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Sample records for ceria solid solutions

  1. Statistical thermodynamics of non-stoichiometric ceria and ceria zirconia solid solutions.

    PubMed

    Bulfin, B; Hoffmann, L; de Oliveira, L; Knoblauch, N; Call, F; Roeb, M; Sattler, C; Schmücker, M

    2016-08-17

    The thermodynamic redox properties of ceria and ceria zirconia solid solutions are analysed with a new methodology for modelling such systems based on the statistical mechanics of lattice configurations. Experimental thermogravimetric equilibrium data obtained for small non-stoichiometry measurements are combined with literature data to cover a large range of non-stoichiometry (CeO2-δ, δ = 0.001-0.32), temperature (1073-1773 K) and oxygen partial pressure (1-10(-13) bar). A dilute species model of defect clusters , obeying the law of mass action, was sufficient to describe the system over the whole range of conditions, leading to a simple analytical equation of state for the system. This offers new physical insight into the redox properties of ceria based materials, and the theoretical methods developed should also be of great interest for other materials which exhibit continuous oxygen non-stoichiometry similar to ceria, such as perovskite oxides.

  2. The complex synthesis and solid state chemistry of ceria-lanthana solid solutions prepared via a hexamethylenetetramine precipitation

    SciTech Connect

    Fleming, P.G.; Holmes, J.D.; Otway, D.J.; Morris, M.A.

    2011-09-15

    Mixed oxide solid solutions are becoming ever more commercially important across a range of applications. However, their synthesis can be problematical. Here, we show that ceria-lanthana solid solutions can be readily prepared via simple precipitation using hexamethylenetetramine. However, the solution chemistry can be complex, which results in the precipitated particles having a complex structure and morphology. Great care must be taken in both the synthesis and characterisation to quantify the complexity of the product. Even very high heat treatments were not able to produce highly homogeneous materials and X-ray diffractions reveals the non-equilibrium form of particles prepared in this way. Unexpected crystal structures are revealed including a new metastable cubic La{sub 2}O{sub 3} phase. - Graphical abstract: The suggested mechanism for the formation of dual fluorite phase particles, where Step 1 corresponds to room temperature aging, Step 2; heating the solution to 90 deg. C, Step 3; cooling of the solution to room temperature, Step 4; calcination to 500 deg. C, Step 5; calcination to 700 deg. C and Step 6; calcination to 1300 deg. C. The terminology of e.g. La{sub 1-x}Ce{sub x}(OH){sub 3} is used to indicate the formation of a mixed oxy-hydroxy participate rather than a definitive assignment of stoichiometry. Similarly, La{sub 1-y}Ce{sub y}O{sub 2} only implies a mixed solid solution. Highlights: > Mol% of prepared Ce-La oxides did not follow that of reactant mol%. > Complex reaction pathway found to be dependent on metal solution concentrations. > At certain concentrations core shell particles were found to form. > A reaction model was produced based on cationic solubility. > Report lanthana solubility higher than previously reported in CeO{sub 2}.

  3. Application of rare earth modified Zr-based ceria-zirconia solid solution in three-way catalyst for automotive emission control.

    PubMed

    Wang, Qiuyan; Zhao, Bo; Li, Guangfeng; Zhou, Renxian

    2010-05-15

    Automotive exhaust emission is a major cause of air pollution. Three-way catalyst (TWC) which can eliminate CO, HC (hydrocarbons), and NO(x) simultaneously has been used to control exhaust emissions. Ceria-zirconia is a key component in TWC and most researchers pay attention to Ceria-Zirconia (Ce-rich) solid solution. The research presented in this paper is focused on the intrinsic structure of Ceria-Zirconia (Zr-based) solid solution and its application in TWC. A series of Ce(0.2)Zr(0.8)O(2) modified with rare earths (La, Nd, Pr, Sm, and Y) have been prepared by coprecipitation method combined with supercritical drying technique. All samples showed single tetragonal solid solution, indicating that the rare earth ion inserted into the lattice structure completely, and an approximately linearly relationship between lattice parameter a and the ionic radius of doped rare earth was observed. The catalytic performances of corresponding Pd-only catalysts were investigated in simulated exhaust gas. The presence of La, Nd, and Pr was favorable to the catalytic activity and wide air/fuel operation window. The relationship between the intrinsic structure of the Zr-based ceria-zirconia solid solution and catalytic activity was discussed in detail, which has some reference value for catalyst design and application.

  4. The effect of Nd on the properties of ceria-zirconia solid solution and the catalytic performance of its supported Pd-only three-way catalyst for gasoline engine exhaust reduction.

    PubMed

    Wang, Qiuyan; Li, Guangfeng; Zhao, Bo; Zhou, Renxian

    2011-05-15

    A series of ceria-zirconia-neodymia mixed oxides with different contents of neodymia and the supported Pd-only three-way catalysts before and after aging have been prepared and characterized. The influence of Nd doping on the structural/textural properties of ceria-zirconia (CZ) and the effect on the three-way catalytic performance are also investigated. The results demonstrate that the addition of neodymia results in the formation of ceria-zirconia-neodymia ternary solid solution (CZN) with better textural and structural properties as well as improved reducibility and redox behavior, leading to the promoted three-way catalytic activity and enlarged air/fuel operation window. The modified solid solution with 5 wt.% neodymia shows the preferable textural/structural properties considering that the capacity of foreign cation is limited in the crystal lattice of ceria-zirconia solid solution, and Pd/CZN5 shows the optimum three-way catalytic performance and wider air/fuel operation window, especially for the corresponding aged one.

  5. Isn't the space-charge potential in ceria-based solid electrolytes largely overestimated?

    PubMed

    Kim, Sangtae

    2016-07-20

    The effective ionic conductivity of polycrystalline solid electrolytes that conduct oxide ions or protons is known to be markedly below those of the corresponding single crystals due to substantial current obstruction across the grain boundary. Numerous studies have previously demonstrated that the ionic charge carriers deplete in the vicinity of the grain boundary to form a potential barrier at the grain boundary, which further impedes the current across the grain boundary. Hence an accurate estimation of the barrier height is essential to acquire a comprehensive and precise mechanistic picture of the ionic current in solid electrolytes. The values of the potential barrier height, i.e. equivalent to the equilibrium space-charge potential with the opposite sign, in prominent solid electrolytes such as ceria solid solutions are available in the literature and were determined exclusively from the ratio of the resistivity of the grain boundary to that of the crystal interior. Here I present the results clearly demonstrating that the resistivity ratio yields considerable overestimation of the barrier height even in relatively diluted solid solutions of ceria. These results imply that the space charge is unlikely the sole origin of the large current obstruction across the grain boundary in ceria-based solid electrolytes.

  6. UV-shielding property, photocatalytic activity and photocytotoxicity of ceria colloid solutions.

    PubMed

    Zholobak, N M; Ivanov, V K; Shcherbakov, A B; Shaporev, A S; Polezhaeva, O S; Baranchikov, A Ye; Spivak, N Ya; Tretyakov, Yu D

    2011-01-10

    UV-shielding property, photocatalytic activity and cytotoxicity (including photocytotoxicity) of citrate-stabilized ceria colloid solutions were studied. It was established that UV-shielding property (namely, the sun protection factor, the critical absorption wavelength and the UVA/UVB-ratio) of ceria nanoparticles are as good as those of titanium dioxide and zinc oxide nanoparticles. It was further demonstrated that ceria nanoparticles possesses substantially lower photocatalytic activity, which additionally decreases upon decrease in ceria particle size. It was found that colloid ceria solutions are non-toxic to mouse fibroblasts (L929) and fibroblast-like cells of African Green monkey (VERO). Moreover, ceria nanoparticles are capable to protect these cells from UV-irradiation-induced damage. It was proposed that nanocrystalline ceria could be used not only as UV-blocking material, but also as prophylactic and even therapeutic compound for sunburns treatment.

  7. Solid Solutions

    NASA Astrophysics Data System (ADS)

    Lee, Go-Eun; Kim, Il-Ho; Lim, Young Soo; Seo, Won-Seon; Choi, Byeong-Jun; Hwang, Chang-Won

    2014-06-01

    Since Bi2Te3 and Bi2Se3 have the same crystal structure, they form a homogeneous solid solution. Therefore, the thermal conductivity of the solid solution can be reduced by phonon scattering. The thermoelectric figure of merit can be improved by controlling the carrier concentration through doping. In this study, Bi2Te2.85Se0.15:D m (D: dopants such as I, Cu, Ag, Ni, Zn) solid solutions were prepared by encapsulated melting and hot pressing. All specimens exhibited n-type conduction in the measured temperature range (323 K to 523 K), and their electrical conductivities decreased slightly with increasing temperature. The undoped solid solution showed a carrier concentration of 7.37 × 1019 cm-3, power factor of 2.1 mW m-1 K-1, and figure of merit of 0.56 at 323 K. The figure of merit ( ZT) was improved due to the increased power factor by I, Cu, and Ag dopings, and maximum ZT values were obtained as 0.76 at 323 K for Bi2Te2.85Se0.15:Cu0.01 and 0.90 at 423 K for Bi2Te2.85Se0.15:I0.005. However, the thermoelectric properties of Ni- and Zn-doped solid solutions were not enhanced.

  8. Nanostructured gadolinium-doped ceria microsphere synthesis from ion exchange resin: Multi-scale in-situ studies of solid solution formation

    SciTech Connect

    Caisso, Marie; Lebreton, Florent; Horlait, Denis; Neuville, Daniel R.; Dardenne, Kathy; Rothe, Jörg; Delahaye, Thibaud

    2014-10-15

    In the current nano-sized material revolution, the main limitations to a large-scale deployment of nanomaterials involve health concerns related to nano-dissemination via air. Developing new chemical routes benefiting from nano-size advantages while avoiding their hazards could overcome these limitations. Addressing this need, a chemical route leading to soft nano-particle agglomerates, i.e., macroscopic precursors presenting the ability to be decomposed into nano-sized materials, was developed and applied to Ce{sub 0.8}Gd{sub 0.2}O{sub 2−δ}. Using cerium/gadolinium-loaded ion exchange resin, the Ce{sub 0.8}Gd{sub 0.2}O{sub 2−δ} solid solution formation as a function of temperature was studied in-situ through X-ray diffraction, X-ray absorption spectroscopy and Raman spectroscopy. Temperatures corresponding to the organic skeleton decomposition and to the mixed oxide crystallization were identified. An optimal heat treatment, leading to nanostructured soft agglomerates, was established. Microsphere processing capabilities were evaluated and particle size distribution measurements were recorded. A very low fracture strength was calculated, and a nanometric particle size distribution (170 nm) was determined. - Graphical abstract: The elaboration of micro-spherical precursors leading to the formation of nano-oxide soft agglomerates was studied and approved through the use of ion exchange resin loaded with cerium and gadolinium. The formation of the solid solution was followed through in-situ measurements such as XAS, XRD, Raman, TGA and DSC. Key temperatures were identified for the formation of the mixed-oxide. Following this study, the microstructure and particle size of oxide microspheres formed highlight the formation of soft nano-arrangments. - Highlights: • Soft microspherical agglomerates able to be decomposed into nano-sized materials. • In situ study of cerium/gadolinium-loaded ion exchange resin conversion in oxide. • In situ multi-scale study

  9. Controlled synthesis, characterization, and morphology-dependent reducibility of ceria-zirconia-yttria solid solutions with nanorod-like, microspherical, microbowknot-like, and micro-octahedral shapes.

    PubMed

    Zhang, Yujuan; Zhang, Lei; Deng, Jiguang; Dai, Hongxing; He, Hong

    2009-03-02

    By adopting the strategy of triblock copolymer (Pluronic P123) or cetyltrimethylammonium bromide (CTAB) assisted hydrothermal treatment, we fabricated cubic fluorite-type Ce(0.6)Zr(0.3)Y(0.1)O(2) (CZY) solid solution polycrystallites with various morphologies. These materials were characterized by means of techniques such as X-ray diffraction, scanning electron microscopy, transmission electron microscopy, selected-area electron diffraction, X-ray photoelectron spectroscopy, thermogravimetry, laser Raman, Fourier-transfer infrared spectroscopy, hydrogen temperature-programmed reduction, and surface area measurements. It is found that the nanorod-like, microspherical, microbowknot-like, and micro-octahedral CZY particles were respectively generated hydrothermally with CTAB at 120 degrees C for 72 h and with P123 at 100, 120, and 240 degrees C for 48 h after calcination at 550 degrees C for 3 h. There was a copresence of Ce(3+) and Ce(4+) in the CZY samples that led to the formation of oxygen vacancies. We observed a good correlation of low-temperature reducibility with the morphology of the CZY samples. The reducibility of these nano- and micromaterials at low temperatures (240-550 degrees C) enhanced in the order micro-octahedral CZY < microspherical CZY < microbowknot-like CZY < nanorod-like CZY. The formation mechanism of CZY with various morphologies was discussed.

  10. Ceria-based solid catalysts for organic chemistry.

    PubMed

    Vivier, Laurence; Duprez, Daniel

    2010-06-21

    Ceria has been the subject of thorough investigations, mainly because of its use as an active component of catalytic converters for the treatment of exhaust gases. However, ceria-based catalysts have also been developed for different applications in organic chemistry. The redox and acid-base properties of ceria, either alone or in the presence of transition metals, are important parameters that allow to activate complex organic molecules and to selectively orient their transformation. Pure ceria is used in several organic reactions, such as the dehydration of alcohols, the alkylation of aromatic compounds, ketone formation, and aldolization, and in redox reactions. Ceria-supported metal catalysts allow the hydrogenation of many unsaturated compounds. They can also be used for coupling or ring-opening reactions. Cerium atoms can be added as dopants to catalytic system or impregnated onto zeolites and mesoporous catalyst materials to improve their performances. This Review demonstrates that the exceptional surface (and sometimes bulk) properties of ceria make cerium-based catalysts very effective for a broad range of organic reactions.

  11. Energetics of Intermediate Temperature Solid Oxide Fuel Cell Electrolytes: Singly and Doubly doped Ceria Systems

    NASA Astrophysics Data System (ADS)

    Buyukkilic, Salih

    Solid oxide fuel cells (SOFCs) have potential to convert chemical energy directly to electrical energy with high efficiency, with only water vapor as a by-product. However, the requirement of extremely high operating temperatures (~1000 °C) limits the use of SOFCs to only in large scale stationary applications. In order to make SOFCs a viable energy solution, enormous effort has been focused on lowering the operating temperatures below 700 °C. A low temperature operation would reduce manufacturing costs by slowing component degradation, lessening thermal mismatch problems, and sharply reducing costs of operation. In order to optimize SOFC applications, it is critical to understand the thermodynamic stabilities of electrolytes since they directly influence device stability, sustainability and performance. Rare-earth doped ceria electrolytes have emerged as promising materials for SOFC applications due to their high ionic conductivity at the intermediate temperatures (500--700 °C). However there is a fundamental lack of understanding regarding their structure, thermodynamic stability and properties. Therefore, the enthalpies of formation from constituent oxides and ionic conductivities were determined to investigate a relationship between the stability, composition, structural defects and ionic conductivity in rare earth doped ceria systems. For singly doped ceria electrolytes, we investigated the solid solution phase of bulk Ce1-xLnxO2-0.5x where Ln = Sm and Nd (0 ≤ x ≤ 0.30) and analyzed their enthalpies of formation, mixing and association, and bulk ionic conductivities while considering cation size mismatch and defect associations. It was shown that for ambient temperatures in the dilute dopant region, the positive heat of formation reaches a maximum as the system becomes increasingly less stable due to size mismatch. In concentrated region, stabilization to a certain solubility limit was observed probably due to the defect association of trivalent cations

  12. Synthesis and atomic level in situ redox characterization in ceria and ceria zirconia

    NASA Astrophysics Data System (ADS)

    Wang, Ruigang

    2007-12-01

    Nanocrystalline ceria-based oxides are widely used in automotive three-way catalytic converters to reduce the emissions of carbon monoxide, nitrogen oxides, and unburned hydrocarbons. The primary function of ceria-based oxides in the catalytic process is to adjust the local oxygen partial pressure and maintain an air-to-fuel ratio near the stoichiometric value (˜14.5) required for the optimal catalyst performance for carbon monoxide, hydrocarbon oxidation, and nitrogen oxides reduction. In this dissertation, a study of the relationship between the nanoscale structure, chemistry, and the redox behavior on high surface area ceria and ceria zirconia is presented. Precipitation and spray freezing methods were used to synthesize nanocrystalline ceria and ceria zirconia solid solution powders respectively. The effect of thermal treatments in oxidizing and reducing atmospheres on the reducibility of the materials has been systematically investigated. X-ray diffraction and thermogravimetric analysis were used to characterize the average structure and reducibility. In situ environmental transmission electron microscope was exploited to visualize the dynamic changes during redox processes at the atomic level. This resulted in the identification of the nanoscale structure and chemistry for the most active nanoparticles in these oxides. The correlation between ex situ macroscopic redox properties and in situ redox behavior of individual nanoparticles is demonstrated. The addition of zirconia to ceria clearly enhances the reducibility and thermal stability of ceria. A fundamental difference between ceria and ceria zirconia during in situ redox processes is related to oxygen vacancy ordering. Ceria showed oxygen vacancy ordering during reduction, whereas ceria zirconia did not. It is suggested that the absence of oxygen vacancy ordering might be a fundamental factor for improved redox properties of ceria zirconia compared with pure ceria. The 50% ceria-50% zirconia solid

  13. Nanocrystalline ceria coatings on solid oxide fuel cell anodes: the role of organic surfactant pretreatments on coating microstructures and sulfur tolerance

    PubMed Central

    Wu, Chieh-Chun; Tang, Ling

    2014-01-01

    Summary Treatments with organic surfactants, followed by the deposition of nanocrystalline ceria coatings from aqueous solution, were applied to anodes of solid oxide fuel cells. The cells were then operated in hydrogen/nitrogen fuel streams with H2S contents ranging from 0 to 500 ppm. Two surfactant treatments were studied: immersion in dodecanethiol, and a multi-step conversion of a siloxy-anchored alkyl bromide to a sulfonate functionality. The ceria coatings deposited after the thiol pretreatment, and on anodes with no pretreatment, were continuous and uniform, with thicknesses of 60–170 nm and 100–140 nm, respectively, and those cells exhibited better lifetime performance and sulfur tolerance compared to cells with untreated anodes and anodes with ceria coatings deposited after the sulfonate pretreatment. Possible explanations for the effects of the treatments on the structure of the coatings, and for the effects of the coatings on the performance of the cells, are discussed. PMID:25383282

  14. Study of gadolinia-doped ceria solid electrolyte surface by XPS

    SciTech Connect

    Datta, Pradyot Majewski, Peter; Aldinger, Fritz

    2009-02-15

    Gadolinia-doped ceria (CGO) is an important material to be used as electrolyte for solid oxide fuel cell for intermediate temperature operation. Ceria doped with 10 mol% gadolinia (Ce{sub 0.9}Gd{sub 0.1}O{sub 1.95}) was prepared by conventional solid state synthesis and found to be single phase by room temperature X-ray diffraction (XRD). The chemical states of the surface of the prepared sample were analyzed by X-ray photoelectron spectroscopy (XPS). Though Gd was present in its characteristic chemical state, Ce was found in both Ce{sup 4+} and Ce{sup 3+} states. Presence of Ce{sup 3+} state was ascribed to the differential yield of oxygen atoms in the sputtering process.

  15. Mixed oxide solid solutions

    DOEpatents

    Magno, Scott; Wang, Ruiping; Derouane, Eric

    2003-01-01

    The present invention is a mixed oxide solid solution containing a tetravalent and a pentavalent cation that can be used as a support for a metal combustion catalyst. The invention is furthermore a combustion catalyst containing the mixed oxide solid solution and a method of making the mixed oxide solid solution. The tetravalent cation is zirconium(+4), hafnium(+4) or thorium(+4). In one embodiment, the pentavalent cation is tantalum(+5), niobium(+5) or bismuth(+5). Mixed oxide solid solutions of the present invention exhibit enhanced thermal stability, maintaining relatively high surface areas at high temperatures in the presence of water vapor.

  16. Highly efficient solid state catalysis by reconstructed (001) Ceria surface

    PubMed Central

    Solovyov, Vyacheslav F.; Ozaki, Toshinori; Atrei, Andrea; Wu, Lijun; Al-Mahboob, Abdullah; Sadowski, Jerzy T.; Tong, Xiao; Nykypanchuk, Dmytro; Li, Qiang

    2014-01-01

    Substrate engineering is a key factor in the synthesis of new complex materials. The substrate surface has to be conditioned in order to minimize the energy threshold for the formation of the desired phase or to enhance the catalytic activity of the substrate. The mechanism of the substrate activity, especially of technologically relevant oxide surfaces, is poorly understood. Here we design and synthesize several distinct and stable CeO2 (001) surface reconstructions which are used to grow epitaxial films of the high-temperature superconductor YBa2Cu3O7. The film grown on the substrate having the longest, fourfold period, reconstruction exhibits a twofold increase in performance over surfaces with shorter period reconstructions. This is explained by the crossover between the nucleation site dimensions and the period of the surface reconstruction. This result opens a new avenue for catalysis mediated solid state synthesis. PMID:24717357

  17. Highly efficient solid state catalysis by reconstructed (001) Ceria surface

    SciTech Connect

    Solovyov, VF; Ozaki, T; Atrei, A; Wu, LJ; Al-Mahboob, A; Sadowski, JT; Tong, X; Nykypanchuk, D; Li, Q

    2014-04-10

    Substrate engineering is a key factor in the synthesis of new complex materials. The substrate surface has to be conditioned in order to minimize the energy threshold for the formation of the desired phase or to enhance the catalytic activity of the substrate. The mechanism of the substrate activity, especially of technologically relevant oxide surfaces, is poorly understood. Here we design and synthesize several distinct and stable CeO2 (001) surface reconstructions which are used to grow epitaxial films of the high-temperature superconductor YBa2Cu3O7. The film grown on the substrate having the longest, fourfold period, reconstruction exhibits a twofold increase in performance over surfaces with shorter period reconstructions. This is explained by the crossover between the nucleation site dimensions and the period of the surface reconstruction. This result opens a new avenue for catalysis mediated solid state synthesis.

  18. Low-temperature ceria-electrolyte solid oxide fuel cells for efficient methanol oxidation

    NASA Astrophysics Data System (ADS)

    Meng, Xie; Zhan, Zhongliang; Liu, Xuejiao; Wu, Hao; Wang, Shaorong; Wen, Tinglian

    Low temperature anode-supported solid oxide fuel cells with thin films of samarium-doped ceria (SDC) as electrolytes, graded porous Ni-SDC anodes and composite La 0.6Sr 0.4Co 0.2Fe 0.8O 3 (LSCF)-SDC cathodes are fabricated and tested with both hydrogen and methanol fuels. Power densities achieved with hydrogen are between 0.56 W cm -2 at 500 °C and 1.09 W cm -2 at 600 °C, and with methanol between 0.26 W cm -2 at 500 °C and 0.82 W cm -2 at 600 °C. The difference in the cell performance can be attributed to variation in the interfacial polarization resistance due to different fuel oxidation kinetics, e.g., 0.21 Ω cm 2 for methanol versus 0.10 Ω cm 2 for hydrogen at 600 °C. Further analysis suggests that the leakage current densities as high as 0.80 A cm -2 at 600 °C and 0.11 A cm -2 at 500 °C, resulting from the mixed electronic and ionic conductivity in the SDC electrolyte and thus reducing the fuel efficiency, can nonetheless help remove any carbon deposit and thereby ensure stable and coking-free operation of low temperature SOFCs in methanol fuels.

  19. Shape-Dependent Activity of Ceria for Hydrogen Electro-Oxidation in Reduced-Temperature Solid Oxide Fuel Cells.

    PubMed

    Tong, Xiaofeng; Luo, Ting; Meng, Xie; Wu, Hao; Li, Junliang; Liu, Xuejiao; Ji, Xiaona; Wang, Jianqiang; Chen, Chusheng; Zhan, Zhongliang

    2015-11-04

    Single crystalline ceria nanooctahedra, nanocubes, and nanorods are hydrothermally synthesized, colloidally impregnated into the porous La0.9Sr0.1Ga0.8Mg0.2O3-δ (LSGM) scaffolds, and electrochemically evaluated as the anode catalysts for reduced temperature solid oxide fuel cells (SOFCs). Well-defined surface terminations are confirmed by the high-resolution transmission electron microscopy--(111) for nanooctahedra, (100) for nanocubes, and both (110) and (100) for nanorods. Temperature-programmed reduction in H2 shows the highest reducibility for nanorods, followed sequentially by nanocubes and nanooctahedra. Measurements of the anode polarization resistances and the fuel cell power densities reveal different orders of activity of ceria nanocrystals at high and low temperatures for hydrogen electro-oxidation, i.e., nanorods > nanocubes > nanooctahedra at T ≤ 450 °C and nanooctahedra > nanorods > nanocubes at T ≥ 500 °C. Such shape-dependent activities of these ceria nanocrystals have been correlated to their difference in the local structure distortions and thus in the reducibility. These findings will open up a new strategy for design of advanced catalysts for reduced-temperature SOFCs by elaborately engineering the shape of nanocrystals and thus selectively exposing the crystal facets.

  20. Solid oxide fuel cell bi-layer anode with gadolinia-doped ceria for utilization of solid carbon fuel

    NASA Astrophysics Data System (ADS)

    Kellogg, Isaiah D.; Koylu, Umit O.; Dogan, Fatih

    Pyrolytic carbon was used as fuel in a solid oxide fuel cell (SOFC) with a yttria-stabilized zirconia (YSZ) electrolyte and a bi-layer anode composed of nickel oxide gadolinia-doped ceria (NiO-GDC) and NiO-YSZ. The common problems of bulk shrinkage and emergent porosity in the YSZ layer adjacent to the GDC/YSZ interface were avoided by using an interlayer of porous NiO-YSZ as a buffer anode layer between the electrolyte and the NiO-GDC primary anode. Cells were fabricated from commercially available component powders so that unconventional production methods suggested in the literature were avoided, that is, the necessity of glycine-nitrate combustion synthesis, specialty multicomponent oxide powders, sputtering, or chemical vapor deposition. The easily-fabricated cell was successfully utilized with hydrogen and propane fuels as well as carbon deposited on the anode during the cyclic operation with the propane. A cell of similar construction could be used in the exhaust stream of a diesel engine to capture and utilize soot for secondary power generation and decreased particulate pollution without the need for filter regeneration.

  1. Calcium-doped ceria materials for anode of solid oxide fuel cells running on methane fuel

    NASA Astrophysics Data System (ADS)

    Zhao, Kai; Du, Yanhai

    2017-04-01

    A calcium-doped ceria with nominal compositions of Ce1-xCaxO2-δ (0.00 ≤ x ≤ 0.30) has been developed as an anode component for solid oxide fuel cells running on methane fuel. Crystal phases of Ce1-xCaxO2-δ are investigated with respect to the amount of calcium dopant. The Ce1-xCaxO2-δ shows single fluorite phase when the calcium is within 15 mol.%, and higher calcium doping levels lead to the appearance of a secondary phase (CaO). Conductivities of Ce1-xCaxO2-δ ceramics are studied by a four-probe method in air and the composition of Ce0.9Ca0.1O2-δ (x = 0.10) is found exhibiting the highest conductivity among the samples investigated in this work. Electrocatalytic properties of Ce0.9Ca0.1O2-δ are evaluated based on Ni-Ce1-xCaxO2-δ anode supported single cell running on methane fuel. At 800 °C, the single cell with Ni-Ce0.9Ca0.1O2-δ (x = 0.10) anode exhibits an optimum maximum powder density (618 mW cm-2) and good performance stability during 30 h operation in methane fuel. The promising findings substantiate the good performance of Ni-Ce0.9Ca0.1O2-δ anode for electrochemical oxidation of methane fuel.

  2. Hierarchically oriented macroporous anode-supported solid oxide fuel cell with thin ceria electrolyte film.

    PubMed

    Chen, Yu; Zhang, Yanxiang; Baker, Jeffrey; Majumdar, Prasun; Yang, Zhibin; Han, Minfang; Chen, Fanglin

    2014-04-09

    Application of anode-supported solid oxide fuel cell (SOFC) with ceria based electrolyte has often been limited by high cost of electrolyte film fabrication and high electrode polarization. In this study, dense Gd0.1Ce0.9O2 (GDC) thin film electrolytes have been fabricated on hierarchically oriented macroporous NiO-GDC anodes by a combination of freeze-drying tape-casting of the NiO-GDC anode, drop-coating GDC slurry on NiO-GDC anode, and co-firing the electrolyte/anode bilayers. Using 3D X-ray microscopy and subsequent analysis, it has been determined that the NiO-GDC anode substrates have a porosity of around 42% and channel size from around 10 μm at the electrolyte side to around 20 μm at the other side of the NiO-GDC (away from the electrolyte), indicating a hierarchically oriented macroporous NiO-GDC microstructure. Such NiO-GDC microstructure shows a tortuosity factor of ∼1.3 along the thickness direction, expecting to facilitate gas diffusion in the anode during fuel cell operation. SOFCs with such Ni-GDC anode, GDC film (30 μm) electrolyte, and La0.6Sr0.4Co0.2Fe0.8O3-GDC (LSCF-GDC) cathode show significantly enhanced cell power output of 1.021 W cm(-2) at 600 °C using H2 as fuel and ambient air as oxidant. Electrochemical Impedance Spectroscopy (EIS) analysis indicates a decrease in both activation and concentration polarizations. This study has demonstrated that freeze-drying tape-casting is a very promising approach to fabricate hierarchically oriented porous substrate for SOFC and other applications.

  3. Ceria-Based Anodes for Next Generation Solid Oxide Fuel Cells

    NASA Astrophysics Data System (ADS)

    Mirfakhraei, Behzad

    Mixed ionic and electronic conducting materials (MIECs) have been suggested to represent the next generation of solid oxide fuel cell (SOFC) anodes, primarily due to their significantly enhanced active surface area and their tolerance to fuel components. In this thesis, the main focus has been on determining and tuning the physicochemical and electrochemical properties of ceria-based MIECs in the versatile perovskite or fluorite crystal structures. In one direction, BaZr0.1Ce0.7Y0.1 M0.1O3-delta (M = Fe, Ni, Co and Yb) (BZCY-M) perovskites were synthesized using solid-state or wet citric acid combustion methods and the effect of various transition metal dopants on the sintering behavior, crystal structure, chemical stability under CO2 and H 2S, and electrical conductivity, was investigated. BZCY-Ni, synthesized using the wet combustion method, was the best performing anode, giving a polarization resistance (RP) of 0.4 O.cm2 at 800 °C. Scanning electron microscopy and X-ray diffraction analysis showed that this was due to the exsolution of catalytic Ni nanoparticles onto the oxide surface. Evolving from this promising result, the effect of Mo-doped CeO 2 (nCMO) or Ni nanoparticle infiltration into a porous Gd-doped CeO 2 (GDC) anode (in the fluorite structure) was studied. While 3 wt. % Ni infiltration lowered RP by up to 90 %, giving 0.09 O.cm2 at 800 °C and exhibiting a ca. 5 times higher tolerance towards 10 ppm H2, nCMO infiltration enhanced the H2 stability by ca. 3 times, but had no influence on RP. In parallel work, a first-time study of the Ce3+ and Ce 4+ redox process (pseudocapacitance) within GDC anode materials was carried out using cyclic voltammetry (CV) in wet H2 at high temperatures. It was concluded that, at 500-600 °C, the Ce3+/Ce 4+ reaction is diffusion controlled, probably due to O2- transport limitations in the outer 5-10 layers of the GDC particles, giving a very high capacitance of ca. 70 F/g. Increasing the temperature ultimately

  4. Ceria catalyst for inert-substrate-supported tubular solid oxide fuel cells running on methane fuel

    NASA Astrophysics Data System (ADS)

    Zhao, Kai; Kim, Bok-Hee; Du, Yanhai; Xu, Qing; Ahn, Byung-Guk

    2016-05-01

    A ceria catalyst is applied to an inert-substrate supported tubular single cell for direct operation on methane fuel. The tubular single cell comprises a porous yttria-stabilized zirconia (YSZ) supporter, a Ni-Ce0.8Sm0.2O1.9 anode, a YSZ/Ce0.8Sm0.2O1.9 bi-layer electrolyte, and a La0.6Sr0.4Co0.2Fe0.8O3-δ cathode. The ceria catalyst is incorporated into the porous YSZ supporter layer by a cerium nitrate impregnation. The effects of ceria on the microstructure and electrochemical performance of the tubular single cell are investigated with respect to the number of impregnations. The optimum number of impregnations is determined to be four based on the maximum power density and polarization property of the tubular single cell in hydrogen and methane fuels. At 700 °C, the tubular single cell shows similar maximum power densities of ˜260 mW cm-2 in hydrogen and methane fuels, respectively. Moreover, the ceria catalyst significantly improves the performance stability of the cell running on methane fuel. At a current density of 350 mA cm-2, the single cell shows a low degradation rate of 2.5 mV h-1 during the 13 h test in methane fuel. These results suggest the feasibility of applying the ceria catalyst to the inert-substrate supported tubular single cell for direct operation on methane fuel.

  5. Ceria and copper/ceria functional coatings for electrochemical applications: Materials preparation and characterization

    NASA Astrophysics Data System (ADS)

    Melnik, J.; Fu, X. Z.; Luo, J. L.; Sanger, A. R.; Chuang, K. T.; Yang, Q. M.

    Following preliminary investigations, two electrodeposition techniques (electrophoretic and electrolytic) were selected and adapted for deposition of doped ceria ceramic and copper/doped ceria composite coatings on Ni substrates (foil and foam). The copper/doped ceria composites have potential value as protective functional coatings for current collectors in electrochemical cells including solid oxide fuel sells (SOFC). The doped ceria ceramic coating has potential application as a porous matrix for anodes of SOFCs operating on syngas, sour gas, or hydrocarbons.

  6. Multi-scale analysis of the diffusion barrier layer of gadolinia-doped ceria in a solid oxide fuel cell operated in a stack for 3000 h

    NASA Astrophysics Data System (ADS)

    Morales, M.; Miguel-Pérez, V.; Tarancón, A.; Slodczyk, A.; Torrell, M.; Ballesteros, B.; Ouweltjes, J. P.; Bassat, J. M.; Montinaro, D.; Morata, A.

    2017-03-01

    The state-of-the-art materials for SOFCs are yttria-stabilized zirconia as electrolyte and lanthanum strontium cobalt ferrite as cathode. However, the formation of insulating phases between them requires the use of diffusion barriers, typically made of gadolinia doped ceria. The study of the stability of this layer during the fabrication and in operando is currently one of the major goals of the SOFC industry. In this work, the cation inter-diffusion at the cathode/barrier layer/electrolyte region is analysed for an anode-supported cell industrially fabricated by conventional techniques, assembled in a short-stack and tested under real operation conditions for 3000 h. A comprehensive study of this cell, and an equivalent non-operated one, is performed in order to understand the inter-diffusion mechanisms with possible effects on the final performance. The analyses evidence that the cation diffusion is occurring during the fabrication process. Despite the significant diffusion of Ce,Gd, Zr, Y and Sr cations, the formation of typically reported CGO-YSZ solid solution is not observed while the presence of isolated grains of SrZrO3 is proved. All in all, this study presents new insights into the stability of the typically employed diffusion barriers for solid oxide cells that will guide future strategies to improve their performance and durability.

  7. Detonation nanodiamond introduced into samarium doped ceria electrolyte improving performance of solid oxide fuel cell

    NASA Astrophysics Data System (ADS)

    Pei, Kai; Li, Hongdong; Zou, Guangtian; Yu, Richeng; Zhao, Haofei; Shen, Xi; Wang, Liying; Song, Yanpeng; Qiu, Dongchao

    2017-02-01

    A novel electrolyte materials of introducing detonation nanodiamond (DNDs) into samarium doped ceria (SDC) is reported here. 1%wt. DNDs doping SDC (named SDC/ND) can enlarge the electrotyle grain size and change the valence of partial ceria. DNDs provide the widen channel to accelerate the mobility of oxygen ions in electrolyte. Larger grain size means that oxygen ions move easier in electrolyte, it can also reduce the alternating current (AC) impedance spectra of internal grains. The lower valence of partial Ce provides more oxygen vacancies to enhance mobility rate of oxygen ions. Hence all of them enhance the transportation of oxygen ions in SDC/ND electrolyte and the OCV. Ultimately the power density of SOFC can reach 762 mw cm-2 at 800 °C (twice higher than pure SDC, which is 319 mw cm-2 at 800 °C), and it remains high power density in the intermediate temperature (600-800 °C). It is relatively high for the electrolyte supported (300 μm) cells.

  8. H2 and CO oxidation process at the three-phase boundary of Cu-ceria cermet anode for solid oxide fuel cell

    NASA Astrophysics Data System (ADS)

    Zheng, Minghao; Wang, Shuang; Li, Mei; Xia, Changrong

    2017-03-01

    Cu-ceria cermets have been widely investigated as the anode materials for solid oxide fuel cells (SOFCs) that operated with hydrocarbon fuels. However, the anode reaction processes are not clear yet, especially those at the ceria-Cu-gas three phase boundary (3 PB). This work investigates samaria-doped ceria (SDC)-Cu-gas 3 PB reaction kinetics for the oxidation of H2 and CO, the products from hydrocarbons via external and internal reforming. Electrochemical conductivity relaxation measurement demonstrates that Cu is a synergistic catalyst that can significantly increase the reaction rate. The reaction at 3 PB contributes 81.3/66.8% of H2/CO oxidation when 5.4% SDC surface is covered with Cu particles. Combining with AC impedance analysis, elementary steps are proposed for the reaction at 3 PB. Water vapor combining to oxygen vacancy and carbon monoxide transforming to carbonate are the rate-determining steps for the oxidation of H2 and CO, respectively. Cu-SDC has shown much higher catalytic activity, i.e. about fivefold reaction rate, for the oxidation of CO than H2. In addition, Cu-SDC electrodes exhibit lower interfacial polarization resistance and lower activation energy for the electrochemical oxidation of CO than H2. Consequently, CO is easier to be oxidized than H2 when the Cu-ceria anode is fueled with syngas, the reforming product from hydrocarbons.

  9. Hardness of cubic solid solutions

    PubMed Central

    Gao, Faming

    2017-01-01

    We demonstrate that a hardening rule exists in cubic solid solutions with various combinations of ionic, covalent and metallic bonding. It is revealed that the hardening stress ∆τFcg is determined by three factors: shear modulus G, the volume fraction of solute atoms fv, and the size misfit degree δb. A simple hardening correlation in KCl-KBr solid-solution is proposed as ∆τFcg = 0.27 G. It is applied to calculate the hardening behavior of the Ag-Au, KCl-KBr, InP-GaP, TiN-TiC, HfN-HfC, TiC-NbC and ZrC-NbC solid-solution systems. The composition dependence of hardness is elucidated quantitatively. The BN-BP solid-solution system is quantitatively predicted. We find a hardening plateau region around the x = 0.55–0.85 in BNxP1−x, where BNxP1−x solid solutions are far harder than cubic BN. Because the prediction is quantitative, it sets the stage for a broad range of applications. PMID:28054659

  10. Hardness of cubic solid solutions

    NASA Astrophysics Data System (ADS)

    Gao, Faming

    2017-01-01

    We demonstrate that a hardening rule exists in cubic solid solutions with various combinations of ionic, covalent and metallic bonding. It is revealed that the hardening stress ∆τFcg is determined by three factors: shear modulus G, the volume fraction of solute atoms fv, and the size misfit degree δb. A simple hardening correlation in KCl-KBr solid-solution is proposed as ∆τFcg = 0.27 G. It is applied to calculate the hardening behavior of the Ag-Au, KCl-KBr, InP-GaP, TiN-TiC, HfN-HfC, TiC-NbC and ZrC-NbC solid-solution systems. The composition dependence of hardness is elucidated quantitatively. The BN-BP solid-solution system is quantitatively predicted. We find a hardening plateau region around the x = 0.55–0.85 in BNxP1‑x, where BNxP1‑x solid solutions are far harder than cubic BN. Because the prediction is quantitative, it sets the stage for a broad range of applications.

  11. Enhanced ceria solid electrolyte fuel cell development. Reduction of electronic conductivity permits use of a solid ceria electrolyte in high efficiency high power density fuel cells at temperatures compatible with metallic cell hardware

    NASA Astrophysics Data System (ADS)

    Maricle, D. L.

    1990-01-01

    The high operating temperature of zirconia based solid oxide fuel cells has been shown in many studies to have advantages for both space and terrestrial applications. The high heat rejection temperature minimizes radiator size and weight for high atmospheric and space applications. Mobile and stationary terrestrial applications take advantage of a cell temperature high enough to directly reform hydro-carbon fuels, achieving high efficiency and energy density. Government funded solid oxide fuel cell (SOFC) efforts are concentrated on the monolithic and tubular cell designs employing zirconia as the oxide ion conduction membrane. Zirconia requires an operating temperature of 1000 C to achieve adequate electrolyte conductivity. All-ceramic cell structures are used in both cases, leading to fragile, failure prone cells, and manufacturing steps which are difficult to scale up and costly. IFC's molten carbonate fuel cell development demonstrates the reliability of ductile sheet metal parts used for gas flow fields, separator plates, and frames in the 650 C temperature range. Ceria doped with gadolinium has ionic conductivity at 700 C comparable to zirconia at 1000 C. At 700 C a variety of stainless steels offer acceptable strength and oxidation resistance for use as cell hardware.

  12. STRUCTURE AND PROPERTIES OF SOLID SOLUTIONS.

    DTIC Science & Technology

    Contents: solid solution strengthening and strain aging in Ag-base Al alloys; solid solution strengthening and aging in Cu-base Al alloys; solid ... solution strengthening in NaCl-base NaBr solutions; short-range order; solid solution strength in the gold-silver system.

  13. Tuning the Thickness of Ba-Containing "Functional" Layer toward High-Performance Ceria-Based Solid Oxide Fuel Cells.

    PubMed

    Gong, Zheng; Sun, Wenping; Shan, Duo; Wu, Yusen; Liu, Wei

    2016-05-04

    Developing highly efficient ceria-based solid oxide fuel cells with high power density is still a big concern for commercial applications. In this work, a novel structured Ce0.8Sm0.2O2-δ (SDC)-based fuel cell with a bilayered anode consisting of Ni-SDC and Ni-BaZr0.1Ce0.7Y0.2O3-δ (Ni-BZCY) was designed. In addition to the catalysis function, the Ni-BZCY anode "functional" layer also provides Ba source for generating an electron-blocking layer in situ at the anode/electrolyte interface during sintering. The Ni-BZCY thickness significantly influences the quality of the electron-blocking layer and electrochemical performances of the cell. The cell with a 50 μm thick Ni-BZCY layer exhibits the best performance in terms of open circuit voltage (OCV) and peak power density (1068 mW cm(-2) at 650 °C). The results demonstrate that this cell with an optimal structure has a distinct advantage of delivering high power performance with a high efficiency at reduced temperatures.

  14. La2NiO4+δ infiltrated into gadolinium doped ceria as novel solid oxide fuel cell cathodes: Electrochemical performance and impedance modelling

    NASA Astrophysics Data System (ADS)

    Nicollet, C.; Flura, A.; Vibhu, V.; Rougier, A.; Bassat, J. M.; Grenier, J. C.

    2015-10-01

    This paper is devoted to the study of composite cathodes of La2NiO4+δ infiltrated into a Gd-doped ceria backbone. Porous Gd-doped ceria backbones are screen printed onto yttria-stabilized zirconia or Gd-doped ceria dense electrolytes, and infiltrated with a La and Ni nitrate solution (2:1 stoichiometry ratio). The influence of the preparation parameters on the polarization resistance, such as the concentration of the infiltration solution, the amount of infiltrated phase, the annealing temperature, the thickness of the electrode, and the nature of the electrolyte, is characterized by impedance spectroscopy performed on symmetrical cells. The optimization of these parameters results in a decrease of the polarization resistance down to 0.15 Ω cm2 at 600 °C. Using the Adler-Lane-Steele model, the modelling of the impedance diagrams leads to the determination of the ionic conductivity as well as the surface exchange rate of the infiltrated electrode.

  15. Defects clustering and ordering in di- and trivalently doped ceria

    SciTech Connect

    Li, Zhi-Peng; Mori, Toshiyuki; Zou, Jin; Drennan, John

    2013-02-15

    Graphical abstract: Display Omitted Highlights: ► Defect structures in trivalently and divalently doped ceria has been elucidated. ► Dumbbell structure is a universal basic vacancy structure in fluorite oxides. ► Electrostatic attraction dominates elastic interaction in doped ceria. ► Provide a physical picture of conductivity behavior in aliovalently doped ceria. -- Abstract: The formation and growth of defect clusters in CeO{sub 2}-M{sub 2}O{sub 3} (M = La{sup 3+}, Pr{sup 3+}, Sm{sup 3+}, Gd{sup 3+}, Dy{sup 3+}, Y{sup 3+}, Yb{sup 3+}) and CeO{sub 2}-DO (N = Cd{sup 2+}, Ca{sup 2+}, Sr{sup 2+}, Ba{sup 2+}) binary solid solutions have been comparatively studied by atomistic simulations based on energy minimization of atomic interactions. The calculation ensemble, including both divalent and trivalent dopants, shows a similar energetic tendency for defect species (dopants and associated oxygen vacancies) to aggregate and grow. The dumbbell structure has been verified as a universal vacancy structure in oxygen deficient fluorite lattice. Nevertheless, it also demonstrates different tendencies of dopant–vacancy associations that depend on dopant valence and radius. The dopant is site-selective in trivalent defect clusters correlated with dopant size. While in divalent solid solutions, clusters adopt similar dopant–vacancy locations. Furthermore, all clusters in divalently doped ceria have stronger dopant–vacancy associations/interactions compared to those in trivalent ones. As a consequence, the correlation of the dopant size as well as valence effects on oxygen-ion conductivity has been illustrated based on an ordered defect cluster model. This study thereby offers insight into the physical picture of ionic conductivity behavior experimentally obtained in aliovalently doped ceria.

  16. Germanium-silicon solid solutions

    NASA Technical Reports Server (NTRS)

    Zemskov, V. S.; Kubasov, V. N.; Belokurova, I. N.; Titkov, A. N.; Shulpina, I. L.; Safarov, V. I.; Guseva, N. B.

    1977-01-01

    An experiment on melting and directional crystallization of an antimony (Sb) doped germanium silicon (GeSi) solid solution was designed for the Apollo-Soyuz Test Project (ASTP) to study the possibility of using zero-g conditions for obtaining solid-solution monocrystals with uniformly distributed components. Crystallization in the zero-g environment did not occur under ideal stationary growth and segregation conditions. Crystallization under zero-g conditions revealed the heterogeneous nature of Si and Sb distribution in the cross sections of crystals. The presence of the radial thermal gradient in the multipurpose furnace could be one of the reasons for such Si and Sb distribution. The structure of space-grown crystals correlates with the nature of heterogeneities of Si and Sb distribution in crystals. The type of surface morphology and the contour observed in space-grown crystals were never observed in ground-based crystals and indicate the absence of wetting of the graphitized walls of the ampoule by the melt during melting and crystallization.

  17. Growth of Solid Solution Crystals

    NASA Technical Reports Server (NTRS)

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

    1985-01-01

    The major objective of this program is to determine the conditions under which single crystals of solid solutions can be grown from the melt in a Bridgman configuration with a high degree of chemical homogeneity. The central aim is to assess the role of gravity in the growth process and to explore the possible advantages for growth in the absence of gravity. The alloy system being investigated is the solid solution semiconductor with x-values appropriate for infrared detector applications in Hg sub (1-x) Cd sub x Te the 8 to 14 micro m wavelength region. Both melt and Te-solvent growth are being considered. The study consists of an extensive ground-based experimental and theoretical research effort followed by flight experimentation where appropriate. Experimental facilities have been established for the purification, casting, and crystal growth of the alloy system. Facilities have been also established for the metallurgical, compositional, electric and optical characterization of the alloys. Crystals are being grown by the Bridgman-Stockbarger method and are analyzed by various experimental techniques to evaluate the effects of growth conditions on the longitudinal and radial compositional variations and defect densities in the crystals.

  18. Composite ceria-coated aerogels and methods of making the same

    DOEpatents

    Eyring, Edward M; Ernst, Richard D; Turpin, Gregory C; Dunn, Brian C

    2013-05-07

    Ceria-coated aerogels can include an aerogel support material having a stabilized ceria coating thereon. The ceria coating can be formed by solution or vapor deposition of alcogels or aerogels. Additional catalytic metal species can also be incorporated into the coating to form multi-metallic compounds having improved catalytic activity. Further, the ceria coated aerogels retain high surface areas at elevated temperatures. Thus, improvements in catalytic activity and thermal stability can be achieved using these ceria-coated composite aerogels.

  19. A novel Ni/ceria-based anode for metal-supported solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Rojek-Wöckner, Veronika A.; Opitz, Alexander K.; Brandner, Marco; Mathé, Jörg; Bram, Martin

    2016-10-01

    For optimization of ageing behavior, electrochemical performance, and sulfur tolerance of metal-supported solid oxide fuel cells a new anode concept is introduced, which is based on a Ni/GDC cermet replacing the established Ni/YSZ anodes. In the present work optimized processing parameters compatible with MSC substrates are specified by doing sintering studies on pressed bulk specimen and on real porous anode structures. The electrochemical performance of the Ni/GDC anodes was characterized by means of symmetrical electrolyte supported model-type cells. In this study, three main objectives are pursued. Firstly, the effective technical realization of the Ni/GDC concept is demonstrated. Secondly, the electrochemical behavior of Ni/GDC porous anodes is characterized by impedance spectroscopy and compared with the current standard Ni/YSZ anode. Further, a qualitative comparison of the sulfur poisoning behavior of both anode types is presented. Thirdly, preliminary results of a successful implementation of the Ni/GDC cermet into a metal-supported single cell are presented.

  20. Composite solid oxide fuel cell anode based on ceria and strontium titanate

    DOEpatents

    Marina, Olga A.; Pederson, Larry R.

    2008-12-23

    An anode and method of making the same wherein the anode consists of two separate phases, one consisting of a doped strontium titanate phase and one consisting of a doped cerium oxide phase. The strontium titanate phase consists of Sr.sub.1-xM.sub.xTiO.sub.3-.delta., where M is either yttrium (Y), scandium (Sc), or lanthanum (La), where "x" may vary typically from about 0.01 to about 0.5, and where .delta. is indicative of some degree of oxygen non-stoichiometry. A small quantity of cerium may also substitute for titanium in the strontium titanate lattice. The cerium oxide consists of N.sub.yCe.sub.1-yO.sub.2-.delta., where N is either niobium (Nb), vanadium (V), antimony (Sb) or tantalum (Ta) and where "y" may vary typically from about 0.001 to about 0.1 and wherein the ratio of Ti in said first phase to the sum of Ce and N in the second phase is between about 0.2 to about 0.75. Small quantities of strontium, yttrium, and/or lanthanum may additionally substitute into the cerium oxide lattice. The combination of these two phases results in better performance than either phase used separately as an anode for solid oxide fuel cell or other electrochemical device.

  1. Mesoporous NiO-samaria doped ceria for low-temperature solid oxide fuel cells.

    PubMed

    Kim, Jin-Yeop; Kim, Ji Hyeon; Choi, Hyung Wook; Kim, Kyung Hwan; Park, Sang Joon

    2014-08-01

    In order to prepare anode material for low-temperature solid oxide fuel cells (SOFCs), the mesoporous NiO-SDC was synthesized using a cationic surfactant (cetyltrimethyl-ammonium bromide; CTAB) for obtaining wide triple-phase boundary (TPB). In addition, Ni-SDC anode-supported SOFC single cells with YSZ electrolyte and LSM cathode were fabricated and the performance of single cells was evaluated at 600 °C. The microstructure of NiO-SDC was characterized by XRD, EDX, SEM, and BET, and the results showed that the mesoporous NiO-SDC with 10 nm pores could be obtained. It was found that the surface area and the electrical performance were strongly influenced by the Ni content in Ni-SDC cermets. After calcined at 600 °C, the surface area of NiO-SDC was between 90-117 m2/g at 35-45 Ni wt%, which was sufficiently high for providing large TPB in SOFC anode. The optimum Ni content for cell performance was around 45 wt% and the corresponding MPD was 0.36 W/cm2. Indeed, the mesoporous NiO-SDC cermet may be of interest for use as an anode for low-temperature SOFCs.

  2. Gadolinia-doped ceria mixed with alkali carbonates for solid oxide fuel cell applications: I. A thermal, structural and morphological insight

    NASA Astrophysics Data System (ADS)

    Benamira, M.; Ringuedé, A.; Albin, V.; Vannier, R.-N.; Hildebrandt, L.; Lagergren, C.; Cassir, M.

    Ceria-based composites are developed and considered as potential electrolytes for intermediate solid oxide fuel cell applications (ITSOFC). After giving a survey of the most relevant results in the literature, the structural, thermal and morphological properties of composite materials based on gadolinia-doped ceria (GDC) and alkali carbonates (Li 2CO 3-K 2CO 3 or Li 2CO 3-Na 2CO 3) are carefully examined. Thermal analyses demonstrate the stability of the composite with very low weight losses of both water and CO 2 during thermal cycling and after 168 h ageing. High-temperature and room-temperature X-ray diffraction allowed determining the precise structure of the composite and its regular and reversible evolution with the temperature. The microstructure and morphology of electrolyte pellets, as observed by scanning electron microscopy (SEM), show two-well separated phases: nanocrystals of GDC and a well-distributed carbonate phase. Finally, electrical conductivity determined by impedance spectroscopy is presented as a function of time to highlight the stability of such composites over 1500 h.

  3. Biogas as a fuel for solid oxide fuel cells and synthesis gas production: effects of ceria-doping and hydrogen sulfide on the performance of nickel-based anode materials.

    PubMed

    Laycock, Christian J; Staniforth, John Z; Ormerod, R Mark

    2011-05-28

    tolerance of Ni/YSZ, however, in the presence of H(2)S ceria did not promote the reverse Boudouard reaction and at high temperatures carbon deposition was greater over ceria-doped Ni/YSZ. In order to further study the effects of ceria-doping, a solid oxide fuel cell (SOFC) was constructed with a ceria-doped anode cermet and its electrical performance on simulated biogas compared to hydrogen was tested. This fuel cell was subsequently ran for 1000 h on simulated biogas with no degradation in its overall electrical performance.

  4. Catalytic modification of Ni-Sm-doped ceria anodes with copper for direct utilization of dry methane in low-temperature solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Wang, Zhicheng; Weng, Wenjian; Cheng, Kui; Du, Piyi; Shen, Ge; Han, Gaorong

    2008-05-01

    A Cu/Ni/Sm-doped ceria (SDC) anode has been designed for direct utilization of dry methane in low-temperature anode-supported solid oxide fuel cells. The anode is prepared by the impregnation method, whereby a small amount of Cu is incorporated into the previously prepared Ni/SDC porous matrix. After reduction, Cu nanoparticles adhere to and are uniformly distributed on the surface of the Ni/SDC matrix. For the resulting Cu/Ni/SDC anode-supported cell, maximum power density of 317 mW cm-2 is achieved at 600 °C. The power density shows only ∼2% loss after 12-h operation. The results demonstrate that the Cu/Ni/SDC anode effectively suppresses carbon deposition by decreasing the Ni surface area available and the level of carbon monoxide disproportionation. This combination of effects results in very low-power density loss over the operating time.

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

    SciTech Connect

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

    2011-12-11

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

  6. Single crystals of metal solid solutions

    NASA Technical Reports Server (NTRS)

    Miller, J. F.; Austin, A. E.; Richard, N.; Griesenauer, N. M.; Moak, D. P.; Mehrabian, M. R.; Gelles, S. H.

    1974-01-01

    The following definitions were sought in the research on single crystals of metal solid solutions: (1) the influence of convection and/or gravity present during crystallization on the substructure of a metal solid solution; (2) the influence of a magnetic field applied during crystallization on the substructure of a metal solid solution; and (3) requirements for a space flight experiment to verify the results. Growth conditions for the selected silver-zinc alloy system are described, along with pertinent technical and experimental details of the project.

  7. Embedded Ceria Nanoparticles in Crosslinked PVA Electrospun Nanofibers as Optical Sensors for Radicals.

    PubMed

    Shehata, Nader; Samir, Effat; Gaballah, Soha; Hamed, Aya; Elrasheedy, Asmaa

    2016-08-26

    This work presents a new nanocomposite of cerium oxide (ceria) nanoparticles embedded in electrospun PVA nanofibers for optical sensing of radicals in solutions. Our ceria nanoparticles are synthesized to have O-vacancies which are the receptors for the radicals extracted from peroxide in water solution. Ceria nanoparticles are embedded insitu in PVA solution and then formed as nanofibers using an electrospinning technique. The formed nanocomposite emits visible fluorescent emissions under 430 nm excitation, due to the active ceria nanoparticles with fluorescent Ce(3+) ionization states. When the formed nanocomposite is in contact with peroxide solution, the fluorescence emission intensity peak has been found to be reduced with increasing concentration of peroxide or the corresponding radicals through a fluorescence quenching mechanism. The fluorescence intensity peak is found to be reduced to more than 30% of its original value at a peroxide weight concentration up to 27%. This work could be helpful in further applications of radicals sensing using a solid mat through biomedical and environmental monitoring applications.

  8. Embedded Ceria Nanoparticles in Crosslinked PVA Electrospun Nanofibers as Optical Sensors for Radicals

    PubMed Central

    Shehata, Nader; Samir, Effat; Gaballah, Soha; Hamed, Aya; Elrasheedy, Asmaa

    2016-01-01

    This work presents a new nanocomposite of cerium oxide (ceria) nanoparticles embedded in electrospun PVA nanofibers for optical sensing of radicals in solutions. Our ceria nanoparticles are synthesized to have O-vacancies which are the receptors for the radicals extracted from peroxide in water solution. Ceria nanoparticles are embedded insitu in PVA solution and then formed as nanofibers using an electrospinning technique. The formed nanocomposite emits visible fluorescent emissions under 430 nm excitation, due to the active ceria nanoparticles with fluorescent Ce3+ ionization states. When the formed nanocomposite is in contact with peroxide solution, the fluorescence emission intensity peak has been found to be reduced with increasing concentration of peroxide or the corresponding radicals through a fluorescence quenching mechanism. The fluorescence intensity peak is found to be reduced to more than 30% of its original value at a peroxide weight concentration up to 27%. This work could be helpful in further applications of radicals sensing using a solid mat through biomedical and environmental monitoring applications. PMID:27571083

  9. Solution-solid-solid mechanism: superionic conductors catalyze nanowire growth.

    PubMed

    Wang, Junli; Chen, Kangmin; Gong, Ming; Xu, Bin; Yang, Qing

    2013-09-11

    The catalytic mechanism offers an efficient tool to produce crystalline semiconductor nanowires, in which the choice, state, and structure of catalysts are active research issues of much interest. Here we report a novel solution-solid-solid (SSS) mechanism for nanowire growth catalyzed by solid-phase superionic conductor nanocrystals in low-temperature solution. The preparation of Ag2Se-catalyzed ZnSe nanowires at 100-210 °C is exampled to elucidate the SSS model, which can be extendable to grow other II-VI semiconductor (e.g., CdSe, ZnS, and CdS) nanowires by the catalysis of nanoscale superionic-phase silver or copper(I) chalcogenides (Ag2Se, Ag2S, and Cu2S). The exceptional catalytic ability of these superionic conductors originates from their structure characteristics, known for high-density vacancies and fast mobility of silver or copper(I) cations in the rigid sublattice of Se(2-) or S(2-) ions. Insights into the SSS mechanism are provided based on the formation of solid solution and the solid-state ion diffusion/transport at solid-solid interface between catalyst and nanowire.

  10. Energetics of Rare Earth Doped Uranium Oxide Solid Solutions

    NASA Astrophysics Data System (ADS)

    Zhang, Lei

    J/mol. Since all the other doped fluorite oxides based on zirconia, hafnia, ceria, and thoria are in the oxygen deficit (oxygen vacancy formation) regime, a systematic study of these rare earth doped fluorite oxides (LnxA 1-xO2-0.5x) was made comparing experimental and computational results. A consistent trend suggested by both calorimetry and computation, was found for all oxygen vacancy containing systems (actinide and non-actinide oxide systems). Larger size mismatch between the smaller host cation (A 4+) and the larger rare earth dopant cation (Ln3+) generally produces more stable solid solutions. The energetics of these systems is the result of competition between strain energy arising from size mismatch (endothermic) and defect association (exothermic). The formation enthalpies of LnxU1-xO2-0.5x obtained from calculation are slightly positive.

  11. Study on the CO Oxidation over Ceria-Based Nanocatalysts.

    PubMed

    Piumetti, Marco; Andana, Tahrizi; Bensaid, Samir; Russo, Nunzio; Fino, Debora; Pirone, Raffaele

    2016-12-01

    A series of ceria nanocatalysts have been prepared to study the structure dependency of the CO oxidation reaction. The ceria samples with well-defined nanostructures (nanocubes/Ce-NC and nanorods/Ce-NR) have been prepared using the hydrothermal method. Mesoporous ceria (Ce-MES) and ceria synthesized with solution combustion technique (Ce-SCS) have also been prepared for comparison. The lowest CO oxidation temperature has been reached by using ceria nanocubes (Ce-NC). This high activity draws immense contributions from the highly reactive (100) and (110) surfaces of the truncated nanocubes. The Ce-MES and Ce-SCS samples, despite their high surface areas, are unable to outdo the activity of Ce-NC and Ce-NR due to the abundant presence of (111) crystalline planes. This finding confirms the structure sensitivity of CO oxidation reaction catalyzed with ceria.

  12. Study on the CO Oxidation over Ceria-Based Nanocatalysts

    NASA Astrophysics Data System (ADS)

    Piumetti, Marco; Andana, Tahrizi; Bensaid, Samir; Russo, Nunzio; Fino, Debora; Pirone, Raffaele

    2016-03-01

    A series of ceria nanocatalysts have been prepared to study the structure dependency of the CO oxidation reaction. The ceria samples with well-defined nanostructures (nanocubes/Ce-NC and nanorods/Ce-NR) have been prepared using the hydrothermal method. Mesoporous ceria (Ce-MES) and ceria synthesized with solution combustion technique (Ce-SCS) have also been prepared for comparison. The lowest CO oxidation temperature has been reached by using ceria nanocubes (Ce-NC). This high activity draws immense contributions from the highly reactive (100) and (110) surfaces of the truncated nanocubes. The Ce-MES and Ce-SCS samples, despite their high surface areas, are unable to outdo the activity of Ce-NC and Ce-NR due to the abundant presence of (111) crystalline planes. This finding confirms the structure sensitivity of CO oxidation reaction catalyzed with ceria.

  13. Computer simulation of concentrated solid solution strengthening

    NASA Technical Reports Server (NTRS)

    Kuo, C. T. K.; Arsenault, R. J.

    1976-01-01

    The interaction forces between a straight edge dislocation moving through a three-dimensional block containing a random array of solute atoms were determined. The yield stress at 0 K was obtained by determining the average maximum solute-dislocation interaction force that is encountered by edge dislocation, and an expression relating the yield stress to the length of the dislocation and the solute concentration is provided. The magnitude of the solid solution strengthening due to solute atoms can be determined directly from the numerical results, provided the dislocation line length that moves as a unit is specified.

  14. Pyrolysis result of polyethylene waste as fuel for solid oxide fuel cell with samarium doped-ceria (SDC)-carbonate as electrolyte

    NASA Astrophysics Data System (ADS)

    Syahputra, R. J. E.; Rahmawati, F.; Prameswari, A. P.; Saktian, R.

    2017-02-01

    In this research, the result of pyrolysis on polyethylene was used as fuel for a solid oxide fuel cell (SOFC). The pyrolysis result is a liquid which consists of hydrocarbon chains. According to GC-MS analysis, the hydrocarbons mainly consist of C7 to C20 hydrocarbon chain. Then, the liquid was applied to a single cell of NSDC-L | NSDC | NSDC-L. NSDC is a composite SDC (samarium doped-ceria) with sodium carbonate. Meanwhile, NSDC-L is a composite of NSDC with LiNiCuO (LNC). NSDC and LNC were analyzed by X-ray diffraction to understand their crystal structure. The result shows that presence of carbonate did not change the crystal structure of SDC. SEM EDX analysis for fuel cell before and after being loaded with polyethylene oil to get information of element diffusion to the electrolyte. Meanwhile, the conductivity properties were investigated through impedance measurement. The presence of carbonate even increases the electrical conductivity. The single cell test with the pyrolysis result of polyethylene at 300 – 600 °C, found that the highest power density is at 600 °C with the maximum power density of 0.14 mW/cm2 and open circuit voltage of 0.4 Volt. Elemental analysis at three point spots of single cell NDSC-L |NSDC|NSDC-L found that a migration of ions was occurred during fuel operation at 300 – 600 °C.

  15. Synthesis and characterization of scandia ceria stabilized zirconia powders prepared by polymeric precursor method for integration into anode-supported solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Tu, Hengyong; Liu, Xin; Yu, Qingchun

    2011-03-01

    Scandia ceria stabilized zirconia (10Sc1CeSZ) powders are synthesized by polymeric precursor method for use as the electrolyte of anode-supported solid oxide fuel cell (SOFC). The synthesized powders are characterized in terms of crystalline structure, particle shape and size distribution by X-ray diffraction (XRD), transmission electron microscopy (TEM) and photon correlation spectroscopy (PCS). 10Sc1CeSZ electrolyte films are deposited on green anode substrate by screen-printing method. Effects of 10Sc1CeSZ powder characteristics on sintered films are investigated regarding the integration process for application as the electrolytes in anode-supported SOFCs. It is found that the 10Sc1CeSZ films made from nano-sized powders with average size of 655 nm are very porous with many open pores. In comparison, the 10Sc1CeSZ films made from micron-sized powders with average size of 2.5 μm, which are obtained by calcination of nano-sized powders at higher temperatures, are much denser with a few closed pinholes. The cell performances are 911 mW cm-2 at the current density of 1.25 A cm-2 and 800 °C by application of Ce0.8Gd0.2O2 (CGO) barrier layer and La0.6Sr0.4CoO3 (LSC) cathode.

  16. Evaluation of the Effect of Sulfur on the Performance of Nickel/Gadolinium‐Doped Ceria Based Solid Oxide Fuel Cell Anodes

    PubMed Central

    Yurkiv, Vitaliy; Costa, Rémi; Schiller, Günter; Friedrich, K. Andreas

    2016-01-01

    Abstract The focus of this study is the measurement and understanding of the sulfur poisoning phenomena of Ni/gadolinium‐doped ceria (CGO) based solid oxide fuel cells (SOFC). Cells with Ni/CGO10 and NiCu5/CGO40 anodes were characterized by using impedance spectroscopy at different temperatures and H2/H2O fuel ratios. The short‐term sulfur poisoning behavior was investigated systematically at temperatures of 800–950 °C, current densities of 0–0.75 A cm−2, and H2S concentrations of 1–20 ppm. A sulfur poisoning mitigation effect was observed at high current loads and temperatures. The poisoning behavior was reversible for short exposure times. It was observed that the sulfur‐affected processes exhibited significantly different relaxation times that depend on the Gd content in the CGO phase. Moreover, it was demonstrated that the capacitance of Ni/CGO10 anodes is strongly dependent on the temperature and gas‐phase composition, which reflects a changing Ce3+/Ce4+ ratio. PMID:27863123

  17. Proton-conducting Micro-solid Oxide Fuel Cells with Improved Cathode Reactions by a Nanoscale Thin Film Gadolinium-doped Ceria Interlayer

    PubMed Central

    Li, Yong; Wang, Shijie; Su, Pei-Chen

    2016-01-01

    An 8 nm-thick gadolinium-doped ceria (GDC) layer was inserted as a cathodic interlayer between the nanoscale proton-conducting yttrium-doped barium zirconate (BZY) electrolyte and the porous platinum cathode of a micro-solid oxide fuel cell (μ-SOFC), which has effectively improved the cathode reaction kinetics and rendered high cell power density. The addition of the GDC interlayer significantly reduced the cathodic activation loss and increased the peak power density of the μ-SOFC by 33% at 400 °C. The peak power density reached 445 mW/cm2 at 425 °C, which is the highest among the reported μ-SOFCs using proton-conducting electrolytes. The impressive performance was attributed to the mixed protonic and oxygen ionic conducting properties of the nano-granular GDC, and also to the high densities of grain boundaries and lattice defects in GDC interlayer that favored the oxygen incorporation and transportation during the oxygen reduction reaction (ORR) and the water evolution reaction at cathode. PMID:26928192

  18. Proton-conducting Micro-solid Oxide Fuel Cells with Improved Cathode Reactions by a Nanoscale Thin Film Gadolinium-doped Ceria Interlayer.

    PubMed

    Li, Yong; Wang, Shijie; Su, Pei-Chen

    2016-02-29

    An 8 nm-thick gadolinium-doped ceria (GDC) layer was inserted as a cathodic interlayer between the nanoscale proton-conducting yttrium-doped barium zirconate (BZY) electrolyte and the porous platinum cathode of a micro-solid oxide fuel cell (μ-SOFC), which has effectively improved the cathode reaction kinetics and rendered high cell power density. The addition of the GDC interlayer significantly reduced the cathodic activation loss and increased the peak power density of the μ-SOFC by 33% at 400 °C. The peak power density reached 445 mW/cm(2) at 425 °C, which is the highest among the reported μ-SOFCs using proton-conducting electrolytes. The impressive performance was attributed to the mixed protonic and oxygen ionic conducting properties of the nano-granular GDC, and also to the high densities of grain boundaries and lattice defects in GDC interlayer that favored the oxygen incorporation and transportation during the oxygen reduction reaction (ORR) and the water evolution reaction at cathode.

  19. Slurry spin coating of thin film yttria stabilized zirconia/gadolinia doped ceria bi-layer electrolytes for solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Kim, Hyun Joong; Kim, Manjin; Neoh, Ke Chean; Han, Gwon Deok; Bae, Kiho; Shin, Jong Mok; Kim, Gyu-Tae; Shim, Joon Hyung

    2016-09-01

    Thin ceramic bi-layered membrane comprising yttria-stabilized zirconia (YSZ) and gadolinia-doped ceria (GDC) is fabricated by the cost-effective slurry spin coating technique, and it is evaluated as an electrolyte of solid oxide fuel cells (SOFCs). It is demonstrated that the slurry spin coating method is capable of fabricating porous ceramic films by adjusting the content of ethyl-cellulose binders in the source slurry. The porous GDC layer deposited by spin coating under an optimal condition functions satisfactorily as a cathode-electrolyte interlayer in the test SOFC stack. A 2-μm-thick electrolyte membrane of the spin-coated YSZ/GDC bi-layer is successfully deposited as a dense and stable film directly on a porous NiO-YSZ anode support without any interlayers, and the SOFC produces power output over 200 mW cm-2 at 600 °C, with an open circuit voltage close to 1 V. Electrochemical impedance spectra analysis is conducted to evaluate the performance of the fuel cell components in relation with the microstructure of the spin-coated layers.

  20. Proton-conducting Micro-solid Oxide Fuel Cells with Improved Cathode Reactions by a Nanoscale Thin Film Gadolinium-doped Ceria Interlayer

    NASA Astrophysics Data System (ADS)

    Li, Yong; Wang, Shijie; Su, Pei-Chen

    2016-02-01

    An 8 nm-thick gadolinium-doped ceria (GDC) layer was inserted as a cathodic interlayer between the nanoscale proton-conducting yttrium-doped barium zirconate (BZY) electrolyte and the porous platinum cathode of a micro-solid oxide fuel cell (μ-SOFC), which has effectively improved the cathode reaction kinetics and rendered high cell power density. The addition of the GDC interlayer significantly reduced the cathodic activation loss and increased the peak power density of the μ-SOFC by 33% at 400 °C. The peak power density reached 445 mW/cm2 at 425 °C, which is the highest among the reported μ-SOFCs using proton-conducting electrolytes. The impressive performance was attributed to the mixed protonic and oxygen ionic conducting properties of the nano-granular GDC, and also to the high densities of grain boundaries and lattice defects in GDC interlayer that favored the oxygen incorporation and transportation during the oxygen reduction reaction (ORR) and the water evolution reaction at cathode.

  1. Radiation-Induced Reduction of Ceria in Single and Polycrystalline Thin Films

    SciTech Connect

    Kumar, Amit; Devanathan, Ramaswami; Shutthanandan, V.; Kuchibhatla, Satyanarayana V N T; Karakoti, Ajay S.; Yang, Yong; Thevuthasan, Suntharampillai; Seal, Sudipta

    2012-01-12

    Ceria (CeO{sub 2}) is a technologically important ceramic material with a wide range of neoteric applications in catalysis, solid oxide fuel cells, oxygen gas sensors, hydrogen production, and ultraviolet shielding. Recent research has revealed promising biomedical applications of ceria. Nanoparticles of ceria have been shown to protect healthy cells from radiation-induced cellular damage. The mechanisms governing the radioprotection characteristics of ceria nanoparticles are not well understood and it has been hypothesized that reversible switching between Ce{sup 4+} and Ce{sup 3+} states may enable ceria nanoparticles to mop up free radicals.

  2. Silica Supported Ceria Nanoparticles: A Hybrid Nanostructure To Increase Stability And Surface Reactivity Of Nano-crystalline Ceria

    SciTech Connect

    Munusamy, Prabhakaran; Sanghavi, Shail P.; Varga, Tamas; Thevuthasan, Suntharampillai

    2014-01-21

    The mixed oxidation state (3+/4+) of ceria nanoparticles of smaller sizes make them attractive materials for their catalytic antioxidant biological properties. However the unmodified smaller ceria nanoparticles are limited in their use due to particles agglomeration and reduced surface chemical reactivity in the solutions used to disperse the nanoparticles. This work describes an effort to stabilize small ceria nanoparticles, retaining their desired activity, on a larger stable silica support. The ceria nanoparticles attached to silica was synthesized by a solution synthesis technique in which the surface functional groups of silica nanoparticles were found to be essential for the formation of smaller ceria nanoparticles. The surface chemical and vibrational spectroscopy analysis revealed cerium–silicate (Ce-O-Si) covalent bond linkage between silica and cerium oxide nanoparticles. The colloidal properties (agglomerate particle size and suspension stability) of ceria attached to silica was significantly improved due to inherent physico-chemical characteristics of silica against random collision and gravitation settling as opposed to unmodified ceria nanoparticles in solution. The bio-catalytic activity of ceria nanoparticles in the 3+ oxidation state was not found to be limited by attachment to the silica support as measured by free radical scavenging activity in different biological media conditions.

  3. Effects of some rare earth and carbonate-based co-dopants on structural and electrical properties of samarium doped ceria (SDC) electrolytes for solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Anwar, Mustafa; Khan, Zuhair S.; Mustafa, Kamal; Rana, Akmal

    2015-09-01

    In the present study, samarium doped ceria (SDC) and SDC-based composite with the addition of K2CO3 were prepared by co-precipitation route and effects of pH of the solution and calcination temperature on microstructure of SDC and SDC-K2CO3, respectively, were investigated. Furthermore, experimentation was performed to investigate into the ionic conductivity of pure SDC by co-doping with yttrium i.e., YSDC, XRD and SEM studies show that the crystallite size and particle size of SDC increases with the increase in pH. The SEM images of all the samples of SDC synthesized at different pH values showed the irregular shaped and dispersed particles. SDC-K2CO3 was calcined at 600∘C, 700∘C and 800∘C for 4 h and XRD results showed that crystallite size increases while lattice strain, decreases with the increase in calcination temperature and no peaks were detected for K2CO3 as it is present in an amorphous form. The ionic conductivity of the electrolytes increases with the increase in temperature and SDC-K2CO3 shows the highest value of ionic conductivity as compared to SDC and YSDC. Chemical compatibility tests were performed between the co-doped electrolyte and lithiated NiO cathode at high temperature. It revealed that the couple could be used up to the temperature of 700∘C.

