Science.gov

Sample records for lanthanum carbide halide

  1. Structural Characterization of Methanol Substituted Lanthanum Halides

    PubMed Central

    Boyle, Timothy J.; Ottley, Leigh Anna M.; Alam, Todd M.; Rodriguez, Mark A.; Yang, Pin; Mcintyre, Sarah K.

    2010-01-01

    The first study into the alcohol solvation of lanthanum halide [LaX3] derivatives as a means to lower the processing temperature for the production of the LaBr3 scintillators was undertaken using methanol (MeOH). Initially the de-hydration of {[La(µ-Br)(H2O)7](Br)2}2 (1) was investigated through the simple room temperature dissolution of 1 in MeOH. The mixed solvate monomeric [La(H2O)7(MeOH)2](Br)3 (2) compound was isolated where the La metal center retains its original 9-coordination through the binding of two additional MeOH solvents but necessitates the transfer of the innersphere Br to the outersphere. In an attempt to in situ dry the reaction mixture of 1 in MeOH over CaH2, crystals of [Ca(MeOH)6](Br)2 (3) were isolated. Compound 1 dissolved in MeOH at reflux temperatures led to the isolation of an unusual arrangement identified as the salt derivative {[LaBr2.75•5.25(MeOH)]+0.25 [LaBr3.25•4.75(MeOH)]−0.25} (4). The fully substituted species was ultimately isolated through the dissolution of dried LaBr3 in MeOH forming the 8-coordinated [LaBr3(MeOH)5] (5) complex. It was determined that the concentration of the crystallization solution directed the structure isolated (4 concentrated; 5 dilute) The other LaX3 derivatives were isolated as [(MeOH)4(Cl)2La(µ-Cl)]2 (6) and [La(MeOH)9](I)3•MeOH (7). Beryllium Dome XRD analysis indicated that the bulk material for 5 appear to have multiple solvated species, 6 is consistent with the single crystal, and 7 was too broad to elucidate structural aspects. Multinuclear NMR (139La) indicated that these compounds do not retain their structure in MeOD. TGA/DTA data revealed that the de-solvation temperatures of the MeOH derivatives 4 – 6 were slightly higher in comparison to their hydrated counterparts. PMID:20514349

  2. Investigation into Nanostructured Lanthanum Halides and CeBr{sub 3} for Nuclear Radiation Detection

    SciTech Connect

    Guss, P., Guise, R., Mukhopadhyay, S., Yuan, D.

    2011-06-22

    This slide-show presents work on radiation detection with nanostructured lanthanum halides and CeBr{sub 3}. The goal is to extend the gamma energy response on both low and high-energy regimes by demonstrating the ability to detect low-energy x-rays and relatively high-energy activation prompt gamma rays simultaneously using the nano-structured lanthanum bromide, lanthanum fluoride, cerium bromide, or other nanocrystal material. Homogeneous and nano structure cases are compared.

  3. Lanthanum halide scintillators for time-of-flight 3-D pet

    DOEpatents

    Karp, Joel S [Glenside, PA; Surti, Suleman [Philadelphia, PA

    2008-06-03

    A Lanthanum Halide scintillator (for example LaCl.sub.3 and LaBr.sub.3) with fast decay time and good timing resolution, as well as high light output and good energy resolution, is used in the design of a PET scanner. The PET scanner includes a cavity for accepting a patient and a plurality of PET detector modules arranged in an approximately cylindrical configuration about the cavity. Each PET detector includes a Lanthanum Halide scintillator having a plurality of Lanthanum Halide crystals, a light guide, and a plurality of photomultiplier tubes arranged respectively peripherally around the cavity. The good timing resolution enables a time-of-flight (TOF) PET scanner to be developed that exhibits a reduction in noise propagation during image reconstruction and a gain in the signal-to-noise ratio. Such a PET scanner includes a time stamp circuit that records the time of receipt of gamma rays by respective PET detectors and provides timing data outputs that are provided to a processor that, in turn, calculates time-of-flight (TOF) of gamma rays through a patient in the cavity and uses the TOF of gamma rays in the reconstruction of images of the patient.

  4. Nanostructured Lanthanum Halides and CeBr3 for Nuclear Radiation and Detection

    SciTech Connect

    Paul Guss, Sanjoy Mukhopadhyay, Ron Guise, Ding Yuan

    2010-06-09

    Scintillator materials are used to detect, and in some cases identify, gamma rays. Higher performance scintillators are expensive, hard to manufacture, fragile, and sometimes require liquid nitrogen or cooling engines. But whereas lower-quality scintillators are cheap, easy to manufacture, and more rugged, their performance is lower. At issue: can the desirable qualities of high-and low-performance scintillators be combined to achieve better performance at lower cost? Preliminary experiments show that a LaF{sub 3}:Ce oleic acid-based nanocomposite exhibits a photopeak when exposed to {sup 137}Cs source gamma-radiation. The chemical synthesis of the cerium-doped lanthanum halide nanoparticles are scalable and large quantities of material can be produced at a time, unlike typical crystal growth processes such as the Bridgeman process. Using a polymer composite (Figure 1), produced by LANL, initial measurements of the unloaded and 8% LaF{sub 3}:Ce-loaded sample have been made using {sup 137}Cs sources. Figure 2 shows an energy spectrum acquired for CeF{sub 3}. The lighter plot is the measured polymer-only spectrum and the black plot is the spectrum from the nanocomposite scintillator. As the development of this material continues, the energy resolution is expected to improve and the photopeak-to-Compton ratio will become greater at higher loadings. These measurements show the expected Compton edge in the polymer-only sample, and the Compton edge and photo-peak expected in the nanophosphor composites that LANL has produced. Using a porous VYCORR with CdSe/ZnS core shell quantum dots, Letant has demonstrated that he has obtained signatures of the 241Am photopeak with energy resolution as good at NaI (Figure 3). We begin with the fact that CeBr{sub 3} crystals do not have a self-activity component as strong as the lanthanum halides. The radioactive 0.090% {sup 138}La component of lanthanum leads to significant self-activity, which will be a problem for very large

  5. Application of lanthanum halide scintillators and low-resolution dense plastics for modern MC&A needs.

    SciTech Connect

    Chung, K.; Belian, A. P.; McKigney E. A.; Russo, P. A.

    2004-01-01

    Recent developments in lanthanum halide scintillators and low-resolution dense plastics give breadth to gamma-ray methods of nuclear material detection suitable for modern MC and A needs. Demanding goals for modernization of MC and A cover both portable and continuous on-line measurement applications that are quantitative for inventory/verification, and that serve those quantitative measurement needs plant-wide. Improved performance (sensitivity and reoslution) is important for portable applications in which a single detector must measure many types of materials. Budget is a major issue for continuous inventory measurements with hundreds or even thousands of detectors placed throughout a facility. Experimentally proven resolution of under 4% for 662 keV {sup 137}Cs gamma rays measured with large cerium-doped LaCl{sub 3} (lanthanum chloride) crystals set a new performance standard for versatile, efficient portable applications comparable in price to NaI(Tl), which has been dominant for decades. While the relatively high cost of crystals remains an obstacle for the application of very large numbers of lanthanum halide scintillators as distributed networked detectors, scintillators made from high-density plastic offer a different type of solution for these gamma-ray measurements. Compared to lanthanum halide crystals they are inexpensive and can be larger in size. Despite lower resolution than NaI(Tl), a quantitative interpretation of the photopeak response of the low-cost dense plastic detectors can be tailored to the unique mechanical and spectral properties of different materials at each of hundreds of fixed on-line locations in a plant. This paper describes the properties and presents experimental results for the two new spectrometer types that, together, bracket NaI(Tl) detectors in both performance and cost, fulfilling modern demands for portable and continuous on-line accountability of uranium and plutonium.

  6. Theoretical investigation of structural and thermodynamic properties of lanthanum carbides LaC{sub n} (n=2{endash}6)

    SciTech Connect

    Roszak, S. |; Balasubramanian, K.

    1997-01-01

    Theoretical studies of monolanthanum carbides, LaC{sub n} for n=2{endash}6, are presented. The fan structures were found as ground states in most cases studied. The computed enthalpies of formation of LaC{sub n} and atomization energies of these species are close to the corresponding experimental data. The agreement is even closer when experimental Gibbs energy functions are corrected using theoretical ground state structures and partition functions. The La{endash}C bond is strongly ionic due to electronic charge transfer from lanthanum to carbon atoms. {copyright} {ital 1997 American Institute of Physics.}

  7. Fabrication of large-volume, low-cost ceramic lanthanum halide scintillators for gamma ray detection : final report for DHS/DNDO/TRDD project TA-01-SL01.

    SciTech Connect

    Boyle, Timothy J.; Ottley, Leigh Anna M.; Yang, Pin; Chen, Ching-Fong; Sanchez, Margaret R.; Bell, Nelson Simmons

    2008-10-01

    This project uses advanced ceramic processes to fabricate large, optical-quality, polycrystalline lanthanum halide scintillators to replace small single crystals produced by the conventional Bridgman growth method. The new approach not only removes the size constraint imposed by the growth method, but also offers the potential advantages of both reducing manufacturing cost and increasing production rate. The project goal is to fabricate dense lanthanum halide ceramics with a preferred crystal orientation by applying texture engineering and solid-state conversion to reduce the thermal mechanical stress in the ceramic and minimize scintillation light scattering at grain boundaries. Ultimately, this method could deliver the sought-after high sensitivity and <3% energy resolution at 662 keV of lanthanum halide scintillators and unleash their full potential for advanced gamma ray detection, enabling rapid identification of radioactive materials in a variety of practical applications. This report documents processing details from powder synthesis, seed particle growth, to final densification and texture development of cerium doped lanthanum bromide (LaBr{sub 3}:Ce{sup +3}) ceramics. This investigation demonstrated that: (1) A rapid, flexible, cost efficient synthesis method of anhydrous lanthanum halides and their solid solutions was developed. Several batches of ultrafine LaBr{sub 3}:Ce{sup +3} powder, free of oxyhalide, were produced by a rigorously controlled process. (2) Micron size ({approx} 5 {micro}m), platelet shape LaBr{sub 3} seed particles of high purity can be synthesized by a vapor phase transport process. (3) High aspect-ratio seed particles can be effectively aligned in the shear direction in the ceramic matrix, using a rotational shear-forming process. (4) Small size, highly translucent LaBr{sub 3} (0.25-inch diameter, 0.08-inch thick) samples were successfully fabricated by the equal channel angular consolidation process. (5) Large size, high density

  8. Two-dimensional rectangular tantalum carbide halides TaCX (X = Cl, Br, I): novel large-gap quantum spin Hall insulators

    NASA Astrophysics Data System (ADS)

    Zhou, Liujiang; Shi, Wujun; Sun, Yan; Shao, Bin; Felser, Claudia; Yan, Binghai; Frauenheim, Thomas

    2016-09-01

    Quantum spin Hall (QSH) insulates exist in special two-dimensional (2D) semiconductors, possessing the quantized spin-Hall conductance that are topologically protected from backscattering. Based on the first-principles calculations, we predict a novel family of QSH insulators in 2D tantalum carbide halides TaCX (X = Cl, Br, and I) with unique rectangular lattice and large direct energy gaps. The mechanism for 2D QSH effect originates from an intrinsic d-d band inversion in the process of chemical bonding. Further, stain and intrinsic electric field can be used to tune the electronic structure and enhance the energy gap. TaCX nanoribbon, which has the single-Dirac-cone edge states crossing the bulk band gap, exhibits a linear dispersion with a high Fermi velocity comparable to that of graphene. These 2D materials with considerable nontrivial gaps promise great application potential in the new generation of dissipationless electronics and spintronics.

  9. The gas phase emitter effect of lanthanum within ceramic metal halide lamps and its dependence on the La vapor pressure and operating frequency

    SciTech Connect

    Ruhrmann, C.; Hoebing, T.; Bergner, A.; Groeger, S.; Awakowicz, P.; Mentel, J.; Denissen, C.; Suijker, J.

    2015-08-07

    The gas phase emitter effect increases the lamp lifetime by lowering the work function and, with it, the temperature of the tungsten electrodes of metal halide lamps especially for lamps in ceramic vessels due to their high rare earth pressures. It is generated by a monolayer on the electrode surface of electropositive atoms of certain emitter elements, which are inserted into the lamp bulb by metal iodide salts. They are vaporized, dissociated, ionized, and deposited by an emitter ion current onto the electrode surface within the cathodic phase of lamp operation with a switched-dc or ac-current. The gas phase emitter effect of La and the influence of Na on the emitter effect of La are studied by spatially and phase-resolved pyrometric measurements of the electrode tip temperature, La atom, and ion densities by optical emission spectroscopy as well as optical broadband absorption spectroscopy and arc attachment images by short time photography. An addition of Na to the lamp filling increases the La vapor pressure within the lamp considerably, resulting in an improved gas phase emitter effect of La. Furthermore, the La vapor pressure is raised by a heating of the cold spot. In this way, conditions depending on the La vapor pressure and operating frequency are identified, at which the temperature of the electrodes becomes a minimum.

  10. The gas phase emitter effect of lanthanum within ceramic metal halide lamps and its dependence on the La vapor pressure and operating frequency

    NASA Astrophysics Data System (ADS)

    Ruhrmann, C.; Hoebing, T.; Bergner, A.; Groeger, S.; Denissen, C.; Suijker, J.; Awakowicz, P.; Mentel, J.

    2015-08-01

    The gas phase emitter effect increases the lamp lifetime by lowering the work function and, with it, the temperature of the tungsten electrodes of metal halide lamps especially for lamps in ceramic vessels due to their high rare earth pressures. It is generated by a monolayer on the electrode surface of electropositive atoms of certain emitter elements, which are inserted into the lamp bulb by metal iodide salts. They are vaporized, dissociated, ionized, and deposited by an emitter ion current onto the electrode surface within the cathodic phase of lamp operation with a switched-dc or ac-current. The gas phase emitter effect of La and the influence of Na on the emitter effect of La are studied by spatially and phase-resolved pyrometric measurements of the electrode tip temperature, La atom, and ion densities by optical emission spectroscopy as well as optical broadband absorption spectroscopy and arc attachment images by short time photography. An addition of Na to the lamp filling increases the La vapor pressure within the lamp considerably, resulting in an improved gas phase emitter effect of La. Furthermore, the La vapor pressure is raised by a heating of the cold spot. In this way, conditions depending on the La vapor pressure and operating frequency are identified, at which the temperature of the electrodes becomes a minimum.

  11. Lanthanum carbonate (Shire).

    PubMed

    Locatelli, Francesco; D'Amico, Marco; Pontoriero, Giuseppe

    2003-07-01

    Shire Pharmaceuticals Group plc, under exclusive license from AnorMED Inc (a subsidiary of Johnson Matthey), is developing lanthanum carbonate, a phosphate-binding lanthanum salt, for the potential treatment of hyperphosphatemia in dialysis patients. It is currently in pre-registration in the US, Canada and Western Europe, and earlier stage clinical trials are ongoing in Japan.

  12. Metals fact sheet - lanthanum

    SciTech Connect

    1995-04-01

    Mosander was the first to extract the elusive rare earth, lanthanum, from unrefined cerium nitrate in 1839. The name was derived from the Greek word lanthanein, meaning {open_quotes}to escape notice.{close_quotes} Lanthanum is the lightest rare earth and a very malleable metal-soft enough to be cut with a knife. Used primarily as an additive in steels and non-ferrous metals, lanthanum is the lightest rare earth element and one of four rare earths from which mischmetal is made. Additional applications include advanced batteries, optical fibers, and phosphors.

  13. Nickel/magnesium-lanthanum mixed oxide catalyst in the Kumada-coupling.

    PubMed

    Kiss, Arpád; Hell, Zoltán; Bálint, Mária

    2010-01-21

    A new, heterogeneous, magnesium-lanthanum mixed oxide solid base-supported nickel(ii) catalyst was developed. The catalyst was used successfully in the Kumada coupling of aryl halides, especially aryl bromides. The optimal reaction conditions of the coupling were determined.

  14. Stabilized Lanthanum Sulphur Compounds

    NASA Technical Reports Server (NTRS)

    Reynolds, George H. (Inventor); Elsner, Norbert B. (Inventor); Shearer, Clyde H. (Inventor)

    1985-01-01

    Lanthanum sulfide is maintained in the stable cubic phase form over a temperature range of from 500 C to 1500 C by adding to it small amounts of calcium, barium. or strontium. This novel compound is an excellent thermoelectric material.

  15. Method of coating graphite tubes with refractory metal carbides

    DOEpatents

    Wohlberg, C.

    1973-12-11

    A method of coating graphite tubes with a refractory metal carbide is described. An alkali halide is reacted with a metallic oxide, the metallic portion being selected from the IVth or Vth group of the Periodic Table, the resulting salt reacting in turn with the carbon to give the desired refractory metal carbide coating. (Official Gazette)

  16. The Silver Halides

    ERIC Educational Resources Information Center

    Sahyun, M. R. V.

    1977-01-01

    Illustrates the type of fractional bonding for solid silver halides. Treats the silver halides as electron excess compounds, and develops a model of a localized bonding unit that may be iterated in three dimensions to describe the bulk phase. (MLH)

  17. Encephalopathy caused by lanthanum carbonate.

    PubMed

    Fraile, Pilar; Cacharro, Luis Maria; Garcia-Cosmes, Pedro; Rosado, Consolacion; Tabernero, Jose Matias

    2011-06-01

    Lanthanum carbonate is a nonaluminum, noncalcium phosphate-binding agent, which is widely used in patients with end-stage chronic kidney disease. Until now, no significant side-effects have been described for the clinical use of lanthanum carbonate, and there are no available clinical data regarding its tissue stores. Here we report the case of a 59-year-old patient who was admitted with confusional syndrome. The patient received 3750 mg of lanthanum carbonate daily. Examinations were carried out, and the etiology of the encephalopathy of the patient could not be singled out. The lanthanum carbonate levels in serum and cerebrospinal fluid were high, and the syndrome eased after the drug was removed. The results of our study confirm that, in our case, the lanthanum carbonate did cross the blood-brain barrier (BBB). Although lanthanum carbonate seems a safe drug with minimal absorption, this work reveals the problem derived from the increase of serum levels of lanthanum carbonate, and the possibility that it may cross the BBB. Further research is required on the possible pathologies that increase serum levels of lanthanum carbonate, as well as the risks and side-effects derived from its absorption.

  18. Recent advances in technetium halide chemistry.

    PubMed

    Poineau, Frederic; Johnstone, Erik V; Czerwinski, Kenneth R; Sattelberger, Alfred P

    2014-02-18

    (IV)) to d(5) (Tc(II)) is accompanied by the formation of metal-metal bonds in the coordination polyhedra. There is no metal-metal interaction in TcX4, a Tc═Tc double bond is present in α/β-TcCl3, and a Tc≡Tc triple bond is present in α/β-TcCl2. We investigated the thermal behavior of these binary halides in sealed tubes under vacuum at elevated temperature. Technetium tetrachloride decomposes stepwise to α-TcCl3 and β-TcCl2 at 450 °C, while β-TcCl3 converts to α-TcCl3 at 280 °C. The technetium dichlorides disproportionate to Tc metal and TcCl4 above ∼600 °C. At 450 °C in a sealed Pyrex tube, TcBr3 decomposes to Na{[Tc6Br12]2Br}, while TcI3 decomposes to Tc metal. We have used technetium tribromide in the preparation of new divalent complexes; we expect that the other halides will also serve as starting materials for the synthesis of new compounds (e.g., complexes with a Tc3(9+) core, divalent iodide complexes, binary carbides, nitrides, and phosphides, etc.). Technetium halides may also find applications in the nuclear fuel cycle; their thermal properties could be utilized in separation processes using halide volatility. In summary, we hope that these new insights on technetium binary halides will contribute to a better understanding of the chemistry of this fascinating element.

  19. Lanthanum Bromide Detectors for Safeguards Measurements

    SciTech Connect

    Wright, J.

    2011-05-25

    Lanthanum bromide has advantages over other popular inorganic scintillator detectors. Lanthanum bromide offers superior resolution, and good efficiency when compared to sodium iodide and lanthanum chloride. It is a good alternative to high purity germanium detectors for some safeguards applications. This paper offers an initial look at lanthanum bromide detectors. Resolution of lanthanum bromide will be compared lanthanum chloride and sodium-iodide detectors through check source measurements. Relative efficiency and angular dependence will be looked at. Nuclear material spectra, to include plutonium and highly enriched uranium, will be compared between detector types.

  20. Thermodynamic properties of higher lanthanum silicide

    SciTech Connect

    Polotskaya, R.I.

    1988-07-01

    The thermodynamic properties of lanthanum disilicide were examined for the first time in the 960-1050/sup 0/K range by measuring the electromotive force of a galvanic cell based on LaSn, the chlorides of potassium, sodium, and lanthanum, and lanthanum silicide and silicon. Reference electrodes were used to prevent lanthanum interaction with the electrolyte. The alloys were melted in an electric arc furnace in purified argon from lanthanum and silicon and followed by two-stage annealing. It was found that the resulting value of the enthalpy formation differed from the estimated value for lanthanum disilicide calculated by Miedema's model.

  1. Binary technetium halides

    NASA Astrophysics Data System (ADS)

    Johnstone, Erik Vaughan

    In this work, the synthetic and coordination chemistry as well as the physico-chemical properties of binary technetium (Tc) chlorides, bromides, and iodides were investigated. Resulting from these studies was the discovery of five new binary Tc halide phases: alpha/beta-TcCl3, alpha/beta-TcCl 2, and TcI3, and the reinvestigation of the chemistries of TcBr3 and TcX4 (X = Cl, Br). Prior to 2009, the chemistry of binary Tc halides was poorly studied and defined by only three compounds, i.e., TcF6, TcF5, and TcCl4. Today, ten phases are known (i.e., TcF6, TcF5, TcCl4, TcBr 4, TcBr3, TcI3, alpha/beta-TcCl3 and alpha/beta-TcCl2) making the binary halide system of Tc comparable to those of its neighboring elements. Technetium binary halides were synthesized using three methods: reactions of the elements in sealed tubes, reactions of flowing HX(g) (X = Cl, Br, and I) with Tc2(O2CCH3)4Cl2, and thermal decompositions of TcX4 (X = Cl, Br) and alpha-TcCl 3 in sealed tubes under vacuum. Binary Tc halides can be found in various dimensionalities such as molecular solids (TcF6), extended chains (TcF5, TcCl4, alpha/beta-TcCl2, TcBr 3, TcI3), infinite layers (beta-TcCl3), and bidimensional networks of clusters (alpha-TcCl3); eight structure-types with varying degrees of metal-metal interactions are now known. The coordination chemistry of Tc binary halides can resemble that of the adjacent elements: molybdenum and ruthenium (beta-TcCl3, TcBr3, TcI 3), rhenium (TcF5, alpha-TcCl3), platinum (TcCl 4, TcBr4), or can be unique (alpha-TcCl2 and beta-TcCl 2) in respect to other known transition metal binary halides. Technetium binary halides display a range of interesting physical properties that are manifested from their electronic and structural configurations. The thermochemistry of binary Tc halides is extensive. These compounds can selectively volatilize, decompose, disproportionate, or convert to other phases. Ultimately, binary Tc halides may find application in the nuclear fuel

  2. Chlorination of lanthanum oxide.

    PubMed

    Gaviría, Juan P; Navarro, Lucas G; Bohé, Ana E

    2012-03-08

    The reactive system La(2)O(3)(s)-Cl(2)(g) was studied in the temperature range 260-950 °C. The reaction course was followed by thermogravimetry, and the solids involved were characterized by X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy. The results showed that the reaction leads to the formation of solid LaOCl, and for temperatures above 850 °C, the lanthanum oxychloride is chlorinated, producing LaCl(3)(l). The formation of the oxychloride progresses through a nucleation and growth mechanism, and the kinetic analysis showed that at temperatures below 325 °C the system is under chemical control. The influence of diffusive processes on the kinetics of production of LaOCl was evaluated by studying the effect of the reactive gas flow rate, the mass of the sample, and the chlorine diffusion through the boundary layer surrounding the solid sample. The conversion curves were analyzed and fitted according to the Johnson-Mehl-Avrami description, and the reaction order with respect to the chlorine partial pressure was obtained by varying this partial pressure between 10 and 70 kPa. The rate equation was obtained, which includes the influence of the temperature, chlorine partial pressure, and reaction degree.

  3. Ternary Silver Halide Nanocrystals.

    PubMed

    Abeyweera, Sasitha C; Rasamani, Kowsalya D; Sun, Yugang

    2017-07-18

    Nanocrystalline silver halides (AgX) such as AgCl, AgBr, and AgI, a class of semiconductor materials with characteristics of both direct and indirect band gaps, represent the most crucial components in traditional photographic processing. The nanocrystal surfaces provide sensitivity specks that can turn into metallic silver, forming an invisible latent image, upon exposure to light. The photographic processing implies that the AgX nanoparticles possess unique properties. First, pristine AgX nanoparticles absorb light only at low efficiency to convert surface AgX into tiny clusters of silver atoms. Second, AgX nanoparticles represent an excellent class of materials to capture electrons efficiently. Third, small metallic silver clusters can catalyze the reduction of AgX nanoparticles to Ag nanoparticles in the presence of mild reducing reagents, known as self-catalytic reduction. These properties indicate that AgX nanoparticles can be partially converted to metallic silver with high precision, leading to the formation of hybrid AgX/Ag nanoparticles. The nanosized metallic Ag usually exhibit intense absorption bands in the visible spectral region due to their strong surface plasmon resonances, which make the AgX/Ag nanoparticles a class of promising visible-light-driven photocatalysts for environmental remediation and CO2 reduction. Despite the less attention paid to their ability of capturing electrons, AgX nanoparticles might be a class of ideal electron shuttle materials to bridge light absorbers and catalysts on which electrons can drive chemical transformations. In this Account, we focus on ternary silver halide alloy (TSHA) nanoparticles, containing two types of halide ions, which increase the composition complexity of the silver halide nanoparticles. Interdiffusion of halide ions between two types of AgX at elevated temperatures has been developed for fabricating ternary silver halide alloy crystals, such as silver chlorobromide optical fibers for infrared

  4. Preparation of porous lanthanum phosphate with templates

    SciTech Connect

    Onoda, Hiroaki; Ishima, Yuya; Takenaka, Atsushi; Tanaka, Isao

    2009-08-05

    Malonic acid, propionic acid, glycine, n-butylamine, and urea were added to the preparation of lanthanum phosphate from lanthanum nitrate and phosphoric acid solutions. All additives were taken into lanthanum phosphate particles. The additives that have a basic site were easy to contain in precipitates. The addition of templates improved the specific surface area of lanthanum phosphate. The amount of pore, with radius smaller than 4 nm, increased with the addition of templates. The remained additives had influence on the acidic properties of lanthanum phosphate.

  5. Phase separation in lanthanum manganites

    NASA Astrophysics Data System (ADS)

    Sedykh, Vera D.

    2016-10-01

    The structural transformations in doped lanthanum manganites La1-xMexMnO3+δ (Me = Ca, Sr, Ba) (with a small amount of 57Fe (2%) for Mössbauer experiments) have been studied in a wide concentration range of a doping element (0 < x < 0.2) by Mössbauer spectroscopy and X-ray diffraction analysis. A mixture of three orthorhombic phases has been shown to be formed in all these compounds of a stoichiometric composition, i.e., a structural phase separation takes place. The phase relations for different doping element types and contents significantly differ. The reasons of phase separation in lanthanum manganites are discussed.

  6. Ames Lab 101: Lanthanum Decanting

    ScienceCinema

    Riedemann, Trevor

    2016-07-12

    Ames Laboratory scientist Trevor Riedemann explains the process that allows Ames Laboratory to produce some of the purest lanthanum in the world. This and other high-purity rare-earth elements are used to create alloys used in various research projects and play a crucial role in the Planck satellite mission.

  7. Melt synthesis of inorganic nitrides and halides

    NASA Astrophysics Data System (ADS)

    Molstad, Jay Clark

    Novel halide chlorides Sr7Cl2H12, Sr 7Br2H12, and Ba2ClH3 were formed from sodium chloride and strontium metal in sodium metal melts at 900°C. Sr7Br2H12 crystallizes in the anti-Fe 12Zr2P7 structure type, and Sr7Cl 2H12 crystallizes in a slightly distorted variant of this structure. Ba2ClH3 crystallizes in a structure containing infinite two-dimensional sheets of edge-sharing Ba6Cl chlorine-centered octahedra. Single crystals of gallium nitride can be obtained by reaction of gallium metal and dinitrogen gas at 750°C. Small amounts of alkaline earth metals added to the reaction mixture promote the formation of large crystals. Polycrystalline GaN nucleates rapidly under these conditions on the surface of a stainless steel autoclave; nucleation is far less pronounced on tungsten surfaces. Trace concentrations of hydrogen greatly enhance GaN nucleation. Melts of magnesium metal with cerium, gadolinium, and lanthanum were exposed to ammonia and nitrogen gas at temperatures from 700°C to 900°C. Binary rare earth and magnesium nitrides and hydrides are formed, but no ternary compounds are seen. The absence of ternary compounds is discussed in the light of a thermodynamic model predicting ternary formation in these systems.

  8. Silicon carbide

    SciTech Connect

    Ault, N.N.; Crowe, J.T. )

    1991-05-01

    This paper reports that, since silicon carbide (SiC) does not occur in nature, it must be synthesized by a high-temperature chemical reaction. The first commercial production began at the end of the 19th century when Acheson developed a process of reacting sand and coke in a resistance furnace. This process is still the basic SiC manufacturing process used today. High-quality silica sand (99.5% SiO{sub 2}), low-sulfur petroleum coke, and electricity (23.8 MJ/kg) are the major ingredients in the production of SiC. The reaction takes place in a trough-like furnace with a removable refractory side (or some similar configuration) and with permanent refractory ends holding carbon electrodes. When the furnace is started, the carbon electrodes are joined by the graphite core laid the length of the furnace near the center of the mixture which fills the furnace.

  9. DISSOLUTION OF LANTHANUM FLUORIDE PRECIPITATES

    DOEpatents

    Fries, B.A.

    1959-11-10

    A plutonium separatory ore concentration procedure involving the use of a fluoride type of carrier is presented. An improvement is given in the derivation step in the process for plutonium recovery by carrier precipitation of plutonium values from solution with a lanthanum fluoride carrier precipitate and subsequent derivation from the resulting plutonium bearing carrier precipitate of an aqueous acidic plutonium-containing solution. The carrier precipitate is contacted with a concentrated aqueous solution of potassium carbonate to effect dissolution therein of at least a part of the precipitate, including the plutonium values. Any remaining precipitate is separated from the resulting solution and dissolves in an aqueous solution containing at least 20% by weight of potassium carbonate. The reacting solutions are combined, and an alkali metal hydroxide added to a concentration of at least 2N to precipitate lanthanum hydroxide concomitantly carrying plutonium values.

  10. Thermoelectric Properties of Lanthanum Sulfide

    NASA Technical Reports Server (NTRS)

    Wood, C.; Lockwood, R.; Parker, J. B.; Zoltan, A.; Zoltan, L. D.; Danielson, L.; Raag, V.

    1987-01-01

    Report describes measurement of Seebeck coefficient, electrical resistivity, thermal conductivity, and Hall effect in gamma-phase lanthanum sulfide with composition of La3-x S4. Results of study, part of search for high-temperature thermoelectric energy-conversion materials, indicate this sulfide behaves like extrinsic semiconductor over temperature range of 300 to 1,400 K, with degenerate carrier concentration controlled by stoichiometric ratio of La to S.

  11. Thermoelectric Properties of Lanthanum Sulfide

    NASA Technical Reports Server (NTRS)

    Wood, C.; Lockwood, R.; Parker, J. B.; Zoltan, A.; Zoltan, L. D.; Danielson, L.; Raag, V.

    1987-01-01

    Report describes measurement of Seebeck coefficient, electrical resistivity, thermal conductivity, and Hall effect in gamma-phase lanthanum sulfide with composition of La3-x S4. Results of study, part of search for high-temperature thermoelectric energy-conversion materials, indicate this sulfide behaves like extrinsic semiconductor over temperature range of 300 to 1,400 K, with degenerate carrier concentration controlled by stoichiometric ratio of La to S.

  12. Multifunctionality of nanocrystalline lanthanum ferrite

    NASA Astrophysics Data System (ADS)

    Rai, Atma; Thakur, Awalendra K.

    2016-05-01

    Nanocrystalline lanthanum ferrite has been synthesized by adopting modified Pechini route. No evidence of impurity or secondary phase has been detected up to the detection of error limit of X-ray diffractometer (XRD). Rietveld refinement of X-ray diffraction pattern reveals orthorhombic crystal system with space group Pnma (62).Crystallite size and lattice strain was found to be ˜42.8nm and 0.306% respectively. Optical band gap was found to be 2.109 eV, by UV-Visible diffused reflectance spectrum (DRS). Brunauer-Emmet-Teller (BET) surface area was found to be ˜3.45 m2/g. Magnetization-hysteresis (M-H) loop was recorded at room temperature (300K) reveals weak ferromagnetism in Nanocrystalline lanthanum ferrite. The weak ferromagnetism in lanthanum ferrite is due to the uncompensated antiferromagnetic spin ordering. Ferroelectric loop hysteresis observed at room temperature at 100Hz depicts the presence of ferroelectric ordering in LaFeO3.Simultanious presence of magnetic and ferroelectric ordering at room temperature makes it suitable candidate of Multiferroic family.

  13. Multifunctionality of nanocrystalline lanthanum ferrite

    SciTech Connect

    Rai, Atma; Thakur, Awalendra K.

    2016-05-06

    Nanocrystalline lanthanum ferrite has been synthesized by adopting modified Pechini route. No evidence of impurity or secondary phase has been detected up to the detection of error limit of X-ray diffractometer (XRD). Rietveld refinement of X-ray diffraction pattern reveals orthorhombic crystal system with space group Pnma (62).Crystallite size and lattice strain was found to be ∼42.8nm and 0.306% respectively. Optical band gap was found to be 2.109 eV, by UV-Visible diffused reflectance spectrum (DRS). Brunauer-Emmet-Teller (BET) surface area was found to be ∼3.45 m{sup 2}/g. Magnetization-hysteresis (M-H) loop was recorded at room temperature (300K) reveals weak ferromagnetism in Nanocrystalline lanthanum ferrite. The weak ferromagnetism in lanthanum ferrite is due to the uncompensated antiferromagnetic spin ordering. Ferroelectric loop hysteresis observed at room temperature at 100Hz depicts the presence of ferroelectric ordering in LaFeO{sub 3}.Simultanious presence of magnetic and ferroelectric ordering at room temperature makes it suitable candidate of Multiferroic family.

  14. [Histochemical staining methods for lanthanum].

    PubMed

    Miyagawa, Makoto

    2011-09-01

    In recent years lanthanum compounds have been widely used in the optical and electronic industries. Although release of lanthanum (La) into the environment and exposure to humans are feared, acute or chronic biologic effects of La remain to be elucidated. The present study was undertaken to establish the experimental animal model for La toxicity and histological staining methods for La. After intraperitoneal injections of lanthanum chloride, white precipitates deposited on the surface of the liver. Existence of La in the precipitates was confirmed by a X-ray fluorescent microanalysis. Liver tissues from La treated rats were fixed in paraformaldehyde, embedded in paraffin and cut into thin sections which were used as a La containing standard section. Several reagents for histological stains and spectrophotometry for metals were applied in both test-tube experiments and stainings of tissue sections to test for La. Alizarin complexone (ALC) was found of capable of staining La in tissue. A simple new technique used was described for light microscopic detection of La.

  15. PREPARATION OF HALIDES OF PLUTONIUM

    DOEpatents

    Garner, C.S.; Johns, I.B.

    1958-09-01

    A dry chemical method is described for preparing plutonium halides, which consists in contacting plutonyl nitrate with dry gaseous HCl or HF at an elevated temperature. The addition to the reaction gas of a small quantity of an oxidizing gas or a reducing gas will cause formation of the tetra- or tri-halide of plutonium as desired.

  16. Halide laser glasses

    SciTech Connect

    Weber, M.J.

    1982-01-14

    Energy storage and energy extraction are of prime importance for efficient laser action and are affected by the line strengths and linewidths of optical transitions, excited-state lifetimes, nonradiative decay processes, spectroscopic inhomogeneities, nonlinear refractive index, and damage threshold. These properties are all host dependent. To illustrate this, the spectroscopic properties of Nd/sup 3 +/ have been measured in numerous oxide, oxyhalide, and halide glasses. A table summarizes the reported ranges of stimulated emission cross sections, peak wavelengths, linewidths, and radiative lifetimes associated with the /sup 4/F/sub 3/2/ ..-->.. /sup 4/I/sub 11/2/ lasing transition.

  17. Resonant halide perovskite nanoparticles

    NASA Astrophysics Data System (ADS)

    Tiguntseva, Ekaterina Y.; Ishteev, Arthur R.; Komissarenko, Filipp E.; Zuev, Dmitry A.; Ushakova, Elena V.; Milichko, Valentin A.; Nesterov-Mueller, Alexander; Makarov, Sergey V.; Zakhidov, Anvar A.

    2017-09-01

    The hybrid halide perovskites is a prospective material for fabrication of cost-effective optical devices. Unique perovskites properties are used for solar cells and different photonic applications. Recently, perovskite-based nanophotonics has emerged. Here, we consider perovskite like a high-refractive index dielectric material, which can be considered to be a basis for nanoparticles fabrication with Mie resonances. As a result, we fabricate and study resonant perovskite nanoparticles with different sizes. We reveal, that spherical nanoparticles show enhanced photoluminescence signal. The achieved results lay a cornerstone in the field of novel types of organic-inorganic nanophotonics devices with optical properties improved by Mie resonances.

  18. Silver-halide gelatin holograms

    NASA Astrophysics Data System (ADS)

    Chang, B. J.; Winick, K.

    1980-05-01

    The use of a silver-halide gelatin for volume phase holograms having a wide spectral response and lower exposure requirements than alternatives and using commercially available silver salts, is proposed. The main difference between the dichromated gelatin and silver-halide processes is the creation of a hologram latent image, which is given in the form of a hardness differential between exposed and unexposed regions in the silver halide hologram; the differential is in turn created by the reaction products of either tanning development or tanning bleach, which harden the gelatin with link-bonds between molecules.

  19. Actinide halide complexes

    SciTech Connect

    Avens, L.R.; Zwick, B.D.; Sattelberger, A.P.; Clark, D.L.; Watkin, J.G.

    1991-02-07

    A compound of the formula MX{sub n}L{sub m} wherein M = Th, Pu, Np,or Am thorium, X = a halide atom, n = 3 or 4, L is a coordinating ligand selected from the group consisting of aprotic Lewis bases having an oxygen-, nitrogen-, sulfur-, or phosphorus-donor, and m is 3 or 4 for monodentate ligands or is 2 for bidentate ligands, where n + m = 7 or 8 for monodentate ligands or 5 or 6 for bidentate ligands, a compound of the formula MX{sub n} wherein M, X, and n are as previously defined, and a process of preparing such actinide metal compounds including admixing the actinide metal in an aprotic Lewis base as a coordinating solvent in the presence of a halogen-containing oxidant, are provided.

  20. METHOD OF PREPARING METAL HALIDES

    DOEpatents

    Hendrickson, A.V.

    1958-11-18

    The conversion of plutonium halides from plutonium peroxide can be done by washing the peroxide with hydrogen peroxide, drying the peroxide, passing a dry gaseous hydrohalide over the surface of the peroxide at a temperature of about lOO icient laborato C until the reaction rate has stabillzed, and then ralsing the reaction temperature to between 400 and 600 icient laborato C until the conversion to plutonium halide is substantially complete.

  1. Silver-Halide Gelatin Holograms.

    DTIC Science & Technology

    1980-02-01

    PREPARATION OF R-10 TYPE BLEACHES Stock Solution A: Distilled water - 500 ml Ammonium dichromate - 20g Concentrated sulfuric acid - 14 ml Distilled water to...for the preparation of a bleach solution 5 Rinse in running water for 15 seconds Red Light 6 Soak in 0.5% ammonium dichromate for 5 minutes Red Light...those of con- ventional dichromated gelatin holograms, can be formed employing commercial silver-halide films. Major advantages of silver-halide

  2. Stabilized lanthanum sulphur compounds. [thermoelectric materials

    NASA Technical Reports Server (NTRS)

    Reynolds, G. H.; Elsner, N. B.; Shearer, C. H. (Inventor)

    1983-01-01

    Lanthanum sulfide is maintained in the stable cubic phase form over a temperature range of from 500 C to 1500 C by adding to it small amounts of calcium, barium, or strontium. This compound is an excellent thermoelectric material.

  3. Field free, directly heated lanthanum boride cathode

    DOEpatents

    Leung, Ka-Ngo; Moussa, D.; Wilde, S.B.

    1987-02-02

    A directly heated cylindrical lanthanum boride cathode assembly is disclosed which minimizes generation of magnetic field which would interfere with electron emission from the cathode. The cathode assembly comprises a lanthanum boride cylinder in electrical contact at one end with a central support shaft which functions as one electrode to carry current to the lanthanum boride cylinder and in electrical contact, at its opposite end with a second electrode which is coaxially position around the central support shaft so that magnetic fields generated by heater current flowing in one direction through the central support shaft are cancelled by an opposite magnetic field generated by current flowing through the lanthanum boride cylinder and the coaxial electrode in a direction opposite to the current flow in the central shaft.

  4. Field free, directly heated lanthanum boride cathode

    DOEpatents

    Leung, Ka-Ngo; Moussa, David; Wilde, Stephen B.

    1991-01-01

    A directly heated cylindrical lanthanum boride cathode assembly is disclosed which minimizes generation of magnetic fields which would interfere with electron emission from the cathode. The cathode assembly comprises a lanthanum boride cylinder in electrical contact at one end with a central support shaft which functions as one electrode to carry current to the lanthanum boride cylinder and in electrical contact, at its opposite end with a second electrode which is coaxially position around the central support shaft so that magnetic fields generated by heater current flowing in one direction through the central support shaft are cancelled by an opposite magnetic field generated by current flowing through the lanthanum boride cylinder and the coaxial electrode in a direction opposite to the current flow in the central shaft.

  5. Compact lanthanum hexaboride hollow cathode.

    PubMed

    Goebel, Dan M; Watkins, Ronald M

    2010-08-01

    A compact lanthanum hexaboride hollow cathode has been developed for space applications where size and mass are important and research and industrial applications where access for implementation might be limited. The cathode design features a refractory metal cathode tube that is easily manufactured, mechanically captured orifice and end plates to eliminate expensive e-beam welding, graphite sleeves to provide a diffusion boundary to protect the LaB6 insert from chemical reactions with the refractory metal tube, and several heater designs to provide long life. The compact LaB(6) hollow cathode assembly including emitter, support tube, heater, and keeper electrode is less than 2 cm in diameter and has been fabricated in lengths of 6-15 cm for different applications. The cathode has been operated continuously at discharge currents of 5-60 A in xenon. Slightly larger diameter versions of this design have operated at up to 100 A of discharge current.

  6. Pharmacology of the Phosphate Binder, Lanthanum Carbonate

    PubMed Central

    Damment, Stephen JP

    2011-01-01

    Studies were conducted to compare the phosphate-binding efficacy of lanthanum carbonate directly with other clinically used phosphate binders and to evaluate any potential adverse pharmacology. To examine the phosphate-binding efficacy, rats with normal renal function and chronic renal failure received lanthanum carbonate, aluminum hydroxide, calcium carbonate, or sevelamer hydrochloride in several experimental models. Lanthanum carbonate and aluminum hydroxide markedly increased excretion of [32P]-phosphate in feces and reduced excretion in urine in rats with normal renal function (p < 0.05), indicating good dietary phosphate-binding efficacy. In rats with chronic renal failure, lanthanum carbonate and aluminum hydroxide reduced urinary phosphate excretion to a greater degree and more rapidly than calcium carbonate, which in turn was more effective than sevelamer hydrochloride. The potential to induce adverse pharmacological effects was assessed systematically in mice, rats, and dogs with normal renal function using standard in vivo models. There was no evidence of any adverse secondary pharmacological effects of lanthanum carbonate on the central nervous, cardiovascular, respiratory, or gastrointestinal systems. These studies indicate that lanthanum carbonate is the more potent of the currently available dietary phosphate binders. No adverse secondary pharmacological actions were observed in vivo in a systematic evaluation at high doses. PMID:21332344

  7. Pharmacology of the phosphate binder, lanthanum carbonate.

    PubMed

    Damment, Stephen J P

    2011-01-01

    Studies were conducted to compare the phosphate-binding efficacy of lanthanum carbonate directly with other clinically used phosphate binders and to evaluate any potential adverse pharmacology. To examine the phosphate-binding efficacy, rats with normal renal function and chronic renal failure received lanthanum carbonate, aluminum hydroxide, calcium carbonate, or sevelamer hydrochloride in several experimental models. Lanthanum carbonate and aluminum hydroxide markedly increased excretion of [(32)P]-phosphate in feces and reduced excretion in urine in rats with normal renal function (p < 0.05), indicating good dietary phosphate-binding efficacy. In rats with chronic renal failure, lanthanum carbonate and aluminum hydroxide reduced urinary phosphate excretion to a greater degree and more rapidly than calcium carbonate, which in turn was more effective than sevelamer hydrochloride. The potential to induce adverse pharmacological effects was assessed systematically in mice, rats, and dogs with normal renal function using standard in vivo models. There was no evidence of any adverse secondary pharmacological effects of lanthanum carbonate on the central nervous, cardiovascular, respiratory, or gastrointestinal systems. These studies indicate that lanthanum carbonate is the more potent of the currently available dietary phosphate binders. No adverse secondary pharmacological actions were observed in vivo in a systematic evaluation at high doses.

  8. Lanthanum

    MedlinePlus

    ... clsas of medications called phosphate binders. It binds phosphorus that you get from foods in your diet ... doctor may instruct you to follow a low-phosphorus diet. Follow these directions carefully. Talk to your ...

  9. Methyl Halide Production by Fungi

    NASA Astrophysics Data System (ADS)

    Dailey, G. D.; Varner, R. K.; Blanchard, R. O.; Sive, B. C.; Crill, P. M.

    2005-12-01

    Methyl chloride (CH3Cl), methyl bromide (CH3Br) and methyl iodide (CH3I) are methyl halide gases that contribute significant amounts of halogen radicals to the atmosphere. In an effort to better understand the global budget of methyl halides and their impact on the atmosphere, we need to identify the natural sources in addition to the known anthropogenic sources of these compounds. We are investigating the role of fungi in the production of methyl halides in the soils and wetlands in southern New Hampshire, USA. Previous research has shown that wood decay fungi and ectomycorrhizal fungi, which are within a group of fungi called basidiomycetes, emit methyl halides. In our study, measurements of headspace gas extracted from flasks containing fungi grown in culture demonstrate that a variety of fungi, including basidiomycetes and non-basidiomycetes, emit methyl halides. Our research sites include four ecosystems: an agricultural field, a temperate forest, a fresh water wetland, and coastal salt marshes. We have collected and isolated fungi at each site by culturing tissue samples of fruiting bodies and plant material, by using wood baits, and from the direct culture of soil. We compared the rates of methyl halide emissions from the fungi in the four ecosystems. In addition, we measured emissions from previously assayed fungal isolates after reintroducing them to sterilized soils that were collected from their original environments. Fungal biomass was determined by substrate-induced respiration (SIR). The emission rate by the fungus was determined by a linear regression of the concentration of methyl halide in the sample headspace over time divided by the fungal biomass.

  10. SILICON CARBIDE FOR SEMICONDUCTORS

    DTIC Science & Technology

    This state-of-the-art survey on silicon carbide for semiconductors includes a bibliography of the most important references published as of the end...of 1964. The various methods used for growing silicon carbide single crystals are reviewed, as well as their properties and devices fabricated from...them. The fact that the state of-the-art of silicon carbide semiconductors is not further advanced may be attributed to the difficulties of growing

  11. Silicon Carbide Shapes.

    DTIC Science & Technology

    Free-standing silicon carbide shapes are produced by passing a properly diluted stream of a reactant gas, for example methyltrichlorosilane, into a...reaction chamber housing a thin walled, hollow graphite body heated to 1300-1500C. After the graphite body is sufficiently coated with silicon carbide , the...graphite body is fired, converting the graphite to gaseous CO2 and CO and leaving a silicon carbide shaped article remaining.

  12. Corrosion resistant cemented carbide

    SciTech Connect

    Hong, J.

    1990-10-16

    This paper describes a corrosion resistant cemented carbide composite. It comprises: a granular tungsten carbide phase, a semi-continuous solid solution carbide phase extending closely adjacent at least a portion of the grains of tungsten carbide for enhancing corrosion resistance, and a substantially continuous metal binder phase. The cemented carbide composite consisting essentially of an effective amount of an anti-corrosion additive, from about 4 to about 16 percent by weight metal binder phase, and with the remaining portion being from about 84 to about 96 percent by weight metal carbide wherein the metal carbide consists essentially of from about 4 to about 30 percent by weight of a transition metal carbide or mixtures thereof selected from Group IVB and of the Periodic Table of Elements and from about 70 to about 96 percent tungsten carbide. The metal binder phase consists essentially of nickel and from about 10 to about 25 percent by weight chromium, the effective amount of an anti-corrosion additive being selected from the group consisting essentially of copper, silver, tine and combinations thereof.

  13. Actinide halide complexes

    DOEpatents

    Avens, L.R.; Zwick, B.D.; Sattelberger, A.P.; Clark, D.L.; Watkin, J.G.

    1992-11-24

    A compound is described of the formula MX[sub n]L[sub m] wherein M is a metal atom selected from the group consisting of thorium, plutonium, neptunium or americium, X is a halide atom, n is an integer selected from the group of three or four, L is a coordinating ligand selected from the group consisting of aprotic Lewis bases having an oxygen-, nitrogen-, sulfur-, or phosphorus-donor, and m is an integer selected from the group of three or four for monodentate ligands or is the integer two for bidentate ligands, where the sum of n+m equals seven or eight for monodentate ligands or five or six for bidentate ligands. A compound of the formula MX[sub n] wherein M, X, and n are as previously defined, and a process of preparing such actinide metal compounds are described including admixing the actinide metal in an aprotic Lewis base as a coordinating solvent in the presence of a halogen-containing oxidant.

  14. Actinide halide complexes

    DOEpatents

    Avens, Larry R.; Zwick, Bill D.; Sattelberger, Alfred P.; Clark, David L.; Watkin, John G.

    1992-01-01

    A compound of the formula MX.sub.n L.sub.m wherein M is a metal atom selected from the group consisting of thorium, plutonium, neptunium or americium, X is a halide atom, n is an integer selected from the group of three or four, L is a coordinating ligand selected from the group consisting of aprotic Lewis bases having an oxygen-, nitrogen-, sulfur-, or phosphorus-donor, and m is an integer selected from the group of three or four for monodentate ligands or is the integer two for bidentate ligands, where the sum of n+m equals seven or eight for monodentate ligands or five or six for bidentate ligands, a compound of the formula MX.sub.n wherein M, X, and n are as previously defined, and a process of preparing such actinide metal compounds including admixing the actinide metal in an aprotic Lewis base as a coordinating solvent in the presence of a halogen-containing oxidant, are provided.

  15. Gastric mucosal status susceptible to lanthanum deposition in patients treated with dialysis and lanthanum carbonate.

    PubMed

    Ban, Shinichi; Suzuki, Syunji; Kubota, Kenji; Ohshima, Susumu; Satoh, Hideaki; Imada, Hiroki; Ueda, Yoshihiko

    2017-02-01

    Lanthanum carbonate is a popular chemical which is administered for patients with end-stage kidney disease to reduce the absorption of phosphate, and lanthanum deposition in the gastroduodenal mucosa has recently been reported. The aim of this study was to assess whether any histologic changes of the gastric mucosa are related to the deposition of lanthanum. Twenty-four patients who revealed the histology of lanthanum deposition on gastroduodenal biopsy between 2011 and 2014 were included in the study, and their clinical records and gastroduodenal biopsies obtained from 2011 to 2015 were reviewed, adding the review of gastroduodenal biopsies before 2011 if possible. Analysis of the deposited materials by scanning electron microscopy-energy dispersive x-ray spectroscopy was performed for a representative gastric biopsy. All patients were diagnosed as having renal insufficiency due to chronic kidney disease and treated with dialysis for more than 5 years, with confirmation of lanthanum carbonate use for 22 patients. Of 121 gastric biopsies and 10 duodenal ones between 2011 and 2015, 86 gastric biopsies (71.1%) and 3 duodenal biopsies (30%), respectively, revealed histology consistent with lanthanum deposition, which was confirmed by scanning electron microscopy-energy dispersive x-ray spectroscopy analysis for a representative case. The deposition tended to occur in the gastric mucosa with regenerative change, intestinal metaplasia, or foveolar hyperplasia (P<.05). Such mucosal changes were observed in about half of the gastric biopsy samples obtained prior to 2010, in which no lanthanum deposition was identified irrespective of the gastric mucosal status. Although direct association between lanthanum deposition and clinical symptoms is not clear, the evaluation of the gastric mucosal status (prior to administration) seems to be important to predict lanthanum deposition when lanthanum carbonate is administered for patients with chronic kidney disease treated with

  16. Radiochemical synthesis of pure anhydrous metal halides

    NASA Technical Reports Server (NTRS)

    Philipp, W. H.; Marsik, S. J.; May, C. E.

    1973-01-01

    Method uses radiation chemistry as practical tool for inorganic preparations and in particular deposition of metals by irradiation of their aqueous metal salt solutions with high energy electrons. Higher valence metal halide is dissolved in organic liquid and exposed to high energy electrons. This causes metal halide to be reduced to a lower valence metal halide.

  17. 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.

  18. Synthesis of lanthanum chromite with additions of lithium oxide

    SciTech Connect

    Spitsyn, V.I.; Pitov, V.A.; Kolesnikova, A.K.; Kuznetsov, D.G.; Suponitskii, Yu.L.; Spiridonov, F.M.

    1981-01-01

    Chromites of the rare-earth elements (in particular, lanthanum chromite LaCrO/sub 3/) are used for the preparation of chemically stable refractory objects. The method of production of lanthanum chromite by the introduction of lithium oxide into a stoiciometric mixture of chromium and lanthanum oxides has been proposed by some of the authors of this work. The present work is devoted to a study of the influence of additions of lithium oxide on the synthesis of lanthanum chromite.

  19. METHOD FOR DISSOLVING LANTHANUM FLUORIDE CARRIER FOR PLUTONIUM

    DOEpatents

    Koshland, D.E. Jr.; Willard, J.E.

    1961-08-01

    A method is described for dissolving lanthanum fluoride precipitates which is applicable to lanthanum fluoride carrier precipitation processes for recovery of plutonium values from aqueous solutions. The lanthanum fluoride precipitate is contacted with an aqueous acidic solution containing dissolved zirconium in the tetravalent oxidation state. The presence of the zirconium increases the lanthanum fluoride dissolved and makes any tetravalent plutonium present more readily oxidizable to the hexavalent state. (AEC)

  20. Silicon carbide ceramic production

    NASA Technical Reports Server (NTRS)

    Suzuki, K.; Shinohara, N.

    1984-01-01

    A method to produce sintered silicon carbide ceramics in which powdery carbonaceous components with a dispersant are mixed with silicon carbide powder, shaped as required with or without drying, and fired in nonoxidation atmosphere is described. Carbon black is used as the carbonaceous component.

  1. Stoichiometric tungsten carbide coatings

    NASA Astrophysics Data System (ADS)

    Hirata, G. A.; Contreras, O.; Farías, M. H.; Cota-Araiza, L.

    1996-07-01

    Filament Assisted Chemical Vapor Deposition (FA-CVD) technique has been used to prepare tungsten carbide (WC) thin films. With this simple technique we obtained polycrystalline and stoichiometric WC coatings deposited on crystalline silicon and on stainless steel substrates. Tungsten carbide coatings were studied with Auger Electron Spectroscopy and Scanning Electron Microscopy.

  2. Silicon Carbide Photoconductive Switches

    DTIC Science & Technology

    1994-09-01

    The optoelectronic properties of p-type 6-H silicon carbide (6H-SiC) have been investigated in an experiment that used lateral and vertical...and the bandgap was determined to be approximately 3.1 eV. 6H-SiC, Photoconductive, Photovoltaic, Absorption coefficient, Switch, Silicon carbide

  3. SILICON CARBIDE DATA SHEETS

    DTIC Science & Technology

    These data sheets present a compilation of a wide range of electrical, optical and energy values for alpha and beta- silicon carbide in bulk and film...spectrum. Energy data include energy bands, energy gap and energy levels for variously-doped silicon carbide , as well as effective mass tables, work

  4. Deposition of tantalum carbide coatings on graphite by laser interactions

    NASA Technical Reports Server (NTRS)

    Veligdan, James; Branch, D.; Vanier, P. E.; Barietta, R. E.

    1994-01-01

    Graphite surfaces can be hardened and protected from erosion by hydrogen at high temperatures by refractory metal carbide coatings, which are usually prepared by chemical vapor deposition (CVD) or chemical vapor reaction (CVR) methods. These techniques rely on heating the substrate to a temperature where a volatile metal halide decomposes and reacts with either a hydrocarbon gas or with carbon from the substrate. For CVR techniques, deposition temperatures must be in excess of 2000 C in order to achieve favorable deposition kinetics. In an effort to lower the bulk substrate deposition temperature, the use of laser interactions with both the substrate and the metal halide deposition gas has been employed. Initial testing involved the use of a CO2 laser to heat the surface of a graphite substrate and a KrF excimer laser to accomplish a photodecomposition of TaCl5 gas near the substrate. The results of preliminary experiments using these techniques are described.

  5. Microwave sintering of boron carbide

    DOEpatents

    Blake, R.D.; Katz, J.D.; Petrovic, J.J.; Sheinberg, H.

    1988-06-10

    A method for forming boron carbide into a particular shape and densifying the green boron carbide shape. Boron carbide in powder form is pressed into a green shape and then sintered, using a microwave oven, to obtain a dense boron carbide body. Densities of greater than 95% of theoretical density have been obtained. 1 tab.

  6. Sprayed lanthanum doped zinc oxide thin films

    NASA Astrophysics Data System (ADS)

    Bouznit, Y.; Beggah, Y.; Ynineb, F.

    2012-01-01

    Lanthanum doped zinc oxide thin films were deposited on soda-lime glass substrates using a pneumatic spray pyrolysis technique. The films were prepared using different lanthanum concentrations at optimum deposition parameters. We studied the variations in structural, morphological and optical properties of the samples due to the change of doping concentration in precursor solutions. X-ray diffraction (XRD) patterns show that pure and La-doped ZnO thin films are highly textured along c-axis perpendicular to the surface of the substrate. Scanning electron micrographs show that surface morphology of ZnO films undergoes a significant change according to lanthanum doping. All films exhibit a transmittance higher than 80% in the visible region.

  7. Organometal Halide Perovskite Artificial Synapses.

    PubMed

    Xu, Wentao; Cho, Himchan; Kim, Young-Hoon; Kim, Young-Tae; Wolf, Christoph; Park, Chan-Gyung; Lee, Tae-Woo

    2016-07-01

    Organometal halide perovskite synaptic devices are fabricated; they emulate important working principles of a biological synapse, including excitatory postsynaptic current, paired-pulse facilitation, short-term plasticity, long-term plasticity, and spike-timing dependent plasticity. These properties originate from possible ion migration in the ion-rich perovskite matrix. This work has extensive applicability and practical significance in neuromorphic electronics.

  8. Development of Lanthanum Ferrite SOFC Cathodes

    SciTech Connect

    Simner, Steve P.; Bonnett, Jeff F.; Canfield, Nathan L.; Meinhardt, Kerry D.; Shelton, Jayne P.; Sprenkle, Vince L.; Stevenson, Jeffry W.

    2003-01-01

    A number of studies have been conducted concerning compositional/microstructural modifications of a Sr-doped lanthanum ferrite (LSF) cathode and protective Sm-doped ceria (SDC) layer in an anode supported solid oxide fuel cell (SOFC). Emphasis was placed on achieving enhanced low temperature (700-800 degrees C) performance, and long-term cell stability. Investigations involved manipulation of the lanthanum ferrite chemistry, addition of noble metal oxygen reduction catalysts, incorporation of active cathode layer compositions containing Co, Fe and higher Sr contents, and attempts to optimize the ceria barrier layer between the LSF cathode and YSZ electrolyte.

