bluuebunny/crossref_metadata_2025_split huggingface dataset:
Impurity Free Vacancy Disordering Using Phosphorus Doped SiO2 and Pure SiO2 Caps
Authors: Cusumano P. , Saher Helmy A. , Ooi B. S. , De La Rue R. M. , Bryce A. C. , Marsh J. H. 
Published: April 2011

ABSTRACTA spatially selective quantum well intermixing process, using phosphorus-doped silica (SiO2:P) containing 5 wt% P to inhibit intermixing and pure SiO2 to enhance intermixing, is presented. The SiO2:P cap has been found to suppress bandgap shifts in both p-i-n and n-i-p GaAs/AlGaAs quantum well laser structures, with bandgap shift differences as large as 100 meV observed from samples capped with SiO2 and with SiO2:P after rapid thermal processing at temperatures as high as 950 °C for 60 s. Extended cavity ridge lasers exhibited low threshold currents with TE losses of 3.2 cm−1 measured in the passive waveguide sections at the lasing wavelength using the Fabry-Perot resonance method. This value is among the lowest reported so far using an impurity-free disordering technique.
Xps Study of the PbSe/CaF2(111) Interface Grown on Si by MBE
Authors: Fang X. M. , Liu W. K. , McCann P. J. , Strecker B. N. , Santos M. B. 
Published: April 2011

ABSTRACTThe initial stages of MBE growth of PbSe on CaF2/Si(111) were studied by in situ XPS. The surface reaction between CaF2 and elemental Se is also studied as a comparison. Ca 2p, F 1s, Pb 4f and Se 3d peaks all shift to lower binding energies (1.2 – 1.6 eV) with increasing PbSe coverage. This indicates a strong interaction between the PbSe overlayer and the underlying CaF2 and the formation of Pb-F and Ca-Se interfacial bonds. No chemically graded reaction products are detected at the PbSe/CaF2 interface. A transition layer of about 6 ML is observed which can be partially accounted for by the open 3D structure of CaF2 where three layers of atoms are available for bonding with the deposited material. This structure allows interpenetration of the PbSe and CaF2 layers which necessarily leads to a thin transition layer. Based on our XPS results, we propose a model for the bonding arrangements at the PbSe/CaF2(111) interface.
Mechanisms of Shear-Induced Solid-State Reactions
Authors: Gilman J. J. 
Published: April 2011

AbstractBoth experiments and band-structure calculations indicate that shear strains lead to closure of energy band gaps in periodic solids, and closure of the LUMO-HOMO gaps in molecules (this is also expected for non-metallic glasses). It allows athermal and ultrafast mechano-chemical reactions to occur. Simple models account for the phenomena. For periodic solids, shear shortens one axis and extends another. In contrast, hydrostatic compression causes both axes to contract. Thus the former shifts the band gaps oppositely for the two directions, causing a reduction in the minimum gap. For molecules, shear tends to increase the bonding orbitals while decreasing the antibonding orbitals, thereby reducing the LUMO-HOMO gaps. The models are consistent with band structure models for diamond.Shear-induced gap reductions account for the athermal chemical reactions observed by Bridgman, Enikolopyan, Boldyrev, and others. They account for the ultra-fast reactions that occur in explosives.
Crystal Chemistry and Electronic Properties of the N = 2 Ruddlesden-Popper Manganates: Unconventional CMR Materials
Authors: Battle P. D. , Blundell S. J. , Cox D. E. , Green M. A. , Millburn J. E. , Radaelli P. G. , Rosseinsky M. J. , Singleton J. , Spring L. E. , Vente J. F. 
Published: April 2011

AbstractThe crystallography and electronic properties of the Ln2-xSr1+xMn2O7 manganese oxides adopting the n = 2 Ruddlesden-Popper (RP) structure are discussed, focusing on the structural phase diagrams and electronic properties in the vicinity of the Mn +3.5 oxidation state and in particular the ease of synthesis of single phases of these materials.
The Synthesis of Transition Metal Sulfides and Sulfo-Salt Crystals in Hydrothermal Brines
Authors: Kolis J. W. , Korzenski M. B. 
Published: April 2011

