permit reaction between the hydrogen sulfide and cadmium telluride to thereby form a cadmium sulfide layer on the cadmium telluride surface and accomplish passivation. In addition to passivation, a heterojunction at the interface of the cadmium sulfide and the cadmium telluride can be formed when the layer of cadmium sulfide formed on the cadmium telluride is of sufficient thickness. 12 figs.

  7. Investigation of copper telluride nanowires synthesized by electrochemical method

    NASA Astrophysics Data System (ADS)

    Kumar, Suresh; Kundu, Virender; Vohra, Anil; Chakarvarti, S. K.

    2011-07-01

    In the present study the copper telluride (Cu2Te) nanostructures of 100 nm diameter have been fabricated using electro deposition method from an aqueous solution on copper (Cu) and indium tin oxide (ITO) substrates. The synthesized nanostructures are characterized by scanning electron microscope and X-ray diffraction. The XRD analysis confirmed the formation of nanowires of copper telluride. The photoluminescence emission spectrum was obtained at 457.56 nm for 100 nm copper telluride nanowires.

  8. Growth of lead tin telluride crystals in gels

    NASA Technical Reports Server (NTRS)

    Barber, Patrick G.

    1986-01-01

    Improved gels and several geometries were investigated for use in growing crystals. The use of lead sulfide test crystals proved workable, but it was impossible to obtain and maintain a sufficiently concentrated telluride ion solution to successfully grow lead telluride crystals. It appears that oxygen in the solution is capable of oxidizing the telluride ion up to tellurium metal. The method may still be successful, but only if precautions are taken to eliminate dissolved oxygen from the gels and aqueous solutions and to maintain a suitable concentration of telluride, Te(2)-(aq.).

  9. Electron mobility in mercury cadmium telluride

    NASA Technical Reports Server (NTRS)

    Patterson, James D.

    1988-01-01

    A previously developed program, which includes all electronic interactions thought to be important, does not correctly predict the value of electron mobility in mercury cadmium telluride particularly near room temperature. Part of the reason for this discrepancy is thought to be the way screening is handled. It seems likely that there are a number of contributors to errors in the calculation. The objective is to survey the calculation, locate reasons for differences between experiment and calculation, and suggest improvements.

  10. ADSORPTION OF CERIUM VALUES FROM AQUEOUS SOLUTIONS

    DOEpatents

    Roberts, F.P.

    1963-08-13

    Cerium can be removed from aqueous nitric acid (2 to 13 M) solutions by passing the latter over a PbO/sub 2/-containing anion exchange resin. The cerium is taken up by the resin, while any lanthanides, yttrium, and strontium present remain in the solution. (AEC)

  11. Formulation and method for preparing gels comprising hydrous cerium oxide

    DOEpatents

    Collins, Jack L; Chi, Anthony

    2013-05-07

    Formulations useful for preparing hydrous cerium oxide gels contain a metal salt including cerium, an organic base, and a complexing agent. Methods for preparing gels containing hydrous cerium oxide include heating a formulation to a temperature sufficient to induce gel formation, where the formulation contains a metal salt including cerium, an organic base, and a complexing agent.

  12. Virus removal by biogenic cerium.

    PubMed

    De Gusseme, Bart; Du Laing, Gijs; Hennebel, Tom; Renard, Piet; Chidambaram, Dev; Fitts, Jeffrey P; Bruneel, Els; Van Driessche, Isabel; Verbeken, Kim; Boon, Nico; Verstraete, Willy

    2010-08-15

    The rare earth element cerium has been known to exert antifungal and antibacterial properties in the oxidation states +III and +IV. This study reports on an innovative strategy for virus removal in drinking water by the combination of Ce(III) on a bacterial carrier matrix. The biogenic cerium (bio-Ce) was produced by addition of aqueous Ce(III) to actively growing cultures of either freshwater manganese-oxidizing bacteria (MOB) Leptothrix discophora or Pseudomonas putida MnB29. X-ray absorption spectroscopy results indicated that Ce remained in its trivalent state on the bacterial surface. The spectra were consistent with Ce(III) ions associated with the phosphoryl groups of the bacterial cell wall. In disinfection assays using a bacteriophage as model, it was demonstrated that bio-Ce exhibited antiviral properties. A 4.4 log decrease of the phage was observed after 2 h of contact with 50 mg L(-1) bio-Ce. Given the fact that virus removal with 50 mg L(-1) Ce(III) as CeNO(3) was lower, the presence of the bacterial carrier matrix in bio-Ce significantly enhanced virus removal. PMID:20704235

  13. Virus Removal by Biogenic Cerium

    SciTech Connect

    De Gusseme, B.; Du Laing, G; Hennebel, T; Renard, P; Chidambaram, D; Fitts, J; Bruneel, E; Van Driessche, I; Verbeken, K; et. al.

    2010-01-01

    The rare earth element cerium has been known to exert antifungal and antibacterial properties in the oxidation states +III and +IV. This study reports on an innovative strategy for virus removal in drinking water by the combination of Ce(III) on a bacterial carrier matrix. The biogenic cerium (bio-Ce) was produced by addition of aqueous Ce(III) to actively growing cultures of either freshwater manganese-oxidizing bacteria (MOB) Leptothrix discophora or Pseudomonas putida MnB29. X-ray absorption spectroscopy results indicated that Ce remained in its trivalent state on the bacterial surface. The spectra were consistent with Ce(III) ions associated with the phosphoryl groups of the bacterial cell wall. In disinfection assays using a bacteriophage as model, it was demonstrated that bio-Ce exhibited antiviral properties. A 4.4 log decrease of the phage was observed after 2 h of contact with 50 mg L{sup -1} bio-Ce. Given the fact that virus removal with 50 mg L{sup -1} Ce(III) as CeNO{sub 3} was lower, the presence of the bacterial carrier matrix in bio-Ce significantly enhanced virus removal.

  14. Electron irradiation of N type cadmium telluride

    NASA Astrophysics Data System (ADS)

    Bauer, C. P., Jr.

    1985-03-01

    An experiment is described in which 30 MeV electrons were used to irradiate a sample of cadmium telluride. A brief history of irradiation studies of cadmium telluride is given, followed by the description of the construction of a laboratory used in the taking of Hall measurements and resistivity versus temperature data. The irradiation was performed at the Naval Postgraduate School linear accelerator facility and damage was observed in the CdTe sample at doses above 10 to the 13th power electrons/sq cm. The sample was held at 100 K for the irradiation. Three results were noted from the Hall and resistivity data. First, the resistivity increased by a factor of two at radiation doses of 10 to the 15th power electrons/sq cm. Secondly, there was a 10% lowering of the electron mobility at 77 K. Finally, possible annealing was seen at 160 K for the 10 to the 13th power electrons/sq cm dose resistivity versus temperature graph. Photoluminescence measurements confirmed the existence of damage by an increase of a broad maximum associated with defects.

  15. Pharmacological potential of cerium oxidenanoparticles

    NASA Astrophysics Data System (ADS)

    Celardo, Ivana; Pedersen, Jens Z.; Traversa, Enrico; Ghibelli, Lina

    2011-04-01

    Nanotechnology promises a revolution in pharmacology to improve or create ex novo therapies. Cerium oxidenanoparticles (nanoceria), well-known as catalysts, possess an astonishing pharmacological potential due to their antioxidant properties, deriving from a fraction of Ce3+ ions present in CeO2. These defects, compensated by oxygen vacancies, are enriched at the surface and therefore in nanosized particles. Reactions involving redox cycles between the Ce3+ and Ce4+oxidation states allow nanoceria to react catalytically with superoxide and hydrogen peroxide, mimicking the behavior of two key antioxidant enzymes, superoxide dismutase and catalase, potentially abating all noxious intracellularreactive oxygen species (ROS) via a self-regenerating mechanism. Hence nanoceria, apparently well tolerated by the organism, might fight chronic inflammation and the pathologies associated with oxidative stress, which include cancer and neurodegeneration. Here we review the biological effects of nanoceria as they emerge from in vitro and in vivo studies, considering biocompatibility and the peculiar antioxidant mechanisms.

  16. The single molecular precursor approach to metal telluride thin films: imino-bis(diisopropylphosphine tellurides) as examples.

    PubMed

    Ritch, Jamie S; Chivers, Tristram; Afzaal, Mohammad; O'Brien, Paul

    2007-10-01

    Interest in metal telluride thin films as components in electronic devices has grown recently. This tutorial review describes the use of single-source precursors for the preparation of metal telluride materials by aerosol-assisted chemical vapour deposition (AACVD) and acquaints the reader with the basic techniques of materials characterization. The challenges in the design and synthesis of suitable precursors are discussed, focusing on metal complexes of the recently-developed imino-bis(diisopropylphosphine telluride) ligand. The generation of thin films and nanoplates of CdTe, Sb(2)Te(3) and In(2)Te(3) from these precursors are used as illustrative examples. PMID:17721586

  17. Polycrystalline Thin-Film Research: Cadmium Telluride (Fact Sheet)

    SciTech Connect

    Not Available

    2013-06-01

    This National Center for Photovoltaics sheet describes the capabilities of its polycrystalline thin-film research in the area of cadmium telluride. The scope and core competencies and capabilities are discussed.

  18. Polycrystalline Thin-Film Research: Cadmium Telluride (Fact Sheet)

    SciTech Connect

    Not Available

    2011-06-01

    Capabilities fact sheet that includes scope, core competencies and capabilities, and contact/web information for Polycrystalline Thin-Film Research: Cadmium Telluride at the National Center for Photovoltaics.

  19. A new occurrence of telluride minerals in South Carolina.

    USGS Publications Warehouse

    Bell, H.; Larson, R.R.

    1984-01-01

    A study of drill cores from the Haile gold mine, Lancaster County, South Carolina, has revealed grains containing large amounts of Te with various combinations of Pb, Ag and Au in pyrite. These telluride minerals have so far not been identified. The nearby Brewer mine, on the basis of chemical evidence, also contains tellurides. The probable telluride localities in South Carolina are now expanded to three, significantly increasing the few reports of Te minerals from the Au deposits of the southeastern Piedmont, many of which are now considered to be volcanogenic. The occurrence of telluride minerals in gold ore from the Haile-Brewer area may help to explain the divergence in Au/Ag ratios reported in chemical analyses of drill core, ore samples and production records. Te, in addition, may be useful in geochemical exploration programmes in the SE Piedmont, including programmes using heavy mineral concentrates derived from stream alluvium. -R.S.M.

  20. Cerium anomaly at microscale in fossils.

    PubMed

    Gueriau, Pierre; Mocuta, Cristian; Bertrand, Loïc

    2015-09-01

    Patterns in rare earth element (REE) concentrations are essential instruments to assess geochemical processes in Earth and environmental sciences. Excursions in the "cerium anomaly" are widely used to inform on past redox conditions in sediments. This proxy resources to the specificity of cerium to adopt both the +III and +IV oxidation states, while most rare earths are purely trivalent and share very similar reactivity and transport properties. In practical terms, the level of cerium anomaly is established through elemental point quantification and profiling. All these models rely on a supposed homogeneity of the cerium oxidation state within the samples. However, this has never been demonstrated, whereas the cerium concentration can significantly vary within a sample, as shown for fossils, which would vastly complicate interpretation of REE patterns. Here, we report direct micrometric mapping of Ce speciation through synchrotron X-ray absorption spectroscopy and production of local rare earth patterns in paleontological fossil tissues through X-ray fluorescence mapping. The sensitivity of the approach is demonstrated on well-preserved fishes and crustaceans from the Late Cretaceous (ca. 95 million years (Myr) old). The presence of Ce under the +IV form within the fossil tissues is attributed to slightly oxidative local conditions of burial and agrees well with the limited negative cerium anomaly observed in REE patterns. The [Ce(IV)]/[Ce(tot)] ratio appears remarkably stable at the microscale within each fossil and is similar between fossils from the locality. Speciation maps were obtained from an original combination of synchrotron microbeam X-ray fluorescence, absorption spectroscopy, and diffraction, together with light and electron microscopy. This work also highlights the need for more systematic studies of cerium geochemistry at the microscale in paleontological contexts, in particular across fossil histologies.

  1. Cerium anomaly at microscale in fossils.

    PubMed

    Gueriau, Pierre; Mocuta, Cristian; Bertrand, Loïc

    2015-09-01

    Patterns in rare earth element (REE) concentrations are essential instruments to assess geochemical processes in Earth and environmental sciences. Excursions in the "cerium anomaly" are widely used to inform on past redox conditions in sediments. This proxy resources to the specificity of cerium to adopt both the +III and +IV oxidation states, while most rare earths are purely trivalent and share very similar reactivity and transport properties. In practical terms, the level of cerium anomaly is established through elemental point quantification and profiling. All these models rely on a supposed homogeneity of the cerium oxidation state within the samples. However, this has never been demonstrated, whereas the cerium concentration can significantly vary within a sample, as shown for fossils, which would vastly complicate interpretation of REE patterns. Here, we report direct micrometric mapping of Ce speciation through synchrotron X-ray absorption spectroscopy and production of local rare earth patterns in paleontological fossil tissues through X-ray fluorescence mapping. The sensitivity of the approach is demonstrated on well-preserved fishes and crustaceans from the Late Cretaceous (ca. 95 million years (Myr) old). The presence of Ce under the +IV form within the fossil tissues is attributed to slightly oxidative local conditions of burial and agrees well with the limited negative cerium anomaly observed in REE patterns. The [Ce(IV)]/[Ce(tot)] ratio appears remarkably stable at the microscale within each fossil and is similar between fossils from the locality. Speciation maps were obtained from an original combination of synchrotron microbeam X-ray fluorescence, absorption spectroscopy, and diffraction, together with light and electron microscopy. This work also highlights the need for more systematic studies of cerium geochemistry at the microscale in paleontological contexts, in particular across fossil histologies. PMID:26239283

  2. α-Radioactivity of cerium-142

    USGS Publications Warehouse

    Senftle, F.E.; Stern, T.W.; Alekna, V.P.

    1959-01-01

    JOHNSON AND NIER1 have measured the atomic masses of some of the rare-earth isotopes and have shown that the mass difference cerium-142—(barium-138 + helium-4) is equivalent to 1.68 ± 0.10 MeV. Similar results for the naturally occurring samarium and neodymium isotopes show that the α-active isotope of each element is the one having the largest possible decay energy. Rasmussen and others2 suggest that the two or three neutrons just beyond the closed shell of 82 neutrons have decreased binding energies and hence the α-energy has a maximum about 84 neutrons. Johnson and Nier suggest that the α-decay of cerium-142 may take place with enough energy to be experimentally observable. Porschen and Riezler3 examined a sample of un-enriched cerium ammonium citrate using nuclear track plates sensitive to α-particles. No α-activity was observed after a 30-day exposure of 1.2 mgm. of the cerium salt. In 1957 Riezler and Kauw4 reported an alpha activity for an enriched sample of cerium-142. From their results they calculated a half-life of 5.1 × 1015 years with an uncertainty factor of 2.

  3. Nanocrystalline cerium oxide materials for solid fuel cell systems

    SciTech Connect

    Brinkman, Kyle S

    2015-05-05

    Disclosed are solid fuel cells, including solid oxide fuel cells and PEM fuel cells that include nanocrystalline cerium oxide materials as a component of the fuel cells. A solid oxide fuel cell can include nanocrystalline cerium oxide as a cathode component and microcrystalline cerium oxide as an electrolyte component, which can prevent mechanical failure and interdiffusion common in other fuel cells. A solid oxide fuel cell can also include nanocrystalline cerium oxide in the anode. A PEM fuel cell can include cerium oxide as a catalyst support in the cathode and optionally also in the anode.

  4. Divalent fluoride doped cerium fluoride scintillator

    DOEpatents

    Anderson, David F.; Sparrow, Robert W.

    1991-01-01

    The use of divalent fluoride dopants in scintillator materials comprising cerium fluoride is disclosed. The preferred divalent fluoride dopants are calcium fluoride, strontium fluoride, and barium fluoride. The preferred amount of divalent fluoride dopant is less than about two percent by weight of the total scintillator. Cerium fluoride scintillator crystals grown with the addition of a divalent fluoride have exhibited better transmissions and higher light outputs than crystals grown without the addition of such dopants. These scintillators are useful in radiation detection and monitoring applications, and are particularly well suited for high-rate applications such as positron emission tomography (PET).

  5. Cerium migration during PEM fuel cell accelerated stress testing

    SciTech Connect

    Baker, Andrew M.; Mukundan, Rangachary; Borup, Rodney L.; Spernjak, Dusan; Judge, Elizabeth J.; Advani, Suresh G.; Prasad, Ajay K.

    2016-01-01

    Cerium is a radical scavenger which improves polymer electrolyte membrane (PEM) fuel cell durability. During operation, however, cerium rapidly migrates in the PEM and into the catalyst layers (CLs). In this work, membrane electrode assemblies (MEAs) were subjected to accelerated stress tests (ASTs) under different humidity conditions. Cerium migration was characterized in the MEAs after ASTs using X-ray fluorescence. During fully humidified operation, water flux from cell inlet to outlet generated in-plane cerium gradients. Conversely, cerium profiles were flat during low humidity operation, where in-plane water flux was negligible, however, migration from the PEM into the CLs was enhanced. Humidity cycling resulted in both in-plane cerium gradients due to water flux during the hydration component of the cycle, and significant migration into the CLs. Fluoride and cerium emissions into effluent cell waters were measured during ASTs and correlated, which signifies that ionomer degradation products serve as possible counter-ions for cerium emissions. Fluoride emission rates were also correlated to final PEM cerium contents, which indicates that PEM degradation and cerium migration are coupled. Lastly, it is proposed that cerium migrates from the PEM due to humidification conditions and degradation, and is subsequently stabilized in the CLs by carbon catalyst supports.

  6. Cerium migration during PEM fuel cell accelerated stress testing

    DOE PAGES

    Baker, Andrew M.; Mukundan, Rangachary; Borup, Rodney L.; Spernjak, Dusan; Judge, Elizabeth J.; Advani, Suresh G.; Prasad, Ajay K.

    2016-01-01

    Cerium is a radical scavenger which improves polymer electrolyte membrane (PEM) fuel cell durability. During operation, however, cerium rapidly migrates in the PEM and into the catalyst layers (CLs). In this work, membrane electrode assemblies (MEAs) were subjected to accelerated stress tests (ASTs) under different humidity conditions. Cerium migration was characterized in the MEAs after ASTs using X-ray fluorescence. During fully humidified operation, water flux from cell inlet to outlet generated in-plane cerium gradients. Conversely, cerium profiles were flat during low humidity operation, where in-plane water flux was negligible, however, migration from the PEM into the CLs was enhanced. Humiditymore » cycling resulted in both in-plane cerium gradients due to water flux during the hydration component of the cycle, and significant migration into the CLs. Fluoride and cerium emissions into effluent cell waters were measured during ASTs and correlated, which signifies that ionomer degradation products serve as possible counter-ions for cerium emissions. Fluoride emission rates were also correlated to final PEM cerium contents, which indicates that PEM degradation and cerium migration are coupled. Lastly, it is proposed that cerium migrates from the PEM due to humidification conditions and degradation, and is subsequently stabilized in the CLs by carbon catalyst supports.« less

  7. An investigation of the continuum resonance effect in cerium and cerium oxide

    NASA Astrophysics Data System (ADS)

    Roberts, Mark W.

    1998-10-01

    Large x-ray emission resonances associated with the M shell in cerium and cerium oxide were investigated. The device used in this investigation consisted of an energy dispersive x-ray detector and a double-pass cylindrical mirror electron analyzer within an ultra-high vacuum system. Observations were made of the x-ray and electron emissions from samples bombarded by mono-energetic electrons from an electron gun. The x-ray and electron data were recorded with the system pressure in the low 10-9 torr range. X-ray data were obtained using incident electron energies from 865 eV to 925 eV; the binding energies of the cerium M5 and M4 subshells and the x-ray continuum resonances are contained within this energy range. The x- ray detector was set to count x-rays in a fixed energy window 120 eV wide, centered on 900 eV. Differentiated electron spectra from the samples were recorded using a lock-in amplifier. Vacuum evaporation and condensation were used to deposit cerium metal samples onto a wheel which was then rotated to position a given sample in front of the electron gun. Cerium oxide samples were obtained by exposing cerium metal deposits to room air at atmospheric pressure and then repumping the system. The x-ray yield spectra from the cerium and cerium oxide samples show large resonances for incident electron energies near the M5 and M4 level ionization energies. There are no features in the electron spectra which correspond to the large resonances observed in the x-ray yield spectra. These findings are in agreement with results previously obtained by Chamberlain et al. and by Mason. The maxima in the x-ray resonances for cerium oxide occur at slightly lower incident electron energy than those for cerium metal. There is also a large increase in the intensity of the x-ray continuum resonance yield in cerium oxide above that in the metal. Possible explanations for these observations are presented.

  8. Substrate Configuration Cadmium Telluride Solar Cells

    NASA Astrophysics Data System (ADS)

    Matulionis, Ilvydas

    2002-03-01

    Cadmium telluride/cadmium sulfide substrate type thin-film solar cells were fabricated on 0.1 mm thick molybdenum and stainless steel substrates. The deposition method was radio frequency plasma sputtering in argon at pressures of 10 - 20 mTorr. The structure was: substrate/(ZnTe:N)/CdTe/CdS/TCO. The Transparent Conducting Oxide (TCO) was ITO or ZnO:Al. This is an inverted configuration compared to the conventional glass/TCO/CdS/CdTe/contact devices. Solar cells on Mo substrates exhibited up to 7.8(the highest value reported so far for this type of devices) and the cells on stainless steel or with ZnO:Al were about 3above 70shape at the red and blue edges of the spectrum show that there is less CdTe-CdS interdiffusion during the post-growth heat treatment compared to the conventional superstrate cells. This is attributed to the fully developed CdTe grains at the CdTe-CdS interface. Also, the current is limited at voltages above 0.8 V which indicates a back-diode effect at the metal-CdTe or CdS-TCO interface. Supported by the National Renewable Energy Laboratory.

  9. Ion beam sputter deposited zinc telluride films

    NASA Technical Reports Server (NTRS)

    Gulino, D. A.

    1985-01-01

    Zinc telluride is of interest as a potential electronic device material, particularly as one component in an amorphous superlattice, which is a new class of interesting and potentially useful materials. Some structural and electronic properties of ZnTe films deposited by argon ion beam sputter depoairion are described. Films (up to 3000 angstroms thick) were deposited from a ZnTe target. A beam energy of 1000 eV and a current density of 4 mA/sq. cm. resulted in deposition rates of approximately 70 angstroms/min. The optical band gap was found to be approximately 1.1 eV, indicating an amorphous structure, as compared to a literature value of 2.26 eV for crystalline material. Intrinsic stress measurements showed a thickness dependence, varying from tensile for thicknesses below 850 angstroms to compressive for larger thicknesses. Room temperature conductivity measurement also showed a thickness dependence, with values ranging from 1.86 x to to the -6/ohm. cm. for 300 angstrom film to 2.56 x 10 to the -1/ohm. cm. for a 2600 angstrom film. Measurement of the temperature dependence of the conductivity for these films showed complicated behavior which was thickness dependent. Thinner films showed at least two distinct temperature dependent conductivity mechanisms, as described by a Mott-type model. Thicker films showed only one principal conductivity mechanism, similar to what might be expected for a material with more crystalline character.

  10. Ion beam sputter deposited zinc telluride films

    NASA Technical Reports Server (NTRS)

    Gulino, D. A.

    1986-01-01

    Zinc telluride is of interest as a potential electronic device material, particularly as one component in an amorphous superlattice, which is a new class of interesting and potentially useful materials. Some structural and electronic properties of ZnTe films deposited by argon ion beam sputter deposition are described. Films (up to 3000 angstroms thick) were deposited from a ZnTe target. A beam energy of 1000 eV and a current density of 4 mA/sq cm resulted in deposition rates of approximately 70 angstroms/min. The optical band gap was found to be approximately 1.1 eV, indicating an amorphous structure, as compared to a literature value of 2.26 eV for crystalline material. Intrinsic stress measurements showed a thickness dependence, varying from tensile for thicknesses below 850 angstroms to compressive for larger thicknesses. Room temperature conductivity measurement also showed a thickness dependence, with values ranging from 1.86 x 10 to the -6th/ohm cm for 300 angstrom film to 2.56 x 10 to the -1/ohm cm for a 2600 angstrom film. Measurement of the temperature dependence of the conductivity for these films showed complicated behavior which was thickness dependent. Thinner films showed at least two distinct temperature dependent conductivity mechanisms, as described by a Mott-type model. Thicker films showed only one principal conductivity mechanism, similar to what might be expected for a material with more crystalline character.

  11. Synthesis and evaluation of lead telluride/bismuth antimony telluride nanocomposites for thermoelectric applications

    NASA Astrophysics Data System (ADS)

    Ganguly, Shreyashi; Zhou, Chen; Morelli, Donald; Sakamoto, Jeffrey; Uher, Ctirad; Brock, Stephanie L.

    2011-12-01

    Heterogeneous nanocomposites of p-type bismuth antimony telluride (Bi 2- xSb xTe 3) with lead telluride (PbTe) nanoinclusions have been prepared by an incipient wetness impregnation approach. The Seebeck coefficient, electrical resistivity, thermal conductivity and Hall coefficient were measured from 80 to 380 K in order to investigate the influence of PbTe nanoparticles on the thermoelectric performance of nanocomposites. The Seebeck coefficients and electrical resistivities of nanocomposites decrease with increasing PbTe nanoparticle concentration due to an increased hole concentration. The lattice thermal conductivity decreases with the addition of PbTe nanoparticles but the total thermal conductivity increases due to the increased electronic thermal conductivity. We conclude that the presence of nanosized PbTe in the bulk Bi 2- xSb xTe 3 matrix results in a collateral doping effect, which dominates transport properties. This study underscores the need for immiscible systems to achieve the decreased thermal transport properties possible from nanostructuring without compromising the electronic properties.

  12. Uptake and accumulation of bulk and nanosized cerium oxide particles and ionic cerium by radish (Raphanus sativus L.).

    PubMed

    Zhang, Weilan; Ebbs, Stephen D; Musante, Craig; White, Jason C; Gao, Cunmei; Ma, Xingmao

    2015-01-21

    The potential toxicity and accumulation of engineered nanomaterials (ENMs) in agricultural crops has become an area of great concern and intense investigation. Interestingly, although below-ground vegetables are most likely to accumulate the highest concentrations of ENMs, little work has been done investigating the potential uptake and accumulation of ENMs for this plant group. The overall objective of this study was to evaluate how different forms of cerium (bulk cerium oxide, cerium oxide nanoparticles, and the cerium ion) affected the growth of radish (Raphanus sativus L.) and accumulation of cerium in radish tissues. Ionic cerium (Ce(3+)) had a negative effect on radish growth at 10 mg CeCl3/L, whereas bulk cerium oxide (CeO2) enhanced plant biomass at the same concentration. Treatment with 10 mg/L cerium oxide nanoparticles (CeO2 NPs) had no significant effect on radish growth. Exposure to all forms of cerium resulted in the accumulation of this element in radish tissues, including the edible storage root. However, the accumulation patterns and their effect on plant growth and physiological processes varied with the characteristics of cerium. This study provides a critical frame of reference on the effects of CeO2 NPs versus their bulk and ionic counterparts on radish growth.

  13. Synthesis and evaluation of lead telluride/bismuth antimony telluride nanocomposites for thermoelectric applications

    SciTech Connect

    Ganguly, Shreyashi; Zhou Chen; Morelli, Donald; Sakamoto, Jeffrey; Uher, Ctirad; Brock, Stephanie L.

    2011-12-15

    Heterogeneous nanocomposites of p-type bismuth antimony telluride (Bi{sub 2-x}Sb{sub x}Te{sub 3}) with lead telluride (PbTe) nanoinclusions have been prepared by an incipient wetness impregnation approach. The Seebeck coefficient, electrical resistivity, thermal conductivity and Hall coefficient were measured from 80 to 380 K in order to investigate the influence of PbTe nanoparticles on the thermoelectric performance of nanocomposites. The Seebeck coefficients and electrical resistivities of nanocomposites decrease with increasing PbTe nanoparticle concentration due to an increased hole concentration. The lattice thermal conductivity decreases with the addition of PbTe nanoparticles but the total thermal conductivity increases due to the increased electronic thermal conductivity. We conclude that the presence of nanosized PbTe in the bulk Bi{sub 2-x}Sb{sub x}Te{sub 3} matrix results in a collateral doping effect, which dominates transport properties. This study underscores the need for immiscible systems to achieve the decreased thermal transport properties possible from nanostructuring without compromising the electronic properties. - Graphical abstract: PbTe nanoparticles introduced into p-type Bi{sub 2}Te{sub 3} by incipient wetness results in decreased lattice thermal conductivity, but also acts as an electronic dopant, resulting in an overall decrease in thermoelectric performance. Highlights: Black-Right-Pointing-Pointer Composites of PbTe nanoparticles in Bi{sub 2-x}Sb{sub x}Te{sub 3} were formed by incipient wetness. Black-Right-Pointing-Pointer PbTe nanoparticles leads to decreased {kappa}{sub l}, consistent with phonon scattering. Black-Right-Pointing-Pointer PbTe nanoparticles lead to decreased S and {rho}, due to increased carriers. Black-Right-Pointing-Pointer Collateral doping from PbTe leads to decreased ZT with increasing concentration. Black-Right-Pointing-Pointer Immiscible systems are preferred for improved ZT.

  14. Ultrasonication of Bismuth Telluride Nanocrystals Fabricated by Solvothermal Method

    NASA Technical Reports Server (NTRS)

    Chu, Sang-Hyon; Choi, Sang H.; Kim, Jae-Woo; King, Glen C.; Elliott, James R.

    2006-01-01

    The objective of this study is to evaluate the effect of ultrasonication on bismuth telluride nanocrystals prepared by solvothermal method. In this study, a low dimensional nanocrystal of bismuth telluride (Bi2Te3) was synthesized by a solvothermal process in an autoclave at 180 C and 200 psi. During the solvothermal reaction, organic surfactants effectively prevented unwanted aggregation of nanocrystals in a selected solvent while controlling the shape of the nanocrystal. The atomic ratio of bismuth and tellurium was determined by energy dispersive spectroscopy (EDS). The cavitational energy created by the ultrasonic probe was varied by the ultrasonication process time, while power amplitude remained constant. The nanocrystal size and its size distribution were measured by field emission scanning electron microscopy (FESEM) and a dynamic light scattering system. When the ultrasonication time increased, the average size of bismuth telluride nanocrystal gradually increased due to the direct collision of nanocrystals. The polydispersity of the nanocrystals showed a minimum when the ultrasonication was applied for 5 min. Keywords: bismuth telluride, nanocrystal, low-dimensional, ultrasonication, solvothermal

  15. VIEW, LOOKING SOUTHEAST, OF TELLURIDE IRON WORKS RETORT USED FOR ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    VIEW, LOOKING SOUTHEAST, OF TELLURIDE IRON WORKS RETORT USED FOR FLASHING MERCURY OFF OF GOLD TO CREATE SOFT INGOTS CALLED "SPONGES." AT RIGHT ARE SAFES FOR STORING 22-POUND SPONGES WORTH OVER $60,000 EACH, CA. 1985. - Shenandoah-Dives Mill, 135 County Road 2, Silverton, San Juan County, CO

  16. Synthesis of Cerium-Doped Titania Nanoparticles and Nanotubes.

    PubMed

    Cao, Wei; Suzuki, Takuya; Elsayed-Ali, Hani E; Abdel-Fattah, Tarek M

    2015-03-01

    Cerium-doped titania nanoparticles and nanotubes were synthesized via hydrothermal processes. X-Ray Diffraction revealed that cerium-doped titania nanoparticles have an anatase crystal structure, while cerium-doped titania nanotubes have an H2Ti3O7-type structure. Scanning electron microscopy and high resolution transmission electron microscopy showed that both types of titania are well crystallized with relatively uniform size distribution. The photocatalytic degradation of methylthioninium chloride known as methylene blue dye was tested and both cerium-doped titania nanoparticles and nanotubes. The preliminary photocatalytic degradation of Methylene Blue data showed significantly improved visible light photocatalytic activities as compared to commercial titania powders.

  17. Antimony promoted bismuth cerium molybdate catalysts

    SciTech Connect

    Brazdil, J.F.; Glaeser, L.C.; Grasselli, R.K.

    1990-05-01

    This patent describes an improvement in antimony-promoted bismuth cerium molybdate whereby the tendency of the catalyst to lose efectiveness over time is significantly reduced. This patent describes new catalysts which are also useful in other oxidation-type reactions such as the oxidation of acrolein and methacrolein to produce the corresponding unsaturated aldehydes and acids and the oxydehydrogenation of various olefins such as isoamylenes to produce the corresponding diolefins such as isoprene.

  18. Atomic Transition Probabilities for Neutral Cerium

    NASA Astrophysics Data System (ADS)

    Lawler, J. E.; den Hartog, E. A.; Wood, M. P.; Nitz, D. E.; Chisholm, J.; Sobeck, J.

    2009-10-01

    The spectra of neutral cerium (Ce I) and singly ionized cerium (Ce II) are more complex than spectra of other rare earth species. The resulting high density of lines in the visible makes Ce ideal for use in metal halide (MH) High Intensity Discharge (HID) lamps. Inclusion of cerium-iodide in a lamp dose can improve both the Color Rendering Index and luminous efficacy of a MH-HID lamp. Basic spectroscopic data including absolute atomic transition probabilities for Ce I and Ce II are needed for diagnosing and modeling these MH-HID lamps. Recent work on Ce II [1] is now being augmented with similar work on Ce I. Radiative lifetimes from laser induced fluorescence measurements [2] on neutral Ce are being combined with emission branching fractions from spectra recorded using a Fourier transform spectrometer. A total of 14 high resolution spectra are being analyzed to determine branching fractions for 2000 to 3000 lines from 153 upper levels in neutral Ce. Representative data samples and progress to date will be presented. [4pt] [1] J. E. Lawler, C. Sneden, J. J. Cowan, I. I. Ivans, and E. A. Den Hartog, Astrophys. J. Suppl. Ser. 182, 51-79 (2009). [0pt] [2] E. A. Den Hartog, K. P. Buettner, and J. E. Lawler, J. Phys. B: Atomic, Molecular & Optical Physics 42, 085006 (7pp) (2009).

  19. Local Structure of Cerium in Aluminophosphate and Silicophosphate Glasses

    SciTech Connect

    Rygel, Jennifer L.; Chen, Yongsheng; Pantano, Carlo G.; Shibata, Tomohiro; Du, Jincheng; Kokou, Leopold; Woodman, Robert; Belcher, James

    2011-09-20

    The local structure of cerium in two systematic compositional series of glasses, nominally CeP{sub 3}O{sub 9}-AlP{sub 3}O{sub 9} and CeP{sub 3}O{sub 9}-SiP{sub 2}O{sub 7}, was interrogated using X-ray photoelectron spectroscopy (XPS) and X-ray absorption fine structure (XAFS) spectroscopy. XPS revealed that, for glasses melted in air, {>=}95% of cerium ions are Ce{sup 3+}. This was independently confirmed using X-ray absorption near edge spectroscopy (XANES). Ce K-edge extended X-ray absorption fine structure (EXAFS) has been used to determine the local structure of Ce{sup 3+}. Near the metaphosphate composition, cerium was found to have an average cerium coordination number of {approx}7.0 and an average cerium-oxygen bond length of 2.41 {angstrom}. The average cerium coordination number and average cerium-oxygen bond distance were found to increase with decreasing cerium concentration in both compositional series. Rare-earth clustering is suggested based on numerical calculations for glasses containing {>=}14 and {>=}15 mol% Ce{sub 2}O{sub 3} for the aluminophosphate and silicophosphate series, respectively.

  20. Study of the cerium(IV)-picrate system in acetonitrile.

    PubMed

    Kratochvil, B; Tipler, M; McKay, B

    1966-07-01

    A potentiometric and spectrophotometric study has been made of the reaction between hexanitratocerate and picrate in dry acetonitrile. Several cerium(IV)-picrate complexes are formed; the formation constant for the first is estimated to be 4 from spectrophotometric measurements. The catalytic effect of picrate on hydroquinone oxidation by nitratocerate is postulated to be due to more rapid electron transfer by cerium picrate complexes.

  1. RECOVERY OF Pu FROM CERIUM TRIFLUORIDE BY FLUORINATION

    DOEpatents

    Brown, H.S.; Bohlmann, E.G.

    1959-02-10

    An improved process is prcsented for selectively recovering plutonium from a solution containing fission products comprising precipitating cerium trifluoride in the solution for effccting carrier precipitation of plutonium. The resulting carrier precipitate is dried and subjected to fluorination at about 600 C. The plutonium forms a volatile fiuoridc and is so separated from the nonvolatile cerium fluoride.

  2. Cerium migration during PEM fuel cell assembly and operation

    SciTech Connect

    Baker, Andrew M.; Torraco, Dennis; Judge, Elizabeth J.; Spernjak, Dusan; Mukundan, Rangachary; Borup, Rod L.; Advani, Suresh G.; Prasad, Ajay K.

    2015-10-02

    Cerium migration between PEM fuel cell components is influenced by potential-driven mobility, ionic diffusion, and gradients in water content. These factors were investigated in ex situ experiments and in operating fuel cells. Potential-induced migration was measured ex situ in hydrated window cells. Cerium-containing MEAs were also fabricated and tested under ASTs. MEA disassembly and subsequent XRF analysis were used to observe rapid cerium migration during cell assembly and operation. During MEA hot pressing, humidification, and low RH operation at OCV, ionic diffusion causes uniform migration from the membrane into the catalyst layers. During high RH operation at OCV, in-plane cerium gradients arise due to variations in water content. These gradients may diminish the scavenging efficacy of cerium by reducing its proximity to generated radicals.

  3. Cerium migration during PEM fuel cell assembly and operation

    SciTech Connect

    Baker, Andrew M.; Torraco, Dennis; Judge, Elizabeth J.; Spernjak, Dusan; Mukundan, Rangachary; Borup, Rod L.; Advani, Suresh G.; Prasad, Ajay K.

    2015-09-14

    Cerium migration between PEM fuel cell components is influenced by potential-driven mobility, ionic diffusion, and gradients in water content. These factors were investigated in ex situ experiments and in operating fuel cells. Potential-induced migration was measured ex situ in hydrated window cells. Cerium-containing MEAs were also fabricated and tested under ASTs. MEA disassembly and subsequent XRF analysis were used to observe rapid cerium migration during cell assembly and operation. During MEA hot pressing, humidification, and low RH operation at OCV, ionic diffusion causes uniform migration from the membrane into the catalyst layers. During high RH operation at OCV, in-plane cerium gradients arise due to variations in water content. These gradients may diminish the scavenging efficacy of cerium by reducing its proximity to generated radicals.

  4. Thin film cadmium telluride, zinc telluride, and mercury zinc telluride solar cells. Final subcontract report, 1 July 1988--31 December 1991

    SciTech Connect

    Chu, T.L.

    1992-04-01

    This report describes research to demonstrate (1) thin film cadmium telluride solar cells with a quantum efficiency of 75% or higher at 0. 44 {mu}m and a photovoltaic efficiency of 11.5% or greater, and (2) thin film zinc telluride and mercury zinc telluride solar cells with a transparency to sub-band-gap radiation of 65% and a photovoltaic conversion efficiency of 5% and 8%, respectively. Work was directed at (1) depositing transparent conducting semiconductor films by solution growth and metal-organic chemical vapor deposition (MOCVD) technique, (2) depositing CdTe films by close-spaced sublimation (CSS) and MOCVD techniques, (3) preparing and evaluating thin film CdTe solar cells, and (4) preparing and characterizing thin film ZnTe, CD{sub 1-x}Zn{sub 1-x}Te, and Hg{sub 1-x}Zn{sub x}Te solar cells. The deposition of CdS films from aqueous solutions was investigated in detail, and their crystallographic, optical, and electrical properties were characterized. CdTe films were deposited from DMCd and DIPTe at 400{degrees}C using TEGa and AsH{sub 3} as dopants. CdTe films deposited by CSS had significantly better microstructures than those deposited by MOCVD. Deep energy states in CdTe films deposited by CSS and MOCVD were investigated. Thin films of ZnTe, Cd{sub 1- x}Zn{sub x}Te, and Hg{sub 1-x}Zn{sub x}Te were deposited by MOCVD, and their crystallographic, optical, and electrical properties were characterized. 67 refs.

  5. Transient Response of Cadmium Telluride Modules to Light Exposure: Preprint

    SciTech Connect

    Deline, C.; del Cueto, J.; Albin, D. S.; Petersen, C.; Tyler, L.; TamizhMani, G.

    2011-07-01

    Commercial cadmium telluride (CdTe) photovoltaic (PV) modules from three different manufacturers were monitored for performance changes during indoor and outdoor light-exposure. Short-term transients in Voc were recorded on some modules, with characteristic times of ~1.1 hours. Outdoor performance data shows a similar drop in Voc after early morning light exposure. Preliminary analysis of FF changes show light-induced changes on multiple time scales, including a long time scale.

  6. Gamma-ray peak shapes from cadmium zinc telluride detectors

    SciTech Connect

    Namboodiri, M.N.; Lavietes, A.D.; McQuaid, J.H.

    1996-09-01

    We report the results of a study of the peak shapes in the gamma spectra measured using several 5 x 5 x 5 mm{sup 3} cadmium zinc telluride (CZT) detectors. A simple parameterization involving a Gaussian and an exponential low energy tail describes the peak shapes sell. We present the variation of the parameters with gamma energy. This type of information is very useful in the analysis of complex gamma spectra consisting of many peaks.

  7. Ultrathin, epitaxial cerium dioxide on silicon

    NASA Astrophysics Data System (ADS)

    Flege, Jan Ingo; Kaemena, Björn; Höcker, Jan; Bertram, Florian; Wollschläger, Joachim; Schmidt, Thomas; Falta, Jens

    2014-03-01

    It is shown that ultrathin, highly ordered, continuous films of cerium dioxide may be prepared on silicon following substrate prepassivation using an atomic layer of chlorine. The as-deposited, few-nanometer-thin Ce2O3 film may very effectively be converted at room temperature to almost fully oxidized CeO2 by simple exposure to air, as demonstrated by hard X-ray photoemission spectroscopy and X-ray diffraction. This post-oxidation process essentially results in a negligible loss in film crystallinity and interface abruptness.

  8. Ultrathin, epitaxial cerium dioxide on silicon

    SciTech Connect

    Flege, Jan Ingo Kaemena, Björn; Höcker, Jan; Schmidt, Thomas; Falta, Jens; Bertram, Florian; Wollschläger, Joachim

    2014-03-31

    It is shown that ultrathin, highly ordered, continuous films of cerium dioxide may be prepared on silicon following substrate prepassivation using an atomic layer of chlorine. The as-deposited, few-nanometer-thin Ce{sub 2}O{sub 3} film may very effectively be converted at room temperature to almost fully oxidized CeO{sub 2} by simple exposure to air, as demonstrated by hard X-ray photoemission spectroscopy and X-ray diffraction. This post-oxidation process essentially results in a negligible loss in film crystallinity and interface abruptness.

  9. Solvothermal synthesis and study of nonlinear optical properties of nanocrystalline thallium doped bismuth telluride

    SciTech Connect

    Molli, Muralikrishna; Parola, Sowmendran; Avinash Chunduri, L.A.; Aditha, Saikiran; Sai Muthukumar, V; Mimani Rattan, Tanu; Kamisetti, Venkataramaniah

    2012-05-15

    Nanocrystalline Bismuth telluride and thallium (4 mol %) doped Bismuth telluride were synthesized through hydrothermal method. The as-prepared products were characterized using Powder X-ray Diffraction, High Resolution Transmission Electron Microscopy, Energy Dispersive X-Ray Spectroscopy, UV-Visible spectroscopy and Fourier Transform Infrared Spectroscopy. Powder XRD results revealed the crystalline nature of the obtained phases. HRTEM showed the particle-like morphology of the products. The decrease in the absorption coefficient due to thallium doping was observed in FTIR spectra. The intensity dependent nonlinear optical properties of nanocrystalline bismuth telluride and thallium doped bismuth telluride were studied using the Z-scan technique in open-aperture configuration. Bismuth telluride doped with thallium showed enhanced nonlinear optical response compared to pristine bismuth telluride and hence could be used as a potential candidate for optical power limiting applications. - Graphical Abstract: Nonlinear transmission (Z-scan) curves of nanocrystalline bismuth telluride ({Delta}) and thallium doped bismuth telluride ({open_square}). Thallium doped bismuth telluride showed enhanced nonlinear absorption compared to bismuth telluride. Inset: TEM micrograph of bismuth telluride nanocrystallites. Highlights: Black-Right-Pointing-Pointer Synthesis of Nanocrystalline Bi{sub 2}Te{sub 3} and Thallium doped Bi{sub 2}Te{sub 3} through solvothermal method. Black-Right-Pointing-Pointer Reduced absorption coefficient due to thallium doping found from IR spectroscopy. Black-Right-Pointing-Pointer Open-aperture Z-scan technique for nonlinear optical studies. Black-Right-Pointing-Pointer Two photon absorption based model for theoretical fitting of Z-scan data. Black-Right-Pointing-Pointer Enhanced nonlinear absorption in Thallium doped Bi{sub 2}Te{sub 3} - potential candidate for optical power limiting applications.

  10. Photodissociation of Cerium Oxide Nanocluster Cations.

    PubMed

    Akin, S T; Ard, S G; Dye, B E; Schaefer, H F; Duncan, M A

    2016-04-21

    Cerium oxide cluster cations, CexOy(+), are produced via laser vaporization in a pulsed nozzle source and detected with time-of-flight mass spectrometry. The mass spectrum displays a strongly preferred oxide stoichiometry for each cluster with a specific number of metal atoms x, with x ≤ y. Specifically, the most prominent clusters correspond to the formula CeO(CeO2)n(+). The cluster cations are mass selected and photodissociated with a Nd:YAG laser at either 532 or 355 nm. The prominent clusters dissociate to produce smaller species also having a similar CeO(CeO2)n(+) formula, always with apparent leaving groups of (CeO2). The production of CeO(CeO2)n(+) from the dissociation of many cluster sizes establishes the relative stability of these clusters. Furthermore, the consistent loss of neutral CeO2 shows that the smallest neutral clusters adopt the same oxidation state (IV) as the most common form of bulk cerium oxide. Clusters with higher oxygen content than the CeO(CeO2)n(+) masses are present with much lower abundance. These species dissociate by the loss of O2, leaving surviving clusters with the CeO(CeO2)n(+) formula. Density functional theory calculations on these clusters suggest structures composed of stable CeO(CeO2)n(+) cores with excess oxygen bound to the surface as a superoxide unit (O2(-)). PMID:27035210

  11. The surface chemistry of cerium oxide

    SciTech Connect

    Mullins, David R.

    2015-01-29

    Our review covers the structure of, and chemical reactions on, well-defined cerium oxide surfaces. Ceria, or mixed oxides containing ceria, are critical components in automotive three-way catalysts due to their well-known oxygen storage capacity. Ceria is also emerging as an important material in a number of other catalytic processes, particularly those involving organic oxygenates and the water–gas shift reaction. Ceria's acid–base properties, and thus its catalytic behavior, are closely related to its surface structure where different oxygen anion and cerium cation environments are present on the low-index structural faces. The actual structure of these various faces has been the focus of a number of theoretical and experimental investigations. Ceria is also easily reducible from CeO2 to CeO2-X. The presence of oxygen vacancies on the surface often dramatically alters the adsorption and subsequent reactions of various adsorbates, either on a clean surface or on metal particles supported on the surface. We conducted surface science studies on the surfaces of thin-films rather than on the surfaces of bulk single crystal oxides. The growth, characterization and properties of these thin-films are also examined.

  12. The surface chemistry of cerium oxide

    DOE PAGES

    Mullins, David R.

    2015-01-29

    Our review covers the structure of, and chemical reactions on, well-defined cerium oxide surfaces. Ceria, or mixed oxides containing ceria, are critical components in automotive three-way catalysts due to their well-known oxygen storage capacity. Ceria is also emerging as an important material in a number of other catalytic processes, particularly those involving organic oxygenates and the water–gas shift reaction. Ceria's acid–base properties, and thus its catalytic behavior, are closely related to its surface structure where different oxygen anion and cerium cation environments are present on the low-index structural faces. The actual structure of these various faces has been the focusmore » of a number of theoretical and experimental investigations. Ceria is also easily reducible from CeO2 to CeO2-X. The presence of oxygen vacancies on the surface often dramatically alters the adsorption and subsequent reactions of various adsorbates, either on a clean surface or on metal particles supported on the surface. We conducted surface science studies on the surfaces of thin-films rather than on the surfaces of bulk single crystal oxides. The growth, characterization and properties of these thin-films are also examined.« less

  13. The surface chemistry of cerium oxide

    NASA Astrophysics Data System (ADS)

    Mullins, David R.

    2015-03-01

    This review covers the structure of, and chemical reactions on, well-defined cerium oxide surfaces. Ceria, or mixed oxides containing ceria, are critical components in automotive three-way catalysts due to their well-known oxygen storage capacity. Ceria is also emerging as an important material in a number of other catalytic processes, particularly those involving organic oxygenates and the water-gas shift reaction. Ceria's acid-base properties, and thus its catalytic behavior, are closely related to its surface structure where different oxygen anion and cerium cation environments are present on the low-index structural faces. The actual structure of these various faces has been the focus of a number of theoretical and experimental investigations. Ceria is also easily reducible from CeO2 to CeO2-X. The presence of oxygen vacancies on the surface often dramatically alters the adsorption and subsequent reactions of various adsorbates, either on a clean surface or on metal particles supported on the surface. Most surface science studies have been conducted on the surfaces of thin-films rather than on the surfaces of bulk single crystal oxides. The growth, characterization and properties of these thin-films are also examined.

  14. Microstructure of surface cerium hydride growth sites

    SciTech Connect

    Brierley, Martin; Knowles, John; Montgomery, Neil; Preuss, Michael

    2014-05-15

    Samples of cerium were exposed to hydrogen under controlled conditions causing cerium hydride sites to nucleate and grow on the surface. The hydriding rate was measured in situ, and the hydrides were characterised using secondary ion mass spectrometry, scanning electron microscopy, and optical microscopy. The results show that the hydriding rate proceeded more quickly than earlier studies. Characterisation confirmed that the hydrogen is confined to the sites. The morphology of the hydrides was confirmed to be oblate, and stressed material was observed surrounding the hydride, in a number of cases lathlike features were observed surrounding the hydride sites laterally with cracking in the surface oxide above them. It is proposed that during growth the increased lattice parameter of the CeH{sub 2} induces a lateral compressive stress around the hydride, which relieves by the ca. 16% volume collapse of the γ-Ce to α-Ce pressure induced phase transition. Cracking of the surface oxide above the laths reduces the diffusion barrier to hydrogen reaching the metal/oxide interface surrounding the hydride site and contributes to the anisotropic growth of the hydrides.

  15. Optical properties of cerium-codoped high power laser fibers

    NASA Astrophysics Data System (ADS)

    Unger, S.; Schwuchow, A.; Jetschke, S.; Grimm, S.; Scheffel, A.; Kirchhof, J.

    2013-03-01

    The photodarkening resistivity of ytterbium doped alumosilicate fibers can be remarkably improved by cerium codoping. Here we report on systematical investigations of the influence of cerium on an optimized fiber design. Fibers with different ytterbium, aluminium and cerium contents have been prepared both under reducing and oxydizing conditions and characterized concerning refractive index, absorption and emission from UV to NIR. Typical spectral features in the UV and visible range have been analysed with respect to the ratio of Ce3+ / Ce4+. Photodarkening tests have been accomplished in order to correlate the power stability with the Ce content and valency state.

  16. Antibacterial activity of cerium colloids against opportunistic microorganisms in vitro.

    PubMed

    Babenko, L P; Zholobak, N M; Shcherbakov, A B; Voychuk, S I; Lazarenko, L M; Spivak, M Ya

    2012-01-01

    The CeO2 sol with the size of nanoparticles 2-4 nm has been synthesized. It has been determined that the synthesized nanocrystalline cerium has antibacterial activity in vitro against different groups of opportunistic microorganisms: clinical strains of Escherichia coli, Staphylococcus aureus and Candida albicans. The rate of viability depression of test-cultures depends on the concentration of cerium dioxide nanoparticles and time of incubation. It is shown that the sol interacts with the bacterial cell surface. It is suggested that the observed differences of antibacterial action of nanocrystalline cerium dioxide can be related to the structural characteristics of the cell surface.

  17. 78 FR 68052 - Town of Telluride, Colorado; Notice of Preliminary Determination of a Qualifying Conduit...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-11-13

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF ENERGY Federal Energy Regulatory Commission Town of Telluride, Colorado; Notice of Preliminary Determination of a... Works Project Manager, P.O. Box 397, Telluride, CO 81435, Phone No. (970) 728-0190. FERC...

  18. Method of Creating Micro-scale Silver Telluride Grains Covered with Bismuth Nanoparticles

    NASA Technical Reports Server (NTRS)

    Kim, Hyun-Jung (Inventor); Choi, Sang Hyouk (Inventor); King, Glen C. (Inventor); Park, Yeonjoon (Inventor); Lee, Kunik (Inventor)

    2014-01-01

    Provided is a method of enhancing thermoelectric performance by surrounding crystalline semiconductors with nanoparticles by contacting a bismuth telluride material with a silver salt under a substantially inert atmosphere and a temperature approximately near the silver salt decomposition temperature; and recovering a metallic bismuth decorated material comprising silver telluride crystal grains.

  19. Optical glass surfaces polishing by cerium oxide particles

    NASA Astrophysics Data System (ADS)

    Bouzid, D.; Belkhie, N.; Aliouane, T.

    2012-02-01

    The use of powders in metallic oxides as means of grinding and polishing of the optical glass components have seen recently a large application in optical industry. In fact, cerium oxide abrasive is more used in the optical glass polishing. It is used as grains abrasive in suspension or fixed abrasive (pellets); these pellets are manufactured from a mixture made of cerium oxide abrasive and a organic binder. The cerium oxide used in the experiments is made by (Logitech USA) of 99 % purity, the average grain size of the particle is 300 nm, the density being 6,74 g /cm3 and the specific surface is 3,3042 m2/g. In this study, we are interested in the surfaces quality of the optical glass borosilicate crown (BK7) polished by particles in cerium oxide bounded by epoxy. The surfaces of the optical glass treated are characterized by the roughness, the flatness by using the microscope Zygo and the SEM.

  20. Cerium migration during PEM fuel cell assembly and operation

    DOE PAGES

    Baker, Andrew M.; Torraco, Dennis; Judge, Elizabeth J.; Spernjak, Dusan; Mukundan, Rangachary; Borup, Rod L.; Advani, Suresh G.; Prasad, Ajay K.

    2015-09-14

    Cerium migration between PEM fuel cell components is influenced by potential-driven mobility, ionic diffusion, and gradients in water content. These factors were investigated in ex situ experiments and in operating fuel cells. Potential-induced migration was measured ex situ in hydrated window cells. Cerium-containing MEAs were also fabricated and tested under ASTs. MEA disassembly and subsequent XRF analysis were used to observe rapid cerium migration during cell assembly and operation. During MEA hot pressing, humidification, and low RH operation at OCV, ionic diffusion causes uniform migration from the membrane into the catalyst layers. During high RH operation at OCV, in-plane ceriummore » gradients arise due to variations in water content. These gradients may diminish the scavenging efficacy of cerium by reducing its proximity to generated radicals.« less

  1. Effects of the Rare Earth Cerium on Escherichia coli

    PubMed Central

    Sobek, Joseph M.; Talburt, Dwight E.

    1968-01-01

    The rare earth cerium was found to bind rapidly to Escherichia coli. Cerium inhibited oxygen uptake in the presence of glucose as well as the endogenous respiration of glucose-grown cells. For a cell concentration of 4 mg per ml, maximal inhibition was obtained at 120 μg per ml. Greater concentrations did not increase the inhibitory effect. Cerium inhibited 14CO2 evolution and 14C uptake from uniformly labeled glucose. Marked changes in the distribution of 14C incorporated into different chemical fractions of the cell were noted. The most striking changes occurred in the alcohol- and alcohol ether-soluble fractions, in which the 14C activity was increased 5- to 20-fold in the presence of cerium. PMID:4866102

  2. Heteroaggregation of cerium oxide nanoparticles and nanoparticles of pyrolyzed biomass

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Heteroaggregation with indigenous particles is an important process controlling the mobility of engineered nanomaterials in the environment. We studied heteroaggregation of cerium oxide nanoparticles (n-CeO2), which are widely used commercially, with nanoparticles of pyrogenic carbonaceous material ...

  3. Method of applying a cerium diffusion coating to a metallic alloy

    DOEpatents

    Jablonski, Paul D.; Alman, David E.

    2009-06-30

    A method of applying a cerium diffusion coating to a preferred nickel base alloy substrate has been discovered. A cerium oxide paste containing a halide activator is applied to the polished substrate and then dried. The workpiece is heated in a non-oxidizing atmosphere to diffuse cerium into the substrate. After cooling, any remaining cerium oxide is removed. The resulting cerium diffusion coating on the nickel base substrate demonstrates improved resistance to oxidation. Cerium coated alloys are particularly useful as components in a solid oxide fuel cell (SOFC).

  4. Control of cerium oxidation state through metal complex secondary structures

    DOE PAGES

    Levin, Jessica R.; Dorfner, Walter L.; Carroll, Patrick J.; Schelter, Eric J.

    2015-08-11

    A series of alkali metal cerium diphenylhydrazido complexes, Mx(py)y[Ce(PhNNPh)4], M = Li, Na, and K, x = 4 (Li and Na) or 5 (K), and y = 4 (Li), 8 (Na), or 7 (K), were synthesized to probe how a secondary coordination sphere would modulate electronic structures at a cerium cation. The resulting electronic structures of the heterobimetallic cerium diphenylhydrazido complexes were found to be strongly dependent on the identity of the alkali metal cations. When M = Li+ or Na+, the cerium(III) starting material was oxidized with concomitant reduction of 1,2-diphenylhydrazine to aniline. Reduction of 1,2-diphenylhydrazine was not observedmore » when M = K+, and the complex remained in the cerium(III) oxidation state. Oxidation of the cerium(III) diphenylhydrazido complex to the Ce(IV) diphenylhydrazido one was achieved through a simple cation exchange reaction of the alkali metals. As a result, UV-Vis spectroscopy, FTIR spectroscopy, electrochemistry, magnetic susceptibility, and DFT studies were used to probe the oxidation state and the electronic changes that occurred at the metal centre.« less

  5. Control of cerium oxidation state through metal complex secondary structures

    SciTech Connect

    Levin, Jessica R.; Dorfner, Walter L.; Carroll, Patrick J.; Schelter, Eric J.

    2015-08-11

    A series of alkali metal cerium diphenylhydrazido complexes, Mx(py)y[Ce(PhNNPh)4], M = Li, Na, and K, x = 4 (Li and Na) or 5 (K), and y = 4 (Li), 8 (Na), or 7 (K), were synthesized to probe how a secondary coordination sphere would modulate electronic structures at a cerium cation. The resulting electronic structures of the heterobimetallic cerium diphenylhydrazido complexes were found to be strongly dependent on the identity of the alkali metal cations. When M = Li+ or Na+, the cerium(III) starting material was oxidized with concomitant reduction of 1,2-diphenylhydrazine to aniline. Reduction of 1,2-diphenylhydrazine was not observed when M = K+, and the complex remained in the cerium(III) oxidation state. Oxidation of the cerium(III) diphenylhydrazido complex to the Ce(IV) diphenylhydrazido one was achieved through a simple cation exchange reaction of the alkali metals. As a result, UV-Vis spectroscopy, FTIR spectroscopy, electrochemistry, magnetic susceptibility, and DFT studies were used to probe the oxidation state and the electronic changes that occurred at the metal centre.

  6. High pressure phase transition and elastic properties of americium telluride

    NASA Astrophysics Data System (ADS)

    Aynyas, Mahendra; Rukmangad, Aditi; Arya, B. S.; Sanyal, S. P.

    2013-06-01

    The structural and elastic properties of Americium Telluride (AmTe) have been investigated by using a modified inter-ionic potential theory (MIPT). This theory is capable of explaining first order phase transition with a crystallographic change NaCl to CsCl structure for this compound. The values of optimized lattice constant, phase transition pressure, zero pressure bulk modulus and second order elastic constants (C11, C44) agree well with their corresponding experimental data. Debye temperature (θD) is also calculated for this compound for the first time.

  7. Thermodynamics of defect subsystem in zinc telluride crystals

    NASA Astrophysics Data System (ADS)

    Horichok, I. V.; Nykyruy, L. I.; Parashchuk, T. O.; Bardashevska, S. D.; Pylyponuk, M. P.

    2016-06-01

    Using method on the base of minimizing of thermodynamic potential in “crystal-vapor” system as a function of defect concentration the equilibrium concentration of point defects and free charge carriers in zinc telluride (ZnTe) crystals have been calculated depending on the technological factors of two-temperature annealing (annealing temperature T and vapor pressure PZn of zinc or PTe of tellurium). It is shown that the dominant defects are zinc vacancies the charge state of which depends on the technological conditions of annealing.

  8. Ultrafast carrier dynamics in polycrystalline bismuth telluride nanofilm

    SciTech Connect

    Jia, Lin; Ma, Weigang; Zhang, Xing

    2014-06-16

    In this study, the dynamics of energy carriers in polycrystalline bismuth telluride nanofilm are investigated by the ultrafast pump-probe method. The energy relaxation processes are quantitatively analyzed by using the numerical fitting models. The extracted hot carrier relaxation times of photon excitation, thermalization, and diffusion are around sub-picosecond. The initial reflectivity recovery is found to be dominantly determined by the carrier diffusion, electron-phonon coupling, and photo-generated carriers trapping processes. High-frequency and low-frequency oscillations are both observed and attributed to coherent optical phonons and coherent acoustic phonons, respectively.

  9. Photoreflectance Study of Boron Ion-Implanted (100) Cadmium Telluride

    NASA Technical Reports Server (NTRS)

    Amirtharaj, P. M.; Odell, M. S.; Bowman, R. C., Jr.; Alt, R. L.

    1988-01-01

    Ion implanted (100) cadmium telluride was studied using the contactless technique of photoreflectance. The implantations were performed using 50- to 400-keV boron ions to a maximum dosage of 1.5 x 10(16)/sq cm, and the annealing was accomplished at 500 C under vacuum. The spectral measurements were made at 77 K near the E(0) and E(1) critical points; all the spectra were computer-fitted to Aspnes' theory. The spectral line shapes from the ion damaged, partially recovered and undamaged, or fully recovered regions could be identified, and the respective volume fraction of each phase was estimated.

  10. Thin film cadmium telluride solar cells. Technical progress report No. 2, October 1-December 31, 1979

    SciTech Connect

    Chu, T.L.

    1980-01-01

    The objectives of this contract are to investigate thin films of cadmium telluride on low cost substrates and to demonstrate the feasibility of producing thin film cells with a conversion efficiency of 10% or higher. The chemical vapor deposition of cadmium telluride films on foreign substrates by the direct combination of the elements has been further investigated. Inert substrates such as graphite and tungsten/graphite are not suitable for the deposition of device quality cadmium telluride films because of the rectifying interface and pinhole problems. Indium coated W/graphite forms an ohmic contact with n-type cadmium telluride, and the deposited films are essentially free of pinholes. The properties of Ag/n-CdTe/In/W/graphite structures, such as the current-voltage characteristics as a function of temperature, the barrier height, the photovoltaic properties, and the intragrain diffusion length in cadmium telluride, have been investigated. Preliminary work has also been carried out on the deposition of p-type cadmium telluride films on Sb/W/graphite substrates. The reaction between cadmium iodide and tellurium in a hydrogen atmosphere has been concluded to be unsuitable for the deposition of cadmium telluride films.

  11. Thin-film cadmium telluride and zinc phosphide solar cells

    NASA Astrophysics Data System (ADS)

    Chu, T. L.

    1981-06-01

    Major efforts during this quarter were directed to the deposition and characterization of zinc phosphide and cadmium telluride films and solar cells. The deposition of zinc phosphide films by the reaction of zinc and phosphine in a hydrogen atmosphere was continued and the composition of deposited films was determined. For more efficient utilization of phosphine, a 8500 C zone was added to the deposition. The in-situ annealing of zinc phosphide in phosphine was carried out. Attempts to prepare solar cell structures by depositing a thin film of zinc phosphide on an annealed film were made; however, the results are inconclusive. The deposition of cadmium telluride films by the direct combination of the elements under reduced pressure and under atmospheric pressure was carried out. Films deposited under reduced pressure exhibited more compact grain structures, however, they showed poor photoresponse. The composition of the films deposited under atmospheric pressure were analyzed and the dependence of short circuit density on the reactant composition was investigated.

  12. TOP as ligand and solvent to synthesize silver telluride nanosheets

    SciTech Connect

    Chen, Shutang; Lee, Soonil

    2015-11-15

    Highlights: • Silver telluride nanosheets were prepared through one-pot synthetic strategy. • TOP as both ligand and solvent favors silver telluride nanosheets growth. • The I–V curve of an Ag{sub 2}Te-nanosheet film indicates that as-prepared Ag{sub 2}Te nanosheets have good electric conductivity. - Abstract: Ag{sub 2}Te nanosheets are synthesized by a simple one-pot route using trioctylphosphine (TOP) as both solvent and stabilizer. Various controlling parameters were examined, such as molar ratios of AgNO{sub 3} to tellurium powder, reaction temperature and time, and precursor concentration. The morphology and composition of the products were characterized by X-ray diffraction, field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, and transmission electron microscopy. On the basis of a series of synthesis and characterizations, the formation mechanism of the Ag{sub 2}Te nanosheets are discussed. The I–V curve of an Ag{sub 2}Te-nan osheet film indicates that as-prepared Ag{sub 2}Te nanosheets have good electric conductivity.

  13. Superconductivity in oxygen doped iron telluride by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Zheng, Mao

    Iron base superconductor have gained much attention in the research community. They offer great potentials to improve our understanding of the subject of superconductivity by having another family of high temperature superconductors to compare and contrast to the cuprates. Practically, the iron based superconductors seems to be even better candidates for applications in power generation and power transmission. Iron telluride is regarded as the parent compound of the "11" family, the family of iron chalcogenide that has the simplest structure. Iron telluride itself is not a superconductor, by can become one when doped with oxygen. In this investigation, we developed the growth recipe of thin film iron telluride by Molecular Beam Epitaxy (MBE). We found the growth to be self-regulated, similar to that of GaAs. The initial layers of growth seem to experience a spontaneous crystallization, as the film quickly go from the initial polycrystalline phase to highly crystalline in just a few unit cells. We studied oxygen doping to the iron telluride thin films and the resultant superconductivity. We characterized the sample with AFM, XRD, transport, and STEM-EELS, and we found that interfacial strain is not an essential ingredient of superconductivity in this particular case. We investigated the doping conditions for two candidate oxygen doping modes: substitution and interstitial. We found that substitution occurs when the film grown in oxygen, while interstitial oxygen is primarily incorporated during annealing after growth. The substitutional oxygen are concentrated in small local regions where substitution is around 100%, but does not contribute to superconductivity. We estimated substitutional oxygen to be about 5%, and is the proximate cause of superconductivity. Hall experiment on our sample showed a shift of dominant carrier type from holes to electrons around 35 K, but the transition was set in motion as early as the structural phase transition around 70 K. We

  14. Cadmium Telluride-Titanium Dioxide Nanocomposite for Photodegradation of Organic Substance.

    PubMed

    Ontam, Areeporn; Khaorapapong, Nithima; Ogawa, Makoto

    2015-12-01

    Cadmium telluride-titanium dioxide nanocomposite was prepared by hydrothermal reaction of sol-gel derived titanium dioxide and organically modified cadmium telluride. The crystallinity of titanium dioxide in the nanocomposite was higher than that of pure titanium dioxide obtained by the reaction under the same temperature and pressure conditions, showing that cadmium telluride induced the crystallization of titanium dioxide. Diffuse reflectance spectrum of the nanocomposite showed the higher absorption efficiency in the UV-visible region due to band-gap excitation of titanium dioxide. The nanocomposite significantly showed the improvement of photocatalytic activity for 4-chlorophenol with UV light.

  15. IRIS TOXICOLOGICAL REVIEW AND SUMMARY DOCUMENTS FOR CERIUM OXIDE (STABLE) AND COMPOUNDS

    EPA Science Inventory

    Cerium is a member of the lanthanoid series of rare earth metals. It is also the most abundant and most reactive of the rare earth metals. Cerium oxidizes at room temperature and forms a variety of salt compounds including oxides, hydroxides, sulfates and chlorides. Cerium is ...

  16. Potential for recovery of cerium contained in automotive catalytic converters

    USGS Publications Warehouse

    Bleiwas, Donald I.

    2013-01-01

    Catalytic converters (CATCONs) are required by Federal law to be installed in nearly all gasoline- and diesel-fueled onroad vehicles used in the United States. About 85 percent of the light-duty vehicles and trucks manufactured worldwide are equipped with CATCONs. Portions of the CATCONs (called monoliths) are recycled for their platinum-group metal (PGM) content and for the value of the stainless steel they contain. The cerium contained in the monoliths, however, is disposed of along with the slag produced from the recycling process. Although there is some smelter capacity in the United States to treat the monoliths in order to recover the PGMs, a great percentage of monoliths is exported to Europe and South Africa for recycling, and a lesser amount is exported to Japan. There is presently no commercial-scale capacity in place domestically to recover cerium from the monoliths. Recycling of cerium or cerium compounds from the monoliths could help ensure against possible global supply shortages by increasing the amount that is available in the supply chain as well as the number and geographic distribution of the suppliers. It could also reduce the amount of material that goes into landfills. Also, the additional supply could lower the price of the commodity. This report analyzes how much cerium oxide is contained in CATCONs and how much could be recovered from used CATCONs.

