bluuebunny/crossref_metadata_2025_split huggingface dataset:
MBE Growth of Oxides for III–N MOSFETs
Authors: Gila B. , Lee K N. , Laroche J , Ren F , Donovan S. M. , Abernathy C. R. , Han J. 
Published: April 2011

ABSTRACTReproducible fabrication of high performance metal oxide semiconductor field effect transistors (MOSFETs) from compound semiconductors will require both good interfacial electrical characteristics and good thermal stability. While dielectrics such as SiO2, AIN, and GdGaOx have demonstrated low to moderate interface state densities, questions remain about their thermal stability and reliability, particularly for use in high power or high temperature widebandgap devices. In this paper we will compare the utility of two potential gate dielectric materials: GdOx and GaOx. GdOx has been found to produce layers with excellent surface morphologies as evidenced by surface roughness of less than I nm. Stoichiometric films can be easily obtained over a range of deposition conditions, though deposition temperatures of 500°C appear to offer the optimum interfacial electrical quality. By contrast GaOx films are quite rough, polycrystalline and show poor thermal stability. Further they exhibit a range of stoichiometries depending upon deposition temperature, Ga flux and oxygen flux. This paper will describe the relationship between deposition conditions and film characteristics for both materials, and will present electrical characterization of capacitors fabricated from GdOx on Si.
Interface State Densities for SiNx: H on Cleaved GaAs and InP(110)
Authors: Landheer D. , Hulse J. E. , Rajesh K. 
Published: April 2011

ABSTRACTSilicon nitride was deposited in-situ by electron-cyclotron resonance plasma chemical-vapour deposition (ECR-CVD) on (110) surfaces formed by cleaving GaAs and InP(100) substrates in an ultra-high vacuum processing system. Capacitors formed by depositing Al gates on the facet surfaces were analyzed by the high-low frequency capacitance-voltage (CV) technique. The minimum interface-state densities obtained for the cleaved GaAs (110) surfaces were 1–2 × 1012 eV−1cm−2. For cleaved InP facets the measured minimum interface state densities were a factor of two higher; however, they exhibited a smaller hysteresis in the CV characteristics and a smaller modulation in the surface potential. The interface state densities did not change significantly for the GaAs(110) facets if a Si interface control layer 0.8–2 nm thick was deposited prior to silicon nitride deposition; however, a larger effect was observed for the hysteresis and flatband voltage shift of the CV characteristics. The effect of annealing on the interfaces with Si was investigated and the performance compared with published results for GaAs(100) surfaces prepared by molecular-beam epitaxy.
Effect on Performance of Composition of Li-ion carbon Anodes derived from PMAN/DVB copolymers
Authors: Guidotti Ronald A. , Even William R. 
Published: April 2011

ABSTRACTThe effects on electrochemical performance of the nitrogen content of disordered carbons derived from polymethacryonitrile (PMAN)-divinylbenzene (DVB) copolymers were examined in galvanostatic cycling tests between 2 V and 0.01 V vs. Li/Li+ in IM LiPF6/ethylene carbonate (EC)-dimethyl carbonate (DMC). The first-cycle reversible capacities and coulombic efficiencies increased with increase in the level of nitrogen for samples prepared at 7000°C. However, the degree of fade also increased. Similar tests were performed on materials that were additionally heated at 1,000° and 1,300°C for five hours. Loss of nitrogen, oxygen, and hydrogen occurred under these conditions, with none remaining at the highest temperature in all cases but one. The pyrolysis temperature dominated the electrochemical performance for these samples, with lower reversible and irreversible capacities for the first intercalation cycle as the pyrolysis temperature was increased. Fade was reduced and coulombic efficiencies also improved with increase in temperate. The large irreversible capacities and high fade of these materials makes them unsuitable for use in Li-ion cells.
The Role of Oxygen in Low-potential Li Insertion in Metal Oxide Anode Materials
Authors: Leroux F. , Nazar L. F. 
Published: April 2011

ABSTRACTTransition metal oxides are high-capacity lithium storage materials of interest as possible anode materials in the next generation of Li ion batteries. By using X-ray absorption spectroscopy we have obtained an understanding of the process of Li uptake and removal within Na0.25MoO3. Our results show the Li2O matrix on reduction is not inert; Mo-O bonds are reversibly consumed on discharge and are regenerated on charge, with the Li2O matrix acting as the oxygen reservoir. The migration of oxygen atoms from the matrix to the active centers occurs at a voltage below that expected for the Li2O free energy of formation. Polarization on charge is not due only to oxygen migration but also to metal rearrangement within the electrode material. The reversibility of the Mo-O bond formation on repeated cycles is a function of the depth of discharge, with 200 mV being the lower limit.
PEMFC Development at Asahi Glass Co., Ltd.
Authors: Yoshitake M. , Yanagisawa E. , Naganuma T. , Kunisa Y. 
Published: April 2011