  9. Abrasive wear of cemented carbides

    SciTech Connect

    Hawk, Jeffrey A.; Wilson, Rick D.

    2003-10-01

    Cemented carbides are used for a wide variety of applications where wear is a problem. Usually the wear of the cemented carbides is a combination of metal-to-metal and abrasion. Wear can occur at room or elevated temperatures. This research summarizes initial research to understand the abrasive wear of various cemented carbides (various grain sizes, carbide types, carbide grain sizes and binder compositions) in terms of absolute material removal rates and material removal mechanisms.

  10. Development of Halide and Oxy-Halides for Isotopic Separations

    SciTech Connect

    Martin, Leigh R.; Johnson, Aaron T.; Pfeiffer, Jana; Finck, Martha R.

    2014-10-01

    The goal of this project was to synthesize a volatile form of Np for introduction into mass spectrometers at INL. Volatile solids of the 5f elements are typically those of the halides (e.g. UF6), however fluorine is highly corrosive to the sensitive internal components of the mass separator, and the other volatile halides exist as several different stable isotopes in nature. However, iodide is both mono-isotopic and volatile, and as such presents an avenue for creation of a form of Np suitable for introduction into the mass separator. To accomplish this goal, the technical work in the project sought to establish a novel synthetic route for the conversion NpO2+ (dissolved in nitric acid) to NpI3 and NpI4.

  11. The hard X-ray response of Ce-doped lanthanum halide scintillators

    NASA Astrophysics Data System (ADS)

    Owens, Alan; Bos, A. J. J.; Brandenburg, S.; Dorenbos, P.; Drozdowski, W.; Ostendorf, R. W.; Quarati, F.; Webb, A.; Welter, E.

    2007-04-01

    We summarize the results of a number of hard X-ray measurements on cerium-doped LaCl 3 and LaBr 3 scintillators. The experiment was carried out at the HASYLAB synchrotron radiation facility using highly monochromatic pencil beams across the energy range 10.5-100 keV. Additional full-area measurements were carried out using radioactive sources. All measurements were carried out at room temperature. The measured FWHM energy resolutions (Δ E/ E) under pencil beam illumination were 29% (LaBr 3) and 32.4% (LaCl 3) at 10.5 keV falling to 7.8% (LaBr 3) and 9.2% (LaCl 3) at 100 keV. At 662 keV, the energy resolutions were 3.9% and 3.0% FWHM. The proportionality of the energy responses shows marked deviations from linearity above and below the La edge at 39.8 keV. At the edge the energy response changes by 3%. Fine structure across the edge was also investigated using single photon count rate measurements taken in 1 eV steps across the edge. The data show considerable near-edge structure when compared to curves generated from standard atomic data tables. However, very little evidence was found for extended X-ray fine structure suggesting that the bulk of the structure arises from the local coordination environment.

  12. TRANSURANIC METAL HALIDES AND A PROCESS FOR THE PRODUCTION THEREOF

    DOEpatents

    Fried, S.

    1951-03-20

    Halides of transuranic elements are prepared by contacting with aluminum and a halogen, or with an aluminum halide, a transuranic metal oxide, oxyhalide, halide, or mixture thereof at an elevated temperature.

  13. Metal halide perovskite light emitters

    PubMed Central

    Kim, Young-Hoon; Cho, Himchan; Lee, Tae-Woo

    2016-01-01

    Twenty years after layer-type metal halide perovskites were successfully developed, 3D metal halide perovskites (shortly, perovskites) were recently rediscovered and are attracting multidisciplinary interest from physicists, chemists, and material engineers. Perovskites have a crystal structure composed of five atoms per unit cell (ABX3) with cation A positioned at a corner, metal cation B at the center, and halide anion X at the center of six planes and unique optoelectronic properties determined by the crystal structure. Because of very narrow spectra (full width at half-maximum ≤20 nm), which are insensitive to the crystallite/grain/particle dimension and wide wavelength range (400 nm ≤ λ ≤ 780 nm), perovskites are expected to be promising high-color purity light emitters that overcome inherent problems of conventional organic and inorganic quantum dot emitters. Within the last 2 y, perovskites have already demonstrated their great potential in light-emitting diodes by showing high electroluminescence efficiency comparable to those of organic and quantum dot light-emitting diodes. This article reviews the progress of perovskite emitters in two directions of bulk perovskite polycrystalline films and perovskite nanoparticles, describes current challenges, and suggests future research directions for researchers to encourage them to collaborate and to make a synergetic effect in this rapidly emerging multidisciplinary field. PMID:27679844

  14. Halide Welding for Silver Nanowire Network Electrode.

    PubMed

    Kang, Hyungseok; Kim, Yeontae; Cheon, Siuk; Yi, Gi-Ra; Cho, Jeong Ho

    2017-09-13

    We developed a method of chemically welding silver nanowires (AgNWs) using an aqueous solution containing sodium halide salts (NaF, NaCl, NaBr, or NaI). The halide welding was performed simply by immersing the as-coated AgNW film into the sodium halide solution, and the resulting material was compared with those obtained using two typical thermal and plasmonic welding techniques. The halide welding dramatically reduced the sheet resistance of the AgNW electrode because of the strong fusion among nanowires at each junction while preserving the optical transmittance. The dramatic decrease in the sheet resistance was attributed to the autocatalytic addition of dissolved silver ions to the nanowire junction. Unlike thermal and plasmonic welding methods, the halide welding could be applied to AgNW films with a variety of deposition densities because the halide ions uniformly contacted the surface or junction regions. The optimized AgNW electrodes exhibited a sheet resistance of 9.3 Ω/sq at an optical transmittance of 92%. The halide welding significantly enhanced the mechanical flexibility of the electrode compared with the as-coated AgNWs. The halide-welded AgNWs were successfully used as source-drain electrodes in a transparent and flexible organic field-effect transistor (OFET). This simple, low-cost, and low-power consumption halide welding technique provides an innovative approach to preparing transparent electrodes for use in next-generation flexible optoelectronic devices.

  15. [Determination of trace barium in environmental samples by electric-heated AAS with lanthanum-coated graphite tube].

    PubMed

    Han, Hua-yun; Lin, Lin; Chen, Ke; Wang, Feng

    2002-02-01

    In this paper a new method was established for determination of trace barium in environmental samples by graphite furnace atomic absorption spectrometry. In the presence of matrix modifier magnesium nitrate, the matrix inference was eliminated efficiently. To avoid producing barium carbide, the graphite tubes were coated differently with lanthanum, zirconium, tungsten, molybdenum, and tantalum. Results showed that the tube with lanthanum was the best. The atomization temperature was diminished. The sensitivity was improved, and the tube with lanthanum gave the longest service life. So we used the tube to determine trace barium. The trace barium in Geodchemical Standard Reference Sample Soil-1 (GSS-1) was determined by the new method, the test results showed that the method was reliability and accurate. The method has been used for the determination of trace barium in environmental samples and in water of Yellow River. The detection limit for Ba was 2.1 x 10(-12) g and the relative standard deviation(RSD) was 5.4% for 15 ng.mL-1 Ba.

  16. Lanthanum-catalysed synthesis of microporous 3D graphene-like carbons in a zeolite template

    NASA Astrophysics Data System (ADS)

    Kim, Kyoungsoo; Lee, Taekyoung; Kwon, Yonghyun; Seo, Yongbeom; Song, Jongchan; Park, Jung Ki; Lee, Hyunsoo; Park, Jeong Young; Ihee, Hyotcherl; Cho, Sung June; Ryoo, Ryong

    2016-07-01

    Three-dimensional graphene architectures with periodic nanopores—reminiscent of zeolite frameworks—are of topical interest because of the possibility of combining the characteristics of graphene with a three-dimensional porous structure. Lately, the synthesis of such carbons has been approached by using zeolites as templates and small hydrocarbon molecules that can enter the narrow pore apertures. However, pyrolytic carbonization of the hydrocarbons (a necessary step in generating pure carbon) requires high temperatures and results in non-selective carbon deposition outside the pores. Here, we demonstrate that lanthanum ions embedded in zeolite pores can lower the temperature required for the carbonization of ethylene or acetylene. In this way, a graphene-like carbon structure can be selectively formed inside the zeolite template, without carbon being deposited at the external surfaces. X-ray diffraction data from zeolite single crystals after carbonization indicate that electron densities corresponding to carbon atoms are generated along the walls of the zeolite pores. After the zeolite template is removed, the carbon framework exhibits an electrical conductivity that is two orders of magnitude higher than that of amorphous mesoporous carbon. Lanthanum catalysis allows a carbon framework to form in zeolite pores with diameters of less than 1 nanometre; as such, microporous carbon nanostructures can be reproduced with various topologies corresponding to different zeolite pore sizes and shapes. We demonstrate carbon synthesis for large-pore zeolites (FAU, EMT and beta), a one-dimensional medium-pore zeolite (LTL), and even small-pore zeolites (MFI and LTA). The catalytic effect is a common feature of lanthanum, yttrium and calcium, which are all carbide-forming metal elements. We also show that the synthesis can be readily scaled up, which will be important for practical applications such as the production of lithium-ion batteries and zeolite-like catalyst

  17. Thermodynamic properties of lanthanum in gallium-zinc alloys

    NASA Astrophysics Data System (ADS)

    Dedyukhin, A. S.; Shepin, I. E.; Kharina, E. A.; Shchetinskiy, A. V.; Volkovich, V. A.; Yamshchikov, L. F.

    2016-09-01

    Thermodynamic properties of lanthanum were determined in gallium-zinc alloys of the eutectic and over-eutectic compositions. The electromotive force measurements were used to determine thermodynamic activity and sedimentation technique to measure solubility of lanthanum in liquid metal alloys. Temperature dependencies of lanthanum activity, solubility and activity coefficients in alloys with Ga-Zn mixtures containing 3.64, 15 and 50 wt. % zinc were obtained.

  18. Permeability of the Body Wall of Romanomermis culicivorax to Lanthanum

    PubMed Central

    Platzer, Ann; Platzer, Edward G.

    1985-01-01

    Ultrastructural study of the body wall of preparasitic, parasitic, and postparasitic stages of Romanomermis culicivorax showed that the cuticle of all three stages was permeable to lanthanum. The cuticle of the parasitic stage was the thinnest and showed the greatest permeability. Lanthanum accumulated on the apical surfaces of the hypodermal cells but was not found intracellularly. The negative staining characteristics of lanthanum enhanced the detection of numerous smooth septate junctions in the hypodermis of the parasitic stage. PMID:19294092

  19. Peculiar histiocytic lesions with massive lanthanum deposition in dialysis patients treated with lanthanum carbonate.

    PubMed

    Haratake, Joji; Yasunaga, Chikao; Ootani, Akifumi; Shimajiri, Shohei; Matsuyama, Atsuji; Hisaoka, Masanori

    2015-06-01

    Pathologic lesions caused by lanthanum carbonate (LC), a recently developed phosphate-binding agent, have not been recorded. A peculiar gastroduodenal histiocytic lesion associated with a mucosal lanthanum overload was reported. Our routine gastrointestinal biopsy series included 6 cases with heavy lanthanum burden in the gastroduodenal mucosa. In addition to routine histopathologic examinations, a series of immunohistochemical analysis and electron microscopic examinations associated with x-ray diffraction and elemental analysis were performed. Six cases, 3 of male and 3 of female individuals with ages from 59 to 69 years, were all patients of end-stage renal diseases managed under dialysis and treated with LC for >21 months. Endoscopic examinations demonstrated gastric erosions in 3, gastric polyps in 2, and duodenal ulcer in 1. In the mucosal layer, there were numerous non-Langerhans cell histiocytes, stained with CD68 but not S100 protein, engulfing a large amount of mineral-like materials. An electron microscopic and elemental analysis revealed a similar distribution of lanthanum and phosphorus in the histiocytes. Long-standing LC administration can cause massive mucosal accumulation of lanthanum in the tissue histiocytes associated with several forms of gastroduodenal lesions. A long-standing outcome is not clear at present; hence, careful follow-up studies of these patients may be needed.

  20. Adsorption of lanthanum to goethite in the presence of gluconate

    SciTech Connect

    Hull, Laurence C.; Sarah Pepper; Sue Clark

    2005-05-01

    Adsorption of Lanthanum to Goethite in the Presence of Gluconic Acid L. C. HULL,1 S. E. PEPPER2 AND S. B. CLARK2 1Idaho National Engineering and Environmental Laboratory, Idaho Falls, ID (hulllc@inel.gov) 2Washington State University, Pullman, WA (spepper@wsu.edu), (s_clark@wsu.edu) Lanthanide and trivalent-actinide elements in radioactive waste can pose risks to humans and ecological systems for many years. Organic complexing agents, from natural organic matter or the degradation of waste package components, can alter the mobility of these elements. We studied the effect of gluconic acid, as an analogue for cellulose degradation products, on the adsorption of lanthanum, representing lanthanide and trivalent-actinide elments, to goethite, representing natural iron minearals and degradation products of waste packages. Batch pH adsorption edge experiments were conducted with lanthanum alone, and with lanthanum and gluconate at a 1:1 mole ratio. Lanthanum concentrations studied were 0.1, 1, and 10 mM, covering a range from 10% to 1000% of the calculated available adsorption sites on goethite. In the absence of gluconate, lanthanum was primarily present in solution as free lanthanum ion. With gluconate present, free lanthanum concentration in solution decreased with increasing pH as step-wise deprotonation of the gluconate molecule increased the fraction lanthanum complexed with gluconate. Adsorption to the goethite surface was represented with the diffuse double-layer model. The number of adsorption sites and the intrinsic binding constants for the surface complexes were estimated from the pH adsorption edge data using the computer code FITEQL 4.0. Two surface reactions were used to fit the adsorption data in the absence of gluconate. A strong binding site with no proton release and a much higher concentration of weak binding sites with release of two protons per lanthanum adsorbed. The adsorption of lanthanum was not measurably affected by the presence of gluconate

  1. Sorption of lanthanum ions by natural clinoptilolite tuff

    NASA Astrophysics Data System (ADS)

    Dampilova, B. V.; Zonkhoeva, E. L.

    2013-08-01

    The equilibrium and kinetics of sorption of lanthanum ions on natural clinoptilolite tuff are studied. It is demonstrated that sorption of lanthanum ions from diluted solutions occurs in micropores of clinoptilolite, and from concentrated solutions in the mesoporous structure of tuff. The main capacity of zeolite tuff is found in the secondary porous structure. The sorption of lanthanum ions is limited by diffusion in tuff grains. Lanthanum ions are regularly distributed in the tuff phase and interact with the Brønsted centers of large clinoptilolite cavities.

  2. Systemic lanthanum is excreted in the bile of rats.

    PubMed

    Damment, Stephen J P; Pennick, Michael

    2007-06-15

    Lanthanum carbonate is a non-calcium-based oral phosphate binder for the control of hyperphosphataemia in patients with chronic kidney disease Stage 5. As part of its pre-clinical safety evaluation, studies were conducted in rats to determine the extent of absorption and routes of excretion. Following oral gavage of a single 1500 mg/kg dose, the peak plasma lanthanum concentration was 1.04+/-0.31 ng/mL, 8 h post-dose. Lanthanum was almost completely bound to plasma proteins (>99.7%). Within 24h of administration of a single oral dose, 97.8+/-2.84% of the lanthanum was recovered in the faeces of rats. Comparing plasma exposure after oral and intravenous administration of lanthanum yielded an absolute oral bioavailability of 0.0007%. Following intravenous administration of lanthanum chloride (0.3 mg/kg), 74.1+/-5.82% of the dose (96.9+/-0.50% of recovered lanthanum) was excreted in faeces in 42 days, and in bile-duct cannulated rats, 10.0+/-2.46% of the dose (85.6+/-2.97% of recovered lanthanum) was excreted in bile in 5 days. Renal excretion was negligible, with <2% of the intravenous dose recovered in urine. These studies demonstrate that lanthanum undergoes extremely low intestinal absorption and that absorbed drug is predominantly excreted in the bile.

  3. Cohesive Energy-Lattice Constant and Bulk Modulus-Lattice Constant Relationships: Alkali Halides, Ag Halides, Tl Halides

    NASA Technical Reports Server (NTRS)

    Schlosser, Herbert

    1992-01-01

    In this note we present two expressions relating the cohesive energy, E(sub coh), and the zero pressure isothermal bulk modulus, B(sub 0), of the alkali halides. Ag halides and TI halides, with the nearest neighbor distances, d(sub nn). First, we show that the product E(sub coh)d(sub 0) within families of halide crystals with common crystal structure is to a good approximation constant, with maximum rms deviation of plus or minus 2%. Secondly, we demonstrate that within families of halide crystals with a common cation and common crystal structure the product B(sub 0)d(sup 3.5)(sub nn) is a good approximation constant, with maximum rms deviation of plus or minus 1.36%.

  4. Cohesive Energy-Lattice Constant and Bulk Modulus-Lattice Constant Relationships: Alkali Halides, Ag Halides, Tl Halides

    NASA Technical Reports Server (NTRS)

    Schlosser, Herbert

    1992-01-01

    In this note we present two expressions relating the cohesive energy, E(sub coh), and the zero pressure isothermal bulk modulus, B(sub 0), of the alkali halides. Ag halides and TI halides, with the nearest neighbor distances, d(sub nn). First, we show that the product E(sub coh)d(sub 0) within families of halide crystals with common crystal structure is to a good approximation constant, with maximum rms deviation of plus or minus 2%. Secondly, we demonstrate that within families of halide crystals with a common cation and common crystal structure the product B(sub 0)d(sup 3.5)(sub nn) is a good approximation constant, with maximum rms deviation of plus or minus 1.36%.

  5. Silicon carbide thyristor

    NASA Technical Reports Server (NTRS)

    Edmond, John A. (Inventor); Palmour, John W. (Inventor)

    1996-01-01

    The SiC thyristor has a substrate, an anode, a drift region, a gate, and a cathode. The substrate, the anode, the drift region, the gate, and the cathode are each preferably formed of silicon carbide. The substrate is formed of silicon carbide having one conductivity type and the anode or the cathode, depending on the embodiment, is formed adjacent the substrate and has the same conductivity type as the substrate. A drift region of silicon carbide is formed adjacent the anode or cathode and has an opposite conductivity type as the anode or cathode. A gate is formed adjacent the drift region or the cathode, also depending on the embodiment, and has an opposite conductivity type as the drift region or the cathode. An anode or cathode, again depending on the embodiment, is formed adjacent the gate or drift region and has an opposite conductivity type than the gate.

  6. Multiple-Wavelength Metal/Halide Laser

    NASA Technical Reports Server (NTRS)

    Nerheim, N. M.

    1984-01-01

    Single device produces multiple lasing lines. Laser capable of producing many lasing lines has several reservoirs of halide lasant mixed with chlorides of copper, manganese and iron. Convection-control technique possible to rapidly change from one metal halide to another at maximum energy.

  7. Synthesis of aryl halides via organoborane chemistry

    SciTech Connect

    Kabalka, G.W.; Sastry, K.A.R.; Sastry, U.; Somayaji, V.

    1982-01-01

    A method for the rapid synthesis of a variety of substituted aryl halides by the reaction of organoboranes with halide ions in the presence of chloramine-T is described in detail. The products were purified by column chromatography on silica gel using a mixture of petroleum ether-ethyl acetate as eluent.

  8. Lanthanum fluoride nanoparticles for radiosensitization of tumors

    NASA Astrophysics Data System (ADS)

    Kudinov, Konstantin; Bekah, Devesh; Cooper, Daniel; Shastry, Sathvik; Hill, Colin; Bradforth, Stephen; Nadeau, Jay

    2016-03-01

    Dense inorganic nanoparticles have recently been identified as promising radiosensitizers. In addition to dose enhancement through increased attenuation of ionizing radiation relative to biological tissue, scintillating nanoparticles can transfer energy to coupled photosensitizers to amplify production of reactive oxygen species, as well as provide UVvisible emission for optical imaging. Lanthanum fluoride is a transparent material that is easily prepared as nanocrystals, and which can provide radioluminescence at a number of wavelengths through simple substitution of lanthanum ions with other luminescent lanthanides. We have prepared lanthanum fluoride nanoparticles doped with cerium, terbium, or both, that have good spectral overlap with chlorine6 or Rose Bengal photosensitizer molecules. We have also developed a strategy for stable conjugation of the photosensitizers to the nanoparticle surface, allowing for high energy transfer efficiencies on a per molecule basis. Additionally, we have succeeded in making our conjugates colloidally stable under physiological conditions. Here we present our latest results, using nanoparticles and nanoparticle-photosensitizer conjugates to demonstrate radiation dose enhancement in B16 melanoma cells. The effects of nanoparticle treatment prior to 250 kVp x-ray irradiation were investigated through clonogenic survival assays and cell cycle analysis. Using a custom apparatus, we have also observed scintillation of the nanoparticles and conjugates under the same conditions that the cell samples are irradiated.

  9. Effects of lanthanum and lanthanum-modified clay on growth, survival and reproduction of Daphnia magna.

    PubMed

    Lürling, Miquel; Tolman, Yora

    2010-01-01

    The novel lanthanum-modified clay water treatment technology (Phoslock seems very promising in remediation of eutrophied waters. Phoslock is highly efficient in stripping dissolved phosphorous from the water column and in intercepting phosphorous released from the sediments. The active phosphorous-sorbent in Phoslock is the Rare Earth Element lanthanum. A leachate experiment revealed that lanthanum could be released from the clay, but only in minute quantities of 0.13-2.13microgl(-1) for a worst-case Phoslock dosage of 250mgl(-1). A life-history experiment with the zooplankton grazer Daphnia magna revealed that lanthanum, up to the 1000microgl(-1) tested, had no toxic effect on the animals, but only in medium without phosphorous. In the presence of phosphorous, rhabdophane (LaPO(4).nH(2)O) formation resulted in significant precipitation of the food algae and consequently affected life-history traits. With increasing amounts of lanthanum, in the presence of phosphate, animals remained smaller, matured later, and reproduced less, resulting in lower population growth rates. Growth rates were not affected at 33microgLal(-1), but were 6% and 7% lower at 100 and 330microgl(-1), respectively, and 20% lower at 1000microgl(-1). A juvenile growth assay with Phoslock tested in the range 0-5000mgl(-1), yielded EC(50) (NOEC) values of 871 (100) and 1557 (500)mg Phoslock l(-1) for weight and length based growth rates, respectively. The results of this study show that no major detrimental effects on Daphnia are to be expected from Phoslock or its active ingredient lanthanum when applied in eutrophication control.

  10. Freeze Enhanced Halate Halide Reactions

    NASA Astrophysics Data System (ADS)

    Newberg, J. T.; Weaver, K.; Broderick, A.

    2014-12-01

    Relatively little is known about halate ion species (XO3-; X = I, Br, Cl) in atmospheric condensed phases. It was initial thought that iodate was a terminal stable species upon iodide oxidation. However, it is becoming increasingly recognized that reactions involving iodate can lead to reactive iodine, and this chemistry is accelerated under acidic conditions. The environmental concentrations and chemistry of bromate and chlorate are largely unexplored in environmental ices. We present results from a series of aqueous phase halate ion reactions with halides under acidic conditions, showing that the kinetics are strongly enhanced upon freezing. The products of these reactions are reactive halogens, which have important implications to marine boundary layer chemistry.

  11. Rare Gas Halide (RGH) Kinetics.

    DTIC Science & Technology

    1988-02-01

    Technolog , Inc.. 2755 Northup Way, Bellevue, Washington 98004-1495 (Received Il August 1987; accepted for publication 12 October 1987) Time-dependent density...8217 - Z ¢L --- ;-; Z¢ < : 2 2 2 e - 2 l ¢ - -- - P-2 -V, 2 " ’ ’’’ 2.,..’ * -x ’ ,’* - SSpectra Technology flT U Fr CoPY CContract N00014-85-C-084 3...RARE GAS HALIDE (RGH) in KINETICS FINAL REPORT< S Submitted to OFFICE OF NAVAL RESEARCH DEPARTMENT OF THE NAVY Submitted by SPECTRA TECHNOLOGY , INC

  12. Hygroscopicity Evaluation of Halide Scintillators

    SciTech Connect

    Zhuravleva, M; Stand, L; Wei, H; Hobbs, C. L.; Boatner, Lynn A; Ramey, Joanne Oxendine; Burger, Arnold; Rowe, E; Bhattacharya, P.; Tupitsyn, E; Melcher, Charles L

    2014-01-01

    A collaborative study of relative hygroscopicity of anhydrous halide scintillators grown at various laboratories is presented. We have developed a technique to evaluate moisture sensitivity of both raw materials and grown crystals, in which the moisture absorption rate is measured using a gravimetric analysis. Degradation of the scintillation performance was investigated by recording gamma-ray spectra and monitoring the photopeak position, count rate and energy resolution. The accompanying physical degradation of the samples exposed to ambient atmosphere was photographically recorded as well. The results were compared with ben

  13. Silicon carbide reinforced silicon carbide composite

    NASA Technical Reports Server (NTRS)

    Lau, Sai-Kwing (Inventor); Calandra, Salvatore J. (Inventor); Ohnsorg, Roger W. (Inventor)

    2001-01-01

    This invention relates to a process comprising the steps of: a) providing a fiber preform comprising a non-oxide ceramic fiber with at least one coating, the coating comprising a coating element selected from the group consisting of carbon, nitrogen, aluminum and titanium, and the fiber having a degradation temperature of between 1400.degree. C. and 1450.degree. C., b) impregnating the preform with a slurry comprising silicon carbide particles and between 0.1 wt % and 3 wt % added carbon c) providing a cover mix comprising: i) an alloy comprising a metallic infiltrant and the coating element, and ii) a resin, d) placing the cover mix on at least a portion of the surface of the porous silicon carbide body, e) heating the cover mix to a temperature between 1410.degree. C. and 1450.degree. C. to melt the alloy, and f) infiltrating the fiber preform with the melted alloy for a time period of between 15 minutes and 240 minutes, to produce a ceramic fiber reinforced ceramic composite.

  14. Improved toughness of silicon carbide

    NASA Technical Reports Server (NTRS)

    Palm, J. A.

    1975-01-01

    Several techniques were employed to apply or otherwise form porous layers of various materials on the surface of hot-pressed silicon carbide ceramic. From mechanical properties measurements and studies, it was concluded that although porous layers could be applied to the silicon carbide ceramic, sufficient damage was done to the silicon carbide surface by the processing required so as to drastically reduce its mechanical strength. It was further concluded that there was little promise of success in forming an effective energy absorbing layer on the surface of already densified silicon carbide ceramic that would have the mechanical strength of the untreated or unsurfaced material. Using a process for the pressureless sintering of silicon carbide powders it was discovered that porous layers of silicon carbide could be formed on a dense, strong silicon carbide substrate in a single consolidation process.

  15. Silicon Carbide Metallization

    NASA Astrophysics Data System (ADS)

    Lescoat, F.; Tanguy, F.; Durand, P.

    2016-05-01

    A study has been done to assess the feasibility of metallization of Silicon Carbide (SiC) in order to simplify design and mounting of one or more ground reference rail needed to provide an electrical reference for electronics mounted on an SiC structure.

  16. Composition Comprising Silicon Carbide

    NASA Technical Reports Server (NTRS)

    Mehregany, Mehran (Inventor); Zorman, Christian A. (Inventor); Fu, Xiao-An (Inventor); Dunning, Jeremy L. (Inventor)

    2012-01-01

    A method of depositing a ceramic film, particularly a silicon carbide film, on a substrate is disclosed in which the residual stress, residual stress gradient, and resistivity are controlled. Also disclosed are substrates having a deposited film with these controlled properties and devices, particularly MEMS and NEMS devices, having substrates with films having these properties.

  17. Characterization of Silicon Carbide.

    DTIC Science & Technology

    The various electrical and structural measurement techniques for silicon carbide are described. The electrical measurements include conductivity, resistivity, carrier concentration, mobility, doping energy levels, and lifetime. The structural measurements include polytype determination and crystalline perfection. Both bulk and epitaxial films are included.

  18. 40 CFR 721.10601 - Lanthanum lead titanium zirconium oxide.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Lanthanum lead titanium zirconium... Specific Chemical Substances § 721.10601 Lanthanum lead titanium zirconium oxide. (a) Chemical substance... titanium zirconium oxide (PMN P-11-273; CAS No. 1227908-26-0) is subject to reporting under this...

  19. 40 CFR 721.10601 - Lanthanum lead titanium zirconium oxide.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Lanthanum lead titanium zirconium... Specific Chemical Substances § 721.10601 Lanthanum lead titanium zirconium oxide. (a) Chemical substance... titanium zirconium oxide (PMN P-11-273; CAS No. 1227908-26-0) is subject to reporting under this...

  20. Modulating the phases of iron carbide nanoparticles: from a perspective of interfering with the carbon penetration of Fe@Fe3O4 by selectively adsorbed halide ions† †Electronic supplementary information (ESI) available. See DOI: 10.1039/c6sc01819j Click here for additional data file.

    PubMed Central

    Yang, Ziyu; Zhao, Tianshan; Huang, Xiaoxiao; Chu, Xin; Tang, Tianyu; Ju, Yanmin; Wang, Qian; Gao, Song

    2017-01-01

    Iron carbide nanoparticles (ICNPs) are considered to have great potential in new energy conversion, nanomagnets and biomedical applications due to their intrinsically peculiar magnetic and catalytic properties. However, the synthetic routes were greatly limited in morphology and phase controlled synthesis. In this article, we present a versatile solution chemistry route towards colloidal ICNPs (Fe2C-hexagonal and monoclinic syngony, Fe5C2-monoclinic syngony and Fe3C-orthorhombic syngony) derived from body centered cubic Fe@Fe3O4 by introducing heteroatoms to restrain their phase transformation. We found that the phases of Fe2C NPs could be controlled by direct phase transformation in the drastic thermally driven procedure (defined as thermodynamical manner). Meanwhile, the selective adsorption of Cl ions weakened the bonding between Fe and C atoms, thus interfering with the penetration of C atoms to form lower carbon content Fe5C2 and Fe3C NPs. The kinetic mechanisms were evaluated using density functional theory (DFT) simulations focusing on the bonding energy between Fe–C and Fe–Cl atoms. All the obtained ICNPs exhibited typically soft ferromagnetic properties with the highest saturation magnetization value of 101.2 emu g–1 and the highest Curie temperature of 497.8 K. PMID:28451194

  1. Characterization of gadolinium and lanthanum oxide films on Si (100)

    NASA Astrophysics Data System (ADS)

    Wu, X.; Landheer, D.; Sproule, G. I.; Quance, T.; Graham, M. J.; Botton, G. A.

    2002-05-01

    High-resolution transmission electron microscopy, electron energy loss spectroscopy, and Auger electron spectroscopy, were used to study gadolinium and lanthanum oxide films deposited on Si (100) substrates using electron-beam evaporation from pressed-powder targets. As-deposited films consist of a crystalline oxide layer and an amorphous interfacial layer. A complicated distinct multilayer structure consisting of oxide layers, silicate layers, and SiO2-rich layers in thick (~30 nm) annealed films has been observed for both gadolinium and lanthanum films. For thinner annealed films (~8 nm), there is no longer a crystalline oxide layer but an amorphous gadolinium or lanthanum silicate layer and an interfacial SiO2-rich layer. The formation of the lanthanum silicate by annealing lanthanum oxide is found to be thermodynamically more favorable than the formation of gadolinium silicate.

  2. Preparation of high purity lanthanum compounds for use in fluoride optical fibers

    SciTech Connect

    Ewing, K.J.; Buckner, L.; Jaganathan, J.; Ginther, R.; Aggarwal, I.D. . Optical Sciences Div.)

    1989-02-01

    The preparation of ultra-pure lanthanum nitrate by co-precipitation is described. Preparation of high purity lanthanum carbonate from the pure nitrate is also described. Hydrofluorination of pure lanthanum carbonate produces high purity lanthanum fluoride used in the preparation of heavy metal fluoride glasses.

  3. Shallow halogen vacancies in halide optoelectronic materials

    DOE PAGES

    Shi, Hongliang; Du, Mao -Hua

    2014-11-05

    Halogen vacancies (VH) are usually deep color centers (F centers) in halides and can act as major electron traps or recombination centers. The deep VH contributes to the typically poor carrier transport properties in halides. However, several halides have recently emerged as excellent optoelectronic materials, e.g., CH3NH3PbI3 and TlBr. Both CH3NH3PbI3 and TlBr have been found to have shallow VH, in contrast to commonly seen deep VH in halides. In this paper, several halide optoelectronic materials, i.e., CH3NH3PbI3, CH3NH3SnI3 (photovoltaic materials), TlBr, and CsPbBr3, (gamma-ray detection materials) are studied to understand the material chemistry and structure that determine whether VHmore » is a shallow or deep defect in a halide material. It is found that crystal structure and chemistry of ns2 ions both play important roles in creating shallow VH in halides such as CH3NH3PbI3, CH3NH3SnI3, and TlBr. The key to identifying halides with shallow VH is to find the right crystal structures and compounds that suppress cation orbital hybridization at VH, such as those with long cation-cation distances and low anion coordination numbers, and those with crystal symmetry that prevents strong hybridization of cation dangling bond orbitals at VH. Furthermore, the results of this paper provide insight and guidance to identifying halides with shallow VH as good electronic and optoelectronic materials.« less

  4. Shallow halogen vacancies in halide optoelectronic materials

    NASA Astrophysics Data System (ADS)

    Shi, Hongliang; Du, Mao-Hua

    2014-11-01

    Halogen vacancies (VH ) are usually deep color centers (F centers) in halides and can act as major electron traps or recombination centers. The deep VH contributes to the typically poor carrier transport properties in halides. However, several halides have recently emerged as excellent optoelectronic materials, e.g., C H3N H3Pb I3 and TlBr. Both C H3N H3Pb I3 and TlBr have been found to have shallow VH , in contrast to commonly seen deep VH in halides. In this paper, several halide optoelectronic materials, i.e., C H3N H3Pb I3 , C H3N H3Sn I3 (photovoltaic materials), TlBr, and CsPbB r3 (gamma-ray detection materials) are studied to understand the material chemistry and structure that determine whether VH is a shallow or deep defect in a halide material. It is found that crystal structure and chemistry of n s2 ions both play important roles in creating shallow VH in halides such as C H3N H3Pb I3 , C H3N H3Sn I3 , and TlBr. The key to identifying halides with shallow VH is to find the right crystal structures and compounds that suppress cation orbital hybridization at VH , such as those with large cation-cation distances and low anion coordination numbers and those with crystal symmetry that prevents strong hybridization of cation dangling bond orbitals at VH . The results of this paper provide insight and guidance to identifying halides with shallow VH as good electronic and optoelectronic materials.

  5. Lanthanum carbonate: safety data after 10 years

    PubMed Central

    Wilson, Rosamund J; Garafola, Svetlana; Copley, John Brian

    2016-01-01

    Abstract Despite 10 years of post‐marketing safety monitoring of the phosphate binder lanthanum carbonate, concerns about aluminium‐like accumulation and toxicity persist. Here, we present a concise overview of the safety profile of lanthanum carbonate and interim results from a 5‐year observational database study (SPD405‐404; ClinicalTrials.gov identifier: NCT00567723). The pharmacokinetic paradigms of lanthanum and aluminium are different in that lanthanum is minimally absorbed and eliminated via the hepatobiliary pathway, whereas aluminium shows appreciable absorption and is eliminated by the kidneys. Randomised prospective studies of paired bone biopsies revealed no evidence of accumulation or toxicity in patients treated with lanthanum carbonate. Patients treated with lanthanum carbonate for up to 6 years showed no clinically relevant changes in liver enzyme or bilirubin levels. Lanthanum does not cross the intact blood–brain barrier. The most common adverse effects are mild/moderate nausea, diarrhoea and flatulence. An interim Kaplan–Meier analysis of SPD405‐404 data from the United States Renal Data System revealed that the median 5‐year survival was 51.6 months (95% CI: 49.1, 54.2) in patients who received lanthanum carbonate (test group), 48.9 months (95% CI: 47.3, 50.5) in patients treated with other phosphate binders (concomitant therapy control group) and 40.3 months (95% CI: 38.9, 41.5) in patients before the availability of lanthanum carbonate (historical control group). Bone fracture rates were 5.9%, 6.7% and 6.4%, respectively. After more than 850 000 person‐years of worldwide patient exposure, there is no evidence that lanthanum carbonate is associated with adverse safety outcomes in patients with end‐stage renal disease. PMID:27479781

  6. Lanthanum carbonate: safety data after 10 years.

    PubMed

    Hutchison, Alastair J; Wilson, Rosamund J; Garafola, Svetlana; Copley, John Brian

    2016-12-01

    Despite 10 years of post-marketing safety monitoring of the phosphate binder lanthanum carbonate, concerns about aluminium-like accumulation and toxicity persist. Here, we present a concise overview of the safety profile of lanthanum carbonate and interim results from a 5-year observational database study (SPD405-404; ClinicalTrials.gov identifier: NCT00567723). The pharmacokinetic paradigms of lanthanum and aluminium are different in that lanthanum is minimally absorbed and eliminated via the hepatobiliary pathway, whereas aluminium shows appreciable absorption and is eliminated by the kidneys. Randomised prospective studies of paired bone biopsies revealed no evidence of accumulation or toxicity in patients treated with lanthanum carbonate. Patients treated with lanthanum carbonate for up to 6 years showed no clinically relevant changes in liver enzyme or bilirubin levels. Lanthanum does not cross the intact blood-brain barrier. The most common adverse effects are mild/moderate nausea, diarrhoea and flatulence. An interim Kaplan-Meier analysis of SPD405-404 data from the United States Renal Data System revealed that the median 5-year survival was 51.6 months (95% CI: 49.1, 54.2) in patients who received lanthanum carbonate (test group), 48.9 months (95% CI: 47.3, 50.5) in patients treated with other phosphate binders (concomitant therapy control group) and 40.3 months (95% CI: 38.9, 41.5) in patients before the availability of lanthanum carbonate (historical control group). Bone fracture rates were 5.9%, 6.7% and 6.4%, respectively. After more than 850 000 person-years of worldwide patient exposure, there is no evidence that lanthanum carbonate is associated with adverse safety outcomes in patients with end-stage renal disease.

  7. Rare-Earth Tri-Halide Methanol-Adduct Single-Crystal Scintillators for Gamma Ray and Neutron Detection - 8/17/09

    SciTech Connect

    Boatner, Lynn A; Wisniewski, D.; Neal, John S; Bell, Zane W; Ramey, Joanne Oxendine; Kolopus, James A; Chakoumakos, Bryan C; Custelcean, Radu; Wisniewska, Monika; Peña, K. E.

    2009-01-01

    Cerium activated rare-earth tri- halides represent a well-known family of high performance inorganic rare-earth scintillators - including the high-light-yield, high-energy-resolution scintillator, cerium-doped lanthanum tribromide. These hygroscopic inorganic rare-earth halides are currently grown as single crystals from the melt - either by the Bridgman or Czochralski techniques slow and expensive processes that are frequently characterized by severe cracking of the material due to anisotropic thermal stresses and cleavage effects. We have recently discovered a new family of cerium-activated rare-earth metal organic scintillators consisting of tri-halide methanol adducts of cerium and lanthanum namely CeCl3(CH3OH)4 and LaBr3(CH3OH)4:Ce. These methanol-adduct scintillator materials can be grown near room temperature from a methanol solution, and their high solubility is consistent with the application of the rapid solution growth methods that are currently used to grow very large single crystals of potassium dihydrogen phosphate. The structures of these new rare-earth metal-organic scintillating compounds were determined by single crystal x-ray refinements, and their scintillation response to both gamma rays and neutrons, as presented here, was characterized using different excitation sources. Tri-halide methanol-adduct crystals activated with trivalent cerium apparently represent the initial example of a solution-grown rare-earth metal-organic molecular scintillator that is applicable to gamma ray, x-ray, and fast neutron detection.

  8. Gallium Lanthanum Sulphide Fibers for Infrared Transmission

    NASA Astrophysics Data System (ADS)

    West, Y. D.; Schweizer, T.; Brady, D. J.; Hewak, D. W.

    Gallium lanthanum sulphide (GLS) glass and fiber have potential for use in both active and passive infrared applications. In this paper the optical, thermal, and other key properties, which are essential for understanding the applications and crucial in the quest for practical fibres, are discussed. Glass preparation by melt-quenchingand subsequent fibre fabrication is described using both rod-in-tube and extruded preforms. Absorptive and scattering losses are explored as they could represent a fundamental limitation to successful device fabrication. Potential passive and active applications are reported and the prospects for a future generation of sulphide fiber-based devices examined.

  9. Oxidation of hydrogen halides to elemental halogens

    DOEpatents

    Rohrmann, Charles A.; Fullam, Harold T.

    1985-01-01

    A process for oxidizing hydrogen halides having substantially no sulfur impurities by means of a catalytically active molten salt is disclosed. A mixture of the subject hydrogen halide and an oxygen bearing gas is contacted with a molten salt containing an oxidizing catalyst and alkali metal normal sulfates and pyrosulfates to produce an effluent gas stream rich in the elemental halogen and substantially free of sulfur oxide gases.

  10. Reflection silver-halide gelatin holograms

    NASA Astrophysics Data System (ADS)

    Usanov, Yuri E.; Vavilova, Ye. A.; Kosobokova, N. L.; Shevtsov, Michail K.

    1991-02-01

    A new principle of reflection silverhalide gelatin (SHG) holograms generation is presented. The formation mechanism of the micro-cavity structure of holographic gratings is investigated. Based on the principle discussed here three methods of processing are suggested for making highly efficient SHG reflection holograms in the blue the green and the red regions of spectra with properties similar to those of conventional dichromated gelatin (DCG) holograms. 2. SHG HOLOGRAMS AND ANALYSIS OF THE PRINCIPAL OF THEIR FABRICATION Optical properties of DCG holograms and high light sensitivity of silver halide materials in the whole visible spectrum range can be combined in SHG holograms in which light field interference pattern recording is realized on silver halide grains while the light diffraction during the reconstruction takes place on a gelatin layer similar to DCG layer having a refractive index modulation. There exist a number of methods for transforming a ''silver'' structure into refracted index modulation structure. They are based on selective hardening of silver-halide layer gelatin. According to Pennington et. al. [1] selective hardening takes place as a result of the effect of laser or UV light on a silver halide developed fixed bleached and ammonium dichromate sensitized. A gelatin in isophase grating planes is hardened to a less degree that between planes due to high adsorption of a halide silver. After the removal of halide silver from the layer during the next fixing process

  11. Epitaxial Halide Perovskite Lateral Double Heterostructure.

    PubMed

    Wang, Yiping; Chen, Zhizhong; Deschler, Felix; Sun, Xin; Lu, Toh-Ming; Wertz, Esther A; Hu, Jia-Mian; Shi, Jian

    2017-03-28

    Epitaxial III-V semiconductor heterostructures are key components in modern microelectronics, electro-optics, and optoelectronics. With superior semiconducting properties, halide perovskite materials are rising as promising candidates for coherent heterostructure devices. In this report, spinodal decomposition is proposed and experimentally implemented to produce epitaxial double heterostructures in halide perovskite system. Pristine epitaxial mixed halide perovskites rods and films were synthesized via van der Waals epitaxy by chemical vapor deposition method. At room temperature, photon was applied as a knob to regulate the kinetics of spinodal decomposition and classic coarsening. By this approach, halide perovskite double heterostructures were created carrying epitaxial interfaces and outstanding optical properties. Reduced Fröhlich electron-phonon coupling was discovered in coherent halide double heterostructure, which is hypothetically attributed to the classic phonon confinement effect widely existing in III-V double heterostructures. As a proof-of-concept, our results suggest that halide perovskite-based epitaxial heterostructures may be promising for high-performance and low-cost optoelectronics, electro-optics, and microelectronics. Thus, ultimately, for practical device applications, it may be worthy to pursue these heterostructures via conventional vapor phase epitaxy approaches widely practised in III-V field.

  12. Filamentation and supercontinuum generation in lanthanum glass

    NASA Astrophysics Data System (ADS)

    Yang, Yuxia; Liao, Meisong; Li, Xia; Bi, Wanjun; Ohishi, Yasutake; Cheng, Tonglei; Fang, Yongzheng; Zhao, Guoying; Gao, Weiqing

    2017-01-01

    A broadband supercontinuum (SC) covering 400-2800 nm in a 20 dB dynamic range is reported in a piece of highly nonlinear, low-dispersion bulk lanthanum glass without employing any lens to focus the pump pulse. The spectrum width obtained in this study is broader than the maximum spectrum width obtained in silica photonic crystal fibers. The filaments and bright conical visible emission patterns of the SC are analyzed. Under optimum pump conditions, an SC conversion efficiency of 75% is obtained. The SC conversion efficiency is confirmed to be stable. Additionally, the relationship between the input peak intensity and the output beam radius is elucidated by simulating the propagation of a Gaussian beam in the bulk lanthanum glass. A 0.20 mm stable laser beam radius at the end of the propagation domain is demonstrated in a certain input peak intensity range. This small value of the beam radius indicates that most of the output power is localized over a small region because of the Kerr focusing effect despite the existence of conical emission in the SC generation by filamentation. The findings of this study are of significance for the development of ultra-broadband SC sources based on bulk glasses and high peak power lasers.

  13. Process for microwave sintering boron carbide

    DOEpatents

    Holcombe, Cressie E.; Morrow, Marvin S.

    1993-01-01

    A method of microwave sintering boron carbide comprises leaching boron carbide powder with an aqueous solution of nitric acid to form a leached boron carbide powder. The leached boron carbide powder is coated with a glassy carbon precursor to form a coated boron carbide powder. The coated boron carbide powder is consolidated in an enclosure of boron nitride particles coated with a layer of glassy carbon within a container for microwave heating to form an enclosed coated boron carbide powder. The enclosed coated boron carbide powder is sintered within the container for microwave heating with microwave energy.

  14. Process for microwave sintering boron carbide

    DOEpatents

    Holcombe, C.E.; Morrow, M.S.

    1993-10-12

    A method of microwave sintering boron carbide comprises leaching boron carbide powder with an aqueous solution of nitric acid to form a leached boron carbide powder. The leached boron carbide powder is coated with a glassy carbon precursor to form a coated boron carbide powder. The coated boron carbide powder is consolidated in an enclosure of boron nitride particles coated with a layer of glassy carbon within a container for microwave heating to form an enclosed coated boron carbide powder. The enclosed coated boron carbide powder is sintered within the container for microwave heating with microwave energy.

  15. Methods for producing single crystal mixed halide perovskites

    DOEpatents

    Zhu, Kai; Zhao, Yixin

    2017-07-11

    An aspect of the present invention is a method that includes contacting a metal halide and a first alkylammonium halide in a solvent to form a solution and maintaining the solution at a first temperature, resulting in the formation of at least one alkylammonium halide perovskite crystal, where the metal halide includes a first halogen and a metal, the first alkylammonium halide includes the first halogen, the at least one alkylammonium halide perovskite crystal includes the metal and the first halogen, and the first temperature is above about 21.degree. C.

  16. Silicon Carbide Integrated Circuit Chip

    NASA Image and Video Library

    2015-02-17

    A multilevel interconnect silicon carbide integrated circuit chip with co-fired ceramic package and circuit board recently developed at the NASA GRC Smart Sensors and Electronics Systems Branch for high temperature applications. High temperature silicon carbide electronics and compatible packaging technologies are elements of instrumentation for aerospace engine control and long term inner-solar planet explorations.

  17. Deposition and modification of tantalum carbide coatings on graphite by laser interactions

    SciTech Connect

    Veligdan, J.; Branch, D.; Vanier, P.E.; Barletta, R.E.

    1992-01-01

    Graphite surfaces can be hardened and protected from erosion by hydrogen at high temperatures by refractory metal carbide coatings, which are usually prepared by chemical vapor deposition (CVD) or chemical vapor reaction (CVR) methods. These techniques rely on heating the substrate to a temperature where a volatile metal halide decomposes and reacts with either a hydrocarbon gas or with carbon from the substrate. For CVR techniques, deposition temperatures must be in excess of 2000[degrees]C in order to achieve favorable deposition kinetics. In an effort to lower the bulk substrate deposition temperature, the use of laser interactions with both the substrate and the metal halide deposition gas has been employed. Initial testing, involved the use of a CO[sub 2] laser to heat the surface of a graphite substrate and a KrF excimer laser to accomplish a photodecomposition of TaCl[sub 5] gas near the substrate. Results of preliminary experiments using these techniques are described.

  18. Deposition and modification of tantalum carbide coatings on graphite by laser interactions

    SciTech Connect

    Veligdan, J.; Branch, D.; Vanier, P.E.; Barletta, R.E.

    1992-12-31

    Graphite surfaces can be hardened and protected from erosion by hydrogen at high temperatures by refractory metal carbide coatings, which are usually prepared by chemical vapor deposition (CVD) or chemical vapor reaction (CVR) methods. These techniques rely on heating the substrate to a temperature where a volatile metal halide decomposes and reacts with either a hydrocarbon gas or with carbon from the substrate. For CVR techniques, deposition temperatures must be in excess of 2000{degrees}C in order to achieve favorable deposition kinetics. In an effort to lower the bulk substrate deposition temperature, the use of laser interactions with both the substrate and the metal halide deposition gas has been employed. Initial testing, involved the use of a CO{sub 2} laser to heat the surface of a graphite substrate and a KrF excimer laser to accomplish a photodecomposition of TaCl{sub 5} gas near the substrate. Results of preliminary experiments using these techniques are described.

  19. Silicon carbide sewing thread

    NASA Technical Reports Server (NTRS)

    Sawko, Paul M. (Inventor)

    1995-01-01

    Composite flexible multilayer insulation systems (MLI) were evaluated for thermal performance and compared with currently used fibrous silica (baseline) insulation system. The systems described are multilayer insulations consisting of alternating layers of metal foil and scrim ceramic cloth or vacuum metallized polymeric films quilted together using ceramic thread. A silicon carbide thread for use in the quilting and the method of making it are also described. These systems provide lightweight thermal insulation for a variety of uses, particularly on the surface of aerospace vehicles subject to very high temperatures during flight.

  20. The energetics of lanthanum tantalate materials

    SciTech Connect

    Forbes, Tori Z.; Nyman, May; Rodriguez, Mark A.; Navrotsky, Alexandra

    2010-11-15

    Lanthanum tantalates are important refractory materials with application in photocatalysis, solid oxide fuel cells, and phosphors. Soft-chemical synthesis utilizing the Lindqvist ion, [Ta{sub 6}O{sub 19}]{sup 8-}, has yielded a new phase, La{sub 2}Ta{sub 2}O{sub 7}(OH){sub 2}. Using the hydrated phase as a starting material, a new lanthanum orthotantalate polymorph was formed by heating to 850 {sup o}C, which converts to a previously reported LaTaO{sub 4} polymorph at 1200 {sup o}C. The stabilities of La{sub 2}Ta{sub 2}O{sub 7}(OH){sub 2} (LaTa-OH), the intermediate LaTaO{sub 4} polymorph (LaTa-850), and the high temperature phase (LaTa-1200) were investigated using high-temperature oxide melt solution calorimetry. The enthalpy of formation from the oxides were calculated from the enthalpies of drop solution to be -87.1{+-}9.6, -94.9{+-}8.8, and -93.1{+-}8.7 kJ/mol for LaTa-OH, LaTa-850, and LaTa-1200, respectively. These results indicate that the intermediate phase, LaTa-850, is the most stable. This pattern of energetics may be related to cation-cation repulsion of the tantalate cations. We also investigated possible LnTaO{sub 4} and Ln{sub 2}Ta{sub 2}O{sub 7}(OH){sub 2} analogues of Ln=Pr, Nd to examine the relationship between cation size and the resulting phases. - Graphical abstract: The energetics of three lanthanum tantalates were investigated by the high-temperature oxide melt solution calorimetry. The enthalpies of formation from the oxides were calculated from the enthalpies of drop solution to be -87.1{+-}9.6, -94.9{+-}8.8, and -93.1{+-}8.7 kJ/mol for La{sub 2}Ta{sub 2}O{sub 7}(OH){sub 2}, LaTaO{sub 4} (850 {sup o}C), and LaTaO{sub 4} (1200 {sup o}C), respectively. These results indicate that the intermediate phase, LaTaO{sub 4} (850 {sup o}C), is the most stable in energy. Display Omitted

  1. Dimming of metal halide lamps

    NASA Astrophysics Data System (ADS)

    Schurer, Kees

    1994-03-01

    We ran some tests on the effect of dimming of metal halide (MH) lamps upon the stability and the spectral quality of the light output. Lamps used were a new Philips lamp HPI-T 250W, a similar Philips lamp with a few thousand burning hours and a new Osram lamp HQI-T 250W/D. The ballast was a BBC type DJ 250/2KS, the starter a BAS TORGI type MZN 250 SE and the dimmer an Elstrom Control System type ERHQ-T 250. Power was derived from a Philips stabilizer, type PE 1602. Lamp output was monitored with a PAR meter. Spectra were taken at 100% and at 50% output as measured with the PAR meter. Lamps were allowed to stabilize at any setting for 30 minutes before measurements were made. Lamp manufacturers advise against dimming for fear of poor stability and intolerable changes of the spectrum. However, none of the lamps showed a decrease in stability, no flicker or wandering of the discharge, and the changes of the spectrum were not negligible, but certainly not dramatic. Lamps of either manufacture retain their white color, relative peak heights of spectral lines did shift, but no gaps in the spectrum occurred. Spectra taken at 50% with 30 minutes intervals coincided. Differences between the new and the older Philips lamp were noticeable, but not really significant.

  2. Dimming of metal halide lamps

    NASA Technical Reports Server (NTRS)

    Schurer, Kees

    1994-01-01

    We ran some tests on the effect of dimming of metal halide (MH) lamps upon the stability and the spectral quality of the light output. Lamps used were a new Philips lamp HPI-T 250W, a similar Philips lamp with a few thousand burning hours and a new Osram lamp HQI-T 250W/D. The ballast was a BBC type DJ 250/2KS, the starter a BAS TORGI type MZN 250 SE and the dimmer an Elstrom Control System type ERHQ-T 250. Power was derived from a Philips stabilizer, type PE 1602. Lamp output was monitored with a PAR meter. Spectra were taken at 100% and at 50% output as measured with the PAR meter. Lamps were allowed to stabilize at any setting for 30 minutes before measurements were made. Lamp manufacturers advise against dimming for fear of poor stability and intolerable changes of the spectrum. However, none of the lamps showed a decrease in stability, no flicker or wandering of the discharge, and the changes of the spectrum were not negligible, but certainly not dramatic. Lamps of either manufacture retain their white color, relative peak heights of spectral lines did shift, but no gaps in the spectrum occurred. Spectra taken at 50% with 30 minutes intervals coincided. Differences between the new and the older Philips lamp were noticeable, but not really significant.

  3. Clinical pharmacokinetics of the phosphate binder lanthanum carbonate.

    PubMed

    Damment, Stephen J P; Pennick, Michael

    2008-01-01

    Lanthanum carbonate is considered to be the most potent of a new generation of noncalcium phosphate binders used to treat hyperphosphataemia in chronic kidney disease (CKD), a condition associated with progressive bone and cardiovascular pathology and a markedly elevated risk of death. Its phosphate-binding action involves ionic binding and precipitation of insoluble complexes within the lumen of the intestine, thereby preventing absorption of dietary phosphate. While pharmacokinetics have little relevance to the efficacy of lanthanum carbonate, they are of fundamental importance when it comes to evaluating safety. When administered as lanthanum carbonate, the oral bioavailability of lanthanum is low (approximately 0.001%). The small absorbed fraction is excreted predominantly in bile, with less than 2% being eliminated by the kidneys. Predictably, therefore, plasma exposure and pharmacokinetics have been shown to be similar in healthy human volunteers and CKD stage 5 patients. With almost complete plasma protein binding, free lanthanum concentrations in patients at steady state are <3 pg/mL. These properties greatly reduce systemic exposure, tissue deposition and the potential for adverse effects. While lanthanum has a variety of calcium-like actions in vitro, there is little or no evidence that these occur in vivo. This paradox is explained by the very low concentrations of circulating free lanthanum ions, which are many orders of magnitude lower than reported effect concentrations in vitro. Safety pharmacology and toxicology evaluations have failed to reveal any significant calcium-like actions in vivo, despite inclusion of high intravenous doses in some cases.Lanthanum carbonate has a low propensity to cause systemic drug interactions due to its poor absorption. However, the higher concentrations present in the gastrointestinal tract can form chelates with some drugs, such as fluoroquinolones, and reduce their absorption. The improved understanding of the

  4. Diminiode thermionic energy conversion with lanthanum-hexaboride electrodes

    NASA Technical Reports Server (NTRS)

    Kroeger, E. W.; Bair, V. L.; Morris, J. F.

    1978-01-01

    Thermionic conversion data obtained from a variable gap cesium diminiode with a hot pressed, sintered lanthanum hexaboride emitter and an arc melted lanthanum hexaboride collector are presented. Performance curves cover a range of temperatures: emitter 1500 to 1700 K, collector 750 to 1000 K, and cesium reservoir 370 to 510 K. Calculated values of emitter and collector work functions and barrier index are also given.

  5. The Remarkable Reactivity of Aryl Halides with Nucleophiles

    ERIC Educational Resources Information Center

    Bunnett, Joseph F.

    1974-01-01

    Discusses the reactivity of aryl halides with nucleophilic or basic reagents, including nucleophilic attacks on carbon, hydrogen, halogen, and arynes. Suggestions are made concerning revisions of the sections on aryl halide chemistry courses and the corresponding chapters in textbooks. (CC)

  6. The Remarkable Reactivity of Aryl Halides with Nucleophiles

    ERIC Educational Resources Information Center

    Bunnett, Joseph F.

    1974-01-01

    Discusses the reactivity of aryl halides with nucleophilic or basic reagents, including nucleophilic attacks on carbon, hydrogen, halogen, and arynes. Suggestions are made concerning revisions of the sections on aryl halide chemistry courses and the corresponding chapters in textbooks. (CC)

  7. Shallow halogen vacancies in halide optoelectronic materials

    SciTech Connect

    Shi, Hongliang; Du, Mao -Hua

    2014-11-05

    Halogen vacancies (VH) are usually deep color centers (F centers) in halides and can act as major electron traps or recombination centers. The deep VH contributes to the typically poor carrier transport properties in halides. However, several halides have recently emerged as excellent optoelectronic materials, e.g., CH3NH3PbI3 and TlBr. Both CH3NH3PbI3 and TlBr have been found to have shallow VH, in contrast to commonly seen deep VH in halides. In this paper, several halide optoelectronic materials, i.e., CH3NH3PbI3, CH3NH3SnI3 (photovoltaic materials), TlBr, and CsPbBr3, (gamma-ray detection materials) are studied to understand the material chemistry and structure that determine whether VH is a shallow or deep defect in a halide material. It is found that crystal structure and chemistry of ns2 ions both play important roles in creating shallow VH in halides such as CH3NH3PbI3, CH3NH3SnI3, and TlBr. The key to identifying halides with shallow VH is to find the right crystal structures and compounds that suppress cation orbital hybridization at VH, such as those with long cation-cation distances and low anion coordination numbers, and those with crystal symmetry that prevents strong hybridization of cation dangling bond orbitals at VH. Furthermore, the results of this paper provide insight and guidance to identifying halides with shallow VH as good electronic and optoelectronic materials.

