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Sample records for doped lanthanum chromites

  1. Mechanical properties of magnesia-doped lanthanum chromite versus temperature

    SciTech Connect

    Montross, C.S.; Yokokawa, Harumi; Dokiya, Masayuki; Bekessy, L.

    1995-07-01

    Magnesia-doped lanthanum chromite is a potential material for use in solid oxide fuel cells as an interconnector due to its resistance to oxidation and reduction. The strength and toughness of La(Cr{sub 0.9}Mg{sub 0.1})O{sub 3} were measured from 25 to 1,000 C in the as-fired reduced state and after oxidation. The as-fired samples showed a peak in toughness of approximately 3.9 MPa{center_dot}m{sup 1/2} at 125 C which decreased to approximately 1.4 MPa{center_dot}m{sup 1/2} at 600 C and 2.8 MPa{center_dot}m{sup 1/2} at room temperature. This peak in toughness is hypothesized to be due to the rhombohedral-to-orthorhombic phase transition by a toughening mechanism that is currently being investigated. The strength was also affected by the phase transition for both the as-fired reduced and the oxidized samples.

  2. 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.

  3. 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.

  4. Bulk and surface structure characterization of nanoscopic silver doped lanthanum chromites

    NASA Astrophysics Data System (ADS)

    Desai, P. A.; Joshi, P. N.; Patil, K. R.; Athawale, Anjali A.

    2013-01-01

    Crystalline state of lanthanum chromites with silver as a dopant has been studied by X-ray diffraction and transmission electron microscopy reveals microscopic properties of grain boundaries. X-ray photoelectron spectroscopy has been used to analyze surface states with atomic ratio of La, Cr, O and Ag as a dopant. LaCrO3 shows mixed valence states of chromium while the silver doped samples exhibit differences in chromium concentration with the oxidation of Cr3+ to Cr6+ in presence of chromium nitrate as a precursor salt. Trivalent stable state of chromium is observed for samples synthesized by chromic acetate as a precursor salt.

  5. Nickel and titanium doubly doped lanthanum strontium chromite for high temperature electrochemical devices

    NASA Astrophysics Data System (ADS)

    Gupta, Sapna; Singh, Prabhakar

    2016-02-01

    Lanthanum chromite based materials are promising candidate for use as electrochemical components in high temperature electrochemical devices. In this study, nickel and titanium doubly doped lanthanum strontium chromites are developed and the effects of nickel and titanium co-doping of the chromite perovskite La0.85Sr0.15Cr1-2yNiyTiyO3-δ (0.05 ≤ y ≤ 0.3) on the electrical conductivity, chemical stability, microstructure, density, thermal expansion and electrochemical performance are measured. Density and the electrical conductivity increases with nickel concentration whereas Sr-segregation on the surface of La0.85Sr0.15Cr1-2yNiyTiyO3-δ has been observed for y ≥ 0.2 and is associated with reduction in the electrical conductivity. For y = 0.1, La0.85Sr0.15Cr1-2yNiyTiyO3-δ shows the highest electrical conductivity in air and reducing atmosphere (PO2 ∼10-24 atm). The conductivity of La0.85Sr0.15Cr1-2yNiyTiyO3-δ (y = 0.1) in reducing atmosphere (3.58 S cm-1 at 950 °C) also remains higher than the most widely investigated compositions such as (La0.75Sr0.25)0.95Cr0.5Mn0.5O3-δ (2.81 S cm-1) and (La0.75Sr0.25)0.95Cr0.7Fe0.3O3-δ (1.41 S cm-1). Smaller deviation in the oxygen stoichiometry is similarly observed for La0.85Sr0.15Cr0.8Ni0.1Ti0.1O3-δ (δ = 0.011) when compared to La0.75Sr0.25CrO3-δ (δ = 0.091), La0.75Sr0.25Cr0.5Mn0.5O3-δ (δ = 0.175) and La0.75Sr0.25Cr0.5Fe0.5O3-δ (δ = 0.148) at 1000 °C and ∼10-24 atm. Highest electrochemical performance and structural/interfacial stability is obtained for new composition La0.85Sr0.15Cr0.8Ni0.1Ti0.1O3-δ (LSCNT0.1) when mixed with 8YSZ in both oxidizing and reducing atmosphere.

  6. Toughening in lanthanum chromite due to metastable phase

    SciTech Connect

    Montross, C.S.; Yokokawa, Harumi; Dokiya, Masayuki

    1996-03-15

    Alkali earth doped lanthanum chromite ceramics are preferred for use in solid oxide fuel cells because of their electronic conductivity and resistance to both oxidizing and reducing atmospheres. However, there is a phase transformation that can be disruptive which occurs at approximately 300 to 400 C at the orthorhombic to rhombohedral phase boundary in undoped and in magnesia or calcia doped lanthanum chromite. The purpose of this research was to investigate air sinterable, chromia deficient, calcia doped lanthanum chromite by 4 point bending for strength (MOR), and toughness (K{sub IC}) versus temperature to 1,000 C. The initial analysis was to verify the results of Mori et al. As-fired specimens sintered at 1,600 C were compared with specimens aged at 1,000 C for 48 hours after sintering at 1,600 C to investigate the effect of any residual transient phases on the properties.

  7. Method and closing pores in a thermally sprayed doped lanthanum chromite interconnection layer

    DOEpatents

    Singh, Prabhakar; Ruka, Roswell J.

    1995-01-01

    A dense, substantially gas-tight electrically conductive interconnection layer is formed on an air electrode structure of an electrochemical cell by (A) providing an air electrode surface; (B) forming on a selected portion of the electrode surface, a layer of doped LaCrO.sub.3 particles doped with an element or elements selected from Ca, Sr, Ba, Mg, Co, Ni, Al and mixtures thereof by thermal spraying doped LaCrO.sub.3 particles, either by plasma arc spraying or flame spraying; (C) depositing a mixture of CaO and Cr.sub.2 O.sub.3 on the surface of the thermally sprayed layer; and (D) heating the doped LaCrO.sub.3 layer coated with CaO and Cr.sub.2 O.sub.3 surface deposit at from about 1000.degree. C. to 1200.degree. C. to substantially close the pores, at least at a surface, of the thermally sprayed doped LaCrO.sub.3 layer. The result is a dense, substantially gas-tight, highly doped, electrically conductive interconnection material bonded to the electrode surface. A solid electrolyte layer can be applied to the nonselected portion of the air electrode. A fuel electrode can be applied to the solid electrolyte, to form an electrochemical cell, for example for generation of electrical power.

  8. Method and closing pores in a thermally sprayed doped lanthanum chromite interconnection layer

    DOEpatents

    Singh, P.; Ruka, R.J.

    1995-02-14

    A dense, substantially gas-tight electrically conductive interconnection layer is formed on an air electrode structure of an electrochemical cell by (A) providing an air electrode surface; (B) forming on a selected portion of the electrode surface, a layer of doped LaCrO{sub 3} particles doped with an element or elements selected from Ca, Sr, Ba, Mg, Co, Ni, Al and mixtures thereof by thermal spraying doped LaCrO{sub 3} particles, either by plasma arc spraying or flame spraying; (C) depositing a mixture of CaO and Cr{sub 2}O{sub 3} on the surface of the thermally sprayed layer; and (D) heating the doped LaCrO{sub 3} layer coated with CaO and Cr{sub 2}O{sub 3} surface deposit at from about 1,000 C to 1,200 C to substantially close the pores, at least at a surface, of the thermally sprayed doped LaCrO{sub 3} layer. The result is a dense, substantially gas-tight, highly doped, electrically conductive interconnection material bonded to the electrode surface. A solid electrolyte layer can be applied to the nonselected portion of the air electrode. A fuel electrode can be applied to the solid electrolyte, to form an electrochemical cell, for example for generation of electrical power. 5 figs.

  9. 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.

  10. 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.

  11. Magnetic properties of nano-clusters lanthanum chromite powders doped with samarium and strontium ions synthesized via a novel combustion method

    SciTech Connect

    Rashad, M.M.; El-Sheikh, S.M.

    2011-03-15

    Graphical abstract: Nanocrystalline Sm{sup 3+} and Sr{sup 2+} doped LaCrO{sub 3} powders have been synthesized through a novel gel combustion synthesis using triethanol amine (TEA). The saturation magnetization of the LaCrO{sub 3} increased with an increase Sm{sup 3+} ion and it decreased with an increase in the Sr{sup 3+} ion to 0.3 at temperature 1000 {sup o}C for 2 h due to the formation of a monodispersed uniform octahedral structure as shown in the Fig. Research highlights: {yields} Single-phase orthorhombic lanthanum chromite LaCrO{sub 3} nanoclusters have been successfully synthesized through a novel gel combustion synthesis using triethanol amine (TEA). {yields} Sr{sup 2+} ions doped LaCrO{sub 3} increased the unit cell volume and the crystallite size whereas Sm{sup 3+} ions doped LaCrO{sub 3} decreased the unit cell volume and the crystallite size. {yields} The saturation magnetization of the LaCrO{sub 3} powders increased continuously with an increase in the Sm concentration and it decreased with an increase in the Sr ion up to 0.3 at annealing temperature of 1000 {sup o}C for 2 h. -- Abstract: A novel approach to synthesize a single-phase orthorhombic perovskite lanthanum chromite LaCrO{sub 3} clusters doped with Sm{sup 3+} and Sr{sup 2+} ions via gel combustion route was reported. The producing materials were synthesized using metal nitrates as oxidizers and triethanol amine (TEA), N-butyl amine (NBA) or ethylene diamine (EDA) as a fuel. The effect of the annealing temperature, type of organic fuel and the variation of the samarium and/or strontium substitution and its impact on crystal structure, crystallite size, microstructure and magnetic properties of the LaCrO{sub 3} powders formed was systematically studied. The results revealed that a well crystalline single phase of pure LaCrO{sub 3} can be achieved at annealing temperature from 800 to 1000 {sup o}C for 2 h. Moreover, each organic carrier materials exhibited a different degree of effectiveness

  12. Tape method of forming a thin layer of doped lanthanum chromite particles and of bonding such on an electrode

    DOEpatents

    Richards, Von L.; Singhal, Subhash C.; Pal, Uday B.

    1992-01-01

    A combustible polymer film, useful for application of an interconnection on an electrode is made by: (1) providing doped LaCro.sub.3 particles; (2) dispersing doped LaCrO.sub.3 particles in a solvent, to provide a dispersion; (3) screening the dispersion to provide particles in the range of from 30 micrometers to 80 micrometers; (4) admixing a fugitive polymer with the particles; (5) casting the dispersion to provide a film; (6) drying the film; and (7) stripping the film. The film can then be applied to a porous, preheated electrode top surface, and then electrochemical vapor depositing a dense skeletal LaCrO.sub.3 structure, between and around the doped LaCrO.sub.3 particles. Additional solid oxide electrolyte and fuel electrode layers can then be added to provide a fuel cell.

  13. Tape method of forming a thin layer of doped lanthanum chromite particles and of bonding such on an electrode

    DOEpatents

    Richards, V.L.; Singhal, S.C.; Pal, U.B.

    1992-07-21

    A combustible polymer film, useful for application of an interconnection on an electrode is made by: (1) providing doped LaCro[sub 3] particles; (2) dispersing doped LaCrO[sub 3] particles in a solvent, to provide a dispersion; (3) screening the dispersion to provide particles in the range of from 30 micrometers to 80 micrometers; (4) admixing a fugitive polymer with the particles; (5) casting the dispersion to provide a film; (6) drying the film; and (7) stripping the film. The film can then be applied to a porous, preheated electrode top surface, and then a dense skeletal LaCrO[sub 3] structure is electrochemically vapor deposited between and around the doped LaCrO[sub 3] particles. Additional solid oxide electrolyte and fuel electrode layers can then be added to provide a fuel cell. 4 figs.

  14. Preparation and Charge Density in (Co, Fe)-Doped La-Ca-Based Chromite

    NASA Astrophysics Data System (ADS)

    Saravanan, R.; Thenmozhi, N.; Fu, Yen-Pei

    2016-08-01

    Transition metal-doped lanthanum chromites (La0.8Ca0.2)(Cr0.9- x Co0.1Fe x )O3 ( x = 0.03, 0.06, 0.09, 0.12) have been synthesized by solid state reaction method. The synthesized samples were characterized for their structural properties using powder x-ray diffraction analysis, which shows that the grown samples are orthorhombic in structure with single phase. The nature of bonding and the charge distribution of the grown samples have been analyzed by maximum entropy method. Further, the samples were characterized for their optical and magnetic properties using ultraviolet-visible spectra and vibrating sample magnetometry. The microstructural studies were carried by scanning electron microscopy/electron dispersive x-ray spectroscopy techniques. From the optical absorption spectra, it was found that the energy band gap of the samples ranges from 2.135 eV to 2.405 eV. From vibrating sample magnetometer measurements, ferromagnetic like behaviour with large coercive field was observed for Fe doping concentration of x = 0.12. Since the doped lanthanum chromites have good mechanical properties and electrical conductivity at high temperature, these materials are used in solid oxide fuel cells.

  15. Method of making highly sinterable lanthanum chromite powder

    DOEpatents

    Richards, V.L.; Singhal, S.C.

    1992-09-01

    A highly sinterable powder consisting essentially of LaCrO[sub 3], containing from 5 weight % to 20 weight % of a chromite of dopant Ca, Sr, Co, Ba, or Mg and a coating of a chromate of dopant Ca, Sr, Co, Ba, or Mg; is made by (1) forming a solution of La, Cr, and dopant; (2) heating their solutions; (3) forming a combined solution having a desired ratio of La, Cr, and dopant and heating to reduce solvent; (4) forming a foamed mass under vacuum; (5) burning off organic components and forming a charred material; (6) grinding the charred material; (7) heating the char at from 590 C to 950 C in inert gas containing up to 50,000 ppm O[sub 2] to provide high specific surface area particles; (8) adding that material to a mixture of a nitrate of Cr and dopant to form a slurry; (9) grinding the particles in the slurry; (10) freeze or spray drying the slurry to provide a coating of nitrates on the particles; and (11) heating the coated particles to convert the nitrate coating to a chromate coating and provide a highly sinterable material having a high specific surface area of over 7 m[sup 2]/g. 2 figs.

  16. Method of making highly sinterable lanthanum chromite powder

    DOEpatents

    Richards, Von L.; Singhal, Subhash C.

    1992-01-01

    A highly sinterable powder consisting essentially of LaCrO.sub.3, containing from 5 weight % to 20 weight % of a chromite of dopant Ca, Sr, Co, Ba, or Mg and a coating of a chromate of dopant Ca, Sr, Co, Ba, or Mg; is made by (1) forming a solution of La, Cr, and dopant; (2) heating their solutions; (3) forming a combined solution having a desired ratio of La, Cr, and dopant and heating to reduce solvent; (4) forming a foamed mass under vacuum; (5) burning off organic components and forming a charred material; (6) grinding the charred material; (7) heating the char at from 590.degree. C. to 950 C. in inert gas containing up to 50,000 ppm O.sub.2 to provide high specific surface area particles; (8) adding that material to a mixture of a nitrate of Cr and dopant to form a slurry; (9) grinding the particles in the slurry; (10) freeze or spray drying the slurry to provide a coating of nitrates on the particles; and (11) heating the coated particles to convert the nitrate coating to a chromate coating and provide a highly sinterable material having a high specific surface area of over 7 m.sup.2 /g.

  17. High Performance Ceramic Interconnect Material for Solid Oxide Fuel Cells (SOFCs): Ca- and Transition Metal-doped Yttrium Chromite

    SciTech Connect

    Yoon, Kyung J.; Stevenson, Jeffry W.; Marina, Olga A.

    2011-10-15

    The effect of transition metal substitution on thermal and electrical properties of Ca-doped yttrium chromite was investigated in relation to use as a ceramic interconnect in high temperature solid oxide fuel cells (SOFCs). 10 at% Co, 4 at% Ni, and 1 at% Cu substitution on B-site of 20 at% Ca-doped yttrium chromite led to a close match of thermal expansion coefficient (TEC) with that of 8 mol% yttria-stabilized zirconia (YSZ), and a single phase Y0.8Ca0.2Cr0.85Co0.1Ni0.04Cu0.01O3 remained stable between 25 and 1100 degree C over a wide oxygen partial pressure range. Doping with Cu significantly facilitated densification of yttrium chromite. Ni dopant improved both electrical conductivity and dimensional stability in reducing environments, likely through diminishing the oxygen vacancy formation. Substitution with Co substantially enhanced electrical conductivity in oxidizing atmosphere, which was attributed to an increase in charge carrier density and hopping mobility. Electrical conductivity of Y0.8Ca0.2Cr0.85Co0.1Ni0.04Cu0.01O3 at 900 degree C is 57 S/cm in air and 11 S/cm in fuel (pO2=5×10^-17 atm) environments. Chemical compatibility of doped yttrium chromite with other cell components was verified at the processing temperatures. Based on the chemical and dimensional stability, sinterability, and thermal and electrical properties, Y0.8Ca0.2Cr0.85Co0.1Ni0.04Cu0.01O3 is suggested as a promising SOFC ceramic interconnect to potentially overcome technical limitations of conventional acceptor-doped lanthanum chromites.

  18. High performance ceramic interconnect material for solid oxide fuel cells (SOFCs): Ca- and transition metal-doped yttrium chromite

    NASA Astrophysics Data System (ADS)

    Yoon, Kyung Joong; Stevenson, Jeffrey W.; Marina, Olga A.

    2011-10-01

    The effect of transition metal substitution on thermal and electrical properties of Ca-doped yttrium chromite was investigated in relation to use as a ceramic interconnect in high temperature solid oxide fuel cells (SOFCs). 10 at.% Co, 4 at.% Ni, and 1 at.% Cu substitution on B-site of 20 at.% Ca-doped yttrium chromite led to a close match of thermal expansion coefficient (TEC) with that of 8 mol% yttria-stabilized zirconia (YSZ), and a single phase Y0.8Ca0.2Cr0.85Co0.1Ni0.04Cu0.01O3 remained stable between 25 and 1100 °C over a wide oxygen partial pressure range. Doping with Cu significantly facilitated densification of yttrium chromite. Ni dopant improved both electrical conductivity and dimensional stability in reducing environments, likely through diminishing the oxygen vacancy formation. Substitution with Co substantially enhanced electrical conductivity in oxidizing atmosphere, which was attributed to an increase in charge carrier density and hopping mobility. Electrical conductivity of Y0.8Ca0.2Cr0.85Co0.1Ni0.04Cu0.01O3 at 900 °C is 57 S cm-1 in air and 11 S cm-1 in fuel (pO2 = 5 × 10-17 atm) environments. Chemical compatibility of doped yttrium chromite with other cell components was verified at the processing temperatures. Based on the chemical and dimensional stability, sinterability, and thermal and electrical properties, Y0.8Ca0.2Cr0.85Co0.1Ni0.04Cu0.01O3 is suggested as a promising SOFC ceramic interconnect to potentially overcome technical limitations of conventional acceptor-doped lanthanum chromites.

  19. Electrical properties of lanthanum chromite based ceramics in hydrogen and oxidizing atmospheres at high temperatures. Second quarterly report, January-March 1980

    SciTech Connect

    Pollina, R.

    1980-01-01

    The immediate purpose of this work is to determine whether hydrogen has a deleterious effect on lanthanum chromite in solid oxide fuel cells. Westinghouse personnel have noted that the In/sub 2/O/sub 3/ electrode connection to the electronically conducting LaCrO/sub 3/-based intercell connectors becomes loose, possibly because of hydrogen reducing the In/sub 2/O/sub 3/ and forming a steam layer which mechanically separates the two materials. Another possibility, which Westinghouse is pursuing, is that oxygen diffusion through the lanthanum chromite is the origin of this problem. A longer-range potential side benefit of this work is a contribution to understanding of conduction mechanisms in lanthanum chromite based ceramics. Such understanding would likely benefit other energy-related programs, such as the coal-fired MHD program in which yttrium chromite is a possible electrode material. Procedures and results of measurements of Hall effect, electric conductivity, and hydrogen diffusion are described.

  20. Electrical properties of lanthanum doped barium titanate ceramics

    SciTech Connect

    Vijatovic Petrovic, M.M.; Bobic, J.D.; Ramoska, T.; Banys, J.; Stojanovic, B.D.

    2011-10-15

    Pure and lanthanum doped barium titanate (BT) ceramics were prepared by sintering pellets at 1300 deg. C for 8 h, obtained from nanopowders synthesized by the polymeric precursor method. XRD results showed formation of a tetragonal structure. The presence of dopants changed the tetragonal structure to pseudo-cubic. The polygonal grain size was reduced up to 300 nm with addition of lanthanum as a donor dopant. Determined dielectric properties revealed that lanthanum modified BT ceramics possessed a diffused ferroelectric character in comparison with pure BT that is a classical ferroelectric material. In doped BT phase transition temperatures were shifted to lower temperatures and dielectric constant values were much higher than in pure BT. A modified Currie Weiss law was used to explore the connection between the doping level and degree of diffuseness of phase transitions. Impedance spectroscopy measurements were carried out at different temperatures in order to investigate electrical resistivity of materials and appearance of a PTCR effect. - Highlights: {yields} Pure and lanthanum doped BaTiO{sub 3} were prepared by polymeric precursors method. {yields} Change of structure from tetragonal to pseudo-cubic. {yields} Lanthanum as a donor dopant influenced on change of ferro-para phase transition. {yields} The diffuseness factor indicated the formation of diffuse ferroelectric material. {yields} Lanthanum affected on PTCR effect appearance in BT ceramics.

  1. 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.

  2. Stability of chromite interconnections in dual environments

    NASA Astrophysics Data System (ADS)

    Armstrong, T. R.; Stevenson, J. W.; Raney, P.; Pederson, L. R.

    1994-11-01

    One of the most critical technical concerns in high-temperature SOFC's is the physical, chemical, and electrical stability of the interconnect (typically a doped lanthanum chromite) in the dual (oxidizing and reducing atmosphere) SOFC environment. The reducing or fuel side may experience oxygen partial pressures (P(O2)) from 10(exp -18) to 10(exp -6) atmospheres, while the oxidizing side may have P(O2) from 10(exp -6) to greater than 1 atm. These conditions limit the possible candidate materials to lanthanum or yttrium chromites. In the past decade, much work has centered on development of air-sinterable chromites and understanding their physical properties; little work, however, has focused on the stability of these chromites in dual environments. Chromite powders were synthesized using the glycine-nitrate process. The powders were calcined at 1,000 C for 1 hour and then uniaxially pressed into bars (46mm x 16mm x 3mm) at 55 MPa and isostatically pressed at 138 MPa. Samples were sintered in air. The dependence of the physical properties of sintered lanthanum chromites upon ambient P(O2) and temperature (using dilatometry, thermogravimetric analysis, and oxygen permeation measurements) were studied. La(1-x)A(x)CrO3 and Y(1-x)Ca(x)CrO3, where A is Ca or Sr and x was varied from 0.1 to 0.4 were evaluated in this study. The P(O2) was varied using a buffered CO2/Ar-4%H2 gas system, enabling expansion measurements to be made over a partial pressure range from 10(exp -5) to 10(exp -18) atmosphere at 800, 900, and 1,000 C.

  3. Stability of chromite interconnections in dual environments

    SciTech Connect

    Armstrong, T.R.; Stevenson, J.W.; Raney, P.; Pederson, L.R.

    1994-11-01

    One of the most critical technical concerns in high-temperature SOFCs is the physical, chemical, and electrical stability of the interconnect (typically a doped lanthanum chromite) in the dual (oxidizing and reducing atmosphere) SOFC environment. The reducing or fuel side may experience oxygen partial pressures (P(O{sub 2})) from 10{sup {minus}18} to 10{sup {minus}6} atmospheres, while the oxidizing side may have P(O{sub 2}) from 10{sup {minus}6} to greater than 1 atm. These conditions limit the possible candidate materials to lanthanum or yttrium chromites. In the past decade, much work has centered on development of air-sinterable chromites and understanding their physical properties; little work, however, has focused on the stability of these chromites in dual environments. Chromite powders were synthesized using the glycine-nitrate process. The powders were calcined at 1,000 C for 1 hour and then uniaxially pressed into bars (46mm x 16mm x 3mm) at 55 MPa and isostatically pressed at 138 MPa. Samples were sintered in air. The dependence of the physical properties of sintered lanthanum chromites upon ambient P(O{sub 2}) and temperature (using dilatometry, thermogravimetric analysis, and oxygen permeation measurements) were studied. La{sub 1{minus}x}A{sub x}CrO{sub 3} and Y{sub 1{minus}x}Ca{sub x}CrO{sub 3}, where A is Ca or Sr and x was varied from 0.1 to 0.4 were evaluated in this study. The P(O{sub 2}) was varied using a buffered CO{sub 2}/Ar-4%H{sub 2} gas system, enabling expansion measurements to be made over a partial pressure range from 10{sup {minus}5} to 10{sup {minus}18} atmosphere at 800, 900, and 1,000 C.

  4. Thermal conductivity analysis of lanthanum doped manganites

    SciTech Connect

    Mansuri, Irfan; Shaikh, M. W.; Khan, E.; Varshney, Dinesh

    2014-04-24

    The temperature-dependent thermal conductivity of the doped manganites La{sub 0.7}Ca{sub 0.3}MnO{sub 3} is theoretically analyzed within the framework of Kubo formulae. The Hamiltonian consists of phonon, electron and magnon thermal conductivity contribution term. In this process we took defects, carrier, grain boundary, scattering process term and then calculate phonon, electron and magnon thermal conductivity.

  5. Altering the equilibrium condition in Sr-doped lanthanum manganite.

    SciTech Connect

    Carter, J. D.; Krumpelt, M.; Vaughey, J.; Wang, X.

    1999-05-28

    The material of choice for a solid oxide fuel cell cathode based on a yttria-stabilized zirconia (YSZ) electrolyte is doped lanthanum manganite, (La, Sr)MnO{sub 3}. It excels at many of the attributes necessary for a system to work at the required operating temperature and is flexible enough to allow for materials optimization. Although strontium-doping increases the electronic conductivity of the material, the ionic conductivity of the material remains negligible under operating conditions. Studies have shown that the internal equilibrium of the material heavily favors oxidation of the manganese and rather than the loss of lattice oxygen as a charge compensation mechanism. This lack of oxygen vacancies in the structure retards the ability of the material to conduct oxygen ions; thus the optimized system requires a large number of engineered triple point boundary locations to work efficiently. We have successfully doped the host LSM lattice to alter the interred equilibrium of the material to increase its ionic conductivity and thus lower the cathodic overpotential of the system. Our presentation will discuss these new materials, the results of cell tests, and a number of characterization experiments performed.

  6. 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.

  7. Calcium- and Cobalt-doped Yttrium Chromites as an Interconnect Material for Solid Oxide Fuel Cells

    SciTech Connect

    Yoon, Kyung J.; Cramer, Carolyn N.; Thomsen, Edwin C.; Coyle, Christopher A.; Coffey, Greg W.; Marina, Olga A.

    2010-04-23

    The structural, thermal and electrical characteristics of calcium- and cobalt-doped yttrium chromites were studied for a potential use as the interconnect material in high temperature solid oxide fuel cells (SOFCs) as well as other high temperature electrochemical and thermoelectric devices. The Y0.8Ca0.2Cr1-xCoxO3±δ (x=0, 0.1, 0.2, 0.3) compositions had single phase orthorhombic perovskite structures in the wide range of oxygen pressures. Sintering behavior was remarkably enhanced upon cobalt doping and densities 95% and 97% of theoretical density were obtained after sintering at 1300oC in air, when x was 0.2 and 0.3, respectively. The electrical conductivity in both oxidizing and reducing atmospheres was significantly improved with cobalt content, and values of 49 and 10 S/cm at 850oC and 55 and 14 S/cm at 950oC in air and forming gas, respectively, were reported for x=0.2. The conductivity increase was attributed to the charge carrier density increase upon cobalt substitution for chromium confirmed with Seebeck measurements. The thermal expansion coefficient (TEC) was increased with cobalt content and closely matched to that of an 8 mol% yttria-stabilized zirconia (YSZ) electrolyte for 0.1 ≤ x ≤ 0.2. The chemical compatibility between Y0.8Ca0.2Cr1-xCoxO3±δ and YSZ was evaluated firing the two at 1400oC and no reaction products were found if x value was kept lower than 0.2.

  8. Crystallinity and magnetoresistance in calcium doped lanthanum manganites

    SciTech Connect

    Gillman, E.S.; Dahmen, K.H.

    1998-12-31

    Thin films of calcium doped lanthanum manganites La{sub 1{minus}x}Ca{sub x}MnO{sub 3} (LCMO) with x {approximately} 0.41 have been prepared on LaAlO{sub 3}(001) (LAO) Y-stabilized ZrO{sub 2}(001) (YSZ), and Al{sub 2}O{sub 3}(0001) (SAP) substrates by liquid delivery metal-organic chemical vapor deposition (LD-MOCVD). The films on YSZ and SAP substrates have a textured, polycrystalline morphology with a preferred orientation of (110). The films on LAO show a single-crystalline morphology and a (100) orientation. Transport measurements show the polycrystalline films have a resistance peak approximately 60 K lower than the films on LAO and, in general, have a much higher overall resistance. The magnetoresistance (MR) ratio ([R(H) - R(0)]/R(H)) is sharply peaked near the maximum in resistance for the films on LAO, while the polycrystalline films show a noticeable absence of this sharply peaked behavior and a flat, rather large ({approximately} 100%) MR ratio over a large temperature range. These results will be discussed in terms of grain boundary scattering, crystallite size, and magnetization.

  9. Effect of rare-earth chromites on sintering of magnesia

    SciTech Connect

    Kashcheev, I.D.

    1994-09-01

    The effect of neodymium, cerium, lanthanum, and ytrrium chromites, added in amounts of not more than 8%, on the sintering of magnesia in air and in vacuum has been studied. On addition of rare-earth chromites, the initial magnesia is sintered to a density of 0.98. By their sintering action, these chromites fall into the following sequence: neodymium chromite-lanthanum chromite-yttrium chromite-cerium chromite. The highest density (0.98-0.99) and the lowest porosity (1-2%) are obtained on addition of 2% of neodymium chromite to magnesia. The process of sintering of magnesia is accompanied by an increase in the size of periclase crystals from 12 to 38-56 {mu}m.

  10. Effect of Nickel Substitution on Defect Chemistry, Electrical Properties, and Dimensional Stability of Calcium-Doped Yttrium Chromite

    SciTech Connect

    Yoon, Kyung J.; Stevenson, Jeffry W.; Marina, Olga A.

    2011-06-30

    The effect of nickel substitution on defect chemistry, electrical properties, and dimensional stability of calcium-doped yttrium chromite was studied for use as an interconnect material in high temperature solid oxide fuel cells (SOFCs). The compositions of Y0.8Ca0.2Cr1-xNixO3±δ (x=0-0.15), prepared using the glycine nitrate process, showed single phase orthorhombic perovskite structures over a wide range of oxygen partial pressures (10^-17 atm ≤ pO2 ≤ 0.21 atm). X-ray diffraction (XRD) analysis indicated that most of the nickel ions replacing chromium ions are divalent and act as acceptor dopants, leading to a substantial increase in conductivity. In particular, the conductivity at 900 degree C in air increased from 10 S/cm to 34 S/cm with 15% nickel substitution, and an increase in charge carrier density was confirmed by Seebeck measurements. A point defect model was derived, and the relationship between electrical conductivity and oxygen partial pressure was successfully fitted into the proposed model. The defect modeling results indicated that nickel substitution improves the stability of calcium-doped yttrium chromite toward reduction and suppresses the oxygen vacancy formation, which results in significantly increased electrical conductivity in reducing environment. The electrical conductivity of Y0.8Ca0.2Cr0.85Ni0.15O3±δ at 900 degree C in reducing atmosphere (pO2=10^-17 atm) was 5.8 S/cm, which was more than an order of magnitude higher than that of Y0.8Ca0.2CrO3±δ (0.2 S/cm). Improved stability in reducing atmosphere was further confirmed by dilatometry measurements showing reduced isothermal "chemical" expansion, and the isothermal expansion in reducing atmosphere (pO2=10^-17 atm) at 900 degree C decreased from 0.07% for Y0.8Ca0.2CrO3±δ to 0.03% for Y0.8Ca0.2Cr0.85Ni0.15O3±δ. Based on these results, enhanced electrical performance and mechanical integrity is expected with nickel substitution on calcium-doped yttrium chromite in SOFC

  11. Nanocrystalline brookite with enhanced stability and photocatalytic activity: influence of lanthanum(III) doping.

    PubMed

    Perego, Céline; Wang, Yu-Heng; Durupthy, Olivier; Cassaignon, Sophie; Revel, Renaud; Jolivet, Jean-Pierre

    2012-02-01

    Metastable TiO(2) polymorphs are more promising materials than rutile for specific applications such as photocatalysis or catalysis support. This was clearly demonstrated for the anatase phase but still under consideration for brookite, which is difficult to obtain as pure phase. Moreover, the surface doping of anatase with lanthanum ions is known to both increase the thermal stability of the metastable phase and improve its photocatalytic activity. In this study, TiO(2) nanoparticles of almost only the brookite structure were prepared by a simple sol-gel procedure in aqueous solution. The nanoparticles were then doped with lanthanum(III) ions. The thermal stability of the nanoparticles was analyzed by X-ray diffraction and kinetic models were successfully applied to quantify phases evolutions. The presence of surface-sorbed lanthanum(III) ions increased the phase stability of at least 200 °C and this temperature shift was attributed to the selective phase stabilization of metastable TiO(2) polymorphs. Moreover, the combination of the surface doping ions and the thermal treatment induces the vanishing of the secondary anatase phase, and the photocatalytic tests on the doped brookite nanoparticles demonstrated that the doping increased photocatalytic activity and that the extent depended on the duration of the sintering treatment.

  12. Continuous-wave laser action of Yb3+-doped lanthanum scandium borate

    NASA Astrophysics Data System (ADS)

    Romero, J. J.; Johannsen, J.; Mond, M.; Petermann, K.; Huber, G.; Heumann, E.

    2005-02-01

    Lanthanum scandium borate (LSB) has been proved to be an interesting laser matrix when doped with Nd3+ and Er3+ ions. In this paper, we demonstrate that it is also a very efficient laser material when doped with Yb3+ ions. The main spectroscopic characteristics of the system are presented, showing very broad absorption and emission bands, comparable to those found in Yb-doped GdCOB and YCOB crystals. From spectroscopic measurements the relevant laser parameters have been obtained, and a tunability of about 50 nm could be deduced. Room-temperature, continuous-wave laser action of Yb-doped LSB is demonstrated at a wavelength of 1045 nm with a slope efficiency as high as 64%.

  13. Effect of a-site cation deficiency and YSZ additions on sintering and properties of doped lanthanum manganite

    SciTech Connect

    Stevenson, J.W.; Armstrong, T.R.; Weber, W.J.

    1995-06-01

    The sintering behavior of Ca- and Sr-doped lanthanum manganite (the preferred SOFC cathode material) is highly dependent on the relative proportion of A and B site cations in the material. In general, A-site cation deficiency increases sintered density. The effect of additions of YSZ to lanthanum manganite (to expand the reactive region at the cathode/electrolyte interface and improve thermal expansion and sintering shrinkage matches) on sintering and other properties will also be reported.

  14. Crystal structure and physicochemical properties of doped lanthanum manganites

    NASA Astrophysics Data System (ADS)

    Aksenova, T. V.; Gavrilova, L. Ya.; Cherepanov, V. A.

    2012-12-01

    Substituted lanthanum-strontium manganites La0.7Sr0.3Mn0.9Me0.1O3 ± δ (Me = Ti, Cr, Fe, and Cu) are obtained by standard ceramic and glycerin-nitrate techniques. High-temperature powder X-ray diffraction is employed to study the crystal structure of La0.7Sr0.3Mn0.9Me0.1O3 ± δ oxides. It is shown that in the range 298-1023 K in air, La0.7Sr0.3Mn0.9Me0.103 ± δ manganites crystallized in an orthorhombic cell (space group R-3c). The isobaric temperature dependences of unit cell parameters are determined. Thermal expansion coefficients are calculated for La0.7Sr0.3Mn0.9Me0.103 ± δ oxides. The conductivity of La0.7Sr0.3Mn0.9Me0.103 ± δ is studied as a function of temperature in the range 500 K ≤ T ≤ 1200 K in air. It is shown that substituting 3 d metal for manganese considerably lowers the conductivity of basic La0.7Sr0.3Mn0.9O3 ± δ. The chemical stability of iron-substituted manganite La0.7Sr0.3Mn0.9Fe0.1O3 ± δ is studied with respect to the electrolyte material.

  15. Energetics of magnesium, strontium, and barium doped lanthanum gallate perovskites

    NASA Astrophysics Data System (ADS)

    Cheng, Jihong; Navrotsky, Alexandra

    2004-01-01

    LaGaO 3 perovskites doped with Sr or Ba at the La site and Mg at the Ga site were prepared by solid-state reaction or sol-gel method and characterized. Enthalpies of formation from constituent oxides at 298 K were determined by high-temperature oxide melt solution calorimetry. Energetic trends are discussed in terms of defect chemistry. As oxygen deficiency increases, formation enthalpies define three trends, LaGa 1- yMg yO 3- δ (LGM), La 1- xSr xGa 1- yMg yO 3- δ (LSGM), and La 1- xBa xGa 1- yMg yO 3- δ (LBGM). They become less exothermic with increasing doping, suggesting a dominant destabilization effect from oxygen vacancies. The endothermic enthalpy of vacancy formation is 275±37, 166±18 and 138±12 kJ/mol of VO·· for LGM, LBGM and LSGM, respectively. Tolerance factor and ion size mismatch also affect enthalpies. In terms of energetics, Sr is the best dopant for the La site and Mg for the Ga site, supporting earlier studies, including oxygen ion conductivity and computer modeling.

  16. Optical, luminescent and laser properties of highly transparent ytterbium doped yttrium lanthanum oxide ceramics

    NASA Astrophysics Data System (ADS)

    Ivanov, M.; Kopylov, Yu.; Kravchenko, V.; Li, Jiang; Pan, Yubai; Kynast, U.; Leznina, M.; Strek, W.; Marciniak, Lukasz; Palashov, O.; Snetkov, I.; Mukhin, I.; Spassky, D.

    2015-12-01

    This paper describes the fabrication and investigation of highly transparent Yb-doped yttrium lanthanum oxide ceramics. For sintering of the ceramics we used a technology, which consists of several consecutive steps: (a) synthesis of weakly agglomerated nanopowder by laser ablation, (b) compacting of the green body with cold isostatic pressing (CIP), and (c) sintering in vacuum. After calcinations of the synthesized nanopowder at 1200 °C, a pure single-phase solid solution Yb3+:(LaxY1-x)2O3 was formed. The lanthanum ions proved to be a good aid to sinter yttria ceramics doped with Yb3+ at comparatively moderate temperatures of about 1650 °C. The ceramics have a relative density higher than 99.99% and grain sizes around 40 μm. The absorption coefficient of 3.2 mm thick Yb0.12La0.27Y1.61O3 ceramics is 0.01 cm-1 at 1150 nm. Laser oscillation at a wavelength of 1033 nm is demonstrated.

  17. Doped Yttrium Chromite-Ceria Composite as a Redox-Stable and Sulfur-Tolerant Anode for Solid Oxide Fuel Cells

    SciTech Connect

    Yoon, Kyung J.; Coyle, Christopher A.; Marina, Olga A.

    2011-12-11

    A Ca- and Co-doped yttrium chromite (YCCC) - samaria-doped ceria (SDC) composite was studied in relation to a potential use as a solid oxide fuel cell (SOFC) anode material. Tests performed using the yttria-stabilized zirconia (YSZ) electrolyte-supported cells revealed that the electrocatalytic activity of the YCCC-SDC anode towards hydrogen oxidation at 800 C was comparable to that of the Ni-YSZ anode. In addition, the YCCC-SDC anode exhibited superior sulfur tolerant characteristics showing less than 10% increase in a polarization resistance, fully reversible, upon exposure to 20 ppm H2S at 800 C. No performance degradation was observed during multiple reduction-oxidation (redox) cycles when the anode was intentionally exposed to the air environment followed by the reduction in hydrogen. The redox tolerance of the YCCC-SDC anode was attributed to the dimensional and chemical stability of the YCCC exhibiting minimal isothermal chemical expansion upon redox cycling.

  18. Room temperature optical and dielectric properties of Sr and Ni doped lanthanum ferrite nanoparticles

    SciTech Connect

    Naseem, Swaleha; Khan, Wasi Singh, B. R.; Naqvi, A. H.

    2015-06-24

    Strontium and nickel doped lanthanum ferrite (LaFeO{sub 3}) nanoparticles (NPs) were prepared reverse micelle (RM) and calcinated at 700°C. Microstructural studies were carried by XRD and SEM/EDS techniques. The results of structural characterization show the formation of all samples in single phase without any impurity. Optical properties were studied by UV- visible spectroscopy and band gap energy was estimated 3.89 eV. Room temperature dielectric constant (ε’) decreases abruptly at lower frequencies owing to the charge transport relaxation time. The observed behavior of the dielectric properties can be attributed on the basis of Koop’s theory based on Maxwell-Wagner’s two layer model in studied nanoparticles.

  19. Low-threshold and broadly tunable lasers of Yb3+-doped yttrium lanthanum oxide ceramic

    NASA Astrophysics Data System (ADS)

    Hao, Qiang; Li, Wenxue; Zeng, Heping; Yang, Qiuhong; Dou, Chuanguo; Zhou, Hongxu; Lu, Wei

    2008-05-01

    We experimentally demonstrated diode-pumped continuous wave and tunable laser operation of Yb3+-doped yttrium lanthanum oxide transparent ceramic [Yb:(Y1-xLax)2O3,x=0.1], which was fabricated with nanopowders and sintered in H2 atmosphere. As low as 400mW pumping threshold and a slope efficiency of 52% were realized at 1080nm under a high-brightness 976nm diode pump with a fiber core of 50μm and a numerical aperture of 0.22. A maximum output power of 2.1W was obtained when the non-lasing absorbed pump power was 19.5W at 976nm with diode laser of 400μm fiber core. A smooth tunable curve from 1018to1086nm was achieved at 940nm diode pump. Broadband lasing spectra up to 30nm were observed in the tunable laser experiment.

  20. Bismuth doped lanthanum ferrite perovskites as novel cathodes for intermediate-temperature solid oxide fuel cells.

    PubMed

    Li, Mei; Wang, Yao; Wang, Yunlong; Chen, Fanglin; Xia, Changrong

    2014-07-23

    Bismuth is doped to lanthanum strontium ferrite to produce ferrite-based perovskites with a composition of La(0.8-x)Bi(x)Sr0.2FeO(3-δ) (0 ≤ x ≤ 0.8) as novel cathode material for intermediate-temperature solid oxide fuel cells. The perovskite properties including oxygen nonstoichiometry coefficient (δ), average valence of Fe, sinterability, thermal expansion coefficient, electrical conductivity (σ), oxygen chemical surface exchange coefficient (K(chem)), and chemical diffusion coefficient (D(chem)) are explored as a function of bismuth content. While σ decreases with x due to the reduced Fe(4+) content, D(chem) and K(chem) increase since the oxygen vacancy concentration is increased by Bi doping. Consequently, the electrochemical performance is substantially improved and the interfacial polarization resistance is reduced from 1.0 to 0.10 Ω cm(2) at 700 °C with Bi doping. The perovskite with x = 0.4 is suggested as the most promising composition as solid oxide fuel cell cathode material since it has demonstrated high electrical conductivity and low interfacial polarization resistance.

  1. Microstructure evolution and electrical characterization of Lanthanum doped Barium Titanate (BaTiO3) ceramics

    NASA Astrophysics Data System (ADS)

    Billah, Masum; Ahmed, A.; Rahman, Md. Miftaur; Mahbub, Rubbayat; Gafur, M. A.; Bashar, M. Shahriar

    2016-07-01

    In the current work, we investigated the structural and dielectric properties of Lanthanum oxide (La2O3) doped Barium Titanate (BaTiO3) ceramics and established a correlation between them. Solid state sintering method was used to dope BaTiO3 with 0.3, 0.5 and 0.7 mole% La2O3 under different sintering parameters. The raw materials used were La2O3 nano powder of ~80nm grain size and 99.995% purity and BaTiO3 nano powder of 100nm grain size and 99.99% purity. Grain size distribution and morphology of fracture surface of sintered pellets were examined by Field Emission Scanning Electron Microscope and X-Ray Diffraction analysis was conducted to confirm the formation of desired crystal structure. The research result reveal that grain size and electrical properties of BaTiO3 ceramic significantly enhanced for small amount of doping (up to 0.5 mole% La2O3) and then decreased with increasing doping concentration. Desired grain growth (0.80-1.3 µm) and high densification (<90% theoretical density) were found by proper combination of temperature, sintering parameters and doping concentration. We found the resultant stable value of dielectric constant was 10000-12000 at 100-300 Hz in the temperature range of 30°-50° C for 0.5 mole% La2O3 with corresponding shift of curie temperature around 30° C. So overall this research showed that proper La3+ concentration can control the grain size, increase density, lower curie temperature and hence significantly improve the electrical properties of BaTiO3 ceramics.

  2. Crystal structures and magnetic properties of strontium and copper doped lanthanum ferrites

    SciTech Connect

    Sora, Isabella Natali; Caronna, Tullio; Fontana, Francesca; Julian Fernandez, Cesar de; Caneschi, Andrea; Green, Mark

    2012-07-15

    The crystal and magnetic structures of La{sub 0.8}Sr{sub 0.2}Fe{sub 1-x}Cu{sub x}O{sub 3-w} compounds, which exhibit coercive fields larger than any others reported for iron-based perovskites, have been analyzed at room temperature with the neutron powder diffraction technique and the Rietveld method of profile fitting. For x in the range 0.05-0.10 the material is monophasic with orthorhombic symmetry (space group Pnma), and crystallizes in the perovskite-like cell of LaFeO{sub 3}, Fe/Cu cations occupy octahedral sites, La/Sr cations are twelve-fold coordinated. For x=0.20 the material is biphasic, with a main orthorhombic phase (space group Pnma) and a secondary rhombohedral phase with space group R-3c (hexagonal setting). The structural transition from the orthorhombic to the rhombohedral phase reduces the structural distortion of the (Fe/Cu)O{sub 6} octahedron. The average bond distance (Fe/Cu)-O and the pseudo-cubic unit cell volume decrease with increasing Cu content in accordance with the presence of higher valence states of the transition metals. The magnetic structure was modeled for the monophasic samples (x=0.05 and 0.10) assuming an antiferromagnetic interaction between Fe/Cu neighboring cations (G-type): the magnetic moments order antiferromagnetically along the b-axis, with the spin direction along a-axis. The magnetic moments of the Fe/Cu atoms are {mu}{sub x}=2.66(3){mu}{sub B} and 2.43(3){mu}{sub B} for the compositions x=0.05 and 0.10, respectively. By measuring the first magnetization curve and the hysteresis loops, coexisting antiferromagnetic and weak ferromagnetic interactions were observed for all samples. - Graphical abstract: Hysteresis loops measured at room temperature of the sample with x=0.05. Highlights: Black-Right-Pointing-Pointer Iron based perovskites with the largest coercive fields. Black-Right-Pointing-Pointer Sr and Cu lanthanum ferrites as magnetic materials. Black-Right-Pointing-Pointer Doped lanthanum ferrites show

  3. Probing highly luminescent europium-doped lanthanum orthophosphate nanorods for strategic applications.

    PubMed

    Saraf, Mohit; Kumar, Pawan; Kedawat, Garima; Dwivedi, Jaya; Vithayathil, Sajna Antony; Jaiswal, Nagendra; Kaipparettu, Benny Abraham; Gupta, Bipin Kumar

    2015-03-16

    Herein we have established a strategy for the synthesis of highly luminescent and biocompatible europium-doped lanthanum orthophosphate (La0.85PO4Eu0.15(3+)) nanorods. The structure and morphogenesis of these nanorods have been probed by XRD, SEM, and TEM/HRTEM techniques. The XRD result confirms that the as-synthesized nanorods form in a monazite phase with a monoclinic crystal structure. Furthermore, the surface morphology shows that the synthesized nanorods have an average diameter of ∼90 nm and length of ∼2 μm. The HRTEM images show clear lattice fringes that support the presence of better crystal quality and enhanced photoluminescence hypersensitive red emission at 610 nm ((5)D0-(7)F2) upon 394 nm wavelength excitation. Furthermore, time-resolved spectroscopy and an MTT assay of these luminescent nanorods demonstrate a photoluminescent decay time of milliseconds with nontoxic behavior. Hence, these obtained results suggest that the as-synthesized luminescent nanorods could be potentially used in invisible security ink and high-contrast bioimaging applications.

  4. Dynamic Nuclear Polarization in Samarium Doped Lanthanum Magnesium Nitrate. Ph.D. Thesis - Va. Polytechnic Inst.

    NASA Technical Reports Server (NTRS)

    Byvik, C. E.

    1971-01-01

    The dynamic nuclear polarization of hydrogen nuclei by the solid effect in single crystals of samarium doped lanthanum magnesium nitrate (Sm:LMN) was studied theoretically and experimentally. The equations of evolution governing the dynamic nuclear polarization by the solid effect were derived in detail using the spin temperature theory and the complete expression for the steady state enhancement of the nuclear polarization was calculated. Experimental enhancements of the proton polarization were obtained for eight crystals at 9.2 GHz and liquid helium temperatures. The samarium concentration ranged from 0.1 percent to 1.1 percent as determined by X-ray fluorescence. A peak enhancement of 181 was measured for a 1.1 percent Sm:LMN crystal at 3.0 K. The maximum enhancements extrapolated with the theory using the experimental data for peak enhancement versus microwave power and correcting for leakage, agree with the ideal enhancement (240 in this experiment) within experimental error for three of the crystals.

  5. Chemical compatibility between strontium-doped lanthanum manganite and yttria-stabilized zirconia

    SciTech Connect

    Stochniol, G.; Syskakis, E.; Naoumidis, A.

    1995-04-01

    Equimolar powder mixtures and multilayer pellets of single-phase Sr-doped lanthanum manganite perovskite materials La{sub y{minus}x}Sr{sub x}MnO{sub 3} with La content y = 1 and 0.95 and Sr content 0 {<=} x {<=} 0.5 were annealed in air with 8 mol% Y{sub 2}O{sub 3}ZrO{sub 2} at 1470 K up to 400 h and at 1670 K up to 200 h. X-ray diffraction and electron probe microanalysis confirmed the formation of La{sub 2}Zr{sub 2}O{sub 7} or SrZrO{sub 3} depending on the composition of the perovskites. No reaction products could be detected for La{sub 0.95 {minus}x}Sr{sub x}MnO{sub 3} with 0.2 {<=} x {<=} 0.4 after annealing for 400 h at 1470 K, and for the perovskite La{sub 0.65}Sr{sub 0.3}MnO{sub 3} even after annealing for 200 h at 1,670 K. The results demonstrate the improved chemical compatibility of La-deficient perovskites against reaction with zirconia and can provide a basis for the selection of a sufficiently chemically stable material for the air electrode of solid oxide fuel cells.

  6. Electrocatalytic Properties of Nanocrystalline Calcium-Doped Lanthanum Cobalt Oxide for Bifunctional Oxygen Electrodes

    SciTech Connect

    Malkhandi, S; Yang, B; Manohar, AK; Manivannan, A; Prakash, GKS; Narayanan, SR

    2012-04-19

    Calcium-doped lanthanum cobalt oxide is a promising electrocatalyst for oxygen evolution and oxygen reduction in rechargeable metal air batteries and water electrolyzers operating with alkaline electrolyte. Nanocrystalline perovskite of composition La0.6Ca0.4CoO3 with a unique cellular internal structure was prepared at 350 degrees C and then annealed in air at progressively higher temperatures in the range of 600-750 degrees C. The samples were characterized by electrochemical techniques and X-ray photoelectron spectroscopy. The area-specific electrocatalytic activity for oxygen evolution/oxygen reduction, the oxidation state of cobalt, and the crystallite size increased with annealing temperature, while the Tafel slope remained constant. These trends provide new insights into the role of the cobalt center in oxygen evolution and oxygen reduction, and how preparation conditions can be altered to tune the activity of the cobalt center for electrocatalysis. We expect these findings to guide the design of electrocatalysts for bifunctional oxygen electrodes, in general.

  7. Electrical performance of nanostructured strontium-doped lanthanum manganite impregnated onto yttria-stabilized zirconia backbone

    NASA Astrophysics Data System (ADS)

    Ju, Jiangwei; Lin, Jie; Wang, Yusu; Zhang, Yanxiang; Xia, Changrong

    2016-01-01

    Strontium-doped lanthanum manganite (LSM) nanoparticles are deposited onto porous yttria-stabilized zirconia frameworks via an ion impregnation/infiltration process. The apparent conductivity of the impregnated LSM nanostructure is investigated regarding the fabricating parameters including LSM loading, heat treatment temperature, heating rate, and annealing at 750 °C for 400 h. Besides, the conductivity, the intrinsic conductivity as well as Bruggeman factor of the impregnated LSM is estimated from the apparent conductivity using the analytical model for the three-dimensional impregnate network. The conductivity increases with LSM loading while the interfacial polarization resistance exhibits the lowest value at an optimal loading of about 5 vol.%, which corresponds to the largest three-phase boundary as predicted using the numerical infiltration methodology. At the optimal loading, the area specific ohmic resistance of the impregnated LSM is about 0.032 Ω cm2 at 700 °C for a typical impregnated cathode of 30 μm thick. It is only 5.5% of the cathode interfacial polarization resistance and 3.3% of the total resistance for a single cell consisting of a Ni-YSZ support, a 10 μm thick electrolyte and a 30 μm thick cathode, demonstrating that the ohmic resistance is negligible in the LSM impregnated cathode for SOFCs.

  8. Blocking effect of crystal–glass interface in lanthanum doped barium strontium titanate glass–ceramics

    SciTech Connect

    Wang, Xiangrong; Zhang, Yong; Baturin, Ivan; Liang, Tongxiang

    2013-10-15

    Graphical abstract: The blocking effect of the crystal–glass interface on the carrier transport behavior in the lanthanum doped barium strontium titanate glass–ceramics: preparation and characterization. - Highlights: • La{sub 2}O{sub 3} addition promotes the crystallization of the major crystalline phase. • The Z″ and M″ peaks exist a significant mismatch for 0.5 mol% La{sub 2}O{sub 3} addition. • The Z″ and M″ peaks separate obviously for 1.0 mol% La{sub 2}O{sub 3} addition. • Crystallite impedance decreases while crystal–glass interface impedance increases. • La{sub 2}O{sub 3} addition increases blocking factor of the crystal–glass interface. - Abstract: The microstructures and dielectric properties in La{sub 2}O{sub 3}-doped barium strontium titanate glass–ceramics have been investigated by scanning electron microscopy (SEM) and impedance spectroscopy. SEM analysis indicated that La{sub 2}O{sub 3} additive decreases the average crystallite size. Impedance spectroscopy revealed that the positions of Z″ and M″ peaks are close for undoped samples. When La{sub 2}O{sub 3} concentration is 0.5 mol%, the Z″ and M″ peaks show a significant mismatch. Furthermore, these peaks separate obviously for 1.0 mol% La{sub 2}O{sub 3} addition. With increasing La{sub 2}O{sub 3} concentration, the contribution of the crystallite impedance becomes smaller, while the contribution of the crystal–glass interface impedance becomes larger. More interestingly, it was found that La{sub 2}O{sub 3} additive increases blocking factor of the crystal–glass interface in the temperature range of 250–450 °C. This may be attributed to a decrease of activation energy of the crystallite and an increase of the crystal–glass interface area.

  9. Enhanced ionic conductivity of apatite-type lanthanum silicate electrolyte for IT-SOFCs through copper doping

    NASA Astrophysics Data System (ADS)

    Ding, Xifeng; Hua, Guixiang; Ding, Dong; Zhu, Wenliang; Wang, Hongjin

    2016-02-01

    Apatite-type Lanthanum silicate (LSO) is among the most promising electrolyte for intermediate temperature solid oxide fuel cells (IT-SOFCs) owing to the high conductivity and low activation energy at lower temperature than traditional doped-zirconia electrolyte. The ionic conductivity as well as the sintering density of lanthanum silicate oxy-apatite, La10Si6-xCuxO27-δ (LSCO, 0 ≤ x ≤ 2), was effectively enhanced through a small amount of doped copper. The phase composition, relative density, ionic conductivity and thermal expansion behavior of La10Si6-xCuxO27-δ was systematically investigated by X-ray diffraction (XRD), Archimedes' drainage method, scanning electron microscope (SEM), electrochemical impedance spectra (EIS) and thermal dilatometer techniques. With increasing copper doping content, the ionic conductivity of La10Si6-xCuxO27-δincreased, reaching a maximum of 4.8 × 10-2 S cm-1 at 800 °C for x = 1.5. The improved ionic conductivity could be primarily associated with the enhanced grain conductivity. The power output performance of NiO-LSCO/LSCO/LSCF single cell was superior to that obtained on NiO-LSO/LSO/LSCF at different temperatures using hydrogen as fuel and oxygen as oxidant, which could be attributed to the enhanced oxygen ionic conductivity as well as the sintering density for the copped doped lanthanum silicate. In conclusion, the apatite La10Si4.5Cu1.5O25.5 is a promising candidate electrolyte for IT-SOFCs.

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

    DOE PAGES

    Foley, Brian M.; Brown-Shaklee, Harlan J.; Campion, Michael J.; Medlin, Douglas L.; Clem, Paul G.; Ihlefeld, Jon F.; Hopkins, Patrick E.

    2014-11-08

    We have measured the cross-plane thermal conductivity (κ) of (010)-textured, undoped, and lanthanum-doped strontium niobate (Sr2-xLaxNb2O7-δ) thin films via time-domain thermoreflectance. Then the thin films were deposited on (001)-oriented SrTiO3 substrates via the highly-scalable technique of chemical solution deposition. We find that both film thickness and lanthanum doping have little effect on κ, suggesting that there is a more dominant phonon scattering mechanism present in the system; namely the weak interlayer-bonding along the b-axis in the Sr2Nb2O7 parent structure. We also compare our experimental results with two variations of the minimum-limit model for κ and discuss the nature of transportmore » in material systems with weakly-bonded layers. The low cross-plane κ of these scalably-fabricated films is comparable to that of similarly layered niobate structures grown epitaxially.« less

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

    SciTech Connect

    Foley, Brian M.; Brown-Shaklee, Harlan J.; Campion, Michael J.; Medlin, Douglas L.; Clem, Paul G.; Ihlefeld, Jon F.; Hopkins, Patrick E.

    2014-11-08

    We have measured the cross-plane thermal conductivity (κ) of (010)-textured, undoped, and lanthanum-doped strontium niobate (Sr2-xLaxNb2O7-δ) thin films via time-domain thermoreflectance. Then the thin films were deposited on (001)-oriented SrTiO3 substrates via the highly-scalable technique of chemical solution deposition. We find that both film thickness and lanthanum doping have little effect on κ, suggesting that there is a more dominant phonon scattering mechanism present in the system; namely the weak interlayer-bonding along the b-axis in the Sr2Nb2O7 parent structure. We also compare our experimental results with two variations of the minimum-limit model for κ and discuss the nature of transport in material systems with weakly-bonded layers. The low cross-plane κ of these scalably-fabricated films is comparable to that of similarly layered niobate structures grown epitaxially.

  12. Phase Stability Analysis of Lanthanum-Doped Alumina During Synthesis and Sintering

    NASA Astrophysics Data System (ADS)

    Ngwa Nforbi, Lum-Ngwegia

    The aim of this research was to study the phase stability during synthesis and consolidation of nanocrystalline lanthanum-doped gamma-Al2O 3 powders. We used solution combustion synthesis by dissolving precursor nitrate compounds and an organic fuel in a pre-heated muffle furnace at 500°C. Several preliminary syntheses were carried out in order to obtain the correct fuel-to-oxidizer ratio necessary for the production of the desired lanthanum-doped gamma-Al 2O3. The as-synthesized powders were then heat-treated at 1000°C for 2 hours in order to remove impurities and improve the crystallinity of the powders. Sintered circular specimens were made by pressing the heat-treated powders and subsequently annealing them at 1800°C for 4 hours. The use of this material in optical windows requires that the material have high strength and optical transparency. Elimination of all the pores during sintering is therefore crucial. In addition, preparing specimens of the gamma-Al2O3 phase is optimal, since the crystal structure is cubic and transparency is more readily achievable. Several different samples with varying weight percents of La were attempted to determine how much of the La could effectively prevent the gamma-Al2O 3 phase from transforming into the more stable alpha-Al2O 3 phase. The different phases of compounds produced with increasing amounts of La were also identified. The as-synthesized and heat-treated powders as well as the annealed circular discs were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The average particle sizes of the powders were determined by dynamic light scattering (DLS). XRD experiments showed that the gamma-alumina phase was stabilized when the powders were calcined at 1000°C with 5 wt% La, 10 wt% La and 13 wt% La. Increasing the amount of La resulted in the formation of the La compounds LaAlO3 in the heat-treated powders containing 15 wt% La and above and LaAl11O18 in the sintered specimens. Crystallite

  13. High-temperature superconductivity in space-charge regions of lanthanum cuprate induced by two-dimensional doping.

    PubMed

    Baiutti, F; Logvenov, G; Gregori, G; Cristiani, G; Wang, Y; Sigle, W; van Aken, P A; Maier, J

    2015-10-20

    The exploitation of interface effects turned out to be a powerful tool for generating exciting material properties. Such properties include magnetism, electronic and ionic transport and even superconductivity. Here, instead of using conventional homogeneous doping to enhance the hole concentration in lanthanum cuprate and achieve superconductivity, we replace single LaO planes with SrO dopant planes using atomic-layer-by-layer molecular beam epitaxy (two-dimensional doping). Electron spectroscopy and microscopy, conductivity measurements and zinc tomography reveal such negatively charged interfaces to induce layer-dependent superconductivity (Tc up to 35 K) in the space-charge zone at the side of the planes facing the substrate, where the strontium (Sr) profile is abrupt. Owing to the growth conditions, the other side exhibits instead a Sr redistribution resulting in superconductivity due to conventional doping. The present study represents a successful example of two-dimensional doping of superconducting oxide systems and demonstrates its power in this field.

  14. High-temperature superconductivity in space-charge regions of lanthanum cuprate induced by two-dimensional doping

    PubMed Central

    Baiutti, F.; Logvenov, G.; Gregori, G.; Cristiani, G.; Wang, Y.; Sigle, W.; van Aken, P. A.; Maier, J.

    2015-01-01

    The exploitation of interface effects turned out to be a powerful tool for generating exciting material properties. Such properties include magnetism, electronic and ionic transport and even superconductivity. Here, instead of using conventional homogeneous doping to enhance the hole concentration in lanthanum cuprate and achieve superconductivity, we replace single LaO planes with SrO dopant planes using atomic-layer-by-layer molecular beam epitaxy (two-dimensional doping). Electron spectroscopy and microscopy, conductivity measurements and zinc tomography reveal such negatively charged interfaces to induce layer-dependent superconductivity (Tc up to 35 K) in the space-charge zone at the side of the planes facing the substrate, where the strontium (Sr) profile is abrupt. Owing to the growth conditions, the other side exhibits instead a Sr redistribution resulting in superconductivity due to conventional doping. The present study represents a successful example of two-dimensional doping of superconducting oxide systems and demonstrates its power in this field. PMID:26481902

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

    NASA Astrophysics Data System (ADS)

    Song, Myoung Geun; Bark, Chung Wung

    2016-06-01

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

  16. On magnetic ordering in heavily sodium substituted hole doped lanthanum manganites

    NASA Astrophysics Data System (ADS)

    Sethulakshmi, N.; Unnimaya, A. N.; Al-Omari, I. A.; Al-Harthi, Salim; Sagar, S.; Thomas, Senoy; Srinivasan, G.; Anantharaman, M. R.

    2015-10-01

    Mixed valence manganite system with monovalent sodium substituted lanthanum manganites form the basis of the present work. Lanthanum manganites belonging to the series La1-xNaxMnO3 with x=0.5-0.9 were synthesized using modified citrate gel method. Variation of lattice parameters and unit cell volume with Na concentration were analyzed and the magnetization measurements indicated ferromagnetic ordering in all samples at room temperature. Low temperature magnetization behavior indicated that all samples exhibit antiferromagnetism along with ferromagnetism and it has also been observed that antiferromagnetic ordering dominates ferromagnetic ordering as concentration is increased. Evidence for such a magnetic inhomogeneity in these samples has been confirmed from the variation in Mn3+/Mn4+ ion ratio from X-ray Photoelectron Spectroscopy and from the absorption peak studies using Ferromagnetic Resonance Spectroscopy.

  17. Stratiform chromite deposit model

    USGS Publications Warehouse

    Schulte, Ruth F.; Taylor, Ryan D.; Piatak, Nadine M.; Seal, Robert R., II

    2010-01-01

    Stratiform chromite deposits are of great economic importance, yet their origin and evolution remain highly debated. Layered igneous intrusions such as the Bushveld, Great Dyke, Kemi, and Stillwater Complexes, provide opportunities for studying magmatic differentiation processes and assimilation within the crust, as well as related ore-deposit formation. Chromite-rich seams within layered intrusions host the majority of the world's chromium reserves and may contain significant platinum-group-element (PGE) mineralization. This model of stratiform chromite deposits is part of an effort by the U.S. Geological Survey's Mineral Resources Program to update existing models and develop new descriptive mineral deposit models to supplement previously published models for use in mineral-resource and mineral-environmental assessments. The model focuses on features that may be common to all stratiform chromite deposits as a way to gain insight into the processes that gave rise to their emplacement and to the significant economic resources contained in them.

  18. Atomic-absorption determination of rhodium in chromite concentrates

    USGS Publications Warehouse

    Schnepfe, M.M.; Grimaldi, F.S.

    1969-01-01

    Rhodium is determined in chromite concentrates by atomic absorption after concentration either by co-precipitation with tellurium formed by the reduction of tellurite with tin(II) chloride or by fire assay into a gold bead. Interelement interferences in the atomic-absorption determination are removed by buffering the solutions with lanthanum sulphate (lanthanum concentration 1%). Substantial amounts of Ag, Al, Au, Bi, Ca, Cd, Co, Cr, Cu, Fe, Ho, Hg, K, La, Mg, Mn, Mo, Na, Ni, Pb, Te, Ti, V, Y, Zn and platinum metals can be tolerated. A lower limit of approximately 0.07 ppm Rh can be determined in a 3-g sample. ?? 1969.

  19. Electronic structure and photocatalytic water splitting of lanthanum-doped Bi{sub 2}AlNbO{sub 7}

    SciTech Connect

    Li Yingxuan; Chen Gang Zhang Hongjie; Li Zhonghua

    2009-04-02

    Bi{sub 2-x}La{sub x}AlNbO{sub 7} (0 {<=} x {<=} 0.5) photocatalysts were synthesized by the solid-state reaction method and characterized by powder X-ray diffraction (XRD), infrared (IR) spectra and ultraviolet-visible (UV-vis) spectrophotometer. The band gaps of the photocatalysts were estimated from absorption edge of diffuse reflectance spectra, which were increased by the doping of lanthanum. It was found from the electronic band structure study that orbitals of La 5d, Bi 6p and Nb 4d formed a conduction band at a more positive level than Bi 6p and Nb 4d orbitals, which results in increasing the band gap. Photocatalytic activity for water splitting of Bi{sub 1.8}La{sub 0.2}AlNbO{sub 7} was about 2 times higher than that of nondoped Bi{sub 2}AlNbO{sub 7}. The increased photocatalytic activity of La-doped Bi{sub 2}AlNbO{sub 7} was discussed in relation to the band structure and the strong absorption of OH groups at the surface of the catalyst.

