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Sample records for lanthanum chromites-based materials

  1. Stabilized lanthanum sulphur compounds. [thermoelectric materials

    NASA Technical Reports Server (NTRS)

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

    1983-01-01

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

  2. Cost Reduction of Lanthanum Chromite Materials

    SciTech Connect

    Simner, Steve P. ); Stevenson, Jeffry W. ); Hardy, John S. ); Chick, Lawrence A. )

    2000-01-01

    Acceptor doped lanthanum chromite (LaCrO3) has long been the interconnect material of choice for high temperature SOFCs, typically operating at 1000?C. However, lanthanum chromite is relatively expensive, and many developers are currently pursuing SOFCs operating at lower temperatures. As the operating temperature is lowered, metal interconnects (e.g., ferritic steels or chromium alloys) become increasingly viable, but they have their own unique problems (including Cr-oxide formation and Cr volatilization), and it is therefore likely that uncoated metals cannot be used at temperatures greater than 700?C. For intermediate operating temperatures (700-800?C), the application of protective oxide coatings may allow the use of metal interconnects (if such coatings can be applied cost-effectively), but lanthanum chromite may offer better long-term performance. While the electrical conductivity of lanthanum chromite does decrease as temperature decreases, the conductivity at 800?C is only about 10% less than the conductivity at 1000?C. In this study, the authors have investigated the viability of replacing pure La in the acceptor doped LaCrO3 with a less expensive mixed lanthanide (Ln) precursor containing La3+ as the principle cation, but also Ce4+, Nd3+ and Pr3+ in significant proportions. Typical compositions investigated were of the formula Ln0.85Sr0.15Cr1-yMyO3, where 0.02?y?0.1 and M= Co, Cu, Ni, and V. Samples were studied with respect to sinterability in air, thermal expansion, conductivity in air and at low pO2, phase stability, and dilation under reducing atmospheres.

  3. Lanthanum

    MedlinePlus

    Lanthanum is used to reduce blood levels of phosphate in patients with kidney disease. High levels of phosphate in the blood can cause bone problems. Lanthanum is in a class of medications called phosphate ...

  4. 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.

  5. 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.

  6. 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

  7. Lanthanum sulfides as high temperature thermoelectric materials

    NASA Technical Reports Server (NTRS)

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

    1984-01-01

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

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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

  13. Stabilized Lanthanum Sulphur Compounds

    NASA Technical Reports Server (NTRS)

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

    1985-01-01

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

  14. 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.

  15. 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

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

    SciTech Connect

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

    2014-11-30

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

  17. [Study on preparation of lanthanum-doped TiO2 nanometer thin film materials and its photocatalytic activity].

    PubMed

    Zheng, Huai-li; Tang, Ming-fang; Gong, Ying-kun; Deng, Xiao-jun; Wu, Bang-hua

    2003-04-01

    In this paper, lanthanum-doped TiO2 nanometer film materials coated on glass were prepared in Ti(OBu)4 precursor solutions by sol-gel processing. Transmittance and photocatalytic activity were respectively investigated and tested for these nanometer thin films prepared with different amount of lanthanum (La), different amount of polyethylene glycol (PEG), and different coating layer times. Some reactive mechanisms were also discussed. For one layer La-addition had little effect on the film transmissivity; but the photocatalytic activity was significantly improved due to La-addition. With increasing PEG, the transmittance of the film decreased for one layer film; but its photocatalytic activity did not rise. Increasing layer number did not affect the transmissivity of multilayer film. After coating two times, increasing layer number did not significantly improve the photocatalytic activity. The highest photocatalytic activity and best transmissivity were obtained for two layer TiO2 film when the dosage of lanthanum was 0.5 g and the dosage of polyethylene was 0.2 g in the precursor solutions. These materials will probably be used in the protection of environment, waste water treatment, and air purification. PMID:12961861

  18. 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.

  19. Fabrication of Sr- and Co-doped lanthanum chromite interconnectors for SOFC

    SciTech Connect

    Setz, L.F.G.; Colomer, M.T.; Mello-Castanho, S.R.H.

    2011-07-15

    Graphical abstract: FESEM micrographs of the fresh fracture surfaces for the La{sub 0.80}Sr{sub 0.20}Cr{sub 0.92}Co{sub 0.08}O{sub 3} sintered specimens cast from optimised suspensions with 13.5, 15 and 17.5 vol.% solids loading. Aqueous suspensions were prepared using ammonium polyacrylate (PAA) as dispersant and tetramethylammonium hydroxide (TMAH) to assure a basic pH and providing stabilization. Sintering of the green discs was performed in air at 1600 {sup o}C for 4 h. Highlights: {yields} Optimum casting slips were achieved with 3 wt.% of ammonium polyacrylate and 1 wt.% of tetramethylammonium hydroxide. -- Abstract: Many studies have been performed dealing with the processing conditions of electrodes and electrolytes in solid oxide fuel cells (SOFCs). However, the processing of the interconnector material has received less attention. Lanthanum chromite (LaCrO{sub 3}) is probably the most studied material as SOFCs interconnector. This paper deals with the rheology and casting behaviour of lanthanum chromite based materials to produce interconnectors for SOFCs. A powder with the composition La{sub 0.80}Sr{sub 0.20}Cr{sub 0.92}Co{sub 0.08}O{sub 3} was obtained by combustion synthesis. Aqueous suspensions were prepared to solids loading ranging from 8 to 17.5 vol.%, using ammonium polyacrylate (PAA) as dispersant and tetramethylammonium hydroxide (TMAH) to assure a basic pH and providing stabilization. The influence of the additives concentrations and suspension ball milling time were studied. Suspensions prepared with 24 h ball milling, with 3 wt.% and 1 wt.% of PAA and TMAH, respectively, yielded the best conditions for successful slip casting. Sintering of the green discs was performed in air at 1600 {sup o}C for 4 h leading to relatively dense materials.

  20. 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.

  1. 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.

  2. [Radiographic disappearance of lanthanum].

    PubMed

    Pastori, Giordano

    2015-01-01

    In 2006, Cerny and Kunzendorf in the New England Journal of Medicine Images in clinical medicine, showed the radiographic appearance of lanthanum for the first time. After many years we noticed the inverse phenomenon. In a peritoneal dialysis patient treated with lanthanum carbonate, we had two radiography of the abdomen for monitoring the peritoneal catheter. In the first radiography contrast material was seen in colon. In the most recent radiography contrast material disappeared. The patient was always taking the same dose of lanthanum carbonate (1000 mg bid), although at the time of the first radiography he took the chewable tablets, for the last radiography he took the new powder formulation. We found a report in literature highlighting this phenomenon meanwhile indicating a greater chelating effect for the powder. Our hypothesis is that despite the same lanthanum dose, powder provides a greater surface area of binding and a more dispersed bowel distribution to explain a masked radio-opacity. Considering the wide availability of the powder, this must be taken into account especially in evaluating therapeutic compliance. PMID:25774580

  3. 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

  4. 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.

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

    SciTech Connect

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

    1995-12-31

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

  6. Thermoelectric Properties of Lanthanum Sulfide

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

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

  7. 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.

  8. Lanthanum halide nanoparticle scintillators for nuclear radiation detection

    SciTech Connect

    Guss, Paul; Guise, Ronald; Yuan, Ding; Mukhopadhyay, Sanjoy; O'Brien, Robert; Lowe, Daniel; Kang, Zhitao; Menkara, Hisham; Nagarkar, Vivek V.

    2013-01-01

    Nanoparticles with sizes <10 nm were fabricated and characterized for their nanocomposite radiation detector properties. This work investigated the properties of several nanostructured radiation scintillators, in order to determine the viability of using scintillators employing nanostructured lanthanum tribromide, lanthanum trifluoride, or cerium tribromide. Preliminary results of this investigation are consistent with the idea that these materials have an intrinsic response to nuclear radiation that may be correlated to the energy of the incident radiation.

  9. 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.

  10. A positron study of the colossal magnetoresistive material lanthanum(0.7) strontium(0.3) manganite

    NASA Astrophysics Data System (ADS)

    Livesay, Eric Anton

    2000-10-01

    We have performed a spin-dependent 2D-ACAR study of a single crystal sample of La0.7Sr0.3MnO3 (a manganite perovskite that exhibits colossal magnetoresistance). Measurements were made at three well-separated temperatures, two of which were below the ferromagnetic to paramagnetic transition temperature. It is believed that these measurements constitute the first detailed experimental study of the electronic structure of this material. Of the many properties of the electronic structure of a material, the Fermi surface is one of the most important. The most recent self-consistent band structure and momentum density calculations predict La0.7Sr0.3MnO3 to have only two significant Fermi surface features, large R-centered cubic hole pockets and a Gamma-centered electron spheroid. Both of these features result from the Fermi level crossing majority bands. The Fermi level sits only slightly above a gap in the minority bands, that is, those bands behave as in an semi-conductor. As a result, electron transport is largely spin-polarized and the material is referred to as being nearly half-metallic. These theoretical predictions are supported by the results of the experimental measurements. Clear indications of the large cubic Fermi surface are observed in our data and, although some evidence is also seen for the electron spheroid, this is decidedly weaker. The experimental results also qualitatively support the supposed spin-polarized transport in this material. This agreement between experiment and theory indicate that the theoretical description is, to a large degree, valid.

  11. 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.

  12. 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.

  13. Extensive lanthanum deposition in the gastric mucosa: the first histopathological report.

    PubMed

    Makino, Mutsuki; Kawaguchi, Kenji; Shimojo, Hisashi; Nakamura, Hironori; Nagasawa, Masaki; Kodama, Ryo

    2015-01-01

    Lanthanum carbonate is one of the new phosphate binders used for the treatment of hyperphosphatemia in patients with chronic kidney disease. It is poorly absorbed from the gastrointestinal tract, forms insoluble complexes within the lumen, and prevents the absorption of dietary phosphate. A 63-year-old female with a 7-year history of peritoneal dialysis, who was treated with lanthanum carbonate for four years, underwent endoscopic submucosal dissection for intramucosal gastric cancer. Resected specimens showed massive accumulation of macrophages containing fine, granular, brown material in the lamina propria. This was confirmed as lanthanum deposition by scanning electron microscopy with energy dispersive x-ray spectroscopy. Although lanthanum may be poorly absorbed, increased tissue accumulation of lanthanum, particularly in the liver and bone, has been reported in animals with chronic kidney disease. This report indicates enhanced gastrointestinal absorption of lanthanum in some patients or conditions, although its clinical significance awaits further studies. PMID:25413959

  14. Thermoelectric properties of non-stoichiometric lanthanum sulfides

    NASA Technical Reports Server (NTRS)

    Shapiro, E.; Danielson, L. R.

    1983-01-01

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

  15. 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.

  16. Metallic behavior of lanthanum disilicide

    NASA Technical Reports Server (NTRS)

    Long, Robert G.; Bost, M. C.; Mahan, John E.

    1988-01-01

    Polycrystalline thin films of LaSi2 were prepared by reaction of sputter-deposited lanthanum layers with silicon wafers. Samples of the low-temperature tetragonal and the high-temperature orthorhombic phases were separately obtained. The room-temperature intrinsic resistivities were 24 and 57 microohm cm for the low- and high-temperature structures, respectively. Although lanthanum disilicide had been previously reported to be a semiconductor, classical metallic behavior was found for both phases.

  17. [Lanthanum carbonate in clinical practice].

    PubMed

    Torregrosa Prats, V

    2008-01-01

    Lanthanum is an element belonging to the group called rare earths. Due to its low solubility, lanthanum carbonate has been widely studied as an intestinal phosphate binder. The results of different clinical trials show that it is an effective and well-tolerated phosphate binder used in monotherapy. Serum phosphate levels are controlled in approximately 70% of patients at 5 years without causing hypercalcemia. The only significant adverse effects observed are a low percentage of gastrointestinal disturbances (6%). Lanthanum carbonate does not alter serum values of liposoluble vitamins or affect the pharmacokinetics of digoxin, warfarin, furosemide, phenytoin, ACE inhibitors or beta-blockers. However, it does alter the pharmacokinetics of ciprofloxacin (quinolones in general), tetracyclines and doxycycline. Lanthanum carbonate (Fosrenol) is available in Spain as 500 mg, 750 mg, and 1,000 mg chewable tablets, which should not be swallowed without chewing to avoid loss of efficacy. The initial dose recommended by the WHO is 2,250 mg/day, which is equivalent to one 750 mg at each meal. Lanthanum carbonate or lanthanum phosphate can be clearly visualized on a plain x-ray of the abdomen in patients who have recently ingested it. In summary, lanthanum carbonate is a widely studied potent phosphate binder, which offers the possibility of improving control of serum phosphate in patients with chronic kidney disease, without significant side effects. The fact that it is available as chewable tablets and that the number of daily tablets required has been significantly reduced will probably facilitate better patient compliance. PMID:18847414

  18. 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

  19. 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.

  20. 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.

  1. 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.

  2. Ames Lab 101: Lanthanum Decanting

    ScienceCinema

    Riedemann, Trevor

    2012-08-29

    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.

  3. Ab initio energetics of lanthanum substitution in ferroelectric bismuth titanate

    NASA Astrophysics Data System (ADS)

    Shah, S. H.; Bristowe, P. D.

    2011-04-01

    Using first principles calculations and atomistic thermodynamics the bulk and defect properties of orthorhombic bismuth titanate (Bi4Ti3O12) and bismuth lanthanum titanate (Bi3.25La0.75Ti3O12) have been investigated. Heats of formation, valid chemical conditions for synthesis, lanthanum substitution energies and oxygen and bismuth vacancy formation energies have been computed. The study improves our understanding of how native point defects and substitutional impurities influence the ferroelectric properties of these layered perovskite materials. It is found that lanthanum incorporation could occur on either of the two distinct bismuth sites in the structure and that the effect of substitution is to increase the formation energy of nearby native oxygen vacancies. The results provide direct atomistic evidence over a range of chemical conditions supporting the suggestion that lanthanum incorporation reduces the oxygen vacancy concentration. Oxygen vacancies contribute to ferroelectric fatigue by interacting strongly with domain walls, and therefore a decrease in their concentration is beneficial. The conditions that favor the greatest reduction in oxygen vacancy concentration are described.

  4. Rapid Synthesis of Nonstoichiometric Lanthanum Sulfide

    NASA Technical Reports Server (NTRS)

    Matsuda, S.; Shapiro, E.; Danielson, L.; Hardister, H.

    1987-01-01

    New process relatively fast and simple. Improved method of synthesizing nonstoichiometric lanthanum sulfide faster and simpler. Product purer because some of prior sources of contamination eliminated.

  5. 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.

  6. 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.

  7. 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.

  8. Lanthanum halide nanoparticle scintillators for nuclear radiation detection

    SciTech Connect

    Guss, Paul; Guise, Ronald; O'Brien, Robert; Lowe, Daniel; Kang Zhitao; Menkara, Hisham; Nagarkar, Vivek V.

    2013-02-14

    Nanoparticles with sizes <10 nm were fabricated and characterized for their nanocomposite radiation detector properties. This work investigated the properties of several nanostructured radiation scintillators, in order to determine the viability of using scintillators employing nanostructured lanthanum trifluoride. Preliminary results of this investigation are consistent with the idea that these materials have an intrinsic response to nuclear radiation that may be correlated to the energy of the incident radiation.

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

    NASA Astrophysics Data System (ADS)

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

    2009-07-01

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

  10. 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.

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

    NASA Astrophysics Data System (ADS)

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

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

  12. Absolute bioavailability and disposition of lanthanum in healthy human subjects administered lanthanum carbonate.

    PubMed

    Pennick, Michael; Dennis, Kerry; Damment, Stephen J P

    2006-07-01

    Lanthanum carbonate [La2(CO3)3] is a noncalcium, non-aluminum phosphate binder indicated for hyperphosphatemia treatment in end-stage renal disease. A randomized, open-label, parallel-group, phase I study was conducted to determine absolute bioavailability and investigate excretory routes for systemic lanthanum in healthy subjects. Twenty-four male subjects were randomized to a single lanthanum chloride (LaCl3) intravenous infusion (120 microg elemental lanthanum over a 4-hour period), a single 1-g oral dose [chewable La2(CO3)3 tablets; 4 x 250 mg elemental lanthanum], or no treatment (control). Serial blood, urine, and fecal samples were collected for 7 days postdosing. The absolute bioavailability of lanthanum [administered as La2(CO3)3] was extremely low (0.00127% +/- 0.00080%), with individual values in the range of 0.00015% to 0.00224%. Renal clearance was negligible following oral administration (1.36 +/- 1.43 mL/min). Intravenous administration confirmed low renal clearance (0.95 +/- 0.60 mL/min), just 1.7% of total plasma clearance. Fecal lanthanum excretion was not quantifiable after intravenous administration owing to high and variable background fecal lanthanum and constraints on the size of the intravenous dose. These findings demonstrate that lanthanum absorption from the intestinal tract into the systemic circulation is extremely low and that absorbed drug is cleared predominantly by nonrenal mechanisms. PMID:16809799

  13. 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. PMID:23325290

  14. Field free, directly heated lanthanum boride cathode

    DOEpatents

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

    1987-02-02

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

  15. Field free, directly heated lanthanum boride cathode

    DOEpatents

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

    1991-01-01

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

  16. 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.

  17. Lanthanum

    MedlinePlus

    ... medications called phosphate binders. It works by preventing absorption of phosphate from food in the stomach. ... it at room temperature and away from excess heat and moisture (not in the bathroom). Throw away ...

  18. Large-area lanthanum hexaboride electron emitter

    SciTech Connect

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

    1985-09-01

    A large-area cathode assembly which is capable of continuous, high-current electron emission is described. The cathode utilizes an indirectly heated lanthanum hexaboride (LaB/sub 6/) disk as the thermionic electron emitter. The LaB/sub 6/ cathode emits over 600 A of electrons at an average of 20 A/cm/sup 2/ continuously with no observable lifetime limits to date after about 400 h of operation in a plasma discharge. Proper clasping of the LaB/sub 6/ disk is required to avoid impurity production from chemical reactions with the holder and to provide adequate support if the disk fractures during rapid thermal cycling. Modification of the LaB/sub 6/ surface composition due to preferential sputtering of boron by hydrogen and argon ions in the plasma discharge has been observed. The surface appearance is consistent with the formation of LaB/sub 4/ as a result of boron depletion. The electron emission capability of the cathode is not significantly altered by the surface change. This surface modification by preferential sputtering is not observed in hollow cathodes where the ion energy from the cathode sheath voltage is typically less than 50 V. The electron emission by the cathode has not been affected by exposure to both air and water during operation. Utilizing thick disks of this intermediate temperature cathode material results in reliable, high-current, long-lifetime electron emitter assemblies.

  19. 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

  20. 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)

  1. 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.

  2. 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

  3. Development of Lanthanum Ferrite SOFC Cathodes

    SciTech Connect

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

    2003-01-01

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

  4. 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

  5. Thermopower of lanthanum monochalcogenides subjected to uniform compression up to 22 GPa

    NASA Astrophysics Data System (ADS)

    Stepanov, N. N.; Morozova, N. V.; Kar'kin, A. E.; Korobeinikov, I. V.; Golubkov, A. V.; Kaminskii, V. V.

    2015-03-01

    It is shown that lanthanum monochalcogenides (LaS, LaSe, LaTe), in which metal ions are trivalent at least up to 22 GPa, may be used as reference materials in finding the stability domains of a variable-valence state in rare-earth elements in different compounds studied under pressure. The thermopower of these materials throughout the pressure interval studied varies between 1 and 4 μV/K.

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

    SciTech Connect

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

    1984-08-15

    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.

  7. 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.

  8. 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

  9. Sorption of lanthanum ions by natural clinoptilolite tuff

    NASA Astrophysics Data System (ADS)

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

    2013-08-01

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

  10. Structural Characterization of Methanol Substituted Lanthanum Halides

    PubMed Central

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

    2010-01-01

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

  11. 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.

  12. Deposition and investigation of lanthanum cerium hexaboride thin films

    NASA Astrophysics Data System (ADS)

    Kuzanyan, A. S.; 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.; Gulian, A. M.

    2006-09-01

    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 °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 ρ( 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.

  13. 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.

  14. Synthesis and characterization of strontium-lanthanum apatites

    SciTech Connect

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

    2007-07-03

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

  15. 40 CFR 721.10601 - Lanthanum lead titanium zirconium oxide.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

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

  16. 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.

  17. Highly stable, mesoporous mixed lanthanum-cerium oxides with tailored structure and reducibility

    SciTech Connect

    Liang, Shuang; Broitman, Esteban; Wang, Yanan; Cao, Anmin; Veser, Goetz

    2011-05-01

    Pure and mixed lanthanum and cerium oxides were synthesized via a reverse microemulsion-templated route. This approach yields highly homogeneous and phase-stable mixed oxides with high surface areas across the entire range of La:Ce ratios from pure lanthana to pure ceria. Surprisingly, all mixed oxides show the fluorite crystal structure of ceria, even for lanthanum contents as high as 90%. Varying the La:Ce ratio not only allows tailoring of the oxide morphology (lattice parameter, pore structure, particle size, and surface area), but also results in a fine-tuning of the reducibility of the oxide which can be explained by the creation of oxygen vacancies in the ceria lattice upon La addition. Such finely controlled syntheses, which enable the formation of stable, homogeneous mixed oxides across the entire composition range, open the path towards functional tailoring of oxide materials, such as rational catalyst design via fine-tuning of redox activity.

  18. Lanthanum(III)-catalyzed degradation of cellulose at 250 degrees C.

    PubMed

    Seri, Kei-ichi; Sakaki, Tsuyoshi; Shibata, Masao; Inoue, Yoshihisa; Ishida, Hitoshi

    2002-02-01

    Lanthanum(III) chloride was found to effectively catalyze the degradation of cellulose in water at 250 degrees C. The degradation conversion of cellulose in the presence of a catalytic amount of lanthanum chloride reached 80.3% after 180 s, which corresponded to the turnover number of 83, whereas the reaction did scarcely proceed in the absence of the catalyst. The degradation products were separately quantified as water-soluble (WS), methanol-soluble (MS), methanol-insoluble (MI), and gaseous (G) products. The HPLC and GC analyses revealed that the WS materials are mainly composed of 5-hydroxymethyl-2-furaldehyde (HMF), D-glucose, and levulinic acid. Cellobiose, the disaccharide component of cellulose, was scarcely detected during the reaction. PMID:11800491

  19. Thermoelectric properties of lanthanum sulfide

    NASA Technical Reports Server (NTRS)

    Wood, C.; Lockwood, A.; Parker, J.; Zoltan, A.; Zoltan, D.

    1985-01-01

    The Seebeck coefficient, electrical resistivity, thermal conductivity, and Hall effect have been studied in gamma-phase La(3-x)S4(LaS/y/) for compositions with x in the range from 0.04 to 0.3 (y in the range from 1.35 to 1.48) in order to ascertain its suitability for high-temperature (300 to 1400 K) thermoelectric energy conversion. In this temperature and composition range the material behaves as an extrinsic semiconductor whose degenerate carrier concentration is controlled by the stoichiometric ratio of La to S. A maximum figure-of-merit (Z) of approximately 0.0005 per K at a composition x = 0.3, y = 1.48 (LaS/1.48/) was obtained.

  20. Thermal stability of lanthanum scandate dielectrics on Si(100)

    SciTech Connect

    Sivasubramani, P.; Lee, T. H.; Kim, M. J.; Kim, J.; Gnade, B. E.; Wallace, R. M.; Edge, L. F.; Schlom, D. G.; Stevie, F. A.; Garcia, R.; Zhu, Z.; Griffis, D. P.

    2006-12-11

    The authors have examined the thermal stability of amorphous, molecular beam deposited lanthanum scandate dielectric thin films on top of Si (100) after a 1000 deg. C, 10 s rapid thermal anneal. After the anneal, crystallization of LaScO{sub 3} is observed. Excellent suppression of lanthanum and scandium diffusion into the substrate silicon is indicated by the back-side secondary ion mass spectrometry (SIMS) analyses. In contrast, front-side SIMS and high-resolution electron energy loss analyses of the amorphous Si/LaScO{sub 3}/Si (100) stack indicated the outdiffusion of lanthanum and scandium into the silicon capping layer during the anneal.

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

    PubMed

    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

  2. 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. PMID:22201282

  3. 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

  4. Room temperature synthesis of high temperature stable lanthanum phosphate–yttria nano composite

    SciTech Connect

    Sankar, Sasidharan; Raj, Athira N.; Jyothi, C.K.; Warrier, K.G.K.; Padmanabhan, P.V.A.

    2012-07-15

    Graphical abstract: A facile aqueous sol–gel route involving precipitation–peptization mechanism followed by electrostatic stabilization is used for synthesizing nanocrystalline composite containing lanthanum phosphate and yttria. Highlights: ► A novel lanthanum phosphate–Y{sub 2}O{sub 3} nano composite is synthesized for the first time using a modified facile sol gel process. ► The composite becomes crystalline at 600 °C and X-ray diffraction pattern is indexed for monoclinic LaPO{sub 4} and cubic yttria. ► The composite synthesized was tested up to 1300 °C and no reaction between the phases of the constituents is observed with the morphologies of the phases being retained. -- Abstract: A facile aqueous sol–gel route involving precipitation–peptization mechanism followed by electrostatic stabilization is used for synthesizing nanocrystalline composite containing lanthanum phosphate and yttria. Lanthanum phosphate (80 wt%)–yttria (20 wt%) nano composite (LaPO{sub 4}–20%Y{sub 2}O{sub 3}), has an average particle size of ∼70 nm after heat treatment of precursor at 600 °C. TG–DTA analysis reveals that stable phase of the composite is formed on heating the precursor at 600 °C. The TEM images of the composite show rod shape morphology of LaPO{sub 4} in which yttria is acquiring near spherical shape. Phase identification of the composite as well as the phase stability up to 1300 °C was carried out using X-ray diffraction technique. With the phases being stable at higher temperatures, the composite synthesized should be a potential material for high temperature applications like thermal barrier coatings and metal melting applications.

  5. 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

  6. 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.

  7. 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

    This paper presents 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. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. Deposition of Lanthanum Strontium Cobalt Ferrite (LSCF) Using Suspension Plasma Spraying for Oxygen Transport Membrane Applications

    NASA Astrophysics Data System (ADS)

    Fan, E. S. C.; Kesler, O.

    2015-08-01

    Suspension plasma spray deposition was utilized to fabricate dense lanthanum strontium cobalt ferrite oxygen separation membranes (OSMs) on porous metal substrates for mechanical support. The as-sprayed membranes had negligible and/or reversible material decomposition. At the longer stand-off distance (80 mm), smooth and dense membranes could be manufactured using a plasma with power below approximately 81 kW. Moreover, a membrane of 55 μm was observed to have very low gas leakage rates desirable for OSM applications. This thickness could potentially be decreased further to improve oxygen diffusion by using metal substrates with finer surface pores.

  15. The strong influence of iron additions on the lead-lanthanum-titanate ceramics

    NASA Astrophysics Data System (ADS)

    Omari, Lhaj el Hachemi; Sayouri, Salaheddine

    2013-11-01

    In the present work, phase transitions and electrical characteristics of iron and lanthanum substituted lead titanate are reported. Structural analysis of the prepared samples was carried out to confirm the formation of the compounds in the proper phase. The average grain size was estimated using Scherrer's equation. Dielectric properties of the samples have been studied as functions of temperature and frequency. Variations of the dielectric constant (ɛr) as function of temperature show a diffuse ferro-paraelectric phase transition. The diffusivity and the relaxation strength were estimated using the modified Uchino-law, and the relaxation time of these materials satisfies the Vogel-Fulcher equation.

  16. Temperature-Dependent Electrical and Micromechanical Properties of Lanthanum Titanate with Additions of Yttria

    NASA Technical Reports Server (NTRS)

    Goldsby, Jon C.

    2010-01-01

    Temperature-dependent elastic properties were determined by establishing continuous flexural vibrations in the material at its lowest resonance frequency of 31tHz. The imaginary part of the complex impedance plotted as a function of frequency and temperature reveals a thermally activated peak, which decreases in magnitude as the temperature increases. Additions of yttria do not degrade the electromechanical in particularly the elastic and anelastic properties of lanthanum titanate. Y2O3/La2Ti2O7 exhibits extremely low internal friction and hence may be more mechanical fatigue-resistant at low strains.

  17. Temperature Dependent Electrical and Micromechanical Properties of Lanthanum Titanate with Additions of Yttria

    NASA Technical Reports Server (NTRS)

    Goldsby, Jon C.

    2003-01-01

    Lanthanum titanate (La2Ti2O7) a layered distorted perovskite (1) with space group Pna2(sub 1) has been shown to have potential as a high temperature piezoelectric (2). However this highly refractory oxide compound must be consolidated at relatively high temperatures approximately 1400 C. Commercial La2Ti207 powders were mechanically alloyed with additions of Y2O3 to lower the consolidation temperature by 300 C and to provide post processing mechanical stability. Temperature dependent electrical, elastic and anelastic behavior were selected as nondestructive means of evaluating the effects of yttria on the properties of this ferroceramic material.

  18. 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....

  19. 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....

  20. 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....

  1. Toward laser cooling of negative lanthanum

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

  2. Phosphate adsorption on lanthanum loaded biochar.

    PubMed

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

    2016-05-01

    To attain a low-cost and high-efficient phosphate adsorbent, lanthanum (La) loaded biochar (La-BC) prepared by a chemical precipitation method was developed. La-BC and its pristine biochar (CK-BC) were comparatively characterized using zeta potential, BET surface area, scanning electron microscopy/energy dispersive spectrometer (SEM-EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR). The adsorption ability and the mechanisms during adsorption process for the La-BC samples were also investigated. La loaded on the surface of biochar can be termed as La-composites (such as LaOOH, LaONO3 and La(OH)3), leading to the decrease of negative charge and surface area of biochar. La-BC exhibited the high adsorption capacity to phosphate compared to CK-BC. Adsorption isotherm and adsorption kinetic studies showed that the Langmuir isotherm and second order model could well describe the adsorption process of La-BC, indicating that the adsorption was dominated by a homogeneous and chemical process. The calculated maximum adsorption capacity was as high as 46.37 mg g(-1) (computed in P). Thermodynamic analysis revealed that the adsorption was spontaneous and endothermic. SEM, XRD, XPS and FT-IR analysis suggested that the multi-adsorption mechanisms including precipitation, ligand exchange and complexation interactions can be evidenced during the phosphate adsorption process by La-composites in La-BC. PMID:26871732

  3. 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. PMID:23428822

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

    SciTech Connect

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

    2004-01-01

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

  5. Calcium and lanthanum solid base catalysts for transesterification

    DOEpatents

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

    2015-07-28

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

  6. 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

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

    NASA Astrophysics Data System (ADS)

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

    2011-07-01

    Titania-lanthanum phosphate nanocomposites with multifunctional properties have been synthesized by aqueous sol-gel method. The precursor sols with varying TiO 2:LaPO 4 ratios were applied as thin coating on glass substrates in order to be transparent, hydrophobic, photocatalytically active coatings. The phase compositions of the composite powders were identified by powder X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HR-TEM). The anatase phase of TiO 2 in TiO 2-LaPO 4 composite precursors was found to be stable even on annealing at 800 °C. The glass substrates, coated with TL1 (TiO 2-LaPO 4 composition with 1 mol% LaPO 4) and TL50 (composite precursor containing TiO 2 and LaPO 4 with molar ratio 1:1) sols and annealed at 400 °C, produced contact angles of 74° and 92°, respectively, though it is only 62° for pure TiO 2 coating. The glass substrates, coated with TL50 sol, produced surfaces with relatively high roughness and uneven morphology. The TL1 material, annealed at 800 °C, has shown the highest UV photoactivity with an apparent rate constant, kapp=24×10 -3 min -1, which is over five times higher than that observed with standard Hombikat UV 100 ( kapp=4×10 -3 min -1). The photoactivity combined with a moderate contact angle (85.3°) shows that this material has a promise as an efficient self-cleaning precursor.

