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Sample records for lanthanum chromites-based materials

  1. 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.

  2. Scintillator materials containing lanthanum fluorides

    DOEpatents

    Moses, William W.

    1991-01-01

    An improved radiation detector containing a crystalline mixture of LaF.sub.3 and CeF.sub.3 as the scintillator element is disclosed. Scintillators made with from 25% to 99.5% LaF.sub.3 and the remainder CeF.sub.3 have been found to provide a balance of good stopping power, high light yield and short decay constant that is equal to or superior to other known scintillator materials, and which may be processed from natural starting materials containing both rare earth elements. The radiation detectors disclosed are favorably suited for use in general purpose detection and in positron emission tomography.

  3. Scintillator materials containing lanthanum fluorides

    DOEpatents

    Moses, W.W.

    1991-05-14

    An improved radiation detector containing a crystalline mixture of LaF[sub 3] and CeF[sub 3] as the scintillator element is disclosed. Scintillators made with from 25% to 99.5% LaF[sub 3] and the remainder CeF[sub 3] have been found to provide a balance of good stopping power, high light yield and short decay constant that is equal to or superior to other known scintillator materials, and which may be processed from natural starting materials containing both rare earth elements. The radiation detectors disclosed are favorably suited for use in general purpose detection and in positron emission tomography. 2 figures.

  4. 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

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  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. 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

  11. 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.

  12. Adsorption studies of chromium (VI) removal from water by lanthanum diethanolamine hybrid material.

    PubMed

    Mandal, Sandip; Sahu, Manoj Kumar; Giri, Anil Kumar; Patel, Raj Kishore

    2014-01-01

    In the present research work, lanthanum diethanolamine hybrid material is synthesized by co-precipitation method and used for the removal of Cr(VI) from synthetic dichromate solution and hand pump water sample. The sorption experiments were carried out in batch mode to optimize various influencing parameters such as adsorbent dose, contact time, pH, competitive anions and temperature. The characterization of the material and mechanism of Cr(VI) adsorption on the material was studied by using scanning electron microscope, Fourier transform infrared, X-ray diffraction, Brunauer-Emmett-Teller and thermogravimetric analysis-differential thermal analysis. Adsorption kinetics studies reveal that the adsorption process followed first-order kinetics and intraparticle diffusion model with correlation coefficients (R2) of 0.96 and 0.97, respectively. The adsorption data were best fitted to linearly transformed Langmuir isotherm with correlation coefficient (R2) of 0.997. The maximum removal of Cr(VI) is found to be 99.31% at optimal condition: pH = 5.6 of the solution, adsorbent dose of 8 g L(-1) with initial concentration of 10mgL(-1) of Cr(VI) solution and an equilibrium time of 50 min. The maximum adsorption capacity of the material is 357.1 mg g(-1). Thermodynamic parameters were evaluated to study the effect of temperature on the removal process. The study shows that the adsorption process is feasible and endothermic in nature. The value of E (260.6 kJ mol(-1)) indicates the chemisorption nature of the adsorption process. The material is difficult to be regenerated. The above studies indicate that the hybrid material is capable of removing Cr(VI) from water. PMID:24645464

  13. 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.

  14. 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.

  15. 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

  16. Synthesis and characterization of a new photoluminescent material tris (2-methyl-8-hydroxy quinoline) lanthanum La(mq)3

    NASA Astrophysics Data System (ADS)

    Kumar, Rahul; Bhargava, Parag

    2016-05-01

    A new photoluminescence material, tris (2-methyl-8-hydroxy quinoline) lanthanum has been synthesized and characterized by different techniques. The prepared material La(mq)3 was characterized for structural, thermal and photoluminescence analysis. Structural analysis of this material was done by fourier transformed infrared spectroscopy (FTIR) and mass spectroscopy. Thermal analysis of this material was done by thermal gravimetric analysis (TGA) shows the thermal stability up to 400°C. Absorption and emission spectra of the material was measured by UV-visible spectroscopy and photoluminescence spectroscopy. Solution of this material La(mq)3 in ethanol showed absorption peak at 385nm respectively which may be attributed due to (π - π*) transitions. The photoluminescence spectra of La(mq)3 in ethanol solution showed intense peak at 430 nm.

  17. CRADA (AL-C-2009-02) Final Report: Phase I. Lanthanum-based Start Materials for Hydride Batteries

    SciTech Connect

    Gschneidner, Jr., Karl; Schmidt, Frederick; Frerichs, A. E.; Ament, Katherine A.

    2013-05-01

    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 (La{sub 1-x}R{sub x})(Ni{sub 1-y}M{sub y})(Si{sub z}), 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.

  18. Phosphate removal from water by a novel zeolite/lanthanum hydroxide hybrid material prepared from coal fly ash.

    PubMed

    Xie, Jie; Lai, Li; Lin, Lidan; Wu, Deyi; Zhang, Zhenjia; Kong, Hainan

    2015-01-01

    This study was undertaken to investigate the effectiveness of the hybrid adsorbent, which was synthesized from coal fly ash and was composed of lanthanum hydroxide and zeolite (La-ZFA), for phosphate removal from water. Long-term repeated adsorption tests for 30 days showed that the maximum removal capacity of the material reached 66.09 mg P/g. The fractionation of adsorbed phosphorus indicated that phosphate immobilized by La-ZFA was quite irreversible and was dominated by HCl-P fraction. It was suggested that the immobilization of phosphate was mainly attributed to lanthanum hydroxide and was slightly influenced by coexistence of other anions (Cl(-), NO3(-), SO4(2-), and HCO3(-)). At a La/P molar ratio between 1.5:1 and 2.0:1, a nearly complete removal (above 98%) of phosphate could be achieved. La-ZFA also exhibited great performance for removing phosphate from lake water (97.29%) as well as the effluent from wastewater treatment plant (97.86%), respectively. In addition, based on the results of the present study, it was believed that La-ZFA could be a potential material for phosphate removal in practical application.

  19. Phosphate removal from water by a novel zeolite/lanthanum hydroxide hybrid material prepared from coal fly ash.

    PubMed

    Xie, Jie; Lai, Li; Lin, Lidan; Wu, Deyi; Zhang, Zhenjia; Kong, Hainan

    2015-01-01

    This study was undertaken to investigate the effectiveness of the hybrid adsorbent, which was synthesized from coal fly ash and was composed of lanthanum hydroxide and zeolite (La-ZFA), for phosphate removal from water. Long-term repeated adsorption tests for 30 days showed that the maximum removal capacity of the material reached 66.09 mg P/g. The fractionation of adsorbed phosphorus indicated that phosphate immobilized by La-ZFA was quite irreversible and was dominated by HCl-P fraction. It was suggested that the immobilization of phosphate was mainly attributed to lanthanum hydroxide and was slightly influenced by coexistence of other anions (Cl(-), NO3(-), SO4(2-), and HCO3(-)). At a La/P molar ratio between 1.5:1 and 2.0:1, a nearly complete removal (above 98%) of phosphate could be achieved. La-ZFA also exhibited great performance for removing phosphate from lake water (97.29%) as well as the effluent from wastewater treatment plant (97.86%), respectively. In addition, based on the results of the present study, it was believed that La-ZFA could be a potential material for phosphate removal in practical application. PMID:26301857

  20. Synthesis and characterization of a new photoluminescent material (8-hydroxy quinoline) bis (2-2'bipyridine) lanthanum La(Bpy)2q

    NASA Astrophysics Data System (ADS)

    Kumar, Rahul; Bhargava, Parag

    2016-05-01

    A new photoluminescence material, (8-hydroxy quinoline) bis (2-2'bipyridine) lanthanum has been synthesized and characterized by different techniques. The prepared material La(Bpy)2q was characterized for structural, thermal and photoluminescence analysis. Structural analysis of this material was done by Fourier transformed infrared spectroscopy (FTIR) and mass spectroscopy. Thermal analysis of this material was done by thermal gravimetric analysis (TGA) shows the thermal stability up to 190°C.Absorption and emission spectra of the material was measured by UV-visible spectroscopy and photoluminescence spectroscopy. Solution of this material La(Bpy)2q in ethanol showed absorption peak at 385nm, which may be attributed due to (π - π*) transitions. The photoluminescence spectra of La(Bpy)2q in ethanol solution showed intense peak at 490 nm

  1. 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.

  2. 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.

  3. High-Temperature Transport in Lanthanum Telluride and Other Modern Thermoelectric Materials

    NASA Astrophysics Data System (ADS)

    May, Andrew F.

    This manuscript discusses the materials physics of thermal and electrical transport in the solid state. In particular, the focus is on thermoelectric materials, which enable the direct conversion between thermal and electrical energy. The ability of simple approximations and semiclassical models to describe transport is explored in a variety of systems. In some cases, the traditional models provide a very accurate description of the transport for the compositions of interest to thermoelectric applications. This is the case for n-type Ba8Ga16-xGe30+x, where a single, parabolic band model captures the electrical transport and thus allows the accurate prediction of optimal composition for energy conversion. This is not found to be true in La3-xTe4, and more than one parabolic conduction band is required to describe the electrical transport. In this case, the use of ab initio electronic band structure calculations provided critical knowledge for physical models to be developed. The influence of structure on thermal transport is also examined in detail. The compounds considered typically possess low lattice thermal conductivity, with values often being less than or equal to 1 W/m/K at 300 K. This can generally be associated with large unit cells, where the high number of atoms per unit cell results in a large number of optical modes, which carry little heat due to their low group velocities. Phonon scattering is also considered, and the cation vacancies in La3-xTe 4 are found to reduce the lattice thermal conductivity by over 100% at room temperature. Finally, the resulting thermoelectric efficiency is discussed, where leg efficiencies near 20% of the Carnot efficiency are predicted in segmented legs. The work detailed here has led to the continued development of La3-xTe4 by the Jet Propulsion Laboratory, where it is a top candidate for future use in deep-space power-generation systems.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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

  9. 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.

  10. 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.

  11. 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

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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 ...

  6. 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

  7. 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)

  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. 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.

  11. 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

  12. 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).

  13. 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

  14. 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.

  15. Development of advanced thermoelectric materials, phase A

    NASA Technical Reports Server (NTRS)

    1980-01-01

    Work performed on the chemical system characterized by chrome sulfide, chrome selenide, lanthanum selenide, and lanthanum sulfide is described. Most materials within the chemical systems possess the requisites for attractive thermoelectric materials. The preparation of the alloys is discussed. Graphs show the Seebeck coefficient, electrical resistivity, and thermal conductivity of various materials within the chemical systems. The results of selected doping are included.

  16. 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.

  17. 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

  18. 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.

  19. 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.

  20. 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

  1. 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.

  2. 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.

  3. Development of advanced thermoelectric materials

    NASA Technical Reports Server (NTRS)

    1984-01-01

    The development of an advanced thermoelectric material for radioisotope thermoelectric generator (RTG) applications is reported. A number of materials were explored. The bulk of the effort, however, was devoted to improving silicon germanium alloys by the addition of gallium phosphide, the synthesis and evaluation of lanthanum chrome sulfide and the formulation of various mixtures of lanthanum sulfide and chrome sulfide. It is found that each of these materials exhibits promise as a thermoelectric material.

  4. 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.

  5. 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

  6. 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

  7. 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.

  8. 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

  9. Synthesis, characterization and photocatalytic properties of lanthanum oxy-carbonate, lanthanum oxide and lanthanum hydroxide nanoparticles

    NASA Astrophysics Data System (ADS)

    Ghiasi, Mahnaz; Malekzadeh, Azim

    2015-01-01

    A simple thermal decomposition route has been developed to prepare La2O3 and La2O2CO3 nanoparticles. Sonication of La2O3 nanoparticles in water at room temperature is accompanied to the formation of La(OH)3 nanoparticles. The effect of addition of citric acid, as disperser, was also investigated on the phase formation and particle size distribution of the products. It is observed that citric acid has no effect on the particle size of the samples. The prepared nanoparticles were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM) and atomic force microscopy (AFM) analyses. Photocatalytic activity of the products was examined for degradation of methyl orange, a common reactive dye, as a pollutant under ultraviolet irradiation in the wastewater. The results show that La2O2CO3 nanoparticles are promising materials in this photocatalytic degradation with no significant loss of activity even after four cycles of successive uses. A pseudo-first-order kinetic is obtained for the photocatalytic degradation of methyl orange over La2O2CO3 nanoparticles according to the Langmuir-Hinshelwood analysis.

  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. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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}.

  18. 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.

  19. Muscle cell membranes from early degeneration muscle cell fibers in Solenopsis are leaky to lanthanum: electron microscopy and X-ray analysis

    SciTech Connect

    Jones, R.G.; Davis, W.L.

    1985-06-01

    Lanthanum infusion techniques, transmission electron microscopy, and X-ray microanalysis were utilized to compare the permeability of muscle cell membranes from normal and degenerating muscle fibers of Solenopsis spp. In normal fibers, the electron-dense tracer was limited to components of the sarcotubular system. However, the insemination-induced degeneration of muscle fibers was characterized by the presence of an electron-dense precipitate within the myofibrils and mitochondria as well as in the extramyofibrillar spaces. The electron-dense material was subsequently identified by elemental analysis to be lanthanum. Such data indicate that one of the earliest stages of muscle degeneration involves an alteration in cell membrane permeability.

  20. 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....

  1. 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....

  2. 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....

  3. 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.

  4. 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).

  5. 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

  6. 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

    flocculent electron dense material is observed apposed to the external lamina of the plasma membrane. The distribution of this material on the membrane is described. Antimycin A leads to cellular changes corresponding to the irreversible inhibition of cellular respiration. It is concluded from the results that cobalt acts on the process of granule formation inside the cell, while lanthanum by its binding to the plasma membrane may alter molecules involved in secretagogue binding and transport systems into the cell.

  7. 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.

  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. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  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. 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

  20. Effects of anode material on arcjet performance

    NASA Technical Reports Server (NTRS)

    Sankovic, John M.; Curran, Frank M.; Larson, C. A.

    1992-01-01

    Anodes fabricated from four different materials were tested in a modular arcjet thruster at 1 kW power level on nitrogen/hydrogen mixtures. A two-percent thoriated tungsten anode served as the control. Graphite was chosen for its ease in fabrication, but experienced severe erosion in the constrictor and diverging side. Hafnium carbide and lanthanum hexaboride were chosen for their low work functions but failed due to thermal stress and reacted with the propellant. When compared to the thoriated tungsten nozzle, thruster performance was significantly lower for the lanthanum hexaboride insert and the graphite nozzle, but was slightly higher for the hafnium carbide nozzle. Both the lanthanum hexaboride and hafnium carbide nozzle operated at higher voltages. An attempt was made to duplicate higher performance hafnium carbide results, but repeated attempts at machining a second anode insert were unsuccessful. Graphite, hafnium carbide, and lanthanum hexaboride do not appear viable anode materials for low power arcjet thrusters.

  1. 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

  2. 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.

  3. 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

  4. 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.

  5. 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.

  6. 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%.

  7. 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.

  8. 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.

  9. Oxygen transport in nanostructured lanthanum manganites.

    PubMed

    Rossetti, Ilenia; Allieta, Mattia; Biffi, Cesare; Scavini, Marco

    2013-10-21

    Methods and models describing oxygen diffusion and desorption in oxides have been developed for slightly defective and well crystallised bulky materials. Does nanostructuring change the mechanism of oxygen mobility? In such a case, models should be properly checked and adapted to take into account new material properties. In order to do so, temperature programmed oxygen desorption and thermogravimetric analysis, either in isothermal or ramp mode, have been used to investigate some nanostructured La1-xAxMnO3±δ samples (A = Sr and Ce, 20-60 nm particle size) with perovskite-like structure. The experimental data have been elaborated by means of different models to define a set of kinetic parameters able to describe oxygen release properties and oxygen diffusion through the bulk. Different rate-determining steps have been identified, depending on the temperature range and oxygen depletion of the material. In particular, oxygen diffusion was shown to be rate-limiting at low temperature and at low defect concentration, whereas oxygen recombination at the surface seems to be the rate-controlling step at high temperature. However, the oxygen recombination step is characterised by an activation energy much lower than that for diffusion. In the present paper oxygen transport in nanosized materials is quantified by making use of widely diffused experimental techniques and by critically adapting to nanoparticles suitably chosen models developed for bulk materials.

  10. 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

  11. Materials for high-temperature hydrogen fluorine environments. Final report, June 1976-December 1978

    SciTech Connect

    Holcombe, C.E. Jr.; Kovach, L.

    1981-03-01

    A determination has been made of the stability of 35 materials under high-temperature, fluorine rich, hydrogen fluoride torch testing. Refractory materials tested included 4 borides, 3 carbides, 3 nitrides, 12 oxides, 1 oxynitride, 1 sulfide, 10 metals, and carbon (10 types). Three materials distinctly performed better than nickel: lanthanum hexaboride, calcium hexaboride, and lanthanum silicon oxynitride. Of these, lanthanum hexaboride is the best candidate tested since it has an estimated upper use temperature > 1726 K, which is above the melting point and more than 300 K above the upper use temperature of nickel.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. Selective oxidation of methanol to hydrogen over gold catalysts promoted by alkaline-earth-metal and lanthanum oxides.

    PubMed

    Hereijgers, Bart P C; Weckhuysen, Bert M

    2009-01-01

    A series of alumina-supported gold catalysts was investigated for the CO-free production of hydrogen by partial oxidation of methanol. The addition of alkaline-earth metal oxide promoters resulted in a significant improvement of the catalytic performance. The methanol conversion was ca. 85 % with all studied catalyst materials, however, the selectivity for hydrogen increased from 15 % to 51 % when going from the unpromoted to a BaO-promoted catalyst. The formation of the undesired byproducts CO, methane, and dimethyl ether was considerably reduced as well. The observed trend in catalyst performance follows the trend in increasing basicity of the studied promoter elements, indicating a chemical effect of the promoter material. Superior catalytic performance, in terms of H(2) and CO selectivity, was obtained with a Au/La(2)O(3) catalyst. At 300 degrees C the hydrogen selectivity reached 80 % with only 2 % CO formation, and the catalyst displayed a stable performance over at least 24 h on-stream. Furthermore, the formation of CO was found to be independent of the oxygen concentration in the feed. The commercial lanthanum oxide used in this study had a low specific surface area, which led to the formation of relative large gold particles. Therefore, the catalytic activity could be enhanced by decreasing the gold particle size through deposition on lanthanum oxide supported on high-surface-area alumina.

  17. 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

  18. [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-.

  19. Determination of in vitro lung solubility and intake-to-dose conversion factor for tritiated lanthanum nickel aluminum alloy.

    PubMed

    Farfán, Eduardo B; Labone, Thomas R; Staack, Gregory C; Cheng, Yung-Sung; Zhou, Yue; Varallo, Thomas P

    2012-09-01

    A sample of tritiated lanthanum nickel aluminum alloy (LaNi4.25Al0.75 or LANA.75) similar to that used at the Savannah River Site Tritium Facilities was analyzed to estimate the particle size distribution of this metal tritide powder and the rate at which this material dissolves in the human respiratory tract after it is inhaled. This information is used to calculate the committed effective dose received by a worker after inhaling the material. These doses, which were calculated using the same methodology given in the U.S. Department of Energy Tritium Handbook, are presented as inhalation intake-to-dose conversion factors (DCF). The DCF for this metal tritide was determined to be 9.4 × 10 Sv Bq, which is less than the DCF for tritiated water. Therefore, the radiation worker bioassay programs designed for tritiated water are adequate to monitor for intakes of this material.

  20. DETERMINATION OF IN-VITRO LUNG SOLUBILITY AND INTAKE-TO-DOSE CONVERSION FACTOR FOR TRITIATED LANTHANUM NICKEL ALUMINUM ALLOY

    SciTech Connect

    Farfan, E.; Labone, T.; Staack, G.; Cheng, Y.; Zhou, Y.; Varallo, T.

    2011-11-11

    A sample of tritiated lanthanum nickel aluminum alloy (LaNi4.25Al0.75 or LANA.75) similar to that used at the Savannah River Site Tritium Facilities was analyzed to estimate the particle size distribution of this metal tritide powder and the rate, at which this material dissolves in the human respiratory tract after it is inhaled. This information is used to calculate the committed effective dose received by a worker after inhaling the material. These doses, which were calculated using the same methodology given in the DOE Tritium Handbook, are presented as inhalation intake-to-dose conversion factors (DCF). The DCF for this metal tritide is less than the DCF for tritiated water and radiation worker bioassay programs designed for tritiated water are adequate to monitor for intakes of this material.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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

  8. 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.

  9. 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.

  10. Dehydration of lactic acid to acrylic acid over lanthanum phosphate catalysts: the role of Lewis acid sites.

    PubMed

    Guo, Zhen; Theng, De Sheng; Tang, Karen Yuanting; Zhang, Lili; Huang, Lin; Borgna, Armando; Wang, Chuan

    2016-09-14

    Lanthanum phosphate (LaP) nano-rods were synthesized using n-butylamine as a shape-directing agent (SDA). The resulting catalysts were applied in the dehydration of lactic acid to acrylic acid. Aiming to understand the nature of the active sites, the chemical and physical properties of LaP materials were studied using a variety of characterization techniques. This study showed that the SDA not only affected the porosity of the LaP materials but also modified the acid-base properties. Clearly, the modification of the acid-base properties played a more critical role in determining the catalytic performance than porosity. An optimized catalytic performance was obtained on the LaP catalyst with a higher concentration of Lewis acid sites. Basic sites showed negative effects on the stability of the catalysts. Good stability was achieved when the catalyst was prepared using the appropriate SDA/La ratio. PMID:27514871

  11. Dehydration of lactic acid to acrylic acid over lanthanum phosphate catalysts: the role of Lewis acid sites.

    PubMed

    Guo, Zhen; Theng, De Sheng; Tang, Karen Yuanting; Zhang, Lili; Huang, Lin; Borgna, Armando; Wang, Chuan

    2016-09-14

    Lanthanum phosphate (LaP) nano-rods were synthesized using n-butylamine as a shape-directing agent (SDA). The resulting catalysts were applied in the dehydration of lactic acid to acrylic acid. Aiming to understand the nature of the active sites, the chemical and physical properties of LaP materials were studied using a variety of characterization techniques. This study showed that the SDA not only affected the porosity of the LaP materials but also modified the acid-base properties. Clearly, the modification of the acid-base properties played a more critical role in determining the catalytic performance than porosity. An optimized catalytic performance was obtained on the LaP catalyst with a higher concentration of Lewis acid sites. Basic sites showed negative effects on the stability of the catalysts. Good stability was achieved when the catalyst was prepared using the appropriate SDA/La ratio.

  12. 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

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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

  19. 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.

  20. 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.

  1. Advanced materials for solid oxide fuel cells

    SciTech Connect

    Armstrong, T.R.; Stevenson, J.; Paulik, S.

    1996-12-31

    Purpose of the research is to improve the properties of current state- of-the-art materials used for SOFCs. The project includes interconnect development, high-performance cathode, electrochemical testing, and accelerated testing. This document reports results of mechanical tests (bend strength, elastic modulus, fracture strength) of acceptor-substituted lanthanum chromite (interconnect material).

  2. 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

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. Modified Johnson model for ferroelectric lead lanthanum zirconate titanate at very high fields and below Curie temperature.

    SciTech Connect

    Narayanan, M.; Tong, S.; Ma, B.; Liu, S.; Balachandran, U.

    2012-01-01

    A modified Johnson model is proposed to describe the nonlinear field dependence of the dielectric constant ({var_epsilon}-E loop) in ferroelectric materials below the Curie temperature. This model describes the characteristic ferroelectric 'butterfly' shape observed in typical {var_epsilon}-E loops. The predicted nonlinear behavior agreed well with the measured values in both the low- and high-field regions for lead lanthanum zirconate titanate films. The proposed model was also validated at different temperatures below the ferroelectric-to-paraelectric Curie point. The anharmonic coefficient in the model decreased from 6.142 x 10{sup -19} cm{sup 2}/V{sup 2} to 2.039 x 10{sup -19} cm{sup 2}/V{sup 2} when the temperature increased from 25 C to 250 C.

  8. Kinetics of thermolysis of lanthanum nitrate with hexamethylenetetramine: Crystal structure, TG-DSC, impact and friction sensitivity studies, Part-96

    NASA Astrophysics Data System (ADS)

    Nibha; Baranwal, B. P.; Singh, Gurdip; Singh, C. P.; Daniliuc, Constantin G.; Soni, P. K.; Nath, Yogeshwar

    2014-11-01

    The development of high energetic materials includes process ability and the ability to attain insensitive munitions (IM). This paper investigates the preparation of lanthanum metal nitrate complex of hexamethylenetetramine in water at room temperature. This complex of molecular formulae [La (NO3)2(H2O)6] (2HMTA) (NO3-) (H2O) was characterized by X-ray crystallography. Thermal decomposition was investigated using TG, TG-DSC and ignition delay measurements. Kinetic analysis of isothermal TG data has been investigated using model fitting methods as well as model free isoconversional methods. The sensitivity measurements towards mechanical destructive stimuli such as impact and friction were carried out and the complex was found to be insensitive. In order to identify the end product of thermolysis, X-ray diffraction patterns of end product was carried out which proves the formation of La2O3.

  9. 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

  10. Fabrication and characterization of protonic-ceramic fuel cells and electrolysis cells utilizing infiltrated lanthanum nickelate electrodes

    NASA Astrophysics Data System (ADS)

    Babiniec, Sean M.

    High-temperature protonic ceramics (HTPCs) have gained interest as fuel cell and electrolysis cell electrolytes, as well as hydrogen separation membranes. The transport of hydrogen as opposed to oxygen results in several benefits and applications, including higher fuel efficiency, dehydrogenation of fuel streams, and hydrogen-based chemical synthesis. However, limited work has been done in the development of air/steam electrodes for these devices. This work presents the characterization of lanthanum nickelate, La 2NiO4+delta (LN), as a potential air/steam electrode material for use with BaCe0.2Zr0.7Y0.1O3-delta (BCZY27) HTPC electrolytes fabricated by the solid-state reactive sintering technique. Two types of devices were made; a symmetric cell used for electrode characterization, and a full fuel cell/electrolysis cell used for device performance characterization. The symmetric cell consists of a 1 mm thick BCZY27 substrate with identical air/steam electrodes on both sides. Air/steam electrodes were made by infiltrating ˜ 50 nm lanthanum nickelate nanoparticles into a BCZY27 porous backbone. The fuel cell/electrolysis cell consists of a 1mm thick Ni/BCZY27 anode support, a 25 mum thick BCZY27 electrolyte, and a 50 mum thick porous BCZY27 backbone infiltrated with lanthanum nickelate. Through symmetric cell testing, it was found that the electrode polarization resistance decreases with increasing oxygen content, indicating good oxygen reduction reaction characteristics. A minimum polarization resistance was found as 2.58 Ohm-cm2 in 3% humidied oxygen at 700 °C. Full cell testing revealed a peak power density of 27 mW-cm-2 at 700 °C. Hydrogen flux measurements were also taken in the both galvanic/post-galvanic and electrolytic operation. Galvanic/post-galvanic fluxes exhibit a very high faradaic efficiency. However, electrolytic hydrogen fluxes were much lower than the calculated hydrogen faradaic flux, indicating a different charge carrier other than protons is

  11. 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.

  12. 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

  13. 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.

  14. 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.

  15. 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.

  16. 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

  17. 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%.

  18. 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

  19. 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

  20. 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}

  1. 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.

  2. 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.

  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. 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.

  5. 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

  6. 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.

  7. 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

  8. 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.

  9. Intermediate temperature solid oxide fuel cell based on lanthanum gallate electrolyte

    NASA Astrophysics Data System (ADS)

    Inagaki, Toru; Nishiwaki, Futoshi; Yamasaki, Satoru; Akbay, Taner; Hosoi, Kei

    The Kansai Electric Power Co. Inc. (KEPCO) and Mitsubishi Materials Corporation (MMC) have been developing intermediate temperature solid oxide fuel cells (IT-SOFCs) which are operable at a temperature range between 600 and 800 °C. There are some significant features in IT-SOFC of KEPCO-MMC: (1) highly conductive lanthanum gallate-based oxide is adopted as an electrolyte to realize high-performance disk-type electrolyte-supported cells; (2) the cell-stacks with seal-less structure using metallic separators allow residual fuel to burn around the stack and the combustion heat is utilized for thermally self-sustainable operation; (3) the separators have flexible arms by which separate compressive forces can be applied for manifold parts and interconnection parts. We are currently participating in the project by New Energy and Industrial Technology Development Organization (NEDO) to develop 10 kW-class combined heat and power (CHP) systems. In FY2006, a 10 kW-class module was developed, with which the electrical efficiency of 50%HHV was obtained based on DC 12.6 kW. In the first quarter of FY2007, the 10 kW-class CHP system using the module gave the electrical efficiency of 41%HHV on AC 10 kW and the overall efficiency of 82%HHV when exhaust heat was recovered as 60 °C hot water. Currently, the operation has been accumulated for about 2500 h to evaluate the long-term stability of the system.

  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. Comparison between methods using copper, lanthanum, and colorimetry for the determination of the cation exchange capacity of plant cell walls.

    PubMed

    Wehr, J Bernhard; Blamey, F Pax C; Menzies, Neal W

    2010-04-28

    The determination of the cation exchange capacity (CEC) of plant cell walls is important for many physiological studies. We describe the determination of cell wall CEC by cation binding, using either copper (Cu) or lanthanum (La) ions, and by colorimetry. Both cations are strongly bound by cell walls, permitting fast and reproducible determinations of the CEC of small samples. However, the dye binding methods using two cationic dyes, Methylene Blue and Toluidine Blue, overestimated the CEC several-fold. Column and centrifugation methods are proposed for CEC determination by Cu or La binding; both provide similar results. The column method involves packing plant material (2-10 mg dry mass) in a chromatography column (10 mL) and percolating with 20 bed volumes of 1 mM La or Cu solution, followed by washing with deionized water. The centrifugation method uses a suspension of plant material (1-2 mL) that is centrifuged, and the pellet is mixed three times with 10 pellet volumes of 1 mM La or Cu solution followed by centrifugation and final washing with deionized water. In both methods the amount of La or Cu bound to the material was determined by spectroscopic methods.

  13. 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.

  14. Lanthanum-containing hydroxyapatite coating on ultrafine-grained titanium by micro-arc oxidation: a promising strategy to enhance overall performance of titanium.

    PubMed

    Deng, Zhennan; Wang, LiLi; Zhang, Dafeng; Liu, Jinsong; Liu, Chuantong; Ma, Jianfeng

    2014-01-31

    Titanium is widely used in biomedical materials, particularly in dental implants, because of its excellent biocompatibility and mechanical characteristics. However, titanium implant failures still remain in some cases, varying with implantation sites and patients. Improving its overall performance is a major focus of dental implant research. Equal-channel angular pressing (ECAP) can result in ultrafine-grained titanium with superior mechanical properties and better biocompatibility, which significantly benefits dental implants, and without any harmful alloying elements. Lanthanum (La) can inhibit the acidogenicity of dental plaque and La-containing hydroxyapatite (La-HA) possesses a series of attractive properties, in contrast to La-free HA. Micro-arc oxidation (MAO) is a promising technology that can produce porous and firmly adherent hydroxyapatite (HA) coatings on titanium substrates. Therefore, we hypothesize that porous La-containing hydroxyapatite coatings with different La content (0.89%, 1.3% and 1.79%) can be prepared on ultrafine-grained (~200-400 nm) titanium by ECAP and MAO in electrolytic solution containing 0.2 mol/L calcium acetate, 0.02 mol/L beta-glycerol phosphate disodium salt pentahydrate (beta-GP), and lanthanum nitrate with different concentrations to further improve the overall performance of titanium, which are expected to have great potential in medical applications as a dental implant.

  15. 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

  16. 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.

  17. 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

  18. Stability of solid oxide fuel cell materials

    SciTech Connect

    Armstrong, T.R.; Bates, J.L.; Chick, L.A.

    1996-04-01

    Interconnection materials in a solid oxide fuel cell are exposed to both highly oxidizing conditions at the cathode and to highly reducing conditions at the anode. The thermal expansion characteristics of substituted lanthanum and yttrium chromite interconnect materials were evaluated by dilatometry as a function of oxygen partial pressures from 1 atm to 10{sup -18} atm, controlled using a carbon dioxide/hydrogen buffer.

  19. 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.

  20. 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+.

  1. 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.

  2. 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+.

  3. 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.

  4. 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.

  5. 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.

  6. 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

  7. 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.

  8. 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.

  9. [Adsorption of Phosphate by Lanthanum Hydroxide/Natural Zeolite Composites from Low Concentration Phosphate Solution].

    PubMed

    Lin, Jian-wei; Wang, Hong; Zhan, Yan-hui; Chen, Dong-mei

    2016-01-15

    A series of composites of lanthanum hydroxide/natural zeolite ( La( OH) 3/NZ composites) were prepared by co-precipitation method, and these composites were used as adsorbents to remove phosphate from aqueous solution. The phosphate adsorption capacities of different composites prepared with different precipitated pH values were compared in batch mode. The adsorption characteristics of phosphate from aqueous solution on the La(OH)3/NZ composite prepared with the precipitated pH value of 11 was investigated using batch experiments. The results showed that the La(OH)3/NZ composite prepared with the precipitated pH values of 5-7 and 13 had a low adsorption capacity for phosphate in aqueous solution, while the La( OH) 3/NZ composites prepared with the precipitated pH values of 9-12 exhibited much higher phosphate adsorption capacity. The phosphate adsorption capacity of the La (OH)3/NZ composite increased with the increase of the precipitated pH value from 9 to 11, but remained basically unchanged with the increase of the precipitated pH value from 11 to 12. The equilibrium adsorption data of phosphate from aqueous solution on the La ( OH ) 3/NZ composite prepared with the precipitated pH value of 11 could be described by the Langmuir isotherm model with the predicted maximum phosphate adsorption of 44 mg x g(-1) (phosphate solution pH 7 and 30 degrees C). The kinetic data of phosphate adsorption from low concentration phosphate solution on the La(OH)3/NZ composite prepared with the precipitated pH value of 11 well followed a pseudo-second-order model. The presence of Cl- and SO4(2-) in low concentration phosphate solution had no negative effect on phosphate adsorption onto the La(OH)3/NZ composite prepared with the precipitated pH value of 11, while the presence of HCO3- slightly inhibited the adsorption of phosphate. Coexisting humic acid had a negative effect on the adsorption of phosphate at low concentration on the La(OH)3/NZ composite prepared with the

  10. [Adsorption of Phosphate by Lanthanum Hydroxide/Natural Zeolite Composites from Low Concentration Phosphate Solution].