  20. Highly active lanthanum doped ZnO nanorods for photodegradation of metasystox.

    PubMed

    Korake, P V; Dhabbe, R S; Kadam, A N; Gaikwad, Y B; Garadkar, K M

    2014-01-01

    La-doped ZnO nanorods with different La contents were synthesized by microwave assisted method and characterized by various sophisticated techniques such as XRD, UV-Vis., EDS, XPS, SEM and TEM. The XRD patterns of the La-doped ZnO indicate hexagonal crystal structure with an average crystallite size of 30nm. It was found that the crystallite size of La-doped ZnO is much smaller as compared to pure ZnO and decreases with increasing La content. The photocatalytic activity of 0.5mol% La-doped ZnO in the degradation of metasystox was studied. It was observed that degradation efficiency of metasystox over La-doped ZnO increases up to 0.5mol% doping then decreases for higher doping levels. Among the catalyst studied, the 0.5mol% La-doped ZnO was the most active, showing high photocatalytic activity for the degradation of metasystox. The maximum reduction of concentration of metasystox was observed under static condition at pH 8. Reduction in the Chemical Oxygen Demand (COD) of metasystox was observed after 150min. The cytotoxicological studies of meristematic root tip cells of Allium cepa were studied. The results obtained indicate that photocatalytically degraded products of metasystox were less toxic as compared to metasystox. PMID:24231392

  1. The effect of induced strains on the optical band gaps in lanthanum-doped zinc ferrite nanocrystalline powders

    NASA Astrophysics Data System (ADS)

    Hamed, Fathalla; Ramachandran, Tholkappiyan; Kurapati, Vishista

    2016-07-01

    ZnFe1.96La0.04O4 nanocrystalline powders were synthesized by auto-combustion with the aid of glycine as fuel. The synthesized powders were subjected to heat treatment in air at constant temperatures (600-970∘C) for a period of 2 h. The annealed powders were characterized by X-ray diffraction (XRD), Fourier transformation infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and UV-Vis-NIR spectroscopy. The as-synthesized and annealed powders formed spongy porous network structure with voids and pores. All the powders were found to be single phase nanomaterial with cubic spinel crystal structure and the desired composition; however, they contained strains, dislocations and lattice distortions. Some of these strains and dislocations are relaxed as a function of annealing temperature. The powders displayed direct and indirect optical band gaps. The energies of these band gaps were found to vary as a function of the induced strains and dislocations. It is suggested that the energy of the optical band gap in lanthanum-doped zinc ferrite nanocrystalline powders can be varied as a function of induced strains if the initial preparation conditions and the following heat treatments are controlled.

  2. The effect of induced strains on the optical band gaps in lanthanum-doped zinc ferrite nanocrystalline powders

    NASA Astrophysics Data System (ADS)

    Hamed, Fathalla; Ramachandran, Tholkappiyan; Kurapati, Vishista

    2016-07-01

    ZnFe1.96La0.04O4 nanocrystalline powders were synthesized by auto-combustion with the aid of glycine as fuel. The synthesized powders were subjected to heat treatment in air at constant temperatures (600-970∘C) for a period of 2 h. The annealed powders were characterized by X-ray diffraction (XRD), Fourier transformation infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and UV-Vis-NIR spectroscopy. The as-synthesized and annealed powders formed spongy porous network structure with voids and pores. All the powders were found to be single phase nanomaterial with cubic spinel crystal structure and the desired composition; however, they contained strains, dislocations and lattice distortions. Some of these strains and dislocations are relaxed as a function of annealing temperature. The powders displayed direct and indirect optical band gaps. The energies of these band gaps were found to vary as a function of the induced strains and dislocations. It is suggested that the energy of the optical band gap in lanthanum-doped zinc ferrite nanocrystalline powders can be varied as a function of induced strains if the initial preparation conditions and the following heat treatments are controlled.

  3. First-principles study of Ce3 +-doped lanthanum silicate nitride phosphors: Neutral excitation, Stokes shift, and luminescent center identification

    NASA Astrophysics Data System (ADS)

    Jia, Yongchao; Miglio, Anna; Poncé, Samuel; Gonze, Xavier; Mikami, Masayoshi

    2016-04-01

    We study from first principles two lanthanum silicate nitride compounds, LaSi3N5 and La3Si6N11 , pristine as well as doped with Ce3 + ion, in view of explaining their different emission color, and characterizing the luminescent center. The electronic structures of the two undoped hosts are similar, and do not give a hint to quantitatively describe such difference. The 4 f →5 d neutral excitation of the Ce3 + ions is simulated through a constrained density functional theory method coupled with a Δ SCF analysis of total energies, yielding absorption energies. Afterwards, atomic positions in the excited state are relaxed, yielding the emission energies and Stokes shifts. Based on these results, the luminescent centers in LaSi3N5 :Ce and La3Si6N11 :Ce are identified. The agreement with the experimental data for the computed quantities is quite reasonable and explains the different color of the emitted light. Also, the Stokes shifts are obtained within 20% difference relative to experimental data.

  4. 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}

  5. Temperature dependent emission and absorption cross section of Yb3+ doped yttrium lanthanum oxide (YLO) ceramic and its application in diode pumped amplifier.

    PubMed

    Banerjee, Saumyabrata; Koerner, Joerg; Siebold, Mathias; Yang, Qiuhong; Ertel, Klaus; Mason, Paul D; Phillips, P Jonathan; Loeser, Markus; Zhang, Haojia; Lu, Shenzhou; Hein, Joachim; Schramm, Ulrich; Kaluza, Malte C; Collier, John L

    2013-07-01

    Temperature dependent absorption and emission cross-sections of 5 at% Yb(3+) doped yttrium lanthanum oxide (Yb:YLO) ceramic between 80K and 300 K are presented. In addition, we report on the first demonstration of ns pulse amplification in Yb:YLO ceramic. A pulse energy of 102 mJ was extracted from a multi-pass amplifier setup. The amplification bandwidth at room temperature confirms the potential of Yb:YLO ceramic for broad bandwidth amplification at cryogenic temperatures.

  6. Manganese-doped lanthanum calcium titanate as an interconnect for flat-tubular solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Raeis Hosseini, Niloufar; Sammes, Nigel Mark; Chung, Jong Shik

    2014-01-01

    A cost-effective screen-printing process is developed to fabricate a dense layer of solid oxide fuel cell (SOFC) interconnect material. A series of lanthanum-manganese-doped CaTiO3 perovskite oxides (La0.4Ca0.6Ti1-xMnxO3-δ; (x = 0.0, 0.2, 0.4, 0.6)) powders is successfully synthesized using an EDTA-citrate method and co-sintered as an interconnect material on an extruded porous anode substrate in a flat-tubular solid oxide fuel cell. All samples adopt a single perovskite phase after calcination at 950 °C for 5 h. High-temperature XRD confirms that the perovskite structure is thermally stable in both oxidizing and reducing conditions. The highest electrical conductivity occurs when x = 0.6; at 12.20 S cm-1 and 2.70 S cm-1 under oxidizing and reducing conditions. The thermal expansion coefficient of La0.4Ca0.6Ti0.4Mn0.6O3 is 10.76 × 10-6 K-1, which closely matches that of 8 mol% yttria-stabilized zirconia. Chemical compatibility of samples and their reduction stability are verified at the operating temperature. The power density and area-specific resistance value at x = 0.6 is 208 mW cm-1 and 1.23 Ω cm2 at 800 °C under open circuit voltage, and 200 mV signal amplitude under 3% humidified hydrogen and air respectively. This performance indicates that La0.4Ca0.6Ti0.4Mn0.6O3-δ has potential for use as interconnect in a flat tubular SOFC.

  7. Phosphate content influence on structural, spectroscopic, and lasing properties of Er,Yb-doped potassium-lanthanum phosphate glasses

    NASA Astrophysics Data System (ADS)

    Šulc, Jan; Švejkar, Richard; Jelínková, Helena; Nejezchleb, Karel; Nitsch, Karel; Cihlář, Antonín; Král, Robert; Ledinský, Martin; Fejfar, Antonn; Rodová, Miroslava; Zemenová, Petra; Nikl, Martin

    2016-04-01

    The influence of the phosphorus pentoxide (P2O5) content on the material properties of Er,Yb-doped potassium-lanthanum phosphate glass was studied. Glass samples of the following nominal composition 35.0K2O-6.8Yb2O3-8.0La2O3-0.2Er2O3-50.0P2O5 (in mol%) were prepared from starting materials mixed with five additional amounts of P2O5 (0, 7.5, 15.0, 30.0, and 45.0 mol% related to the nominal glass composition). The P2O5 addition influence on properties of prepared glasses was studied using Raman, absorption, and fluorescence spectroscopy. The glass residual IR absorption and Judd-Ofelt intensity parameters together with absorption and emission cross sections were estimated. The results showed the increasing polymerization of glass and the P-O bond shortening with P2O5 content increase. The spectroscopy of Er and Yb ions was affected only marginally by the glass composition. It was found that fluorescence decay time corresponding to upper-laser-level I increased with the decrease of P2O5 content in the glasses, which was related to increasing OH- contamination of the glass. The laser action at 1.53 μm under 975-nm pulsed laser diode pumping was successfully demonstrated. Low threshold and laser slope efficiency up to 21% in respect to absorbed pumping power were obtained.

  8. Doped Lanthanum Hafnates as Scintillating Materials for High-Energy Photon Detection

    NASA Astrophysics Data System (ADS)

    Wahid, Kareem; Pokhrel, Madhab; Mao, Yuanbing

    Recent years have seen the emergence of nanocrystalline complex oxide scintillators for use in X-ray and gamma-ray detection. In this study, we investigate the structural and optical properties of La2Hf2O7 nanoparticles doped with varying levels of Eu3+ or Ce3+ by use of X-ray diffraction, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, and optical photoluminescence. In addition, scintillation response under X-ray and gamma-ray exposure is reported. The authors thank the support from the Defense Threat Reduction Agency (DTRA) of the U.S. Department of Defense (Award #HDTRA1-10-1-0114).

  9. Dielectric relaxation and alternating current conductivity of lanthanum, gadolinium, and erbium-polyvinyl alcohol doped films.

    PubMed

    Hanafy, Taha A

    2012-08-01

    Fourier transform infrared (FTIR) spectrum dielectric constant, ε', loss tangent, tan(δ), electric modulus, M*, and ac conductivity, σ(ac), of pure polyvinyl alcohol (PVA) as well as La-, Gd-, and Er-PVA doped samples have been carried out. The dielectric properties have been studied in the temperature and frequency ranges; 300-450 K and 1 kHz-4 MHz, respectively. FTIR measurements reveal that La(3+), Gd(3+), and Er(3+) ions form complex configuration within PVA structure. Two relaxation processes, namely, ρ and α were observed in pure PVA sample. The first process is due to the interfacial or Maxwell-Wagner-Sillers polarization. The second one is related to the micro-Brownian motion of the main chains. For doped PVA samples, α-relaxation process splits into α(a) and α(c). This splitting is due to the segmental motion in the amorphous (α(a)) and crystalline (α(c)) phases of PVA matrix. Electric modulus analysis was discussed to understand the mechanism of the electrical transport process. The behavior of ac conductivity for all PVA samples indicates that the conduction mechanism is correlated barrier hopping.

  10. Development of zirconia electrolyte films on porous doped lanthanum manganite cathodes by electrophoretic deposition

    SciTech Connect

    Basu, R.N.; Randall, C.A.; Mayo, M.J.

    2000-07-01

    Electrophoretic deposition (EPD) was explored as an inexpensive route for fabricating the 8 mol% yttria stabilized zirconia electrolyte in solid oxide fuel cells (SOFCs). Normally, deposition of particulate ceramic powders onto a sintered porous surface yields a non uniform coating which, after sintering, results in porosity, surface roughness and cracking in the coating. To overcome this problem, the present study used a fugitive graphite interlayer between the porous air electrode supported (AES) cathode tube (doped-LaMnO{sub 3}) and the deposited zirconia film. By this approach, a fairly dense green coating ({approximately}60%) was obtained, which yielded a smooth surface and pore-free microstructure after sintering. Preliminary results on the effect of a fugitive interlayer on the unfired (green) and fired zirconia coatings are discussed.

  11. Synthesis and characterization of calcium and iron co-doped lanthanum silicate oxyapatites by sol-gel process for solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Cao, Xiao Guo; Jiang, San Ping; Li, Yun Yong

    2015-10-01

    Lanthanum silicate oxyapatites with and without calcium (Ca) and iron (Fe) doping, La10Si5FeO26.5 (LSFO) and La9.5Ca0.5Si5.5Fe0.5O26.5 (LCSFO), are synthesized by sol-gel process (SGP) and solid state reaction process (SSP). The phase formation, microstructure and conductivities of LSFO and LCSFO oxyapatites are characterized by X-ray diffraction (XRD), scanning electron spectroscopy (SEM) and complex impedance analysis. The morphologies of LCSFO oxyapatite nanoparticles synthesized by SGP were characterized by transmission electron microscope (TEM). The thermal and decomposition properties of the LCSFO gel were analyzed by simultaneous differential scanning calorimetry and thermal gravimetric analysis (DSC-TGA). The results show that the phase formation of LCSFO synthesized by SGP occurs at temperatures as low as 750 °C, significantly lower than ∼1500 °C required for LCSFO synthesized by SSP. Co-doping of Ca and Fe significantly improves the densification, sinterability and oxide-ion conductivity of lanthanum silicate oxyapatites. The best results were obtained on LCSFO synthesized by SGP, achieving oxide-ion conductivity of 2.08 × 10-2 S cm-1 at 800 °C, which is higher than 5.68 × 10-3 S cm-1 and 1.04 × 10-2 S cm-1 for LSFO and LCSFO synthesized by SSP, respectively, under the identical test conditions.

  12. Impact of Thermal Aging on the Microstructure Evolution and Mechanical Properties of Lanthanum-Doped Tin-Silver-Copper Lead-Free Solders

    NASA Astrophysics Data System (ADS)

    Sadiq, Muhammad; Pesci, Raphaël; Cherkaoui, Mohammed

    2013-03-01

    An extensive study is made to analyze the impact of pure lanthanum on the microstructure and mechanical properties of Sn-Ag-Cu (SAC) alloys at high temperatures. Different compositions are tested; the temperature applied for the isothermal aging is 150°C, and aging times of 10 h, 25 h, 50 h, 100 h, and 200 h are studied. Optical microscopy with cross-polarized light is used to follow the grain size, which is refined from 8 mm to 1 mm for as-cast samples and is maintained during thermal aging. Intermetallic compounds (IMCs) present inside the bulk Sn matrix affect the mechanical properties of the SAC alloys. Due to high-temperature exposure, these IMCs grow and hence their impact on mechanical properties becomes more significant. This growth is followed by scanning electron microscopy, and energy-dispersive spectroscopy is used for elemental mapping of each phase. A significant refinement in the average size of IMCs of up to 40% is identified for the as-cast samples, and the coarsening rate of these IMCs is slowed by up to 70% with no change in the interparticle spacing. Yield stress and tensile strength are determined through tensile testing at 20°C for as-cast samples and after thermal aging at 150°C for 100 h and 200 h. Both yield stress and tensile strength are increased by up to 20% by minute lanthanum doping.

  13. Variation in band gap of lanthanum chromate by transition metals doping LaCr{sub 0.9}A{sub 0.1}O{sub 3} (A:Fe/Co/Ni)

    SciTech Connect

    Naseem, Swaleha Khan, Wasi Saad, A. A. Shoeb, M. Ahmed, Hilal Naqvi, A. H.; Husain, Shahid

    2014-04-24

    Transition metal (Fe, Co, Ni) doped lanthanum chromate (LaCrO{sub 3}) nanoparticles (NPs) were prepared by gel combustion method and calcinated at 800°C. Microstructural studies were carried by XRD and SEM/EDS techniques. The results of structural characterization show the formation of all samples in single phase without any impurity. Optical properties were studied by UV- visible and photoluminescence techniques. The energy band gap was calculated and the variation was observed with the doping of transition metal ions. Photoluminescence spectra show the emission peak maxima for the pure LaCrO{sub 3} at about 315 nm. Influence of Fe, Co, Ni doping was studied and compared with pure lanthanum chromate nanoparticles.

  14. CW blue laser emission by second harmonic generation of 900-nm oscillation of Nd-doped strontium and lanthanum aluminate (ASL)

    NASA Astrophysics Data System (ADS)

    Varona, C.; Loiseau, P.; Aka, G.; Ferrand, B.; Lupei, V.

    2006-04-01

    Nd-doped strontium and lanthanum (ASL) crystals Sr 1-xLa x-yNd yMg xAl 12-xO 19 (0.05 <= x <= 0.5; y = 0.05) were grown by Czochralski pulling technique. Up to 1.67W of 900nm IR output laser power for an absorbed power of 2.53W was obtained under Ti:sapphire pumping at 792nm. Intracavity second harmonic generation experiments led to 320mW of blue laser power at 450nm with a 10mm-long BiB 3O 6 nonlinear crystal. Other nonlinear crystals were also evaluated such as LBO.

  15. Formation mechanism and characteristics of lanthanum-doped BaTiO{sub 3} powders and ceramics prepared by the sol–gel process

    SciTech Connect

    Ianculescu, Adelina Carmen; Vasilescu, Catalina Andreea; Crisan, Maria; Raileanu, Malina; Vasile, Bogdan Stefan; Calugaru, Mihai; Crisan, Dorel; Dragan, Nicolae; Curecheriu, Lavinia; Mitoseriu, Liliana

    2015-08-15

    Pure and lanthanum-doped barium titanate nanopowders described by two different formulae, as Ba{sub 1−x}La{sub x}TiO{sub 3}, for lower La concentrations (0 ≤ x ≤ 0.005) and Ba{sub 1−x}La{sub x}Ti{sub 1−x/4}O{sub 3} for higher La concentration (x = 0.025) were prepared by an alkoxide sol–gel method. Single phase compositions were obtained after annealing at 900 °C for 2 h, in air. The increase of the lanthanum content causes structural and morphological changes in the oxide powders, including the evolution of the unit cell from tetragonal toward a cubic symmetry, the particle size decrease and a higher aggregation tendency. SEM investigations of the ceramics sintered at 1300 °C for 4 h indicate significant changes of the microstructural features (strong decrease of the average grain size and increase of the intergranular porosity) with the raise of La amount. Lanthanum addition to barium titanate prepared by sol–gel induces a more significant shift of the Curie temperature toward lower values, than that one reported in literature for ceramics of similar compositions, but processed by the conventional solid state method. The compositions with smaller La amount (x ≤ 0.005) show semiconducting properties at room temperature and high relative dielectric permittivity values, while the undoped ceramics and those doped with higher La content (x = 0.025) are good dielectrics. The ceramic with x = 0.025 exhibits acceptable low losses, a very diffuse ferroelectric–paraelectric transition and Curie temperature closed to the room temperature, being thus susceptible for high tunability applications. - Highlights: • Ba{sub 1−x}La{sub x}TiO{sub 3} (x ≤ 0.005) and Ba{sub 1−x}La{sub x}Ti{sub 1−x/4}O{sub 3} (x = 0.025) were prepared by sol–gel. • Ceramics with x < 0.5 exhibit semiconductor and high dielectric properties. • Ceramic with x = 0.025 exhibits acceptable low losses and diffuse phase transition.

  16. Study of the Durability of Doped Lanthanum Manganite and Cobaltite Cathode Materials under ''Real World'' Air Exposure Atmospheres

    SciTech Connect

    Singh, Prabhakar; Mahapatra, Manoj; Ramprasad, Rampi; Minh, Nguyen; Misture, Scott

    2014-11-30

    The overall objective of the program is to develop and validate mechanisms responsible for the overall structural and chemical degradation of lanthanum manganite as well as lanthanum ferrite cobaltite based cathode when exposed to “real world” air atmosphere exposure conditions during SOFC systems operation. Of particular interest are the evaluation and analysis of degradation phenomena related to and responsible for (a) products formation and interactions with air contaminants, (b) dopant segregation and oxide exolution at free surfaces, (c) cation interdiffusion and reaction products formation at the buried interfaces, (d) interface morphology changes, lattice transformation and the development of interfacial porosity and (e) micro-cracking and delamination from the stack repeat units. Reaction processes have been studied using electrochemical and high temperature materials compatibility tests followed by structural and chemical characterization. Degradation hypothesis has been proposed and validated through further experimentation and computational simulation.

  17. Design and fabrication of lanthanum-doped tin-silver-copper lead-free solder for the next generation of microelectronics applications in severe environment

    NASA Astrophysics Data System (ADS)

    Sadiq, Muhammad

    Tin-Lead solder (Sn-Pb) has long been used in the Electronics industry. But, due to its toxic nature and environmental effects, certain restrictions are made on its use by the European Rehabilitation of Hazardous Substances (RoHS) directive, and therefore, many researchers are looking to replace it. The urgent need for removing lead from solder alloys led to the very fast introduction of lead-free solder alloys without a deep knowledge of their behavior. Therefore, an extensive knowledge and understanding of the mechanical behavior of the emerging generation of lead-free solders is required to satisfy the demands of structural reliability. Sn-Ag-Cu (SAC) solders are widely used as lead-free replacements but their coarse microstructure and formation of hard and brittle Inter-Metallic Compounds (IMCs) have limited their use in high temperature applications. Many additives are studied to refine the microstructure and improve the mechanical properties of SAC solders including iron (Fe), bismuth (Bi), antimony (Sb) and indium (In) etc. Whereas many researchers studied the impact of novel rare earth (RE) elements like lanthanum (La), cerium (Ce) and lutetium (Lu) on SAC solders. These RE elements are known as “vitamins of metals” because of their special surface active properties. They reduce the surface free energy, refine the grain size and improve the mechanical properties of many lead free solder alloys like Sn-Ag, Sn-Cu and SAC but still a systematic study is required to explore the special effects of “La” on the eutectic SAC alloys. The objective of this PhD thesis is to extend the current knowledge about lead free solders of SAC alloys towards lanthanum doping with varying environmental conditions implemented during service. This thesis is divided into six main parts.

  18. Stability of the Zhang-Rice Singlet with Doping in Lanthanum Strontium Copper Oxide Across the Superconducting Dome and Above

    NASA Astrophysics Data System (ADS)

    Brookes, N. B.; Ghiringhelli, G.; Charvet, A.-M.; Fujimori, A.; Kakeshita, T.; Eisaki, H.; Uchida, S.; Mizokawa, T.

    2015-07-01

    The spin character of the states at the top of the valence band in doped La2 -xSrxCuO4 (x =0.03 , 0.07, 0.15, 0.22, and 0.30) has been investigated using spin-polarized resonant photoemission. A clear Zhang-Rice singlet (ZRS) is observed at all doping levels. Its stability and polarization are preserved as a function of doping, suggesting that the concept of the ZRS can be used across a wide doping range and up to the metallic nonsuperconducting overdoped regime. The results are significant for theoretical models that use the ZRS approximation and for the understanding of the peculiar interplay between the ZRS and the remaining localized spins.

  19. Hydrothermal synthesis of doped lanthanum zirconate nanomaterials and the effect of V–Ge substitution on their structural, electrical and dielectric properties

    SciTech Connect

    Farid, Muhammad Asim; Asghar, Muhammad Adnan; Ashiq, Muhammad Naeem Ehsan, Muhammad Fahad; Athar, Muhammad

    2014-11-15

    Graphical abstract: Variation of dielectric constant with frequency for all the synthesized materials. - Highlights: • Hydrothermal method has been successfully employed to synthesize the zirconates. • XRD confirmed the formation of required phase. • Increased electrical resistivity makes these materials useful for microwave devices. • Dielectric parameters of zirconates decrease with increasing frequency. • Dielectric constant decreases with increasing substituents concentration. - Abstract: A hydrothermal method was successfully employed for the synthesis of a series of vanadium and germanium co-doped pyrochlore lanthanum zirconates with composition La{sub 2−x}V{sub x}Zr{sub 2−y}Ge{sub y}O{sub 7} (where x, y = 0.0, 0.25, 0.50, 0.75 and 1.0). The XRD and FTIR analyses confirmed the formation of single phase except vanadium and germanium substituted samples and the crystallite sizes are in the range of 7–31 nm for V{sup 3+}–Ge{sup 4+} substituted samples. The theoretical compositions are confirmed by the ED-XRF studies. The room temperature electrical resistivity increase with the substituents concentration which suggests that the synthesized materials can be used for microwave devices as such devices required highly resistive materials. Dielectric properties were measured in the frequency range of 6 kHz to 1 MHz. The dielectric parameters decrease with increase in frequency. The DC resistivity data is in good agreement with the dielectric data.

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

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

  1. Structure and properties of antimony-doped lanthanum molybdate La{sub 2}Mo{sub 2}O{sub 9}

    SciTech Connect

    Alekseeva, O. A. Verin, I. A.; Sorokina, N. I.; Kharitonova, E. P.; Voronkova, V. I.

    2011-05-15

    Polycrystalline samples of the composition La{sub 2}Mo{sub 2-x}Sb{sub x}O{sub 9-y}, where 0 {<=} x {<=} 0.05, were prepared by solid-phase synthesis. Single crystals of La{sub 2}Mo{sub 1.96}Sb{sub 0.04}O{sub 8.17} were obtained by spontaneous crystallization from flux. The structure of the metastable {beta}{sub ms} phase of this compound was determined at room temperature by X-ray diffraction. It was found that the La, Mo, and O1 atoms are displaced from the threefold axis on which they are located in the high-temperature {beta} phase. It was shown that molybdenum atoms in the crystal structure are partially replaced by antimony atoms, which are located on the threefold axis. In antimony-doped crystals, lanthanum atoms partially return to the site on the threefold axis and the coordination environment of molybdenum cations becomes more ordered, thus facilitating the stabilization of the cubic phase at room temperature. Calorimetric measurements (DSC) showed that the introduction of Sb as the dopant into the La{sub 2}Mo{sub 2}O{sub 9} structure leads to a decrease in the temperature of the {alpha} {yields} {beta} phase transition from 570 to 520 Degree-Sign C and to the partial suppression of this transition. The temperature behavior of the conductivity confirms the DSC data. Thus, doping with Sb contributes to the stabilization of the cubic phase at room temperature.

  2. Structural and magnetic properties of yttrium and lanthanum-doped Ni-Co and Ni-Co-Zn spinel ferrites

    NASA Astrophysics Data System (ADS)

    Stergiou, Charalampos; Litsardakis, George

    2014-11-01

    Rare earth doping of Co-rich spinel ferrites is investigated through the preparation of two groups of polycrystalline Ni-Co and Ni-Co-Zn ferrites, where Fe is partly substituted by Y and La. The characterization of the sintered ferrites by means of X-ray powder diffraction and Rietveld profile analysis, indicates the subtle expansion of the spinel unit cell and the cation redistribution in the doped ferrites in order to accommodate the incorporation of Y and La in the lattice. The impurity traces, detected only in the Ni-Co-Zn group, is ascribed to the Zn population in the tetrahedral A-sites impeding the cation transfer. Moreover, the examined microstructure of the doped Ni-Co samples comprises enlarged and more homogeneous grains, whereas grain growth is moderated in the doped Ni-Co-Zn ferrites. The discussed characteristics of the crystal and magnetic structure along with the morphological aspects define the impact of Y and La doping on the static magnetic properties of Ni-Co and Ni-Co-Zn ferrites, saturation magnetization MS and coercivity HC, which were extracted from the respective hysteresis loops.

  3. Photocatalytic degradation of Reactive Black 5 and Malachite Green with ZnO and lanthanum doped nanoparticles

    NASA Astrophysics Data System (ADS)

    Kaneva, N.; Bojinova, A.; Papazova, K.

    2016-02-01

    Here we report the preparation of ZnO particles with different concentrations of La3+ doping (0, 0.5 and 1 wt%) via sol-gel method. The nanoparticles are synthesized directly from Zn(CH3COO)2.2H2O in the presence of 1-propanol and triethylamine at 80°C. The conditions are optimized to obtain particles of uniform size, easy to isolate and purify. The nanoparticles are characterized by SEM, XRD and UV-Vis analysis. The photocatalytic properties of pure and La-doped ZnO are studied in the photobleaching of Malachite Green (MG) and Reactive Black 5 (RB5) dyes in aqueous solutions upon UV illumination. It is observed that the rate constant increases with the La loading up to 1 wt%. The doping helps to achieve complete mineralization of MG within a short irradiation time. 1 wt% La-doped ZnO nanoparticles show highest photocatalytic activity. The La3+ doped ZnO particles degrade faster RB5 than MG. The reason is weaker N=N bond in comparison with the C-C bond between the central carbon atom and N,N-dimethylaminobenzyl in MG. The as-prepared ZnO particles can find practical application in photocatalytic purification of textile wastewaters.

  4. Structural and magnetic properties of yttrium and lanthanum-doped Ni-Co and Ni-Co-Zn spinel ferrites

    SciTech Connect

    Stergiou, Charalampos; Litsardakis, George

    2014-11-05

    Rare earth doping of Co-rich spinel ferrites is investigated through the preparation of two groups of polycrystalline Ni-Co and Ni-Co-Zn ferrites, where Fe is partly substituted by Y and La. The characterization of the sintered ferrites by means of X-ray powder diffraction and Rietveld profile analysis, indicates the subtle expansion of the spinel unit cell and the cation redistribution in the doped ferrites in order to accommodate the incorporation of Y and La in the lattice. The impurity traces, detected only in the Ni-Co-Zn group, is ascribed to the Zn population in the tetrahedral A-sites impeding the cation transfer. Moreover, the examined microstructure of the doped Ni-Co samples comprises enlarged and more homogeneous grains, whereas grain growth is moderated in the doped Ni-Co-Zn ferrites. The discussed characteristics of the crystal and magnetic structure along with the morphological aspects define the impact of Y and La doping on the static magnetic properties of Ni-Co and Ni-Co-Zn ferrites, saturation magnetization MS and coercivity HC, which were extracted from the respective hysteresis loops.

  5. Scanning tunneling microscopy studies of an electron-doped high-Tc superconductor, praseodymium lanthanum cerium copper oxide

    NASA Astrophysics Data System (ADS)

    Kunwar, Shankar

    It has been more than two decades since the first high temperature superconductor was discovered. In this time there has been tremendous progress in understanding these materials both theoretically and experimentally. Some important questions however remain to be answered; one of them is the temperature dependence of the superconducting gap which is in turn tied to question of the origin of the pseudogap and its connection with superconductivity. In this thesis, we present detailed Scanning Tunneling Microscopy (STM) spectroscopic studies of an electron doped superconductor, Pr0.88LaCe 0.12CuO4-delta (PLCCO). The electron doped compounds form an interesting venue for STM studies for many reasons. In the hole-doped materials, especially in the underdoped side of the phase diagram, there is mounting evidence of a second gap that survives to high temperatures (high temperature pseudogap) that may have a different origin from superconductivity. This complicates studies of the temperature dependence of the superconducting gap in these materials. In PLCCO however, there is little evidence for a high temperature pseudogap potentially allowing us to address the question of the temperature evolution of the superconducting gap without the complication of a second gap. Secondly, the low Tc of the optimally doped materials makes it easily accessible to temperature dependent STM studies. Finally, while hole-doped materials have been extensively studied by scanning tunneling microscopy (STM), there have been no detailed STM spectroscopic studies on the electron doped compounds. In the first part of the thesis, we investigate the effect of temperature on the superconducting gap of optimally doped PLCCO with Tc = 24K. STM spectroscopy data is analyzed to obtain the gap as a function of temperature from 5K to 35K. The gap is parameterized with a d-wave form and the STM spectra are fit at each temperature to extract the gap value. A plot of this gap value as a function of

  6. Novel Au/La-SrTiO3 microspheres: superimposed effect of gold nanoparticles and lanthanum doping in photocatalysis.

    PubMed

    Wang, Guannan; Wang, Pei; Luo, He-Kuan; Hor, T S Andy

    2014-07-01

    Novel multielement Au/La-SrTiO(3) microspheres were synthesized by a solvothermal method using monodisperse gold and La-SrTiO(3) nanocrystals as building blocks. The porous Au/La-SrTiO(3) microspheres had a large surface area of 94.6 m(2)  g(-1). The stable confined Au nanoparticles demonstrated strong surface plasmon resonance effect, leading to enhanced absorption in a broad UV/Vis/NIR range. Doping of rare-earth metal La also broadened the absorption band to the visible region. Both the conduction and valence bands of Au/La-SrTiO(3) microspheres thus show favorable potential for proton reduction under visible light. The superimposed effect of Au nanoparticles and La doping in Au/La-SrTiO(3) microspheres led to high photocurrent density in photoelectrochemical water splitting and good photocatalytic activity in photodegradation of rhodamine B. The photocatalytic activities are in the order of the following: Au/La-SrTiO(3) microspheres>Au/SrTiO(3) microspheres>La-SrTiO(3) microspheres>SrTiO(3) microspheres.

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

    NASA Astrophysics Data System (ADS)

    Chien, Teyu; Liu, Jian; Yost, Andrew J.; Chakhalian, Jak; Freeland, John W.; Guisinger, Nathan P.

    2016-01-01

    The interactions between electric field and the mechanical properties of materials are important for the applications of microelectromechanical and nanoelectromechanical systems, but relatively unexplored for nanoscale materials. Here, we observe an apparent correlation between the change of the fractured topography of Nb-doped SrTiO3 (Nb:STO) within the presence of a built-in electric field resulting from the Schottky contact at the interface of a metallic LaNiO3 thin film utilizing cross-sectional scanning tunneling microscopy and spectroscopy. The change of the inter-atomic bond length mechanism is argued to be the most plausible origin. This picture is supported by the strong-electric-field-dependent permittivity in STO and the existence of the dielectric dead layer at the interfaces of STO with metallic films. These results provided direct evidence and a possible mechanism for the interplay between the electric field and the mechanical properties on the nanoscale for perovskite materials.

  8. Field effect and magnetically induced capacitive tuning in hole doped lanthanum(1-x) strontium(x) manganese oxide

    NASA Astrophysics Data System (ADS)

    Marton, Zsolt

    Electrostatic modulation of interface conduction between semiconductors and insulating oxides is the foundation of semiconductor technology. This field effect concept can be applied on complex oxides, such as high temperature superconductors and colossal magnetoresistive manganites, in order to create new electronic and magnetic phases. Competition and coexistence of multiple nanoscale phases make them exciting to study around phase transitions. This study on hole doped La1-xSrxMnO3 systems has a two-fold purpose. One is the demonstration of the field effect on La1-xSr xMnO3 (x = 0.125, 0.2, 0.3, 0.5) thin films. It is an important step towards electrostatic control of material properties, however, a challenging task because of their charge carrier densities of 0.01-1 hole/unit cell, a few orders of magnitude larger than in doped semiconductors. Control by linear dielectrics needs huge, constantly applied bias. Energy efficient tuning with low voltages requires highly polar ferroelectric. Pb(Zr0.2Ti 0.8)O3 was chosen, whose remanence provides 0.5 charge carrier/unit cell on the manganite/ferroelectric interface. La1-xSrxMnO 3/Pb(Zr0.2Ti0.8)O3 heterostructures were synthesized by pulsed laser epitaxy and remarkable conduction modifications were observed in the La1-xSrxMnO3. This can be a strong foundation of a new tool to research electronic oxides. The second purpose of this work is to utilize the phase separation in manganites. There has been extensive research on multiferroic materials, in which dielectric and magnetic responses are controlled by magnetic and electric field, respectively. In order to demonstrate magnetically tuned capacitance, insulating La7/8Sr1/8MnO3 was studied. Drastic capacitance change in magnetic field was shown through a phase transitions and explained in the framework of electronic phase separation. It makes this material eligible for high frequency magnetoelectric applications. Modulating charge carriers, mobility and magnetism in

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

    PubMed Central

    Chien, TeYu; Liu, Jian; Yost, Andrew J.; Chakhalian, Jak; Freeland, John W.; Guisinger, Nathan P.

    2016-01-01

    The interactions between electric field and the mechanical properties of materials are important for the applications of microelectromechanical and nanoelectromechanical systems, but relatively unexplored for nanoscale materials. Here, we observe an apparent correlation between the change of the fractured topography of Nb-doped SrTiO3 (Nb:STO) within the presence of a built-in electric field resulting from the Schottky contact at the interface of a metallic LaNiO3 thin film utilizing cross-sectional scanning tunneling microscopy and spectroscopy. The change of the inter-atomic bond length mechanism is argued to be the most plausible origin. This picture is supported by the strong-electric-field-dependent permittivity in STO and the existence of the dielectric dead layer at the interfaces of STO with metallic films. These results provided direct evidence and a possible mechanism for the interplay between the electric field and the mechanical properties on the nanoscale for perovskite materials. PMID:26743875

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

    PubMed

    Chien, TeYu; Liu, Jian; Yost, Andrew J; Chakhalian, Jak; Freeland, John W; Guisinger, Nathan P

    2016-01-01

    The interactions between electric field and the mechanical properties of materials are important for the applications of microelectromechanical and nanoelectromechanical systems, but relatively unexplored for nanoscale materials. Here, we observe an apparent correlation between the change of the fractured topography of Nb-doped SrTiO3 (Nb:STO) within the presence of a built-in electric field resulting from the Schottky contact at the interface of a metallic LaNiO3 thin film utilizing cross-sectional scanning tunneling microscopy and spectroscopy. The change of the inter-atomic bond length mechanism is argued to be the most plausible origin. This picture is supported by the strong-electric-field-dependent permittivity in STO and the existence of the dielectric dead layer at the interfaces of STO with metallic films. These results provided direct evidence and a possible mechanism for the interplay between the electric field and the mechanical properties on the nanoscale for perovskite materials. PMID:26743875

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

    DOE PAGES

    Chien, TeYu; Liu, Jian; Yost, Andrew J.; Chakhalian, Jak; Freeland, John W.; Guisinger, Nathan P.

    2016-01-08

    The interactions between electric field and the mechanical properties of materials are important for the applications of microelectromechanical and nanoelectromechanical systems, but relatively unexplored for nanoscale materials. Here, we observe an apparent correlation between the change of the fractured topography of Nb-doped SrTiO3 (Nb:STO) within the presence of a built-in electric field resulting from the Schottky contact at the interface of a metallic LaNiO3 thin film utilizing cross-sectional scanning tunneling microscopy and spectroscopy. The change of the inter-atomic bond length mechanism is argued to be the most plausible origin. This picture is supported by the strong-electric-field-dependent permittivity in STO andmore » the existence of the dielectric dead layer at the interfaces of STO with metallic films. Finally, these results provided direct evidence and a possible mechanism for the interplay between the electric field and the mechanical properties on the nanoscale for perovskite materials.« less

  12. Ferrochromium from Domestic Lateritic Chromites

    NASA Astrophysics Data System (ADS)

    Nafziger, R. H.

    1988-09-01

    As part of its effort to devise suitable technology for processing low-grade domestic materials and recycling wastes, the U.S. Bureau of Mines has evaluated the feasibility of smelting a chromite concentrate derived from residues generated by the processing of nickel and cobalt from domestic later-ites. The product sought was a high-carbon ferrochromium suitable for stainless- and alloy-steel production. The concentrate was blended with re-ductants and fluxing constituents and was smelted under submerged arc conditions in a laboratory-scale, single-phase ac electric arc furnace. The results revealed that metallurgical-grade coke provides the best quality product. High-carbon ferrochromium, which met ASTM specifications except for phosphorus and sulfur, was obtained. Agglomeration of the charge materials was not required.

  13. Effect of sintering time on structural, microstructural and chemical composition of Ni-doped lanthanum gallate perovskites

    SciTech Connect

    Colomer, M.T.

    2015-08-15

    This work reports the effect of two different sintering times, 6 and 48 h on the structural, microstructural, and chemical features of Ni-doped La{sub 0.90}Sr{sub 0.10}GaO{sub 3.00−δ}. Independently of the sintering time, La{sub 0.90}Sr{sub 0.10}Ga{sub 1−x}Ni{sub x}O{sub 3.00−δ} (where x=0.10, and 0.20 (mol)) presents a rhombohedral symmetry with a lattice volume that decreases when NiO dopant increases. Besides the perovskite, LaSrGa{sub 3.00}O{sub 7.00} (nominal composition) is present as second phase in all cases. When the samples are doped with NiO, the peaks of this second phase are shifted with respect to the peaks of the pure phase. These shifts suggest that this second phase could admit some Ni ions in its structure. According to the XRD patterns, the amount of the latter phase is larger when sintering time is increased. Electron probe microanalysis (EPMA) indicated that the matrix of the samples sintered for 6 h is constituted by a perovskite with an experimental composition very close to the nominal one. However, when the samples are sintered for 48 h the matrix of each sample is constituted by two perovskites; both with compositional deviations with respect to their nominal one. In particular, a significant Sr depletion compensated by a La increment in the A site is observed. Those compositional deviations could be mainly due to the diffusion of the cations in the bulk and/or from the bulk to the surface of the samples. That diffusion can favour the formation, not only, of a second perovskite with a different composition in relation with the first one formed, but also, the formation of second phases. In addition, a very slight broadening of Bragg peaks of the perovskites sintered for 48 h is observed by XRD and can be related to the presence of two different perovskites in each sample according to EPMA results. By BSEM and EPMA analyses La{sub 4.00}Ga{sub 2.00}O{sub 9.00} (nominal composition) is also observed as second phase when samples are

  14. Crystal structure and ionic conductivity of Mg-doped apatite-type lanthanum silicates La10Si6-xMgxO27-x (x = 0-0.4)

    NASA Astrophysics Data System (ADS)

    Yin, Guang-Chao; Yin, Hong; Zhong, Lin-Hong; Sun, Mei-Ling; Zhang, Jun-Kai; Xie, Xiao-Jun; Cong, Ri-Dong; Wang, Xin; Gao, Wei; Cui, Qi-Liang

    2014-04-01

    Lanthanum silicates La10Si6-xMgxO27-x (x = 0-0.4) were prepared by solid state synthesis to investigate the effect of Mg doping on crystal structure and ionic conductivity. Rietveld analysis of the powder XRD patterns reveals that Mg substitution on Si site results in significant enlargement of channel triangles, favoring oxide-ion conduction. Furthermore, an increase of Mg concentration significantly influences the linear density of interstitial oxygen, which plays an important role in ionic conductivity. The Arrhenius plots of La10Si6-xMgxO27-x (x = 0-0.4) suggest that Mg-doped samples present higher conductivity and lower activation energy than non-doped La10Si6O27, and La10Si5.8Mg0.2O26.8 exhibits the highest conductivity with a value of 3.0×10-2 S ·cm-1 at 700 °C. Such conductive behavior agrees well with the refined results. The corresponding mechanism has been discussed in this paper.

  15. Effects of rapid thermal annealing on structural, chemical, and electrical characteristics of atomic-layer deposited lanthanum doped zirconium dioxide thin film on 4H-SiC substrate

    NASA Astrophysics Data System (ADS)

    Lim, Way Foong; Quah, Hock Jin; Lu, Qifeng; Mu, Yifei; Ismail, Wan Azli Wan; Rahim, Bazura Abdul; Esa, Siti Rahmah; Kee, Yeh Yee; Zhao, Ce Zhou; Hassan, Zainuriah; Cheong, Kuan Yew

    2016-03-01

    Effects of rapid thermal annealing at different temperatures (700-900 °C) on structural, chemical, and electrical characteristics of lanthanum (La) doped zirconium oxide (ZrO2) atomic layer deposited on 4H-SiC substrates have been investigated. Chemical composition depth profiling analysis using X-ray photoelectron spectroscopy (XPS) and cross-sectional studies using high resolution transmission electron microscopy equipped with energy dispersive X-ray spectroscopy line scan analysis were insufficient to justify the presence of La in the investigated samples. The minute amount of La present in the bulk oxide was confirmed by chemical depth profiles of time-of-flight secondary ion mass spectrometry. The presence of La in the ZrO2 lattice led to the formation of oxygen vacancies, which was revealed through binding energy shift for XPS O 1s core level spectra of Zrsbnd O. The highest amount of oxygen vacancies in the sample annealed at 700 °C has yielded the acquisition of the highest electric breakdown field (∼ 6.3 MV/cm) and dielectric constant value (k = 23) as well as the highest current-time (I-t) sensor response towards oxygen gas. The attainment of both the insulating and catalytic properties in the La doped ZrO2 signified the potential of the doped ZrO2 as a metal reactive oxide on 4H-SiC substrate.

  16. Nitride tuning of lanthanide chromites.

    PubMed

    Black, Ashley P; Johnston, Hannah E; Oró-Solé, Judith; Bozzo, Bernat; Ritter, Clemens; Frontera, Carlos; Attfield, J Paul; Fuertes, Amparo

    2016-03-21

    LnCrO(3-x)N(x) perovskites with Ln = La, Pr and Nd and nitrogen contents up to x = 0.59 have been synthesised through ammonolysis of LnCrO4 precursors. These new materials represent one of the few examples of chromium oxynitrides. Hole-doping through O(2-)/N(3-) anion substitution suppresses the magnetic transition far less drastically than Ln(3+)/M(2+) (M = Ca, Sr) cation substitutions because of the greater covalency of metal-nitride bonds. Hence, nitride-doping is a more benign method for doping metal oxides without suppressing electronic transitions. PMID:26916315

  17. 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.

  18. Podiform chromite deposits--database and grade and tonnage models

    USGS Publications Warehouse

    Mosier, Dan L.; Singer, Donald A.; Moring, Barry C.; Galloway, John P.

    2012-01-01

    Chromite ((Mg, Fe++)(Cr, Al, Fe+++)2O4) is the only source for the metallic element chromium, which is used in the metallurgical, chemical, and refractory industries. Podiform chromite deposits are small magmatic chromite bodies formed in the ultramafic section of an ophiolite complex in the oceanic crust. These deposits have been found in midoceanic ridge, off-ridge, and suprasubduction tectonic settings. Most podiform chromite deposits are found in dunite or peridotite near the contact of the cumulate and tectonite zones in ophiolites. We have identified 1,124 individual podiform chromite deposits, based on a 100-meter spatial rule, and have compiled them in a database. Of these, 619 deposits have been used to create three new grade and tonnage models for podiform chromite deposits. The major podiform chromite model has a median tonnage of 11,000 metric tons and a mean grade of 45 percent Cr2O3. The minor podiform chromite model has a median tonnage of 100 metric tons and a mean grade of 43 percent Cr2O3. The banded podiform chromite model has a median tonnage of 650 metric tons and a mean grade of 42 percent Cr2O3. Observed frequency distributions are also given for grades of rhodium, iridium, ruthenium, palladium, and platinum. In resource assessment applications, both major and minor podiform chromite models may be used for any ophiolite complex regardless of its tectonic setting or ophiolite zone. Expected sizes of undiscovered podiform chromite deposits, with respect to degree of deformation or ore-forming process, may determine which model is appropriate. The banded podiform chromite model may be applicable for ophiolites in both suprasubduction and midoceanic ridge settings.

  19. Lanthanum-Induced Gastrointestinal Histiocytosis

    PubMed Central

    Araya, Hiwot; Longacre, Teri A.; Pasricha, Pankaj J.

    2015-01-01

    A patient with end-stage renal disease (ESRD) on hemodialysis presented with fever, anorexia, and nausea shortly after starting oral lanthanum carbonate for phosphate control. Gastric and duodenal biopsies demonstrated diffuse histiocytosis with intracellular aggregates of basophilic foreign material. Transmission electron microscopy, an underutilized diagnostic test, revealed the nature of the aggregates as heavy metal particles, consistent with lanthanum. Symptoms and histiocytosis improved after discontinuation of lanthanum. Lanthanum may be an underdiagnosed cause of gastrointestinal histiocytosis. PMID:26157959

  20. Pneumoconiosis in Chromite Miners in South Africa1

    PubMed Central

    Sluis-Cremer, G. K.; Du Toit, R. S. J.

    1968-01-01

    Ten chromite miners in South Africa have been found to show radiological evidence of a fine nodulation; five of these miners had worked only in chromite mines. These cases occurred in a labour force of some 1,500 persons subjected to regular examination. Clinical evidence and the results of intratracheal injection of chromite suspension into rats indicate that the radiological changes are due not to fibrosis but to a benign deposition of chromite (Cr2O3FeO) dust in the lungs. Images PMID:5642648

  1. Chromite from the Blue Ridge province of North Carolina.

    USGS Publications Warehouse

    Lipin, B.R.

    1984-01-01

    Chromite is found as ubiquitous accessory grains and occasional segregations within dunite bodies. Results of analysis of chromite textures and chemistry and estimation of equilibration T of olivine-chromite pairs are cited as evidence that the dunites are metamorphic rocks rather than primary mantle peridotites. They are considered to be disrupted fragments of ophiolites that were emplaced before or during the peak of Ordovician metamorphism which was responsible for dehydration of serpentine-bearing rocks and alteration of chromite compositions and textures.-M.S.

  2. Tunable quasi-cw two-micron lasing in diode-pumped crystals of mixed Tm{sup 3+}-doped sodium - lanthanum - gadolinium molybdates and tungstates

    SciTech Connect

    Bol'shchikov, F A; Ryabochkina, P A; Zharikov, Evgeny V; Lis, Denis A; Subbotin, Kirill A; Zakharov, N G; Antipov, Oleg L

    2010-12-09

    Two-micron lasing is obtained for the first time on the {sup 3}F{sub 4} {yields} {sup 3}H{sub 6} transition of Tm{sup 3+} ions in diode-pumped crystals of mixed sodium - lanthanum - gadolinium tungstate Tm:NaLa{sub 1/2}Gd{sub 1/2}(WO{sub 4}){sub 2} (C{sub Tm} = 3.6 at %) (3.6Tm : NLGW) and molybdate Tm:NaLa{sub 1/3}Gd{sub 2/3}(MoO{sub 4}){sub 2} (C{sub Tm} = 4.8 at %) (4.8Tm : NLGM). For the 3.6Tm : NLGW crystal, the quasi-cw laser output power exceeded 200 mW and the slope efficiency (with respect to absorbed pump power) for the {pi}- and {sigma}-polarisations at wavelengths of 1908 and 1918 nm was 34% and 30%, respectively. The laser wavelength of this crystal was continuously tuned within the spectral range of 1860 - 1935 nm. For the 4.8Tm : NLGM crystal, the slope efficiency for the {pi}- and {sigma}-polarisations at wavelengths of 1910 and 1918 nm was 27% and 23%, respectively, and the laser wavelength was tunable within the spectral range of 1870 - 1950 nm. (lasers)

  3. 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.

  4. ZIRCONIA-BASED MIXED POTENTIAL CARBON MONOXIDE/HYDROCARBON SENSORS WITH LANTHANUM MAGNESIUM OXIDE, AND TERBIUM-DOPED YTTRIUM STABILIZED ZIRCONIA ELECTRODES

    SciTech Connect

    E. L. BROSHA; R. MUKUNDAN; ET AL

    2000-10-01

    We have investigated the performance of dual metal oxide electrode mixed potential sensors in an engine-out, dynamometer environment. Sensors were fabricated by sputtering thin films of LaMnO{sub 3} and Tb-doped YSZ onto YSZ electrolyte. Au gauze held onto the metal oxide thin films with Au ink was used for current collection. The exhaust gas from a 4.8L, V8 engine operated in open loop, steady-state mode around stoichiometry at 1500 RPM and 50 Nm. The sensor showed a stable EMF response (with no hysteresis) to varying concentrations of total exhaust gas HC content. The sensor response was measured at 620 and 670 C and shows temperature behavior characteristic of mixed potential-type sensors. The results of these engine-dynamometer tests are encouraging; however, the limitations associated with Au current collection present the biggest impediment to automotive use.

  5. High temperature mechanical properties of calendar-rolled lanthanum chromite interconnect material

    SciTech Connect

    Sammes, N.M.; Ratnaraj, R.; Hatchwell, C.E.

    1995-12-31

    La{sub 1{minus}x}Sr{sub x}Cr{sub 1{minus}y}Co{sub y}O{sub 3} was fabricated using a calendar rolling technique. The green tapes were cut into bars and fired under various heating and cooling regimes. The high temperature mechanical properties of the material were then investigated as a function of the fabrication conditions employed. It was observed, for example, that the modulus of rupture of calendar-rolled La{sub 0.7}Sr{sub 0.3}Cr{sub 0.9}Co{sub 0.1}O{sub 3}, 95MPa at 1,000 C, was similar to the dry pressed sample which gave a value of 105MPa at 1,000 C. This paper will describe the significance of this result, and other results, in relation to the stacked planar SOFC system.

  6. Oxidation and electrical behavior of nickel/lanthanum chromite-coated stainless steel interconnects

    NASA Astrophysics Data System (ADS)

    Shaigan, Nima; Ivey, Douglas G.; Chen, Weixing

    Solving the contact resistance and cathode-chromium-poisoning problems associated with the application of ferritic stainless steel as solid oxide fuel cell interconnects is the objective of numerous current research efforts. In this work, the application of electrodeposited Ni/LaCrO 3 composites for AISI 430 stainless steel as protective/conductive coatings has been studied, with emphasis on the oxidation behavior, scale structure and electronic conductivity of these coatings. The oxidation tests were performed at 800 °C in air for up to 2040 h. The results showed that the scale is a double layer consisting of a particle filled chromia-rich subscale and an outer Ni/Fe-rich spinel together with NiO. The addition of LaCrO 3 particles greatly enhances the high-temperature oxidation resistance of Ni-coated ferritic stainless steel. Cavities, which form beneath the scale for uncoated steels as a result of cation outward diffusion, reduce the actual contact area between the scale and the alloy resulting in a high area specific resistance (ASR) as well as scale spallation. Excellent, stable ASR (0.005 Ω cm 2 after 400 h) was achieved with the application of Ni/LaCrO 3 coatings.

  7. Fluid-present deformation aids chemical modification of chromite: Insights from chromites from Golyamo Kamenyane, SE Bulgaria

    NASA Astrophysics Data System (ADS)

    Satsukawa, Takako; Piazolo, Sandra; González-Jiménez, José María; Colás, Vanessa; Griffin, William L.; O'Reilly, Suzanne Y.; Gervilla, Fernando; Fanlo, Isabel; Kerestedjian, Thomas N.

    2015-07-01

    Chemical signatures of chromitites are commonly used to track the evolution of the Earth's mantle. However, chemical modification during deformation may have important implications for the interpretation of chromites' signatures. Here, we describe the details of how deformation promotes chemical modification in chromite. Physicochemical characteristics of the chromites were quantified by measuring crystallographic orientation relationships using Electron Back-Scattered Diffraction (EBSD) and electron microprobe analysis (EMP). Chromites show porphyroclastic textures with coarse-grained porphyroclasts (ca. 0.2-5 mm) and fine-grained neoblasts (< 200 μm). Coarse-grained chromites are chemically zoned in terms of major elements from core to rim, preserving this initial igneous feature in the cores, while the outer rims reveal a metamorphic signature. Large chromite grains are characterized by local crystal-plastic deformation, exhibiting distinct inter-crystalline deformation including continuous crystal bending and subgrain boundaries as well as chemical modification in their outer, deformed parts. Two types of fine-grained chromite, F1 and F2, are present. While F1 exhibits a well-developed polygonal texture, straight grain boundaries and low intercrystal misorientation (< 1°), F2 shows low-angle boundaries and significant intercrystalline misorientation (2-8°). Both F1 and F2 have higher Fe3 + and Cr and lower Mg# values than the cores of large grains. We interpret F1 and F2 to represent chromite recrystallized by heterogeneous nucleation and subgrain rotation recrystallization, respectively. Crystallographic preferred orientation (CPO) and misorientation data on the well-developed low-angle (subgrain) boundaries in coarse grains and F2 grains indicate that deformation in chromite was accommodated mainly by dislocation creep with the dominant activation of the {111}<100 > slip system. The retrograde P-T exhumation path predicted by thermodynamic and chemical

  8. Tunable band gap of iron-doped lanthanum-modified bismuth titanate synthesized by using the thermal decomposition of a secondary phase

    NASA Astrophysics Data System (ADS)

    Han, Jun Young; Bark, Chung Wung

    2015-05-01

    The photoelectric properties of complex oxides have prompted interest in materials with a tunable band gap because of the absorption. The substitution of iron atoms in La-modified bismuth titanate (BLT) can lead to dramatic improvements in the band gap; however, the substitution of iron atoms while maintaining the original bismuth layer structure without forming a BiFeO3 secondary phase is quite challenging. Therefore, a series of Fe-doped BLT (Fe-BLT) samples were synthesized using a solid reaction at various calcination temperatures (300 ˜ 900°C) to remove the secondary phase. The structural and the optical properties were analyzed by using X-ray diffraction and ultraviolet-visible absorption spectroscopy. This paper reports a new route by using high-temperature calcination, to synthesize the Aurivillius phase with a reduced optical band gap due to the thermal decomposition of BiFeO3 during high-temperature calcination. This simple route to reduce the second phase can be adapted to other complex oxides for use in emerging oxide optoelectronic devices.

  9. Encephalopathy caused by lanthanum carbonate

    PubMed Central

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

    2011-01-01

    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. PMID:25984155

  10. Functionally graded doped lanthanum cobalt ferrite and ceria-based composite interlayers for advancing the performance stability in solid oxide fuel cell

    NASA Astrophysics Data System (ADS)

    Ghosh, Koyel Banerjee; Mukhopadhyay, Jayanta; Basu, Rajendra N.

    2016-10-01

    Functionally graded composite interlayer based on 50% of La0.54Sr0.4Co0.2Fe0.8O3-δ and 50% of La0.54Sr0.4Fe0.2Co0.8O3-δ (CF-1) and cobalt and gadolinium doped ceria (CoCGO) is synthesized varying the mass ratio as CF-1:CoCGO = 80:20(L80-C20), 50:50(L50-C50) and 20:80(L20-C80). Detail study using impedance spectroscopy of symmetrical cell fabricated with CoCGO as electrolyte reveals the lowest electrode polarization 0.04 Ω cm2 at 800 °C for L80-C20 composite. Electrode and ohmic polarization is also evaluated configuring the symmetric cell as CF-1/L80-C20||CoCGO||L80-C20/CF-1. Symmetric cell with varying composition of the composite interlayer (L80-C20/L50-C50/L20-C80||CoCGO||L20-C80/L50-C50/L80-C20) shows considerably low electrode polarization of 0.067 Ω cm2 at 800 °C with activation energy 1.19 eV. Electrochemical performances evaluated using single cell configuration Ni-YSZ||YSZ||CoCGO/L20-C80/L50-C50/L80-C20/CF-1 shows power density as high as 2.03 W cm-2 at 800 °C at 0.7 V. Addition of composite interlayers increases the stability significantly and the voltage degradation is found negligible (0.9%) for first 300 h at a constant load of 0.5 A cm-2 which is further increased to 2.9% for next 300 h. The cell stability is clinically correlated with layer wise elemental 'Sr' mapping in the applied quad interlayers.

  11. Occupational health assessment of chromite toxicity among Indian miners

    PubMed Central

    Das, Alok Prasad; Singh, Shikha

    2011-01-01

    Elevated concentration of hexavalent chromium pollution and contamination has contributed a major health hazard affecting more than 2 lakh mine workers and inhabitants residing in the Sukinda chromite mine of Odisha, India. Despite people suffering from several forms of ill health, physical and mental deformities, constant exposure to toxic wastes and chronic diseases as a result of chromite mining, there is a tragic gap in the availability of 'scientific’ studies and data on the health hazards of mining in India. Occupational Safety and Health Administration, Odisha State Pollution Control Board and the Odisha Voluntary Health Association data were used to compile the possible occupational health hazards, hexavalent chromium exposure and diseases among Sukinda chromite mines workers. Studies were reviewed to determine the routes of exposure and possible mechanism of chromium induced carcinogenicity among the workers. Our studies suggest all forms of hexavalent chromium are regarded as carcinogenic to workers however the most important routes of occupational exposure to Cr (VI) are inhalation and dermal contact. This review article outlines the physical, chemical, biological and psychosocial occupational health hazards of chromite mining and associated metallurgical processes to monitor the mining environment as well as the miners exposed to these toxicants to foster a safe work environment. The authors anticipate that the outcome of this manuscript will have an impact on Indian chromite mining industry that will subsequently bring about improvements in work conditions, develop intervention experiments in occupational health and safety programs. PMID:21808494

  12. 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.

  13. SOFC chromite sintering and electrolyte/air-electrode interface reactions

    SciTech Connect

    Bates, J.L.; Chick, L.A.; Youngblood, G.E.

    1992-04-01

    Air sintering of chromites was investigated in La(Sr)CrO[sub 3], La(Ca)CrO[sub 3], and Y(Ca)CrO[sub 3]. Effects of alkaline earth dopant level and chromium enrichment/depletion on chromite sintered densities and microstructures are discussed. Ac impedance spectroscopy and dc polarization coupled with an unbonded interface cell were used to examine SOFC (solid oxide fuel cells) electrochemical reactions at solid-solid-gas interfaces, particularly for La[sub 1-x]Sr[sub x]MnO[sub 3]. 5 refs.

  14. SOFC chromite sintering and electrolyte/air-electrode interface reactions

    SciTech Connect

    Bates, J.L.; Chick, L.A.; Youngblood, G.E.

    1992-04-01

    Air sintering of chromites was investigated in La(Sr)CrO{sub 3}, La(Ca)CrO{sub 3}, and Y(Ca)CrO{sub 3}. Effects of alkaline earth dopant level and chromium enrichment/depletion on chromite sintered densities and microstructures are discussed. Ac impedance spectroscopy and dc polarization coupled with an unbonded interface cell were used to examine SOFC (solid oxide fuel cells) electrochemical reactions at solid-solid-gas interfaces, particularly for La{sub 1-x}Sr{sub x}MnO{sub 3}. 5 refs.

  15. SEM, optical, and Moessbauer studies of submicrometer chromite in Allende

    NASA Technical Reports Server (NTRS)

    Housley, R. M.

    1982-01-01

    New scanning electron and optical microscope results are presented showing that sub-micrometer chromite is abundant along healed cracks and grain boundaries in Allende chondrule olivine. Some wider healed cracks also contain pentlandite and euhedral Ni3Fe grains. Also reported are Moessbauer measurements on Allende HF-HCl residues confirming a high Fe(+++)/Fe(++) ratio.

  16. Chlorination of lanthanum oxide.

    PubMed

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

    2012-03-01

    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.

  17. Chlorination of lanthanum oxide.

    PubMed

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

    2012-03-01

    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. PMID:22280490

  18. 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.

  19. 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.

  20. Ames Lab 101: Lanthanum Decanting

    SciTech Connect

    Riedemann, Trevor

    2010-01-01

    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.

  1. Conditional estimates of the number of podiform chromite deposits

    USGS Publications Warehouse

    Singer, D.A.

    1994-01-01

    A desirable guide for estimating the number of undiscovered mineral deposits is the number of known deposits per unit area from another well-explored permissive terrain. An analysis of the distribution of 805 podiform chromite deposits among ultramafic rocks in 12 subareas of Oregon and 27 counties of California is used to examine and extend this guide. The average number of deposits in this sample of 39 areas is 0.225 deposits per km2 of ultramafic rock; the frequency distribution is significantly skewed to the right. Probabilistic estimates can be made by using the observation that the lognormal distribution fits the distribution of deposits per unit area. A further improvement in the estimates is available by using the relationship between the area of ultramafic rock and the number of deposits. The number (N) of exposed podiform chromite deposits can be estimated by the following relationship: log10(N)=-0.194+0.577 log10(area of ultramafic rock). The slope is significantly different from both 0.0 and 1.0. Because the slope is less than 1.0, the ratio of deposits to area of permissive rock is a biased estimator when the area of ultramafic rock is different from the median 93 km2. Unbiased estimates of the number of podiform chromite deposits can be made with the regression equation and 80 percent confidence limits presented herein. ?? 1994 Oxford University Press.

  2. Chromite deposits of the north-central Zambales Range, Luzon, Philippines

    USGS Publications Warehouse

    Rossman, D.L.

    1970-01-01

    Peridotite and gabbro form an intrusive complex which is exposed over an area about 35 km wide and 150 km long in the center of the Zambales Range of western Luzon. The Zambales Complex is remarkable for its total known resources, mined and still remaining, of about 15 million metric tons of chromite ore. Twenty percent of Free World production was obtained from this area between 1950 and the end of 1964; in 1960 production reached a high of 606,103 metric tons of refractory-grade ore, mostly from the Coto mine near Masinloc, and 128,426 metric tons of metallurgical ore from the Acoje mine. The United States imports 80 to 90 percent of its refractory-grade chromite from the Philippines, and its basic refractory technology has been designed upon the chemical and physical characteristics of Coto high-alumina chromite ore. Continuation of this pattern will depend upon discovery of additional ore reserves to replace those depleted by mining. The Zambales Ultramafic Complex is of the alpine type in which lenticular or podiform deposits of chromite lie in peridotite or dunite, mostly near Contacts with gabbroic rocks. Layered structures, foliation, and lineation commonly are well developed and transect boundaries between major rock units, including chromite deposits, at any angle. Accordingly, these structures cannot be used as guides in exploration and mining as they are used in stratiform complexes such as the Bushveld, where chromite layers extend for many miles. Probably 90 percent of the known deposits in the Zambales Complex are located in two belts in its northern part. One zone containing high-aluminua refractory-grade deposits extends northeast from the Coto mine and Chromite Reservation No. I along a peridotite contact with olivine gabbro, and another of high-chromium metallurgical grade chromite extends south through the Zambales and Acoje properties, and swings westward around the south side of Mount Lanai along a peridotite contact with norite. The textures

  3. Cr-Al Diffusion in Chromite Spinel at High Pressure

    NASA Astrophysics Data System (ADS)

    Suzuki, A.; Yasuda, A.; Ozawa, K.

    2005-12-01

    Compositional zoning in chromite spinel gives us important information to constrain thermal and deformation history of ultramafic-mafic rocks. For the quantitative estimation, diffusivity of elements in spinel is a critical parameter. Although the Mg-Fe2+ interdiffusion coefficient in MgAl2O4 spinel has experimentally studied by Freer & O'Reilly (1980) and Liemann & Ganguly (2002), Cr-Al interdiffusion coefficient has not been determined yet. In this study, we have experimentally determined Cr-Al interdiffusion coefficient in chromite spinel at temperatures ranging 1400-1700 °C and pressures ranging 3-7 GPa, by using diffusion couple of natural single crystals of spinel and chromite. Experiments were carried out with a multi-anvil type (MA-8 type) high-pressure apparatus at the Earthquake Research Institute, University of Tokyo. After experiments, the samples were cut perpendicular to the contact plane and analyzed with EPMA and EBSD. The elemental mapping showed that Cr, Al, Fe3+, Fe2+, and Mg diffused perpendicular to the contact plane. The Cr-Al diffusion profiles are complementary with each other and asymmetric with steeper profile in the spinel side suggesting a compositional dependence of Cr-Al diffusion in spinel. The Cr-Al interdiffusion coefficient was estimated by the Boltzmann-Matano method. The coefficient decreases with Cr# (=Cr/(Cr+Al)) of spinel, which varies more than one order of magnitude as the Cr# changes from 0.1 to 0.85 at 3 GPa and 1600 °C. It is concluded that the self-diffusion coefficient of Al is more than one order of magnitude larger than that of Cr. The Cr-Al interdiffusion coefficient is expressed by D=D0exp(-Q/RT), where D0=2.8×10-2 m2/s and Q=498 kJ/mol at Cr#=0.2. This relation is applicable up to Cr#=0.5. Extrapolation of the self-diffusion coefficient of Cr to the lower temperature shows that Cr is the slowest diffusion species in chromite spinel including oxygen. This extremely slow Cr self-diffusion is consistent with the Cr

  4. 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.