  4. Extremely thin bilayer electrolyte for solid oxide fuel cells (SOFCs) fabricated by chemical solution deposition (CSD).

    PubMed

    Oh, Eun-Ok; Whang, Chin-Myung; Lee, Yu-Ri; Park, Sun-Young; Prasad, Dasari Hari; Yoon, Kyung Joong; Son, Ji-Won; Lee, Jong-Ho; Lee, Hae-Weon

    2012-07-03

    An extremely thin bilayer electrolyte consisting of yttria-stabilized zirconia (YSZ) and gadolinia-doped ceria (GDC) is successfully fabricated on a sintered NiO-YSZ substrate. Major processing flaws are effectively eliminated by applying local constraints to YSZ nanoparticles, and excellent open circuit voltage and cell performance are demonstrated in a solid oxide fuel cell (SOFC) at intermediate operating temperatures.

  5. Growth of Solid Solution Single Crystals

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

    The objective of the study is to establish the effects of processing semiconducting, solid solution, single crystals in a microgravity environment on the metallurgical, compositional, electrical, and optical characteristics of the crystals. The alloy system being investigated is the solid solution semiconductor Hg(1-x)Cd(x)Te, with x-values appropriate for infrared detector applications in the 8 to 14 mm wavelength region. Both melt and Te-solvent growth are being performed. The study consists of an extensive ground-based experimental and theoretical research effort followed by flight experimentation where appropriate. The ground-based portion of the investigation also includes the evaluation of the relative effectiveness of stabilizing techniques, such as applied magnetic fields, for suppressing convective flow during the melt growth of the crystals.

  6. Defect equilibria and chemical expansion in undoped and doped ceria and strontium doped lanthanum cobalt iron oxide oxygen conducting materials and their applications in solid-state electrochemical cells

    NASA Astrophysics Data System (ADS)

    Bishop, Sean R.

    Ceramic oxygen conducting materials are used in many energy-related applications from fuel reforming to electricity generation. In a typical ceramic oxygen conductor, oxygen ions are transmitted through a dense membrane via defects in the material. Hence, defects control the performance of these materials. In low oxygen partial pressure, ceria based materials become non-stoichiometric and can form defect complexes that hinder ionic conductivity. In addition, oxygen non-stoichiometry induces strain (chemical expansion) that can result in stresses for composite or constrained applications. In this dissertation the non-stoichiometry and chemical expansion behavior is reported as a function of PO2 for undoped ceria, gadolinium doped ceria (GDC) and strontium doped lanthanum cobalt iron oxide (LSCF). Undoped ceria was measured at 800°C and GDC and LSCF at 600--900°C in a wide PO2 range. It was found that defect interactions could effectively be modeled in ceria based materials using defect complex formation in a mass action formalism and the results were used to model nonlinear chemical expansion behavior. In LSCF, non-stoichiometry and chemical expansion were modeled using using metallic and semi-conductor models. A semi-conductor model with B-site small polarons best represented the measured behavior. The resulting models and parameters can be used to predict mechanical and electrical behavior of SOFC components. Surface oxygen non-stoichiometry has also been measured by comparing low surface area to high surface area samples. It was found that surface defect concentration previously ignored in the literature can result in erroneous non-stoichiometry measurements. In the latter half of this dissertation these materials are applied in SOFC and ceramic oxygen generator (COG) technology. A strategy is presented here for advanced life support systems employs a catalytic layer combined with a COG cell so that CO2 is reduced all the way to solid carbon and oxygen without

  7. Magnetic Damping of Solid Solution Semiconductor Alloys

    NASA Technical Reports Server (NTRS)

    Szofran, Frank R.; Benz, K. W.; Corell, Arne; Dold, Peter; Cobb, Sharon D.; Volz, Martin P.; Motakef, Shariar

    1998-01-01

    The objective of this study is to conduct the Earth-based research sufficient to successfully propose a flight experiment (1) to experimentally test the validity of the modeling predictions applicable to the magnetic damping of convective flows in conductive melts as this applies to the bulk growth of solid solution semiconducting materials in the reduced gravitational levels available in low Earth orbit and (2) to assess the effectiveness of steady magnetic fields in reducing the fluid flows occurring in these materials during space processing. To achieve the objectives of this investigation, we are carrying out a comprehensive program in the Bridgman and floating-zone configurations using the solid solution alloy system Ge-Si. This alloy system was chosen because it has been studied extensively in environments that have not simultaneously included both low gravity and an applied magnetic field. Also, all compositions have a high electrical conductivity, and the materials parameters permit high growth rates compared to many other commonly studied alloy semiconductors. An important supporting investigation is determining the role, if any, that thermoelectromagnetic convection (TEMC) plays during growth of these materials in a magnetic field. Some compositional anomalies observed by us in magnetic grown crystals can only be explained by TEMC; this has significant implications for the deployment of a Magnetic Damping Furnace in space. This effect will be especially important in solid solutions where the growth interface is, in general, neither isothermal nor isoconcentrational. It could be important in single melting point materials, also, if faceting takes place producing a non-isothermal interface.

  8. Magnetic Damping of Solid Solution Semiconductor Alloys

    NASA Technical Reports Server (NTRS)

    Szofran, Frank R.; Benz, K. W.; Croell, Arne; Dold, Peter; Cobb, Sharon D.; Volz, Martin P.; Motakef, Shariar

    1999-01-01

    The objective of this study is to: (1) experimentally test the validity of the modeling predictions applicable to the magnetic damping of convective flows in electrically conductive melts as this applies to the bulk growth of solid solution semiconducting materials; and (2) assess the effectiveness of steady magnetic fields in reducing the fluid flows occurring in these materials during processing. To achieve the objectives of this investigation, we are carrying out a comprehensive program in the Bridgman and floating-zone configurations using the solid solution alloy system Ge-Si. This alloy system has been studied extensively in environments that have not simultaneously included both low gravity and an applied magnetic field. Also, all compositions have a high electrical conductivity, and the materials parameters permit reasonable growth rates. An important supporting investigation is determining the role, if any, that thermoelectromagnetic convection (TEMC) plays during growth of these materials in a magnetic field. TEMC has significant implications for the deployment of a Magnetic Damping Furnace in space. This effect will be especially important in solid solutions where the growth interface is, in general, neither isothermal nor isoconcentrational. It could be important in single melting point materials, also, if faceting takes place producing a non-isothermal interface. In conclusion, magnetic fields up to 5 Tesla are sufficient to eliminate time-dependent convection in silicon floating zones and possibly Bridgman growth of Ge-Si alloys. In both cases, steady convection appears to be more significant for mass transport than diffusion, even at 5 Tesla in the geometries used here. These results are corroborated in both growth configurations by calculations.

  9. Lattice thermal expansion and solubility limits of neodymium-doped ceria

    NASA Astrophysics Data System (ADS)

    Zhang, Jinhua; Ke, Changming; Wu, Hongdan; Yu, Jishun; Wang, Jingran

    2016-11-01

    NdxCe1-xO2-0.5x (x=0-1.0) powders were prepared by reverse coprecipitation-calcination method and characterized by XRD. The crystal structure of product powders transformed from single fluorite structure to the complex of fluorite and C-type cubic structure, and finally to trigonal structure with the increase of x-value. An empirical equation simulating the lattice parameter of neodymium doped ceria was established based on the experimental data. The lattice parameters of the fluorite structure solid solutions increased with extensive adoption of Nd3+, and the heating temperature going up. The average thermal expansion coefficients of neodymium doped ceria with fluorite structure are higher than 13.5×10-6 °C-1 from room temperature to 1200 °C.

  10. Polypropylene oil as fuel for solid oxide fuel cell with samarium doped-ceria (SDC)-carbonate as electrolyte

    NASA Astrophysics Data System (ADS)

    Syahputra, R. J. E.; Rahmawati, F.; Prameswari, A. P.; Saktian, R.

    2017-03-01

    The research focusses on converting polypropylene oil as pyrolysis product of polypropylene plastic into an electricity. The converter was a direct liquid fuel-solid oxide fuel cell (SOFC) with cerium oxide based material as electrolyte. The polypropylene vapor flowed into fuel cell, in the anode side and undergo oxidation reaction, meanwhile, the Oxygen in atmosphere reduced into oxygen ion at cathode. The fuel cell test was conducted at 400 - 600 °C. According to GC-MS analysis, the polypropylene oil consist of C8 to C27 hydrocarbon chain. The XRD analysis result shows that Na2CO3 did not change the crystal structure of SDC even increases the electrical conductivity. The maximum power density is 0.079 mW.cm-2 at 773 K. The open circuite voltage is 0.77 volt. Chemical stability test by analysing the single cell at before and after fuel cell test found that ionic migration occured during fuel cell operation. It is supported by the change of elemental composition in the point position of electrolyte and at the electrolyte-electrode interface

  11. Carbon deposition behaviour in metal-infiltrated gadolinia doped ceria electrodes for simulated biogas upgrading in solid oxide electrolysis cells

    NASA Astrophysics Data System (ADS)

    Duboviks, V.; Lomberg, M.; Maher, R. C.; Cohen, L. F.; Brandon, N. P.; Offer, G. J.

    2015-10-01

    One of the attractive applications for reversible Solid Oxide Cells (SOCs) is to convert CO2 into CO via high temperature electrolysis, which is particularly important for biogas upgrading. To improve biogas utility, the CO2 component can be converted into fuel via electrolysis. A significant issue for SOC operation on biogas is carbon-induced catalyst deactivation. Nickel is widely used in SOC electrodes for reasons of cost and performance, but it has a low tolerance to carbon deposition. Two different modes of carbon formation on Ni-based electrodes are proposed in the present work based on ex-situ Raman measurements which are in agreement with previous studies. While copper is known to be resistant towards carbon formation, two significant issues have prevented its application in SOC electrodes - namely its relatively low melting temperature, inhibiting high temperature sintering, and low catalytic activity for hydrogen oxidation. In this study, the electrodes were prepared through a low temperature metal infiltration technique. Since the metal infiltration technique avoids high sintering temperatures, Cu-Ce0.9Gd0.1O2-δ (Cu-CGO) electrodes were fabricated and tested as an alternative to Ni-CGO electrodes. We demonstrate that the performance of Cu-CGO electrodes is equivalent to Ni-CGO electrodes, whilst carbon formation is fully suppressed when operated on biogas mixture.

  12. Electrical, Electrochemical, and Optical Characterization of Ceria Films

    NASA Astrophysics Data System (ADS)

    Oh, Tae-Sik

    Acceptor-doped ceria has been recognized as a promising intermediate temperature solid oxide fuel cell electrode/electrolyte material. For practical implementation of ceria as a fuel cell electrolyte and for designing model experiments for electrochemical activity, it is necessary to fabricate thin films of ceria. Here, metal-organic chemical vapor deposition was carried out in a homemade reactor to grow ceria films for further electrical, electrochemical, and optical characterization. Doped/undoped ceria films are grown on single crystalline oxide wafers with/without Pt line pattern or Pt solid layer. Deposition conditions were varied to see the effect on the resultant film property. Recently, proton conduction in nanograined polycrystalline pellets of ceria drew much interest. Thickness-mode (through-plane, z-direction) electrical measurements were made to confirm the existence of proton conductivity and investigate the nature of the conduction pathway: exposed grain surfaces and parallel grain boundaries. Columnar structure presumably favors proton conduction, and we have found measurable proton conductivity enhancement. Electrochemical property of gas-columnar ceria interface on the hydrogen electrooxidation is studied by AC impedance spectroscopy. Isothermal gas composition dependence of the electrode resistance was studied to elucidate Sm doping level effect and microstructure effect. Significantly, preferred orientation is shown to affect the gas dependence and performance of the fuel cell anode. A hypothesis is proposed to explain the origin of this behavior. Lastly, an optical transmittance based methodology was developed to obtain reference refractive index and microstructural parameters (thickness, roughness, porosity) of ceria films via subsequent fitting procedure.

  13. Plasma sprayed ceria-containing interlayer

    DOEpatents

    Schmidt, Douglas S.; Folser, George R.

    2006-01-10

    A plasma sprayed ceria-containing interlayer is provided. The interlayer has particular application in connection with a solid oxide fuel cell used within a power generation system. The fuel cell advantageously comprises an air electrode, a plasma sprayed interlayer disposed on at least a portion of the air electrode, a plasma sprayed electrolyte disposed on at least a portion of the interlayer, and a fuel electrode applied on at least a portion of the electrolyte.

  14. A correlation between the ionic conductivities and the formation enthalpies of trivalent-doped ceria at relatively low temperatures.

    PubMed

    Avila-Paredes, Hugo J; Shvareva, Tatiana; Chen, Weiqun; Navrotsky, Alexandra; Kim, Sangtae

    2009-10-14

    We report a correlation between oxygen ionic conductivity and the enthalpy of formation of trivalent-doped ceria from the component binary oxides observed at relatively low temperatures (150-275 degrees C). The bulk conductivities of La-doped ceria samples identical to those previously examined by thermochemical studies were measured as a function of La content for a direct comparison. The conductivity showed a maximum at a La concentration of 5 mol%, implying that the number of freely mobile oxygen vacancies reaches a maximum near that doping level in the temperature range of interest. The formation enthalpies previously reported by Chen and Navrotsky also show a maximum, indicating destabilization near that composition. Additional measurements show that this maximum is very pronounced and sharply peaked near that composition. These enthalpies suggest that the energetically favorable long-range interactions between the charged defects that trap the oxygen vacancies become dominant above 5 mol% doping in the CeO2-LaO1.5 solid solution. In addition, the conductivities measured from independently prepared Gd-doped ceria samples show a maximum at around 10 mol% doping below 450 degrees C as anticipated from a pronounced maximum in the formation enthalpies of the CeO2-GdO1.5 solid solution. These empirical findings confirm that the ionic conductivity of trivalent-doped ceria is strongly enough correlated with its formation enthalpy at relatively low temperatures so that information about the critical dopant concentration associated with the conductivity maximum may be gained from the formation enthalpies of the solid solutions, and vice versa. We have no direct information about this correlation at higher temperatures; both thermodynamics and conductivity maximum might change if the defect clusters dissociate to any significant extent.

  15. End-Member Formulation of Solid Solutions and Reactive Transport

    SciTech Connect

    Lichtner, Peter C.

    2015-09-01

    A model for incorporating solid solutions into reactive transport equations is presented based on an end-member representation. Reactive transport equations are solved directly for the composition and bulk concentration of the solid solution. Reactions of a solid solution with an aqueous solution are formulated in terms of an overall stoichiometric reaction corresponding to a time-varying composition and exchange reactions, equivalent to reaction end-members. Reaction rates are treated kinetically using a transition state rate law for the overall reaction and a pseudo-kinetic rate law for exchange reactions. The composition of the solid solution at the onset of precipitation is assumed to correspond to the least soluble composition, equivalent to the composition at equilibrium. The stoichiometric saturation determines if the solid solution is super-saturated with respect to the aqueous solution. The method is implemented for a simple prototype batch reactor using Mathematica for a binary solid solution. Finally, the sensitivity of the results on the kinetic rate constant for a binary solid solution is investigated for reaction of an initially stoichiometric solid phase with an undersaturated aqueous solution.

  16. Growth of Solid Solution Single Crystals

    NASA Technical Reports Server (NTRS)

    Lehoczky, Sandor L.; Szofran, F. R.; Gillies, Donald C.

    2001-01-01

    The solidification of a solid solution semiconductor, having a wide separation between liquidus and solidus has been extensively studied in ground based, high magnetic field and Spacelab experiments. Two alloys of mercury cadmium telluride have been studied; with 80.0 mole percent of HgTe and 84.8 mole percent of HgTe respectively, the remainder being cadmium telluride. Such alloys are extremely difficult to grow by directional solidification on earth due to high solutal and thermal density differences that give rise to fluid flow and consequent loss of interface shape and composition. Diffusion controlled growth is therefore impossible to achieve in conventional directional solidification. The ground based experiments consisted of growing crystals in several different configurations of heat pipe furnaces, NASA's Advanced Automated Directional Solidification Furnace (AADSF), and a similar furnace incorporated in a superconducting magnet capable of operating at up to 5T. The first microgravity experiment took place during the flight of STS-62 in March 1994, with the AADSF installed on the second United States Microgravity Payload (USMP-2). The alloy was solidified at 3/4 inch per day over a 9 day period, and for the first time a detailed evaluation was performed correlating composition variations to measured residual acceleration. The second flight experiment took place in the fourth United States Microgravity Payload Mission (USMP-4) in November 1997. Due to contamination of the furnace system, analysis shows that the conditions prevailing during the experiment were quite different from the requirements requested prior to the mission. The results indicate that the sample did accomplish the desired objectives.

  17. Special quasirandom structure modeling of fluorite-structured oxide solid solutions with aliovalent cation substitutions

    NASA Astrophysics Data System (ADS)

    Wolff-Goodrich, Silas; Hanken, Benjamin E.; Solomon, Jonathan M.; Asta, Mark

    2015-07-01

    The accuracy of the special quasirandom structure (SQS) approach for modeling the structure and energetics of fluorite-structured oxide solid solutions with aliovalent cation substitutions is assessed in an ionic-pair potential study of urania and ceria based systems mixed with trivalent rare-earth ions. Mixing enthalpies for SQS supercells containing 96 and 324 lattice sites were calculated using ionic pair potentials for U0.5La0.5O1.75, U0.5Y0.5O1.75, Ce0.5La0.5O1.75, Ce0.5Y0.5O1.75, and Ce0.5Gd0.5O1.75, which all have stoichiometries of pyrochlores. The SQS results were compared to benchmark values for random substitutional disorder obtained using large supercell models. The calculations show significant improvement of the mixing enthalpy for the larger 324 site SQS, which is attributed to a better description of the structural distortions, as characterized by the radial distribution functions in relaxed systems.

  18. Highly CO2-Tolerant Cathode for Intermediate-Temperature Solid Oxide Fuel Cells: Samarium-Doped Ceria-Protected SrCo0.85Ta0.15O3-δ Hybrid.

    PubMed

    Li, Mengran; Zhou, Wei; Zhu, Zhonghua

    2017-01-25

    Susceptibility to CO2 is one of the major challenges for the long-term stability of the alkaline-earth-containing cathodes for intermediate-temperature solid oxide fuel cells. To alleviate the adverse effects from CO2, we incorporated samarium-stabilized ceria (SDC) into a SrCo0.85Ta0.15O3-δ (SCT15) cathode by either mechanical mixing or a wet impregnation method and evaluated their cathode performance stability in the presence of a gas mixture of 10% CO2, 21% O2, and 69% N2. We observed that the CO2 tolerance of the hybrid cathode outperforms the pure SCT15 cathode by over 5 times at 550 °C. This significant enhancement is likely attributable to the low CO2 adsorption and reactivity of the SDC protective layer, which are demonstrated through thermogravimetric analysis, energy-dispersive spectroscopy, and electrical conductivity study.

  19. Compositional Segregation in Unidirectionally Solidified Solid Solution Crystals

    NASA Technical Reports Server (NTRS)

    Wang, J. C.

    1983-01-01

    A computer program was developed to model compositional segregation in unidrectionally solidified solid-solution-semiconducting crystals. The program takes into account the variations of the interface segregation constant and solidification rate with composition. Calculations are performed for the HgCdTe solid solution system that is compared with experimental data.

  20. Growth of Solid Solution Single Crystals

    NASA Technical Reports Server (NTRS)

    Lehoczky, Sandor L.; Szofran, F. R.; Gillies, Donald C.; Watring, D. A.

    1999-01-01

    The solidification of a solid solution semiconductor, having a wide separation between liquidus and serious has been extensively studied in ground based, high magnetic field and Spacelab experiments. Two alloys of mercury cadmium telluride have been studied; mercury cadmium telluride with 80.0 mole percent of HgTe and 84.8 mole percent respectively. These alloys are extremely difficult to grow by directional solidification on earth due to high solutal and thermal density differences that give rise to fluid flow and consequent loss of interface shape and composition. Diffusion controlled growth is therefore impossible to achieve in conventional directional solidification. The ground based experiments consisted of growing crystals in several different configurations of heat pipe furnaces, NASA's Advanced Automated Directional Solidification Furnace (AADSF), and a similar furnace incorporated in a superconducting magnet capable of operating at up to 5T. The first microgravity experiment took place during the flight of STS-62 in March 1994, with the AADSF installed on the second United States Microgravity Payload (USMP-2). The alloy was solidified at 3/4 inch per day over a 9 day period, and for the first time a detailed evaluation was performed of residual acceleration effects. The second flight experiment took place in the fourth United States Microgravity Payload Mission (USMP-4) in November 1997. Due to contamination of the furnace system by a previously processed sample, the sample was not received until May 1998, and the preliminary analysis shows that the conditions prevailing during the experiment were quite different from the requirements requested prior to the mission. Early results are indicating that the sample may not accomplish the desired objectives. As with the USMP-2 mission, the results of the ground based experiments were compared with the crystal grown in orbit under microgravity conditions. On the earth, it has been demonstrated that the

  1. Special quasirandom structures for perovskite solid solutions

    NASA Astrophysics Data System (ADS)

    Jiang, Zhijun; Nahas, Yousra; Xu, Bin; Prosandeev, Sergey; Wang, Dawei; Bellaiche, Laurent

    2016-11-01

    Special quasirandom structures (SQS) are presently generated for disordered (A‧1-x {{\\text{A}}\\prime \\prime} x )BX3 and A(B‧1-x {{\\text{B}}\\prime \\prime} x )X3 perovskite solid solutions, with x  =  1/2 as well as 1/3 and 2/3. These SQS configurations are obtained by imposing that the so-called Cowley parameters are as close to zero as possible for the three nearest neighboring shells. Moreover, these SQS configurations are slightly larger in size than those available in the literature for x  =  1/2, mostly because of the current capabilities of atomistic techniques. They are used here within effective Hamiltonian schemes to predict various properties, which are then compared to those associated with large random supercells, in a variety of compounds, namely (Ba1-x Sr x )TiO3, Pb(Zr1-x Ti x )O3, Pb(Sc0.5Nb0.5)O3, Ba(Zr1-x Ti x )O3, Pb(Mg1/3Nb2/3)O3 and (Bi1-x Nd x )FeO3. It is found that these SQS configurations can reproduce many properties of large random supercells of most of these disordered perovskite alloys, below some finite material-dependent temperature. Examples of these properties are electrical polarization, anti-phase and in-phase octahedral tiltings, antipolar motions, antiferromagnetism, strain, piezoelectric coefficients, dielectric response, specific heat and even the formation of polar nanoregions (PNRs) in some relaxors. Some limitations of these SQS configurations are also pointed out and explained.

  2. Optimization of ionic conductivity in doped ceria

    PubMed Central

    Andersson, David A.; Simak, Sergei I.; Skorodumova, Natalia V.; Abrikosov, Igor A.; Johansson, Börje

    2006-01-01

    Oxides with the cubic fluorite structure, e.g., ceria (CeO2), are known to be good solid electrolytes when they are doped with cations of lower valence than the host cations. The high ionic conductivity of doped ceria makes it an attractive electrolyte for solid oxide fuel cells, whose prospects as an environmentally friendly power source are very promising. In these electrolytes, the current is carried by oxygen ions that are transported by oxygen vacancies, present to compensate for the lower charge of the dopant cations. Ionic conductivity in ceria is closely related to oxygen-vacancy formation and migration properties. A clear physical picture of the connection between the choice of a dopant and the improvement of ionic conductivity in ceria is still lacking. Here we present a quantum-mechanical first-principles study of the influence of different trivalent impurities on these properties. Our results reveal a remarkable correspondence between vacancy properties at the atomic level and the macroscopic ionic conductivity. The key parameters comprise migration barriers for bulk diffusion and vacancy–dopant interactions, represented by association (binding) energies of vacancy–dopant clusters. The interactions can be divided into repulsive elastic and attractive electronic parts. In the optimal electrolyte, these parts should balance. This finding offers a simple and clear way to narrow the search for superior dopants and combinations of dopants. The ideal dopant should have an effective atomic number between 61 (Pm) and 62 (Sm), and we elaborate that combinations of Nd/Sm and Pr/Gd show enhanced ionic conductivity, as compared with that for each element separately. PMID:16478802

  3. Structural analysis of 5-fluorouracil and thymine solid solutions

    NASA Astrophysics Data System (ADS)

    Vogt, Frederick G.; Vena, Joseph A.; Chavda, Manisha; Clawson, Jacalyn S.; Strohmeier, Mark; Barnett, Maria E.

    2009-08-01

    Solid-state analysis with powder X-ray diffraction (PXRD), solid-state NMR (SSNMR), and other spectroscopic and physical methods can provide detailed structural information about organic and pharmaceutical cocrystals. In this study, a range of solid-state analysis methods are used to characterize co-crystallized solid solutions of 5-fluorouracil and thymine. 1H, 13C and 19F SSNMR and PXRD methods are used to study the structure and disorder present in a solid solution previously prepared by solution evaporation methods; here the solid solution is prepared over a wider stoichiometric range by solvent-drop grinding techniques. Long-range perturbations of key chemical shifts are detectable by SSNMR, indicating that the solid solution is not random. Cross-polarization and heteronuclear correlation SSNMR experiments between 1H, 13C, and 19F nuclei offer insight into the structure of this solid solution, and density functional theory (DFT) methods are applied to calculate lattice energies and NMR properties in order to understand the population of the two primary disordered sites in the crystal structure. In addition, a second solid solution of 5-fluorouracil and thymine is reported and analyzed. This solid solution, which was produced by solvent-drop grinding experiments and characterized by SSNMR and powder X-ray diffraction methods, is determined to be an isostructural phase to that of anhydrous thymine with the inclusion of 5-fluorouracil defects. A similar effect does not occur under excess 5-fluorouracil conditions; instead, phase-separated Form 1 of 5-fluorouracil and anhydrous thymine are obtained. DFT calculations are applied to offer a possible explanation for this disparity.

  4. Enhanced superhydrophilicity and thermal stability of ITO surface with patterned ceria coatings

    NASA Astrophysics Data System (ADS)

    Xue, Mingshan; Peng, Na; Li, Changquan; Ou, Junfei; Wang, Fajun; Li, Wen

    2015-02-01

    Surface wettability of solid materials is significant for both fundamental research and engineering applications. Compared with most existing fabrication methods of superhydrophilic surfaces by UV exposure or chemical modification, in this work, a superhydrophilic ceria coating on ITO substrate is developed by a fast, simple one-step method. It is found that the superhydrophilicity of ceria coatings is strongly dependent on both the patterned microstructures benefiting the capillary effect and the peculiar chemical composition of ceria inducing numerous oxygen vacancies and large surface free energy. Owing to the inherent physical stability of ceria, such a superhydrophilic ceria coating exhibits an excellently thermal stability at both room temperature and higher temperature. These results open up new avenues for the underlying applications of superhydrophilic coatings, such as heat transfer/dissipation.

  5. Solid solution hardening of molecular crystals: tautomeric polymorphs of omeprazole.

    PubMed

    Mishra, Manish Kumar; Ramamurty, Upadrasta; Desiraju, Gautam R

    2015-02-11

    In the context of processing of molecular solids, especially pharmaceuticals, hardness is an important property that often determines the manufacturing steps employed. Through nanoindentation studies on a series of omeprazole polymorphs, in which the proportions of the 5- and 6-methoxy tautomers vary systematically, we demonstrate that solid-solution strengthening can be effectively employed to engineer the hardness of organic solids. High hardness can be attained by increasing lattice resistance to shear sliding of molecular layers during plastic deformation.

  6. Plurality of inherent states in equiatomic solid solutions

    NASA Astrophysics Data System (ADS)

    Demkowicz, M. J.

    2017-03-01

    We show that single-crystal, equiatomic solid solutions of Lennard-Jones particles have a plurality of inherent states: mechanically stable configurations with identical lattice site occupancies, yet distinct potential-energy minima. External loading triggers transitions between inherent states via localized shear transformations. A plurality of inherent states and mechanically activated transitions between them make equiatomic solid solutions an unusual form of matter: one that is crystalline like single-component metals, yet exhibits localized shear transformations like metallic glasses.

  7. Surface structure of coherently strained ceria ultrathin films

    NASA Astrophysics Data System (ADS)

    Shi, Yezhou; Stone, Kevin H.; Guan, Zixuan; Monti, Matteo; Cao, Chuntian; El Gabaly, Farid; Chueh, William C.; Toney, Michael F.

    2016-11-01

    Cerium oxide, or ceria, is an important material for solid oxide fuel cells and water splitting devices. Although the ceria surface is active in catalytic and electrochemical reactions, how its catalytic properties are affected by the surface structure under operating conditions is far from understood. We investigate the structure of the coherently strained Ce O2 ultrathin films on yttria-stabilized zirconia (001) single crystals by specular synchrotron x-ray diffraction (XRD) under oxidizing conditions as a first step to study the surface structure in situ. An excellent agreement between the experiment data and the model is achieved by using a "stacks and islands" model that has a two-component roughness. One component is due to the tiny clusters of nanometer scale in lateral dimensions on each terrace, while the other component is due to slightly different Ce O2 thickness that span over hundreds of nanometers on neighboring terraces. We attribute the nonuniform thickness to step depairing during the thin film deposition that is supported by the surface morphology results on the microscopic level. Importantly, our model also shows that the polarity of the ceria surface is removed by a half monolayer surface coverage of oxygen. The successful resolution of the ceria surface structure using in situ specular synchrotron XRD paves the way to study the structural evolution of ceria as a fuel cell electrode under catalytically relevant temperatures and gas pressures.

  8. Silica-Ceria Hybrid Nanostructures

    SciTech Connect

    Munusamy, Prabhakaran; Sanghavi, Shail P.; Nachimuthu, Ponnusamy; Baer, Donald R.; Thevuthasan, Suntharampillai

    2012-04-25

    A new hybrid material system that consists of ceria attached silica nanoparticles has been developed. Because of the versatile properties of silica and versatile properties of silica and versatile properties of silica and versatile properties of silica and versatile properties of silica and versatile properties of silica and versatile properties of silica and versatile properties of silica and versatile properties of silica and versatile properties of silica and versatile properties of silica and versatile properties of silica and antioxidant properties of ceria nanoparticles, this material system is ideally suited for biomedical applications. The silica particles of size ~50nm were synthesized by the Stöber synthesis method and ceria nanoparticles of size ~2-3nm was attached to the silica surface using a hetrocoagulation method. The presence of silanol groups on the surface of silica particles mediated homogenous nucleation of ceria which were attached to silica surface by Si-O-Ce bonding. The formations of silica-ceria hybrid nanostructures were characterized by X-photoelectron spectroscopy (XPS) and high resolution transmission electron microscopy (HRTEM). The HRTEM image confirms the formation of individual crystallites of ceria nanoparticles attached to the silica surface. The XPS analysis indicates that ceria nanoparticles are chemically bonded to surface of silica and possess mixture of +3 and +4 chemical states.

  9. Analytical Solution for Isentropic Flows in Solids

    NASA Astrophysics Data System (ADS)

    Heuzé, Olivier

    2009-12-01

    In the XIXth century, Riemann gave the equations system and the exact solution for the isentropic flows in the case of the ideal gas. But to our knowledge, nothing has been done to apply it to condensed media. Many materials of practical interest, for instance metals, obey to the linear law D = c+s u, where D is the shock velocity, u the particle velocity, and c and s properties of the material. We notice that s is strongly linked to the fundamental derivative. This means that the assumption of constant fundamental derivative is useful in this case, as it was with the isentropic gamma in the Riemann solution. Then we can apply the exact Riemann solution for these materials. Although the use of the hypergeometric function is complicated in this case, we obtain a very good approximation with the development in power series.

  10. Solid state synthesis, crystal growth and optical properties of urea and p-chloronitrobenzene solid solution

    SciTech Connect

    Rai, R.N.; Kant, Shiva; Reddi, R.S.B.; Ganesamoorthy, S.; Gupta, P.K.

    2016-01-15

    Urea is an attractive material for frequency conversion of high power lasers to UV (for wavelength down to 190 nm), but its usage is hindered due to its hygroscopic nature, though there is no alternative organic NLO crystal which could be transparent up to 190 nm. The hygroscopic character of urea has been modified by making the solid solution (UCNB) of urea (U) and p-chloronitrobenzene (CNB). The formation of the solid solution of CNB in U is explained on the basis of phase diagram, powder XRD, FTIR, elemental analysis and single crystal XRD studies. The solubility of U, CNB and UCNB in ethanol solution is evaluated at different temperatures. Transparent single crystals of UCNB are grown from its saturated solution in ethanol. Optical properties e.g., second harmonic generation (SHG), refractive index and the band gap for UCNB crystal were measured and their values were compared with the parent compounds. Besides modification in hygroscopic nature, UCNB has also shown the higher SHG signal and mechanical hardness in comparison to urea crystal. - Highlights: • The hygroscopic character of urea was modified by making the solid solutionSolid solution formation is support by elemental, powder- and single crystal XRD • Crystal of solid solution has higher SHG signal and mechanical stability. • Refractive index and band gap of solid solution crystal have determined.

  11. Optical sensing of peroxide using ceria nanoparticles via fluorescence quenching technique

    NASA Astrophysics Data System (ADS)

    Shehata, Nader; Samir, Effat; Gaballah, Soha; Salah, Mohammed

    2016-07-01

    This study introduces the application of ceria nanoparticles (NPs) as an optical sensor for peroxide using fluorescence quenching technique. Our synthesized ceria NPs have the ability to adsorb peroxides via its oxygen vacancies. Ceria NPs solution with added variable concentrations of hydrogen peroxides is exposed through near-UV excitation and the detected visible fluorescent emission is found to be at ˜520 nm. The fluorescent intensity peak is found to be reduced with increasing the peroxide concentrations due to static fluorescence quenching technique. The relative intensity change of the visible fluorescent emission has been reduced to more than 50% at added peroxide concentrations up to 10 wt. %. In order to increase ceria peroxides sensing sensitivity, lanthanide elements such as samarium (Sm) are used as ceria NPs dopant. This research work could be applied further in optical sensors of radicals in biomedical engineering and environmental monitoring.

  12. Effect of tar fractions from coal gasification on nickel-yttria stabilized zirconia and nickel-gadolinium doped ceria solid oxide fuel cell anode materials

    NASA Astrophysics Data System (ADS)

    Lorente, E.; Berrueco, C.; Millan, M.; Brandon, N. P.

    2013-11-01

    The allowable tar content in gasification syngas is one of the key questions for the exploitation of the full potential of fuel cell concepts with integrated gasification systems. A better understanding of the interaction between tars and the SOFC anodes which leads to carbon formation and deposition is needed in order to design systems where the extent of gas cleaning operations is minimized. Model tar compounds (toluene, benzene, naphthalene) have been used in experimental studies to represent those arising from biomass/coal gasification. However, the use of toluene as a model tar overestimates the negative impact of a real gasification tar on SOFC anode degradation associated with carbon formation. In the present work, the effect of a gasification tar and its distillation fractions on two commercially available fuel cell anodes, Ni/YSZ (yttria stabilized zirconia) and Ni/CGO (gadolinium doped ceria), is reported. A higher impact of the lighter tar fractions was observed, in terms of more carbon formation on the anodes, in comparison with the whole tar sample. The characterization of the recovered tars after contact with the anode materials revealed a shift towards a heavier molecular weight distribution, reinforcing the view that these fractions have reacted on the anode.

  13. Samarium doped ceria-(Li/Na) 2CO 3 composite electrolyte and its electrochemical properties in low temperature solid oxide fuel cell

    NASA Astrophysics Data System (ADS)

    Di, Jing; Chen, Mingming; Wang, Chengyang; Zheng, Jiaming; Fan, Liangdong; Zhu, Bin

    A composite of samarium doped ceria (SDC) and a binary carbonate eutectic (52 mol% Li 2CO 3/48 mol% Na 2CO 3) is investigated with respect to its morphology, conductivity and fuel cell performances. The morphology study shows the composition could prevent SDC particles from agglomeration. The conductivity is measured under air, argon and hydrogen, respectively. A sharp increase in conductivity occurs under all the atmospheres, which relates to the superionic phase transition in the interface phases between SDC and carbonates. Single cells with the composite electrolyte are fabricated by a uniaxial die-press method using NiO/electrolyte as anode and lithiated NiO/electrolyte as cathode. The cell shows a maximum power density of 590 mW cm -2 at 600 °C, using hydrogen as the fuel and air as the oxidant. Unlike that of cells based on pure oxygen ionic conductor or pure protonic conductor, the open circuit voltage of the SDC-carbonate based fuel cell decreases with an increase in water content of either anodic or cathodic inlet gas, indicating the electrolyte is a co-ionic (H +/O 2-) conductor. The results also exhibit that oxygen ionic conductivity contributes to the major part of the whole conductivity under fuel cell circumstances.

  14. Ceria-based SOFC development

    SciTech Connect

    Doshi, R.; Krumpelt, M.

    1996-02-01

    The advantages of lowering the operating temperature of solid oxide fuel cells have led to efforts to develop fuel cells based on electrolytes like ceria which have a higher conductivity than zirconia. Lowering the operating temperature, however, causes increased electrode polarization. The currently used cathode material for higher temperature operation, lanthanum manganite, is inadequate for operation below 650--700{degrees}C. Therefore, to develop fuel cells for operation at 500{degrees}C, new electrode materials need to be. developed. It is recognized that the cathode performance requires the most improvement due to significantly slower oxygen reduction kinetics and/or oxygen diffusion kinetics through the electrode. In fact, for fuel cells made with thin electrolytes, the cathode accounts for up to 90% of the total voltage loss under load. Results on fuel cell tests in methanol and hydrogen and on new cathode materials are reported here. The results on new cathode materials are compared with known material properties, like nonstoichiometry and oxygen diffusion coefficients.

  15. Alloy softening in binary iron solid solutions

    NASA Technical Reports Server (NTRS)

    Stephens, J. R.; Witzke, W. R.

    1976-01-01

    An investigation was conducted to determine softening and hardening behavior in 19 binary iron-alloy systems. Microhardness tests were conducted at four temperatures in the range 77 to 411 K. Alloy softening was exhibited by 17 of the 19 alloy systems. Alloy softening observed in 15 of the alloy systems was attributed to an intrinsic mechanism, believed to be lowering of the Peierls (lattice friction) stress. Softening and hardening rates could be correlated with the atomic radius ratio of solute to iron. Softening observed in two other systems was attributed to an extrinsic mechanism, believed to be associated with scavenging of interstitial impurities.

  16. Highly sensitive and robust peroxidase-like activity of porous nanorods of ceria and their application for breast cancer detection.

    PubMed

    Tian, Zhimin; Li, Jing; Zhang, Zhiyun; Gao, Wei; Zhou, Xuemei; Qu, Yongquan

    2015-08-01

    Porous nanorods of ceria (PN-Ceria), a novel ceria nanostructure with a large surface area and a high surface Ce(3+) fraction, exhibited strong intrinsic peroxidase activity toward a classical peroxidase substrate in the presence of H2O2. Peroxidase-like activity of ceria originated from surface Ce(3+) species as the catalytic center, thereby explaining the high performance of PN-Ceria as an artificial enzyme mimicking peroxidase. Compared with the natural enzyme horseradish peroxidase (HRP), PN-Ceria showed several advantages such as low cost, easy storage, high sensitivity, and, prominently, chemical and catalytic stability under harsh conditions. Importantly, the enzymatic activity of PN-Ceria remained nearly constant and stable over a wide range of temperature and pH values, ensuring the accuracy and reliability of measurements of its peroxidase-like activity. A PN-Ceria based novel diagnostic system was developed for breast cancer detection with a higher sensitivity than the standard HRP detection system. Our work has laid a solid foundation for the development of PN-Ceria as a novel diagnostic tool for clinical use.

  17. The interaction of biomass gasification syngas components with tar in a solid oxide fuel cell and operational conditions to mitigate carbon deposition on nickel-gadolinium doped ceria anodes

    NASA Astrophysics Data System (ADS)

    Mermelstein, J.; Millan, M.; Brandon, N. P.

    The combination of biomass gasification with solid oxide fuel cells (SOFCs) is gaining increasing interest as an efficient and environmentally benign method of producing electricity and heat. However, tars in the gas stream arising from the gasification of biomass material can deposit carbon on the SOFC anode, having detrimental effects to the life cycle and operational characteristics of the fuel cell. This work examines the impact of biomass gasification syngas components combined with benzene as a model tar, on carbon formation on Ni/CGO (gadolinium-doped ceria) SOFC anodes. Thermodynamic calculations suggest that SOFCs operating at temperatures > 750 °C are not susceptible to carbon deposition from a typical biomass gasification syngas containing 15 g m -3 benzene. However, intermediate temperature SOFCs operating at temperatures < 650 °C require threshold current densities well above what is technologically achievable to inhibit the effects of carbon deposition. SOFC anodes have been shown to withstand tar levels of 2-15 g m -3 benzene at 765 °C for 3 h at a current density of 300 mA cm -2, with negligible impact on the electrochemical performance of the anode. Furthermore, no carbon could be detected on the anode at this current density when benzene levels were <5 g m -3.

  18. Forces between hydrophobic solids in concentrated aqueous salt solution.

    PubMed

    Mastropietro, Dean J; Ducker, William A

    2012-03-09

    Much research has focused on the discovery and description of long-ranged forces between hydrophobic solids immersed in water. Here we show that the force between high contact-angle solids in concentrated salt solution (1 M KCl) agrees very well with van der Waals forces calculated from Lifshitz theory for separations greater than 5 nm. The hydrophobic solids are octadecyltrichlorosilane-coated glass, with an advancing contact angle of 108°. Thus, in 1 M salt solution, it is unnecessary to invoke the presence of a hydrophobic force at separations greater than 5 nm. Through measurement in salt solution, we avoid the necessity of accounting for large electrostatic forces that frequently occur in pure water and may obscure resolution of other forces.

  19. Alloy softening in binary iron solid solutions

    NASA Technical Reports Server (NTRS)

    Stephens, J. R.; Witzke, W. R.

    1976-01-01

    An experimental study was conducted to determine whether alloy softening in Fe alloys is dependent on electron concentration and to provide a direct comparison of alloy softening and hardening in several binary Fe alloy systems having the same processing history. Alloy additions to Fe included the elements in the Periods 4-6 and the Groups IV-VIII with the exception of technetium. A total of 19 alloy systems was investigated, and hardness testing was the primary means of evaluation. Testing was carried out at four temperatures over a homologous temperature range of 0.043-0.227 times the absolute melting temperature of unalloyed Fe. Major conclusions are that the atomic radius ratio of solute-to-Fe is the key factor in controlling low-temperature hardness of the binary Fe alloys and that alloy softening rates at 77 K and alloy hardening rates at 411 K are correlated with this atomic radius ratio for 15 of the binary alloy systems. Mechanisms of alloy softening and hardening are proposed.

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

    NASA Astrophysics Data System (ADS)

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

    2016-10-01

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

  1. Ozonation of bezafibrate over ceria and ceria supported on carbon materials.

    PubMed

    Gonçalves, Alexandra G; Órfão, José J M; Pereira, Manuel Fernando R

    2015-01-01

    Two catalysts containing ceria dispersed on the surface of multi-walled carbon nanotubes and activated carbon were investigated as ozonation catalysts for the mineralization of bezafibrate (BZF). The results were compared with those obtained in the absence of the catalyst and in the presence of the parent carbon materials, as well as in the presence of ceria (CeO2). Carbon materials containing ceria showed an interesting catalytic effect. Both materials enhanced the mineralization of BZF relatively to single ozonation and ozonation catalysed by the corresponding carbon materials. In the catalytic ozonation with these materials, both surface and bulk reactions are supposed to occur. The BZF ozonation catalysed by CeO2 leaded to the highest mineralization degrees, indicating that the reaction mechanism followed in the presence of CeO2 (free radical oxidation in solution) leads to the formation of intermediates more easily degradable, mainly after 120 min of reaction. Some primary products and refractory final oxidation compounds in single and catalytic ozonation of BZF were followed. The original chlorine present on the BZF molecule is completely converted to chloride anion and part of the nitrogen is mainly converted to NO3- along with smaller amounts of NO2- and NH4+. Microtox tests revealed that simultaneous use of ozone and CeO2 originated lower acute toxicity.

  2. Suppression of vacancy cluster growth in concentrated solid solution alloys

    SciTech Connect

    Zhao, Shijun; Velisa, Gihan; Xue, Haizhou; Bei, Hongbin; Weber, William J.; Zhang, Yanwen

    2016-12-13

    Large vacancy clusters, such as stacking-fault tetrahedra, are detrimental vacancy-type defects in ion-irradiated structural alloys. Suppression of vacancy cluster formation and growth is highly desirable to improve the irradiation tolerance of these materials. In this paper, we demonstrate that vacancy cluster growth can be inhibited in concentrated solid solution alloys by modifying cluster migration pathways and diffusion kinetics. The alloying effects of Fe and Cr on the migration of vacancy clusters in Ni concentrated alloys are investigated by molecular dynamics simulations and ion irradiation experiment. While the diffusion coefficients of small vacancy clusters in Ni-based binary and ternary solid solution alloys are higher than in pure Ni, they become lower for large clusters. This observation suggests that large clusters can easily migrate and grow to very large sizes in pure Ni. In contrast, cluster growth is suppressed in solid solution alloys owing to the limited mobility of large vacancy clusters. Finally, the differences in cluster sizes and mobilities in Ni and in solid solution alloys are consistent with the results from ion irradiation experiments.

  3. KNH2-KH: a metal amide-hydride solid solution.

    PubMed

    Santoru, Antonio; Pistidda, Claudio; Sørby, Magnus H; Chierotti, Michele R; Garroni, Sebastiano; Pinatel, Eugenio; Karimi, Fahim; Cao, Hujun; Bergemann, Nils; Le, Thi T; Puszkiel, Julián; Gobetto, Roberto; Baricco, Marcello; Hauback, Bjørn C; Klassen, Thomas; Dornheim, Martin

    2016-09-27

    We report for the first time the formation of a metal amide-hydride solid solution. The dissolution of KH into KNH2 leads to an anionic substitution, which decreases the interaction among NH2(-) ions. The rotational properties of the high temperature polymorphs of KNH2 are thereby retained down to room temperature.

  4. Preparation of Sic/AIN Solid Solutions Using Organometallic Precursors

    DTIC Science & Technology

    1989-02-15

    studies suggested that RAINH phase separation from the liquid polycarbosilane might be avoided by carrying out the pyrolyses at elevated temperatures, where... Pyrolyses Involving [Aethvl 2AMN21 3 In the last few months of this program, an alternative route to SiC/AlN solid solutions was discovered which obviates the

  5. Brazing method produces solid-solution bond between refractory metals

    NASA Technical Reports Server (NTRS)

    1965-01-01

    Brazing two refractory metals by diffusion bonding minimizes distortion and avoids excessive grain growth in the metals. This method requires the selection of an interface metal that forms intermediate low-melting eutectics or solid solutions with the metals to be brazed.

  6. On the solution of a lubrication problem with particulate solids

    NASA Technical Reports Server (NTRS)

    Dai, F.; Khonsari, M. M.

    1991-01-01

    The lubrication characteristic of a fluid with solid particles is studied using the continuum theory of mixtures. The governing equations are formulated and appropriate boundary conditions are introduced for an arbitrary-shaped lubricant film thickness. As a special case, closed-form analytical perturbation solutions for pressure and shear stress are obtained for a mixture of a conventional oil and solid particles with small values of solid-volume fraction sheared in the clearance space of an infinitely long slider bearing. It is found that when compared with a pure fluid, the mixture of the fluid and solid generates a higher pressure and therefore a higher load-carrying capacity with the added advantage of a reduction in the coefficient of friction.

  7. Deep eutectic-solvothermal synthesis of nanostructured ceria

    PubMed Central

    Hammond, Oliver S.; Edler, Karen J.; Bowron, Daniel T.; Torrente-Murciano, Laura

    2017-01-01

    Ceria is a technologically important material with applications in catalysis, emissions control and solid-oxide fuel cells. Nanostructured ceria becomes profoundly more active due to its enhanced surface area to volume ratio, reactive surface oxygen vacancy concentration and superior oxygen storage capacity. Here we report the synthesis of nanostructured ceria using the green Deep Eutectic Solvent reline, which allows morphology and porosity control in one of the less energy-intensive routes reported to date. Using wide Q-range liquid-phase neutron diffraction, we elucidate the mechanism of reaction at a molecular scale at considerably milder conditions than the conventional hydrothermal synthetic routes. The reline solvent plays the role of a latent supramolecular catalyst where the increase in reaction rate from solvent-driven pre-organization of the reactants is most significant. This fundamental understanding of deep eutectic-solvothermal methodology will enable future developments in low-temperature synthesis of nanostructured ceria, facilitating its large-scale manufacturing using green, economic, non-toxic solvents. PMID:28120829

  8. Deep eutectic-solvothermal synthesis of nanostructured ceria

    NASA Astrophysics Data System (ADS)

    Hammond, Oliver S.; Edler, Karen J.; Bowron, Daniel T.; Torrente-Murciano, Laura

    2017-01-01

    Ceria is a technologically important material with applications in catalysis, emissions control and solid-oxide fuel cells. Nanostructured ceria becomes profoundly more active due to its enhanced surface area to volume ratio, reactive surface oxygen vacancy concentration and superior oxygen storage capacity. Here we report the synthesis of nanostructured ceria using the green Deep Eutectic Solvent reline, which allows morphology and porosity control in one of the less energy-intensive routes reported to date. Using wide Q-range liquid-phase neutron diffraction, we elucidate the mechanism of reaction at a molecular scale at considerably milder conditions than the conventional hydrothermal synthetic routes. The reline solvent plays the role of a latent supramolecular catalyst where the increase in reaction rate from solvent-driven pre-organization of the reactants is most significant. This fundamental understanding of deep eutectic-solvothermal methodology will enable future developments in low-temperature synthesis of nanostructured ceria, facilitating its large-scale manufacturing using green, economic, non-toxic solvents.

  9. Deep eutectic-solvothermal synthesis of nanostructured ceria.

    PubMed

    Hammond, Oliver S; Edler, Karen J; Bowron, Daniel T; Torrente-Murciano, Laura

    2017-01-25

    Ceria is a technologically important material with applications in catalysis, emissions control and solid-oxide fuel cells. Nanostructured ceria becomes profoundly more active due to its enhanced surface area to volume ratio, reactive surface oxygen vacancy concentration and superior oxygen storage capacity. Here we report the synthesis of nanostructured ceria using the green Deep Eutectic Solvent reline, which allows morphology and porosity control in one of the less energy-intensive routes reported to date. Using wide Q-range liquid-phase neutron diffraction, we elucidate the mechanism of reaction at a molecular scale at considerably milder conditions than the conventional hydrothermal synthetic routes. The reline solvent plays the role of a latent supramolecular catalyst where the increase in reaction rate from solvent-driven pre-organization of the reactants is most significant. This fundamental understanding of deep eutectic-solvothermal methodology will enable future developments in low-temperature synthesis of nanostructured ceria, facilitating its large-scale manufacturing using green, economic, non-toxic solvents.

  10. Characterization of ceria-based SOFCs

    SciTech Connect

    Doshi, R.; Routbort, J.; Krumpelt, M.

    1996-12-31

    Solid Oxide Fuel Cells (SOFCs) operating at low temperatures (500-700{degrees}C) offer many advantages over the conventional zirconia-based fuel cells operating at higher temperatures. Reduced operating temperatures result in: (1) Application of metallic interconnects with reduced oxidation problems (2) Reduced time for start-up and lower energy consumption to reach operating temperatures (3) Increased thermal cycle ability for the cell structure due to lower thermal stresses of expansion mismatches. While this type of fuel cell may be applied to stationary applications, mobile applications require the ability for rapid start-up and frequent thermal cycling. Ceria-based fuel cells are currently being developed in the U.K. at Imperial College, Netherlands at ECN, and U.S.A. at Ceramatec. The cells in each case are made from a doped ceria electrolyte and a La{sub 1-x}Sr{sub x}Co{sub 1-y}Fe{sub y}O{sub 3} cathode.

  11. Suppression of vacancy cluster growth in concentrated solid solution alloys

    DOE PAGES

    Zhao, Shijun; Velisa, Gihan; Xue, Haizhou; ...

    2016-12-13

    Large vacancy clusters, such as stacking-fault tetrahedra, are detrimental vacancy-type defects in ion-irradiated structural alloys. Suppression of vacancy cluster formation and growth is highly desirable to improve the irradiation tolerance of these materials. In this paper, we demonstrate that vacancy cluster growth can be inhibited in concentrated solid solution alloys by modifying cluster migration pathways and diffusion kinetics. The alloying effects of Fe and Cr on the migration of vacancy clusters in Ni concentrated alloys are investigated by molecular dynamics simulations and ion irradiation experiment. While the diffusion coefficients of small vacancy clusters in Ni-based binary and ternary solid solutionmore » alloys are higher than in pure Ni, they become lower for large clusters. This observation suggests that large clusters can easily migrate and grow to very large sizes in pure Ni. In contrast, cluster growth is suppressed in solid solution alloys owing to the limited mobility of large vacancy clusters. Finally, the differences in cluster sizes and mobilities in Ni and in solid solution alloys are consistent with the results from ion irradiation experiments.« less

  12. Phosphate modified ceria as a Brønsted acidic/redox multifunctional catalyst

    DOE PAGES

    Nelson, Nicholas C.; Wang, Zhuoran; Naik, Pranjali; ...

    2017-01-06

    Deposition of trimethylphosphate onto ceria followed by thermal treatment resulted in the formation of surface phosphates with retention of the ceria fluorite structure. The structural and chemical properties of the phosphate-functionalized ceria were studied using 31P solid-state NMR, XPS, zeta titration, ammonia thermal desorption, pyridine adsorption, and model reactions. The introduction of phosphates generated Brønsted acid sites and decreased the number of Lewis acid sites on the surface. The relative amount of Lewis and Brønsted acids can be controlled by the amount of trimethylphosphate used in the synthesis. Upon deposition of Pd, the multifunctional material showed enhanced activity for themore » hydrogenolysis of eugenol and guaiacol compared to Pd on the unmodified ceria support. As a result, this was attributed to the cooperativity between the Lewis acid sites, which activate the substrate for dearomatization, and the redox/Brønsted acid properties, which catalyze hydrogenolysis.« less

  13. Comparison Between Simulated And Experimental Au-ion Profiles Implanted in nanocrystalline ceria

    SciTech Connect

    Moll, Sandra J.; Zhang, Yanwen; Zhu, Zihua; Edmondson, Philip D.; Namavar, Fereydoon; Weber, William J.

    2013-07-15

    Radiation response of nanocrystalline ceria films deposited on a silicon substrate was investigated under a 3-MeV Au-ion irradiation at 300 K. A uniform grain growth cross the ceria films is observed and effective densification of the ceria thin films occurs during irradiation. The Au ion profiling was measured by secondary ion mass spectrometry (SIMS) and compared to the Au ion distribution predicted by the Stopping and Range of Ions in Solids (SRIM) code. It is observed that the Au-ion penetration depth is underestimated in comparison with the SIMS measurements. An overestimation of the electronic stopping power for heavy incident ions in the SRIM program may account for the discrepancies between the calculations and the SIMS experimental results. This work presents an approach to compensate the overestimation of the electronic stopping powers in the SRIM program by adjusting the nanocrystalline ceria target density to better predict the ion implantation profile.

  14. Comparison between simulated and experimental Au-ion profiles implanted in nanocrystalline ceria

    SciTech Connect

    Moll, Sandra; Zhang, Yanwen; Zhu, Zihua; Edmondson, Dr. Philip; Namavar, Fereydoon; Weber, William J

    2013-01-01

    Radiation response of nanocrystalline ceria films deposited on a silicon substrate was investigated under a 3-MeV Au-ion irradiation at 300 K. A uniform grain growth cross the ceria films is observed and effective densification of the ceria thin films occurs during irradiation. The Au ion profiling was measured by secondary ion mass spectrometry (SIMS) and compared to the Au ion distribution predicted by the Stopping and Range of Ions in Solids (SRIM) code. It is observed that the Au-ion penetration depth is underestimated in comparison with the SIMS measurements. An overestimation of the electronic stopping power for heavy incident ions in the SRIM program may account for the discrepancies between the calculations and the SIMS experimental results. This work presents an approach to compensate the overestimation of the electronic stopping powers in the SRIM program by adjusting the nanocrystalline ceria target density to better predict the ion implantation profile.

  15. Modification of solid oxide fuel cell anodes with cerium oxide coatings

    NASA Astrophysics Data System (ADS)

    Tang, Ling

    A priority for research in solid oxide fuel cells (SOFCs) is to develop cells that can maintain adequate performance in sulfur-containing fuel streams. There has been evidence that cerium oxide in the anode or electrolyte is associated with sulfur tolerance of the cell, but the mechanism underlying this effect is not well understood. The objective of the present research is to show that the porous cermet SOFC anodes can be coated with cerium oxide films, so that the cell performance can be evaluated as a function of the anode structure and the microstructure of the film. Three types of anodes---Ni/yttria-stabilized zirconia (YSZ), Ni/gadolinia-doped ceria (GDC), and Ni/GDC with GDC interlayer were infiltrated with an aqueous solution to deposit nanocrystalline ceria films. The cells were then tested in hydrogen/nitrogen fuel containing hydrogen sulfide at levels up to 500 ppm. Modification of the anodes with thiol-terminated and trichlorosilane-terminated surfactants was explored. Different ceria film morphology was achieved for each surface treatment. In the cells that underwent performance testing, the thiol treatment promoted ceria film deposition, while the sulfonate treatment suppressed ceria deposition. Uniform ceria films up to 100 nm thick could be deposited in 48 h. Results on cell testing conditions, e.g. current, time, and H2S exposure were related to different anode structures and ceria coating morphologies. In general, the Ni/GDC anodes showed better performance than the Ni/YSZ anode. The introduction of ceria films often resulted in higher cell current and longer testing time, including operation under H2S exposure. Post-testing characterization revealed that, for some anodes, microstructure changes such as coarsening of Ni in the anode, migration of Ni to the anode surface, and depletion of Ni occurred. These changes in microstructure were irreversible and might account for permanent loss of cell performance. The presence of ceria films delayed these

  16. Improved performance of a symmetrical solid oxide fuel cell by swapping the roles of doped ceria and La0.6Sr1.4MnO4+δ in the electrode

    NASA Astrophysics Data System (ADS)

    Shen, Jian; Yang, Guangming; Zhang, Zhenbao; Tadé, Moses O.; Zhou, Wei; Shao, Zongping

    2017-02-01

    Symmetrical solid oxide fuel cells (SSOFCs) show many advantageous features as compared with conventional cells with nickel cermet anode and oxide cathode. A K2NiF4-type layer-structured oxide, La0.6Sr1.4MnO4+δ (LSMO4), was reported to be a potential electrode for SSOFCs, and the modification of LSMO4 surface with samaria-doped ceria (SDC) and NiO was found to be the key in improving performance. In this study, the swapping of roles for SDC and LSMO4 in electrodes of SSOFCs is exploited, i.e., SDC is applied as the scaffold and LSMO4 as the surface modifier. Different from pristine LSMO4, the impregnated LSMO4 demonstrates amorphous phase. Compared to NiO-SDC impregnated LSMO4, NiO-LSMO4/SDC electrodes show a superior cathodic performance with an area specific resistance of 0.1 Ω cm2 at 700 °C. Under optimized conditions, maximum power densities of 714 and 108 mW cm-2 at 800 °C are achieved for an electrolyte-supported symmetrical single cell with a NiO-LSMO4/SDC electrode operating with hydrogen and methane, respectively. The difference in performance of the electrodes built by swapping the role and function of the SDC and LSMO4 phases is discussed, and a possible mechanism responsible for such different behaviours in cell power outputs via the impregnation of LSMO4 (NiO)+SDC electrodes is proposed.

  17. Tailoring gadolinium-doped ceria-based solid oxide fuel cells to achieve 2 W cm(-2) at 550 °C.

    PubMed

    Lee, Jin Goo; Park, Jeong Ho; Shul, Yong Gun

    2014-06-04

    Low-temperature operation is necessary for next-generation solid oxide fuel cells due to the wide variety of their applications. However, significant increases in the fuel cell losses appear in the low-temperature solid oxide fuel cells, which reduce the cell performance. To overcome this problem, here we report Gd0.1Ce0.9O1.95-based low-temperature solid oxide fuel cells with nanocomposite anode functional layers, thin electrolytes and core/shell fibre-structured Ba0.5Sr0.5Co0.8Fe0.2O3-δ-Gd0.1Ce0.9O1.95 cathodes. In particular, the report describes the use of the advanced electrospinning and Pechini process in the preparation of the core/shell-fibre-structured cathodes. The fuel cells show a very high performance of 2 W cm(-2) at 550 °C in hydrogen, and are stable for 300 h even under the high current density of 1 A cm(-2). Hence, the results suggest that stable and high-performance solid oxide fuel cells at low temperatures can be achieved by modifying the microstructures of solid oxide fuel cell components.

  18. Interdiffusion in Ternary Magnesium Solid Solutions of Aluminum and Zinc

    DOE PAGES

    Kammerer, Catherine; Kulkarni, Nagraj S; Warmack, Robert J Bruce; ...

    2016-01-11

    Al and Zn are two of the most common alloying elements in commercial Mg alloys, which can improve the physical properties through solid solution strengthening and precipitation hardening. Diffusion plays a key role in the kinetics of these and other microstructural design relevant to Mg-alloy development. However, there is a lack of multicomponent diffusion data available for Mg alloys. Through solid-to-solid diffusion couples, diffusional interactions of Al and Zn in ternary Mg solid-solution at 400° and 450 °C were examined by an extension of the Boltzmann-Matano analysis based on Onsager s formalism. Concentration profiles of Mg-Al-Zn ternary alloys were determinedmore » by electron probe microanalysis, and analyzed to determine the ternary interdiffusion coefficients as a function of composition. Zn was determined to interdiffuse the fastest, followed by Mg and Al. Appreciable diffusional interactions among Mg, Al, and Zn were observed by variations in sign and magnitude of cross interdiffusion coefficients. In particular, Zn was found to significantly influence the interdiffusion of Mg and Al significantly: the and ternary cross interdiffusion coefficients were both negative, and large in magnitude, in comparison to and , respectively. Al and Mg were observed influence the interdiffusion of Mg and Al, respectively, with positive and interdiffusion coefficients, but their influence on the Zn interdiffusion was negligible.« less

  19. Interdiffusion in Ternary Magnesium Solid Solutions of Aluminum and Zinc

    SciTech Connect

    Kammerer, Catherine; Kulkarni, Nagraj S; Warmack, Robert J Bruce; Sohn, Yong Ho

    2016-01-11

    Al and Zn are two of the most common alloying elements in commercial Mg alloys, which can improve the physical properties through solid solution strengthening and precipitation hardening. Diffusion plays a key role in the kinetics of these and other microstructural design relevant to Mg-alloy development. However, there is a lack of multicomponent diffusion data available for Mg alloys. Through solid-to-solid diffusion couples, diffusional interactions of Al and Zn in ternary Mg solid-solution at 400° and 450 °C were examined by an extension of the Boltzmann-Matano analysis based on Onsager s formalism. Concentration profiles of Mg-Al-Zn ternary alloys were determined by electron probe microanalysis, and analyzed to determine the ternary interdiffusion coefficients as a function of composition. Zn was determined to interdiffuse the fastest, followed by Mg and Al. Appreciable diffusional interactions among Mg, Al, and Zn were observed by variations in sign and magnitude of cross interdiffusion coefficients. In particular, Zn was found to significantly influence the interdiffusion of Mg and Al significantly: the and ternary cross interdiffusion coefficients were both negative, and large in magnitude, in comparison to and , respectively. Al and Mg were observed influence the interdiffusion of Mg and Al, respectively, with positive and interdiffusion coefficients, but their influence on the Zn interdiffusion was negligible.

  20. Adsorption and desorption characteristics of arsenic onto ceria nanoparticles

    NASA Astrophysics Data System (ADS)

    Feng, Qinzhong; Zhang, Zhiyong; Ma, Yuhui; He, Xiao; Zhao, Yuliang; Chai, Zhifang

    2012-01-01

    The rapid increase in the use of engineered nanoparticles [ENPs] has resulted in an increasing concern over the potential impacts of ENPs on the environmental and human health. ENPs tend to adsorb a large variety of toxic chemicals when they are emitted into the environment, which may enhance the toxicity of ENPs and/or adsorbed chemicals. The study was aimed to investigate the adsorption and desorption behaviors of arsenic on ceria NPs in aqueous solution using batch technique. Results show that the adsorption behavior of arsenic on ceria NPs was strongly dependent on pH and independent of ionic strength, indicating that the electrostatic effect on the adsorption of these elements was relatively not important compared to surface chemical reactions. The adsorption isotherms fitted very well to both the Langmuir and Freundlich models. The thermodynamic parameters (Δ H 0 , Δ S 0 , and Δ G 0 ) for the adsorption of arsenic were determined at three different temperatures of 283, 303, and 323 K. The adsorption reaction was endothermic, and the process of adsorption was favored at high temperature. The desorption data showed that desorption hysteresis occurred at the initial concentration studied. High adsorption capacity of arsenic on ceria NPs suggests that the synergistic effects of ceria NPs and arsenic on the environmental systems may exist when they are released into the environment.

  1. Evaluation of experimental parameters for growth of homogeneous solid solutions

    NASA Astrophysics Data System (ADS)

    Scheel, Hans J.; Swendsen, Robert H.

    2001-12-01

    In this paper, we discuss the experimental conditions required to grow large two-component crystals from homogeneous solid solutions. Building on the work of Burton, Prim, and Slichter and that of Van Erk, we are able to establish that the concentration fluctuations for diffusion-limited growth are rather insensitive to hydrodynamic fluctuations. This enables a crystal grower to take advantage of forced convection to optimize growth rates without aggravating the striation problem.

  2. Characteristics of photosensors based on solid solutions of AII BVIcompounds

    NASA Astrophysics Data System (ADS)

    Lubegin, Gennady V.; Gusliannikov, Vladimir V.

    1999-10-01

    In the work there are submitted the results of the research of photosensors on a base of solid solutions of A(superscript II)B(superscript VI) compounds for measurement and control of intensity of low-level light in narrow areas of spectrum. The basic principles of technological process of manufacturing of injection photo diodes are described. The results of measurements of voltage-current characteristics and spectral characteristics of photo diodes, received in laboratory technological process with the various contents of cadmy and zinc in ZnCd(subscript 1-x)S(subscript x) solid solutions, and also sulfur and selen in CdS(subscript 1-x)Se(subscript x) solid solutions are submitted. The investigation results have shown, that photosensors work at low positive bias voltage, do not require cooling, have high sensitivity in a maximum and narrow selectivity. In CdS(subscript 1-x)Se(subscript x)- photosensors the photosensitive protecting coverage of transparent films on the base of As(subscript 2)S(subscript 3) compounds is applied. The opportunity of creation of a wide discrete range of photo diodes with the sensitivity in range from near ultraviolet up to near infrared area of spectrum is shown.

  3. Solid-solution nanocrystallite formation by high-energy milling.

    PubMed

    Kwon, Hanjung; Jung, Suna; Cho, Sung-Wook; Kil, Dae-Sup; Roh, Ki-Min; Lim, Jae-Won

    2013-09-01

    Solid-solution nanocrystalline powders were prepared by the high-energy milling of Ti alloys with graphite. The B1 structure (NaCl-like structure) phases, (Ti, Cr)C and (Ti, Al)C, were formed during the milling process of Ti-Cr + graphite and Ti-Al + graphite, and the synthetic procedures were investigated in terms of the phase evolution from XRD data. The (Ti, Al)C phase was obtained after milling for 20 hr at BPR = 40:1 (under a more severe condition), while the (Ti, Cr)C phase formed after milling for 20 hr at BPR = 20:1 (a relatively soft condition). The difference in the tendency to create a solid solution with Ti in the B1 structure caused a difference in the synthetic behavior of (Ti, Al)C and (Ti, Cr)C. In other words, (Ti, Cr)C is formed earlier than (Ti, Al)C during milling because the atomic size of Cr (0.166 nm) is similar to that of Ti (0.176 nm), which leads to the straightforward formation of the solid-solution (Ti, Cr)C as compared to when (Ti, Al)C is used. As a result, the crystallite size of the (Ti, Al)C phase (2-3 nm) synthesized at a later stage becomes smaller than that of the (Ti, Cr)C phase (5 10 nm) formed at an earlier stage during milling.

  4. Effects of different precursors on size and optical properties of ceria nanoparticles prepared by microwave-assisted method

    SciTech Connect

    Samiee, Sara; Goharshadi, Elaheh K.

    2012-04-15

    Highlights: Black-Right-Pointing-Pointer A rapid and efficient microwave method was applied for synthesis of nano ceria. Black-Right-Pointing-Pointer Changing precursor has great effects on optical properties and size of nano ceria. Black-Right-Pointing-Pointer Fabrication of ceria nanoparticles using Ce{sup 4+} salts leads to better results. Black-Right-Pointing-Pointer Band gap energies of ceria nanoparticles were evaluated by UV-vis spectroscopy. -- Abstract: Cerium oxide, ceria (CeO{sub 2}), is one of the favourable nanoparticles (NPs) that possesses many remarkable properties so that it can be used in medicine, chemistry, environment, energy, information, industry, and so on. In this study, the crystalline ceria NPs were successfully prepared by an efficient microwave-assisted heating technique from an aqueous solution using different cerium salts (Ce(IV) and Ce(III) salts). The products were characterized by X-ray powder diffraction (XRD), transmission electron microscope (TEM), FTIR spectroscopy, Raman spectroscopy, and UV-vis absorption spectroscopy. The results revealed that changing the precursor led to great effects on size, band gap energy, and the reaction time of preparing the ceria NPs. The significant feature of this manuscript is that the effects of different precursors on the structural and optical properties of ceria NPs were investigated for the first time. The average particle size of different samples was below 8 nm.

  5. Flow-based solution-liquid-solid nanowire synthesis

    NASA Astrophysics Data System (ADS)

    Laocharoensuk, Rawiwan; Palaniappan, Kumaranand; Smith, Nickolaus A.; Dickerson, Robert M.; Werder, Donald J.; Baldwin, Jon K.; Hollingsworth, Jennifer A.

    2013-09-01

    Discovered almost two decades ago, the solution-liquid-solid (SLS) method for semiconductor nanowire synthesis has proven to be an important route to high-quality, single-crystalline anisotropic nanomaterials. In execution, the SLS technique is similar to colloidal quantum-dot synthesis in that it entails the injection of chemical precursors into a hot surfactant solution, but mechanistically it is considered the solution-phase analogue to vapour-liquid-solid (VLS) growth. Both SLS and VLS methods make use of molten metal nanoparticles to catalyse the nucleation and elongation of single-crystalline nanowires. Significantly, however, the methods differ in how chemical precursors are introduced to the metal catalysts. In SLS, precursors are added in a one-off fashion in a flask, whereas in VLS they are carried by a flow of gas through the reaction chamber, and by-products are removed similarly. The ability to dynamically control the introduction of reactants and removal of by-products in VLS synthesis has enabled a degree of synthetic control not possible with SLS growth. We show here that SLS synthesis can be transformed into a continuous technique using a microfluidic reactor. The resulting flow-based SLS (`flow-SLS') platform allows us to slow down the synthesis of nanowires and capture mechanistic details concerning their growth in the solution phase, as well as synthesize technologically relevant axially heterostructured semiconductor nanowires, while maintaining the propensity of SLS for accessing ultrasmall diameters below 10 nm.

  6. Extended Hansen approach: calculating partial solubility parameters of solid solutes.

    PubMed

    Wu, P L; Beerbower, A; Martin, A

    1982-11-01

    A multiple linear regression method, known as the extended Hansen solubility approach, was used to estimate the partial solubility parameters, delta d, delta p, and delta h for crystalline solutes. The method is useful, since organic compounds may decompose near their melting points, and it is not possible, to determine solubility parameters for these solid compounds by the methods used for liquid solvents. The method gives good partial and total solubility parameters for naphthalene; with related compounds, less satisfactory results were obtained. At least three conditions, pertaining to the regression equation and the solvent systems, must be met in order to obtain reasonable solute solubility parameters. In addition to providing partial solubility parameters, the regression equations afford a calculation of solute solubility in both polar and nonpolar solvents.

  7. Improving the dissolution rate of poorly water soluble drug by solid dispersion and solid solution: pros and cons.

    PubMed

    Chokshi, Rina J; Zia, Hossein; Sandhu, Harpreet K; Shah, Navnit H; Malick, Waseem A

    2007-01-01

    The solid dispersions with poloxamer 188 (P188) and solid solutions with polyvinylpyrrolidone K30 (PVPK30) were evaluated and compared in an effort to improve aqueous solubility and bioavailability of a model hydrophobic drug. All preparations were characterized by differential scanning calorimetry, powder X-ray diffraction, intrinsic dissolution rates, and contact angle measurements. Accelerated stability studies also were conducted to determine the effects of aging on the stability of various formulations. The selected solid dispersion and solid solution formulations were further evaluated in beagle dogs for in vivo testing. Solid dispersions were characterized to show that the drug retains its crystallinity and forms a two-phase system. Solid solutions were characterized to be an amorphous monophasic system with transition of crystalline drug to amorphous state. The evaluation of the intrinsic dissolution rates of various preparations indicated that the solid solutions have higher initial dissolution rates compared with solid dispersions. However, after storage at accelerated conditions, the dissolution rates of solid solutions were lower due to partial reversion to crystalline form. The drug in solid dispersion showed better bioavailability in comparison to solid solution. Therefore, considering physical stability and in vivo study results, the solid dispersion was the most suitable choice to improve dissolution rates and hence the bioavailability of the poorly water soluble drug.

  8. Multiparametric dissolution of thorium-cerium dioxide solid solutions.

    PubMed

    Claparede, Laurent; Clavier, Nicolas; Dacheux, Nicolas; Mesbah, Adel; Martinez, Julien; Szenknect, Stéphanie; Moisy, Philippe

    2011-11-21

    The dissolution of Th(1-x)Ce(x)O(2) solid solutions samples prepared by thermal conversion of oxalate precursors was studied by varying independently several parameters (such as chemical composition, leachate acidity, leaching temperature, firing temperature, and crystallization state). The relative effects of these parameters on the normalized dissolution rate were examined. Either the obtained partial order related to the proton activity (n = 0.50 ± 0.01) or the activation energy (E(A) = 57 ± 6 kJ.mol(-1)) suggested that the dissolution was mainly driven by surface reactions occurring at the solid/liquid interface. Conversely to that observed for Th(1-x)U(x)O(2) and Ce(1-x)Nd(x)O(2-x/2) solid solutions, the chemical composition did not induce strong modifications of the chemical durability of the leached samples. While the initial normalized dissolution rate slightly depended on the elimination of crystal defects for firing temperatures below 800 °C, it was mainly independent of the crystallite size (T ≥ 900 °C). The role of crystal defects (then that of preparation conditions) appeared thus important to consider since they contributed to modifications of the normalized dissolution rates of the same order of magnitude than that of the leachate acidity.

  9. Crystallization in solid solution-aqueous solution systems: Thermodynamic and kinetic approaches

    SciTech Connect

    Shtukenberg, A. G. Punin, Yu. O.; Azimov, P. Ya.

    2010-03-15

    A new phenomenological approach is proposed to describe the crystallization kinetics in solid solution-aqueous solution binary systems. The phase diagrams, equilibria, and quasie-quilibria are considered within this approach. The crystallization kinetics near the true equilibrium and the crystallization features at large deviations from equilibrium are discussed on this basis. Special attention is paid to possible interactions in a solution with a seed crystal placed in it. In particular, the interactions leading to the seed's crystal growth or dissolution and to a possible exchange or metasomatic reactions are considered. In addition, the effect of the generated mismatch stress on the crystal growth rate and composition is analyzed.