  17. Mechanical and Thermophysical Properties of Cerium Monopnictides

    NASA Astrophysics Data System (ADS)

    Bhalla, Vyoma; Singh, Devraj; Jain, S. K.

    2016-03-01

    The ultrasonic attenuation due to phonon-phonon interaction, thermoelastic relaxation and dislocation damping mechanisms has been investigated in cerium monopnictides CeX (X: N, P, As, Sb and Bi) for longitudinal and shear waves along {< }100{rangle }, {< }110{rangle } and {< }111{rangle } directions. The second- and third-order elastic constants of CeX have also been computed in the temperature range 0 K to 500 K using Coulomb and Born-Mayer potential upto second nearest neighbours. The computed values of these elastic constants have been applied to find out Young's moduli, bulk moduli, Breazeale's non-linearity parameters, Zener anisotropy, ultrasonic velocity, ultrasonic Grüneisen parameter, thermal relaxation time, acoustic coupling constants and ultrasonic attenuation. The fracture/toughness ratio is less than 1.75, which shows that the chosen materials are brittle in nature as found for other monopnictides. The drag coefficient acting on the motion of screw and edge dislocations due to shear and compressional phonon viscosities of the lattice have also been evaluated for both the longitudinal and shear waves. The thermoelastic loss and dislocation damping loss are negligible in comparison to loss due to Akhieser damping (phonon-phonon interaction). The obtained results for CeX are in qualitative agreement with other semi-metallic monopnictides.

  18. Characterization of cerium fluoride nanocomposite scintillators

    SciTech Connect

    Stange, Sy; Esch, Ernst I; Brown, Leif O; Couture, Aaron J; Mckigney, Edward A; Muenchausen, Ross E; Del Sesto, Rico E; Gilbertson, Robert D; Mccleskey, T Mark; Reifarth, Rene

    2009-01-01

    Measurement of the neutron capture cross-sections of a number of short-lived isotopes would advance both pure and applied scientific research. These cross-sections are needed for calculation of criticality and waste production estimates for the Advanced Fuel Cycle Initiative, for analysis of data from nuclear weapons tests, and to improve understanding of nucleosynthesis. However, measurement of these cross-sections would require a detector with a faster signal decay time than those used in existing neutron capture experiments. Crystals of faster detector materials are not available in sufficient sizes and quantities to supply these large-scale experiments. Instead, we propose to use nanocomposite detectors, consisting of nanoscale particles of a scintillating material dispersed in a matrix material. We have successfully fabricated cerium fluoride (CeF{sub 3}) nanoparticles and dispersed them in a liquid matrix. We have characterized this scintillator and have measured its response to neutron capture. Results of the optical, structural, and radiation characterization will be presented.

  19. Environmental Geochemistry of Cerium: Applications and Toxicology of Cerium Oxide Nanoparticles

    PubMed Central

    Dahle, Jessica T.; Arai, Yuji

    2015-01-01

    Cerium is the most abundant of rare-earth metals found in the Earth’s crust. Several Ce-carbonate, -phosphate, -silicate, and -(hydr)oxide minerals have been historically mined and processed for pharmaceutical uses and industrial applications. Of all Ce minerals, cerium dioxide has received much attention in the global nanotechnology market due to their useful applications for catalysts, fuel cells, and fuel additives. A recent mass flow modeling study predicted that a major source of CeO2 nanoparticles from industrial processing plants (e.g., electronics and optics manufactures) is likely to reach the terrestrial environment such as landfills and soils. The environmental fate of CeO2 nanoparticles is highly dependent on its physcochemical properties in low temperature geochemical environment. Though there are needs in improving the analytical method in detecting/quantifying CeO2 nanoparticles in different environmental media, it is clear that aquatic and terrestrial organisms have been exposed to CeO2 NPs, potentially yielding in negative impact on human and ecosystem health. Interestingly, there has been contradicting reports about the toxicological effects of CeO2 nanoparticles, acting as either an antioxidant or reactive oxygen species production-inducing agent). This poses a challenge in future regulations for the CeO2 nanoparticle application and the risk assessment in the environment. PMID:25625406

  20. A preliminary study on the use of cadmium telluride detectors in the scintigraphy of thyroid gland

    NASA Astrophysics Data System (ADS)

    Mancini, A. M.; Quirini, A.; Vasanelli, L.; Bacci, C.; Bernabei, R.; Pani, R.; Rispoli, B.; Ballesio, P. L.; Furetta, C.

    1981-10-01

    A cadmium telluride gamma detector has been used for monitoring the activity of a radioactive tracer in a thyroid gland. Preliminary measurements are reported in comparison with those obtained with a standard NaI(Tl) scintillator.

  1. Thermodynamic Calculation among Cerium, Oxygen, and Sulfur in Liquid Iron

    PubMed Central

    Pan, Fei; Zhang, Jian; Chen, Hao-Long; Su, Yen-Hsun; Su, Yen-Hao; Hwang, Weng-Sing

    2016-01-01

    Thermodynamic calculation has been applied to predict the inclusion formation in molten SS400 steel. When the Cerium addition in liquid iron is 70 ppm and the initial Oxygen and Sulphur are both 110 ppm, the formation of oxides containing Cerium would experience the transformation from Ce2O3 to CeO2 and also the formation of sulfides containing Cerium would experience the transformation from CeS to Ce2S3 and then to Ce3S4. Below 2000 K the most thermodynamic stable matter is CeO2 and the less thermodynamic stable inclusion is CeS. Only when the amount of [O] is extremely low and the amount of [S] and [Ce] is relatively high, Ce2S3 has the possibility to form. PMID:27767092

  2. Dehydrogenation of isopropanol on a cerium-nickel catalyst

    NASA Astrophysics Data System (ADS)

    Platonov, E. A.; Naumkin, A. V.; Maslakov, K. I.; Yagodovskii, V. D.

    2012-12-01

    The effect of a cerium additive on the catalytic activity of a 2 wt % Ni/SiO2 catalyst is studied. It found that under both flow and static conditions the activity of (2 wt % Ni + 0.2 wt % Ce)/SiO2 catalyst is higher than that of the original sample; the increase in activity results from a sharp increase in the number of active sites. A change in the composition of the surface layer of the catalysts is analyzed by X-ray photoelectron spectroscopy. It was found that the fraction of nickel decreases and the fraction of carbon increases in cerium-containing catalyst. An explanation of the change in the elemental composition of the catalytic active sites of a nickel catalyst in the presence of cerium is proposed on the basis of XPS data and previous quantum chemical calculations.

  3. Diameter Dependence of the Transport Properties of Antimony Telluride Nanowires

    NASA Astrophysics Data System (ADS)

    Zuev, Yuri; Lee, Jin Sook; Park, Hongkun; Kim, Philip

    2010-03-01

    We report measurements of electronic, thermoelectric, and galvanometric properties of individual semimetallic single crystal antimony telluride (Sb2Te3) nanowires. Microfabricated heater and thermometer electrodes were used to probe the transport properties of the nanowires with diameters in the range of 22 - 95nm and temperatures in the range of 2 - 300K. Temperature dependent resistivity varies depending on nanowire diameter. Thermoelectric power (TEP) measurements indicate hole dominant diffusive thermoelectric generation, with an enhancement of the TEP for smaller diameter wires. The large surface-to-volume ratio of Sb2Te3 nanowires makes them an excellent platform to explore novel phenomena in this predicted topological insulator. We investigate mesoscopic magnetoresistance effects in magnetic fields both parallel and perpendicular to the nanowire axis.

  4. Study on thermal annealing of cadmium zinc telluride (CZT) crystals

    SciTech Connect

    Yang, G.; Bolotnikov, A.E.; Fochuk, P.M.; Camarda, G.S.; Cui, Y.; Hossain, A.; Kim, K.; Horace, J.; McCall, B.; Gul, R.; Xu, L.; Kopach, O.V.; and James, R.B.

    2010-08-01

    Cadmium Zinc Telluride (CZT) has attracted increasing interest with its promising potential as a room-temperature nuclear-radiation-detector material. However, different defects in CZT crystals, especially Te inclusions and dislocations, can degrade the performance of CZT detectors. Post-growth annealing is a good approach potentially to eliminate the deleterious influence of these defects. At Brookhaven National Laboratory (BNL), we built up different facilities for investigating post-growth annealing of CZT. Here, we report our latest experimental results. Cd-vapor annealing reduces the density of Te inclusions, while large temperature gradient promotes the migration of small-size Te inclusions. Simultaneously, the annealing lowers the density of dislocations. However, only-Cd-vapor annealing decreases the resistivity, possibly reflecting the introduction of extra Cd in the lattice. Subsequent Te-vapor annealing is needed to ensure the recovery of the resistivity after removing the Te inclusions.

  5. Tunable split-ring resonators using germanium telluride

    NASA Astrophysics Data System (ADS)

    Kodama, C. H.; Coutu, R. A.

    2016-06-01

    We demonstrate terahertz (THz) split-ring resonator (SRR) designs with incorporated germanium telluride (GeTe) thin films. GeTe is a chalcogenide that undergoes a nonvolatile phase change from the amorphous to crystalline state at approximately 200 °C, depending on the film thickness and stoichiometry. The phase change also causes a drop in the material's resistivity by six orders of magnitude. In this study, two GeTe-incorporated SRR designs were investigated. The first was an SRR made entirely out of GeTe and the second was a gold SRR structure with a GeTe film incorporated into the gap region of the split ring. These devices were characterized using THz time-domain spectroscopy and were heated in-situ to determine the change in the design operation with varying temperatures.

  6. Ion implantation of erbium into polycrystalline cadmium telluride

    SciTech Connect

    Ushakov, V. V. Klevkov, Yu. V.; Dravin, V. A.

    2015-05-15

    The specific features of the ion implantation of polycrystalline cadmium telluride with grains 20–1000 μm in dimensions are studied. The choice of erbium is motivated by the possibility of using rare-earth elements as luminescent “probes” in studies of the defect and impurity composition of materials and modification of the composition by various technological treatments. From the microphotoluminescence data, it is found that, with decreasing crystal-grain dimensions, the degree of radiation stability of the material is increased. Microphotoluminescence topography of the samples shows the efficiency of the rare-earth probe in detecting regions with higher impurity and defect concentrations, including regions of intergrain boundaries.

  7. Comparison of Germanium Telluride (GeTe) Crystals

    NASA Technical Reports Server (NTRS)

    2004-01-01

    Comparison of Germanium Telluride (GeTe) Crystals grown on Earth (left) and in space (right) during the Skylab SL-3 mission. These crystals were grown using a vapor transport crystal growth method in the Multipurpose Electric Furnace System (MEFS). Crystals grown on earth are needles and platelettes with distorted surfaces and hollow growth habits. The length of the ground-based needle is approximately 2 mm and the average lenth of the platelets is 1 mm. The dull appearance of the Skylab crystals resulted from condensation of the transport agent during the long cooling period dictated by the Skylab furnace. In a dedicated process, this would be prevented by removing the ampoule from the furnace and quenching the vapor source.

  8. Ion Beam Layer Separation of Cadmium Zinc Telluride

    SciTech Connect

    Bhattacharya, Rabi S.; He, P.; Xu, Y.; Goorsky, M.

    2008-11-03

    We have investigated the approach of ion induced layer separation process for layer splitting from Cadmium Zinc Telluride (CZT) bulk single crystal and transferring and bonding the separated layers with Silicon (Si) wafers. Layer separation experiments have been carried out at UES using 1 MeV H{sup +} ions from the high energy accelerator (1.7 MV Tandetron). Ion dose and annealing temperature for complete separation of 1 cmx1 cm size layers have been optimized. Bonding of CZT with Si was accomplished using various IR transmitting chalcogenide glasses. Cracking of separated CZT films was occurring for chalcogenide glass bonded films. Optimization of thermal treatment has led to the minimization of such cracks. Detailed characterizations of the separated films will be presented.

  9. Towards understanding junction degradation in cadmium telluride solar cells

    SciTech Connect

    Nardone, Marco

    2014-06-21

    A degradation mechanism in cadmium telluride (CdTe/CdS) solar cells is investigated using time-dependent numerical modeling to simulate various temperature, bias, and illumination stress conditions. The physical mechanism is based on defect generation rates that are proportional to nonequilibrium charge carrier concentrations. It is found that a commonly observed degradation mode for CdTe/CdS solar cells can be reproduced only if defects are allowed to form in a narrow region of the absorber layer close to the CdTe/CdS junction. A key aspect of this junction degradation is that both mid-gap donor and shallow acceptor-type defects must be generated simultaneously in response to photo-excitation or applied bias. The numerical approach employed here can be extended to study other mechanisms for any photovoltaic technology.

  10. Process dependent thermoelectric properties of EDTA assisted bismuth telluride

    NASA Astrophysics Data System (ADS)

    Kulsi, Chiranjit; Kargupta, Kajari; Banerjee, Dipali

    2016-04-01

    Comparison between the structure and thermoelectric properties of EDTA (Ethylene-diamine-tetra-acetic acid) assisted bismuth telluride prepared by electrochemical deposition and hydrothermal route is reported in the present work. The prepared samples have been structurally characterized by high resolution X-ray diffraction spectra (HRXRD), field emission scanning electron microscopy (FESEM) and high resolution transmission electron microscopic images (HRTEM). Crystallite size and strain have been determined from Williamson-Hall plot of XRD which is in conformity with TEM images. Measurement of transport properties show sample in the pellet form (S1) prepared via hydrothermal route has higher value of thermoelectric power (S) than the electrodeposited film (S2). But due to a substantial increase in the electrical conductivity (σ) of the film (S2) over the pellet (S1), the power factor and the figure of merit is higher for sample S2 than the sample S1 at room temperature.

  11. Sn-doped bismuth telluride nanowires with high conductivity.

    PubMed

    Mi, Gang; Li, Likai; Zhang, Yuanbo; Zheng, Gengfeng

    2012-10-21

    Bismuth telluride (Bi(2)Te(3)) nanowires with sub-100 nm diameters were synthesized by Au-Sn co-catalyzed chemical vapor deposition. These Bi(2)Te(3) nanowires were single crystals with a hexagonal lattice. The Sn catalyst played a key role in achieving the one-dimensional nanowire structures, while the absence of Sn resulted in other morphologies such as nanoplates, nanooctahedrons and nanospheres. Raman spectra revealed that compared to the Bi(2)Te(3) bulk materials, the Bi(2)Te(3) nanowires displayed an A(1u) spectral peak, implying the breaking of symmetry. The temperature-dependent electrical measurement indicated that these Sn-doped Bi(2)Te(3) nanowires were metallic, with a high conductivity of 1.6 × 10(5) S m(-1) at 300 K. PMID:22990308

  12. Polycrystalline thin film cadmium telluride solar cells fabricated by electrodeposition

    NASA Astrophysics Data System (ADS)

    Trefny, J. U.; Furtak, T. E.; Williamson, D. L.; Kim, D.

    1994-07-01

    This report describes the principal results of work performed during the second year of a 3-year program at the Colorado School of Mines (CSM). The work on transparent conducting oxides was carried out primarily by CSM students at NREL and is described in three publications listed in Appendix C. The high-quality ZnO produced from the work was incorporated into a copper indium diselenide cell that exhibited a world-record efficiency of 16.4%. Much of the time was devoted to the improvement of cadmium sulfide films deposited by chemical bath deposition methods and annealed with or without a cadmium chloride treatment. Progress was also made in the electrochemical deposition of cadmium telluride. High-quality films yielding CdS/CdTe/Au cells of greater than 10% efficiency are now being produced on a regular basis. We explored the use of zinc telluride back contacts to form an n-i-p cell structure as previously used by Ametek. We began small-angle x-ray scattering (SAXS) studies to characterize crystal structures, residual stresses, and microstructures of both CdTe and CdS. Large SAXS signals were observed in CdS, most likely because of scattering from gain boundaries. The signals observed to date from CdTe are much weaker, indicating a more homogeneous microstructure. We began to use the ADEPT modeling program, developed at Purdue University, to guide our understanding of the CdS/CdTe cell physics and the improvements that will most likely lead to significantly enhanced efficiencies.

  13. Ligand Control of Manganese Telluride Molecular Cluster Core Nuclearity.

    PubMed

    Choi, Bonnie; Paley, Daniel W; Siegrist, Theo; Steigerwald, Michael L; Roy, Xavier

    2015-09-01

    We report the synthesis, structural diversity, and chemical behavior of a family of manganese telluride molecular clusters whose charge-neutral cores are passivated by two-electron donor ligands. We describe three different core structures: a cubane-type Mn4Te4, a prismane Mn6Te6, and a dicubane Mn8Te8. We use various trialkylphosphines and N-heterocyclic carbenes (NHCs) as surface ligands and demonstrate that the formation of the different cluster core structures is controlled by the choice of ligand: bulky ligands such as P(i)Pr3, PCy3, or (i)Pr2NHC ((i)Pr2NHC = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene) form the cubane-type core, while the smaller PMe3 produces the prismane core. The intermediate-sized PEt3 produces both cubane and prismane species. These manganese telluride molecular clusters are labile, and the capping phosphines can be replaced by stronger ligands, while the internal core structure of the cluster remains intact. The interplay of structural diversity and ligand versatility and lability makes these clusters potentially useful building blocks for the assembly of larger aggregates and extended structures. We demonstrate the simplest prototype of these solid-forming reactions: the direct coupling of two Mn4Te4((i)Pr2NHC)4 units to form the dicubane Mn8Te8((i)Pr2NHC)6. We also postulate the prismatic Mn6Te6 as the common ancestor of both Chevrel-type M6E8 and octanuclear rhombododecahedral M8E6 molecular clusters (M = transition metal and E = chalcogen), and we discuss the core structure of our molecular clusters as recognizable building units for the zinc blende and the hypothetical wurtzite lattices of MnTe.

  14. Cadmium Telluride Solar Cells with PEDOT:PSS Back Contact

    NASA Astrophysics Data System (ADS)

    Mount, Michael; Duarte, Fernanda; Paudel, Naba; Yan, Yanfa; Wang, Weining

    Cadmium Telluride (CdTe) solar cell is one of the most promising thin film solar cells and its highest efficiency has reached 21%. To keep improving the efficiency of CdTe solar cells, a few issues need to be addressed, one of which is the back contact. The back contact of CdTe solar cells are mostly Cu-base, and the problem with Cu-based back contact is that Cu diffuses into the grain boundary and into the CdS/CdTe junction, causing degradation problem at high temperature and under illumination. To continue improving the efficiency of CdTe/CdS solar cells, a good ohmic back contact with high work function and long term stability is needed. In this work, we report our studies on the potential of conducting polymer being used as the back contact of CdTe/CdS solar cells. Conducting polymers are good candidates because they have high work functions and high conductivities, are easy to process, and cost less, meeting all the requirements of a good ohmic back contact for CdTe. In our studies, we used poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) with different conductivities and compared them with traditional Cu-based back contact. It was observed that the CdTe solar cell performance improves as the conductivity of the PEDOT:PSS increase, and the efficiency (9.1%) is approaching those with traditional Cu/Au back contact (12.5%). Cadmium Telluride Solar Cells with PEDOT:PSS Back Contact.

  15. Synthesis and characterization of magnesium doped cerium oxide for the fuel cell application

    NASA Astrophysics Data System (ADS)

    Kumar, Amit; Kumari, Monika; Kumar, Mintu; Kumar, Sacheen; Kumar, Dinesh

    2016-05-01

    Cerium oxide has attained much attentions in global nanotechnology market due to valuable application for catalytic, fuel additive, and widely as electrolyte in solid oxide fuel cell. Doped cerium oxide has large oxygen vacancies that allow for greater reactivity and faster ion transport. These properties make cerium oxide suitable material for SOFCs application. Cerium oxide electrolyte requires lower operation temperature which shows improvement in processing and the fabrication technique. In our work, we synthesized magnesium doped cerium oxide by the co-precipitation method. With the magnesium doping catalytic reactivity of CeO2 was increased. Synthesized nanoparticle were characterized by the XRD and UV absorption techniques.

  16. In situ growth of epitaxial cerium tungstate (100) thin films.

    PubMed

    Skála, Tomáš; Tsud, Nataliya; Orti, Miguel Ángel Niño; Menteş, Tevfik Onur; Locatelli, Andrea; Prince, Kevin Charles; Matolín, Vladimír

    2011-04-21

    The deposition of ceria on a preoxidized W(110) crystal at 870 K has been studied in situ by photoelectron spectroscopy and low-energy electron diffraction. Formation of an epitaxial layer of crystalline cerium tungstate Ce(6)WO(12)(100), with the metals in the Ce(3+) and W(6+) chemical states, has been observed. The interface between the tungsten substrate and the tungstate film consists of WO suboxide. At thicknesses above 0.89 nm, cerium dioxide grows on the surface of Ce(6)WO(12), favoured by the limited diffusion of tungsten from the substrate. PMID:21399780

  17. Optical and electrical studies of cerium mixed oxides

    SciTech Connect

    Sherly, T. R.; Raveendran, R.

    2014-10-15

    The fast development in nanotechnology makes enthusiastic interest in developing nanomaterials having tailor made properties. Cerium mixed oxide materials have received great attention due to their UV absorption property, high reactivity, stability at high temperature, good electrical property etc and these materials find wide applications in solid oxide fuel cells, solar control films, cosmetics, display units, gas sensors etc. In this study cerium mixed oxide compounds were prepared by co-precipitation method. All the samples were doped with Zn (II) and Fe (II). Preliminary characterizations such as XRD, SEM / EDS, TEM were done. UV - Vis, Diffuse reflectance, PL, FT-IR, Raman and ac conductivity studies of the samples were performed.

  18. The effective thermal conductivity of an adsorbent - Praseodymium cerium oxide

    NASA Technical Reports Server (NTRS)

    Secary, J. J.; Tong, T. W.

    1992-01-01

    The results of an experimental study to determine the effective thermal conductivity of praseodymium cerium oxide are reported. Praseodymium cerium oxide is an adsorbent used in the development of adsorption compressors for spaceborne refrigeration systems. A guarded-hot-plate apparatus was built for this study. Measurements were carried out for mean temperatures ranging from 300 to 600 C under a vacuum of 10 exp -5 torr. For the temperature range studied, the effective thermal conductivity increased from 0.14 to 0.76 W/m per C with increasing temperature, while displaying a cubic temperature dependency.

  19. Cerium phosphate nanotubes: synthesis, characterization and biosensing

    NASA Astrophysics Data System (ADS)

    Meng, Ling; Yang, Lige; Zhou, Bo; Cai, Chenxin

    2009-01-01

    Cerium phosphate (CeP) nanotubes have been synthesized and confirmed by x-ray diffraction (XRD) and transmission electron microscopy (TEM). The 1D nanomaterial has a monoclinic crystal structure with a mean width of 15-20 nm and a length up to several micrometers. The nanotubes have been employed as electrode substrates for immobilization and direct electrochemistry of heme proteins/enzymes with myoglobin (Mb) as a model. The electrochemical characteristics of the Mb-CeP/GC electrode were studied by voltammetry. After being immobilized on the nanotubes, Mb can keep its natural structure and undergo effective direct electron transfer reaction with a pair of well-defined redox peaks at -(367 ± 3) mV (pH 7.5). The apparent electron transfer rate constant is (9.1 ± 1.4) s-1. The electrode displays good features in the electrocatalytic reduction of H2O2, and thus can be used as a biosensor for detecting the substrate with a low detection limit (0.5 ± 0.05 µM), a wide linear range (0.01-2 mM), high sensitivity (14.4 ± 1.2 µA mM-1), as well as good stability and reproducibility. CeP nanotubes can become a simple and effective biosensing platform for the integration of heme proteins/enzymes and electrodes, which can provide analytical access to a large group of enzymes for a wide range of bioelectrochemical applications.

  20. Nanoparticulate cerium dioxide and cerium dioxide-titanium dioxide composite thin films on glass by aerosol assisted chemical vapour deposition

    NASA Astrophysics Data System (ADS)

    Qureshi, Uzma; Dunnill, Charles W.; Parkin, Ivan P.

    2009-11-01

    Two series of composite thin films were deposited on glass by aerosol assisted chemical vapour deposition (AACVD)—nanoparticulate cerium dioxide and nanoparticulate cerium dioxide embedded in a titanium dioxide matrix. The films were analysed by a range of techniques including UV-visible absorption spectroscopy, X-ray diffraction, scanning electron microscopy and energy dispersive analysis by X-rays. The AACVD prepared films showed the functional properties of photocatalysis and super-hydrophilicity. The CeO 2 nanoparticle thin films displaying photocatalysis and photo-induced hydrophilicity almost comparable to that of anatase titania.

  1. Hydrothermal preparation of fractal dendrites: Cerium carbonate hydroxide and cerium oxide

    SciTech Connect

    Wu Mingzai; Zhang Qihua; Liu Yanmei; Fang Qingqing; Liu Xiansong

    2009-06-03

    The surfactant-assisted hydrothermal route was used to prepare fractal dendrite cerium carbonate hydroxide (CeOHCO{sub 3}) microstructures. After annealing at 600 deg. C for 4 h, the products were transformed to CeO{sub 2}. The crystal structures of the two compounds were determined by X-ray diffraction (XRD). The morphologies and microstructures were characterized by field emission scanning electron microscopy (FESEM) and high-resolution transmission electron microscopy (HRTEM). Room temperature photoluminescence (PL) showed that a strong ultraviolet emission at 336 nm was observed for CeOHCO{sub 3}, and that centered at 415 nm for CeO{sub 2} microstructures. Both of these emission peaks are different from those reported for CeOHCO{sub 3} and CeO{sub 2} with other shapes. In addition, the possible growth mechanism of dendrite CeOHCO{sub 3} microstructures and the role of surfactant polyvinyl pyrrolidone (PVP) were also investigated in this paper.

  2. Purification of cerium, neodymium and gadolinium for low background experiments

    NASA Astrophysics Data System (ADS)

    Boiko, R. S.; Barabash, A. S.; Belli, P.; Bernabei, R.; Cappella, F.; Cerulli, R.; Danevich, F. A.; Incicchitti, A.; Laubenstein, M.; Mokina, V. M.; Nisi, S.; Poda, D. V.; Polischuk, O. G.; Tretyak, V. I.

    2014-01-01

    Cerium, neodymium and gadolinium contain double beta active isotopes. The most interesting are 150Nd and 160Gd (promising for 0ν2β search), 136Ce (2β+ candidate with one of the highest Q2β). The main problem of compounds containing lanthanide elements is their high radioactive contamination by uranium, radium, actinium and thorium. The new generation 2β experiments require development of methods for a deep purification of lanthanides from the radioactive elements. A combination of physical and chemical methods was applied to purify cerium, neodymium and gadolinium. Liquid-liquid extraction technique was used to remove traces of Th and U from neodymium, gadolinium and for purification of cerium from Th, U, Ra and K. Co-precipitation and recrystallization methods were utilized for further reduction of the impurities. The radioactive contamination of the samples before and after the purification was tested by using ultra-low-background HPGe gamma spectrometry. As a result of the purification procedure the radioactive contamination of gadolinium oxide (a similar purification efficiency was reached also with cerium and neodymium oxides) was decreased from 0.12 Bq/kg to 0.007 Bq/kg in 228Th, from 0.04 Bq/kg to <0.006 Bq/kg in 226Ra, and from 0.9 Bq/kg to 0.04 Bq/kg in 40K. The purification methods are much less efficient for chemically very similar radioactive elements like actinium, lanthanum and lutetium.

  3. Cerium; crystal structure and position in the periodic table.

    PubMed

    Johansson, Börje; Luo, Wei; Li, Sa; Ahuja, Rajeev

    2014-09-17

    The properties of the cerium metal have intrigued physicists and chemists for many decades. In particular a lot of attention has been directed towards its high pressure behavior, where an isostructural volume collapse (γ phase → α phase) has been observed. Two main models of the electronic aspect of this transformation have been proposed; one where the 4f electron undergoes a change from being localized into an itinerant metallic state, and one where the focus is on the interaction between the 4f electron and the conduction electrons, often referred to as the Kondo volume collapse model. However, over the years it has been repeatedly questioned whether the cerium collapse really is isostructural. Most recently, detailed experiments have been able to remove this worrisome uncertainty. Therefore the isostructural aspect of the α-γ transition has now to be seriously addressed in the theoretical modeling, something which has been very much neglected. A study of this fundamental characteristic of the cerium volume collapse is made in present paper and we show that the localized [rlhar2 ] delocalized 4f electron picture provides an adequate description of this unique behavior. This agreement makes it possible to suggest that an appropriate crossroad position for cerium in The Periodic Table.

  4. Cerium; Crystal Structure and Position in The Periodic Table

    PubMed Central

    Johansson, Börje; Luo, Wei; Li, Sa; Ahuja, Rajeev

    2014-01-01

    The properties of the cerium metal have intrigued physicists and chemists for many decades. In particular a lot of attention has been directed towards its high pressure behavior, where an isostructural volume collapse (γ phase → α phase) has been observed. Two main models of the electronic aspect of this transformation have been proposed; one where the 4f electron undergoes a change from being localized into an itinerant metallic state, and one where the focus is on the interaction between the 4f electron and the conduction electrons, often referred to as the Kondo volume collapse model. However, over the years it has been repeatedly questioned whether the cerium collapse really is isostructural. Most recently, detailed experiments have been able to remove this worrisome uncertainty. Therefore the isostructural aspect of the α-γ transition has now to be seriously addressed in the theoretical modeling, something which has been very much neglected. A study of this fundamental characteristic of the cerium volume collapse is made in present paper and we show that the localized ⇌ delocalized 4f electron picture provides an adequate description of this unique behavior. This agreement makes it possible to suggest that an appropriate crossroad position for cerium in The Periodic Table. PMID:25227991

  5. 40 CFR 721.8657 - Cerium, hydroxy oleate propionate complexes.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... complexes. 721.8657 Section 721.8657 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED... Specific Chemical Substances § 721.8657 Cerium, hydroxy oleate propionate complexes. (a) Chemical substance..., hydroxy oleate propionate complexes (PMN P-99-0026) is subject to reporting under this section for...

  6. Electrode electrolyte interlayers containing cerium oxide for electrochemical fuel cells

    DOEpatents

    Borglum, Brian P.; Bessette, Norman F.

    2000-01-01

    An electrochemical cell is made having a porous fuel electrode (16) and a porous air electrode (13), with solid oxide electrolyte (15) therebetween, where the air electrode surface opposing the electrolyte has a separate, attached, dense, continuous layer (14) of a material containing cerium oxide, and where electrolyte (16) contacts the continuous oxide layer (14), without contacting the air electrode (13).

  7. Cerium as a surrogate in the plutonium immobilization waste form

    NASA Astrophysics Data System (ADS)

    Marra, James Christopher

    In the aftermath of the Cold War, approximately 50 tonnes (MT) of weapons useable plutonium (Pu) has been identified as excess. The U.S. Department of Energy (DOE) has decided that at least a portion of this material will be immobilized in a titanate-based ceramic for final disposal in a geologic repository. The baseline formulation was designed to produce a ceramic consisting primarily of a highly substituted pyrochlore with minor amounts of brannerite and hafnia-substituted rutile. Since development studies with actual actinide materials is difficult, surrogates have been used to facilitate testing. Cerium has routinely been used as an actinide surrogate in actinide chemistry and processing studies. Although cerium appeared as an adequate physical surrogate for powder handling and general processing studies, cerium was found to act significantly different from a chemical perspective in the Pu ceramic form. The reduction of cerium at elevated temperatures caused different reaction paths toward densification of the respective forms resulting in different phase assemblages and microstructural features. Single-phase fabrication studies and cerium oxidation state analyses were performed to further quantify these behavioral differences. These studies indicated that the major phases in the final phase assemblages contained point defects likely leading to their stability. Additionally, thermochemical arguments predicted that the predominant pyrochlore phase in the ceramic was metastable. The apparent metastabilty associated with primary phase in the Pu ceramic form indicated that additional studies must be performed to evaluate the thermodynamic properties of these compounds. Moreover, the metastability of this predominant phase must be considered in assessment of long-term behavior (e.g. radiation stability) of this ceramic.

  8. [Determination of silver and cerium in the liver and the kidney from a severely burned infant treated with silver sulfadiazine and cerium nitrate].

    PubMed

    Hirakawa, K

    1983-02-01

    Silver and cerium in the liver and the kidney from severely burned infant were analyzed by neutron activation method. The patient was treated topically with cerium nitrate/silver sulfadiazine cream and cerium nitrate solution for 3 months. Then, the treatment with these drugs was stopped because of abdominal distention. The patient died 1 month after the cessation of the treatment with these drugs. The tissue specimens, blank liver sample and reference standards were irradiated with TRIGA MARK II Reactor of Rikkyo University. About 1 month after the irradiation, the activities were measured with a Ge(Li) detector coupled to a 4096 channel pulse height analyzer. A large amount of silver was detected both in the liver and in the kidney and a trace of cerium only in the liver. A considerable amount of silver was detected in the liver and its quantity was about 1600 times more than that of normal livers reported by Hamilton, Minski and Cleary (1972-73). Neither silver nor cerium were detected in the blank liver. These results suggest that prolonged topical chemotherapy of cerium nitrate/silver sulfadiazine cream and cerium nitrate solution for the extensive burn injuries causes considerable absorption of silver and cerium into the liver and the kidney. PMID:6867381

  9. Thin tungsten telluride layer preparation by thermal annealing.

    PubMed

    Lu, Wei; Zhang, Yudao; Zhu, Zusong; Lai, Jiawei; Zhao, Chuan; Liu, Xuefeng; Liu, Jing; Sun, Dong

    2016-10-14

    We report a simple method to prepare a thin Tungsten Telluride (WTe2) flake with accurate thickness control, which allows preparing and studying this two dimensional material conveniently. First, the WTe2 flake, which is relatively thick due to its strong interlayer van der Waals forces, is obtained by a conventional mechanical exfoliation method. Then, the exfoliated flake is annealed at 600 °C under a constant Ar protecting flow. Raman and atomic force spectroscopy characterizations demonstrate that thermal annealing can effectively thin down the WTe2 flake and retain its original lattice structure, though its surface smoothness is slightly deteriorated. Additionally, systematical study indicates that the thinning process strongly depends on the initial thickness of the WTe2 flake before annealing: the thinning rate increases from 0.12 nm min(-1) to 0.36 nm min(-1) as the initial thickness increases from 10 nm to 45 nm, while the roughness of the final product also increases with the increase of its initial thickness. However, the method fails when it is applied to WTe2 flakes thicker than 100 nm, resulting in uneven or burnt surface, which is possibly caused by big cavities formed by a large amount of defects gathered at the top surface.

  10. Bismuth telluride nanostructures: preparation, thermoelectric properties and topological insulating effect

    NASA Astrophysics Data System (ADS)

    Ashalley, Eric; Chen, Haiyuan; Tong, Xin; Li, Handong; Wang, Zhiming M.

    2015-05-01

    Bismuth telluride is known to wield unique properties for a wide range of device applications. However, as devices migrate to the nanometer scale, significant amount of studies are being conducted to keep up with the rapidly growing nanotechnological field. Bi2Te3 possesses distinctive properties at the nanometer level from its bulk material. Therefore, varying synthesis and characterization techniques are being employed for the realization of various Bi2Te3 nanostructures in the past years. A considerable number of these works have aimed at improving the thermoelectric (TE) figure-of-merit (ZT) of the Bi2Te3 nanostructures and drawing from their topological insulating properties. This paper reviews the various Bi2Te3 and Bi2Te3-based nanostructures realized via theoretical and experimental procedures. The study probes the preparation techniques, TE properties and the topological insulating effects of 0D, 1D, 2D and Bi2Te3 nanocomposites. With several applications as a topological insulator (TI), the topological insulating effect of the Bi2Te3 is reviewed in detail with the time reversal symmetry (TRS) and surface state spins which characterize TIs. Schematics and preparation methods for the various nanostructural dimensions are accordingly categorized.

  11. Quasiparticle electronic structure of bismuth telluride in the GW approximation

    NASA Astrophysics Data System (ADS)

    Kioupakis, Emmanouil; Tiago, Murilo L.; Louie, Steven G.

    2010-12-01

    The quasiparticle band structure of bismuth telluride (Bi2Te3) , an important thermoelectric material that exhibits topologically insulating surface states, is calculated from first principles in the GW approximation. The quasiparticle energies are evaluated in fine detail in the first Brillouin zone using a Wannier-function interpolation method, allowing the accurate determination of the location of the band extrema (which is in the mirror plane) as well as the values of the quasiparticle band gap (0.17 eV) and effective-mass tensors. Spin-orbit interaction effects were included. The valence band exhibits two distinct maxima in the mirror plane that differ by just 1 meV, giving rise to one direct and one indirect band gap of very similar magnitude. The effective-mass tensors are in reasonable agreement with experiment. The Wannier interpolation coefficients can be used for the tight-binding parametrization of the band structure. Our work elucidates the electronic structure of Bi2Te3 and sheds light on its exceptional thermoelectric and topologically insulating properties.

  12. Thickness-induced structural phase transformation of layered gallium telluride.

    PubMed

    Zhao, Q; Wang, T; Miao, Y; Ma, F; Xie, Y; Ma, X; Gu, Y; Li, J; He, J; Chen, B; Xi, S; Xu, L; Zhen, H; Yin, Z; Li, J; Ren, J; Jie, W

    2016-07-28

    The thickness-dependent electronic states and physical properties of two-dimensional materials suggest great potential applications in electronic and optoelectronic devices. However, the enhanced surface effect in ultra-thin materials might significantly influence the structural stability, as well as the device reliability. Here, we report a spontaneous phase transformation of gallium telluride (GaTe) that occurred when the bulk was exfoliated to a few layers. Transmission electron microscopy (TEM) results indicate a structural variation from a monoclinic to a hexagonal structure. Raman spectra suggest a critical thickness for the structural transformation. First-principle calculations and thermodynamic analysis show that the surface energy and the interlayer interaction compete to dominate structural stability in the thinning process. A two-stage transformation process from monoclinic (m) to tetragonal (T) and then from tetragonal to hexagonal (h) is proposed to understand the phase transformation. The results demonstrate the crucial role of interlayer interactions in the structural stability, which provides a phase engineering strategy for device applications. PMID:27198938

  13. In-Plane Optical Anisotropy of Layered Gallium Telluride.

    PubMed

    Huang, Shengxi; Tatsumi, Yuki; Ling, Xi; Guo, Huaihong; Wang, Ziqiang; Watson, Garrett; Puretzky, Alexander A; Geohegan, David B; Kong, Jing; Li, Ju; Yang, Teng; Saito, Riichiro; Dresselhaus, Mildred S

    2016-09-27

    Layered gallium telluride (GaTe) has attracted much attention recently, due to its extremely high photoresponsivity, short response time, and promising thermoelectric performance. Different from most commonly studied two-dimensional (2D) materials, GaTe has in-plane anisotropy and a low symmetry with the C2h(3) space group. Investigating the in-plane optical anisotropy, including the electron-photon and electron-phonon interactions of GaTe is essential in realizing its applications in optoelectronics and thermoelectrics. In this work, the anisotropic light-matter interactions in the low-symmetry material GaTe are studied using anisotropic optical extinction and Raman spectroscopies as probes. Our polarized optical extinction spectroscopy reveals the weak anisotropy in optical extinction spectra for visible light of multilayer GaTe. Polarized Raman spectroscopy proves to be sensitive to the crystalline orientation of GaTe, and shows the intricate dependences of Raman anisotropy on flake thickness, photon and phonon energies. Such intricate dependences can be explained by theoretical analyses employing first-principles calculations and group theory. These studies are a crucial step toward the applications of GaTe especially in optoelectronics and thermoelectrics, and provide a general methodology for the study of the anisotropy of light-matter interactions in 2D layered materials with in-plane anisotropy. PMID:27529802

  14. Ambient temperature cadmium zinc telluride radiation detector and amplifier circuit

    DOEpatents

    McQuaid, James H.; Lavietes, Anthony D.

    1998-05-29

    A low noise, low power consumption, compact, ambient temperature signal amplifier for a Cadmium Zinc Telluride (CZT) radiation detector. The amplifier can be used within a larger system (e.g., including a multi-channel analyzer) to allow isotopic analysis of radionuclides in the field. In one embodiment, the circuit stages of the low power, low noise amplifier are constructed using integrated circuit (IC) amplifiers , rather than discrete components, and include a very low noise, high gain, high bandwidth dual part preamplification stage, an amplification stage, and an filter stage. The low noise, low power consumption, compact, ambient temperature amplifier enables the CZT detector to achieve both the efficiency required to determine the presence of radio nuclides and the resolution necessary to perform isotopic analysis to perform nuclear material identification. The present low noise, low power, compact, ambient temperature amplifier enables a CZT detector to achieve resolution of less than 3% full width at half maximum at 122 keV for a Cobalt-57 isotope source. By using IC circuits and using only a single 12 volt supply and ground, the novel amplifier provides significant power savings and is well suited for prolonged portable in-field use and does not require heavy, bulky power supply components.

  15. Ambient temperature cadmium zinc telluride radiation detector and amplifier circuit

    DOEpatents

    McQuaid, J.H.; Lavietes, A.D.

    1998-05-26

    A low noise, low power consumption, compact, ambient temperature signal amplifier for a Cadmium Zinc Telluride (CZT) radiation detector is disclosed. The amplifier can be used within a larger system (e.g., including a multi-channel analyzer) to allow isotopic analysis of radionuclides in the field. In one embodiment, the circuit stages of the low power, low noise amplifier are constructed using integrated circuit (IC) amplifiers , rather than discrete components, and include a very low noise, high gain, high bandwidth dual part preamplification stage, an amplification stage, and an filter stage. The low noise, low power consumption, compact, ambient temperature amplifier enables the CZT detector to achieve both the efficiency required to determine the presence of radionuclides and the resolution necessary to perform isotopic analysis to perform nuclear material identification. The present low noise, low power, compact, ambient temperature amplifier enables a CZT detector to achieve resolution of less than 3% full width at half maximum at 122 keV for a Cobalt-57 isotope source. By using IC circuits and using only a single 12 volt supply and ground, the novel amplifier provides significant power savings and is well suited for prolonged portable in-field use and does not require heavy, bulky power supply components. 9 figs.

  16. A cadmium-zinc-telluride crystal array spectrometer

    SciTech Connect

    H. R. McHugh; W. Quam; T. DeVore; R. Vogle; J. Weslowski

    2003-09-01

    This paper describes a gamma detector employing an array of eight cadmium-zinc-telluride (CZT) crystals configured as a high resolution gamma ray spectrometer. This detector is part of a more complex instrument that identifies the isotope,displays this information, and records the gamma spectrum. Various alarms and other operator features are incorporated in this battery operated rugged instrument. The CZT detector is the key component of this instrument and will be described in detail in this paper. We have made extensive spectral measurements of the usual laboratory gamma sources, common medical isotopes, and various Special Nuclear Materials (SNM) with this detector. Some of these data will be presented as spectra. We will also present energy resolution and detection efficiency for the basic 8-crystal array. Additional data will also be presented for a 32-crystal array. The basic 8-crystal array development was completed two years ago, and the system electronic design has been imp roved recently. This has resulted in significantly improved noise performance. We expect to have a much smaller detector package, using 8 crystals, in a few months. This package will use flip-chip packaging to reduce the electronics physical size by a factor of 5.

  17. Vapor crystal growth technology development: Application to cadmium telluride

    NASA Technical Reports Server (NTRS)

    Rosenberger, Franz; Banish, Michael; Duval, Walter M. B.

    1991-01-01

    Growth of bulk crystals by physical vapor transport was developed and applied to cadmium telluride. The technology makes use of effusive ampoules, in which part of the vapor contents escapes to a vacuum shroud through defined leaks during the growth process. This approach has the advantage over traditional sealed ampoule techniques that impurity vapors and excess vapor constituents are continuously removed from the vicinity of the growing crystal. Thus, growth rates are obtained routinely at magnitudes that are rather difficult to achieve in closed ampoules. Other advantages of this effusive ampoule physical vapor transport (EAPVT) technique include the predetermination of transport rates based on simple fluid dynamics and engineering considerations, and the growth of the crystal from close to congruent vapors, which largely alleviates the compositional nonuniformities resulting from buoyancy driven convective transport. After concisely reviewing earlier work on improving transport rates, nucleation control, and minimization of crystal wall interactions in vapor crystal growth, a detail account is given of the largely computer controlled EAPVT experimentation.

  18. Transient Response of Cadmium Telluride Modules to Light Exposure

    SciTech Connect

    Deline, C.; Del Cueto, J.; Albin, D. S.; Petersen, C.; Tyler, L.; TamizhMani, G.

    2011-01-01

    Commercial cadmium telluride (CdTe) photovoltaic (PV) modules from three different manufacturers were monitored for performance changes during indoor and outdoor light-exposure. Short-term transients in V{sub oc} were recorded on some modules, with characteristic times of {approx}1.1 hours. Outdoor performance data shows a similar drop in V{sub oc} after early morning light exposure. Preliminary analysis of FF changes show light-induced changes on multiple time scales, including a long time scale. Multiple methods of measuring {beta}V{sub oc} resulted in a range of values on the same CdTe PV module between -0.25%/C and -0.4%/C, possibly due to concurrent light-induced V{sub oc} transients and temperature changes. This paper highlights the need for rapid performance measurement of PV samples following light exposure and the possibility of incorrect results when using outdoor light exposure to collect values of {beta}V{sub oc} for CdTe modules.

  19. Compensation mechanism of bromine dopants in cadmium telluride single crystals

    DOE PAGES

    Bolotnikov, A. E.; Fochuk, P. M.; Verzhak, Ye. V.; Parashchuk, T. O.; Freik, D. M.; Panchuk, O. E.; James, R. B.; Gorichok, I. V.

    2015-01-02

    We grew single crystals of cadmium telluride, doped with bromine by the Bridgman method, annealed them under a cadmium overpressure (PCd = 10² - 10⁵ Pa) at 800-1100 K, and investigated their electrical properties at high- and low-temperature. The influence of impurities on the crystals' electrical properties were analyzed using the defect subsystem model; the model includes the possibility of the formation of point intrinsic defects (V²⁻Cd, Cd²⁺i, V²⁺Te, Te²⁻i), and substitutional ones (Br⁰Te, Br⁺Te), as well as complexes of point defects, i.e., (Br⁺Te V²⁻Cd)⁻ and (2Br⁺Te V²⁻Cd)⁰. We established the concentration dependence between free charge carriers and themore » parameters of the annealing process. Here, n(T) and n(PCd) are determined by two dominant defects – Br⁺Te and (2Br⁺Te V²⁻Cd)⁰. Their content varies with the annealing temperature and the vapor pressure of the component; the concentration of other defects is much smaller and almost does not affect the electron density.« less

  20. Thickness-induced structural phase transformation of layered gallium telluride.

    PubMed

    Zhao, Q; Wang, T; Miao, Y; Ma, F; Xie, Y; Ma, X; Gu, Y; Li, J; He, J; Chen, B; Xi, S; Xu, L; Zhen, H; Yin, Z; Li, J; Ren, J; Jie, W

    2016-07-28

    The thickness-dependent electronic states and physical properties of two-dimensional materials suggest great potential applications in electronic and optoelectronic devices. However, the enhanced surface effect in ultra-thin materials might significantly influence the structural stability, as well as the device reliability. Here, we report a spontaneous phase transformation of gallium telluride (GaTe) that occurred when the bulk was exfoliated to a few layers. Transmission electron microscopy (TEM) results indicate a structural variation from a monoclinic to a hexagonal structure. Raman spectra suggest a critical thickness for the structural transformation. First-principle calculations and thermodynamic analysis show that the surface energy and the interlayer interaction compete to dominate structural stability in the thinning process. A two-stage transformation process from monoclinic (m) to tetragonal (T) and then from tetragonal to hexagonal (h) is proposed to understand the phase transformation. The results demonstrate the crucial role of interlayer interactions in the structural stability, which provides a phase engineering strategy for device applications.

  1. Induced Positron Annihiliation Investigation of Cadmium Zinc Telluride Crystal Microstructures

    SciTech Connect

    D. W. Akers

    2005-06-01

    Cadmium-Zinc-Telluride (CZT) crystals are used in semiconductor radiation detectors for the detection of x-ray and gamma radiation. However, production of detector grade crystals is difficult as small variations in compositional uniformity and primarily the zinc content can significantly affect the ability of the CZT crystal to function as a radiation detector. Currently there are no known nondestructive methods that can be used to identify detector grade crystals. The current test method is to fabricate and test the detector to determine if the crystal is sufficiently uniform and of the correct composition to be considered a detector grade crystal. Consequently, nondestructive detection methods are needed to identify detector grade crystals prior to the fabrication process. The purpose of this feasibility study was to perform a preliminary assessment of the ability of several new, nondestructive technologies based on Induced Positron Annihilation (IPA) to determine if detector grade CZT crystals can be identified. Results of measurements performed on specimens from Fisk University and EV Products, Inc. indicate that both the near surface Distributed Source Positron Annihilation (up to 3 mm penetration) and the volumetric Photon Induced Positron Annihilation methods may be suitable for determining CZT crystal quality. Further work on CZT crystals with a broader range of compositions and detector characteristics is needed to provide a well defined, calibrated, method for assessing CZT crystal quality.

  2. Brief review of cadmium telluride-based photovoltaic technologies

    NASA Astrophysics Data System (ADS)

    Başol, Bülent M.; McCandless, Brian

    2014-01-01

    Cadmium telluride (CdTe) is the most commercially successful thin-film photovoltaic technology. Development of CdTe as a solar cell material dates back to the early 1980s when ˜10% efficient devices were demonstrated. Implementation of better quality glass, more transparent conductive oxides, introduction of a high-resistivity transparent film under the CdS junction-partner, higher deposition temperatures, and improved Cl-treatment, doping, and contacting approaches yielded >16% efficient cells in the early 2000s. Around the same time period, use of a photoresist plug monolithic integration process facilitated the demonstration of the first 11% efficient module. The most dramatic advancements in CdTe device efficiencies were made during the 2013 to 2014 time frame when small-area cell conversion efficiency was raised to 20% range and a champion module efficiency of 17% was reported. CdTe technology is attractive in terms of its limited life-cycle greenhouse gas and heavy metal emissions, small carbon footprint, and short energy payback times. Limited Te availability is a challenge for the growth of this technology unless Te utilization rates are greatly enhanced along with device efficiencies.

  3. Thin tungsten telluride layer preparation by thermal annealing.

    PubMed

    Lu, Wei; Zhang, Yudao; Zhu, Zusong; Lai, Jiawei; Zhao, Chuan; Liu, Xuefeng; Liu, Jing; Sun, Dong

    2016-10-14

    We report a simple method to prepare a thin Tungsten Telluride (WTe2) flake with accurate thickness control, which allows preparing and studying this two dimensional material conveniently. First, the WTe2 flake, which is relatively thick due to its strong interlayer van der Waals forces, is obtained by a conventional mechanical exfoliation method. Then, the exfoliated flake is annealed at 600 °C under a constant Ar protecting flow. Raman and atomic force spectroscopy characterizations demonstrate that thermal annealing can effectively thin down the WTe2 flake and retain its original lattice structure, though its surface smoothness is slightly deteriorated. Additionally, systematical study indicates that the thinning process strongly depends on the initial thickness of the WTe2 flake before annealing: the thinning rate increases from 0.12 nm min(-1) to 0.36 nm min(-1) as the initial thickness increases from 10 nm to 45 nm, while the roughness of the final product also increases with the increase of its initial thickness. However, the method fails when it is applied to WTe2 flakes thicker than 100 nm, resulting in uneven or burnt surface, which is possibly caused by big cavities formed by a large amount of defects gathered at the top surface. PMID:27608057

  4. Compensation mechanism of bromine dopants in cadmium telluride single crystals

    SciTech Connect

    Bolotnikov, A. E.; Fochuk, P. M.; Verzhak, Ye. V.; Parashchuk, T. O.; Freik, D. M.; Panchuk, O. E.; James, R. B.; Gorichok, I. V.

    2015-01-02

    We grew single crystals of cadmium telluride, doped with bromine by the Bridgman method, annealed them under a cadmium overpressure (PCd = 10² - 10⁵ Pa) at 800-1100 K, and investigated their electrical properties at high- and low-temperature. The influence of impurities on the crystals' electrical properties were analyzed using the defect subsystem model; the model includes the possibility of the formation of point intrinsic defects (V²⁻Cd, Cd²⁺i, V²⁺Te, Te²⁻i), and substitutional ones (Br⁰Te, Br⁺Te), as well as complexes of point defects, i.e., (Br⁺Te V²⁻Cd)⁻ and (2Br⁺Te V²⁻Cd)⁰. We established the concentration dependence between free charge carriers and the parameters of the annealing process. Here, n(T) and n(PCd) are determined by two dominant defects – Br⁺Te and (2Br⁺Te V²⁻Cd)⁰. Their content varies with the annealing temperature and the vapor pressure of the component; the concentration of other defects is much smaller and almost does not affect the electron density.

  5. Thin tungsten telluride layer preparation by thermal annealing

    NASA Astrophysics Data System (ADS)

    Lu, Wei; Zhang, Yudao; Zhu, Zusong; Lai, Jiawei; Zhao, Chuan; Liu, Xuefeng; Liu, Jing; Sun, Dong

    2016-10-01

    We report a simple method to prepare a thin Tungsten Telluride (WTe2) flake with accurate thickness control, which allows preparing and studying this two dimensional material conveniently. First, the WTe2 flake, which is relatively thick due to its strong interlayer van der Waals forces, is obtained by a conventional mechanical exfoliation method. Then, the exfoliated flake is annealed at 600 °C under a constant Ar protecting flow. Raman and atomic force spectroscopy characterizations demonstrate that thermal annealing can effectively thin down the WTe2 flake and retain its original lattice structure, though its surface smoothness is slightly deteriorated. Additionally, systematical study indicates that the thinning process strongly depends on the initial thickness of the WTe2 flake before annealing: the thinning rate increases from 0.12 nm min-1 to 0.36 nm min-1 as the initial thickness increases from 10 nm to 45 nm, while the roughness of the final product also increases with the increase of its initial thickness. However, the method fails when it is applied to WTe2 flakes thicker than 100 nm, resulting in uneven or burnt surface, which is possibly caused by big cavities formed by a large amount of defects gathered at the top surface.

  6. High efficiency thin film cadmium telluride solar cells

    NASA Astrophysics Data System (ADS)

    Chu, T. L.; Chu, Shirley S.; Britt, J.; Chen, G.; Ferekides, C.; Schultz, N.; Wang, C.; Wu, C. Q.

    1992-12-01

    Cadmium sulfide (CdS), grown from an aqueous solution, and zinc oxide (ZnO), cadmium zinc sulfide (Cd1-xZnxS), and zinc selenide (ZnSe), deposited by metalorganic chemical vapor deposition (MOCVD), have been used as the window for thin film cadmium telluride (CdTe) solar cells. Thin film solar cells were prepared by the successive deposition of the window and p-CdTe (by MOCVD and close-spaced sublimation, CSS) on SnO2:F/glass substrates. CdS/CdTe(CSS) solar cells show considerably better characteristics than CdS/CdTe(MOCVD) solar cells because of the better microstructure of CSS CdTe films. Total area conversion efficiency of 14.6%, verified by the National Renewable Energy Laboratory, has been achieved for solar cells of about 1 cm2 area. Solar cell prepared by using ZnO, ZnSe, or Cd1-xZnxS as window have significantly lower photovoltage than CdS/CdTe solar cells.

  7. In-Plane Optical Anisotropy of Layered Gallium Telluride.

    PubMed

    Huang, Shengxi; Tatsumi, Yuki; Ling, Xi; Guo, Huaihong; Wang, Ziqiang; Watson, Garrett; Puretzky, Alexander A; Geohegan, David B; Kong, Jing; Li, Ju; Yang, Teng; Saito, Riichiro; Dresselhaus, Mildred S

    2016-09-27

    Layered gallium telluride (GaTe) has attracted much attention recently, due to its extremely high photoresponsivity, short response time, and promising thermoelectric performance. Different from most commonly studied two-dimensional (2D) materials, GaTe has in-plane anisotropy and a low symmetry with the C2h(3) space group. Investigating the in-plane optical anisotropy, including the electron-photon and electron-phonon interactions of GaTe is essential in realizing its applications in optoelectronics and thermoelectrics. In this work, the anisotropic light-matter interactions in the low-symmetry material GaTe are studied using anisotropic optical extinction and Raman spectroscopies as probes. Our polarized optical extinction spectroscopy reveals the weak anisotropy in optical extinction spectra for visible light of multilayer GaTe. Polarized Raman spectroscopy proves to be sensitive to the crystalline orientation of GaTe, and shows the intricate dependences of Raman anisotropy on flake thickness, photon and phonon energies. Such intricate dependences can be explained by theoretical analyses employing first-principles calculations and group theory. These studies are a crucial step toward the applications of GaTe especially in optoelectronics and thermoelectrics, and provide a general methodology for the study of the anisotropy of light-matter interactions in 2D layered materials with in-plane anisotropy.

  8. Fundamental aspects of regenerative cerium oxide nanoparticles and their applications in nanobiotechnology

    NASA Astrophysics Data System (ADS)

    Patil, Swanand D.

    Cerium oxide has been used extensively for various applications over the past two decades. The use of cerium oxide nanoparticles is beneficial in present applications and can open avenues for future applications. The present study utilizes the microemulsion technique to synthesize uniformly distributed cerium oxide nanoparticles. The same technique was also used to synthesize cerium oxide nanoparticles doped with trivalent elements (La and Nd). The fundamental study of cerium oxide nanoparticles identified variations in properties as a function of particle size and also due to doping with trivalent elements (La and Nd). It was found that the lattice parameter of cerium oxide nanoparticles increases with decrease in particle size. Also Raman allowed mode shift to lower energies and the peak at 464 cm-1 becomes broader and asymmetric. The size dependent changes in cerium oxide were correlated to increase in oxygen vacancy concentration in the cerium oxide lattice. The doping of cerium oxide nanoparticles with trivalent elements introduces more oxygen vacancies and expands the cerium oxide lattice further (in addition to the lattice expansion due to the size effect). The lattice expansion is greater for La-doped cerium oxide nanoparticles compared to Nd-doping due to the larger ionic radius of La compared to Nd, the lattice expansion is directly proportional to the dopant concentration. The synthesized cerium oxide nanoparticles were used to develop an electrochemical biosensor of hydrogen peroxide (H2O2). The sensor was useful to detect H2O2 concentrations as low as 1muM in water. Also the preliminary testing of the sensor on tomato stem and leaf extracts indicated that the sensor can be used in practical applications such as plant physiological studies etc. The nanomolar concentrations of cerium oxide nanoparticles were also found to be useful in decreasing ROS (reactive oxygen species) mediated cellular damages in various in vitro cell cultures. Cerium oxide

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

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaodong; Moore, Michael E.; Lee, Kyung-Min; Lukosi, Eric D.; Hayward, Jason P.

    2016-07-01

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

  10. Fabrication of Nanovoid-Imbedded Bismuth Telluride with Low Dimensional System

    NASA Technical Reports Server (NTRS)

    Chu, Sang-Hyon (Inventor); Choi, Sang H. (Inventor); Kim, Jae-Woo (Inventor); Park, Yeonjoon (Inventor); Elliott, James R. (Inventor); King, Glen C. (Inventor); Stoakley, Diane M. (Inventor)

    2013-01-01

    A new fabrication method for nanovoids-imbedded bismuth telluride (Bi--Te) material with low dimensional (quantum-dots, quantum-wires, or quantum-wells) structure was conceived during the development of advanced thermoelectric (TE) materials. Bismuth telluride is currently the best-known candidate material for solid-state TE cooling devices because it possesses the highest TE figure of merit at room temperature. The innovative process described here allows nanometer-scale voids to be incorporated in Bi--Te material. The final nanovoid structure such as void size, size distribution, void location, etc. can be also controlled under various process conditions.

  11. Isomorphic phase transformation in shocked cerium using molecular dynamics

    SciTech Connect

    Dupont, Virginie; Germann, Timothy C; Chen, Shao - Ping

    2010-08-12

    Cerium (Ce) undergoes a significant ({approx}16%) volume collapse associated with an isomorphic fcc-fcc phase transformation when subject to compressive loading. We present here a new Embedded Atom Method (EAM) potential for Cerium that models two minima for the two fcc phases. We show results from its use in Molecular Dynamics (MD) simulations of Ce samples subjected to shocks with pressures ranging from 0.5 to 25 GPa. A split wave structure is observed, with an elastic precursor followed by a plastic wave. The plastic wave causes the expected fcc-fcc phase transformation. Comparisons to experiments and MD simulations on Cesium (Cs) indicate that three waves could be observed. The construction of the EAM potential may be the source of the difference.

  12. Liquid-phase oxidation of cyclohexanone over cerium oxide catalyst

    SciTech Connect

    Shen, H.C. ); Weng, H.S. )

    1990-05-01

    Catalytic oxidation of cyclohexanone in the liquid phase with glacial acetic acid as the solvent over cerium oxide was studied between 5 and 15 atm and 98 and 118 {degrees} C in a batch reactor. The products were adipic acid, glutaric acid, succinic acid, caprolactone, carbon oxides, etc. The reaction undergoes a short induction period prior to a rapid reaction regime. In both regimes, the reaction is independent of oxygen pressure when the system pressure is above 10 atm. The induction period is inversely proportional to both of the catalyst weight and cyclohexanone concentration.During the rapid reaction regime, the reaction rate was found to be proportional to the 0.5 power of the catalyst weight and to the 1.5 power of the cyclohexanone concentration. Reaction mechanisms and rate expressions are proposed. The carbon oxides produced in this study were much lower than those previously reported. The cerium oxide catalyst is stable during the reaction.

  13. Engineered cerium oxide nanoparticles: Effects on bacterial growth and viability

    SciTech Connect

    Pelletier, Dale A; Suresh, Anil K; Holton, Gregory A; McKeown, Catherine K; Wang, Wei; Gu, Baohua; Mortensen, Ninell P; Allison, David P; Joy, David Charles; Allison, Martin R; Brown, Steven D; Phelps, Tommy Joe; Doktycz, Mitchel John

    2010-01-01

    Interest in engineered nanostructures has risen in recent years due to their use in energy conservation strategies and biomedicine. To ensure prudent development and use of nanomaterials, the fate and effects of such engineered structures on the environment should be understood. Interactions of nanomaterials with environmental microorganisms are inevitable, but the general consequences of such interactions remain unclear. Further, standardized methods for assessing such interactions are lacking. Therefore, we have initiated a multianalytical approach to understand the interactions of synthesized nanoparticles with bacterial systems. These efforts are focused initially on cerium oxide nanoparticles and model bacteria in order to evaluate characterization procedures and the possible fate of such materials in the environment. In this study the effects of cerium oxide nanoparticles on the growth and viability of Gram-negative Escherichia coli and Shewanella oneidensis, a metal-reducing bacteria, and Gram-positive Bacillus subtilis were examined relative to particle size, growth media, pH, and dosage. A hydrothermal based synthesis procedure was used to prepare cerium oxide nanoparticles of defined sizes in order to eliminate complications originating from the use of organic solvents and surfactants. Bactericidal effects were determined by minimum inhibitory concentration, colony forming units, disc diffusion tests and Live/Dead assays. In growth inhibition experiments involving E. coli and B. subtilis, a clear strain and size-dependent inhibition was observed. S. oneidensis appeared to be unaffected by the cerium oxide nanoparticles. Transmission electron microscopy along with microarray-based transcriptional profiling have been used to understand the response mechanism of the bacteria. The use of multiple analytical approaches adds confidence to toxicity assessments while the use of different bacterial systems highlights the potential wide-ranging effects of

  14. Monomers, Dimers, and Helices: Complexities of Cerium and Plutonium Phenanthrolinecarboxylates.

    PubMed

    Cary, Samantha K; Ferrier, Maryline G; Baumbach, Ryan E; Silver, Mark A; Lezama Pacheco, Juan; Kozimor, Stosh A; La Pierre, Henry S; Stein, Benjamin W; Arico, Alexandra A; Gray, Danielle L; Albrecht-Schmitt, Thomas E

    2016-05-01

    The reaction of Ce(III) or Pu(III) with 1,10-phenanthroline-2,9-dicarboxylic acid (PDAH2) results in the formation of new f-element coordination complexes. In the case of cerium, Ce(PDA)(H2O)2Cl·H2O (1) or [Ce(PDAH)(PDA)]2[Ce(PDAH)(PDA)] (2) was isolated depending on the Ce/ligand ratio in the reaction. The structure of 2 is composed of two distinct substructures that are constructed from the same monomer. This monomer is composed of a Ce(III) cation bound by one PDA(2-) dianionic ligand and one PDAH(-) monoanionic ligand, both of which are tetradentate. Bridging by the carboxylate moieties leads to either [Ce(PDAH)(PDA)]2 dimers or [Ce(PDAH)(PDA)]1∞ helical chains. For plutonium, Pu(PDA)2 (3) was the only product isolated regardless of the Pu/ligand ratio employed in the reaction. During the reaction of plutonium with PDAH2, Pu(III) is oxidized to Pu(IV), generating 3. This assignment is consistent with structural metrics and the optical absorption spectrum. Ambiguity in the assignment of the oxidation state of cerium in 1 and 2 from UV-vis-near-IR spectra invoked the use of Ce L3,2-edge X-ray absorption near-edge spectroscopy, magnetic susceptibility, and heat capacity measurements. These experiments support the assignment of Ce(III) in both compounds. The bond distances and coordination numbers are also consistent with these assignments. 3 contains 8-coordinate Pu(IV), whereas the cerium centers in 1 and 2 are 9- and/or 10-coordinate, which correlates with the increased size of Ce(III) versus Pu(IV). Taken together, these data provide an example of a system where the differences in the redox behavior between these f elements creates more complex chemistry with cerium than with plutonium. PMID:27070401

  15. Fungus mediated synthesis of biomedically important cerium oxide nanoparticles

    SciTech Connect

    Khan, Shadab Ali; Ahmad, Absar

    2013-10-15

    Graphical abstract: - Highlights: • First time biological synthesis of cerium oxide oxide nanoparticles using fungus Humicola sp. • Complete characterization of cerium oxide nanoparticles. • Biosynthesis of naturally protein capped, luminescent and water dispersible CeO{sub 2} nanoparticles. • Biosynthesized CeO{sub 2} nanoparticles can be used for many biomedical applications. - Abstract: Nanomaterials can be synthesized by chemical, physical and the more recently discovered biological routes. The biological routes are advantageous over the chemical and physical ones as unlike these, the biological synthesis protocols occur at ambient conditions, are cheap, non-toxic and eco-friendly. Although purely biological and bioinspired methods for the synthesis of nanomaterials are environmentally benign and energy conserving processes, their true potential has not been explored yet and attempts are being made to extend the formation of technologically important nanoparticles using microorganisms like fungi. Though there have been reports on the biosynthesis of oxide nanoparticles by our group in the past, no attempts have been made to employ fungi for the synthesis of nanoparticles of rare earth metals or lanthanides. Here we report for the first time, the bio-inspired synthesis of biomedically important cerium oxide (CeO{sub 2}) nanoparticles using the thermophilic fungus Humicola sp. The fungus Humicola sp. when exposed to aqueous solutions of oxide precursor cerium (III) nitrate hexahydrate (CeN{sub 3}O{sub 9}·6H{sub 2}O) results in the extracellular formation of CeO{sub 2} nanoparticles containing Ce (III) and Ce (IV) mixed oxidation states, confirmed by X-ray Photoemission Spectroscopy (XPS). The formed nanoparticles are naturally capped by proteins secreted by the fungus and thus do not agglomerate, are highly stable, water dispersible and are highly fluorescent as well. The biosynthesized nanoparticles were characterized by UV–vis spectroscopy

  16. Optical Response of Shocked Cerium-Doped Lutetium Oxyorthosilicate

    SciTech Connect

    G. D. Stevens

    2003-03-01

    Shock experiments were performed in order to characterize the triboluminescent signature of cerium-doped lutetium oxyorthosilicate (LSO:Ce). This material shows prompt, nano-second timescale light emission when driven by explosive detonation. When properly applied to a surface, it may be used as a shock arrival sensor, and also for imaging the propagation of a shock front. Triboluminescent rise times, spectral content, and spatial resolution measurements are presented.

  17. Directional Solidification of Mercury Cadmium Telluride in Microgravity

    NASA Technical Reports Server (NTRS)

    Lechoczhy, Sandor L.; Gillies, Donald C.; Szofran, Frank R.; Watring, Dale A.

    1998-01-01

    Mercury cadmium telluride (MCT) has been directionally solidified for ten days in the Advanced Automated Directional Solidification Furnace (AADSF) on the second United States Microgravity Payload Mission (USMP-2). A second growth experiment is planned for the USMP-4 mission in November 1997. Results from USMP-2 demonstrated significant changes between microgravity and ground-based experiments, particularly in the compositional homogeneity. Changes were also observed during the microgravity mission which were dependent on the attitude of the space shuttle and the relative magnitudes of axial and transverse residual accelerations with respect to the growth axis of the crystal. Issues of shuttle operation, especially those concerned with safety and navigation, and the science needs of other payloads dictated the need for changes in attitude. One consequence for solidification of MCT in the USMP4 mission is the desire for a shorter growth time to complete the experiment without subjecting the sample to shuttle maneuvers. By using a seeded technique and a pre-processed boule of MCT with an established diffusion layer quenched into the solid, equilibrium steady state growth can be established within 24 hours, rather than the three days needed in USMP-2. The growth of MCT in AADSF during the USMP-4 mission has been planned to take less than 72 hours with 48 hours of actual growth time. A review of the USMP-2 results will be presented, and the rationale for the USMP-4 explained. Pre-mission ground based tests for the USN4P-4 mission will be presented, as will any available preliminary flight results from the mission.

  18. Equilibrium composition in II?VI telluride MOCVD systems

    NASA Astrophysics Data System (ADS)

    Ben-Dor, L.; Greenberg, J. H.