  5. 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.

  6. Development of Ceramic Interconnect Materials for SOFC

    SciTech Connect

    Yoon, Kyung J.; Stevenson, Jeffry W.; Marina, Olga A.

    2010-08-05

    Currently, acceptor-doped lanthanum chromite is the state-of-the-art ceramic interconnect material for high temperature solid oxide fuel cells (SOFCs) due to its fairly good electronic conductivity and chemical stability in both oxidizing and reducing atmospheres, and thermal compatibility with other cell components. The major challenge for acceptor-doped lanthanum chromite for SOFC interconnect applications is its inferior sintering behavior in air, which has been attributed to the development of a thin layer of Cr2O3 at the interparticle necks during the initial stages of sintering. In addition, lanthanum chromite is reactive with YSZ electrolyte at high temperatures, forming a highly resistive lanthanum zirconate phase (La2Zr2O7), which further complicates co-firing processes. Acceptor-doped yttrium chromite is considered to be one of the promising alternatives to acceptor-doped lanthanum chromite because it is more stable with respect to the formation of hydroxides in SOFC operating conditions, and the formation of impurity phases can be effectively avoided at co-firing temperatures. In addition, calcium-doped yttrium chromite exhibits higher mechanical strength than lanthanum chromite-based materials. The major drawback of yttrium chromite is considered to be its lower electrical conductivity than lanthanum chromite. The properties of yttrium chromites could possibly be improved and optimized by partial substitution of chromium with various transition metals. During FY10, PNNL investigated the effect of various transition metal doping on chemical stability, sintering and thermal expansion behavior, microstructure, electronic and ionic conductivity, and chemical compatibility with other cell components to develop the optimized ceramic interconnect material.

  7. Effect of Lanthanum Doping on Ferroelectric and Strain Properties of 0.96Bi1/2(Na0.84K0.16)1/2TiO3-0.04SrTiO3 Lead-Free Ceramics

    NASA Astrophysics Data System (ADS)

    Tran, Vu Diem Ngoc; Ullah, Aman; Dinh, Thi Hinh; Lee, Jae-Shin

    2016-05-01

    Lead-free 0.96[Bi1/2(Na0.84K0.16)1/2](1- x)La x TiO3-0.04SrTiO3 (BNKTLa x-ST, with x = 0.00, 0.01, 0.02, 0.03, 0.04, and 0.05) ceramics have been synthesized using a conventional solid-state reaction method and their phase transition, dielectric, ferroelectric, and strain properties investigated. X-ray diffraction patterns revealed formation of pure perovskite phase. A phase transition from coexistence of rhombohedral and tetragonal to a pseudocubic phase was observed at x = 0.02. Polarization and bipolar strain hysteresis loops indicated that the ferroelectric order (FE) of BNKT-ST is significantly disrupted by lanthanum doping. The destabilization of the FE order results in degradation of the remanent polarization, coercive field, depolarization temperature ( T d), electromechanical coupling factor ( k p), and static d 33, accompanied by large electric-field-induced strain of 0.34% at 60 kV/cm with normalized strain of d 33 * = S max/ E max = 600 pm/V at a critical composition of around x = 0.02.

  8. Stratiform chromite deposit model: Chapter E in Mineral deposit models for resource assessment

    USGS Publications Warehouse

    Schulte, Ruth F.; Taylor, Ryan D.; Piatak, Nadine M.; Seal, Robert R., II

    2012-01-01

    Most environmental concerns associated with the mining and processing of chromite ore focus on the solubility of chromium and its oxidation state. Although trivalent chromium (Cr3+) is an essential micronutrient for humans, hexavalent chromium (Cr6+) is highly toxic. Chromium-bearing solid phases that occur in the chromite ore-processing

  9. PROMOTED ZINC CHROMITE CATALYSTS FOR HIGHER ALCOHOL SYNTHESIS

    SciTech Connect

    Ms. Xiaolei Sun; Professor George W. Roberts

    2000-06-21

    Work during the report period was concentrated on developing analytical techniques. Thin-layer chromatography (TLC) was used in an attempt to define the best mobile phase to separate the components of ''spent'' tetrahydroquinoline by liquid chromatography in a silica gel column. Conditions have been defined for separating the light gases produced by the reaction of carbon monoxide (CO) and hydrogen (H{sub 2}) over promoted ''zinc chromite'' catalysts. This will be done with a temperature-programmed Carboxen-1000 column, using a thermal conductivity detector for analysis. A Petrocol DM 150 capillary column will be purchased to separate the heavier products, which will be analyzed using a flame ionization detector.

  10. Synthesis and Characterization of Hydrophilic and Semiconductor Cadmium Chromite Nanostructures

    NASA Astrophysics Data System (ADS)

    Mousavi, Zahra; Salavati-Niasari, Masoud; Soofivand, Faezeh; Esmaeili-Zare, Mahdiyeh; Hamadanian, Masood

    2016-11-01

    Cadmium chromite nanostructures were synthesized in high yield by a simple co-precipitation method. CdCr2O4 nanostructures have been achieved using cadmium nitrate tetrahydrate and CrCl3·6H2O as precursors by a co-precipitation method. The effects of various parameters including alkaline agent, pH value, reaction temperature, and surfactant type were investigated to discover the optimum conditions, and it was found that the size and morphology of products can be affected by these parameters. The structure, morphology and surface chemistry of CdCr2O4 powder were investigated by x-ray diffraction, scanning electron microscopy and energy dispersive x-ray spectroscopy. X-ray diffraction patterns indicated the chromite spinel phase with good crystallinity and an average crystallite size of approximately 20 nm. The hydrophilicity of the calcined oxides was investigated by wetting experiments and the sessile drop technique which were carried out at room temperature in air to determine the surface and interfacial interactions.

  11. Synthesis and Characterization of Hydrophilic and Semiconductor Cadmium Chromite Nanostructures

    NASA Astrophysics Data System (ADS)

    Mousavi, Zahra; Salavati-Niasari, Masoud; Soofivand, Faezeh; Esmaeili-Zare, Mahdiyeh; Hamadanian, Masood

    2016-07-01

    Cadmium chromite nanostructures were synthesized in high yield by a simple co-precipitation method. CdCr2O4 nanostructures have been achieved using cadmium nitrate tetrahydrate and CrCl3·6H2O as precursors by a co-precipitation method. The effects of various parameters including alkaline agent, pH value, reaction temperature, and surfactant type were investigated to discover the optimum conditions, and it was found that the size and morphology of products can be affected by these parameters. The structure, morphology and surface chemistry of CdCr2O4 powder were investigated by x-ray diffraction, scanning electron microscopy and energy dispersive x-ray spectroscopy. X-ray diffraction patterns indicated the chromite spinel phase with good crystallinity and an average crystallite size of approximately 20 nm. The hydrophilicity of the calcined oxides was investigated by wetting experiments and the sessile drop technique which were carried out at room temperature in air to determine the surface and interfacial interactions.

  12. Chromite in Lower Pennsylvanian Nuttall sandstone from West Virginia - Possible Blue Ridge province source

    SciTech Connect

    O'Connor, J.T. )

    1989-08-01

    Detrital chromite grains from heavy mineral separates of three samples of the Lower Pennsylvanian Nuttall Sandstone Member of the New River Formation were examined by use of a reflected-light petrographic microscope, a scanning electron microscope, and an electron microprobe. Some textures observed microscopically in the chromite grains are similar to those in chromite grains in dunite from the Blue Ridge province of North Carolina that has undergone regional metamorphism. Additional exsolution features are also observed in the chromites of this study. The major-oxide compositions of the detrital chromite grains vary more widely than those of the chromites of the Blue Ridge, possibly due to a larger sampling base. The detrital grain compositions (Cr/(Cr + Al), Mg/(Mg + Fe{sup +2})) plot near the fields of the Blue Ridge chromites, although the appearance of both more aluminum-rich and magnesium-poor compositions possibly indicate a higher facies of metamorphism than the Blue Ridge samples studied to date.

  13. Neurodevelopmental effects of lanthanum in mice.

    PubMed

    Briner, W; Rycek, R F; Moellenberndt, A; Dannull, K

    2000-01-01

    Mice were exposed to lanthanum chloride in drinking water at 0, 125, 250, and 500 mg/liter concentration prior to conception, during gestation, and until 30 days postnatally. Developing mice were assessed for the development of swimming and walking behavior and ear and eye opening. At 30 days of age the mice were assessed with a standard neurologic scale. Differences were found in the emergence of swimming and walking behavior and ear and eye opening. Differences were also found for touch response and visual placing responses. The brains of lanthanum-exposed mice were also smaller than controls. These findings indicate that lanthanum is a potential behavioral teratogen. Possible mechanisms are discussed.

  14. Experimental determination of the activity of chromite in multicomponent spinels

    NASA Astrophysics Data System (ADS)

    Kessel, Ronit; Beckett, John R.; Stolper, Edward M.

    2003-08-01

    We determined activity-composition relationships in Pt-Cr and Pt-Fe-Cr alloys at 1300°C experimentally and used the results to constrain the thermodynamic properties of chromite-picrochromite spinels. The Pt-Cr binary is characterized by strong negative deviations from ideality throughout the investigated composition range and the activity-composition relationship can be fit by a four-suffix asymmetric regular solution with three binary interaction parameters. The ternary alloy was modeled as a four-suffix asymmetric regular solution; the three ternary interaction parameters in this model were constrained by combining interaction parameters for the three bounding binaries taken from this and previous work with results for a set of experiments in which the activity of Cr in Pt-Fe-Cr-alloys was fixed by coexisting Cr 2O 3 at known fO2. The free energy of formation of FeCr 2O 4 at 1300°C was determined using the activities of Fe and Cr in Pt-alloys in equilibrium with oxide mixes of FeCr 2O 4 and Cr 2O 3. The free energy of formation of chromite from Fe+Cr 2O 3+O 2 is -202.7 ± 0.4 kJ/mol (1σ), indistinguishable from literature values. The corresponding free energy of formation of FeCr 2O 4 from the elements is -923.5 ± 2.1 kJ/mol (1σ), and the enthalpy of formation at 298 K is -1438 kJ/mol. The activity-composition relationship for the chromite component in (Fe,Mg)Cr 2O 4 solid solutions was determined from a set of experiments in which Pt-alloys were equilibrated with spinel + Cr 2O 3. (Fe,Mg)Cr 2O 4 spinels are nearly ideal at 1300°C; modeling our data with a one-site symmetric regular solution yields an interaction parameter of +2.14 ± 0.62 kJ/mol (1σ), similar to values based on data from the literature.

  15. Synthesis, characterization and photoluminescence property of La-doped ZnO nanoparticles

    NASA Astrophysics Data System (ADS)

    Lang, Jihui; Fang, Yue; Zhang, Qi; Wang, Jiaying; Li, Tianshun; Li, Xiuyan; Han, Qiang; Wang, Dandan; Wei, Maobin; Yang, Jinghai

    2016-10-01

    La-doped ZnO nanoparticles were synthesized via a facile and surfactant-free chemical precipitation route, and the effects of lanthanum doping concentration on the structures, morphologies and photoluminescence properties were investigated by XRD, TEM, EDX, PL and UV-Vis absorption spectra. The results showed that the La3+ ions were successfully incorporated into the ZnO host, and the products were well-crystalline. The average size and band gap of La-doped ZnO nanoparticles were varied with the lanthanum doping concentration. The average size of doped nanoparticles was much smaller as compared to that of undoped ZnO. The increasing of lanthanum doping concentration increased the defects in ZnO and resulted in a red shift of UV emission, indicating the narrow band gap in doped nanoparticles. This was probably attributed to the impurity energy levels in band gap introduced by substitutional La3+ ions.

  16. Lanthanum

    MedlinePlus

    ... in, tightly closed, and out of reach of children. Store it at room temperature and away from excess heat and moisture (not in the bathroom).Unneeded medications should be disposed of in special ways to ensure that pets, children, and other people cannot consume them. However, you ...

  17. Use in open-hearth roofs of periclase-chromite parts made from electrofused periclase-chromite

    SciTech Connect

    Simonov, K.V.; Bocharov, L.D.; Kapichev, A.G.; Kukushkin, A.P.; Solyanikov, B.G.; Tyvlebaev, V.G.

    1986-03-01

    The authors investigate the influence of the quality of periclasechromite parts on their wear rate and the life of open hearth roofs. The experimental parts met the property requirements of TU 14-8368-81 for dense PKhPPP, packed PKhPU, and medium density PKhPS; the experimental parts are characterized by a coarse-grained structure and high properties. The low silica and silicate content in the parts is responsible for their high temperature of deformation under load, and the heat resistance of the refractories is good. It was shown that the main improvement in the quality of the refractories is a signifigant reserve for increasing the life of open hearth roofs. The use in open hearth roofs of parts of electrofused periclase-chromite makes it possible to decrease the refractory consumption by 3.36 kg per ton of steel and to reduce the cost of a ton of steel.

  18. Stratiform chromite deposit model: Chapter E in Mineral deposit models for resource assessment

    USGS Publications Warehouse

    Schulte, Ruth F.; Taylor, Ryan D.; Piatak, Nadine M.; Seal, Robert R., II

    2012-01-01

    Most environmental concerns associated with the mining and processing of chromite ore focus on the solubility of chromium and its oxidation state. Although trivalent chromium (Cr3+) is an essential micronutrient for humans, hexavalent chromium (Cr6+) is highly toxic. Chromium-bearing solid phases that occur in the chromite ore-processing residue, for example, can effect the geochemical behavior and oxidation state of chromium in the environment.

  19. Energy stabilization of the s -symmetry superatom molecular orbital by endohedral doping of C 82 fullerene with a lanthanum atom

    SciTech Connect

    Feng, Min; Shi, Yongliang; Lin, Chungwei; Zhao, Jin; Liu, Fupin; Yang, Shangfeng; Petek, Hrvoje

    2013-08-01

    Energy stabilization of the superatom molecular orbitals (SAMOs) in fullerenes is investigated with the goal of involving their nearly free-electron bands in practical charge transport applications. Combining low-temperature scanning tunneling microscopy-based spectroscopic methods and density functional theory calculations on an endohedral metallofullerene La@C82, we confirm that the s-SAMO of C82 fullerene is stabilized by as much as 2 eV with respect to that of C60 by endohedral doping with the La atom. On the copper metal substrate, the s-SAMO energy is further lowered to just 1 eV above the Fermi level, making the applications of s-SAMO state in transport more plausible. We conclude that in an endohedral metallofullerene, the s-SAMO state is stabilized through the hybridization with the s-symmetry valence state of the metal atom and the stabilization energy correlates with the ionization potential of the free atom.

  20. Palladium, platinum, rhodium, iridium and ruthenium in chromite- rich rocks from the Samail ophiolite, Oman.

    USGS Publications Warehouse

    Page, N.J.; Pallister, J.S.; Brown, M.A.; Smewing, J.D.; Haffty, J.

    1982-01-01

    30 samples of chromitite and chromite-rich rocks from two stratigraphic sections, 250 km apart, through the basal ultramafic member of the Samail ophiolite were spectrographically analysed for platinum-group elements (PGE) and for Co, Cu, Ni and V. These data are reported as are Cr/(Cr + Al), Mg/(Mg + Fe) and wt.% TiO2 for most samples. The chromitite occurs as pods or lenses in rocks of mantle origin or as discontinuous layers at the base of the overlying cumulus sequence. PGE abundances in both sections are similar, with average contents in chromite-rich rocks: Pd 8 ppb, Pt 14 ppb, Rh 6 ppb, Ir 48 ppb and Ru 135 ppb. The PGE data, combined with major-element and petrographic data on the chromitite, suggest: 1) relatively larger Ir and Ru contents and highest total PGE in the middle part of each section; 2) PGE concentrations and ratios do not correlate with coexisting silicate and chromite abundances or chromite compositions; 3) Pd/PGE, on average, increases upward in each section; 4) Samail PGE concentrations, particularly Rh, Pt and Pd, are lower than the average values for chromite-rich rocks in stratiform intrusions. 2) suggests that PGEs occur in discrete alloy or sulphide phases rather than in the major oxides or silicates, and 4) suggests that chromite-rich rocks from the oceanic upper mantle are depleted in PGE with respect to chondrites. L.C.C.

  1. Chromite oxidation by manganese oxides in subseafloor basalts and the presence of putative fossilized microorganisms

    PubMed Central

    2011-01-01

    Chromite is a mineral with low solubility and is thus resistant to dissolution. The exception is when manganese oxides are available, since they are the only known naturally occurring oxidants for chromite. In the presence of Mn(IV) oxides, Cr(III) will oxidise to Cr(VI), which is more soluble than Cr(III), and thus easier to be removed. Here we report of chromite phenocrysts that are replaced by rhodochrosite (Mn(II) carbonate) in subseafloor basalts from the Koko Seamount, Pacific Ocean, that were drilled and collected during the Ocean Drilling Program (ODP) Leg 197. The mineral succession chromite-rhodochrosite-saponite in the phenocrysts is interpreted as the result of chromite oxidation by manganese oxides. Putative fossilized microorganisms are abundant in the rhodochrosite and we suggest that the oxidation of chromite has been mediated by microbial activity. It has previously been shown in soils and in laboratory experiments that chromium oxidation is indirectly mediated by microbial formation of manganese oxides. Here we suggest a similar process in subseafloor basalts. PMID:21639896

  2. Messengers from the deep: Fossil wadsleyite-chromite microstructures from the Mantle Transition Zone

    PubMed Central

    Satsukawa, Takako; Griffin, William L.; Piazolo, Sandra; O’Reilly, Suzanne Y.

    2015-01-01

    Investigations of the Mantle Transition Zone (MTZ; 410–660 km deep) by deformation experiments and geophysical methods suggest that the MTZ has distinct rheological properties, but their exact cause is still unclear due to the lack of natural samples. Here we present the first direct evidence for crystal-plastic deformation by dislocation creep in the MTZ using a chromitite from the Luobusa peridotite (E. Tibet). Chromite grains show exsolution of diopside and SiO2, suggesting previous equilibration in the MTZ. Electron backscattered diffraction (EBSD) analysis reveals that olivine grains co-existing with exsolved phases inside chromite grains and occurring on chromite grain boundaries have a single pronounced crystallographic preferred orientation (CPO). This suggests that olivine preserves the CPO of a high-pressure polymorph (wadsleyite) before the high-pressure polymorph of chromite began to invert and exsolve. Chromite also shows a significant CPO. Thus, the fine-grained high-pressure phases were deformed by dislocation creep in the MTZ. Grain growth in inverted chromite produced an equilibrated microstructure during exhumation to the surface, masking at first sight its MTZ deformation history. These unique observations provide a window into the deep Earth, and constraints for interpreting geophysical signals and their geodynamic implications in a geologically robust context. PMID:26563583

  3. Messengers from the deep: Fossil wadsleyite-chromite microstructures from the Mantle Transition Zone.

    PubMed

    Satsukawa, Takako; Griffin, William L; Piazolo, Sandra; O'Reilly, Suzanne Y

    2015-11-13

    Investigations of the Mantle Transition Zone (MTZ; 410-660 km deep) by deformation experiments and geophysical methods suggest that the MTZ has distinct rheological properties, but their exact cause is still unclear due to the lack of natural samples. Here we present the first direct evidence for crystal-plastic deformation by dislocation creep in the MTZ using a chromitite from the Luobusa peridotite (E. Tibet). Chromite grains show exsolution of diopside and SiO2, suggesting previous equilibration in the MTZ. Electron backscattered diffraction (EBSD) analysis reveals that olivine grains co-existing with exsolved phases inside chromite grains and occurring on chromite grain boundaries have a single pronounced crystallographic preferred orientation (CPO). This suggests that olivine preserves the CPO of a high-pressure polymorph (wadsleyite) before the high-pressure polymorph of chromite began to invert and exsolve. Chromite also shows a significant CPO. Thus, the fine-grained high-pressure phases were deformed by dislocation creep in the MTZ. Grain growth in inverted chromite produced an equilibrated microstructure during exhumation to the surface, masking at first sight its MTZ deformation history. These unique observations provide a window into the deep Earth, and constraints for interpreting geophysical signals and their geodynamic implications in a geologically robust context.

  4. Messengers from the deep: Fossil wadsleyite-chromite microstructures from the Mantle Transition Zone.

    PubMed

    Satsukawa, Takako; Griffin, William L; Piazolo, Sandra; O'Reilly, Suzanne Y

    2015-01-01

    Investigations of the Mantle Transition Zone (MTZ; 410-660 km deep) by deformation experiments and geophysical methods suggest that the MTZ has distinct rheological properties, but their exact cause is still unclear due to the lack of natural samples. Here we present the first direct evidence for crystal-plastic deformation by dislocation creep in the MTZ using a chromitite from the Luobusa peridotite (E. Tibet). Chromite grains show exsolution of diopside and SiO2, suggesting previous equilibration in the MTZ. Electron backscattered diffraction (EBSD) analysis reveals that olivine grains co-existing with exsolved phases inside chromite grains and occurring on chromite grain boundaries have a single pronounced crystallographic preferred orientation (CPO). This suggests that olivine preserves the CPO of a high-pressure polymorph (wadsleyite) before the high-pressure polymorph of chromite began to invert and exsolve. Chromite also shows a significant CPO. Thus, the fine-grained high-pressure phases were deformed by dislocation creep in the MTZ. Grain growth in inverted chromite produced an equilibrated microstructure during exhumation to the surface, masking at first sight its MTZ deformation history. These unique observations provide a window into the deep Earth, and constraints for interpreting geophysical signals and their geodynamic implications in a geologically robust context. PMID:26563583

  5. Messengers from the deep: Fossil wadsleyite-chromite microstructures from the Mantle Transition Zone

    NASA Astrophysics Data System (ADS)

    Satsukawa, Takako; Griffin, William L.; Piazolo, Sandra; O'Reilly, Suzanne Y.

    2015-11-01

    Investigations of the Mantle Transition Zone (MTZ; 410-660 km deep) by deformation experiments and geophysical methods suggest that the MTZ has distinct rheological properties, but their exact cause is still unclear due to the lack of natural samples. Here we present the first direct evidence for crystal-plastic deformation by dislocation creep in the MTZ using a chromitite from the Luobusa peridotite (E. Tibet). Chromite grains show exsolution of diopside and SiO2, suggesting previous equilibration in the MTZ. Electron backscattered diffraction (EBSD) analysis reveals that olivine grains co-existing with exsolved phases inside chromite grains and occurring on chromite grain boundaries have a single pronounced crystallographic preferred orientation (CPO). This suggests that olivine preserves the CPO of a high-pressure polymorph (wadsleyite) before the high-pressure polymorph of chromite began to invert and exsolve. Chromite also shows a significant CPO. Thus, the fine-grained high-pressure phases were deformed by dislocation creep in the MTZ. Grain growth in inverted chromite produced an equilibrated microstructure during exhumation to the surface, masking at first sight its MTZ deformation history. These unique observations provide a window into the deep Earth, and constraints for interpreting geophysical signals and their geodynamic implications in a geologically robust context.

  6. 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)

  7. Composite Gel Polymer Electrolyte Based on Poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) with Modified Aluminum-Doped Lithium Lanthanum Titanate (A-LLTO) for High-Performance Lithium Rechargeable Batteries.

    PubMed

    Le, Hang T T; Ngo, Duc Tung; Kalubarme, Ramchandra S; Cao, Guozhong; Park, Choong-Nyeon; Park, Chan-Jin

    2016-08-17

    A composite gel polymer electrolyte (CGPE) based on poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) polymer that includes Al-doped Li0.33La0.56TiO3 (A-LLTO) particles covered with a modified SiO2 (m-SiO2) layer was fabricated through a simple solution-casting method followed by activation in a liquid electrolyte. The obtained CGPE possessed high ionic conductivity, a large electrochemical stability window, and interfacial stability-all superior to that of the pure gel polymer electrolyte (GPE). In addition, under a highly polarized condition, the CGPE effectively suppressed the growth of Li dendrites due to the improved hardness of the GPE by the addition of inorganic A-LLTO/m-SiO2 particles. Accordingly, the Li-ion polymer and Li-O2 cells employing the CGPE exhibited remarkably improved cyclability compared to cells without CGPE. In particular, the CGPE as a protection layer for the Li metal electrode in a Li-O2 cell was effective in blocking the contamination of the Li electrode by oxygen gas or impurities diffused from the cathode side while suppressing the Li dendrites. PMID:27463563

  8. 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 and significant new uses subject to reporting. (1) The chemical substance identified as lanthanum...

  9. 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 and significant new uses subject to reporting. (1) The chemical substance identified as lanthanum...

  10. PROMOTED ZINC CHROMITE CATALYSTS FOR HIGHER ALCOHOL SYNTHESIS

    SciTech Connect

    Ms. Xiaolei Sun; Professor George W. Roberts

    2001-06-15

    This report describes the analytical protocols that were developed during the last two years to analyze ''spent'' THQ (tetrahydroquinoline) slurry liquid. Identification of the components of the ''spent'' THQ should help to understand the influence of the slurry medium on the methanol synthesis reaction, and on other reactions with THQ as the slurry liquid. Silica gel liquid chromatography and high performance liquid chromatography (HPLC) were used to isolate and purify the major compounds in the ''spent'' slurry liquid. Gas chromatography/mass spectroscopy (GC/MS), Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) were applied to identify the major compounds. Methyl-, dimethyl-, and trimethyl-THQ were found to comprise more than 80% of the ''spent'' liquid. The balance was various methylated indoles. A methyl group always is attached to the N atom in the ring structure. Speculative mechanisms are presented that may help to understand the interaction between the catalyst and the alkylated THQ slurry liquid, and the effect of liquid composition on the methanol synthesis reaction. A poster entitled ''Promoted Zinc Chromite Catalyst for Higher Alcohol Synthesis in a Slurry Reactor-2. Spent Liquid Analysis'' was presented at the AIChE National Meeting, Los Angeles, CA, Nov 12-17, 2000.

  11. Cation distribution and magnetic properties of natural chromites

    NASA Astrophysics Data System (ADS)

    Rais, A.; Yousif, A. A.; Al-Shihi, M. H.; Al-Rawas, A. D.; Gismelseed, A. M.; El-Zain, M. E.

    2003-10-01

    Ten specimens of chromites from Oman ophiolites have been studied using magnetic susceptibility measurements, Mössbauer spectroscopy (MS), Scanning electron microscopy (SEM), and X-ray diffraction (XRD). XRD shows that all samples have a face-centered cubic spinel structure. MS analysis and SEM data at room temperature enabled to derive the chemical formula and the cations distribution among tetrahedral (A1 and A2) and octahedral (B) sites. For all specimens, paramagnetic variations of 1/ with the temperature T show a systematic curve bending at a critical temperature T0, which indicates a change of the effective paramagnetic moment μeff. This deviation from Curie-Weiss law is interpreted as due to spin inversion of a fraction δ of Cr3+ cations located in the octahedral sites of the spinel structure. This interpretation is supported by a decrease in the Mössbauer peak areas of Fe2+ located in A1 sites from 300 to 80 K at the expense of Fe2+ located in A2 sites. The values of δ and μeff for each specimen are calculated by fitting this model separately to the experimental 1/χ versus T above and below T0.

  12. PROMOTED ZINC CHROMITE CATALYSTS FOR HIGHER ALCOHOL SYNTHESIS

    SciTech Connect

    Ms. Xiaolei Sun; Professor George W. Roberts

    2000-08-29

    During this reporting period, a ''zinc chromite'' catalyst promoted with 6 wt.% cesium (Cs) was evaluated at the following conditions: Temperature--375 C; Total Pressure--6.8 MPa (1000 psig); Gas Hourly Space Velocity (GHSV) - 5000 standard liters/kg(cat)-hr, and; H{sub 2}/CO feed ratio--1.0 mole/mole. Decahydronaphthalene (DHN) was used as the slurry liquid. The experiment lasted for eight days of continuous operation. Although the experimental data once again did not exhibit the desired degree of consistency, the data did show that methanol was the primary reaction product. The slurry liquid did not decompose or alkylate to a measurable extent during the continuous 8-day experiment. There was a relatively significant loss of catalyst surface area during the experiment. Gas chromatography/mass spectrometry (GC/MS) analysis of various fractions of ''spent'' THQ was carried out. The fractions were prepared by silica gel liquid chromatography (LC). Chemical formuli and probable structures for each major compound were obtained. However, a higher degree of purification will be necessary to allow nuclear magnetic resonance (NMR) analysis to be used for definitive compound identification. A new Maxpro gas booster (DLE 15-75) was purchased because the existing Haskel gas booster once again developed a severe leak of carbon monoxide and hydrogen, and was judged to be unworthy of repair.

  13. Determination of lanthanum by flame photometric titration.

    PubMed

    Svehla, G; Slevin, P J

    1968-09-01

    The flame emission of lanthanum at 560 mmu decreases linearly with phosphate concentration until a 1:1 molar ratio is reached, and then remains practically constant. Lanthanum can be titrated with phosphate, the equivalence point being detected from the change in emission intensity. Errors due to consumption of solution by the atomizer can be kept low by using short spraying times and low galvanometer damping. The average error is about -1% for 0.1M solutions and less than -5% for 0.01M. The method gives good results in the presence of titanium(III), zirconium, thorium and aluminium but cerium(III) and yttrium seriously interfere. PMID:18960392

  14. Steady photodarkening of thulium alumino-silicate fibers pumped at 1.07  μm: quantitative effect of lanthanum, cerium, and thulium.

    PubMed

    Lupi, Jean-François; Vermillac, Manuel; Blanc, Wilfried; Mady, Franck; Benabdesselam, Mourad; Dussardier, Bernard; Neuville, Daniel R

    2016-06-15

    By pumping thulium-doped silica-based fibers at 1.07 μm, rapid generation of absorbing centers leads to photoinduced attenuation (PIA). This detrimental effect prevents exploiting laser emissions in the visible and near infrared. We report on the characterization of the PIA versus the fiber core composition, particularly the concentration of thulium (Tm), lanthanum (La), and cerium (Ce) ions. We show that UV emission induced by Tm-Tm energy transfers is the source of photodarkening and that lanthanum and cerium are efficient hardeners against PIA. PMID:27304285

  15. Steady photodarkening of thulium alumino-silicate fibers pumped at 107 μm: quantitative effect of lanthanum, cerium, and thulium

    NASA Astrophysics Data System (ADS)

    Lupi, Jean-François; Vermillac, Manuel; Blanc, Wilfried; Mady, Franck; Benabdesselam, Mourad; Dussardier, Bernard; Neuville, Daniel R.

    2016-06-01

    By pumping thulium-doped silica-based fibers at 1.07~\\mu m, rapid generation of absorbing centers leads to photo-induced attenuation (PIA). This detrimental effect prevents exploiting laser emissions in the visible and near infrared. We report on the characterization of the PIA versus the fiber core composition, particularly the concentration of thulium (Tm), lanthanum (La) and cerium (Ce) ions. We show that UV emision induced by Tm-Tm energy transfers is the source of photo-darkening, and that lanthanum and cerium are efficient hardeners against PIA.

  16. Steady photodarkening of thulium alumino-silicate fibers pumped at 1.07  μm: quantitative effect of lanthanum, cerium, and thulium.

    PubMed

    Lupi, Jean-François; Vermillac, Manuel; Blanc, Wilfried; Mady, Franck; Benabdesselam, Mourad; Dussardier, Bernard; Neuville, Daniel R

    2016-06-15

    By pumping thulium-doped silica-based fibers at 1.07 μm, rapid generation of absorbing centers leads to photoinduced attenuation (PIA). This detrimental effect prevents exploiting laser emissions in the visible and near infrared. We report on the characterization of the PIA versus the fiber core composition, particularly the concentration of thulium (Tm), lanthanum (La), and cerium (Ce) ions. We show that UV emission induced by Tm-Tm energy transfers is the source of photodarkening and that lanthanum and cerium are efficient hardeners against PIA.

  17. Thermal metamorphism of mantle chromites and the stability of noble-metal nanoparticles

    NASA Astrophysics Data System (ADS)

    González-Jiménez, José M.; Reich, Martin; Camprubí, Antoni; Gervilla, Fernando; Griffin, William L.; Colás, Vanessa; O'Reilly, Suzanne Y.; Proenza, Joaquín A.; Pearson, Norman J.; Centeno-García, Elena

    2015-08-01

    The Loma Baya complex in south-western Mexico is a volume of chromitite-bearing oceanic mantle that records a complex metamorphic history, defined by a first stage of hydrous metamorphism overprinted by a short-lived thermal event associated with an Eocene granite intrusion. During the hydrous metamorphism, the primary magmatic chromite-olivine assemblage was replaced by a secondary, porous intergrowth of Fe2+-rich chromite and chlorite. The heat supplied by an Eocene-age granite intrusion reversed the hydration reaction, producing chromite rims with perfectly developed crystal faces. This third-generation chromite is in equilibrium with highly magnesian (neoformed) olivine and defines a chemical trend analogous to the original magmatic one. The preservation of both reactions in the Loma Baya chromitite provides compelling evidence that the hydration of chromite can be reversed by either prograde metamorphism or any heating event, confirming previous thermodynamic predictions. Understanding these complex features is of particular interest due to the fact that changes in temperature and variable degrees of fluid/rock interaction during metamorphism and intrusion have also significantly affected the chromite-hosted IPGE carrier phases. Here, we propose that the metamorphic fluids involved in the hydrous metamorphism have caused the desulphurization of laurite RuS2, releasing minute particles of Ru-Os-Ir alloys <50 nm in diameter. The following short-lived thermal event that promoted dehydration in the chromitite had the opposite effect on nanoparticle stability, producing a significant coarsening of metal nanoparticles to dimensions larger than a micron. Based on such observations, we argue that IPGE nanoparticles can be exsolved and grown (or coarsen) from sulphide matrices during prograde metamorphism or heating and not exclusively upon cooling under magmatic conditions as it has been previously suggested. These results provide new insights on the relevant role of

  18. Osmium, ruthenium, iridium and uranium in silicates and chromite from the eastern Bushveld Complex, South Africa

    USGS Publications Warehouse

    Gijbels, R.h.; Millard, H.T.; Desborough, G.A.; Bartel, A.J.

    1974-01-01

    Osmium, ruthenium, iridium and uranium contents were determined in eight ortho pyroxene, seven plagioclase, and three chromite mineral separates from the eastern Bushveld Complex. Neutron activation analysis was used to measure the platinum metals, and uranium was determined by a fission track technique. The platinum metals were found to be present within each mine??ral in the proportions Os:Ru:Ir = 1:7:1, while the concentrations of these metals in the minerals are in the ratios orthopyroxene:plagioclase:chromite = 1:16:700. The concentration of uranium was found to range from 11 to 66 ppb (parts per billion) and not to vary significantly from mineral to mineral. The data for the platinum metals are consistent with a model in which the eastern Bushveld Complex was formed by the fractional crystallization of two separately injected magmas. A computer fit of this model to these data indicates that the initial concentrations of Os, Ru and Ir in the first magma were 0.24, 2.0 and 0.21 ppb and in the second magma were 0.16, 1.1 and 0.18 ppb, respectively. The fit also yields the distribution coefficients for the partitioning between the liquid and cumulus orthopyroxene, cumulus plagioclase and cumulus chromite. These coefficients (mineral/liquid) for osmium are 4.5, 66 and 2700; for ruthenium, they are 5, 65 and 2700; and for iridium, they are 4, 60 and 1600. To make this fit, it was necessary to hypothesize the existence of two types of chromite: one type with a large distribution coefficient, presumably formed as a cumulus phase at high temperature, and another, more prevalent type with a smaller distribution coefficient, which may have been formed by postcumulus growth at a lower temperature. This hypothesis is supported by data for coexisting chromite-silicate pairs, which indicate that the chromite grains expelled these platinum metals as they cooled. ?? 1974.

  19. Zircon and chromite crystals in a muong nong-type tektite.

    PubMed

    Glass, B P

    1970-08-21

    Chromite, zircon, and quartz crystals (identified by x-ray diffraction) have been recovered from a 2.07-gram sample of Muong Nong-type tektite. The absence of eskolaite (Cr(2)O(3)) and baddeleyite (ZrO(2)) supports a previous conclusion that Muong Nong-type tektites were not heated as intensely as other tektite groups. X-ray asterism studies indicate that the crystals are shocked, which supports an impact origin. The presence of chromite and zircon together suggests that the Muong Nong-type tektite was produced from sedimentary material.

  20. Zircon and chromite crystals in a muong nong-type tektite.

    PubMed

    Glass, B P

    1970-08-21

    Chromite, zircon, and quartz crystals (identified by x-ray diffraction) have been recovered from a 2.07-gram sample of Muong Nong-type tektite. The absence of eskolaite (Cr(2)O(3)) and baddeleyite (ZrO(2)) supports a previous conclusion that Muong Nong-type tektites were not heated as intensely as other tektite groups. X-ray asterism studies indicate that the crystals are shocked, which supports an impact origin. The presence of chromite and zircon together suggests that the Muong Nong-type tektite was produced from sedimentary material. PMID:17820307

  1. Chromite-plagioclase assemblages as a new shock indicator; implications for the shock and thermal histories of ordinary chondrites

    NASA Astrophysics Data System (ADS)

    Rubin, Alan E.

    2003-07-01

    Chromite in ordinary chondrites (OC) can be used as a shock indicator. A survey of 76 equilibrated H, L and LL chondrites shows that unshocked chromite grains occur in equant, subhedral and rounded morphologies surrounded by silicate or intergrown with metallic Fe-Ni and/or troilite. Some unmelted chromite grains are fractured or crushed during whole-rock brecciation. Others are transected by opaque veins; the veins form when impacts cause localized heating of metal-troilite intergrowths above the Fe-FeS eutectic (988°C), mobilization of metal-troilite melts, and penetration of the melt into fractures in chromite grains. Chromite-plagioclase assemblages occur in nearly every shock-stage S3-S6 OC; the assemblages range in size from 20-300 μm and consist of 0.2-20-μm-size euhedral, subhedral, anhedral and rounded chromite grains surrounded by plagioclase or glass of plagioclase composition. Plagioclase has a low impedance to shock compression. Heat from shock-melted plagioclase caused adjacent chromite grains to melt; chromite grains crystallized from this melt. Those chromite grains in the assemblages that are completely surrounded by plagioclase are generally richer in Al 2O 3 than unmelted, matrix chromite grains in the same meteorite. Chromite veinlets (typically 0.5-2 μm thick and 10-300 μm long) occur typically in the vicinity of chromite-plagioclase assemblages. The veinlets formed from chromite-plagioclase melts that were injected into fractures in neighboring silicate grains; chromite crystallized in the fractures and the residual plagioclase-rich melt continued to flow, eventually pooling to form plagioclase-rich melt pockets. Chromite-rich "chondrules" (consisting mainly of olivine, plagioclase-normative mesostasis, and 5-15 vol.% chromite) occur in many shocked OC and OC regolith breccias but they are absent from primitive type-3 OC. They may have formed by impact melting chromite, plagioclase and adjacent mafic silicates during higher-energy shock

  2. Chromite-Plagioclase Assemblages as a New Shock Indicator; Implications for the Shock and Thermal Histories of Ordinary Chondrites

    NASA Technical Reports Server (NTRS)

    Rubin, Alan E.

    2006-01-01

    Chromite in ordinary chondrites (OC) can be used as a shock indicator. A survey of 76 equilibrated H, L and LL chondrites shows that unshocked chromite grains occur in equant, subhedral and rounded morphologies surrounded by silicate or intergrown with metallic Fe-Ni and/or troilite. Some unmelted chromite grains are fractured or crushed during whole-rock brecciation. Others are transected by opaque veins; the veins form when impacts cause localized heating of metal-troilite intergrowths above the Fe-FeS eutectic (988 C), mobilization of metal-troilite melts, and penetration of the melt into fractures in chromite grains. Chromite-plagioclase assemblages occur in nearly every shock-stage S3-S6 OC; the assemblages range in size from 20-300 microns and consist of 0.2-20-micron-size euhedral, subhedral, anhedral and rounded chromite grains surrounded by plagioclase or glass of plagioclase composition. Plagioclase has a low impedance to shock compression. Heat from shock-melted plagioclase caused adjacent chromite grains to melt; chromite grains crystallized from this melt. Those chromite grains in the assemblages that are completely surrounded by plagioclase are generally richer in Al2O3, than unmelted, matrix chromite grains in the same meteorite. Chromite veinlets (typically 0.5-2 microns thick and 10-300 microns long) occur typically in the vicinity of chromite-plagioclase assemblages. The veinlets formed from chromite-plagioclase melts that were injected into fractures in neighboring silicate grains; chromite crystallized in the fractures and the residual plagioclase-rich melt continued to flow, eventually pooling to form plagioclase-rich melt pockets. Chromite-rich chondrules (consisting mainly of olivine, plagioclase-normative mesostasis, and 5-15 vol.% chromite) occur in many shocked OC and OC regolith breccias but they are absent from primitive type-3 OC. They may have formed by impact melting chromite, plagioclase and adjacent mafic silicates during higher

  3. 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.

  4. An Exercise in X-Ray Diffraction Using the Polymorphic Transition of Nickel Chromite.

    ERIC Educational Resources Information Center

    Chipman, David W.

    1980-01-01

    Describes a laboratory experiment appropriate for a course in either x-ray crystallography or mineralogy. The experiment permits the direct observation of a polymorphic transition in nickel chromite without the use of a special heating stage or heating camera. (Author/GS)

  5. Beneficiation of Konya-Beyşehir Chromite for Producing Concentrates Suitable for Industry

    NASA Astrophysics Data System (ADS)

    Öztürk, Fatma Deniz; Abakay Temel, Halime

    2016-06-01

    Turkey has a 6% share of world chromite mining and possesses 25 million tons of reserves. Despite their economic importance, the most important Turkish chromite reserves have not been extensively studied with respect to their composition. In this study, the possibility of upgrading Konya-Beyşehir (Turkey) chromite to produce chromite concentrates suitable for industry is investigated. Two groups of enrichment experiments were made. The effects of some parameters that markedly influence the separation of a shaking table, such as the amplitude and slope of the shaking table and the frequency of strokes were investigated in the first group of experiments, The shaking table experiments were planned and carried out using the statistical methods of Design of Experiments (Yate's and ANOVA) in the second group of experiments. As a result, it was found that a concentrate containing 46.89% Cr2O3 content with a yield of 85.18% was obtained from a feed containing 3.98% Cr2O3 content in 0.2 + 0.1 mm size fraction.

  6. Petrology of chromite in ureilites: Deconvolution of primary oxidation states and secondary reduction processes

    NASA Astrophysics Data System (ADS)

    Goodrich, Cyrena Anne; Harlow, George E.; Van Orman, James A.; Sutton, Stephen R.; Jercinovic, Michael J.; Mikouchi, Takashi

    2014-06-01

    Ureilites are ultramafic achondrites thought to be residues of partial melting on a carbon-rich asteroid. They show a trend of FeO-variation (olivine Fo from ∼74 to 95) that suggests variation in oxidation state. Whether this variation was established during high-temperature igneous processing on the ureilite parent body (UPB), or preserved from nebular precursors, is a subject of debate. The behavior of chromium in ureilites offers a way to assess redox conditions during their formation and address this issue, independent of Fo. We conducted a petrographic and mineral compositional study of occurrences of chromite (Cr-rich spinel) in ureilites, aimed at determining the origin of the chromite in each occurrence and using primary occurrences to constrain models of ureilite petrogenesis. Chromite was studied in LEW 88774 (Fo 74.2), NWA 766 (Fo 76.7), NWA 3109 (Fo 76.3), HaH 064 (Fo 77.5), LAP 03587 (Fo 74.9), CMS 04048 (Fo 76.4), LAP 02382 (Fo 78.6) and EET 96328 (Fo 85.2). Chromite occurs in LEW 88774 (∼5 vol.%), NWA 766 (<1 vol.%), NWA 3109 (<1 vol.%) and HaH 064 (<1 vol.%) as subhedral to anhedral grains comparable in size (∼30 μm to 1 mm) and/or textural setting to the major silicates (olivine and pyroxenes[s]) in each rock, indicating that it is a primary phase. The most FeO-rich chromites in these sample (rare grain cores or chadocrysts in silicates) are the most primitive compositions preserved (fe# = 0.55-0.6; Cr# varying from 0.65 to 0.72 among samples). They record olivine-chromite equilibration temperatures of ∼1040-1050 °C, reflecting subsolidus Fe/Mg reequilibration during slow cooling from ∼1200 to 1300 °C. All other chromite in these samples is reduced. Three types of zones are observed. (1) Inclusion-free interior zones showing reduction of FeO (fe# ∼0.4 → 0.28); (2) Outer zones showing further reduction of FeO (fe# ∼0.28 → 0.15) and containing abundant laths of eskolaite-corundum (Cr2O3-Al2O3); (3) Outermost zones showing extreme

  7. Beneficiation of Konya-Beyşehir Chromite for Producing Concentrates Suitable for Industry

    NASA Astrophysics Data System (ADS)

    Öztürk, Fatma Deniz; Abakay Temel, Halime

    2016-09-01

    Turkey has a 6% share of world chromite mining and possesses 25 million tons of reserves. Despite their economic importance, the most important Turkish chromite reserves have not been extensively studied with respect to their composition. In this study, the possibility of upgrading Konya-Beyşehir (Turkey) chromite to produce chromite concentrates suitable for industry is investigated. Two groups of enrichment experiments were made. The effects of some parameters that markedly influence the separation of a shaking table, such as the amplitude and slope of the shaking table and the frequency of strokes were investigated in the first group of experiments, The shaking table experiments were planned and carried out using the statistical methods of Design of Experiments (Yate's and ANOVA) in the second group of experiments. As a result, it was found that a concentrate containing 46.89% Cr2O3 content with a yield of 85.18% was obtained from a feed containing 3.98% Cr2O3 content in 0.2 + 0.1 mm size fraction.

  8. A MIXED CHEMICAL REDUCTANT FOR TREATING HEXAVALENT CHROMIUM IN A CHROMITE ORE PROCESSING SOLID WASTE

    EPA Science Inventory

    We evaluated a method for delivering ferrous iron into the subsurface to enhance chemical reduction of Cr(VI) in a chromite ore processing solid waste (COPSW). The COPSW is characterized by high pH (8.5 -11.5), high Cr(VI) concentrations in the solid phase (up to 550 mg kg-1) and...

  9. 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

  10. Epitaxial superconducting structure on lattice matched lanthanum orthogallate

    SciTech Connect

    Belt, R.F.; Uhrin, R.

    1990-10-09

    This patent describes an improvement in a superconducting device comprising a high T{sub c} superconducting thin film of metal oxide based perovskite deposited on a crystalline substrate. The improvement comprises providing as the crystalline substrate of the device monocrystalline lanthanum orthogallate grown from a pure melt of lanthanum and gallium oxides while controlling the major crystallographic direction of solidification or a mixed single crystal of lanthanum orthogallate grown from a melt of lanthanum, gallium and additive oxides while controlling the major crystallographic direction of solidification.

  11. Insight into the Consolidation Mechanism of Oxidized Pellets Made from the Mixture of Magnetite and Chromite Concentrates

    NASA Astrophysics Data System (ADS)

    Zhu, Deqing; Yang, Congcong; Pan, Jian; Zhang, Qiang; Shi, Benjing; Zhang, Feng

    2016-04-01

    To produce more competitive stainless steel products, the utilization of low-cost chromite concentrate is of great importance. In a previous study, a high-quality product pellet (CMP) for blast furnace smelting process made from a mixture of 40 wt pct chromite and 60 wt pct magnetite concentrates was manufactured by a high-pressure grinding rollers pretreatment. In this work, an insight into the consolidation mechanism of CMP is taken in comparison with the oxidized pellets (MP) made from 100 pct magnetite concentrate by adopting the scanning electron microscopy, energy-dispersive spectrometer, and X-ray diffractometer. The mineralogy of the pellets and the morphology of the preheated and roasted mineral particles are demonstrated. To gain better understanding of the consolidation mechanism of CMP, the thermodynamics of chromite-magnetite spinel system and hematite-sesquioxide corundum system in air are considered by using FactSage software. It can be found that the solid-state bonding is the dominant form in the consolidation of CMP, which mainly depends on the recrystallization of hematite, the solid solution bonding in adjacent areas of both magnetite-chromite particles and chromite-chromite particles. The latter two bonds rely on the formation of the miscible sesquioxide and spinel solid solution at the contact areas of particles, which is largely affected by the oxidizability of magnetite and chromite spinels. When more chromite concentrate is blended, the weak bonding among the chromite particles gradually becomes the dominant factor, which will lead to the decrease of the mechanical strength of fired pellets. The presence of a small quantity of siliceous liquid phase in CMP is believed to be beneficial to the hardening by accelerating the ion diffusion rate and forming slag bonds.

  12. Large-area lanthanum hexaboride electron emitter

    NASA Astrophysics Data System (ADS)

    Goebel, D. M.; Hirooka, Y.; Sketchley, T. A.

    1985-09-01

    The characteristics of lanthanum-boron thermionic electron emitters are discussed, and a large-area, continuously operating cathode assembly and heater are described. Impurity production and structural problems involving the support of the LaB6 have been eliminated in the presented configuration. The performance of the cathode in a plasma discharge, where surface modification occurs by ion sputtering, is presented. Problem areas which affect lifetime and emission current capability are discussed.

  13. Chromite and olivine in type II chondrules in carbonaceous and ordinary chondrites - Implications for thermal histories and group differences

    NASA Technical Reports Server (NTRS)

    Johnson, Craig A.; Prinz, Martin

    1991-01-01

    Unequilibrated chromite and olivine margin compositions in type II chondrules are noted to differ systematically among three of the chondrite groups, suggesting that type II liquids differed in composition among the groups. These differences may be interpreted as indicators of different chemical compositions of the precursor solids which underwent melting, or, perhaps, as differences in the extent to which immiscible metal sulfide droplets were lost during chondrule formation. Because zinc is detectable only in type II chromites which have undergone reequilibration, the high zinc contents reported for chondritic chromites in other studies probably reflect redistribution during thermal metamorphism.

  14. 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. PMID:19801159

  15. Photoluminescence properties of cerium oxide nanoparticles as a function of lanthanum content

    SciTech Connect

    Deus, R.C.; Cortés, J.A.; Ramirez, M.A.; Ponce, M.A.; Andres, J.; Rocha, L.S.R.; and others

    2015-10-15

    Highlights: • CeO{sub 2} nanoparticles were obtained by microwave-hydrothermal method. • Rietveld refinement reveals a cubic structure. • KOH mineralizer agent exhibit weak agglomeration at low temperature and shorter time. - Abstract: The structural and photoluminescent properties at room temperature of CeO{sub 2} and La-doped CeO{sub 2} particles were undertaken. The obtained particles were synthesized by a microwave-assisted hydrothermal method (MAH) under different lanthanum contents. X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Fourier transform Raman (FT-Raman), Ultra-violet spectroscopy (UV–vis) and photoluminescence (PL) measurements were carried out. XRD revealed that the powders are free of secondary phases and crystallize in the cubic structure. Raman data show that increasing La doping content increase oxygen vacancies due to lattice expansion. The UV/vis absorption spectroscopy suggested the presence of intermediate energy levels in the band gap of structurally ordered powders. Lanthanum addition creates oxygen vacancies and shifts the photoluminescence in the low energy range leading to intense PL emission.

  16. Self-activating and doped tantalate phosphors.

    SciTech Connect

    Nyman, May Devan; Rohwer, Lauren Elizabeth Shea

    2011-01-01

    An ideal red phosphor for blue LEDs is one of the biggest challenges for the solid-state lighting industry. The appropriate phosphor material should have good adsorption and emission properties, good thermal and chemical stability, minimal thermal quenching, high quantum yield, and is preferably inexpensive and easy to fabricate. Tantalates possess many of these criteria, and lithium lanthanum tantalate materials warrant thorough investigation. In this study, we investigated red luminescence of two lithium lanthanum tantalates via three mechanisms: (1) Eu-doping, (2) Mn-doping and (3) self-activation of the tantalum polyhedra. Of these three mechanisms, Mn-doping proved to be the most promising. These materials exhibit two very broad adsorption peaks; one in the UV and one in the blue region of the spectrum; both can be exploited in LED applications. Furthermore, Mn-doping can be accomplished in two ways; ion-exchange and direct solid-state synthesis. One of the two lithium lanthanum tantalate phases investigated proved to be a superior host for Mn-luminescence, suggesting the crystal chemistry of the host lattice is important.

  17. The Oxidation State Of Iron In Chromite As A Record Of Deep Earth Processes

    NASA Astrophysics Data System (ADS)

    McGowan, N.; Griffin, W. L.; Pearson, N.; O'Reilly, S. Y.; Clark, S. M.; Roque-Rosell, J.; Marcus, M.; McCammon, C. A.

    2015-12-01

    Recent work on podiform chromitite from the Luobusa massif, Tibet, suggests that a lithospheric slab containing the chromitite was driven into the Transition Zone (>400 km) after primary crystallisation at shallow depth [1]. Exsolution of coesite and pyroxenes from chromite is believed to reflect conversion from the spinel structure to the ultra-high pressure (UHP) calcium ferrite (CF) polymorph below 400 km [2]. Experimental studies report that UHP polymorphs can have a high affinity for Fe3+, leading to disproportionation of Fe2+ to Fe3+ + Fe0 [3], despite low fO2 as evidenced by inclusions of diamond, native metals and alloys, moissanite, and Cr2+-bearing chromite. Luobusa chromitites may be the first natural example of this phenomenon; one study reported a massive chromitite with higher Fe3+/∑Fe than nodular or disseminated varieties with lower modal chromite [4]. The absence of indicators of oxidation implies that the high Fe3+/∑Fe was not produced by formation or alteration of chromite at Earth's surface. A study using samples from Luobusa and the low-pressure Antalya Complex, Turkey was carried out to investigate relationships between pressure, fO2 and Fe3+/∑Fe. In the first application of μ-X-ray absorption near edge structure (μ-XANES) spectroscopy to measure chromite Fe3+/∑Fe, we constructed calibration curves for the pre-edge centroid and main edge maximum features using Fe3+/∑Fe (from Mössbauer spectroscopy) in synthetic and natural spinels. Pre-edge results show that Fe3+/∑Fe increases with vol.% chromite in chromitites from Luobusa, but not from Antalya (fig. 1). High Fe3+/∑Fe thus appears to be a consequence of crystallographic stabilisation of Fe3+ in the UHP polymorph stable below 400 km, despite low-fO2 conditions. The rapid upwelling of the Luobusa chromitite to the uppermost mantle (<10 Ma) has preserved the high Fe3+/∑Fe in samples where re-equilibration with olivine was limited. [1] McGowan et al., Geology (2015) 43, 179

  18. The origin of chromitic chondrules and the volatility of Cr under a range of nebular conditions

    NASA Technical Reports Server (NTRS)

    Krot, Alexander; Ivanova, Marina A.; Wasson, John T.

    1993-01-01

    We characterize ten chromatic chondrules, two spinelian chondrules andd one spinel-bearing chondrule and summarize data for 120 chromitic inclusions discovered in an extensive survey of ordinary chondrites. Compositional and petrographic evidence suggests that chromitic chondrules and inclusions are closely related. The Cr/(Cr + Al) ratios in the spinal of these objects range from 0.5 to 0.9 and bulk Al2O3 contents are uniformly high (greater than 10 wt%, except for one with 8 wt%). No other elements having comparable solar abundances are so stongly enriched, and alkali feldspar and merrillite are more common than in normal chondrules. The Cr/Mg ratios in chromitic chondrules are 180-750 times the ratios in the bulk chondrite. With the possible exception of magnetic clumping of chromite in the presolar cloud, mechanical processes cannot account for this enrichment. Examination of nebular equilibrium processes shows that 50%-condensation temperatures of Cr at pH2/pH2O of 1500 are several tens of degrees below those of Mg as Mg2SiO4; the condensation of Cr is primarily as MgCr2O4 dissolved in MgAl2O4 at nebular pressures of 10(exp -4) atm or below. At pH2 = 10(exp -3) atm condesation as Cr in Fe-Ni is favored. Making the nebula much more oxidizing reduces the difference in condensation temperatures but Mg remains more refractory. We conclude that nebular equilibrium processes are not responsible for the enhanced Cr/Mg ratios. We propose that both Cr and Al became enriched in residues formed by incomplete evaporation of presolar lumps. We suggest that spinals remained as solid phases when the bulk of the silicates were incorporated into the evaporating melt; vaporization of Al and Cr were inhibited by the slow kinetics of diffusion. Subsequent melting and crystallization of these residues fractionated Cr from Al. The resulting materials constituted major components in the precursors of chromitic chondrules. Our model implies that chromitic chondrules and inclusions

  19. Diverse Chemical Zoning Trends in Acapulco Chromites: How Many Sources for the Parental Materials?

    NASA Astrophysics Data System (ADS)

    El Goresy, A.; Janicke, J.

    1995-09-01

    Acapulco is considered to be a link between primitive chondritic meteorites and the differentiated achondrites. Its parent body presumably formed by accretion of material of chondritic compositions at an fO2 that lies between that of H- and enstatite chondrites [1]. The accreted chondritic material was subjected 4.557 Gyr ago to peak temperatures close to 1200 degrees C that lead to partial melting and extensive recrystallization [1, 2]. Seven morphologically different types of graphite with large variations in C- and N-isotopic compositions were recently reported from Acapulco [3, 4]. At least four distinct isotopic reservoirs are required to explain the C- and N-isotopic compositions of these graphites [3, 4]. While the silicate minerals in Acapulco have isotopically heavy N (delta^(15)N = + 15 per mil) chromites were found to be isotopically light (delta^(15)N = _ 75 to _ 82 per mil). Chromite occurs in Acapulco in six different assemblages: (1) as inclusions in silicates, (2) in FeNi, (3) in troilite, (4) with FeNi and troilite, (5) with FeNi and silicates, and (6) with troilite and silicates. It is also rarely present as small idiomorphic inclusions in plagioclase. Chromites in contact with silicates display no chemical zoning for Cr, Al, Ti, Fe, Mg, Mn, or Zn to the silicate borders thus indicating high degree of equilibration with the silicate neighbours. The MgO-contents of chromites in metals and troilites (4.74 to 7.2 %) are relatively lower and their compositional ranges are relatively wider than those in contact with silicates (6.1 to 7.69 %). Zoning profiles of MgO and FeO in chromites in all assemblages are quite flat. Chromites in contact with metals and troilite display a variety of zoning patterns of Cr, Al, Ti, and Zn. All these chromite types , however, depict the same MnO zoning trends with low MnO-contents in their cores (0.96 to 2.14 %) than in their rims to metal or troilite (1.7 to 3.1 %). With few exceptions, the zoning behaviour of Cr, Al

  20. The features of structural transformations in lanthanum manganites La{sub 1−x}A{sub x}MnO{sub 3+δ} (A = Ca, Sr, Ba)

    SciTech Connect

    Sedykh, Vera D.

    2014-10-27

    In this work, the effect of the ionic radius and concentration of a doping element on the features of the structural transformations in polycrystalline lanthanum manganites, La{sub 1−x}A{sub x}MnO{sub 3+δ} (A = Ca, Sr, Ba), has been studied by Mössbauer spectroscopy and X-ray diffraction analysis. For Mössbauer investigations, a small amount of {sup 57}Fe (2 at%) Mössbauer isotope was introduced into the samples. It follows from the analysis of the obtained data that both common features of the structural transformations and differences between them exist in lanthanum manganites depending on ionic radius and concentration of a doping element.

  1. Comparative Planetary Mineralogy: Co, Ni Systematics in Chromite from Planetary Basalts

    NASA Technical Reports Server (NTRS)

    Karner, J. M.; Shearer, C. K.; Papike, J. J.; Righter,K.

    2005-01-01

    Spinel is a minor but important phase in planetary basalts because its variable composition often reflects basalt petrogenesis. For example, complicated zoning trends in spinel can give clues to melt evolution [1], and V concentrations in chromite lend insight into magma oxygen fugacity (fO2) conditions [2]. Nickel and Co are two elements that are commonly used as a measure of melt fractionation, and their partitioning between olivine and melt is fairly well understood. Less clear is their partitioning into spinel, although [3] has explored Ni and Co systematics in experimental charges. This study documents Ni and Co behavior in early crystallizing spinel (chromite) from several planetary basalts in an attempt to compare our results with [3], and also gain insight into basalt evolution on the three planets.

  2. Optical constants of various chromites as determined by Kramers-Kronig analysis.

    PubMed

    Anki, M M; Lefez, B

    1996-03-20

    The infrared optical constants of a few different powders of chromites, XCr(2)O(4) (where X is Fe, Ni, Mg, Zn, or Cu), have been determined by Kramers-Kronig analysis of their infrared transmission and reflection spectra. The knowledge of these constants allows one to predict the different thin-layer infrared reflection spectra and to compare them, when it is possible, with the reflection spectra calculated with n and k obtained by the use of the classical oscillator method.

  3. Peridotite hosted chromite, magnesite and olivine deposits of West Anatolia: A review

    NASA Astrophysics Data System (ADS)

    Zedef, Veysel

    2016-04-01

    Turkey has important chromite, magnesite and olivine deposits within peridotite host rocks. The peridotites (harzburgite, verlite, lherzolite and dunite) are mostly serpentinised as a result of metasomatic reaction of olivine and pyroxene minerals with percolating water. The serpentinites are generally an important part of ophiolitic complexes which displays a discontinuous belts all over the country. The chromite deposits are often related to cumulates and tectonites (as Alpine and/or podiform type deposits) and despite their small reserves, their grade can reach up to 58 %. In most deposits, a little enrichment efforts, the grade of chromite can easily be reached from 25 % to 40-45 %. The magnesite deposits of West Anatolia is especially concentrated in three provinces. These provinces are Konya, Kutahya and Eskisehir. The magnesites are of cryptocrystalline type and, like chromite deposits, their reserve are small but have high grade with low FeO-CaO and high MgO ratio. Once again, these deposits are found within serpentinised peridotites of ultramafic belts. The total (proven and inferred) magnesite reserves are approximately 200 million tons, and these are mostly cryptocrystalline character. A small amount of sedimentary magnesite deposits also present in Denizli (SW Anatolia) and Erzincan (Eastern Anatolia). The olivine deposits are found within peridotites of Western Anatolia. Especially, the Kızıldag olivine deposits (located between the border of Antalya and Konya provinces) are noteworthy with its huge (9 billion tons) reserves. The main olivine mineral is forsterite (Mg2SiO4) which has economically important when compared to other olivine mineral fayalite. The deposits have no quality problem but have a serious disadvantages since its location far from the ports and railway stations.

  4. The reduction mechanism of a natural chromite at 1416 °C

    NASA Astrophysics Data System (ADS)

    Soykan, O.; Eric, R. H.; King, R. P.

    1991-02-01

    The behavior of a natural chromite from the Bushveld Complex, Transvaal, South Africa, during reduction at 1416 °C by graphite was studied by means of thermogravimetric analysis, X-ray diffraction (XRD) analysis, energy-dispersive X-ray analysis (EDAX), and metallographic analysis. Experimental runs were allowed to proceed up to 120 minutes, resulting in 99 pct reduction. The specific objective of this study was to delineate the reduction mechanism of chromite by graphite. Zoning was observed in partially reduced chromites with degrees of reduction of up to about 70 pct. The inner cores were rich in iron, while the outer cores were depleted of iron. Energy-dispersive X-ray analysis revealed that Fe2+ and Cr3+ ions had diffused outward, whereas Cr2+, Al3+, and Mg2+ ions had diffused inward. The following mechanism of reduction, which is based on the assumption that the composition of the spinel phase remains stoichiometric with increasing degree of reduction, is proposed, (a) Initially, Fe3+ and Fe2+ ions at the surface of the chromite particle are reduced to the metallic state. This is followed immediately by the reduction of Cr3+ ions to the divalent state, (b) Cr2+ ions diffusing toward the center of the particle reduce the Fe3+ ions in the spinel under the surface of the particle to Fe2+ at the interface between the inner and outer cores. Fe2+ ions diffuse toward the surface, where they are reduced to metallic iron, (c) After the iron has been completely reduced, Cr3+ and any Cr2+ that is present are reduced to the metallic state, leaving an iron- and chromium-free spinel, MgAl2O4.

  5. Postmortem Study of a Magnesia-Chromite Brick from a Lead Recycling Furnace

    NASA Astrophysics Data System (ADS)

    Gregurek, D.; Reinharter, K.; Reiter, V.; Wenzl, C.; Spanring, A.

    2015-09-01

    This study provides an example of a detailed postmortem analysis carried out on a used silicate-bonded magnesia-chromite brick out of a lead recycling furnace. The magnesia-chromite brick suffered from a high chemical attack due to the process slag. The high CaO, BaO, and sulfur-bearing silicate slag, as well as a high Na2O supply from soda resulted not only in a deep-reaching infiltration of the brick microstructure but also in a severe corrosion of the brick components. Both the sintered magnesia and chromite were attacked chemically. The FactSage calculations showed the formation of high amounts of liquid phase in the infiltrated microstructure and the formation of various Na-Ca-Al-silicates. A detailed investigation of the wear mechanisms through "postmortem studies" is a crucial prerequisite for every refractory producer to understand the interactions between slag and refractory materials. The obtained information and insights serve as a basis for improving refractory materials (i.e., choice of refractories for individual process and new developments) and consequently furnace operations (i.e., prolonged furnace campaigns).

  6. Assessment and prediction of contaminant migration in ground water from chromite waste dump

    NASA Astrophysics Data System (ADS)

    Tiwary, R. K.; Dhakate, R.; Ananda Rao, V.; Singh, V. S.