  10. Interfacial Free Energy of Cu-Co Solid Solutions

    NASA Astrophysics Data System (ADS)

    Zhevnenko, S. N.

    2013-06-01

    The surface energies of Cu-Co solid solutions in hydrogen atmosphere were measured. The measurements were performed on pure copper and copper alloys containing 0.45, 0.7, 1.4, 2.25, 2.50, and 2.8 at. pct Co and 4.1 at. pct Co for the temperature range 1245 K to 1349 K (972 °C to 1076 °C). The experiments were conducted using the zero creep method for 18 mcm foils. The modified method allowed " in situ" determining of the surface energy. It was shown that the surface energy increases as the concentration increases up to 1.4 at. pct Co and then decreases. Such extreme behavior was obtained by the direct method for the first time in a solid metallic system.

  11. Grain Size Hardening Effects in Mg-Gd Solid Solutions

    NASA Astrophysics Data System (ADS)

    Nagarajan, Devarajan; Cáceres, Carlos H.; Griffiths, John R.

    2016-11-01

    Pure Mg and alloys with 0.4, 1.3, and 3.8 at. pct Gd were cast with grain sizes between 700 and 35 µm and tested in tension and compression after solid solution heat treatment and quenching. The grain structure of the castings was random, that is, there was no preferred orientation, unlike the situation in extrusions and forgings usually reported in the literature. The results are compared to earlier work on Mg-Zn alloys. A tension-compression asymmetry in which the yield strength in compression is less than in tension was observed in pure Mg but was reversed for the concentrated alloys. The Hall-Petch stress intensity factor, k, first increased then decreased with the amount of Gd in solution. It is noted that defining the friction stress by extrapolating the data to infinite grain size should be treated with caution in Mg and its alloys: nevertheless, a rationale involving solid solution softening/hardening and twinning is offered for the observed values of the friction stress. The reversion of the tension-compression asymmetry is explained by the operation of { {10bar{1}1} } (contraction) twinning in the concentrated alloys in place of { {10bar{1}2} } (extension) twinning in pure Mg and the dilute alloys. It is argued that the activation of { {10bar{1}1} } twinning in the more concentrated alloys accounts for their lower k-value.

  12. Room-Temperature Tensile Behavior of Oriented Tungsten Single Crystals with Rhenium in Dilute Solid Solution

    DTIC Science & Technology

    1966-01-01

    SINGLE CRYSTALS WITH RHENIUM IN DILUTE SOLID SOLUTION Sby M. Garfinkle Lewis Research Center Cleveland, Ohio 20060516196 NATIONAL AERONAUTICS AND...WITH RHENIUM IN DILUTE SOLID SOLUTION By M. Garfinkle Lewis Research Center Cleveland, Ohio NATIONAL AERONAUTICS AND SPACE ADMINISTRATION For sale by...ORIENTED TUNGSTEN SINGLE CRYSTALS WITH RHENIUM IN DILUTE SOLID SOLUTION * by M. Garfinkle Lewis Research Center SUMMARY Tungsten single crystals

  13. Incubational domain characterization in lightly doped ceria

    SciTech Connect

    Li Zhipeng; Mori, Toshiyuki; John Auchterlonie, Graeme; Zou Jin; Drennan, John

    2012-08-15

    Microstructures of both Gd- and Y-doped ceria with different doping level (i.e., 10 at% and 25 at%) have been comprehensively characterized by means of high resolution transmission electron microscopy and selected area electron diffraction. Coherent nano-sized domains can be widely observed in heavily doped ceria. Nevertheless, it was found that a large amount of dislocations actually exist in lightly doped ceria instead of heavily doped ones. Furthermore, incubational domains can be detected in lightly doped ceria, with dislocations located at the interfaces. The interactions between such linear dislocations and dopant defects have been simulated accordingly. As a consequence, the formation mechanism of incubational domains is rationalized in terms of the interaction between intrinsic dislocations of doped ceria and dopant defects. This study offers the insights into the initial state and related mechanism of the formation of nano-sized domains, which have been widely observed in heavily rare-earth-doped ceria in recent years. - Graphical abstract: Interactions between dislocations and dopants lead to incubational domain formation in lightly doped ceria. Highlights: Black-Right-Pointing-Pointer Microstructures were characterized in both heavily and light Gd-/Y-doped ceria. Black-Right-Pointing-Pointer Dislocations are existed in lightly doped ceria rather than heavily doped one. Black-Right-Pointing-Pointer Interactions between dislocations and dopant defects were simulated. Black-Right-Pointing-Pointer Formation of dislocation associated incubational domain is rationalized.

  14. Features of luminescence of liquid and solid solutions of dibenzopyrenequinnone

    SciTech Connect

    Nurmukhametov, R.N.; Baskakova, Z.M.; Khachatorova, G.T.; Mil'khiker, P.D.

    1986-01-01

    This paper reports on a study of the fluorescence characteristics of DBPQ in liquid and solid media with various polarities. The absorption, fluorescence, and fluorescence excitation spectra of the dye are investigated in a series of solvents and polymeric matrices. In liquid solutions, no new fluorescence band appears. The unusual fluorescence properties of DBPQ can be attributed to inversion of closely positioned energy levels of the S..pi pi..* and Tn..pi..* states under the influence of the medium and on the ability of the dye molecules to be photoreduced to the leuco form.

  15. REVIEWS OF TOPICAL PROBLEMS: Diffusive decomposition of solid solutions

    NASA Astrophysics Data System (ADS)

    Slezov, V. V.; Sagalovich, V. V.

    1987-01-01

    The present status of the theory of the late stage of diffusive decomposition of multicomponent solid solutions, owing to diffusive interaction of macrodefects, is reviewed. Methods for solving the systems of equations describing the decomposition process are analyzed. The evolution of the critical dimensions of precipitates and the transformation of an arbitrary distribution function into a universal function for different mechanisms of mass transfer are studied in detail. The conditions for coexistence of phases in the presence of decomposition of multicomponent systems are examined. The results of the theory are compared with experiment.

  16. Diffusion of Chromium in Alpha Cobalt-Chromium Solid Solutions

    NASA Technical Reports Server (NTRS)

    Weeton, John W

    1951-01-01

    Diffusion of chromium in cobalt-chromium solid solutions was investigated in the range 0 to 40 atomic percent at temperatures of 1360 degrees, 1300 degrees, 1150 degrees, and 10000 degrees c. The diffusion coefficients were found to be relatively constant within the composition range covered by each specimen. The activation heat of diffusion was determined to be 63,000 calories per mole. This value agrees closely with the value of 63,400 calories per mole calculated by means of the Dushman-Langmuir equation.

  17. Temperature dependence of nucleation rate in a binary solid solution

    NASA Astrophysics Data System (ADS)

    Wang, H. Y.; Philippe, T.; Duguay, S.; Blavette, D.

    2012-12-01

    The influence of regression (partial dissolution) effects on the temperature dependence of nucleation rate in a binary solid solution has been studied theoretically. The results of the analysis are compared with the predictions of the simplest Volmer-Weber theory. Regression effects are shown to have a strong influence on the shape of the curve of nucleation rate versus temperature. The temperature TM at which the maximum rate of nucleation occurs is found to be lowered, particularly for low interfacial energy (coherent precipitation) and high-mobility species (e.g. interstitial atoms).

  18. Thermal Conductivity in Nanocrystalline Ceria Thin Films

    SciTech Connect

    Marat Khafizov; In-Wook Park; Aleksandr Chernatynskiy; Lingfeng He; Jianliang Lin; John J. Moore; David Swank; Thomas Lillo; Simon R. Phillpot; Anter El-Azab; David H. Hurley

    2014-02-01

    The thermal conductivity of nanocrystalline ceria films grown by unbalanced magnetron sputtering is determined as a function of temperature using laser-based modulated thermoreflectance. The films exhibit significantly reduced conductivity compared with stoichiometric bulk CeO2. A variety of microstructure imaging techniques including X-ray diffraction, scanning and transmission electron microscopy, X-ray photoelectron analysis, and electron energy loss spectroscopy indicate that the thermal conductivity is influenced by grain boundaries, dislocations, and oxygen vacancies. The temperature dependence of the thermal conductivity is analyzed using an analytical solution of the Boltzmann transport equation. The conclusion of this study is that oxygen vacancies pose a smaller impediment to thermal transport when they segregate along grain boundaries.

  19. Electronic origin of solid solution softening in bcc molybdenum alloys.

    PubMed

    Medvedeva, N I; Gornostyrev, Yu N; Freeman, A J

    2005-04-08

    The intrinsic mechanism of solid solution softening in bcc molybdenum alloys due to 5d transition metal additions is investigated on the basis of ab initio electronic-structure calculations that model the effect of alloying elements on the generalized stacking fault (GSF) energies. We demonstrate that additions with an excess of electrons (Re, Os, Ir, and Pt) lead to a decrease in the GSF energy and those with a lack of electrons (Hf and Ta) to its sharp increase. Using the generalized Peierls-Nabarro model for a nonplanar core, we associate the local reduction of the GSF energy with an enhancement of double kink nucleation and an increase of the dislocation mobility, and we reveal the electronic reasons for the observed dependence of the solution softening on the atomic number of the addition.

  20. A Thermodynamic Investigation of the Redox Properties of Ceria-Titania Mixed Oxides

    SciTech Connect

    Zhou,G.; Hanson, J.; Gorte, R.

    2008-01-01

    Ceria-titania solutions with compositions of Ce0.9Ti0.1O2 and Ce0.8Ti0.2O2 were prepared by the citric-acid (Pechini) method and characterized using X-ray diffraction (XRD) for structure, coulometric titration for redox thermodynamics, and water-gas-shift (WGS) reaction rates. Following calcination at 973 K, XRD suggests that the mixed oxides exist as single phase, fluorite structures, although there was no significant change in the lattice parameter compared to pure ceria. The mixed oxides are shown to be significantly more reducible than bulk ceria, with enthalpies for re-oxidation being approximately -500 kJ/mol O2, compared to -760 kJ/mol O2 for bulk ceria. However, WGS rates over 1 wt% Pd supported on ceria, Ce0.8Ti0.2O2, and Ce0.8Zr0.2O2 were nearly the same. For calcination at 1323 K, the mixed oxides separated into ceria and titania phases, as indicated by both the XRD and thermodynamic results.

  1. Isomorphism and solid solutions among Ag- and Au-selenides

    NASA Astrophysics Data System (ADS)

    Palyanova, Galina A.; Seryotkin, Yurii V.; Kokh, Konstantin A.; Bakakin, Vladimir V.

    2016-09-01

    Au-Ag selenides were synthesized by heating stoichiometric mixtures of elementary substances of initial compositions Ag2-xAuxSe with a step of x=0.25 (0≤x≤2) to 1050 °C and annealing at 500 °C. Scanning electron microscopy, optical microscopy, electron microprobe analysis and X-ray powder diffraction methods have been applied to study synthesized samples. Results of studies of synthesized products revealed the existence of three solid solutions with limited isomorphism Ag↔Au: naumannite Ag2Se - Ag1.94Au0.06Se, fischesserite Ag3AuSe2 - Ag3.2Au0.8Se2 and gold selenide AuSe - Au0.94Ag0.06Se. Solid solutions and AgAuSe phases were added to the phase diagram of Ag-Au-Se system. Crystal-chemical interpretation of Ag-Au isomorphism in selenides was made on the basis of structural features of fischesserite, naumannite, and AuSe.

  2. Kinetics of the cellular decomposition of supersaturated solid solutions

    NASA Astrophysics Data System (ADS)

    Ivanov, M. A.; Naumuk, A. Yu.

    2014-09-01

    A consistent description of the kinetics of the cellular decomposition of supersaturated solid solutions with the development of a spatially periodic structure of lamellar (platelike) type, which consists of alternating phases of precipitates on the basis of the impurity component and depleted initial solid solution, is given. One of the equations, which determines the relationship between the parameters that describe the process of decomposition, has been obtained from a comparison of two approaches in order to determine the rate of change in the free energy of the system. The other kinetic parameters can be described with the use of a variational method, namely, by the maximum velocity of motion of the decomposition boundary at a given temperature. It is shown that the mutual directions of growth of the lamellae of different phases are determined by the minimum value of the interphase surface energy. To determine the parameters of the decomposition, a simple thermodynamic model of states with a parabolic dependence of the free energy on the concentrations has been used. As a result, expressions that describe the decomposition rate, interlamellar distance, and the concentration of impurities in the phase that remain after the decomposition have been derived. This concentration proves to be equal to the half-sum of the initial concentration and the equilibrium concentration corresponding to the decomposition temperature.

  3. Solid-solution semiconductor nanowires in pseudobinary systems.

    PubMed

    Liu, Baodan; Bando, Yoshio; Liu, Lizhao; Zhao, Jijun; Masanori, Mitome; Jiang, Xin; Golberg, Dmitri

    2013-01-09

    Pseudobinary solid-solution semiconductor nanowires made of (GaP)(1-x)(ZnS)(x), (ZnS)(1-x)(GaP)(x) and (GaN)(1-x)(ZnO)(x) were synthesized based on an elaborative compositional, structural, and synthetic designs. Using analytical high-resolution transmission electron microscopy (HRTEM) and energy dispersive X-ray spectroscopy (EDS), we confirmed that the structure uniformity and a lattice match between the two constituting binary components play the key roles in the formation of quaternary solid-solution nanostructures. Electrical transport measurements on individual GaP and (GaP)(1-x)(ZnS)(x) nanowires indicated that a slight invasion of ZnS in the GaP host could lead to the abrupt resistance increase, resulting in the semiconductor-to-insulator transition. The method proposed here may be extended to the rational synthesis of many other multicomponent nanosystems with tunable and intriguing optoelectronic properties for specific applications.

  4. Zn₃P₂-Zn₃As₂ solid solution nanowires.

    PubMed

    Im, Hyung Soon; Park, Kidong; Jang, Dong Myung; Jung, Chan Su; Park, Jeunghee; Yoo, Seung Jo; Kim, Jin-Gyu

    2015-02-11

    Semiconductor alloy nanowires (NWs) have recently attracted considerable attention for applications in optoelectronic nanodevices because of many notable properties, including band gap tunability. Zinc phosphide (Zn3P2) and zinc arsenide (Zn3As2) belong to a unique pseudocubic tetragonal system, but their solid solution has rarely been studied. Here In this study, we synthesized composition-tuned Zn3(P1-xAsx)2 NWs with different crystal structures by controlling the growth conditions during chemical vapor deposition. A first type of synthesized NWs were single-crystalline and grew uniformly along the [110] direction (in a cubic unit cell) over the entire compositional range (0 ≤ x ≤ 1) explored. The use of an indium source enabled the growth of a second type of NWs, with remarkable cubic-hexagonal polytypic twinned superlattice and bicrystalline structures. The growth direction of the Zn3P2 and Zn3As2 NWs was also switched to [111] and [112], respectively. These structural changes are attributable to the Zn-depleted indium catalytic nanoparticles which favor the growth of hexagonal phases. The formation of a solid solution at all compositions allowed the continuous tuning of the band gap (1.0-1.5 eV). Photocurrent measurements were performed on individual NWs by fabricating photodetector devices; the single-crystalline NWs with [110] growth direction exhibit a higher photoconversion efficiency compared to the twinned crystalline NWs with [111] or [112] growth direction.

  5. Irradiation-induced composition patterns in binary solid solutions

    SciTech Connect

    Dubey, Santosh; El-Azab, Anter

    2013-09-28

    A theoretical/computational model for the irradiation-driven compositional instabilities in binary solid solutions has been developed. The model is suitable for investigating the behavior of structural alloys and metallic nuclear fuels in a reactor environment as well as the response of alloy thin films to ion beam irradiation. The model is based on a set of reaction-diffusion equations for the dynamics of vacancies, interstitials, and lattice atoms under irradiation. The dynamics of these species includes the stochastic generation of defects by collision cascades as well as the defect reactions and diffusion. The atomic fluxes in this model are derived based on the transitions of lattice defects. The set of reaction-diffusion equations are stiff, hence a stiffly stable method, also known as the Gear method, has been used to numerically approximate the equations. For the Cu-Au alloy in the solid solution regime, the model results demonstrate the formation of compositional patterns under high-temperature particle irradiation, with Fourier space properties (Fourier spectrum, average wavelength, and wavevector) depending on the cascade damage characteristics, average composition, and irradiation temperature.

  6. Formation of solid solutions between racemic and enantiomeric citalopram oxalate.

    PubMed

    de Diego, Heidi Lopez; Bond, Andrew D; Dancer, Robert James

    2011-05-01

    The X-ray powder diffractograms of racemic citalopram oxalate and (S)-citalopram oxalate are very similar, but the melting point of the racemate is higher than that of the pure enantiomer. The higher melting point indicates that the racemate is a racemic compound, rather than a conglomerate. The crystal structure of the enantiomer contains two molecules of (S)-citalopram in the asymmetric unit. The conformation of the two molecules is different but they approximate mirror images of each other if the aromatic groups are interchanged. The crystal structure of the racemate is essentially isostructural with that of the enantiomer, having almost the same cell parameters but containing a crystallographic inversion centre that is not retained in the enantiomer structure. The closely-comparable crystal structures permit solid solutions to be formed between racemic and enantiomeric citalopram oxalate. Phase diagrams of the (R)-citalopram and (S)-citalopram oxalate system are constructed, and they show that solid solutions are formed at all ratios of the two enantiomers.

  7. Performance studies of copper-iron/ceria-yttria stabilized zirconia anode for electro-oxidation of butane in solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Kaur, Gurpreet; Basu, Suddhasatwa

    2013-11-01

    Addition of second metal to Cu is useful for electro-oxidation of hydrocarbons in solid oxide fuel cells (SOFC). In this work, electro-catalysts based on Cu-Fe bimetallic anode for use of both H2 and n-C4H10 in SOFC is prepared by wet impregnation method into a porous CeO2-YSZ matrix. The prepared Cu-Fe/CeO2-YSZ anodes are then characterized by thermo-gravimetric analysis (TGA), X-ray diffraction (XRD), elemental dispersive X-ray (EDX) and scanning electron microscopy (SEM). Carbonaceous deposits formed on Cu-Fe/CeO2-YSZ anodes after exposure to n-C4H10 are studied using a combination of i-V characteristics and TGA measurements. It is observed that the addition of Fe to Cu in CeO2-YSZ cermet anode enhance the performance in H2 and n-C4H10 fuels. The performance of cell having molar ratio of Cu-Fe of 1:1 in Cu-Fe/CeO2-YSZ anode shows power density of 240 mW cm-2 and 260 mW cm-2 in n-C4H10 and in H2 after n-C4H10 flow at 800 °C. The i-V curve shows that the conductivity of the anode improves after exposure to n-C4H10. No apparent degradation in performance is observed after n-C4H10 flow except for carbon fibre formation indicating Cu-Fe bimetallic is worth considering as an anode for direct butane SOFC.

  8. Solid state synthesis, crystal growth and optical properties of urea and p-chloronitrobenzene solid solution

    NASA Astrophysics Data System (ADS)

    Rai, R. N.; Kant, Shiva; Reddi, R. S. B.; Ganesamoorthy, S.; Gupta, P. K.

    2016-01-01

    Urea is an attractive material for frequency conversion of high power lasers to UV (for wavelength down to 190 nm), but its usage is hindered due to its hygroscopic nature, though there is no alternative organic NLO crystal which could be transparent up to 190 nm. The hygroscopic character of urea has been modified by making the solid solution (UCNB) of urea (U) and p-chloronitrobenzene (CNB). The formation of the solid solution of CNB in U is explained on the basis of phase diagram, powder XRD, FTIR, elemental analysis and single crystal XRD studies. The solubility of U, CNB and UCNB in ethanol solution is evaluated at different temperatures. Transparent single crystals of UCNB are grown from its saturated solution in ethanol. Optical properties e.g., second harmonic generation (SHG), refractive index and the band gap for UCNB crystal were measured and their values were compared with the parent compounds. Besides modification in hygroscopic nature, UCNB has also shown the higher SHG signal and mechanical hardness in comparison to urea crystal.

  9. Comparison of ceria nanoparticle concentrations in effluent from chemical mechanical polishing of silicon dioxide.

    PubMed

    Zazzera, Larry; Mader, Brian; Ellefson, Mark; Eldridge, Jess; Loper, Steve; Zabasajja, John; Qian, Julie

    2014-11-18

    This work measured and compared the effluent from the chemical mechanical polishing (CMP) of silicon dioxide using ceria slurry and ceria fixed abrasive. CMP waste streams were tested for total solids, cerium, silicon, and 6 nm to 20 μm diameter particles. The concentration of cerium and total solids in the effluent were very different for the two polishes studied. The fixed abrasive polish produced 94% less CeO2 emissions per SiO2 removed. The higher ceria levels in the slurry effluent are associated with 99-279 nm particles, and attributed to ceria abrasive. The lower concentration of ceria in the effluent from the fixed abrasive process is due to the lower wear rate of mineral from the fixed abrasive, compared to the more environmentally mobile mineral in the slurry. These results support the "bonded" nature of the abrasive particles in fixed abrasive polishing and are relevant to sustainability strategies that seek to reduce particle emissions in surface conditioning technology.

  10. Creep Behavior of Solid Solution Strengthened Y3Al5O12

    DTIC Science & Technology

    2007-11-02

    DATES COVERED Final Technical Report 15 Feb 97 to 29 Aug 97 4. TITLE AND SUBTITLE Creep Behavior of Solid Solution Strengthened Y3A15012 6...Final Report Title: Creep Behavior of Solid Solution Strengthened Y3AI5012 Award Number: F49620-97-1-0097 For the period of: 2/14/97-8/31/97...been investigated at present in these oxides is through the formation of solid solution alloys. For the case of oxides two different possible solid

  11. Reaction paths and equilibrium end-points in solid-solution aqueous-solution systems

    USGS Publications Warehouse

    Glynn, P.D.; Reardon, E.J.; Plummer, L.N.; Busenberg, E.

    1990-01-01

    Equations are presented describing equilibrium in binary solid-solution aqueous-solution (SSAS) systems after a dissolution, precipitation, or recrystallization process, as a function of the composition and relative proportion of the initial phases. Equilibrium phase diagrams incorporating the concept of stoichiometric saturation are used to interpret possible reaction paths and to demonstrate relations between stoichiometric saturation, primary saturation, and thermodynamic equilibrium states. The concept of stoichiometric saturation is found useful in interpreting and putting limits on dissolution pathways, but there currently is no basis for possible application of this concept to the prediction and/ or understanding of precipitation processes. Previously published dissolution experiments for (Ba, Sr)SO4 and (Sr, Ca)C??O3orth. solids are interpreted using equilibrium phase diagrams. These studies show that stoichiometric saturation can control, or at least influence, initial congruent dissolution pathways. The results for (Sr, Ca)CO3orth. solids reveal that stoichiometric saturation can also control the initial stages of incongruent dissolution, despite the intrinsic instability of some of the initial solids. In contrast, recrystallisation experiments in the highly soluble KCl-KBr-H2O system demonstrate equilibrium. The excess free energy of mixing calculated for K(Cl, Br) solids is closely modeled by the relation GE = ??KBr??KClRT[a0 + a1(2??KBr-1)], where a0 is 1.40 ?? 0.02, a1, is -0.08 ?? 0.03 at 25??C, and ??KBr and ??KCl are the mole fractions of KBr and KCl in the solids. The phase diagram constructed using this fit reveals an alyotropic maximum located at ??KBr = 0.676 and at a total solubility product, ???? = [K+]([Cl-] + [Br-]) = 15.35. ?? 1990.

  12. Kinetics of CO/CO2 and H2/H2O reactions at Ni-based and ceria-based solid-oxide-cell electrodes.

    PubMed

    Graves, Christopher; Chatzichristodoulou, Christodoulos; Mogensen, Mogens B

    2015-01-01

    The solid oxide electrochemical cell (SOC) is an energy conversion technology that can be operated reversibly, to efficiently convert chemical fuels to electricity (fuel cell mode) as well as to store electricity as chemical fuels (electrolysis mode). The SOC fuel-electrode carries out the electrochemical reactions CO2 + 2e(-) ↔ CO + O(2-) and H2O + 2e(-) ↔ H2 + O(2-), for which the electrocatalytic activities of different electrodes differ considerably. The relative activities in CO/CO2 and H2/H2O and the nature of the differences are not well studied, even for the most common fuel-electrode material, a composite of nickel and yttria/scandia stabilized zirconia (Ni-SZ). Ni-SZ is known to be more active for H2/H2O than for CO/CO2 reactions, but the reported relative activity varies widely. Here we compare AC impedance and DC current-overpotential data measured in the two gas environments for several different electrodes comprised of Ni-SZ, Gd-doped CeO2 (CGO), and CGO nanoparticles coating Nb-doped SrTiO3 backbones (CGOn/STN). 2D model and 3D porous electrode geometries are employed to investigate the influence of microstructure, gas diffusion and impurities.Comparing model and porous Ni-SZ electrodes, the ratio of electrode polarization resistance in CO/CO2vs. H2/H2O decreases from 33 to 2. Experiments and modelling suggest that the ratio decreases due to a lower concentration of impurities blocking the three phase boundary and due to the nature of the reaction zone extension into the porous electrode thickness. Besides showing higher activity for H2/H2O reactions than CO/CO2 reactions, the Ni/SZ interface is more active for oxidation than reduction. On the other hand, we find the opposite behaviour in both cases for CGOn/STN model electrodes, reporting for the first time a higher electrocatalytic activity of CGO nanoparticles for CO/CO2 than for H2/H2O reactions in the absence of gas diffusion limitations. We propose that enhanced surface reduction at the

  13. Stable high conductivity ceria/bismuth oxide bilayered electrolytes

    SciTech Connect

    Wachsman, E.D.; Jayaweera, P.; Jiang, N.; Lowe, D.M.; Pound, B.G.

    1997-01-01

    The authors have developed a high conductivity bilayered ceria/bismuth oxide anolyte/electrolyte that uses the Po{sub 2} gradient to obtain stability at the anolyte-electrolyte interface and reduced electronic conduction due to the electrolyte region. Results in terms of solid oxide fuel cell (SOFC) performance and stability are presented. These results include a 90 to 160 mV increase in open-circuit potential, depending on temperature, with the bilayered structure as compared to SOFCs fabricated from a single ceria layer. An open-circuit potential of >1.0 V was obtained at 500 C with the bilayered structure. This increase in open-circuit potential is obtained without any measurable increase in cell resistance and is stable for over 1,400 h of testing, under both open-circuit and maximum power conditions. Moreover, SOFCs fabricated from the bilayered structure result in a 33% greater power density as compared to cells with a single ceria electrolyte layer.

  14. Direct Single-Enzyme Biomineralization of Catalytically Active Ceria and Ceria-Zirconia Nanocrystals.

    PubMed

    Curran, Christopher D; Lu, Li; Jia, Yue; Kiely, Christopher J; Berger, Bryan W; McIntosh, Steven

    2017-02-21

    Biomineralization is an intriguing approach to the synthesis of functional inorganic materials for energy applications whereby biological systems are engineered to mineralize inorganic materials and control their structure over multiple length scales under mild reaction conditions. Herein we demonstrate a single-enzyme-mediated biomineralization route to synthesize crystalline, catalytically active, quantum-confined ceria (CeO2-x) and ceria-zirconia (Ce1-yZryO2-x) nanocrystals for application as environmental catalysts. In contrast to typical anthropogenic synthesis routes, the crystalline oxide nanoparticles are formed at room temperature from an otherwise inert aqueous solution without the addition of a precipitant or additional reactant. An engineered form of silicatein, rCeSi, as a single enzyme not only catalyzes the direct biomineralization of the nanocrystalline oxides but also serves as a templating agent to control their morphological structure. The biomineralized nanocrystals of less than 3 nm in diameter are catalytically active toward carbon monoxide oxidation following an oxidative annealing step to remove carbonaceous residue. The introduction of zirconia into the nanocrystals leads to an increase in Ce(III) concentration, associated catalytic activity, and the thermal stability of the nanocrystals.

  15. Lattice Strain Defects in a Ceria Nanolayer

    PubMed Central

    2016-01-01

    An ultrathin two-dimensional CeO2 (ceria) phase on a Cu(110) surface has been fabricated and fully characterized by high-resolution scanning tunneling microscopy, photoelectron spectroscopy, and density functional theory. The atomic lattice structure of the ceria/Cu(110) system is revealed as a hexagonal CeO2(111)-type monolayer separated from the Cu(110) surface by a partly disordered Cu–O intercalated buffer layer. The epitaxial coupling of the two-dimensional ceria overlayer to the Cu(110)-O surface leads to a nanoscopic stripe pattern, which creates defect regions of quasi-periodic lattice distortions. The symmetry and lattice mismatch at the interface is clarified to be responsible for the topographic stripe geometry and the related anisotropic strain defect regions at the ceria surface. This ceria monolayer is in a fully oxidized and thermodynamically stable state. PMID:26988695

  16. Lattice Strain Defects in a Ceria Nanolayer.

    PubMed

    Ma, Liying; Doudin, Nassar; Surnev, Svetlozar; Barcaro, Giovanni; Sementa, Luca; Fortunelli, Alessandro; Netzer, Falko P

    2016-04-07

    An ultrathin two-dimensional CeO2 (ceria) phase on a Cu(110) surface has been fabricated and fully characterized by high-resolution scanning tunneling microscopy, photoelectron spectroscopy, and density functional theory. The atomic lattice structure of the ceria/Cu(110) system is revealed as a hexagonal CeO2(111)-type monolayer separated from the Cu(110) surface by a partly disordered Cu-O intercalated buffer layer. The epitaxial coupling of the two-dimensional ceria overlayer to the Cu(110)-O surface leads to a nanoscopic stripe pattern, which creates defect regions of quasi-periodic lattice distortions. The symmetry and lattice mismatch at the interface is clarified to be responsible for the topographic stripe geometry and the related anisotropic strain defect regions at the ceria surface. This ceria monolayer is in a fully oxidized and thermodynamically stable state.

  17. Solid state and solution nitrate photochemistry: photochemical evolution of the solid state lattice.

    PubMed

    Asher, Sanford A; Tuschel, David D; Vargson, Todd A; Wang, Luling; Geib, Steven J

    2011-05-05

    We examined the deep UV 229 nm photochemistry of NaNO(3) in solution and in the solid state. In aqueous solution excitation within the deep UV NO(3)¯ strong π → π* transition causes the photochemical reaction NO(3)¯ → NO(2)¯ + O·. We used UV resonance Raman spectroscopy to examine the photon dose dependence of the NO(2)¯ band intensities and measure a photochemical quantum yield of 0.04 at pH 6.5. We also examined the response of solid NaNO(3) samples to 229 nm excitation and also observe formation of NO(2)¯. The quantum yield is much smaller at ∼10(-8). The solid state NaNO(3) photochemistry phenomena appear complex by showing a significant dependence on the UV excitation flux and dose. At low flux/dose conditions NO(2)¯ resonance Raman bands appear, accompanied by perturbed NO(3)¯ bands, indicating stress in the NaNO(3) lattice. Higher flux/dose conditions show less lattice perturbation but SEM shows surface eruptions that alleviate the stress induced by the photochemistry. Higher flux/dose measurements cause cratering and destruction of the NaNO(3) surface as the surface layers are converted to NO(2)¯. Modest laser excitation UV beams excavate surface layers in the solid NaNO(3) samples. At the lowest incident fluxes a pressure buildup competes with effusion to reach a steady state giving rise to perturbed NO(3)¯ bands. Increased fluxes result in pressures that cause the sample to erupt, relieving the pressure.

  18. Nucleation of the diamond phase in aluminium-solid solutions

    NASA Technical Reports Server (NTRS)

    Hornbogen, E.; Mukhopadhyay, A. K.; Starke, E. A., Jr.

    1993-01-01

    Precipitation was studied from fcc solid solutions with silicon, germanium, copper and magnesium. Of all these elements only silicon and germanium form diamond cubic (DC) precipitates in fcc Al. Nucleation of the DC structure is enhanced if both types of atom are dissolved in the fcc lattice. This is interpreted as due to atomic size effects in the prenucleation stage. There are two modes of interference of fourth elements with nucleation of the DC phase in Al + Si, Ge. The formation of the DC phase is hardly affected if the atoms (for example, copper) are rejected from the (Si, Ge)-rich clusters. If additional types of atom are attracted by silicon and/or germanium, DC nuclei are replaced by intermetallic compounds (for example Mg2Si).

  19. Dielectric properties of the multicomponent PZT-type solid solution

    NASA Astrophysics Data System (ADS)

    Bochenek, Dariusz; Niemiec, Przemysław; Adamczyk, Małgorzata; Machnik, Zbigniew; Dercz, Grzegorz

    2015-10-01

    In this paper the multicomponent PZT-type solid solution doped by barium, calcium, strontium, bismuth and germanium with composition: Pb0.975Ba0.01Ca0.01Sr0.005(Zr0.52Ti0.48)O3 + 1.4 wt.% Bi2O3 + 0.3 wt.% GeO obtained by hot uniaxial pressing method is described. The results of structural, dielectric, ferroelectric and electromechanical studies of these ceramics are presented. It has been stated that introduction to the basic composition PZT admixtures of the barium, calcium, strontium, bismuth and germanium has a positive effect on the electro-physic parameters of obtained ceramic samples. This material has good microstructure, with high value of the dielectric permittivity (with the high temperature of phase transition) as well as low dielectric losses. It allows considering this material as elements for low frequency and high temperature electromechanical transducers.

  20. Lattice thermal conductivity of nanograined half-Heusler solid solutions

    SciTech Connect

    Geng, Huiyuan Meng, Xianfu; Zhang, Hao; Zhang, Jian

    2014-05-19

    We report a phenomenological model of atomic weight, lattice constant, temperature, and grain size to calculate the high-temperature lattice thermal conductivity of nanograined solid solutions. The theoretical treatment developed here is reasonably consistent with the experimental results of n-type MNiSn and p-type MCoSb alloys, where M is the combination of Hf, Zr, and Ti. For disordered half-Heusler alloys with moderated grain sizes, we predict that the reduction in lattice thermal conductivity due to grain boundary scattering is independent of the scattering parameter, which characterizes the phonon scattering cross section of point defects. In addition, the lattice thermal conductivity falls off with temperature as T{sup –1∕2} around the Debye temperature.

  1. A solid dielectric gated graphene nanosensor in electrolyte solutions.

    PubMed

    Zhu, Yibo; Wang, Cheng; Petrone, Nicholas; Yu, Jaeeun; Nuckolls, Colin; Hone, James; Lin, Qiao

    2015-03-23

    This letter presents a graphene field effect transistor (GFET) nanosensor that, with a solid gate provided by a high-κ dielectric, allows analyte detection in liquid media at low gate voltages. The gate is embedded within the sensor and thus is isolated from a sample solution, offering a high level of integration and miniaturization and eliminating errors caused by the liquid disturbance, desirable for both in vitro and in vivo applications. We demonstrate that the GFET nanosensor can be used to measure pH changes in a range of 5.3-9.3. Based on the experimental observations and quantitative analysis, the charging of an electrical double layer capacitor is found to be the major mechanism of pH sensing.

  2. Environment-mediated structure, surface redox activity and reactivity of ceria nanoparticles

    NASA Astrophysics Data System (ADS)

    Sayle, Thi X. T.; Molinari, Marco; Das, Soumen; Bhatta, Umananda M.; Möbus, Günter; Parker, Stephen C.; Seal, Sudipta; Sayle, Dean C.

    2013-06-01

    Nanomaterials, with potential application as bio-medicinal agents, exploit the chemical properties of a solid, with the ability to be transported (like a molecule) to a variety of bodily compartments. However, the chemical environment can change significantly the structure and hence properties of a nanomaterial. Accordingly, its surface reactivity is critically dependent upon the nature of the (biological) environment in which it resides. Here, we use Molecular Dynamics (MD) simulation, Density Functional Theory (DFT) and aberration corrected TEM to predict and rationalise differences in structure and hence surface reactivity of ceria nanoparticles in different environments. In particular we calculate reactivity `fingerprints' for unreduced and reduced ceria nanoparticles immersed in water and in vacuum. Our simulations predict higher activities of ceria nanoparticles, towards oxygen release, when immersed in water because the water quenches the coordinative unsaturation of surface ions. Conversely, in vacuum, surface ions relax into the body of the nanoparticle to relieve coordinative unsaturation, which increases the energy barriers associated with oxygen release. Our simulations also reveal that reduced ceria nanoparticles are more active towards surface oxygen release compared to unreduced nanoceria. In parallel, experiment is used to explore the activities of ceria nanoparticles that have suffered a change in environment. In particular, we compare the ability of ceria nanoparticles, in an aqueous environment, to scavenge superoxide radicals compared to the same batch of nanoparticles, which have first been dried and then rehydrated. The latter show a distinct reduction in activity, which we correlate to a change in the redox chemistry associated with moving between different environments. The reactivity of ceria nanoparticles is therefore not only environment dependent, but is also influenced by the transport pathway or history required to reach the particular

  3. Environment-mediated structure, surface redox activity and reactivity of ceria nanoparticles.

    PubMed

    Sayle, Thi X T; Molinari, Marco; Das, Soumen; Bhatta, Umananda M; Möbus, Günter; Parker, Stephen C; Seal, Sudipta; Sayle, Dean C

    2013-07-07

    Nanomaterials, with potential application as bio-medicinal agents, exploit the chemical properties of a solid, with the ability to be transported (like a molecule) to a variety of bodily compartments. However, the chemical environment can change significantly the structure and hence properties of a nanomaterial. Accordingly, its surface reactivity is critically dependent upon the nature of the (biological) environment in which it resides. Here, we use Molecular Dynamics (MD) simulation, Density Functional Theory (DFT) and aberration corrected TEM to predict and rationalise differences in structure and hence surface reactivity of ceria nanoparticles in different environments. In particular we calculate reactivity 'fingerprints' for unreduced and reduced ceria nanoparticles immersed in water and in vacuum. Our simulations predict higher activities of ceria nanoparticles, towards oxygen release, when immersed in water because the water quenches the coordinative unsaturation of surface ions. Conversely, in vacuum, surface ions relax into the body of the nanoparticle to relieve coordinative unsaturation, which increases the energy barriers associated with oxygen release. Our simulations also reveal that reduced ceria nanoparticles are more active towards surface oxygen release compared to unreduced nanoceria. In parallel, experiment is used to explore the activities of ceria nanoparticles that have suffered a change in environment. In particular, we compare the ability of ceria nanoparticles, in an aqueous environment, to scavenge superoxide radicals compared to the same batch of nanoparticles, which have first been dried and then rehydrated. The latter show a distinct reduction in activity, which we correlate to a change in the redox chemistry associated with moving between different environments. The reactivity of ceria nanoparticles is therefore not only environment dependent, but is also influenced by the transport pathway or history required to reach the particular

  4. High electrochemical activity of the oxide phase in model ceria-Pt and ceria-Ni composite anodes.

    PubMed

    Chueh, William C; Hao, Yong; Jung, WooChul; Haile, Sossina M

    2011-12-04

    Fuel cells, and in particular solid-oxide fuel cells (SOFCs), enable high-efficiency conversion of chemical fuels into useful electrical energy and, as such, are expected to play a major role in a sustainable-energy future. A key step in the fuel-cell energy-conversion process is the electro-oxidation of the fuel at the anode. There has been increasing evidence in recent years that the presence of CeO(2)-based oxides (ceria) in the anodes of SOFCs with oxygen-ion-conducting electrolytes significantly lowers the activation overpotential for hydrogen oxidation. Most of these studies, however, employ porous, composite electrode structures with ill-defined geometry and uncontrolled interfacial properties. Accordingly, the means by which electrocatalysis is enhanced has remained unclear. Here we demonstrate unambiguously, through the use of ceria-metal structures with well-defined geometries and interfaces, that the near-equilibrium H(2) oxidation reaction pathway is dominated by electrocatalysis at the oxide/gas interface with minimal contributions from the oxide/metal/gas triple-phase boundaries, even for structures with reaction-site densities approaching those of commercial SOFCs. This insight points towards ceria nanostructuring as a route to enhanced activity, rather than the traditional paradigm of metal-catalyst nanostructuring.

  5. Crystal-chemical features of the solid solutions

    SciTech Connect

    Titov, V.V.; Kesler, Ya.A.; Gordeev, I.V.; Mozhaev, A.P.

    1988-04-01

    The unusual magnetic properties of the solid solutions of CuCr/sub 2/S/sub 4/ in Cu/sub 0.5/Mo/sub 0.5/Cr/sub 2/S/sub 4/ (M = Al, Ga, In) are closely related to the crystal chemistry of these compounds. Specimens for structural investigation were obtained by solid-phase synthesis in evacuated quartz capsules. X-ray phase analysis of all the compounds was made by the powder method in a DRON-1 diffractometer with Cu K..cap alpha.. filtered radiation. The experimental confirmation of the ordering of the cations in the tetrahedral sublattice of the investigated spinels was obtained by the authors from their IR absorption spectra taken in the range 400-33 cm/sup /minus/1/. The presence of seven intense absorption bands in the spectra of the specimens indicates that these materials belong to the space group F/anti/43m, i.e., that there is ordering in the A sublattice. Their investigation led them to the conclusion that in a number of cases the vibrational spectra of the crystals are more sensitive in the investigation of atomic ordering than the spectra of x-ray and neutron diffraction, in agreement with the theoretical predictions.

  6. Thermal expansion of solid solutions in apatite binary systems

    SciTech Connect

    Knyazev, Alexander V.; Bulanov, Evgeny N. Korokin, Vitaly Zh.

    2015-01-15

    Graphical abstract: Thermal dependencies of volume thermal expansion parameter for with thermal expansion diagrams for Pb{sub 5}(PO{sub 4}){sub 3}F{sub x}Cl{sub 1−x}. - Highlights: • Solid solutions in three apatitic binary systems were investigated via HT-XRD. • Thermal expansion coefficients of solid solutions in the systems were calculated. • Features of the thermal deformation of the apatites were described. • Termoroentgenography is a sensitive method for the investigation of isomorphism. - Abstract: High-temperature insitu X-ray diffraction was used to investigate isomorphism and the thermal expansion of apatite-structured compounds in three binary systems in the entire temperature range of the existence of its hexagonal modifications. Most of the studied compounds are highly expandable (α{sub l} > 8 × 10{sup 6} (K{sup −1})). In Pb{sub 5}(PO{sub 4}){sub 3}F–Pb{sub 5}(PO{sub 4}){sub 3}Cl system, volume thermal expansion coefficient is independence from the composition at 573 K. In Pb{sub 5}(PO{sub 4}){sub 3}Cl–Pb{sub 5}(VO{sub 4}){sub 3}Cl, the compound with equimolar ratio of substituted atoms has constant volume thermal expansion coefficient in temperature range 298–973 K. Ca{sub 5}(PO{sub 4}){sub 3}Cl–Pb{sub 5}(PO{sub 4}){sub 3}Cl system is characterized by the most thermal sensitive composition, in which there is an equal ratio of isomorphic substituted atoms.

  7. Purification of uranothorite solid solutions from polyphase systems

    NASA Astrophysics Data System (ADS)

    Clavier, Nicolas; Szenknect, Stéphanie; Costin, Dan Tiberiu; Mesbah, Adel; Ravaux, Johann; Poinssot, Christophe; Dacheux, Nicolas

    2013-10-01

    The mineral coffinite, nominally USiO4, and associated Th1-xUxSiO4 uranothorite solid solutions are of great interest from a geochemical point of view and in the case of the direct storage of spent nuclear fuels. Nevertheless, they clearly exhibit a lack in the evaluation of their thermodynamic data, mainly because of the difficulties linked with their preparation as pure phases. This paper thus presents physical and chemical methods aiming to separate uranothorite solid solutions from oxide additional phases such as amorphous SiO2 and nanometric crystallized Th1-yUyO2. The repetition of centrifugation steps envisaged in first place was rapidly dropped due to poor recovery yields, to the benefit of successive washings in acid then basic media. Under both static and dynamic flow rates (i.e. low or high rate of leachate renewal), ICP-AES (Inductively Coupled Plasma - Atomic Emission Spectroscopy) analyses revealed the systematic elimination of Th1-yUyO2 in acid media and of SiO2 in basic media. Nevertheless, two successive steps were always needed to reach pure samples. On this basis, a first cycle performed in static conditions was chosen to eliminate the major part of the accessory phases while a second one, in dynamic conditions, allowed the elimination of the residual impurities. The complete purification of the samples was finally evidenced through the characterization of the samples by the means of PXRD (Powder X-Ray Diffraction), SEM (Scanning Electron Microscopy) observations and X-EDS (X-Ray Energy Dispersive Spectroscopy) analyses.

  8. The effect of solute distribution on the strain rate sensitivity of solid solutions

    NASA Astrophysics Data System (ADS)

    Xu, Zhijie

    Several aspects of the physics of the interaction of mobile solute atoms and dislocations in dilute solid solution alloys are studied in this thesis. Solute is added to pure metals in order to improve their strength. Alloying also leads to a number of other effects, some of which are undesirable. For example, it leads to reduced ductility and may cause plastic instabilities. Both of these limit material formability. Here, understanding is added regarding the physical basis of these phenomena. Reduced formability is associated with the occurrence of plastic instabilities which are caused either by low strain hardening or by low (negative) strain rate sensitivity (SRS). The current study is focused on the second effect. The strain rate sensitivity has an instantaneous component (always positive), which is associated with the thermally activated motion of dislocations, and a transient component (which may be either positive or negative), which is associated with the correlated motion of dislocations and solute. Negative SRS results when the transient component is sufficiently negative and is presumably due to clustering of solute at dislocations. The study has a multiscale nature. On the nanoscale, the formation of solute clusters at stationary dislocation cores is studied using Monte Carlo simulations and EAM potentials in an Al-Mg alloy. The size of the thermodynamically stable cluster and the binding energy of the dislocation to its cluster are evaluated as a function of the average solute concentration and temperature. Such data enter all existing constitutive models of DSA. On the mesoscale, we investigate how solute structures (concentration fluctuations) defined on longer length scales affect dislocation motion and hence the strain rate sensitivity of the material. This investigation is performed using 2D dislocation dynamics simulations. On the macroscopic scale, parametric constitutive modeling is used to investigate the effect of mesoscopic solute structures

  9. A thermochemical study of ceria: exploiting an old material for new modes of energy conversion and CO2 mitigation.

    PubMed

    Chueh, William C; Haile, Sossina M

    2010-07-28

    We present a comprehensive thermodynamic and kinetic analysis of the suitability of cerium oxide (ceria) for thermochemical fuel production. Both portions of the two-step cycle, (i) oxygen release from the oxide at 1773 and 1873 K under inert atmosphere, and (ii) hydrogen release upon hydrolysis at 1073 K, are examined theoretically as well as experimentally. We observe gravimetric fuel productivity that is in quantitative agreement with equilibrium, thermogravimetric studies of ceria. Despite the non-stoichiometric nature of the redox cycle, in which only a portion of the cerium atoms change their oxidation state, the fuel productivity of 8.5-11.8 ml of H(2) per gram of ceria is competitive with that of other solid-state thermochemical cycles currently under investigation. The fuel production rate, which is also highly attractive, at a rate of 4.6-6.2 ml of H(2) per minute per gram of ceria, is found to be limited by a surface-reaction step rather than by ambipolar bulk diffusion of oxygen through the solid ceria. An evaluation of the thermodynamic efficiency of the ceria-based thermochemical cycle suggests that, even in the absence of heat recovery, solar-to-fuel conversion efficiencies of 16 to 19 per cent can be achieved, assuming a suitable method for obtaining an inert atmosphere for the oxygen release step.

  10. From cerium oxycarbonate to nanostructured ceria: Relations between synthesis, thermal process and morphologies

    NASA Astrophysics Data System (ADS)

    Bakiz, Bahcine; Guinneton, Frédéric; Dallas, Jean-Pierre; Villain, Sylvie; Gavarri, Jean-Raymond

    2008-06-01

    Nanostructured cerium dioxide rods and powders were synthesized via two sol-gel routes, respectively at 200 °C, and in room conditions without any thermal treatment. The initial solution involved nitrates, urea and polyvinyl-pyrrolidine in aqueous medium. In a first step, we synthesized cerium oxycarbonate by heating the solution at 80 °C: crystalline grains of (Ce 3+) 2O(CO 3) 2, H 2O phase were obtained in the form of elongated crystalline spindles (5-10 μm long). Thermal decomposition of these spindle-like crystals gave rise to smaller elongated rods of nanostructured ceria. A second sol-gel route allowed obtaining nanosized ceria, after NH 4OH addition and without any heating process. X-ray diffraction, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses allowed characterizing the oxycarbonate polycrystalline samples and the two types of nanocrystalline ceria phases.

  11. Mechanical characterization of hydroxyapatite, thermoelectric materials and doped ceria

    NASA Astrophysics Data System (ADS)

    Fan, Xiaofeng

    For a variety of applications of brittle ceramic materials, porosity plays a critical role structurally and/or functionally, such as in engineered bone scaffolds, thermoelectric materials and in solid oxide fuel cells. The presence of porosity will affect the mechanical properties, which are essential to the design and application of porous brittle materials. In this study, the mechanical property versus microstructure relations for bioceramics, thermoelectric (TE) materials and solid oxide fuel cells were investigated. For the bioceramic material hydroxyapatite (HA), the Young's modulus was measured using resonant ultrasound spectroscopy (RUS) as a function of (i) porosity and (ii) microcracking damage state. The fracture strength was measured as a function of porosity using biaxial flexure testing, and the distribution of the fracture strength was studied by Weibull analysis. For the natural mineral tetrahedrite based solid solution thermoelectric material (Cu10Zn2As4S13 - Cu 12Sb4S13), the elastic moduli, hardness and fracture toughness were studied as a function of (i) composition and (ii) ball milling time. For ZiNiSn, a thermoelectric half-Heusler compound, the elastic modulus---porosity and hardness---porosity relations were examined. For the solid oxide fuel cell material, gadolina doped ceria (GDC), the elastic moduli including Young's modulus, shear modulus, bulk modulus and Poisson's ratio were measured by RUS as a function of porosity. The hardness was evaluated by Vickers indentation technique as a function of porosity. The results of the mechanical property versus microstructure relations obtained in this study are of great importance for the design and fabrication of reliable components with service life and a safety factor. The Weibull modulus, which is a measure of the scatter in fracture strength, is the gauge of the mechanical reliability. The elastic moduli and Poisson's ratio are needed in analytical or numerical models of the thermal and

  12. Crystalline structure of ceria particles controlled by the oxygen partial pressure and STI CMP performances.

    PubMed

    Kim, Ye-Hwan; Kim, Sang-Kyun; Kim, Namsoo; Park, Jea-Gun; Paik, Ungyu

    2008-09-01

    The effect of the crystalline structures of nano-sized ceria particles on shallow trench isolation (STI) chemical mechanical planarization (CMP) performance was investigated. The ceria particles were synthesized via a solid-state displacement reaction method, and their crystalline structure was controlled by regulating the oxygen partial pressure at the reaction site on the precursor. The crystalline structures of ceria particles were analyzed by the high-resolution TEM nano-beam diffraction pattern. In a calcination process with a high oxygen concentration, the synthesized ceria particles had a cubic fluorite structure (CeO(2)), because of the decarbonation of the cerium precursor. However, a low oxygen concentration results in a hexagonal phase cerium oxide (Ce(2)O(3)) rather than the cubic phase due to the insufficient oxidation of Ce(3+) to Ce(4+). In the STI CMP evaluation, the ceria slurry prepared with the cubic CeO(2) shows enhanced performances of the oxide-to-nitride removal selectivity.

  13. ON THE THERMODYNAMICS OF SOLID INTRUSION SOLUTIONS WITH BODY-CENTERED CUBIC LATTICE

    DTIC Science & Technology

    THE PROPERTIES OF AN ELASTICALLY DEFORMED SOLID INTRUSION SOLUTION WITH BODY - CENTERED CUBIC LATTICE, UNBALANCED WITH RESPECT TO ENERGETICALLY DIFFERENT POSITIONS OF THE ATOMS OF THE DISSOLVED SUBSTANCE.

  14. Investigation of Propellant and Explosive Solid Solution Systems II X-Ray Studies

    DTIC Science & Technology

    1978-03-01

    A\\Yj* ^\\C/*^ ^ 1 tatf AD 7t ott w AD-E400 125 TECHNICAL REPORT ARLCD-TR-77066 INVESTIGATION OF PROPELLANT AND EXPLOSIVE SOLID SOLUTION SYSTEMS...Report ARLCD-TR-77066 2. GOVT ACCESSION NO. *. TITLE (and Subtitle) INVESTIGATION OF PROPELLANT AND EXPLOSIVE SOLID SOLUTION SYSTEMS II X-RAY...Interplanar spacings and x-ray diffraction 9 intensities of AP, KP and their physical mixtures and solid solutions 4 X-ray data of 3 AN: KP solid solution and

  15. Thermal Expansion of Fluorapatite-Chlorapatite Solid Solutions

    NASA Astrophysics Data System (ADS)

    Hovis, Guy; Abraham, Tony; Hudacek, William; Wildermuth, Sarah; Scott, Brian; Altomare, Caitlin; Medford, Aaron; Conlon, Maricate; Morris, Matthew; Leaman, Amanda; Almer, Christine; Tomaino, Gary; Harlov, Daniel

    2015-04-01

    X-ray powder diffraction experiments have been performed on fifteen fluorapatite-chlorapatite solid solutions synthesized and chemically characterized at the GeoForschungsZentrum - Potsdam (Hovis and Harlov, 2010; Schettler, Gottschalk, and Harlov, 2011), as well as two natural near-end-member samples, from room temperature to ~900 °C at 50 to 75 °C intervals. NIST 640a Si was employed as an internal standard; data from Parrish (1953) were used to determine Si peak positions at elevated temperatures. Unit-cell parameters calculated using the software of Holland and Redfern (1997) result in volume-temperature (V-T) plots that are linear or slightly concave up (V plotted as the vertical axis) over the T range investigated. Relations for the "a" and "c" unit-cell dimensions with T for these hexagonal minerals are nearly linear, but as with V, commonly improved by quadratic fits to the data. Coefficients of thermal expansion for volume (αV ), calculated as (1/V0°C) x (ΔV/ΔT) based on linear V-T relationships, mostly fall within the range 42 ± 2 x 10-6 deg-1 and show no obvious dependence on composition. Thermal expansion coefficients for individual unit-cell axes, however, do show clear relationships to composition, αa increasing from ~9.5 to ~13.5 x 10-6 deg-1 and αc decreasing from ~19.5 to ~13 x 10-6 deg-1 from the Cl to the F end member. Clearly, a compensating structural relationship accounts for the observed relationships. Such compositional dependence was not seen in the thermal expansion data for F-OH apatite solid solutions (Hovis, Scott, Altomare, Leaman, Morris, and Tomaino, American Mineralogist, in press). This difference can be explained by the similar sizes of F- and (OH)- versus the much greater size contrast between F- and Cl-. Sincere thanks to the National Science Foundation for support of this work, which has provided numerous research experiences for Lafayette College undergraduates. Thanks also to the Earth Sciences Department, University

  16. Thermal Expansion of Fluorapatite-Chlorapatite Solid Solutions

    NASA Astrophysics Data System (ADS)

    Hovis, G. L.; Abraham, T.; Hudacek, W.; Wildermuth, S.; Scott, B.; Altomare, C.; Medford, A.; Conlon, M.; Morris, M.; Leaman, A.; Almer, C.; Tomaino, G.; Harlov, D. E.

    2014-12-01

    X-ray powder diffraction experiments have been performed on fifteen fluorapatite-chlorapatite solid solutions synthesized and chemically characterized at the GeoForschungsZentrum - Potsdam (Hovis and Harlov, 2010; Schettler, Gottschalk, and Harlov, 2011), as well as two natural near-end-member samples, from room temperature to ~900 °C at 50 to 75 °C intervals. NIST 640a Si was employed as an internal standard; data from Parrish (1953) were used to determine Si peak positions at elevated temperatures. Unit-cell parameters calculated using the software of Holland and Redfern (1997) result in volume-temperature (V-T) plots that are linear or slightly concave up (V plotted as the vertical axis) over the T range investigated. Relations for the "a" and "c" unit-cell dimensions with T for these hexagonal minerals are nearly linear but, as with V, commonly improved by quadratic fits to the data. Coefficients of thermal expansion for volume (αV), calculated as (1/V0°C) x (ΔV/ΔT) based on linear V-T relationships, mostly fall within the range 42 ± 2 x 10-6 deg-1 and show no obvious dependence on composition. Thermal expansion coefficients for individual unit-cell axes, however, do show clear relationships to composition, αa increasing from ~9.5 to ~13.5 x 10-6 deg-1 and αc decreasing from ~19.5 to ~13 x 10-6 deg-1 from the Cl to the F end member. Clearly, a compensating structural relationship accounts for the observed relationships. Such compositional dependence was not seen in the thermal expansion data for F-OH apatite solid solutions (Hovis, Scott, Altomare, Leaman, Morris, and Tomaino, American Mineralogist, in press). This difference can be explained by the similar sizes of F- and (OH)- versus the much greater size contrast between F- and Cl-. Sincere thanks to the National Science Foundation for support of this work, which has provided numerous research experiences for Lafayette College undergraduates. Thanks also to the Earth Sciences Department, University

  17. Stability region of the liebermannite-lingunite solid solution

    NASA Astrophysics Data System (ADS)

    Zhou, Y.; Irifune, T.; Ohfuji, H.; Shinmei, T.; DU, W.

    2015-12-01

    Aluminosilicate hollandite, with the chemical formula of (K,Na)AlSi3O8, is a potential host mineral of K and Na in the deep Earth [1,2]. The Na hollandite end member is called lingunite, and the K hollandite end member was named liebermannite recently. Phase relations in the system KAlSi3O8-NaAlSi3O8 under conditions of the Earth mantle transition zone and uppermost lower mantle [3,4] are essential to understanding the behavior of the liebermannite-lingunite solid solution under high pressure and high temperature, however, it is still not clear whether or not the end members can form complete solid solutions with the hollandite structure under some conditions. Previous high pressure experiments obtained the K hollandite with the limited Na content up to 50 mol % [3,4], while the Na-rich hollandite with the Na content of about 80 mol % was discovered in some meteorites [5,6]. Here we report our successful synthesis of the Na-rich hollandite with the Na content of 78 mol % at 22 GPa, 2273 K, the same condition under which the Na-rich hollandite found in the meteorite was inferred to be formed during the shock event [5]. Phase relations around 22 GPa at 1873 and 2273 K determined by our experiments indicate the solubility of NaAlSi3O8 in K hollandite is sensitive to both pressure and temperature, especially around the pressure corresponding to the dissociation of jadeite into the calcium ferrite type NaAlSiO4and stishovite, and there may be a stability region for the Na hollandite end member at temperatures slightly higher than 2273 K. Our improved phase relations provide a reasonable access to estimate the composition of hollandite in the Earth's interior and a supportive evidence to interpret the formation of the Na-rich hollandite found in meteorites via phase equilibria. [1] Irifune T., Ringwood A.E. and Hibberson W.O. (1994) Earth Planet. Sci. Lett. 126: 351-368. [2] Ishii T., Kojitani H. and Akaogi M. (2012) Earth Planet. Sci. Lett. 357-358: 34-41. [3] Yagi A

  18. Sustainable solutions for solid waste management in Southeast Asian countries.

    PubMed

    Ngoc, Uyen Nguyen; Schnitzer, Hans

    2009-06-01

    Human activities generate waste and the amounts tend to increase as the demand for quality of life increases. Today's rate in the Southeast Asian Nations (ASEANs) is alarming, posing a challenge to governments regarding environmental pollution in the recent years. The expectation is that eventually waste treatment and waste prevention approaches will develop towards sustainable waste management solutions. This expectation is for instance reflected in the term 'zero emission systems'. The concept of zero emissions can be applied successfully with today's technical possibilities in the agro-based processing industry. First, the state-of-the-art of waste management in Southeast Asian countries will be outlined in this paper, followed by waste generation rates, sources, and composition, as well as future trends of waste. Further on, solutions for solid waste management will be reviewed in the discussions of sustainable waste management. The paper emphasizes the concept of waste prevention through utilization of all wastes as process inputs, leading to the possibility of creating an ecosystem in a loop of materials. Also, a case study, focusing on the citrus processing industry, is displayed to illustrate the application of the aggregated material input-output model in a widespread processing industry in ASEAN. The model can be shown as a closed cluster, which permits an identification of opportunities for reducing environmental impacts at the process level in the food processing industry. Throughout the discussion in this paper, the utilization of renewable energy and economic aspects are considered to adapt to environmental and economic issues and the aim of eco-efficiency. Additionally, the opportunities and constraints of waste management will be discussed.

  19. Sustainable solutions for solid waste management in Southeast Asian countries

    SciTech Connect

    Uyen Nguyen Ngoc Schnitzer, Hans

    2009-06-15

    Human activities generate waste and the amounts tend to increase as the demand for quality of life increases. Today's rate in the Southeast Asian Nations (ASEANs) is alarming, posing a challenge to governments regarding environmental pollution in the recent years. The expectation is that eventually waste treatment and waste prevention approaches will develop towards sustainable waste management solutions. This expectation is for instance reflected in the term 'zero emission systems'. The concept of zero emissions can be applied successfully with today's technical possibilities in the agro-based processing industry. First, the state-of-the-art of waste management in Southeast Asian countries will be outlined in this paper, followed by waste generation rates, sources, and composition, as well as future trends of waste. Further on, solutions for solid waste management will be reviewed in the discussions of sustainable waste management. The paper emphasizes the concept of waste prevention through utilization of all wastes as process inputs, leading to the possibility of creating an ecosystem in a loop of materials. Also, a case study, focusing on the citrus processing industry, is displayed to illustrate the application of the aggregated material input-output model in a widespread processing industry in ASEAN. The model can be shown as a closed cluster, which permits an identification of opportunities for reducing environmental impacts at the process level in the food processing industry. Throughout the discussion in this paper, the utilization of renewable energy and economic aspects are considered to adapt to environmental and economic issues and the aim of eco-efficiency. Additionally, the opportunities and constraints of waste management will be discussed.

  20. Surface characterization of acidic ceria-zirconia prepared by direct sulfation

    NASA Astrophysics Data System (ADS)

    Azambre, B.; Zenboury, L.; Weber, J. V.; Burg, P.

    2010-05-01

    Acidic ceria-zirconia (SCZ) solid acid catalysts with a nominal surface density of ca 2 SO 42-/nm 2 were prepared by a simple route consisting in soaking high specific surface area Ce xZr 1- xO 2 (with x = 0.21 and 0.69) mixed oxides solutions in 0.5 M sulphuric acid. Characterizations by TPD-MS, TP-DRIFTS and FT-Raman revealed that most of surface structures generated by sulfation are stable at least up to 700 °C under inert atmosphere and consist mainly as isolated sulfates located on defects or crystal planes and to a lesser extent as polysulfates. Investigations by pyridine adsorption/desorption have stated that: SCZ possess both strong Brønsted (B) and Lewis (L) acid sites, some of them being presumably superacidic; the B/L site ratio was found to be more dependent on the temperature and hydration degree than on the composition of the ceria-zirconia. By contrast, the reactivity of the parent Ce xZr 1- xO 2 materials towards pyridine is mostly driven by redox properties resulting in the formation of Py-oxide with the participation of Lewis acid sites of moderate strength ( cus Ce x+ and Zr x+ cations). Basicity studies by CO 2 adsorption/desorption reveal that SCZ surfaces are solely acidic whereas the number and strength of Lewis basic sites increases with the Ce content for the parent Ce xZr 1- xO 2 materials.

  1. Relaxor-based solid solutions for piezoelectric and electrostrictive applications

    NASA Astrophysics Data System (ADS)

    Alberta, Edward F.

    This thesis explores the dielectric, piezoelectric, and electrostrictive properties of a number of relaxor ferroelectric-based solid solution systems. The components of these solid solution systems have a variety of characteristics ranging from normal- to relaxor- to anti-ferroelectric. Some of the relaxor end-members investigated were Pb(In1/2Nb1/2)O3 [PIN], Pb(In1/2Ta1/2)O3 [PIT], Pb(Sc 1/2Nb1/2)O3 [PSN], Pb(Ni1/3Nb 2/3)O3 [PNN], Pb(Mg1/3Nb2/3)O 3 [PMN], and Pb(Zn1/3Nb2/3)O3 [PZN]. Several of these systems have Curie temperatures [Tc] that are among the highest known for MPB compositions. Some examples are PIN-0.38PT with a Tc of 319°C, PIT-0.38PT with a Tc of 248°C, and PSN 0.42PT with a Tc of 254°C. While these are slightly lower that those of typically found in PZT, the temperature dependence of the piezoelectric properties was found to be minimal. The electromechanical coupling coefficients were largely unchanged upon heating to as high as 150°C. This is approximately equal to the Tc of PMN-PT and PZN-PT and significantly exceeds the generally accepted maximum operating temperature for these materials. Many of the materials studied were found to have very large electromechanical coupling factors and produce extraordinarily high field-induced strains. Both PSN-0.42PT and PNN-0.15PZ-0.34PT were found to produce strain levels of ˜0.30% under unipolar drive with limited hysteresis. Peak-to-peak strain levels of as much as 0.60% were possible under bipolar drive conditions. Both of these MPB compositions had very large piezoelectric properties, with the slightly larger values of d33 = 810pC/N, kp = 0.69, kt = 0.56, and k33 = 0.80 occurring in PNN-PZ-PT. Each of the MPB compositions studied has features that can be exploited for specific applications. The combination of high Tc and coercive field found in both PIN-PT and Bi(Ni1/2T1/2)O3 -PT should allow these materials to be used at high drive levels and/or at high temperatures. The high strain, low hysteresis

  2. Magnetic properties of Co-Cu metastable solid solution alloys

    NASA Astrophysics Data System (ADS)

    Fan, Xu; Mashimo, Tsutomu; Huang, Xinsheng; Kagayama, Tomoko; Chiba, Akira; Koyama, Keiichi; Motokawa, Mitsuhiro

    2004-03-01

    Metastable solid solution alloy powders and bulk alloys in the cobalt(Co)-copper(Cu) (10 90 mol % Co) system, which is an almost immiscible system at the ambient state, were prepared by mechanical alloying (MA) and shock compression. All MA-treated powders showed the x-ray diffraction patterns of a single phase of fcc structure. The lattice parameter increases with Cu concentration and is fundamentally on the line with Vegard’s law. The magnetization curves of CoxCu100-x (x=20 80) metastable bulk alloys at room temperature showed ferromagnetism, while the one of Co10Cu90 system showed paramagnetism. The saturation magnetic moment (Ms) curve versus electron numbers per atom at 0 K was found to be similar to the Slater-Pauling curves of other transition-metal binary systems and decreased with increasing Cu concentration and approached zero at about 28.8 electrons per atom. The magnetoresistance ratio at room temperature increased with Cu content in the ferromagnetic region, while the one of the paramagnetic Co10Cu90 alloy was negligibly small.

  3. Vacancy diffusion in magnetite-hercynite solid solution

    NASA Astrophysics Data System (ADS)

    Yamauchi, Shigeru; Nakamura, Akio; Shimizu, Toshiaki; Fueki, Kazuo

    1983-11-01

    To extend the chemical relaxation technique to ternary oxide systems, theoretical analysis was made to obtain an expression for the chemical diffusion coefficient in terms of the vacancy diffusion coefficient. An equation, D˜ = [ {C O}/{(C 1 + C 2) }] D v( {1}/{2})( {∂ ln P( O2) }/{∂ ln C v}) , was derived. This is similar to the one for the binary oxide system. Chemical relaxation experiments were made on the magnetite-hercynite solid solutions, (Fe 1- yAl y) 3-δO 4 with y = 0.0, 0.067, 0.133, and 0.20, at temperatures between 1300 and 1400°C. The vacancy diffusion coefficient decreased remarkably with an increase in y. The activation energy was found to be 20.8 ± 3.7, 33.5 ± 4.2, 50.4 ± 3.6, and 66.3 ± 4.5 kcal/mole for y = 0.0, 0.067, 0.133, and 0.20, respectively. A strong dependence on y was also found. The dependence of the vacancy diffusion coefficient on y was interpreted to indicate that the jump frequency of cation vacancies is decreased by the introduction of aluminium ion.

  4. Solidification and crystal growth of solid solution semiconducting alloys

    NASA Technical Reports Server (NTRS)

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

    1984-01-01

    Problems associated with the solidification and crytal growth of solid-solution semiconducting alloy crystals in a terrestrial environment are described. A detailed description is given of the results for the growth of mercury cadmium telluride (HgCdTe) alloy crystals by directional solidification, because of their considerable technological importance. A series of HgCdTe alloy crystals are grown from pseudobinary melts by a vertical Bridgman method using a wide range of growth rates and thermal conditions. Precision measurements are performed to establish compositional profiles for the crystals. The compositional variations are related to compositional variations in the melts that can result from two-dimensional diffusion or density gradient driven flow effects ahead of the growth interface. These effects are discussed in terms of the alloy phase equilibrium properties, the recent high temperature thermophysical data for the alloys and the highly unusual heat transfer characteristics of the alloy/ampule/furnace system that may readily lead to double diffusive convective flows in a gravitational environment.

  5. Intrinsic luminescence centers in scandia, yttria, and their solid solutions

    NASA Astrophysics Data System (ADS)

    Solomonov, V. V.; Spirina, A. V.; Spirin, A. V.; Paranin, S. N.

    2016-11-01

    Pulsed cathodoluminescence (PCL) of Y2O3 and Sc2O3 powders, as well as of ceramic samples of binary (11 mol % Sc2O3-ZrO2 and 10 mol % Y2O3-ZrO2) and ternary ( xSc2O3-(10-x)Y2O3-ZrO2) ( x = 5, 6, 7, 8 mol %) solid solutions are studied in the range of 300-850 nm at room temperature. In Y2O3 and Sc2O3, series of strong narrow luminescence bands emitted by surface bound radicals ...0 ...0 >-Y= O and ...0 ...0 >-Sc= O are found. The PCL spectra of xSc2O3-(10-x)Y2O3-ZrO2 ceramic samples showed the same series of narrow bands at 543, 551, 555, 572, 583, 594, 614, and 639 nm as the yttrium oxide spectra. The existence of these luminescence bands, which correspond to the emission of the ...0 ...0 >-Y= O radical, and the absence of the emission lines of the ...0 ...0 >-Sc= O radical indicate that yttrium ions, due to their larger radius, are the first that are displaced to the surface of crystallites in these systems, which is accompanied by the formation of the second phase in subsurface layers.

  6. Study of fluorescence quenching in aluminum-doped ceria nanoparticles: potential molecular probe for dissolved oxygen.

    PubMed

    Shehata, N; Meehan, K; Leber, D

    2013-05-01

    This work investigates a novel usage of aluminum-doped ceria nanoparticles (ADC-NPs), as the molecular probe in optical fluorescence quenching for sensing the dissolved oxygen (DO). Cerium oxide (ceria) nanoparticles can be considered one of the most unique nanomaterials that are being studied today due to the diffusion and reactivity of oxygen vacancies in ceria, which contributes to its high oxygen storage capability. Aluminum can be considered a promising dopant to increase the oxygen ionic conductivity in ceria nanoparticles which can improve the sensitivity of ceria nanoparticles to DO. The fluorescence intensity of ADC-NPs, synthesized via chemical precipitation, is found to have a strong inverse relationship with the DO concentration in aqueous solutions. Stern-Volmer constant of ADC-NPs at room temperature is determined to be 454.6 M(-1), which indicates that ADC-NPs have a promising sensitivity to dissolved oxygen, compared to many presently used fluorophores. In addition, Stern-Volmer constant is found to have a relatively small dependence on temperature between 25 °C to 50 °C, which shows excellent thermal stability of ADC-NPs sensitivity. Our work suggests that ADC-NPs, at 6 nm, are the smallest diameter DO molecular probes between the currently used optical DO sensors composed of different nanostructures. This investigation can improve the performance of fluorescence-quenching DO sensors for industrial and environmental applications.

  7. Optical sensing of peroxide using ceria nanoparticles via fluorescence quenching technique

    NASA Astrophysics Data System (ADS)

    Shehata, N.; Samir, E.; Gaballah, S.

    2016-04-01

    This study introduces the application of small ceria nanoparticles (NPs) as optical sensor for peroxide using fluorescence quenching technique. Our synthesized ceria nanoparticles have the ability to adsorb peroxides via its oxygen vacancies. Ceria nanoparticles (NPs) solution with added variable concentrations of hydrogen peroxides is exposed through near UV excitation and the detected visible fluorescent emission is found to be at 520nm, with reduced peak intensity peaks with increasing the peroxide concentrations due to static fluorescence quenching technique. The relative intensity change of the visible fluorescent emission has been reduced to more than 50% at added peroxide concentrations up to 10 wt.%. This research work could be applied further in optical sensors of radicals in biomedical engineering and environmental monitoring.

  8. Alloying Solid Solution Strengthening of Fe-Ga Alloys: A First-Principle Study

    DTIC Science & Technology

    2006-01-01

    effect from alloying additions of Nb, Mo, V, Cr and Co in cubic solid solution of Fe-Ga alloys. Mayer bond order "BO" values were used to evaluate the...that transition metal Nb achieves the best strengthening effect in Fe-Ga alloys. The solid solution strengthening follows a trend from larger to

  9. The behavior of Gliclazide in solution and in the solid state: a case of organic compound presenting a solid-solution structure.

    PubMed

    Santa María, Dolores; Claramunt, Rosa M; Alkorta, Ibon; Elguero, José

    2009-06-01

    The structure of the hypoglycemic agent Gliclazide has been studied by (1)H, (13)C, and (15)N NMR in solution (CDCl(3) and DMSO-d(6)) and in the solid state. In the solid state, the compound crystallizes as an EZ isomer without dynamic properties. In CDCl(3) solution, the structure is still EZ but with a slow nitrogen inversion about the pyrrolidine nitrogen: two invertomers have been observed and characterized. In DMSO-d(6), the rate is faster and only averaged signals were observed. GIAO calculated absolute shieldings were used to confirm the nature of the observed species. In the solid state, Gliclazide presents the phenomenon of solid-solution with two disordered conformations present in the crystal at a 90:10 ratio.

  10. Investigation of droplet collisions for solutions with different solids content

    NASA Astrophysics Data System (ADS)

    Kuschel, Matthias; Sommerfeld, Martin

    2013-02-01

    The collision behaviour of droplets and the collision outcome are investigated for high viscous polymer solutions. For that purpose, two droplet chains produced by piezoelectric droplet generators are directed towards each other at a certain angle so that individual droplet pairs collide. For recording the collision event, one double-image and one high-speed CCD camera were used. One camera is positioned perpendicular to the collision plane recording the outcome of the collision, and the second camera is aligned parallel to the collision plane to assure that the droplet chains are exactly in one plane. A new approach for tracking droplets in combination with an extended particle tracking velocimetry algorithm has been developed. Time-resolved series of pictures were used to analyse the dynamics of droplet collisions. The three different water soluble substances were saccharose and 1-Ethenyl-2-pyrrolidone (PVP) with different molecular weights (K17, K30). The solvent was demineralised water. The solids contents ranged from 20 to 60 %, 5 to 25 % and 5 to 35 %, yielding dynamic viscosities in the range of 2-60 mPa s. Results were collected for different pairs of impact angles and Weber numbers in order to establish common collision maps for characterising the outcomes. Here, relative velocities between 0.5 and 4 m/s and impact parameters in the interval from 0 to 1 for equal-sized droplets (Δ = 1) have been investigated. Additionally, satellite formation will be discussed exemplarily for K30. A comparison with common models of different authors (Ashgriz and Poo in J Fluid Mech 221:183-204, 1990; Estrade et al. in Int J Heat Fluid Flow 20:486-491, 1999) mainly derived for low viscous droplets revealed that the upper limit of their validity is given by an Ohnesorge number of Oh = 0.115 and a capillary number of Ca = 0.577. For higher values of these non-dimensional parameters and hence higher dynamic viscosities, these models are unable to predict correctly the

  11. Release of ceria nanoparticles grafted on hybrid organic-inorganic films for biomedical application.

    PubMed

    Pinna, Alessandra; Figus, Cristiana; Lasio, Barbara; Piccinini, Massimo; Malfatti, Luca; Innocenzi, Plinio

    2012-08-01

    The controlled release of nanoparticles from a hybrid organic-inorganic surface allows for developing several applications based on a slow delivery of oxygen scavengers into specific environments. We have successfully grafted ceria nanoparticles on a hybrid film surface and tested their release in a buffer solution; the tests have shown that the particles are continuously delivered within a time scale of hours. The hybrid film has been synthesized using 3-glycidoxypropyltrimethoxysilane as precursor alkoxide; the synthesis has been performed in highly basic conditions to control the polycondensation reactions of both organic and inorganic networks via controlled aging of the solution. Only films prepared from aged solutions are able to graft ceria nanoparticles on their surface. The ceria nanoparticles have been characterized by X-ray diffraction, transmission electron microscopy and UV-vis spectroscopy, the hybrid films have been analyzed by Fourier transform infrared spectroscopy, atomic force microscopy and Raman spectroscopy. Raman imaging has been used for the release test. The hybrid film-ceria nanoparticles system fulfils the requirements of optical transparency and stability in buffer solutions which are necessary for biomedical applications.