AbstractA new procedure for the synthesis of transition metal sulfosalts in hydrothermal brines is presented. Large, well formed crystals of metal antimony sulfides can be prepared under appropriate conditions in supercritical brines. A new compound prepared by this method, MnSb2S4, is structurally characterized.
Synthesis, Structures and Magnetic Properties of a Family of One-Dimensional Oxides
Authors: Zur Loye H.-C. , Núñez P. , Rzeznik M. A. 
Published: April 2011

AbstractThe one-dimensional compounds Sr3MgPtO6, Sr3MgIrO6, Sr3MgRhO6, Sr3GdRhO6, have been synthesized and structurally characterized by Rietveld refinement of powder X-ray diffraction data. All four compounds are isostructural with the rhombohedral K4CdCl6-type structure. The structure consists of infinite one-dimensional chains of alternating face-shared MO6 octahedra (M = Pt, Ir, Rh) and M′O6 (M′ = Gd, Mg) trigonal prisms. The strontium cations are located in a distorted square antiprismatic environment. Magnetic susceptibility data show that both Sr3MgIrO6 and Sr3MgRhO6 obey the Curie-Weiss law with θ = −6(1) K, and θ= −15(3)K, respectively. Sr3GdRhO6 obeys the Curie law with μeff = 7.80 B.M, consistent with an oxidation state of +3 for both rhodium and gadolinium.
Crystallization of Perovskites from Solutions
Authors: Maurin I. , Barboux P. , Boilot J. P. 
Published: April 2011

AbstractLaMnO3 and PbZrO3 perovskites have been synthesized through coprecipitation and sol-gel techniques. After the drying and calcination steps, amorphous mixtures of oxides have been obtained. They are unstable towards phase separation. Therefore, their homogeneity and reactivity strongly depend on the parameters of the calcination, such as the temperature and heating rate. In all cases, the perovskite structure crystallizes around 600°C through nucleation- or diffusion-limited kinetics. The reaction rate depends on the history of the material. A mechanistic interpretation of the reaction, based on the similarity between the structures of PbO, ZrO2, Mn2O3 and La2O3 is proposed.
Domainlike Organizations in Ferroelectrics Containing Quenched Randomness
Authors: Viehland Dwight , Kim M. Y. , Xu Z. , Li Jie-Fang 
Published: April 2011

AbstractTransmission electron microscopy studies of the (1-x)Pb(Mg1/3Nb2/3)O3-(x)PbTiO3 (PMN-PT (1-x)/x) crystalline solution have been performed for x=0.1, 0.2, 0.35, and 0.60. Bright-field imaging has revealed a common sequence of domain-like states with increasing x. Normal micron-sized ferroelectric domains were found for x>0.40. Tweed-like structures were found for x∼0.35. These tweedlike structures are similar to those previously reported in pre-martensitic states. Paraelectric clusters were found for x<0.30. The paraelectric cluster state was characterized by the lack of self-assembly amongst embryos and the presence of relaxor behavior in the macroscopic response characteristics. The composition PMN-PT 65/35 was then modified with La for a detailed study of the transition between the tweed-like precursor and paraelectric cluster states with increasing impurity content.
Synthesis of Terbia Doped Yttria Stabilized Zirconia Thin Films by Using the Electrostatic Spray Deposition (ESD) Technique
Authors: Stelzer N.H.J. , Goossens A. , Schoonman J. 
Published: April 2011