  8. Structural effects in molecular metal halides.

    PubMed

    Hargittai, Magdolna

    2009-03-17

    Metal halides are a relatively large class of inorganic compounds that participate in many industrial processes, from halogen metallurgy to the production of semiconductors. Because most metal halides are ionic crystals at ambient conditions, the term "molecular metal halides" usually refers to vapor-phase species. These gas-phase molecules have a special place in basic research because they exhibit the widest range of chemical bonding from the purely ionic to mostly covalent bonding through to weakly interacting systems. Although our focus is basic research, knowledge of the structural and thermodynamic properties of gas-phase metal halides is also important in industrial processes. In this Account, we review our most recent work on metal halide molecular structures. Our studies are based on electron diffraction and vibrational spectroscopy, and increasingly, we have augmented our experimental work with quantum chemical computations. Using both experimental and computational techniques has enabled us to determine intriguing structural effects with better accuracy than using either technique alone. We loosely group our discussion based on structural effects including "floppiness", relativistic effects, vibronic interactions, and finally, undiscovered molecules with computational thermodynamic stability. Floppiness, or serious "nonrigidity", is a typical characteristic of metal halides and makes their study challenging for both experimentalists and theoreticians. Relativistic effects are mostly responsible for the unique structure of gold and mercury halides. These molecules have shorter-than-expected bonds and often have unusual geometrical configurations. The gold monohalide and mercury dihalide dimers and the molecular-type crystal structure of HgCl(2) are examples. We also examined spin-orbit coupling and the possible effect of the 4f electrons on the structure of lanthanide trihalides. Unexpectedly, we found that the geometry of their dimers depends on the f

  9. Lanthanum tetrazinc, LaZn4.

    PubMed

    Oshchapovsky, Igor; Pavlyuk, Volodymyr; Dmytriv, Grygoriy; Griffin, Alexandra

    2012-06-01

    The structure of lanthanum tetrazinc, LaZn(4), has been determined from single-crystal X-ray diffraction data for the first time, approximately 70 years after its discovery. The compound exhibits a new structure type in the space group Cmcm, with one La atom and two Zn atoms occupying sites with m2m symmetry, and one Zn atom occupying a site with 2.. symmetry. The structure is closely related to the BaAl(4), La(3)Al(11), BaNi(2)Si(2) and CaCu(5) structure types, which can be presented as close-packed arrangements of 18-vertex clusters, in this case LaZn(18). The kindred structure types contain related 18-vertex clusters around atoms of the rare earth or alkaline earth metal.

  10. Laser glazing of lanthanum magnesium hexaaluminate

    NASA Astrophysics Data System (ADS)

    Zhang, Yanfei; Wang, Yaomin; Jarligo, Maria Ophelia; Zhong, Xinghua; Li, Qin; Cao, Xueqiang

    2008-08-01

    Lanthanum magnesium hexaalumminate (LMA) is an important candidate for thermal barrier coatings due to its thermal stability and low thermal conductivity. On the other hand, laser glazing method can potentially make thermal barrier coatings impermeable, resistant to corrosion on the surface and porous at bulk. LMA powder was synthesized at 1600 °C by solid-state reaction, pressed into tablet and laser glazed with a 5-kW continuous wave CO2 laser. Dendritic structures were observed on the surface of the laser-glazed specimen. The thicker the tablet, the easier the sample cracks. Cracking during laser glazing is attributed to the low thermal expansion coefficient and large thickness of the sample.

  11. Phases in lanthanum-nickel-aluminum alloys

    SciTech Connect

    Mosley, W.C.

    1992-01-01

    Lanthanum-nickel-aluminum (LANA) alloys will be used to pump, store and separate hydrogen isotopes in the Replacement Tritium Facility (RTF). The aluminum content (y) of the primary LaNi{sub 5}-phase is controlled to produce the desired pressure-temperature behavior for adsorption and desorption of hydrogen. However, secondary phases cause decreased capacity and some may cause undesirable retention of tritium. Twenty-three alloys purchased from Ergenics, Inc. for development of RTF processes have been characterized by scanning electron microscopy (SEM) and by electron microprobe analysis (EMPA) to determine the distributions and compositions of constituent phases. This memorandum reports the results of these characterization studies. Knowledge of the structural characteristics of these alloys is a useful first step in selecting materials for specific process development tests and in interpreting results of those tests. Once this information is coupled with data on hydrogen plateau pressures, retention and capacity, secondary phase limits for RTF alloys can be specified.

  12. Sintering aid for lanthanum chromite refractories

    DOEpatents

    Flandermeyer, Brian K.; Poeppel, Roger B.; Dusek, Joseph T.; Anderson, Harlan U.

    1988-01-01

    An electronically conductive interconnect layer for use in a fuel cell or other electrolytic device is formed with sintering additives to permit densification in a monolithic structure with the electrode materials. Additions including an oxide of boron and a eutectic forming composition of Group 2A metal fluorides with Group 3B metal fluorides and Group 2A metal oxides with Group 6B metal oxides lower the required firing temperature of lanthanum chromite to permit densification to in excess of 94% of theoretical density without degradation of electrode material lamina. The monolithic structure is formed by tape casting thin layers of electrode, interconnect and electrolyte materials and sintering the green lamina together under common densification conditions.

  13. Lanthanum sulfides as high temperature thermoelectric materials

    NASA Technical Reports Server (NTRS)

    Danielson, L. R.; Matsuda, S.; Raag, V.

    1984-01-01

    Thermoelectric property measurements have been made for the nonstoichiometric lanthanum sulfides, LaS(R) with R in the range 1.33-1.50. The Seebeck coefficients and electrical resistivities increase with temperature from 200 to 1100 C. Power factors (defined as Seebeck coefficient squared divided by electrical resistivity) generally increase both as the temperature is increased and as the compound composition is varied from LaS(1.48) to LaS(1.35). The power factor values combined with estimates of thermal conductivities for LaS(1.38) and LaS(1.4) yield figures of merit greater than 0.0005 at 1000 C.

  14. Localized holes in superconducting lanthanum cuprate

    SciTech Connect

    Hammel, P.C.; Statt, B.W.; Martin, R.L.; Chou, F.C.; Johnston, D.C.; Cheong, S.

    1998-01-01

    Copper NQR spectra demonstrate the existence of a second, anomalous copper site in lanthanum cuprate whose character is independent of the method of doping. We present a systematic NMR/NQR study of La{sub 2}CuO{sub 4+{delta}} for a range of {delta}, which demonstrates that the density of such sites increases with {delta}. Analysis of our results and of published data from La{sub 2{minus}x}Sr{sub x}CuO{sub 4} indicate that a substantial fraction of the doped holes in these materials localize in CuO{sub 6} octahedra adjacent to the out-of-plane dopants, and that the anomalous sites are those neighboring a site occupied by such a pinned hole. Thus, superconductivity occurs in a CuO{sub 2} plane containing many localized holes. {copyright} {ital 1998} {ital The American Physical Society}

  15. Phase Stability of the Lanthanum Strontium Manganites

    NASA Astrophysics Data System (ADS)

    Zheng, Feng; Pederson, Larry

    1996-03-01

    Phase diagram and thermodynamic data of the La-Sr-Mn-O system has been studied. The ABO3 -type perovskite of this system is presently the preferred cathode material for application in solid oxide fuel cells. And the phase stability of the lanthanum strontium manganites at elevated temperature is vital to fuel cell operation. Measuring the electromotive force through solid galvanic cell (-) Air,Pt|SrF_2,SrO||CaF_2||La_1-xSr_xMnO_3,SrF_2|Pt,Air (+) and the like enable us to derive the strontium oxide activity and other thermodynamic parameters such as Gibbs free energy of reaction, etc, which help us to understand the materials in using.

  16. PREPARATION AND PURIFICATION OF SILICON CARBIDE.

    DTIC Science & Technology

    the materials were divided into two parts. Part I covers problems of silicon carbide preparation and the growing of silicon carbide single crystals...and thin films for semiconductor devices. Part II treats problems of purity, including the purification and chemical analysis of silicon carbide and of starting materials for silicon carbide preparation.

  17. Methods of producing continuous boron carbide fibers

    SciTech Connect

    Garnier, John E.; Griffith, George W.

    2015-12-01

    Methods of producing continuous boron carbide fibers. The method comprises reacting a continuous carbon fiber material and a boron oxide gas within a temperature range of from approximately 1400.degree. C. to approximately 2200.degree. C. Continuous boron carbide fibers, continuous fibers comprising boron carbide, and articles including at least a boron carbide coating are also disclosed.

  18. Scintillators with potential to supersede lanthanum bromide

    SciTech Connect

    Cherepy, Nerine; Payne, Steven; Aszatlos, Steve; Hull, Giulia; Kuntz, J.; Niedermayr, Tom; Pimputkar, S.; Roberts, J.; Sanner, R.; Tillotson, T.; van Loef, Edger; Wilson, Cody; Shah, Kanai; Roy, U.; Hawrami, R.; Burger, Arnold; Boatner, Lynn; Choong, Woon-Seng; Moses, William

    2009-06-01

    New scintillators for high-resolution gamma ray spectroscopy have been identified, grown and characterized. Our development efforts have focused on two classes of high light yield materials: Europium-doped alkaline earth halides and Cerium-doped garnets. Of the halide single crystals we have grown by the Bridgman method - SrI{sub 2}, CaI{sub 2}, SrBr{sub 2}, BaI{sub 2} and BaBr{sub 2} - SrI{sub 2} is the most promising. SrI{sub 2}(Eu) emits into the Eu{sup 2+} band, centered at 435 nm, with a decay time of 1.2 {micro}s and a light yield of up to 115,000 photons/MeV. It offers energy resolution better than 3% FWHM at 662 keV, and exhibits excellent light yield proportionality. Transparent ceramics fabrication allows production of Gadolinium- and Terbium-based garnets which are not growable by melt techniques due to phase instabilities. While scintillation light yields of Cerium-doped ceramic garnets are high, light yield non-proportionality and slow decay components appear to limit their prospects for high energy resolution. We are developing an understanding of the mechanisms underlying energy dependent scintillation light yield non-proportionality and how it affects energy resolution. We have also identified aspects of optical design that can be optimized to enhance energy resolution.

  19. Method for recovering hydrocarbons from molten metal halides

    DOEpatents

    Pell, Melvyn B.

    1979-01-01

    In a process for hydrocracking heavy carbonaceous materials by contacting such carbonaceous materials with hydrogen in the presence of a molten metal halide catalyst to produce hydrocarbons having lower molecular weights and thereafter recovering the hydrocarbons so produced from the molten metal halide, an improvement comprising injecting into the spent molten metal halide, a liquid low-boiling hydrocarbon stream is disclosed.

  20. Hydrogen-silicon carbide interactions

    NASA Technical Reports Server (NTRS)

    Eckel, Andrew J.; Jacobson, Nathan S.; Misra, Ajay K.; Humphrey, Donald L.

    1989-01-01

    A study of the thermochemistry and kinetics of hydrogen environmental attack of silicon carbide was conducted for temperatures in the range from 1100 C to 1400 C. Thermodynamic maps based on the parameters of pressure and oxygen/moisture content were constructed. With increasing moisture levels, four distinct regions of attack were identified. Each region is defined by the thermodynamically stable solid phases. The theoretically stable solid phases of Region 1 are silicon carbide and silicon. Experimental evidence is provided to support this thermodynamic prediction. Silicon carbide is the single stable solid phase in Region 2. Active attack of the silicon carbide in this region occurs by the formation of gases of SiO, CO, CH4, SiH4, and SiH. Analysis of the kinetics of reaction for Region 2 at 1300 C show the attack of the silicon carbide to be controlled by gas phase diffusion of H2O to the sample. Silicon carbide and silica are the stable phases common to Regions 3 and 4. These two regions are characterized by the passive oxidation of silicon carbide and formation of a protective silica layer.

  1. Hydrogen-silicon carbide interactions

    NASA Technical Reports Server (NTRS)

    Eckel, Andrew J.; Misra, Ajay K.; Humphrey, Donald L.; Jacobson, Nathan S.

    1990-01-01

    A study of the thermochemistry and kinetics of hydrogen environmental attack of silicon carbide was conducted for temperatures in the range from 1100 C to 1400 C. Thermodynamics maps based on the parameters of pressure and oxygen/moisture content were constructed. With increasing moisture levels, four distinct regions of attack were identified. Each region is defined by the thermodynamically stable solid phases. The theoretically stable solid phases of region 1 are silicon carbide and silicon. Experimental evidence is provided to support this thermodynamic prediction. Silicone carbide is the single stable solid phase in region 2. Active attack of the silicon carbide in this region occurs by the formation of gases of SiO, CO, CH4, SiH4 and SiH. Analyses of the kinetics of reaction for region 2 at 1300 C show the attack of the silicon carbide to be controlled by gas phase diffusion of H2O to the sample. Silicon carbide and silica are the stable phases common to regions 3 and 4. These two regions are characterized by the passive oxidation of silicon carbide and formation of a protective silica layer.

  2. Atomic Resolution Imaging of Halide Perovskites.

    PubMed

    Yu, Yi; Zhang, Dandan; Kisielowski, Christian; Dou, Letian; Kornienko, Nikolay; Bekenstein, Yehonadav; Wong, Andrew B; Alivisatos, A Paul; Yang, Peidong

    2016-12-14

    The radiation-sensitive nature of halide perovskites has hindered structural studies at the atomic scale. We overcome this obstacle by applying low dose-rate in-line holography, which combines aberration-corrected high-resolution transmission electron microscopy with exit-wave reconstruction. This technique successfully yields the genuine atomic structure of ultrathin two-dimensional CsPbBr3 halide perovskites, and a quantitative structure determination was achieved atom column by atom column using the phase information of the reconstructed exit-wave function without causing electron beam-induced sample alterations. An extraordinarily high image quality enables an unambiguous structural analysis of coexisting high-temperature and low-temperature phases of CsPbBr3 in single particles. On a broader level, our approach offers unprecedented opportunities to better understand halide perovskites at the atomic level as well as other radiation-sensitive materials.

  3. Triiodide and mixed tri-halide anions from negative ion electrospray ionization of alkali halide solutions

    NASA Astrophysics Data System (ADS)

    Shukla, Anil

    2017-10-01

    Electrospray ionization of alkali halide solutions in the negative ion mode results in the formation of cluster ions of the general formula, (MX)nX-. However, alkali iodides form triiodide anion, I3-, in high abundance in addition to cluster ions. Br3- ions are observed in low abundance. Also, mixed tri-halide anions, I2Y-, are observed in high abundance when a small amount (<1%) of KI is added to other alkali halide solutions. These results are explained by the uniquely different physical characteristics of lithium and the iodide ions compared with others in the series.

  4. Microwave processing of silicon carbide. CRADA final report

    SciTech Connect

    Kimrey, H.D.; Kiggans, J.O.; Ness, E.A.; Rafaniello, W.

    1998-02-01

    A Cooperative Research and Development Agreement (CRADA) between Lockheed Martin Energy Systems, Inc. (LMES) and Dow Chemical Company was initiated on May 3, 1993. (Lockheed Martin Energy Research Inc. (LMER) replaced LMES). The completion date for the Agreement was December 1996. The purpose of this project is to develop microwave processing techniques to produce superior silicon carbide. Sintered silicon carbide is an attractive material for use in high-stress, high-temperature, high-wear, or highly corrosive applications. However, use in these applications has been hampered by a lack of consistency in strength, density, and other physical properties. It is proposed that the enhanced sintering that has been achieved using microwaves in oxide and halide systems be applied to the sintering of these materials to produce a more highly controlled density and microstructure. This will, in turn, increase the strength and Weibull modulus of the sintered body. The use of microwave energy to anneal for a moderate temperature (1,400--1,600 C) anneal in a high vacuum (< 10{sup {minus}4} Torr) results in an improvement in the sintered density and density distribution. These changes in turn result in improved properties of the sintered compacts. Further, scale up of the process has resulted in the routine production of 3 kg components in excess of 4 cm in thickness.

  5. Multiline operation of mercury halide lasers

    SciTech Connect

    Kushawaha, M.; Mahmood, M.

    1988-01-01

    Emission spectrum of the (B-X) band system of HgX radicals (X=chlorine, bromine, iodine) was observed by passing electrical discharge through flowing vapors of mercury halides. The emission intensity of the most intense band of the (B-X) system of these radicals was observed to decrease in the presence of other mercury halide vapors at temperatures higher than 130C. Laser action was observed from the (B-X) transition of mercurous chloride, mercurous bromide, and mercurous iodide radicals by electrical discharge pumping of mercuric chloride, mercuric bromide and mercuric iodide vapors individually.

  6. Silicon Carbide Electronic Devices

    NASA Technical Reports Server (NTRS)

    Neudeck, P. G.

    2001-01-01

    The status of emerging silicon carbide (SiC) widebandgap semiconductor electronics technology is briefly surveyed. SiC-based electronic devices and circuits are being developed for use in high-temperature, high-power, and/or high-radiation conditions under which conventional semiconductors cannot function. Projected performance benefits of SiC electronics are briefly illustrated for several applications. However, most of these operational benefits of SiC have yet to be realized in actual systems, primarily owing to the fact that the growth techniques of SiC crystals are relatively immature and device fabrication technologies are not yet sufficiently developed to the degree required for widespread, reliable commercial use. Key crystal growth and device fabrication issues that limit the performance and capability of high-temperature and/or high-power SiC electronics are identified. The electrical and material quality differences between emerging SiC and mature silicon electronics technology are highlighted.

  7. Silicon Carbide Electronic Devices

    NASA Technical Reports Server (NTRS)

    Neudeck, P. G.

    2001-01-01

    The status of emerging silicon carbide (SiC) widebandgap semiconductor electronics technology is briefly surveyed. SiC-based electronic devices and circuits are being developed for use in high-temperature, high-power, and/or high-radiation conditions under which conventional semiconductors cannot function. Projected performance benefits of SiC electronics are briefly illustrated for several applications. However, most of these operational benefits of SiC have yet to be realized in actual systems, primarily owing to the fact that the growth techniques of SiC crystals are relatively immature and device fabrication technologies are not yet sufficiently developed to the degree required for widespread, reliable commercial use. Key crystal growth and device fabrication issues that limit the performance and capability of high-temperature and/or high-power SiC electronics are identified. The electrical and material quality differences between emerging SiC and mature silicon electronics technology are highlighted.

  8. Silicon Carbide Technology

    NASA Technical Reports Server (NTRS)

    Neudeck, Philip G.

    2006-01-01

    Silicon carbide based semiconductor electronic devices and circuits are presently being developed for use in high-temperature, high-power, and high-radiation conditions under which conventional semiconductors cannot adequately perform. Silicon carbide's ability to function under such extreme conditions is expected to enable significant improvements to a far-ranging variety of applications and systems. These range from greatly improved high-voltage switching for energy savings in public electric power distribution and electric motor drives to more powerful microwave electronics for radar and communications to sensors and controls for cleaner-burning more fuel-efficient jet aircraft and automobile engines. In the particular area of power devices, theoretical appraisals have indicated that SiC power MOSFET's and diode rectifiers would operate over higher voltage and temperature ranges, have superior switching characteristics, and yet have die sizes nearly 20 times smaller than correspondingly rated silicon-based devices [8]. However, these tremendous theoretical advantages have yet to be widely realized in commercially available SiC devices, primarily owing to the fact that SiC's relatively immature crystal growth and device fabrication technologies are not yet sufficiently developed to the degree required for reliable incorporation into most electronic systems. This chapter briefly surveys the SiC semiconductor electronics technology. In particular, the differences (both good and bad) between SiC electronics technology and the well-known silicon VLSI technology are highlighted. Projected performance benefits of SiC electronics are highlighted for several large-scale applications. Key crystal growth and device-fabrication issues that presently limit the performance and capability of high-temperature and high-power SiC electronics are identified.

  9. 40 CFR 721.10370 - Phosphonic acid, p-octyl-, lanthanum (3+) salt (2:1).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Phosphonic acid, p-octyl-, lanthanum... New Uses for Specific Chemical Substances § 721.10370 Phosphonic acid, p-octyl-, lanthanum (3+) salt... substance identified as phosphinic acid, p-octyl-, lanthanum (3+) salt (2:1) (PMN P-10-99; CAS No....

  10. 40 CFR 721.10370 - Phosphonic acid, p-octyl-, lanthanum (3+) salt (2:1).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Phosphonic acid, p-octyl-, lanthanum... New Uses for Specific Chemical Substances § 721.10370 Phosphonic acid, p-octyl-, lanthanum (3+) salt... substance identified as phosphinic acid, p-octyl-, lanthanum (3+) salt (2:1) (PMN P-10-99; CAS No....

  11. 40 CFR 721.10370 - Phosphonic acid, p-octyl-, lanthanum (3+) salt (2:1).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Phosphonic acid, p-octyl-, lanthanum... New Uses for Specific Chemical Substances § 721.10370 Phosphonic acid, p-octyl-, lanthanum (3+) salt... substance identified as phosphinic acid, p-octyl-, lanthanum (3+) salt (2:1) (PMN P-10-99; CAS No....

  12. The Additive Coloration of Alkali Halides

    ERIC Educational Resources Information Center

    Jirgal, G. H.; and others

    1969-01-01

    Describes the construction and use of an inexpensive, vacuum furnace designed to produce F-centers in alkali halide crystals by additive coloration. The method described avoids corrosion or contamination during the coloration process. Examination of the resultant crystals is discussed and several experiments using additively colored crystals are…

  13. Localized corrosion in halides other than chlorides

    SciTech Connect

    Koch, G.H.

    1995-12-31

    This literature survey characterizes the effects of non-chloride halides on localized corrosion. It includes published material and unpublished data obtained through a questionnaire. Chapters cover Stainless Steels, Nickel, Titanium, and Zirconium. The engineer can use this information for material selection.

  14. The Additive Coloration of Alkali Halides

    ERIC Educational Resources Information Center

    Jirgal, G. H.; and others

    1969-01-01

    Describes the construction and use of an inexpensive, vacuum furnace designed to produce F-centers in alkali halide crystals by additive coloration. The method described avoids corrosion or contamination during the coloration process. Examination of the resultant crystals is discussed and several experiments using additively colored crystals are…

  15. Molecular compressibility of some halides in alcohols

    NASA Technical Reports Server (NTRS)

    Serban, C.; Auslaender, D.

    1974-01-01

    After measuring ultrasonic velocity and density, the molecular compressibility values from Wada's formula were calculated, for alkali metal halide solutions in methyl, ethyl, butyl, and glycol alcohol. The temperature and concentration dependence were studied, finding deviations due to the hydrogen bonds of the solvent.

  16. Mechanical resistance of silver halide infrared fibers

    NASA Astrophysics Data System (ADS)

    Barkay, Nitzan; Katzir, Abraham

    1992-01-01

    Flexibility resistance of silver-halide infrared fibers was investigated in the plastic bending regime, which is especially useful for internal medical applications. The CO2 laser transmission of the fibers was measured in several positions while being bent. The fibers have been found to operate even after large plastic deformations, and values for various fibers and bending conditions are reported.

  17. Cytocompatibility of a free machining titanium alloy containing lanthanum.

    PubMed

    Feyerabend, Frank; Siemers, Carsten; Willumeit, Regine; Rösler, Joachim

    2009-09-01

    Titanium alloys like Ti6Al4V are widely used in medical engineering. However, the mechanical and chemical properties of titanium alloys lead to poor machinability, resulting in high production costs of medical products. To improve the machinability of Ti6Al4V, 0.9% of the rare earth element lanthanum (La) was added. The microstructure, the mechanical, and the corrosion properties were determined. Lanthanum containing alloys exhibited discrete particles of cubic lanthanum. The mechanical properties and corrosion resistance were slightly decreased but are still sufficient for many applications in the field of medical engineering. In vitro experiments with mouse macrophages (RAW 264.7) and human bone-derived cells (MG-63, HBDC) were performed and revealed that macrophages showed a dose response below and above a LaCl3 concentration of 200 microM, while MG-63 and HBDC tolerated three times higher concentrations without reduction of viability. The viability of cells cultured on disks of the materials showed no differences between the reference and the lanthanum containing alloy. We therefore propose that lanthanum containing alloy appears to be a good alternative for biomedical applications, where machining of parts is necessary.

  18. Methyl chloride production from methane over lanthanum-based catalysts.

    PubMed

    Podkolzin, Simon G; Stangland, Eric E; Jones, Mark E; Peringer, Elvira; Lercher, Johannes A

    2007-03-07

    The mechanism of selective production of methyl chloride by a reaction of methane, hydrogen chloride, and oxygen over lanthanum-based catalysts was studied. The results suggest that methane activation proceeds through oxidation-reduction reactions on the surface of catalysts with an irreducible metal-lanthanum, which is significantly different from known mechanisms for oxidative chlorination. Activity and spectroscopic measurements show that lanthanum oxychloride (LaOCl), lanthanum trichloride (LaCl3), and lanthanum phases with an intermediate extent of chlorination are all active for this reaction. The catalyst is stable with no noticeable deactivation after three weeks of testing. Kinetic measurements suggest that methane activation proceeds on the surface of the catalyst. Flow and pulse experiments indicate that the presence of hydrogen chloride is not required for activity, and its role appears to be limited to maintaining the extent of catalyst chlorination. In contrast, the presence of gas-phase oxygen is essential for catalytic activity. Density-functional theory calculations suggest that oxygen can activate surface chlorine species by adsorbing dissociatively and forming OCl surface species, which can serve as an active site for methane activation. The proposed mechanism, thus, involves changing of the formal oxidation state of surface chlorine from -1 to +1 without any changes in the oxidation state of the underlying metal.

  19. Ionic alkali halide XUV laser feasibility study

    SciTech Connect

    Yang, T.T.; Gylys, V.T.; Bower, R.D.; Harris, D.G.; Blauer, J.A.; Turner, C.E.; Hindy, R.N.

    1989-11-10

    The objective of this work is to assess the feasibility of a select set of ionic alkali halide XUV laser concepts by obtaining the relevant kinetic and spectroscopic parameters required for a proof-of-principle and conceptual design. The proposed lasers operate in the 80--200 nm spectral region and do not require input from outside radiation sources for their operation. Frequency up-conversion and frequency mixing techniques and therefore not considered in the work to be described. An experimental and theoretical study of a new type of laser operating in the extreme ultraviolet wavelength region has been conducted. The lasing species are singly ionized alkali halide molecules such as Rb{sup 2+}F{sub {minus}}, Rb{sup 2+}Br{sup {minus}} and Cs{sup 2+}F{sup {minus}}. These species are similar in electronic structure to the rare gas halide excimers, such as XeF and Krf, except that the ionic molecules emit at wavelengths of 80--200 nm, much shorter than the conventional rare-gas halide excimer laser. The radiative lifetime of these molecules are typically near 1 ns, which is about an order of magnitude shorter than that for rare-gas halide systems. The values of the cross section for stimulated emission are on the order of 1 {times} 10{sup {minus}16}cm{sup 2}. Because of the fundamental similarity to existing UV lasers, these systems show promise as a high power, efficient XUV lasers. 55 refs., 50 figs., 5 tabs.

  20. Mechanical properties of lanthanum and yttrium chromites

    SciTech Connect

    Paulik, S.W.; Armstrong, T.R.

    1996-12-31

    In an operating high-temperature (1000{degrees}C) solid oxide fuel cell (SOFC), the interconnect separates the fuel (P(O{sub 2}){approx}10{sup -16} atm) and the oxidant (P(O2){approx}10{sup 0.2} atm), while being electrically conductive and connecting the cells in series. Such severe atmospheric and thermal demands greatly reduce the number of viable candidate materials. Only two materials, acceptor substituted lanthanum chromite and yttrium chromite, meet these severe requirements. In acceptor substituted chromites (Sr{sup 2+} or Ca{sup 2+} for La{sup 3+}), charge compensation is primarily electronic in oxidizing conditions (through the formation of Cr{sup 4+}). Under reducing conditions, ionic charge compensation becomes significant as the lattice becomes oxygen deficient. The formation of oxygen vacancies is accompanied by the reduction of Cr{sup 4+} ions to Cr{sup 3+} and a resultant lattice expansion. The lattice expansion observed in large chemical potential gradients is not desirable and has been found to result in greatly reduced mechanical strength.

  1. Toward laser cooling of negative lanthanum

    NASA Astrophysics Data System (ADS)

    Jordan, Elena; Cerchiari, Giovanni; Erlewein, Stefan; Kellerbauer, Alban; UNIC Team

    2016-05-01

    Anion laser cooling holds the potential to allow the production of ultracold ensembles of any negatively charged species by sympathetic cooling. It is a promising technique for cooling of antiprotons to a few mK and could clear the way for precision measurements on cold antihydrogen. Laser cooling of negative ions has never been achieved, since most species have no bound-bound electric dipole transitions. Negative lanthanum (La-) is one of the few anions with multiple electric dipole transitions. The bound-bound transition from the 3F2e ground state to the 3D1o excited state in La- has been proposed theoretically as a candidate for laser cooling. The potential laser cooling transition was identified using laser photodetachment spectroscopy and its excitation energy was measured. We have studied the aforementioned transition in a beam of La anions by high-resolution laser photodetachment spectroscopy. Seven of the nine expected hyperfine structure transitions have been resolved and the transition cross sections have been estimated from experimental observations. It was found that presently La- is the most promising candidate among the atomic anions. We plan to demonstrate the first direct laser cooling of negative ions in a linear radio frequency trap. We gratefully acknowledge support from the European Research Council (ERC).

  2. Phosphate adsorption on lanthanum loaded biochar.

    PubMed

    Wang, Zhanghong; Shen, Dekui; Shen, Fei; Li, Tianyu

    2016-05-01

    To attain a low-cost and high-efficient phosphate adsorbent, lanthanum (La) loaded biochar (La-BC) prepared by a chemical precipitation method was developed. La-BC and its pristine biochar (CK-BC) were comparatively characterized using zeta potential, BET surface area, scanning electron microscopy/energy dispersive spectrometer (SEM-EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR). The adsorption ability and the mechanisms during adsorption process for the La-BC samples were also investigated. La loaded on the surface of biochar can be termed as La-composites (such as LaOOH, LaONO3 and La(OH)3), leading to the decrease of negative charge and surface area of biochar. La-BC exhibited the high adsorption capacity to phosphate compared to CK-BC. Adsorption isotherm and adsorption kinetic studies showed that the Langmuir isotherm and second order model could well describe the adsorption process of La-BC, indicating that the adsorption was dominated by a homogeneous and chemical process. The calculated maximum adsorption capacity was as high as 46.37 mg g(-1) (computed in P). Thermodynamic analysis revealed that the adsorption was spontaneous and endothermic. SEM, XRD, XPS and FT-IR analysis suggested that the multi-adsorption mechanisms including precipitation, ligand exchange and complexation interactions can be evidenced during the phosphate adsorption process by La-composites in La-BC.

  3. Processing of boron carbide

    NASA Astrophysics Data System (ADS)

    Cho, Namtae

    The processing of boron carbide powder including sintering optimization, green body optimization and sintering behavior of nano-sized boron carbide was investigated for the development of complex shaped body armor. Pressureless sintered B4C relative densities as high as 96.7% were obtained by optimizing the soak temperature, and holding at that temperature for the minimum time required to reach terminal density. Although the relative densities of pressureless sintered specimens were lower than that of commercially produced hot-pressed B4C, their (Vickers) hardness values were comparable. For 4.45 cm dia. 1.35 cm height disk-shaped specimens, pressureless sintered to at least 93.0% relative density, post-hot isostatic pressing resulted in vast increases in relative densities (e.g. 100.0%) and hardness values significantly greater than that of commercially produced hot-pressed B 4C. The densification behavior of 20-40nm graphite-coated B4C nano-particles was studied using dilatometry, x-ray diffraction and electron microscopy. The higher than expected sintering onset from a nano-scale powder (˜1500°C) was caused by remnant B2O3 not removed by methanol washing, keeping particles separated until volatilization, and the carbon coatings, which imposed particle to particle contact of a substance more refractory than B4C. Solid state sintering (1500-1850°C) was followed by an arrest in contraction attributed to formation of eutectic liquid droplets of size more than 10X the original nano-particles. These droplets, induced to form well below known B4C-graphite eutectic temperatures by the high surface energy of nanoparticles, are interpreted to have quickly solidified to form a vast number of voids in particle packing, which in turn, impeded continued solid state sintering. Starting at 2200°C, a permanent liquid phase formed which facilitated a rapid measured contraction by liquid phase sintering and/or compact slumping.

  4. Calcium and lanthanum solid base catalysts for transesterification

    DOEpatents

    Ng, K. Y. Simon; Yan, Shuli; Salley, Steven O.

    2015-07-28

    In one aspect, a heterogeneous catalyst comprises calcium hydroxide and lanthanum hydroxide, wherein the catalyst has a specific surface area of more than about 10 m.sup.2/g. In another aspect, a heterogeneous catalyst comprises a calcium compound and a lanthanum compound, wherein the catalyst has a specific surface area of more than about 10 m.sup.2/g, and a total basicity of about 13.6 mmol/g. In further another aspect, a heterogeneous catalyst comprises calcium oxide and lanthanum oxide, wherein the catalyst has a specific surface area of more than about 10 m.sup.2/g. In still another aspect, a process for preparing a catalyst comprises introducing a base precipitant, a neutral precipitant, and an acid precipitant to a solution comprising a first metal ion and a second metal ion to form a precipitate. The process further comprises calcining the precipitate to provide the catalyst.

  5. Thermoelectric properties of non-stoichiometric lanthanum sulfides

    NASA Technical Reports Server (NTRS)

    Shapiro, E.; Danielson, L. R.

    1983-01-01

    The lanthanum sulfides are promising candidate materials for high-efficiency thermoelectric applications at temperatures up to 1300 C. The non-stoichiometric lanthanum sulfides (LaS(x), where x is in the range 1.33-1.50) appear to possess the most favorable thermoelectric properties. The Seebeck coefficient and resistivity vary significantly with composition, so that an optimum value of alpha sq/rho (where alpha is the Seebeck coefficient and rho is the resistivity) can be chosen. The thermal conductivity remains approximately constant with stoichiometry, so a material with an optimum value of alpha sq/rho should possess the optimum figure-of-merit. Data for the Seebeck coefficient and electrical resistivity of non-stoichiometric lanthanum sulfides will be pressed, together with structural properties of these materials.

  6. Electro-optical polycrystalline barium lanthanum titanium niobate

    SciTech Connect

    Mehrotra, A.K.

    1991-02-19

    This patent describes a transparent electro-optic article. It comprises: of a barium lanthanum titanium niobate wherein substantially all grains are of a grain size between about 2 and about 20 micron, the article has a pore volume of less than about 1 percent, and the article has a grain size of between about 2 and about 20 microns. This patent also describes a method of forming transparent electro-optical barium lanthanum titanium niobate. It comprises: providing particles of barium carbonate, lanthanum oxide, titanium oxide, and niobium oxide, calcining the particles, sintering the calcined particles at a temperature of between about 1200{degrees} C and 1300{degrees} C. and a vacuum of between about 10{sup {minus}3} and 10{sup {minus}4} torr while under pressure to form a sintered mass, cooling the sintered mass, slicing the mass to form wafers, heating the wafers in an oxidizing atmosphere.

  7. Palladium interaction with silicon carbide

    NASA Astrophysics Data System (ADS)

    Gentile, M.; Xiao, P.; Abram, T.

    2015-07-01

    In this work the palladium interaction with silicon carbide is investigated by means of complementary analytical techniques such as thermogravimetry (TG), differential scanning calorimetry (DSC), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Thermoscans were carried out on pellets of palladium, α-SiC and β-SiC high purity powders in the temperature range comprised between 293 K and 1773 K, in order to study the effect of temperature on the palladium-silicon carbide reaction. Thermoscans of α-SiC pellets containing 5 at.%Pd show that during differential calorimetry scans three exothermic peaks occurred at 773 K, 1144 K and 1615 K, while thermoscans of β-SiC pellets containing 3 at.%Pd and 5 at.%Pd do not show peaks. For the pellet α-SiC-5 at.%Pd XRD spectra reveal that the first peak is associated with the formation of Pd3Si and SiO2 phases, while the second peak and the third peak are correlated with the formation of Pd2Si phase and the active oxidation of silicon carbide respectively. Thermogravimetry scans show weight gain and weight loss peaks due to the SiO2 phase formation and the active oxidation. Additionally XPS fittings reveal the development of SiCxOy phase during the first exothermic peak up to the temperature of 873 K. The experimental data reveals that alpha silicon carbide is attacked by palladium at lower temperatures than beta silicon carbide and the reaction mechanism between silicon carbide and palladium is strongly affected by silicon carbide oxidation.

  8. Wettability of boron carbide

    SciTech Connect

    Torvund, T.; Akselsen, O.M.; Ulvensoeen, J.H.; Grong, O.

    1994-12-31

    The wettability of boron carbide has been examined by means of the sessile drop method, using the following candidate alloys: (96wt%AG-4wt%Ti), (Ag-26.5wt%Cu-3wt%Ti), (Sn-10wt%Ag-4wt%Ti), Sn(99.95wt%) and Al(99.99wt%). The results show that B{sub 4}C is completely wetted by the Ag-based alloys. Sn-10wt%Ag-4wt%Ti alloy and pure Al partly wet the B{sub 4}C surface, while pure Sn does not wet B{sub 4}C at all. For all the alloys used, except pure Sn, a reaction layer was observed at the interface between the ceramic part and the metal drop. Although the spreading kinetics of the Al-drop was much slower compared with the Ti-containing alloys, the reaction rate was considerably higher in the former case. This suggests that aluminium is an attractive candidate material for brazing of B{sub 4}C. Formation of the low melting B{sub 2}O{sub 3} at the B{sub 4}C surface may cause oxidation of the filler metal during joining, which, in turn, leads to a low bond strength.

  9. Silicon carbide photoconductive switches

    NASA Astrophysics Data System (ADS)

    Saddow, Stephen E.

    1994-09-01

    The optoelectronic properties of p-type 6-H silicon carbide (6H-SiC) have been investigated in an experiment that used lateral and vertical photoconductive (PC) switches. Both photovoltaic and photoconductive effects are reported, which were observed on switches using both geometries and measured at several wavelengths near the 6H-SiC absorption edge. PC techniques were employed to measure the surface and bulk carrier lifetimes of 40 and 200 ns, respectively. The switches displayed a high-speed photovoltaic response to picosecond laser excitations in the UV and visible spectral regions. In particular, efficient subnanosecond optical absorption processes were observed in the visible region. The photovoltage was measured as a function of both laser wavelength (and hence absorption depth) and laser beam position within the switching gap. The switch response to picosecond laser pulses in the UV, violet, green, and red spectral regions was shown to have subnanosecond photovoltaic response times. Finally, since the optical absorption coefficient had not been well established for device-grade 6H-SiC, the optical absorption coefficient near the 6H-SiC bandgap energy (Eg) was also measured, and the bandgap was determined to be approximately 3.1 eV.

  10. Silicon Carbide Growth

    NASA Technical Reports Server (NTRS)

    2005-01-01

    Andrew Trunek has focused on supporting the Sic team through the growth of Sic crystals, making observations and conducting research that meets the collective needs and requirements of the team while fulfilling program commitments. Cancellation of the Ultra Efficient Engine Technology (UEET) program has had a significant negative impact on resources and research goals. This report highlights advancements and achievements made with this cooperative agreement over the past year. NASA Glenn Research Center (GRC) continues to make advances in silicon carbide (SiC) research during the past year. Step free surfaces were used as substrates for the deposition of GaN epilayers that yielded very low dislocation densities. Defect free 3C- SiC was successfully nucleated on step free mesas and test diodes were fabricated. Web growth techniques were used to increase the usable surface area of dislocation free SiC by approximately equal to 40%. The greatest advancement has been attained on stepped surfaces of SiC. A metrology standard was developed using high temperature etching techniques titled "Nanometer Step Height Standard". This development culminated in being recognized for a 2004 R&D100 award and the process to produce the steps received a NASA Space Act award.

  11. Synthesis of lanthanum aluminate by reverse chemical precipitation using pseudoboehmite as alumina precursor.

    PubMed

    Wilson, Hernández Muñoz; Juan, Serrato Rodríguez; Juan, Muñoz Saldaña; Juan, Zárate Medina

    2016-11-01

    Lanthanum aluminate was synthesized by using reverse precipitation. A lanthanum nitrate salt in solution allowed the precipitation of lanthanum hydroxide onto the surface of the pseudoboehmite particles. Pseudoboehmite was previously synthesized out of aluminum sulfate which after characterization presents a poor crystallized structure. A Perovskite-type lanthanum aluminate was obtained at different temperature and calcination time. When calcination was set up to 1500°C to 3°C/min pure, high crystallinity and highly agglomerated lanthanum aluminate is obtained, relative density of 94% was reached.

  12. SEPARATION OF PLUTONIUM FROM LANTHANUM BY CHELATION-EXTRACTION

    DOEpatents

    James, R.A.; Thompson, S.G.

    1958-12-01

    Plutonium can be separated from a mixture of plutonlum and lanthanum in which the lanthanum to plutonium molal ratio ls at least five by adding the ammonium salt of N-nitrosoarylhydroxylamine to an aqueous solution having a pH between about 3 and 0.2 and containing the plutonium in a valence state of at least +3, to form a plutonium chelate compound of N-nitrosoarylhydroxylamine. The plutonium chelate compound may be recovered from the solution by extracting with an immiscible organic solvent such as chloroform.

  13. Enhancement of superconductivity of lanthanum and yttrium sesquicarbide

    DOEpatents

    Krupka, M.C.; Giorgi, A.L.; Krikorian, N.H.; Szklarz, E.G.

    1971-06-22

    A method of enhancing the superconductivity of body-centered cubic lanthanum and yttrium sesquicarbide through formation of the sesquicarbides from ternary alloys of novel composition (N/sub x/M/sub 1-x/)C/sub z/, where N is yttrium or lanthanum, M is thorium, any of the Group IV and VI transition metals, or gold, germanium or silicon, and z is approximately 1.2 to 1.6. These ternary sesquicarbides have superconducting transition temperatures as high as 17.0/sup 0/K.

  14. Enhancement of Superconductivity of Lanthanum and Yttrium Sesquicarbide

    DOEpatents

    Krupka, M. C.; Giorgi, A. L.; Krikorian, N. H.; Szklarz, E. G.

    1972-06-22

    A method of enhancing the superconductivity of body-centered cubic lanthanum and yttrium sesquicarbide through formation of the sesquicarbides from ternary alloys of novel composition (N/sub x/M/sub 1-x/)C/sub z/, where N is yttrium or lanthanum, M is thorium, any of the Group IV and VI transition metals, or gold, germanium or silicon, and z is approximately 1.2 to 1.6. These ternary sesquicarbides have superconducting transition temperatures as high as 17.0/sup 0/K.

  15. Syntesis of lanthanum zirconate hydrosols by the ion exchange method

    NASA Astrophysics Data System (ADS)

    Bovina, E. A.; Tarasova, J. V.; Chibirova, F. Kh

    2011-04-01

    Ion exchange of LaCl3 and ZrOCl2 aqueous solutions with anion-exchanger AV-17-8 was used to synthesize finely dispersed hydrosol of amorphous lanthanum zirconate La2Zr2O7. Heat treatment of dried La2Zr2O7 hydrosols at 700°C and 1100°C resulted in the formation of powders with fluorite and pyrochlore type structures, respectively. Epitaxial La2Zr2O7 films were obtained on SrTiO3 (001) single crystals. The substrate has an influence on the lanthanum zirconate crystal orientation, as well as strong inhibitory effect on sintering processes.

  16. Synthesis and characterization of lanthanum doped zinc oxide nanoparticles

    NASA Astrophysics Data System (ADS)

    Kumar, Vinod; Sonia, Suman, Kumar, Sacheen; Kumar, Dinesh

    2016-05-01

    La doped ZnO (Zn1-xLaxO, x = 0, 3, 6 and 9) were prepared via chemical co-precipitation method using Zinc Acetate, Lanthanum Acetate and Sodium Hydroxide at 50°C. Hydrate nanoparticles were annealed in air at 300°C for 3 hours. The synthesized samples have been characterized by powder X-ray diffraction and UV-Visiblespectrophotometer. The XRD measurement revealsthat the prepared nanoparticles have different microstructure without changing a hexagonal wurtzite structure. The result shows the change in nanoparticles size with the increment of lanthanum concentration for lower concentration for x = 0 to 6 and decreases at x = 9.

  17. Laser melting of uranium carbides

    NASA Astrophysics Data System (ADS)

    Utton, C. A.; De Bruycker, F.; Boboridis, K.; Jardin, R.; Noel, H.; Guéneau, C.; Manara, D.

    2009-03-01

    In the context of the material research aimed at supporting the development of nuclear plants of the fourth Generation, renewed interest has recently arisen in carbide fuels. A profound understanding of the behaviour of nuclear materials in extreme conditions is of prime importance for the analysis of the operation limits of nuclear fuels, and prediction of possible nuclear reactor accidents. In this context, the main goal of the present paper is to demonstrate the feasibility of laser induced melting experiments on stoichiometric uranium carbides; UC, UC1.5 and UC2. Measurements were performed, at temperatures around 3000 K, under a few bars of inert gas in order to minimise vaporisation and oxidation effects, which may occur at these temperatures. Moreover, a recently developed investigation method has been employed, based on in situ analysis of the sample surface reflectivity evolution during melting. Current results, 2781 K for the melting point of UC, 2665 K for the solidus and 2681 K for the liquidus of U2C3, 2754 K for the solidus and 2770 K for the liquidus of UC2, are in fair agreement with early publications where the melting behaviour of uranium carbides was investigated by traditional furnace melting methods. Further information has been obtained in the current research about the non-congruent (solidus-liquidus) melting of certain carbides, which suggest that a solidus-liquidus scheme is followed by higher ratio carbides, possibly even for UC2.

  18. Porous silicon carbide (SIC) semiconductor device

    NASA Technical Reports Server (NTRS)

    Shor, Joseph S. (Inventor); Kurtz, Anthony D. (Inventor)

    1996-01-01

    Porous silicon carbide is fabricated according to techniques which result in a significant portion of nanocrystallites within the material in a sub 10 nanometer regime. There is described techniques for passivating porous silicon carbide which result in the fabrication of optoelectronic devices which exhibit brighter blue luminescence and exhibit improved qualities. Based on certain of the techniques described porous silicon carbide is used as a sacrificial layer for the patterning of silicon carbide. Porous silicon carbide is then removed from the bulk substrate by oxidation and other methods. The techniques described employ a two-step process which is used to pattern bulk silicon carbide where selected areas of the wafer are then made porous and then the porous layer is subsequently removed. The process to form porous silicon carbide exhibits dopant selectivity and a two-step etching procedure is implemented for silicon carbide multilayers.

  19. Transport of Soil Halides through Rice Paddies: A Viable Mechanism for Rapid Dispersion of the Soil Halide Reservoir

    NASA Astrophysics Data System (ADS)

    Redeker, K. R.; Manley, S.; Wang, N.; Cicerone, R.

    2002-05-01

    On short time scales (1-10 years) soil halide concentrations have been assumed to be primarily driven by leaching and deposition processes. Recent results however, have shown that terrestrial plants volatilize soil halides in the form of methyl halides. Emissions of methyl chloride, methyl bromide and methyl iodide represent major pathways for delivery of inorganic halogen radicals to the atmosphere. Inorganic halogen radicals destroy ozone in the stratosphere and modify the oxidative capacity of the lower atmosphere. We have previously shown that rice paddies emit methyl halides and that emissions depend on growth stage of the rice plant as well as field water management. We show here that rice grown in a greenhouse at UCI is capable of volatilizing and/or storing up to 30%, 5%, and 10% of the available chloride, bromide and iodide within the top meter of soil. The percent of plant tissue halide volatilized as methyl halide over the course of the season is calculated to be 0.05%, 0.25% and 85.0% for chloride, bromide and iodide. We compare our greenhouse soil halide concentrations to other commercial rice fields around the world and estimate the e-folding time for soil halides within each region. We suggest that rice agriculture is the driving removal mechanism for halides within rice paddies and that terrestrial plants play a larger role in global cycling of halides than previously estimated.

  20. 500 C SILICON CARBIDE RECTIFIER PROGRAM.

    DTIC Science & Technology

    Efforts were continued on the development of 500 degree C silicon carbide rectifiers. The growth rate of silicon carbide crystals prepared by the...as obtained from a simple model. All values agree within a factor of five. The use of molten borax as an etchant for silicon carbide was studies...is possible. Details are given on the life and storage tests which were successfully passed by two silicon carbide rectifiers. An open tube-flowing

  1. Flame inhibition by hydrogen halides - Some spectroscopic measurements

    NASA Technical Reports Server (NTRS)

    Lerner, N. R.; Cagliostro, D. E.

    1973-01-01

    The far-ultraviolet absorption spectrum of an air-propane diffusion flame inhibited with hydrogen halides has been studied. Plots of the absorption of light by hydrogen halides as a function of position in the flame and also as a function of the amount of hydrogen halide added to the flame have been obtained. The hydrogen halides are shown to be more stable on the fuel side of the reaction zone than they are on the air side. Thermal diffusion is seen to be important in determining the concentration distribution of the heavier hydrogen halides in diffusion flames. The relationship between the concentration distribution of the hydrogen halides in the flame and the flame inhibition mechanism is discussed.

  2. Flame inhibition by hydrogen halides - Some spectroscopic measurements

    NASA Technical Reports Server (NTRS)

    Lerner, N. R.; Cagliostro, D. E.

    1973-01-01

    The far-ultraviolet absorption spectrum of an air-propane diffusion flame inhibited with hydrogen halides has been studied. Plots of the absorption of light by hydrogen halides as a function of position in the flame and also as a function of the amount of hydrogen halide added to the flame have been obtained. The hydrogen halides are shown to be more stable on the fuel side of the reaction zone than they are on the air side. Thermal diffusion is seen to be important in determining the concentration distribution of the heavier hydrogen halides in diffusion flames. The relationship between the concentration distribution of the hydrogen halides in the flame and the flame inhibition mechanism is discussed.

  3. Morphology-Controlled Synthesis of Organometal Halide Perovskite Inverse Opals.

    PubMed

    Chen, Kun; Tüysüz, Harun

    2015-11-09

    The booming development of organometal halide perovskites in recent years has prompted the exploration of morphology-control strategies to improve their performance in photovoltaic, photonic, and optoelectronic applications. However, the preparation of organometal halide perovskites with high hierarchical architecture is still highly challenging and a general morphology-control method for various organometal halide perovskites has not been achieved. A mild and scalable method to prepare organometal halide perovskites in inverse opal morphology is presented that uses a polystyrene-based artificial opal as hard template. Our method is flexible and compatible with different halides and organic ammonium compositions. Thus, the perovskite inverse opal maintains the advantage of straightforward structure and band gap engineering. Furthermore, optoelectronic investigations reveal that morphology exerted influence on the conducting nature of organometal halide perovskites.

  4. Silicon Carbide Semiconductor Device Fabrication and Characterization

    DTIC Science & Technology

    1990-02-08

    SPACE ADMINISTRATION For Grant NAG 3-782 S- 1 entitled SILICON CARBIDE SEMICONDUCTOR DEVICE FABRICATION AND CHARACTERIZATION For the Period 10 February...NUMBERS Silicon Carbide ..Semiconductor Device Fabrication and PR# 335820 Characterization __________________________________________________ APP# 505-62-01...also been demonstrated. _________ 14. SUBJECT TERMS 15. NuMBER OF PACiES -~- Silicon carbide , Ysemiconductor devices, ion implantation aseeI4i

  5. Method of Fabricating Silicon Carbide Articles.

    DTIC Science & Technology

    The patent relates to a method for fabricating silicon carbide articles which comprises hot pressing a homogeneous mixture of carbonaceous particles...and silicon carbide powder. The presence of the carbon limits grain growth so that a silicon carbide product having greatly improved physical

  6. Chiral Alkyl Halides: Underexplored Motifs in Medicine

    PubMed Central

    Gál, Bálint; Bucher, Cyril; Burns, Noah Z.

    2016-01-01

    While alkyl halides are valuable intermediates in synthetic organic chemistry, their use as bioactive motifs in drug discovery and medicinal chemistry is rare in comparison. This is likely attributable to the common misconception that these compounds are merely non-specific alkylators in biological systems. A number of chlorinated compounds in the pharmaceutical and food industries, as well as a growing number of halogenated marine natural products showing unique bioactivity, illustrate the role that chiral alkyl halides can play in drug discovery. Through a series of case studies, we demonstrate in this review that these motifs can indeed be stable under physiological conditions, and that halogenation can enhance bioactivity through both steric and electronic effects. Our hope is that, by placing such compounds in the minds of the chemical community, they may gain more traction in drug discovery and inspire more synthetic chemists to develop methods for selective halogenation. PMID:27827902

  7. Lanthanide-halide based humidity indicators

    DOEpatents

    Beitz, James V.; Williams, Clayton W.

    2008-01-01

    The present invention discloses a lanthanide-halide based humidity indicator and method of producing such indicator. The color of the present invention indicates the humidity of an atmosphere to which it is exposed. For example, impregnating an adsorbent support such as silica gel with an aqueous solution of the europium-containing reagent solution described herein, and dehydrating the support to dryness forms a substance with a yellow color. When this substance is exposed to a humid atmosphere the water vapor from the air is adsorbed into the coating on the pore surface of the silica gel. As the water content of the coating increases, the visual color of the coated silica gel changes from yellow to white. The color change is due to the water combining with the lanthanide-halide complex on the pores of the gel.

  8. Low-temperature thermoluminescence spectra of rare-earth-doped lanthanum fluoride

    SciTech Connect

    Yang, B.; Townsend, P.D.; Rowlands, A.P.

    1998-01-01

    Lanthanum fluoride consistently shows two strong thermoluminescence glow peaks at low temperature in pure material near 90 and 128 K. A model is proposed in which these thermoluminescence peaks arise from the annealing of halogen defect sites, similar to the H and V{sub k} centers of the alkali halides. Relaxation and decay of these defects in the pure LaF{sub 3} lattice results in broad-band intrinsic luminescence. Addition of rare-earth-impurity ions has two effects. First, the broad-band emission is replaced by narrow-band line emission defined by the trivalent rare-earth dopants. Second, it preferentially determines the formation of the halogen defect sites at impurity lattice sites and such sites appear to increase in thermal stability since the glow peak temperature increases from 128 K in the intrinsic material up to 141 K through the sequence of rare-earth dopants from La to Er. The temperature movement directly correlates with the changes in ionic size of the rare-earth ions, when allowance is made for differences in effective coordination number of the impurity ions. The data suggest two alternative lattice sites can be occupied. The model emphasizes that the intense thermoluminescence signals arise from internal charge rearrangements and annealing of defect complexes, rather than through the more conventional model of separated charge traps and recombination centers. At higher temperatures there is a complex array of glow peaks which depend not only on the dopant concentration but also are specific to each rare earth. Such effects imply defect models giving thermoluminescence within localized complexes and possible reasons are mentioned. {copyright} {ital 1998} {ital The American Physical Society}

  9. Low-temperature thermoluminescence spectra of rare-earth-doped lanthanum fluoride

    NASA Astrophysics Data System (ADS)

    Yang, B.; Townsend, P. D.; Rowlands, A. P.

    1998-01-01

    Lanthanum fluoride consistently shows two strong thermoluminescence glow peaks at low temperature in pure material near 90 and 128 K. A model is proposed in which these thermoluminescence peaks arise from the annealing of halogen defect sites, similar to the H and Vk centers of the alkali halides. Relaxation and decay of these defects in the pure LaF3 lattice results in broad-band intrinsic luminescence. Addition of rare-earth-impurity ions has two effects. First, the broad-band emission is replaced by narrow-band line emission defined by the trivalent rare-earth dopants. Second, it preferentially determines the formation of the halogen defect sites at impurity lattice sites and such sites appear to increase in thermal stability since the glow peak temperature increases from 128 K in the intrinsic material up to 141 K through the sequence of rare-earth dopants from La to Er. The temperature movement directly correlates with the changes in ionic size of the rare-earth ions, when allowance is made for differences in effective coordination number of the impurity ions. The data suggest two alternative lattice sites can be occupied. The model emphasizes that the intense thermoluminescence signals arise from internal charge rearrangements and annealing of defect complexes, rather than through the more conventional model of separated charge traps and recombination centers. At higher temperatures there is a complex array of glow peaks which depend not only on the dopant concentration but also are specific to each rare earth. Such effects imply defect models giving thermoluminescence within localized complexes and possible reasons are mentioned.

  10. Interpulse kinetics in copper and copper halide lasers

    NASA Technical Reports Server (NTRS)

    Harstad, K. G.

    1983-01-01

    The various rate processes that govern the interpulse relaxation in metal vapor and metal halide vapor lasers are considered. Computer calculations indicate that the rapid metastable levels relaxation observed in copper and copper halide laser experiments requires the existence of a relatively small resonance in the cross section for metastable excitation or deexcitation near threshold. The accurate calculation of interpulse relaxation requires knowledge of rate constants presently not well known; this is especially so for metal halide lasers.

  11. Process and composition for drying of gaseous hydrogen halides

    DOEpatents

    Tom, Glenn M.; Brown, Duncan W.

    1989-08-01

    A process for drying a gaseous hydrogen halide of the formula HX, wherein X is selected from the group consisting of bromine, chlorine, fluorine, and iodine, to remove water impurity therefrom, comprising: contacting the water impurity-containing gaseous hydrogen halide with a scavenger including a support having associated therewith one or more members of the group consisting of: (a) an active scavenging moiety selected from one or more members of the group consisting of: (i) metal halide compounds dispersed in the support, of the formula MX.sub.y ; and (ii) metal halide pendant functional groups of the formula -MX.sub.y-1 covalently bonded to the support, wherein M is a y-valent metal, and y is an integer whose value is from 1 to 3; (b) corresponding partially or fully alkylated compounds and/or pendant functional groups, of the metal halide compounds and/or pendant functional groups of (a); wherein the alkylated compounds and/or pendant functional groups, when present, are reactive with the gaseous hydrogen halide to form the corresponding halide compounds and/or pendant functional groups of (a); and M being selected such that the heat of formation, .DELTA.H.sub.f of its hydrated halide, MX.sub.y.(H.sub.2 O).sub.n, is governed by the relationship: .DELTA.H.sub.f .gtoreq.n.times.10.1 kilocalories/mole of such hydrated halide compound wherein n is the number of water molecules bound to the metal halide in the metal halide hydrate. Also disclosed is an appertaining scavenger composition and a contacting apparatus wherein the scavenger is deployed in a bed for contacting with the water impurity-containing gaseous hydrogen halide.

  12. Comparison of model fitting and gated integration for pulse shape discrimination and spectral estimation of digitized lanthanum halide scintillator pulses

    NASA Astrophysics Data System (ADS)

    McFee, J. E.; Mosquera, C. M.; Faust, A. A.

    2016-08-01

    An analysis of digitized pulse waveforms from experiments with LaBr3(Ce) and LaCl3(Ce) detectors is presented. Pulse waveforms from both scintillator types were captured in the presence of 22Na and 60Co sources and also background alone. Two methods to extract pulse shape discrimination (PSD) parameters and estimate energy spectra were compared. The first involved least squares fitting of the pulse waveforms to a physics-based model of one or two exponentially modified Gaussian functions. The second was the conventional gated integration method. The model fitting method produced better PSD than gated integration for LaCl3(Ce) and higher resolution energy spectra for both scintillator types. A disadvantage to the model fitting approach is that it is more computationally complex and about 5 times slower. LaBr3(Ce) waveforms had a single decay component and showed no ability for alpha/electron PSD. LaCl3(Ce) was observed to have short and long decay components and alpha/electron discrimination was observed.

  13. Anomalous Alloy Properties in Mixed Halide Perovskites.

    PubMed

    Yin, Wan-Jian; Yan, Yanfa; Wei, Su-Huai

    2014-11-06

    Engineering halide perovskite through mixing halogen elements, such as CH3NH3PbI3-xClx and CH3NH3PbI3-xBrx, is a viable way to tune its electronic and optical properties. Despite many emerging experiments on mixed halide perovskites, the basic electronic and structural properties of the alloys have not been understood and some crucial questions remain, for example, how much Cl can be incorporated into CH3NH3PbI3 is still unclear. In this Letter, we chose CsPbX3 (X = I, Br, Cl) as an example and use a first-principle calculation together with cluster-expansion methods to systematically study the structural, electronic, and optical properties of mixed halide perovskites and find that unlike conventional semiconductor alloys, they exhibit many anomalous alloy properties such as small or even negative formation energies at some concentrations and negligible or even negative band gap bowing parameters at high temperature. We further show that mixed-(I,Cl) perovskite is hard to form at temperature below 625 K, whereas forming mixed-(Br,Cl) and (I,Br) alloys are easy at room temperature.