ABSTRACTPerfluorinated ion exchange membranes were studied and the membrane technology for PEMFC has been developed. Thermal stability, mechanical strength, water content, AC specific resistance and gas permeability were measured. The influence of membrane thickness on gas permeability and the influence of incorporation of cations on water content and AC specific resistance of Flemion® and Nafion® 117 were estimated. Gas permeation rates of the membranes decreased in inverse proportion to the increase of the membrane thickness and gas permeability coefficients were nearly constant and independent of the thickness. Hydrogen permeation rates of Flemion®S at 70°C were converted to 2.1 mA/cm2 as cunent density. Flemion®R-electrode assembly showed to maintain stable perfonnance for over 3,500hr. Furthermore, it was found that usage of thinner membranes or one with higher ion-exchange capacity gave not only lower intemal cell voltage but also higher iR-free cell voltage. PTFE-yam embedded type membrane (Flemion®Mc and Sc) and PTFE-flbril dispersed type (Flemion®R12) was examined to afford improvement in mechanical strength at moist and high temperature atmosphere. Flemion®Sc (80!am) was examined to give high cell performance of 0.67V at 0.5A/cm2, 80°C, I ata. Flemior®Mc-electrode assembly was examined to keep stable performance during the life test of over 1,500hr.
Control of A Running H2/02 Fuel Cell With Filled Polymeric Membranes by IMPEDANCE SPECTROSCOPY
Authors: Poinsignon C. , gorrec B Le , Vitter G. , Montella C. , Diard J. P 
Published: April 2011

ABSTRACTPerformances of a H2/O2 polymeric electrolyte fuel cell running at 80°C under 3 bars of gas pressure and using a new filled thermostable ionomeric membrane [sulfonated polysulfone (SPS) filled with phosphatoantimonic acid particles] are analysed with a recent experimental method established for impedance measurements of electrochemical batteries during discharge. A classical impedance-measurement set controls under sinusoidal current perturbation a PEMFC connected in parallel to the load into which it discharges. The impedance diagrams present at high frequencies an inductive behaviour analogous to that observed for batteries, one or two capacitive arcs. The internal resistance of the PEMFC can be estimated. The results demonstrate the possibility to study with classical equipment the impedance of high-capacity and low-impedance FC during their discharge through a constant load.
Improving Gd-Doped Ceria Electrolytes for Low Temperature Solid Oxide Fuel Cells
Authors: Ralph J. M. , Kilner J. A. , Steele B. C. H. 
Published: April 2011

ABSTRACTGadolinia-doped ceria electrolyte is being investigated as an alternative electrolyte for solid oxide fuel cells operating at temperatures below 700°C. Measurements were made to determine the effects that small additions of Ca, Pr and Fe to gadolinia-doped ceria have on the bulk and grain boundary conductivities. These small additions (1–2%) of dopant did not alter the bulk conductivity significantly but resulted in a large increase in the grain boundary conductivity. The grain boundary conductivity was similar for all three electrolyte compositions. These results are explained by the possible formation of second phases at the grain boundary, which can incorporate impurity elements. The electronic conductivity in these electrolyte materials was also evaluated, but it was found that the Ca, Pr and Fe additions do not reduce the electronic conductivity compared to a standard Gd-doped ceria sample.
Relationship Between Crystal Structure and Li+-Conductivity in La0.5 Li0.5TiO3 Perovskite
Authors: Alonso J. A. , Ibarra J. , Paris M. A. , Sanz J. , Santamaria J. , LeÓn C. , Vdrez A. , Fermandez M. T. 
Published: April 2011

ABSTRACTFor the first time Li+ cations have been localized within the perovskite structure of the fast Liconductor La0 5Li0.5TiO3 from neutron powder diffraction data. Li cations are fourfold oxygen coordinated, located in the middle of the almost square windows determined by every four TiO6 octahedra, far away from the 12-fold coordinated La vacancy sites that, nevertheless, take part of the path for Li motion across the solid. The large multiplicity of the sites where Li reside (1/6 occupied) accounts for the huge ionic conductivity of this promising Li-conducting material.
Performance of Capacitors Using Organic Electrolytes
Authors: Morimoto T. , Tsushima M. , Che Y. 
Published: April 2011

