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Naperville, IL, United States

Liu G.,U.S. National Institute of Standards and Technology | Wong-Ng W.,U.S. National Institute of Standards and Technology | Yang Z.,U.S. National Institute of Standards and Technology | Kaduk J.A.,Poly Crystallography Inc. | And 2 more authors.
Journal of Solid State Chemistry

The complex phase relationships near the BaO-poor region of the quaternary BaSmYCuO oxide system prepared in pure air (pO2=22 kPa, 950 °C) and in 0.1% O2 (pO2=100 Pa, 810 °C) have been determined. This investigation also included the subsolidus compatibilities in ten subsystems (Ba-Sm-Y-O, Ba-Sm-Cu-O, Ba-Y-Cu-O, Sm-Y-Cu-O, Ba-Sm-O, Ba-Y-O, Ba-Cu-O, Sm-Y-O, Sm-Cu-O, and Y-Cu-O), and the homogeneity range of five solid solutions (Ba(Sm xY2-x)CuO5, (Sm,Y)2O3, (Sm,Y)2CuO4, (Y,Sm)2Cu2O 5, and Ba(Sm,Y)2O4). The single phase range of the superconductor solid solution, (Ba2-xSmx)(Sm 1-yYy)Cu3O6z, and the phase compatibilities in its vicinity, which are particularly important for processing, are described in detail. The phase equilibrium data of the BaSmYCuO system will enable the improvement of the intrinsic superconducting properties of second-generation wires, and facilitate the flux-pinning process. Source

Yan Y.G.,Wuhan University of Technology | Yan Y.G.,U.S. National Institute of Standards and Technology | Wong-Ng W.,U.S. National Institute of Standards and Technology | Kaduk J.A.,Poly Crystallography Inc. | And 3 more authors.
Applied Physics Letters

We have demonstrated the effect of gradients in phase composition and microstructure of p-type CeFe4Sb12 melt-spun ribbons on Seebeck coefficient by using a thermoelectric (TE) screening tool in conjunction with x-ray diffraction. The spatial Seebeck coefficient variation was found to correlate with the changes in the phase composition and microstructure. The observed gradient was the result of a postannealing effect caused by the thermal lag between the contact surface with the roller and the free surface. Our results illustrate the application of our screening tool to the three-dimensional variation in Seebeck coefficient in a model TE material. © 2011 American Institute of Physics. Source

Brazdil J.F.,Ineos Technologies Inc. | Toft M.A.,Ineos Technologies Inc. | Lin S.S.-Y.,Ineos Technologies Inc. | McKenna S.T.,Ineos Technologies Inc. | And 4 more authors.
Applied Catalysis A: General

Acrylonitrile is a major chemical intermediate used in the production of a wide range of chemical and polymer products. Central to the commercial process is a proprietary catalyst consisting of a complex mixture of metal oxides containing a bismuth-containing molybdate phase that is active and selective for propylene ammoxidation to acrylonitrile. Among the most active and selective is a solid solution of bismuth and cerium molybdate. Solid state structural studies were undertaken to characterize this active phase. The results show that the mixed bismuth-cerium molybdate consists of a solid solution phase having the scheelite-related structure of cerium molybdate with a monoclinic unit cell. Analysis of the cation site occupancy using synchrotron X-ray diffraction indicates that bismuth preferentially occupies the Ce(3) site of the monoclinic cerium molybdate structure. It is therefore possible to singularly identify the structure of the active site for propylene ammoxidation given that bismuth is a necessary constituent of a site for selective propylene (amm)oxidation. The proposed active site consists of bismuth located next to a cation vacancy in the structure, presumably in order to accommodate its lone pair of electrons. Bismuth serves as the site for the rate determining α-hydrogen abstraction from propylene to form an allyl intermediate and subsequent nitrogen insertion and loss of lattice oxygen. The bismuth site is surrounded by two cerium cations in this active site configuration. Thus the model that emerges from this study is Bi3+ and Ce3+ in a molybdate structural framework with cerium readily able to undergo Ce3+ 虠 Ce4+ redox that facilitates lattice oxygen transfer to the active site as required by the operative Mars-van Krevelen mechanism for selective propylene ammoxidation. The presence of two cerium cations adjacent to bismuth as a key component of the active site is expected to promote the rapid re-oxidation of the catalytic site effecting enhanced catalytic performance with respect to selective product yields and productivity. © 2015 Elsevier B.V. All rights reserved. Source

Knight D.A.,Savannah River National Laboratory | Zidan R.,Savannah River National Laboratory | Lascola R.,Savannah River National Laboratory | Mohtadi R.,Toyota Motor Corporation | And 6 more authors.
Journal of Physical Chemistry C

The recent discovery of a new class of negative ions called hyperhalogens allows us to characterize this complex as belonging to a unique class of materials called hypersalts. Hyperhalogen materials are important while serving as the building blocks for the development of new materials having enhanced magnetic or oxidative properties. One prime example of a hydperhalogen is the Al(BH4)4 - anion. Aluminum borohydride (17 wt % H) in itself is a volatile, pyrophoric compound that has a tendency to release diborane at room temperature, making its handling difficult and very undesirable for use in practical applications. Here we report that the combination of Al(BH4)3 with the alkaline metal borohydride KBH 4 results in the formation of a new compound KAl(BH4) 4 which is a white solid that exhibits remarkable thermal stability up to 154 C and has the typical makeup of a hypersalt material. Using a variety of characterization tools and theoretical calculations, we study and analyze the physical characteristics of this compound and show its potential for stabilizing high hydrogen capacity, energetic materials. © 2013 American Chemical Society. Source

Liu G.,U.S. National Institute of Standards and Technology | Wong-Ng W.,U.S. National Institute of Standards and Technology | Kaduk J.A.,Poly Crystallography Inc. | Cook L.P.,U.S. National Institute of Standards and Technology
Physica C: Superconductivity and its Applications

Chemical interactions between the Ba2YCu3O6+x superconductor and the LaMnO3 buffer layers employed in coated conductors have been investigated experimentally by determining the phases formed in the Ba2YCu3O6+x-LaMnO 3 system. The Ba2YCu3O6+x-LaMnO 3 join within the BaO-(Y2O3-La2O3)- MnO2-CuOx multi-component system is non-binary. At 810 °C (pO2 = 100 Pa) and at 950 °C in purified air, four phases are consistently present along the join, namely, Ba2-x(La1+x- yYy)Cu3O6+z, Ba(Y2-xLax)CuO5, (La1-xYx)MnO3, (La,Y)Mn2O5. The crystal chemistry and crystallography of Ba(Y2-xLax)CuO5 and (La1-xYx)Mn2O5 were studied using the X-ray Rietveld refinement technique. The Y-rich and La-rich solid solution limits for Ba(Y2-xLax)CuO5 are Ba(Y1.8La0.2)CuO5 and Ba(Y0.1La1.9)CuO5, respectively. The structure of Ba(Y1.8La0.2)CuO5 is Pnma (No. 62), a = 12.2161(5) Å, b = 5.6690(2) Å, c = 7.1468(3) Å, V = 494.94(4) Å3, and Dx = 6.29 g cm-3. YMn2O5 and LaMn2O5 do not form solid solution at 810 °C (pO2 = 100 Pa) or at 950 °C (in air). The structure of YMn2O5 was confirmed to be Pbam (No. 55), a = 7.27832(14) Å, b = 8.46707(14) Å, c = 5.66495(10) Å, and V = 349.108(14) Å3. A reference X-ray pattern was prepared for YMn2O5. Source

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