    1999-03-01

    Thermodynamic calculations, or computer simulation of the equilibrium composition, offer an excellent possibility to reduce drastically the elaborate trial-and-error experimental efforts of finding the optimal preparation conditions for MOCVD processes (temperature T, pressure P, initial composition of the vapors X), to limit them only to the P- T- X field of existence of the solid to be prepared and an acceptable yield of the product. In this communication equilibrium composition was investigated for MOCVD processes of CdTe, ZnTe, HgTe and solid solutions Cd xZn 1- xTe and Hg xCd 1- xTe. A number of volatile organometallic compounds have been used as precursors for MOCVD growth. These are dimethylcadmium (CH 3) 2Cd, DMCd; diethylzinc (C 2H 5) 2Zn, DEZn; diisopropylzinc [CH(CH 3) 2] 2Zn, DiPZn; diethyltellurium (C 2H 5) 2Te, DETe; diisopropyltellurium [CH(CH 3) 2] 2Te, DiPTe; methylallyltellurium CH 3TeCH 2CHCH 2, MATe. A choice of the particular combination of the precursors largely depends on the desired composition of the film to be prepared, especially in cases of solid solutions Cd xZn 1- xTe and Hg xCd 1- xTe where the vapor pressure of the precursors is instrumental for the composition of the vapor in the reaction zone and, ultimately, for the composition x of the solid solution. Equilibrium composition for II-VI telluride MOCVD systems was investigated at temperatures up to 873 K in hydrogen and inert gas atmospheres at pressures up to 1 atm. P- T- X regions of existence were outlined for each of the five materials.

  19. Current transport mechanisms in mercury cadmium telluride diode

    NASA Astrophysics Data System (ADS)

    Gopal, Vishnu; Li, Qing; He, Jiale; He, Kai; Lin, Chun; Hu, Weida

    2016-08-01

    This paper reports the results of modelling of the current-voltage characteristics (I-V) of a planar mid-wave Mercury Cadmium Telluride photodiode in a gate controlled diode experiment. It is reported that the diode exhibits nearly ideal I-V characteristics under the optimum surface potential leading to the minimal surface leakage current. Deviations from the optimum surface potential lead to non ideal I-V characteristics, indicating a strong relationship between the ideality factor of the diode with its surface leakage current. Diode's I-V characteristics have been modelled over a range of gate voltages from -9 V to -2 V. This range of gate voltages includes accumulation, flat band, and depletion and inversion conditions below the gate structure of the diode. It is shown that the I-V characteristics of the diode can be very well described by (i) thermal diffusion current, (ii) ohmic shunt current, (iii) photo-current due to background illumination, and (iv) excess current that grows by the process of avalanche multiplication in the gate voltage range from -3 V to -5 V that corresponds to the optimum surface potential. Outside the optimum gate voltage range, the origin of the excess current of the diode is associated with its high surface leakage currents. It is reported that the ohmic shunt current model applies to small surface leakage currents. The higher surface leakage currents exhibit a nonlinear shunt behaviour. It is also shown that the observed zero-bias dynamic resistance of the diode over the entire gate voltage range is the sum of ohmic shunt resistance and estimated zero-bias dynamic resistance of the diode from its thermal saturation current.

  20. Antibacterial Activity of Polymer Coated Cerium Oxide Nanoparticles

    PubMed Central

    Shah, Vishal; Shah, Shreya; Shah, Hirsh; Rispoli, Fred J.; McDonnell, Kevin T.; Workeneh, Selam; Karakoti, Ajay; Kumar, Amit; Seal, Sudipta

    2012-01-01

    Cerium oxide nanoparticles have found numerous applications in the biomedical industry due to their strong antioxidant properties. In the current study, we report the influence of nine different physical and chemical parameters: pH, aeration and, concentrations of MgSO4, CaCl2, KCl, natural organic matter, fructose, nanoparticles and Escherichia coli, on the antibacterial activity of dextran coated cerium oxide nanoparticles. A least-squares quadratic regression model was developed to understand the collective influence of the tested parameters on the anti-bacterial activity and subsequently a computer-based, interactive visualization tool was developed. The visualization allows us to elucidate the effect of each of the parameters in combination with other parameters, on the antibacterial activity of nanoparticles. The results indicate that the toxicity of CeO2 NPs depend on the physical and chemical environment; and in a majority of the possible combinations of the nine parameters, non-lethal to the bacteria. In fact, the cerium oxide nanoparticles can decrease the anti-bacterial activity exerted by magnesium and potassium salts. PMID:23110109

  1. Synthesis and characterization of polyvinylpyrrolidone coated cerium oxide nanoparticles.

    PubMed

    Merrifield, Ruth C; Wang, Zhi Wei; Palmer, Richard E; Lead, Jamie R

    2013-01-01

    There is a pressing need for the development of standard and reference nanomaterials for environmental nanoscience and nanotoxicology. To that aim, suspensions of polyvinylpyrrolidone (PVP)-coated ceria nanoparticles (NPs) were produced. Four differently sized monodispersed samples were produced by using different PVP chain lengths. The chemical and physical properties of these NPs were characterized as prepared and in different ecotoxicology exposure media. Dynamic light scattering analysis showed that the samples were monodispersed, with an unchanged size when suspended in the different media over a 72 h period. Electron microscopy confirmed this and revealed that the larger (ca. 20 nm) particles were aggregates composed of the smaller individual particles (4-5 nm). Electron energy loss spectroscopy (EELS) showed that the smallest and largest samples were composed almost entirely of cerium(III) oxide, with only small amounts of cerium(IV) present in the largest sample. Dissolved cerium concentrations in media were low and constant, showing that the NPs did not dissolve over time. The simple synthesis of the these NPs and their physical and chemical stability in different environmental conditions make them potentially suitable for use as reference materials for (eco)toxicology and surface water environmental studies.

  2. Jet formation in cerium metal to examine material strength

    SciTech Connect

    Jensen, B. J. Cherne, F. J.; Prime, M. B.; Yeager, J. D.; Ramos, K. J.; Hooks, D. E.; Cooley, J. C.; Dimonte, G.; Fezzaa, K.; Iverson, A. J.; Carlson, C. A.

    2015-11-21

    Examining the evolution of material properties at extreme conditions advances our understanding of numerous high-pressure phenomena from natural events like meteorite impacts to general solid mechanics and fluid flow behavior. Recent advances in synchrotron diagnostics coupled with dynamic compression platforms have introduced new possibilities for examining in-situ, spatially resolved material response with nanosecond time resolution. In this work, we examined jet formation from a Richtmyer-Meshkov instability in cerium initially shocked into a transient, high-pressure phase, and then released to a low-pressure, higher-temperature state. Cerium's rich phase diagram allows us to study the yield stress following a shock induced solid-solid phase transition. X-ray imaging was used to obtain images of jet formation and evolution with 2–3 μm spatial resolution. From these images, an analytic method was used to estimate the post-shock yield stress, and these results were compared to continuum calculations that incorporated an experimentally validated equation-of-state (EOS) for cerium coupled with a deviatoric strength model. Reasonable agreement was observed between the calculations and the data illustrating the sensitivity of jet formation on the yield stress values. The data and analysis shown here provide insight into material strength during dynamic loading which is expected to aid in the development of strength aware multi-phase EOS required to predict the response of matter at extreme conditions.

  3. Induction of pulmonary fibrosis by cerium oxide nanoparticles

    SciTech Connect

    Ma, Jane Y.; Mercer, Robert R.; Barger, Mark; Schwegler-Berry, Diane; Scabilloni, James; Ma, Joseph K.; Castranova, Vincent

    2012-08-01

    Cerium compounds have been used as a diesel engine catalyst to lower the mass of diesel exhaust particles, but are emitted as cerium oxide (CeO{sub 2}) nanoparticles in the diesel exhaust. In a previous study, we have demonstrated a wide range of CeO{sub 2}-induced lung responses including sustained pulmonary inflammation and cellular signaling that could lead to pulmonary fibrosis. In this study, we investigated the fibrogenic responses induced by CeO{sub 2} in a rat model at various time points up to 84 days post-exposure. Male Sprague Dawley rats were exposed to CeO{sub 2} by a single intratracheal instillation. Alveolar macrophages (AM) were isolated by bronchial alveolar lavage (BAL). AM-mediated cellular responses, osteopontin (OPN) and transform growth factor (TGF)-β1 in the fibrotic process were investigated. The results showed that CeO{sub 2} exposure significantly increased fibrotic cytokine TGF-β1 and OPN production by AM above controls. The collagen degradation enzymes, matrix metalloproteinase (MMP)-2 and -9 and the tissue inhibitor of MMP were markedly increased in the BAL fluid at 1 day- and subsequently declined at 28 days after exposure, but remained much higher than the controls. CeO{sub 2} induced elevated phospholipids in BAL fluid and increased hydroxyproline content in lung tissue in a dose- and time-dependent manner. Immunohistochemical analysis showed MMP-2, MMP-9 and MMP-10 expressions in fibrotic regions. Morphological analysis noted increased collagen fibers in the lungs exposed to a single dose of 3.5 mg/kg CeO{sub 2} and euthanized at 28 days post-exposure. Collectively, our studies show that CeO{sub 2} induced fibrotic lung injury in rats, suggesting it may cause potential health effects. -- Highlights: ► Cerium oxide exposure significantly affected the following parameters in the lung. ► Induced fibrotic cytokine OPN and TGF-β1 production and phospholipidosis. ► Caused imbalance of the MMP-9/ TIMP-1 ratio that favors fibrosis

  4. FRONT ELEVATION OF TELLURIDE IRON WORKS 2.5 BY 4FOOT RETORT, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    FRONT ELEVATION OF TELLURIDE IRON WORKS 2.5 BY 4-FOOT RETORT, USED TO FLASH MERCURY FROM GOLD. MERCURY VAPOR THEN CONDENSED ON INSIDE OF HOOD AND WAS COLLECTED FOR REUSE. - Shenandoah-Dives Mill, 135 County Road 2, Silverton, San Juan County, CO

  5. Method and making group IIB metal - telluride films and solar cells

    DOEpatents

    Basol, Bulent M.; Kapur, Vijay K.

    1990-08-21

    A technique is disclosed forming thin films (13) of group IIB metal-telluride, such as Cd.sub.x Zn.sub.1-x Te (0.ltoreq.x.ltoreq.1), on a substrate (10) which comprises depositing Te (18) and at least one of the elements (19) of Cd, Zn, and Hg onto a substrate and then heating the elements to form the telluride. A technique is also provided for doping this material by chemically forming a thin layer of a dopant on the surface of the unreacted elements and then heating the elements along with the layer of dopant. A method is disclosed of fabricating a thin film photovoltaic cell which comprises depositing Te and at least one of the elements of Cd, Zn, and Hg onto a substrate which contains on its surface a semiconductor film (12) and then heating the elements in the presence of a halide of the Group IIB metals, causing the formation of solar cell grade Group IIB metal-telluride film and also causing the formation of a rectifying junction, in situ, between the semiconductor film on the substrate and the Group IIB metal-telluride layer which has been formed.

  6. Growth of Cadmium-Zinc Telluride Crystals by Controlled Seeding Contactless Physical Vapor Transport

    NASA Technical Reports Server (NTRS)

    Palosz, W.; Grasza, K.; Gillies, D.; Jerman, G.

    1996-01-01

    Bulk crystals of cadmium-zinc telluride, 23 mm in diameter and up to 45 grams in weight were grown. Controlled seed formation procedure was used to limit the number of grains in the crystal. Most uniform distribution of ZnTe in the crystals was obtained using excess (Cd + Zn) pressure in the ampoule.

  7. Terrestrial growth of lead-tin-telluride by techniques related to low G growth

    NASA Technical Reports Server (NTRS)

    Jesser, W. A.

    1982-01-01

    A modified Bridgman-Stockbarger furnace was constructed for a study of the solidification of silver, germanium and lead-tin-telluride. The melt-solid interface position with respect to the furnace and its temperature profile was determined by measuring the discontinuity in the slope of temperature as a function of position in the melt and in the solid. The results show that the interface position of the semiconductors germanium and lead-tin-telluride was essentially constant with respect to the furnace and hence the growth rate was constant and equal to the sample translation rate of 0.046 cm/min and 0.178 cm/min in each case. The metal, silver, on the other hand showed a continuous interface migration toward the hot zone of the furnace and always exhibited a growth rate which was higher than the ampoule translation rate. The K sub L/K sub S ratio of lead-tin-telluride was determined to be 2.33 + or - 0.06 where K sub L,S denotes the thermal conductivity of the liquid, solid respectively. The value of K sub L was calculated to be about 0.054 Watt 0.1 cm 0.1 K. The diffusion boundary layer thickness was calculated for lead-tin-telluride to be about 0.05 cm using a liquid diffusivity of .00007 sq cm/sec.

  8. Structural Engineering of Vacancy Defected Bismuth Tellurides for Thermo-electric Applications

    NASA Astrophysics Data System (ADS)

    Termentzidis, K.; Pokropivny, A.; Xiong, S.-Y.; Chumakov, Y.; Cortona, P.; Volz, S.

    2012-10-01

    Molecular Dynamics and ab-initio simulations are used to find the most stable stoichiometries of Bismuth Tellurides with vacancy defects. The interest is to decrease the thermal conductivity of these compounds a key point to achieve high figure of merits. A reduction of 70% of the thermal conductivity is observed with Te vacancies of only 5%.

  9. Equation of state of quartz glass and cerium in their abnormal compressibility range

    NASA Astrophysics Data System (ADS)

    Molodets, A. M.

    2016-09-01

    In this work, the semiempirical equation of state of quartz glass and polycrystalline γ-cerium are plotted and verified at the compressive pressures to 3 GPa. The proposed equations are shown to uniformly describe the thermophysical and physicomechanical properties of quartz glass and polycrystalline γ-cerium at their abnormal compressibility in compression. The room isotherms of these materials are discussed, as well.

  10. Cerium doped red mud catalytic ozonation for bezafibrate degradation in wastewater: Efficiency, intermediates, and toxicity.

    PubMed

    Xu, Bingbing; Qi, Fei; Sun, Dezhi; Chen, Zhonglin; Robert, Didier

    2016-03-01

    In this study, the performance of bezafibrate (BZF) degradation and detoxification in the aqueous phase using cerium-modified red mud (RM) catalysts prepared using different cerium sources and synthesis methods were evaluated. Experimental results showed that the surface cerium modification was responsible for the development of the catalytic activity of RM and this was influenced by the cerium source and the synthesis method. Catalyst prepared from cerium (IV) by precipitation was found to show the best catalytic activity in BZF degradation and detoxification. Reactive oxygen species including peroxides, hydroxyl radicals, and super oxide ions were identified in all reactions and we proposed the corresponding catalytic reaction mechanism for each catalyst that prepared from different cerium source and method. This was supported by the intermediates profiles that were generated upon BZF degradation. The surface and the structural properties of cerium-modified RM were characterized in detail by several analytical methods. Two interesting findings were made: (1) the surface texture (specific surface area and mesoporous volume) influenced the catalytic reaction pathway; and (2) Ce(III) species and oxygen vacancies were generated on the surface of the catalyst after cerium modification. This plays an important role in the development of the catalytic activity. PMID:26706928

  11. Reactions of carbonyl compounds with Grignard reagents in the presence of cerium chloride

    SciTech Connect

    Imamoto, Tsuneo; Takiyama, Nobuyuki; Nakamura, Kimikazu; Hatajima, Toshihiko; Kamiya, Yasuo )

    1989-06-07

    The addition of Grignard reagents to ketones is significantly enhanced by cerium chloride with remarkable suppression of side reactions, particularly enolization. Some esters, which are prone to side reactions, also react readily with Grignard reagents in the presence of cerium chloride to give normal reaction products in reasonable to high yields.

  12. The Electrodeposition of Lead Telluride Nanowires for Thermoelectric Applications

    NASA Astrophysics Data System (ADS)

    Hillman, Peter

    The electrodeposition of PbTe nanowires for thermoelectric applications is presented in this thesis. The Pb-Te electrochemical system was investigated to determine the optimal conditions for deposition. It was found that citric acid complexed tellurium in solution shifting its reduction potential cathodically. The shift in reduction potential led to the deposition of pure PbTe without any observable excess tellurium. Nanowires of PbTe were doped p-type and n-type through the addition of thallium and indium to the plating solution. Indium-doped nanowire arrays showed a linear relation between lattice parameter and atomic percent indium confirming successful incorporation. The lattice parameter trend in thallium-doped nanowire arrays was linear only after annealing. In the case of thallium doping, thallium tellurides were formed, which upon annealing formed a solid solution with PbTe. The results of the thallium doping study led to the investigation of the Tl-Te electrochemical system. Cyclic voltammagrams were used to determine the deposition mechanism of TlTe and Tl5Te3. Thin films and nanowire arrays of these compounds were deposited. This was the first study of the electrochemical Tl-Te system and the first report of the electrodeposition of TlTe and Tl5Te3. Thermoelectric measurements were conducted on thin films and nanowire arrays of PbTe. The Seebeck coefficient and resistivity of PbTe thin film were measured. Results from thin films were complicated by the Pt substrate on which PbTe was deposited. Subtracting the effects of the Pt layer suggested PbTe thin films could have a large zT, however further work is needed to confirm this result. Resistivity measurements on nanowire arrays were also conducted. Despite efforts to minimize the oxidation of PbTe nanowires, good electrical contacts could not be created. The resistivity of nanowire arrays were orders of magnitude higher than expected. As a result of their low conductivity, the thermoelectric efficiency

  13. Thin film cadmium telluride solar cells. Final technical report, July 1, 1979-August 31, 1980

    SciTech Connect

    Chu, T.L.

    1980-08-01

    Efforts during this program have been directed to the construction of apparatus for the chemical vapor deposition of cadmium telluride films, the selection and preparation of substrates, the deposition and characterization of cadmium telluride films, and the fabrication and characterization of solar cells. Cadmium telluride films have been deposited on a number of substrates by the direct combination of cadmium and tellurium on the substrate surface at 500/sup 0/C or higher at rates of up to 0.6 ..mu..m/min. The structural, crystallographic, and electrical properties of cadmium telluride films deposited over a wide range of conditions have been evaluated. A series of doping experiments have been carried out using iodine and indium as the n-type dopant, and phosphorus, arsenic, and antimony as the p-type dopant. Low resistivity films have not been produced thus far. In/W/graphite substrates have been used for the deposition of n-type films with an ohmic interface. However, no suitable substrates have been found to form an ohmic interface with p-type films. Solar cells prepared from these films exhibit relatively good short-circuit current density, up to 15 mA/cm/sup 2/, but their conversion efficiencies are severely limited by the high series resistance of the devices. It is believed that low resistivity cadmium telluride films can be prepared by optimizing the deposition conditions. In parallel with the search of substrates with low interface resistance, back wall cells, such as p-CdTe/n-CdS/ITO/glass(substrate), should be investigated.

  14. Hydrocarbon-based polymer electrolyte cerium composite membranes for improved proton exchange membrane fuel cell durability

    NASA Astrophysics Data System (ADS)

    Lee, Hyejin; Han, Myungseong; Choi, Young-Woo; Bae, Byungchan

    2015-11-01

    Hydrocarbon-based cerium composite membranes were prepared for proton exchange membrane fuel cell applications to increase oxidative stability. Different amounts of cerium ions were impregnated in sulfonated poly(arylene ether sulfone) (SPES) membranes and their physicochemical properties were investigated according to the cerium content. Field-emission scanning electron microscopy and inductively coupled plasma analyses confirmed the presence of cerium ions in the composite membranes and 1H NMR indicated the successful coordination of sulfonic acid groups with the metal ions. Increasing amounts of cerium ions resulted in decreases in the proton conductivity and water uptake, but enhanced oxidative stability. The oxidative stability of the composite membranes was proven via a hydrogen peroxide exposure experiment which mimicked fuel cell operating conditions. In addition, more than 2200 h was achieved with the composite membrane under in situ accelerated open circuit voltage (OCV) durability testing (DOE protocol), whereas the corresponding pristine SPES membrane attained only 670 h.

  15. Tuning Reactivity and Electronic Properties through Ligand Reorganization within a Cerium Heterobimetallic Framework

    SciTech Connect

    Robinson, Jerome R.; Gordon, Zachary; Booth, Corwin H.; Carroll, Patrick J.; Walsh, Patrick J.; Schelter, Eric J.

    2014-06-24

    Cerium compounds have played vital roles in organic, inorganic, and materials chemistry due to their reversible redox chemistry between trivalent and tetravalent oxidation states. However, attempts to rationally access molecular cerium complexes in both oxidation states have been frustrated by unpredictable reactivity in cerium(III) oxidation chemistry. Such oxidation reactions are limited by steric saturation at the metal ion, which can result in high energy activation barriers for electron transfer. An alternative approach has been realized using a rare earth/alkali metal/1,1'-BINOLate (REMB) heterobimetallic framework, which uses redox-inactive metals within the secondary coordination sphere to control ligand reorganization. The rational syntheses of functionalized cerium(IV) products and a mechanistic examination of the role of ligand reorganization in cerium(III) oxidation are presented.

  16. Effects of uncoated and citric acid coated cerium oxide nanoparticles, bulk cerium oxide, cerium acetate, and citric acid on tomato plants.

    PubMed

    Barrios, Ana Cecilia; Rico, Cyren M; Trujillo-Reyes, Jesica; Medina-Velo, Illya A; Peralta-Videa, Jose R; Gardea-Torresdey, Jorge L

    2016-09-01

    Little is known about the physiological and biochemical responses of plants exposed to surface modified nanomaterials. In this study, tomato (Solanum lycopersicum L.) plants were cultivated for 210days in potting soil amended with uncoated and citric acid coated cerium oxide nanoparticles (nCeO2, CA+nCeO2) bulk cerium oxide (bCeO2), and cerium acetate (CeAc). Millipore water (MPW), and citric acid (CA) were used as controls. Physiological and biochemical parameters were measured. At 500mg/kg, both the uncoated and CA+nCeO2 increased shoot length by ~9 and ~13%, respectively, while bCeO2 and CeAc decreased shoot length by ~48 and ~26%, respectively, compared with MPW (p≤0.05). Total chlorophyll, chlo-a, and chlo-b were significantly increased by CA+nCeO2 at 250mg/kg, but reduced by bCeO2 at 62.5mg/kg, compared with MPW. At 250 and 500mg/kg, nCeO2 increased Ce in roots by 10 and 7 times, compared to CA+nCeO2, but none of the treatments affected the Ce concentration in above ground tissues. Neither nCeO2 nor CA+nCeO2 affected the homeostasis of nutrient elements in roots, stems, and leaves or catalase and ascorbate peroxidase in leaves. CeAc at 62.5 and 125mg/kg increased B (81%) and Fe (174%) in roots, while at 250 and 500mg/kg, increased Ca in stems (84% and 86%, respectively). On the other hand, bCeO2 at 62.5 increased Zn (152%) but reduced P (80%) in stems. Only nCeO2 at 62.5mg/kg produced higher total number of tomatoes, compared with control and the rest of the treatments. The surface coating reduced Ce uptake by roots but did not affect its translocation to the aboveground organs. In addition, there was no clear effect of surface coating on fruit production. To our knowledge, this is the first study comparing the effects of coated and uncoated nCeO2 on tomato plants.

  17. Effects of uncoated and citric acid coated cerium oxide nanoparticles, bulk cerium oxide, cerium acetate, and citric acid on tomato plants.

    PubMed

    Barrios, Ana Cecilia; Rico, Cyren M; Trujillo-Reyes, Jesica; Medina-Velo, Illya A; Peralta-Videa, Jose R; Gardea-Torresdey, Jorge L

    2016-09-01

    Little is known about the physiological and biochemical responses of plants exposed to surface modified nanomaterials. In this study, tomato (Solanum lycopersicum L.) plants were cultivated for 210days in potting soil amended with uncoated and citric acid coated cerium oxide nanoparticles (nCeO2, CA+nCeO2) bulk cerium oxide (bCeO2), and cerium acetate (CeAc). Millipore water (MPW), and citric acid (CA) were used as controls. Physiological and biochemical parameters were measured. At 500mg/kg, both the uncoated and CA+nCeO2 increased shoot length by ~9 and ~13%, respectively, while bCeO2 and CeAc decreased shoot length by ~48 and ~26%, respectively, compared with MPW (p≤0.05). Total chlorophyll, chlo-a, and chlo-b were significantly increased by CA+nCeO2 at 250mg/kg, but reduced by bCeO2 at 62.5mg/kg, compared with MPW. At 250 and 500mg/kg, nCeO2 increased Ce in roots by 10 and 7 times, compared to CA+nCeO2, but none of the treatments affected the Ce concentration in above ground tissues. Neither nCeO2 nor CA+nCeO2 affected the homeostasis of nutrient elements in roots, stems, and leaves or catalase and ascorbate peroxidase in leaves. CeAc at 62.5 and 125mg/kg increased B (81%) and Fe (174%) in roots, while at 250 and 500mg/kg, increased Ca in stems (84% and 86%, respectively). On the other hand, bCeO2 at 62.5 increased Zn (152%) but reduced P (80%) in stems. Only nCeO2 at 62.5mg/kg produced higher total number of tomatoes, compared with control and the rest of the treatments. The surface coating reduced Ce uptake by roots but did not affect its translocation to the aboveground organs. In addition, there was no clear effect of surface coating on fruit production. To our knowledge, this is the first study comparing the effects of coated and uncoated nCeO2 on tomato plants. PMID:26672385

  18. Thermal Signatures of The Kondo Volume Collapse in Cerium

    SciTech Connect

    Lipp, M; Jackson, D; Cynn, H; Aracne, C; Evans, W; McMahan, A

    2008-05-23

    X-ray diffraction measurements of cerium in the vicinity of the isostructural {gamma}-{alpha} transition have been performed with high precision and accuracy from room temperature to almost 800 K. The disputed location of the critical point has been found to occur at 1.5 {+-} 0.1 GPa and 480 {+-} 10 K. The data is well fit by the Kondo volume collapse model plus a quasiharmonic representation of the phonons. The resultant free energy is validated against data for the thermodynamic Grueneisen parameter, and beyond the dominant spin fluctuation contribution, indicates a dramatic change in the lattice Grueneisen parameter across the transition.

  19. Identification of the Charge Carriers in Cerium Phosphate Ceramics

    SciTech Connect

    Ray, Hannah L.; Jonghe, Lutgard C. De

    2010-06-02

    The total conductivity of Sr-doped cerium orthophosphate changes by nearly two orders of magnitude depending on the oxygen and hydrogen content of the atmosphere. The defect model for the system suggests that this is because the identity of the dominant charge carrier can change from electron holes to protons when the sample is in equilibrium with air vs. humidified hydrogen. In this work are presented some preliminary measurements that can help to clarify this exchange between carriers. The conduction behavior of a 2percent Sr-doped CePO4 sample under symmetric atmospheric conditions is investigated using several techniques, including AC impedance, H/D isotope effects, and chronoamperometry.

  20. Properties of hot liquid cerium by LDA + U molecular dynamics.

    PubMed

    Siberchicot, Bruno; Clérouin, Jean

    2012-11-14

    We present ab initio simulations of liquid cerium in the framework of the LDA + U formulation. The liquid density has been determined self-consistently by searching for the zero pressure equilibrium state at 1320 K with the same set of parameters (U and J) and occupation matrices as those optimized for the γ phase. We have computed static and transport properties. The liquid produced by the simulations appears more structured than the available measurements. This raises questions regarding the ability of the theory to describe such a complex liquid. Conductivity calculations and temperature dependences are nevertheless in reasonable agreement with data.

  1. Indium telluride nanotubes: Solvothermal synthesis, growth mechanism, and properties

    SciTech Connect

    Zhou, Liyan; Yan, Shancheng; Lu, Tao; Shi, Yi; Wang, Jianyu; Yang, Fan

    2014-03-15

    hydrogen storage, compared with the nanowires. The nanotube device also has a broad light detection range from 300 nm to 1100 nm, covering the UV–visible–NIR region. This good performance of In{sub 2}Te{sub 3} nanotubes may enable significant advancements of new photodetection and photosensing applications. Highlights: • The In{sub 2}Te{sub 3} nanotube device also has a broad light detection range from 300 nm to 1100 nm. • The nanotube is 137.85 m{sup 2} g{sup −1}, which makes it suitable for gas sensing and hydrogen storage. • A possible growth mechanism of the indium telluride nanotubes was proposed. • In addition, no In{sub 2}Te{sub 3} nanotubes have been reported until now.

  2. Soil organic matter influences cerium translocation and physiological processes in kidney bean plants exposed to cerium oxide nanoparticles.

    PubMed

    Majumdar, Sanghamitra; Peralta-Videa, Jose R; Trujillo-Reyes, Jesica; Sun, Youping; Barrios, Ana C; Niu, Genhua; Margez, Juan P Flores-; Gardea-Torresdey, Jorge L

    2016-11-01

    Soil organic matter plays a major role in determining the fate of the engineered nanomaterials (ENMs) in the soil matrix and effects on the residing plants. In this study, kidney bean plants were grown in soils varying in organic matter content and amended with 0-500mg/kg cerium oxide nanoparticles (nano-CeO2) under greenhouse condition. After 52days of exposure, cerium accumulation in tissues, plant growth and physiological parameters including photosynthetic pigments (chlorophylls and carotenoids), net photosynthesis rate, transpiration rate, and stomatal conductance were recorded. Additionally, catalase and ascorbate peroxidase activities were measured to evaluate oxidative stress in the tissues. The translocation factor of cerium in the nano-CeO2 exposed plants grown in organic matter enriched soil (OMES) was twice as the plants grown in low organic matter soil (LOMS). Although the leaf cover area increased by 65-111% with increasing nano-CeO2 concentration in LOMS, the effect on the physiological processes were inconsequential. In OMES leaves, exposure to 62.5-250mg/kg nano-CeO2 led to an enhancement in the transpiration rate and stomatal conductance, but to a simultaneous decrease in carotenoid contents by 25-28%. Chlorophyll a in the OMES leaves also decreased by 27 and 18% on exposure to 125 and 250mg/kg nano-CeO2. In addition, catalase activity increased in LOMS stems, and ascorbate peroxidase increased in OMES leaves of nano-CeO2 exposed plants, with respect to control. Thus, this study provides clear evidence that the properties of the complex soil matrix play decisive roles in determining the fate, bioavailability, and biological transport of ENMs in the environment.

  3. Soil organic matter influences cerium translocation and physiological processes in kidney bean plants exposed to cerium oxide nanoparticles.

    PubMed

    Majumdar, Sanghamitra; Peralta-Videa, Jose R; Trujillo-Reyes, Jesica; Sun, Youping; Barrios, Ana C; Niu, Genhua; Margez, Juan P Flores-; Gardea-Torresdey, Jorge L

    2016-11-01

    Soil organic matter plays a major role in determining the fate of the engineered nanomaterials (ENMs) in the soil matrix and effects on the residing plants. In this study, kidney bean plants were grown in soils varying in organic matter content and amended with 0-500mg/kg cerium oxide nanoparticles (nano-CeO2) under greenhouse condition. After 52days of exposure, cerium accumulation in tissues, plant growth and physiological parameters including photosynthetic pigments (chlorophylls and carotenoids), net photosynthesis rate, transpiration rate, and stomatal conductance were recorded. Additionally, catalase and ascorbate peroxidase activities were measured to evaluate oxidative stress in the tissues. The translocation factor of cerium in the nano-CeO2 exposed plants grown in organic matter enriched soil (OMES) was twice as the plants grown in low organic matter soil (LOMS). Although the leaf cover area increased by 65-111% with increasing nano-CeO2 concentration in LOMS, the effect on the physiological processes were inconsequential. In OMES leaves, exposure to 62.5-250mg/kg nano-CeO2 led to an enhancement in the transpiration rate and stomatal conductance, but to a simultaneous decrease in carotenoid contents by 25-28%. Chlorophyll a in the OMES leaves also decreased by 27 and 18% on exposure to 125 and 250mg/kg nano-CeO2. In addition, catalase activity increased in LOMS stems, and ascorbate peroxidase increased in OMES leaves of nano-CeO2 exposed plants, with respect to control. Thus, this study provides clear evidence that the properties of the complex soil matrix play decisive roles in determining the fate, bioavailability, and biological transport of ENMs in the environment. PMID:27343939

  4. Hydrothermal synthesis of cerium titanate nanorods and its application in visible light photocatalysis

    SciTech Connect

    Pei, L.Z. Liu, H.D.; Lin, N.; Yu, H.Y.

    2015-01-15

    Highlights: • Cerium titanate nanorods have been synthesized by a simple hydrothermal process. • The size of the cerium titanate nanorods can be controlled by growth conditions. • Cerium titanate nanorods exhibit good photocatalytic activities for methyl blue. - Abstract: Cerium titanate nanorods have been prepared via a hydrothermal process using sodium dodecyl sulfate (SDS) as the surfactant. The cerium titanate nanorods have been analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), and ultraviolet–visible (UV–vis) diffuse reflectance spectrum. XRD shows that the nanorods are composed of CeTi{sub 21}O{sub 38} phase. Electron microscopy observations indicate that the nanorods have good single crystalline nature. The diameter and length of the nanorods are about 50–200 nm and 1–2 μm, respectively. Cerium titanate nanorods have a band gap of 2.65 eV. The photocatalytic activities of the nanorods have been investigated by degrading methylene blue (MB) under visible light irradiation. MB solution with the concentration of 10 mg L{sup −1} can be degraded totally with the irradiation time increasing to 240 min. Cerium titanate nanorods exhibit great potential in photocatalytic degradation of MB under visible light irradiation.

  5. Altering properties of cerium oxide thin films by Rh doping

    SciTech Connect

    Ševčíková, Klára; Nehasil, Václav; Vorokhta, Mykhailo; Haviar, Stanislav; Matolín, Vladimír; and others

    2015-07-15

    Highlights: • Thin films of ceria doped by rhodium deposited by RF magnetron sputtering. • Concentration of rhodium has great impact on properties of Rh–CeO{sub x} thin films. • Intensive oxygen migration in films with low concentration of rhodium. • Oxygen migration suppressed in films with high amount of Rh dopants. - Abstract: Ceria containing highly dispersed ions of rhodium is a promising material for catalytic applications. The Rh–CeO{sub x} thin films with different concentrations of rhodium were deposited by RF magnetron sputtering and were studied by soft and hard X-ray photoelectron spectroscopies, Temperature programmed reaction and X-ray powder diffraction techniques. The sputtered films consist of rhodium–cerium mixed oxide where cerium exhibits a mixed valency of Ce{sup 4+} and Ce{sup 3+} and rhodium occurs in two oxidation states, Rh{sup 3+} and Rh{sup n+}. We show that the concentration of rhodium has a great influence on the chemical composition, structure and reducibility of the Rh–CeO{sub x} thin films. The films with low concentrations of rhodium are polycrystalline, while the films with higher amount of Rh dopants are amorphous. The morphology of the films strongly influences the mobility of oxygen in the material. Therefore, varying the concentration of rhodium in Rh–CeO{sub x} thin films leads to preparing materials with different properties.

  6. Pulmonary toxicity in mice following exposure to cerium chloride.

    PubMed

    Hong, Jie; Yu, Xiaohong; Pan, Xiaoyu; Zhao, Xiaoyang; Sheng, Lei; Sang, Xuezi; Lin, Anan; Zhang, Chi; Zhao, Yue; Gui, Suxin; Sun, Qingqing; Wang, Ling; Hong, Fashui

    2014-06-01

    The widespread application of lanthanoids (Lns) in manufacturing industries has raised occupational and environmental health concerns about the possible increased health risks to humans exposed to Lns in their working and living environments. Numerous studies have shown that exposures to Ln cause pulmonary injury in animals, but very little is known about the molecular mechanisms of the pulmonary inflammation caused by cerium chloride (CeCl3) exposure. In this study, we evaluated the oxidative stress and molecular mechanism underlying with the pulmonary inflammation associated with chronic lung toxicity in mice treated with nasally instilled CeCl3 for 90 consecutive days. Our findings suggest that significant cerium accumulated in the lung, leading the obvious increase of the lung indices, significant increases in inflammatory cells and levels of lactate dehydrogenase, alkaline phosphate, and total protein, overproduction of reactive oxygen species and peroxidation of lipids, reduced antioxidant capacity, and pulmonary inflammation. CeCl3 exposure also activated nuclear factor κB, increased the expression of tumor necrosis factor α, cyclooxygenase-2, heme oxygenase 1, interleukin 2, interleukin 4, interleukin 6, interleukin 8, interleukin 10, interleukin 18, interleukin 1β, and CYP1A1. However, CeCl3 reduced the expression of nuclear factor κB (NF-κB)-inhibiting factor and heat shock protein 70. These findings suggest that the pulmonary inflammation caused by CeCl3 in mice is closely associated with oxidative stress and inflammatory cytokine expression. PMID:24736977

  7. Serum ornithine carbamoyltransferase (OCT) in rats poisoned with lanthanum, cerium and praseodymium.

    PubMed

    Marciniak, M; Bałtrukiewicz, Z

    1977-01-01

    Serum ornithine carbamoyltransferase (OCT) in rats poisoned with lanthanum, cerium and praseodymium. Acta Physiol. Pol., 1977, 28 (6): 589-594. The serum ornithine carbamoyltransferase in relation to doses of lanthanum, cerium and praseodymium, administered intravenously as chlorides, was investigated. A directly proportional relationship was found between the doses of these compounds and the serum enzyme level in rats. The lowest doses at which a rise in the serum OCT level occured were determined. They were: lanthanum - 0.75 mg/kg of body weight, cerium - 1.5 mg/kg, and praseodymium - 3 mh/kg. A decreasing toxicity of these elements with increasing value of atomic number was observed.

  8. Cerium-Based Magnets: Novel High Energy Permanent Magnet Without Critical Elements

    SciTech Connect

    2012-01-01

    REACT Project: Ames Laboratory will develop a new class of permanent magnets based on the more commonly available element cerium for use in both EVs and renewable power generators. Cerium is 4 times more abundant and significantly less expensive than the rare earth element neodymium, which is frequently used in today’s most powerful magnets. Ames Laboratory will combine other metal elements with cerium to create a new magnet that can remain stable at the high temperatures typically found in electric motors. This new magnetic material will ultimately be demonstrated in a prototype electric motor, representing a cost-effective and efficient alternative to neodymium-based motors.

  9. Ab initio lattice dynamics and thermochemistry of layered bismuth telluride (Bi2Te3)

    NASA Astrophysics Data System (ADS)

    Zurhelle, Alexander F.; Deringer, Volker L.; Stoffel, Ralf P.; Dronskowski, Richard

    2016-03-01

    We present density-functional theory calculations of the lattice dynamics of bismuth telluride, yielding force constants, mean-square displacements and partial densities of phonon states which corroborate and complement previous nuclear inelastic scattering experiments. From these data, we derive an element- and energy-resolved view of the vibrational anharmonicity, quantified by the macroscopic Grüneisen parameter γ which results in 1.56. Finally, we calculate thermochemical properties in the quasiharmonic approximation, especially the heat capacity at constant pressure and the enthalpy of formation for bismuth telluride; the latter arrives at ▵H f (Bi2Te3)  =  -102 kJ mol-1 at 298 K.

  10. Ab initio lattice dynamics and thermochemistry of layered bismuth telluride (Bi2Te3).

    PubMed

    Zurhelle, Alexander F; Deringer, Volker L; Stoffel, Ralf P; Dronskowski, Richard

    2016-03-23

    We present density-functional theory calculations of the lattice dynamics of bismuth telluride, yielding force constants, mean-square displacements and partial densities of phonon states which corroborate and complement previous nuclear inelastic scattering experiments. From these data, we derive an element- and energy-resolved view of the vibrational anharmonicity, quantified by the macroscopic Grüneisen parameter γ which results in 1.56. Finally, we calculate thermochemical properties in the quasiharmonic approximation, especially the heat capacity at constant pressure and the enthalpy of formation for bismuth telluride; the latter arrives at ΔHf (Bi2Te3)  =  -102 kJ mol(-1) at 298 K.

  11. Kelvin probe studies of cesium telluride photocathode for the AWA photoinjector

    SciTech Connect

    Velazquez, D.; Wisniewski, E. E.; Yusof, Z.; Harkay, K.; Spentzouris, L.; Terry, J.

    2012-12-21

    Cesium telluride is an important photocathode as an electron source for particle accelerators. It has a relatively high quantum efficiency (> 1%), is robust in a photoinjector, and long lifetime. This photocathode is fabricated in-house for a new Argonne Wakefield Accelerator (AWA) beamline to produce high charge per bunch ({approx}50 nC) in a long bunch train. We present some results from a study of the work function of cesium telluride photocathode using the Kelvin Probe technique. The study includes an investigation of the correlation between the quantum efficiency and the work function, the effect of photocathode aging, the effect of UV light exposure on the work function, and the evolution of the work function during and after photocathode rejuvenation via heating.

  12. Effect of self-compensation on the electron lifetime in gallium-doped cadmium telluride

    SciTech Connect

    Rabenok, E. V.; Galanovich, M. V.; Novikov, G. F. Odin, I. N.

    2009-07-15

    Using the methods of microwave photoconductivity and cathodoluminescence, elementary processes with the participation of charged particles in polycrystalline alloys on the basis of cadmium telluride CdTe-GaTe and CdTe-Ga{sub 2}Te{sub 3}-promising active media for radiation detectors in low-dose human introscopy-are studied. It is established experimentally that the amplitude, characteristic time, and shape of decay of the photoresponse depend on the doping level, and the characteristic time of the photoresponse increases as the doping level is increased. It is shown that the change in the kinetics of annihilation of photo-generated electrons in doped cadmium telluride (compared with the starting one) is caused by the effect of self-compensation, which leads to redistribution of traps by energies.

  13. Method for improving the growth of cadmium telluride on a gallium arsenide substrate

    SciTech Connect

    Reno, J.L.

    1990-12-31

    A method for preparing a gallium arsenide substrate, prior to growing a layer of cadmium telluride on a support surface thereof. The preparation includes the steps of cleaning the gallium arsenide substrate and thereafter forming prepatterned shapes on the support surface of the gallium arsenide substrate. The layer of cadmium telluride then grown on the prepared substrate results in dislocation densities of approximately 1{times}10{sup 6}/cm{sup 2} or less. The prepatterned shapes on the support surface of the gallium arsenide substrate are formed by reactive ion etching an original outer surface of the gallium arsenide substrate and into the body of the gallium arsenide substrate to a depth of at least two microns. The prepatterned shapes have the appearance of cylindrical mesas each having a diameter of at lease twelve microns. After the mesas are formed on the support surface of the gallium arsenide substrate, the substrate is again cleaned.

  14. Ab initio lattice dynamics and thermochemistry of layered bismuth telluride (Bi2Te3).

    PubMed

    Zurhelle, Alexander F; Deringer, Volker L; Stoffel, Ralf P; Dronskowski, Richard

    2016-03-23

    We present density-functional theory calculations of the lattice dynamics of bismuth telluride, yielding force constants, mean-square displacements and partial densities of phonon states which corroborate and complement previous nuclear inelastic scattering experiments. From these data, we derive an element- and energy-resolved view of the vibrational anharmonicity, quantified by the macroscopic Grüneisen parameter γ which results in 1.56. Finally, we calculate thermochemical properties in the quasiharmonic approximation, especially the heat capacity at constant pressure and the enthalpy of formation for bismuth telluride; the latter arrives at ΔHf (Bi2Te3)  =  -102 kJ mol(-1) at 298 K. PMID:26894844

  15. Evaluation of the efficiency curve of a Cadmiun Telluride detector for low-energy photon spectrometry.

    PubMed

    Correia, Amanda Ribeiro; Iwahara, Akira; da Cruz, Paulo Alberto Lima; da Silva, Carlos José; Tauhata, Luiz; Poledna, Roberto; da Silva, Ronaldo Lins; de Queiroz Filho, Pedro Pacheco; Lopes, Ricardo Tadeu

    2016-10-01

    The performance of a Cadmiun Telluride (CdTe) detector for low energy photon spectrometry was evaluated. Collected data were analyzed using the basic software package available with the CdTe detector system and the COLEGRAM code developed for photopeak deconvolution at LNHB/France. Several calibrated point sources were used to determine the energy versus efficiency curve. The efficiency curve was used in the determination of main X-ray intensities of (153)Sm and (177)Lu.

  16. Evaluation of the efficiency curve of a Cadmiun Telluride detector for low-energy photon spectrometry.

    PubMed

    Correia, Amanda Ribeiro; Iwahara, Akira; da Cruz, Paulo Alberto Lima; da Silva, Carlos José; Tauhata, Luiz; Poledna, Roberto; da Silva, Ronaldo Lins; de Queiroz Filho, Pedro Pacheco; Lopes, Ricardo Tadeu

    2016-10-01

    The performance of a Cadmiun Telluride (CdTe) detector for low energy photon spectrometry was evaluated. Collected data were analyzed using the basic software package available with the CdTe detector system and the COLEGRAM code developed for photopeak deconvolution at LNHB/France. Several calibrated point sources were used to determine the energy versus efficiency curve. The efficiency curve was used in the determination of main X-ray intensities of (153)Sm and (177)Lu. PMID:27544313

  17. Aqueous-solution route to zinc telluride films for application to CO₂ reduction.

    PubMed

    Jang, Ji-Wook; Cho, Seungho; Magesh, Ganesan; Jang, Youn Jeong; Kim, Jae Young; Kim, Won Yong; Seo, Jeong Kon; Kim, Sungjee; Lee, Kun-Hong; Lee, Jae Sung

    2014-06-01

    As a photocathode for CO2 reduction, zinc-blende zinc telluride (ZnTe) was directly formed on a Zn/ZnO nanowire substrate by a simple dissolution-recrystallization mechanism without any surfactant. With the most negative conduction-band edge among p-type semiconductors, this new photocatalyst showed efficient and stable CO formation in photoelectrochemical CO2 reduction at -0.2--0.7 V versus RHE without a sacrificial reagent.

  18. Structure and dynamics of cadmium telluride studied by x-ray and inelastic neutron scattering

    SciTech Connect

    Niedziela, Jennifer L; Stone, Matthew B

    2014-01-01

    We present a combined study of density functional theory, x-ray diffraction, and inelastic neutron scattering examining the temperature dependent structure and lattice dynamics of commercially available cadmium telluride. A subtle change in the structure is evinced near 80~K, which manifests also in the measured phonon density of states. There is no change to the long-range ordered structure. The implications of the change in relation to structural defects are discussed.

  19. Structure and dynamics of cadmium telluride studied by x-ray and inelastic neutron scattering

    SciTech Connect

    Niedziela, J. L.; Stone, M. B.

    2014-09-08

    We present a combined study of density functional theory, x-ray diffraction, and inelastic neutron scattering examining the temperature dependent structure and lattice dynamics of commercially available cadmium telluride. A subtle change in the structure is evinced near 80 K, which manifests also in the measured phonon density of states. There is no change to the long-range ordered structure. The implications of the change in relation to structural defects are discussed.

  20. Exfoliation and characterization of bismuth telluride atomic quintuples and quasi-two-dimensional crystals.

    PubMed

    Teweldebrhan, Desalegne; Goyal, Vivek; Balandin, Alexander A

    2010-04-14

    Bismuth telluride (Bi(2)Te(3)) and its alloys are the best bulk thermoelectric materials known today. In addition, stacked quasi-two-dimensional (2D) layers of Bi(2)Te(3) were recently identified as promising topological insulators. In this Letter we describe a method for "graphene-inspired" exfoliation of crystalline bismuth telluride films with a thickness of a few atoms. The atomically thin films were suspended across trenches in Si/SiO(2) substrates, and subjected to detail material characterization, which included atomic force microscopy and micro-Raman spectroscopy. The presence of the van der Waals gaps allowed us to disassemble Bi(2)Te(3) crystal into its quintuple building blocks-five monatomic sheets-consisting of Te((1))-Bi-Te((2))-Bi-Te((1)). By altering the thickness and sequence of atomic planes, we were able to create "designer" nonstoichiometric quasi-2D crystalline films, change their composition and doping, the type of charge carriers as well as other properties. The exfoliated quintuples and ultrathin films have low thermal conductivity, high electrical conductivity, and enhanced thermoelectric properties. The obtained results pave the way for producing stacks of crystalline bismuth telluride quantum wells with the strong spatial confinement of charge carriers and acoustic phonons, beneficial for thermoelectric devices. The developed technology for producing free-standing quasi-2D layers of Te((1))-Bi-Te((2))-Bi-Te((1)) creates an impetus for investigation of the topological insulators and their possible practical applications.

  1. Studies of Solution Deposited Cerium Oxide Thin Films on Textured Ni-Alloy Substractes for YBCO Superconductor

    SciTech Connect

    Stewart, Erin L; Bhuiyan, Md S; Sathyamurthy, Srivatsan; Paranthaman, Mariappan Parans

    2006-01-01

    Cerium oxide (CeO2) buffer layers play an important role for the development of YBa2Cu3O7-x (YBCO) based superconducting tapes using the rolling assisted biaxially textured substrates (RABiTS) approach. The chemical solution deposition (CSD) approach has been used to grow epitaxial CeO2 films on textured Ni-3 a 4% W alloy substrates with various starting precursors of ceria. Precursors such as cerium acetate, cerium acetylacetonate, cerium 2-ethylhexanoate, cerium nitrate, and cerium trifluoroacetate were prepared in suitable solvents. The optimum growth conditions for these cerium precursors were Ar-4% H2 gas processing atmosphere, solution concentration levels of 0.2-0.5 M, a dwell time of 15 min, and a process temperature range of 1050-1150 degrees C. X-ray diffraction, AFM, SEM, and optical microscopy were used to characterize the CeO2 films. Highly textured CeO2 layers were obtained on Ni-W substrates with both cerium acetate and cerium acetylacetonate as starting precursors. YBCO films with a Jc of 1.5 MA/cm2 were obtained on cerium acetylacetonate-based CeO2 films with sputtered YSZ and CeO2 cap layers.

  2. Electronic characterization of defects in narrow gap semiconductors: Comparison of electronic energy levels and formation energies in mercury cadmium telluride, mercury zinc telluride, and mercury zinc selenide

    NASA Astrophysics Data System (ADS)

    Patterson, James D.; Li, Wei-Gang

    1995-03-01

    The project has evolved to that of using Green's functions to predict properties of deep defects in narrow gap materials. Deep defects are now defined as originating from short range potentials and are often located near the middle of the energy gap. They are important because they affect the lifetime of charge carriers and hence the switching time of transistors. We are now moving into the arena of predicting formation energies of deep defects. This will also allow us to make predictions about the relative concentrations of the defects that could be expected at a given temperature. The narrow gap materials mercury cadmium telluride (MCT), mercury zinc telluride (MZT), and mercury zinc selenide (MZS) are of interest to NASA because they have commercial value for infrared detecting materials, and because there is a good possibility that they can be grown better in a microgravity environment. The uniform growth of these crystals on earth is difficult because of convection (caused by solute depletion just ahead of the growing interface, and also due to thermal gradients). In general it is very difficult to grow crystals with both radial and axial homogeneity.

  3. Electronic characterization of defects in narrow gap semiconductors: Comparison of electronic energy levels and formation energies in mercury cadmium telluride, mercury zinc telluride, and mercury zinc selenide

    NASA Technical Reports Server (NTRS)

    Patterson, James D.; Li, Wei-Gang

    1995-01-01

    The project has evolved to that of using Green's functions to predict properties of deep defects in narrow gap materials. Deep defects are now defined as originating from short range potentials and are often located near the middle of the energy gap. They are important because they affect the lifetime of charge carriers and hence the switching time of transistors. We are now moving into the arena of predicting formation energies of deep defects. This will also allow us to make predictions about the relative concentrations of the defects that could be expected at a given temperature. The narrow gap materials mercury cadmium telluride (MCT), mercury zinc telluride (MZT), and mercury zinc selenide (MZS) are of interest to NASA because they have commercial value for infrared detecting materials, and because there is a good possibility that they can be grown better in a microgravity environment. The uniform growth of these crystals on earth is difficult because of convection (caused by solute depletion just ahead of the growing interface, and also due to thermal gradients). In general it is very difficult to grow crystals with both radial and axial homogeneity.

  4. The effect of different annealing temperatures on tin and cadmium telluride phases obtained by a modified chemical route

    SciTech Connect

    Mesquita, Anderson Fuzer; Porto, Arilza de Oliveira; Magela de Lima, Geraldo; Paniago, Roberto; Ardisson, José Domingos

    2012-11-15

    Graphical abstract: Display Omitted Highlights: ► Synthesis of cadmium and tin telluride. ► Chemical route to obtain pure crystalline cadmium and tin telluride. ► Effect of the annealing temperature on the crystalline phases. ► Removal of tin oxide as side product through thermal treatment. -- Abstract: In this work tin and cadmium telluride were prepared by a modification of a chemical route reported in the literature to obtain metallacycles formed by oxidative addition of tin-tellurium bonds to platinum (II). Through this procedure it was possible to obtain tin and cadmium telluride. X-ray diffraction and X-ray photoelectron spectroscopy were used to identify the crystalline phases obtained as well as the presence of side products. In the case of tin telluride it was identified potassium chloride, metallic tellurium and tin oxide as contaminants. The tin oxidation states were also monitored by {sup 119}Sn Mössbauer spectroscopy. The annealing in hydrogen atmosphere was chosen as a strategy to reduce the tin oxide and promote its reaction with the excess of tellurium present in the medium. The evolution of this tin oxide phase was studied through the annealing of the sample at different temperatures. Cadmium telluride was obtained with high degree of purity (98.5% relative weight fraction) according to the Rietveld refinement of X-ray diffraction data. The modified procedure showed to be very effective to obtain amorphous tin and cadmium telluride and the annealing at 450 °C has proven to be useful to reduce the amount of oxide produced as side product.

  5. Correction: Single-molecule magnet behaviour in polynuclear assembly of trivalent cerium ions with polyoxomolybdates.

    PubMed

    Khélifa, A Ben; Belkhiria, M Salah; Huang, G; Freslon, S; Guillou, O; Bernot, K

    2016-06-01

    Correction for 'Single-molecule magnet behaviour in polynuclear assembly of trivalent cerium ions with polyoxomolybdates' by A. Ben Khélifa, et al., Dalton Trans., 2015, 44, 16458-16464. PMID:27161299

  6. Calculation of a volume effect accompanying an electronic topological transition in pure cerium

    NASA Astrophysics Data System (ADS)

    Ponomaryova, S. O.; Koval', Yu. M.; Ponomaryov, O. P.

    2012-10-01

    An analytic expression for estimating the volume effect accompanying an electronic topological transition (ETT) in pure cerium is derived on the basis of the microscopic Falikov-Ramirez-Kimball model.

  7. Recent advances (2010-2015) in studies of cerium oxide nanoparticles' health effects.

    PubMed

    Li, Yan; Li, Peng; Yu, Hua; Bian, Ying

    2016-06-01

    Cerium oxide nanoparticles, widespread applied in our life, have attracted much concern for their human health effects. However, most of the works addressing cerium oxide nanoparticles toxicity have only used in vitro models or in vivo intratracheal instillation methods. The toxicity studies have varied results and not all are conclusive. The information about risk assessments derived from epidemiology studies is severely lacking. The knowledge of occupational safety and health (OSH) for exposed workers is very little. Thus this review focuses on recent advances in studies of toxicokinetics, antioxidant activity and toxicity. Additionally, aim to extend previous health effects assessments of cerium oxide nanoparticles, we summarize the epidemiology studies of engineered cerium oxide nanoparticles used as automotive diesel fuel additive, aerosol particulate matter in air pollution, other industrial ultrafine and nanoparticles (e.g., fumes particles generated in welding and flame cutting processes). PMID:27088851

  8. Direct growth of cerium oxide nanorods on diverse substrates for superhydrophobicity and corrosion resistance

    NASA Astrophysics Data System (ADS)

    Cho, Young Jun; Jang, Hanmin; Lee, Kwan-Soo; Kim, Dong Rip

    2015-06-01

    Superhydrophobic surfaces with anti-corrosion properties have attracted great interest in many industrial fields, particularly to enhance the thermal performance of offshore applications such as heat exchangers, pipelines, power plants, and platform structures. Nanostructures with hydrophobic materials have been widely utilized to realize superhydrophobicity of surfaces, and cerium oxide has been highlighted due to its good corrosion resistive and intrinsically hydrophobic properties. However, few studies of direct growth of cerium oxide nanostructures on diverse substrates have been reported. Herein we report a facile hydrothermal method to directly grow cerium oxide nanorods on diverse substrates, such as aluminum alloy, stainless steel, titanium, and silicon. Diverse substrates with cerium oxide nanorods exhibited superhydrophobicity with no hydrophobic modifiers on their surfaces, and showed good corrosion resistive properties in corrosive medium. We believe our method could pave the way for realization of scalable and sustainable corrosion resistive superhydrophobic surfaces in many industrial fields.

  9. Inhaled Diesel Emissions Generated with Cerium Oxide Nanoparticle Fuel Additive Induce Adverse Pulmonary and Systemic Effects

    EPA Science Inventory

    Diesel exhaust (DE) exposure induces adverse cardiopulmonary effects. Cerium oxide nanoparticles added to diesel fuel (DECe) increases fuel burning efficiency but leads to altered emission characteristics and potentially altered health effects. Here, we evaluated whether DECe res...

  10. Antioxidant properties of cerium oxide nanocrystals as a function of nanocrystal diameter and surface coating.

    PubMed

    Lee, Seung Soo; Song, Wensi; Cho, Minjung; Puppala, Hema L; Nguyen, Phuc; Zhu, Huiguang; Segatori, Laura; Colvin, Vicki L

    2013-11-26

    This work examines the effect of nanocrystal diameter and surface coating on the reactivity of cerium oxide nanocrystals with H2O2 both in chemical solutions and in cells. Monodisperse nanocrystals were formed in organic solvents from the decomposition of cerium precursors, and subsequently phase transferred into water using amphiphiles as nanoparticle coatings. Quantitative analysis of the antioxidant capacity of CeO2-x using gas chromatography and a luminol test revealed that 2 mol of H2O2 reacted with every mole of cerium(III), suggesting that the reaction proceeds via a Fenton-type mechanism. Smaller diameter nanocrystals containing more cerium(III) were found to be more reactive toward H2O2. Additionally, the presence of a surface coating did not preclude the reaction between the nanocrystal surface cerium(III) and hydrogen peroxide. Taken together, the most reactive nanoparticles were the smallest (e.g., 3.8 nm diameter) with the thinnest surface coating (e.g., oleic acid). Moreover, a benchmark test of their antioxidant capacity revealed these materials were 9 times more reactive than commercial antioxidants such as Trolox. A unique feature of these antioxidant nanocrystals is that they can be applied multiple times: over weeks, cerium(IV) rich particles slowly return to their starting cerium(III) content. In nearly all cases, the particles remain colloidally stable (e.g., nonaggregated) and could be applied multiple times as antioxidants. These chemical properties were also observed in cell culture, where the materials were able to reduce oxidative stress in human dermal fibroblasts exposed to H2O2 with efficiency comparable to their solution phase reactivity. These data suggest that organic coatings on cerium oxide nanocrystals do not limit the antioxidant behavior of the nanocrystals, and that their redox cycling behavior can be preserved even when stabilized. PMID:24079896

  11. Static and dynamic high pressure experiments on cerium

    SciTech Connect

    Jensen, Brian J; Velisavljevic, Nenad; Cherne, Frank J; Stevens, Gerald; Tschauner, Oliver

    2011-01-25

    There is a scientific need to obtain dynamic data to develop and validate multi phase equation-of-state (EOS) models for metals. Experiments are needed to examine the relevant pure phases, to locate phase boundaries and the associated transition kinetics, and other material properties such as strength. Cerium is an ideal material for such work because it exhibits a complex multiphase diagram at relatively moderate pressures readily accessible using standard shock wave methods. In the current work, shock wave (dynamic) and diamond anvil cell (static) experiments were performed to examine the high pressure, low temperature region of the phase diagram to obtain EOS data and to search for the {alpha}-{var_epsilon} boundary. Past work examining the shock-melt transition and the low-pressure {gamma}-{alpha} transition will be presented in brief followed by details of recent results obtained from DAC and double-shock experiments.

  12. The Spin Glass-Kondo Competition in Disordered Cerium Systems

    NASA Astrophysics Data System (ADS)

    Magalhaes, S. G.; Zimmer, F.; Coqblin, B.

    2013-10-01

    We discuss the competition between the Kondo effect, the spin glass state and a magnetic order observed in disordered Cerium systems. We present firstly the experimental situation of disordered alloys such as CeNi1 - xCux and then the different theoretical approaches based on the Kondo lattice model, with different descriptions of the intersite exchange interaction for the spin glass. After the gaussian approach of the Sherrington-Kirkpatrick model, we discuss the Mattis and the van Hemmen models. Then, we present simple cluster calculations in order to describe the percolative evolution of the clusters from the cluster spin glass to the inhomogeneous ferromagnetic order recently observed in CeNi1 - xCux disordered alloys and finally we discuss the effect of random and transverse magnetic field.

  13. Growth of transition metals on cerium tungstate model catalyst layers

    NASA Astrophysics Data System (ADS)

    Skála, T.; Tsud, N.; Stetsovych, V.; Mysliveček, J.; Matolín, V.

    2016-10-01

    Two model catalytic metal/oxide systems were investigated by photoelectron spectroscopy and scanning tunneling microscopy. The mixed-oxide support was a cerium tungstate epitaxial thin layer grown in situ on the W(1 1 0) single crystal. Active particles consisted of palladium and platinum 3D islands deposited on the tungstate surface at 300 K. Both metals were found to interact weakly with the oxide support and the original chemical state of both support and metals was mostly preserved. Electronic and morphological changes are discussed during the metal growth and after post-annealing at temperatures up to 700 K. Partial transition-metal coalescence and self-cleaning from the CO and carbon impurities were observed.

  14. Characterization of a zinc-cerium flow battery

    NASA Astrophysics Data System (ADS)

    Leung, P. K.; Ponce-de-León, C.; Low, C. T. J.; Shah, A. A.; Walsh, F. C.

    The performance of a divided, parallel-plate zinc-cerium redox flow battery using methanesulfonic acid electrolytes was studied. Eight two and three-dimensional electrodes were tested under both constant current density and constant cell voltage discharge. Carbon felt and the three-dimensional platinised titanium mesh electrodes exhibited superior performance over the 2-dimensional electrodes. The charge and discharge characteristics of the redox flow battery were studied under different operating conditions and Zn/Ce reactant, as well as methansulfonic acid concentration. The cell performance improved at higher operating temperatures and faster electrolyte flow velocities. The number of possible cycles increased at reduced states of charge. During 15 min charge/discharge per cycle experiment, 57 cycles were obtained and the zinc reaction was found to be the limiting process during long term operation.

  15. Redox reactivity of cerium oxide nanoparticles against dopamine.

    PubMed

    Hayat, Akhtar; Andreescu, Daniel; Bulbul, Gonca; Andreescu, Silvana

    2014-03-15

    The interaction between dopamine and the redox active cerium oxide nanoparticles, or nanoceria was studied using a suite of spectroscopic and surface characterization methods. Changes in the chemical reactivity and concentration of dopamine upon exposure to nanoceria was assessed in aqueous solutions and a human physiological fluid--human serum. The results indicate strong attachment of dopamine to the nanoparticle surface through oxidation followed by chemisorption of the oxidative product with formation of a charge transfer complex. Such oxidation/surface adsorption processes between nanoceria and dopamine lead to a reduction of the concentration of free dopamine in aqueous environments. These findings suggest that the redox reactivity of nanoceria may alter dopamine levels in biological systems exposed to these particles and indicate the need for a comprehensive assessment of the potential neurological consequences that might result from intended or unintended exposure to these particles. PMID:24461841

  16. Growth of transition metals on cerium tungstate model catalyst layers.

    PubMed

    Skála, T; Tsud, N; Stetsovych, V; Mysliveček, J; Matolín, V

    2016-10-01

    Two model catalytic metal/oxide systems were investigated by photoelectron spectroscopy and scanning tunneling microscopy. The mixed-oxide support was a cerium tungstate epitaxial thin layer grown in situ on the W(1 1 0) single crystal. Active particles consisted of palladium and platinum 3D islands deposited on the tungstate surface at 300 K. Both metals were found to interact weakly with the oxide support and the original chemical state of both support and metals was mostly preserved. Electronic and morphological changes are discussed during the metal growth and after post-annealing at temperatures up to 700 K. Partial transition-metal coalescence and self-cleaning from the CO and carbon impurities were observed. PMID:27494195

  17. An Alkali Metal-Capped Cerium(IV) Imido Complex.

    PubMed

    Solola, Lukman A; Zabula, Alexander V; Dorfner, Walter L; Manor, Brian C; Carroll, Patrick J; Schelter, Eric J

    2016-06-01

    Structurally authenticated, terminal lanthanide-ligand multiple bonds are rare and expected to be highly reactive. Even capped with an alkali metal cation, poor orbital energy matching and overlap of metal and ligand valence orbitals should result in strong charge polarization within such bonds. We expand on a new strategy for isolating terminal lanthanide-ligand multiple bonds using cerium(IV) complexes. In the current case, our tailored tris(hydroxylaminato) ligand framework, TriNOx(3-), provides steric protection against ligand scrambling and metal complex oligomerization and electronic protection against reduction. This strategy culminates in isolation of the first formal Ce═N bonded moiety in the complex [K(DME)2][Ce═N(3,5-(CF3)2C6H3)(TriNOx)], whose Ce═N bond is the shortest known at 2.119(3) Å. PMID:27163651

  18. Role of nanocrystalline cerium oxide coatings on austenitic stainless steels

    NASA Astrophysics Data System (ADS)

    Zhang, Haiying

    Protective nanocrystalline cerium oxide coating has been applied to ASTM grade 304L and 304 austenitic stainless steels to improve its oxidation resistance at elevated temperatures. Experimentally, the selected alloy was exposed to 800°C/1000°C under dry air conditions. Weight changes (DeltaW/A) were monitored as a function of time and the results were compared with uncoated alloys tested under similar conditions. It was found that the oxidation resistances of 304L and 304 stainless steels were significantly improved. A comparison of the oxidation rates indicated that the nanocrystalline cerium oxide coating reduced the rate of oxidation by more than two orders of magnitude. Nevertheless, a comprehensive understanding of the mechanisms responsible for the reduction in the oxidation rate is not clear. Consequently, this work is aimed at investigating the mechanisms involved during scale growth in the presence or absence of nanocrystalline coatings. For this purpose, density functional theory was carried out in order to predict oxygen and iron diffusion microscopic activation energies and reveal the intrinsic characteristics of nanocrystalline coatings. A numerical simulation of corrosion process has also been conducted to predict the corrosion rates of alloys with and without coatings. Hence, the results from simulations are compared with the experimental outcome, and possible explanations are given to account for the reduction in the exhibited oxidation rates. The simulation results will provide a highly valuable tool for the realization of functional nanostructures and architectures "by design", particularly in the development of novel coatings, and a new approach of life assessment.

  19. Induction of pulmonary fibrosis by cerium oxide nanoparticles

    PubMed Central

    Ma, Jane Y.; Mercer, Robert R.; Barger, Mark; Schwegler-Berry, Diane; Scabilloni, James; Ma, Joseph K.; Castranova, Vincent

    2015-01-01

    Cerium compounds have been used as a diesel engine catalyst to lower the mass of diesel exhaust particles, but are emitted as cerium oxide (CeO2) nanoparticles in the diesel exhaust. In a previous study, we have demonstrated a wide range of CeO2-induced lung responses including sustained pulmonary inflammation and cellular signaling that could lead to pulmonary fibrosis. In this study, we investigated the fibrogenic responses induced by CeO2 in a rat model at various time points up to 84 days post-exposure. Male Sprague Dawley rats were exposed to CeO2 by a single intratracheal instillation. Alveolar macrophages (AM) were isolated by bronchial alveolar lavage (BAL). AM-mediated cellular responses, osteopontin (OPN) and transform growth factor (TGF)-β1 in the fibrotic process were investigated. The results showed that CeO2 exposure significantly increased fibrotic cytokine TGF-β1 and OPN production by AM above controls. The collagen degradation enzymes, matrix metalloproteinase (MMP)-2 and -9 and the tissue inhibitor of MMP were markedly increased in the BAL fluid at 1 day- and subsequently declined at 28 days after exposure, but remained much higher than the controls. CeO2 induced elevated phospholipids in BAL fluid and increased hydroxyproline content in lung tissue in a dose- and time-dependent manner. Immunohistochemical analysis showed MMP-2, MMP-9 and MMP-10 expressions in fibrotic regions. Morphological analysis noted increased collagen fibers in the lungs exposed to a single dose of 3.5 mg/kg CeO2 and euthanized at 28 days post-exposure. Collectively, our studies show that CeO2 induced fibrotic lung injury in rats, suggesting it may cause potential health effects. PMID:22613087

  20. Synthesis and catalytic properties of microemulsion-derived cerium oxide nanoparticles

    SciTech Connect

    Kockrick, Emanuel; Schrage, Christian; Grigas, Anett; Geiger, Dorin; Kaskel, Stefan

    2008-07-15

    The synthesis of cerium dioxide nanoparticles using an inverse microemulsion technique and precipitation method was investigated. Cerium hydroxide nanoparticles were synthesized by adding diluted ammonia to n-heptane-surfactant-cerium nitrate system. The micelle and particle size in the range of 5-12 nm were controlled by varying the molar water to surfactant ratio and analyzed by dynamic light scattering (DLS), small angle X-ray scattering (SAXS) and high-resolution transmission electron microscopy (HRTEM). Cerium hydroxide nanoparticles were isolated and subsequently treated at 100-600 deg. C to obtain nanoscale ceria. Crystallite sizes of cerium dioxide in the range of 6-16 nm were estimated by Scherrer analysis by X-ray diffraction (XRD) and HRTEM. The catalytic activity of particles annealed at 400 and 600 deg. C in soot combustion reactions was characterized by temperature-programmed oxidation (TPO) indicating a size-dependant activity. Crystallite sizes and catalytic stability of elevated ceria systems were tested in second combustion cycles. - Graphical abstract: The synthesis of cerium dioxide nanoparticles using an inverse microemulsion technique and precipitation method was investigated using small angle X-ray scattering, dynamic light scattering and high-resolution transmission electron microscopy. Catalytic activity of ceria nanoparticles was tested in soot combustion reaction indicating size-dependent reactivity.