ABSTRACTElectric double-layer capacitors(EDLC) based on charge storage at the interface between a high surface area activated carbon electrode and an electrolyte solution are characterized by their long cycle life and high power density in comparison with batteries. However, energy density of electric double-layer capacitors obtained at present is at most 1Wh/kg at a power density of 600W/kg and smaller compared with that of batteries, which limits the applications of the capacitor. Therefore, new capacitors which show larger energy density than that of electric-double layer capacitors are proposed. The new capacitors are hybrid capacitors consisting of activated carbon cathode, Li-doped graphite anode and an organic electrolyte. Maximum voltage applicable to the cell becomes over 4.OV which is larger than that of the electric double-layer capacitor. As a result, discharged energy density of the cell becomes 4Wh/kg at a power density of 600W/kg.
Novel Electrode Materials for Ultracapacitors:Structural and Electrochemical Properties of Sol-Gel-Derived Manganese Dioxide Thin Films
Authors: Pang Suh-Cern , Anderson MarcA 
Published: April 2011

ABSTRACTNanoparticulate MnO2thin films fabricated by the sol-gel process have been shown to be an outstanding novel electrode material for Ultracapacitors. The average specific capacitance of sol-gel-derived MnO2thin-films on nickel substrates as determined by cyclic voltammetry ranged from 566 to 698 F/g. These films also exhibited good cycling stability within the potential range of 0.0-0.9V (vs SCE) in unbuffered aqueous electrolyte. Both CV and XPS studies showed that MnO2films have remained chemically and structurally intact after 1,500 cycles. The XRD spectra and SEM micrographs showed that the microstructure of MnO2thin films are highly porous, and poorly crystalline or amorphous in nature. The high specific capacitance of MnO2may be predominantly due to pseudocapacitance associated with homogenous and reversible redox reactions of proton insertion into and out of the MnO2lattice. Any variation in the microstructure and thickness of films might affect proton mobility within the oxide matrix and thereby affecting their cycling behaviors. Further optimization of the cycling behaviors is envisaged with better microstructural and thickness control of these sol-gelderived nanoparticulate MnO2thin films.
Pulsed laser deposition and characterization of LiMn2O4thin Films for applications in Li Ion rechargeable battery systems
Authors: Singh D. , Houriet R. , Vacassy R. , Hofinann H. , Craciun V. , Singh R.K 
Published: April 2011

ABSTRACTMost studies focused on fundamental aspects of cathode materials in lithium ion battery employ porous electrodes, which are made of polymer bonded transition metal oxide powders mixed with conductors such as carbon. However, the powder morphology and the presence of carbon and polymeric binders affect the physical, chemical and electrochemical behaviors significantly. Therefore, transition metal oxide based materials in thin film form, which are dense and contain no additives, are emerging as promising alternatives to study fundamental properties in lithium ion batteries. Pulsed laser ablation (PLD) was used to deposit highly textured thin and thick porous films of LiMn2O4. Effect of various parameters such as substrates and deposition conditions were studied on the microstructure of these films. Microstructure studies of these films were carried out using x-ray diffraction and scanning electron microscopy. The electrochemical measurements were carried out in a glove box using cyclic voltammetery, electrochemical cycling and AC Impedance spectroscopy in a half-cell configuration with lithium metal as an anode and reference electrode and LiMn2O4film as a cathode. Results indicate differences in film morphology greatly effect electrochemical kinetics of Li intercalation and de-intercalation. Thin films show good electrochemical characteristics such as high rate capability, good coulombic efficiency and rechargeability till 400 cycles.
Self-Assembly of Meso- and Nanoparticles into 3d Ordered Arrays and its Applications
Authors: Gates Byron , Xia Younan 
Published: April 2011

ABSTRACTThis presentation describes a simple and practical method for self-assembling meso- and nanoparticles into three-dimensionally ordered lattices (opals) over large areas, and the use of these lattices as templates in fabricating highly ordered porous structures such as inverse opals. This method has been applied to a variety of colloidal particles, including silica colloids and polymer beads with diameters in the range of˜50 nm to ˜50 μm. Templating against the 3D opaline lattices provides an effective route to inorganic-organic composite materials and inverse opals having 3D periodic structures.
Formation And Hydrolytic Stabilty Of Oxygen Bridged Heterometal Bonds (Si-O-Ti, Si-O-Zr, Si-O-Ta) In Sol - Gel Materials
Authors: Nacken M. , Hoebbel D. , Schmidt H. 
Published: April 2011