AbstractTerbia doped yttria stabilized zirconia (Tb-YSZ) thin films have been deposited on various substrates by applying the electrostatic spray deposition (ESD) technique. Yttrium- and zirconium-acetylacetonate as well as terbium-acetate hydrate were used as precursors. Butyl carbitol-ethanol mixed alcohol's with ratios of 50:50 vol% and 80:20 vol% were used as solvents for precursor solutions with total metal concentrations between 0.09 M and 0.009 M. Tb-YSZ thin films were deposited at temperatures between 520 K and 730 K. Surface morphology, chemistry, and crystal structure were studied using scanning electron microscopy (SEM), energy dispersive X-ray (EDX), and X-ray diffraction (XRD). The Tb-YSZ layers consist of a fully stabilized cubic phases. The surface morphology of deposited Tb-YSZ layers can be controlled by changing different deposition parameters. The adhesion of Tb-YSZ to the substrate can be improved by a high temperature treatment.
Defects and Ion Transport Properties of Yttrium Doped Zirconia
Authors: Chaba P. J. , Ngoepe P. E. 
Published: April 2011

AbstractA comparison of calculated and experimental temperature variation of elastic constants were used to predict types of oxygen—vacancy dopant clusters in yttria stabilised cubic zirconia, which serves as an electrolyte in solid oxide fuelcells. Such clusters were incorporated in supercells set up for molecular dynamics studies, where oxygen transport properties were investigated at concentrations of 9.4 and 24 mol % of yttrium oxide and up to 1600K.
Mechanochemical Preparation of Ceramic Metal Oxide Electrolytes with Enhanced Conductivity
Authors: Vitlov-Audino R. , Lincoln F. J. 
Published: April 2011

AbstractIn this study, mechanochemical milling (also known as mechanical alloying), has been used as an alternative means of synthesis of ceramic metal oxide electrolytes at room temperature and compared to the conventional calcination methods. The oxide electrolytes prepared by mechanical milling, were, the lanthanide-doped fcc Bismuth Oxides and Cerium Oxides, both of which are oxygen deficient. Conductivities for some of these milled oxides, measured by the four probe technique, were found to be enhanced when compared to those for conventionally prepared materials.
Chemical Diffusion in Mixed Conductors with Comparable Ionic and Electronic Transport Numbers: Results for Ag1.92Te
Authors: Preis W. , Sitte W. 
Published: April 2011

AbstractGalvanostatic polarization of a mixed conductor located between an ionically blocking electrode and an electronically blocking electrode in an asymmetric electrochemical cell is treated in detail. Evaluation formulae for the determination of the chemical diffusion coefficient of mixed conductors with comparable ionic and electronic transport numbers are introduced. They allow the determination of the chemical diffusion coefficient of Ag1.92Te as a function of composition at 160°C from galvanostatic polarization and depolarization experiments on the asymmetric cell Ag | AgI | Ag1.92Te | Pt. The chemical diffusion coefficient shows composition dependent values between 0.002 and 0.004 cm2s-1. The electronic transport numbers are obtained independently from four-point van der Pauw measurements with typical values around 0.8–0.9.
Characterization of Proton Conducting Antimonic Acids with Amorphous, Cubic and Monoclinic Structures
Authors: Sakka Y. , Sodeyama K. , Uchikoshi T. , Ozawa K. , Amano M. 
Published: April 2011

AbstractPowders and films of amorphous, cubic and monoclinic antimonic acids are prepared. Their water sorptioh isotherms and the water desorption spectra are measured. The protonie conductivities are very sensitive to water vapor pressure and are discussed with the amount of water. The amorphous and cubic antimonic acids contain larger amounts of water than the monoclinic acid, which can be attributed to the existence of micropores in the structures.
Capillary Condensation of Light Hydrocarbons in MCM-41 - Type Mesoporous Materials
Authors: Ioneva M. A. , Mallinson R. G. , Harwell J. H. 
Published: April 2011