    2005-08-01

    Sukinda chromite valley is one of the largest chromite deposits of the country and produces nearly 8% of chromite ore. It greatly contributes towards the economic development but at the same time deteriorates the natural environment. It is generally excavated by opencast mining method. In the Sukinda mining area, around 7.6 million tons of solid waste have been generated in the form of rejected minerals, overburden material/waste rock and sub-grade ore that may be resulting in environmental degradation, mainly causing lowering in the water table vis-à-vis deterioration in surface and ground water quality. The study conducted in and around one of the chromite mine of the valley reveals that the concentration of hexavalent chromium is found in the water samples of ground and surface water, mine effluents and seepage water. Hexavalent Chromium (Cr+6) have been found varying between 0.02 mg/l and 0.12 mg/l in mine effluents and 0.03 0.8 mg/l in shallow hand pumps and 0.05 and 1.22 mg/l in quarry seepage. The concentration of Cr+6 in Damsal nalah, the main surface water source in the area, is found varying between 0.03 mg/l and 0.14 mg/l and a increasing trend, which is in the downstream of mining activities, has been observed. Leachate study clearly shows that the soil lying in the vicinity of mine waste dump shows highest concentration of Cr+6. Contaminant migration in ground water depends upon various geohydrological conditions of the area. The study shows that aquifer resistivity varies between 15 Ωm to 150 Ωm and aquifer depth varies from 4 m to 26 m below ground level. The ground water flow and mass transport models were constructed with the help of geo-hydrological and geophysical informations using Visual Modflow software. Contaminant migration and path lines for 20 years have been predicted in two layers model of ground water. The study provided an insight into the likely migration of contaminant in ground water due to leaching from overburden dump of

  7. Massive Chromite in the Brenham Pallasite and the Fractionation of Cr During the Crystallization of Asteroidal Cores

    NASA Technical Reports Server (NTRS)

    Wasson, John T.; Lange, David E.; Francis, Carl A.; Ulff-Moller, Finn

    1999-01-01

    Large (greater than or equal to 2 mm) chromite grains are present in IIIAB iron meteorites and in the main-group a pallasites (PMG), closely related to high-Au IIIAB irons, Pallasites seem to have formed by the intrusion of a highly evolved metallic magma from a IIIAB-like core into fragmented olivine of the overlying dunite mantle. High Cr contents are commonly encountered during the analyses of metallic samples of high-Au IIIAB irons and main-group pallasites, an indication that Cr contents were high in the intruding liquid and that Cr behaved as an incompatible element during the crystallization of the IIIAB magma, contrary to expectations based on the negative IIIAB Cr-Ni and Cr-Au trends among low-Au IIIAB irons. In a region about 10 cm across in the Brenham main-group pallasite massive chromite fills the interstices between olivine grains, the site normally occupied by metal in Brenham and other pallasites. The massive chromite may have formed as a late cumulus phase; because Fe-Ni was also crystallizing, its absence in the chromite-rich region suggests a separation associated with differences in liquid buoyancy. The coexisting chromite and olivine are zoned; in the olivine FeO is highest in pallasitic (olivine-metal) regions, lowest in rims adjacent to chromite, and intermediate in the cores of these olivines. Chromite shows the opposite zoning, with the highest FeO contents at grain edges adjacent to olivine. The observed gradients are those expected to form by Fe-Mg exchange between olivine and chromite during slow cooling at subsolidus temperatures. Compared to normal Brenham, contents of phosphoran olivine and phosphates are higher in the chromitic pallasitic region. We also report data for large-to-massive chromites present in PMG Molong and in high-Au IIIAB Bear Creek that, like Brenham, formed from a highly evolved magma. The Bear Creek chromite has a much lower Mg content than that in the pallasites, implying that, in the PMG, the Mg was extracted

  8. 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

  9. Lutetium-doped EuO films grown by molecular-beam epitaxy

    SciTech Connect

    Melville, A.; Heeg, T.; Mairoser, T.; Schmehl, A.; Shai, D. E.; Monkman, E. J.; Harter, J. W.; Hollaender, B.; Schubert, J.; Shen, K. M.; Mannhart, J.; Schlom, D. G.

    2012-05-28

    The effect of lutetium doping on the structural, electronic, and magnetic properties of epitaxial EuO thin films grown by reactive molecular-beam epitaxy is experimentally investigated. The behavior of Lu-doped EuO is contrasted with doping by lanthanum and gadolinium. All three dopants are found to behave similarly despite differences in electronic configuration and ionic size. Andreev reflection measurements on Lu-doped EuO reveal a spin-polarization of 96% in the conduction band, despite non-magnetic carriers introduced by 5% lutetium doping.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. Chromite-rich mafic silicate chondrules in ordinary chondrites: Formation by impact melting

    NASA Technical Reports Server (NTRS)

    Krot, Alexander N.; Rubin, Alan E.

    1993-01-01

    Chromium-rich chondrules constitute less than 0.1 percent of all ordinary chondrite (OC) chondrules and comprise three groups: chromian-spinel chondrules, chromian-spinel inclusions, and chromite-rich mafic silicate (CRMS) chondrules. Chromian-spinel chondrules (typically 100-300 microns in apparent diameter) exhibit granular, porphyritic and unusual textures and occur mainly in H chondrites. Their morphologies are distinct from the irregularly shaped chromian-spinel inclusions of similar mineralogy. Chromian-spinel chondrules and inclusions consist of grains of chromian-spinel embedded in plagioclase (Pl) or mesostasis of Pl composition. Many also contain accessory ilmenite (Ilm), high-Ca pyroxene (Px), merrillite (Mer), and rare olivine (Ol); some exhibit concentric mineral and chemical zoning. CRMS chondrules (300-1100 microns in apparent diameter) are generally larger than chromian-spinel chondrules and occur in all metamorphosed OC groups. Most CRMS chondrules are nearly spherical although a few are ellipsoidal with a/b aspect ratios ranging up to 1.7. Textures include cryptocrystalline, granular, radial, barred, and porphyritic varieties; some contain apparently relict grains. The chondrules consist of chromite (Chr), Ol and Pl, along with accessory Mer, troilite (Tr), metallic Fe-Ni (Met), Px and Ilm. The mesostasis in CRMS chondrules is nearly opaque in transmitted light; thus, they can be easily recognized in the optical microscope. Based on the similarity of mineralogy and chemistry between CRMS chondrules of different textures (opaque chromite-rich mesostasis, skeletal morphology of Ol grains, similar bulk compositions) we suggest that these chondrules form a genetically related population.

  15. From spin induced ferroelectricity to dipolar glasses: Spinel chromites and mixed delafossites

    SciTech Connect

    Maignan, A.

    2012-11-15

    Magnetoelectric multiferroics showing coupling between polarization and magnetic order are attracting much attention. For instance, they could be used in memory devices. Metal-transition oxides are provided several examples of inorganic magnetoelectric multiferroics. In the present short review, spinel and delafossite chromites are described. For the former, an electric polarization is evidenced in the ferrimagnetic state for ACr{sub 2}O{sub 4} polycrystalline samples (A=Ni, Fe, Co). The presence of a Jahn-Teller cation such as Ni{sup 2+} at the A site is shown to yield larger polarization values. In the delafossites, substitution by V{sup 3+} at the Cr or Fe site in CuCrO{sub 2} (CuFeO{sub 2}) suppresses the complex antiferromagnetic structure at the benefit of a spin glass state. The presence of cation disorder, probed by transmission electron microscopy, favors relaxor-like ferroelectricity. The results on the ferroelectricity of ferrimagnets and insulating spin glasses demonstrate that, in this research field, transition-metal oxides are worth to be studied. - Graphical abstract: Electric polarization as a function of temperature is measured up to T{sub C} in three chromite ferrimagnetic spinels. Largest values are reached for spinels with Jahn-Teller cations at the A site (Ni or Fe). Highlights: Black-Right-Pointing-Pointer Electric polarization is evidenced in the ferrimagnetic state of the chromite spinels. Black-Right-Pointing-Pointer Jahn-Teller cations at the A site of these spinels lead to larger polarization values. Black-Right-Pointing-Pointer Vanadium substituted at the Cr (or Fe) site of delafossites changes the antiferromagnetic state to spin glass. Black-Right-Pointing-Pointer Electric polarization is not the result of magnetic ordering but magnetic disordering in Cr or Fe delafossites. Black-Right-Pointing-Pointer Relaxor-type ferroelectricity or spin induced ferroelectricity can be observed in the delafossites.

  16. Chemical and mineralogical characterization of chromite ore processing residue from two recent Indian disposal sites.

    PubMed

    Matern, Katrin; Kletti, Holger; Mansfeldt, Tim

    2016-07-01

    Chromite ore processing residue (COPR) is a hazardous waste. Nevertheless, deposition of COPR in uncontrolled surface landfills is still common practice in some countries. Whereas old (between at least 40 and 180 years) COPR from the temperate zone has been intensively investigated, information on COPR in other regions is restricted. Relatively young (<25 years) COPR samples obtained from two abandoned landfill sites in India were investigated by a modified total microwave digestion method, X-ray powder diffraction (XRPD), and scanning electron microscopy (SEM) in order to determine their chemical and mineralogical nature. By the use of microwave digestion with acid mixtures of HNO3, H3PO4, and HBF4 (5:3:2 vol), COPR was completely dissolved and element contents similar to those obtained by X-ray fluorescence were found. Total Cr contents of the two COPR accounted for 81 and 74 g kg(-1), of which 20 and 13% were present in the carcinogenic hexavalent form (CrVI). Apart from the common major mineral phases present in COPR reported earlier, a further Cr host mineral, grimaldiite [CrO(OH)], could be identified by XRPD and SEM. Additionally, well soluble Na2CrO4 was present. Improving the effectiveness of chromite ore processing and preventing the migration of Cr(VI) into water bodies are the main challenges when dealing with these COPR. PMID:27111471

  17. Microbial leaching of chromite overburden from Sukinda mines, Orissa, India using Aspergillus niger

    NASA Astrophysics Data System (ADS)

    Biswas, Supratim; Samanta, Saikat; Dey, Rajib; Mukherjee, Siddhartha; Banerjee, Pataki C.

    2013-08-01

    Leaching of nickel and cobalt from two physical grades (S1, 125-190 μm, coarser and S3, 53-75 μm, finer) of chromite overburden was achieved by treating the overburden (2% pulp density) with 21-d culture filtrate of an Aspergillus niger strain grown in sucrose medium. Metal dissolution increases with ore roasting at 600°C and decreasing particle size due to the alteration of microstructural properties involving the conversion of goethite to hematite and the increase in surface area and porosity as evident from X-ray diffraction (XRD), thermogravimetry-differential thermal analysis (DT-TGA), and field emission scanning electron microscopy (FESEM). About 65% Ni and 59% Co were recovered from the roasted S3 ore employing bioleaching against 26.87% Ni and 31.3% Co using an equivalent amount of synthetic oxalic acid under identical conditions. The results suggest that other fungal metabolites in the culture filtrate played a positive role in the bioleaching process, making it an efficient green approach in Ni and Co recovery from lateritic chromite overburden.

  18. Tuning oxygen vacancy photoluminescence in monoclinic Y2WO6 by selectively occupying yttrium sites using lanthanum

    PubMed Central

    Ding, Bangfu; Han, Chao; Zheng, Lirong; Zhang, Junying; Wang, Rongming; Tang, Zilong

    2015-01-01

    The effect of isovalent lanthanum (La) doping on the monoclinic Y2WO6 photoluminescence was studied. Introducing the non-activated La3+ into Y2WO6 brings new excitation bands from violet to visible regions and strong near-infrared emission, while the bands position and intensity depend on the doping concentration. It is interesting to find that doping La3+ into Y2WO6 promotes the oxygen vacancy formation according to the first-principle calculation, Raman spectrum, and synchrotron radiation analysis. Through the Rietveld refinement and X-ray photoelectron spectroscopy results, La3+ is found to mainly occupy the Y2 (2f) site in low-concentration doped samples. With increasing doping concentration, the La3+ occupation number at the Y3 (4g) site increases faster than those at the Y1 (2e) and Y2 (2f) sites. When La3+ occupies different Y sites, the localized energy states caused by the oxygen vacancy pair change their position in the forbidden band, inducing the variation of the excitation and emission bands. This research proposes a feasible method to tune the oxygen vacancy emission, eliminating the challenge of precisely controlling the calcination atmosphere. PMID:25821078

  19. 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....

  20. 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....

  1. 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....

  2. Effect of counterions on lanthanum biosorption by Sargassum polycystum.

    PubMed

    Diniz, Vivian; Volesky, Bohumil

    2005-06-01

    The effect of the presence of different anions on the biosorption of La(3+) (Lanthanum) using Sargassum polycystum Ca-loaded biomass was studied in this work. Different types of metal salts were used, such as nitrate, sulphate and chloride. The presence of the anion sulphate decreased the metal uptake for tested pH values of 3--5 when compared to the nitrate and chloride systems. The presence of chloride ions did not seem to interfere with the lanthanum removal. The speciation of lanthanum in solution could explain the differences obtained for the different systems and the Mineql+ program was used for the calculations. A monovalent complex with sulphate and lanthanum was formed that had lower apparent affinity towards the biomass compared to the free trivalent metal ion. The La uptake varied from 0.6 to 1.0 mmol g(-1). The Langmuir model was used to describe quantitatively the sorption isotherms. The addition of sulphuric acid for pH adjustment decreased the metal uptake from lanthanum sulphate solutions when compared to the nitric acid addition. The effect was more pronounced with sulphuric acid due to the formation of complexes.

  3. 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).

  4. 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. PMID:26871732

  5. PGE distribution in the Chromite bearing mafic-ultramafic Kondapalli Layered Complex, Krishna district, Andhra Pradesh, India

    NASA Astrophysics Data System (ADS)

    Meshram, Tushar M.; Nannaware, Shraddha. B.; Nannaware, B.; Bhatacharjee, Shantanu; Waghmare, Minakshi. M.; Rajakumar, T.

    2015-09-01

    The Kondapalli Layered Complex (KLC) is a dismembered mafic-ultramafic layered intrusion, mainly composed of gabbroic and anorthositic rocks with subordinate ultramafics and chromitite. Chromitite occurs as lenses, pods, bands and disseminations. Platinum group of minerals (PGMs) occur as inclusions within chromite and silicates. The study indicates an inhomogeneous distribution of PGMs and distinct dominance of IPGEs over the PPGEs. The average ΣPGE content of chromite of KLC varies from 64 ppb to 576 ppb with Pt ranging from 5 to 495 ppb, Pd 5 to 191 ppb, Ir 3 to 106 ppb, Ru 3 to 376 ppb and Rh 3 to 135 ppb. The PGMs identified in the KLC indicate primary deposition of the IPGE, preceding chromite, indicating its orthomagmatic nature. Most of the PGM grains are usually below 10 μm. The identified PGMs are Laurite (RuS2), irarsite (Ir, As, S), iridosmine (Os, Ir), undetermined Os-Ir sulphide and Ru-Os-Ir-Zn alloys. Chromite also contains inclusions of pentlandite, millerite, chalcopyrite and pyrite. Study indicating that the KLC have orthomagmatic origin for PGE which are dominated by IPGE group and formed under surpa-subduction zone peridotite setting.

  6. Zoned chromites with high Mn-contents in the Fe-Ni-Cr-laterite ore deposits from the Edessa area in Northern Greece

    NASA Astrophysics Data System (ADS)

    Michailidis, K. M.

    1990-07-01

    The mineralogy of the transported Fe-Ni-Cr-laterite ore bodies from the Edessa area in Northern Greece was studied. The special emphasis was on the textural features and chemistry of chromite. The chromite was residually inherited in laterites from weathered ultramafic rocks and it displays zonation. Three main zones were optically distinguished: an inner chromite zone, an intermediate ferritechromite zone and a magnetite rim. These three zones have distinct compositions. The major oxides MgO and Al2O3 decrease from the chromite core to the ferritechromite zone, while FeOt increases and Cr2O3 either increases or decreases. A characteristic chemical feature of the chromite is the very high Mn-content in the ferritechromite zone, up to 20%wt MnO. Chemical zonation has, however, been detected in optically unzoned chromite cores rimmed by magnetite. The zoning and the high Mn-content of the chromite is a result of serpentinization in the presence of Mn-rich fluids, following lateritic weathering and finally Alpine low-grade metamorphism.

  7. Platinum-group element abundance and distribution in chromite deposits of the Acoje Block, Zambales Ophiolite Complex, Philippines

    USGS Publications Warehouse

    Bacuta, G.C.; Kay, R.W.; Gibbs, A.K.; Lipin, B.R.

    1990-01-01

    Platinum-group elements (PGE) occur in ore-grade concentration in some of the chromite deposits related to the ultramafic section of the Acoje Block of the Zambales Ophiolite Complex. The deposits are of three types: Type 1 - associated with cumulate peridotites at the base of the crust; Type 2 - in dunite pods from the top 1 km of mantle harzburgite; and Type 3 - like Type 2, but in deeper levels of the harzburgite. Most of the deposites have chromite compositions that are high in Cr with Cr/(Cr + Al) (expressed as chromium index, Cr#) > 0.6; high-Al (Cr# Pd, thought to be characteristic of PGE-barren deposits) and positive slope (Ir < Pd, characteristic of PGE-rich deposits). Iridium, Ru and Os commonly occur as micron-size laurite (sulfide) inclusions in unfractured chromite. Laurite and native Os are also found as inclusions in interstitial sulfides. Platinum and Pd occur as alloy inclusions (and possibly as solid solution) in interstitial Ni-Cu sulfides and as tellurobismuthides in serpentine and altered sulfides. Variability of PGE distribution may be explained by alteration, crystal fractionation or partial melting processes. Alteration and metamorphism were ruled out, because PGE contents do not correlate with degree of serpentinization or the abundance and type (hydroxyl versus non-hydroxyl) of silicate inclusions in chromite. Preliminary Os isotopic data do not support crustal contamination as a source of the PGEs in the Acoje deposits. The anomalous PGE concentrations in Type 1 high-Cr chromite deposits are attributed to two stages of enrichment: an early enrichment of their mantle source from previous melting events and a later stage of sulfide segregation accompanying chromite crystallization. High-Al chromite deposits which crystallized from basalts derived from relatively low degrees of melting owe their low PGE content to partitioning of PGEs in sulfides and alloys that remain in the mantle. High-Cr deposits crystallized from melts that were

  8. 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

  9. Calcium and lanthanum solid base catalysts for transesterification

    SciTech Connect

    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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. Methanol synthesis using a catalyst combination of alkali or alkaline earth salts and reduced copper chromite

    DOEpatents

    Tierney, John W.; Wender, Irving; Palekar, Vishwesh M.

    1995-01-01

    The present invention relates to a novel route for the synthesis of methanol, and more specifically to the production of methanol by contacting synthesis gas under relatively mild conditions in a slurry phase with a catalyst combination comprising reduced copper chromite and basic alkali salts or alkaline earth salts. The present invention allows the synthesis of methanol to occur in the temperature range of approximately 100.degree.-160.degree. C. and the pressure range of 40-65 atm. The process produces methanol with up to 90% syngas conversion per pass and up to 95% methanol selectivity. The only major by-product is a small amount of easily separated methyl formate. Very small amounts of water, carbon dioxide and dimethyl ether are also produced. The present catalyst combination also is capable of tolerating fluctuations in the H.sub.2 /CO ratio without major deleterious effect on the reaction rate. Furthermore, carbon dioxide and water are also tolerated without substantial catalyst deactivation.

  15. Methanol synthesis using a catalyst combination of alkali or alkaline earth salts and reduced copper chromite

    DOEpatents

    Tierney, J.W.; Wender, I.; Palekar, V.M.

    1995-01-24

    The present invention relates to a novel route for the synthesis of methanol, and more specifically to the production of methanol by contacting synthesis gas under relatively mild conditions in a slurry phase with a catalyst combination comprising reduced copper chromite and basic alkali salts or alkaline earth salts. The present invention allows the synthesis of methanol to occur in the temperature range of approximately 100--160 C and the pressure range of 40--65 atm. The process produces methanol with up to 90% syngas conversion per pass and up to 95% methanol selectivity. The only major by-product is a small amount of easily separated methyl formate. Very small amounts of water, carbon dioxide and dimethyl ether are also produced. The present catalyst combination also is capable of tolerating fluctuations in the H[sub 2]/CO ratio without major deleterious effect on the reaction rate. Furthermore, carbon dioxide and water are also tolerated without substantial catalyst deactivation.

  16. The structural evolution of dunite and chromite ore from the Kharcheruz Massif, the Polar Urals

    NASA Astrophysics Data System (ADS)

    Chernyshov, A. I.; Yurichev, A. N.

    2016-03-01

    The Kharcheruz block of the Syumkeu ultramafic massif is a southern fragment of the Khadata ophiolitic belt, which closes the ophiolites of the Polar Urals in the north. The block, striking in the latitudinal direction, is sheetlike in shape and primarily composed of dunite with nearly latitudinal zones of chromite mineralization. The dunites are subject to ductile deformation various in intensity, and this variability is displayed in their heterogeneous structure and texture. The following microstructural types are distinguished by the variety and intensity of their deformation: protogranular → mesogranular → porphyroclastic → porphyrolath → mosaic. The petrostructural patterns of olivines pertaining to the above types reflect conditions of ductile deformation. Protogranular dunite is formed as a product of pyroxene decomposition in mantle harzburgite accompanied by annealing recrystallization at a temperature above 1000°C. Mesogranular dunite is formed as a product of high-temperature plastic flow by means of translation sliding in olivine and diffuse creep at a temperature dropping from 1000 to 650°C and at a low rate (<10-6 s-1). Cr-spinel segregates into linear zones of disseminated chromite mineralization within zones of bedding-plane plastic flow. Porphyroclastic and mosaic dunites are formed under conditions of intense deformation at a temperature of 500-750°C and at a significant rate (>10-6 s-1). Dunite is deformed by means of syntectonic recrystallization and subordinate translation gliding. Linear zones of disseminated mineralization undergo destruction thereby, with the formation of lenticular chromitite bodies from which ductile olivine is squeezed out with the formation of densely impregnated and massive ores.

  17. 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.

  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. Geology and economic potential for chromite in the Zhob Valley ultramafic rock complex, Hindubagh, Quetta division, West Pakistan

    USGS Publications Warehouse

    Rossman, D.L.; Ahmad, Zaki; Rahman, Hamidur

    1971-01-01

    The ultramafic rocks making up the Zhob Valley igneous complex have yielded small amounts of metallurgical-grade chromite since the early part of the century. From 1968-1970 a cooperative study undertaken by the Geological Survey of Pakistan and the U. S. Geological Survey, under the auspices of the Government of Pakistan and the Agency for International Development, evaluated the chromite potential of the Zhob Valley area and provided data for effective exploration. The Jung Tor Ghar ultramafic rock mass, covering an area of about 45 square miles, is a thrust-fault block completely surrounded and underlain (?) by sedimentary rocks as young as Late Cretaceous in age. The igneous rocks were thrust from the northwest along an east-trending, north-dipping fault in Late Cretaceous or Paleocene time and were peneplaned, dissected, and deeply laterized by mid-Eocene time. The ultramafic rocks consist of interlayered harzburgite and dunite and a cross-cutting dunite here called transgressive dunite. Layered structure passes without discernible deviation from the interlayered harzburgite-dunite through the transgressive dunite. The lowest rocks in the mass, composed mainly of transgressive dunite, grade upward into the interlayered rock about 3,000 feet above the fault block base. The upper transgressive dunites tend to form interconnecting linear networks and probably a few pipe-like structures. The transgressive dunite is thought to have formed by action of water derived from the underlying sedimentary rocks; the water heated by the hot ultramafic rock (at the time of emplacement) altered the pyroxene to olivine and talc, and, with lowering temperature, to serpentine. Other interpretations are possible. Virtually all the chromite in the Jung Tor Ghar lies in or immediately above the masses of transgressive dunite. This fact provides a key to chromite exploration: The most favorable zone for prospecting lies in the vicinity of the upper contacts of the transgressive

  20. Combustion synthesis and photoluminescence of Tb3+ doped LaAlO3 nanophosphors

    NASA Astrophysics Data System (ADS)

    Dhahri, A.; Horchani-Naifer, K.; Benedetti, A.; Enrichi, F.; Férid, M.; Riello, P.

    2013-04-01

    Terbium doped lanthanum aluminate (LaAlO3) nanophosphors were successfully synthesized by a combustion process using concentrated solution of lanthanum nitrates and aluminate as oxidiser, and glycine acid as fuel. The powders were characterized by infrared spectroscopy (IR), X-ray diffraction (XRD), Rietveld refinement, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and fluorescence spectroscopy. Pure LaAlO3 phase was obtained at 800 °C heated for 4 h, without formation of any intermediate phase, with an average crystal size, as determined by TEM, of 60 nm. Intense green emission is reported at 542 nm, from the 5D level, which intensity depends on Tb concentration.

  1. Genesis of sulfide-rich chromite ores by the interaction between chromitite and pegmatitic olivine-norite dikes in the Potosí Mine (Moa-Baracoa ophiolitic massif, eastern Cuba)

    NASA Astrophysics Data System (ADS)

    Proenza, J.; Gervilla, F.; Melgarejo, J.; Vera, O.; Alfonso, P.; Fallick, A.

    2001-10-01

    The Potosí Mine is located in the Moa-Baracoa massif in the easternmost part of the Cuban Ophiolitic Belt. Chromite mineralization occurs within the mantle-crust transition zone. Two events of magma intrusion overprint the chromitite bodies: one gave rise to the crystallization of pegmatitic olivine-norite dikes, and the other produced pegmatitic gabbro dikes. Sulfide-poor chromite ores, brecciated chromite ores, and sulfide-rich chromite ores can be distinguished in the different chromitite bodies. Sulfide-poor ores represent more than 80 vol% of the chromitites. This type occurs far from the zones intruded by pegmatitic gabbro dikes and shows petrographic and chemical features similar to other chromitite bodies described in the Moa-Baracoa massif. Brecciated chromite ores occur within pegmatitic gabbro dikes. In this type, chromite crystals occur included within chromian diopside and plagioclase. These silicates often contain droplet-like sulfide aggregates. Sulfide-rich ores are spatially associated to the contacts between sulfide-poor chromite and pegmatitic olivine-norite dikes. These ores mainly consist of recrystallized (coarse) chromite with interstitial pyrrhotite, pentlandite, cubanite, and chalcopyrite. Chromite from sulfide-rich ores exhibits TiO2, FeO, V2O3, MnO, and especially, Fe2O3 contents, higher than those of chromite from brecciated ores and much higher than those of chromite from sulfide-poor ores. The sulfide-rich ores are PGE-rich (up to 1,113 ppb of total PGE), and show nearly flat chondrite-normalized PGE patterns, slightly above 0.1 times chondritic values. Mineralogical and chemical data indicate that the chromite ores of the Potosí Mine were modified by the intrusions of olivine-norite and gabbro dikes. The interaction between pre-existing sulfide-poor chromite ores and the intruding volatile-rich silicate melts produced strong brecciation, partial dissolution, and recrystallization (coarsening) of chromite. The sulfide assemblage

  2. Comparative Planetary Mineralogy: V/(Cr+Al) Systematics in Chromites as an Indicator of Relative Oxygen Fugacity

    NASA Technical Reports Server (NTRS)

    Papike, J. J.; Kamer, J. M.; Shearer, C. K.

    2004-01-01

    As our contribution to the new "Oxygen in the Solar System" initiative of the Lunar and Planetary Institute and the NASA Cosmochemistry Program, we have been developing oxygen barometers based largely on behavior of V which can occur in four valence states V2+, V3+, V4+, and V5+, and record at least 8 orders of magnitude of fO2. Our first efforts in measuring these valence proportions were by XANES techniques in basaltic glasses from Earth, Moon, and Mars. We now address the behavior of V valence states in chromite in basalts from Earth, Moon, and Mars. We have been looking for a "V in chromite oxybarometer" that works with data collected by the electron microprobe and thus is readily accessible to a large segment of the planetary materials community. This paper describes very early results that will be refined over the next two years.

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

    NASA Astrophysics Data System (ADS)

    Ismail, Fatin Adila; Osman, Rozana Aina Maulat; Idris, Mohd Sobri

    2016-07-01

    Rare earth doped Barium Titanate (BaTiO3) were studied due to high permittivity, excellent electrical properties and have wide usage in various applications. This paper reviewed on the electrical properties of RE doped BaTiO3 (RE: Lanthanum (La), Erbium (Er), Samarium (Sm), Neodymium (Nd), Cerium (Ce)), processing method, phase transition occurred and solid solution range for complete study. Most of the RE doped BaTiO3 downshifted the Curie temperature (TC). Transition temperature also known as Curie temperature, TC where the ceramics had a transition from ferroelectric to a paraelectric phase. In this review, the dielectric constant of La-doped BaTiO3, Er-doped BaTiO3, Sm-doped BaTiO3, Nd-doped BaTiO3 and Ce-doped BaTiO3 had been proved to increase and the transition temperature or also known as TC also lowered down to room temperature as for all the RE doped BaTiO3 except for Er-doped BaTiO3.

  4. Distribution of platinum-group elements in the Bati Kef chromite deposit, Guleman-Elazig area, eastern Turkey.

    USGS Publications Warehouse

    Page, N.J.; Engin, T.; Singer, D.A.; Haffty, J.

    1984-01-01

    The distribution of platinum-group elements (PGE) within chromite deposits from an ophiolite is determined and their geochemistry compared with chromitites from ophiolites and from stratiform layered complexes elsewhere in the world. The Guleman area chromitites are lenses of layered massive to disseminated chromite in dunite or sheared harzburgite along and near the dunite-harzburgite contact. PGE were analysed by a fire assay/spectrographic method. The analyses, in ppb, varied narrowly near the detection limits; only Ir was mostly detected (24-27 ppb) . The data plot as independent, slight variations of individual PGE with crude and irregular spatial distributions, oriented with respect to the land surface. Based on studies elsewhere, the PGE reside mostly in laurite, erlichmanite and Os/Ir alloys included within or interstitial to chromite. Average values for each PGE were normalized with respect to average chondrite concentrations for these elements. All patterns for ophiolite-chromitites (5) show depletion of these elements relative to chondrite average concentrations, with greater depletion in Pt and Pd than in Ir and Ru, to produce patterns with negative slopes. Chromitites from differentiated stratiform complexes (2) yield patterns with positive slopes. -G.J.N.

  5. 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.

  6. A comparison of selected Precambrian Brazilian chromitites: Chromite, PGE-PGM, and Re/Os as parental source indicators

    NASA Astrophysics Data System (ADS)

    Girardi, V. A. V.; Ferrario, A.; Correia, C. T.; Diella, V.

    2006-03-01

    Mineralogical and geochemical studies were carried out in chromitites belonging to the mafic-ultramafic bodies of Niquelândia, Luanga, and Campo Formoso, which are, respectively, included in the Goiás Massif and the Amazon and São Francisco cratons. The main platinum-group minerals (PGM) included or associated with chromite grains are laurite in Niquelândia and Campo Formoso and sperrylite and braggite in Luanga. The most common primary base metal sulfides (BMS) are pentlandite, chalcopyrite, and minor pyrrhotite. Also present are base metal alloys (BMA), such as awaruite, and the BMS millerite, pyrite, and copper as secondary mineral phases linked to later alteration process. The Luanga chromites display the lowest Cr 2O 3/Al 2O 3 and Cr 2O 3/FeO t ratios. The chondrite-normalized profiles are strongly enriched in the platinum PGE subgroup (PPGE, Pt, Pd, Rh). The average Pd/Ir ratio (24.2) and 187Os/ 188Os values (0.17869-0.18584) are very high. Niquelândia chromites have higher Cr 2O 3/Al 2O 3 and Cr 2O 3/FeO t ratios than Luanga. Its PGE contents are low and chondrite-normalized profiles depleted, mainly in the PPGE subgroup. The average Pd/Ir ratio (0.45) and 187Os/ 188Os values (0.12598-0.12777) are low. Campo Formoso chromites have the highest Cr 2O 3/Al 2O 3 and Cr 2O 3/FeO t ratios; its average Pd/Ir ratio (0.72) and chondrite-normalized profiles (except the pronounced Ru spike) are closer to those of Niquelândia. The remarkable differences in terms of chromite bulk-composition, PGE contents and patterns, Pd/Ir ratios, and 187Os/ 188Os values associated with probable distinctions in the inferred geochemical compositions of the respective parental magmas indicate that the Luanga and Niquelândia complexes originated from distinct parental sources. Geochemical and isotopic features indicate that Luanga chromitites and associated rocks are consistent with a parental magma, either originated from an enriched mantle reservoir or strongly contaminated

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

    NASA Astrophysics Data System (ADS)

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

    2015-02-01

    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.

  8. 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

  9. A search for H-chondritic chromite grains in sediments that formed immediately after the breakup of the L-chondrite parent body 470 Ma ago

    NASA Astrophysics Data System (ADS)

    Heck, Philipp R.; Schmitz, Birger; Rout, Surya S.; Tenner, Travis; Villalon, Krysten; Cronholm, Anders; Terfelt, Fredrik; Kita, Noriko T.

    2016-03-01

    A large abundance of L-chondritic material, mainly in the form of fossil meteorites and chromite grains from micrometeorites, has been found in mid-Ordovician 470 Ma old sediments globally. The material has been determined to be ejecta from the L chondrite parent body breakup event, a major collision in the asteroid belt 470 Ma ago. In this study we search the same sediments for H-chondritic chromite grains in order to improve our understanding of the extraterrestrial flux to Earth after the asteroid breakup event. We have used SIMS in conjunction with quantitative SEM/EDS to determine the three oxygen isotopic and elemental compositions, respectively, of a total of 120 randomly selected, sediment-dispersed extraterrestrial chromite grains mainly representing micrometeorites from 470 Ma old post-breakup limestone from the Thorsberg quarry in Sweden and the Lynna River site in Russia. We show that 99% or more of the grains are L-chondritic, whereas the H-chondritic fraction is 1% or less. The L-/H-chondrite ratio after the breakup thus was >99 compared to 1.1 in today's meteoritic flux. This represents independent evidence, in agreement with previous estimates based on sediment-dispersed extraterrestrial chromite grain abundances and sedimentation rates, of a two orders of magnitude higher post-breakup flux of L-chondritic material in the micrometeorite fraction. Finally, we confirm the usefulness of three oxygen isotopic SIMS analyses of individual extraterrestrial chromite grains for classification of equilibrated ordinary chondrites. The H- and L-chondritic chromites differ both in their three oxygen isotopic and elemental compositions, but there is some overlap between the groups. In chromite, TiO2 is the oxide most resistant to diagenesis, and the combined application of TiO2 and oxygen three-isotope analysis can resolve uncertainties arising from the compositional overlaps.

  10. High temperature stability of lanthanum silicate dielectric on Si (001)

    SciTech Connect

    Jur, J. S.; Lichtenwalner, D. J.; Kingon, A. I.

    2007-03-05

    Integration of a high-{kappa} dielectric into complementary metal-oxide-semiconductor devices requires thermal stability of the amorphous dielectric phase and chemical compatibility with silicon. The stability of amorphous lanthanum silicate on Si (001) is investigated by means of metal-insulator-semiconductor capacitor measurements, back side secondary ion mass spectrometry (SIMS) depth profiling, and high-resolution transmission electron microscopy (HRTEM) after a 1000 deg. C, 10 s anneal in nitrogen ambient. Back side SIMS depth profiling of the TaN/LaSiO{sub x}/Si gate stack reveals no detectable lanthanum in the silicon substrate, and HRTEM shows stability of the amorphous LaSiO{sub x}. An effective work function near 4.0 eV is obtained for these gate stacks, making the stack design ideal for n-type metal-oxide-semiconductor device fabrication.

  11. Phytotoxicity of lanthanum in rice in haplic acrisols and cambisols.

    PubMed

    Zeng, Q; Zhu, J G; Cheng, H L; Xie, Z B; Chu, H Y

    2006-06-01

    Growth and physiological responses of rice to lanthanum were studied to elucidate the function of lanthanum in plants and its critical concentration relative to environmental safety. Shoot La content increased with the increasing added La concentrations. When shoot La content exceeded a toxic value, plant growth and chlorophyll a/b decreased and peroxidase (POD) activity, cell membrane permeability, and content of proline in the leaf increased. Leaf chlorophyll a/b and POD activity might provide useful criteria for early diagnoses of phytotoxicity of soil contaminated by La. In the present study, the critical concentration of La for rice relative to environmental safety was suggested to be 42.03 mg kg(-1) in red soil and 83.33 mg kg(-1) in paddy soil.

  12. Calcium polysulfide remediation of hexavalent chromium contamination from chromite ore processing residue.

    PubMed

    Graham, Margaret C; Farmer, John G; Anderson, Peter; Paterson, Edward; Hillier, Stephen; Lumsdon, David G; Bewley, Richard J F

    2006-07-01

    Past disposal of high-lime chromite ore processing residue (COPR) from a chemical works in S.E. Glasgow, UK, has led to continuing release of toxic and carcinogenic hexavalent chromium (Cr(VI)) to groundwaters which are highly contaminated with Cr(VI)O4(2-). Traditional methods of remediating Cr(VI)-contaminated land, e.g. using ferrous sulfate and organic matter, have had limited success in converting Cr(VI) to less harmful and insoluble Cr(III). This paper describes the first application of calcium polysulfide (CaS(x)) to the remediation of contaminated groundwater and high-lime COPR in a series of laboratory experiments, which have demonstrated the effectiveness of the treatment in quantitatively and rapidly reducing Cr(VI) to Cr(III) over the pH range (8-12.5) typically found at the sites. Cr(III)-organic complexes, present in groundwater at one location, were also effectively precipitated upon treatment with CaS(x). The potential for large-scale use of CaS(x) in the remediation of Cr(VI) from COPR is also discussed.

  13. Evaluation of the treatment of chromite ore processing residue by ferrous sulfate and asphalt.

    PubMed

    Moon, Deok Hyun; Wazne, Mahmoud; Koutsospyros, Agamemnon; Christodoulatos, Christos; Gevgilili, Halil; Malik, Moinuddin; Kalyon, Dilhan M

    2009-07-15

    The effectiveness of the treatment of chromite ore processing residue (COPR) with ferrous sulfate and encapsulation into asphalt were explored separately and in combination. The asphalt treatment was conducted by mixing COPR or ferrous sulfate pretreated COPR with varying amounts of asphalt. To assess the efficacy of the treatment, the leachability of toxicity characteristic leaching procedure (TCLP) total chromium (Cr) from all treated samples was determined for curing periods up to 16 months. X-ray absorption near edge structure (XANES) analyses were also performed to evaluate the Cr(6+) concentration in the selected samples. The combination treatment of ferrous sulfate and the encapsulation of the treated COPR into asphalt reduced the TCLP total Cr concentration to lower than the regulatory limit of 5mg/L for Cr contaminated soils, after 16 months. However, the Cr concentrations were still higher than the universal treatment standards (UTS) of 0.6 mg/L for hazardous waste. On the other hand, treatment with ferrous sulfate alone or the encapsulation of the COPR in asphalt failed to meet the TCLP total Cr concentration of 5mg/L, after 16 months. XANES analyses results showed that more than 75% Cr(6+) reduction was achieved upon pretreatment with ferrous sulfate.

  14. Application of the Rietveld method to assess chromium(VI) speciation in chromite ore processing residue.

    PubMed

    Chrysochoou, Maria; Dermatas, Dimitris

    2007-03-15

    The Rietveld method allows the quantification of crystalline phases and amorphous material identified by X-ray powder diffraction (XRPD) and other diffraction methods. The method assists in determining the speciation of contaminants in solid matrices both qualitatively and quantitatively in a statistically defensible approach, as it does not focus on a microscale. Rietveld was applied to chromite ore processing residue (COPR), a cementitious waste containing hexavalent chromium. Calcium aluminum chromium oxide hydrates (CACs) were the crystalline phases identified by XRPD that bind Cr(6+) in COPR according to their chemical formula. Rietveld quantification, combined with mass balances on Cr(6+), showed that CACs may bind Cr(6+) in variable percentages, ranging from 25% to 85%. Analysis of duplicate samples showed that material variability is the predominant factor of uncertainty in evaluating the role of CACs in Cr(6+) speciation, provided that a consistent quantification strategy is pursued. The choice of strategy was performed on the basis of the pertinent literature, preliminary analyses of the equipment and the software settings, and mass balances. The correlation between the average CAC-bound Cr(6+) concentration and the total Cr(6+) for five samples (R(2)=0.94), extracted from different zones and soil borings, suggests that CACs are a primary sink for Cr(6+) in COPR. PMID:16842911

  15. Microstructural analyses of Cr(VI) speciation in chromite ore processing Residue (COPR)

    SciTech Connect

    CHRYSOCHOOU, MARIA; FAKRA, SIRINE C .; Marcus, Matthew A.; Moon, Deok Hyun; Dermatas, Dimitris

    2010-03-01

    The speciation and distribution of Cr(VI) in the solid phase was investigated for two types of chromite ore processing residue (COPR) found at two deposition sites in the United States: gray-black (GB) granular and hard brown (HB) cemented COPR. COPR chemistry and mineralogy were investigated using micro-X-ray absorption spectroscopy and micro-X-ray diffraction, complemented by laboratory analyses. GB COPR contained 30percent of its total Cr(VI) (6000 mg/kg) as large crystals(>20 ?m diameter) of a previously unreported Na-rich analog of calcium aluminum chromate hydrates. These Cr(VI)-rich phases are thought to be vulnerable to reductive and pH treatments. More than 50percent of the Cr(VI) was located within nodules, not easily accessible to dissolved reductants, and bound to Fe-rich hydrogarnet, hydrotalcite, and possibly brucite. These phases are stable over a large pH range, thus harder to dissolve. Brownmilleritewasalso likely associated with physical entrapment of Cr(VI) in the interior of nodules. HB COPR contained no Cr(VI)-rich phases; all Cr(VI) was diffuse within the nodules and absent from the cementing matrix, with hydrogarnet and hydrotalcite being the main Cr(VI) binding phases. Treatment ofHBCOPRis challenging in terms of dissolving the acidity-resistant, inaccessible Cr(VI) compounds; the same applies to ~;;50percent of Cr(VI) in GB COPR.

  16. Swelling related to ettringite crystal formation in chromite ore processing residue.

    PubMed

    Moon, Deok Hyun; Dermatas, Dimitris; Wazne, Mahmoud; Sanchez, Adriana M; Chrysochoou, Maria; Grubb, Dennis G

    2007-08-01

    Several million tons of Chromite Ore Processing Residue (COPR) were deposited at two sites in New Jersey and Maryland, USA, and over time they exhibited extensive heaving phenomena. Ettringite, a needle-shaped mineral and an expansive mineral commonly recognized in the literature concerning cement- and soil, has been identified extensively in numerous COPR samples collected from these sites. It was therefore believed that ettringite formation and its crystal growth are strongly associated with COPR heaving. We investigated the correlation between ettringite and the heaving phenomena in COPR materials that contained no initial ettringite. Two identical COPR samples were exposed to a 4% w/w sulfate solution (25 degrees C, 50 degrees C) in a confined swell test apparatus. Both swell test samples were analyzed by means of X-ray powder diffraction. The peak intensities of newly formed ettringite were more pronounced in the sample tested at 50 degrees C, and swell development was only observed in this sample. Scanning electron microscopy analyses revealed well-crystallized ettringite needles exceeding 40 microm in length for this sample, while ettringite crystals less than 15 microm in length formed in the sample tested at 25 degrees C. Therefore, the results suggest that the quantity of ettringite and the extent of crystallization play a key role in the heave of COPR. PMID:17505893

  17. Microstructural analyses of Cr(VI) speciation in chromite ore processing residue (COPR).

    PubMed

    Chrysochoou, Maria; Fakra, Sirine C; Marcus, Matthew A; Moon, Deok Hyun; Dermatas, Dimitris

    2009-07-15

    The speciation and distribution of Cr(VI) in the solid phase was investigated for two types of chromite ore processing residue (COPR) found at two deposition sites in the United States: gray-black (GB) granular and hard brown (HB) cemented COPR. COPR chemistry and mineralogy were investigated using micro-X-ray absorption spectroscopy and micro-X-ray diffraction, complemented by laboratory analyses. GB COPR contained 30% of its total Cr(VI) (6000 mg/kg) as large crystals (>20 microm diameter) of a previously unreported Na-rich analog of calcium aluminum chromate hydrates. These Cr(VI)-rich phases are thought to be vulnerable to reductive and pH treatments. More than 50% of the Cr(VI) was located within nodules, not easily accessible to dissolved reductants, and bound to Fe-rich hydrogarnet, hydrotalcite, and possibly brucite. These phases are stable over a large pH range, thus harder to dissolve. Brownmillerite was also likely associated with physical entrapment of Cr(VI) in the interior of nodules. HB COPR contained no Cr(VI)-rich phases; all Cr(VI) was diffuse within the nodules and absent from the cementing matrix, with hydrogarnet and hydrotalcite being the main Cr(VI) binding phases. Treatment of HB COPR is challenging in terms of dissolving the acidity-resistant, inaccessible Cr(VI) compounds; the same applies to approximately 50% of Cr(VI) in GB COPR.

  18. 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.

  19. Low-temperature sintering and phase changes in chromite interconnect materials

    SciTech Connect

    Chick, L.A.; Armstrong, T.R.; McCready, D.E.; Coffey, G.W.; Maupin, G.D.; Bates, J.L.

    1993-05-01

    Sintering shrinkage curves and phase changes were compared for calcium-substituted lanthanum chromates with either slight Asite enrichment or depletion. Of the former type, La[sub 0.7]Ca[sub 0.31],CrO[sub 3] that was synthesized by the glycine-nitrate method sintered to high density in air at 1250C, exhibiting two rapid-shrinkage events. Weight loss measurements corroborated XRD data showing that, prior to densiflcation, over half the Ca resided in non-perovskite phases, including CaCrO[sub 4]. In the La[sub 0.7]Ca[sub 0.31]CrO[sub 3], densification was closely associated with re-dissolution of the Ca into the perovskite.

  20. Low-temperature sintering and phase changes in chromite interconnect materials

    SciTech Connect

    Chick, L.A.; Armstrong, T.R.; McCready, D.E.; Coffey, G.W.; Maupin, G.D.; Bates, J.L.

    1993-05-01

    Sintering shrinkage curves and phase changes were compared for calcium-substituted lanthanum chromates with either slight Asite enrichment or depletion. Of the former type, La{sub 0.7}Ca{sub 0.31},CrO{sub 3} that was synthesized by the glycine-nitrate method sintered to high density in air at 1250C, exhibiting two rapid-shrinkage events. Weight loss measurements corroborated XRD data showing that, prior to densiflcation, over half the Ca resided in non-perovskite phases, including CaCrO{sub 4}. In the La{sub 0.7}Ca{sub 0.31}CrO{sub 3}, densification was closely associated with re-dissolution of the Ca into the perovskite.

  1. Luminescent and scintillating properties of lanthanum fluoride nanocrystals in response to gamma/neutron irradiation: codoping with Ce activator, Yb wavelength shifter, and Gd neutron captor

    NASA Astrophysics Data System (ADS)

    Vargas, J. M.; Blostein, J. J.; Sidelnik, I.; Rondón Brito, D.; Rodríguez Palomino, L. A.; Mayer, R. E.

    2016-09-01

    A novel concept for gamma radiation detection and spectroscopy, and detection of thermal neutrons based on co-doped lanthanum fluoride nanocrystals containing gadolinium is presented. The trends of colloidal synthesis of the mentioned material, LaF3 co-doped with Ce3+ as the activator, Yb3+ as the wavelength-shifter and Gd3+ as the neutron captor, is reported. Nanocrystals of the mentioned material were characterized by transmission electron microscopy, X ray diffraction, energy dispersive X ray spectroscopy, optical absorption, and photoluminescence spectroscopy. Gamma detection and its potential spectroscopy feature have been confirmed. The neutron detection capability has been confirmed by experiments performed using a 252Cf neutron source.

  2. Enhanced field emission from lanthanum hexaboride coated multiwalled carbon nanotubes: Correlation with physical properties

    NASA Astrophysics Data System (ADS)

    Patra, Rajkumar; Ghosh, S.; Sheremet, E.; Jha, Menaka; Rodriguez, R. D.; Lehmann, D.; Ganguli, A. K.; Schmidt, H.; Schulze, S.; Hietschold, M.; Zahn, D. R. T.; Schmidt, O. G.

    2014-10-01

    Detailed results from field emission studies of lanthanum hexaboride (LaB6) coated multiwalled carbon nanotube (MWCNT) films, pristine LaB6 films, and pristine MWCNT films are reported. The films have been synthesized by a combination of chemical and physical deposition processes. An impressive increase in field enhancement factor and temporal stability as well as a reduction in turn-on field and threshold field are observed in LaB6-coated MWCNTs compared to pristine MWCNT and pristine LaB6 films. Surface morphology of the films has been examined by scanning electron microscopy. Introduction of LaB6 nanoparticles on the outer walls of CNTs LaB6-coated MWCNTs films is confirmed by transmission electron microscopy. The presence of LaB6 was confirmed by X-ray photoelectron spectroscopy results and further validated by the Raman spectra. Raman spectroscopy also shows 67% increase in defect concentration in MWCNTs upon coating with LaB6 and an upshift in the 2D band that could be attributed to p-type doping. Ultraviolet photoelectron spectroscopy studies reveal a reduction in the work function of LaB6-coated MWCNT with respect to its pristine counterpart. The enhanced field emission properties in LaB6-coated MWCNT films are correlated with a change in microstructure and work function.

  3. Enhanced field emission from lanthanum hexaboride coated multiwalled carbon nanotubes: Correlation with physical properties

    SciTech Connect

    Patra, Rajkumar; Ghosh, S.; Sheremet, E.; Rodriguez, R. D.; Lehmann, D.; Zahn, D. R. T.; Jha, Menaka; Ganguli, A. K.; Schmidt, H.; Schulze, S.; Hietschold, M.; Schmidt, O. G.

    2014-10-28

    Detailed results from field emission studies of lanthanum hexaboride (LaB{sub 6}) coated multiwalled carbon nanotube (MWCNT) films, pristine LaB{sub 6} films, and pristine MWCNT films are reported. The films have been synthesized by a combination of chemical and physical deposition processes. An impressive increase in field enhancement factor and temporal stability as well as a reduction in turn-on field and threshold field are observed in LaB{sub 6}-coated MWCNTs compared to pristine MWCNT and pristine LaB{sub 6} films. Surface morphology of the films has been examined by scanning electron microscopy. Introduction of LaB{sub 6} nanoparticles on the outer walls of CNTs LaB{sub 6}-coated MWCNTs films is confirmed by transmission electron microscopy. The presence of LaB{sub 6} was confirmed by X-ray photoelectron spectroscopy results and further validated by the Raman spectra. Raman spectroscopy also shows 67% increase in defect concentration in MWCNTs upon coating with LaB{sub 6} and an upshift in the 2D band that could be attributed to p-type doping. Ultraviolet photoelectron spectroscopy studies reveal a reduction in the work function of LaB{sub 6}-coated MWCNT with respect to its pristine counterpart. The enhanced field emission properties in LaB{sub 6}-coated MWCNT films are correlated with a change in microstructure and work function.

  4. Structure, stoichiometry, and phase purity of calcium substituted lanthanum manganite powders

    SciTech Connect

    Faaland, S.; Einarsrud, M.A.; Roermark, L.; Hoeier, R.; Grande, T.; Knudsen, K.D.

    1998-11-01

    Calcium-doped lanthanum manganite La{sub 1{minus}x}Ca{sub x}MnO{sub 3}, synthesized by the glycine/nitrate method, was characterized by high resolution synchrotron X-ray powder diffraction, electron diffraction, and infrared spectroscopy. A strong correlation was observed between the cooling rate from the calcination temperature and the powder quality, indicating the importance of a homogeneous oxygen stoichiometry. The structure refinement reveals that La{sub 1{minus}x}Ca{sub x}MnO{sub 3} with x = 0.2, 0.3, 0.4, and 0.6 has orthorhombic symmetry with space group Pnma. The MnO{sub 6} octahedra are fairly symmetrical, but the octahedra are tilted about 20{degree} relative to the ideal perovskite structure. Infrared spectroscopy revealed that only the O-Mn-O bending mode is significantly influenced by the substitution of La with Ca. In La{sub 0.8}Ca{sub 0.2}MnO{sub 3} the authors found diffraction evidence of a superstructure in domains in some of the grains. They propose that the superstructure in La{sub 0.8}Ca{sub 0.2}MnO{sub 3} is due to ordering of Ca{sup 2+} ions on A (La{sup 3+}) sites in the perovskite ABO{sub 3} structure.

  5. Infrared luminescence of Tm{sup 3+}/Yb{sup 3+} codoped lanthanum aluminum germanate glasses

    SciTech Connect

    Zhang Qiang; Zhang Guang; Chen Guorong; Qiu Jianrong; Chen Danping

    2010-01-15

    Tm{sup 3+} doped and Tm{sup 3+}/Yb{sup 3+} codoped lanthanum aluminum germanate (LAG) glasses are prepared by melt-quenching method and characterized optically. Based on the measurement of absorption spectrum, Judd-Ofelt intensity parameters ({Omega}{sub 2},{Omega}{sub 4},{Omega}{sub 6}) are calculated. The radiation emission rates, branching ratios, and lifetimes of Tm{sup 3+} are calculated to evaluate the spectroscopic properties of Tm{sup 3+} in LAG glass. The infrared emission properties of the samples are investigated and the results show that the 1.8 {mu}m emission can be greatly enhanced by adding proper amount of Yb{sup 3+} under the excitation of 980 nm. The energy transfer processes of Yb{sup 3+}-Yb{sup 3+} and Yb{sup 3+}-Tm{sup 3+} are analyzed, and the results show that Yb{sup 3+} ions can transfer their energy to Tm{sup 3+} ions with high efficiency and large energy transfer coefficient.

  6. Comparison of the Oxidation Behaviors of High FeO Chromite and Magnetite Concentrates Relevant to the Induration of Ferrous Pellets

    NASA Astrophysics Data System (ADS)

    Zhu, Deqing; Yang, Congcong; Pan, Jian; Li, Xiaobo

    2016-10-01

    Oxidation process plays an important role in producing sufficiently strong ferrous pellets for blast furnace, and the oxidation behavior of pellet feed greatly affects the quality of pellets. As a supplementary research to earlier published work, the present study fixes its particular attention on the fundamental oxidation behavior of a high FeO South African chromite concentrate in comparison to that of typical magnetite concentrate using differential scanning calorimetry, X-ray diffraction analysis, and thermogravimetry at various temperatures ranging from 473 K to 1273 K (200 °C to 1000 °C). The reaction mechanism and phase transformation during the oxidation process of chromite spinel is further explained by thermodynamics calculation performed by FactSage software. Besides, routine laboratory preheating-roasting test of single ore pellets is also conducted to reveal the relevance of oxidizability to the consolidation of pellets. The results show that the chromite spinel possesses much poorer oxidizability than magnetite, usually accompanying complex phase transformations via a preferential nucleation of Fe-rich sesquioxide from the chromite spinel matrix at low temperatures and thereafter the formation of Cr-rich sesquioxide on the substrate of Fe-rich phase at high temperatures. The oxidation of chromite spinel is inferior to that of magnetite from the viewpoint of thermodynamics and dynamic kinetics. Good inherent oxidizability of raw materials is found to have a positive effect on the induration process of pellet.

  7. Comparison of the Oxidation Behaviors of High FeO Chromite and Magnetite Concentrates Relevant to the Induration of Ferrous Pellets

    NASA Astrophysics Data System (ADS)

    Zhu, Deqing; Yang, Congcong; Pan, Jian; Li, Xiaobo

    2016-08-01

    Oxidation process plays an important role in producing sufficiently strong ferrous pellets for blast furnace, and the oxidation behavior of pellet feed greatly affects the quality of pellets. As a supplementary research to earlier published work, the present study fixes its particular attention on the fundamental oxidation behavior of a high FeO South African chromite concentrate in comparison to that of typical magnetite concentrate using differential scanning calorimetry, X-ray diffraction analysis, and thermogravimetry at various temperatures ranging from 473 K to 1273 K (200 °C to 1000 °C). The reaction mechanism and phase transformation during the oxidation process of chromite spinel is further explained by thermodynamics calculation performed by FactSage software. Besides, routine laboratory preheating-roasting test of single ore pellets is also conducted to reveal the relevance of oxidizability to the consolidation of pellets. The results show that the chromite spinel possesses much poorer oxidizability than magnetite, usually accompanying complex phase transformations via a preferential nucleation of Fe-rich sesquioxide from the chromite spinel matrix at low temperatures and thereafter the formation of Cr-rich sesquioxide on the substrate of Fe-rich phase at high temperatures. The oxidation of chromite spinel is inferior to that of magnetite from the viewpoint of thermodynamics and dynamic kinetics. Good inherent oxidizability of raw materials is found to have a positive effect on the induration process of pellet.

  8. Long-term treatment issues with chromite ore processing residue (COPR): Cr(6+) reduction and heave.

    PubMed

    Moon, Deok Hyun; Wazne, Mahmoud; Dermatas, Dimitris; Christodoulatos, Christos; Sanchez, Adriana M; Grubb, Dennis G; Chrysochoou, Maria; Kim, Min Gyu

    2007-05-17

    A pugmill treatability study was conducted to remediate chromite ore processing residue (COPR) using ferrous sulfate heptahydrate (FeSO(4) x 7H(2)O) as a reductant. Two different types of COPR, with respect to particle size and mineralogy, were tested in this study. Two different stoichiometric ratios of FeSO(4) x 7H(2)O to Cr(6+) (5x and 8x) were applied to reduce Cr(6+) to Cr(3+). The effectiveness of FeSO(4).7H(2)O treatment was assessed using the toxicity characteristic leaching procedure (TCLP) tests and X-ray absorption near edge structure (XANES) analyses. TCLP results obtained from the pugmill treatability study showed that TCLP Cr concentrations were less than the TCLP regulatory limit of 5mg/L upon 8x FeSO(4) x 7H(2)O treatment for up to 420 days but may fail to meet this regulatory limit in the long-term. XANES results obtained from samples cured for 300 days showed that all of the treated samples failed the New Jersey Department of Environmental Protection (NJDEP) clean up level for Cr(6+) of 240 mg/kg. However, the Cr(6+) concentration from the sample with the smaller particle size approached 240 mg/kg (338 mg/kg), suggesting that particle size reduction prior to the addition of reductant may improve the effectiveness of the treatment. COPR heaving was investigated with unconfined swell tests upon 5x and 8x FeSO(4) x 7H(2)O treatment. The formation of ettringite, an expansive material, was investigated following the swell tests using X-ray powder diffraction (XRPD). Significant heaving (>50 vol%) was observed at curing times of 138 days for the 5x treatment and the ettringite formation was identified by XRPD analyses.

  9. Assessment of ferrous chloride and Portland cement for the remediation of chromite ore processing residue.

    PubMed

    Jagupilla, Santhi C; Wazne, Mahmoud; Moon, Deok Hyun

    2015-10-01

    Chromite Ore Processing Residue (COPR) is an industrial waste containing up to 7% chromium (Cr) including up to 5% hexavalent chromium [Cr(VI)]. The remediation of COPR has been challenging due to the slow release of Cr(VI) from a clinker like material and thereby the incomplete detoxification of Cr(VI) by chemical reagents. The use of sulfur based reagents such as ferrous sulfate and calcium polysulfide to detoxify Cr(VI) has exasperated the swell potential of COPR upon treatment. This study investigated the use of ferrous chloride alone and in combination with Portland cement to address the detoxification of Cr(VI) in COPR and the potential swell of COPR. Chromium regulatory tests, X-ray powder diffraction (XRPD) analyses and X-ray absorption near edge structure (XANES) analyses were used to assess the treatment results. The treatment results indicated that Cr(VI) concentrations for the acid pretreated micronized COPR as measured by XANES analyses were below the New Jersey Department of Environmental Protection (NJDEP) standard of 20 mg kg(-1). The Toxicity characteristic leaching procedure (TCLP) Cr concentrations for all acid pretreated samples also were reduced below the TCLP regulatory limit of 5 mg L(-1). Moreover, the TCLP Cr concentration for the acid pretreated COPR with particle size ⩽0.010 mm were less than the universal treatment standard (UTS) of 0.6 mg L(-1). The treatment appears to have destabilized all COPR potential swell causing minerals. The unconfined compressive strength (UCS) for the treated samples increased significantly upon treatment with Portland cement. PMID:25966327

  10. Heavy metal and nutrient concentration in soil and plants growing on a metalliferous chromite minespoil.

    PubMed

    Samantaray, S; Rout, G R; Das, P

    2001-10-01

    Metal contamination in soil and plant samples from a chromite mine and its adjoining regions was determined. The metal concentration varied in stem, leaf and root of different tree species. In the case of shrubs, the highest concentration of iron (18.5 mg kg(-1) was detected in the stem of Combretum roxburghii. The concentration of aluminium varied from 1.8 - 5.3 mg kg(-1) dry weight, whereas the nickel content was found to be the highest in the stem of Calotropis gigantea. In the case of herbs, chromium concentration was highest (60.9 mg kg(-1) dry weight) in Evovulus alsenoides and the lowest (18.8 mg kg(-1) dry weight) in Andrographis paniculata. There was a significant correlation observed between chromium in soil with the root of tree species like Lagerstroemia parviflora, Madhuca longifolia, Anogeissus latifolia and Haldina cordyfolia. Nickel in soil was significantly correlated with the stem and leaf of all the tree species except Chlroxylon sweitenta. Iron in soil showed correlation with the stem and leaf of Chloroxylon sweitenia. Among the shrubs (Calotropis gigantea, Combretum roxburghii and Smilax zeylancia), chromium in soil showed a correlation with the root. Nickel in soil was positively correlated with the stem and leaf of Calotropis gigantea and Combretum roxburghii. Among the herbs, chromium in the whole plant of Evolvulus alsenoids, Solanum surattense and Phyllanthus fraternus showed significant positive correlation with soil; nickel in Solanum surattense showed significant positive correlation with soil. The positive correlation coefficient was observed between iron in the whole plant and soil on Phyllanthus virgatus, Phyllanthus fraternus and Andrographis paniculata. The above information would be useful for the establishment of a vegetation cover on the minewaste heaps.

  11. Morphology and composition of chalcopyrite, chromite, Cu, Ni-Fe, pentlandite, and troilite in vugs of 76015 and 76215

    NASA Technical Reports Server (NTRS)

    Carter, J. L.; Clanton, U. S.; Laughon, R. B.; Mckay, D. S.; Usselman, T. M.; Fuhrman, R.

    1975-01-01

    Vugs from 76015 and 76215 are lined with euhedral crystals of plagioclase, pyroxene, ilmenite, Ni-Fe, and troilite. Smaller crystals of chromite, pentlandite, and chalcopyrite occur on the surface of the troilite in 76015. Wire Cu and dendritic-metallic Cu occurs with metallic Ni-Fe and troilite in some vugs of 76215. Troilite in both samples may have crystallized from an immiscible sulfide liquid. With falling temperature, chalcopyrite, and pentlandite may have exsolved from the troilite in 76015. By contrast, metallic Cu may have formed in 76215 by thermal breakdown of a bornite, troilite, and Ni-Fe assemblage which originally crystallized from a low-Ni immiscible sulfide liquid.

  12. Secular Changes in Lava/Magma Channelization and the Volcanic/Subvolcanic/Plutonic Settings of Magmatic Ni-Cu-PGE and Chromite Mineralization on Earth

    NASA Astrophysics Data System (ADS)

    Lesher, C. M.

    2015-12-01

    The degree of channelization in magmatic systems is controlled by magma density, viscosity, and flux; environment of emplacement (subaerial/submarine) and substrate topography if volcanic; and country rock density/rheology/structure and degree/orientation of differential stress if subvolcanic/plutonic. Lower viscosity Archean komatiites ascended rapidly, producing lava channels (e.g., Kambalda) and subvolcanic feeder sills (e.g., Mt. Keith). Higher viscosity Proterozoic komatiitic basalts/ferropicrites/picrites had more difficulty ascending through the crust and produced subvolcanic feeder dikes (e.g., Eagle-Tamarack, Voisey's Bay) and sills (e.g., Thompson, Pechenga) and fewer lava channels (e.g., Raglan). Phanerozoic picrites/basalts produced mainly dikes (e.g., Kalatongke) and feeder sills (e.g., Noril'sk, Jinchuan). All were capable of eroding S-rich substrates/wall rocks and generating magmatic Ni-Cu-PGE deposits. Some chromite deposits appear to have formed in channelized magmatic systems, and although typically finer-grained chromite is much easier to transport than typically larger sulfide melt droplets, almost all known volcanic Ni-Cu-PGE deposits formed during lava emplacement and no volcanic chromite deposits have yet been identified. This suggests that Fe-Ni-Cu-(PGE) sulfides and chromite are more easily transported horizontally within sills and lava channels, but less easily transported vertically. If magmatic Fe-Ni-Cu-(PGE) deposits can form by partial melting of Fe sulfide-rich sediments underneath lava/magma channels and dynamic upgrading of sulfide xenomelts by reaction with the magma (the prevailing model), then magmatic chromite deposits can form by partial melting of Fe oxide-rich sediments underneath lava/magma channels and dynamic upgrading of oxide xenocrysts by reaction with the magma. The anomalously thick (up to 100m) Black Thor-Blackbird, Inyala, Ipueira-Medrado, Kemi, Nkomati, and Sukinda chromite deposits may be examples of this process.

  13. Colloidal lanthanum as a marker for impaired plasma membrane permeability in ischemic dog myocardium.

    PubMed Central

    Hoffstein, S.; Gennaro, D. E.; Fox, A. C.; Hirsch, J.; Streuli, F.; Weissmann, G.

    1975-01-01

    Colloidal lanthanum salts have an average particle size of 40 degrees A; consequently, this electron-opaque marker remains extracellular and does not cross the intact plasma membrane. The affinity of lanthanum for calcium-binding sites on mitochondrial membranes makes it possible to demonstrate loss of plasma membrane integrity at the cellular level in ischemic myocardium. Biopsies were obtained from infarcted, marginal and normal areas 3 1/2 hours after ischemia was produced in 9 anesthetized closed-chest dogs by electrically induced thrombosis of the left anterior descending coronary artery. The tissue was immediately fixed in 4% glutaraldehyde and 0.1 M cacodylate buffer containing 1.3% La(NO3)3, pH 7.4, for 2 hours. In normal control tissue prepared this way the lanthanum tracer, as expected, was confirmed to the extracellular spaces, including, basement membranes, gap junctions and portions of the intercalated discs. Specimens taken near the center of frank infarctions all contained intracellular as well as extracellular lanthanum. Intracellular lanthanum could be seen evenly distributed around lipid droplets and in focal deposits around mitochondria. Only when mitochondria were disrupted did lanthanum gain access to internal sites on mitochondrial membranes. Areas marginal to the infarct contained cells in varying stages of degeneration including many that appeared normal by morphologic criteria alone. Intracellular lanthanum was present in many but not all of the marginal cells in which degenerative changes could be seen. Similarly a few of the cells that appeared morphologically normal contained intracellular lanthanum. The entry of lanthanum into some of these marginal cells and its exclusion from adjacent cells demonstrated that ischemic injury affects the permeability properties of the plasma membrane and independently of other intracellular morphologic changes and that lanthanum can be a sensitive indicator of such alteration in membrane permeability

  14. 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.

  15. 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.

  16. Corrosion Investigations of Black Chromite Films on Zn and Zn-Co Coatings with Low Cobalt Content

    NASA Astrophysics Data System (ADS)

    Boshkov, Nikolai; Boshkova, Neli; Bachvarov, Vasil; Peshova, Miglena; Lutov, Ludmil

    2015-12-01

    The corrosion resistance and protective ability of black-colored chromite (Cr3+ based) and chromium-free conversion films (CFs) on electrodeposited zinc and Zn-Co alloy coatings having low cobalt content in a neutral model medium of 3% NaCl solution have been investigated and characterized. Test methods such as polarization resistance measurements, scanning electron microscopy, EDS, x-ray diffraction analysis, and x-ray photoelectron spectroscopy analyses have been applied in order to scrutinize the actual protective characteristics of these films as well as to determine the composition of the corrosion products appearing as a result of the treatment in the corrosion medium. The experimental results revealed better protective characteristics, consequently superior performance of the electrodeposits with chromite films compared to these with chromium free or without any additional CF. The processes occurring on the sample's surface during the immersion in the chemical conversion solutions as well as the influence of the H3PO4 in the course of the treatment are also commented on and discussed.

  17. Stability of solid oxide fuel cell materials

    SciTech Connect

    Armstrong, T.R.; Pederson, L.R.; Stevenson, J.W.; Raney, P.E.