  8. Lanthanum Carbonate for Hyperphosphatemia in Patients on Peritoneal Dialysis

    PubMed Central

    Ohno, Michiya; Ohashi, Hiroshige; Oda, Hiroshi; Yokoyama, Haruko; Okada, Miho; Nagaya, Mayu; Izumi, Kumiko; Ito, Hitomi; Katoh, Shuji

    2013-01-01

    ♦ Background: The efficacy of the phosphate binder lanthanum carbonate has been demonstrated for hemodialysis patients, but no studies have focused on patients undergoing continuous ambulatory peritoneal dialysis (CAPD). We evaluated whether lanthanum carbonate could control phosphate levels in patients on CAPD. ♦ Methods: In this 48-week open-label prospective study, 28 patients on CAPD with a phosphate level of 6 mg/dL or greater were given lanthanum carbonate titrated from 750 mg to 2250 mg daily to achieve a target serum phosphate level of less than 6 mg/dL. The primary efficacy endpoint was reduction of serum phosphate to less than 6 mg/dL. Serum levels of calcium and parathyroid hormone were also evaluated, as were the Ca×P product and adverse effects. ♦ Results: From week 4 to the end of the study at week 48, we observed a significant reduction of serum phosphate to 5.25 ± 0.97 mg/dL from 6.88 ± 1.06 mg/dL at study start (p < 0.01). At the end of the study, 78.6% of participants had achieved the target of less than 6 mg/dL. Because no change of serum calcium occurred, the Ca×P product declined significantly during the study. Intact parathyroid hormone declined gradually over the study period, but the change had not reached significance at the end of the study (p = 0.11). The mean final dose of lanthanum carbonate was 946 mg daily. The only adverse effect reported was mild nausea in 1 patient. ♦ Conclusions: Lanthanum carbonate is an effective phosphate binder that can control serum phosphate and Ca×P product in CAPD patients with hyperphosphatemia. Lanthanum carbonate was well tolerated in our population. PMID:23209037

  9. 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.

  10. 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.

  11. Effects of lanthanum in cellular systems. A review.

    PubMed

    Das, T; Sharma, A; Talukder, G

    1988-12-01

    Lanthanum belongs to the group of elements known as "lanthanons," which also includes cerium, europium, promethium, and thulium. It is the most electropositive element of the rare earth group, is uniformly trivalent, and is similar in its chemical properties to the alkaline earth elements. The effects of this element and its compounds on cellular systems are of considerable interest because of their increasing use in industry and as a substitute or antagonist for calcium in a variety of cellular reactions. Lanthanum is also being employed extensively in studying anatomical barriers, membrane structure, and subcellular transport systems, particularly the calcium pathway. PMID:2484565

  12. 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.

  13. SEPARATION OF PLUTONIUM FROM LANTHANUM BY CHELATION-EXTRACTION

    DOEpatents

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

    1958-12-01

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

  14. Preconcentration of some metal ions with lanthanum-8-hydroxyquinoline co-precipitation system.

    PubMed

    Feist, Barbara; Mikula, Barbara

    2014-03-15

    A method of separation and preconcentration of cadmium, copper, nickel, lead and zinc at trace level using 8-hydroxyquinoline as a chelating agent and lanthanum(III) as a carrier element is proposed. The heavy metals were determined after preconcentration by inductively coupled plasma optical emission spectrometry (ICP-OES). The results were compared with those obtained using flame atomic absorption spectrometry (F-AAS). The influence of several parameters such as pH, amount of lanthanum(III) as a carrier element, amount of 8-hydroxyquinoline, duration of co-precipitation was examined. Moreover, effects of inorganic matrix on recovery of the determined elements were studied. The detection limits (DL) for ICP-OES were 0.31, 2.9, 1.4, 3.2 and 1.2 μg L(-1) for Cd, Cu, Ni, Pb and Zn, respectively, whereas for F-AAS DL were 0.63, 1.1, 3.2, 2.7 and 0.74 μg L(-1). The recovery of the method for the determined elements was better than 94% with relative standard deviation between 0.63% and 2.9%. The preconcentration factor was 60. The proposed method was successfully applied for determination of Cd, Cu, Ni, Pb, and Zn in plant materials. Accuracy of the proposed method was verified using certified reference material (NCS ZC85006 Tomato). PMID:24206710

  15. 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.

  16. 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.

  17. Kinetic study of the formation of oxygen vacancy on lanthanum manganite electrodes

    SciTech Connect

    Jiang, Y.; Wang, S.; Zhang, Y.; Yan, J.; Li, W.

    1998-02-01

    Strontium doped lanthanum manganite (LSM) has been considered one of the most promising cathode materials for solid oxide fuel cells (SOFC). The electrochemical reduction of oxygen on lanthanum manganite (LSM) electrodes has been investigated by cyclic voltammetry, alternating current (ac) impedance, and, in particular, potential step. An emphasis was given to the study of the kinetics of the formation of oxygen vacancy, which is shown to be the main cause for the reversed hysteresis in cyclic voltammograms and for the increase in the electrochemical activity of oxygen reduction on the cathodically polarized LSM electrode observed in both ac impedance and in potential step experiments. The potential step experiments show that the oxygen vacancy concentration increases exponentially with time when the LSM is under a cathodic polarization. In the present study, the rate controlling step for the formation of oxygen vacancies is the oxygen vacancy generation step. The cathodic current rising from the reaction on oxygen vacancies can make a significant contribution to the total reduction current.

  18. Responses in sediment phosphorus and lanthanum concentrations and composition across 10 lakes following applications of lanthanum modified bentonite.

    PubMed

    Dithmer, Line; Nielsen, Ulla Gro; Lürling, Miquel; Spears, Bryan M; Yasseri, Said; Lundberg, Daniel; Moore, Alanna; Jensen, Nicholai D; Reitzel, Kasper

    2016-06-15

    A combined field and laboratory scale study of 10 European lakes treated between 2006 and 2013 with a lanthanum (La) modified bentonite (LMB) to control sediment phosphorus (P) release was conducted. The study followed the responses in sediment characteristics including La and P fractions and binding forms, P adsorption capacity of discrete sediment layers, and pore water P concentrations. Lanthanum phosphate mineral phases were confirmed by solid state (31)P MAS NMR and LIII EXAFS spectroscopy. Rhabdophane (LaPO4 · nH2O) was the major phase although indications of monazite (LaPO4) formation were also reported, in the earliest treated lake. Molar ratios between La and P in the sediments were generally above 1, demonstrating excess La relative to P. Lanthanum was vertically mixed in the sediment down to a depth of 10 cm for eight of the ten lakes, and recovery of La in excess of 100% of the theoretical aerial load indicated translocation of the LMB towards the deepest areas of the lakes. Lanthanum was generally recovered from bed sediment samples following sequential chemical extraction from the HCl fraction. Soluble reactive P (SRP) release experiments on intact sediment cores indicated conditions of P retention (with the exception of two lakes) by sediments, indicating effective control of sediment P release, i.e. between two and nine years after treatment. PMID:26971297

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

    PubMed

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

    2011-01-01

    Lanthanum carbonate, a chewable noncalcium-containing phosphorus (P) binder, is useful for treating secondary hyperparathyroidism in patients who have hypercalcemia and cannot swallow whole tablets. However, some patients cannot chew tablets or prefer to crush and mix them with food. This study was conducted to determine the P-binding efficacy of crushed lanthanum and compare it with chewed lanthanum in hemodialysis (HD) patients. After a 1-week washout period, 11 hemodialysis patients (7 men, 4 women) were randomized to receive, in a crossover fashion, lanthanum 1000 mg 3 times daily chewed with meals and lanthanum 1000 mg 3 times daily crushed into a fine powder, mixed with applesauce and taken with meals, for 4 weeks each. Serum P was measured at the end of each washout (baseline) and weekly during treatment. Changes in serum P from baseline for crushed lanthanum were compared with chewed lanthanum using paired sample t test. Administration of crushed lanthanum resulted in a significant reduction in serum P from baseline (P reduction [mg/dL] for crushed lanthanum in week 1: 2.1 ± 0.4, week 2: 1.7 ± 0.5, week 3: 1.7 ± 0.5, week 4: 1.7 ± 0.4, P<0.05). No statistically significant differences were observed in serum P reduction from baseline and serum P attained during treatment with crushed when compared with chewed lanthanum. Crushed lanthanum is effective in reducing serum P and have similar P-binding efficacy to chewed lanthanum. Crushing lanthanum and mixing it with food can thus be an option for patients who are unable to chew or swallow whole tablets. PMID:21138519

  20. An Integrated Approach for Structural Characterization of Complex Solid State Electrolytes: The Case of Lithium Lanthanum Titanate

    SciTech Connect

    Cheng, Yongqiang; Bi,; Huq, Ashfia; Feygenson, Mikhail; Bridges, Craig A; Paranthaman, Mariappan Parans; Sumpter, Bobby G

    2014-01-01

    Neutron scattering and first principles simulation are integrated to reveal the atomic-level to nanoscale structure of lithium lanthanum titanate (LLTO), a representative solid electrolyte material with applications in Li-ion batteries. The integrated approach solves the hierarchical local structure of LLTO in detail, including the coupled chemical order and topological distortion, as well as their correlation length scale and the spatial modulation with coherent boundaries. Ab initio molecular dynamics simulations are used to map out the distribution of the mobile ions and identify the migration pathway. Overall, this integrated approach provides a powerful means for detailed study of materials with complex local chemical and topological environment.

  1. A simple spectrophotometric assay for micromolar amounts of lanthanum in the presence of calcium and phosphate.

    PubMed

    Fernandez-Gavarron, F; Brand, J G; Rabinowitz, J L

    1987-10-01

    A sensitive spectrophotometric assay for micromolar amounts of lanthanum in the presence of calcium and phosphate (as hydroxyapatite) was developed utilizing the change in absorption (at 652 nm) when the dye arsenazo III was complexed with lanthanum. Arsenazo III was used at a level of 25 microM and the solution pH was maintained at 3.1 with 0.2 M sodium acetate. Lanthanum concentrations down to 0.5 microM could be reliably assayed. Calcium ion did not complex well with arsenazo III at pH 3.1. With calcium present at 100 microM and lanthanum at 10 microM, the assay was 115 times more sensitive for lanthanum. The assay is simple, rapid, reproducible and, unlike the assay using radioactive lanthanum, can be performed at any time. PMID:3455624

  2. 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.

  3. 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.

  4. 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

  5. Conformational effects, molecular orbitals, and reaction activities of bis(phthalocyaninato) lanthanum double-deckers: density functional theory calculations.

    PubMed

    Qi, Dongdong; Zhang, Lijuan; Wan, Liang; Zhang, Yuexing; Bian, Yongzhong; Jiang, Jianzhuang

    2011-08-01

    The conformational effects on the frontier molecular orbital energy and stability for reduced, neutral, and oxidized bis(phthalocyaninato) lanthanum double-deckers have been revealed on the basis of density functional theory calculations. Calculation results indicate that the frontier orbital coupling degree changes along with the molecular conformation of the double-decker compound, first decreasing along with the increase of rotation angle β from 0 to 20° and then increasing along with the increase of rotation angle β from 20 to 45°. In addition, the stability for the three forms of double-decker changes in the same order, but first increasing and then decreasing along with the change of the rotation angle β in the range of 0 to 45° with a rotation energy barrier of (31.3 ± 3.1) kJ mol(-1) at 20°. This reveals that the rotation of the two phthalocyanine rings for the reduced, neutral, and oxidized bis(phthalocyaninato) lanthanum double-deckers are able to occur at room temperature. Nevertheless, the superior coordination reaction activity of the neutral bis(phthalocyaninato) lanthanum double-decker complex over their reduced form in forming sandwich-type tris(phthalocyaninato) lanthanum triple-decker compounds has also been clearly clarified on the basis of comparative calculations on the Fukui function of [La(Pc)(2)] and [La(Pc)(2)](-) using the DFT method. Fukui function analysis reveals the reaction center of the 18-electron-π-conjugated core in the bis(phthalocyaninato) lanthanum double-decker molecule against both electrophilic and radical attack. Nevertheless, the larger global chemical softness (S) for the neutral [La(Pc)(2)] than the reduced form [La(Pc)(2)](-) indicates the higher reaction activity of the former form over the latter one. This explains well the experimental findings that only the neutral instead of the reduced form of bis(tetrapyrrole) rare earth double-decker complexes, containing at least one phthalocyanine ligand, could be

  6. 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.

  7. Radiative lifetimes and transition probabilities of neutral lanthanum

    NASA Astrophysics Data System (ADS)

    Den Hartog, E. A.; Palmer, A. J.; Lawler, J. E.

    2015-08-01

    The radiative lifetimes of 72 odd-parity levels of neutral lanthanum are measured to ±5% accuracy using time-resolved laser-induced fluorescence on a slow atomic beam. The levels range in energy from 15031 to 32140 cm-1. Branching fraction measurements using Fourier-transform spectroscopy are attempted and completed for all of the 72 levels. The branching fractions, when combined with the radiative lifetimes, yield new transition probabilities for 315 lines of the first spectrum of lanthanum (La i ). This study is part of a larger body of work on the radiative properties of rare earth neutral atoms, and is motivated by research needs in lighting science and astrophysics.

  8. Magnetoresistance of lanthanum manganites with activation-type conductivity

    SciTech Connect

    Kurkin, M. I. Neifeld, E. A.; Korolev, A. V.; Ugryumova, N. A.; Gudin, S. A.; Gapontseva, N. N.

    2013-05-15

    The temperature dependence of the resistivity and magnetic moment of La{sub 0.85}Ba{sub 0.15}MnO{sub 3} and La{sub 0.85}Sr{sub 0.15}MnO{sub 3} manganite single crystals in magnetic fields up to 90 kOe is investigated. Analysis of the experimental results shows that the magnetoresistance of lanthanum manganites far from the Curie temperature T{sub C} can be described quantitatively by the s-d model normally used for ferromagnets and taking into account only the exchange interaction between the spins of charge carriers and magnetic moments. These data also show that the features of lanthanum manganites responsible for colossal magnetoresistance (CMR) are manifested in a narrow temperature interval {delta}T Almost-Equal-To 20 K near T{sub C}. Our results suggest a CMR mechanism analogous to the mechanism of giant magnetoresistance (GMR) observed in Fe/Cr-type multilayers with nanometer layer thickness. The nanostratification observed in lanthanum manganites and required for GMR can be described taking into account the spread in T{sub C} in the CMR range {delta}T.

  9. Recovery of zinc, cadmium, and lanthanum by biopolymer gel particles of alginic acid

    SciTech Connect

    Konishi, Yasuhiro; Asai, Satoru; Midoh, Yuji; Oku, Muneharu )

    1993-07-01

    Biopolymer gel particles of alginic acid were found to be a useful material for recovering zinc, cadmium, and lanthanum from aqueous solutions. The metals sorbed by the gel particles could be completely eluted by using dilute HCl solution of 0.1 kmol/m[sup 3]. The distribution ratios of the individual metals between the gel and liquid phases were measured by using a batch method. The equilibrium data were consistent with predictions made assuming that sorption takes place with the ion-exchange reaction between metal ions and alginic acid. The maximum sorption capacity of the gel particles and the distribution equilibrium constants for the metals were determined by comparing the experimental data with the theoretical predictions. The observed effect of temperature on the distribution equilibrium was insignificant in the range from 15 to 35[degrees]C. 17 refs., 6 figs., 1 tab.

  10. Observations of Multiple Bound-Bound Transitions in the Negative Ion of Lanthanum La-

    NASA Astrophysics Data System (ADS)

    Walter, C. W.; Gibson, N. D.; Matyas, D. J.; Crocker, C. T.; Dungan, K. A.; Matola, B. R.; Scharpf, M. T.; Rohlén, J.

    2013-05-01

    The negative ion of lanthanum has been investigated with tunable infrared laser photodetachment spectroscopy. The relative signal of neutral atom production was measured with a crossed laser-ion beam apparatus over the photon energy range 0.29 - 0.77 eV. The spectrum reveals a number of sharp peaks due to bound-bound electric-dipole transitions in La-, observed here through a two-step process of excitation followed by photodetachment of the upper state. The observed photodetachment spectrum is compared to theoretical calculations of energy levels and transition strengths by O'Malley and Beck. The richness of the observed bound state spectrum is unprecedented for atomic negative ions, and it highlights the unique properties of La- for applications such as laser cooling. This material is based on work supported by the National Science Foundation under Grant Nos. 0757976 and 1068308.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. Antibacterial effect of lanthanum calcium manganate (La0.67Ca0.33MnO3) nanoparticles against Pseudomonas aeruginosa ATCC 27853.

    PubMed

    De, Debasis; Mandal, Santi M; Gauri, Samiran S; Bhattacharya, Rabindranath; Ram, S; Roy, Sanat K

    2010-04-01

    Nanotechnology based water purification system and treatment of human diseases are of higher priority in the immediate future for economic and undetermined health purpose. Nanoparticles offer the possibility of an efficient removal of pollutants and microbes in water treatment. Here we have used colossal magnetoresistance (CMR) materials, lanthanum calcium manganate (LCMO) and Eu3+ doped lanthanum calcium manganate (LECMO) nanoparticles, to determine the antibacterial efficacy against Pseudomonas aeruginosa-ATCC 27853, a soil and water born pathogenic bacteria. The average size of the synthesized nanoparticles was varied from 50 nm to 200 nm and X-ray diffraction pattern showed the formation of a single phase LCMO or LECMO of an orthorhombic crystal structure after annealing the precursor at 1000 degrees C for 2 h in air. The data revealed that LCMO nanoparticle have higher antibacterial activity compared to LECMO nanoparticle. Thus, LCMO nanoparticles can offer future applications as antimicrobial drug and in water purification technology. PMID:20738067

  16. 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.

  17. Stability of solid oxide fuel cell materials

    SciTech Connect

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

    1995-08-01

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

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

    SciTech Connect

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

    2012-10-15

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

  19. MOCVD of very thin films of lead lanthanum titanate

    SciTech Connect

    Beach, D.B.; Vallet, C.E.

    1995-12-31

    Films of lead lanthanum titanate were deposited using metal-organic chemical vapor deposition (MOCVD) at temperatures between 500 and 550{degrees}C in a hot-wall reactor. The precursors used were Pb(THD){sub 2}, La(THD){sub 3}, and Ti(THD){sub 2}(I-OPr){sub 2} where THD = 2,2,6,6-tetramethyl-3,5-heptanedionate, O{sub 2}C{sub 11}H{sub 19}, and I-OPr = isopropoxide, OC{sub 3}H{sub 7}. The three precursors were delivered to the reactor using a single solution containing all three precursors dissolved in tetraglyme and the precursor solution was volatilized at 225{degrees}C. Films were deposited on Si and Si/Ti/Pt substrates, and characterized using Rutherford Backscattering Spectroscopy (RPS) and X-ray diffraction(XRD). Films deposited at 550{degrees}C had a composition which was close to that of the precursor solution while films deposited at 500{degrees}C were deficient in lanthanum. Even at 500{degrees}C, the desired perovskite phase showed an increase in the intensity of the X-ray lines, but did not change the width of these lines, implying the grain sizes had remained unchanged.

  20. Synthesis of lanthanum zirconium oxide nanomaterials through composite-hydroxide-mediated approach

    SciTech Connect

    Jin, Hongyun; Huang, Dan; Gao, Qiang; Li, Li; Wang, Ning; Wang, Yongqian; Hou, Shuen

    2012-01-15

    Graphical abstract: Lanthanum zirconium oxide (La{sub 2}Zr{sub 2}O{sub 7}) with cubic pyrochlore structure thermal barrier coatings (TBCs) materials have been synthesized through composite-hydroxide-mediated method at 200 Degree-Sign C. Compared with YSZ TBCs material, La{sub 2}Zr{sub 2}O{sub 7} showed more excellent thermal stability and lower thermal conductivity. Highlights: Black-Right-Pointing-Pointer La{sub 2}Zr{sub 2}O{sub 7} TBCs were synthesized through composite-hydroxide-mediated method. Black-Right-Pointing-Pointer The XRD patterns showed a single phase for La{sub 2}Zr{sub 2}O{sub 7} after treated at 1300 Degree-Sign C. Black-Right-Pointing-Pointer The thermal conductivity value of La{sub 2}Zr{sub 2}O{sub 7} was lower than that of YSZ. Black-Right-Pointing-Pointer La{sub 2}Zr{sub 2}O{sub 7} showed more excellent stability and lower thermal conductivity than YSZ. -- Abstract: A novel thermal barrier coating material, lanthanum zirconium oxide (La{sub 2}Zr{sub 2}O{sub 7}) has been synthesized through the composite-hydroxide-mediated method at low temperature. The phase structures, morphology, thermal stability and thermal conductivity of the as-synthesized La{sub 2}Zr{sub 2}O{sub 7} were investigated systematically. The X-ray diffraction (XRD) patterns revealed a single phase with cubic pyrochlore structure for La{sub 2}Zr{sub 2}O{sub 7} after treated at 1300 Degree-Sign C for 100 h. The transmission electron microscope (TEM) and scanning electron microscope (SEM) analyses showed that the sample was made up of sphere-like nanoparticles with the size between 50 and 100 nm. Furthermore, the thermal analysis result demonstrated the La{sub 2}Zr{sub 2}O{sub 7} sample had high thermal stability even at 1300 Degree-Sign C. As the temperature increased to 1200 Degree-Sign C, the thermal conductivity value could be as low as 1.75 W m{sup -1} K{sup -1}. Due to the high-temperature stability and lower thermal conductivity, the La{sub 2}Zr{sub 2}O{sub 7} material is

  1. Kr and Xe irradiations in lanthanum (La) doped ceria: Study at the high dose regime

    NASA Astrophysics Data System (ADS)

    Yun, Di; Oaks, Aaron J.; Chen, Wei-ying; Kirk, Marquis A.; Rest, Jeffrey; Insopov, Zinetula Z.; Yacout, Abdellatif M.; Stubbins, James F.

    2011-11-01

    In order to understand cavity and bubble formation and growth in oxide nuclear fuel materials, ion beam irradiation experiments were conducted with two common fission gas species: Kr and Xe. Ceria (CeO 2) was selected as a surrogate material for uranium dioxide (UO 2) due to its many similar properties to UO 2. Ion beam energies were chosen such that both cavities and gas bubbles structures were induced by ion irradiations. The ion irradiation experiments were carried out at 600 °C, at which temperature, cavity/gas bubble structures are believed to be immobile in this material. Lanthanum (La) was chosen as a dopant in CeO 2 to investigate the effect of impurities. The presence of La in the CeO 2 lattice also introduces a predictable initial concentration of oxygen vacancies, similar to the introduction of oxygen vacancies by the existence of Pu 3+ in MOX fuel [1]. The influence of two La concentrations, 5% and 25%, were examined. The study focused on the high dose regime where cavity/gas bubble structures were clearly identifiable with their sizes and number densities readily measurable. Cavity/gas bubble coarsening by coalescence was identified with TEM (Transmission Electron Microscopy) characterizations of as-irradiated La doped CeO 2 specimens. The results revealed that lanthanum trapping has significant influence on the cavity/bubble growth in the material lattice by comparing the cavity/gas bubble size distributions between 5% La doped ceria and 25% La doped ceria. Lattice and kinetic Monte Carlo calculations described in a previous work have provided insights to the interpretations of the experimental results [2]. Solid state Xe precipitates were observed in low energy Xe implantation in 5% La doped ceria to a very high fluence of 1 × 10 17 ions/cm 2 at 600 °C. The solid state Xe precipitate structures are represented by faceted morphology. Very similar observations of solid state/near solid state Xe bubbles were made by Nogita et al. in the outer region

  2. 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.

  3. 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.

  4. Waveshifting fiber readout of lanthanum halide scintillators

    NASA Astrophysics Data System (ADS)

    Case, G. L.; Cherry, M. L.; Stacy, J. G.

    2006-07-01

    Newly developed high-light-yield inorganic scintillators coupled to waveshifting optical fibers provide the capability of efficient X-ray detection and millimeter scale position resolution suitable for high-energy cosmic ray instruments, hard X-ray/gamma ray astronomy telescopes and applications to national security. The CASTER design for NASA's proposed Black Hole Finder Probe mission, in particular, calls for a 6 8 m2 hard X-ray coded aperture imaging telescope operating in the 20 600 keV energy band, putting significant constraints on cost and readout complexity. The development of new inorganic scintillator materials (e.g., cerium-doped LaBr3 and LaCl3) provides improved energy resolution and timing performance that is well suited to the requirements for national security and astrophysics applications. LaBr3 or LaCl3 detector arrays coupled with waveshifting fiber optic readout represent a significant advance in the performance capabilities of scintillator-based gamma cameras and provide the potential for a feasible approach to affordable, large area, extremely sensitive detectors. We describe some of the applications and present laboratory test results demonstrating the expected scintillator performance.

  5. 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.

  6. 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.

  7. Silver and lanthanum as effective modifiers in trace determination of cadmium in nickel-base alloys by electrothermal atomic absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Tsai, Suh-Jen Jane; Chang, Li-Lin; Chang, Shiow-Ing

    1997-01-01

    Trace cadmium in nickel-base superalloys was determined by a stabilized temperature platform furnace using atomic absorption spectrometry with a deuterium arc background correction system. The volatility of cadmium limits the pyrolysis temperature. This prevents the removal of the interfering alloy matrix at the thermal pretreatment step. Hence, an enormously high background signal has been observed. Chemical modifiers including ammonium citrate, 1-(2-pyridylazo)-naphthol, 4-(2pyridylazo)resorcinol, 2-(5-bromo-2-pyridylazo)-5-(diethylamino)-phenol, Triton-X 100, EDTA, potassium nitrate, palladium nitrate, magnesium nitrate, aluminum chloride, ammonium dihydrogen phosphate, lanthanum oxide, lanthanum chloride and silver nitrate have been studied. Matrix interferences were effectively reduced by silver and lanthanum. The 100-300°C increase in the pyrolysis temperature effectively reduced the non-specific absorption from the alloy matrix. Interferences from foreign ions were also investigated. The merit of the proposed method was increased by the excellent agreement between the certified and the experimental values of Cd in the standard reference material, IN100, and the recovery obtained (100-104%). The precision of six successive replicate measurements was 4.9% with Ag modifier and 2.5% with La modifier, respectively. The results of analysing Tracealloy B were also satisfactory.

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

    DOE PAGESBeta

    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

  10. 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.

  11. Phase transformation, thermal expansion and electrical conductivity of lanthanum chromite

    SciTech Connect

    Gupta, Sapna; Mahapatra, Manoj K.; Singh, Prabhakar

    2013-09-01

    Graphical abstract: - Highlights: • Orthorhombic and rhombohedral phases co-exist at ≥260 °C and cubic above 1000 °C. • Polymorphic changes with temperature in air and Ar–3%H{sub 2} are observed. • Lattice volume change in Ar–3%H{sub 2} atmosphere corresponds to Cr{sup 4+} → Cr{sup 3+} transition. • Change in valence state of Cr{sup 4+} to Cr{sup 3+} results in lower electrical conductivity. • Experimental evidence is provided for poor densification of LaCrO{sub 3} in air. - Abstract: This paper addresses discrepancies pertaining to structural, thermal and electrical properties of lanthanum chromite. Experimental evidence is provided to support the hypothesis for poor densification in air as well as reduction in electrical conductivity in reducing atmosphere. Sintering condition for the synthesis of LaCrO{sub 3} was optimized to 1450 °C and 10 h. Thermo-analytical (differential scanning calorimetry – DSC) and high temperature X-ray diffraction (HT-XRD) studies show that orthorhombic lanthanum chromite transforms into rhombohedral structure at ∼260 °C and cubic structure above 1000 °C. Co-existence of the structural phases and the variation in each polymorph with temperature in both air and 3%H{sub 2}–Ar atmosphere is reported. Presence and absence of Cr-rich phase at inter-particle neck are observed in oxidizing and reducing atmospheres respectively. The linear thermal expansion co-efficient was calculated to be 10.8 ± 0.2 × 10{sup −6} °C{sup −1} in the temperature range of RT–1400 °C. Electrical conductivity of lanthanum chromite was found to be 0.11 S/cm in air. A decrease in electrical conductivity (0.02 S/cm at 800 °C) of LaCrO{sub 3}, as observed in reducing atmosphere (3%H{sub 2}–Ar), corresponds to lattice volume change as indicated by peak shift in HT-XRD results.

  12. Effect of Adsorbed Nitrogen on the Thermionic Emission from Lanthanum Hexaboride

    NASA Technical Reports Server (NTRS)

    Carter, Arlen F.; Wood, George P.

    1959-01-01

    The emission properties of lanthanum hexaboride in an atmosphere of nitrogen were investigated. The emitter was not poisoned by adsorbed nitrogen. This result should have application to magnetohydrodynamic devices in which electron flow from channel walls is required.

  13. METAL INTERACTIONS AT SULFIDE MINERAL SURFACES. PART 2. ADSORPTION AND DESORPTION OF LANTHANUM

    EPA Science Inventory

    Batch-type adsorption experiments with four sulfide minerals (chalcocite, galena, pyrite, and sphalerite) were used to investigate the adsorption and desorption behavior of lanthanum (III) in the presence of ethylenediaminetetraacetic acid (EDTA), a model humic substance. Linear ...

  14. 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

  15. Thermoelectric Power Generation from Lanthanum Strontium Titanium Oxide at Room Temperature through the Addition of Graphene.

    PubMed

    Lin, Yue; Norman, Colin; Srivastava, Deepanshu; Azough, Feridoon; Wang, Li; Robbins, Mark; Simpson, Kevin; Freer, Robert; Kinloch, Ian A

    2015-07-29

    The applications of strontium titanium oxide based thermoelectric materials are currently limited by their high operating temperatures of >700 °C. Herein, we show that the thermal operating window of lanthanum strontium titanium oxide (LSTO) can be reduced to room temperature by the addition of a small amount of graphene. This increase in operating performance will enable future applications such as generators in vehicles and other sectors. The LSTO composites incorporated one percent or less of graphene and were sintered under an argon/hydrogen atmosphere. The resultant materials were reduced and possessed a multiphase structure with nanosized grains. The thermal conductivity of the nanocomposites decreased upon the addition of graphene, whereas the electrical conductivity and power factor both increased significantly. These factors, together with a moderate Seebeck coefficient, meant that a high power factor of ∼2500 μWm(-1)K(-2) was reached at room temperature at a loading of 0.6 wt % graphene. The highest thermoelectric figure of merit (ZT) was achieved when 0.6 wt % graphene was added (ZT = 0.42 at room temperature and 0.36 at 750 °C), with >280% enhancement compared to that of pure LSTO. A preliminary 7-couple device was produced using bismuth strontium cobalt oxide/graphene-LSTO pucks. This device had a Seebeck coefficient of ∼1500 μV/K and an open voltage of 600 mV at a mean temperature of 219 °C. PMID:26095083

  16. 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. PMID:24971668

  17. 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.

  18. 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.