ABSTRACTThe MCM-41 family of surfactant templated materials were used as model mesoporous sorbents for storage of light hydrocarbon vapors, by utilizing the phenomenon of capillary condensation. The experimental data show that, because of the fine tunability of MCM-41 type materials (mesopore diameter was controlled between 20 and 40 Å), the onset of capillary condensation can be controlled, and from here the point of achieving liquid-like fluid density in the pores. Such a unique characteristic makes the MCM-41 family of materials a potential media for sorptive fractionation.
Catalysts Supported by Porous Ceramic Layers on Ceramic or Metallic Substrates
Authors: Geus John W. , Van Giezen J. 
Published: April 2011

ABSTRACTAfter mentioning the need for integration of the catalyst and the catalytic reactor, it is argued that thin (thickness up to about 50 μm) porous layers applied on ceramic or metallic surfaces are presenting interesting possibilities for the development of new catalytic reactors. The first type of reactions that can benefit from the new reactors are liquid-phase reactions catalyzed by a solid. Especially the selectivity of the reactions can be significantly improved. The second type of reactions are gas-phase reactions with a large thermal effect. It is argued that the rate of transport of thermal energy can be greatly improved by using sintered metal bodies within the reactor coated with highly porous ceramic layers. Finally utilization of thin ceramic porous layers in separations combined with catalytic reactions is shortly dealt with.A very efficient procedure for application of the porous ceramic layers is presented, viz., pyro-lysis of thin layer of silicone rubber or analogous compounds. Addition of, e.g., aluminum or titanium ions can be used to control the thermostability and the pore-size distribution of the layers resulting after combustion of the organic constituents.
Highly Dispersed Partially Stabilized Zirconias: Synthesis, Bulk and Surface Properties, Performance in the Selective Reduction of Nitrogen Oxides by Propane in the Excess of Oxygen
Authors: Sadykov Vladislav A. , Ivanova A. S. , Alikina G. M. , Ivanov V. P. , Bulgakov N. N. , Kharlanov A. N. , Lunina E. V. , Lunin V. V. , Zubareva N. A. , Matyshak V. A. , Rozovskii A. Ya. 
Published: April 2011

ABSTRACTBulk and surface properties of dispersed partially stabilized zirconias (PSZ) prepared via coprecipitation of zirconium and alkaline-earth metal hydroxides have been studied by XPD, SIMS, IR spectroscopy of surface hydroxyls and adsorbed C.O. For Sr- and Ca-PSZ, the number of the Lewis acid centers, surface concentration of the guest cation and Zr-O bonding strength at the surface have been found to deviate substantially from the values predicted by a bulk truncation model, while for Ba-PSZ it seems to be valid. A local reconstruction of the near-surface layer into the perovskite-like structure was proposed for the first two systems, which explained satisfactorily their surface properties including catalytic performance in the selective reduction of nitrogen oxides by propane in the excess of oxygen. Such reconstruction is probably facilitated by segregation of the guest cations in the subsurface layer. The driving force for this process depends upon site preference of the alkaline-earth cations to cubooctahedrons and steric factors.
Synthesis and Characterization of GaPO4 Molecular Sieves Using Metal Complexes as Templates
Authors: Balkus Kenneth J. , Kim Sung J. , Sargeson Alan M. 
Published: April 2011

ABSTRACTOur work on the preparation of zeolite ship-in-a-bottle complexes, which involves the encapsulation of metal complexes during zeolite synthesis, encouraged us to explore the relatively unknown structure directing properties of metal complexes. In particular, we have shown that bis(pentamethylcyclopentadienyl) cobalt(III) hydroxide, Cp*2CoOH was a template for the novel high silica zeolite UTD-1 which is the first zeolite having greater than a 12 membered ring pore structure. We have extended this strategy to other oxide compositions and metal complexes. In this paper we describe the preparation and characterization (XRD, SEM) of the gallophosphates Cloverite and UTD-10 using the metal complex [Co(NMe3)2sar]5+ (where (NMe3)2sar = 1,8-bis(trimethylammonio)-3,6,10,13,16,19-hexaazabicyclo[6.6.6]-icosane) as the template.
Synthesis of Hydrotalcites Using Microwave Irradiation
Authors: Fetter G. , Bosch P. , Hernandez F. A. 
Published: April 2011