    1995-08-01

    The phase stability and sintering behavior of materials used in SOFCs has been evaluated. The sintering behavior of Ca and Sr doped lanthanum. manganite (the preferred SOFC cathode material) is highly dependent on the relative proportion of A and B site cations in the material. Ca and Sr doped lanthanum chromite (the preferred interconnect material) have been shown to rapidly expand in reducing atmospheres at temperatures as low as 700{degrees}C. This expansion is due to the reduction of Cr{sup 4+} to Cr{sup 3+} in reducing environments.

  18. Structural, magnetic and catalytic properties of cobalt chromite obtained through precursor method

    SciTech Connect

    Gingasu, Dana; Mindru, Ioana; Culita, Daniela C.; Patron, Luminita; Calderon-Moreno, Jose Maria; Osiceanu, Petre; Preda, Silviu; Oprea, Ovidiu; Parvulescu, Viorica; Teodorescu, Valentin; Walsh, James P.S.

    2015-02-15

    Highlights: • CoCr{sub 2}O{sub 4} was synthesized through the tartarate and gluconate precursor routes. • Both routes led to the formation of the single-phase CoCr{sub 2}O{sub 4}. • The crystallite size was in the range of 14–21 nm. • CoCr{sub 2}O{sub 4} samples presented ferrimagnetic ordering below Currie temperature T{sub c} = 97 K. • CoCr{sub 2}O{sub 4} samples presented catalytic performance in the total oxidation of CH{sub 4}. - Abstract: Cobalt chromite (CoCr{sub 2}O{sub 4}) was synthesized through the precursor method. The precursors: (NH{sub 4}){sub 3}[CoCr{sub 2}(C{sub 4}O{sub 6}H{sub 4}){sub 4}(OH){sub 3}]·4H{sub 2}O, (NH{sub 4}){sub 3}[CoCr{sub 2}(C{sub 6}O{sub 7}H{sub 10}){sub 4}(C{sub 6}O{sub 7}H{sub 9})]·5H{sub 2}O were characterized by elemental chemical analysis, infrared (IR) and ultraviolet–visible (UV–vis) spectroscopy, and thermal analysis. The final oxides were characterized by X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM/TEM), UV–vis, IR, Raman spectroscopy (RS), magnetic measurements, N{sub 2} adsorption–desorption analyses and X-ray photoelectron spectroscopy (XPS). XRD confirmed the cubic CoCr{sub 2}O{sub 4} phase only and determined average crystallite sizes between 14 and 21 nm. Electron microscopy revealed morphology corresponding to the complete crystallization into cubic CoCr{sub 2}O{sub 4}. All the samples presented ferrimagnetic ordering below the Currie temperature (T{sub c}), and a phase transition at T{sub s} ∼26 K attributed to the onset of long-range spiral magnetic order. The CoCr{sub 2}O{sub 4} nanoparticles generated through the gluconate route following calcination at 700 °C for 1 h were found to have the best catalytic activity in the total oxidation of methane.

  19. Blast from the past: the aluminum's ghost on the lanthanum salts.

    PubMed

    Canavese, Caterina; Mereu, Cristina; Nordio, Maurizio; Sabbioni, Enrico; Aime, Silvio

    2005-01-01

    Hyperphosphatemia is a common serious complication of chronic renal diseases, which needs appropriate continuous treatment in order to avoid ominous side effects. Therefore, oral chelating agents able to avoid phosphate absorption by the gut are mandatory. In the past, Aluminium salts, and more recently Calcium and Magnesium salts, and a synthetic resin polyallylamine hydrochloride have been employed, but Aluminium was later abandoned, because it has been a silent killer of many uremic patients, due to subtle absorption eventually leading to toxicity on Central Nervous System and bone, with allucinations, seizures, dementia, and osteomalacia, bone pain, fracturing osteodystrophy, and death. Recently, a new chelating agent able to bind dietary phosphate, namely Lanthanum carbonate has been introduced, with a proven efficacy profile for short-term treatment. However, after careful examination of the very few scientific papers available to date, we strongly advise caution before adopting, at present, lanthanum carbonate as a phosphate binder in uremic patients. In fact, notwithstanding minimized, some data are worrying: first, Lanthanum ions are absorbed, though at a minimal extent, by human gut; 2) pharmacokinetic evaluations show a greater exposure to Lanthanum in uremic patients;3) Lanthanum concentration is increased tenfold in blood and fivefold in bone after short-term supplementation in uremic patients; 4) there is no proofs that Lanthanum cannot cross the blood brain barrier in uremic patients; 5)Lanthanum has many biological effects and is potentially highly toxic. The Aluminum story should serve as cautionary tale when considering the use of new metal ions. PMID:16022663

  20. [Fluoride adsorption form drinking water by granular lanthanum alginate].

    PubMed

    Huo, Ya-Kun; Ding, Wen-Ming; Huang, Xia

    2010-11-01

    Granular lanthanum alginate was prepared by dripping solved sodium alginate into lanthanum chloride solution. After washed and dried, sorbent with 1-1.5 mm diameter, 25% (mass fraction) La content was made and applied for fluoride removal from drinking test. Adsorption performance such as adsorption rate, adsorption isotherm, pH and disturbing ions effects were tested in batch adsorption. The changes of adsorbent surface and the solution composition before and after adsorption were also studied. Results showed that the adsorption rate was fast, fluoride concentration trend to stable after 2h reaction, and the adsorption rate fit for pseudo second order equation. The adsorption was significantly affected by pH and some disturbing ions, optimum pH = 4, phosphate and carbonate reduced adsorption. Adsorption isotherm fitted Langmuir equation well; the max adsorption capacity was 197.2 mg x g(-1). SEM photographs of sorbent before and after adsorption showed significantly different surface morphology; EDX composition analysis of sorbent surface and solution concentration changes before and after adsorption showed that ion exchange take placed between solution F- and sorbent surface Cl- and OH-.

  1. Airplane dopes and doping

    NASA Technical Reports Server (NTRS)

    Smith, W H

    1919-01-01

    Cellulose acetate and cellulose nitrate are the important constituents of airplane dopes in use at the present time, but planes were treated with other materials in the experimental stages of flying. The above compounds belong to the class of colloids and are of value because they produce a shrinking action on the fabric when drying out of solution, rendering it drum tight. Other colloids possessing the same property have been proposed and tried. In the first stages of the development of dope, however, shrinkage was not considered. The fabric was treated merely to render it waterproof. The first airplanes constructed were covered with cotton fabric stretched as tightly as possible over the winds, fuselage, etc., and flying was possible only in fine weather. The necessity of an airplane which would fly under all weather conditions at once became apparent. Then followed experiments with rubberized fabrics, fabrics treated with glue rendered insoluble by formaldehyde or bichromate, fabrics treated with drying and nondrying oils, shellac, casein, etc. It was found that fabrics treated as above lost their tension in damp weather, and the oil from the motor penetrated the proofing material and weakened the fabric. For the most part the film of material lacked durability. Cellulose nitrate lacquers, however were found to be more satisfactory under varying weather conditions, added less weight to the planes, and were easily applied. On the other hand, they were highly inflammable, and oil from the motor penetrated the film of cellulose nitrate, causing the tension of the fabric to be relaxed.

  2. 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.

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

    PubMed

    Marciniak, M; Bałtrukiewicz, Z

    1977-01-01

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

  4. 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.

  5. TREATMENT OF HEXAVALENT CHROMIUM IN CHROMITE ORE PROCESSING SOLID WASTE USING A MIXED REDUCTANT SOLUTION OF FERROUS SULFATE AND SODIUM DITHIONITE

    EPA Science Inventory

    We developed a method for disseminating ferrous iron in the subsurface to enhance chemical reduction of hexavalent chromium (Cr(VI)) in a chromite ore processing solid waste derived from the production of ferrochrome alloy. The method utilizes ferrous sulfate (FeSO4) in combinati...

  6. Optical amplification in disordered electrooptic Tm{sup 3+} and Ho{sup 3+} codoped lanthanum-modified lead zirconate titanate ceramics and study of spectroscopy and communication between cations

    SciTech Connect

    Zhao, Hua; Zhang, Kun; Xu, Long; Sun, Fankui; Zhang, Jingwen; Chen, Xuesheng; Li, Kewen K.

    2014-02-21

    Rare earth doped electro-optic (EO) ceramics of lanthanum-modified lead zirconate titanate (PLZT) are promising in building multifunctional optical devices, by taking advantage of both EO effect and optical activity. In this work, the combination of the measured spectra of absorption and photoluminescence, the fluorescent decay, the calculated Judd-Ofelt parameters, and measured single pass gain in Tm{sup 3+}, Ho{sup 3+} codoped PLZT ceramics have marked them out as promising gain media in building electrically controllable lasers/optical amplifiers and other multifunctional devices. Optical energy storage was also observed in the optical amplification dynamics.

  7. Application of artificial neural network in 3D imaging with lanthanum bromide calorimeter

    NASA Astrophysics Data System (ADS)

    Gostojic, A.; Tatischeff, V.; Kiener, J.; Hamadache, C.; Karkour, N.; Linget, D.; Grave, X.; Gibelin, L.; Travers, B.; Blin, S.; Barrillon, P.

    2015-07-01

    Gamma-ray astronomy in the energy range from 0.1 up to 100 MeV holds many understudied questions connected with e.g. stellar nucleosynthesis, the active Sun, neutron stars and black holes. To access the physics behind, a significant improvement in detection sensitivity is needed compared to previous missions, e.g. CGRO and INTEGRAL. One of the promising concepts for a future gamma-ray mission is an Advanced Compton Telescope. Under the project of creating a prototype of such instrument, we study the perspectives of using a novel inorganic scintillator as a calorimeter part. Modern inorganic crystal or ceramics scintillators are constantly improving on qualities such as energy resolution and radiation hardness, and this makes them a smart choice for a new space-borne telescope. At CSNSM Orsay, we have assembled a detection module from a 5 × 5cm2 area and 1 cm thick, cerium-doped lanthanum (III) bromide (LaBr3:Ce) inorganic scintillator coupled to a 64 channel multi-anode photomultiplier. The readout of the PMT signals is carried out with the ASIC MAROC, used previously for the luminometer of the ATLAS detector (CERN). Characterization, thorough measurements with various radioactive sources, as well as, single photoelectron detection have been done. Furthermore, we made a comparison of measurements with a detailed GEANT4-based simulation which includes tracking of the optical photons. Finally, we have studied the 3D reconstruction of the first interaction point of incident gamma rays, utilizing a neural network algorithm. This spatial position resolution plays a crucial part in the future implementations and, together with the other measured properties, it makes our detector module very interesting for the next generation of space telescopes operating in the MeV range.

  8. Cellulose-lanthanum hydroxide nanocomposite as a selective marker for detection of toxic copper

    NASA Astrophysics Data System (ADS)

    Marwani, Hadi M.; Lodhi, Mazhar Ullah; Khan, Sher Bahadar; Asiri, Abdullah M.

    2014-09-01

    In this current report, a simple, reliable, and rapid method based on modifying the cellulose surface by doping it with different percentages of lanthanum hydroxide (i.e., 1% La(OH)3-cellulose (LC), 5% La(OH)3-cellulose (LC2), and 10% La(OH)3-cellulose (LC3)) was proposed as a selective marker for detection of copper (Cu(II)) in aqueous medium. Surface properties of the newly modified cellulose phases were confirmed by Fourier transform infrared spectroscopy, field emission scanning electron microscope, energy dispersive X-ray spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopic analysis. The effect of pH on the adsorption of modified cellulose phases for Cu(II) was evaluated, and LC3 was found to be the most selective for Cu(II) at pH 6.0. Other parameters, influencing the maximum uptake of Cu(II) on LC3, were also investigated for a deeper mechanistic understanding of the adsorption phenomena. Results showed that the adsorption capacity for Cu(II) was improved by 211% on the LC3 phase as compared to diethylaminoethyl cellulose phase after only 2 h contact time. Adsorption isotherm data established that the adsorption process nature was monolayer with a homogeneous adsorbent surface. Results displayed that the adsorption of Cu(II) onto the LC3 phase obeyed a pseudo-second-order kinetic model. Selectivity studies toward eight metal ions, i.e., Cd(II), Co(II), Cr(III), Cr(VI), Cu(II), Fe(III), Ni(II), and Zn(II), were further performed at the optimized pH value. Based on the selectivity study, it was found that Cu(II) is highly selective toward the LC3 phase. Moreover, the efficiency of the proposed method was supported by implementing it to real environmental water samples with adequate results.

  9. Cellulose-lanthanum hydroxide nanocomposite as a selective marker for detection of toxic copper.

    PubMed

    Marwani, Hadi M; Lodhi, Mazhar Ullah; Khan, Sher Bahadar; Asiri, Abdullah M

    2014-01-01

    In this current report, a simple, reliable, and rapid method based on modifying the cellulose surface by doping it with different percentages of lanthanum hydroxide (i.e., 1% La(OH)3-cellulose (LC), 5% La(OH)3-cellulose (LC2), and 10% La(OH)3-cellulose (LC3)) was proposed as a selective marker for detection of copper (Cu(II)) in aqueous medium. Surface properties of the newly modified cellulose phases were confirmed by Fourier transform infrared spectroscopy, field emission scanning electron microscope, energy dispersive X-ray spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopic analysis. The effect of pH on the adsorption of modified cellulose phases for Cu(II) was evaluated, and LC3 was found to be the most selective for Cu(II) at pH 6.0. Other parameters, influencing the maximum uptake of Cu(II) on LC3, were also investigated for a deeper mechanistic understanding of the adsorption phenomena. Results showed that the adsorption capacity for Cu(II) was improved by 211% on the LC3 phase as compared to diethylaminoethyl cellulose phase after only 2 h contact time. Adsorption isotherm data established that the adsorption process nature was monolayer with a homogeneous adsorbent surface. Results displayed that the adsorption of Cu(II) onto the LC3 phase obeyed a pseudo-second-order kinetic model. Selectivity studies toward eight metal ions, i.e., Cd(II), Co(II), Cr(III), Cr(VI), Cu(II), Fe(III), Ni(II), and Zn(II), were further performed at the optimized pH value. Based on the selectivity study, it was found that Cu(II) is highly selective toward the LC3 phase. Moreover, the efficiency of the proposed method was supported by implementing it to real environmental water samples with adequate results. PMID:25258599

  10. Cellulose-lanthanum hydroxide nanocomposite as a selective marker for detection of toxic copper

    PubMed Central

    2014-01-01

    In this current report, a simple, reliable, and rapid method based on modifying the cellulose surface by doping it with different percentages of lanthanum hydroxide (i.e., 1% La(OH)3-cellulose (LC), 5% La(OH)3-cellulose (LC2), and 10% La(OH)3-cellulose (LC3)) was proposed as a selective marker for detection of copper (Cu(II)) in aqueous medium. Surface properties of the newly modified cellulose phases were confirmed by Fourier transform infrared spectroscopy, field emission scanning electron microscope, energy dispersive X-ray spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopic analysis. The effect of pH on the adsorption of modified cellulose phases for Cu(II) was evaluated, and LC3 was found to be the most selective for Cu(II) at pH 6.0. Other parameters, influencing the maximum uptake of Cu(II) on LC3, were also investigated for a deeper mechanistic understanding of the adsorption phenomena. Results showed that the adsorption capacity for Cu(II) was improved by 211% on the LC3 phase as compared to diethylaminoethyl cellulose phase after only 2 h contact time. Adsorption isotherm data established that the adsorption process nature was monolayer with a homogeneous adsorbent surface. Results displayed that the adsorption of Cu(II) onto the LC3 phase obeyed a pseudo-second-order kinetic model. Selectivity studies toward eight metal ions, i.e., Cd(II), Co(II), Cr(III), Cr(VI), Cu(II), Fe(III), Ni(II), and Zn(II), were further performed at the optimized pH value. Based on the selectivity study, it was found that Cu(II) is highly selective toward the LC3 phase. Moreover, the efficiency of the proposed method was supported by implementing it to real environmental water samples with adequate results. PMID:25258599

  11. Hearing Threshold, Loss, Noise Levels and Worker’s Profiles of an Open Cast Chromite Mines in Odisha, India

    PubMed Central

    Kerketta, Sunamani; Gartia, Rajendra; Bagh, Somanath

    2012-01-01

    Objectives: The aims of the study were to describe the noise levels at an open cast chromite mine in Odisha, India, and the hearing threshold of its workers and to associate their hearing loss with their age, work station and length of employment at the mine. Methods: We performed a cross-sectional study of the hearing threshold of chromite mine workers. Audiometric data from 500 subjects was collected at the mines’ hospital in the Sukinda Valley of Jajpur, Odisha, India. The latest audiometry data available for the period 2002 to 2008 was used in the analysis. Audiometric screening was performed using an audiometer (TRIVENI TAM-25 6025A) in a quiet environment by qualified technicians, audiologists or physicians. Tests were conducted on the subjects after they had completely rested for 16 hours or more after their day shift. Results: A maximum of 262 subjects (52.4%) were employed in the work zone area and a minimum of 2 subjects (0.4%) had less than 5 years working experience. The age of the subjects ranged from 29 to 59 years and their working experience ranged from 4 to 37 years. The subjects’ average mean hearing thresholds at 4, 6 and 8 kHz were 21.53 dBA, 23.40 dBA and 21.90 dBA, respectively. The maximum Leq and L90 levels exceeded the prescribed limits for commercial, residential and silence zones. The maximum Leq levels exceeded 95 dBA for large and medium heavy earth moving machineries (HEMMs), both outside and at the operator’s position. Hearing loss due to the subjects’ work experience was found to be greater than that attributable to age and workstation. Conclusion: In our study population, the maximum noise levels for large and medium HEMMs and inside the cabins of HEMMs were found to be more than 95 dBA. This indicates that operators in this particular chromite mine at Odisha, India were exposed to noise levels exceeding 95 dBA for more than 10% of the monitoring time. The subjects’ hearing loss was also found to increase for every 10-year

  12. 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.

  13. Garnet and chromite- bearing mantle peridotite xenoliths from Komsomolskaya pipe, Alakit field, Yakutia

    NASA Astrophysics Data System (ADS)

    Ashchepkov, Igor; Logvinova, Alla; Valdykin, Nikolai; Makovchuk, Igor; Karpenko, Mikhail; Spetsius, Zdislav; Khmelnikova, Olga; Palessky, Stanislav

    2014-05-01

    Fresh xenoliths in Alakit field in Siberian platform are rare. In the xenoliths from Komsomolskaya pipe there were found 30 xenoliths with fresh Cpx, Gar as well as chromites, phlogopites and ilmenites which allows to construct the Cpx - based geotherm which was before constructed for the Yubileynaya pipe (Ashchepkov et al., 2004). The comparison of the garnets from the breccias and porphyric kimberlites show more depleted and Cr- rich varieties of garnets as it is common for the other pipes. Only relatively fresh material from the dark - grey breccia good relatively fresh xenoliths could be used for the mineral thermobarometry. Large xenolths from the Komsomolskaya pipe belong mainly to the Gar harzburgite or refertilized lherzolite types as also detected on the Cr2O3 - CaO diagram where they belong mainly to the 5-11% Cr2O3 interval. The low Cr varieties are mainly referring to the Fe- enriched pyroxenites or to Phl metasomatites. In SCLM beneath Komsomolskaya pipe is essentially more heated then those beneath Yubileynaya and Sytykanskaya pipes and in lower part they are close to the PTXFO2 are closer in conditrions to the ilmenites which determined the . Peridotites from the lithosphere base (7-6GPa) are enriched in Fe and belong to the porphyroclustic or deformed type by chemistry Fe# =0.14-0.15. the relatively HT conditions were determined also for the peridotites from the 5.0-4. GPa. The most of the Cpx- refertilized varieties give the conditions of the middle part of the mantle section. Their garnest are enriched in CaO probably reflection reactions with the Ca- rich protokimberlites. The Na- richterite bearin xenoliths are from the same PT interval The cold clot in the 60-5.5 GPa (34 mwm-2) are represented by the peridotites of low Fe# 7-9 Fe- low peridotites with the garnets of sub-Ca types. But there are also varieties of reduced Cr and the Fe-enriched which are closer to the pyroxenites or Phl metasomatites which in Pt are from the upper part of mantle

  14. 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

  15. Complete zircon and chromite digestion by sintering of granite, rhyolite, andesite and harzburgite rock reference materials for geochronological purposes

    NASA Astrophysics Data System (ADS)

    Bokhari, Syed Nadeem H.; Meisel, Thomas

    2014-05-01

    Zircon (ZrSiO4) is a common accessory mineral in nature that occurs in a wide variety of sedimentary, igneous, and metamorphic rocks. Zircon has the ability to retain substantial chemical and isotopic information that are used in range of geochemical and geo- chronological investigations. Sample digestion of such rock types is a limiting factor due to the chemical inertness of zircon (ZrSiO4) tourmaline, chromite, barite, monazite, sphene, xenotime etc. as the accuracy of results relies mainly on recovery of analytes from these minerals. Dissolution by wet acid digestions are often incomplete and high blank and total dissolved solids (TDS) contents with alkali fusions lead to an underestimation of analyte concentrations. Hence an effective analytical procedure, that successfully dissolves refractory minerals such as zircon is needed to be employed for reliable analytical results. Na2O2 digestion [1] was applied in characterisation of granite (G-3), rhyolite (MRH), andesite (MGL-AND) and harzburgite (MUH-1) powdered reference material with solution based ICP-MS analysis. In this study we undertake a systematic evaluation of decomposition time and sample:Na2O2 ratio and test portion size after minimising effect of all other constraints that makes homogeneity ambiguous. In recovering zircon and chromite 100 mg test portion was mixed with different amounts of Na2O2 i.e. 100-600 mg. Impact of decomposition time was observed by systematically increasing heating time from 30-45 minutes to 90-120 minutes at 480°C. Different test portion sizes 100-500 mg of samples were digested to control variance of inhomogeneity. An improved recovery of zirconium in zircon in granite (G-3), rhyolite MRH), andesite (MGL-AND) and chromite in harzburgite (MUH-1) was obtained by increasing heating time (2h) at 480°C and by keeping (1:6) ratio of sample:Na2O2. Through this work it has been established that due to presence of zircon and chromite, decomposition time and sample:Na2O2 ratio has

  16. Methanol synthesis using a catalyst combination of alkali or alkaline earth salts and reduced copper chromite for methanol synthesis

    DOEpatents

    Tierney, John W.; Wender, Irving; Palekar, Vishwesh M.

    1993-01-01

    The present invention relates to a novel route for the synthesis of methanol, and more specifically to the production of methanol by contacting synthesis gas under relatively mild conditions in a slurry phase with a catalyst combination comprising reduced copper chromite and basic alkali salts or alkaline earth salts. The present invention allows the synthesis of methanol to occur in the temperature range of approximately 100.degree.-160.degree. C. and the pressure range of 40-65 atm. The process produces methanol with up to 90% syngas conversion per pass and up to 95% methanol selectivity. The only major by-product is a small amount of easily separated methyl formate. Very small amounts of water, carbon dioxide and dimethyl ether are also produced. The present catalyst combination also is capable of tolerating fluctuations in the H.sub.2 /CO ratio without major deleterious effect on the reaction rate. Furthermore, carbon dioxide and water are also tolerated without substantial catalyst deactivation.

  17. The implications of integrated assessment and modelling studies for the future remediation of chromite ore processing residue disposal sites.

    PubMed

    Farmer, J G; Paterson, E; Bewley, R J F; Geelhoed, J S; Hillier, S; Meeussen, J C L; Lumsdon, D G; Thomas, R P; Graham, M C

    2006-05-01

    Chromite ore processing residue (COPR) waste from a former chromium chemical works (1830-1968) is still contaminating groundwater in Glasgow, Scotland, with carcinogenic hexavalent chromium, Cr(VI). An integrated analytical, experimental and modelling approach has identified and accounted for mineral phases and processes responsible for the retention and release of Cr(VI) under prevailing field conditions. Both the nature of mineral phase retention and the buffered high pH of the sites, however, militate against direct remediative treatment of the source material, for example by the application of generic methods (e.g. FeSO4) that have been successfully employed elsewhere for the reduction of Cr(VI) to Cr(III) in other matrices. The interception and treatment of groundwater to remove Cr(VI) and the capping of sites to reduce human exposure to airborne Cr(VI)-contaminated dust may well be more realistic and effective, at least in the short to medium term.

  18. 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.

  19. 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.

  20. 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

  1. Health risk assessment from contaminated foodstuffs: a field study in chromite mining-affected areas northern Pakistan.

    PubMed

    Nawab, Javed; Li, Gang; Khan, Sardar; Sher, Hassan; Aamir, Muhammad; Shamshad, Isha; Khan, Anwarzeb; Khan, Muhammad Amjad

    2016-06-01

    This study aimed to investigate the potential health risk associated with toxic metals in contaminated foodstuffs (fruits, vegetables, and cereals) collected from various agriculture fields present in chromite mining-affected areas of mafic and ultramafic terrains (northern Pakistan). The concentrations of Cr, Ni, Zn, Cd, and Pb were quantified in both soil and food samples. The soil samples were highly contaminated with Cr (320 mg/kg), Ni (108 mg/kg), and Cd (2.55 mg/kg), which exceeded their respective safe limits set by FAO/WHO. Heavy metal concentrations in soil were found in the order of Cr>Ni>Pb>Zn>Cd and showed significantly (p < 0.001) higher concentrations as compared to reference soil. The integrated pollution load index (PLI) value was observed greater than three indicating high level of contamination in the study area. The concentrations of Cr (1.80-6.99 mg/kg) and Cd (0.21-0.90 mg/kg) in foodstuffs exceeded their safe limits, while Zn, Pb, and Ni concentrations were observed within their safe limits. In all foodstuffs, the selected heavy metal concentrations were accumulated significantly (p < 0.001) higher as compared to the reference, while some heavy metals were observed higher but not significant like Zn in pear, persimmon, white mulberry, and date-plum; Cd in pear, fig and white mulberry; and Pb in walnut, fig, and pumpkin. The health risk assessment revealed no potential risk for both adults and children for the majority of heavy metals, except Cd, which showed health risk index (HRI) >1 for children and can pose potential health threats for local inhabitants. Graphical Abstract Heavy metals released from chromite mining lead to soil and foodstuff contamination and human health risk.

  2. Health risk assessment from contaminated foodstuffs: a field study in chromite mining-affected areas northern Pakistan.

    PubMed

    Nawab, Javed; Li, Gang; Khan, Sardar; Sher, Hassan; Aamir, Muhammad; Shamshad, Isha; Khan, Anwarzeb; Khan, Muhammad Amjad

    2016-06-01

    This study aimed to investigate the potential health risk associated with toxic metals in contaminated foodstuffs (fruits, vegetables, and cereals) collected from various agriculture fields present in chromite mining-affected areas of mafic and ultramafic terrains (northern Pakistan). The concentrations of Cr, Ni, Zn, Cd, and Pb were quantified in both soil and food samples. The soil samples were highly contaminated with Cr (320 mg/kg), Ni (108 mg/kg), and Cd (2.55 mg/kg), which exceeded their respective safe limits set by FAO/WHO. Heavy metal concentrations in soil were found in the order of Cr>Ni>Pb>Zn>Cd and showed significantly (p < 0.001) higher concentrations as compared to reference soil. The integrated pollution load index (PLI) value was observed greater than three indicating high level of contamination in the study area. The concentrations of Cr (1.80-6.99 mg/kg) and Cd (0.21-0.90 mg/kg) in foodstuffs exceeded their safe limits, while Zn, Pb, and Ni concentrations were observed within their safe limits. In all foodstuffs, the selected heavy metal concentrations were accumulated significantly (p < 0.001) higher as compared to the reference, while some heavy metals were observed higher but not significant like Zn in pear, persimmon, white mulberry, and date-plum; Cd in pear, fig and white mulberry; and Pb in walnut, fig, and pumpkin. The health risk assessment revealed no potential risk for both adults and children for the majority of heavy metals, except Cd, which showed health risk index (HRI) >1 for children and can pose potential health threats for local inhabitants. Graphical Abstract Heavy metals released from chromite mining lead to soil and foodstuff contamination and human health risk. PMID:26971962

  3. Stability of solid oxide fuel cell materials

    SciTech Connect

    Armstrong, T.R.; Bates, J.L.; Coffey, G.W.; Pederson, L.R.

    1996-08-01

    Chromite interconnection materials in an SOFC are exposed to both highly oxidizing conditions at the cathode and to highly reducing conditions at the anode. Because such conditions could lead to component failure, the authors have evaluated thermal, electrical, chemical, and structural stabilities of these materials as a function of temperature and oxygen partial pressure. The crystal lattice of the chromites was shown to expand for oxygen partial pressures smaller than 10{sup {minus}10} atm, which could lead to cracking and debonding in an SOFC. Highly substituted lanthanum chromite compositions were the most susceptible to lattice expansion; yttrium chromites showed better dimensional stability by more than a factor of two. New chromite compositions were developed that showed little tendency for lattice expansion under strongly reducing conditions, yet provided a good thermal expansion match to other fuel cell components. Use of these new chromite interconnect compositions should improve long-term SOFC performance, particularly for planar cell configurations. Thermodynamic properties of substituted lanthanum manganite cathode compositions have been determined through measurement of electromotive force as a function of temperature. Critical oxygen decomposition pressures for Sr and Ca-substituted lanthanum manganites were established using cells based on a zirconia electrolyte. Strontium oxide and calcium oxide activities in a lanthanum manganite matrix were determined using cells based on strontium fluoride and calcium fluoride electrolytes, respectively. The compositional range of single-phase behavior of these ABO{sub 3}-type perovskites was established as a function of A/B cation ratios and the extent of acceptor doping. Before this work, very little thermodynamic information was in existence for substituted manganite compositions. Such information is needed to predict the long-term stability of solid oxide fuel cell assemblies.

  4. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2007-07-01

    The preparation of lanthanum hydroxide and manganese oxide nanoparticles is presented, based on a nonaqueous sol-gel process involving the reaction of La(O iPr) 3 and KMnO 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) 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 4 plays a crucial role in determining the particle morphology of La(OH) 3. The reason lies in the fact that KMnO 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(O iPr) 3-to-KMnO 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) 3 nanoparticles. Postsynthetic thermal treatment of the sample containing La(OH) 3 nanofibers and β-MnOOH nanoparticles at the temperature of 800 °C for 8 h yielded polyhedral LaMnO 3 and worm-like La 2O 3 nanoparticles as final products.

  6. Chromites from the Gogoł;ów-Jordanów Serpentinite Massif (SW Poland) - evidence of the arc setting magmatism

    NASA Astrophysics Data System (ADS)

    Wojtulek, Piotr; Puziewicz, Jacek; Ntaflos, Theodoros; Bukała, Michał

    2014-05-01

    The Gogołów-Jordanów Serpentinite Massif (GJSM) is a peridotitic member of the Variscan Ślęża Ophiolite (SW Poland). Chromitite veinlets and pockets occur in the central part of the massif in the Czernica Hill area within completely serpentinized rocks. Chromitites consist of rounded chromite grains up to 4 cm and chlorite filling the interstices. The veins are embedded in serpentine-olivine-chlorite aggregates. Chemical composition of chromite occurring in chromitites defines two varieties. Chromite I (Cr# = 0.49 - 0.58) contains 23.32 - 28.36 wt.% Al2O3, 40.29 - 48.10 wt.% Cr2O3, 15.10 - 15.50 wt.% FeO, 14.50 - 15.50 wt.% MgO and ~0.1 wt.% TiO2. Chromite II (Cr# = 0.71 - 0.73) contains 13.83 - 15.24 wt.% Al2O3, 54.85 - 56.65 wt.% Cr2O3, 16.71 - 18.04 wt.% FeO, 10.62 - 11.59 wt.% MgO and 0.1 wt.% TiO2. Chromite grains are composed mostly of chromite I. Chromite II forms irregular spongy domains up to 150 µm, located at fissures or forming grain rims. The bulk chromitite composition of the massive ores reveals Rb, Ba, Pb and Sb enrichment relative to primitive mantle; Pt and Pd (up to 36 ppb) are also enriched relative to primitive mantle. Other phases coexisting with chromite are chlorite and olivine. Chlorite (Fe# = 0.02) contains 17.5 - 23.0 wt.% Al2O3, 0.6 - 1.8 wt.% Cr2O3 and 31.8 - 34.2 wt.% MgO. Olivine (Fo93.5-96.2) contains 0.44- 0.51 wt.% NiO. Olivine grains are zoned - the low-forsteritic cores are surrounded by high-forsteritic domain. Chromite II and chlorite are secondary phases and were probably formed due to greenschist facies metamorphism. Chromitites are cumuletes of melt blocked during its flow through peridotitic host. Low TiO2 content and moderate chromian number of the GJSM chromitites is typical for chromian spinels originated from melt derived from back arc depleted source (cf. Python et al., 2008, Gonzalez-Jimenez, 2011). The GJSM chromitites are rich in Al and poor in Pt and Pd what is typical for chromitites occurring in the

  7. Interplay Between Structural, Jahn-Teller, and Magnetic States of Slightly Doped Lanthanum Manganites

    NASA Astrophysics Data System (ADS)

    Golenishchev-Kutuzov, V. A.; Golenishchev-Kutuzov, A. V.; Kalimullin, R. I.; Semennikov, A. V.

    2016-03-01

    By combining the results of elastic moduli, electrical resistivity, and magnetization measurements for La_{1-x} Srx MnO3 (x = 0.125, x = 0.15, and x = 0.175), we have constructed a phase diagram that describes the structural, magnetic, transport properties and the relationships among them as a function of the composition and temperature (140-340 K). The local, intermediate, and cooperative Jahn-Teller distortions of the octahedral structural units MnO6 have been studied. It is common for these distortions to be observed using probes of intermediate structures (domains or super-cells), but they are absent in the averaged crystallographic structure. In the cooperative Jahn-Teller distorted phase, the macroscopic sample length is temperature dependent. We presume that the structural transitions from the cooperative Jahn-Teller phase to the charge ordering phase at low temperatures (150 and 180 K at x = 0.125 and x = 0.15) are due to the increase in the spontaneous magnetization with the conservation of the local deformations of separate octahedra. The agreement between the types of the orbital ordering and the local, intermediate, and Jahn-Teller cooperative distortions of octahedra was established.

  8. Fabrication and spectral properties of Nd 3+-doped yttrium lanthanum oxide transparent ceramics

    NASA Astrophysics Data System (ADS)

    Hu, Xiaoman; Yang, Qiuhong; Dou, Chuanguo; Xu, Jun; Zhou, Hongxu

    2008-06-01

    Transparent 1 at% Nd3+:Y1.9La0.1O3 ceramics were fabricated with nanopowders prepared by carbonate coprecipitation method. The powder compacts were sintered in H2 atmosphere at 1550 °C for 30 h. The Nd3+:Y1.9La0.1O3 ceramics display uniform grains of about 50 μm and high transparency. The highest transmittance of the ceramics reaches 67%. The strongest absorption peak is in the wavelength of 820 nm with absorption cross section of 2.48 × 10-20 cm2. The absorption is still high at LD wavelength 806 nm with absorption cross section of 1.78 × 10-20 cm2 and broad full width at half maximum (FWHM) of about 6.3 nm. The strongest emission peak was centered at 1078 nm with large stimulated emission cross section of 9.63 × 10-20 cm2 and broad FWHM of about 7.8 nm. The broad absorption and emission bandwidth of Nd3+:Y1.9La0.1O3 transparent ceramics are favorable to achieve the miniaturized LD pumping apparatus and ultrashort modelocked pulse laser output, respectively.

  9. Structure and magnetic interactions in (Sr, Sb)-doped lanthanum manganites

    NASA Astrophysics Data System (ADS)

    Karpinsky, D. V.; Troyanchuk, I. O.; Silibin, M. V.; Gavrilov, S. A.; Bushinky, M. V.; Sikolenko, V.; Frontzek, M.

    2016-05-01

    Ceramic samples La1-2xSr2xMn1-xSbxO3 (x≤0.2) have been studied by X-ray and neutron powder diffraction, magnetization measurements and charge density calculations have also been performed. The compounds are characterized by the rhombohedral structure at room temperature; temperature decrease causes structural transition to the orthorhombic structure. La1-2xSr2xMn1-xSbxO3 ceramics are characterized by homovalent manganese ions and have long range ferromagnetic order which gradually diminishes with the chemical substitution. It is considered that magnetic properties of the compounds are determined by the dominance of ferromagnetic superexchange interactions stabilized in the orbital disordered orthorhombic phase. Significant covalent component of the Mn-O chemical bonds contributes to the long-range ferromagnetic order of the compounds, the covalency of the chemical bonds is assumed to be isotropically distributed over the orthorhombic phase.

  10. Preparation and laser performance of Nd-doped yttrium lanthanum oxide transparent ceramic

    NASA Astrophysics Data System (ADS)

    Yang, Qiuhong; Lu, Shenzhou; Zhang, Bin; Zhang, Haojia; Zhou, Jun; Yuan, Zhijun; Qi, Yunfeng; Lou, Qihong

    2011-03-01

    1.5 at.% Nd:Y 1.8La 0.2O 3 transparent ceramic was fabricated by a solid-state reaction method and sintered at 1650-1700 °C for 40-50 h under H 2 atmosphere. The spectroscopic properties were investigated at room temperature. The transparent ceramic has excellent spectroscopic properties, with the absorption cross section of 1.50 × 10 -20 cm 2 and broad full width at half maximum (FWHM) of about 8 nm at LD wavelength 806 nm, the emission cross section of 2.03 × 10 -20 cm 2 at 1079 nm, and the decay lifetime of 200 μs. Laser performance was carried out using an uncoated Nd:Y 1.8La 0.2O 3 ceramic plate under laser diode end-pumping without any water cooling device. The room temperature thermal conductivity of this ceramic is 6.20 W/mK. For Nd:Y 1.8La 0.2O 3 ceramic laser, a maximum output power of 62 mW was obtained at 1079 nm under a 808 nm diode pump.

  11. Fabrication and XAFS analysis of Yb3+ doped yttrium lanthanum oxide transparent ceramics

    NASA Astrophysics Data System (ADS)

    Jiang, Cen; Yang, Qiuhong; Lu, Qing; Zhang, Haojia

    2013-12-01

    (YbxY0.90-xLa0.10)2O3 (x = 0.01-0.10) transparent ceramics were fabricated and their structural properties were investigated. The XRD showed our samples exhibited single cubic Y2O3 phase. The lattice parameters were refined with the Rietveld method. The compact structure and an average grain size of 40-50 μm were revealed by the microstructure. The local fine structure around Yb ions was investigated by using the XAFS (X-ray absorption fine structure) technique. The results showed that: the local structure around Yb ions in the samples with different concentration of Yb ions was basically similar, and Yb ions replaced Y position to form the solid solution. The Yb ions were trivalent. With the concentration of Yb2O3 increased, the coordination number (N) and first shell Yb-O bond length (R) decreased, and the degree of disorder (σ) increased.

  12. Chalcophile and platinum-group element distribution in the Ultramafic series of the Stillwater Complex, MT, USA—implications for processes enriching chromite layers in Os, Ir, Ru, and Rh

    NASA Astrophysics Data System (ADS)

    Barnes, Sarah-Jane; Pagé, P.; Prichard, H. M.; Zientek, M. L.; Fisher, P. C.

    2016-01-01

    All of the rocks from the Ultramafic series of the Stillwater Complex are enriched in PGE relative to most mafic magmas. Furthermore, the chromite layers are particularly enriched in IPGE (Os, Ir, and Ru) and Rh. This enrichment appears to be a common characteristic of ultramafic rocks from many types of settings, layered intrusions, ophiolites, and zoned complexes. We have carried out a petrological, mineralogical, and geochemical study to assess how the enrichment occurred in the case of the Stillwater Complex and applied our results to the chromite layers of the Bushveld and Great Dyke complexes. The minerals that now host the PGE are laurite and fine-grained intergrowths of pentlandite, millerite, and chalcopyrite. The laurite occurs as inclusions in chromite, and mass balance calculations indicate that it hosts most of the Os, Ir, and Ru. The sulfide minerals occur both as inclusions in chromite and as interstitial grains. The sulfides host much of the Pd and Rh. The IPGE and Rh correlate with Cr but not with S or Se, indicating that these elements were not collected by a sulfide liquid. Palladium, Cu, and Se correlate with each other, but not with S. The low S/Se (<1500) of the whole rock and magnetite rims around the sulfides indicate some S has been lost from the rocks. We conclude that to account for all observations, the IPGE and Rh were originally collected by chromite, and subsequently, small quantities of base metal sulfide liquid was added to the chromite layers from the overlying magma. The IPGE and Rh in the chromite diffused from the chromite into the base metal sulfides and converted some of the sulfides to laurite.

  13. Toxicity of Two Different Sized Lanthanum Oxides in Cultured Cells and Sprague-Dawley Rats

    PubMed Central

    2015-01-01

    In recent years, the use of both nano- and micro-sized lanthanum has been increasing in the production of optical glasses, batteries, alloys, etc. However, a hazard assessment has not been performed to determine the degree of toxicity of lanthanum. Therefore, the purpose of this study was to identify the toxicity of both nano- and micro-sized lanthanum oxide in cultured cells and rats. After identifying the size and the morphology of lanthanum oxides, the toxicity of two different sized lanthanum oxides was compared in cultured RAW264.7 cells and A549 cells. The toxicity of the lanthanum oxides was also analyzed using rats. The half maximal inhibitory concentrations of micro-La2O3 in the RAW264.7 cells, with and without sonication, were 17.3 and 12.7 times higher than those of nano-La2O3, respectively. Similar to the RAW264.7 cells, the toxicity of nano-La2O3 was stronger than that of micro-La2O3 in the A549 cells. We found that nano-La2O3 was absorbed in the lungs more and was eliminated more slowly than micro-La2O3. At a dosage that did not affect the body weight, numbers of leukocytes, and concentrations of lactate dehydrogenase and albumin in the bronchoalveolar lavage (BAL) fluids, the weight of the lungs increased. Inflammatory effects on BAL decreased over time, but lung weight increased and the proteinosis of the lung became severe over time. The effects of particle size on the toxicity of lanthanum oxides in rats were less than in the cultured cells. In conclusion, smaller lanthanum oxides were more toxic in the cultured cells, and sonication decreased their size and increased their toxicity. The smaller-sized lanthanum was absorbed more into the lungs and caused more toxicity in the lungs. The histopathological symptoms caused by lanthanum oxide in the lungs did not go away and continued to worsen until 13 weeks after the initial exposure. PMID:26191385

  14. Temperature-Induced Magnetization Reversal in the Mn^{3+}-Doped SmCrO3

    NASA Astrophysics Data System (ADS)

    Wu, Yuying; Xu, Jian; Xia, Zhengcai

    2016-04-01

    The temperature dependence of dc magnetization is investigated for the rare earth chromites SmCrO3 and the doped compound SmCr_{0.9}Mn_{0.1}O3. Different from the magnetization behavior of SmCrO3, temperature-induced magnetization reversals are observed in the Mn^{3+}-doped compound. Moreover, low-temperature isothermal magnetization measurement indicates the magnetic ground state of SmCr_{0.9}Mn_{0.1}O3 to be antiferromagnetic with a spin canting. The field-cooling magnetic hysteresis loop reveals that an exchange bias (EB) phenomenon is present in the sample. The reversal of magnetization and the corresponding EB field is discussed on the basis of the competitive interaction between the antiferromagnetically coupled Cr-rich clusters and Cr-Mn ordered clusters.

  15. Process Developed for Generating Ceramic Interconnects With Low Sintering Temperatures for Solid Oxide Fuel Cells

    NASA Technical Reports Server (NTRS)

    Zhong, Zhi-Min; Goldsby, Jon C.

    2005-01-01

    Solid oxide fuel cells (SOFCs) have been considered as premium future power generation devices because they have demonstrated high energy-conversion efficiency, high power density, and extremely low pollution, and have the flexibility of using hydrocarbon fuel. The Solid-State Energy Conversion Alliance (SECA) initiative, supported by the U.S. Department of Energy and private industries, is leading the development and commercialization of SOFCs for low-cost stationary and automotive markets. The targeted power density for the initiative is rather low, so that the SECA SOFC can be operated at a relatively low temperature (approx. 700 C) and inexpensive metallic interconnects can be utilized in the SOFC stack. As only NASA can, the agency is investigating SOFCs for aerospace applications. Considerable high power density is required for the applications. As a result, the NASA SOFC will be operated at a high temperature (approx. 900 C) and ceramic interconnects will be employed. Lanthanum chromite-based materials have emerged as a leading candidate for the ceramic interconnects. The interconnects are expected to co-sinter with zirconia electrolyte to mitigate the interface electric resistance and to simplify the processing procedure. Lanthanum chromites made by the traditional method are sintered at 1500 C or above. They react with zirconia electrolytes (which typically sinter between 1300 and 1400 C) at the sintering temperature of lanthanum chromites. It has been envisioned that lanthanum chromites with lower sintering temperatures can be co-fired with zirconia electrolyte. Nonstoichiometric lanthanum chromites can be sintered at lower temperatures, but they are unstable and react with zirconia electrolyte during co-sintering. NASA Glenn Research Center s Ceramics Branch investigated a glycine nitrate process to generate fine powder of the lanthanum-chromite-based materials. By simultaneously doping calcium on the lanthanum site, and cobalt and aluminum on the

  16. Electric properties and phase transition behavior in lead lanthanum zirconate stannate titanate ceramics with low zirconate content

    NASA Astrophysics Data System (ADS)

    Zeng, Tao; Lou, Qi-Wei; Chen, Xue-Feng; Zhang, Hong-Ling; Dong, Xian-Lin; Wang, Gen-Shui

    2015-11-01

    The phase transitions, dielectric properties, and polarization versus electric field (P-E) hysteresis loops of Pb0.97La0.02(Zr0.42Sn0.58-xTix)O3 (0.13≤ x ≤0.18) (PLZST) bulk ceramics were systematically investigated. This study exhibited a sequence of phase transitions by analyzing the change of the P-E hysteresis loops with increasing temperature. The antiferroelectric (AFE) to ferroelectric (FE) phase boundary of PLZST with the Zr content of 0.42 was found to locate at the Ti content between 0.14 and 0.15. This work is aimed to improve the ternary phase diagram of lanthanum-doped PZST with the Zr content of 0.42 and will be a good reference for seeking high energy storage density in the PLZST system with low-Zr content. Project supported by the National Natural Science Foundation of China (Grant Nos. 51202273, 11204304, and 11304334) and the Science and Technology Commission of Shanghai Municipality, China (Grant No. 14DZ2261000).

  17. 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

  18. 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.

  19. 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

  20. 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.

  1. Sorption of noble gases by solids, with reference to meteorites. II - Chromite and carbon. III - Sulfides, spinels, and other substances; on the origin of planetary gases

    NASA Technical Reports Server (NTRS)

    Yang, J.; Anders, E.

    1982-01-01

    The trapping of noble gases by chromite and carbon, two putative carriers of primordial noble gases in meteorites, was studied by synthesizing 19 samples in a Ne-Ar-Kr-Xe atmosphere at 440-720 K. Noble gas contents are found to approximately obey Henry's Law, but only slight correlations are found with composition, surface area, or adsorption temperature. Geometric mean distribution coefficients for bulk samples and HCl residues in 10 cu cm STP/g atm are: Xe 100, Kr 15, Ar 3.5, and Ne 0.62. Elemental fractionation data support the suggestion of Lewis et al. (1977) that chromite and carbon in C2 and C3 chondrites were formed by the reaction: Fe, Cr + 4CO yields (Fe, Cr)3O4 + 4C + carbides. In contrast to meteoritic minerals, the synthetic specimens show no isotopic fractionation of noble gases. In a subsequent study, attention is given to the cases of sulfides and spinels, on the way to consideration of the origin of planetary gases. Sulfides showed three distinctive trends relative to chromite or magnetite. The elemental fractionation pattern of Ar, Kr and Xe in meteorites, terrestrial rocks and planets resembles the adsorption patterns on the carbons, spinels, sulfides, and other solids studied. The high release temperature of meteoritic noble gases may be explained by transformation of the physisorbed or chemisorbed gas. The ready loss of meteoritic heavy gases on surficial oxidation is consistent with adsorption, as is the high abundance.

  2. 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.

  3. 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.

  4. 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.

  5. 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. PMID:24126694

  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. Deposition and investigation of lanthanum-cerium hexaboride thin films

    SciTech Connect

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

    2006-09-15

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

  8. Observation of the highly excited states of Lanthanum

    SciTech Connect

    Xue, P.; Xu, X. Y.; Huang, W.; Xu, C. B.; Zhao, R. C.; Xie, X. P.

    1997-01-15

    The highly excited states of Lanthanum are studied by means of laser resonance ionization time-of-flight spectrometer. Based on the two-step laser resonance excitation with intermediate state 5d{sup 2}({sup 3}F)6p {sup 2}D{sub 5/2}{sup 0}, three new Rydberg state (RS) series (5d{sup 2}(a{sup 3}F{sub 2})ns, 5d{sup 2}(a{sup 3}F{sub 3})nd and 5d{sup 2}(a{sup 1}D{sub 2})ns) and a number of autoionizing states (AIS) are obtained. Theoretical calculation leads the quantum defects of ns and nd series to the value {delta}s=4.35 and {delta}{sub d}=2.80 respectively, which are very close to the experimental results. The Rydberg state series 5d{sup 2}(a{sup 3}F{sub 2})ns gives the first ionization limit to be 44979.8{+-}0.3 cm{sup -1}, which is an order more accurate than ever.

  9. Photodarkening and paramagnetism in ultraviolet exposed lead lanthanum zirconate ceramics

    NASA Astrophysics Data System (ADS)

    Seager, C. H.; Warren, W. L.

    1993-06-01

    Electron paramagnetic resonance (EPR) and photothermal deflection spectroscopy (PDS) have been utilized to characterize samples of lead lanthanum zirconate titanate (PLZT) ceramics before and after ultraviolet (uv) irradiation. We find a variety of EPR resonances in the unirradiated samples, including those attributable to Cu+2, Fe+3, Pb+3, and Ti+3 ions. The dark optical absorption spectra show broad, exponential subgap absorption tails which increase in magnitude with decreasing grain size. In addition, some of the larger grain ceramics show a prominent absorption enhancement which seems to correlate well with the density of Ti+3 centers. During and after uv illumination with light near the PLZT band gap, substantial increases are seen in the density of paramagnetic Ti+3 and Pb+3 ions, and a broad absorption peak appears at ˜2.6 eV. The spatial distribution of the induced absorption correlates well with the location of the absorbed uv, suggesting that photoproduced carrier pairs are trapped at Ti+4 and Pb+2 ions producing the observed paramagnetism. The Ti+3 EPR spectra can be successfully fit using the crystal-field-splitting parameters derived from the PDS data. We also observe that both the paramagnetism and the induced absorption are readily bleached by light absorbed in the spectral region where the photoinduced peak is located. We suggest that this effect is due to photoionization of the localized charges.

  10. 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.

  11. 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

  12. Gene doping.

    PubMed

    Harridge, Stephen D R; Velloso, Cristiana P

    2008-01-01

    Gene doping is the misuse of gene therapy to enhance athletic performance. It has recently been recognised as a potential threat and subsequently been prohibited by the World Anti-Doping Agency. Despite concerns with safety and efficacy of gene therapy, the technology is progressing steadily. Many of the genes/proteins which are involved in determining key components of athletic performance have been identified. Naturally occurring mutations in humans as well as gene-transfer experiments in adult animals have shown that altered expression of these genes does indeed affect physical performance. For athletes, however, the gains in performance must be weighed against the health risks associated with the gene-transfer process, whereas the detection of such practices will provide new challenges for the anti-doping authorities.

  13. 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

  14. 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%.

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

    PubMed

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

    2014-12-01

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

  16. Lanthanum phosphate deposition in the gastric mucosa of patients with chronic renal failure.

    PubMed

    Iwamuro, Masaya; Kanzaki, Hiromitzu; Tanaka, Takehiro; Kawano, Seiji; Kawahara, Yoshiro; Okada, Hiroyuki

    2016-07-01

    A 77-year-old Japanese man underwent endoscopic submucosal dissection twice over a 5-year period for the treatment of two separate early gastric cancers. He had been taking lanthanum carbonate, an orally administered phosphate binder, for 3 years. Esophagogastroduodenoscopy revealed reddish mucosa in the greater curvature and anterior wall of the gastric angle, while granular, white deposits were also observed in some areas of this reddish mucosa. Additionally, biopsy specimens from the gastric mucosa revealed the deposition of fine, amorphous, eosinophilic material, which appeared bright on scanning electron microscopy. Energy dispersive X-ray spectroscopy revealed the presence of lanthanum and phosphate in these bright areas, and elemental mapping confirmed that their distribution was identical to that seen in the bright areas. Based on these findings, the diagnosis of lanthanum phosphate deposition in the gastric mucosa was determined. PMID:27383105

  17. 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. PMID:26706125

  18. Pressure increases, the formation of chromite seams, and the development of the ultramafic series in the Stillwater Complex, Montana

    USGS Publications Warehouse

    Lipin, B.R.

    1993-01-01

    This paper explores the hypothesis that chromate seams in the Stillwater Complex formed in response to periodic increases in total pressure in the chamber. Total pressure increased because of the positive ??V of nucleation of CO2 bubbles in the melt and their subsequent rise through the magma chamber, during which the bubbles increased in volume by a factor of 4-6. By analogy with the pressure changes in the summit chambers of Kilauea and Krafla volcanoes, the maximum variation was 0.2-0.25 kbar, or 5-10% of the total pressure in the Stillwater chamber. An evaluation of the likelihood of fountaining and mixing of a new, primitive liquid that entered the chamber with the somewhat more evolved liquid already in the chamber is based upon calculations using observed and inferred velocities and flow rates of basaltic magmas moving through volcanic fissures. The calculations indicate that hot, dense magma would have oozed, rather than fountained into the chamber, and early mixing of the new and residual magmas that could have resulted in chromite crystallizing alone did not take place. -from Author

  19. Early chromite mining and agricultural clearance: Opportunities for the investigation of agricultural sediment dynamics in the Eastern Piedmont (USA)

    USGS Publications Warehouse

    Bain, D.J.; Brush, G.S.

    2005-01-01

    Many flood plains in the Eastern Piedmont (USA) are buried under deposits of sediment resulting from European agricultural clearance. Classic radioisotopic dating techniques cover temporal periods too short (137Cs, 210Pb) or too long (14C) to reliably date sediments deposited during periods of local European activity (1660-1900). Moreover, many potential biomarkers, such as pollen, degrade in oxic flood plain sediments. In the Baltimore, Maryland (USA) region, early chromite mining (1820 - 1880) occurred during periods of rapid agricultural clearance. Use of chromium (Cr) chemostratigraphic profiles in flood plain sediments tied to historical mining activity can provide improved precision in overbank accumulation rates and timing. Sediment cores were collected from the Red Run basin, which is part of the Baltimore Ecosystem Study, an urban Long-Term Ecological Research site. Trace metal chemostratigraphic profiles were measured and peaks in Cr concentration tied to historic mining activity. Dates from Cr chemostratigraphic profiles were combined with 137Cs dating to reconstruct flood plain sedimentation rates. Red Run early sedimentation rates (1820 - 1880) were higher (0.45 - 1.19 cm/yr) than more recent (1880 - 1963) rates (0.08 - 0.46 cm/yr). This indicates that Piedmont flood plain vertical sediment accumulation might have peaked before the peak in agricultural clearance, earlier than assumed by regional models. The Cr chemostratigraphy is applicable to a wider region including much of the Maryland and Pennsylvania (USA) Piedmont.

  20. 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.

  1. Equilibrium distribution of lanthanum, neodymium, and thorium between lithium chloride melt and liquid bismuth

    NASA Astrophysics Data System (ADS)

    Zagnit'ko, A. V.; Ignat'ev, V. V.

    2013-04-01

    The distribution of lanthanum, neodymium, and thorium between a lithium chloride melt and liquid bismuth with additions of lithium as a reducing agent are investigated at 650°C. Equilibrium values of their distribution constants are measured. It is shown that in contrast to neodymium and lanthanum, thorium cannot be extracted from bismuth into lithium chloride. This allows us to propose an efficient scheme for separating lanthanides and thorium in a system for the extraction of fuel salts in molten-salt nuclear reactors.

  2. 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.

  3. 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.

  4. A new large area lanthanum hexaboride plasma source

    NASA Astrophysics Data System (ADS)

    Cooper, C. M.; Gekelman, W.; Pribyl, P.; Lucky, Z.

    2010-08-01

    A new 18×18 cm2 active area lanthanum hexaboride (LaB6) plasma source for use in a dc discharge has been developed at UCLA. The cathode consists of four tiled LaB6 pieces indirectly heated to electron emission (1750 °C) by a graphite heater. A molybdenum mesh anode 33 cm in front of the LaB6 accelerates the electrons, ionizing a fill gas to create a 20×20 cm2 nearly square plasma. The source is run in pulsed operation with the anode biased up to +400 V dc with respect to the cathode for up to 100 ms at a 1 Hz repetition rate. Both the cathode and anode "float" electrically with respect to the chamber walls. The source is placed in a toroidal chamber 2 m wide and 3 m tall with a major radius of 5 m. Toroidal and vertical magnetic fields confine the current-free plasma which follows the field in a helix. The plasma starts on the bottom of the machine and spirals around it up to four times (120 m) and can be configured to terminate either on the top wall or on the neutral gas itself. The source typically operates with a discharge current up to 250 A in helium making plasmas with Te<30 eV, Ti<16 eV, and ne<3×1013 cm-3 in a background field of 100 G

  5. 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.

  6. A new large area lanthanum hexaboride plasma source

    SciTech Connect

    Cooper, C. M.; Gekelman, W.; Pribyl, P.; Lucky, Z.

    2010-08-15

    A new 18x18 cm{sup 2} active area lanthanum hexaboride (LaB{sub 6}) plasma source for use in a dc discharge has been developed at UCLA. The cathode consists of four tiled LaB{sub 6} pieces indirectly heated to electron emission (1750 deg. C) by a graphite heater. A molybdenum mesh anode 33 cm in front of the LaB{sub 6} accelerates the electrons, ionizing a fill gas to create a 20x20 cm{sup 2} nearly square plasma. The source is run in pulsed operation with the anode biased up to +400 V dc with respect to the cathode for up to 100 ms at a 1 Hz repetition rate. Both the cathode and anode ''float'' electrically with respect to the chamber walls. The source is placed in a toroidal chamber 2 m wide and 3 m tall with a major radius of 5 m. Toroidal and vertical magnetic fields confine the current-free plasma which follows the field in a helix. The plasma starts on the bottom of the machine and spirals around it up to four times (120 m) and can be configured to terminate either on the top wall or on the neutral gas itself. The source typically operates with a discharge current up to 250 A in helium making plasmas with T{sub e}<30 eV, T{sub i}<16 eV, and n{sub e}<3x10{sup 13} cm{sup -3} in a background field of 100 G

  7. Fluoride removal in water by a hybrid adsorbent lanthanum-carbon.

    PubMed

    Vences-Alvarez, Esmeralda; Velazquez-Jimenez, Litza Halla; Chazaro-Ruiz, Luis Felipe; Diaz-Flores, Paola E; Rangel-Mendez, Jose Rene

    2015-10-01

    Various health problems associated with drinking water containing high fluoride levels, have motivated researchers to develop more efficient adsorbents to remove fluoride from water for beneficial concentrations to human health. The objective of this research was to anchor lanthanum oxyhydroxides on a commercial granular activated carbon (GAC) to remove fluoride from water considering the effect of the solution pH, and the presence of co-existing anions and organic matter. The activated carbon was modified with lanthanum oxyhydroxides by impregnation. SEM and XRD were performed in order to determine the crystal structure and morphology of the La(III) particles anchored on the GAC surface. FT-IR and pK(a)'s distribution were determined in order to elucidate both the possible mechanism of the lanthanum anchorage on the activated carbon surface and the fluoride adsorption mechanism on the modified material. The results showed that lanthanum ions prefer binding to carboxyl and phenolic groups on the activated carbon surface. Potentiometric titrations revealed that the modified carbon (GAC-La) possesses positive charge at a pH lower than 9. The adsorption capacity of the modified GAC increased five times in contrast to an unmodified GAC adsorption capacity at an initial F(-) concentration of 20 mg L(-1). Moreover, the presence of co-existing anions had no effect on the fluoride adsorption capacity at concentrations below 30 mg L(-1), that indicated high F(-) affinity by the modified adsorbent material (GAG-La).

  8. Fluoride removal in water by a hybrid adsorbent lanthanum-carbon.

    PubMed

    Vences-Alvarez, Esmeralda; Velazquez-Jimenez, Litza Halla; Chazaro-Ruiz, Luis Felipe; Diaz-Flores, Paola E; Rangel-Mendez, Jose Rene

    2015-10-01

    Various health problems associated with drinking water containing high fluoride levels, have motivated researchers to develop more efficient adsorbents to remove fluoride from water for beneficial concentrations to human health. The objective of this research was to anchor lanthanum oxyhydroxides on a commercial granular activated carbon (GAC) to remove fluoride from water considering the effect of the solution pH, and the presence of co-existing anions and organic matter. The activated carbon was modified with lanthanum oxyhydroxides by impregnation. SEM and XRD were performed in order to determine the crystal structure and morphology of the La(III) particles anchored on the GAC surface. FT-IR and pK(a)'s distribution were determined in order to elucidate both the possible mechanism of the lanthanum anchorage on the activated carbon surface and the fluoride adsorption mechanism on the modified material. The results showed that lanthanum ions prefer binding to carboxyl and phenolic groups on the activated carbon surface. Potentiometric titrations revealed that the modified carbon (GAC-La) possesses positive charge at a pH lower than 9. The adsorption capacity of the modified GAC increased five times in contrast to an unmodified GAC adsorption capacity at an initial F(-) concentration of 20 mg L(-1). Moreover, the presence of co-existing anions had no effect on the fluoride adsorption capacity at concentrations below 30 mg L(-1), that indicated high F(-) affinity by the modified adsorbent material (GAG-La). PMID:26070190

  9. Methods of investigation and properties of powder materials: Thermodynamic properties of lanthanum silicides at high temperatures

    SciTech Connect

    Bolgar, A.S.; Gorbachuk, N.P.; Blinder, A.V.

    1994-09-01

    The enthalpies of five lanthanum silicides were determined over the temperature range 380-2225 K by the method of mixtures. Values of the basic thermodynamic functions of the materials were calculated and tabulated, as well as the temperatures, enthalpies, and entropies of fusion. The temperatures and enthalpies of fusion were related to the relative concentrations of silicon in the compounds.

  10. PROCESS USING POTASSIUM LANTHANUM SULFATE FOR FORMING A CARRIER PRECIPITATE FOR PLUTONIUM VALUES

    DOEpatents

    Angerman, A.A.

    1958-10-21

    A process is presented for recovering plutonium values in an oxidation state not greater than +4 from fluoride-soluble fission products. The process consists of adding to an aqueous acidic solution of such plutonium values a crystalline potassium lanthanum sulfate precipitate which carries the plutonium values from the solution.

  11. Spacecraft charging control by thermal, field emission with lanthanum-hexaboride emitters

    NASA Technical Reports Server (NTRS)

    Morris, J. F.

    1978-01-01

    Thermal, field emitters of lanthanum (or perhaps cerium) hexaboride (LaB6) with temperature variability up to about 1500K are suggested for spacecraft charging control. Such emitters operate at much lower voltages with considerably more control and add plasma-diagnostic versatility. These gains should outweigh the additional complexity of providing heat for the LaB6 thermal, field emitter.

  12. Bio-concentration of chromium--an in situ phytoremediation study at South Kaliapani chromite mining area of Orissa, India.

    PubMed

    Mohanty, Monalisa; Pattnaik, Mausumi M; Mishra, Aruna K; Patra, Hemanta K

    2012-01-01

    Mine waste water at South Kaliapani usually contains toxic levels of hexavalent Cr(VI). The present in situ study was conducted at South Kaliapani chromite mine area in Orissa state, India, to assess the phytoremediation ability of three plants, namely, rice (Oryza sativa L.), paragrass (Brachiaria mutica), and an aquatic weed (Eichhornia crassipes), in attenuating Cr(VI) from mine waste water and to correlate the bio-concentration factors (BCF) of Cr. Water hyacinth (E. crassipes) showed 24% to 54% reduction whereas paragrass (B. mutica) was able to reduce 18% to 33% of Cr(VI) from mine water. This reduction was studied over a period of 100 days of plant growth. The reduction was observed through a passage of a sum total of 2,000 sq. ft. cultivated plots and ponds separately. Reduction in Cr(VI) content in mine water varies with plant age as well as with the distance of passage. Cr accumulation and BCF values increased with high soil Cr levels as well as the age of plants. High BCF and transportation index (Ti) values, i.e., 10,924 and 32.09, respectively, were noted for water hyacinth. The Ti values indicated that the root-to-shoot translocation of Cr was very high after 100 days of growth. The total accumulation rate was maximum (8.29 mg Cr kg dry biomass(-1) day (-1)) in paragrass. The BCF values for roots were noted to be higher than those of leaves, stems, and grains of the 125-day-old plants. Hence, paragrass and water hyacinth may be used as tools of phytoremediation to combat the problem of in situ Cr contamination. PMID:21487717

  13. A Russian record of a Middle Ordovician meteorite shower: Extraterrestrial chromite at Lynna River, St. Petersburg region

    NASA Astrophysics Data System (ADS)

    Lindskog, Anders; Schmitz, Birger; Cronholm, Anders; Dronov, Andrei

    2012-08-01

    Numerous fossil meteorites and high concentrations of sediment-dispersed extraterrestrial chromite (EC) grains with ordinary chondritic composition have previously been documented from 467 ± 1.6 Ma Middle Ordovician (Darriwilian) strata. These finds probably reflect a temporarily enhanced influx of L-chondritic matter, following the disruption of the L-chondrite parent body in the asteroid belt 470 ± 6 Ma. In this study, a Volkhovian-Kundan limestone/marl succession at Lynna River, northwestern Russia, has been searched for EC grains (>63 μm). Eight samples, forming two separate sample sets, were collected. Five samples from strata around the Asaphus expansus-A. raniceps trilobite Zone boundary, in the lower-middle Kundan, yielded a total of 496 EC grains in 65.5 kg of rock (average 7.6 EC grains kg-1, but up to 10.2 grains kg-1). These are extremely high concentrations, three orders of magnitude higher than "background" levels in similar condensed sediment from other periods. EC grains are typically about 50 times more abundant than terrestrial chrome spinel in the samples and about as common as terrestrial ilmenite. Three stratigraphically lower lying samples, close to the A. lepidurus-A. expansus trilobite Zone boundary, at the Volkhov-Kunda boundary, yielded only two EC grains in 38.2 kg of rock (0.05 grains kg-1). The lack of commonly occurring EC grains in the lower interval probably reflects that these strata formed before the disruption of the L-chondrite parent body. The great similarity in EC chemical composition between this and other comparable studies indicates that all or most EC grains in these Russian mid-Ordovician strata share a common source--the L-chondrite parent body.