  12. Solid solution, phase separation, and cathodoluminescence of GaP-ZnS nanostructures.

    PubMed

    Liu, Baodan; Bando, Yoshio; Dierre, Benjamin; Sekiguchi, Takashi; Golberg, Dmitri; Jiang, Xin

    2013-09-25

    Quaternary solid-solution nanowires made of GaP and ZnS have been synthesized through well-designed synthetic routines. The as-synthesized GaP-ZnS solid-solution nanowires exhibit decent crystallinity with the GaP phase as the host, while a large amount of twin structural defects are observed in ZnS-rich nanowires. Cathodoluminescence studies showed that GaP-rich solid-solution nanowires have a strong visible emission centered at 600 nm and the ZnS-rich solid-solution nanowires exhibited a weak emission peak in the UV range and a broad band in the range 400-600 nm. The formation mechanism, processes, and optical emissions of GaP-ZnS solid-solution nanowires were discussed in detail.

  13. Solid-solution aqueous-solution equilibria: thermodynamic theory and representation

    USGS Publications Warehouse

    Glynn, P.D.; Reardon, E.J.

    1990-01-01

    Thorstenson and Plummer's (1977) "stoichiometric saturation' model is reviewed, and a general relation between stoichiometric saturation Kss constants and excess free energies of mixing is derived for a binary solid-solution B1-xCxA: GE = RT[ln Kss - xln(xKCA) - (l-x)ln((l-x)KBA)]. This equation allows a suitable excess free energy function, such as Guggenheim's (1937) sub-regular function, to be fitted from experimentally determined Kss constants. Solid-phase free energies and component activity-coefficients can then be determined from one or two fitted parameters and from the endmember solubility products KBA and KCA. A general form of Lippmann's (1977,1980) "solutus equation is derived from an examination of Lippmann's (1977,1980) "total solubility product' model. Lippmann's ??II or "total solubility product' variable is used to represent graphically not only thermodynamic equilibrium states and primary saturation states but also stoichiometric saturation and pure phase saturation states. -from Authors

  14. Oxygen nonstoichiometry and thermodynamic characterization of Zr doped ceria in the 1573-1773 K temperature range.

    PubMed

    Takacs, M; Scheffe, J R; Steinfeld, A

    2015-03-28

    This work encompasses the thermodynamic characterization and critical evaluation of Zr(4+) doped ceria, a promising redox material for the two-step solar thermochemical splitting of H2O and CO2 to H2 and CO. As a case study, we experimentally examine 5 mol% Zr(4+) doped ceria and present oxygen nonstoichiometry measurements at elevated temperatures ranging from 1573 K to 1773 K and oxygen partial pressures ranging from 4.50 × 10(-3) atm to 2.3 × 10(-4) atm, yielding higher reduction extents compared to those of pure ceria under all conditions investigated, especially at the lower temperature range and at higher pO2. In contrast to pure ceria, a simple ideal solution model accounting for the formation of isolated oxygen vacancies and localized electrons accurately describes the defect chemistry. Thermodynamic properties are determined, namely: partial molar enthalpy, entropy, and Gibbs free energy. In general, partial molar enthalpy and entropy values of Zr(4+) doped ceria are lower. The equilibrium hydrogen yields are subsequently extracted as a function of the redox conditions for dopant concentrations as high as 20%. Although reduction extents increase greatly with dopant concentration, the oxidation of Zr(4+) doped ceria is thermodynamically less favorable compared to pure ceria. This leads to substantially larger temperature swings between reduction and oxidation steps, ultimately resulting in lower theoretical solar energy conversion efficiencies compared to ceria under most conditions. In effect, these results point to the importance of considering oxidation thermodynamics in addition to reduction when screening potential redox materials.

  15. Solid lipid nanoparticles suspension versus commercial solutions for dermal delivery of minoxidil.

    PubMed

    Padois, Karine; Cantiéni, Céline; Bertholle, Valérie; Bardel, Claire; Pirot, Fabrice; Falson, Françoise

    2011-09-15

    Solid lipid nanoparticles have been reported as possible carrier for skin drug delivery. Solid lipid nanoparticles are produced from biocompatible and biodegradable lipids. Solid lipid nanoparticles made of semi-synthetic triglycerides stabilized with a mixture of polysorbate and sorbitan oleate were loaded with 5% of minoxidil. The prepared systems were characterized for particle size, pH and drug content. Ex vivo skin penetration studies were performed using Franz-type glass diffusion cells and pig ear skin. Ex vivo skin corrosion studies were realized with a method derived from the Corrositex(®) test. Solid lipid nanoparticles suspensions were compared to commercial solutions in terms of skin penetration and skin corrosion. Solid lipid nanoparticles suspensions have been shown as efficient as commercial solutions for skin penetration; and were non-corrosive while commercial solutions presented a corrosive potential. Solid lipid nanoparticles suspensions would constitute a promising formulation for hair loss treatment.

  16. Continuum Modeling of Mixed Conductors: a Study of Ceria

    NASA Astrophysics Data System (ADS)

    Ciucci, Francesco

    In this thesis we have derived a new way to analyze the impedance response of mixed conducting materials for use in solid oxide fuel cells (SOFCs), with the main focus on anodic materials, in particular cerium oxides. First we have analyzed the impact of mixed conductivity coupled to electrocatalytic behavior in the linear time-independent domain for a thick ceria sample. We have derived that, for a promising fuel cell material, Samarium Doped Ceria, chemical reactions are the determining component of the polarization resistance. As a second step we have extended the previous model to the time-dependent case, where we focused on single harmonic excitation, the impedance spectroscopy conditions. We extended the model to the case where some input diffusivities are spatially nonuniform. For instance we considered the case where diffusivities change significantly in the vicinity of the electrocatalytic region. As a third and final step we use to model to capture the two dimensional behavior of mixed conducting thin films, where the electronic motion from one side of the sample to the other is impeded. Such conditions are similar to those encountered in fuel cells where an electrolyte conducting exclusively oxygen ions is placed between the anode and the cathode. The framework developed was also extended to study a popular cathodic material, Lanthanum Manganite. The model is used to give unprecedented insight in SOFC polarization resistance analysis of mixed conductors. It helps elucidate rigorously rate determining steps and to address the interplay of diffusion with diffusion losses. Electrochemical surface losses dominate for most experimental conditions of Samarium Doped Ceria and they are shown to be strongly dependent on geometry.

  17. Evolution of mixed surfactant aggregates in solutions and at solid/solution interfaces

    NASA Astrophysics Data System (ADS)

    Zhang, Rui

    Surfactant systems have been widely used in such as enhanced oil recovery, waste treatment and metallurgy, etc., in order to solve the problem of global energy crisis, to remove the pollutants and to generate novel energy resources. Almost all surfactant systems are invariably mixtures due to beneficial and economic considerations. The sizes and shapes of aggregates in solutions and at solid/solution interfaces become important, since the nanostructures of mixed aggregates determine solution and adsorption properties. A major hurdle in science is the lack of information on the type of complexes and aggregates formed by mixtures and the lack of techniques for deriving such information. Using techniques such as analytical ultracentrifuge, small angle neutron scattering, surface tension, fluorescence, cryo-TEM, light scattering and ultrafiltration, the nanostructures of aggregates of sugar based n-dodecyl-beta-D-maltoside (DM) and nonionic pentaethyleneglycol monododecyl ether or nonyl phenol ethoxylated decyl ether (NP-10) and their mixtures have been investigated to prove the hypothesis that the aggregation behavior is linked to packing of the surfactant governed by the molecular interactions as well as the molecular structures. The results from both sedimentation velocity and sedimentation equilibrium experiments suggest coexistence of two types of micelles in nonyl phenol ethoxylated decyl ether solutions and its mixtures with n-dodecyl-beta-D-maltoside while only one micellar species is present in n-dodecyl-beta-D-maltoside solutions, in good agreement with those from small angle neutron scattering, cryo-TEM, light scattering and ultrafiltration. Type I micelles were primary micelles at cmc while type II micelles were elongated micelles. On the other hand, the nanostructures of mixed surface aggregates have been quantitatively predicted for the first time using a modified packing index. As a continuation of the Somasundaran-Fuersteneau adsorption model, a

  18. Kinetic analysis for formation of Cd1-xZnxSe solid-solution nanocrystals.

    PubMed

    Sung, Yun-Mo; Lee, Yong-Ji; Park, Kyung-Soo

    2006-07-19

    Kinetic analysis on the nanocrystal solid-solution formation was performed by heat treating CdSe/ZnSe core/shell nanocrystals, synthesized via a typical TOP/TOPO approach, at different temperatures for different time periods. X-ray diffraction (XRD) peak shifts in Cd1-xZnxSe cores according to the solid-solution treatments were monitored and used for the estimation of the lattice parameter change. The degree of solid-solution formation was determined considering the compositional variation in Cd1-xZnxSe cores, which was obtained from the Vegard's law. The degree of solid-solution formation (x) was applied to Jander analysis, and an Arrhenius-type plot was produced using the slopes of Jander plots. The activation energy for solid-solution formation was determined as approximately 152 kJ/mol, which evidently indicates that the diffusion of Zn2+ ions in the CdSe-ZnSe system is the governing mechanism for the Cd1-xZnxSe solid-solution formation. The Jander equation to predict the solid-solution formation kinetics for the CdSe/ZnSe core/shell systems was completed using the reaction rate constant (k).

  19. Synthesis of the bismuth oxyhalide solid solutions with tunable band gap and photocatalytic activities.

    PubMed

    Ren, Kuaixia; Liu, Jie; Liang, Jie; Zhang, Kun; Zheng, Xiao; Luo, Hongde; Huang, Yunbo; Liu, Pujun; Yu, Xibin

    2013-07-14

    Three series of BiOM(x)R(1-x) (M, R = Cl, Br, I) solid solutions were systematically synthesized through a low-temperature precipitation. These solid solutions were characterized by XRD, FESEM, TEM, EDS, UV-vis spectra, nitrogen sorption/desorption, and PL. The tunable band gaps of the as-prepared solid solutions were realized via only changing the molar ratio of two halide ions. Meanwhile, the influence of citric acid in the formations of controllable morphological structures was discussed to study the growth mechanism of solid solutions. The photocatalytic activities of the bismuth oxyhalide solid solutions have also been investigated by the degradation of Rhodamine-B (RhB) under visible light irradiation. The optimized solid solutions possess higher photocatalytic activity than pure ones [BiOM (M = Cl, Br, I)] due to the broadened range of visible light response and the reduced recombination rate of electron-holes pairs. The results show that the synthesis of BiOM(x)R(1-x) (M, R = Cl, Br, I) solid solutions have profound significance for the design of the novel photocatalyst materials.

  20. Analysis of solid solutions stability in scheelite-type molybdates and tungstates

    SciTech Connect

    Zhuravlev, V.D.; Reznitskikh, O.G.; Velikodnyi, Yu.A.; Patrusheva, T.A.; Sivtsova, O.V.

    2011-10-15

    Mutual solubility of bivalent metal molybdates and tungstates with scheelite structure was theoretically estimated by calculating formation enthalpies and the maximal decomposition temperatures of solid solutions at different temperatures. The theoretical stability of continuous solid solutions in binary systems of bivalent metal molybdates and tungstates was found to be higher than reported literature data. After cooling down continuous substitution solid solution should remain in following systems: CaMoO{sub 4}-CdMoO{sub 4}, SrMoO{sub 4}-MMoO{sub 4} (M=Ba, Pb), BaMoO{sub 4}-PbMoO{sub 4}, SrWO{sub 4}-MWO{sub 4} (M=Ca, Pb), and BaWO{sub 4}-PbWO{sub 4}. There is a probability that at room temperature in systems CaMoO{sub 4}-SrMoO{sub 4,} CaWO{sub 4}-PbWO{sub 4}, and BaWO{sub 4}-SrWO{sub 4} the single homogeneity region may decompose to limited solid solutions. It was shown experimentally that a continuous series of scheelite-structure solid solutions M{sub 1-x}M{sup I}{sub x}TO{sub 4} can be formed via citrate synthesis at temperatures below 500 deg. S. - Graphical abstract: Calculated boundaries of solid solutions in BaWO{sub 4}-CaWO{sub 4} (1) and PbMoO{sub 4}-CaMoO{sub 4} (2) systems. Highlights: > Stability of solid solutions molybdates and tungstates has been investigated. > The ionic model for isovalent substitutions was used. > In 'polyhedral substitution model' enthalphies of mixing were calculated. > Most of the examined series of solid solutions is stable at room temperatures. > Solid solutions M{sub 1-x}M{sup I}{sub x}Mo(W)O{sub 4} (x=0-1) were formed via citrate synthesis below 500 S.

  1. Investigation of compositional segregation during unidirectional solidification of solid solution semiconducting alloys

    NASA Technical Reports Server (NTRS)

    Wang, J. C.

    1982-01-01

    Compositional segregation of solid solution semiconducting alloys in the radial direction during unidirectional solidification was investigated by calculating the effect of a curved solid liquid interface on solute concentration at the interface on the solid. The formulation is similar to that given by Coriell, Boisvert, Rehm, and Sekerka except that a more realistic cylindrical coordinate system which is moving with the interface is used. Analytical results were obtained for very small and very large values of beta with beta = VR/D, where V is the velocity of solidification, R the radius of the specimen, and D the diffusivity of solute in the liquid. For both very small and very large beta, the solute concentration at the interface in the solid C(si) approaches C(o) (original solute concentration) i.e., the deviation is minimal. The maximum deviation of C(si) from C(o) occurs for some intermediate value of beta.

  2. Al and Zn Impurity Diffusion in Binary and Ternary Magnesium Solid-Solutions

    SciTech Connect

    Kammerer, Catherine; Kulkarni, Nagraj S; Warmack, Robert J Bruce; Sohn, Yong Ho

    2014-01-01

    Magnesium alloys are considered for implementation into structural components where energy-efficiency and light-weighting are important. Two of the most common alloying elements in magnesium alloys are Aluminum and Zinc. The present work examines impurity diffusion coefficients of Al and Zn in Mg(Zn) and Mg(Al) binary solid solutions, respectively. Experimental investigation is carried out with ternary diffusion couples with polycrystalline alloys. Concentration profiles were measured by electron microprobe micro-analysis and the impurity diffusion coefficients were determined by the Hall Method. Results of Al and Zn impurity diffusion in Mg solid solutions are reported, and examined as a function of composition of Mg solid solution.

  3. The Effect of Hydrogen on the Solid Solution Strengthening and Softening of Nickel.

    DTIC Science & Technology

    1981-11-01

    Afl-A108 654e ILLINOIS UNIV AT URBANA DEPT OF METALLURGY AND MININS--ETC F/6 11/6 THE EFFECT OF HYDROGEN ON THE SOLID SOLUTION STRFNSTNFNING ANfl...RESOLUTION TEST CHART NATIONAL HUR[AU OF STANDARDS 1963 A, " , ..... . .... .. i ....... .. .. . t , LEVEL THE EFFECT OF HYDROGEN ON THE SOLID SOLUTION STRENGTHENING...Availability Codes IIAvail and/or Dist Special THE EFFECT OF HYDROGEN ON THE SOLID SOLUTION STRENGTHENING AND SOFTENING OF NICKEL J. Eastman, F. Heuhaum, T

  4. Oxygen vacancy migration in ceria and Pr-doped ceria: a DFT+U study.

    PubMed

    Dholabhai, Pratik P; Adams, James B; Crozier, Peter; Sharma, Renu

    2010-03-07

    Oxygen vacancy formation and migration in ceria (CeO(2)) is central to its performance as an ionic conductor. It has been observed that ceria doped with suitable aliovalent cationic dopants improves its ionic conductivity. To investigate this phenomenon, we present total energy calculations within the framework of density functional theory to study oxygen vacancy migration in ceria and Pr-doped ceria (PDC). We report activation energies for oxygen vacancy formation and migration in undoped ceria and for different migration pathways in PDC. The activation energy value for oxygen vacancy migration in undoped ceria was found to be in reasonable agreement with the available experimental and theoretical results. Conductivity values for reduced undoped ceria calculated using theoretical activation energy and attempt frequency were found in reasonably good agreement with the experimental data. For PDC, oxygen vacancy formation and migration were investigated at first, second, and third nearest neighbor positions to a Pr ion. The second nearest neighbor site is found to be the most favorable vacancy formation site. Vacancy migration between first, second, and third nearest neighbors was calculated (nine possible jumps), with activation energies ranging from 0.41 to 0.78 eV for first-nearest-neighbor jumps. Overall, the presence of Pr significantly affects vacancy formation and migration, in a complex manner requiring the investigation of many different migration events. We propose a relationship illuminating the role of additional dopants toward lowering the activation energy for vacancy migration in PDC.

  5. Is Steam an Oxidant or a Reductant for Nickel/Doped-Ceria Cermets?

    PubMed

    Papaefthimiou, Vasiliki; Niakolas, Dimitris K; Paloukis, Fotios; Dintzer, Thierry; Zafeiratos, Spyridon

    2017-01-04

    Nickel/doped-ceria composites are promising electrocatalysts for solid-oxide fuel and electrolysis cells. Very often steam is present in the feedstock of the cells, frequently mixed with other gases, such as hydrogen or CO2 . An increase in the steam concentration in the feed mixture is considered accountable for the electrode oxidation and the deactivation of the device. However, direct experimental evidence of the steam interaction with nickel/doped-ceria composites, with adequate surface specificity, are lacking. Herein we explore in situ the surface state of nickel/gadolinium-doped ceria (NiGDC) under O2 , H2 , and H2 O environments by using near-ambient-pressure X-ray photoelectron and absorption spectroscopies. Changes in the surface oxidation state and composition of NiGDC in response to the ambient gas are observed. It is revealed that, in the mbar pressure regime and at intermediate temperature conditions (500-700 °C), steam acts as an oxidant for nickel but has a dual oxidant/reductant function for doped ceria.

  6. Synthesis of (U,Zr)C solid solutions under exothermic conditions. Revision

    SciTech Connect

    Wang, Lily L.; Moore, H.G.; Gladson, J.W.

    1993-10-01

    The reactions of forming (U,Zr)C solid solutions from their elemental components or similarly less stable reactants such as UC{sub 2} are strongly exothermic due to the high stability of these solid solutions. A simple approach of utilizing this heat of formation energy to assist the solid solution reaction process is intimately mix the less stable reactant powders and pressed them into compact; the compact is then heated to the ignition temperature of the reaction. The feasibility of this reaction method to synthesize (U,Zr) solid solutions has been demonstrated in this study. The preliminary results also show that both the initial composition and the heating rate have a significant effect on the nature of the reaction process. As expected the degree of powder mixing was also found to affect the completeness of the reaction.

  7. Infrared Spectra of Simple Inorganic Ion Pairs in Solid Solution: A Physical Inorganic Chemistry Experiment.

    ERIC Educational Resources Information Center

    Miller, Philip J.; Tong, William G.

    1980-01-01

    Presents a physical inorganic experiment in which large single crystals of the alkali halides doped with divalent ion impurities are prepared easily. Demonstrates the ion pairing of inorganic ions in solid solution. (CS)

  8. THE ROLE OF ELECTRON CONFIGURATION ON PROPERTIES IN DILUTE SOLID SOLUTION ALLOYS

    DTIC Science & Technology

    THE ROLE OF ELECTRON CONFIGURATION ON THE PROPERTIES OF DILUTE SOLID SOLUTION ALLOYS IS DISCUSSED IN TERMS OF THE EFFECT OF DILUTE IMPURITIES ON THE RECRYSTALLIZATION CHARACTERISTICS OF PURE METALLIC ELEMENTS.

  9. Surface Faceting and Reconstruction of Ceria Nanoparticles.

    PubMed

    Yang, Chengwu; Yu, Xiaojuan; Heißler, Stefan; Nefedov, Alexei; Colussi, Sara; Llorca, Jordi; Trovarelli, Alessandro; Wang, Yuemin; Wöll, Christof

    2017-01-02

    The surface atomic arrangement of metal oxides determines their physical and chemical properties, and the ability to control and optimize structural parameters is of crucial importance for many applications, in particular in heterogeneous catalysis and photocatalysis. Whereas the structures of macroscopic single crystals can be determined with established methods, for nanoparticles (NPs), this is a challenging task. Herein, we describe the use of CO as a probe molecule to determine the structure of the surfaces exposed by rod-shaped ceria NPs. After calibrating the CO stretching frequencies using results obtained for different ceria single-crystal surfaces, we found that the rod-shaped NPs actually restructure and expose {111} nanofacets. This finding has important consequences for understanding the controversial surface chemistry of these catalytically highly active ceria NPs and paves the way for the predictive, rational design of catalytic materials at the nanoscale.

  10. Planet Patrol. An Educational Unit on Solid Waste Solutions for Grades 4-6.

    ERIC Educational Resources Information Center

    Shively, Patti J.; And Others

    This educational unit on solid waste solutions is intended to convey to students an understanding of the four methods of solid waste handling, in priority order, as recommended by the Environmental Protection Agency: (1) reduction in the volume of waste produced; (2) recycling and composting; (3) waste combustion, i.e., incineration of waste; and…

  11. CoSb3-IrSb3 solid solutions: preparation and characterization

    NASA Astrophysics Data System (ADS)

    Borshchevsky, Alex; Fleurial, Jean-Pierre; Allevato, Eugene; Caillat, Thierry

    1994-08-01

    The binary antimonide compounds of the skutterudite family have a good potential for thermoelectric applications as recent results at the Jet Propulsion Laboratory (JPL) have shown. However, the room temperature thermal conductivity of these materials is about 10 Wm-1K-1 with an estimated 80% contribution from the lattice. To achieve maximum ZT values, the lattice thermal conductivity needs to be lowered. Because the lattice thermal conductivity of solid solutions can substantially decrease due to the addition of point defect phonon scattering (all state of the art thermoelectric materials are solid solutions), a study of the formation of solid solutions between the antimonide skutterudite compounds is of interest. The existence of CoP3-CoAs3 and CoAs3-CoSb3 solid solutions was already reported in the literature. The preparation and characterization of both p-type and n-type CoSb3-IrSb3 solid solutions by several techniques is reviewed in this paper. The homogeneity of the samples and the existence of solid solutions were investigated using mass density measurements, X-ray diffractometry, microprobe analysis and optical microscopy. The thermal conductivity, the electrical resistivity, and the Hall mobility were measured from 25 to 500 °C. Experimental results showed that solid solutions were successfully formed in a wide range of compositions. Some immiscibility was observed but may be due to the preparation conditions. The changes in the thermoelectric properties indicated the influence of a strong point defect scattering, resulting in large decreases in Hall mobility and thermal conductivity. The potential for high ZT values in CoSb3-IrSb3 solid solutions is discussed.

  12. Structural and catalytic properties of lanthanide (La, Eu, Gd) doped ceria

    SciTech Connect

    Hernandez, W.Y.; Laguna, O.H.; Centeno, M.A.; Odriozola, J.A.

    2011-11-15

    Ce{sub 0.9}M{sub 0.1}O{sub 2-{delta}} mixed oxides (M=La, Eu and Gd) were synthesized by coprecipitation. Independent of the dopant cation, the obtained solids maintain the F-type crystalline structure, characteristic of CeO{sub 2} (fluorite structure) without phase segregation. The ceria lattice expands depending on the ionic radii of the dopant cation, as indicated by X-ray diffraction studies. This effect also agrees with the observed shift of the F{sub 2g} Raman vibrational mode. The presence of the dopant cations in the ceria lattice increases the concentration of structural oxygen vacancies and the reducibility of the redox pair Ce{sup 4+}/Ce{sup 3+}. All synthesized materials show higher catalytic activity for the CO oxidation reaction than that of bare CeO{sub 2}, being Eu-doped solid the one with the best catalytic performances despite of its lower surface area. - Graphical abstract: In this work, Ce{sub 0.9}M{sub 0.1}O{sub 2-{delta}} mixed oxides (M=La, Eu and Gd) were synthesized by coprecipitation. Independent of the dopant cation, the obtained solids maintain the F-type crystalline structure, characteristic of CeO{sub 2} (fluorite structure) without phase segregation. The ceria lattice expands depending on the ionic radii of the dopant cation, as indicated by X-ray diffraction studies. This effect also agrees with the observed shift of the F{sub 2g} Raman vibrational mode. The presence of the dopant cations in the ceria lattice increases the concentration of structural oxygen vacancies and the reducibility of the redox pair Ce{sup 4+}/Ce{sup 3+}. All synthesized materials show higher catalytic activity for the CO oxidation reaction than that of bare CeO{sub 2}, being Eu-doped solid the one with the best catalytic performances despite of its lower surface area. Highlights: > Lanthanide doped ceria as catalytic supports for CO oxidation reaction. > A higher concentration of oxygen vacancies promotes a higher catalytic activity. > Eu-doped ceria shows

  13. Effect of Er, Gd, and Nd Co-Dopants on the Properties of Sm-Doped Ceria Electrolyte for IT-SOFC

    NASA Astrophysics Data System (ADS)

    Arabacı, Aliye

    2017-02-01

    Doped ceria electrolytes of Ce0.8Sm0.20O1.90 (SDC), Ce0.8Er0.08Sm0.12O1.90 (ESDC), Ce0.8Gd0.08Sm0.12O1.90 (GSDC), and Ce0.8Nd0.08Sm0.12O1.90 (NSDC) were prepared by a citric-nitrate combustion process. The thermal decomposition of the precursor was investigated by simultaneous thermogravimetric analysis and differential thermal analysis experiments. The phase structure of the calcined and sintered powders was characterized by X-ray diffraction analysis. All of the samples were fluorite-type ceria-based solid solutions. The calcined and sintered powders were also characterized by Fourier transform infrared spectroscopy. Scanning electron microscopy was used to characterize the samples after calcination and sintering. A relative density over 95 percent of the theoretical density was achieved after the sintering process. Electrical conductivities of the sintered samples were measured using the impedance spectra method. The highest ionic conductivity value was found to be 5.28 × 10-2 S cm-1 at 1023 K (750 °C) for GSDC sintered at 1673 K (1400 °C) for 6 hours.

  14. Superficial composition in binary solid solutions A(B): Drastic effect of pure element surface tensions

    NASA Astrophysics Data System (ADS)

    Rolland, A.; Aufray, B.

    1985-10-01

    This paper deals with a comparative study of surface segragation of Pb and Ni respectively from Ag(Pb)(111) and Ag(Ni)(111) solid solutions. A high level of segregation of the solute is observed for both systems characterized by very low solute solubility. However, the superficial composition strongly depends on the relative surface tensions of the pure elements: the solute atoms are strictly on superficial sites when γ solute is smaller than γ solvent; in contrast uppermost layer consists purely of solvent when γ solute is greater than γ solvent. Two schematic distributions in close proximity to the surface are proposed in the last case.

  15. Electrochemical properties of ceria-based intermediate temperature solid oxide fuel cell using microwave heat-treated La0.1Sr0.9Co0.8Fe0.2O3-δ as a cathode

    NASA Astrophysics Data System (ADS)

    Choi, M.-B.; Lee, K.-T.; Yoon, H.-S.; Jeon, S.-Y.; Wachsman, E. D.; Song, S.-J.

    2012-12-01

    The temperature dependence of the chemical diffusion coefficient and the surface exchange coefficient of LSCF1982 is successfully determined from the D.C. conductivity relaxation in the temperature range of 500 ≤ T/°C ≤ 700 and an oxygen partial pressure of 0.21 atm. The kinetic values of chemical diffusion coefficient (D˜) and surface exchange coefficient (k) are 1.85 × 10-5 cm2 s-1 and 2.42 × 10-4 cm s-1 at 650 °C, respectively. The electrochemical properties of La0.1Sr0.9Co0.8Fe0.2O3-δ (LSCF1982) as a cathode for ceria based IT-SOFC are successfully characterized by I-V performance measurement and electrochemical impedance spectroscopy (EIS) in terms of cathode microstructure effects by using microwave heat treatment. The cell with microwave heat-treated cathode shows the higher performance than conventional heat treated cathode. At 650 °C the open circuit potential (OCP) and maximum power density are respectively 0.753 V and 1.79 W cm-2 under 150 sccm of wet hydrogen and air gas flow conditions, and the ohmic and electrode area specific resistance (ASR) are 0.037 and 0.014 Ω cm2, respectively.

  16. Solid-solute phase equilibria in aqueous solution: VII. A re-interpretation of magnesian calcite stabilities

    NASA Astrophysics Data System (ADS)

    Königsberger, Erich; Gamsjäger, Heinz

    1992-11-01

    It is proposed to model magnesian calcites thermodynamically as dilute solid solutions of MgCO 3 in CaCO 3 according to the Unified Interaction Parameter Formalism ( BALE and PELTON, Met. Trans. A21A, 1997-2002, 1990). In this case both stoichiometric saturation and precipitation data of synthetic magnesian calcites taken from literature can consistently be explained.

  17. Oversolubility in the microvicinity of solid-solution interfaces.

    PubMed

    Bergonzi, Isabelle; Mercury, Lionel; Simon, Patrick; Jamme, Frédéric; Shmulovich, Kirill

    2016-06-01

    Water-solid interactions at the macroscopic level (beyond tens of nanometers) are often viewed as the coexistence of two bulk phases with a sharp interface in many areas spanning from biology to (geo)chemistry and various technological fields (membranes, microfluidics, coatings, etc.). Here we present experimental evidence indicating that such a view may be a significant oversimplification. High-resolution infrared and Raman experiments were performed in a 60 × 20 μm(2) quartz cavity, synthetically created and initially filled with demineralized water. The IR mapping (3 × 3 μm(2) beam size) performed using the SOLEIL synchrotron radiation source displays two important features: (i) the presence of a dangling free-OH component, a signature of hydrophobic inner walls; (ii) a shift of the OH-stretching band which essentially makes the 3200 cm(-1) sub-band predominate over the usual main component at around 3400 cm(-1). Raman maps confirmed these signatures (though less marked than IR's) and afforded a refined spatial distribution of this interfacial signal. This spatial resolution, statistically treated, results in a puzzling image of a 1-3 μm thick marked-liquid layer along the entire liquid-solid interface. The common view is then challenged by this strong evidence that a μm-thick layer analogous to an interphase forms at the solid-liquid interface. The thermodynamic counterpart of the vibrational shifts amounts to around +1 kJ mol(-1) at the interface with a rapidly decreasing signature towards the cavity centre, meaning that vicinal water may form a reactive layer, of micrometer thickness, expected to have an elevated melting point, a depressed boiling temperature, and enhanced solvent properties.

  18. Control of molecular rotor rotational frequencies in porous coordination polymers using a solid-solution approach.

    PubMed

    Inukai, Munehiro; Fukushima, Tomohiro; Hijikata, Yuh; Ogiwara, Naoki; Horike, Satoshi; Kitagawa, Susumu

    2015-09-30

    Rational design to control the dynamics of molecular rotors in crystalline solids is of interest because it offers advanced materials with precisely tuned functionality. Herein, we describe the control of the rotational frequency of rotors in flexible porous coordination polymers (PCPs) using a solid-solution approach. Solid-solutions of the flexible PCPs [{Zn(5-nitroisophthalate)x(5-methoxyisophthalate)1-x(deuterated 4,4'-bipyridyl)}(DMF·MeOH)]n allow continuous modulation of cell volume by changing the solid-solution ratio x. Variation of the isostructures provides continuous changes in the local environment around the molecular rotors (pyridyl rings of the 4,4'-bipyridyl group), leading to the control of the rotational frequency without the need to vary the temperature.

  19. On the structure of vanadia supported on ceria nanoshapes

    SciTech Connect

    Wu, Zili; Li, Meijun; Overbury, Steven {Steve} H

    2012-01-01

    Vanadia supported on ceria nanocrystals with defined surface planes, i.e., ceria nanoshapes including rods, cubes and octahedra were successfully synthesized. The effect of surface structure of these ceria nanoshapes on the structure of surface vanadia species as well as the formation of CeVO4 was investigated in details via in situ visible and UV Raman spectroscopy. The surface vanadia species on ceria nanoshapes evolve from monomeric vanadia to dimeric, trimeric, polymeric vanadia, and eventually crystalline V2O5 and CeVO4 as a function of vanadia loading. As expected, the nanoshaped ceria provides a rather homogeneous platform for anchoring vanadia, especially at low vanadia loading leading to only monomeric species, in contrast to the co-existence of different vanadia species on polycrystalline ceria even at extremely low vanadia loading. The formation of CeVO4 from the reaction between surface vanadia species and ceria was compared on the three ceria nanoshapes with similar surface vanadia density. It was found that both the surface structure and amount of defect sites of the ceria nanoshapes play major roles in the production of CeVO4. The easiest formation of CeVO4 on ceria rods is attributed to the lowest surface oxygen vacancy formation energy and the largest amount of defect sites available on the rods surface.

  20. Precipitation in Al–Mg solid solution prepared by solidification under high pressure

    SciTech Connect

    Jie, J.C.; Wang, H.W.; Zou, C.M.; Wei, Z.J.; Li, T.J.

    2014-01-15

    The precipitation in Al–Mg solid solution containing 21.6 at.% Mg prepared by solidification under 2 GPa was investigated. The results show that the γ-Al{sub 12}Mg{sub 17} phase is formed and the β′ phase cannot be observed in the solid solution during ageing process. The precipitation of γ and β phases takes place in a non-uniform manner during heating process, i.e. the γ and β phases are first formed in the interdendritic region, which is caused by the inhomogeneous distribution of Mg atoms in the solid solution solidified under high pressure. Peak splitting of X-ray diffraction patterns of Al(Mg) solid solution appears, and then disappears when the samples are aged at 423 K for different times, due to the non-uniform precipitation in Al–Mg solid solution. The direct transformation from the γ to β phase is observed after ageing at 423 K for 24 h. It is considered that the β phase is formed through a peritectoid reaction of α + γ → β which needs the diffusion of Mg atoms across the interface of α/γ phases. - Highlights: • The γ phase is formed and the β′ phase is be observed in Al(Mg) solid solution. • Peak splitting of XRD pattern of Al(Mg) solid solution appears during aged at 150 °C. • The β phase is formed through a peritectoid reaction of α + γ → β.

  1. Ab initio identified design principles of solid-solution strengthening in Al.

    PubMed

    Ma, Duancheng; Friák, Martin; von Pezold, Johann; Raabe, Dierk; Neugebauer, Jörg

    2013-04-01

    Solid-solution strengthening in six Al-X binary systems is investigated using first-principle methods. The volumetric mismatch parameter and the solubility enthalpy per solute were calculated. We derive three rules for designing solid-solution strengthened alloys: (i) the solubility enthalpy per solute is related to the volumetric mismatch by a power law; (ii) for each annealing temperature, there exists an optimal solute-volume mismatch to achieve maximum strength; and (iii) the strengthening potential of high volumetric mismatch solutes is severely limited by their low solubility. Our results thus show that the thermodynamic properties of the system (here Al-X alloys) set clear upper bounds to the achievable strengthening effects owing to the reduced solubility with increasing volume mismatch.

  2. Characterization of Cu, Ag and Pt added La 0.6Sr 0.4Co 0.2Fe 0.8O 3- δ and gadolinia-doped ceria as solid oxide fuel cell electrodes by temperature-programmed techniques

    NASA Astrophysics Data System (ADS)

    Huang, Ta-Jen; Shen, Xian-De; Chou, Chien-Liang

    Cu, Ag and Pt added La 0.6Sr 0.4Co 0.2Fe 0.8O 3- δ (LSCF) and gadolinia-doped ceria (GDC) were analyzed by the temperature-programmed techniques for their characteristics as either the cathode or the anode of the solid oxide fuel cells (SOFCs). Temperature-programmed oxidation using CO 2 was used to characterize the cathode materials while temperature-programmed reduction (TPR) using H 2 and TPR using CO were used to characterize the anode materials. These techniques can offer an easy screening of the materials as the SOFC electrodes. The effects of adding Cu, Ag and Pt to LSCF for the cathodic reduction activity and the anodic oxidation activity are different-Cu > Ag > Pt for reduction and Pt > Cu > Ag for oxidation. The CO oxidation activities are higher than the H 2 oxidation activities. Adding GDC to LSCF can increase both reduction and oxidation activities. The LSCF-GDC composite has a maximum activity for either reduction or oxidation when LSCF/GDC is 2 in weight.

  3. Colloidal quantum dot solids for solution-processed solar cells

    NASA Astrophysics Data System (ADS)

    Yuan, Mingjian; Liu, Mengxia; Sargent, Edward H.

    2016-03-01

    Solution-processed photovoltaic technologies represent a promising way to reduce the cost and increase the efficiency of solar energy harvesting. Among these, colloidal semiconductor quantum dot photovoltaics have the advantage of a spectrally tuneable infrared bandgap, which enables use in multi-junction cells, as well as the benefit of generating and harvesting multiple charge carrier pairs per absorbed photon. Here we review recent progress in colloidal quantum dot photovoltaics, focusing on three fronts. First, we examine strategies to manage the abundant surfaces of quantum dots, strategies that have led to progress in the removal of electronic trap states. Second, we consider new device architectures that have improved device performance to certified efficiencies of 10.6%. Third, we focus on progress in solution-phase chemical processing, such as spray-coating and centrifugal casting, which has led to the demonstration of manufacturing-ready process technologies.

  4. Functional Ceramic Ferroelectromagnetic Materials in Single Phase Solid-Solutions

    DTIC Science & Technology

    2007-12-05

    materials of 99.9% purity ( Aldrich) ( Bi2O3 , La2O3, PbO, Fe2O3, TiO2) were weighed in a stochiometirc proportion and ball milled in acetone medium for...Aldrich) ( Bi2O3 , MgO, ZrO2, PbO, Fe2O3, TiO2) were weighed in a stochiometirc proportion and ball milled in acetone medium for 24 hours.The mixture...prepared using conventional solid- state reaction route. The raw materials of 99.9% purity ( Aldrich) ( Bi2O3 , La2O3, PbO, Fe2O3, TiO2) were weighed in a

  5. Hierarchically nanoporous ceria nanoparticles with a high-surface area: synthesis, characterization, and their catalytic activity.

    PubMed

    Ge, Jiechao; Zhong, Liangshu; Zhuo, Linhai; Tang, Bo; Song, Weiguo

    2011-01-01

    A redox route based on ethylene glycol mediated process was developed to synthesize hierarchically nanoporpous ceria nanoparticles (ceria HNPNPs). The synthesized ceria HNPNPs are composed of building blocks fabricated with cubic ceria nanocrystals of several nanometers in diameter. Scanning electron microscopy was performed to investigate the evolution process of ceria precursor, and a two-step growth process was suggested for the morphology evolution. The synthesized ceria HNPNPs exhibit high surface area, which lead to high catalytic activity for CO oxidation.

  6. Surface Defects Enhanced Visible Light Photocatalytic H2 Production for Zn-Cd-S Solid Solution.

    PubMed

    Zhang, Xiaoyan; Zhao, Zhao; Zhang, Wanwan; Zhang, Guoqiang; Qu, Dan; Miao, Xiang; Sun, Shaorui; Sun, Zaicheng

    2016-02-10

    In order to investigate the defect effect on photocatalytic performance of the visible light photocatalyst, Zn-Cd-S solid solution with surface defects is prepared in the hydrazine hydrate. X-ray photoelectron spectra and photoluminescence results confirm the existence of defects, such as sulfur vacancies, interstitial metal, and Zn and Cd in the low valence state on the top surface of solid solutions. The surface defects can be effectively removed by treating with sulfur vapor. The solid solution with surface defect exhibits a narrower band gap, wider light absorption range, and better photocatalytic perfomance. The optimized solid solution with defects exhibits 571 μmol h(-1) for 50 mg photocatalyst without loading Pt as cocatalyst under visible light irradiation, which is fourfold better than that of sulfur vapor treated samples. The wavelength dependence of photocatalytic activity discloses that the enhancement happens at each wavelength within the whole absorption range. The theoretical calculation shows that the surface defects induce the conduction band minimum and valence band maximum shift downward and upward, respectively. This constructs a type I junction between bulk and surface of solid solution, which promotes the migration of photogenerated charges toward the surface of nanostructure and leads to enhanced photocatalytic activity. Thus a new method to construct highly efficient visible light photocatalysts is opened.

  7. Organic solid solution composed of two structurally similar porphyrins for organic solar cells.

    PubMed

    Zhen, Yonggang; Tanaka, Hideyuki; Harano, Koji; Okada, Satoshi; Matsuo, Yutaka; Nakamura, Eiichi

    2015-02-18

    A solid solution of a 75:25 mixture of tetrabenzoporphyrin (BP) and dichloroacenaphtho[q]tribenzo[b,g,l]porphyrin (CABP) forms when they are generated in a matrix of (dimethyl(o-anisyl)silylmethyl)(dimethylphenylsilylmethyl)[60]fullerene. This solid solution provides structural and optoelectronic properties entirely different from those of either pristine compounds or a mixture at other blending ratios. The use of this BP:CABP solid solution for organic solar cell (OSC) devices resulted in a power conversion efficiency (PCE) value higher by 16 and 300% than the PCE values obtained for the devices using the single donor BP and CABP, respectively, in a planar heterojunction architecture. This increase originates largely from the increase in short circuit current density, and hence by enhanced charge carrier separation at the donor/acceptor interface, which was probably caused by suitable energy level for the solid solution state, where electronic coupling between the two porphyrins occurred. The results suggest that physical and chemical modulation in solid solution is beneficial as an operationally simple method to enhance OSC performance.

  8. Template engaged synthesis of hollow ceria-based composites

    NASA Astrophysics Data System (ADS)

    Chen, Guozhu; Rosei, Federico; Ma, Dongling

    2015-03-01

    Hollow ceria-based composites, which consist of noble metal nanoparticles or metal oxides as a secondary component, are being studied extensively for potential applications in heterogeneous catalysis. This is due to their unique features, which exhibit the advantages of a hollow structure (e.g. high surface area and low weight), and also integrate the properties of ceria and noble metals/metal oxides. More importantly, the synergistic effect between constituents in hollow ceria-based composites has been demonstrated in various catalytic reactions. In this feature article, we summarize the state-of-the-art in the synthesis of hollow ceria-based composites, including traditional hard-templates and more recently, sacrificial-template engaged strategies, highlighting the key role of selected templates in the formation of hollow composites. In addition, the catalytic applications of hollow ceria-based composites are briefly surveyed. Finally, challenges and perspectives on future advances of hollow ceria-based composites are outlined.

  9. Template engaged synthesis of hollow ceria-based composites.

    PubMed

    Chen, Guozhu; Rosei, Federico; Ma, Dongling

    2015-03-19

    Hollow ceria-based composites, which consist of noble metal nanoparticles or metal oxides as a secondary component, are being studied extensively for potential applications in heterogeneous catalysis. This is due to their unique features, which exhibit the advantages of a hollow structure (e.g. high surface area and low weight), and also integrate the properties of ceria and noble metals/metal oxides. More importantly, the synergistic effect between constituents in hollow ceria-based composites has been demonstrated in various catalytic reactions. In this feature article, we summarize the state-of-the-art in the synthesis of hollow ceria-based composites, including traditional hard-templates and more recently, sacrificial-template engaged strategies, highlighting the key role of selected templates in the formation of hollow composites. In addition, the catalytic applications of hollow ceria-based composites are briefly surveyed. Finally, challenges and perspectives on future advances of hollow ceria-based composites are outlined.

  10. Characterization of mesoporosity in ceria particles using electron microscopy.

    PubMed

    Shih, Shao-Ju; Herrero, Pilar Rodrigo; Li, Guoqiang; Chen, Chin-Yi; Lozano-Perez, Sergio

    2011-02-01

    The geometry and three-dimensional (3D) morphology of the ceria particles synthesized by spray pyrolysis (SP) from two different precursors--cerium acetate hydrate and cerium nitrate hydrate (CeA and CeN ceria particles)--were characterized by transmission electron microscopy and electron tomography. Results were compared with surface area measurements, confirming that the surface area of CeA ceria particles is twice as large as that of CeN ceria particles. This result was supported by 3D microstructural observations, which have revealed that CeA ceria particles contain open pores (connected to surfaces) and closed pores (embedded in particles), while CeN ceria particles only contained closed pores. This experimental result suggests that the type of porosity is controlled by the precursors and could be related to their melting temperature during the heating process in SP.

  11. Surface stabilized nanosized Ce(x)Zr(1-x)O(2) solid solutions over SiO(2): characterization by XRD, Raman, and HREM techniques.

    PubMed

    Reddy, Benjaram M; Lakshmanan, Pandian; Khan, Ataullah; Loridant, Stéphane; López-Cartes, Carlos; Rojas, Teresa C; Fernandez, Asunción

    2005-07-21

    Ce(x)Zr(1)(-)(x)O(2) solid solutions deposited over silica surface were investigated by X-ray diffraction (XRD), Raman spectroscopy (RS), and high-resolution transmission electron microscopy (HREM) techniques in order to understand the role of silica support and the temperature stability of these composite oxides. For the purpose of comparison, an unsupported Ce(x)Zr(1)(-)(x)O(2) was also synthesized and subjected to characterization by various techniques. The Ce(x)Zr(1)(-)(x)O(2)/SiO(2) (CZ/S) (1:1:2 mole ratio based on oxides) was synthesized by depositing Ce(x)Zr(1)(-)(x)O(2) solid solution over a colloidal SiO(2) support by a deposition precipitation method and unsupported Ce(x)Zr(1)(-)(x)O(2) (CZ) (1:1 mole ratio based on oxides) was prepared by a coprecipitation procedure, and the obtained catalysts were subjected to thermal treatments from 773 to 1073 K. The XRD measurements disclose the presence of cubic phases with the composition Ce(0.75)Zr(0.25)O(2) and Ce(0.6)Zr(0.4)O(2) in CZ samples, while CZ/S samples possess Ce(0.75)Zr(0.25)O(2), Ce(0.6)Zr(0.4)O(2), and Ce(0.5)Zr(0.5)O(2) in different proportions. The crystallinity of these phases increased with increasing calcination temperature. The cell a parameter estimations indicate contraction of ceria lattice due to the incorporation of zirconium cations into the CeO(2) unit cell. Raman measurements indicate the presence of oxygen vacancies, lattice defects, and displacement of oxygen ions from their normal lattice positions in both the series of samples. The HREM results reveal, in the case of CZ/S samples, a well-dispersed nanosized Ce-Zr-oxides over the surface of amorphous SiO(2). The structural features of these crystals as determined by digital diffraction analysis of experimental images reveal that the Ce-Zr-oxides are mainly in the cubic geometry and exhibit high thermal stability. Oxygen storage capacity measurements by a thermogravimetric method reveal a substantial enhancement in the oxygen

  12. Charge distribution and local structure of americium-bearing thorium oxide solid solutions.

    PubMed

    Carvajal-Nunez, U; Prieur, D; Vitova, T; Somers, J

    2012-11-05

    The electronical and structural properties of Th(0.80)Am(0.20)O(2-x) materials have been studied by the coupling of X-ray diffraction and X-ray absorption spectroscopy techniques. A substoichiometric fluorite Th(IV)(0.80)Am(III)(0.20)O(1.90) solid solution is found following sintering in moisturized Ar-H(2). In contrast, heating of this sample in air leads to a nondefective fluorite Th(IV)(0.80)Am(IV)(0.20)O(2.00) solid solution. The structures of these solid solution compounds were fully characterized by assessing the interatomic distances, the coordination numbers, and the structural disorder. The effect of the sintering atmosphere on these crystallographical parameters and on the cation valences has been determined and the capability of ThO(2) to accommodate tri- and tetravalent actinides in the fluorite structure assessed.

  13. Visualization of the atomic structure of solid solutions with the NaCl structure

    NASA Astrophysics Data System (ADS)

    Babanov, Yu. A.; Ponomarev, D. A.; Ustinov, V. V.

    2015-04-01

    It has been shown how an atomic cluster for a solid solution with a rock salt structure can be constructed using the Pauling model. Simulation has been performed for 343000 ions of Ni x Zn1 - x O3 ( x = 0, 0.3, 0.5, 0.7, 1.0) oxide substitutional solid solutions. Coordinates of all cluster ions are obtained and distribution functions of ion pairs (Ni-O, Ni-Ni, Ni-Zn, Zn-Zn, Zn-O, O-O) are constructed as functions of distance. The shape of the normal distribution indicates the existence of bounded chaos in the system of oxide solid solutions. The width of the Gaussian distribution function is determined by the difference of metal ionic radii. The results are in agreement with both X-ray diffraction and EXAFS spectroscopy data.

  14. Isotope Labeling for Solution and Solid-State NMR Spectroscopy of Membrane Proteins

    PubMed Central

    Verardi, Raffaello; Traaseth, Nathaniel J.; Masterson, Larry R.; Vostrikov, Vitaly V.; Veglia, Gianluigi

    2013-01-01

    In this chapter, we summarize the isotopic labeling strategies used to obtain high-quality solution and solid-state NMR spectra of biological samples, with emphasis on integral membrane proteins (IMPs). While solution NMR is used to study IMPs under fast tumbling conditions, such as in the presence of detergent micelles or isotropic bicelles, solid-state NMR is used to study the structure and orientation of IMPs in lipid vesicles and bilayers. In spite of the tremendous progress in biomolecular NMR spectroscopy, the homogeneity and overall quality of the sample is still a substantial obstacle to overcome. Isotopic labeling is a major avenue to simplify overlapped spectra by either diluting the NMR active nuclei or allowing the resonances to be separated in multiple dimensions. In the following we will discuss isotopic labeling approaches that have been successfully used in the study of IMPs by solution and solid-state NMR spectroscopy. PMID:23076578

  15. Mechanosynthesis and structural characterization of nanocrystalline Ce{sub 1–x}Y{sub x}O{sub 2–δ} (x=0.1–0.35) solid solutions

    SciTech Connect

    Fabián, Martin; Antić, Bratislav; Girman, Vladimír; Vučinić-Vasić, Milica; Kremenović, Aleksandar; Suzuki, Shigeru; Hahn, Horst; Šepelák, Vladimír

    2015-10-15

    A series of nanostructured fluorite-type Ce{sub 1–x}Y{sub x}O{sub 2–δ} (0≤x≤0.35) solid solutions, prepared via high-energy milling of the CeO{sub 2}/Y{sub 2}O{sub 3} mixtures, are investigated by XRD, HR-TEM, EDS and Raman spectroscopy. For the first time, complementary information on both the long-range and short-range structural features of mechanosynthesized Ce{sub 1–x}Y{sub x}O{sub 2–δ}, obtained by Rietveld analysis of XRD data and Raman spectroscopy, is provided. The lattice parameters of the as-prepared solid solutions decrease with increasing yttrium content. Rietveld refinements of the XRD data reveal increase in microstrains in the host ceria lattice as a consequence of yttrium incorporation. Raman spectra are directly affected by the presence of oxygen vacancies; their existence is evidenced by the presence of vibration modes at ~560 and ~600 cm{sup –1}. The detailed spectroscopic investigations enable us to separate extrinsic and intrinsic origin of oxygen vacancies. It is demonstrated that mechanosynthesis can be successfully employed in the one-step preparation of nanocrystalline Ce{sub 1–x}Y{sub x}O{sub 2–δ} solid solutions. - Graphical abstract: Mechanosynthesis of nanocrystalline Ce{sub 1–x}Y{sub x}O{sub 2–δ} (x=0.1–0.35) solid solutions. - Highlights: • One-step mechanosynthesis of nanoscale Ce{sub 1–x}Y{sub x}O{sub 2–δ} (0≤x≤0.35) solid solutions. • Complementary information on the long-range and short-range structural features of mechanosynthesized Ce{sub 1–x}Y{sub x}O{sub 2–δ} is provided. • Structural variations as a response to the yttrium doping. • Separation of extrinsic and intrinsic origin of the induced oxygen vacancies.

  16. Catalytic properties of nanoscale iron-doped zirconia solid-solution aerogels.

    PubMed

    Chen, Lifang; Hu, Juncheng; Richards, Ryan M

    2008-05-16

    Nanoscale iron-doped zirconia solid-solution aerogels are prepared via a simple ethanol thermal route using zirconyl nitrate and iron nitrate as starting materials, followed by a supercritical fluid drying process. Structural characteristics are investigated by means of powder X-ray diffraction (XRD), thermal analyses (TG/DTA), N(2) adsorption measurements and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The results show that the resulting iron-doped solid solutions are metastable tetragonal zirconia which exhibit excellent dispersibility and high solubility of iron oxide. Further, when the Fe:(Fe+Zr) ratio x is lower than 0.10, all of the Fe(3+) ions can be incorporated into ZrO(2) by substituting Zr(4+) to form Zr(1-) (x)Fe(x)O(y) solid solutions. Moreover, for the first time, an additional hydroxyl group band that is not present in pure ZrO(2) is observed by DRIFTS for the Zr(Fe)O(2) solid solution. This is direct evidence of Fe(3+) ions incorporated into ZrO(2). These Zr(1-) (x)Fe(x)O(y) solid solutions are excellent catalysts for the solvent-free aerobic oxidation of n-hexadecane using air as the oxidant under ambient conditions. The Zr(0.8)Fe(0.2)O(y) solid-solution catalyst demonstrates the best catalytic properties, with the conversion of n-hexadecane reaching 36.2 % with 48 % selectivity for ketones and 24 % selectivity for alcohols and it can be recycled five times without significant loss of activity.

  17. Crystal Chemistry of MgAl2O4 Spinel Solid Solution

    NASA Astrophysics Data System (ADS)

    Yoshiasa, Akira; Maekawa, Hidemi; Sugiyama, Kazumasa

    Considerable efforts have been devoted to the structural studies of spinel group minerals or type compounds because of their importance as constituents of the Earth’s crust and mantle. Despite their simple structures, many spinel type compounds exhibit complex disordering phenomena involving the mixing of cation on two sites, which have important consequences for both thermodynamic and physical properties. The cation distributions and the structural variation in MgAl2-xGaxO4 solid-solution have been clarified using 27Al MAS NMR measurements and single crystal X-ray diffraction. The determined local distance in the solid solution corresponds with the bond distance expected from the effective ionic radii except Al-O distance in the tetrahedral site. We have revealed that the Al-O distance in the tetrahedral site in spinel solid solution is about 0.15 Å longer than the expected value. Boron is the same group element as Al and Ga and its ionic radius is considerably small. Single crystals of MgAl2-xBxO4 spinel were synthesized under high pressure and high temperature. The maximum content of boron was about x = 0.13 at 1273 K and 11 GPa. The smallest B ion occupies the octahedral site in top priority in the spinel solid solution of the Mg-Al-B systems. The B3+ ions can replace considerably bigger Al3+ ion under pressure. These spinel solid-solutions are largely disordered crystals. Only the positional shifts of oxygen ion have been relaxing the disorder in the solid solution.

  18. Ferroelectromagnetic solid solutions on the base piezoelectric ceramic materials for components of micromechatronics

    NASA Astrophysics Data System (ADS)

    Bochenek, Dariusz; Zachariasz, Radosław; Niemiec, Przemysław; Ilczuk, Jan; Bartkowska, Joanna; Brzezińska, Dagmara

    2016-10-01

    In the presented work, a ferroelectromagnetic solid solutions based on PZT and ferrite powders have been obtained. The main aim of combination of ferroelectric and magnetic powders was to obtain material showing both electric and magnetic properties. Ferroelectric ceramic powder (in amount of 90%) was based on the doped PZT type solid solution while magnetic component was nickel-zinc ferrite Ni1-xZnxFe2O4 (in amount of 10%). The synthesis of components of ferroelectromagnetic solid solutions was performed using the solid phase sintering. Final densification of synthesized powder has been done using free sintering. The aim of the work was to obtain and examine in the first multicomponent PZT type ceramics admixed with chromium with the following chemical composition Pb0.94Sr0.06(Zr0.46Ti0.54)O3+0.25 at% Cr2O3 and next ferroelectromagnetic solid solution based on a PZT type ferroelectric powder (Pb0.94Sr0.06(Zr0.46Ti0.54)O3+0.25 at% Cr2O3) and nickel-zinc ferrite (Ni0.64Zn0.36Fe2O4), from the point of view of their mechanical and electric properties, such as: electric permittivity, ε; dielectric loss, tanδ; mechanical losses, Q-1; and Young modulus, E.

  19. Structural and magnetic properties of mechanically alloyed Co 20Cu 80 solid solution

    NASA Astrophysics Data System (ADS)

    Yoo, Y. G.; Yang, D. S.; Yu, S. C.; Kim, W. T.; M. Lee, J.

    1999-08-01

    Microstructural change during the mechanical alloying of Co 20Cu 80 has been studied by X-ray diffractometry (XRD) and extended X-ray absorption fine structure (EXAFS) techniques. EXAFS analysis shows clearly the formation of supersaturated Co 20Cu 80 solid solution with FCC crystal structure during mechanical alloying, which is in good agreement with XRD analysis. Magnetic properties also have been studied by SQUID magnetometer from 4 to 290 K. The supersaturated Co 20Cu 80 solid solution shows wide distribution in Co cluster size due to the continuous blocking of Co cluster as a function of temperature.

  20. Exciton mobility edge in CdS 1-xSe x solid solutions

    NASA Astrophysics Data System (ADS)

    Permogorov, S.; Reznitsky, A.; Verbin, S.; Lysenko, V.

    1983-07-01

    Low temperature emission spectra of localized excitons in CdS 1-xSe x solid solutions under the monochromatic excitation with tunable laser have been studied. It has been found that the luminescence of localized excitons has a high degree of linear polarization with respect to the polarization direction of exciting light. This polarization reflects the "hidden" anisotropy of macroscopically isotropic localized exciton system and strongly depends on the frequency of exciting light. Study of this dependence has permitted for the first time a determination of position of the "mobility edge" for exciton migration in disordered semiconductor solid solution.

  1. Magnetism and Solid Solution Effects in NiAI (40% AI) Alloys

    SciTech Connect

    Liu, Chain T; Fu, Chong Long; Chisholm, Matthew F; Thompson, James R; Krcmar, Maja; Wang, Xun-Li

    2007-01-01

    The solid solution effects of ternary additions of transition elements in intermetallic Ni-40% Al were investigated by both experimental studies and theoretical calculations. Co solute atoms when sitting at Ni sublattice sites do not affect the lattice parameter and hardening behavior of Ni-40Al. On the other hand, Fe, Mn, and Cr solutes, which are mainly on Al sublattice sites, substantially expand the lattice parameter and produce an unusual solid solution softening effect. First-principles calculations predict that these solute atoms with large unfilled d-band electrons develop large magnetic moments and effectively expand the lattice parameter when occupying Al sublattice sites. The theoretical predictions were verified by both electron loss-energy spectroscopy (EELS) analyses and magnetic susceptibility measurements. The observed softening behavior can be explained quantitatively by the replacement of Ni anti-site defects (potent hardeners) by Fe, Mn, and Cr anti-site defects with smaller atom size mismatch between solute and Al atoms. This study has led to the identification of magnetic interaction as an important physical parameter affecting the solid solution hardening in intermetallic alloys containing transition elements.

  2. Activities of the components in a spinel solid solution of the Fe-Al-O system

    NASA Astrophysics Data System (ADS)

    Lykasov, A. A.; Kimyashev, A. A.

    2011-09-01

    The conditions of the equilibrium between the Fe3O4-FeAl2O4 solution and wustite are determined by measuring the EMF of galvanic cells containing a solid electrolyte, and the activities of the components in the Fe3O4-FeAl2O4 solution are calculated by treating the results of the experiment on the equilibrium between the spinel solution and wustite. Their properties are found to be different from those of ideal solutions at temperatures of 1000-1300 K. A significant positive deviation from the Raoult's law is believed to indicate the tendency of the solution to decompose. The experimental data are treated in terms of the theory of regular solutions, assuming the energy of mixing to be a function of temperature only. The critical temperature of decomposition for the Fe3O4-FeAl2O4 solution is found to be 1084 K.

  3. Study for recycling of ceria-based glass polishing powder

    SciTech Connect

    Kato, Kazuhiro; Yoshioka, Toshiaki; Okuwaki, Akitsugu

    2000-04-01

    The recycling of ceria-based glass polishing powder by alkali treatment was investigated. Major impurities in the waste, a SiO{sub 2} component from fine glass powder and an Al{sub 2}O{sub 3} component from coagulating agents, could be removed easily at 50--60 C in a 4 mol/kg NaOH solution within 1 h. These impurities react with NaOH to precipitate as zeolite at higher temperature. Thus, it is expected that a recycling process which can regenerate polishing powder and convert SiO{sub 2} and Al{sub 2}O{sub 3} components into zeolite can be designed.

  4. Morphological Control and Characterization of Monodispersed Ceria Particles

    SciTech Connect

    Minamidate, Y.; Yin, S.; Devaraju, M. K.; Sato, T.

    2010-11-24

    The morphological control of cerium oxide particles was carried out by a homogeneous precipitation followed by calcination in air at 400 deg. C. The effects of pre-aging temperature, aging time and precipitation reagents on the morphologies of final products were investigated. When urea was used as a precipitation reagent, monodispersed spherical and flake-like cerium carbonate hydroxide precursor was precipitated in the solution at 90 deg. C for 2 h after pre-aging at 25 deg. C - 50 deg. C for 24-72 h. On the other hand, monodispersed nanosize rod-like cerium hydroxide particles were obtained using triethanolamine as precipitation reagent. Ceria particles with the same morphologies and slightly smaller particle size than those of as-prepared cerium precursor could be obtained after calcination in air at 400 deg. C. Physical-chemical characteristics of the monodispersed cerium oxide particles were evaluated.

  5. Continuous Precipitation of Ceria Nanoparticles from a Continuous Flow Micromixer

    SciTech Connect

    Tseng, Chih Heng; Paul, Brian; Chang, Chih-hung; Engelhard, Mark H.

    2013-01-01

    Cerium oxide nanoparticles were continuously precipitated from a solution of cerium(III) nitrate and ammonium hydroxide using a micro-scale T-mixer. Findings show that the method of mixing is important in the ceria precipitation process. In batch mixing and deposition, disintegration and agglomeration dominates the deposited film. In T-mixing and deposition, more uniform nanorod particles are attainable. In addition, it was found that the micromixing approach reduced the exposure of the Ce(OH)3 precipates to oxygen, yielding hydroxide precipates in place of CeO2 precipitates. Advantages of the micro-scale T-mixing approach include shorter mixing times, better control of nanoparticle shape and less agglomeration.

  6. The Effect of Exposed Facets of Ceria to the Nickel Species in Nickel-Ceria Catalysts and Their Performance in a NO + CO Reaction.

    PubMed

    Tang, Ke; Liu, Wei; Li, Jing; Guo, Jinxin; Zhang, Jingcai; Wang, Shuping; Niu, Shengli; Yang, Yanzhao

    2015-12-09

    CeO2 rods with {110} facets and cubes with {100} facets were utilized as catalyst supports to probe the effect of crystallographic facets on the nickel species and the structure-dependent catalytic performance. Various analysis methods (ex and in situ XRD, TEM, Raman, XPS, TPR, TPD) were used to investigate the structural forms of the catalysts, and these results indicated that the deposition of nickel species resulted in the formation of two main active types of the catalyst components: NiO strongly or weakly interacted with the surface and Ni-Ce-O solid solution. Notably, the states and distribution ratio of nickel species were related to the shape of CeO2. It was found that CeO2 rods had more active sites to coordinate with nickel species to form a strong interaction with NiO on the surface and a more stable construction when compared to cubes. Furthermore, the nickel-ceria catalysts with rod shape were more active towards NO oxidation with complete conversion below 191 °C, but for cube shape, complete conversion occurred above 229 °C (e.g., for nickel loading of ∼5%, the complete conversion temperature was 154 °C for the rod shape and 229 °C for the cube shape). On the basis of the analysis of the catalysts structure, the superior catalytic activity was due to a combination of surface structures of NiO (mainly strongly interacting with the surface) and nickel ions Ni(2+) in the Ni-Ce-O bulk phase.

  7. First-principles investigation of solute-hydrogen interaction in a α-Ti solid solution

    NASA Astrophysics Data System (ADS)

    Hu, Q. M.; Xu, D. S.; Yang, R.; Li, D.; Wu, W. T.

    2002-08-01

    In this paper, a first-principles method is used to calculate the interaction energy between substitutional solute atoms and hydrogen in α-Ti. The results show that simple metal (SM) solute atoms are repulsive to H and therefore are detraps for H, whereas transition metal (TM) solute atoms, with smaller sizes than that of the host atoms, attract H and provide traps for H. The relationship between the interaction energy and lattice distortion as well as the electronic structure is investigated. The SM-H and TM-H interactions are dominated by different factors. The repulsive interaction between SM atoms and H is mainly due to the hybridization between the electrons of SM atoms and H when they are close to each other. The interaction between the TM solutes and H is attributable to the atomic size effect, and can be described satisfactorily by Matsumoto's strain field relaxation model. From the solute-H interaction energy and available measured terminal solubility of hydrogen (TSH), the relationship between the solute trapping of hydrogen and TSH in α-Ti is discussed. No coherent relationship is found between the theoretical hydrogen trapping effect and the experimental TSH in α-Ti alloys.

  8. REMOVAL OF SOLIDS FROM HIGHLY ENRICHED URANIUM SOLUTIONS USING THE H-CANYON CENTRIFUGE

    SciTech Connect

    Rudisill, T; Fernando Fondeur, F

    2009-01-15

    Prior to the dissolution of Pu-containing materials in HB-Line, highly enriched uranium (HEU) solutions stored in Tanks 11.1 and 12.2 of H-Canyon must be transferred to provide storage space. The proposed plan is to centrifuge the solutions to remove solids which may present downstream criticality concerns or cause operational problems with the 1st Cycle solvent extraction due to the formation of stable emulsions. An evaluation of the efficiency of the H-Canyon centrifuge concluded that a sufficient amount (> 90%) of the solids in the Tank 11.1 and 12.2 solutions will be removed to prevent any problems. We based this conclusion on the particle size distribution of the solids isolated from samples of the solutions and the calculation of particle settling times in the centrifuge. The particle size distributions were calculated from images generated by scanning electron microscopy (SEM). The mean particle diameters for the distributions were 1-3 {micro}m. A significant fraction (30-50%) of the particles had diameters which were < 1 {micro}m; however, the mass of these solids is insignificant (< 1% of the total solids mass) when compared to particles with larger diameters. It is also probable that the number of submicron particles was overestimated by the software used to generate the particle distribution due to the morphology of the filter paper used to isolate the solids. The settling times calculated for the H-Canyon centrifuge showed that particles with diameters less than 1 to 0.5 {micro}m will not have sufficient time to settle. For this reason, we recommend the use of a gelatin strike to coagulate the submicron particles and facilitate their removal from the solution; although we have no experimental basis to estimate the level of improvement. Incomplete removal of particles with diameters < 1 {micro}m should not cause problems during purification of the HEU in the 1st Cycle solvent extraction. Particles with diameters > 1 {micro}m account for > 99% of the

  9. Co-existence of Distinct Supramolecular Assemblies in Solution and in the Solid State.

    PubMed

    Reddy, G N Manjunatha; Huqi, Aida; Iuga, Dinu; Sakurai, Satoshi; Marsh, Andrew; Davis, Jeffery T; Masiero, Stefano; Brown, Steven P

    2017-02-16

    The formation of distinct supramolecular assemblies, including a metastable species, is revealed for a lipophilic guanosine (G) derivative in solution and in the solid state. Structurally different G-quartet-based assemblies are formed in chloroform depending on the nature of the cation, anion and the salt concentration, as characterized by circular dichroism and time course diffusion-ordered NMR spectroscopy data. Intriguingly, even the presence of potassium ions that stabilize G-quartets in chloroform was insufficient to exclusively retain such assemblies in the solid state, leading to the formation of mixed quartet and ribbon-like assemblies as revealed by fast magic-angle spinning (MAS) NMR spectroscopy. Distinct N-H⋅⋅⋅N and N-H⋅⋅⋅O intermolecular hydrogen bonding interactions drive quartet and ribbon-like self-assembly resulting in markedly different 2D (1) H solid-state NMR spectra, thus facilitating a direct identification of mixed assemblies. A dissolution NMR experiment confirmed that the quartet and ribbon interconversion is reversible-further demonstrating the changes that occur in the self-assembly process of a lipophilic nucleoside upon a solid-state to solution-state transition and vice versa. A systematic study for complexation with different cations (K(+) , Sr(2+) ) and anions (picrate, ethanoate and iodide) emphasizes that the existence of a stable solution or solid-state structure may not reflect the stability of the same supramolecular entity in another phase.

  10. Interdiffusion and impurity diffusion in polycrystalline Mg solid solution with Al or Zn

    SciTech Connect

    Kammerer, Catherine; Kulkarni, Nagraj S; Warmack, Robert J Bruce; Sohn, Yong Ho

    2014-01-01

    Interdiffusion and impurity diffusion in Mg binary solid solutions, Mg(Al) and Mg(Zn) were investigated at temperatures ranging from 623 to 723 K. Interdiffusion coef cients were determined via the Boltzmann Matano Method using solid-to-solid diffusion couples assembled with polycrystalline Mg and Mg(Al) or Mg(Zn) solid solutions. In addition, the Hall method was employed to extrapolate the impurity diffusion coef cients of Al and Zn in pure polycrystalline Mg. For all diffusion couples, electron micro-probe analysis was utilized for the measurement of concentration pro les. The interdiffusion coef cient in Mg(Zn) was higher than that of Mg(Al) by an order of magnitude. Additionally, the interdiffusion coef cient increased signi cantly as a function of Al content in Mg(Al) solid solution, but very little with Zn content in Mg(Zn) solid solution. The activation energy and pre-exponential factor for the average effective interdiffusion coef cient in Mg(Al) solid solution were determined to be 186.8 ( 0.9) kJ/mol and 7.69 x 10-1 ( 1.80 x 10-1) m2/s, respectively, while those determined for Mg(Zn) solid solution were 139.5 ( 4.0) kJ/mol and 1.48 x 10-3 ( 1.13 x 10-3) m2/s. In Mg, the Zn impurity diffusion coef cient was an order of magnitude higher than the Al impurity diffusion coef cient. The activation energy and pre-exponential factor for diffusion of Al impurity in Mg were determined to be 139.3 ( 14.8) kJ/mol and 6.25 x 10-5 ( 5.37 x 10-4) m2/s, respectively, while those for diffusion of Zn impurity in Mg were determined to be 118.6 ( 6.3) kJ/mol and 2.90 x 10-5 ( 4.41 x 10-5) m2/s.

  11. Damage accumulation in ion-irradiated Ni-based concentrated solid-solution alloys

    DOE PAGES

    Ullah, Mohammad W.; Aidhy, Dilpuneet S.; Zhang, Yanwen; ...

    2016-01-01

    We investigate Irradiation-induced damage accumulation in Ni0.8Fe0.2 and Ni0.8Cr0.2 alloys by using molecular dynamics simulations to assess possible enhanced radiation-resistance in these face-centered cubic (fcc), single-phase, concentrated solid-solution alloys, as compared with pure fcc Ni.

  12. Preparation and Analysis of Solid Solutions in the Potassium Perchlorate-Permanganate System.

    ERIC Educational Resources Information Center

    Johnson, Garrett K.

    1979-01-01

    Describes an experiment, designed for and tested in an advanced inorganic laboratory methods course for college seniors and graduate students, that prepares and analyzes several samples in the nearly ideal potassium perchlorate-permanganate solid solution series. The results are accounted for by a theoretical treatment based upon aqueous…

  13. Thermal transport properties of halide solid solutions: Experiments vs equilibrium molecular dynamics

    NASA Astrophysics Data System (ADS)

    Gheribi, Aïmen E.; Salanne, Mathieu; Chartrand, Patrice

    2015-03-01

    The composition dependence of thermal transport properties of the (Na,K)Cl rocksalt solid solution is investigated through equilibrium molecular dynamics (EMD) simulations in the entire range of composition and the results are compared with experiments published in recent work [Gheribi et al., J. Chem. phys. 141, 104508 (2014)]. The thermal diffusivity of the (Na,K)Cl solid solution has been measured from 473 K to 823 K using the laser flash technique, and the thermal conductivity was deduced from critically assessed data of heat capacity and density. The thermal conductivity was also predicted at 900 K in the entire range of composition by a series of EMD simulations in both NPT and NVT statistical ensembles using the Green-Kubo theory. The aim of the present paper is to provide an objective analysis of the capability of EMD simulations in predicting the composition dependence of the thermal transport properties of halide solid solutions. According to the Klemens-Callaway [P. G. Klemens, Phys. Rev. 119, 507 (1960) and J. Callaway and H. C. von Bayer, Phys. Rev. 120, 1149 (1960)] theory, the thermal conductivity degradation of the solid solution is explained by mass and strain field fluctuations upon the phonon scattering cross section. A rigorous analysis of the consistency between the theoretical approach and the EMD simulations is discussed in detail.

  14. Linear structural evolution induced tunable photoluminescence in clinopyroxene solid-solution phosphors.

    PubMed

    Xia, Zhiguo; Zhang, Yuanyuan; Molokeev, Maxim S; Atuchin, Victor V; Luo, Yi

    2013-11-22

    Clinopyroxenes along the Jervisite (NaScSi2O6)-Diopside (CaMgSi2O6) join have been studied, and a solid-solution of the type (Na(1-x)Ca(x))(Sc(1-x)Mg(x))Si2O6 has been identified in the full range of 0 ≤ x ≤ 1. The powder X-ray patterns of all the phases indicate a structural similarity to the end compounds and show smooth variation of structural parameters with composition. The linear structural evolution of iso-structural (Na(1-x)Ca(x))(Sc(1-x)Mg(x))Si2O6 solid-solutions obeying Vegard's rule has also been examined and verified by high resolution transmission electron microscopy (HRTEM). The continuous solid-solutions show the same structural type, therefore the photoluminescence spectra of Eu(2+) doped samples possess the superposition of spectral features from blue-emitting component (CaMgSi2O6:Eu(2+)) and yellow-emitting one (NaScSi2O6:Eu(2+)). This indicates that the spectroscopic properties of (Na(1-x)Ca(x))(Sc(1-x)Mg(x))Si2O6 clinopyroxene solid-solutions are in direct relations with structural parameters, and it is helpful for designing color-tunable photoluminescence with predetermined parameters.

  15. Magnetic properties of solid solutions based on UFe 10Si 2

    NASA Astrophysics Data System (ADS)

    Homma, Y.; Andreev, A. V.; Shiokawa, Y.; Miyashita, J.

    2002-04-01

    Magnetization of interstitial (UFe 10Si 2C x) and substitution (U 1- xR xFe 10Si 2, R=Nd, Er) solid solutions based on UFe 10Si 2 has been studied as a function of magnetic field and temperature on aligned powders. The results point to the considerable contribution of the U sublattice to the magnetic anisotropy.