ABSTRACTHydrotalcites are mineral anion exchangers whose exchange capacity is determined by the amount of structural magnesium atoms (octahedrally coordinated) substituted by aluminium atoms. In this work we study the synthesis of hydrotalcites using a domestic microwave oven at room pressure. The effect of the oven power on the composition and on the resulting structure of two hydrotalcites differing on their nominal Al/Al+Mg ratio is presented.
A Comparison Between the Structural and Catalytic Properties of Supported W2C, WC and WC1−x
Authors: Choi Saemin , Thompson Levi T. 
Published: April 2011

ABSTRACTA series of γ-Al2O3 and SiO2 supported tungsten carbides was synthesized by the temperature programmed reaction of supported tungstates with CH4/H2 mixtures. The three known phases, W2C, WC and WC1−x, were evaluated as butane dehydrogenation catalysts. The microstructure and composition of the supported carbides depended on the loading and final synthesis temperature. The low and medium loaded materials were x-ray amorphous suggesting highly dispersed carbide domains on the support. The high loaded materials possessed small crystallites of W2C, WC or WC1-x. The supported carbides were as active as a commercial dehydrogenation catalyst with comparable selectivities in several cases. The butane conversion activity decreased in the following order: W2C > WC > WC1-x. The dehydrogenation selectivity decreased as the activity increased. The results suggest that there were two different types of sites, those catalyzing the selective dehydrogenation of butane and those capable of butane hydrogenolysis. The activity of these latter sites declined significantly with time on stream. We believe the hydrogenolysis activity was due to acid sites on the supported carbides.
Preparation and Characterization of High-Surface-Area Aluminum Nitride Thin Films
Authors: Monie S. A. , Pantano C. G. 
Published: April 2011

ABSTRACTFree-standing aluminum nitride (AlN) films were prepared by ammonia heat-treatment of pseudoboehmite [AIO(OH)] gels derived from an alumina sol. Supported films on sapphire substrates were also made by spin-coating the alumina sol, followed by ammonia nitridation. The conversion of the specimens to AIN as a function of heat-treatment temperature was studied using various characterization techniques.For the free-standing films, X-ray diffraction (XRD) showed that upon ammonia treatment, the specimens were first transformed from pseudoboehmite to η-alumina and finally to A1N above 1000°C. 27Al magic-angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopy confirmed the appearance of Al[N]4 coordination at 1000°C, indicative of AlN. Complete conversion to AlN was achieved after 5 hour nitridation at 1200°C. The 1200°C heat-treated films consisted of crystallites of AlN in the size range 0.01 − 0.15 μm, with pores between 0.03 − 0.25 μm in diameter, as observed by TEM/electron diffraction analyses. These films had BET surface areas of approximately 25 m2/g. Nitridation of the supported films to AlN occurred at lower temperatures (∼900°C), as shown by secondary ion mass spectrometry (SIMS) and X-ray photoelectron spectroscopy (XPS).
Active Sites of Iron Catalysts for Oxidation Reactions - H2O Oxidation and H2O2 Decomposition
Authors: Kuznetsov V. L. , Elizarova G. L. , Usoltseva A. N. , Matvienko L. G. , Shchegolikhina O. I. 
Published: April 2011