  14. Helium and neon in presolar silicon carbide grains and in relict chromite grains from fossil meteorites and micrometeorites as tracers of their origin

    NASA Astrophysics Data System (ADS)

    Heck, Philipp Reza

    This Ph.D. thesis is dedicated to the study of helium and neon, from dust-sized extraterrestrial samples, to gain insight on their provenance; in particular presolar silicon carbide (SiC) stardust from primitive meteorites (Murchison and Murray) and relict chromite grains from fossil meteorites and micrometeorites. Noble gas analyses were conducted with an ultra-high sensitivity noble gas mass spectrometer coupled with infrared laser gas extraction. The primary objective of the first study was to determine the fraction of single sub-micron to micron-sized presolar SiC grains containing detectable nucleosynthetic noble gases. This was combined with NanoSIMS analyses of silicon, carbon and nitrogen isotopes to constrain the origin of the grains. About 40 percent of the samples studied contain nucleosynthetic noble gases. The majority formed as circumstellar condensates around low-mass carbon stars on the Asymptotic Giant Branch (AGB). A small fraction of the gas-rich grains might have originated in other types of stars and in the ejecta of supernovae and arguably novae. The second part is dedicated to fossil meteorites and sediment-dispersed extraterrestrial chromite grains from 480 Myr old marine sediments from Sweden to constrain the delivery of extraterrestrial material from the asteroid belt to Earth. An important result are the unusually low cosmic-ray exposure ages (about 100 kyr to 1 Myr) of a suite of fossil meteorites, determined from noble gas concentrations in relict chromite grains. Exposure ages increase in younger sediments and the difference between the meteorites found in the youngest sediments and the ones from the oldest is ~1 Myr, corresponding to the age difference of the host sediments. The short exposure ages are consistent with model predictions of space residence times of meteorites generated by a major asteroid collision close to regions where orbits are unstable due to resonances. Surprisingly, extraterrestrial chromite grains dispersed in

  15. Combustion synthesis and photoluminescence of Eu3+ doped LaAlO3 nanophosphors

    NASA Astrophysics Data System (ADS)

    Dhahri, A.; Horchani-Naifer, K.; Benedetti, A.; Enrichi, F.; Ferid, M.

    2012-09-01

    Eu3+ doped LaAlO3 nanophosphors were successfully synthesized by a combustion process using concentrated solution of lanthanum nitrates and aluminate as oxidiser, and glycine acid as fuel. The powders were characterized by infrared spectroscopy (IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and fluorescence spectroscopy. Pure LaAlO3 phase was obtained at 800 °C heated for 4 h, without formation of any intermediate phase, with an average crystal size, as determined by TEM, of 60 nm. Intense photoluminescence emission is reported at 616 nm, allowing the use of this material as red phosphor.

  16. REFOS study: efficacy and safety of lanthanum carbonate in clinical practice in Spain.

    PubMed

    Torregrosa, José-Vicente; González-Parra, Emilio; González, M Teresa; Cannata-Andía, Jorge

    2014-05-21

    Lanthanum carbonate is a powerful phosphate binder that has shown efficacy and safety in clinical trials for hyperphosphataemia management, although there are few data in regular clinical practice. The study's objective was to evaluate, in regular clinical practice, its efficacy and safety in patients on dialysis. We retrospectively collected data from 15 months of monitoring, corresponding to 3 months prior to the start of treatment with lanthanum carbonate until 12 months after the start. Results included values of serum calcium, phosphorus, alkaline phosphatase, iPTH, hepatic enzymes and haemogram, as well as the daily-prescribed dose of lanthanum carbonate, the concomitant medication, treatment compliance and adverse events. 647 patients were included of which 522 completed the study. Abandonment, for the most part, was due to gastrointestinal disorders (26%) and hypophosphatemia (19%). Serum phosphorus decreased from 6.4±1.7 mg/dl (start) to 4.9±1.4 mg/dl (12 months) (P<.001). At the end of the monitoring period, 47% were within the desired phosphorus range (3.5-5mg/dl). There were no significant variations in the remaining parameters. Initial dose of lanthanum carbonate: 1900 mg/day; and end dose: 2300 mg/day. The variables independently associated with phosphataemia were baseline serum phosphorus and treatment compliance. In relation to safety, we observed 238 slight or moderate adverse effects in 117 patients, with 88% linked to gastrointestinal abnormalities. In conclusion, lanthanum carbonate reduces the serum phosphorus values in patients on dialysis with a good safety profile and acceptable adherence to that profile, with gastrointestinal disorders being the most frequent adverse effect.

  17. A Nodular Foreign Body Reaction in a Dialysis Patient Receiving Long-term Treatment With Lanthanum Carbonate.

    PubMed

    Valika, Aziz K; Jain, Dhanpat; Jaffe, Phillip E; Moeckel, Gilbert; Brewster, Ursula C

    2016-01-01

    A 63-year-old man with HIV (human immunodeficiency virus) infection and end-stage renal disease, treated with lanthanum carbonate phosphate binder for 4 years, presented with anemia and an upper gastrointestinal bleed. Upper endoscopy revealed a nodular hyperplastic epithelium, with an endoscopic ultrasound confirming hyperechoic material within the nodules. Light microscopy showed collections of histiocytes and multinucleated giant cells containing brown granular cytoplasmic material and extracellular crystalline material, a finding confirmed by electron microscopy. Similar pathologic findings associated with lanthanum exposure have been described recently. In our patient, lanthanum carbonate treatment was withdrawn and gastrointestinal bleeding has since ceased. The patient was exposed to a high amount of lanthanum over a long period, which may explain his adverse reaction. However, other contributing factors, such as competing medications or comorbid conditions, also may have increased his sensitivity to the drug.

  18. Facile preparation of apatite-type lanthanum silicate by a new water-based sol–gel process

    SciTech Connect

    Yamagata, Chieko; Elias, Daniel R.; Paiva, Mayara R.S.; Misso, Agatha M.; Castanho, Sonia R.H. Mello

    2013-06-01

    Highlights: ► We use a Na{sub 2}SiO{sub 3} waste solution as source of Si. ► We present a simple, rapid and low temperature method of lanthanum silicate apatite preparation. ► TEOS, a high cost reagent, was successfully substituted by a cheap price Na{sub 2}SiO{sub 3}, to obtain pure La{sub 9.56}(SiO{sub 4})6O{sub 2.33} lanthanum silicate apatite. - Abstract: In recent years, apatite-type lanthanum silicates ([Ln{sub 10−x}(XO{sub 4})6O{sub 3–1.5x}] (X = Si or Ge)) have been studied for use in SOFC (solid oxide fuel cells), at low temperature (600–800 °C), due to its ionic conductivity which is higher than that of YSZ (Yttrium Stabilized Zirconia) electrolyte. For this reason they are very promising materials as solid electrolyte for SOFCs. Synthesis of functional nanoparticles is a challenge in the nanotechnology. In this work, apatite-type lanthanum silicate nanoparticles were synthesized by a water-based sol–gel process, i.e., sol–gel technique followed by chemical precipitation of lanthanum hydroxide on the gel of the silica. Na{sub 2}SiO{sub 3} waste solution was used as silica source. Spherical aerogel silica was prepared by acid catalyzed reaction, followed by precipitation of lanthanum hydroxide to obtain the precursor of apatite-type lanthanum silicate. Powders of apatite-type lanthanum silicate achieved from the precursor were characterized by thermal analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM) and specific surface area measurements (BET). The apatite phase was formed at 900 °C.

  19. Effect of Organic Manures on the Growth of Cymbopogon citratus and Chrysopogon zizanioides for the Phytoremediation of Chromite-Asbestos Mine Waste: A Pot Scale Experiment.

    PubMed

    Kumar, Adarsh; Maiti, Subodh Kumar

    2015-01-01

    The abandoned chromite-asbestos mines are located in the Roro hills, West Singhbhum, Jharkhand, India, where mining operation ceased in 1983, and since then these mines are causing environmental pollution. The present study was planned to phytoremediate these metalloid and metal contaminated mine waste by using two aromatic grasses, Cymbopogon citratus and Chrysopogon zizanioides by applying different proportions of amendments (chicken manure, farmyard manure and garden soil). Mine waste has neutral pH, low electrical conductivity and organic carbon with higher concentration of total metals (Cr and Ni) as compared to soil. Application of manures resulted significant improvements of mine waste characteristics and plant growth, reduction in the availability of total extractable toxic metals (Cr, Ni) and increase in Mn, Zn and Cu concentration in the substrate. The maximum growth and biomass production for C. citratus and C. zizanioides were found in T-IV combination comprising of mine waste (90%), chicken manure (2.5%), farmyard manure (2.5%) and garden soil (5%). Addition of T-IV combination also resulted in low Cr and Ni accumulation in roots and reduction in translocation to shoots. Study indicates that C. citratus and C. zizanioides can be used for phytostabilization of abandoned chromite-asbestos mine waste with amendments. PMID:25495934

  20. Effect of Organic Manures on the Growth of Cymbopogon citratus and Chrysopogon zizanioides for the Phytoremediation of Chromite-Asbestos Mine Waste: A Pot Scale Experiment.

    PubMed

    Kumar, Adarsh; Maiti, Subodh Kumar

    2015-01-01

    The abandoned chromite-asbestos mines are located in the Roro hills, West Singhbhum, Jharkhand, India, where mining operation ceased in 1983, and since then these mines are causing environmental pollution. The present study was planned to phytoremediate these metalloid and metal contaminated mine waste by using two aromatic grasses, Cymbopogon citratus and Chrysopogon zizanioides by applying different proportions of amendments (chicken manure, farmyard manure and garden soil). Mine waste has neutral pH, low electrical conductivity and organic carbon with higher concentration of total metals (Cr and Ni) as compared to soil. Application of manures resulted significant improvements of mine waste characteristics and plant growth, reduction in the availability of total extractable toxic metals (Cr, Ni) and increase in Mn, Zn and Cu concentration in the substrate. The maximum growth and biomass production for C. citratus and C. zizanioides were found in T-IV combination comprising of mine waste (90%), chicken manure (2.5%), farmyard manure (2.5%) and garden soil (5%). Addition of T-IV combination also resulted in low Cr and Ni accumulation in roots and reduction in translocation to shoots. Study indicates that C. citratus and C. zizanioides can be used for phytostabilization of abandoned chromite-asbestos mine waste with amendments.

  1. Origins of chromite and magnetite in sedimentary rocks deposited in a shallow water environment in the 3.2 Ga Moodies Group, South Africa

    NASA Astrophysics Data System (ADS)

    Otake, T.; Sakamoto, Y.; Itoh, S.; Yurimoto, H.; Kakegawa, T.

    2012-12-01

    *Otake, T. totake@eng.hokudai.ac.jp Div. of Sustainable Resources Engineering, Hokkaido Univ., Sapporo, Japan Sakamoto, Y. yu.sakamoto12@gmail.com Dep. of Earth Science, Tohoku Univ., Sendai, Japan Itoh, S. sitoh@ep.sci.hokudai.ac.jp Dep. of Natural History Sciences, Hokkaido Univ., Sapporo, Japan Yurimoto. H. yuri@ep.sci.hokudai.ac.jp Dep. of Natural History Sciences, Hokkaido Univ., Sapporo, Japan Kakegawa, T. kakegawa@m.tohoku.ac.jp Dep. of Earth Science, Tohoku Univ., Sendai, Japan Geochemical data from ferruginous chemical sedimentary rocks (e.g., Banded Iron Formation: BIF) have been used to reconstruct the surface environments of early Earth. However, only a few studies have investigated the geochemical characteristics of BIFs deposited in a shallow water environment during the Archean, which may have differed from those deposited in a deep water environment. Therefore, we investigated geological, petrographic and geochemical characteristics of ferruginous rocks deposited in a shallow water environment in the Moodies group, in the Barberton Greenstone Belt, South Africa. We obtained ferruginous rock samples in the Moodies group from both an outcrop and underground gold mine, and compared the characteristics of these samples. The 70 sedimentary rock samples were divided into groups based on the dominant Fe minerals they contain: Hematite-rich jaspilite (HM group), Magnetite-rich iron formation/shale/sandstone (MT group), and Siderite-rich sandstone (SD group). Samples in the HM group are predominantly composed of fine-grained quartz (< 20 μm) and hematite (< 5 μm), which are interpreted to be chemical precipitates. Samples in the MT group contain quartz, magnetite, siderite, ankerite, chlorite, biotite and chromite. The grain size of magnetite is much larger (20-150 μm) than that of hematite in the HM group. The magnetite is interpreted as a secondary mineral transformed from hematite during early diagenesis. Results of in situ oxygen isotope analysis by

  2. Single grain estimations of oxygen fugacity in subcratonic mantle lithosphere using compositions of Ilmenite, Chromite , Garnet and Pyroxenes.

    NASA Astrophysics Data System (ADS)

    Ashchepkov, I.

    2012-04-01

    Calculated oxygen fugacity conditions for ilmenites and chromites were obtained using the monomineral version of the Taylor (1998) oxygen barometers with the calculation of Fe#Ol according to (Ashchepkov et al., 2010). The monomineral version of the Gar- Ol- Opx method (Gudmundsson & Wood, 1995) was obtained using the regression between FO2 and Fe3 in garnet and additional correlation to P and T. F5=Fe#Gar/FeGar; Fo2= 2030.2*Ff5**3-1061.4*F5**2+190.89*F5-12.644 Fo2 = (Fo2-0.01*P (kbar)+(ToC-500)/(3500 -05.)*0.9 The obtained values wee regression and the new Cpx method constructed by the cross correlations of the Fe3+ in Cpx with the oxygen fugacity values obtained for garnets were used for the additional characterization of the mantle SCLM section. The statistical between regression obtained from the work (Gudmundsson, Wood , 1995) and corrections for the temperature and pressure justified by the comparisons obtained with the Ol- Sp and Ilm- Ol oxybarometers (Taylor et al., 1998) allow to estimate the FO2 (Δ log QMF) by following simple equations: For clinopyroxene the cross calibration allow to receive the following regression. Fo2=-186.71*Fe3**2+48.617*Fe3 - 2.3262; Fo2 = Fo2+(T0-500)/3500-0.01*P Fo2 = (Fo2-0.01*P (kbar)+(ToC-500)/3500 -05.)*0.7 For clinopyroxene the cross calibration allow to receive the following regression. Fo2=-186.71*Fe3**2+48.617*Fe3 - 2.3262; Fo2 = Fo2+(T0-500)/3500-0.01*P Fo2=(Fo2-0.5)*0.8 For the orthopyroxene the correlating with the CPx parameter was calculated as following The Fe3'Opx was corrected as Fe3Opx-0.03;Fo2=23.882*Fe3'Opx*(Fe1*15)**2-1.8805 Fo2= Fo2+((T0-400)/1000)*(Fe1*20)-0.0175*P; Fo2=(Fo2*(Fe1*15)**2-0.9*P/70)*0.9 Fo2=(Fo2-0.5)*0.9 Despite on the rather low resolution of the Fe3+ EPMA estimates statistically the determined parameters are rather useful and mark major levels in the SCLM beneath Siberian and other cratons. The rise of FO2 is marked in the three major intervals - in the lithosphere base near the base of

  3. Investigation of band gap narrowing in nitrogen-doped La2Ti2O7 with transient absorption spectroscopy.

    PubMed

    Yost, Brandon T; Cushing, Scott K; Meng, Fanke; Bright, Joeseph; Bas, Derek A; Wu, Nianqiang; Bristow, Alan D

    2015-12-14

    Doping a semiconductor can extend the light absorption range, however, it usually introduces mid-gap states, reducing the charge carrier lifetime. This report shows that doping lanthanum dititinate (La2Ti2O7) with nitrogen extends the valence band edge by creating a continuum of dopant states, increasing the light absorption edge from 380 nm to 550 nm without adding mid-gap states. The dopant states are experimentally resolved in the excited state by correlating transient absorption spectroscopy with a supercontinuum probe and DFT prediction. The lack of mid-gap states is further confirmed by measuring the excited state lifetimes, which reveal the shifted band edge only increased carrier thermalization rates to the band edge and not interband charge recombination under both ultraviolet and visible excitation. Terahertz (time-domain) spectroscopy also reveals that the conduction mechanism remains unchanged after doping, suggesting the states are delocalized. PMID:26531849

  4. Ca2+-Doped CeBr3 Scintillating Materials

    SciTech Connect

    Guss, Paul; Foster, Michael E.; Wong, Bryan M.; Doty, F. Patrick; Shah, Kanai; Squillante, Michael R.; Shirwadkar, Urmila; Hawrami, Rastgo; Tower, Josh; Yuan, Ding

    2014-01-01

    Despite the outstanding scintillation performance characteristics of cerium tribromide (CeBr3) and cerium-activated lanthanum tribromide, their commercial availability and application are limited due to the difficulties of growing large, crack-free single crystals from these fragile materials. This investigation employed aliovalent doping to increase crystal strength while maintaining the optical properties of the crystal. One divalent dopant (Ca2+) was used as a dopant to strengthen CeBr3 without negatively impacting scintillation performance. Ingots containing nominal concentrations of 1.9% of the Ca2+ dopant were grown. Preliminary scintillation measurements are presented for this aliovalently doped scintillator. Ca2+-doped CeBr3 exhibited little or no change in the peak fluorescence emission for 371 nm optical excitation for CeBr3. The structural, electronic, and optical properties of CeBr3 crystals were studied using the density functional theory within the generalized gradient approximation. The calculated lattice parameters are in good agreement with the experimental data. The energy band structures and density of states were obtained. The optical properties of CeBr3, including the dielectric function, were calculated.

  5. Enhancing the stability of copper chromite catalysts for the selective hydrogenation of furfural with ALD overcoating (II) – Comparison between TiO2 and Al2O3 overcoatings

    SciTech Connect

    Zhang, Hongbo; Canlas, Christian; Kropf, A. Jeremy; Elam, Jeffrey W.; Dumesic, James A; Marshall, Christopher L.

    2015-01-01

    TiO2 atomic layer deposition (ALD) overcoatings were applied to copper chromite catalysts to increase the stability for 2-furfuraldehyde (“furfural”) hydrogenation. After overcoating, about 75% activity was preserved compared to neat copper chromite: much higher activity than an alumina ALD overcoated catalyst with a similar number of ALD cycles. The effects of ALD TiO2 on the active Cu nanoparticles were studied extensively using both in-situ TPR/isothermal-oxidation and in-situ furfural hydrogenation via Cu XAFS. The redox properties of Cu were modified only slightly by the TiO2 ALD overcoat. However, a subtle electronic interaction was observed between the TiO2 ALD layers and the Cu nanoparticles. With calcination at 500 °C the interaction between the TiO2 overcoat and the underlying catalyst is strong enough to inhibit migration and site blocking by chromite, but is sufficiently weaker than the interaction between the Al2O3 overcoat and copper chromite that it does not strongly inhibit the catalytic activity of the copper nanoparticles.

  6. 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.

  7. Lanthanum(III) and praseodymium(III) derivatives with dithiocarbamates derived from α-amino acids

    NASA Astrophysics Data System (ADS)

    Rai, Anita; Sengupta, Soumitra K.; Pandey, Om P.

    2006-06-01

    Lanthanum(III) and praseodymium(III) complexes with dithiocarbamates have been synthesized by the reactions of lanthanum(III) and praseodymium(III) chloride with barium dithiocarbamate and complexes of type [LnCl(L)H 2O] n have been obtained (where Ln = La(III) or Pr(III); L = barium salt of dithiocarbamate derived from glycine, L-leucine, L-valine, DL-alanine). The complexes have been characterized by elemental analysis, molar conductance, electronic absorption and fluorescence, infrared, far infrared, 1H NMR spectral studies. The presence of coordinated water molecule is inferred from thermogravimetric analysis which indicates the loss of one water molecule at 150-170 °C. The oscillator strength, Judd-Ofelt intensity parameter, stimulated emission cross-section, etc. have been obtained for different transitions of Pr 3+.

  8. Near fifty percent sodium substituted lanthanum manganites—A potential magnetic refrigerant for room temperature applications

    SciTech Connect

    Sethulakshmi, N.; Anantharaman, M. R.; Al-Omari, I. A.; Suresh, K. G.

    2014-03-03

    Nearly half of lanthanum sites in lanthanum manganites were substituted with monovalent ion-sodium and the compound possessed distorted orthorhombic structure. Ferromagnetic ordering at 300 K and the magnetic isotherms at different temperature ranges were analyzed for estimating magnetic entropy variation. Magnetic entropy change of 1.5 J·kg{sup −1}·K{sup −1} was observed near 300 K. An appreciable magnetocaloric effect was also observed for a wide range of temperatures near 300 K for small magnetic field variation. Heat capacity was measured for temperatures lower than 300 K and the adiabatic temperature change increases with increase in temperature with a maximum of 0.62 K at 280 K.

  9. Lanthanum(III) and praseodymium(III) derivatives with dithiocarbamates derived from alpha-amino acids.

    PubMed

    Rai, Anita; Sengupta, Soumitra K; Pandey, Om P

    2006-06-01

    Lanthanum(III) and praseodymium(III) complexes with dithiocarbamates have been synthesized by the reactions of lanthanum(III) and praseodymium(III) chloride with barium dithiocarbamate and complexes of type [LnCl(L)H2O]n have been obtained (where Ln=La(III) or Pr(III); L=barium salt of dithiocarbamate derived from glycine, L-leucine, L-valine, DL-alanine). The complexes have been characterized by elemental analysis, molar conductance, electronic absorption and fluorescence, infrared, far infrared, 1H NMR spectral studies. The presence of coordinated water molecule is inferred from thermogravimetric analysis which indicates the loss of one water molecule at 150-170 degrees C. The oscillator strength, Judd-Ofelt intensity parameter, stimulated emission cross-section, etc. have been obtained for different transitions of Pr3+.

  10. Sorption of tartrate ions to lanthanum (III)-modified calcium fluor- and hydroxyapatite.

    PubMed

    Aissa, Abdallah; Debbabi, Mongi; Gruselle, Michel; Thouvenot, René; Flambard, Alexandrine; Gredin, Patrick; Beaunier, Patricia; Tõnsuaadu, Kaia

    2009-02-01

    The present article details the formation of lanthanum-modified apatites and the binding process of tartrate ions with these obtained apatites. Chemical analyses, FT-IR and (31)P NMR spectroscopies, XRD powder, TGA, and TEM analyses were employed for studying the reaction between Ca(10)(PO(4))(6)(OH)(2) (HAp) or Ca(10)(PO(4))(6)(F)(2) (FAp) and LaCl(3). The reaction was found to take place mainly through partial dissolution of the apatite followed by precipitation of a new phase containing lanthanum phosphate. When La(3+) was introduced in the presence of L(+)-tartaric acid (TAH(2)), no fundamental changes were observed in the HAp or FAp structures. However, there did occur a formation of a new phase of Ca or/and La tartrate salt.

  11. Measurement of lanthanum and technetium in uranium fuels by inductively coupled plasma atomic emission spectroscopy.

    SciTech Connect

    Carney, K.; Crane, P.; Cummings, D.; Krsul, J.; McKnight, R.

    1999-06-10

    An important parameter in characterizing an irradiated nuclear fuel is determining the amount of uranium fissioned. By determining the amount of uranium fissioned in the fuel a burnup performance parameter can be calculated, and the amount of fission products left in the fuel can be predicted. The quantity of uranium fissioned can be calculated from the amount of lanthanum and technetium present in the fuel. Lanthanum and technetium were measured in irradiated fuel samples using an Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) instrument and separation equipment located in a shielded glove-box. A discussion of the method, interferences, detection limits, quality control and a comparison to other work will be presented.

  12. Lanthanum carbonate oral powder: satisfaction, preference and adherence in French and Spanish patients with end-stage renal disease

    PubMed Central

    Keith, Michael; de Sequera, Patricia; Clair, François; Pedersini, Riccardo

    2016-01-01

    Background Phosphate binders, such as lanthanum carbonate, control elevated serum-phosphate levels in patients with end-stage renal disease (ESRD). Lanthanum carbonate is available in oral powder and tablet form. The aim of this survey was to investigate satisfaction with, preference for, and adherence to lanthanum carbonate oral powder in patients with ESRD. Scope Patients from France and Spain who had been taking lanthanum carbonate powder for at least 4 weeks, and who had experience of other phosphate binders of any formulation, were asked to complete an online or telephone survey. Treatment satisfaction was measured using the Treatment Satisfaction Questionnaire for Medication-9; preference was measured using 5-point Likert scale agreement ratings; and adherence was measured using the Morisky Medication Adherence Scale-4. Data were evaluated using bivariate analyses. Findings Overall, 160 patients participated (80 per country). Lanthanum carbonate powder was reported to have a higher effectiveness rating (p<0.05), be more convenient (p<0.05), and provide a higher level of satisfaction (p<0.01) than previous binders. There was an overall preference for lanthanum carbonate powder over previous binders of any formulation (p<0.001). Adherence to medication was similar for all binders analysed: 66.3% of French patients adhered to lanthanum carbonate powder, and 65.0% adhered to previous binder treatment (p=not significant); 52.5% of Spanish patients adhered to lanthanum carbonate powder, and 56.3% adhered to previous binder treatment (p=not significant). Limitations The survey enrolled patients who had already experienced phosphate binders before the study began. Information on patient preferences for and adherence to previous phosphate binders was therefore based on the patients’ memories of these experiences, which may have been subject to change over time. Although most participants completed the online survey in this study, a telephone survey was used for

  13. Optical absorption in ion-implanted lead lanthanum zirconate titanate ceramics

    NASA Astrophysics Data System (ADS)

    Seager, C. H.; Land, C. E.

    1984-08-01

    Optical absorption measurements have been performed on unmodified and on ion-implanted lead lanthanum zirconate titanate ceramics using the photothermal deflection spectroscopy technique. Bulk absorption coefficients depend on the average grain size of the material while the absorption associated with the ion-damaged layers does not. The damage-induced surface absorptance correlates well with the photosensitivity observed in implanted PLZT devices, supporting earlier models for the enhanced imaging efficiency of the materials.

  14. Chromium and copper substituted lanthanum nano-ferrites: Their synthesis, characterization and application studies

    NASA Astrophysics Data System (ADS)

    Jauhar, Sheenu; Singhal, Sonal

    2014-10-01

    Nano-crystalline lanthanum ferrites substituted by chromium and copper having formula LaMxFe1-xO3 (M = Cr, Cu; 0.0 ⩽ x ⩽ 0.5) were synthesized using sol-gel auto-combustion method. The formation of ferrite particles was confirmed using Fourier Transform Infra-Red (FT-IR) spectra and powder X-ray Diffraction (XRD) techniques. The entire ferrite compositions were found to be pure phased with same symmetry as LaFeO3. The average crystallite size was calculated to be ∼60 nm. The ferrite compositions were observed to behave as semi-conductors, as their resistivity decreased with increasing temperature. These ferrite compositions were employed as catalysts in the decomposition of hydrogen peroxide solution (0.17 M). Pure LaFeO3 was found to have a very low catalytic activity towards the decomposition of hydrogen peroxide solution, while presence of copper in the lanthanum ferrite lattice was found to significantly enhance its catalytic activity. The rate constant in case of reactions catalysed by LaCu0.5Fe0.5O3 was nearly 25 times larger than that obtained from reactions catalysed by pure LaFeO3. However, chromium substitution was not found to influence the catalytic activity of lanthanum ferrites as chromium substituted lanthanum ferrites exhibited very low catalytic activity. This was explained on the basis of relative stability of oxidation states of the substituent ions and the presence of defects in the crystal lattice.

  15. Effect of chloride incorporation on the crystallization of zirconium-barium-lanthanum-aluminum fluoride glass

    NASA Technical Reports Server (NTRS)

    Neilson, G. F.; Smith, G. L.; Weinberg, M. C.

    1985-01-01

    One aspect of the influence of preparation procedure on the crystallization behavior of a zirconium-barium-lanthanum-aluminum fluoride glass was studied. The crystallization pattern of this glass may be affected by the chlorine concentration within it. In particular, when such glasses are heated at low temperatures, the alpha-Ba-Zr-F6 crystalline phase forms only in those glasses which contain chloride.

  16. Facile and efficient one-pot synthesis of benzimidazoles using lanthanum chloride

    PubMed Central

    2013-01-01

    Background We report the synthesis of benzimidazoles using lanthanum chloride as an efficient catalyst. One-pot synthesis of 2-substituted benzimidazole derivatives from o-phenylenediamine and a variety of aldehydes were developed under mild reaction conditions. Results We have examined the effect of different solvents using the same reaction conditions. The yield of the product varied with the nature of the solvents, and better conversion and easy isolation of products were found with acetonitrile. In a similar manner, the reaction with o-phenylenediamine and 3,4,5-trimethoxybenzaldehyde was carried out without any solvents. The observation shows that the reaction was not brought into completion, even after starting for a period of 9 h, and the reaction mixture showed a number of spots in thin-layer chromatography. Conclusions In conclusion, lanthanum chloride has been employed as a novel and efficient catalyst for the synthesis of benzimidazoles in good yields from o-phenylenediamine and a wide variety of aldehydes. All of the reactions were carried out in the presence of lanthanum chloride (10 mol%) in acetonitrile at room temperature. PMID:23919542

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

    DOEpatents

    Karp, Joel S.; Surti, Suleman

    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.

  18. Preparation and Characterization of Lanthanum-Incorporated Hydroxyapatite Coatings on Titanium Substrates

    PubMed Central

    Lou, Weiwei; Dong, Yiwen; Zhang, Hualin; Jin, Yifan; Hu, Xiaohui; Ma, Jianfeng; Liu, Jinsong; Wu, Gang

    2015-01-01

    Titanium (Ti) has been widely used in clinical applications for its excellent biocompatibility and mechanical properties. However, the bioinertness of the surface of Ti has motivated researchers to improve the physicochemical and biological properties of the implants through various surface modifications, such as coatings. For this purpose, we prepared a novel bioactive material, a lanthanum-incorporated hydroxyapatite (La-HA) coating, using a dip-coating technique with a La-HA sol along with post-heat treatment. The XRD, FTIR and EDX results presented in this paper confirmed that lanthanum was successfully incorporated into the structure of HA. The La-HA coating was composed of rod-like particles which densely compacted together without microcracks. The results of the interfacial shear strength test indicated that the incorporation of lanthanum increased the bonding strength of the HA coating. The mass loss ratios under acidic conditions (pH = 5.5) suggested that the La-HA coatings have better acid resistance. The cytocompatibility of the La-HA coating was also revealed by the relative activity of alkaline phosphatase, cellular morphology and cell proliferation assay in vitro. The present study suggested that La-HA coated on Ti has promising potential for applications in the development of a new type of bioactive coating for metal implants. PMID:26404255

  19. Controlling the reaction between boron-containing sealing glass and a lanthanum-containing cathode by adding Nb2O5

    NASA Astrophysics Data System (ADS)

    Zhao, Dandan; Fang, Lihua; Tang, Dian; Zhang, Teng

    2016-09-01

    In solid oxide fuel cell (SOFC) stacks, the volatile boron species present in the sealing glass often react with the lanthanum-containing cathode, degrading the activity of the cathode (this phenomenon is known as boron poisoning). In this work, we report that this detrimental reaction can be effectively reduced by doping bismuth-containing borosilicate sealing glass-ceramic with a niobium dopant. The addition of Nb2O5 not only condenses the [SiO4] structural units in the glass network, but also promotes the conversion of [BO3] to [BO4]. Moreover, the Nb2O5 dopant enhances the formation of boron-containing phases (Ca3B2O6 and CaB2Si2O8), which significantly reduces the volatility of boron compounds in the sealing glass, suppressing the formation of LaBO3 in the reaction couple between the glass and the cathode. The reported results provide a new approach to solve the problem of boron poisoning.

  20. Long-term treatment with lanthanum carbonate reduces mineral and bone abnormalities in rats with chronic renal failure

    PubMed Central

    Damment, Stephen; Secker, Roger; Shen, Victor; Lorenzo, Victor; Rodriguez, Mariano

    2011-01-01

    Background. Lanthanum carbonate (FOSRENOL®, Shire Pharmaceuticals) is an effective non-calcium, non-resin phosphate binder for the treatment of hyperphosphataemia in patients with chronic kidney disease (CKD). In this study, we used a rat model of chronic renal failure (CRF) to examine the long-term effects of controlling serum phosphorus with lanthanum carbonate treatment on the biochemical and bone abnormalities associated with CKD–mineral and bone disorder (CKD–MBD). Methods. Rats were fed a normal diet (normal renal function, NRF), or a diet containing 0.75% adenine for 3 weeks to induce CRF. NRF rats continued to receive normal diet plus vehicle or normal diet supplemented with 2% (w/w) lanthanum carbonate for 22 weeks. CRF rats received a diet containing 0.1% adenine, with or without 2% (w/w) lanthanum carbonate. Blood and urine biochemistry were assessed, and bone histomorphometry was performed at study completion. Results. Treatment with 0.75% adenine induced severe CRF, as demonstrated by elevated serum creatinine. Hyperphosphataemia, hypocalcaemia, elevated calcium × phosphorus product and secondary hyperparathyroidism were evident in CRF + vehicle animals. Treatment with lanthanum carbonate reduced hyperphosphataemia and secondary hyperparathyroidism in CRF animals (P < 0.05), and had little effect in NRF animals. Bone histomorphometry revealed a severe form of bone disease with fibrosis in CRF + vehicle animals; lanthanum carbonate treatment reduced the severity of the bone abnormalities observed, particularly woven bone formation and fibrosis. Conclusions. Long-term treatment with lanthanum carbonate reduced the biochemical and bone abnormalities of CKD–MBD in a rat model of CRF. PMID:21098011

  1. Lanthanum Nitrate As Electrolyte Additive To Stabilize the Surface Morphology of Lithium Anode for Lithium-Sulfur Battery.

    PubMed

    Liu, Sheng; Li, Guo-Ran; Gao, Xue-Ping

    2016-03-01

    Lithium-sulfur (Li-S) battery is regarded as one of the most promising candidates beyond conventional lithium ion batteries. However, the instability of the metallic lithium anode during lithium electrochemical dissolution/deposition is still a major barrier for the practical application of Li-S battery. In this work, lanthanum nitrate, as electrolyte additive, is introduced into Li-S battery to stabilize the surface of lithium anode. By introducing lanthanum nitrate into electrolyte, a composite passivation film of lanthanum/lithium sulfides can be formed on metallic lithium anode, which is beneficial to decrease the reducibility of metallic lithium and slow down the electrochemical dissolution/deposition reaction on lithium anode for stabilizing the surface morphology of metallic Li anode in lithium-sulfur battery. Meanwhile, the cycle stability of the fabricated Li-S cell is improved by introducing lanthanum nitrate into electrolyte. Apparently, lanthanum nitrate is an effective additive for the protection of lithium anode and the cycling stability of Li-S battery. PMID:26981849

  2. Lanthanum Nitrate As Electrolyte Additive To Stabilize the Surface Morphology of Lithium Anode for Lithium-Sulfur Battery.

    PubMed

    Liu, Sheng; Li, Guo-Ran; Gao, Xue-Ping

    2016-03-01

    Lithium-sulfur (Li-S) battery is regarded as one of the most promising candidates beyond conventional lithium ion batteries. However, the instability of the metallic lithium anode during lithium electrochemical dissolution/deposition is still a major barrier for the practical application of Li-S battery. In this work, lanthanum nitrate, as electrolyte additive, is introduced into Li-S battery to stabilize the surface of lithium anode. By introducing lanthanum nitrate into electrolyte, a composite passivation film of lanthanum/lithium sulfides can be formed on metallic lithium anode, which is beneficial to decrease the reducibility of metallic lithium and slow down the electrochemical dissolution/deposition reaction on lithium anode for stabilizing the surface morphology of metallic Li anode in lithium-sulfur battery. Meanwhile, the cycle stability of the fabricated Li-S cell is improved by introducing lanthanum nitrate into electrolyte. Apparently, lanthanum nitrate is an effective additive for the protection of lithium anode and the cycling stability of Li-S battery.

  3. First-principles study of codoping in lanthanum bromide

    NASA Astrophysics Data System (ADS)

    Erhart, Paul; Sadigh, Babak; Schleife, André; Åberg, Daniel

    2015-04-01

    Codoping of Ce-doped LaBr3 with Ba, Ca, or Sr improves the energy resolution that can be achieved by radiation detectors based on these materials. Here, we present a mechanism that rationalizes this enhancement on the basis of first-principles electronic structure calculations and point defect thermodynamics. It is shown that incorporation of Sr creates neutral VBr-SrLa complexes that can temporarily trap electrons. As a result, Auger quenching of free carriers is reduced, allowing for a more linear, albeit slower, scintillation light yield response. Experimental Stokes shifts can be related to different CeLa-SrLa-VBr triple complex configurations. Codoping with other alkaline as well as alkaline-earth metals is considered as well. Alkaline elements are found to have extremely small solubilities on the order of 0.1 ppm and below at 1000 K. Among the alkaline-earth metals the lighter dopant atoms prefer interstitial-like positions and create strong scattering centers, which has a detrimental impact on carrier mobilities. Only the heavier alkaline-earth elements (Ca, Sr, Ba) combine matching ionic radii with sufficiently high solubilities. This provides a rationale for the experimental finding that improved scintillator performance is exclusively achieved using Sr, Ca, or Ba. The present mechanism demonstrates that codoping of wide-gap materials can provide an efficient means for managing charge carrier populations under out-of-equilibrium conditions. In the present case dopants are introduced that manipulate not only the concentrations but also the electronic properties of intrinsic defects without introducing additional gap levels. This leads to the availability of shallow electron traps that can temporarily localize charge carriers, effectively deactivating carrier-carrier recombination channels. The principles of this mechanism are therefore not specific to the material considered here but can be adapted for controlling charge carrier populations and

  4. Nonaqueous synthesis of metal oxide nanoparticles: Short review and doped titanium dioxide as case study for the preparation of transition metal-doped oxide nanoparticles

    SciTech Connect

    Djerdj, Igor Arcon, Denis; Jaglicic, Zvonko; Niederberger, Markus

    2008-07-15

    The liquid-phase synthesis of metal oxide nanoparticles in organic solvents under exclusion of water is nowadays a well-established alternative to aqueous sol-gel chemistry. In this article, we highlight some of the advantages of these routes based on selected examples. The first part reviews some recent developments in the synthesis of ternary metal oxide nanoparticles by surfactant-free nonaqueous sol-gel routes, followed by the discussion of the morphology-controlled synthesis of lanthanum hydroxide nanoparticles, and the presentation of structural peculiarities of manganese oxide nanoparticles with an ordered Mn vacancy superstructure. These examples show that nonaqueous systems, on the one hand, allow the preparation of compositionally complex oxides, and, on the other hand, make use of the organic components (initially present or formed in situ) in the reaction mixture to tailor the morphology. Furthermore, obviously even the crystal structure can differ from the corresponding bulk material like in the case of MnO nanoparticles. In the second part of the paper we present original results regarding the synthesis of dilute magnetic semiconductor TiO{sub 2} nanoparticles doped with cobalt and iron. The structural characterization as well as the magnetic properties with special attention to the doping efficiency is discussed. - Graphical abstract: In the first part of this article, nonaqueous sol-gel routes to ternary metal oxide nanoparticles are briefly reviewed, followed by the discussion of the morphology-controlled synthesis of lanthanum hydroxide nanoparticles, and the appearance of an unprecedented superstructure in MnO nanoparticles. In the second part, doping experiments of TiO{sub 2} with Fe and Co are presented, along with their characterization including magnetic measurements.

  5. The Thermal Conductivity of Lanthanum TRI-FLURIDE:0.1% Erbium from 1.8 K to 100 K.

    NASA Astrophysics Data System (ADS)

    Vinson, Wayne Wright

    1987-12-01

    Scope of Study. The purpose of this study was to obtain and analyse the principal thermal conductivities of crystalline lanthanum tri-fluoride (doped with 0.1% erbium), and calcuim fluoride. The conductivity for LaF _3 was measured parallel and perpendicular to the high-symmentry axis; and for face-centered cubic CaF_2, along one of the (100) directions. The measurements were taken from 1.8 K to 100 K using a ^4He cryostat of standard design, where the lowest temperatures were obtained by pumping ^4 He vapor. The data were analyzed for each sample by using a Gaussian numerical integration routine to calculate appropriate Debye integrals to model the curves obtained. A scattering rate of the form tau^{-1} = v/L + Aomega^4 + (B_1 + B_2exp (-Theta/aT) omega^4 T + Domega where each of the coefficients A, B_1, B _2, and D were initially estimated from theoretical considerations, was adjusted to obtain the best fit to the data. The form of the normal phonon-phonon term, B omega^4T, was obtained by thermalizing the anharmonic decay rates, tau ^{-11} = C_{ rm m}omega^5, as predicted by precious theories and verified for each of the samples in studies in the literature. Findings and Conclusions. Practically all the features of the thermal conductivities obtained which can be accounted for by the model employed have met with satisfactory agreement, certainly qualitatively, and no significant inconsistencies arose from the quantitative treatment. Because of the satisfactory comparison of the results of this study with those of phonon spectroscopy, we suggest that the form of the phonon-phonon interaction term might behave as omega^4T rather than the omega^2T and omega ^2T^3 forms extensively employed in the literature. Prediction of the anharmonic decay rates for various other technologically important crystals were done by applying the methods of this study to their thermal conductivities obtained from the literature, thus suggesting directions for further investigation.

  6. Studies on Synthesis, Structural and Electrical Properties of Complex Oxide Thin Films: Barium Strontium Titanate and Lanthanum Strontium Nickelate

    NASA Astrophysics Data System (ADS)

    Podpirka, Adrian A.

    High performance miniaturized passives are of great importance for advanced nanoelectronic packages for several applications including efficient power delivery. Low cost thin film capacitors fabricated directly on package (and/or on-chip) are an attractive approach towards realizing such devices. This thesis aims to explore fundamental frequency dependent dielectric and insulating properties of thin film high-k dielectric constant in the perovskite and perovskite-related complex oxides. Throughout this thesis, we have successfully observed the role of structure, strain and oxygen stoichiometry on the dielectric properties of thin film complex oxides, allowing a greater understanding of processing conditions and polarization mechanisms. In the first section of the thesis, we explore novel processing methods in the conventional ferroelectric, barium strontium titanate, Ba1-xSr xTiO3 (BST), using ultraviolet enhanced oxidation techniques in order to achieve improvements in the dielectric properties. Using this method, we also explore the growth of BST on inexpensive non-noble metals such as Ni which presents technical challenges due to the ability to oxidize at high temperatures. We observe a significant lowering of the dielectric loss while also lowering the process temperature which allows us to maintain an intimate interface between the dielectric layer and the metal electrode. The second section of this thesis explores the novel dielectric material, Lanthanum Strontium Nickelate, La2-xSrxNiO4 (LSNO), which exhibits a colossal dielectric response. For the first time, we report on the colossal dielectric properties of polycrystalline and epitaxial thin film LSNO. We observe a significant polarization dependence on the microstructure due to the grain/grain boundary interaction with charged carriers. We next grew epitaxial films on various insulating oxide substrates in order to decouple the grain boundary interaction. Here we observed substrate dependent dielectric

  7. 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

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

    PubMed

    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

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

    PubMed

    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

  10. Thermochemistry of perovskites in the lanthanum-strontium-manganese-iron oxide system

    NASA Astrophysics Data System (ADS)

    Marinescu, Cornelia; Vradman, Leonid; Tanasescu, Speranta; Navrotsky, Alexandra

    2015-10-01

    The enthalpies of formation from binary oxides of perovskites (ABO3) based on lanthanum strontium manganite La(Sr)MnO3 (LSM) and lanthanum strontium ferrite La(Sr)FeO3 (LSF) and mixed lanthanum strontium manganite ferrite La(Sr)Mn(Fe)O3 (LSMF) were measured by high temperature oxide melt solution calorimetry. Using iodometric titration, the oxygen content was derived. The perovskites with A-site cation deficiency have greater oxygen deficiency than the corresponding A-site stoichiometric series. Stability of LSMF decreases with increasing iron content. Increasing oxygen deficiency clearly destabilizes the perovskites. The results suggest an enthalpy of oxygen incorporation that is approximately independent of composition. 0.35La2O3 (xl, 25 °C)+Mn2O3 (xl, 25 °C)+0.3SrO (xl, 25 °C)+Fe2O3 (xl, 25 °C)+O2 (g, 25 °C)→La0.7Sr0.3Mn1-yFeyO3-δ (xl, 25 °C). (b) ∆ Hf,ox* (La0.7Sr0.3Mn1-yFeyO3-δ) .0.35 La2O3 (xl, 25 ººC) + (0.7-y+ 2δ)/2 Mn2O3 (xl, 25 ºC) + 0.3 SrO (xl, 25 ºC) + y/2Fe2O3 (xl, 25 ºC) + (0.3-2δ) MnO2 (xl, 25 ºC)→La0.7Sr0.3Mn1-yFeyO3-δ (xl, 25 ºC).

  11. High-current density, high-brightness electron beams from large-area lanthanum hexaboride cathodes

    NASA Astrophysics Data System (ADS)

    Loschialpo, P.; Kapetanakos, C. A.

    1987-12-01

    Large (approx. 5 cm) diameter lanthanum hexaboride (LaB6) cathodes operated at 10 kV have produced 1 to 5 micro electron pulses with current density between 10 and 20 A/sq cm. Normalized beam brightness, has been consistently measured. To obtain this high current density, the LaB6 cathodes have been heated to temperatures between approximately 1600 to 1800 C. Very uniform temperature profiles are obtained by applying a carefully tailored electron bombardment heating power distribution. These measurements have been made between pressure .000001 to .00001 Torr, i.e., under much less demanding vacuum conditions than that required by conventional dispenser type cathodes.

  12. Studies on sprayed lanthanum sulphide (La 2S 3) thin films from non-aqueous medium

    NASA Astrophysics Data System (ADS)

    Bagde, G. D.; Pathan, H. M.; Lokhande, C. D.; Patil, S. A.; Muller, M.

    2005-12-01

    Thin films of lanthanum sulphide (La 2S 3) have been deposited onto glass substrates by spray pyrolysis technique from non-aqueous (methanol) medium. The structural, morphological, optical, dielectric, electric and thermoemf properties were studied. The films were polycrystalline with an irregular shaped particles present over the porous structure within a fibrous network structure. The optical band gap was estimated to be 2.50 eV. The dielectric properties were measured in the range 100 Hz-1 MHz. The electrical resistivity was of the order of 10 4 to 10 5 Ω cm. Thermoemf study revealed that the La 2S 3 films exhibit p-type electrical conductivity.

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

    NASA Technical Reports Server (NTRS)

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

    2010-01-01

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

  14. High-current lanthanum-hexaboride electron emitter for a quasi-stationary arc plasma generator

    SciTech Connect

    Davydenko, V. I. Ivanov, A. A. Shul’zhenko, G. I.

    2015-11-15

    A high-current electron emitter on the basis of lanthanum hexaboride is developed for quasi-stationary arc plasma generators of ion sources. The emitter consists of a set of LaB{sub 6} washers interleaved with washers made of thermally extended graphite. The emitter is heated by the current flowing through the graphite washers. The thermal regime of emitter operation during plasma generation is considered. The emitter has been successfully used in the ion sources of the diagnostic injectors of fast hydrogen atomic beams.

  15. Investigation of the elemental composition of lanthanum-cerium hexaboride crystals

    NASA Astrophysics Data System (ADS)

    Badalyan, Georgi; Kuzanyan, Armen; Petrosyan, Vahagn; Kuzanyan, Vazgen; Gulian, Armen

    2010-10-01

    Crystals of solid solutions of lanthanum-cerium hexaborides (La1-xCex)B6 possess unique thermoelectric properties in the temperature range of 0.3-9 K and they can be used in thermoelectric single-photon detectors as a sensor. One can observe a wide spread in thermoelectric measurement values reported in the literature, which is because of different qualities of studied crystals. The greatest influence on both the Seebeck coefficient and electrical resistivity of samples is exercised by the presence of uncontrolled impurities in crystals and the deviation from stoichiometry. In this work we have studied just the aforementioned parameters of the crystals obtained by three different methods.

  16. Efficacy of crushed lanthanum carbonate for hyperphosphatemia in hemodialysis patients undergoing tube feeding.

    PubMed

    Kitajima, Yukie; Takahashi, Taeko; Sato, Yuzuru; Nakaya, Yutaka

    2011-08-01

    Lanthanum carbonate (LaC) is a non-calcium-based phosphate binder used to treat hyperphosphatemia in patients with chronic kidney disease. Oral administration of LaC is difficult in patients undergoing tube feeding or those who are of advanced age because it is essential to chew the LaC tablet sufficiently before swallowing it. We report two cases in whom crushed LaC was used in hemodialysis patients undergoing tube feeding. In both cases, previously crushed LaC was mixed into enteral nutrients. We found that LaC administered this way was effective for decreasing serum phosphorus levels.

  17. Bistable optical information storage using antiferroelectric-phase lead lanthanum zirconate titanate ceramics

    SciTech Connect

    Land, C.E.

    1988-11-01

    A recently discovered photostorage effect in antiferroelectric-phase (AFE-phase) lead lanthanum zirconate titanate (PLZT) compositions appears to be particularly applicable to binary optical information storage. The basis for bistable optical information storage is that exposure to near-UV or visible light shifts the electric field threshold of the phase transition between the field-induced ferroelectric (FE) phase and the stable AFE phase in the direction of the initial AFE /yields/ FE phase transition. Properties of this photoactivated shift of the FE /yields/ AFE phase transition, including preliminary photosensitivity measurements and photostorage mechanisms, are presented. Photosensitivity enhancement by ion implantation is also discussed.

  18. Use of optically transparent lead lanthanum zirconate titanate as actuators and sensors

    NASA Astrophysics Data System (ADS)

    Luo, Quantian; Tong, Liyong

    2009-07-01

    The photo-induced strain in transparent lead lanthanum zirconate titanate (PLZT) materials is due to a process of superposition of photovoltaic and converse piezoelectric effects. The photovoltaic effect in PLZT materials is observed only in the direction of spontaneous polarization of ferroelectric materials. In this paper, electrical and mechanical performance of PLZT ceramics polarized in 0-1 or 0-3 direction are investigated, and PLZT actuators and sensors with the 0-3 polarization are studied. For multilayer PLZT actuators, presented also are the formulas for the calculation of energy release rates due to debonding.

  19. Small yttrium-carbon and lanthanum-carbon clusters: Rings are most stable

    SciTech Connect

    Strout, D.L.; Hall, M.B.

    1996-11-14

    A theoretical study has been undertaken to determine the energetics of a variety of neutral and cationic isomeric forms of metal clusters MC{sub x}, where M = Y or La and x = 3-6. Included in this study are cyclic molecules and linear molecules, as well as recently-proposed `kite` structures. Geometries are optimized by the B3LYP density functional method, and energies are computed with the coupled-cluster method. The major conclusion of this work is that cyclic structures are the most stable, a result which holds for both yttrium and lanthanum and for both cations and neutral molecules. 19 refs., 1 fig., 2 tabs.

  20. High-current lanthanum-hexaboride electron emitter for a quasi-stationary arc plasma generator

    NASA Astrophysics Data System (ADS)

    Davydenko, V. I.; Ivanov, A. A.; Shul'zhenko, G. I.

    2015-11-01

    A high-current electron emitter on the basis of lanthanum hexaboride is developed for quasi-stationary arc plasma generators of ion sources. The emitter consists of a set of LaB6 washers interleaved with washers made of thermally extended graphite. The emitter is heated by the current flowing through the graphite washers. The thermal regime of emitter operation during plasma generation is considered. The emitter has been successfully used in the ion sources of the diagnostic injectors of fast hydrogen atomic beams.

  1. Niobium doped lanthanum calcium ferrite perovskite as a novel electrode material for symmetrical solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Kong, Xiaowei; Zhou, Xiaoliang; Tian, Yu; Wu, Xiaoyan; Zhang, Jun; Zuo, Wei

    2016-09-01

    Development of cost-effective and efficient electrochemical catalysts for the fuel cells electrode is of prime importance to emerging renewable energy technologies. Here, we report for the first time the novel La0.9Ca0.1Fe0.9Nb0.1O3-δ (LCFNb) perovskite with good potentiality for the electrode material of the symmetrical solid oxide fuel cells (SSOFC). The Sc0.2Zr0.8O2-δ (SSZ) electrolyte supported symmetrical cells with impregnated LCFNb and LCFNb/SDC (Ce0.8Sm0.2O2-δ) electrodes achieve relatively high power outputs with maximum power densities (MPDs) reaching up to 392 and 528.6 mW cm-2 at 850 °C in dry H2, respectively, indicating the excellent electro-catalytic activity of LCFNb towards both hydrogen oxidation and oxygen reduction. Besides, the MPDs of the symmetrical cells with LCFNb/SDC composite electrodes in CO and syngas (CO: H2 = 1:1) are almost identical to those in H2, implying that LCFNb material has similar catalytic activities to carbon monoxide compared with hydrogen. High durability in both H2, CO and syngas during the short term stability tests for 50 h are also obtained, showing desirable structure stability, and carbon deposition resistance of LCFNb based electrodes. The present results indicate that the LCFNb perovskite with remarkable cell performance is a promising electrode material for symmetrical SOFCs.

  2. Barium carbonate nanoparticle to enhance oxygen reduction activity of strontium doped lanthanum ferrite for solid oxide fuel cell

    NASA Astrophysics Data System (ADS)

    Hong, Tao; Chen, Fanglin; Xia, Changrong

    2015-03-01

    BaCO3 nanoparticles are demonstrated as outstanding catalysts for high-temperature oxygen reduction reaction (ORR) on the La0.8Sr0.2FeO3-δ (LSF) cathode for solid oxide fuel cells (SOFCs) based on ytrria-stabilized zirconia (YSZ) electrolytes. Thermal gravitational and X-ray diffraction measurements show that BaCO3 is stable and chemically compatible with LSF under the fabrication and operation conditions of intermediate-temperature SOFCs. The BaCO3 nanoparticles can greatly reduce the interfacial polarization resistance; from 2.96 to 0.84 Ω cm2 at 700 °C when 12.9wt% BaCO3 is infiltrated to the porous LSF electrode on the YSZ electrolyte. Electrochemical impedance spectroscopy shows that there is about one order of magnitude decrease in the low-frequency resistance, indicating that BaCO3 nanoparticles can greatly enhance the surface steps for ORR. Electrical conductivity relaxation investigation indicates about one order of magnitude increase in the chemical oxygen surface exchange coefficient when BaCO3 is applied, directly demonstrating significant increase in the kinetics for ORR. In addition, LSF cathodes with infiltrated BaCO3 nanoparticles have shown excellent stability and substantially enhanced cell performance as demonstrated with single cells, suggesting BaCO3 nanoparticles are very effective in enhancing ORR on LSF.

  3. Phase Constitution in Sr and Mg doped LaGaO3 System

    SciTech Connect

    Zheng, F; Bordia, Rajendra K.; Pederson, Larry R.

    2004-01-03

    Sr and Mg doped lanthanum gallate perovskites (La1-xSrxGa1-yMgyO3-delta, shortened as LSGM-XY where X and Y are the doping levels in mole percentage (mol%) at the La- or A-site and the Ga- or B-site, respectively) are promising electrolyte materials for intermediate temperature solid oxide fuel cells (SOFCs). In this study, we have investigated the primary perovskites as well as the secondary phases formed in terms of doping content changes and A/B ratio variations in these materials. Fifteen powder compositions (three doping levels, X = Y = 0, 0.1, and 0.2 mol; and five A/B ratios 0.95, 0.98, 1.00, 1.02, and 1.05) were synthesized by the glycine-nitrate combustion process (GNP). These powders were equilibrated by calcining at 1500 degreesC for 9 h prior to crystalline phase characterization by X-ray powder diffraction (XRD). From the results of this study and the available phase diagrams in the literature on constituent binary oxide systems, we propose a crystalline phase diagram of the La2O3-SrO-Ga2O3-MgO quaternary system at elevated temperature (1500 degreesC). (C) 2003 Elsevier Ltd. All rights reserved

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

    NASA Astrophysics Data System (ADS)

    Laha, Suvra; Lawes, Gavin

    2012-10-01

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

  5. Aquatic ecotoxicity of lanthanum - A review and an attempt to derive water and sediment quality criteria.

    PubMed

    Herrmann, Henning; Nolde, Jürgen; Berger, Svend; Heise, Susanne

    2016-02-01

    Rare earth elements (REE) used to be taken as tracers of geological origin for fluvial transport. Nowadays their increased applications in innovative environmental-friendly technology (e.g. in catalysts, superconductors, lasers, batteries) and medical applications (e.g. MRI contrast agent) lead to man-made, elevated levels in the environment. So far, no regulatory thresholds for REE concentrations and emissions to the environment have been set because information on risks from REE is scarce. However, evidence gathers that REE have to be acknowledged as new, emerging contaminants with manifold ways of entry into the environment, e.g. through waste water from hospitals or through industrial effluents. This paper reviews existing information on bioaccumulation and ecotoxicity of lanthanum in the aquatic environment. Lanthanum is of specific interest as one of the major lanthanides in industrial effluents. This review focuses on the freshwater and the marine environment, and tackles the water column and sediments. From these data, methods to derive quality criteria for sediment and water are discussed and preliminary suggestions are made.

  6. Localization and health effects of lanthanum chloride instilled intratracheally into rats.

    PubMed

    Suzuki, K T; Kobayashi, E; Ito, Y; Ozawa, H; Suzuki, E

    1992-11-30

    Lanthanum (La) is one of the rare earths used in diverse high technology fields for which sufficient data for assessing its health effects have been lacking. The biological effects and metabolic behaviors of La were studied by instilling lanthanum chloride intratracheally into male Wistar rats. The distribution of La among tissues revealed that the metal remains mostly in the lung with a biological half-time of 244 days. The subcellular localization by transmission electron microscopy with an X-ray microanalyzer indicated that La localizes in macrophages as high electron-dense granular inclusions in lysosomes and on the cell surface and basement membranes of type I pneumocytes among lung cells. The pulmonary health effects were examined by biological indices of the bronchoalveolar lavage fluid (BALF) and lung tissue. The acute toxicity estimated by lactate dehydrogenase activity in BALF was comparable to those of yttrium and copper that had been determined under the same protocol. Microscopic examination of the lung indicated a characteristic increase in the number of eosinophils.

  7. Syntheses, Characterization, Thermal, and Antimicrobial Studies of Lanthanum(III) Tolyl/Benzyldithiocarbonates

    PubMed Central

    Andotra, Savit; Kalgotra, Nidhi; Pandey, Sushil K.

    2014-01-01

    Lanthanum(III) tris(O-tolyl/benzyldithiocarbonates), [La(ROCS2)] (R = o-, m-, p-CH3C6H4 and C6H5CH2), were isolated as yellow solid by the reaction of LaCl3·7H2O with sodium salt of tolyl/benzyldithiocarbonates, ROCS2Na (R = o-, m-, p-CH3C6H4 and C6H5CH2), in methanol under anhydrous conditions in 1 : 3 molar ratio. These complexes have formed adducts with nitrogen and phosphorus donor molecules by straightforward reaction of these complexes with donor ligands, which have the composition of the type [La(ROCS2)3·nL] (where n = 2, L = NC5H5 or P(C6H5)3 and n = 1, L = N2C12H8 or N2C10H8). Elemental analyses, mass, IR, TGA, and heteronuclear NMR (1H, 13C and 31P) spectroscopic studies indicated bidentate mode of bonding by dithiocarbonate ligands leading to hexacoordinated and octacoordinated geometry around the lanthanum atom. Antimicrobial (antifungal and antibacterial) activity of the free ligands and some of the complexes have also been investigated which exhibited significantly more activity for the complexes than the free ligands. PMID:24817836

  8. Cr(VI) Adsorption on Red Mud Modified by Lanthanum: Performance, Kinetics and Mechanisms

    PubMed Central

    Cui, You-Wei; Li, Jie; Du, Zhao-Fu; Peng, Yong-Zhen

    2016-01-01

    Water pollution caused by the highly toxic metal hexavalent chromium (Cr(VI)) creates significant human health and ecological risks. In this study, a novel adsorbent was used to treat Cr(VI)-containing wastewater; the adsorbent was prepared using red mud (RM) generated from the alumina production industry and the rare earth element lanthanum. This study explored adsorption performance, kinetics, and mechanisms. Results showed that the adsorption kinetics of the RM modified by lanthanum (La-RM), followed the pseudo-second-order model, with a rapid adsorption rate. Cr(VI) adsorption was positively associated with the absorbent dose, pH, temperature, and initial Cr(VI) concentration; coexisting anions had little impact. The maximum Cr(VI) adsorption capacity was 17.35 mg/g. Cr(VI) adsorption on La-RM was a mono-layer adsorption pattern, following the Langmuir isotherm model. Thermodynamic parameters showed the adsorption was spontaneous and endothermic. The adsorption of Cr(VI) on La-RM occurred as a result of LaOCl formation on the RM surface, which in turn further reacted with Cr(VI) in the wastewater. This study highlighted a method for converting industrial waste into a valuable material for wastewater treatment. The novel absorbent could be used as a potential adsorbent for treating Cr(VI)-contaminating wastewater, due to its cost-effectiveness and high adsorption capability. PMID:27658113

  9. Aquatic ecotoxicity of lanthanum - A review and an attempt to derive water and sediment quality criteria.

    PubMed

    Herrmann, Henning; Nolde, Jürgen; Berger, Svend; Heise, Susanne

    2016-02-01

    Rare earth elements (REE) used to be taken as tracers of geological origin for fluvial transport. Nowadays their increased applications in innovative environmental-friendly technology (e.g. in catalysts, superconductors, lasers, batteries) and medical applications (e.g. MRI contrast agent) lead to man-made, elevated levels in the environment. So far, no regulatory thresholds for REE concentrations and emissions to the environment have been set because information on risks from REE is scarce. However, evidence gathers that REE have to be acknowledged as new, emerging contaminants with manifold ways of entry into the environment, e.g. through waste water from hospitals or through industrial effluents. This paper reviews existing information on bioaccumulation and ecotoxicity of lanthanum in the aquatic environment. Lanthanum is of specific interest as one of the major lanthanides in industrial effluents. This review focuses on the freshwater and the marine environment, and tackles the water column and sediments. From these data, methods to derive quality criteria for sediment and water are discussed and preliminary suggestions are made. PMID:26528910

  10. Biodiesel production by free fatty acid esterification using Lanthanum (La3+) and HZSM-5 based catalysts.

    PubMed

    Vieira, Sara S; Magriotis, Zuy M; Santos, Nadiene A V; Saczk, Adelir A; Hori, Carla E; Arroyo, Pedro A

    2013-04-01

    In this work the use of the heterogeneous catalysts pure (LO) and sulfated (SLO) lanthanum oxide, pure HZSM-5 and SLO/HZSM-5 (HZSM-5 impregnated with sulfated lanthanum oxide (SO4(2-)/La2O3)) was evaluated. The structural characterization of the materials (BET) showed that the sulfation process led to a reduction of the SLO and SLO/HZSM-5 surface area values. FTIR showed bands characteristic of the materials and, FTIR-pyridine indicated the presence of strong Brønsted sites on the sulfated material. In the catalytic tests the temperature was the parameter that most influenced the reactions. The best reaction conditions were: 10% catalyst, 100°C temperature and 1:5 m(OA)/m(meOH) for LO, SLO, SLO/HZSM-5 and 10% catalyst, 100°C temperature and 1:20 m(OA)/m(meOH) for HZSM-5. Under these conditions the conversions were: 67% and 96%, for LO and SLO, respectively and 80% and 100%, for HZSM-5 and SLO/HZSM-5, respectively. All catalysts deactivated after the first use, but the deactivation of SLO/HZSM-5 was smaller.

  11. Lanthanum chloride impairs spatial memory through ERK/MSK1 signaling pathway of hippocampus in rats.

    PubMed

    Liu, Huiying; Yang, Jinghua; Liu, Qiufang; Jin, Cuihong; Wu, Shengwen; Lu, Xiaobo; Zheng, Linlin; Xi, Qi; Cai, Yuan

    2014-12-01

    Rare earth elements (REEs) are used in many fields for their diverse physical and chemical properties. Surveys have shown that REEs can impair learning and memory in children and cause neurobehavioral defects in animals. However, the mechanism underlying these impairments has not yet been completely elucidated. Lanthanum (La) is often selected to study the effects of REEs. The aim of this study was to investigate the spatial memory impairments induced by lanthanum chloride (LaCl3) and the probable underlying mechanism. Wistar rats were exposed to LaCl3 in drinking water at 0 % (control, 0 mM), 0.25 % (18 mM), 0.50 % (36 mM), and 1.00 % (72 mM) from birth to 2 months after weaning. LaCl3 considerably impaired the spatial learning and memory of rats in the Morris water maze test, damaged the synaptic ultrastructure and downregulated the expression of p-MEK1/2, p-ERK1/2, p-MSK1, p-CREB, c-FOS and BDNF in the hippocampus. These results indicate that LaCl3 exposure impairs the spatial learning and memory of rats, which may be attributed to disruption of the synaptic ultrastructure and inhibition of the ERK/MSK1 signaling pathway in the hippocampus.

  12. Thermal stability and microstructure of catalytic alumina composite support with lanthanum species

    NASA Astrophysics Data System (ADS)

    Ozawa, Masakuni; Nishio, Yoshitoyo

    2016-09-01

    Lanthanum (La) modified γ-alumina composite was examined for application toward thermostable catalytic support at elevated temperature. La added alumina was prepared through an aqueous process using lanthanum (III) nitrate and then characterized by surface area measurement, X-ray powder diffraction (XRD), differential thermal analysis (DTA), scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray photoemission spectroscopy (XPS) and surface desorption of CO2. It was found that the properties depended on the La content and heat treatment temperatures. The characterization of the surface, structural and chemical properties of La-Al2O3 showed the existence of a strong interaction between the La species and alumina via formation of new phase and modified surface in Al2O3 samples. LaAlO3 nanoparticle formed among alumina particles by the solid phase reaction of Al2O3 and La2O3. The increase of the surface basicity of La modified alumina was demonstrated using CO2 temperature programmed desorption experiments. The controlled surface interaction between La oxide and alumina provide the unique surface and structural properties of the resulting mixed oxides as catalysts and catalytic supports.

  13. Influence of dissolved organic carbon on the efficiency of P sequestration by a lanthanum modified clay.

    PubMed

    Dithmer, Line; Nielsen, Ulla Gro; Lundberg, Daniel; Reitzel, Kasper

    2016-06-15

    A laboratory scale experiment was set up to test the effect of dissolved organic carbon (DOC) as well as ageing of the La-P complex formed during phosphorus (P) sequestration by a La modified clay (Phoslock(®)). Short term (7 days) P adsorption studies revealed a significant negative effect of added DOC on the P sequestration of Phoslock(®), whereas a long-term P adsorption experiment revealed that the negative effect of added DOC was reduced with time. The reduced P binding efficiency is kinetic, as evident from solid-state (31)P magic-angle spinning (MAS) NMR spectroscopy, who showed that the P binding did not change in the presence of DOC. (31)P MAS NMR also reveals that up to 26% of the sequestered phosphate is as loosely bound redox-sensitive P species on the surface of rhabdophane (LaPO4 · nH2O, n ≤ 3). The ratio between the loosely bound P and lanthanum phosphate did not change with time, however both NMR and La LIII-extended x-ray absorption fine structure (EXAFS) spectroscopy shows a transformation of lanthanum phosphate from the initially formed rhabdophane towards the more stable monazite (LaPO4). Furthermore, the effect of natural DOC on the P binding capacity was tested using water and pore water from 16 Danish lakes. Whilst DOC has an immediate negative impact on P binding in the lake water, with time this effect is reduced.

