bluuebunny/crossref_metadata_2025_split huggingface dataset:
Studies of Surface State Densities of Semiconductors by Room-Temperature Photoreflectance
Authors: Hwan J. S. , Chang G. S. 
Published: April 2011

ABSTRACTIn this study, we develop a novel approach to determine the surface Fermi level and the surface state densities of semiconductors. The built-in electric field and thus the surface barrier height are evaluated from the Franz-Keldysh oscillations in the PR spectra. Based on the thermionic-emission theory and current-transport theory, the surface state density as well as the pinning position of the surface Fermi level can be determined from the dependence of the surface barrier height on the pump beam intensity. Even though this method is significantly simpler, easier to perform, and time efficient compared with other approaches, the results obtained agree with the literature.
Passivation of InGaAs/InP heterostructures
Authors: Driad R. , Lu Z. H. , McKinnon W. R. , Laframboise S. , McAlister S. P. , Poole P. J. , Raymond S. , Charbonneau S. 
Published: April 2011

ABSTRACTIn this study we report different surface treatments and device designs that can be used to improve the performance of InGaAs/InP heterostructure devices. The surface properties of InGaAs (100) after sulfur or UV-ozone passivation were investigated by photoluminescence and high energy-resolution X-ray photoelectron spectroscopy. The base leakage current and the dc current gain of InGaAs/InP heterostructure bipolar transistors (HBTs) have been used to evaluate the efficiency of the passivation treatments. Although these treatments successfully passivated large area HBTs, the improved device characteristics degraded after a dielectric was deposited by plasma enhanced chemical vapor deposition (PECVD) or even just with time. Nevertheless, we found a combined surface treatment that is successful even under PECVD deposition – a UV-ozone treatment that produces a sacrificial oxide that is then removed by HF. This approach will be contrasted with a different method based on an optimized HBT layer structure with a thin InP emitter. In this case, the thin layer of depleted InP from the emitter left on the extrinsic base passivates the surface, and no treatment is required.
Surface-modified manganese dioxide for alkaline-manganese battery
Authors: Nunome Jun , Nakashima Takuya , Yoshizawa Hiroshi , Nitta Yoshiaki 
Published: April 2011

ABSTRACTThe surface-modification of manganese dioxide has been carried out for the purpose of increasing the discharge capacity of alkaline manganese battery. The characteristics of the obtained material has been investigated by using XAFS (X-ray absorption fine structure), Raman spectroscopy and ESR. It seems that composite oxide of Ti and Mn is formed on the surface of the surface-modified manganese dioxide (SMMD) particles. XRD measurement data on the discharged product demonstrates that SMMD suppresses the byproduct, and discharge characteristics of SMMD is improved compared to the conventional manganese dioxide.
A new family of salts for lithium Secondary batteries
Authors: Baril D. , Brranger S. , Ravet N. , Michot C. , Armand M. 
Published: April 2011

ABSTRACTA novel family of salts suitable for lithium battery application was synthesized and characterized. These salts have a large delocalized anion whose charge is spread over a single SO2and a phenyl ring. Remarkable properties were obtained for the lithium N-(3-trifluoromethyl phenyl) trifluoromethanesulfonamide salt or LiTFPTS. The electrochemical stability window is around 4.0 V and its conductivity in solid poly(ethylene oxide) or PEO is close to the one of the lithium perchlorate salt. Calorimetric analysis also showed that LiTFPTS behaves as a plasticizer since it hinders, to a certain extent, the PEO crystallization when it is used in a solid polymer matrix. Above all, its synthesis is quite straightforward and leads to potentially inexpensive salts as the starting amines are made commercially on a large scale.
Enhanced Ion mobility in Aluminosilicate/Polysiloxane Network Polyelectrolytes
Authors: Siska David P. , Shriver Duward F. 
Published: April 2011