ABSTRACTSystems containing metal ions stabilized in Si-O matrix are perspective for the development of new selective oxidation catalysts. The comparative study of the following catalysts were performed to elucidate the influence of structural factors on the catalytic properties of iron systems in the reactions H2O oxidation, H2O2 decomposition, N2O decomposition and 16O2 ⇔ O18O2 exchange. The following catalysts were used: A) carbon-supported polyhedral silsesquioxanes (PhSiO1.5)12(MO)nL ((MO)n = (FeO)6, Fe2Ni4O6, (NiO)6; L=ROH, H2O); B) Fe-containing zeolites ZSM-5 (0.1−3.5 wt.% Fe); C) hydroxocomplexes Fe4(OH)10SO4 and NaFe3(OH)6(SO4)2). Fe silsesquoxanes in contrast to Fe-ZSM5 do not activate N2O decomposition and isotopie oxygen exchange. However, they are active in H2O oxidation and H2O2 decomposition. It was found that both reactions proceed via nonradical mechanism in the presence of Fe heterogeneous catalysts. For H2O oxidation active site contains at least two Fe atoms situated at appropriate distance from each other. H2O2 decomposition can proceed with participation either one and two metal active sites.
Effects of Potassium Chemisorption on the Electronic Structure of VxOy/TiO2 Surfaces
Authors: Parmigiani Fulvio , Depero Laura E. , Sangaletti Luigi 
Published: April 2011

ABSTRACTX-ray photoelectron spectroscopy of pure and K chemisorbed VxOy/TiO2 powders are reported. Core-line and valence band spectra suggest the presence of vanadium open shell ions on the pure VxOy/TiO2 interface, whereas potassium vanadate seems to form after K chemisorption. That results in the presence of a significant amount of gap states, with vanadium character, just above the O2p band edge, for the pure VxOy/TiO2 powder, while K chemisorption, reducing significantly the open shell vanadium ions, quenches the gap emission in the XPS valence band spectra.
Possible Causes of the Change of Dynamics in Glass-Forming Materials Subjected to Reduced Dimension
Authors: Ngai K. L. , Rizos A. K. 
Published: April 2011

ABSTRACTThere is currently many ongoing investigations of the change in the glass transition temperature when a material is reduced in dimension from the normal bulk state. The reduction in dimension can be accomplished by casting the material as thin films with or without a substrate or putting it in nanometer size pores. In this work, we explore possible causes of the change in dynamics of the bulk material when the glass-former is subjected to such modifications. The existence of a growing cooperative length scale L(T) with decreasing temperature in bulk fragile glass-forming liquids reaching the size of approximately 1.5–2.0 nm at the glass transition temperature is the basis of our consideration. When the reduced dimension is comparable to L(Tg), cooperative dynamics within a lengthscale equal to L(Tg) can no longer be maintained in all three dimensions throughout the sample. The imposed reduction of the cooperative length scale speeds up the dynamics and causes a reduction of the glass transition temperature. For polymeric glass-formers particularly at higher molecular weights, reduction of one dimension in thin films engenders orientation of the polymer chains when their radius of gyration becomes comparable to the film thickness. The latter is known to cause also a reduction of the glass transition temeperature.
Dynamics in a Nonfragile Glass-Forming Liquid
Authors: Rufflé B. , Beaufils S. , Etrillard J. , Gallier J. , Toudic B. , Ecolivet C. , Coddens G. , Ambroise J. P. , Guéguen E. , Marchand R. 
Published: April 2011

ABSTRACTThe dynamics of Na0.5Li0.5PO3 (Tg = 515 K, Tm = 749 K) a non fragile glass forming liquid has been investigated over a large temperature range (300 − 1000 K.) and in a wide energy window using various experimental techniques. The susceptibility spectra obtained by coherent neutron scattering and depolarized light scattering between 1 and 104 GHz show mainly two contributions: a low frequency vibrational peak, the so-called Boson peak and a quasielastic component, referred to the βfast process in the mode coupling theory (MCT).The data are discussed in relation to the mode coupling theory for the liquid glass transition. In particular, the temperature evolution of the susceptibility height in the βfast region is compatible with a crossover temperature Tc ∼ 620 K which is also deduced from a power law temperature dependence of the structural relaxation timescale. As a secondary βslow process, observed by 31P NMR, decouples from the structural relaxation timescale also below 600 K, a real change in the dynamics seems to occur around Tc ∼ 620 K = 1.2 Tg in this non fragile glass Conning liquid.