  14. Solution processed lanthanum aluminate gate dielectrics for use in metal oxide-based thin film transistors

    NASA Astrophysics Data System (ADS)

    Esro, M.; Mazzocco, R.; Vourlias, G.; Kolosov, O.; Krier, A.; Milne, W. I.; Adamopoulos, G.

    2015-05-01

    We report on ZnO-based thin-film transistors (TFTs) employing lanthanum aluminate gate dielectrics (LaxAl1-xOy) grown by spray pyrolysis in ambient atmosphere at 440 °C. The structural, electronic, optical, morphological, and electrical properties of the LaxAl1-xOy films and devices as a function of the lanthanum to aluminium atomic ratio were investigated using a wide range of characterization techniques such as UV-visible absorption spectroscopy, impedance spectroscopy, spectroscopic ellipsometry, atomic force microscopy, x-ray diffraction, and field-effect measurements. As-deposited LaAlOy dielectrics exhibit a wide band gap (˜6.18 eV), high dielectric constant (k ˜ 16), low roughness (˜1.9 nm), and very low leakage currents (<3 nA/cm2). TFTs employing solution processed LaAlOy gate dielectrics and ZnO semiconducting channels exhibit excellent electron transport characteristics with hysteresis-free operation, low operation voltages (˜10 V), high on/off current modulation ratio of >106, subthreshold swing of ˜650 mV dec-1, and electron mobility of ˜12 cm2 V-1 s-1.

  15. Solution processed lanthanum aluminate gate dielectrics for use in metal oxide-based thin film transistors

    SciTech Connect

    Esro, M.; Adamopoulos, G.; Mazzocco, R.; Kolosov, O.; Krier, A.; Vourlias, G.; Milne, W. I.

    2015-05-18

    We report on ZnO-based thin-film transistors (TFTs) employing lanthanum aluminate gate dielectrics (La{sub x}Al{sub 1−x}O{sub y}) grown by spray pyrolysis in ambient atmosphere at 440 °C. The structural, electronic, optical, morphological, and electrical properties of the La{sub x}Al{sub 1−x}O{sub y} films and devices as a function of the lanthanum to aluminium atomic ratio were investigated using a wide range of characterization techniques such as UV-visible absorption spectroscopy, impedance spectroscopy, spectroscopic ellipsometry, atomic force microscopy, x-ray diffraction, and field-effect measurements. As-deposited LaAlO{sub y} dielectrics exhibit a wide band gap (∼6.18 eV), high dielectric constant (k ∼ 16), low roughness (∼1.9 nm), and very low leakage currents (<3 nA/cm{sup 2}). TFTs employing solution processed LaAlO{sub y} gate dielectrics and ZnO semiconducting channels exhibit excellent electron transport characteristics with hysteresis-free operation, low operation voltages (∼10 V), high on/off current modulation ratio of >10{sup 6}, subthreshold swing of ∼650 mV dec{sup −1}, and electron mobility of ∼12 cm{sup 2} V{sup −1} s{sup −1}.

  16. Ultrasonic mediated synthesis of monodispersed lanthanum hydroxide nanorods for possible bioimplant application.

    PubMed

    Harini, Dhandapani; Rajaram, Anantanarayanan; Rajaram, Rama

    2015-01-01

    Monodispersed lanthanum hydroxide nano-rods (LaNRs) were synthesized for prospective biomedical application using a microwave heating and ultrasonic agitation methodology which does not require any toxic stabilizing agent. The average length and diameter of the LaNRs thus obtained were 183.4 ± 3.6 and 9.9 ± 0.2 nm respectively, as analyzed by HRTEM. FTIR spectrum confirmed the presence of OH groups. The thermal transformation of lanthanum hydroxide (La(OH)3) was studied by thermogravimetric analysis. The synthesized LaNRs were found to be stable for a period of 1 month at room temperature. They were biocompatible as evaluated by haemocompatibility assay and viability assay using human peripheral blood mononuclear cells. The pro-angiogenic property of LaNRs was demonstrated by in vivo chick chorioallantoic membrane assay. The LaNRs induced osteoblast differentiation of human adipose derived stem cells with significant calcium (Ca(2+)) deposition indicating potential applications in bone tissue engineering. PMID:25601669

  17. Enhancement of thermal shock resistance of reaction sintered mullite–zirconia composites in the presence of lanthanum oxide

    SciTech Connect

    Kumar, P.; Nath, M.; Ghosh, A.; Tripathi, H.S.

    2015-03-15

    Mullite–zirconia composites containing 20 wt.% zirconia were prepared by reaction sintering of zircon flour, sillimanite beach sand and calcined alumina. 0 to 8 mol% of La{sub 2}O{sub 3} with respect to zirconia was used as sintering aid. The effect of additive on the various physical, microstructures, mechanical and thermo-mechanical properties was studied. Quantitative phase analysis shows the change in tetragonal zirconia content with incorporation of lanthanum oxide. La{sub 2}O{sub 3} addition has significantly improved the thermal shock resistance of the samples. Samples without additive retained only 20% of initial flexural strength after 5 cycles, whereas samples containing 5 mol% La{sub 2}O{sub 3} retained almost 78% of its initial flexural strength even after 15 thermal shock cycles. - Highlights: • Mullite–zirconia composites were prepared by reaction sintering route utilizing zircon and sillimanite beach sand. • Lanthanum oxide was used as sintering aid. • The presence of lanthanum oxide decreased the densification temperature. • Lanthanum oxide significantly improved the thermal shock resistance of the composites.

  18. Ionic liquid-mediated synthesis of meso-scale porous lanthanum-transition-metal perovskites with high CO oxidation performance

    DOE PAGES

    Lu, Hanfeng; Zhang, Pengfei; Qiao, Zhen-An; Zhang, Jinshui; Zhu, Huiyuan; Chen, Jihua; Chen, Yinfei; Dai, Sheng

    2015-02-19

    Lanthanum-transition-metal perovskites with robust meso-scale porous frameworks (meso-LaMO3) are synthesized through use of ionic liquids. The resultant samples demonstrate a rather high activity for CO oxidation, by taking advantage of unique nanostructure-derived benefits. This synthesis strategy opens up a new opportunity for preparing functional mesoporous complex oxides of various compositions.

  19. Ionic liquid-mediated synthesis of meso-scale porous lanthanum-transition-metal perovskites with high CO oxidation performance

    SciTech Connect

    Lu, Hanfeng; Zhang, Pengfei; Qiao, Zhen-An; Zhang, Jinshui; Zhu, Huiyuan; Chen, Jihua; Chen, Yinfei; Dai, Sheng

    2015-02-19

    Lanthanum-transition-metal perovskites with robust meso-scale porous frameworks (meso-LaMO3) are synthesized through use of ionic liquids. The resultant samples demonstrate a rather high activity for CO oxidation, by taking advantage of unique nanostructure-derived benefits. This synthesis strategy opens up a new opportunity for preparing functional mesoporous complex oxides of various compositions.

  20. The Anti-Doping Movement.

    PubMed

    Willick, Stuart E; Miller, Geoffrey D; Eichner, Daniel

    2016-03-01

    Historical reports of doping in sports date as far back as the ancient Greek Olympic Games. The anti-doping community considers doping in sports to be cheating and a violation of the spirit of sport. During the past century, there has been an increasing awareness of the extent of doping in sports and the health risks of doping. In response, the anti-doping movement has endeavored to educate athletes and others about the health risks of doping and promote a level playing field. Doping control is now undertaken in most countries around the world and at most elite sports competitions. As athletes have found new ways to dope, however, the anti-doping community has endeavored to strengthen its educational and deterrence efforts. It is incumbent upon sports medicine professionals to understand the health risks of doping and all doping control processes. PMID:26972261

  1. The Anti-Doping Movement.

    PubMed

    Willick, Stuart E; Miller, Geoffrey D; Eichner, Daniel

    2016-03-01

    Historical reports of doping in sports date as far back as the ancient Greek Olympic Games. The anti-doping community considers doping in sports to be cheating and a violation of the spirit of sport. During the past century, there has been an increasing awareness of the extent of doping in sports and the health risks of doping. In response, the anti-doping movement has endeavored to educate athletes and others about the health risks of doping and promote a level playing field. Doping control is now undertaken in most countries around the world and at most elite sports competitions. As athletes have found new ways to dope, however, the anti-doping community has endeavored to strengthen its educational and deterrence efforts. It is incumbent upon sports medicine professionals to understand the health risks of doping and all doping control processes.

  2. Polarization induced doped transistor

    DOEpatents

    Xing, Huili; Jena, Debdeep; Nomoto, Kazuki; Song, Bo; Zhu, Mingda; Hu, Zongyang

    2016-06-07

    A nitride-based field effect transistor (FET) comprises a compositionally graded and polarization induced doped p-layer underlying at least one gate contact and a compositionally graded and doped n-channel underlying a source contact. The n-channel is converted from the p-layer to the n-channel by ion implantation, a buffer underlies the doped p-layer and the n-channel, and a drain underlies the buffer.

  3. Magnetic and Magneto-Optical Properties of Doped Oxides

    NASA Astrophysics Data System (ADS)

    Alqahtani, Mohammed

    This thesis describes the growth, structural characterisation, magnetic and magneto-optics properties of lanthanum strontium manganite (LSMO), GdMnO3 and transition metal (TM)-doped In2O3 thin films grown under different conditions. The SrTiO3 has been chosen as a substrate because its structure is suitable to grow epitaxial LSMO and GdMnO3 films. However, the absorption of SrTiO3 above its band gap at about 3.26 eV is actually a limitation in this study. The LSMO films with 30% Sr, grown on both SrTiO3 and sapphire substrates, exhibit a high Curie temperature (Tc) of 340 K. The magnetic circular dichroism (MCD) intensity follows the magnetisation for LSMO on sapphire; however, the measurements on SrTiO3 were dominated by the birefringence and magneto-optical properties of the substrate. In the GdMnO3 thin films, there are two well-known features in the optical spectrum; the charge transfer transition between Mn d states at 2 eV and the band edge transition from the oxygen p band to d states at about 3 eV; these are observed in the MCD. This has been measured at remanence as well as in a magnetic field. The optical absorption at 3 eV is much stronger than at 2 eV, however, the MCD is considerably stronger at 2 eV. The MCD at 2 eV correlates well with the Mn spin ordering and it is very notable that the same structure appears in this spectrum, as is seen in LaMnO3. The results of the investigations of Co and Fe-doped In2O3 thin films show that TM ions in the films are TM2+ and substituted for In3+. The room temperature ferromagnetism observed in TM-doped In2O3 is due to the polarised electrons in localised donor states associated with oxygen vacancies. The formation of Fe3O4 nanoparticles in some Fe-doped films is due the fact that TM-doped In2O3 thin films are extremely sensitive to the growth method and processing condition. However, the origin of the magnetisation in these films is due to both the Fe-doped host matrix and also to the nanoparticles of Fe3O4.

  4. Lake responses following lanthanum-modified bentonite clay (Phoslock®) application: an analysis of water column lanthanum data from 16 case study lakes.

    PubMed

    Spears, Bryan M; Lürling, Miquel; Yasseri, Said; Castro-Castellon, Ana T; Gibbs, Max; Meis, Sebastian; McDonald, Claire; McIntosh, John; Sleep, Darren; Van Oosterhout, Frank

    2013-10-01

    Phoslock(®) is a lanthanum (La) modified bentonite clay that is being increasingly used as a geo-engineering tool for the control of legacy phosphorus (P) release from lake bed sediments to overlying waters. This study investigates the potential for negative ecological impacts from elevated La concentrations associated with the use of Phoslock(®) across 16 case study lakes. Impact-recovery trajectories associated with total lanthanum (TLa) and filterable La (FLa) concentrations in surface and bottom waters were quantified over a period of up to 60 months following Phoslock(®) application. Both surface and bottom water TLa and FLa concentrations were <0.001 mg L(-1) in all lakes prior to the application of Phoslock(®). The effects of Phoslock(®) application were evident in the post-application maximum TLa and FLa concentrations reported for surface waters between 0.026 mg L(-1)-2.30 mg L(-1) and 0.002 mg L(-1) to 0.14 mg L(-1), respectively. Results of generalised additive modelling indicated that recovery trajectories for TLa and FLa in surface and bottom waters in lakes were represented by 2nd order decay relationships, with time, and that recovery reached an end-point between 3 and 12 months post-application. Recovery in bottom water was slower (11-12 months) than surface waters (3-8 months), most probably as a result of variation in physicochemical conditions of the receiving waters and associated effects on product settling rates and processes relating to the disturbance of bed sediments. CHEAQS PRO modelling was also undertaken on 11 of the treated lakes in order to predict concentrations of La(3+) ions and the potential for negative ecological impacts. This modelling indicated that the concentrations of La(3+) ions will be very low (<0.0004 mg L(-1)) in lakes of moderately low to high alkalinity (>0.8 mEq L(-1)), but higher (up to 0.12 mg L(-1)) in lakes characterised by very low alkalinity. The effects of elevated La(3+) concentrations following

  5. Synthesis of La{sup 3+} doped nanocrystalline ceria powder by urea-formaldehyde gel combustion route

    SciTech Connect

    Biswas, M.; Bandyopadhyay, S.

    2012-03-15

    Highlights: Black-Right-Pointing-Pointer Nano LC synthesized by gel combustion, using urea-formaldehyde fuel for first time. Black-Right-Pointing-Pointer Largely single crystals were produced in average range of 20-30 nm. Black-Right-Pointing-Pointer La{sup 3+} doping increases cell dimension linearly. Black-Right-Pointing-Pointer La{sup 3+} doping introduces ionic point defects but does not change electronic band gap. Black-Right-Pointing-Pointer Presence of Ce{sup 3+} indicates that this synthesis route produces reactive powders. -- Abstract: Nanocrystalline ceria powders doped with various concentrations of lanthanum oxide have been prepared following gel combustion route using for the first time urea-formaldehyde as fuel. The synthesized products were characterized by XRD, FESEM, TEM, PL and UV-vis spectroscopy. Peak positions of XRD were refined and the lattice parameters were obtained by applying Cohen's method. Unit cell parameter increases with concentration of La{sup 3+} ion and the variation is consistently linear. XRD calculations showed the dependence of crystallite size on dopant concentrations at lower level. TEM observation revealed unagglomerated particles to be single crystals in the average range of 20-30 nm. Band gap of the La{sup 3+} doped ceria materials does not change with doping. Spectroscopic experiments proved the existence of Ce{sup 3+} in the formed powder.

  6. The enhancement effect of pre-reduction using zero-valent iron on the solidification of chromite ore processing residue by blast furnace slag and calcium hydroxide.

    PubMed

    Li, Jinchunzi; Chen, Zhonglin; Shen, Jimin; Wang, Binyuan; Fan, Leitao

    2015-09-01

    A bench scale study was performed to assess the effectiveness of the solidification of chromite ore processing residue (COPR) by blast furnace slag and calcium hydroxide, and investigate the enhancement effect of pre-reduction using zero-valent iron (ZVI) on the solidification treatment. The degree of Cr immobilization was evaluated using the Toxicity Characteristic Leaching Procedure (TCLP) as well as the solid waste-extraction procedure for leaching toxicity-sulfuric acid & nitric acid method (Chinese standard HJ/T299-2007). Strength tests and semi-dynamic leaching tests were implemented to investigate the potential for reusing the final treatment product as a readily available construction material. The experimental results showed that the performance of pre-reduction/solidification (S/S) was superior to that of solidification alone. After pre-reduction, all of the S/S treated COPR samples met the TCLP limit for total Cr (5 mg L(-1)), whereas the samples with a COPR content below 40% met the pollution control limit of bricks and building block products (Chinese standard HJ/T 301-2007) produced with COPR for total Cr (0.3 mg L(-1)). At the same time, all of the S/S treated specimens tested were suitable for utilization at certain levels.

  7. [Solidification/Stabilization of Chromite Ore Processing Residue (COPR) Using Zero-Valent Iron and Lime-Activated Ground Granulated Blast Furnace Slag].

    PubMed

    Chen, Zhong-lin; Li, Jin-chunzi; Wang, Bin-yuan; Fan, Lei-tao; Shen, Ji-min

    2015-08-01

    The solidification/stabilization (S/S) of chromite ore processing residue (COPR) was performed using zero-valent iron (ZVI) and lime-activated ground granulated blast furnace slag (GGBFS). The degree of Cr immobilization was evaluated using the leaching procedure, mineral composition analysis and morphology analysis. Semi-dynamic leaching tests were implemented to investigate the potential for reusing the final treatment product as a readily available construction material. The results showed that after reduction, all of the S/S treated COPR samples met the pollution control limit of bricks and building block products (Chinese standard HJ/T 301-2007) produced with COPR for total Cr (0.3 mg x L(-1)), the compressive strength of all the S/S samples could meet the compressive strength standard (15 MPa) for producing clay bricks, and Cr existed as the specie that bound to Fe/Mn oxides in the S/S samples. At the same time, all of the S/S treated specimens tested were suitable for utilization at certain levels.

  8. Translocation and bioaccumulation of metals in Oryza sativa and Zea mays growing in chromite-asbestos contaminated agricultural fields, Jharkhand, India.

    PubMed

    Kumar, Adarsh; Maiti, Subodh Kumar

    2014-10-01

    The present study involves the assessment of metals (Cr, Ni, Pb and Cd) in contaminated agricultural soil (CAS) and abandoned chromite-asbestos waste (CW). High concentrations of Cr and Ni were found in CW (1,121-2,802 mg Cr kg(-1); 985-1,720 mg Ni kg(-1)), which CAS (1,058-1,242 mg Cr kg(-1); 1,002-1,295 mg Ni kg(-1)). Zea mays and Oryza sativa showed significant amounts of metals in root and aerial parts. The primary factors only consider the changes in metal concentrations in soil and plant, while dynamic factor includes both changes in metal concentration and environmental processes. In spite of the high concentration of Cr present in contaminated soils and crops, significant translocation of metals (>1) were found only for Pb and Ni, when primary factor was used. When dynamic factor was used, higher translocation (>1) and bioaccumulation (>1) were found for Cr along with Pb and Ni. The current study concludes that assessment of metal toxicity in CAS and crops could be better evaluated by using both primary and dynamic factors.

  9. Aero dopes and varnishes

    NASA Technical Reports Server (NTRS)

    Britton, H T S

    1927-01-01

    Before proceeding to discuss the preparation of dope solutions, it will be necessary to consider some of the essential properties which should be possessed of a dope film, deposited in and on the surface of an aero fabric. The first is that it should tighten the material and second it should withstand weathering.

  10. [Doping and sports].

    PubMed

    Lippi, G; Guidi, G

    1999-09-01

    Doping is widely known as the use of banned substances and practices by athletes in an attempt to improve sporting performances. The term doping likely derives from "dope", an ancient expression referred to a primitive alcoholic drink that was used as a stimulant in South African ceremonial dances; gradually, the term was extended and finally adopted his current significance. There are at least two essential reasons to support the fight against doping: the potential harmful effects on athletes and the depth corruption of the fair competition. An exhaustive list of banned substances and methods has been drawn by the International Olympic Committee and further accepted by other International Sport Authorities and Federations. This list, regularly updated, is basically divided into doping substances (stimulants, narcotic analgesics, anabolic agents, diuretics, peptide and glycoprotein hormones and analogues), doping methods (blood doping, pharmacological, chemical and physical manipulation) and drugs subjected to certain restrictions (alcohol, marijuana, local anesthetics, corticosteroids and beta-blockers). Although there might be some medical conditions, which could legitimate the need of these substances or methods, there is no place for their use in sport. Thus, an athlete's consume of any of these substances or methods will result in disqualification. Aim of the present review is to provide a synthetic description of both the desirable effects and the potentially harmful consequences of the use of some of the major doping substances and methods.

  11. Doped graphene supercapacitors

    NASA Astrophysics Data System (ADS)

    Ashok Kumar, Nanjundan; Baek, Jong-Beom

    2015-12-01

    Heteroatom-doped graphitic frameworks have received great attention in energy research, since doping endows graphitic structures with a wide spectrum of properties, especially critical for electrochemical supercapacitors, which tend to complement or compete with the current lithium-ion battery technology/devices. This article reviews the latest developments in the chemical modification/doping strategies of graphene and highlights the versatility of such heteroatom-doped graphitic structures. Their role as supercapacitor electrodes is discussed in detail. This review is specifically focused on the concept of material synthesis, techniques for electrode fabrication and metrics of performance, predominantly covering the last four years. Challenges and insights into the future research and perspectives on the development of novel electrode architectures for electrochemical supercapacitors based on doped graphene are also discussed.

  12. High-current density, high-brightness electron beams from large-area lanthanum hexaboride cathodes

    NASA Astrophysics Data System (ADS)

    Loschialpo, P.; Kapetanakos, C. A.

    1988-04-01

    Large diameter lanthanum hexaboride (LaB6) cathodes operated at 10 kV have produced 1-5-microsec electron pulses with current density between 10 and 20 A/sq cm. Normalized beam brightness, approximately 300,000 A/sq cm sq rad has been consistently measured. To obtain this high-current density, the LaB6 cathodes have been heated to temperatures between about 1600 and 1800 C. Very uniform temperature profiles are obtained by applying a carefully tailored electron bombardment heating power distribution. These measurements have been made between pressure 10 to the -6th to -10 to the -5th Torr, i.e., under much less demanding vacuum conditions than that required by conventional dispenser-type cathodes.

  13. Ba11La4Br34: a new barium lanthanum bromide

    PubMed Central

    Eagleman, Yetta; Wu, Guang; Gundiah, Gautam; Bourret-Courchesne, Edith; Derenzo, Stephen

    2011-01-01

    The structure of the title compound, barium lanthanum bromide (11/4/34), can be derived from the fluorite structure. The asymmetric unit contains two Ba sites (one with site symmetry 4/m..), one La site (site symmetry 4..), one mixed-occupied Ba and La site (ratio 1:1, site symmetry m..) and six Br sites (one with site symmetry \\=4.., one with 2.., one with m.., the latter being disordered over two positions with a 0.86:0.14 ratio). The fundamental building units of the structure are edge-sharing polyhedral clusters made up of Ba and La bromide clusters inter­connected to BaBr8 square prisms and BaBr10 groups. PMID:22064368

  14. Complex formation of quercetin with lanthanum enhances binding to plant viral satellite double stranded RNA.

    PubMed

    Rusak, Gordana; Piantanida, Ivo; Bretschneider, Sabine; Ludwig-Müller, Jutta

    2009-12-01

    Due to the broad spectrum of biological activities of flavonoids, their target molecules in the cell are intensively studied. We examined the interactions of the flavonoid quercetin (Q) and its lanthanum complex (QLa(3+)) with very recently isolated plant viral satellite (sat) dsRNA. Comparison of the cumulative binding affinity and the estimated intercalative binding constant pointed towards an additional binding mode of quercetin to exclusively viral dsRNA, which is not recorded for synthetic dsRNAs. The QLa(3+) showed significantly higher affinity toward viral dsRNA than Q and La(3+) alone, most likely as the consequence of quercetin intercalation accompanied by additional electrostatic interaction of La(3+) with the negatively charged viral RNA backbone.

  15. Data for effects of lanthanum complex on the thermo-oxidative aging of natural rubber.

    PubMed

    Zheng, Wei; Liu, Li; Zhao, Xiuying; He, Jingwei; Wang, Ao; Chan, Tung W; Wu, Sizhu

    2015-12-01

    Novel mixed antioxidants composed of antioxidant IPPD and lanthanum (La) complex were added as a filler to form natural rubber (NR) composites. By mechanical testing, Fourier transform infrared spectroscopy with attenuated total reflectance (FTIR-ATR) and thermogravimetric analysis (TGA), a string of data, including the mechanical properties, the variation of internal groups and the thermal and thermo-oxidative decompositions of NR, was presented in this data article. The data accompanying its research article [1] studied the thermo-oxidative aging properties of NR in detail. The density function theoretical (DFT) calculations were also used as an assistant to study the thermo-oxidative aging mechanism of NR. The data revealed that this new rare-earth antioxidant could indeed enhance the thermo-oxidative aging resistance of NR, which is associated with its different function mechanism from that of the pure antioxidant IPPD. PMID:26693513

  16. Large area directly heated lanthanum hexaboride cathode structure having predetermined emission profile

    DOEpatents

    Leung, Ka-Ngo; Gordon, K.C.; Kippenhan, D.O.; Purgalis, P.; Moussa, D.; Williams, M.D.; Wilde, S.B.; West, M.W.

    1987-10-16

    A large area directly heated lanthanum hexaboride (LaB/sub 6/) cathode system is disclosed. The system comprises a LaB/sub 6/ cathode element generally circular in shape about a central axis. The cathode element has a head with an upper substantially planar emission surface, and a lower downwardly and an intermediate body portion which diminishes in cross-section from the head towards the base of the cathode element. A central rod is connected to the base of the cathode element and extends along the central axis. Plural upstanding spring fingers are urged against an outer peripheral contact surface of the head end to provide a mechanical and electrical connection to the cathode element. 7 figs

  17. Accomplishment of highly porous-lithium lanthanum titanate through microwave treatment

    NASA Astrophysics Data System (ADS)

    Lakshmi, D.; Nalini, B.; Abhilash, K. P.; Selvin, P. Christopher

    2016-05-01

    Perovskite structured (ABO3) lithium lanthanum titanate (LLTO) is a successful electrolyte reported by several scientists in the recent past. It is believed that intercalation and de-intercalation of Li ions inside solid electrolyte can be improved by increasing the porosity of the material. Hence in this research work, an attempt is made to increase the porosity of the LLTO electrolyte by rapid-microwave synthesis route. The microwave prepared LLTO is compared with the sol-gel synthesized LLTO. The prepared samples are analyzed with XRD, SEM, PL and cyclic Voltammetry studies. Morphological analysis proves that microwave synthesized LLTO contains much pores compared to the Sol-gel LLTO. A remarkable difference in its electrochemical property is also demonstrated and analysed with cyclic voltammetric studies and the results are presented.

  18. A multi-scale study of the adsorption of lanthanum on the (110) surface of tungsten

    NASA Astrophysics Data System (ADS)

    Samin, Adib J.; Zhang, Jinsuo

    2016-07-01

    In this study, we utilize a multi-scale approach to studying lanthanum adsorption on the (110) plane of tungsten. The energy of the system is described from density functional theory calculations within the framework of the cluster expansion method. It is found that including two-body figures up to the sixth nearest neighbor yielded a reasonable agreement with density functional theory calculations as evidenced by the reported cross validation score. The results indicate that the interaction between the adsorbate atoms in the adlayer is important and cannot be ignored. The parameterized cluster expansion expression is used in a lattice gas Monte Carlo simulation in the grand canonical ensemble at 773 K and the adsorption isotherm is recorded. Implications of the obtained results for the pyroprocessing application are discussed.

  19. Large area directly heated lanthanum hexaboride cathode structure having predetermined emission profile

    DOEpatents

    Leung, Ka-Ngo; Gordon, Keith C.; Kippenham, Dean O.; Purgalis, Peter; Moussa, David; Williams, Malcom D.; Wilde, Stephen B.; West, Mark W.

    1989-01-01

    A large area directly heated lanthanum hexaboride (LaB.sub.6) cathode system (10) is disclosed. The system comprises a LaB.sub.6 cathode element (11) generally circular in shape about a central axis. The cathode element (11) has a head (21) with an upper substantially planar emission surface (23), and a lower downwardly and an intermediate body portion (26) which diminishes in cross-section from the head (21) towards the base (22) of the cathode element (11). A central rod (14) is connected to the base (22) of the cathode element (11) and extends along the central axis. Plural upstanding spring fingers (37) are urged against an outer peripheral contact surface (24) of the head end (21) to provide a mechanical and electrical connection to the cathode element (11).

  20. Spectroscopic properties of Ho3+/Yb3+ codoped lanthanum aluminum germanate glasses with efficient energy transfer

    NASA Astrophysics Data System (ADS)

    Zhang, Qiang; Chen, Guorong; Zhang, Guang; Qiu, Jianrong; Chen, Danping

    2009-12-01

    Ho3+/Yb3+ codoped lanthanum aluminum germanate glasses are prepared simply by melt-quenching method. The 2 μm emission characteristic and energy transfer from Yb3+ to Ho3+ upon excitation of a conventional 980 nm laser diode is investigated and the energy transfer efficiency is as high as 83%. The spectroscopic parameters are calculated based on Judd-Ofelt (J-O) theory, the intensity parameters Ω2, Ω4, and Ω6 are 4.44, 1.92, and 1.11×10-20 cm2, respectively. The transition probabilities and branching ratios are also estimated by using the J-O parameters. Beer-Lambert and Fuchtbauer-Ladenburg theories are applied to calculate the absorption, emission, and gain cross sections of I57→I58 transition.

  1. Electric field induced phase transition of antiferroelectric lead lanthanum zirconate titanate stannate ceramics

    SciTech Connect

    Park, S.; Pan, M.; Markowski, K.; Yoshikawa, S.; Cross, L.E.

    1997-08-01

    The electric field induced phase transition behavior of lead lanthanum zirconate titanate stannate (PLZTS) ceramics was investigated. PLZTS undergoes a tetragonal antiferroelectric (AFE{sub Tet}) to rhombohedral ferroelectric (FE{sub Rh}) phase transition with the application of an electric field. The volume increase associated with this antiferroelectric (AFE){endash}ferroelectric (FE) phase transition plays an important role with respect to actuator applications. This volume increase involves an increase in both transverse and longitudinal strains. The E field at which the transverse strain increases is accompanied by an abrupt jump in polarization. The longitudinal strain, however, lags behind this polarization jump exhibiting a slight decrease at the onset of phase switching. This decoupling was related to the preferentially oriented AFE domain configuration, with its tetragonal c-axis perpendicular to the applied electric field. It is suggested that phase switching involves multiple steps involving both structural transformation and domain reorientation. {copyright} {ital 1997 American Institute of Physics.}

  2. Effect of R(3+) ions on the structure and properties of lanthanum borate glasses

    NASA Technical Reports Server (NTRS)

    Chakraborty, I. N.; Day, D. E.

    1985-01-01

    The present investigation of glass formation in the (mole percent) systems 25La2O3 (x)R2O3 (75-x)B2O3, where R = Al, Ga, and (25-x)La2O3 (x)Ln2O3 75B2O3, where Ln = Gd, Er, Y, notes that up to 25 mol pct Al2O3 or Ga2O3 can be substituted for B2O3, while no more than about 5 mol pct Ln2O3, substituted for La2O3, caused macro-phase separation. The substitution of either R2O3 or Ln2O3 in the lanthanum borate system changes the separation distance between adjacent B3O6 chains. The effect of this structural change on the molar volume, transformation temperature, thermal expansion coefficient, and transformation-range viscosity is discussed.

  3. Data for effects of lanthanum complex on the thermo-oxidative aging of natural rubber.

    PubMed

    Zheng, Wei; Liu, Li; Zhao, Xiuying; He, Jingwei; Wang, Ao; Chan, Tung W; Wu, Sizhu

    2015-12-01

    Novel mixed antioxidants composed of antioxidant IPPD and lanthanum (La) complex were added as a filler to form natural rubber (NR) composites. By mechanical testing, Fourier transform infrared spectroscopy with attenuated total reflectance (FTIR-ATR) and thermogravimetric analysis (TGA), a string of data, including the mechanical properties, the variation of internal groups and the thermal and thermo-oxidative decompositions of NR, was presented in this data article. The data accompanying its research article [1] studied the thermo-oxidative aging properties of NR in detail. The density function theoretical (DFT) calculations were also used as an assistant to study the thermo-oxidative aging mechanism of NR. The data revealed that this new rare-earth antioxidant could indeed enhance the thermo-oxidative aging resistance of NR, which is associated with its different function mechanism from that of the pure antioxidant IPPD.

  4. Lanthanum gallate substrates for epitaxial high-temperature superconducting thin films

    SciTech Connect

    Sandstrom, R.L.; Giess, E.A.; Gallagher, W.J.; Segmueller, A.; Cooper, E.I.; Chisholm, M.F.; Gupta, A.; Shinde, S.; Laibowitz, R.B.

    1988-11-07

    We demonstrate that lanthanum gallate (LaGaO/sub 3/) has considerable potential as an electronic substrate material for high-temperature superconducting films. It provides a good lattice and thermal expansion match to YBa/sub 2/Cu/sub 3/O/sub 7-//sub x/, can be grown in large crystal sizes, is compatible with high-temperature film processing, and has a reasonably low dielectric constant (epsilonapprox. =25) and low dielectric losses. Epitaxial YBa/sub 2/Cu/sub 3/O/sub 7-//sub x/ films grown on LaGaO/sub 3/ single-crystal substrates by three techniques have zero resistance between 87 and 91 K.

  5. Photoemission spectroscopy study of the lanthanum lutetium oxide/silicon interface

    SciTech Connect

    Nichau, A.; Schnee, M.; Schubert, J.; Bernardy, P.; Hollaender, B.; Buca, D.; Mantl, S.; Besmehn, A.; Breuer, U.; Rubio-Zuazo, J.; Castro, G. R.; Muecklich, A.; Borany, J. von

    2013-04-21

    Rare earth oxides are promising candidates for future integration into nano-electronics. A key property of these oxides is their ability to form silicates in order to replace the interfacial layer in Si-based complementary metal-oxide field effect transistors. In this work a detailed study of lanthanum lutetium oxide based gate stacks is presented. Special attention is given to the silicate formation at temperatures typical for CMOS processing. The experimental analysis is based on hard x-ray photoemission spectroscopy complemented by standard laboratory experiments as Rutherford backscattering spectrometry and high-resolution transmission electron microscopy. Homogenously distributed La silicate and Lu silicate at the Si interface are proven to form already during gate oxide deposition. During the thermal treatment Si atoms diffuse through the oxide layer towards the TiN metal gate. This mechanism is identified to be promoted via Lu-O bonds, whereby the diffusion of La was found to be less important.

  6. Nonuniform paramagnetic state in nonstoichiometric lanthanum manganites La1- x Mn1- y O3

    NASA Astrophysics Data System (ADS)

    Arbuzova, T. I.; Naumov, S. V.

    2016-06-01

    The magnetic properties of nonstoichiometric lanthanum manganites La1- x Mn1- y O3 have been studied in the temperature range 80 K < T < 650 K. The Curie temperature T C changes nonmonotonically as the number of Mn4+ ions increases. In the paramagnetic region, there exist isolated Mn ions and magnetic polarons which can be conserved to T ⩽ 4 T C, independent of the lattice symmetry. In the T C < T < T pol region, the temperature dependences of the magnetic susceptibility are nonlinear and can be described by the Curie law with a temperature-dependent Curie constant C. The sample has been prepared having a composition near the O' → O structural transition; the spontaneous magnetization of the sample at T ⩽ 1.6 T C is associated to correlated polarons forming due to the double exchange in chains of the E-type antiferromagnetic phase.

  7. Processing and structural properties of random oriented lead lanthanum zirconate titanate thin films

    SciTech Connect

    Araújo, E.B.; Nahime, B.O.; Melo, M.; Dinelli, F.; Tantussi, F.; Baschieri, P.; Fuso, F.; Allegrini, M.

    2015-01-15

    Highlights: • Pyrochlore phase crystallizes near the bottom film-electrode interface. • PLZT films show a non-uniform microstrain and crystallite size in depth profile. • Complex grainy structure leads to different elastic modulus at the nanoscale. - Abstract: Polycrystalline lead lanthanum zirconate titanate (PLZT) thin films have been prepared by a polymeric chemical route to understand the mechanisms of phase transformations and map the microstructure and elastic properties at the nanoscale in these films. X-ray diffraction, atomic force microscopy (AFM) and ultrasonic force microscopy (UFM) have been used as investigative tools. On one side, PLZT films with mixed-phase show that the pyrochlore phase crystallizes predominantly in the bottom film-electrode interface while a pure perovskite phase crystallizes in top film surface. On the contrary, pyrochlore-free PLZT films show a non-uniform microstrain and crystallite size along the film thickness with a heterogeneous complex grainy structure leading to different elastic properties at nanoscale.

  8. Dielectric and Ferroelectric Properties of Lead Lanthanum Zirconate Titanate Thin Films for Capacitive Energy Storage

    NASA Astrophysics Data System (ADS)

    Tong, Sheng

    As the increasing requirement of alternative energy with less pollution influence and higher energy efficient, new energy source and related storage methods are hot topic nowadays. Capacitors that supply high instant power are one of the keys in this application for both economic and functional design aspects. To lower the cost and increases the volumetric efficiency and reliability, relaxor thin films are considered as one of the candidates of the next generation capacitors. The research mainly focuses on dielectric and ferroelectric properties of lead lanthanum zirconate titanate or Pb1-xLax(ZryTi1-y)O3 (PLZT, x/y/1-y) relaxor thin films deposited on silicon (Si) and nickel (Ni) substrates in a range of thickness with different bottom electrodes, e.g. Platinum (Pt) and LaNiO3 (LNO). The final fabricated PLZT film capacitors will show strong potential for the energy storage application. The method adopted is the acetic acid assisted sol-gel deposition for the PLZT thin films. The wet chemical process is cost-effective and easily to scale up for plant/industrial products. We investigated the different bottom electrode/substrate influence in structure, microstructure, phases/defects, and heat-treatment conditions to achieve the optimized PLZT thin films. Issues of basic physical size effects in the PLZT thin films were also investigated, including thickness effects in the dielectric and ferroelectric properties of the films in a wide range of temperatures, the phase transition of the thin-film relaxors, lanthanum content effect, electrode-dielectric junction, misfit strain effect, etc. Based on the results and analysis, optimum PLZT film capacitors can be determined of proper substrate/electrode/dielectric that achieves the desired dielectric properties required for different applications, especially a more cost-effective method to develop volumetrically efficient capacitors with high charge density, energy density, dielectric breakdown strength, energy storage

  9. Synthesis of nanoparticles of barium lanthanum hafnium oxide by a modified combustion process.

    PubMed

    John, Asha M; Jose, R; Divakar, R; Koshy, J

    2002-02-01

    Barium lanthanum hafnium oxide, a complex perovskite ceramic, has been synthesized as nanoparticles by a modified combustion process for the first time. The Ba, La, and Hf ions required for the formation of Ba2LaHfO5.5 were obtained in solution by dissolving in boiling nitric acid a stoichiometric mixture of BaCO3, La2O3, and HfO2 that had been heated at 1200 degrees C for 4 h. By complexing the ions with citric acid and using ammonia as fuel, it was possible to get Ba2LaHfO5.5 as nanoparticles in a single-step combustion process. The powder obtained by the present combustion process was characterized by X-ray diffraction, BET surface area analysis, differential thermal analysis, thermogravimetric analysis, infrared spectroscopy, and scanning and high-resolution transmission electron microscopy. According to the results of X-ray and electron diffraction, the powder synthesized through the combustion process showed single-phase barium lanthanum hafnium oxide. The transmission electron microscopic investigations showed a grain size of 42 nm, with a standard deviation of 8 nm. The nanoparticles of Ba2LaHfO5.5 synthesized by the present combustion technique could be sintered to > 97% of the theoretical density at a relatively low temperature of 1425 degrees C. Scanning electron microscopic studies on the sintered Ba2LaHfO5.5 samples showed that the final grain size of the sintered specimen was < 500 nm.

  10. Thermionic emission and surface composition of the lanthanum-boron and yttrium-boron systems

    SciTech Connect

    Jaskie, J.E.

    1981-12-01

    At thermionic temperatures, a difference between bulk and surface composition will exist unless the interior happens to be at the congruently vaporizing composition (CVC). Vaporization rates from the surface compete with diffusion rates in the bulk to cause this difference. The surface composition will tend toward the congruently vaporizing composition which is YB/sub 4/ in the yttrium-Boron system and LaB/sub 6/ in the Lanthanum-Boron system. The CVC is also a function of temperature and may vary slightly for the same bulk composition at different temperature. Four Yttrium-Boron (Y-B) compounds, YB/sub 2/ /sub 5/, YB/sub 5/, YB/sub 6/ /sub 4/, YB/sub 14/ and three Lanthanum-Boron (La-B) compounds, LaB/sub 6/ /sub 01/, LaB/sub 8/ /sub 5/ and LaB/sub 5/ /sub 9/ were tested in a variable spacing vacuum emission system with a guard assembly. Emitted current measurements were made with interelctrode potentials between 250 and 1400 volts. Schottky plots were used to extrapolate the zero field currents. When a sample is taken from equilibrium to a new temperature, a definite time lag appears while vaporization rates change to bring about a new equilibrium surface composition. This manifests itself in the recorded emission currents. After thermal equilibrium is reached a distinct change is seen in emission currents. A higher density is measured, reflecting the emission of a surface that has been raised to a higher temperature. But with time, at this temperature, the surface reacts through vaporization and a new composition appears that is closer to the congruently vaporizing composition, and hence, has a work function nearer that of the CVC.

  11. The combination of lanthanum chloride and the calcimimetic calindol delays the progression of vascular smooth muscle cells calcification

    SciTech Connect

    Ciceri, Paola; Volpi, Elisa; Brenna, Irene; Elli, Francesca; Borghi, Elisa; Brancaccio, Diego; Cozzolino, Mario

    2012-02-24

    Highlights: Black-Right-Pointing-Pointer Lanthanum reduces the progression of high phosphate-induced calcium deposition. Black-Right-Pointing-Pointer Calcium receptor agonists and the calcimimetic calindol reduce calcium deposition. Black-Right-Pointing-Pointer Lanthanum and calindol cooperate on reducing calcium deposition. Black-Right-Pointing-Pointer Lanthanum and calindol may interact with the same receptor. -- Abstract: Phosphate (Pi)-binders are commonly used in dialysis patients to control high Pi levels, that associated with vascular calcification (VC). The aim of this study was to investigate the effects of lanthanum chloride (LaCl{sub 3}) on the progression of high Pi-induced VC, in rat vascular smooth muscle cells (VSMCs). Pi-induced Ca deposition was inhibited by LaCl{sub 3}, with a maximal effect at 100 {mu}M (59.0 {+-} 2.5% inhibition). Furthermore, we studied the effects on VC of calcium sensing receptor (CaSR) agonists. Gadolinium chloride, neomycin, spermine, and the calcimimetic calindol significantly inhibited Pi-induced VC (55.9 {+-} 2.2%, 37.3 {+-} 4.7%, 30.2 {+-} 5.7%, and 63.8 {+-} 5.7%, respectively). To investigate the hypothesis that LaCl{sub 3} reduces the progression of VC by interacting with the CaSR, we performed a concentration-response curve of LaCl{sub 3} in presence of a sub-effective concentration of calindol (10 nM). Interestingly, this curve was shifted to the left (IC{sub 50} 9.6 {+-} 2.6 {mu}M), compared to the curve in the presence of LaCl{sub 3} alone (IC{sub 50} 19.0 {+-} 4.8 {mu}M). In conclusion, we demonstrated that lanthanum chloride effectively reduces the progression of high phosphate-induced vascular calcification. In addition, LaCl{sub 3} cooperates with the calcimimetic calindol in decreasing Ca deposition in this in vitro model. These results suggest the potential role of lanthanum in the treatment of VC induced by high Pi.

  12. Studies on intracellular transport of secretory proteins in the rat exocrine pancreas. III. Effect of cobalt, lanthanum and antimycin A.

    PubMed

    Bieger, W; Seybold, J; Kern, H F

    1975-11-28

    The effects of cobalt and lanthanum on the secretory process of the rat exocrine pancreas was studied in vitro using isolated pancreatic lobules. Cobalt in concentrations between 10(-3) to 10(-5) M has no effect on the rate of protein synthesis, intracellular transport, or discharge of zymogen granules, if the total population of stored granules is considered. It has, however, a marked effect on the release of newly packed zymogen granules which are formed during incubation in 10(-3) M CoC1(2). Determination of specific radioactivity in amylase released under the stimulation of 5X10(-6) M carbamylcholine and of total proteins retained in the zymogen granule fraction during stimulation indicate that granules formed during incubation in CoC1(2) are excluded from discharge. Lanthanum, on the other hand, has a differential effect on protein synthesis, intracellular transport, and discharge. Incorporation of tritiated leucine into TCA-precipitable proteins is inhibited by 50% at 10(-3) M LaC1(3). Intracellular transport as studied by cell fractionation is not changed during the first 35 min post pulse but is delayed from then on. This late effect is more pronounced if pancreatic lobules are preincubated for 60 min in 10(-3) M LaC1(3). Discharge of amylase and newly synthesized proteins is inhibited dose-dependently up to 80% by 10(-3) M LaC1(3). The effects of both cobalt and lanthanum are not due to an inhibition of cellular respiration. Comparison of these results with the inhibitory action of antimycin A between 10(-4) to 10(-8) M concentrations reveals a dose-dependent diminution of the rate of protein synthesis and intracellular transport, while discharge of granules is less energy dependent. The fine structural appearance of pancreatic lobules after 3 hrs incubation in 10(-3) M CoC1(2) is not altered, while in 5X10(-3) and 10(-3) M lanthanum acinar lumina are enlarged and the apical cytoplasm contains large vacuoles. At the highest concentration of lanthanum a

  13. Simulation of an erbium-doped chalcogenide micro-disk mid-infrared laser source.

    PubMed

    Al Tal, Faleh; Dimas, Clara; Hu, Juejun; Agarwal, Anu; Kimerling, Lionel C

    2011-06-20

    The feasibility of mid-infrared (MIR) lasing in erbium-doped gallium lanthanum sulfide (GLS) micro-disks was examined. Lasing condition at 4.5 µm signal using 800 nm pump source was simulated using rate equations, mode propagation and transfer matrix formulation. Cavity quality (Q) factors of 1.48 × 10(4) and 1.53 × 10(6) were assumed at the pump and signal wavelengths, respectively, based on state-of-the-art chalcogenide micro-disk resonator parameters. With an 80 µm disk diameter and an active erbium concentration of 2.8 × 10(20) cm(-3), lasing was shown to be possible with a maximum slope efficiency of 1.26 × 10(-4) and associated pump threshold of 0.5 mW.

  14. Gene doping in sports.

    PubMed

    Unal, Mehmet; Ozer Unal, Durisehvar

    2004-01-01

    Gene or cell doping is defined by the World Anti-Doping Agency (WADA) as "the non-therapeutic use of genes, genetic elements and/or cells that have the capacity to enhance athletic performance". New research in genetics and genomics will be used not only to diagnose and treat disease, but also to attempt to enhance human performance. In recent years, gene therapy has shown progress and positive results that have highlighted the potential misuse of this technology and the debate of 'gene doping'. Gene therapies developed for the treatment of diseases such as anaemia (the gene for erythropoietin), muscular dystrophy (the gene for insulin-like growth factor-1) and peripheral vascular diseases (the gene for vascular endothelial growth factor) are potential doping methods. With progress in gene technology, many other genes with this potential will be discovered. For this reason, it is important to develop timely legal regulations and to research the field of gene doping in order to develop methods of detection. To protect the health of athletes and to ensure equal competitive conditions, the International Olympic Committee, WADA and International Sports Federations have accepted performance-enhancing substances and methods as being doping, and have forbidden them. Nevertheless, the desire to win causes athletes to misuse these drugs and methods. This paper reviews the current status of gene doping and candidate performance enhancement genes, and also the use of gene therapy in sports medicine and ethics of genetic enhancement.

  15. Neoproterozoic chromite-bearing high-Mg diorites in the western part of the Jiangnan orogen, southern China: Geochemistry, petrogenesis and tectonic implications

    NASA Astrophysics Data System (ADS)

    Chen, Xin; Wang, Di; Wang, Xiao-Lei; Gao, Jian-Feng; Shu, Xu-Jie; Zhou, Jin-Cheng; Qi, Liang

    2014-07-01

    High-Mg diorites were discovered in the southern part of the ca. 830 Ma Dongma Pluton, northern Guangxi Province of southern China. The diorites (SiO2 = 59-65 wt%) are characterized by high MgO (6.7-8.9 wt%) contents and Mg-number [Mg# = 100 × Mg/(Mg + Fe)] (69-73), in contrary to the associated medium-Mg (MgO = 3.4-3.8 wt%, Mg# = 59-63) granodiorites in the Dongma main body and the low-Mg (MgO = 1.4-1.9 wt%, Mg# = 46-51) granodiorites in the Bendong Pluton to the north. Moreover, the high-Mg diorites show surprisingly high Cr (595-640 ppm) and Ni (171-194 ppm) concentrations, which are beyond the ranges of most coeval mafic rocks in the study area. Correspondingly, chromite crystals were separated from the high-Mg diorites and some of the medium-Mg granodiorites, and they show high Cr# [100 × Cr/(Cr + Al)] (average of 75), but low Mg# (0.34-2.51) and low Fe3 +. The decoupling of Cr# and Mg# and the existence of quartz + apatite mineral inclusion in chromites suggest Mg-Fe exchange that may be facilitated by the disequilibrium resulted from magma mixing. The high-Mg diorites show low La/Yb (6.8-8.5) and Sr/Y (2.1-3.1) ratios, significant negative anomalies of Nb and Ti and positive anomaly of Pb, resembling the Setouchi high-Mg andesites, despite of their relatively low Sr (71-100 ppm). All of the studied diorites and granodiorites show enriched Nd isotope compositions, with εNd(t) values (- 3.2 to - 5.9) a bit higher than some of the associated mafic rocks. Some of the high-Mg diorites show whole-rock εHf(t) (- 6.0 to - 6.2) coupled with Nd isotopes, similar to the associated mafic-ultramafic rocks in northern Guangxi, suggesting the metasomatism by melts of subducting sediments in the mantle source. Whereas, others show decoupled Nd-Hf isotopes that are similar to the medium- and low-Mg granodiorites [εHf(t) = - 1.8 to + 0.05], probably indicating the late magma mixing with granitic magmas at a crustal level for the dioritic magmas. We propose a two

  16. Isoelectronic co-doping

    DOEpatents

    Mascarenhas, Angelo

    2004-11-09

    Isoelectronic co-doping of semiconductor compounds and alloys with deep acceptors and deep donors is used to decrease bandgap, to increase concentration of the dopant constituents in the resulting alloys, and to increase carrier mobilities lifetimes. Group III-V compounds and alloys, such as GaAs and GaP, are isoelectronically co-doped with, for example, N and Bi, to customize solar cells, thermal voltaic cells, light emitting diodes, photodetectors, and lasers on GaP, InP, GaAs, Ge, and Si substrates. Isoelectronically co-doped Group II-VI compounds and alloys are also included.

  17. Role of vacancies, light elements and rare-earth metals doping in CeO2.

    PubMed

    Shi, H; Hussain, T; Ahuja, R; Kang, T W; Luo, W

    2016-01-01

    The magnetic properties and electronic structures of pure, doped and defective cerium oxide (CeO2) have been studied theoretically by means of ab initio calculations based on the density function theory (DFT) with the hybrid HF/DFT technique named PBE0. Carbon (C), nitrogen (N), phosphorus (P), sulphur (S), lanthanum (La) and praseodymium (Pr) doped in CeO2 and CeO2 containing oxygen vacancies (Ov) were considered. Our spin-polarized calculations show that C, N, Pr dopants and Ov defects magnetize the non-magnetic CeO2 in different degree. The optical band gap related to photocatalysis for pure CeO2, corresponding to the ultraviolet region, is reduced obviously by C, N, S, Pr impurities and oxygen vacancies, shifting to the visible region and even further to the infrared range. Especially, N-, S- and Pr-doped CeO2 could be used to photocatalytic water splitting for hydrogen production. As the concentration of Ov increasing up to 5%, the CeO2 exhibits a half-metallic properties. PMID:27554285

  18. Role of vacancies, light elements and rare-earth metals doping in CeO2

    PubMed Central

    Shi, H.; Hussain, T.; Ahuja, R.; Kang, T. W.; Luo, W.

    2016-01-01

    The magnetic properties and electronic structures of pure, doped and defective cerium oxide (CeO2) have been studied theoretically by means of ab initio calculations based on the density function theory (DFT) with the hybrid HF/DFT technique named PBE0. Carbon (C), nitrogen (N), phosphorus (P), sulphur (S), lanthanum (La) and praseodymium (Pr) doped in CeO2 and CeO2 containing oxygen vacancies (Ov) were considered. Our spin-polarized calculations show that C, N, Pr dopants and Ov defects magnetize the non-magnetic CeO2 in different degree. The optical band gap related to photocatalysis for pure CeO2, corresponding to the ultraviolet region, is reduced obviously by C, N, S, Pr impurities and oxygen vacancies, shifting to the visible region and even further to the infrared range. Especially, N-, S- and Pr-doped CeO2 could be used to photocatalytic water splitting for hydrogen production. As the concentration of Ov increasing up to 5%, the CeO2 exhibits a half-metallic properties. PMID:27554285

  19. Role of vacancies, light elements and rare-earth metals doping in CeO2.

    PubMed

    Shi, H; Hussain, T; Ahuja, R; Kang, T W; Luo, W

    2016-08-24

    The magnetic properties and electronic structures of pure, doped and defective cerium oxide (CeO2) have been studied theoretically by means of ab initio calculations based on the density function theory (DFT) with the hybrid HF/DFT technique named PBE0. Carbon (C), nitrogen (N), phosphorus (P), sulphur (S), lanthanum (La) and praseodymium (Pr) doped in CeO2 and CeO2 containing oxygen vacancies (Ov) were considered. Our spin-polarized calculations show that C, N, Pr dopants and Ov defects magnetize the non-magnetic CeO2 in different degree. The optical band gap related to photocatalysis for pure CeO2, corresponding to the ultraviolet region, is reduced obviously by C, N, S, Pr impurities and oxygen vacancies, shifting to the visible region and even further to the infrared range. Especially, N-, S- and Pr-doped CeO2 could be used to photocatalytic water splitting for hydrogen production. As the concentration of Ov increasing up to 5%, the CeO2 exhibits a half-metallic properties.

  20. Role of vacancies, light elements and rare-earth metals doping in CeO2

    NASA Astrophysics Data System (ADS)

    Shi, H.; Hussain, T.; Ahuja, R.; Kang, T. W.; Luo, W.

    2016-08-01

    The magnetic properties and electronic structures of pure, doped and defective cerium oxide (CeO2) have been studied theoretically by means of ab initio calculations based on the density function theory (DFT) with the hybrid HF/DFT technique named PBE0. Carbon (C), nitrogen (N), phosphorus (P), sulphur (S), lanthanum (La) and praseodymium (Pr) doped in CeO2 and CeO2 containing oxygen vacancies (Ov) were considered. Our spin-polarized calculations show that C, N, Pr dopants and Ov defects magnetize the non-magnetic CeO2 in different degree. The optical band gap related to photocatalysis for pure CeO2, corresponding to the ultraviolet region, is reduced obviously by C, N, S, Pr impurities and oxygen vacancies, shifting to the visible region and even further to the infrared range. Especially, N-, S- and Pr-doped CeO2 could be used to photocatalytic water splitting for hydrogen production. As the concentration of Ov increasing up to 5%, the CeO2 exhibits a half-metallic properties.

  1. Studies on Ca2+-Doped CeBr3 Scintillating Materials

    SciTech Connect

    Guss, P.; Foster, M. E.; Wong, B. M.; Doty, F. P.; Shah, K.; Squillante, M. R.; Shirwadkar, U.; Hawrami, R.; Tower, J.; Yuan, D.

    2013-09-01

    Despite the outstanding scintillation performance characteristics of cerium tribromide (CeBr3) and cerium-activated lanthanum tribromide (LaBr3:Ce), their commercial availability and application is limited due to the difficulties of growing large, crack-free single crystals from these fragile materials. The objective of this investigation was to employ aliovalent doping to increase crystal strength while maintaining the optical properties of the crystal. One divalent dopant (Ca2+) was investigated as a dopant to strengthen CeBr3 without negatively impacting scintillation performance. Ingots containing nominal concentrations of 1.9% of the Ca2+ dopant were grown. Preliminary scintillation measurements are presented for this aliovalently doped scintillator. Ca2+-doped CeBr3 exhibited little or no change in the peak fluorescence emission for 371 nm optical excitation for CeBr3. The structural, electronic, and optical properties of CeBr3 crystals were investigated using the density functional theory within generalized gradient approximation. The calculated lattice parameters are in good agreement with the experimental data. The energy band structures and density of states were obtained. The optical properties of CeBr3, including the dielectric function, were calculated.

  2. Studies on Ca2+-Doped CeBr3 Scintillating Materials

    SciTech Connect

    Guss, P.; Foster, M. E.; Wong, B. M.; Doty, F. P.; Shah, K.; Squillante, M.; Glodo, J.; Yuan, D.

    2013-07-03

    Despite the outstanding scintillation performance characteristics of cerium tribromide (CeBr3) and cerium-activated lanthanum tribromide (LaBr3:Ce), their commercial availability and application is limited due to the difficulties of growing large, crack-free single crystals from these fragile materials. The objective of this investigation was to employ aliovalent doping to increase crystal strength while maintaining the optical properties of the crystal. One divalent dopant (Ca2+) was investigated as a dopant to strengthen CeBr3 without negatively impacting scintillation performance. Ingots containing nominal concentrations of 1.9% of the Ca2+ dopant were grown. Preliminary scintillation measurements are presented for this aliovalently doped scintillator. Ca2+-doped CeBr3 exhibited little or no change in the peak fluorescence emission for 371 nm optical excitation for CeBr3. The structural, electronic, and optical properties of CeBr3 crystals were investigated using the density functional theory within generalized gradient approximation. The calculated lattice parameters are in good agreement with the experimental data. The energy band structures and density of states were obtained. The optical properties of CeBr3, including the dielectric function, were calculated.

  3. Meteorology drives ambient air quality in a valley: a case of Sukinda chromite mine, one among the ten most polluted areas in the world.

    PubMed

    Mishra, Soumya Ranjan; Pradhan, Rudra Pratap; Prusty, B Anjan Kumar; Sahu, Sanjat Kumar

    2016-07-01

    The ambient air quality (AAQ) assessment was undertaken in Sukinda Valley, the chromite hub of India. The possible correlations of meteorological variables with different air quality parameters (PM10, PM2.5, SO2, NO2 and CO) were examined. Being the fourth most polluted area in the globe, Sukinda Valley has always been under attention of researchers, for hexavalent chromium contamination of water. The monitoring was carried out from December 2013 through May 2014 at six strategic locations in the residential and commercial areas around the mining cluster of Sukinda Valley considering the guidelines of Central Pollution Control Board (CPCB). In addition, meteorological parameters viz., temperature, relative humidity, wind speed, wind direction and rainfall, were also monitored. The air quality data were subjected to a general linear model (GLM) coupled with one-way analysis of variance (ANOVA) test for testing the significant difference in the concentration of various parameters among seasons and stations. Further, a two-tailed Pearson's correlation test helped in understanding the influence of meteorological parameters on dispersion of pollutants in the area. All the monitored air quality parameters varied significantly among the monitoring stations suggesting (i) the distance of sampling location to the mine site and other allied activities, (ii) landscape features and topography and (iii) meteorological parameters to be the forcing functions. The area was highly polluted with particulate matters, and in most of the cases, the PM level exceeded the National Ambient Air Quality Standards (NAAQS). The meteorological parameters seemed to play a major role in the dispersion of pollutants around the mine clusters. The role of wind direction, wind speed and temperature was apparent in dispersion of the particulate matters from their source of generation to the surrounding residential and commercial areas of the mine.

  4. Detrital magnetite and chromite in Jack Hills quartzite cobbles: Further evidence for the preservation of primary magnetizations and new insights into sediment provenance

    NASA Astrophysics Data System (ADS)

    Dare, Matthew S.; Tarduno, John A.; Bono, Richard K.; Cottrell, Rory D.; Beard, James S.; Kodama, Kenneth P.

    2016-10-01

    The magnetization of zircons from sedimentary rocks of the Jack Hills (Yilgarn Craton, Western Australia) provide evidence for a Hadean to Paleoarchean geodynamo, 4.0 to 4.2 billion years old. These magnetizations pass a microconglomerate test, attesting to the fidelity of Jack Hills zircons as recorders of these most ancient magnetic signals. The lack of pervasive remagnetization of the Jack Hills is also documented through a positive conglomerate test conducted on cobble-sized clasts. A key element of the latter test is the preservation of a high unblocking temperature magnetization that can survive peak metamorphic temperatures. Rock magnetic studies suggest the mineral carrier is magnetite. Herein, we investigate the magnetic mineral carriers in cobble samples through scanning electron microscope and microprobe analyses, conduct an inter-laboratory paleomagnetic study to evaluate sensitivities required to evaluate the weak magnetizations carried by the Jack Hills sediments, and assess provenance information constrained by the opaque minerals. These data confirm magnetite as a detrital phase and the presence of high unblocking temperature magnetizations, further supporting the posit that the Jack Hills sediments can preserve primary magnetic signatures. We note that some of these magnetizations are near the measurement resolution of standard cryogenic magnetometers and thus exacting laboratory procedures are required to uncover these signals. In addition to magnetite, the cobbles contain an assemblage of Mg poor Cr-Fe chromites, Ni-sulfides and pyrrhotite that suggest a source in a layered intrusion different from the granitoid source of the zircons. Any Hadean rock fragment in these sediments, if present, remains elusive.

  5. Meteorology drives ambient air quality in a valley: a case of Sukinda chromite mine, one among the ten most polluted areas in the world.

    PubMed

    Mishra, Soumya Ranjan; Pradhan, Rudra Pratap; Prusty, B Anjan Kumar; Sahu, Sanjat Kumar

    2016-07-01

    The ambient air quality (AAQ) assessment was undertaken in Sukinda Valley, the chromite hub of India. The possible correlations of meteorological variables with different air quality parameters (PM10, PM2.5, SO2, NO2 and CO) were examined. Being the fourth most polluted area in the globe, Sukinda Valley has always been under attention of researchers, for hexavalent chromium contamination of water. The monitoring was carried out from December 2013 through May 2014 at six strategic locations in the residential and commercial areas around the mining cluster of Sukinda Valley considering the guidelines of Central Pollution Control Board (CPCB). In addition, meteorological parameters viz., temperature, relative humidity, wind speed, wind direction and rainfall, were also monitored. The air quality data were subjected to a general linear model (GLM) coupled with one-way analysis of variance (ANOVA) test for testing the significant difference in the concentration of various parameters among seasons and stations. Further, a two-tailed Pearson's correlation test helped in understanding the influence of meteorological parameters on dispersion of pollutants in the area. All the monitored air quality parameters varied significantly among the monitoring stations suggesting (i) the distance of sampling location to the mine site and other allied activities, (ii) landscape features and topography and (iii) meteorological parameters to be the forcing functions. The area was highly polluted with particulate matters, and in most of the cases, the PM level exceeded the National Ambient Air Quality Standards (NAAQS). The meteorological parameters seemed to play a major role in the dispersion of pollutants around the mine clusters. The role of wind direction, wind speed and temperature was apparent in dispersion of the particulate matters from their source of generation to the surrounding residential and commercial areas of the mine. PMID:27289470

  6. Performance of a Lanthanum Bromide Detector and a New Conception Collimator for Radiopharmaceuticals Molecular Imaging in Oncology

    SciTech Connect

    Pani, Roberto; Pellegrini, Rosanna; Bennati, Paolo; Cinti, Maria Nerina; Scafe, Raffaele; De Vincentis, Giuseppe; Navarria, Francesco; Moschini, Giuliano; Rossi, Paolo; Cencelli, Valentino Orsolini; De Notaristefani, Francesco

    2009-03-10

    We have realized and tested a new-design compact gamma camera for high resolution SPET (Single Photon Emission Tomography), and small animals' radio-pharmaceutical molecular imaging. The camera is based on a 'continuous' Lanthanum tri-Bromide crystal, and a new Low Energy (LE) collimator. The crystal is interfaced to a 2x2 array of Hamamatsu-H8500 position sensitive photo-multipliers. The lead collimator features parallel hexagonal 1.0 mm holes, 18 mm length, 0.2 mm septa and 10x10 cm{sup 2} detection area. It was newly designed to fully exploit the high spatial resolution a Lanthanum crystal may provide. To better evaluate its role, we have compared our camera to three other systems with similar crystals and photomultipliers, but employing traditional collimators, either pinhole or parallel. The new camera seems to be complementary to pinhole systems and shows a very attractive trade-off between spatial resolution and detection area.

  7. Performance of a Lanthanum Bromide Detector and a New Conception Collimator for Radiopharmaceuticals Molecular Imaging in Oncology

    NASA Astrophysics Data System (ADS)

    Pani, Roberto; Pellegrini, Rosanna; Bennati, Paolo; Cinti, Maria Nerina; Scafè, Raffaele; De Vincentis, Giuseppe; Navarria, Francesco; Moschini, Giuliano; Cencelli, Valentino Orsolini; De Notaristefani, Francesco; Rossi, Paolo

    2009-03-01

    We have realized and tested a new-design compact gamma camera for high resolution SPET (Single Photon Emission Tomography), and small animals' radio-pharmaceutical molecular imaging. The camera is based on a "continuous" Lanthanum tri-Bromide crystal, and a new Low Energy (LE) collimator. The crystal is interfaced to a 2×2 array of Hamamatsu-H8500 position sensitive photo-multipliers. The lead collimator features parallel hexagonal 1.0 mm holes, 18 mm length, 0.2 mm septa and 10×10 cm2 detection area. It was newly designed to fully exploit the high spatial resolution a Lanthanum crystal may provide. To better evaluate its role, we have compared our camera to three other systems with similar crystals and photomultipliers, but employing traditional collimators, either pinhole or parallel. The new camera seems to be complementary to pinhole systems and shows a very attractive trade-off between spatial resolution and detection area.

  8. Experimental investigation on the concentration and voltage effects on the characteristics of deposited magnesium-lanthanum powder

    NASA Astrophysics Data System (ADS)

    Sahli, M.; Chetehouna, K.; Faubert, F.; Bariki, C.; Gascoin, N.; Bellel, N.

    2015-06-01

    In this paper, magnesium-lanthanum powders were synthesized by an electrodeposition technique using an aqueous solution, based on magnesium chloride hexahydrate and lanthanum nitrate for different values of voltage and La weight percentage. A copper cathode plate and a tungsten thread anode were used for the preparation of the Mg-La layers. The as-deposited powders were characterized by energy dispersive spectroscopy (EDS) to determine the chemical composition, scanning electron microscope to describe the morphology, X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectra in order to define the chemical structure. EDS analyses indicate the presence of three elements (Mg, La and O) in the different deposited layers, and the major one is O (51-74.2 at.%). The two other elements, Mg and La, are, respectively, ranked 2 and 3 in the different powders. Morphological description reveals the formation of heterogeneous chemical structures on the surfaces of specimens. They are characterized by aggregates with different sizes. The dark aggregates are associated with magnesium, and the bright ones are attributed to lanthanum. X-ray results showed the existence of two distinct phases in the obtained deposits which are magnesium hydroxide (Mg(OH)2) and lanthanum hydroxide (La(OH)3). FTIR analyses confirm the presence of the two phases identified in XRD diffractograms, and they can be exhibited by clear peaks. In the studied ranges of voltage and La weight percentage, their peak transmittances have non-monotonic behaviors. A design of experiments was used to determine the influence of these two processing parameters and their interaction on the products formation. The parameter effects were ranked as follow: The first was the voltage then the interaction between the two parameters and finally the La content.

  9. De Haas-van Alphen oscillations in the charge-density wave compound lanthanum tritelluride (LaTe3)

    SciTech Connect

    Ru, N.; Borzi, R.A.; Rost, A.; Mackenzie, A.P.; Laverock, J.; Dugdale, S.B.; Fisher, I.R.; /Stanford U., Geballe Lab.