  1. Thin film cadmium telluride solar cells. Final technical report for period July 1, 1979-August 31, 1980

    SciTech Connect

    Chu, T.L.

    1980-08-01

    The objectives of this contract are to investigate thin films of cadmium telluride on low cost substrates and to determine the feasibility of using these films for high efficiency solar cells. Efforts during this program have been directed to the construction of apparatus for the chemical vapor deposition of cadmium telluride films, the selection and preparation of substrates, the deposition and characterization of cadmium telluride films, and the fabrication and characterization of solar cells. Cadmium telluride films have been deposited on a number of substrates by the direct combination of cadmium and tellurium on the substrate surface at 500/sup 0/C or higher at rates of up to 0.6 ..mu..m/min. The structural, crystallographic, and electrical properties of cadmium telluride films deposited over a wide range of conditions have been evaluated. A series of doping experiments have been carried out using iodine and indium as the n-type dopant, and phosphorus, arsenic, and antimony as the p-type dopant. Low resistivity films have not been produced thus far. In/W/graphite substrates have been used for the deposition of n-type films with an ohmic interface. However, no suitable substrates have been found to form an ohmic interface with p-type films. Solar cells prepared from these films exhibit relatively good short-circuit current density, up to 15 mA/cm/sup 2/, but their conversion efficiencies are severely limited by the high series resistance of the devices.

  2. Seebeck and figure of merit enhancement in nanostructured antimony telluride by antisite defect suppression through sulfur doping.

    PubMed

    Mehta, Rutvik J; Zhang, Yanliang; Zhu, Hong; Parker, David S; Belley, Matthew; Singh, David J; Ramprasad, Ramamurthy; Borca-Tasciuc, Theodorian; Ramanath, Ganpati

    2012-09-12

    Antimony telluride has a low thermoelectric figure of merit (ZT < ∼0.3) because of a low Seebeck coefficient α arising from high degenerate hole concentrations generated by antimony antisite defects. Here, we mitigate this key problem by suppressing antisite defect formation using subatomic percent sulfur doping. The resultant 10-25% higher α in bulk nanocrystalline antimony telluride leads to ZT ∼ 0.95 at 423 K, which is superior to the best non-nanostructured antimony telluride alloys. Density functional theory calculations indicate that sulfur increases the antisite formation activation energy and presage further improvements leading to ZT ∼ 2 through optimized doping. Our findings are promising for designing novel thermoelectric materials for refrigeration, waste heat recovery, and solar thermal applications.

  3. Formation of Semimetallic Cobalt Telluride Nanotube Film via Anion Exchange Tellurization Strategy in Aqueous Solution for Electrocatalytic Applications.

    PubMed

    Patil, Supriya A; Kim, Eun-Kyung; Shrestha, Nabeen K; Chang, Jinho; Lee, Joong Kee; Han, Sung-Hwan

    2015-11-25

    Metal telluride nanostructures have demonstrated several potential applications particularly in harvesting and storing green energy. Metal tellurides are synthesized by tellurization process performed basically at high temperature in reducing gas atmosphere, which makes the process expensive and complicated. The development of a facile and economical process for desirable metal telluride nanostructures without complicated manipulation is still a challenge. In an effort to develop an alternative strategy of tellurization, herein we report a thin film formation of self-standing cobalt telluride nanotubes on various conducting and nonconducting substrates using a simple binder-free synthetic strategy based on anion exchange transformation from a thin film of cobalt hydroxycarbonate nanostructures in aqueous solution at room temperature. The nanostructured films before and after ion exchange transformation reaction are characterized using field emission scanning electron microscope, energy dispersive X-ray analyzer, X-ray photoelectron spectroscopy, thin film X-ray diffraction technique, high resolution transmission electron microscope, and selected area electron diffraction analysis technique. After the ion exchange transformation of nanostructures, the film shows conversion from insulator to highly electrical conductive semimetallic characteristic. When used as a counter electrode in I3(-)/I(-) redox electrolyte based dye-sensitized solar cells, the telluride film exhibits an electrocatalytic reduction activity for I3(-) with a demonstration of solar-light to electrical power conversion efficiency of 8.10%, which is highly competitive to the efficiency of 8.20% exhibited by a benchmarked Pt-film counter electrode. On the other hand, the telluride film electrode also demonstrates electrocatalytic activity for oxygen evolution reaction from oxidation of water.

  4. Electronic Characterization of Defects in Narrow Gap Semiconductors-Comparison of Electronic Energy Levels and Formation Energies in Mercury Cadmium Telluride, Mercury Zinc Telluride, and Mercury Zinc Selenide

    NASA Technical Reports Server (NTRS)

    Patterson, James D.

    1996-01-01

    We have used a Green's function technique to calculate the energy levels and formation energy of deep defects in the narrow gap semiconductors mercury cadmium telluride (MCT), mercury zinc telluride (MZT) and mercury zinc selenide (MZS). The formation energy is calculated from the difference between the total energy with an impurity cluster and the total energy for the perfect crystal. Substitutional (including antisite), interstitial (self and foreign), and vacancy deep defects are considered. Relaxation effects are calculated (with molecular dynamics). By use of a pseudopotential, we generalize the ideal vacancy model so as to be able to consider relaxation for vacancies. Different charge states are considered and the charged state energy shift (as computed by a modified Haldane-Anderson model) can be twice that due to relaxation. Different charged states for vacancies were not calculated to have much effect on the formation energy. For all cases we find deep defects in the energy gap only for cation site s-like orbitals or anion site p-like orbitals, and for the substitutional case only the latter are appreciably effected by relaxation. For most cases for MCT, MZT, MZS, we consider x (the concentration of Cd or Zn) in the range appropriate for a band gap of 0.1 eV. For defect energy levels, the absolute accuracy of our results is limited, but the precision is good, and hence chemical trends are accurately predicted. For the same reason, defect formation energies are more accurately predicted than energy level position. We attempt, in Appendix B, to calculate vacancy formation energies using relatively simple chemical bonding ideas due to Harrison. However, these results are only marginally accurate for estimating vacancy binding energies. Appendix C lists all written reports and publications produced for the grant. We include abstracts and a complete paper that summarizes our work which is not yet available.

  5. Copper, Boron, and Cerium Additions in Type 347 Austenitic Steel to Improve Creep Rupture Strength

    NASA Astrophysics Data System (ADS)

    Laha, Kinkar; Kyono, J.; Shinya, Norio

    2012-04-01

    Type 347 austenitic stainless steel (18Cr-12Ni-Nb) was alloyed with copper (3 wt pct), boron (0.01 to 0.06 wt pct), and cerium (0.01 wt pct) with an aim to increase the creep rupture strength of the steel through the improved deformation and cavitation resistance. Short-term creep rupture strength was found to increase with the addition of copper in the 347 steel, but the long-term strength was inferior. Extensive creep cavitation deprived the steel of the beneficial effect of creep deformation resistance induced by nano-size copper particles. Boron and cerium additions in the copper-containing steel increased its creep rupture strength and ductility, which were more for higher boron content. Creep deformation, grain boundary sliding, and creep cavity nucleation and growth in the steel were found to be suppressed by microalloying the copper-containing steel with boron and cerium, and the suppression was more for higher boron content. An auger electron spectroscopic study revealed the segregation of boron instead of sulfur on the cavity surface of the boron- and cerium-microalloyed steel. Cerium acted as a scavenger for soluble sulfur in the steels through the precipitation of cerium sulfide (CeS). This inhibited the segregation of sulfur and facilitated the segregation of boron on cavity surface. Boron segregation on the nucleated cavity surface reduced its growth rate. Microalloying the copper-containing 347 steel with boron and cerium thus enabled to use the full extent of creep deformation resistance rendered by copper nano-size particle by increase in creep rupture strength and ductility.

  6. Feasibility of preparing patterned molybdenum coatings on bismuth telluride thermoelectric modules.

    SciTech Connect

    Sarobol, Pylin; Hall, Aaron Christopher; Miller, Stephen Samuel; Knight, Marlene E.; LePage, William S.; Sobczak, Catherine Elizabeth.; Wesolowski, Daniel Edward

    2013-09-01

    Molybdenum electrical interconnects for thermoelectric modules were produced by air plasma spraying a 30%CE%BCm size molybdenum powder through a laser-cut Kapton tape mask. Initial feasibility demonstrations showed that the molybdenum coating exhibited excellent feature and spacing retention (~170%CE%BCm), adhered to bismuth-telluride, and exhibited electrical conductivity appropriate for use as a thermoelectric module interconnect. A design of experiments approach was used to optimize air plasma spray process conditions to produce a molybdenum coating with low electrical resistivity. Finally, a molybdenum coating was successfully produced on a fullscale thermoelectric module. After the addition of a final titanium/gold layer deposited on top of the molybdenum coating, the full scale module exhibited an electrical resistivity of 128%CE%A9, approaching the theoretical resistivity value for the 6mm module leg of 112%CE%A9. Importantly, air plasma sprayed molybdenum did not show significant chemical reaction with bismuth-telluride substrate at the coating/substrate interface. The molybdenum coating microstructure consisted of lamellar splats containing columnar grains. Air plasma sprayed molybdenum embedded deeply (several microns) into the bismuth-telluride substrate, leading to good adhesion between the coating and the substrate. Clusters of round pores (and cracks radiating from the pores) were found immediately beneath the molybdenum coating. These pores are believed to result from tellurium vaporization during the spray process where the molten molybdenum droplets (2623%C2%B0C) transferred their heat of solidification to the substrate at the moment of impact. Substrate cooling during the molybdenum deposition process was recommended to mitigate tellurium vaporization in future studies.

  7. Exposure and Health Effects Review of Engineered Nanoscale Cerium and Cerium Dioxide Associated with its Use as a Fuel Additive - NOW IN PRINT IN THE JOURNAL

    EPA Science Inventory

    Advances of nanoscale science have produced nanomaterials with unique physical and chemical properties at commercial levels that are now incorporated into over 1000 products. Nanoscale cerium (di) oxide (Ce02) has recently gained a wide range of applications which includes coatin...

  8. Exposure, Health and Ecological Effects Review of Engineered Nanoscale Cerium and Cerium Oxide Associated with its Use as a Fuel Additive

    EPA Science Inventory

    Advances of nanoscale science have produced nanomaterials with unique physical and chemical properties at commercial levels which are now incorporated into over 1000 products. Nanoscale cerium (di) oxide (CeO(2)) has recently gained a wide range of applications which includes coa...

  9. High resolution X-ray diffraction imaging of lead tin telluride

    NASA Technical Reports Server (NTRS)

    Steiner, Bruce; Dobbyn, Ronald C.; Black, David; Burdette, Harold; Kuriyama, Masao; Spal, Richard; Simchick, Richard; Fripp, Archibald

    1991-01-01

    High resolution X-ray diffraction images of two directly comparable crystals of lead tin telluride, one Bridgman-grown on Space Shuttle STS 61A and the other terrestrially Bridgman-grown under similar conditions from identical material, present different subgrain structure. In the terrestrial, sample 1 the appearance of an elaborate array of subgrains is closely associated with the intrusion of regions that are out of diffraction in all of the various images. The formation of this elaborate subgrain structure is inhibited by growth in microgravity.

  10. Hexavalent chromium in the ground and surface waters near Telluride, Colorado; preliminary data report

    USGS Publications Warehouse

    Grove, David B.; Miller, R.L.; Konikow, L.F.; O'Boyle, P. S.

    1979-01-01

    Data showing results of 38 groundwater and 25 surface-water samples analyzed for hexavalent chromium are presented. Most samples were taken within the Telluride, Colo., city limits during October 1978. Twenty-four of the 38 groundwater samples (63%) contained more than 50 micrograms per liter of hexavalent chromium. Excluding the mill tailings pond 6 of the 23 surface-water samples (26%) contained more than 50 micrograms per liter of hexavalent chromium. Hexavalent chromium concentrations in groundwaters ranged from 0 to 2700 micrograms per liter and in surface waters from 0 to 160 micrograms per liter. (USGS)

  11. Fabrication of Lanthanum Telluride 14-1-11 Zintl High-Temperature Thermoelectric Couple

    NASA Technical Reports Server (NTRS)

    Ravi, Vilupanur A.; Li, Billy Chun-Yip; Fleurial, Pierre; Star, Kurt

    2010-01-01

    The development of more efficient thermoelectric couple technology capable of operating with high-grade heat sources up to 1,275 K is key to improving the performance of radioisotope thermoelectric generators. Lanthanum telluride La3-xTe4 and 14-1-11 Zintls (Yb14MnSb11) have been identified as very promising materials. The fabrication of advanced high-temperature thermoelectric couples requires the joining of several dissimilar materials, typically including a number of diffusion bonding and brazing steps, to achieve a device capable of operating at elevated temperatures across a large temperature differential (up to 900 K). A thermoelectric couple typically comprises a heat collector/ exchanger, metallic interconnects on both hot and cold sides, n-type and ptype conductivity thermoelectric elements, and cold-side hardware to connect to the cold-side heat rejection and provide electrical connections. Differences in the physical, mechanical, and chemical properties of the materials that make up the thermoelectric couple, especially differences in the coefficients of thermal expansion (CTE), result in undesirable interfacial stresses that can lead to mechanical failure of the device. The problem is further complicated by the fact that the thermoelectric materials under consideration have large CTE values, are brittle, and cracks can propagate through them with minimal resistance. The inherent challenge of bonding brittle, high-thermal-expansion thermoelectric materials to a hot shoe material that is thick enough to carry the requisite electrical current was overcome. A critical advantage over prior art is that this device was constructed using all diffusion bonds and a minimum number of assembly steps. The fabrication process and the materials used are described in the following steps: (1) Applying a thin refractory metal foil to both sides of lanthanum telluride. To fabricate the n-type leg of the advanced thermoelectric couple, the pre-synthesized lanthanum

  12. Specific features of the photoconductivity of semi-insulating cadmium telluride

    SciTech Connect

    Golubyatnikov, V. A.; Grigor’ev, F. I.; Lysenko, A. P. Strogankova, N. I.; Shadov, M. B.; Belov, A. G.

    2014-12-15

    The effect of local illumination providing a high level of free-carrier injection on the conductivity of a sample of semi-insulating cadmium telluride and on the properties of ohmic contacts to the sample is studied. It is found that, irrespective of the illumination region, the contact resistance of ohmic contacts decreases and the concentration of majority carriers in the sample grows in proportion to the illumination intensity. It is shown that inherent heterogeneities in crystals of semi-insulating semiconductors can be studied by scanning with a light probe.

  13. Seeded Physical Vapor Transport of Cadmium-Zinc Telluride Crystals: Growth and Characterization

    NASA Technical Reports Server (NTRS)

    Palosz, W.; George, M. A.; Collins, E. E.; Chen, K.-T.; Zhang, Y.; Burger, A.

    1997-01-01

    Crystals of Cd(1-x)Zn(x)Te with x = 0.2 and 40 g in weight were grown on monocrystalline cadmium-zinc telluride seeds by closed-ampoule physical vapor transport with or without excess (Cd + Zn) in the vapor phase. Two post-growth cool-down rates were used. The crystals were characterized using low temperature photoluminescence, atomic force microscopy, chemical etching, X-ray diffraction and electrical measurements. No formation of a second, ZnTe-rich phase was observed.

  14. Advanced methods for preparation and characterization of infrared detector materials. [mercury cadmium telluride alloys

    NASA Technical Reports Server (NTRS)

    Lehoczky, S. L.; Szofran, F. R.

    1981-01-01

    Differential thermal analysis data were obtained on mercury cadmium telluride alloys in order to establish the liquidus temperatures for the various alloy compositions. Preliminary theoretical analyses was performed to establish the ternary phase equilibrium parameters for the metal rich region of the phase diagram. Liquid-solid equilibrium parameters were determined for the pseudobinary alloy system. Phase equilibrium was calculated and Hg(l-x) Cd(x) Te alloys were directionally solidified from pseudobinary melts. Electrical resistivity and Hall coefficient measurements were obtained.

  15. A passively mode locked thulium doped fiber laser using bismuth telluride deposited multimode interference

    NASA Astrophysics Data System (ADS)

    Jung, M.; Lee, J.; Song, W.; Lee, J. H.; Shin, W.

    2016-03-01

    We experimentally demonstrate a passively mode-locked thulium doped fiber laser using a bismuth telluride deposited multimode interference (MMI) fiber at a wavelength of 1958 nm. Our MMI based saturable absorber was fabricated by fusion splicing with single mode fiber and null core fiber. The center wavelength and insertion loss of MMI fiber were measured to be ~ 1958 nm and 3.4 dB. We observed a passively mode locked thulium doped fiber laser operating at a wavelength of 1958 nm. The temporal pulse width of output pulses is 4.2 ps with repetition rate of 22.7 MHz.

  16. Observation of defects in mercury cadmium telluride crystals grown by chemical vapor transport

    NASA Technical Reports Server (NTRS)

    Irene, E. A.; Tierney, E.; Wiedemeier, H.; Chandra, D.

    1983-01-01

    A mixture of nitric and hydrochloric acids was found to yield etch pits on mercury cadmium telluride crystals grown by chemical vapor transport using iodine or mercuric iodide as the transport agent. Two types of pits were observed by optical microscopy: triangular pyramidal and round saucer shaped pits. Transmission electron microscopy confirmed that two types of defects were present: dislocations and second phase occlusions. The present study suggests that the defects are near the crystal surface and therefore will probably not significantly affect the electrical characteristics.

  17. Operational Studies of Cadmium Zinc Telluride Microstrip Detectors using SVX ASIC Electronics

    NASA Astrophysics Data System (ADS)

    Krizmanic, John; Barbier, L. M.; Barthelmy, S.; Bartlett, L.; Birsa, F.; Gehrels, N.; Hanchak, C.; Kurczynski, P.; Odom, J.; Parsons, A.; Palmer, D.; Sheppard, D.; Snodgrass, S.; Stahle, C. M.; Teegarden, B.; Tueller, J.

    1997-04-01

    We have been investigating the operational properties of cadmium zinc telluride (CZT) microstrip detectors by using SVX ASIC readout electronics. This research is in conjunction with the development of a CZT-based, next generation gamma-ray telescope for use in the gamma-ray Burst ArcSecond Imaging and Spectroscopy (BASIS) experiment. CZT microstrip detectors with 128 channels and 100 micron strip pitch have been fabricated and were interfaced to SVX electronics at Goddard Space Flight Center. Experimental results involving position sensing, spectroscopy, and CZT operational properties will be presented.

  18. Thermochemical Modeling of the Uranium-Cerium-Oxygen System

    SciTech Connect

    Voit, Stewart L; Besmann, Theodore M

    2010-10-01

    with actinide materials, fundamental studies with uranium are performed using surrogate materials as stand-ins for transuranic elements. In most cases, cerium can be used as a suitable substitute for plutonium when performing O:M and sintering kinetics studies because of identical valence states. Differences exist between the magnitude of reported thermodynamic data of (U,Pu)O{sub x} and (U,Ce)O{sub x}, however the change in oxygen potential versus O:M follows the same trend for both systems. Cerium is also a major fission product element, and thus understanding its behavior in fuel is an important issue as well.

  19. Coupled redox transformations of catechol and cerium at the surface of a cerium(III) phosphate mineral

    NASA Astrophysics Data System (ADS)

    Cervini-Silva, Javiera; Gilbert, Benjamin; Fakra, Sirine; Friedlich, Stephan; Banfield, Jillian

    2008-05-01

    Highly insoluble Ce-bearing phosphate minerals form by weathering of apatite [Ca5(PO4)3.(OH,F,Cl)], and are important phosphorous repositories in soils. Although these phases can be dissolved via biologically-mediated pathways, the dissolution mechanisms are poorly understood. In this paper we report spectroscopic evidence to support coupling of redox transformations of organic carbon and cerium during the reaction of rhabdophane (CePO4·H2O) and catechol, a ubiquitous biogenic compound, at pH 5. Results show that the oxic-anoxic conditions influence the mineral dissolution behavior. Under anoxic conditions, the release of P and Ce occurs stoichiometrically. In contrast, under oxic conditions, the mineral dissolution behavior is incongruent, with dissolving Ce3+ ions oxidizing to CeO2. Reaction product analysis shows the formation of CO2, polymeric C, and oxalate and malate. The presence of more complex forms of organic carbon was also confirmed. Near edge X-ray absorption fine structure spectroscopy measurements at Ce-M4,5 and C-K absorption edges on reacted CePO4·H2O samples in the absence or presence of catechol and dissolved oxygen confirm that (1) the mineral surface converts to the oxide during this reaction, while full oxidation is limited to the near-surface region only; (2) the Ce valence remains unchanged when the reaction between CePO4·H2O and O2 but in the absence of catechol. Carbon K-edge spectra acquired from rhabdophane reacted with catechol under oxic conditions show spectral features before and after reaction that are considerably different from catechol, indicating the formation of more complex organic molecules. Decreases in intensity of characteristic catechol peaks are accompanied by the appearance of new π∗ resonances due to carbon in carboxyl (ca. 288.5 eV) and carbonyl (ca. 289.3 eV) groups, and the development of broad structure in the σ∗ region characteristic of aliphatic carbon. Evolution of the C K-edge spectra is consistent

  20. A new class of homogeneous visible-light photocatalysts: molecular cerium vanadium oxide clusters.

    PubMed

    Seliverstov, Andrey; Streb, Carsten

    2014-07-28

    The first systematic access to molecular cerium vanadium oxides is presented. A family of structurally related, di-cerium-functionalized vanadium oxide clusters and their use as visible-light-driven photooxidation catalysts is reported. Comparative analyses show that photocatalytic activity is controlled by the cluster architecture. Increased photoreactivity of the cerium vanadium oxides in the visible range compared with nonfunctionalized vanadates is observed. Based on the recent discovery of the first molecular cerium vanadate cluster, (nBu4 N)2 [(Ce(dmso)3 )2 V12 O33 Cl]⋅2 DMSO (1), two new di-cerium-containing vanadium oxide clusters [(Ce(dmso)4 )2 V11 O30 Cl]⋅DMSO (2) and [(Ce(nmp)4 )2 V12 O32 Cl]⋅NMP⋅Me2 CO (3; NMP=N-methyl-2-pyrrolidone) were obtained by using a novel fragmentation and reassembly route. Pentagonal building units {(V)M5 } (M=V, Ce) reminiscent of "Müller-type" pentagons are observed in 2 and 3. Compounds 1-3 feature high visible-light photooxidative activity, and quantum efficiencies >10 % for indigo photooxidation are observed. Photocatalytic performance increases in the order 1<3<2. Mechanistic studies show that the irradiation wavelength and the presence of oxygen strongly affect photoreactivity. Initial findings suggest that the photooxidation mechanism proceeds by intermediate formation of hydroxyl radicals. The findings open new avenues for the bottom-up design of sunlight-driven photocatalysts.

  1. Exposure of cerium oxide nanoparticles to kidney bean shows disturbance in the plant defense mechanisms.

    PubMed

    Majumdar, Sanghamitra; Peralta-Videa, Jose R; Bandyopadhyay, Susmita; Castillo-Michel, Hiram; Hernandez-Viezcas, Jose-Angel; Sahi, Shivendra; Gardea-Torresdey, Jorge L

    2014-08-15

    Overwhelming use of engineered nanoparticles demands rapid assessment of their environmental impacts. The transport of cerium oxide nanoparticles (nCeO2) in plants and their impact on cellular homeostasis as a function of exposure duration is not well understood. In this study, kidney bean plants were exposed to suspensions of ∼ 8 ± 1 nm nCeO2 (62.5 to 500 mg/L) for 15 days in hydroponic conditions. Plant parts were analyzed for cerium accumulation after one, seven, and 15 days of nCeO2 exposure. The primary indicators of stress like lipid peroxidation, antioxidant enzyme activities, total soluble protein and chlorophyll contents were studied. Cerium in tissues was localized using scanning electron microscopy and synchrotron μ-XRF mapping, and the chemical forms were identified using μ-XANES. In the root epidermis, cerium was primarily shown to exist as nCeO2, although a small fraction (12%) was biotransformed to Ce(III) compound. Cerium was found to reach the root vascular tissues and translocate to aerial parts with time. Upon prolonged exposure to 500 mg nCeO2/L, the root antioxidant enzyme activities were significantly reduced, simultaneously increasing the root soluble protein by 204%. In addition, leaf's guaiacol peroxidase activity was enhanced with nCeO2 exposure in order to maintain cellular homeostasis. PMID:24981679

  2. Catalysts with Cerium in a Membrane Reactor for the Removal of Formaldehyde Pollutant from Water Effluents.

    PubMed

    Gutiérrez-Arzaluz, Mirella; Noreña-Franco, Luis; Ángel-Cuevas, Saúl; Mugica-Álvarez, Violeta; Torres-Rodríguez, Miguel

    2016-01-01

    We report the synthesis of cerium oxide, cobalt oxide, mixed cerium, and cobalt oxides and a Ce-Co/Al₂O₃ membrane, which are employed as catalysts for the catalytic wet oxidation (CWO) reaction process and the removal of formaldehyde from industrial effluents. Formaldehyde is present in numerous waste streams from the chemical industry in a concentration low enough to make its recovery not economically justified but high enough to create an environmental hazard. Common biological degradation methods do not work for formaldehyde, a highly toxic but refractory, low biodegradability substance. The CWO reaction is a recent, promising alternative that also permits much lower temperature and pressure conditions than other oxidation processes, resulting in economic benefits. The CWO reaction employing Ce- and Co-containing catalysts was carried out inside a slurry batch reactor and a membrane reactor. Experimental results are reported. Next, a mixed Ce-Co oxide film was supported on an γ-alumina membrane used in a catalytic membrane reactor to compare formaldehyde removal between both types of systems. Catalytic materials with cerium and with a relatively large amount of cerium favored the transformation of formaldehyde. Cerium was present as cerianite in the catalytic materials, as indicated by X-ray diffraction patterns. PMID:27231888

  3. Precipitation-Redispersion of Cerium Oxide Nanoparticles with Poly(acrylic acid): Toward Stable Dispersions

    SciTech Connect

    Sehgal,A.; Lalatonne, Y.; Berret, J.; Morvan, M.

    2005-01-01

    We exploit a precipitation-redispersion mechanism for complexation of short chain polyelectrolytes with cerium oxide nanoparticles to extend their stability ranges. As synthesized, cerium oxide sols at pH 1.4 consist of monodisperse cationic nanocrystalline particles having a hydrodynamic diameter of 10 nm and a molecular weight of 400 000 g mol{sup -1}. We show that short chain uncharged poly(acrylic acid) at low pH when added to a cerium oxide sols leads to macroscopic precipitation. As the pH is increased, the solution spontaneously redisperses into a clear solution of single particles with an anionic poly(acrylic acid) corona. The structure and dynamics of cerium oxide nanosols and their hybrid polymer-inorganic complexes in solution are investigated by static and dynamic light scattering, X-ray scattering, and chemical analysis. Quantitative analysis of the redispersed sol gives rise to an estimate of 40-50 polymer chains per particle for stable suspension. This amount represents 20% of the mass of the polymer-nanoparticle complexes. This complexation adds utility to the otherwise unstable cerium oxide dispersions by extending the range of stability of the sols in terms of pH, ionic strength, and concentration.

  4. Antioxidant Cerium Oxide Nanoparticles in Biology and Medicine

    PubMed Central

    Nelson, Bryant C.; Johnson, Monique E.; Walker, Marlon L.; Riley, Kathryn R.; Sims, Christopher M.

    2016-01-01

    Previously, catalytic cerium oxide nanoparticles (CNPs, nanoceria, CeO2-x NPs) have been widely utilized for chemical mechanical planarization in the semiconductor industry and for reducing harmful emissions and improving fuel combustion efficiency in the automobile industry. Researchers are now harnessing the catalytic repertoire of CNPs to develop potential new treatment modalities for both oxidative- and nitrosative-stress induced disorders and diseases. In order to reach the point where our experimental understanding of the antioxidant activity of CNPs can be translated into useful therapeutics in the clinic, it is necessary to evaluate the most current evidence that supports CNP antioxidant activity in biological systems. Accordingly, the aims of this review are three-fold: (1) To describe the putative reaction mechanisms and physicochemical surface properties that enable CNPs to both scavenge reactive oxygen species (ROS) and to act as antioxidant enzyme-like mimetics in solution; (2) To provide an overview, with commentary, regarding the most robust design and synthesis pathways for preparing CNPs with catalytic antioxidant activity; (3) To provide the reader with the most up-to-date in vitro and in vivo experimental evidence supporting the ROS-scavenging potential of CNPs in biology and medicine. PMID:27196936

  5. Deposition and investigation of lanthanum-cerium hexaboride thin films

    SciTech Connect

    Kuzanyan, A.S. . E-mail: akuzan@ipr.sci.am; Harutyunyan, S.R.; Vardanyan, V.O.; Badalyan, G.R.; Petrosyan, V.A.; Kuzanyan, V.S.; Petrosyan, S.I.; Karapetyan, V.E.; Wood, K.S.; Wu, H.-D.

    2006-09-15

    Thin films of lanthanum-cerium hexaboride, the promising thermoelectric material for low-temperature applications, are deposited on various substrates by the electron-beam evaporation, pulsed laser deposition and magnetron sputtering. The influence of the deposition conditions on the films X-ray characteristics, composition, microstructure and physical properties, such as the resistivity and Seebeck coefficient, is studied. The preferred (100) orientation of all films is obtained from XRD traces. In the range of 780-800 deg. C deposition temperature the highest intensity of diffractions peaks and the highest degree of the preferred orientation are observed. The temperature dependence of the resistivity and the Seebeck coefficient of films are investigated in the temperature range of 4-300 K. The features appropriate to Kondo effect in the dependences {rho}(T) and S(T) are detected at temperatures below 20 K. Interplay between the value of the Seebeck coefficient, metallic parameters and Kondo scattering of investigated films is discussed. - Graphical abstract: Kondo scattering in (La,Ce)B{sub 6} films: temperature dependence of the resistivity of (La,Ce)B{sub 6} films on various substrates and the ceramics La{sub 0.99}Ce{sub 0.01}B{sub 6}.

  6. Toxicity of Cerium Oxide Nanoparticles in Human Lung Cancer Cells

    SciTech Connect

    Weisheng, Lin; Huang, Yue-wern; Zhou, Xiao Dong; Ma, Yinfa

    2006-12-31

    With the fast development of nanotechnology, the nanomaterials start to cause people's attention for potential toxic effect. In this paper, the cytotoxicity and oxidative stress caused by 20-nm cerium oxide (CeO2) nanoparticles in cultured human lung cancer cells was investigated. The sulforhodamine B method was employed to assess cell viability after exposure to 3.5, 10.5, and 23.3 μg/ml of CeO2 nanoparticles for 24, 48, and 72 h. Cell viability decreased significantly as a function of nanoparticle dose and exposure time. Indicators of oxidative stress and cytotoxicity, including total reactive oxygen species, glutathione, malondialdehyde, α-tocopherol, and lactate dehydrogenase, were quantitatively assessed. It is concluded from the results that free radicals generated by exposure to 3.5 to 23.3 μg/ml CeO2 nanoparticles produce significant oxidative stress in the cells, as reflected by reduced glutathione and α-tocopherol levels; the toxic effects of CeO2 nanoparticles are dose dependent and time dependent; elevated oxidative stress increases the production of malondialdehyde and lactate dehydrogenase, which are indicators of lipid peroxidation and cell membrane damage, respectively.

  7. Antioxidant Cerium Oxide Nanoparticles in Biology and Medicine.

    PubMed

    Nelson, Bryant C; Johnson, Monique E; Walker, Marlon L; Riley, Kathryn R; Sims, Christopher M

    2016-05-17

    Previously, catalytic cerium oxide nanoparticles (CNPs, nanoceria, CeO2-x NPs) have been widely utilized for chemical mechanical planarization in the semiconductor industry and for reducing harmful emissions and improving fuel combustion efficiency in the automobile industry. Researchers are now harnessing the catalytic repertoire of CNPs to develop potential new treatment modalities for both oxidative- and nitrosative-stress induced disorders and diseases. In order to reach the point where our experimental understanding of the antioxidant activity of CNPs can be translated into useful therapeutics in the clinic, it is necessary to evaluate the most current evidence that supports CNP antioxidant activity in biological systems. Accordingly, the aims of this review are three-fold: (1) To describe the putative reaction mechanisms and physicochemical surface properties that enable CNPs to both scavenge reactive oxygen species (ROS) and to act as antioxidant enzyme-like mimetics in solution; (2) To provide an overview, with commentary, regarding the most robust design and synthesis pathways for preparing CNPs with catalytic antioxidant activity; (3) To provide the reader with the most up-to-date in vitro and in vivo experimental evidence supporting the ROS-scavenging potential of CNPs in biology and medicine.

  8. Antioxidant cerium oxide nanoparticle hydrogels for cellular encapsulation.

    PubMed

    Weaver, Jessica D; Stabler, Cherie L

    2015-04-01

    Oxidative stress and the resulting radical by-products cause significant toxicity and graft loss in cellular transplantation. Here, the engineering of an auto-catalytic, antioxidant, self-renewing cerium oxide nanoparticle (CONP)-composite hydrogel is reported. This enzyme-mimetic material ubiquitously scavenges ambient free radicals, with the potential to provide indefinite antioxidant protection. The potential of this system to enhance the protection of encapsulated beta cells was evaluated. Co-incubation of CONPs free in solution with beta cells demonstrated potent cytoprotection from superoxide exposure; however, phagocytosis of the CONPs by the beta cells resulted in cytotoxicity at concentrations as low as 1mM. When CONPs were embedded within alginate hydrogels, the composite hydrogel provided cytoprotection to encapsulated beta cells from free radical attack without cytotoxicity, even up to 10mM. This nanocomposite hydrogel has wide applicability in cellular transplantation, with the unique advantage of localization of these potent antioxidant CONPs and their capacity for sustained, long-term scavenging. PMID:25620795

  9. Catalytic Properties and Biomedical Applications of Cerium Oxide Nanoparticles

    PubMed Central

    Walkey, Carl; Das, Soumen; Seal, Sudipta; Erlichman, Joseph; Heckman, Karin; Ghibelli, Lina; Traversa, Enrico; McGinnis, James F.; Self, William T.

    2014-01-01

    Cerium oxide nanoparticles (Nanoceria) have shown promise as catalytic antioxidants in the test tube, cell culture models and animal models of disease. However given the reactivity that is well established at the surface of these nanoparticles, the biological utilization of Nanoceria as a therapeutic still poses many challenges. Moreover the form that these particles take in a biological environment, such as the changes that can occur due to a protein corona, are not well established. This review aims to summarize the existing literature on biological use of Nanoceria, and to raise questions about what further study is needed to apply this interesting catalytic material to biomedical applications. These questions include: 1) How does preparation, exposure dose, route and experimental model influence the reported effects of Nanoceria in animal studies? 2) What are the considerations to develop Nanoceria as a therapeutic agent in regards to these parameters? 3) What biological targets of reactive oxygen species (ROS) and reactive nitrogen species (RNS) are relevant to this targeting, and how do these properties also influence the safety of these nanomaterials? PMID:26207185

  10. Antioxidant Cerium Oxide Nanoparticle Hydrogels for Cellular Encapsulation

    PubMed Central

    Weaver, Jessica D; Stabler, Cherie L

    2015-01-01

    Oxidative stress and the resulting radical by-products cause significant toxicity and graft loss in cellular transplantation. Here, the engineering of an auto-catalytic, antioxidant, self-renewing cerium oxide nanoparticle (CONP)-composite hydrogel is reported. This enzyme-mimetic material ubiquitously scavenges ambient free radicals, with the potential to provide indefinite antioxidant protection. Here, we evaluated the potential of this system to enhance the protection of encapsulated beta cells. Co-incubation of CONPs, free in solution with beta cells, demonstrated potent cytoprotection from superoxide exposure; however, phagocytosis of the CONPs by the beta cells resulted in cytotoxicity at concentrations as low as 1 mM. When CONPs were embedded within alginate hydrogels, the composite hydrogel provided cytoprotection to encapsulated beta cells from free radical attack without cytotoxicity, even up to 10 mM concentrations. This nanocomposite hydrogel has wide applicability in cellular transplantation, with the unique advantage of localization of these potent antioxidant CONPs and their capacity for sustained, long-term scavenging. PMID:25620795

  11. Atomic layer-by-layer thermoelectric conversion in topological insulator bismuth/antimony tellurides.

    PubMed

    Sung, Ji Ho; Heo, Hoseok; Hwang, Inchan; Lim, Myungsoo; Lee, Donghun; Kang, Kibum; Choi, Hee Cheul; Park, Jae-Hoon; Jhi, Seung-Hoon; Jo, Moon-Ho

    2014-07-01

    Material design for direct heat-to-electricity conversion with substantial efficiency essentially requires cooperative control of electrical and thermal transport. Bismuth telluride (Bi2Te3) and antimony telluride (Sb2Te3), displaying the highest thermoelectric power at room temperature, are also known as topological insulators (TIs) whose electronic structures are modified by electronic confinements and strong spin-orbit interaction in a-few-monolayers thickness regime, thus possibly providing another degree of freedom for electron and phonon transport at surfaces. Here, we explore novel thermoelectric conversion in the atomic monolayer steps of a-few-layer topological insulating Bi2Te3 (n-type) and Sb2Te3 (p-type). Specifically, by scanning photoinduced thermoelectric current imaging at the monolayer steps, we show that efficient thermoelectric conversion is accomplished by optothermal motion of hot electrons (Bi2Te3) and holes (Sb2Te3) through 2D subbands and topologically protected surface states in a geometrically deterministic manner. Our discovery suggests that the thermoelectric conversion can be interiorly achieved at the atomic steps of a homogeneous medium by direct exploiting of quantum nature of TIs, thus providing a new design rule for the compact thermoelectric circuitry at the ultimate size limit. PMID:24937706

  12. Atomic layer-by-layer thermoelectric conversion in topological insulator bismuth/antimony tellurides.

    PubMed

    Sung, Ji Ho; Heo, Hoseok; Hwang, Inchan; Lim, Myungsoo; Lee, Donghun; Kang, Kibum; Choi, Hee Cheul; Park, Jae-Hoon; Jhi, Seung-Hoon; Jo, Moon-Ho

    2014-07-01

    Material design for direct heat-to-electricity conversion with substantial efficiency essentially requires cooperative control of electrical and thermal transport. Bismuth telluride (Bi2Te3) and antimony telluride (Sb2Te3), displaying the highest thermoelectric power at room temperature, are also known as topological insulators (TIs) whose electronic structures are modified by electronic confinements and strong spin-orbit interaction in a-few-monolayers thickness regime, thus possibly providing another degree of freedom for electron and phonon transport at surfaces. Here, we explore novel thermoelectric conversion in the atomic monolayer steps of a-few-layer topological insulating Bi2Te3 (n-type) and Sb2Te3 (p-type). Specifically, by scanning photoinduced thermoelectric current imaging at the monolayer steps, we show that efficient thermoelectric conversion is accomplished by optothermal motion of hot electrons (Bi2Te3) and holes (Sb2Te3) through 2D subbands and topologically protected surface states in a geometrically deterministic manner. Our discovery suggests that the thermoelectric conversion can be interiorly achieved at the atomic steps of a homogeneous medium by direct exploiting of quantum nature of TIs, thus providing a new design rule for the compact thermoelectric circuitry at the ultimate size limit.

  13. The Effect of Microgravity on the Growth of Lead Tin Telluride

    NASA Technical Reports Server (NTRS)

    Narayanan, R.

    2000-01-01

    The main objective of this research was to present a model for the prediction of the effect of the microgravity environment on the growth of Lead Tin Telluride. The attitude change and its relation to the experimental objectives: The main objective for the AADSF experiment on USMP 3 involving LTT growth was to estimate the effect of ampoule orientation on the axial and radial segregation of tin telluride. As the furnace was not situated on a gimbal there was no possibility to reorient the ampoule during the flight. Instead the only way to change the growth orientation was to change the attitude of the orbiter. This was accomplished by vernier rocket firings. In what follows it must be noted that the orbiter body coordinates are such that the positive z axis points outward from the 'belly', the positive 'x' axis points outwards from the nose and the positive 'y' axis points outwards from the starboard side. The furnace which was in the pay load had its axis aligned with the orbiter's 'z' axis with the hot end closest to the shuttle body. There were basically three orientations that were desired. These corresponded to the ampoule being seen as a heated from above (thermally stable-solutally unstable) configuration, the heated from below (where the instabilities were reversed from the first orientation) configuration and an 'in between' case where the ampoule axis was misaligned with respect to the orbiters 'g(sub z)' axis.

  14. Facile production of thermoelectric bismuth telluride thick films in the presence of polyvinyl alcohol.

    PubMed

    Lei, C; Burton, M R; Nandhakumar, I S

    2016-06-01

    Bismuth telluride is currently the best performing thermoelectric material for room temperature operations in commercial thermoelectric devices. We report the reproducible and facile production of 600 micron thick bismuth telluride (Bi2Te3) layers by low cost and room temperature pulsed and potentiostatic electrodeposition from a solution containing bismuth and tellurium dioxide in 2 M nitric acid onto nickel in the presence of polyvinyl alcohol (PVA). This was added to the electrolyte to promote thick layer formation and its effect on the structure, morphology and composition of the electrodeposits was investigated by SEM and EDX. Well adherent, uniform, compact and stoichiometric n-type Bi2Te3 films with a high Seebeck coefficient of up to -200 μV K(-1) and a high electrical conductivity of up to 400 S cm(-1) resulting in a power factor of 1.6 × 10(-3) W m(-1) K(-2) at film growth rates of 100 μm h(-1) for potentiostatic electrodeposition were obtained. The films also exhibited a well defined hexagonal structure as determined by XRD.

  15. Telluride buried channel waveguides operating from 6 to 20 μm for photonic applications

    NASA Astrophysics Data System (ADS)

    Vigreux, C.; Escalier, R.; Pradel, A.; Bastard, L.; Broquin, J.-E.; Zhang, X.; Billeton, T.; Parent, G.; Barillot, M.; Kirschner, V.

    2015-11-01

    One of the technological challenges of direct observation of extra-solar planets by nulling interferometry is the development of a modal filter operating from 6 to 20 μm. In the present paper a candidate technology for the fabrication of such modal filters is presented: Integrated Optics. A solution based on all-telluride buried channel waveguides is considered. In the proposed waveguides, vertical guiding of light is achieved by a 15 μm-thick Te83Ge17 core film deposited onto a lower-index Te75Ge15Ga10 substrate, and covered by a 15 μm-thick Te76Ge24 superstrate. Horizontal guiding of light is obtained by modifying the geometry of the core layer by ion beam etching. As this stage, all-telluride buried channel waveguide prototypes demonstrate light guiding and transmission from 2 to 20 μm. The validity of the technology and the good quality of the fabrication process, in particular the input and output facets surface finish are thus confirmed. These results consolidate the potential of Te-based integrated optics components for nulling interferometry.

  16. A density-functional study on the electronic and vibrational properties of layered antimony telluride

    NASA Astrophysics Data System (ADS)

    Stoffel, Ralf P.; Deringer, Volker L.; Simon, Ronnie E.; Hermann, Raphaël P.; Dronskowski, Richard

    2015-03-01

    We present a comprehensive survey of electronic and lattice-dynamical properties of crystalline antimony telluride (Sb2Te3). In a first step, the electronic structure and chemical bonding have been investigated, followed by calculations of the atomic force constants, phonon dispersion relationships and densities of states. Then, (macroscopic) physical properties of Sb2Te3 have been computed, namely, the atomic thermal displacement parameters, the Grüneisen parameter γ, the volume expansion of the lattice, and finally the bulk modulus B. We compare theoretical results from three popular and economic density-functional theory (DFT) approaches: the local density approximation (LDA), the generalized gradient approximation (GGA), and a posteriori dispersion corrections to the latter. Despite its simplicity, the LDA shows excellent performance for all properties investigated—including the Grüneisen parameter, which only the LDA is able to recover with confidence. In the absence of computationally more demanding hybrid DFT methods, the LDA seems to be a good choice for further lattice dynamical studies of Sb2Te3 and related layered telluride materials.

  17. THERMAL EFFECTS ON MASS AND SPATIAL RESOLUTION DURING LASER PULSE ATOM PROBE TOMOGRAPHY OF CERIUM OXIDE

    SciTech Connect

    Rita Kirchhofer; Melissa C. Teague; Brian P. Gorman

    2013-05-01

    Cerium oxide (CeO2) is an ideal surrogate material for trans-uranic elements and fission products found in nuclear fuels due to similarities in their thermal properties; therefore, cerium oxide was used to determine the best run condition for atom probe tomography (APT). Laser pulse APT is a technique that allows for spatial resolution in the nm scale and isotopic/elemental chemical identification. A systematic study of the impact of laser pulse energy and specimen base temperature on the mass resolution, measurement of stoichiometry, multiples, and evaporation mechanisms are reported in this paper. It was demonstrated that using laser pulse APT stoichiometric field evaporation of cerium oxide was achieved at 1 pJ laser pulse energy and 20 K specimen base temperature.

  18. Synthesis and characterization of cerium and yttrium alkoxide complexes supported by ferrocene-based chelating ligands.

    PubMed

    Broderick, Erin M; Thuy-Boun, Peter S; Guo, Neng; Vogel, Carola S; Sutter, Jörg; Miller, Jeffrey T; Meyer, Karsten; Diaconescu, Paula L

    2011-04-01

    Two series of Schiff base metal complexes were investigated, where each series was supported by an ancillary ligand incorporating a ferrocene backbone and different N=X functionalities. One ligand is based on an imine, while the other is based on an iminophosphorane group. Cerium(IV), cerium(III), and yttrium(III) alkoxide complexes supported by the two ligands were synthesized. All metal complexes were characterized by cyclic voltammetry. Additionally, NMR, Mössbauer, X-ray absorption near-edge structure (XANES), and absorption spectroscopies were used. The experimental data indicate that iron remains in the +2 oxidation state and that cerium(IV) does not engage in a redox behavior with the ancillary ligand.

  19. Photoemission of the Oxidation of Cerium Overlayers on GaSb(110) Surface

    NASA Astrophysics Data System (ADS)

    Liang, Qi; Wu, Jian-xin; Ji, Ming-rong; Ma, Mao-sheng; Liu, Xian-ming; Zhang, Yu-heng

    1997-10-01

    We have used x-ray photoelectron spectroscopy to study the oxidation of cerium overlayers on a semiconductor GaSb(110) surface. A GaSb(110) sample covered with 10 monolayers Ce was used to adsorb oxygen. When the exposure of O2 was up to 50 L, the oxide of cerium, Ce2O3, began to change into unstable CeO2. The dissociation of CeO2 resulted in strong oxidation of the substrate. The main products are Ga2O3, Sb2O3, and then Sb2O5. After annealing, a part of the oxygen atoms transferred from cerium dioxide toward Ga and Sb.

  20. Excitation induced spectroscopic study and quenching effect in cerium samarium codoped lithium aluminoborate glasses

    NASA Astrophysics Data System (ADS)

    Kaur, Parvinder; Kaur, Simranpreet; Singh, Gurinder Pal; Arora, Deepawali; Kumar, Sunil; Singh, D. P.

    2016-08-01

    Lithium aluminium borate host has been codoped with cerium and samarium to prepare glass by conventional melt quench technique. Their structural and spectroscopic investigation has been carried out using XRD, FTIR and density measurements. The UV-Vis absorption spectra and fluorescence spectra (λexc.=380 nm and 400 nm) have been studied for spectroscopic analysis. The amorphous nature of the prepared samples is shown by XRD. The density is increasing with addition of cerium at the expense of aluminium, keeping other components constant. FTIR study also shows the presence of compact and stable tetrahedral BO4 units thus supporting the density results. The UV- Vis absorption spectra show a shift of optical absorption edge towards longer wavelength along with an increase in intensity of peaks with rising samarium concentration. The fluorescence spectra show a blue shift and subsequent suppression of cerium peaks with addition of samarium.

  1. Development of graphene-nanometre-sized cerium oxide-incorporated aluminium and its electrochemical evaluation

    NASA Astrophysics Data System (ADS)

    Ashraf, P. Muhamed; Thomas, Saly N.; Edwin, Leela

    2016-02-01

    Graphene-nanometre-sized cerium oxide-incorporated aluminium was prepared and its electrochemical and surface morphological characteristics were studied. The atomic force micrographs and scanning electron micrographs evaluation highlighted that the graphene and nanometre-sized cerium oxide in aluminium had decreased the surface roughness and improved the surface morphological characteristics. The graphene: nanometre-sized cerium oxide (ratios 1:2 or 2:1) with lesser amounts of particle in the matrix showed excellent corrosion resistance in the marine environment as evidenced by linear polarization, electrochemical impedance and weight loss studies. Introduction of graphene in the aluminium matrix showed a barrier separation between the outermost layer and inner layer, increased roughness and increased corrosion. The material is found to be a potential candidate for use in marine environment.

  2. Fabrication of Cerium Oxide and Uranium Oxide Microspheres for Space Nuclear Power Applications

    SciTech Connect

    Jeffrey A. Katalenich; Michael R. Hartman; Robert C. O'Brien

    2013-02-01

    Cerium oxide and uranium oxide microspheres are being produced via an internal gelation sol-gel method to investigate alternative fabrication routes for space nuclear fuels. Depleted uranium and non-radioactive cerium are being utilized as surrogates for plutonium-238 (Pu-238) used in radioisotope thermoelectric generators and for enriched uranium required by nuclear thermal rockets. While current methods used to produce Pu-238 fuels at Los Alamos National Laboratory (LANL) involve the generation of fine powders that pose a respiratory hazard and have a propensity to contaminate glove boxes, the sol-gel route allows for the generation of oxide microsphere fuels through an aqueous route. The sol-gel method does not generate fine powders and may require fewer processing steps than the LANL method with less operator handling. High-quality cerium dioxide microspheres have been fabricated in the desired size range and equipment is being prepared to establish a uranium dioxide microsphere production capability.

  3. Green synthesized cerium oxide nanoparticle: A prospective drug against oxidative harm.

    PubMed

    Dutta, Debanjan; Mukherjee, Riya; Patra, Mousumi; Banik, Milon; Dasgupta, Rakhi; Mukherjee, Manabendra; Basu, Tarakdas

    2016-11-01

    Cerium oxide nanoparticle (CeONP) of size 2-3nm was synthesized by a new, simple and green method at ambient temperature, using cerium nitrate as prime precursor and Aloe vera leaf extract as stabilizing agent. Of the two oxidation states (+3) and (+4) of cerium, it was dominantly present in (+3) state in CeONP and cyclic conversion of Ce(III)O→Ce(IV)O→Ce(III)O by reaction with H2O2 implied uninterrupted antioxidant property of CeONP. Moreover, the higher oxygen defect in the crystal lattice produced particles with higher antioxidant activity. CeONP was found to neutralize the deleterious effects of H2O2 viz., cell death, generation of intracellular reactive oxygen species and loss of connectivity in mouse neural cells. Therefore, CeONP might have potential use in future as an anti-oxidant drug.

  4. Eucalyptus tolerance mechanisms to lanthanum and cerium: subcellular distribution, antioxidant system and thiol pools.

    PubMed

    Shen, Yichang; Zhang, Shirong; Li, Sen; Xu, Xiaoxun; Jia, Yongxia; Gong, Guoshu

    2014-12-01

    Guanglin 9 (Eucalyptus grandis × Eucalyptus urophlla) and Eucalyptus grandis 5 are two eucalyptus species which have been found to grow normally in soils contaminated with lanthanum and cerium, but the tolerance mechanisms are not clear yet. In this study, a pot experiment was conducted to investigate the tolerance mechanisms of the eucalyptus to lanthanum and cerium. Cell walls stored 45.40-63.44% of the metals under lanthanum or cerium stress. Peroxidase and catalase activities enhanced with increasing soil La or Ce concentrations up to 200 mg kg(-1), while there were no obvious changes in glutathione and ascorbate concentrations. Non-protein thiols concentrations increased with increasing treatment levels up to 200 mg kg(-1), and then decreased. Phytochelatins concentrations continued to increase under La or Ce stress. Therefore, the two eucalyptus species are La and Ce tolerant plants, and the tolerance mechanisms include cell wall deposition, antioxidant system response, and thiol compound synthesis. PMID:25303462

  5. Green synthesized cerium oxide nanoparticle: A prospective drug against oxidative harm.

    PubMed

    Dutta, Debanjan; Mukherjee, Riya; Patra, Mousumi; Banik, Milon; Dasgupta, Rakhi; Mukherjee, Manabendra; Basu, Tarakdas

    2016-11-01

    Cerium oxide nanoparticle (CeONP) of size 2-3nm was synthesized by a new, simple and green method at ambient temperature, using cerium nitrate as prime precursor and Aloe vera leaf extract as stabilizing agent. Of the two oxidation states (+3) and (+4) of cerium, it was dominantly present in (+3) state in CeONP and cyclic conversion of Ce(III)O→Ce(IV)O→Ce(III)O by reaction with H2O2 implied uninterrupted antioxidant property of CeONP. Moreover, the higher oxygen defect in the crystal lattice produced particles with higher antioxidant activity. CeONP was found to neutralize the deleterious effects of H2O2 viz., cell death, generation of intracellular reactive oxygen species and loss of connectivity in mouse neural cells. Therefore, CeONP might have potential use in future as an anti-oxidant drug. PMID:27478962

  6. Synthesis and photocatalytic activity of mesoporous cerium doped TiO{sub 2} as visible light sensitive photocatalyst

    SciTech Connect

    Aman, Noor; Satapathy, P.K.; Mishra, T.; Mahato, M.; Das, N.N.

    2012-02-15

    Graphical abstract: Cerium doped titania having optimum 5 wt% of cerium can decompose methylene blue and reduce selenium (IV) efficiently under visible light. Highlights: Black-Right-Pointing-Pointer Effect of cerium doping on the surface properties and visible light mediated photocatalytic reaction is studied. Black-Right-Pointing-Pointer Cerium doping increases the anatase phase stability, surface area (up to 137 m{sup 2}/g) and visible light absorption. Black-Right-Pointing-Pointer Importance of Ce{sup 3+}/Ce{sup 4+}, oxygen vacancy, surface area and crystallinity is correlated with improved catalytic activity. Black-Right-Pointing-Pointer Material with 5 wt% Ce is found to be most active photocatalyst for methylene blue decomposition and Se (IV) reduction. -- Abstract: Cerium doped titania materials were synthesized varying the cerium concentration from 0 to 10 wt%. Materials are characterised by XRD, TEM, XPS and N{sub 2} adsorption desorption method. Surface area and visible light absorption substantially increases and crystallite size decreases with the increasing cerium content. Cerium doping stabilizes the anatase phase and surface area even at 600 Degree-Sign C calcination. Photocatalytic activity towards methylene blue decomposition and selenium (IV) reduction is found to increase with the cerium content up to 5 wt% and then decreases. Materials calcined at 600 Degree-Sign C shows better activity than that calcined at 400 Degree-Sign C, even though surface area decreases. Anatase crystallinity mostly decides the photocatalytic activity rather than only surface area. It can be concluded that the optimum visible light absorption and oxygen vacancy with 5% cerium doping enhances the photocatalytic activity. In addition photocatalytic performance is found to depend on the presence of Ce{sup 4+}/Ce{sup 3+} rather than only visible light absorption.

  7. Ab initio studies of anisotropic magnetism in uranium and cerium monopnictides and monochalcogenides

    NASA Astrophysics Data System (ADS)

    Collins, Eric Mason

    We have applied two ab initio based methods to investigate the origin in the electronic structure of the unusual magnetic behavior of the cerium and uranium monopnictides and monochalcogenides. First, we have carried out spin-polarized electronic structure calculations, based on the full potential linear muffin tin (FPLMTO) method, with spin polarization (orbital polarization only via spin-orbit coupling) and also with orbital polarization correction. Second, we have carried out ab initio based calculations synthesizing (1) a phenomenological theory of orbitally driven magnetism based on the Anderson and Kondo, lattice model which incorporates explicitly the hybridization induced and the Coulomb exchange interactions on an equal footing, and (2) FPLMTO electronic structure calculations allowing a first principles evaluation of all the parameters entering the model Hamiltonian. For the cerium compounds, we also include the crystal field interactions on an equal footing with the hybridization and Coulomb exchange interactions with a scaling determined by experiment. The results for the uranium compound calculations show that both methods are limited to the extremes to which they are best suited. The pure band structure calculations provide the best agreement for the lighter uranium compounds, while the model hamiltonian approach provides better agreement for the heavier uranium compounds. In the case of the cerium compounds, while the pure FPLMTO calculations yield values for the magnetic moment in agreement with experiment for the lighter cerium chalcogenides, they fail to give, even qualitatively, the magnetic properties for all other systems. On the other hand, the ab initio based model Hamiltonian calculations reveal for the first time the interplay of hybridization, Coulomb exchange, and crystal field interactions across the cerium series, and give results for the low-temperature moment and ordering temperature in excellent agreement with experiment, for the

  8. The investigation of cerium as a cathodic inhibitor for aluminum-copper alloys

    SciTech Connect

    Aldykewicz, A.J. Jr.; Isaacs, H.S.; Davenport, A.J.

    1995-10-01

    In situ current density mapping, scanning electron microscopy , and energy dispersive spectroscopy were used to study the effects of cerium as a corrosion inhibitor for an aluminum copper alloy (Al 2024-T4) in chloride containing solutions. It was found that cerium inhibits corrosion of this alloy by reducing the rate of the cathodic reaction. This was due to the carried out on an aluminum/copper galvanic couple, which was used to simulate the electrochemical behavior of the copper containing intermetallics, showed that corrosion inhibition was associated with the formation of a Ce-rich film over the copper in agreement with that observed for the alloy.

  9. Synthesis and characterization of two dimensional metal organic framework of cerium with tetraaza macrocyclic

    SciTech Connect

    Bt Safiin, Nurul Atikah; Yarmo, Ambar; Yamin, Bohari M.

    2013-11-27

    A two dimensional metal organic framework containing cerium sufate layers and ethylenediaminium between layers was obtained by refluxing the mixture of cerium sulphate and 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradeca-7, 14-diene bromide. The complex was characterized by infrared spectroscopy and microelemental analysis. X-ray study showed that the complex adopts eleven coordination environments about the central atom. Thermogravimetric study showed the removal of water molecules at about 70°C followed by a gradual mass loss until the whole structure collapsed at about 400°C.

  10. METHOD OF SEPARATING TETRAVALENT PLUTONIUM VALUES FROM CERIUM SUB-GROUP RARE EARTH VALUES

    DOEpatents

    Duffield, R.B.; Stoughton, R.W.

    1959-02-01

    A method is presented for separating plutonium from the cerium sub-group of rare earths when both are present in an aqueous solution. The method consists in adding an excess of alkali metal carbonate to the solution, which causes the formation of a soluble plutonium carbonate precipitate and at the same time forms an insoluble cerium-group rare earth carbonate. The pH value must be adjusted to bctween 5.5 and 7.5, and prior to the precipitation step the plutonium must be reduced to the tetravalent state since only tetravalent plutonium will form the soluble carbonate complex.

  11. Systematic variation of rare-earth elements in cerium-earth minerals

    USGS Publications Warehouse

    Murata, K.J.; Rose, H.J.; Carron, M.K.; Glass, J.J.

    1957-01-01

    In a continuation of a study reported previously, rare-earth elements and thorium have been determined in monazite, allanite, cerite, bastnaesite, and a number of miscellaneous cerium-earth minerals. A quantity called sigma (???), which is the sum of the atomic percentages of La, Ce, and Pr, is proposed as an index of composition of all cerium-earth minerals with respect to the rare-earth elements. The value of ??? for all of the minerals analysed falls between 58 and 92 atomic per cent. Monazites, allanites, and cerites cover the entire observed range, whereas bastnaesites are sharply restricted to the range between 80 and 92 atomic per cent. The minimum value of ??? for a cerium-earth mineral corresponds to the smallest possible unit-cell size of the mineral. In monazite, this structurally controlled minimum value of ??? is estimated to be around 30 atomic per cent. Neodymium, because of its abundance, and yttrium, because of its small size, have dominant roles in contraction of the structure. In the other direction, the limit of variation in composition will be reached when lanthanum becomes the sole rare-earth element in a cerium-earth mineral. Cerium-earth minerals from alkalic rocks are all characterized by values of ??? greater than 80 atomic per cent, indicating that the processes that formed these rocks were unusually efficient in fractionating the rare-earth elements-efficient in the sense that a highly selected assemblage is produced without eliminating the bulk of these elements. Analyses of inner and outer parts of two large crystals of monazite from different deposits show no difference in ??? in one crystal and a slightly smaller value of ??? in the outer part of the other crystal compared to the inner part. The ??? of monazites from pegmatites that intrude genetically related granitic rocks in North Carolina is found to be either higher or lower than the ??? of monazites in the intruded host rock. These results indicate that the fractionation of the

  12. Variations in Reactivity on Different Crystallographic Orientations of Cerium Oxide

    SciTech Connect

    Mullins, David R; Albrecht, Peter M; Calaza, Florencia C

    2013-01-01

    Cerium oxide is a principal component in many heterogeneous catalytic processes. One of its key characteristics is the ability to provide or remove oxygen in chemical reactions. The different crystallographic faces of ceria present significantly different surface structures and compositions that may alter the catalytic reactivity. The structure and composition determine the number of coordination vacancies surrounding surface atoms, the availability of adsorption sites, the spacing between adsorption sites and the ability to remove O from the surface. To investigate the role of surface orientation on reactivity, CeO2 films were grown with two different orientations. CeO2(100) films were grown ex situ by pulsed laser deposition on Nb-doped SrTiO3(100). CeO2(111) films were grown in situ by thermal deposition of Ce metal onto Ru(0001) in an oxygen atmosphere. The chemical reactivity was characterized by the adsorption and decomposition of various molecules such as alcohols, aldehydes and organic acids. In general the CeO2(100) surface was found to be more active, i.e. molecules adsorbed more readily and reacted to form new products, especially on a fully oxidized substrate. However the CeO2(100) surface was less selective with a greater propensity to produce CO, CO2 and water as products. The differences in chemical reactivity are discussed in light of possible structural terminations of the two surfaces. Recently nanocubes and nano-octahedra have been synthesized that display CeO2(100) and CeO2(111) faces, respectively. These nanoparticles enable us to correlate reactions on high surface area model catalysts at atmospheric pressure with model single crystal films in a UHV environment.

  13. Effect of cerium oxide nanoparticles on intestinal serotonin in zebrafish

    PubMed Central

    Özel, Rıfat Emrah; Hayat, Akhtar; Wallace, Kenneth N.; Andreescu, Silvana

    2013-01-01

    Cerium oxide nanoparticles or nanoceria are emerging as a new and promising class of nanoparticle technology for biomedical applications. The safe implementation of these particles in clinical applications requires evaluation of their redox properties and reactivity that might cause neurotoxic effects by interacting with redox components of the physiological environment. We report in vitro and in vivo studies to evaluate the impact of nanoceria exposure on serotonin (5-HT), an important neurotransmitter that plays a critical role in various physiological processes including motility and secretion in the digestive system. In vitro studies of 5-HT in the presence of nanoceria using spectroscopic, electrochemical and surface characterization methods demonstrate that nanoceria interacts with 5-HT and forms a surface adsorbed 5-HT-nanoceria complex. Further in vivo studies in live zebrafish embryos indicate depletion of the 5-HT level in the intestine for exposure periods longer than three days. Intestinal 5-HT was assessed quantitatively in live embryos using implantable carbon fiber microelectrodes and the results were compared to immunohistochemistry of the dissected intestine. 20 and 50 ppm nanoparticle exposure decreased the 5-HT level to 20.5 (±1.3) and 5.3 (±1.5) nM respectively as compared to 30.8 (±3.4) nM for unexposed control embryos. The results suggest that internalized nanoceria particles can concentrate 5-HT at the nanoparticle accumulation site depleting it from the surrounding tissue. This finding might have long term implications in the neurophysiology and functional development of organisms exposed to these particles through intended or unintended exposure. PMID:24015353

  14. Cerium oxide nanoparticle treatment ameliorates peritonitis-induced diaphragm dysfunction

    PubMed Central

    Asano, Shinichi; Arvapalli, Ravikumar; Manne, Nandini DPK; Maheshwari, Mani; Ma, Bing; Rice, Kevin M; Selvaraj, Vellaisamy; Blough, Eric R

    2015-01-01

    The severe inflammation observed during sepsis is thought to cause diaphragm dysfunction, which is associated with poor patient prognosis. Cerium oxide (CeO2) nanoparticles have been posited to exhibit anti-inflammatory and antioxidative activities suggesting that these particles may be of potential use for the treatment of inflammatory disorders. To investigate this possibility, Sprague Dawley rats were randomly assigned to the following groups: sham control, CeO2 nanoparticle treatment only (0.5 mg/kg iv), sepsis, and sepsis+CeO2 nanoparticles. Sepsis was induced by the introduction of cecal material (600 mg/kg) directly into the peritoneal cavity. Nanoparticle treatment decreased sepsis-associated impairments in diaphragmatic contractile (Po) function (sham: 25.6±1.6 N/cm2 vs CeO2: 23.4±0.8 N/cm2 vs Sep: 15.9±1.0 N/cm2 vs Sep+CeO2: 20.0±1.0 N/cm2, P<0.05). These improvements in diaphragm contractile function were accompanied by a normalization of protein translation signaling (Akt, FOXO-1, and 4EBP1), diminished proteolysis (caspase 8 and ubiquitin levels), and decreased inflammatory signaling (Stat3 and iNOS). Histological analysis suggested that nanoparticle treatment was associated with diminished sarcolemma damage and diminished inflammatory cell infiltration. These data indicate CeO2 nanoparticles may improve diaphragmatic function in the septic laboratory rat. PMID:26491293

  15. Effect of cerium oxide nanoparticles on intestinal serotonin in zebrafish.

    PubMed

    Ozel, Rıfat Emrah; Hayat, Akhtar; Wallace, Kenneth N; Andreescu, Silvana

    2013-09-21

    Cerium oxide nanoparticles or nanoceria are emerging as a new and promising class of nanoparticle technology for biomedical applications. The safe implementation of these particles in clinical applications requires evaluation of their redox properties and reactivity that might cause neurotoxic effects by interacting with redox components of the physiological environment. We report in vitro and in vivo studies to evaluate the impact of nanoceria exposure on serotonin (5-HT), an important neurotransmitter that plays a critical role in various physiological processes including motility and secretion in the digestive system. In vitro studies of 5-HT in the presence of nanoceria using spectroscopic, electrochemical and surface characterization methods demonstrate that nanoceria interacts with 5-HT and forms a surface adsorbed 5-HT-nanoceria complex. Further in vivo studies in live zebrafish embryos indicate depletion of the 5-HT level in the intestine for exposure periods longer than three days. Intestinal 5-HT was assessed quantitatively in live embryos using implantable carbon fiber microelectrodes and the results were compared to immunohistochemistry of the dissected intestine. 20 and 50 ppm nanoparticle exposure decreased the 5-HT level to 20.5 (±1.3) and 5.3 (±1.5) nM respectively as compared to 30.8 (±3.4) nM for unexposed control embryos. The results suggest that internalized nanoceria particles can concentrate 5-HT at the nanoparticle accumulation site depleting it from the surrounding tissue. This finding might have long term implications in the neurophysiology and functional development of organisms exposed to these particles through intended or unintended exposure. PMID:24015353

  16. Effects of Cerium Oxide Nanoparticles on Sorghum Plant Traits

    NASA Astrophysics Data System (ADS)

    Mu, L.; Chen, Y.; Darnault, C. J. G.; Rauh, B.; Kresovich, S.; Korte, C.

    2015-12-01

    Nanotechnology and nanomaterials are considered as the development of the modern science. However, besides with that wide application, nanoparticles arouse to the side effects on the environment and human health. As the catalyst of ceramics and fuel industry, Cerium (IV) oxide nanoparticles (CeO2 NPs) can be found in the environment following their use and life-cycle. Therefore, it is critical to assess the potential effects that CeO2 NPs found in soils may have on plants. In this study, CeO2 NPs were analyzed for the potential influence on the sorghum [Sorghum bicolor (L.) Moench] (Reg. no. 126) (PI 154844) growth and traits. The objectives of this research were to determine whether CeO2 NPs impact the sorghum germination and growth characteristics. The sorghum was grown in the greenhouse located at Biosystems Research Complex, Clemson University under different CeO2 NPs treatments (0mg; 100mg; 500mg; 1000mg CeO2 NPs/Kg soil) and harvested around each month. At the end of the each growing period, above ground vegetative tissue was air-dried, ground to 2mm particle size and compositional traits estimated using near-infrared spectroscopy. Also, the NPK value of the sorghum tissue was tested by Clemson Agriculture Center. After the first harvest, the result showed that the height of above ground biomass under the nanoparticles stress was higher than that of control group. This difference between the control and the nanoparticles treatments was significant (F>F0.05; LSD). Our results also indicated that some of the compositional traits were impacted by the different treatments, including the presence and/or concentrations of the nanoparticles.