ABSTRACTGlycidoxypropyltrimethoxysilane (GPTS) and metal alkoxides are frequently used in preparation of heterometal hybrid polymers and find application e. g. as contact lens materials and hard coatings on polymers. Such materials require a high homogeneity of the structural unit at the molecular level, which is supported by the formation of oxygen bridged heterometal bonds and their hydrolytic stability. By means of 29Si and 17O NMR the formation of heterometal bonds like Si-O-Ti, Si-O-Zr, Si-O-Ta was evidenced in GPTS-hydrolysates with Ti(OEt)4, Ti(OEt)3AcAc, Zr(OBun)4, Zr(OBun)3AcAc, Ta(OEt)5 or Ta(OEt)4AcAc (AcAc = acetylacetone ligand) as additives. Signals of heterometal bonds can be detected in 17O NMR spectra in the range of 170 to 350 ppm and are characterized in 29Si NMIR spectra by defined chemical shifts to low (Si-O-Ta) and high magnetic fields (Si-O-Ti, Si-O-Zr) in comparison with signals of Si-O-Si bonds. The use of AcAc modified metal alkoxides leads to well resolved 29Si NMR spectra, which make the distinction between homo- and heterocondensed species easier. The addition of water to the sols (2 H2O / alkoxy group) leads to a degradation of heterometal bonds in favour of more homocondensed species, which reduces the homogeneity of such hybrid materials at the molecular level.
In Situ Intercalation/Polymerization of Melanin into Vanadium Pentoxide
Authors: Oliveira H. P. , Zanta C. L. P. S. , Galina A. C. , Graeff C. F. O. 
Published: April 2011

ABSTRACTIn this work, intercalated material was prepared consisting of a regular interchange of organic/inorganic layers. The products were obtained by reacting 3,4-dihidroxi-fenilalanina (DL-DOPA) in a solution with V2O5.nH2O gel, which suffered an oxidative polymerization/intercalation process, forming a film with a dark blue metallic color. The films were characterized using UV\Vis transmission spectroscopy, FTLR, ESR, X-ray diffraction, dc conductivity, and cyclic voltammetry. The X-ray diffractograms indicate that the lamellar structure of the V2O5 is preserved but the inter-planar space increase from 1.18 nm to 1.38 nm. The FTIR and ESR spectra confirms that the V2O5 structure is preserved, however the presence of melanin induces the reduction of Vv ions to Viv. The increase in the inter-planar spacing is observed to increase the stability and reproducibility of the electrochemical insertion/de-insertion of Li+. This increase in stability is also observed in the electrochromic properties of the film, which are fully reproducible even after more than 60 oxidation-reduction cycles. The melanin affects also the activation energy of the dc conductivity which changes from 0.35 eV to 0.20 eV.
Surface Modification Of Polymers With Grafting And Coating Of Silane Hybrids And Their Bioactivity
Authors: Kubo Masaaki , Takashima Seisuke , Tsuru Kanji , Hayakawa Satoshi , Osaka Akiyoshi , Ohtsuki Chikara 
Published: April 2011

ABSTRACTHydrated silica rich Si-OH and Si-0- groups serve in a body environment as sites for nucleation of apatite, and are known as an essential chemical species for bioactive materials. Organic polymers having surface modified with the hydrated silica will show bioactivity: bone tissues grow toward the apatite layer and bond to materials. Thus MOPS-M (3-methacryloxypropyltrimethoxysilane) was grafted under emulsion polymerization procedure to high density polyethylene (HDPE), poly (vinyl chloride) (PVC) and polyamide (PA) substrates to examine in vitro deposition of apatite (bioactivity) after soaking in a simulated body fluid (Kokubo solution). Bioactivity was confirmed for the grafted PVC and PA substrates and discussed in terms of contact angle and relative amount of grafted silane molecules.
Electronic Properties Of The Model Organometallic Polymer [M-C=C(N)]n (M = Cu(I), Ag(I), Au(I))
Authors: Su Z. M. , Wang R. S. , Che C. M. 
Published: April 2011

ABSTRACTThe organometallic complexes of transition metal M = Cu(I), Ag(I), Au(I) with d10 electronic configuration have interesting optical, electronic and magnetic properties. It is possible to prepare the high functional organometallic polymer materials by coordinating π-conjugated organic molecules with d10 metals. According to the experimental structures, the model polymers [M-C-C(N)]n are built up and quantum chemistry methods are used to calculate their properties. It is indicated from theoretical analysis that the organometallic polymers would have comparable conductivity when interactions exist between metals and π electrons of different chains.
Sol-Gel Nir-Reflective Multilayer Coatings On Glass Through Uvpolymerizable Ceramic Nanoparticles
Authors: Mennig M. , Oliveira P. W. , Schmidt H. 
Published: April 2011