  14. Lanthanide doped strontium-barium cesium halide scintillators

    DOEpatents

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

    2015-06-09

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

  15. Reinforcement of tungsten carbide grains by nanoprecipitates in cemented carbides.

    PubMed

    Liu, Xingwei; Song, Xiaoyan; Wang, Haibin; Hou, Chao; Liu, Xuemei; Wang, Xilong

    2016-10-14

    In contrast to the conventional method that obtains a high fracture strength of tungsten carbide-cobalt (WC-Co) cemented carbides by reducing WC grain size to near-nano or nanoscale, a new approach has been developed to achieve ultrahigh fracture strength by strengthening the WC grains through precipitate reinforcement. The cemented carbides were prepared by liquid-state sintering the in situ synthesized WC-Co composite powders with a little excess carbon and pre-milled Cr3C2 particles having different size scales. It was found that the nanoscale dispersed particles precipitate in the WC grains, which mainly have a coherent or semi-coherent interface with the matrix. The pinning effect of the nanoparticles on the motion of dislocations within the WC grains was observed. The mechanisms for the precipitation of nanoparticles in the WC grains were discussed, based on which a new method to enhance the resistance against the transgranular fracture of cemented carbides was proposed.

  16. Reinforcement of tungsten carbide grains by nanoprecipitates in cemented carbides

    NASA Astrophysics Data System (ADS)

    Liu, Xingwei; Song, Xiaoyan; Wang, Haibin; Hou, Chao; Liu, Xuemei; Wang, Xilong

    2016-10-01

    In contrast to the conventional method that obtains a high fracture strength of tungsten carbide-cobalt (WC-Co) cemented carbides by reducing WC grain size to near-nano or nanoscale, a new approach has been developed to achieve ultrahigh fracture strength by strengthening the WC grains through precipitate reinforcement. The cemented carbides were prepared by liquid-state sintering the in situ synthesized WC-Co composite powders with a little excess carbon and pre-milled Cr3C2 particles having different size scales. It was found that the nanoscale dispersed particles precipitate in the WC grains, which mainly have a coherent or semi-coherent interface with the matrix. The pinning effect of the nanoparticles on the motion of dislocations within the WC grains was observed. The mechanisms for the precipitation of nanoparticles in the WC grains were discussed, based on which a new method to enhance the resistance against the transgranular fracture of cemented carbides was proposed.

  17. Orthophosphate sorption onto lanthanum-treated lignocellulosic sorbents

    Treesearch

    Eun Woo Shin; K. G. Karthikeyan; Mandla A. Tshabalala

    2005-01-01

    Inorganic/organic hybrid adsorbents for removing orthophosphate from water were prepared by lanthanum (La) treatment of bark fiber, a lignocellulosic material obtained from juniper (Juniperusmonosperma). The La was anchored to the juniper bark (JB) fiber by ion exchange with Ca in the bark and was responsible for removing orthophosphate. Two La concentrations (0.01 and...

  18. Discovery of cesium, lanthanum, praseodymium and promethium isotopes

    SciTech Connect

    May, E.; Thoennessen, M.

    2012-09-15

    Currently, forty-one cesium, thirty-five lanthanum, thirty-two praseodymium, and thirty-one promethium isotopes have been observed and the discovery of these isotopes is described here. For each isotope a brief synopsis of the first refereed publication, including the production and identification method, is presented.

  19. Solid-state halide ion-selective electrodes: studies of quaternary ammonium halide solutions and determination of surfactants.

    PubMed

    Gomathi, H; Subramanian, G; Chandra, N; Rao, G P

    1983-11-01

    The feasibility of using homogeneous membrane-type halide ion-selective electrodes in solutions containing cationic surfactant compounds was examined. The results established the applicability of these electrodes for monitoring halide ions in solution without interference by the surfactants. The data also provided a basis for estimation of the surfactant in solution through the halide content. Two typical plating-bath compositions containing CTAB have been successfully analysed for their surfactant content by this procedure.

  20. Anisotropic Tribological Properties of Silicon Carbide

    NASA Technical Reports Server (NTRS)

    Miyoshi, K.; Buckley, D. H.

    1980-01-01

    The anisotropic friction, deformation and fracture behavior of single crystal silicon carbide surfaces were investigated in two categories. The categories were called adhesive and abrasive wear processes, respectively. In the adhesive wear process, the adhesion, friction and wear of silicon carbide were markedly dependent on crystallographic orientation. The force to reestablish the shearing fracture of adhesive bond at the interface between silicon carbide and metal was the lowest in the preferred orientation of silicon carbide slip system. The fracturing of silicon carbide occurred near the adhesive bond to metal and it was due to primary cleavages of both prismatic (10(-1)0) and basal (0001) planes.

  1. Mechanism and Selectivity in Nickel-Catalyzed Cross-Electrophile Coupling of Aryl Halides with Alkyl Halides

    PubMed Central

    Biswas, Soumik; Weix, Daniel J.

    2013-01-01

    The direct cross-coupling of two different electrophiles, such as an aryl halide with an alkyl halide, offers many advantages over conventional cross-coupling methods that require a carbon nucleophile. Despite its promise as a versatile synthetic strategy, a limited understanding of the mechanism and origin of cross selectivity has hindered progress in reaction development and design. Herein, we shed light on the mechanism for the nickel-catalyzed cross-electrophile coupling of aryl halides with alkyl halides and demonstrate that the selectivity arises from an unusual catalytic cycle that combines both polar and radical steps to form the new C-C bond. PMID:23952217

  2. Making and Breaking of Lead Halide Perovskites.

    PubMed

    Manser, Joseph S; Saidaminov, Makhsud I; Christians, Jeffrey A; Bakr, Osman M; Kamat, Prashant V

    2016-02-16

    A new front-runner has emerged in the field of next-generation photovoltaics. A unique class of materials, known as organic metal halide perovskites, bridges the gap between low-cost fabrication and exceptional device performance. These compounds can be processed at low temperature (typically in the range 80-150 °C) and readily self-assemble from the solution phase into high-quality semiconductor thin films. The low energetic barrier for crystal formation has mixed consequences. On one hand, it enables inexpensive processing and both optical and electronic tunability. The caveat, however, is that many as-formed lead halide perovskite thin films lack chemical and structural stability, undergoing rapid degradation in the presence of moisture or heat. To date, improvements in perovskite solar cell efficiency have resulted primarily from better control over thin film morphology, manipulation of the stoichiometry and chemistry of lead halide and alkylammonium halide precursors, and the choice of solvent treatment. Proper characterization and tuning of processing parameters can aid in rational optimization of perovskite devices. Likewise, gaining a comprehensive understanding of the degradation mechanism and identifying components of the perovskite structure that may be particularly susceptible to attack by moisture are vital to mitigate device degradation under operating conditions. This Account provides insight into the lifecycle of organic-inorganic lead halide perovskites, including (i) the nature of the precursor solution, (ii) formation of solid-state perovskite thin films and single crystals, and (iii) transformation of perovskites into hydrated phases upon exposure to moisture. In particular, spectroscopic and structural characterization techniques shed light on the thermally driven evolution of the perovskite structure. By tuning precursor stoichiometry and chemistry, and thus the lead halide charge-transfer complexes present in solution, crystallization

  3. Phosphate-binding efficacy of crushed vs. chewed lanthanum carbonate in hemodialysis patients.

    PubMed

    How, Priscilla P; Anattiwong, Prathana; Mason, Darius L; Arruda, Jose A; Lau, Alan H

    2011-01-01

    Lanthanum carbonate, a chewable noncalcium-containing phosphorus (P) binder, is useful for treating secondary hyperparathyroidism in patients who have hypercalcemia and cannot swallow whole tablets. However, some patients cannot chew tablets or prefer to crush and mix them with food. This study was conducted to determine the P-binding efficacy of crushed lanthanum and compare it with chewed lanthanum in hemodialysis (HD) patients. After a 1-week washout period, 11 hemodialysis patients (7 men, 4 women) were randomized to receive, in a crossover fashion, lanthanum 1000 mg 3 times daily chewed with meals and lanthanum 1000 mg 3 times daily crushed into a fine powder, mixed with applesauce and taken with meals, for 4 weeks each. Serum P was measured at the end of each washout (baseline) and weekly during treatment. Changes in serum P from baseline for crushed lanthanum were compared with chewed lanthanum using paired sample t test. Administration of crushed lanthanum resulted in a significant reduction in serum P from baseline (P reduction [mg/dL] for crushed lanthanum in week 1: 2.1 ± 0.4, week 2: 1.7 ± 0.5, week 3: 1.7 ± 0.5, week 4: 1.7 ± 0.4, P<0.05). No statistically significant differences were observed in serum P reduction from baseline and serum P attained during treatment with crushed when compared with chewed lanthanum. Crushed lanthanum is effective in reducing serum P and have similar P-binding efficacy to chewed lanthanum. Crushing lanthanum and mixing it with food can thus be an option for patients who are unable to chew or swallow whole tablets.

  4. Lanthanum hexaboride for solar energy applications.

    PubMed

    Sani, Elisa; Mercatelli, Luca; Meucci, Marco; Zoli, Luca; Sciti, Diletta

    2017-04-06

    We investigate the optical properties of LaB6 - based materials, as possible candidates for solid absorbers in Concentrating Solar Power (CSP) systems. Bulk LaB6 materials were thermally consolidated by hot pressing starting from commercial powders. To assess the solar absorbance and spectral selectivity properties, room-temperature hemispherical reflectance spectra were measured from the ultraviolet to the mid-infrared, considering different compositions, porosities and surface roughnesses. Thermal emittance at around 1100 K has been measured. Experimental results showed that LaB6 can have a solar absorbance comparable to that of the most advanced solar absorber material in actual plants such as Silicon Carbide, with a higher spectral selectivity. Moreover, LaB6 has also the appealing characteristics to be a thermionic material, so that it could act at the same time both as direct high-temperature solar absorber and as electron source, significantly reducing system complexity in future concentrating solar thermionic systems and bringing a real innovation in this field.

  5. [Emissions of methyl halides from coastal salt marshes: A review].

    PubMed

    Xie, Wen-xia; Zhao, Quan-sheng; Cui, Yu-qian; Du, Hui-na; Ye, Si-yuan

    2015-11-01

    Methyl halides are the major carrier of halogens in the atmosphere, and they play an important role in tropospheric and stratospheric ozone depletion. Meanwhile, methyl halides can act as greenhouse gases in the atmosphere, and they are also environmentally significant because of their toxicity. Coastal salt marshes, the important intertidal ecosystems at the land-ocean interface, have been considered to be a large potential natural source of methyl halides. In this paper, the research status of the natural source or sink of methyl halides, the mechanisms of their emission from coastal salt marshes and affecting factors were summarized. In view of this, the following research fields need to be strengthened in the future: 1) Long time-scale and large region-range researches about the emission of methyl halides and the evaluation of their source and sink function, 2) Accurate quantification of contribution rates of different plant species and various biological types to fluxes of methyl halides, 3) Further researches on effects of the tidal fluctuation process and flooding duration on methyl halides emission, 4) Effects of the global change and human activities on methyl halides emission.

  6. Hydrogen storage and ionic mobility in amide-halide systems.

    PubMed

    Anderson, Paul A; Chater, Philip A; Hewett, David R; Slater, Peter R

    2011-01-01

    We report the results of a systematic study of the effect of halides on hydrogen release and uptake in lithium amide and lithium imide, respectively. The reaction of lithium amide and lithium imide with lithium or magnesium chloride, bromide and iodide resulted in a series of amide-halide and imide-halide phases, only two of which have been reported previously. On heating with LiH or MgH2, the amide-halides synthesised all released hydrogen more rapidly than lithium amide itself, accompanied by much reduced, or in some cases undetectable, release of ammonia by-product. The imide-halides produced were found to hydrogenate more rapidly than lithium imide, reforming related amide-halide phases. The work was initiated to test the hypothesis that the incorporation of halide anions might improve the lithium ion conductivity of lithium amide and help maintain high lithium ion mobility at all stages of the de/rehydrogenation process, enhancing the bulk hydrogen storage properties of the system. Preliminary ionic conductivity measurements indicated that the most conducting amide- and imide-halide phases were also the quickest to release hydrogen on heating and to hydrogenate. We conclude that ionic conductivity may be an important parameter in optimising the materials properties of this and other hydrogen storage systems.

  7. Radiotracer study of the preparation of high-purity lanthanum fluoride

    SciTech Connect

    Ewing, K.J.; Jaganathan, J.; Peitersen, L.; Aggarwal, I.D. ); Sommers, J.A.; Fahey, J.V. )

    1992-06-01

    This paper reports that the behavior of the impurities iron, cobalt, yttrium, and cerium is determined via radiotracer techniques for the preparation of high-purity lanthanum fluoride. The behavior of nickel and copper during the coprecipitation of a lanthanum nitrate solution is determined by graphite furnace atomic absorption spectrometric (GFAAS) analysis. There is no commercially available radiotracer for neodymium, a key impurity associated with absorption losses in fluoride glasses. However, the chemical behavior of neodymium and that of yttrium are very similar and, therefore, it is reasonable to assume that the behavior of yttrium throughout the processing is indicative of the behavior of neodymium. The concentrations of impurities in lanthanum nitrate, carbonate, and fluoride are estimated using the radiotracer and GFAAS data for each processing step. Results indicate that while high-purity lanthanum carbonate can be prepared, any impurities present in the lanthanum carbonate will be carried quantitatively into lanthanum fluoride upon hydrofluorination.

  8. Silicon carbide semiconductor technology for high temperature and radiation environments

    NASA Technical Reports Server (NTRS)

    Matus, Lawrence G.

    1993-01-01

    Viewgraphs on silicon carbide semiconductor technology and its potential for enabling electronic devices to function in high temperature and high radiation environments are presented. Topics covered include silicon carbide; sublimation growth of 6H-SiC boules; SiC chemical vapor deposition reaction system; 6H silicon carbide p-n junction diode; silicon carbide MOSFET; and silicon carbide JFET radiation response.

  9. How specific halide adsorption varies hydrophobic interactions.

    PubMed

    Stock, Philipp; Müller, Melanie; Utzig, Thomas; Valtiner, Markus

    2016-03-11

    Hydrophobic interactions (HI) are driven by the water structure around hydrophobes in aqueous electrolytes. How water structures at hydrophobic interfaces and how this influences the HI was subject to numerous studies. However, the effect of specific ion adsorption on HI and hydrophobic interfaces remains largely unexplored or controversial. Here, the authors utilized atomic force microscopy force spectroscopy at well-defined nanoscopic hydrophobic interfaces to experimentally address how specific ion adsorption of halide ions as well as NH4 (+), Cs(+), and Na(+) cations alters interaction forces across hydrophobic interfaces. Our data demonstrate that iodide adsorption at hydrophobic interfaces profoundly varies the hydrophobic interaction potential. A long-range and strong hydration repulsion at distances D > 3 nm, is followed by an instability which could be explained by a subsequent rapid ejection of adsorbed iodides from approaching hydrophobic interfaces. In addition, the authors find only a weakly pronounced influence of bromide, and as expected no influence of chloride. Also, all tested cations do not have any significant influence on HI. Complementary, x-ray photoelectron spectroscopy and quartz-crystal-microbalance with dissipation monitoring showed a clear adsorption of large halide ions (Br(-)/I(-)) onto hydrophobic self-assembled monolayers (SAMs). Interestingly, iodide can even lead to a full disintegration of SAMs due to specific and strong interactions of iodide with gold. Our data suggest that hydrophobic surfaces are not intrinsically charged negatively by hydroxide adsorption, as it was generally believed. Hydrophobic surfaces rather interact strongly with negatively charged large halide ions, leading to a surface charging and significant variation of interaction forces.

  10. Development of novel growth methods for halide single crystals

    NASA Astrophysics Data System (ADS)

    Yokota, Yuui; Kurosawa, Shunsuke; Shoji, Yasuhiro; Ohashi, Yuji; Kamada, Kei; Yoshikawa, Akira

    2017-03-01

    We developed novel growth methods for halide scintillator single crystals with hygroscopic nature, Halide micro-pulling-down [H-μ-PD] method and Halide Vertical Bridgman [H-VB] method. The H-μ-PD method with a removable chamber system can grow a single crystal of halide scintillator material with hygroscopicity at faster growth rate than the conventional methods. On the other hand, the H-VB method can grow a large bulk single crystal of halide scintillator without a quartz ampule. CeCl3, LaBr3, Ce:LaBr3 and Eu:SrI2 fiber single crystals could be grown by the H-μ-PD method and Eu:SrI2 bulk single crystals of 1 and 1.5 inch in diameter could be grown by the H-VB method. The grown fiber and bulk single crystals showed comparable scintillation properties to the previous reports using the conventional methods.

  11. Ultrasonic characterization of microwave joined silicon carbide/silicon carbide

    SciTech Connect

    House, M.B.; Day, P.S.

    1997-05-01

    High frequency (50--150 MHz), ultrasonic immersion testing has been used to characterize the surface and interfacial joint conditions of microwave bonded, monolithic silicon carbide (SiC) materials. The high resolution ultrasonic C-scan images point to damage accumulation after thermal cycling. Image processing was used to study the effects of the thermal cycling on waveform shape, amplitude and distribution. Such information is useful for concurrently engineering material fabrication processes and suitable nondestructive test procedures.

  12. Research Update: Luminescence in lead halide perovskites

    NASA Astrophysics Data System (ADS)

    Srimath Kandada, Ajay Ram; Petrozza, Annamaria

    2016-09-01

    Efficiency and dynamics of radiative recombination of carriers are crucial figures of merit for optoelectronic materials. Following the recent success of lead halide perovskites in efficient photovoltaic and light emitting technologies, here we review some of the noted literature on the luminescence of this emerging class of materials. After outlining the theoretical formalism that is currently used to explain the carrier recombination dynamics, we review a few significant works which use photoluminescence as a tool to understand and optimize the operation of perovskite based optoelectronic devices.

  13. Synthesis of lithium cobaltate in halide melts

    NASA Astrophysics Data System (ADS)

    Modenov, D. V.; Dokutovich, V. N.; Khokhlov, V. A.; Antonov, B. D.; Kochedykov, V. A.; Zakir'yanova, I. D.

    2013-02-01

    A new method for the synthesis of lithium cobaltate LiCoo2 in salt melts is proposed and tested. The method is based on the oxidation of halide ions with molecular oxygen in Li X-CoCl2 mixtures ( X = Cl, Br, I). The chemical and phase compositions of the prepared powders and the crystal structure of the synthesized compound are studied by Fourier transform infrared spectroscopy and X-ray diffraction analysis. The average size of LiCoO2 crystallites is estimated from the X-ray diffraction data.

  14. Nanoscale investigation of organic - inorganic halide perovskites

    NASA Astrophysics Data System (ADS)

    Cacovich, S.; Divitini, G.; Vrućinić, M.; Sadhanala, A.; Friend, R. H.; Sirringhaus, H.; Deschler, F.; Ducati, C.

    2015-10-01

    Over the last few years organic - inorganic halide perovskite-based solar cells have exhibited a rapid evolution, reaching certified power conversion efficiencies now surpassing 20%. Nevertheless the understanding of the optical and electronic properties of such systems on the nanoscale is still an open problem. In this work we investigate two model perovskite systems (based on iodine - CH3NH3PbI3 and bromine - CH3NH3PbBr3), analysing the local elemental composition and crystallinity and identifying chemical inhomogeneities.

  15. Improved processing for silver halide pulse holography

    NASA Astrophysics Data System (ADS)

    Mikhailov, Viktor N.; Son, Jung-Young; Grinevitskaya, Olga V.; Lee, Hyuk-Soo; Choi, Yong-Jin

    1996-04-01

    Using of an improved developer with optical latensification allowed to significantly increase exposure sensitivity of currently in use silver halide materials. Transmission large-scale holograms (30 X 40 cm2) of diffused objects have been recorded under pulse exposure of about 6.5 X 10-6 J/cm2 for VRP and of about 2 X 10-6 J/cm2 for Agfa-Gavaert 8E56HD, in both cases without appreciable contrast deterioration. Results of the first experiments on pulse reflection holography are also discussed.

  16. Alkali Halide Nanotubes: Structure and Stability

    PubMed Central

    Fernandez-Lima, Francisco A.; Henkes, Aline Verônica; da Silveira, Enio F.; Nascimento, Marco Antonio Chaer

    2013-01-01

    Accurate density functional theory (DFT) and coupled-cluster (CCSD) calculations on a series of (LiF)n=2,36 neutral clusters suggest that nanotube structures with hexagonal and octagonal transversal cross sections show stability equal to or greater than that of the typical cubic form of large LiF crystals. The nanotube stability was further corroborated by quantum dynamic calculations at room temperature. The fact that stable nanotube structures were also found for other alkali halides (e.g., NaCl and KBr) suggests that this geometry may be widely implemented in material sciences. PMID:24376901

  17. Gastric lanthanosis (lanthanum deposition) in dialysis patients treated with lanthanum carbonate.

    PubMed

    Shitomi, Yuki; Nishida, Haruto; Kusaba, Takahiro; Daa, Tsutomu; Yano, Shinji; Arakane, Motoki; Kondo, Yoshiyuki; Nagai, Takayuki; Abe, Takashi; Gamachi, Ayako; Murakami, Kazunari; Etoh, Tsuyoshi; Shiraishi, Norio; Inomata, Masafumi; Yokoyama, Shigeo

    2017-08-01

    Lanthanum carbonate (LaC) is used to prevent hyperphosphatemia in dialysis patients. It is commonly believed that there is little LaC absorption from the intestines. However, La deposition in the gastric mucosa, which we coined "gastric lanthanosis", was recently reported. We describe here the clinicopathological features of and a possible mechanism for gastric lanthanosis. This study included 23 patients with definite gastric lanthanosis. We extracted characteristic clinicopathological features of gastric lanthanosis by computed tomography (CT) imaging and endoscopic, histologic, electron-microscopic, and element analysis examinations. The Helicobacter pylori infection rate in the lanthanosis group was much lower than that among the general population. The clinicopathological features characteristic of gastric lanthanosis were mucosal high-density linear appearance by CT, reflective bright-white spots (BWS) by gastroscopy, eosinophilic histiocytes occasionally phagocytizing foreign materials by histology, and numerous electron-dense particles in the histiocytes. The particles had burr-like skeletons resembling La crystals. Gastric lanthanosis is an under-reported, but not a rare lesion. It is characterized by endoscopic BWS and histologic eosinophilic histiocytes in dialysis patients treated with LaC. The proposed mechanism for gastric lanthanosis is that LaC is dissolved by gastric juice, crystallized within the mucosa and is phagocytized by histiocytes. © 2017 Japanese Society of Pathology and John Wiley & Sons Australia, Ltd.

  18. Lanthanum carbonate - a new phosphate binding drug in advanced renal failure.

    PubMed

    Aaseth, Jan; Bjørke-Monsen, Anne-Lise

    2017-05-09

    Lanthanum (La) is considered to be a non-essential element. La has been used for several decades in China to improve yield in plant production and has also been shown to have significant performance enhancing effects in feeding trials on animal husbandry. The estimated dietary intake of La in humans is below 150 µg, which is lower than 10% of the estimated limit of safe and acceptable daily intake. Upon ingestion of La as carbonate the lanthanum ion (La3+) is released in the stomach and traps dietary phosphate as insoluble lanthanum phosphate complexes in the gut, thereby inhibiting phosphate absorption. Lanthanum carbonate as a drug to lower serum phosphate in end-stage kidney failure was approved for human use by the US FDA in 2004 and by the EU in 2006. When used to treat patients with advanced renal insufficiency, lanthanum carbonate is administered orallyat a dose of maximally 3000 mg per day. The uptake of lanthanum ions from the gut to the circulation is negligible. And few systemic side effects have been recorded upon the use of lanthanum carbonate as a phosphate binding drug, although gastrointestinal discomfort with pain, vomiting and diarrhea may occur. Lanthanum carbonate has the potential to chelate to drugs with anionic groups and therapeutic coadministration with lanthanum carbonate may reduce the bioavailibility of drugs like tetracyclines, quinolones and levothyroxine. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

  19. Nanoscale assembly of lanthanum silica with dense and porous interfacial structures

    PubMed Central

    Ballinger, Benjamin; Motuzas, Julius; Miller, Christopher R.; Smart, Simon; Diniz da Costa, João C.

    2015-01-01

    This work reports on the nanoscale assembly of hybrid lanthanum oxide and silica structures, which form patterns of interfacial dense and porous networks. It was found that increasing the molar ratio of lanthanum nitrate to tetraethyl orthosilicate (TEOS) in an acid catalysed sol-gel process alters the expected microporous metal oxide silica structure to a predominantly mesoporous structure above a critical lanthanum concentration. This change manifests itself by the formation of a lanthanum silicate phase, which results from the reaction of lanthanum oxide nanoparticles with the silica matrix. This process converts the microporous silica into the denser silicate phase. Above a lanthanum to silica ratio of 0.15, the combination of growth and microporous silica consumption results in the formation of nanoscale hybrid lanthanum oxides, with the inter-nano-domain spacing forming mesoporous volume. As the size of these nano-domains increases with concentration, so does the mesoporous volume. The absence of lanthanum hydroxide (La(OH)3) suggests the formation of La2O3 surrounded by lanthanum silicate. PMID:25644988

  20. Lanthanum Deposition in the Stomach: Usefulness of Scanning Electron Microscopy for Its Detection.

    PubMed

    Iwamuro, Masaya; Urata, Haruo; Tanaka, Takehiro; Ando, Akemi; Nada, Takahiro; Kimura, Kosuke; Yamauchi, Kenji; Kusumoto, Chiaki; Otsuka, Fumio; Okada, Hiroyuki

    2017-02-01

    After having been treated with lanthanum carbonate administration for 4 years for hyperphosphatemia, a 75-year-old Japanese woman undergoing hemodialysis was diagnosed with lanthanum phosphate deposition in the stomach. The deposition, seen as white microgranules, was observed using esophagogastroduodenoscopy with magnifying observation. To the best of our knowledge, these are the minutest endoscopy images of lanthanum phosphate deposition in the gastric mucosa. Scanning electron microscopy (SEM) observation enabled easier identification of the deposited material, which was visible as bright areas. The present case suggests the usefulness of SEM observation in the detection of lanthanum phosphate deposition in the gastrointestinal tract.

  1. Diamond-silicon carbide composite

    DOEpatents

    Qian, Jiang; Zhao, Yusheng

    2006-06-13

    Fully dense, diamond-silicon carbide composites are prepared from ball-milled microcrystalline diamond/amorphous silicon powder mixture. The ball-milled powder is sintered (P=5–8 GPa, T=1400K–2300K) to form composites having high fracture toughness. A composite made at 5 GPa/1673K had a measured fracture toughness of 12 MPa.dot.m1/2. By contrast, liquid infiltration of silicon into diamond powder at 5 GPa/1673K produces a composite with higher hardness but lower fracture toughness. X-ray diffraction patterns and Raman spectra indicate that amorphous silicon is partially transformed into nanocrystalline silicon at 5 GPa/873K, and nanocrystalline silicon carbide forms at higher temperatures.

  2. 10 CFR 429.54 - Metal halide lamp ballasts and fixtures.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 10 Energy 3 2014-01-01 2014-01-01 false Metal halide lamp ballasts and fixtures. 429.54 Section... CONSUMER PRODUCTS AND COMMERCIAL AND INDUSTRIAL EQUIPMENT Certification § 429.54 Metal halide lamp ballasts... are applicable to metal halide lamp ballasts; and (2) For each basic model of metal halide...

  3. 10 CFR 429.54 - Metal halide lamp ballasts and fixtures.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 10 Energy 3 2013-01-01 2013-01-01 false Metal halide lamp ballasts and fixtures. 429.54 Section... CONSUMER PRODUCTS AND COMMERCIAL AND INDUSTRIAL EQUIPMENT Certification § 429.54 Metal halide lamp ballasts... are applicable to metal halide lamp ballasts; and (2) For each basic model of metal halide...

  4. 10 CFR 429.54 - Metal halide lamp ballasts and fixtures.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 10 Energy 3 2012-01-01 2012-01-01 false Metal halide lamp ballasts and fixtures. 429.54 Section... CONSUMER PRODUCTS AND COMMERCIAL AND INDUSTRIAL EQUIPMENT Certification § 429.54 Metal halide lamp ballasts... are applicable to metal halide lamp ballasts; and (2) For each basic model of metal halide...

  5. Synthesis and characterization of lanthanum doped zinc oxide nanoparticles

    SciTech Connect

    Kumar, Vinod; Sonia,; Suman,; Kumar, Sacheen Kumar, Dinesh

    2016-05-06

    La doped ZnO (Zn{sub 1-x}La{sub x}O, x = 0, 3, 6 and 9) were prepared via chemical co-precipitation method using Zinc Acetate, Lanthanum Acetate and Sodium Hydroxide at 50°C. Hydrate nanoparticles were annealed in air at 300°C for 3 hours. The synthesized samples have been characterized by powder X-ray diffraction and UV–Visible spectrophotometer. The XRD measurement revealsthat the prepared nanoparticles have different microstructure without changing a hexagonal wurtzite structure. The result shows the change in nanoparticles size with the increment of lanthanum concentration for lower concentration for x = 0 to 6 and decreases at x = 9.

  6. Microwave processing of silicon carbide

    SciTech Connect

    Akerman, M.A.; Baity, F.W. Jr.; Caughman, J.B.; Forrester, S.C.; Kass, M.D.; Morrow, M.S.; Holcombe, C.E. Jr.; Moyer, M.W.; Dews, T.W.

    1994-12-31

    Reaction-bonded silicon carbide ({alpha}-SiC) armor tiles were annealed at 2100{degree}C using microwave radiation at 2.45 GHz. Ultrasonic velocity measurements showed that the longitudinal and shear velocities, acoustic impedances, and acoustic moduli of the post-annealed tiles were statistically higher than for the unannealed tiles. However, the exposed surfaces of the annealed tiles experienced slight degradation, which was attributed to the high annealing temperatures.

  7. Conduction mechanism in boron carbide

    NASA Technical Reports Server (NTRS)

    Wood, C.; Emin, D.

    1984-01-01

    Electrical conductivity, Seebeck-coefficient, and Hall-effect measurements have been made on single-phase boron carbides, B(1-x)C(x), in the compositional range from 0.1 to 0.2 X, and between room temperature and 1273 K. The results indicate that the predominant conduction mechanism is small-polaron hopping between carbon atoms at geometrically inequivalent sites.

  8. Conduction mechanism in boron carbide

    NASA Technical Reports Server (NTRS)

    Wood, C.; Emin, D.

    1984-01-01

    Electrical conductivity, Seebeck-coefficient, and Hall-effect measurements have been made on single-phase boron carbides, B(1-x)C(x), in the compositional range from 0.1 to 0.2 X, and between room temperature and 1273 K. The results indicate that the predominant conduction mechanism is small-polaron hopping between carbon atoms at geometrically inequivalent sites.

  9. Lanthanum(III) catalysts for highly efficient and chemoselective transesterification.

    PubMed

    Hatano, Manabu; Ishihara, Kazuaki

    2013-03-11

    A facile, atom-economical, and chemoselective esterification is crucial in modern organic synthesis, particularly in the areas of pharmaceutical, polymer, and material science. However, a truly practical catalytic transesterification of carboxylic esters with various alcohols has not yet been well established, since, with many conventional catalysts, the substrates are limited to 1°- and cyclic 2°-alcohols. In sharp contrast, if we take advantage of the high catalytic activities of La(Oi-Pr)(3), La(OTf)(3), and La(NO(3))(3) as ligand-free catalysts, ligand-assisted or additive-enhanced lanthanum(III) catalysts can be highly effective acid-base combined catalysts in transesterification. A highly active dinuclear La(III) catalyst, which is prepared in situ from lanthanum(III) isopropoxide and 2-(2-methoxyethoxy)ethanol, is effective for the practical transesterification of methyl carboxylates, ethyl acetate, weakly reactive dimethyl carbonate, and much less-reactive methyl carbamates with 1°-, 2°-, and 3°-alcohols. As the second generation, nearly neutral "lanthanum(III) nitrate alkoxide", namely La(OR)(m)(NO(3))(3-m), has been developed. This catalyst is prepared in situ from inexpensive, stable, low-toxic lanthanum(III) nitrate hydrate and methyltrioctylphosphonium methyl carbonate, and is highly useful in the non-epimerized transesterification of α-substituted chiral carboxylic esters, even under azeotropic reflux conditions. In these practical La(III)-catalyzed transesterifications, colorless esters can be obtained in small- to large-scale synthesis without the need for inconvenient work-up or careful purification procedures.

  10. Methyl halide production associated with kelp

    NASA Technical Reports Server (NTRS)

    Dastoor, Minoo N.; Manley, Steven L.

    1985-01-01

    Methyl halides (MeX) are important trace constituents of the atmosphere because they, mostly MeCl, have a major impact on the atmospheric ozone layer. Also, MeCl may account for 5 pct. of the total Cl budget and MeI may have a central role in the biogeochemical cycling of iodine. High MeI concentrations were found in seawater from kelp beds and it has been suggested that MeI is produced by kelps and that MeI and MeBr along with numerous other halocarbons were released by non-kelp marine macroalgae. The objective was to determine if kelps (and other seaweeds) are sources of MeX and to assess their contribution to the estimated global source strength (EGSS) of MeX. Although the production of MeX appears to be associated with kelp, microbes involved with kelp degradation also produce MeX. Microbial MeX production may be of global significance. The microbial MeX production potential, assuming annual kelp production equals kelp degradation and 100 pct. conversion of kelp halides to MeX, is approx. 2 x the EGSS. This is not achieved but indicates that microbial production of MeX may be of global significance.

  11. Intriguing Optoelectronic Properties of Metal Halide Perovskites.

    PubMed

    Manser, Joseph S; Christians, Jeffrey A; Kamat, Prashant V

    2016-11-09

    A new chapter in the long and distinguished history of perovskites is being written with the breakthrough success of metal halide perovskites (MHPs) as solution-processed photovoltaic (PV) absorbers. The current surge in MHP research has largely arisen out of their rapid progress in PV devices; however, these materials are potentially suitable for a diverse array of optoelectronic applications. Like oxide perovskites, MHPs have ABX3 stoichiometry, where A and B are cations and X is a halide anion. Here, the underlying physical and photophysical properties of inorganic (A = inorganic) and hybrid organic-inorganic (A = organic) MHPs are reviewed with an eye toward their potential application in emerging optoelectronic technologies. Significant attention is given to the prototypical compound methylammonium lead iodide (CH3NH3PbI3) due to the preponderance of experimental and theoretical studies surrounding this material. We also discuss other salient MHP systems, including 2-dimensional compounds, where relevant. More specifically, this review is a critical account of the interrelation between MHP electronic structure, absorption, emission, carrier dynamics and transport, and other relevant photophysical processes that have propelled these materials to the forefront of modern optoelectronics research.

  12. Large polarons in lead halide perovskites

    PubMed Central

    Miyata, Kiyoshi; Meggiolaro, Daniele; Trinh, M. Tuan; Joshi, Prakriti P.; Mosconi, Edoardo; Jones, Skyler C.; De Angelis, Filippo; Zhu, X.-Y.

    2017-01-01

    Lead halide perovskites show marked defect tolerance responsible for their excellent optoelectronic properties. These properties might be explained by the formation of large polarons, but how they are formed and whether organic cations are essential remain open questions. We provide a direct time domain view of large polaron formation in single-crystal lead bromide perovskites CH3NH3PbBr3 and CsPbBr3. We found that large polaron forms predominantly from the deformation of the PbBr3− frameworks, irrespective of the cation type. The difference lies in the polaron formation time, which, in CH3NH3PbBr3 (0.3 ps), is less than half of that in CsPbBr3 (0.7 ps). First-principles calculations confirm large polaron formation, identify the Pb-Br-Pb deformation modes as responsible, and explain quantitatively the rate difference between CH3NH3PbBr3 and CsPbBr3. The findings reveal the general advantage of the soft [PbX3]− sublattice in charge carrier protection and suggest that there is likely no mechanistic limitations in using all-inorganic or mixed-cation lead halide perovskites to overcome instability problems and to tune the balance between charge carrier protection and mobility. PMID:28819647

  13. Intriguing optoelectronic properties of metal halide perovskites

    DOE PAGES

    Manser, Joseph S.; Christians, Jeffrey A.; Kamat, Prashant V.

    2016-06-21

    Here, a new chapter in the long and distinguished history of perovskites is being written with the breakthrough success of metal halide perovskites (MHPs) as solution-processed photovoltaic (PV) absorbers. The current surge in MHP research has largely arisen out of their rapid progress in PV devices; however, these materials are potentially suitable for a diverse array of optoelectronic applications. Like oxide perovskites, MHPs have ABX3 stoichiometry, where A and B are cations and X is a halide anion. Here, the underlying physical and photophysical properties of inorganic (A = inorganic) and hybrid organic-inorganic (A = organic) MHPs are reviewed withmore » an eye toward their potential application in emerging optoelectronic technologies. Significant attention is given to the prototypical compound methylammonium lead iodide (CH3NH3PbI3) due to the preponderance of experimental and theoretical studies surrounding this material. We also discuss other salient MHP systems, including 2- dimensional compounds, where relevant. More specifically, this review is a critical account of the interrelation between MHP electronic structure, absorption, emission, carrier dynamics and transport, and other relevant photophysical processes that have propelled these materials to the forefront of modern optoelectronics research.« less

  14. Finding New Perovskite Halides via Machine learning

    NASA Astrophysics Data System (ADS)

    Pilania, Ghanshyam; Balachandran, Prasanna V.; Kim, Chiho; Lookman, Turab

    2016-04-01

    Advanced materials with improved properties have the potential to fuel future technological advancements. However, identification and discovery of these optimal materials for a specific application is a non-trivial task, because of the vastness of the chemical search space with enormous compositional and configurational degrees of freedom. Materials informatics provides an efficient approach towards rational design of new materials, via learning from known data to make decisions on new and previously unexplored compounds in an accelerated manner. Here, we demonstrate the power and utility of such statistical learning (or machine learning) via building a support vector machine (SVM) based classifier that uses elemental features (or descriptors) to predict the formability of a given ABX3 halide composition (where A and B represent monovalent and divalent cations, respectively, and X is F, Cl, Br or I anion) in the perovskite crystal structure. The classification model is built by learning from a dataset of 181 experimentally known ABX3 compounds. After exploring a wide range of features, we identify ionic radii, tolerance factor and octahedral factor to be the most important factors for the classification, suggesting that steric and geometric packing effects govern the stability of these halides. The trained and validated models then predict, with a high degree of confidence, several novel ABX3 compositions with perovskite crystal structure.

  15. Finding new perovskite halides via machine learning

    DOE PAGES

    Pilania, Ghanshyam; Balachandran, Prasanna V.; Kim, Chiho; ...

    2016-04-26

    Advanced materials with improved properties have the potential to fuel future technological advancements. However, identification and discovery of these optimal materials for a specific application is a non-trivial task, because of the vastness of the chemical search space with enormous compositional and configurational degrees of freedom. Materials informatics provides an efficient approach toward rational design of new materials, via learning from known data to make decisions on new and previously unexplored compounds in an accelerated manner. Here, we demonstrate the power and utility of such statistical learning (or machine learning, henceforth referred to as ML) via building a support vectormore » machine (SVM) based classifier that uses elemental features (or descriptors) to predict the formability of a given ABX3 halide composition (where A and B represent monovalent and divalent cations, respectively, and X is F, Cl, Br, or I anion) in the perovskite crystal structure. The classification model is built by learning from a dataset of 185 experimentally known ABX3 compounds. After exploring a wide range of features, we identify ionic radii, tolerance factor, and octahedral factor to be the most important factors for the classification, suggesting that steric and geometric packing effects govern the stability of these halides. As a result, the trained and validated models then predict, with a high degree of confidence, several novel ABX3 compositions with perovskite crystal structure.« less

  16. Finding new perovskite halides via machine learning

    SciTech Connect

    Pilania, Ghanshyam; Balachandran, Prasanna V.; Kim, Chiho; Lookman, Turab

    2016-04-26

    Advanced materials with improved properties have the potential to fuel future technological advancements. However, identification and discovery of these optimal materials for a specific application is a non-trivial task, because of the vastness of the chemical search space with enormous compositional and configurational degrees of freedom. Materials informatics provides an efficient approach toward rational design of new materials, via learning from known data to make decisions on new and previously unexplored compounds in an accelerated manner. Here, we demonstrate the power and utility of such statistical learning (or machine learning, henceforth referred to as ML) via building a support vector machine (SVM) based classifier that uses elemental features (or descriptors) to predict the formability of a given ABX3 halide composition (where A and B represent monovalent and divalent cations, respectively, and X is F, Cl, Br, or I anion) in the perovskite crystal structure. The classification model is built by learning from a dataset of 185 experimentally known ABX3 compounds. After exploring a wide range of features, we identify ionic radii, tolerance factor, and octahedral factor to be the most important factors for the classification, suggesting that steric and geometric packing effects govern the stability of these halides. As a result, the trained and validated models then predict, with a high degree of confidence, several novel ABX3 compositions with perovskite crystal structure.

  17. Abrasive slurry composition for machining boron carbide

    DOEpatents

    Duran, E.L.

    1984-11-29

    An abrasive slurry particularly suited for use in drilling or machining boron carbide consists essentially of a suspension of boron carbide and/or silicon carbide grit in a carrier solution consisting essentially of a dilute solution of alkylaryl polyether alcohol in octyl alcohol. The alkylaryl polyether alcohol functions as a wetting agent which improves the capacity of the octyl alcohol for carrying the grit in suspension, yet without substantially increasing the viscosity of the carrier solution.

  18. Abrasive slurry composition for machining boron carbide

    DOEpatents

    Duran, Edward L.

    1985-01-01

    An abrasive slurry particularly suited for use in drilling or machining boron carbide consists essentially of a suspension of boron carbide and/or silicon carbide grit in a carrier solution consisting essentially of a dilute solution of alkylaryl polyether alcohol in octyl alcohol. The alkylaryl polyether alcohol functions as a wetting agent which improves the capacity of the octyl alcohol for carrying the grit in suspension, yet without substantially increasing the viscosity of the carrier solution.

  19. Silicon carbide fibers and articles including same

    DOEpatents

    Garnier, John E; Griffith, George W

    2015-01-27

    Methods of producing silicon carbide fibers. The method comprises reacting a continuous carbon fiber material and a silicon-containing gas in a reaction chamber at a temperature ranging from approximately 1500.degree. C. to approximately 2000.degree. C. A partial pressure of oxygen in the reaction chamber is maintained at less than approximately 1.01.times.10.sup.2 Pascal to produce continuous alpha silicon carbide fibers. Continuous alpha silicon carbide fibers and articles formed from the continuous alpha silicon carbide fibers are also disclosed.

  20. Methods for producing silicon carbide fibers

    DOEpatents

    Garnier, John E.; Griffith, George W.

    2016-03-01

    Methods of producing silicon carbide fibers. The method comprises reacting a continuous carbon fiber material and a silicon-containing gas in a reaction chamber at a temperature ranging from approximately 1500.degree. C. to approximately 2000.degree. C. A partial pressure of oxygen in the reaction chamber is maintained at less than approximately 1.01.times.10.sup.2 Pascal to produce continuous alpha silicon carbide fibers. Continuous alpha silicon carbide fibers and articles formed from the continuous alpha silicon carbide fibers are also disclosed.

  1. METHOD OF JOINING CARBIDES TO BASE METALS

    DOEpatents

    Krikorian, N.H.; Farr, J.D.; Witteman, W.G.

    1962-02-13

    A method is described for joining a refractory metal carbide such as UC or ZrC to a refractory metal base such as Ta or Nb. The method comprises carburizing the surface of the metal base and then sintering the base and carbide at temperatures of about 2000 deg C in a non-oxidizing atmosphere, the base and carbide being held in contact during the sintering step. To reduce the sintering temperature and time, a sintering aid such as iron, nickel, or cobait is added to the carbide, not to exceed 5 wt%. (AEC)

  2. Nickel-Catalyzed Borylation of Halides and Pseudo-Halides with Tetrahydroxydiboron [B2(OH)4

    PubMed Central

    Molander, Gary A.; Cavalcanti, Livia N.; García-García, Carolina

    2013-01-01

    Arylboronic acids are gaining increased importance as reagents and target structures in a variety of useful applications. Recently, the palladium-catalyzed synthesis of arylboronic acids employing the atom economical tetrahydroxydiboron (BBA) reagent has been reported. The high cost associated with palladium, combined with several limitations of both palladium and copper-catalyzed processes, prompted us to develop an alternative method. Thus, the nickel-catalyzed borylation of aryl and heteroaryl halides and pseudo-halides using tetrahydroxydiboron (BBA) has been formulated. The reaction proved to be widely functional group tolerant and applicable to a number of heterocyclic systems. To the best of our knowledge, the examples presented here represent the only effective Ni-catalyzed Miyaura borylations conducted at room temperature. PMID:23777538

  3. Engineered hydrochar composites for phosphorus removal/recovery: Lanthanum doped hydrochar prepared by hydrothermal carbonization of lanthanum pretreated rice straw.

    PubMed

    Dai, Lichun; Wu, Bo; Tan, Furong; He, Mingxiong; Wang, Wenguo; Qin, Han; Tang, Xiaoyu; Zhu, Qili; Pan, Ke; Hu, Qichun

    2014-06-01

    Engineered hydrochar composites (EHC) were synthesized by hydrothermal carbonization (HTC) of lanthanum pretreated rice straw. The as-prepared composite with about 30% lanthanum content showed greater P removal potential than La(OH)3, indicating the synergistic effect of hydrochar and lanthanum in P removal. The adsorption results showed that EHC showed great P adsorption capacities (>50mgPg(-1)) in the pH range of 2.5-10.5, and the presence of competing anions had little negative effects on P adsorption on EHC. The equilibrium time for P adsorption on EHC was considerably reduced under acid condition (12h) compared to alkaline condition (48h). The maximum adsorption capacity was 61.57mgPg(-1) according to Langmuir isotherms. These results suggested that EHC was highly effective in P adsorption in a wide range of pH and the presence of competing anions, thus EHC could be a promising adsorbent for phosphorus removal/recovery from wastewater.

  4. Alkali metal and alkali earth metal gadolinium halide scintillators

    DOEpatents

    Bourret-Courchesne, Edith; Derenzo, Stephen E.; Parms, Shameka; Porter-Chapman, Yetta D.; Wiggins, Latoria K.

    2016-08-02

    The present invention provides for a composition comprising an inorganic scintillator comprising a gadolinium halide, optionally cerium-doped, having the formula A.sub.nGdX.sub.m:Ce; wherein A is nothing, an alkali metal, such as Li or Na, or an alkali earth metal, such as Ba; X is F, Br, Cl, or I; n is an integer from 1 to 2; m is an integer from 4 to 7; and the molar percent of cerium is 0% to 100%. The gadolinium halides or alkali earth metal gadolinium halides are scintillators and produce a bright luminescence upon irradiation by a suitable radiation.

  5. Unraveling the Role of Monovalent Halides in Mixed-Halide Organic-Inorganic Perovskites.

    PubMed

    Deepa, Melepurath; Ramos, F Javier; Shivaprasad, S M; Ahmad, Shahzada

    2016-03-16

    The performance of perovskite solar cells is strongly influenced by the composition and microstructure of the perovskite. A recent approach to improve the power conversion efficiencies utilized mixed-halide perovskites, but the halide ions and their roles were not directly studied. Unraveling their precise location in the perovskite layer is of paramount importance. Here, we investigated four different perovskites by using X-ray photoelectron spectroscopy, and found that among the three studied mixed-halide perovskites, CH3 NH3 Pb(I0.74 Br0.26 )3 and CH3 NH3 PbBr3-x Clx show peaks that unambiguously demonstrate the presence of iodide and bromide in the former, and bromide and chloride in the latter. The CH3 NH3 PbI3-x Clx perovskite shows anomalous behavior, the iodide content far outweighs that of the chloride; a small proportion of chloride, in all likelihood, resides deep within the TiO2 /absorber layer. Our study reveals that there are many distinguishable structural differences between these perovskites, and that these directly impact the photovoltaic performances.

  6. Tellurium halide IR fibers for remote spectroscopy

    NASA Astrophysics Data System (ADS)

    Zhang, Xhang H.; Ma, Hong Li; Blanchetiere, Chantal; Le Foulgoc, Karine; Lucas, Jacques; Heuze, Jean; Colardelle, P.; Froissard, P.; Picque, D.; Corrieu, G.

    1994-07-01

    The new family of IR transmitting glasses, the TeX glasses, based on the association of tellurium and halide (Cl, Br, or I) are characterized by a wide optical window extending from 2 to 18 micrometers and a strong stability towards devitrification. Optical fibers drawn from these glasses exhibit low losses in the 7 - 10 micrometers range (less than 1 dB/m for single index fibers, 1 - 2 dB/m for fibers having a core-clad structure). The TeX glass fibers have been used in a remote analysis set-up which is mainly composed of a FTIR spectrometer coupled with a HgCdTe detector. This prototype system permits qualitative and quantitative analysis in a wide wavelength region lying from 3 to 13 micrometers , covering the fundamental absorption of more organic species. The evolution of a lactic and an alcoholic fermentation has been monitored by means of this set-up.

  7. Metal halide perovskites for energy applications

    NASA Astrophysics Data System (ADS)

    Zhang, Wei; Eperon, Giles E.; Snaith, Henry J.

    2016-06-01

    Exploring prospective materials for energy production and storage is one of the biggest challenges of this century. Solar energy is one of the most important renewable energy resources, due to its wide availability and low environmental impact. Metal halide perovskites have emerged as a class of semiconductor materials with unique properties, including tunable bandgap, high absorption coefficient, broad absorption spectrum, high charge carrier mobility and long charge diffusion lengths, which enable a broad range of photovoltaic and optoelectronic applications. Since the first embodiment of perovskite solar cells showing a power conversion efficiency of 3.8%, the device performance has been boosted up to a certified 22.1% within a few years. In this Perspective, we discuss differing forms of perovskite materials produced via various deposition procedures. We focus on their energy-related applications and discuss current challenges and possible solutions, with the aim of stimulating potential new applications.

  8. Passive particle dosimetry. [silver halide crystal growth

    NASA Technical Reports Server (NTRS)

    Childs, C. B.

    1977-01-01

    Present methods of dosimetry are reviewed with emphasis on the processes using silver chloride crystals for ionizing particle dosimetry. Differences between the ability of various crystals to record ionizing particle paths are directly related to impurities in the range of a few ppm (parts per million). To understand the roles of these impurities in the process, a method for consistent production of high purity silver chloride, and silver bromide was developed which yields silver halides with detectable impurity content less than 1 ppm. This high purity silver chloride was used in growing crystals with controlled doping. Crystals were grown by both the Czochalski method and the Bridgman method, and the Bridgman grown crystals were used for the experiments discussed. The distribution coefficients of ten divalent cations were determined for the Bridgman crystals. The best dosimeters were made with silver chloride crystals containing 5 to 10 ppm of lead; other impurities tested did not produce proper dosimeters.

  9. Titanium Carbide Bipolar Plate for Electrochemical Devices

    SciTech Connect

    LaConti, Anthony B.; Griffith, Arthur E.; Cropley, Cecelia C.; Kosek, John A.

    1998-05-08

    Titanium carbide comprises a corrosion resistant, electrically conductive, non-porous bipolar plate for use in an electrochemical device. The process involves blending titanium carbide powder with a suitable binder material, and molding the mixture, at an elevated temperature and pressure.

  10. Titanium carbide bipolar plate for electrochemical devices

    DOEpatents

    LaConti, Anthony B.; Griffith, Arthur E.; Cropley, Cecelia C.; Kosek, John A.

    2000-07-04

    A corrosion resistant, electrically conductive, non-porous bipolar plate is made from titanium carbide for use in an eletrochemical device. The process involves blending titanium carbide powder with a suitable binder material, and molding the mixture, at an elevated temperature and pressure.

  11. Silicon nitride/silicon carbide composite powders

    DOEpatents

    Dunmead, Stephen D.; Weimer, Alan W.; Carroll, Daniel F.; Eisman, Glenn A.; Cochran, Gene A.; Susnitzky, David W.; Beaman, Donald R.; Nilsen, Kevin J.

    1996-06-11

    Prepare silicon nitride-silicon carbide composite powders by carbothermal reduction of crystalline silica powder, carbon powder and, optionally, crystalline silicon nitride powder. The crystalline silicon carbide portion of the composite powders has a mean number diameter less than about 700 nanometers and contains nitrogen. The composite powders may be used to prepare sintered ceramic bodies and self-reinforced silicon nitride ceramic bodies.

  12. 500 C SILICON CARBIDE RECTIFIER PROGRAM

    DTIC Science & Technology

    Silicon carbide crystals of the hexagonal type were grown in a Kroll-type furnace by the sublimation technique. Both homogeneous and grown junction...feasibility of vapor-phase chemical reaction methods was investigated for the controlled growth of silicon carbide platelets and sheets. The growth of

  13. Bleaching mechanism of silver halide photochromic glasses

    NASA Astrophysics Data System (ADS)

    Caurant, D.; Gourier, D.; Vivien, D.; Prassas, M.

    1993-02-01

    Thermal bleaching of silver halide photochromic glasses is studied by electron paramagnetic resonance spectroscopy of photoinduced CuII centers. During exposure to ultraviolet light, the only stable CuII species is the (CuIIVAg)A center, which is a CuII-silver vacancy complex with the vacancy in a nearest position. In the dark, this center rapidly decays via two parallel channels. The first involves the dissociation of the complex by displacement of the vacancy along a [110] direction, with an activation energy E3=0.44 eV and a frequency factor k30=3.4×105 s-1. The second channel involves the conversion of the (CuIIVAg)A center into a (CuIICl-VAg)B center, where the silver vacancy is in the next nearest position along the [100] direction. This process occurs with an activation energy E1=0.44 eV and a frequency factor k10=3.1×105 s-1. The (CuIICl-VAg)B center slowly decays by a vacancy hopping mechanism, with an activation energy E2=0.22 eV and a frequency factor k20=4.6 s-1. To explain these two decay channels, it is proposed that the (CuIIVAg)A and (CuIICl-VAg)B centers annihilate via the formation of a CuI ion and a neutral complex (AgIIVAg)A which migrates to the surface of the silver halide particle, where electron-hole recombination occurs.

  14. Tungsten carbide production from ore concentrates by molten salt-natural gas sparging treatment

    SciTech Connect

    Carnahan, T.G.; Kazonich, G.; Raddatz, A.E.

    1988-01-01

    The U.S. Bureau of Mines conducted a bench-scale study to delineate the important parameters in a three-step process to produce commercial-quality tungsten carbide (WC) directly from tungsten minerals. In the process, tungsten concentrates of wolframite or wolframite and scheelite are decomposed at 1,050{sup 0}C in a molten mixture of NcCl and Na{sub 2}SiO{sub 3} that forms two immiscible phases. Tungsten, as sodium tungstate, reports to the halide phase and is separated from the gangue constituents, which report to the silicate phase. After decanting to separate the two phases, natural gas is sparged into the molten halide phase a 1,070{sup 0}C. Submicrometer crystals of WC are initially produced. These crystals grow into thin triangular-shaped plates up to 100 {mu}m on a side or into popcorn-shaped conglomerates. Sparged WC was examined for its suitability for use in sintered carbide products. In physical evaluations, sparged WC ground to an average particle size of 1.52 {mu}m and compacted with 10 pct Co binder into standard 6-by 22-mm test bars had a density of 14.35 and a Rockwell A hardness of 89.6. This compared favorably with 14.39 and 89.7 respectively, for test bars made from a standard commercial 1.52-{mu}m WC powder. Test bars made from Bureau of Mines WC had no C'' porosity or eta phase.

  15. Photocatalytic hydrogen generation over lanthanum doped TiO2 under UV light irradiation.

    PubMed

    Liu, Y; Xie, L; Li, Y; Qu, J L; Zheng, J; Li, X G

    2009-02-01

    TiO2 nanoparticles doped with different amount of lanthanum were obtained by sol-gel approach and followed annealing at different temperature. The crystal size of TiO2 doped with lanthanum was smaller than that of pure TiO2. Photocatalytic activity of TiO2 doped with lanthanum for water splitting into H2 was investigated. The photocatalytic activity of TiO2 doped with lanthanum for water splitting into H2 is higher than that of pure TiO2. It was found that the optimal photocatalyst was TiO2 doped with 2 wt% lanthanum and calcined at 600 degrees C for 4 h which had hydrogen generation rate 700.6 micromol h(-1).

  16. Effect of trace lanthanum ion on dissolution and crystal growth of calcium carbonate

    NASA Astrophysics Data System (ADS)

    Kamiya, Natsumi; Kagi, Hiroyuki; Tsunomori, Fumiaki; Tsuno, Hiroshi; Notsu, Kenji

    2004-07-01

    Impurity effects of trace lanthanum ion (La 3+) on the dissolution and growth of calcium carbonate were studied with in situ observation techniques. Dissolution kinetics of two polymorphs of calcium carbonate, calcite and vaterite, were investigated by monitoring the pH in the solution with laser-induced fluorescence spectroscopy using a pH-sensitive reagent, seminaphthorhodafluors. No effect on dissolution of vaterite was observed with the spectroscopic observations, whereas calcite dissolution was significantly inhibited by lanthanum ion with concentrations higher than 1 μM. Crystal growth and dissolution processes of calcite under the lanthanum-doped condition were observed by means of atomic force microscopy. Step propagations during crystal growth and dissolution of calcite were inhibited by trace lanthanum ion (5 μM). An insoluble thin layer of lanthanum carbonate deposited on the step site of the calcite surface could be a possible cause of the inhibitions observed both for dissolution and growth.

  17. Process for making silicon carbide reinforced silicon carbide composite

    NASA Technical Reports Server (NTRS)

    Lau, Sai-Kwing (Inventor); Calandra, Salavatore J. (Inventor); Ohnsorg, Roger W. (Inventor)

    1998-01-01

    A process comprising the steps of: a) providing a fiber preform comprising a non-oxide ceramic fiber with at least one coating, the coating comprising a coating element selected from the group consisting of carbon, nitrogen, aluminum and titanium, and the fiber having a degradation temperature of between 1400.degree. C. and 1450.degree. C., b) impregnating the preform with a slurry comprising silicon carbide particles and between 0.1 wt % and 3 wt % added carbon c) providing a cover mix comprising: i) an alloy comprising a metallic infiltrant and the coating element, and ii) a resin, d) placing the cover mix on at least a portion of the surface of the porous silicon carbide body, e) heating the cover mix to a temperature between 1410.degree. C. and 1450.degree. C. to melt the alloy, and f) infiltrating the fiber preform with the melted alloy for a time period of between 15 minutes and 240 minutes, to produce a ceramic fiber reinforced ceramic composite.

  18. Electronic and Ionic Transport Dynamics in Organolead Halide Perovskites.

    PubMed

    Li, Dehui; Wu, Hao; Cheng, Hung-Chieh; Wang, Gongming; Huang, Yu; Duan, Xiangfeng

    2016-07-26

    Ion migration has been postulated as the underlying mechanism responsible for the hysteresis in organolead halide perovskite devices. However, the electronic and ionic transport dynamics and how they impact each other in organolead halide perovskites remain elusive to date. Here we report a systematic investigation of the electronic and ionic transport dynamics in organolead halide perovskite microplate crystals and thin films using temperature-dependent transient response measurements. Our study reveals that thermally activated ionic and electronic conduction coexist in perovskite devices. The extracted activation energies suggest that the electronic transport is easier, but ions migrate harder in microplates than in thin films, demonstrating that the crystalline quality and grain boundaries can fundamentally modify electronic and ionic transport in perovskites. These findings offer valuable insight on the electronic and ionic transport dynamics in organolead halide perovskites, which is critical for optimizing perovskite devices with reduced hysteresis and improved stability and efficiency.

  19. Preparation of silicon carbide fibers

    DOEpatents

    Wei, G.C.

    1983-10-12

    Silicon carbide fibers suitable for use in the fabrication of dense, high-strength, high-toughness SiC composites or as thermal insulating materials in oxidizing environments are fabricated by a new, simplified method wherein a mixture of short-length rayon fibers and colloidal silica is homogenized in a water slurry. Water is removed from the mixture by drying in air at 120/sup 0/C and the fibers are carbonized by (pyrolysis) heating the mixture to 800 to 1000/sup 0/C in argon. The mixture is subsequently reacted at 1550 to 1900/sup 0/C in argon to yield pure ..beta..-SiC fibers.

  20. Damage kinetics in silicon carbide

    NASA Astrophysics Data System (ADS)

    Pickup, I. M.; Barker, A. K.

    1998-07-01

    Three silicon carbides of similar density and grain size but manufactured via different routes (reaction bonded, pressureless sintered and pressure assisted densification) have been investigated. High speed photography in conjunction with Hopkinson pressure bar compression tests has revealed that not only does the manufacturing route confer a significant difference in failure kinetics but also modifies the phenomenology of failure. Plate impact experiments using lateral and longitudinal manganin stress gauges have been used to study shear strength behaviour of damaged material. Failure waves have been observed in all three materials and characteristically different damaged material shear strength relationships with pressure have been observed.