    PubMed

    Lin, Jian-wei; Wang, Hong; Zhan, Yan-hui; Chen, Dong-mei

    2016-01-15

    A series of composites of lanthanum hydroxide/natural zeolite ( La( OH) 3/NZ composites) were prepared by co-precipitation method, and these composites were used as adsorbents to remove phosphate from aqueous solution. The phosphate adsorption capacities of different composites prepared with different precipitated pH values were compared in batch mode. The adsorption characteristics of phosphate from aqueous solution on the La(OH)3/NZ composite prepared with the precipitated pH value of 11 was investigated using batch experiments. The results showed that the La(OH)3/NZ composite prepared with the precipitated pH values of 5-7 and 13 had a low adsorption capacity for phosphate in aqueous solution, while the La( OH) 3/NZ composites prepared with the precipitated pH values of 9-12 exhibited much higher phosphate adsorption capacity. The phosphate adsorption capacity of the La (OH)3/NZ composite increased with the increase of the precipitated pH value from 9 to 11, but remained basically unchanged with the increase of the precipitated pH value from 11 to 12. The equilibrium adsorption data of phosphate from aqueous solution on the La ( OH ) 3/NZ composite prepared with the precipitated pH value of 11 could be described by the Langmuir isotherm model with the predicted maximum phosphate adsorption of 44 mg x g(-1) (phosphate solution pH 7 and 30 degrees C). The kinetic data of phosphate adsorption from low concentration phosphate solution on the La(OH)3/NZ composite prepared with the precipitated pH value of 11 well followed a pseudo-second-order model. The presence of Cl- and SO4(2-) in low concentration phosphate solution had no negative effect on phosphate adsorption onto the La(OH)3/NZ composite prepared with the precipitated pH value of 11, while the presence of HCO3- slightly inhibited the adsorption of phosphate. Coexisting humic acid had a negative effect on the adsorption of phosphate at low concentration on the La(OH)3/NZ composite prepared with the

  11. 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

  12. 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.

  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. Synthesis and characterization of lanthanum silicate apatite by gel-casting route as electrolytes for solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Jiang, San Ping; Zhang, Lan; He, Hong Quan; Yap, Rong Keng; Xiang, Yan

    Lanthanum silicate oxyapatite, La 10Si 6O 27 is successfully synthesized by a water-based gel-casting technique. The effect of calcination and sintering temperatures on the conductivity is investigated in detail in the temperature range between 300 and 800 °C by the impedance spectroscopy. The highest oxygen ion conductivity is 1.50 × 10 -3 S cm -1 at 500 °C and 3.46 × 10 -2 S cm -1 at 800 °C for an apatite electrolyte sintered at 1650 °C, which is one order of magnitude higher than that synthesized by the conventional solid state reaction route under the same sintering conditions. The thermal expansion coefficient (TEC) of the as-synthesized apatite is 9.7 × 10 -6 K -1. A solid oxide fuel cell using La 10Si 6O 27 as an electrolyte shows an open circuit potential of 1.06 V and power output of 7.89 mW cm -2 at 800 °C. The results demonstrate the potential of the silicate oxyapatite materials synthesized by the gel-casting as an alternative electrolyte in solid oxide fuel cells.

  15. 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

  16. 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

  17. Fabrication of lanthanum strontium cobalt ferrite (LSCF) cathodes for high performance solid oxide fuel cells using a low price commercial inkjet printer

    NASA Astrophysics Data System (ADS)

    Han, Gwon Deok; Neoh, Ke Chean; Bae, Kiho; Choi, Hyung Jong; Park, Suk Won; Son, Ji-Won; Shim, Joon Hyung

    2016-02-01

    In this study, we investigate a method to fabricate high quality lanthanum strontium cobalt ferrite (LSCF) cathodes for solid oxide fuel cells (SOFCs) using a commercial low price inkjet printer. The ink source is synthesized by dissolving the LSCF nanopowder in a water-based solvent with a proper amount of surfactants. Microstructures of the LSCF layer, including porosity and thickness per printing scan cycle, are adjusted by grayscale in the printing image. It is successfully demonstrated that anode-supported SOFCs with optimally printed LSCF cathodes can produce decent power output, i.e., a maximum peak power density of 377 mW cm-2 at 600 °C, in our experiment. We expect that this approach can support the quick and easy prototyping and evaluating of a variety of cathode materials in SOFC research.

  18. 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

  19. 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

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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).

  6. 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

  7. 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

  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. 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).

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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

  20. Superconductivity in the lanthanum-yttrium-manganese alloy system

    SciTech Connect

    Stierman, R.J.

    1980-03-01

    An empirical approach involving lattice instabilities was investigated in the search for new superconducting materials. Pseudo-lanthanide compounds using La and Y were prepared for the system La/sub 1-x/Y/sub x/Mn/sub 2/ by arc melting and subsequent heat treatment. Low temperature magnetic susceptibility and low temperature heat capacity measurements were made. The unit cell lattice parameters were determined from x-ray powder patterns taken on most samples and metallographic examination was carried out on selected samples. Alloys with low La concentrations (x greater than or equal to 0.6) showed RMn/sub 2/ in the cubic C15 Laves phase as the major component with second phase material present. The magnetic susceptibility and x-ray data indicated a superconducting phase which seemed to be the RMn/sub 2/ phase, but heat capacity measurements showed the second phase material was the superconductor, while the RMn/sub 2/ was not. Failure to form compounds with higher La content was experienced and may be due to the lattice instability expected at x = 0.56. This indicates that perhaps more stingent conditions are required to form pseudo-lanthanide compounds than were previously considered. More systems should be investigated to see if this is true, and to determine the possibilities of this approach.

  1. Materials

    NASA Technical Reports Server (NTRS)

    Glaessgen, Edward H.; Schoeppner, Gregory A.

    2006-01-01

    NASA Langley Research Center has successfully developed an electron beam freeform fabrication (EBF3) process, a rapid metal deposition process that works efficiently with a variety of weldable alloys. The EBF3 process can be used to build a complex, unitized part in a layer-additive fashion, although the more immediate payoff is for use as a manufacturing process for adding details to components fabricated from simplified castings and forgings or plate products. The EBF3 process produces structural metallic parts with strengths comparable to that of wrought product forms and has been demonstrated on aluminum, titanium, and nickel-based alloys to date. The EBF3 process introduces metal wire feedstock into a molten pool that is created and sustained using a focused electron beam in a vacuum environment. Operation in a vacuum ensures a clean process environment and eliminates the need for a consumable shield gas. Advanced metal manufacturing methods such as EBF3 are being explored for fabrication and repair of aerospace structures, offering potential for improvements in cost, weight, and performance to enhance mission success for aircraft, launch vehicles, and spacecraft. Near-term applications of the EBF3 process are most likely to be implemented for cost reduction and lead time reduction through addition of details onto simplified preforms (casting or forging). This is particularly attractive for components with protruding details that would require a significantly large volume of material to be machined away from an oversized forging, offering significant reductions to the buy-to-fly ratio. Future far-term applications promise improved structural efficiency through reduced weight and improved performance by exploiting the layer-additive nature of the EBF3 process to fabricate tailored unitized structures with functionally graded microstructures and compositions.

  2. 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.

  3. 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.

  4. 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.

  5. 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

  6. 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.

  7. 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

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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}.

  14. 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

  15. EXAFS studies on gold nanoparticles over novel catalytic materials

    NASA Astrophysics Data System (ADS)

    Akolekar, Deepak B.; Bhargava, Suresh K.; Foran, Garry

    2006-11-01

    Novel nanogold catalytic systems made up of gold nanoparticles (˜2-6 nm) supported on niobium, ytterbium, lanthanum and cerium oxide materials were synthesized. XAS is uniquely suited for studying catalytic systems with low metal and high metal dispersion. Au L 3 edge X-ray absorption spectroscopic measurements were carried out over a series of supported gold nanoparticles. The interesting results obtained from EXAFS and XANES confirms the typical characteristics and structure of gold nanoparticles in these materials.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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

  1. Investigation of metal hydride materials as hydrogen reservoirs for metal-hydrogen batteries

    NASA Technical Reports Server (NTRS)

    ONISCHAK

    1976-01-01

    The performance and suitability of various metal hydride materials were examined for use as possible hydrogen storage reservoirs for secondary metal-hydrogen batteries. Lanthanum pentanickel hydride appears as a probable candidate in terms of stable hydrogen supply under feasible thermal conditions. A kinetic model describing the decomposition rate data of the hydride has been developed.

  2. 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.

  3. 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

  4. 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.

  5. 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

  6. 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

  7. 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.

  8. 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.

  9. 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).

  10. 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.

  11. 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.}

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  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. 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.

  8. 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

  9. 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.

  10. 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.

  11. 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

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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

  17. 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

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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

  1. Refractive index and dispersion control of ultrafast laser inscribed waveguides in gallium lanthanum sulphide for near and mid-infrared applications.

    PubMed

    Demetriou, Giorgos; Bérubé, Jean-Philippe; Vallée, Réal; Messaddeq, Younès; Petersen, Christian R; Jain, Deepak; Bang, Ole; Craig, Chris; Hewak, Daniel W; Kar, Ajoy K

    2016-03-21

    The powerful ultrafast laser inscription technique is used to fabricate optical waveguides in gallium lanthanum sulphide substrates. For the first time the refractive index profile and the dispersion of such ultrafast laser inscribed waveguides are experimentally measured. In addition the Zero Dispersion Wavelength of both the waveguides and bulk substrate is experimentally determined. The Zero Dispersion Wavelength was determined to be between 3.66 and 3.71 μm for the waveguides and about 3.61 μm for the bulk. This work paves the way for realizing ultrafast laser inscribed waveguide devices in gallium lanthanum sulphide glasses for near and mid-IR applications. PMID:27136826

  2. 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

  3. 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.

  4. 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.

  5. Angle resolved x-ray photoelectron spectroscopy (ARXPS) analysis of lanthanum oxide for micro-flexography printing

    NASA Astrophysics Data System (ADS)

    Hassan, S.; Yusof, M. S.; Embong, Z.; Maksud, M. I.

    2016-01-01

    Micro-flexography printing was developed in patterning technique from micron to nano scale range to be used for graphic, electronic and bio-medical device on variable substrates. In this work, lanthanum oxide (La2O3) has been used as a rare earth metal candidate as depositing agent. This metal deposit was embedded on Carbon (C) and Silica (Si) wafer substrate using Magnetron Sputtering technique. The choose of Lanthanum as a target is due to its wide application in producing electronic devices such as thin film battery and printed circuit board. The La2O3 deposited on the surface of Si wafer substrate was then analyzed using Angle Resolve X-Ray Photoelectron Spectroscopy (ARXPS). The position for each synthetic component in the narrow scan of Lanthanum (La) 3d and O 1s are referred to the electron binding energy (eV). The La 3d narrow scan revealed that the oxide species of this particular metal is mainly contributed by La2O3 and La(OH)3. The information of oxygen species, O2- component from O 1s narrow scan indicated that there are four types of species which are contributed from the bulk (O2-), two chemisorb component (La2O3) and La(OH)3 and physisorp component (OH). Here, it is proposed that from the adhesive and surface chemical properties of La, it is suitable as an alternative medium for micro-flexography printing technique in printing multiple fine solid lines at nano scale. Hence, this paper will describe the capability of this particular metal as rare earth metal for use in of micro-flexography printing practice. The review of other parameters contributing to print fine lines will also be described later.

  6. 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.

  7. Interactions between metal ions and carbohydrates. The coordination behavior of neutral erythritol to lanthanum and erbium ions.

    PubMed

    Yang, Limin; Xu, Yizhuang; Wang, Yalei; Zhang, Shiwei; Weng, Shifu; Zhao, Kui; Wu, Jinguang

    2005-12-30

    Lanthanide ions and erythritol form metal-alditol complexes with various structures. Lanthanum nitrate and erbium chloride coordinate to erythritol to give new coordination structures. The lanthanum nitrate-erythritol complex (LaEN), 2La(NO3)3.C4H10O(4).8H2O, La3+ exhibits the coordination number of 11 (namely 11 polar atoms bound to one lanthanum) and is 11-coordinated to two hydroxyl groups from one erythritol molecule, six oxygen atoms from three nitrate ions and three water molecules. One erythritol molecule is coordinated to two La3+ ions and links the two metal ions together. The ratio of M:L is 2:1. The erbium chloride-erythritol complex (ErE), ErCl2.C4H9O(4).2C2H5OH was obtained from ErCl3 and erythritol in aqueous ethanol solution and the structure shows that deprotonation reaction occurs in the reaction process. The Er3+ cation is 8-coordinated with three hydroxyl groups of one erythritol molecule, two hydroxyl groups from another erythritol molecule, two ethanol molecules, and one chloride ion. Erythritol provides its three hydroxyl groups to one erbium cation and two hydroxyl groups to another erbium cation, that is, one hydroxyl group is coordinated to two metal ions and therefore loses its hydrogen atom and becomes a oxygen bridge. Another chloride ion is hydrogen bonded in the structure. The results indicate the complexity of metal-sugar coordination.

  8. Ion-solvent interactions in lanthanum(III) chloride and D-glucose-water mixed solvent systems: An ultrasonic study

    NASA Astrophysics Data System (ADS)

    Dash, J. K.; Kamila, Susmita

    2015-09-01

    Acoustic parameters such as isentropic compressibility, βs, intermolecular free length, Lf, apparent molar volume (ϕv), solvation number, Sn, viscosity B coefficients of Jones-Dole equation etc., have been evaluated from the measured values of ultrasonic velocity, density and viscosity for the solutions of lanthanum(III) chloride in d-glucose (dextrose)-water mixed solvent system of various proportions at 303.15 K temperature and atmospheric pressure. The results are discussed in the light of ion-solvent interactions and the structural effect of the solute on the solvent in the solution.

  9. Shear strain mediated magneto-electric effects in composites of piezoelectric lanthanum gallium silicate or tantalate and ferromagnetic alloys

    NASA Astrophysics Data System (ADS)

    Sreenivasulu, G.; Qu, P.; Piskulich, E.; Petrov, V. M.; Fetisov, Y. K.; Nosov, A. P.; Qu, Hongwei; Srinivasan, G.

    2014-07-01

    Shear strain mediated magneto-electric (ME) coupling is studied in composites of piezoelectric Y-cut lanthanum gallium silicate (LGS) or tantalate (LGT) and ferromagnetic Fe-Co-V alloys. It is shown that extensional strain does not result in ME effects in these layered composites. Under shear strain generated by an ac and dc bias magnetic fields along the length and width of the sample, respectively, strong ME coupling is measured at low-frequencies and at mechanical resonance. A model is discussed for the ME effects. These composites of Y-cut piezoelectrics and ferromagnetic alloys are of importance for shear strain based magnetic field sensors.

  10. Shear strain mediated magneto-electric effects in composites of piezoelectric lanthanum gallium silicate or tantalate and ferromagnetic alloys

    SciTech Connect

    Sreenivasulu, G.; Piskulich, E.; Srinivasan, G.; Qu, P.; Qu, Hongwei; Petrov, V. M.; Fetisov, Y. K.; Nosov, A. P.

    2014-07-21

    Shear strain mediated magneto-electric (ME) coupling is studied in composites of piezoelectric Y-cut lanthanum gallium silicate (LGS) or tantalate (LGT) and ferromagnetic Fe-Co-V alloys. It is shown that extensional strain does not result in ME effects in these layered composites. Under shear strain generated by an ac and dc bias magnetic fields along the length and width of the sample, respectively, strong ME coupling is measured at low-frequencies and at mechanical resonance. A model is discussed for the ME effects. These composites of Y-cut piezoelectrics and ferromagnetic alloys are of importance for shear strain based magnetic field sensors.

  11. Phase equilibrium and preparation, crystallization and viscous sintering of glass in the alumina-silica-lanthanum phosphate system

    NASA Astrophysics Data System (ADS)

    He, Feng

    The phase equilibrium, viscosity of melt-quenched glasses, and processing of sol-gel glasses of the alumina-silica-lanthanum phosphate system were studied. These investigations were directed towards serving the objective of synthesizing nano-structured ceramic-matrix-composites via controlled crystallization of glass precursors. The thermal stability, phase equilibrium, and liquidus temperatures of the alumina- and mullite-lanthanum phosphate systems are determined. An iridium wire heater was constructed to anneal samples up to 2200°C. Phosphorus evaporation losses were significant at high temperatures, especially over 1800°C. The tentative phase diagrams of the two quasi-binary systems were presented. The viscosity of the melt-quenched mullite-lanthanum phosphate glasses was measured by three different methods, including viscous sintering of glass powder compacts, neck formation between two Frenkel glass beads, and thermal analysis of the glass transition. Improved methodologies were developed for applying the interpretative mathematical models to the results of the sintered powder and thermal analytical experiments. Good agreement was found between all three methods for both absolute values and temperature dependence. A sol-gel process was developed as a low temperature route to producing glasses. A unique, single phase mullite gel capable of low temperature (575°C) mullitization was made from tetraethoxysilane and aluminum isopropoxide at room temperature in three days. Low temperature crystallization was attributed to the avoidance of phase segregation during gel formation and annealing. This was greatly enhanced by a combination of low temperature preheating in the amorphous state, a high heating rate during crystallization and low water content. The Al2O3 content in mullite (61-68 mol%) depended on the highest annealing temperature. Two mullite-lanthanum phosphate gels were made based upon modifying the chemical procedures used for the homogeneous single

  12. Size effects of polycrystalline lanthanum modified Bi{sub 4}Ti{sub 3}O{sub 12} thin films

    SciTech Connect

    Simoes, A.Z. Riccardi, C.S.; Cavalcante, L.S.; Gonzalez, A.H.M.; Longo, E.; Varela, J.A.

    2008-01-08

    The film thickness dependence on the ferroelectric properties of lanthanum modified bismuth titanate Bi{sub 3.25}La{sub 0.75}Ti{sub 3}O{sub 12} was investigated. Films with thicknesses ranging from 230 to 404 nm were grown on platinum-coated silicon substrates by the polymeric precursor method. The internal strain is strongly influenced by the film thickness. The morphology of the film changes as the number of layers increases indicating a thickness dependent grain size. The leakage current, remanent polarization and drive voltage were also affected by the film thickness.

  13. 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.

  14. Phosphate adsorption by lanthanum modified bentonite clay in fresh and brackish water.

    PubMed

    Reitzel, Kasper; Andersen, Frede Ø; Egemose, Sara; Jensen, Henning S

    2013-05-15

    Effects of pH, alkalinity and conductivity on the adsorption of soluble reactive phosphorus (SRP) onto lanthanum (La) modified bentonite clay (Phoslock(®)) were investigated in laboratory experiments using eight different types of filtered water representing freshwater with low and normal alkalinity and brackish water with high alkalinity. Different dose ratios (0-200; w/w) of Phoslock(®):P were applied to determine the maximum P binding capacity of Phoslock(®) at SRP concentrations typical of those of sediment pore water. The 100:1 Phoslock(®:)P dose ratio, recommended by the manufacturer, was tested with 12 days exposure time and generally found to be insufficient at binding whole target SRP pool. The ratio performed best in the soft water from Danish Lake Hampen and less good in the hard water from Danish Lake Langesø and in brackish water. The explanation may be an observed negative relationship between alkalinity and the SRP binding capacity of Phoslock(®). A comparative study of Lake Hampen and Lake Langesø suggested that the recorded differences in P adsorption between the two lakes could be attributed to a more pronounced dispersion of Phoslock(®) in the soft water of Lake Hampen, leading to higher fractions of dissolved (<0.2 μm) La and of La in fine particles. In the same two lakes, pH affected the SRP binding of Phoslock(®) negatively at a pH level above 8.1, the effect being reversible, however. The negative pH effect was most significant in hard water Lake Langesø, most likely because of higher [Formula: see text] concentrations.

  15. Thermal Properties, Thermal Shock, and Thermal Cycling Behavior of Lanthanum Zirconate-Based Thermal Barrier Coatings

    NASA Astrophysics Data System (ADS)

    Guo, Xingye; Lu, Zhe; Jung, Yeon-Gil; Li, Li; Knapp, James; Zhang, Jing

    2016-06-01

    Lanthanum zirconate (La2Zr2O7) coatings are newly proposed thermal barrier coating (TBC) systems which exhibit lower thermal conductivity and potentially higher thermal stability compared to other traditional thermal barrier systems. In this work, La2Zr2O7 and 8 wt pct yttria stabilized zirconia (8YSZ) single-layer and double-layer TBC systems were deposited using the air plasma spray technique. Thermal properties of the coatings were measured. Furnace heat treatment and jet engine thermal shock tests were implemented to evaluate coating performance during thermal cycling. The measured average thermal conductivity of porous La2Zr2O7 coating ranged from 0.59 to 0.68 W/m/K in the temperature range of 297 K to 1172 K (24 °C to 899 °C), which was approximately 25 pct lower than that of porous 8YSZ (0.84 to 0.87 W/m/K) in the same temperature range. The coefficients of thermal expansion values of La2Zr2O7 were approximately 9 to 10 × 10-6/K from 400 K to 1600 K (127 °C to 1327 °C), which were about 10 pct lower than those of porous 8YSZ. The double-layer coating system consisting of the porous 8YSZ and La2Zr2O7 layers had better thermal shock resistance and thermal cycling performance than those of single-layer La2Zr2O7 coating and double-layer coating with dense 8YSZ and La2Zr2O7 coatings. This study suggests that porous 8YSZ coating can be employed as a buffer layer in La2Zr2O7-based TBC systems to improve the overall coating durability during service.

  16. 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.

  17. A comparison of the use of sodium iodide and lanthanum bromide scintillation crystals for airborne surveys

    NASA Astrophysics Data System (ADS)

    Bailey, Derek M.

    The Environmental Protection Agency (EPA) Aerial Spectral Environmental Collection Technology (ASPECT) program performs aerial radiological and chemical characterization of geographical regions of interest. Airborne surveys are performed to characterize environmental radionuclide content, for mineral exploration, as well as for emergency scenarios such as major releases or lost sources. Two radiological detection systems are used by the ASPECT team for gamma-ray detection and characterization: lanthanum bromide [LaBr 3(Ce)] and sodium iodide [NaI(Tl)] scintillation systems. An aerial survey of a uranium mine in the western United States was performed using both NaI(Tl) and LaBr3(Ce) detection systems. Analyses of the survey data were performed with RadAssist software and applying International Atomic Energy Agency (IAEA) airborne gamma ray mapping guidelines. The data for the survey were corrected for cross-over, which is spectral interference from higher energy photons as a result of Compton scattering, height attenuation, cosmic ray contribution to signal, and Radon contribution to signal. Two radiation survey contours were generated from each discrete data set. Based on analysis of the uranium mine survey results, LaBr3(Ce) produced a product comparable to that of NaI(Tl). The LaBr3(Ce) detection system contained 1/16th the scintillating volume and had a total system weight that was 1/4th that of the NaI(Tl) system. LaBr3(Ce) demonstrated a clear advantage over NaI(Tl) detectors in system mobility, and weight factors in airborne gamma ray spectroscopy.

  18. Combined Effects of Lanthanum (III) and Acid Rain on Antioxidant Enzyme System in Soybean Roots.

    PubMed

    Zhang, Xuanbo; Du, Yuping; Wang, Lihong; Zhou, Qing; Huang, Xiaohua; Sun, Zhaoguo

    2015-01-01

    Rare earth element pollution (REEs) and acid rain (AR) pollution simultaneously occur in many regions, which resulted in a new environmental issue, the combined pollution of REEs and AR. The effects of the combined pollution on the antioxidant enzyme system of plant roots have not been reported. Here, the combined effects of lanthanum ion (La3+), one type of REE, and AR on the antioxidant enzyme system of soybean roots were investigated. In the combined treatment of La3+ (0.08 mM) and AR, the cell membrane permeability and the peroxidation of cell membrane lipid of soybean roots increased, and the superoxide dismutase, catalase, peroxidase and reduced ascorbic acid served as scavengers of reactive oxygen species. In other combined treatments of La3+ (0.40 mM, 1.20 mM) and AR, the membrane permeability, malonyldialdehyde content, superoxide dismutase activity, peroxidase activity and reduced ascorbic acid content increased, while the catalase activity decreased. The increased superoxide dismutase activity, peroxidase activity and reduced ascorbic acid content were inadequate to scavenge the excess hydrogen peroxide and superoxide, leading to the damage of the cell membrane, which was aggravated with the increase in the concentration of La3+ and the level of AR. The deleterious effects of the combined treatment of La3+ and AR were stronger than those of the single treatment of La3+ or AR. Moreover, the activity of antioxidant enzyme system in the combined treatment group was affected directly and indirectly by mineral element content in soybean plants. PMID:26230263

  19. 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.

  20. 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

  1. Antioxidant response of soybean seedlings to joint stress of lanthanum and acid rain.

    PubMed

    Liang, Chanjuan; Wang, Weimin

    2013-11-01

    Excess of rare earth elements in soil can be a serious environmental stress on plants, in particular when acid rain coexists. To understand how such a stress affects plants, we studied antioxidant response of soybean leaves and roots exposed to lanthanum (0.06, 0.18, and 0.85 mmol L(-1)) under acid rain conditions (pH 4.5 and 3.0). We found that low concentration of La3+ (0.06 mmol L(-1)) did not affect the activity of antioxidant enzymes (catalase and peroxidase) whereas high concentration of La3+ (≥0.18 mmol L(-1)) did. Compared to treatment with acid rain (pH 4.5 and pH 3.0) or La3+ alone, joint stress of La3+ and acid rain affected more severely the activity of catalase and peroxidase, and induced more H2O2 accumulation and lipid peroxidation. When treated with high level of La3+ (0.85 mmol L(-1)) alone or with acid rain (pH 4.5 and 3.0), roots were more affected than leaves regarding the inhibition of antioxidant enzymes, physiological function, and growth. The severity of oxidative damage and inhibition of growth caused by the joint stress associated positively with La3+ concentration and soil acidity. These results will help us understand plant response to joint stress, recognize the adverse environmental impact of rare earth elements in acidic soil, and develop measures to eliminate damage caused by such joint stress.

  2. [Combined injured effects of acid rain and lanthanum on growth of soybean seedling].

    PubMed

    Liang, Chan-juan; Pan, Dan-yun; Xu, Qiu-rong; Zhou, Qing

    2010-07-01

    Combined effects of acid rain and lanthanum on growth of soybean seedling (Glycine max) and its inherent mechanism were studied in this paper. Compared with treatments by simulated acid rain (pH 3.0, 3.5, 4.5) or rare earth La(III) (60, 100 and 300 mg x L(-1)), the decrease degree of growth parameters in combined treatments was higher, indicating that there were a synergistic effects between acid rain and La. Moreover,the inhibition effects of acid rain and La(III) were more obvious when pH value of acid rain was lower or the concentration of La(III) was higher. The changes of photosynthetic parameters were similar to those of growth, but the decrease degree of each parameter was not same in the same treatment group. The decrease degree of optimal PSII photochemical efficiency (Fv/Fm) and chlorophyll content (Chl) were 9.35%-22.75% and 9.14%-24.53%, respectively, lower than that of photosynthetic rate Pn (22.78%-84.7%), Hill reaction rate (15.52%-73.38%) and Mg2+ -ATPase activity (14.51%-71.54%), showing that the sensitivity of photosynthetic parameters to the combined factors was different. Furthermore, relative analysis showed that the change of Pn were mainly affected by Hill reaction rate and Mg2+ -ATPase activity, and was less influenced by Chl and Fv/Fm. It indicates that the effect of acid rain and La on each reaction in photosynthesis was different, and the inhibition of combined treatments on photosynthesis in plants was one of the main factors affecting growth of plant.

  3. Combined effects of lanthanum (III) chloride and acid rain on photosynthetic parameters in rice.

    PubMed

    Wang, Lihong; Wang, Wen; Zhou, Qing; Huang, Xiaohua

    2014-10-01

    Rare earth elements (REEs) pollution and acid rain are environmental issues, and their deleterious effects on plants attract worldwide attention. These two issues exist simultaneously in many regions, especially in some rice-growing areas. However, little is known about the combined effects of REEs and acid rain on plants. Here, the combined effects of lanthanum chloride (LaCl3), one type of REE salt, and acid rain on photosynthesis in rice were investigated. We showed that the combined treatment of 81.6 μM LaCl3 and acid rain at pH 4.5 increased net photosynthetic rate (Pn), stomatic conductance (Gs), intercellular CO2 concentration (Ci), Hill reaction activity (HRA), apparent quantum yield (AQY) and carboxylation efficiency (CE) in rice. The combined treatment of 81.6 μM LaCl3 and acid rain at pH 3.5 began to behave toxic effects on photosynthesis (decreasing Pn, Gs, HRA, AQY and CE, and increasing Ci), and the maximally toxic effects were observed in the combined treatment of 2449.0 μM LaCl3 and acid rain at pH 2.5. Moreover, the combined effects of LaCl3 and acid rain on photosynthesis in rice depended on the growth stage of rice, with the maximal effects occurring at the booting stage. Furthermore, the combined treatment of high-concentration LaCl3 and low-pH acid rain had more serious effects on photosynthesis in rice than LaCl3 or acid rain treatment alone. Finally, the combined effect of LaCl3 and acid rain on Pn in rice resulted from the changes in stomatic (Gs, Ci) and non-stomatic (HRA, AQY and CE) factors.

  4. Combined Effects of Lanthanum (III) and Acid Rain on Antioxidant Enzyme System in Soybean Roots.

    PubMed

    Zhang, Xuanbo; Du, Yuping; Wang, Lihong; Zhou, Qing; Huang, Xiaohua; Sun, Zhaoguo

    2015-01-01

    Rare earth element pollution (REEs) and acid rain (AR) pollution simultaneously occur in many regions, which resulted in a new environmental issue, the combined pollution of REEs and AR. The effects of the combined pollution on the antioxidant enzyme system of plant roots have not been reported. Here, the combined effects of lanthanum ion (La3+), one type of REE, and AR on the antioxidant enzyme system of soybean roots were investigated. In the combined treatment of La3+ (0.08 mM) and AR, the cell membrane permeability and the peroxidation of cell membrane lipid of soybean roots increased, and the superoxide dismutase, catalase, peroxidase and reduced ascorbic acid served as scavengers of reactive oxygen species. In other combined treatments of La3+ (0.40 mM, 1.20 mM) and AR, the membrane permeability, malonyldialdehyde content, superoxide dismutase activity, peroxidase activity and reduced ascorbic acid content increased, while the catalase activity decreased. The increased superoxide dismutase activity, peroxidase activity and reduced ascorbic acid content were inadequate to scavenge the excess hydrogen peroxide and superoxide, leading to the damage of the cell membrane, which was aggravated with the increase in the concentration of La3+ and the level of AR. The deleterious effects of the combined treatment of La3+ and AR were stronger than those of the single treatment of La3+ or AR. Moreover, the activity of antioxidant enzyme system in the combined treatment group was affected directly and indirectly by mineral element content in soybean plants.

  5. Syntheses, crystal structures, and properties of three new lanthanum(III) vanadium iodates.

    PubMed

    Sun, Chuan-Fu; Hu, Ting; Xu, Xiang; Mao, Jiang-Gao

    2010-09-14

    Systematic explorations of new compounds in the La(3+)-V(4+)/V(5+)-iodate system led to three new lanthanum(III) vanadium iodates, namely, LaVO(IO(3))(5), LaV(2)O(6)(IO(3)), and LaVO(2)(IO(3))(4).H(2)O. LaVO(IO(3))(5) is isostructural with LaTiO(IO(3))(5) and its structure contains a 0D [VO(IO(3))(5)](3-) anionic unit composed of one VO(6) octahedron linked to five IO(3)(-) groups. Such 0D anionic units are separated by La(3+) ions. LaV(2)O(6)(IO(3)) exhibits a unique 3D framework composed of 1D [V(2)O(6)](2-) ladder like chains and 2D [La(IO(3))](2+) layers. LaVO(2)(IO(3))(4).H(2)O is isostructural with LnMoO(2)(IO(3))(4)(OH) (Ln = La, Nd, Sm, Eu) with a polar space group P2(1), its structure contains a novel 0D [VO(2)(IO(3))(4)](3-) anionic unit composed of one VO(6) octahedron linked with four IO(3)(-) groups and two terminal O(2-) anions. Such 0D anionic units are separated by La(3+) ions. The structure of LaVO(2)(IO(3))(4).H(2)O can also be described as the 8-MR channels of the 3D [La(IO(3))(4)](-) anion being filled by the VO(6) octahedra and lattice water molecules. LaVO(2)(IO(3))(4).H(2)O displays a weak SHG response of about 0.2 times that of KDP. Optical, thermal stability and magnetic susceptibility measurements as well as theoretical calculations have also been performed.