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

    DOE PAGESBeta

    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

  20. Timing resolution measurements of a 3 in. lanthanum bromide detector

    NASA Astrophysics Data System (ADS)

    Galli, L.; De Gerone, M.; Dussoni, S.; Nicolò, D.; Papa, A.; Tenchini, F.; Signorelli, G.

    2013-08-01

    Cerium-doped lanthanum bromide (LaBr3:Ce) is a scintillator that presents very good energy and timing resolutions and it is a perfect candidate for photon detector in future experiments to search for lepton flavor violation as in μ → eγ or μ → e conversion. While energy resolution was thoroughly investigated, timing resolution at several MeV presents some experimental challenge. We measured the timing resolution of a 3 in.×3 in. cylindrical LaBr3(Ce) crystal versus few reference detectors by means of a nuclear reaction from a Cockcroft-Walton accelerator that produces coincident γ-rays in the 4.4-11.6 MeV range. Preliminary results allow us to extrapolate the properties of a segmented γ-ray detector in the 50-100 MeV range.

  1. Sputtering studies during lanthanum implantation in stainless steels

    NASA Astrophysics Data System (ADS)

    Ager, F. J.; Respaldiza, M. A.; Soares, J. C.; da Silva, M. F.; Odriozola, J. A.

    1997-05-01

    Lanthanum ions of 100 keV have been implanted in AISI304 specimens at different doses. The erosion or sputtering of the surface atoms, either from the steel matrix or already implanted, during the implantation process imposes a limitation on the maximum implantable dose. Hoping to increase this dose, we deposited thin layers of aluminium and alumina (Al 2O 3) on top of steel samples of similar composition and sputtering behaviour (AISI302), as the sputtering effect is much weaker on such species and this layer could also prevent the steel atoms from being removed from the surface. The experimental determination of the sputtering coefficients, total or partial, and its comparison with theoretical values, when possible, is another aim of this work.

  2. Tribological behaviors of lanthanum-based phosphonate 3-aminopropyltriethoxysilane self-assembled films

    NASA Astrophysics Data System (ADS)

    Gu, Qinlin; Cheng, Xianhua

    2007-06-01

    Lanthanum-based thin films deposited on the phosphonate 3-aminopropyltriethoxysilane (APTES) self-assembled monolayer (SAM) were prepared on the hydroxylated glass substrate by a self-assembling process from specially formulated solution. Chemical compositions of the films and chemical state of the elements were detected by X-ray photoelectron spectrometry (XPS). The thickness of the films was determined with an ellipsometer, while the morphologies of the original and worn surfaces of the samples were analyzed by means of atomic force microscopy (AFM) and scanning electron microscopy (SEM), respectively. The tribological properties of the films sliding against GCr15 steel ball were evaluated on a UMT-2MT reciprocating friction and wear tester. As the results, the target film was obtained and reaction may have taken place between the film and the glass substrate. The tribological results show that lanthanum-based thin films are superior in reducing friction and resisting wear compared with APTES-SAM and phosphorylated APTES-SAM. SEM observation of the morphologies of worn surfaces indicates that the wear of APTES-SAM and the phosphorylated APTES-SAM is characteristic of brittle fracture and severe abrasion. Differently, slight abrasion and micro-crack dominate the wear of lanthanum-based thin films. The superior friction reduction and wear resistance of lanthanum-based thin films are attributed to the enhanced load-carrying capacity of the inorganic lanthanum particles in the lanthanum-based thin films as well as good adhesion of the films to the substrate.

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

    PubMed Central

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

    2012-01-01

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

  4. 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

  5. Boron ion beam generation utilizing lanthanum hexaboride cathodes: Comparison of vacuum arc and planar magnetron glow

    NASA Astrophysics Data System (ADS)

    Nikolaev, A. G.; Oks, E. M.; Vizir, A. V.; Yushkov, G. Yu.; Frolova, V. P.

    2016-02-01

    Boron ion beams are widely used for semiconductor ion implantation and for surface modification for improving the operating parameters and increasing the lifetime of machine parts and tools. For the latter application, the purity requirements of boron ion beams are not as stringent as for semiconductor technology, and a composite cathode of lanthanum hexaboride may be suitable for the production of boron ions. We have explored the use of two different approaches to boron plasma production: vacuum arc and planar high power impulse magnetron in self-sputtering mode. For the arc discharge, the boron plasma is generated at cathode spots, whereas for the magnetron discharge, the main process is sputtering of cathode material. We present here the results of comparative test experiments for both kinds of discharge, aimed at determining the optimal discharge parameters for maximum yield of boron ions. For both discharges, the extracted ion beam current reaches hundreds of milliamps and the fraction of boron ions in the total extracted ion beam is as high as 80%.

  6. Infiltrated lanthanum strontium chromite anodes for solid oxide fuel cells: Structural and catalytic aspects

    NASA Astrophysics Data System (ADS)

    Oh, Tae-Sik; Yu, Anthony S.; Adijanto, Lawrence; Gorte, Raymond J.; Vohs, John M.

    2014-09-01

    Infiltration is a widely used fabrication method for solid oxide fuel cell (SOFC) composite electrodes. Here we report a study of the structure and electrocatalytic properties of SOFC anodes composed of a layer of lanthanum, strontium chromite (La0.8Sr0.2CrO3, LSCr), both with and without added transition metal dopants, infiltrated into a porous yttria-stabilized zirconia (YSZ) matrix. The structural evolution of the electrode upon reduction and under typical SOFC operating conditions is compared to that reported previously for La0.8Sr0.2Cr0.5Mn0.5O3-YSZ composite anodes. For the transition metal doped materials, a portion of the metal dopants were found to be exsolved from the LSCr lattice upon reduction and to be effective in promoting electro-oxidation of hydrogen. Exsolved cobalt particles were also found to be relatively stable when exposed to hydrocarbon fuels with low activity for the formation of carbon deposits.

  7. Boron ion beam generation utilizing lanthanum hexaboride cathodes: Comparison of vacuum arc and planar magnetron glow.

    PubMed

    Nikolaev, A G; Oks, E M; Vizir, A V; Yushkov, G Yu; Frolova, V P

    2016-02-01

    Boron ion beams are widely used for semiconductor ion implantation and for surface modification for improving the operating parameters and increasing the lifetime of machine parts and tools. For the latter application, the purity requirements of boron ion beams are not as stringent as for semiconductor technology, and a composite cathode of lanthanum hexaboride may be suitable for the production of boron ions. We have explored the use of two different approaches to boron plasma production: vacuum arc and planar high power impulse magnetron in self-sputtering mode. For the arc discharge, the boron plasma is generated at cathode spots, whereas for the magnetron discharge, the main process is sputtering of cathode material. We present here the results of comparative test experiments for both kinds of discharge, aimed at determining the optimal discharge parameters for maximum yield of boron ions. For both discharges, the extracted ion beam current reaches hundreds of milliamps and the fraction of boron ions in the total extracted ion beam is as high as 80%. PMID:26931963

  8. 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.

  9. Growth of Lithium Lanthanum Titanate Nanosheets and Their Application in Lithium-Ion Batteries.

    PubMed

    Lin, Xi; Wang, Hongqiang; Du, Haiwei; Xiong, Xinrun; Qu, Bo; Guo, Zaiping; Chu, Dewei

    2016-01-20

    In this work, lithium-doped lanthanum titanate (LLTO) nanosheets have been prepared by a facile hydrothermal approach. It is found that with the incorporation of lithium ions, the morphology of the product transfers from rectangular nanosheets to irregular nanosheets along with a transition from La2Ti2O7 to Li0.5La0.5TiO3. The as-prepared LLTO nanosheets are used to enhance electrochemical performance of the LiCo1/3Ni1/3Mn1/3O2 (CNM) electrode by forming a higher lithium-ion conductive network. The LiCo1/3Ni1/3Mn1/3O2-Li0.5La0.5TiO3 (CNM-LLTO) electrode shows better a lithium diffusion coefficient of 1.5 × 10(-15) cm(2) s(-1), resulting from higher lithium-ion conductivity of LLTO and shorter lithium diffusion path, compared with the lithium diffusion coefficient of CNM electrode (5.44 × 10(-16) cm(2) s(-1)). Superior reversibility and stability are also found in the CNM-LLTO electrode, which retains a capacity at 198 mAh/g after 100 cycles at a rate of 0.1 C. Therefore, it can be confirmed that the existence of LLTO nanosheets can act as bridges to facilitate the lithium-ion diffusion between the active materials and electrolytes. PMID:26697735

  10. Photocatalytic conversion of gaseous ethylbenzene on lanthanum-doped titanium dioxide nanotubes.

    PubMed

    Cheng, Zhuo-Wei; Feng, Li; Chen, Jian-Meng; Yu, Jian-Ming; Jiang, Yi-Feng

    2013-06-15

    The photocatalytic properties of titanium dioxide (TiO₂) make it an attractive material for environmental remediation. In the present study, lanthanum (La(3+))-doped TiO2 nanotubes with excellent photocatalytic activity were fabricated by a combination of sol-gel method and hydrothermal technique. The optimal preparation parameters were determined by the structural characterization using a range of methods and the photocatalytic degradation of gaseous ethylbenzene (EB). Compared with pure TiO₂ nanoparticles, 1.2%-La(3+)-doped - titania nanotubes (1.2%-La(3+)-TNTs) exhibited higher activity under 254 nm UV for conversion of EB. The initial EB concentrations and relative humidity (RH) obviously influenced the photocatalytic activity of 1.2%-La(3+)-TNTs. Kinetic analysis showed that surface adsorption and surface reaction controlled the rate-determining step for RH of 40-50% and >80%, respectively. Gas chromatography and mass spectrometry were used to analyze the intermediates generated in the conversion of EB, allowing a tentative decomposition pathway to be proposed. The prepared photocatalyst exhibited enhanced EB conversion compared with undoped TiO₂, and showed a promise for the decomposition of recalcitrant compounds before subsequent biopurification. PMID:23643959

  11. Thermal and mechanical effects on large field dielectric loss in lanthanum-doped lead zirconate titanate

    NASA Astrophysics Data System (ADS)

    Gallagher, John A.; Jo, Hwan Ryul; Lynch, Christopher S.

    2013-04-01

    Ferroelectric material losses in devices ranging from sonar transducers to energy harvesters result in the conversion of energy to heat. Under small amplitude sinusoidal drive, either electrical or mechanical, the losses are expressed in terms of a loss tangent. This study addressed the effects of temperature and bias stress on large field dielectric loss in the presence of thermal and mechanical loading in lanthanum-doped lead zirconate titanate, Pb0.92La0.08(Zr0.65Ti0.35)0.98O3 (PLZT 8/65/35). This loss is associated with domain wall motion. Large field dielectric loss was experimentally measured using a technique that matches the area within a unipolar electric displacement - electric field hysteresis loop to an equivalent area ellipse-shaped hysteresis loop. The results indicate that the dependence of dielectric loss on bias stress changes with the onset of a thermally induced transition to slim loop behavior. Stress causes the dielectric loss to increase at low temperature and decrease at high temperature. This is consistent with changes in remnant polarization and saturation of the unipolar electric field - electric displacement hysteresis loops.

  12. Tuning the architecture and properties of microstructured yttrium tungstate oxide hydroxide and lanthanum tungstate.

    PubMed

    Kaczmarek, Anna M; Liu, Ying-Ya; Van der Voort, Pascal; Van Deun, Rik

    2013-04-21

    In this paper, various microstructures of yttrium and lanthanum tungstates were synthesized under hydrothermal conditions, at pH 5, in a ligand-free environment, and in the presence of a dioctyl sodium sulfosuccinate (DSS) surfactant. It was observed that the shape of the nanobuilding blocks, and therefore the architecture of the microstructures, could be tuned by controlling the reaction conditions, such as the source of the rare earth, the amount of a surfactant and the reaction time. X-ray powder diffraction (XRD), elemental analysis, scanning electron microscopy (SEM), and N2 adsorption were employed to characterize the obtained products. The photoluminescent properties of Eu(3+) and Dy(3+) doped tungstate materials were investigated. Luminescence measurements showed an efficient charge transfer from the WO4(2-) groups to Eu(3+) and Dy(3+) ions. It was found that under UV excitation the Dy(3+) doped Y(WO3)2(OH)3 and La2(WO4)3 precursors exhibit white emission. PMID:23426044

  13. High temperature thermal conductivity measurements on lanthanum sulfides using the flash method

    NASA Technical Reports Server (NTRS)

    Vandersande, J. W.; Wood, C.; Zoltan, A.; Whittenberger, D.

    1988-01-01

    In the past, high temperature specific heat and hence thermal conductivity measurements, using the flash method have not been very accurate. This is due to the difficulty of exactly determining the amount of heat deposited on the front face of a sample during each flash. This problem has now been solved by sputtering a thin layer of graphite on the standard reference and test samples. Data taken shows that the amount of heat deposited can now be determined to within about 2 percent resulting in more accurate thermal conductivity data. The results of measurements on several lanthanum sulfides with stoichiometries between LaS(1.35) and LaS(1.48) are reported and show a minimum in the lattice thermal conductivity at a composition of around LaS(1.41). This is believed to be due to the scattering of low-frequency phonons by large defects, i.e., second phase material (beta-phase) and pores.

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

    PubMed

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

    2013-02-01

    A conventional human pharmacokinetic (PK) in vivo study is often considered as the "gold standard" to determine bioequivalence (BE) of drug products. However, this BE approach is not always applicable to the products not intended to be delivered into the systemic circulation. For locally acting gastrointestinal (GI) products, well designed in vitro approaches might be more practical in that they are able not only to qualitatively predict the presence of the active substance at the site of action but also to specifically assess the performance of the active substance. For example, lanthanum carbonate chewable tablet, a locally acting GI phosphate binder when orally administrated, can release free lanthanum ions in the acid environment of the upper GI tract. The lanthanum ions directly reach the site of action to bind with dietary phosphate released from food to form highly insoluble lanthanum-phosphate complexes. This prevents the absorption of phosphate consequently reducing the serum phosphate. Thus, using a conventional PK approach to demonstrate BE is meaningless since plasma levels are not relevant for local efficacy in the GI tract. Additionally the bioavailability of lanthanum carbonate is less than 0.002%, and therefore, the PK approach is not feasible. Therefore, an alternative assessment method is required. This paper presents an in vitro approach that can be used in lieu of PK or clinical studies to determine the BE of lanthanum carbonate chewable tablets. It is hoped that this information can be used to finalize an in vitro guidance for BE studies of lanthanum carbonate chewable tablets as well as to assist with "in vivo" biowaiver decision making. The scientific information might be useful to the pharmaceutical industry for the purpose of planning and designing future BE studies. PMID:23249191

  15. Crystal structure of Eu-doped magnetoplumbite-type lanthanum aluminum oxynitride with emission site splitting

    SciTech Connect

    Masubuchi, Yuji; Hata, Tomoyuki; Motohashi, Teruki; Kikkawa, Shinichi

    2011-09-15

    Eu-doped lanthanum aluminum oxynitride (LaAl{sub 12}(O,N){sub 19}) with magnetoplumbite structure was prepared by nitridation of the oxide precursor obtained from aluminum glycine gel and subsequent post-annealing. Eu-doped lanthanum aluminum oxynitride exhibited blue light emission at 440 nm with a shoulder at 464 nm under excitation at 254 nm. Isostructural Eu-doped calcium aluminum oxide (CaAl{sub 12}O{sub 19}) exhibited a single emission peak at 415 nm. Structural refinement using neutron powder diffraction indicated that the lanthanum site occupied partially by Eu{sup 2+} splits into 2d and 6h sites in the aluminum oxynitride. The longer emission and the shoulder peak in the former aluminum oxynitride were observed in relation to the increasing covalency as well as crystal field splitting around doped Eu{sup 2+} induced by site splitting involved with the two kinds of anions. - Graphical Abstract: Magnetoplumbite type Eu-doped lanthanum aluminum oxynitride has lanthanum site splitting induced by two kinds of anions, causing two emission peaks. Highlights: > Magnetoplumbite type LaAl{sub 12}(O,N){sub 19} doped with Eu shows emission peak splitting. > ND analysis is performed on La{sub 0.97}Eu{sub 0.03}Al{sub 12}(O,N){sub 19} and Ca{sub 0.97}Eu{sub 0.03}Al{sub 12}O{sub 19}. > La{sub 0.97}Eu{sub 0.03}Al{sub 12}(O,N){sub 19} has lanthanum site splitting. > The lanthanum site splitting is induced by coexisting of two kinds of anions.

  16. 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.

  17. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

    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.

  19. 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

  20. Development of Lanthanum Bromide and Lanthanum Chloride Scintillator Detectors for Hard X-ray Astronomy

    NASA Astrophysics Data System (ADS)

    Bloser, Peter F.; Budden, B. S.; Case, G. L.; Cherry, M. L.; Macri, J. R.; McConnell, M. L.; Ryan, J. M.

    2006-09-01

    Advanced scintillator materials such as LaBr3:Ce and LaCl3:Ce hold great promise for future hard X-ray and gamma-ray astrophysics missions due to their high density, high light output, good linearity, and fast decay times. Of particular importance for future space-based imaging instruments, such as coded-aperture telescopes, are the precise spatial location of individual gamma-ray interactions and the susceptibility of the material to radiation damage. We have investigated the position and energy resolution achievable within LaBr3:Ce and LaCl3:Ce crystals (both monolithic and pixellated) using a variety of readout techniques, including position-sensitive photomultiplier tubes, multi-anode photomultiplier tubes, and orthogonal layers of wavelength-shifting fibers. We have also exposed LaBr3:Ce and LaCl3:Ce detectors to high-energy proton irradiation in order to study any radiation damage and activation. We present the results of these tests and discuss the applicability of such advanced scintillators to future high-energy imaging astrophysics missions.

  1. 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

  2. Lanthanum: new drug. Hyperphosphataemia in dialysis patients: more potential problems than benefits.

    PubMed

    2007-04-01

    (1) In dialysis patients with chronic renal failure, hyperphosphataemia can cause osteorenal dystrophy, leading to bone pain, fractures and excess cardiovascular mortality. In addition to a low-phosphorus diet and dialysis, phosphorus chelators are usually needed to control blood phosphorus levels. The first choice is calcium carbonate, and sevelamer is an alternative. (2) Lanthanum carbonate, a phosphorus chelator, is now also licensed for the treatment of hyperphosphataemia in dialysis patients with chronic renal failure. (3) In addition to three dose-finding placebo-controlled studies, clinical evaluation includes 2 comparative randomised unblinded trials: one 6-month trial versus calcium carbonate and a 2-year trial versus other phosphorus chelators. During these trials, lanthanum was no more effective than the comparators in terms of effects on the mortality rate, incidence of fractures, or blood phosphorus level. (4) During these trials, adverse events attributed to treatment were more frequent with lanthanum than with the other phosphorus chelators. The main problems were gastrointestinal disorders (nausea, vomiting, diarrhoea, constipation and abdominal pain), headaches, seizures, and encephalopathy. (5) The accumulation of lanthanum in the bones and brain is troubling. The known long-term adverse effects of aluminium, another trivalent cation with weak gastrointestinal absorption, suggest that caution is also required with lanthanum. (6) In practice, when a phosphorus chelator is needed to treat hyperphosphataemia in dialysis patients with chronic renal failure, calcium carbonate is the first choice and sevelamer remains the best alternative. PMID:17458039

  3. Enhancement of ferromagnetic and dielectric properties of lanthanum doped bismuth ferrite nanostructures

    SciTech Connect

    Chaudhuri, A.; Mandal, K.

    2012-04-15

    Highlights: Black-Right-Pointing-Pointer Rod shaped lanthanum doped bismuth ferrite was obtained. Black-Right-Pointing-Pointer The diameter of the particles were found to be decreasing on doping with lanthanum. Black-Right-Pointing-Pointer Both ferromagnetic and dielectric properties enhanced. Black-Right-Pointing-Pointer A transition due to spin canting is observed near 550 Degree-Sign C. Black-Right-Pointing-Pointer Electron spin resonance study shows the breakage of spin cycloid due to doping. -- Abstract: Cylindrical-shaped multiferroic Bi{sub 1-x}La{sub x}FeO{sub 3} (x = 0.0, 0.05, 0.1 and 0.15) were synthesized successfully by hydrothermal method. All samples were found to be rhombohedrally distorted perovskite structure. Diameter of the cylindrical particles reduces from {approx}450 nm for x = 0.0 to {approx}100 nm for x = 0.1 prepared under the same conditions. The Neel temperature as well as the dielectric constant was also found to increase with the increase in lanthanum content. Lanthanum doping also enhanced the magnetic properties. Magnetization measurements above room temperature show a significant increase in magnetization at around 400 Degree-Sign C. Enhanced magnetic properties due to lanthanum doping are caused by the breakage of spin cycloid as observed by electron spin resonance study.

  4. Column biosorption of lanthanum and europium by Sargassum.

    PubMed

    Diniz, Vivian; Weber, Martin E; Volesky, Bohumil; Naja, Ghinwa

    2008-01-01

    Batch and column biosorption of La(3+) (lanthanum) and Eu(3+) (europium) was studied using protonated Sargassum polycystum biomass. The ion exchange sorption mechanism was confirmed by the proportional release of protons and by the total normality of the solution, which remained constant during the process. Equilibrium isotherms were determined for the binary systems, La/H and Eu/H for a total normality of 3 meq g(-1), which produced separation factors of 2.7 and 4.7, respectively, demonstrating a higher affinity of the biomass towards europium. Column runs with a single metal feed were used to estimate the intra-particle mass transfer coefficients for La and Eu (6.0 x 10(-4) and 3.7 x 10(-4) min(-1), respectively). Modeling batch and column binary systems with proton as the common ion was able to predict reasonably well the behavior of a ternary system containing protons. The software FEMLAB was used for solving the set of coupled partial differential equations. Moreover, a series of consecutive sorption/desorption runs demonstrated that the metal could be recovered and the biomass reused in multiple cycles by using 0.1N HCl with no apparent loss in the biosorbent metal uptake capacity. PMID:17707878

  5. Transport properties of silver-calcium doped lanthanum manganite

    NASA Astrophysics Data System (ADS)

    Cherif, B.; Rahmouni, H.; Smari, M.; Dhahri, E.; Moutia, N.; Khirouni, K.

    2015-01-01

    Electrical properties of silver-calcium doped lanthanum manganite (La0.5Ca0.5-xAgxMnO3 with 0.0

  6. 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

  7. Performance of Lanthanum Strontium Manganite Electrodes at High Pressure

    SciTech Connect

    Thomsen, Edwin C.; Coffey, Greg W.; Pederson, Larry R.; Marina, Olga A.

    2009-06-15

    The high-pressure performance of lanthanum strontium manganite (LSM), LSM-zirconia, and LSM/ceria composite electrodes was studied by impedance spectroscopy and dc methods. Electrode resistances decreased in proportion to P(O2)1/2 for the LSM electrode in both cathodic and anodic directions to at least 100 atm, a decrease that was attributed to dissociative oxygen adsorption, surface diffusion, and related phenomena. For the LSM-20/zirconia composite electrode, resistances decreased in proportion to P(O2)1/4 across the entire pressure range considered. Two principal features appeared in the impedance spectra, one that showed a P(O2)1/4 dependence attributed to charge transfer reactions, and one that was nearly pressure-independent, possibly due to transport in the zirconia portion of the composite. For the LSM-20/ceria composite electrode, resistances decreased as P(O2)0.3-0.4 at high pressure, depending on temperature. Two features appeared in the impedance spectra: one at low to intermediate frequency having a P(O2)1/2 dependence and one at high frequency having a P(O2)1/4 dependence. These features are attributed to dissociative oxygen adsorption and to charge transfer reactions, respectively. Results suggest that cathodic losses can be substantially lowered by operation of solid oxide fuel cells at greater than ambient pressure.

  8. Ecotoxicological assessment of lanthanum with Caenorhabditis elegans in liquid medium.

    PubMed

    Zhang, Haifeng; He, Xiao; Bai, Wei; Guo, Xiaomei; Zhang, Zhiyong; Chai, Zhifang; Zhao, Yuliang

    2010-12-01

    With their widespread applications in industry, agriculture and many other fields, more and more rare earth elements (REEs) are getting into the environment, especially the aquatic systems. Therefore, understanding the aquatic ecotoxicity of REEs has become more and more important. In the present work, Caenorhabditis elegans (C. elegans) was used as a test organism and life-cycle endpoints were chosen along with elemental assay to evaluate the aquatic toxicity of lanthanum (La), a representative of REEs. The results show La³+ had significant adverse effects on the growth and reproduction of worms above a concentration of 10 μmol L⁻¹. The elemental mapping by microbeam synchrotron radiation X-ray fluorescence (μ-SRXRF) illustrated how La treatment disturbed the metals distribution in the whole body of a single tiny nematode at lower levels. Our results suggested that the high-level REEs in some polluted water bodies would lead to an aquatic ecological crisis. The assessment we performed in the present work could be developed as a standardized test design for aquatic toxicological research. PMID:21510015

  9. Proton-Proton Correlation in Central Collisions of Lanthanum + Lanthanum at 1.2 Gev/a

    NASA Astrophysics Data System (ADS)

    Chang, James W.

    1992-01-01

    Central collisions between 1.2 GeV/A lanthanum projectiles and lanthanum nuclei are analysed for HBT-based proton-proton (pp) correlation. The La + La collision system is unique in that it has both the largest beam and beam + target size in any of the pp correlation analyses performed. The data is obtained from LBL's BEVALAC experiment E684HX. The time-of-flight system also with the Heavy Ion Spectrometer System (HISS) allows identification of protons at average mass resolution of 40.6 MeV (5%). The systematic background is removed from the correlation by the event-mixing method. The correlation from data is compared to the calculated correlation which uses a Gaussian source distribution and pp wavefunction resulting from Fermi statistics, S-wave Reid soft-core nuclear potential, and full Coulomb potential. The RMS radius of the La + La system is found to be 4.90 +/- 0.22 fm when systematic corrections are applied. When this radius (r_sp{RMS}{p }) is compared to the radius obtained using pion-pion correlation on the same data (r_sp {RMS}{pi} = 7.31 +/- 0.29 fm), it is found that the r _sp{RMS}{p}/r_sp{RMS }{pi} ratio is 0.67. Survey of other proton and pion correlation results from same systems reveal that r_sp{RMS} {p} < r_sp{RMS}{pi } in general, with the ratio r_sp {RMS}{p}/r_sp{RMS} {pi} decreasing with increase in colliding system size. Survey of pp correlation results from other experiments are considered to test the bore -cut and billiard-ball models. It is found that when the system is large (A_{total} > 118), the bore-cut model underestimates the size, and the billiard-ball model overestimates the size. The billiard -ball model looks attractive due to the smoothness of the transition between correct size estimation and overestimation. A conjecture is made that if this model is true, then the over-estimation of size may be a signature of nucleon density increase at large colliding systems. Compromise scenarios between the bore-cut and billiard-ball models

  10. Effect of production conditions on the corrosion resistance of lanthanum hexaboride powders and parts made from them

    SciTech Connect

    Paderno, Y.B.; Dudnik, E.M.; Masyuk, T.V.; Tkasch, A.V.; Zaitseva, A.Z.

    1985-10-01

    The authors studied the effect of chemical and thermal treatments of an industrial LaB6 powder on the corrosion resistance of the powder itself and parts pressed hot from it. To start, two batches of an industrial lanthanum hexaboride powder were used; and any boron oxide present removed by washing the powders with warm distilled water. To free the powders of lanthanum borates and lanthanum oxide, the powders were treated with a hydrochloric acid solution. The authors determine that this hydrochloric acid cleaning method is an effective means of ridding an industrial lanthanum hexaboride powder of impurities. It is also shown that acid treatment of industrial LaB6 powders substantially improves the corrosion resistance of parts made from them by powder metallurgy techniques. Also, a mechanism of rupture of hotpressed and sintered lanthanum hexaboride parts is proposed.

  11. Oxygen sorption and desorption properties of selected lanthanum manganites and lanthanum ferrite manganites.

    PubMed

    Nielsen, Jimmi; Skou, Eivind M; Jacobsen, Torben

    2015-06-01

    Temperature-programmed desorption (TPD) with a carrier gas was used to study the oxygen sorption and desorption properties of oxidation catalysts and solid-oxide fuel cell (SOFC) cathode materials (La(0.85) Sr(0.15)0.95 MnO(3+δ) (LSM) and La(0.60) Sr(0.40) Fe(0.80) Mn(0.20) O(3-δ) (LSFM). The powders were characterized by X-ray diffractometry, atomic force microscopy (AFM), and BET surface adsorption. Sorbed oxygen could be distinguished from oxygen originating from stoichiometry changes. The results indicated that there is one main site for oxygen sorption/desorption. The amount of sorbed oxygen was monitored over time at different temperatures. Furthermore, through data analysis it was shown that the desorption peak associated with oxygen sorption is described well by second-order desorption kinetics. This indicates that oxygen molecules dissociate upon adsorption and that the rate-determining step for the desorption reaction is a recombination of monatomic oxygen. Typical problems with re-adsorption in this kind of TPD setup were revealed to be insignificant by using simulations. Finally, different key parameters of sorption and desorption were determined, such as desorption activation energies, density of sorption sites, and adsorption and desorption reaction order. PMID:25784205

  12. Eutrophication management in surface waters using lanthanum modified bentonite: A review.

    PubMed

    Copetti, Diego; Finsterle, Karin; Marziali, Laura; Stefani, Fabrizio; Tartari, Gianni; Douglas, Grant; Reitzel, Kasper; Spears, Bryan M; Winfield, Ian J; Crosa, Giuseppe; D'Haese, Patrick; Yasseri, Said; Lürling, Miquel

    2016-06-15

    This paper reviews the scientific knowledge on the use of a lanthanum modified bentonite (LMB) to manage eutrophication in surface water. The LMB has been applied in around 200 environments worldwide and it has undergone extensive testing at laboratory, mesocosm, and whole lake scales. The available data underline a high efficiency for phosphorus binding. This efficiency can be limited by the presence of humic substances and competing oxyanions. Lanthanum concentrations detected during a LMB application are generally below acute toxicological threshold of different organisms, except in low alkalinity waters. To date there are no indications for long-term negative effects on LMB treated ecosystems, but issues related to La accumulation, increase of suspended solids and drastic resources depletion still need to be explored, in particular for sediment dwelling organisms. Application of LMB in saline waters need a careful risk evaluation due to potential lanthanum release. PMID:26706125

  13. Improved chemical stability and conductivity of barium cerate nanopowders by Lanthanum doping.

    PubMed

    Lee, Hunhyeong; Park, Inyu; Shin, Dongwook

    2013-09-01

    Despite of the highest proton conductivity, barium cerate electrolytes are well known for the deficiency of chemical stability at elevated temperature under CO2 atmosphere. This work is focused on improving chemical stability of lanthanum doped barium cerate (BCL) powder for electrolyte. Although lanthanum doping causes distortion of perovskite structure lattice, immoderate doping could stabilize structure due to increasing symmetry of structure lattices. The thermogravimetric analysis and AC impedance measurements revealed that the lanthanum doping suppresses the reaction between barium and carbonate and this effect results in sufficient improvement in ionic conductivity in operating temperatures range. It was confirmed that BaCe0.7La0.3O3-delta (BCL30) was the most stable composition and the conductivity of BCL30 is high as 3.8 S x cm(-1) x K at 700 degrees C. PMID:24205607

  14. Fabrication of Nanosized Lanthanum Zirconate Powder and Deposition of Thermal Barrier Coating by Plasma Spray Process

    NASA Astrophysics Data System (ADS)

    Mishra, S. K.; Jagdeesh, N.; Pathak, L. C.