  1. Damage kinetics in silicon carbide

    SciTech Connect

    Pickup, I. M.; Barker, A. K.

    1998-07-10

    Three silicon carbides of similar density and grain size but manufactured via different routes (reaction bonded, pressureless sintered and pressure assisted densification) have been investigated. High speed photography in conjunction with Hopkinson pressure bar compression tests has revealed that not only does the manufacturing route confer a significant difference in failure kinetics but also modifies the phenomenology of failure. Plate impact experiments using lateral and longitudinal manganin stress gauges have been used to study shear strength behaviour of damaged material. Failure waves have been observed in all three materials and characteristically different damaged material shear strength relationships with pressure have been observed.

  2. Binding and Selectivity of Halides with Macrocyclic polyamines

    PubMed Central

    Hossain, Md. Alamgir; Saeed, Musabbir A.

    2010-01-01

    This review covers the binding and selectivity aspects of halide anions in positively charged polyammonium hosts including monocyclic, bicyclic and tricyclic systems. The binding affinity and selectivity of host molecules for halides are largely depended on the shape, charges, and ring size of the host molecules. In general, a monocycle that has a flexible cavity binds an anion from both side, however a bicyclic or tricyclic molecule tends to bind a single anion in its cavity. PMID:21037945

  3. Substrate inhibition competes with halide inhibition in polyphenol oxidase.

    PubMed

    Lim, Giselle Grace Fernando; Imura, Yuki; Yoshimura, Etsuro

    2012-10-01

    Polyphenol oxidase (PPO) is a ubiquitous enzyme important in the food industry. Although PPO activity followed Michaelis-Menten kinetics at catechol concentrations of up to 1 mM, it slowly decreased at catechol concentrations above 2 mM. This result indicated that in addition to the active site (site A), the enzyme possesses a second catechol-binding site (site B) that exerts an inhibitory effect on PPO activity. Halides inhibit PPO activity in such a way that substrate inhibition is lessened when halide concentration is increased. Furthermore, elevated concentrations of catechol diminished the degree of inhibition by halides. These findings suggest that halides also bind to site B to inhibit PPO activity. A steady-state kinetic analysis demonstrated that the dissociation constant between catechol and PPO depended on the binding of halides to site B. The dissociation constants were greatest when chloride bound to the site. Bromide and iodide yielded lower dissociation constants, in that order. These data indicate that the binding of halide to site B modulated the structure of site A, thereby exerting an inhibitory effect.

  4. Relation between the electroforming voltage in alkali halide-polymer diodes and the bandgap of the alkali halide

    SciTech Connect

    Bory, Benjamin F.; Wang, Jingxin; Janssen, René A. J.; Meskers, Stefan C. J.; Gomes, Henrique L.; De Leeuw, Dago M.

    2014-12-08

    Electroforming of indium-tin-oxide/alkali halide/poly(spirofluorene)/Ba/Al diodes has been investigated by bias dependent reflectivity measurements. The threshold voltages for electrocoloration and electroforming are independent of layer thickness and correlate with the bandgap of the alkali halide. We argue that the origin is voltage induced defect formation. Frenkel defect pairs are formed by electron–hole recombination in the alkali halide. This self-accelerating process mitigates injection barriers. The dynamic junction formation is compared to that of a light emitting electrochemical cell. A critical defect density for electroforming is 10{sup 25}/m{sup 3}. The electroformed alkali halide layer can be considered as a highly doped semiconductor with metallic transport characteristics.

  5. METHOD OF SEPARATING PLUTONIUM FROM LANTHANUM FLUORIDE CARRIER

    DOEpatents

    Watt, G.W.; Goeckermann, R.H.

    1958-06-10

    An improvement in oxidation-reduction type methods of separating plutoniunn from elements associated with it in a neutron-irradiated uranium solution is described. The method relates to the separating of plutonium from lanthanum ions in an aqueous 0.5 to 2.5 N nitric acid solution by 'treating the solution, at room temperature, with ammonium sulfite in an amount sufficient to reduce the hexavalent plutonium present to a lower valence state, and then treating the solution with H/sub 2/O/sub 2/ thereby forming a tetravalent plutonium peroxide precipitate.

  6. Phase I. Lanthanum-based Start Materials for Hydride Batteries

    SciTech Connect

    Gschneidner, K. A.; Schmidt, F. A.; Frerichs, A. E.; Ament, K. A.

    2013-08-20

    The purpose of Phase I of this work is to focus on developing a La-based start material for making nickel-metal (lanthanum)-hydride batteries based on our carbothermic-silicon process. The goal is to develop a protocol for the manufacture of (La1-xRx)(Ni1-yMy)(Siz), where R is a rare earth metal and M is a non-rare earth metal, to be utilized as the negative electrode in nickel-metal hydride (NiMH) rechargeable batteries.

  7. a Bombardment Heated Lanthanum-Hexaboride Thermionic Cathode Electron Gun.

    NASA Astrophysics Data System (ADS)

    Herniter, Marc Efrem

    This dissertation concerns the development and operation of a high current density Pierce-type electron gun with a 0.75-inch-diameter lanthanum hexaboride (LaB _6) thermionic cathode. The objective of this research is to achieve as high a current density as possible from the lanthanum hexaboride cathode. The topics which are addressed are the cathode heating and control system, the Pierce-type electron gun design, and the high voltage pulsing and isolation system. Lanthanum hexaboride is used as a cathode material in applications where high current density and resistance to chemical poisoning are important. Applications include free electron lasers and high power microwave generation. A four stage Marx generator capable of producing 140-kV-peak pulses with a 16 mus decay time constant is used to pulse the electron gun. The cathode is heated to temperatures greater than 1800 ^circ C by electron bombardment from a tungsten filament. Both temperature-limited and space -charge-limited bombardment methods have been investigated. The temperature-limited method is open-loop unstable. Analog and digital control circuits have been developed to control this instability. A simple heating model has been developed and criteria for constructing a controllable system have been established. An instability in the heating system which is caused by evaporation of lanthanum hexaboride from the cathode is discussed. This evaporation reduces the work function of the bombarding filament and makes the temperature -limited bombardment system uncontrollable. The gun has been operated up to voltages of 115 kV achieving beam current densities of 30 A/cm ^2. The electron gun operated dependably up to voltages of 90 kV achieving temperature-limited currents of 50 A. Due to the high fields at the tip of the Pierce -focusing electrode the gun would usually arc at voltages greater than 90 kV. Electron gun operation has been observed in the temperature-limited and space-charge-limited regimes. The

  8. Silicon halide-alkali metal flames as a source of solar grade silicon

    NASA Technical Reports Server (NTRS)

    Olson, D. B.; Miller, W. J.; Gould, R. K.

    1980-01-01

    The feasibility of using continuous high-temperature reactions of alkali metals and silicon halides to produce silicon in large quantities and of suitable purity for use in the production of photovoltaic solar cells was demonstrated. Low pressure experiments were performed demonstrating the production of free silicon and providing experience with the construction of reactant vapor generators. Further experiments at higher reagent flow rates were performed in a low temperature flow tube configuration with co-axial injection of reagents and relatively pure silicon was produced. A high temperature graphite flow tube was built and continuous separation of Si from NaCl was demonstrated. A larger scaled well stirred reactor was built. Experiments were performed to investigate the compatability of graphite based reactor materials of construction with sodium. At 1100 to 1200 K none of these materials were found to be suitable. At 1700 K the graphites performed well with little damage except to coatings of pyrolytic graphite and silicon carbide which were damaged.

  9. Silicon halide-alkali metal flames as a source of solar grade silicon. Final report

    SciTech Connect

    Olson, D.B.; Miller, W.J.; Gould, R.K.

    1980-01-01

    The object of this program was to determine the feasibility of using continuous high-temperature reactions of alkali metals and silicon halides to produce silicon in large quantities and of suitable purity for use in the production of photovoltaic solar cells. Equilibrium calculations showed that a range of conditions were available where silicon was produced as a condensed phase but the byproduct alkali metal salt was a vapor. A process was proposed using the vapor phase reaction of Na with SiCl/sub 4/. Low pressure experiments were performed demonstrating that free silicon was produced and providing experience with the construction of reactant vapor generators. Further experiments at higher reagent flow rates were performed in a low temperature flow tube configuration with co-axial injection of reagents. Relatively pure silicon was produced in these experiments. A high temperature graphite flow tube was built and continuous separation of Si from NaCl was demonstrated. A larger-scaled well-stirred reactor was built. Experiments were performed to investigate the compatibility of graphite-based reactor materials of construction with sodium. At 1100 to 1200 K none of these materials were found to be suitable. At 1700 K the graphites performed well with little damage except to coatings of pyrolytic graphite and silicon carbide which were damaged.

  10. Electron Microscopy Studies of Carbon Nanotubes, Metal Encapsulation, Fullerides, and Dispersed Carbide.

    NASA Astrophysics Data System (ADS)

    Liu, Mingqi

    The structures and morphologies of some carbon -related nanometer-size particles, including carbon nanotubes, nanoparticles, palladium (Pa) fullerides, hafnium carbide (HfC) dispersoids, and encapsulated lanthanum carbide (LaC _2), yttrium carbide (YC _2), cobalt carbide (Co_2 C), and manganese carbides (Mn_3 C, Mn_5C_2, Mn_7C_3, and Mn _{23}C_6), have been studied with high-resolution electron microscopy (HREM), scanning transmission electron microscopy (STEM), electron energy-loss spectroscopy (EELS), and electron diffraction. The formation mechanisms and growth behavior of these small particles have been examined based upon their images and diffraction patterns. A wide variety of nanotube morphologies have been observed, such as helical, nonhelical, circular cylindrical, and polygonal tubes. The helix angle within a tube changes every 3 to 5 sheets by a stepwise rotation of the hexagons. The neighboring sheets within a sheet group maintain the same helix angle by increasing the pitch number so that the helix angles existing in a tube are limited to some well -defined values. The most probable nucleation sites of tubes are the apex of nanoparticles and the half-domes of C_{60} molecules. Several tube growth defects have been identified, such as incomplete carbon sheets, U-turn growth, disordered sheet stacking, growth step, dividing wall, and tube bends. Encapsulation of LaC_2, YC_2, Mn_3C _, Mn_5C_2, Mn_7C_3, Mn _{23}C_6, and Co _2C nanocrystals have been observed within nanotubes and nanoparticles. Most encapsulated materials are perfect single crystals but some twins, faults, polycrystals, and incomplete carbides have also been found. Partial filling is the most typical growth characteristic for encapsulated LaC_2 and YC_2 while complete or near-complete filling is most often seen for manganese carbides and Co_2C. Several unique features are found in encapsulated manganese carbides, such as modulated structure, encapsulation-induced tube distortion, and carbon

  11. Methyldichloroborane evidenced as an intermediate in the chemical vapour deposition synthesis of boron carbide.

    PubMed

    Reinisch, G; Patel, S; Chollon, G; Leyssale, J-M; Alotta, D; Bertrand, N; Vignoles, G L

    2011-09-01

    The most recent ceramic-matrix composites (CMC) considered for long-life applications as thermostructural parts in aerospace propulsion contain, among others, boron-rich phases like boron carbide. This compound is prepared by thermal Chemical Vapour Infiltration (CVI), starting from precursors like boron halides and hydrocarbons. We present a study aiming at a precise knowledge of the gas-phase composition in a hot-zone LPCVD reactor fed with BCl3, CH4 and H2, which combines experimental and theoretical approaches. This work has brought strong evidences of the presence of Methydichloroborane (MDB, BCl2CH3) in the process. It is demonstrated that this intermediate, the presence of which had never been formally proved before, appears for processing temperatures slightly lower than the deposition temperature of boron carbide. The study features quantum chemical computations, which provide several pieces of information like thermochemical and kinetic data, as well as vibration and rotation frequencies, reaction kinetics computations, and experimental gas-phase characterization of several species by FTIR, for several processing parameter sets. The main results are presented, and the place of MDB in the reaction scheme is discussed.

  12. The evolution mechanism of the dislocation loops in irradiated lanthanum doped cerium oxide

    NASA Astrophysics Data System (ADS)

    Miao, Yinbin; Aidhy, Dilpuneet; Chen, Wei-Ying; Mo, Kun; Oaks, Aaron; Wolf, Dieter; Stubbins, James F.

    2014-02-01

    Cerium dioxide, a non-radioactive surrogate of uranium dioxide, is useful for simulating the radiation responses of uranium dioxide and mixed oxide fuel (MOX). Controlled additions of lanthanum can also be used to form various levels of lattice oxide or anion vacancies. In previous transmission electron microscopy (TEM) experimental studies, the growth rate of dislocation loops in irradiated lanthanum doped ceria was reported to vary with lanthanum concentration. This work reports findings of the evolution mechanisms of the dislocation loops in cerium oxide with and without lanthanum dopants based on a combination of molecular statics and molecular dynamics simulations. These dislocation loops are found to be b = 1 / 3 < 1 1 1 > interstitial type Frank loops. Calculations of the defect energy profiles of the dislocation loops with different structural configurations and radii reveal the basis for preference of nucleation as well as the driving force of growth. Frenkel pair evolution simulations and displacement cascade overlaps simulations were conducted for a variety of lanthanum doping conditions. The nucleation and growth processes of the Frank loop were found to be controlled by the mobility of cation interstitials, which is significantly influenced by the lanthanum doping concentration. Competition mechanisms coupled with the mobility of cation point defects were discovered, and can be used to explain the lanthanum effects observed in experiments.

  13. Novel borothermal route for the synthesis of lanthanum cerium hexaborides and their field emission properties

    SciTech Connect

    Menaka; Patra, Rajkumar; Ghosh, Santanu; Ganguli, Ashok K.

    2012-10-15

    The present study describes the development of a simple approach to stabilize polycrystalline lanthanum cerium hexaborides without using any flux and at ambient pressure. The nanostructured lanthanum-cerium borides were synthesized using hydroxide precursors. These precursors (La{sub 1-x}Ce{sub x}(OH){sub 3}, x=0.1, 0.2, 0.3 and 0.5) were synthesized via hydrothermal route in the presence of Tergitol (surfactant, nonylphenol ethoxylate) as a capping agent. The precursors on heating with boron at 1300 Degree-Sign C lead to the formation of nanostructures (cubes, rods and pyramids) of lanthanum cerium hexaboride. We have investigated the field emission behaviour of the hexaboride films fabricated by spin coating. It was observed that the pyramidal shaped nanostructures of La{sub 0.5}Ce{sub 0.5}B{sub 6} shows excellent field emission characteristics with high field enhancement factor of 4502. - Graphical abstract: Nanostructured lanthanum cerium hexaboride with efficient field emission have fabricated by low temperature hydroxide precursor mediated route. Highlights: Black-Right-Pointing-Pointer New methodology to prepare lanthanum cerium hexaboride at 1300 Degree-Sign C via borothermal route. Black-Right-Pointing-Pointer Nanostructured lanthanum cerium hexaboride film by spin coating process. Black-Right-Pointing-Pointer Nanopyramids based lanthanum cerium hexaboride shows excellent field emission.

  14. An antiemission coating based on zirconium carbide

    NASA Astrophysics Data System (ADS)

    Lisenkov, A. A.; Vetrov, N. Z.; Kostrin, D. K.

    2017-04-01

    The main requirement for the formation of an antiemission coating of intermetallic Pt3Zr compound is the presence of a buffer layer of stoichiometric zirconium carbide (ZrC) that can be formed with the aid a vacuum-arc plasma source. It is shown that ZrC layer can be obtained through vacuum annealing of a multilayer film comprising nanolayers of zirconium (Zr), nonstoichiometric zirconium carbide (ZrC1 - x ), and zirconium carbide with excess carbon (ZrC + C) sequentially deposited from vacuum-arc-discharge plasma.

  15. Manufacture of silicon carbide using solar energy

    DOEpatents

    Glatzmaier, Gregory C.

    1992-01-01

    A method is described for producing silicon carbide particles using solar energy. The method is efficient and avoids the need for use of electrical energy to heat the reactants. Finely divided silica and carbon are admixed and placed in a solar-heated reaction chamber for a time sufficient to cause a reaction between the ingredients to form silicon carbide of very small particle size. No grinding of silicon carbide is required to obtain small particles. The method may be carried out as a batch process or as a continuous process.

  16. LIQUID PHASE SINTERING OF METALLIC CARBIDES

    DOEpatents

    Hammond, J.; Sease, J.D.

    1964-01-21

    An improved method is given for fabricating uranium carbide composites, The method comprises forming a homogeneous mixture of powdered uranium carbide, a uranium intermetallic compound which wets and forms a eutectic with said carbide and has a non-uranium component which has a relatively high vapor pressure at a temperature in the range 1200 to 1500 deg C, and an organic binder, pressing said mixture to a composite of desired green strength, and then vacuum sintering said composite at the eutectic forming temperature for a period sufficient to remove at least a portion of the non-uranium containing component of said eutectic. (AEC)

  17. Anion-mediated negative thermal expansion in lanthanum hexaboride

    NASA Astrophysics Data System (ADS)

    Mattox, Tracy M.; Groome, Chloe; Doran, Andrew; Beavers, Christine M.; Urban, Jeffrey J.

    2017-10-01

    Lanthanum hexaboride (LaB6) is well known for its thermionic emission, mechanical hardness, and intriguing optical properties. Though this material has been studied for decades, it is difficult to design LaB6 to meet application needs because little is understood about the mechanistic details of the synthesis. The ability to observe lattice formation during the reaction through in-situ x-ray diffraction is helping improve our knowledge. We report here the strong influence of anion size of the lanthanum precursor in the solid state reaction of LaX3 (X = Cl or I) and NaBH4. The Cl atom of the precursor remains within LaB6 post-synthesis and causes negative thermal expansion when the lattice is heated. Replacing Cl with the larger I atom has a larger impact on crystal growth; however, I does not remain within the lattice post-synthesis. These results suggest subtle new synthetic knobs may be available to optimize the synthesis of LaB6 that have previously gone unexplored.

  18. Formation of lanthanum beryllate real structure under different crystallization conditions

    SciTech Connect

    Tsvetkov, E.G. . E-mail: tsvetkov@uiggm.nsc.ru; Rylov, G.M.; Matrosov, V.N.

    2006-02-02

    The aim of this paper is to characterize the major structural defects of lanthanum beryllate single crystals grown by the Czochralski method, including those doped with rare-earth elements, and to reveal their relationship to specific properties of the crystal structure of La{sub 2}Be{sub 2}O{sub 5} and with their crystallization conditions. As a basic method for research, we used transmission X-ray topography. It was established that the defect state of La{sub 2}Be{sub 2}O{sub 5} crystals prepared by this method can be caused by different types of dislocations and their ordered assemblies, solid-phase inclusions of crucible metal and eutectically co-crystallizing phases, as well as by face growth sectors with elevated content of dopant. We show a possibility for growing single crystals of doped lanthanum beryllate having a minimum quantity of structural defects that could be suitable for manufacture of high quality laser rods.

  19. Thermal Expansion of Hafnium Carbide

    NASA Technical Reports Server (NTRS)

    Grisaffe, Salvatore J.

    1960-01-01

    Since hafnium carbide (HfC) has a melting point of 7029 deg. F, it may have many high-temperature applications. A literature search uncovered very little information about the properties of HfC, and so a program was initiated at the Lewis Research Center to determine some of the physical properties of this material. This note presents the results of the thermal expansion investigation. The thermal-expansion measurements were made with a Gaertner dilatation interferometer calibrated to an accuracy of +/- 1 deg. F. This device indicates expansion by the movement of fringes produced by the cancellation and reinforcement of fixed wave-length light rays which are reflected from the surfaces of two parallel quartz glass disks. The test specimens which separate these disks are three small cones, each approximately 0.20 in. high.

  20. Improved consolidation of silicon carbide

    NASA Technical Reports Server (NTRS)

    Freedman, M. R.; Millard, M. L.

    1986-01-01

    Alpha silicon carbide powder was consolidated by both dry and wet methods. Dry pressing in a double acting steel die yielded sintered test bars with an average flexural strength of 235.6 MPa with a critical flaw size of approximately 100 micro m. An aqueous slurry pressing technique produced sintered test bars with an average flexural strength of 440.8 MPa with a critical flaw size of approximately 25 micro m. Image analysis revealed a reduction in both pore area and pore size distribution in the slurry pressed sintered test bars. The improvements in the slurry pressed material properties are discussed in terms of reduced agglomeration and improved particle packing during consolidation.

  1. Color silver halide hologram production and mastering

    NASA Astrophysics Data System (ADS)

    Bjelkhagen, Hans I.; Huang, Qiang

    1997-04-01

    Color reflection holograms recorded with the Denisyuk geometry have been demonstrated by the recently formed HOLOS Corporation in New Hampshire. The Slavich red-green-blue (RGB) sensitized ultra-high resolution silver halide emulsion was used for the hologram recording. The employed laser wavelengths were 647 nm, 532 nm, and 476 nm, generated by an argon ion, a frequency doubled Nd:YAG, and a krypton ion laser, respectively. A beam combination mechanism with dichroic filters enabled a simultaneous RGB exposure, which made the color balance and overall exposure energy easy to control as well as simplifying the recording procedure. HOLOS has been producing limited edition color holograms in various sizes from 4' X 5' to 12' X 16'. A 30 foot long optical table and high power lasers will enable HOLOS to record color holograms up to the size of one meter square in the near future. Various approaches have been investigated in generating color hologram masters which have sufficiently high diffraction efficiency to contact copy the color images onto photopolymer materials. A specially designed test object including the 1931 CIE chromaticity diagram, a rainbow ribbon cable, pure yellow dots, and a cloisonne elephant was used for color recording experiments. In addition, the Macbeth Color Checker chart was used. Both colorimetric evaluation and scattering noise measurements were performed using the PR-650 Photo Research SpectraScan SpectraCalorimeter.

  2. Perspectives on organolead halide perovskite photovoltaics

    NASA Astrophysics Data System (ADS)

    Hariz, Alex

    2016-07-01

    A number of photovoltaic technologies have been developed for large-scale solar-power production. The single-crystal first-generation photovoltaic devices were followed by thin-film semiconductor absorber layers layered between two charge-selective contacts, and more recently, by nanostructured or mesostructured solar cells that utilize a distributed heterojunction to generate charge carriers and to transport holes and electrons in spatially separated conduits. Even though a number of materials have been trialed in nanostructured devices, the aim of achieving high-efficiency thin-film solar cells in such a manner as to rival the silicon technology has yet to be attained. Organolead halide perovskites have recently emerged as a promising material for high-efficiency nanoinfiltrated devices. An examination of the efficiency evolution curve reveals that interfaces play a paramount role in emerging organic electronic applications. To optimize and control the performance in these devices, a comprehensive understanding of the contacts is essential. However, despite the apparent advances made, a fundamental theoretical analysis of the physical processes taking place at the contacts is still lacking. However, experimental ideas, such as the use of interlayer films, are forging marked improvements in efficiencies of perovskite-based solar cells. Furthermore, issues of long-term stability and large-area manufacturing have some way to go before full commercialization is possible.

  3. Charge carrier mobility in hybrid halide perovskites

    PubMed Central

    Motta, Carlo; El-Mellouhi, Fedwa; Sanvito, Stefano

    2015-01-01

    The charge transport properties of hybrid halide perovskites are investigated with a combination of density functional theory including van der Waals interaction and the Boltzmann theory for diffusive transport in the relaxation time approximation. We find the mobility of electrons to be in the range 5–10 cm2V−1s−1 and that for holes within 1–5 cm2V−1s−1, where the variations depend on the crystal structure investigated and the level of doping. Such results, in good agreement with recent experiments, set the relaxation time to about 1 ps, which is the time-scale for the molecular rotation at room temperature. For the room temperature tetragonal phase we explore two possible orientations of the organic cations and find that the mobility has a significant asymmetry depending on the direction of the current with respect to the molecular axis. This is due mostly to the way the PbI3 octahedral symmetry is broken. Interestingly we find that substituting I with Cl has minor effects on the mobilities. Our analysis suggests that the carrier mobility is probably not a key factor in determining the high solar-harvesting efficiency of this class of materials. PMID:26235910

  4. Ultrathin Colloidal Cesium Lead Halide Perovskite Nanowires.

    PubMed

    Zhang, Dandan; Yu, Yi; Bekenstein, Yehonadav; Wong, Andrew B; Alivisatos, A Paul; Yang, Peidong

    2016-10-12

    Highly uniform single crystal ultrathin CsPbBr3 nanowires (NWs) with diameter of 2.2 ± 0.2 nm and length up to several microns were successfully synthesized and purified using a catalyst-free colloidal synthesis method followed by a stepwise purification strategy. The NWs have bright photoluminescence (PL) with a photoluminescence quantum yield (PLQY) of about 30% after surface treatment. Large blue-shifted UV-vis absorption and PL spectra have been observed due to strong two-dimensional quantum confinement effects. A small angle X-ray scattering (SAXS) pattern shows the periodic packing of the ultrathin NWs along the radial direction, demonstrates the narrow radial distribution of the wires, and emphasizes the deep intercalation of the surfactants. Despite the extreme aspect ratios of the ultrathin NWs, their composition and the resulting optical properties can be readily tuned by an anion-exchange reaction with good morphology preservation. These bright ultrathin NWs may be used as a model system to study strong quantum confinement effects in a one-dimensional halide perovskite system.

  5. Charge carrier mobility in hybrid halide perovskites.

    PubMed

    Motta, Carlo; El-Mellouhi, Fedwa; Sanvito, Stefano

    2015-08-03

    The charge transport properties of hybrid halide perovskites are investigated with a combination of density functional theory including van der Waals interaction and the Boltzmann theory for diffusive transport in the relaxation time approximation. We find the mobility of electrons to be in the range 5-10 cm(2)V(-1)s(-1) and that for holes within 1-5 cm(2)V(-1)s(-1), where the variations depend on the crystal structure investigated and the level of doping. Such results, in good agreement with recent experiments, set the relaxation time to about 1 ps, which is the time-scale for the molecular rotation at room temperature. For the room temperature tetragonal phase we explore two possible orientations of the organic cations and find that the mobility has a significant asymmetry depending on the direction of the current with respect to the molecular axis. This is due mostly to the way the PbI3 octahedral symmetry is broken. Interestingly we find that substituting I with Cl has minor effects on the mobilities. Our analysis suggests that the carrier mobility is probably not a key factor in determining the high solar-harvesting efficiency of this class of materials.

  6. Metal halide perovskite nanomaterials: synthesis and applications.

    PubMed

    Ha, Son-Tung; Su, Rui; Xing, Jun; Zhang, Qing; Xiong, Qihua

    2017-04-01

    Nanomaterials refer to those with at least one dimension being at the nanoscale (i.e. <100 nm) such as quantum dots, nanowires, and nanoplatelets. These types of materials normally exhibit optical and electrical properties distinct from their bulk counterparts due to quantum confinement or strong anisotropy. In this perspective, we will focus on a particular material family: metal halide perovskites, which have received tremendous interest recently in photovoltaics and diverse photonic and optoelectronic applications. The different synthesis approaches and growth mechanisms will be discussed along with their novel characteristics and applications. Taking perovskite quantum dots as an example, the quantum confinement effect and high external quantum efficiency are among these novel properties and their excellent performance in applications, such as single photon emitters and LEDs, will be discussed. Understanding the mechanism behind the formation of these nanomaterial forms of perovskite will help researchers to come up with effective strategies to combat the emerging challenges of this family of materials, such as stability under ambient conditions and toxicity, towards next generation applications in photovoltaics and optoelectronics.

  7. Structural diversity in lithium carbides

    NASA Astrophysics Data System (ADS)

    Lin, Yangzheng; Strobel, Timothy A.; Cohen, R. E.

    2015-12-01

    The lithium-carbon binary system possesses a broad range of chemical compounds, which exhibit fascinating chemical bonding characteristics, which give rise to diverse and technologically important properties. While lithium carbides with various compositions have been studied or suggested previously, the crystal structures of these compounds are far from well understood. In this work, we present the first comprehensive survey of all ground state (GS) structures of lithium carbides over a broad range of thermodynamic conditions, using ab initio density functional theory (DFT) crystal structure searching methods. Thorough searches were performed for 29 stoichiometries ranging from Li12C to LiC12 at 0 and 40 GPa. Based on formation enthalpies from optimized van der Waals density functional calculations, three thermodynamically stable phases (Li4C3 , Li2C2 , and LiC12) were identified at 0 GPa, and seven thermodynamically stable phases (Li8C , Li6C , Li4C , Li8C3 , Li2C , Li3C4 , and Li2C3 ) were predicted at 40 GPa. A rich diversity of carbon bonding, including monomers, dimers, trimers, nanoribbons, sheets, and frameworks, was found within these structures, and the dimensionality of carbon connectivity existing within each phase increases with increasing carbon concentration. We find that the well-known composition LiC6 is actually a metastable one. We also find a unique coexistence of carbon monomers and dimers within the predicted thermodynamically stable phase Li8C3 , and different widths of carbon nanoribbons coexist in a metastable phase of Li2C2 (Imm2). Interesting mixed sp2-sp3 carbon frameworks are predicted in metastable phases with composition LiC6.

  8. Crystal Growth of: Yttrium Phosphate Ce3+:Thorium Dioxide Ce3+:Lanthanum Aluminate.

    DTIC Science & Technology

    1982-10-01

    OF S7ANOARDS1963-A c; CRYSTAL WRONTH Or: gIUm PRSHATI Ce :TUORIUK DIOXIDZ Ce * LANTHANUM ALUMIRATH PHILIPS LABO0MIORXES A Division of North American...PERFORMING ORG. REPORT NUMBER Ce : LANTHANUM ALUMINATE 7. AUTHOR(&) S. CONTRACT OR GRANT NUMOER(a) W. Zwicker E. Abelaf S. Colak T. Kovats N00014-79-C-0180...Thorium Oxide (Ce :ThO )..........................16 3.3 Ce3 : Lanthanum Aluminate (Ce3 :LaA1O 3) ........... ........ 21 4. CRYSTAL EVALUATION

  9. Lanthanum-hexaboride carbon composition for use in corrosive hydrogen-fluorine environments

    DOEpatents

    Holcombe, C.E. Jr.; Kovach, L.; Taylor, A.J.

    1980-01-22

    The present invention relates to a structural composition useful in corrosive hydrogen-fluorine environments at temperatures in excess of 1400/sup 0/K. The composition is formed of a isostatically pressed and sintered or a hot-pressed mixture of lanthanum hexaboride particles and about 10 to 30 vol% carbon. The lanthanum-hexaboride reacts with the high-temperature fluorine-containing gases to form an adherent layer of corrosion-inhibiting lanthanum trifluoride on exposed surfaces of the composition. The carbon in the composite significantly strengthens the composite, enhances thermal shock resistance, and significantly facilitates the machining of the composition.

  10. Radio-opaque fecal impaction and pseudo-occlusion in a dialyzed patient taking lanthanum carbonate.

    PubMed

    Muller, Clotilde; Muller, Sandrine; Sissoko, Aicha; Klein, Alexandre; Faller, Bernadette; Chantrel, Francois

    2012-10-01

    Lanthanum therapy is an efficient therapy of hyperphosphoremia by chelating phosphore in the digestive tract. Lanthanum is a silvery white metallic element that belongs to group 3 of the periodic table. This drug is lightly absorbed and has low water solubility. It should be borne in mind that abdominal X-rays of patients taking lanthanum carbonate may have a radio-opaque appearance typical of imaging agents. This characteristic is suggested to confirm adherence of the patient by doing an abdominal X-ray. We describe in our case a particular good compliant patient with slow digestive transit, which ends by pseudo-occlusion.

  11. Lanthanum-hexaboride carbon composition for use in corrosive hydrogen-fluorine environments

    DOEpatents

    Holcombe, Cressie E.; Kovach, Louis; Taylor, Albert J.

    1981-01-01

    The present invention relates to a structural composition useful in corrosive hydrogen-fluorine environments at temperatures in excess of 1400.degree. K. The composition is formed of a isostatically pressed and sintered or a hot-pressed mixture of lanthanum hexaboride particles and about 10-30 vol. % carbon. The lanthanum-hexaboride reacts with the high-temperature fluorine-containing bases to form an adherent layer of corrosion-inhibiting lanthanum trifluoride on exposed surfaces of the composition. The carbon in the composite significantly strengthens the composite, enhances thermal shock resistance, and significantly facilitates the machining of the composition.

  12. Mn(2+)-Doped Lead Halide Perovskite Nanocrystals with Dual-Color Emission Controlled by Halide Content.

    PubMed

    Liu, Wenyong; Lin, Qianglu; Li, Hongbo; Wu, Kaifeng; Robel, István; Pietryga, Jeffrey M; Klimov, Victor I

    2016-11-16

    Impurity doping has been widely used to endow semiconductor nanocrystals with novel optical, electronic, and magnetic functionalities. Here, we introduce a new family of doped NCs offering unique insights into the chemical mechanism of doping, as well as into the fundamental interactions between the dopant and the semiconductor host. Specifically, by elucidating the role of relative bond strengths within the precursor and the host lattice, we develop an effective approach for incorporating manganese (Mn) ions into nanocrystals of lead-halide perovskites (CsPbX3, where X = Cl, Br, or I). In a key enabling step not possible in, for example, II-VI nanocrystals, we use gentle chemical means to finely and reversibly tune the nanocrystal band gap over a wide range of energies (1.8-3.1 eV) via postsynthetic anion exchange. We observe a dramatic effect of halide identity on relative intensities of intrinsic band-edge and Mn emission bands, which we ascribe to the influence of the energy difference between the corresponding transitions on the characteristics of energy transfer between the Mn ion and the semiconductor host.

  13. Lead Halide Perovskites and Other Metal Halide Complexes As Inorganic Capping Ligands for Colloidal Nanocrystals

    PubMed Central

    2014-01-01

    Lead halide perovskites (CH3NH3PbX3, where X = I, Br) and other metal halide complexes (MXn, where M = Pb, Cd, In, Zn, Fe, Bi, Sb) have been studied as inorganic capping ligands for colloidal nanocrystals. We present the methodology for the surface functionalization via ligand-exchange reactions and the effect on the optical properties of IV–VI, II–VI, and III–V semiconductor nanocrystals. In particular, we show that the Lewis acid–base properties of the solvents, in addition to the solvent dielectric constant, must be properly adjusted for successful ligand exchange and colloidal stability. High luminescence quantum efficiencies of 20–30% for near-infrared emitting CH3NH3PbI3-functionalized PbS nanocrystals and 50–65% for red-emitting CH3NH3CdBr3- and (NH4)2ZnCl4-capped CdSe/CdS nanocrystals point to highly efficient electronic passivation of the nanocrystal surface. PMID:24746226

  14. Ni doping of semiconducting boron carbide

    SciTech Connect

    Hong, Nina; Liu Jing; Adenwalla, S.; Langell, M. A.; Kizilkaya, Orhan

    2010-01-15

    The wide band gap, temperature stability, high resistivity, and robustness of semiconducting boron carbide make it an attractive material for device applications. Undoped boron carbide is p type; Ni acts as a n-type dopant. Here we present the results of controlled doping of boron carbide with Ni on thin film samples grown using plasma enhanced chemical vapor deposition. The change in the dopant concentration within the thin film as a function of the dopant flow rate in the precursor gas mixture was confirmed by x-ray photoelectron spectroscopy measurements; with increasing dopant concentration, current-voltage (I-V) curves clearly establish the trend from p-type to n-type boron carbide.

  15. Bipolaron Hopping Conduction in Boron Carbides

    SciTech Connect

    ASELAGE, TERRENCE L.; EMIN, D.; MCCREADY, STEVEN S.

    1999-09-20

    The electrical conductivities of boron carbides, B{sub 12+x}C{sub 3{minus}x} with 0.1 < x < 1.7, between 300 and 1200K suggest the hopping of a nearly temperature-independent density of small (bi)polarons. The activation energies of the nobilities are low, {approx} 0.16 eV, and are nearly independent of the composition. At lower temperatures, conductivities have non-Arrhenius temperature dependencies and strong sensitivity to carbon concentration. Percolative aspects of low-temperature hopping are evident in this sensitivity to composition. Boron carbides' Seebeck coefficients are anomalous in that (1) they are much larger than expected from boron carbides' large carrier densities and (2) they depend only weakly on the carrier density. Carrier-induced softening of local vibrations gives contributions to the Seebeck coefficient that mirror the magnitudes and temperature dependencies found in boron carbides.

  16. Calcium carbide poisoning via food in childhood.

    PubMed

    Per, Hüseyin; Kurtoğlu, Selim; Yağmur, Fatih; Gümüş, Hakan; Kumandaş, Sefer; Poyrazoğlu, M Hakan

    2007-02-01

    The fast ripening of fruits means they may contain various harmful properties. A commonly used agent in the ripening process is calcium carbide, a material most commonly used for welding purposes. Calcium carbide treatment of food is extremely hazardous because it contains traces of arsenic and phosphorous. Once dissolved in water, the carbide produces acetylene gas. Acetylene gas may affect the neurological system by inducing prolonged hypoxia. The findings are headache, dizziness, mood disturbances, sleepiness, mental confusion, memory loss, cerebral edema and seizures. We report the case of a previously healthy 5 year-old girl with no chronic disease history who was transferred to our Emergency Department with an 8-h history of coma and delirium. A careful history from her father revealed that the patient ate unripe dates treated with calcium carbide.

  17. Method for preparing boron-carbide articles

    DOEpatents

    Benton, S.T.; Masters, D.R.

    1975-10-21

    The invention is directed to the preparation of boron carbide articles of various configurations. A stoichiometric mixture of particulate boron and carbon is confined in a suitable mold, heated to a temperature in the range of about 1250 to 1500$sup 0$C for effecting a solid state diffusion reaction between the boron and carbon for forming the boron carbide (B$sub 4$C), and thereafter the resulting boron-carbide particles are hot-pressed at a temperature in the range of about 1800 to 2200$sup 0$C and a pressure in the range of about 1000 to 4000 psi for densifying and sintering the boron carbide into the desired article.

  18. Electroextraction of boron from boron carbide scrap

    SciTech Connect

    Jain, Ashish; Anthonysamy, S.; Ghosh, C.; Ravindran, T.R.; Divakar, R.; Mohandas, E.

    2013-10-15

    Studies were carried out to extract elemental boron from boron carbide scrap. The physicochemical nature of boron obtained through this process was examined by characterizing its chemical purity, specific surface area, size distribution of particles and X-ray crystallite size. The microstructural characteristics of the extracted boron powder were analyzed by using scanning electron microscopy and transmission electron microscopy. Raman spectroscopic examination of boron powder was also carried out to determine its crystalline form. Oxygen and carbon were found to be the major impurities in boron. Boron powder of purity ∼ 92 wt. % could be produced by the electroextraction process developed in this study. Optimized method could be used for the recovery of enriched boron ({sup 10}B > 20 at. %) from boron carbide scrap generated during the production of boron carbide. - Highlights: • Recovery of {sup 10}B from nuclear grade boron carbide scrap • Development of process flow sheet • Physicochemical characterization of electroextracted boron • Microscopic examination of electroextracted boron.

  19. Stabilization of boron carbide via silicon doping.

    PubMed

    Proctor, J E; Bhakhri, V; Hao, R; Prior, T J; Scheler, T; Gregoryanz, E; Chhowalla, M; Giulani, F

    2015-01-14

    Boron carbide is one of the lightest and hardest ceramics, but its applications are limited by its poor stability against a partial phase separation into separate boron and carbon. Phase separation is observed under high non-hydrostatic stress (both static and dynamic), resulting in amorphization. The phase separation is thought to occur in just one of the many naturally occurring polytypes in the material, and this raises the possibility of doping the boron carbide to eliminate this polytype. In this work, we have synthesized boron carbide doped with silicon. We have conducted a series of characterizations (transmission electron microscopy, scanning electron microscopy, Raman spectroscopy and x-ray diffraction) on pure and silicon-doped boron carbide following static compression to 50 GPa non-hydrostatic pressure. We find that the level of amorphization under static non-hydrostatic pressure is drastically reduced by the silicon doping.

  20. Stabilization of boron carbide via silicon doping

    NASA Astrophysics Data System (ADS)

    Proctor, J. E.; Bhakhri, V.; Hao, R.; Prior, T. J.; Scheler, T.; Gregoryanz, E.; Chhowalla, M.; Giulani, F.

    2015-01-01

    Boron carbide is one of the lightest and hardest ceramics, but its applications are limited by its poor stability against a partial phase separation into separate boron and carbon. Phase separation is observed under high non-hydrostatic stress (both static and dynamic), resulting in amorphization. The phase separation is thought to occur in just one of the many naturally occurring polytypes in the material, and this raises the possibility of doping the boron carbide to eliminate this polytype. In this work, we have synthesized boron carbide doped with silicon. We have conducted a series of characterizations (transmission electron microscopy, scanning electron microscopy, Raman spectroscopy and x-ray diffraction) on pure and silicon-doped boron carbide following static compression to 50 GPa non-hydrostatic pressure. We find that the level of amorphization under static non-hydrostatic pressure is drastically reduced by the silicon doping.

  1. Vitrification of IFR and MSBR halide salt reprocessing wastes

    SciTech Connect

    Siemer, D.D.

    2013-07-01

    Both of the genuinely sustainable (breeder) nuclear fuel cycles (IFR - Integral Fast Reactor - and MSBR - Molten Salt Breeder Reactor -) studied by the USA's national laboratories would generate high level reprocessing waste (HLRW) streams consisting of a relatively small amount ( about 4 mole %) of fission product halide (chloride or fluoride) salts in a matrix comprised primarily (about 95 mole %) of non radioactive alkali metal halide salts. Because leach resistant glasses cannot accommodate much of any of the halides, most of the treatment scenarios previously envisioned for such HLRW have assumed a monolithic waste form comprised of a synthetic analog of an insoluble crystalline halide mineral. In practice, this translates to making a 'substituted' sodalite ('Ceramic Waste Form') of the IFR's chloride salt-based wastes and fluoroapatite of the MSBR's fluoride salt-based wastes. This paper discusses my experimental studies of an alternative waste management scenario for both fuel cycles that would separate/recycle the waste's halide and immobilize everything else in iron phosphate (Fe-P) glass. It will describe both how the work was done and what its results indicate about how a treatment process for both of those wastes should be implemented (fluoride and chloride behave differently). In either case, this scenario's primary advantages include much higher waste loadings, much lower overall cost, and the generation of a product (glass) that is more consistent with current waste management practices. (author)

  2. Process for oxidation of hydrogen halides to elemental halogens

    DOEpatents

    Lyke, Stephen E.

    1992-01-01

    An improved process for generating an elemental halogen selected from chlorine, bromine or iodine, from a corresponding hydrogen halide by absorbing a molten salt mixture, which includes sulfur, alkali metals and oxygen with a sulfur to metal molar ratio between 0.9 and 1.1 and includes a dissolved oxygen compound capable of reacting with hydrogen halide to produce elemental halogen, into a porous, relatively inert substrate to produce a substrate-supported salt mixture. Thereafter, the substrate-supported salt mixture is contacted (stage 1) with a hydrogen halide while maintaining the substrate-supported salt mixture during the contacting at an elevated temperature sufficient to sustain a reaction between the oxygen compound and the hydrogen halide to produce a gaseous elemental halogen product. This is followed by purging the substrate-supported salt mixture with steam (stage 2) thereby recovering any unreacted hydrogen halide and additional elemental halogen for recycle to stage 1. The dissolved oxygen compound is regenerated in a high temperature (stage 3) and an optical intermediate temperature stage (stage 4) by contacting the substrate-supported salt mixture with a gas containing oxygen whereby the dissolved oxygen compound in the substrate-supported salt mixture is regenerated by being oxidized to a higher valence state.

  3. Two Dimensional Organometal Halide Perovskite Nanorods with Tunable Optical Properties.

    PubMed

    Aharon, Sigalit; Etgar, Lioz

    2016-05-11

    Organo-metal halide perovskite is an efficient light harvester in photovoltaic solar cells. Organometal halide perovskite is used mainly in its "bulk" form in the solar cell. Confined perovskite nanostructures could be a promising candidate for efficient optoelectronic devices, taking advantage of the superior bulk properties of organo-metal halide perovskite, as well as the nanoscale properties. In this paper, we present facile low-temperature synthesis of two-dimensional (2D) lead halide perovskite nanorods (NRs). These NRs show a shift to higher energies in the absorbance and in the photoluminescence compared to the bulk material, which supports their 2D structure. X-ray diffraction (XRD) analysis of the NRs demonstrates their 2D nature combined with the tetragonal 3D perovskite structure. In addition, by alternating the halide composition, we were able to tune the optical properties of the NRs. Fast Fourier transform, and electron diffraction show the tetragonal structure of these NRs. By varying the ligands ratio (e.g., octylammonium to oleic acid) in the synthesis, we were able to provide the formation mechanism of these novel 2D perovskite NRs. The 2D perovskite NRs are promising candidates for a variety of optoelectronic applications, such as light-emitting diodes, lasing, solar cells, and sensors.

  4. Genetic Control of Methyl Halide Production in Arabidopsis

    NASA Astrophysics Data System (ADS)

    Rhew, R. C.; Ostergaard, L.; Saltzman, E. S.; Yanofsky, M. F.

    2003-12-01

    Methyl chloride and methyl bromide are the primary carriers of natural chlorine and bromine to the stratosphere where they catalyze the destruction of ozone, whereas methyl iodide influences aerosol formation and ozone loss in the troposphere. Methyl bromide is also an agricultural fumigant whose use is scheduled to be phased out by international agreement. Despite the economic and environmental importance of these methyl halides, their natural sources and biological production mechanisms are poorly understood. Currently identified sources include oceans, biomass burning, industrial and agricultural use, fuel combustion, salt marshes, wetlands, rice paddies, certain terrestrial plants and fungi, and abiotic processes. We demonstrate that the model plant Arabidopsis thaliana produces and emits methyl halides and that the enzyme primarily responsible for the production is encoded by the HARMLESS TO OZONE LAYER (HOL) gene located on chromosome II. In mutant plants that have a disruption of the HOL gene, methyl halide production is largely eliminated. A phylogenetic analysis using the HOL gene suggests that the ability to produce methyl halides is widespread among vascular plants. This approach provides a genetic basis for understanding and predicting patterns of methyl halide production by plants.

  5. Hemibonding of hydroxyl radical and halide anion in aqueous solution.

    PubMed

    Yamaguchi, Makoto

    2011-12-29

    Molecular geometries and properties of the possible reaction products between the hydroxyl radical and the halide anions in aqueous solution were investigated. The formation of two-center three-electron bonding (hemibonding) between the hydroxyl radical and halide anions (Cl, Br, I) was examined by density functional theory (DFT) calculation with a range-separated hybrid (RSH) exchange-correlation functional. The long-range corrected hybrid functional (LC-ωPBE), which have given quantitatively satisfactory results for odd electron systems and excited states, was examined by test calculations for dihalogen radical anions (X(2)(-); X = Cl, Br, I) and hydroxyl radical-water clusters. Equilibrium geometries with hemibonding between the hydroxyl radical and halide anions were located by including four hydrogen-bonded water molecules. Excitation energies and oscillator strengths of σ-σ* transitions calculated by the time-dependent DFT method showed good agreement with observed values. Calculated values of the free energy of reaction on the formation of hydroxyl halide radical anion from the hydroxyl radical and halide anion were endothermic for chloride but exothermic for bromide and iodide, which is consistent with experimental values of equilibrium constants.

  6. Halide Perovskites: Poor Man's High-Performance Semiconductors.

    PubMed

    Stoumpos, Constantinos C; Kanatzidis, Mercouri G

    2016-07-01

    Halide perovskites are a rapidly developing class of medium-bandgap semiconductors which, to date, have been popularized on account of their remarkable success in solid-state heterojunction solar cells raising the photovoltaic efficiency to 20% within the last 5 years. As the physical properties of the materials are being explored, it is becoming apparent that the photovoltaic performance of the halide perovskites is just but one aspect of the wealth of opportunities that these compounds offer as high-performance semiconductors. From unique optical and electrical properties stemming from their characteristic electronic structure to highly efficient real-life technological applications, halide perovskites constitute a brand new class of materials with exotic properties awaiting discovery. The nature of halide perovskites from the materials' viewpoint is discussed here, enlisting the most important classes of the compounds and describing their most exciting properties. The topics covered focus on the optical and electrical properties highlighting some of the milestone achievements reported to date but also addressing controversies in the vastly expanding halide perovskite literature. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Selective etching of silicon carbide films

    DOEpatents

    Gao, Di; Howe, Roger T.; Maboudian, Roya

    2006-12-19

    A method of etching silicon carbide using a nonmetallic mask layer. The method includes providing a silicon carbide substrate; forming a non-metallic mask layer by applying a layer of material on the substrate; patterning the mask layer to expose underlying areas of the substrate; and etching the underlying areas of the substrate with a plasma at a first rate, while etching the mask layer at a rate lower than the first rate.

  8. Whatever happened to silicon carbide. [semiconductor devices

    NASA Technical Reports Server (NTRS)

    Campbell, R. B.

    1981-01-01

    The progress made in silicon carbide semiconductor devices in the 1955 to 1975 time frame is examined and reasons are given for the present lack of interest in the material. Its physical and chemical properties and methods of preparation are discussed. Fabrication techniques and the characteristics of silicon carbide devices are reviewed. It is concluded that a combination of economic factors and the lack of progress in fabrication techniques leaves no viable market for SiC devices in the near future.

  9. Fabrication of thorium bearing carbide fuels

    DOEpatents

    Gutierrez, R.L.; Herbst, R.J.; Johnson, K.W.R.

    Thorium-uranium carbide and thorium-plutonium carbide fuel pellets have been fabricated by the carbothermic reduction process. Temperatures of 1750/sup 0/C and 2000/sup 0/C were used during the reduction cycle. Sintering temperatures of 1800/sup 0/C and 2000/sup 0/C were used to prepare fuel pellet densities of 87% and > 94% of theoretical, respectively. The process allows the fabrication of kilogram quantities of fuel with good reproductibility of chemical and phase composition.

  10. Regeneration of zinc halide catalyst used in the hydrocracking of polynuclear hydrocarbons

    DOEpatents

    Gorin, Everett

    1978-01-01

    Improved recovery of spent molten zinc halide hydro-cracking catalyst is achieved in the oxidative vapor phase regeneration thereof by selective treatment of the zinc oxide carried over by the effluent vapors from the regeneration zone with hydrogen halide gas under conditions favoring the reaction of the zinc oxide with the hydrogen halide, whereby regenerated zinc halide is recovered in a solids-free state with little loss of zinc values.

  11. Combustion synthesis of novel boron carbide

    NASA Astrophysics Data System (ADS)

    Harini, R. Saai; Manikandan, E.; Anthonysamy, S.; Chandramouli, V.; Eswaramoorthy, D.

    2013-02-01

    The solid-state boron carbide is one of the hardest materials known, ranking third behind diamond and cubic boron nitride. Boron carbide (BxCx) enriched in the 10B isotope is used as a control rod material in the nuclear industry due to its high neutron absorption cross section and other favorable physico-chemical properties. Conventional methods of preparation of boron carbide are energy intensive processes accompanied by huge loss of boron. Attempts were made at IGCAR Kalpakkam to develop energy efficient and cost effective methods to prepare boron carbide. The products of the gel combustion and microwave synthesis experiments were characterized for phase purity by XRD. The carbide formation was ascertained using finger-print spectroscopy of FTIR. Samples of pyrolized/microwave heated powder were characterized for surface morphology using SEM. The present work shows the recent advances in understanding of structural and chemical variations in boron carbide and their influence on morphology, optical and vibrational property results discussed in details.

  12. Formation of dysprosium carbide on the graphite (0001) surface

    NASA Astrophysics Data System (ADS)

    Lii-Rosales, Ann; Zhou, Yinghui; Wallingford, Mark; Wang, Cai-Zhuang; Tringides, Michael C.; Thiel, P. A.

    2017-07-01

    Using scanning tunneling microscopy, we characterize a surface carbide that forms when Dy is deposited on the basal plane of graphite. To form carbide islands on terraces, Dy is first deposited at 650-800 K, which forms large metallic islands. Upon annealing at 1000 K, these clusters convert to carbide. Deposition directly at 1000 K is ineffective because nucleation on terraces is inhibited. Reaction is signaled by the fact that each carbide cluster is partially or totally surrounded by an etch pit. The etch pit is one carbon layer deep for most carbide clusters. Carbide clusters are also identifiable by striations on their surfaces. Based on mass balance, and assuming that only the surface layer of carbon is involved in the reaction, the carbide has stoichiometry D y2C . This is Dy-rich compared with the most common bulk carbide Dy C2 , which may reflect limited surface carbon transport to the carbide.

  13. 40 CFR 721.10181 - Halide salt of an alkylamine (generic).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Halide salt of an alkylamine (generic... Specific Chemical Substances § 721.10181 Halide salt of an alkylamine (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as halide salt...

  14. 40 CFR 721.10181 - Halide salt of an alkylamine (generic).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Halide salt of an alkylamine (generic... Specific Chemical Substances § 721.10181 Halide salt of an alkylamine (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as halide salt...

  15. 40 CFR 721.10181 - Halide salt of an alkylamine (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Halide salt of an alkylamine (generic... Specific Chemical Substances § 721.10181 Halide salt of an alkylamine (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as halide salt...

  16. 40 CFR 721.10181 - Halide salt of an alkylamine (generic).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Halide salt of an alkylamine (generic... Specific Chemical Substances § 721.10181 Halide salt of an alkylamine (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as halide salt...

  17. 40 CFR 721.10181 - Halide salt of an alkylamine (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Halide salt of an alkylamine (generic... Specific Chemical Substances § 721.10181 Halide salt of an alkylamine (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as halide salt...

  18. 10 CFR 431.322 - Definitions concerning metal halide lamp ballasts and fixtures.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 10 Energy 3 2010-01-01 2010-01-01 false Definitions concerning metal halide lamp ballasts and... FOR CERTAIN COMMERCIAL AND INDUSTRIAL EQUIPMENT Metal Halide Lamp Ballasts and Fixtures § 431.322 Definitions concerning metal halide lamp ballasts and fixtures. Ballast efficiency means, in the case of...

  19. 75 FR 5544 - Energy Conservation Program: Energy Conservation Standards for Metal Halide Lamp Fixtures: Public...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-02-03

    ... for Metal Halide Lamp Fixtures: Public Meeting and Availability of the Framework Document AGENCY... conservation standards for certain metal halide lamp fixtures. This document announces that the period for... metal halide lamp fixtures and provide docket number EERE-2009-BT-STD-0018 and/or RIN number 1904-...

  20. Morphology-controlled nonaqueous synthesis of anisotropic lanthanum hydroxide nanoparticles

    SciTech Connect

    Djerdj, Igor; Garnweitner, Georg; Sheng Su, Dang; Niederberger, Markus

    2007-07-15

    The preparation of lanthanum hydroxide and manganese oxide nanoparticles is presented, based on a nonaqueous sol-gel process involving the reaction of La(OiPr){sub 3} and KMnO{sub 4} with organic solvents such as benzyl alcohol, 2-butanone and a 1:1 vol. mixture thereof. The lanthanum manganese oxide system is highly complex and surprising results with respect to product composition and morphology were obtained. In dependence of the reaction parameters, the La(OH){sub 3} nanoparticles undergo a shape transformation from short nanorods with an average aspect ratio of 2.1 to micron-sized nanofibers (average aspect ratio is more than 59.5). Although not directly involved, KMnO{sub 4} plays a crucial role in determining the particle morphology of La(OH){sub 3}. The reason lies in the fact that KMnO{sub 4} is able to oxidize the benzyl alcohol to benzoic acid, which presumably induces the anisotropic particle growth in [0 0 1] direction upon preferential coordination to the {+-}(1 0 0), {+-}(0 1 0) and {+-}(-110) crystal facets. By adjusting the molar La(OiPr){sub 3}-to-KMnO{sub 4} ratio as well as by using the appropriate solvent mixture it is possible to tailor the morphology, phase purity and microstructure of the La(OH){sub 3} nanoparticles. Postsynthetic thermal treatment of the sample containing La(OH){sub 3} nanofibers and {beta}-MnOOH nanoparticles at the temperature of 800 deg. C for 8 h yielded polyhedral LaMnO{sub 3} and worm-like La{sub 2}O{sub 3} nanoparticles as final products. - Graphical abstract: Lanthanum hydroxide nanoparticles are synthesized based on a nonaqueous sol-gel process involving the reaction of La(OiPr){sub 3} and KMnO{sub 4} with organic solvents such as benzyl alcohol, 2-butanone and a 1:1 vol. mixture thereof. In dependence of the reaction parameters, the La(OH){sub 3} nanoparticles undergo a shape transformation from short nanorods to micron-sized nanofibers.

  1. Electrochemical Doping of Halide Perovskites with Ion Intercalation.

    PubMed

    Jiang, Qinglong; Chen, Mingming; Li, Junqiang; Wang, Mingchao; Zeng, Xiaoqiao; Besara, Tiglet; Lu, Jun; Xin, Yan; Shan, Xin; Pan, Bicai; Wang, Changchun; Lin, Shangchao; Siegrist, Theo; Xiao, Qiangfeng; Yu, Zhibin

    2017-01-24

    Halide perovskites have recently been investigated for various solution-processed optoelectronic devices. The majority of studies have focused on using intrinsic halide perovskites, and the intentional incoporation of dopants has not been well explored. In this work, we discovered that small alkali ions, including lithium and sodium ions, could be electrochemically intercalated into a variety of halide and pseudohalide perovskites. The ion intercalation caused a lattice expansion of the perovskite crystals and resulted in an n-type doping of the perovskites. Such electrochemical doping improved the conductivity and changed the color of the perovskites, leading to an electrochromism with more than 40% reduction of transmittance in the 450-850 nm wavelength range. The doped perovskites exhibited improved electron injection efficiency into the pristine perovskite crystals, resulting in bright light-emitting diodes with a low turn-on voltage.

  2. Local polar fluctuations in lead halide perovskite crystals

    DOE PAGES

    Yaffe, Omer; Guo, Yinsheng; Tan, Liang Z.; ...

    2017-03-28

    Hybrid lead-halide perovskites have emerged as an excellent class of photovoltaic materials. Recent reports suggest that the organic molecular cation is responsible for local polar fluctuations that inhibit carrier recombination. We combine low-frequency Raman scattering with first-principles molecular dynamics (MD) to study the fundamental nature of these local polar fluctuations. Our observations of a strong central peak in the cubic phase of both hybrid (CH3NH3PbBr3) and all-inorganic (CsPbBr3) lead-halide perovskites show that anharmonic, local polar fluctuations are intrinsic to the general lead-halide perovskite structure, and not unique to the dipolar organic cation. Furthermore, MD simulations indicate that head-to-head Cs motionmore » coupled to Br face expansion, occurring on a few hundred femtosecond time scale, drives the local polar fluctuations in CsPbBr3.« less

  3. Metal-halide mixtures for latent heat energy storage

    NASA Technical Reports Server (NTRS)

    Chen, K.; Manvi, R.

    1981-01-01

    Alkali metal and alkali halide mixtures are identified which may be suitable for thermal energy storage at temperatures above 600 C. The use of metal-halides is appropriate because of their tendency to form two immiscible melts with a density difference, which reduces scale formation and solidification on heat transfer surfaces. Also, the accumulation of phase change material along the melt interface is avoided by the self-dispersing characteristic of some metal-halides, in particular Sr-SrCl2, Ba-BaCl2, and Ba-BaBr2 mixtures. Further advantages lie in their high thermal conductivities, ability to cope with thermal shock, corrosion inhibition, and possibly higher energy densities.

  4. Metamagnetism of η-carbide-type transition-metal carbides and nitrides

    NASA Astrophysics Data System (ADS)

    Waki, T.; Terazawa, S.; Umemoto, Y.; Tabata, Y.; Sato, K.; Kondo, A.; Kindo, K.; Nakamura, H.

    2011-09-01

    η-carbide-type transition-metal compounds include the frustrated stella quadran-gula lattice. Due to characteristics of the lattice, we expect subtle transitions between frustrated and non-frustrated states. Here, we report metamagnetic transitions newly found in η-carbide-type compounds Fe3W3C, Fe6W6C and Co6W6C.