  6. Humic substances interfere with phosphate removal by Lanthanum modified clay in controlling eutrophication.

    PubMed

    Lürling, Miquel; Waajen, Guido; van Oosterhout, Frank

    2014-05-01

    The lanthanum (La) modified bentonite Phoslock(®) has been proposed as dephosphatisation technique aiming at removing Filterable Reactive Phosphorus (FRP) from the water and blocking the release of FRP from the sediment. In the modified clay La is expected the active ingredient. We conducted controlled laboratory experiments to measure the FRP removal by Phoslock(®) in the presence and absence of humic substances, as La complexation with humic substances might lower the effectiveness of La (Phoslock(®)) to bind FRP. The results of our study support the hypothesis that the presence of humic substances can interfere with the FRP removal by the La-modified bentonite. Both a short-term (1 d) and long-term (42 d) experiment were in agreement with predictions derived from chemical equilibrium modelling and showed lower FRP removal in presence of humic substances. This implies that in DOC-rich inland waters the applicability of exclusively Phoslock(®) as FRP binder should be met critically. In addition, we observed a strong increase of filterable La in presence of humic substances reaching in a week more than 270 μg La l(-1) that would infer a violation of the Dutch La standard for surface water, which is 10.1 μg La l(-1). Hence, humic substances are an important factor that should be given attention when considering chemical FRP inactivation as they might play a substantial role in lowering the efficacy of metal-based FRP-sorbents, which makes measurements of humic substances (DOC) as well as controlled experiments vital. PMID:24565799

  7. A lanthanum chelate possessing an open-channel framework with water nanotubes: properties and desalination.

    PubMed

    Chen, Mao-Long; Guo, Yi-Chao; Yang, Fang; Liang, Jin-Xia; Cao, Ze-Xing; Zhou, Zhao-Hui

    2014-04-28

    A new type of thermally stable chelate {La(H2O)4[La(1,3-pdta)(H2O)]3}n · 12nH2O (1) [1,3-H4pdtaCH2[CH2N(CH2CO2H)2]2] with an open-channel shows significant and unusual solvent transport properties and demonstrates a use for low-pressure desalination, which is constructed by cheap and available lanthanum salt and 1,3-propanediaminetetraacetate. The chelate could be converted reversibly to its trihydrate {La(H2O)4[La(1,3-pdta)(H2O)]3}n · 3nH2O (1a), dehydrated product {La(H2O)4[La(1,3-pdta)(H2O)]3}n (1b) and ethanol adduct {La(H2O)4[La(1,3-pdta)(H2O)]3}n · 3nH2O · 3nEtOH (1c). The latter nano-confined ethanol shows a remarkable downfield shift (Δδ = 6.0 ppm) for the methylene group in the solid 13C NMR spectrum compared with that of the free EtOH. Crystal 1 with a regular hexagonal appearance can be used directly for saline water desalination on a small-scale at an ambient temperature, demonstrating a low energy consumption and environmentally friendly method. This is attributed to the 10.0 Å hydrophobic open-channel containing water nanotubes (WNTs, Φ = 4.2 Å). The nano-confined WNTs can be removed at a low temperature (45 °C).

  8. 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

  9. Antioxidant response of soybean seedlings to joint stress of lanthanum and acid rain.

    PubMed

    Liang, Chanjuan; Wang, Weimin

    2013-11-01

    Excess of rare earth elements in soil can be a serious environmental stress on plants, in particular when acid rain coexists. To understand how such a stress affects plants, we studied antioxidant response of soybean leaves and roots exposed to lanthanum (0.06, 0.18, and 0.85 mmol L(-1)) under acid rain conditions (pH 4.5 and 3.0). We found that low concentration of La3+ (0.06 mmol L(-1)) did not affect the activity of antioxidant enzymes (catalase and peroxidase) whereas high concentration of La3+ (≥0.18 mmol L(-1)) did. Compared to treatment with acid rain (pH 4.5 and pH 3.0) or La3+ alone, joint stress of La3+ and acid rain affected more severely the activity of catalase and peroxidase, and induced more H2O2 accumulation and lipid peroxidation. When treated with high level of La3+ (0.85 mmol L(-1)) alone or with acid rain (pH 4.5 and 3.0), roots were more affected than leaves regarding the inhibition of antioxidant enzymes, physiological function, and growth. The severity of oxidative damage and inhibition of growth caused by the joint stress associated positively with La3+ concentration and soil acidity. These results will help us understand plant response to joint stress, recognize the adverse environmental impact of rare earth elements in acidic soil, and develop measures to eliminate damage caused by such joint stress. PMID:23653318

  10. Combined effects of lanthanum (III) chloride and acid rain on photosynthetic parameters in rice.

    PubMed

    Wang, Lihong; Wang, Wen; Zhou, Qing; Huang, Xiaohua

    2014-10-01

    Rare earth elements (REEs) pollution and acid rain are environmental issues, and their deleterious effects on plants attract worldwide attention. These two issues exist simultaneously in many regions, especially in some rice-growing areas. However, little is known about the combined effects of REEs and acid rain on plants. Here, the combined effects of lanthanum chloride (LaCl3), one type of REE salt, and acid rain on photosynthesis in rice were investigated. We showed that the combined treatment of 81.6 μM LaCl3 and acid rain at pH 4.5 increased net photosynthetic rate (Pn), stomatic conductance (Gs), intercellular CO2 concentration (Ci), Hill reaction activity (HRA), apparent quantum yield (AQY) and carboxylation efficiency (CE) in rice. The combined treatment of 81.6 μM LaCl3 and acid rain at pH 3.5 began to behave toxic effects on photosynthesis (decreasing Pn, Gs, HRA, AQY and CE, and increasing Ci), and the maximally toxic effects were observed in the combined treatment of 2449.0 μM LaCl3 and acid rain at pH 2.5. Moreover, the combined effects of LaCl3 and acid rain on photosynthesis in rice depended on the growth stage of rice, with the maximal effects occurring at the booting stage. Furthermore, the combined treatment of high-concentration LaCl3 and low-pH acid rain had more serious effects on photosynthesis in rice than LaCl3 or acid rain treatment alone. Finally, the combined effect of LaCl3 and acid rain on Pn in rice resulted from the changes in stomatic (Gs, Ci) and non-stomatic (HRA, AQY and CE) factors. PMID:25048927

  11. Combined Effects of Lanthanum (III) and Acid Rain on Antioxidant Enzyme System in Soybean Roots

    PubMed Central

    Zhang, Xuanbo; Du, Yuping; Wang, Lihong; Zhou, Qing; Huang, Xiaohua; Sun, Zhaoguo

    2015-01-01

    Rare earth element pollution (REEs) and acid rain (AR) pollution simultaneously occur in many regions, which resulted in a new environmental issue, the combined pollution of REEs and AR. The effects of the combined pollution on the antioxidant enzyme system of plant roots have not been reported. Here, the combined effects of lanthanum ion (La3+), one type of REE, and AR on the antioxidant enzyme system of soybean roots were investigated. In the combined treatment of La3+ (0.08 mM) and AR, the cell membrane permeability and the peroxidation of cell membrane lipid of soybean roots increased, and the superoxide dismutase, catalase, peroxidase and reduced ascorbic acid served as scavengers of reactive oxygen species. In other combined treatments of La3+ (0.40 mM, 1.20 mM) and AR, the membrane permeability, malonyldialdehyde content, superoxide dismutase activity, peroxidase activity and reduced ascorbic acid content increased, while the catalase activity decreased. The increased superoxide dismutase activity, peroxidase activity and reduced ascorbic acid content were inadequate to scavenge the excess hydrogen peroxide and superoxide, leading to the damage of the cell membrane, which was aggravated with the increase in the concentration of La3+ and the level of AR. The deleterious effects of the combined treatment of La3+ and AR were stronger than those of the single treatment of La3+ or AR. Moreover, the activity of antioxidant enzyme system in the combined treatment group was affected directly and indirectly by mineral element content in soybean plants. PMID:26230263

  12. Humic substances interfere with phosphate removal by Lanthanum modified clay in controlling eutrophication.

    PubMed

    Lürling, Miquel; Waajen, Guido; van Oosterhout, Frank

    2014-05-01

    The lanthanum (La) modified bentonite Phoslock(®) has been proposed as dephosphatisation technique aiming at removing Filterable Reactive Phosphorus (FRP) from the water and blocking the release of FRP from the sediment. In the modified clay La is expected the active ingredient. We conducted controlled laboratory experiments to measure the FRP removal by Phoslock(®) in the presence and absence of humic substances, as La complexation with humic substances might lower the effectiveness of La (Phoslock(®)) to bind FRP. The results of our study support the hypothesis that the presence of humic substances can interfere with the FRP removal by the La-modified bentonite. Both a short-term (1 d) and long-term (42 d) experiment were in agreement with predictions derived from chemical equilibrium modelling and showed lower FRP removal in presence of humic substances. This implies that in DOC-rich inland waters the applicability of exclusively Phoslock(®) as FRP binder should be met critically. In addition, we observed a strong increase of filterable La in presence of humic substances reaching in a week more than 270 μg La l(-1) that would infer a violation of the Dutch La standard for surface water, which is 10.1 μg La l(-1). Hence, humic substances are an important factor that should be given attention when considering chemical FRP inactivation as they might play a substantial role in lowering the efficacy of metal-based FRP-sorbents, which makes measurements of humic substances (DOC) as well as controlled experiments vital.

  13. Insight into mechanism of lanthanum (III) induced damage to plant photosynthesis.

    PubMed

    Hu, Huiqing; Wang, Lihong; Li, Yueli; Sun, Jingwen; Zhou, Qing; Huang, Xiaohua

    2016-05-01

    A great deal of literature is available regarding the environmental and ecological effects of rare earth element pollution on plants. These studies have shown that excess lanthanum (La) (III) in the environment can inhibit plant growth and even cause plant death. Moreover, inhibition of plant photosynthesis is known to be one of the physiological bases of these damages. However, the mechanism responsible for these effects is still unclear. In this study, the mechanism of La(III)-induced damage to plant photosynthesis was clarified from the viewpoint of the chloroplast ultrastructure, the contents of chloroplast mineral elements and chlorophyll, the transcription of chloroplast ATPase subunits and chloroplast Mg(2+)-ATPase activity, in which rice was selected as a study object. Following treatment with low level of La(III), the chloroplast ultrastructure of rice was not changed, and the contents of chloroplast mineral elements (Mg, P, K, Ca, Mn, Fe, Ni, Cu, and Zn) increased, but the chlorophyll content did not change significantly. Moreover, the transcription of chloroplast ATPase subunits, chloroplast Mg(2+)-ATPase activity, the net photosynthetic rate and growth indices increased. Following treatment with high levels of La(III), the chloroplast ultrastructure was damaged, chloroplast mineral elements (except Cu and Zn) and chlorophyll contents decreased, and the transcription of chloroplast ATPase subunits, chloroplast Mg(2+)-ATPase activity, the net photosynthetic rate and growth indices decreased. Based on these results, a possible mechanism of La(III)-induced damage to plant photosynthesis was proposed to provide a reference for scientific evaluation of the potential ecological risk of rare earth elements in the environment.

  14. HIGH-RESOLUTION FOURIER TRANSFORM SPECTROSCOPY OF LANTHANUM IN Ar DISCHARGE IN THE NEAR-INFRARED

    SciTech Connect

    Güzelçimen, F.; Başar, Gö.; Tamanis, M.; Kruzins, A.; Ferber, R.; Windholz, L.; Kröger, S. E-mail: sophie.kroeger@htw-berlin.de

    2013-10-01

    A high-resolution spectrum of lanthanum has been recorded by a Fourier Transform spectrometer in the wavelength range from 833 nm to 1666 nm (6000 cm{sup –1} to 12,000 cm{sup –1}) using as light source a hollow cathode lamp operated with argon as the discharge carrier gas. In total, 2386 spectral lines were detected in this region, of which 555 lines could be classified as La I transitions and 10 lines as La II transitions. All La II transitions and 534 of these La I transitions were classified for the first time, and 6 of the La II transitions and 433 of the classified La I transitions appear to be new lines, which could not be found in the literature. The corresponding energy level data of classified lines are given. Additionally, 430 lines are assigned as Ar I lines and 394 as Ar II lines, of which 179 and 77, respectively, were classified for the first time. All 77 classified Ar II transitions as well as 159 of the classified Ar I transitions are new lines. Furthermore, the wavenumbers of 997 unclassified spectral lines were determined, 235 of which could be assigned as La lines, because of their hyperfine pattern. The remaining 762 lines may be either unclassified Ar lines or unresolved and unclassified La lines with only one symmetrical peak with an FWHM in the same order of magnitude as the Ar lines. The accuracy of the wavenumber for the classified lines with signal-to-noise-ratio higher than four is better than 0.006 cm{sup –1} which corresponds to an accuracy of 0.0004 nm at 830 nm and 0.0017 nm at 1660 nm, respectively.

  15. 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

  16. Nickel/carbon core/shell nanotubes: Lanthanum nickel alloy catalyzed synthesis, characterization and studies on their ferromagnetic and lithium-ion storage properties

    SciTech Connect

    Anthuvan Rajesh, John; Pandurangan, Arumugam; Senthil, Chenrayan; Sasidharan, Manickam

    2014-12-15

    Highlights: • Ni/CNTs core/shell structure was synthesized using LaNi{sub 5} alloy catalyst by CVD. • The magnetic and lithium-ion storage properties of Ni/CNTs structure were studied. • The specific Ni/CNTs structure shows strong ferromagnetic property with large coercivity value of 446.42 Oe. • Ni/CNTs structure shows enhanced electrochemical performance in terms of stable capacity and better rate capability. - Abstract: A method was developed to synthesize ferromagnetic nickel core/carbon shell nanotubes (Ni/CNTs) by chemical vapor deposition using Pauli paramagnetic lanthanum nickel (LaNi{sub 5}) alloy both as a catalyst and as a source for the Ni-core. The Ni-core was obtained through oxidative dissociation followed by hydrogen reduction during the catalytic growth of the CNTs. Transmission electron microscopy (TEM), selected area electron diffraction (SAED) and X-ray diffraction (XRD) analyses reveal that the Ni-core exists as a face centered cubic single crystal. The magnetic hysteresis loop of Ni/CNTs particle shows increased coercivity (446.42 Oe) than bulk Ni at room temperature. Furthermore, the Ni/CNTs core/shell particles were investigated as anode materials in lithium-ion batteries. The Ni/CNTs electrode delivered a high discharge capacity of 309 mA h g{sup −1} at 0.2 C, and a stable cycle-life, which is attributed to high structural stability of Ni/CNTs electrode during electrochemical lithium-ion insertion and de-insertion redox reactions.

  17. Capillary microextraction combined with fluorinating assisted electrothermal vaporization inductively coupled plasma optical emission spectrometry for the determination of trace lanthanum, europium, dysprosium and yttrium in human hair.

    PubMed

    Wu, Shaowei; Hu, Chengguo; He, Man; Chen, Beibei; Hu, Bin

    2013-10-15

    In this work, a congo red modified single wall carbon nanotubes (CR-SWCNTs) coated fused-silica capillary was prepared and used for capillary microextraction (CME) of trace amounts of lanthanum (La), europium (Eu), dysprosium (Dy) and yttrium (Y) in human hair followed by fluorinating assisted electrothermal vaporization-inductively coupled plasma-optical emission spectrometry (FETV-ICP-OES) determination. The adsorption properties and stability of the prepared CR-SWCNTs coated capillary along with the various factors affecting the separation/preconcentration of La, Eu, Dy and Y by CME were investigated in detail. Under the optimized conditions, with a consumption of 2 mL sample solution, a theoretical enrichment factor of 50 and a detection limit (3σ) of 0.12 ng mL(-1) for La, 0.03 ng mL(-1) for Eu, 0.11 ng mL(-1) for Dy and 0.03 ng mL(-1) for Y were obtained, respectively. The preparation reproducibility of the CR-SWCNTs coated capillary was investigated and the relative standard deviations (RSDs) were ranging from 4.1% (Eu) to 4.4% (La) (CLa, Dy=1.4 ng mL(-1); CY, Eu=0.25 ng mL(-1), n=7) in one batch, and from 5.7% (Eu) to 6.1% (Y) (CLa, Dy=1.4 ng mL(-1); CY, Eu=0.25 ng mL(-1), n=5) among different batches. The proposed method was applied to the analysis of real-world human hair sample and the recoveries for the spiked sample were in the range of 93-105%. The method was also applied to the determination of La, Eu, Dy and Y in Certified Reference Material of GBW07601 human hair, and the determined values were in good agreement with the certified values.

  18. Capillary microextraction combined with fluorinating assisted electrothermal vaporization inductively coupled plasma optical emission spectrometry for the determination of trace lanthanum, europium, dysprosium and yttrium in human hair.

    PubMed

    Wu, Shaowei; Hu, Chengguo; He, Man; Chen, Beibei; Hu, Bin

    2013-10-15

    In this work, a congo red modified single wall carbon nanotubes (CR-SWCNTs) coated fused-silica capillary was prepared and used for capillary microextraction (CME) of trace amounts of lanthanum (La), europium (Eu), dysprosium (Dy) and yttrium (Y) in human hair followed by fluorinating assisted electrothermal vaporization-inductively coupled plasma-optical emission spectrometry (FETV-ICP-OES) determination. The adsorption properties and stability of the prepared CR-SWCNTs coated capillary along with the various factors affecting the separation/preconcentration of La, Eu, Dy and Y by CME were investigated in detail. Under the optimized conditions, with a consumption of 2 mL sample solution, a theoretical enrichment factor of 50 and a detection limit (3σ) of 0.12 ng mL(-1) for La, 0.03 ng mL(-1) for Eu, 0.11 ng mL(-1) for Dy and 0.03 ng mL(-1) for Y were obtained, respectively. The preparation reproducibility of the CR-SWCNTs coated capillary was investigated and the relative standard deviations (RSDs) were ranging from 4.1% (Eu) to 4.4% (La) (CLa, Dy=1.4 ng mL(-1); CY, Eu=0.25 ng mL(-1), n=7) in one batch, and from 5.7% (Eu) to 6.1% (Y) (CLa, Dy=1.4 ng mL(-1); CY, Eu=0.25 ng mL(-1), n=5) among different batches. The proposed method was applied to the analysis of real-world human hair sample and the recoveries for the spiked sample were in the range of 93-105%. The method was also applied to the determination of La, Eu, Dy and Y in Certified Reference Material of GBW07601 human hair, and the determined values were in good agreement with the certified values. PMID:24054601

  19. Analysis of Induced Gamma Activation by D-T Neutrons in Selected Fusion Reactor Relevant Materials with EAF-2010

    NASA Astrophysics Data System (ADS)

    Klix, Axel; Fischer, Ulrich; Gehre, Daniel

    2016-02-01

    Samples of lanthanum, erbium and titanium which are constituents of structural materials, insulating coatings and tritium breeder for blankets of fusion reactor designs have been irradiated in a fusion peak neutron field. The induced gamma activities were measured and the results were used to check calculations with the European activation system EASY-2010. Good agreement for the prediction of major contributors to the contact dose rate of the materials was found, but for minor contributors the calculation deviated up to 50%.

  20. Application of a one-dimensional TEC code to the characterization of a lanthanum-hexaboride diode

    NASA Astrophysics Data System (ADS)

    van Dam, Scott A.; Ramalingam, Mysore L.

    A one-dimensional thermionic energy conversion (TEC) computer code has been utilized to provide a theoretical basis of comparison for experimentally derived data obtained from a lanthanum hexaboride cesium vapor thermionic diode. Although the code-generated predictions obtained were not in precise agreement with the experimental results, they do provide a basis for establishing the validity of the experimental results from an analytical framework. Certain discrepancies are thus identified, and an attempt is made to account for them in terms of code inaccuracies and/or possible experimental error. Experimental lanthanum-hexaboride (LaB6) cesium-vapor TEC diode characteristics are compared to those predicted by the TEC code. The diode used was activated by electron-bombardment heating in a rejuvenated diode testing facility. A DOS loop and auxiliary Fortran program were used in conjunction with the original TEC code to generate both general and LaB6 simulated diode current density vs. output voltage characteristics. The effects of changing the emitter and collector work functions and the operating cesium-vapor pressure were studied for both cases.

  1. Novel multifunctional titania-silica-lanthanum phosphate nanocomposite coatings through an all aqueous sol-gel process.

    PubMed

    Smitha, Venu Sreekala; Jyothi, Chembolli Kunhatta; Peer, Mohamed A; Pillai, Saju; Warrier, Krishna Gopakumar

    2013-04-01

    A novel nanocomposite coating containing titania, silica and lanthanum phosphate prepared through an all aqueous sol-gel route exhibits excellent self-cleaning ability arising from the synergistic effect of the constituents in the nanocomposite. A highly stable titania-silica-lanthanum phosphate nanocomposite sol having particle size in the range of 30-50 nm has been synthesized starting from a titanyl sulphate precursor, which was further used for the development of photocatalytically active composite coatings on glass. The coatings prepared by the dip coating technique as well as the nanocomposite powders are heat treated and characterized further for their morphology and multifunctionality. The nanocomposite containing 1.5 wt% LaPO4 has shown a surface area as high as 138 m(2) g(-1) and a methylene blue degradation efficiency of 94% in two hours of UV exposure. The composite coating has shown very good homogeneity evidenced by transparency as high as 99.5% and low wetting behaviour. The present novel approach for energy conserving, aqueous derived, self-cleaning coatings may be suitable for large scale industrial applications.

  2. Complexation study of cryptand 222 with lanthanum(III) cation in binary mixed non-aqueous solvents

    NASA Astrophysics Data System (ADS)

    Dolatshahi, S.; Rounaghi, G. H.; Tarahomi, S.

    2013-10-01

    Conductometric titrations have been performed in some binary solvent solutions of acetonitrile (AN), 1,2-dichloroethane (DCE), ethylacetate (EtOAc) and methylacetate (MeOAc) with methanol (MeOH), at 288, 298, 308, and 318 K to give the complex stability constant and the thermodynamic parameters for the complexation of lanthanum(III) cation with 4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]-hexacosane (cryptand 222). The stability constant of the resulting 1:1 complex at each temperature was determined from computer fitting of the conductance-mole ratio data. The results revealed that, the stoichiometry and the stability order of (cryptand 222 · La)3+ complex changes with the nature and also the composition of the solvent system. A non-linear relationship was observed between the stability constant (log K f) of (cryptand 222 · La)3+ complex versus the composition of the binary mixed solvents. Thermodynamically, the complexation of lanthanum(III) cation with the cryptand 222, is mainly entropy governed and the values of these parameters are influenced by the nature and composition of the binary mixed solvent solutions.

  3. Characterization of phosphate sequestration by a lanthanum modified bentonite clay: A solid- state NMR, EXAFS and PXRD study

    SciTech Connect

    Dithmer, Line; Lipton, Andrew S.; Reitzel, Kasper; Warner, Terence E.; Lundberg, Daniel; Nielsen, Ulla Gro

    2015-04-07

    Phosphate (P) sequestration by a lanthanum (La) exchanged bentonite (a clay mineral), which is extensively used in chemical lake restoration, was investigated on the molecular level using a combination of 31P and 139La solid state NMR spectroscopy (SSNMR), extended X-ray absorption spectroscopy (EX-AFS) and powder X-ray diffraction (PXRD) in combination with sorption studies. 31P SSNMR show that all phosphate is immobilized as rhabdophane, LaPO4·xH2O, which is further supported by 139La SSNMR and EXAFS; whereas PXRD results are ambiguous with respect to rhabdophane and monazite (LaPO4). Adsorption studies show that, at humic acids (HA) concentrations above ca. 250 μM the binding capacity is only 50 % of the theoretical value or even less. No other lanthanum or phosphate phases are detected by SSNMR and EXAFS indicating the effect of HA is kinetic. Moreover, 31P SSNMR shows that rhabdophane formed upon P sequestration is in close proximity to the clay matrix.

  4. Production of light olefins by catalytic conversion of lignocellulosic biomass with HZSM-5 zeolite impregnated with 6wt.% lanthanum.

    PubMed

    Huang, Weiwei; Gong, Feiyan; Fan, Minghui; Zhai, Qi; Hong, Chenggui; Li, Quanxin

    2012-10-01

    Catalytic conversion of rice husk, sawdust, sugarcane bagasse, cellulose, hemicellulose and lignin into olefins was performed with HZSM-5 containing 6 wt.% lanthanum. The olefins yields for different feedstocks decreased in the order: cellulose>hemicellulose>sugarcane bagasse>rice husk>sawdust>lignin. Biomass containing higher content of cellulose or hemicellulose produced more olefins than feedstocks with higher content of lignin. Among the biomass types, sugarcane bagasse provided the highest olefin yield of 0.12 kg olefins/(kg dry biomass) and carbon yield of 21.2C-mol%. Temperature, residence time and the catalyst/feed ratio influenced olefin yield and selectivity. While the HZSM-5 zeolite was catalytically active, the incorporation of lanthanum at 2.9, and 6.0 wt.% increased the production of olefins from rice husk by 15.6% and 26.5%, respectively. The conversion of biomass to light olefins potentially provides an alternative and sustainable route for production of the key petrochemicals. PMID:22858493

  5. Lanthanum chloride impairs spatial learning and memory and downregulates NF-κB signalling pathway in rats.

    PubMed

    Zheng, Linlin; Yang, Jinghua; Liu, Qiufang; Yu, Fei; Wu, Shengwen; Jin, Cuihong; Lu, Xiaobo; Zhang, Lifeng; Du, Yanqiu; Xi, Qi; Cai, Yuan

    2013-12-01

    Exposure to rare earth elements (REEs) is known to impair intelligence in children and cause neurobehavioral abnormalities in animals. However, the mechanisms underlying these phenomena are not clear. Lanthanum is often used to study the effects of REEs. The aim of this study was to investigate the influence of lanthanum chloride (LaCl3) on spatial learning and memory and a possible underlying mechanism involving nuclear factor-kappa B (NF-κB) signalling pathway expression in the hippocampus. The rats were exposed to 0, 0.25, 0.50 or 1.00 % LaCl3 in drinking water during pregnancy and lactation (i.e. while feeding their offspring). After weaning, young rats continued to receive 0, 0.25, 0.50 and 1.00 % LaCl3 in the drinking water for 1 month. LaCl3 exposure impaired the spatial learning and memory of young rats and significantly decreased the expression of phosphorylated IκB kinase complex, phosphorylated IκBα, NF-κB, c-fos, c-jun and brain-derived neurotrophic factor in the hippocampus. These results indicate that LaCl3 exposure impairs spatial learning and memory in rats by inhibiting NF-κB signalling pathway.

  6. Effect of the addition of low rare earth elements (lanthanum, neodymium, cerium) on the biodegradation and biocompatibility of magnesium.

    PubMed

    Willbold, Elmar; Gu, Xuenan; Albert, Devon; Kalla, Katharina; Bobe, Katharina; Brauneis, Maria; Janning, Carla; Nellesen, Jens; Czayka, Wolfgang; Tillmann, Wolfgang; Zheng, Yufeng; Witte, Frank

    2015-01-01

    Rare earth elements are promising alloying element candidates for magnesium alloys used as biodegradable devices in biomedical applications. Rare earth elements have significant effects on the high temperature strength as well as the creep resistance of alloys and they improve magnesium corrosion resistance. We focused on lanthanum, neodymium and cerium to produce magnesium alloys with commonly used rare earth element concentrations. We showed that low concentrations of rare earth elements do not promote bone growth inside a 750 μm broad area around the implant. However, increased bone growth was observed at a greater distance from the degrading alloys. Clinically and histologically, the alloys and their corrosion products caused no systematic or local cytotoxicological effects. Using microtomography and in vitro experiments, we could show that the magnesium-rare earth element alloys showed low corrosion rates, both in in vitro and in vivo. The lanthanum- and cerium-containing alloys degraded at comparable rates, whereas the neodymium-containing alloy showed the lowest corrosion rates.

  7. Lanthanum enhances glutamate-nitric oxide-3',5'-cyclic guanosine monophosphate pathway in the hippocampus of rats.

    PubMed

    Du, Yanqiu; Yang, Jinghua; Yan, Bo; Bai, Yan; Zhang, Lifeng; Zheng, Linlin; Cai, Yuan

    2016-10-01

    Lanthanum (La) appears to impair learning and memory and increase the toxicity of excitatory amino acids in the central nervous system. The mechanism underlying excitotoxicity induced by La is still unclear. The purpose of this study was to investigate the hippocampal impairment of La exposure and possible mechanism involving the glutamate-nitric oxide (NO)-3'-5'-cyclic guanosine monophosphate (cGMP) pathway. In this study, lactating rats were exposed to 0, 0.25, 0.50, and 1.0% lanthanum chloride (LaCl3) in drinking water, respectively. Their offsprings were exposed to LaCl3 by parental lactation and then administrated with 0, 0.25, 0.50, and 1.0% LaCl3 in drinking water for 1 month. The results showed that La exposure impaired the neuronal ultrastructure and significantly increased the glutamate level, intracellular calcium ion concentrations, and NR1 and NR2B expression in the hippocampi. La exposure significantly enhanced messenger RNA expression and activity levels of inducible NO synthase and increased NO and cGMP levels in the hippocampi in a dose-dependent manner. These results indicate that the mechanism underlying excitotoxicity induced by La is possibly due to alterations of the glutamate-NO-cGMP signaling pathway in the hippocampus. The study provides new findings that may help prevent and improve treatments for La-induced neurotoxicity.

  8. Effect of the addition of low rare earth elements (lanthanum, neodymium, cerium) on the biodegradation and biocompatibility of magnesium.

    PubMed

    Willbold, Elmar; Gu, Xuenan; Albert, Devon; Kalla, Katharina; Bobe, Katharina; Brauneis, Maria; Janning, Carla; Nellesen, Jens; Czayka, Wolfgang; Tillmann, Wolfgang; Zheng, Yufeng; Witte, Frank

    2015-01-01

    Rare earth elements are promising alloying element candidates for magnesium alloys used as biodegradable devices in biomedical applications. Rare earth elements have significant effects on the high temperature strength as well as the creep resistance of alloys and they improve magnesium corrosion resistance. We focused on lanthanum, neodymium and cerium to produce magnesium alloys with commonly used rare earth element concentrations. We showed that low concentrations of rare earth elements do not promote bone growth inside a 750 μm broad area around the implant. However, increased bone growth was observed at a greater distance from the degrading alloys. Clinically and histologically, the alloys and their corrosion products caused no systematic or local cytotoxicological effects. Using microtomography and in vitro experiments, we could show that the magnesium-rare earth element alloys showed low corrosion rates, both in in vitro and in vivo. The lanthanum- and cerium-containing alloys degraded at comparable rates, whereas the neodymium-containing alloy showed the lowest corrosion rates. PMID:25278442

  9. Pyrophoricity of tritium-storage bed materials

    SciTech Connect

    Longhurst, G. R.

    1988-03-01

    Experiments were conducted on samples of depleted uranium and on intermetallic compounds of zirconium--cobalt and lanthanum--nickel--aluminide to evaluate the pyrophoricity of the activated materials and their hydrides and deuterides on exposure to air. It was found that none of the materials spontaneously ignited when exposed to room temperature air, but the uranium and the zirconium--cobalt both ignited in air at moderately elevated temperatures. Activated (dehydrided) materials showed stronger reactions than did the hydrides, but they ignited at essentially the same temperatures. Deuterides showed effectively the same characteristics as the hydrides except the ignition temperature of zirconium--cobalt deuteride was reduced by 20--50 K from that of the hydride. The possibility of a fire in tritium storage beds is real, especially if uranium or zirconium--cobalt are used as storage materials, but fires may not occur until the bed is heated. 9 refs., 12 figs., 1 tab.

  10. Pyrophoricity of tritium-storage bed materials

    SciTech Connect

    Longhurst, G.R.

    1988-09-01

    Experiments were conducted on samples of depleted uranium and on intermetallic compounds of zirconium-cobalt and lanthanum-nickel-aluminide to evaluate the pyrophoricity of the activated materials and their hydrides and deuterides on exposure to air. None of the materials spontaneously ignited when exposed to room temperature air, but the uranium and the zirconium-cobalt both ignited in air at moderately elevated temperatures. Activated dehyrdided materials ignited at essentially the same temperatures. Deuterides showed effectively the same characteristics as the hydrides except the ignition temperature of zirconium-cobalt deuteride was reduced by 20 - 50 K from that of the hydride. The pyrophoricity of these materials raises concern about the possibility of fires in tritium-storage beds with attendant damage to the bed and dispersal of tritiated debris, but fires may not occur until the bed is heated.