ABSTRACTA new preparation route for an dielectric NIR-reflexion filter on glass is described. Coating sols are synthesized from SiO2 and TiO2 nanoparticles with photopolymerizable surface ligands. A 5-layer stack consisting of 2 SiO2 and 3 TiO2 layers was deposited on float glass by angledependent dip-coating (ADDC) with a fixed angle of 4° to the vertical and subsequent UV-curing. Finally, the whole stack was densified at 450 °C without cracking or discolouring. UV-vis-NIR transmittance and reflectance spectra show a steep increase of reflectance at 750 nm. In the range between 800 nm and 1200 nm, the reflectance is > 80 %. The visible transmittance is about 72 % due to single reflexion peaks. The bandwidth of the NIR reflection filter prepared by ADDC is about 200 nm larger and its maximum reflectance is only 5 % smaller compared to vertical dip-coating. The interference layer stack shows excellent stability in Taber Abraser, rubber, saline and UV tests, indicating a high potential for practical application.
Inorganic Quantum Dot - Organic Dendrimer Nanocomposite Materials
Authors: Sooklal K. , Huang J. , Murphy C. J. , Hanus L. , Ploehn H. J. 
Published: April 2011

ABSTRACTSemiconductor quantum dots are of great current interest for their optical properties. We have developed a method for preparing CdS quantum dots in commercially available PAMAM Starburst dendrimers. The resulting CdS-dendrimer nanocomposites are exceptionally stable and emit brightly in the blue. The size of the dendrimer (its “generation”) has a surprisingly small effect on the optical properties of the resulting nanocomposites. The dot-dendrimer nanocomposites can be captured in a silica sol-gel matrix to yield a stable, bright blue-emitting glass.
Electronic Structure and Magnetic Properties of Nd5Fe17
Authors: Sabiryanov R. F. , Jaswal S. S. 
Published: April 2011

ABSTRACTThe Nd5Fel compound has attracted some attention lately as a possible permanent-magnet material. This compound has a very complicated crystal structure (264 atoms per unit cell with 14 and 7 different Fe and Nd sites respectively!) Using linear-muffin-tin-orbital method, self-consistent spin-polarized studies of NdFe1 - have been carried out to determine the electronic structure, magnetic moments, and the Curie temperature. The results show strong effect of the local environment on the magnetic properties of individual Fe sites. The calculated moments are compared with the magnetization data. The Curie temperature estimated for the iron sublattice using the mean-field approximation is in a reasonable agreement with the experimental result.
Hard Magnetic Nanoparticles and Nanocomposites
Authors: Giri Anit , Chowdary Krishna , Majetich Sara A. 
Published: April 2011

ABSTRACTMany high performance permanent magnets are nanostructured materials. The magnetic properties of nanoparticles are discussed in terms of characteristic length scales, including the maximum monodomain size and the exchange length. Experimental results for ball milled SmCo5 nanoparticles are presented, showing deviations from idealized behavior. Because of the short exchange length, this can be understood in terms of independent nucleation of reverse domains in grains within larger particles. With a much longer exchange length, FeCo alloy nanoparticles show reduced coercivity in a high density compact, in accordance with the random anisotropy model. The SmCo5 and FeCo nanoparticles were mixed and compacted in an attempt to make an exchange spring nanocomposite. However, significant exchange between the hard and soft phases was not observed because the sample density was too low. Processing considerations for improved co-compaction of these nanoparticles are discussed.
The Kinetics of Formation Of Nanocrystalline γ-Ni-Fe During Mechano-Chemical Synthesis
Authors: Knorr P. , Kim B.S. , Lee J.S. 
Published: April 2011

ABSTRACTAn experimental study of the kinetics of the three partial processes involved in the mechano-chemical synthesis of nanocrystalline (nc) Ni-Fe is presented. These processes are the reduction of nc NiO, the reduction of nc Fe2O3, and the alloying of Ni and Fe to a γ-Ni-Fe solid solution. Fr the reaction rates of the reduction of nc NiO and nc Fe2O3 activation enthalpies of 82 kJ mol−1 and 47 kJ mol− were obtained. The progress of the overall synthesis was found to follow the sequence ‘NiO red. → Fe2O3 red. → γ-Ni-Fe form.’.