  17. Exploring Tellurides: Synthesis and Characterization of New Binary, Ternary, and Quaternary Compounds

    NASA Astrophysics Data System (ADS)

    Li, Jing; Guo, Hong-You; Proserpio, Davide M.; Sironi, Angelo

    1995-07-01

    A fast-growing interest in solid state telluride chemistry has taken place during the past several years. Our research in this area has been primarily on the development and applications of several synthetic techniques that can be applied to the synthesis of the tellurides over a wide temperature range (100-1200°C). These techniques include chemical vapor transport, molten-salt, and hydro(solvo)thermal methods. In this article, we report five binary, ternary, and quaternary metal tellurides, BaTe2, TaCu3Te4, RbTaCu2Te4, K2BaSnTe4, and K2Ag2SnTe4, synthesized by the molten-salt (alkali-metal polytelluride flux) reactions at intermediate temperatures (400-550°C). The crystal structures of these compounds have been determined by single crystal X-ray diffraction techniques. Crystal data: BaTe2, space group I4/mcm (No. 140), a = 7.181(1), c = 8.898(2) Å, Z = 4, R1 = 1.55%, wR2 = 3.46%; RbTaCu2Te4, space group P21cn (No. 33), a = 5.982(2), b = 20.316(3), c = 8.192(2) Å, Z = 4, R1 = 7.13%, wR2 = 4.95%; TaCu3Te4, space group P-43m (No. 215), a = 5.930(2) Å,Z = 1, R1 = 2.40%, wR2 = 6.48%; K2BaSnTe4, space group I-43m (No. 217), a = 8.393(1) Å, Z = 2, R1 = 2.52%, wR2 = 3.56%; K2Ag2SnTe4, space group I -42m (No. 121), a = 8.732(5), c = 7.425(3) Å, Z = 2, R1 = 3.06%, wR2 = 7.25%.

  18. Pd-BISMUTHOTELLURIDES and Other Tellurides from Some Cu-Ni-PGE Deposits, Eastern Desert, Egypt

    NASA Astrophysics Data System (ADS)

    Helmy, H. M.

    2003-04-01

    Pd-bismuthotellurides and other tellurides are described from three Cu-Ni-PGE deposits in the Eastern Desert, Egypt: Abu Swayl, Genina Gharbia, Gabbro Akarem. The deposits are hosted in Late Precambrian mafic-ultramafic rocks and have different geologic histories. The Abu Swayel deposit occurs in conformable, lens-like mafic-ultramafic rocks in metasediments. Mineralization and host rocks are metamorphosed (amphibolite facies; 550-650ºC, 4-5 kbar) and syn-metamorphically sheared. Metamorphism and associated fluid regimes resulted in remobilization and transport of Cu-sulfides and PGE, and development of hydrosilicates. Michenerite, merenskyite, Pd-Bi-melonite, (NiPdBi)Te2, melonite, hessite, altaite and joséite-B occur as inclusions in mobilized sulfides and along cracks in garnet and plagioclase. The Genina Gharbia and Gabbro Akarem deposits are hosted in concentrically zoned, Alaskan-type, complexes; neither is metamorphosed. At Genina Gharbia, ore forms either disseminations in peridotite or massive patches in hornblende-pyroxenite in the vicinity of metasediments. Important petrographic features are a dominance of hornblende, biotite and chlorapatite and alteration of plagioclase to epidote. Disseminated and network sulfide ores are dominated by po, pn, cp and minor py; accessories are cobaltite, molybdenite and valleriite. Sulfide textures and host rock petrography suggest a prolonged late-magmatic hydrothermal event. Michenerite, merenskyite, Pd-Bi-melonite, altaite, hessite, tsumoite and native-Te are mainly present at sulfide-silicate contacts. The Gabbro Akarem deposit is hosted in dunite pipes where net-textured and massive sulfides are associated with spinel and Cr-magnetite. Michenerite, merenskyite, Pd-Bi-melonite and hessite occur mainly as inclusions in sulfides. Typical magmatic textures indicate the limited role of late- and post-magmatic hydrothermal processes. Different geological history of the different deposits enables examination of the

  19. Cerium Oxide Nanoparticles and Bulk Cerium Oxide Leading to Different Physiological and Biochemical Responses in Brassica rapa.

    PubMed

    Ma, Xingmao; Wang, Qiang; Rossi, Lorenzo; Zhang, Weilan

    2016-07-01

    Cerium oxide nanoparticles (CeO2NPs) have been incorporated into many commercial products, and their potential release into the environment through the use and disposal of these products has caused serious concerns. Despite the previous efforts and rapid progress on elucidating the environmental impact of CeO2NPs, the long-term impact of CeO2NPs to plants, a key component of the ecosystem, is still not well understood. The potentially different impact of CeO2NPs and their bulk counterparts to plants is also unclear. The main objectives of this study were (1) to investigate whether continued irrigation with solutions containing different concentrations of CeO2NPs (0, 10, and 100 mg/L) would induce physiological and biochemical adjustments in Brassica rapa in soil growing conditions and (2) to determine whether CeO2NPs and bulk CeO2 particles exert different impacts on plants. The results indicated that bulk CeO2 at 10 and 100 mg/L enhanced plant biomass by 28% and 35%, respectively, while CeO2NPs at equivalent concentrations did not. While the bulk CeO2 treatment resulted in significantly higher concentrations of hydrogen peroxide (H2O2) in plant tissues at the vegetative stage, CeO2NPs led to significantly higher H2O2 levels in plant tissues at the floral stage. The activity of superoxide dismutase (SOD) in Brassica rapa also displayed a growth-stage dependent response to different sizes of CeO2 while catalase (CAT) activity was not affected by either size of CeO2 throughout the life cycle of Brassica rapa. Altogether, the results demonstrated that plant responses to CeO2 exposure varied with the particle sizes and the growth stages of plants.

  20. Cerium Oxide Nanoparticles and Bulk Cerium Oxide Leading to Different Physiological and Biochemical Responses in Brassica rapa.

    PubMed

    Ma, Xingmao; Wang, Qiang; Rossi, Lorenzo; Zhang, Weilan

    2016-07-01

    Cerium oxide nanoparticles (CeO2NPs) have been incorporated into many commercial products, and their potential release into the environment through the use and disposal of these products has caused serious concerns. Despite the previous efforts and rapid progress on elucidating the environmental impact of CeO2NPs, the long-term impact of CeO2NPs to plants, a key component of the ecosystem, is still not well understood. The potentially different impact of CeO2NPs and their bulk counterparts to plants is also unclear. The main objectives of this study were (1) to investigate whether continued irrigation with solutions containing different concentrations of CeO2NPs (0, 10, and 100 mg/L) would induce physiological and biochemical adjustments in Brassica rapa in soil growing conditions and (2) to determine whether CeO2NPs and bulk CeO2 particles exert different impacts on plants. The results indicated that bulk CeO2 at 10 and 100 mg/L enhanced plant biomass by 28% and 35%, respectively, while CeO2NPs at equivalent concentrations did not. While the bulk CeO2 treatment resulted in significantly higher concentrations of hydrogen peroxide (H2O2) in plant tissues at the vegetative stage, CeO2NPs led to significantly higher H2O2 levels in plant tissues at the floral stage. The activity of superoxide dismutase (SOD) in Brassica rapa also displayed a growth-stage dependent response to different sizes of CeO2 while catalase (CAT) activity was not affected by either size of CeO2 throughout the life cycle of Brassica rapa. Altogether, the results demonstrated that plant responses to CeO2 exposure varied with the particle sizes and the growth stages of plants. PMID:26691446

  1. The effects of cerium doping on the size, morphology, and optical properties of α-hematite nanoparticles for ultraviolet filtration

    SciTech Connect

    Cardillo, Dean; Konstantinov, Konstantin; Devers, Thierry

    2013-11-15

    Highlights: • Possible application of cerium-doped α-hematite as ultraviolet filter. • Nanoparticles obtained through co-precipitation technique using various cerium doping levels followed by annealing. • Comprehensive materials characterisation utilizing XRD, DSC/TGA, STEM, UV–vis spectroscopy. • Increasing cerium content reduces particle sizing and alters morphology. • Solubility of cerium in hematite seen between 5 and 10% doping, 10% cerium doping greatly enhances attenuation in ultraviolet region and increases optical bandgap. - Abstract: Metal oxide nanoparticles have potential use in energy storage, electrode materials, as catalysts and in the emerging field of nanomedicine. Being able to accurately tailor the desirable properties of these nanoceramic materials, such as particle size, morphology and optical bandgap (E{sub g}) is integral in the feasibility of their use. In this study we investigate the altering of both the structure and physical properties through the doping of hematite (α-Fe{sub 2}O{sub 3}) nanocrystals with cerium at a range of concentrations, synthesised using a one-pot co-precipitation method. This extremely simple synthesis followed by thermal treatment results in stable Fe{sub 2−x}Ce{sub x}O{sub y} nanoceramics resulting from the burning of any unreacted precursors and transformation of goethite-cerium doped nanoparticle intermediate. The inclusion of Ce into the crystal lattice of these α-Fe{sub 2}O{sub 3} nanoparticles causes a significantly large reduction in mean crystalline size and alteration in particle morphology with increasing cerium content. Finally we report an increase optical semiconductor bandgap, along with a substantial increase in the ultraviolet attenuation found for a 10% Ce-doping concentration which shows the potential application of cerium-doped hematite nanocrystals to be used as a pigmented ultraviolet filter for cosmetic products.

  2. Time resolved photo-luminescent decay characterization of mercury cadmium telluride focal plane arrays

    DOE PAGES

    Soehnel, Grant

    2015-01-20

    The minority carrier lifetime is a measurable material property that is an indication of infrared detector device performance. To study the utility of measuring the carrier lifetime, an experiment has been constructed that can time resolve the photo-luminescent decay of a detector or wafer sample housed inside a liquid nitrogen cooled Dewar. Motorized stages allow the measurement to be scanned over the sample surface, and spatial resolutions as low as 50µm have been demonstrated. A carrier recombination simulation was developed to analyze the experimental data. Results from measurements performed on 4 mercury cadmium telluride focal plane arrays show strong correlationmore » between spatial maps of the lifetime, dark current, and relative response.« less

  3. Evaluation of DAST and zinc telluride nonlinear crystals for efficient terahertz generation

    SciTech Connect

    Venkatesh, M.; Chaudhary, A. K.; Rao, K. S.

    2015-07-31

    Terahertz (THz) signal is generated from 4-N, N-dimethylamino-4’-N’-methyl-stilbazolium tosylate (i.e. DAST Crystal) and Zinc telluride (ZnTe) nonlinear crystals by employing 140 fs laser pulses at 800 nm with 80 MHz repetition rate. The semi insulating gallium arsenide photoconductive stripline antennas (gap =5 µm, length = 20 µm) is used as a Terahertz detector. The detected temporal profile of Terahertz radiation generated from DAST crystal is high as compared to ZnTe crystal in terms of amplitude. THz effective bandwidths of these crystals are extended up to 1.1 THz range. The potential of THz generation of DAST and ZnTe crystals are evaluated with respect to incident laser power.

  4. Nanoscale arrays of antimony telluride single crystals by selective chemical vapor deposition.

    PubMed

    Huang, Ruomeng; Benjamin, Sophie L; Gurnani, Chitra; Wang, Yudong; Hector, Andrew L; Levason, William; Reid, Gillian; De Groot, C H Kees

    2016-01-01

    Arrays of individual single nanocrystals of Sb2Te3 have been formed using selective chemical vapor deposition (CVD) from a single source precursor. Crystals are self-assembled reproducibly in confined spaces of 100 nm diameter with pitch down to 500 nm. The distribution of crystallite sizes across the arrays is very narrow (standard deviation of 15%) and is affected by both the hole diameter and the array pitch. The preferred growth of the crystals in the <1 1 0> orientation along the diagonal of the square holes strongly indicates that the diffusion of adatoms results in a near thermodynamic equilibrium growth mechanism of the nuclei. A clear relationship between electrical resistivity and selectivity is established across a range of metal selenides and tellurides, showing that conductive materials result in more selective growth and suggesting that electron donation is of critical importance for selective deposition. PMID:27283116

  5. Flexible cadmium telluride thin films grown on electron-beam-irradiated graphene/thin glass substrates

    SciTech Connect

    Seo, Won-Oh; Kim, Jihyun; Koo, Yong Hwan; Kim, Byungnam; Lee, Byung Cheol; Kim, Donghwan

    2014-08-25

    We demonstrate the close-spaced sublimation growth of polycrystalline cadmium telluride (CdTe) thin films on a flexible graphene electrode/thin glass substrate structure. Prior to the growth of CdTe films, chemical-vapor-deposited graphene was transferred onto a flexible glass substrate and subjected to electron-beam irradiation at an energy of 0.2 MeV in order to intentionally introduce the defects into it in a controlled manner. Micro-Raman spectroscopy and sheet resistance measurements were employed to monitor the damage and disorder in the electron-beam irradiated graphene layers. The morphology and optical properties of the CdTe thin films deposited on a graphene/flexible glass substrate were systematically characterized. The integration of the defective graphene layers with a flexible glass substrate can be a useful platform to grow various thin-film structures for flexible electronic and optoelectronic devices.

  6. Transport properties of lithium- lead-vanadium-telluride glass and glass ceramics

    SciTech Connect

    Sathish, M.; Eraiah, B.

    2014-04-24

    Glasses with the chemical composition 35Li{sub 2}O-(45-x)V{sub 2}O{sub 5−}20PbO-xTeO{sub 2} (where x = 2.5, 5, 7.5, 10, 15 mol %) have prepared by conventional melt quenching method. The electrical conductivity of Li{sup +} ion conducting lead vanadium telluride glass samples has been carried out both as a function of temperature and frequency in the temperature range 503K-563K and over frequencies 40 Hz to 10 MHz. The electronic conduction has been observed in the present systems. When these samples annealed around 400°C for 2hour become the glass ceramic, which also shows increase tendency of conductivity. SEM confines glass and glass ceramic nature of the prepared samples.

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

    SciTech Connect

    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.

  8. Effect of different surfactants and thicknesses on electrodeposited films of bismuth telluride and its thermoelectric performance

    NASA Astrophysics Data System (ADS)

    Kulsi, Chiranjit; Mitra, Mousumi; Kargupta, Kajari; Ganguly, Saibal; Banerjee, Dipali; Goswami, Shyamaprosad

    2015-10-01

    Thin films of bismuth telluride using various surfactants such as sodium dodecyl sulfate (SDS) and polyvinylpyrrolidone (PVP) have been electrochemically deposited. The influence of different surfactants on crystal orientation and morphology was investigated and correlated with the thermoelectric performance of the electrodeposited films. Since thickness affects the thermoelectric performance compared to the surfactant, thickness- dependent thermoelectric performance has also been investigated. The carrier mobilities of the films obtained are significantly enhanced due to improved surface morphology using different surfactants. Between the two surfactants, films with SDS exhibited the higher value of thermoelectric power, power factor, and figure of merit, which is due to the effect of micelle formation. The XRD pattern of all the films, which are electrodeposited without surfactant or using SDS and PVP, showed preferred crystal orientation along the (018) direction. The roles of organic molecules in the development of nanoparticles with improved thermoelectric properties have been investigated.

  9. Experimenting with hot isostatically pressed (HIP) nano grained bismuth-telluride-based alloys

    NASA Astrophysics Data System (ADS)

    Virta, Jouko; Tervo, Jyrki

    2012-06-01

    Hot Isostatic Pressing (HIP) is was used for compaction of nano grained bismuth-telluride samples and results were compared to Spark Plasma Sintered (SPS) samples of the same materials. The powders were essentially the same as presented by Vasilevskiy1 et al, 2010. The (BixSb1-x)2(TeySe1-y)3 thermoelectric alloys studied in this article were produced by mechanical alloying under an inert atmosphere. The p-type alloy composition corresponds to x = 0.2, y = 1 and for the n-type material x = 0.95, y = 0.95. For HIP treatment the n-and p-type powders were encapsulated in copper cylinders under protective argon atmosphere. The HIP temperature was kept low to avoid excess grain growth of the materials. The electrical conductivity, carrier mobility, carrier concentration and Seebeck coefficient of HIP and SPS compacted materials were measured and compared.

  10. Cd-rich and Te-rich low-temperature photoluminescence in cadmium telluride

    SciTech Connect

    Albin, D. S. Kuciauskas, D.; Ma, J.; Metzger, W. K.; Burst, J. M.; Moutinho, H. R.; Dippo, P. C.

    2014-03-03

    Low-temperature photoluminescence emission spectra were measured in cadmium telluride (CdTe) samples in which composition was varied to promote either Cd or Te-rich stoichiometry. The ability to monitor stoichiometry is important, since it has been shown to impact carrier recombination. Te-rich samples show transitions corresponding to acceptor-bound excitons (∼1.58 eV) and free-electron to acceptor transitions (∼1.547 eV). In addition to acceptor-bound excitons, Cd-rich samples show transitions assigned to donor-bound excitons (1.591 eV) and Te vacancies at 1.552 eV. Photoluminescence is a noninvasive way to monitor stoichiometric shifts induced by post-deposition anneals in polycrystalline CdTe thin films deposited by close-spaced sublimation.

  11. Correlation Between Bulk Material Defects and Spectroscopic Response in Cadmium Zinc Telluride Detectors

    NASA Technical Reports Server (NTRS)

    Parker, Bradford H.; Stahle, C. M.; Barthelmy, S. D.; Parsons, A. M.; Tueller, J.; VanSant, J. T.; Munoz, B. F.; Snodgrass, S. J.; Mullinix, R. E.

    1999-01-01

    One of the critical challenges for large area cadmium zinc telluride (CdZnTe) detector arrays is obtaining material capable of uniform imaging and spectroscopic response. Two complementary nondestructive techniques for characterizing bulk CdZnTe have been developed to identify material with a uniform response. The first technique, infrared transmission imaging, allows for rapid visualization of bulk defects. The second technique, x-ray spectral mapping, provides a map of the material spectroscopic response when it is configured as a planar detector. The two techniques have been used to develop a correlation between bulk defect type and detector performance. The correlation allows for the use of infrared imaging to rapidly develop wafer mining maps. The mining of material free of detrimental defects has the potential to dramatically increase the yield and quality of large area CdZnTe detector arrays.

  12. Charge Sharing and Charge Loss in a Cadmium-Zinc-Telluride Fine-Pixel Detector Array

    NASA Technical Reports Server (NTRS)

    Gaskin, J. A.; Sharma, D. P.; Ramsey, B. D.; Six, N. Frank (Technical Monitor)

    2002-01-01

    Because of its high atomic number, room temperature operation, low noise, and high spatial resolution a Cadmium-Zinc-Telluride (CZT) multi-pixel detector is ideal for hard x-ray astrophysical observation. As part of on-going research at MSFC (Marshall Space Flight Center) to develop multi-pixel CdZnTe detectors for this purpose, we have measured charge sharing and charge loss for a 4x4 (750micron pitch), lmm thick pixel array and modeled these results using a Monte-Carlo simulation. This model was then used to predict the amount of charge sharing for a much finer pixel array (with a 300micron pitch). Future work will enable us to compare the simulated results for the finer array to measured values.

  13. Characterization of a 2-mm thick, 16x16 Cadmium-Zinc-Telluride Pixel Array

    NASA Technical Reports Server (NTRS)

    Gaskin, Jessica; Richardson, Georgia; Mitchell, Shannon; Ramsey, Brian; Seller, Paul; Sharma, Dharma

    2003-01-01

    The detector under study is a 2-mm-thick, 16x16 Cadmium-Zinc-Telluride pixel array with a pixel pitch of 300 microns and inter-pixel gap of 50 microns. This detector is a precursor to that which will be used at the focal plane of the High Energy Replicated Optics (HERO) telescope currently being developed at Marshall Space Flight Center. With a telescope focal length of 6 meters, the detector needs to have a spatial resolution of around 200 microns in order to take full advantage of the HERO angular resolution. We discuss to what degree charge sharing will degrade energy resolution but will improve our spatial resolution through position interpolation. In addition, we discuss electric field modeling for this specific detector geometry and the role this mapping will play in terms of charge sharing and charge loss in the detector.

  14. M-lines characterization of selenide and telluride thick films for mid-infrared interferometry.

    PubMed

    Labadie, Lucas; Vigreux-Bercovici, Caroline; Pradel, Annie; Kern, Pierre; Arezki, Brahim; Broquin, Jean-Emmanuel

    2006-09-01

    Nulling interferometry is an astronomical technique that requires to combine extremely flat wavefronts to achieve a deep rejection ratio in order to detect Earth-like planets in the mid-infrared band [5 - 20 microm]. Similarly to what is done in the near-infrared, high spatial filtering of the incoming beams can be achieved using single-mode waveguides operating in the mid-infrared. An appreciable reduction of the instrumental complexity is also possible using integrated optics (IO) devices in this spectral range. The lack of single-mode guided optics in the mid-infrared has motivated the present technological study to demonstrate the feasibility of dielectric waveguides functioning at longer wavelengths. We propose to use selenide and telluride components to pursue the development of more complex IO functions. PMID:19529223

  15. One-step chemical synthesis of samarium telluride thin films and their supercapacitive properties

    NASA Astrophysics Data System (ADS)

    Kumbhar, V. S.; Lokhande, A. C.; Gaikwad, N. S.; Lokhande, C. D.

    2016-02-01

    The letter reports synthesis of samarium telluride (Sm2Te3) thin films through a one-step chemical route. The formation of Sm2Te3 is confirmed by X-ray diffraction and X-ray photoelectron spectroscopy studies. The surface morphological study is carried out using field emission scanning electron microscopy and contact angle measurement techniques. The film shows barley-like microstructure with an average length of barley of about 5 μm and diameter of about 300 nm. The Sm2Te3 film surface exhibits lyophilic nature with contact angle of 21.3° for propylene carbonate electrolyte. Cyclic voltammetry results revealed specific capacitance of 207 F g-1 with power density of 14.18 kW kg-1 in LiClO4-propylene carbonate electrolyte.

  16. Sign reversal of dielectric anisotropy of ferroelectric liquid crystals doped with cadmium telluride quantum dots

    NASA Astrophysics Data System (ADS)

    Kumar, A.; Silotia, P.; Biradar, A. M.

    2011-08-01

    A small amount of cadmium telluride quantum dots (CdTe QDs) has been doped into various ferroelectric liquid crystals (FLCs) to observe the modifications in the alignment and dielectric anisotropy (Δɛ) of the composites. The CdTe QDs have induced a uniform homeotropic (HMT) alignment in most of the FLC mixtures. We observed an unexpected switching (from HMT to homogeneous configuration) of CdTe QDs doped FLC CS1026 (having positive Δɛ) by the application of high dc bias. This reverse switching has been attributed to the interaction between FLC molecules and CdTe QDs which caused the sign reversal of Δɛ of FLC CS1026.

  17. An optically-interrogated microwave-Poynting-vector sensor using cadmium manganese telluride.

    PubMed

    Chen, Chia-Chu; Whitaker, John F

    2010-06-01

    A single <110> cadmium-manganese-telluride crystal that exhibits both the Pockels and Faraday effects is used to produce a Poynting-vector sensor for signals in the microwave regime. This multi-birefringent crystal can independently measure either electric or magnetic fields through control of the polarization of the optical probe beam. After obtaining all the relevant electric and magnetic field components, a map of the Poynting vector along a 50-Omega microstrip was experimentally determined without the need for any further transformational calculations. The results demonstrate that this sensor can be used for near-field mapping of the Poynting vector. Utilizing both amplitude and phase information from the fields in the microwave signal, it was confirmed for the case of an open-terminated microstrip that no energy flowed to the load, while for a microstrip with a matched termination, the energy flowed consistently along the transmission line. PMID:20588348

  18. Nanowires as Building Blocks to Fabricate Flexible Thermoelectric Fabric: The Case of Copper Telluride Nanowires.

    PubMed

    Zhou, Chongjian; Dun, Chaochao; Wang, Qiong; Wang, Ke; Shi, Zhongqi; Carroll, David L; Liu, Guiwu; Qiao, Guanjun

    2015-09-30

    A general approach to fabricate nanowires based inorganic/organic composite flexible thermoelectric fabric using a simple and efficacious five-step vacuum filtration process is proposed. As an excellent example, the performance of freestanding flexible thermoelectric thin film using copper telluride nanowires/polyvinylidene fluoride (Cu1.75Te NWs/PVDF = 2:1) as building block is demonstrated. By burying the Cu1.75Te NWs into the PVDF polymer agent, the flexible fabric exhibits room-temperature Seebeck coefficient and electric conductivity of 9.6 μV/K and 2490 S/cm, respectively, resulting in a power factor of 23 μW/(mK(2)) that is comparable to the bulk counterpart. Furthermore, this NW-based flexible fabric can endure hundreds of cycles of bending tests without significant performance degradation. PMID:26376703

  19. Suppression of Grain Growth by Additive in Nanostructured P-type Bismuth Antimony Tellurides

    SciTech Connect

    Zhang, Qian; Zhang, Qinyong; Chen, S.; Liu, W S; Lukas, K; Yan, X; Wang, H; Wang, D.; Opeil, C; Chen, Gang; Ren, Z. F.

    2011-01-01

    Grain growth is a major issue in the preparation of nanostructured bismuth-antimony-tellurides during hot pressing the nanopowders into dense bulk samples. To prevent grain agglomeration during ball milling and growth during hot pressing, organic agent (Oleic Acid, OA) as additive was added into the materials at the beginning of the ball milling process. With different concentrations of OA (0.5, 1.0, 1.5, 2.0, and 2.5 wt%), grains with different sizes are obtained. Structural analysis clearly shows that it is the particle size of the nanopowders that determines the final grain size in the densely compacted bulk samples. A combination of small grains ~200–500 nm and nanopores leads to effective phonon scattering, which results in the decrease of lattice thermal conductivity, and ZT of ~1.3 at 373 K for the sample with 2.0 wt% OA.

  20. Time resolved photo-luminescent decay characterization of mercury cadmium telluride focal plane arrays

    SciTech Connect

    Soehnel, Grant

    2015-01-20

    The minority carrier lifetime is a measurable material property that is an indication of infrared detector device performance. To study the utility of measuring the carrier lifetime, an experiment has been constructed that can time resolve the photo-luminescent decay of a detector or wafer sample housed inside a liquid nitrogen cooled Dewar. Motorized stages allow the measurement to be scanned over the sample surface, and spatial resolutions as low as 50µm have been demonstrated. A carrier recombination simulation was developed to analyze the experimental data. Results from measurements performed on 4 mercury cadmium telluride focal plane arrays show strong correlation between spatial maps of the lifetime, dark current, and relative response.

  1. Nanoscale arrays of antimony telluride single crystals by selective chemical vapor deposition

    PubMed Central

    Huang, Ruomeng; Benjamin, Sophie L.; Gurnani, Chitra; Wang, Yudong; Hector, Andrew L.; Levason, William; Reid, Gillian; De Groot, C. H. (Kees)

    2016-01-01

    Arrays of individual single nanocrystals of Sb2Te3 have been formed using selective chemical vapor deposition (CVD) from a single source precursor. Crystals are self-assembled reproducibly in confined spaces of 100 nm diameter with pitch down to 500 nm. The distribution of crystallite sizes across the arrays is very narrow (standard deviation of 15%) and is affected by both the hole diameter and the array pitch. The preferred growth of the crystals in the <1 1 0> orientation along the diagonal of the square holes strongly indicates that the diffusion of adatoms results in a near thermodynamic equilibrium growth mechanism of the nuclei. A clear relationship between electrical resistivity and selectivity is established across a range of metal selenides and tellurides, showing that conductive materials result in more selective growth and suggesting that electron donation is of critical importance for selective deposition. PMID:27283116

  2. Internal Electric Field Behavior of Cadmium Zinc Telluride Radiation Detectors Under High Carrier Injection

    SciTech Connect

    Yang, G.; Bolotnikov, A.E.; Camarda, G.S.; Cui, Y.; Hossain, A.; Kim, K.H.; Gul, R.; and James, R.B.

    2010-10-26

    The behavior of the internal electric-field of nuclear-radiation detectors substantially affects the detector's performance. We investigated the distribution of the internal field in cadmium zinc telluride (CZT) detectors under high carrier injection. We noted the build-up of a space charge region near the cathode that produces a built-in field opposing the applied field. Its presence entails the collapse of the electric field in the rest of detector, other than the portion near the cathode. Such a space-charge region originates from serious hole-trapping in CZT. The device's operating temperature greatly affects the width of the space-charge region. With increasing temperature from 5 C to 35 C, its width expanded from about 1/6 to 1/2 of the total depth of the detector.

  3. Experiments and Monte Carlo modeling of a higher resolution Cadmium Zinc Telluride detector for safeguards applications

    NASA Astrophysics Data System (ADS)

    Borella, Alessandro

    2016-09-01

    The Belgian Nuclear Research Centre is engaged in R&D activity in the field of Non Destructive Analysis on nuclear materials, with focus on spent fuel characterization. A 500 mm3 Cadmium Zinc Telluride (CZT) with enhanced resolution was recently purchased. With a full width at half maximum of 1.3% at 662 keV, the detector is very promising in view of its use for applications such as determination of uranium enrichment and plutonium isotopic composition, as well as measurement on spent fuel. In this paper, I report about the work done with such a detector in terms of its characterization. The detector energy calibration, peak shape and efficiency were determined from experimental data. The data included measurements with calibrated sources, both in a bare and in a shielded environment. In addition, Monte Carlo calculations with the MCNPX code were carried out and benchmarked with experiments.

  4. A passively mode locked thulium doped fiber laser using bismuth telluride deposited multimode interference

    NASA Astrophysics Data System (ADS)

    Jung, M.; Lee, J.; Song, W.; Lee, Y. L.; Lee, J. H.; Shin, W.

    2016-05-01

    We proposed a multimode interference (MMI) fiber based saturable absorber using bismuth telluride at  ∼2 μm region. Our MMI based saturable absorber was fabricated by fusion splicing with single mode fiber and null core fiber. The MMI functioned as both wavelength fixed filter and saturable absorber. The 3 dB bandwidth and insertion loss of MMI were 42 nm and 3.4 dB at wavelength of 1958 nm, respectively. We have also reported a passively mode locked thulium doped fiber laser operating at a wavelength of 1958 nm using a multimode interference. A temporal bandwidth of  ∼46 ps was experimentally obtained at a repetition rate of 8.58 MHz.

  5. M-lines characterization of selenide and telluride thick films for mid-infrared interferometry.

    PubMed

    Labadie, Lucas; Vigreux-Bercovici, Caroline; Pradel, Annie; Kern, Pierre; Arezki, Brahim; Broquin, Jean-Emmanuel

    2006-09-01

    Nulling interferometry is an astronomical technique that requires to combine extremely flat wavefronts to achieve a deep rejection ratio in order to detect Earth-like planets in the mid-infrared band [5 - 20 microm]. Similarly to what is done in the near-infrared, high spatial filtering of the incoming beams can be achieved using single-mode waveguides operating in the mid-infrared. An appreciable reduction of the instrumental complexity is also possible using integrated optics (IO) devices in this spectral range. The lack of single-mode guided optics in the mid-infrared has motivated the present technological study to demonstrate the feasibility of dielectric waveguides functioning at longer wavelengths. We propose to use selenide and telluride components to pursue the development of more complex IO functions.

  6. Synthesis and characterization of linear cerium(IV) Schiff-base coordination polymers

    SciTech Connect

    Chen, H.; Cronin, J.A.; Archer, R.D. . Dept. of Chemistry)

    1994-04-11

    The first soluble linear Schiff-base rare earth coordination polymer, catena-poly[cerium-(4)-[mu]-N,N[prime],N[double prime],N[prime][double prime]-tetrasalicylidene (3,3[prime]-diaminobenzidinato)-O,N,N[prime],O[prime],O[double prime],N[double prime],N[prime][double prime],O[prime][double prime

  7. Cerium (IV) oxide nanotubes prepared by low temperature deposition at normal pressure.

    PubMed

    Boehme, M; Fu, G; Ionescu, E; Ensinger, W

    2011-02-11

    This paper reports the synthesis of cerium dioxide nanotubes (CeNTs) by electroless deposition using ion-track-etched polycarbonate templates. To achieve nanotubes with thin walls and small surface roughness the tubes were generated by a several-step-containing procedure under aqueous conditions. The approach reported below will process open end nanotubes with well-defined outer diameter and wall thickness.

  8. Pits confined in ultrathin cerium(IV) oxide for studying catalytic centers in carbon monoxide oxidation

    NASA Astrophysics Data System (ADS)

    Sun, Yongfu; Liu, Qinghua; Gao, Shan; Cheng, Hao; Lei, Fengcai; Sun, Zhihu; Jiang, Yong; Su, Haibin; Wei, Shiqiang; Xie, Yi

    2013-11-01

    Finding ideal material models for studying the role of catalytic active sites remains a great challenge. Here we propose pits confined in an atomically thin sheet as a platform to evaluate carbon monoxide catalytic oxidation at various sites. The artificial three-atomic-layer thin cerium(IV) oxide sheet with approximately 20% pits occupancy possesses abundant pit-surrounding cerium sites having average coordination numbers of 4.6 as revealed by X-ray absorption spectroscopy. Density-functional calculations disclose that the four- and five-fold coordinated pit-surrounding cerium sites assume their respective role in carbon monoxide adsorption and oxygen activation, which lowers the activation barrier and avoids catalytic poisoning. Moreover, the presence of coordination-unsaturated cerium sites increases the carrier density and facilitates carbon monoxide diffusion along the two-dimensional conducting channels of surface pits. The atomically thin sheet with surface-confined pits exhibits lower apparent activation energy than the bulk material (61.7 versus 122.9 kJ mol-1), leading to reduced conversion temperature and enhanced carbon monoxide catalytic ability.

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

    SciTech Connect

    Jin Yi; Zhu Yihua Yang Xiaoling; Li Chunzhong; Zhou Jinghong

    2007-01-15

    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 allows 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.

  10. Calculation of the volume effect at an electron phase transition in pure cerium and praseodymium

    NASA Astrophysics Data System (ADS)

    Ponomareva, S. A.; Koval', Yu. N.; Ponomarev, A. P.

    2014-03-01

    The experimental values of the volume effect at an electronic phase transition in several rare-earth metals are discussed. Specifically, volume changes at phase transitions in cerium and praseodymium are calculated using a semiphenomenological relationship derived in terms of the Falikov-Ramirez-Kimball model. A number of factors influencing the amount of the volume effect at electronic phase transitions are analyzed.

  11. Synthesis, electrical and dielectric characterization of cerium doped nano copper ferrites

    SciTech Connect

    Malana, Muhammad Aslam Qureshi, Raheela Beenish; Ashiq, Muhammad Naeem; Zafar, Zafar Iqbal

    2013-11-15

    Graphical abstract: Lattice constant (a) and activation energy (Ea) as a function of Ce (cerium) content. - Highlights: • The simple and economic method has been adopted for the synthesis of nanoferrites. • The electrical resistivity increases with cerium concentration. • DC electrical resistivity of these materials favours their use in microwave devices. • Dielectric measurements show semiconductor nature of the synthesized ferrites. - Abstract: The nanosized CuFe{sub 2−x}Ce{sub x}O{sub 4} (x = 0.0, 0.2, 0.4, 0.6, 0.8) ferrites doped with cerium are synthesized by chemical co-precipitation method. The synthesized materials are characterized by XRD, FTIR, TGA and SEM. XRD analysis of cerium substituted copper ferrites confirms the cubic spinel structure. The average crystallite size calculated by using Scherrer's formula ranges from 37 to 53 nm. The values of cell constant and cell volume vary with the dopant concentration. These variations can be explained in terms of their ionic radii. The DC electrical resistivity, measured by two point probe method, increases with increase in dopant concentration while it decreases with rise in temperature exhibiting semiconductor behaviour. Energy of activation of these ferrites is calculated by using Arrhenius type resistivity plots. Dielectric measurements of the synthesized compounds show exponential decrease in dielectric constant and dielectric loss factor with increase in frequency. This indicates the normal dielectric behaviour of ferrites.

  12. Phenotypic and genomic responses to titanium dioxide and cerium oxide nanoparticles in Arabidopsis germinants

    EPA Science Inventory

    The effects of exposure to two nanoparticles (NPs) -titanium dioxide (nano-titania) and cerium oxide (nano-ceria) at 500 mg NPs L-1 on gene expression and growth in Arabidopsis thaliana germinants were studied using microarrays and phenotype studies. After 12 days post treatment,...

  13. Cyclic thermochemical process for producing hydrogen using cerium-titanium compounds

    DOEpatents

    Bamberger, Carlos E.

    1980-01-01

    A thermochemical cyclic process for producing hydrogen employs the reaction between ceric oxide and titanium dioxide to form cerium titanate and oxygen. The titanate is treated with an alkali metal hydroxide to give hydrogen, ceric oxide, an alkali metal titanate and water. Alkali metal titanate and water are boiled to give titanium dioxide which, along with ceric oxide, is recycled.

  14. Cyclic thermochemical process for producing hydrogen using cerium-titanium compounds

    DOEpatents

    Bamberger, C.E.

    A thermochemical cyclic process for producing hydrogen employs the reaction between ceric oxide and titanium dioxide to form cerium titanate and oxygen. The titanate is treated with an alkali metal hydroxide to give hydrogen, ceric oxide, an alkali metal titanate and water. Alkali metal titanate and water are boiled to give titanium dioxide which, along with ceric oxide, is recycled.

  15. Pits confined in ultrathin cerium(IV) oxide for studying catalytic centers in carbon monoxide oxidation.

    PubMed

    Sun, Yongfu; Liu, Qinghua; Gao, Shan; Cheng, Hao; Lei, Fengcai; Sun, Zhihu; Jiang, Yong; Su, Haibin; Wei, Shiqiang; Xie, Yi

    2013-01-01

    Finding ideal material models for studying the role of catalytic active sites remains a great challenge. Here we propose pits confined in an atomically thin sheet as a platform to evaluate carbon monoxide catalytic oxidation at various sites. The artificial three-atomic-layer thin cerium(IV) oxide sheet with approximately 20% pits occupancy possesses abundant pit-surrounding cerium sites having average coordination numbers of 4.6 as revealed by X-ray absorption spectroscopy. Density-functional calculations disclose that the four- and five-fold coordinated pit-surrounding cerium sites assume their respective role in carbon monoxide adsorption and oxygen activation, which lowers the activation barrier and avoids catalytic poisoning. Moreover, the presence of coordination-unsaturated cerium sites increases the carrier density and facilitates carbon monoxide diffusion along the two-dimensional conducting channels of surface pits. The atomically thin sheet with surface-confined pits exhibits lower apparent activation energy than the bulk material (61.7 versus 122.9 kJ mol(-1)), leading to reduced conversion temperature and enhanced carbon monoxide catalytic ability.

  16. Cerium oxide coated anodes for aluminum electrowinning: Topical report, October 1, 1986-June 30, 1987

    SciTech Connect

    Walker, J. K.

    1987-12-01

    Because of the cost of building and maintaining a carbon anode plant and the energy penalties associated with the use of carbon anodes in the production of aluminum, the use of inert anodes has long been proposed. Various cermet anodes have been investigated. In this paper, tests on a material, cerium oxyfluoride (CEROX), deposited in situ as an anode, are reported. (JDH)

  17. Demonstration of enhanced K-edge angiography using a cerium target x-ray generator

    SciTech Connect

    Sato, Eiichi; Tanaka, Etsuro; Mori, Hidezo; Kawai, Toshiaki; Ichimaru, Toshio; Sato, Shigehiro; Takayama, Kazuyoshi; Ido, Hideaki

    2004-11-01

    The cerium target x-ray generator is useful in order to perform enhanced K-edge angiography using a cone beam because K-series characteristic x rays from the cerium target are absorbed effectively by iodine-based contrast mediums. The x-ray generator consists of a main controller, a unit with a Cockcroft-Walton circuit and a fixed anode x-ray tube, and a personal computer. The tube is a glass-enclosed diode with a cerium target and a 0.5-mm-thick beryllium window. The maximum tube voltage and current were 65 kV and 0.4 mA, respectively, and the focal-spot sizes were 1.0x1.3 mm. Cerium K{alpha} lines were left using a barium sulfate filter, and the x-ray intensity was 0.48 {mu}C/kg at 1.0 m from the source with a tube voltage of 60 kV, a current of 0.40 mA, and an exposure time of 1.0 s. Angiography was performed with a computed radiography system using iodine-based microspheres. In coronary angiography of nonliving animals, we observed fine blood vessels of approximately 100 {mu}m with high contrasts.

  18. Phosphate ester hydrolysis of biologically relevant molecules by cerium oxide nanoparticles.

    PubMed

    Kuchma, Melissa Hirsch; Komanski, Christopher B; Colon, Jimmie; Teblum, Andrew; Masunov, Artëm E; Alvarado, Beatrice; Babu, Suresh; Seal, Sudipta; Summy, Justin; Baker, Cheryl H

    2010-12-01

    In an effort to characterize the interaction of cerium oxide nanoparticles (CNPs) in biological systems, we explored the reactivity of CNPs with the phosphate ester bonds of p-nitrophenylphosphate (pNPP), ATP, o-phospho-l-tyrosine, and DNA. The activity of the bond cleavage for pNPP at pH 7 is calculated to be 0.860 ± 0.010 nmol p-nitrophenol/min/μg CNPs. Interestingly, when CNPs bind to plasmid DNA, no cleavage products are detected. While cerium(IV) complexes generally exhibit the ability to break phosphorus-oxygen bonds, the reactions we report appear to be dependent on the availability of cerium(III) sites, not cerium(IV) sites. We investigated the dephosphorylation mechanism from the first principles and find the reaction proceeds through inversion of the phosphate group similar to an S(N)2 mechanism. The ability of CNPs to interact with phosphate ester bonds of biologically relevant molecules has important implications for their use as potential therapeutics.

  19. Long range ordered alloys modified by addition of niobium and cerium

    DOEpatents

    Liu, C.T.

    1984-08-22

    Long range ordered alloys are described having the nominal composition (Fe,Ni,Co)/sub 3/ (V,M) where M is a ductility enhancing metal selected from the group Ti, Zr, Hf with additions of small amounts of cerium and niobium to dramatically enhance the creep properties of the resulting alloys.

  20. Long range ordered alloys modified by addition of niobium and cerium

    DOEpatents

    Liu, Chain T.

    1987-01-01

    Long range ordered alloys are described having the nominal composition (Fe,Ni,Co).sub.3 (V,M) where M is a ductility enhancing metal selected from the group Ti, Zr, Hf with additions of small amounts of cerium and niobium to drammatically enhance the creep properties of the resulting alloys.

  1. Resonant photoemission study of the 4f spectral function of cerium in Ce/Fe(100) interfaces

    SciTech Connect

    Witkowski, N.; Bertran, F.; Gourieux, T.; Kierren, B.; Malterre, D.; Panaccione, G. |

    1997-11-01

    In this paper, we present a resonant photoemission study of the cerium 4f spectral function in Ce/Fe(100) interfaces. By covering cerium ultrathin films with lanthanum, we completely suppress the surface contribution of the spectra. Then we show that the cerium atoms at the interface are in an intermediate valent state, whereas the f{sup 1} configuration is stabilized in the top layer. This method allows us to obtain the genuine 4f spectral function of the interface, and could be extended to a study of Ce-based compounds. {copyright} {ital 1997} {ital The American Physical Society}

  2. Geochronological and He-Ar-S isotopic constraints on the origin of the Sandaowanzi gold-telluride deposit, northeastern China

    NASA Astrophysics Data System (ADS)

    Zhai, Degao; Liu, Jiajun; Ripley, Edward M.; Wang, Jianping

    2015-01-01

    Northeastern China is characterized by widespread Mesozoic volcanic rocks and Au-Cu-Mo mineral deposits with a total gold reserve of > 2000 t. Amongst those gold deposits, the newly discovered Sandaowanzi has a total reserve of ≥ 25 t of Au and an average grade of 15 g/t. This deposit is important because it is the first reported case of a dominantly Au(± Ag)-telluride deposit containing economically valuable bonanza Au- and Ag-telluride ores in the region. The Sandaowanzi quartz vein system and associated Au-(± Ag)-telluride mineralization are mainly hosted by trachyandesites and andesitic breccias. Native gold is closely associated with abundant tellurides including petzite, sylvanite, calaverite, hessite, and altaite. Twelve pyrite samples from the alteration zone yield a well defined Rb-Sr isochron age of 119.1 ± 3.9 Ma, which is in agreement with a robust Rb-Sr isochron age of 121.3 ± 2.6 Ma derived from 10 auriferous quartz samples. The obtained isochron age of ~ 120 Ma represents the formation of the Sandaowanzi gold-telluride epithermal system, which is much younger than the host trachyandesite with a zircon U-Pb age of 312.5 ± 0.5 Ma and the spatially associated monzogranite with a zircon U-Pb age of 182.2 ± 1.1 Ma. Dating results indicate a close relationship between the local Au-Ag-Te mineralization and a magmatism episode in the Early Cretaceous. Noble gas (He and Ar) isotopes obtained from telluride, sulfide and quartz and sulfur isotopes determined from sulfides including chalcopyrite, sphalerite and pyrite demonstrate clear mixing trends between crustal and mantle-derived components, confirming a significant contribution of fluid produced from mantle-derived magmas into the epithermal system. Like many Mesozoic porphyry Cu-Mo ± Au deposits, the coeval epithermal Au-Ag ± Te deposits in the region are genetically related to magmatism triggered by the subduction of the Pacific oceanic plate beneath the Eurasian continent at the time.

  3. 4d → 4f resonance in photoabsorption of cerium ion Ce3+ and endohedral cerium in fullerene complex {\\rm{Ce}}@{{{\\rm{C}}}_{82}}^{+}

    NASA Astrophysics Data System (ADS)

    Schrange-Kashenock, G.

    2016-09-01

    The theoretical investigation of the single-photoionization spectra in the 4d-resonance region (120-150 eV) for the ionic cerium Ce3+ and cerium in the endohedral complex {{Ce}}@{{{{C}}}82}+ (in practice, {{{Ce}}}3+@{{{{C}}}82}2-) is presented. The fullerene cage is modeled by ab initio spherical jellium shell with an accurate account for the real distribution of carbon electron density. The oscillator strengths are calculated within the multiconfiguration Dirac-Fock (MCDF) approach for phototransitions from the outermost shells of the ion Ce3+ with and without the influence of the potential generated by a fullerene cage. It is shown that the integrated oscillator strengths have the main contribution from the Ce3+ 4d → 4f (ten possible from the phototransitions {}2F{7/2,5/2}\\to {}2D{3/2,5/2},{}2F{5/2,7/2},{}2G{5/2,7/2}) resonance photoexcitations. The corresponding precise MCDF values for the oscillator strengths and the transition energies are presented for the first time. It is demonstrated that the resonance {f}4d\\to 4f oscillator strengths are slightly affected by the presence of the cage potential, despite the fact that the spectral levels structure is changed when the effect of this potential is included. The Auger 4d -1 decay from the cerium free ion Ce3+ and the encapsulated endohedral ion Ce3+@ are considered within the two-step model and the corresponding Lorentzian profiles are presented. This model clearly reveals the correspondence of the complex resonance profile in the Ce3+ photoabsorption to the fine structure of ion energy levels. The smoothing of the resonance profile in the photoabsorption of the endohedral system {{Ce}}@{{{{C}}}82}+ compared with the free ion Ce3+ is attributed to increasing the linewidths of the Auger transitions. This increase is estimated from the relevant experiment (Müller et al 2008 Phys. Rev. Lett. 101 133001) to be strong; as at least three times the value for an isolated ion. The presence of the confining fullerene

  4. 4d → 4f resonance in photoabsorption of cerium ion Ce3+ and endohedral cerium in fullerene complex {\\rm{Ce}}@{{{\\rm{C}}}_{82}}^{+}

    NASA Astrophysics Data System (ADS)

    Schrange-Kashenock, G.

    2016-09-01

    The theoretical investigation of the single-photoionization spectra in the 4d-resonance region (120–150 eV) for the ionic cerium Ce3+ and cerium in the endohedral complex {{Ce}}@{{{{C}}}82}+ (in practice, {{{Ce}}}3+@{{{{C}}}82}2-) is presented. The fullerene cage is modeled by ab initio spherical jellium shell with an accurate account for the real distribution of carbon electron density. The oscillator strengths are calculated within the multiconfiguration Dirac–Fock (MCDF) approach for phototransitions from the outermost shells of the ion Ce3+ with and without the influence of the potential generated by a fullerene cage. It is shown that the integrated oscillator strengths have the main contribution from the Ce3+ 4d → 4f (ten possible from the phototransitions {}2F{7/2,5/2}\\to {}2D{3/2,5/2},{}2F{5/2,7/2},{}2G{5/2,7/2}) resonance photoexcitations. The corresponding precise MCDF values for the oscillator strengths and the transition energies are presented for the first time. It is demonstrated that the resonance {f}4d\\to 4f oscillator strengths are slightly affected by the presence of the cage potential, despite the fact that the spectral levels structure is changed when the effect of this potential is included. The Auger 4d ‑1 decay from the cerium free ion Ce3+ and the encapsulated endohedral ion Ce3+@ are considered within the two-step model and the corresponding Lorentzian profiles are presented. This model clearly reveals the correspondence of the complex resonance profile in the Ce3+ photoabsorption to the fine structure of ion energy levels. The smoothing of the resonance profile in the photoabsorption of the endohedral system {{Ce}}@{{{{C}}}82}+ compared with the free ion Ce3+ is attributed to increasing the linewidths of the Auger transitions. This increase is estimated from the relevant experiment (Müller et al 2008 Phys. Rev. Lett. 101 133001) to be strong; as at least three times the value for an isolated ion. The presence of the confining

  5. Cerium, uranium, and plutonium behavior in glass-bonded sodalite, a ceramic nuclear waste form.

    SciTech Connect

    Lewis, M. A.; Lexa, D.; Morss, L. R.; Richmann, M. K.

    1999-09-03

    Glass-bonded sodalite is being developed as a ceramic waste form (CWF) to immobilize radioactive fission products, actinides, and salt residues from electrometallurgical treatment of spent nuclear reactor fuel. The CWF consists of about 75 mass % sodalite, 25 mass % glass, and small amounts of other phases. This paper presents some results and interpretation of physical measurements to characterize the CWF structure, and dissolution tests to measure the release of matrix components and radionuclides from the waste form. Tests have been carried out with specimens of the CWF that contain rare earths at concentrations similar to those expected in the waste form. Parallel tests have been carried out on specimens that have uranium or plutonium as well as the rare earths at concentrations similar to those expected in the waste forms; in these specimens UCl{sub 3} forms UO{sub 2} and PuCl{sub 3} forms PuO{sub 2}. The normalized releases of rare earths in dissolution tests were found to be much lower than those of matrix elements (B, Si, Al, Na). When there is no uranium in the CWF, the release of cerium is two to ten times lower than the release of the other rare earths. The low release of cerium may be due to its tetravalent state in uranium-free CWF. However, when there is uranium in the CWF, the release of cerium is similar to that of the other rare earths. This trivalent behavior of cerium is attributed to charge transfer or covalent interactions among cerium, uranium, and oxygen in (U,Ce)O{sub 2}.

  6. Preparation and characterization of copper telluride thin films by modified chemical bath deposition (M-CBD) method

    NASA Astrophysics Data System (ADS)

    Pathan, H. M.; Lokhande, C. D.; Amalnerkar, D. P.; Seth, T.

    2003-09-01

    Copper telluride thin films were deposited using modified chemical method using copper(II) sulphate; pentahydrate [CuSO 4·5H 2O] and sodium tellurite [Na 2TeO 3] as cationic and anionic sources, respectively. Modified chemical method is based on the immersion of the substrate into separately placed cationic and anionic precursors. The preparative conditions such as concentration, pH, immersion time, immersion cycles, etc. were optimized to get good quality copper telluride thin films at room temperature. The films have been characterized for structural, compositional, optical and electrical transport properties by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX), Rutherford back scattering (RBS), optical absorption/transmission, electrical resistivity and thermoemf measurement techniques.

  7. Radioactive waste forms stabilized by ChemChar gasification: characterization and leaching behavior of cerium, thorium, protactinium, uranium, and neptunium.

    PubMed

    Marrero, T W; Morris, J S; Manahan, S E

    2004-02-01

    The uses of a thermally reductive gasification process in conjunction with vitrification and cementation for the long-term disposal of low level radioactive materials have been investigated. gamma-ray spectroscopy was used for analysis of carrier-free protactinium-233 and neptunium-239 and a stoichiometric amount of cerium (observed cerium-141) subsequent to gasification and leaching, up to 48 days. High resolution ICP-MS was used to analyze the cerium, thorium, and uranium from 46 to 438 days of leaching. Leaching procedures followed the guidance of ASTM Procedure C 1220-92, Standard Test Method for Static Leaching of Monolithic Waste Forms for Disposal of Radioactive Waste. The combination of the thermally reductive pretreatment, vitrification and cementation produced a highly non-leachable form suitable for long-term disposal of cerium, thorium, protactinium, uranium, and neptunium.

  8. Radioactive waste forms stabilized by ChemChar gasification: characterization and leaching behavior of cerium, thorium, protactinium, uranium, and neptunium.

    PubMed

    Marrero, T W; Morris, J S; Manahan, S E

    2004-02-01

    The uses of a thermally reductive gasification process in conjunction with vitrification and cementation for the long-term disposal of low level radioactive materials have been investigated. gamma-ray spectroscopy was used for analysis of carrier-free protactinium-233 and neptunium-239 and a stoichiometric amount of cerium (observed cerium-141) subsequent to gasification and leaching, up to 48 days. High resolution ICP-MS was used to analyze the cerium, thorium, and uranium from 46 to 438 days of leaching. Leaching procedures followed the guidance of ASTM Procedure C 1220-92, Standard Test Method for Static Leaching of Monolithic Waste Forms for Disposal of Radioactive Waste. The combination of the thermally reductive pretreatment, vitrification and cementation produced a highly non-leachable form suitable for long-term disposal of cerium, thorium, protactinium, uranium, and neptunium. PMID:14637345

  9. A chemical-spectrochemical method for the determination of rare earth elements and thorium in cerium minerals

    USGS Publications Warehouse

    Rose, H.J.; Murata, K.J.; Carron, M.K.

    1954-01-01

    In a combined chemical-spectrochemical procedure for quantitatively determining rare earth elements in cerium minerals, cerium is determined volumetrically, a total rare earths plus thoria precipitate is separated chemically, the ceria content of the precipitate is raised to 80??0 percent by adding pure ceria, and the resulting mixture is analyzed for lanthanum, praseodymium, neodymium, samarium, gadolinium, yttrium, and thorium spectrochemically by means of the d.c. carbon arc. Spectral lines of singly ionized cerium are used as internal standard lines in the spectrochemical determination which is patterned after Fassel's procedure [1]. Results of testing the method with synthetic mixtures of rare earths and with samples of chemically analyzed cerium minerals show that the coefficient of variation for a quadruplicate determination of any element does not exceed 5??0 (excepting yttrium at concentrations less than 1 percent) and that the method is free of serious systematic error. ?? 1954.

  10. Enhanced thermoelectric properties of phase-separating bismuth selenium telluride thin films via a two-step method

    SciTech Connect

    Takashiri, Masayuki Kurita, Kensuke; Hagino, Harutoshi; Miyazaki, Koji; Tanaka, Saburo

    2015-08-14

    A two-step method that combines homogeneous electron beam (EB) irradiation and thermal annealing has been developed to enhance the thermoelectric properties of nanocrystalline bismuth selenium telluride thin films. The thin films, prepared using a flash evaporation method, were treated with EB irradiation in a N{sub 2} atmosphere at room temperature and an acceleration voltage of 0.17 MeV. Thermal annealing was performed under Ar/H{sub 2} (5%) at 300 °C for 60 min. X-ray diffraction was used to determine that compositional phase separation between bismuth telluride and bismuth selenium telluride developed in the thin films exposed to higher EB doses and thermal annealing. We propose that the phase separation was induced by fluctuations in the distribution of selenium atoms after EB irradiation, followed by the migration of selenium atoms to more stable sites during thermal annealing. As a result, thin film crystallinity improved and mobility was significantly enhanced. This indicates that the phase separation resulting from the two-step method enhanced, rather than disturbed, the electron transport. Both the electrical conductivity and the Seebeck coefficient were improved following the two-step method. Consequently, the power factor of thin films that underwent the two-step method was enhanced to 20 times (from 0.96 to 21.0 μW/(cm K{sup 2}) that of the thin films treated with EB irradiation alone.

  11. Effects of chemical intermixing on electrical and thermal contact conductances at metallized bismuth and antimony telluride interfaces

    SciTech Connect

    Devender,; Mehta, Rutvik J.; Ramanath, Ganpati; Lofgreen, Kelly; Mahajan, Ravi; Yamaguchi, Masashi; Borca-Tasciuc, Theodorian

    2015-03-15

    Tailoring electrical and thermal contact conductivities (Σ{sub c} and Γ{sub c}) across metallized pnictogen chalcogenide interfaces is key for realizing efficient thermoelectric devices. The authors report that Cu, Ni, Ti, and Ta diffusion and interfacial telluride formation with n-Bi{sub 2}Te{sub 3} and p-Sb{sub 2}Te{sub 3} influence both Σ{sub c} and Γ{sub c}. Cu metallization yields the highest Γ{sub c} and the lowest Σ{sub c}, correlating with maximal metal diffusion and copper telluride formation. Ni diffuses less and yields the highest Σ{sub c} with Sb{sub 2}Te{sub 3} due to p-type nickel telluride formation, which diminishes Σ{sub c} improvement with n-Bi{sub 2}Te{sub 3} interfaces. Ta and Ti contacts yield the lowest properties similar to that in Ni-metallized structures. These correlations between interfacial diffusion and phase formation on electronic and thermal transport properties will be important for devising suitable metallization for thermoelectric devices.

  12. Synthesis and characterization of bismuth telluride based nanostructured thermoelectric composite materials

    NASA Astrophysics Data System (ADS)

    Keshavarz Khorasgani, Mohsen

    Thermoelectric (TE) materials and devices are attractive in solid-state energy conversion applications such as waste heat recovery, air-conditioning, and refrigeration. Since the 1950's lots of unremitting efforts have been made to enhance the efficiency of energy conversion in TE materials (i. e. improving the figure of merit (ZT)), however, most of commercial bulk TE materials still suffer from low efficiency with ZTs around unity. To enhance the performance of bismuth telluride based TE alloys, we have developed composite TE materials, based on the idea that introducing more engineered interfaces in the bulk TE materials may lead to thermal conductivity reduction due to increased phonon scattering by these interfaces. In this approach it is expected that the electronic transport properties of the material are not effectively affected. Consequently, ZT enhancement can be achieved. In this dissertation we will discuss synthesis and characterization of two types of bismuth telluride based bulk composite TE materials. The first type is engineered to contain the presence of coherent interfaces between phases in the material resulting from different mixtures of totally miscible compounds with similar composition. The second type includes the nanocomposites with embedded foreign nano-particles in which the matrix and the particles are delimited by incoherent interfaces. The synthesis procedure, micro- and nano-structures as well as thermoelectric properties of these composites will be presented. In our study on the composites with coherent interfaces, we produced a series of different composites of p-type bismuth antimony telluride alloys and studied their microstructure and thermoelectric properties. Each composite consists of two phases that were obtained in powder form by mechanical alloying. Mixed powders in various proportions of the two different phases were consolidated by hot extrusion to obtain each bulk composite. The minimum grain size of bulk composites as

  13. Long-term testing of in-situ cerium oxide coated anodes for aluminum electrowinning

    SciTech Connect

    King, H.L.

    1989-10-01

    The ELTECH Anode Phase 2 Project (Contract Number AC07-86ID12655), as supported by the Department of Energy (DOE) from December 1988 through April 1989, focused on long-term testing of in-situ anodically deposited cerium oxide (CEROX) coatings on nickel ferrite/Cu cermets. The specific objective of this research was to determine the effectiveness of the CEROX coating in reducing the transfer of cermet components to the produced aluminum. A dosing regimen was first established for the minimum addition of cerium to the cell necessary to produce targeted CEROX coatings on the cermet anode and the periodic additions necessary to maintain coating thicknesses. The effects of the addition of CeF{sub 3} on CEROX coating formation was evaluated for targeted coating thicknesses at three different current densities. Analytical procedures were identified for determining alumina concentrations and the cryolite bath ratio for quasi-commercial baths.

  14. A DFT + U study of cerium solubility in La₂Zr₂O₇

    SciTech Connect

    Wang, X. J.; Xiao, Haiyan Y.; Zu, Xiaotao; Weber, William J.

    2012-02-17

    Density functional theory plus Hubbard U correction is employed to study the solubility of cerium in La₂Zr₂O₇. The results show that La₂Zr₂O₇ and Ce₂Zr₂O₇ form a solid solution over the whole range of cerium content. The solubility of Ce in La₂Zr₂O₇ can be partially attributed to the similar ionic radii of La³+ and Ce³+. Electronic structures of the La₂₋yCeyZr₂O₇ solid solution have been analyzed. The Ce 4ƒ states are found to be partially occupied, and Ce in the La₂₋yCeyZr₂O₇ solid solution exhibits a reduced charge state.

  15. Cerium Binding Activity of Pectins Isolated from the Seagrasses Zostera marina and Phyllospadix iwatensis

    PubMed Central

    Khotimchenko, Yuri; Khozhaenko, Elena; Kovalev, Valeri; Khotimchenko, Maxim

    2012-01-01

    Cerium binding activity of three different water soluble pectin compounds of different origin was studied in a batch sorption system. The Langmuir, Freundlich and BET sorption models were adopted to describe the binding reactions between metal ions and pectin molecules. The Langmuir model provided the best fit. Within the pH range from 4.0 to 6.0, the largest amount of the cerium ions was bound by pectin isolated from the seagrass Phylospadix iwatensis in comparison to pectin extracted from the seagrass Zostera marina and pectin obtained from citrus peel (commercial grade). The Langmuir constants were also highest for the pectin samples isolated from the seagrass P. iwatensis. The results obtained from this study suggest that pectin is a prospective source for the development of radioisotope-removing pharmaceuticals. PMID:22690146

  16. Measurement of the magnetic behaviour of 147Eu and 149Eu in cerium and platinum

    NASA Astrophysics Data System (ADS)

    Dietrich, M.; Zeitz, W.-D.; Weber, A.; Potzger, K.; Unterricker, S.; Schneider, F.; Samokhvalov, V.; Isolde Collaboration

    2005-07-01

    The local magnetism at europium in platinum and in cerium was studied using perturbed angular correlation (PAC) spectroscopy. In platinum, europium shows the electronic properties of the trivalent status, which has a non-magnetic ground state ( J=0). As a consequence, the Van Vleck contributions from the complete multiplet-level system predominantly determine the magnetic behaviour. In cerium, the measured data are close to the predictions for divalent europium. Here, only the electronic ground state, the pure spin state ( J=5/2), has to be taken into account. The measurements were done utilising the isomeric 11/2 - nuclear levels in 147Eu and 149Eu at 625 and 496 keV, respectively, after the precursors had been produced at the ion beam laboratory ISL Berlin or the on-line mass separator ISOLDE in Geneva.

  17. Luminescent Properties of Cerium Doped Potassium Iodide Single Crystals in Response to γ-irradiation.

    PubMed

    Bangaru, S; Saradha, K; Muralidharan, G

    2015-05-01

    Potassium iodide doped with cerium ions were prepared by Bridgemann Stockbarger technique and investigated by optical absorption, Photoluminescence(PL), Thermoluminescence(TL), Photostimulated Luminescence(PSL) and TL emission. The optical absorption measurement indicates that F and V centers are formed in the crystals during the γ-ray irradiation process. Optical absorption and Photoluminescence studies confirm the presence of cerium ions in the trivalent state. Spectral distribution under the Thermoluminescence Emission(TLE) and Optically Stimulated Luminescence(OSL) support the idea that the defect annihilation process to be due to thermal release of F-electron in KI:Ce(3+) crystals. Both Ce(3+) and Ce(2+) emissions were observed in the Thermoluminescence emission of the crystals. Thermoluminescence(TL) has been identified to be due to thermal release of electron produced during colouration process. PMID:25744528

  18. Variation of electronic transitions and reduction potentials of cerium(IV) complexes.

    PubMed

    Williams, Ursula J; Schneider, David; Dorfner, Walter L; Maichle-Mössmer, Cäcilia; Carroll, Patrick J; Anwander, Reiner; Schelter, Eric J

    2014-11-21

    The trivalent compound K[Ce[N(SiHMe2)2]4] was synthesized and oxidized, providing a convenient route to the reported cerium(IV) compound Ce[N(SiHMe2)2]4. Protonolysis reactions of Ce[N(SiHMe2)2]4 with tert-butanol, substituted benzyl alcohols, and 2,6-diphenylphenol yielded the neutral tetravalent compounds Ce(O(t)Bu)4(py)2, Ce2(OCH2C6R5)8(thf)2 (R = Me, F), and Ce(Odpp)4 (dpp = 2,6-(C6H5)2-C6H3). Spectroscopic and electrochemical characterization of the monometallic cerium(IV) silylamide, alkoxide, and aryloxide compounds revealed variable ligand-to-metal charge transfer transitions and metal-based reduction potentials. Computational bonding analyses were performed to complement the physical characterization of the complexes.

  19. Thermodynamics of the α -γ transition in cerium studied by an LDA + Gutzwiller method

    NASA Astrophysics Data System (ADS)

    Tian, Ming-Feng; Song, Hai-Feng; Liu, Hai-Feng; Wang, Cong; Fang, Zhong; Dai, Xi

    2015-03-01

    Utilizing the local-density approximation (LDA) + Gutzwiller method, we have studied the α -γ transition in cerium. Our results indicate that the volume collapse transition between α and γ phases is present at zero temperature with negative pressure. By further providing a newly finite temperature generalization of the LDA + Gutzwiller method (using the mean-field potential approach), the entropy contributed by both electronic quasiparticles and lattice vibration included, we obtain the Gibbs free energy at a given volume and temperature, from which we get the α -γ transition at finite temperature and pressure. Our results indicate that the electronic entropy and lattice vibrational entropy both play important roles in the α -γ transition. We also calculated the equation of state and phase diagram of cerium, finding good agreement with the experiments.

  20. A cerium-lead redox flow battery system employing supporting electrolyte of methanesulfonic acid

    NASA Astrophysics Data System (ADS)

    Na, Zhaolin; Xu, Shengnan; Yin, Dongming; Wang, Limin

    2015-11-01

    A novel cerium-lead redox flow battery (RFB) employing Ce(IV)/Ce(III) and Pb(II)/Pb redox couples in the supporting electrolyte of methanesulfonic acid (MSA) is developed and preliminarily investigated. The RFB requires no additional catalyst and uses kinetically favorable reactions between low-cost reactants, and provides a desirable discharge voltage of approximately 1.7 V, with high average coulombic efficiency (CE) of 92% and energy efficiency (EE) of 86% over 800 cycles at 298 K. Stable cycling with an acceptable performance is achieved for a board operating temperature range of 253 K-313 K. The excellent performance obtained from the preliminary study suggests that the cerium-lead RFB promises to be applicable to large-scale energy storage for electricity grids.

  1. Improvement and analysis of the hydrogen-cerium redox flow cell

    NASA Astrophysics Data System (ADS)

    Tucker, Michael C.; Weiss, Alexandra; Weber, Adam Z.

    2016-09-01

    The H2-Ce redox flow cell is optimized using commercially-available cell materials. Cell performance is found to be sensitive to the upper charge cutoff voltage, membrane boiling pretreatment, methanesulfonic-acid concentration, (+) electrode surface area and flow pattern, and operating temperature. Performance is relatively insensitive to membrane thickness, Cerium concentration, and all features of the (-) electrode including hydrogen flow. Cell performance appears to be limited by mass transport and kinetics in the cerium (+) electrode. Maximum discharge power of 895 mW cm-2 was observed at 60 °C; an energy efficiency of 90% was achieved at 50 °C. The H2-Ce cell is promising for energy storage assuming one can optimize Ce reaction kinetics and electrolyte.

  2. Cerium Regulates Expression of Alternative Methanol Dehydrogenases in Methylosinus trichosporium OB3b

    PubMed Central

    Farhan Ul Haque, Muhammad; Kalidass, Bhagyalakshmi; Bandow, Nathan; Turpin, Erick A.; DiSpirito, Alan A.

    2015-01-01

    Methanotrophs have multiple methane monooxygenases that are well known to be regulated by copper, i.e., a “copper switch.” At low copper/biomass ratios the soluble methane monooxygenase (sMMO) is expressed while expression and activity of the particulate methane monooxygenase (pMMO) increases with increasing availability of copper. In many methanotrophs there are also multiple methanol dehydrogenases (MeDHs), one based on Mxa and another based on Xox. Mxa-MeDH is known to have calcium in its active site, while Xox-MeDHs have been shown to have rare earth elements in their active site. We show here that the expression levels of Mxa-MeDH and Xox-MeDH in Methylosinus trichosporium OB3b significantly decreased and increased, respectively, when grown in the presence of cerium but the absence of copper compared to the absence of both metals. Expression of sMMO and pMMO was not affected. In the presence of copper, the effect of cerium on gene expression was less significant, i.e., expression of Mxa-MeDH in the presence of copper and cerium was slightly lower than in the presence of copper alone, but Xox-MeDH was again found to increase significantly. As expected, the addition of copper caused sMMO and pMMO expression levels to significantly decrease and increase, respectively, but the simultaneous addition of cerium had no discernible effect on MMO expression. As a result, it appears Mxa-MeDH can be uncoupled from methane oxidation by sMMO in M. trichosporium OB3b but not from pMMO. PMID:26296730

  3. PURIFICATION OF PLUTONIUM USING A CERIUM PRECIPITATE AS A CARRIER FOR FISSION PRODUCTS

    DOEpatents

    Faris, B.F.; Olson, C.M.

    1961-07-01

    Bismuth phosphate carrier precipitation processes are described for the separation of plutonium from fission products wherein in at least one step bismuth phosphate is precipitated in the presence of hexavalent plutonium thereby carrying a portion of the fission products from soluble plu tonium values. In this step, a cerium phosphate precipitate is formed in conjunction with the bismuth phosphate precipitate, thereby increasing the amount of fission products removed from solution.

