bluuebunny/crossref_metadata_2025_split huggingface dataset:
The (Ga2O3)1−x(Gd2O3)x, Oxides with x = 0–1.0 for GaAs Passivation
Authors: Kwo J. , Hong M. , Kortan A. R. , Murphy D. W. , Mannaerts J. P. , Sergent A. M. , Wang Y. C. , Hsieh K. C. 
Published: April 2011

ABSTRACTGa2O3(Gd2O3) film was previously discovered to effectively passivate GaAs surface, and the employment of this oxide as gate dielectric has led to the first demonstration of the enhancement-mode GaAs metal oxide semiconductor field effect transistors (MOSFETs) with inversion. In order to gain insight into the passivation mechanism and elucidate the role of Gd2O3, we have carried out a systematic study of the dependence of the structural and dielectric properties of (Ga2O3)1−x(Gd2O3) on the Gd (x) content. Our studies indicate that it is necessary to have the Gd addition exceeding 14% in order to form an electrically insulating dielectric with low interfacial state density. Furthermore, we found that pure Gd2O3 film grows epitaxially on GaAs in the single domain, (110) oriented Mn2O3 structure. This new crystalline dielectric has a dielectric constant ∼10, and shows excellent dielectric properties with low leakage and high breakdown strength even for films as thin as 2.5 nm. We expect that epitaxial growth of the Mn2O3 structure can be extended to other rare earth oxides, and to other semiconductor substrates like Si.
Selective Oxidation to Form Dielectric Apertures for Low Threshold VCSELs and Microcavity Spontaneous Light Emitters
Authors: Deppe D. G. , Huffaker D. L. , Graham L. A. , Zou Z. , Csutak S. 
Published: April 2011

ABSTRACTSelective oxidation of AlAs (or AlGaAs) can be used to form buried, low refractive index apertures within high Q Fabry-Perot microcavities. These apertures provide electrical and optical confinement, and for vertical-cavity surface-emitting lasers (VCSELs) have resulted in ultra-low threshold room temperature lasing with threshold currents under 25 μA. When used with quantum dot light emitters, the oxide-apertured microcavity can also be used to control the spontaneous lifetime. We describe the microcavity fabrication based on high Q Fabry-Perot microcavities and selective oxidation, and design and cavity Q constraints for apertured microcavities for quantum well and quantum dot VCSELs and microcavity LEDs. Threshold current densities of quantum well VCSELs are as low as 98 A/cm2, while ground state lasing is also obtained for quantum dot VCSELs. Our initial experiments on microcavities with very small apertures and quantum dot emitters demonstrate up to a factor of 2.3 increase in the spontaneous emission rate.
Chemical Interactions in Ionomers and Ionomer Membranes Containing Metal particles and Ions
Authors: Risen William M. 
Published: April 2011

ABSTRACTIonomer membranes are employed in PEM fuel cells as the proton conducting element, but they also hold potential for catalytic applications in both hydrogen based and other low temperature fuel cells. In these applications the reactions of H2, CO, 02, H20 and other small molecules with metal-based catalysts are important to consider. Reactions of these species with perfluorocarbonsulfonic acid based ionomers (PFSA), of which Nafionsa are prototypical, containing Rh, Ru, Pt and other metal ions and particles are shown. Metal carbonyls form with metal ions that have been reduced in situ to reduced valence ions or to metal particles, by the combination of CO and H2O or with H2 directly. Metal nitrogen complexes also can be formed. In addition, the interactions of dissimilar metal ions leads to distinct species with NO or CO, for example, that are different from the products with either ion separately.
Low-Cost Pemfc Development at Siemens - Material Aspects
Authors: Waidhas M. , Datz A. , Gebhardt U. , vhelmolt R. , Hornung R. , Luft G. 
Published: April 2011

ABSTRACTA state of the art review is given on conceivable concepts of cost reduction for PEM fuel cell systems with specific respect to mobile applications. Achieved results at Siemens are described and will be taken as a basis to assess how close this technology is to the market.
Characterization and Fuel Cell Testing of Radiation-Grafted Psi Membranes
Authors: Brack H.-P. , Koebel M. M. , Tsukada A. , Huslage J. , Buechi F. , Geiger F. , Rota M , Scherer G. G. 
Published: April 2011