ABSTRACTA new series of polysiloxane-based single-ion conductors was prepared. These contain solvating oligoether sidechains and covalently linked aluminosilicate or alkoxy/siloxy-aluminate anions attached to the polysiloxane backbone. Of these two systems, the polymers containing aluminosilicate [(SiO)4Al]− anions show higher room temperature conductivities (10−6 S/cm) than those with alkoxy/siloxyaluminate [(SiO)2(CH2O)2A1]− anions (10−7 S/cm). The incorporation of longer covalent tethers between the alkoxy/siloxyaluminate anion and the polymer backbone results in enhanced room temperature conductivities at high ion loadings. Differential scanning calorimetry data provide a rationale for the high conductivity.
Nanocomposite Based Electrolytes for Lithium-Ion Batteries
Authors: Riley M.W. , Fedkiw P.S. , Khan S.A. 
Published: April 2011

ABSTRACTNanocomposite electrolytes based on lithium hectorite (LiHect) clay dispersed in highdielectric organic solvents such as ethylene carbonate (EC) and propylene carbonate (PC) are shown to exhibit room-temperature conductivities exceeding 10−4 S/cm. The LiHect-based composites reveal lithium ion transference numbers of ∼0.8, as measured by the steady-state current method. In addition, dynamic rheological techniques show this system to be mechanically stable with elastic modulus G' exceeding 107 dynes/cm 2 and yield stress exceeding 104 dynes/cm2.
Surface Structure and Electrochemical Characteristics of Ti-V-Cr BCC-Type Solid Solution Alloys Sintered with NI
Authors: Tsuji Yoichiro , Yamamoto Osamu , Matsuda Hiromu , Toyoguchi Yoshinori 
Published: April 2011

ABSTRACTTi-V-Cr bcc-type solid solution alloys can absorb a large amount of hydrogen and be applied to active materials of the negative electrode in Ni-MH batteries. However, because of the insolubility of Ni into these alloys, the electrochemical characteristics like discharge capacity and cycle life were poor. In order to increase the discharge capacity of hydrogen absorbing alloy electrodes, Ti-V-Cr bcc-type alloy powders were sintered with Ni in order to form Ni contained surface layer on the alloy surface. As sintering temperature rose up, the surface composition changed from TiNi to Ti2Ni. TiNi surface layer showed better electrochemical characteristics. For the Ni adding method, Ni electroless plating was preferred because of good adhesion. As a result of optimized conditions, a discharge capacity of 570 mAh/g and an improvement of cycle life were achieved.
Transition Metal D$ LaGaO3 Perovskite Fast Oxide Ion Conductor and Intermediate Temperature Solid Oxide Fuel Cell
Authors: Ishihara Tatsumi , Shibayama Takaaki , Honda Miho , Nishiguchi Hiroyasu , Takita Yusaku 
Published: April 2011

ABSTRACTDoping transition metal cation is known to enhance the electric conduction of solid electrolytes, however, the ionic conduction can be improved by doping the small amount of transition metal, in particular, doping Co is effective for improving the oxide ion conductivity. In this investigation, oxide ion conductivity of LaGaO3 based oxide doped with Co were investigated in detail. It was found that LaGaO3 doped with Co for Ga site (LSGMC) show a notable oxide ion conductivity over a wide range of oxygen partial pressures, although a hole conduction was appeared by addition of excess amount of Co. Considering the electrical conductivity and transport number of oxide ion, the optimized composition of LSGMC seems to be existed at La0.8.Sr0.2, Ga0.8,.Mg0.115 CO0.085O3. Power generation characteristics of fuel cells was greatly improved by using LSGMC for electrolyte and extremely large power density can be obtained on both H2- O2 and H2-air cells. In particular, the maximum power density was attained to a value of 1.53 and 0.50 W/cm2 at 1073 and 873 K, respectively, on H2–O2 cell when the thickness of electrolyte was 0.18 mm. Furthermore, almost similar large power density was attained when air was used as oxidant. The high power density of cell demonstrated in this study suggests that the operating temperature of SOFC can be decreased by using LSGMC for electrolyte.
Effects of Microstructure on the Electrical Conductivity of SrCo0.8Fe0. 2O3_δ
Authors: Zhang K. , Miranova M. , Yang Y. L. , Jacobson A. J. , Salama K. 
Published: April 2011