  11. Low-cost and large-scale synthesis of functional porous materials for phosphate removal with high performance

    NASA Astrophysics Data System (ADS)

    Emmanuelawati, Irene; Yang, Jie; Zhang, Jun; Zhang, Hongwei; Zhou, Liang; Yu, Chengzhong

    2013-06-01

    A facile spray drying technique has been developed for large-scale and template-free production of nanoporous silica with controlled morphology, large pore size, and high pore volume, using commercially available fumed silica, Aerosil 200, as a sole precursor. This approach can be applied to the preparation of functional nanoporous materials, in this study, lanthanum oxide functionalised silica microspheres by introducing lanthanum nitrate in situ during the spray drying process and followed by a post-calcination process. The resultant lanthanum functionalised Aerosil microspheres manifest high phosphate adsorption capacity (up to 2.317 mmol g-1), fast kinetics, and excellent adsorption performance at a low phosphate concentration (1 mg L-1). In virtue of the easy and scalable synthesis method, low cost and high performances of the product, the materials we reported here are promising for water treatment. Our approach may be general and extended to the synthesis of other functional nanoporous materials with versatile applications.A facile spray drying technique has been developed for large-scale and template-free production of nanoporous silica with controlled morphology, large pore size, and high pore volume, using commercially available fumed silica, Aerosil 200, as a sole precursor. This approach can be applied to the preparation of functional nanoporous materials, in this study, lanthanum oxide functionalised silica microspheres by introducing lanthanum nitrate in situ during the spray drying process and followed by a post-calcination process. The resultant lanthanum functionalised Aerosil microspheres manifest high phosphate adsorption capacity (up to 2.317 mmol g-1), fast kinetics, and excellent adsorption performance at a low phosphate concentration (1 mg L-1). In virtue of the easy and scalable synthesis method, low cost and high performances of the product, the materials we reported here are promising for water treatment. Our approach may be general and

  12. Materials System for Intermediate Temperature Solid Oxide Fuel Cell

    SciTech Connect

    Uday B. Pal; Srikanth Gopalan

    2005-01-24

    AC complex impedance spectroscopy studies were conducted between 600-800 C on symmetrical cells that employed strontium-and-magnesium-doped lanthanum gallate electrolyte, La{sub 0.9}Sr{sub 0.1}Ga{sub 0.8}Mg{sub 0.2}O{sub 3} (LSGM). The objective of the study was to identify the materials system for fabrication and evaluation of intermediate temperature (600-800 C) solid oxide fuel cells (SOFCs). The slurry-coated electrode materials had fine porosity to enhance catalytic activity. Cathode materials investigated include La{sub 1-x}Sr{sub x}MnO{sub 3} (LSM), LSCF (La{sub 1-x}Sr{sub x}Co{sub y}Fe{sub 1-y}O{sub 3}), a two-phase particulate composite consisting of LSM-doped-lanthanum gallate (LSGM), and LSCF-LSGM. The anode materials were Ni-Ce{sub 0.85}Gd{sub 0.15}O{sub 2} (Ni-GDC) and Ni-Ce{sub 0.6}La{sub 0.4}O{sub 2} (Ni-LDC) composites. Experiments conducted with the anode materials investigated the effect of having a barrier layer of GDC or LDC in between the LSGM electrolyte and the Ni-composite anode to prevent adverse reaction of the Ni with lanthanum in LSGM. For proper interpretation of the beneficial effects of the barrier layer, similar measurements were performed without the barrier layer. The ohmic and the polarization resistances of the system were obtained over time as a function of temperature (600-800 C), firing temperature, thickness, and the composition of the electrodes. The study revealed important details pertaining to the ohmic and the polarization resistances of the electrode as they relate to stability and the charge-transfer reactions that occur in such electrode structures.

  13. Characterization and adsorption properties of a lanthanum-loaded magnetic cationic hydrogel composite for fluoride removal.

    PubMed

    Dong, Shuoxun; Wang, Yili

    2016-01-01

    In this study, a novel lanthanum-loaded magnetic cationic hydrogel (MCH-La) was synthesized for fluoride adsorption from drinking water. The adsorption kinetics, isotherms, and effects of pH and co-existing anions on fluoride uptake by MCH-La were evaluated. FTIR, Raman and XPS were used to analyze the fluoride adsorption mechanism of MCH-La. Results showed that MCH-La had positive zeta potential values of 23.6-8.0 mV at pH 3.0-11.0, with the magnitude of saturation magnetization up to 10.3 emu/g. The fluoride adsorption kinetics by MCH-La fitted well with the fractal-like-pseudo-second-order model, and the adsorption capacity reached 93% of the ultimate adsorption capacity within the first 10 min. The maximum fluoride adsorption capacity for MCH-La was 136.78 mg F(-)/g at an equilibrium fluoride concentration of 29.3 mg/L and pH 7.0. Equilibrium adsorption data showed that the Sips model was more suitable than the Langmuir and Freundlich models. MCH-La still had more than 100 mg of F(-)/g adsorption capacity at a strongly alkaline solution (pH > 10). The adsorption process was highly pH-dependent, and the optimal adsorption was attained at pH 2.8-4.0, corresponding to ligand exchange, electrostatic interactions, and Lewis acid-base interactions. With the exception of both anions of HCO3(-) and SiO4(4-), Cl(-), NO3(-), and SO4(2-) did not evidently prevent fluoride removal by MCH-La at their real concentrations in natural groundwater. The fluoride adsorption capacity of the regenerated MCH-La approached 70% of the fresh MCH-La from the second to fifth recycles. FTIR and Raman spectra revealed that C-O and CO functional groups on MCH contributed to the fluoride adsorption, this finding was also confirmed by the XPS F 1s spectra. Deconvolution of C 1s spectra before and after fluoride adsorption indicated that the carboxyl, anhydride, and phenol groups of MCH were involved in the fluoride removal.

  14. Modified Lanthanum Zirconium Oxide buffer layers for low-cost, high performance YBCO coated conductors

    NASA Astrophysics Data System (ADS)

    Parans Paranthaman, M.; Sathyamurthy, S.; Li, Xiaoping; Specht, E. D.; Wee, S. H.; Cantoni, C.; Goyal, A.; Rupich, M. W.

    2010-03-01

    The pyrochlore Lanthanum Zirconium Oxide, La 2Zr 2O 7 (LZO), has been developed as a potential replacement barrier layer in the standard RABiTS three-layer architecture of physical vapor deposited CeO 2 cap/YSZ barrier/Y 2O 3 seed on Ni-5%W metal tape. The main focus of this research is to ascertain whether: (i) we can further improve the barrier properties of LZO; (ii) we can modify the LZO cation ratio and still achieve a high level of performance; and (iii) it is possible to reduce the number of buffer layers. We report a systematic investigation of the LZO film growth with varying compositions of La:Zr ratio in the La 2O 3-ZrO 2 system. Using a metal-organic deposition (MOD) process, we have grown smooth, crack-free, epitaxial thin films of La xZr 1-xO y ( x = 0.2-0.6) on standard Y 2O 3 buffered Ni-5W substrates in short lengths. Detailed XRD studies indicate that a single epitaxial LZO phase with only (0 0 1) texture can be achieved in a broad compositional range of x = 0.2-0.6 in La xZr 1-xO y. Both CeO 2 cap layers and MOD-YBCO films were grown epitaxially on these modified LZO barriers. High critical currents per unit width, Ic of 274-292 A/cm at 77 K and self-field were achieved for MOD-YBCO films grown on La xZr 1-xO y ( x = 0.4-0.6) films. These results indicate that LZO films can be grown with a broad compositional range and still support high performance YBCO coated conductors. In addition, epitaxial MOD La xZr 1-xO y ( x = 0.25) films were grown directly on biaxially textured Ni-3W substrates. About 3 μm thick YBCO films grown on a single MOD-LZO buffered Ni-3W substrates using pulsed laser deposition show a critical current density, Jc, of 0.55 MA/cm 2 ( Ic of 169 A/cm) at 77 K and 0.01 T. This work holds promise for a route for producing simplified buffer architecture for RABiTS based YBCO coated conductors.

  15. Modified Lanthanum Zirconium Oxide Buffer for Low-Cost, High Performance YBCO Coated Conductors

    SciTech Connect

    Paranthaman, Mariappan Parans; Sathyamurthy, Srivatsan; Li, Xiaoping; Specht, Eliot D; Wee, Sung Hun; Cantoni, Claudia; Goyal, Amit; Rupich, M. W.

    2010-01-01

    Lanthanum Zirconium Oxide, La2Zr2O7 (LZO) has been developed as a potential replacement barrier layer in the standard RABiTS three-layer architecture of physical vapor deposited CeO2 cap/YSZ barrier/Y2O3 seed/Ni-5W. The main focus of this research is to see (i) whether we can improve further the barrier properties of LZO; (ii) can we widen the LZO composition and still achieve the high performance?; and (iii) is it possible to reduce the number of buffer layers? We report a systematic investigation of the LZO film growth with varying compositions of La:Zr ratio in the La2O3-ZrO2 system. Using metal-organic deposition (MOD) process, we have grown smooth, crack-free, epitaxial thin films of LaxZr1-xOy (x = 0.2-0.6) on standard Y2O3 buffered Ni-5W substrates in short lengths. Detailed XRD studies indicate that a single epitaxial LZO phase without the (111) texture can be achieved in a wider compositional window of x = 0.2-0.6 in LaxZr1-xOy. Both CeO2 cap layers and MOD-YBCO films were grown 2 epitaxially on these modified LZO barriers. Transport property measurements indicate that we can achieve a higher critical current, Ic of 274-292 A/cm at 77 K and self-field on MOD-YBCO films grown on LaxZr1-xOy (x = 0.4-0.6) films. These results indicate that LZO films can be grown with a wider compositional window and still achieve high performance YBCO coated conductors. In addition, epitaxial MOD LaxZr1-xOy (x = 0.25) films were grown directly on biaxially textured Ni-3W substrates. About 3 m thick YBCO films with a Jc of 0.55 MA/cm2 at 77 K and 0.01 T were grown on a single MOD LZO buffered Ni-3W substrate using pulsed laser deposition. This work promises a route for producing simplified buffer architecture for RABiTS based YBCO coated conductors.

  16. Calcium, lanthanum, pyrophosphate, and hydroxyapatite: a comparative study in fibroblast mitogenicity.

    PubMed

    Praeger, F C; Gilchrest, B A

    1989-01-01

    Calcium-containing crystals and elevated levels of calcium chloride (CaCl2) and lanthanum chloride (LaCl3) have been previously reported to enhance the proliferative activity of cultured fibroblasts. We have investigated the relative mitogenicity of these agents, whether they function via precipitation on the cell surface and whether they interact with one another. Confluent cultures of newborn foreskin fibroblasts provided with fresh medium containing 10% fetal bovine serum (FBS) in the presence of hydroxyapatite (HA), pyrophosphate (PPi), LaCl3 (La), or additional CaCl2 (Ca) were all stimulated more than control cultures provided with fresh medium and 10% FBS alone as assessed by cell counts 5 days later. Increases in cell yield above the original confluent cell density were 316% for La, 271% for Ca, 189% for HA, 131% for PPi, and 45% for controls. Addition of fresh medium containing 10% FBS and epidermal growth factor or fresh medium containing 20% FBS as additional points of reference yielded increases of 204 and 107%, respectively, over original confluent density. Stimulation induced by La or Ca was significantly greater (P less than 0.001) than the stimulation induced by each of the other treatments. The same treatments added to confluent cultures without a change of medium also renewed mitotic activity, with La and Ca again the most mitogenic and approximately doubling the pretreatment cell yields. Cultures incubated in an inverted position to avoid cell contact with precipitates in the medium were also stimulated by La and Ca, but not by HA and PPi. When added to confluent cultures simultaneously supplemented with optimal additional Ca, La decreased Day 5 cell yields in a dose-dependent manner at low concentrations (0.03-0.2 mM) but increased cell yields over those obtained with 0.2 mM LaCl3 again in a dose-dependent manner at higher concentrations. Thus, while HA and PPi act via precipitation on the cell surface, the more mitogenic agents La and Ca

  17. Phytoplankton community responses in a shallow lake following lanthanum-bentonite application.

    PubMed

    Lang, P; Meis, S; Procházková, L; Carvalho, L; Mackay, E B; Woods, H J; Pottie, J; Milne, I; Taylor, C; Maberly, S C; Spears, B M

    2016-06-15

    The release of phosphorus (P) from bed sediments to the overlying water can delay the recovery of lakes for decades following reductions in catchment contributions, preventing water quality targets being met within timeframes set out by environmental legislation (e.g. EU Water Framework Directive: WFD). Therefore supplementary solutions for restoring lakes have been explored, including the capping of sediment P sources using a lanthanum (La)-modified bentonite clay to reduce internal P loading and enhance the recovery process. Here we present results from Loch Flemington where the first long-term field trial documenting responses of phytoplankton community structure and abundance, and the UK WFD phytoplankton metric to a La-bentonite application was performed. A Before-After-Control-Impact (BACI) analysis was used to distinguish natural variability from treatment effect and confirmed significant reductions in the magnitude of summer cyanobacterial blooms in Loch Flemington, relative to the control site, following La-bentonite application. However this initial cyanobacterial response was not sustained beyond two years after application, which implied that the reduction in internal P loading was short-lived; several possible explanations for this are discussed. One reason is that this ecological quality indicator is sensitive to inter-annual variability in weather patterns, particularly summer rainfall and water temperature. Over the monitoring period, the phytoplankton community structure of Loch Flemington became less dominated by cyanobacteria and more functionally diverse. This resulted in continual improvements in the phytoplankton compositional and abundance metrics, which were not observed at the control site, and may suggest an ecological response to the sustained reduction in filterable reactive phosphorus (FRP) concentration following La-bentonite application. Overall, phytoplankton classification indicated that the lake moved from poor to moderate

  18. Management of eutrophication in Lake De Kuil (The Netherlands) using combined flocculant - Lanthanum modified bentonite treatment.

    PubMed

    Waajen, Guido; van Oosterhout, Frank; Douglas, Grant; Lürling, Miquel

    2016-06-15

    Eutrophication of Lake De Kuil (The Netherlands, 6.7 ha, maximum depth 9 m) has frequently caused cyanobacterial blooms resulting in swimming bans or the issue of water quality warnings during summer. The eutrophication was mainly driven by sediment phosphorus (P)-release. The external P-loading was in the range of the critical loading for phytoplankton blooms. Hence, the reduction of the internal P-loading provided a promising way to reduce cyanobacterial blooms. To mitigate the cyanobacterial blooms, the combination of a low dose flocculant (iron(III)chloride; Flock) and a solid phase phosphate fixative (lanthanum modified bentonite; Lock) was applied in May 2009. This combined approach both removed cyanobacterial biomass from the water column and also intercepted P released from the bottom sediments. Immediately after treatment, the Secchi depth increased from 1.5 m up to 5 m. Sediment P-release decreased from 5.2 mg P m(-2) d(-1) (2009) to 0.4 mg P m(-2) d(-1) (2010) but increased in later years. Mean summer concentrations of total P decreased from 0.05 mg L(-1) (1992-2008) to 0.02 mg L(-1) (2009-2014) and chlorophyll-a from 16 μg L(-1) (1992-2008) to 6 μg L(-1) (2009-2014). Mean summer Secchi depth increased from 2.31 m (1992-2008) to 3.12 m (2009-2014). The coverage of macrophytes tripled from 2009 to 2011. In the winter of 2010/2011 Planktothrix rubescens bloomed, but cyanobacterial biomass decreased during the summers after the Flock and Lock treatment in comparison to prior years. After the Flock & Lock the bathing water requirements have been fulfilled for six consecutive summers. As the sediment P-release has gradually increased in recent years, there is a risk of a reversion from the present mesotrophic state to a eutrophic state.

  19. Phytoplankton community responses in a shallow lake following lanthanum-bentonite application.

    PubMed

    Lang, P; Meis, S; Procházková, L; Carvalho, L; Mackay, E B; Woods, H J; Pottie, J; Milne, I; Taylor, C; Maberly, S C; Spears, B M

    2016-06-15

    The release of phosphorus (P) from bed sediments to the overlying water can delay the recovery of lakes for decades following reductions in catchment contributions, preventing water quality targets being met within timeframes set out by environmental legislation (e.g. EU Water Framework Directive: WFD). Therefore supplementary solutions for restoring lakes have been explored, including the capping of sediment P sources using a lanthanum (La)-modified bentonite clay to reduce internal P loading and enhance the recovery process. Here we present results from Loch Flemington where the first long-term field trial documenting responses of phytoplankton community structure and abundance, and the UK WFD phytoplankton metric to a La-bentonite application was performed. A Before-After-Control-Impact (BACI) analysis was used to distinguish natural variability from treatment effect and confirmed significant reductions in the magnitude of summer cyanobacterial blooms in Loch Flemington, relative to the control site, following La-bentonite application. However this initial cyanobacterial response was not sustained beyond two years after application, which implied that the reduction in internal P loading was short-lived; several possible explanations for this are discussed. One reason is that this ecological quality indicator is sensitive to inter-annual variability in weather patterns, particularly summer rainfall and water temperature. Over the monitoring period, the phytoplankton community structure of Loch Flemington became less dominated by cyanobacteria and more functionally diverse. This resulted in continual improvements in the phytoplankton compositional and abundance metrics, which were not observed at the control site, and may suggest an ecological response to the sustained reduction in filterable reactive phosphorus (FRP) concentration following La-bentonite application. Overall, phytoplankton classification indicated that the lake moved from poor to moderate

  20. The nss mutation or lanthanum inhibits light-induced Ca2+ influx into fly photoreceptors.

    PubMed

    Rom-Glas, A; Sandler, C; Kirschfeld, K; Minke, B

    1992-11-01

    Ion-selective calcium microelectrodes were inserted into the compound eyes of the wild-type sheep blowfly Lucilia or into the retina of the no steady state (nss) mutant of Lucilia. These electrodes monitored light-induced changes in the extracellular concentration of calcium (delta[Ca2+]o) together with the extracellularly recorded receptor potential. Prolonged dim lights induced a steady reduction in [Ca2+]o during light in the retina of normal Lucilia, while relatively little change in [Ca2+]o was observed in the retina of the nss mutant. Prolonged intense light induced a multiphasic change in [Ca2+]o: the [Ca2+]o signal became transient, reaching a minimum within 6 s after light onset, and then rose to a nearly steady-state phase below the dark concentration. When lights were turned off, a rapid increase in [Ca2+]o was observed, reaching a peak above the dark level and then declining again to the dark level within 1 min. In analogy to similar studies conduced in the honeybee drone, we suggest that the reduction in [Ca2+]o reflects light-induced Ca2+ influx into the photoreceptors, while the subsequent increase in [Ca2+]o reflects the activation of the Na-Ca exchange which extrudes Ca2+ from the cells. In the nss mutant in response to intense prolonged light, the receptor potential declines to baseline during light while the Ca2+ signal is almost abolished, revealing only a short transient reduction in [Ca2+]o. Application of lanthanum (La3+), but not nickel (Ni2+), into the retinal extracellular space of normal Lucilia mimicked the effect of the nss mutation on the receptor potential, while complete elimination of the Ca2+ signal in a reversible manner was observed. The results suggest that La3+ and the nss mutation inhibit light-induced Ca2+ influex into the photoreceptor in a manner similar to the action of the trp mutation in Drosophila, which has been shown to block specifically a light-activated Ca2+ channel necessary to maintain light excitation.

  1. Induction of early bolting in Arabidopsis thaliana by triacontanol, cerium and lanthanum is correlated with increased endogenous concentration of isopentenyl adenosine (iPAdos).

    PubMed

    He, Ya-Wen; Loh, Chiang-Shiong

    2002-03-01

    The effects of triacontanol (TRIA), applied singly or in combination with cerium nitrate and lanthanum nitrate, on bolting of Arabidopsis thaliana were studied. Triacontanol (0.1 to 0.6 microM) added to the culture medium induced early bolting. TRIA (0.3 microM) applied with low concentrations of cerium and lanthanum caused a synergistic stimulation of bolting. In medium containing 0.3 microM TRIA, 0.1 microM cerium nitrate and 0.1 mM lanthanum nitrate, 82% of the plants bolted 20 d after seed sowing compared to only 8.6% in basal medium and 47.8% in medium with TRIA only. The changes in the endogenous concentrations of total cytokinins of the isopentenyl adenine (IP) subfamily in the leaf and root tissues were correlated with TRIA-induced early bolting. The combined treatment of TRIA (0.3 microM), cerium nitrate (0.1 microM) and lanthanum nitrate (0.1 mM) resulted in a significant increase in the endogenous concentrations of total cytokinins of the IP subfamily in the root and leaf tissues compared to plants growing in the basal medium and medium with TRIA. The exogenous application of six natural cytokinins to the plants revealed that only isopentenyl adenosine (iPAdos) was as effective as TRIA on floral bud formation. iPAdos was also found to have similar effects as TRIA on root growth and reproductive growth. These results suggest a correlation between the early bolting induced by TRIA, cerium and lanthanum and the production of higher concentrations of endogenous iPAdos.

  2. Electrical Properties of Ferroelectric Lead Lanthanum Zirconate Titanate as an Energy Transducer for Application to Electrostatic-Optical Motor

    NASA Astrophysics Data System (ADS)

    Ichiki, Masaaki; Morikawa, Yasushi; Nakada, Takeshi

    2002-11-01

    An electrostatic-optical motor has been proposed as a new application device using lead lanthanum zirconate titanate (PLZT) as an energy transducer from optical energy to electrical energy. Photovoltaic electrical power output of the PLZT is transformed into electrostatic force for actuation of the rotation of the optical motor. Electrical conductivity including dark conductivity and photovoltaic conductivity plays an essential role in mechanisms of the photovoltaic effect. An electrical property of photovoltaic PLZT is examined quantitatively. Uniform illumination is realized with the homogeneous irradiation lens. As a result, it becomes possible to realize uniform illumination one order stronger than previously reported. We confirm that there is a linear relationship between electrical conductivity and light intensity in this experiment.

  3. Lanthanum induced B-to-Z transition in self-assembled Y-shaped branched DNA structure.

    PubMed

    Nayak, Ashok K; Mishra, Aseem; Jena, Bhabani S; Mishra, Barada K; Subudhi, Umakanta

    2016-01-01

    Controlled conversion of right-handed B-DNA to left-handed Z-DNA is one of the greatest conformational transitions in biology. Recently, the B-Z transition has been explored from nanotechnological points of view and used as the driving machinery of many nanomechanical devices. Using a combination of CD spectroscopy, fluorescence spectroscopy, and PAGE, we demonstrate that low concentration of lanthanum chloride can mediate B-to-Z transition in self-assembled Y-shaped branched DNA (bDNA) structure. The transition is sensitive to the sequence and structure of the bDNA. Thermal melting and competitive dye binding experiments suggest that La(3+) ions are loaded to the major and minor grooves of DNA and stabilize the Z-conformation. Our studies also show that EDTA and EtBr play an active role in reversing the transition from Z-to-B DNA. PMID:27241949

  4. Modification of radiation sensitivity by salts of the metals beryllium and indium and the rare earths cerium, lanthanum and scandium.

    PubMed

    Floersheim, G L

    1995-03-01

    The LD50 of 46 salts of metals and rare earths (lanthanoids) was determined in mice. Half the LD50 of the compounds was then combined with lethal radiation (10.5 Gy) and the modification of survival time was scored. Only the metals beryllium and indium and the rare earths cerium, lanthanum and scandium displayed activity in our assay. They were then tested at a wider range of lower doses and reduced survival time in a dose-dependent fashion. This appears to be compatible with enhancement of radiation sensitivity. The interaction of these metals and rare earths with radiation adds a new facet to their toxicological spectrum and, by enhancing radiation effects, may influence estimates of risk. On the other hand, the radiosensitizing properties of the metals may be useful for further development of compounds to be used as adjuncts in specific situations of cancer radiotherapy.

  5. A Lanthanum-Tagged Chemotherapeutic Agent HA-Pt to Track the In Vivo Distribution of Hyaluronic Acid Complexes

    PubMed Central

    Forrest, W.C.; Cai, Shuang; Aires, Daniel; Forrest, M. Laird

    2015-01-01

    Hyaluronic acid drug conjugates can target anti-cancer drugs directly to tumor tissue for loco-regional treatment with enhanced bioavailability, local efficacy and reduced toxicity. In this study, the distribution and pharmacokinetics of hyaluronic acid carrier and a conjugated cisplatin anti-cancer drug were tracked by lanthanum (III) [La(III)] affinity tagging of the nanocarrier. The strong binding affinity of La(III) to HA enabled the simple preparation of a physiologically stable complex HA-Pt-La and straightforward simultaneous detection of HA-La and Pt in biological matrices using inductively coupled plasma-mass spectrometry (ICP-MS). Consequently, after subcutaneous injection of HA-Pt-La nanoparticles in human head and neck squamous cell carcinoma (HNSCC) tumor-bearing mice, the HA and Pt content were detected and quantified simultaneously in the plasma, primary tumor, liver and spleen. PMID:26756040

  6. Lanthanum Tricyanide-Catalyzed Acyl Silane-Ketone Benzoin Additions and Kinetic Resolution of Resultant α-Silyloxyketones

    PubMed Central

    Tarr, James C.

    2010-01-01

    We report the full account of our efforts on the lanthanum tricyanide-catalyzed acyl silane-ketone benzoin reaction. The reaction exhibits a wide scope in both acyl silane (aryl, alkyl) and ketone (aryl-alkyl, alkyl-alkyl, aryl-aryl, alkenyl-alkyl, alkynyl-alkyl) coupling partners. The diastereoselectivity of the reaction has been examined in both cyclic and acyclic systems. Cyclohexanones give products arising from equatorial attack by the acyl silane. The diastereoselectivity of acyl silane addition to acyclic α-hydroxy ketones can be controlled by varying the protecting group to obtain either Felkin-Ahn or chelation control. The resultant α-silyloxyketone products can be resolved with selectivity factors from 10 to 15 by subjecting racemic ketone benzoin products to CBS reduction. PMID:20392127

  7. Effects and mechanisms of the combined pollution of lanthanum and acid rain on the root phenotype of soybean seedlings.

    PubMed

    Sun, Zhaoguo; Wang, Lihong; Zhou, Qing; Huang, Xiaohua

    2013-09-01

    Rare earth pollution and acid rain pollution are both important environmental issues worldwide. In regions which simultaneously occur, the combined pollution of rare earth and acid rain becomes a new environmental issue, and the relevant research is rarely reported. Accordingly, we investigated the combined effects and mechanisms of lanthanum ion (La(3+)) and acid rain on the root phenotype of soybean seedlings. The combined pollution of low-concentration La(3+) and acid rain exerted deleterious effects on the phenotype and growth of roots, which were aggravated by the combined pollution of high-concentration La(3+) and acid rain. The deleterious effects of the combined pollution were stronger than those of single La(3+) or acid rain pollution. These stronger deleterious effects on the root phenotype and growth of roots were due to the increased disturbance of absorption and utilization of mineral nutrients in roots.

  8. Lanthanum induced B-to-Z transition in self-assembled Y-shaped branched DNA structure

    PubMed Central

    Nayak, Ashok K.; Mishra, Aseem; Jena, Bhabani S.; Mishra, Barada K.; Subudhi, Umakanta

    2016-01-01

    Controlled conversion of right-handed B-DNA to left-handed Z-DNA is one of the greatest conformational transitions in biology. Recently, the B-Z transition has been explored from nanotechnological points of view and used as the driving machinery of many nanomechanical devices. Using a combination of CD spectroscopy, fluorescence spectroscopy, and PAGE, we demonstrate that low concentration of lanthanum chloride can mediate B-to-Z transition in self-assembled Y-shaped branched DNA (bDNA) structure. The transition is sensitive to the sequence and structure of the bDNA. Thermal melting and competitive dye binding experiments suggest that La3+ ions are loaded to the major and minor grooves of DNA and stabilize the Z-conformation. Our studies also show that EDTA and EtBr play an active role in reversing the transition from Z-to-B DNA. PMID:27241949

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

    SciTech Connect

    Loschialpo, P.; Kapetanakos, C.A.

    1987-12-13

    Large (approx. 5 cm) diameter lanthanum hexaboride (LaB/sub 6/) cathodes operated at 10 kV produced 1-5 micro electron pulses with current density between 10 and 20 A/sq. cm. Normalized beam brightness was consistently measured. To obtain this high current density, the LaB/sub 6/ cathodes have been heated to temperatures between approx 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.

  10. Effects and mechanisms of the combined pollution of lanthanum and acid rain on the root phenotype of soybean seedlings.

    PubMed

    Sun, Zhaoguo; Wang, Lihong; Zhou, Qing; Huang, Xiaohua

    2013-09-01

    Rare earth pollution and acid rain pollution are both important environmental issues worldwide. In regions which simultaneously occur, the combined pollution of rare earth and acid rain becomes a new environmental issue, and the relevant research is rarely reported. Accordingly, we investigated the combined effects and mechanisms of lanthanum ion (La(3+)) and acid rain on the root phenotype of soybean seedlings. The combined pollution of low-concentration La(3+) and acid rain exerted deleterious effects on the phenotype and growth of roots, which were aggravated by the combined pollution of high-concentration La(3+) and acid rain. The deleterious effects of the combined pollution were stronger than those of single La(3+) or acid rain pollution. These stronger deleterious effects on the root phenotype and growth of roots were due to the increased disturbance of absorption and utilization of mineral nutrients in roots. PMID:23726884

  11. Thickness effect on the structure, grain size, and local piezoresponse of self-polarized lead lanthanum zirconate titanate thin films

    NASA Astrophysics Data System (ADS)

    Melo, M.; Araújo, E. B.; Shvartsman, V. V.; Shur, V. Ya.; Kholkin, A. L.

    2016-08-01

    Polycrystalline lanthanum lead zirconate titanate (PLZT) thin films were deposited on Pt/TiO2/SiO2/Si substrates to study the effects of the thickness and grain size on their structural and piezoresponse properties at nanoscale. Thinner PLZT films show a slight (100)-orientation tendency that tends to random orientation for the thicker film, while microstrain and crystallite size increases almost linearly with increasing thickness. Piezoresponse force microscopy and autocorrelation function technique were used to demonstrate the existence of local self-polarization effect and to study the thickness dependence of correlation length. The obtained results ruled out the bulk mechanisms and suggest that Schottky barriers near the film-substrate are likely responsible for a build-in electric field in the films. Larger correlation length evidence that this build-in field increases the number of coexisting polarization directions in larger grains leading to an alignment of macrodomains in thinner films.

  12. Dielectric properties of lead lanthanum zirconate titanate thin films with and without ZrO2 insertion layers

    NASA Astrophysics Data System (ADS)

    Liu, Shanshan; Ma, Beihai; Narayanan, Manoj; Tong, Sheng; Koritala, Rachel E.; Hu, Zhongqiang; Balachandran, Uthamalingam

    2013-05-01

    The dielectric properties of lead lanthanum zirconate titanate (PLZT) thin films on platinized silicon (Pt/Si) with and without ZrO2 insertion layers were investigated in the temperature range from 20 °C to 300 °C. Permittivity, dielectric loss tangent, and tunability were reduced for the samples with ZrO2 insertion layers compared to those without the layers. Additionally, the permittivity was less dependent on frequency over the broad temperature range studied (20-300 °C). The leakage current behavior of the PLZT films with and without ZrO2 insertion layers was also investigated, and on the basis of those results, a probable conduction mechanism has been suggested. The improved electrical properties in the PLZT with ZrO2 layers are attributed to the ZrO2 layer blocking the mobile ionic defects and reducing free charge carriers to transport.

  13. Some metal-graphite and metal-ceramic composites for use as high energy brake lining materials

    NASA Technical Reports Server (NTRS)

    Bill, R. C.

    1974-01-01

    Materials were studied as candidates for development as potential new aircraft brake lining materials. These families were (1) copper-graphite composites; (2) nickel-graphite composites; (3) copper - rare-earth-oxide (gadolinium oxide (Gd2O3) or lanthanum oxide (La2O3)) composites and copper - rare-earth-oxide (La2O3) - rare-earth-fluoride (lanthanum fluoride (LaF3)) composites; (4) nickel - rare-earth-oxide composites and nickel - rare-earth-oxide - rare-earth-fluoride composites. For comparison purposes, a currently used metal-ceramic composite was also studied. Results showed that the nickel-Gd2O3 and nickel-La2O3-LaF3 composites were comparable or superior in friction and wear performance to the currently used composite and therefore deserve to be considered for further development.

  14. Influence of citrate-nitrate reaction mixture packing on ceramic powder properties

    NASA Astrophysics Data System (ADS)

    Zupan, Klementina; Kolar, Drago; Marinšek, Marjan

    Lanthanum chromite-based materials have a good prospect for use in various high temperature applications, as well as an SOFC separator. A citrate-nitrate gel combustion reaction was used for the preparation of submicron crystalline strontium-substituted lanthanum chromite (LSC). The effect of the fuel-oxidant molar ratio and sample form prior to combustion was investigated in terms of reaction period, phase formation, particle size, morphology and agglomerate formation. Several characterization methods including scanning electron microscopy, mercury porosimetry, BET measurement, X-ray powder diffraction and thermal analysis were used to evaluate the influence of reaction mixture packing on powder characteristics for different citrate-nitrate (c/n) ratios. It was shown that the reaction period depends on the fuel/oxidant ratio and reaction mixture packing. The LSC powders prepared via the combustion route exhibited surface areas of about 12 m 2/g for the loose packed layer prepared samples and 7 to 11 m 2/g for samples prepared from a pellet. The nature of the agglomerates was studied from the pore size distribution in the green compacts pressed at different pressures. The sintering behaviour of powders and some of the electrical properties of sintered samples are reported. Sintering tests on LSC powders prepared via the combustion route showed that the sintering process started at about 900°C and proceeded in two steps in the presence of a liquid phase.

  15. 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.

  16. Thermal expansion of lanthanum silicate oxyapatite (La9.33+2x(SiO4)6O2+3x), lanthanum oxyorthosilicate (La2SiO5) and lanthanum sorosilicate (La2Si2O7)

    NASA Astrophysics Data System (ADS)

    Fukuda, Koichiro; Asaka, Toru; Uchida, Tomohiro

    2012-10-01

    Four types of powder specimens of La9.33(SiO4)6O2 (space group P63/m and Z=1), La9.33+2x(SiO4)6O2+3x with 0.06≤x≤0.13 (P63/m and Z=1), La2SiO5 (P21/c and Z=4) and La2Si2O7 (P21/c and Z=4) were examined by high-temperature X-ray powder diffractometry to determine the changes in unit-cell dimensions up to 1473 K. The anisotropy of thermal expansion was demonstrated for the former two crystals to clarify the thermal behaviors of the highly c-axis-oriented polycrystals. With La9.33(SiO4)6O2, the linear expansion coefficient of the a-axis (αa) was 4.8×10-6 K-1 and that of the c-axis (αc) was 1.8×10-6 K-1 in the temperature range from 298 to 1473 K. The αa- and αc-values of La9.33+2x(SiO4)6O2+3x (0.06≤x≤0.13) were, respectively, 5.9×10-6 K-1 and 2.3×10-6 K-1. The coefficients of mean linear thermal expansion were 4.9×10-6 K-1 for La2SiO5 and 6.0×10-6 K-1 for La2Si2O7, which describe the thermal expansion behaviors of the randomly grain-oriented polycrystalline materials.