    2016-07-01

    The present manuscript discusses our findings on fabrication of nanosized lanthanum zirconate powder for thermal barrier coating application and its coating by plasma spray on nickel-based superalloy substrate. Single-phase La2Zr2O7 coating of thickness of the order of 45 µm on the Ni-Cr-Al bond coat coated Ni-based superalloy substrate was deposited by plasma spray process. The layers at the interface did not show spallation and inter diffusion was very less. The microstructure, interface, porosity, and mechanical properties of different layers are investigated. The lanthanum zirconate hardness and modulus were 10.5 and 277 GPa, respectively. The load depth curve for lanthanum zirconate showed good elastic recovery around 74%.

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

    PubMed

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

    2014-12-01

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

  16. Effects of verapamil, dantrolene and lanthanum on catecholamine release from rat adrenal medulla.

    PubMed Central

    Cohen, J; Gutman, Y

    1979-01-01

    1. The release of catecholamines (CA) from rat adrenal incubated in vivo in Locke solution was studied. 2. Acetylcholine-induced release of CA and CA release by 56 mM KCl were inhibited by verapamil and lanthanum chloride which block calcium permeability. 3. CA secretion induced by salbutamol or by theophylline was unaffected by either verapamil or lanthanum chloride. 4. Dantrolene-sodium inhibited the CA secretion induced by theophylline but only partially reduced potassium-induced release of CA. 5. Verapamil enhanced the secretion of CA induced by salbutamol (in a calcium-free medium). 6. Tyramine-induced secretion of CA was unaffected by lanthanum chloride, verapamil or dantrolene-sodium. 7. It is suggested that cyclic adenosine 3',5'-monophosphate-mediated CA secretion (induced by theophylline or salbutamol) depends on release of calcium from intracellular stores, and that CA secretion induced by tyramine is independent of intra- or extracellular calcium. PMID:435689

  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.

    2016-05-01

    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. Nanocomposite Lanthanum Zirconate Thermal Barrier Coating Deposited by Suspension Plasma Spray Process

    NASA Astrophysics Data System (ADS)

    Wang, Chaohui; Wang, You; Wang, Liang; Hao, Guangzhao; Sun, Xiaoguang; Shan, Fan; Zou, Zhiwei

    2014-10-01

    This work seeks to develop an innovative nanocomposite thermal barrier coating (TBC) exhibiting low thermal conductivity and high durability compared with that of current TBCs. To achieve this objective, nanosized lanthanum zirconate particles were selected for the topcoat of the TBC system, and a new process—suspension plasma spray—was employed to produce desirable microstructural features: the nanocomposite lanthanum zirconate TBC contains ultrafine splats and high volume porosity, for lower thermal conductivity, and better durability. The parameters of plasma spray experiment included two main variables: (i) spray distance varying from 40 to 80 mm and (ii) the concentration of suspension 20, 25, and 30 wt.%, respectively. The microstructure of obtained coatings was characterized with scanning electron microscope and x-ray diffraction. The porosity of coatings is in the range of 6-10%, and the single phase in the as-sprayed coatings was pyrochlore lanthanum zirconate.

  19. 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}

  20. The effect of sevelamer carbonate and lanthanum carbonate on the pharmacokinetics of oral calcitriol

    PubMed Central

    Pierce, David; Hossack, Stuart; Poole, Lynne; Robinson, Antoine; Van Heusen, Heather; Martin, Patrick; Smyth, Michael

    2011-01-01

    Background. Lanthanum carbonate and sevelamer carbonate are non-calcium-based phosphate binders used to manage hyperphosphataemia in patients with chronic kidney disease (CKD). Patients with CKD may require intravenous or oral active vitamin D. We investigated the effects of lanthanum carbonate and sevelamer carbonate on the bioavailability of oral calcitriol. Methods. This was a three-period, crossover study in healthy volunteers. Forty-one individuals were randomized to one of six possible sequences, each consisting of three treatment periods separated by washouts. The treatments were calcitriol (1 μg at lunch), calcitriol with lanthanum carbonate (3000 mg/day) and calcitriol with sevelamer carbonate (7200 mg/day). Serum calcitriol levels were assessed at baseline and throughout the study. Results. Co-administration of lanthanum carbonate with calcitriol had no significant effect on area under the curve over 48 h (AUC0–48) for serum exogenous calcitriol [least-squares (LS) mean, calcitriol with lanthanum carbonate vs calcitriol alone: 429 pg h/mL vs 318 pg h/mL, respectively; P = 0.171]. Similarly, there was no significant effect on maximum concentration (Cmax). In contrast, co-administration with sevelamer was associated with a significant reduction in bioavailability parameters for calcitriol (calcitriol with sevelamer carbonate vs calcitriol alone, LS mean AUC0–48: 137 pg h/mL vs 318 pg h/mL, respectively; P = 0.024; LS mean Cmax: 40.1 pg/mL vs 49.7 pg/mL, respectively; P < 0.001). Conclusions. Sevelamer carbonate significantly reduces serum concentrations of exogenous calcitriol when administered concomitantly with oral calcitriol, whereas lanthanum carbonate has no significant effect. This should be considered when treating CKD patients who require phosphate binders and oral vitamin D. PMID:20921291

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

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

  2. 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.

  3. Selective isotope determination of lanthanum by diode-laser-initiated resonance-ionization mass spectrometry

    NASA Astrophysics Data System (ADS)

    Young, J. P.; Shaw, R. W.

    1995-08-01

    A diode-laser step has been incorporated into a resonance-ionization mass spectrometry optical excitation process to enhance the isotopic selectivity of the technique. Lanthanum isotope ratio enhancements as high as 103 were achieved by use of a single-frequency cw diode laser tuned to excite the first step of a three-step excitation-ionization optical process; the subsequent steps were excited by use of a pulsed dye laser. Applying the same optical technique, we measured atomic hyperfine constants for the high-lying even-parity 4D5/2 state of lanthanum at 30354 cm-1 . The general utility of this spectral approach is discussed.

  4. LaZnB(5)O(10), the first lanthanum zinc borate.

    PubMed

    Jiao, Zhi-Wei; Wang, Ru-Ji; Wang, Xiao-Qing; Shen, De-Zhong; Shen, Guang-Qiu

    2009-01-01

    Lanthanum zinc penta-borate, LaZnB(5)O(10), was synthesized by flux-supported solid-state reaction. It is a member of the LnMB(5)O(10) (Ln = rare earth ion and M = divalent metal ion) structure type. The crystal shows a three-dimensional structure constructed from two-dimensional {[B(5)O(10)](5-)}(n) layers with the lanthanum (coordination number nine) and zinc (coordination number six) ions filling in the inter-layers. PMID:21579905

  5. Europium doped lanthanum zirconate nanoparticles with high concentration quenching

    SciTech Connect

    Alaparthi, Suresh B.; Lu, Long; Tian, Yue; Mao, Yuanbing

    2014-01-01

    Graphical abstract: - Highlights: • Eu:La{sub 2}Zr{sub 2}O{sub 7} nanoparticles were prepared facilely by a kinetically modified molten salt method. • High color purity and concentration quenching were achieved in these La{sub 2}Zr{sub 2}O{sub 7}:Eu nanoparticles. • Concentration quenching mechanism was discussed for Eu{sup 3+} in these Eu:La{sub 2}Zr{sub 2}O{sub 7} nanoparticles. - Abstract: A series of Eu{sup 3+} doped lanthanum zirconate (La{sub 2}Zr{sub 2}O{sub 7}) nanoparticles (NPs, 20 ± 5 nm in diameter) with cubic fluorite structure were facilely synthesized by a kinetically modified molten salt synthetic (MSS) process and characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and photoluminescence spectra (PL). Under the excitation of 405 nm, intense red emission with high color purity can be observed in the Eu{sup 3+} doped La{sub 2}Zr{sub 2}O{sub 7} NPs. Moreover, the as-prepared Eu:La{sub 2}Zr{sub 2}O{sub 7} NPs possess high concentration quenching, which is as high as ∼32.5 mol% of europium dopants in the La{sub 2}Zr{sub 2}O{sub 7} host. The corresponding concentration quenching mechanism was discussed as well. Our results confirm that the kinetically modified MSS process is a promising approach for preparing rare earth (RE) ions doped A{sub 2}B{sub 2}O{sub 7} nanoparticles with uniform RE doping and high concentration quenching.

  6. A new large area lanthanum hexaboride plasma source

    SciTech Connect

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

    2010-08-15

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

  7. Structural, dielectric and impedance characteristics of lanthanum-modified BiFeO3-PbTiO3 electronic system

    NASA Astrophysics Data System (ADS)

    Pradhan, S. K.; Das, S. N.; Bhuyan, S.; Behera, C.; Padhee, R.; Choudhary, R. N. P.

    2016-06-01

    A lanthanum-modified BiFeO3-PbTiO3 binary electronic system has been fabricated by a high-temperature solid-state reaction technique. The structural, dielectric and electrical properties of a single phase of multicomponent system are investigated to understand its ferroelectrics as well as relaxation behavior. The X-ray diffraction structural analysis substantiates the formation of a new stable phase of tetragonal system (with a large c/a ratio 1.23) without any trace of impurity phase. The electrical behavior of the processed material is characterized through impedance spectroscopy in a wide frequency range (1 kHz-1 MHz) over a temperature range of 25-500 °C. It is observed that the substitution of lanthanum-modified PbTiO3 (PT) into BiFeO3 (BFO) reveals enviable multiferroic property which is evident from the ME coefficient measurement and ferroelectric loop. It also reduces the electrical leakage current or tangent loss. The ac conductivity of the solid solution increases with increase in frequency in the low-temperature region. The impedance spectroscopy of the synthesized material reflects the dielectric relaxation of non-Debye type.

  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. 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.

  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. Comparative evaluation of the in vitro efficacy of lanthanum carbonate chewable tablets.

    PubMed

    Yang, Yongsheng; Bykadi, Srikant; Carlin, Alan S; Shah, Rakhi B; Yu, Lawrence X; Khan, Mansoor A

    2013-04-01

    The aims of this study were to systematically evaluate the effects of pH levels, phosphate concentrations, and tablet integrity on the phosphate binding profiles of lanthanum carbonate chewable tablets, and to compare the in vitro phosphate binding efficacy of one reference and two test products of lanthanum carbonate chewable tablets. Langmuir equation was utilized to calculate the binding constants k1 and k2 . The phosphate binding to the tablets of lanthanum carbonate product was pH dependent, with a faster binding rate at low pH. The crushed tablets bind phosphate more rapid. Compared with the whole tablets, the kinetic binding profiles from the crushed tablets were less variable under all conditions for both test and reference products. The phosphate level has a significant impact on the phosphate binding for both whole and crushed tablets under all pH conditions, with more binding at higher phosphate concentration. The phosphate binding profiles displayed significant difference among the products. For a crushed tablet, the phosphate binding to lanthanum reached equilibrium within 8 h under all conditions. The 90% confidence interval for the k2 ratio (test/reference) was well within the 80%-125% under all pH conditions. However, the k1 ratio varies from 54% to 144%. © 2013 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 102:1370-1381, 2013. PMID:23334989

  12. First-principles study of the solid solution of hydrogen in lanthanum

    SciTech Connect

    Schoellhammer, Gunther; Herzig, Peter; Wolf, Walter; Vajda, Peter; Yvon, Klaus

    2011-09-01

    Results from first-principles investigations of the energetical, structural, electronic, and vibrational properties of model structures probing the metal-rich region of the lanthanum-hydrogen system, i.e., the region of the solid solution of hydrogen in lanthanum, are presented. We have studied the site preference and the ordering tendency of hydrogen atoms interstitially bonded in close-packed lanthanum. Spatially separated hydrogen atoms have turned out to exhibit an energetical preference for the occupation of octahedral interstitial sites at low temperature. Indications for a reversal of the site preference in favor of the occupation of tetrahedral interstitial sites at elevated temperature have been found. Linear arrangements consisting of pairs of octahedrally and/or tetrahedrally coordinated hydrogen atoms collinearly bonded to a central lanthanum atom have turned out to be energetically favorable structure elements. Further stabilization is achieved if such hydrogen pairs are in turn linked together so that extended chains of La-H bonds are formed. Pair formation and chain linking counteract the energetical preference for octahedral coordination observed for separated hydrogen atoms.

  13. 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

    2014-01-01

    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. PMID:24487779

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

    PubMed Central

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

    2014-01-01

    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 β-glycerol phosphate disodium salt pentahydrate (β-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. PMID:24487779

  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. 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

  17. Beam-hardening artifacts on computed tomography images caused by lanthanum carbonate hydrate in a patient on dialysis.

    PubMed

    Hayashi, Hiromitsu; Machida, Minoru; Sekine, Tetsuro; Yamaguchi, Hidenori; Kiriyama, Tomonari; Kumita, Shin-Ichiro

    2010-05-01

    Lanthanum carbonate hydrate is a nonaluminum, noncalcium phosphate binder containing lanthanum (La). It is effective in decreasing the serum phosphate level in patients on dialysis. Because the atomic number of the La contained in lanthanum carbonate hydrate is relatively high, at 57, this agent may cause strong artifacts on computed tomography (CT) images, which may be mistakenly interpreted as foreign bodies. We recently performed CT examination of a patient on Fosrenol chewable tablets (i.e., lanthanum carbonate hydrate). The CT images were difficult to evaluate because of strong beam hardening artifacts, and differentiation from foreign body aspiration was required. We report here our experience and a discussion of the characteristics of this artifact. PMID:20512553

  18. Materialism.

    PubMed

    Melnyk, Andrew

    2012-05-01

    Materialism is nearly universally assumed by cognitive scientists. Intuitively, materialism says that a person's mental states are nothing over and above his or her material states, while dualism denies this. Philosophers have introduced concepts (e.g., realization and supervenience) to assist in formulating the theses of materialism and dualism with more precision, and distinguished among importantly different versions of each view (e.g., eliminative materialism, substance dualism, and emergentism). They have also clarified the logic of arguments that use empirical findings to support materialism. Finally, they have devised various objections to materialism, objections that therefore serve also as arguments for dualism. These objections typically center around two features of mental states that materialism has had trouble in accommodating. The first feature is intentionality, the property of representing, or being about, objects, properties, and states of affairs external to the mental states. The second feature is phenomenal consciousness, the property possessed by many mental states of there being something it is like for the subject of the mental state to be in that mental state. WIREs Cogn Sci 2012, 3:281-292. doi: 10.1002/wcs.1174 For further resources related to this article, please visit the WIREs website. PMID:26301463

  19. 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.

  20. 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.

  1. Plasma Spray Deposition of Lanthanum Phosphate and Phase Structure of the Resultant Coatings

    NASA Astrophysics Data System (ADS)

    Pragatheeswaran, A.; Ananthapadmanabhan, P. V.; Chakravarthy, Y.; Chaturvedi, Vandana; Bhandari, Subhankar; Ramachandran, K.

    2015-12-01

    Plasma-sprayed lanthanum phosphate coatings were prepared on stainless steel substrates at different input powers from 16 to 24 kW. Coatings were characterized by x-ray diffraction, scanning electron microscopy, and Fourier transformed infrared spectroscopy. Results showed that the as-sprayed coatings consist of lanthanum ortho (LaPO4), poly(La2P4O13), and oxy(La3PO7) phosphates. Subsequent heat treatment of the coatings resulted in the recombination of the La-polyphosphate and La-oxyphosphate to form LaPO4. SEM images of microstructure of the coatings and coating-substrate interface showed micro-cracks, voids, and porosity that were found to decrease with deposition power.

  2. Infrared multiple-photon dissociation spectroscopy of tripositive ions: lanthanum-tryptophan complexes.

    PubMed

    Verkerk, Udo H; Zhao, Junfang; Saminathan, Irine S; Lau, Justin Kai-Chi; Oomens, Jos; Hopkinson, Alan C; Siu, K W Michael

    2012-04-16

    Collision-induced charge disproportionation limits the stability of triply charged metal ion complexes and has thus far prevented successful acquisition of their gas-phase IR spectra. This has curtailed our understanding of the structures of triply charged metal complexes in the gas phase and in biological environments. Herein we report the first gas-phase IR spectra of triply charged La(III) complexes with a derivative of tryptophan (N-acetyl tryptophan methyl ester), and an unusual dissociation product, a lanthanum amidate. These spectra are compared with those predicted using density functional theory. The best structures are those of the lowest energies that differ by details in the π-interaction between La(3+) and the indole rings. Other binding sites on the tryptophan derivative are the carbonyl oxygens. In the lanthanum amidate, La(3+) replaces an H(+) in the amide bond of the tryptophan derivative. PMID:22455512

  3. 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+.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. [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

  9. 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.

  10. Impact of lanthanum carbonate on cortical bone in dialysis patients with adynamic bone disease.

    PubMed

    Yajima, Aiji; Inaba, Masaaki; Tominaga, Yoshihiro; Tanaka, Motoko; Otsubo, Shigeru; Nitta, Kosaku; Ito, Akemi; Satoh, Shigeru

    2013-04-01

    Among the most serious problems in patients with chronic kidney disease (CKD) is fragility of cortical bone caused by cortical thinning and increased cortical porosity; the cortical fragility is sometimes irreversible, with fractures generally initiating from cortical bone. Therefore, development of treatments for problems of cortical bone is urgently desired. Cortical bone has the three surfaces, including the periosteal surface, intracortical spaces and endocortical surface. Bone turnover at the endocortical surface and intracortical resorption spaces are increased as compared with that at cancellous surface. Bone growth sometimes depends on apposition at the periosteal surface. We treated hyperphosphatemia in two hemodialysis patients with adynamic bone disease with 750-1500 mg/day of lanthanum carbonate, which is a non-calcium containing phosphate binder; the treatment resulted in a decrease of the serum phosphorus levels (P levels), without significant change of the serum intact parathyroid hormone levels. We now report that treatment of these patients with lanthanum carbonate increased mineralization of the periosteal surface, increased bone mass within the intracortical resorption spaces and increased mineralization of the minimodeling surface at the endocortical surface. In addition, woven bone volume in cortical bone was decreased and mineralization of bone units, namely, osteons, was increased. Although these findings were not observed across all surfaces of the cortical bone in the patients, it is expected that lanthanum carbonate would increase the cortical stability in CKD patients, with consequent reduction in the fracture rate in these patients. PMID:23586512

  11. Lanthanum Carbonate Reduces Urine Phosphorus Excretion: Evidence of High-Capacity Phosphate Binding

    PubMed Central

    Pennick, Michael; Poole, Lynne; Dennis, Kerry; Smyth, Michael

    2012-01-01

    The effectiveness of phosphate binders can be assessed by evaluating urinary phosphorus excretion in healthy volunteers, which indicates the ability of the phosphate binder to reduce gastrointestinal phosphate absorption. Healthy volunteers were enrolled into one of five separate randomized trials; four were open label and one double blind. Following a screening period of <28 days, participants received differing tablets containing lanthanum carbonate [LC, 3000 mg/day of elemental lanthanum (in one study other doses were also used)]. Participants received a standardized phosphate diet and remained in the relevant study center throughout the duration of each treatment period. The end point in all studies was the reduction in urinary phosphorus excretion. Reductions in mean 24-h urinary phosphorus excretion in volunteers receiving a lanthanum dose of 3000 mg/day were between 236 and 468 mg/day over the five separate studies. These data in healthy volunteers can be used to estimate the amount of reduction of dietary phosphate absorption by LC. The reduction in 24-h urinary phosphorus excretion per tablet was compared with published data on other phosphate binders. Although there are limitations, evidence suggests that LC is a very effective phosphate binder in terms of binding per tablet. PMID:22250993

  12. 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

  13. Single crystal growth and characterization of lanthanum-neodymium oxalate octahydrate

    NASA Astrophysics Data System (ADS)

    Want, Basharat

    2011-11-01

    Single crystals of mixed lanthanum-neodymium oxalates are grown by gel diffusion method using agar gel as a medium of growth. The crystals grow in the agar gel with hexagonal morphology having (001), (110) and (010) as habit faces. Single crystal X-ray diffraction results show that the crystals belong to monoclinic system with cell parameters; a=10.344(2) Å, b=9.643(6) Å, c=11.721(2) Å, β=118.7 (2)° , bearing the space group P2/c. Fourier transform infrared spectrum of the crystals indicates the presence of water and other functional groups associated with the oxalate ions. Thermogravimetric and differential thermal analysis support the presence of 8H 2O molecules attached to the lanthanum-neodymium crystal lattice. The thermal decomposition in the nitrogen atmosphere leads to the formation of mixed lanthanum-neodymium oxide as the final product. Energy dispersive analysis of X-rays along with elemental analysis suggests the stoichiometry of the gel grown crystals to be La 1.5Nd 0.5(C 2O 4) 3·8H 2O.

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

    PubMed Central

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

    2015-01-01

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

  15. Assessment of changes in potential nutrient limitation in an impounded river after application of lanthanum-modified bentonite.

    PubMed

    Douglas, Grant B; Lurling, Miquel; Spears, Bryan M

    2016-06-15

    With the advent of phosphorus (P)-adsorbent materials and techniques to address eutrophication in aquatic systems, there is a need to develop interpretive techniques to rapidly assess changes in potential nutrient limitation. In a trial application of the P-adsorbent, lanthanum-modified bentonite (LMB) to an impounded section of the Canning River, Western Australia, a combination of potential P, nitrogen (N) and silicon (Si) nutrient limitation diagrams based on dissolved molar nutrient ratios and actual dissolved nutrient concentrations have been used to interpret trial outcomes. Application of LMB resulted in rapid and effective removal of filterable reactive P (FRP) from the water column and also effectively intercepted FRP released from bottom sediments until the advent of a major unseasonal flood event. A shift from potential N-limitation to potential P-limitation also occurred in surface waters. In the absence of other factors, the reduction in FRP was likely to be sufficient to induce actual nutrient limitation of phytoplankton growth. The outcomes of this experiment underpins the concept that, where possible in the short-term, in managing eutrophication the focus should not be on the limiting nutrient under eutrophic conditions (here N), but the one that can be made limiting most rapidly and cost-effectively (P). PMID:26879191

  16. Development and validation of an ion chromatography method for the determination of phosphate-binding of lanthanum carbonate.

    PubMed

    Samy, Raghu; Faustino, Patrick J; Adams, Wallace; Yu, Lawrence; Khan, Mansoor A; Yang, Yongsheng

    2010-04-01

    Lanthanum carbonate is indicated to reduce serum phosphate in patients with end stage renal disease (ESRD). When given orally, lanthanum carbonate dissociates in the acid environment of the upper gastrointestinal tract to release lanthanum ions. The free lanthanum ions bind with dietary phosphate released from food during digestion to form highly insoluble lanthanum-phosphate complexes which prevent the absorption of phosphate, consequently reduce the serum phosphate. In order to evaluate the in vitro binding capacity of lanthanum carbonate, a simple and efficient ion chromatography (IC) method was developed and validated for determination of phosphate across the pH range encountered in the gastrointestinal tract. Chromatographic separation was achieved on a Dionex ICS-2000 IC system using a Dionex AS16, IonPac (4mmx250mm) analytical column and Dionex AG16, IonPac (4mmx50mm) guard column. Column temperature was maintained at 30 degrees C. Injection volume was 10microL. The compounds were eluted isocratically at a flow rate of 1mL/min and detected by suppressed conductivity. The analytical method was validated according to USP Category I requirements. The validation characteristics included accuracy, precision, quantification limit, linearity, and stability. The intra-day accuracy ranged from 89% to 103% for the solutions of pH 1.2-6.8. The intra-day precision (RSD) ranged from 0.6% to 3.7% for the solutions of pH 1.2-6.8. The analytical range was linear from 2 to 200ppm (mg/L). The R(2) ranged from 0.9998 to 1.0. This method was found to be simple, robust, sensitive, specific, and accurate. It has been successfully applied for determination of phosphate binding to lanthanum carbonate over the human gastrointestinal pH range at different time-points (from 0.5 to 24h). PMID:20031362

  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. DETERMINATION OF LEAD AND CADMIUM IN FISH AND CLAM TISSUE BY ATOMIC ABSORPTION SPECTROMETRY WITH A MOLYBDENUM AND LANTHANUM TREATED PYROLYTIC GRAPHITE ATOMIZER

    EPA Science Inventory

    A molybdenum and lanthanum treated pyrolytically coated graphite tube is employed for the furnace atomic absorption spectrometric determination of lead and cadmium directly in nitric-perchloric acid tissue digests. Lanthanum tends to promote the formation of a smooth lead atomiza...

  1. 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).

  2. 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.

  3. 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.

  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. 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.

  6. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

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

  8. 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).

  9. Lanthanum oxide-coated stainless steel for bipolar plates in solid oxide fuel cells (SOFCs)

    NASA Astrophysics Data System (ADS)

    Yoon, Jong Seol; Lee, Jun; Hwang, Hae Jin; Whang, Chin Myung; Moon, Ji-Woong; Kim, Do-Hyeong

    Solid oxide fuel cells typically operate at temperatures of about 1000 °C. At these temperatures only ceramic interconnects such as LaCrO 3 can be employed. The development of intermediate-temperature solid oxide fuel cells (IT-SOFCs) can potentially bring about reduced manufacturing costs as it makes possible the use of an inexpensive ferritic stainless steel (STS) interconnector. However, the STS suffers from Cr 2O 3 scale formation and a peeling-off phenomenon at the IT-SOFC operating temperature in an oxidizing atmosphere. Application of an oxidation protective coating is an effective means of providing oxidation resistance. In this study, we coated an oxidation protective layer on ferritic stainless steel using a precursor solution prepared from lanthanum nitrate, ethylene glycol, and nitric acid. Heating the precursor solution at 80 °C yielded a spinable solution for coating. A gel film was coated on a STS substrate by a dip coating technique. At the early stage of the heat-treatment, lanthanum-containing oxides such as La 2O 3 and La 2CrO 6 formed, and as the heat-treatment temperature was increased, an oxidation protective perovskite-type LaCrO 3 layer was produced by the reaction between the lanthanum-containing oxide and the Cr 2O 3 scale on the SUS substrate. As the concentration of La-containing precursor solution was increased, the amount of La 2O 3 and La 2CrO 6 phases was gradually increased. The coating layer, which was prepared from a precursor solution of 0.8 M, was composed of LaCrO 3 and small amounts of (Mn,Cr)O 4 spinel. A relatively dense coating layer without pin-holes was obtained by heating the gel coating layer at 1073 K for 2 h. Microstructures and oxidation behavior of the La 2O 3-coated STS444 were investigated.

  10. 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

  11. Influence of lanthanum doping on the dielectric, ferroelectric and relaxor behaviour of barium bismuth titanate ceramics

    NASA Astrophysics Data System (ADS)

    Kumar, Sunil; Varma, K. B. R.

    2009-04-01

    Barium lanthanum bismuth titanate (Ba1-(3/2)xLaxBi4Ti4O15, x = 0-0.4) ceramics were fabricated using the powders synthesized via the solid-state reaction route. X-ray powder diffraction analysis confirmed the above compositions to be monophasic and belonged to the m = 4 member of the Aurivillius family of oxides. The effect of the partial presence of La3+ on Ba2+ sites on the microstructure, dielectric and relaxor behaviour of BaBi4Ti4O15 (BBT) ceramics was investigated. For the compositions pertaining to x <= 0.1, the dielectric constant at both room temperature and in the vicinity of the temperature of the dielectric maximum (Tm) of the parent phase (BBT) increased significantly with an increase in x while Tm remained almost constant. Tm shifted towards lower temperatures accompanied by a decrease in the magnitude of the dielectric maximum (ɛm) with an increase in the lanthanum content (0.1 < x <= 0.4). The dielectric relaxation was modelled using the Vogel-Fulcher relation and a decrease in the activation energy for frequency dispersion with increasing x was observed. The frequency dispersion of Tm was found to decrease with an increase in lanthanum doping, and for compositions corresponding to x >= 0.3, Tm was frequency independent. Well-developed P(polarization)-E(electric field) hysteresis loops were observed at 150 °C for all the samples and the remanent polarization (2Pr) was improved from 6.3 µC cm-2 for pure BBT to 13.4 µC cm-2 for Ba0.7La0.2Bi4Ti4O15 ceramics. Dc conductivities and associated activation energies were evaluated using impedance spectroscopy.

  12. Structural stability and catalytic activity of lanthanum-based perovskites

    SciTech Connect

    Sergey N. Rashkeev; Lucia M. Petkovic

    2011-05-01

    Perovskite-type oxide materials with a general formula La(1-x)A(x)Fe(1-y)Co(y)O(3-delta), where A is an alkaline earth metal Sr or Ba have been studied as cathode materials for catalytic reduction of oxygen in solid oxide fuel cells (SOFC), as well as combustion catalysts. In this study, we use a combination of temperature programmed reduction measurements, X-ray diffraction, carbon black catalytic oxidation measurements, and first-principles, density-functional-theory (DFT) calculations to elucidate the main processes that contribute into the structural stability and catalytic activity for soot oxidation of these materials. In particular, we investigate the dynamics of the structure reconstruction with oxygen loss during the regulated increase of the temperature. The calculations are in good qualitative agreement with catalytic experiments and allow identify special combinations of the perovskite chemical composition and local surface structures for which one could expect the highest catalytic activity for the soot oxidation process.

  13. 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.

  14. Programmable diffractive optical element using a multichannel lanthanum-modified lead zirconate titanate phase modulator

    NASA Astrophysics Data System (ADS)

    Thomas, James A.; Fainman, Yeshaiahu

    1995-07-01

    We introduce a programmable diffractive optical element based on an electro-optic phased array implemented with a multichannel lanthanum-modified lead zirconate titanate phase modulator. The design and fabrication procedures are outlined, along with an experimental demonstration of the device. Experimental results from a 16-channel device operating with a 2 pi voltage of 300 V demonstrate selective beam steering. The programmable diffractive optical element allows for efficient, high-speed high-resolution random-access optical beam steering over a continuous scanning range.

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

    NASA Astrophysics Data System (ADS)

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

    2010-10-01

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

  16. 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.

  17. Photosensitivity enhancement by H- and He-ion implantation in lead lanthanum zirconate titanate ceramics

    SciTech Connect

    Land, C.E.; Peercy, P.S.

    1980-07-01

    H- and He-ion implantation has been used to increase the photoferroelectric image storage sensitivity of lead lanthanum zirconium titanate ceramics by factors of approx.10 and approx.30, respectively. The increased photosensitivity can be attributed primarily to implantation-produced disorder, which increases the efficiency of carrier photoexcitation and trapping and reduces the exposure energy required to establish nonvolatile space-charge fields. Implantation-induced disorder may also contribute to a substantial increase in photoconductivity in the ion-damaged near-surface region.

  18. Performance of planar single cell lanthanum gallate based solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Maffei, N.; Kuriakose, A. K.

    A novel synthesis of high purity, single phase strontium-magnesium doped lanthanum gallate through a nitrate route is described. The prepared powder is formed into planar monolithic elements by uniaxial pressing followed by isostatic pressing and sintering. XRD analysis of the sintered elements reveal no detectable secondary phases. The performance of the electrolyte in solid oxide fuel cells (SOFC) with three different anode/cathode combinations tested at 700°C with respect to the J- V and power density is reported. The data show that the characteristics of this SOFC are strongly dependent on the particular anode/cathode system chosen.