  4. Cerium regulates expression of alternative methanol dehydrogenases in Methylosinus trichosporium OB3b.

    PubMed

    Farhan Ul Haque, Muhammad; Kalidass, Bhagyalakshmi; Bandow, Nathan; Turpin, Erick A; DiSpirito, Alan A; Semrau, Jeremy D

    2015-11-01

    Methanotrophs have multiple methane monooxygenases that are well known to be regulated by copper, i.e., a "copper switch." At low copper/biomass ratios the soluble methane monooxygenase (sMMO) is expressed while expression and activity of the particulate methane monooxygenase (pMMO) increases with increasing availability of copper. In many methanotrophs there are also multiple methanol dehydrogenases (MeDHs), one based on Mxa and another based on Xox. Mxa-MeDH is known to have calcium in its active site, while Xox-MeDHs have been shown to have rare earth elements in their active site. We show here that the expression levels of Mxa-MeDH and Xox-MeDH in Methylosinus trichosporium OB3b significantly decreased and increased, respectively, when grown in the presence of cerium but the absence of copper compared to the absence of both metals. Expression of sMMO and pMMO was not affected. In the presence of copper, the effect of cerium on gene expression was less significant, i.e., expression of Mxa-MeDH in the presence of copper and cerium was slightly lower than in the presence of copper alone, but Xox-MeDH was again found to increase significantly. As expected, the addition of copper caused sMMO and pMMO expression levels to significantly decrease and increase, respectively, but the simultaneous addition of cerium had no discernible effect on MMO expression. As a result, it appears Mxa-MeDH can be uncoupled from methane oxidation by sMMO in M. trichosporium OB3b but not from pMMO. PMID:26296730

  5. Cerium Oxide Nanoparticles Reduce Microglial Activation and Neurodegenerative Events in Light Damaged Retina

    PubMed Central

    Fiorani, Lavinia; Passacantando, Maurizio; Santucci, Sandro; Di Marco, Stefano; Bisti, Silvia; Maccarone, Rita

    2015-01-01

    The first target of any therapy for retinal neurodegeneration is to slow down the progression of the disease and to maintain visual function. Cerium oxide or ceria nanoparticles reduce oxidative stress, which is known to play a pivotal role in neurodegeneration. Our aim was to investigate whether cerium oxide nanoparticles were able to mitigate neurodegeneration including microglial activation and related inflammatory processes induced by exposure to high intensity light. Cerium oxide nanoparticles were injected intravitreally or intraveinously in albino Sprague-Dawley rats three weeks before exposing them to light damage of 1000 lux for 24 h. Electroretinographic recordings were performed a week after light damage. The progression of retinal degeneration was evaluated by measuring outer nuclear layer thickness and TUNEL staining to quantify photoreceptors death. Immunohistochemical analysis was used to evaluate retinal stress, neuroinflammatory cytokines and microglial activation. Only intravitreally injected ceria nanoparticles were detected at the level of photoreceptor outer segments 3 weeks after the light damage and electoretinographic recordings showed that ceria nanoparticles maintained visual response. Moreover, this treatment reduced neuronal death and “hot spot” extension preserving the outer nuclear layer morphology. It is noteworthy that in this work we demonstrated, for the first time, the ability of ceria nanoparticles to reduce microglial activation and their migration toward outer nuclear layer. All these evidences support ceria nanoparticles as a powerful therapeutic agent in retinal neurodegenerative processes. PMID:26469804

  6. Application of cerium nitrate-silver sulphadiazine allows for postponement of excision and grafting.

    PubMed

    Vehmeyer-Heeman, M; Tondu, T; Van den Kerckhove, E; Boeckx, W

    2006-02-01

    Early excision and grafting cannot always be performed due to patient's medical status, and the lack of adequate donor sites. The use of cerium nitrate-silver sulphadiazine cream, which causes the formation of a leather-like eschar with excellent resistance to infection, is an alternative method. In order to postpone operations by using cerium nitrate-silver sulphadiazine, we compared the differences in contamination of the grafted areas between early and delayed excision. Eighteen patients underwent excision and grafting within 5 days post burn and nineteen patients were surgically treated after 5 days. Twelve months later the grafted areas were evaluated. Contamination of the grafted area occurred in 17 patients. No differences in contamination occurred between the early and delayed excision group, 8 versus 9. Also no differences in type of organism cultured and follow-up results were found between the early and delayed excision group. Cerium nitrate-silver sulphadiazine allows surgical treatment to be delayed without an increase of contamination of the grafted area and does not adversely affect the long-term outcome.

  7. Cerium Biomagnification in a Terrestrial Food Chain: Influence of Particle Size and Growth Stage.

    PubMed

    Majumdar, Sanghamitra; Trujillo-Reyes, Jesica; Hernandez-Viezcas, Jose A; White, Jason C; Peralta-Videa, Jose R; Gardea-Torresdey, Jorge L

    2016-07-01

    Mass-flow modeling of engineered nanomaterials (ENMs) indicates that a major fraction of released particles partition into soils and sediments. This has aggravated the risk of contaminating agricultural fields, potentially threatening associated food webs. To assess possible ENM trophic transfer, cerium accumulation from cerium oxide nanoparticles (nano-CeO2) and their bulk equivalent (bulk-CeO2) was investigated in producers and consumers from a terrestrial food chain. Kidney bean plants (Phaseolus vulgaris var. red hawk) grown in soil contaminated with 1000-2000 mg/kg nano-CeO2 or 1000 mg/kg bulk-CeO2 were presented to Mexican bean beetles (Epilachna varivestis), which were then consumed by spined soldier bugs (Podisus maculiventris). Cerium accumulation in plant and insects was independent of particle size. After 36 days of exposure to 1000 mg/kg nano- and bulk-CeO2, roots accumulated 26 and 19 μg/g Ce, respectively, and translocated 1.02 and 1.3 μg/g Ce, respectively, to shoots. The beetle larvae feeding on nano-CeO2 exposed leaves accumulated low levels of Ce since ∼98% of Ce was excreted in contrast to bulk-CeO2. However, in nano-CeO2 exposed adults, Ce in tissues was higher than Ce excreted. Additionally, Ce content in tissues was biomagnified by a factor of 5.3 from the plants to adult beetles and further to bugs.

  8. Application of Cerium (IV) as an Oxidimetric Agent for the Determination of Ethionamide in Pharmaceutical Formulations

    PubMed Central

    2016-01-01

    Two simple methods are described for the determination of ethionamide (ETM) in bulk drug and tablets using cerium (IV) sulphate as the oxidimetric agent. In both methods, the sample solution is treated with a measured excess of cerium (IV) solution in H2SO4 medium, and after a fixed standing time, the residual oxidant is determined either by back titration with standard iron (II) solution to a ferroin end point in titrimetry or by reacting with o-dianisidine followed by measurement of the absorbance of the orange-red coloured product at 470 nm in spectrophotometry. In titrimetry, the reaction proceeded with a stoichiometry of 1 : 2 (ETM : Ce (IV)) and the amount of cerium (IV) consumed by ETM was related to the latter's amount, and the method was applicable over 1.0–8.0 mg of drug. In spectrophotometry, Beer's law was obeyed over the concentration range of 0.5–5.0 μg/mL ETM with a molar absorptivity value of 2.66 × 104 L/(mol·cm). The limits of detection (LOD) and quantification (LOQ) calculated according to ICH guidelines were 0.013 and 0.043 μg/mL, respectively. The proposed titrimetric and spectrophotometric methods were found to yield reliable results when applied to bulk drug and tablets analysis, and hence they can be applied in quality control laboratories.

  9. Unveiling the mechanism of uptake and sub-cellular distribution of cerium oxide nanoparticles†

    PubMed Central

    Singh, Sanjay; Kumar, Amit; Karakoti, Ajay; Seal, Sudipta; Self, William T.

    2011-01-01

    Cerium oxide nanoparticles (CNPs) have been recently studied for their potent superoxide scavenging properties in both cell and animal model systems. Data from these model systems have shown that exposure of cells to CNPs results in the protection against reactive oxygen species (ROS). Despite these exciting findings, very little is known regarding the uptake or subcellular distribution of these nanomaterials inside cells. In this study we utilized fluorophore (carboxyfluorescein) conjugated cerium oxide NPs (CCNPs) to study the mechanism of uptake and to elucidate the subcellular localization of CNPs using a keratinocyte model system. We observed rapid uptake (within 3 h) of CCNPs that was governed by energy-dependent, clathrin-mediated and caveolae-mediated endocytic pathways. We found CCNPs co-localized with mitochondria, lysosomes and endoplasmic reticulum as well as being abundant in the cytoplasm and the nucleus. Given the radical scavenging properties of cerium oxide and the widespread cellular disposition we observed, CNPs likely act as cellular antioxidants in multiple compartments of the cell imparting protection against a variety of oxidant injuries. PMID:20697616

  10. The role of hydrogen peroxide in the deposition of cerium-based conversion coatings

    NASA Astrophysics Data System (ADS)

    Scholes, F. H.; Soste, C.; Hughes, A. E.; Hardin, S. G.; Curtis, P. R.

    2006-12-01

    Cerium-based conversion coatings are progressing as an effective alternative to hazardous chromate-based systems used in the treatment of metal surfaces. However, there is still considerable debate over the mechanism by which these coatings are formed. Here, titrations of cerium-based conversion coating solutions were carried out in order to model the reactions that occur at the metal-solution interface during coating, with a particular emphasis on investigating the role of hydrogen peroxide (H 2O 2). The titration curves obtained support the proposed formation of Ce(III) peroxo complexes such as Ce(H 2O 2) 3+ as an initial step, followed by deprotonation, oxidation and precipitation to form peroxo-containing Ce(IV) species such as Ce (IV)(O 2)(OH) 2. The precipitates resulting from titrations were characterised by Raman spectroscopy, X-ray diffraction and thermogravimetric analysis, confirming the presence of peroxo bonds, and nano-sized CeO 2 crystallites that decreased in size with increasing H 2O 2 concentration. Characterisation of cerium conversion coatings on aluminium alloy surfaces confirmed the presence of peroxo species in the coatings, thereby supporting the titration model.

  11. Aqueous Co-precipitation of Pd-doped Cerium Oxide Nanoparticles: Chemistry Structure and Particle Growth

    SciTech Connect

    Liang H.; Zhang L.; Raitano J.M.; He G.; Akey A.J.; Herman I.P.; Chan S.-W.

    2012-01-01

    Nanoparticles of palladium-doped cerium oxide (Pd-CeO{sub 2}) have been prepared by aqueous co-precipitation resulting in a single phase cubic structure after calcination according to X-ray diffraction (XRD). Inhomogeneous strain, calculated using the Williamson-Hall method, was found to increase with palladium content, and the lattice contracts slightly, relative to nano-cerium oxide, as palladium content is increased. Moreover, high resolution transmission electron microscopy reveals some instances of defective microstructure. These factors combined imply that palladium is in solid solution with CeO{sub 2} in these nanoparticles, but palladium (II) oxide (PdO) peaks in the Raman spectra indicate that solid solution formation is partial and that highly dispersed PdO is present as well as the solid solution. Nevertheless, the addition of palladium to the CeO{sub 2} lattice inhibits the growth of the 6% Pd-CeO{sub 2} particles compared to pure CeO{sub 2} between 600 and 850 C. Activation energies for grain growth of 54 {+-} 7 and 79 {+-} 8 kJ/mol were determined for 6% Pd-CeO{sub 2} and pure CeO{sub 2}, respectively, along with pre-exponential Arrhenius factors of 10 for the doped sample and 600 for pure cerium oxide.

  12. Cerium, gallium and zinc containing mesoporous bioactive glass coating deposited on titanium alloy

    NASA Astrophysics Data System (ADS)

    Shruti, S.; Andreatta, F.; Furlani, E.; Marin, E.; Maschio, S.; Fedrizzi, L.

    2016-08-01

    Surface modification is one of the methods for improving the performance of medical implants in biological environment. In this study, cerium, gallium and zinc substituted 80%SiO2-15%CaO-5%P2O5 mesoporous bioactive glass (MBG) in combination with polycaprolactone (PCL) were coated over Ti6Al4 V substrates by dip-coating method in order to obtain an inorganic-organic hybrid coating (MBG-PCL). Structural characterization was performed using XRD, nitrogen adsorption, SEM-EDXS, FTIR. The MBG-PCL coating uniformly covered the substrate with the thickness found to be more than 1 μm. Glass and polymer phases were detected in the coating along with the presence of biologically potent elements cerium, gallium and zinc. In addition, in vitro bioactivity was investigated by soaking the coated samples in simulated body fluid (SBF) for up to 30 days at 37 °C. The apatite-like layer was monitored by FTIR, SEM-EDXS and ICP measurements and it formed in all the samples within 15 days except zinc samples. In this way, an attempt was made to develop a new biomaterial with improved in vitro bioactive response due to bioactive glass coating and good mechanical strength of Ti6Al4 V alloy along with inherent biological properties of cerium, gallium and zinc.

  13. Controlled Redox Chemistry at Cerium within a Tripodal Nitroxide Ligand Framework.

    PubMed

    Bogart, Justin A; Lippincott, Connor A; Carroll, Patrick J; Booth, Corwin H; Schelter, Eric J

    2015-12-01

    Ligand reorganization has been shown to have a profound effect on the outcome of cerium redox chemistry. Through the use of a tethered, tripodal, trianionic nitroxide ligand, [((2-tBuNOH)C6 H4 CH2 )3 N](3-) (TriNOx (3-) ), controlled redox chemistry at cerium was accomplished, and typically reactive complexes of tetravalent cerium were isolated. These included rare cationic complexes [Ce(TriNOx )thf][BAr(F) 4 ], in which Ar(F) =3,5-(CF3 )2 -C6 H3 , and [Ce(TriNOx )py][OTf]. A rare complete Ce-halide series, Ce(TriNOx )X, in which X=F(-) , Cl(-) , Br(-) , I(-) , was also synthesized. The solution chemistry of these complexes was explored through detailed solution-phase electrochemistry and (1) H NMR experiments and showed a unique shift in the ratio of species with inner- and outer-sphere anions with size of the anionic X(-) group. DFT calculations on the series of calculations corroborated the experimental findings.

  14. Microstructure and electrochemical behavior of cerium conversion coating modified with silane agent on magnesium substrates

    NASA Astrophysics Data System (ADS)

    Lei, Li; Shi, Jing; Wang, Xin; Liu, Dan; Xu, Haigang

    2016-07-01

    The cerium conversion coating with and without different concentrations of silane agent bis-(γ-triethoxysilylpropyl)-tetrasulfide (BTESPT) modification is obtained on magnesium alloys. Detailed properties of the coatings and the role of BTESPT as an additive are studied and followed with careful discussion. The coating morphology, wettability, chemical composition and corrosion resistance are characterized by scanning electronic microscope (SEM), water contact-angle, X-ray photoelectron spectroscopy (XPS), potentiodynamic measurements and electrochemical impedance spectroscopy (EIS). The electrochemical behavior of the coatings is investigated using EIS. The results indicate that the coating morphology and composition can be controlled by changing silane concentration. The combination of cerium ions and silane molecules could promote the formation of more homogenous and higher hydrophobic coating. The coating turns to be more compact and the adhesive strength between the coating and the magnesium substrate are strongly improved with the formation of Sisbnd Osbnd Si and Sisbnd Osbnd M chemical bonds. The optimum corrosion resistance of the coating in the corrosive media is obtained by 25 ml L-1 BTESPT modification. This whole study implies that the cerium conversion coating modified with certain silane agent deserves cautiousness before its application for corrosion resistance.

  15. A novel approach of chemical mechanical polishing for cadmium zinc telluride wafers

    NASA Astrophysics Data System (ADS)

    Zhang, Zhenyu; Wang, Bo; Zhou, Ping; Kang, Renke; Zhang, Bi; Guo, Dongming

    2016-05-01

    A novel approach of chemical mechanical polishing (CMP) is developed for cadmium zinc telluride (CdZnTe or CZT) wafers. The approach uses environment-friendly slurry that consists of mainly silica, hydrogen peroxide, and citric acid. This is different from the previously reported slurries that are usually composed of strong acid, alkali, and bromine methanol, and are detrimental to the environment and operators. Surface roughness 0.5 nm and 4.7 nm are achieved for Ra and peak-to-valley (PV) values respectively in a measurement area of 70 × 50 μm2, using the developed novel approach. Fundamental polishing mechanisms are also investigated in terms of X-ray photoelectron spectroscopy (XPS) and electrochemical measurements. Hydrogen peroxide dominates the passivating process during the CMP of CZT wafers, indicating by the lowest passivation current density among silica, citric acid and hydrogen peroxide solution. Chemical reaction equations are proposed during CMP according to the XPS and electrochemical measurements.

  16. Directional Solidification of Mercury Cadmium Telluride During the Second United States Microgravity Payload Mission (USMP-2)

    NASA Technical Reports Server (NTRS)

    Gillies, D. C.; Lehoczky, S. L.; Szofran, F. R.; Watring, D. A.; Alexander, H. A.; Jerman, G. A.

    1996-01-01

    As a solid solution semiconductor having, a large separation between liquidus and solidus, mercury cadmium telluride (MCT) presents a formidable challenge to crystal growers desiring an alloy of high compositional uniformity. To avoid constitutional supercooling during Bridgman crystal growth it is necessary to solidify slowly in a high temperature gradient region. The necessary translation rate of less than 1 mm/hr results in a situation where fluid flow induced by gravity on earth is a significant factor in material transport. The Advanced Automated Directional Solidification Furnace (AADSF) is equipped to provide the stable thermal environment with a high gradient, and the required slow translation rate needed. Ground based experiments in AADSF show clearly the dominance of flow driven transport. The first flight of AADSF in low gravity on USMP-2 provided an opportunity to test theories of fluid flow in MCT and showed several solidification regimes which are very different from those observed on earth. Residual acceleration vectors in the orbiter during the mission were measured by the Orbital Acceleration Research Experiment (OARE), and correlated well with observed compositional differences in the samples.

  17. Novel Cadmium Zinc Telluride Devices for Myocardial Perfusion Imaging-Technological Aspects and Clinical Applications.

    PubMed

    Ben-Haim, Simona; Kennedy, John; Keidar, Zohar

    2016-07-01

    Myocardial perfusion imaging plays an important role in the assessment of patients with known or suspected coronary artery disease and is well established for diagnosis and for prognostic evaluation in these patients. The dedicated cardiac SPECT cameras with solid-state cadmium zinc telluride (CZT) detectors were first introduced a decade ago. A large body of evidence is building up, showing the superiority of the new technology compared with conventional gamma cameras. Not only the CZT detectors, but also new collimator geometries, the ability to perform focused imaging optimized for the heart and advances in data processing algorithms all contribute to the significantly improved sensitivity up to 8-10 times, as well as improved energy resolution and improved reconstructed spatial resolution compared with conventional technology. In this article, we provide an overview of the physical characteristics of the CZT cameras, as well as a review of the literature published so far, including validation studies in comparison with conventional myocardial perfusion imaging and with invasive coronary angiography, significant reduction in radiation dose, and new imaging protocols enabled by the new technology.

  18. Inhibition of autophagy contributes to the toxicity of cadmium telluride quantum dots in Saccharomyces cerevisiae

    PubMed Central

    Fan, Junpeng; Shao, Ming; Lai, Lu; Liu, Yi; Xie, Zhixiong

    2016-01-01

    Cadmium telluride quantum dots (CdTe QDs) are used as near-infrared probes in biologic and medical applications, but their cytological effects and mechanism of potential toxicity are still unclear. In this study, we evaluated the toxicity of CdTe QDs of different sizes and investigated their mechanism of toxicity in the yeast Saccharomyces cerevisiae. A growth inhibition assay revealed that orange-emitting CdTe (O-CdTe) QDs (half inhibitory concentration [IC50] =59.44±12.02 nmol/L) were more toxic than green-emitting CdTe QDs (IC50 =186.61±19.74 nmol/L) to S. cerevisiae. Further studies on toxicity mechanisms using a transmission electron microscope and green fluorescent protein tagged Atg8 processing assay revealed that O-CdTe QDs could partially inhibit autophagy at a late stage, which differs from the results reported in mammalian cells. Moreover, autophagy inhibited at a late stage by O-CdTe QDs could be partially recovered by enhancing autophagy with rapamycin (an autophagy activator), combined with an increased number of living cells. These results indicate that inhibition of autophagy acts as a toxicity mechanism of CdTe QDs in S. cerevisiae. This work reports a novel toxicity mechanism of CdTe QDs in yeast and provides valuable information on the effect of CdTe QDs on the processes of living cells. PMID:27524895

  19. Displaying and evaluating engineering properties and natural hazards using geomorphic mapping techniques: Telluride, Colorado

    SciTech Connect

    Gunawan, I.; Giardino, J.R.; Tchakerian, V.P. . Geography Dept.)

    1992-01-01

    Telluride, located in the San Juan mountains of southwestern Colorado, is situated in a glacially carved, fluvially modified alpine valley. Today this chic setting is experiencing rapid urban development resulting from flourishing tourist traffic during both the winter ski season and the summer vacation period. A new development, Mountain Village, is being built on an extensive and complex landslide that has only received superficial scrutiny. Recent fast growth is placing considerable pressure on pristine, undeveloped land. This timely quandary incorporates the interaction between prospective development, geomorphic processes, engineering factors, economic feasibility, and landuse adjudication. In an attempt to respond to these issues the State of Colorado enacted Senate Bill 35 (1972) and House Bills 1034 (1974) and 1041 (1974), all mandating assessment of the natural hazards of an area, preparatory to development. The key to evaluating the natural hazards is to comprehend the geomorphic processes. The area is highly-faulted with associated mineralization. Whereas the upper slopes are composed of massive rhyodacitic-tuff breccias and flows, the valley is sculpted from shales, sandstones, and conglomerates. Several periods of glaciation occurred in the area. Glacial till, talus slopes, avalanche chutes and cones, rock glaciers, alluvium, and landslides have been identified in the field and mapped on aerial photographs. Many of the slopes in the area are active. The authors have constructed a geomorphic map (1:12,500) that shows geology, landforms, geomorphic processes and engineering properties. This map can be used by regulatory agencies in identifying areas of natural hazards potentially sensitive to development.

  20. Reproductive toxicity and gender differences induced by cadmium telluride quantum dots in an invertebrate model organism

    PubMed Central

    Yan, Si-Qi; Xing, Rui; Zhou, Yan-Feng; Li, Kai-Le; Su, Yuan-Yuan; Qiu, Jian-Feng; Zhang, Yun-Hu; Zhang, Ke-Qin; He, Yao; Lu, Xiao-Ping; Xu, Shi-Qing

    2016-01-01

    Sexual glands are key sites affected by nanotoxicity, but there is no sensitive assay for measuring reproductive toxicity in animals. The aim of this study was to investigate the toxic effects of cadmium telluride quantum dots (CdTe-QDs) on gonads in a model organism, Bombyx mori. After dorsal vein injection of 0.32 nmol of CdTe-QDs per individual, the QDs passed through the outer membranes of gonads via the generation of ROS in the membranes of spermatocysts and ovarioles, as well as internal germ cells, thereby inducing early germ cell death or malformations via complex mechanisms related to apoptosis and autophagy through mitochondrial and lysosomal pathways. Histological observations of the gonads and quantitative analyses of germ cell development showed that the reproductive toxicity was characterized by obvious male sensitivity. Exposure to QDs in the early stage of males had severe adverse effects on the quantity and quality of sperm, which was the main reason for the occurrence of unfertilized eggs. Ala- or Gly-conjugated QDs could reduce the nanotoxicity of CdTe-QDs during germ cell development and fertilization of their offspring. The results demonstrate that males are preferable models for evaluating the reproductive toxicity of QDs in combined in vivo/in vitro investigations. PMID:27669995

  1. In-Situ growth of cadmium telluride nanocrystals in poly(3-hexylthiophene) matrix for photovoltaic application

    NASA Astrophysics Data System (ADS)

    Taukeer Khan, Mohd; Kaur, Amarjeet; Dhawan, S. K.; Chand, Suresh

    2011-08-01

    In the present study, nanocrystals of cadmium telluride (CdTe) have been directly synthesized in poly(3-hexylthiophene) (P3HT) matrix without use of any surfactant. In situ synthesis of nanoparticles in polymer matrix improves the polymer-nanoparticles interface, which facilitates efficient electronic interaction between them. Spectral results suggest that CdTe nanocrystals are bound with P3HT via dipole-dipole interaction and form a charge transfer complex. Structural and morphological studies reveal that CdTe works as transport media along/between the polymer chains, which facilitate percolation pathways for charge transport. Therefore, enhancement in current density has been observed for the bulk heterojunction (BHJ) device of P3HT-CdTe nanocomposites blended with PCBM. An open circuit voltage (VOC) of 0.80 V was obtained from the BHJ device due to the increase in the energy level offset between the donor and acceptor. This new photovoltaic element could provide a new nanoscale criterion for the investigation of photoinduced energy/charge transport in organic-inorganic interfaces.

  2. Influence of germanium nano-inclusions on the thermoelectric power factor of bulk bismuth telluride alloy

    SciTech Connect

    Satyala, Nikhil; Zamanipour, Zahra; Norouzzadeh, Payam; Krasinski, Jerzy S.; Vashaee, Daryoosh; Tahmasbi Rad, Armin; Tayebi, Lobat

    2014-05-28

    Nanocomposite thermoelectric compound of bismuth telluride (Bi{sub 2}Te{sub 3}) with 5 at. % germanium nano-inclusions was prepared via mechanically alloying and sintering techniques. The influence of Ge nano-inclusions and long duration annealing on the thermoelectric properties of nanostructured Bi{sub 2}Te{sub 3} were investigated. It was found that annealing has significant effect on the carrier concentration, Seebeck coefficient, and the power factor of the thermoelectric compound. The systematic heat treatment also reduced the density of donor type defects thereby decreasing the electron concentration. While the as-pressed nanocomposite materials showed n-type properties, it was observed that with the increase of annealing time, the nanocomposite gradually transformed to an abundantly hole-dominated (p-type) sample. The long duration annealing (∼500 h) resulted in a significantly enhanced electrical conductivity pertaining to the augmentation in the density and the structural properties of the sample. Therefore, a simultaneous enhancement in both electrical and Seebeck coefficient characteristics resulted in a remarkable increase in the thermoelectric power factor.

  3. Reproductive toxicity and gender differences induced by cadmium telluride quantum dots in an invertebrate model organism

    NASA Astrophysics Data System (ADS)

    Yan, Si-Qi; Xing, Rui; Zhou, Yan-Feng; Li, Kai-Le; Su, Yuan-Yuan; Qiu, Jian-Feng; Zhang, Yun-Hu; Zhang, Ke-Qin; He, Yao; Lu, Xiao-Ping; Xu, Shi-Qing

    2016-09-01

    Sexual glands are key sites affected by nanotoxicity, but there is no sensitive assay for measuring reproductive toxicity in animals. The aim of this study was to investigate the toxic effects of cadmium telluride quantum dots (CdTe-QDs) on gonads in a model organism, Bombyx mori. After dorsal vein injection of 0.32 nmol of CdTe-QDs per individual, the QDs passed through the outer membranes of gonads via the generation of ROS in the membranes of spermatocysts and ovarioles, as well as internal germ cells, thereby inducing early germ cell death or malformations via complex mechanisms related to apoptosis and autophagy through mitochondrial and lysosomal pathways. Histological observations of the gonads and quantitative analyses of germ cell development showed that the reproductive toxicity was characterized by obvious male sensitivity. Exposure to QDs in the early stage of males had severe adverse effects on the quantity and quality of sperm, which was the main reason for the occurrence of unfertilized eggs. Ala- or Gly-conjugated QDs could reduce the nanotoxicity of CdTe-QDs during germ cell development and fertilization of their offspring. The results demonstrate that males are preferable models for evaluating the reproductive toxicity of QDs in combined in vivo/in vitro investigations.

  4. Atomic ordering in cubic bismuth telluride alloy phases at high pressure

    NASA Astrophysics Data System (ADS)

    Loa, I.; Bos, J.-W. G.; Downie, R. A.; Syassen, K.

    2016-06-01

    Pressure-induced transitions from ordered intermetallic phases to substitutional alloys to semi-ordered phases were studied in a series of bismuth tellurides. By using angle-dispersive x-ray diffraction, the compounds Bi4Te5 , BiTe, and Bi2Te were observed to form alloys with the disordered body-centered cubic (bcc) crystal structure upon compression to above 14-19 GPa at room temperature. The BiTe and Bi2Te alloys and the previously discovered high-pressure alloys of Bi2Te3 and Bi4Te3 were all found to show atomic ordering after gentle annealing at very moderate temperatures of ˜100 ∘C . Upon annealing, BiTe transforms from bcc to the B2 (CsCl) crystal-structure type, and the other phases adopt semi-disordered variants thereof, featuring substitutional disorder on one of the two crystallographic sites. The transition pressures and atomic volumes of the alloy phases show systematic variations across the BimTen series including the end members Bi and Te. First-principles calculations were performed to characterize the electronic structure and chemical bonding properties of B2-type BiTe and to identify the driving forces of the ordering transition. The calculated Fermi surface of B2-type BiTe has an intricate structure and is predicted to undergo three topological changes between 20 and 60 GPa.

  5. A novel approach of chemical mechanical polishing for cadmium zinc telluride wafers.

    PubMed

    Zhang, Zhenyu; Wang, Bo; Zhou, Ping; Kang, Renke; Zhang, Bi; Guo, Dongming

    2016-01-01

    A novel approach of chemical mechanical polishing (CMP) is developed for cadmium zinc telluride (CdZnTe or CZT) wafers. The approach uses environment-friendly slurry that consists of mainly silica, hydrogen peroxide, and citric acid. This is different from the previously reported slurries that are usually composed of strong acid, alkali, and bromine methanol, and are detrimental to the environment and operators. Surface roughness 0.5 nm and 4.7 nm are achieved for Ra and peak-to-valley (PV) values respectively in a measurement area of 70 × 50 μm(2), using the developed novel approach. Fundamental polishing mechanisms are also investigated in terms of X-ray photoelectron spectroscopy (XPS) and electrochemical measurements. Hydrogen peroxide dominates the passivating process during the CMP of CZT wafers, indicating by the lowest passivation current density among silica, citric acid and hydrogen peroxide solution. Chemical reaction equations are proposed during CMP according to the XPS and electrochemical measurements. PMID:27225310

  6. Morphological evolution, growth mechanism, and magneto-transport properties of silver telluride one-dimensional nanostructures

    PubMed Central

    2013-01-01

    Single crystalline one-dimensional (1D) nanostructures of silver telluride (Ag2Te) with well-controlled shapes and sizes were synthesized via the hydrothermal reduction of sodium tellurite (Na2TeO3) in a mixed solution. The morphological evolution of various 1D nanostructures was mainly determined by properly controlling the nucleation and growth process of Ag2Te in different reaction times. Based on the transmission electron microscopy and scanning electron microscopy studies, the formation mechanism for these 1D nanostructures was rationally interpreted. In addition, the current–voltage (I-V) characteristics as a function of magnetic field of the highly single crystal Ag2Te nanowires were systematically measured. From the investigation of I-V characteristics, we have observed a rapid change of the current in low magnetic field, which can be used as the magnetic field sensor. The magneto-resistance behavior of the Ag2Te nanowires with monoclinic structure was also investigated. Comparing to the bulk and thin film materials, we found that there is generally a larger change in R (T) as the sample size is reduced, which indicates that the size of the sample has a certain impact on magneto-transport properties. Simultaneously, some possible reasons resulting in the observed large positive magneto-resistance behavior are discussed. PMID:23958372

  7. Semiconductor nanocrystals functionalized with antimony telluride zintl ions for nanostructured thermoelectrics.

    PubMed

    Kovalenko, Maksym V; Spokoyny, Boris; Lee, Jong-Soo; Scheele, Marcus; Weber, Andrew; Perera, Susanthri; Landry, Daniel; Talapin, Dmitri V

    2010-05-19

    The energy efficiency of heat engines could be improved by the partial recovery of waste heat using thermoelectric (TE) generators. We show the possibility of designing nanostructured TE materials using colloidal inorganic nanocrystals functionalized with molecular antimony telluride complexes belonging to the family of Zintl ions. The unique advantage of using Zintl ions as the nanocrystal surface ligands is the possibility to convert them into crystalline metal chalcogenides, thus linking individual nanobuilding blocks into a macroscopic assembly of electronically coupled functional modules. This approach allows preserving the benefits of nanostructuring and quantum confinement while enabling facile charge transport through the interparticle boundaries. A developed methodology was applied for solution-based fabrication of nanostructured n- and p-type Bi(2-x)Sb(x)Te(3) alloys with tunable composition and PbTe-Sb(2)Te(3) nanocomposites with controlled grain size. Characterization of the TE properties of these materials showed that their Seebeck coefficients, electrical and thermal conductivities, and ZT values compared favorably with those of previously reported solution-processed TE materials.

  8. Two-color detector: Mercury-cadmium-telluride as a terahertz and infrared detector

    SciTech Connect

    Sizov, F.; Zabudsky, V.; Petryakov, V.; Golenkov, A.; Andreyeva, K.; Tsybrii, Z.; Dvoretskii, S.

    2015-02-23

    In this paper, issues associated with the development of infrared (IR) and terahertz (THz) radiation detectors based on HgCdTe are discussed. Two-color un-cooled and cooled to 78 K narrow-gap mercury-cadmium-telluride semiconductor thin layers with antennas were considered both as sub-THz (sub-THz) direct detection bolometers and 3–10 μm IR photoconductors. The noise equivalent power (NEP) for one of the detectors studied at ν ≈ 140 GHz reaches NEP{sub 300 K} ≈ 4.5 × 10{sup −10} W/Hz{sup 1/2} and NEP{sub 78 K} ≈ 5 × 10{sup −9} W/Hz{sup 1/2}. The same detector used as an IR photoconductor showed the responsivity at temperatures T = 78 K and 300 K with signal-to-noise ratio S/N ≈ 750 and 50, respectively, under illumination by using IR monochromator and globar as a thermal source.

  9. Characterization of Pixelated Cadmium-Zinc-Telluride Detectors for Astrophysical Applications

    NASA Technical Reports Server (NTRS)

    Gaskin, Jessica; Sharma, Dharma; Ramsey, Brian; Seller, Paul

    2003-01-01

    Comparisons of charge sharing and charge loss measurements between two pixelated Cadmium-Zinc-Telluride (CdZnTe) detectors are discussed. These properties along with the detector geometry help to define the limiting energy resolution and spatial resolution of the detector in question. The first detector consists of a 1-mm-thick piece of CdZnTe sputtered with a 4x4 array of pixels with pixel pitch of 750 microns (inter-pixel gap is 100 microns). Signal readout is via discrete ultra-low-noise preamplifiers, one for each of the 16 pixels. The second detector consists of a 2-mm-thick piece of CdZnTe sputtered with a 16x16 array of pixels with a pixel pitch of 300 microns (inter-pixel gap is 50 microns). This crystal is bonded to a custom-built readout chip (ASIC) providing all front-end electronics to each of the 256 independent pixels. These detectors act as precursors to that which will be used at the focal plane of the High Energy Replicated Optics (HERO) telescope currently being developed at Marshall Space Flight Center. With a telescope focal length of 6 meters, the detector needs to have a spatial resolution of around 200 microns in order to take full advantage of the HERO angular resolution. We discuss to what degree charge sharing will degrade energy resolution but will improve our spatial resolution through position interpolation.

  10. Advanced methods for preparation and characterization of infrared detector materials. [mercury cadmium tellurides

    NASA Technical Reports Server (NTRS)

    Lehoczky, S. L.; Szofran, F. R.; Martin, B. G.

    1980-01-01

    Mercury cadmium telluride crystals were prepared by the Bridgman method with a wide range of crystal growth rates and temperature gradients adequate to prevent constitutional supercooling under diffusion-limited, steady state, growth conditions. The longitudinal compositional gradients for different growth conditions and alloy compositions were calculated and compared with experimental data to develop a quantitative model of the crystal growth kinetics for the Hg(i-x)CdxTe alloys, and measurements were performed to ascertain the effect of growth conditions on radial compositional gradients. The pseudobinary HgTe-CdTe constitutional phase diagram was determined by precision differential thermal analysis measurements and used to calculate the segregation coefficient of Cd as a function of x and interface temperature. Computer algorithms specific to Hg(1-x)CdxTe were developed for calculations of the charge carrier concentrations, charge carrier mobilities, Hall coefficient, optical absorptance, and Fermi energy as functions of x, temperature, ionized donor and acceptor concentrations, and neutral defect concentrations.

  11. Studies on the diffusion of zinc in cadmium telluride at 800°C

    NASA Astrophysics Data System (ADS)

    Jones, E. D.; Clark, J. C.; Mullin, J. B.; Brinkman, A. W.

    1994-04-01

    The diffusion of zinc into bulk grown cadmium telluride has been studied at 800°C as a function of anneal time and mass of the diffusion source. The diffusions were carried out in evacuated silica ampoules and the diffusion profiles were measured using a radiotracer sectioning technique, although some measurements were obtained using scanning electron microscopy with an EDAX attachment. When the mass of zinc placed in the ampoule exceeded 2 mg, a ternary compound of Zn xCd 1- xTe, with x = 0.8, was formed on the surface of the slice early on in the diffusion and the diffusion profiles consisted of two components. Two values of the diffusivity were obtained, Dslow → 2 × 10 -11 cm 2 s -1 and Dfast → 2 × 10 -10 cm 2 s -1, for anneal times exceeding 6 h and a mass of zinc of 8 mg placed in the ampoule. This contrasted with the results when the mass of zinc was less than 2 mg when no effective surface layer of the ternary compound was formed and diffusion profiles consisting of a single component were obtained. It is proposed that two diffusion mechanisms are operating, one due to zinc atoms diffusing from the vapour into the Zn xCd 1- xTe layer and the second an interdiffusion between the ternary compound in the surface of the slice and the CdTe in the bulk.

  12. Low-bias electron transport properties of germanium telluride ultrathin films

    NASA Astrophysics Data System (ADS)

    Liu, Jie; Anantram, M. P.

    2013-02-01

    The nanometer-scale size-dependent electronic transport properties of crystalline (c-) and amorphous (a-) germanium telluride (GeTe) ultrathin films sandwiched by titanium nitride (TiN) electrodes are investigated using ab initio molecular dynamics, density functional theory, and Green's function calculations. We find that a-GeTe ultrathin films scaled down to about 38 Å (12 atomic layers) still show a band gap and the electrical conductance is mainly due to electron transport via intra-gap states. If the ultrathin films are further scaled, the a-GeTe band gap disappears due to overlap of the two metal induced gap states (MIGS) regions near the TiN electrodes, leading to sharp increase of a-GeTe conductance and significant decrease of c-GeTe/a-GeTe conductance ratio. The c-GeTe/a-GeTe conductance ratio drops below one order of magnitude if the ultrathin films are scaled below about 33 Å, making it difficult to reliably perform read operations in thin film based phase change memory devices. This overlap of the MIGS regions sets up the ultimate scaling limit of phase change memory technology. Our results suggest that the ultimate scaling limit can be pushed to even smaller size, by using phase change material with larger amorphous phase band gap than a-GeTe.

  13. Investigation of the Electronic Properties of Cadmium Zinc Telluride (CZT) Detectors using a Nuclear Microprobe

    SciTech Connect

    BRUNETT,BRUCE A.; DOYLE,BARNEY L.; JAMES,RALPH B.; VIZKELETHY,GYORGY; WALSH,DAVID S.

    1999-10-18

    The electronic transport properties of Cadmium Zinc Telluride (CZT) determine the charge collection efficiency (i.e. the signal quality) of CZT detectors. These properties vary on both macroscopic and microscopic scale and depend on the presence of impurities and defects introduced during the crystal growth. Ion Beam Induced Charge Collection (IBICC) is a proven method to measure the charge collection efficiency. Using an ion microbeam, the charge collection efficiency can be mapped with submicron resolution, and the map of electronic properties (such as drift length) can be calculated from the measurement. A more sophisticated version of IBICC, the Time Resolved IBICC (TRIBICC) allows them to determine the mobility and the life time of the charge carriers by recording and analyzing the transient waveform of the detector signal. Furthermore, lateral IBICC and TRIBICC can provide information how the charge collection efficiency depends on the depth where the charge carriers are generated. This allows one to deduce information on the distribution of the electric field and transport properties of the charge carriers along the detector axis. IBICC and TRIBICC were used at the Sandia microbeam facility to image electronic properties of several CZT detectors. From the lateral TRIBICC measurement the electron and hole drift length profiles were calculated.

  14. Adsorption and desorption of hexavalent chromium in an alluvial aquifer near Telluride, Colorado

    USGS Publications Warehouse

    Stollenwerk, K.G.; Grove, D.B.

    1985-01-01

    A laboratory investigation of reactions between hexavalent chromium [Cr(VI)] and alluvium was conducted to evaluate reactions of Cr(VI) contaminating an alluvial aquifer near Telluride, CO and to determine the mechanisms responsible for these reactions. Uncontaminated alluvium and groundwater (spiked with CrO42-) from the study site were used in batch and column experiments. Results of these experiments show that Cr(VI) was adsorbed by the alluvium. Distribution coefficients from batch experiments ranged from 52 L/kg at an equilibrium CrO42- concentration of 0.4 ??mol/L to 1.7 L/kg at an equilibrium concentration of 1400 ??mol/L. The zero point of charge for the alluvium was approximately 8.3, and the alluvium had a positive net charge at the groundwater pH of 6.8. Visual and chemical evidence indicated that Fe oxide and hydroxide coatings on the alluvial particles principally were responsible for the absorption of Cr(VI). During column experiments, Cr(VI) initially was desorbed easily from the alluvium by Cr-free groundwater; however, the rate of desorption decreased rapidly, and > 60 pore volumes of groundwater were required to decrease the effluent concentration of Cr(VI) to 3 ??mol/L [drinking water standard for Cr(VI) = 1 ??mol/L]. The quantity of Cr(VI) adsorbed varied with the type and concentration of other anions in solution.

  15. Measurement and Modeling of Blocking Contacts for Cadmium Telluride Gamma Ray Detectors

    SciTech Connect

    Beck, Patrick R.

    2010-01-07

    Gamma ray detectors are important in national security applications, medicine, and astronomy. Semiconductor materials with high density and atomic number, such as Cadmium Telluride (CdTe), offer a small device footprint, but their performance is limited by noise at room temperature; however, improved device design can decrease detector noise by reducing leakage current. This thesis characterizes and models two unique Schottky devices: one with an argon ion sputter etch before Schottky contact deposition and one without. Analysis of current versus voltage characteristics shows that thermionic emission alone does not describe these devices. This analysis points to reverse bias generation current or leakage through an inhomogeneous barrier. Modeling the devices in reverse bias with thermionic field emission and a leaky Schottky barrier yields good agreement with measurements. Also numerical modeling with a finite-element physics-based simulator suggests that reverse bias current is a combination of thermionic emission and generation. This thesis proposes further experiments to determine the correct model for reverse bias conduction. Understanding conduction mechanisms in these devices will help develop more reproducible contacts, reduce leakage current, and ultimately improve detector performance.

  16. Macro-loading Effects in Inductively Coupled Plasma Etched Mercury Cadmium Telluride

    NASA Astrophysics Data System (ADS)

    Apte, Palash; Rybnicek, Kimon; Stoltz, Andrew

    2016-09-01

    This paper reports the effect of macro-loading on mercury cadmium telluride (Hg1- x Cd x Te) and Photoresist (PR) etched in an inductively coupled plasma (ICP). A significant macro-loading effect is observed, which affects the etch rates of both PR and Hg1- x Cd x Te. It is observed that the exposed silicon area has a significant effect on the PR etch rate, but not on the Hg1- x Cd x Te etch rate. It is also observed that the exposed Hg1- x Cd x Te area has a significant effect on the etch rate of the PR, but the exposed PR area does not seem to have an effect on the Hg1- x Cd x Te etch rate. Further, the exposed Hg1- x Cd x Te area is shown to affect the etch rate of the Hg1- x Cd x Te, but there does not seem to be a similar effect for the exposed PR area on the etch rate of the PR. Since the macro-loading affects the selectivity significantly, this effect can cause significant problems in the etching of deep trenches. A few techniques to reduce the effect of macro-loading on the etch rates of the PR and Hg1- x Cd x Te are listed, herein.

  17. Simulation study comparing high-purity germanium and cadmium zinc telluride detectors for breast imaging.

    PubMed

    Campbell, D L; Peterson, T E

    2014-11-21

    We conducted simulations to compare the potential imaging performance for breast cancer detection with High-Purity Germanium (HPGe) and Cadmium Zinc Telluride (CZT) systems with 1% and 3.8% energy resolution at 140 keV, respectively. Using the Monte Carlo N-Particle (MCNP5) simulation package, we modelled both 5 mm-thick CZT and 10 mm-thick HPGe detectors with the same parallel-hole collimator for the imaging of a breast/torso phantom. Simulated energy spectra were generated, and planar images were created for various energy windows around the 140 keV photopeak. Relative sensitivity and scatter and the torso fractions were calculated along with tumour contrast and signal-to-noise ratios (SNR). Simulations showed that utilizing a ±1.25% energy window with an HPGe system better suppressed torso background and small-angle scattered photons than a comparable CZT system using a -5%/+10% energy window. Both systems provided statistically similar contrast and SNR, with HPGe providing higher relative sensitivity. Lowering the counts of HPGe images to match CZT count density still yielded equivalent contrast between HPGe and CZT. Thus, an HPGe system may provide equivalent breast imaging capability at lower injected radioactivity levels when acquiring for equal imaging time.

  18. Resonant Enhancement of Charge Density Wave Diffraction in the Rare-Earth Tri-Tellurides

    SciTech Connect

    Lee, W.S.; Sorini, A.P.; Yi, M.; Chuang, Y.D.; Moritz, B.; Yang, W.L.; Chu, J.-H.; Kuo, H.H.; Gonzalez, A.G.Cruz; Fisher, I.R.; Hussain, Z.; Devereau, T.P.; Shen, Z.X.

    2012-05-15

    We performed resonant soft X-ray diffraction on known charge density wave (CDW) compounds, rare earth tri-tellurides. Near the M{sub 5} (3d - 4f) absorption edge of rare earth ions, an intense diffraction peak is detected at a wavevector identical to that of CDW state hosted on Te{sub 2} planes, indicating a CDW-induced modulation on the rare earth ions. Surprisingly, the temperature dependence of the diffraction peak intensity demonstrates an exponential increase at low temperatures, vastly different than that of the CDW order parameter. Assuming 4f multiplet splitting due to the CDW states, we present a model to calculate X-ray absorption spectrum and resonant profile of the diffraction peak, agreeing well with experimental observations. Our results demonstrate a situation where the temperature dependence of resonant X-ray diffraction peak intensity is not directly related to the intrinsic behavior of the order parameter associated with the electronic order, but is dominated by the thermal occupancy of the valence states.

  19. Inhibition of autophagy contributes to the toxicity of cadmium telluride quantum dots in Saccharomyces cerevisiae.

    PubMed

    Fan, Junpeng; Shao, Ming; Lai, Lu; Liu, Yi; Xie, Zhixiong

    2016-01-01

    Cadmium telluride quantum dots (CdTe QDs) are used as near-infrared probes in biologic and medical applications, but their cytological effects and mechanism of potential toxicity are still unclear. In this study, we evaluated the toxicity of CdTe QDs of different sizes and investigated their mechanism of toxicity in the yeast Saccharomyces cerevisiae. A growth inhibition assay revealed that orange-emitting CdTe (O-CdTe) QDs (half inhibitory concentration [IC50] =59.44±12.02 nmol/L) were more toxic than green-emitting CdTe QDs (IC50 =186.61±19.74 nmol/L) to S. cerevisiae. Further studies on toxicity mechanisms using a transmission electron microscope and green fluorescent protein tagged Atg8 processing assay revealed that O-CdTe QDs could partially inhibit autophagy at a late stage, which differs from the results reported in mammalian cells. Moreover, autophagy inhibited at a late stage by O-CdTe QDs could be partially recovered by enhancing autophagy with rapamycin (an autophagy activator), combined with an increased number of living cells. These results indicate that inhibition of autophagy acts as a toxicity mechanism of CdTe QDs in S. cerevisiae. This work reports a novel toxicity mechanism of CdTe QDs in yeast and provides valuable information on the effect of CdTe QDs on the processes of living cells. PMID:27524895

  20. Effect of silicon and sodium on thermoelectric properties of thallium doped lead telluride based materials

    SciTech Connect

    Zhang, Qinyong; Wang, H; Zhang, Qian; Liu, W.; Yu, Bo; Wang, H; Wang, D.; Ni, G; Chen, Gang; Ren, Z. F.

    2012-01-01

    Thallium (Tl)-doped lead telluride (Tl0.02Pb0.98Te) thermoelectric materials fabricated by ball milling and hot pressing have decent thermoelectric properties but weak mechanical strength. Addition of silicon (Si) nanoparticles strengthened the mechanical property by reducing the grain size and defect density but resulted in low electrical conductivity that was not desired for any thermoelectric materials. Fortunately, doping of sodium (Na) into the Si added Tl0.02Pb0.98Te brings back the high electrical conductivity and yields higher figure-of-merit ZT values of ~1.7 at 770 K. The ZT improvement by Si addition and Na doping in Tl0.02Pb0.98Te sample is the direct result of concurrent electron and phonon engineering by improving the power factor and lowering the thermal conductivity, respectively.

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

    SciTech Connect

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

    2009-10-06

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

  2. Novel Cadmium Zinc Telluride Devices for Myocardial Perfusion Imaging-Technological Aspects and Clinical Applications.

    PubMed

    Ben-Haim, Simona; Kennedy, John; Keidar, Zohar

    2016-07-01

    Myocardial perfusion imaging plays an important role in the assessment of patients with known or suspected coronary artery disease and is well established for diagnosis and for prognostic evaluation in these patients. The dedicated cardiac SPECT cameras with solid-state cadmium zinc telluride (CZT) detectors were first introduced a decade ago. A large body of evidence is building up, showing the superiority of the new technology compared with conventional gamma cameras. Not only the CZT detectors, but also new collimator geometries, the ability to perform focused imaging optimized for the heart and advances in data processing algorithms all contribute to the significantly improved sensitivity up to 8-10 times, as well as improved energy resolution and improved reconstructed spatial resolution compared with conventional technology. In this article, we provide an overview of the physical characteristics of the CZT cameras, as well as a review of the literature published so far, including validation studies in comparison with conventional myocardial perfusion imaging and with invasive coronary angiography, significant reduction in radiation dose, and new imaging protocols enabled by the new technology. PMID:27237438

  3. Nanostructure Characterization of Bismuth Telluride-Based Powders and Extruded Alloys by Various Experimental Methods

    NASA Astrophysics Data System (ADS)

    Vasilevskiy, D.; Bourbia, O.; Gosselin, S.; Turenne, S.; Masut, R. A.

    2011-05-01

    High-resolution transmission electron microscopy (HRTEM) observations of mechanically alloyed powders and bulk extruded alloys give experimental evidence of nanosized grains in bismuth telluride-based materials. In this study we combine HRTEM observations and x-ray diffraction (XRD) measurements, of both mechanically alloyed powders and extruded samples, with mechanical spectroscopy (MS) of extruded rods. Both HRTEM and XRD show that nanostructures with an average grain size near 25 nm can be achieved within 2 h of mechanical alloying from pure elements in an attritor-type milling machine. Residual strain orthogonal to the c-axis of powder nanoparticles has been evaluated at about 1.2% by XRD peak broadening. In contrast, XRD has been found unreliable for evaluation of grain size in highly textured extruded materials for which diffraction conditions are similar to those of single crystals, while MS appears promising for study of bulk extruded samples. Nanostructured extruded alloys at room temperature exhibit an internal friction (IF) background that is one order of magnitude higher than that of conventional zone-melted material with a grain size of several millimeters. IF as a function of sample temperature gives activation energies that are also different between bulk materials having nano- and millimeter-size grains, a result that is attributed to different creep mechanisms. Nanograin size, as well as orientation and volumetric proportion, provide valuable information for optimization of technological parameters of thermoelectric alloys and should be carefully cross-examined by various independent methods.

  4. Cadmium telluride nanoparticles loaded on activated carbon as adsorbent for removal of sunset yellow

    NASA Astrophysics Data System (ADS)

    Ghaedi, M.; Hekmati Jah, A.; Khodadoust, S.; Sahraei, R.; Daneshfar, A.; Mihandoost, A.; Purkait, M. K.

    2012-05-01

    Adsorption is a promising technique for decolorization of effluents of textile dyeing industries but its application is limited due to requirement of high amounts of adsorbent required. The objective of this study was to assess the potential of cadmium telluride nanoparticles loaded onto activated carbon (CdTN-AC) for the removal of sunset yellow (SY) dye from aqueous solution. Adsorption studies were conducted in a batch mode varying solution pH, contact time, initial dye concentration, CdTN-AC dose, and temperature. In order to investigate the efficiency of SY adsorption on CdTN-AC, pseudo-first-order, pseudo-second-order, Elovich, and intra-particle diffusion kinetic models were studied. It was observed that the pseudo-second-order kinetic model fits better than other kinetic models with good correlation coefficient. Equilibrium data were fitted to the Langmuir model. Thermodynamic parameters such as enthalpy, entropy, activation energy, and sticking probability were also calculated. It was found that the sorption of SY onto CdTN-AC was spontaneous and endothermic in nature. The proposed adsorbent is applicable for SY removal from waste of real effluents including pea-shooter, orange drink and jelly banana with efficiency more than 97%.

  5. A novel approach of chemical mechanical polishing for cadmium zinc telluride wafers

    PubMed Central

    Zhang, Zhenyu; Wang, Bo; Zhou, Ping; Kang, Renke; Zhang, Bi; Guo, Dongming

    2016-01-01

    A novel approach of chemical mechanical polishing (CMP) is developed for cadmium zinc telluride (CdZnTe or CZT) wafers. The approach uses environment-friendly slurry that consists of mainly silica, hydrogen peroxide, and citric acid. This is different from the previously reported slurries that are usually composed of strong acid, alkali, and bromine methanol, and are detrimental to the environment and operators. Surface roughness 0.5 nm and 4.7 nm are achieved for Ra and peak-to-valley (PV) values respectively in a measurement area of 70 × 50 μm2, using the developed novel approach. Fundamental polishing mechanisms are also investigated in terms of X-ray photoelectron spectroscopy (XPS) and electrochemical measurements. Hydrogen peroxide dominates the passivating process during the CMP of CZT wafers, indicating by the lowest passivation current density among silica, citric acid and hydrogen peroxide solution. Chemical reaction equations are proposed during CMP according to the XPS and electrochemical measurements. PMID:27225310

  6. Temperature dependent van der Pauw-Hall measurements on sodium doped single crystalline cadmium telluride

    SciTech Connect

    Ahmad, Faisal R.

    2015-03-21

    In this report, results of the temperature dependent electrical conductivity measurements conducted on single crystalline cadmium telluride (CdTe), containing sodium (Na) impurities are presented and discussed. The electrical conductivity measurements were conducted using an apparatus that allowed the implementation of a standard van der Pauw-Hall effect technique through which the electrical resistivity, concentration of majority carriers, as well as the carrier mobility were determined for temperatures ranging between 24 K and 350 K. Over this temperature range, the electrical resistivity was observed to change by 7 orders of magnitude. Hall measurements showed that the hole concentration at 300 K was ∼3 × 10{sup 15 }cm{sup –3} and the hole mobility at the same temperature was ∼80 cm{sup 2}/V s. Measuring the concentration of holes as a function of the sample temperature enabled the estimation of the acceptor energy level with respect to the valence band maximum to be ∼60 meV. The same data also revealed the potential presence of a compensating donor level. Furthermore, the hole mobility was also analyzed over the entire temperature range and the data revealed that above 100 K, the carrier mobility was dominated by the scattering of holes from lattice vibrations.

  7. Toward Nanostructured Thermoelectrics. Synthesis and Characterization of Lead Telluride Gels and Aerogels

    SciTech Connect

    Ganguly, Shreyashi; Brock, Stephanie L.

    2011-05-12

    The synthesis and characterization of lead telluride (PbTe) gels and aerogels with nanostructured features of potential benefit for enhanced thermoelectrics is reported. In this approach, discrete thiolate-capped PbTe nanoparticles were synthesized by a solution-based approach followed by oxidation-induced nanoparticle assembly with tetranitromethane or hydrogen peroxide to form wet gels. Drying of the wet gels by supercritical CO₂ extraction yielded aerogels, whereas xerogels were produced by ambient pressure bench top drying. The gels consist of an interconnected network of colloidal nanoparticles and pores with surface areas up to 74 m² g-1. The thermal stability of the nanostructures relative to nanoparticles was probed with the help of in situ transmission electron microscopy (TEM), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The aerogels were observed to sublime at a higher temperature and over a larger range (425–500 °C) relative to the precursor nanoparticles. TGA-DSC suggests that organic capping groups can be removed in the region 250–450 °C, and melting of PbTe nanoparticles occurs near the temperature for bulk materials (ca. 920 °C). The good thermal stability combined with the presence of nanoscale interfaces suggests PbTe gels may show promise in thermoelectric devices.

  8. Study of a high-resolution, 3-D positioning cadmium zinc telluride detector for PET

    PubMed Central

    Gu, Y; Matteson, J L; Skelton, R T; Deal, A C; Stephan, E A; Duttweiler, F; Gasaway, T M; Levin, C S

    2011-01-01

    This paper investigates the performance of 1 mm resolution Cadmium Zinc Telluride (CZT) detectors for positron emission tomography (PET) capable of positioning the 3-D coordinates of individual 511 keV photon interactions. The detectors comprise 40 mm × 40 mm × 5 mm monolithic CZT crystals that employ a novel cross-strip readout with interspersed steering electrodes to obtain high spatial and energy resolution. The study found a single anode FWHM energy resolution of 3.06±0.39% at 511 keV throughout most the detector volume. Improved resolution is expected with properly shielded front-end electronics. Measurements made using a collimated beam established the efficacy of the steering electrodes in facilitating enhanced charge collection across anodes, as well as a spatial resolution of 0.44±0.07 mm in the direction orthogonal to the electrode planes. Finally, measurements based on coincidence electronic collimation yielded a point spread function with 0.78±0.10 mm FWHM, demonstrating 1 mm spatial resolution capability transverse to the anodes – as expected from the 1 mm anode pitch. These findings indicate that the CZT-based detector concept has excellent performance and shows great promise for a high-resolution PET system. PMID:21335649

  9. Low-cost cadmium zinc telluride radiation detectors based on electron-transport-only designs

    SciTech Connect

    B. A. Brunett; J. C. Lund; J. M. Van Scyoc; N. R. Hilton; E. Y. Lee; R. B. James

    1999-01-01

    The goal of this project was to utilize a novel device design to build a compact, high resolution, room temperature operated semiconductor gamma ray sensor. This sensor was constructed from a cadmium zinc telluride (CZT) crystal. It was able to both detect total radiation intensity and perform spectroscopy on the detected radiation. CZT detectors produced today have excellent electron charge carrier collection, but suffer from poor hole collection. For conventional gamma-ray spectrometers, both the electrons and holes must be collected with high efficiency to preserve energy resolution. The requirement to collect the hole carriers, which have relatively low lifetimes, limits the efficiency and performance of existing experimental devices. By implementing novel device designs such that the devices rely only on the electron signal for energy information, the sensitivity of the sensors for detecting radiation can be increased substantially. In this report the authors describe a project to develop a new type of electron-only CZT detector. They report on their successful efforts to design, implement and test these new radiation detectors. In addition to the design and construction of the sensors the authors also report, in considerable detail, on the electrical characteristics of the CZT crystals used to make their detectors.

  10. Simulation study comparing high-purity germanium and cadmium zinc telluride detectors for breast imaging

    PubMed Central

    Campbell, DL; Peterson, TE

    2014-01-01

    We conducted simulations to compare the potential imaging performance for breast cancer detection with High-Purity Germanium (HPGe) and Cadmium Zinc Telluride (CZT) systems with 1% and 3.8% energy resolution at 140 keV, respectively. Using the Monte Carlo N-Particle (MCNP5) simulation package, we modelled both 5 mm-thick CZT and 10 mm-thick HPGe detectors with the same parallel-hole collimator for the imaging of a breast/torso phantom. Simulated energy spectra were generated, and planar images were created for various energy windows around the 140-keV photopeak. Relative sensitivity and scatter and the torso fractions were calculated along with tumour contrast and signal-to-noise ratios (SNR). Simulations showed that utilizing a ±1.25% energy window with an HPGe system better suppressed torso background and small-angle scattered photons than a comparable CZT system using a −5%/+10% energy window. Both systems provided statistically similar contrast and SNR, with HPGe providing higher relative sensitivity. Lowering the counts of HPGe images to match CZT count density still yielded equivalent contrast between HPGe and CZT. Thus, an HPGe system may provide equivalent breast imaging capability at lower injected radioactivity levels when acquiring for equal imaging time. PMID:25360792

  11. Spectroscopic ellipsometry as a process control tool for manufacturing cadmium telluride thin film photovoltaic devices

    NASA Astrophysics Data System (ADS)

    Smith, Westcott P.

    In recent decades, there has been concern regarding the sustainability of fossil fuels. One of the more promising alternatives is Cadmium Telluride (CdTe) thin-film photovoltaic (PV) devices. Improved quality measurement techniques may aid in improving this existing technology. Spectroscopic ellipsometry (SE) is a common, non-destructive technique for measuring thin films in the silicon wafer industry. SE results have also been tied to properties believed to play a role in CdTe PV device efficiency. A study assessing the potential of SE for use as a quality measurement tool had not been previously reported. Samples of CdTe devices produced by both laboratory and industrial scale processes were measured by SE and Scanning Electron Microscopy (SEM). Mathematical models of the optical characteristics of the devices were developed and fit to SE data from multiple angles and locations on each sample. Basic statistical analysis was performed on results from the automated fits to provide an initial evaluation of SE as a quantitative quality measurement process. In all cases studied, automated SE models produced average stack thickness values within 10% of the values produced by SEM, and standard deviations for the top bulk layer thickness were less than 1% of the average values.

  12. Cadmium telluride photovoltaic manufacturing technology. Annual subcontract report, 7 January 1994--6 January 1995

    SciTech Connect

    Weisiger, D.; Albright, S.P.; Brines, J.; Thompson, R.

    1995-11-01

    This report describes work performed by Golden Photon, Inc. (GPI), to conduct research under the PVMaT program, Phase 2B. The objective of the research is to advance GPI`s manufacturing technology, reduce module production costs, increase average module performance, and identify ways to expand production capacity. More specifically, the tasks established for Phase I were to design and install leasehold improvements for the 2-MW production line; to improve and develop product design, efficiency, and marketability; to ensure uninterrupted qualified supplies and raw materials for production; to address environmental, health, and safety issues encountered during production of photovoltaic modules; and to reduce the cost of manufacturing modules. During the first half of this reporting period, the development, design, and debugging of cell interconnection equipment critical to start-up was completed. During the second and third quarters, the primary focus was on the substrate deposition steps (tin oxide, cadmium sulfide, and cadmium telluride) and cell interconnection steps (division). In general, process development, engineering, and quality teams continued to focus on identifying, baselining, and improving (through redesign) actual process equipment operation parameters to meet the required PV panel specifications and improve process throughput rates and yields.

  13. Transition-metal doped sulfide, selenide, and telluride laser crystal and lasers

    DOEpatents

    Krupke, W.F.; Page, R.H.; DeLoach, L.D.; Payne, S.A.

    1996-07-30

    A new class of solid state laser crystals and lasers are formed of transition metal doped sulfide, selenide, and telluride host crystals which have four fold coordinated substitutional sites. The host crystals include II-VI compounds. The host crystal is doped with a transition metal laser ion, e.g., chromium, cobalt or iron. In particular, Cr{sup 2+}-doped ZnS and ZnSe generate laser action near 2.3 {micro}m. Oxide, chloride, fluoride, bromide and iodide crystals with similar structures can also be used. Important aspects of these laser materials are the tetrahedral site symmetry of the host crystal, low excited state absorption losses and high luminescence efficiency, and the d{sup 4} and d{sup 6} electronic configurations of the transition metal ions. The same materials are also useful as saturable absorbers for passive Q-switching applications. The laser materials can be used as gain media in amplifiers and oscillators; these gain media can be incorporated into waveguides and semiconductor lasers. 18 figs.

  14. Transition-metal doped sulfide, selenide, and telluride laser crystal and lasers

    DOEpatents

    Krupke, William F.; Page, Ralph H.; DeLoach, Laura D.; Payne, Stephen A.

    1996-01-01

    A new class of solid state laser crystals and lasers are formed of transition metal doped sulfide, selenide, and telluride host crystals which have four fold coordinated substitutional sites. The host crystals include II-VI compounds. The host crystal is doped with a transition metal laser ion, e.g., chromium, cobalt or iron. In particular, Cr.sup.2+ -doped ZnS and ZnSe generate laser action near 2.3 .mu.m. Oxide, chloride, fluoride, bromide and iodide crystals with similar structures can also be used. Important aspects of these laser materials are the tetrahedral site symmetry of the host crystal, low excited state absorption losses and high luminescence efficiency, and the d.sup.4 and d.sup.6 electronic configurations of the transition metal ions. The same materials are also useful as saturable absorbers for passive Q-switching applications. The laser materials can be used as gain media in amplifiers and oscillators; these gain media can be incorporated into waveguides and semiconductor lasers.

  15. Fate and transport evaluation of potential leaching risks from cadmium telluride photovoltaics.

    PubMed

    Sinha, Parikhit; Balas, Robert; Krueger, Lisa; Wade, Andreas

    2012-07-01

    Fate and transport analysis has been performed to evaluate potential exposures to cadmium (Cd) from cadmium telluride (CdTe) photovoltaics (PV) for rainwater leaching from broken modules in a commercial building scenario. Leaching from broken modules is modeled using the worst-case scenario of total release of Cd, and residential screening levels are used to evaluate potential health impacts to on-site workers and off-site residents. A rooftop installation was considered rather than a ground-mount installation because rainwater runoff is concentrated via building downspouts in a rooftop installation rather than being dispersed across large areas in a ground-mount installation. Fate and transport of Cd from leachate to soil are modeled using equilibrium soil/soil-water partitioning. Subsequent migration to ambient air as windblown dust is evaluated with a screening Gaussian plume dispersion model, and migration to groundwater is evaluated with a dilution-attenuation factor approach. Exposure point concentrations in soil, air, and groundwater are one to six orders of magnitude below conservative (residential soil, residential air, drinking water) human health screening levels in both a California and southern Germany (Baden-Württemberg) exposure scenario. Potential exposures to Cd from rainwater leaching of broken modules in a commercial building scenario are highly unlikely to pose a potential health risk to on-site workers or off-site residents.

  16. Thermal transport in bismuth telluride quintuple layer: mode-resolved phonon properties and substrate effects

    PubMed Central

    Shao, Cheng; Bao, Hua

    2016-01-01

    The successful exfoliation of atomically-thin bismuth telluride (Bi2Te3) quintuple layer (QL) attracts tremendous research interest in this strongly anharmonic quasi-two-dimensional material. The thermal transport properties of this material are not well understood, especially the mode-wise properties and when it is coupled with a substrate. In this work, we have performed molecular dynamics simulations and normal mode analysis to study the mode-resolved thermal transport in freestanding and supported Bi2Te3 QL. The detailed mode-wise phonon properties are calculated and the accumulated thermal conductivities with respect to phonon mean free path (MFP) are constructed. It is shown that 60% of the thermal transport is contributed by phonons with MFP longer than 20 nm. Coupling with a-SiO2 substrate leads to about 60% reduction of thermal conductivity. Through varying the interfacial coupling strength and the atomic mass of substrate, we also find that phonon in Bi2Te3 QL is more strongly scattered by interfacial potential and its transport process is less affected by the dynamics of substrate. Our study provides an in-depth understanding of heat transport in Bi2Te3 QL and is helpful in further tailoring its thermal property through nanostructuring. PMID:27263656

  17. Grain Growth Behavior, Tensile Impact Ductility, and Weldability of Cerium-Doped Iridium Alloys

    SciTech Connect

    McKamey, C.G.

    2002-05-28

    An iridium alloy doped with small amounts of cerium and thorium is being developed as a potential replacement for the iridium-based DOP-26 alloy (doped with thorium only) that is currently used by the National Aeronautics and Space Administration (NASA) for cladding and post-impact containment of the radioactive fuel in radioisotope thermoelectric generator (RTG) heat sources which provide electric power for interplanetary spacecraft. This report summarizes results of studies conducted to date under the Iridium Alloy Characterization and Development subtask of the Radioisotope Power System Materials Production and Technology Program to characterize the properties of the iridium-based alloy (designated as DOP-40) containing both cerium and thorium. Included within this report are data on grain growth of sheet material in vacuum and low-pressure oxygen environments, grain growth in vacuum of the clad vent set cup material, weldability, and the effect of grain size and test temperature on tensile properties. Where applicable, data for the DOP-26 alloy are included for comparison. Both grain size and grain-boundary cohesion affect the ductility of iridium alloys. In this study it was found that cerium and thorium, when added together, refine grain size more effectively than when thorium is added by itself (especially at high temperatures). In addition, the effect of cerium additions on grain-boundary cohesion is similar to that of thorium. Mechanical testing at both low ({approx} 10{sup -3}s{sup -1}) and high ({approx} 10{sup -3}s{sup -1}) strain rates showed that the Ce/Th-doped alloys have tensile ductilities that are as good or better than the DOP-26 alloy. The general conclusion from these studies is that cerium can be used to replace some of the radioactive thorium currently used in DOP-26 while maintaining or improving its metallurgical properties. The current DOP-26 alloy meets all requirements for cladding the radioactive fuel in the RTG heat source, but the

  18. Using cerium anomaly as an indicator of redox reactions in constructed wetland

    NASA Astrophysics Data System (ADS)

    Liang, R.

    2013-12-01

    dissolved oxygen (5 ppm) but the NH4 content is still high, which indicates a non-equilibrium condition. In this study, the cerium anomaly is alternatively utilized to evaluate the water redox state. The results demonstrate that the input water has the negative cerium anomaly of -0.16. Along the flow path, the cerium negative anomaly does not change in the first two cells and dramatically becomes -0.23 in cell 3. The trend of cerium anomaly is more close to the removal efficiency of NH4 rather than dissolve oxygen. Accordingly, cerium anomaly could become a better indicator of removal efficiency of constructed wetland.

