Winnie Wong-Ng

Crystal chemistry and phase equilibria studies of theBaO(BaCO3)R2O3CuOsystems. IV. Crystal chemistry and subsolidus phase relationship studies of the CuO-rich region of the ternary diagrams,R =lanthanides

Abstract In theBaO(BaCO3) R2O3 CuOsystems, whereR =lanthanidesand yttrium, general trends of phase formation, solid solution formation, and phase relationships are correlated with the ionic size ofR.In air at 950°C the phase relationships in the CuO-rich region of these ternary diagrams progressively change from the La system through the Nd, Sm, Eu, Gd, Y, Ho systems to the Er system. First, the La system has the greatest number of ternary compounds. Second, the superconductor material,Ba2RCu3O6+x,exhibits a solid solution ofBa2−zR1+zCu3O6+xfor the first half of the lanthanide elements with a range of formation which varies with the ionic size ofR.Third, a trend is observed regarding the tie-line connections betweenBaR2CuO5, CuO, the phasesBa2−zR1+zCu3O6+x, and the binary phaseR2CuO4orR2Cu2O5.For the first half of the lanthanides, except for La, a compatibility join is found to connectR2CuO4and the tetragonal end member of theBa2−zR1+zCu3O6+xphase. In systems whereRhas a smaller ionic size,R =Euand beyond, the tie-line connection switches to join theBaR2CuO5phase and the CuO phase. ForR =Dyand beyond, the binary phaseR2CuO4is replaced by the binary phaseR2Cu2O5.

Methods of Producing Standard X-Ray Diffraction Powder Patterns

Patterns useful for identification are obtained by automated diffractometer methods. The lattice constants from the experimental work are refined by least-squares methods; reflections are assigned hkl indices consistent with space group extinctions. Relative intensities, calculated densities, literature references, and other relevant data are included.

Measurement, standards, and data needs for CO2 capture materials: a critical review.

The commercial deployment of cost-effective carbon capture technology is hindered partially by the lack of a proper suite of materials-related measurements, standards, and data, which would provide critical information for the systematic design, evaluation, and performance of CO2 separation materials. Based on a literature search and conversations with the carbon capture community, we review the current status of measurements, standards, and data for the three major carbon capture materials in use today: solvents, solid sorbents, and membranes. We highlight current measurement, standards and data activities aimed to advance the development and use of carbon capture materials and major research needs that are critical to meet if innovation in carbon capture materials is to be achieved. The review reveals that although adsorbents are considered to have great potential to reduce carbon capture cost, there is no consensus on the experimental parameters to be used for evaluating sorbent properties. Another important finding is the lack of in situ experimental tools for the structural characterization of solid porous materials during CO2 adsorption, and computational methods that would enable a materials-by-design approach for their development.

Selective Adsorption of CO2 from Light Gas Mixtures by Using a Structurally Dynamic Porous Coordination Polymer

The selective adsorption of CO{sub 2} from mixtures with N{sub 2}, CH{sub 4}, and N{sub 2}O in a dynamic porous coordination polymer (see monomer structure) was evaluated by ATR-FTIR spectroscopy, GC, and SANS. All three techniques indicate highly selective adsorption of CO{sub 2} from CO{sub 2}/CH{sub 4} and CO{sub 2}/N{sub 2} mixtures at 30 C, with no selectivity observed for the CO{sub 2}/N{sub 2}O system.

A high-throughput thermoelectric power-factor screening tool for rapid construction of thermoelectric property diagrams

The authors have developed a high-throughput screening tool that maps out thermoelectric power factors of combinatorial composition-spread film libraries. The screening tool allows one to measure the electrical conductivity and Seebeck coefficient of over 1000 sample points within 6h. Seebeck coefficients of standard films measured with the screening tool are in good agreement with those measured by traditional thermoelectric measurement apparatus. The rapid construction of thermoelectric property diagrams is illustrated for two systems: (Zn, Al)–O binary composition-spread film on Al2O3 (0001) and (Ca,Sr,La)3Co4O9 ternary composition-spread film on Si (100).