  19. Precipitation of copper and chromium impurities in lanthanum magnesium aluminate crystals during thermochemical reduction

    SciTech Connect

    Ballesteros, C. ); Gonzalez, R. ); Chen, Y. ); Kokta, M.R. )

    1993-02-01

    Thermochemical reduction at high temperatures has been performed on chromium-doped lanthanum magnesium aluminate crystals. Analytical transmission-electron-microscopy and optical-absorption techniques were used to characterize the crystals. Copper impurities inherently present in the crystals began to aggregate and form Cu-rich particles at 1500 K near the surface region. Below 1870 K there was no evidence of chromium precipitates being formed. However, Cr-rich particles were formed at 2020 K. The distribution of the precipitates was very inhomogeneous and the precipitates were also concentrated near the surface region.

  20. 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.

  1. 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.

  2. 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.

  3. Structural phase transitions and superconductivity in lanthanum copper oxides

    SciTech Connect

    Crawford, M.K.; Harlow, R.L.; McCarron, E.M.

    1996-12-31

    Despite the enormous effort expended over the past ten years to determine the mechanism underlying high temperature superconductivity in cuprates there is still no consensus on the physical origin of this fascinating phenomenon. This is a consequence of a number of factors, among which are the intrinsic difficulties in understanding the strong electron correlations in the copper oxides, determining the roles played by antiferromagnetic interactions and low dimensionality, analyzing the complex phonon dispersion relationships, and characterizing the phase diagrams which are functions of the physical parameters of temperature and pressure, as well as the chemical parameters of stoichiometry and hole concentration. In addition to all of these intrinsic difficulties, extrinsic materials issues such as sample quality and homogeneity present additional complications. Within the field of high temperature superconductivity there exists a subfield centered around the material originally reported to exhibit high temperature superconductivity by Bednorz and Mueller, Ba doped La{sub 2}CuO{sub 4}. This is structurally the simplest cuprate superconductor. The authors report on studies of phase differences observed between such base superconductors doped with Ba or Sr. What these studies have revealed is a fascinating interplay of structural, magnetic and superconducting properties which is unique in the field of high temperature superconductivity and is summarized in this paper.

  4. 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.

  5. Relaxor properties of lanthanum-doped bismuth layer-structured ferroelectrics

    NASA Astrophysics Data System (ADS)

    Chen, Xiao-Bing; Hui, Rong; Zhu, Jun; Lu, Wang-Ping; Mao, Xiang-Yu

    2004-11-01

    Several polycrystalline samples of bismuth layer-structured ferroelectrics (BLSF) family doped by lanthanum, Bi4-xLaxTi3O12, SrBi4-xLaxTi4O15, Sr2Bi4-xLaxTi5O18, and (Bi,La)4Ti3O12-Sr(Bi,La)4Ti4O15, were prepared by the traditional solid-state reaction method. Their ferroelectric and dielectric properties were investigated. The dielectric measurement data showed that the content of lanthanum determined the ferroelectric characteristics of the compounds. In each series samples, they behaved as normal ferroelectrics for small x, but all of them tended to become relaxors when x was increased. The critical value of the La content causing relaxor characteristics is different for the different BLSFs due to the difference of the number of strontium atoms in their crystal structures. The appearance of the relaxor behavior was attributed to a ferroelectric microdomain state induced by random fields.

  6. 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

  7. Structures, Stabilities, and Electronic Properties for Rare-Earth Lanthanum Doped Gold Clusters

    NASA Astrophysics Data System (ADS)

    Zhao, Ya-Ru

    2015-02-01

    The structures, stabilities, and electronic properties of rare-earth lanthanum doped gold La2Aun (n = 1-9) and pure gold Aun (n ≤ 11) clusters have been investigated by using density functional theory. The optimized geometries show that the lowest energy structures of La2Aun clusters favour the 3D structure at n ≥ 3. The lanthanum atoms can strongly enhance the stabilities of gold clusters and tend to occupy the most highly coordinated position. By analysing the gap, vertical ionization potential, and chemical hardness, it is found that the La2Au6 isomer possesses higher stability for small-sized La2Aun clusters (n = 1-9). The charges in the La2Aun clusters transfer from La atoms to the Aun host. In addition, Wiberg bond indices analysis reveals that the intensity of different bonds of La2Aun clusters exhibits a sequence of La-La bond > La-Au bond > Au-Au bond.

  8. 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

  9. 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.

  10. Chemically produced nanostructured ODS-lanthanum oxide-tungsten composites sintered by spark plasma

    NASA Astrophysics Data System (ADS)

    Yar, Mazher Ahmed; Wahlberg, Sverker; Bergqvist, Hans; Salem, Hanadi G.; Johnsson, Mats; Muhammed, Mamoun

    2011-01-01

    High purity W and W-0.9La 2O 3 (wt.%) nanopowders were produced by a wet chemical route. The precursor was prepared by the reaction of ammonium paratungstate (APT) with lanthanum salt in aqueous solutions. High resolution electron microscopy investigations revealed that the tungstate particles were coated with oxide precipitates. The precursor powder was reduced to tungsten metal with dispersed lanthanum oxide. Powders were consolidated by spark plasma sintering (SPS) at 1300 and 1400 °C to suppress grain growth during sintering. The final grain size relates to the SPS conditions, i.e. temperature and heating rate, regardless of the starting powder particle size. Scanning electron microscopy revealed that oxide phases were mainly accumulated at grain boundaries while the tungsten matrix constituted of nanosized sub-grains. The transmission electron microscopy revealed that the tungsten grains consist of micron-scale grains and finer sub-grains. EDX analysis confirmed the presence of W in dispersed oxide phases with varying chemical composition, which evidenced the presence of complex oxide phases (W-O-La) in the sintered metals.

  11. 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.

  12. 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}.

  13. 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.

  14. A polynuclear coordination glutarate of lanthanum(III) with an uncommon cage feature.

    PubMed

    Benmerad, Belkacem; Guehria-Laïdoudi, Acoura; Dahaoui, Slimane; Lecomte, Claude

    2004-03-01

    The title compound, triaquatris(glutarato)dilanthanum(III) dihydrate, [[La2(C5H6O4)3(H2O)3] x 2H2O]n, is the first reported glutarate coordination polymer of lanthanum(III) without a protonated ligand. The noteworthy features in the structure are, firstly, the unusual binuclear lanthanum cage formed by three bridging bonds through O atoms involved in different coordination modes and, secondly, the very rare 'malonate' mode exhibited by a dicarboxylate ligand with an alkyl chain of five C atoms. To our knowledge, this eta7 chelation for the glutarate ligand has not been reported and was thought to be forbidden for steric reasons. The gauche-gauche conformation of the corresponding ligand favours cage formation, but trans geometries created along the ligating O atoms prevent cluster packing. The two independent La atoms are nine- and tenfold coordinated, leading to distorted one-face-sharing LaO7(H2O)2 and LaO9(H2O) polyhedra, respectively. In the three-dimensional framework, these asymmetric subunits are linked in a zigzag manner via one-edge-sharing LaO9(H2O) polyhedra and are connected by the carbon backbone chains of the ligands. The structure is very compact and, unlike many other reported dicarboxylate lanthanides, connectivity between the two metal atoms and the three ligands yields a crystal packing with cavities accommodating two guest water molecules but without an open framework. PMID:15004362

  15. Pre-existing oral contrast from lanthanum carbonate: a confounding factor in CT mesenteric angiography

    PubMed Central

    Bull, M D; Shrimanker, R; Thomas, M R M; Mulgrew, C J

    2012-01-01

    A 69-year-old male was referred from the renal unit to radiology for investigation of bleeding per rectum. A CT mesenteric angiogram was performed. However, it was noted on the pre-contrast images that the large bowel contained positive oral contrast media. The procedure was abandoned as it would have been difficult to see extravasation of intravenous contrast from a bleeding point in the large bowel. The initial belief was that either the patient had been given oral contrast by ward staff on the assumption that it would be needed, or had had a recent radiological study requiring contrast, which was still present. Neither was the case; it emerged that the patient was taking Fosrenol (Shire Pharmaceuticals, Wayne, PA), a lanthanum carbonate medication used in the treatment of hyperphosphataemia. Lanthanum is densely radio-opaque and appears as positive bowel contrast on CT and plain radiography studies. When considering radiological studies specifically requiring the absence of oral contrast, it is important to be aware of the patient's drug history to avoid non-diagnostic scans with the associated radiation exposure. PMID:22457410

  16. 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.

  17. Lanthanum carbonate has a radiopaque appearance on the plain abdominal radiography.

    PubMed

    Ruiz Pardo, José; Ibáñez Cánovas, Noelia; Abrisqueta Carrión, Jesús; Luján Mompeán, Juan Antonio; Parrilla Paricio, Pascual

    2016-06-01

    An 84-year-old woman presented to her local emergency department for abdominal pain. Her medical history included hemodialysis in the treatment of chronic renal failure, Parkinson's disease, chronic atrial fibrillation, chronic constipation, appendicectomy and cholecystectomy. The patient complained of diffuse abdominal pain for 4 days, associated with nausea and vomiting in the last 24 hours. Physical examination revealed a soft and depressible abdomen, diffusely painful, without signs of peritoneal irritation. A digital rectal exam revealed large amount of stool in the rectal vault without palpable masses. Blood tests showed a creatinine level of 2.7 mg/dl due to chronic renal failure and the plain abdominal radiography revealed a dolichocolon completely contrasted. The patient denied the realization of any medical imaging-proofs with oral or rectal contrast. Reviewing home treatment, the patient was taking lanthanum carbonate (2 tablets of 750 mg per day) since 1 month ago, a drug that contrasts the digestive tract. Appreciating contrast in the colon, intestinal subocclusion was excluded and the clinical picture was attributed to her chronic constipation. In conclusion, it should be noted that lanthanum carbonate contrasts the digestive tract, with radiopaque appearance on the plain abdominal radiography and without any pathological significance. PMID:27324519

  18. Intrinsic inhomogeneities of low-doped lanthanum manganites in the paramagnetic temperature range

    SciTech Connect

    Solin, N. I.

    2012-01-15

    The nature of the electrical resistivity for low-doped lanthanum manganites is elucidated. The electrical resistivity is described by the Efros-Shklovskii law (ln{rho} {radical} (T{sub 0}/T){sup -1/2}, where T{sub 0} {radical} 1/R{sub ls}) in the temperature range from T* Almost-Equal-To 300 K Almost-Equal-To T{sub C} (T{sub C} is the Curie temperature for conducting manganites) to their T{sub C} and is explained by the tunneling of carriers between localized states. The magnetoresistance is explained by a change in the size of localized states R{sub ls} in a magnetic field. The patterns of change in R{sub ls} with temperature and magnetic field strength determined from magnetotransport properties are satisfactorily described in the model of phase separation into small-radius metallic droplets in a paramagnetic matrix. The sizes R{sub ls} and their temperature dependence have been estimated through magnetic measurements. The results confirm the existence of a Griffith phase. The intrinsic inhomogeneities produced by thermodynamic phase separation determine the electrical resistivity and magnetoresistance of lanthanum manganites.

  19. 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

  20. 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.

  1. Ionic liquid-mediated synthesis of meso-scale porous lanthanum-transition-metal perovskites with high CO oxidation performance

    DOE PAGESBeta

    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.

  2. 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.

  3. Stability of solid oxide fuel cell materials

    SciTech Connect

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

    1996-08-01

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

  4. AFM Nanolithography of Lanthanum Barium Manganese Oxide (LaBaMnO3)Thin Films: The Effect of Oxygen Pressure Variations During Film Growth

    NASA Astrophysics Data System (ADS)

    Stumpf, Christoper; Schaefer, David; Kolagani, Rajeswari; Yong, Grace; Warecki, Zoey

    2014-03-01

    In AFM nanolithography, a bias voltage applied between the tip of an atomic force microscope (AFM) and a sample is used to produce nanoscale modifications of material surfaces. AFM nanolithography has been studied extensively on a variety of materials, but limited studies have been performed on perovskite manganites such as Lanthanum Barium Manganese Oxide (LBMO). Studying such materials is important because of their potential applications for room-temperature nanoscale spintronic devices. Previous research on LBMO by our group has focused on how parameters such as applied tip voltage, temperature, and humidity affect the creation of nanopatterns. This paper reports on the influence of growth pressure of the LBMO films grown by pulsed laser deposition. Films grown on (100) SrTiO3 were studied for growth pressures ranging between 100 mTorr to 400 mTorr. Our studies indicate that the type of nanopatterns induced by AFM and the relaxation dynamics of these patterns are sensitive to the film growth pressure. The growth pressure is mainly known to affect the oxygen concentration and the surface roughness, but possible variations in cationic stoichiometry could also contribute to these results. RK and GY acknowledge support from the National Science Foundation Grant ECCS 1128586.

  5. 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

  6. 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.

  7. Effects of lanthanum carbonate on vascular calcification in elderly maintenance hemodialysis patients.

    PubMed

    Wang, Xiao-Hui; Zhang, Xin; Mu, Chang-Jun; He, Yong; Peng, Qing-Ping; Yang, Guo-Sheng; Li, Ming-Mei; Liu, Duan; Li, Jing; Ding, Guo-Hua

    2015-08-01

    The effect of lanthanum carbonate on abdominal aortic calcification (AAC) in the elderly maintenance hemodialysis (MHD) patients was investigated. Fifty-four cases subjected to routine MHD complicated with skin pruritus admitted to our hospital were selected and randomly divided into case group (n=28) and control group (n=26). The control group was given routine MHD alone. The case group was given lanthanum carbonate additionally on the basis of routine MHD. The changes of itching degrees at first and third month, and serum calcium, phosphorus, calcium-phosphorus products, intact parathyroid hormone (iPTH) levels and AAC scores at third month after treatments were compared between the two groups. The correlation between calcium-phosphorus products and AAC scores was also analyzed. There was no significant difference in the baseline of blood urea nitrogen (BUN), serum creatinine (Scr), uric acid, albumin, hemoglobin, C reactive protein (CRP), low density lipoprotein (LDL), high density lipoprotein (HDL), triglyceride, total cholesterol between case group and control group (P>0.05 for all). There was also no significant difference in the baseline itching scores between the case group and the control group (P>0.05). At 1st and 3rd month after treatment, the itching scores in the case group were 14.2 ± 3.2 and 10.5 ± 2.3, respectively, which were significantly lower than the baseline and those in the control group (P<0.05 for all). At 1st and 3rd month after treatment, the itching scores in the control group were 23.6 ± 5.9 and 24.8 ± 6.3, respectively, which were significantly higher than the baseline (P<0.05). There was no significant difference in the baseline of serum calcium, phosphorus, calcium-phosphorus products, iPTH levels between the case group and control group (P>0.05). At 3rd month after treatment, serum phosphorus, calcium-phosphorus products and iPTH levels in the case group were decreased significantly as compared with the baseline (P<0.05), and

  8. Effect of CO2 on the stability of strontium doped lanthanum manganite cathode

    NASA Astrophysics Data System (ADS)

    Hu, Boxun; Mahapatra, Manoj K.; Keane, Michael; Zhang, Heng; Singh, Prabhakar

    2014-12-01

    Strontium doped lanthanum manganite cathode stability in 0-10% carbon dioxide containing air has been studied in the temperature range of 1023-1123 K with cathodic biases of 0 V and 0.5 V. The current density of the LSM cathode remains stable after an initial decrease. Surface analyses of the pre-test and post-test LSM cathodes using Auger electron spectroscopy (AES) and attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) techniques suggest that the formation of SrCO3 at the LSM surface leads to initial performance degradation. Our observations also indicate that CO2 does not affect the current density after an initial LSM activation in air. Overall, the LSM performance degradation in CO2-containing air is less severe than in humidified air.

  9. Intense laser-induced electron emission from prepoled lead-lanthanum-zirconium-titanate ceramics

    NASA Astrophysics Data System (ADS)

    Geissler, K.; Gundel, H.; Riege, H.; Handerek, J.

    1990-03-01

    A sample of lead-lanthanum-zirconium-titanate (PLZT 9/65/35) has been exposed to 6-ns-long laser pulses of 266 nm wavelength. The maximum output pulse energy of the laser beam was 300 μJ, the output power density on the sample 5×105 W/cm2, and the beam diameter 3 mm. By applying a moderate extraction voltage of several kilovolts, intense electron beam pulses are emitted from the free sample surface. Their time structure corresponds to the time structure of the laser pulse. Electron beam current intensities of up to 0.1 A and 2 A/cm2 and total charges of 1 nC (corresponding to 20 nC/cm2 ) were measured with a simple Faraday cup. In the range where the parameters of laser intensity and of extraction voltage could be varied their influence on the emitted electron beam current amplitude was determined.

  10. 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.

  11. Preparation of Lanthanum Zirconate Coatings by the Solution Precursor Plasma Spray

    NASA Astrophysics Data System (ADS)

    Wang, W. Z.; Coyle, T.; Zhao, D.

    2014-06-01

    Solution precursor plasma spray (SPPS) can synthesize powders and deposit the coatings synchronously. The lanthanum zirconate coatings are deposited by SPPS in the present study, and the dense coating can be obtained through changing the precursor solution. The addition of urea can change the heat exchange process for some precursor mixtures. However, almost no effect can be found on the microstructure of powder and coating by the addition of urea. The extra heat energy caused by the addition of urea is so small, as compared with the heat input by the present plasma jet, so that the heating effect can be ignored. The porosity of coatings increase when the LaCl3·7H2O instead of La(NO3)3·6H2O reacts with Zr(CH3CO2)4.

  12. Data for effects of lanthanum complex on the thermo-oxidative aging of natural rubber

    PubMed Central

    Zheng, Wei; Liu, Li; Zhao, Xiuying; He, Jingwei; Wang, Ao; Chan, Tung W.; Wu, Sizhu

    2015-01-01

    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

  13. Model for ion-implantation-induced improvements of photoferroelectric imaging in lead lanthanum zirconate titanate ceramics

    SciTech Connect

    Peercy, P.S.; Land, C.E.

    1980-11-01

    Studies of photoferroelectric image storage in H-, He-, and, more recently, Ar-implanted /(PLZT) lead lanthanum zirconate titanate reveal that the photosensitivity can be significantly increased by ion implantation into the image storage surface. For example, the photosensitivity after implantation with 5 x 10/sup 14/ 500-keV Ar/cm/sup 2/ is increased by about three orders of magnitude over that of unimplanted PLZT. The increase in photosensitivity results from a decrease in dark conductivity and changes in the photoconductivity of the implanted layer. We present a phenomenological model which describes the photosensitivity enhancement obtained by ion implantation. This model takes into account both light- and ion- implantation-induced changes in conductivity and gives quantitative agreement with the measured changes in the coercive voltage with near-UV light intensity for ion-implantated PLZT.

  14. Effects of ion implantation on the photoferroelectric properties of lead lanthanum zirconate titanate ceramics

    SciTech Connect

    Land, C.E.; Peercy, P.S.

    1981-01-01

    Earlier studies of Ar-, Ar + Ne- and Ar + Ne + He- implanted ferroelectric-phase lead lanthanum zirconate titanate (PLZT) ceramics indicate that ion implantation can increase the intrinsic (near-uv) photoferroelectric sensitivity by more than four orders of magnitude compared to that of unimplanted PLZT. More recent studies involving implantation of chemically active ions, e.g., Al and Cr, indicate that the absorption spectrum of the implanted region can be extended from the near-uv to the visible, and that the extrinsic (visible-light) photoferroelectric sensitivity can be improved substantially with respect to that of PLZT implanted with inert ions. The results of these studies are reviewed and photographic sensitivities of Ar-, Ar + Ne-, Ar + Ne + He-, Al-, Cr-, Fe-, and Fe + Ne- implanted PLZT at both near-uv and visible-light wavelengths are compared with the sensitivities of other image storage media.

  15. Processing and electrical properties of alkaline earth-doped lanthanum gallate

    SciTech Connect

    Stevenson, J.W.; Armstrong, T.R.; McCready, D.E.; Pederson, L.R.; Weber, W.J.

    1997-10-01

    Oxides exhibiting substantial oxygen ion conductivity are utilized in a number of high-temperature applications, including solid oxide fuel cells, oxygen separation membranes, membrane reactors, and oxygen sensors. Alkaline earth-doped lanthanum gallate powders were prepared by glycine/nitrate combustion synthesis. Compacts of powders synthesized under fuel-rich conditions were sintered to densities greater than 97% of theoretical. Appropriate doping with Sr or Ba on the A-site of the perovskite structure, and Mg on the B-site, resulted in oxygen ion conductivity higher than that of yttria-stabilized zirconia (YSZ), and high ionic transference numbers. Doping with Ca and Mg resulted in lower conductivity than YSZ. Thermal expansion coefficients of the doped gallates were higher than that of YSZ.

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

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

    Strontium and nickel doped lanthanum ferrite (LaFeO3) 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 (ɛ') 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.

  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. 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).

  19. 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

  20. Toxicity of lanthanum oxide (La2O3) nanoparticles in aquatic environments.

    PubMed

    Balusamy, Brabu; Taştan, Burcu Ertit; Ergen, Seyda Fikirdesici; Uyar, Tamer; Tekinay, Turgay

    2015-07-01

    This study demonstrates the acute toxicity of lanthanum oxide nanoparticles (La2O3 NP) on two sentinel aquatic species, fresh-water microalgae Chlorella sp. and the crustacean Daphnia magna. The morphology, size and charge of the nanoparticles were systematically studied. The algal growth inhibition assay confirmed absence of toxic effects of La2O3 NP on Chlorella sp., even at higher concentration (1000 mg L(-1)) after 72 h exposure. Similarly, no significant toxic effects were observed on D. magna at concentrations of 250 mg L(-1) or less, and considerable toxic effects were noted in higher concentrations (effective concentration [EC50] 500 mg L(-1); lethal dose [LD50] 1000 mg L(-1)). In addition, attachment of La2O3 NP on aquatic species was demonstrated using microscopy analysis. This study proved to be beneficial in understanding acute toxicity in order to provide environmental protection as part of risk assessment strategies. PMID:26022751

  1. 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.

  2. Waveguide amplifiers in sputtered films of Er3+-doped gallium lanthanum sulfide glass.

    PubMed

    Frantz, J A; Shaw, L B; Sanghera, J S; Aggarwal, I D

    2006-03-01

    Waveguide amplifiers fabricated in Er3+-doped gallium lanthanum sulfide (GLS) glass are demonstrated. GLS is deposited onto fused silica substrates by RF magnetron sputtering, and waveguides are patterned by use of the lift-off technique. The waveguides exhibit a total internal gain of 6.7 dB (2.8 dB/cm) for a signal with a wavelength of 1.55 mum. This experiment is, to the best of our knowledge, the first demonstration of gain in an Er3+-doped chalcogenide glass waveguide. The fabrication methods we apply, if used with other rare earth dopants, could potentially be employed to produce sources operating in the mid-IR. PMID:19503508

  3. Chemical solution deposition of the highly c-axis oriented apatite type lanthanum silicate thin films.

    PubMed

    Hori, Shigeo; Takatani, Yasuhiro; Kadoura, Hiroaki; Uyama, Takeshi; Fujita, Satoru; Tani, Toshihiko

    2015-10-28

    Highly c-axis oriented apatite-type lanthanum silicate (LSO) thin films were fabricated by a simple solution coating method. In the solution coating method, LSO thin films are obtained by crystallization of initially deposited amorphous LSO precursor thin films. The degree of orientation was influenced by the precursor morphologies and a dense LSO precursor led to a high c-axis orientation perpendicular to the substrate. The oriented LSO thin films were composed of columnar grains with a single crystal orientation over the entire film thickness. In-plane orientation was not detected, which indicates that the c-axis orientation of the LSO thin films can be attributed to self-orientation. PMID:26391101

  4. 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.

  5. 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.

  6. 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.

  7. A nuclear magnetic resonance study of amorphous and crystalline lanthanum-aluminates

    SciTech Connect

    Iuga, D.; Simon, S.; Boer, E. de; Kentgens, A.P.M.

    1999-09-09

    Lanthanum-aluminates of the composition (1 {minus} x)Al{sub 2}O{sub 3}{center_dot}xLa{sub 2}O{sub 3} (0 < x < 0.7) were prepared by sol-gel synthesis. Subsequent heat-treatment temperatures ranging from 200 to 1,200 C were applied. The resulting samples were characterized by X-ray powder diffraction and {sup 27}Al MAS NMR. The most complex spectra were analyzed by MQMAS NMR in order to get insight in the number of sites and the possible distribution of the NMR parameters in the amorphous samples. Analysis of the MQMAS spectra, taking the efficiency of this experiment for different sites into account, helped to resolve ambiguities in the MAS spectra, which could otherwise not be deconvoluted in a unique way. The analyses show that, except for the sample with the lowest La (x = 0.085) concentration, hardly any pentacoordinated aluminum is observed over the whole temperature treatment range. For all samples the concentration of six-coordinated aluminum decreases as the heating temperature increases until the point where crystallization occurs. The concentration of 4-fold coordinated aluminum shows the opposite behavior. When crystallization occurs, a remarkable transformation between four- and six-coordinated aluminum takes place. Crystallization of the samples occurs at lower temperatures for samples with high amounts of lanthanum. At low La content crystallization is shifted to higher temperatures and thus the lower Al (four and five) coordinations are maintained over a larger temperature range. Storage of the samples in a water-saturated atmosphere leads to a conversion of four- to six-coordinated aluminum. This shows that the low-coordinated Al atoms are accessible to water molecules and must therefore be situated at the surface.

  8. Surface complexation modeling of uranium(VI) sorbed onto lanthanum monophosphate.

    PubMed

    Ordoñez-Regil, E; Drot, R; Simoni, E

    2003-07-15

    Sorption/desorption are basic processes in the field of contaminant transport. In order to develop mechanistically accurate thermodynamic sorption models, the simulation of retention data has to take into account molecular scale informations provided by structural investigations. In this way, the uranyl sorption constants onto lanthanum monophosphate (LaPO(4)) were determined on the basis of a previously published structural investigation. The surface complexation modeling of U(VI) retention onto LaPO(4) has been performed using the constant capacitance model included in the FITEQLv3.2 program. The electrical behavior of the solid surface was investigated using electrophoretic measurements and potentiometric titration experiments. The point of zero charge was found to be 3.5 and surface complexation modeling has made it possible to calculate the surface acidity constants. The fitting procedure was done with respect to the spectroscopic results, which have shown that LaPO(4) presents two kinds of reactive surface sites (lanthanum atoms and phosphate groups). The uranyl sorption edges were determined for two surface coverages: 40 and 20% of the surface sites that are occupied, assuming complete sorption. The modeling of these experimental data was realized by considering two uranyl species ("free" uranyl and uranyl nitrate complex) sorbed only onto phosphate surface groups according to the previously published structural investigation. The obtained sorption constants present similar values for both surface complexes and make it possible to fit both sorption edges: logK(U)=9.4 for z.tbnd;P(OH)(2)+UO(2)(2+)<-->z.tbnd;P(OH)(2)UO(2)(2+) and logK(UN)=9.7 for z.tbnd;P(OH)(2)+UO(2)NO(3)(+)<-->z.tbnd;P(OH)(2)UO(2)NO(3)(+). PMID:12909028

  9. 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.

  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. PMID:26277214

  11. The combination of lanthanum chloride and the calcimimetic calindol delays the progression of vascular smooth muscle cells calcification

    SciTech Connect

    Ciceri, Paola; Volpi, Elisa; Brenna, Irene; Elli, Francesca; Borghi, Elisa; Brancaccio, Diego; Cozzolino, Mario

    2012-02-24

    Highlights: Black-Right-Pointing-Pointer Lanthanum reduces the progression of high phosphate-induced calcium deposition. Black-Right-Pointing-Pointer Calcium receptor agonists and the calcimimetic calindol reduce calcium deposition. Black-Right-Pointing-Pointer Lanthanum and calindol cooperate on reducing calcium deposition. Black-Right-Pointing-Pointer Lanthanum and calindol may interact with the same receptor. -- Abstract: Phosphate (Pi)-binders are commonly used in dialysis patients to control high Pi levels, that associated with vascular calcification (VC). The aim of this study was to investigate the effects of lanthanum chloride (LaCl{sub 3}) on the progression of high Pi-induced VC, in rat vascular smooth muscle cells (VSMCs). Pi-induced Ca deposition was inhibited by LaCl{sub 3}, with a maximal effect at 100 {mu}M (59.0 {+-} 2.5% inhibition). Furthermore, we studied the effects on VC of calcium sensing receptor (CaSR) agonists. Gadolinium chloride, neomycin, spermine, and the calcimimetic calindol significantly inhibited Pi-induced VC (55.9 {+-} 2.2%, 37.3 {+-} 4.7%, 30.2 {+-} 5.7%, and 63.8 {+-} 5.7%, respectively). To investigate the hypothesis that LaCl{sub 3} reduces the progression of VC by interacting with the CaSR, we performed a concentration-response curve of LaCl{sub 3} in presence of a sub-effective concentration of calindol (10 nM). Interestingly, this curve was shifted to the left (IC{sub 50} 9.6 {+-} 2.6 {mu}M), compared to the curve in the presence of LaCl{sub 3} alone (IC{sub 50} 19.0 {+-} 4.8 {mu}M). In conclusion, we demonstrated that lanthanum chloride effectively reduces the progression of high phosphate-induced vascular calcification. In addition, LaCl{sub 3} cooperates with the calcimimetic calindol in decreasing Ca deposition in this in vitro model. These results suggest the potential role of lanthanum in the treatment of VC induced by high Pi.

  12. 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.

  13. 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.

  14. 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.

  15. 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

  16. 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

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

    PubMed

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

    2002-02-01

    In this paper a new method was established for determination of trace barium in environmental samples by graphite furnace atomic absorption spectrometry. In the presence of matrix modifier magnesium nitrate, the matrix inference was eliminated efficiently. To avoid producing barium carbide, the graphite tubes were coated differently with lanthanum, zirconium, tungsten, molybdenum, and tantalum. Results showed that the tube with lanthanum was the best. The atomization temperature was diminished. The sensitivity was improved, and the tube with lanthanum gave the longest service life. So we used the tube to determine trace barium. The trace barium in Geodchemical Standard Reference Sample Soil-1 (GSS-1) was determined by the new method, the test results showed that the method was reliability and accurate. The method has been used for the determination of trace barium in environmental samples and in water of Yellow River. The detection limit for Ba was 2.1 x 10(-12) g and the relative standard deviation(RSD) was 5.4% for 15 ng.mL-1 Ba. PMID:12940053

  18. Lanthanum Molybdate Nanoparticles from the Bradley Reaction: Factors Influencing Their Composition, Structure, and Functional Characteristics as Potential Matrixes for Luminescent Phosphors

    PubMed Central

    2014-01-01

    Interaction of lanthanum isopropoxide with molybdenum(VI) alkoxides in La/Mo ratios varying from 3:1 to 1:1 in acetophenon or allyl alcohol as solvents offers nanosized poorly crystalline products of complex composition, where the precipitation of Mo-rich ones is followed by the formation of La-rich ones with conservation of the reaction stoichiometry in total. Thermal treatment of the precipitates at temperatures over 700 °C leads to the formation of stoichiometric phases of the α- and β-La2Mo2O9 compositions. Introduction of smaller Re3+ cations such as Sm3+ by doping favors stabilization of the La2–xRExMo2O9 phase with improved crystallinity even after lower-temperature thermal treatment. The doping is successful only when the Re3+ (Sm3+, Eu3+, and Tb3+) is introduced as an alkoxide: application of Re3+(acac)3 as Re3+ sources leads to materials free from Re3+. The produced samples were characterized by XPD, TGA, SEM, and TEM studies as well as the luminescent properties for the Sm3+-doped phases. PMID:24392745

  19. Advanced materials for high-temperature thermoelectric energy conversion

    NASA Technical Reports Server (NTRS)

    Vining, Cronin B.; Vandersande, Jan W.; Wood, Charles

    1992-01-01

    A number of refractory semiconductors are under study at the Jet Propulsion Laboratory for application in thermal to electric energy conversion for space power. The main thrust of the program is to improve or develop materials of high figure of merit and, therefore, high conversion efficiencies over a broad temperature range. Materials currently under investigation are represented by silicon-germanium alloys, lanthanum telluride, and boron carbide. The thermoelectric properties of each of these materials, and prospects for their further improvements, are discussed. Continued progress in thermoelectric materials technology can be expected to yield reliable space power systems with double to triple the efficiency of current state of the art systems.