  19. Self-poled transparent and flexible UV light-emitting cerium complex-PVDF composite: a high-performance nanogenerator.

    PubMed

    Garain, Samiran; Sinha, Tridib Kumar; Adhikary, Prakriti; Henkel, Karsten; Sen, Shrabanee; Ram, Shanker; Sinha, Chittaranjan; Schmeißer, Dieter; Mandal, Dipankar

    2015-01-21

    Cerium(III)-N,N-dimethylformamide-bisulfate [Ce(DMF)(HSO4)3] complex is doped into poly(vinylidene fluoride) (PVDF) to induce a higher yield (99%) of the electroactive phases (β- and γ-phases) of PVDF. A remarkable enhancement of the output voltage (∼32 V) of a nanogenerator (NG) based on a nonelectrically poled cerium(III) complex containing PVDF composite film is achieved by simple repeated human finger imparting, whereas neat PVDF does not show this kind of behavior. This high electrical output resembles the generation of self-poled electroactive β-phase in PVDF due to the electrostatic interactions between the fluoride of PVDF and the surface-active positive charge cloud of the cerium complex via H-bonding and/or bipolar interaction among the opposite poles of cerium complex and PVDF, respectively. The capacitor charging capability of the flexible NG promises its applicability as piezoelectric-based energy harvester. The cerium(III) complex doped PVDF composite film exhibit an intense photoluminescence in the UV region, which might be due to a participation of electron cloud from negative pole of bipolarized PVDF. This fact may open a new area for prospective development of high-performance energy-saving flexible solid-state UV light emitters. PMID:25523039

  20. Cyanex 923 as the extractant in a rare earth element impurity analysis of high-purity cerium oxide.

    PubMed

    Duan, Taicheng; Li, Hongfei; Kang, JianZhen; Chen, Hangting

    2004-06-01

    In this work, the feasibility of employing Cyanex 923 as an extractant into the non-cerium REE (rare earth elements) impurity analysis of high-purity cerium oxide was investigated. Through investigations on the choice of the extraction medium, the optimium extraction acidity, matrix Ce4+ effect on the non-cerium REE ion extraction, the optimium extractant concentration and suitable extracting time, and oscillation strengh, it was found that when the phase ratio was at 1:1 and the acicidity was about 2% H2SO4, by gently shaking by hand for about 2 min, 10 mL of 30% Cyanex 923 could not extract even for a 20 ng amount of non-cerium REE3+ ions. However, the extraction efficiency for Ce4+ of 100 mg total amount under the same conditions was about 96%, indicating that a 25-fold preconcentration factor could be achieved. Thus, it was concluded that Cyanex 923 could be used in a REE impurity analysis of 99.9999% or so pure cerium oxide for primary sepapation to elimilate matrix-induced interferences encountered in an ICP-MS (inductively coupled plasma mass spectroscopy) determination.

  1. Field and photo-emission in a short-pulse, high-charge Cesium telluride RF photoinjector

    NASA Astrophysics Data System (ADS)

    Wisniewski, Eric E.

    A new high-charge RF gun is now operating at the Argonne Wakefield Accelerator (AWA) facility at Argonne National Laboratory (ANL). The 1.5 cell 1.3 GHz gun uses a Cesium telluride photocathode driven with a 248 nm laser to provide short-pulse, high charge electron beams for the new 75 MeV drive beamline. The high-gradient RF gun (peak field on the cathode > 80MV/m) is a key piece of the facility upgrade. The large Cs2Te photocathode (diameter > 30 mm) was fabricated in-house. The photo-injector will be used to generate high-charge, short pulse, single bunches (Q > 100 nC) and bunch-trains (Q > 1000 nC) for wakefield experiments, typically involving dielectric-loaded accelerating structures. Details of the photocathode fabrication process and the results of associated diagnostic measurements are presented, including QE measurements and work function measurements performed with a Kelvin probe. Fieldemitted dark current from the Cs2Te cathode was measured during RF conditioning and characterized. Fowler-Nordheim plots of the data are presented and compared to similar measurements made using a copper cathode in the initial phase of conditioning. The results for cesium telluride exhibited non-linear regions within the Fowler-Nordheim plots similar to previous experimental results for other p-type semiconductors. Results of quantum efficiency (QE) studies are presented with the cathode operating in both single and bunch-train modes. QE uniformity and lifetime studies are presented. During commissioning, the cesium telluride photocathode produced bunch-charge of 100 nC, breaking the previous record. No evidence of bunch-train position-dependence of QE was found when generating four-bunch trains with total charge up to 200 nC.

  2. Chemiluminescence studies between aqueous phase synthesized mercaptosuccinic acid capped cadmium telluride quantum dots and luminol-H2O2.

    PubMed

    Kaviyarasan, Kulandaivelu; Anandan, Sambandam; Mangalaraja, Ramalinga Viswanathan; Asiri, Abdullah M; Wu, Jerry J

    2016-08-01

    Mercaptosuccinic acid capped Cadmium telluride quantum dots have been successfully synthesized via aqueous phase method. The products were well characterized by a number of analytical techniques, including FT-IR, XRD, HRTEM, and a corrected particle size analysis by the statistical treatment of several AFM measurements. Chemiluminescence experiments were performed to explore the resonance energy transfer between chemiluminescence donor (luminol-H2O2 system) and acceptor CdTe QDs. The combination of such donor and acceptor dramatically reduce the fluorescence while compared to pristine CdTe QDs without any exciting light source, which is due to the occurrence of chemiluminescence resonance energy transfer (CRET) processes. PMID:27131144

  3. Internal Electric Field Investigations of a Cadmium Zinc Telluride Detector Using Synchrotron X-ray Mapping and Pockels Effect Measurements

    SciTech Connect

    Yang, G.; Bolotnikov, A; Camarda, G; Cui, Y; Hossain, A; Yao, H; James, R

    2009-01-01

    Cadmium zinc telluride (CZT) has remained a major focus of research due to its promising application as a room-temperature nuclear radiation detector material. Among the several parameters that substantially affect the detectors' performance, an important one is the distribution of the internal electric field. Brookhaven National Laboratory (BNL) employed synchrotron x-ray microscale mapping and measurements of the Pockels effect to investigate the distribution of the internal electric field in a CZT strip detector. Direct evidence that dislocations can distort the internal electric field of the detector was obtained. Furthermore, it was found that 'star' defects in the CZT crystal, possibly ascribed to dislocation loop punching, cause charge trapping.

  4. The effects of nanoparticle inclusions upon the microstructure and thermoelectric transport properties of bismuth telluride-based composites

    NASA Astrophysics Data System (ADS)

    Gothard, Nicholas Wesley

    Research into materials that have high efficiencies of thermoelectric heat-energy conversion has been at a plateau since the middle of the last century. During this time, efficiencies have been engineered high enough for several interesting niche applications but not high enough for widespread adaptation into traditional power generation or refrigeration technologies. The past decade has seen considerable advancement, as a number of theoretical works have suggested that lower dimensional structures could hold the key for enhanced efficiency, and several experiments have provided the proof of principle needed to inspire just such a research direction. The benefit of low dimensional structures for thermoelectric efficiency comes from both the potential enhancement of the electronic properties due to quantum confinement effects as well as from the potential for increased scattering of heat-carrying phonons. Widespread application of these principles for technological application requires the creation of composites of nanostructures that can be manufactured easily with dimensions on the bulk materials scale. A good starting point for such materials research is to manufacture composites of materials that are currently known to have high thermoelectric efficiencies by incorporating nanostructures into a bulk matrix. The goal of this project is to create nanocomposites using bismuth telluride, a compound known to have one of the highest thermoelectric efficiencies at room temperature, as a matrix material. Various methods of synthesizing sufficient quantities of bismuth telluride nanostructures were attempted, including pulsed laser vaporization, chemical vapor deposition, and solvothermal synthesis. The method of solvothermal synthesis was found to be the simplest approach for producing high yields of bismuth telluride nanostructures. In the initial stages of the project, cold pressing was tested as a means of compaction, but in the end a uniaxial hot pressing technique

  5. Chemiluminescence studies between aqueous phase synthesized mercaptosuccinic acid capped cadmium telluride quantum dots and luminol-H2O2

    NASA Astrophysics Data System (ADS)

    Kaviyarasan, Kulandaivelu; Anandan, Sambandam; Mangalaraja, Ramalinga Viswanathan; Asiri, Abdullah M.; Wu, Jerry J.

    2016-08-01

    Mercaptosuccinic acid capped Cadmium telluride quantum dots have been successfully synthesized via aqueous phase method. The products were well characterized by a number of analytical techniques, including FT-IR, XRD, HRTEM, and a corrected particle size analysis by the statistical treatment of several AFM measurements. Chemiluminescence experiments were performed to explore the resonance energy transfer between chemiluminescence donor (luminol-H2O2 system) and acceptor CdTe QDs. The combination of such donor and acceptor dramatically reduce the fluorescence while compared to pristine CdTe QDs without any exciting light source, which is due to the occurrence of chemiluminescence resonance energy transfer (CRET) processes.

  6. Iron isotope constraints on the mineralization processes of the Sandaowanzi telluride gold deposit, NE China

    NASA Astrophysics Data System (ADS)

    Li, Xingxing; Liu, Junlai; Lu, Di; Ren, Shunli; Liu, Zhengyang

    2016-04-01

    Iron isotopes have been widely applied to interpret the fluid evolution, supergene alteration and the metallogenic material sources of the hydrothermal deposit. It may also have significant potentials on the research of the deposit. The Sandaowanzi telluride gold deposit, located in the Great Hinggan Range metallogenic Belt in NE China, is a large epithermal gold deposit of low-sulphidation type. It has a total reserve of ≥25t of Au and an average of 15 g/t. Gold-bearing quartz veins or gold lodes strike to the NW and dip 50-80°northeastward. Ore bodies, including low-grade ores along margins and high-grade ores in the central parts, principally occur in quartz veins. More than the 95 percent Au budgets are hosted in gold-silver tellurides. A six-stage paragenetic sequence of mineralization is revealed according to the compositions and microstructures of the mineral assemblages. Although sulfide minerals in the bonanza quartz veins are rare, pyrite are widespread in quartz veins and altered host rocks. Meanwhile there are always chalcopyrite veins within bonanza quartz veins. Pyrite Fe isotope compositions from different levels (from +50m to +210m) of the main ore body of the Sandaowanzi gold ore deposit are investigated. There is an overall variation in δ57Fe values from -0.09 to +0.99 (av. 0.33). Among them, twenty three samples from different mining levels give positiveδ57Fe values, with the maximum positive value at the economic bonanza ores (level +130m). Four samples, however, possess negative values, one at level 170m, one at level 130m, and two at level 50m, respectively. The two negative values from the levels 170m and 130m are near the cores of the high grade ore body. The two negative values from the level 50m occur at one end of the lode ore body. The above data set shows that the δ57Fe values are not homogeneous at different levels of the ore body. On the other hand, a general trend for the positive values is that the highest δ57Fe value is

  7. Development of radiation dose reduction techniques for cadmium zinc telluride detectors in molecular breast imaging

    NASA Astrophysics Data System (ADS)

    O'Connor, Michael K.; Hruska, Carrie B.; Weinmann, Amanda; Manduca, Armando; Rhodes, Deborah J.

    2010-08-01

    Background: Molecular breast imaging (MBI) is a novel breast imaging technique that uses Cadmium Zinc Telluride (CZT) gamma cameras to detect the uptake of Tc-99m sestamibi in breast tumors. Current techniques employ an administered dose of 20-30 mCi Tc-99m, delivering an effective dose of 6.5-10 mSv to the body. This is ~ 5-10 times that of mammography. The goal of this study was to reduce the radiation dose by a factor of 5-10, while maintaining image quality. Methods: A total of 4 dose reduction schemes were evaluated - a) optimized collimation, b) improved utilization of the energy spectrum below the photopeak, c) adaptive geometric mean algorithm developed for combination of images from opposing detectors, and d) non local means filtering (NLMF) for noise reduction and image enhancement. Validation of the various schemes was performed using a breast phantom containing a variety of tumors and containing activity matched to that observed in clinical studies. Results: Development of tungsten collimators with holes matched to the CZT pixels yielded a 2.1-2.9 gain in system sensitivity. Improved utilization of the energy spectra yielded a 1.5-2.0 gain in sensitivity. Development of a modified geometric mean algorithm yielded a 1.4 reduction in image noise, while retaining contrast. Images of the breast phantom demonstrated that a factor of 5 reduction in dose was achieved. Additional refinements to the NLMF should enable an additional factor of 2 reduction in dose. Conclusion: Significant dose reduction in MBI to levels comparable to mammography can be achieved while maintaining image quality.

  8. Friction Consolidation Processing of n-Type Bismuth-Telluride Thermoelectric Material

    NASA Astrophysics Data System (ADS)

    Whalen, Scott; Jana, Saumyadeep; Catalini, David; Overman, Nicole; Sharp, Jeffrey

    2016-07-01

    Refined grain sizes and texture alignment have been shown to improve transport properties in bismuth-telluride (Bi2Te3) based thermoelectric materials. In this work we demonstrate a new approach, called friction consolidation processing (FCP), for consolidating Bi2Te3 thermoelectric powders into bulk form with a high degree of grain refinement and texture alignment. FCP is a solid-state process wherein a rotating tool is used to generate severe plastic deformation within the Bi2Te3 powder, resulting in a recrystallizing flow of material. Upon cooling, the far-from-equilibrium microstructure within the flow can be retained in the material. FCP was demonstrated on n-type Bi2Te3 feedstock powder having a -325 mesh size to form pucks with a diameter of 25.4 mm and thickness of 4.2 mm. Microstructural analysis confirmed that FCP can achieve highly textured bulk materials, with sub-micrometer grain size, directly from coarse feedstock powders in a single process. An average grain size of 0.8 μm was determined for regions of one sample and a multiple of uniform distribution (MUD) value of 15.49 was calculated for the (0001) pole figure of another sample. These results indicate that FCP can yield ultra-fine grains and textural alignment of the (0001) basal planes in Bi2Te3. ZT = 0.37 at 336 K was achieved for undoped stoichiometric Bi2Te3, which approximates literature values of ZT = 0.4-0.5. These results point toward the ability to fabricate bulk thermoelectric materials with refined microstructure and desirable texture using far-from-equilibrium FCP solid-state processing.

  9. Cadmium zinc telluride based infrared interferometry for X-ray detection

    SciTech Connect

    Lohstroh, A. Della Rocca, I.; Parsons, S.; Langley, A.; Shenton-Taylor, C.; Blackie, D.

    2015-02-09

    Cadmium Zinc Telluride (CZT) is a wide band gap semiconductor for room temperature radiation detection. The electro-optic Pockels effect of the material has been exploited in the past to study electric field non-uniformities and their consequence on conventional detector signals in CZT, by imaging the intensity distribution of infrared (IR) light transmitted through a device placed between crossed polarizers. Recently, quantitative monitoring of extremely high intensity neutron pulses through the change of transmitted IR intensity was demonstrated, offering the advantage to place sensitive electronics outside the measured radiation field. In this work, we demonstrate that X-ray intensity can be deduced directly from measuring the change in phase of 1550 nm laser light transmitted through a 7 × 7 × 2 mm{sup 3} CZT based Pockels cell in a simple Mach Zehnder interferometer. X-rays produced by a 50 kVp Mo X-ray tube incident on the CZT cathode surface placed at 7 mm distance cause a linearly increasing phase shift above 0.3 mA tube current, with 1.58 ± 0.02 rad per mA for an applied bias of 500 V across the 2 mm thick device. Pockels images confirm that the sample properties are in agreement with the literature, exhibiting electric field enhancement near the cathode under irradiation, which may cause the non-linearity at low X-ray tube anode current settings. The laser used to probe the X-ray intensity causes itself some space charge, whose spatial distribution does not seem to be exclusively determined by the incident laser position, i.e., charge carrier generation location, with respect to the electrodes.

  10. Development and evaluation of polycrystalline cadmium telluride dosimeters for accurate quality assurance in radiation therapy

    NASA Astrophysics Data System (ADS)

    Oh, K.; Han, M.; Kim, K.; Heo, Y.; Moon, C.; Park, S.; Nam, S.

    2016-02-01

    For quality assurance in radiation therapy, several types of dosimeters are used such as ionization chambers, radiographic films, thermo-luminescent dosimeter (TLD), and semiconductor dosimeters. Among them, semiconductor dosimeters are particularly useful for in vivo dosimeters or high dose gradient area such as the penumbra region because they are more sensitive and smaller in size compared to typical dosimeters. In this study, we developed and evaluated Cadmium Telluride (CdTe) dosimeters, one of the most promising semiconductor dosimeters due to their high quantum efficiency and charge collection efficiency. Such CdTe dosimeters include single crystal form and polycrystalline form depending upon the fabrication process. Both types of CdTe dosimeters are commercially available, but only the polycrystalline form is suitable for radiation dosimeters, since it is less affected by volumetric effect and energy dependence. To develop and evaluate polycrystalline CdTe dosimeters, polycrystalline CdTe films were prepared by thermal evaporation. After that, CdTeO3 layer, thin oxide layer, was deposited on top of the CdTe film by RF sputtering to improve charge carrier transport properties and to reduce leakage current. Also, the CdTeO3 layer which acts as a passivation layer help the dosimeter to reduce their sensitivity changes with repeated use due to radiation damage. Finally, the top and bottom electrodes, In/Ti and Pt, were used to have Schottky contact. Subsequently, the electrical properties under high energy photon beams from linear accelerator (LINAC), such as response coincidence, dose linearity, dose rate dependence, reproducibility, and percentage depth dose, were measured to evaluate polycrystalline CdTe dosimeters. In addition, we compared the experimental data of the dosimeter fabricated in this study with those of the silicon diode dosimeter and Thimble ionization chamber which widely used in routine dosimetry system and dose measurements for radiation

  11. Charge Loss and Charge Sharing Measurements for Two Different Pixelated Cadmium-Zinc-Telluride Detectors

    NASA Technical Reports Server (NTRS)

    Gaskin, Jessica; Sharma, Dharma; Ramsey, Brian; Seller, Paul

    2003-01-01

    As part of ongoing research at Marshall Space Flight Center, Cadmium-Zinc- Telluride (CdZnTe) pixilated detectors are being developed for use at the focal plane of the High Energy Replicated Optics (HERO) telescope. HERO requires a 64x64 pixel array with a spatial resolution of around 200 microns (with a 6m focal length) and high energy resolution (< 2% at 60keV). We are currently testing smaller arrays as a necessary first step towards this goal. In this presentation, we compare charge sharing and charge loss measurements between two devices that differ both electronically and geometrically. The first device consists of a 1-mm-thick piece of CdZnTe that is sputtered with a 4x4 array of pixels with pixel pitch of 750 microns (inter-pixel gap is 100 microns). The signal is read out using discrete ultra-low-noise preamplifiers, one for each of the 16 pixels. The second detector consists of a 2-mm-thick piece of CdZnTe that is sputtered with a 16x16 array of pixels with a pixel pitch of 300 microns (inter-pixel gap is 50 microns). Instead of using discrete preamplifiers, the crystal is bonded to an ASIC that provides all of the front-end electronics to each of the 256 pixels. what degree the bias voltage (i.e. the electric field) and hence the drift and diffusion coefficients affect our measurements. Further, we compare the measured results with simulated results and discuss to

  12. Electronic control of germanium telluride (GeTe) phase transition for electronic memory applications

    NASA Astrophysics Data System (ADS)

    Gwin, Alex H.; Coutu, Ronald A.

    2014-03-01

    Germanium telluride (GeTe) is a phase change material (PCM) that undergoes an exponential decrease in resistance from room temperature to its transition temperature at approximately 200 °C. Its resistivity decreases by as much as six orders of magnitude between amorphous and crystalline phases as it is heated. Chalcogenides such as GeTe have been utilized typically in nonvolatile optical memories such as CDs, DVDs, and Blu-ray discs, where the change in reflectivity between phases gives enough contrast for ON and OFF bits. Research over the past several years has begun to characterize the electronic control of PCM thin films for advanced electronic memory applications. By applying a voltage to control its resistance and crystallinity, GeTe has become a candidate for ultra-fast switching electronic memory, perhaps as an alternative to Flash memory. In this research, micro-scale PCM cells were fabricated using RF sputtering of a GeTe target and electron-beam evaporation on c-Si, SiO2/Si, Si3N4/Si, and Al2O3. Characterizations of the crystallization process were completed with spectroscopic ellipsometry (SE), varied voltage, and varied temperature in order to draw a comparison of the switching mechanism between thermally and electronically induced transition. The results show an optical contrast of Δn + iΔk = -0.858 + i1.056. Heat conduction experiments prove a growthdominated crystallization and fracturing of conductive crystallites when deposited on Al2O3. PCM cells exhibit memory-like I-V curves for smaller cell dimensions according to the trap-limited conduction model in chalcogenides. RF structures show the capability of being utilized as improved RF switches.

  13. Telluride, Tom Cruise, and Land Use Codes: Science, Policy, and Community Response

    NASA Astrophysics Data System (ADS)

    Raby, K. S.; Williams, M. W.

    2003-12-01

    Mountain areas throughout the western US have experienced a surge in popularity in the last decade, resulting in degradation of the resources that drew people to the area in the first place. Traditional economic interests, recreational users, and environmentalists all have opposing priorities. Thus, resource managers and planners face increasingly critical and controversial decisions regarding development and protection of watersheds. Best Management Practices (BMPs) are generally an attempt to improve land and water quality after degradation. Here we report on our work with local stakeholders in the San Miguel River drainage-home of Telluride Ski Area and Hollywood moguls such as Tom Cruise-to prevent degradation of headwater catchments while providing for reasonable economic and recreational activities. We developed new tools for resource managers by mapping landscape types and associated water quality parameters so as to develop sensitivity criteria that are displayed visually using GIS maps. Using these results, San Miguel County Commissioners adopted land use codes to restrict development, including an 800-sqft building footprint, and bans on septic systems and winter plowing. This case study lays the foundation for science-based policy at the catchment scale, but is dependent on local culture and politics. Preliminary fieldwork was conducted in the summer of 2003 as the first steps toward similar work in adjacent San Juan County, which has a strong mining heritage. The San Juan County Planning Commission identified priority basins for study, and extensive physical field surveys were conducted in these drainages to map spatial distribution and aerial extent of numerous landscape types. Again, water quality parameters will be associated with different land covers to enable alpine sensitivity analysis at the landscape unit scale. Results will be provided to the San Juan Planning Commission to augment current planning tools. However, because of the different

  14. Evaluation of Fully 3-D Emission Mammotomography With a Compact Cadmium Zinc Telluride Detector

    PubMed Central

    Tornai, Martin P.; McKinley, Randolph L.; Bowsher, James E.

    2015-01-01

    A compact, dedicated cadmium zinc telluride (CZT) gamma camera coupled with a fully three-dimensional (3-D) acquisition system may serve as a secondary diagnostic tool for volumetric molecular imaging of breast cancers, particularly in cases when mammographic findings are inconclusive. The developed emission mammotomography system comprises a medium field-of-view, quantized CZT detector and 3-D positioning gantry. The intrinsic energy resolution, sensitivity and spatial resolution of the detector are evaluated with Tc-99m (140 keV) filled flood sources, capillary line sources, and a 3-D frequency-resolution phantom. To mimic realistic human pendant, uncompressed breast imaging, two different phantom shapes of an average sized breast, and three different lesion diameters are imaged to evaluate the system for 3-D mammotomography. Acquisition orbits not possible with conventional emission, or transmission, systems are designed to optimize the viewable breast volume while improving sampling of the breast and anterior chest wall. Complications in camera positioning about the patient necessitate a compromise in these two orbit design criteria. Image quality is evaluated with signal-to-noise ratios and contrasts of the lesions, both with and without additional torso phantom background. Reconstructed results indicate that 3-D mammotomography, incorporating a compact CZT detector, is a promising, dedicated breast imaging technique for visualization of tumors <1 cm in diameter. Additionally, there are no outstanding trajectories that consistently yield optimized quantitative lesion imaging parameters. Qualitatively, imaging breasts with realistic torso backgrounds (out-of-field activity) substantially alters image characteristics and breast morphology unless orbits which improve sampling are utilized. In practice, the sampling requirement may be less strict than initially anticipated. PMID:16011316

  15. A Cadmium telluride micro-Spectometers Hard X ray Polarimeter for a balloon borne payload

    NASA Astrophysics Data System (ADS)

    Caroli, Ezio; Hernanz, Margarita; Ferrando, Philippe; Del Sordo, Stefano; Stephen, John; Laurent, Philippe; Alvarez, Jose M.; Auricchio, Natalia; Budtz-Jorgensen, Carl; Curado da Silva4, Rui M.; Limousin, Olivier; Galvez, Jose L.; Gloster, Paul Colin; Isern, Jordi; Maia, Jorge M.

    2012-07-01

    In the next generation of space instrumentation for hard X-ray astrophysics, the measurement of the polarization status of cosmic sources will be a key observational parameter in order to help understand the various production mechanisms and the source geometry. As polarisation observations are very difficult to perform, new telescopes operating in this energy range should be optimized for this type of measurement. In this perspective, we present the concept of a small high-performance spectrometer designed to operate as a scattering polarimeter between 100 and 500 keV and suitable for a stratospheric balloon-borne payload: CμSP (Cadmium telluride μ-Spectrometers Polarimeter). This instrument will be dedicated to perform an accurate and reliable measurement of the polarization status of the Crab pulsar, i.e. the polarization level and direction. The detector with 3D spatial resolution is made of CZT spectrometers in a highly segmented configuration in order to enhance as much as possible the sensitivity to the linear polarisation of detected photons. We discuss different configurations based on recent development results as well as possible improvements under study. Furthermore we describe a possible baseline design of the payload, which can also be seen as a pathfinder for a high performance detector for the next generation of hard X and soft gamma ray telescopes based on high energy focussing optics (e.g. Laue lenses) and/or advanced Compton instruments. Finally, we present Monte Carlo evaluations of the achievable sensitivity to polarisation as a function of different detector characteristics.

  16. Thermoelectric properties of bismuth telluride nanowires in the constant relaxation-time approximation

    NASA Astrophysics Data System (ADS)

    Bejenari, I.; Kantser, V.

    2008-09-01

    Electronic structure of bismuth telluride nanowires with the growth directions [110] and [015] is studied in the framework of the anisotropic effective-mass method using the parabolic band approximation. The components of the electron and hole effective-mass tensors for six valleys are calculated for both growth directions. For a square nanowire, in the temperature range from 77 to 500 K, the dependence of the Seebeck coefficient S , the thermal κ , and electrical conductivity σ , as well as the figure of merit ZT on the nanowire thickness and on the excess hole concentration pex , are investigated in the constant relaxation-time approximation. The carrier confinement is shown to play essential role for nanowires with cross section less than 30×30nm2 . In contrast to the excess holes (impurities), the confinement decreases both the carrier concentration and the thermal conductivity but increases the maximum value of the Seebeck coefficient. The confinement effect is stronger for the direction [015] than for the direction [110] due to the carrier mass difference for these directions. In the restricted temperature range, the size quantum limit is valid when the P -type nanowire cross section is smaller than 8×10nm2 ( 6×7 and 5×5nm2 ) at the excess hole concentration pex=2×1018cm-3 ( pex=5×1018cm-3 and pex=1×1019cm-3 correspondingly). The carrier confinement increases the maximum value of ZT and shifts it toward high temperatures. For the growth direction [110], the maximum value of the figure of merit for the P -type nanowire is equal to 1.4, 1.6, and 2.8, correspondingly, at temperatures 310, 390, and 480 K and the cross sections 30×30 , 15×15 , and 7×7nm2 (pex=5×1018cm-3) . At room temperature, the figure of merit equals 1.2, 1.3, and 1.7, respectively.

  17. Cadmium zinc telluride based infrared interferometry for X-ray detection

    NASA Astrophysics Data System (ADS)

    Lohstroh, A.; Della Rocca, I.; Parsons, S.; Langley, A.; Shenton-Taylor, C.; Blackie, D.

    2015-02-01

    Cadmium Zinc Telluride (CZT) is a wide band gap semiconductor for room temperature radiation detection. The electro-optic Pockels effect of the material has been exploited in the past to study electric field non-uniformities and their consequence on conventional detector signals in CZT, by imaging the intensity distribution of infrared (IR) light transmitted through a device placed between crossed polarizers. Recently, quantitative monitoring of extremely high intensity neutron pulses through the change of transmitted IR intensity was demonstrated, offering the advantage to place sensitive electronics outside the measured radiation field. In this work, we demonstrate that X-ray intensity can be deduced directly from measuring the change in phase of 1550 nm laser light transmitted through a 7 × 7 × 2 mm3 CZT based Pockels cell in a simple Mach Zehnder interferometer. X-rays produced by a 50 kVp Mo X-ray tube incident on the CZT cathode surface placed at 7 mm distance cause a linearly increasing phase shift above 0.3 mA tube current, with 1.58 ± 0.02 rad per mA for an applied bias of 500 V across the 2 mm thick device. Pockels images confirm that the sample properties are in agreement with the literature, exhibiting electric field enhancement near the cathode under irradiation, which may cause the non-linearity at low X-ray tube anode current settings. The laser used to probe the X-ray intensity causes itself some space charge, whose spatial distribution does not seem to be exclusively determined by the incident laser position, i.e., charge carrier generation location, with respect to the electrodes.

  18. Mercury-Cadmium-Telluride Focal Plane Array Performance Under Non-Standard Operating Conditions

    NASA Technical Reports Server (NTRS)

    Richardson, Brandon S.; Eastwood, Michael L.; Bruce, Carl F.; Green, Robert O.; Coles, J. B.

    2011-01-01

    This paper highlights a new technique that allows the Teledyne Scientific & Imaging LLC TCM6604A Mercury-Cadmium-Telluride (MCT) Focal Plane Array (FPA) to operate at room temperature. The Teledyne MCT FPA has been a standard in Imaging Spectroscopy since its creation in the 1980's. This FPA has been used in applications ranging from space instruments such as CRISM, M3 and ARTEMIS to airborne instruments such as MaRS and the Next Generation AVIRIS Instruments1. Precise focal plane alignment is always a challenge for such instruments. The current FPA alignment process results in multiple cold cycles requiring week-long durations, thereby increasing the risk and cost of a project. These alignment cycles are necessary because optimal alignment is approached incrementally and can only be measured with the FPA and Optics at standard operating conditions, requiring a cold instrument. Instruments using this FPA are normally cooled to temperatures below 150K for the MCT FPA to properly function. When the FPA is run at higher temperatures the dark current increases saturating the output. This paper covers the prospect of warm MCT FPA operation from a theoretical and experimental perspective. We discuss the empirical models and physical laws that govern MCT material properties and predict the optimal settings that will result in the best MCT PA performance at 300K. Theoretical results are then calculated for the proposed settings. We finally present the images and data obtained using the actual system with the warm MCT FPA settings. The paper concludes by emphasizing the strong positive correlation between the measured values and the theoretical results.

  19. Mitochondrial Toxicity of Cadmium Telluride Quantum Dot Nanoparticles in Mammalian Hepatocytes

    PubMed Central

    Nguyen, Kathy C.; Rippstein, Peter; Tayabali, Azam F.; Willmore, William G.

    2015-01-01

    There are an increasing number of studies indicating that mitochondria are relevant targets in nanomaterial-induced toxicity. However, the underlying mechanisms by which nanoparticles (NPs) interact with these organelles and affect their functions are unknown. The aim of this study was to investigate the effects of cadmium telluride quantum dot (CdTe-QD) NPs on mitochondria in human hepatocellular carcinoma HepG2 cells. CdTe-QD treatment resulted in the enlargement of mitochondria as examined with transmission electron microscopy and confocal microscopy. CdTe-QDs appeared to associate with the isolated mitochondria as detected by their inherent fluorescence. Further analyses revealed that CdTe-QD caused disruption of mitochondrial membrane potential, increased intracellular calcium levels, impaired cellular respiration, and decreased adenosine triphosphate synthesis. The effects of CdTe-QDs on mitochondrial oxidative phosphorylation were evidenced by changes in levels and activities of the enzymes of the electron transport chain. Elevation of peroxisome proliferator-activated receptor-γ coactivator levels after CdTe-QD treatment suggested the effects of CdTe-QDs on mitochondrial biogenesis. Our results also showed that the effects of CdTe-QDs were similar or greater to those of cadmium chloride at equivalent concentrations of cadmium, suggesting that the toxic effects of CdTe-QDs were not solely due to cadmium released from the NPs. Overall, the study demonstrated that CdTe-QDs induced multifarious toxicity by causing changes in mitochondrial morphology and structure, as well as impairing their function and stimulating their biogenesis. PMID:25809595

  20. Synthesis and characterization of silicon and germanium nanowires, silica nanotubes, and germanium telluride/tellurium nanostructures

    NASA Astrophysics Data System (ADS)

    Tuan, Hsing-Yu

    A supercritical fluid-liquid solid (SFLS) nanowire growth process using alkanethiol-coated Au nanoparticles to seed silicon nanowires was developed for synthesizing silicon nanowires in solution. The organic solvent was found to significantly influence the silicon precursor decomposition in solution. 46.8 mg of silicon nanowires with 63% yield of silicon nanowire synthesis were achieved while using benzene as a solvent. The most widely used metal for seeding Si and Ge nanowires is Au. However, Au forms deep trap in both Si and Ge and alternative metal seeds are more desirable for electronic applications. Different metal nanocrystals were studied for Si and Ge nanowire synthesis, including Co, Ni, CuS, Mn, Ir, MnPt 3, Fe2O3, and FePt. All eight metals have eutectic temperatures with Si and Ge that are well above the nanowire growth temperature. Unlike Au nanocrystals, which seed nanowire growth through the formation of a liquid Au:Si (Au:Ge) alloy, these other metals seed nanowires by forming solid silicide alloys, a process we have called "supercritical fluid-solid-solid" (SFSS) growth. Moreover, Co and Ni nanoparticles were found to catalyze the decomposition of various silane reactants that do not work well to make Si nanowires using Au seeds. In addition to seeding solid nanowires, CuS nanoparticles were found to seed silica nanotubes via a SFSS like mechanism. 5% of synthesized silica nanotubes were coiled. Heterostructured nanomaterials are interesting since they merge the properties of the individual materials and can be used in diverse applications. GeTe/Te heterostructures were synthesized by reacting diphenylgermane (DPG) and TOP-Te in the presence of organic surfactants. Aligned Te nanorods were grown on the surface facets of micrometer-size germanium telluride particles.

  1. Implementation of a complex multi-phase equation of state for cerium and its correlation with experiment

    SciTech Connect

    Cherne, Frank J; Jensen, Brian J; Elkin, Vyacheslav M

    2009-01-01

    The complexity of cerium combined with its interesting material properties makes it a desirable material to examine dynamically. Characteristics such as the softening of the material before the phase change, low pressure solid-solid phase change, predicted low pressure melt boundary, and the solid-solid critical point add complexity to the construction of its equation of state. Currently, we are incorporating a feedback loop between a theoretical understanding of the material and an experimental understanding. Using a model equation of state for cerium we compare calculated wave profiles with experimental wave profiles for a number of front surface impact (cerium impacting a plated window) experiments. Using the calculated release isentrope we predict the temperature of the observed rarefaction shock. These experiments showed that the release state occurs at different magnitudes, thus allowing us to infer where dynamic {gamma} - {alpha} phase boundary is.

  2. Ab initio molecular dynamics study of the properties of cerium in liquid sodium at 1000 K temperature

    SciTech Connect

    Samin, Adib; Li, Xiang; Zhang, Jinsuo; Mariani, R. D.; Unal, Cetin

    2015-12-21

    For liquid-sodium-cooled fast nuclear reactor systems, it is crucial to understand the behavior of lanthanides and other potential fission products in liquid sodium or other liquid metal solutions such as liquid cesium-sodium. In this study, we focus on lanthanide behavior in liquid sodium. Using ab initio molecular dynamics, we found that the solubility of cerium in liquid sodium at 1000 K was less than 0.78 at. %, and the diffusion coefficient of cerium in liquid sodium was calculated to be 5.57 × 10{sup −9} m{sup 2}/s. Furthermore, it was found that cerium in small amounts may significantly alter the heat capacity of the liquid sodium system. Our results are consistent with the experimental results for similar materials under similar conditions.

  3. Corrosion resistance of flaky aluminum pigment coated with cerium oxides/hydroxides in chloride and acidic electrolytes

    NASA Astrophysics Data System (ADS)

    Niroumandrad, S.; Rostami, M.; Ramezanzadeh, B.

    2015-12-01

    The objective of this study was to enhance the corrosion resistance of lamellar aluminum pigment through surface treatment by cerium oxides/hydroxides. The surface composition of the pigments was studied by energy-dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The corrosion resistance of the pigment was evaluated by conventional hydrogen evolution measurements in acidic solution and electrochemical impedance spectroscopy (EIS) in 3.5% NaCl solution. Results showed that the Ce-rich coating composed of Ce2O3 and CeO2 was precipitated on the pigment surface after immersion in the cerium solution. The corrosion resistance of pigment was significantly enhanced after modification with cerium layer.

  4. Determination of Ideal Broth Formulations Needed to Prepare Hydrous Cerium Oxide Microspheres via the Internal Gelation Process

    SciTech Connect

    Collins, Jack Lee; Chi, Anthony

    2009-02-01

    A simple test tube methodology was used to determine optimum process parameters for preparing hydrous cerium oxide microspheres via the internal gelation process.1 Broth formulations of cerium ammonium nitrate [(NH4)2Ce(NO3)6], hexamethylenetetramine, and urea were found that can be used to prepare hydrous cerium oxide gel spheres in the temperature range of 60 to 90 C. A few gel-forming runs were made in which microspheres were prepared with some of these formulations to be able to equate the test-tube gelation times to actual gelation times. These preparations confirmed that the test-tube methodology is reliable for determining the ideal broth formulations.

  5. Ab initio molecular dynamics study of the properties of cerium in liquid sodium at 1000 K temperature

    NASA Astrophysics Data System (ADS)

    Samin, Adib; Li, Xiang; Zhang, Jinsuo; Mariani, R. D.; Unal, Cetin

    2015-12-01

    For liquid-sodium-cooled fast nuclear reactor systems, it is crucial to understand the behavior of lanthanides and other potential fission products in liquid sodium or other liquid metal solutions such as liquid cesium-sodium. In this study, we focus on lanthanide behavior in liquid sodium. Using ab initio molecular dynamics, we found that the solubility of cerium in liquid sodium at 1000 K was less than 0.78 at. %, and the diffusion coefficient of cerium in liquid sodium was calculated to be 5.57 × 10-9 m2/s. Furthermore, it was found that cerium in small amounts may significantly alter the heat capacity of the liquid sodium system. Our results are consistent with the experimental results for similar materials under similar conditions.

  6. Production of CeO2 Nanoparticles by Method of Laser Ablation of Bulk Metallic Cerium Targets in Liquid

    NASA Astrophysics Data System (ADS)

    Svetlichnyi, V. A.; Lapin, I. N.

    2016-03-01

    The method of pulsed laser ablation in liquid was used to synthesize dispersions of cerium oxide nanoparticles when subjecting a metallic cerium target in water and alcohol to basic frequency radiation of the nanosecond Nd:YAG laser (1064 nm, 7 ns, 20 Hz). Researchers have studied the effect of laser radiation parameters, duration of impact, and optical scheme of experiment on the ablation process. The average rate of nanoparticle production was 50 mg/h in water and 25 mg/h in alcohol. Researchers have studied the size characteristics and crystalline structure of the nanoparticles produced. The particles have bimodal size distribution with 6 nm and 25 nm maximums. The average crystallite size is 17-19 nm. The crystalline structure of nanoparticles, namely cubic cerium oxide (fluorite structure), space group Fm-3m, is confirmed by the X-ray diffraction data, as well as optical absorption spectra and Raman spectroscopy.

  7. Influence of agglomeration of cerium oxide nanoparticles and speciation of cerium(III) on short term effects to the green algae Chlamydomonas reinhardtii.

    PubMed

    Röhder, Lena A; Brandt, Tanja; Sigg, Laura; Behra, Renata

    2014-07-01

    Cerium oxide nanoparticles (CeO2 NP) are increasingly used in industrial applications and may be released to the aquatic environment. The fate of CeO2 NP and effects on algae are largely unknown. In this study, the short term effects of CeO2 NP in two different agglomeration states on the green algae Chlamydomonas reinhardtii were examined. The role of dissolved cerium(III) on toxicity, its speciation and the dissolution of CeO2 NP were considered. The role of cell wall of C. reinhardtii as a barrier and its influence on the sensitivity to CeO2 NP and cerium(III) was evaluated by testing both, the wild type and the cell wall free mutant of C. reinhardtii. Characterization showed that CeO2 NP had a surface charge of ∼0mV at physiological pH and agglomerated in exposure media. Phosphate stabilized CeO2 NP at pH 7.5 over 24h. This effect was exploited to test CeO2 NP dispersed in phosphate with a mean size of 140nm and agglomerated in absence of phosphate with a mean size of 2000nm. The level of dissolved cerium(III) in CeO2 NP suspensions was very low and between 0.1 and 27nM in all tested media. Exposure of C. reinhardtii to Ce(NO3)3 decreased the photosynthetic yield in a concentration dependent manner with EC50 of 7.5±0.84μM for wild type and EC50 of 6.3±0.53μM for the cell wall free mutant. The intracellular level of reactive oxygen species (ROS) increased upon exposure to Ce(NO3)3 with effective concentrations similar to those inhibiting photosynthesis. The agglomerated CeO2 NP caused a slight decrease of photosynthetic yield at the highest concentrations (100μM), while no effect was observed for dispersed CeO2 NP. The low toxicity of agglomerated CeO2 NP was attributed quantitatively to Ce(3+) ions co-occurring in the nanoparticle suspension whereas for dispersed CeO2 NP, dissolved Ce(3+) was precipitated with phosphate and not bioavailable. Furthermore CeO2 NP did not affect the intracellular ROS level. The cell wall free mutant and wild type of C

  8. Influence of agglomeration of cerium oxide nanoparticles and speciation of cerium(III) on short term effects to the green algae Chlamydomonas reinhardtii.

    PubMed

    Röhder, Lena A; Brandt, Tanja; Sigg, Laura; Behra, Renata

    2014-07-01

    Cerium oxide nanoparticles (CeO2 NP) are increasingly used in industrial applications and may be released to the aquatic environment. The fate of CeO2 NP and effects on algae are largely unknown. In this study, the short term effects of CeO2 NP in two different agglomeration states on the green algae Chlamydomonas reinhardtii were examined. The role of dissolved cerium(III) on toxicity, its speciation and the dissolution of CeO2 NP were considered. The role of cell wall of C. reinhardtii as a barrier and its influence on the sensitivity to CeO2 NP and cerium(III) was evaluated by testing both, the wild type and the cell wall free mutant of C. reinhardtii. Characterization showed that CeO2 NP had a surface charge of ∼0mV at physiological pH and agglomerated in exposure media. Phosphate stabilized CeO2 NP at pH 7.5 over 24h. This effect was exploited to test CeO2 NP dispersed in phosphate with a mean size of 140nm and agglomerated in absence of phosphate with a mean size of 2000nm. The level of dissolved cerium(III) in CeO2 NP suspensions was very low and between 0.1 and 27nM in all tested media. Exposure of C. reinhardtii to Ce(NO3)3 decreased the photosynthetic yield in a concentration dependent manner with EC50 of 7.5±0.84μM for wild type and EC50 of 6.3±0.53μM for the cell wall free mutant. The intracellular level of reactive oxygen species (ROS) increased upon exposure to Ce(NO3)3 with effective concentrations similar to those inhibiting photosynthesis. The agglomerated CeO2 NP caused a slight decrease of photosynthetic yield at the highest concentrations (100μM), while no effect was observed for dispersed CeO2 NP. The low toxicity of agglomerated CeO2 NP was attributed quantitatively to Ce(3+) ions co-occurring in the nanoparticle suspension whereas for dispersed CeO2 NP, dissolved Ce(3+) was precipitated with phosphate and not bioavailable. Furthermore CeO2 NP did not affect the intracellular ROS level. The cell wall free mutant and wild type of C

  9. Change of the cerium valence with temperature - Structure and chemical bonding of HT-CeRhGe

    NASA Astrophysics Data System (ADS)

    Svitlyk, Volodymyr; Hermes, Wilfried; Chevalier, Bernard; Matar, Samir F.; Gaudin, Etienne; Voßwinkel, Daniel; Chernyshov, Dmitry; Hoffmann, Rolf-Dieter; Pöttgen, Rainer

    2013-07-01

    Polycrystalline CeRhGe was prepared via arc-melting of the elements. Its TiNiSi-related structures (space groups Pnma) were studied by powder diffraction using synchrotron radiation over the temperature range of 315-770 K. CeRhGe shows a first-order structural phase transition at 520 K upon heating. Ab initio elelectronic structure calculations give evidence for the depletion of the cerium 4f band in HT-CeRhGe and in consequence a redistribution of the electron density from the cerium to the rhodium atoms. Purely trivalent cerium atoms in the low-temperature modification (LT) change to intermediate-valent cerium in the high-temperature modification (HT). The integrated crystal orbital Hamilton populations show an enhancement of the Ce-Rh bonding in HT-CeRhGe. The three-dimensional [RhGe] polyanionic network shows drastic puckering of the [Rh3Ge3] hexagons in LT-CeRhGe and a flattening in HT-CeRhGe. The cerium valence change is accompanied by a drastic jump in the lattice parameters: a = 7.42249(8), b = 4.46699(5) and c = 7.1276(1) Å at 315 K vs. a = 7.24579(6), b = 4.47506(4) and c = 7.43579(6) Å at 570 K. Large shifts occur for the x parameter of the rhodium and the z parameter of the cerium atomic positions (Wyckoff sites 4c (x 1/4 z)).

  10. Effect of ultrasound on the structural and textural properties of copper-impregnated cerium-modified zirconium-pillared bentonite

    NASA Astrophysics Data System (ADS)

    Tomul, Fatma

    2011-12-01

    In this study, the synthesis of zirconium-pillared bentonite modified with cerium was performed via two different methods by the application of conventional and ultrasonic treatments during the intercalation stage. To synthesise copper-impregnated pillared clays by wet impregnation, cerium-modified zirconium-pillared clays were used as supportive materials after being calcined at 300 °C. Ultrasonic treatment significantly decreased the required processing time compared with the conventional treatment of the synthesised pillared bentonites. Chemical analysis confirmed the incorporation of Zr 4+, Ce 4+ and Cu 2+ species into the pillared bentonites. X-ray diffraction (XRD) patterns of zirconium- and cerium/zirconium-pillared bentonites prepared by conventional treatment show that one large d-spacing above 3.5 nm corresponds to the mesoporous delaminated part, and another small d-spacing above 1.7 nm is indicative of the microporous pillared part. Zirconium- and cerium/zirconium-pillared bentonites prepared via ultrasonic treatment exhibited similar results, with the same high d-spacing but with a second low-intensity d-spacing above 1.9 nm. The delaminated structures of the pillared bentonites synthesised by both methods were conserved after copper impregnation. Nitrogen-adsorption isotherm analysis showed that the textural characteristics of products synthesised by ultrasonic treatment were comparable to those of products synthesised by conventional treatment. Fourier-transform infrared spectroscopy (FTIR) analyses showed the presence of Brønsted- and Lewis-acid sites, and zirconium-pillared clays synthesised by conventional treatment exhibited increased numbers of Brønsted- and Lewis-acid sites after cerium addition and copper impregnation. However, the products synthesised by ultrasonic treatment exhibited an increased number of Brønsted- and Lewis-acid sites after cerium addition, but a decreased number of acid sites after copper impregnation.

  11. Inhaled Diesel Emissions Generated with Cerium Oxide Nanoparticle Fuel Additive Induce Adverse Pulmonary and Systemic Effects

    PubMed Central

    Snow, Samantha J.; McGee, John; Miller, Desinia B.; Bass, Virginia; Schladweiler, Mette C.; Thomas, Ronald F.; Krantz, Todd; King, Charly; Ledbetter, Allen D.; Richards, Judy; Weinstein, Jason P.; Conner, Teri; Willis, Robert; Linak, William P.; Nash, David; Wood, Charles E.; Elmore, Susan A.; Morrison, James P.; Johnson, Crystal L.; Gilmour, Matthew Ian; Kodavanti, Urmila P.

    2014-01-01

    Diesel exhaust (DE) exposure induces adverse cardiopulmonary effects. Cerium oxide nanoparticles added to diesel fuel (DECe) increases fuel burning efficiency but leads to altered emission characteristics and potentially altered health effects. Here, we evaluated whether DECe results in greater adverse pulmonary effects compared with DE. Male Sprague Dawley rats were exposed to filtered air, DE, or DECe for 5 h/day for 2 days. N-acetyl glucosaminidase activity was increased in bronchial alveolar lavage fluid (BALF) of rats exposed to DECe but not DE. There were also marginal but insignificant increases in several other lung injury biomarkers in both exposure groups (DECe > DE for all). To further characterize DECe toxicity, rats in a second study were exposed to filtered air or DECe for 5 h/day for 2 days or 4 weeks. Tissue analysis indicated a concentration- and time-dependent accumulation of lung and liver cerium followed by a delayed clearance. The gas-phase and high concentration of DECe increased lung inflammation at the 2-day time point, indicating that gas-phase components, in addition to particles, contribute to pulmonary toxicity. This effect was reduced at 4 weeks except for a sustained increase in BALF γ-glutamyl transferase activity. Histopathology and transmission electron microscopy revealed increased alveolar septa thickness due to edema and increased numbers of pigmented macrophages after DECe exposure. Collectively, these findings indicate that DECe induces more adverse pulmonary effects on a mass basis than DE. In addition, lung accumulation of cerium, systemic translocation to the liver, and delayed clearance are added concerns to existing health effects of DECe. PMID:25239632

  12. High temperature stability of a 316 austenitic stainless steel coated with cerium oxide nanoparticles

    NASA Astrophysics Data System (ADS)

    Mendoza Del Angel, Humberto

    Cerium oxide (CeO2-x) nanoparticles were used for coating protection on a 316 Austenitic Stainless Steel (Aust. SS) to enhance the thermal stability of the oxide films formed at high temperatures. Three simple coating methods were used, dipping, spraying and spinning in order to explore the coating film morphology, nanoparticle distribution and its effect on thermal stability of the steel substrates. Experimentally, the selected steel was exposed to 800°C/1000°C under dry air conditions. Weight changes (DeltaW/A) were monitored as a function of time and the results were compared with uncoated alloys tested under similar conditions. The cerium oxide nanoparticles used on the three methods were synthesized in the laboratory obtaining nanoparticles in the range of 3.5 to 6.2 nanometers. It was found that cerium oxide particle size is affected by temperature. In this case, the activation energy for particle growth was estimated to be around 21,1 kJ/mol. Characterization of the film morphologies before and after oxidation were carried out using Atomic Force Microscopy (AFM), Surface Profilometry, Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD). A comparison of the three coating methods was carried out for the particular case of the 316 Aust. SS coupons. In addition, the oxidation kinetics was experimentally investigated for the coated samples. For this purpose thermal gravimetric determinations were made at 800°C, 900°C, and 1000°C and oxidation rate constants were calculated at each temperature.

  13. Inhaled diesel emissions generated with cerium oxide nanoparticle fuel additive induce adverse pulmonary and systemic effects.

    PubMed

    Snow, Samantha J; McGee, John; Miller, Desinia B; Bass, Virginia; Schladweiler, Mette C; Thomas, Ronald F; Krantz, Todd; King, Charly; Ledbetter, Allen D; Richards, Judy; Weinstein, Jason P; Conner, Teri; Willis, Robert; Linak, William P; Nash, David; Wood, Charles E; Elmore, Susan A; Morrison, James P; Johnson, Crystal L; Gilmour, Matthew Ian; Kodavanti, Urmila P

    2014-12-01

    Diesel exhaust (DE) exposure induces adverse cardiopulmonary effects. Cerium oxide nanoparticles added to diesel fuel (DECe) increases fuel burning efficiency but leads to altered emission characteristics and potentially altered health effects. Here, we evaluated whether DECe results in greater adverse pulmonary effects compared with DE. Male Sprague Dawley rats were exposed to filtered air, DE, or DECe for 5 h/day for 2 days. N-acetyl glucosaminidase activity was increased in bronchial alveolar lavage fluid (BALF) of rats exposed to DECe but not DE. There were also marginal but insignificant increases in several other lung injury biomarkers in both exposure groups (DECe > DE for all). To further characterize DECe toxicity, rats in a second study were exposed to filtered air or DECe for 5 h/day for 2 days or 4 weeks. Tissue analysis indicated a concentration- and time-dependent accumulation of lung and liver cerium followed by a delayed clearance. The gas-phase and high concentration of DECe increased lung inflammation at the 2-day time point, indicating that gas-phase components, in addition to particles, contribute to pulmonary toxicity. This effect was reduced at 4 weeks except for a sustained increase in BALF γ-glutamyl transferase activity. Histopathology and transmission electron microscopy revealed increased alveolar septa thickness due to edema and increased numbers of pigmented macrophages after DECe exposure. Collectively, these findings indicate that DECe induces more adverse pulmonary effects on a mass basis than DE. In addition, lung accumulation of cerium, systemic translocation to the liver, and delayed clearance are added concerns to existing health effects of DECe.

  14. Reactions of a cerium(iii) amide with heteroallenes: insertion, silyl-migration and de-insertion.

    PubMed

    Yin, Haolin; Carroll, Patrick J; Schelter, Eric J

    2016-07-28

    Reactions of Ce[N(SiMe3)Ph(F)]3 (-Ph(F) = pentafluorophenyl) toward small molecules of the type E1[double bond, length as m-dash]C[double bond, length as m-dash]E2 (E1, E2 = O, S, NR), including carbon disulfide, carbodiimide, carbon dioxide, isocyanate and isothiocyanate are reported, resulting in distinct products, including cerium(iii) dithiocarbamate, cerium(iii) guanidinate, isocyanates and unsymmetric carbodiimides. These reactions were rationalized as three consecutive stages of the same reaction pathway: insertion, silyl-migration and de-insertion. PMID:27416923

  15. Structural, optical, and transport properties of nanocrystalline bismuth telluride thin films treated with homogeneous electron beam irradiation and thermal annealing

    NASA Astrophysics Data System (ADS)

    Takashiri, Masayuki; Asai, Yuki; Yamauchi, Kazuki

    2016-08-01

    We investigated the effects of homogeneous electron beam (EB) irradiation and thermal annealing treatments on the structural, optical, and transport properties of bismuth telluride thin films. Bismuth telluride thin films were prepared by an RF magnetron sputtering method at room temperature. After deposition, the films were treated with homogeneous EB irradiation, thermal annealing, or a combination of both the treatments (two-step treatment). We employed Williamson–Hall analysis for separating the strain contribution from the crystallite domain contribution in the x-ray diffraction data of the films. We found that strain was induced in the thin films by EB irradiation and was relieved by thermal annealing. The crystal orientation along c-axis was significantly enhanced by the two-step treatment. Scanning electron microscopy indicated the melting and aggregation of nano-sized grains on the film surface by the two-step treatment. Optical analysis indicated that the interband transition of all the thin films was possibly of the indirect type, and that thermal annealing and two-step treatment methods increased the band gap of the films due to relaxation of the strain. Thermoelectric performance was significantly improved by the two-step treatment. The power factor reached a value of 17.2 μW (cm‑1 K‑2), approximately 10 times higher than that of the as-deposited thin films. We conclude that improving the crystal orientation and relaxing the strain resulted in enhanced thermoelectric performance.

  16. Structural, optical, and transport properties of nanocrystalline bismuth telluride thin films treated with homogeneous electron beam irradiation and thermal annealing.

    PubMed

    Takashiri, Masayuki; Asai, Yuki; Yamauchi, Kazuki

    2016-08-19

    We investigated the effects of homogeneous electron beam (EB) irradiation and thermal annealing treatments on the structural, optical, and transport properties of bismuth telluride thin films. Bismuth telluride thin films were prepared by an RF magnetron sputtering method at room temperature. After deposition, the films were treated with homogeneous EB irradiation, thermal annealing, or a combination of both the treatments (two-step treatment). We employed Williamson-Hall analysis for separating the strain contribution from the crystallite domain contribution in the x-ray diffraction data of the films. We found that strain was induced in the thin films by EB irradiation and was relieved by thermal annealing. The crystal orientation along c-axis was significantly enhanced by the two-step treatment. Scanning electron microscopy indicated the melting and aggregation of nano-sized grains on the film surface by the two-step treatment. Optical analysis indicated that the interband transition of all the thin films was possibly of the indirect type, and that thermal annealing and two-step treatment methods increased the band gap of the films due to relaxation of the strain. Thermoelectric performance was significantly improved by the two-step treatment. The power factor reached a value of 17.2 μW (cm(-1) K(-2)), approximately 10 times higher than that of the as-deposited thin films. We conclude that improving the crystal orientation and relaxing the strain resulted in enhanced thermoelectric performance. PMID:27389820

  17. Surface structures of cerium oxide nanocrystalline particles from the size dependence of the lattice parameters

    NASA Astrophysics Data System (ADS)

    Tsunekawa, S.; Ito, S.; Kawazoe, Y.

    2004-10-01

    Cerium oxide nanocrystalline particles are synthesized and monodispersed in the size range from 2 to 8nm in diameter. The dependence of the lattice parameters on particle size is obtained by x-ray and electron diffraction analyses. The size dependence well coincides with the estimation based on the assumption that the surface is composed of one layer of Ce2O3 and the inside consists of CeO2. The effect of particle size on lattice parameters is discussed from the differences in the fabrication method and the surface structure.

  18. Investigation of the elemental composition of lanthanum-cerium hexaboride crystals

    NASA Astrophysics Data System (ADS)

    Badalyan, Georgi; Kuzanyan, Armen; Petrosyan, Vahagn; Kuzanyan, Vazgen; Gulian, Armen

    2010-10-01

    Crystals of solid solutions of lanthanum-cerium hexaborides (La1-xCex)B6 possess unique thermoelectric properties in the temperature range of 0.3-9 K and they can be used in thermoelectric single-photon detectors as a sensor. One can observe a wide spread in thermoelectric measurement values reported in the literature, which is because of different qualities of studied crystals. The greatest influence on both the Seebeck coefficient and electrical resistivity of samples is exercised by the presence of uncontrolled impurities in crystals and the deviation from stoichiometry. In this work we have studied just the aforementioned parameters of the crystals obtained by three different methods.

  19. Silicate-free growth of high-quality ultrathin cerium oxide films on Si(111)

    SciTech Connect

    Flege, Jan Ingo; Kaemena, Bjoern; Wilkens, Torsten; Schmidt, Thomas; Falta, Jens; Gevers, Sebastian; Bruns, Daniel; Wollschlaeger, Joachim; Bertram, Florian; Baetjer, Jan

    2011-12-15

    Ultrathin Ce{sub 2}O{sub 3} layers have been grown on Si(111) by reactive metal deposition in an oxygen background and characterized by x-ray standing waves, x-ray diffraction, x-ray photoelectron spectroscopy, and low-energy electron diffraction to elucidate and quantify both atomic structure and chemical composition. It is demonstrated that highly ordered, mostly B-oriented, epitaxial ceria films can be achieved by preadsorption of a monolayer of atomic chlorine, effectively passivating the substrate and thereby suppressing cerium silicate and silicon oxide formation at the interface.

  20. β Coronae Bolealis: Lithium and Cerium Contribution to the Blend at 6708 Å

    NASA Astrophysics Data System (ADS)

    Drake, N. A.; Hubrig, S.; Polosukhina, N. S.; de La Reza, R.

    2006-06-01

    We analyze the Li I 6708 Å spectral region of the chemically peculiar Ap star βCrB using high resolution, high signal-to-noise spectra obtained at different rotation phases. Our study shows that the Ce II line at 6708.099 Å is a main contributor to the spectral feature at 6708 Å. This fact explains the observed red shift of the Li I doublet of about 0.2 Å found by Hack et al. (1997). We derive the values of lithium and cerium abundances for different rotation phases and show that βCrB has ``cosmic'' Li abundance.

  1. Influence of the Ion Coordination Number on Cation Exchange Reactions with Copper Telluride Nanocrystals.

    PubMed

    Tu, Renyong; Xie, Yi; Bertoni, Giovanni; Lak, Aidin; Gaspari, Roberto; Rapallo, Arnaldo; Cavalli, Andrea; Trizio, Luca De; Manna, Liberato

    2016-06-01

    Cu2-xTe nanocubes were used as starting seeds to access metal telluride nanocrystals by cation exchanges at room temperature. The coordination number of the entering cations was found to play an important role in dictating the reaction pathways. The exchanges with tetrahedrally coordinated cations (i.e., with coordination number 4), such as Cd(2+) or Hg(2+), yielded monocrystalline CdTe or HgTe nanocrystals with Cu2-xTe/CdTe or Cu2-xTe/HgTe Janus-like heterostructures as intermediates. The formation of Janus-like architectures was attributed to the high diffusion rate of the relatively small tetrahedrally coordinated cations, which could rapidly diffuse in the Cu2-xTe NCs and nucleate the CdTe (or HgTe) phase in a preferred region of the host structure. Also, with both Cd(2+) and Hg(2+) ions the exchange led to wurtzite CdTe and HgTe phases rather than the more stable zinc-blende ones, indicating that the anion framework of the starting Cu2-xTe particles could be more easily deformed to match the anion framework of the metastable wurtzite structures. As hexagonal HgTe had never been reported to date, this represents another case of metastable new phases that can only be accessed by cation exchange. On the other hand, the exchanges involving octahedrally coordinated ions (i.e., with coordination number 6), such as Pb(2+) or Sn(2+), yielded rock-salt polycrystalline PbTe or SnTe nanocrystals with Cu2-xTe@PbTe or Cu2-xTe@SnTe core@shell architectures at the early stages of the exchange process. In this case, the octahedrally coordinated ions are probably too large to diffuse easily through the Cu2-xTe structure: their limited diffusion rate restricts their initial reaction to the surface of the nanocrystals, where cation exchange is initiated unselectively, leading to core@shell architectures. Interestingly, these heterostructures were found to be metastable as they evolved to stable Janus-like architectures if annealed at 200 °C under vacuum. PMID:27177274

  2. Influence of the Ion Coordination Number on Cation Exchange Reactions with Copper Telluride Nanocrystals.

    PubMed

    Tu, Renyong; Xie, Yi; Bertoni, Giovanni; Lak, Aidin; Gaspari, Roberto; Rapallo, Arnaldo; Cavalli, Andrea; Trizio, Luca De; Manna, Liberato

    2016-06-01

    Cu2-xTe nanocubes were used as starting seeds to access metal telluride nanocrystals by cation exchanges at room temperature. The coordination number of the entering cations was found to play an important role in dictating the reaction pathways. The exchanges with tetrahedrally coordinated cations (i.e., with coordination number 4), such as Cd(2+) or Hg(2+), yielded monocrystalline CdTe or HgTe nanocrystals with Cu2-xTe/CdTe or Cu2-xTe/HgTe Janus-like heterostructures as intermediates. The formation of Janus-like architectures was attributed to the high diffusion rate of the relatively small tetrahedrally coordinated cations, which could rapidly diffuse in the Cu2-xTe NCs and nucleate the CdTe (or HgTe) phase in a preferred region of the host structure. Also, with both Cd(2+) and Hg(2+) ions the exchange led to wurtzite CdTe and HgTe phases rather than the more stable zinc-blende ones, indicating that the anion framework of the starting Cu2-xTe particles could be more easily deformed to match the anion framework of the metastable wurtzite structures. As hexagonal HgTe had never been reported to date, this represents another case of metastable new phases that can only be accessed by cation exchange. On the other hand, the exchanges involving octahedrally coordinated ions (i.e., with coordination number 6), such as Pb(2+) or Sn(2+), yielded rock-salt polycrystalline PbTe or SnTe nanocrystals with Cu2-xTe@PbTe or Cu2-xTe@SnTe core@shell architectures at the early stages of the exchange process. In this case, the octahedrally coordinated ions are probably too large to diffuse easily through the Cu2-xTe structure: their limited diffusion rate restricts their initial reaction to the surface of the nanocrystals, where cation exchange is initiated unselectively, leading to core@shell architectures. Interestingly, these heterostructures were found to be metastable as they evolved to stable Janus-like architectures if annealed at 200 °C under vacuum.

  3. Thin film cadmium telluride solar cells. Progress report, 1 October 1983-30 September 1984

    SciTech Connect

    Chu, T.L.

    1985-04-01

    During this reporting period, the deposition of CdTe films by the direct combination of the Cd and Te vapor on foreign substrates has been continued with emphasis on the resistivity control of p-type films and the reduction of p-CdTe/substrate interface resistance. CdTe films deposited on graphite substrates were all p-type, irrespective of the substrate temperature and the reactant composition. This result indicates that carbon is incorporated into CdTe presumably thru its reaction with Te and that carbon is electrically active in CdTe. Using W/graphite as substrates, the change in conductivity type of nearly stoichiometric films has been found to take place over a very narrow range of the reactant composition. In addition to using a Cd-deficient reactant mixture, the resistivity of p-type CdTe films may also be controlled by adding a dopant to the reactant mixture. The effect of reactant composition and substrate temperature on the resistivity of the reactant mixture was studied in detail. The effect of adding oxygen to the reactant was also investigated. Using CdTe films deposited on Corning 7059 glass substrates, the optical band gap of CdTe films was found to be 1.50 eV at room temperature. The preparation and characterization of thin film cadium telluride heterojunction solar cells have been continued. The open-circuit voltage (up to 0.75V) and short-circuit current density (up to 20mA/cm/sup 2/) are reasonably reproducible; however, the high p-CdTe/substrate interface resistance remains to be a problem in the fabrication of thin film CdTe solar cells. Because of the uncontrolled series resistance, the best CdS/CdTe cells have an AM1 efficiency of about 6.5% and the best ITO/CdTe cell has an AM1 efficiency of about 8%. Further work will be directed to the use of inverted structures.

  4. Thermodynamics of post-growth annealing of cadmium zinc telluride nuclear radiation detectors

    NASA Astrophysics Data System (ADS)

    Adams, Aaron Lee

    Nuclear Radiation Detectors are used for detecting, tracking, and identifying radioactive materials which emit high-energy gamma and X-rays. The use of Cadmium Zinc Telluride (CdZnTe) detectors is particularly attractive because of the detector's ability to operate at room temperature and measure the energy spectra of gamma-ray sources with a high resolution, typically less than 1% at 662 keV. While CdZnTe detectors are acceptable imperfections in the crystals limit their full market potential. One of the major imperfections are Tellurium inclusions generated during the crystal growth process by the retrograde solubility of Tellurium and Tellurium-rich melt trapped at the growth interface. Tellurium inclusions trap charge carriers generated by gamma and X-ray photons and thus reduce the portion of generated charge carriers that reach the electrodes for collection and conversion into a readable signal which is representative of the ionizing radiation's energy and intensity. One approach in resolving this problem is post-growth annealing which has the potential of removing the Tellurium inclusions and associated impurities. The goal of this project is to use experimental techniques to study the thermodynamics of Tellurium inclusion migration in post-growth annealing of CdZnTe nuclear detectors with the temperature gradient zone migration (TGZM) technique. Systematic experiments will be carried out to provide adequate thermodynamic data that will inform the engineering community of the optimum annealing parameters. Additionally, multivariable correlations that involve the Tellurium diffusion coefficient, annealing parameters, and CdZnTe properties will be analyzed. The experimental approach will involve systematic annealing experiments (in Cd vapor overpressure) on different sizes of CdZnTe crystals at varying temperature gradients ranging from 0 to 60°C/mm (used to migrate the Tellurium inclusion to one side of the crystal), and at annealing temperatures ranging

  5. Studies on luminescence from a cerium-doped strontium stannate phosphor.

    PubMed

    Karabulut, Yüksel; Ayvacikli, Mehmet; Canimoglu, Adil; Garcia Guinea, Javier; Can, Nurdogan

    2015-06-01

    The crystal structure and morphology of Ce(3+) -doped SrSnO3 materials prepared using the solid-state reaction method were extensively characterized using experimental techniques. X-Ray diffraction results show that the cerium substitution of strontium does not change the structure of the strontium stannate. Raman spectroscopy was used to investigate the microstructures and lattice vibrations. Environmental scanning electron microscopy images showed that phosphors aggregate and their particles form irregular shapes. SrSnO3 exhibits an intense green emission with a broad band originating from the 5d(1)  → 4f(1) transition of cerium. It was observed that, after exposure to beta-irradiation, the glow curve of this material has two broad thermoluminescence peaks, one centered at ~ 127°C and the other at ~ 245°C for a heating rate of 5 K/s. The kinetic parameters, which include the frequency factor and the activation energy of the material, were calculated using Chen's method, after beta-irradiation. The fading and reusability of the phosphor were also studied and it was found that the phosphor is suitable for radiation dosimetry.

  6. The role of cerium redox state in the SOD mimetic activity of nanoceria

    PubMed Central

    Heckert, Eric; Karakoti, Ajay; Seal, Sudipta; Self, William T.