ABSTRACTWe have demonstrated earlier the useful performance of our PSI radiation-grafted membranes in terms of the current-voltage characteristics of 30 cm2 active area fuel cells containing these membranes and their long-term testing over 6,000 h at 60 °C. We report here on testing of PSI radiation-grafted membranes in these fuel cells at 80 °C and in short stacks comprised of two or four 100 cm2 active area cells. The in-situ degradation of membranes has been investigated by characterizing membranes both before testing in fuel cells and post-mortem after testing in fuel cells. Characterization was accomplished by means of ion-exchange capacity and infrared and Raman spectroscopic measurements. In addition, a rapid screening method for our ex-situ testing of the oxidative stability of proton-conducting membranes was developed in this work. Comparison of the initial screening test results concerning the oxidative stability of some perfluorinated, partially-fluorinated, and non-fluorinated membranes compare well qualitatively with the relative stability of these same membranes during their long-term testing in fuel cells.
Electrolytic V2O5: Synthesis, Characterization and Lithium Insertion Behavior
Authors: Potiron E. , Salle A. Le Galla , Verbaere A. , Piffard Y , Guyomard D. 
Published: April 2011

ABSTRACTElectrolytic V2O5 materials were prepared by electrochemical oxidation of vanadyl ions in aqueous solution. The electrodeposition reaction includes two steps: an oxidation into soluble species followed by a precipitation. With the use of various electrodeposition conditions and subsequent heat treatment it is possible to obtain e-V2O5 compounds with different VIV and water contents.e-V2O5 compounds are mixed valence, hydrated vanadic acids and their formula can be written as H0.4V2O5.2−δ.nH2 with 0.04<8<0.22 and 0<n<1.8. These poorly crystallized layered compounds undergo a phase transformation into α-V2O5 starting at 240°C.The electrochemical intercalation of lithium into these compounds shows two main single phase phenomena at ≈3.2V/Li and ≈2.6V/Li. Their capacity retention is better than that of other V2O5 reference compounds, but the reversible capacity down to 2V is only ≈100Ah/kg at a rate faster than C/5, due to kinetic limitations.
Investigations of Fe-Cr Ferritic Steels as Sofc Interconnect Material
Authors: Linderoth S. , Larsen P. H. 
Published: April 2011

ABSTRACTPure Fe-Cr alloys with a Cr-content between zero and 60 wt% have been investigated with respect to their thermal expansion from room temperature to 1100°C and their corrosion resistance in air and humidified hydrogen up to 1300'C. The thermal expansion coefficient of the ferritic Fe-Cr steels is close to that of the supports used in the manufacture of thin-electrolyte cells. The corrosion resistance in air and humidified hydrogen appears to be best for a Cr content around 20 wt%. In addition, a ceria coating is found to reduce significantly the scale growth. Preliminary results for a Fe78Cr22foil indicates that an electrical contact resistance less than 3 mQcm2can be obtained between the alloy and a Ni/YSZ anode.
Electrochemical Lithium Intercalation into Nb2O5Cathode for 2 V Class-Secondary Lithium Batteries
Authors: Kumagai Naoaki , Komaba Shinichi , Kumagai Nobuko 
Published: April 2011

ABSTRACTNb2O5powder was prepared by heating niobium hydroxide in the temperature range from 600 to 1000°C. The crystal system of Nb2O5compounds depended on the heating temperatures,i.e., hexagonal, orthorhombic and monoclinic Nb2O5compounds were obtained at 600, 800 and 1000°C, respectively. Electrochemical lithium intercalation into the three Nb2O compounds was investigated in a cell with an LiClO4-propylene carbonate electrolytic solution for the application as lithium battery cathodes. As a result, they displayed good charge-discharge performance as the cathode of 2 V class-lithium battery, which will play important role in power supply for IC memory backup developed recently. The thermodynamics and kinetics of the lithium intercalation into the Nb2O5cathode have been investigated. The thermodynamic parameters, such as standard free energies, lithium partial molar entropy, interaction energies between ions, the crystal lattice parameters, and the kinetic parameters, such as chemical and self diffusion constants, have been obtained as a function ofx-value in LiNb2O5.
Preparation and Electrochemical Characterization of LiCoO2 Single Crystal Particles prepared by Super Critical Water Synthesis (SCWS)
Authors: Kanamura Kiyoshi , Umegaki Takao , Toyoshima Katsunori , Okada Ken-ichi , Hakuta Yukiya , Adschiri Masafumi , Arai Kunio 
Published: April 2011