  17. Preparation of three-dimensionally ordered macroporous perovskite-type lanthanum-iron-oxide LaFeO{sub 3} with tunable pore diameters: High porosity and photonic property

    SciTech Connect

    Sadakane, Masahiro; Horiuchi, Toshitaka; Kato, Nobuyasu; Sasaki, Keisuke; Ueda, Wataru

    2010-06-15

    Three-dimensionally ordered macroporous (3DOM) lanthanum-iron-oxide (LaFeO{sub 3}) with different pore diameters was prepared using a colloidal crystal of polymer spheres with different diameters as templates. Ethylene glycol-methanol mixed solution of metal nitrates was infiltrated into the void of the colloidal crystal template of a monodispersed poly(methyl methacrylate) (PMMA) sphere. Heating of this PMMA-metal salt-ethylene glycol composite produced the desired well-ordered 3DOM LaFeO{sub 3} with a high pore fraction, which was confirmed by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), mercury (Hg) porosimetry, and ultraviolet-visible (UV-vis) diffuse reflectance spectra. 3DOM LaFeO{sub 3} with pore diameters of 281 and 321 nm shows opalescent colors because of photonic stop band properties. Catalytic activity of the 3DOM LaFeO{sub 3} for combustion of carbon particles was enhanced by a potassium cation, which was involved from K{sub 2}S{sub 2}O{sub 8} used as a polymerization initiator. - Graphical abstract: Well-ordered three-dimensionally ordered macroporous LaFeO{sub 3} materials with pore sizes ranging from 127 to 321 nm were obtained in a high pore fraction.

  18. Local Structure of Proton-Conducting Lanthanum Tungstate La28-xW4+xO54+δ: a Combined Density Functional Theory and Pair Distribution Function Study

    SciTech Connect

    Kalland, Liv-Elisif; Magrasó, Anna; Mancini, Alessandro; Tealdi, Cristina; Malavasi, Lorenzo

    2013-10-02

    Lanthanum tungstate (La28–xW4+xO54+δ) is a good proton conductor and exhibits a complex fluorite-type structure. To gain further understanding of the short-range order in the structure we correlate the optimized configurations obtained by density functional theory (DFT) with the experimental atomic pair distribution function analysis (PDF) of time-of-flight neutron and synchrotron X-ray data, collected at room temperature. The local atomic arrangements cannot be described by means of any average symmetric structure. Tungsten forms WO6 octahedra in alternating directions, La1 is mainly 8-fold coordinated in relatively symmetric cubes, and La2 is coordinated with 6 or 7 oxygens in heavily distorted cubes. Both DFT and PDF confirm that the excess tungsten (x) is incorporated in La2 (1/4, 1/4, 1/4) sites in the La27W5O55.5 composition. This additional tungsten can be considered as a donor self-dopant in the material and has implications to the conducting properties and the defect structure.

  19. Low cost stable air electrode material for high temperature solid oxide electrolyte electrochemical cells

    DOEpatents

    Kuo, Lewis J. H.; Singh, Prabhakar; Ruka, Roswell J.; Vasilow, Theodore R.; Bratton, Raymond J.

    1997-01-01

    A low cost, lanthanide-substituted, dimensionally and thermally stable, gas permeable, electrically conductive, porous ceramic air electrode composition of lanthanide-substituted doped lanthanum manganite is provided which is used as the cathode in high temperature, solid oxide electrolyte fuel cells and generators. The air electrode composition of this invention has a much lower fabrication cost as a result of using a lower cost lanthanide mixture, either a natural mixture or an unfinished lanthanide concentrate obtained from a natural mixture subjected to incomplete purification, as the raw material in place of part or all of the higher cost individual lanthanum. The mixed lanthanide primarily contains a mixture of at least La, Ce, Pr, and Nd, or at least La, Ce, Pr, Nd and Sm in its lanthanide content, but can also include minor amounts of other lanthanides and trace impurities. The use of lanthanides in place of some or all of the lanthanum also increases the dimensional stability of the air electrode. This low cost air electrode can be fabricated as a cathode for use in high temperature, solid oxide fuel cells and generators.

  20. Low cost stable air electrode material for high temperature solid oxide electrolyte electrochemical cells

    DOEpatents

    Kuo, L.J.H.; Singh, P.; Ruka, R.J.; Vasilow, T.R.; Bratton, R.J.

    1997-11-11

    A low cost, lanthanide-substituted, dimensionally and thermally stable, gas permeable, electrically conductive, porous ceramic air electrode composition of lanthanide-substituted doped lanthanum manganite is provided which is used as the cathode in high temperature, solid oxide electrolyte fuel cells and generators. The air electrode composition of this invention has a much lower fabrication cost as a result of using a lower cost lanthanide mixture, either a natural mixture or an unfinished lanthanide concentrate obtained from a natural mixture subjected to incomplete purification, as the raw material in place of part or all of the higher cost individual lanthanum. The mixed lanthanide primarily contains a mixture of at least La, Ce, Pr, and Nd, or at least La, Ce, Pr, Nd and Sm in its lanthanide content, but can also include minor amounts of other lanthanides and trace impurities. The use of lanthanides in place of some or all of the lanthanum also increases the dimensional stability of the air electrode. This low cost air electrode can be fabricated as a cathode for use in high temperature, solid oxide fuel cells and generators. 4 figs.

  1. Bulk crystal growth of scintillator materials for gamma ray detectors

    NASA Astrophysics Data System (ADS)

    Aggarwal, Mohan

    2008-10-01

    Within the past few years, it has been demonstrated that several new rare earth halide scintillation detector crystals such as cerium doped lanthanum bromide (LaBr3:Ce) have high output and improved energy deposit to light linearity and thus they can substantially enhance the performance of the next generation of gamma ray detectors. These detectors have a variety of applications in NASA hard x-ray and gamma ray missions, high energy physics, home land security and medical imaging applications. This cerium doped lanthanum bromide crystal has ˜1100% the light output of BGO, resulting in better energy resolution than conventional scintillators. This is equivalent to 60000 photons per MeV of deposited energy. This new series of scintillator materials promise to usher a breakthrough in the field, if sufficiently large and clear crystals of this material can be grown. These halides however are highly hygroscopic and hence pose some difficulty in growing crystals. Efforts are being made to grow this and other materials in this family of crystals and successful results have been achieved. An overview of the challenges encountered during the synthesis and melt crystal growth of these rare earth halide scintillators shall be presented.

  2. MATERIALS SYSTEM FOR INTERMEDIATE TEMPERATURE SOLID OXIDE FUEL CELL

    SciTech Connect

    Uday B. Pal; Srikanth Gopalan

    2004-02-15

    AC complex impedance spectroscopy studies were conducted on symmetrical cells of the type [gas, electrode/LSGM electrolyte/electrode, gas]. The electrode materials were slurry-coated on both sides of the LSGM electrolyte support. The electrodes selected for this investigation are candidate materials for SOFC electrodes. Cathode materials include La{sub 1-x}Sr{sub x}MnO{sub 3} (LSM), LSCF (La{sub 1-x}Sr{sub x}Co{sub y}Fe{sub 1-y}O{sub 3}), a two-phase particulate composite consisting of LSM + doped-lanthanum gallate (LSGM), and LSCF + LSGM. Pt metal electrodes were also used for the purpose of comparison. Anode material investigated was the Ni + GDC composite. The study revealed important details pertaining to the charge-transfer reactions that occur in such electrodes. The information obtained can be used to design electrodes for intermediate temperature SOFCs based on LSGM electrolyte.

  3. Increase in the dosage amount of vitamin D3 preparations by switching from calcium carbonate to lanthanum carbonate.

    PubMed

    Hyodo, Toru; Kawakami, Junko; Mikami, Noriko; Wakai, Haruki; Ishii, Daisuke; Yoshida, Kazunari; Iwamura, Masatsugu; Hida, Miho; Kurata, Yasuhisa

    2014-06-01

    It is widely known that dialysis patients who are administered vitamin D preparations have a better prognosis than patients who are not. In this study, of 22 patients on maintenance dialysis who had been administered calcium (Ca) carbonate in our hospital, we investigated the dosage amount of vitamin D3 preparations after the phosphorus (P) binder was switched from Ca carbonate to the newly developed lanthanum carbonate (LC). After completely switching to LC, the dosage amount of oral vitamin D3 preparation (alfacalcidol equivalent) was significantly increased from 0.094 μg/day to 0.375 μg/day (P = 0.0090). No significant changes were observed in the values of serum corrected Ca, alkaline phosphatase, intact parathyroid hormone and P after switching. The administration of LC enabled complete cessation of the administration of Ca carbonate preparations, and increased the dosage amount of vitamin D3 preparations. Therefore, LC may be a useful P binder to improve patient prognosis.

  4. Polarization fluctuation behavior of lanthanum substituted Bi{sub 4}Ti{sub 3}O{sub 12} thin films

    SciTech Connect

    Zhong, Ni; Xiang, Ping-Hua Zhang, Yuan-Yuan; Wu, Xing; Tang, Xiao-Dong; Yang, Ping-Xiong; Duan, Chun-Gang; Chu, Jun-Hao

    2015-09-14

    Polarization fluctuation behavior of lanthanum substituted Bi{sub 4}Ti{sub 3}O{sub 12} (Bi{sub 4−x}La{sub x}Ti{sub 3}O{sub 12}, BLT) ferroelectric thin films has been examined. Remnant polarization exhibits an initial increase (P{sub up}, 1–10{sup 6} cycles) and a subsequent decrease (P{sub down}, 10{sup 6}–10{sup 9} cycles) with switching cycles, whereas the dielectric constant exhibits a continuous decrease. By careful investigations on the effect of switching frequency and annealing atmosphere on the polarization fluctuation characteristics, we propose that this polarization fluctuation characteristic of BLT films is attributed to the competition between domain pinning and passive layer growing effect, due to the redistribution of oxygen vacancy related defect under external applied field. P{sub up} behavior is dominated by the unpinning of pinned domain, while P{sub down} behavior is dominated by the reduction of applied field on BLT bulk layer, due to the growing of the passive layer between BLT and Pt electrode. By assuming the dielectric constant and initial thickness of passive layer, the passive layer was estimated to be about 2–5 times thicker than the initial state after 10{sup 9} cycling.

  5. Expanded graphite loaded with lanthanum oxide used as a novel adsorbent for phosphate removal from water: performance and mechanism study.

    PubMed

    Zhang, Ling; Gao, Yan; Li, Mengxue; Liu, Jianyong

    2015-01-01

    A novel adsorbent of expanded graphite (EG) loaded with lanthanum oxide (EG-LaO) was prepared for phosphate removal from water and characterized by scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) spectroscopy. The effects of impregnation time, La3+ concentration, activation time, and activation temperature on the phosphate removal performance of the adsorbent were studied for optimization of preparation conditions. Isothermal adsorption studies suggested that the Langmuir model fits the experimental data well. Adsorption kinetics investigation showed that the pseudo-second-order model fits the experimental data quite well, indicating that the adsorption process is mainly a process of chemical adsorption, and chloride ions compete to react with the active sites of the adsorbent but do not prevent phosphate from adsorbing onto EG-LaO. The adsorption mechanism studies were performed by a pH dependence study of the adsorption amount. The results demonstrated that the probable mechanisms of phosphate adsorption on EG-LaO were electrostatic and Lewis acid-base interactions in addition to ion exchange.

  6. Characterization of phosphate sequestration by a lanthanum modified bentonite clay: a solid-state NMR, EXAFS, and PXRD study.

    PubMed

    Dithmer, Line; Lipton, Andrew S; Reitzel, Kasper; Warner, Terence E; Lundberg, Daniel; Nielsen, Ulla Gro

    2015-04-01

    Phosphate (Pi) sequestration by a lanthanum (La) exchanged clay mineral (La-Bentonite), which is extensively used in chemical lake restoration, was investigated on the molecular level using a combination of (31)P and (139)La solid state NMR spectroscopy (SSNMR), extended X-ray absorption spectroscopy (EXAFS), powder X-ray diffraction (PXRD) and sorption studies. (31)P SSNMR show that all Pi was immobilized as rhabdophane (LaPO4·n H2O, n ≤ 3), which was further supported by (139)La SSNMR and EXAFS. However, PXRD results were ambiguous with respect to rhabdophane and monazite (LaPO4). Adsorption studies showed that at dissolved organic carbon (DOC) concentration above ca. 250 μM the binding capacity was only 50% of the theoretical value or even less. No other La or Pi phases were detected by SSNMR and EXAFS indicating the effect of DOC is kinetic. Moreover, (31)P SSNMR showed that rhabdophane formed upon Pi sequestration is in close proximity to the clay matrix. PMID:25747941

  7. 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.

  8. 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.

  9. Alterations in cytosol free calcium in horseradish roots simultaneously exposed to lanthanum(III) and acid rain.

    PubMed

    Zhang, Xuanbo; Wang, Lihong; Zhou, Anhua; Zhou, Qing; Huang, Xiaohua

    2016-04-01

    The extensive use of rare earth elements (REEs) has increased their environmental levels. REE pollution concomitant with acid rain in many agricultural regions can affect crop growth. Cytosol free calcium ions (Ca(2+)) play an important role in almost all cellular activities. However, no data have been reported regarding the role of cytosol free Ca(2+) in plant roots simultaneously exposed to REE and acid rain. In this study, the effects of exposures to lanthanum(III) and acid rain, independently and in combination, on cytosol free Ca(2+) levels, root activity, metal contents, biomass, cytosol pH and La contents in horseradish roots were investigated. The simultaneous exposures to La(III) and acid rain increased or decreased the cytosol free Ca(2+) levels, depending on the concentration of La(III), and these effects were more evident than independent exposure to La(III) or acid rain. In combined exposures, cytosol free Ca(2+) played an important role in the regulation of root activity, metal contents and biomass. These roles were closely related to La(III) dose, acid rain strength and treatment mode (independent exposure or simultaneous exposure). A low concentration of La(III) (20 mg L(-1)) could alleviate the adverse effects on the roots caused by acid rain, and the combined exposures at higher concentrations of La(III) and acid rain had synergic effects on the roots. PMID:26720810

  10. {sup 139}La NMR in lanthanum manganites: Indication of the presence of magnetic polarons from spectra and nuclear relaxations

    SciTech Connect

    Allodi, G.; De Renzi, R.; Guidi, G.

    1998-01-01

    We present {sup 139}La NMR experiments on five powder samples of lanthanum manganites, with a Mn{sup 4+} concentration ranging from the antiferromagnetic-insulator (AFM) to the ferromagnetic-conducting (FM) region of the phase diagram. We measure a positive hyperfine coupling C=0.13 T/{mu}{sub B}. A signal from nuclei in a FM environment is present at all compositions, as evidenced by a hyperfine frequency in zero-field experiments, by a positive hyperfine shift in NMR experiments below T{sub c}, and by a paramagnetic frequency shift following Curie-Weiss law. A signal from nuclei in an AFM environment is identified by a similar negative intercept Curie-Weiss law. The NMR spectra reveal a large temperature dependent fraction of static spin defects below T{sub c} in the FM domains. Nuclear relaxation indicates that the FM regions are influenced by diffusing, AFM-correlated excitations, while the AFM regions probe spin fluctuations from diffusing, FM correlated excitations. These results are interpreted in terms of electronic inhomogeneities due to the presence of a magnetic small polaron. {copyright} {ital 1998} {ital The American Physical Society}

  11. 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.

  12. Alterations in cytosol free calcium in horseradish roots simultaneously exposed to lanthanum(III) and acid rain.

    PubMed

    Zhang, Xuanbo; Wang, Lihong; Zhou, Anhua; Zhou, Qing; Huang, Xiaohua

    2016-04-01

    The extensive use of rare earth elements (REEs) has increased their environmental levels. REE pollution concomitant with acid rain in many agricultural regions can affect crop growth. Cytosol free calcium ions (Ca(2+)) play an important role in almost all cellular activities. However, no data have been reported regarding the role of cytosol free Ca(2+) in plant roots simultaneously exposed to REE and acid rain. In this study, the effects of exposures to lanthanum(III) and acid rain, independently and in combination, on cytosol free Ca(2+) levels, root activity, metal contents, biomass, cytosol pH and La contents in horseradish roots were investigated. The simultaneous exposures to La(III) and acid rain increased or decreased the cytosol free Ca(2+) levels, depending on the concentration of La(III), and these effects were more evident than independent exposure to La(III) or acid rain. In combined exposures, cytosol free Ca(2+) played an important role in the regulation of root activity, metal contents and biomass. These roles were closely related to La(III) dose, acid rain strength and treatment mode (independent exposure or simultaneous exposure). A low concentration of La(III) (20 mg L(-1)) could alleviate the adverse effects on the roots caused by acid rain, and the combined exposures at higher concentrations of La(III) and acid rain had synergic effects on the roots.

  13. 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

  14. PLZT (lead-lanthanum-zirconium-titanium) electro-optic photographic system. Technical report, 14 July-31 July 1987

    SciTech Connect

    Brown, L.L.

    1987-07-31

    The challenge of this effort was to develop and field a lead-lanthanum-zirconium-titanium (PLZT) electro-optic enhanced photographic system, for high-speed photographic documentation of Thermal Radiation Sources (TRS)/High explosive (H.E.) detonations. Operational design parameters of this system were to have a 6 f-stop dynamic range and pulse response of 100 micro-seconds or less. A prototype PLZT system was designed/fabricated and laboratory tested with a wide variety of dynamic light sources that had substantially different spectral characteristics and radiant output. The prototype system performed satisfactorily for these test series and consequently a semi-hardened unit was fabricated for field use. The fabricated field unit was successfully tested with rocket-propellant burns that simulated light intensities within the camera/PLZT systems field of view (FOV). These test results provided the confidence that the system was ready for deployment to a large-scale test site. The PLZT photographic system was fielded on Project MISTY PICTURE to record the total TRS burn at the 10-psi (69 Kpa) overpressure environment. Several pre-vent TRS burns were recorded. These film records were analyzed and electronic adjustments were made to optimize the dynamic range of the PLZT system. The PLZT system was subsequently tested on the MISTY PICTURE event. Film analysis of the event shows that the system performed over its 6 f-stop range, allowing one camera to record the total TRS burn.

  15. 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).

  16. The effect of lanthanum(III) and cerium(III) ions between layers of manganese oxide on water oxidation.

    PubMed

    Najafpour, Mohammad Mahdi; Isaloo, Mohsen Abbasi; Hołyńska, Małgorzata; Shen, Jian-Ren; Allakhverdiev, Suleyman I; Allakhverdiev, Suleyman

    2015-12-01

    Manganese oxide structure with lanthanum(III) or cerium(III) ions between the layers was synthesized by a simple method. The ratio of Mn to Ce or La in samples was 0.00, 0.04, 0.08, 0.16, 0.32, 0.5, 0.82, or 1.62. The compounds were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction studies, and atomic absorption spectroscopy. The compounds show efficient catalytic activity of water oxidation in the presence of cerium(IV) ammonium nitrate with a turnover frequency of 1.6 mmol O2/mol Mn.s. In contrast to the water-oxidizing complex in Photosystem II, calcium(II) has no specific role to enhance the water-oxidizing activity of the layered manganese oxides and other cations can be replaced without any significant decrease in water-oxidizing activities of these layered Mn oxides. Based on this and previously reported results from oxygen evolution in the presence of H 2 (18) O, we discuss the mechanism and the important factors influencing the water-oxidizing activities of the manganese oxides. PMID:25701552

  17. 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.

  18. Characterization of phosphate sequestration by a lanthanum modified bentonite clay: a solid-state NMR, EXAFS, and PXRD study.

    PubMed

    Dithmer, Line; Lipton, Andrew S; Reitzel, Kasper; Warner, Terence E; Lundberg, Daniel; Nielsen, Ulla Gro

    2015-04-01

    Phosphate (Pi) sequestration by a lanthanum (La) exchanged clay mineral (La-Bentonite), which is extensively used in chemical lake restoration, was investigated on the molecular level using a combination of (31)P and (139)La solid state NMR spectroscopy (SSNMR), extended X-ray absorption spectroscopy (EXAFS), powder X-ray diffraction (PXRD) and sorption studies. (31)P SSNMR show that all Pi was immobilized as rhabdophane (LaPO4·n H2O, n ≤ 3), which was further supported by (139)La SSNMR and EXAFS. However, PXRD results were ambiguous with respect to rhabdophane and monazite (LaPO4). Adsorption studies showed that at dissolved organic carbon (DOC) concentration above ca. 250 μM the binding capacity was only 50% of the theoretical value or even less. No other La or Pi phases were detected by SSNMR and EXAFS indicating the effect of DOC is kinetic. Moreover, (31)P SSNMR showed that rhabdophane formed upon Pi sequestration is in close proximity to the clay matrix.

  19. Investigation of LaxSr1-xCoyM1-yO3-δ (M = Mn Fe) perovskite materials as thermochemical energy storage media

    DOE PAGES

    Babiniec, Sean Michael; Coker, Eric Nicholas; Miller, James E.; Ambrosini, Andrea

    2015-06-23

    Materials in the LaxSr1–xCoyMn1–yO3–δ (LSCM) and LaxSr1–xCoyFe1–yO3–δ (LSCF) families are candidates for high-temperature thermochemical energy storage due to their facility for cyclic endothermic reduction and exothermic oxidation. A set of 16 LSCM and 21 LSCF compositions were synthesized by a modified Pechini method and characterized by powder X-ray diffraction and thermogravimetric analysis. All materials were found to be various symmetries of the perovskite phase. LSCM was indexed as tetragonal, cubic, rhombohedral, or orthorhombic as a function of increased lanthanum content. For LSCF, compositions containing low lanthanum content were indexed as cubic while materials with high lanthanum content were indexed asmore » rhombohedral. An initial screening of redox activity was completed by thermogravimetric analysis for each composition. The top three compositions with the greatest recoverable redox capacity for each family were further characterized in equilibrium thermogravimetric experiments over a range of temperatures and oxygen partial pressures. As a result, these equilibrium experiments allowed the extraction of thermodynamic parameters for LSCM and LSCF compositions operated in thermochemical energy storage conditions.« less

  20. Study of the formation of the apatite-type phases La9.33+x(SiO4)6O2+3x/2 synthesized from a lanthanum oxycarbonate La2O2CO3

    NASA Astrophysics Data System (ADS)

    Pons, A.; Jouin, J.; Béchade, E.; Julien, I.; Masson, O.; Geffroy, P. M.; Mayet, R.; Thomas, P.; Fukuda, K.; Kagomiya, I.

    2014-12-01

    Lanthanum silicated apatites with nominal composition La9.33+x(SiO4)6O2+3x/2 (-0.2 < x < 0.27) have been successfully synthesized by solid state reaction using a new reagent La2O2CO3 and amorphous SiO2 precursors. The formation mechanism of La2O2CO3 reagent, which cannot be purchased, has been followed by in-situ temperature depend XRD of La2O3 under CO2 atmosphere. The stability of this reagent during the synthesis step allowed to limit the formation of secondary phase La2Si2O7 and made the weighting of the reagent easier. High purity powders could be synthesized at the temperature of 1400 °C. Dense pellets (more than 98.5%) were obtained by isostatic pressing of powders calcined at 1200 °C and then sintered at 1550 °C. Traces of La2SiO5 secondary phase present in synthesized powder disappeared after densification and pure oxyapatite materials were obtained for all the compositions. Electrical measurements confirmed that conductivity behaviors of the sintered pellets were dependent to the oxygen over-stoichiometry. Indeed, a relatively high conductivity of 1 × 10-2 S cm-1 was exhibited at 800 °C for the nominal composition La9.60(SiO4)6O2.405 with low activation energy around 0.79 eV. The ionic conductivity properties were comparable with that of the earlier obtained materials.

  1. Lanthanum complexes containing a bis(phenolate) ligand with a ferrocene-1,1'-diyldithio backbone: synthesis, characterization, and ring-opening polymerization of rac-lactide.

    PubMed

    Hermans, Catherine; Rong, Weifeng; Spaniol, Thomas P; Okuda, Jun

    2016-05-10

    Lanthanum complexes [(L)LaX] (X = N(SiMe3)2, O(i)Pr , BH4) supported by a ferrocene-based (OSSO)-type ligand LH2 were synthesized and characterized by elemental analysis, NMR spectroscopy and cyclic voltammetry. The structure of was confirmed by single crystal X-ray diffraction. These complexes were highly active initiators for the ring-opening polymerization of rac-lactide (rac-LA). The activity depended on the initiating group in the order of ≈ > . The activities of and during polymerization were controlled in situ with external redox reagents by reversibly switching the oxidation state of the iron center.

  2. 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.

  3. Determination of Protein by Fluorescence Enhancement of Curcumin in Lanthanum-Curcumin-Sodium Dodecyl Benzene Sulfonate-Protein System

    SciTech Connect

    Wang, Feng; Huang, Wei; Zhang, Yunfeng; Wang, Mingyin; Sun, Lina; Tang, Bo; Wang, Wei

    2011-01-01

    We found that the fluorescence intensity of the lanthanum (La(3+))-curcumin (CU) complex can be highly enhanced by proteins in the presence of sodium dodecyl benzene sulphonate (SDBS). Based on this finding, a new fluorimetric method for the determination of protein was developed. Under optimized conditions, the enhanced intensities of fluorescence are quantitatively in proportion to the concentrations of proteins in the range 0.0080-20.0 g mL(-1) for bovine serum albumin (BSA) and 0.00080-20.0 g mL(-1) for human serum albumin (HSA) with excitation of 425 nm, and 0.00020-20.0 g mL(-1) for bovine serum albumin (BSA) and 0.00080-20.0 g mL(-1)for human serum albumin (HSA) with excitation of 280 nm, while corresponding qualitative detection limits (S/N 3) are as low as 5.368, 0.573, 0.049, 0.562 g mL(-1), respectively. Study on reaction mechanism reveals that proteins can bind with La(3+), CU and SDBS through self-assembling function with electrostatic attraction, hydrogen bonding, hydrophobic interaction and van der Waals forces, etc. The proteins form a supermolecular association with multilayer structure, in which La(3+)-CU is clamped between BSA and SDBS. The unique high fluorescence enhancement of CU is resulted through synergic effects of favorable hydrophobic microenvironment provided by BSA and SDBS, and efficient intermolecular energy transfer among BSA, SDBS and CU. In energy transfer process, La(3+) plays a crucial role because it not only shortens the distance between SDBS and CU, but also acts as a "bridge" for transferring the energy from BSA to CU.

  4. Nanoscale precipitates strengthened lanthanum-bearing Mg-3Sn-1Mn alloys through continuous rheo-rolling

    PubMed Central

    Guan, R. G.; Shen, Y. F.; Zhao, Z. Y.; Misra, R. D. K.

    2016-01-01

    We elucidate the effect of lanthanum (La) on the microstructure and mechanical properties of Mg-3Sn-1Mn-xLa (wt.%) alloy plates processed through continuous rheo-rolling for the first time. At x = 0.2 wt.%, La dissolved completely in the α-Mg matrix. As the La content was increased to 0.6 wt.%, a new plate-shaped three-phase compound composed of La5Sn3, Mg2Sn and Mg17La2 phases was formed with an average length of 380 ± 10 nm and an average width of 110 ± 5 nm. This compound had a pinning effect on the α-Mg grain boundary and on dislocations. With further increase in La-content to 1.0 wt.%, the length of the plate-shaped compound increased to an average length of 560 ± 10 nm, while the width was reduced to 90 ± 5 nm. The particle size of Mg2Sn decreased from 100 nm to 50 nm with increase in La-content from 0.2 to 1.4 wt.%. At La content of 1.0 wt.%, the tensile strength and elongation of the alloy was maximum, with 29% and 32% increase, respectively, compared to the Mg-3Sn-1Mn (wt.%) alloy, and 37% and 89% increase, in comparison to the Mg-3Sn-1Mn-0.87 Ce (wt.%) alloy. PMID:26988533

  5. Dehydrogenation of amine-borane Me2NH·BH3 catalyzed by a lanthanum-hydride complex.

    PubMed

    Cui, Peng; Spaniol, Thomas P; Maron, Laurent; Okuda, Jun

    2013-09-27

    The rare-earth-metal-hydride complexes [{(1,7-Me2TACD)LnH}4] (Ln=La 1 a, Y 1 b; (1,7-Me2TACD)H2 =1,7-dimethyl-1,4,7,10-tetraazacyclododecane, 1,7-Me2[12]aneN4) were synthesized by hydrogenolysis of [{(1,7-Me2TACD)Ln(η(3)-C3H5)}2] with 1 bar H2. The tetrameric structures were confirmed by (1)H NMR spectroscopy and single-crystal X-ray diffraction of compound 1 a. Both complexes catalyze the dehydrogenation of secondary amine-borane Me2NH·BH3 to afford the cyclic dimer (Me2NBH2)2 and (Me2N)2BH under mild conditions. Whilst the complete conversion of Me2NH·BH3 was observed within 2 h with lanthanum-hydride 1 a, the yttrium homologue 1 b required 48 h to reach 95% conversion. Further reactions of compound 1 a with Me2NH·BH3 in various stoichiometric ratios gave a series of intermediate products, [{(1,7-Me2TACD)LaH}4](Me2NBH2)2 (2 a), [(1,7-Me2TACDH)La(Me2NBH3)2] (3 a), [(1,7-Me2TACD)(Me2NBH2)La(Me2NBH3)] (4 a), and [(1,7-Me2TACD)(Me2NBH2)2La(Me2NBH3)] (5 a). Complexes 2 a, 3 a, and 5 a were isolated and characterized by multinuclear NMR spectroscopy and single-crystal X-ray diffraction studies. These intermediates revealed the activation and coordination modes of "Me2NH·BH3 " fragments that were trapped within the coordination sphere of a rare-earth-metal center. PMID:23946160

  6. Combined effects of simulated acid rain and lanthanum chloride on chloroplast structure and functional elements in rice.

    PubMed

    Hu, Huiqing; Wang, Lihong; Zhou, Qing; Huang, Xiaohua

    2016-05-01

    Acid rain and rare earth element (REE) pollution exist simultaneously in many agricultural regions. However, how REE pollution and acid rain affect plant growth in combination remains largely unknown. In this study, the combined effects of simulated acid rain and lanthanum chloride (LaCl3) on chloroplast morphology, chloroplast ultrastructure, functional element contents, chlorophyll content, and the net photosynthetic rate (P n) in rice (Oryza sativa) were investigated by simulating acid rain and rare earth pollution. Under the combined treatment of simulated acid rain at pH 4.5 and 0.08 mM LaCl3, the chloroplast membrane was smooth, proteins on this membrane were uniform, chloroplast structure was integrated, and the thylakoids were orderly arranged, and simulated acid rain and LaCl3 exhibited a mild antagonistic effect; the Mg, Ca, Mn contents, the chlorophyll content, and the P n increased under this combined treatment, with a synergistic effect of simulated acid rain and LaCl3. Under other combined treatments of simulated acid rain and LaCl3, the chloroplast membrane surface was uneven, a clear "hole" was observed on the surface of chloroplasts, and the thylakoids were dissolved and loose; and the P n and contents of functional elements (P, Mg, K, Ca, Mn, Fe, Ni, Cu, Zn and Mo) and chlorophyll decreased. Under these combined treatments, simulated acid rain and LaCl3 exhibited a synergistic effect. Based on the above results, a model of the combined effects of simulated acid rain and LaCl3 on plant photosynthesis was established in order to reveal the combined effects on plant photosynthesis, especially on the photosynthetic organelle-chloroplast. Our results would provide some references for further understanding the mechanism of the combined effects of simulated acid rain and LaCl3 on plant photosynthesis. PMID:26815371

  7. Extending framework based on the linear coordination polymers: Alternative chains containing lanthanum ion and acrylic acid ligand

    NASA Astrophysics Data System (ADS)

    Li, Hui; Guo, Ming; Tian, Hong; He, Fei-Yue; Lee, Gene-Hsiang; Peng, Shie-Ming

    2006-11-01

    One-dimensional alternative chains of two lanthanum complexes: [La( L1) 3(CH 3OH)(H 2O) 2]·5H 2O ( L1=anion of α-cyano-4-hydroxycinnamic acid ) 1 and [La( L2) 3(H 2O) 2]·3H 2O ( L2=anion of trans-3-(4-methyl-benzoyl)-acrylic acid) 2 were synthesized and structurally characterized by single-crystal X-ray diffraction, element analysis, IR and thermogravimetric analysis. The crystal structure data are as follows for 1: C 31H 36LaN 3O 17, triclinic, P-1, a=9.8279(4) Å, b=11.8278(5) Å, c=17.8730(7) Å, α=72.7960(10)°, β=83.3820(10)°, γ=67.1650(10)º, Z=2, R1=0.0377, wR2=0.0746; for 2: C 33H 37LaO 14, triclinic, P-1, a=8.7174(5) Å, b=9.9377(5) Å, c=21.153(2) Å, α=81.145(2)°, β=87.591(2)°, γ=67.345(5)°, Z=2, R1=0.0869, wR2=0.220. 1 is a rare example of the alternative chain constructed by syn-syn and anti-syn coordination mode of carboxylato ligand arranged along the chain alternatively. La(III) ions in 2 are linked by two η3-O bridges and four bridges (two η2-O and two η3-O) alternatively. Both of the linear coordination polymers grow into two- and three-dimensional networks by packing through extending hydrogen-bond network directed by ligands.

  8. Effects of rare earth element lanthanum on rumen methane and volatile fatty acid production and microbial flora in vitro.