  5. Handbook of refractory carbides and nitrides: Properties, characteristics, processing and applications

    SciTech Connect

    Pierson, H.O.

    1997-12-31

    This reference work provides a complete review of the structure properties, processing and applications of refractory carbides and nitrides. The contents include: the refractory carbides; interstitial carbides, structure and composites; titanium, zirconium, and hafnium carbides; vanadium, niobium and tantalum carbides; chromium, molybdenum, and tungsten carbides; covalent carbides--structure and composition; characteristics and properties of silicon carbide and boron carbide; the refractory nitrides; interstitial nitrides--structure and composition; interstitial nitrides--properties and general characteristics; covalent nitrides--composition and structure; covalent nitrides--properties and general characteristics; processing of refractory carbides and nitrides and applications of refractory carbides and nitrides.

  6. Lanthanum Probe Studies of Cellular Pathophysiology Induced by Hypoxia in Isolated Cardiac Muscle

    PubMed Central

    Burton, Karen P.; Hagler, Herbert K.; Templeton, Gordon H.; Willerson, James T.; Buja, L. Maximilian

    1977-01-01

    This study was undertaken to evaluate directly the relationship between evolution of irreversible myocardial injury induced by hypoxia in an isolated papillary muscle preparation and the development of pathophysiological alterations related to severely impaired membrane function. An ionic lanthanum probe technique was employed as a cytochemical marker to monitor the progression of cellular injury, and data from this cytologic technique were correlated with ultrastructure and measurements of contractile parameters in a total of 67 muscles subjected to control conditions or to graded intervals of hypoxia with or without reoxygenation. Marked depression of developed tension and rate of tension development occurred after 30 min of hypoxia. Contractile function showed significant recovery with reoxygenation after 1 h and 15 min of hypoxia but remained depressed when reoxygenation was provided after 2 or 3 h of hypoxia. Examination by transmission and analytical electron microscopy (energy dispersive X-ray microanalysis) revealed lanthanum deposition only in extracellular regions of control muscles and muscles subjected to 30 min of hypoxia. After hypoxic intervals of over 1 h, abnormal intracytoplasmic and intramitochondrial localization of lanthanum were detected. After 1 h and 15 min of hypoxia, abnormal intracellular lanthanum accumulation was associated with only minimal ultrastructural evidence of injury; muscle provided reoxygenation after 1 h and 15 min of hypoxia showed improved ultrastructure and did not exhibit intracellular lanthanum deposits upon exposure to lanthanum during the reoxygenation period. After 2 to 3 h of hypoxia, abnormal intracellular lanthanum accumulation was associated with ultrastructural evidence of severe muscle injury which persisted after reoxygenation. Thus, the data support the conclusion that cellular and membrane alterations responsible for abnormal intracellular lanthanum deposition precede the development of irreversible injury

  7. Density Optimization of Lithium Lanthanum Titanate Ceramics for Lightweight Lithium-Air Batteries

    DTIC Science & Technology

    2014-11-01

    Thangadurai V, Weppner W. Lithium lanthanum titanates: a review. Chemistry of Materials. 2003;15:3974–3990. 4. Knauth P. Inorganic solid Li ion conductors...an overview. Solid State Ionics. 2009;180:911–916. 5. Ban CW, Choi GM. The effect of sintering on the grain boundary conductivity of lithium ...lanthanum titanates. Solid State Ionics. 2001;140:285–292. 6. Inada R, Kimura K, Kusakabe K, Tojo T, Sakurai Y. Synthesis and lithium -ion conductivity

  8. Activation volumes in lead halides and other solids

    NASA Astrophysics Data System (ADS)

    Alexopoulos, K.; Lazaridou, M.; Varotsos, P.

    1986-02-01

    Conductivity measurements of PbCl2 and PbBr2 under pressure have been carried out by Oberschmidt and Lazarus. The migration and activation volumes scale with the corresponding enthalpies in a manner predetermined by the bulk properties. By considering the existing data for a large variety of solids (rare-gas solids, lithium halides, lead halides, SrF2, and olivine) in which the defect enthalpies vary by two orders of magnitude we conclude that there is a curve which connects in a unified manner the point-defect data with the bulk properties.

  9. Thermodynamic reactivity, growth and characterization of mercurous halide crystals

    NASA Technical Reports Server (NTRS)

    Singh, N. B.; Gottlieb, M.; Henningsen, T.; Hopkins, R. H.; Mazelsky, R.; Singh, M.; Glicksman, M. E.; Paradies, C.

    1992-01-01

    Thermodynamic calculations were carried out for the Hg-X-O system (X = Cl, Br, I) to identify the potential sources of contamination and relative stability of oxides and oxy-halide phases. The effect of excess mercury vapor pressure on the optical quality of mercurous halide crystal was studied by growing several mercurous chloride crystals from mercury-rich composition. The optical quality of crystals was examined by birefringence interferometry and laser scattering studies. Crystals grown in slightly mercury-rich composition showed improved optical quality relative to stoichiometric crystals.

  10. Thallous halide materials for use in cryogenic applications

    NASA Technical Reports Server (NTRS)

    Lawless, William N. (Inventor)

    1981-01-01

    Thallous halides, either alone or in combination with other ceramic materials, are used in cryogenic applications such as heat exchange material for the regenerator section of a closed-cycle cryogenic refrigeration section, as stabilizing coatings for superconducting wires, and as dielectric insulating materials. The thallous halides possess unusually large specific heats at low temperatures, have large thermal conductivities, are nonmagnetic, and are nonconductors of electricity. They can be formed into a variety of shapes such as spheres, bars, rods, or the like and can be coated onto substrates.

  11. Lanthanum carbonate: a review of its use in lowering serum phosphate in patients with end-stage renal disease.

    PubMed

    Curran, Monique P; Robinson, Dean M

    2009-11-12

    Orally administered lanthanum carbonate (Fosrenol) dissociates in the acid environment of the upper gastrointestinal tract to release the cation lanthanum, which then binds dietary phosphate. Lanthanum carbonate was effective in reducing levels of serum phosphate and serum calcium x phosphate product and then maintaining these levels within target ranges for up to 6 years in adult patients with end-stage renal disease (ESRD) on haemodialysis or peritoneal dialysis. The reduction in serum phosphate levels with lanthanum carbonate was generally similar to that with calcium carbonate or sevelamer hydrochloride. This agent was generally well tolerated, with the most frequently reported adverse events being gastrointestinal in nature and occurring at a similar rate to that with calcium carbonate. However, lanthanum carbonate was associated with fewer episodes of hypercalcaemia than calcium carbonate. Overall, lanthanum carbonate is a valuable option for the reduction of serum phosphate levels in patients with ESRD on haemodialysis or peritoneal dialysis.

  12. Chemical and Thermal Expansion of Calcium-Doped Lanthanum Chromite

    NASA Astrophysics Data System (ADS)

    Williford, R. E.; Armstrong, T. R.; Gale, J. D.

    2000-02-01

    Atomistic free-energy minimization techniques were used to simulate three simultaneous volumetric shrinkage/expansion phenomena in calcium-doped lanthanum chromite solid oxide fuel cell (SOFC) interconnect materials. Four sets of interatomic potentials were developed and tested over the temperature range 0-1273 K. The predicted unit-cell volumes, elastic properties, volumetric shrinkage due to A-site doping of the ABO3 perovskite (La1-xCax)CrO3, defect-induced volumetric expansion due to reducing atmospheres, and thermal expansion were in reasonable agreement with experiment, though not all concurrently with a single set of potentials. Potentials based either on simple oxides or on partial charge models appeared to give the best overall predictions. Additional experimental data are needed to improve the potentials.

  13. Synthesis and characterization of strontium-lanthanum apatites

    SciTech Connect

    Boughzala, K.; Salem, E. Ben; Chrifa, A. Ben; Gaudin, E.; Bouzouita, K. . E-mail: khaled.bouzouita@ipeim.rnu.tn

    2007-07-03

    Two series of strontium-lanthanum apatites, Sr{sub 10-x}La {sub x}(PO{sub 4}){sub 6-x}(SiO{sub 4}) {sub x}F{sub 2} and Sr{sub 10-x}La {sub x}(PO{sub 4}){sub 6-x}(SiO{sub 4}) {sub x}O with 0 {<=} x {<=} 6, were synthesized by solid state reaction in the temperature range of 1200-1400 deg. C. The obtained materials were characterized by powder X-ray diffraction, infrared absorption spectroscopy and solid {sup 31}P Nuclear Magnetic Resonance. Pure solid solutions were obtained within a limited range of unsubstituted phosphate and silicate apatites. A variation of the lattice parameters was observed, with an increase of a and a decrease of c parameters, related to the radius of the corresponding substituted ions.

  14. Phosphate modulated luminescence in lanthanum vanadate nanorods- Catechin, polyphenolic ligand

    NASA Astrophysics Data System (ADS)

    Tamilmani, Vairapperumal; Nair, Balachandran Unni; Sreeram, Kalarical Janardhanan

    2017-08-01

    Rare earth orthovanadates and phosphates offer a very high opportunity for fabrication of nanoscale devices that exploit their luminescence properties. Optimization of luminescence by way of modulation of size, shape, structure, and morphology has been an area of study for several researchers. There has been a debate as to whether doped orthophosphate or orthovanadate is better luminescent material as both are chemically similar. It has been reported earlier that catechin hydrate can play the role of a structure director and thus influence the luminescence properties of orthovanadates. In this work, a catechin modulated the synthesis of Eu-doped lanthanum orthophosphate by phosphate substitution into vanadate host lattice is reported. A mechanistic understanding of the luminescence changes in LaMO4 has been proposed. During the substitution of V with P, catechin modulates the structure between 1D nanorods and nanowires. The host crystal structure, shape, and size influence the luminescence properties in doped LaMO4.

  15. Recent advances of lanthanum-based perovskite oxides for catalysis

    DOE PAGES

    Zhu, Huiyuan; Zhang, Pengfei; Dai, Sheng

    2015-09-21

    There is a need to reduce the use of noble metal elements especially in the field of catalysis, where noble metals are ubiquitously applied. To this end, perovskite oxides, an important class of mixed oxide, have been attracting increasing attention for decades as potential replacements. Benefiting from the extraordinary tunability of their compositions and structures, perovskite oxides can be rationally tailored and equipped with targeted physical and chemical properties e.g. redox behavior, oxygen mobility, and ion conductivity for enhanced catalysis. Recently, the development of highly efficient perovskite oxide catalysts has been extensively studied. This review article summarizes the recent developmentmore » of lanthanum-based perovskite oxides as advanced catalysts for both energy conversion applications and traditional heterogeneous reactions.« less

  16. Recent advances of lanthanum-based perovskite oxides for catalysis

    SciTech Connect

    Zhu, Huiyuan; Zhang, Pengfei; Dai, Sheng

    2015-09-21

    There is a need to reduce the use of noble metal elements especially in the field of catalysis, where noble metals are ubiquitously applied. To this end, perovskite oxides, an important class of mixed oxide, have been attracting increasing attention for decades as potential replacements. Benefiting from the extraordinary tunability of their compositions and structures, perovskite oxides can be rationally tailored and equipped with targeted physical and chemical properties e.g. redox behavior, oxygen mobility, and ion conductivity for enhanced catalysis. Recently, the development of highly efficient perovskite oxide catalysts has been extensively studied. This review article summarizes the recent development of lanthanum-based perovskite oxides as advanced catalysts for both energy conversion applications and traditional heterogeneous reactions.

  17. Phases in lanthanum-nickel-aluminum alloys. Part 2

    SciTech Connect

    Mosley, W.C.

    1992-08-01

    Lanthanum-nickel-aluminum (LANA) alloys will be used to pump, store and separate hydrogen isotopes in the Replacement Tritium Facility (RTF). The aluminum content (y) of the primary LaNi{sub 5}-phase is controlled to produce the desired pressure-temperature behavior for adsorption and desorption of hydrogen. However, secondary phases cause decreased capacity and some may cause undesirable retention of tritium. Twenty-three alloys purchased from Ergenics, Inc. for development of RTF processes have been characterized by scanning electron microscopy (SEM) and by electron microprobe analysis (EMPA) to determine the distributions and compositions of constituent phases. This memorandum reports the results of these characterization studies. Knowledge of the structural characteristics of these alloys is a useful first step in selecting materials for specific process development tests and in interpreting results of those tests. Once this information is coupled with data on hydrogen plateau pressures, retention and capacity, secondary phase limits for RTF alloys can be specified.

  18. Cobalt doped lanthanum chromite material suitable for high temperature use

    DOEpatents

    Ruka, R.J.

    1986-12-23

    A high temperature, solid electrolyte electrochemical cell, subject to thermal cycling temperatures of between about 25 C and about 1,200 C, capable of electronic interconnection to at least one other electrochemical cell and capable of operating in an environment containing oxygen and a fuel, is made; where the cell has a first and second electrode with solid electrolyte between them, where an improved interconnect material is applied along a portion of a supporting electrode; where the interconnect is made of a chemically modified lanthanum chromite, containing cobalt as the important additive, which interconnect allows for adjustment of the thermal expansion of the interconnect material to more nearly match that of other cell components, such as zirconia electrolyte, and is stable in oxygen containing atmospheres such as air and in fuel environments. 2 figs.

  19. Cobalt doped lanthanum chromite material suitable for high temperature use

    DOEpatents

    Ruka, Roswell J.

    1986-01-01

    A high temperature, solid electrolyte electrochemical cell, subject to thermal cycling temperatures of between about 25.degree. C. and about 1200.degree. C., capable of electronic interconnection to at least one other electrochemical cell and capable of operating in an environment containing oxygen and a fuel, is made; where the cell has a first and second electrode with solid electrolyte between them, where an improved interconnect material is applied along a portion of a supporting electrode; where the interconnect is made of a chemically modified lanthanum chromite, containing cobalt as the important additive, which interconnect allows for adjustment of the thermal expansion of the interconnect material to more nearly match that of other cell components, such as zirconia electrolyte, and is stable in oxygen containing atmospheres such as air and in fuel environments.

  20. Fabrication of calcium lanthanum sulfide ceramic by carbonate coprecipitating method

    SciTech Connect

    Tsai, M.S.; Hon, M.H. . Dept. of Materials Science and Engineering)

    1995-03-01

    Translucent CLS (calcium lanthanum sulfide) pellets were formed by the carbonate coprecipitation method, CS[sub 2] sulfurization, and hot press sintering. For a La/Ca = 2.5 pellet with 1.3 mm in thickness, the transmittance at 13 [mu]m is about 25% after sintering at 1,150 C for 30 minutes and resulfurizing at 950 C for 1 hour. For a La/Ca = 15 pellet with 0.9 mm in thickness the IR transmittance is about 51% at 13 [mu]m after sintering at 1,050 C for 2 hours and resulfurizing at 950 C for 1 hour. Beta-La[sub 2]S[sub 3] is present as a second phase after sintering at 1,150 C for 30 minutes. After resulfurization, the second phase disappears for the La/Ca = 2.5 pellet, but still exists in the La/Ca = 15 pellet.

  1. Phase separation of lanthanum hydride under high pressure

    NASA Astrophysics Data System (ADS)

    Machida, A.; Watanuki, T.; Kawana, D.; Aoki, K.

    2011-02-01

    Structural change of lanthanum dihydride LaH2.3, which has a face-centered-cubic (fcc) metal lattice with tetrahedral interstitial sites fully occupied with hydrogen atoms and partially occupied octahedral sites, has been investigated at high pressures up to 20 GPa at ambient temperature by synchrotron radiation x-ray diffraction. Additional Bragg reflections appear just on higher angle sides of the original ones at ~11 GPa and their peak intensities increase gradually on further compression. The coexistence state of two fcc metal lattices thus observed above 11 GPa is interpreted in terms of phase separation or disproportionation reaction from the dihydride toward a solid solution and trihydride states, in both of which the octahedral interstitial sites are partially occupied with hydrogen atoms. A gradual distortion from the cubic to a tetragonal lattice is observed prior to the phase separation. The coexistence phase goes back to the dihydride fcc phase via the lattice distorted phase with decreasing pressure.

  2. Infrared spectra of oxygen-rich yttrium and lanthanum dioxygen/ozonide complexes in solid argon.

    PubMed

    Gong, Yu; Ding, Chuanfan; Zhou, Mingfei

    2009-07-30

    The reactions of yttrium and lanthanum atoms with O(2) have been reinvestigated using matrix isolation infrared spectroscopy and theoretical calculations. The ground-state yttrium and lanthanum atoms react with O(2) to produce the inserted yttrium and lanthanum dioxide molecules as the initial products. The yttrium dioxide molecule interacts spontaneously with additional O(2) molecules to form the oxygen-rich OY(eta(2)-O(3)) complex and possibly the (eta(2)-O(2))Y(eta(2)-O(3))(2) complexes upon sample annealing, which can be regarded as the side-on bonded yttrium monoxide ozonide complex and the superoxo yttrium bisozonide complex, respectively. Visible irradiation induces the isomerization of the OY(eta(2)-O(3)) complex to the superoxo yttrium peroxide Y(eta(2)-O(2))(2) isomer, in which both the superoxo and peroxo ligands are side-on bonded to the yttrium center. The lanthanum dioxide molecule reacts with additional O(2) molecules to form the lanthanum dioxide-dioxygen complex with planar C(2v) symmetry, which rearranges to the lanthanum monoxide ozonide complex, OLa(eta(2)-O(3)), under near-infrared excitation.

  3. The management of hyperphosphatemia by lanthanum carbonate in chronic kidney disease patients

    PubMed Central

    Shigematsu, Takashi; Nakashima, Yuri; Ohya, Masaki; Tatsuta, Koichi; Koreeda, Daisuke; Yoshimoto, Wataru; Yamanaka, Shintaro; Sakaguchi, Toshifumi; Hanba, Yoshiyuki; Mima, Toru; Negi, Shigeo

    2012-01-01

    Hyperphosphatemia has been shown to be involved not only in the onset and progression of secondary hyperparathyroidism but also in vascular calcification. In addition, it influences the clinical course of patients with chronic kidney disease. Phosphate (Pi) binder is required in the management of hyperparaphosphatemia, because dietary Pi restriction and Pi removal by hemodialysis alone are insufficient. Lanthanum carbonate, a powerful Pi binder, has a similar effect to aluminum hydroxide in reducing serum Pi levels. As it is excreted via the liver, lanthanum carbonate has an advantage in patients with renal failure. The effect of lanthanum carbonate on serum Pi levels is almost two times higher than that of calcium (Ca) carbonate, which is commonly used. Lanthanum carbonate and Ca carbonate have an additive effect. Worldwide, there is 6 years worth of clinical treatment data on lanthanum carbonate; however, we have 3 years of clinical use in Japanese patients with hyperphosphatemia. No serious side effects have been reported. However, the most important concern is bone toxicity, which has been observed with use of aluminum hydroxide. For this study, clinical research involved analysis of bone biopsies. Although osteomalacia is the most noticeable side effect, this was not observed. Both the high- and the low-turnover bone disease concentrated into a normal bone turnover state. However, as the authors have less than 10 years’ clinical experience with lanthanum carbonate, patients should be monitored carefully. In addition, it is necessary to demonstrate whether potent treatment effects on hyperphosphatemia improve the long-term outcome. PMID:22723728

  4. The management of hyperphosphatemia by lanthanum carbonate in chronic kidney disease patients.

    PubMed

    Shigematsu, Takashi; Nakashima, Yuri; Ohya, Masaki; Tatsuta, Koichi; Koreeda, Daisuke; Yoshimoto, Wataru; Yamanaka, Shintaro; Sakaguchi, Toshifumi; Hanba, Yoshiyuki; Mima, Toru; Negi, Shigeo

    2012-01-01

    Hyperphosphatemia has been shown to be involved not only in the onset and progression of secondary hyperparathyroidism but also in vascular calcification. In addition, it influences the clinical course of patients with chronic kidney disease. Phosphate (Pi) binder is required in the management of hyperparaphosphatemia, because dietary Pi restriction and Pi removal by hemodialysis alone are insufficient. Lanthanum carbonate, a powerful Pi binder, has a similar effect to aluminum hydroxide in reducing serum Pi levels. As it is excreted via the liver, lanthanum carbonate has an advantage in patients with renal failure. The effect of lanthanum carbonate on serum Pi levels is almost two times higher than that of calcium (Ca) carbonate, which is commonly used. Lanthanum carbonate and Ca carbonate have an additive effect. Worldwide, there is 6 years worth of clinical treatment data on lanthanum carbonate; however, we have 3 years of clinical use in Japanese patients with hyperphosphatemia. No serious side effects have been reported. However, the most important concern is bone toxicity, which has been observed with use of aluminum hydroxide. For this study, clinical research involved analysis of bone biopsies. Although osteomalacia is the most noticeable side effect, this was not observed. Both the high- and the low-turnover bone disease concentrated into a normal bone turnover state. However, as the authors have less than 10 years' clinical experience with lanthanum carbonate, patients should be monitored carefully. In addition, it is necessary to demonstrate whether potent treatment effects on hyperphosphatemia improve the long-term outcome.

  5. Studies on gel-grown pure and strontium-modified lanthanum tartrate crystals

    NASA Astrophysics Data System (ADS)

    Firdous, A.; Quasim, I.; Ahmad, M. M.; Kotru, P. N.

    2009-07-01

    Crystals of pure and strontium-modified lanthanum tartrate bearing composition (La) 1-x(Sr) xC 4H 4O 6· nH 2O (where x=0, 0.04, 0.10, 0.15; n=5,5,6,8) were obtained using gel method. The materials were studied using CH analysis, X-ray powder diffraction, FTIR, EDAX and thermoanalytical techniques. X-ray powder diffraction results analyzed by using suitable software suggest that while unmodified lanthanum tartrate has a monoclinic structure with the space group P 21, the entry of strontium into its lattice changes the system to orthorhombic with the space group P 2121. The unit cell volume is observed to decrease with increase in the concentration of strontium in lanthanum tartrate. Thermal analysis suggests that pure lanthanum tartrate starts decomposing at 41.31 °C whereas the strontium-modified lanthanum tartrate brings about better thermal stability which increases with an increase in strontium concentration. The percentage weight loss calculations from the thermogram supplemented by EDAX, CH analysis and FTIR spectroscopy suggest that both unmodified and strontium-modified lanthanum tartrate spherulitic crystals contain water of hydration; the amount of water of hydration being different for crystals with different content of strontium.

  6. Electronic states and spin-orbit splitting of lanthanum dimer

    NASA Astrophysics Data System (ADS)

    Liu, Yang; Wu, Lu; Zhang, Chang-Hua; Krasnokutski, Serge A.; Yang, Dong-Sheng

    2011-07-01

    Lanthanum dimer (La2) was studied by mass-analyzed threshold ionization (MATI) spectroscopy and a series of multi-configuration ab initio calculations. The MATI spectrum exhibits three band systems originating from ionization of the neutral ground electronic state, and each system shows vibrational frequencies of the neutral molecule and singly charged cation. The three ionization processes are La2+ (a2∑g+) ← La2 (X1∑g+), La2+ (b2Π3/2, u) ← La2 (X1∑g+), and La2+ (b2Π1/2, u) ← La2 (X1∑g+), with the ionization energies of 39 046, 40 314, and 40 864 cm-1, respectively. The vibrational frequency of the X1Σg+ state is 207 cm-1, and those of the a2Σg+, b2Π3/2, u and b2Π1/2, u are 235.7, 242.2, and 240 cm-1. While X1Σg+ is the ground state of the neutral molecule, a2Σg+ and b2Πu are calculated to be the excited states of the cation. The spin-orbit splitting in the b2Πu ion is 550 cm-1. An X4Σg- state of La2+ was predicted by theory, but not observed by the experiment. The determination of a singlet ground state of La2 shows that lanthanum behaves differently from scandium and yttrium.

  7. Selective surface reactions of single crystal metal carbides: alkene production from short chain alcohols on titanium carbide and vanadium carbide

    NASA Astrophysics Data System (ADS)

    Guenard, Rebecca L.; Fernández-Torres, Luis C.; Kim, Byung-Il; Perry, Scott S.; Frantz, Peter; Didziulis, Stephen V.

    2002-08-01

    The adsorption and reaction of ethanol and 2-propanol on the (1 0 0) surface of single crystal vanadium carbide (VC) and titanium carbide (TiC) have been studied using temperature programmed desorption (TPD) and high-resolution electron energy loss spectroscopy. A mixture of molecular and dissociative adsorption is observed at cryogenic temperatures on both of the carbide surfaces. Dissociative adsorption of the short chain alcohols leads to the formation of an alkoxy intermediate at 153 K on both VC(1 0 0) and TiC(1 0 0). With increasing temperature, the alkoxy intermediate selectively reacts with the carbide surfaces to produce an alkene. A comparison of TPD intensities indicates that dissociative adsorption occurs to a greater extent on TiC; however, the reaction yield for dehydration of the alkoxy surface species is ˜20% greater on VC(1 0 0) as compared to TiC(1 0 0). Specific isotopic labeling studies of the ethanol reaction identify γ-hydride elimination as a key step in alkene formation on VC(1 0 0). This pattern of reactivity on metal carbide surfaces significantly differs from the decomposition reactions, producing carbon monoxide and hydrogen, or the β-hydride elimination reactions, producing an aldehyde and hydrogen, that are observed on most transition metal surfaces.

  8. Photovoltaic Rudorffites: Lead-Free Silver Bismuth Halides Alternative to Hybrid Lead Halide Perovskites.

    PubMed

    Turkevych, Ivan; Kazaoui, Said; Ito, Eisuke; Urano, Toshiyuki; Yamada, Koji; Tomiyasu, Hiroshi; Yamagishi, Hideo; Kondo, Michio; Aramaki, Shinji

    2017-06-28

    Hybrid CPbX3 (C: Cs, CH3 NH3 ; X: Br, I) perovskites possess excellent photovoltaic properties but are highly toxic, which hinders their practical application. Unfortunately, all Pb-free alternatives based on Sn and Ge are extremely unstable. Although stable and non-toxic C2 ABX6 double perovskites based on alternating corner-shared AX6 and BX6 octahedra (A=Ag, Cu; B=Bi, Sb) are possible, they have indirect and wide band gaps of over 2 eV. However, is it necessary to keep the corner-shared perovskite structure to retain good photovoltaic properties? Here, we demonstrate another family of photovoltaic halides based on edge-shared AX6 and BX6 octahedra with the general formula Aa Bb Xx (x=a+3 b) such as Ag3 BiI6 , Ag2 BiI5 , AgBiI4 , AgBi2 I7 . As perovskites were named after their prototype oxide CaTiO3 discovered by Lev Perovski, we propose to name these new ABX halides as rudorffites after Walter Rüdorff, who discovered their prototype oxide NaVO2 . We studied structural and optoelectronic properties of several highly stable and promising Ag-Bi-I photovoltaic rudorffites that feature direct band gaps in the range of 1.79-1.83 eV and demonstrated a proof-of-concept FTO/c-m-TiO2 /Ag3 BiI6 /PTAA/Au (FTO: fluorine-doped tin oxide, PTAA: poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine], c: compact, m: mesoporous) solar cell with photoconversion efficiency of 4.3 %. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. The effects of halide anions on the dielectric response of potassium halide solutions in visible, UV and far UV region.

    PubMed

    Shagieva, F M; Boinovich, L B

    2013-06-07

    Based on the experimentally measured dispersion of refractive indices, we studied the effects of halide anions on the dielectric response of potassium halide solutions in the visible, UV and far UV regions. It was shown that a specific ion effect according to the Hofmeister series is clearly demonstrated for the visible range of spectra. For the near-, mid-, and far UV ranges of spectra, the specific ion effect essentially depends on solution concentration and temperature. The influence of ions on the behavior of dynamic dielectric permittivity of a solution is discussed on the basis of ion/water and ion/ion electrostatic and electrodynamic interactions and hydration shell structure.

  10. FTIR study of matrix-isolated halides of dysprosium and thulium and their gaseous heterocomplexes with alkali halides

    SciTech Connect

    Feltrin, A.; Cesaro, S.N.

    1996-06-01

    Vibrational spectra of dysprosium and thulium chlorides, bromides, and iodides isolated in argon have been studied for the first time. The appearance of a single band, even in heavy deposits, suggested a planar geometry for all the samples examined. The complexity of Dy and Tm chlorides spectra, partly because of isotopic patterns, required a reinvestigation of NdCl{sub 3} isolated in argon and have been explained by comparison. Vapors in equilibrium over heated equimolar mixtures of a number of Dy, Tm, and Nd halides with alkali halides trapped in argon have been also investigated. FTIR measurements gave experimental evidence for the formation of gaseous heterocomplexes whose geometry is discussed.

  11. Lanthanum carbonate possibly responsible for acute liver failure in a patient with Child–Pugh stage A liver cirrhosis

    PubMed Central

    De Leeuw, Kathleen; Woestenburg, Annemie; Verbeelen, Dierik

    2008-01-01

    The majority of patients with end-stage renal disease have hyperphosphataemia, which is associated with significant morbidity and mortality. Lanthanum carbonate has been introduced as a new treatment modality to lower serum phosphorus. But there has been ongoing concern about lanthanum accumulation in tissues, especially in liver. We describe the case of a woman with pre-existing liver disease, who presented with acute liver failure after introduction of lanthanum carbonate to her treatment. The condition was fully reversible after stopping lanthanum carbonate. PMID:28657006

  12. 64. INTERIOR VIEW OF THE CARBIDE COOLING SHED. VIEW IS ...

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

    64. INTERIOR VIEW OF THE CARBIDE COOLING SHED. VIEW IS SHOWING CALCIUM CARBIDE IN COOLING CARS ON THE FLOOR. DECEMBER 26, 1918. - United States Nitrate Plant No. 2, Reservation Road, Muscle Shoals, Muscle Shoals, Colbert County, AL

  13. As-cast carbides in high-speed steels

    NASA Astrophysics Data System (ADS)

    Ding, Peidao; Shi, Gongqi; Zhou, Shouze

    1993-06-01

    The spatial distribution and structure of as-cast carbides and the effects of W, Mo, and V content on the morphology and amount of as-cast carbides in high-speed steels were studied systematically. It was shown that increasing the Mo and decreasing the W content led to a decrease in the amount of total eutectic carbide and an increase in the MC and M2C carbides. The eutectic morphology changed from skeletal to platelike when the content of Mo increased. The presence of V favored not only the formation of MC carbide but also the formation of M2C carbide and reduced the formation of M2C carbide. Increasing V led to an increase in the size of the eutectic carbides.

  14. Method of fabricating porous silicon carbide (SiC)

    NASA Technical Reports Server (NTRS)

    Shor, Joseph S. (Inventor); Kurtz, Anthony D. (Inventor)

    1995-01-01

    Porous silicon carbide is fabricated according to techniques which result in a significant portion of nanocrystallites within the material in a sub 10 nanometer regime. There is described techniques for passivating porous silicon carbide which result in the fabrication of optoelectronic devices which exhibit brighter blue luminescence and exhibit improved qualities. Based on certain of the techniques described porous silicon carbide is used as a sacrificial layer for the patterning of silicon carbide. Porous silicon carbide is then removed from the bulk substrate by oxidation and other methods. The techniques described employ a two-step process which is used to pattern bulk silicon carbide where selected areas of the wafer are then made porous and then the porous layer is subsequently removed. The process to form porous silicon carbide exhibits dopant selectivity and a two-step etching procedure is implemented for silicon carbide multilayers.

  15. Students' Understanding of Alkyl Halide Reactions in Undergraduate Organic Chemistry

    ERIC Educational Resources Information Center

    Cruz-Ramirez de Arellano, Daniel

    2013-01-01

    Organic chemistry is an essential subject for many undergraduate students completing degrees in science, engineering, and pre-professional programs. However, students often struggle with the concepts and skills required to successfully solve organic chemistry exercises. Since alkyl halides are traditionally the first functional group that is…

  16. Formation of autocomplexes in halide melts of trivalent metals

    NASA Astrophysics Data System (ADS)

    Peshkina, K. G.; Tkachev, N. K.

    2014-09-01

    Chemical equilibrium with respect to the dissociation of charged autocomplexes (MX6)3- in ionic melts of the MX3 type is analyzed. The chemical equilibrium M3+ + 6X- = (MX6)3- in salt melts of trivalent metal halides shifts strongly toward dissociation, due to the electrostatic interactions between charged particles in the melts.

  17. Method for calcining nuclear waste solutions containing zirconium and halides

    DOEpatents

    Newby, Billie J.

    1979-01-01

    A reduction in the quantity of gelatinous solids which are formed in aqueous zirconium-fluoride nuclear reprocessing waste solutions by calcium nitrate added to suppress halide volatility during calcination of the solution while further suppressing chloride volatility is achieved by increasing the aluminum to fluoride mole ratio in the waste solution prior to adding the calcium nitrate.

  18. Semiempirical and DFT Investigations of the Dissociation of Alkyl Halides

    ERIC Educational Resources Information Center

    Waas, Jack R.

    2006-01-01

    Enthalpy changes corresponding to the gas phase heats of dissociation of 12 organic halides were calculated using two semiempirical methods, the Hartree-Fock method, and two DFT methods. These calculated values were compared to experimental values where possible. All five methods agreed generally with the expected empirically known trends in the…

  19. Miscellaneous Lasing Actions in Organo-Lead Halide Perovskite Films.

    PubMed

    Duan, Zonghui; Wang, Shuai; Yi, Ningbo; Gu, Zhiyuan; Gao, Yisheng; Song, Qinghai; Xiao, Shumin

    2017-06-21

    Lasing actions in organo-lead halide perovskite films have been heavily studied in the past few years. However, due to the disordered nature of synthesized perovskite films, the lasing actions are usually understood as random lasers that are formed by multiple scattering. Herein, we demonstrate the miscellaneous lasing actions in organo-lead halide perovskite films. In addition to the random lasers, we show that a single or a few perovskite microparticles can generate laser emissions with their internal resonances instead of multiple scattering among them. We experimentally observed and numerically confirmed whispering gallery (WG)-like microlasers in polygon shaped and other deformed microparticles. Meanwhile, owing to the nature of total internal reflection and the novel shape of the nanoparticle, the size of the perovskite WG laser can be significantly decreased to a few hundred nanometers. Thus, wavelength-scale lead halide perovskite lasers were realized for the first time. All of these laser behaviors are complementary to typical random lasers in perovskite film and will help the understanding of lasing actions in complex lead halide perovskite systems.

  20. Semiempirical and DFT Investigations of the Dissociation of Alkyl Halides

    ERIC Educational Resources Information Center

    Waas, Jack R.

    2006-01-01

    Enthalpy changes corresponding to the gas phase heats of dissociation of 12 organic halides were calculated using two semiempirical methods, the Hartree-Fock method, and two DFT methods. These calculated values were compared to experimental values where possible. All five methods agreed generally with the expected empirically known trends in the…

  1. International Symposium on Halide Glasses (2nd) (Extended Abstracts).

    DTIC Science & Technology

    1983-08-05

    Rennes, France The structural studies carried out so far upon heavy metal flouride glasses (Raman, I.R., NMR and X-ray diffraction) indicate that there...Poulain, U. Rennes, Rennes, France The glass forming ability of cadmium halides CdF 2 and CdCI2 has been demonstrated in flouride , chloride and mixed

  2. On the Boiling Points of the Alkyl Halides.

    ERIC Educational Resources Information Center

    Correia, John

    1988-01-01

    Discusses the variety of explanations in organic chemistry textbooks of a physical property of organic compounds. Focuses on those concepts explaining attractive forces between molecules. Concludes that induction interactions play a major role in alkyl halides and other polar organic molecules and should be given wider exposure in chemistry texts.…

  3. On the Boiling Points of the Alkyl Halides.

    ERIC Educational Resources Information Center

    Correia, John

    1988-01-01

    Discusses the variety of explanations in organic chemistry textbooks of a physical property of organic compounds. Focuses on those concepts explaining attractive forces between molecules. Concludes that induction interactions play a major role in alkyl halides and other polar organic molecules and should be given wider exposure in chemistry texts.…

  4. Students' Understanding of Alkyl Halide Reactions in Undergraduate Organic Chemistry

    ERIC Educational Resources Information Center

    Cruz-Ramirez de Arellano, Daniel

    2013-01-01

    Organic chemistry is an essential subject for many undergraduate students completing degrees in science, engineering, and pre-professional programs. However, students often struggle with the concepts and skills required to successfully solve organic chemistry exercises. Since alkyl halides are traditionally the first functional group that is…

  5. Kinetic Studies of the Solvolysis of Two Organic Halides

    ERIC Educational Resources Information Center

    Duncan, J. A.; Pasto, D. J.

    1975-01-01

    Describes an undergraduate organic chemistry laboratory experiment which utilizes the solvolysis of organic halides to demonstrate first and second order reaction kinetics. The experiment also investigates the effect of a change of solvent polarity on reaction rate, common-ion and noncommon-ion salt effects, and the activation parameters of a…

  6. Students' understanding of alkyl halide reactions in undergraduate organic chemistry

    NASA Astrophysics Data System (ADS)

    Cruz-Ramirez de Arellano, Daniel

    Organic chemistry is an essential subject for many undergraduate students completing degrees in science, engineering, and pre-professional programs. However, students often struggle with the concepts and skills required to successfully solve organic chemistry exercises. Since alkyl halides are traditionally the first functional group that is studied in undergraduate organic chemistry courses, establishing a robust understanding of the concepts and reactions related to them can be beneficial in assuring students' success in organic chemistry courses. Therefore, the purpose of this study was to elucidate and describe students' understanding of alkyl halide reactions in an undergraduate organic chemistry course. Participants were interviewed using a think-aloud protocol in which they were given a set of exercises dealing with reactions and mechanisms of alkyl halide molecules in order to shed light on the students' understanding of these reactions and elucidate any gaps in understanding and incorrect warrants that may be present. These interviews were transcribed and analyzed using qualitative inquiry approaches. In general, the findings from this study show that the students exhibited gaps in understanding and incorrect warrants dealing with: (1) classifying substances as bases and/or nucleophiles, (2) assessing the basic or nucleophilic strength of substances, (3) accurately describing the electron movement of the steps that take place during alkyl halide reaction mechanisms, and (4) assessing the viability of their proposed reactive intermediates and breakage of covalent bonds. In addition, implications for teaching and future research are proposed.

  7. The diffusion bonding of silicon carbide and boron carbide using refractory metals

    SciTech Connect

    Cockeram, B.V.

    1999-10-01

    Joining is an enabling technology for the application of structural ceramics at high temperatures. Metal foil diffusion bonding is a simple process for joining silicon carbide or boron carbide by solid-state, diffusive conversion of the metal foil into carbide and silicide compounds that produce bonding. Metal diffusion bonding trials were performed using thin foils (5 {micro}m to 100 {micro}m) of refractory metals (niobium, titanium, tungsten, and molybdenum) with plates of silicon carbide (both {alpha}-SiC and {beta}-SiC) or boron carbide that were lapped flat prior to bonding. The influence of bonding temperature, bonding pressure, and foil thickness on bond quality was determined from metallographic inspection of the bonds. The microstructure and phases in the joint region of the diffusion bonds were evaluated using SEM, microprobe, and AES analysis. The use of molybdenum foil appeared to result in the highest quality bond of the metal foils evaluated for the diffusion bonding of silicon carbide and boron carbide. Bonding pressure appeared to have little influence on bond quality. The use of a thinner metal foil improved the bond quality. The microstructure of the bond region produced with either the {alpha}-SiC and {beta}-SiC polytypes were similar.

  8. Deposition method for producing silicon carbide high-temperature semiconductors

    DOEpatents

    Hsu, George C.; Rohatgi, Naresh K.

    1987-01-01

    An improved deposition method for producing silicon carbide high-temperature semiconductor material comprising placing a semiconductor substrate composed of silicon carbide in a fluidized bed silicon carbide deposition reactor, fluidizing the bed particles by hydrogen gas in a mildly bubbling mode through a gas distributor and heating the substrate at temperatures around 1200.degree.-1500.degree. C. thereby depositing a layer of silicon carbide on the semiconductor substrate.

  9. Carrier lifetimes in silicon carbide

    NASA Astrophysics Data System (ADS)

    Nigam, Saurav

    Carrier lifetimes are one of the most crucial parameters that govern the performance of high voltage/high power devices. The lack of understanding of the factors that determine the carrier lifetimes in silicon carbide is currently a major impediment in the development of high voltage/high power technology based on this material. The objective of this dissertation was to identify and subsequently, characterize various recombination channels present in silicon carbide. Of special importance was identification of lifetime limiting defects in the high quality epitaxial layers grown by state-of-the-art chemical vapor deposition technique for high voltage application. The effect of growth conditions (C/Si ratio, growth temperature, seed polarity, epilayer thickness, and background doping) on the concentrations of various defects were investigated with the aim of manipulating carrier lifetimes by controlling different growth parameters. Based on the qualitative correlations between various point defects and carrier lifetimes in more than thirty epitaxial layers, three defects (Z-defect, EH6/7 center, and P1 center) were identified as potential lifetime limiting defects. The P1 center was shown to act as efficient recombination channel whenever present in concentrations greater than 1013 cm-3. Such concentrations were observed in layers grown on the C-face and at low C/Si ratio (less than 1.5). The measurement of recombination rates of electrons and holes via the Z-defect and the EH6/7 center (as a function of temperature) were performed by analyzing the carrier dynamics in specially designed p-n diodes. At 300 K, the capture cross section of the two states of the Z-defect were sigman1˜6x10-15 cm2 (electron capture at the donor state), sigmap1˜2x1014 cm2 (hole capture at the donor state), sigman2˜1x10 16 cm2 (electron capture at the acceptor state), and sigma p2˜1e-13 cm2 (hole capture at the acceptor state). The electron capture cross section for the EH6/7 centers was

  10. Silicon Carbide Solar Cells Investigated

    NASA Technical Reports Server (NTRS)

    Bailey, Sheila G.; Raffaelle, Ryne P.

    2001-01-01

    The semiconductor silicon carbide (SiC) has long been known for its outstanding resistance to harsh environments (e.g., thermal stability, radiation resistance, and dielectric strength). However, the ability to produce device-quality material is severely limited by the inherent crystalline defects associated with this material and their associated electronic effects. Much progress has been made recently in the understanding and control of these defects and in the improved processing of this material. Because of this work, it may be possible to produce SiC-based solar cells for environments with high temperatures, light intensities, and radiation, such as those experienced by solar probes. Electronics and sensors based on SiC can operate in hostile environments where conventional silicon-based electronics (limited to 350 C) cannot function. Development of this material will enable large performance enhancements and size reductions for a wide variety of systems--such as high-frequency devices, high-power devices, microwave switching devices, and high-temperature electronics. These applications would supply more energy-efficient public electric power distribution and electric vehicles, more powerful microwave electronics for radar and communications, and better sensors and controls for cleaner-burning, more fuel-efficient jet aircraft and automobile engines. The 6H-SiC polytype is a promising wide-bandgap (Eg = 3.0 eV) semiconductor for photovoltaic applications in harsh solar environments that involve high-temperature and high-radiation conditions. The advantages of this material for this application lie in its extremely large breakdown field strength, high thermal conductivity, good electron saturation drift velocity, and stable electrical performance at temperatures as high as 600 C. This behavior makes it an attractive photovoltaic solar cell material for devices that can operate within three solar radii of the Sun.

  11. Titanium carbide nanocrystals in circumstellar environments.

    PubMed

    von Helden, G; Tielens, A G; van Heijnsbergen, D; Duncan, M A; Hony, S; Waters, L B; Meijer, G

    2000-04-14

    Meteorites contain micrometer-sized graphite grains with embedded titanium carbide grains. Although isotopic analysis identifies asymptotic giant branch stars as the birth sites of these grains, there is no direct observational identification of these grains in astronomical sources. We report that infrared wavelength spectra of gas-phase titanium carbide nanocrystals derived in the laboratory show a prominent feature at a wavelength of 20.1 micrometers, which compares well to a similar feature in observed spectra of postasymptotic giant branch stars. It is concluded that titanium carbide forms during a short (approximately 100 years) phase of catastrophic mass loss (>0.001 solar masses per year) in dying, low-mass stars.

  12. Varying potential silicon carbide gas sensor

    NASA Technical Reports Server (NTRS)

    Shields, Virgil B. (Inventor); Ryan, Margaret A. (Inventor); Williams, Roger M. (Inventor)

    1997-01-01

    A hydrocarbon gas detection device operates by dissociating or electro-chemically oxidizing hydrocarbons adsorbed to a silicon carbide detection layer. Dissociation or oxidation are driven by a varying potential applied to the detection layer. Different hydrocarbon species undergo reaction at different applied potentials so that the device is able to discriminate among various hydrocarbon species. The device can operate at temperatures between 100.degree. C. and at least 650.degree. C., allowing hydrocarbon detection in hot exhaust gases. The dissociation reaction is detected either as a change in a capacitor or, preferably, as a change of current flow through an FET which incorporates the silicon carbide detection layers. The silicon carbide detection layer can be augmented with a pad of catalytic material which provides a signal without an applied potential. Comparisons between the catalytically produced signal and the varying potential produced signal may further help identify the hydrocarbon present.

  13. Joining of porous silicon carbide bodies

    DOEpatents

    Bates, Carl H.; Couhig, John T.; Pelletier, Paul J.

    1990-05-01

    A method of joining two porous bodies of silicon carbide is disclosed. It entails utilizing an aqueous slip of a similar silicon carbide as was used to form the porous bodies, including the sintering aids, and a binder to initially join the porous bodies together. Then the composite structure is subjected to cold isostatic pressing to form a joint having good handling strength. Then the composite structure is subjected to pressureless sintering to form the final strong bond. Optionally, after the sintering the structure is subjected to hot isostatic pressing to further improve the joint and densify the structure. The result is a composite structure in which the joint is almost indistinguishable from the silicon carbide pieces which it joins.

  14. METHOD FOR COATING GRAPHITE WITH METALLIC CARBIDES

    DOEpatents

    Steinberg, M.A.

    1960-03-22

    A method for producing refractory coatings of metallic carbides on graphite was developed. In particular, the graphite piece to be coated is immersed in a molten solution of 4 to 5% by weight of zirconium, titanium, or niobium dissolved in tin. The solution is heated in an argon atmosphere to above 1400 deg C, whereby the refractory metal reacts with the surface of the graphite to form a layer of metalic carbide. The molten solution is cooled to 300 to 400 deg C, and the graphite piece is removed. Excess tin is wiped from the graphite, which is then heated in vacuum to above 2300 deg C. The tin vaporizes from the graphite surface, leaving the surface coated with a tenacious layer of refractory metallic carbide.

  15. Metallicity of boron carbides at high pressure

    NASA Astrophysics Data System (ADS)

    Dekura, Haruhiko; Shirai, Koun; Yanase, Akira

    2010-03-01

    Electronic structure of semiconducting boron carbide at high pressure has been theoretically investigated, because of interests in the positive pressure dependence of resistivity, in the gap closure, and in the phase transition. The most simplest form B12(CCC) is assumed. Under assumptions of hydrostatic pressure and neglecting finite-temperature effects, boron carbide is quite stable at high pressure. The crystal of boron carbide is stable at least until a pressure higher than previous experiments showed. The gap closure occurs only after p=600 GPa on the assumption of the original crystal symmetry. In the low pressure regime, the pressure dependence of the energy gap almost diminishes, which is an exceptional case for semiconductors, which could be one of reasons for the positive pressure dependence of resistivity. A monotonous increase in the apex angle of rhombohedron suggests that the covalent bond continues to increase. The C chain inserted in the main diagonal of rhombohedral structure is the chief reason of this stability.

  16. Mechanical Properties of Crystalline Silicon Carbide Nanowires.

    PubMed

    Zhang, Huan; Ding, Weiqiang; Aidun, Daryush K

    2015-02-01

    In this paper, the mechanical properties of crystalline silicon carbide nanowires, synthesized with a catalyst-free chemical vapor deposition method, were characterized with nanoscale tensile testing and mechanical resonance testing methods inside a scanning electron microscope. Tensile testing of individual silicon carbide nanowire was performed to determine the tensile properties of the material including the tensile strength, failure strain and Young's modulus. The silicon carbide nanowires were also excited to mechanical resonance in the scanning electron microscope vacuum chamber using mechanical excitation and electrical excitation methods, and the corresponding resonance frequencies were used to determine the Young's modulus of the material according to the simple beam theory. The Young's modulus values from tensile tests were in good agreement with the ones obtained from the mechanical resonance tests.

  17. Silicon carbide, an emerging high temperature semiconductor

    NASA Technical Reports Server (NTRS)

    Matus, Lawrence G.; Powell, J. Anthony

    1991-01-01

    In recent years, the aerospace propulsion and space power communities have expressed a growing need for electronic devices that are capable of sustained high temperature operation. Applications for high temperature electronic devices include development instrumentation within engines, engine control, and condition monitoring systems, and power conditioning and control systems for space platforms and satellites. Other earth-based applications include deep-well drilling instrumentation, nuclear reactor instrumentation and control, and automotive sensors. To meet the needs of these applications, the High Temperature Electronics Program at the Lewis Research Center is developing silicon carbide (SiC) as a high temperature semiconductor material. Research is focussed on developing the crystal growth, characterization, and device fabrication technologies necessary to produce a family of silicon carbide electronic devices and integrated sensors. The progress made in developing silicon carbide is presented, and the challenges that lie ahead are discussed.

  18. Fabrication of thorium bearing carbide fuels

    DOEpatents

    Gutierrez, Rueben L.; Herbst, Richard J.; Johnson, Karl W. R.

    1981-01-01

    Thorium-uranium carbide and thorium-plutonium carbide fuel pellets have been fabricated by the carbothermic reduction process. Temperatures of 1750.degree. C. and 2000.degree. C. were used during the reduction cycle. Sintering temperatures of 1800.degree. C. and 2000.degree. C. were used to prepare fuel pellet densities of 87% and >94% of theoretical, respectively. The process allows the fabrication of kilogram quantities of fuel with good reproducibility of chemicals and phase composition. Methods employing liquid techniques that form carbide microspheres or alloying-techniques which form alloys of thorium-uranium or thorium-plutonium suffer from limitation on the quantities processed of because of criticality concerns and lack of precise control of process conditions, respectively.

  19. Carbides composite surface layers produced by (PTA)

    SciTech Connect

    Tajoure, Meloud; Tajouri, Ali E-mail: dr.mokhtarphd@yahoo.com; Abuzriba, Mokhtar E-mail: dr.mokhtarphd@yahoo.com; Akreem, Mosbah

    2013-12-16

    The plasma transferred arc technique was applied to deposit a composite layer of nickel base with tungsten carbide in powder form on to surface of low alloy steel 18G2A type according to polish standard. Results showed that, plasma transferred arc hard facing process was successfully conducted by using Deloro alloy 22 plus tungsten carbide powders. Maximum hardness of 1489 HV and minimum dilution of 8.4 % were achieved by using an arc current of 60 A. However, when the current was further increased to 120 A and the dilution increases with current increase while the hardness decreases. Microstructure of the nickel base deposit with tungsten carbide features uniform distribution of reinforcement particles with regular grain shape half - dissolved in the matrix.

  20. In vitro bioequivalence approach for a locally acting gastrointestinal drug: lanthanum carbonate.

    PubMed

    Yang, Yongsheng; Shah, Rakhi B; Yu, Lawrence X; Khan, Mansoor A

    2013-02-04

    A conventional human pharmacokinetic (PK) in vivo study is often considered as the "gold standard" to determine bioequivalence (BE) of drug products. However, this BE approach is not always applicable to the products not intended to be delivered into the systemic circulation. For locally acting gastrointestinal (GI) products, well designed in vitro approaches might be more practical in that they are able not only to qualitatively predict the presence of the active substance at the site of action but also to specifically assess the performance of the active substance. For example, lanthanum carbonate chewable tablet, a locally acting GI phosphate binder when orally administrated, can release free lanthanum ions in the acid environment of the upper GI tract. The lanthanum ions directly reach the site of action to bind with dietary phosphate released from food to form highly insoluble lanthanum-phosphate complexes. This prevents the absorption of phosphate consequently reducing the serum phosphate. Thus, using a conventional PK approach to demonstrate BE is meaningless since plasma levels are not relevant for local efficacy in the GI tract. Additionally the bioavailability of lanthanum carbonate is less than 0.002%, and therefore, the PK approach is not feasible. Therefore, an alternative assessment method is required. This paper presents an in vitro approach that can be used in lieu of PK or clinical studies to determine the BE of lanthanum carbonate chewable tablets. It is hoped that this information can be used to finalize an in vitro guidance for BE studies of lanthanum carbonate chewable tablets as well as to assist with "in vivo" biowaiver decision making. The scientific information might be useful to the pharmaceutical industry for the purpose of planning and designing future BE studies.

  1. Thermal conductivity behavior of boron carbides

    NASA Technical Reports Server (NTRS)

    Wood, C.; Zoltan, A.; Emin, D.; Gray, P. E.

    1983-01-01

    Knowledge of the thermal conductivity of boron carbides is necessary to evaluate its potential for high temperature thermoelectric energy conversion applications. The thermal diffusivity of hot pressed boron carbide B/sub 1-x/C/sub x/ samples as a function of composition, temperature and temperature cycling was measured. These data in concert with density and specific heat data yield the thermal conductivities of these materials. The results in terms of a structural model to explain the electrical transport data and novel mechanisms for thermal conduction are discussed.

  2. On the sintering of silicon carbide

    NASA Technical Reports Server (NTRS)

    Gugel, E.

    1986-01-01

    This document deals with the sintering of silicon carbide using pressureless sintering. This technique makes it possible to sinter a primarily covalent material to usable densities up to over 98% thD without having to use a high amount of sinter additives as is the case with other non-oxide ceramic materials. The process takes place rapidly, and it is also possible to produce relatively thick-walled structural parts without major problems. This sheds more light on the true characteristics of silicon carbide in one structural part, since there is no second or nearly no second phase. Heat pressing has improved stability.

  3. Carbide to close HDPE recycling plant

    SciTech Connect

    1996-07-24

    Union Carbide says it will close its high-density polyethylene (HDPE) recycling facility in Piscataway, New Jersey on October 1 because of unacceptable earnings potential. The plant closure--which will affect about 50 Carbide jobs--follows the announcement that another HDPE producer, Quantum Chemical, plans to bow out of recycling (CW, April 17, p.28). The sale of Quantum`s 32-million lbs/year HDPE recycling plant in Health, OH to 3DM fell through early this summer, and the facility has been put back on the market.

  4. Ablation of carbide materials with femtosecond pulses

    NASA Astrophysics Data System (ADS)

    Dumitru, Gabriel; Romano, Valerio; Weber, Heinz P.; Sentis, Marc; Marine, Wladimir

    2003-01-01

    The response of cemented tungsten carbide and of titanium carbonitride was investigated with respect to damage and ablation properties, under interaction with ultrashort laser pulses. These carbide materials present high microhardness and are of significant interest for tribological applications. The experiments were carried out in air with a commercial Ti:sapphire laser at energy densities on the target up to 6.5 J/cm 2. The irradiated target surfaces were analyzed with optical, SEM and AFM techniques and the damage and ablation threshold values were determined using the measured spot diameters and the calculated incident energy density distributions.

  5. Liquid phase sintering of silicon carbide

    DOEpatents

    Cutler, R.A.; Virkar, A.V.; Hurford, A.C.

    1989-05-09

    Liquid phase sintering is used to densify silicon carbide based ceramics using a compound comprising a rare earth oxide and aluminum oxide to form liquids at temperatures in excess of 1,600 C. The resulting sintered ceramic body has a density greater than 95% of its theoretical density and hardness in excess of 23 GPa. Boron and carbon are not needed to promote densification and silicon carbide powder with an average particle size of greater than one micron can be densified via the liquid phase process. The sintered ceramic bodies made by the present invention are fine grained and have secondary phases resulting from the liquid phase. 4 figs.

  6. Liquid phase sintering of silicon carbide

    DOEpatents

    Cutler, Raymond A.; Virkar, Anil V.; Hurford, Andrew C.

    1989-01-01

    Liquid phase sintering is used to densify silicon carbide based ceramics using a compound comprising a rare earth oxide and aluminum oxide to form liquids at temperatures in excess of 1600.degree. C. The resulting sintered ceramic body has a density greater than 95% of its theoretical density and hardness in excess of 23 GPa. Boron and carbon are not needed to promote densification and silicon carbide powder with an average particle size of greater than one micron can be densified via the liquid phase process. The sintered ceramic bodies made by the present invention are fine grained and have secondary phases resulting from the liquid phase.

  7. Silicon Carbide Thyristors for Power Applications

    DTIC Science & Technology

    1995-07-01

    Silicon carbide has the potential to make high-performance power devices. Its high thermal conductivity, wide bandgap, high breakdown field and high saturated electron drift velocity imply a clear superiority over Si and GaAs. This work reports the fabrication and testing of three-terminal 6H-SiC thyristors. The silicon carbide thyristors show higher current density and higher temperature operation than is possible with silicon devices. Switching measurements at room temperature and at elevated temperatures are reported. SiC thyristors have

  8. Conversion to lanthanum carbonate monotherapy effectively controls serum phosphorus with a reduced tablet burden: a multicenter open-label study

    PubMed Central

    2011-01-01

    Abstract Background Lanthanum carbonate (FOSRENOL®) is an effective, well-tolerated phosphate binder. The ability of lanthanum to reduce serum phosphorus levels to ≤5.5 mg/dL in patients with end-stage renal disease (ESRD) was assessed in a clinical practice setting. Methods A 16-week, phase IV study enrolled 2763 patients at 223 US sites to evaluate the efficacy of lanthanum carbonate in controlling serum phosphorus in patients with ESRD, and patient and physician satisfaction with, and preference for, lanthanum carbonate after conversion from other phosphate-binder medications. Patients received lanthanum carbonate prescriptions from physicians. These prescriptions were filled at local pharmacies rather than obtaining medication at the clinical trial site. Changes from serum phosphorus baseline values were analyzed using paired t tests. Patient and physician preferences for lanthanum carbonate versus previous medications were assessed using binomial proportion tests. Satisfaction was analyzed using the McNemar test. Daily dose, tablet burden, and laboratory values including albumin-adjusted serum calcium, calcium × phosphorus product, and parathyroid hormone levels were secondary endpoints. Results Serum phosphorus control (≤5.5 mg/dL) was effectively maintained in patients converting to lanthanum carbonate monotherapy; 41.6% of patients had controlled serum phosphate levels at 16 weeks. Patients and physicians expressed markedly higher satisfaction with lanthanum carbonate, and preferred lanthanum carbonate over previous medication. There were significant reductions in daily dose and daily tablet burden after conversion to lanthanum carbonate. Conclusions Serum phosphorus levels were effectively maintained in patients converted from other phosphate-binder medications to lanthanum carbonate, with increased satisfaction and reduced tablet burden. Trial Registration ClinicalTrials.gov: NCT0016012 PMID:21962172

  9. Potentiometric measurement of polymer-membrane electrodes based on lanthanum

    SciTech Connect

    Saefurohman, Asep Buchari, Noviandri, Indra; Syoni

    2014-03-24

    Quantitative analysis of rare earth elements which are considered as the standard method that has a high accuracy, and detection limits achieved by the order of ppm is inductively coupled plasma atomic emission spectroscopy (ICPAES). But these tools are expensive and valuable analysis of the high cost of implementation. In this study be made and characterized selective electrode for the determination of rare earth ions is potentiometric. Membrane manufacturing techniques studied is based on immersion (liquid impregnated membrane) in PTFE 0.5 pore size. As ionophores to be used tri butyl phosphate (TBP) and bis(2-etylhexyl) hydrogen phosphate. There is no report previously that TBP used as ionophore in polymeric membrane based lanthanum. Some parameters that affect the performance of membrane electrode such as membrane composition, membrane thickness, and types of membrane materials studied in this research. Manufacturing of Ion Selective Electrodes (ISE) Lanthanum (La) by means of impregnation La membrane in TBP in kerosene solution has been done and showed performance for ISE-La. FTIR spectrum results for PTFE 0.5 pore size which impregnated in TBP and PTFE blank showed difference of spectra in the top 1257 cm{sup −1}, 1031 cm{sup −1} and 794.7 cm{sup −1} for P=O stretching and stretching POC from group −OP =O. The result showed shift wave number for P =O stretching of the cluster (−OP=O) in PTFE-TBP mixture that is at the peak of 1230 cm{sup −1} indicated that no interaction bond between hydroxyl group of molecules with molecular clusters fosforil of TBP or R{sub 3}P = O. The membrane had stable responses in pH range between 1 and 9. Good responses were obtained using 10{sup −3} M La(III) internal solution, which produced relatively high potential. ISE-La showed relatively good performances. The electrode had a response time of 29±4.5 second and could be use for 50 days. The linear range was between 10{sup −5} and 10{sup −1} M.