    2008-01-01

    Cerium oxide nanoparticles (nanoceria) have recently been shown to protect cells against oxidative stress in both cell culture and animal models. Nanoceria has been shown to exhibit superoxide dismutase (SOD) activity using a ferricytochrome C assay, and it is this mimetic activity that has been postulated to be responsible for cellular protection by nanoceria. The nature of nanoceria’s antioxidant properties, specifically what physical characteristics make nanoceria effective at scavenging superoxide anion, is poorly understood. In this study electron paramagnetic resonance (EPR) analysis confirms the reactivity of nanoceria as an SOD mimetic. X-ray photoelectron spectroscopy (XPS) and UV-visible analysis of nanoceria treated with hydrogen peroxide demonstrate that a decrease in the Ce 3+/4+ ratio correlates directly with a loss of SOD mimetic activity. These results strongly suggest that the surface oxidation state of nanoceria plays an integral role in the SOD mimetic activity of nanoceria and that ability of nanoceria to scavenge superoxide is directly related to cerium (III) concentrations at the surface of the particle. PMID:18395249

  7. Cerium oxide for the destruction of chemical warfare agents: A comparison of synthetic routes.

    PubMed

    Janoš, Pavel; Henych, Jiří; Pelant, Ondřej; Pilařová, Věra; Vrtoch, Luboš; Kormunda, Martin; Mazanec, Karel; Štengl, Václav

    2016-03-01

    Four different synthetic routes were used to prepare active forms of cerium oxide that are capable of destroying toxic organophosphates: a sol-gel process (via a citrate precursor), homogeneous hydrolysis and a precipitation/calcination procedure (via carbonate and oxalate precursors). The samples prepared via homogeneous hydrolysis with urea and the samples prepared via precipitation with ammonium bicarbonate (with subsequent calcination at 500°C in both cases) exhibited the highest degradation efficiencies towards the extremely dangerous nerve agents soman (O-pinacolyl methylphosphonofluoridate) and VX (O-ethyl S-[2-(diisopropylamino)ethyl] methylphosphonothioate) and the organophosphate pesticide parathion methyl. These samples were able to destroy more than 90% of the toxic compounds in less than 10 min. The high degradation efficiency of cerium oxide is related to its complex surface chemistry (presence of surface OH groups and surface non-stoichiometry) and to its nanocrystalline nature, which promotes the formation of crystal defects on which the decomposition of organophosphates proceeds through a nucleophilic substitution mechanism that is not dissimilar to the mechanism of enzymatic hydrolysis of organic phosphates by phosphotriesterase. PMID:26561750

  8. Gene-Expression Changes in Cerium Chloride-Induced Injury of Mouse Hippocampus

    PubMed Central

    Sheng, Lei; Zhu, Liyuan; Guan, Ning; Gui, Suxin; Sang, Xuezi; Zhao, Xiaoyang; Sun, Qingqing; Wang, Ling; Cheng, Jie; Hu, Renping; Hong, Fashui

    2013-01-01

    Cerium is widely used in many aspects of modern society, including agriculture, industry and medicine. It has been demonstrated to enter the ecological environment, is then transferred to humans through food chains, and causes toxic actions in several organs including the brain of animals. However, the neurotoxic molecular mechanisms are not clearly understood. In this study, mice were exposed to 0.5, 1, and 2 mg/kg BW cerium chloride (CeCl3) for 90 consecutive days, and their learning and memory ability as well as hippocampal gene expression profile were investigated. Our findings suggested that exposure to CeCl3 led to hippocampal lesions, apoptosis, oxidative stress and impairment of spatial recognition memory. Furthermore, microarray data showed marked alterations in the expression of 154 genes involved in learning and memory, immunity and inflammation, signal transduction, apoptosis and response to stress in the 2 mg/kg CeCl3 exposed hippocampi. Specifically, the significant up-regulation of Axud1, Cdc37, and Ube2v1 caused severe apoptosis, and great suppression of Adcy8, Fos, and Slc5a7 expression led to impairment of mouse cognitive ability. Therefore, Axud1, Cdc37, Ube2v1, Adcy8, Fos, and Slc5a7 may be potential biomarkers of hippocampal toxicity caused by CeCl3 exposure. PMID:23573234

  9. Cerium oxide for the destruction of chemical warfare agents: A comparison of synthetic routes.

    PubMed

    Janoš, Pavel; Henych, Jiří; Pelant, Ondřej; Pilařová, Věra; Vrtoch, Luboš; Kormunda, Martin; Mazanec, Karel; Štengl, Václav

    2016-03-01

    Four different synthetic routes were used to prepare active forms of cerium oxide that are capable of destroying toxic organophosphates: a sol-gel process (via a citrate precursor), homogeneous hydrolysis and a precipitation/calcination procedure (via carbonate and oxalate precursors). The samples prepared via homogeneous hydrolysis with urea and the samples prepared via precipitation with ammonium bicarbonate (with subsequent calcination at 500°C in both cases) exhibited the highest degradation efficiencies towards the extremely dangerous nerve agents soman (O-pinacolyl methylphosphonofluoridate) and VX (O-ethyl S-[2-(diisopropylamino)ethyl] methylphosphonothioate) and the organophosphate pesticide parathion methyl. These samples were able to destroy more than 90% of the toxic compounds in less than 10 min. The high degradation efficiency of cerium oxide is related to its complex surface chemistry (presence of surface OH groups and surface non-stoichiometry) and to its nanocrystalline nature, which promotes the formation of crystal defects on which the decomposition of organophosphates proceeds through a nucleophilic substitution mechanism that is not dissimilar to the mechanism of enzymatic hydrolysis of organic phosphates by phosphotriesterase.

  10. Phenotypic and genomic responses to titanium dioxide and cerium oxide nanoparticles in Arabidopsis germinants.

    PubMed

    Tumburu, Laxminath; Andersen, Christian P; Rygiewicz, Paul T; Reichman, Jay R

    2015-01-01

    The effects of exposure to nanoparticles of titanium dioxide (nano-titanium) and cerium oxide (nano-cerium) on gene expression and growth in Arabidopsis thaliana germinants were studied by using microarrays and quantitative real-time polymerase chain reaction (qPCR), and by evaluating germinant phenotypic plasticity. Exposure to 12 d of either nano-titania or nano-ceria altered the regulation of 204 and 142 genes, respectively. Genes induced by the nanoparticles mainly include ontology groups annotated as stimuli responsive, including both abiotic (oxidative stress, salt stress, water transport) and biotic (respiratory burst as a defense against pathogens) stimuli. Further analysis of the differentially expressed genes indicates that both nanoparticles affected a range of metabolic processes (deoxyribonucleic acid [DNA] metabolism, hormone metabolism, tetrapyrrole synthesis, and photosynthesis). Individual exposures to the nanoparticles increased percentages of seeds with emergent radicles, early development of hypocotyls and cotyledons, and those with fully grown leaves. Although there were distinct differences between the nanoparticles in their affect on molecular mechanisms attributable to enhancing germinant growth, both particles altered similar suites of genes related to various pathways and processes related to enhanced growth.

  11. Controlling the physics and chemistry of binary and ternary praseodymium and cerium oxide systems.

    PubMed

    Niu, Gang; Zoellner, Marvin Hartwig; Schroeder, Thomas; Schaefer, Andreas; Jhang, Jin-Hao; Zielasek, Volkmar; Bäumer, Marcus; Wilkens, Henrik; Wollschläger, Joachim; Olbrich, Reinhard; Lammers, Christian; Reichling, Michael

    2015-10-14

    Rare earth praseodymium and cerium oxides have attracted intense research interest in the last few decades, due to their intriguing chemical and physical characteristics. An understanding of the correlation between structure and properties, in particular the surface chemistry, is urgently required for their application in microelectronics, catalysis, optics and other fields. Such an understanding is, however, hampered by the complexity of rare earth oxide materials and experimental methods for their characterisation. Here, we report recent progress in studying high-quality, single crystalline, praseodymium and cerium oxide films as well as ternary alloys grown on Si(111) substrates. Using these well-defined systems and based on a systematic multi-technique surface science approach, the corresponding physical and chemical properties, such as the surface structure, the surface morphology, the bulk-surface interaction and the oxygen storage/release capability, are explored in detail. We show that specifically the crystalline structure and the oxygen stoichiometry of the oxide thin films can be well controlled by the film preparation method. This work leads to a comprehensive understanding of the properties of rare earth oxides and highlights the applications of these versatile materials. Furthermore, methanol adsorption studies are performed on binary and ternary rare earth oxide thin films, demonstrating the feasibility of employing such systems for model catalytic studies. Specifically for ceria systems, we find considerable stability against normal environmental conditions so that they can be considered as a "materials bridge" between surface science models and real catalysts.

  12. [XPS study on the influence of calcination conditions to cerium ion valence].

    PubMed

    Mei, Yan; Yan, Jian-ping; Nie, Zuo-ren

    2010-01-01

    For the system of Ce(NO3)2.6H2O and urea solution during homogeneous precipitation method, X-ray diffraction (XRD), infrared spectrum (IR) and especially X-ray photoelectron spectroscopy (XPS) were used to study and characterize the product structure, variety of cerium ion valence, compound surface character and kernel electronic configurations. The results of XRD and IR showed that calcination temperature had a great effect on the cerium ion valence. The products are orthorhombic Ce2 O(CO3)2.H2O with valence III by using homogeneous precipitation method directly. When heated from the temperature 200 degrees C to 250 degrees C, the product of CeO(CO3)2.H2O with valence VI was finally changed into stable CeO2 with valence IV. XPS was used to study the surface character and kernel electronic configurations of the three different compounds through fine scanning of O(1s), Ce(3d) and Ce(4d) apices, and the results approved that the compounds with different valences are caused by the different valence electronic configurations of the products.

  13. Neuroprotective mechanisms of cerium oxide nanoparticles in a mouse hippocampal brain slice model of ischemia.

    PubMed

    Estevez, A Y; Pritchard, S; Harper, K; Aston, J W; Lynch, A; Lucky, J J; Ludington, J S; Chatani, P; Mosenthal, W P; Leiter, J C; Andreescu, S; Erlichman, J S

    2011-09-15

    Cerium oxide nanoparticles (nanoceria) are widely used as catalysts in industrial applications because of their potent free radical-scavenging properties. Given that free radicals play a prominent role in the pathology of many neurological diseases, we explored the use of nanoceria as a potential therapeutic agent for stroke. Using a mouse hippocampal brain slice model of cerebral ischemia, we show here that ceria nanoparticles reduce ischemic cell death by approximately 50%. The neuroprotective effects of nanoceria were due to a modest reduction in reactive oxygen species, in general, and ~15% reductions in the concentrations of superoxide (O(2)(•-)) and nitric oxide, specifically. Moreover, treatment with nanoceria markedly decreased (~70% reduction) the levels of ischemia-induced 3-nitrotyrosine, a modification to tyrosine residues in proteins induced by the peroxynitrite radical. These findings suggest that scavenging of peroxynitrite may be an important mechanism by which cerium oxide nanoparticles mitigate ischemic brain injury. Peroxynitrite plays a pivotal role in the dissemination of oxidative injury in biological tissues. Therefore, nanoceria may be useful as a therapeutic intervention to reduce oxidative and nitrosative damage after a stroke. PMID:21704154

  14. Custom cerium oxide nanoparticles protect against a free radical mediated autoimmune degenerative disease in the brain.

    PubMed

    Heckman, Karin L; DeCoteau, William; Estevez, Ana; Reed, Kenneth J; Costanzo, Wendi; Sanford, David; Leiter, James C; Clauss, Jennifer; Knapp, Kylie; Gomez, Carlos; Mullen, Patrick; Rathbun, Elle; Prime, Kelly; Marini, Jessica; Patchefsky, Jamie; Patchefsky, Arthur S; Hailstone, Richard K; Erlichman, Joseph S

    2013-12-23

    Cerium oxide nanoparticles are potent antioxidants, based on their ability to either donate or receive electrons as they alternate between the +3 and +4 valence states. The dual oxidation state of ceria has made it an ideal catalyst in industrial applications, and more recently, nanoceria's efficacy in neutralizing biologically generated free radicals has been explored in biological applications. Here, we report the in vivo characteristics of custom-synthesized cerium oxide nanoparticles (CeNPs) in an animal model of immunological and free-radical mediated oxidative injury leading to neurodegenerative disease. The CeNPs are 2.9 nm in diameter, monodispersed and have a -23.5 mV zeta potential when stabilized with citrate/EDTA. This stabilizer coating resists being 'washed' off in physiological salt solutions, and the CeNPs remain monodispersed for long durations in high ionic strength saline. The plasma half-life of the CeNPs is ∼4.0 h, far longer than previously described, stabilized ceria nanoparticles. When administered intravenously to mice, the CeNPs were well tolerated and taken up by the liver and spleen much less than previous nanoceria formulations. The CeNPs were also able to penetrate the brain, reduce reactive oxygen species levels, and alleviate clinical symptoms and motor deficits in mice with a murine model of multiple sclerosis. Thus, CeNPs may be useful in mitigating tissue damage arising from free radical accumulation in biological systems.

  15. Mixed mode and sequential oscillations in the cerium-bromate-4-aminophenol photoreaction

    SciTech Connect

    Bell, Jeffrey G.; Wang Jichang

    2013-09-15

    Cerium was introduced to the bromate-aminophenol photochemical oscillator to implement coupled autocatalytic feedbacks. Mixed mode and sequential oscillations emerged in the studied system, making it one of the few chemical oscillators known to support consecutive bifurcations in a batch system. The complex reaction behavior showed a strong dependence on the intensity of illumination supplied to the system. Removal of illumination during an oscillatory window affected both the frequency and amplitude of the oscillation but did not fully extinguish them, indicating that the cerium-bromate-4-aminophenol oscillator was photosensitive rather than photo-controlled. A moderate light intensity allowed for a slow evolution of the system, which proved to be critical for the emergence of transient complex oscillations. Variation of individual reaction parameters was carried out, which indicated that the development of complex oscillations occur in a narrow region and a phase diagram in the 4-aminophenol and sulfuric acid plane demonstrated this. Simulations provide strong support that transient complex oscillations observed experimentally arise from the coupling of two autocatalytic cycles.

  16. Phenotypic and genomic responses to titanium dioxide and cerium oxide nanoparticles in Arabidopsis germinants.

    PubMed

    Tumburu, Laxminath; Andersen, Christian P; Rygiewicz, Paul T; Reichman, Jay R

    2015-01-01

    The effects of exposure to nanoparticles of titanium dioxide (nano-titanium) and cerium oxide (nano-cerium) on gene expression and growth in Arabidopsis thaliana germinants were studied by using microarrays and quantitative real-time polymerase chain reaction (qPCR), and by evaluating germinant phenotypic plasticity. Exposure to 12 d of either nano-titania or nano-ceria altered the regulation of 204 and 142 genes, respectively. Genes induced by the nanoparticles mainly include ontology groups annotated as stimuli responsive, including both abiotic (oxidative stress, salt stress, water transport) and biotic (respiratory burst as a defense against pathogens) stimuli. Further analysis of the differentially expressed genes indicates that both nanoparticles affected a range of metabolic processes (deoxyribonucleic acid [DNA] metabolism, hormone metabolism, tetrapyrrole synthesis, and photosynthesis). Individual exposures to the nanoparticles increased percentages of seeds with emergent radicles, early development of hypocotyls and cotyledons, and those with fully grown leaves. Although there were distinct differences between the nanoparticles in their affect on molecular mechanisms attributable to enhancing germinant growth, both particles altered similar suites of genes related to various pathways and processes related to enhanced growth. PMID:25242526

  17. Kinetics of Cerium(IV) Extraction from H(2)SO(4)-HF Medium with Cyanex 923.

    PubMed

    Liao, Wuping; Yu, Guihong; Yue, Shantang; Li, Deqian

    2002-03-11

    Studies of the extraction kinetics of cerium(IV) from H(2)SO(4)-HF solutions with Cyanex 923 in n-heptane have been carried out using a constant interfacial area cell with laminar flow. The experimental hydrodynamic conditions were chosen so that the contribution of diffusion to the measured rate of reaction was minimized. The data were analyzed in terms of pseudo-first order constants. The results were compared with those of the system without HF. It was concluded that the addition of HF reduces the activation energy for the forward rate from 46.2 to 36.5 kJ mol(-1) while it has an opposite effect on the activation energy for the reverse process(the activation energy increased from 23.3 to 90.8 kJ mol(-1)). Thus, HF can accelerate the rate of cerium(IV) extraction. At the same time, the extraction rate is controlled by a mixed chemical reaction-diffusion rather than by a chemical reaction alone. A rate equation has also been obtained.

  18. Controlling the physics and chemistry of binary and ternary praseodymium and cerium oxide systems.

    PubMed

    Niu, Gang; Zoellner, Marvin Hartwig; Schroeder, Thomas; Schaefer, Andreas; Jhang, Jin-Hao; Zielasek, Volkmar; Bäumer, Marcus; Wilkens, Henrik; Wollschläger, Joachim; Olbrich, Reinhard; Lammers, Christian; Reichling, Michael

    2015-10-14

    Rare earth praseodymium and cerium oxides have attracted intense research interest in the last few decades, due to their intriguing chemical and physical characteristics. An understanding of the correlation between structure and properties, in particular the surface chemistry, is urgently required for their application in microelectronics, catalysis, optics and other fields. Such an understanding is, however, hampered by the complexity of rare earth oxide materials and experimental methods for their characterisation. Here, we report recent progress in studying high-quality, single crystalline, praseodymium and cerium oxide films as well as ternary alloys grown on Si(111) substrates. Using these well-defined systems and based on a systematic multi-technique surface science approach, the corresponding physical and chemical properties, such as the surface structure, the surface morphology, the bulk-surface interaction and the oxygen storage/release capability, are explored in detail. We show that specifically the crystalline structure and the oxygen stoichiometry of the oxide thin films can be well controlled by the film preparation method. This work leads to a comprehensive understanding of the properties of rare earth oxides and highlights the applications of these versatile materials. Furthermore, methanol adsorption studies are performed on binary and ternary rare earth oxide thin films, demonstrating the feasibility of employing such systems for model catalytic studies. Specifically for ceria systems, we find considerable stability against normal environmental conditions so that they can be considered as a "materials bridge" between surface science models and real catalysts. PMID:26355535

  19. Near-road modeling and measurement of cerium-containing particles generated by nanoparticle diesel fuel additive use

    EPA Science Inventory

    Cerium oxide nanoparticles (nCe) are used as a fuel-borne catalyst in diesel engines to reduce particulate emissions, yet the environmental and human health impacts of the exhaust particles are not well understood. To bridge the gap between emission measurements and ambient impac...

  20. A mixed acid based vanadium-cerium redox flow battery with a zero-gap serpentine architecture

    NASA Astrophysics Data System (ADS)

    Leung, P. K.; Mohamed, M. R.; Shah, A. A.; Xu, Q.; Conde-Duran, M. B.

    2015-01-01

    This paper presents the performance of a vanadium-cerium redox flow battery using conventional and zero-gap serpentine architectures. Mixed-acid solutions based on methanesulfonate-sulfate anions (molar ratio 3:1) are used to enhance the solubilities of the vanadium (>2.0 mol dm-3) and cerium species (>0.8 mol dm-3), thus achieving an energy density (c.a. 28 Wh dm-3) comparable to that of conventional all-vanadium redox flow batteries (20-30 Wh dm-3). Electrochemical studies, including cyclic voltammetry and galvanostatic cycling, show that both vanadium and cerium active species are suitable for energy storage applications in these electrolytes. To take advantage of the high open-circuit voltage (1.78 V), improved mass transport and reduced internal resistance are facilitated by the use of zero-gap flow field architecture, which yields a power density output of the battery of up to 370 mW cm-2 at a state-of-charge of 50%. In a charge-discharge cycle at 200 mA cm-2, the vanadium-cerium redox flow battery with the zero-gap architecture is observed to discharge at a cell voltage of c.a. 1.35 V with a coulombic efficiency of up to 78%.

  1. Predicting the Effects of Nano-Scale Cerium Additives in Diesel Fuel on Regional-Scale Air Quality

    EPA Science Inventory

    Diesel vehicles are a major source of air pollutant emissions. Fuel additives containing nanoparticulate cerium (nCe) are currently being used in some diesel vehicles to improve fuel efficiency. These fuel additives also reduce fine particulate matter (PM2.5) emissio...

  2. Germination and early plant development of ten plant species exposed to titanium dioxide and cerium oxide nanoparticles

    EPA Science Inventory

    Ten agronomic plant species were exposed to different concentrations of nano titanium dioxide (nTiO2) or nano cerium oxide (nCeO2) (0, 250, 500 and 1000 mg/L) to examine potential effects on germination and early seedling development. We modified a standard test protocol develop...

  3. Structural and Optical Properties of Sputtered Cadmium Telluride Thin Films Deposited on Flexible Substrates for Photovoltaic Applications.

    PubMed

    Song, Woochang; Lee, Kiwon; Kim, Donguk; Lee, Jaehyeong

    2016-05-01

    Cadmium telluride (CdTe) is a photovoltaic technology based on the use of thin films of CdTe to absorb and convert sunlight into electricity. In this paper, polycrystalline CdTe thin films were deposited using radio frequency magnetron sputtering onto flexible substrates including polyimide and molybdenum foil. The structural and optical properties of the films grown at various sputtering pressures were investigated using X-ray diffraction (XRD), field-emission scanning electron microscope (FE-SEM), and UV/Nis/NIR spectrophotometry. The sputtering pressure was found to have significant effects on the structural properties, including crystallinity, preferential orientation, and microstructure. Deterioration of the optical properties of CdTe thin films were observed at high sputtering pressure. PMID:27483904

  4. Thin-film cadmium telluride photovoltaic cells. Final subcontract report, 1 November 1992--1 January 1994

    SciTech Connect

    Compaan, A.D.; Bohn, R.G.

    1994-09-01

    This report describes work to develop and optimize radio-frequency (rf) sputtering for the deposition of thin films of cadmium telluride (CdTe) and related semiconductors for thin-film solar cells. Pulsed laser physical vapor deposition was also used for exploratory work on these materials, especially where alloying or doping are involved, and for the deposition of cadmium chloride layers. The sputtering work utilized a 2-in diameter planar magnetron sputter gun. The film growth rate by rf sputtering was studied as a function of substrate temperature, gas pressure, and rf power. Complete solar cells were fabricated on tin-oxide-coated soda-lime glass substrates. Currently, work is being done to improve the open-circuit voltage by varying the CdTe-based absorber layer, and to improve the short-circuit current by modifying the CdS window layer.

  5. Mercury-cadmium-telluride waveguides--a novel strategy for on-chip mid-infrared sensors.

    PubMed

    Wang, Xiaofeng; Antoszewski, Jarek; Putrino, Gino; Lei, Wen; Faraone, Lorenzo; Mizaikoff, Boris

    2013-11-19

    We report the first planar waveguides made from mercury-cadmium-telluride (MCT)-a material to date exclusively used for mid-infrared (MIR) detector elements-serving as on-chip MIR evanescent field transducers in combination with tunable quantum cascade lasers (tQCLs) emitting in the spectral regime of 5.78-6.35 μm. This novel MIR sensing approach utilizes structured MCT chips fabricated via molecular beam epitaxy (MBE) as waveguide enabling sensing via evanescent field absorption spectroscopy, as demonstrated by the detection of 1 nL of acetone. Complementary finite difference time domain (FDTD) simulations fit well with the experimentally obtained data and predict an improvement of the limit of detection by at least 2 orders of magnitude upon implementation of thinner MCT waveguides. With the first demonstration of chemical sensing using on-chip MCT waveguides, monolithically fabricated IR sensing systems directly interfacing the waveguide with the MCT detector element may be envisaged.

  6. A rapid and sensitive assay for determination of doxycycline using thioglycolic acid-capped cadmium telluride quantum dots

    NASA Astrophysics Data System (ADS)

    Tashkhourian, Javad; Absalan, Ghodratollah; Jafari, Marzieh; Zare, Saber

    2016-01-01

    A rapid, simple and inexpensive spectrofluorimetric sensor for determination of doxycycline based on its interaction with thioglycolic acid-capped cadmium telluride quantum dots (TGA/CdTe QDs) has been developed. Under the optimum experimental conditions, the sensor exhibited a fast response time of <10 s. The results revealed that doxycycline could quench the fluorescence of TGA/CdTe QDs via electron transfer from the QDs to doxycycline through a dynamic quenching mechanism. The sensor permitted determination of doxycycline in a concentration range of 1.9 × 10-6-6.1 × 10-5 mol L-1 with a detection limit of 1.1 × 10-7 mol L-1. The sensor was applied for determination of doxycycline in honey and human serum samples.

  7. Effect of cadmium telluride quantum dots on the dielectric and electro-optical properties of ferroelectric liquid crystals.

    PubMed

    Kumar, A; Biradar, A M

    2011-04-01

    We present here the dielectric and electro-optical studies of cadmium telluride quantum dots (CdTe QDs) doped ferroelectric liquid crystals (FLCs). It has been observed that the doping of CdTe QDs not only induced a pronounced memory effect but also affected the physical parameters of FLC material (LAHS19). The modifications in the physical parameters and memory effect of LAHS19 are found to depend on the concentration ratio of CdTe QDs. The lower concentration of CdTe QDs (1-3 wt%) enhanced the values of spontaneous polarization and rotational viscosity of LAHS19 material but did not favor the memory effect, whereas a higher concentration of CdTe QDs (>5 wt%) degraded the alignment of LAHS19 material. The doping of ∼5 wt% of CdTe QDs is found to be the most suitable for achieving good memory effect without significantly affecting the material parameters.

  8. Synthesis and characterization of an electro-deposited polyaniline-bismuth telluride nanocomposite - A novel thermoelectric material

    SciTech Connect

    Chatterjee, Krishanu; Suresh, Asaithambi; Ganguly, Saibal; Kargupta, Kajari; Banerjee, Dipali

    2009-12-15

    The present work consists of synthesis and characterization of a novel thermoelectric material polyaniline (PANI)-bismuth telluride (Bi{sub 2}Te{sub 3}) nanocomposite using simultaneous electrochemical reactions and deposition method. The inorganic bismuth nitrate has been used as a dopant for polyaniline to achieve high electrical conductivity. A semi-batch mode of operation has been employed to control the rate of deposition of an individual component and thus the molecular architecture of the composite. The electro-deposited composite film on ITO coated glass substrate has been characterized by X-ray diffraction analysis (XRD), FTIR analysis, scanning electron microscope (SEM), and transmission electron microscope (TEM). The microscopic analysis reveals the formation of rod-like nanostructures of diameter less than 100 nm. It has been found that smaller molecules of Bi{sub 2}Te{sub 3} are dispersed in the macromolecules of PANI. The nanocomposite has been characterized by thermoelectric power.

  9. Polycrystalline thin film cadmium telluride solar cells fabricated by electrodeposition. Annual subcontract report, 20 March 1993--19 March 1994

    SciTech Connect

    Trefny, J.U.; Furtak, T.E.; Williamson, D.L.; Kim, D.

    1994-07-01

    This report describes the principal results of work performed during the second year of a 3-year program at the Colorado School of Mines (CSM). The work on transparent conducting oxides was carried out primarily by CSM students at NREL and is described in three publications listed in Appendix C. The high-quality ZnO produced from the work was incorporated into a copper indium diselenide cell that exhibited a world-record efficiency of 16.4%. Much of the time was devoted to the improvement of cadmium sulfide films deposited by chemical bath deposition methods and annealed with or without a cadmium chloride treatment. Progress was also made in the electrochemical deposition of cadmium telluride. High-quality films yielding CdS/CdTe/Au cells of greater than 10% efficiency are now being produced on a regular basis. We explored the use of zinc telluride back contacts to form an n-i-p cell structure as previously used by Ametek. We began small-angle x-ray scattering (SAXS) studies to characterize crystal structures, residual stresses, and microstructures of both CdTe and CdS. Large SAXS signals were observed in CdS, most likely because of scattering from gain boundaries. The signals observed to date from CdTe are much weaker, indicating a more homogeneous microstructure. We began to use the ADEPT modeling program, developed at Purdue University, to guide our understanding of the CdS/CdTe cell physics and the improvements that will most likely lead to significantly enhanced efficiencies.

  10. Charge carrier effective mass and concentration derived from combination of Seebeck coefficient and Te125 NMR measurements in complex tellurides

    DOE PAGES

    Levin, E. M.

    2016-06-27

    Thermoelectric materials utilize the Seebeck effect to convert heat to electrical energy. The Seebeck coefficient (thermopower), S, depends on the free (mobile) carrier concentration, n, and effective mass, m*, as S ~ m*/n2/3. The carrier concentration in tellurides can be derived from 125Te nuclear magnetic resonance (NMR) spin-lattice relaxation measurements. The NMR spin-lattice relaxation rate, 1/T1, depends on both n and m* as 1/T1~(m*)3/2n (within classical Maxwell-Boltzmann statistics) or as 1/T1~(m*)2n2/3 (within quantum Fermi-Dirac statistics), which challenges the correct determination of the carrier concentration in some materials by NMR. Here it is shown that the combination of the Seebeck coefficientmore » and 125Te NMR spin-lattice relaxation measurements in complex tellurides provides a unique opportunity to derive the carrier effective mass and then to calculate the carrier concentration. This approach was used to study AgxSbxGe50–2xTe50, well-known GeTe-based high-efficiency tellurium-antimony-germanium-silver thermoelectric materials, where the replacement of Ge by [Ag+Sb] results in significant enhancement of the Seebeck coefficient. Thus, values of both m* and n derived using this combination show that the enhancement of thermopower can be attributed primarily to an increase of the carrier effective mass and partially to a decrease of the carrier concentration when the [Ag+Sb] content increases.« less

  11. Bulk growth and surface characterization of epitaxy ready cadmium zinc telluride substrates for use in IR imaging applications

    NASA Astrophysics Data System (ADS)

    Flint, J. P.; Martinez, B.; Betz, T. E. M.; MacKenzie, J.; Kumar, F. J.; Bindley, G.

    2016-05-01

    Cadmium Zinc Telluride (CZT) is an important compound semiconductor material upon which Mercury Cadmium Telluride (MCT) layers are deposited epitaxially to form structures that are used in high performance detectors covering a wide infrared (IR) spectral band. The epitaxial growth of high quality MCT layers presents many technical challenges and a critical determinant of material performance is the quality of the underlying bulk CZT substrate. CZT itself is a difficult material to manufacture where traditional methods of bulk growth are complex and low yielding, which constrains the supply of commercially available substrates. In this work we report on the epitaxy-ready finishing of Travelling Heather Method (THM) grown Cd0.96Zn0.04Te substrates. The THM method is well established for the growth of high quality CZT crystals used in nuclear, X-ray and spectroscopic imaging applications and in this work we demonstrate the application of this technique to the growth of IR specification CZT substrates with areas of up to 5 cm x 5 cm square. We will discuss the advantages of the THM method over alternative methods of bulk CZT growth where the high yield and material uniformity advantages of this technique will be demonstrated. Chemo-mechanical polishing (CMP) of 4 cm x 4 cm CZT substrates reveals that III-V (InSb/GaSb) like levels of epitaxy-ready surface finishing may be obtained with modified process chemistries. Surface quality assessments will be made by various surface analytical and microscopy techniques from which the suitability of the material for subsequent assessment of quality by epitaxial growth will be ascertained.

  12. Crystal Growth, Characterization and Fabrication of Cadmium Zinc Telluride-based Nuclear Detectors

    NASA Astrophysics Data System (ADS)

    Krishna, Ramesh M.

    In today's world, nuclear radiation is seeing more and more use by humanity as time goes on. Nuclear power plants are being built to supply humanity's energy needs, nuclear medical imaging is becoming more popular for diagnosing cancer and other diseases, and control of weapons-grade nuclear materials is becoming more and more important for national security. All of these needs require high-performance nuclear radiation detectors which can accurately measure the type and amount of radiation being used. However, most current radiation detection materials available commercially require extensive cooling, or simply do not function adequately for high-energy gamma-ray emitting nuclear materials such as uranium and plutonium. One of the most promising semiconductor materials being considered to create a convenient, field-deployable nuclear detector is cadmium zinc telluride (CdZnTe, or CZT). CZT is a ternary semiconductor compound which can detect high-energy gamma-rays at room temperature. It offers high resistivity (≥ 1010 O-cm), a high band gap (1.55 eV), and good electron transport properties, all of which are required for a nuclear radiation detector. However, one significant issue with CZT is that there is considerable difficulty in growing large, homogeneous, defect-free single crystals of CZT. This significantly increases the cost of producing CZT detectors, making CZT less than ideal for mass-production. Furthermore, CZT suffers from poor hole transport properties, which creates significant problems when using it as a high-energy gamma-ray detector. In this dissertation, a comprehensive investigation is undertaken using a successful growth method for CZT developed at the University of South Carolina. This method, called the solvent-growth technique, reduces the complexity required to grow detector-grade CZT single crystals. It utilizes a lower growth temperature than traditional growth methods by using Te as a solvent, while maintaining the advantages of

  13. Geology and geochemistry of telluride-bearing Au deposits in the Pingyi area, Western Shandong, China

    NASA Astrophysics Data System (ADS)

    Hu, H.-B.; Mao, J.-W.; Niu, S.-Y.; Li, Y.-F.; Li, M.-W.

    2006-07-01

    Telluride-bearing gold deposits of the Pingyi area, western Shandong, China, are located on the southeastern margin of the North China Craton. There are two main types of deposits: (i) mineralized cryptoexplosive breccia, e.g., Guilaizhuang; and (ii) stratified, finely-disseminated mineralization hosted in carbonate rocks, e.g., Lifanggou and Mofanggou deposits. In Guilaizhuang, the cryptoexplosive breccia is formed within rocks of the Tongshi complex and Ordovician dolomite. The mineralization is controlled by an E-W-trending listric fault. Stratified orebodies of the Lifanggou and Mofanggou deposits are placed along a NE-trending, secondary detachment zone. They are hosted within dolomitic limestone, micrite and dolomite of the Early-Middle Cambrian Changqing Group. The mineralization in the ore districts is considered to be related to the Early Jurassic Tongshi magmatic complex that formed in a continental arc setting on the margin of the North China Craton. The host rocks are porphyritic and consist predominantly of medium- to fine-grained diorite and pyroxene (hornblende)-bearing monzonite. SHRIMP U-Pb zircon dating of diorites give a 206Pb/238U weighted mean age of 175.7 ± 3.8 Ma. This is interpreted as representing the crystallization age of the Tongshi magmatic complex. Considering the contact relationships between the magmatic and host sedimentary rocks, as well as the genetic link with the deposits, we conclude that this age is relevant also for the formation of mineralization in the Pingyi area. We hence consider that the deposits formed in the Jurassic. The principal gold minerals are native gold, electrum and calaverite. Wall-rock alteration comprises pyritization, fluoritization, silicification, carbonatization and chloritization. Fluid inclusion studies indicate that all the analyzed inclusions are of two-phase vapor-liquid NaCl-H2O type. Homogenization temperatures of the fluid inclusions vary from 103 °C to 250 °C, and the ice melting

  14. Freshwater dispersion stability of PAA-stabilised cerium oxide nanoparticles and toxicity towards Pseudokirchneriella subcapitata.

    PubMed

    Booth, Andy; Størseth, Trond; Altin, Dag; Fornara, Andrea; Ahniyaz, Anwar; Jungnickel, Harald; Laux, Peter; Luch, Andreas; Sørensen, Lisbet

    2015-02-01

    An aqueous dispersion of poly (acrylic acid)-stabilised cerium oxide (CeO₂) nanoparticles (PAA-CeO₂) was evaluated for its stability in a range of freshwater ecotoxicity media (MHRW, TG 201 and M7), with and without natural organic matter (NOM). In a 15 day dispersion stability study, PAA-CeO₂ did not undergo significant aggregation in any media type. Zeta potential varied between media types and was influenced by PAA-CeO₂ concentration, but remained constant over 15 days. NOM had no influence on PAA-CeO₂ aggregation or zeta potential. The ecotoxicity of the PAA-CeO₂ dispersion was investigated in 72 h algal growth inhibition tests using the freshwater microalgae Pseudokirchneriella subcapitata. PAA-CeO₂ EC₅₀ values for growth inhibition (GI; 0.024 mg/L) were 2-3 orders of magnitude lower than pristine CeO₂ EC₅₀ values reported in the literature. The concentration of dissolved cerium (Ce(3+)/Ce(4+)) in PAA-CeO₂ exposure suspensions was very low, ranging between 0.5 and 5.6 μg/L. Free PAA concentration in the exposure solutions (0.0096-0.0384 mg/L) was significantly lower than the EC10 growth inhibition (47.7 mg/L) value of pure PAA, indicating that free PAA did not contribute to the observed toxicity. Elemental analysis indicated that up to 38% of the total Cerium becomes directly associated with the algal cells during the 72 h exposure. TOF-SIMS analysis of algal cell wall compounds indicated three different modes of action, including a significant oxidative stress response to PAA-CeO₂ exposure. In contrast to pristine CeO₂ nanoparticles, which rapidly aggregate in standard ecotoxicity media, PAA-stabilised CeO₂ nanoparticles remain dispersed and available to water column species. Interaction of PAA with cell wall components, which could be responsible for the observed biomarker alterations, could not be excluded. This study indicates that the increased dispersion stability of PAA-CeO₂ leads to an increase in toxicity compared to

  15. Adsorption and dissociation of methanol on the fully oxidized and partially reduced (111) cerium oxide surface: dependence on the configuration of the cerium 4f electrons

    SciTech Connect

    Beste, Ariana; Mullins, David R; Overbury, Steven {Steve} H; Harrison, Robert J

    2008-01-01

    The adsorption and dissociation of methanol on the fully oxidized and partially reduced (111) cerium oxide surface is studied using the PW91 functional as well as the PW91+U scheme. We investigate the influence of the detailed electronic structure of the Ce 4f band on the chemistry of methanol on the surface. For the partially reduced surface we obtain a spin delocalized, a ferromagnetic, and an anti-ferromagnetic solution. We find that the qualitative conclusions are independent of the surface type used. Methanol adsorption is exothermic on the fully oxidized as well as on the partially reduced surface. Also dissociation of methanol on the surface is exothermic but strongly enhanced by the presence of a vacancy. We localize an on-top methoxy species as a dissociation product on the fully oxidized surface and a triply bridged methoxy species on the partially reduced surface where the methoxy oxygen partly fills the oxygen vacancy in the surface. Adsorption energies are influenced by the introduction of the repulsive Hubbard (U) term. On the other hand, relative surface stabilities like dissociation energies are less sensitive.

  16. Cerium-based binary and ternary oxides in the transesterification of dimethylcarbonate with phenol.

    PubMed

    Dibenedetto, Angela; Angelini, Antonella; di Bitonto, Luigi; De Giglio, Elvira; Cometa, Stefania; Aresta, Michele

    2014-04-01

    Diphenyl carbonate (DPC) plays a key role in phosgene-free carbonylation processes. It can be produced by transesterification of dimethyl carbonate (DMC) with phenol in the presence of catalysts. Methyl phenyl carbonate (MPC) is first produced that is then converted into DPC by either disproportionation or further transesterification with phenol. Cerium-based bimetallic oxides (with the heterometal being niobium, iron, palladium, or aluminum) are used as catalysts in the transesterification of DMC to synthesize MPC. The catalytic activity is affected by the type and concentration of the heterometal. XPS, IR and elementary analyses are employed to characterize the new catalysts. Differently from pure oxides, the mixed oxides produce a significant increase of the conversion and selectivity towards MPC. PMID:24616260

  17. Stability and morphology of cerium oxide surfaces in an oxidizing environment: A first-principles investigation

    NASA Astrophysics Data System (ADS)

    Fronzi, Marco; Soon, Aloysius; Delley, Bernard; Traversa, Enrico; Stampfl, Catherine

    2009-09-01

    We present density functional theory investigations of the bulk properties of cerium oxides (CeO2 and Ce2O3) and the three low index surfaces of CeO2, namely, (100), (110), and (111). For the surfaces, we consider various terminations including surface defects. Using the approach of "ab initio atomistic thermodynamics," we find that the most stable surface structure considered is the stoichiometric (111) surface under "oxygen-rich" conditions, while for a more reducing environment, the same (111) surface, but with subsurface oxygen vacancies, is found to be the most stable one, and for a highly reducing environment, the (111) Ce-terminated surface becomes energetically favored. Interestingly, this latter surface exhibits a significant reconstruction in that it becomes oxygen terminated and the upper layers resemble the Ce2O3(0001) surface. This structure could represent a precursor to the phase transition of CeO2 to Ce2O3.

  18. Cerium oxide-chitosan based nanobiocomposite for food borne mycotoxin detection

    NASA Astrophysics Data System (ADS)

    Kaushik, Ajeet; Solanki, Pratima R.; Pandey, M. K.; Ahmad, Sharif; Malhotra, Bansi D.

    2009-10-01

    Cerium oxide nanoparticles (NanoCeO2) and chitosan (CH) based nanobiocomposite film deposited onto indium-tin-oxide coated glass substrate has been used to coimmobilize rabbit immunoglobin (r-IgGs) and bovine serum albumin (BSA) for food borne mycotoxin [ochratoxin-A (OTA)] detection. Electrochemical studies reveal that presence of NanoCeO2 increases effective electro-active surface area of CH-NanoCeO2/indium tin oxide (ITO) nanobiocomposite resulting in high loading of r-IgGs. BSA/r-IgGs/CH-NanoCeO2/ITO immunoelectrode exhibits improved linearity (0.25-6.0 ng/dl), detection limit (0.25 ng/dl), response time (25 s), sensitivity (18 μA/ng dl-1 cm-2), and regression coefficient (r2˜0.997).

  19. Cerium-activated sol-gel silica glasses for radiation dosimetry in harsh environment

    NASA Astrophysics Data System (ADS)

    El Hamzaoui, Hicham; Capoen, Bruno; Helou, Nissrine Al; Bouwmans, Géraud; Ouerdane, Youcef; Boukenter, Aziz; Girard, Sylvain; Marcandella, Claude; Duhamel, Olivier; Chadeyron, Geneviève; Mahiou, Rachid; Bouazaoui, Mohamed

    2016-04-01

    Cerium-doped silica glass has been prepared for ionizing radiation dosimetry applications, using the sol-gel route and densification under different atmospheres. In comparison with the glass densified under air atmosphere, the one obtained after sintering the xerogel under helium gas presents improved optical properties, with an enhancement of the photoluminescence quantum yield up to 33%, which is attributed to a higher Ce3+ ions concentration. Such a glassy rod has been jacketed in a quartz tube and then drawn at high temperature to a cane, which has been used as active material in a fibered remote x-ray radiation dosimeter. The sample exhibited a reversible linear radioluminescence intensity response versus the dose rate up to 30 Gy s-1. These results confirm the potentialities of this material for in vivo or high rate dose remote dosimetry measurements.

  20. Adsorption of Magnesium Sulfate from Desulfurization Industrial Wastewater by Nano-Cerium Loaded Recycled Aggregates.

    PubMed

    Yoon, Hyung-Sun; Bak, Somi; Seo, Seong-Gyu; Choi, Jeongdong; Kim, Eun-Sik

    2016-02-01

    In this research, the recycled aggregates (RAs) from blast furnace were solidified with nano-cerium (Ce), and applied to reduce the ionic species (e.g., magnesium sulfate) in the desulfurization industrial wastewater. Static batch experiments were performed based on different loading of recycled aggregates. Sulfate sorption isotherm studies were performed by Langmuir adsorption model. The physical morphologies were determined using scanning electron microscope. The results presented that the partial ions were captured with the different loading of the recycled aggregates during the batch tests. It was observed that 8 hr batch reaction equilibrated the electrical conductivity reduction, and 13% mass loading was estimated an optimal dosage of adsorbent. This study showed the nano-Ce loaded RAs could reduce ionic species in wastewater, and expected to be an economical adsorbent for wastewater treatment process.

  1. The induction of angiogenesis by cerium oxide nanoparticles through the modulation of oxygen in intracellular environments

    PubMed Central

    Das, Soumen; Singh, Sanjay; Dowding, Janet M.; Oommen, Saji; Kumar, Amit; Sayle, Thi X. T.; Saraf, Shashank; Patra, Chitta Ranjan; Vlahakis, Nicholas E.; Sayle, Dean C.; Self, William T.; Seal, Sudipta

    2012-01-01

    Angiogenesis is the formation of new blood vessels from existing blood vessels and is critical for many physiological and pathophysiological processes. In this study we have shown the unique property of cerium oxide nanoparticle (CNPs) to induce angiogenesis, observed using both in vitro and in vivo model systems. In particular, CNPs trigger angiogenesis by modulating the intracellular oxygen environment and stabilizing hypoxia inducing factor 1α endogenously. Furthermore, correlations between angiogenesis induction and CNPs physicochemical properties including: surface Ce3+/Ce4+ ratio, surface charge, size, and shape were also explored. High surface area and increased Ce3+/Ce4+ ratio make CNPs more catalytically active towards regulating intracellular oxygen, which in turn led to more robust induction of angiogenesis. Atomistic simulation was also used, in partnership with in vitro and in vivo experimentation, to reveal that the surface reactivity of CNPs and facile oxygen transport promotes pro-angiogenesis. PMID:22858004

  2. Adsorption of Magnesium Sulfate from Desulfurization Industrial Wastewater by Nano-Cerium Loaded Recycled Aggregates.

    PubMed

    Yoon, Hyung-Sun; Bak, Somi; Seo, Seong-Gyu; Choi, Jeongdong; Kim, Eun-Sik

    2016-02-01

    In this research, the recycled aggregates (RAs) from blast furnace were solidified with nano-cerium (Ce), and applied to reduce the ionic species (e.g., magnesium sulfate) in the desulfurization industrial wastewater. Static batch experiments were performed based on different loading of recycled aggregates. Sulfate sorption isotherm studies were performed by Langmuir adsorption model. The physical morphologies were determined using scanning electron microscope. The results presented that the partial ions were captured with the different loading of the recycled aggregates during the batch tests. It was observed that 8 hr batch reaction equilibrated the electrical conductivity reduction, and 13% mass loading was estimated an optimal dosage of adsorbent. This study showed the nano-Ce loaded RAs could reduce ionic species in wastewater, and expected to be an economical adsorbent for wastewater treatment process. PMID:27433701

  3. Sorptive separation of yttrium and cerium on a weakly basic anionite

    NASA Astrophysics Data System (ADS)

    Cheremisina, O. V.; Ponomareva, M. A.; Chirkst, D. E.; Lobacheva, O. L.; Shul'gin, I. A.

    2015-01-01

    The sorption of complex yttrium ions with Trilon B onto the weakly basic anionite D-403 in nitrate form from an acidic medium at pH 3 with constant ionic strength (NaNO3, 1 mol/kg) is investigated. A thermodynamic evaluation of the sorption isotherm of anionic yttrium complexes is performed using a method based on the linearization of the equation of the law of active mass, modified for ionic exchange reactions. The ionic exchange constant, the Gibbs free energy of ionic exchange, the capacity of the anionite, and the sorption limit of ethylenediaminetetraacetatoyttrate ions (EDTA yttrate ions) are calculated. Using a frontal version of ion exchange chromatography, cerium and yttrium are separated on D-403 anionite with a fraction of pure yttrium at the column outlet of no less than 30%.

  4. Optical Evidence of Itinerant-Localized Crossover of 4f Electrons in Cerium Compounds

    NASA Astrophysics Data System (ADS)

    Kimura, Shin-ichi; Kwon, Yong Seung; Matsumoto, Yuji; Aoki, Haruyoshi; Sakai, Osamu

    2016-08-01

    Cerium (Ce)-based heavy-fermion materials have a characteristic double-peak structure (mid-IR peak) in the optical conductivity [σ(ω)] spectra originating from the strong conduction (c)-f electron hybridization. To clarify the behavior of the mid-IR peak at a low c-f hybridization strength, we compared the σ(ω) spectra of the isostructural antiferromagnetic and heavy-fermion Ce compounds with the calculated unoccupied density of states and the spectra obtained from the impurity Anderson model. With decreasing c-f hybridization intensity, the mid-IR peak shifts to the low-energy side owing to the renormalization of the unoccupied 4f state, but suddenly shifts to the high-energy side owing to the f-f on-site Coulomb interaction at a slight localized side from the quantum critical point (QCP). This finding gives us information on the change in the electronic structure across QCP.

  5. Impact of electrolyte composition on the performance of the zinc-cerium redox flow battery system

    NASA Astrophysics Data System (ADS)

    Nikiforidis, Georgios; Berlouis, Léonard; Hall, David; Hodgson, David

    2013-12-01

    The zinc-cerium redox flow battery has the highest open circuit cell voltage (Ecell = 2.4 V) of all the common redox flow battery (RFB) systems being investigated. In this paper, carbon polymer composite materials based on polyvinyl ester and polyvinylidene difluoride are investigated as the negative electrode for this RFB system. Electrolyte composition, particularly on the negative side, is found to play a key role in maintaining high (˜90%) coulombic efficiencies for the different charge durations, from 10 min to 4 h, examined. Energy efficiencies >60% are obtained for temperatures in the range 45 °C-55 °C when the zinc ion concentration in the methanesulfonic acid electrolyte is 2.5 mol dm-3. No dependence of the energy efficiency on the flow velocity is found, over the range 7.5 cm s-1-13.5 cm-1.

  6. Predicting Cerium + H2O Cluster Formation with Simulated and Experimental Spectroscopy

    NASA Astrophysics Data System (ADS)

    Topolski, Josey E.; Kafader, Jared O.; Ray, Manisha; Chick Jarrold, Caroline

    2016-06-01

    Ceria (CeO2) has been established as a good support in heterogeneous catalysts for the water gas shift reaction. This study looks into cerium's reactivity with water, a water gas shift reagent, and aims to build an understanding of the three reactions which can occur: direct oxidation, -OH abstraction, and H2O addition. Through the use of anion photoelectron spectroscopy and density functional theory calculations we have been able to determine that the reactivity is dependent on (1) the oxidation states of the metal centers, (2) the availability of 5d orbitals to form metal oxide bonds, and (3) the presence of electrons in the 6s* orbital. The results of this study can be used to inform design of catalytic materials for the water gas shift reaction.

  7. Transition Probabilities for Neutral Cerium from Boltzmann Analysis of Fourier Transform Spectra

    NASA Astrophysics Data System (ADS)

    Nitz, D. E.; Curry, J. J.; Buuck, M. J.; Mitchell, N. P.; Demann, A. D.; Shull, W. E.

    2012-06-01

    The recent availability of a large set of absolute transition probabilities for neutral cerium (Lawler et. al., J. Phys. B 43, 85701 (2010)) makes it possible to investigate the relative populations of the upper levels of these lines in radiometrically-calibrated spectra. In cases where these populations can be characterized by a single effective Boltzmann temperature, applying this temperature enables one to determine additional absolute transition probabilities for observable decay branches of nearby levels. While not as accurate as measurements based on branching fractions and lifetimes, the method can be applied to levels whose lifetimes are not known and does not require accounting for all of the branches. We are analyzing Fourier Transform spectra from NIST and from the National Solar Observatory data archive at Kitt Peak via this technique, seeking to increase the set of known transition probabilities for Ce I by a factor of 2-3. A summary of results obtained to date will be presented.

  8. Sensitization of Pancreatic Cancer Cells to Radiation by Cerium Oxide Nanoparticle-Induced ROS Production

    PubMed Central

    Wason, Melissa S.; Colon, Jimmie; Das, Soumen; Seal, Sudipta; Turkson, James; Zhao, Jihe; Baker, Cheryl H.

    2012-01-01

    Side effect of radiation therapy (RT) remains the most challenging issue for pancreatic cancer treatment. In this report we determined whether and how cerium oxide nanoparticles (CONPs) sensitize pancreatic cancer cells to RT. CONP pretreatment enhanced radiation-induced reactive oxygen species (ROS) production preferentially in acidic cell-free solutions as well as acidic human pancreatic cancer cells. In acidic environments, CONPs favor the scavenging of superoxide radical over the hydroxyl peroxide resulting in accumulation of the latter whereas in neutral pH CONPs scavenge both. CONP treatment prior to RT markedly potentiated the cancer cell apoptosis both in culture and in tumors and the inhibition of the pancreatic tumor growth without harming the normal tissues or host mice. Taken together, these results identify CONPs as a potentially novel RT-sensitizer as well as protectant for improving pancreatic cancer treatment. PMID:23178284

  9. Potential of using cerium oxide nanoparticles for protecting healthy tissue during accelerated partial breast irradiation (APBI)

    PubMed Central

    Ouyang, Zi; Mainali, Madan Kumar; Sinha, Neeharika; Strack, Guinevere; Altundal, Yucel; Hao, Yao; Winningham, Thomas Andrew; Sajo, Erno; Celli, Jonathan; Ngwa, Wilfred

    2016-01-01

    The purpose of this study is to investigate the feasibility of using cerium oxide nanoparticles (CONPs) as radical scavengers during accelerated partial breast irradiation (APBI) to protect normal tissue. We hypothesize that CONPs can be slowly released from the routinely used APBI balloon applicators—via a degradable coating—and protect the normal tissue on the border of the lumpectomy cavity over the duration of APBI. To assess the feasibility of this approach, we analytically calculated the initial concentration of CONPs required to protect normal breast tissue from reactive oxygen species (ROS) and the time required for the particles to diffuse to various distances from the lumpectomy wall. Given that cerium has a high atomic number, we took into account the possible inadvertent dose enhancement that could occur due to the photoelectric interactions with radiotherapy photons. To protect against a typical MammoSite treatment fraction of 3.4 Gy, 5 ng-g−1 of CONPs is required to scavenge hydroxyl radicals and hydrogen peroxide. Using 2 nm sized NPs, with an initial concentration of 1 mg-g−1, we found that 2–10 days of diffusion is required to obtain desired concentrations of CONPs in regions 1–2 cm away from the lumpectomy wall. The resultant dose enhancement factor (DEF) is less than 1.01 under such conditions. Our results predict that CONPs can be employed for radioprotection during APBI using a new design in which balloon applicators are coated with the NPs for sustained/controlled in-situ release from within the lumpectomy cavity. PMID:27053452

  10. Interactive effects of cerium oxide and diesel exhaust nanoparticles on inducing pulmonary fibrosis

    PubMed Central

    Ma, Jane Y.C.; Young, Shih-Houng; Mercer, Robert R.; Barger, Mark; Schwegler-Berry, Diane; Ma, Joseph K.; Castranova, Vincent

    2015-01-01

    Cerium compounds have been used as a fuel-borne catalyst to lower the generation of diesel exhaust particles (DEPs), but are emitted as cerium oxide nanoparticles (CeO2) along with DEP in the diesel exhaust. The present study investigates the effects of the combined exposure to DEP and CeO2 on the pulmonary system in a rat model. Specific pathogen-free male Sprague–Dawley rats were exposed to CeO2 and/or DEP via a single intratracheal instillation and were sacrificed at various time points post-exposure. This investigation demonstrated that CeO2 induces a sustained inflammatory response, whereas DEP elicits a switch of the pulmonary immune response from Th1 to Th2. Both CeO2 and DEP activated AM and lymphocyte secretion of the proinflammatory cytokines IL-12 and IFN-γ respectively. However, only DEP enhanced the anti-inflammatory cytokine IL-10 production in response to ex vivo LPS or Concanavalin A challenge that was not affected by the presence of CeO2, suggesting that DEP suppresses host defense capability by inducing the Th2 immunity. The micrographs of lymph nodes show that the particle clumps in DEP + CeO2 were significantly larger than CeO2 or DEP, exhibiting dense clumps continuous throughout the lymph nodes. Morphometric analysis demonstrates that the localization of collagen in the lung tissue after DEP + CeO2 reflects the combination of DEP-exposure plus CeO2-exposure. At 4 weeks post-exposure, the histological features demonstrated that CeO2 induced lung phospholipidosis and fibrosis. DEP induced lung granulomas that were not significantly affected by the presence of CeO2 in the combined exposure. Using CeO2 as diesel fuel catalyst may cause health concerns. PMID:24793434

  11. Air, aqueous and thermal stabilities of Ce3+ ions in cerium oxide nanoparticle layers with substrates.

    PubMed

    Naganuma, Tamaki; Traversa, Enrico

    2014-06-21

    Abundant oxygen vacancies coexisting with Ce(3+) ions in fluorite cerium oxide nanoparticles (CNPs) have the potential to enhance catalytic ability, but the ratio of unstable Ce(3+) ions in CNPs is typically low. Our recent work, however, demonstrated that the abundant Ce(3+) ions created in cerium oxide nanoparticle layers (CNPLs) by Ar ion irradiation were stable in air at room temperature. Ce valence states in CNPs correlate with the catalytic ability that involves redox reactions between Ce(3+) and Ce(4+) ions in given application environments (e.g. high temperature in carbon monoxide gas conversion and immersion conditions in biomedical applications). To better understand the mechanism by which Ce(3+) ions achieve stability in CNPLs, we examined (i) extra-long air-stability, (ii) thermal stability up to 500 °C, and (iii) aqueous stability of Ce(3+) ions in water, buffer solution and cell culture medium. It is noteworthy that air-stability of Ce(3+) ions in CNPLs persisted for more than 1 year. Thermal stability results showed that oxidation of Ce(3+) to Ce(4+) occurred at 350 °C in air. Highly concentrated Ce(3+) ions in ultra-thin CNPLs slowly oxidized in water within 1 day, but stability was improved in the cell culture medium. Ce(3+) stability of CNPLs immersed in the medium was associated with phosphorus adsorption on the Ce(3+) sites. This study also illuminates the potential interaction mechanisms of stable Ce(3+) ions in CNPLs. These findings could be utilized to understand catalytic mechanisms of CNPs with abundant oxygen vacancies in their application environments.

  12. Falsely raised whole blood chloride caused by systemic absorption of cerium nitrate cream for burns.

    PubMed

    Ha, Leah Y; Woollard, Gerald A; Chiu, Weldon W

    2015-03-01

    Whole blood, serum or plasma chloride is almost exclusively measured by potentiometry with an ion-selective chloride electrode which utilizes membrane selectivity to chloride ions. Other anions such as bromide, iodide and thiosulphate can interfere but usually are not present in high enough concentration to cause significant cross reactivity. A patient from our burns unit had serial chloride measurements on a Radiometer ABL800 blood gas analyser. The results were higher in contrast to plasma measurements on the Abbott Architect Ci8200, which were within reference intervals and in line with the patient's pathophysiological status. This indicated a likely interference with the blood gas analyser chloride estimation. The chloride results on the ABL800 for 3rd, 4th and 5th day after the burn accident were 170, 137 and 119 mmol/L. Corresponding plasma chloride results on the Ci8200 were all around 105 mmol/L. Nitrate was found to be markedly elevated in these samples, and the results were 6.7, 4.9 and 1.1 mmol/L, respectively (reference limit < 0.08 mmol/L). To further demonstrate nitrate was the causative agent, pooled plasma spiked with 7 mmol/L of sodium nitrate caused a rise in the ABL800 chloride from 105 to 202 mmol/L. Later we confirmed that the patient was topically medicated with cerium nitrate cream (Flammacerium®, Sinclair IS Pharma, UK) for his burns. In summary, the results clearly indicated nitrate was the interferent with the ABL800 chloride estimation and the source was the topical burns cerium nitrate cream.

  13. Cerium stable isotope ratios in ferromanganese deposits and their potential as a paleo-redox proxy

    NASA Astrophysics Data System (ADS)

    Nakada, Ryoichi; Takahashi, Yoshio; Tanimizu, Masaharu

    2016-05-01

    The cerium (Ce) anomaly observed in rare earth element (REE) patterns has been used to estimate the redox state of paleo-marine environments. Cerium is unique because it forms tetravalent cations under oxic conditions, in contrast to the other REEs that occur in a trivalent state. This characteristic leads to anomalously high or low Ce concentrations relative to neighboring REEs. However, the use of Ce anomaly as a paleo-redox proxy is not well calibrated. This study shows that coupling of the Ce anomaly and Ce stable isotope ratio (δ142Ce) is more quantitative redox proxy to distinguish suboxic and oxic redox conditions. Our results revealed a progressive enrichment in heavy Ce isotopes in consecutive formations of iron (Fe) and manganese (Mn) precipitate from hot spring water without any associated change in REE patterns. The δ142Ce values of Mn precipitates were approximately 0.35‰ heavier than those of the Fe precipitates, which was consistent with experiment-based predictions. The δ142Ce values of marine ferromanganese deposits with three different formation processes were hydrogenetic (+0.25‰) > diagenetic (+0.10‰) ⩾ hydrothermal (+0.05‰), which also reflects redox conditions of their formation environment. These observations suggest that the Ce stable isotope ratios yield more quantitative information regarding redox state than REE patterns alone. We thus suggest that this novel proxy can be successfully utilized to reconstruct marine redox states, particularly from slightly oxic to highly oxic conditions such as the Great Oxidation Event (GOE).

  14. Interactive effects of cerium oxide and diesel exhaust nanoparticles on inducing pulmonary fibrosis.

    PubMed

    Ma, Jane Y C; Young, Shih-Houng; Mercer, Robert R; Barger, Mark; Schwegler-Berry, Diane; Ma, Joseph K; Castranova, Vincent

    2014-07-15

    Cerium compounds have been used as a fuel-borne catalyst to lower the generation of diesel exhaust particles (DEPs), but are emitted as cerium oxide nanoparticles (CeO2) along with DEP in the diesel exhaust. The present study investigates the effects of the combined exposure to DEP and CeO2 on the pulmonary system in a rat model. Specific pathogen-free male Sprague-Dawley rats were exposed to CeO2 and/or DEP via a single intratracheal instillation and were sacrificed at various time points post-exposure. This investigation demonstrated that CeO2 induces a sustained inflammatory response, whereas DEP elicits a switch of the pulmonary immune response from Th1 to Th2. Both CeO2 and DEP activated AM and lymphocyte secretion of the proinflammatory cytokines IL-12 and IFN-γ, respectively. However, only DEP enhanced the anti-inflammatory cytokine IL-10 production in response to ex vivo LPS or Concanavalin A challenge that was not affected by the presence of CeO2, suggesting that DEP suppresses host defense capability by inducing the Th2 immunity. The micrographs of lymph nodes show that the particle clumps in DEP+CeO2 were significantly larger than CeO2 or DEP, exhibiting dense clumps continuous throughout the lymph nodes. Morphometric analysis demonstrates that the localization of collagen in the lung tissue after DEP+CeO2 reflects the combination of DEP-exposure plus CeO2-exposure. At 4 weeks post-exposure, the histological features demonstrated that CeO2 induced lung phospholipidosis and fibrosis. DEP induced lung granulomas that were not significantly affected by the presence of CeO2 in the combined exposure. Using CeO2 as diesel fuel catalyst may cause health concerns.

  15. Potential of using cerium oxide nanoparticles for protecting healthy tissue during accelerated partial breast irradiation (APBI).

    PubMed

    Ouyang, Zi; Mainali, Madan Kumar; Sinha, Neeharika; Strack, Guinevere; Altundal, Yucel; Hao, Yao; Winningham, Thomas Andrew; Sajo, Erno; Celli, Jonathan; Ngwa, Wilfred

    2016-04-01

    The purpose of this study is to investigate the feasibility of using cerium oxide nanoparticles (CONPs) as radical scavengers during accelerated partial breast irradiation (APBI) to protect normal tissue. We hypothesize that CONPs can be slowly released from the routinely used APBI balloon applicators-via a degradable coating-and protect the normal tissue on the border of the lumpectomy cavity over the duration of APBI. To assess the feasibility of this approach, we analytically calculated the initial concentration of CONPs required to protect normal breast tissue from reactive oxygen species (ROS) and the time required for the particles to diffuse to various distances from the lumpectomy wall. Given that cerium has a high atomic number, we took into account the possible inadvertent dose enhancement that could occur due to the photoelectric interactions with radiotherapy photons. To protect against a typical MammoSite treatment fraction of 3.4Gy, 5ng·g(-1) of CONPs is required to scavenge hydroxyl radicals and hydrogen peroxide. Using 2nm sized NPs, with an initial concentration of 1mg·g(-1), we found that 2-10days of diffusion is required to obtain desired concentrations of CONPs in regions 1-2cm away from the lumpectomy wall. The resultant dose enhancement factor (DEF) is less than 1.01 under such conditions. Our results predict that CONPs can be employed for radioprotection during APBI using a new design in which balloon applicators are coated with the NPs for sustained/controlled in-situ release from within the lumpectomy cavity. PMID:27053452

  16. Redox conditions in the Late Cretaceous Chalk Sea: the possible use of cerium anomalies as palaeoredox indicators in the Cenomanian and Turonian Chalk of England

    NASA Astrophysics Data System (ADS)

    Jeans, Christopher V.; Wray, David S.; Williams, C. Terry

    2015-09-01

    The cerium anomalies preserved in the Chalk have been investigated as possible palaeoredox indicators of the Late Cretaceous Sea and its sediment. This has been based upon over a hundred new rare earth element analyses of selected samples and grain size fractions from the Chalk. Particular attention has been given to the methodology of differentiating between the cerium anomalies preserved in the bioclastic calcite and those in carbonate-fluorapatite preserved in the acetic acid insoluble residues of chalks. Variations in the cerium anomaly of different particle size fractions of uncemented chalks suggest that fractionation of rare earth elements between the Chalk's seawater and the various organisms that contributed skeletal material to the bioclastic calcite of the Chalk may have occurred. Post-depositional processes of calcite cementation and late diagenetic sulphidisation have had no apparent effect on the cerium anomaly of the acetic acid insoluble residues. The cerium anomalies associated with the acetic acid insoluble residues from (1) an alternating sequence of chalks and marls from Ballard Cliff (Dorset, UK) typical of Milankovitch cyclicity show a marked diagenetic pattern, whereas those from (2) non-volcanic and volcanic marls display a pattern that is best explained by the variations in the availability of phosphorus and the timing of argillisation of volcanic glass during diagenesis. The general conclusion is drawn that the cerium anomalies preserved in the Chalk can provide an insight into the changing palaeoredox conditions in the Late Cretaceous Sea as well as in the pore fluids of its sediments.

  17. Strong Infrared NLO Tellurides with Multifunction: CsX(II)4In5Te12 (X(II) = Mn, Zn, Cd).

    PubMed

    Lin, Hua; Liu, Yi; Zhou, Liu-Jiang; Zhao, Hua-Jun; Chen, Ling

    2016-05-01

    Chalcogenides are the most promising mid- and far-infrared materials for nonlinear optical (NLO) applications. Yet, most of them are sulfides and selenides, and tellurides are still rare. Herein, we report three new KCd4Ga5S12-structure type NLO-active tellurides, CsX(II)4In5Te12 (X(II) = Mn, Zn, Cd), synthesized by solid-state reactions. The structure features a 3D diamond-like framework constructed by vertex-sharing asymmetric MTe4 tetrahedra that are stacked along the c-axis. CsCd4In5Te12 exhibits the strongest powder second-harmonic generation (SHG) intensity at 2050 nm (0.61 eV) among tellurides to date, 9 × benchmark AgGaS2 in the range of 46-74 μm particle size. The primary studies reveal the 1.42 eV direct band gap and high absorption coefficient in the visible spectral region for CsCd4In5Te12, suggesting it is a new potential solar cell absorber material. In addition, CsMn4In5Te12 also displays a spin-canted antiferromagnetic property below 50 K.

  18. Strong Infrared NLO Tellurides with Multifunction: CsX(II)4In5Te12 (X(II) = Mn, Zn, Cd).

    PubMed

    Lin, Hua; Liu, Yi; Zhou, Liu-Jiang; Zhao, Hua-Jun; Chen, Ling

    2016-05-01

    Chalcogenides are the most promising mid- and far-infrared materials for nonlinear optical (NLO) applications. Yet, most of them are sulfides and selenides, and tellurides are still rare. Herein, we report three new KCd4Ga5S12-structure type NLO-active tellurides, CsX(II)4In5Te12 (X(II) = Mn, Zn, Cd), synthesized by solid-state reactions. The structure features a 3D diamond-like framework constructed by vertex-sharing asymmetric MTe4 tetrahedra that are stacked along the c-axis. CsCd4In5Te12 exhibits the strongest powder second-harmonic generation (SHG) intensity at 2050 nm (0.61 eV) among tellurides to date, 9 × benchmark AgGaS2 in the range of 46-74 μm particle size. The primary studies reveal the 1.42 eV direct band gap and high absorption coefficient in the visible spectral region for CsCd4In5Te12, suggesting it is a new potential solar cell absorber material. In addition, CsMn4In5Te12 also displays a spin-canted antiferromagnetic property below 50 K. PMID:27070041

  19. Panthenol-stabilized cerium dioxide nanoparticles for cosmeceutic formulations against ROS-induced and UV-induced damage.

    PubMed

    Zholobak, N M; Shcherbakov, A B; Bogorad-Kobelska, A S; Ivanova, O S; Baranchikov, A Ye; Spivak, N Ya; Ivanov, V K

    2014-01-01

    A method of panthenol-stabilized cerium dioxide nanoparticles synthesis was developed and their effect on the survival rate of human epidermoid cancer cells HEp-2 and diploid epithelial swine testicular cell line (ST-cells) under oxidative stress conditions induced by hydrogen peroxide introduction and UV irradiation was studied. The results obtained indicate that the use of panthenol as a stabilizer supposedly provides a substantial increase in the efficiency of protection. The degree of protection is determined by panthenol-to-ceria molar ratio. The combination of panthenol and nano-ceria protects biological objects under study from reactive oxygen species (ROS) and UV-irradiation more effectively than individual panthenol or ceria. The protective action of panthenol-stabilized cerium dioxide nanoparticles depends strongly on their composition and the means of their application.

  20. Structure phase transformation and equation of state of cerium metal under pressures up to 51 GPa

    NASA Astrophysics Data System (ADS)

    Ce, Ma; Zuo-Yong, Dou; Hong-Yang, Zhu; Guang-Yan, Fu; Xiao, Tan; Bin, Bai; Peng-Cheng, Zhang; Qi-Liang, Cui

    2016-04-01

    This study presents high pressure phase transitions and equation of states of cerium under pressures up to 51 GPa at room temperature. The angle-dispersive x-ray diffraction experiments are carried out using a high energy synchrotron x-ray source. The bulk moduli of high pressure phases of cerium are calculated using the Birch–Murnaghan equation. We discuss and correct several previous controversial conclusions, which are caused by the measurement accuracy or personal explanation. The c/a axial ratio of ε-Ce has a maximum value at about 29 GPa, i.e., c/a ≈ 1.690. Project supported by the National Natural Science Foundation of China (Grant No. NSAF.U1330115) and the National Major Scientific Instrument and Equipment Development Project of China (Grant No. 2012YQ130234).