    PubMed

    Zhang, T T; Zhao, G Y; Zheng, W S; Niu, W J; Wei, C; Lin, S X

    2015-06-01

    The objectives of the trial were to study the effects of rare earth element (REE) lanthanum (La) on the in vitro rumen methane (CH4 ) and volatile fatty acid (VFA) production and the microbial flora of feeds. Four feed mixtures with different levels of neutral detergent fibre (NDF), that is 20.0% (I), 31.0% (II), 41.9% (III) and 52.7% (IV), were formulated as substrates. Five levels of LaCl3 , that is 0, 0.4, 0.6, 0.8 and 1.0 mmol/kg dry matter (DM), were added to the feed mixtures, respectively, as experimental treatments in a two-factor 5 × 4 randomized design. The in vitro incubation lasted for 24 h. The results showed that supplementing LaCl3 increased the total gas (p < 0.001) production and tended to increase the total VFA production (p = 0.072) and decreased the CH4 production (p = 0.001) and the ratios of acetate/propionate (p = 0.019) and CH4 /total VFA (p < 0.001). Interactions between LaCl3 and NDF were significant in total gas production (p = 0.030) and tended to be significant in CH4 production (p = 0.071). Supplementing LaCl3 at the level of 0.8 mmol/g DM decreased the relative abundance of methanogens and protozoa in the total bacterial 16S rDNA analysed using the real-time PCR (p < 0.0001), increased F. succinogenes (p = 0.0003) and decreased R. flavefaciens (p < 0.0001) whereas did not affect R. albus and anaerobic fungi (p > 0.05). It was concluded that LaCl3 decreased the CH4 production without negatively affecting feed digestion through manipulating rumen microbial flora when feed mixtures with different levels of NDF were used as substrates.

  9. Combined effects of lanthanum ion and acid rain on growth, photosynthesis and chloroplast ultrastructure in soybean seedlings.

    PubMed

    Wen, Kejia; Liang, Chanjuan; Wang, Lihong; Hu, Gang; Zhou, Qing

    2011-07-01

    Rare earth elements (REEs) have been accumulated in the agricultural environment. Acid rain is a serious environmental issue. In the present work, the effects of lanthanum ion (La(3+)) and acid rain on the growth, photosynthesis and chloroplast ultrastructure in soybean seedlings were investigated using the gas exchange measurements system, chlorophyll fluorometer, transmission electron microscopy and some biochemical techniques. It was found that although the growth and photosynthesis of soybean seedlings treated with the low concentration of La(3+) was improved, the growth and photosynthesis of soybean seedlings were obviously inhibited in the combined treatment with the low concentration of La(3+) and acid rain. At the same time, the chloroplast ultrastructure in the cell of soybean seedlings was destroyed. Under the combined treatment with the high concentration of La(3+) and acid rain, the chloroplast ultrastructure in the cell of soybean seedlings was seriously destroyed, and the growth and of photosynthesis were greatly decreased compared with those of the control, the single treatment with the high concentration of La(3+) and the single treatment with acid rain, respectively. The degree of decrease and destruction on chloroplast ultrastructure depended on the increases in the concentration of La(3+) and acid rain (H(+)). In conclusion, the combined pollution of La(3+) and acid rain obviously destroyed the chloroplast ultrastructure of cell and aggravated the harmful effect of the single La(3+) and acid rain on soybean seedlings. As a new combined pollutant, the harmful effect of REEs ions and acid rain on plant should be paid attention to.

  10. Combined effects of simulated acid rain and lanthanum chloride on chloroplast structure and functional elements in rice.

    PubMed

    Hu, Huiqing; Wang, Lihong; Zhou, Qing; Huang, Xiaohua

    2016-05-01

    Acid rain and rare earth element (REE) pollution exist simultaneously in many agricultural regions. However, how REE pollution and acid rain affect plant growth in combination remains largely unknown. In this study, the combined effects of simulated acid rain and lanthanum chloride (LaCl3) on chloroplast morphology, chloroplast ultrastructure, functional element contents, chlorophyll content, and the net photosynthetic rate (P n) in rice (Oryza sativa) were investigated by simulating acid rain and rare earth pollution. Under the combined treatment of simulated acid rain at pH 4.5 and 0.08 mM LaCl3, the chloroplast membrane was smooth, proteins on this membrane were uniform, chloroplast structure was integrated, and the thylakoids were orderly arranged, and simulated acid rain and LaCl3 exhibited a mild antagonistic effect; the Mg, Ca, Mn contents, the chlorophyll content, and the P n increased under this combined treatment, with a synergistic effect of simulated acid rain and LaCl3. Under other combined treatments of simulated acid rain and LaCl3, the chloroplast membrane surface was uneven, a clear "hole" was observed on the surface of chloroplasts, and the thylakoids were dissolved and loose; and the P n and contents of functional elements (P, Mg, K, Ca, Mn, Fe, Ni, Cu, Zn and Mo) and chlorophyll decreased. Under these combined treatments, simulated acid rain and LaCl3 exhibited a synergistic effect. Based on the above results, a model of the combined effects of simulated acid rain and LaCl3 on plant photosynthesis was established in order to reveal the combined effects on plant photosynthesis, especially on the photosynthetic organelle-chloroplast. Our results would provide some references for further understanding the mechanism of the combined effects of simulated acid rain and LaCl3 on plant photosynthesis.

  11. Combined effects of Lanthanum(III) and elevated Ultraviolet-B radiation on root nitrogen nutrient in soybean seedlings.

    PubMed

    Huang, Guangrong; Wang, Lihong; Sun, Zhaoguo; Li, Xiaodong; Zhou, Qing; Huang, Xiaohua

    2015-02-01

    Rare earth element pollution and elevated ultraviolet-B (UV-B) radiation occur simultaneously in some regions, but the combined effects of these two factors on plants have not attracted enough attention. Nitrogen nutrient is vital to plant growth. In this study, the combined effects of lanthanum(III) and elevated UV-B radiation on nitrate reduction and ammonia assimilation in soybean (Glycine max L.) roots were investigated. Treatment with 0.08 mmol L(-1) La(III) did not change the effects of elevated UV-B radiation on nitrate reductase (NR), nitrite reductase (NiR), glutamine synthetase (GS), glutamate synthase (GOGAT), glutamate dehydrogenase (GDH), nitrate, ammonium, amino acids, or soluble protein in the roots. Treatment with 0.24 mmol L(-1) La(III) and elevated UV-B radiation synergistically decreased the NR, NiR, GS, and GOGAT activities as well as the nitrate, amino acid, and soluble protein levels, except for the GDH activity and ammonium content. Combined treatment with 1.20 mmol L(-1) La(III) and elevated UV-B radiation produced severely deleterious effects on all test indices, and these effects were stronger than those induced by La(III) or elevated UV-B radiation treatment alone. Following the withdrawal of La(III) and elevated UV-B radiation, all test indices for the combined treatments with 0.08/0.24 mmol L(-1) La(III) and elevated UV-B radiation recovered to a certain extent, but they could not recover for treatments with 1.20 mmol L(-1) La(III) and elevated UV-B radiation. In summary, combined treatment with La(III) and elevated UV-B radiation seriously affected nitrogen nutrition in soybean roots through the inhibition of nitrate reduction and ammonia assimilation.

  12. Lanthanum, cerium, praseodymium and yttrium in waters in an upland acidic and acid sensitive environment, mid-Wales

    NASA Astrophysics Data System (ADS)

    Nea, C.

    2005-12-01

    The less than 0.45 mm filterable lanthanum (La), cerium (Ce), praseodymium (Pr) and yttrium (Y) concentrations in rainfall, cloud water, stream and groundwater in the upper River Severn catchments of mid-Wales are presented, based on up to ten years of weekly data. Results show that for rainfall, there is enrichment in the rare earth (RE) elements, especially under conditions of small volume of catch. However, within the correlations, there is a 'forked' relationship, with one line of high La, Ce and Pr with low Y, corresponding to clear pollutant events and the other with relatively low La, Ce and Pr and higher Y to background conditions. Cloud water and stream waters show a simpler relationship indicating two types of source. Cloud, stream and ground water show no split in pattern, with singular linear relationships between the rare La, Ce, Pr and Y. However, in many cases the monitoring of the streams and groundwaters post-dates the rainfall period with high pollutant Ce inputs. RE element concentrations vary systematically, in general decreasing with increasing volume of catch for cloud-water. For the streams, occasionally, there are relatively high Ce and La concentrations (up to about a tenth the maximum in rainfall), which occur in the same year as the corresponding high values in rainfall. Apart from these anomalous periods, RE element concentrations increase with decreasing pH and increasing aluminium concentrations; RE elements are mobilised under acidic conditions. The river waters are particularly enriched in Y relative to La, Ce and Pr, both in terms of average concentrations and values normalised to standard continental shales. The RE element level in the streams is variable and seems to be linked to the main soil types within the catchment; gleys in particular show higher concentrations than their peat and podzolic counterparts. On average, groundwaters are enriched in the RE elements relative to the stream but the link with pH and aluminium observed

  13. Lanthanum from a modified clay used in eutrophication control is bioavailable to the marbled crayfish (Procambarus fallax f. virginalis).

    PubMed

    van Oosterhout, Frank; Goitom, Eyerusalem; Roessink, Ivo; Lürling, Miquel

    2014-01-01

    To mitigate eutrophication in fresh standing waters the focus is on phosphorus (P) control, i.e. on P inflows to a lake as well as a lake's sediment as internal P source. The in-lake application of the lanthanum (La) modified clays - i.e. La modified bentonite (Phoslock) or La modified kaolinite, aim at dephosphatising the water column and at reducing the release of P from a lake's sediment. Application of these clays raises the question whether La from these clays can become bioavailable to biota. We investigated the bioavailability of La from Phoslock in a controlled parallel groups experiment in which we measured the La in carapace, gills, ovaries, hepatopancreas and abdominal muscle after 0, 14 and 28 days of exposure to Phoslock. Expressing the treatment effect as the difference of the median concentration between the two treatment groups (Phoslock minus control group) yield the following effects, the plus sign (+) indicating an increase, concentrations in µg g(-1) dry weight: Day 14: carapace +10.5 µg g(-1), gills +112 µg g(-1), ovaries +2.6 µg g(-1), hepatopancreas +32.9 µg g(-1) and abodminal muscle +3.2 µg g(-1). Day 28: carapace +17.9 µg g(-1); gills +182 µg g(-1); ovaries +2.2 µg g(-1); hepatopancreas +41.9 µg g(-1) and abdominal muscle +7.6 µg g(-1), all effects were statistically significant. As La from Phoslock is bio-available to and taken up by the marbled crayfishes (Procambarus fallax f. virginalis), we advocate that the application of in-lake chemical water treatments to mitigate eutrophication should be accompanied by a thorough study on potential side effects.

  14. Lanthanum from a Modified Clay Used in Eutrophication Control Is Bioavailable to the Marbled Crayfish (Procambarus fallax f. virginalis)

    PubMed Central

    van Oosterhout, Frank; Goitom, Eyerusalem; Roessink, Ivo; Lürling, Miquel

    2014-01-01

    To mitigate eutrophication in fresh standing waters the focus is on phosphorus (P) control, i.e. on P inflows to a lake as well as a lake's sediment as internal P source. The in-lake application of the lanthanum (La) modified clays – i.e. La modified bentonite (Phoslock) or La modified kaolinite, aim at dephosphatising the water column and at reducing the release of P from a lake's sediment. Application of these clays raises the question whether La from these clays can become bioavailable to biota. We investigated the bioavailability of La from Phoslock in a controlled parallel groups experiment in which we measured the La in carapace, gills, ovaries, hepatopancreas and abdominal muscle after 0, 14 and 28 days of exposure to Phoslock. Expressing the treatment effect as the difference of the median concentration between the two treatment groups (Phoslock minus control group) yield the following effects, the plus sign (+) indicating an increase, concentrations in µg g−1 dry weight: Day 14: carapace +10.5 µg g−1, gills +112 µg g−1, ovaries +2.6 µg g−1, hepatopancreas +32.9 µg g−1 and abodminal muscle +3.2 µg g−1. Day 28: carapace +17.9 µg g−1; gills +182 µg g−1; ovaries +2.2 µg g−1; hepatopancreas +41.9 µg g−1 and abodminal muscle +7.6 µg g−1, all effects were statistically significant. As La from Phoslock is bio-available to and taken up by the marbled crayfishes (Procambarus fallax f. virginalis), we advocate that the application of in-lake chemical water treatments to mitigate eutrophication should be accompanied by a thorough study on potential side effects. PMID:25068309

  15. The impact of crystal symmetry on the electronic structure and functional properties of complex lanthanum chromium oxides

    SciTech Connect

    Qiao, Liang; Xiao, Haiyan Y.; Heald, Steve M.; Bowden, Mark E.; Varga, Tamas; Exarhos, Gregory J.; Biegalski, Michael D.; Ivanov, Ilia N.; Weber, William J.; Droubay, Timothy C.; Chambers, Scott A.

    2013-06-14

    Complex oxides exhibit a wide range of crystal structures, chemical compositions and physical properties. The underlying drivers determining the complicated structure-composition-property phase diagrams are the relative positions and orbital overlaps between the metal cations and the oxygen anions. Here we report a combined experimental and theoretical investigation of the structure and bonding in a series of lanthanum chromium oxides prepared by reactive molecular beam epitaxy. Of particular interest is the charge state and local coordination of the Cr. We have stabilized LaCrO3, LaCrO4 and La2CrO6 films by controlling the three elemental fluxes during deposition, and have carried out x-ray diffraction, x-ray photoemission, and x-ray absorption spectroscopy, as well as first-principles calculations, to determine structure, charge state, chemical bonding, and electronic structure. Significant changes in bonding character and orbital interaction are revealed with decreasing ligand symmetry from octahedral to tetrahedral Cr coordination. Both LaCrO4 and LaCrO6 with tetrahedrally coordinated Cr show strong pre-edge features in the Cr K-edge near-edge structure whereas LaCrO3 with octahedrally coordinated Cr exhibits very weak pre-edge features. The origin of these pre-edge features is discussed based on various selection rules and ligand symmetry. We also demonstrate an increase in cation-anion orbital hybridization and a decrease in long-range ligand coupling induced by this symmetry reduction. These in turn result in dramatic modifications of the macroscopic optical and magnetic properties.

  16. The impact of crystal symmetry on the electronic structure and functional properties of complex lanthanum chromium oxides

    SciTech Connect

    Qiao, Liang; Xiao, Haiyan; Heald, Steve M.; Bowden, Mark E; Varga, Tamas; Exarhos, Gregory J.; Biegalski, Michael D; Ivanov, Ilia N; Weber, W J; Droubay, Timothy; Chambers, S. A.

    2013-01-01

    Complex oxides exhibit a wide range of crystal structures, chemical compositions and physical properties. The underlying drivers determining the complicated structure composition property phase diagrams are the relative positions and orbital overlaps between the metal cations and the oxygen anions. Here we report a combined experimental and theoretical investigation of the structure and bonding in a series of lanthanum chromium oxides prepared by molecular beam epitaxy. Of particular interest is the charge state and local coordination of the Cr. We have stabilized LaCrO3, LaCrO4 and La2CrO6 films by controlling the three elemental fluxes during deposition, and have carried out X-ray diffraction, X-ray photoemission, and X-ray absorption spectroscopy, as well as first-principles calculations, to determine structure, charge state, chemical bonding, and electronic structure. Significant changes in bonding character and orbital interaction are revealed with decreasing ligand symmetry from octahedral to tetrahedral Cr coordination. Both LaCrO4 and La2CrO6 with tetrahedrally coordinated Cr show strong pre-edge features in the Cr K-edge near-edge structure whereas LaCrO3 with octahedrally coordinated Cr exhibits very weak pre-edge features. The origin of these pre-edge features is discussed based on various selection rules and ligand symmetry. We also demonstrate an increase in cation anion orbital hybridization and a decrease in long-range ligand coupling induced by this symmetry reduction. These in turn result in dramatic modifications of the macroscopic optical and magnetic properties.

  17. Microwave-assisted synthesis: A fast and efficient route to produce LaMO{sub 3} (M = Al, Cr, Mn, Fe, Co) perovskite materials

    SciTech Connect

    Prado-Gonjal, J.; Arevalo-Lopez, A.M.; Moran, E.

    2011-02-15

    Research highlights: {yields} Lanthanum perovskites can be prepared by microwave irradiation in a domestic set-up. {yields} Microwave-assisted synthesis yields well crystallized and pure materials, sometimes nanosized. {yields} Rietveld analysis has been performed to refine the structures. {yields} Magnetic and electric measurements are similar to those previously reported. {yields} Microwave-assisted synthesis is a fast and efficient method for the synthesis of lanthanum perovskites. -- Abstract: A series of lanthanum perovskites, LaMO{sub 3} (M = Al, Cr, Mn, Fe, Co), having important technological applications, have been successfully prepared by a very fast, inexpensive, reproducible, environment-friendly method: the microwave irradiation of the corresponding mixtures of nitrates. Worth to note, the microwave source is a domestic microwave oven. In some cases the reaction takes place in a single step, while sometimes further annealings are necessary. For doped materials the method has to be combined with others such as sol-gel. Usually, nanopowders are produced which yield high density pellets after sintering. Rietveld analysis, oxygen stoichiometry, microstructure and magnetic measurements are presented.

  18. Hydrophobic and Metallophobic Surfaces: Highly Stable Non-wetting Inorganic Surfaces Based on Lanthanum Phosphate Nanorods.

    PubMed

    Sankar, Sasidharan; Nair, Balagopal N; Suzuki, Takehiro; Anilkumar, Gopinathan M; Padmanabhan, Moothetty; Hareesh, Unnikrishnan Nair S; Warrier, Krishna G

    2016-01-01

    Metal oxides, in general, are known to exhibit significant wettability towards water molecules because of the high feasibility of synergetic hydrogen-bonding interactions possible at the solid-water interface. Here we show that the nano sized phosphates of rare earth materials (Rare Earth Phosphates, REPs), LaPO4 in particular, exhibit without any chemical modification, unique combination of intrinsic properties including remarkable hydrophobicity that could be retained even after exposure to extreme temperatures and harsh hydrothermal conditions. Transparent nanocoatings of LaPO4 as well as mixture of other REPs on glass surfaces are shown to display notable hydrophobicity with water contact angle (WCA) value of 120° while sintered and polished monoliths manifested WCA greater than 105°. Significantly, these materials in the form of coatings and monoliths also exhibit complete non-wettability and inertness towards molten metals like Ag, Zn, and Al well above their melting points. These properties, coupled with their excellent chemical and thermal stability, ease of processing, machinability and their versatile photo-physical and emission properties, render LaPO4 and other REP ceramics utility in diverse applications. PMID:26955962

  19. Hydrophobic and Metallophobic Surfaces: Highly Stable Non-wetting Inorganic Surfaces Based on Lanthanum Phosphate Nanorods

    NASA Astrophysics Data System (ADS)

    Sankar, Sasidharan; Nair, Balagopal N.; Suzuki, Takehiro; Anilkumar, Gopinathan M.; Padmanabhan, Moothetty; Hareesh, Unnikrishnan Nair S.; Warrier, Krishna G.

    2016-03-01

    Metal oxides, in general, are known to exhibit significant wettability towards water molecules because of the high feasibility of synergetic hydrogen-bonding interactions possible at the solid-water interface. Here we show that the nano sized phosphates of rare earth materials (Rare Earth Phosphates, REPs), LaPO4 in particular, exhibit without any chemical modification, unique combination of intrinsic properties including remarkable hydrophobicity that could be retained even after exposure to extreme temperatures and harsh hydrothermal conditions. Transparent nanocoatings of LaPO4 as well as mixture of other REPs on glass surfaces are shown to display notable hydrophobicity with water contact angle (WCA) value of 120° while sintered and polished monoliths manifested WCA greater than 105°. Significantly, these materials in the form of coatings and monoliths also exhibit complete non-wettability and inertness towards molten metals like Ag, Zn, and Al well above their melting points. These properties, coupled with their excellent chemical and thermal stability, ease of processing, machinability and their versatile photo-physical and emission properties, render LaPO4 and other REP ceramics utility in diverse applications.

  20. Hydrophobic and Metallophobic Surfaces: Highly Stable Non-wetting Inorganic Surfaces Based on Lanthanum Phosphate Nanorods

    PubMed Central

    Sankar, Sasidharan; Nair, Balagopal N.; Suzuki, Takehiro; Anilkumar, Gopinathan M.; Padmanabhan, Moothetty; Hareesh, Unnikrishnan Nair S.; Warrier, Krishna G.

    2016-01-01

    Metal oxides, in general, are known to exhibit significant wettability towards water molecules because of the high feasibility of synergetic hydrogen-bonding interactions possible at the solid-water interface. Here we show that the nano sized phosphates of rare earth materials (Rare Earth Phosphates, REPs), LaPO4 in particular, exhibit without any chemical modification, unique combination of intrinsic properties including remarkable hydrophobicity that could be retained even after exposure to extreme temperatures and harsh hydrothermal conditions. Transparent nanocoatings of LaPO4 as well as mixture of other REPs on glass surfaces are shown to display notable hydrophobicity with water contact angle (WCA) value of 120° while sintered and polished monoliths manifested WCA greater than 105°. Significantly, these materials in the form of coatings and monoliths also exhibit complete non-wettability and inertness towards molten metals like Ag, Zn, and Al well above their melting points. These properties, coupled with their excellent chemical and thermal stability, ease of processing, machinability and their versatile photo-physical and emission properties, render LaPO4 and other REP ceramics utility in diverse applications. PMID:26955962

  1. Ceramic Interconnects with Low Sintering Temperature

    NASA Technical Reports Server (NTRS)

    Zhong, Zhi-Min; Goldsby, Jon C.

    2004-01-01

    Ceramic interconnects for use in solid oxide he1 cells are expected to operate between 900 to approximately 1000 C, sinter below 1400 C to allow co-firing and meet a number thermal mechanical requirements. The pervoskite type (ABO3) lanthanum chromite based materials have emerged as a leading candidate that will meet these criteria by varying the composition on the A and B sites. A need therefore exists to determine this material's temperature dependent electrical and mechanical properties with respect to these site substitutions. In this investigation oxide powders were prepared by the glycine-nitrate process. Ionic substitutions were carried out on A sites with Ca or Sr, and B sites with Co and Al, respectively. Only stoichiometric compositions were considered for the sake of stability. The powders and their ability to sinter were investigated by XRD, SEM, dilatometry and density measurements. The sintered materials were further examined by SEM, thermal expansion and electric conductivity measurements in order to elucidate the resulting microstructure, electrical and mechanical properties. In addition quantum mechanical calculations were performed to obtain insight into the effects of these dopants on the materials electronic band structure and lattice parameter.

  2. Atomic Scale Picture of the Ion Conduction Mechanism in Tetrahedral Network of Lanthanum Barium Gallate

    SciTech Connect

    Jalarvo, Niina H; Gourdon, Olivier; Bi, Zhonghe; Gout, Delphine J; Ohl, Michael E; Paranthaman, Mariappan Parans

    2013-01-01

    Combined experimental study of impedance spectroscopy, neutron powder diffraction and quasielastic neutron scattering was performed to shed light into the atomic scale ion migration processes in proton and oxide ion conductor; La0.8Ba1.2GaO3.9 . This material consist of tetrahedral GaO4 units, which are rather flexible and rocking motion of these units promotes the ionic migration process. The oxide ion (vacancy) conduction takes place on channels along c axis, involving a single elementary step, which occurs between adjacent tetrahedron (inter-tetrahedron jump). The proton conduction mechanism consists of intra-tetrahedron and inter-tetrahedron elementary processes. The intra-tetrahedron proton transport is the rate-limiting process, with activation energy of 0.44 eV. The rocking motion of the GaO4 tetrahedron aids the inter-tetrahedral proton transport, which has the activation energy of 0.068 eV.

  3. Investigation on the co-luminescence effect of europium (III)-lanthanum(III)-dopamine-sodium dodecylbenzene sulfonate system and its application.

    PubMed

    Si, Hailin; Zhao, Fang; Cai, Huan

    2013-01-01

    A novel luminescence, enhancement phenomenon in the europium(III)-dopamine-sodium dodecylbenzene sulfonate system was observed when lanthanum(III) was added. Based on this, a sensitive co-luminescence method was established for the determination of dopamine. The luminescence signal for the europium (III)-lanthanum(III)-dopamine-sodium dodecylbenzene sulfonate system was monitored at λ(ex) = 300 nm, λ(em) = 618 nm and pH 8.3. Under optimized conditions, the enhanced luminescence signal responded linearly to the concentration of dopamine in the range 1.0 × 10(-10)-5.0 × 10(-7) mol/L with a correlation coefficient of 0.9993 (n = 11). The detection limit (3σ) was 2.7 × 10(-11) mol/L and the relative standard deviation for 11 parallel measurements of 3.0 × 10(-8) mol/L dopamine was 1.9%. The presented method was successfully applied for the estimation of dopamine in samples of pharmaceutical preparations, human serum and urine. The possible luminescence enhancement mechanism of the system is discussed briefly.

  4. Application of internal standardization to rapid coprecipitation technique using lanthanum phosphate for flame atomic absorption spectrometric determination of iron and lead.

    PubMed

    Kagaya, Shigehiro; Malek, Zanariah Abdul; Araki, Yasuko; Hasegawa, Kiyoshi

    2002-08-01

    By applying an internal standardization, we could use a rapid coprecipitation technique using lanthanum phosphate as a coprecipitant for preconcentration of iron(III) and lead in their flame atomic absorption spectrometric determination. Indium as an internal standard was added to the initial sample solution together with lanthanum and phosphoric acid; the coprecipitation of iron(III) and lead was then carried out at pH about 3. After measuring the atomic absorbances of iron, lead, and indium in the final sample solution, we determined the contents of iron(III) and lead in the original sample solution by using the internal standardization with indium. In this method, complete collection of the precipitate was not required after the coprecipitation of iron(III), lead, and indium, because the ratio of the recovery of iron(III) or lead to that of indium was almost constant regardless of the recovery of the precipitate. This method was simple and rapid, and was available for the determination of 2-300 micrograms L-1 of iron(III) and 5-400 micrograms L-1 of lead in some water samples.

  5. Lanthanum carbonate for the control of hyperphosphatemia in chronic renal failure patients: a new oral powder formulation – safety, efficacy, and patient adherence

    PubMed Central

    Lloret, MªJesús; Ruiz-García, César; DaSilva, Iara; Furlano, Mónica; Barreiro, Yaima; Ballarín, José; Bover, Jordi

    2013-01-01

    Chronic kidney disease (CKD) is associated with very high mortality rates, mainly of cardiovascular origin. The retention of phosphate (P) and increased fibroblast growth factor-23 levels are common, even at early stages of CKD, due to disturbances in normal P homeostasis. Later, hyperphosphatemia appears, which has also been strongly associated with high mortality rates linked to P-mediated cardiovascular and procalcifying effects. Treatment guidelines for these patients continue to be poorly implemented, at least partially due to the lack of adherence to a P-restricted diet and P-binder therapy. Calcium-free P binders, such as lanthanum carbonate, have been associated with a decreased progression of vascular calcification, rendering them an important therapeutic alternative for these high cardiovascular risk CKD patients. Lanthanum carbonate has typically been available as chewable tablets, and the new presentation as an oral powder may provide a useful alternative in the therapeutic armamentarium. This powder is a tasteless, odorless, and colorless semisolid compound miscible with food. In a recent study in healthy individuals, the safety and efficacy of this novel form were evaluated, and it was concluded that it is well tolerated and pharmacodynamically equivalent to the chewable form. In the long run, individualization of preferences and treatments seems an achievable goal prior to final demonstration of improvements in hard outcomes in wide clinical trials in CKD patients. PMID:24235818

  6. 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.

  7. 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.

  8. Thermodynamically stable [4 + 2] cycloadducts of lanthanum-encapsulated endohedral metallofullerenes

    PubMed Central

    Takano, Yuta; Nagashima, Yuki; Herranz, M Ángeles

    2014-01-01

    Summary The [4 + 2] cycloaddition of o-quinodimethanes, generated in situ from the sultine 4,5-benzo-3,6-dihydro-1,2-oxathiin 2-oxide and its derivative, to La metal-encapsulated fullerenes, La2@C80 or La@C82, afforded the novel derivatives of endohedral metallofullerenes (3a,b, 4a,b and 5b). Molecular structures of the resulting compounds were elucidated using spectroscopic methods such as MALDI–TOF mass, optical absorption, and NMR spectroscopy. The [4 + 2] adducts of La2@C80 (3a,b, and 4a,b) and La@C82 (5b), respectively, retain diamagnetic and paramagnetic properties, as confirmed by EPR spectroscopy. Dynamic NMR measurements of 4a at various temperatures demonstrated the boat-to-boat inversions of the addend. In addition, 5b revealed remarkable thermal stability in comparison with the reported [4 + 2] cycloadduct of pentamethylcyclopentadiene and La@C82 (6). These findings demonstrate the utility of sultines to afford thermodynamically stable endohedral metallofullerene derivatives for the use in material science. PMID:24778724

  9. Thermodynamically stable [4 + 2] cycloadducts of lanthanum-encapsulated endohedral metallofullerenes.

    PubMed

    Takano, Yuta; Nagashima, Yuki; Herranz, M Ángeles; Martín, Nazario; Akasaka, Takeshi

    2014-01-01

    The [4 + 2] cycloaddition of o-quinodimethanes, generated in situ from the sultine 4,5-benzo-3,6-dihydro-1,2-oxathiin 2-oxide and its derivative, to La metal-encapsulated fullerenes, La2@C80 or La@C82, afforded the novel derivatives of endohedral metallofullerenes (3a,b, 4a,b and 5b). Molecular structures of the resulting compounds were elucidated using spectroscopic methods such as MALDI-TOF mass, optical absorption, and NMR spectroscopy. The [4 + 2] adducts of La2@C80 (3a,b, and 4a,b) and La@C82 (5b), respectively, retain diamagnetic and paramagnetic properties, as confirmed by EPR spectroscopy. Dynamic NMR measurements of 4a at various temperatures demonstrated the boat-to-boat inversions of the addend. In addition, 5b revealed remarkable thermal stability in comparison with the reported [4 + 2] cycloadduct of pentamethylcyclopentadiene and La@C82 (6). These findings demonstrate the utility of sultines to afford thermodynamically stable endohedral metallofullerene derivatives for the use in material science.

  10. 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.

  11. From Minor Side Phases to Bulk Samples of Lanthanum Oxonitridosilicates: An Investigation with Microfocused Synchrotron Radiation.

    PubMed

    Durach, Dajana; Schultz, Peter; Oeckler, Oliver; Schnick, Wolfgang

    2016-04-01

    Microcrystals of the oxonitridosilicate oxide La(11)Si(13)N(27.636)O(1.046):Ce(3+) were obtained by exploratory high-temperature synthesis starting from La, La(NH2)3, Si(NH)2, BaH2, and CeF3. Owing to the small size of the crystals, microfocused synchrotron radiation was used for structure investigations (space group Cmc21 (No. 36), a = 9.5074(4) Å, b = 32.0626(9) Å, c = 18.5076(8) Å, Z = 8, R1(all) = 0.0267). The crystal structure consists of an unprecedented interrupted three-dimensional network of vertex-sharing SiN(4-x)O(x) tetrahedra that form channels of siebener rings along [100]. Moreover, the structure is characterized by layers of condensed sechser rings in a boat conformation and vierer rings, which are alternatingly stacked with layers of vierer and dreier rings. Several split positions indicate two different local structure variants. Infrared spectroscopy confirms the absence of N-H bonds. Powder X-ray diffraction data show that bulk samples contain only a small amount of La(11)Si(13)N(27.636)O1.046:Ce(3+). However, once the exact composition was determined from structure analysis, it was possible to optimize the synthesis using fluorides as starting materials. Thereby, bulk samples of the homeotypic compound La(11)Si(13)N(27.376)O(0.936)F were obtained and investigated. PMID:26978044

  12. 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.

  13. Tracking Petroleum Refinery Emission Events Using Lanthanum and Lanthanides as Elemental Markers for Fine Particulate Matter

    NASA Astrophysics Data System (ADS)

    Kulkarni, P.; Chellam, S.; Fraser, M. P.

    2007-12-01

    This presentation reports the development and application of an analytical method to quantify the rare earth elements (REEs) in atmospheric particulate matter and emissions of catalyst material from the petroleum refining industry. Inductively coupled plasma - mass spectrometry following high temperature/high pressure microwave digestion has been used to study the REE composition of several fresh and spent catalysts used in fluidized-bed catalytic cracking (FCC) units in petroleum refineries as well as in ambient atmospheric fine particulate matter collected in Houston, TX. The results show that the routine emissions from local FCC units in Houston contribute a constant and low amount to ambient PM2.5 of ~0.1 micrograms per cubic meter. However, a significant (33 - 106 fold) increase in the contributions of FCC emissions to PM2.5 is quantified during an upset emission event compared with background levels associated with routine operation. The impact of emissions from the local refinery that reported the emission event was tracked to a site approximately 50 km downwind from the source, illustrating the potential exposure of humans over a large geographical area through the long-range transport of atmospheric fine particles as well as the power of elemental signatures to understand the sources of fine particles.

  14. Microstructural and ionic transport studies of hydrothermally synthesized lanthanum fluoride nanoparticles

    SciTech Connect

    Patro, L. N. E-mail: kbharath@umd.edu; Kamala Bharathi, K. E-mail: kbharath@umd.edu; Ravi Chandra Raju, N.

    2014-12-15

    This article presents the structural and transport characteristics of hydrothermally synthesized LaF{sub 3} nanoparticles with an average crystallite size of 35nm. The phase formation of the material is confirmed by both X-ray diffraction and transmission electron microscopy techniques. In addition, phase purity of the LaF{sub 3} nanoparticles is corroborated by micro-Raman spectroscopy studies. The complex impedance plots at different temperatures reveal that the conductivity is predominantly due to the intrinsic bulk grains and the conductivity relaxation is non-Debye in nature. The frequency variation of conductivity exhibits dispersion at higher frequencies that can be explained with the frame work of Almond-West formalism. The conduction process is controlled by the mobility of the charge carriers and the charge of transport of mobile fluoride ions occur through hopping mechanism. The scaling behavior of both frequency dependence of conductivity and complex impedance plots at different temperatures confirm that the relaxation mechanism of the mobile fluoride ions is independent of temperature.