  16. Thermal transport properties of halide solid solutions: Experiments vs equilibrium molecular dynamics

    SciTech Connect

    Gheribi, Aïmen E. Chartrand, Patrice; Salanne, Mathieu

    2015-03-28

    The composition dependence of thermal transport properties of the (Na,K)Cl rocksalt solid solution is investigated through equilibrium molecular dynamics (EMD) simulations in the entire range of composition and the results are compared with experiments published in recent work [Gheribi et al., J. Chem. phys. 141, 104508 (2014)]. The thermal diffusivity of the (Na,K)Cl solid solution has been measured from 473 K to 823 K using the laser flash technique, and the thermal conductivity was deduced from critically assessed data of heat capacity and density. The thermal conductivity was also predicted at 900 K in the entire range of composition by a series of EMD simulations in both NPT and NVT statistical ensembles using the Green-Kubo theory. The aim of the present paper is to provide an objective analysis of the capability of EMD simulations in predicting the composition dependence of the thermal transport properties of halide solid solutions. According to the Klemens-Callaway [P. G. Klemens, Phys. Rev. 119, 507 (1960) and J. Callaway and H. C. von Bayer, Phys. Rev. 120, 1149 (1960)] theory, the thermal conductivity degradation of the solid solution is explained by mass and strain field fluctuations upon the phonon scattering cross section. A rigorous analysis of the consistency between the theoretical approach and the EMD simulations is discussed in detail.

  17. Exact Solution of the Two-Level System and the Einstein Solid in the Microcanonical Formalism

    ERIC Educational Resources Information Center

    Bertoldi, Dalia S.; Bringa, Eduardo M.; Miranda, E. N.

    2011-01-01

    The two-level system and the Einstein model of a crystalline solid are taught in every course of statistical mechanics and they are solved in the microcanonical formalism because the number of accessible microstates can be easily evaluated. However, their solutions are usually presented using the Stirling approximation to deal with factorials. In…

  18. Hydrogen-storage properties of solid-solution alloys of immiscible neighboring elements with Pd.

    PubMed

    Kusada, Kohei; Yamauchi, Miho; Kobayashi, Hirokazu; Kitagawa, Hiroshi; Kubota, Yoshiki

    2010-11-17

    Rh and Ag are the elements neighboring Pd, which is well known as a hydrogen-storage metal. Although Rh and Ag do not possess hydrogen-storage properties, can Ag-Rh alloys actually store hydrogen? Ag-Rh solid-solution alloys have not been explored in the past because they do not mix with each other at the atomic level, even in the liquid phase. We have used the chemical reduction method to obtain such Ag-Rh alloys, and XRD and STEM-EDX give clear evidence that the alloys mixed at the atomic level. From the measurements of hydrogen pressure-composition isotherms and solid-state (2)H NMR, we have revealed that Ag-Rh solid-solution alloys absorb hydrogen, and the total amount of hydrogen absorbed reached a maximum at the ratio of Ag:Rh = 50:50, where the electronic structure is expected to be similar to that of Pd.

  19. The synthesis and chemical durability of Nd-doped single-phase zirconolite solid solutions

    NASA Astrophysics Data System (ADS)

    Cai, Xin; Teng, Yuancheng; Wu, Lang; Zhang, Kuibao; Huang, Yi

    2016-10-01

    Nd-doped single-phase zirconolite solid solutions was synthesized by solid-state reaction and following two steps of acid treatment. The phase composition, microstructure, and chemical durability of the zirconolite solid solutions were investigated. About 15 at% Nd was successfully stabilized into the zirconolite. The element mapping images of Ca, Zr, Nd and Ti show that all the elements are almost distributed homogeneously in the zirconolite waste forms. Product Consistency Test (PCT) was conducted under different pH values (pH = 5, 7 and 9) to evaluate the chemical durability of the Nd-doped zirconolite waste forms. The normalized element release rate of Ca (LRCa) in pH = 5 medium is higher than that of pH = 7 and 9, while the LRNd value remains almost unchanged under different pH values. The LRNd value is as low as 10-5 g m-2 d-1 after 42 days.

  20. Role of associated defects in oxygen ion conduction and surface exchange reaction for epitaxial samaria-doped ceria thin films as catalytic coatings

    DOE PAGES

    Yang, Nan; Shi, Yanuo; Schweiger, Sebastian; ...

    2016-05-18

    Samaria-doped ceria (SDC) thin films are particularly important for energy and electronic applications such as micro-solid oxide fuel cells, electrolysers, sensors and memristors. In this paper we report a comparative study investigating ionic conductivity and surface reactions for well-grown epitaxial SDC films varying the samaria doping concentration. With increasing doping above 20 mol% of samaria, an enhancement in the defect association was observed by Raman spectroscopy. The role of such defect associates on the films` oxygen ion transport and exchange was investigated by electrochemical impedance spectroscopy and electrochemical strain microscopy (ESM). The measurements reveal that the ionic transport has amore » sharp maximum in ionic conductivity and drop in its activation energy down to 0.6 eV for 20 mol% doping. Increasing the doping concentration further up to 40 mol%, raises the activation energy substantially by a factor of two. We ascribe the sluggish transport kinetics to the "bulk" ionic-near ordering in case of the heavily doped epitaxial films. Analysis of the ESM first order reversal curve measurements indicate that these associated defects may have a beneficial role by lowering the activation of the oxygen exchange "surface" reaction for heavily doped 40 mol% of samaria. We reveal in a model experiment through a solid solution series of samaria doped ceria epitaxial films that the occurrence of associate defects in the bulk affects the surface charging state of the films to increase the exchange rates. Lastly, the implication of these findings are the design of coatings with tuned oxygen surface exchange by control of bulk associate clusters for future electro-catalytic applications.« less

  1. Role of associated defects in oxygen ion conduction and surface exchange reaction for epitaxial samaria-doped ceria thin films as catalytic coatings

    SciTech Connect

    Yang, Nan; Shi, Yanuo; Schweiger, Sebastian; Strelcov, Evgheni; Foglietti, Vittorio; Orgiani, Pasquale; Balestrino, Giuseppe; Kalinin, Sergei V.; Jennifer L. M. Rupp; Aruta, Carmela; Belianinov, Alex

    2016-05-18

    Samaria-doped ceria (SDC) thin films are particularly important for energy and electronic applications such as micro-solid oxide fuel cells, electrolysers, sensors and memristors. In this paper we report a comparative study investigating ionic conductivity and surface reactions for well-grown epitaxial SDC films varying the samaria doping concentration. With increasing doping above 20 mol% of samaria, an enhancement in the defect association was observed by Raman spectroscopy. The role of such defect associates on the films` oxygen ion transport and exchange was investigated by electrochemical impedance spectroscopy and electrochemical strain microscopy (ESM). The measurements reveal that the ionic transport has a sharp maximum in ionic conductivity and drop in its activation energy down to 0.6 eV for 20 mol% doping. Increasing the doping concentration further up to 40 mol%, raises the activation energy substantially by a factor of two. We ascribe the sluggish transport kinetics to the "bulk" ionic-near ordering in case of the heavily doped epitaxial films. Analysis of the ESM first order reversal curve measurements indicate that these associated defects may have a beneficial role by lowering the activation of the oxygen exchange "surface" reaction for heavily doped 40 mol% of samaria. We reveal in a model experiment through a solid solution series of samaria doped ceria epitaxial films that the occurrence of associate defects in the bulk affects the surface charging state of the films to increase the exchange rates. Lastly, the implication of these findings are the design of coatings with tuned oxygen surface exchange by control of bulk associate clusters for future electro-catalytic applications.

  2. Controlled synthesis of ceria nanoparticles for the design of nanohybrids.

    PubMed

    Nguyen, Thanh-Dinh; Dinh, Cao-Thang; Mrabet, Driss; Tran-Thi, Minh-Nguyet; Do, Trong-On

    2013-03-15

    Ceria nanoparticles were synthesized from reaction mixture of cerium nitrate/hexamethylenediamine/water-ethylene glycol. Lamellar, particle-aggregated array, platelet, rice, cube, quasi-sphere shapes of the ceria nanoparticles can be controlled by tuning reaction parameters (reagent concentration, reagent components, pH, and reaction conditions). Studies on shape-dependent catalysis of the bare ceria samples toward CO oxidation indicated that the cube-shaped ceria nanoparticles show better catalytic activity than the nanospheres and the commercial micropowders. As capped by hexamethylenediamine (HEA) molecules, amine-functionalized ceria nanoparticles act as platforms for depositing copper particles to produce efficient Cu/CeO(2) hybrid nanocatalysts for CO conversion. Coupling of the copper clusters with the HEA-capped ceria nanocubes was achieved with the Cu contents up to 15 wt.%. The Cu/CeO(2) nanohybrids show an enhanced catalytic efficiency of low temperature CO conversion. This could be due to high exposure of the reactive {100} facets in the ceria nanocubes and interfacial copper-ceria interactions.

  3. Fuel reforming and electrical performance studies in intermediate temperature ceria-gadolinia-based SOFCs

    NASA Astrophysics Data System (ADS)

    Livermore, Stephanie J. A.; Cotton, John W.; Ormerod, R. Mark

    The methane reforming and carbon deposition characteristics of two nickel/ceria-gadolinia cermet anodes have been studied over the temperature range 550-700°C, for use in intermediate temperature ceria-gadolinia (CGO)-based solid oxide fuel cells (SOFCs), using conventional catalytic methods and temperature-programmed spectroscopy. The electrical performance and durability of planar CGO-based SOFCs with a 280-μm-thick CGO electrolyte, screen printed cathode and different screen printed nickel/CGO cermet anodes have been studied over the temperature range 500-650°C. Temperature-programmed reduction has been used to study the reduction characteristics of the anodes, and indicates the presence of "bulk" NiO particles and smaller NiO particles in intimate contact with the ceria. Both anodes show good activity towards methane steam reforming with methane activation occurring at temperatures as low as 210°C; steady-state steam reforming of methane was observed using a methane-rich mixture at 650°C, with 20% methane conversion. Post-reaction temperature-programmed oxidation has been used to determine the amount of carbon deposited during reforming and the strength of its interaction with the anode.

  4. Different routes towards oscillatory zoning in the growth of solid solutions.

    PubMed

    Lubashevsky, Ihor; Mues, Tanja; Heuer, Andreas

    2008-10-01

    Oscillatory zoning, i.e., self-formation of spatial quasiperiodic oscillations in the composition of solid growing from aqueous solution, is analyzed theoretically. Keeping in mind systems like (Ba,Sr)SO4 , we propose a one-dimensional model that takes into account the nonideality of the solid solution and the system asymmetry, in particular, reflecting itself in different solubilities for such systems. Based on a linear stability analysis, different parameter regions can be identified. Even an ideal solution with a sufficiently large asymmetry can display oscillatory zoning. Numerical simulations complement the linear stability analysis as well as the qualitative consideration of the instability development and reveal the nature of the limit cycles.

  5. Mitochondria-Targeting Ceria Nanoparticles as Antioxidants for Alzheimer's Disease.

    PubMed

    Kwon, Hyek Jin; Cha, Moon-Yong; Kim, Dokyoon; Kim, Dong Kyu; Soh, Min; Shin, Kwangsoo; Hyeon, Taeghwan; Mook-Jung, Inhee

    2016-02-23

    Mitochondrial oxidative stress is a key pathologic factor in neurodegenerative diseases, including Alzheimer's disease. Abnormal generation of reactive oxygen species (ROS), resulting from mitochondrial dysfunction, can lead to neuronal cell death. Ceria (CeO2) nanoparticles are known to function as strong and recyclable ROS scavengers by shuttling between Ce(3+) and Ce(4+) oxidation states. Consequently, targeting ceria nanoparticles selectively to mitochondria might be a promising therapeutic approach for neurodegenerative diseases. Here, we report the design and synthesis of triphenylphosphonium-conjugated ceria nanoparticles that localize to mitochondria and suppress neuronal death in a 5XFAD transgenic Alzheimer's disease mouse model. The triphenylphosphonium-conjugated ceria nanoparticles mitigate reactive gliosis and morphological mitochondria damage observed in these mice. Altogether, our data indicate that the triphenylphosphonium-conjugated ceria nanoparticles are a potential therapeutic candidate for mitochondrial oxidative stress in Alzheimer's disease.

  6. Thermodynamic considerations in solid adsorption of bound solutes for patient support in liver failure.

    PubMed

    Patzer, John F

    2008-07-01

    New detoxification modes of treatment for liver failure that use solid adsorbents to remove toxins bound to albumin in the patient bloodstream are entering clinical evaluations, frequently in head-to-head competition. While generally effective in reducing toxin concentration beyond that obtainable by conventional dialysis procedures, the solid adsorbent processes are largely the result of heuristic development. Understanding the principles and limitations inherent in competitive toxin binding, albumin versus solid adsorbent, will enhance the design process and, possibly, improve detoxification performance. An equilibrium thermodynamic analysis is presented for both the molecular adsorbent recirculating system (MARS) and fractionated plasma separation, adsorption, and dialysis system (Prometheus), two advanced systems with distinctly different operating modes but with similar equilibrium limitations. The Prometheus analysis also applies to two newer approaches: sorbent suspension reactor and microsphere-based detoxification system. Primary results from the thermodynamic analysis are that: (i) the solute-albumin binding constant is of minor importance to equilibrium once it exceeds about 10(5) L/mol; (ii) the Prometheus approach requires larger solid adsorbent columns than calculated by adsorbent solute capacity alone; and (iii) the albumin-containing recycle stream in the MARS approach is a major reservoir of removed toxin. A survey of published results indicates that MARS is operating under mass transfer control dictated by solute-albumin equilibrium in the recycle stream, and Prometheus is approaching equilibrium limits under current clinical protocols.

  7. Soot combustion over Ce1-xFexO2-δ and CeO2/Fe2O3 catalysts: Roles of solid solution and interfacial interactions in the mixed oxides

    NASA Astrophysics Data System (ADS)

    Li, Hongcheng; Li, Kongzhai; Wang, Hua; Zhu, Xing; Wei, Yonggang; Yan, Dongxia; Cheng, Xianming; Zhai, Kang

    2016-12-01

    Two series of CeO2-Fe2O3 catalysts (CeO2-based and Fe2O3-supported oxides) with varying composition were synthesized by a hydrothermal method and characterized using various techniques. The comparison on the activity and thermal stability of different catalysts for low-temperature soot oxidation was also performed. The presence of both Ce-Fe-O solid solution and CeO2-Fe2O3 interaction were observed over the two types of catalysts. The oxygen vacancy in the solid solution is the crucial active site to facilitating the soot combustion over the CeO2-based samples. Small CeO2 nanoparticles are well dispersed on the Fe2O3-supported catalysts, which results in the formation of Fe-O-Ce species due to the strong CeO2-Fe2O3 interaction. The Fe-O-Ce species could achieve the coupling of the Ce4+-Ce3+ and Fe3+-Fe2+ couples in the CeO2-Fe2O3 interface, which is also identified as an active species for catalytic soot oxidation. The concentration of oxygen vacancy is closely related to the content of iron in ceria lattice, while the formation of Fe-O-Ce species strongly relies on the particle size of CeO2. It is also found that the oxygen vacancy is more active than the Fe-O-Ce species for soot oxidation, but it is very easy to decompose at high temperature, resulting in obvious deactivation of catalysts. By contrast, the Fe-O-Ce species is very stable under high-temperature treatments. For the fresh samples, the CeO2-based and Fe2O3-supported catalysts showed comparable catalytic activity. After long term aging at 800 °C, the loss on activity over the CeO2-based catalyst (Ce-Fe-O solid solution) is much higher than that over the Fe2O3-supported sample. The Fe2O3-supported catalysts are more suitable for practical application than the Ce-Fe-O solid solution.

  8. Biocompatibility evaluation of porous ceria foams for orthopedic tissue engineering.

    PubMed

    Ball, Jordan P; Mound, Brittnee A; Monsalve, Adam G; Nino, Juan C; Allen, Josephine B

    2015-01-01

    Ceria ceramics have the unique ability to protect cells from free radical-induced damage, making them materials of interest for biomedical applications. To expand upon the understanding of the potential of ceria as a biomaterial, porous ceria, fabricated via direct foaming, was investigated to assess its biocompatibility and its ability to scavenge free radicals. A mouse osteoblast (7F2) cell line was cultured with the ceria foams to determine the extent of the foams' toxicity. Toxicity assessments indicate that mouse osteoblasts cultured directly on the ceria scaffold for 72 h did not show a significant (p > 0.05) increase in toxicity, but rather show comparable toxicity to cells cultured on porous 45S5 Bioglass. The in vitro inflammatory response elicited from porous ceria foams was measured as a function of tumor necrosis factor alpha (TNF-α) secreted from a human monocytic leukemia cell line. Results indicate that the ceria foams do not cause a significant inflammatory response, eliciting a response of 27.1 ± 7.1 pg mL(-1) of TNF-α compared to 36.3 ± 5.8 pg mL(-1) from cells on Bioglass, and 20.1 ± 2.9 pg mL(-1) from untreated cells. Finally, we report cellular toxicity in response to free radicals from tert-butyl hydroperoxide with and without foamed ceria. Our preliminary results show that the foamed ceria is able to decrease the toxic effect of induced oxidative stress. Collectively, this study demonstrates that foamed ceria scaffolds do not activate an inflammatory response, and show potential free radical scavenging ability, thus they have promise as an orthopedic biomaterial.

  9. INTERNATIONAL CONFERENCE ON SEMICONDUCTOR INJECTION LASERS SELCO-87: Simple formula for the thermal conductivity of a quaternary solid solution

    NASA Astrophysics Data System (ADS)

    Nakwaski, W.

    1988-11-01

    An analysis is made of the thermal conductivity of quaternary solid solutions (alloys) allowing for their disordered structure on the basis of a phenomenological analysis proposed by Abeles. This method is applied to a quaternary solid solution In1 - xGaxAsyP1 - y. A simple analytic expression is derived for the thermal conductivity of this material.

  10. Study of Decomposition of a Highly Supersaturated Solid Solution of a Granulated Alloy, Al-1, 5Cr-1, 5Zr,

    DTIC Science & Technology

    The mechanism and kinetics of decomposition of a highly supersaturated solid solution in an alloy is of importance in stating the proper technology...that during annealing up to 250 C, there is a great density of dislocations. A hypothesis is presented concerning the structural changes occurring at heating the highly supersaturated solid solution of this alloy.

  11. Thermodynamics and solubility of (UxNp1-x) O2(am) solid solution in the carbonate system

    SciTech Connect

    Rai, Dhanpat; Hess, Nancy J.; Yui, Mikazu; Felmy, Andrew R.; Moore, D. A.

    2004-12-31

    SUMMARY-The formation of a solid solution can significantly affect the solubility of a minor component. The objectives of this study were to determine the nature of U(IV) and Np(IV) solid solutions and their thermodynamic properties. For this purpose...

  12. Uncertainties associated with lacking data for predictions of solid-solution partitioning of metals in soil.

    PubMed

    Le, T T Yen; Hendriks, A Jan

    2014-08-15

    Soil properties, i.e., pH and contents of soil organic matter (SOM), dissolved organic carbon (DOC), clay, oxides, and reactive metals, are required inputs to both mechanistic and empirical modeling in assessing metal solid-solution partitioning. Several of these properties are rarely measured in site-specific risk assessment. We compared the uncertainties induced by lacking data on these soil properties in estimating metal soil solution concentrations. The predictions by the Orchestra framework were more sensitive to lacking soil property data than the predictions by the transfer functions. The deviations between soil solution concentrations of Cd, Ni, Zn, Ba, and Co estimated with measured SOM and those estimated with generic SOM by the Orchestra framework were about 10 times larger than the deviations in the predictions by the transfer functions. High uncertainties were induced by lacking data in assessing solid-solution partitioning of oxy-anions like As, Mo, Sb, Se, and V. Deviations associated with lacking data in predicting soil solution concentrations of these metals by the Orchestra framework reached three-to-six orders of magnitude. The solid-solution partitioning of metal cations was strongly influenced by pH and contents of organic matter, oxides, and reactive metals. Deviations of more than two orders of magnitude were frequently observed between the estimates of soil solution concentrations with the generic values of these properties and the estimates based on the measured data. Reliable information on these properties is preferred to be included in the assessment by either the Orchestra framework or transfer functions.

  13. On the difference of equilibrium constants of DNA hybridization in bulk solution and at the solid-solution interface.

    PubMed

    Oliviero, Giulio; Federici, Stefania; Colombi, Paolo; Bergese, Paolo

    2011-01-01

    The origin of the difference between the equilibrium (affinity) constants of ligand-receptor binding in bulk solution and at a solid-solution interface is discussed in terms of Gibbsian interfacial thermodynamics. It results that the difference is determined by the surface work that the ligand-receptor interaction spends to accommodate surface binding, and in turn that the value of the surface equilibrium constant (strongly) depends on the surface that confines the event. This framework consistently describes a wide set of experimental observations of DNA surface hybridization, correctly predicting that within the surface work window for DNA hybridization, that ranges from -90 to 75 kJ mol(-1), the ratio between surface and bulk equilibrium constants ranges from 10(-16) to 10(13), spanning 29 orders of magnitude.

  14. Structural, vibrational, and thermochemical properties of the monazite-type solid solution La1-xPrxPO4

    NASA Astrophysics Data System (ADS)

    Hirsch, A.; Kegler, P.; Alencar, I.; Ruiz-Fuertes, J.; Shelyug, A.; Peters, L.; Schreinemachers, C.; Neumann, A.; Neumeier, S.; Liermann, H.-P.; Navrotsky, A.; Roth, G.

    2017-01-01

    The monazite-type solid solution La1-xPrxPO4 was synthesized by solid-state reaction and extensively investigated using electron microprobe and thermogravimetric analyses, differential scanning and high-temperature oxide melt solution calorimetry, powder X-ray diffraction, infrared and Raman spectroscopy. Lattice parameters and Ln-O bond lengths show a decrease with increasing Pr content. A small excess volume is observed for the solid solution. IR spectra of the solid solution members present no detectable differences, while a blue shift of the PO4-related modes is seen in the Raman data. This shift can be attributed to the lanthanide contraction. Within errors, calorimetry data show no systematic deviation from an ideal behavior, though one might interpret the data as an indication of a slightly asymmetric mixture. All data indicate that deviations from ideality of the solid solution - if present - are very small.

  15. A fluorescent chemosensor for Zn(II). Exciplex formation in solution and the solid state.

    PubMed

    Bencini, Andrea; Berni, Emanuela; Bianchi, Antonio; Fornasari, Patrizia; Giorgi, Claudia; Lima, Joao C; Lodeiro, Carlos; Melo, Maria J; de Melo, J Seixas; Parola, Antonio Jorge; Pina, Fernando; Pina, Joao; Valtancoli, Barbara

    2004-07-21

    The macrocyclic phenanthrolinophane 2,9-[2,5,8-triaza-5-(N-anthracene-9-methylamino)ethyl]-[9]-1,10-phenanthrolinophane (L) bearing a pendant arm containing a coordinating amine and an anthracene group forms stable complexes with Zn(II), Cd(II) and Hg(II) in solution. Stability constants of these complexes were determined in 0.10 mol dm(-3) NMe(4)Cl H(2)O-MeCN (1:1, v/v) solution at 298.1 +/- 0.1 K by means of potentiometric (pH metric) titration. The fluorescence emission properties of these complexes were studied in this solvent. For the Zn(II) complex, steady-state and time-resolved fluorescence studies were performed in ethanol solution and in the solid state. In solution, intramolecular pi-stacking interaction between phenanthroline and anthracene in the ground state and exciplex emission in the excited state were observed. From the temperature dependence of the photostationary ratio (I(Exc)/I(M)), the activation energy for the exciplex formation (E(a)) and the binding energy of the exciplex (-DeltaH) were determined. The crystal structure of the [ZnLBr](ClO(4)).H(2)O compound was resolved, showing that in the solid state both intra- and inter-molecular pi-stacking interactions are present. Such interactions were also evidenced by UV-vis absorption and emission spectra in the solid state. The absorption spectrum of a thin film of the solid complex is red-shifted compared with the solution spectra, whereas its emission spectrum reveals the unique featureless exciplex band, blue shifted compared with the solution. In conjunction with X-ray data the solid-state data was interpreted as being due to a new exciplex where no pi-stacking (full overlap of the pi-electron cloud of the two chromophores - anthracene and phenanthroline) is observed. L is a fluorescent chemosensor able to signal Zn(II) in presence of Cd(II) and Hg(II), since the last two metal ions do not give rise either to the formation of pi-stacking complexes or to exciplex emission in solution.

  16. Thermodynamic properties of carbon in b.c.c. and f.c.c. iron-silicon-carbon solid solutions.

    NASA Technical Reports Server (NTRS)

    Chraska, P.; Mclellan, R. B.

    1971-01-01

    The equilibrium between hydrogen-methane gas mixtures and Fe-Si-C solid solutions has been investigated both as a function of temperature and carburizing gas composition. The thermodynamic properties of the carbon atoms in both b.c.c. and f.c.c. solid solution have been derived from the equilibrium measurements. The results found have been compared with those of earlier investigations and with the predictions of recent theoretical models on ternary solid solutions containing both substitutional and interstitial solute atoms.

  17. Thermodynamic analysis of the concentration profiles of epitaxial layers of nonideal solid solutions

    SciTech Connect

    Kazakov, A.I.; Kishmar, I.N.; Mokritskii, V.A.; Yakubovskii, M.V.

    1988-03-01

    Based on thermodynamic analysis employing the quasiregular approach a mathematical model of the process of equilibrium crystallization of nonideal three-component solid solutions of compounds of the type A/sup III/B/sup V/ from a restricted volume of a solution in a melt was constructed. This model enables calculation of the distribution of the components over the thickness of the epitaxial layer for low rates of cooling of the solution in a melt. The computer calculations of the concentration profiles of the epitaxial layers of Ga/sub 1-x/Al/sub x/ agreed well with the experimental data for thicknesses of the epitaxial layers up to 20 ..mu..m. For high rates of cooling the mass transfer in the volume of the solution in a melt must be taken into account.

  18. A combined analytical solution for Chemical Exchange Saturation Transfer and semi-solid Magnetization Transfer

    PubMed Central

    Zaiss, Moritz; Zu, Zhongliang; Xu, Junzhong; Schuenke, Patrick; Gochberg, Daniel F.; Gore, John C.; Ladd, Mark E.; Bachert, Peter

    2015-01-01

    Off-resonant radiofrequency irradiation in tissue indirectly lowers the water signal by saturation transfer processes: On the one hand, there are selective chemical exchange saturation transfer (CEST) effects originating from exchanging endogenous protons resonating a few ppm from water; on the other hand, there is the broad semi-solid magnetization transfer (MT) originating from immobile protons associated with the tissue matrix with kHz line-widths. Recently it was shown that endogenous CEST contrasts can be strongly affected by the MT background so that corrections are needed to derive accurate estimates of CEST effects. Herein we show that a full analytical solution of the underlying Bloch-McConnell equations for both MT and CEST provides insights into their interaction and suggests a simple means to isolate their effects. The presented analytical solution, based on the eigenspace solution of the Bloch-McConnell equations, extends previous treatments by allowing arbitrary line-shapes for the semi-solid MT effects and simultaneously describing multiple CEST pools in the presence of a large MT pool for arbitrary irradiation. The structure of the model indicates that semi-solid MT and CEST effects basically add up inversely in determining the steady-state Z-spectrum, as previously shown for direct saturation and CEST effects. Implications for existing previous CEST analyses in the presence of a semi-solid MT are studied and discussed. It turns out that to accurately quantify CEST contrast, a good reference Z-value, the observed longitudinal relaxation rate of water, and the semi-solid MT pool size fraction, must all be known. PMID:25504828

  19. Influence of chemical disorder on energy dissipation and defect evolution in concentrated solid solution alloys.

    PubMed

    Zhang, Yanwen; Stocks, G Malcolm; Jin, Ke; Lu, Chenyang; Bei, Hongbin; Sales, Brian C; Wang, Lumin; Béland, Laurent K; Stoller, Roger E; Samolyuk, German D; Caro, Magdalena; Caro, Alfredo; Weber, William J

    2015-10-28

    A grand challenge in materials research is to understand complex electronic correlation and non-equilibrium atomic interactions, and how such intrinsic properties and dynamic processes affect energy transfer and defect evolution in irradiated materials. Here we report that chemical disorder, with an increasing number of principal elements and/or altered concentrations of specific elements, in single-phase concentrated solid solution alloys can lead to substantial reduction in electron mean free path and orders of magnitude decrease in electrical and thermal conductivity. The subsequently slow energy dissipation affects defect dynamics at the early stages, and consequentially may result in less deleterious defects. Suppressed damage accumulation with increasing chemical disorder from pure nickel to binary and to more complex quaternary solid solutions is observed. Understanding and controlling energy dissipation and defect dynamics by altering alloy complexity may pave the way for new design principles of radiation-tolerant structural alloys for energy applications.

  20. Structure and magnetic properties of metastable Co-Cu solid solution nanowire arrays fabricated by electrodeposition

    NASA Astrophysics Data System (ADS)

    Wang, Tao; Li, Fashen; Wang, Ying; Song, Lijing

    2006-08-01

    Nanowire arrays of the metastable Cox Cu1-x (0.20 x 0.85) solid solution system which can not be obtained by equilibrium methods, were prepared by electrodeposition in pores of anodic aluminum oxide (AAO) template, and subsequently annealed at different temperatures. The as-deposited samples all show single phase of fcc structure, and lattice parameters decrease with the increase of Co content and fundamentally accord with Vegard's law. The phase transition with heat treatment was investigated by X-ray diffraction and differential thermal analysis (DTA) which further confirmed the formation of solid solution. With Co content increasing, the coercivity along nanowire axis for as-deposited samples increases, but it decreases for the annealed samples at 700 °C. This phenomenon was explained considering the interaction of Co particles through Cu in nanowires after phase separation.

  1. Accelerated exploration of multi-principal element alloys with solid solution phases.

    PubMed

    Senkov, O N; Miller, J D; Miracle, D B; Woodward, C

    2015-03-05

    Recent multi-principal element, high entropy alloy (HEA) development strategies vastly expand the number of candidate alloy systems, but also pose a new challenge--how to rapidly screen thousands of candidate alloy systems for targeted properties. Here we develop a new approach to rapidly assess structural metals by combining calculated phase diagrams with simple rules based on the phases present, their transformation temperatures and useful microstructures. We evaluate over 130,000 alloy systems, identifying promising compositions for more time-intensive experimental studies. We find the surprising result that solid solution alloys become less likely as the number of alloy elements increases. This contradicts the major premise of HEAs--that increased configurational entropy increases the stability of disordered solid solution phases. As the number of elements increases, the configurational entropy rises slowly while the probability of at least one pair of elements favouring formation of intermetallic compounds increases more rapidly, explaining this apparent contradiction.

  2. Accelerated exploration of multi-principal element alloys with solid solution phases

    NASA Astrophysics Data System (ADS)

    Senkov, O. N.; Miller, J. D.; Miracle, D. B.; Woodward, C.

    2015-03-01

    Recent multi-principal element, high entropy alloy (HEA) development strategies vastly expand the number of candidate alloy systems, but also pose a new challenge—how to rapidly screen thousands of candidate alloy systems for targeted properties. Here we develop a new approach to rapidly assess structural metals by combining calculated phase diagrams with simple rules based on the phases present, their transformation temperatures and useful microstructures. We evaluate over 130,000 alloy systems, identifying promising compositions for more time-intensive experimental studies. We find the surprising result that solid solution alloys become less likely as the number of alloy elements increases. This contradicts the major premise of HEAs—that increased configurational entropy increases the stability of disordered solid solution phases. As the number of elements increases, the configurational entropy rises slowly while the probability of at least one pair of elements favouring formation of intermetallic compounds increases more rapidly, explaining this apparent contradiction.

  3. Influence of chemical disorder on energy dissipation and defect evolution in concentrated solid solution alloys

    SciTech Connect

    Zhang, Yanwen; Stocks, George Malcolm; Jin, Ke; Lu, Chenyang; Bei, Hongbin; Sales, Brian C.; Wang, Lumin; Béland, Laurent K.; Stoller, Roger E.; Samolyuk, German D.; Caro, Magdalena; Caro, Alfredo; Weber, William J.

    2015-10-28

    A long-standing objective in materials research is to understand how energy is dissipated in both the electronic and atomic subsystems in irradiated materials, and how related non-equilibrium processes may affect defect dynamics and microstructure evolution. Here we show that alloy complexity in concentrated solid solution alloys having both an increasing number of principal elements and altered concentrations of specific elements can lead to substantial reduction in the electron mean free path and thermal conductivity, which has a significant impact on energy dissipation and consequentially on defect evolution during ion irradiation. Enhanced radiation resistance with increasing complexity from pure nickel to binary and to more complex quaternary solid solutions is observed under ion irradiation up to an average damage level of 1 displacement per atom. Understanding how materials properties can be tailored by alloy complexity and their influence on defect dynamics may pave the way for new principles for the design of radiation tolerant structural alloys.

  4. Point defect concentrations and solid solution hardening in NiAl with Fe additions

    SciTech Connect

    Pike, L.M.; Chang, Y.A.; Liu, C.T.

    1997-08-01

    The solid solution hardening behavior exhibited when Fe is added to NiAl is investigated. This is an interesting problem to consider since the ternary Fe additions may choose to occupy either the Ni or the Al sublattice, affecting the hardness at differing rates. Moreover, the addition of Fe may affect the concentrations of other point defects such as vacancies and Ni anti-sites. As a result, unusual effects ranging from rapid hardening to solid solution softening are observed. Alloys with varying amounts of Fe were prepared in Ni-rich (40 at. % Al) and stoichiometric (50 at. % Al) compositions. Vacancy concentrations were measured using lattice parameter and density measurements. The site occupancy of Fe was determined using ALCHEMI. Using these two techniques the site occupancies of all species could be uniquely determined. Significant differences in the defect concentrations as well as the hardening behavior were encountered between the Ni-rich and stoichiometric regimes.

  5. Influence of chemical disorder on energy dissipation and defect evolution in concentrated solid solution alloys

    PubMed Central

    Zhang, Yanwen; Stocks, G. Malcolm; Jin, Ke; Lu, Chenyang; Bei, Hongbin; Sales, Brian C.; Wang, Lumin; Béland, Laurent K.; Stoller, Roger E.; Samolyuk, German D.; Caro, Magdalena; Caro, Alfredo; Weber, William J.

    2015-01-01

    A grand challenge in materials research is to understand complex electronic correlation and non-equilibrium atomic interactions, and how such intrinsic properties and dynamic processes affect energy transfer and defect evolution in irradiated materials. Here we report that chemical disorder, with an increasing number of principal elements and/or altered concentrations of specific elements, in single-phase concentrated solid solution alloys can lead to substantial reduction in electron mean free path and orders of magnitude decrease in electrical and thermal conductivity. The subsequently slow energy dissipation affects defect dynamics at the early stages, and consequentially may result in less deleterious defects. Suppressed damage accumulation with increasing chemical disorder from pure nickel to binary and to more complex quaternary solid solutions is observed. Understanding and controlling energy dissipation and defect dynamics by altering alloy complexity may pave the way for new design principles of radiation-tolerant structural alloys for energy applications. PMID:26507943

  6. Flexible, Luminescent Metal-Organic Frameworks Showing Synergistic Solid-Solution Effects on Porosity and Sensitivity.

    PubMed

    Liu, Si-Yang; Zhou, Dong-Dong; He, Chun-Ting; Liao, Pei-Qin; Cheng, Xiao-Ning; Xu, Yan-Tong; Ye, Jia-Wen; Zhang, Jie-Peng; Chen, Xiao-Ming

    2016-12-23

    Mixing molecular building blocks in the solid solution manner is a valuable strategy to obtain structures and properties in between the isostructural parent metal-organic frameworks (MOFs). We report nonlinear/synergistic solid-solution effects using highly related yet non-isostructural, phosphorescent Cu(I) triazolate frameworks as parent phases. Near the phase boundaries associated with conformational diversity and ligand heterogeneity, the porosity (+150 %) and optical O2 sensitivity (410 times, limit of detection 0.07 ppm) can be drastically improved from the best-performing parent MOFs and even exceeds the records hold by precious-metal complexes (3 ppm) and C70 (0.2 ppm).

  7. Isomorphism and solid solution as shown by an accurate high-resolution diffraction experiment.

    PubMed

    Poulain, Agnieszka; Kubicki, Maciej; Lecomte, Claude

    2014-12-01

    High-resolution crystal structure determination and spherical and multipolar refinement enabled an organic solid solution of 1-(4'-chlorophenyl)-2-methyl-4-nitro-1H-imidazole-5-carbonitrile and 5-bromo-1-(4'-chlorophenyl)-2-methyl-4-nitro-1H-imidazole to be found, which would not normally be revealed using only standard resolution data (ca 0.8 Å), as the disordered part is only visible at high resolution. Therefore, this new structure would have been reported as just another polymorphic form, even more reasonably as isostructural with other derivatives. To the best of our knowledge this is the first example of organic solid solution modelled via charge density Hansen-Coppens formalism and analysed by means of quantum theory of atoms in molecules (QTAIM) theory.

  8. Tunable catalytic activity of solid solution metal-organic frameworks in one-pot multicomponent reactions.

    PubMed

    Aguirre-Díaz, Lina María; Gándara, Felipe; Iglesias, Marta; Snejko, Natalia; Gutiérrez-Puebla, Enrique; Monge, M Ángeles

    2015-05-20

    The aim of this research is to establish how metal-organic frameworks (MOFs) composed of more than one metal in equivalent crystallographic sites (solid solution MOFs) exhibit catalytic activity, which is tunable by virtue of the metal ions ratio. New MOFs with general formula [InxGa1-x(O2C2H4)0.5(hfipbb)] were prepared by the combination of Ga and In. They are isostructural with their monometal counterparts, synthesized with Al, Ga, and In. Differences in their behavior as heterogeneous catalysts in the three-component, one pot Strecker reaction illustrate the potential of solid solution MOFs to provide the ability to address the various stages involved in the reaction mechanism.

  9. Preparation of Li2S-P2S5 solid electrolyte from N-methylformamide solution and application for all-solid-state lithium battery

    NASA Astrophysics Data System (ADS)

    Teragawa, Shingo; Aso, Keigo; Tadanaga, Kiyoharu; Hayashi, Akitoshi; Tatsumisago, Masahiro

    2014-02-01

    Electrode-solid electrolyte composite materials for all-solid-state lithium batteries were prepared by coating of the Li2S-P2S5 solid electrolyte onto LiCoO2 particles using a N-methylformamide (NMF) solution of 80Li2S·20P2S5 (mol%) solid electrolyte. SEM and EDX analysis showed that the Li2S-P2S5 solid electrolyte was uniformly coated on LiCoO2 particles. The all-solid-state cell using the LiCoO2 particles coated with the solid electrolyte showed higher charge-discharge capacity than the cells using uncoated LiCoO2 particles.

  10. Solution-Liquid-Solid Synthesis of Hexagonal Nickel Selenide Nanowire Arrays with a Nonmetal Catalyst.

    PubMed

    Xu, Kun; Ding, Hui; Jia, Kaicheng; Lu, Xiuli; Chen, Pengzuo; Zhou, Tianpei; Cheng, Han; Liu, Si; Wu, Changzheng; Xie, Yi

    2016-01-26

    Inorganic nanowire arrays hold great promise for next-generation energy storage and conversion devices. Understanding the growth mechanism of nanowire arrays is of considerable interest for expanding the range of applications. Herein, we report the solution-liquid-solid (SLS) synthesis of hexagonal nickel selenide nanowires by using a nonmetal molecular crystal (selenium) as catalyst, which successfully brings SLS into the realm of conventional low-temperature solution synthesis. As a proof-of-concept application, the NiSe nanowire array was used as a catalyst for electrochemical water oxidation. This approach offers a new possibility to design arrays of inorganic nanowires.

  11. Photoinduced processes in solid polymer solutions of dyes in an interference field of laser radiation

    SciTech Connect

    Sizykh, A G; Tarakanova, E A

    1998-12-31

    An investigation was made of the relationships governing the photochemical mechanism of formation of light-induced gratings in solid polymer solutions of a dye with a high quantum yield of the triplet states. The combined analysis of the results of real and numerical experiments was made for a solution of eosin K in gelatin. The protonation rate constant of the dye was measured and the dependence of the diffraction efficiency on the duration of irradiation was explained taking diffusion of the dye into account. A method was proposed for determination of the duffusion coefficient in a spatially modified interference field of the laser radiation. The diffusion coefficients were found. (nonlinear optical phenomena)

  12. Solution-Processed Ambipolar Organic Thin-Film Transistors by Blending p- and n-Type Semiconductors: Solid Solution versus Microphase Separation.

    PubMed

    Xu, Xiaomin; Xiao, Ting; Gu, Xiao; Yang, Xuejin; Kershaw, Stephen V; Zhao, Ni; Xu, Jianbin; Miao, Qian

    2015-12-30

    Here, we report solid solution of p- and n-type organic semiconductors as a new type of p-n blend for solution-processed ambipolar organic thin film transistors (OTFTs). This study compares the solid-solution films of silylethynylated tetraazapentacene 1 (acceptor) and silylethynylated pentacene 2 (donor) with the microphase-separated films of 1 and 3, a heptagon-embedded analogue of 2. It is found that the solid solutions of (1)x(2)1-x function as ambipolar semiconductors, whose hole and electron mobilities are tunable by varying the ratio of 1 and 2 in the solid solution. The OTFTs of (1)0.5(2)0.5 exhibit relatively balanced hole and electron mobilities comparable to the highest values as reported for ambipolar OTFTs of stoichiometric donor-acceptor cocrystals and microphase-separated p-n bulk heterojunctions. The solid solution of (1)0.5(2)0.5 and the microphase-separated blend of 1:3 (0.5:0.5) in OTFTs exhibit different responses to light in terms of absorption and photoeffect of OTFTs because the donor and acceptor are mixed at molecular level with π-π stacking in the solid solution.

  13. X-ray diffraction study of gold nitride films: Observation of a solid solution phase

    NASA Astrophysics Data System (ADS)

    Alves, L.; Hase, T. P. A.; Hunt, M. R. C.; Brieva, A. C.; Šiller, L.

    2008-12-01

    The structure of nitride containing gold films produced by reactive ion sputtering and nitrogen plasma etching is investigated using x-ray photoelectron spectroscopy and x-ray diffraction. It is found that gold nitride is a solid solution of nitrogen atoms dissolved in a fcc gold matrix. Differences between the strain and lattice parameters of gold and gold nitride films were observed and are explained by interstitial nitrogen present in the latter.

  14. Properties of solid solutions, doped film, and nanocomposite structures based on zinc oxide

    NASA Astrophysics Data System (ADS)

    Lashkarev, G. V.; Shtepliuk, I. I.; Ievtushenko, A. I.; Khyzhun, O. Y.; Kartuzov, V. V.; Ovsiannikova, L. I.; Karpyna, V. A.; Myroniuk, D. V.; Khomyak, V. V.; Tkach, V. N.; Timofeeva, I. I.; Popovich, V. I.; Dranchuk, N. V.; Khranovskyy, V. D.; Demydiuk, P. V.

    2015-02-01

    A study of the properties of materials based on the wide bandgap zinc oxide semiconductor, which are promising for application in optoelectronics, photovoltaics and nanoplasmonics. The structural and optical properties of solid solution Zn1-xCdxO films with different cadmium content, are studied. The samples are grown using magnetron sputtering on sapphire backing. Low-temperature photoluminescence spectra revealed emission peaks associated with radiative recombination processes in those areas of the film that have varying amounts of cadmium. X-ray phase analysis showed the presence of a cadmium oxide cubic phase in these films. Theoretical studies of the solid solution thermodynamic properties allowed for a qualitative interpretation of the observed experimental phenomena. It is established that the growth of the homogeneous solid solution film is possible only at high temperatures, whereas regions of inhomogeneous composition can be narrowed through elastic deformation, caused by the mismatch of the film-backing lattice constants. The driving forces of the spinodal decomposition of the Zn1-xCdxO system are identified. Fullerene-like clusters of Znn-xCdxOn are used to calculate the bandgap and the cohesive energy of ZnCdO solid solutions. The properties of transparent conductive ZnO films, doped with Group III donor impurities (Al, Ga, In), are examined. It is shown that oxygen vacancies are responsible for the hole trap centers in the zinc oxide photoconductivity process. We also examine the photoluminescence properties of metal-ZnO nanocomposite structures, caused by surface plasmons.

  15. Saturation magnetization in supersaturated solid solution of Co-Cu alloy

    NASA Astrophysics Data System (ADS)

    Yuasa, Motohiro; Kajikawa, Kota; Hakamada, Masataka; Mabuchi, Mamoru

    2009-10-01

    The magnetovolume effect has been investigated using a supersaturated solid solution of a Co-19 at. %Cu alloy processed by electrodeposition. The enhanced saturation magnetization of the Co-Cu alloy was attributed to both metastable fcc Co and lattice expansion. The density functional theory using the CASTEP code revealed that an enhanced magnetic moment due to the magnetovolume effect is obtained in fcc Co, but not in hcp Co.

  16. Damage accumulation in ion-irradiated Ni-based concentrated solid-solution alloys

    SciTech Connect

    Ullah, Mohammad W.; Aidhy, Dilpuneet S.; Zhang, Yanwen; Weber, William J.

    2016-01-01

    We investigate Irradiation-induced damage accumulation in Ni0.8Fe0.2 and Ni0.8Cr0.2 alloys by using molecular dynamics simulations to assess possible enhanced radiation-resistance in these face-centered cubic (fcc), single-phase, concentrated solid-solution alloys, as compared with pure fcc Ni.

  17. Molecular tectonics: crystal engineering of mixed valence Fe(II)/Fe(III) solid solutions.

    PubMed

    Dechambenoit, Pierre; Ferlay, Sylvie; Kyritsakas, Nathalie; Hosseini, Mir Wais

    2010-02-14

    Based on isostructurality between crystals formed upon combining the dicationic tecton 2 with either M(3)Fe(III)(CN)(6) or M(4)Fe(II)(CN)(6) (M = Cs), a rare example of an H-bonded mixed valence Fe(ii)-Fe(iii) solid solution ((Cs(2)2(3)-[Fe(II)(CN)(6)](2))(0.83)(2(3)-[Fe(III)(CN)(6)](2))(0.17))) and curious necklace-like composite crystals were generated.

  18. A novel quaternary solid solution photo-absorber material for photoelectrochemical hydrogen generation.

    PubMed

    Hong, Tiantian; Liu, Zhifeng; Yan, Weiguo; Wang, Bo; Zhang, Xueqi; Liu, Junqi; Wang, Junkai; Han, Jianhua

    2015-09-14

    We report a novel quaternary solid solution (Ag-Cu-Sb-S or ACSS) serving as a photo-absorber material in the photoelectrochemical field for the first time, and ZnO/ACSS nanoarrays exhibited a photocurrent density of 4.45 mA cm(-2). The research indicates that ZnO/ACSS composite structures have enormous potential in PEC hydrogen generation systems.

  19. Investigation of Self-Organized Nanoheterostructure Properties in InGaAsP Solid Solutions

    DTIC Science & Technology

    1998-06-01

    UNCLASSIFIED Defense Technical Information Center Compilation Part Notice ADP012787 TITLE: Investigation of Self-Organized Nanoheterostructure ... nanoheterostructure properties in InGaAsP solid solutions I S. Tarasov, 1. N. Arsent’ev, N. A. Bert, L. S. Vavilova, V.A. Kapitonov, A. V. Murashova...organized InGaAsP nanoheterostructures grown on InP and GaAs substrates have been investigated by photoluminescence and transmission electron microscopy

  20. Experimental and theoretical investigation of Cr1-xScxN solid solutions for thermoelectrics

    NASA Astrophysics Data System (ADS)

    Kerdsongpanya, Sit; Sun, Bo; Eriksson, Fredrik; Jensen, Jens; Lu, Jun; Koh, Yee Kan; Nong, Ngo Van; Balke, Benjamin; Alling, Björn; Eklund, Per

    2016-12-01

    The ScN- and CrN-based transition-metal nitrides have recently emerged as a novel and unexpected class of materials for thermoelectrics. These materials constitute well-defined model systems for investigating mixing thermodynamics, phase stability, and band structure aiming for property tailoring. Here, we demonstrate an approach to tailor their thermoelectric properties by solid solutions. The trends in mixing thermodynamics and densities-of-states (DOS) of rocksalt-Cr1-xScxN solid solutions (0 ≤ x ≤ 1) are investigated by first-principles calculations, and Cr1-xScxN thin films are synthesized by magnetron sputtering. Pure CrN exhibits a high power factor, 1.7 × 10-3 W m-1 K-2 at 720 K, enabled by a high electron concentration thermally activated from N vacancies. Disordered rocksalt-Cr1-xScxN solid solutions are thermodynamically stable, and calculated DOS suggest the possibility for power-factor improvement by Sc3d orbital delocalization on Cr3d electrons giving decreasing electrical resistivity, while localized Cr3d orbitals with a large DOS slope may yield an improved Seebeck coefficient. Sc-rich solid solutions show a large improvement in power factor compared to pure ScN, and all films have power factors above that expected from the rule-of-mixture. These results corroborate the theoretical predictions and enable tailoring and understanding of structure-transport-property correlations of Cr1-xScxN.

  1. Precipitation of Ordered Phases in Metallic Solid Solutions: A Synergistic Clustering and Ordering Process (Preprint)

    DTIC Science & Technology

    2011-07-01

    of such concurrent clustering and ordering processes in metallic solid solutions including Fe-Al [4], Ni-Al [5,6], Ni-Ti [7,8], and Cu -Ti [9,10...ordering reaction to take place. The proposition is that since the Cu -15Ni-8Sn alloy composition cannot undergo congruent ordering, spinodal...interpretation of their results. For example, Wendt and Hassan noted from [14] that in samples of the quenched alloy that have been briefly aged

  2. High-Performance Hydrogen Evolution from MoS2(1-x) P(x) Solid Solution.

    PubMed

    Ye, Ruquan; del Angel-Vicente, Paz; Liu, Yuanyue; Arellano-Jimenez, M Josefina; Peng, Zhiwei; Wang, Tuo; Li, Yilun; Yakobson, Boris I; Wei, Su-Huai; Yacaman, Miguel Jose; Tour, James M

    2016-02-17

    A MoS2(1-x) P(x) solid solution (x = 0 to 1) is formed by thermally annealing mixtures of MoS2 and red phosphorus. The effective and stable electrocatalyst for hydrogen evolution in acidic solution holds promise for replacing scarce and expensive platinum that is used in present catalyst systems. The high performance originates from the increased surface area and roughness of the solid solution.

  3. Shape-controlled ceria-based nanostructures for catalysis applications.

    PubMed

    Qiao, Zhen-An; Wu, Zili; Dai, Sheng

    2013-10-01

    Among oxide catalysts, ceria is a technologically important material because of its wide applications as a promoter in three-way catalysts for the elimination of toxic exhaust gases, low-temperature water-gas-shift reaction, oxygen sensors, oxygen permeation membrane systems, and fuel cells. The catalytic activities of cerium oxide are highly dependent on interfacial structures and nanocrystal morphologies. This Minireview highlights the recent progress in the research of ceria nanoshapes as both catalysts and catalyst supports, including the synthesis, structure characterization, catalytic properties, surface chemistry, as well as reaction mechanisms. Insights from in situ spectroscopy study and theoretical modeling of nanostructured ceria-based materials have shed light on the origin of the ceria shape effect. It is suggested that the surface structure of ceria controls the catalytic activity and selectivity through structure-dependent surface-site geometry, surface vacancy formation energy, defect sites, and coordinatively unsaturated sites on ceria. The morphology-dependent catalysis in ceria has offered a new strategy to finely tune the catalytic activity and selectivity through shape control without altering the catalyst composition. A brief summary and an outlook on this research field will be presented at the end.

  4. Pulmonary toxicity of ceria nanoparticles in mice after intratracheal instillation.

    PubMed

    Xue, Lingxi; He, Xiao; Li, Yuanyuan; Qu, Meihua; Zhang, Zhiyong

    2013-10-01

    Ceria nanoparticles (nano-ceria) are widely used for various applications such as catalytic converters for automobile exhaust, ultraviolet absorber, and electrolyte in fuel cells. Their potential impacts on the environment and human health have also drawn people's attention. The present study was designed to explore the pulmonary toxicity of nano-ceria in mice after an acute intratracheal instillation. CD-1 mice were exposed to 0.04, 0.4, 4 and 40 microg nano-ceria (corresponding to 10, 100, 1000 and 10000 times of the maximum exposure dose, respectively) and sacrificed at 1, 7, and 28 d post-exposure. Lung injury was assessed by bronchoalveolar ravage fluid (BALF) analysis, cell counts, biochemical analysis of lung homogenate, and histopathology. Cell differential analysis of the BALF show that the numbers of neutrophils and lymphocytes increased significantly in the mice exposed to 40 microg nano-ceria at 1 d after instillation, and returned to control levels by 7 d. The lactate dehydrogenate activity in the BALF from the 40 microg group increased significantly during the whole experimental period. Pathological changes were only found in the lung tissues from the mice of 40 microg nano-ceria group. The changes were most obvious by 7 d post-exposure, and returned to normal by 28 d. No other changes were found. The results of the present study suggest that exposure to nano-ceria at the current levels in the ambient air may not cause respiratory toxicity.

  5. Uptake and distribution of ceria nanoparticles in cucumber plants.

    PubMed

    Zhang, Zhiyong; He, Xiao; Zhang, Haifeng; Ma, Yuhui; Zhang, Peng; Ding, Yayun; Zhao, Yuliang

    2011-08-01

    The presence and release of nanoparticles (NPs) into the environment have important implications for human health and the environment. A critical aspect of the risk assessment of nanoparticles is to understand the interactions of manufactured nanoparticles with plants. In this study, the uptake and distribution characteristics of two types of ceria nanoparticles with sizes of ca. 7 nm and 25 nm in cucumber plants were investigated using a radiotracer method and other techniques. With increasing concentration of the nanoparticles, concentration dependent absorption by the plant roots was noticed, but the majority of the particles only loosely adhered to the root surface. The seedlings treated with 7 nm ceria particles showed significantly higher ceria contents in both roots and shoots than those exposed to 25 nm ceria particles at all test concentrations (2, 20, and 200 mg L(-1)). Only very limited amounts of ceria nanoparticles could be transferred from the roots to shoots because the entry of nanoparticles into the roots was difficult. However, the results of tissue distributions of ceria nanoparticles in the plants and two dimensional distributions of the particles in the leaves imply that once they have entered into the vascular cylinder, ceria nanoparticles could move smoothly to the end of the vascular bundle along with water flow. To the best of our knowledge, this is the first detailed study of uptake and distribution of metal oxide nanoparticles in plants.

  6. Synthesis of nanocrystalline yttria doped ceria powder by urea-formaldehyde polymer gel auto-combustion process

    SciTech Connect

    Biswas, M.; Prabhakaran, K. . E-mail: kp2952002@yahoo.co.uk; Gokhale, N.M.; Sharma, S.C.

    2007-04-12

    Nanocrystalline yttria doped ceria powder has been prepared by auto-combustion of a transparent gel formed by heating an aqueous acidic solution containing methylol urea, urea, cerium(III) nitrate and yttrium(III) nitrate. The TGA and DSC studies showed the combustion reaction of the gel initiated at 225 deg. C and completed within a short period of time. XRD spectrum of the combustion product reveals the formation of phase pure cubic yttria doped ceria during the combustion process. Loose agglomerate of yttria doped ceria particle obtained by the combustion reaction could be easily deagglomerated by planetary ball milling and the powder obtained contains particles in the size range of 0.05-3.3 {mu}m with D {sub 50} value of 0.13 {mu}m. The powder particles are aggregate of nanocrystallites with a wide size range of 14-105 nm. Pellets prepared by pressing the yttria doped ceria powder sintered to 95.2% TD at 1400 deg. C.

  7. CSBB-ConeExclusion, adapting structure based solution virtual screening to libraries on solid support.

    PubMed

    Shave, Steven; Auer, Manfred

    2013-12-23

    Combinatorial chemical libraries produced on solid support offer fast and cost-effective access to a large number of unique compounds. If such libraries are screened directly on-bead, the speed at which chemical space can be explored by chemists is much greater than that addressable using solution based synthesis and screening methods. Solution based screening has a large supporting body of software such as structure-based virtual screening tools which enable the prediction of protein-ligand complexes. Use of these techniques to predict the protein bound complexes of compounds synthesized on solid support neglects to take into account the conjugation site on the small molecule ligand. This may invalidate predicted binding modes, the linker may be clashing with protein atoms. We present CSBB-ConeExclusion, a methodology and computer program which provides a measure of the applicability of solution dockings to solid support. Output is given in the form of statistics for each docking pose, a unique 2D visualization method which can be used to determine applicability at a glance, and automatically generated PyMol scripts allowing visualization of protein atom incursion into a defined exclusion volume. CSBB-ConeExclusion is then exemplarically used to determine the optimum attachment point for a purine library targeting cyclin-dependent kinase 2 CDK2.

  8. Characterizing SiC-AlN semiconductor solid solutions with indirect and direct bandgaps

    NASA Astrophysics Data System (ADS)

    Dallaeva, Dinara; Ramazanov, Shikhgasan; Ramazanov, Gusejn; Akhmedov, Ramazan; Tománek, Pavel

    2015-01-01

    The objective of the study is to characterize the dependence of the optical properties of solid solutions of silicon carbide and aluminum nitride on composition. Even small differences in composition provide manipulation of band gap features over a wide range. Data for this paper were collected by X-ray diffraction, photoluminescence and absorption spectroscopy. The evolution of the observed optical properties as a result of compositional changes were studied. X-ray studies confirm the presence of a(SiC)1-x(AlN)x solid solution. Investigation of absorption spectra shows the optical band gap of the sample with composition (SiC)0,88(AlN)0,12 is 3.5eV, and 4.24 eV for the (SiC)0,36(AlN)0,64 solid solution. The photoluminescence spectra demonstrate the strong dependence of the spectra on composition x. The experimental results are in agreement with theory. These data demonstrate the optimization of optical properties for particular optoelectronic applications by varying the (SiC)1-x(AlN)xcomposition.

  9. Synthesis of complex metal oxides using hydroxide, cyanide, and nitrate solid solution precursors

    NASA Astrophysics Data System (ADS)

    Vidyasagar, K.; Gopalakrishnan, J.; Rao, C. N. R.

    1985-06-01

    Precursor solid solutions provide convenient routes for preparing complex metal oxides. Hydroxide solid solutions of the general formula Ln1- xMx(OH) 3 (where Ln = La or Nd and M = Al, Cr, Fe, Co, or Ni) and La 1- x- yM' xM″ y(OH) 3 (where M' = Ni and M″ = Co or Cu) crystallize in the rare earth trihydroxide structure and can be decomposed at relatively low temperatures to yield complex metal oxides. Several oxides of the type LaNiO 3, NdNiO 3, LaNi 1- xCo xO 3, and LaNi 1- xCu xO 3 have been prepared by the hydroxide precursor route. Thermal decomposition of cyanide precursors of the type Ln[ M1- xM' x(CN) 6] · 5H 2O and Ln1- xLn' x[ M(CN) 6] · 5H 2O yields the quaternary oxides which are not readily made by ceramic methods. Nitrate solid solution precursors of the type Ba 1- xPb x(NO 3) 2, Sr 1- xPb x(NO 3) 2, and BaSrPb(NO 3) 6 have been used for preparing several interesting oxides such as BaPbO 3, Ba 2PbO 4, and BaSrPbO 4.

  10. Controls of carbonate mineralogy and solid-solution of Mg in calcite: evidence from spelean systems

    SciTech Connect

    Gonzalez, L.A.; Lohmann, K.C.

    1985-01-01

    Precipitation of carbonate minerals in spelean systems occurs under a wide range of fluid chemistry, Mg-Ca ratios, alkalinities, pH and temperatures; thus, spelean systems provide ideal settings to determine factors controlling the mineralogy of precipitated carbonates and solid-solution of Mg in calcite. Cave waters and actively-precipitating carbonate speleothems were collected from Carlsbad Caverns National Park, New Mexico and the Mammoth-Flint Cave System, Kentucky. Carbonate mineralogy of precipitated phases was determined by x-ray diffraction, and major and minor element composition of waters and accompanying minerals were determined by Atomic Absorption Spectrophotometry. Results demonstrate that at a constant CO3 concentration the precipitation threshold for calcite to aragonite is controlled dominantly by the Mg/Ca ratio of the ambient fluid. Aragonite precipitation is favored by high Mg/Ca ratios. Conversely, with increasing CO3 concentration at constant fluid Mg/Ca ratios, calcite is preferentially precipitated. Solid-solution of Mg in calcite is positively correlated with both increased Mg/Ca ratios and CO3 concentrations. These data suggest that Mg contents of calcite can not be defined solely in terms of a homogeneous distribution coefficient. Rather, Mg concentrations can be also be affected by the CO3 concentration and degree of calcite saturation, suggesting that the rate of crystal growth also plays and important role in Mg solid-solution in calcites.

  11. Solid solution partitioning of Sr 2+, Ba 2+, and Cd 2+ to calcite

    NASA Astrophysics Data System (ADS)

    Tesoriero, Anthony J.; Pankow, James F.

    1996-03-01

    Although solid solutions play important roles in controlling the concentrations of minor metal ions in natural waters, uncertainties regarding their compositions, thermodynamics, and kinetics usually prevent them from being considered. A range of precipitation rates was used here to study the nonequilibrium and equilibrium partitioning behaviors of Sr 2+, Ba 2+, and Cd 2+ to calcite (CaCO 3(s)). The distribution coefficient of a divalent metal ion Me 2+ for partitioning from an aqueous solution into calcite is given by DMe = ( XMeCO 3(s)/[Me 2+])/( XCaCO 3(s)/[Ca 2+]). The X values are solid-phase mole fractions; the bracketed values are the aqueous molal concentrations. In agreement with prior work, at intermediate to high precipitation rates R (nmol/mg-min), DSr, DBa, and DCd were found to depend strongly on R. At low R, the values of DSr, DBa, and DCd became constant with R. At 25 °C, the equilibrium values for DSr, DBa, and DCd for dilute solid solutions were estimated to be 0.021 ± 0.003, 0.012 ± 0.005, and 1240 ± 300, respectively. Calculations using these values were made to illustrate the likely importance of partitioning of these ions to calcite in groundwater systems. Due to its large equilibrium DMe value, movement of Cd 2+ will be strongly retarded in aquifers containing calcite; Sr 2+ and Ba 2+ will not be retarded nearly as much.

  12. Local structure in the disordered solid solution of cis- and trans-perinones.

    PubMed

    Teteruk, Jaroslav L; Glinnemann, Jürgen; Heyse, Winfried; Johansson, Kristoffer E; van de Streek, Jacco; Schmidt, Martin U

    2016-06-01

    The cis- and trans-isomers of the polycyclic aromatic compound perinone, C26H12N4O2, form a solid solution (Vat Red 14). This solid solution is isotypic to the crystal structures of cis-perinone (Pigment Red 194) and trans-perinone (Pigment Orange 34) and exhibits a combined positional and orientational disorder: In the crystal, each molecular position is occupied by either a cis- or trans-perinone molecule, both of which have two possible molecular orientations. The structure of cis-perinone exhibits a twofold orientational disorder, whereas the structure of trans-perinone is ordered. The crystal structure of the solid solution was determined by single-crystal X-ray analysis. Extensive lattice-energy minimizations with force-field and DFT-D methods were carried out on combinatorially complete sets of ordered models. For the disordered systems, local structures were calculated, including preferred local arrangements, ordering lengths, and probabilities for the arrangement of neighbouring molecules. The superposition of the atomic positions of all energetically favourable calculated models corresponds well with the experimentally determined crystal structures, explaining not only the atomic positions, but also the site occupancies and anisotropic displacement parameters.

  13. Solid Solution Photocatalyst with Spontaneous Polarization Exhibiting Low Recombination Toward Efficient CO2 Photoreduction.

    PubMed

    Zhou, Peng; Wang, Xin; Yan, Shicheng; Zou, Zhigang

    2016-08-23

    Decreasing the recombination of photogenerated carriers is a major challenge for efficiently converting solar energy into chemical energy by photocatalysis. Here, we have demonstrated that growth of a polar GaN:ZnO solid solution single crystal along its polarization axis is beneficial to efficient separation of photogenerated carriers, owing to the periodic potential barriers and wells generated from the periodically positive and negative atom arrangements in crystal structure. Local charge imbalance caused by replacing Ga(3+) with Zn(2+) leads to a polarization vector in the {0 0 0 1} planes of GaN:ZnO solid solution, thus forming a 1 D electron transport path along [2 1‾  1‾  0] in the {0 0 0 1} planes of GaN:ZnO solid solution to decrease recombination. Shorting the hole-transport distance by synthesizing porous nanoplates can further decrease recombination under the polarization field and improve the performance of polar photocatalyst in photoreduction of CO2 into CH4 .

  14. Solid solution partitioning of Sr2+, Ba2+, and Cd2+ to calcite

    USGS Publications Warehouse

    Tesoriero, A.J.; Pankow, J.F.

    1996-01-01

    Although solid solutions play important roles in controlling the concentrations of minor metal ions in natural waters, uncertainties regarding their compositions, thermodynamics, and kinetics usually prevent them from being considered. A range of precipitation rates was used here to study the nonequilibrium and equilibrium partitioning behaviors of Sr2+, Ba2+, and Cd2+ to calcite (CaCO3(s)). The distribution coefficient of a divalent metal ion Me2+ for partitioning from an aqueous solution into calcite is given by DMe = (XMeCO3(s)/[Me2+])/(XCaCO3(s)/[Ca 2+]). The X values are solid-phase mole fractions; the bracketed values are the aqueous molal concentrations. In agreement with prior work, at intermediate to high precipitation rates R (nmol/mg-min), DSr, DBa, and DCd were found to depend strongly on R. At low R, the values of DSr, DBa, and DCd became constant with R. At 25??C, the equilibrium values for DSr, DBa, and DCd for dilute solid solutions were estimated to be 0.021 ?? 0.003, 0.012 ?? 0.005, and 1240 ?? 300, respectively. Calculations using these values were made to illustrate the likely importance of partitioning of these ions to calcite in groundwater systems. Due to its large equilibrium DMe value, movement of Cd2+ will be strongly retarded in aquifers containing calcite; Sr2+ and Ba2+ will not be retarded nearly as much.

  15. A decontamination system for chemical weapons agents using a liquid solution on a solid sorbent.

    PubMed

    Waysbort, Daniel; McGarvey, David J; Creasy, William R; Morrissey, Kevin M; Hendrickson, David M; Durst, H Dupont

    2009-01-30

    A decontamination system for chemical warfare agents was developed and tested that combines a liquid decontamination reagent solution with solid sorbent particles. The components have fewer safety and environmental concerns than traditional chlorine bleach-based products or highly caustic solutions. The liquid solution, based on Decon Greentrade mark, has hydrogen peroxide and a carbonate buffer as active ingredients. The best solid sorbents were found to be a copolymer of ethylene glycol dimethacrylate and n-lauryl methacrylate (Polytrap 6603 Adsorber); or an allyl methacrylate cross-linked polymer (Poly-Pore E200 Adsorber). These solids are human and environmentally friendly and are commonly used in cosmetics. The decontaminant system was tested for reactivity with pinacolyl methylphosphonofluoridate (Soman, GD), bis(2-chloroethyl)sulfide (Mustard, HD), and S-(2-diisopropylaminoethyl) O-ethyl methylphosphonothioate (VX) by using NMR Spectroscopy. Molybdate ion (MoO(4)(-2)) was added to the decontaminant to catalyze the oxidation of HD. The molybdate ion provided a color change from pink to white when the oxidizing capacity of the system was exhausted. The decontaminant was effective for ratios of agent to decontaminant of up to 1:50 for VX (t(1/2) < or = 4 min), 1:10 for HD (t(1/2) < 2 min with molybdate), and 1:10 for GD (t(1/2) < 2 min). The vapor concentrations of GD above the dry sorbent and the sorbent with decontamination solution were measured to show that the sorbent decreased the vapor concentration of GD. The E200 sorbent had the additional advantage of absorbing aqueous decontamination solution without the addition of an organic co-solvent such as isopropanol, but the rate depended strongly on mixing for HD.

  16. Influence of the activation conditions on the elimination of residual impurities on ceria-zirconia mixed oxides

    NASA Astrophysics Data System (ADS)

    Daturi, M.; Binet, C.; Lavalley, J. C.; Vidal, H.; Kaspar, J.; Graziani, M.; Blanchard, G.

    1998-10-01

    A series of samples belonging to the ceria-zirconia solid solution has been investigated from the point of view of surface impurities, via TPO/TPD and FTIR spectroscopy. Species likely due either to the precursors or to atmospheric contamination have been taken into account and their stability has been studied following two different thermal treatments. A complete cleaning treatment is proposed in order to obtain powders of satisfactory quality for catalytic purposes. Les impuretés superficielles contenues dans une série d'oxydes mixtes cérine- zircone ont été étudiées par TPO/TPD et spectroscopie infrarouge. Les impuretés provenant soit des précurseurs soit de la contamination atmosphérique (carbonates) ont été identifiées et leur stabilité thermique a été étudiée en fonction de différents traitements thermiques. Une méthode thermique de purification est proposée afin d'obtenir des poudres de qualité suffisante pour les applications catalytiques.

  17. High temperature structural study of Gd-doped ceria by synchrotron X-ray diffraction (673 K ≤ T ≤ 1073 K).

    PubMed

    Artini, Cristina; Pani, Marcella; Lausi, Andrea; Masini, Roberto; Costa, Giorgio A

    2014-10-06

    The crystallographic features of Gd-doped ceria were investigated at the operating temperature of solid oxides fuel cells, where these materials are used as solid electrolytes. (Ce(1-x)Gd(x))O(2-x/2) samples (x = 0.1, 0.3, 0.5, 0.7) were prepared by coprecipitation of mixed oxalates, treated at 1473 K in air, and analyzed by synchrotron X-ray diffraction in the temperature range 673 K ≤ T ≤ 1073 K at the Elettra synchrotron radiation facility located in Trieste, Italy. In the whole temperature span a boundary was found at x ∼ 0.2 between a CeO2-based solid solution (for x ≤ 0.2) and a structure where Gd2O3 microdomains grow within the CeO2 matrix, taking advantage of the similarity between Gd(3+) and Ce(4+) sizes; the existence of the boundary at x ∼ 0.2 was confirmed also by measurements of ionic conductivity performed by impedance spectroscopy. Similar to what observed at room temperature, the trend of the cell parameter shows the presence of a maximum; with increasing temperature, the composition corresponding to the maximum moves toward lower Gd content. This evidence can be explained by analyzing the behavior of the coefficient of thermal expansion as a function of composition.

  18. Structures in solid state and solution of dimethoxy curcuminoids: regioselective bromination and chlorination

    PubMed Central

    2013-01-01

    Background Several papers described the structure of curcumin and some other derivatives in solid and in solution. In the crystal structure of curcumin, the enol H atom is located symmetrically between both oxygen atoms of the enolone fragment with an O···O distance of 2.455 Å, which is characteristic for symmetrical H-bonds. In the solution, the geometry of the enolone fragment is attributed to the inherent disorder of the local environment, which solvates one of the basic sites better than the other, stabilizing one tautomer over the other. In this paper, how the position of methoxy groups in dimethoxy curcuminoids influence the conformation of molecules and how the halogen atoms change it when they are bonded at α-position in keto-enol part of molecules is described. Results Six isomers of dimethoxy curcuminoids were prepared. Conformations in solid state, which were determined by X-ray single crystallography and 1H MAS and 13C CPMAS NMR measurements, depend on the position of methoxy groups in curcuminoid molecules. In solution, a fast equilibrium between both keto-enol forms exists. A theoretical calculation finding shows that the position of methoxy groups changes the energy of HOMO and LUMO. An efficient protocol for the highly regioselective bromination and chlorination leading to α-halogenated product has been developed. All α-halogenated compounds are present mainly in cis keto-enol form. Conclusions The structures in solid state of dimethoxy curcuminoids depend on the position of methoxy groups. The NMR data of crystalline solid samples of 3,4-diOCH3 derivative, XRD measurements and X-ray structures lead us to the conclusion that polymorphism exists in solids. The same conclusion can be done for 3,5-diOCH3 derivative. In solution, dimethoxy curcuminoids are present in the forms that can be described as the coexistence of two equivalent tautomers being in fast equilibrium. The position of methoxy groups has a small influence on the enolic hydrogen

  19. Transport properties of dilute α -Fe (X ) solid solutions (X = C, N, O)

    NASA Astrophysics Data System (ADS)

    Schuler, Thomas; Nastar, Maylise

    2016-06-01

    We extend the self-consistent mean field (SCMF) method to the calculation of the Onsager matrix of Fe-based interstitial solid solutions. Both interstitial jumps and substitutional atom-vacancy exchanges are accounted for. A general procedure is introduced to split the Onsager matrix of a dilute solid solution into intrinsic cluster Onsager matrices, and extract from them flux-coupling ratios, mobilities, and association-dissociation rates for each cluster. The formalism is applied to vacancy-interstitial solute pairs in α -Fe (V X pairs, X = C, N, O), with ab initio based thermodynamic and kinetic parameters. Convergence of the cluster mobility contribution gives a controlled estimation of the cluster definition distance, taking into account both its thermodynamic and kinetic properties. Then, the flux-coupling behavior of each V X pair is discussed, and qualitative understanding is achieved from the comparison between various contributions to the Onsager matrix. Also, the effect of low-activation energy second-nearest-neighbor interstitial solute jumps around a vacancy on these results is addressed.

  20. Differences in physical chemistry and dissolution rate of solid particle aerosols from solution pressurised inhalers.

    PubMed

    Buttini, Francesca; Miozzi, Michele; Balducci, Anna Giulia; Royall, Paul G; Brambilla, Gaetano; Colombo, Paolo; Bettini, Ruggero; Forbes, Ben

    2014-04-25

    Solution composition alters the dynamics of beclomethasone diproprionate (BDP) particle formation from droplets emitted by pressurised metered dose inhalers (pMDIs). The hypothesis that differences in inhaler solutions result in different solid particle physical chemistry was tested using a suite of complementary calorimetric techniques. The atomisation of BDP-ethanol solutions from commercial HFA-pMDI produced aerodynamically-equivalent solid particle aerosols. However, differences in particle physico-chemistry (morphology and solvate/clathrate formation) were detected by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and supported by hot stage microscopy (HSM). Increasing the ethanol content of the formulation from 8 to 12% (w/w), which retards the evaporation of propellant and slows the increase in droplet surface viscosity, enhanced the likelihood of particles drying with a smooth surface. The dissolution rate of BDP from the 12% (w/w) ethanol formulation-derived particles (63% dissolved over 120 min) was reduced compared to the 8% (w/w) ethanol formulation-derived particles (86% dissolved over 120 min). The addition of 0.01% (w/w) formoterol fumarate or 1.3% (w/w) glycerol to the inhaler solution modified the particles and reduced the BDP dissolution rate further to 34% and 16% dissolved in 120 min, respectively. These data provide evidence that therapeutic aerosols from apparently similar inhaler products, including those with similar aerodynamic performance, may behave non-equivalently after deposition in the lungs.

  1. Energetics of a uranothorite (Th1–xUxSiO4) solid solution

    DOE PAGES

    Guo, Xiaofeng; Szenknect, Stephanie; Mesbah, Adel; ...