  20. Lanthanum carbonate versus placebo for management of hyperphosphatemia in patients undergoing peritoneal dialysis: a subgroup analysis of a phase 2 randomized controlled study of dialysis patients

    PubMed Central

    2013-01-01

    Background This short-term study assessed the efficacy and safety of lanthanum carbonate in the treatment of hyperphosphatemia in dialysis patients; here, we report a prespecified subgroup analysis of patients undergoing peritoneal dialysis. Methods Men and women (n = 39) who had received continuous ambulatory peritoneal dialysis for chronic kidney disease for 6 months or more were enrolled in eight renal medicine departments in the United Kingdom. A 2-week washout period was followed by a 4-week dose-titration phase during which patients received lanthanum carbonate titrated up to 2250 mg/day. This was followed by a 4-week, randomized, placebo-controlled, parallel-group phase during which patients continued to receive either lanthanum carbonate at the titrated dose, or a matched dose of placebo. The main outcome measure was control of serum phosphate levels (1.3-1.8 mmol/l) at the end of the parallel-group phase. Results Serum phosphate was controlled in 3/39 (8%) patients at the beginning of the dose-titration phase (after washout) and in 18/31 (58%) patients treated with lanthanum carbonate at its end. After the parallel-group phase, 60% of lanthanum carbonate-treated patients and 10% of those receiving placebo had controlled serum phosphate. There was no difference in mean (95% confidence interval) serum phosphate levels between groups at randomization: lanthanum carbonate, 1.57 (1.34-1.81) mmol/l; placebo, 1.58 (1.40-1.76) mmol/l (p = 0.96). However, a difference was seen at the end of the parallel-group phase: lanthanum carbonate, 1.56 (1.33-1.79) mmol/l; placebo, 2.25 (1.81-2.68) mmol/l (p = 0.0015). There were no clinically important changes in nutritional parameters and no serious treatment-related adverse events were recorded. Conclusions At doses up to 2250 mg/day, lanthanum carbonate is well tolerated and controls hyperphosphatemia effectively. Treatment with higher doses of lanthanum carbonate may allow patients undergoing peritoneal dialysis the

  1. Separation of plutonium from lanthanum by electrolysis in LiCl KCl onto molten bismuth electrode

    NASA Astrophysics Data System (ADS)

    Serp, J.; Lefebvre, P.; Malmbeck, R.; Rebizant, J.; Vallet, P.; Glatz, J.-P.

    2005-04-01

    This work presents a study on the electroseparation of plutonium from lanthanum using molten bismuth electrodes in LiCl-KCl eutectic at 733 K. The reduction potentials of Pu3+ and La3+ ions were measured on a Bi thin film electrode using cyclic voltammetry (CV). A difference between the peak potentials for the formation of PuBi2 and LaBi2 of approximately 100 mV was found. Separation tests were then carried out using different current densities and salt phase compositions between a plutonium rod anode and an unstirred molten Bi cathode in order to evaluate the efficiency of an electrolytic separation process. At a current density of 12 mA/cm2/wt% (Pu3+), only Pu3+ ions are reduced into the molten Bi electrode, leaving La3+ ions in the salt melt. Similar results were found at two different Pu/La concentration ratios ([Pu]/[La] = 4 and 10). At a current density of 26 mA/cm2/wt% (Pu3+), co-reduction of Pu and La was observed as expected by the large negative potential of the Bi cathode during the separation test.

  2. Preparation, Characterization and Photocatalytic Activity of Lanthanum Doped Mesoporous Titanium Dioxide

    NASA Astrophysics Data System (ADS)

    Shi, Zhong-liang; Lai, Hong; Yao, Shu-hua; Wang, Shao-feng

    2012-02-01

    Lanthanum doped mesoporous titanium dioxide photocatalysts with different La content were synthesized by template method using tetrabutyltitanate (Ti(OC4H9)4) as precursor and Pluronic P123 as template. The catalysts were characterized by thermogravimetric differential thermal analysis, N2 adsorption-desorption measurements, X-ray diffraction, and UV-Vis adsorption spectroscopy. The effect of La3+ doping concentration from 0.1% to 1% on the photocatalytic activity of mesoporous TiO2 was investigated. The characterizations indicated that the photocatalysts possessed a homogeneous pore diameter of about 10 nm with high surface area of 165 m2/g. X-ray photoelectron spectroscopy measurements indicated the presence of C in the doped samples in addition to La. Compared with pure mesoporous TiO2, the La-doped samples extended the photoabsorption edge into the visible light region. The results of phenol photodecomposition showed that La-doped mesoporous TiO2 exhibited higher photocatalytic activities than pure mesoporous TiO2 under UV and visible light irradiation.

  3. Influence of lanthanum doping on the morphotropic phase boundary of lead zirconate titanate

    NASA Astrophysics Data System (ADS)

    Hinterstein, Manuel; Schoenau, Kristin A.; Kling, Jens; Fuess, Hartmut; Knapp, Michael; Kungl, Hans; Hoffmann, Michael J.

    2010-07-01

    A phase diagram for morphotropic (Pb0.985La0.01)(Zr1-xTix)O3 is proposed based on a combination of X-ray and neutron powder diffraction experiments and complemented by transmission electron microscopy. Dependent on composition three regions are characterized. The stability range of tetragonal microdomains for high Ti contents, the stability range of rhombohedral microdomains for low Ti contents, and an intermediate stability range of nanodomains. All three regions exhibit a corresponding low temperature configuration. Temperature dependent diffraction revealed that lanthanum doping reduces the sensitivity of the structure to changes in temperature and composition. A continuous transition from pseudorhombohedral to tetragonal symmetry with an intermediate two-phase region at the morphotropic phase boundary is observed. A similar transition of low temperature superstructure phases from pseudorhombohedral to pseudotetragonal with an intermediate monoclinic phase governed by a continuous change in the oxygen octahedral tilt system from a-a-a- over a-a-c- to a0a0c- is identified.

  4. 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

  5. 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

  6. 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.

  7. 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.

  8. 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.

  9. Phase dependent structural and electronic properties of Lanthanum Orthophosphate (LaPO4)

    NASA Astrophysics Data System (ADS)

    Neupane, Mahesh; Garrett, Gregory; Rudin, Sergey; Andzelm, Jan

    Lanthanum orthophosphate (LaPO4) belongs to the family of rare-earth (RE) orthophosphates. The La-ion lacks valence 4f-electron, so for it to exhibit f-electron dependent physics, it must be doped with additional RE elements. In the bulk form, LaPO4 exist in both a stable monoclinic and a metastable hexagonal phase, which both possess indirect energy transition characteristics. Though the overall optoelectronic properties of the RE-doped LaPO4 depend on the accuracy of the observed bulk energy gap, the reported experimental and theoretical energy gaps varies between ~81,2 and ~53 eV, respectively. Through this theoretical study, we attempt to establish a correlation between electronic properties of bulk LaPO4 and various levels of first principle theories. Compared to experimental data, the PBE0 functional over-predicts energy gaps and the energy differences between the indirect-to-direct transition energies by 25%. The HSE06 gives a good description of electronic properties and predicts the energy gaps to be 7.68 (monoclinic) and 7.29 eV (hexagonal). Analysis on the structural stability also reveals that the total energy difference between the two phases is 6meV, consistent with the experimentally observed instantaneous pressure and temperature dependent phase transition.

  10. 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.

  11. Metal-insulator transition at lanthanum aluminate-strontium titanate interface induced by oxygen plasma treatment

    NASA Astrophysics Data System (ADS)

    Dai, Weitao; Cen, Cheng

    The formation of two-dimensional electron gas (2DEG) at lanthanum aluminate (LAO)-strontium titanate (STO) interface, as well as the 2DEG's unique characters in metal-insulator transition, have evoked widespread interest. Highly insulating interfaces are obtained for the structures with LAO thickness below 3 unit cell (uc) and abrupt transition from an insulating to conducting interface was observed for samples with thicker LAO layers. For 3uc LAO/STO samples, reversible nanoscale control of the metal-insulator transition was implemented by a conductive AFM writing. Our research furtherly discovered a very stable metal-insulator transition can be achieved by oxygen plasma (OP) treatment for samples with thicker LAO layers. AFM imaging and XPS measurement demonstrated the low energy OP treatment altered only the surface bonds, which confirmed the importance of surface properties in the heterostructures. Then microscale Hall bars were patterned at the interface and imaged by electrostatic force microscope. Their transport and magnetic properties were measured. This research will promote deeper understanding about the interfacial metal-insulator transition mechanism and open new device opportunities. This work is supported by the Department of Energy Grant No. DE-SC-0010399 and National Science Foundation Grant No. NSF-1454950.

  12. Highly selective water adsorption in a lanthanum metal-organic framework.

    PubMed

    Plessius, Raoul; Kromhout, Rosa; Ramos, André Luis Dantas; Ferbinteanu, Marilena; Mittelmeijer-Hazeleger, Marjo C; Krishna, Rajamani; Rothenberg, Gadi; Tanase, Stefania

    2014-06-23

    We present a new metal-organic framework (MOF) built from lanthanum and pyrazine-2,5-dicarboxylate (pyzdc) ions. This MOF, [La(pyzdc)1.5(H2O)2]⋅2 H2O, is microporous, with 1D channels that easily accommodate water molecules. Its framework is highly robust to dehydration/hydration cycles. Unusually for a MOF, it also features a high hydrothermal stability. This makes it an ideal candidate for air drying as well as for separating water/alcohol mixtures. The ability of the activated MOF to adsorb water selectively was evaluated by means of thermogravimetric analysis, powder and single-crystal X-ray diffraction and adsorption studies, indicating a maximum uptake of 1.2 mmol g(-1) MOF. These results are in agreement with the microporous structure, which permits only water molecules to enter the channels (alcohols, including methanol, are simply too large). Transient breakthrough simulations using water/methanol mixtures confirm that such mixtures can be separated cleanly using this new MOF. PMID:24867871

  13. Uniform dispersion of lanthanum hexaboride nanoparticles in a silica thin film: synthesis and optical properties.

    PubMed

    Jiang, Fei; Leong, Yee-Kwong; Saunders, Martine; Martyniuk, Mariusz; Faraone, Lorenzo; Keating, Adrian; Dell, John M

    2012-11-01

    Silica thin films containing uniformly dispersed lanthanum hexaboride (LaB₆) nanoparticles have been prepared by spin-coating a sol-gel silica solution containing cetyltrimethyl ammonium bromide (CTAB)-stabilized LaB₆ nanoparticles onto a glass substrate followed by a standard heat treatment. The production of this thin film involved three steps: (i) a CTAB-stabilized LaB₆ nanoparticle dispersion was prepared in water and then dried, (ii) the dried nanoparticles were redispersed in a small amount of water and mixed with tetraethoxyorthosilane (TEOS), ethanol, and a little acid to initiate the sol-gel reaction, and (iii) this reaction mixture was spun to produce a thin film and then was annealed. A range of techniques such as zeta potential, laser sizing, energy-filtered transmission electron microscopy (EFTEM), scanning TEM (STEM), scanning electron microscopy (SEM), and energy dispersive X-ray spectrum (EDS) were employed to characterize the particle's size, elemental composition, and stability and the optical properties of silica thin films with LaB₆ nanoparticles. On the basis of the optical transmittance and reflectance spectra of an annealed silica thin film with LaB₆ nanoparticles, the annealed thin films clearly showed positive absorption of radiation in the near infrared (NIR) region meeting a main objective of this study. A potential optical micro-electromechanical sensing system in the NIR range can be realized on the basis of this silica thin film with LaB₆ nanoparticles. PMID:23057614

  14. Develop techniques for ion implantation of PLZT (lead-lanthanum-zirconate-titanate) for adaptive optics

    SciTech Connect

    Batishko, C.R.; Brimhall, J.L.; Pawlewicz, W.T.; Stahl, K.A.; Toburen, L.H.

    1987-07-01

    Research was conducted at Pacific Northwest Laboratory to develop high photosensitivity adaptive optical elements utilizing ion implanted lanthanum-doped lead-zirconate-titanate (PLZT). One centimeter square samples were prepared by implanting ferroelectric and anti-ferroelectric PLZT with a variety of species or combinations of species. These included Ne, O, Ni, Ne/Cr, Ne/Al, Ne/Ni, Ne/O, and Ni/O, at a variety of energies and fluences. An indium-tin oxide (ITO) electrode coating was designed to give a balance of high conductivity and optical transmission at near uv to near ir wavelengths. Samples were characterized for photosensitivity; implanted layer thickness, index of refraction, and density; electrode (ITO) conductivity; and in some cases, residual stress curvature. Thin film anti-ferroelectric PLZT was deposited in a preliminary experiment. The structure was amorphous with x-ray diffraction showing the beginnings of a structure at substrate temperatures of approximately 550/sup 0/C. This report summarizes the research and provides a sampling of the data taken during the report period.

  15. Modification of carbon derived from Sargassum sp. by lanthanum for enhanced adsorption of fluoride.

    PubMed

    Yu, Yang; Wang, Chenghong; Guo, Xue; Paul Chen, J

    2015-03-01

    Excessive fluoride in water causes serious environmental issues and adverse impacts on human health. In this study, an innovative lanthanum-modified carbon (LMC) adsorbent rooted in Sargassum sp. was developed for fluoride removal. Excellent removal efficiency was observed over a wide pH range of 3-9. Almost 90% of fluoride adsorption occurred within the first 1h; the equilibrium was established within 4h. The maximum adsorption capacity of LMC could reach 94.34 mg/g at neutral pH, much higher than many commercial adsorbents. Although the presence of such competitive anions as SiO3(2-), SO4(2-), HCO3(-), PO4(3-) and AsO3(-) had certain interference on fluoride uptake, it was noticed that there was no significant impact in the presence of humic acid. Furthermore, according to the instrumental analysis, the fluoride removal was majorly controlled by outer-sphere complex adsorption, while electrostatic attraction and ion exchange mechanisms could also be observed in the fluoride adsorption process. The findings from this study suggest that our adsorbent may have a great potential in industrial applications. PMID:25498487

  16. 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.

  17. RM1 Semiempirical Quantum Chemistry: Parameters for Trivalent Lanthanum, Cerium and Praseodymium

    PubMed Central

    Dutra, José Diogo L.; Filho, Manoel A. M.; Rocha, Gerd B.; Simas, Alfredo M.; Freire, Ricardo O.

    2015-01-01

    The RM1 model for the lanthanides is parameterized for complexes of the trications of lanthanum, cerium, and praseodymium. The semiempirical quantum chemical model core stands for the [Xe]4fn electronic configuration, with n =0,1,2 for La(III), Ce(III), and Pr(III), respectively. In addition, the valence shell is described by three electrons in a set of 5d, 6s, and 6p orbitals. Results indicate that the present model is more accurate than the previous sparkle models, although these are still very good methods provided the ligands only possess oxygen or nitrogen atoms directly coordinated to the lanthanide ion. For all other different types of coordination, the present RM1 model for the lanthanides is much superior and must definitely be used. Overall, the accuracy of the model is of the order of 0.07Å for La(III) and Pr(III), and 0.08Å for Ce(III) for lanthanide-ligand atom distances which lie mostly around the 2.3Å to 2.6Å interval, implying an error around 3% only. PMID:26132289

  18. 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.

  19. 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

  20. 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.

  1. Wave and transport studies utilizing dense plasma filaments generated with a lanthanum hexaboride cathode

    SciTech Connect

    Van Compernolle, B.; Gekelman, W.; Pribyl, P.; Cooper, C. M.

    2011-12-15

    A portable lanthanum hexaboride (LaB{sub 6}) cathode has been developed for use in the LArge Plasma Device (LAPD) at UCLA. The LaB{sub 6} cathode can be used as a tool for many different studies in experimental plasma physics. To date, the cathode has been used as a source of a plasma with a hot dense core for transport studies and diagnostics development, as a source of gradient driven modes, as a source of shear Alfven waves, and as a source of interacting current channels in reconnection experiments. The LaB{sub 6} cathode is capable of higher discharge current densities than the main barium oxide coated LAPD cathode and is therefore able to produce plasmas of higher densities and higher electron temperatures. The 8.25 cm diameter cathode can be introduced into the LAPD at different axial locations without the need to break vacuum. The cathode can be scaled up or down for use as a portable secondary plasma source in other machines.

  2. In vitro anticancer activities of Schiff base and its lanthanum complex

    NASA Astrophysics Data System (ADS)

    Neelima; Poonia, Kavita; Siddiqui, Sahabjada; Arshad, Md; Kumar, Dinesh

    2016-02-01

    Schiff base metal complexes are well-known to intercalate DNA. The La(III) complexes have been synthesized such that they hinder with the role of the topoisomerases, which control the topology of DNA during the cell-division cycle. Although several promising chemotherapeutics have been developed, on the basis of Schiff base metal complex DNA intercalating system they did not proceed past clinical trials due to their dose-limiting toxicity. Herein, we discuss an alternative compound, the La(III) complex, [La(L1)2Cl3]·7H2O based on a Schiff base ligand 2,3-dihydro-1H-indolo-[2,3-b]-phenazin-4(5H)-ylidene)benzothiazole-2-amine (L1), and report in vitro cell studies. Results of antitumor activity using cell viability assay, reactive oxygen species (ROS) generation and nuclear condensation in PC-3 (Human, prostate carcinoma) cells show that the metal complex is more potent than ligand. La(III) complexes have been synthesized by reaction of lanthanum(III) salt in 1:2 M ratio with ligands L1 and 3-(ethoxymethylene)-2,3-dihydro-1H-indolo[2,3-b]-phenazin-4(5H)-ylidene)benzathiazole-2-amine (L2) in methanol. The ligands and their La(III) complexes were characterized by molar conductance, magnetic susceptibility, elemental analyses, FT-IR, UV-Vis, 1H/13C NMR, thermogravimetric, XRD, and SEM analysis.

  3. Inhibitory Effects of Lanthanum Chloride on Wear Particle-Induced Osteolysis in a Mouse Calvarial Model.

    PubMed

    Shang, Jiang-Yin-Zi; Zhan, Ping; Jiang, Chuan; Zou, Yang; Liu, Hucheng; Zhang, Bin; Dai, Min

    2016-02-01

    Osteolysis is a bone disorder associated with progressive destruction of bone tissues. However, the effects of lanthanum chloride (LaCl3) on osteolysis remain unknown. Therefore, the aim of this study was to determine the effects of LaCl3 on osteolysis in vivo. In a mouse calvarial model, C57BL/6J mice were injected with wear particles with or without LaCl3. Microcomputed tomography, hematoxylin and eosin staining, and tartrate-resistant acid phosphatase staining were performed for the pathological characterization of calvariae, and eight calvariae per group were prepared for the assay of TNF-α, IL-1β, and RANKL secretion using quantitative enzyme-linked immunosorbent assay (ELISA). In mice treated with high-dose LaCl3, particle-induced osteolysis and inflammatory reaction were reduced compared with that in the vehicle-treated control. Moreover, treatment with high-dose LaCl3 suppressed the wear particle-induced decrease in bone mineral content, bone mineral density, and bone volume fraction. Bone destruction and resorption were higher in the LaCl3-treated group than in the saline-treated group but lower than those in the wear particle group. Finally, our results showed that treatment with a high dose of LaCl3 suppressed osteoclastogenesis. Thus, LaCl3 may represent a novel therapeutic agent for the treatment or prevention of wear particle-induced osteolysis and aseptic loosening. PMID:26105543

  4. 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.

    2016-05-01

    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.

  5. 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. PMID:26232040

  6. 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

  7. Effect of lanthanum ions (La3+) on the reactive oxygen species scavenging enzymes in wheat leaves.

    PubMed

    Zhang, Lijing; Zeng, Fuli; Xiao, Rong

    2003-03-01

    Physiological effects of lanthanum ions on the activities of the enzymes in the reactive oxygen species (ROS) scavenging system in leaves of wheat (Triticum aestivum L.) seedlings were studied. Wheat leaves treated in Hogland solution with 0.1 mM LaCl(3) for 48 h showed increased levels of superoxide dismutase (SOD), catalase (CAT), ascorbate-specific peroxidase (AsA-POD), and dehydroascorbate reductase (DHAR). However, a minor effect was observed on the levels of monodehydroascorbate reductase (MDAR) and glutathione reductase (GR), which regulate the release of energy required by the ROS scavenging system. The whole system was linked up by H(+) transmission. Our results indicated that the activities of the enzymes that function directly to remove ROS were elevated by La(3+) treatment, which is consistent with the observations that La(3+)-treated plants had increased tolerance to environmental stresses. The remaining levels of MDAR and GR suggested that these two enzymes might be regulated differently from that of the other four enzymes studied. PMID:12663948

  8. Lanthanum carbonate versus sevelamer hydrochloride: improvement of metabolic acidosis and hyperkalemia in hemodialysis patients.

    PubMed

    Filiopoulos, Vassilis; Koutis, Ioannis; Trompouki, Sofia; Hadjiyannakos, Dimitrios; Lazarou, Dimitrios; Vlassopoulos, Dimosthenis

    2011-02-01

    Sevelamer hydrochloride (SH) has been reported to aggravate metabolic acidosis and hyperkalemia. This study was performed to evaluate acid-base status and serum potassium changes after replacing SH with lanthanum carbonate (LC) in hemodialysis patients. SH was prescribed for 24 weeks in 14 stable hemodialysis patients and replaced by LC in a similar treatment schedule. Laboratory tests, including indices of acid-base status, nutrition, bone/mineral metabolism, and dialysis adequacy, were performed monthly during the study. Dialysate bicarbonate, potassium and calcium concentrations remained constant. Serum bicarbonate and pH rose, and serum potassium dropped significantly under LC. Alkaline phosphatase also decreased significantly under LC. No significant differences were observed in the other studied parameters between the two treatment periods. Control of serum phosphate was similar under both phosphate-binders and no differences were observed in calcium, Ca × P product, CRP, or lipid levels. Dialysis adequacy was constantly kept within K/DOQI target-range. Although full compliance to treatment was reported, three patients on LC complained of gastrointestinal upset and/or a metallic taste, and four had difficulty chewing the LC tablet. LC improves metabolic acidosis and hyperkalemia in hemodialysis patients previously under SH. Although both medications are well-tolerated, the gastrointestinal side-effects appear to occur more frequently with LC; a fact that, together with difficulties in chewing the tablet, may result in decreased compliance. PMID:21272248

  9. Effects of change in the formulation of lanthanum carbonate on laboratory parameters.

    PubMed

    Takita, Takako; Furuhashi, Mitsuyoshi; Fujimoto, Taiki; Suzuki, Hiroo; Harada, Masaki; Maruyama, Satoshi; Tamiya, Rika; Kamiya, Eri; Okamoto, Mari; Tukada, Atsuyo; Furuhashi, Mikako; Kato, Akihiko

    2014-06-01

    Lanthanum carbonate (LC) is available in the two formulations of chewable tablets and granules. In this study, we changed the formulation of LC from chewable tablet to granules, and compared the laboratory parameters for 3 months before and after changing formulation in 58 hemodialysis (HD) patients. We also surveyed patients about their preferences for the two formulations. The mean serum phosphorus (P) levels decreased significantly (P < 0.01) from 6.7 mg/dL to 6.4 mg/dL after the change. The levels for serum albumin and geriatric nutritional risk index increased significantly (P < 0.01). Serum calcium levels also increased significantly (P < 0.01), while serum intact parathyroid hormone levels decreased significantly (P < 0.01). In the survey, approximately half of the patients responded that the granules were easier to take than the chewable tablets. These findings suggest that changing the formulation of LC to granules may reduce serum P levels of the HD patients in clinical practices. PMID:24953762

  10. Is granular formulation of lanthanum carbonate more effective than chewable tablets?

    PubMed

    Okamoto, Hidekazu; Haruhara, Koutarou; Kamejima, Sahoko; Mafune, Hana; Manabe, Mayumi; Kanzaki, Goh; Mashiko, Hiroshi; Yokoo, Takashi

    2014-06-01

    Maintenance dialysis patients at our hospital who had been receiving lanthanum carbonate (LC) chewable tablets were switched to the same dosage of the granules, and the differences in serum phosphorus (P) levels were compared, together with stratifying patients at the baseline characteristics. Compared to average serum P level of 5.48 mg/dL for 2 months prior to switching, the average level for 2 months after switching was 4.99 mg/dL (P = 0.049). For patients who were under 60, serum P levels were significantly improved after switching (P = 0.016), and for patients who were concomitantly taking many kinds of medications, a correlation to high reductions of serum P level after switching was shown (R = -0.635, P = 0.015). In order to maximize pharmaceutical potential of LC, we think that it is not only necessary to provide patients with how to take the medication, but it is also important to take into consideration the patients' baseline characteristics. PMID:24953763

  11. The interfaces of lanthanum oxide-based subnanometer EOT gate dielectrics

    PubMed Central

    2014-01-01

    When pushing the gate dielectric thickness of metal-oxide-semiconductor (MOS) devices down to the subnanometer scale, the most challenging issue is the interface. The interfacial transition layers between the high-k dielectric/Si and between the high-k dielectric/gate metal become the critical constraints for the smallest achievable film thickness. This work presents a detailed study on the interface bonding structures of the tungsten/lanthanum oxide/silicon (W/La2O3/Si) MOS structure. We found that both W/La2O3 and La2O3/Si are thermally unstable. Thermal annealing can lead to W oxidation and the forming of a complex oxide layer at the W/La2O3 interface. For the La2O3/Si interface, thermal annealing leads to a thick low-k silicate layer. These interface layers do not only cause significant device performance degradation, but also impose a limit on the thinnest equivalent oxide thickness (EOT) to be achievable which may be well above the requirements of our future technology nodes. PMID:25246873

  12. 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.

  13. 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.

  14. 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.

  15. Lanthanum chloride enhances cisplatin-induced apoptosis in ovarian cancer cells.

    PubMed

    Wang, F; Zhu, Y; Fang, S; Li, S; Liu, S

    2016-01-01

    Ovarian cancer begins in an ovary. It is the leading cause of mortality from gynecologic cancer. Cisplatin is an anti-ovarian tumor drug. However, repeated use of cisplatin causes serious resistance. Recently, Lanthanum chloride (LaCl3) was found to inhibit the proliferation and promote the apoptosis in some cancer cells. In this study, we investigated the influence of LaCl3 on cisplatin-induced apoptosis in the ovarian cell line (COC1). Cell-based assays and analysis of cellular ultra structure were used. Result showed that LaCl3 enhanced cisplatin-induced apoptosis in COC1. Furthermore, the application of Cisplatin also altered the expression level of tumor related proteins, such as ERCC1, Ki67, and CDK6. Overall, we determined the inhibitory effect of LaCl3 on the COC1 growth when treated with Cisplatin, which may serve as a basis for the clinical application of LaCl3 in the treatment of ovarian cancer. PMID:27453264

  16. 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.

  17. 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

  18. 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.

  19. 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.

  20. Effects of calcination on microscopic and mesoscopic structures in Ca- and Sr-doped nano-crystalline lanthanum chromites

    SciTech Connect

    Bhatt, Himal; Bahadur, J.; Deo, M.N.; Ramanathan, S.; Pandey, K.K.; Sen, D.; Mazumder, S.; Sharma, Surinder M.

    2011-01-15

    Calcination behavior of nano-crystalline lanthanum chromites doped with calcium and strontium has been probed by Fourier transform infrared spectroscopy, X-ray diffraction and small-angle neutron scattering as a function of temperature. Infrared spectroscopic results imply that over a range of temperatures, some intermediate phase of dopant chromates evolve and then dissolve back, which has also been confirmed by the XRD. Neutron scattering data reveal a fractal type correlation of building blocks in virgin powders. Increase in fractal dimension and reduction in upper cutoff vis-a-vis the densification of agglomerates were found with increasing calcination temperature. Calcination, beyond 900 {sup o}C, results in breaking down of the fractal morphology almost completely. Such shrinkage event also results in a modification of the microscopic structure. These changes have been attributed to the compaction of agglomerates of both Ca- and Sr-doped lanthanum chromites, assisted via liquid state sintering by the melting of the intermediate phases at intermediate calcination stages. -- Graphical Abstract: Dopant chromates evolve as intermediate phases during calcination of Ca- and Sr-doped nano-crystalline lanthanum chromites at intermediate temperatures, around 900 {sup o}C, evident from infrared spectroscopy. Such an event results in a modification of the microscopic and mesoscopic structures. Display Omitted Research highlights: {yields} Meso/microscopic structures of La{sub 0.7}Ca{sub 0.3}CrO{sub 3} and La{sub 0.8}Sr{sub 0.2}CrO{sub 3} modify during calcination. {yields} Transient phases CaCrO{sub 4} and SrCrO{sub 4} appear at intermediate temperatures. {yields} Bond length, unit cell volume, etc. modify as intermediate phases evolve and extinct. {yields} Compaction of the agglomerates takes place due to liquid state assisted sintering.

  1. 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

  2. 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.

  3. Development of scintillation materials for PET scanners

    NASA Astrophysics Data System (ADS)

    Korzhik, Mikhail; Fedorov, Andrei; Annenkov, Alexander; Borissevitch, Andrei; Dossovitski, Alexei; Missevitch, Oleg; Lecoq, Paul

    2007-02-01

    The growing demand on PET methodology for a variety of applications ranging from clinical use to fundamental studies triggers research and development of PET scanners providing better spatial resolution and sensitivity. These efforts are primarily focused on the development of advanced PET detector solutions and on the developments of new scintillation materials as well. However Lu containing scintillation materials introduced in the last century such as LSO, LYSO, LuAP, LuYAP crystals still remain the best PET species in spite of the recent developments of bright, fast but relatively low density lanthanum bromide scintillators. At the same time Lu based materials have several drawbacks which are high temperature of crystallization and relatively high cost compared to alkali-halide scintillation materials. Here we describe recent results in the development of new scintillation materials for PET application.

  4. Doped lanthanum nickelates with a layered perovskite structure as bifunctional cathode catalysts for rechargeable metal-air batteries.

    PubMed

    Jung, Kyu-Nam; Jung, Jong-Hyuk; Im, Won Bin; Yoon, Sukeun; Shin, Kyung-Hee; Lee, Jong-Won

    2013-10-23

    Rechargeable metal-air batteries have attracted a great interest in recent years because of their high energy density. The critical challenges facing these technologies include the sluggish kinetics of the oxygen reduction-evolution reactions on a cathode (air electrode). Here, we report doped lanthanum nickelates (La2NiO4) with a layered perovskite structure that serve as efficient bifunctional electrocatalysts for oxygen reduction and evolution in an aqueous alkaline electrolyte. Rechargeable lithium-air and zinc-air batteries assembled with these catalysts exhibit remarkably reduced discharge-charge voltage gaps (improved round-trip efficiency) as well as high stability during cycling. PMID:24053465

  5. 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.

  6. 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.

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

    SciTech Connect

    Roszak, S.; Balasubramanian, K.