Neutron diffraction study of the brown phase BaNd2CuO5

Abstract A neutron Rietveld refinement study of the “brown phase” BaNd 2 CuO 5 shows that this material is isostructural with the La analog, but adopts a totally different structure from that of the “green phase” BaR 2 CuO 5 formed for R = Y and most lanthanide elements. BaNd 2 CuO 5 is tetragonal, space group P4/mbm(126), with Z =2 and refined cell parameters a = 6.7015(1) and c =5.8211 (1) A. The BaNd 2 CuO 5 framework is built from edge- and face-sharing BaO 10 and NdO 8 polyhedra, while in the green phase structure the smaller R 3+ ion is surrounded by seven oxygen atoms. The square-planar CuO 4 groups are isolated in the structure.

Preparation and crystal structure of Sr5TiNb4O17

Abstract The compound Sr 5 TiNb 4 O 17 was prepared and its crystal structure determined by single-crystal X-ray diffraction. This compound crystallizes with an orthorhombic unit cell (space group Pnnm (No. 58); a = 5.6614(4), b = 32.515(7), c = 3.9525(3)A; Z = 2). The structure consists of alternating perovskite-like slabs offset with respect to each other by a 2 and c 2 . The Sr 2+ ions occupy two 12-fold coordinated sites within the slabs and a distorted (7 + 1)-fold coordinated site in the gap separating the slabs. Nb 5+ and Ti 4+ are distributed among the octahedral sites of the sperovskite slabs with preferential ordering of Ti 4+ on octahedral sites in the center of the slabs and Nb 5+ in the octahedral sites at the edges of the slabs adjacent to the gap. This compound is the n = 5 member of a structural series A n B n O 3n+2 , (A = Sr; B = Ti,Nb) where n is the number of perovskite layers within each slab.

Recent Advances of Graphitic Carbon Nitride-Based Structures and Applications in Catalyst, Sensing, Imaging, and LEDs

Abstract The graphitic carbon nitride (g-C3N4) which is a two-dimensional conjugated polymer has drawn broad interdisciplinary attention as a low-cost, metal-free, and visible-light-responsive photocatalyst in the area of environmental remediation. The g-C3N4-based materials have excellent electronic band structures, electron-rich properties, basic surface functionalities, high physicochemical stabilities and are “earth-abundant.” This review summarizes the latest progress related to the design and construction of g-C3N4-based materials and their applications including catalysis, sensing, imaging, and white-light-emitting diodes. An outlook on possible further developments in g-C3N4-based research for emerging properties and applications is also included.

Structural and thermoelectric properties of Bi2Sr2Co2Oy thin films on LaAlO3 (100) and fused silica substrates

We have grown Bi2Sr2Co2Oy thin films on LaAlO3 (100) and fused silica substrates by pulsed laser deposition. The films on LaAlO3 are c-axis oriented and partially in-plane aligned with multiple domains, while the films on fused silica are preferred c-axis oriented without in-plane alignment. The Seebeck coefficient and resistivity of films on both substrates are comparable to those of single crystals. An oxide p-n heterojunction was formed by depositing Bi2Sr2Co2Oy film on Nb-doped SrTiO3 single crystal, which showed a rectifying behavior. These thin films and heterostructures may be used for future thermoelectric applications.

Phase compatibility and thermoelectric properties of compounds in the Sr–Ca–Co–O system

Two low-dimensional cobaltite series in the Sr–Ca–Co–O system have been investigated for their solid solution limit, structure, and compatibility phase relationships (850 °C in air). Thermoelectric properties have been measured for selected members of these solid solutions. In (Ca,Sr)3Co4O9, which has a misfit layered structure, Sr was found to substitute in the Ca site to a limit of (Ca0.8Sr0.2)3Co4O9. Compounds in the homologous series, An+2ConCo′O3n+3 [where A=Sr, Ca, (Ca,Sr), or (Sr,Ca)], consist of one-dimensional parallel Co2O66− chains that are built from successive alternating face-sharing CoO6 trigonal prisms and “n” units of CoO6 octahedra along the hexagonal c-axis. In the Can+2ConCo′O3n+3 series, only the n=1 phase (Ca3Co2O6) could be prepared under the present synthesis conditions. Sr substitutes in the Ca site of Ca3Co2O6 to a limit of (Ca0.9Sr0.1)3Co2O6. In the Srn+2ConCo′O3n+3 series, Ca substitutes in the Sr site of the n=2, 3, and 4 members to a limit of (Sr0.7Ca0.3)4Co3O9, (Sr0.67Ca0.33...