ABSTRACTThe effect of microstructure on the electrical conductivity of SrCO0.8Fe0.2O3_δ (SCFO) was investigated in air using a four-point dc method. In the test temperature range of 200 to 900 °C, the electrical conductivity of this material was observed to increase with the increase of the average grain size in the lower temperature region where the conductivity increases with the increase of the temperature. The activation energy is decreased with the increase of the grain size in this region, 0.04 ± 0.004 ev for 4.1μm sample and 0.01 ± 0.001 ev for 14.8 μm sample. When temperature is further increased, the conductivity of this material decreases with the increase of the temperature, and the grain size effect becomes less noticeable.
Recent DOE Sponsored Electrochemical Capacitor Test Results
Authors: Wright R. B. , Murphy T. C. , Jamison D. K. , Rogers S. A. 
Published: April 2011

ABSTRACTElectrochemical capacitors (ultracapacitors) are being developed for hybrid vehicles as candidate power assist devices for the fast response engine and for other energy storage systems that can utilize the high power densities available from these devices. Ultracapacitors show promise toward being able to accept high regenerative pulses and high power delivery capabilities while exhibiting very high cycle life. This paper will present recent test data from two U.S. Department of Energy (DOE) supported ultracapacitor projects designed to meet the fast response engine requirements. Constant-current and constant-power test results will be presented that have been acquired from recent prototype capacitors supplied by SAFT America, Inc. (ten devices), and Maxwell Energy Products, Inc. (two devices). The SAFT capacitors are rated at 0.5 V to 3 V with capacitance ratings ranging from 135 F to 138 F. Capacitor cells rated at 2.3 V and 101.4 F were also evaluated that were produced by Maxwell Energy Products, Inc. Both sets of devices used proprietary carbon electrodes with non-aqueous electrolytes in their design. From the constant-current discharge tests, the discharge current dependence of the capacitance, equivalent series resistance, and RC-time constant were determined as well as the capacitors’ voltage dependence of the capacitance. Constant-power discharge tests permitted the specific energy as a function of the specific power to be determined, and also the discharge/charge round trip efficiency as a function of the magnitude of the constant-power discharge.
The stabilization of layered Manganese Oxides for use in Rechargeable Lithium Batteries
Authors: Whittingham M. Stanley , Zavalij Peter , Zhang Fan , Sharma Pramod , Moore Gregory 
Published: April 2011

ABSTRACTThe layered structure LixTiS2 and LixCoO2 are excellent reversible cathodes for lithium batteries. However, layered lithium manganese oxides are metastable relative to the spinel form on cycling in lithium batteries. They may be stabilized in the layer form by insertion of larger ions such as potassium in the interlayer region, which minimizes the diffusion of the manganese ions from the MnO2 blocks. Their low conductivity is an impediment to their use in high rate batteries. Cobalt can be doped into the layered alkali manganese dioxides, MxMn1-yCoyO2 for M = K or Na, during the hydrothermal synthesis from the alkali permanganates. A single phase is obtained up to about 5% mole cobalt. The cobalt doping is found to enhance the conductivity by two orders of magnitude relative to pure KxMnO2.
Phosphazene Backbones for Siloxanes and Organic Polymers
Authors: Kickelbick Guido , Miller Peter J. , Matyjaszewski Krzysztof 
Published: April 2011

ABSTRACT2,2,4,4,6,6-Hexachlorocyclotriphosphazene was modified by nucleophilic substitution to obtain building blocks for organic polymers and siloxane networks. 2,2,4,4,6,6-Hexachlorocyclotriphosphazene was substituted with functional groups to enable atom transfer radical polymerization (ATRP) as well as silicon alkoxide as precursors for the sol-gel process. ATRP was carried out with methyl acrylate followed by a chain extension with iso-bornyl acrylate to obtain new thermoplastic elastomers. The sol-gel process was carried out with acid, base and fluoride catalysts and the resulting materials were compared by TGA and DSC measurements.
Synthesis of Hybrid Organic-Inorganic Sol-Gel Coatings for Corrosion Resistance
Authors: Metroke T. L. , Parkhill R. L. , Knobbe E. T. 
Published: April 2011