  10. Titania-lanthanum phosphate photoactive and hydrophobic new generation catalyst

    SciTech Connect

    Jyothi, Chembolli K.; Jaimy, Kanakkanmavudi B.; Ghosh, Swapankumar; Sankar, Sasidharan; Smitha, V.S.; Warrier, K.G.K.

    2011-07-15

    Titania-lanthanum phosphate nanocomposites with multifunctional properties have been synthesized by aqueous sol-gel method. The precursor sols with varying TiO{sub 2}:LaPO{sub 4} ratios were applied as thin coating on glass substrates in order to be transparent, hydrophobic, photocatalytically active coatings. The phase compositions of the composite powders were identified by powder X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HR-TEM). The anatase phase of TiO{sub 2} in TiO{sub 2}-LaPO{sub 4} composite precursors was found to be stable even on annealing at 800 deg. C. The glass substrates, coated with TL1 (TiO{sub 2}-LaPO{sub 4} composition with 1 mol% LaPO{sub 4}) and TL50 (composite precursor containing TiO{sub 2} and LaPO{sub 4} with molar ratio 1:1) sols and annealed at 400 deg. C, produced contact angles of 74 deg. and 92 deg., respectively, though it is only 62 deg. for pure TiO{sub 2} coating. The glass substrates, coated with TL50 sol, produced surfaces with relatively high roughness and uneven morphology. The TL1 material, annealed at 800 deg. C, has shown the highest UV photoactivity with an apparent rate constant, k{sub app}=24x10{sup -3} min{sup -1}, which is over five times higher than that observed with standard Hombikat UV 100 (k{sub app}=4x10{sup -3} min{sup -1}). The photoactivity combined with a moderate contact angle (85.3 deg.) shows that this material has a promise as an efficient self-cleaning precursor. - Graphical abstract: Multifunctional TiO{sub 2}-LaPO{sub 4} composite stabilizes anatase phase with enhanced photocatalytic activity, and moderately higher hydrophobicity is a promising material for self-cleaning application. Highlights: > Titania-lanthanum phosphate nanocomposites were synthesized by aqueous sol-gel method. > Transparent, hydrophobic, photoactive coatings were developed on glass substrates. > The glass substrates, coated with TL1 annealed at 400 deg. C, produced a contact angle of 74 deg

  11. Potentiometric measurement of polymer-membrane electrodes based on lanthanum

    NASA Astrophysics Data System (ADS)

    Saefurohman, Asep; Buchari, Noviandri, Indra; Syoni

    2014-03-01

    Quantitative analysis of rare earth elements which are considered as the standard method that has a high accuracy, and detection limits achieved by the order of ppm is inductively coupled plasma atomic emission spectroscopy (ICPAES). But these tools are expensive and valuable analysis of the high cost of implementation. In this study be made and characterized selective electrode for the determination of rare earth ions is potentiometric. Membrane manufacturing techniques studied is based on immersion (liquid impregnated membrane) in PTFE 0.5 pore size. As ionophores to be used tri butyl phosphate (TBP) and bis(2-etylhexyl) hydrogen phosphate. There is no report previously that TBP used as ionophore in polymeric membrane based lanthanum. Some parameters that affect the performance of membrane electrode such as membrane composition, membrane thickness, and types of membrane materials studied in this research. Manufacturing of Ion Selective Electrodes (ISE) Lanthanum (La) by means of impregnation La membrane in TBP in kerosene solution has been done and showed performance for ISE-La. FTIR spectrum results for PTFE 0.5 pore size which impregnated in TBP and PTFE blank showed difference of spectra in the top 1257 cm-1, 1031 cm-1 and 794.7 cm-1 for P=O stretching and stretching POC from group -OP =O. The result showed shift wave number for P =O stretching of the cluster (-OP=O) in PTFE-TBP mixture that is at the peak of 1230 cm-1 indicated that no interaction bond between hydroxyl group of molecules with molecular clusters fosforil of TBP or R3P = O. The membrane had stable responses in pH range between 1 and 9. Good responses were obtained using 10-3 M La(III) internal solution, which produced relatively high potential. ISE-La showed relatively good performances. The electrode had a response time of 29±4.5 second and could be use for 50 days. The linear range was between 10-5 and 10-1 M.

  12. Reactive deposition of tungsten and titanium carbides by induction plasma

    NASA Astrophysics Data System (ADS)

    Jiang, X. L.; Gitzhofer, F.; Boulos, M. I.; Tiwari, R.

    1995-05-01

    A study is reported on the use of induction plasma technology for the preparation of dense free-standing deposits of tungsten carbide and titanium carbide from metallic powders and methane. Phase analysis by X-ray diffraction indicates that primary carburization of the particles takes place in-flight giving rise to the formation of W2C and TiC(1 - x). Secondary carburization occurs in the deposits resulting in the formation of tungsten and titanium carbides. Microstructures revealed by optical and scanning electron microscopy show uniform small grains of the carbides. The reactive plasma spray-formed tungsten carbide shows transgranular fracture, while pure tungsten deposits show intergranular fracture.

  13. Ordered mesoporous silica modified with lanthanum for ibuprofen loading and release behaviour.

    PubMed

    Goscianska, Joanna; Olejnik, Anna; Nowak, Izabela; Marciniak, Michal; Pietrzak, Robert

    2015-08-01

    The ordered mesoporous silicas SBA-15 and KIT-6, modified with lanthanum, have been for the first time applied in investigation of ibuprofen adsorption and release. The materials of hexagonal and regular structure were obtained by the hydrothermal method using a triblock copolymer Pluronic P123 as a template. The mesoporous silicas were impregnated with an aqueous solution of lanthanum(III) chloride in the amount necessary to obtain 1, 3 and 5wt.% La loading. The physicochemical properties of the modified silicas were characterised by X-ray diffraction, transmission electron microscopy, UV-Vis spectrophotometry and low-temperature nitrogen sorption. The results showed that lanthanum strongly determined structural as well as textural properties of the silicas. The samples of modified silica were checked for the ability to adsorb and release of ibuprofen. The storage capacity of the modified silicas obtained increased with increasing their average pore diameter and percentage content of lanthanum. The amount of ibuprofen adsorbed onto KIT-6 silica modified with La was higher than that adsorbed onto SBA-15 materials. The high coverage of lanthanum on the surface of KIT-6 and SBA-15 solids was found to increase the amount of ibuprofen and the rate of its release.

  14. Processing Techniques Developed to Fabricate Lanthanum Titanate Piezoceramic Material for High-Temperature Smart Structures

    NASA Technical Reports Server (NTRS)

    Goldsby, Jon C.; Farmer, Serene C.; Sayir, Ali

    2004-01-01

    Piezoelectric ceramic materials are potential candidates for use as actuators and sensors in intelligent gas turbine engines. For piezoceramics to be applied in gas turbine engines, they will have to be able to function in temperatures ranging from 1000 to 2500 F. However, the maximum use temperature for state-of-the-art piezoceramic materials is on the order of 300 to 400 F. Research activities have been initiated to develop high-temperature piezoceramic materials for gas turbine engine applications. Lanthanum titanate has been shown to have high-temperature piezoelectric properties with Curie temperatures of T(sub c) = 1500 C and use temperatures greater than 1000 C. However, the fabrication of lanthanum titanate poses serious challenges because of the very high sintering temperatures required for densification. Two different techniques have been developed at the NASA Glenn Research Center to fabricate dense lanthanum titanate piezoceramic material. In one approach, lower sintering temperatures were achieved by adding yttrium oxide to commercially available lanthanum titanate powder. Addition of only 0.1 mol% yttrium oxide lowered the sintering temperature by as much as 300 C, to just 1100 C, and dense lanthanum titanate was produced by pressure-assisted sintering. The second approach utilized the same commercially available powders but used an innovative sintering approach called differential sintering, which did not require any additive.

  15. Influence of lanthanum oxide as quality promoter on cathodes for MCFC

    NASA Astrophysics Data System (ADS)

    Escudero, M. J.; Nóvoa, X. R.; Rodrigo, T.; Daza, L.

    A novel material based on lithium nickel mixed oxides modified by lanthanum impregnation was investigated as an alternative cathode for molten carbonate fuel cells (MCFCs). The electrochemical behaviour of the new cathode material was evaluated in an eutectic mixture of lithium and potassium (Li:K, 62:38) at 650 °C by electrochemical impedance spectroscopy (EIS) as a function of lanthanum content, immersion time and gas composition. The impedance spectra inform on electrode structural changes during the first 100 h. The loss of lithium and the low dissolution of nickel and lanthanum are responsible of these changes. Later on, the structure reaches a stable state. The lanthanum-impregnated cathodes show higher catalytic activity for oxygen reduction and lower dissolution of nickel oxide than the lanthanum-free sample. The cathode material having 0.3 wt.% of La 2O 3 shows the best behaviour. The loss of lithium was confirmed by X-ray diffraction (XRD) and inductive coupled plasma-atomic emission spectroscopy (ICP-AES).

  16. Silica-lanthanum oxide: pioneer composite of rare-Earth metal oxide in selective phosphopeptides enrichment.

    PubMed

    Jabeen, Fahmida; Hussain, Dilshad; Fatima, Batool; Musharraf, S Ghulam; Huck, Christian W; Bonn, Gűnther K; Najam-ul-Haq, Muhammad

    2012-12-04

    Relying on the successful journey of metal oxides in phosphoproteomics, lanthanum oxide is employed for the engineering of an affinity material for phosphopeptide enrichment. The lanthanum oxide is chemically modified on the surface of silica and characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and Fourier transform infrared spectroscopy (FTIR). The obtained silica-lanthanum oxide composite is applied for the selective enrichment of phosphopeptides from tryptic digest of standard protein (α-casein, β-casein, and commercially available casein mixtures from bovine milk). The enriched entities are analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The mass spectroscopy (MS) results show that the silica-lanthanum oxide composite exhibits enhanced capability for phosphopeptide enrichment with sensitivity assessed to be 50 fmol. Sequence coverage of casein is interpreted showing successful recovery. As a real sample, a protein digest of nonfat milk is applied. Also, the ability of lanthanum in different formats is checked in the selective phosphopeptides enrichment. The composite holds promising future in economic ground as it also possesses the regenerative ability for repetitive use.

  17. Lanthanum carbonate stimulates bone formation in a rat model of renal insufficiency with low bone turnover.

    PubMed

    Fumoto, Toshio; Ito, Masako; Ikeda, Kyoji

    2014-09-01

    Control of phosphate is important in the management of chronic kidney disease with mineral and bone disorder (CKD-MBD), for which lanthanum carbonate, a non-calcium phosphate-binding agent, has recently been introduced; however, it remains to be determined whether it has any beneficial or deleterious effect on bone remodeling. In the present study, the effects of lanthanum carbonate were examined in an animal model that mimics low turnover bone disease in CKD, i.e., thyroparathyroidectomized (TPTX) and 5/6 nephrectomized (NX) rats undergoing a constant infusion of parathyroid hormone (PTH) and thyroxine injections (TPTX-PTH-5/6NX). Bone histomorphometry at the second lumbar vertebra and tibial metaphysis revealed that both bone formation and resorption were markedly suppressed in the TPTX-PTH-5/6NX model compared with the sham-operated control group, and treatment with lanthanum carbonate was associated with the stimulation of bone formation but not an acceleration of bone resorption. Lanthanum treatment caused a robust stimulation of bone formation with an activation of osteoblasts on the endosteal surface of femoral diaphysis, leading to an increase in cortical bone volume. Thus, lanthanum carbonate has the potential to stimulate bone formation in cases of CKD-MBD with suppressed bone turnover.

  18. Spectroscopic effects of disorder and vibrational localization in mixed-halide metal-halide chain solids

    SciTech Connect

    Love, S.P.; Scott, B.; Worl, L.A.; Huckett, S.C.; Saxena, A.; Huang, X.Z.; Bishop, A.R.; Swanson, B.I.

    1993-02-01

    Resonance Raman techniques, together with lattice-dynamics and Peierls-Hubbard modelling, are used to explore the electronic and vibrational dynamics of the quasi-one-dimensional metal-halogen chain solids [Pt(en){sub 2}][R(en){sub 2}X{sub 2}](ClO{sub 4}){sub 4}, (en = C{sub 2}H{sub 8}N{sub 2} and X=Cl, Br), abbreviated ``PLX.`` The mixed-halide materials PtCl{sub 1-x}Br{sub x} and PtCl{sub 1-x}I{sub x} consist of long mixed chains with heterojunctions between segments of the two constituent materials. Thus, in addition to providing mesoscale modulation of the chain electronic states, they serve as prototypes for elucidating the properties to be expected for macroscopic heterojunctions of these highly nonlinear materials. Once a detailed understanding of the various local vibrational modes occurring in these disordered solids is developed, the electronic structure of the chain segments and junctions can be probed by tuning the Raman excitation through their various electronic resonances.

  19. Matrix isolation infrared spectra of hydrogen halide and halogen complexes with nitrosyl halides

    NASA Technical Reports Server (NTRS)

    Allamandola, Louis J.; Lucas, Donald; Pimentel, George C.

    1982-01-01

    Matrix isolation infrared spectra of nitrosyl halide (XNO) complexes with HX and X2 (X = Cl, Br) are presented. The relative frequency shifts of the HX mode are modest (ClNO H-Cl, delta-nu/nu = -0.045; BrNO H-Br, delta-nu/nu = -0.026), indicating weak hydrogen bonds 1-3 kcal/mol. These shifts are accompanied by significant shifts to higher frequencies in the XN-O stretching mode (CIN-O HCl, delta-nu/nu = +0.016; BrN-O HBr, delta-nu/nu = +0.011). Similar shifts were observed for the XN-O X2 complexes (ClN-O Cl2, delta-nu/nu = +0.009; BrN-O-Br2, delta-nu/nu = +0.013). In all four complexes, the X-NO stretching mode relative shift is opposite in sign and about 1.6 times that of the NO stretching mode. These four complexes are considered to be similar in structure and charge distribution. The XN-O frequency shift suggests that complex formation is accompanied by charge withdrawal from the NO bond ranging from about .04 to .07 electron charges. The HX and X2 molecules act as electron acceptors, drawing electrons out of the antibonding orbital of NO and strengthening the XN-O bond. The implications of the pattern of vibrational shifts concerning the structure of the complexes are discussed.

  20. Matrix isolation infrared spectra of hydrogen halide and halogen complexes with nitrosyl halides

    NASA Technical Reports Server (NTRS)

    Allamandola, Louis J.; Lucas, Donald; Pimentel, George C.

    1982-01-01

    Matrix isolation infrared spectra of nitrosyl halide (XNO) complexes with HX and X2 (X = Cl, Br) are presented. The relative frequency shifts of the HX mode are modest (ClNO H-Cl, delta-nu/nu = -0.045; BrNO H-Br, delta-nu/nu = -0.026), indicating weak hydrogen bonds 1-3 kcal/mol. These shifts are accompanied by significant shifts to higher frequencies in the XN-O stretching mode (CIN-O HCl, delta-nu/nu = +0.016; BrN-O HBr, delta-nu/nu = +0.011). Similar shifts were observed for the XN-O X2 complexes (ClN-O Cl2, delta-nu/nu = +0.009; BrN-O-Br2, delta-nu/nu = +0.013). In all four complexes, the X-NO stretching mode relative shift is opposite in sign and about 1.6 times that of the NO stretching mode. These four complexes are considered to be similar in structure and charge distribution. The XN-O frequency shift suggests that complex formation is accompanied by charge withdrawal from the NO bond ranging from about .04 to .07 electron charges. The HX and X2 molecules act as electron acceptors, drawing electrons out of the antibonding orbital of NO and strengthening the XN-O bond. The implications of the pattern of vibrational shifts concerning the structure of the complexes are discussed.

  1. Microstructure Analysis of Tungsten Carbide Hardfacing on Carbon Steel Blade

    NASA Astrophysics Data System (ADS)

    Nagentrau, M.; Tobi, A. L. Mohd; Kamdi, Z.; Ismail, M. I.; Sambu, M.

    2017-05-01

    Tungsten carbide (WC) hardfacing coating is commonly used to enhance carbon steel blade performance which works in acidic and abrasive condition during production process. This paper deals with tungsten carbide (WC) hardfacing microstructure analysis on a carbon steel blade. Mixing of ilmenite ore with sulphuric acid is performed by the carbon steel blade as part of a production process. Tungsten carbide hardfacing is deposited on the carbon steel blade to enhance its wear resistance. The carbide distribution along with elemental composition analysis of the hardfaced carbon steel blade specimens is examined using Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS) and X-Ray Diffraction (XRD) respectively. Microstructure analysis revealed that different sizes of carbides with non-uniform distribution are found around the coating region. The carbide region is contains high percentage of tungsten (W) meanwhile, non-carbide region rich in tungsten (W) and iron (Fe).

  2. PWR cores with silicon carbide cladding

    SciTech Connect

    Dobisesky, J. P.; Carpenter, D.; Pilat, E.; Kazimi, M. S.

    2012-07-01

    The feasibility of using silicon carbide rather than Zircaloy cladding, to reach higher power levels and higher discharge burnups in PWRs has been evaluated. A preliminary fuel design using fuel rods with the same dimensions as in the Westinghouse Robust Fuel Assembly but with fuel pellets having 10 vol% central void has been adopted to mitigate the higher fuel temperatures that occur due to the lower thermal conductivity of the silicon carbide and to the persistence of the open clad-pellet gap over most of the fuel life. With this modified fuel design, it is possible to achieve 18 month cycles that meet present-day operating constraints on peaking factor, boron concentration, reactivity coefficients and shutdown margin, while allowing batch average discharge burnups up to 80 MWD/kgU and peak rod burnups up to 100 MWD/kgU. Power uprates of 10% and possibly 20% also appear feasible. For non-uprated cores, the silicon carbide-clad fuel has a clear advantage that increases with increasing discharge burnup. Even for comparable discharge burnups, there is a savings in enriched uranium. Control rod configuration modifications may be required to meet the shutdown margin criterion for the 20% up-rate. Silicon carbide's ability to sustain higher burnups than Zircaloy also allows the design of a licensable two year cycle with only 96 fresh assemblies, avoiding the enriched uranium penalty incurred with use of larger batch sizes due to their excessive leakage. (authors)

  3. Power MOSFETs Formed In Silicon Carbide

    NASA Technical Reports Server (NTRS)

    Palmour, John W.

    1995-01-01

    High-performance power metal/oxide/semiconductor field-effect transistors (MOSFETs) fabricated in silicon carbide. Devices offer potential advantages over silicon-based MOSFETs, including lower "on" - state resistances at same rated voltages, ability to operate at higher temperatures, and higher thermal conductivity. Also more resistant to damage by ionizing radiation, an advantage for switching appications in nuclear facilities.

  4. Boron Carbides As Thermo-electric Materials

    NASA Technical Reports Server (NTRS)

    Wood, Charles

    1988-01-01

    Report reviews recent theoretical and experimental research on thermoelectric materials. Recent work with narrow-band semiconductors demonstrated possibility of relatively high thermoelectric energy-conversion efficiencies in materials withstanding high temperatures needed to attain such efficiencies. Among promising semiconductors are boron-rich borides, especially boron carbides.

  5. Ceramic Fabric Coated With Silicon Carbide

    NASA Technical Reports Server (NTRS)

    Riccitiello, S. R.; Smith, M.; Goldstein, H.; Zimmerman, N.

    1988-01-01

    Material used as high-temperature shell. Ceramic fabric coated with silicon carbide (SiC) serves as tough, heat-resistant covering for other refractory materials. Developed to protect reusable insulating tiles on advanced space transportation systems. New covering makes protective glaze unnecessary. Used on furnace bricks or on insulation for engines.

  6. Prealloyed catalyst for growing silicon carbide whiskers

    DOEpatents

    Shalek, Peter D.; Katz, Joel D.; Hurley, George F.

    1988-01-01

    A prealloyed metal catalyst is used to grow silicon carbide whiskers, especially in the .beta. form. Pretreating the metal particles to increase the weight percentages of carbon or silicon or both carbon and silicon allows whisker growth to begin immediately upon reaching growth temperature.

  7. High-temperature carbidization of carboniferous rocks

    NASA Astrophysics Data System (ADS)

    Goldin, B. A.; Grass, V. E.; Nadutkin, A. V.; Nazarova, L. Yu.

    2009-08-01

    Processes of thermal metamorphism of carboniferous rocks have been studied experimentally. The conditions of high-temperature interaction of shungite carbon with components of the contained rocks, leading to formation of carbide compounds, have been determined. The results of this investigation contribute to the works on searching for new raw material for prospective material production.

  8. Evidence of hydrogen embrittlement of tungsten carbide.

    PubMed

    Kennedy, G C

    1978-02-01

    Tungsten carbide vessels containing materials at high temperature and high pressure are used in many laboratories. We note that any oils at medium to high temperature which can break down and liberate hydrogen cause rapid failure of the pressure vessel, whereas perfluorated kerosenes used as lubricants inside a pressure vessel give sharply increased life of the vessel.

  9. Micromachining of Silicon Carbide using femtosecond lasers

    NASA Astrophysics Data System (ADS)

    Farsari, M.; Filippidis, G.; Zoppel, S.; Reider, G. A.; Fotakis, C.

    2007-04-01

    We have demonstrated micromachining of bulk 3C silicon carbide (3C- SiC) wafers by employing 1028nm wavelength femtosecond laser pulses of energy less than 10 nJ directly from a femtosecond laser oscillator, thus eliminating the need for an amplified system and increasing the micromachining speed by more than four orders of magnitude.

  10. High Q silicon carbide microdisk resonator

    SciTech Connect

    Lu, Xiyuan; Lee, Jonathan Y.; Feng, Philip X.-L.; Lin, Qiang

    2014-05-05

    We demonstrate a silicon carbide (SiC) microdisk resonator with optical Q up to 5.12 × 10{sup 4}. The high optical quality, together with the diversity of whispering-gallery modes and the tunability of external coupling, renders SiC microdisk a promising platform for integrated quantum photonics applications.

  11. Bioactivation of biomorphous silicon carbide bone implants.

    PubMed

    Will, Julia; Hoppe, Alexander; Müller, Frank A; Raya, Carmen T; Fernández, Julián M; Greil, Peter

    2010-12-01

    Wood-derived silicon carbide (SiC) offers a specific biomorphous microstructure similar to the cellular pore microstructure of bone. Compared with bioactive ceramics such as calcium phosphate, however, silicon carbide is considered not to induce spontaneous interface bonding to living bone. Bioactivation by chemical treatment of biomorphous silicon carbide was investigated in order to accelerate osseointegration and improve bone bonding ability. Biomorphous SiC was processed from sipo (Entrandrophragma utile) wood by heating in an inert atmosphere and infiltrating the resulting carbon replica with liquid silicon melt at 1450°C. After removing excess silicon by leaching in HF/HNO₃ the biomorphous preform consisted of β-SiC with a small amount (approximately 6wt.%) of unreacted carbon. The preform was again leached in HCl/HNO₃ and finally exposed to CaCl₂ solution. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared analyses proved that oxidation of the residual carbon at the surface induced formation of carboxyl [COO⁻] groups, which triggered adsorption of Ca(2+), as confirmed by XPS and inductively coupled plasma optical emission spectroscopy measurements. A local increase in Ca(2+) concentration stimulated in vitro precipitation of Ca₅(PO₄)₃OH (HAP) on the silicon carbide preform surface during exposure to simulated body fluid, which indicates a significantly increased bone bonding activity compared with SiC. Copyright © 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  12. Silicon Carbide Power Devices and Integrated Circuits

    NASA Technical Reports Server (NTRS)

    Lauenstein, Jean-Marie; Casey, Megan; Samsel, Isaak; LaBel, Ken; Chen, Yuan; Ikpe, Stanley; Wilcox, Ted; Phan, Anthony; Kim, Hak; Topper, Alyson

    2017-01-01

    An overview of the NASA NEPP Program Silicon Carbide Power Device subtask is given, including the current task roadmap, partnerships, and future plans. Included are the Agency-wide efforts to promote development of single-event effect hardened SiC power devices for space applications.

  13. Silicon carbide diode for increased light output

    NASA Technical Reports Server (NTRS)

    Griffiths, L. B.; Mlavsky, A. I.

    1969-01-01

    Transition metals improve the overall light output and the output in particular regions of the electroluminescent of a silicon carbide semiconductor device. These metals /impurities/ introduce levels that can be pumped electrically and affect the efficiency of the recombination process involved in emission of radiation.

  14. Removing Phosphorus from Aqueous Solutions Using Lanthanum Modified Pine Needles.

    PubMed

    Wang, Xianze; Liu, Zhongmou; Liu, Jiancong; Huo, Mingxin; Huo, Hongliang; Yang, Wu

    2015-01-01

    The renewable pine needles was used as an adsorbent to remove phosphorus from aqueous solutions. Using batch experiments, pine needles pretreated with alkali-isopropanol (AI) failed to effectively remove phosphorus, while pine needles modified with lanthanum hydroxide (LH) showed relatively high removal efficiency. LH pine needles were effective at a wide pH ranges, with the highest removal efficiency reaching approximately 85% at a pH of 3. The removal efficiency was kept above 65% using 10 mg/L phosphorus solutions at desired pH values. There was no apparent significant competitive behavior between co-existing anions of sulfate, nitrate, and chloride (SO4(2-), NO3(-) and Cl(-)); however, CO3(2-) exhibited increased interfering behavior as concentrations increased. An intraparticle diffusion model showed that the adsorption process occurred in three phases, suggesting that a boundary layer adsorption phenomena slightly affected the adsorption process, and that intraparticle diffusion was dominant. The adsorption process was thermodynamically unfavorable and non-spontaneous; temperature increases improved phosphorus removal. Total organic carbon (TOC) assays indicated that chemical modification reduced the release of soluble organic compounds from 135.6 mg/L to 7.76 mg/L. This new information about adsorption performances provides valuable information, and can inform future technological applications designed to remove phosphorus from aqueous solutions.

  15. Amorphous lithium lanthanum titanate for solid-state microbatteries

    DOE PAGES

    Lee, Jungwoo Z.; Wang, Ziying; Xin, Huolin L.; ...

    2016-12-16

    Lithium lanthanum titanate (LLTO) is a promising solid state electrolyte for solid state batteries due to its demonstrated high bulk ionic conductivity. However, crystalline LLTO has a relatively low grain boundary conductivity, limiting the overall material conductivity. In this work, we investigate amorphous LLTO (a-LLTO) thin films grown by pulsed laser deposition (PLD). By controlling the background pressure and temperature we are able to optimize the ionic conductivity to 3 × 10–4 S/cm and electronic conductivity to 5 × 10–11 S/cm. XRD, TEM, and STEM/EELS analysis confirm that the films are amorphous and indicate that oxygen background gas is necessarymore » during the PLD process to decrease the oxygen vacancy concentration, decreasing the electrical conductivity. Amorphous LLTO is deposited onto high voltage LiNi0.5Mn1.5O4 (LNMO) spinel cathode thin films and cycled up to 4.8 V vs. Li showing excellent capacity retention. Finally, these results demonstrate that a-LLTO has the potential to be integrated into high voltage thin film batteries.« less

  16. Mechanical properties of thermoelectric lanthanum telluride from quantum mechanics

    NASA Astrophysics Data System (ADS)

    Li, Guodong; Aydemir, Umut; Wood, Max; Goddard, William A., III; Zhai, Pengcheng; Zhang, Qingjie; Snyder, G. Jeffrey

    2017-07-01

    Lanthanum telluride (La3Te4) is an n-type high-performance thermoelectric material in the high temperature range, but its mechanical properties remain unknown. Since we want robust mechanical properties for their integration into industrial applications, we report here quantum mechanics (QM) simulations to determine the ideal strength and deformation mechanisms of La3Te4 under pure shear deformations. Among all plausible shear deformation paths, we find that shearing along the (0 0 1)/< \\text{1} 0 0> slip system has the lowest ideal shear strength of 0.99 GPa, making it the most likely slip system to be activated under pressure. We find that the long range La-Te ionic interactions play the predominant role in resisting shear deformation. To enhance the mechanical strength, we suggest improving the long ionic La-Te bond stiffness to strengthen the ionic La-Te framework in La3Te4 by a defect-engineering strategy, such as partial substitution of La by Ce or Pr having isotypic crystal structures. This work provides the fundamental information to understand the intrinsic mechanics of La3Te4.

  17. The Bayo Canyon/radioactive lanthanum (RaLa) program

    SciTech Connect

    Dummer, J.E.; Taschner, J.C.; Courtright, C.C.

    1996-04-01

    LANL conducted 254 radioactive lanthanum (RaLa) implosion experiments Sept. 1944-March 1962, in order to test implosion designs for nuclear weapons. High explosives surrounding common metals (surrogates for Pu) and a radioactive source containing up to several thousand curies of La, were involved in each experiment. The resulting cloud was deposited as fallout, often to distances of several miles. This report was prepared to summarize existing records as an aid in evaluating the off-site impact, if any, of this 18-year program. The report provides a historical setting for the program, which was conducted in Technical Area 10, Bayo Canyon about 3 miles east of Los Alamos. A description of the site is followed by a discussion of collateral experiments conducted in 1950 by US Air Force for developing an airborne detector for tracking atmospheric nuclear weapons tests. All known off-site data from the RaLa program are tabulated and discussed. Besides the radiolanthanum, other potential trace radioactive material that may have been present in the fallout is discussed and amounts estimated. Off-site safety considerations are discussed; a preliminary off-site dose assessment is made. Bibliographical data on 33 persons important to the program are presented as footnotes.

  18. Removing Phosphorus from Aqueous Solutions Using Lanthanum Modified Pine Needles

    PubMed Central

    Wang, Xianze; Liu, Zhongmou; Liu, Jiancong; Huo, Mingxin; Huo, Hongliang; Yang, Wu

    2015-01-01

    The renewable pine needles was used as an adsorbent to remove phosphorus from aqueous solutions. Using batch experiments, pine needles pretreated with alkali-isopropanol (AI) failed to effectively remove phosphorus, while pine needles modified with lanthanum hydroxide (LH) showed relatively high removal efficiency. LH pine needles were effective at a wide pH ranges, with the highest removal efficiency reaching approximately 85% at a pH of 3. The removal efficiency was kept above 65% using 10 mg/L phosphorus solutions at desired pH values. There was no apparent significant competitive behavior between co-existing anions of sulfate, nitrate, and chloride (SO42-, NO3- and Cl-); however, CO32- exhibited increased interfering behavior as concentrations increased. An intraparticle diffusion model showed that the adsorption process occurred in three phases, suggesting that a boundary layer adsorption phenomena slightly affected the adsorption process, and that intraparticle diffusion was dominant. The adsorption process was thermodynamically unfavorable and non-spontaneous; temperature increases improved phosphorus removal. Total organic carbon (TOC) assays indicated that chemical modification reduced the release of soluble organic compounds from 135.6 mg/L to 7.76 mg/L. This new information about adsorption performances provides valuable information, and can inform future technological applications designed to remove phosphorus from aqueous solutions. PMID:26630014

  19. Chemical synthesis and supercapacitive properties of lanthanum telluride thin film.

    PubMed

    Patil, S J; Lokhande, A C; Lee, D-W; Kim, J H; Lokhande, C D

    2017-03-15

    Lanthanum telluride (La2Te3) thin films are synthesized via a successive ionic layer adsorption and reaction (SILAR) method. The crystal structure, surface morphology and surface wettability properties are investigated using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Field emission scanning electron microscopy (FE-SEM) and contact angle goniometer techniques, respectively. The La2Te3 material exhibits a specific surface area of 51m(2)g(-1) determined by Brunauer-Emmett-Teller (BET) method. La2Te3 thin film electrode has a hydrophilic surface which consists of interconnected pine leaf-like flaky arrays that affect the performance of the supercapacitor. The supercapacitive performance of La2Te3 film electrode is evaluated in 1M LiClO4/PC electrolyte using cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy techniques. La2Te3 film electrode exhibits a specific capacitance of 194Fg(-1) at a scan rate of 5mVs(-1) and stored energy density of 60Whkg(-1) with delivering power density of 7.22kWkg(-1). La2Te3 film electrode showed capacitive retention of 82% over 1000cycles at a scan rate of 100mVs(-1). Further, flexible La2Te3|LiClO4-PVA|La2Te3 supercapacitor cell is fabricated.

  20. Genetics of superionic conductivity in lithium lanthanum titanates.

    PubMed

    Jay, E E; Rushton, M J D; Chroneos, A; Grimes, R W; Kilner, J A

    2015-01-07

    The self-diffusion of ions is a fundamental mass transport process in solids and has a profound impact on the performance of electrochemical devices such as the solid oxide fuel cell, batteries and electrolysers. The perovskite system lithium lanthanum titanate, La2/3-xLi3xTiO3 (LLTO) has been the subject of much academic interest as it displays very high lattice conductivity for a solid state Li conductor; making it a material of great technological interest for deployment in safe durable mobile power applications. However, so far, a clear picture of the structural features that lead to efficient ion diffusion pathways in LLTO, has not been fully developed. In this work we show that a genetic algorithm in conjunction with molecular dynamics can be employed to elucidate diffusion mechanisms in systems such as LLTO. Based on our simulations we provide evidence that there is a three-dimensional percolated network of Li diffusion pathways. The present approach not only reproduces experimental ionic conductivity results but the method also promises straightforward investigation and optimisation of the properties relating to superionic conductivity in materials such as LLTO. Furthermore, this method could be used to provide insights into related materials with structural disorder.

  1. Ambi-site substitution of Mn in lanthanum germanate apatites

    SciTech Connect

    Kendrick, E.; Knight, K.S.; Slater, P.R.

    2009-08-05

    A neutron diffraction study at 4 K of the Mn doped lanthanum germanate apatite-type oxide ion conductor of nominal starting composition 'La{sub 9.5}Mn{sub 0.5}(GeO{sub 4}){sub 6}O{sub 2.75}' is reported. The structure was refined in space group P6{sub 3}/m, although high thermal displacement parameters were observed for the oxide ion sites (particularly O3, and O4). Reduced thermal displacement parameters were obtained by splitting the O3 site, and allowing the O4 oxygen to move off site, which may indicate local regions of lower symmetry within the structure. In addition, the data suggested ambi-site substitution of Mn, with it being present on both the Ge site and the La site. Assuming no change in La:Mn:Ge ratio, a composition of La{sub 9.18}Mn{sub 0.28}(GeO{sub 4}){sub 5.8}(MnO{sub 4}){sub 0.2}O{sub 2} was determined. As such there are nominally no interstitial oxide ions, but rather cation vacancies on the La site. Therefore, the high conductivity for this sample is most likely related to the introduction of Frenkel-type defects at higher temperature, as previously proposed for other apatite-type systems containing vacancies on the La site.

  2. Lanthanum Titanate Nanoparticles ER Fluids with High Performance

    NASA Astrophysics Data System (ADS)

    Wang, De; Shen, Rong; Wei, Shiqiang; Lu, Kunquan

    A new type of electrorheological (ER) fluid consisting of lanthanum titanate (LTO) nanoparticles is developed. The ER fluids were prepared by suspending LTO powder in silicone oil and the particles were fabricated by wet chemical method. This ER fluid shows excellent ER properties: The static yield stress reaches over 150 kPa under 5 kV/mm with linear dependence on the applied DC electric field, and the current density is below 10 μA/cm2. In order to investigate the affect factor on the ER behavior, the LTO powder were heated under different temperatures. The ER performances of two particles treated under different temperatures were compared and the composition changes for those particles were analyzed with TG-FTIR technique. It was found that the static yield stress of the suspensions fell from over 150 kPa to about 40 kPa and the current densities decreased prominently as the rise of the heating temperature. TG-FTIR analysis indicated that polar groups remained in the particles such as alkyl group, hydroxyl group and carbonyl group etc., contribute to the ER effect significantly. The experimental results are helpful to understand the mechanism of the high ER effect and to synthesize better ER materials.

  3. Structural phase transition in lanthanum monochalcogenides induced by hydrostatic pressure

    NASA Astrophysics Data System (ADS)

    Varshney, Dinesh; Kaurav, N.; Sharma, P.; Shah, S.; Singh, R. K.

    2004-11-01

    An effective interionic interaction potential (EIOP) is developed to investigate the pressure induced phase transitions from NaCl-type (B1) to CsCl-type (B2) structure in lanthanum monochalcogenides LaX [X = S, Se, Te] compounds. The long range Coulomb, van der Waals (vdW) interaction and the short-range repulsive interaction up to second-neighbor ions within the Hafemeister and Flygare approach with modified ionic charge are properly incorporated in EIOP. The vdW coefficients are computed following the Slater-Kirkwood variational method, as both the ions are polarizable. The estimated value of the phase transition pressure (Pt) and the magnitude of the discontinuity in volume at the transition pressure are consistent with the reported data. A large volume discontinuity in the pressure-volume phase diagram identifies the structural phase transition from B1 to B2 structure. We also study the second order elastic constants for these La compounds. It appears that the vdW interaction is effective in determining the elastic and structural properties of these test compounds.

  4. Electronic Transitions and Spin-Orbit Splitting of Lanthanum Dimer

    NASA Astrophysics Data System (ADS)

    Liu, Yang; Wu, Lu; Zhang, Changhua; Yang, Dong-Sheng

    2011-06-01

    Lanthanum dimer (La_2) was studied by mass-analyzed threshold ionization (MATI) spectroscopy and a series of high-level multi-configuration ab initio calculations (CASSCF, CASPT2, and MRCI). The MATI spectrum exhibits three band systems originating at 39044, 40312, and 40862 Cm-1, respectively. Above the band origin, the first band system displays a vibrational progression of ˜232 Cm-1, and the other two show vibrational progression with the same interval of ˜240 Cm-1. Below the band origin, the three systems exhibit the same vibrational interval of ˜207 Cm-1. These band systems are assigned to three electronic transitions from the ground state of La_2 to the low-lying electronic states of La_2^+: ^2Σ^+_g ← ^1Σ^+_g, ^2Πu,1/2 ← ^1Σ^+_g, and ^2Πu,3/2 ← ^1Σ^+_g. The spin-orbit splitting in the ^2ΠU ion state is 550 Cm-1. In addition, the electronic states and bonding of La_2 will be compared with those of Sc_2 and Y_2.

  5. Amorphous lithium lanthanum titanate for solid-state microbatteries

    SciTech Connect

    Lee, Jungwoo Z.; Wang, Ziying; Xin, Huolin L.; Wynn, Thomas A.; Meng, Ying Shirley

    2016-12-16

    Lithium lanthanum titanate (LLTO) is a promising solid state electrolyte for solid state batteries due to its demonstrated high bulk ionic conductivity. However, crystalline LLTO has a relatively low grain boundary conductivity, limiting the overall material conductivity. In this work, we investigate amorphous LLTO (a-LLTO) thin films grown by pulsed laser deposition (PLD). By controlling the background pressure and temperature we are able to optimize the ionic conductivity to 3 × 10–4 S/cm and electronic conductivity to 5 × 10–11 S/cm. XRD, TEM, and STEM/EELS analysis confirm that the films are amorphous and indicate that oxygen background gas is necessary during the PLD process to decrease the oxygen vacancy concentration, decreasing the electrical conductivity. Amorphous LLTO is deposited onto high voltage LiNi0.5Mn1.5O4 (LNMO) spinel cathode thin films and cycled up to 4.8 V vs. Li showing excellent capacity retention. Finally, these results demonstrate that a-LLTO has the potential to be integrated into high voltage thin film batteries.

  6. Work function measurement of lanthanum-boron compounds

    NASA Technical Reports Server (NTRS)

    Jacobson, D. L.; Storms, E. K.

    1978-01-01

    The relationship between emission properties and sample composition is studied for lanthanum-boron compounds. Specifically, the La-B system is considered between 1400 and 2100 K and between LaB(4.24) and LaB(29.2) to determine the phase relationship, chemical activity of the compounds, vapor composition, and vaporization rate. The results indicate that: (1) a blue-colored phase near LaB(9) exists between a purple-colored LaB(6) and elemental boron, (2) vaporization is sufficiently more rapid than diffusion so that great compositional differences exist between the surface and the interior, (3) an activation energy lowers the boron vaporization rate from LaB(6), and (4) a steady-state surface composition between LaB(6.04) and LaB(6.07) exists for freely vaporizing materials as a function of interior composition, purity, and temperature. It is noted that the ultimate life of a thermionic diode is governed by electrode vaporization rate whereas efficiency is governed by the electrode work function.

  7. Methods and Mechanisms for Cross-Electrophile Coupling of Csp2 Halides with Alkyl Electrophiles

    PubMed Central

    2016-01-01

    Conspectus Cross-electrophile coupling, the cross-coupling of two different electrophiles, avoids the need for preformed carbon nucleophiles, but development of general methods has lagged behind cross-coupling and C–H functionalization. A central reason for this slow development is the challenge of selectively coupling two substrates that are alike in reactivity. This Account describes the discovery of generally cross-selective reactions of aryl halides and acyl halides with alkyl halides, the mechanistic studies that illuminated the underlying principles of these reactions, and the use of these fundamental principles in the rational design of new cross-electrophile coupling reactions. Although the coupling of two different electrophiles under reducing conditions often leads primarily to symmetric dimers, the subtle differences in reactivity of aryl halides and alkyl halides with nickel catalysts allowed for generally cross-selective coupling reactions. These conditions could also be extended to the coupling of acyl halides with alkyl halides. These reactions are exceptionally functional group tolerant and can be assembled on the benchtop. A combination of stoichiometric and catalytic studies on the mechanism of these reactions revealed an unusual radical-chain mechanism and suggests that selectivity arises from (1) the preference of nickel(0) for oxidative addition to aryl halides and acyl halides over alkyl halides and (2) the greater propensity of alkyl halides to form free radicals. Bipyridine-ligated arylnickel intermediates react with alkyl radicals to efficiently form, after reductive elimination, new C–C bonds. Finally, the resulting nickel(I) species is proposed to regenerate an alkyl radical to carry the chain. Examples of new reactions designed using these principles include carbonylative coupling of aryl halides with alkyl halides to form ketones, arylation of epoxides to form β-aryl alcohols, and coupling of benzyl sulfonate esters with aryl

  8. Boron carbide nanowires: Synthesis and characterization

    NASA Astrophysics Data System (ADS)

    Guan, Zhe

    Bulk boron carbide has been widely used in ballistic armored vest and the property characterization has been heavily focused on mechanical properties. Even though boron carbides have also been projected as a promising class of high temperature thermoelectric materials for energy harvesting, the research has been limited in this field. Since the thermal conductivity of bulk boron carbide is still relatively high, there is a great opportunity to take advantage of the nano effect to further reduce it for better thermoelectric performance. This dissertation work aims to explore whether improved thermoelectric performance can be found in boron carbide nanowires compared with their bulk counterparts. This dissertation work consists of four main parts. (1) Synthesis of boron carbide nanowires. Boron carbide nanowires were synthesized by co-pyrolysis of diborane and methane at low temperatures (with 879 °C as the lowest) in a home-built low pressure chemical vapor deposition (LPCVD) system. The CVD-based method is energy efficient and cost effective. The as-synthesized nanowires were characterized by electron microscopy extensively. The transmission electron microscopy (TEM) results show the nanowires are single crystalline with planar defects. Depending on the geometrical relationship between the preferred growth direction of the nanowire and the orientation of the defects, the as-synthesized nanowires could be further divided into two categories: transverse fault (TF) nanowires grow normal to the defect plane, while axial fault (AF) ones grow within the defect plane. (2) Understanding the growth mechanism of as-synthesized boron carbide nanowires. The growth mechanism can be generally considered as the famous vapor-liquid-solid (VLS) mechanism. TF and AF nanowires were found to be guided by Ni-B catalysts of two phases. A TF nanowire is lead by a hexagonal phase catalyst, which was proved to be in a liquid state during reaction. While an AF nanowires is catalyzed by a

  9. Nonstoichiometry and growth of some Fe carbides

    NASA Astrophysics Data System (ADS)

    Walker, D.; Dasgupta, R.; Li, J.; Buono, A.

    2013-09-01

    Iron carbides containing from 31 to 17 atomic % carbon, with cohenite XRD structure and optical properties, were grown in experiments in Fe-Ni-S-C, Fe-Ni-C, and in Fe-C at 1, 6, and 7 GPa. X-ray cell volumes increase with C content. Compositions listed above vary considerably outside the nominal (Fe,Ni)3C stoichiometry of cohenite/cementite. Cohenites coexisting with Fe-C liquid are carbon poor. The Eckstrom-Adcock carbide, nominally Fe7C3, was found to show compositions from 29 to 36 atomic % C at 7 GPa in Fe-C. Both these materials are better regarded as solutions than as stoichiometric compounds, and their properties such as volume have compositional dependencies, as do the iron oxides, sulfides, silicides, and hydrides. The fraction of C dissolved in cohenite-saturated alloy is found to become smaller between 1 and 7 GPa. If this trend continues at higher pressures, the deep mantle should be easier to saturate with carbide than the shallow mantle, whether or not carbide is metastable as at ambient pressure. At temperatures below the cohenite-graphite peritectic, cohenite may grow as a compositionally zoned layer between Fe and graphite. The Eckstrom-Adcock carbide joins the assemblage at 7 GPa. Phases appear between Fe and C in an order consistent with metasomatic interface growth between chemically incompatible feed stocks. Diffusion across the carbide layer is not the growth rate limiting step. Carbon transport along the grain boundaries of solid Fe source stock at 1 GPa, to form C-saturated Fe alloy, is observed to be orders of magnitude faster than the cohenite layer growth. Growth stagnates too rapidly to be consistent with diffusion control. Furthermore, lateral variations in carbide layer thickness, convoluted inert marker horizons, and variable compositional profiles within the layers suggest that there are local transport complexities not covered by one-dimensional diffusive metasomatic growth. In contrast to many transport phenomena which slow with

  10. Electrolytic systems and methods for making metal halides and refining metals

    SciTech Connect

    Holland, Justin M.; Cecala, David M.

    2015-05-26

    Disclosed are electrochemical cells and methods for producing a halide of a non-alkali metal and for electrorefining the halide. The systems typically involve an electrochemical cell having a cathode structure configured for dissolving a hydrogen halide that forms the halide into a molten salt of the halogen and an alkali metal. Typically a direct current voltage is applied across the cathode and an anode that is fabricated with the non-alkali metal such that the halide of the non-alkali metal is formed adjacent the anode. Electrorefining cells and methods involve applying a direct current voltage across the anode where the halide of the non-alkali metal is formed and the cathode where the non-alkali metal is electro-deposited. In a representative embodiment the halogen is chlorine, the alkali metal is lithium and the non-alkali metal is uranium.

  11. Structure and Phase Composition of Ni-Al-Cr Alloy Alloyed by Rhenium and Lanthanum

    NASA Astrophysics Data System (ADS)

    Nikonenko, E. L.; Popova, N. A.; Dement, T. V.; Koneva, N. A.

    2017-06-01

    The paper presents the transmission and the scanning electron microscope investigations of the phase composition and fine structure of Ni-Al-Cr-based alloy alloyed by rhenium and lanthanum. The alloy is prepared by the directional crystallization technique and then subjected to 1150°C annealing during 1 hour. It is shown that γ- and γ'-phases are major and have a face-centered cubic crystal system. Solid solutions of γ- and γ'-phase have a disordered and an ordered atom arrangement, respectively. The latter has L12 superstructure. It is found that rhenium and lanthanum alloying leads to the structural modification of γ'-phase quasi-cuboids. Not dissolving in major phases, rhenium and lanthanum are phase-formation elements and form σ-phase. The phase composition and morphology of these phases are studied and described.

  12. Eutrophication management in surface waters using lanthanum modified bentonite: A review.

    PubMed

    Copetti, Diego; Finsterle, Karin; Marziali, Laura; Stefani, Fabrizio; Tartari, Gianni; Douglas, Grant; Reitzel, Kasper; Spears, Bryan M; Winfield, Ian J; Crosa, Giuseppe; D'Haese, Patrick; Yasseri, Said; Lürling, Miquel

    2016-06-15

    This paper reviews the scientific knowledge on the use of a lanthanum modified bentonite (LMB) to manage eutrophication in surface water. The LMB has been applied in around 200 environments worldwide and it has undergone extensive testing at laboratory, mesocosm, and whole lake scales. The available data underline a high efficiency for phosphorus binding. This efficiency can be limited by the presence of humic substances and competing oxyanions. Lanthanum concentrations detected during a LMB application are generally below acute toxicological threshold of different organisms, except in low alkalinity waters. To date there are no indications for long-term negative effects on LMB treated ecosystems, but issues related to La accumulation, increase of suspended solids and drastic resources depletion still need to be explored, in particular for sediment dwelling organisms. Application of LMB in saline waters need a careful risk evaluation due to potential lanthanum release.

  13. Distribution of intravascularly injected lanthanum ions in ganglia of the autonomic nervous system of the rat.

    PubMed

    DePace, D M

    1984-12-01

    Intravascular injection of lanthanum revealed that tight junctions of capillaries in sympathetic ganglia are impermeable to small ions and thus behave like capillaries of the blood-brain barrier. The failure of lanthanum to accumulate in the extracellular space suggests that fenestrated capillaries are not as ion-permeable as use of horseradish peroxidase (HRP) by some authors has indicated. A possible toxic action associated with high concentrations of HRP may be responsible for the high permeability of this substance. Testing with lanthanum demonstrated that sympathetic ganglia possess anatomic features that provide a hematic barrier. The blood-ganglion barrier resembles, but has not yet been demonstrated to be as absolute as the blood-brain barrier.

  14. Nanocomposite Lanthanum Zirconate Thermal Barrier Coating Deposited by Suspension Plasma Spray Process

    NASA Astrophysics Data System (ADS)

    Wang, Chaohui; Wang, You; Wang, Liang; Hao, Guangzhao; Sun, Xiaoguang; Shan, Fan; Zou, Zhiwei

    2014-10-01

    This work seeks to develop an innovative nanocomposite thermal barrier coating (TBC) exhibiting low thermal conductivity and high durability compared with that of current TBCs. To achieve this objective, nanosized lanthanum zirconate particles were selected for the topcoat of the TBC system, and a new process—suspension plasma spray—was employed to produce desirable microstructural features: the nanocomposite lanthanum zirconate TBC contains ultrafine splats and high volume porosity, for lower thermal conductivity, and better durability. The parameters of plasma spray experiment included two main variables: (i) spray distance varying from 40 to 80 mm and (ii) the concentration of suspension 20, 25, and 30 wt.%, respectively. The microstructure of obtained coatings was characterized with scanning electron microscope and x-ray diffraction. The porosity of coatings is in the range of 6-10%, and the single phase in the as-sprayed coatings was pyrochlore lanthanum zirconate.

  15. Lanthanum nitrate genotoxicity evaluation: Ames test, mouse micronucleus assay, and chromosome aberration test.

    PubMed

    Yang, Hui; Zhang, Xiaopeng; Liu, Haibo; Cui, Wenming; Zhang, Qiannan; Li, Yongning; Yu, Zhou; Jia, Xudong

    2016-11-01

    The increasing use of rare-earth elements (REE) and their compounds has led to their accumulation in the environment and has raised concern about their safety. The toxic effects of REE such as lanthanum are largely unknown; genotoxicity studies have been limited and results are controversial. We evaluated the genotoxicity of lanthanum nitrate (La(NO3)3) in several in vitro and in vivo tests, including bacterial reverse mutation assay (Ames test), mouse bone marrow micronucleus assay, and chromosome aberration assay. La(NO3)3 was not mutagenic in the Ames test. La(NO3)3 did not increase the frequencies of bone marrow micronuclei or chromosome aberration in the mouse after repeated treatments at oral doses up to 735 (females) and 855mg/kg (males). The compound did not increase the frequency of chromosome aberrations in CHO cells in vitro. These results indicate that lanthanum is not a genotoxic hazard.

  16. Fabrication of Nanosized Lanthanum Zirconate Powder and Deposition of Thermal Barrier Coating by Plasma Spray Process

    NASA Astrophysics Data System (ADS)

    Mishra, S. K.; Jagdeesh, N.; Pathak, L. C.

    2016-07-01

    The present manuscript discusses our findings on fabrication of nanosized lanthanum zirconate powder for thermal barrier coating application and its coating by plasma spray on nickel-based superalloy substrate. Single-phase La2Zr2O7 coating of thickness of the order of 45 µm on the Ni-Cr-Al bond coat coated Ni-based superalloy substrate was deposited by plasma spray process. The layers at the interface did not show spallation and inter diffusion was very less. The microstructure, interface, porosity, and mechanical properties of different layers are investigated. The lanthanum zirconate hardness and modulus were 10.5 and 277 GPa, respectively. The load depth curve for lanthanum zirconate showed good elastic recovery around 74%.

  17. [Efficacy and safety of lanthanum carbonate in chronic kidney disease patients with hyperphosphataemia].

    PubMed

    Laville, Maurice

    2011-06-01

    Hyperphosphataemia is a frequent complication in patients with chronic kidney disease and is associated with increased cardiovascular morbidity. Lanthanum carbonate is a calcium-free phosphate binder indicated in patients with chronic kidney disease. Its digestive absorption is minimal (<0,002%). This minimal quantity is rapidly excreted by the hepatobiliary system, but there is an initial accumulation in liver and bone, which reaches a plateau within a few weeks. Long-term follow-up until six years did not show any bone or liver toxicity. Efficacy and safety of lanthanum carbonate have been assessed in randomized trials. The most common side effects reported were gastrointestinal and occurred with a similar incidence than with placebo and other phosphate binders. Hypercalcemia was less frequent than with calcium carbonate. This review highlights pharmacokinetic, pharmacodynamic and clinical (efficacy and safety) properties of lanthanum carbonate and discusses its place in the management of hyperphosphataemia in patients with chronic kidney disease.

  18. The role of chemical interactions between thorium, cerium, and lanthanum in lymphocyte toxicity.

    PubMed

    Oliveira, Monica S; Duarte, Isabelle M; Paiva, Amanda V; Yunes, Samira N; Almeida, Carlos E; Mattos, Rita C; Sarcinelli, Paula N

    2014-01-01

    Thorium, cerium, and lanthanum are metals present in several types of minerals, the most common of which is monazite. Cerium and lanthanum are elements in the lanthanides series. Thorium, an actinide metal, is a hazardous element due to its radioactive characteristics. There is a lack of information describing the possible chemical interactions among these elements and the effects they may have on humans. Toxicological analyses were performed using cell viability, cell death, and DNA damage assays. Chemical interactions were evaluated based on the Loewe additivity model. The results indicate that thorium and cerium individually have no toxic effects on lymphocytes. However, thorium associated with lanthanum increases the toxicity of this element, thereby reducing the viability of lymphocytes at low concentrations of metals in the mixture.

  19. Enhanced Born charge and proximity to ferroelectricity in thallium halides

    NASA Astrophysics Data System (ADS)

    Du, Mao-Hua; Singh, David J.

    2010-04-01

    Electronic-structure and lattice-dynamics calculations on thallium halides show that the Born effective charges in these compounds are more than twice larger than the nominal ionic charges. This is a result of cross-band-gap hybridization between Tlp and halogen- p states. The large Born charges cause giant splitting between longitudinal and transverse-optic phonon modes, bringing the lattice close to ferroelectric instability. Our calculations indeed show that cubic TlBr develops ferroelectric instabilities upon lattice expansion starting at 2%. It is remarkable that the apparently ionic thallium halides with a simple cubic CsCl structure and large differences in electronegativity between cations and anions can be very close to ferroelectricity. This can lead to effective screening of defects and impurities that would otherwise be strong carrier traps and may therefore contribute to the relatively good carrier transport properties in TlBr radiation detectors.

  20. Laser Direct Write Synthesis of Lead Halide Perovskites

    DOE PAGES

    Chou, Stanley S.; Swartzentruber, Brian S.; Janish, Matthew T.; ...

    2016-09-05

    Lead halide perovskites are increasingly considered for applications beyond photovoltaics, for example, light emission and detection, where an ability to pattern and prototype microscale geometries can facilitate the incorporation of this class of materials into devices. In this study, we demonstrate laser direct write of lead halide perovskites, a remarkably simple procedure that takes advantage of the inverse dependence between perovskite solubility and temperature by using a laser to induce localized heating of an absorbing substrate. We also demonstrate arbitrary pattern formation of crystalline CH3NH3PbBr3 on a range of substrates and fabricate and characterize a microscale photodetector using this approach.more » This direct write methodology provides a path forward for the prototyping and production of perovskite-based devices.« less

  1. Laser Direct Write Synthesis of Lead Halide Perovskites

    SciTech Connect

    Chou, Stanley S.; Swartzentruber, Brian S.; Janish, Matthew T.; Meyer, Kristin C.; Biedermann, Laura B.; Okur, Serdal; Burckel, D. Bruce; Carter, C. Barry; Kaehr, Bryan

    2016-09-05

    Lead halide perovskites are increasingly considered for applications beyond photovoltaics, for example, light emission and detection, where an ability to pattern and prototype microscale geometries can facilitate the incorporation of this class of materials into devices. In this study, we demonstrate laser direct write of lead halide perovskites, a remarkably simple procedure that takes advantage of the inverse dependence between perovskite solubility and temperature by using a laser to induce localized heating of an absorbing substrate. We also demonstrate arbitrary pattern formation of crystalline CH3NH3PbBr3 on a range of substrates and fabricate and characterize a microscale photodetector using this approach. This direct write methodology provides a path forward for the prototyping and production of perovskite-based devices.

  2. Alkali halide microstructured optical fiber for X-ray detection

    SciTech Connect

    DeHaven, S. L. E-mail: russel.a.wincheski@nasa.gov; Wincheski, R. A. E-mail: russel.a.wincheski@nasa.gov; Albin, S.

    2015-03-31

    Microstructured optical fibers containing alkali halide scintillation materials of CsI(Na), CsI(Tl), and NaI(Tl) are presented. The scintillation materials are grown inside the microstructured fibers using a modified Bridgman-Stockbarger technique. The x-ray photon counts of these fibers, with and without an aluminum film coating are compared to the output of a collimated CdTe solid state detector over an energy range from 10 to 40 keV. The photon count results show significant variations in the fiber output based on the materials. The alkali halide fiber output can exceed that of the CdTe detector, dependent upon photon counter efficiency and fiber configuration. The results and associated materials difference are discussed.

  3. Double Charged Surface Layers in Lead Halide Perovskite Crystals.

    PubMed

    Sarmah, Smritakshi P; Burlakov, Victor M; Yengel, Emre; Murali, Banavoth; Alarousu, Erkki; El-Zohry, Ahmed M; Yang, Chen; Alias, Mohd S; Zhumekenov, Ayan A; Saidaminov, Makhsud I; Cho, Namchul; Wehbe, Nimer; Mitra, Somak; Ajia, Idris; Dey, Sukumar; Mansour, Ahmed E; Abdelsamie, Maged; Amassian, Aram; Roqan, Iman S; Ooi, Boon S; Goriely, Alain; Bakr, Osman M; Mohammed, Omar F

    2017-03-08

    Understanding defect chemistry, particularly ion migration, and its significant effect on the surface's optical and electronic properties is one of the major challenges impeding the development of hybrid perovskite-based devices. Here, using both experimental and theoretical approaches, we demonstrated that the surface layers of the perovskite crystals may acquire a high concentration of positively charged vacancies with the complementary negatively charged halide ions pushed to the surface. This charge separation near the surface generates an electric field that can induce an increase of optical band gap in the surface layers relative to the bulk. We found that the charge separation, electric field, and the amplitude of shift in the bandgap strongly depend on the halides and organic moieties of perovskite crystals. Our findings reveal the peculiarity of surface effects that are currently limiting the applications of perovskite crystals and more importantly explain their origins, thus enabling viable surface passivation strategies to remediate them.

  4. Alkali Halide Microstructured Optical Fiber for X-Ray Detection

    NASA Technical Reports Server (NTRS)

    DeHaven, S. L.; Wincheski, R. A.; Albin, S.