  15. Microstructural and ionic transport studies of hydrothermally synthesized lanthanum fluoride nanoparticles

    NASA Astrophysics Data System (ADS)

    Patro, L. N.; Kamala Bharathi, K.; Ravi Chandra Raju, N.

    2014-12-01

    This article presents the structural and transport characteristics of hydrothermally synthesized LaF3 nanoparticles with an average crystallite size of 35nm. The phase formation of the material is confirmed by both X-ray diffraction and transmission electron microscopy techniques. In addition, phase purity of the LaF3 nanoparticles is corroborated by micro-Raman spectroscopy studies. The complex impedance plots at different temperatures reveal that the conductivity is predominantly due to the intrinsic bulk grains and the conductivity relaxation is non-Debye in nature. The frequency variation of conductivity exhibits dispersion at higher frequencies that can be explained with the frame work of Almond-West formalism. The conduction process is controlled by the mobility of the charge carriers and the charge of transport of mobile fluoride ions occur through hopping mechanism. The scaling behavior of both frequency dependence of conductivity and complex impedance plots at different temperatures confirm that the relaxation mechanism of the mobile fluoride ions is independent of temperature.

  16. Investigation of LaxSr1-xCoyM1-yO3-δ (M = Mn Fe) perovskite materials as thermochemical energy storage media

    SciTech Connect

    Babiniec, Sean Michael; Coker, Eric Nicholas; Miller, James E.; Ambrosini, Andrea

    2015-06-23

    Materials in the LaxSr1–xCoyMn1–yO3–δ (LSCM) and LaxSr1–xCoyFe1–yO3–δ (LSCF) families are candidates for high-temperature thermochemical energy storage due to their facility for cyclic endothermic reduction and exothermic oxidation. A set of 16 LSCM and 21 LSCF compositions were synthesized by a modified Pechini method and characterized by powder X-ray diffraction and thermogravimetric analysis. All materials were found to be various symmetries of the perovskite phase. LSCM was indexed as tetragonal, cubic, rhombohedral, or orthorhombic as a function of increased lanthanum content. For LSCF, compositions containing low lanthanum content were indexed as cubic while materials with high lanthanum content were indexed as rhombohedral. An initial screening of redox activity was completed by thermogravimetric analysis for each composition. The top three compositions with the greatest recoverable redox capacity for each family were further characterized in equilibrium thermogravimetric experiments over a range of temperatures and oxygen partial pressures. As a result, these equilibrium experiments allowed the extraction of thermodynamic parameters for LSCM and LSCF compositions operated in thermochemical energy storage conditions.

  17. 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.

  18. Evaluation of lanthanum tungstates as electrolytes for proton conductors Solid Oxide Fuel Cells

    NASA Astrophysics Data System (ADS)

    Zayas-Rey, M. J.; dos Santos-Gómez, L.; Porras-Vázquez, J. M.; Losilla, E. R.; Marrero-López, D.

    2015-10-01

    La27W4NbO55-δ (LWNO) has been tested as electrolyte for proton conductor Solid Oxide Fuel Cells (PC-SOFCs). For this purpose, different electrodes and composite electrodes are considered, including: La0.8Sr0.2MnO3-δ, La0.6Sr0.4Co1-xFexO3-δ, La0.75Sr0.25Cr0.5Mn0.5O3-δ, SrFe0.75Nb0.25O3-δ and NiO. Chemical compatibility between the cell components is investigated by X-ray powder diffraction (XRPD) and energy dispersive spectroscopy (EDS). Furthermore, area specific resistance (ASR) for the different electrodes is determined in symmetrical cells by impedance spectroscopy. XRPD and EDS analysis does not reveal significant bulk reactivity between most of these electrodes and LWNO electrolyte in the typical operating temperature range of an SOFC (600-900 °C). However, minor interdiffusion of elements at the electrolyte/electrode interface has negative effects on both the ohmic losses and electrode polarization of the cells. ASR values are significantly improved by using a porous buffer layer of Ce0.8Gd0.2O1.9 (CGO), deposited between the electrolyte and electrode materials, to prevent reactivity. A single cell with a 350 μm-thick electrolyte, NiO-CGO and La0.6Sr0.4Co0.8Fe0.2O3-δ-CGO composite as anode and cathode, respectively, generates maximum power densities of 140 and 18 mWcm-2 at 900 and 650 °C, respectively.

  19. Hard X-ray Fluorescence Measurements of Heteroepitaxial Solid Oxide Fuel Cell Cathode Materials

    SciTech Connect

    Davis, Jacob N.; Miara, Lincoln J.; Saraf, Laxmikant V.; Kaspar, Tiffany C.; Gopalan, Srikanth; Pal, Uday B.; Woicik, Joseph C.; Basu, Soumendra N.; Ludwig, Karl F.

    2012-12-01

    Commonly, SOFCs are operated at high temperatures (above 800°C). At these temperatures expensive housing is needed to contain an operating stack as well as coatings to contain the oxidation of the metallic interconnects. Lowering the temperature of an operating device would allow for more conventional materials to be used, thus lowering overall cost. Understanding the surface chemical states of cations in the surface of the SOFC cathode is vital to designing a system that will perform well at lower temperatures. The samples studied were grown by pulsed laser deposition (PLD) at the Environmental Molecular Sciences Laboratory (EMSL) at Pacific Northwest National Laboratory (PNNL). 20% strontium doped lanthanum manganite (LSM-20) was grown on YSZ and NGO (neodymium gallate). The films on YSZ have a fiber texture. LSM-20 on NGO is heteroepitaxial. Lanthanum strontium cobalt ferrite (LSCF-6428) films were grown on LAO and YSZ with a GDC barrier layer. Total X-ray Reflection Fluorescence (TXRF) was used to depth profile the samples. In a typical experiment, the angle of the incident beam is varied though the critical angle. Below the critical angle, the x-ray decays as an evanescent wave and will only penetrate the top few nanometers. TXRF experiments done on LSM films have suggested strontium segregates to the surface and form strontium enriched nanoparticles (1). It should be pointed out that past studies have focused on 30% strontium A-site doping, but this project uses 20% strontium doped lanthanum manganite. XANES and EXAFS data were taken as a function of incoming angle to probe composition as a function of depth. XANES spectra can be difficult to analyze fully. For other materials density functional theory calculations compared to near edge measurements have been a good way to understand the 3d valence electrons (2).

  20. Growth of lanthanum manganate buffer layers for coated conductors via a metal-organic decomposition process

    NASA Astrophysics Data System (ADS)

    Venkataraman, Kartik

    LaMnO3 (LMO) was identified as a possible buffer material for YBa2Cu3O7-x conductors due to its diffusion barrier properties and close lattice match with YBa2Cu 3O7-x. Growth of LMO films via a metal-organic decomposition (MOD) process on Ni, Ni-5at.%W (Ni-5W), and single crystal SrTiO3 substrates was investigated. Phase-pure LMO was grown via MOD on Ni and SrTiO 3 substrates at temperatures and oxygen pressures within a thermodynamic "process window" wherein LMO, Ni, Ni-5W, and SrTiO3 are all stable components. LMO could not be grown on Ni-5W in the "process window" because tungsten diffused from the substrate into the overlying film, where it reacted to form La and Mn tungstates. The kinetics of tungstate formation and crystallization of phase-pure LMO from the La and Mn acetate precursors are competitive in the temperature range explored (850--1100°C). Temperatures <850°C might mitigate tungsten diffusion from the substrate to the film sufficiently to obviate tungstate formation, but LMO films deposited via MOD require temperatures ≥850°C for nucleation and grain growth. Using a Y2O3 seed layer on Ni-5W to block tungsten from diffusing into the LMO film was explored; however, Y2O3 reacts with tungsten in the "process window" at 850--1100°C. Tungsten diffusion into Y2O3 can be blocked if epitaxial, crack-free NiWO4 and NiO layers are formed at the interface between Ni-5W and Y2O3. NiWO 4 only grows epitaxially if the overlying NiO and buffer layers are thick enough to mechanically suppress (011)-oriented NiWO4 grain growth. This is not the case when a bare 75 nm-thick Y2O3 film on Ni-5W is processed at 850°C. These studies show that the Ni-5W substrate must be at a low temperature to prevent tungsten diffusion, whereas the LMO precursor film must be at elevated temperature to crystallize. An excimer laser-assisted MOD process was used where a Y2O 3-coated Ni-5W substrate was held at 500°C in air and the pulsed laser photo-thermally heated the Y2O3 and LMO

  1. Kinetics of Formation of Yttrium Barium Copper Oxide Superconductor and Lanthanum Strontium Chromium Oxide Interconnects.

    NASA Astrophysics Data System (ADS)

    Milonopoulou, Vassiliki

    This work studied the reaction mechanism and kinetics of formation of two ceramic materials: (a) rm YBa_2Cu_3O_{7-x} superconductor and (b) rm La_{0.84 }Sr_{0.16}CrO_3 interconnects for solid oxide fuel cells. In situ, time-resolved X-ray diffraction was used to follow the formation kinetics in both cases. The rm YBa_2Cu_3O _{7-x} formation kinetics from a spray-roasted precursor powder containing an intimate mixture of rm Y_2O_3, BaCO_3 and CuO, was studied as a function of gas atmosphere and temperature. It was found that in an oxygen containing environment, high temperatures (800 -840^circC) increased the rm YBa_2Cu_3O_{7 -x} yield. In nitrogen, decomposition of the product occurred at temperatures exceeding 725 ^circC with Y_2BaCuO _5 being one of the decomposition products. The extent of the decomposition was strongly influenced by the temperature. Thus, inert atmosphere is not optimal for rapid rm YBa_2Cu _3O_{7-x} formation. In oxidizing atmospheres, the formation of rm YBa_2Cu_3O_{7-x} involved the formation of BaCuO_2, instead of rm BaCu_2O_2, which was the intermediate in inert atmospheres. At low temperatures ({<}760^circ C) and highly oxidizing environments, one more barium -copper oxide was formed. The presence of CO_2 in the environment inhibited the rm YBa_2Cu_3O_{7-x} formation. Only 1% CO_2 in air completely ceased the reaction at 840^circ C. The experimental data were adequately described by a nuclei growth model assuming two-dimensional, diffusion controlled growth with second-order nucleation rate. The formation of rm La_{0.84 }Sr_{0.16}CrO_3 solid solution from an intimate stoichiometric mixture of LaCrO _3 and SrCrO_4 was also investigated. Unlike the rm YBa _2Cu_3O_{7-x}, the kinetics of rm La_{0.84}Sr _{0.16}CrO_3 formation does not involve the appearance of new diffraction peaks which correspond to the formation of this product. A novel data reduction technique was developed to determine quantitatively phase abundances from in situ high

  2. Lanthanum and zinc sensitivity of GABAA-activated currents in adult medial septum/diagonal band neurons from ethanol dependent rats.

    PubMed

    Frye, G D; Fincher, A S; Grover, C A; Jayaprabhu, S

    1996-05-13

    The impact of chronic ethanol treatment, sufficient to induce tolerance and physical dependence, on GABAA receptor function was studied in acutely isolated neurons from the medial septum/nucleus diagonal band (MS/nDB) of adult rats using whole cell, patch-clamp recordings. In ethanol-naive Controls, GABA (0.3-300 microM) induced concentration-dependent increases in Cl- current with a threshold of 0.3-1 microM, a mean maximal current of 7645 +/- 2148 pA at 100-300 microM, an EC50 of 11.3 +/- 1.3 microM and a slope of 1.53 +/- 0.07. GABA-activated currents in neurons from animals receiving two weeks of ethanol liquid diet treatment did not differ significantly on any of these measures. The rate of GABAA receptor desensitization (t1/2 = 6.49 +/- 1.19 s) estimated as the time required for loss of 50% of peak current during sustained application of 10 microM GABA, as well as the residual steady state current remaining following complete desensitization for controls was unchanged by chronic ethanol. The impact of chronic ethanol treatment on the GABAA receptor modulation by lanthanum and zinc which act as positive and negative allosteric modulators, respectively, was also evaluated. Test pulses of 3 microM GABA in control neurons showed maximal potentiation by 141 +/- 30% at approximately 1000 microM lanthanum with an EC50 of 107 +/- 34 microM and a slope of approximately 1. Lanthanum potentiation remained the same following chronic ethanol treatment. Initial estimates based on fitted concentration response curves suggested that maximal inhibition of 3 microM GABA responses by zinc at the level of 70.2 +/- 8.5% in control cells was significantly increased by chronic ethanol treatment to 95.3 +/- 2.5%, although the IC50 of 60.2 +/- 25 microM was not changed. However, this difference was not supported by direct tests of maximal 3-10 mM zinc concentrations. These results suggest that chronic ethanol treatment, sufficient to induce tolerance and physical dependence, probably

  3. 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.

  4. 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.

  5. Penta­lanthanum zinc diplumbide, La5Zn1−xPb2+x (x ≃ 0.6)

    PubMed Central

    Oshchapovsky, Igor; Pavlyuk, Volodymyr; Dmytriv, Grygoriy; Harbrecht, Bernd

    2014-01-01

    The title non-stoichiometric penta­lanthanum zinc diplumbide, La5Zn1−xPb2+x (x ≃ 0.6), was prepared from the elements in an evacuated silica ampoule. It adopts the Nb5Sn2Si-type structure (space group I4/mcm, Pearson symbol tI32), a ternary ordered superstructure of the W5Si3 type. Among the four independent crystallographic positions, three are fully occupied by La (Wyckoff 16k), La (4b), and Pb (8h) and one is occupied by a statistical mixture [occupancy ratio 0.394 (12):0.606 (12)] of Zn and Pb (4a). The structure is constructed by face-sharing 10-vertex polyhedra around the unmixed Pb sites. These fragments enclose channels of trans-face-sharing tetra­gonal anti­prisms occupied by the disordered Zn and Pb sites. PMID:24526938

  6. Lanthanum(III)-Catalyzed Three-Component Reaction of Coumarin-3-carboxylates for the Synthesis of Indolylmalonamides and Analysis of Their Photophysical Properties.

    PubMed

    Jennings, Julia J; Bhatt, Chinmay P; Franz, Annaliese K

    2016-08-01

    New methodology has been developed for the Lewis acid catalyzed synthesis of malonamides. First, the scandium(III)-catalyzed addition of diverse nucleophiles (e.g., indoles, N,N-dimethyl-m-anisidine, 2-ethylpyrrole, and 2-methylallylsilane) to coumarin-3-carboxylates has been developed to afford chromanone-3-carboxylates in high yields as a single diastereomer. Upon investigating a subsequent lanthanum(III)-catalyzed amidation reaction, a new multicomponent reaction was designed by bringing together coumarin-3-carboxylates with indoles and amines to afford indolylmalonamides, which were identified to exhibit fluorescent properties. The photophysical properties for selected compounds have been analyzed, including quantum yield, molar absorptivity, and Stokes shift. Synthetic studies of several reaction byproducts involved in the network of reaction equilibria for the three-component reaction provide mechanistic insight for the development of this methodology. PMID:27304909

  7. Synthesis and spectroscopic studies of 4-phenylacetyl-3-methyl-1-phenylpyrazolone-5 and its thorium(VI), lanthanum(III) and lead(II) complexes

    NASA Astrophysics Data System (ADS)

    Uzoukwu, Bieluonwu Augustus; Adiukwu, Patricia Ugboaku

    1995-12-01

    The synthesis of 4-phenylacetyl-3-methyl-1-phenylpyrazolone-5 is reported. Analysis of its IR and NMR spectral data has revealed that the ligand is bidentate and has spectral properties that resemble neither those of the 4-benzoyl, 4-acetyl derivatives nor those of the trihaloacetyl derivatives which have p Ka values < 4.0. Instead the spectral properties are similar to those of the 4-alkanoyl derivatives which have p Ka values . 4.0. The thorium(VI), lanthanum(III) and lead(II) complexes were isolated and characterized by UV, IR and 1H, 13C NMR spectral studies. The complexes were anhydrous and conform to a general molecular formula ML n where M( n) is Th(VI), La(III), Pb(II).

  8. Charge transition levels of oxygen, lanthanum, and fluorine related defect structures in bulk hafnium dioxide (HfO2): An ab initio investigation

    NASA Astrophysics Data System (ADS)

    Leitsmann, Roman; Lazarevic, Florian; Nadimi, Ebrahim; Öttking, Rolf; Plänitz, Philipp; Erben, Elke

    2015-06-01

    Intrinsic defect structures and impurity atoms are one of the main sources of leakage current in metal-oxide-semiconductor devices. Using state of the art density functional theory, we have investigated oxygen, lanthanum, and fluorine related defect structures and possible combinations of them. In particular, we have calculated their charge transition levels in bulk m-HfO2. For this purpose, we have developed a new scaling scheme to account for the band gap underestimation within the density functional theory. The obtained results are able to explain the recent experimental observation of a reduction of the trap density near the silicon valence band edge after NF3 treatment and the associated reduction of the device degradation.

  9. Investigation of concentration-dependence of thermodynamic properties of lanthanum, yttrium, scandium and terbium in eutectic LiCl-KCl molten salt

    NASA Astrophysics Data System (ADS)

    Wang, Yafei; Zhou, Wentao; Zhang, Jinsuo

    2016-09-01

    Thermodynamic properties of rare earth metals in LiCl-KCl molten salt electrolyte are crucial to the development of electrochemical separation for the treatment of used nuclear fuels. In the present study, activity coefficient, apparent potential, and diffusion coefficient of lanthanum, yttrium, scandium, and terbium in the molten salt (58 at% LiCl and 42 at% KCl) were calculated by the method of molecular dynamics simulation up to a concentration around 3 at% at temperatures of 723 K and 773 K. It was found that the activity coefficient and the apparent potential increase with the species concentration while diffusion coefficient shows a trend of increase followed by decrease. The calculated results were validated by available measurement data of dilution cases. This research extends the range of data to a wide component and would provide further insight to the pyroprocessing design and safeguards.

  10. 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.

  11. Charge transition levels of oxygen, lanthanum, and fluorine related defect structures in bulk hafnium dioxide (HfO{sub 2}): An ab initio investigation

    SciTech Connect

    Leitsmann, Roman Lazarevic, Florian; Plänitz, Philipp; Nadimi, Ebrahim; Öttking, Rolf; Erben, Elke

    2015-06-28

    Intrinsic defect structures and impurity atoms are one of the main sources of leakage current in metal-oxide-semiconductor devices. Using state of the art density functional theory, we have investigated oxygen, lanthanum, and fluorine related defect structures and possible combinations of them. In particular, we have calculated their charge transition levels in bulk m-HfO{sub 2}. For this purpose, we have developed a new scaling scheme to account for the band gap underestimation within the density functional theory. The obtained results are able to explain the recent experimental observation of a reduction of the trap density near the silicon valence band edge after NF{sub 3} treatment and the associated reduction of the device degradation.

  12. ATOMIC AND MOLECULAR PHYSICS: Theoretical analysis of ionic autoionization spectra of lanthanum via an intermediate state [Xe]5d6d 1P1

    NASA Astrophysics Data System (ADS)

    Zhong, Yin-Peng; Jia, Feng-Dong; Zhong, Zhi-Ping

    2009-10-01

    In the framework of multi-channel quantum defect theory, eigenquantum defects μα and the transformation matrices Uiα of La+ are calculated from first principles by relativistic multi-channel theory, while the dipole matrix elements Dα are obtained by fitting with experimental data. Then the ionic autoionization spectra of lanthanum via the intermediate state [Xe]5d6d 1P1 in the energy region of 90213-91905 cm-1 are obtained. Experimental peaks are classified and assigned by comparing with the corresponding calculated spectra. More specifically, four ionic autoionization Rydberg series converging to La2+ 5d5/2 2D5/2 and several states converging to higher lying states of La2+ are found and assigned.

  13. Near-ambient X-ray photoemission spectroscopy and kinetic approach to the mechanism of carbon monoxide oxidation over lanthanum substituted cobaltites

    SciTech Connect

    Hueso, J. L.; Martinez-Martinez, D.; Cabalerro, Alfonso; Gonzalez-Elipe, Agustin Rodriguez; Mun, Bongjin Simon; Salmeron, Miquel

    2009-07-31

    We have studied the oxidation of carbon monoxide over a lanthanum substituted perovskite (La0.5Sr0.5CoO3-d) catalyst prepared by spray pyrolysis. Under the assumption of a first-order kinetics mechanism for CO, it has been found that the activation energy barrier of the reaction changes from 80 to 40 kJ mol-1 at a threshold temperature of ca. 320 oC. In situ XPS near-ambient pressure ( 0.2 torr) shows that the gas phase oxygen concentration over the sample decreases sharply at ca. 300 oC. These two observations suggest that the oxidation of CO undergoes a change of mechanism at temperatures higher than 300 oC.

  14. 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.

  15. Lanthanum nickel aluminum alloy

    DOEpatents

    Gruen, Dieter M.; Mendelsohn, Marshall H.; Dwight, Austin E.

    1979-01-01

    A ternary intermetallic compound capable of reversible sorption of hydrogen having the chemical formula LaNi.sub.5-x Al.sub.x, where x is in the range of about 0.01 to 1.5 and the method of storing hydrogen using the intermetallic compound.

  16. Fluoride glass starting materials - Characterization and effects of thermal treatment

    NASA Technical Reports Server (NTRS)

    Chen, William; Dunn, Bruce; Shlichta, Paul; Neilson, George F.; Weinberg, Michael C.

    1987-01-01

    The production of heavy metal fluoride (HMF) glasses, and the effects of thermal treatments on the HMF glasses are investigated. ZrF4, BaF2, AlF3, LaF3, and NaF were utilized in the synthesis of zirconium-barium-lanthanum-aluminum-sodium fluoride glass. The purity of these starting materials, in particular ZrF4, is evaluated using XRD analysis. The data reveal that low temperature heating of ZrF4-H2O is effective in removing the water of hydration, but causes the production of ZrF4 and oxyfluorides; however, dehydration followed by sublimation results in the production of monoclinic ZrFe without water or oxyfluoride contaminants.

  17. Work function determination of promising electrode materials for thermionic converters

    NASA Technical Reports Server (NTRS)

    Jacobson, D.

    1977-01-01

    Work performed on this contract was primarily for the evaluation of selected electrode materials for thermionic energy converters. The original objective was to characterize selected nickel based superalloys up to temperatures of 1400 K. It was found that an early selection, Inconel 800 produced a high vapor pressure which interfered with the vacuum emission measurements. The program then shifted to two other areas. The first area was to obtain emission from the superalloys in a cesiated atmosphere. The cesium plasma helps to suppress the vaporization interference. The second area involved characterization of the Lanthanum-Boron series as thermionic emitters. These final two areas resulted in three journal publications which are attached to this report.

  18. 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.

  19. Ternary lanthanum sulfide selenides {alpha}-LaS{sub 2-x}Se{sub x} (0

    SciTech Connect

    Bartsch, Christian; Doert, Thomas

    2012-01-15

    Mixed lanthanum sulfide selenides LaS{sub 2-x}Se{sub x} (0lanthanum chloride and alkali metal polychalcogenides. The LaS{sub 2-x}Se{sub x} compounds crystallize in space group P2{sub 1}/a, no. 14, and adopt the {alpha}-LnS{sub 2} (Ln=Y, La-Lu) structure type with a pronounced site preference for the chalcogen atoms. The mixed chalcogenides form a complete miscible series with lattice parameters a=820-849 pm, b=413-425 pm and c=822-857 pm ({beta} Almost-Equal-To 90 Degree-Sign) following Vegard's rule. Raman signals indicate the presence of mixed X{sub 2}{sup 2-} dianions, a species rarely evidenced in literature, besides the well known anions S{sub 2}{sup 2-} and Se{sub 2}{sup 2-}. The band gaps of the LaS{sub 2-x}Se{sub x} compounds, determined by optical spectroscopy, decrease nearly linearly with increasing amount of selenium. - Graphical abstract: Raman spectra and site occupancies in the structures of selected lanthanum sulfide selenides. Highlights: Black-Right-Pointing-Pointer Vegard series of mixed lanthanum sulfide selenides LaS{sub 2-x}Se{sub x} (0

  20. [La(UO2)V2O7][(UO2)(VO4)] the first lanthanum uranyl-vanadate with structure built from two types of sheets based upon the uranophane anion-topology

    NASA Astrophysics Data System (ADS)

    Mer, A.; Obbade, S.; Rivenet, M.; Renard, C.; Abraham, F.

    2012-01-01

    The new lanthanum uranyl vanadate divanadate, [La(UO2)V2O7][(UO2)(VO4)] was obtained by reaction at 800 °C between lanthanum chloride, uranium oxide (U3O8) and vanadium oxide (V2O5) and the structure was determined from single-crystal X-ray diffraction data. This compound crystallizes in the orthorhombic system with space group P212121 and unit-cell parameters a=6.9470(2) Å, b=7.0934(2) Å, c=25.7464(6) Å, V=1268.73(5) Å3, Z=4. A full matrix least-squares refinement yielded R1=0.0219 for 5493 independent reflections. The crystal structure is characterized by the stacking of uranophane-type sheets [(UO2)(VO4)]-∞2 and double layers [La(UO2)(V2O7)]+∞2 connected through La-O bonds involving the uranyl oxygen of the uranyl-vanadate sheets. The double layers result from the connection of two [La(UO2)(VO4)2]-∞2 sheets derived from the uranophane anion-topology by replacing half of the uranyl ions by lanthanum atoms and connected through the formation of divanadate entities.

  1. Direct Quantification of Rare Earth Elements Concentrations in Urine of Workers Manufacturing Cerium, Lanthanum Oxide Ultrafine and Nanoparticles by a Developed and Validated ICP-MS.

    PubMed

    Li, Yan; Yu, Hua; Zheng, Siqian; Miao, Yang; Yin, Shi; Li, Peng; Bian, Ying

    2016-03-22

    Rare earth elements (REEs) have undergone a steady spread in several industrial, agriculture and medical applications. With the aim of exploring a sensitive and reliable indicator of estimating exposure level to REEs, a simple, accurate and specific ICP-MS method for simultaneous direct quantification of 15 REEs ((89)Y, (139)La, (140)Ce, (141)Pr, (146)Nd, (147)Sm, (153)Eu, (157)Gd, (159)Tb, (163)Dy, (165)Ho, (166)Er, (169)Tm, (172)Yb and (175)Lu) in human urine has been developed and validated. The method showed good linearity for all REEs in human urine in the concentrations ranging from 0.001-1.000 μg ∙ L(-1) with r² > 0.997. The limits of detection and quantification for this method were in the range of 0.009-0.010 μg ∙ L(-1) and 0.029-0.037 μg ∙ L(-1), the recoveries on spiked samples of the 15 REEs ranged from 93.3% to 103.0% and the relative percentage differences were less than 6.2% in duplicate samples, and the intra- and inter-day variations of the analysis were less than 1.28% and less than 0.85% for all REEs, respectively. The developed method was successfully applied to the determination of 15 REEs in 31 urine samples obtained from the control subjects and the workers engaged in work with manufacturing of ultrafine and nanoparticles containing cerium and lanthanum oxide. The results suggested that only the urinary levels of La (1.234 ± 0.626 μg ∙ L(-1)), Ce (1.492 ± 0.995 μg ∙ L(-1)), Nd (0.014 ± 0.009 μg ∙ L(-1)) and Gd (0.023 ± 0.010 μg ∙ L(-1)) among the exposed workers were significantly higher (p < 0.05) than the levels measured in the control subjects. From these, La and Ce were the primary components, and accounted for 88% of the total REEs. Lanthanum comprised 27% of the total REEs while Ce made up the majority of REE content at 61%. The remaining elements only made up 1% each, with the exception of Dy which was not detected. Comparison with the previously published data, the levels of urinary La and Ce in workers and

  2. Direct Quantification of Rare Earth Elements Concentrations in Urine of Workers Manufacturing Cerium, Lanthanum Oxide Ultrafine and Nanoparticles by a Developed and Validated ICP-MS

    PubMed Central

    Li, Yan; Yu, Hua; Zheng, Siqian; Miao, Yang; Yin, Shi; Li, Peng; Bian, Ying

    2016-01-01

    Rare earth elements (REEs) have undergone a steady spread in several industrial, agriculture and medical applications. With the aim of exploring a sensitive and reliable indicator of estimating exposure level to REEs, a simple, accurate and specific ICP-MS method for simultaneous direct quantification of 15 REEs (89Y, 139La, 140Ce, 141Pr, 146Nd, 147Sm, 153Eu, 157Gd, 159Tb, 163Dy, 165Ho, 166Er, 169Tm, 172Yb and 175Lu) in human urine has been developed and validated. The method showed good linearity for all REEs in human urine in the concentrations ranging from 0.001–1.000 μg∙L−1 with r2 > 0.997. The limits of detection and quantification for this method were in the range of 0.009–0.010 μg∙L−1 and 0.029–0.037 μg∙L−1, the recoveries on spiked samples of the 15 REEs ranged from 93.3% to 103.0% and the relative percentage differences were less than 6.2% in duplicate samples, and the intra- and inter-day variations of the analysis were less than 1.28% and less than 0.85% for all REEs, respectively. The developed method was successfully applied to the determination of 15 REEs in 31 urine samples obtained from the control subjects and the workers engaged in work with manufacturing of ultrafine and nanoparticles containing cerium and lanthanum oxide. The results suggested that only the urinary levels of La (1.234 ± 0.626 μg∙L−1), Ce (1.492 ± 0.995 μg∙L−1), Nd (0.014 ± 0.009 μg∙L−1) and Gd (0.023 ± 0.010 μg∙L−1) among the exposed workers were significantly higher (p < 0.05) than the levels measured in the control subjects. From these, La and Ce were the primary components, and accounted for 88% of the total REEs. Lanthanum comprised 27% of the total REEs while Ce made up the majority of REE content at 61%. The remaining elements only made up 1% each, with the exception of Dy which was not detected. Comparison with the previously published data, the levels of urinary La and Ce in workers and the control subjects show a higher trend

  3. Sustainable materials

    NASA Astrophysics Data System (ADS)

    Allwood, Julian M.

    2016-01-01

    Materials influence every aspect of the energy system; therefore, as well as developing new materials for energy generation, materials scientists should engage in public debate about the limitations of future innovations and the conservation of existing materials.

  4. Evolution of the corrosion process of AA 2024-T3 in an alkaline NaCl solution with sodium dodecylbenzenesulfonate and lanthanum chloride inhibitors

    NASA Astrophysics Data System (ADS)

    Zhou, Biner; Wang, Yishan; Zuo, Yu

    2015-12-01

    The evolution of the corrosion process of AA 2024-T3 in 0.58 g L-1 NaCl solution (pH 10) with sodium dodecylbenzenesulfonate (SDBS) and lanthanum chloride inhibitors was studied with electrochemical and surface analysis methods. With the addition of the compounded LaCl3 and SDBS inhibitors, in the early stage the polarization behavior of AA 2024-T3 changed from active corrosion to passivation, and both the general corrosion and pitting corrosion were inhibited. However, with the immersion time extended, the passive behavior gradually disappeared and pitting happened at the Cu-rich phases. After 24 h immersion, the compounded inhibitors still showed good inhibition for general corrosion, but the polarization curve again presented the characteristic similar to active polarization. The compounded inhibitors also inhibited the pitting corrosion to some extent. The acting mechanism of the inhibitors SDBS and La3Cl on the corrosion process of AA 2024-T3 in the test solution was discussed.

  5. 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.

  6. Biosorption and desorption of lanthanum(III) and neodymium(III) in fixed-bed columns with Sargassum sp.: perspectives for separation of rare earth metals.

    PubMed

    Oliveira, Robson C; Guibal, Eric; Garcia, Oswaldo

    2012-01-01

    Rare earth (RE) metals are essentials for the manufacturing of high-technology products. The separation of RE is complex and expensive; biosorption is an alternative to conventional processes. This work focuses on the biosorption of monocomponent and bicomponent solutions of lanthanum(III) and neodymium(III) in fixed-bed columns using Sargassum sp. biomass. The desorption of metals with HCl 0.10 mol L(-1) from loaded biomass is also carried out with the objective of increasing the efficiency of metal separation. Simple models have been successfully used to model breakthrough curves (i.e., Thomas, Bohart-Adams, and Yoon-Nelson equations) for the biosorption of monocomponent solutions. From biosorption and desorption experiments in both monocomponent and bicomponent solutions, a slight selectivity of the biomass for Nd(III) over La(III) is observed. The experiments did not find an effective separation of the RE studied, but their results indicate a possible partition between the metals, which is the fundamental condition for separation perspectives.

  7. Effects of Sucroferric Oxyhydroxide Compared to Lanthanum Carbonate and Sevelamer Carbonate on Phosphate Homeostasis and Vascular Calcifications in a Rat Model of Chronic Kidney Failure

    PubMed Central

    Phan, Olivier; Maillard, Marc; Malluche, Hartmut H.; Stehle, Jean-Christophe; Funk, Felix; Burnier, Michel

    2015-01-01

    Elevated serum phosphorus, calcium, and fibroblast growth factor 23 (FGF23) levels are associated with cardiovascular disease in chronic renal disease. This study evaluated the effects of sucroferric oxyhydroxide (PA21), a new iron-based phosphate binder, versus lanthanum carbonate (La) and sevelamer carbonate (Se), on serum FGF23, phosphorus, calcium, and intact parathyroid hormone (iPTH) concentrations, and the development of vascular calcification in adenine-induced chronic renal failure (CRF) rats. After induction of CRF, renal function was significantly impaired in all groups: uremic rats developed severe hyperphosphatemia, and serum iPTH increased significantly. All uremic rats (except controls) then received phosphate binders for 4 weeks. Hyperphosphatemia and increased serum iPTH were controlled to a similar extent in all phosphate binder-treatment groups. Only sucroferric oxyhydroxide was associated with significantly decreased FGF23. Vascular calcifications of the thoracic aorta were decreased by all three phosphate binders. Calcifications were better prevented at the superior part of the thoracic and abdominal aorta in the PA21 treated rats. In adenine-induced CRF rats, sucroferric oxyhydroxide was as effective as La and Se in controlling hyperphosphatemia, secondary hyperparathyroidism, and vascular calcifications. The role of FGF23 in calcification remains to be confirmed. PMID:26221597

  8. The preparation of large surface area lanthanum based perovskite supports for AuPt nanoparticles: tuning the glycerol oxidation reaction pathway by switching the perovskite B site

    PubMed Central

    Evans, Christopher D.; Smith, Paul J.; Manning, Troy D.; Miedziak, Peter J.; Brett, Gemma L.; Armstrong, Robert D.; Bartley, Jonathan K.; Taylor, Stuart H.; Rosseinsky, Matthew J.; Hutchings, Graham J.