    2016-10-11

    High-temperature oxide melt solution calorimetric measurements were completed to determine the enthalpies of formation of the uranothorite, (USiO4)x–(ThSiO4)1–x, solid solution. Phase-pure samples with x values of 0, 0.11, 0.21, 0.35, 0.71, and 0.84 were prepared, purified, and characterized by powder X-ray diffraction, electron probe microanalysis, thermogravimetric analysis and differential scanning calorimetry coupled with in situ mass spectrometry, and high-temperature oxide melt solution calorimetry. This work confirms the energetic metastability of coffinite, USiO4, and U-rich intermediate silicate phases with respect to a mixture of binary oxides. Furthermore, variations in unit cell parameters and negative excess volumes of mixing, coupled with stronglymore » exothermic enthalpies of mixing in the solid solution, suggest short-range cation ordering that can stabilize intermediate compositions, especially near x = 0.5.« less

  2. Study of solid-solution hardening in binary aluminium-based alloys

    NASA Astrophysics Data System (ADS)

    Draissia, Mohamed; Debili, Mohamed-Yacine

    2005-09-01

    Solid-solution formation in binary aluminium-based alloys is due essentially to the combined effects of the size and valence of solvent and solute atoms, as expected by the four Hume-Rothery rules. The lattice parameter of aluminium in the solid solution of the sputtered Al-Fe films is [Al-a (Å)=4.052-6.6×10-3Y]. The increasing and decreasing evolution of the lattice parameter of copper [Cu-a (Å)=3.612+1.8×10-3Z] and aluminium [Al-a (Å)=4.048-1.6×10-3X] in the sputtered Al-1.8 to 92.5 at. % Cu films is a result of the difference in size between the aluminium and copper atoms. The low solubility of copper in aluminium (<1.8 at % Cu) is due to the valences of solvent and solute atoms in contrast with other sputtered films prepared under similar conditions, such as Al-Mg (20 at. % Mg), Al-Ti (27 at. % Ti), Al-Cr (5at. % Cr) and Al-Fe (5.5 at. % Fe) where the solubility is due to the difference in size.

  3. Role of Associated Defects in Oxygen Ion Conduction and Surface Exchange Reaction for Epitaxial Samaria-Doped Ceria Thin Films as Catalytic Coatings.

    PubMed

    Yang, Nan; Shi, Yanuo; Schweiger, Sebastian; Strelcov, Evgheni; Belianinov, Alex; Foglietti, Vittorio; Orgiani, Pasquale; Balestrino, Giuseppe; Kalinin, Sergei V; Rupp, Jennifer L M; Aruta, Carmela

    2016-06-15

    Samaria-doped ceria (SDC) thin films are particularly important for energy and electronic applications such as microsolid oxide fuel cells, electrolyzers, sensors, and memristors. In this paper, we report a comparative study investigating ionic conductivity and surface reactions for well-grown epitaxial SDC films varying the samaria doping concentration. With increasing doping above 20 mol % of samaria, an enhancement in the defect association is observed by Raman spectroscopy. The role of such associated defects on the films̀ oxygen ion transport and exchange is investigated by electrochemical impedance spectroscopy and electrochemical strain microscopy (ESM). The measurements reveal that the ionic transport has a sharp maximum in ionic conductivity and drops in its activation energy down to 0.6 eV for 20 mol % doping. Increasing the doping concentration further up to 40 mol %, it raises the activation energy substantially by a factor of 2. We ascribe the sluggish transport kinetics to the "bulk" ionic-near ordering in case of the heavily doped epitaxial films. Analysis of the ESM first-order reversal curve measurements indicates that these associated defects may have a beneficial role by lowering the activation of the oxygen exchange "surface" reaction for heavily doped 40 mol % of samaria. In a model experiment, through a solid solution series of samaria doped ceria epitaxial films, we reveal that the occurrence of associated defects in the bulk affects the surface charging state of the SDC films to increase the exchange rates. The implication of these findings is the design of coatings with tuned oxygen surface exchange by controlling the bulk associated clusters for future electrocatalytic applications.

  4. Structural investigations of aroylhydrazones derived from nicotinic acid hydrazide in solid state and in solution

    NASA Astrophysics Data System (ADS)

    Galić, Nives; Brođanac, Ivan; Kontrec, Darko; Miljanić, Snežana

    2013-04-01

    Structural forms of aroylhydrazones derived from nicotinic acid hydrazide have been studied in the solid state by FT-IR spectroscopy and in solution by NMR, UV-Vis and ATR spectroscopy. The studied compounds were N'-benzylidene-3-pyridinecarbohydrazide (1), N'-(2,4-dihydroxyphenylmethylidene)-3-pyridinecarbohydrazide (2), N'-(5-chloro-2-hydroxyphenylmethylidene)-3-pyridinecarbohydrazide (3), and N'-(3,5-dichloro-2-hydroxymethoxyphenylmethylidene)-3-pyridinecarbohydrazide (4). The compound 1 adopted the most stable ketoamine form (form I, sbnd COsbnd NHsbnd Ndbnd Csbnd ) in the solid state as well as in various organic solvents. In mixtures of organic solvents with water the UV-Vis and ATR spectra implied intermolecular hydrogen bonding of 1 with water molecules. The presence of both tautomeric forms I and II (form II, sbnd COHdbnd Nsbnd Ndbnd Csbnd ) was proposed for the solid substance and highly concentrated solutions of 2, whereas form I was detected as the predominant one in diluted solutions. For compounds 3 and 4 a coexistence of forms I and III (form III, sbnd COsbnd NHsbnd NHsbnd Cdbnd Csbnd COsbnd ) was noticed in the solid state and in polar protic organic solvents. The conversion to form III was induced by increasing the water content in the solvent mixtures. This process was the most pronounced for compound 4. When exposed to daylight, an appearance of a new band was observed during time in the UV-Vis spectrum of 4 in organic solvent/water 1/1 mixtures, which implied that tautomeric interconversion was most likely followed by E/Z isomerisation.

  5. Efficient screening of 2D molecular polymorphs at the solution-solid interface

    NASA Astrophysics Data System (ADS)

    Lee, Shern-Long; Adisoejoso, Jinne; Fang, Yuan; Tahara, Kazukuni; Tobe, Yoshito; Mali, Kunal S.; de Feyter, Steven

    2015-03-01

    Formation of multiple polymorphs during two-dimensional (2D) crystallization of organic molecules is more of a routine occurrence than rarity. Although such diverse crystalline structures provide exciting possibilities for studying crystal engineering in 2D, predicting the occurrence of polymorphs for a given building block is often non-trivial. Moreover, there is scarcity of methods that can experimentally verify the presence of such crystalline polymorphs in a straightforward fashion. Here we demonstrate a relatively simple experimental approach for screening of 2D polymorphs formed at the solution-solid interface. The strategy involves use of solution flow produced by contacting a piece of tissue paper to the sample to generate a lateral density gradient along the substrate surface. In situ generation of such gradient allows rapid discovery and nanoscale separation of multiple 2D polymorphs in a single experiment. The concept is demonstrated using three structurally different building blocks that differ in terms of intermolecular interactions responsible for 2D crystal formation. The method described here represents a powerful tool for efficient screening of 2D polymorphs formed at the solution-solid interface.Formation of multiple polymorphs during two-dimensional (2D) crystallization of organic molecules is more of a routine occurrence than rarity. Although such diverse crystalline structures provide exciting possibilities for studying crystal engineering in 2D, predicting the occurrence of polymorphs for a given building block is often non-trivial. Moreover, there is scarcity of methods that can experimentally verify the presence of such crystalline polymorphs in a straightforward fashion. Here we demonstrate a relatively simple experimental approach for screening of 2D polymorphs formed at the solution-solid interface. The strategy involves use of solution flow produced by contacting a piece of tissue paper to the sample to generate a lateral density

  6. Exploring hardness enhancement in superhard tungsten tetraboride-based solid solutions using radial X-ray diffraction

    SciTech Connect

    Xie, Miao; Mohammadi, Reza; Turner, Christopher L.; Kaner, Richard B.; Kavner, Abby; Tolbert, Sarah H.

    2015-07-29

    In this paper, we explore the hardening mechanisms in WB4-based solid solutions upon addition of Ta, Mn, and Cr using in situ radial X-ray diffraction techniques under nonhydrostatic pressure. By examining the lattice-supported differential strain, we provide insights into the mechanism for hardness increase in binary solid solutions at low dopant concentrations. Speculations on the combined effects of electronic structure and atomic size in ternary WB4 solid solutions containing Ta with Mn or Cr are also included to understand the extremely high hardness of these materials.

  7. Exploring hardness enhancement in superhard tungsten tetraboride-based solid solutions using radial X-ray diffraction

    SciTech Connect

    Xie, Miao; Turner, Christopher L.; Mohammadi, Reza; Kaner, Richard B. E-mail: akavner@ucla.edu Tolbert, Sarah H. E-mail: akavner@ucla.edu; Kavner, Abby E-mail: akavner@ucla.edu

    2015-07-27

    In this work, we explore the hardening mechanisms in WB{sub 4}-based solid solutions upon addition of Ta, Mn, and Cr using in situ radial X-ray diffraction techniques under non-hydrostatic pressure. By examining the lattice-supported differential strain, we provide insights into the mechanism for hardness increase in binary solid solutions at low dopant concentrations. Speculations on the combined effects of electronic structure and atomic size in ternary WB{sub 4} solid solutions containing Ta with Mn or Cr are also included to understand the extremely high hardness of these materials.

  8. Exploring hardness enhancement in superhard tungsten tetraboride-based solid solutions using radial X-ray diffraction

    DOE PAGES

    Xie, Miao; Mohammadi, Reza; Turner, Christopher L.; ...

    2015-07-29

    In this paper, we explore the hardening mechanisms in WB4-based solid solutions upon addition of Ta, Mn, and Cr using in situ radial X-ray diffraction techniques under nonhydrostatic pressure. By examining the lattice-supported differential strain, we provide insights into the mechanism for hardness increase in binary solid solutions at low dopant concentrations. Speculations on the combined effects of electronic structure and atomic size in ternary WB4 solid solutions containing Ta with Mn or Cr are also included to understand the extremely high hardness of these materials.

  9. A Study of Diffusivity in the BCC Solid Solution of Nb-Al and Nb-Ti-Al System

    DTIC Science & Technology

    1990-01-01

    A STUDY OF DIFFUSIVITY IN THE BCC SOLID SOLUTION OF Nb-Al AND Nb-Ti-Al SYSTEM P DTIC ELECTE NOV 3o01993 A- J.BY JOSE GUADALUPE LUIS RUIZ APARICIO A...analysis was employed for the evaluation of composition profiles in all the diffusion couples. Tne interdiffusion coefficient for the 0 solid solution of Nb...system suggest that Ti is the fastest element in the J0 solid solution . Qualitatively the penetration tendencies correlate with the melting point of

  10. Solid-solution CrCoCuFeNi high-entropy alloy thin films synthesized by sputter deposition

    DOE PAGES

    An, Zhinan; Jia, Haoling; Wu, Yueying; ...

    2015-05-04

    The concept of high configurational entropy requires that the high-entropy alloys (HEAs) yield single-phase solid solutions. However, phase separations are quite common in bulk HEAs. A five-element alloy, CrCoCuFeNi, was deposited via radio frequency magnetron sputtering and confirmed to be a single-phase solid solution through the high-energy synchrotron X-ray diffraction, energy-dispersive spectroscopy, wavelength-dispersive spectroscopy, and transmission electron microscopy. The formation of the solid-solution phase is presumed to be due to the high cooling rate of the sputter-deposition process.

  11. Long-term behavior of refractory thorium-plutonium dioxide solid solutions

    NASA Astrophysics Data System (ADS)

    Claparede, Laurent; Guigue, Mireille; Jouan, Gauthier; Nadah, Nassima; Dacheux, Nicolas; Moisy, Philippe

    2017-01-01

    The long-term behavior of Th0.87Pu0.13O2 was examined in nitric acid concentrations. The normalized dissolution rates after 3380 days, range from (1.4 ± 0.2) × 10-6 g m-2 d-1 in 5 M HNO3 down to (3.2 ± 0.4) × 10-8 g m-2 d-1 in 10-3 M HNO3, which confirms the high chemical durability of this solid solution. The amounts of plutonium measured in solution lead to 0.9% and 2.1% of dissolved solid in 1 M and 5 M HNO3, respectively. In such conditions, the time required to reach the full dissolution of the material varies from 430 years (5 M HNO3) to 18,000 years (10-3 M HNO3). Moreover, the partial order related to the proton activity (n = 0.45 ± 0.03) suggests that the dissolution is mainly driven by surface reactions occurring at the solid/liquid interface. The characterization of the leached samples by SEM shows small microstructural modifications (i.e. detachment of crystallites) and the absence of neoformed phase while from PXRD, the unit cell parameter and crystallite size are not significantly affected.

  12. B-site substituted solid solutions on the base of sodium-bismuth titanate

    NASA Astrophysics Data System (ADS)

    Ishchuk, V. M.; Gusakova, L. G.; Kisel, N. G.; Kuzenko, D. V.; Spiridonov, N. A.; Sobolev, V. L.

    The paper presents results of studies of the formation of phases during the solid-state synthesis in the [(Na0.5Bi0.5)0.80Ba0.20](Ti1-yBy)O3 system of solid solutions with B-site substitutions. The substitutions by zirconium, tin and ion complexes (In0.5Nb0.5) and (Fe0.5Nb0.5) have been studied. It has been found that the synthesis is a multi-step process associated with the formation of a number of intermediate phases (depending on the compositions and calcination temperatures). Single-phase solid solutions have been produced at the calcination temperatures in the interval 1000-1100∘C. An increase in the substituting ions concentration leads to a linear increase of the crystal cell size. At the same time, the tolerance factor gets reduced boosting the stability of the antiferroelectric phase as compared to that of the ferroelectric phase.

  13. Luminescence properties of the Ca-alpha-sialon:Eu solid solution

    NASA Astrophysics Data System (ADS)

    Pawlik, Tomasz; Michalik, Daniel; Sopicka-Lizer, Malgorzata; Lisiecki, Radosław; Adamczyk, Barbara; Pławecki, Materusz; Mieszczak, Łukasz; Walerczyk, Wiktoria

    2016-09-01

    The Ca,Eu-α-sialon powders with the mixed solid solution composition have been manufactured via the solid-state reaction process in flowing nitrogen in a graphite furnace at a relatively low temperature of 1650 °C without an external overpressure. XRD data with Rielveld refinement and XPS measurements were used for characterization of the lattice constants and the surface chemical composition. The monophase Ca-Eu-α-sialon was obtained with the nominal composition of Eu0.048Ca0.702Si7.75Al2.25O0.75N15.25. The highest emission intensity in a yellow-orange region at 590 nm and quantum efficiency of 66% was found for this pure Ca,Eu-α-sialon. Estimation of m,n values from the lattice constant and EDS results showed a small deviation from the nominal composition of designed α-sialon. XPS results demonstrated significant changes of the chemical composition in the oxidized surface of phosphor particles. Possible reasons of emission redshift and relationship between the actual solid solution composition and luminescence properties are discussed in terms of simultaneous presence of Eu2+ and Eu3+ ions in the sialon crystal lattice and residual oxynitride glass.

  14. Gadolinia-Doped Ceria Cathodes for Electrolysis of CO2

    NASA Technical Reports Server (NTRS)

    Adler, Stuart B.

    2009-01-01

    Gadolinia-doped ceria, or GDC, (Gd(0.4)Ce(0.6)O(2-delta), where the value of delta in this material varies, depending on the temperature and oxygen concentration in the atmosphere in which it is being used) has shown promise as a cathode material for high-temperature electrolysis of carbon dioxide in solid oxide electrolysis cells. The polarization resistance of a GDC electrode is significantly less than that of an otherwise equivalent electrode made of any of several other materials that are now in use or under consideration for use as cathodes for reduction of carbon dioxide. In addition, GDC shows no sign of deterioration under typical temperature and gas-mixture operating conditions of a high-temperature electrolyzer. Electrolysis of CO2 is of interest to NASA as a way of generating O2 from the CO2 in the Martian atmosphere. On Earth, a combination of electrolysis of CO2 and electrolysis of H2O might prove useful as a means of generating synthesis gas (syngas) from the exhaust gas of a coal- or natural-gas-fired power plant, thereby reducing the emission of CO2 into the atmosphere. The syngas a mixture of CO and H2 could be used as a raw material in the manufacture, via the Fisher-Tropsch process, of synthetic fuels, lubrication oils, and other hydrocarbon prod

  15. Supramolecular stabilization of metastable tautomers in solution and the solid state.

    PubMed

    Juribašić, Marina; Bregović, Nikola; Stilinović, Vladimir; Tomišić, Vladislav; Cindrić, Marina; Sket, Primož; Plavec, Janez; Rubčić, Mirta; Užarević, Krunoslav

    2014-12-22

    This work presents a successful application of a recently reported supramolecular strategy for stabilization of metastable tautomers in cocrystals to monocomponent, non-heterocyclic, tautomeric solids. Quantum-chemical computations and solution studies show that the investigated Schiff base molecule, derived from 3-methoxysalicylaldehyde and 2-amino-3-hydroxypyridine (ap), is far more stable as the enol tautomer. In the solid state, however, in all three obtained polymorphic forms it exists solely as the keto tautomer, in each case stabilized by an unexpected hydrogen-bonding pattern. Computations have shown that hydrogen bonding of the investigated Schiff base with suitable molecules shifts the tautomeric equilibrium to the less stable keto form. The extremes to which supramolecular stabilization can lead are demonstrated by the two polymorphs of molecular complexes of the Schiff base with ap. The molecules of both constituents of molecular complexes are present as metastable tautomers (keto anion and protonated pyridine, respectively), which stabilize each other through a very strong hydrogen bond. All the obtained solid forms proved stable in various solid-state and solvent-mediated methods used to establish their relative thermodynamic stabilities and possible interconversion conditions.

  16. Optical characterization of CdSe quantum dots with metal chalcogenide ligands in solutions and solids

    NASA Astrophysics Data System (ADS)

    Zhang, Y. Q.; Cao, X. A.

    2011-07-01

    The exchange of the original organic ligands of colloidal CdSe core and CdSe/CdS/ZnS core/multishell quantum dots (QDs) with inorganic metal chalcogenide ligands (SnS44-) resulted in carrier delocalization in solutions and enhanced inter-QD electronic coupling in solids, as inferred from peak redshift and broadening of the absorption and photoluminescence (PL) spectra. The SnS4-capped QDs retained strong excitonic absorption but suffered significant PL quenching. Mild thermal treatment below 350 °C transformed the SnS4 ligands into a more conductive phase, leading to stronger coupling yet complete PL quenching. These findings suggest that QD solids with metal chalcogenide ligands may have high quantum yields of photocurrent generation and can be used as functional blocks in thin-film solar cells for efficient solar energy conversion.

  17. Modelling of solid polymer and direct methanol fuel cells: Phenomenological equations and analytical solutions

    NASA Astrophysics Data System (ADS)

    Kauranen, P. S.

    1993-04-01

    In the solid state concept of a direct methanol fuel cell (DMFC), methanol is directly oxidized at the anode of a solid polymer electrolyte fuel cell (SPEFC). Mathematical modelling of the transport and reaction phenomena within the electrodes and the electrolyte membrane is needed in order to get a closer insight into the operation of the fuel cell. In the work, macro-homogenous porous electrode and dilute solution theories are used to derive the phenomenological equations describing the transport and reaction mechanisms in a SPEFC single cell. The equations are first derived for a conventional H2/air SPEFC, and then extended for a DMFC. The basic model is derived in a one dimensional form in which it is assumed that species transport take place only in the direction crossing the cell sandwich. In addition, two dimensional descriptions of the catalyst layer are reviewed.

  18. Multivalent-Counterion-Induced Surfactant Multilayer Formation at Hydrophobic and Hydrophilic Solid-Solution Interfaces.

    PubMed

    Penfold, Jeffrey; Thomas, Robert K; Li, Peixun; Xu, Hui; Tucker, Ian M; Petkov, Jordan T; Sivia, Devinderjit S

    2015-06-23

    Surface multilayer formation from the anionic-nonionic surfactant mixture of sodium dodecyl dioxyethylene sulfate, SLES, and monododecyl dodecaethylene glycol, C12E12, by the addition of multivalent Al(3+) counterions at the solid-solution interface is observed and characterized by neutron reflectivity, NR. The ability to form surface multilayer structures on hydrophobic and hydrophilic silica and cellulose surfaces is demonstrated. The surface multilayer formation is more pronounced and more well developed on the hydrophilic and hydrophobic silica surfaces than on the hydrophilic and hydrophobic cellulose surfaces. The less well developed multilayer formation on the cellulose surfaces is attributed to the greater surface inhomogeneities of the cellulose surface which partially inhibit lateral coherence and growth of the multilayer domains at the surface. The surface multilayer formation is associated with extreme wetting properties and offers the potential for the manipulation of the solid surfaces for enhanced adsorption and control of the wetting behavior.

  19. Joule-Thomson Inversion in Vapor-Liquid-Solid Solution Systems

    NASA Astrophysics Data System (ADS)

    Nichita, Dan Vladimir; Pauly, Jerome; Daridon, Jean-Luc

    2009-07-01

    Solid phase precipitation can greatly affect thermal effects in isenthalpic expansions; wax precipitation may occur in natural hydrocarbon systems in the range of operating conditions, the wax appearance temperature being significantly higher (as high as 350 K) for hyperbaric fluids. Recently, methods for calculating the Joule-Thomson inversion curve (JTIC) for two-phase mixtures, and for three-phase vapor-liquid-multisolid systems have been proposed. In this study, an approach for calculating the JTIC for the vapor-liquid-solid solution systems is presented. The JTIC is located by tracking extrema and angular points of enthalpy departure variations versus pressure at isothermal conditions. The proposed method is applied to several complex synthetic and naturally occurring hydrocarbon systems. The JTIC can exhibit several distinct branches (which may lie within two- or three-phase regions or follow phase boundaries), multiple inversion temperatures at fixed pressure, as well as multiple inversion pressures at given temperature.

  20. Solution- and solid-phase oligosaccharide synthesis using glucosyl iodides: a comparative study.

    PubMed

    Lam, Son N; Gervay-Hague, Jacquelyn

    2002-11-19

    Glycosyl iodide donors have been used in both solid- and solution-phase syntheses yielding alpha-(1 --> 6)-linked glucosyl oligomers in highly efficient protocols. While the solid-phase strategy offers advantages in terms of ease of purification, it requires a total of 7.5 equiv of donor and approximately 12 h to complete the incorporation of one monosaccharide unit. In contrast, solution-phase methods require only 2.5 equiv of donor and 2-3 h reaction time per glycosylation. Moreover, since the reactions are virtually quantitative (> 90%) column chromatography of the material is facile. The overall advantages of solution-phase oligosaccharide synthesis were further illustrated in the convergent synthesis of a hexamer (methoxycarbonylmethyl 6-O-acetyl-2,3,4-tri-O-benzyl-alpha-D-glucopyranosyl-(1 --> 6)-tetrakis-(2,3,4-tri-O-benzyl-alpha-D-glucopyranosyl-(1 --> 6))-2,3,4-tri-O-benzyl-1-thio-alpha-D-glucopyranoside) that was constructed from dimer donor iodides in a two-plus-two and a two-plus-four fashion.

  1. Ruthenium complexes of substituted hydrazine: new solution- and solid-state binding modes.

    PubMed

    Dabb, Serin L; Messerle, Barbara A; Otting, Gottfried; Wagler, Jörg; Willis, Anthony

    2008-01-01

    The methylhydrazine complex [Ru(NH(2)NHMe)(PyP)(2)]Cl(BPh(4)) (PyP=1-[2-(diphenylphosphino)ethyl]pyrazole) was synthesised by addition of methylhydrazine to the bimetallic complex [Ru(mu-Cl)(PyP)(2)](2)(BPh(4))(2). The methylhydrazine ligand of the ruthenium complex has two different binding modes: side-on (eta(2)-) when the complex is in the solid state and end-on (eta(1)-) when the complex is in solution. The solid-state structure of [Ru(PyP)(2)(NH(2)NHMe)]Cl(BPh(4)) was determined by X-ray crystallography. 2D NMR spectroscopic experiments with (15)N at natural abundance confirmed that in solution the methylhydrazine is bound to the metal centre by only the -NH(2) group and the ruthenium complex retains an octahedral conformation. Hydrazine complexes [RuCl(PyP)(2)(eta(1)-NH(2)NRR')]OSO(2)CF(3) (in which R=H, R'=Ph, R=R'=Me and NRR'=NC(5)H(10)) were formed in situ by the addition of phenylhydrazine, 1,1-dimethylhydrazine and N-aminopiperidine, respectively, to a solution of the bimetallic complex [Ru(mu-Cl)(PyP)(2)](2)(OSO(2)CF(3))(2) in dichloromethane. These substituted hydrazine complexes of ruthenium were shown to exist in an equilibrium mixture with the bimetallic starting material.

  2. Microstructural and Electrical Characterization of Barium Strontium Titanate-Based Solid Solution Thin Films Deposited on Ceramic Substrates by Pulsed Laser Deposition

    DTIC Science & Technology

    2003-04-03

    Strontium Titanate-Based Solid Solution Thin Films Deposited on Ceramic Substrates by Pulsed Laser Deposition DISTRIBUTION: Approved for public...Society H2.4 Microstructural and Electrical Characterization of Barium Strontium Titanate- based Solid Solution Thin Films Deposited on Ceramic...investigated and report the microstructural and electrical characterization of selected barium strontium titanate-based solid solution thin films

  3. Nano-ceria pre-infiltration improves La0.6Sr0.4Co0.8Fe0.2O3-x infiltrated Solid Oxide Fuel Cell cathode performance

    NASA Astrophysics Data System (ADS)

    Burye, Theodore E.; Nicholas, Jason D.

    2015-12-01

    Here, scanning electron microscopy, X-ray diffraction, and thermo-gravimetric analysis experiments show that the pre-infiltration of Ce0.9Gd0.1O1.95 (GDC) nano-particles reduces the average size of La0.6Sr0.4Co0.8Fe0.2O3-x (LSCF) produced from the subsequent infiltration of precursor nitrate solutions containing the surfactant Triton X-100 or the chelating agent citric acid. In contrast, GDC pre-infiltration has no effect on the average size of LSCF particles produced from precursor solutions containing only lanthanum, strontium, cobalt, and iron nitrate. Consistent with the observed particle size trends, electrochemical impedance spectroscopy measurements show that GDC pre-infiltration improves the performance of Triton X-100 Derived (TXD) LSCF-GDC cathodes and Citric Acid Derived (CAD) LSCF-GDC cathodes, but has no effect on the performance of Pure Nitrate Derived (PND) LSCF-GDC cathodes. In particular, TXD LSCF-GDC cathodes with more than ∼5 vol% of GDC pre-infiltration display average LSCF particle sizes of 21 nm and open-circuit polarization resistance values of 0.10 Ωcm2 at 540 °C, compared to 48 nm and 640 °C without GDC pre-infiltration. Results suggest that this 100 °C reduction in cathode operating temperature is caused solely by LSCF particle size reductions. 7.4 vol% GDC pre-infiltrated TXD LSCF-GDC cathodes also display lower 540 °C degradation rates than conventionally infiltrated PND LSCF-GDC cathodes.

  4. Solid-gel precursor solutions and methods for the fabrication of polymetallicsiloxane coating films

    DOEpatents

    Sugama, Toshifumi

    1993-01-01

    Solutions and preparation methods necessary for the fabrication of metal oxide cross-linked polysiloxane coating films are disclosed. The films are useful in provide heat resistance against oxidation, wear resistance, thermal insulation, and corrosion resistance of substrates. The sol-gel precursor solution comprises a mixture of a monomeric organoalkoxysilane, a metal alkoxide M(OR).sub.n (wherein M is Ti, Zr, Ge or Al; R is CH.sub.3, C.sub.2 H.sub.5 or C.sub.3 H.sub.7 ; and n is 3 or 4), methanol, water, HCl and NaOH. The invention provides a sol-gel solution, and a method of use thereof, which can be applied and processed at low temperatures (i.e., <1000.degree. C.). The substrate can be coated by immersing it in the above mentioned solution at ambient temperature. The substrate is then withdrawn from the solution. Next, the coated substrate is heated for a time sufficient and at a temperature sufficient to yield a solid coating. The coated substrate is then heated for a time sufficient, and temperature sufficient to produce a polymetallicsiloxane coating.

  5. Solid-gel precursor solutions and methods for the fabrication of polymetallicsiloxane coating films

    DOEpatents

    Sugama, Toshifumi

    1992-01-01

    Solutions and preparation methods necessary for the fabrication of metal oxide cross-linked polysiloxane coating films are disclosed. The films are useful in provide heat resistance against oxidation, wear resistance, thermal insulation, and corrosion resistance of substrates. The sol-gel precursor solution comprises a mixture of a monomeric organoalkoxysilane, a metal alkoxide M(OR).sub.n (wherein M is Ti, Zr, Ge or Al; R is CH.sub.3, C.sub.2 H.sub.5 or C.sub.3 H.sub.7 ; and n is 3 or 4), methanol, water, HCl and NaOH. The invention provides a sol-gel solution, and a method of use thereof, which can be applied and processed at low temperatures (i.e., <1000.degree. C.). The substrate can be coated by immersing it in the above mentioned solution at ambient temperature. The substrate is then withdrawn from the solution. Next, the coated substrate is heated for a time sufficient and at a temperature sufficient to yield a solid coating. The coated substrate is then heated for a time sufficient, and temperature sufficient to produce a polymetallicsiloxane coating.

  6. Solid-gel precursor solutions and methods for the fabrication of polymetallicsiloxane coating films

    DOEpatents

    Toshifumi Sugama.

    1993-04-06

    Solutions and preparation methods necessary for the fabrication of metal oxide cross-linked polysiloxane coating films are disclosed. The films are useful in provide heat resistance against oxidation, wear resistance, thermal insulation, and corrosion resistance of substrates. The sol-gel precursor solution comprises a mixture of a monomeric organoalkoxysilane, a metal alkoxide M(OR)[sub n] (wherein M is Ti, Zr, Ge or Al; R is CH[sub 3], C[sub 2]H[sub 5] or C[sub 3]H[sub 7]; and n is 3 or 4), methanol, water, HCl and NaOH. The invention provides a sol-gel solution, and a method of use thereof, which can be applied and processed at low temperatures (i.e., < 1,000 C.). The substrate can be coated by immersing it in the above mentioned solution at ambient temperature. The substrate is then withdrawn from the solution. Next, the coated substrate is heated for a time sufficient and at a temperature sufficient to yield a solid coating. The coated substrate is then heated for a time sufficient, and temperature sufficient to produce a polymetallicsiloxane coating.

  7. Leaching heavy metals in municipal solid waste incinerator fly ash with chelator/biosurfactant mixed solution.

    PubMed

    Xu, Ying; Chen, Yu

    2015-07-01

    The chelator [S,S]-ethylene diamine disuccinic acid, citric acid, and biosurfactant saponin are selected as leaching agents. In this study, the leaching effect of saponin mixed with either ethylene diamine disuccinic acid or citric acid on the levels of copper, zinc, lead, and cadmium in municipal solid waste incinerator fly ash is investigated. Results indicate that saponin separately mixed with ethylene diamine disuccinic acid and citric acid exhibits a synergistic solubilisation effect on copper, zinc, lead, and cadmium leaching from fly ash. However, saponin and ethylene diamine disuccinic acid mixed solution exhibits a synergistic solubilisation effect that is superior to that of a saponin and citric acid mixed solution. The extraction rate of heavy metal in fly ash leached with a saponin and chelator mixed solution is related to the pH of the leaching solution, and the optimal range of the pH is suggested to be approximately neutral. After leaching with a saponin and chelator mixed solution, copper, zinc, lead, and cadmium contents significantly decreased (p < 0.05) in the extractable or acid-soluble and reducible fractions. By adopting the proposed approach, the leaching concentrations of copper, zinc, lead, and cadmium in treated fly ash are in accordance with Standard for Pollution Control on the Security Landfill Site for Hazardous Wastes GB18598-2001.

  8. One-Dimensional Ceria as Catalyst for the Low-Temperature Water-Gas Shift Reaction

    SciTech Connect

    Han, W.; Wen, W; Hanson, J; Teng, X; Marinkovic, N; Rodriguez, J

    2009-01-01

    Synchrotron-based in situ time-resolved X-ray diffraction and X-ray absorption spectroscopy were used to study pure ceria and Pd-loaded ceria nanotubes and nanorods (1D-ceria) as catalysts for the water-gas shift (WGS) reaction. While bulk ceria is very poor as WGS catalysts, pure 1D-ceria displayed catalytic activity at a temperature as low as 300 C. The reduction of the pure 1D-ceria in pure hydrogen started at 150 C, which is a much lower temperature than those previously reported for the reduction of 3D ceria nanoparticles. This low reduction temperature reflects the novel morphology of the oxide systems and may be responsible for the low-temperature WGS catalytic activity seen for the 1D-ceria. Pd-loaded 1D ceria displayed significant WGS activity starting at 200 C. During pretreatment in H{sub 2}, the ceria lattice parameter increased significantly around 60 C, which indicates that Pd-oxygen interactions may facilitate the reduction of Pd-loaded 1D-ceria. Pd and ceria both participate in the formation of the active sites for the catalytic reactions. The low-temperature hydrogen pretreatment results in higher WGS activity for Pd-loaded 1D-ceria.

  9. Multifunctional imidazobenzothiadiazole probe displaying solvatofluorochromism and ability to form ion-pair complexes in solid state and in solution.

    PubMed

    Alfonso, María; Fernández, Israel; Tárraga, Alberto; Molina, Pedro

    2015-05-15

    Fluorescent solid 5-pyridylimidazobenzothiadiazole displays a remarkable solvatofluorochromism and with Zn(AcO)2 and Cd(AcO)2, either in solution or under solvent-free conditions, forms ion-pair complexes that in the solid state can be discriminated and separated by fluorescence measurements and selective extraction with diethyl ether or chloroform.

  10. Coupling between magnetic and optical properties of stable Au-Fe solid solution nanoparticles

    NASA Astrophysics Data System (ADS)

    de Julián Fernández, C.; Mattei, G.; Paz, E.; Novak, R. L.; Cavigli, L.; Bogani, L.; Palomares, F. J.; Mazzoldi, P.; Caneschi, A.

    2010-04-01

    Au-Fe nanoparticles constitute one of the simplest prototypes of a multifunctional nanomaterial that can exhibit both magnetic and optical (plasmonic) properties. This solid solution, not feasible in the bulk phase diagram in thermal equilibrium, can be formed as a nanostructure by out-of-equilibrium processes. Here, the novel magnetic, optical and magneto-optical properties of ion-implanted Au-Fe solid solution nanoparticles dispersed in a SiO2 matrix are investigated and correlated. The surface plasmon resonance of the Au-Fe nanoparticles with almost equicomposition is strongly damped when compared to pure Au and to Au-rich Au-Fe nanoparticles. In all cases, the Au atoms are magnetically polarized, as measured by x-ray magnetic circular dichroism, and ferromagnetically coupled with Fe atoms. Although the chemical stability of Au-Fe nanoparticles is larger than that of Fe nanoparticles, both the magnetic moment per Fe atom and the order temperature are smaller. These results suggest that electronic and magnetic properties are more influenced by the hybridization of the electronic bands in the Au-Fe solid solution than by size effects. On the other hand, the magneto-optical transitions allowed in the vis-nIR spectral regions are very similar. In addition, we also observe, after studying the properties of thermally treated samples, that the Au-Fe alloy is stabilized, not by surface effects, but by the combination of the out-of-equilibrium nature of the ion implantation technique and by changes in the properties due to size effects.

  11. SOLID SOLUTION CARBIDES ARE THE KEY FUELS FOR FUTURE NUCLEAR THERMAL PROPULSION

    NASA Technical Reports Server (NTRS)

    Panda, Binayak; Hickman, Robert R.; Shah, Sandeep

    2005-01-01

    Nuclear thermal propulsion uses nuclear energy to directly heat a propellant (such as liquid hydrogen) to generate thrust for space transportation. In the 1960 s, the early Rover/Nuclear Engine for Rocket Propulsion Application (NERVA) program showed very encouraging test results for space nuclear propulsion but, in recent years, fuel research has been dismal. With NASA s renewed interest in long-term space exploration, fuel researchers are now revisiting the RoverMERVA findings, which indicated several problems with such fuels (such as erosion, chemical reaction of the fuel with propellant, fuel cracking, and cladding issues) that must be addressed. It is also well known that the higher the temperature reached by a propellant, the larger the thrust generated from the same weight of propellant. Better use of fuel and propellant requires development of fuels capable of reaching very high temperatures. Carbides have the highest melting points of any known material. Efforts are underway to develop carbide mixtures and solid solutions that contain uranium carbide, in order to achieve very high fuel temperatures. Binary solid solution carbides (U, Zr)C have proven to be very effective in this regard. Ternary carbides such as (U, Zr, X) carbides (where X represents Nb, Ta, W, and Hf) also hold great promise as fuel material, since the carbide mixtures in solid solution generate a very hard and tough compact material. This paper highlights past experience with early fuel materials and bi-carbides, technical problems associated with consolidation of the ingredients, and current techniques being developed to consolidate ternary carbides as fuel materials.

  12. Ab Initio Calculations and Synthesis of Sc2InC-Y2InC Solid Solution

    DTIC Science & Technology

    2010-02-03

    tribological materials. It will study a solid solution of this fascinating new class of nanolaminated materials using both theoretical and experimental means...Sc2InC-Y2InC solid solution using ab initio calculations and 2) to synthesize Sc2InC-Y2InC thin films using magnetron sputtering and to determine the correlation between composition, structure, and mechanical properties thereof.

  13. PZT-like structural phase transitions in the BiFeO3-KNbO3 solid solution.

    PubMed

    Lennox, Robert C; Taylor, Daniel D; Vera Stimpson, Laura J; Stenning, Gavin B G; Jura, Marek; Price, Mark C; Rodriguez, Efrain E; Arnold, Donna C

    2015-06-21

    Despite the high prominence of the perovskites BiFeO(3) and KNbO(3) the solid solution between the two has received little attention. We report a detailed neutron and synchrotron X-ray powder diffraction, and Raman spectroscopy study which demonstrates an R3c→P4mm→Amm2 series of structural phase transitions similar to that exhibited by the PbZrO(3)-PbTiO(3) solid solution.

  14. Adhesion and Atomic Structures of Gold on Ceria Nanostructures: The Role of Surface Structure and Oxidation State of Ceria Supports.

    PubMed

    Lin, Yuyuan; Wu, Zili; Wen, Jianguo; Ding, Kunlun; Yang, Xiaoyun; Poeppelmeier, Kenneth R; Marks, Laurence D

    2015-08-12

    We report an aberration-corrected electron microscopy analysis of the adhesion and atomic structures of gold nanoparticle catalysts supported on ceria nanocubes and nanorods. Under oxidative conditions, the as-prepared gold nanoparticles on the ceria nanocubes have extended atom layers at the metal-support interface. In contrast, regular gold nanoparticles and rafts are present on the ceria nanorod supports. Under the reducing conditions of water-gas shift reaction, the extended gold atom layers and rafts vanish. In addition, the gold particles on the nanocubes change in morphology and increase in size while those on the nanorods are almost unchanged. The size, morphology, and atomic interface structures of gold strongly depend on the surface structures of ceria supports ((100) surface versus (111) surface) and the reaction environment (reductive versus oxidative). These findings provide insights into the deactivation mechanisms and the shape-dependent catalysis of oxide supported metal catalysts.

  15. Synthesis of dental enamel-like hydroxyapatite through solution mediated solid-state conversion.

    PubMed

    Zhang, Junling; Jiang, Dongliang; Zhang, Jingxian; Lin, Qingling; Huang, Zhengren

    2010-03-02

    An ordered dental enamel-like structure of hydroxyapatite (HAp) was achieved through a solution mediated solid-state conversion process with organic phosphate surfactant and gelatin as the mediating agent. Transmission electron microscopy (TEM) tests demonstrated uniform sizes in the obtained apatite nanorods which arranged in parallel to each other along the c-axis and formed organized microarchitectural units over 10 microm in size. The sizes of the synthetic hydroxyapatite nanorods were similar to that observed in enamel from human teeth. The formation and regulation of the orientation and size of HAp nanorods might lead to a better understanding of the biomineralization process for the preparation of high performance biomaterials.

  16. NMR in Chevrel-phase solid solution Mo 6Se 8- xTe x

    NASA Astrophysics Data System (ADS)

    Hamard, C.; Le Floch, M.; Peña, O.; Wojakowski, A.

    1999-01-01

    The Mo 6Se 8-Mo 6Te 8 solid solution was studied by X-ray diffraction, magnetic susceptibility and 77Se and 125Te NMR. Dynamic studies show that substitution occurs differently when Se replaces Te in Mo 6Te 8 than when Te replaces Se in Mo 6Se 8. Selenium first fills the high-symmetry sites and then it becomes statistically distributed on the 6f positions of the R3¯ symmetry. In the second case, Te occupies randomly the 8 X sites of the Mo 6X 8 structure, creating large perturbations of the 125Te NMR spectra over the whole range of x.

  17. Solid-Solution Alloying of Immiscible Ru and Cu with Enhanced CO Oxidation Activity.

    PubMed

    Huang, Bo; Kobayashi, Hirokazu; Yamamoto, Tomokazu; Matsumura, Syo; Nishida, Yoshihide; Sato, Katsutoshi; Nagaoka, Katsutoshi; Kawaguchi, Shogo; Kubota, Yoshiki; Kitagawa, Hiroshi

    2017-03-24

    We report on novel solid-solution alloy nanoparticles (NPs) of Ru and Cu that are completely immiscible even above melting point in bulk phase. Powder X-ray diffraction, scanning transmission electron microscopy, and energy-dispersive X-ray measurements demonstrated that Ru and Cu atoms were homogeneously distributed in the alloy NPs. Ru0.5Cu0.5 NPs demonstrated higher CO oxidation activity than fcc-Ru NPs, which are known as one of the best monometallic CO oxidation catalysts.

  18. Synthesis and characterization of the LDH hydrotalcite-pyroaurite solid-solution series

    SciTech Connect

    Rozov, K.; Berner, U.; Taviot-Gueho, C.; Leroux, F.; Renaudin, G.; Kulik, D.; Diamond, L.W.

    2010-08-15

    A layered double hydroxide (LDH) hydrotalcite-pyroaurite solid-solution series Mg{sub 3}(Al{sub x}Fe{sub 1-x})(CO{sub 3}){sub 0.5}(OH){sub 8} with 1 - x = 0.0, 0.1...1.0 was prepared by co-precipitation at 23 {+-} 2 {sup o}C and pH = 11.40 {+-} 0.03. The compositions of the solids and the reaction solutions were determined using ICP-OES (Mg, Al, Fe, and Na) and TGA techniques (CO{sub 3}{sup 2-}, OH{sup -}, and H{sub 2}O). Powder X-ray diffraction was employed for phase identification and determination of the unit cell parameters a{sub o} and c{sub o} from peak profile analysis. The parameter a{sub o} = b{sub o} was found to be a linear function of the composition. This dependency confirms Vegard's law and indicates the presence of a continuous solid-solution series in the hydrotalcite-pyroaurite system. TGA data show that the temperatures at which interlayer H{sub 2}O molecules and CO{sub 3}{sup 2-} anions are lost, and at which dehydroxylation of the layers occurs, all decrease with increasing mole fraction of iron within the hydroxide layers. Features of the Raman spectra also depend on the iron content. The absence of Raman bands for Fe-rich members (x{sub Fe} > 0.5) is attributed to possible fluorescence phenomena. Based on chemical analysis of both the solids and the reaction solutions after synthesis, preliminary Gibbs free energies of formation have been estimated. Values of {Delta}G{sup o}{sub f}(hydrotalcite) = - 3773.3 {+-} 51.4 kJ/mol and {Delta}G{sup o}{sub f}(pyroaurite) = - 3294.5 {+-} 95.8 kJ/mol were found at 296.15 K. The formal uncertainties of these formations constants are very high. Derivation of more precise values would require carefully designed solubility experiments and improved analytical techniques.

  19. Atomistic simulation of local structure and mixing properties of mineral solid solutions

    NASA Astrophysics Data System (ADS)

    Urusov, V. S.

    2009-04-01

    At present there are several ways to simulate solid solution structure and properties by using ab initio as well as semi-empirical (atomistic) approaches [1]. The main problem of each approach is a reasonable representation of random distribution of atoms substituting each other over common positions. A procedure in operation here used large supercells and generation of most disordered atomic configurations for some selected compositions of solid solution (1:1, 1:3, 3:1, 4:1, 1:4, etc.). The following binary systems were studied by such a way: NaCl - KCl [2, 3, 4], CaO - MgO, CaO - SrO, SrO - BaO (supercell 444, 512 atoms) [3], TiO2 - SnO2 (444, 384 atoms), Al2O3 - Cr2O3, Al2O3 - Fe2O3, Fe2O3 - Cr2O3 (441, 480 atoms) [5]. The calculation technique was based on the method of semi-empirical potentials using the GULP program [6]. Potential parameters of ionic (halides) or partially covalent (oxides) interatomic interactions were optimized by using of structural, thermodynamic and elastic properties of pure components. Calculated heat capacities and entropies as a function of temperature were in a good agreement with experimental data. Excess mixing properties (enthalpy, volume, bulk modulus, vibrational entropy) were calculated for different compositions of the solid solutions. This allowed to reproduce Gibbs energy as a function of temperature and composition and estimate critical temperature of decomposition and miscibility gap of a solid solution. Statistical analysis of bond lengths frequencies for the nearest and next-nearest neighbors in (Na0.5K0.5)Cl, (Ca0.5Mg0.5)O, (Ti0.5Sn0.5)O2, (Al1.0Cr1.0)O3 solid solutions revealed a detailed picture of the lattice relaxation. These results were compared with earlier predictions made by phenomenological crystal chemical models [7, 8] and available EXAFS data. References 1. V.S.Urusov. J.Solid State Chem. 2000. V.153. 357. 2. Urusov V.S., Petrova T.G., Leonenko E.V., Eremin N.N. Vestn. Mosc. Univ. 2008

  20. Reduced ceria nanofilms from structure prediction.

    PubMed

    Kozlov, Sergey M; Demiroglu, Ilker; Neyman, Konstantin M; Bromley, Stefan T

    2015-03-14

    Experimentally, Ce2O3 films are used to study cerium oxide in its fully or partially reduced state, as present in many applications. We have explored the space of low energy Ce2O3 nanofilms using structure prediction and density functional calculations, yielding more than 30 distinct nanofilm structures. First, our results help to rationalize the roles of thermodynamics and kinetics in the preparation of reduced ceria nanofilms with different bulk crystalline structures (e.g. A-type or bixbyite) depending on the support used. Second, we predict a novel, as yet experimentally unresolved, nanofilm which has a structure that does not correspond to any previously reported bulk A2B3 phase and which has an energetic stability between that of A-type and bixbyite. To assist identification and fabrication of this new Ce2O3 nanofilm we calculate some observable properties and propose supports for its epitaxial growth.

  1. A well-structured metastable ceria surface

    SciTech Connect

    Olbrich, R.; Pieper, H. H.; Oelke, R.; Wilkens, H.; Wollschläger, J.; Reichling, M.; Zoellner, M. H.; Schroeder, T.

    2014-02-24

    By the growth of a 180 nm thick film on Si(111), we produce a metastable ceria surface with a morphology dominated by terraced pyramids with an oriented triangular base. Changes in the nanoscale surface morphology and local surface potential due to annealing at temperatures ranging from 300 K to 1150 K in the ultra-high vacuum are studied with non-contact atomic force microscopy and Kelvin probe force microscopy. As the surface is stable in the temperature range of 300 K to 850 K, it is most interesting for applications requiring regular steps with a height of one O-Ce-O triple layer.

  2. Phase separation in dilute solutions of 3He in solid 4He

    NASA Astrophysics Data System (ADS)

    Huan, C.; Yin, L.; Xia, J. S.; Candela, D.; Cowan, B. P.; Sullivan, N. S.

    2017-03-01

    We report the results of studies of the phase separation of solid solutions of dilute concentrations of 3He in 4He. The temperatures and the kinetics of the phase separation were determined from NMR experiments for 3He concentrations 1.6 ×10-5solution theory as augmented by Edwards and Balibar [Phys. Rev. B 39, 4083 (1989), 10.1103/PhysRevB.39.4083]. The growth of 3He droplets shows a t1 /3 time dependence at long times consistent with Ostwald ripening.

  3. NEXAFS Chemical State and Bond Lengths of p-Aminobenzoic Acid in Solution and Solid State

    NASA Astrophysics Data System (ADS)

    Stevens, J. S.; Gainar, A.; Suljoti, E.; Xiao, J.; Golnak, R.; Aziz, E. F.; Schroeder, S. L. M.

    2016-05-01

    Solid-state and solution pH-dependent NEXAFS studies allow direct observation of the electronic state of para-aminobenzoic acid (PABA) as a function of its chemical environment, revealing the chemical state and bonding of the chemical species. Variations in the ionization potential (IP) and 1s→π* resonances unequivocally identify the chemical species (neutral, cationic, or anionic) present and the varying local environment. Shifts in σ* shape resonances relative to the IP in the NEXAFS spectra vary with C-N bond length, and the important effect of minor alterations in bond length is confirmed with nitrogen FEFF calculations, leading to the possibility of bond length determination in solution.

  4. Silicon nitride-aluminum oxide solid solution (SiAION) formation and densification by pressure sintering

    NASA Technical Reports Server (NTRS)

    Yeh, H. C.; Sanders, W. A.; Fiyalko, J. L.

    1975-01-01

    Stirred-ball-mill-blended Si3N4 and Al2O3 powders were pressure sintered in order to investigate the mechanism of solid solution formation and densification in the Si3N4-Al2O3 system. Powder blends with Si3N4:Al2O3 mole ratios of 4:1, 3:2, and 2:3 were pressure sintered at 27.6-MN/sq m pressure at temperatures to 17000 C (3090 F). The compaction behavior of the powder blends during pressure sintering was determined by observing the density of the powder compact as a function of temperature and time starting from room temperature. This information, combined with the results of X-ray diffraction and metallographic analyses regarding solutioning and phase transformation phenomena in the Si3N4-Al2O3 system, was used to describe the densification behavior.

  5. Effective distribution coefficients of a binary ideal solid solution controlled by kink kinetics

    NASA Astrophysics Data System (ADS)

    Matsumoto, Naoko; Kitamura, Masao

    2001-01-01

    Effective distribution coefficients of a binary ideal solid solution growing from dilute surroundings are derived for the steady state using a model in which atoms attach and detach only at kink sites on a (0 0 1) surface of a simple cubic crystal. A system of equations is presented to give the step-edge, terrace, and bulk compositions in terms of attachment and detachment frequencies. The total net flux of atoms from the mother phase to kink sites is also formulated as a function of these compositions and the frequencies. Numerical solutions to the system of equations show that the step-edge, terrace, and bulk compositions are different from one another and that the step-edge, terrace, and bulk distribution coefficients will all approach unity from their respective equilibrium values as the total net flux increases.

  6. Exact solution of the two-level system and the Einstein solid in the microcanonical formalism

    NASA Astrophysics Data System (ADS)

    Bertoldi, Dalía S.; Bringa, Eduardo M.; Miranda, E. N.

    2011-11-01

    The two-level system and the Einstein model of a crystalline solid are taught in every course of statistical mechanics and they are solved in the microcanonical formalism because the number of accessible microstates can be easily evaluated. However, their solutions are usually presented using the Stirling approximation to deal with factorials. In this paper, those two models are solved without any approximation, using the gamma function and its derivatives. Exact values are calculated for the entropy, temperature and specific heat, and the relative error between our exact solution and the approximate one using the Stirling approximation. This error is significant for small systems, with a number of particles N ~ 100, as in studies of atomic clusters or nanoscale structures.

  7. Phase decomposition and nano structure evolution of metastable nanocrystalline Cu-Co solid solutions during thermal treatment

    NASA Astrophysics Data System (ADS)

    Bachmaier, A.; Stolpe, M.; Müller, T.; Motz, C.

    2015-08-01

    Nanocrystalline and ultrafine-grained Cu100-xCox (x = 26 and 76) solid solutions have been prepared by severe plastic deformation (SPD) of elemental powder mixtures. For both concentrations a supersaturated solid solution fcc phase was identified after the deformation process with grain sizes of less than 50 nm for Co rich solutions and around 100 nm for Cu rich solutions. Additionally, synthesis of nanocrystalline materials in the Cu-Co alloy system by electrodeposition has been conducted. Microstructural characterization by scanning and transmission electron microscopy, differential scanning calorimetry, and microhardness measurements are used to investigate the structural evolution, the thermal stability and mechanical properties of the different nanocrystalline Cu-Co alloy materials during isothermal and non-isothermal annealing. In this study it is shown that the phase decomposition of the metastable Cu-Co solid solutions has a significant influence on their thermal stability, which can be linked to the underlying microstructure that forms during annealing.

  8. In situ study of the solid-state formation of U(1-x)Am(x)O(2±δ) solid solution.

    PubMed

    Lebreton, Florent; Belin, Renaud C; Prieur, Damien; Delahaye, Thibaud; Blanchart, Philippe

    2012-09-03

    In order to reduce the nuclear waste inventory and radiotoxicity, U(1-x)Am(x)O(2±δ) materials are promising fuels for heterogeneous transmutation. In this context, they are generally fabricated from UO(2+δ) and AmO(2-δ) dioxide powders. In the subsequent solid solution, americium is assumed to be trivalent whereas uranium exhibits a mixed-valence (+IV/+V) state. However, no formation mechanisms were ever evidenced and, more particularly, it was not possible to know whether the reduction of Am(IV) to Am(III) occurs before the solid-solution formation, or only once it is established. In this study, we used high-temperature X-ray diffraction on a UO(2±δ)/AmO(2-δ) (15 mol %) mixture to observe in situ the formation of the U(1-x)Am(x)O(2±δ) solid solution. We show that UO(2+δ) is, at relatively low temperature (<700 K), oxidized to U(4)O(9-δ), which is likely to be caused by oxygen release from the simultaneous AmO(2-δ) reduction to cubic Am(2)O(3±δ). Cubic Am(2)O(3+δ) then transforms to hexagonal Am(2)O(3) at 1300 K. Thus, the initial Am(IV) is fully reduced to Am(III) before the solid solution starts forming at 1740 K. The UO(2) fluorite phase vanishes after 4 h at 1970 K, indicating that the formation of the solid solution is completed, which proves that this solid solution is formed after the complete reduction of Am(IV) to Am(III).

  9. Coordination chemistry study of hydrated and solvated lead(II) ions in solution and solid state.

    PubMed

    Persson, Ingmar; Lyczko, Krzysztof; Lundberg, Daniel; Eriksson, Lars; Płaczek, Anna

    2011-02-07

    The coordination chemistry of lead(II) in the oxygen donor solvents water, dimethylsulfoxide (dmso, Me(2)SO), N,N-dimethylformamide (dmf), N,N-dimethylacetamide (dma), N,N'-dimethylpropyleneurea (dmpu), and 1,1,3,3-tetramethylurea (tmu), as well as in the sulfur donor solvent N,N-dimethylthioformamide (dmtf), has been investigated by extended X-ray absorption fine structure (EXAFS) and/or large angle X-ray scattering (LAXS) in solution, and by single crystal X-ray diffraction and/or EXAFS of solid hydrates and solvates. Lead(II) may either form hemidirected complexes with large bond distance distribution and an apparent gap for excess electron density, or holodirected ones with a symmetric coordination sphere with normal bond distance distribution, depending on the strength of antibonding lead 6s/ligand np molecular orbital interactions and ligand-ligand interactions. The crystallographic data show that the solid lead(II) perchlorate and trifluoromethanesulfonate hydrate structures are hemidirected, while the solid lead(II) solvates of dma and dmpu have regular octahedral configuration with holodirected geometry and mean Pb-O bond distances in the range 2.50-2.52 Å. EXAFS data on the hydrated lead(II) ion in aqueous solution show broad bond distance distribution and a lack of inner-core multiple scattering contributions strongly indicating a hemidirected structure. The Pb-O bond distances found both by EXAFS and LAXS, 2.54(1) Å, point to a six-coordinate hydrated lead(II) ion in hemidirected fashion with an unevenly distributed electron density. The results obtained for the dmso solvated lead(II) ion in solution are ambiguous, but for the most part support a six-coordinate hemidirected complex. The mean Pb-O bond distances determined in dmf and dma solution by LAXS, 2.55(1) and 2.48(1) Å, respectively, indicate that in both solvate complexes lead(II) binds six solvent molecules with the former complex being hemidirected whereas the latter is holodirected. The

  10. Spectroscopic study of mimetite-vanadinite solid solution series - preliminary results

    NASA Astrophysics Data System (ADS)

    Janicka, Urszula; Bajda, Tomasz; Topolska, Justyna; Manecki, Maciej

    2014-05-01

    Mimetite Pb5(AsO4)3Cl and vanadinite Pb5(VO4)3Cl are minerals from the Pb-apatites family which belong to the apatite supergroup. Most often they crystalize under hypergenic conditions, in oxidation zones of Pb ore deposits, where they form paragenesis with pyromorphite Pb5(PO4)3Cl. These minerals are used in the techniques of soils reclamation. Their crystal structure allows substituting of metal cations as well as of anionic complexes. Natural mimetite often contains admixture of phosphates and/or vanadates. Similarly, vanadinite contains admixtures of phosphates and/or arsenates. Among the lead apatites, properties of the minerals from pyromorphite-mimetite solid solution series are well known, while the knowledge about the mimetite-vanadinite series is incomplete. The aim of this research was synthesis and spectroscopic characterization of mimetite-vanadinite solid solution series. Mimetite, vanadinite and their solid solution were synthesized from aqueous solutions by dropwise mixing of Pb(NO3)2, Na3VO4, Na2HAsO4×7H2O and NaCl at 25 ºC and pH = 3.5. Products of the syntheses were analyzed by X-Ray diffraction (XRD), Infrared absorption spectroscopy (FTIR) and Raman spectroscopy. The precipitates formed in the syntheses were identified by the XRD method as mimetite, vanadinite and their solid solutions. Other crystalline phases were not present in synthetic precipitates within the detection limit of XRD. In the Mid-IR spectra of mimetite-vanadinite solid solutions series, bands characteristic for vibrations of As-O bonds of the AsO4 tetrahedra and vibrations of V-O bonds of the VO4 tetrahedra were observed. The band corresponding to stretching ν3vibrations of AsO4 and VO4 occured in the range 700-900 cm-1. In the Raman spectra, bands which are characteristic for vibrations of As-O bonds of the AsO4 tetrahedra and vibrations of V-O bonds of the VO4 tetrahedra were also observed. The bands attributed to vibrations in the AsO4 tetrahedra appeared at 880-740 cm

  11. Synthesis, characterization, and enthalpy of mixing of the (Fe,Mg)C0 3 solid solution

    NASA Astrophysics Data System (ADS)

    Chai, L.; Navrotsky, A.

    1996-11-01

    Solid solutions along the magnesite-siderite join have been synthesized from mechanical mixtures of iron oxalate and basic magnesium carbonate using hydrothermal synthesis techniques at 500°C and about 2 kilobars. The double capsule method was used to provide the atmosphere necessary to prevent decomposition and oxidation of the Fe 2+-bearing carbonate. The synthetic samples were characterized by x-ray diffraction (XRD) and thermogravimetric analysis (TGA). Unit cell parameters, determined from x-ray diffraction in step scan mode, show a linear relationship with composition. The compositions and homogeneity of the sample were confirmed by electron microprobe analysis. Enthalpy of mixing was measured using a Calvet-type calorimeter at 770°C. A two step calorimetric method was developed and confirmed to be successful in determining the energetics of the Fe 2+-bearing carbonates. The first step involved decomposition of the sample in an oxygen atmosphere, and then the decomposition of the sample in an oxygen atmosphere, and then the decomposition products (a mixture of a spinel phase, MgFe 2O 4, and MgO or hematite) were dissolved in lead borate solvent in air as the second step. The enthalpies of mixing are slightly positive, with a regular solution parameter of 4.44 ± 0.75 kJ/mol. Under the assumption of regular solution, the phase diagram of the FeC0 3sbnd MgCO 3 system has been calculated, and the critical temperature for exsolution is about -6°C. Thus, the (Fe,Mg) CO 3 solid solution is expected to be complete and nearly ideal in all geological environments.

  12. Synthesis and crystallographic study of Pb-Sr hydroxyapatite solid solutions by high temperature mixing method under hydrothermal conditions

    SciTech Connect

    Zhu Kongjun; Yanagisawa, Kazumichi; Shimanouchi, Rie; Onda, Ayumu; Kajiyoshi, Koji; Qiu Jinhao

    2009-06-03

    The solid solutions in the system of Pb and Sr hydroxyapatite, Sr{sub 10-x}Pb{sub x}HAp (x = 0-10), were successfully synthesized by high-temperature mixing method (HTMM) at 160 deg. C for 12 h under hydrothermal conditions. The samples were characterized by X-ray diffraction, chemical analysis and electron microscopic observation, and the site of the metal ions in the solid solutions was analyzed with the Rietveld method. The lattice constants, both a and c, of the solid solutions varied linearly with Pb content. It was found that Pb ions in the solid solutions preferentially occupied the M(2) site in the apatite structure. HTMM gives Sr-Pb HAp solid solutions much better crystallization. However, due to the formation of intermediate compound of Pb{sub 3}O{sub 2}(OH){sub 2} in the Pb(NO{sub 3}){sub 2}.4H{sub 2}O solution before mixing with (NH{sub 4}){sub 2}HPO{sub 4} solution at 160 deg. C, HTMM causes the decrease of crystallization of the samples with high Pb content.

  13. Temperature-dependent vibrational spectra of zinc(II) bis-(N,N'-diethyldithiocarbamate) in solid state and solution

    NASA Astrophysics Data System (ADS)

    Trendafilova, N.; Kellner, R.

    The IR spectra of zinc(II) bis-(N,N'-diethyldithiocarbamate) in the solid state (at 20, 80 and 120°C) as well as in solution (20°C) have been recorded and discussed as to the changes in the zinc coordination sphere that may occur upon heating and dissolution. The decreased number of bands in the high-temperature and in the solution specta as compared with the room temperature solid state spectra has been explained by removal of the intermolecular contacts upon dissolution or thermal averaging in the high temperature solid state.

  14. The origin of ultrahigh piezoelectricity in relaxor-ferroelectric solid solution crystals

    PubMed Central

    Li, Fei; Zhang, Shujun; Yang, Tiannan; Xu, Zhuo; Zhang, Nan; Liu, Gang; Wang, Jianjun; Wang, Jianli; Cheng, Zhenxiang; Ye, Zuo-Guang; Luo, Jun; Shrout, Thomas R.; Chen, Long-Qing

    2016-01-01

    The discovery of ultrahigh piezoelectricity in relaxor-ferroelectric solid solution single crystals is a breakthrough in ferroelectric materials. A key signature of relaxor-ferroelectric solid solutions is the existence of polar nanoregions, a nanoscale inhomogeneity, that coexist with normal ferroelectric domains. Despite two decades of extensive studies, the contribution of polar nanoregions to the underlying piezoelectric properties of relaxor ferroelectrics has yet to be established. Here we quantitatively characterize the contribution of polar nanoregions to the dielectric/piezoelectric responses of relaxor-ferroelectric crystals using a combination of cryogenic experiments and phase-field simulations. The contribution of polar nanoregions to the room-temperature dielectric and piezoelectric properties is in the range of 50–80%. A mesoscale mechanism is proposed to reveal the origin of the high piezoelectricity in relaxor ferroelectrics, where the polar nanoregions aligned in a ferroelectric matrix can facilitate polarization rotation. This mechanism emphasizes the critical role of local structure on the macroscopic properties of ferroelectric materials. PMID:27991504

  15. Mesoporous MnCeOx solid solutions for low temperature and selective oxidation of hydrocarbons

    DOE PAGES

    Zhang, Pengfei; Lu, Hanfeng; Zhou, Ying; ...

    2015-10-15

    The development of noble-metal-free heterogeneous catalysts that can realize the aerobic oxidation of C–H bonds at low temperature is a profound challenge in the catalysis community. Here we report the synthesis of a mesoporous Mn0.5Ce0.5Ox solid solution that is highly active for the selective oxidation of hydrocarbons under mild conditions (100–120 °C). Notably, the catalytic performance achieved in the oxidation of cyclohexane to cyclohexanone/cyclohexanol (100 °C, conversion: 17.7%) is superior to those by the state-of-art commercial catalysts (140–160 °C, conversion: 3-5%). Finally, the high activity can be attributed to the formation of a Mn0.5Ce0.5Ox solid solution with an ultrahigh manganesemore » doping concentration in the CeO2 cubic fluorite lattice, leading to maximum active surface oxygens for the activation of C–H bonds and highly reducible Mn4+ ions for the rapid migration of oxygen vacancies from the bulk to the surface.« less

  16. Mesoporous MnCeOx solid solutions for low temperature and selective oxidation of hydrocarbons

    NASA Astrophysics Data System (ADS)

    Zhang, Pengfei; Lu, Hanfeng; Zhou, Ying; Zhang, Li; Wu, Zili; Yang, Shize; Shi, Hongliang; Zhu, Qiulian; Chen, Yinfei; Dai, Sheng

    2015-10-01

    The development of noble-metal-free heterogeneous catalysts that can realize the aerobic oxidation of C-H bonds at low temperature is a profound challenge in the catalysis community. Here we report the synthesis of a mesoporous Mn0.5Ce0.5Ox solid solution that is highly active for the selective oxidation of hydrocarbons under mild conditions (100-120 °C). Notably, the catalytic performance achieved in the oxidation of cyclohexane to cyclohexanone/cyclohexanol (100 °C, conversion: 17.7%) is superior to those by the state-of-art commercial catalysts (140-160 °C, conversion: 3-5%). The high activity can be attributed to the formation of a Mn0.5Ce0.5Ox solid solution with an ultrahigh manganese doping concentration in the CeO2 cubic fluorite lattice, leading to maximum active surface oxygens for the activation of C-H bonds and highly reducible Mn4+ ions for the rapid migration of oxygen vacancies from the bulk to the surface.

  17. Transformation of photophysical properties from solution to solid state in alkoxy-cyano-diphenylacetylene molecules.

    PubMed

    Karunakaran, Venugopal; Prabhu, Deepak D; Das, Suresh; Varughese, Sunil

    2015-07-28

    Detailed photophysical properties of cyano and mono (MA)/bis alkoxy (DA) substituted diphenylacetylene moieties with different alkyl chain lengths (methyl (1), octyl (8) and dodecyl (12)) were investigated in solution and the solid state in an effort to determine the effect of self-aggregation on these properties. The solvated molecules showed a minimal bathochromic shift with an increase of solvent polarity in their absorption spectra, whereas a significant shift was observed in the emission spectra. This could be attributed to the relatively low change in dipole moment between ground and Franck-Condon excited states and luminescence arising from the intramolecular charge transfer state with a dipole moment significantly higher than that of the ground state. In solid state the emission quantum yields of these materials were significantly higher than in solution. For DA1, polymorphic materials with distinct photophysical properties were obtained. The DA1 materials obtained by fast precipitation (DA1) showed broad fluorescence with peaks at 398, 467 and 535 nm upon excitation at different wavelengths. Detailed analysis of absorption, emission and excitation spectra and lifetime experiments indicated that these peaks could be attributed to the monomer, J- and H-type aggregates respectively. Whereas the crystals obtained by slow crystallization (DA1C) showed only one emission peak at around 396 nm attributed to the monomer. This is supported by the single crystal X-ray structure which consists of a monomer molecule having minimal interaction with nearest neighbour molecules.

  18. Electrophysical properties of solid solutions of silver in PbTe

    SciTech Connect

    Sharov, M. K.

    2012-05-15

    The thermopower coefficient {alpha}{sub 0} and the electrical conductivity {sigma} of Pb{sub 1-x}Ag{sub x}Te solid solutions, where x = (0-0.007), are measured at T = 300 K. The hole concentration p is calculated. All samples are of the p type. With increasing silver content, {alpha}{sub 0} decreases, while p and {sigma} increase. For undoped crystals, {alpha}{sub 0} = 251.0 {mu}V/K, p = 1.1 Multiplication-Sign 10{sup 18} cm{sup -3}, and {sigma} = 165 {Omega}{sup -1} cm{sup -1}. At the silver-solubility limit for x = 0.007, {alpha}{sub 0} = 193.8 {mu}V/K, p = 2.3 Multiplication-Sign 10{sup 18} cm{sup -3}, and {sigma} = 216 {Omega}{sup -1} cm{sup -1}. The hole concentration in all samples is much lower than the concentration of introduced silver atoms. The hole gas in Pb{sub 1-x}Ag{sub x}Te solid solutions is weakly degenerate in the entire silver-concentration range.

  19. Solid analyte and aqueous solutions sensing based on a flexible terahertz dual-band metamaterial absorber

    NASA Astrophysics Data System (ADS)

    Yan, Xin; Liang, Lan-Ju; Ding, Xin; Yao, Jian-Quan

    2017-02-01

    A high-sensitivity sensing technique was demonstrated based on a flexible terahertz dual-band metamaterial absorber. The absorber has two perfect absorption peaks, one with a fundamental resonance (f1) of the structure and another with a high-order resonance (f2) originating from the interactions of adjacent unit cells. The quality factor (Q) and figure of merit of f2 are 6 and 14 times larger than that of f1, respectively. For the solid analyte, the changes in resonance frequency are monitored upon variation of analyte thickness and index; a linear relation between the amplitude absorption with the analyte thickness is achieved for f2. The sensitivity (S) is 31.2% refractive index units (RIU-1) for f2 and 13.7% RIU-1 for f1. For the aqueous solutions, the amplitude of absorption decreases linearly with increasing the dielectric constant for the ethanol-water mixture of f1. These results show that the designed absorber cannot only identify a solid analyte but also characterize aqueous solutions through the frequency shift and amplitude absorption. Therefore, the proposed absorber is promising for future applications in high-sensitivity monitoring biomolecular, chemical, ecological water systems, and aqueous biosystems.

  20. Influence of fluorine in the synthesis of apatites. Synthesis of solid solutions of hydroxy-fluorapatite.

    PubMed

    Rodríguez-Lorenzo, L M; Hart, J N; Gross, K A

    2003-09-01

    Hydroxy-fluorapatites (OH-FAps) occur biologically in teeth and form the basis for application as biomaterials. This work aims to synthesize a series of fluoride substituted calcium hydroxyapatites (OHAps) to determine how fluoride influences the synthesis and the resulting characteristics of solid solutions. OH-FAPs powders were synthesized with a chemical composition of Ca(10)(PO(4))(6)(OH)(2-x) F(x), with x=0.0, 0.4, 0.8, 1.2, 1.6 and 2.0. The synthesis of partially substituted OHAp yields materials with lower crystallinity and higher specific surface area than OHAp or fluorapatite (FAp). The smallest crystal size of 263A, occurs at less than 50% hydroxyl substitution with fluoride at x=0.4, and the highest surface area of 132m(2)/g occurs at x=0.8. Reaction kinetics occur faster at higher fluoride content, producing the expected Ca/P ratio of 1.67 only for x=2.0. X-ray and IR studies show that OH-FAPs are homogeneous solid solutions instead of mixtures of OHAp and FAp. The presence of a high fluoride concentration increases the driving force for crystal growth during the calcination process.

  1. Manipulation of σy/κ ratio in single phase FCC solid-solutions

    NASA Astrophysics Data System (ADS)

    Lee, J. I.; Oh, H. S.; Park, E. S.

    2016-08-01

    We investigate how to manipulate the ratio between thermal conductivity (κ) and yield strength (σy) in face-centered cubic solid-solutions by varying the number of principal elements (NPEs) and temperature. The influence of NPEs on κ and its electronic (κe) and lattice (κl) contribution is evaluated using the Wiedemann-Franz law. Positive Δκ/ΔT and the highest κl/κe ratio in high-entropy alloys (HEAs) can be understood by considering severe lattice distortion and compositional complexity. Among the solid-solutions from Ni to quinary alloys, the NiCoFeCrMn HEA exhibits the lowest κ. However, σy increases with increasing NPEs and decreasing temperature. Thus, the NiCoFeCrMn HEA exhibits the highest σy/κ ratio, higher than those of representative cryogenic alloys, which can be distinctively increased with a decrease in temperature. These results would give us a guideline on how to manipulate properties using HEA design concept in order to develop idealized cryogenic materials.

  2. Multiple Multidentate Halogen Bonding in Solution, in the Solid State, and in the (Calculated) Gas Phase.

    PubMed

    Jungbauer, Stefan H; Schindler, Severin; Herdtweck, Eberhardt; Keller, Sandro; Huber, Stefan M

    2015-09-21

    The binding properties of neutral halogen-bond donors (XB donors) bearing two multidentate Lewis acidic motifs toward halides were investigated. Employing polyfluorinated and polyiodinated terphenyl and quaterphenyl derivatives as anion receptors, we obtained X-ray crystallographic data of the adducts of three structurally related XB donors with tetraalkylammonium chloride, bromide, and iodide. The stability of these XB complexes in solution was determined by isothermal titration calorimetry (ITC), and the results were compared to X-ray analyses as well as to calculated binding patterns in the gas phase. Density functional theory (DFT) calculations on the gas-phase complexes indicated that the experimentally observed distortion of the XB donors during multiple multidentate binding can be reproduced in 1:1 complexes with halides, whereas adducts with two halides show a symmetric binding pattern in the gas phase that is markedly different from the solid state structures. Overall, this study demonstrates the limitations in the transferability of binding data between solid state, solution, and gas phase in the study of complex multidentate XB donors.

  3. Specific heat critical behavior in Bi1-xSbx solid solutions

    NASA Astrophysics Data System (ADS)

    Rogacheva, E. I.; Doroshenko, A. N.; Nashchekina, O. N.; Dresselhaus, M. S.

    2016-09-01

    Studies of the specific heat Cp room temperature concentration dependences for the Bi1-xSbx (x = 0-0.12) solid solutions have shown that in the Cp(x) curves, three peaks of Cp are observed near x = 0.015, x = 0.037, and x = 0.07. These peaks are attributed to critical phenomena accompanying second-order concentration phase transitions (PT) from dilute to concentrated solid solutions, to a gapless state, and a semimetal-semiconductor transition, respectively. The numerical values for the critical exponents of the specific heat α for the Cp peaks near x = 0.015 and x = 0.037 have been determined within the framework of fluctuation theory for second-order phase transitions and percolation theory. It was shown that the α values (α = 0.11 ± 0.005) are the same within the margin of error for both peaks and correspond to the values theoretically calculated within the framework of scale-invariant theory for three-dimensional (3D) models and determined experimentally for different physical systems undergoing second-order phase transitions.

  4. Influence of chemical disorder on energy dissipation and defect evolution in concentrated solid solution alloys

    DOE PAGES

    Zhang, Yanwen; Stocks, George Malcolm; Jin, Ke; ...

    2015-10-28

    A long-standing objective in materials research is to understand how energy is dissipated in both the electronic and atomic subsystems in irradiated materials, and how related non-equilibrium processes may affect defect dynamics and microstructure evolution. Here we show that alloy complexity in concentrated solid solution alloys having both an increasing number of principal elements and altered concentrations of specific elements can lead to substantial reduction in the electron mean free path and thermal conductivity, which has a significant impact on energy dissipation and consequentially on defect evolution during ion irradiation. Enhanced radiation resistance with increasing complexity from pure nickel tomore » binary and to more complex quaternary solid solutions is observed under ion irradiation up to an average damage level of 1 displacement per atom. Understanding how materials properties can be tailored by alloy complexity and their influence on defect dynamics may pave the way for new principles for the design of radiation tolerant structural alloys.« less

  5. Mechanistic study of carvacrol processing and stabilization as glassy solid solution and microcapsule.

    PubMed

    Tackenberg, Markus W; Geisthövel, Carola; Marmann, Andreas; Schuchmann, Heike P; Kleinebudde, Peter; Thommes, Markus

    2015-01-30

    Essential oils and other liquid active pharmaceutical ingredients (APIs) are frequently microencapsulated to improve shelf life, handling, and for tailoring release. A glassy solid solution (GSS), a single-phase system, where the excipient is plasticized by the API, could be an alternative formulation system. Thus this study focuses on the investigation of two formulation strategies using carvacrol as a model compound, namely a microcapsule (MC) and a glassy solid solution (GSS). Applying the solubility parameter approach, polyvinylpyrrolidone (PVP) was chosen as a suitable matrix material for a GSS system, whereas maltodextrin and sucrose served as excipients for a microcapsule (MC) system. Differential scanning calorimetry (DSC) measurements of the excipients' glass transition temperatures and the melting point of carvacrol verified plasticizing properties of carvacrol on PVP. Batch mixing processes, as preliminary experiments for future extrusion processes, were performed to prepare GSSs and MCs with various amounts of carvacrol, followed by crushing and sieving. Maximally 4.5% carvacrol was encapsulated in the carbohydrate material, whereas up to 16.3% were stabilized as GSS, which is an outstanding amount. However, grinding of the samples led to a loss of up to 30% of carvacrol.