    1997-01-01

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

  8. 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.

  9. Characterization of historical {sup 131}I emissions from Oak Ridge radioactive lanthanum processing

    SciTech Connect

    Widner, T.E.

    1996-06-01

    As part of the Oak Ridge Dose Reconstruction, a detailed assessment of {sup 131}I releases from radioactive lanthanum (RaLa) processing is being conducted. From 1944 through 1956, fuel slugs from Oak Ridge (X-10) and Hanford reactors were dissolved and processed at Oak Ridge to separate {sup 140}La for Los Alamos weapons development. Fuel cooling times were as short as several hours, and dissolver off-gas passed through a caustic scrubber. In an earlier feasibility study, simple screening analyses identified RaLa processing as one of the largest potential contributors to off-site risk from the three Oak Ridge plants, with releases over 3.7 PBq (100,000 Ci) considered likely. With the close proximity of surrounding populations and potential {sup 131}I releases comparable to those established in the Hanford dose reconstruction, a detailed investigation was initiated. Inventories of {sup 131}I and {sup 140}Ba in X-10 slugs were calculated using the ORIGEN 2.1 code, detailed slug exposure records, and neutron flux distributions determined in the X-10 reactor in 1945. Informal expert elicitation was used to estimate a {sup 131}I release fraction for use in the initial iteration of the assessment. For later iterations, a simple numerical model of iodine distribution in RaLa chemical processing was prepared to predict releases from the dissolver and waste neutralizer tank based on five mass-balance equations. The critical caustic scrubber was then modeled with a kinetic-based model of iodine mass transfer. Separate analyses of release fractions are necessary for a number of off-normal conditions and accidents. The models were integrated for estimation of time histories of {sup 131}I release, interfacing with calculations of environmental transport, off-site exposure, and ranges of historical doses and health risks in a manner that reflects the uncertainty of all components.

  10. 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

  11. 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.

  12. 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

  13. 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.

  14. Synthesis, structural, optical and Raman studies of pure and lanthanum doped ZnSe nanoparticles

    SciTech Connect

    Kumar, Pushpendra; Singh, Jai; Pandey, Mukesh Kumar; Jeyanthi, C.E.; Siddheswaran, R.; Paulraj, M.; Hui, K.N.; Hui, K.S.

    2014-01-01

    Graphical abstract: - Highlights: • Template-free synthesis of ZnSe and ZnSe:La nanoparticles was developed at low temperature 100 °C. • Cubic ZnSe and ZnSe:La nanoparticles were obtained by chemical route. • As-synthesized ZnSe:La nanoparticles showed higher emission intensity than ZnSe nanoparticles. • Band gap (E{sub g}) of ZnSe nanoparticles was bigger than ZnSe nanoparticles due to nanosized effect. - Abstract: In this work, a simple, effective and reproducible chemical synthetic route for the production of high-quality, pure ZnSe nanoparticles (NPs), and lanthanum-doped ZnSe (ZnSe:La) NPs is presented. The wide bandgap, luminescent pure ZnSe and ZnSe:La NPs has been synthesized at a low temperature (100 °C) in a single template-free step. The size and optical bandgap of the NPs was analyzed from powder X-ray diffraction (XRD), UV–visible (UV–vis) spectroscopy, transmission electron microscopy (TEM), and high resolution transmission electron microscopy (HRTEM). A broad photoluminescence (PL) emission across the visible spectrum has been demonstrated by a systematic blue-shift in emission due to the formation of small nanoparticles. Here, contribution to emission intensity from surface states of NPs increases with La doping. TEM data revealed that the average size of ZnSe and ZnSe:La NPs is 14 and 8 nm, respectively. On the other hand, band gap energy E{sub g} of ZnSe and ZnSe:La NPs were found to be 3.59 eV and 3.65 eV, respectively. Results showed that hydrazine hydrate played multiple roles in the formation of ZnSe and ZnSe:La NPs. A possible reaction mechanism for the growth of NPs is also discussed.

  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

    2016-03-01

    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. 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. PMID:20683532

  17. 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.

  18. 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.

  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. 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

  2. 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

  3. Lanthanum Gallium Tin Antimonides LaGa xSn ySb 2

    NASA Astrophysics Data System (ADS)

    Morgan, Mark G.; Wang, Meitian; Mills, Allison M.; Mar, Arthur

    2002-08-01

    A series of quaternary lanthanum gallium tin antimonides LaGa xSn ySb 2 was elaborated to trace the structural evolution between the known end members LaGaSb 2 (SmGaSb 2-type) and LaSn ySb 2 (LaSn 0.75Sb 2-type). Five members of this series were characterized by single-crystal X-ray diffraction. For low Sn content, the Sn atoms disorder with Ga atoms in zigzag chains to form solid solutions LaGa 1- ySn ySb 2 (0≤y≤0.2) adopting the SmGaSb 2-type structure, as exemplified by LaGa 0.92(3)Sn 0.08Sb 2 and LaGa 0.80(3)Sn 0.20Sb 2 (orthorhombic, space group D52- C222 1, Z=4). For higher Sn and lower Ga content, there is a segregation in which the Sn atoms appear in chains of closely spaced partially occupied sites as in the parent LaSn 0.75Sb 2-type structure whereas the Ga atoms remain in zigzag chains as in the parent SmGaSb 2-type structure. This feature is observed in the structures of LaGa 0.68(4)Sn 0.31(3)Sb 2, LaGa 0.62(3)Sn 0.32(3)Sb 2, and LaGa 0.43(3)Sn 0.39(3)Sb 2 (orthorhombic, space group D172 h- Cmcm, Z=4). The last example illustrates that the combined Ga/Sn content can be substoichiometric ( x+ y<1). These compounds have a layered nature, with the chains of Ga or Sn atoms residing between 2∞[LaSb 2] slabs.

  4. 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

  5. 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.

  6. Efficacy of oral powder compared with chewable tablets for lanthanum carbonate administration in hemodialysis patients.

    PubMed

    Sakurada, Tsutomu; Oishi, Daisuke; Shibagaki, Yugo; Yasuda, Takashi; Kimura, Kenjiro

    2013-10-01

    Lanthanum carbonate (LC) has been administered in a chewable tablet form for patients with hyperphosphatemia undergoing dialysis. However, some patients have difficulty chewing the tablets. LC oral powder has recently been released in Japan. The purpose of this study was to clarify the efficacy of LC oral powder form compared with that of chewable tablet form. The efficacy and safety of LC oral powder was retrospectively assessed in hemodialysis patients who switched from chewable tablet form to oral powder form without dose modification. Thirty-six patients (mean age, 66.8 ± 10.5 years; male, 64%; 39% with diabetes; mean duration of dialysis treatment, 99.2 ± 95.6 months) were enrolled in this study between June and July of 2012. Changes in clinical data and adverse events after the switch to oral powder form were investigated. The average dose of LC was 1180 ± 520 mg/day. Serum phosphorus levels were significantly decreased after the switch from chewable tablet form to oral powder form (5.3 ± 1.7 mg/dL at baseline vs. 4.9 ± 1.2 mg/dL at after 1 month after, P = 0.038). In contrast, no significant differences were observed in serum calcium and parathyroid hormone levels. Furthermore, no significant differences were evident in weight gain after the switch to oral powder form (2.5 ± 1.2 kg at baseline vs. 2.4 ± 1.1 kg at 1 month after the switch, P = 0.29). No serious adverse events were recorded. Our results suggest that LC is more effective in oral powder form than chewable tablet form for hemodialysis patients. PMID:24134326

  7. Lanthanum (III) regulates the nitrogen assimilation in soybean seedlings under ultraviolet-B radiation.

    PubMed

    Huang, Guangrong; Wang, Lihong; Zhou, Qing

    2013-01-01

    Ultraviolet-B (UV-B, 280-320 nm) radiation has seriously affected the growth of plants. Finding the technology/method to alleviate the damage of UV-B radiation has become a frontal topic in the field of environmental science. The pretreatment with rare earth elements (REEs) is an effective method, but the regulation mechanism of REEs is unknown. Here, the regulation effects of lanthanum (La(III)) on nitrogen assimilation in soybean seedlings (Glycine max L.) under ultraviolet-B radiation were investigated to elucidate the regulation mechanism of REEs on plants under UV-B radiation. UV-B radiation led to the inhibition in the activities of the key enzymes (nitrate reductase, glutamine synthetase, glutamate synthase) in the nitrogen assimilation, the decrease in the contents of nitrate and soluble proteins, as well as the increase in the content of amino acid in soybean seedlings. The change degree of UV-B radiation at the high level (0.45 W m(-2)) was higher than that of UV-B radiation at the low level (0.15 W m(-2)). The pretreatment with 20 mg L(-1) La(III) could alleviate the effects of UV-B radiation on the activities of nitrate reductase, glutamine synthetase, glutamate synthase, and glutamate dehydrogenase, promoting amino acid conversion and protein synthesis in soybean seedlings. The regulation effect of La(III) under UV-B radiation at the low level was better than that of UV-B radiation at the high level. The results indicated that the pretreatment with 20 mg L(-1) La(III) could alleviate the inhibition of UV-B radiation on nitrogen assimilation in soybean seedlings. PMID:23090712

  8. Arsenic Adsorption on Lanthanum-Impregnated Activated Alumina: Spectroscopic and DFT Study.

    PubMed

    Shi, Qiantao; Yan, Li; Chan, Tingshan; Jing, Chuanyong

    2015-12-01

    Rare earth-modified adsorbents (REMAs) have been widely used to remove oxyanion pollutants from water, including arsenic (As). However, the molecular-level structural information and reactions at the liquid/solid interface are still murky, which limits the design of applicable REMAs. Herein, a lanthanum-impregnated activated alumina (LAA) was synthesized as a representative REMA, and its As uptake mechanisms were explored using multiple complementary characterization techniques. Our adsorption experiments showed that LAA exhibited 2-3 times higher As adsorption capacity than AA. In contrast to the bidentate configuration formed on most metal oxide surfaces, our EXAFS and DFT results suggest that As(III) and As(V) form monodentate surface complexes on LAA through As-O-La coordinative bonding. In situ flow cell ATR-FTIR observed a strong dependence of As-O peak positions on pH, which could be interpreted as the change in the fractions of As(V) surface complexes with zero- to double-protonation on LAA, AA, and LaOOH. As(V) on LAA existed as singly and doubly protonated surface species, and the pKa of transition from double to single protonation (∼5.8) was lower than that for its soluble counterpart (6.97). The surface reaction and structural configuration were incorporated in a CD-MUSIC model to satisfactorily predict macroscopic As adsorption behaviors. The insights gained from the molecular-level reactions shed light on the design and application of REMAs in environmental remediation for As and its structural analogues. PMID:26565426

  9. 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. PMID:26802561

  10. 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

  11. 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

  12. 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.

  13. 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%.

  14. 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

  15. Tracking petroleum refinery emission events using lanthanum and lanthanides as elemental markers for PM2.5.

    PubMed

    Kulkarni, Pranav; Chellam, Shankararaman; Fraser, Matthew P

    2007-10-01

    Fine particulate matter levels at four air sampling stations in the Houston, TX area are apportioned to quantify the impact of emissions from a local refinery during a reported emission event. Through quantification of lanthanum and lanthanides using a recently developed analytical technique, the impacts of emissions from fluidized-bed catalytic cracking (FCC) units are quantitatively tracked across the Houston region. The results show a significant (33-106-fold) increase in contributions of FCC emissions to PM2.5 compared with background levels associated with routine operation. This impact from industrial emissions to ambient air quality occurs simultaneously with a larger, regional haze episode that lead to elevated PM2.5 concentrations throughout the entire region. By focusing on detailed chemical analysis of unique maker metals (lanthanum and lanthanides), the impact of emissions from the FCC unit was tracked from the local refinery that reported the emission event to a site approximately 50 km downwind, illustrating the strength of the analytical method to isolate an important source during a regional haze episode not related to the emission event. While this source apportionment technique could separate contributions from FCC emissions, improved time-resolved sampling is proposed to more precisely quantify the impacts of transient emission events on ambient PM2.5. PMID:17969690

  16. Selective dehydration of bio-ethanol to ethylene catalyzed by lanthanum-phosphorous-modified HZSM-5: influence of the fusel.

    PubMed

    Hu, Yaochi; Zhan, Nina; Dou, Chang; Huang, He; Han, Yuwang; Yu, Dinghua; Hu, Yi

    2010-11-01

    Bio-ethanol dehydration to ethylene is an attractive alternative to oil-based ethylene. The influence of fusel, main byproducts in the fermentation process of bio-ethanol production, on the bio-ethanol dehydration should not be ignored. We studied the catalytic dehydration of bio-ethanol to ethylene over parent and modified HZSM-5 at 250°C, with weight hourly space velocity (WHSV) equal to 2.0/h. The influences of a series of fusel, such as isopropanol, isobutanol and isopentanol, on the ethanol dehydration over the catalysts were investigated. The 0.5%La-2%PHZSM-5 catalyst exhibited higher ethanol conversion (100%), ethylene selectivity (99%), and especially enhanced stability (more than 70 h) than the parent and other modified HZSM-5. We demonstrated that the introduction of lanthanum and phosphorous to HZSM-5 could weaken the negative influence of fusel on the formation of ethylene. The physicochemical properties of the catalysts were characterized by ammonia temperature-programmed desorption (NH(3)-TPD), nitrogen adsorption and thermogravimetry (TG)/differential thermogravimetry (DTG)/differential thermal analysis (DTA) (TG/DTG/DTA) techniques. The results indicated that the introduction of lanthanum and phosphorous to HZSM-5 could inhibit the formation of coking during the ethanol dehydration to ethylene in the presence of fusel. The development of an efficient catalyst is one of the key technologies for the industrialization of bio-ethylene. PMID:21058319

  17. 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.

  18. 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

  19. 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. PMID:23358559

  20. 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.

  1. 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. PMID:26613180

  2. 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.

  3. 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. PMID:26647298

  4. 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

  5. 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.

  6. Design of a dual-effect lens on lanthanum-modified lead zirconate titanate for continuous variation of focal length

    NASA Astrophysics Data System (ADS)

    Castro, Francisco; Nabet, Bahram

    1995-05-01

    The design of a Fresnel lens with continuous focal length is proposed for use in optical processing. A convex lens is induced in lanthanum-modified lead zirconate titanate through the application of an electric-field profile supplied by the indium tin oxide electrodes that make up the zones of a Fresnel lens. The use of a numerical method based on fast Fourier transform algorithms was required to analyze accurately the induced field inside a Fresnel lens with an initial focal length of 0.4 m (at 470 nm) and 20 indium tin oxide electrodes. The effective focal location obtained by the combined mechanisms is derived. This design is expected to produce continuous variations of approximately 16% in focal length; the ability of previous designs to achieve focal length switching is maintained.

  7. 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

  8. 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

  9. C-band single-longitudinal mode lanthanum co-doped bismuth based erbium doped fiber ring laser.

    PubMed

    Qureshi, Khurram Karim; Feng, X H; Zhao, L M; Tam, H Y; Lu, C; Wai, P K A

    2009-08-31

    We propose and demonstrate a stable, tunable and narrow linewidth C-band lanthanum co-doped bismuth based erbium doped fiber (EDF) ring laser with single longitudinal mode (SLM) operation. A free space thin film filter acts as a wavelength discriminative component selecting a few oscillating modes while a Lyot filter formed by a polarization maintaining (PM) fiber and a linear polarizer further discriminates and selects SLM efficiently. A power stability of < or = 0.05 dB, central wavelength variation of < or = 0.02 nm, a side-mode suppression ratio (SMSR) of at least > 43 dB, and a linewidth of about 1.3 kHz have been experimentally demonstrated. PMID:19724634

  10. Thermodynamic analysis of nanoparticle size effect on kinetics in Fischer-Tropsch synthesis by lanthanum promoted iron catalyst

    NASA Astrophysics Data System (ADS)

    Nakhaei Pour, Ali; Housaindokht, Mohammad Reza; Behroozsarand, Alireza; Khodagholi, Mohammad Ali

    2014-08-01

    The kinetic parameters of the Fischer-Tropsch synthesis (FTS) on iron catalyst are analyzed by size-dependent thermodynamic method. A Langmuir-Hinshelwood kinetic equation is considered for evaluation of catalytic activity of lanthanum promoted iron catalyst. A series of unsupported iron catalysts with different particle sizes were prepared via microemulsion method. The experimental results showed that catalyst activity pass from a maximum value by increasing the iron particle size. Also, data presented that iron particle size has considerable effects on adsorption parameters and FTS rates. The ratio of surface tension ( σ) to nanoparticle radius ( r) is important in FTS reaction on iron catalyst. Finally, the results showed that by increasing of iron particle size from 18 to 45 nm the activation energies of catalysts and heats of adsorption of catalysts as two main parameters of FTS reaction increased from 89 to 114 kJ/mol and from 51 to 71 kJ/mol, respectively.

  11. Effects of Cerium and Lanthanum on the Corrosion Behavior of Al-3.0 wt.%Mg Alloy

    NASA Astrophysics Data System (ADS)

    Zhang, Xin; Wang, Zehua; Zhou, Zehua; Xu, Jianming

    2016-03-01

    Effects of rare earth elements (RE: cerium and lanthanum) on the corrosion behavior of Al-3.0 wt.%Mg alloy were investigated by electrochemical measurement and immersion test in 3.5 wt.% NaCl solution. The results indicated that a proper amount of rare earth (about 0.2 wt.%) could improve the corrosion resistance of Al-3.0 wt.%Mg alloy effectively, whereas that excessive rare earth addition would increase the corrosion rate and reduce the corrosion resistance. The corrosion behavior of Al-3.0 wt.%Mg alloys in 3.5 wt.% NaCl solution showed typical characteristics of pitting corrosion at the position of second phases. The more and the bigger the second phases, the more and the larger the pitting holes.

  12. 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

  13. 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.

  14. Top electrode-dependent resistance switching behaviors of lanthanum-doped ZnO film memory devices

    NASA Astrophysics Data System (ADS)

    Xu, Dinglin; Xiong, Ying; Tang, Minghua; Zeng, Baiwen

    2014-03-01

    Lanthanum-doped ZnO (Zn0.99La0.01O) polycrystalline thin films were deposited on Pt/Ti/SiO2/Si substrates by a chemical solution deposition method. Metal/La-doped ZnO/Pt sandwich structures were constructed by depositing different top electrodes (Ag and Pt). Unipolar switching and bipolar switching characteristics were investigated in Pt/La-doped ZnO/Pt and Ag/La-doped ZnO/Pt structures, respectively. Compared with the undoped devices (Pt/ZnO/Pt and Ag/ZnO/Pt), the La-doped devices exhibits superior resistive switching performances, such as narrow distribution of the resistive switching properties ( R ON, R OFF, V Set, and V Reset), higher R OFF/ R ON ratio and sharp switching transition.

  15. Determination of the ionic conductivity of Sr-doped lanthanum manganite by modified Hebb-Wagner technique

    NASA Astrophysics Data System (ADS)

    Miruszewski, T.; Karczewski, J.; Bochentyn, B.; Jasinski, P.; Gazda, M.; Kusz, B.

    2016-04-01

    The Hebb-Wagner polarization method with the electron blocking electrode has been discussed in this paper in aim to determine a partial ionic conductivity of Sr-doped lanthanum manganite. The "limiting current" in the proposed system was measured using the two-point DC technique with additional Pt electrode between LSM and blocking electrode. The electrochemical model based on bulk diffusion processes and Boltzmann statistics has been also described. The ionic conductivity calculated with the use of proposed model for La0.7Sr0.3MnO3+δ was 5.3×10-4 S cm-1 at 800 °C and the activation energy of ionic conductivity was found to be (0.60±0.02) eV. This result is in agreement with previous literature reports and indicates the workability of the modified Hebb-Wagner system.

  16. 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

  17. 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.

  18. Questionnaire survey and serum phosphorus levels in maintenance hemodialysis patients switching lanthanum carbonate formulation from chewable tablets to granules.

    PubMed

    Mukai, Itsumi; Yoshizawa, Taku; Kumagai, Junko; Takahashi, Naoko; Tsuchiya, Shinichiro

    2014-06-01

    We conducted a questionnaire survey of 79 maintenance hemodialysis patients switching lanthanum carbonate (LC) formulation from chewable tablets to granules, to investigate the compliance and patient preferences of these two formulations. For the number of times chewed when taking chewable tablets, the ratio of patients who responded 10 times or more was 54.4%, who responded four to nine times was 24.1% and who responded three times or less was 8.9%. Thirty-seven patients (46.8%) responded "Granules are easier to take", 22 patients (27.8%) responded "Chewable tablets are easier to take", and 20 patients (25.3%) responded "No difference between formulations." Changes in serum phosphorus (P) levels were also measured for 4 weeks after switching formulation, but no significant differences were observed before and after switching. We think that these questionnaire survey results show the compliance status and the patient needs for LC in the clinical practices. PMID:24953764

  19. 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

  20. An Investigation of Lanthanum Coordination Compounds by Using Solid- State 139La NMR Spectroscopy and Relativistic Density Functional Theory

    SciTech Connect

    Willans, Mathew J.; Feindel, Kirk W.; Ooms, Kristopher J.; Wasylishen, Roderick E.

    2005-12-16

    Lanthanum-139 NMR spectra of stationary samples of several solid LaIII coordination compounds have been obtained at applied magnetic fields of 11.75 and 17.60 T. The breadth and shape of the 139La NMR spectra of the central transition are dominated by the interaction between the 139La nuclear quadrupole moment and the electric field gradient (EFG) at that nucleus; however, the influence of chemical-shift anisotropy on the NMR spectra is non-negligible for the majority of the compounds investigated. Analysis of the experimental NMR spectra reveals that the 139La quadrupolar coupling constants (CQ) range from 10.0 to 35.6 MHz, the spans of the chemical-shift tensor (W) range from 50 to 260 ppm, and the isotropic chemical shifts (diso) range from -80 to 178 ppm. In general, there is a correlation between the magnitudes of CQ and W, and diso is shown to depend on the La coordination number. Magnetic shielding tensors, calculated by using relativistic zeroth-order regular approximation density functional theory (ZORA-DFT) and incorporating scalar only or scalar plus spin-orbit relativistic effects, qualitatively reproduce the experimental chemical-shift tensors. In general, the inclusion of spin-orbit coupling yields results that are in better agreement with those from the experiment. The magnetic-shielding calculations and experimentally determined Euler angles can be used to predict the orientation of the chemical-shift and EFG tensors in the molecular frame. This study demonstrates that solid state 139La NMR spectroscopy is a useful characterization method and can provide insight into the molecular structure of lanthanum coordination compounds.

  1. Actin-based endosome and phagosome rocketing in macrophages: activation by the secretagogue antagonists lanthanum and zinc.

    PubMed

    Southwick, Frederick S; Li, Wei; Zhang, Fangliang; Zeile, William L; Purich, Daniel L

    2003-01-01

    Although motile endocytic vesicles form actin-rich rocket tails [Merrifield et al., 1999: Nature Cell Biol 1:72-74], the mechanism of intracellular organelle locomotion remains poorly understood. We now demonstrate that bone marrow macrophages treated with lanthanum and zinc ions, well-known secretagogue antagonists, reliably exhibit vesicle motility. This treatment results in accentuated membrane ruffling and the formation of phagosomes and early endosomes that move rapidly through the cytoplasm by assembling actin filament rocket tails. Protein-specific immunolocalization demonstrated the presence of Arp2/3 complex in the polymerization zone and throughout the actin-rich tail, whereas N-WASP was most abundant in the polymerization zone. Although Arp2/3 and N-WASP play essential roles in nucleating filament assembly, other processes (i.e., elongation and filament cross-linking) are required to produce forces needed for motility. Efficient elongation was found to require zyxin, VASP, and profilin, proteins that interact by means of their ABM-1 and ABM-2 proline-rich motifs. The functional significance of these motifs was demonstrated by inhibition of vesicle motility by the motif-specific ABM-1 and ABM-2 analogues. Furthermore, lanthanum/zinc treatment also facilitated the early onset of actin-based vaccinia motility, a process that also utilizes Arp2/3 and N-WASP for nucleation and the zyxin-VASP-profilin complex for efficient elongation. Although earlier studies using cell extracts clouded the role of oligoproline sequences in activating the polymerization zone, our studies emphasize the importance of evaluating motility in living cells. PMID:12451594

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. Synthesis and EPR Characterization of Exohedrally Perfluoroalkylated Paramagnetic Lanthanum Metallofullerenes: A Fluorous Phase Approach

    NASA Astrophysics Data System (ADS)

    Tagmatarchis, Nikos; Taninaka, Atsushi; Shinohara, Hisanori; Prato, Maurizio

    2002-10-01

    A strategy to chemically derivatize the outer sphere of endohedral metallofullerenes by using a modern organic technique that utilizes 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 systematic study of exohedrally derivatized endohedral metallofullerenes should ultimately provide technologically intriguing novel nano-materials.

  8. 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.

  9. New Scintillator Materials (K2CeBr5) and (Cs2CeBr5)

    NASA Technical Reports Server (NTRS)

    Hawrami, R.; Volz, M. P.; Batra, A. K.; Aggarwal, M. D.; Roy, U. N.; Groza, M.; Burger, A.; Cherepy, Nerine; Niedermayr, Thomas; Payne, Stephen A.

    2008-01-01

    Cesium cerium bromide (Cs2CeBr5) and potassium cerium bromide (K2CeBr5) are new scintillator materials for X-ray and gamma ray detector applications. Recently halide scintillator materials, such as Ce doped lanthanum bromide has been proved to be very important material for the same purpose. These materials are highly hygroscopic; a search for high light yield non-hygroscopic materials was highly desirable to advance the scintillator technology. In this paper, we are reporting the crystal growth of novel scintillator materials, cesium cerium bromide (Cs2CeBr5) and potassium cerium bromide (K2CeBr5). Crystals were successfully grown from the melt using the vertical Bridgman-Stockbarger technique, in a comparison with the high performance LaBr3 or LaCl3 crystals, cerium based alkali halides crystals, (Cs2CeBr5) and (K2CeBr5) have similar scintillation properties, while being much less hygroscopic. Furthermore, cesium based compounds will not suffer from the self-activity present in potassium and lanthanum compounds. However the Cs2CeBr5 crystals did not grow properly probably due to non-congruent melting or to some phase transition during cooling. Keywords." Scintillator materials; Ce3+; Energy resolution; Light yield; K2CeBr5

  10. 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).

  11. 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.

  12. 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

  13. 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

  14. 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.

  15. Lanthanum Hexaboride As Novel Interlayer for Improving the Thermal Stability of P3HT:PCBM Organic Solar Cells.

    PubMed

    Chambon, Sylvain; Murat, Yolande; Wantz, Guillaume; Hirsch, Lionel; Tardy, Pascal

    2015-11-18

    For efficient organic photovoltaic (OPV) solar cells, a low work function electrode is necessary to enhance the built-in voltage of the active layer, thereby improving the overall efficiency. Calcium is often used for this purpose in the laboratory; however, its development on a larger scale is impaired by its high reactivity with oxygen and water and the resulting low stability of solar cells under operation. The influence of a novel interlayer, lanthanum hexaboride (LaB6), on the electronic properties of OPV is studied in this work. Similarly to calcium, when LaB6 is used as an interlayer, it enhances the built-in voltage in the device, leading to a higher fill factor (FF) and optimal open circuit voltage (V(oc)). As a result, optimized LaB6-based devices present significantly improved power conversion efficiencies. More importantly, while calcium/aluminum (Ca/Al) and aluminum (Al) cathodes lose their capacity to enhance the internal electrical field during thermal aging, the LaB6/aluminum (LaB6/Al) electrode remains stable. This remarkable effect results in a highly stable V(oc) and flat-band potential during aging. PMID:26540482

  16. 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.

  17. 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

  18. Supramolecular architectures constructed by lanthanum, amino acids and 1,10-phenanthroline via non-covalent bond interactions

    NASA Astrophysics Data System (ADS)

    Zheng, Xiang-Jun; Jin, Lin-Pei

    2003-07-01

    Three supramolecular lanthanum coordination compounds of amino acids, with 1,10-phenanthroline (phen), [La 2(APA) 6(phen) 2(H 2O) 2](ClO 4) 6(phen) 4·2H 2O ( 1), [La 2(ABA) 6(phen) 2(H 2O) 2](ClO 4) 6 (phen) 6·4H 2O ( 2), and [La 2(AHA) 4(phen) 4](ClO 4) 6(phen) 4·2H 2O ( 3) (APA=3-aminopropionic acid; ABA=4-aminobutanoic acid; AHA=6-aminohexanoic acid) were synthesized and characterized by single crystal X-ray diffraction. The results show that the three coordination compounds are all composed of binuclear coordination cations built by metal-ligand coordination. Through hydrogen bonding and π-π stacking interactions, complex 1 forms a two-dimensional supramolecular sheet structure extending in the (001) plane, complex 2 forms a three-dimensional supramolecular network with many cavities occupied by ClO 4- and lattice H 2O molecules, and complex 3 forms a two-dimensional supramolecular lamellar structure in the (100) plane.

  19. Precise determination of the chemical diffusion coefficient of calcium-doped lanthanum chromites by means of electrical conductivity relaxation

    SciTech Connect

    Yasuda, Isamu; Hikita, Tomoji . Fundamental Technology Research Lab.)

    1994-05-01

    Chemical relaxation experiments were conducted on sintered samples of calcium-doped lanthanum chromites by abruptly changing the oxygen partial pressure in the atmosphere and following the time change of conductivity. The re-equilibration kinetics was analyzed by fitting the relaxation data to the solutions of Fick's second law for appropriate boundary conditions. The diffusion equation ignoring the effect of surface reaction failed to describe the transient behavior especially for the initial stage, while that taking the surface effect into account gave a satisfactory interpretation of the overall relaxation process and allowed a precise determination of the two kinetic parameters: oxygen chemical diffusion coefficient and surface reaction rate constant. The chemical diffusion coefficients increased with a decrease of the oxygen partial pressure due to the corresponding change in the concentration of the moving species. The activation energy was similar to that of oxygen vacancy diffusion coefficients in other monocrystalline perovskites, suggesting that the measured diffusion coefficients were attributable to lattice diffusion. The surface reaction rate constant increased with a decrease of the oxygen partial pressure similarly to the reported oxygen nonstoichiometry, which implies that the presence of oxygen vacancies plays an important role in the surface reaction kinetics.

  20. 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.

  1. 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.

  2. Use of lanthanum to detect changes in the permeability barrier of rat skin after dermal exposure to organic chemicals

    SciTech Connect

    Mattie, D.R.; McDougal, J.N.; Chase, M.R.; Hixson, C.J.

    1987-01-01

    Occupational dermal exposures to organic solvents are of importance due to local effects in the skin and systematic toxicity if penetration occurs through the skin. Repeated or prolonged contact with organic solvents have been shown to penetrate the skin; little information is available however, concerning effects on the barrier properties of skin after dermal exposure to solvents. This investigation examines the ultrastructural changes in rat skin after exposure of 3 organic chemicals and to correlate changes with the location of an electron-dense tracer, lanthanum, which is normally excluded by the permeability barrier in the stratum corneum. Male rats were exposed for 24 h to sterile saline, trichloroethylene (TCE), perchloroethylene (PERC), or toluene using dermal-exposure cells developed in this laboratory. Rat skin exposed to saline for 24 h appeared normal. Rat skin exposed to neat TCE, PERC or toluene for 24 h caused acute, coagulative necrosis of the epidermis and upper 1/2 to 1/3 of the dermis.