    2016-01-01

    Gold and gold alloys, in the form of supported nanoparticles, have been shown over the last three decades to be highly effective oxidation catalysts. Mixed metal oxide perovskites, with their high structural tolerance, are ideal for investigating how changes in the chemical composition of supports affect the catalysts' properties, while retaining similar surface areas, morphologies and metal co-ordinations. However, a significant disadvantage of using perovskites as supports is their high crystallinity and small surface area. We report the use of a supercritical carbon dioxide anti-solvent precipitation methodology to prepare large surface area lanthanum based perovskites, making the deposition of 1 wt% AuPt nanoparticles feasible. These catalysts were used for the selective oxidation of glycerol. By changing the elemental composition of the perovskite B site, we dramatically altered the reaction pathway between a sequential oxidation route to glyceric or tartronic acid and a dehydration reaction pathway to lactic acid. Selectivity profiles were correlated to reported oxygen adsorption capacities of the perovskite supports and also to changes in the AuPt nanoparticle morphologies. Extended time on line analysis using the best oxidation catalyst (AuPt/LaMnO3) produced an exceptionally high tartronic acid yield. LaMnO3 produced from alternative preparation methods was found to have lower activities, but gave comparable selectivity profiles to that produced using the supercritical carbon dioxide anti-solvent precipitation methodology. PMID:27074316

  9. 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.

  10. Effects of Sucroferric Oxyhydroxide Compared to Lanthanum Carbonate and Sevelamer Carbonate on Phosphate Homeostasis and Vascular Calcifications in a Rat Model of Chronic Kidney Failure.

    PubMed

    Phan, Olivier; Maillard, Marc; Malluche, Hartmut H; Stehle, Jean-Christophe; Funk, Felix; Burnier, Michel

    2015-01-01

    Elevated serum phosphorus, calcium, and fibroblast growth factor 23 (FGF23) levels are associated with cardiovascular disease in chronic renal disease. This study evaluated the effects of sucroferric oxyhydroxide (PA21), a new iron-based phosphate binder, versus lanthanum carbonate (La) and sevelamer carbonate (Se), on serum FGF23, phosphorus, calcium, and intact parathyroid hormone (iPTH) concentrations, and the development of vascular calcification in adenine-induced chronic renal failure (CRF) rats. After induction of CRF, renal function was significantly impaired in all groups: uremic rats developed severe hyperphosphatemia, and serum iPTH increased significantly. All uremic rats (except controls) then received phosphate binders for 4 weeks. Hyperphosphatemia and increased serum iPTH were controlled to a similar extent in all phosphate binder-treatment groups. Only sucroferric oxyhydroxide was associated with significantly decreased FGF23. Vascular calcifications of the thoracic aorta were decreased by all three phosphate binders. Calcifications were better prevented at the superior part of the thoracic and abdominal aorta in the PA21 treated rats. In adenine-induced CRF rats, sucroferric oxyhydroxide was as effective as La and Se in controlling hyperphosphatemia, secondary hyperparathyroidism, and vascular calcifications. The role of FGF23 in calcification remains to be confirmed.

  11. The preparation of large surface area lanthanum based perovskite supports for AuPt nanoparticles: tuning the glycerol oxidation reaction pathway by switching the perovskite B site.

    PubMed

    Evans, Christopher D; Kondrat, Simon A; Smith, Paul J; Manning, Troy D; Miedziak, Peter J; Brett, Gemma L; Armstrong, Robert D; Bartley, Jonathan K; Taylor, Stuart H; Rosseinsky, Matthew J; Hutchings, Graham J

    2016-07-01

    Gold and gold alloys, in the form of supported nanoparticles, have been shown over the last three decades to be highly effective oxidation catalysts. Mixed metal oxide perovskites, with their high structural tolerance, are ideal for investigating how changes in the chemical composition of supports affect the catalysts' properties, while retaining similar surface areas, morphologies and metal co-ordinations. However, a significant disadvantage of using perovskites as supports is their high crystallinity and small surface area. We report the use of a supercritical carbon dioxide anti-solvent precipitation methodology to prepare large surface area lanthanum based perovskites, making the deposition of 1 wt% AuPt nanoparticles feasible. These catalysts were used for the selective oxidation of glycerol. By changing the elemental composition of the perovskite B site, we dramatically altered the reaction pathway between a sequential oxidation route to glyceric or tartronic acid and a dehydration reaction pathway to lactic acid. Selectivity profiles were correlated to reported oxygen adsorption capacities of the perovskite supports and also to changes in the AuPt nanoparticle morphologies. Extended time on line analysis using the best oxidation catalyst (AuPt/LaMnO3) produced an exceptionally high tartronic acid yield. LaMnO3 produced from alternative preparation methods was found to have lower activities, but gave comparable selectivity profiles to that produced using the supercritical carbon dioxide anti-solvent precipitation methodology. PMID:27074316

  12. 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)

  13. 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.

  14. Production and EPR characterization of exohedrally perfluoroalkylated paramagnetic lanthanum metallofullerenes: (La@C 82)-(C 8F 17) 2

    NASA Astrophysics Data System (ADS)

    Tagmatarchis, Nikos; Taninaka, Atsushi; Shinohara, Hisanori

    2002-04-01

    A strategy to chemically derivatize the outer sphere of endohedral metallofullerenes by using a fluorous synthesis-partitioning approach has been developed. The newly synthesized materials were found to be paramagnetic species and were characterized by electron paramagnetic resonance spectroscopy (EPR), laser desorption time-of-flight spectrometry (LD-TOF) and electronic absorption spectroscopy (UV-VIS-NIR). The fluorous-phase partitioning method (or liquid-liquid extraction), successfully applied for the first time in fullerene chemistry, aided by multi-stage recycling high performance liquid chromatography (HPLC) resulted in their isolation in isomer-free form. The present study opens the way to organic transformations of fullerene-based materials as a powerful separation technique.

  15. 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.

  16. 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

  17. 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

  18. 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

  19. Assessing soil erosion at landscape level: A step forward in the up-scaling of 137Cs measurements through the use of in-situ lanthanum bromide scintillator

    NASA Astrophysics Data System (ADS)

    Gonsalves, Basil C.; Darby, Iain G.; Toloza, Arsenio; Mabit, Lionel; Kaiser, Ralf B.; Dercon, Gerd

    2014-05-01

    Measuring Fallout Radionuclides (FRN), in particular 137Cs, is a well-established method to estimate soil erosion and deposition in agricultural landscapes. While extremely sensitive, laboratory based gamma-ray spectrometry requires careful handling and preparation of measurement samples with a lengthy measuring time (~1 day), In-situ gamma-ray spectrometry can give near instantaneous results, allowing prompt decisions to be made and identification of critical spots of soil erosion, while the equipment is in the field. The aim of this investigation was to compare the precision of the in-situ FRN measurements, made by a cost-effective lanthanum bromide (LaBr3 (Ce)) scintillation detector of 137Cs against those from conventional (high-purity germanium HPGe detector) but laborious laboratory based gamma-ray spectrometry for assessing soil erosion. As preliminary test, five cores of a gleyic Cambisol - per increments of 5 cm until 1 m depth - were collected at the experimental research station of the Austrian Agency for Health and Food Safety located in Grabenegg 130 km west of Vienna. Three soil cores were sampled at the study site and, in the vicinity of this experimental site, two additional cores were collected at two different undisturbed reference sites. Laboratory gamma analyses were carried out during 50 000 seconds using a HPGe coaxial detector. The gamma measurements performed at the laboratory confirmed the undisturbed status of the two selected reference sites (i.e. exponential decrease with depth of the 137Cs content). Using the surface area of the sampling tool, the 137Cs areal activities of the cores sampled in the study site have been established at 2134±465 Bq m-2, 1835±356 Bq m-2 and 2553±340 Bq m-2, and, for the two reference sites at 3221±444 Bq m-2 and 3946±527 Bq m-2. At the same location and prior to collect the five soil cores, in-situ measurements using a lanthanum bromide (LaBr3 (Ce)) scintillator were performed. The detector was placed

  20. Angle-resolved photoemission spectroscopy of strontium lanthanum copper oxide thin films grown by molecular-beam epitaxy

    NASA Astrophysics Data System (ADS)

    Harter, John Wallace

    Among the multitude of known cuprate material families and associated structures, the archetype is "infinite-layer" ACuO2, where perfectly square and flat CuO2 planes are separated by layers of alkaline earth atoms. The infinite-layer structure is free of magnetic rare earth ions, oxygen chains, orthorhombic distortions, incommensurate superstructures, ordered vacancies, and other complications that abound among the other material families. Furthermore, it is the only cuprate that can be made superconducting by both electron and hole doping, making it a potential platform for decoding the complex many-body interactions responsible for high-temperature superconductivity. Research on the infinite-layer compound has been severely hindered by the inability to synthesize bulk single crystals, but recent progress has led to high-quality superconducting thin film samples. Here we report in situ angle-resolved photoemission spectroscopy measurements of epitaxially-stabilized Sr1-chiLa chiCuO2 thin films grown by molecular-beam epitaxy. At low doping, the material exhibits a dispersive lower Hubbard band typical of other cuprate parent compounds. As carriers are added to the system, a continuous evolution from Mott insulator to superconducting metal is observed as a coherent low-energy band develops on top of a concomitant remnant lower Hubbard band, gradually filling in the Mott gap. For chi = 0.10, our results reveal a strong coupling between electrons and (pi,pi) anti-ferromagnetism, inducing a Fermi surface reconstruction that pushes the nodal states below the Fermi level and realizing nodeless superconductivity. Electron diffraction measurements indicate the presence of a surface reconstruction that is consistent with the polar nature of Sr1-chiLachiCuO2. Most knowledge about the electron-doped side of the cuprate phase diagram has been deduced by generalizing from a single material family, Re2-chi CechiCuO4, where robust antiferromagnetism has been observed past chi

  1. Weird materials

    NASA Astrophysics Data System (ADS)

    Astin, Christina; Talbot, Diane; Goodhew, Peter

    2002-11-01

    Heat a material and it gets hotter; heat it enough and it will melt. But some materials will behave rather unexpectedly when heated, and others can act strangely when deformed. Here, three types of weird materials are described - shape memory alloys, Silly Putty® and thermochromic materials - and examples are given of their uses in manufacturing and in the classroom.

  2. Understanding Materials

    ERIC Educational Resources Information Center

    Katsioloudis, Petros J.

    2010-01-01

    Almost everything people have ever done has involved materials. Historical evidence indicates that "engineered materials" have been available and utilized for the benefit of humankind since the Neolithic period, beginning about 10,000 BC. Some of these materials have been in existence for thousands of years. At first, materials consisted of wood,…

  3. Restoration of parathyroid function after change of phosphate binder from calcium carbonate to lanthanum carbonate in hemodialysis patients with suppressed serum parathyroid hormone.

    PubMed

    Inaba, Masaaki; Okuno, Senji; Nagayama, Harumi; Yamada, Shinsuke; Ishimura, Eiji; Imanishi, Yasuo; Shoji, Shigeichi

    2015-03-01

    Control of phosphate is the most critical in the treatment of chronic kidney disease with mineral and bone disorder (CKD-MBD). Because calcium-containing phosphate binder to CKD patients is known to induce adynamic bone disease with ectopic calcification by increasing calcium load, we examined the effect of lanthanum carbonate (LaC), a non-calcium containing phosphate binder, to restore bone turnover in 27 hemodialysis patients with suppressed parathyroid function (serum intact parathyroid hormone [iPTH] ≦ 150 pg/mL). At the initiation of LaC administration, the dose of calcium-containing phosphate binder calcium carbonate (CaC) was withdrawn or reduced based on serum phosphate. After initiation of LaC administration, serum calcium and phosphate decreased significantly by 4 weeks, whereas whole PTH and iPTH increased. A significant and positive correlation between decreases of serum calcium, but not phosphate, with increases of whole PTH and iPTH, suggested that the decline in serum calcium with reduction of calcium load by LaC might increase parathyroid function. Serum bone resorption markers, such as serum tartrate-resistant acid phosphatase 5b, and N-telopeptide of type I collagen increased significantly by 4 weeks after LaC administration, which was followed by increases of serum bone formation markers including serum bone alkaline phosphatase, intact procollagen N-propeptide, and osteocalcin. Therefore, it was suggested that LaC attenuated CaC-induced suppression of parathyroid function and bone turnover by decreasing calcium load. In conclusion, replacement of CaC with LaC, either partially or totally, could increase parathyroid function and resultant bone turnover in hemodialysis patients with serum iPTH ≦ 150 pg/mL.

  4. Colossal thermoelectric power in charge ordered lanthanum calcium manganites (La{sub 0.5}Ca{sub 0.5}MnO{sub 3})

    SciTech Connect

    Joy, Lija K.; Anantharaman, M. R.; Shanmukharao Samatham, S.; Ganesan, V.; Thomas, Senoy; Al-Harthi, Salim; Liebig, A.; Albrecht, M.

    2014-12-07

    Lanthanum calcium manganites (La{sub 0.5}Ca{sub 0.5}MnO{sub 3}) with a composition close to charge ordering, synthesized by high energy ball milling, was found to exhibit colossal thermoelectric power. Thermoelectric power (TEP) data was systematically analyzed by dividing the entire temperature range (5 K–300 K) into three different regimes to explore different scattering mechanisms involved. Mandal's model has been applied to explain TEP data in the region below the Curie temperature (T{sub C}). It has been found that the variation of thermoelectric power with temperature is pronounced when the system enters the charge ordered region at T < 200 K. For temperatures lower than 120 K, due to the co-existence of charge ordered state with a spin-glass state, the variation of thermoelectric power is maximum and exhibited a peak value of −80 mV/K at 58 K. This has been explained by incorporating Kondo properties of the spin-glass along with magnon scattering. FC-ZFC magnetization measurements indicate the existence of a glassy state in the region corresponding to a maximum value of thermoelectric power. Phonon drag contribution instead of spin-glass contribution is taken into account to explain TEP in the region 120 K < T < T{sub C}. Mott's polaronic contribution of charge carriers are considered to interpret TEP in the high temperature region (T > T{sub C}). The optimal Mn{sup 4+}-Mn{sup 3+} concentration in charge ordered La{sub 0.5}Ca{sub 0.5}MnO{sub 3} was examined by X-ray Photoelectron Spectroscopy analysis which confirms the charge ordered nature of this compound.

  5. 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.

  6. Synthesis, crystal and electronic structure, and physical properties of the new lanthanum copper telluride La{sub 3}Cu{sub 5}Te{sub 7}

    SciTech Connect

    Zelinska, Mariya; Assoud, Abdeljalil; Kleinke, Holger

    2011-03-15

    The new lanthanum copper telluride La{sub 3}Cu{sub 5-x}Te{sub 7} has been obtained by annealing the elements at 1073 K. Single-crystal X-ray diffraction studies revealed that the title compound crystallizes in a new structure type, space group Pnma (no. 62) with lattice dimensions of a=8.2326(3) A, b=25.9466(9) A, c=7.3402(3) A, V=1567.9(1) A{sup 3}, Z=4 for La{sub 3}Cu{sub 4.86(4)}Te{sub 7}. The structure of La{sub 3}Cu{sub 5-x}Te{sub 7} is remarkably complex. The Cu and Te atoms build up a three-dimensional covalent network. The coordination polyhedra include trigonal LaTe{sub 6} prisms, capped trigonal LaTe{sub 7} prisms, CuTe{sub 4} tetrahedra, and CuTe{sub 3} pyramids. All Cu sites exhibit deficiencies of various extents. Electrical property measurements on a sintered pellet of La{sub 3}Cu{sub 4.86}Te{sub 7} indicate that it is a p-type semiconductor in accordance with the electronic structure calculations. -- Graphical abstract: Oligomeric unit comprising interconnected CuTe{sub 3} pyramids and CuTe{sub 4} tetrahedra. Display Omitted Research highlights: {yields} La{sub 3}Cu{sub 5-x}Te{sub 7} adopts a new structure type. {yields} All Cu sites exhibit deficiencies of various extents. {yields} The coordination polyhedra include trigonal LaTe{sub 6} prisms, capped trigonal LaTe{sub 7} prisms, CuTe{sub 4} tetrahedra and CuTe{sub 3} pyramids. {yields} La{sub 3}Cu{sub 5-x}Te{sub 7} is a p-type semiconductor.

  7. Comparison of the effects of lanthanum, cerium and praseodymium on rumen fermentation, nutrient digestion and plasma biochemical parameters in beef cattle.

    PubMed

    Lin, Shixin; Wei, Chen; Zhao, Guangyong; Zhang, Tingting; Yang, Kai

    2015-01-01

    The objectives of the trial were to compare the effects of supplementing rare earth elements (REE) lanthanum (La), cerium (Ce) and praseodymium (Pr) on rumen fermentation, nutrient digestion, methane (CH4) production, nitrogen (N) balance and plasma biochemical parameters in beef cattle. Four Simmental male cattle, aged 12 months, with initial average liveweight of 333 ± 9 kg and fitted with rumen cannulas, were fed with a basal ration composed of concentrate mixture and maize silage. Animals received a basal ration without adding REE (Control) or three treatments, i.e. supplementing LaCl3, CeCl3 or PrCl3 at 204 mg/kg DM to the basal ration, respectively, which were allocated in a 4 × 4 Latin square design. Each experimental period lasted 15 d, consisting of 12 d for pre-treatment and three subsequent days for sampling. Results showed that all tested levels of REE tended to increase neutral detergent fibre digestibility (p = 0.064) and tended to decrease rumen CH4 production (p = 0.056). Supplementing LaCl3 and CeCl3 decreased total N excretion and urinary N excretion, increased N retention (p < 0.05), tended to increase total urinary purine derivatives (PD) (p = 0.053) and microbial N flow (p = 0.095), whereas supplementing PrCl3 did not affect N retention, urinary PD and microbial N flow. No differences were found in the effects of nutrient digestibility, CH4 production and plasma biochemical parameters among LaCl3, CeCl3 and PrCl3. Further trials using graded levels of LaCl3, CeCl3 and PrCl3 in a wide range are needed to obtain more pronounced results for comparing effects of La, Ce and Pr on rumen fermentation and nutrient digestion in beef cattle.

  8. Thermodynamic study of orthorhombic T{sup x} and tetragonal T′ lanthanum cuprate, La{sub 2}CuO{sub 4}

    SciTech Connect

    Lilova, K.I.; Hord, R.; Alff, L.; Albert, B.; Navrotsky, A.

    2013-08-15

    The enthalpies of transition among the T{sup x}, T′, and T–La{sub 2}CuO{sub 4} phases are obtained from a combination of differential scanning calorimetry, high temperature oxide melt solution calorimetry, and transposed temperature drop calorimetry. The enthalpy of transformation of T{sup x} to T is 2.32±0.07 kJ/mol and the corresponding entropy of transition is 4.38±0.13 J/(mol K). The T′ modification, with an average of 1.40 kJ/mol, is less stable in enthalpy than T{sup x} but at 0.96 kJ/mol, more stable in enthalpy than T. Although we cannot rule out a small stability field at temperatures near the T{sup x}–T transition at 530 K, T′ is most likely metastable at all temperatures. - Graphical abstract: Crystal structure of T{sup x} (orthorhombic), T′ and T (tetragonal) modifications of La{sub 2}CuO{sub 4} (left to right). The space group for orthorhombic T{sup x} is Cmce and I4/mmm for both T′ and T structures; copper cations are presented as small purple, lanthanum as large blue and oxygen as large green circles. Highlights: • The enthalpies of transition among the T{sup x} , T′, and T-La{sub 2}CuO{sub 4} phases are obtained. • The T{sup x} phase is the lowest in energy, the T′ higher and the T highest. • T′ phase is metastable at all temperatures.

  9. Lanthanum Chloride Attenuates Osteoclast Formation and Function Via the Downregulation of Rankl-Induced Nf-κb and Nfatc1 Activities.

    PubMed

    Jiang, Chuan; Shang, Jiangyinzi; Li, Zhe; Qin, An; Ouyang, Zhengxiao; Qu, Xinhua; Li, Haowei; Tian, Bo; Wang, Wengang; Wu, Chuanlong; Wang, Jinwu; Dai, Min

    2016-01-01

    The biological activities of lanthanum chloride (LaCl3 ) and the molecular mechanisms of action underlying its anti-inflammatory, anti-hyperphosphatemic, and osteoblast-enhancing effects have been studied previously, but less is known about the effects of LaCl3 on osteoclasts. The present study used in vivo and in vitro approaches to explore the effects of LaCl3 on osteoclasts and osteolysis. The results indicated that LaCl3 concentrations that were non-cytotoxic to mouse bone marrow-derived monocytes attenuated receptor activator of nuclear factor-κB ligand (RANKL)-stimulated osteoclastogenesis, bone resorption, mRNA expression of osteoclastogenic genes in these cells, including cathepsin K, calcitonin receptor, and tartrate-resistant acid phosphatase (TRAP). Further, LaCl3 inhibited RANKL-mediated activation of the nuclear factor-κB (NF-κB) signaling pathway, and downregulated mRNA and protein levels of nuclear factor of activated T-cells, cytoplasmic, calcineurin-dependent 1 (NFATc1), and c-fos. In vivo, LaCl3 attenuated titanium (Ti) particle-induced bone loss in a murine calvarial osteolysis model. Histological analyses revealed that LaCl3 ameliorated bone destruction and decreased the number of TRAP-positive osteoclasts in this model. These results demonstrated that LaCl3 inhibited osteoclast formation, function, and osteoclast-specific gene expression in vitro, and attenuated Ti particle-induced mouse calvarial osteolysis in vivo, where the inhibition of NF-κB signaling and downregulation of NFATc1 and c-fos played an important role.

  10. Comparison of the effects of lanthanum, cerium and praseodymium on rumen fermentation, nutrient digestion and plasma biochemical parameters in beef cattle.

    PubMed

    Lin, Shixin; Wei, Chen; Zhao, Guangyong; Zhang, Tingting; Yang, Kai

    2015-01-01

    The objectives of the trial were to compare the effects of supplementing rare earth elements (REE) lanthanum (La), cerium (Ce) and praseodymium (Pr) on rumen fermentation, nutrient digestion, methane (CH4) production, nitrogen (N) balance and plasma biochemical parameters in beef cattle. Four Simmental male cattle, aged 12 months, with initial average liveweight of 333 ± 9 kg and fitted with rumen cannulas, were fed with a basal ration composed of concentrate mixture and maize silage. Animals received a basal ration without adding REE (Control) or three treatments, i.e. supplementing LaCl3, CeCl3 or PrCl3 at 204 mg/kg DM to the basal ration, respectively, which were allocated in a 4 × 4 Latin square design. Each experimental period lasted 15 d, consisting of 12 d for pre-treatment and three subsequent days for sampling. Results showed that all tested levels of REE tended to increase neutral detergent fibre digestibility (p = 0.064) and tended to decrease rumen CH4 production (p = 0.056). Supplementing LaCl3 and CeCl3 decreased total N excretion and urinary N excretion, increased N retention (p < 0.05), tended to increase total urinary purine derivatives (PD) (p = 0.053) and microbial N flow (p = 0.095), whereas supplementing PrCl3 did not affect N retention, urinary PD and microbial N flow. No differences were found in the effects of nutrient digestibility, CH4 production and plasma biochemical parameters among LaCl3, CeCl3 and PrCl3. Further trials using graded levels of LaCl3, CeCl3 and PrCl3 in a wide range are needed to obtain more pronounced results for comparing effects of La, Ce and Pr on rumen fermentation and nutrient digestion in beef cattle. PMID:25575216

  11. 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

  12. 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

  13. Preparation and Characterization of Grain Size Controlled LaB6 Polycrystalline Cathode Material

    NASA Astrophysics Data System (ADS)

    Bao, Li-Hong; Zhang, Jiu-Xing; Zhou, Shen-Lin; Wei, Yong-Feng

    2010-10-01

    The grain size controlled bulk Lanthanum hexaboride (LaBe) cathode material was prepared by using the spark plasma sintering method in an oxygen free system. The starting precursor nanopowders with average grain size of 50 nm were prepared by high-energy ball milling. The nanopowder was fully densified at 1300° C, which is about 350° C lower than the sintering temperature of the coarse powders. The thermionic emission current density was measured to be 42.0 A/cm2, which is much higher than 24.2 A/cm2 of coarse powders and Vickers hardness to be 1860 kg/mm2, which is also higher than 1700 kg/mm2 of coarse one. These results indicate that refining the powder grain size to nano level was beneficial for reducing the sintering temperature and promoting the thermionic emission and mechanic properties.

  14. High-temperature electrical testing of a solid oxide fuel cell cathode contact material

    SciTech Connect

    Weil, K. Scott

    2004-06-01

    The development of high temperature solid state devices for energy generation and environmental control applications has advanced remarkably over the past decade. However, there remain a number technical barriers that still impede widespread commercial application. One of these, for example, is the development of a robust method of conductively joining the mixed-conducting oxide electrodes that lie at the heart of the device to the heat resistant metal interconnect used to transmit power to or from the electrodes and electrochemically active membrane. In the present study, we have investigated the high-temperature electrical and microstructural characteristics of a series of conductive glass composite paste junctions between two contact materials representative of those employed in solid-state electrochemical devices, lanthanum calcium manganate and 430 stainless steel.

  15. High-temperature electrical testing of a solid oxide fuel cell cathode contact material

    NASA Astrophysics Data System (ADS)

    Weil, K. Scott

    2004-06-01

    The development of high-temperature solid-state devices for energy generation and environmental control applications has advanced remarkably over the past decade. However, there remain a number of technical barriers that still impede widespread commercial application. One of these, for example, is the development of a robust method of conductively joining the mixed-conducting oxide electrodes that lie at the heart of the device to the heat resistant metal interconnect used to transmit power to or from the electrodes and electrochemically active membrane. This study investigated the high-temperature electrical and microstructural characteristics of a series of conductive glass composite paste junctions between two contact materials representative of those used in solid-state electrochemical devices, lanthanum calcium manganate, and 430 stainless steel.

  16. Material selection

    SciTech Connect

    Tucker, W.G.

    1990-08-01

    The paper summarizes various criteria that can be used in selecting material used in the construction, furnishing, maintenance, and operation of a building. It also summarizes the types of material and product testing that can be especially useful in the selection process. In broad terms, materials in buildings are classified as building materials, furnishings, maintenance materials, and other contents. At any given time, emissions from materials and products in any of these four categories can dominate the impact on indoor air quality (IAQ) in a building. Responsibility for the selection of these materials may be that of the designer, owner, or occupants. Information on IAQ impacts of materials therefore needs to be developed for a wide range of people.

  17. Hazardous materials

    MedlinePlus

    ... people how to work with hazardous materials and waste. There are many different kinds of hazardous materials, including: Chemicals, like some that are used for cleaning Drugs, like chemotherapy to treat cancer Radioactive material that is used for x-rays or ...

  18. A comparison of the long-term effects of lanthanum carbonate and calcium carbonate on the course of chronic renal failure in rats with adriamycin-induced nephropathy.

    PubMed

    Takashima, Tsuyoshi; Sanai, Toru; Miyazono, Motoaki; Fukuda, Makoto; Kishi, Tomoya; Nonaka, Yasunori; Yoshizaki, Mai; Sato, Sae; Ikeda, Yuji

    2014-01-01

    Lanthanum carbonate (LA) is an effective phosphate binder. Previous study showed the phosphate-binding potency of LA was twice that of calcium carbonate (CA). No study in which LA and CA were given at an equivalent phosphate-binding potency to rats or humans with chronic renal failure for a long period has been reported to date. The objective of this study was to compare the phosphate level in serum and urine and suppression of renal deterioration during long-term LA and CA treatment when they were given at an equivalent phosphate-binding potency in rats with adriamycin (ADR)-induced nephropathy. Rats were divided into three groups: an untreated group (ADR group), a CA-treated (ADR-CA) group and a LA-treated (ADR-LA) group. The daily oral dose of LA was 1.0 g/kg/day and CA was 2.0 g/kg/day for 24 weeks. The serum phosphate was lower in the ADR-CA or ADR-LA group than in the ADR group and significantly lower in the ADR-CA group than in the ADR group at each point, but there were no significant differences between the ADR and ADR-LA groups. The serum phosphate was also lower in the ADR-CA group than in the ADR-LA group, and there was significant difference at week 8. The urinary phosphate was significantly lower in the ADR-CA group than in the ADR or ADR-LA group at each point. The urinary phosphate was also lower in the ADR-LA group than in the ADR group at each point, and significant difference at week 8. There were no significant differences in the serum creatinine or blood urea nitrogen among the three groups. In conclusion, this study indicated the phosphate-binding potency of LA isn't twice as strong as CA, and neither LA nor CA suppressed the progression of chronic renal failure in the serum creatinine and blood urea nitrogen, compared to the untreated group.

  19. Comparative Study of f-Element Electronic Structure across a Series of Multimetallic Actinide, Lanthanide-Actinide and Lanthanum-Actinide Complexes Possessing Redox-Active Bridging Ligands

    SciTech Connect

    Schelter, Eric J.; Wu, Ruilian; Veauthier, Jacqueline M.; Bauer, Eric D.; Booth, Corwin H.; Thomson, Robert K.; Graves, Christopher R.; John, Kevin D.; Scott, Brian L.; Thompson, Joe D.; Morris, David E.; Kiplinger, Jaqueline L.

    2010-02-24

    A comparative examination of the electronic interactions across a series of trimetallic actinide and mixed lanthanide-actinide and lanthanum-actinide complexes is presented. Using reduced, radical terpyridyl ligands as conduits in a bridging framework to promote intramolecular metal-metal communication, studies containing structural, electrochemical, and X-ray absorption spectroscopy are presented for (C{sub 5}Me{sub 5}){sub 2}An[-N=C(Bn)(tpy-M{l_brace}C{sub 5}Me4R{r_brace}{sub 2})]{sub 2} (where An = Th{sup IV}, U{sup IV}; Bn = CH{sub 2}C{sub 6}H{sub 5}; M = La{sup III}, Sm{sup III}, Yb{sup III}, U{sup III}; R = H, Me, Et) to reveal effects dependent on the identities of the metal ions and R-groups. The electrochemical results show differences in redox energetics at the peripheral 'M' site between complexes and significant wave splitting of the metal- and ligand-based processes indicating substantial electronic interactions between multiple redox sites across the actinide-containing bridge. Most striking is the appearance of strong electronic coupling for the trimetallic Yb{sup III}-U{sup IV}-Yb{sup III}, Sm{sup III}-U{sup IV}-Sm{sup III}, and La{sup III}-U{sup IV}-La{sup III} complexes, [8]{sup -}, [9b]{sup -} and [10b]{sup -}, respectively, whose calculated comproportionation constant K{sub c} is slightly larger than that reported for the benchmark Creutz-Taube ion. X-ray absorption studies for monometallic metallocene complexes of U{sup III}, U{sup IV}, and U{sup V} reveal small but detectable energy differences in the 'white-line' feature of the uranium L{sub III}-edges consistent with these variations in nominal oxidation state. The sum of this data provides evidence of 5f/6d-orbital participation in bonding and electronic delocalization in these multimetallic f-element complexes. An improved, high-yielding synthesis of 4{prime}-cyano-2,2{prime}:6{prime},2{double_prime}-terpyridine is also reported.

  20. Efficacy and safety of lanthanum carbonate on chronic kidney disease–mineral and bone disorder in dialysis patients: a systematic review

    PubMed Central

    2013-01-01

    Background Chronic kidney disease–mineral and bone disorder (CKD–MBD) is a common complication in CKD patients, particularly in those with end-stage renal disease that requires dialysis. Lanthanum carbonate (LC) is a potent, non-aluminum, non-calcium phosphate binder. This systematic review evaluates the efficacy and safety of LC in CKD-MBD treatment for maintenance-dialysis patients. Methods A systematic review and meta-analysis on randomized controlled trials (RCTs) and quasi-RCTs was performed to assess the efficacy and safety of LC in maintenance hemodialysis or peritoneal dialysis patients. Analysis was performed using the statistical software Review Manager 5.1. Results Sixteen RCTs involving 3789 patients were identified and retained for this review. No statistical difference was found in all-cause mortality. The limited number of trials was insufficient to show the superiority of LC over other treatments in lowering vascular calcification or cardiovascular events and in improving bone morphology, bone metabolism, or bone turn-over parameters. LC decreased the serum phosphorus level and calcium × phosphate product (Ca × P) as compared to placebo. LC, calcium carbonate (CC), and sevelamer hydrochloride (SH) were comparable in terms of controlling the serum phosphorus, Ca × P product, and intact parathyroid hormone (iPTH) levels. However, LC resulted in a lower serum calcium level and a higher bone-specific alkaline phosphatase level compared with CC. LC had higher total cholesterol and low-density lipoprotein (LDL) cholesterol levels compared with SH. LC-treated patients appeared to have a higher rate of vomiting and lower risk of hypercalcemia, diarrhea, intradialytic hypotension, cramps or myalgia, and abdominal pain. Meta-analysis showed no significant difference in the incidence of other side effects. Accumulation of LC in blood and bone was below toxic levels. Conclusions LC has high efficacy in lowering serum phosphorus and iPTH levels without