    2009-12-14

    De Haas-van Alphen oscillations were measured in lanthanum tritelluride (LaTe{sub 3}) to probe the partially gapped Fermi surface resulting from charge density wave (CDW) formation. Three distinct frequencies were observed, one of which can be correlated with a FS sheet that is unaltered by CDW formation. The other two frequencies arise from FS sheets that have been reconstructed in the CDW state.

  10. Methods for Doping Detection.

    PubMed

    Ponzetto, Federico; Giraud, Sylvain; Leuenberger, Nicolas; Boccard, Julien; Nicoli, Raul; Baume, Norbert; Rudaz, Serge; Saugy, Martial

    2016-01-01

    Over the past few years, the World Anti-Doping Agency (WADA) has focused its efforts on detecting not only small prohibited molecules, but also larger endogenous molecules such as hormones, in the view of implementing an endocrinological module in the Athlete Biological Passport (ABP). In this chapter, the detection of two major types of hormones used for doping, growth hormone (GH) and endogenous anabolic androgenic steroids (EAASs), will be discussed: a brief historical background followed by a description of state-of-the-art methods applied by accredited anti-doping laboratories will be provided and then current research trends outlined. In addition, microRNAs (miRNAs) will also be presented as a new class of biomarkers for doping detection. PMID:27348309

  11. Influence of environmental factors on the phosphorus adsorption of lanthanum-modified bentonite in eutrophic water and sediment.

    PubMed

    Liu, SheJiang; Li, Jie; Yang, YongKui; Wang, Juan; Ding, Hui

    2016-02-01

    Lanthanum-modified bentonite has potential for wide application in eutrophication control. We investigated P adsorption on a lanthanum-modified bentonite by analysis of adsorption kinetics, equilibrium, and the effect of environmental factors. P adsorption closely followed the pseudo-second-order kinetic model, and the isotherm was well described by the Langmuir model. This adsorbent could effectively immobilize P into the sediment, but the adsorption process was strongly dependent on pH, anions, and low molecular weight organic acids (LMWOAs). P adsorption increased with increasing pH from 0.52 mg P/g at pH 3.0 to 0.93 mg P/g at pH 7.0 with no adsorption at pH 11. P adsorption was strongly inhibited in the presence of anions and three LMWOAs, with P even re-released at high concentrations. These environmental factors should be given significant attention when considering the application of lanthanum-modified bentonite in eutrophication control.

  12. Influence of environmental factors on the phosphorus adsorption of lanthanum-modified bentonite in eutrophic water and sediment.

    PubMed

    Liu, SheJiang; Li, Jie; Yang, YongKui; Wang, Juan; Ding, Hui

    2016-02-01

    Lanthanum-modified bentonite has potential for wide application in eutrophication control. We investigated P adsorption on a lanthanum-modified bentonite by analysis of adsorption kinetics, equilibrium, and the effect of environmental factors. P adsorption closely followed the pseudo-second-order kinetic model, and the isotherm was well described by the Langmuir model. This adsorbent could effectively immobilize P into the sediment, but the adsorption process was strongly dependent on pH, anions, and low molecular weight organic acids (LMWOAs). P adsorption increased with increasing pH from 0.52 mg P/g at pH 3.0 to 0.93 mg P/g at pH 7.0 with no adsorption at pH 11. P adsorption was strongly inhibited in the presence of anions and three LMWOAs, with P even re-released at high concentrations. These environmental factors should be given significant attention when considering the application of lanthanum-modified bentonite in eutrophication control. PMID:26423284

  13. Structural and optical properties of La-doped BaSnO3 thin films grown by PLD

    NASA Astrophysics Data System (ADS)

    James, K. K.; Krishnaprasad, P. S.; Hasna, K.; Jayaraj, M. K.

    2015-01-01

    In this study the structural and optical properties of lanthanum-doped BaSnO3 powder samples and thin films deposited on fused silica were investigaed using laser ablation. Under an oxygen pressure of 5×10-4 mbar, phase pure BaSnO3 films with a lattice constant of 0.417 nm and grain size of 21 nm were prepared at 630 °C. The band gap of BaSnO3 powder sample and thin films was calculated to be 3.36 eV and 3.67 eV, respectively. There was a progressive increase in conductivity for thin films of BaSnO3 doped with 0~7 at% of La. The highest conductivity, 9 Scm-1, was obtained for 7 at% La-doped BaSnO3. Carrier concentration, obtained from Burstein-Moss (B-M) shift, nearly matches the measured values except for 3 at% and 10 at% La-doped BaSnO3 thin films.

  14. Enhanced visible light activity of nano-titanium dioxide doped with multiple ions: Effect of crystal defects

    SciTech Connect

    Jaimy, Kanakkanmavudi B.; Ghosh, Swapankumar; Gopakumar Warrier, Krishna

    2012-12-15

    Titanium dioxide photocatalysts co-doped with iron(III) and lanthanum(III) have been prepared through a modified sol-gel method. Doping with Fe{sup 3+} resulted in a relatively lower anatase to rutile phase transformation temperature, while La{sup 3+} addition reduced the crystal growth and thus retarded the phase transformation of titania nanoparticles. The presence of Fe{sup 3+} ions shifted the absorption profile of titania to the longer wavelength side of the spectrum and enhanced the visible light activity. On the other hand, La{sup 3+} addition improved the optical absorption of titania nanoparticles. Both the dopants improved the life time of excitons by proper transferring and trapping of photoexcited charges. In the present work, considerable enhancement in photocatalytic activity under visible light was achieved through synergistic effect of optimum concentrations of the two dopants and associated crystal defects. - Graphical abstract: Photocatalytic activity studies indicate a synergistic effect of dopants and crystal defects leading to an enhanced photochemical activity. Highlights: Black-Right-Pointing-Pointer An aqueous sol-gel synthesis of Fe{sup 3+} and La{sup 3+} co-doped TiO{sub 2} is being reported. Black-Right-Pointing-Pointer Optical and microstructural properties of titania were modified by co-doping. Black-Right-Pointing-Pointer Enhanced activity of titania by the crystal defects is being reported.

  15. [Blood doping: 2].

    PubMed

    Cristani, Alessandro; Boldrini, Elena; Amateis, Elisa; Arioli, Dimitriy

    2005-01-01

    Blood Doping has recently obtained a large diffusion between professional and nonprofessional athletes, in particular for endurance sports it has almost become a necessary way to warrant best performance. Seven years after the publication of our article "Blood Doping", this second installment was born to emphasize the way the biomedical research supplies (often unintentionally) new drugs and new technology to improve athletic performance and, on the other hand, to underline the antidoping strategies.

  16. Intermediate-Temperature Solid-Oxide Fuel Cells with a Gadolinium-Doped Ceria Anodic Functional Layer Deposited via Radio-Frequency Sputtering.

    PubMed

    Tanveer, Waqas Hassan; Ji, Sanghoon; Yu, Wonjong; Cho, Gu Young; Lee, Yoon Ho; Cha, Suk Won

    2015-11-01

    We investigated the effects of the insertion of a gadolinium-doped ceria (GDC) anodic functional layer (AFL) on the electrochemical performance of intermediate-temperature solid-oxide fuel cells (SOFCs). Fully stabilized yttria-stabilized zirconia (YSZ) was used as an oxygen-ion-conducting and support material. Nickel-Samaria-doped ceriathin film was used as an anode material, while screen-printed lanthanum strontium magnetite served as a cathode material. In order to enhance the interfacial reaction on the anode side, a GDC-AFL with a thickness of about 140 nm, deposited via radio-frequency sputtering, was inserted into the anode-electrolyte interface. SOFCs with and without a GDC-AFL were electrochemically characterized. In an intermediate temperature range of about 700 - 800 degrees C, the application of the GDC-AFL led to an increase in the peak power density of approximately 16%.

  17. Room-temperature scintillation properties of cerium-doped REOX (RE=Y, La, Gd, and Lu; X=F, Cl, Br, and I)

    SciTech Connect

    Eagleman, Yetta; Bourret-Courchesne, Edith; Derenzo, Stephen

    2010-12-10

    The scintillation properties of cerium-doped oxyhalides following the general formula REOX (RE=Y, La, Gd, and Lu; X=F, Cl, Br, and I) are reported. These materials were synthesized under dry conditions as microcrystalline powders from conventional solid state reactions. The room temperature X-ray excited emission and scintillation decay curves were measured and analyzed for each material. Additionally, the hygroscopic nature of the oxychlorides and oxybromides was compared to that of their corresponding rare earth halides. The yttrium, lanthanum, and gadolinium oxychlorides, and all of the oxybromides and oxyiodides are found to be activated by Ce{sup 3+}. GdOBr doped with 0.5% Ce{sup 3+} has the highest light output with a relative luminosity of about one-half that of LaBr{sub 3}: Ce{sup 3+}. It displays a single exponential decay of 30 ns.

  18. Application of Sequential Extractions and X-ray Absorption Spectroscopy to Determine the Speciation of Chromium in Northern New Jersey Marsh Soils Developed in Chromite ore Processing Residue (COPR)

    SciTech Connect

    Elzinga, E.; Cirmo, A

    2010-01-01

    The Cr speciation in marsh soils developed in weathering chromite ore processing residue (COPR) was characterized using sequential extractions and synchrotron microbeam and bulk X-ray absorption spectroscopic (XAS) analyses. The sequential extractions suggested substantial Cr associated with reducible and oxidizable soil components, and significant non-extractable residual Cr. Notable differences in Cr speciation estimates from three extraction schemes underscore the operationally defined nature of Cr speciation provided by these methods. Micro X-ray fluorescence maps and {mu}-XAS data indicated the presence of {micro}m-sized chromite particles scattered throughout the weathered COPR matrix. These particles derive from the original COPR material, and have relatively high resistance towards weathering, and therefore persist even after prolonged leaching. Bulk XAS data further indicated Cr(III) incorporated in Fe(OH){sub 3}, and Cr(III) associated with organic matter. The low Cr contents of the weathered material (200-850 ppm) compared to unweathered COPR (20,000-60,000 ppm) point to substantial Cr leaching during COPR weathering, with partial repartitioning of released Cr into secondary Fe(OH){sub 3} phases and organics. The effects of anoxia on Cr speciation, and the potential of active COPR weathering releasing Cr(VI) deeper in the profile require further study.

  19. Identification and geochemical modeling of processes controlling leaching of Cr(VI) and other major elements from chromite ore processing residue

    NASA Astrophysics Data System (ADS)

    Geelhoed, Jeanine S.; Meeussen, Johannes C. L.; Hillier, Stephen; Lumsdon, David G.; Thomas, Rhodri P.; Farmer, John G.; Paterson, Edward

    2002-11-01

    Chromite ore processing residue (COPR) contains very high levels of chromium as Cr(III) and Cr(VI) and has a pH of ˜11.5 to 12. Millions of tonnes of COPR have in the past been deposited in urban areas. We have studied the factors that control leaching of Cr(VI), Ca, Al, Si, and Mg from COPR by means of batch experiments, mineralogical characterization of COPR via X-ray powder diffraction and scanning electron microscopy, and chemical equilibrium modeling. Batch experiments at a range of pH values and two liquid:solid ratios showed that mineral solubility control exists for aqueous concentrations of Cr(VI) above pH 10. Calculations indicate that the solid phases that control the solubility of Cr(VI) at pH values above 11 are Cr(VI)-substituted hydrogarnet (Ca 3Al 2(H 4O 4,CrO 4) 3) and Cr(VI)-hydrocalumite (Ca 4Al 2(OH) 12CrO 4·6 H 2O), a layered double-hydroxide clay with chromate anions held in the interlayers. In the pH range 9.5 to 11, the description of the Cr(VI) concentration in solution was strongly improved by the incorporation in the model of Cr(VI)-ettringite (Ca 6Al 2(OH) 12(CrO 4) 3·26 H 2O), which precipitates as a secondary phase when hydrocalumite dissolves. The proposed model for leaching of COPR at high pH includes Cr(VI)-bearing hydrogarnet, Cr(VI)-hydrocalumite, Cr(VI)-ettringite, brucite, calcite, Ca 2Al 2(OH) 10·3 H 2O, CaH 2SiO 4, and gehlenite hydrate (Ca 2Al 2(OH) 6SiO 8H 8·H 2O). The model accurately predicts the concentrations of Cr(VI), Ca, Al, Si, and Mg in solution in the pH range 10 to 12 as well as the pH-buffering behavior. Below pH 8, a decrease in the Cr(VI) concentration in solution is observed, which may be attributed to sorption of chromate onto freshly precipitated Al and Fe hydroxide surfaces. Sulfate and carbonate show the same type of behavior as chromate. The chemistry of COPR shows similarities with cement and high-pH municipal waste incinerator bottom ash.

  20. Biogenic nano-magnetite and nano-zero valent iron treatment of alkaline Cr(VI) leachate and chromite ore processing residue

    PubMed Central

    Watts, Mathew P.; Coker, Victoria S.; Parry, Stephen A.; Pattrick, Richard A.D.; Thomas, Russell A.P.; Kalin, Robert; Lloyd, Jonathan R.

    2015-01-01

    Highly reactive nano-scale biogenic magnetite (BnM), synthesized by the Fe(III)-reducing bacterium Geobacter sulfurreducens, was tested for the potential to remediate alkaline Cr(VI) contaminated waters associated with chromite ore processing residue (COPR). The performance of this biomaterial, targeting aqueous Cr(VI) removal, was compared to a synthetic alternative, nano-scale zero valent iron (nZVI). Samples of highly contaminated alkaline groundwater and COPR solid waste were obtained from a contaminated site in Glasgow, UK. During batch reactivity tests, Cr(VI) removal from groundwater was inhibited by ∼25% (BnM) and ∼50% (nZVI) when compared to the treatment of less chemically complex model pH 12 Cr(VI) solutions. In both the model Cr(VI) solutions and contaminated groundwater experiments the surface of the nanoparticles became passivated, preventing complete coupling of their available electrons to Cr(VI) reduction. To investigate this process, the surfaces of the reacted samples were analyzed by TEM-EDX, XAS and XPS, confirming Cr(VI) reduction to the less soluble Cr(III) on the nanoparticle surface. In groundwater reacted samples the presence of Ca, Si and S was also noted on the surface of the nanoparticles, and is likely responsible for earlier onset of passivation. Treatment of the solid COPR material in contact with water, by addition of increasing weight % of the nanoparticles, resulted in a decrease in aqueous Cr(VI) concentrations to below detection limits, via the addition of ⩾5% w/w BnM or ⩾1% w/w nZVI. XANES analysis of the Cr K edge, showed that the % Cr(VI) in the COPR dropped from 26% to a minimum of 4–7% by the addition of 5% w/w BnM or 2% w/w nZVI, with higher additions unable to reduce the remaining Cr(VI). The treated materials exhibited minimal re-mobilization of soluble Cr(VI) by re-equilibration with atmospheric oxygen, with the bulk of the Cr remaining in the solid fraction. Both nanoparticles exhibited a considerable

  1. Treatment of hexavalent chromium in chromite ore processing solid waste using a mixed reductant solution of ferrous sulfate and sodium dithionite.

    PubMed

    Su, Chunming; Ludwig, Ralph D

    2005-08-15

    We investigated a method for delivering ferrous iron into the subsurface to enhance chemical reduction of Cr(VI) in chromite ore processing solid waste (COPSW) derived from the production of ferrochrome alloy. The COPSW is characterized by high pH (8.5-11.5) and high Cr(VI) concentrations in the solid phase (up to 550 mg kg(-1)) and dissolved phase (3-57 mg L(-1)). The dominant solid-phase minerals are forsterite (Mg2SiO4), brucite (Mg-(OH)2), and hydrocalumite [Ca4(Al, Fe)2(OH)12X x 6H2O), X = (OH)2(2-), SO4(2-), CrO4(2-)]. The method utilizes FeSO4 in combination with Na2S2O4 to inhibit oxidation and precipitation of the ferrous iron, thereby preventing well and formation clogging. Laboratory batch tests using a 0.05 M FeSO4 + 0.05 M Na2S2O4 solution indicated effective treatment of both dissolved and solid-phase Cr(VI). Contrary to treatments with FeSO4 and FeCl2 alone, the combination resulted in both complete removal of Cr(VI) from solution and sustained Fe(ll) concentrations in solution after a 24 h period. A field test involving injection of 5700 L of a 0.07 M FeSO4 + 0.07 M Na2S2O4 solution into a COPSW saturated zone (pH 11.5) indicated no well and formation clogging during injection. Examination of a core collected 0.46 m from the injection well following injection indicated effective treatment of the solid phase Cr(VI) based on analysis of water, phosphate solution, and high temperature alkaline extracts. The combined reductant solution also imparted a residual treatment capacity to the COPSW allowing for subsequent treatment of dissolved phase Cr(VI); however, dissemination of the iron in the highly alkaline environment appeared to be impeded by the inability to sufficiently lower the pH with distance from the injection well to avoid precipitation of Fe(OH)2 and likely also FeCO3. Injection of a 0.2 M FeSO4 + 0.2 M Na2S2O4 solution into another COPSW saturated zone (pH 9) indicated much more effective dissemination of the injected iron. PMID:16173583

  2. [Point of view on doping].

    PubMed

    Naeije, R; Pagnamenta, A

    1999-06-01

    Doping is defined as the administration of or use by competing athletes of any substance foreign to the body or of any physiological substance taken in abnormal quantity or taken by an abnormal route of entry into the body with the sole intention of increasing in an artificial and unfair manner his/her performance in competition. The prevalence of doping has been estimated by rigorous methods to be 5-15%. The only two dopings of established efficacy are: anabolic steroids for resistive performance, and blood doping for endurance performance. Although medical control of athletes is reputably poor, reported accidents attributable to doping have been until now very rare. Doping is unfair, and must as such be banned from competitions. Medicalized doping is unethical. More studies are required to improve knowledge of doping as a public health issue. Sports medicine is in need of scientific and moral revalorization.

  3. Effects of switching from calcium carbonate to lanthanum carbonate on bone mineral metabolism in hemodialysis patients.

    PubMed

    Manabe, Rie; Fukami, Kei; Ando, Ryotaro; Sakai, Kazuko; Kusumoto, Takuo; Hazama, Takuma; Adachi, Takeki; Kaida, Yusuke; Nakayama, Yosuke; Ueda, Seiji; Kohno, Keisuke; Wada, Yoshifumi; Yamagishi, Sho-ichi; Okuda, Seiya

    2013-04-01

    Phosphate binders are useful for the treatment of hyperphosphatemia in hemodialysis (HD) patients. This study was performed to examine the effects of switching from calcium carbonate (CC) to lanthanum carbonate (LC) on bone mineral metabolism and inflammatory markers in HD patients. We conducted 29 stable HD patients receiving CC, which was replaced by LC and followed-up for 12 weeks. Patients underwent determinants of blood chemistries such as serum calcium (Ca), phosphorus, parathyroid hormone (PTH) and vitamin D status, and interleukin-6 (IL-6) mRNA levels in whole blood cells were evaluated by real-time PCR just before and after the treatment with LC. Corrected Ca [corrected] levels were significantly reduced, but serum phosphorus levels (P levels) were unchanged after LC treatment. Switching to LC increased whole-PTH, osteocalcin, 1,25(OH)(2) D(3) levels and 1,25(OH)(2) D(3)/25(OH)D(3) ratio. 1,25(OH)(2) D(3)/25(OH)D(3) ratio was negatively correlated with HD duration. Furthermore, whole blood cell IL-6 mRNA levels were significantly reduced by LC treatment. We provided that the switching from CC to LC improved Ca overload and ameliorated vitamin D and inflammatory status in HD patients. These observations suggest that LC may play a protective role for the progression of atherosclerosis and vascular calcification in these patients.

  4. The low-symmetry lanthanum(III) oxotellurate(IV), La10Te12O39

    PubMed Central

    Wang, Peng Li; Mozharivskyj, Yurij

    2013-01-01

    Single crystals of deca­lanthanum(III) dodeca­oxotellurate(IV), La10Te12O39, were obtained by reacting La2O3 and TeO2 in a CsCl flux. Its crystal structure can be viewed as a three-dimensional network of corner- and edge-sharing LaO8 polyhedra with TeIV atoms filling the inter­stitial sites. The TeIV atoms with their 5s 2 electron lone pairs distort the LaO8 polyhedra through variable Te—O bonds. Among the six unique Te sites, four of them define empty channels extending parallel to the a axis. The formation of these channels is a result of the stereochemically active electron lone pairs on the TeIV atoms. The atomic arrangement of the Te—O units can be understood on the basis of the valence shell electron pair repulsion (VSEPR) model. A certain degree of disorder is observed in the crystal structure. As a result, one of the five different La sites is split into two positions with an occupancy ratio of 0.875 (2):0.125 (2). Also, one of the oxygen sites is split into two positions in a 0.559 (13):0.441 (13) ratio, and one O site is half-occupied. Such disorder was observed in all measured La10Te12O39 crystals. PMID:23794967

  5. First principles study of nanoscale mechanism of oxygen adsorption on lanthanum zirconate surfaces

    NASA Astrophysics Data System (ADS)

    Guo, Xingye; Wu, Linmin; Zhang, Yi; Jung, Yeon-Gil; Li, Li; Knapp, James; Zhang, Jing

    2016-09-01

    Lanthanum zirconate (La2Zr2O7) is a rare-earth pyrochlore material, which has been proposed as a promising thermal barrier coating (TBC) material due to its low thermal conductivity and high temperature phase stability. At elevated temperatures, degradation of La2Zr2O7 may occur due to adsorption of oxygen (O2) on La2Zr2O7 surfaces. This paper investigates nanoscale mechanism of O2 adsorption on La2Zr2O7 coating surfaces using the density functional theory (DFT) calculations. La2Zr2O7 surface energies on (001), (011) and (111) planes are calculated. The surface free energy of (011) plane is lower than those of (001) and (111) planes. On (001), (011) and (111) planes of La2Zr2O7, the lowest adsorption energy occurs at 4-fold site, bridge site, and 3-fold-FCC site, respectively. Among all calculated cases, the lowest adsorption energy site is 3-fold-FCC on (111) plane, which is confirmed by the Bader charge transfer analyses. Charge density difference analyses show that the 3-fold-FCC site on (111) surface has the largest charge density, suggesting the strongest interaction between O2 and La2Zr2O7 surface.

  6. Lanthanum-silicon-substituted hydroxyapatite: Mechanochemical synthesis and prospects for medical applications

    NASA Astrophysics Data System (ADS)

    Chaikina, M. V.; Komarova, E. G.; Sharkeev, Yu. P.; Bulina, N. V.; Prosanov, I. Yu.

    2016-08-01

    The paper presents the results of mechanochemical synthesis of hydroxyapatite (HAP) with simultaneous substitutions of lanthanum (La3+) for calcium ions and silicate ((SiO4)4--group) for the phosphate group with the substituent concentrations in the range 0.2-2.0 mol per HAP mol. The use of Si-substituted HAP as a coating material promotes accelerated osteosynthesis and osteointegration of implants into the bone tissue. The replacement of calcium ions by La3+ in the HAP structure plays an antimicrobial role preventing inflammatory processes. Annealing-induced variations in the lattice parameters of synthesized samples indicate the substituent incorporation into the HAP structure. It is known that complex compounds with lanthanides are used for cancer chemotherapy. In particular, La plays a key role in the course of treatment of injured defects of bone tissue. In addition, La-substituted HAP can be used for filling bone defects and coating implants in postoperational areas affected by bone cancer.

  7. Lanthanum manganite-based air electrode for solid oxide fuel cells

    DOEpatents

    Ruka, Roswell J.; Kuo, Lewis; Li, Baozhen

    1999-01-01

    An air electrode material for a solid oxide fuel cell is disclosed. The electrode material is based on lanthanum manganite having a perovskite-like crystal structure ABO.sub.3. The A-site of the air electrode material preferably comprises La, Ca, Ce and at least one lanthanide selected from Sm, Gd, Dy, Er, Y and Nd. The B-site of the electrode material comprises Mn with substantially no dopants. The ratio of A:B is preferably slightly above 1. A preferred air electrode composition is of the formula La.sub.w Ca.sub.x Ln.sub.y Ce.sub.z MnO.sub.3, wherein Ln comprises at least one lanthanide selected from Sm, Gd, Dy, Er, Y and Nd, w is from about 0.55 to about 0.56, x is from about 0.255 to about 0.265, y is from about 0.175 to about 0.185, and z is from about 0.005 to about 0.02. The air electrode material possesses advantageous chemical and electrical properties as well as favorable thermal expansion and thermal cycle shrinkage characteristics.

  8. Lanthanum manganite-based air electrode for solid oxide fuel cells

    DOEpatents

    Ruka, R.J.; Kuo, L.; Li, B.

    1999-06-29

    An air electrode material for a solid oxide fuel cell is disclosed. The electrode material is based on lanthanum manganite having a perovskite-like crystal structure ABO[sub 3]. The A-site of the air electrode material preferably comprises La, Ca, Ce and at least one lanthanide selected from Sm, Gd, Dy, Er, Y and Nd. The B-site of the electrode material comprises Mn with substantially no dopants. The ratio of A:B is preferably slightly above 1. A preferred air electrode composition is of the formula La[sub w]Ca[sub x]Ln[sub y]Ce[sub z]MnO[sub 3], wherein Ln comprises at least one lanthanide selected from Sm, Gd, Dy, Er, Y and Nd, w is from about 0.55 to about 0.56, x is from about 0.255 to about 0.265, y is from about 0.175 to about 0.185, and z is from about 0.005 to about 0.02. The air electrode material possesses advantageous chemical and electrical properties as well as favorable thermal expansion and thermal cycle shrinkage characteristics. 10 figs.

  9. Electrochemical performance of LiCoO 2 cathodes by surface modification using lanthanum aluminum garnet

    NASA Astrophysics Data System (ADS)

    Lu, Cheng-Zhang; Chen, Jin-Ming; Cho, Yung-Da; Hsu, Wen-Hsiang; Muralidharan, P.; Fey, George Ting-Kuo

    LiCoO 2 particles were coated with various wt.% of lanthanum aluminum garnets (3LaAlO 3:Al 2O 3) by an in situ sol-gel process, followed by calcination at 1123 K for 12 h in air. X-ray diffraction (XRD) patterns confirmed the formation of a 3LaAlO 3:Al 2O 3 compound and the in situ sol-gel process synthesized 3LaAlO 3:Al 2O 3-coated LiCoO 2 was a single-phase hexagonal α-NaFeO 2-type structure of the core material without any modification. Scanning electron microscope (SEM) images revealed a modification of the surface of the cathode particles. Transmission electron microscope (TEM) images exposed that the surface of the core material was coated with a uniform compact layer of 3LaAlO 3:Al 2O 3, which had an average thickness of 40 nm. Galvanostatic cycling studies demonstrated that the 1.0 wt.% 3LaAlO 3:Al 2O 3-coated LiCoO 2 cathode showed excellent cycle stability of 182 cycles, which was much higher than the 38 cycles sustained by the pristine LiCoO 2 cathode material when it was charged at 4.4 V.

  10. In vitro anticancer activities of Schiff base and its lanthanum complex.

    PubMed

    Neelima; Poonia, Kavita; Siddiqui, Sahabjada; Arshad, Md; Kumar, Dinesh

    2016-02-15

    Schiff base metal complexes are well-known to intercalate DNA. The La(III) complexes have been synthesized such that they hinder with the role of the topoisomerases, which control the topology of DNA during the cell-division cycle. Although several promising chemotherapeutics have been developed, on the basis of Schiff base metal complex DNA intercalating system they did not proceed past clinical trials due to their dose-limiting toxicity. Herein, we discuss an alternative compound, the La(III) complex, [La(L(1))2Cl3]·7H2O based on a Schiff base ligand 2,3-dihydro-1H-indolo-[2,3-b]-phenazin-4(5H)-ylidene)benzothiazole-2-amine (L(1)), and report in vitro cell studies. Results of antitumor activity using cell viability assay, reactive oxygen species (ROS) generation and nuclear condensation in PC-3 (Human, prostate carcinoma) cells show that the metal complex is more potent than ligand. La(III) complexes have been synthesized by reaction of lanthanum(III) salt in 1:2M ratio with ligands L(1) and 3-(ethoxymethylene)-2,3-dihydro-1H-indolo[2,3-b]-phenazin-4(5H)-ylidene)benzathiazole-2-amine (L(2)) in methanol. The ligands and their La(III) complexes were characterized by molar conductance, magnetic susceptibility, elemental analyses, FT-IR, UV-Vis, (1)H/(13)C NMR, thermogravimetric, XRD, and SEM analysis.

  11. Theoretical and spectroscopic studies of lanthanum (III) complex of 5-aminoorotic acid

    NASA Astrophysics Data System (ADS)

    Kostova, Irena; Peica, Niculina; Kiefer, Wolfgang

    2006-09-01

    The lanthanum (III) complex of 5-aminoorotic acid (HAOA) was synthesized and its structure was determined by means of elemental analysis and IR, Raman, and 1H NMR spectroscopies. Significant differences in the IR, Raman, and 1H NMR spectra of the complex were observed as compared to the spectra of the ligand. The geometry of 5-aminoorotic acid was computed and optimized with the Gaussian 03 program employing the B3PW91 and B3LYP methods with the 6-311++G and LANL2DZ basis sets, while the geometry of the La(III) complex of 5-aminoorotic acid was also calculated and optimized with B3PW91/LANL2DZ and B3LYP/LANL2DZ methods. The density functional calculations revealed that the binding mode in the complex was bidentate through the carboxylic oxygen atoms. Detailed vibrational analysis of HAOA and La(III)-AOA systems based on both the calculated and experimental spectra confirmed the suggested metal-ligand binding mode. The density functional theory (DFT) calculated geometries, harmonic vibrational wavenumbers including IR and Raman scattering activities for the ligand and its La(III) complex were in good agreement with the experimental data, a complete vibrational assignment being proposed.

  12. Lanthanum(III) and praseodymium(III) complexes with isatin thiosemicarbazones

    NASA Astrophysics Data System (ADS)

    Rai, Anita; Sengupta, Soumitra K.; Pandey, Om P.

    2005-09-01

    Ten new lanthanum(III) and praseodymium(III) complexes of the general formula Na[La(L) 2H 2O] (Ln = La(III) or Pr(III); LH 2 = thiosemicarbazones) derived from the condensation of isatin with 4-phenyl thiosemicarbazide, 4-(4-chlorophenyl) thiosemicarbazide, 4-(2-nitrophenyl) thiosemicarbazide, 4-(2-bromophenyl) thiosemicarbazide and 4-(2-methylphenyl) thiosemicarbazide, have been synthesized in methanol in presence of sodium hydroxide. The XRD spectra of the complexes were monitored to verify complex formation. The complexes have also been characterized by elemental analysis, molar conductance, electronic absorption and fluorescence, infrared, far infrared, 1H and 13C NMR spectral studies. Thermal studies of these complexes have been carried out in the temperature range 25-800 °C using TG, DTG and DTA techniques. All these complexes decompose gradually with the formation of Ln 2O 3 as the end product. The Judd-ofelt intensity parameter, oscillator strength, transition probability, stimulated emission cross section for different transitions of Pr 3+ for 4-phenyl thiosemicarbazones have been calculated.

  13. Removal of fluoride from water using a novel sorbent lanthanum-impregnated bauxite.

    PubMed

    Vivek Vardhan, C M; Srimurali, M

    2016-01-01

    A novel sorbent, Lanthanum-Impregnated Bauxite (LIB), was prepared to remove fluoride from water. To understand the surface chemical composition and morphology, LIB was characterized using X-ray diffraction and scanning electron microscopy techniques. Experiments were performed to evaluate the sorption potential, dose of sorbent, kinetics, equilibrium sorption capacity, pH and influence of anions for defluoridation by LIB. Equilibrium isothermal studies were conducted to model the sorption and regeneration studies were carried out to evaluate the reusability of LIB. The results showed that LIB, at a dose of 2 g/L could remove 99 % of fluoride from an initial concentration of 20 mgF/L. Kinetic studies revealed the best fit of pseudo second order model. The sorption followed Langmuir isotherm model and the maximum sorption capacity of LIB for removal of fluoride was found to be 18.18 mg/g. Naturally occurring pH of water was found to be favorable for sorption. Usually occurring anions in water except nitrates influenced sorption of fluoride by LIB. PMID:27625980

  14. Oxidative effects, nutrients and metabolic changes in aquatic macrophyte, Elodea nuttallii, following exposure to lanthanum.

    PubMed

    Zhang, Jingjing; Zhang, Tingting; Lu, Qianqian; Cai, Sanjuan; Chu, Weiyue; Qiu, Han; Xu, Ting; Li, Feifei; Xu, Qinsong

    2015-05-01

    We investigated the phytoremediation potential of Elodea nuttallii to remove rare earth metals from contaminated water. The laboratory experiments were designed to assess the responses induced by lanthanum (5-20mgL(-1)) in E. nuttallii over a period of 7 days. The results showed that most La (approximately 85%) was associated with the cell wall. The addition of La to the culture medium reduced the concentration of K, Ca, Cu, Mg, and Mn. However, O2(·-) levels increased with a concomitant increase in the malondialdehyde (MDA) concentration as the La concentration increased, which indicated that the cells were under oxidative stress. Significant reductions in the levels of chlorophyll (Chl) a, b, and carotenoids (Car) were observed in a concentration-dependent manner. However, the levels of reduced glutathione (GSH), total non-protein thiols (TNP-SH) and phytochelatins (PCs) increased for all La concentrations. The results suggested that La was toxic to E. nuttallii because it induced oxidative stress and disturbed mineral uptake. However, E. nuttallii was able to combat La induced damage via an immobilization mechanism, which involved the cell wall and the activation of non-enzymatic antioxidant. PMID:25700094

  15. Application of graphene oxide/lanthanum-modified carbon paste electrode for the selective determination of dopamine

    NASA Astrophysics Data System (ADS)

    Ye, Fengying; Feng, Chenqi; Fu, Ning; Wu, Huihui; Jiang, Jibo; Han, Sheng

    2015-12-01

    A home-made carbon paste electrode (CPE) was reformed by graphene oxide (GO)/lanthanum (La) complexes, and a modified electrode, called GO-La/CPE, was fabricated for the selective determination of dopamine (DA) by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Several factors affecting the electrocatalytic performance of the modified sensor were investigated. Owning to the combination of GO and La ions, the GO-La/CPE sensor exhibited large surface area, well selectivity, good repeatability and stability in the oxidation reaction of DA. At optimal conditions, the response of the GO-La/CPE electrode for determining DA was linear in the region of 0.01-0.1 μM and 0.1-400.0 μM. The limit of detection was down to 0.32 nM (S/N = 3). In addition, this modified electrode was successfully applied to the detection of DA in real urine and serum samples by using standard adding method, showing its promising application in the electroanalysis of real samples.

  16. The effect of physiologic aqueous solutions on the perovskite material lead-lanthanum-zirconium titanate (PLZT)

    PubMed Central

    Foster, William J.; Meen, James K.; Fox, Donald A.

    2016-01-01

    Context Perovskite compounds, including Lead-Lanthanum-Zirconium Titanate (PLZT), have wide technological application because of their unique physical properties. The use of PLZT in neuro-prosthetic systems, such as retinal implants, have been discussed in a number of publications. Since inorganic lead is a retinotoxic compound that produces retinal degeneration, the long-term stability of PLZT in aqueous biological solutions must be determined. Objective We evaluated the stability and effects of prolonged immersion of a PLZT-coated crystal in a buffered balanced salt solution. Materials and Methods Scanning Electron Microscopy and Electron Dispersive Spectroscopy (EDS) using a JEOL JSM 5410 microscope equipped with EDS were utilized to evaluate the samples before and after prolonged immersion. Results We found that lead and other constituents of PLZT leached into the surrounding aqueous medium. Discussion By comparing the unit cell of PLZT with that of CaTiO3, which has been found to react with aqueous fluids, Lead is in the same site in PLZT as Ca is in CaTiO3. It is thus reasonable that PLZT will react with aqueous solutions. Conclusion The results suggest that PLZT must either be coated with a protective layer or is not appropriate for long-term in vivo or in vitro biological applications. PMID:22697294

  17. RM1 Semiempirical Quantum Chemistry: Parameters for Trivalent Lanthanum, Cerium and Praseodymium

    PubMed Central

    Dutra, José Diogo L.; Filho, Manoel A. M.; Rocha, Gerd B.; Simas, Alfredo M.; Freire, Ricardo O.

    2015-01-01

    The RM1 model for the lanthanides is parameterized for complexes of the trications of lanthanum, cerium, and praseodymium. The semiempirical quantum chemical model core stands for the [Xe]4fn electronic configuration, with n =0,1,2 for La(III), Ce(III), and Pr(III), respectively. In addition, the valence shell is described by three electrons in a set of 5d, 6s, and 6p orbitals. Results indicate that the present model is more accurate than the previous sparkle models, although these are still very good methods provided the ligands only possess oxygen or nitrogen atoms directly coordinated to the lanthanide ion. For all other different types of coordination, the present RM1 model for the lanthanides is much superior and must definitely be used. Overall, the accuracy of the model is of the order of 0.07Å for La(III) and Pr(III), and 0.08Å for Ce(III) for lanthanide-ligand atom distances which lie mostly around the 2.3Å to 2.6Å interval, implying an error around 3% only. PMID:26132289

  18. RM1 Semiempirical Quantum Chemistry: Parameters for Trivalent Lanthanum, Cerium and Praseodymium.

    PubMed

    Dutra, José Diogo L; Filho, Manoel A M; Rocha, Gerd B; Simas, Alfredo M; Freire, Ricardo O

    2015-01-01

    The RM1 model for the lanthanides is parameterized for complexes of the trications of lanthanum, cerium, and praseodymium. The semiempirical quantum chemical model core stands for the [Xe]4fn electronic configuration, with n =0,1,2 for La(III), Ce(III), and Pr(III), respectively. In addition, the valence shell is described by three electrons in a set of 5d, 6s, and 6p orbitals. Results indicate that the present model is more accurate than the previous sparkle models, although these are still very good methods provided the ligands only possess oxygen or nitrogen atoms directly coordinated to the lanthanide ion. For all other different types of coordination, the present RM1 model for the lanthanides is much superior and must definitely be used. Overall, the accuracy of the model is of the order of 0.07Å for La(III) and Pr(III), and 0.08Å for Ce(III) for lanthanide-ligand atom distances which lie mostly around the 2.3Å to 2.6Å interval, implying an error around 3% only.

  19. Lanthanum(III) and praseodymium(III) complexes with isatin thiosemicarbazones.

    PubMed

    Rai, Anita; Sengupta, Soumitra K; Pandey, Om P

    2005-09-01

    Ten new lanthanum(III) and praseodymium(III) complexes of the general formula Na[La(L)2H2O] (Ln=La(III) or Pr(III); LH2=thiosemicarbazones) derived from the condensation of isatin with 4-phenyl thiosemicarbazide, 4-(4-chlorophenyl) thiosemicarbazide, 4-(2-nitrophenyl) thiosemicarbazide, 4-(2-bromophenyl) thiosemicarbazide and 4-(2-methylphenyl) thiosemicarbazide, have been synthesized in methanol in presence of sodium hydroxide. The XRD spectra of the complexes were monitored to verify complex formation. The complexes have also been characterized by elemental analysis, molar conductance, electronic absorption and fluorescence, infrared, far infrared, 1H and 13C NMR spectral studies. Thermal studies of these complexes have been carried out in the temperature range 25-800 degrees C using TG, DTG and DTA techniques. All these complexes decompose gradually with the formation of Ln2O3 as the end product. The Judd-ofelt intensity parameter, oscillator strength, transition probability, stimulated emission cross section for different transitions of Pr3+ for 4-phenyl thiosemicarbazones have been calculated.

  20. Synthesis, characterization, and catalytic activity of Rh-based lanthanum zirconate pyrochlores for higher alcohol synthesis

    SciTech Connect

    Abdelsayed, Victor; Shekhawat, Dushyant; Poston, James A; Spivey, James J

    2013-05-01

    Two lanthanum zirconate pyrochlores (La{sub 2}Zr{sub 2}O{sub 7}; LZ) were prepared by Pechini method and tested for higher alcohols selectivity. In one, Rh was substituted into the pyrochlore lattice (LRZ, 1.7 wt%) while for the second, Rh was supported on an unsubstituted La{sub 2}Zr{sub 2}O{sub 7} (R/LZ, 1.8 wt%). X-ray photoelectron spectroscopy (XPS) and temperature programmed reduction (TPR) results show that the surface reducibility depends on whether the Rh is in (or supported on) the LZ pyrochlore. Rhodium in the LRZ is more reducible than rhodium supported on the R/LZ pyrochlore, likely due to the presence of a perovskite phase (LaRhO{sub 3}; identified by XRD), in which rhodium is more reducible. The formation of the perovskite accompanies that of the pyrochlore. CO hydrogenation results show higher ethanol selectivity for R/LZ than LRZ, possibly due to the strong interaction between Rh and LZ on the R/LZ, forming atomically close Rh{sup +}/Rh{sup 0} sites, which have been suggested to favor ethanol production.

  1. Sugar-metal ion interactions: the coordination behaviors of lanthanum with erythritol.

    PubMed

    Xue, Junhui; Hua, Xiaohui; Li, Weihong; Yang, Limin; Xu, Yizhuang; Zhao, Guozhong; Zhang, Gaohui; Li, Chunping; Liu, Kexin; Chen, Jia'er; Wu, Jinguang

    2012-11-01

    Three novel lanthanum chloride-erythritol complexes (LaCl(3)·C(4)H(10)O(4)·5H(2)O (LaE(I)), LaCl(3)·C(4)H(10)O(4)·3H(2)O (LaE(II)), and LaCl(3)·1.5C(4)H(10)O(4) (LaE(III)) were synthesized and characterized by single crystal X-ray diffraction, FTIR, far-IR, THz, and Raman spectroscopy. The coordination number of La(3+) is nine. LaE(I) and LaE(II) have similar coordination spheres, but their hydrogen bond networks are different. Erythritol exhibits two coordination modes: two bidentate ligands and tridentate ligands in LaE(III). Chloride ions and water coordinate with La(3+) or participate in the hydrogen-bond networks in the three complexes. Crystal structures, FTIR, FIR, THz, and Raman spectra provide detailed information on the structures and coordination of hydroxyl groups to metal ions in the metal-carbohydrate complexes.

  2. In vitro anticancer activities of Schiff base and its lanthanum complex

    NASA Astrophysics Data System (ADS)

    Neelima; Poonia, Kavita; Siddiqui, Sahabjada; Arshad, Md; Kumar, Dinesh

    2016-02-01

    Schiff base metal complexes are well-known to intercalate DNA. The La(III) complexes have been synthesized such that they hinder with the role of the topoisomerases, which control the topology of DNA during the cell-division cycle. Although several promising chemotherapeutics have been developed, on the basis of Schiff base metal complex DNA intercalating system they did not proceed past clinical trials due to their dose-limiting toxicity. Herein, we discuss an alternative compound, the La(III) complex, [La(L1)2Cl3]·7H2O based on a Schiff base ligand 2,3-dihydro-1H-indolo-[2,3-b]-phenazin-4(5H)-ylidene)benzothiazole-2-amine (L1), and report in vitro cell studies. Results of antitumor activity using cell viability assay, reactive oxygen species (ROS) generation and nuclear condensation in PC-3 (Human, prostate carcinoma) cells show that the metal complex is more potent than ligand. La(III) complexes have been synthesized by reaction of lanthanum(III) salt in 1:2 M ratio with ligands L1 and 3-(ethoxymethylene)-2,3-dihydro-1H-indolo[2,3-b]-phenazin-4(5H)-ylidene)benzathiazole-2-amine (L2) in methanol. The ligands and their La(III) complexes were characterized by molar conductance, magnetic susceptibility, elemental analyses, FT-IR, UV-Vis, 1H/13C NMR, thermogravimetric, XRD, and SEM analysis.

  3. Fluorescent complexes of nucleic acids/8-hydroxyquinoline/lanthanum(III) and the fluorometry of nucleic acids

    SciTech Connect

    Cheng Zhi Huang; Ke An Li; Shen Yang Tong

    1996-07-01

    The ternary fluorescent complexes of nucleic acids/8-hydroxyquinoline/lanthanum (III) were studied. Nucleic acids in the study involve natured and thermally denatured calf thymus DNA, fish sperm DNA and yeast RNA. In the range of PH 8.0-8.4 (controlled by NH{sub 3}-NH{sub 4}Cl buffer) ternary fluorescent complexes are formed which emit at 485.0 nm for calf thymus DNA and at 480.0 nm for fish sperm DNA when excited at 265.0 nm. Based on the fluorescence reactions sensitive fluorometric methods for nucleic acids were proposed. Using optimal conditions, the calibration curves were linear in the range of 0.4 --3.6 {mu}g{sup .}ml{sup -1} for calf thymus DNA, 0.4 -- 4.0 {mu}g{sup .}ml{sup -1} for fish sperm DNA and 0.4 --4.0{mu}g{sup .}ml{sup -1} for yeast RNA, respectively. Five synthetic samples were determined with satisfaction.

  4. Effects of compositional modification in lead lanthanum zirconate stannate titanate ceramics on electric energy storage properties

    NASA Astrophysics Data System (ADS)

    Jo, Hwan R.; Lynch, Christopher S.

    2013-04-01

    The effects of compositional modifications on the antiferroelectric (AFE) to ferroelectric (FE) transition of lead lanthanum zirconate stannate titanate, (Pb1-3x/2Lax)(Zr1-v-zSnvTiz)O3 ceramics were used to optimize this material for energy storage. The experimental results show that an increase of Sn4+ respect to Ti4+ increases the coercive field of AFE-FE transition and keeps the hysteresis at the minimal level. This increases both the energy density of material and energy efficiency relative to a linear dielectric. Another advantage of Sn4+ addition was a polarization increase at the switching field. The substitution of Zn4+ for Sn4+ at fixed Ti4+ concentration of 0.1 was, however, undesirable for energy storage applications since this decreased the forward switching field and increased the hysteresis. This lowered both the energy density of the material and energy efficiency. Finally, addition of La3+ was performed and slim hysteresis loops were obtained resulting in energy efficiency of 80.1%. However, the slanted hysteresis behavior with La3+ results in a lower value of the maximum stored energy.

  5. Polarization switching of and electron emission from lead lanthanum zirconate titanate ceramics

    SciTech Connect

    Zhang, W.; Huebner, W.; Sampayan, S.E.; Krogh, M.L.

    1999-03-01

    This paper focuses on understanding the influence of material properties on the complicated ferroelectric (FE) emission process. Three different compositions in the lead lanthanum zirconate titanate (PLZT) system were chosen for study, based on their widely different dielectric and ferroelectric properties: antiferroelectric (AFE) 2/95/5, normal ferroelectric 8/65/35, and nonferroelectric 15/65/35. Repeatable emission was obtained from the 2/95/5 composition, which could also be modulated at high frequency (200 kHz). The fast AFE {r_reversible} FE phase transition is responsible for the FE emission properties of this material, which is supported by the relationship between the switching current and the emission current. Comparatively, FE emission from the 8/65/35 composition degraded rapidly, which was attributed to decreases in the remanent polarization. No emission signal was detected from the 15/65/35 composition, because no switching activity occurs, which can be interpreted as additional evidence that electron emission from the previously mentioned two compositions was indeed a FE emission process.

  6. Effect of compositional variations in the lead lanthanum zirconate stannate titanate system on electrical properties

    SciTech Connect

    Markowski, K.; Park, S.E.; Yoshikawa, Shoko; Cross, L.E.

    1996-12-01

    The purpose of this work was to evaluate the effect of compositional modifications on the electrical properties of lead lanthanum zirconate stannate titanate (PLZST) ceramics, as well as to examine their electrically induced phase-change behavior. Variations in the Ti:Sn ratio were evaluated. Increased Ti{sup 4+} content produced the following: decreased switching field, related to an increased antiferroelectric-ferroelectric (AFE-FE) transition temperature; constant hysteresis ({Delta}E) correlated with a constant temperature of the maximum dielectric constant (T{sub max}); a sharper dielectric-constant maximum peak; and increased room-temperature dielectric constant (K). Variations in the Zr:Sn ratio also were evaluated. Increased Zr{sup 4+} content produced the following: increased hysteresis with increased T{sub max}, decreased maximum dielectric constant, and decreased switching field with increased AFE-FE transition temperature (T{sub AFE-FE}). From these results, with respect to compositional modifications, the AFE-FE switching field (E{sub AFE-FE}) and {Delta}E were observed to be dependent strongly on T{sub AFE-FE} and T{sub max}, respectively. Negligible change existed in the strain achievable at the switching field, which remained constant for all compositions at {approximately}0.16%. The significance of this research was the ability demonstrated to tailor the properties of phase-change materials through compositional modifications.

  7. Bioaccumulation and effects of lanthanum on growth and mitotic index in soybean plants.

    PubMed

    de Oliveira, Cynthia; Ramos, Sílvio J; Siqueira, José O; Faquin, Valdemar; de Castro, Evaristo M; Amaral, Douglas C; Techio, Vânia H; Coelho, Lívia C; e Silva, Pedro H P; Schnug, Ewald; Guilherme, Luiz R G

    2015-12-01

    Rare earth elements such as lanthanum (La) have been used as agricultural inputs in some countries in order to enhance yield and improve crop quality. However, little is known about the effect of La on the growth and structure of soybean, which is an important food and feed crop worldwide. In this study, bioaccumulation of La and its effects on the growth and mitotic index of soybean was evaluated. Soybean plants were exposed to increasing concentrations of La (0, 5, 10, 20, 40, 80, and 160 µM) in nutrient solution for 28 days. Plant response to La was evaluated in terms of plant growth, nutritional characteristics, photosynthetic rate, chlorophyll content, mitotic index, modifications in the ultrastructure of roots and leaves, and La mapping in root and shoot tissues. The results showed that the roots of soybean plants can accumulate sixty-fold more La than shoots. La deposition occurred mainly in cell walls and in crystals dispersed in the root cortex and in the mesophyll. When La was applied, it resulted in increased contents of some essential nutrients (i.e., Ca, P, K, and Mn), while Cu and Fe levels decreased. Moreover, low La concentrations stimulated the photosynthetic rate and total chlorophyll content and lead to a higher incidence of binucleate cells, resulting in a slight increase in roots and shoot biomass. At higher La levels, soybean growth was reduced. This was caused by ultrastructural modifications in the cell wall, thylakoids and chloroplasts, and the appearance of c-metaphases.

  8. Oxidative effects, nutrients and metabolic changes in aquatic macrophyte, Elodea nuttallii, following exposure to lanthanum.

    PubMed

    Zhang, Jingjing; Zhang, Tingting; Lu, Qianqian; Cai, Sanjuan; Chu, Weiyue; Qiu, Han; Xu, Ting; Li, Feifei; Xu, Qinsong

    2015-05-01

    We investigated the phytoremediation potential of Elodea nuttallii to remove rare earth metals from contaminated water. The laboratory experiments were designed to assess the responses induced by lanthanum (5-20mgL(-1)) in E. nuttallii over a period of 7 days. The results showed that most La (approximately 85%) was associated with the cell wall. The addition of La to the culture medium reduced the concentration of K, Ca, Cu, Mg, and Mn. However, O2(·-) levels increased with a concomitant increase in the malondialdehyde (MDA) concentration as the La concentration increased, which indicated that the cells were under oxidative stress. Significant reductions in the levels of chlorophyll (Chl) a, b, and carotenoids (Car) were observed in a concentration-dependent manner. However, the levels of reduced glutathione (GSH), total non-protein thiols (TNP-SH) and phytochelatins (PCs) increased for all La concentrations. The results suggested that La was toxic to E. nuttallii because it induced oxidative stress and disturbed mineral uptake. However, E. nuttallii was able to combat La induced damage via an immobilization mechanism, which involved the cell wall and the activation of non-enzymatic antioxidant.

  9. Stability of manganese-oxide-modified lanthanum strontium cobaltite in the presence of chromia

    NASA Astrophysics Data System (ADS)

    Ou, Ding Rong; Cheng, Mojie

    2014-12-01

    In order to restrain the decomposition and conductivity degradation of perovskite-type conductive material in the presence of chromia, manganese oxide modification of lanthanum strontium cobaltite has been studied. La0.7Sr0.3CoO3-δ (LSC) and MnO2-modified LSC coatings are applied onto Ni-Cr alloy and exposed to long-term oxidation text to examine their chemical stability. In a LSC coating, chromium species migrating from the Ni-Cr alloy could induce the decomposition of LSC and produce SrCrO4 and Co-Cr spinel oxides. In contrast, in the MnO2-modified LSC, Sr is stable and the low-conductivity phase SrCrO4 phase is rarely seen even the coated alloy has gone through 1000 h of oxidation tests at 800 °C. It highlights that MnO2 modification could greatly improve the stability of LSC under Cr-rich conditions. The study of solid state reactions reveals that the influence of MnO2 is mainly due to the reaction between MnO2 and LSC, instead of the direct reaction between MnO2 and chromium oxides.

  10. Sorption of lanthanum and erbium from aqueous solution by activated carbon prepared from rice husk.

    PubMed

    Awwad, N S; Gad, H M H; Ahmad, M I; Aly, H F

    2010-12-01

    A biomass agricultural waste material, rice husk (RH) was used for preparation of activated carbon by chemical activation using phosphoric acid. The effect of various factors, e.g. time, pH, initial concentration and temperature of carbon on the adsorption capacity of lanthanum and erbium was quantitatively determined. It was found that the monolayer capacity is 175.4 mg g(-1) for La(III) and 250 mg g(-1) for Er(III). The calculated activation energy of La(III) adsorption on the activated carbon derived from rice husk was equal to 5.84 kJ/mol while it was 3.6 kJ/mol for Er(III), which confirm that the reaction is mainly particle-diffusion-controlled. The kinetics of sorption was described by a model of a pseudo-second-order. External diffusion and intra-particular diffusion were examined. The experimental data show that the external diffusion and intra-particular diffusion are significant in the determination of the sorption rate. Therefore, the developed sorbent is considered as a better replacement technology for removal of La(III) and Er(III) ions from aqueous solution due to its low-cost and good efficiency, fast kinetics, as well as easy to handle and thus no or small amount of secondary sludge is obtained in this application.

  11. Fracto-emission in lanthanum-based metallic glass microwires under quasi-static tensile loading

    NASA Astrophysics Data System (ADS)

    Banerjee, Amit; Jiang, Chenchen; Lohiya, Lokesh; Yang, Yong; Lu, Yang

    2016-04-01

    Plastic deformation in metallic glasses is highly localized and often associated with shear banding, which may cause momentary release of heat upon fracture. Here, we report an explosive fracture phenomenon associated with momentary (˜10 ms) light emission (flash) in Lanthanum-based (LaAlNi) metallic glass microwires (dia. ˜50 μm) under quasi-static tensile loading. The load-displacement data as well as the visual information of the tensile deformation process were acquired through an in situ measurement set-up, which clearly showed nonlinear stress (σ)-strain ( ɛ) curves prior to yielding and also captured the occurrence of the flash at high fracture stresses (˜1 GPa). Through the postmortem fractographic analysis, it can be revealed that the fracto-emission upon quasi-static loading could be mainly attributed to the localized adiabatic work accumulated at a very large elastic strain confined within the microscale sample volume, followed by a localized high temperature rise up to ˜1000 K at the fracture surface through localized energy dissipation. Our findings suggest that the La-based metallic glass microwires could be useful for energetic microchips, micro-ignition devices, and other functional applications.

  12. Influence of Lanthanum on Solidification, Microstructure, and Mechanical Properties of Eutectic Al-Si Piston Alloy

    NASA Astrophysics Data System (ADS)

    Ahmad, R.; Asmael, M. B. A.

    2016-07-01

    The effects of Lanthanum (La) concentration on the solidification parameters of the α-Al, Al-Si, and Al-Cu phases and on the microstructure, tensile, and hardness properties of eutectic Al-Si-Cu-Mg alloy were systematically investigated. The solidification parameters were examined using computer-aided cooling curve thermal analysis (CA-CCTA). The cooling curve and microstructure analysis showed that La altered the Si structure. The nucleation and growth temperatures of eutectic Si decreased when 0.3 wt.% La was added, and a high depression temperature was obtained with 1.0 wt.% La. High amounts of La considerably modified the Si structure and decreased the area and aspect ratio by 69.9 and 51%, respectively. The thermal analysis result recorded a faster freezing time with the La addition and a 36% alteration in the secondary dendrite arm spacing. Two secondary or ternary La-rich intermetallic phases were formed with needle- and plate-like structures. Furthermore, the mechanical properties were investigated by hardness and tensile tests with different La concentrations. The addition of small amounts of La (0.1 wt.%) significantly improved the ultimate tensile strength and quality index of the Al-Si-Cu-Mg alloy. In addition, the hardness value of Al-11Si-Cu increased by 7-8% with the increasing amount of La added.

  13. RM1 Semiempirical Quantum Chemistry: Parameters for Trivalent Lanthanum, Cerium and Praseodymium.

    PubMed

    Dutra, José Diogo L; Filho, Manoel A M; Rocha, Gerd B; Simas, Alfredo M; Freire, Ricardo O

    2015-01-01

    The RM1 model for the lanthanides is parameterized for complexes of the trications of lanthanum, cerium, and praseodymium. The semiempirical quantum chemical model core stands for the [Xe]4fn electronic configuration, with n =0,1,2 for La(III), Ce(III), and Pr(III), respectively. In addition, the valence shell is described by three electrons in a set of 5d, 6s, and 6p orbitals. Results indicate that the present model is more accurate than the previous sparkle models, although these are still very good methods provided the ligands only possess oxygen or nitrogen atoms directly coordinated to the lanthanide ion. For all other different types of coordination, the present RM1 model for the lanthanides is much superior and must definitely be used. Overall, the accuracy of the model is of the order of 0.07Å for La(III) and Pr(III), and 0.08Å for Ce(III) for lanthanide-ligand atom distances which lie mostly around the 2.3Å to 2.6Å interval, implying an error around 3% only. PMID:26132289

  14. Coadsorption of lanthanum with boron and gadolinium with boron on Mo(1 1 0)

    NASA Astrophysics Data System (ADS)

    Magkoev, Tamerlan T.; Vladimirov, Georgij G.; Rump, Gennadij A.

    2008-05-01

    Submonolayer to multilayer coadsorption of lanthanum (La) with boron (B) and gadolinium (Gd) with boron on the surface of Mo(1 1 0) has been studied by means of Auger electron spectroscopy (AES), electron energy loss spectroscopy (EELS) and work function ( ϕ) measurements. The equilibrium state of double adsorbate systems achieved either by adsorption of rare-earth metal (REM) on boron precovered Mo(1 1 0) surface held at room temperature or after moderate annealing of the system with opposite order of adsorption (B on REM films) is the layer which is the inhomogeneous mixture of boron and REM atoms with preferential concentration of boron in the surface area of the mixed film. The work function of such films even at REM to boron concentration ratio much higher than 1/6 are very close to the values of corresponding bulk LaB 6 and GdB 6, favoring assumption of surface rearrangement as the dominant reason of high electron emission efficiency of hexaborides. Almost total similarity of the results for La-B and Gd-B systems can be viewed as the consequence of weak participation of Gd f-electrons in determining the thermionic properties of corresponding double layers.

  15. Lanthanum-based concentration and microrespirometric detection of microbes in water.

    PubMed

    Zhang, Yanyan; Riley, Lela K; Lin, Mengshi; Hu, Zhiqiang

    2010-06-01

    Rapid concentration and detection of microorganisms, particularly pathogens, are important but remain a challenge. In this research, lanthanum chloride (LaCl(3)) was used to concentrate E. coli in water and the results were compared with those obtained using traditional flocculants, such as ferric sulfate and aluminum sulfate. A turbidimetric assay and a microrespirometric assay were employed to enumerate the bacteria in water samples by monitoring the absorbance of bacteria and the oxygen-based fluorescence intensity, respectively. The microrespirometric method requires less time than the turbidimetric assay. Both assays could linearly enumerate the bacteria at the concentration range from 10(1) to 10(9)cells/mL. Based on the turbidimetric assay, the relative concentration efficiencies of the three flocculants were 75% (LaCl(3)), 40% (FeCl(3)) and 33% (Al(2)(SO(4))(3)), while for the microrespirometric assay, the concentration efficiencies were 85% (LaCl(3)), 34% (FeCl(3)) and 32% (Al(2)(SO(4))(3)). The microbial recovery rates, defined as the ratio of cell number in the sediment after coagulation/flocculation to that of the controls, were 94% (LaCl(3)), 69% (FeCl(3)) and 51% (Al(2)(SO(4))(3)) from the turbidimetric assay. The results demonstrate that compared with traditional flocculants, LaCl(3) has higher relative concentration and recovery efficiencies and thus possesses the potential for microbial concentration in water samples.

  16. Two lanthanum(III) complexes containing η2-pyrazolate and η2-1,2,4-triazolate ligands: intramolecular C-H...N/O interactions and coordination geometries.

    PubMed

    Wang, Yu-Long; Feng, Meng; Tao, Xian; Tang, Qing-Yun; Shen, Ying-Zhong

    2013-01-01

    The lanthanum(III) complexes tris(3,5-diphenylpyrazolato-κ(2)N,N')tris(tetrahydrofuran-κO)lanthanum(III) tetrahydrofuran monosolvate, [La(C(15)H(11)N(2))(3)(C(4)H(8)O)(3)]·C(4)H(8)O, (I), and tris(3,5-diphenyl-1,2,4-triazolato-κ(2)N(1),N(2))tris(tetrahydrofuran-κO)lanthanum(III), [La(C(14)H(10)N(3))(3)(C(4)H(8)O)(3)], (II), both contain La(III) atoms coordinated by three heterocyclic ligands and three tetrahydrofuran ligands, but their coordination geometries differ. Complex (I) has a mer-distorted octahedral geometry, while complex (II) has a fac-distorted configuration. The difference in the coordination geometries and the existence of asymmetric La-N bonding in the two complexes is associated with intramolecular C-H...N/O interactions between the ligands.

  17. Nanoparticle doping for improved Er-doped fiber lasers

    NASA Astrophysics Data System (ADS)

    Baker, Colin C.; Friebele, E. Joseph; Askins, Charles G.; Hunt, Michael P.; Marcheschi, Barbara A.; Fontana, Jake; Peele, John R.; Kim, Woohong; Sanghera, Jasbinder; Zhang, Jun; Pattnaik, Radha K.; Merkle, Larry D.; Dubinskii, Mark; Chen, Youming; Dajani, Iyad A.; Mart, Cody

    2016-03-01

    A nanoparticle (NP) doping technique was used for making erbium-doped fibers (EDFs) for high energy lasers. The nanoparticles were doped into the silica soot of preforms, which were drawn into fibers. The Er luminescence lifetimes of the NP-doped cores are longer than those of corresponding solution-doped silica, and substantially less Al is incorporated into the NP-doped cores. Optical-to-optical slope efficiencies of greater than 71% have been measured. Initial investigations of stimulated Brillouin scattering (SBS) have indicated that SBS suppression is achieved by NP doping, where we observed a low intrinsic Brillouin gain coefficient, of ~1× 10-11 m/W and the Brillouin bandwidth was increased by 2.5x compared to fused silica.

  18. Structural characterization and electron density distribution studies of (La0.8Ca0.2)(Cr0.9-xCo0.1Mnx)O3

    NASA Astrophysics Data System (ADS)

    Saravanan, R.; Thenmozhi, N.; Fu, Yen-Pei

    2016-07-01

    The doped lanthanum chromite (La0.8Ca0.2)(Cr0.9-xCo0.1Mnx)O3 (x=0.03, 0.06, 0.09 and 0.12) were synthesized by solid state reaction technique. The samples have been characterized by X-ray diffraction for structural and charge density analysis. XRD data show that the grown samples are orthorhombic in structure with single phase. The spatial charge density distribution in the unit cell for the synthesized samples has been studied using maximum entropy method. Further, the samples were analyzed by UV-visible spectrometry for optical properties and scanning electron microscopy for surface morphology. From the optical data, it was found that the direct band gap of the samples range from 2.27 to 2.46 eV. The samples were also investigated by vibrating sample magnetometry for magnetic properties. From VSM data, it is inferred that all the samples in this series are found to be predominantly antiferromagnetic in nature. Since the doped lanthanum chromites have good mechanical properties and electrical conductivity at high temperature, these materials are used in solid oxide fuel cells (SOFC).

  19. Higher Strength Lanthanum Carbonate Provides Serum Phosphorus Control With a Low Tablet Burden and Is Preferred by Patients and Physicians: A Multicenter Study

    PubMed Central

    Mehrotra, Rajnish; Martin, Kevin J.; Fishbane, Steven; Sprague, Stuart M.; Zeig, Steven; Anger, Michael

    2008-01-01

    Background and objectives: Management of hyperphosphatemia, a predictor of mortality in chronic kidney disease, is challenging. Nonadherence to dietary phosphate binders, in part, contributes to uncontrolled serum phosphorus levels. This phase IIIb trial assessed the efficacy of increased dosages (3000 to 4500 mg/d) of reformulated lanthanum carbonate (500-, 750-, and 1000-mg tablets) in nonresponders to dosages of up to 3000 mg/d. Design, setting, participants, & measurements: This 8-wk study with a 4-mo open-label extension enrolled 513 patients who were undergoing maintenance hemodialysis. Patients who achieved serum phosphorus control at week 4 with ≤3000 mg/d lanthanum carbonate entered cohort A; nonresponders were randomly assigned to receive 3000, 3750, or 4500 mg/d (cohort B). The primary outcome measure was the control rate for predialysis serum phosphorus levels at the end of week 8, among patients in cohort B. Results: At the end of week 4, 54% of patients achieved serum phosphorus control at dosages ≤3000 mg/d administered as one tablet per meal. Among patients who entered cohort B, control rates of 25, 38, and 32% for patients who were randomly assigned to 3000, 3750, or 4500 mg/d lanthanum carbonate, respectively, were achieved, with no increase in adverse events. Patients and physicians reported significantly higher levels of satisfaction with reformulated lanthanum carbonate compared with previous phosphate binders, partly because of reduced tablet burden with higher dosage strengths. Physicians and patients also expressed a preference for lanthanum carbonate over previous medication. Conclusions: Reformulated lanthanum carbonate is an effective phosphate binder that may reduce daily tablet burden. PMID:18579668

  20. Effect of RF power on structural and magnetic properties of La doped Bi2Fe4O9 thin films

    NASA Astrophysics Data System (ADS)

    Santhiya, M.; Pugazhvadivu, K. S.; Balakrishnan, L.; Tamilarasan, K.

    2016-05-01

    Effect of RF power on structural and magnetic properties of lanthanum (La3+) doped Bi2Fe4O9 thin films grown on p-Si substrates by radio frequency (RF) magnetron sputtering has studied in this investigation. It is observed that the sputtering power affects the crystalline nature and magnetic properties of grown thin films. X-ray diffraction and Raman spectrum confirms that the Bi2Fe4O9 (BFO) thin films were crystallized well with orthorhombic structure. The BFO thin films which was prepared at sputtering power of 100 W have good crystallinity than those prepared at 40 W. The magnetic properties are investigated by vibrating sample magnetometer. The magnetic hysteresis perceptive loop shows that the anti-ferromagnetic behavior of the sample at room temperature. These results confirms that the crystallinity and magnetic properties of the BFO thin films were enhanced at the higher sputtering power (100 W).