ABSTRACTLiCoO2 single crystal particles were obtained by super critical water synthesis (SCWS) under optimized preparation conditions. The particle size of the LiCoO2 was less than 1 μm, which was much smaller than that of LiCoO2 prepared by a standard method. However, some unknown crystalline and amorphous phases coexisted with the well defined LiCoO2 single crystal particles. The discharge and charge characteristics of the LiCoO2 prepared by the SCWS were examined by some electrochemical methods. In the first cycle, an irreversible behavior was observed, and then the gradual decrease of the discharge capacity with discharge and charge cycle was also detected. The stable discharge capacity was estimated to be 80 mA h g−1 after the 100th cycle. This result may be due to the existence of amorphous phases and some structural defects.
In-Situ X-Ray Diffraction Studies On Lithium- Ion Battery Cathodes
Authors: Rodriguez Mark A. , Ingersoll David , Doughty Daniel H. 
Published: April 2011

ABSTRACTLiNi0.8Co0.2O2 and LiNiO2 have been characterized in-situ XRD. LiNi0.8Co0.2O2 does not undergo a monoclinic phase transformation but remains a hexagonal lattice throughout the entire charging cycle. It is hypothesized that Co-doping may help stabilize the hexagonal structure.
Solution-Based Synthesis of Manganese Oxide Cathodes for Lithium Batteries
Authors: Manthiram A. , Kim J. , Choi S. 
Published: April 2011

ABSTRACTWith an objective to overcome the cyclability problems of manganese oxides, solution-based procedures are pursued to synthesize metastable manganese oxides. Reduction of permanganate with lithium iodide in an acetonitrile medium followed by heating at 250 °C in vacuum gives an amorphous lithium sodium manganese oxyiodide that is intimately mixed with crystalline NaIO3. On the other hand, oxidation of manganese acetate with lithium or hydrogen peroxide in presence of lithium hydroxide followed by firing at T < 500 °C gives the metastable spinel oxides, Li4Mn5O12 and Li2Mn4O9-δ. The amorphous manganese oxide exhibits excellent cyclability with a capacity > 275 mAh/g at 4.3-1.5 V. The presence of NaIO3 and a unique microstructure are found to play a critical role in the electrochemical properties. Although Li4Mn5O12 could be achieved without much oxygen vacancies, Li2Mn4O9-δ has significant amount of oxygen vacancies with δ > 0.35. Both Li4Mn5O12 and Li2Mn4O9-δ exhibit capacities around 150 mAh/g with good cyclability in the 3 V region.
Composition-Structure Relations in Organically Modified Silica Gels
Authors: Hüsing Nicola , Schubert Ulrich 
Published: April 2011

ABSTRACTMonolithic silica aerogels modified by functional organic groups were prepared by basecatalyzed sol-gel processing of Si(OR)4 / R'Si(OMe)3 mixtures (R' = organofunctional group), followed by drying of the wet gels with supercritical CO2. When the functional organic group has only weakly or no basic properties, the microstructure of the obtained aerogels is similar to that of an unmodified silica aerogel prepared under the same conditions and quite independent of the kind of functional group. The experimental findings are explained by a two-stage process in which the R'Si≡ units condense to a pre-formed gel network obtained by hydrolysis and condensation of Si(OR)4. An increasing portion of R'Si(OMe)3 has the same effects on the hydrolysis and condensation reactions as decreasing the bulk density of an unmodified silica aerogel and the same structural consequences as increasing the water / silane ratio and the catalyst concentration acting on Si(OR)4. This leads to larger primary particles and, associated with that, smaller specific surface areas. The two-stage process is not observed when R' contains a strongly basic substituent such as NH2 or NHCH2CH2NH2. The structural parameters indicate that in these cases both R'Si(OMe)3 and Si(OR)4 are involved in the built-up of the gel network. This can be explained by extensive hydrogen bonding between the amino groups and silanol groups.
Superlattices of Semiconductor Quantum Size Particles in Layered Organic Acids
Authors: Popovitz-Biro Ronit , Guo Shouwu , Hensel Volker , Shavit Edna , Lahav Meir 
Published: April 2011

ABSTRACTThe preparation of lead sulfide and cadmium sulfide quantum size particles arranged in periodic layers within organic matrices is described. Superlattices of the particles have been generated in crystals or thin films of long chain amphiphilic acids by topotactic gas-solid reactions of the lead or cadmium salts, that pack in layer structures, with H2S gas. X-ray powder diffraction and transmission electron microscopy reveal that the crystalline order of the reactant has been partially retained in the organic-inorganic composite. This approach is demonstrated by examples of organic acids bearing an aromatic ring along the hydrocarbon chain, such as derivatives of phenyl propionic and benzoic acids.
Selective Depositions of Fe-Containing Oxide Films on Mixed Selfassembled Organic Monolayers using Microcontact Printing
Authors: Shin Hyunjung , Im Hyejin , Hong Seungbum , Lee Kyongmi , Lim Geunbae , Jeon Jong Up , Kim Eung Soo , Pak Y. Eugene 
Published: April 2011