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

    PubMed

    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 La(3+) 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 La(3+) 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, La(3+) is found to mainly occupy the Y2 (2f) site in low-concentration doped samples. With increasing doping concentration, the La(3+) occupation number at the Y3 (4g) site increases faster than those at the Y1 (2e) and Y2 (2f) sites. When La(3+) 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

  4. 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

  5. Rare earth elements in the Rhine River, Germany: first case of anthropogenic lanthanum as a dissolved microcontaminant in the hydrosphere.

    PubMed

    Kulaksız, Serkan; Bau, Michael

    2011-07-01

    The distribution of dissolved rare earth elements (REE) in the Rhine River, Germany, shows the anthropogenic gadolinium (Gd) microcontamination that is commonly observed in rivers in densely populated countries with a highly evolved health care system. However, the Rhine River also carries anomalously high concentrations of lanthanum (La), which produce very large positive La anomalies in normalized REE distribution patterns. These positive La anomalies first occur north of the City of Worms and then decrease in size downstream, but are still significant approximately 400 km downstream, close to the German-Dutch border. The strong La enrichment is of anthropogenic origin and can be traced back to effluent from a production plant for fluid catalytic cracking catalysts at Rhine river-km 447.4. This effluent is characterized by extremely high dissolved total REE and La concentrations of up to 52 mg/kg and 49 mg/kg, respectively. Such La concentrations are well-above those at which ecotoxicological effects have been observed. The Rhine River is the first case observed to date, where a river's dissolved REE inventory is affected and even dominated by anthropogenic La. Our results suggest that almost 1.5t of anthropogenic dissolved La is exported via the Rhine River into the North Sea per year. This reveals that the growing industrial use of REE (and other formerly "exotic" elements) results in their increasing release into the environment, and highlights the urgent need to determine their geogenic background concentrations in terrestrial surface waters. PMID:21458860

  6. Effect of the microstructure on the thermoelectric properties of polycrystalline lanthanum chalcogenides

    NASA Technical Reports Server (NTRS)

    Lockwood, A.; Wood, C.; Vandersande, J.; Zoltan, A.; Parker, J.; Danielson, L.; Alexander, M.; Whittenberger, D.

    1987-01-01

    Small amounts of second phase materials can have important effects on the thermoelectric properties of polycrystalline gamma-La(3-x)X4 (X-S, Te; X in the range of 0 to 1/3). Microscopic examination by SEM of hot pressed La(3-x)Te4 samples has revealed from 1-5 vol. pct of La2O2Te, an amount which is not detected by X-ray powder diffraction measurements. This amount of La2O2Te resulting from oxygen contamination can reduce the concentration of electrons by as much as 10 to 75 percent below the electron concentration calculated for single phase La(3-x)Te4 in the composition range of greatest interest. Small amounts of second phase materials can also lower the lattice thermal conductivity by scattering low frequency phonons. These results indicate that microstructural effects should be considered when electrical and thermal properties of polycrystalline materials are analyzed.

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

    DOE PAGESBeta

    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

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

    DOE PAGESBeta

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

    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

  9. 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.

  10. Development of mixed conducting dense nickel/Ca-doped lanthanum zirconate cermet for gas separation application

    SciTech Connect

    Nag, S.; Mukhopadhyay, S.; Basu, R.N.

    2012-03-15

    Highlights: Black-Right-Pointing-Pointer Phase pure La{sub 1.95}Ca{sub 0.05}Zr{sub 2}O{sub 7-{delta}} (LCZ) material is prepared by combustion synthesis. Black-Right-Pointing-Pointer LCZ and Ni-LCZ bulk samples are prepared with theoretical density close to 100%. Black-Right-Pointing-Pointer Bulk electrical conductivity {approx}400 S/cm is obtained for Ni-LCZ cermet at 750 Degree-Sign C. -- Abstract: La{sub 1.95}Ca{sub 0.05}Zr{sub 2}O{sub 7-{delta}} (LCZ) and Ni-LCZ cermet have been prepared by combustion synthesis and conventional solid state mixing methods respectively. Both the materials are sintered in air and controlled atmosphere (5% H{sub 2} in Ar). The density obtained for the material sintered at 1400 Degree-Sign C in controlled atmosphere is found to be more than 99.5%. This sintering temperature (1400 Degree-Sign C) is considered to be much lower compared to the conventional sintering temperature. The corresponding total conductivity for such Ni-LCZ cermet materials is {approx}400 S/cm measured at 750 Degree-Sign C having 40 vol% of Ni and 60 vol% LCZ.

  11. Lanthanum Halide Scintillators and Optical Fiber Readout for X-Ray Astronomy and National Security Applications

    NASA Astrophysics Data System (ADS)

    Cherry, Michael L.; Case, Gary L.; Welch, Christopher E.

    2006-04-01

    The Black Hole Finder Probe (BHFP) mission is intended to survey the local Universe for black holes. One approach to such a survey is a hard X-ray coded aperture imaging telescope operating in the 20 - 600 keV energy band. A sensitive hard X-ray/gamma ray imaging telescope is also well suited to surveillance applications searching for shielded sources of illicit nuclear materials, for example "dirty bomb" materials being smuggled into a harbor or city. The development of new inorganic scintillator materials (e.g., LaBr3 and LaCl3) provides improved energy resolution and timing performance that is well suited to the requirements for these national security and astrophysics applications. LaBr3 or LaCl3 detector arrays coupled with waveshifting fiber optic readout represent a significant advance in the performance capabilities of scintillator-based gamma cameras and provide the potential for a feasible approach to affordable, large area, extremely sensitive detectors. We describe the Coded Aperture Survey Telescope for Energetic Radiation (CASTER), a mission concept for a BHFP, and the High Sensitivity Gamma Ray Imager (HiSGRI), a device intended for surveillance for nuclear materials, and present laboratory test results demonstrating the expected scintillator performance.

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

    NASA Astrophysics Data System (ADS)

    Zheng, Feng

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

  13. Study of the temperature dependent transport properties in nanocrystalline lithium lanthanum titanate for lithium ion batteries

    NASA Astrophysics Data System (ADS)

    Abhilash, K. P.; Christopher Selvin, P.; Nalini, B.; Somasundaram, K.; Sivaraj, P.; Chandra Bose, A.

    2016-04-01

    The nano-crystalline Li0.5La0.5TiO3 (LLTO) was prepared as an electrolyte material for lithium-ion batteries by the sol-gel method. The prepared LLTO material is characterized by structural, morphological and electrical characterizations. The LLTO shows the cubic perovskite structure with superlattice formation. The uniform distribution of LLTO particles has been analyzed by the SEM and TEM analysis of the sample. Impedance measurements at various temperatures were carried out and the temperature dependent conductivity of as prepared LLTO nanopowders at different temperatures from room temperature to 448 K has been analyzed. The transport mechanism has been analyzed using the dielectric and modulus analysis of the sample. Maximum grain conductivity of the order of 10-3 S cm-1 has been obtained for the sample at higher temperatures.

  14. Alternative materials for solid oxide fuel cells

    SciTech Connect

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

    1994-08-01

    The purpose of this research is to develop alternative materials for solid oxide fuel cell (SOFC) interconnections and electrodes with improved electrical, thermal, and electrochemical properties. A second objective is to develop synthesis and fabrication methods for these materials whereby they can be processed in air into SOFCs. The approach is to (1) develop modifications of the current, state-of-the-art materials used in SOFCs, (2) minimize the number of cations used in the SOFC materials to reduce potential deleterious interactions, (3) improve thermal, electrical, and electrochemical properties, (4) develop methods to synthesize both state-of-the-art and alternative materials for the simultaneous fabrication and consolidation in air of the interconnections and electrodes with the solid electrolyte, and (5) understand electrochemical reactions at materials interfaces and the effects of component composition and processing on those reactions. This paper summarizes a comprehensive study that assessed the effect of ambient oxygen partial pressure on the stability of air-sinterable chromites and the sintering behavior of doped lanthanum manganites.

  15. 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. PMID:27088967

  16. Complex permittivity of lanthanum aluminate in the 20 to 300 K temperature range from 26.5 to 40.0 GHz

    NASA Technical Reports Server (NTRS)

    Miranda, F. A.; Gordon, W. L.; Bhasin, K. B.; Ebihara, B. T.; Heinen, V. O.; Chorey, C. M.

    1990-01-01

    Dielectric constants of microwave substrates are required in the design of superconducting microwave circuits at various temperatures. In this paper, the results are reported of a study of the complex permittivity of the newly developed lanthanum aluminate (LaAlO3) substrate, in the 20 to 300 K temperature range at frequencies from 26.5 to 40.0 GHz. The value of the complex permittivity was obtained by measuring the sample scattering parameters using a microwave waveguide technique. It is observed that, while the dielectric constant did not change appreciably with frequency, its value decreased by approximately 14 percent from room temperature to 20 K.

  17. Electrical properties and thermal expansion of cobalt doped apatite-type lanthanum silicates based electrolytes for IT-SOFC

    SciTech Connect

    Shi, Qingle; Lu, Lihua; Jin, Hongjian; Zhang, Hua; Zeng, Yanwei

    2012-03-15

    Graphical abstract: The figure shows the dependence of conductivity on the Co content. It can be seen that La{sub 10}Si{sub 5.2}Co{sub 0.8}O{sub 26.6} exhibits the highest ionic conductivity of 3.33 Multiplication-Sign 10{sup -2} S/cm at 800 Degree-Sign C. When x {<=} 0.8, as doping Co weakens the binding energy and aids the migration of the interstitial oxide ions, the ionic conductivity improves. On the other hand, excess dopant of Co (0.8 < x {<=} 1.5) can decrease the number of interstitial oxide ions and reduce the ionic conductivity. Highlights: Black-Right-Pointing-Pointer The unit volumes of La{sub 10}Si{sub 6-x}Co{sub x}O{sub 27-x/2} increase with increasing cobalt content. Black-Right-Pointing-Pointer Doping Co can increase the thermal expansion because of the larger radius of Co{sup 3+} ion. Black-Right-Pointing-Pointer Conductivities of La{sub 10}Si{sub 6-x}Co{sub x}O{sub 27-x/2} first increase and then decrease with cobalt content. Black-Right-Pointing-Pointer Above 550 Degree-Sign C, La{sub 10}Si{sub 6-x}Co{sub x}O{sub 27-x/2} shows low activation energies of around 0.7 eV. -- Abstract: The thermal expansion and conductivities have been investigated for Co{sup 3+} doped lanthanum silicates. The apatite-type lanthanum silicates with formula La{sub 10}Si{sub 6-x}Co{sub x}O{sub 27-x/2} (x = 0.2, 0.4, 0.6, 0.8, 1.0, 1.5) were synthesized by sol-gel process. The thermal expansion coefficient (TEC) of La{sub 10}Si{sub 6-x}Co{sub x}O{sub 27-x/2} was improved with increasing cobalt content because of the lower valence and larger radius of Co{sup 3+} ion compared to Si{sup 4+}. Analysis of AC impedance spectroscopy showed that conductivity increased first and then decreased with increasing cobalt content. There is an optimum doping amount of cobalt and La{sub 10}Si{sub 5.2}Co{sub 0.8}O{sub 26.6} exhibits the highest conductivity of 3.33 Multiplication-Sign 10{sup -2} S/cm at 800 Degree-Sign C. When x {<=} 0.8, the local distortion caused by doping with Co

  18. 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.

  19. 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

  20. 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

  1. 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

  2. Formation of crystalline dots and lines in lanthanum borogermanate glass by the low pulse repetition rate femtosecond laser

    NASA Astrophysics Data System (ADS)

    Lipateva, Tatiana O.; Lotarev, Sergey V.; Lipatiev, Alexey S.; Kazansky, Peter G.; Sigaev, Vladimir N.

    2015-01-01

    Femtosecond lasers have become a powerful tool for 3D space-selective crystallization of glasses. A laser-induced cumulative heating effect required for crystal growth is usually considered to take place only at pulse repetition rate over 100 or 200 kHz and 200 kHz is known as the lowest repetition rate at which femtosecond laser-induced crystallization has been reported so far. We for the first time demonstrate precipitation of LaBGeO5 crystals in lanthanum borogermanate glass using a femtosecond laser emitting 1030 nm, 300 fs, 110 μJ pulses with adjustable repetition rate below 100 kHz. For the applied laser, minimal repetition rate enabling nucleation of ferroelectric LaBGeO5 crystals inside the glass was shown to be 9 kHz at maximal pulse energy of 110 μJ and growth of a crystalline line from the formed seed crystal was obtained starting from 8 kHz though smooth homogeneous oriented line which might be regarded as quasi-single-crystalline could be grown at 25 kHz or higher and corresponding pulse energy of 18 μJ. Thus, the pulse repetition rate sufficient for a cumulative heating effect and a stable crystal growth was reduced by an order of magnitude as compared to earlier publications due to relatively high pulse energy. Possibility and efficiency of cumulative heating and crystal growth and average time required for forming the seed crystal have been studied for various combinations of the pulse energy and the repetition rate. Obtained crystalline features have been studied by micro-Raman spectroscopy and Raman mapping which confirmed growth of stillwellite-like LaBGeO5 phase and orientation of its polar axis along the direction of the crystalline line.

  3. Synthesis, structure, thermal stability, mechanical and antibacterial behaviour of lanthanum (La³⁺) substitutions in β-tricalciumphosphate.

    PubMed

    Meenambal, Rugmani; Singh, Ram Kishore; Nandha Kumar, P; Kannan, S

    2014-10-01

    Five different concentrations of lanthanum (La(3+)) substituted β-tricalcium phosphate [β-TCP, β-Ca3(PO4)2] were formed through aqueous precipitation technique and the results were compared with stoichiometric β-TCP. All the La(3+) substituted β-TCP powders were characterized using XRD, FT-IR, XRF, Raman spectroscopy and Rietveld refinement of the XRD data. The results from the investigation confirmed the presence of La(3+) in rhombohedral β-TCP structure. The substitution of higher sized of La(3+) led to the considerable enhancement in lattice parameters of β-TCP crystal structure and La(3+) was found to have occupied the eight fold coordinated Ca (3) site of β-TCP structure. La(3+) occupancy at the Ca (3) site resulted in the significant distortions of the associated PO4 tetrahedra, which were supported by the Raman and FT-IR spectroscopic techniques. La(3+) presence in the crystal lattice of β-TCP also led to the delay in allotropic phase transformation of β-TCP to α-TCP till 1300°C, thus signifying the good thermal stability of La(3+) substituted β-TCP powders. The antibacterial efficiency of La(3+) substituted β-TCP powders was confirmed from the in vitro tests done on microbes such as Staphylococcus aureus and Escheria coli. Further, the presence of La(3+) in the crystal lattice of β-TCP did not affect the hardness and Young's modulus values of β-TCP. PMID:25175254

  4. Growth of epitaxial films of sodium potassium tantalate and niobate on single-crystal lanthanum aluminate [100] substrates

    SciTech Connect

    Thomas, George H.; Specht, Eliot D; Larese, John Z; Xue, Ziling; Beach, David B

    2008-01-01

    Epitaxial films of sodium potassium tantalate (Na{sub 0.5}K{sub 0.5}TaO{sub 3}, NKT) and sodium potassium niobate (Na{sub 0.5}K{sub 0.5}NbO{sub 3}, NKN) were grown on single-crystal lanthanum aluminate (LAO) (100) (indexed as a pseudo-cubic unit cell) substrates via an all-alkoxide solution (methoxyethoxide complexes in 2-methoxyethanol) deposition route for the first time. X-ray diffraction studies indicated that the onset of crystallization in powders formed from hydrolyzed gel samples was 550 C. {sup 13}C nuclear magnetic resonance studies of solutions of methoxyethoxide complexes indicated that mixed-metal species were formed, consistent with the low crystallization temperatures observed. Thermal gravimetric analysis with simultaneous mass spectrometry showed the facile loss of the ligand (methoxyethoxide) at temperatures below 400 C. Crystalline films were obtained at temperatures as low as 650 C when annealed in air. {theta}-2{theta} x-ray diffraction patterns revealed that the films possessed c-axis alignment in that only (h00) reflections were observed. Pole-figures about the NKT or NKN (220) reflection indicated a single in-plane, cube-on-cube epitaxy. The quality of the films was estimated via {omega} (out-of-plane) and {psi} (in-plane) scans and full-widths at half-maximum (FWHMs) were found to be reasonably narrow ({approx}1{sup o}), considering the lattice mismatch between the films and the substrate.

  5. Enzymological mechanism for the regulation of lanthanum chloride on flavonoid synthesis of soybean seedlings under enhanced ultraviolet-B radiation.

    PubMed

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

    2014-01-01

    In order to probe into the enzymological mechanism for the regulation of lanthanum chloride (LaCl3) on flavonoid synthesis in plants under enhanced ultraviolet-B (UV-B) radiation, the effects of LaCl₃ (20 and 60 mg l(-1)) on the content of flavonoids as well as the activities of phenylalanine ammonia-lyase (PAL), cinnamate-4-hydroxylase (C4H), 4-coumarate : coenzyme A ligase (4CL), and chalcone synthase (CHS) in soybean seedlings under enhanced UV-B radiation (2.6 and 6.2 kJ m(-2) day(-1)) were investigated. Enhanced UV-B radiation (2.6 and 6.2 kJ m(-2) day(-1)) caused the increase in the content of flavonoids as well as the activities of PAL, C4H, 4CL, and CHS in soybean seedlings. The treatment of 20 mg l(-1) LaCl₃ also efficiently increased these indices, which promoted the flavonoid synthesis and provided protective effects for resisting enhanced UV-B radiation. On the contrary, the treatment of 60 mg l(-1) LaCl₃ decreased the content of flavonoids as well as the activities of C4H, 4CL, and CHS in soybean seedlings except increasing the activity of PAL, which were not beneficial to the flavonoid synthesis and provided negative effects for resisting enhanced UV-B radiation. In conclusion, enhanced UV-B radiation caused the increase in the flavonoid synthesis by promoting the activities of PAL, C4H, 4CL, and CHS in soybean seedlings. The treatment of LaCl₃ could change flavonoid synthesis in soybean seedlings under enhanced UV-B radiation by regulating the activities of PAL, C4H, 4CL, and CHS, which is an enzymological mechanism for the regulation of LaCl₃ on flavonoid synthesis in plants under enhanced UV-B radiation. PMID:24710726

  6. 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.

  7. 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

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

    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.

  9. 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. PMID:25263819

  10. 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.

  11. 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.

  12. 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

  13. 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

  14. 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.

  15. 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.

  16. Development of atomistic models to aid the design of new scintillator materials.

    SciTech Connect

    Doty, F. Patrick; Yang, Pin; Zhou, Xiao Wang

    2010-03-01

    The development of more reliable scintillator materials can significantly advance the gamma-ray detection technology. Scintillator materials such as lanthanum halides (e.g., LaBr{sub 3}, CsBr{sub 3}), elpasolites (e.g., Cs{sub 2}LiLaBr{sub 6}, Cs{sub 2}NaLaBr{sub 6}, and Cs{sub 2}LiLaI{sub 6}), and alkali halides (e.g., CsI, NaI) are extremely brittle. The fracture of the materials is often a problem causing the failure of the devices. Lanthanum halides typically have a hexagonal crystal structure. These materials have highly anisotropic thermal and mechanical properties, and therefore they are likely to fracture under cyclic thermal and mechanical loading conditions. For example, fracture of lanthanum halides is known to occur in the field. Fracture during synthesis also complicates the growth of large lanthanum halide single crystals needed for sensitive radiation detection, and accounts for the high production cost of these materials. Elpasolites can have both cubic and non-cubic crystal structures depending on the constituent elements and composition of the compounds. This provides an opportunity to design cubic elpasolites with more isotropic properties and therefore improved mechanical performances. However, the design of an optimized cubic elpasolite crystal remains elusive because there is a tremendous number of possible elpasolites and the design criterion for cubic crystals is not clear. Alkali halides have cubic crystal structures. Consequently, large CsI and NaI crystals have been grown and used in devices. However, these materials suffer from an aging problem, i.e., the properties decay rapidly over time especially under harsh environment. Unfortunately, the fundamental mechanisms of this aging have not been understood and the path to improve the alkali halide-based scintillators is not developed. Clearly, improved scintillator materials can be achieved via strengthened/toughened lanthanum halides, optimized cubic elpasolites, or new alkali halide

  17. 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.

  18. The effect of cerium and lanthanum surface treatments on early stages of oxidation of A361 aluminium alloy at high temperature

    NASA Astrophysics Data System (ADS)

    Pardo, A.; Feliú, S.; Merino, M. C.; Arrabal, R.; Matykina, E.

    2007-11-01

    X-ray photoelectron spectroscopy analysis has been used to study the surface of A361 aluminium alloy after electrodeposition of cerium and lanthanum compounds followed by oxidation tests in air at 100-500 °C for 2 h. Cerium and lanthanum oxide deposits are found on the β-AlFeSi second phase particles and to a lesser extent on the eutectic Al-Si areas, while the α-Al phase is covered with a thin aluminium oxide film. This uneven deposition may be related either to a preferential nucleation and growth process on active interfaces or to the differing electrical conductivity of the phases and intermetallic compounds of the alloy. Initial stages of oxidation of A361 alloy disclosed thickening of the aluminium oxide layer and Mg enrichment at the surface, especially above 400 °C. Rare earth deposits revealed two different effects: reduced Mg diffusion and enhanced thickening of the aluminium oxide film. A distinctive behaviour of Ce oxide appears at 300-500 °C related with Ce(III) to Ce(IV) transition.

  19. 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. PMID:23418141

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

    PubMed

    Lloret, M Jesús; 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

  1. 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

  2. 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.

  3. Polaronic effects in manganese oxides: Self-trapped electronic states in lanthanum manganate and sodium chloride

    NASA Astrophysics Data System (ADS)

    Perebeinos, Vasili

    2001-12-01

    Self-trapped states occur in many insulating solids but are not especially well-understood. There is a need for better theoretical models and better experimental tools for exploring these states. This thesis provides models for two kinds of materials LaMnO3 and NaCl, and predicts experimental effects which can be used to characterize such states. LaMnO3 is an insulating antiferromagnet which can be doped with holes over a wide concentration range, as in La1- xCaxMnO3. Here I study the regime x << 1 where particularly interesting and simple behavior is predicted. The model has electronic and lattice-vibrational degrees of freedom chosen to represent the Mn ion outer electronic states and their interaction with oxygen motions in the three dimensional perovskite crystal structure. Four independent types of data are available to choose three adjusted parameters. Using electronic structure calculations, optical conductivity and Raman spectra for this choice the predicted magnitude of the static Jahn-Teller distortion agrees within 10-15% with neutron diffraction data. I use the model to analyze and predict the self-localized states which form under optical excitation and under hole doping. In particular five types of behavior are analyzed: (1)the insulating nature of lightly doped LaMnO3 due to the anti-Jahn-Teller polaron formation; (2)phonon broadening due to the exciton formation; (3)polaronic angle-resolved- photoemission-spectra (ARPES); (4)Raman spectra due to the Franck-Condon mechanism; (5)the self-trapped exciton in NaCl and its optical properties including the Franck-Condon effect using the first-principles Density Functional Theory (DFT) calculations. Experimental confirmation of the predicted behavior for LaMnO3 will differentiate the Jahn-Teller model studied here from competing versions. The results given here are novel in five ways. (1)Essentially exact analytical polaronic spectra of the two-orbital model Hamiltonian have been obtained. (2)Self

  4. Au-mixed lanthanum/cerium oxide catalysts for water-gas-shift

    SciTech Connect

    Wang, Yanan; Liang, Shuang; Cao, Anmin; Thompson, Robert L; Veser, Goetz

    2010-08-01

    We report on the synthesis of highly homogeneous mixed La/Ce-oxides via a microemulsion-templated approach, and their evaluation as active supports for Au in the water gas shift (WGS) reaction. Both structure and reducibility of the oxides could be tailored by adjusting the La content across the entire range of La:Ce-ratios. The reducibility of the Au-free oxides shows an optimum at ∼25% La content, which can be traced back to improved oxygen mobility due to formation of oxygen vacancies and to the formation of more strongly bound oxygen upon La addition. Deposition of Au onto these oxides gives rise to an additional, low-temperature reduction peak, presumably due to hydrogen spill-over from the noble metal onto the oxide support. The WGS activity of Au/La{sub x}Ce{sub 1−x}O{sub 2−0.5x} catalysts correlates closely with the reducibility of the oxide supports, and hence with La content, demonstrating that carefully controlled synthesis of nanostructured catalysts with uniform, tailored composition allows for fine control of reactive properties of these materials, and might ultimately open the way towards a more rational design of catalysts.

  5. 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.

  6. 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.

  7. 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. PMID:24778724

  8. Phase dependent structural and electronic properties of lanthanum orthophosphate (LaPO4)

    NASA Astrophysics Data System (ADS)

    Neupane, M. R.; Garrett, G. A.; Rudin, S.; Andzelm, J. W.

    2016-05-01

    We study the phase-dependent structural and electronic properties of bulk LaPO4, using density functional theory (DFT). The applicability of conventional semi-local and hybrid functionals in predicting structural and electronic properties of monoclinic and hexagonal LaPO4 is evaluated by comparing results to available experimental data. The monoclinic LaPO4 was found to be more stable than the hexagonal phase in ambient conditions with a small energy difference, suggesting a possibility of a phase transition. Both the phases in the bulk form are found to be diamagnetic with indirect energy gaps. These results are consistent with available experimental results. In the monoclinic phase, the hybrid functionals predict indirect band gap at about 8 eV. Furthermore, the calculated indirect–direct transition energy offset (ΔE) in the hexagonal phase was three times lower than the monoclinic phase. Our calculations based on hybrid functionals also reveal that the states near the conduction band edge in the hexagonal LaPO4 are strongly hybridized between La and PO4 states. By analyzing the band dispersion around the band edges, we show that the hexagonal phase has lighter electron effective mass, as compared to the monoclinic phase. With a larger energy gap, smaller ΔE, and smaller electron effective mass, the hexagonal LaPO4 might be a promising candidate material as an n-type transparent oxide.

  9. Effect of tri- and tetravalent metal doping on the electrochemical properties of lanthanum tungstate proton conductors.

    PubMed

    Porras-Vázquez, J M; dos Santos-Gómez, L; Marrero-López, D; Slater, P R; Masó, N; Magrasó, A; Losilla, Enrique R

    2016-02-21

    Rare-earth tungstates (La(28-y)W(4+y)O(54+δ)□(2-δ)) have attracted attention recently because of their relatively high proton-electron conductivity and high stability in a CO2 environment. Since doping on the tungsten-site may increase the conductivity, a new series of compounds with composition La(5.5)W(1-x)M(x)O(11.25-δ) (M = Al, Ti and Zr; x = 0, 0.05 and 0.10) have been investigated. The crystal structure of these materials has been studied using X-ray and time-of-flight neutron powder diffraction by Rietveld analysis. The concentration of oxygen vacancies for hydration in the structure has been indirectly determined by thermogravimetric analysis, and the total conductivity in several pO2, pH2O and pD2O atmospheres has been studied by impedance spectroscopy. An increase in the conductivity is observed, ranging from 4.1 mS cm(-1) for the undoped sample to 9.2 mS cm(-1) for La(5.5)W(0.9)Ti(0.1)O(11.25-δ), in wet N2 at 800 °C. PMID:26776842

  10. 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.

  11. 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.

  12. Strain-mediated control of orbital ordering planes in heteroepitaxial lanthanum manganite thin films

    NASA Astrophysics Data System (ADS)

    Kim, Yong-Jin; Lee, Jin Hong; Koo, Tae Yeong; Yang, Chan-Ho

    Strain engineering which controls the misfit strain of heteroepitaxial thin films leads to distinctive physical properties in contrast to the intrinsic properties of unstrained bulk materials Perovskite LaMnO3 (LMO) has attracted considerable attention due to strong coupling among the lattice, charge, spin and orbital degrees of freedom. Bulk LMO is known to be an A-type antiferromagnetic (TN~140 K) Mott insulator, and its orbital ordering plane is established due to cooperative Jahn-Teller distortion below ~750 K. Previous studies have focused on the orbital ordering planes of the bulk LMO but not researched on correlation between orbital planes and misfit stain. To figure out the strain dependence of orbital ordering planes, we have grown LMO thin films on four different substrates, i . e . , DyScO3(110), GaScO3(110), SrTiO3(001), and LSAT(001), using the pulsed laser deposition technique. The films have been characterized by atomic force microscopy and x-ray diffraction. We have performed resonant x-ray scattering to identify orbital ordering plane on each film. We have found that orbital ordering planes can be modulated depending on the misfit strain.

  13. Phase dependent structural and electronic properties of lanthanum orthophosphate (LaPO4).

    PubMed

    Neupane, M R; Garrett, G A; Rudin, S; Andzelm, J W

    2016-05-25

    We study the phase-dependent structural and electronic properties of bulk LaPO4, using density functional theory (DFT). The applicability of conventional semi-local and hybrid functionals in predicting structural and electronic properties of monoclinic and hexagonal LaPO4 is evaluated by comparing results to available experimental data. The monoclinic LaPO4 was found to be more stable than the hexagonal phase in ambient conditions with a small energy difference, suggesting a possibility of a phase transition. Both the phases in the bulk form are found to be diamagnetic with indirect energy gaps. These results are consistent with available experimental results. In the monoclinic phase, the hybrid functionals predict indirect band gap at about 8 eV. Furthermore, the calculated indirect-direct transition energy offset (ΔE) in the hexagonal phase was three times lower than the monoclinic phase. Our calculations based on hybrid functionals also reveal that the states near the conduction band edge in the hexagonal LaPO4 are strongly hybridized between La and PO4 states. By analyzing the band dispersion around the band edges, we show that the hexagonal phase has lighter electron effective mass, as compared to the monoclinic phase. With a larger energy gap, smaller ΔE, and smaller electron effective mass, the hexagonal LaPO4 might be a promising candidate material as an n-type transparent oxide. PMID:27114454

  14. 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.

  15. 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

  16. 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.

  17. 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.

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

    SciTech Connect

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

    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.

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

    SciTech Connect

    Li Hui . E-mail: lihui@bit.edu.cn; Guo Ming; Tian Hong; He Feiyue; Lee, G.-H.; Peng, S.-M.

    2006-11-15

    One-dimensional alternative chains of two lanthanum complexes: [La(L{sup 1}){sub 3}(CH{sub 3}OH)(H{sub 2}O){sub 2}].5H{sub 2}O (L{sup 1}=anion of {alpha}-cyano-4-hydroxycinnamic acid ) 1 and [La(L{sup 2}){sub 3}(H{sub 2}O){sub 2}].3H{sub 2}O (L{sup 2}=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{sub 31}H{sub 36}LaN{sub 3}O{sub 17}, triclinic, P-1, a=9.8279(4)A, b=11.8278(5)A, c=17.8730(7)A, {alpha}=72.7960(10){sup o}, {beta}=83.3820(10){sup o}, {gamma}=67.1650(10)-bar , Z=2, R{sub 1}=0.0377, wR{sub 2}=0.0746; for 2: C{sub 33}H{sub 37}LaO{sub 14}, triclinic, P-1, a=8.7174(5)A, b=9.9377(5)A, c=21.153(2)A, {alpha}=81.145(2){sup o}, {beta}=87.591(2){sup o}, {gamma}=67.345(5){sup o}, Z=2, R{sub 1}=0.0869, wR{sub 2}=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 {eta}{sup 3}-O bridges and four bridges (two {eta}{sup 2}-O and two {eta}{sup 3}-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.

  20. 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).