  6. Thermoelectric properties of the Ca(5)Al(2-x)In(x)Sb(6) solid solution.

    PubMed

    Zevalkink, Alex; Swallow, Jessica; Ohno, Saneyuki; Aydemir, Umut; Bux, Sabah; Snyder, G Jeffrey

    2014-11-14

    Zintl phases are attractive for thermoelectric applications due to their complex structures and bonding environments. The Zintl compounds Ca(5)Al(2)In(x)Sb(6)and Ca(5)Al(2)In(x)Sb(6) have both been shown to have promising thermoelectric properties, with zT values of 0.6 and 0.7, respectively, when doped to control the carrier concentration. Alloying can often be used to further improve thermoelectric materials in cases when the decrease in lattice thermal conductivity outweighs reductions to the electronic mobility. Here we present the high temperature thermoelectric properties of the Ca(5)Al(2-x)In(x)Sb(6)solid solution. Undoped and optimally Zn-doped samples were investigated. X-ray diffraction confirms that a full solid solution exists between the Al and In end-members. We find that the Al : In ratio does not greatly influence the carrier concentration or Seebeck effect. The primary effect of alloying is thus increased scattering of both charge carriers and phonons, leading to significantly reduced electronic mobility and lattice thermal conductivity at room temperature. Ultimately, the figure of merit is unaffected by alloying in this system, due to the competing effects of reduced mobility and lattice thermal conductivity.

  7. Pressureless sintered beta-prime-Si3N4 solid solution - Fabrication, microstructure, and strength

    NASA Technical Reports Server (NTRS)

    Dutta, S.

    1977-01-01

    Pressureless sintering of beta-prime-Si3N4 solid solution was studied as a function of temperature using Si3N4, A1N, and Al2O3 as basic constituents. Y2O3-SiO2 additions were used to promote liquid-phase sintering. The sintered specimens were characterized with respect to density, microstructure, strength, oxidation, and thermal shock resistance. Density greater than 98 percent of theoretical was achieved by pressureless sintering at 1750 C. The microstructure consisted essentially of fine-grained beta-prime-Si3N4 solid solution as the major phase. Modulus of rupture strengths up to 483 M Pa were achieved at moderate temperature (1000 C), but decreased to 228 M Pa at 1380 C. This substantial strength loss was attributed to a 'glassy' grain boundary phase formed during cooling from the sintering temperature. The best oxidation resistance was exhibited by a composition containing 3 mol % Y2O3-SiO2 additives. Water quench thermal shock resistance was equivalent to that of reaction sintered silicon nitride but lower than hot-pressed silicon nitride.

  8. Pressureless sintered beta prime-Si3N4 solid solution: Fabrication, microstructure, and strength

    NASA Technical Reports Server (NTRS)

    Dutta, S.

    1977-01-01

    Si3N4, AlN, and Al2O3 were used as basic constituents in a study of the pressureless sintering of beta prime-Si3N4 solid solution as a function of temperature. Y2O3-SiO2 additions were used to promote liquid-phase sintering. The sintered specimens were characterized with respect to density, microstructure, strength, oxidation, and thermal shock resistance. Density greater than 98 percent of theoretical was achieved by pressureless sintering at 1750 C. The microstructure consisted essentially of fine-grained beta prime-Si3N4 solid solution as the major phase. Modulus of rupture strengths up to 483 MPa were achieved at moderate temperature (1000 C), but decreased to 228 MPa at 1380 C. This substantial strength loss was attributed to a glassy grain boundary phase formed during cooling from the sintering temperature. The best oxidation resistance was exhibited by a composition containing 3 mol % Y2O3-SiO2 additives. Water quench thermal shock resistance was equivalent to that of reaction sintered silicon nitride but lower than hot-pressed silicon nitride.

  9. The origin of ultrahigh piezoelectricity in relaxor-ferroelectric solid solution crystals

    NASA Astrophysics Data System (ADS)

    Li, Fei; Zhang, Shujun; Yang, Tiannan; Xu, Zhuo; Zhang, Nan; Liu, Gang; Wang, Jianjun; Wang, Jianli; Cheng, Zhenxiang; Ye, Zuo-Guang; Luo, Jun; Shrout, Thomas R.; Chen, Long-Qing

    2016-12-01

    The discovery of ultrahigh piezoelectricity in relaxor-ferroelectric solid solution single crystals is a breakthrough in ferroelectric materials. A key signature of relaxor-ferroelectric solid solutions is the existence of polar nanoregions, a nanoscale inhomogeneity, that coexist with normal ferroelectric domains. Despite two decades of extensive studies, the contribution of polar nanoregions to the underlying piezoelectric properties of relaxor ferroelectrics has yet to be established. Here we quantitatively characterize the contribution of polar nanoregions to the dielectric/piezoelectric responses of relaxor-ferroelectric crystals using a combination of cryogenic experiments and phase-field simulations. The contribution of polar nanoregions to the room-temperature dielectric and piezoelectric properties is in the range of 50-80%. A mesoscale mechanism is proposed to reveal the origin of the high piezoelectricity in relaxor ferroelectrics, where the polar nanoregions aligned in a ferroelectric matrix can facilitate polarization rotation. This mechanism emphasizes the critical role of local structure on the macroscopic properties of ferroelectric materials.

  10. Controlling the Electronic Structures of Perovskite Oxynitrides and their Solid Solutions for Photocatalysis.

    PubMed

    Umezawa, Naoto; Janotti, Anderson

    2016-05-10

    Band-gap engineering of oxide materials is of great interest for optoelectronics, photovoltaics, and photocatalysis applications. In this study, electronic structures of perovskite oxynitrides, LaTiO2 N and SrNbO2 N, and solid solutions, (SrTiO3 )1-x (LaTiO2 N)x and (SrTiO3 )1-x (SrNbO2 N)x , are investigated using hybrid density functional calculations. Band gaps of LaTiO2 N and SrNbO2 N are much smaller than that of SrTiO3 owing to the formation of a N 2p band, which is higher in energy than the O 2p band. The valence- and conduction-band offsets of SrTiO3 /LaTiO2 N and SrTiO3 /SrNbO2 N are computed, and the adequacy for H2 evolution is analyzed by comparing the positions of the band edges with respect to the standard hydrogen electrode (SHE). The band gap of (SrTiO3 )1-x (LaTiO2 N)x and (SrTiO3 )1-x (SrNbO2 N)x solid solutions are also discussed.

  11. Mesoporous MnCeOx solid solutions for low temperature and selective oxidation of hydrocarbons

    PubMed Central

    Zhang, Pengfei; Lu, Hanfeng; Zhou, Ying; Zhang, Li; Wu, Zili; Yang, Shize; Shi, Hongliang; Zhu, Qiulian; Chen, Yinfei; Dai, Sheng

    2015-01-01

    The development of noble-metal-free heterogeneous catalysts that can realize the aerobic oxidation of C–H bonds at low temperature is a profound challenge in the catalysis community. Here we report the synthesis of a mesoporous Mn0.5Ce0.5Ox solid solution that is highly active for the selective oxidation of hydrocarbons under mild conditions (100–120 °C). Notably, the catalytic performance achieved in the oxidation of cyclohexane to cyclohexanone/cyclohexanol (100 °C, conversion: 17.7%) is superior to those by the state-of-art commercial catalysts (140–160 °C, conversion: 3-5%). The high activity can be attributed to the formation of a Mn0.5Ce0.5Ox solid solution with an ultrahigh manganese doping concentration in the CeO2 cubic fluorite lattice, leading to maximum active surface oxygens for the activation of C–H bonds and highly reducible Mn4+ ions for the rapid migration of oxygen vacancies from the bulk to the surface. PMID:26469151

  12. Mechanical Properties of Mg-Gd and Mg-Y Solid Solutions

    NASA Astrophysics Data System (ADS)

    Kula, Anna; Jia, Xiaohui; Mishra, Raj K.; Niewczas, Marek

    2016-12-01

    The mechanical properties of Mg-Gd and Mg-Y solid solutions have been studied under uniaxial tension and compression between 4 K and 298 K (-269 °C and 25 °C). The results reveal that Mg-Gd alloys exhibit higher strength and ductility under tension and compression attributed to the more effective solid solution strengthening and grain-boundary strengthening effects. Profuse twinning has been observed under compression, resulting in a material texture with strong dominance of basal component parallel to compression axis. Under tension, twining is less active and the texture evolution is controlled mostly by slip. The alloys exhibit pronounced yield stress asymmetry and significantly different work-hardening behavior under tension and compression. Increasing of Gd and/or Y concentration leads to the reduction of the tension-compression asymmetry due to the weakening of the recrystallization texture and more balanced twinning and slip activity during plastic deformation. The results suggest that under compression of Mg-Y alloys slip is more active than twinning in comparison to Mg-Gd alloys.

  13. The origin of ultrahigh piezoelectricity in relaxor-ferroelectric solid solution crystals

    SciTech Connect

    Li, Fei; Zhang, Shujun; Yang, Tiannan; Xu, Zhuo; Zhang, Nan; Liu, Gang; Wang, Jianjun; Wang, Jianli; Cheng, Zhenxiang; Ye, Zuo-Guang; Luo, Jun; Shrout, Thomas R.; Chen, Long-Qing

    2016-12-19

    The discovery of ultrahigh piezoelectricity in relaxor-ferroelectric solid solution single crystals is a breakthrough in ferroelectric materials. A key signature of relaxor-ferroelectric solid solutions is the existence of polar nanoregions, a nanoscale inhomogeneity, that coexist with normal ferroelectric domains. Despite two decades of extensive studies, the contribution of polar nanoregions to the underlying piezoelectric properties of relaxor ferroelectrics has yet to be established. Here we quantitatively characterize the contribution of polar nanoregions to the dielectric/piezoelectric responses of relaxor-ferroelectric crystals using a combination of cryogenic experiments and phase-field simulations. The contribution of polar nanoregions to the room-temperature dielectric and piezoelectric properties is in the range of 50–80%. A mesoscale mechanism is proposed to reveal the origin of the high piezoelectricity in relaxor ferroelectrics, where the polar nanoregions aligned in a ferroelectric matrix can facilitate polarization rotation. This mechanism emphasizes the critical role of local structure on the macroscopic properties of ferroelectric materials.

  14. All-proportional solid-solution Rh-Pd-Pt alloy nanoparticles by femtosecond laser irradiation of aqueous solution with surfactant

    NASA Astrophysics Data System (ADS)

    Sarker, Md. Samiul Islam; Nakamura, Takahiro; Sato, Shunichi

    2015-06-01

    Formation of Rh-Pd-Pt solid-solution alloy nanoparticles (NPs) by femtosecond laser irradiation of aqueous solution in the presence of polyvinylpyrrolidone (PVP) or citrate as a stabilizer was studied. It was found that the addition of surfactant (PVP or citrate) significantly contributed to reduce the mean size of the particles to 3 nm for PVP and 10 nm for citrate, which was much smaller than that of the particles fabricated without any surfactants (20 nm), and improved the dispersion state as well as the colloidal stability. The solid-solution formation of the Rh-Pd-Pt alloy NPs was confirmed by the XRD results that the diffraction pattern was a single peak, which was found between the positions corresponding to each pure Rh, Pd, and Pt NPs. Moreover, all the elements were homogeneously distributed in every particle by STEM-EDS elemental mapping, strongly indicating the formation of homogeneous solid-solution alloy. Although the Rh-Pd-Pt alloy NPs fabricated with PVP was found to be Pt rich by EDS observation, the composition of NPs fabricated with citrate almost exactly preserved the feeding ratio of ions in the mixed solution. To our best knowledge, these results demonstrated for the first time, the formation of all-proportional solid-solution Rh-Pd-Pt alloy NPs with well size control.

  15. ZrB2-HfB2 solid solutions as electrode materials for hydrogen reaction in acidic and basic solutions

    DOE PAGES

    Sitler, Steven J.; Raja, Krishnan S.; Charit, Indrajit

    2016-11-09

    Spark plasma sintered transition metal diborides such as HfB2, ZrB2 and their solid solutions were investigated as electrode materials for electrochemical hydrogen evolutions reactions (HER) in 1 M H2SO4 and 1 M NaOH electrolytes. HfB2 and ZrB2 formed complete solid solutions when mixed in 1:1, 1:4, and 4:1 ratios and they were stable in both electrolytes. The HER kinetics of the diborides were slower in the basic solution than in the acidic solutions. The Tafel slopes in 1 M H2SO4 were in the range of 0.15 - 0.18 V/decade except for pure HfB2 which showed a Tafel slope of 0.38more » V/decade. In 1 M NaOH the Tafel slopes were in the range of 0.12 - 0.27 V/decade. The composition of HfxZr1-xB2 solid solutions with x = 0.2 - 0.8, influenced the exchange current densities, overpotentials and Tafel slopes of the HER. As a result, the EIS data were fitted with a porous film equivalent circuit model in order to better understand the HER behavior. In addition, modeling calculations, using density functional theory approach, were carried out to estimate the density of states and band structure of the boride solid solutions.« less

  16. Dissolution of aragonite-strontianite solid solutions in nonstoichiometric Sr (HCO3)2-Ca (HCO3)2-CO2-H2O solutions

    USGS Publications Warehouse

    Plummer, L.N.; Busenberg, E.; Glynn, P.D.; Blum, A.E.

    1992-01-01

    Synthetic strontianite-aragonite solid-solution minerals were dissolved in CO2-saturated non-stoichiometric solutions of Sr(HCO3)2 and Ca(HCO3)2 at 25??C. The results show that none of the dissolution reactions reach thermodynamic equilibrium. Congruent dissolution in Ca(HCO3)2 solutions either attains or closely approaches stoichiometric saturation with respect to the dissolving solid. In Sr(HCO3)2 solutions the reactions usually become incongruent, precipitating a Sr-rich phase before reaching stoichiometric saturation. Dissolution of mechanical mixtures of solids approaches stoichiometric saturation with respect to the least stable solid in the mixture. Surface uptake from subsaturated bulk solutions was observed in the initial minutes of dissolution. This surficial phase is 0-10 atomic layers thick in Sr(HCO3)2 solutions and 0-4 layers thick in Ca(HCO3)2 solutions, and subsequently dissolves and/or recrystallizes, usually within 6 min of reaction. The initial transient surface precipitation (recrystallization) process is followed by congruent dissolution of the original solid which proceeds to stoichiometric saturation, or until the precipitation of a more stable Sr-rich solid. The compositions of secondary precipitates do not correspond to thermodynamic equilibrium or stoichiometric saturation states. X-ray photoelectron spectroscopy (XPS) measurements indicate the formation of solid solutions on surfaces of aragonite and strontianite single crystals immersed in Sr(HCO3)2 and Ca(HCO3)2 solutions, respectively. In Sr(HCO3)2 solutions, the XPS signal from the outer ~ 60 A?? on aragonite indicates a composition of 16 mol% SrCO3 after only 2 min of contact, and 14-18 mol% SrCO3 after 3 weeks of contact. The strontianite surface averages approximately 22 mol% CaCO3 after 2 min of contact with Ca(HCO3)2 solution, and is 34-39 mol% CaCO3 after 3 weeks of contact. XPS analysis suggests the surface composition is zoned with somewhat greater enrichment in the outer ~25

  17. Effect of solid solutions and second phases on the thermal conductivity of zirconium diboride ceramics

    NASA Astrophysics Data System (ADS)

    Harrington, Gregory John Kenneth

    The research presented in this dissertation is focused on the thermal conductivity (k) of ZrB2 ceramics. The goal was to develop a better understanding of how various solid solutions and second phases affect the thermal and electrical transport in ZrB2, with a focus on the effect of C, W, and ZrC. The first study showed C additions improved densification and it was proposed that the reduction of boria was the impetus for this result. Boron carbide was formed by the reaction of excess C with reduced B and its formation was mitigated by the addition of ZrH2. This allowed the ZrB2-C binary system to be evaluated for study two. Study two showed the k of ZrB2 is reduced by C in solid solution and as a second phase due to the decrease in the electron contribution to thermal conductivity. Conductivities of 99 (25°C) and 76 W/m*K (2000°C) were obtained for the most pure ZrB2 (0.026 wt% C in solution and 0.2 vol% zirconia) produced in this study, which are the highest reported values for ZrB2 processed using commercial powders since 1980. The third study evaluated the electrical resistivity of ZrB2 up to 1860°C using the van der Pauw technique. Separate linear regimes were observed below and above 950°C, whereas, previous studies assumed a linear relation. Finally the effect of ZrC on the (Zr,W)B2 solid solution was evaluated in study four. The formation of (Zr,W)C initially increased k, but further ZrC additions decreased k. In the end, this research provides both: (1) usable information for the design of future ultra-high temperature ceramic systems; and (2) fundamental research that lays the groundwork for future studies aimed at understanding thermal transport in diboride based materials.

  18. Temperature Dependence of the Mechanical Properties of Equiatomic Solid Solution Alloys with FCC Crystal Structures

    DOE PAGES

    Wu, Zhenggang; Bei, Hongbin; Pharr, George M.; ...

    2014-10-03

    We found that compared to decades-old theories of strengthening in dilute solid solutions, the mechanical behavior of concentrated solid solutions is relatively poorly understood. A special subset of these materials includes alloys in which the constituent elements are present in equal atomic proportions, including the high-entropy alloys of recent interest. A unique characteristic of equiatomic alloys is the absence of “solvent” and “solute” atoms, resulting in a breakdown of the textbook picture of dislocations moving through a solvent lattice and encountering discrete solute obstacles. Likewise, to clarify the mechanical behavior of this interesting new class of materials, we investigate heremore » a family of equiatomic binary, ternary and quaternary alloys based on the elements Fe, Ni, Co, Cr and Mn that were previously shown to be single-phase face-centered cubic (fcc) solid solutions. The alloys were arc-melted, drop-cast, homogenized, cold-rolled and recrystallized to produce equiaxed microstructures with comparable grain sizes. Tensile tests were performed at an engineering strain rate of 10-3 s-1 at temperatures in the range 77–673 K. Unalloyed fcc Ni was processed similarly and tested for comparison. The flow stresses depend to varying degrees on temperature, with some (e.g. NiCoCr, NiCoCrMn and FeNiCoCr) exhibiting yield and ultimate strengths that increase strongly with decreasing temperature, while others (e.g. NiCo and Ni) exhibit very weak temperature dependencies. Moreover, to better understand this behavior, the temperature dependencies of the yield strength and strain hardening were analyzed separately. Lattice friction appears to be the predominant component of the temperature-dependent yield stress, possibly because the Peierls barrier height decreases with increasing temperature due to a thermally induced increase of dislocation width. In the early stages of plastic flow (5–13% strain, depending on material), the temperature

  19. Temperature Dependence of the Mechanical Properties of Equiatomic Solid Solution Alloys with FCC Crystal Structures

    SciTech Connect

    Wu, Zhenggang; Bei, Hongbin; Pharr, George M.; George, Easo P.

    2014-10-03

    We found that compared to decades-old theories of strengthening in dilute solid solutions, the mechanical behavior of concentrated solid solutions is relatively poorly understood. A special subset of these materials includes alloys in which the constituent elements are present in equal atomic proportions, including the high-entropy alloys of recent interest. A unique characteristic of equiatomic alloys is the absence of “solvent” and “solute” atoms, resulting in a breakdown of the textbook picture of dislocations moving through a solvent lattice and encountering discrete solute obstacles. Likewise, to clarify the mechanical behavior of this interesting new class of materials, we investigate here a family of equiatomic binary, ternary and quaternary alloys based on the elements Fe, Ni, Co, Cr and Mn that were previously shown to be single-phase face-centered cubic (fcc) solid solutions. The alloys were arc-melted, drop-cast, homogenized, cold-rolled and recrystallized to produce equiaxed microstructures with comparable grain sizes. Tensile tests were performed at an engineering strain rate of 10-3 s-1 at temperatures in the range 77–673 K. Unalloyed fcc Ni was processed similarly and tested for comparison. The flow stresses depend to varying degrees on temperature, with some (e.g. NiCoCr, NiCoCrMn and FeNiCoCr) exhibiting yield and ultimate strengths that increase strongly with decreasing temperature, while others (e.g. NiCo and Ni) exhibit very weak temperature dependencies. Moreover, to better understand this behavior, the temperature dependencies of the yield strength and strain hardening were analyzed separately. Lattice friction appears to be the predominant component of the temperature-dependent yield stress, possibly because the Peierls barrier height decreases with increasing temperature due to a thermally induced increase of dislocation width. In the early stages of plastic flow (5–13% strain, depending on material), the

  20. THERMODYNAMICS AND SOLUBILITY OF (UxNp1-x)O2(am) SOLID SOLUTION IN THE CARBONATE SYSTEM

    SciTech Connect

    Rai, Dhanpat; Hess, Nancy J.; Yui, Mikazu; Felmy, Andrew R.; Moore, Dean A.

    2004-03-15

    ABSTRACT -The formation of a solid solution can significantly affect the solubility of a minor component. The objectives of this study were to determine the nature of U(IV) and Np(IV) solid solutions and their thermodynamic properties. For this purpose, co-precipitates of U(IV) and Np(IV) [(UxNp1-x )O2(am), with values for x of 0.95, 0.85, 0.50, 0.15, and 0.05] were prepared, characterized, and used to determine their solubility as a function of K2CO3 concentrations ranging from 1.0 m to 5.0 m in the presence of 0.01 m Na2S2O4 and 0.01 m KOH, and as a function of KHCO3 concentrations ranging from 0.1 m to 0.8 m in the presence of 0.01 m Na2S2O4. The solubility data show that the equilibrium in these systems is reached in <7 days, the solubility-controlling solids are amorphous, and that we were successful in maintaining U and Np in the tetravalent state. A scanning electron microscope equipped with energy dispersive spectrometry and x-ray absorption spectroscopic analyses of the solids indicated the equilibrated co-precipitates to be solid solutions. A close agreement between the thermodynamic predictions, assuming an ideal solid solution, and the experimental solubilities shows that U(IV) and Np(IV) form an ideal solid solution and that non-ideal solid solution behavior for this system can be ruled out.

  1. Cobalt incorporation in calcite: thermochemistry of (Ca,Co)CO3 solid solutions from density functional theory simulations

    NASA Astrophysics Data System (ADS)

    González-López, Jorge; Ruiz-Hernández, Sergio E.; Fernández-González, Ángeles; Jiménez, Amalia; de Leeuw, Nora H.; Grau-Crespo, Ricardo

    2015-04-01

    The incorporation of cobalt in mixed metal carbonates is a possible route to the immobilization of this toxic element in the environment. However, the thermodynamics of (Ca,Co)CO3 solid solutions are still unclear due to conflicting data from experiment and from the observation of natural ocurrences. Atomistic computer simulations, which allow the evaluation of thermodynamic properties without the interference of unknown kinetic factors, have been increasingly used in recent years for the investigation of the thermodynamics of mixing and impurity incorporation in carbonate. We report here the results of a computer simulation study of the mixing of calcite (CaCO3) and spherocobaltite (CoCO3), using density functional theory calculations. Our simulations suggest that previously proposed thermodynamic models, based only on observed compositions, significantly overestimate the solubility between the two solids and therefore underestimate the extension of the miscibility gap under ambient conditions. The enthalpy of mixing of the disordered solid solution is strongly positive and moderately asymmetric: calcium incorporation in spherocobaltite is more endothermic than cobalt incorporation in calcite. Ordering of the impurities in (0001) layers is energetically favourable with respect to the disordered solid solution at low temperatures and intermediate compositions, but the ordered phase is still unstable to demixing. The solvus and spinodal lines in the phase diagram using a sub-regular solution model has been also calculated, and conclude that many Ca1-xCoxCO3 mineral solid solutions (with observed compositions of up to x=0.027, and above x=0.93) are metastable with respect to phase separation. The strong non-ideality of this solid solution has an important effect on the solid solution / aqueous solution thermodynamic partitioning: the equilibrium level of substitutional impurities in the endmember solids is always low, regardless of the composition of the aqueous

  2. Solid-State and Solution Metallophilic Aggregation of a Cationic [Pt(NCN)L](+) Cyclometalated Complex.

    PubMed

    Sivchik, Vasily V; Grachova, Elena V; Melnikov, Alexei S; Smirnov, Sergey N; Ivanov, Alexander Yu; Hirva, Pipsa; Tunik, Sergey P; Koshevoy, Igor O

    2016-04-04

    The noncovalent intermolecular interactions (π-π stacking, metallophilic bonding) of the cyclometalated complexes [Pt(NCN)L](+)X(-) (NCN = dipyridylbenzene, L = pyridine (1), acetonitrile (2)) are determined by the steric properties of the ancillary ligands L in the solid state and in solution, while the nature of the counterion X(-) (X(-) = PF6(-), ClO4(-), CF3SO3(-)) affects the molecular arrangement of 2·X in the crystal medium. According to the variable-temperature X-ray diffraction measurements, the extensive Pt···Pt interactions and π-stacking in 2·X are significantly temperature-dependent. The variable concentration (1)H and diffusion coefficients NMR measurements reveal that 2·X exists in the monomeric form in dilute solutions at 298 K, while upon increase in concentration [Pt(NCN)(NCMe)](+) cations undergo the formation of the ground-state oligomeric aggregates with an average aggregation number of ∼3. The photoluminescent characteristics of 1 and 2·X are largely determined by the intermolecular aggregation. For the discrete molecules the emission properties are assigned to metal perturbed IL charge transfer mixed with some MLCT contribution. In the case of oligomers 2·X the luminescence is significantly red-shifted with respect to 1 and originates mainly from the (3)MMLCT excited states. The emission energies depend on the structural arrangement in the crystal and on the complex concentration in solution, variation of which allows for the modulation of the emission color from greenish to deep red. In the solid state the lability of the ligands L leads to vapor-induced reversible transformation 1 ↔ 2 that is accompanied by the molecular reorganization and, consequently, dramatic change of the photophysical properties. Time-dependent density functional theory calculations adequately support the models proposed for the rationalization of the experimental observations.

  3. Solid solution trends that impact electrical design of submicron layers in dielectric capacitors

    NASA Astrophysics Data System (ADS)

    Levi, Roni D.

    It is predictable that future thin layer multilayer dielectrics and thin films embedded capacitors will require higher field and higher reliability performance. This thesis explores the fundamental factors that would limit the high field and reliability performance in thin layer dielectrics based on BaTiO3. Those factors have different origins: On one side, the nature of the metal-dielectric interface was shown to affect the high field dielectric properties of capacitive structures. In addition to that, the intrinsic bulk properties of BaTiO3 based solid solutions affect the high field properties of thin dielectric layers depending on composition and annealing conditions. Both effects were investigated in this study. The temperature dependence of the electrical leakage current density of chemical solution deposited BaTiO3 films on high purity Ni foils was investigated as function of the underlying Ni microstructure. The electrical properties were then characterized on capacitors with and without the presence of Ni grain boundaries. When a Ni grain boundary from the substrate was present in the capacitor used during the electrical measurements, the loss tangent of the capacitor rose rapidly for dc biases exceeding ˜25kV/cm. The critical bias increases to ˜100kV/cm when no substrate grain boundaries are included in the capacitor. In addition, the capacitance-voltage curves are much more symmetric when grain boundaries are absent. This disparity in the electrical behavior was analyzed in terms of the mechanisms of charge conduction across the Ni-dielectric interface. While a reverse biased Schottky emission mechanism dominates the current in areas free of Ni grain boundaries, the Schottky barrier at the cathode is less effective when Ni grain boundaries are present due to local enhancement of the electric field. This, leads to a larger leakage current dominated by the forward biased Schottky barrier at the anode. In addition to the interface influence, the

  4. Computer simulation of the motion of a straight dislocation line in concentrated solid solutions. II. [in fcc alloys

    NASA Technical Reports Server (NTRS)

    Kuo, C. T. K.; Arsenault, R. J.

    1977-01-01

    An investigation was undertaken to determine if the size and modulus interaction of a solute atom with a screw dislocation and the modulus interaction with an edge dislocation contributed to strengthening, in addition to the size interaction with an edge dislocation. The results indicate that the size interaction between solute atom and an edge dislocation accounts for most of the solid solution strengthening in f.c.c. alloys. The contribution to the yield stress from the modulus interaction with an edge dislocation is less than 15%. The interaction between a solute atom and a screw dislocation is much less than that between a solute atom and an edge dislocation.

  5. Iron site occupancies in magnetite-ulvospinel solid solution: A new approach using XMCD

    SciTech Connect

    Pearce, C. I.; Henderson, C. M. B.; Telling, N. D.; Pattrick, R. A.D.; Vaughan, D. J.; Charnock, J. M.; Arenholz, E.; Tuna, F.; Coker, V.S.; Laan, G. van der

    2009-06-22

    Ordering of Fe{sup 3+} and Fe{sup 2+} between octahedral (Oh) and tetrahedral (Td) sites in synthetic members of the magnetite (Fe{sub 3}O{sub 4}) - ulvoespinel (Fe{sub 2}TiO{sub 4}) solid-solution series was determined using Fe L{sub 2,3}-edge X-ray magnetic circular dichroism (XMCD) coupled with electron microprobe and chemical analysis, Ti L-edge spectroscopy, Fe K-edge EXAFS and XANES, Fe{sub 57} Moessbauer spectroscopy, and unit cell parameters. Microprobe analysis, cell edges and chemical FeO determinations showed that the bulk compositions of the samples were stoichiometric magnetite-ulvoespinel solid-solutions. Surface sensitive XMCD showed that the surfaces of these oxide minerals were more sensitive to redox conditions and some samples required re-equilibration with suitable solid-solid buffers. Detailed site-occupancy analysis of these samples gave XMCD-Fe{sup 2+}/Fe{sup 3+} ratios very close to stoichiometric values. L{sub 2,3}-edge spectroscopy showed that Ti{sup 4+} was restricted to Oh sites. XMCD results showed that significant Fe{sup 2+} only entered Td when the Ti content was > 0.40 apfu while Fe{sup 2+} in Oh increased from 1 a.p.f.u in magnetite to a maximum of {approx}1.4 apfu in USP45. As the Ti content increased from this point, the steady increase in Fe{sup 2+} in Td sites was clearly observable in the XMCD spectra, concurrent with a slow decrease in Fe{sup 2+} in Oh sites. Calculated magnetic moments showed a steady decrease from magnetite (4.06 {mu}{sub B}) to USP45 (1.5 {mu}{sub B}) and then a slower decrease towards the value for ulvoespinel (0 {mu}{sub B}). Two of the synthesized samples were also partially maghemitized by re-equilibrating with an oxidizing Ni-NiO buffer and XMCD showed that Fe{sup 2+} oxidation only occurred at Oh sites, with concomitant vacancy formation restricted to this site. This study shows the advantage of using XMCD as a direct measurement of Fe oxidation state in these complex magnetic spinels. These results

  6. Preparation and characterization of carbonated barium-calcium hydroxyapatite solid solutions.

    PubMed

    Yasukawa, Akemi; Ueda, Eiichi; Kandori, Kazuhiko; Ishikawa, Tatsuo

    2005-08-15

    Particles of carbonated barium-calcium hydroxyapatite solid solutions (BaCaHap) with different Ba/(Ba+Ca) (X(Ba)) atomic ratios were prepared by a wet method at 100 degrees C and characterized by various means. The crystal phases and structures of the products strongly depended on the composition of the starting solution, that is, the Ba/(Ba+Ca) atomic ratio ([X(Ba)]) and H3PO4 concentration ([H3PO4]) in the solution. BaCaHap with X(Ba)0.43 could be prepared at [X(Ba)]0.7 by changing [H3PO4], but could never be obtained at [X(Ba)]=0.8-0.95 regardless of [H3PO4]. The carbonated calcium hydroxyapatite particles prepared at [X(Ba)]=0 were fine and short rod-shaped particles (ca. 14x84 nm). With increasing [X(Ba)] from 0 to 0.8, the particles obtained became large spherical agglomerates. The carbonated barium hydroxyapatite particles formed at [X(Ba)]=1 were long rod-shaped agglomerates (ca. 0.2x2 microm) of fine primary particles. The amount of CO2 adsorbed irreversibly on a series of BaCaHaps showed a minimum at (Ba+Ca)/(P+C) atomic ratio of around 1.56, which agreed well with the minimum cation/P ratio obtained for the other hydroxyapatites, as already reported.

  7. One-pot synthesis of a ceria-graphene oxide composite for the efficient removal of arsenic species.

    PubMed

    Sakthivel, Tamil S; Das, Soumen; Pratt, Cameron J; Seal, Sudipta

    2017-03-09

    Arsenic contamination has posed a health risk to millions of people around the world. In this study, we describe a simple and facile one-step hydrothermal synthesis of a ceria-graphene oxide (ceria-GO) composite for the efficient removal of arsenic species. The prepared ceria-GO composite materials exhibited almost complete (over 99.99%) and quick removal of both arsenic species within 0.1 mg L(-1) of the initial concentration. The calculated adsorption capacities were 185 mg g(-1) for As(iii) and 212 mg g(-1) for As(v). It was found that Ce(3+) is an active site and continuously adsorbs arsenic species; there is a concomitant change from Ce(4+) to Ce(3+) due to the solution redox environment. This increase in the Ce(3+) concentration further facilitates the complete removal of arsenic species in solution. Thus our approach offers a promising potential for the treatment of arsenic-contaminated drinking water.

  8. Novel ceria-polymer microcomposites for chemical mechanical polishing

    NASA Astrophysics Data System (ADS)

    Coutinho, Cecil A.; Mudhivarthi, Subrahmanya R.; Kumar, Ashok; Gupta, Vinay K.

    2008-12-01

    Abrasive particles are key components in slurries for chemical mechanical polishing (CMP). Since the particle characteristics determine surface quality of wafers during polishing, in this research, novel abrasive composite particles have been developed. These composite particles contain nanoparticles of ceria dispersed within cross-linked, polymeric microspheres such that the average mass fraction of ceria is approximately 50% in the particles. The microspheres are formed by co-polymerization of N-isopropylacrylamide (NIPAM) with 3-(trimethoxysilyl)propyl methacrylate (MPS) and contain interpenetrating (IP) chains of poly(acrylic acid) (PAAc). Infrared spectroscopy, dynamic light scattering, and transmission electron microscopy are employed to characterize the composite particles. Planarization of silicon dioxide wafers is studied on a bench-top CMP tester and the polished surfaces are characterized by ellipsometry, atomic force and optical microscopy. Slurries formed from the composite ceria-polymer particles lead to lower topographical variations and surface roughness than slurries of only ceria nanoparticles even though both slurries achieve similar removal rates of ˜100 nm/min for similar ceria content. Polishing with the novel composite particles gives surfaces devoid of scratches and particle deposition, which makes these particles suitable for the next generation slurries in CMP.

  9. Temperature evolution of the crystal structure of Bi1 - xPrxFeO3 solid solutions

    NASA Astrophysics Data System (ADS)

    Karpinsky, D. V.; Troyanchuk, I. O.; Sikolenko, V. V.; Efimov, V.; Efimova, E.; Silibin, M. V.; Chobot, G. M.; Willinger, E.

    2014-11-01

    The crystal structure of solid solutions in the Bi1 - xPrxFeO3 system near the structural transition between the rhombohedral and orthorhombic phases (0.125 ≤ x ≤ 0.15) has been studied. The structural phase transitions induced by changes in the concentration of praseodymium ions and in the temperature have been investigated using X-ray diffraction, transmission electron microscopy, and differential scanning calorimetry. It has been established that the sequence of phase transformations in the crystal structure of Bi1 - xPrxFeO3 solid solutions with variations in the temperature differs significantly from the evolution of the crystal structure of the BiFeO3 compounds with the substitution of other rare-earth elements for bismuth ions. The regions of the existence of the single-phase structural state and regions of the coexistence of the structural phases have been determined in the investigation of the crystal structure of the Bi1 - xPrxFeO3 solid solutions. A three-phase structural state has been revealed for the solid solution with x = 0.125 at temperatures near 400°C. The specific features of the structural phase transitions of the compounds in the vicinity of the morphotropic phase boundary have been determined by analyzing the obtained results. It has been found that the solid solutions based on bismuth ferrite demonstrate a significant improvement in their physical properties.

  10. Influence of solid-solution treatment on microstructure, mechanical property and corrosion behavior of biodegradable Mg-Zn-Ca alloy

    NASA Astrophysics Data System (ADS)

    Ly, Xuan Nam; Yang, S.; Qin, Y.

    2017-03-01

    The influence of solid-solution treatment on microstructure, mechanical property and corrosion behavior of Mg-Zn-Ca alloy was studied in the present investigation by SEM, tensile test, electrochemical and immersion test. The results show that the microstructure of Mg alloys after solid solution treatment significantly changed, a large number of the second phase (Ca2Mg6Zn3, Mg2Ca) dissolved into the α-Mg matrix reaching a supersaturated state, and the grains size was bigger than before solid solution treatment; the mechanical properties were obviously improved. In particular the tensile strength of 0.5wt.% Ca of Mg alloy reached 220MPa and the ductility reached 16.6%. Compared with the as-cast Mg alloys, the corrosion potential after solid-solution treatment slightly shifted negative, but the corrosion current density significantly decreased. After solid solution treatment, the surface corrosion was not serious and the result of weight gain was lower compared with those of the as-cast Mg alloys.

  11. Thermodynamics of magnesian calcite solid-solutions at 25°C and 1 atm total pressure

    USGS Publications Warehouse

    Busenberg, Eurybiades; Plummer, L. Niel

    1989-01-01

    The stability of magnesian calcites was reexamined, and new results are presented for 28 natural inorganic, 12 biogenic, and 32 synthetic magnesian calcites. The magnesian calcite solid-solutions were separated into two groups on the basis of differences in stoichiometric solubility and other physical and chemical properties. Group I consists of solids of mainly metamorphic and hydrothermal origin, synthetic calcites prepared at high temperatures and pressures, and synthetic solids prepared at low temperature and very low calcite supersaturations () from artificial sea water or NaClMgCl2CaCl2solutions. Group I solids are essentially binary s of CaCO2 and MgCO2, and are thought to be relatively free of structural defects. Group II solid-solutions are of either biogenic origin or are synthetic magnesian calcites and protodolomites (0–20 and ∼ 45 mole percent MgCO3) prepared at high calcite supersaturations () from NaClNa2SO4MgCl2CaCl2 or NaClMgCl2CaCl2 solutions. Group II solid-solutions are treated as massively defective solids. The defects include substitution foreign ions (Na+ and SO42−) in the magnesian calcite lattice (point defects) and dislocations (~2 · 109 cm−2). Within each group, the excess free energy of mixing, GE, is described by the mixing model , where x is the mole fraction of the end-member Ca0.5Mg0.5CO3 in the solid-solution. The values of A0and A1 for Group I and II solids were evaluated at 25°C. The equilibrium constants of all the solids are closely described by the equation ln , where KC and KD are the equilibrium constants of calcite and Ca0.5Mg0.5CO3. Group I magnesian calcites were modeled as sub-regular solid-solutions between calcite and dolomite, and between calcite and “disordered dolomite”. Both models yield almost identical equilibrium constants for these magnesian calcites. The Group II magnesian calcites were modeled as sub-regular solid-solutions between defective calcite and

  12. Reduced ceria nanofilms from structure prediction

    NASA Astrophysics Data System (ADS)

    Kozlov, Sergey M.; Demiroglu, Ilker; Neyman, Konstantin M.; Bromley, Stefan T.

    2015-02-01

    Experimentally, Ce2O3 films are used to study cerium oxide in its fully or partially reduced state, as present in many applications. We have explored the space of low energy Ce2O3 nanofilms using structure prediction and density functional calculations, yielding more than 30 distinct nanofilm structures. First, our results help to rationalize the roles of thermodynamics and kinetics in the preparation of reduced ceria nanofilms with different bulk crystalline structures (e.g. A-type or bixbyite) depending on the support used. Second, we predict a novel, as yet experimentally unresolved, nanofilm which has a structure that does not correspond to any previously reported bulk A2B3 phase and which has an energetic stability between that of A-type and bixbyite. To assist identification and fabrication of this new Ce2O3 nanofilm we calculate some observable properties and propose supports for its epitaxial growth.Experimentally, Ce2O3 films are used to study cerium oxide in its fully or partially reduced state, as present in many applications. We have explored the space of low energy Ce2O3 nanofilms using structure prediction and density functional calculations, yielding more than 30 distinct nanofilm structures. First, our results help to rationalize the roles of thermodynamics and kinetics in the preparation of reduced ceria nanofilms with different bulk crystalline structures (e.g. A-type or bixbyite) depending on the support used. Second, we predict a novel, as yet experimentally unresolved, nanofilm which has a structure that does not correspond to any previously reported bulk A2B3 phase and which has an energetic stability between that of A-type and bixbyite. To assist identification and fabrication of this new Ce2O3 nanofilm we calculate some observable properties and propose supports for its epitaxial growth. Electronic supplementary information (ESI) available: Graph of IP versus DFT relative energies for nanofilms, GGA + U calculated lattice parameters and

  13. Effect of oxygen defects on thermal conductivity of thorium-cerium dioxide solid solutions

    NASA Astrophysics Data System (ADS)

    Muta, Hiroaki; Kado, Hirohisa; Ohishi, Yuji; Kurosaki, Ken; Yamanaka, Shinsuke

    2017-01-01

    Thermal conductivity of thorium-cerium dioxide solid solutions has been measured and analyzed using the relaxation time approximation. Despite the presence of oxygen defects, the partially reduced Th0.8Ce0.2O1.97 exhibited higher thermal conductivity than the stoichiometric one, Th0.8Ce0.2O2.00, showing the same tendency as that previously reported for Th0.7Pu0.3O2-δ. The increase in thermal conductivity with the oxygen defects can be explained by assuming that cerium ions have an average ionic radius of the ionic radii of Ce3+ and Ce4+ in the description of phonon-impurity scattering. This result indicates that the small reduction of (Th,Pu)O2-δ fuel increases the thermal conductivity, especially at high temperatures.

  14. Gas atomization synthesis of refractory or intermetallic compounds and supersaturated solid solutions

    DOEpatents

    Anderson, Iver E.; Lograsso, Barbara K.; Ellis, Timothy W.

    1994-01-01

    A metallic melt is atomized using a high pressure atomizing gas wherein the temperature of the melt and the composition of the atomizing gas are selected such that the gas and melt react in the atomization spray zone to form a refractory or intermetallic compound in the as-atomized powder particles. A metallic melt is also atomized using a high pressure atomizing gas mixture gas wherein the temperature of the melt and the ratio of a reactive gas to a carrier gas are selected to form powder particles comprising a supersaturated solid solution of the atomic species of the reactive gas in the particles. The powder particles are then heat treated to precipitate dispersoids in-situ therein to form a dispersion strengthened material.

  15. Gas atomization synthesis of refractory or intermetallic compounds and supersaturated solid solutions

    DOEpatents

    Anderson, I.E.; Lograsso, B.K.; Ellis, T.W.

    1994-11-29

    A metallic melt is atomized using a high pressure atomizing gas wherein the temperature of the melt and the composition of the atomizing gas are selected such that the gas and melt react in the atomization spray zone to form a refractory or intermetallic compound in the as-atomized powder particles. A metallic melt is also atomized using a high pressure atomizing gas mixture gas wherein the temperature of the melt and the ratio of a reactive gas to a carrier gas are selected to form powder particles comprising a supersaturated solid solution of the atomic species of the reactive gas in the particles. The powder particles are then heat treated to precipitate dispersoids in-situ therein to form a dispersion strengthened material. 9 figures.

  16. Variable valence of praseodymium in rare-earth oxide solid solutions

    SciTech Connect

    Kravchinskaya, M.V.; Merezhinskii, K.Y.; Tikhonov, P.A.

    1986-06-01

    Solid solutions of elevated praseodymium oxide content have interesting electrical properties, making them the basis for the manufacture of high-temperature electrically conducting materials. Establishment of the composition-structure-valence state relationships enables control of the material properties. The authors performed investigations using a thermogravimetric apparatus with an electronic microbalance of type EM-5-3M, and using x-ray phase analysis of powders (DRON-1 diffractometer, CuK /SUB alpha/ -radiation). The authors also studied the kinetics of praseodymium oxidation with a thermogravimetric apparatus under isothermal conditions. Evaluation of the results with the equation of Kolmogorov, Erofeev, and Avraam indicates that the process is limited by the chemical oxidation of praseodymium and not by diffusion.

  17. Analysis of lasers as a solution to efficiency droop in solid-state lighting

    NASA Astrophysics Data System (ADS)

    Chow, W. W.; Crawford, M. H.

    2015-10-01

    This letter analyzes the proposal to mitigate the efficiency droop in solid-state light emitters by replacing InGaN light-emitting diodes (LEDs) with lasers. The argument in favor of this approach is that carrier-population clamping after the onset of lasing limits carrier loss to that at threshold, while stimulated emission continues to grow with injection current. A fully quantized (carriers and light) theory that is applicable to LEDs and lasers (above and below threshold) is used to obtain a quantitative evaluation. The results confirm the potential advantage of higher laser output power and efficiency above lasing threshold, while also indicating disadvantages including low efficiency prior to lasing onset, sensitivity of lasing threshold to temperature, and the effects of catastrophic laser failure. A solution to some of these concerns is suggested that takes advantage of recent developments in nanolasers.

  18. Analysis of lasers as a solution to efficiency droop in solid-state lighting

    SciTech Connect

    Chow, Weng W.; Crawford, Mary H.

    2015-10-06

    This letter analyzes the proposal to mitigate the efficiency droop in solid-state light emitters by replacing InGaN light-emitting diodes (LEDs) with lasers. The argument in favor of this approach is that carrier-population clamping after the onset of lasing limits carrier loss to that at threshold, while stimulated emission continues to grow with injection current. A fully quantized (carriers and light) theory that is applicable to LEDs and lasers (above and below threshold) is used to obtain a quantitative evaluation. The results confirm the potential advantage of higher laser output power and efficiency above lasing threshold, while also indicating disadvantages including low efficiency prior to lasing onset, sensitivity of lasing threshold to temperature, and the effects of catastrophic laser failure. As a result, a solution to some of these concerns is suggested that takes advantage of recent developments in nanolasers.

  19. Characterization of berkelium(III) dipicolinate and borate compounds in solution and the solid state.

    PubMed

    Silver, Mark A; Cary, Samantha K; Johnson, Jason A; Baumbach, Ryan E; Arico, Alexandra A; Luckey, Morgan; Urban, Matthew; Wang, Jamie C; Polinski, Matthew J; Chemey, Alexander; Liu, Guokui; Chen, Kuan-Wen; Van Cleve, Shelley M; Marsh, Matthew L; Eaton, Teresa M; van de Burgt, Lambertus J; Gray, Ashley L; Hobart, David E; Hanson, Kenneth; Maron, Laurent; Gendron, Frédéric; Autschbach, Jochen; Speldrich, Manfred; Kögerler, Paul; Yang, Ping; Braley, Jenifer; Albrecht-Schmitt, Thomas E

    2016-08-26

    Berkelium is positioned at a crucial location in the actinide series between the inherently stable half-filled 5f(7) configuration of curium and the abrupt transition in chemical behavior created by the onset of a metastable divalent state that starts at californium. However, the mere 320-day half-life of berkelium's only available isotope, (249)Bk, has hindered in-depth studies of the element's coordination chemistry. Herein, we report the synthesis and detailed solid-state and solution-phase characterization of a berkelium coordination complex, Bk(III)tris(dipicolinate), as well as a chemically distinct Bk(III) borate material for comparison. We demonstrate that berkelium's complexation is analogous to that of californium. However, from a range of spectroscopic techniques and quantum mechanical calculations, it is clear that spin-orbit coupling contributes significantly to berkelium's multiconfigurational ground state.

  20. Magnetic properties of Ho1- x Lu x B12 solid solutions

    NASA Astrophysics Data System (ADS)

    Gabáni, S.; Gaz̆o, E.; Pristás̆, G.; Takác̆ová, I.; Flachbart, K.; Shitsevalova, N.; Siemensmeyer, K.; Sluchanko, N.

    2013-05-01

    Magnetic properties of the geometrically frustrated antiferromagnet HoB12 (with T N = 7.4 K) modified by substitution of magnetic Ho atoms through non-magnetic Lu ones are presented and discussed. In this case, in Ho1- x Lu x B12 solid solutions, both chemical pressure resulting from different Lu3+ and Ho3+ radii and magnetic dilution take place with increasing Lu content ( x) that change properties of the system. The received results show strong indication for the existence of a quantum critical point near x = 0.9, which separates the region of magnetic order (starting with HoB12 for x = 0) and the nonmagnetic region (ending with superconducting LuB12 for x = 1).

  1. Diffuse scattering measurements of static atomic displacements in crystalline binary solid solutions

    SciTech Connect

    Ice, G.E.; Sparks, C.J.; Jiang, X.; Robertson, L.

    1997-09-01

    Diffuse x-ray scattering from crystalline solid solutions is sensitive to both local chemical order and local bond distances. In short-range ordered alloys, fluctuations of chemistry and bond distances break the long-range symmetry of the crystal within a local region and contribute to the total energy of the alloy. Recent use of tunable synchrotron radiation to change the x-ray scattering contrast between elements has greatly advanced the measurement of bond distances between the three kinds of atom pairs found in crystalline binary alloys. The estimated standard deviation on these recovered static displacements approaches {+-}0.001 {angstrom} (0.0001 nm) which is an order of magnitude more precise than obtained with EXAFS. In addition, both the radial and tangential displacements can be recovered to five near neighbors and beyond. These static displacement measurements provide new information which challenges the most advanced theoretical models of binary crystalline alloys. 29 refs., 8 figs., 2 tabs.

  2. Analysis of lasers as a solution to efficiency droop in solid-state lighting

    DOE PAGES

    Chow, Weng W.; Crawford, Mary H.

    2015-10-06

    This letter analyzes the proposal to mitigate the efficiency droop in solid-state light emitters by replacing InGaN light-emitting diodes (LEDs) with lasers. The argument in favor of this approach is that carrier-population clamping after the onset of lasing limits carrier loss to that at threshold, while stimulated emission continues to grow with injection current. A fully quantized (carriers and light) theory that is applicable to LEDs and lasers (above and below threshold) is used to obtain a quantitative evaluation. The results confirm the potential advantage of higher laser output power and efficiency above lasing threshold, while also indicating disadvantages includingmore » low efficiency prior to lasing onset, sensitivity of lasing threshold to temperature, and the effects of catastrophic laser failure. As a result, a solution to some of these concerns is suggested that takes advantage of recent developments in nanolasers.« less

  3. Hydration of AMP and ATP molecules in aqueous solution and solid films.

    PubMed

    Faizullin, Dzhigangir; Zakharchenko, Nataliya; Zuev, Yuriy; Puzenko, Alexander; Levy, Evgeniya; Feldman, Yuri

    2013-11-20

    Water enables life and plays a critical role in biology. Considered as a versatile and adaptive component of the cell, water engages a wide range of biomolecular interactions. An organism can exist and function only if its self-assembled molecular structures are hydrated. It was shown recently that switching of AMP/ATP binding to the insulin-independent glucose transporter Human Erythrocyte Glucose Transport Protein (GLUT1) may greatly influence the ratio of bulk and bound water during regulation of glucose uptake by red blood cells. In this paper, we present the results on the hydration properties of AMP/ATP obtained by means of dielectric spectroscopy in aqueous solution and for fully ionized forms in solid amorphous films with the help of gravimetric studies.

  4. Anomalous birefringence in andradite-grossular solid solutions: a quantum-mechanical approach

    NASA Astrophysics Data System (ADS)

    Lacivita, Valentina; D'Arco, Philippe; Orlando, Roberto; Dovesi, Roberto; Meyer, Alessio

    2013-11-01

    The static linear optical properties (refractive indices, birefringence and axial angle) of andradite-grossular (Ca3Fe2Si3O12-Ca3Al2Si3O12) solid solutions have been computed at the ab initio quantum-mechanical level through the Coupled Perturbed Kohn-Sham scheme, using an all-electron Gaussian-type basis set. Geometry relaxation after substitution of 1-8 Al for Fe atoms in the primitive cell of andradite yields 23 non-equivalent configurations ranging from cubic to triclinic symmetry. Refractive indices vary quite regularly between the andradite (1.860) and grossular (1.671) end-members; the birefringence δ and the axial angle 2 V at intermediate compositions can be as large as 0.02° and 89°, respectively. Comparison with experiments suffers from inhomogeneities and impurities of natural samples; however, semi-quantitative agreement is observed.

  5. Atomically resolved three-dimensional structures of electrolyte aqueous solutions near a solid surface.

    PubMed

    Martin-Jimenez, Daniel; Chacon, Enrique; Tarazona, Pedro; Garcia, Ricardo

    2016-07-15

    Interfacial liquid layers play a central role in a variety of phenomena ranging from friction to molecular recognition. Liquids near a solid surface form an interfacial layer where the molecular structure is different from that of the bulk. Here we report atomic resolution three-dimensional images of electrolyte solutions near a mica surface that demonstrate the existence of three types of interfacial structures. At low concentrations (0.01-1 M), cations are adsorbed onto the mica. The cation layer is topped by a few hydration layers. At higher concentrations, the interfacial layer extends several nanometres into the liquid. It involves the alternation of cation and anion planes. Fluid Density Functional calculations show that water molecules are a critical factor for stabilizing the structure of the interfacial layer. The interfacial layer stabilizes a crystal-like structure compatible with liquid-like ion and solvent mobilities. At saturation, some ions precipitate and small crystals are formed on the mica.

  6. Determining the Photoisomerization Quantum Yield of Photoswitchable Molecules in Solution and in the Solid State

    PubMed Central

    Stranius, K.; Börjesson, K.

    2017-01-01

    Photoswitchable molecules are able to isomerize between two metastable forms through light stimuli. Originally being studied by photochemists, this type of molecule has now found a wide range of applications within physics, chemistry and biology. The extensive usage of photochromic molecules is due to the two isomers having fundamentally different physical and chemical properties. The most important attribute of a photoswitch is the photoisomerization quantum yield, which defines the efficiency of the photoisomerization event. Here we show how to determine the photoisomerization quantum yield in the solid state and in solution when taking thermal processes into account. The described method together with provided software allows for rapid and accurate determination of the isomerization process for this important class of molecules. PMID:28117426

  7. Determining the Photoisomerization Quantum Yield of Photoswitchable Molecules in Solution and in the Solid State

    NASA Astrophysics Data System (ADS)

    Stranius, K.; Börjesson, K.

    2017-01-01

    Photoswitchable molecules are able to isomerize between two metastable forms through light stimuli. Originally being studied by photochemists, this type of molecule has now found a wide range of applications within physics, chemistry and biology. The extensive usage of photochromic molecules is due to the two isomers having fundamentally different physical and chemical properties. The most important attribute of a photoswitch is the photoisomerization quantum yield, which defines the efficiency of the photoisomerization event. Here we show how to determine the photoisomerization quantum yield in the solid state and in solution when taking thermal processes into account. The described method together with provided software allows for rapid and accurate determination of the isomerization process for this important class of molecules.

  8. Atomically resolved three-dimensional structures of electrolyte aqueous solutions near a solid surface

    NASA Astrophysics Data System (ADS)

    Martin-Jimenez, Daniel; Chacon, Enrique; Tarazona, Pedro; Garcia, Ricardo

    2016-07-01

    Interfacial liquid layers play a central role in a variety of phenomena ranging from friction to molecular recognition. Liquids near a solid surface form an interfacial layer where the molecular structure is different from that of the bulk. Here we report atomic resolution three-dimensional images of electrolyte solutions near a mica surface that demonstrate the existence of three types of interfacial structures. At low concentrations (0.01-1 M), cations are adsorbed onto the mica. The cation layer is topped by a few hydration layers. At higher concentrations, the interfacial layer extends several nanometres into the liquid. It involves the alternation of cation and anion planes. Fluid Density Functional calculations show that water molecules are a critical factor for stabilizing the structure of the interfacial layer. The interfacial layer stabilizes a crystal-like structure compatible with liquid-like ion and solvent mobilities. At saturation, some ions precipitate and small crystals are formed on the mica.

  9. Temperature dependence of the activity of Al in dilute Ni(Al) solid solutions

    SciTech Connect

    Jiang Yong; Smith, J. R.; Evans, A. G.

    2006-12-01

    Activities of dilute Al solid solutions in Ni are determined from a first-principles approach. Both thermal lattice vibration and electronic contributions to free energies are considered and compared. Vibrational contributions tend to dominate the temperature dependencies of the free energies, though electron thermal effects are significant. Calculations show opposing temperature trends for the formation enthalpies and entropies, leading to a partial cancellation of their role in the overall energetics. Nevertheless, their remaining temperature effects are strong. Over the temperature range, 400 K

  10. Covalent binding of biological samples to solid supports for scanning probe microscopy in buffer solution.

    PubMed Central

    Karrasch, S; Dolder, M; Schabert, F; Ramsden, J; Engel, A

    1993-01-01

    Scanning force microscopy allows imaging of biological molecules in their native state in buffer solution. To this end samples have to be fixed to a flat solid support so that they cannot be displaced by the scanning tip. Here we describe a method to achieve the covalent binding of biological samples to glass surfaces. Coverslips were chemically modified with the photoactivatable cross-linker N-5-azido-2-nitrobenzoyloxysuccinimide. Samples are squeezed between derivatized coverslips and then cross-linked to the glass surface by irradiation with ultraviolet light. Such samples can be imaged repeatedly by the scanning force microscope without loss of image quality, whereas identical but not immobilized samples are pushed away by the stylus. Images FIGURE 4 FIGURE 5 FIGURE 6 FIGURE 7 FIGURE 8 PMID:8312482

  11. Remanent magnetization of a 'paramagnetic' composition in the ilmenite-hematite solid solution stress

    NASA Technical Reports Server (NTRS)

    Lawson, C. A.; Nord, G. L., Jr.

    1984-01-01

    In the ilmenite-hematite solid solution series, compositions more ilmenite-rich than Ilm(73)Hem(27) are classically thought to be paramagnetic at room temperature. Ilm(80)Hem(20) samples have nevertheless been synthesized that acquire hard saturation remanent and thermoremanent moments. From analysis of AC demagnetization data, the source of the measured remanence is believed to be a single-domain (SD) like material within the IlM(80)Hem(20) grains themselves. On the basis of transmission electron microscope observations, it is suggested that transformation-induced domain boundaries, which in part are enriched in hematite component relative to the bulk composition of the grains, could act as the magnetic carrier of the SD-like remanence.

  12. Compression behavior of quaternary and higher order solid-solution L1(2) trialuminides

    NASA Technical Reports Server (NTRS)

    Kumar, K. S.; Brown, S. A.

    1992-01-01

    Results from preliminary studies undertaken to evaluate the existence of single-phase L1(2) solid solutions between pairs of ternary L1(2) trialuminides are presented. Two-kilogram ingots of selected quaternary compositions were cast, homogenized and forged into pancakes; compression specimens were machined from the forgings and tested as a function of temperature. The results are compared against existing data for the ternary alloys. The ternary L1(2) trialuminides Al66Ti25Mn9, Al67Ti25Cr8, and Al22Ti8Fe3 were found to exhibit continuous solubility in one another. The quaternary Cr-Mn composition does not indicate any strength advantage over its ternary counterparts. The continuous replacement of Mn with Fe enhances the strength of the quaternary compound over the ternary Al66Ti25 Mn9.

  13. Transfer functions for solid-solution partitioning of cadmium for Australian soils.

    PubMed

    de Vries, W; McLaughlin, M J; Groenenberg, J E

    2011-12-01

    To assess transport and ecotoxicological risks of metals, such as cadmium (Cd) in soils, models are needed for partitioning and speciation. We derived regression-based "partition-relations" based on adsorption and desorption experiments for main Australian soil types. First, batch adsorption experiments were carried out over a realistic range of dissolved Cd concentrations in agricultural soils in Australia. Results showed linear sorption relationships, implying the adequacy of using Kd values to describe partitioning. Desorption measurements were then carried out to assess in-situ Kd values and relate these to soil properties The best transfer functions for solid-solution partitioning were found for Kd values relating total dissolved Cd concentration to total soil Cd concentrations, accounting for the variation in pH, SOM contents and DOC concentrations. Model predictions compared well with measurements of an independent data set, but there was a tendency to underestimate dissolved Cd concentrations of highly polluted soils.

  14. SOLIEX: A Novel Solid-Liquid Method of Radionuclides Extraction from Radioactive Waste Solutions - 13486

    SciTech Connect

    Shilova, E.; Viel, P.; Huc, V.

    2013-07-01

    This paper describes recent developments in new solid-liquid extraction method, called SOLIEX, to remove cesium from alkaline solutions. SOLIEX relies on the use of a reversible complexing system comprising a carbon felt bearing molecular traps (calixarenes). This complexing system exhibits a high selectivity for Cs, and is thus expected to be helpful for the treatment of highly diluted cesium wastes even with a high concentration of competing alkali metal cations. As additional advantage, this complexing system can be adapted by molecular engineering to capture other radionuclides, such as Sr, Eu, Am. Finally, this complexing system can be easily and efficiently regenerated by using a cost effective stripping procedure, which limits further generation of waste to meet 'zero liquid' discharge requirements for nuclear facilities. (authors)

  15. Strength, thermal defects, and solid solution hardening in nickel-containing B2 iron aluminides

    SciTech Connect

    Schneibel, J.H.; Munroe, P.R.; Pike, L.M.

    1996-12-31

    Nickel-containing ternary iron aluminides with an aluminum concentration of 45 at.% were investigated with respect to room temperature strength, equilibrium vacancy concentration, and the kinetics of vacancy removal. As compared to binary iron aluminides with the same Al concentration, nickel additions reduce the thermal equilibrium vacancy concentration at 1,273 K, whereas they increase this concentration at 973 K. Furthermore, at low temperatures such as 673 K, nickel additions increase dramatically the time needed to reach vacancy equilibrium. During prolonged annealing at 673 K, the density of <001> dislocations in Fe-45Al-3Ni (at.%) increased by an order of magnitude. This suggests that dislocations act as sinks for vacancies. At the same time, the number density of small (20--50 nm) voids decreased, indicating that they were not stable in the absence of substantial vacancy supersaturations. The findings show also that the solid solution strengthening of iron aluminides due to Ni is much weaker than previously thought.

  16. Two-dimensional solid solution alloy of Bi-Pb binary films on Rh(111)

    NASA Astrophysics Data System (ADS)

    Yuhara, J.; Yokoyama, M.; Matsui, T.

    2011-10-01

    We studied the atomic arrangements and phase diagrams of two-dimensional (2D) Bi-Pb binary films on a Rh(111) surface with low-energy electron diffraction (LEED), scanning tunneling microscopy (STM), and Auger electron spectroscopy. The 2D binary films exhibited incommensurate (4 × 4) LEED patterns with any compositional ratio of Bi:Pb. Atomically resolved STM images revealed that the binary films formed hexagonal, close-packed structures in a 2D solid solution alloy. We found that the 2D binary films followed the Hume-Rothery rule. The interatomic distance decreased linearly from 0.359 nm to 0.342 nm with increasing proportions of Pb. This indicated that the lattice constant of the 2D binary films followed Vegard's law.

  17. Photoelectrochemical properties of CdSe /SUB x/ Te /SUB 1-x/ semiconducting solid solutions

    SciTech Connect

    Kolbasov, G.Y.; Karpov, I.I.; Khanat, L.N.; Pavelets, A.M.

    1986-03-01

    This paper studies the photoelectrochemical properties of polycrystalline films of CdSe /SUB x/ Te /SUB 1-x/ solid solutions at x between 0.5 and 0.8. The spectral dependence of photolectro-chemical current is shown measured with a constant number of light quanta striking CdSe /SUB x/ Te /SUP 1-x/ electrodes with compositions. The results obtained indicate that there is no change in potential drop across the Helmholtz layer when the intensity of the light striking the sample is varied, and that ohmic losses at the photoelectrode are low for the light intensities used. Recombination-type losses of the photogenerated carriers which increae with decreasing superficial band bending are chiefly responsible for the decrease in photocurrent.

  18. Structural and dynamical properties of a new family of solid solutions: ?

    NASA Astrophysics Data System (ADS)

    Bordallo, H. N.; Almairac, R.; Bulou, A.; Nouet, J.

    1996-07-01

    The new solid solutions 0953-8984/8/27/010/img8 have been investigated by different experimental methods in the temperature range 10 K - 300 K. X-ray and calorimetric measurements show that the incommensurate phase characteristic of 0953-8984/8/27/010/img9 is also observed for 0953-8984/8/27/010/img10. Raman spectra were obtained for 0953-8984/8/27/010/img11 and 0953-8984/8/27/010/img12. Two low-frequency, temperature-dependent bands were observed over the whole temperature range investigated. These results are discussed in connection with structural disorder and the presence of precursor effects of an incommensurate phase transition.

  19. Colloidal GaAs quantum wires: solution-liquid-solid synthesis and quantum-confinement studies.

    PubMed

    Dong, Angang; Yu, Heng; Wang, Fudong; Buhro, William E

    2008-05-07

    Colloidal GaAs quantum wires with diameters of 5-11 nm and narrow diameter distributions (standard deviation = 12-21% of the mean diameter) are grown by two methods based on the solution-liquid-solid (SLS) mechanism. Resolved excitonic absorption features arising from GaAs quantum wires are detected, allowing extraction of the size-dependent effective band gaps of the wires. The results allow the first systematic comparison of the size dependences of the effective band gaps in corresponding sets of semiconductor quantum wires and quantum wells. The GaAs quantum wire and well band gaps scale according to the prediction of a simple effective-mass-approximation, particle-in-a-box (EMA-PIB) model, which estimates the kinetic confinement energies of electron-hole pairs in quantum nanostructures of different shapes and confinement dimensionalities.

  20. Hydration of AMP and ATP Molecules in Aqueous Solution and Solid Films

    PubMed Central

    Faizullin, Dzhigangir; Zakharchenko, Nataliya; Zuev, Yuriy; Puzenko, Alexander; Levy, Evgeniya; Feldman, Yuri

    2013-01-01

    Water enables life and plays a critical role in biology. Considered as a versatile and adaptive component of the cell, water engages a wide range of biomolecular interactions. An organism can exist and function only if its self-assembled molecular structures are hydrated. It was shown recently that switching of AMP/ATP binding to the insulin-independent glucose transporter Human Erythrocyte Glucose Transport Protein (GLUT1) may greatly influence the ratio of bulk and bound water during regulation of glucose uptake by red blood cells. In this paper, we present the results on the hydration properties of AMP/ATP obtained by means of dielectric spectroscopy in aqueous solution and for fully ionized forms in solid amorphous films with the help of gravimetric studies. PMID:24264037

  1. Type-II heterojunctions in GaSb-InAs solid solutions: physics and applications

    NASA Astrophysics Data System (ADS)

    Mikhailova, Maya P.; Baranov, Alexej N.; Imenkov, Albert N.; Yakovlev, Yury P.

    1991-03-01

    Staggered-''lineup type II heterojunctions have been realized in Ga In As Sb solid solutions lattice matched. to GaSb as well as ones depending on alloy composition (x1 O. 23 or XinO8O)i n Unique features of type II heterojunctions due to carrier localization and spatial separation on the interface have been experixnen tally observed by electroluminescence generation of coherent radiation and photocurrent gain. Distinctive hallmarks of the narrow-''gap GaSbGaInAsSb heterojunctions have been considered in connection with CV 1-. V and spectral response experiments. Energy band schemes of such structures have been analized. GaSbGaInAsSb heterojunctions with x 0. 80 were found to be type II misaligned ones. Novel optoelectronic devices for midIR spectral range of 1 (lasers LID''s and high-. speed photodiodes) were developed on the base of GaSb-GaInAsSb heterojunctions.

  2. Solution-based carbohydrate synthesis of individual solid, hollow, and porous carbon nanospheres using spray pyrolysis.

    PubMed

    Wang, Chengwei; Wang, Yuan; Graser, Jake; Zhao, Ran; Gao, Fei; O'Connell, Michael J

    2013-12-23

    A facile and scalable solution-based, spray pyrolysis synthesis technique was used to synthesize individual carbon nanospheres with specific surface area (SSA) up to 1106 m(2)/g using a novel metal-salt catalyzed reaction. The carbon nanosphere diameters were tunable from 10 nm to several micrometers by varying the precursor concentrations. Solid, hollow, and porous carbon nanospheres were achieved by simply varying the ratio of catalyst and carbon source without using any templates. These hollow carbon nanospheres showed adsorption of to 300 mg of dye per gram of carbon, which is more than 15 times higher than that observed for conventional carbon black particles. When evaluated as supercapacitor electrode materials, specific capacitances of up to 112 F/g at a current density of 0.1 A/g were observed, with no capacitance loss after 20,000 cycles.

  3. Analysis of electrostatic stability and ordering in quaternary perovskite solid solutions

    NASA Astrophysics Data System (ADS)

    Caetano, Clovis; Butler, Keith T.; Walsh, Aron

    2016-04-01

    There are three distinct classes of perovskite structured metal oxides, defined by the charge states of the cations: AIBVO3,AIIBIVO3 , and AIIIBIIIO3 . We investigated the stability of cubic quaternary solid solutions A B O3-A'B'O3 using a model of point-charge lattices. The mixing enthalpies were calculated and compared for the three possible types of combinations of the compounds, both for the random alloys and the ground-state-ordered configurations. The mixing enthalpy of the (I,V)O3-(III,III)O3 alloy is always larger than the other alloys. We found that, different from homovalent alloys, for these heterovalent alloys a lattice constant mismatch between the constituent compounds could contribute to stabilize the alloy. At low temperatures, the alloys present a tendency to spontaneous ordering, forming superlattices consisting of alternated layers of AB O 3 and A'B'O3 along the [110 ] direction.

  4. Polyoxoanion chemistry moves toward the future: From solids and solutions to surfaces

    SciTech Connect

    Klemperer, W.G.; Wall, C.G.

    1998-01-01

    In the context of modern surface science, current understanding of polyoxoanion surface chemistry is truly modest from a structural/mechanistic point of view. Only three techniques have received any attention to date, and none of them has been developed to anywhere near its full potential. The quartz crystal microbalance (QCM) has proven to be a useful qualitative tool for in situ monitoring of polyoxoanion adsorption and adsorption kinetics. A second technique that has shown great potential for in situ study of polyoxoanion surface chemistry at solid-liquid interfaces is modulated infrared spectroscopy. The third and final in situ surface analytical technique that has shown great promise but is yet to be exploited to its full potential is scanning probe microscopy. Sections of the paper discuss scanning probe microscopy; single crystal surfaces; evaporative solution deposition on graphite; electrochemical deposition onto graphite; and self-assembly on metal surfaces.

  5. Flow-Solution-Liquid-Solid Growth of Semiconductor Nanowires: A Novel Approach for Controlled Synthesis

    SciTech Connect

    Hollingsworth, Jennifer A.; Palaniappan, Kumaranand; Laocharoensuk, Rawiwan; Smith, Nickolaus A.; Dickerson, Robert M.; Casson, Joanna L.; Baldwin, Jon K.

    2012-06-07

    Semiconductor nanowires (SC-NWs) have potential applications in diverse technologies from nanoelectronics and photonics to energy harvesting and storage due to their quantum-confined opto-electronic properties coupled with their highly anisotropic shape. Here, we explore new approaches to an important solution-based growth method known as solution-liquid-solid (SLS) growth. In SLS, molecular precursors are reacted in the presence of low-melting metal nanoparticles that serve as molten fluxes to catalyze the growth of the SC-NWs. The mechanism of growth is assumed to be similar to that of vapor-liquid-solid (VLS) growth, with the clear distinctions of being conducted in solution in the presence of coordinating ligands and at relatively lower temperatures (<300 C). The resultant SC-NWs are soluble in common organic solvents and solution processable, offering advantages such as simplified processing, scale-up, ultra-small diameters for quantum-confinement effects, and flexible choice of materials from group III-V to groups II-VI, IV-VI, as well as truly ternary I-III-VI semiconductors as we recently demonstrates. Despite these advantages of SLS growth, VLS offers several clear opportunities not allowed by conventional SLS. Namely, VLS allows sequential addition of precursors for facile synthesis of complex axial heterostructures. In addition, growth proceeds relatively slowly compared to SLS, allowing clear assessments of growth kinetics. In order to retain the materials and processing flexibility afforded by SLS, but add the elements of controlled growth afforded by VLS, we transformed SLS into a flow based method by adapting it to synthesis in a microfluidic system. By this new method - so-called 'flow-SLS' (FSLS) - we have now demonstrated unprecedented fabrication of multi-segmented SC-NWs, e.g., 8-segmented CdSe/ZnSe defined by either compositionally abrupt or alloyed interfaces as a function of growth conditions. In addition, we have studied growth rates as a

  6. Investigating the effect of compression on solute transport through degrading municipal solid waste

    SciTech Connect

    Woodman, N.D. Rees-White, T.C.; Stringfellow, A.M.; Beaven, R.P.; Hudson, A.P.

    2014-11-15

    Highlights: • The influence of compression on MSW flushing was evaluated using 13 tracer tests. • Compression has little effect on solute diffusion times in MSW. • Lithium tracer was conservative in non-degrading waste but not in degrading waste. • Bromide tracer was conservative, but deuterium was not. - Abstract: The effect of applied compression on the nature of liquid flow and hence the movement of contaminants within municipal solid waste was examined by means of thirteen tracer tests conducted on five separate waste samples. The conservative nature of bromide, lithium and deuterium tracers was evaluated and linked to the presence of degradation in the sample. Lithium and deuterium tracers were non-conservative in the presence of degradation, whereas the bromide remained effectively conservative under all conditions. Solute diffusion times into and out of less mobile blocks of waste were compared for each test under the assumption of dominantly dual-porosity flow. Despite the fact that hydraulic conductivity changed strongly with applied stress, the block diffusion times were found to be much less sensitive to compression. A simple conceptual model, whereby flow is dominated by sub-parallel low permeability obstructions which define predominantly horizontally aligned less mobile zones, is able to explain this result. Compression tends to narrow the gap between the obstructions, but not significantly alter the horizontal length scale. Irrespective of knowledge of the true flow pattern, these results show that simple models of solute flushing from landfill which do not include depth dependent changes in solute transport parameters are justified.

  7. Oxygen vacancy ordering within anion-deficient Ceria

    SciTech Connect

    Hull, S.; Norberg, S.T.; Ahmed, I.; Eriksson, S.G.; Marrocchelli, D.; Madden, P.A.