ABSTRACTIn situ patterning of crystalline iron oxide thin layers has been achieved via microcontact printing (μCP) and selective deposition. μCP was used to pattern two different surface moieties of selfassembled organic monolayers (SAMs) on Au/Cr/Si substrates. An elastomeric stamp (poly(dimethylsiloxane); PDMS) having a submicron-size patterned relief structure was used to transfer either hexadecanethiol (HDT) SAMs, which are to sustain deposition of iron oxide precipitates, or hydrophilic SAMs (e.g. dithiothreitol (DTT)). Selective deposition is realized through precipitation of iron oxide phases from aqueous solutions at ambient temperature (<100°C). Aqueous solutions of 0.05 M of iron nitrate (Fe(NO3)2•9H20) containing urea under nitric acid (pH < 2) were prepared for selective depositions. X-ray photoelectron spectroscopic (XPS) results showed that iron oxide precipitates were deposited onto hydrophilic SAMs, but not onto HDT surfaces. As-deposited films onto DTT-SAM surfaces at 80°C were crystalline α-Fe2O3 (hematite). Fe3O4 and γ-Fe2O3 films were synthesized via annealing of as-deposited α-Fe2O3. Scanning electron microscopy, x-ray diffractometry, vibrating sample magnetometry, and optical microscopy were used to characterize the films' microstructures and properties.
Synthesis and Characterization of Titania and Vanadia Thin Films at Organic Self-Assembled Monolayers
Authors: Niesen T. P. , Wolff J. , Bill J. , Guire M. R. De , Aldinger F. 
Published: April 2011

ABSTRACTFunctionalized self-assembled monolayers (SAMs) on single-crystal Si wafers have been used as substrates for the deposition of titania and vanadia thin films. The formation of a titanium chelate was used to stabilize an otherwise spontaneously precipitating aqueous titanium solution. Uniform titania films have been synthesized from Ti(O2)2+ in aqueous HCl solutions at 80°C on sulfonated SAMs. Vanadium oxide hydrate films, V2O5·0.7 H2O, have been directly formed from aqueous vanadate solutions on NH2-terminated SAMs at 45°C. In the as-deposited films, water molecules were intercalated between the vanadium oxide layers. Subsequent annealing at 350°C in air led to nanocrystalline V2O5.
Synthesis of Tio2 Meso-Structured Thin Films
Authors: Zhou H. S. , Honma I. 
Published: April 2011

ABSTRACTHighly ordered self-assembly organized silica meso-structured architecture have attracted increasing attention because these materials provide a rich source for scientific research and technological applications. This approach to meso-structured materials has been extended to non-silica oxides, especially transition-metal-oxides which might promise applications involving electron transfer and photocatalysts. We report the syntheses of TiO2 transition-metal-oxides meso-structured thin films (MSTF) using a surfactant templating processing with spin coating method. X-ray diffraction patterns of the films showed that the films generally oriented in a lamellar structure. The phase transferring in TiO2 MSTF was also investigated.
Characterization of Organically Modified Silicates by 17O Solid State MAS and MQ-MAS NMR
Authors: Gualandris V. , Maquet J. , Babonneau F. , Florian P. , Massiot D. 
Published: April 2011

ABSTRACTOrganically modified silicates have been prepared, using methyltriethoxysilane and tetraethoxysilane in various molar ratios. The final network is thus composed of trifunctionnal T units and tetrafunctionnal Q units. Three types of oxo bridges can be formed through the competitive self-condensation or co-condensation reactions : (T)-O-(T), (Q)-O-(Q) and (T)-O-(Q). 17O-enriched water was used as reactant in order to selectively enrich the various oxo bridges, and to perform 17O solid state MAS-NMR. The combination of MAS experiments recorded at two different magnetic fields, and of the recently discovered MQ-MAS experiments allowed us to identify clearly the three types of oxo bridges. Quantitative analysis was extracted from the MAS-NMR spectra, and compared with calculations based on randomly distributed Si units.
Thermal Stability of Structurally Controlled Lamellae and Hexagonal Mesoporous Silicate Thin Films
Authors: Honma I. , Endo A. , Kundu D. , Zhou H. S. 
Published: April 2011