    2014-01-01

    Microstructured optical fibers containing alkali halide scintillation materials of CsI(Na), CsI(Tl), and NaI(Tl) are presented. The scintillation materials are grown inside the microstructured fibers using a modified Bridgman-Stockbarger technique. The x-ray photon counts of these fibers, with and without an aluminum film coating are compared to the output of a collimated CdTe solid state detector over an energy range from 10 to 40 keV. The photon count results show significant variations in the fiber output based on the materials. The alkali halide fiber output can exceed that of the CdTe detector, dependent upon photon counter efficiency and fiber configuration. The results and associated materials difference are discussed.

  5. Laser Direct Write Synthesis of Lead Halide Perovskites.

    PubMed

    Chou, Stanley S; Swartzentruber, Brian S; Janish, Matthew T; Meyer, Kristin C; Biedermann, Laura B; Okur, Serdal; Burckel, D Bruce; Carter, C Barry; Kaehr, Bryan

    2016-10-06

    Lead halide perovskites are increasingly considered for applications beyond photovoltaics, for example, light emission and detection, where an ability to pattern and prototype microscale geometries can facilitate the incorporation of this class of materials into devices. Here we demonstrate laser direct write of lead halide perovskites, a remarkably simple procedure that takes advantage of the inverse dependence between perovskite solubility and temperature by using a laser to induce localized heating of an absorbing substrate. We demonstrate arbitrary pattern formation of crystalline CH3NH3PbBr3 on a range of substrates and fabricate and characterize a microscale photodetector using this approach. This direct write methodology provides a path forward for the prototyping and production of perovskite-based devices.

  6. Laser Direct Write Synthesis of Lead Halide Perovskites

    SciTech Connect

    Chou, Stanley S.; Swartzentruber, Brian S.; Janish, Matthew T.; Meyer, Kristin C.; Biedermann, Laura B.; Okur, Serdal; Burckel, D. Bruce; Carter, C. Barry; Kaehr, Bryan

    2016-09-05

    Lead halide perovskites are increasingly considered for applications beyond photovoltaics, for example, light emission and detection, where an ability to pattern and prototype microscale geometries can facilitate the incorporation of this class of materials into devices. In this study, we demonstrate laser direct write of lead halide perovskites, a remarkably simple procedure that takes advantage of the inverse dependence between perovskite solubility and temperature by using a laser to induce localized heating of an absorbing substrate. We also demonstrate arbitrary pattern formation of crystalline CH3NH3PbBr3 on a range of substrates and fabricate and characterize a microscale photodetector using this approach. This direct write methodology provides a path forward for the prototyping and production of perovskite-based devices.

  7. Solution-Phase Synthesis of Cesium Lead Halide Perovskite Nanowires.

    PubMed

    Zhang, Dandan; Eaton, Samuel W; Yu, Yi; Dou, Letian; Yang, Peidong

    2015-07-29

    Halide perovskites have attracted much attention over the past 5 years as a promising class of materials for optoelectronic applications. However, compared to hybrid organic-inorganic perovskites, the study of their pure inorganic counterparts, like cesium lead halides (CsPbX3), lags far behind. Here, a catalyst-free, solution-phase synthesis of CsPbX3 nanowires (NWs) is reported. These NWs are single-crystalline, with uniform growth direction, and crystallize in the orthorhombic phase. Both CsPbBr3 and CsPbI3 are photoluminescence active, with composition-dependent temperature and self-trapping behavior. These NWs with a well-defined morphology could serve as an ideal platform for the investigation of fundamental properties and the development of future applications in nanoscale optoelectronic devices based on all-inorganic perovskites.

  8. Gaseous NH3 Confers Porous Pt Nanodendrites Assisted by Halides

    PubMed Central

    Lu, Shuanglong; Eid, Kamel; Li, Weifeng; Cao, Xueqin; Pan, Yue; Guo, Jun; Wang, Liang; Wang, Hongjing; Gu, Hongwei

    2016-01-01

    Tailoring the morphology of Pt nanocrystals (NCs) is of great concern for their enhancement in catalytic activity and durability. In this article, a novel synthetic strategy is developed to selectively prepare porous dendritic Pt NCs with different structures for oxygen reduction reaction (ORR) assisted by NH3 gas and halides (F−, Cl−, Br−). The NH3 gas plays critical roles on tuning the morphology. Previously, H2 and CO gas are reported to assist the shape control of metallic nanocrystals. This is the first demonstration that NH3 gas assists the Pt anisotropic growth. The halides also play important role in the synthetic strategy to regulate the formation of Pt NCs. As-made porous dendritic Pt NCs, especially when NH4F is used as a regulating reagent, show superior catalytic activity for ORR compared with commercial Pt/C catalyst and other previously reported Pt-based NCs. PMID:27184228

  9. Chemical Reactivity Perspective into the Group 2B Metals Halides.

    PubMed

    Özen, Alimet Sema; Akdeniz, Zehra

    2016-06-30

    Chemical reactivity descriptors within the conceptual density functional theory can be used to understand the nature of the interactions between two monomers of the Group 2B metal halides. This information might be valuable in the development of adequate force law parameters for simulations in the liquid state. In this study, MX2 monomers and dimers, where M = Zn, Cd, Hg and X = F, Cl, Br, I, were investigated in terms of chemical reactivity descriptors. Relativistic effects were taken into account using the effective core potential (ECP) approach. Correlations were produced between global and local reactivity descriptors and dimerization energies. Results presented in this work represent the first systematic investigation of Group 2B metal halides in the literature from a combined point of view of both relativistic effects and chemical reactivity descriptors. Steric effects were found to be responsible for the deviation from the chemical reactivity principles. They were introduced into the chemical reactivity descriptors such as local softness.

  10. Solid-state 207Pb NMR studies of mixed lead halides, PbFX (X=Cl, Br, or I).

    PubMed

    Glatfelter, Alicia; Dybowski, Cecil; Kragten, David D; Bai, Shi; Perry, Dale L; Lockard, Jenny

    2007-04-01

    Solid-state 207Pb NMR studies have been conducted on mixed lead(II) halides of the type PbFX, where X=Cl, Br, or I. NMR data for the mixed halides are compared to the solid-state NMR data for the divalent, binary lead halides, PbX2 (X=F, Cl, Br, I). The NMR data are evaluated in the context of the structures of the compounds and the effects of the mixed halides on the electronic structure of the divalent lead. Data sets for the mixed halides are discussed and compared to those for the regular lead(II) halides.

  11. The influence of lake water alkalinity and humic substances on particle dispersion and lanthanum desorption from a lanthanum modified bentonite.

    PubMed

    Reitzel, Kasper; Balslev, Kristiane Astrid; Jensen, Henning S

    2017-08-23

    A 12 days laboratory study on potential desorption of Lanthanum (La) from a commercial La modified clay (Phoslock) was conducted using lake water from 17 Danish lakes with alkalinities between 0.02 and 3.7 meq L(-1) and varying concentrations of DOC and humic acids (HA's). A similar study was conducted in artificial lake water with alkalinities from 0 to 2.5 meq L(-1)in order to exclude interference from dissolved HA's. To test if La in solution (FLa) was associated with fine particles, the water samples were filtered sequentially through three filter sizes (1.2 μm, 0.45 μm and 0.2 μm), and finally, ultracentrifugation was used in an attempt to separate colloidal La from dissolved La. The study showed that higher FLa (up to 2.5 mg L(-1) or 14% of the total La in the Phoslock) concentrations were found in soft water lakes compared to hard water lakes, probably due to dispersion of the clay at low alkalinities. In addition, this study showed that HA's seem to increase the FLa concentrations in soft water lakes, most likely through complexation of La retained in the Phoslock matrix. In summary, we conclude that elevated La concentrations in lake water after a Phoslock treatment should only be expected in soft water lakes rich in DOC and HA's. Copyright © 2017 Elsevier Ltd. All rights reserved.

  12. Copper-catalyzed arylation of alkyl halides with arylaluminum reagents

    PubMed Central

    Shrestha, Bijay

    2015-01-01

    Summary We report a Cu-catalyzed coupling between triarylaluminum reagents and alkyl halides to form arylalkanes. The reaction proceeds in the presence of N,N,N’,N’-tetramethyl-o-phenylenediamine (NN-1) as a ligand in combination with CuI as a catalyst. This catalyst system enables the coupling of primary alkyl iodides and bromides with electron-neutral and electron-rich triarylaluminum reagents and affords the cross-coupled products in good to excellent yields. PMID:26734088

  13. Organolead Halide Perovskites for Low Operating Voltage Multilevel Resistive Switching.

    PubMed

    Choi, Jaeho; Park, Sunghak; Lee, Joohee; Hong, Kootak; Kim, Do-Hong; Moon, Cheon Woo; Park, Gyeong Do; Suh, Junmin; Hwang, Jinyeon; Kim, Soo Young; Jung, Hyun Suk; Park, Nam-Gyu; Han, Seungwu; Nam, Ki Tae; Jang, Ho Won

    2016-08-01

    Organolead halide perovskites are used for low-operating-voltage multilevel resistive switching. Ag/CH3 NH3 PbI3 /Pt cells exhibit electroforming-free resistive switching at an electric field of 3.25 × 10(3) V cm(-1) for four distinguishable ON-state resistance levels. The migration of iodine interstitials and vacancies with low activation energies is responsible for the low-electric-field resistive switching via filament formation and annihilation.

  14. Oxidative alkoxylation of phosphine in alcohol solutions of copper halides

    NASA Astrophysics Data System (ADS)

    Polimbetova, G. S.; Borangazieva, A. K.; Ibraimova, Zh. U.; Bugubaeva, G. O.; Keynbay, S.

    2016-08-01

    The phosphine oxidation reaction with oxygen in alcohol solutions of copper (I, II) halides is studied. Kinetic parameters, intermediates, and by-products are studied by means of NMR 31P-, IR-, UV-, and ESR- spectroscopy; and by magnetic susceptibility, redox potentiometry, gas chromatography, and elemental analysis. A reaction mechanism is proposed, and the optimum conditions are found for the reaction of oxidative alkoxylation phosphine.

  15. Organometal halide perovskites as useful materials in sensitized solar cells.

    PubMed

    Singh, Surya Prakash; Nagarjuna, P

    2014-04-14

    Organometal halide perovskites offer dual potential properties as a light harvester and at the same time as a hole conductor in inorganic-organic hybrid heterojunction solar cells. The sequential deposition route provides a power conversion efficiency of 15% under standard AM1.5G test conditions. In this perspective, we will briefly summarize the development of perovskite-sensitized solar cells from their first report up to the present.

  16. Electronic and structural properties of alkali-halide cluster anions

    NASA Astrophysics Data System (ADS)

    Fatemi, Fredrik Kurosh

    We have used photoelectron spectroscopy to study alkali- halide clusters containing excess electrons. These measurements addressed five major aspects of the electronic and structural properties of the clusters. The underlying motivations for studying these clusters are to understand the transition from atomic to bulk behavior as a function of particle size and to identify those properties which are unique to clusters. We have observed excited states in many of the single excess electron clusters, and tested simple theoretical models against our experimental results. The two excess electron systems also contain excited states. However, the absorption of a photon in these systems often leads to the desorption of a negatively charged alkali ion. The abundance of various isomers of the cesium-halide systems depends strongly on the temperature of the source in which they are created, while those of the potassium and sodium halides do not. We have proven that this behavior indicates that the clusters undergo rapid structural interconversions on a subnanosecond time scale. The properties of alkali-halide clusters usually depend only on the type of alkali in the cluster. To understand the effect of different alkali ions on the electronic and structural properties of the clusters, we have examined mixed clusters which contain more than one alkali species. There properties are influenced most by the larger cations in single excess electron systems, and by the smaller cations in multiple excess electron particles. Finally, our measurements have shown that some of the potassium-rich potassium-iodide cluster anions (KI)m K- n( m=2- 7,n=1- 4) appear to separate into a purely metallic component K-n supported by an ionic component (KI)m. This behavior is clear for m = 2, 3, 4, and 6. For m = 5 and 7, the ions comprising the cluster show a high degree of mixing.

  17. Fluxes of Methyl Halides in Subtropical Salt Marshes

    NASA Astrophysics Data System (ADS)

    Whelan, M. E.; Min, D.; Rhew, R. C.

    2008-12-01

    Atmospheric methyl halides have both natural and anthropogenic origins and play a role in stratospheric ozone depletion. Sources and sinks of methyl chloride and methyl bromide have been measured in a limited number of terrestrial biomes. In addition, the within-biome variability of fluxes is not well quantified, necessitating a wider spatial distribution of sampling sites from different climatic zones. Here we report measurements of methyl halide fluxes from subtropical barrier island salt marshes in Texas (27.8°N, 97.1°W) as a comparison to temperate salt marshes that have been previously studied. Between April 2006 and May 2008, static flux chamber experiments were performed at several salt marsh sites near Port Aransas, Texas. Of the 4 prevalent species of higher plants studied, Batis maritima showed the greatest production of methyl halides, similar to results from southern California. Fluxes from plots of B. maritima were then sampled over the course of a day to investigate how environmental factors affect the magnitude of fluxes. In the May 2008 outing, the highest reported net fluxes for methyl chloride (700μmol/m2d) and methyl bromide (40μmol/m2d) from any salt marsh was observed in association with this species. These high emission rates when compared to more temperate salt marshes may reflect the effect of a warmer climate on the metabolic activity of the plant. Methyl bromide and methyl chloride fluxes are well correlated, suggesting that the same mechanism controls them both. Fluxes normalized by biomass increased with time of day. There was also a weak correlation between net flux and solar insolation averaged over the previous hour and between net flux and internal chamber temperature. These results offer some insight into estimating the global contributions of salt marshes to the methyl halides budgets and provide an important counterpoint to studies from higher latitudes, which have significantly lower fluxes overall.

  18. Fundamentals of Digital Photography 1. Silver Halide Photography and Digital Photography

    NASA Astrophysics Data System (ADS)

    Toyoda, Kenji

    A major difference between silver halide photography and digital photography lies in the way of processing image data. Parallel processing of the whole image area can be accomplished in silver halide photography. However, image data must be processed serially in digital photography, and this serial processing of image data is called "scan". In silver halide photography, an almighty device "film" does everything from signal conversion, signal processing to signal storage. But separate devices take each role in digital photography.

  19. Iron-catalyzed homocoupling of aryl halides and derivatives in the presence of alkyllithiums.

    PubMed

    Toummini, Dounia; Ouazzani, Fouad; Taillefer, Marc

    2013-09-20

    Direct synthesis of biaryl derivatives from aryl halides takes place under very mild temperature conditions by using a ligand-free iron catalytic system. The procedure, which proceeds via an in situ quantitative aryl halide exchange with alkyllithiums, allows for excellent control of the reactivity and is in line with the sustainable development. The method is also applicable to styryl and benzyl halides and to phenylacetylene.

  20. Effects of halides on plasmid-mediated silver resistance in Escherichia coli.

    PubMed

    Gupta, A; Maynes, M; Silver, S

    1998-12-01

    Silver resistance of sensitive Escherichia coli J53 and resistance plasmid-containing J53(pMG101) was affected by halides in the growth medium. The effects of halides on Ag+ resistance were measured with AgNO3 and silver sulfadiazine, both on agar and in liquid. Low concentrations of chloride made the differences in MICs between sensitive and resistant strains larger. High concentrations of halides increased the sensitivities of both strains to Ag+.

  1. Effects of Halides on Plasmid-Mediated Silver Resistance in Escherichia coli

    PubMed Central

    Gupta, Amit; Maynes, Maria; Silver, Simon

    1998-01-01

    Silver resistance of sensitive Escherichia coli J53 and resistance plasmid-containing J53(pMG101) was affected by halides in the growth medium. The effects of halides on Ag+ resistance were measured with AgNO3 and silver sulfadiazine, both on agar and in liquid. Low concentrations of chloride made the differences in MICs between sensitive and resistant strains larger. High concentrations of halides increased the sensitivities of both strains to Ag+. PMID:9835606

  2. The effect of sevelamer carbonate and lanthanum carbonate on the pharmacokinetics of oral calcitriol

    PubMed Central

    Pierce, David; Hossack, Stuart; Poole, Lynne; Robinson, Antoine; Van Heusen, Heather; Martin, Patrick; Smyth, Michael

    2011-01-01

    Background. Lanthanum carbonate and sevelamer carbonate are non-calcium-based phosphate binders used to manage hyperphosphataemia in patients with chronic kidney disease (CKD). Patients with CKD may require intravenous or oral active vitamin D. We investigated the effects of lanthanum carbonate and sevelamer carbonate on the bioavailability of oral calcitriol. Methods. This was a three-period, crossover study in healthy volunteers. Forty-one individuals were randomized to one of six possible sequences, each consisting of three treatment periods separated by washouts. The treatments were calcitriol (1 μg at lunch), calcitriol with lanthanum carbonate (3000 mg/day) and calcitriol with sevelamer carbonate (7200 mg/day). Serum calcitriol levels were assessed at baseline and throughout the study. Results. Co-administration of lanthanum carbonate with calcitriol had no significant effect on area under the curve over 48 h (AUC0–48) for serum exogenous calcitriol [least-squares (LS) mean, calcitriol with lanthanum carbonate vs calcitriol alone: 429 pg h/mL vs 318 pg h/mL, respectively; P = 0.171]. Similarly, there was no significant effect on maximum concentration (Cmax). In contrast, co-administration with sevelamer was associated with a significant reduction in bioavailability parameters for calcitriol (calcitriol with sevelamer carbonate vs calcitriol alone, LS mean AUC0–48: 137 pg h/mL vs 318 pg h/mL, respectively; P = 0.024; LS mean Cmax: 40.1 pg/mL vs 49.7 pg/mL, respectively; P < 0.001). Conclusions. Sevelamer carbonate significantly reduces serum concentrations of exogenous calcitriol when administered concomitantly with oral calcitriol, whereas lanthanum carbonate has no significant effect. This should be considered when treating CKD patients who require phosphate binders and oral vitamin D. PMID:20921291

  3. Properties of volume reflection silver-halide gelatin holograms

    NASA Astrophysics Data System (ADS)

    Kosobokova, N. L.; Usanov, Yuri E.; Shevtsov, Michail K.

    1991-02-01

    Three schemes of realization of micro-cavity method of processing silver halide photomaterials for silver-halide gelatin holograms (SHG) generation are proposed. Factors affecting diffraction efficiency replay wavelength shift and selectivity are discussed. 2. EXPERIMENTAL RESULTS In the previous paper on this issue the principle of SHG hologram formation based on a difference of speed hardening of gelatin mass in a photolayer and in a thin cover of gelatin absorbed on silver or silver halide grains was formulated. The investigation of " swelling" factor for layers both containing and not containing solid grains verified the difference in the hardening degree of these layers and demonstrated a possibility of using this phenomenon for the generation of SHG holograms. As a result we proposed three methods of transforming the structure of distribution of solid particles of a layer into the structure of micro-cavity distribution. Processing procedures realizing the micro-cavity (MC) methods are presented in Fig. l. As seen in Fig. l the differentiating feature of each method is the type of grain in a layer during its hardening. In the course of realization of methods MC-l MC-2 and MC-3 a layer to be hardened contains metallic developed silver rehalogenated silver and silver resulting after reversal bleaching of developed silver respectively. The common feature of all methods is dehydration procedure which results in producing micro cavities in the places of removed silver or silver salt grains.

  4. Lasing in robust cesium lead halide perovskite nanowires.

    PubMed

    Eaton, Samuel W; Lai, Minliang; Gibson, Natalie A; Wong, Andrew B; Dou, Letian; Ma, Jie; Wang, Lin-Wang; Leone, Stephen R; Yang, Peidong

    2016-02-23

    The rapidly growing field of nanoscale lasers can be advanced through the discovery of new, tunable light sources. The emission wavelength tunability demonstrated in perovskite materials is an attractive property for nanoscale lasers. Whereas organic-inorganic lead halide perovskite materials are known for their instability, cesium lead halides offer a robust alternative without sacrificing emission tunability or ease of synthesis. Here, we report the low-temperature, solution-phase growth of cesium lead halide nanowires exhibiting low-threshold lasing and high stability. The as-grown nanowires are single crystalline with well-formed facets, and act as high-quality laser cavities. The nanowires display excellent stability while stored and handled under ambient conditions over the course of weeks. Upon optical excitation, Fabry-Pérot lasing occurs in CsPbBr3 nanowires with an onset of 5 μJ cm(-2) with the nanowire cavity displaying a maximum quality factor of 1,009 ± 5. Lasing under constant, pulsed excitation can be maintained for over 1 h, the equivalent of 10(9) excitation cycles, and lasing persists upon exposure to ambient atmosphere. Wavelength tunability in the green and blue regions of the spectrum in conjunction with excellent stability makes these nanowire lasers attractive for device fabrication.

  5. Lasing in robust cesium lead halide perovskite nanowires

    PubMed Central

    Eaton, Samuel W.; Lai, Minliang; Gibson, Natalie A.; Wong, Andrew B.; Dou, Letian; Ma, Jie; Wang, Lin-Wang; Leone, Stephen R.; Yang, Peidong

    2016-01-01

    The rapidly growing field of nanoscale lasers can be advanced through the discovery of new, tunable light sources. The emission wavelength tunability demonstrated in perovskite materials is an attractive property for nanoscale lasers. Whereas organic–inorganic lead halide perovskite materials are known for their instability, cesium lead halides offer a robust alternative without sacrificing emission tunability or ease of synthesis. Here, we report the low-temperature, solution-phase growth of cesium lead halide nanowires exhibiting low-threshold lasing and high stability. The as-grown nanowires are single crystalline with well-formed facets, and act as high-quality laser cavities. The nanowires display excellent stability while stored and handled under ambient conditions over the course of weeks. Upon optical excitation, Fabry–Pérot lasing occurs in CsPbBr3 nanowires with an onset of 5 μJ cm−2 with the nanowire cavity displaying a maximum quality factor of 1,009 ± 5. Lasing under constant, pulsed excitation can be maintained for over 1 h, the equivalent of 109 excitation cycles, and lasing persists upon exposure to ambient atmosphere. Wavelength tunability in the green and blue regions of the spectrum in conjunction with excellent stability makes these nanowire lasers attractive for device fabrication. PMID:26862172

  6. Fluorescent Properties of Manganese Halide Benzothiazole Inorganic-Organic Hybrids.

    PubMed

    Yu, Hui; Mei, YingXuan; Wei, ZhenHong; Mei, GuangQuan; Cai, Hu

    2016-11-01

    The reaction of manganese (II) halides MnX2 and benzothiazole (btz) in the concentrated acids HX (X = Cl, Br) at 80 °C resulted in the formation of two inorganic-organic hybrid complexes: [(btz)2(MnX4)]·2H2O (X = Cl, 1; X = Br, 2). Both compounds showed green luminescence and exhibited moderate quantum yields of 43.17 % for 1 and 26.18 % for 2, which were directly originated from the tetrahedral coordination of Mn(2+) ion. Two organic - inorganic hybrids [(btz)2(MnX4)]·2H2O based on MnCl2, benzothiazole and halide acids emitted green light with the moderate quantum efficiencies when excited by 365 nm light. Graphical abstract Two organic-inorganic hybrids [(btz)2(MnX4)]·2H2O based on MnCl2, benzothiazole and halide acids emitted green light with the moderate quantum efficiencies when excited by 365 nm light.

  7. Deciphering Halogen Competition in Organometallic Halide Perovskite Growth

    SciTech Connect

    Keum, Jong Kahk; Ovchinnikova, Olga S.; Chen, Shiyou; Du, Mao-Hua; Ivanov, Ilia N; Rouleau, Christopher; Geohegan, David B.; Xiao, Kai

    2016-03-01

    Organometallic halide perovskites (OHPs) hold great promise for next-generation, low-cost optoelectronic devices. During the chemical synthesis and crystallization of OHP thin films a major unresolved question is the competition between multiple halide species (e.g. I-, Cl-, Br-) in the formation of the mixed halide perovskite crystals. Whether Cl- ions are successfully incorporated into the perovskite crystal structure or alternatively, where they are located, is not yet fully understood. Here, in situ X-ray diffraction measurements of crystallization dynamics are combined with ex situ TOF-SIMS chemical analysis to reveal that Br- or Cl- ions can promote crystal growth, yet reactive I- ions prevent them from incorporating into the lattice of the final perovskite crystal structure. The Cl- ions are located in the grain boundaries of the perovskite films. These findings significantly advance our understanding of the role of halogens during synthesis of hybrid perovskites, and provide an insightful guidance to the engineering of high-quality perovskite films, essential for exploring superior-performance and cost-effective optoelectronic devices.

  8. Far Infrared Optical Spectroscopy of Alkali Halide-Polymer Composites

    NASA Astrophysics Data System (ADS)

    McWhirter, J. T.; Broderick, S. D.; Rodriguez, G. A.

    1998-03-01

    Composite samples of small (dimension < 10 =B5m) alkali halide crystallites in a polymer matrix (low density polyethylene and polytetrafluoroethylene) have been prepared. The far infrared optical spectra of these samples are presented, spanning a temperature range of 300 to <10 K, and a dominant absorption feature due to absorption by the transverse optic phonon of the alkali halide constituent is observed. An effective medium analysis of the samples, using the Maxwell-Garnett model, is shown to accurately reproduce the main absorption feature, but requires a shape factor for the inclusion geometry corresponding to flat, plate-like inclusions, and a plausible explanation for such a geometry is proposed. The temperature dependence of the frequency and linewidth of the absorption peak is presented. The temperature shift of the line-center-frequency is found to be adequately described by a quasiharmonic description of the transverse optic phonon energy shift of the alkali halide due to lattice thermal expansion, using published values for the mode Gruneisen parameter and the temperature dependence of the lattice thermal coefficient. In contrast, the linewidth (phonon lifetime) of the composite samples is roughly twice as large as that observed for thin film and bulk crystals, and has a much stronger temperature dependence as well.

  9. Deciphering Halogen Competition in Organometallic Halide Perovskite Growth

    DOE PAGES

    Keum, Jong Kahk; Ovchinnikova, Olga S.; Chen, Shiyou; ...

    2016-03-01

    Organometallic halide perovskites (OHPs) hold great promise for next-generation, low-cost optoelectronic devices. During the chemical synthesis and crystallization of OHP thin films a major unresolved question is the competition between multiple halide species (e.g. I-, Cl-, Br-) in the formation of the mixed halide perovskite crystals. Whether Cl- ions are successfully incorporated into the perovskite crystal structure or alternatively, where they are located, is not yet fully understood. Here, in situ X-ray diffraction measurements of crystallization dynamics are combined with ex situ TOF-SIMS chemical analysis to reveal that Br- or Cl- ions can promote crystal growth, yet reactive I- ionsmore » prevent them from incorporating into the lattice of the final perovskite crystal structure. The Cl- ions are located in the grain boundaries of the perovskite films. These findings significantly advance our understanding of the role of halogens during synthesis of hybrid perovskites, and provide an insightful guidance to the engineering of high-quality perovskite films, essential for exploring superior-performance and cost-effective optoelectronic devices.« less

  10. Lasing in robust cesium lead halide perovskite nanowires

    DOE PAGES

    Eaton, Samuel W.; Lai, Minliang; Gibson, Natalie A.; ...

    2016-02-09

    The rapidly growing field of nanoscale lasers can be advanced through the discovery of new, tunable light sources. The emission wavelength tunability demonstrated in perovskite materials is an attractive property for nanoscale lasers. Whereas organic-inorganic lead halide perovskite materials are known for their instability, cesium lead halides offer a robust alternative without sacrificing emission tunability or ease of synthesis. Here, we report the low-temperature, solution-phase growth of cesium lead halide nanowires exhibiting low-threshold lasing and high stability. The as-grown nanowires are single crystalline with well-formed facets, and act as high-quality laser cavities. The nanowires display excellent stability while stored andmore » handled under ambient conditions over the course of weeks. Upon optical excitation, Fabry-Pérot lasing occurs in CsPbBr3 nanowires with an onset of 5 μJ cm-2 with the nanowire cavity displaying a maximum quality factor of 1,009 ± 5. Lasing under constant, pulsed excitation can be maintained for over 1 h, the equivalent of 109 excitation cycles, and lasing persists upon exposure to ambient atmosphere. Wavelength tunability in the green and blue regions of the spectrum in conjunction with excellent stability makes these nanowire lasers attractive for device fabrication.« less

  11. Iodomethane-Mediated Organometal Halide Perovskite with Record Photoluminescence Lifetime.

    PubMed

    Xu, Weidong; McLeod, John A; Yang, Yingguo; Wang, Yimeng; Wu, Zhongwei; Bai, Sai; Yuan, Zhongcheng; Song, Tao; Wang, Yusheng; Si, Junjie; Wang, Rongbin; Gao, Xingyu; Zhang, Xinping; Liu, Lijia; Sun, Baoquan

    2016-09-07

    Organometallic lead halide perovskites are excellent light harvesters for high-efficiency photovoltaic devices. However, as the key component in these devices, a perovskite thin film with good morphology and minimal trap states is still difficult to obtain. Herein we show that by incorporating a low boiling point alkyl halide such as iodomethane (CH3I) into the precursor solution, a perovskite (CH3NH3PbI3-xClx) film with improved grain size and orientation can be easily achieved. More importantly, these films exhibit a significantly reduced amount of trap states. Record photoluminescence lifetimes of more than 4 μs are achieved; these lifetimes are significantly longer than that of pristine CH3NH3PbI3-xClx films. Planar heterojunction solar cells incorporating these CH3I-mediated perovskites have demonstrated a dramatically increased power conversion efficiency compared to the ones using pristine CH3NH3PbI3-xClx. Photoluminescence, transient absorption, and microwave detected photoconductivity measurements all provide consistent evidence that CH3I addition increases the number of excitons generated and their diffusion length, both of which assist efficient carrier transport in the photovoltaic device. The simple incorporation of alkyl halide to enhance perovskite surface passivation introduces an important direction for future progress on high efficiency perovskite optoelectronic devices.

  12. High-efficiency, low-temperature cesium diodes with lanthanum-hexaboride electrodes

    NASA Technical Reports Server (NTRS)

    Morris, J. F.

    1974-01-01

    Lanthanum hexaboride electrodes in 1700 K cesium diodes may triple power outputs compared with those demonstrated for nuclear thermionic space applications. Still greater relative gains seem possible for emitters below 1700 K. Further improvements in cesium diode performance should result from the lower collector temperatures allowed for earth and low power space duties. Decreased temperatures will lessen thermal transport losses that attend thermionic conversion mechanisms. Such advantages will add to those from collector Carnot and electrode effects. If plasma ignition difficulties impede diode temperature reductions, recycling small fractions of the output power could provide ionization. So high efficiency, low temperature cesium diodes with lanthanum hexaboride electrodes appear feasible.

  13. Synthesis and ion-exchange properties of lanthanum tungstate, a new inorganic ion exchanger

    SciTech Connect

    Husain, S.W.; Rasheedzad, S.; Manzoori, J.L.; Jabbari, Y.

    1982-01-01

    Amorphous samples of a new inorganic ion exchanger, lanthanum tungstate, have been prepared under varying conditions. The material prepared by mixing 0.05 M lanthanum nitrate and 0.05 M sodium tungstate in a ratio of 1:2 was studied in detail for its ion-exchange capacity, chemical stability, ir, thermogravimetry, and K/sub d/ values. Its columns have been used for the separation of C/sup 2 +/ from Pd/sup 2 +/, Mn/sup 2 +/, and Cu/sup 2 +/, and Ni/sup 2 +/ from Pd/sup 2 +/. 3 figures, 4 tables.

  14. Mechanism of the lanthanum bromide assisted electrochemical aldolization of. alpha. -bromo ketones

    SciTech Connect

    Fry, A.J.; Susla, M. )

    1989-04-26

    Linear sweep voltammetry, preparative electrolyses under a variety of experimental conditions, and trapping experiments have been used to explore the mechanism of the formation of the aldol 2-benzoyl-1-phenylpropanol by electrochemical reduction of {alpha}-bromopropiophenone in the presence of benzaldehyde and lanthanum bromide. The aldol condensation occurs by reaction of the free (lithio) enolate with a lanthanum bromide-benzaldehyde-tetrahydrofuran complex. Electrochemical reduction of the bromo ketone forms the Z enolate highly stereospecifically. The erythro aldol is formed stereoselectively initially, but the condensation is reversible, and the equilibrium mixture of aldols, containing mostly the threo isomer, is isolated from the electrolysis.

  15. Preparation of yttrium, lanthanum, cerium, and neodymium basic carbonate particles by homogeneous precipitation

    SciTech Connect

    Akinc, M.; Sordelet, D. )

    1987-07-01

    Uniform yttrium, lanthanum, cerium, and neodymium basic carbonate particles were prepared by homogeneous precipitation. Powders were characterized with respect to size, shape, crystal structure, and thermal decomposition behavior. Yttria precursor particles were spherical, monosized (0.4 {mu}m), and amorphous; whereas lanthana, neodymia, and ceria precursors were prismatic (ranging from 1 to 6 {mu}m in size) and crystalline. Crystal structure was found to be ancylite-type orthorhombic symmetry in all three cases. Upon heating in air, yttrium, lanthanum, and neodymium precursors underwent two-step decomposition to first form oxycarbonate and then oxide. Cerium hydroxycarbonate decomposed in a single step to form the oxide.

  16. Structural and Conductivity Studies on Lanthanum Doped LiNiPO4 Prepared by Polyol Method

    NASA Astrophysics Data System (ADS)

    Karthickprabhu, S.; Hirankumar, G.; Maheswaran, A.; Bella, R. S. Daries; Sanjeeviraja, C.

    2013-07-01

    Pure and Lanthanum doped LiNiPO4 (with different Molar concentrations) have been prepared by polyol method using 1,2 propanediol as a polyol medium. XRD analysis reveal that sample calcined at 650°C for 6 hrs shows good crystalline nature with orthorhombic structure and this result is consistent with TG/DTA result. It is found that the conductivity enhances upon doping of Lanthanum while backhoprate decreases compared with pure LiNiPO4. Dielectric studies have also been discussed.

  17. Systematic analysis of the unique band gap modulation of mixed halide perovskites.

    PubMed

    Kim, Jongseob; Lee, Sung-Hoon; Chung, Choong-Heui; Hong, Ki-Ha

    2016-02-14

    Solar cells based on organic-inorganic hybrid metal halide perovskites have been proven to be one of the most promising candidates for the next generation thin film photovoltaic cells. Mixing Br or Cl into I-based perovskites has been frequently tried to enhance the cell efficiency and stability. One of the advantages of mixed halides is the modulation of band gap by controlling the composition of the incorporated halides. However, the reported band gap transition behavior has not been resolved yet. Here a theoretical model is presented to understand the electronic structure variation of metal mixed-halide perovskites through hybrid density functional theory. Comparative calculations in this work suggest that the band gap correction including spin-orbit interaction is essential to describe the band gap changes of mixed halides. In our model, both the lattice variation and the orbital interactions between metal and halides play key roles to determine band gap changes and band alignments of mixed halides. It is also presented that the band gap of mixed halide thin films can be significantly affected by the distribution of halide composition.

  18. Method for producing hydrocarbon fuels from heavy polynuclear hydrocarbons by use of molten metal halide catalyst

    DOEpatents

    Gorin, Everett

    1979-01-01

    In a process for hydrocracking heavy polynuclear carbonaceous feedstocks to produce lighter hydrocarbon fuels by contacting the heavy feedstocks with hydrogen in the presence of a molten metal halide catalyst, thereafter separating at least a substantial portion of the carbonaceous material associated with the reaction mixture from the spent molten metal halide and thereafter regenerating the metal halide catalyst, an improvement comprising contacting the spent molten metal halide catalyst after removal of a major portion of the carbonaceous material therefrom with an additional quantity of hydrogen is disclosed.

  19. Absorption of inorganic halides produced from Freon 12 by calcium carbonate containing iron(III) oxide

    SciTech Connect

    Imamura, Seiichiro; Matsuba, Yoichi; Yamada, Etsu; Takai, Kenji; Utani, Kazunori

    1997-09-01

    Inorganic halides produced by the catalytic decomposition of Freon 12 were fixed by calcium carbonate, which is the main component of limestone. Iron(III) oxide, which is present as a contaminant in limestone, promoted the absorption of the halides by calcium carbonate at low temperatures. The supposed action of iron(III) oxide was to first react with inorganic halides, forming iron halides, and, then, transfer them to calcium carbonate to replace carbonate ion in a catalytic way. Thus, calcium carbonate containing iron oxides (limestone) can be used as an effective absorbent for the inorganic halogens produced during the decomposition of Freons.

  20. Experimental versus expected halide-ion size differences; structural changes in three series of isotypic bismuth chalcogenide halides.

    PubMed

    Keller, Egbert; Krämer, Volker

    2006-06-01

    Experimentally determined halide-ion size differences are compared with expected size differences in the three series of isotypic bismuth chalcogenide halide compounds, KBi(6)O(9)X (X = Cl, Br and I), BiOX (X = F, Cl, Br and I) and BiSX (X = Cl, Br and I). The strong deviations observed can be assigned to steric strain caused by the heterogeneity of the bond-valence pattern and (for BiOX) to anion-anion repulsion and a change in the connectivity scheme. Some special features of the BiOF structure and the question of "isotypism" within the BiOX series are briefly discussed. Structural changes within the BiSX series are analysed.

  1. Processing development of 4 tantalum carbide-hafnium carbide and related carbides and borides for extreme environments

    NASA Astrophysics Data System (ADS)

    Gaballa, Osama Gaballa Bahig

    Carbides, nitrides, and borides ceramics are of interest for many applications because of their high melting temperatures and good mechanical properties. Wear-resistant coatings are among the most important applications for these materials. Materials with high wear resistance and high melting temperatures have the potential to produce coatings that resist degradation when subjected to high temperatures and high contact stresses. Among the carbides, Al4SiC4 is a low density (3.03 g/cm3), high melting temperature (>2000°C) compound, characterized by superior oxidation resistance, and high compressive strength. These desirable properties motivated this investigation to (1) obtain high-density Al4SiC4 at lower sintering temperatures by hot pressing, and (2) to enhance its mechanical properties by adding WC and TiC to the Al4SiC4. Also among the carbides, tantalum carbide and hafnium carbide have outstanding hardness; high melting points (3880°C and 3890°C respectively); good resistance to chemical attack, thermal shock, and oxidation; and excellent electronic conductivity. Tantalum hafnium carbide (Ta4HfC 5) is a 4-to-1 ratio of TaC to HfC with an extremely high melting point of 4215 K (3942°C), which is the highest melting point of all currently known compounds. Due to the properties of these carbides, they are considered candidates for extremely high-temperature applications such as rocket nozzles and scramjet components, where the operating temperatures can exceed 3000°C. Sintering bulk components comprised of these carbides is difficult, since sintering typically occurs above 50% of the melting point. Thus, Ta4 HfC5 is difficult to sinter in conventional furnaces or hot presses; furnaces designed for very high temperatures are expensive to purchase and operate. Our research attempted to sinter Ta4HfC5 in a hot press at relatively low temperature by reducing powder particle size and optimizing the powder-handling atmosphere, milling conditions, sintering

  2. Abiotic Formation of Methyl Halides in the Terrestrial Environment

    NASA Astrophysics Data System (ADS)

    Keppler, F.

    2011-12-01

    Methyl chloride and methyl bromide are the most abundant chlorine and bromine containing organic compounds in the atmosphere. Since both compounds have relatively long tropospheric lifetimes they can effectively transport halogen atoms from the Earth's surface, where they are released, to the stratosphere and following photolytic oxidation form reactive halogen gases that lead to the chemical destruction of ozone. Methyl chloride and methyl bromide account for more than 20% of the ozone-depleting halogens delivered to the stratosphere and are predicted to grow in importance as the chlorine contribution to the stratosphere from anthropogenic CFCs decline. Today methyl chloride and methyl bromide originate mainly from natural sources with only a minor fraction considered to be of anthropogenic origin. However, until as recently as 2000 most of the methyl chloride and methyl bromide input to the atmosphere was considered to originate from the oceans, but investigations in recent years have clearly demonstrated that terrestrial sources such as biomass burning, wood-rotting fungi, coastal salt marshes, tropical vegetation and organic matter degradation must dominate the atmospheric budgets of these trace gases. However, many uncertainties still exist regarding strengths of both sources and sinks, as well as the mechanisms of formation of these naturally occurring halogenated gases. A better understanding of the atmospheric budget of both methyl chloride and methyl bromide is therefore required for reliable prediction of future ozone depletion. Biotic and abiotic methylation processes of chloride and bromide ion are considered to be the dominant pathways of formation of these methyl halides in nature. In this presentation I will focus on abiotic formation processes in the terrestrial environment and the potential parameters that control their emissions. Recent advances in our understanding of the abiotic formation pathway of methyl halides will be discussed. This will

  3. Microwave absorption in single crystals of lanthanum aluminate

    NASA Astrophysics Data System (ADS)

    Zuccaro, Claudio; Winter, Michael; Klein, Norbert; Urban, Knut

    1997-12-01

    A very sensitive dielectric resonator technique is employed to measure loss tangent tan δ and relative permittivity ɛr of lanthanum aluminate (LaAlO3) single crystals at 4-300 K and 4-12 GHz. A variety of single crystals grown by different techniques and purchased from different suppliers are considered. For T>150 K the loss tangent tan δ is almost sample independent with linear frequency dependence and monotonous temperature variation from 8×10-6 at 300 K to 2.5×10-6 at 150 K and 4.1 GHz. In this temperature range the experimental data are explained by a model based on lifetime broadened two-phonon difference processes. The loss tangent below 150 K is characterized by a peak in tan δ(T) at about 70 K. The height of this peak is frequency and strongly sample dependent. This leads to a variation of the loss tangent from 10-6 to 1.5×10-5 at 77 K and 8.6 GHz, the lowest values are generally achieved with Verneuil grown crystals and approach the intrinsic lower limit predicted by the phonon model. The peak is explained by defect dipole relaxation (local motions of ions). The activation energy of the relaxation process is determined from the measured data to be 31 meV. This low value indicates that the defect dipoles are associated with interstitials, possibly impurities in interstitial positions. Considering absorption due to phonons and due to defect dipole relaxation the loss tangent is calculated for a wide frequency range.

  4. Back bombardment for dispenser and lanthanum hexaboride cathodes

    NASA Astrophysics Data System (ADS)

    Bakr, Mahmoud; Kinjo, R.; Choi, Y. W.; Omer, M.; Yoshida, K.; Ueda, S.; Takasaki, M.; Ishida, K.; Kimura, N.; Sonobe, T.; Kii, T.; Masuda, K.; Ohgaki, H.; Zen, H.

    2011-06-01

    The back bombardment (BB) effect limits wide usage of thermionic rf guns. The BB effect induces not only ramping-up of a cathode’s temperature and beam current, but also degradation of cavity voltage and beam energy during a macropulse. This paper presents a comparison of the BB effect for the case of dispenser tungsten-base (DC) and lanthanum hexaboride (LaB6) thermionic rf gun cathodes. For each, particle simulation codes are used to simulate the BB effect and electron beam dynamics in a thermionic rf gun cathode. A semiempirical equation is also used to investigate the stopping range and deposited heat power of BB electrons in the cathode material. A numerical simulation method is used to calculate the change of the cathode temperature and current density during a single macropulse. This is done by solving two differential equations for the rf gun cavity equivalent circuit and one-dimensional thermal diffusion equation. High electron emission and small beam size are required for generation of a high-brightness electron beam, and so in this work the emission properties of the cathode are taken into account. Simulations of the BB effect show that, for a pulse of 6μs duration, the DC cathode experiences a large change in the temperature compared with LaB6, and a change in current density 6 times higher. Validation of the simulation results is performed using experimental data for beam current beyond the gun exit. The experimental data is well reproduced using the simulation method.

  5. Europium doped lanthanum zirconate nanoparticles with high concentration quenching

    SciTech Connect

    Alaparthi, Suresh B.; Lu, Long; Tian, Yue; Mao, Yuanbing

    2014-01-01

    Graphical abstract: - Highlights: • Eu:La{sub 2}Zr{sub 2}O{sub 7} nanoparticles were prepared facilely by a kinetically modified molten salt method. • High color purity and concentration quenching were achieved in these La{sub 2}Zr{sub 2}O{sub 7}:Eu nanoparticles. • Concentration quenching mechanism was discussed for Eu{sup 3+} in these Eu:La{sub 2}Zr{sub 2}O{sub 7} nanoparticles. - Abstract: A series of Eu{sup 3+} doped lanthanum zirconate (La{sub 2}Zr{sub 2}O{sub 7}) nanoparticles (NPs, 20 ± 5 nm in diameter) with cubic fluorite structure were facilely synthesized by a kinetically modified molten salt synthetic (MSS) process and characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and photoluminescence spectra (PL). Under the excitation of 405 nm, intense red emission with high color purity can be observed in the Eu{sup 3+} doped La{sub 2}Zr{sub 2}O{sub 7} NPs. Moreover, the as-prepared Eu:La{sub 2}Zr{sub 2}O{sub 7} NPs possess high concentration quenching, which is as high as ∼32.5 mol% of europium dopants in the La{sub 2}Zr{sub 2}O{sub 7} host. The corresponding concentration quenching mechanism was discussed as well. Our results confirm that the kinetically modified MSS process is a promising approach for preparing rare earth (RE) ions doped A{sub 2}B{sub 2}O{sub 7} nanoparticles with uniform RE doping and high concentration quenching.

  6. Titania-lanthanum phosphate photoactive and hydrophobic new generation catalyst

    NASA Astrophysics Data System (ADS)

    Jyothi, Chembolli K.; Jaimy, Kanakkanmavudi B.; Ghosh, Swapankumar; Sankar, Sasidharan; Smitha, V. S.; Warrier, K. G. K.

    2011-07-01

    Titania-lanthanum phosphate nanocomposites with multifunctional properties have been synthesized by aqueous sol-gel method. The precursor sols with varying TiO 2:LaPO 4 ratios were applied as thin coating on glass substrates in order to be transparent, hydrophobic, photocatalytically active coatings. The phase compositions of the composite powders were identified by powder X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HR-TEM). The anatase phase of TiO 2 in TiO 2-LaPO 4 composite precursors was found to be stable even on annealing at 800 °C. The glass substrates, coated with TL1 (TiO 2-LaPO 4 composition with 1 mol% LaPO 4) and TL50 (composite precursor containing TiO 2 and LaPO 4 with molar ratio 1:1) sols and annealed at 400 °C, produced contact angles of 74° and 92°, respectively, though it is only 62° for pure TiO 2 coating. The glass substrates, coated with TL50 sol, produced surfaces with relatively high roughness and uneven morphology. The TL1 material, annealed at 800 °C, has shown the highest UV photoactivity with an apparent rate constant, kapp=24×10 -3 min -1, which is over five times higher than that observed with standard Hombikat UV 100 ( kapp=4×10 -3 min -1). The photoactivity combined with a moderate contact angle (85.3°) shows that this material has a promise as an efficient self-cleaning precursor.

  7. Study of prolonged administration of lanthanum carbonate in dialysis patients.

    PubMed

    Gotoh, Junichi; Kukita, Kazutaka; Tsuchihashi, Seiichiro; Hattori, Masahiro; Iida, Junichi; Horie, Takashi; Onodera, Kazuhiko; Furui, Hidenori; Tamaki, Toru; Meguro, Junichi; Yonekawa, Motoki; Kawamura, Akio

    2013-04-01

    Data of 36 months were accumulated regarding the effects of lanthanum carbonate (LA) on serum phosphate concentrations in dialysis patients. Fifty-three patients (average age and dialysis history 58.4 years and 9.1 years) were included in this study who have been receiving outpatient treatment since March 2009, and who have been unable to maintain serum phosphate concentrations of ≤6.0 mg/dL via traditional therapeutic agents used for hyperphosphatemia. Patients were given dosage of LA in addition to, or instead of, co-hyperphosphatemia treatments already being received. Mean dosages of calcium carbonate (CC) and sevelamer hydrochloride (SH) before starting LA administration were 1301.9 mg and 2462.3 mg, respectively. Dosage of LA for all cases was 750 mg at initial dose; 1528.3 mg at 5 months; and 1416.7 mg at 30 months. Dosage of other phosphate binders were 905.7 mg of CC and 820.8 mg of SH at 5 months; and 687.5 mg of CC and 1031.3 mg of SH at 30 months. Serum phosphorus levels (P levels) were significantly decreased at 1 month of LA administration, and continued until 30 months of La treatment. These results suggest that LA successfully controlled serum P and Ca concentrations simultaneously within target ranges without affecting serum intact parathyroid hormone concentration, although further long-term prospective cohort study on LA would be required.

  8. Enantioselective DNA condensation induced by heptameric lanthanum helical supramolecular enantiomers.

    PubMed

    Bao, Fei-Fei; Xu, Xin-Xin; Zhou, Wen; Pang, Chun-Yan; Li, Zaijun; Gu, Zhi-Guo

    2014-09-01

    DNA condensation induced by a pair of heptameric La(III) helical enantiomers M-[La7(S-L)6(CO3)(NO3)6(OCH3)(CH3OH)7]·2CH3OH·5H2O and P-[La7(R-L)6(CO3)(NO3)6(OCH3)(CH3OH)5(H2O)2]·2CH3OH·4H2O (M-La and P-La, L=2-(2-hydroxybenzylamino)-3-carbamoylpropanoic acid) has been investigated by UV/vis spectroscopy, fluorescence spectroscopy, CD spectroscopy, EMSA, RALS, DLS, and SEM. The enantiomers M-La and P-La could induce CT-DNA condensation at a low concentration as observed in UV/vis spectroscopy. DNA condensates possessed globular nanoparticles with nearly homogeneous sizes in solid state determined by SEM (ca. 250 nm for M-La and ca. 200 nm for P-La). The enantiomers bound to DNA through electrostatic attraction and hydrogen bond interactions in a major groove, and rapidly condensed free DNA into its compact state. DNA decompaction has been acquired by using EDTA as disassembly agent, and analyzed by UV/vis spectroscopy, CD spectroscopy and EMSA. Moreover, the enantiomers M-La and P-La displayed discernible discrimination in DNA interaction and DNA condensation, as well as DNA decondensation. Our study suggested that lanthanum(III) enantiomers M-La and P-La were efficient DNA packaging agents with potential applications in gene delivery.

  9. Synthesis and characterization of monometallic niobium carbides and bimetallic niobium carbides using hafnium, titanium, and tantalum

    NASA Astrophysics Data System (ADS)

    Watts, Cassandra Jean

    As fossil fuels are rapidly depleting there is an enormous push for the development of new forms of energy based on renewable resources. Proton Exchange Membrane (PEM) fuel cells are one possible solution, but are constrained by the necessity of the platinum catalyst to initiate the oxygen reduction reaction (ORR). Transition metal carbides, like tungsten and molybdenum carbide, have shown catalytic properties that resemble platinum. This project seeks to synthesize through a low temperature solid state method with a LiCl:KCl:KF salt flux monometallic niobium carbides (NbC, Nb4C3, and Nb2C) and the bimetallic niobium carbides HfNbC, TiNbC, and TaNbC. The synthesized materials are characterized using XRD, SEM, and EDS. The results showed that a pure single phase of NbC and Nb4C 3, and a semi alloyed phase of TiNbC2 are obtainable. The remaining systems yielded phase separated carbide systems and are dominated by irreproducibility or oxidization.

  10. Synthesis and characterization of lanthanum complex (5-choloro-8-hydroxy quinoline) bis (2-2'bipyridine) lanthanum La(Bpy)2(5-Clq)

    NASA Astrophysics Data System (ADS)

    Kumar, Rahul; Soam, Ankur; Bhargava, Parag

    2017-05-01

    Lanthanum complex, (5-choloro 8-hydroxy quinoline) bis (2-2'bipyridine) has been synthesized and characterized by different techniques. Lanthanum complex, La(Bpy)2(5-Clq) was characterized for structural, thermal and photoluminescence analysis. Structural analysis of this material was done by Fourier transformed infrared spectroscopy (FTIR) and mass spectroscopy. Thermal analysis of this material was done by thermal gravimetric analysis (TGA) and material shows the thermal stability up to 400°C. Absorption and emission spectra of the material was measured by UV-visible spectroscopy and photoluminescence spectroscopy. Solution of this material La(Bpy)2(5-Clq) in ethanol showed absorption peak at 332 nm, which may be attributed due to (π - π*) transitions. The photoluminescence spectra of La(Bpy)2(5-Clq) in ethanol solution showed intense peak at 505 nm.

  11. Method for fabricating boron carbide articles

    DOEpatents

    Ardary, Zane L.; Reynolds, Carl D.

    1980-01-01

    The present invention is directed to the fabrication of boron carbide articles having length-to-diameter or width ratios greater than 2 to 1. The process of the present invention is practiced by the steps comprising hot pressing boron carbide powder into article segments or portions in which the segments have a length-to-diameter or width ratio less than 1.5, aligning a plurality of the initially hot-pressed segments in a hot-pressing die with the end surfaces of the segments placed in intimate contact with one another, and then hot pressing the aligned segments into an article of the desired configuration. The resulting article exhibits essentially uniform density throughout the structure with the bonds between the segments being equivalent in hardness, strength, and density to the remainder of the article.

  12. METHOD FOR PRODUCING CEMENTED CARBIDE ARTICLES

    DOEpatents

    Onstott, E.I.; Cremer, G.D.

    1959-07-14

    A method is described for making molded materials of intricate shape where the materials consist of mixtures of one or more hard metal carbides or oxides and matrix metals or binder metals thereof. In one embodiment of the invention 90% of finely comminuted tungsten carbide powder together with finely comminuted cobalt bonding agent is incorporated at 60 deg C into a slurry with methyl alcohol containing 1.5% paraffin, 3% camphor, 3.5% naphthalene, and 1.8% toluene. The compact is formed by the steps of placing the slurry in a mold at least one surface of which is porous to the fluid organic system, compacting the slurry, removing a portion of the mold from contact with the formed object and heating the formed object to remove the remaining organic matter and to sinter the compact.

  13. Shock compression properties of silicon carbide

    SciTech Connect

    Grady, D.E.; Kipp, M.E.

    1993-07-01

    An investigation of the shock compression and release properties of silicon carbide ceramic has been performed. A series of planar impact experiments has been completed in which stationary target discs of ceramic were struck by plates of either similar ceramic or other appropriate material at velocities up to 2.2 km/s with a propellant gun facility. The particle velocity history at the interface between the back of the target ceramic and a lithium-fluoride window material was measured with laser velocity interferometry (VISAR). Impact stresses achieved in these experiments range between about 10 and 50 GPa. Numerical solutions and analytic methods were used to determine the dynamic compression and release stress-strain behavior of the ceramic. Further analysis of the data was performed to determine dynamic strength and compressibility properties of silicon carbide.

  14. Ultrasonic ranking of toughness of tungsten carbide

    NASA Technical Reports Server (NTRS)

    Vary, A.; Hull, D. R.

    1983-01-01

    The feasibility of using ultrasonic attenuation measurements to rank tungsten carbide alloys according to their fracture toughness was demonstrated. Six samples of cobalt-cemented tungsten carbide (WC-Co) were examined. These varied in cobalt content from approximately 2 to 16 weight percent. The toughness generally increased with increasing cobalt content. Toughness was first determined by the Palmqvist and short rod fracture toughness tests. Subsequently, ultrasonic attenuation measurements were correlated with both these mechanical test methods. It is shown that there is a strong increase in ultrasonic attenuation corresponding to increased toughness of the WC-Co alloys. A correlation between attenuation and toughness exists for a wide range of ultrasonic frequencies. However, the best correlation for the WC-Co alloys occurs when the attenuation coefficient measured in the vicinity of 100 megahertz is compared with toughness as determined by the Palmqvist technique.

  15. Carbide coated fibers in graphite-aluminum composites

    NASA Technical Reports Server (NTRS)

    Imprescia, R. J.; Levinson, L. S.; Reiswig, R. D.; Wallace, T. C.; Williams, J. M.

    1975-01-01

    The study of protective-coupling layers of refractory metal carbides on the graphite fibers prior to their incorporation into composites is presented. Such layers should be directly wettable by liquid aluminum and should act as diffusion barriers to prevent the formation of aluminum carbide. Chemical vapor deposition was used to uniformly deposit thin, smooth, continuous coats of ZrC on the carbon fibers of tows derived from both rayon and polyacrylonitrile. A wet chemical coating of the fibers, followed by high-temperature treatment, was used, and showed promise as an alternative coating method. Experiments were performed to demonstrate the ability of aluminum alloys to wet carbide surfaces. Titanium carbide, zirconium carbide and carbide-coated graphite surfaces were successfully wetted. Results indicate that initial attempts to wet surfaces of ZrC-coated carbon fibers appear successful.

  16. Friction and deformation behavior of single-crystal silicon carbide

    NASA Technical Reports Server (NTRS)

    Miyoshi, K.; Buckley, D. H.

    1977-01-01

    Friction and deformation studies were conducted with single-crystal silicon carbide in sliding contact with diamond. When the radius of curvature of the spherical diamond rider was large (0.3), deformation of silicon carbide was primarily elastic. Under these conditions the friction coefficient was low and did not show a dependence on the silicon carbide orientation. Further, there was no detectable cracking of the silicon carbide surfaces. When smaller radii of curvature of the spherical diamond riders (0.15 and 0.02 mm) or a conical diamond rider was used, plastic grooving occured and the silicon carbide exhibited anisotropic friction and deformation behavior. Under these conditions the friction coefficient depended on load. Anisotropic friction and deformation of the basal plane of silicon carbide was controlled by the slip system. 10101120and cleavage of1010.

  17. Synthesis of Fe carbides species by reactive milling

    NASA Astrophysics Data System (ADS)

    Lodya, J. A. L.; Gericke, H.; Ngubane, J.; Dlamini, T. H.

    2009-04-01

    The formation of iron carbides by reactive milling of α-Fe and C powders is reported. The products formed were analyzed by Mössbauer spectroscopy and X-ray diffraction. It was found that iron carbide phases start forming after an incubation period of about 3 h depending on the ball-to-powder weight ratio (BPR). Carbide amounts increased with increasing milling time while α-Fe content decreased. Energy transfer increased with increasing BPR and high BPR resulted in an increase in the reaction rate. Although it was not possible to selectively synthesise a specific Fe x C phase, samples containing predominantly one type of carbide phase, either Hägg carbide or cementite, were successfully prepared. The formation of the different iron carbide phases is discussed within the context of the Fe-C phase diagram for non-equilibrium processes.

  18. Nonlinear optical imaging of defects in cubic silicon carbide epilayers.

    PubMed

    Hristu, Radu; Stanciu, Stefan G; Tranca, Denis E; Matei, Alecs; Stanciu, George A

    2014-06-11

    Silicon carbide is one of the most promising materials for power electronic devices capable of operating at extreme conditions. The widespread application of silicon carbide power devices is however limited by the presence of structural defects in silicon carbide epilayers. Our experiment demonstrates that optical second harmonic generation imaging represents a viable solution for characterizing structural defects such as stacking faults, dislocations and double positioning boundaries in cubic silicon carbide layers. X-ray diffraction and optical second harmonic rotational anisotropy were used to confirm the growth of the cubic polytype, atomic force microscopy was used to support the identification of silicon carbide defects based on their distinct shape, while second harmonic generation microscopy revealed the detailed structure of the defects. Our results show that this fast and noninvasive investigation method can identify defects which appear during the crystal growth and can be used to certify areas within the silicon carbide epilayer that have optimal quality.

  19. High temperature silicon carbide impregnated insulating fabrics

    NASA Technical Reports Server (NTRS)

    Schomburg, C.; Dotts, R. L. (Inventor)

    1982-01-01

    High temperature insulating articles having improved performance characteristics are described. The articles comprise fabrics of closely woven refractory or heat resistant fibers having particles of silicon carbide dispersed at least partially through the fabric and bonded to the fibers with an emulsifiable polyethylene wax. Such articles exhibit significantly increased high temperature emittance characteristics and an improved retention of integrity and flexibility after prolonged exposure to high temperature.

  20. Silicon Carbide Technologies for Lightweighted Aerospace Mirrors

    DTIC Science & Technology

    2008-09-01

    Silicon Carbide Technologies for Lightweighted Aerospace Mirrors Lawrence E. Matson (1) Ming Y. Chen (1) Brett deBlonk (2) Iwona A...glass and beryllium to produce lightweighted aerospace mirror systems has reached its limits due to the long lead times, high processing costs...for making mirror structural substrates, figuring and finishing technologies being investigated to reduce cost time and cost, and non-destructive