    2009-10-15

    The structural properties of anion deficient ceria, CeO{sub 2-{delta}}, have been studied as a function of oxygen partial pressure, p(O{sub 2}), over the range 0>=log{sub 10p}(O{sub 2})>=-18.9 at 1273(2) K using the neutron powder diffraction technique. Rietveld refinement of the diffraction data collected on decreasing p(O{sub 2}) showed increases in the cubic lattice parameter, a, the oxygen nonstoichiometry, delta, and the isotropic thermal vibration parameters, u{sub Ce} and u{sub O}, starting at log{sub 10p}(O{sub 2}){approx}-11. The increases are continuous, but show a distinct kink at log{sub 10p}(O{sub 2}){approx}-14.5. Analysis of the total scattering (Bragg plus diffuse components) using reverse Monte Carlo (RMC) modelling indicates that the O{sup 2-} vacancies preferentially align as pairs in the <111> cubic directions as the degree of nonstoichiometry increases. This behaviour is discussed with reference to the chemical crystallography of the CeO{sub 2}-Ce{sub 2}O{sub 3} system at ambient temperature and, in particular, to the nature of the long-range ordering of O{sup 2-} vacancies within the crystal structure of Ce{sub 7}O{sub 12}. - Graphical abstract: Partial radial distribution function for oxygen vacancies within CeO{sub 1.710} at 1273 K (solid line) showing the increased tendency for local ordering in <111> directions compared to a random distribution (dashed line).

  8. Nanocrystalline Ce1- x La x O2- δ Solid Solutions Synthesized by Hydrolyzing and Oxidizing

    NASA Astrophysics Data System (ADS)

    Hou, Xueling; Xue, Yun; Han, Ning; Lu, Qianqian; Wang, Xiaochen; Phan, Manh-Huong; Zhong, Yunbo

    2016-05-01

    We undertook a novel batch production approach for the synthesis of CeO2 nanopowders doped with rare earth elements. Solid solution nanopowders of Ce1- x La x O2- δ ( x = 0.15) were successfully synthesized in a large-scale and low-cost production by hydrolyzing and oxidizing Ce-La-C alloys at room temperature and subsequent calcining of their powders at different temperatures (873-1073 K) for 1 h. The Ce-La-C alloys were prepared in a vacuum induction melting furnace. The final products were characterized by x-ray diffraction, transmission electron microscopy, Brunner-Emmet-Teller (BET) surface area analyzer, and Raman spectroscopy. The calculated lattice parameters of the cubic fluorite-type phase of CeO2 tended to increase when La3+ was incorporated into CeO2. The F 2g band shift and the absence of a peak corresponding to La2O3 in the Raman spectra consistently confirmed the incorporation of the La3+ ion into CeO2, and the formation of Ce1- x La x O2- δ solid solutions as manifested by increased oxygen vacancy defects. High-quality Ce1- x La x O2- δ nanopowders of ~10-15 nm diameter with a high BET surface area of ~77 m2 g-1 were obtained. The average crystallite size of Ce1- x La x O2- δ was found to be smaller than that of CeO2 for the same calcination temperature of 1073 K, demonstrating that the introduction of La3+ into CeO2 can stabilize the host lattice and refine the grain size at high temperatures.

  9. Detection of nitroaromatics in the solid, solution, and vapor phases using silicon quantum dot sensors

    NASA Astrophysics Data System (ADS)

    Nguyen, An; Gonzalez, Christina M.; Sinelnikov, Regina; Newman, W.; Sun, Sarah; Lockwood, Ross; Veinot, Jonathan G. C.; Meldrum, Al

    2016-03-01

    Silicon quantum dots (Si-QDs) represent a well-known QD fluorophore that can emit throughout the visible spectrum depending on the interface structure and surface functional group. Detection of nitroaromatic compounds by monitoring the luminescence response of the sensor material (typically fluorescent polymers) currently forms the basis of new explosives sensing technologies. Freestanding silicon QDs may represent a benign alternative with a high degree of chemical and physical versatility. Here, we investigate dodecyl and amine-terminated Si-QD luminescence response to the presence of nitrobenzene and dinitrotoluene (DNT) in various solid, solution, and vapor forms. For dinitrotoluene vapor the 3σ detection limit was 6 ppb for monomer-terminated QDs. For nitroaromatics dissolved in toluene the detection limit was on the order of 400 nM, corresponding to ∼100 pg of material distributed over ∼1 cm2 on the sensor surface. Solid traces of nitroaromatics were also easily detectable via a simple ‘touch test’. The samples showed minimal interference effects from common contaminants such as water, ethanol, and acetonitrile. The sensor can be as simple and inexpensive as a small circle of filter paper dipped into a QD solution, with a single vial of QDs able to make hundreds of these sensors. Additionally, a trial fiber-optic sensor device was tested by applying the QDs to one end of a 2 × 2 fiber coupler and exposing them to controlled DNT vapor. Finally, the quenching mechanism was explored via luminescence dynamics measurements and is different for blue (amine) and red (dodecyl) fluorescent silicon QDs.

  10. Solid solution barium–strontium chlorides with tunable ammonia desorption properties and superior storage capacity

    SciTech Connect

    Bialy, Agata; Blanchard, Didier; Vegge, Tejs; Quaade, Ulrich J.

    2015-01-15

    Metal halide ammines are very attractive materials for ammonia absorption and storage—applications where the practically accessible or usable gravimetric and volumetric storage densities are of critical importance. Here we present, that by combining advanced computational materials prediction with spray drying and in situ thermogravimetric and structural characterization, we synthesize a range of new, stable barium-strontium chloride solid solutions with superior ammonia storage densities. By tuning the barium/strontium ratio, different crystallographic phases and compositions can be obtained with different ammonia ab- and desorption properties. In particular it is shown, that in the molar range of 35–50% barium and 65–50% strontium, stable materials can be produced with a practically usable ammonia density (both volumetric and gravimetric) that is higher than any of the pure metal halides, and with a practically accessible volumetric ammonia densities in excess of 99% of liquid ammonia. - Graphical abstract: Thermal desorption curves of ammonia from Ba{sub x}Sr{sub (1−x)}Cl{sub 2} mixtures with x equal to 0.125, 0.25 and 0.5 and atomic structure of Sr(NH{sub 3}){sub 8}Cl{sub 2}. - Highlights: • Solid solutions of strontium and barium chloride were synthesized by spray drying. • Adjusting molar ratios led to different crystallographic phases and compositions. • Different molar ratios led to different ammonia ab-/desorption properties. • 35–50 mol% BaCl{sub 2} in SrCl{sub 2} yields higher ammonia density than any other metal halide. • DFT calculations can be used to predict properties of the mixtures.

  11. BN-coated Ca(1-x)Sr(x)S:Eu solid-solution nanowires with tunable red light emission.

    PubMed

    Lin, Jing; Huang, Yang; Mi, Jiao; Zhang, Xinghua; Lu, Zunming; Xu, Xuewen; Fan, Ying; Zou, Jin; Tang, Chengchun

    2013-10-11

    We report on the controlled growth of novel BN-coated Ca(1-x)Sr(x)S:Eu nanowires via a solid-liquid-solid process. The Ca(1-x)Sr(x)S solid solution forms as one-dimensional nanowires and has been coated with homogeneous protective BN nanolayers. The structure and luminescence properties of this new nanocomposite have been systematically investigated. High-spatial-resolution cathodoluminescence investigations reveal that effective red color tuning has been achieved by tailoring the composition of the Ca(1-x)Sr(x)S nanowires. Moreover, codoping of Ce(3+) and Eu(2+) in the CaS nanowire can induce energy transfer in the matrix and make it possible to obtain enhanced orange color in the nanowires. The BN-coated Ca(1-x)Sr(x)S:Eu solid-solution nanowires are envisaged to be valuable red-emitting nanophosphors and useful in advanced nanodevices and white LEDs.

  12. Influence of gadolinium doping on the structure and defects of ceria under fuel cell operating temperature

    SciTech Connect

    Acharya, S. A. Gaikwad, V. M.; Sathe, V.; Kulkarni, S. K.

    2014-03-17

    Correlation between atomic positional shift, oxygen vacancy defects, and oxide ion conductivity in doped ceria system has been established in the gadolinium doped ceria system from X-ray diffraction (XRD) and Raman spectroscopy study at operating temperature (300–600 °C) of Intermediate Temperature Solid Oxide Fuel Cell (IT-SOFC). High temperature XRD data are used to quantify atomic positional shift from mean position with temperature. The Raman spectroscopy study shows additional vibration modes related to ordering of defect spaces (Gd{sub Ce}{sup ′}−V{sub o}{sup ••}){sup *} and (2Gd{sub Ce}{sup ′}−V{sub o}{sup ••}){sup x} generated due to association of oxygen vacancies and reduced cerium or dopant cations site (Gd{sup 3+}), which disappear at 450 °C; indicating oxygen vacancies dissociation from the defect complex. The experimental evidences of cation-anion positional shifting and oxygen vacancies dissociation from defect complex in the IT-SOFC operating temperature are discussed to correlate with activation energy for ionic conductivity.

  13. Reduction Dynamics of Doped Ceria, Nickel Oxide, and Cermet Composites Probed Using In Situ Raman Spectroscopy

    PubMed Central

    Shearing, Paul R.; Brightman, Edward; Brett, Dan J. L.; Brandon, Nigel P.; Cohen, Lesley F.

    2016-01-01

    The redox properties of gadolinium doped ceria (CGO) and nickel oxide (NiO) composite cermets underpin the operation of solid oxide electrochemical cells. Although these systems have been widely studied, a full comprehension of the reaction dynamics at the interface of these materials is lacking. Here, in situ Raman spectroscopic monitoring of the redox cycle is used to investigate the interplay between the dynamic and competing processes of hydrogen spillover and water dissociation on the doped ceria surface. In order to elucidate these mechanisms, the redox process in pure CGO and NiO is studied when exposed to wet and dry hydrogen and is compared to the cermet behavior. In dry hydrogen, CGO reduces relatively rapidly via a series of intermediate phases, while NiO reduces via a single‐step process. In wet reducing atmospheres, however, the oxidation state of pure CGO is initially stabilized due to the dissociation of water by reduced Ce(III) and subsequent incorporation of oxygen into the structure. In the reduction process involving the composite cermet, the close proximity of the NiO improves the efficiency and speed of the composite reduction process. Although NiO is already incorporated into working cells, these observations suggest direct routes to further improve cell performance. PMID:27595058

  14. Reduction Dynamics of Doped Ceria, Nickel Oxide, and Cermet Composites Probed Using In Situ Raman Spectroscopy.

    PubMed

    Maher, Robert C; Shearing, Paul R; Brightman, Edward; Brett, Dan J L; Brandon, Nigel P; Cohen, Lesley F

    2016-01-01

    The redox properties of gadolinium doped ceria (CGO) and nickel oxide (NiO) composite cermets underpin the operation of solid oxide electrochemical cells. Although these systems have been widely studied, a full comprehension of the reaction dynamics at the interface of these materials is lacking. Here, in situ Raman spectroscopic monitoring of the redox cycle is used to investigate the interplay between the dynamic and competing processes of hydrogen spillover and water dissociation on the doped ceria surface. In order to elucidate these mechanisms, the redox process in pure CGO and NiO is studied when exposed to wet and dry hydrogen and is compared to the cermet behavior. In dry hydrogen, CGO reduces relatively rapidly via a series of intermediate phases, while NiO reduces via a single-step process. In wet reducing atmospheres, however, the oxidation state of pure CGO is initially stabilized due to the dissociation of water by reduced Ce(III) and subsequent incorporation of oxygen into the structure. In the reduction process involving the composite cermet, the close proximity of the NiO improves the efficiency and speed of the composite reduction process. Although NiO is already incorporated into working cells, these observations suggest direct routes to further improve cell performance.

  15. Fast vacancy-mediated oxygen ion incorporation across the ceria-gas electrochemical interface.

    PubMed

    Feng, Zhuoluo A; El Gabaly, Farid; Ye, Xiaofei; Shen, Zhi-Xun; Chueh, William C

    2014-07-09

    Electrochemical incorporation reactions are ubiquitous in energy storage and conversion devices based on mixed ionic and electronic conductors, such as lithium-ion batteries, solid-oxide fuel cells and water-splitting membranes. The two-way traffic of ions and electrons across the electrochemical interface, coupled with the bulk transport of mass and charge, has been challenging to understand. Here we report an investigation of the oxygen-ion incorporation pathway in CeO2-δ (ceria), one of the most recognized oxygen-deficient compounds, during hydrogen oxidation and water splitting. We probe the response of surface oxygen vacancies, electrons and adsorbates to the electrochemical polarization at the ceria-gas interface. We show that surface oxygen-ion transfer, mediated by oxygen vacancies, is fast. Furthermore, we infer that the electron transfer between cerium cations and hydroxyl ions is the rate-determining step. Our in operando observations reveal the precise roles of surface oxygen vacancy and electron defects in determining the rate of surface incorporation reactions.

  16. Smooth and robust solutions for Dirichlet boundary control of fluid-solid conjugate heat transfer problems

    NASA Astrophysics Data System (ADS)

    Yan, Yan; Keyes, David E.

    2015-01-01

    We study a new optimization scheme that generates smooth and robust solutions for Dirichlet velocity boundary control (DVBC) of conjugate heat transfer (CHT) processes. The solutions to the DVBC of the incompressible Navier-Stokes equations are typically nonsmooth, due to the regularity degradation of the boundary stress in the adjoint Navier-Stokes equations. This nonsmoothness is inherited by the solutions to the DVBC of CHT processes, since the CHT process couples the Navier-Stokes equations of fluid motion with the convection-diffusion equations of fluid-solid thermal interaction. Our objective in the CHT boundary control problem is to select optimally the fluid inflow profile that minimizes an objective function that involves the sum of the mismatch between the temperature distribution in the fluid system and a prescribed temperature profile and the cost of the control. Our strategy to resolve the nonsmoothness of the boundary control solution is based on two features, namely, the objective function with a regularization term on the gradient of the control profile on both the continuous and the discrete levels, and the optimization scheme with either explicit or implicit smoothing effects, such as the smoothed Steepest Descent and the Limited-memory Broyden-Fletcher-Goldfarb-Shanno (L-BFGS) methods. Our strategy to achieve the robustness of the solution process is based on combining the smoothed optimization scheme with the numerical continuation technique on the regularization parameters in the objective function. In the section of numerical studies, we present two suites of experiments. In the first one, we demonstrate the feasibility and effectiveness of our numerical schemes in recovering the boundary control profile of the standard case of a Poiseuille flow. In the second one, we illustrate the robustness of our optimization schemes via solving more challenging DVBC problems for both the channel flow and the flow past a square cylinder, which use initial

  17. On the Possibility of Formation and Properties of Copper-Silver Solid Solutions Under Severe Plastic Deformation

    NASA Astrophysics Data System (ADS)

    Pilyugin, V. P.; Solodova, I. L.; Tolmachev, T. P.; Antonova, O. V.; Chernyshev, E. G.; Patselov, A. M.

    2016-01-01

    Mechanical alloying of Cu and Ag powders in concentrations Cu1-x-Agx (x at.% = 0.1, 0.2, …, 0.9) under high-pressure torsion is investigated. The alloys obtained have a structure of nanograined nonequilibrium FCC solid solutions with positive deviation from Vegard's law. The hardness of the alloys is 4-6 times higher than of the initial components - copper and silver. The energy and power parameters of treatment of the solid solutions and stages of their formation are calculated from the shear stress measured in situ under high pressure. Thermally induced decomposition of the solid solutions begins from aging under normal conditions, is accelerated upon heating, and ends by short-term heating up to 500°C. It is accompanied by simultaneous development of the processes of gathering recrystallization.

  18. Polarization-sensitive nanowire photodetectors based on solution-synthesized CdSe quantum-wire solids.

    PubMed

    Singh, Amol; Li, Xiangyang; Protasenko, Vladimir; Galantai, Gabor; Kuno, Masaru; Xing, Huili Grace; Jena, Debdeep

    2007-10-01

    Polarization-sensitive photodetectors are demonstrated using solution-synthesized CdSe nanowire (NW) solids. Photocurrent action spectra taken with a tunable white light source match the solution linear absorption spectra of the NWs, showing that the NW network is responsible for the device photoconductivity. Temperature-dependent transport measurements reveal that carriers responsible for the dark current through the nanowire solids are thermally excited across CdSe band gap. The NWs are aligned using dielectrophoresis between prepatterned electrodes using conventional optical photolithography. The photocurrent through the NW solid is found to be polarization-sensitive, consistent with complementary absorption (emission) measurements of both single wires and their ensembles. The range of solution-processed semiconducting NW materials, their facile synthesis, ease of device fabrication, and compatibility with a variety of substrates make them attractive for potential nanoscale polarization-sensitive photodetectors.

  19. Fluorescent Nanocomposite of Embedded Ceria Nanoparticles in Electrospun Chitosan Nanofibers.

    PubMed

    Shehata, Nader; Samir, Effat; Gaballah, Soha; Hamed, Aya; Saad, Marwa; Salah, Mohammed

    2017-03-01

    This paper introduces a detailed optical characterization for a novel fluorescent biodegradable nanocomposite of electro-spun chitosan nanofibers with in-situ embedded cerium oxide (ceria) nanoparticles as the nanocomposite optical fluorescent material. Under near ultra-violet excitation, this synthesized nanocomposite emits a visible green wavelength at nearly 520nmwith different intensities according to the concentration of the embedded fluorescent material; i.e. ceria nanoparticles. This emission is due to the synthesized ceria nanoparticles optical tri-valiant cerium ions ce(3+), associated with formed oxygen vacancies with a direct allowed bandgap around 3.5 eV. Optical characteristics such as fluorescence emission intensity, absorbance dispersion, and direct bandgap are presented besides structural characteristics such as FTIR spectroscopy, and SEM analysis. The synthesized optical nanocomposite could be helpful in many further applications such as bio-imaging, biomedical engineering, and environmental optical sensors.

  20. Microcosm experiments to study the interaction of solid and solute phases during initial soil development

    NASA Astrophysics Data System (ADS)

    Zimmermann, C.; Chabbi, S.; Schaaf, W.

    2009-04-01

    During the initial phase of soil formation mineral weathering, interactions between the solid and liquid phases as well as accumulation of organic matter play an important role for the development of soil properties and for the establishment of vegetation and the colonization of soil biota. Our study is part of the Transregional Collaborative Research Centre (SFB/TRR 38) ‘Patterns and processes of initial ecosystem development in an artificial catchment' funded by the Deutsche Forschungsgemeinschaft (DFG). The catchment ´Chicken Creeḱ close to Cottbus (Germany) has a size of 6 ha and is composed of a 3-4 m layer of Quaternary loamy to sandy sediments overlying a 1-2 m clay layer. To connect interactions between the soil solid phase and soil solution at the micro-scale with observed processes at the catchment scale we perform microcosm experiments with soil samples from the catchment under controlled laboratory conditions. The microcosm experiments are carried out in a climate chamber at constant 10 °C corresponding to the mean annual temperature of the region. In total 48 soil columns with a diameter of 14.4 cm and height of 30 cm were filled with substrates of two textural compositions reflecting the gradients observed at the catchment and a bulk density of 1.4-1.5 g*cm3. Within the microcosms it is possible to control the gaseous phase and the water fluxes by artificial irrigation. The irrigation runs automated and quasi-continuously four times a day with 6.6 ml each (in total 600 mm*yr-1). Irrigation amount and chemical composition of the artificial rainwater are based on the annual mean at the field site. Litter of two different plant species occurring at the catchment site (Lotus corniculatus, Calamagrostis epigejos) labelled with stable isotopes (δ13C; δ15N) is used for the experiments. All treatments including a control run with four replicates. The gaseous phase in the headspace of the microcosms is analysed continuously for CO2 and N2O contents

  1. Understanding the solution phase chemistry and solid state thermodynamic behavior of pharmaceutical cocrystals

    NASA Astrophysics Data System (ADS)

    Maheshwari, Chinmay

    Cocrystals have drawn a lot of research interest in the last decade due to their potential to favorably alter the physicochemical and biopharmaceutical properties of active pharmaceutical ingredients. This dissertation focuses on the thermodynamic stability and solubility of pharmaceutical cocrystals. Specifically, the objectives are to; (i) investigate the influence of coformer properties such as solubility and ionization characteristics on cocrystal solubility and stability as a function of pH, (ii) to measure the thermodynamic solubility of metastable cocrystals, and study the solubility differences measured by kinetic and equilibrium methods, (iii) investigate the role of surfactants on the solubility and synthesis of cocrystals, (iv) investigate the solid state phase transformation of reactants to cocrystals and the factors that influence the reaction kinetics and, (v) provide models that enable the prediction of cocrystal formation by calculating the free energy of formation for a solid to solid transformation of reactants to cocrystals. Cocrystal solubilities were measured directly when cocrystals were thermodynamically stable, while solubilities were calculated from eutectic concentration measurements when cocrystals were of higher solubility than its components. Cocrystal solubility was highly dependent on coformer solubilities for gabapentin-lactam and lamotrigine cocrystals. It was found that melting point is not a good indicator of cocrystal solubility as solute-solvent interactions quantified by the activity coefficient play a huge role in the observed solubility. Similar to salts, cocrystals also exhibit pHmax, however the salts and cocrystals have different dependencies on the parameters that govern the value of pHmax. It is also shown that cocrystals could provide solubility advantage over salts as lamotrigine-nicotinamide cocrystal hydrate has about 6 fold higher solubility relative to lamotrigine-saccharin salt. In the case of mixtures of solid

  2. Effect of Ceria on the Sulfation and Desulfation Characteristics of a Model Lean NOx Trap Catalyst

    SciTech Connect

    Ji, Yaying; Toops, Todd J; Crocker, Mark

    2009-01-01

    The effect of ceria addition on the sulfation and desulfation characteristics of a model Ba-based lean NO{sub x} trap (LNT) catalyst was studied. According to DRIFTS and NO{sub x} storage capacity measurements, ceria is able to store sulfur during catalyst exposure to SO{sub 2}, thereby helping to limit sulfation of the main (Ba) NO{sub x} storage phase and maintain NO{sub x} storage capacity. Temperature programmed desulfation experiments revealed that desulfation of a model ceria-containing catalyst occurred in two stages, corresponding to sulfur elimination from the ceria phase at {approx}450 C, followed by sulfur loss from the Ba phase at {approx}650 C. Significantly, the ceria-containing catalyst displayed relatively lower sulfur evolution from the Ba phase than its non-ceria analog, confirming that the presence of ceria lessened the degree of sulfur accumulation on the Ba phase.

  3. Cobalt incorporation in calcite: Thermochemistry of (Ca,Co)CO3 solid solutions from density functional theory simulations

    NASA Astrophysics Data System (ADS)

    González-López, Jorge; Ruiz-Hernández, Sergio E.; Fernández-González, Ángeles; Jiménez, Amalia; de Leeuw, Nora H.; Grau-Crespo, Ricardo

    2014-10-01

    The incorporation of cobalt in mixed metal carbonates is a possible route to the immobilisation of this toxic element in the environment. However, the thermodynamics of (Ca,Co)CO3 solid solutions are still unclear due to conflicting data from experiment and from the observation of natural occurrences. We report here the results of a computer simulation study of the mixing of calcite (CaCO3) and spherocobaltite (CoCO3), using density functional theory calculations. Our simulations suggest that previously proposed thermodynamic models, based only on the observed range of compositions, significantly overestimate the solubility between the two solids and therefore underestimate the extension of the miscibility gap under ambient conditions. The enthalpy of mixing of the disordered solid solution is strongly positive and moderately asymmetric: calcium incorporation in spherocobaltite is more endothermic than cobalt incorporation in calcite. Ordering of the impurities in (0001) layers is energetically favourable with respect to the disordered solid solution at low temperatures and intermediate compositions, but the ordered phase is still unstable to demixing. We calculate the solvus and spinodal lines in the phase diagram using a sub-regular solution model, and conclude that many Ca1-xCoxCO3 mineral solid solutions (with observed compositions of up to x = 0.027, and above x = 0.93) are metastable with respect to phase separation. We also calculate solid/aqueous distribution coefficients to evaluate the effect of the strong non-ideality of mixing on the equilibrium with aqueous solution, showing that the thermodynamically-driven incorporation of cobalt in calcite (and of calcium in spherocobaltite) is always very low, regardless of the Co/Ca ratio of the aqueous environment.

  4. Fabrication and Performance of All-Solid-State Chloride Sensors in Synthetic Concrete Pore Solutions

    PubMed Central

    Gao, Xiaojian; Zhang, Jian; Yang, Yingzi; Deng, Hongwei

    2010-01-01

    One type of all-solid-state chloride sensor was fabricated using a MnO2 electrode and a Ag/AgCl electrode. The potentiometric response of the sensor to chloride in synthetic concrete pore solutions was systematically studied, and the polarization performance was also evaluated. The results show a good linear relationship between the potential reading of the sensor and the logarithm of chloride activity (concentration ranges from 0.05 to 5.0 M), and the potential value remains stable with increasing immersion time. The existence of K+, Ca2+, Na+ and SO42− ions have little influence on the potentiometric response of the sensor to chloride, but the pH has a significant influence on the potential value of the sensor at low chloride concentration. The potential reading of the sensor increases linearly with the solution temperature over the range from 5 to 45 °C. Meanwhile, an excellent polarization behavior is proven by galvanostatic and potentiodynamic tests. All of the results reveal that the developed sensor has a great potential for monitoring chloride ions in concrete environments. PMID:22163467

  5. Wetting of a solid substrate by a ``civilized'' model of ionic solutions

    NASA Astrophysics Data System (ADS)

    Oleksy, Anna; Hansen, Jean-Pierre

    2010-05-01

    We use classical density functional theory (DFT) and an explicit solvent description to investigate the wetting and drying behavior of ionic solutions in contact with a charged solid substrate. The solvent is modeled by dipolar hard spheres, while the monovalent ions are oppositely charged hard spheres; cohesion is ensured by a Yukawa attraction between all three species. The free energy functional describing the inhomogeneous solution includes the best available fundamental measure description of excluded volume correlations in a ternary mixture of hard spheres, whereas all electrostatic and cohesive interactions are treated within the mean-field approximation. We find both first and second order wetting transitions which are rather little affected by ions at low and moderate concentrations, compared to the wetting behavior of the pure solvent. A novel drying scenario is predicted, where complete drying is prevented by the electrostatic attraction between a positively charged substrate and the anions, while near a negatively charged substrate, a first order transition with a predrying line is observed. The various scenarios are surprisingly similar to our previous predictions based on a "semiprimitive" model where the solvent particles carry no dipole, but the ion-ion interactions are reduced by a local dielectric permittivity.

  6. A new variable temperature solution-solid interface scanning tunneling microscope

    NASA Astrophysics Data System (ADS)

    Jahanbekam, Abdolreza; Mazur, Ursula; Hipps, K. W.

    2014-10-01

    We present a new solution-solid (SS) interface scanning tunneling microscope design that enables imaging at high temperatures with low thermal drift and with volatile solvents. In this new design, distinct from the conventional designs, the entire microscope is surrounded in a controlled-temperature and controlled-atmosphere chamber. This allows users to take measurements at high temperatures while minimizing thermal drift. By incorporating an open solution reservoir in the chamber, solvent evaporation from the sample is minimized; allowing users to use volatile solvents for temperature dependent studies at high temperatures. The new design enables the user to image at the SS interface with some volatile solvents for long periods of time (>24 h). An increase in the nonlinearity of the piezoelectric scanner in the lateral direction as a function of temperature is addressed. A temperature dependent study of cobalt(II) octaethylporphyrin (CoOEP) at the toluene/Au(111) interface has been performed with this instrument. It is demonstrated that the lattice parameters remain constant within experimental error from 24 °C to 75 °C. Similar quality images were obtained over the entire temperature range. We report the unit cell of CoOEP at the toluene/Au(111) interface (based on two molecules per unit cell) to be A = (1.36 ± 0.04) nm, B = (2.51 ± 0.04) nm, and α = 97° ± 2°.

  7. Novel cellulose-based amorphous solid dispersions enhance quercetin solution concentrations in vitro.

    PubMed

    Gilley, Andrew D; Arca, Hale Cigdem; Nichols, Brittany L B; Mosquera-Giraldo, Laura I; Taylor, Lynne S; Edgar, Kevin J; Neilson, Andrew P

    2017-02-10

    Quercetin (Q) is a bioactive flavonol with potential to benefit human health. However, Q bioavailability is relatively low, due to its poor aqueous solubility and extensive phase-II metabolism. Strategies to increase solution concentrations in the small intestinal lumen have the potential to substantially increase Q bioavailability, and by extension, efficacy. We aimed to achieve this by incorporating Q into amorphous solid dispersions (ASDs) with cellulose derivatives. Q was dispersed in matrices of cellulose esters including 6-carboxycellulose acetate butyrate (CCAB), hydroxypropylmethylcellulose acetate succinate (HPMCAS) and cellulose acetate suberate (CASub) to afford ASDs that provided stability against crystallization, and pH-triggered release. Blends of CASub and CCAB with the hydrophilic polyvinylpyrrolidone (PVP) further enhanced dissolution. The ASD 10% Q:20% PVP:70% CASub most significantly enhanced Q solution concentration under intestinal pH conditions, increasing area under the concentration/time curve (AUC) 18-fold compared to Q alone. This novel ASD method promises to enhance Q bioavailability in vivo.

  8. Adsorption behavior of hydrophobin and hydrophobin/surfactant mixtures at the solid-solution interface.

    PubMed

    Zhang, Xiaoli L; Penfold, Jeffrey; Thomas, Robert K; Tucker, Ian M; Petkov, Jordan T; Bent, Julian; Cox, Andrew

    2011-09-06

    The adsorption of surface-active protein hydrophobin, HFBII, and HFBII/surfactant mixtures at the solid-solution interface has been studied by neutron reflectivity, NR. At the hydrophilic silicon surface, HFBII adsorbs reversibly in the form of a bilayer at the interface. HFBII adsorption dominates the coadsorption of HFBII with cationic and anionic surfactants hexadecyltrimethyl ammonium bromide, CTAB, and sodium dodecyl sulfate, SDS, at concentrations below the critical micellar concentration, cmc, of conventional cosurfactants. For surfactant concentrations above the cmc, HFBII/surfactant solution complex formation dominates and there is little HFBII adsorption. Above the cmc, CTAB replaces HFBII at the interface, but for SDS, there is no affinity for the anionic silicon surface hence there is no resultant adsorption. HFBII adsorbs onto a hydrophobic surface (established by an octadecyl trimethyl silane, OTS, layer on silicon) irreversibly as a monolayer, similar to what is observed at the air-water interface but with a different orientation at the interface. Below the cmc, SDS and CTAB have little impact upon the adsorbed layer of HFBII. For concentrations above the cmc, conventional surfactants (CTAB and SDS) displace most of the HFBII at the interface. For nonionic surfactant C(12)E(6), the pattern of adsorption is slightly different, and although some coadsorption at the interface takes place, C(12)E(6) has little impact on the HFBII adsorption.

  9. Synthesis and solubility of Pb-Ca and P-As hydroxylapatite solid solutions

    NASA Astrophysics Data System (ADS)

    Puzio, Bartosz; Młynarska, Maria; Motyka, Joanna; Oknińska, Joanna; Mandelt, Agnieszka; Chlebowska, Patrycja; Kwaśniak-Kominek, Monika; Manecki, Maciej

    2016-04-01

    The objective of the study are three solid solution series: - HPY hydroxylpyromorphite Pb5(PO4)3OH - HAP hydroxylapatite Ca5(PO4)3OH - HAP hydroxylapatite Ca5(PO4)3OH - JBM johnbaumite Ca5(AsO4)3OH - JBM johnbaumite Ca5(AsO4)3OH - HMI hydroxylmimetite Pb5(AsO4)3OH The phases were synthesized from aqueous solutions at high pH (over 8) at ambient temperature by dropwise mixing of chemical reagents: Pb(NO3)2, Ca(NO3)2.4H2O, (NH4)H2PO4, and Na2AsHO4.7H2O. The products of all syntheses are crystalline, monomineral fine powders (crystal size less than 1 μm). Their chemical composition is close to theoretical. Systematic shift of XRD peaks and FTIR or Raman bands is observed within the solid solution series. Dissolution experiments were run at 5oC, 25oC, 45oC, and 65oC. An aliquot of 0.5g of each phase was dissolved in 250 mL of 0.05M NH4NO3 (pH between 3 and 5) for about 3 months. In all cases dissolution resulted in increase of pH by about 1. The systems were considered in equilibrium when three consecutive samplings (ca. two weeks apart) resulted in similar concentrations (within 3 standard deviations). The dissolution of all phases in question is incongruent. The amount of precipitating secondary phases was too small for identification. The results of HPY - HAP dissolution experiments are inconclusive due to strongly incongruent dissolution. This is partially in contrary to recent report by Zhu et al. (2015). Systematic increase of solubility is observed in HAP - JBM series. Also, the solubility of these phases increases with the increase of temperature. This is more pronounced for HAP than for JBM. Systematic increase of solubility is also observed in HMI - JBM series. This work is partially funded by AGH research grant no 11.11.140.319 and partially by Polish NCN grant No 2014/01/M/ST10/00355. Zhu,Y., Zhu, Z., Zhao, X., Liang, Y., Huang, Y., 2015. Characterization, dissolution, and solubility of lead hydroxypyromorphite Pb5(PO4)3OH at 25-45oC. Journal of Chemistry

  10. Solution and Solid-State Studies of DNA-Programmable Nanoparticle Single Crystals

    NASA Astrophysics Data System (ADS)

    Auyeung, Evelyn

    This thesis lays the foundation for three main areas that have significantly advanced the field of DNA-programmable nanoparticle assembly: (1) the synthesis of nanoparticle superlattices with novel lattice symmetries (2) post-assembly characterization and applications of superlattices that have been transferred from solution to the solid state and (3) the realization of a slow-cooling strategy for synthesizing faceted nanoparticle single crystals. Together, these advances mark a turning point in the evolution of DNA-programmable assembly from a simple proof-of-concept demonstrated in 1996 to a powerful materials development strategy that has inspired many ongoing investigations in fields including catalysis, plasmonics, and electronics. Chapter 1 begins with an overview of controlled crystallization and its importance across fields including chemistry and materials science. This followed by a description of DNA-programmable assembly and a discussion on its advantages as an assembly strategy. Chapter 2 describes a powerful strategy for synthesizing nanoparticle superlattices using a coreless nanoparticle consisting purely of spherically-oriented oligonucleotides. This "three dimensional spacer approach" allows for the synthesis of nanoparticle superlattices with exotic structures, including one with no mineral equivalent. While DNA is a versatile ligand for nanoparticle assembly, the resulting superlattices are only stable in solution. Chapter 3 addresses these limitations and presents a method for transitioning these materials from solution to the solid state through silica encapsulation. This encapsulation process has transformed the ability to interrogate these materials using electron microscopy, and it has enabled all the studies in subsequent chapters of this thesis. In Chapter 4, a slow-cooling crystallization technique is described that allows for the synthesis of single crystalline microcrystals with well-defined facets from DNA-nanoparticle building blocks

  11. Unprecedented synthesis of 1,3-dimethylcyclobutadiene in the solid state and aqueous solution.

    PubMed

    Legrand, Yves-Marie; Gilles, Arnaud; Petit, Eddy; van der Lee, Arie; Barboiu, Mihail

    2011-08-29

    Cyclobutadiene (CBD), the smallest cyclic hydrocarbon bearing conjugated double bonds, has long intrigued chemists because of its chemical characteristics. The question of whether the molecule could be prepared at all has been answered, but the parent compound and its unperturbed derivatives have eluded crystallographic characterization or synthesis "in water". Different approaches have been used to generate and to trap cyclobutadiene in a variety of confined environments: a) an Ar matrix at cryogenic temperatures, b) a hemicarcerand cage enabling the characterization by NMR spectroscopy in solution, and c) a crystalline guanidinium-sulfonate-calixarene G(4)C matrix that is stable enough to allow photoreactions in the solid state. In the latter case, the 4,6-dimethyl-α-pyrone precursor, Me(2)1, has been immobilized in a guanidinium-sulfonate-calixarene G(4)C crystalline network through a combination of non-covalent interactions. UV irradiation of the crystals transforms the entrapped Me(2)1 into a 4,6-dimethyl-Dewar-β-lactone intermediate, Me(2)2, and rectangular-bent 1,3-dimethylcyclobutadiene, Me(2)CBD(R), which are sufficiently stable under the confined conditions at 175 K to allow a conventional structure determination by X-ray diffraction. Further irradiation drives the reaction towards Me(2)3&Me(2)CBD(S)/CO(2) (63.7 %) and Me(2)CBD(R) (37.3 %) superposed crystalline architectures and the amplification of Me(2)CBD(R). The crystallographic models are supported by additional FTIR and Raman experiments in the solid state and by (1)H NMR spectroscopy and ESI mass spectrometry experiments in aqueous solution. Amazingly, the 4,6-dimethyl-Dewar-β-lactone, Me(2)2, the cyclobutadiene-carboxyl zwitterion, Me(2)3, and 1,3-dimethylcyclobutadiene, Me(2)CBD, were obtained by ultraviolet irradiation of an aqueous solution of G(4)C{Me(2)1}. 1,3-Dimethylcyclobutadiene is stable in water at room temperature for several weeks and even up to 50 °C as demonstrated by

  12. Chemically and compositionally modified solid solution disordered multiphase nickel hydroxide positive electrode for alkaline rechargeable electrochemical cells

    DOEpatents

    Ovshinsky, Stanford R.; Corrigan, Dennis; Venkatesan, Srini; Young, Rosa; Fierro, Christian; Fetcenko, Michael A.

    1994-01-01

    A high capacity, long cycle life positive electrode for use in an alkaline rechargeable electrochemical cell comprising: a solid solution nickel hydroxide material having a multiphase structure that comprises at least one polycrystalline .gamma.-phase including a polycrystalline .gamma.-phase unit cell comprising spacedly disposed plates with at least one chemical modifier incorporated around the plates, the plates having a range of stable intersheet distances corresponding to a 2.sup.+ oxidation state and a 3.5.sup.+, or greater, oxidation state; and at least one compositional modifier incorporated into the solid solution nickel hydroxide material to promote the multiphase structure.

  13. The study of magnetic phase diagram of Fe1-xZnxCr2S4 solid solutions

    NASA Astrophysics Data System (ADS)

    Aminov, T. G.; Kirdyankin, D. I.; Shabunina, G. G.; Novotortsev, V. M.

    2013-08-01

    A magnetic phase diagram of Fe1-хZnхCr2S4 solid solutions was studied. The temperature and concentration ranges of existence of magnetoactive phases based on ferrimagnet FeCr2S4 (0≤х≤0.63), antiferromagnet ZnCr2S4 (0.73≤х≤1), and a spin glass (0.63≤х≤0.73) were determined. The concentration dependences of the saturation magnetic moments and Curie temperatures of the solid solutions synthesized were investigated experimentally and theoretically.

  14. Structural stability, mechanical and electronic properties of cubic BC(x)N crystals within a random solid solution model.

    PubMed

    Zhuang, Chunqiang; Zhao, Jijun; Jiang, Xue; Jiang, Xin

    2009-10-07

    We propose a random solution model for cubic BC(x)N (0.21solid solutions are not a simple mixing of diamond and cubic-BN. The computed bandgaps are substantially lower than those of diamond and BN. Compared to BC(2)N, the BC(x)N solids with higher carbon content (x>2) exhibit better structural stability and higher elastic moduli, making them more attractive as potential superhard materials.

  15. Self-catalytic solution-liquid-liquid-solid (SLLS) growth of tapered SnS nanorods

    NASA Astrophysics Data System (ADS)

    Cho, Ki-Hyun; Sung, Yun-Mo

    2013-04-01

    Taper-shaped SnS nanorods were synthesized via mild chemistry, and the self-catalytic solution-liquid-liquid-solid (SLLS) process was proposed as a crystal growth mechanism. There exists a distinct difference in our SLLS growth compared to the well-known SLS growth in that we injected Sn precursors into a hot trioctylphosphine sulfide (TOPS) solution, which is a reverse process of the general SLS growth. This reverse process could prevent the oxidation of Sn precursors and thus it could facilitate the growth of SnS nanorods, since the surface of Sn clusters and droplets could be momentarily passivated by TOPS molecules. Without addition of extra catalyst nanoparticles, the nucleation and growth of SnS nanorods was induced by liquid Sn droplets. Spherical Sn tips existing at the top of the nanorods evidence the self-catalytic growth. The SLLS growth was proposed based upon the large Sn clusters existing at the bottom of the SnS nanorods in an intermediate stage (5 s) of the growth and the tapered morphology of the nanorods. The growth of SnS nanorods could progress by the upward diffusion of Sn atoms from large liquid Sn clusters along the surface of the SnS nanorods to the interfacial liquid layers (neck area) and the diffusion of S decomposed from TOPS in the solution to the neck area. SnS nanorods showed a direct energy band gap of ~1.6 eV, determined by using the Kubelka-Munk transformation of UV-visible spectra. This self-catalytic SLLS growth produced high-quality and single crystalline SnS nanorods within only 15 s at 290 °C.Taper-shaped SnS nanorods were synthesized via mild chemistry, and the self-catalytic solution-liquid-liquid-solid (SLLS) process was proposed as a crystal growth mechanism. There exists a distinct difference in our SLLS growth compared to the well-known SLS growth in that we injected Sn precursors into a hot trioctylphosphine sulfide (TOPS) solution, which is a reverse process of the general SLS growth. This reverse process could

  16. Local structural study of doped-ceria by EXAFS spectroscopy

    NASA Astrophysics Data System (ADS)

    Shirbhate, S. C.; Yadav, A. K.; Acharya, S. A.; Sagdeo, A. P.; Jha, S. N.

    2016-05-01

    In the present work, Structural and Local structural study of Sm, Gd doped and Sm-Gd co-doped ceria system has been studied by Extended X-ray Absorption Fine Structure Spectroscopy (EXAFS). These ceria based systems are synthesized by hydrothermal synthesis route. Fluorite structure is confirmed by X-ray diffraction (XRD) and data is well fitted using Rietveld refinement by Full-Prof suite. Local structural changes in terms of coordination with surrounding, inter atomic distances and Debye Waller factor of nearest neighbor and next nearest neighbor has been discussed.

  17. Structural Modification of Nanocrystalline Ceria using Ion Beams

    SciTech Connect

    Zhang, Yanwen; Edmondson, Philip D; Varga, Tamas; Moll, Sandra; Namavar, Fereydoon; Weber, William J

    2011-01-01

    Exceptional size-dependent electronic-ionic conductivity of nanostructured ceria can significantly alter materials properties in chemical, physical, electronic and optical applications. Using energetic ions, we have demonstrated effective modification of interface volume and grain size in nanocrystalline ceria from a few nm up to ~ 25 nm, which is the critical region for controlling size-dependent material property. The unique self-healing response of radiation damage at grain boundaries is applied to control the grain size at nanoscale as a function of ion dose and irradiation temperature. Structural modification by energetic ions is proposed to achieve disirable electronic-ionic conductivity.

  18. Comparative pulmonary toxicity of two ceria nanoparticles with the same primary size.

    PubMed

    Peng, Lu; He, Xiao; Zhang, Peng; Zhang, Jing; Li, Yuanyuan; Zhang, Junzhe; Ma, Yuhui; Ding, Yayun; Wu, Zhenqiang; Chai, Zhifang; Zhang, Zhiyong

    2014-04-10

    Ceria nanoparticles (nano-ceria) have recently gained a wide range of applications, which might pose unwanted risks to both the environment and human health. The greatest potential for the environmental discharge of nano-ceria appears to be in their use as a diesel fuel additive. The present study was designed to explore the pulmonary toxicity of nano-ceria in mice after a single exposure via intratracheal instillation. Two types of nano-ceria with the same distribution of a primary size (3-5 nm), but different redox activity, were used: Ceria-p, synthesized by a precipitation route, and Ceria-h, synthesized by a hydrothermal route. Both Ceria-p and Ceria-h induced oxidative stress, inflammatory responses and cytotoxicity in mice, but their toxicological profiles were quite different. The mean size of Ceria-p agglomerates was much smaller compared to Ceria-h, thereby causing a more potent acute inflammation, due to their higher number concentration of agglomerates and higher deposition rate in the deep lung. Ceria-h had a higher reactivity to catalyzing the generation of reactive oxygen species (ROS), and caused two waves of lung injury: bronchoalveolar lavage (BAL) inflammation and cytotoxicity in the early stage and redox-activity-evoked lipid peroxidation and pro-inflammation in the latter stage. Therefore, the size distribution of ceria-containing agglomerates in the exhaust, as well as their surface chemistry are essential characteristics to assess the potential risks of using nano-ceria as a fuel additive.

  19. Self-catalytic solution-liquid-liquid-solid (SLLS) growth of tapered SnS nanorods.

    PubMed

    Cho, Ki-Hyun; Sung, Yun-Mo

    2013-05-07

    Taper-shaped SnS nanorods were synthesized via mild chemistry, and the self-catalytic solution-liquid-liquid-solid (SLLS) process was proposed as a crystal growth mechanism. There exists a distinct difference in our SLLS growth compared to the well-known SLS growth in that we injected Sn precursors into a hot trioctylphosphine sulfide (TOPS) solution, which is a reverse process of the general SLS growth. This reverse process could prevent the oxidation of Sn precursors and thus it could facilitate the growth of SnS nanorods, since the surface of Sn clusters and droplets could be momentarily passivated by TOPS molecules. Without addition of extra catalyst nanoparticles, the nucleation and growth of SnS nanorods was induced by liquid Sn droplets. Spherical Sn tips existing at the top of the nanorods evidence the self-catalytic growth. The SLLS growth was proposed based upon the large Sn clusters existing at the bottom of the SnS nanorods in an intermediate stage (5 s) of the growth and the tapered morphology of the nanorods. The growth of SnS nanorods could progress by the upward diffusion of Sn atoms from large liquid Sn clusters along the surface of the SnS nanorods to the interfacial liquid layers (neck area) and the diffusion of S decomposed from TOPS in the solution to the neck area. SnS nanorods showed a direct energy band gap of ∼1.6 eV, determined by using the Kubelka-Munk transformation of UV-visible spectra. This self-catalytic SLLS growth produced high-quality and single crystalline SnS nanorods within only 15 s at 290 °C.

  20. ZrB2-HfB2 solid solutions as electrode materials for hydrogen reaction in acidic and basic solutions

    SciTech Connect

    Sitler, Steven J.; Raja, Krishnan S.; Charit, Indrajit

    2016-11-09

    Spark plasma sintered transition metal diborides such as HfB2, ZrB2 and their solid solutions were investigated as electrode materials for electrochemical hydrogen evolutions reactions (HER) in 1 M H2SO4 and 1 M NaOH electrolytes. HfB2 and ZrB2 formed complete solid solutions when mixed in 1:1, 1:4, and 4:1 ratios and they were stable in both electrolytes. The HER kinetics of the diborides were slower in the basic solution than in the acidic solutions. The Tafel slopes in 1 M H2SO4 were in the range of 0.15 - 0.18 V/decade except for pure HfB2 which showed a Tafel slope of 0.38 V/decade. In 1 M NaOH the Tafel slopes were in the range of 0.12 - 0.27 V/decade. The composition of HfxZr1-xB2 solid solutions with x = 0.2 - 0.8, influenced the exchange current densities, overpotentials and Tafel slopes of the HER. As a result, the EIS data were fitted with a porous film equivalent circuit model in order to better understand the HER behavior. In addition, modeling calculations, using density functional theory approach, were carried out to estimate the density of states and band structure of the boride solid solutions.

  1. Chemical composition and acid-base properties of the surface of GaAs-CdS solid solutions

    NASA Astrophysics Data System (ADS)

    Kirovskaya, I. A.; Zemtsov, A. E.

    2007-01-01

    Chemical composition and acid-base properties of the surfaces of GaAs-CdS solid solutions and the constituent binary compounds exposed to air, vacuum, CO, and NH3 were analyzed using mass spectrometry, IR spectrometry, isoelectric-point pH (pHiso) analysis, and mechanochemical methods. Powders and films were prepared from the solid solutions by isothermal diffusion and discrete vacuum evaporation, respectively. XRD and Raman analysis revealed that a solid solution has a sphalerite or wurtzite structure, depending on its composition. The initial surface of all the systems studied exhibited acidic properties: the pH value ranged from 4.9 to 6.45. The surfaces contained Lewis (electron accepting) and Brönsted (adsorbed H2O and CO2 molecules, OH- groups) sites. The acidity of the surface increased upon treatment with CO and decreased upon treatment with NH3. For all types of treatment, the concentration dependence of the acid-base properties of the surface exhibited an extremum. The strongest acidic sites were revealed on the surface of the (GaAs)0.95 (CdS)0.05 solid solution. The adsorption activity of this solution, a promising material for manufacturing gas sensors, was evaluated.

  2. Growth, Nitrogen Vacancy Reduction and Solid Solution Formation in Cubic GaN Thin Films and the Subsequent Fabrication of Superlattice Structures Using AIN and InN

    DTIC Science & Technology

    1992-12-01

    AD-A258 804 Final Technical Report Ii Growth, Nitrogen Vacancy Reduction and Solid Solution Formation in Cubic GaN Thin Films and the Subsequent...Technical 6/1/86-12/31/92 4. TITLE AND SUBTITLE Growth, Nitrogen Vacancy Reduction and 5. FUNDING NUMBERS Solid Solution Formation in Cubic GaN Thin...According to the structural and chemical analyses, there is no reason to believe that a homogeneous solid solution close to this composition had

  3. Pt/Ceria-based Catalysts for Small Alcohol Electrooxidation

    NASA Astrophysics Data System (ADS)

    Menendez-Mora, Christian L.

    High emissions of fossil-based energy sources have led to scientists around the world to develop new alternatives for the future. In this sense, fuel cells are a remarkable and promising energy option with less environmental impact. The most used fuels for this technology are hydrogen and small chain alcohols, which can be oxidized to transform their chemical energy into electrical power. To do this, fuel cells need catalysts that will act as an active surface where the oxidation can take place. The problem with platinum catalysts is its possible CO poisoning with intermediates that are produced before the complete oxidation of alcohol to CO2. Different approaches have been taken to try to resolve this issue. In this case, cerium oxide (ceria) was selected as a co-catalyst to mitigate the effect of CO poisoning of platinum. Ceria is a compound that has the ability to work as an "oxygen tank" and can donate oxygen to carbon monoxide that is strongly adsorbed at platinum surface to produce CO2 (carbon dioxide), regenerating the Pt surface for further alcohol oxidation. Therefore, enhancing the current density as well as the power output of a fuel cell. First, an occlusion deposition technique was used to prepare platinum/ceria composite electrodes and tested them towards small chain alcohol oxidation such as methanol oxidation reaction in acidic and alkaline media. The preliminary results demonstrated that the Pt/ceria electrodes were more efficient towards methanol electrooxidation when compared to Pt electrodes. This enhancement was attributed to the presence of ceria. A second preparation method was selected for the synthesis of ceria/Pt catalysts. In this case, a hydrothermal method was used and the catalysis were studied for the effect of MeOH, EtOH and n-BuOH oxidation. The observed effect was that electrodes made of Pt/Pt:CeO2-x showed better catalytic effect than Pt/ceria and platinum electrodes. Moreover, a comparison between ceria nanorods versus

  4. Improving the structural consistency of C-S-H solid solution thermodynamic models

    SciTech Connect

    Kulik, Dmitrii A.

    2011-05-15

    Simple aqueous-solid solution models of C-S-H (calcium silicate hydrate) are widely used in studies of cement hydration and waste-cement interactions. Even without a clear structural/mechanistic basis, such thermodynamic models yield a good description of solubility data in [Ca]-C/S space, while only satisfactory in [Si]-C/S, H{sub 2}O-C/S, [Ca]-[Si] spaces and in the 0.1 < C/S < 0.8 range. Here, using a multi-site (sublattice) concept, the ideal solid solution model of C-S-H is revised to make it consistent with the Richardson-Groves structural model of C-S-H and with the modern interpretation of spectroscopic ({sup 29}Si MAS NMR) and solubility data. Consideration of two site substitutions, (1) coupled H{sub 2}OCa{sup 2+} for SiO{sub 2}H{sub 2}{sup 2+} replacement in bridging tetrahedral and adjacent interlayer sites, and (2) substitution of interstitial Ca(OH){sub 2} for a vacancy, leads to a new CSHQ model of (A,B) (C,D)X type composed of two tobermorite-like and two jennite-like end members. Because this ideal sublattice SS model cannot fit solubility data well at 0.8 < C/S < 1.1, a simpler CSH3T model is constructed from a polymeric TobH (CaO){sub 2}(SiO{sub 2}){sub 3}(H{sub 2}O){sub 5}, a dimeric T2C (CaO){sub 3}(SiO{sub 2}){sub 2}(H{sub 2}O){sub 5}, and an ordered pentameric T5C (CaO){sub 2.5}(SiO{sub 2}){sub 2.5}(H{sub 2}O){sub 5} tobermorite-like end members. This solid solution model, limited to the range 0.67 < C/S < 1.5, has a correct built-in dependence of the mean silicate chain length on C/S, yields quite realistic fits to the solubility data, and provides a basis for extensions with foreign cations whose sites in the defect-tobermorite structure of C-S-H are known. To account for C-S-H compositions with C/S > 1.5, CSHQ end members were downscaled to one tetrahedral site and used within the simple mixing model. Despite some loss of structural consistency, the solubility and mean silicate chain length data can be reproduced well with this downscaled

  5. Assessment of a modified and optimised method for determining chemical oxygen demand of solid substrates and solutions with high suspended solid content.

    PubMed

    Raposo, F; de la Rubia, M A; Borja, R; Alaiz, M

    2008-07-15

    A modified approach to determine the chemical oxygen demand (COD) of solid substrates based on the DIN 38414-S9 standard method is proposed. The adapted procedure is assessed and compared with standard methods widely used for water and wastewater such as the American Public Health Association-American Water Works Association-Water Pollution Control Federation (APHA-AWWA-WPCF) standard methods 5220 B-open reflux (SM-OR) and 5220 D-closed reflux colorimetric (SM-CR). Solutions with high suspended concentration of solids, as well as digestates from an anaerobic reactor, were used during the comparative test. For solid substrates, the COD recovery was about 100% when the proposed method was used. For solutions with solid content higher than 20 g TS L(-1), the recovery was only completed when the proposed method was used, showing that the methods traditionally employed are not very appropriate for samples with the described characteristics. For instance, percentages of COD recovery in the ranges of 77.3-87.1% and 89.4-94.1% were achieved when the SM-OR and SM-CR methods were used, respectively.

  6. Thermodynamic Destabilization of Ti-O Solid Solution by H2 and Deoxygenation of Ti Using Mg.

    PubMed

    Zhang, Ying; Fang, Zhigang Zak; Sun, Pei; Zhang, Tuoyang; Xia, Yang; Zhou, Chengshang; Huang, Zhe

    2016-06-08

    Reactive metals including Ti, Zr, Hf, and V, among others, have a strong chemical affinity to oxygen, which makes them difficult to produce and costly to use. It is especially challenging to produce pure or metal alloy powders of these elements when extremely low oxygen content is required, because they have high solubility for oxygen, and the solid solution of these metals with oxygen is often more stable thermodynamically than their oxides. We report a novel thermochemical approach to destabilize Ti(O) solid solutions using hydrogen, thus enabling deoxygenation of Ti powder using Mg, which has not been possible before because of the thermodynamic stability of Ti(O) solid solutions relative to MgO. The work on Ti serves as an example for other reactive metals. Both analytical modeling and experimental results show that hydrogen can indeed increase the oxygen potential of Ti-O solid solution alloys; in other words, the stability of Ti-O solid solutions is effectively decreased, thus increasing the thermodynamic driving force for Mg to react with oxygen in Ti. Because hydrogen can be easily removed from Ti by a simple heat treatment, it is used only as a temporary alloying element to destabilize the Ti-O systems. The thermodynamic approach described here is a breakthrough and is applicable to a range of different materials. This work is expected to provide an enabling solution to overcome one of the key scientific and technological hurdles to the additive manufacturing of metals, which is emerging rapidly as the future of the manufacturing industry.

  7. Comparative analysis of zaleplon complexation with cyclodextrins and hydrophilic polymers in solution and in solid state.

    PubMed

    Jablan, Jasna; Szalontai, Gábor; Jug, Mario

    2012-12-01

    The aim of this work was to investigate the potential synergistic effect of water-soluble polymers (hypromellose, HPMC and polyvinylpyrrolidone, PVP) on zaleplon (ZAL) complexation with parent β-cyclodextrin (βCD) and its randomly methylated derivative (RAMEB) in solution and in solid state. The addition of HPMC to the complexation medium improved ZAL complexation and solubilization with RAMEB (K(ZAL/RAMEB)=156±5M(-1) and K(ZAL/RAMEB/HPMC)=189±8M(-1); p<0.01), while such effect was not observed for βCD (K(ZAL/βCD)=112±2M(-1) and K(ZAL/βCD/HPMC)=119±8M(-1); p>0.05). Although PVP increased the ZAL aqueous solubility from 0.22 to 0.27mg/mL, it did not show any synergistic effects on ZAL solubilization with the cyclodextrins tested. Binary and ternary systems of ZAL with βCD, RAMEB and HPMC were prepared by spray-drying. Differential scanning calorimetry, X-ray powder diffraction and scanning electron microscopy demonstrated a partial ZAL amorphization in spray-dried binary and ternary systems with βCD, while the drug was completely amorphous in all samples with RAMEB. Furthermore, inclusion complex formation in all systems prepared was confirmed by solid-state NMR spectroscopy. The in vitro dissolution rate followed the rank order ZAL/RAMEB/HPMC>ZAL/RAMEB=ZAL/βCD/HPMC>ZAL/βCD≫ZAL, clearly demonstrating the superior performance of RAMEB on ZAL complexation in the solid state and its synergistic effect with HPMC on drug solubility. Surprisingly, when loaded into tablets made with insoluble microcrystalline cellulose, RAMEB complexes had no positive effect on drug dissolution, because HPMC and RAMEB acted as a binders inside the tablets, prolonging their disintegration. Oppositely, the formulation with mannitol, a soluble excipient, containing a ternary RAMEB system, released the complete drug-dose in only 5min, clearly demonstrating its suitability for the development of immediate-release oral formulation of ZAL.

  8. Pressure-volume equation of state for pyrope-almandine solid solutions

    NASA Astrophysics Data System (ADS)

    Nestola, Fabrizio; Milani, Sula; Angel, Ross J.; Pasqual, Daria; Geiger, Charles A.

    2013-04-01

    Garnet is a key phase of Earth's upper mantle and one of the most abundant solid inclusions in diamonds. The pyrope component (Mg3Al2Si3O12, Py) of garnet found in diamonds of peridotitic and eclogitic origin can be as high as about 79 and 43%, respectively and the almandine component (Fe3Al2Si3O12, Al) is about 11 and 33%, respectively. Thus such garnets are largely Py-Al-rich solid solutions (Stachel and Harris, 2008). To determine the depth of formation of diamond-inclusion pairs, precise and accurate thermoelastic parameters for both the diamond and the solid inclusion phase are necessary (e.g. Izraeli et al., 1999; Howell et al., 2010; Nestola et al., 2011; Howell et al., 2012). We are presently investigating the pressure-volume equation of state for a series of synthetic garnets along the binary pyrope-almandine by X-ray single-crystal diffraction using a diamond anvil cell up to a maximum of 8 GPa pressure. We have completed measurements on two crystals of composition Fe3Al2Si3O12 and Fe1.20Mg1.80Al2Si3O12. The equation of state coefficients obtained by fitting a third-order Birch-Murnaghan to the pressure-volume data show that an increase in the pyrope component in garnet causes a slight decrease of the isothermal bulk modulus, KT0, by about 3%, whereas the first pressure derivative term does not vary. Applying our results to obtain the pressure of formation of a natural diamond-garnet pair, and assuming a garnet composition close to Fe1.20Mg1.80Al2Si3O12, we obtain a pressure of encapsulation (or formation if garnet and diamond are syngenetic) of garnet in diamond between 6.5 and 7.0 GPa. References Howell, D., Wood, I.G., Dobson, D.P., Jones, A.P., Nasdala, L., Harris, J.W. (2010) Contrib. Mineral. Petrol., 160, 705-717. Howell, D., Wood, I.G., Nestola, F., Nimis, P., Nasdala, L. (2012) Eur. J. Mineral., ,. Izraeli, E.S., Harris, J.W., Navon, O. (1999) Earth Planet Sci. Lett., 173, 351-360. Nestola, F., Nimis, P., Ziberna, L., Longo, M., Marzoli, A

  9. Photosensitizer-Loaded Branched Polyethylenimine-PEGylated Ceria Nanoparticles for Imaging-Guided Synchronous Photochemotherapy.

    PubMed

    Yang, Zhang-You; Li, Hong; Zeng, Yi-Ping; Hao, Yu-Hui; Liu, Cong; Liu, Jing; Wang, Wei-Dong; Li, Rong

    2015-11-04

    A multifunctional theranostic platform based on photosensitizer (chlorin e6, Ce6)-loaded branched polyethylenimine-PEGylated ceria nanoparticles (PPCNPs-Ce6) was created for the development of effective cancer treatments involving the use of imaging-guided synchronous photochemotherapy. PPCNPs-Ce6 with high Ce6 photosensitizer loading (Ce6: cerium ∼40 wt %) significantly enhanced the delivery of Ce6 into cells and its accumulation in lysosomes, remarkably improving photodynamic therapeutic (PDT) efficacy levels compared to those in the administration of free Ce6 at ultralow drug doses (∼200 nM). Interestingly, PPCNPs-Ce6 efficiently induced HeLa cell death even at low concentrations (∼10 μM) without the use of laser irradiation and exhibit chemocytotoxicity. Inductively coupled plasma mass spectrometry (ICP-MS) and biology transmission electron microscopy (Bio-TEM) analyses demonstrated that ceria nanoparticles enter cells abundantly and accumulate in lysosomes or large vesicles. We then evaluated the effects of the different materials on lysosomal integrity and function, which revealed that PPCNPs-Ce6 catastrophically impaired lysosomal function compared to results with PPCNPs and Ce6. Studies of apoptosis revealed greater induction of apoptosis by PPCNPs-Ce6 treatment. This multifunctional nanocarrier also exhibited a high degree of solubility and stability in aqueous solutions, suggesting its applicability for extensive biomedical application.

  10. Dielectric Function and Interband Transitions in Hg{1-x}Zn{x}Te Solid Solutions

    NASA Astrophysics Data System (ADS)

    Castaing, O.; Benhlal, J. T.; Granger, R.; Triboulet, R.

    1996-07-01

    The dielectric function ɛ_r + iɛ_i in Hg{1-x}Znx Te is found, for the first time, at 293 K. It is deduced from spectroscopic ellipsometry measurements for the entire composition range and for photon energies ranging from 0.75 eV to 5.7 eV. A detailed analysis of the chemical treatments leading to the best surfaces which correspond to the highest values of ɛ_i at the E_2 peak is presented. The oxydation of the surface after the last stripping is also studied. The pseudodielectric function is analysed for the critical point model. The variation, with x of the parameters describing the main critical transitions E_0, E_0 + Δ_0, E_1, E_1 + Δ_1 and E_2 are obtained. The results are discussed in relation to the band structure and to the properties of these compounds. La fonction diélectrique ɛ_r + iɛ_i des solutions solides Hg{1-x}ZnxTe est donnée, pour la première fois, à 293 K. Ces résultats sont déduits de mesures d'ellipsométrie spectroscopique dans tout le domaine de composition et pour des énergies de photon allant de 0,75 eV à 5,7 eV. Les traitements chimiques permettant d'obtenir les meilleures surfaces correspondant aux plus fortes valeurs de ɛ_i au pic E_2 sont analysés en détail. De même, l'oxydation de la surface est suivie par ellipsométrie. La fonction pseudodiélectrique est analysée avec le modèle de points critiques. Les variations des paramètres définissant les principales transitions E_0, E_0 + Δ_0, E_1, E_1 + Δ_1 et E_2 sont données en fonction de la composition x. Ces résultats sont discutés en relation avec la structure de bande et les propriétés de ces solutions solides.

  11. Solid solution directionally solidified eutectics: Model systems for structure-property relationships in interfacial fracture

    NASA Astrophysics Data System (ADS)

    Brewer, Luke Nathaniel

    The next generation of high temperature materials for application in aerospace and power generation systems will be required to withstand temperatures well in excess of 1200°C, often in oxidizing atmospheres. Oxide-oxide directionally solidified eutectics (DSE's) have shown promise as high temperature ceramic materials, only to be limited by their lack of fracture toughness at room temperature. In the case of DSE oxide materials, the interfacial fracture behavior has been blamed for the poor performance in the past and is the subject of interest in this work. In this thesis, the solid solution, directionally solidified quaternary eutectic (SS-DSE), Co1-xNixO/ZrO2(CaO), is developed as a model system for the study of interfacial fracture in oxide-oxide DSE's. A variety of structural and mechanical characterization techniques are applied to investigate structure-property relationships for interfacial fracture behavior. The optical floating zone technique was employed for growing both the eutectic crystals and their single crystal counterparts, Co1-x NixO. Co1-xNixO/ZrO2(CaO) was shown to possess the necessary structural elements to serve as a model system for interfacial fracture. Lamellar microstructures were observed for all compositions. The crystallographic relationships between phases evolved as a model solid solution. Interdiffusion of chemical species was minimal, allowing the layers to treated independently. The core of this thesis is dedicated to studying the nature of interfacial fracture behavior in oxide eutectics. This study is motivated by the novel observation of extensive interfacial delamination for the system CoO/ZrO 2(CaO). A transition from interfacial delamination to interfacial penetration is observed for compositions of Co1-xNixO/ZrO 2(CaO) with x > 0.2. The residual stress state in these materials was investigated using X-ray and neutron diffraction-based techniques. The role of plasticity in interfacial fracture was explored using a

  12. Thermodynamic mixing properties and behavior of almandine-spessartine solid solutions

    NASA Astrophysics Data System (ADS)

    Dachs, Edgar; Geiger, Charles A.; Benisek, Artur; Grodzicki, Michael

    2014-01-01

    The heat capacity, Cp, of five solid-solution members of the almandine(Alm)-spessartine(Sps) binary, consisting of three synthetic polycrystalline and two natural single-crystal samples, was measured in the temperature range between 2 and 300 K using relaxation calorimetry and between 282 and 764 K using DSC methods. All garnets exhibit a λ-type heat-capacity anomaly at low temperatures resulting from a paramagnetic to antiferromagnetic phase transition. The temperature of the magnetic transition in Fe-rich garnets occurs between those of the two end-members (i.e. 9.2 K for almandine and 6.2 K for spessartine), but lies at lower values between 3.5 and 4.5 K for more Sps-rich compositions with XMngrt>0.5. The calorimetric entropy at 298 K shows mechanical-mixture behavior for Sps-rich garnets and a slight possible negative deviation from such behavior for Alm-rich compositions. At the 2σ level all data are, however, consistent with ideal mixing behavior and the Margules entropy interaction parameter, WS,FeMngrt, is zero for the Alm-Sps binary. Thermodynamic analysis of published high P and T phase-equilibrium Fe-Mn exchange experiments between garnet and ilmenite shows that the excess Gibbs free energy of mixing, ΔGex, for Fe-Mn in garnet is positive and asymmetric towards spessartine. Margules enthalpy interaction parameters of WH,FeMngrt=4170±518 J/cationṡmol and WH,MnFe=1221±588 J/cationṡmol are derived giving a maximum of ΔGex≈0.7 kJ/cationṡmol at XMngrt≈0.6. ΔHex obtained using autocorrelation analysis of published IR spectra of Alm-Sps solid solutions is in reasonable agreement with that derived from phase-equilibrium and calorimetry data. Previous diffraction and spectroscopic results on Alm-Sps garnets and quantum mechanical calculations made on almandine are used to interpret the macroscopic thermodynamic behavior from a microscopic basis. The relevance of the new garnet Fe-Mn mixing model for petrological calculations is demonstrated by

  13. Photocatalytic hydrogen production over solid solutions between BiFeO3 and SrTiO3

    NASA Astrophysics Data System (ADS)

    Lu, Lingwei; Lv, Meilin; Liu, Gang; Xu, Xiaoxiang

    2017-01-01

    Constituting solid solutions has been an appealing means to gain control over various physicochemical properties. In this work, we synthesized a series of SrTiO3-BiFeO3 solid solutions and systematically explored their structural, optical and photocatalytic properties. Our results show that all solid solutions crystallize in a primitive cubic structure and their band gap values can be easily tuned by adjusting molar ratios between SrTiO3 and BiFeO3. Photocatalytic hydrogen production under both full range and visible light irradiation is greatly improved after forming solid solutions. The highest hydrogen production rate obtained is ∼180 μmol/h under full range irradiation (λ ≥ 250 nm) and ∼4.2 μmol/h under visible light irradiation (λ ≥ 400 nm), corresponding to apparent quantum efficiency ∼2.28% and ∼0.10%, respectively. The activity is found to be strongly influenced by surface area and light absorption. Theoretical calculation suggests that Fe contributes to the formation of spin-polarized bands in the middle of original band gap and is responsible for the band gap reduction and visible light photocatalytic activity.

  14. Characterizing the Solid-Solution Coefficient and Plant Uptake Factor of As, Cd and Pb in California Croplands

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In risk assessment models, the solid-solution partition coefficient (Kd), and plant uptake factor (PUF), are often employed to model the fate and transport of trace elements in soils. The trustworthiness of risk assessments depends on the reliability of the parameters used. In this study, we exami...

  15. Intramolecular Paternò-Büchi reaction of atropisomeric α-oxoamides in solution and in the solid-state.

    PubMed

    Raghunathan, Ramya; Kumarasamy, Elango; Iyer, Akila; Ugrinov, Angel; Sivaguru, J

    2013-10-07

    Atropisomeric α-oxoamides were synthesized and employed for intramolecular Paternò-Büchi reaction leading to very high enantio- and diastereoselectivity in the bicyclic oxetane photoproduct. A reversal of product selectivity was observed in solution and in the solid-state.

  16. Structural and optical properties of PVP-capped nanocrystalline ZnxCd1-xS solid solutions

    NASA Astrophysics Data System (ADS)

    Askari, Mina; Soltani, Nayereh; Saion, Elias; Yunus, W. Mahmood Mat; Maryam Erfani, H.; Dorostkar, Mahdi

    2015-05-01

    Nanocrystalline ZnxCd1-xS solid solutions were prepared in a microwave-assisted hydrothermal process with gradient distribution of components (x = 0.1, 0.3, 0.5, 0.7, and 0.9). The growth of the cubic-structured quantum dots was observed for all component stoichiometries with the crystallite size between 4.5 and 5.7 nm. The obvious peak shifts have been found in the XRD patterns and the lattice parameters showed linear variation with x increasing. The evolution of the optical properties of obtained solid solutions including absorption and photoemission was also monitored in detail. The solid solutions show a considerable shift in the nanoparticle optical absorption edge from 482 to 343 nm with the increasing of Zn fraction. The band gaps of the solid solutions were estimated to be between 2.94 and 3.40 eV and the position of conduction band was shifted toward more negative potential with x increasing. The photoluminescence spectra showed a broad blue-green emission spreading up to 600 nm with emergence of three dominant peaks belong to sulfur, zinc, and cadmium vacancies.

  17. The formation of supersaturated solid solutions in Fe–Cu alloys deformed by high-pressure torsion

    PubMed Central

    Bachmaier, A.; Kerber, M.; Setman, D.; Pippan, R.

    2012-01-01

    Fully dense bulk nanocomposites have been obtained by a novel two-step severe plastic deformation process in the immiscible Fe–Cu system. Elemental micrometer-sized Cu and Fe powders were first mixed in different compositions and subsequently high-pressure-torsion-consolidated and deformed in a two-step deformation process. Scanning electron microscopy, X-ray diffraction and atom probe investigations were performed to study the evolving far-from-equilibrium nanostructures which were observed at all compositions. For lower and higher Cu contents complete solid solutions of Cu in Fe and Fe in Cu, respectively, are obtained. In the near 50% regime a solid solution face-centred cubic and solid solution body-centred cubic nanograined composite has been formed. After an annealing treatment, these solid solutions decompose and form two-phase nanostructured Fe–Cu composites with a high hardness and an enhanced thermal stability. The grain size of the composites retained nanocrystalline up to high annealing temperatures. PMID:22368454

  18. Virtual Solid Solution Laboratory a tool for quantitative description of mixing and order/disorder effects in minerals

    NASA Astrophysics Data System (ADS)

    Vinograd, V. L.; Gale, J. D.; Winkler, B.

    2006-12-01

    Thermodynamic mixing properties of the majority of pertrologically important mineral phases remain poorly constrained. The Virtual Solid Solution Laboratory (VSSL) is designed to predict unknown mixing properties of solid solutions starting from a well parameterized set of empirical interatomic potentials. The VSSL assists a solid solution modeler in the following tasks: (1) Development of a set of transferable empirical interatomic potentials for a system of interest by fitting to structure and elasticity data of chemically similar minerals; (2) Testing the potentials by comparing the predicted properties of a limited set of ordered structures with the results of quantum mechanical calculations; (3) Static lattice energy calculations on a large set of structures with randomly varied configurations of the exchangeable atoms; (4) Finding a simple equation that describes the energies of the simulated structures. This procedure is known as the cluster expansion (CE); (5) Using the CE model to obtain temperature-dependent mixing properties by Monte Carlo simulations; (6) Calculation of the free energies of mixing by thermodynamic integration of the Monte Carlo results; (7) Calculation of the activity-composition and phase relations from the simulated free energies of mixing. The VSSL results for calcite-magnesite, pyrope-grossular, pyrope-majorite and diopside-jadeite solid solutions are discussed.

  19. Ab initio calculation of excess properties of La1-x(Ln,An)xPO4 solid solutions

    NASA Astrophysics Data System (ADS)

    Li, Yan; Kowalski, Piotr M.; Blanca-Romero, Ariadna; Vinograd, Victor; Bosbach, Dirk

    2014-12-01

    We used ab initio computational approach to predict the excess enthalpy of mixing and the corresponding regular/subregular model parameters for La1-xLnxPO4 (Ln=Ce,…, Tb) and La1-xAnxPO4 (An=Pu, Am and Cm) monazite-type solid solutions. We found that the regular model interaction parameter W computed for La1-xLnxPO4 solid solutions matches the few existing experimental data. Within the lanthanide series W increases quadratically with the volume mismatch between LaPO4 and LnPO4 endmembers (ΔV=VLaPO4-VLnPO4), so that W(kJ/mol)=0.618(. We demonstrate that this relationship also fits the interaction parameters computed for La1-xAnxPO4 solid solutions. This shows that lanthanides can be used as surrogates for investigation of the thermodynamic mixing properties of actinide-bearing solid solutions.

  20. Molten-salt synthesis and composition-dependent luminescent properties of barium tungsto-molybdate-based solid solution phosphors

    NASA Astrophysics Data System (ADS)

    Xiang-Hong, He; Zhao-Lian, Ye; Ming-Yun, Guan; Ning, Lian; Jian-Hua, Sun

    2016-02-01

    Pr3+-activated barium tungsto-molybdate solid solution phosphor Ba(Mo1-zWz)O4:Pr3+ is successfully fabricated via a facile molten-salt approach. The as-synthesized microcrystal is of truncated octahedron and exhibits deep-red-emitting upon blue light excitation. Powder x-ray diffraction and Raman spectroscopy techniques are utilized to investigate the formation of solid solution phosphor. The luminescence behaviors depend on the resulting composition of the microcrystals with fixed Pr3+-doping concentration, while the host lattices remain in a scheelite structure. The forming solid solution via the substitution of [WO4] for [MoO4] can significantly enhance its luminescence, which may be due to the fact that Ba(Mo1-zWz)O4:Pr3+ owns well-defined facets and uniform morphologies. Owing to its properties of high phase purity, well-defined facets, highly uniform morphologies, exceptional chemical and thermal stabilities, and stronger emission intensity, the resulting solid solution phosphor is expected to find potential applications in phosphor-converted white light-emitting diodes (LEDs). Project supported by the Construction Fund for Science and Technology Innovation Group from Jiangsu University of Technology, China, the Key Laboratory of Atmospheric Environment Monitoring and Pollution Control, China (Grant No. KHK1409), the Priority Academic Program Development of Jiangsu Higher Education Institutions, China, and the National Natural Science Foundation of China (Grant No. 21373103).