ABSTRACTThin films of mesoporous materials have been synthesized recently as lamellar, one dimensional hexagonal and cubic structures at substrate surfaces as well as at air/liquid interfaces. The present work investigates thermally induced structural changes of lamellar and one-dimensional hexagonal(1-dH) mesostructured silicate thin films, which is less known at the moment. The 1-dH films proved to be much more thermally stable than the lamellar ones; Open-pore one dimensionalhexagonalmesoporous thin films are obtained by the calcination of the films, where as the lamellarphase has collapsed after the surfactants removal.
Organic/Inorganic Molecular Hybrid Materials From Cubic Silsesquioxanes
Authors: Laine R. M. , Asuncion M. , Baliat S. , Filho N. L. Dias , Harcup J. , Sutorik A. C. , Viculis L. , Yee A. F. , Zhang C. , Zhu Q. 
Published: April 2011

ABSTRACTOctafunctionalized silsesquioxanes [(RsiO1.5)8, cubes] offer potential as rigid, hard nanoplatforms to which a variety of organofunctional groups can be appended. Crosslinking these groups leads to novel organic/inorganic nanocomposites that consist primarily of interfacial interactions. These materials can be 100% interphase. We present efforts to develop nanocomposite materials that consist of both continuous and discontinuous organic/inorganic phases. We then discuss methods of probing the properties of these materials.
X-Ray And Neutron Small Angle Scattering Investigations On Precursor Derived B-C-N Ceramics
Authors: Sauter D. , Schempp S. , Weinmann M. , Müller A. , Bill J. , Lamparter P. , Aldinger F. 
Published: April 2011

ABSTRACTAmorphous11B31,9C36,8N31,3ceramic samples were produced by thermolysis of poly(borosesquicarbodiimide) of idealized formula [B2(NCN)3]nat 1100°C in inert gas atmosphere. Small angle scattering (SAS) experiments reveal, that the as-obtained ceramics are chemically inhomogeneous. Using small angle neutron and X-ray scattering measurements, the temperature dependency of the medium range order was investigated. The SAS curves show a strong temperature dependence of the Guinier-radius (RG) of the scattering regions. Contrast variation by X-ray and neutron diffraction shows that the observed SAS signal is caused by amorphous BC2N enclosing amorphous boron-nitride segregations. The fact, that the measured invariant remains constant over the whole temperature range supports the view of complete phase separation.
Organic-Inorganic Hybrid Materials Processing And Applications
Authors: Schmidt H. K. , Mennig M. , Nonninger R. , Oliveira P. W. , Schirra H. 
Published: April 2011

ABSTRACTHybrid materials as inorganic-organic nanostructured composites require tailored surface chemistry in order to obtain a homogeneous distribution of the nanoparticles in the matrix. For this reason, nanoparticles with organic functions have been synthesized, first, to provide the desired ζ-potential at a given pH value, second, to avoid irreversible agglomeration due to the spacing effect, and third, to provide the appropriate surface chemistry. I could be shown that using this approach, it is possible to switch the ζ-potential of SiO2 nanoparticles from a negative to a positive potential at neutral and to bind DNA fragments to the particles for an effective transfection into cells. Other examples show that nanoparticles (TiO2, SiC2) coated with epoxy and methacryloxy groupings can be used as coating sol for the fabrication of thin films with green densities up to 67 % by volume only by photochemical crosslinking of the polymerizable groupings. Using this approach, interference layers have been fabricated on transparent plastics. In soft matrices, these particles permit to establish appropriate ζ-potentials and in electric fields by electrophoresis, it was possible to up-concentrate them to form gradient index optics. The investigations show that surface chemistry-tailored nanoparticles are a useful tool for the fabrication of nanocomposite hybrids.
Fabrication Of Grin-Lenses By Contactless Electrophoretic-Gradient Formation In Transparent Nanocomposites
Authors: Oliveira P. W. , Mennig M. , Schmidt H. 
Published: April 2011

ABSTRACTA new approach to effective radial gradient refractive index (GRIN) lenses has been developed. It is based on the electrophoresis of ZrO2 nanoparticles with surface charges (ζ-potential) in a solvent free organic-inorganic hybrid matrix, synthesized from dodecandioldimethacrylate (DDDMA), methacryl silane (MPTS) and a complex of zirconium n-propylate (ZR) with methacrylic acid (MA). A DC-electric field of 2000 V/cm is applied by a set of ring electrodes on top and bottom of a cylindrical mould containing the matrix sol. The refractive index profile is measured in situ as a function of time by interferometry. The refractive index profile can be conserved by photopolymerisation of the matrix. The resulting refractive index profiles are calculated by computer simulation based on electrophoretical diffusion theory and they are measured by real time Mach-Zehnder Interferometry. The parabolic refractive index gradient of the lenses obtained by variation of concentration of ZrO2 is in very good agreement with the result of computer simulation. By this method, it is possible to obtain 1 cm radial GRIN lenses with a Δn=0.07 within 5 h.