ABSTRACT1H-13C and 1H- 29Si CP/MAS NMR spectroscopy has been used to characterize the structure of sol-gel derived hybrid materials prepared from 3-glycidoxypropyltrimethoxysilane (GLYMO) and tetraethylorthosilicate (TEOS) as a function of hydrolysis water ratio and organic content. 1H-13C CP/MAS NMR data indicate that the concentration of hydrolysis water (R value) has a fundamental effect on the nature of the acid-catalyzed hydrolysis and ring opening products. 1H-29Si CP/MAS NMR data suggest that for low R values, the ormosils are composed of a silica network with epoxide groups randomly dispersed throughout. At high R values, epoxide functionalities were found to coat the surfaces of dense silica particles. Salt spray analysis indicates that the corrosion resistance behavior of thin films derived from GLYMOTEOS ormosils decreases as the concentration of hydrolysis water increases and improves as the organic content in the film increases. These observations can be related to the underlying thin film structure.
Mechanical Properties of Low Dielectric-Constant Organic-Inorganic Hybrids
Authors: Cook Robert F. 
Published: April 2011

ABSTRACTSpin-on glasses, generated by the condensation of an organic-inorganic hybrid silsesquioxane (SSQ), have great potential as low dielectric-constant semiconductor interconnection materials. After curing and condensation SSQ materials consist of an amorphous, inorganic, –Si–O-Sibridging network with organic, non-bridging –Si–R side groups. Relative dielectric constants in the range 2.5–3.3 are obtained for SSQ materials, depending on the curing conditions, and compare with 4.0 for conventionally-used fused silica. The non-bridging side groups significantly disrupt the SSQ network—occupying more than 25% of the Si bonds—and lead to materials that are considerably less stiff, hard and tough than fused silica. Perhaps more importantly, SSQ materials have thermal expansion coefficients greater than that of the intended Si substrate and therefore finish curing in a state of residual tension, leading to a susceptibility to stress-corrosion cracking. In this paper the development of thermomechanical properties during curing of SSQ spin-on glasses is considered and related to the driving force for film cracking deriving from the residual tension. Various crack suppression schemes involving mechanisms both intrinsic and extrinsic to the base SSQ are discussed.
Effect of Curing Strategies on Porosity in Silanemodified Silica Colloidal Coatings
Authors: Daniels M. W. , Francis L. F. 
Published: April 2011

ABSTRACTSuspensions of silica (20 nim) in propoxyethanol were used to make porous silica coatings. A silane coupling agent, glycidoxypropyltrimethoxysilane (GPS), was added as a binder to increase coating durability and prevent cracking. GPS addition prevented crack formation but only when added in large amounts (GPS to silica weight ratio 0.5 to 1) such that porosity was filled by a GPS-based siloxane polymer. Attempts to enhance the fracture toughness of porous coatings through UV curing and glycol additions failed to lead to improvements in the critical cracking thickness (CCT). However, addition of triethylenetetramine resulted in a 3-fold increase in the CCT. Wear resistance increased for both the UV-cured and amine-cured coatings.
Organic/Inorganic Hybrid Sol-Gel Derived Hard Coatings on Plastics
Authors: Chan C. M. , Cao G. Z. , Fong H. , Sarikaya M. , Robinson T. , Nelson L. 
Published: April 2011

ABSTRACTWe investigated sol-gel derived silica based hard coatings on modified polyester substrates. The silica network was modified by incorporating an organic component and adding transition metal oxides. These modifications resulted in tailored thermal, optical and mechanical properties of the coatings. Various low temperature densification techniques were studied including appropriate sol-preparation procedure, enhanced solvent evaporation, ultraviolet (UV) irradiation, and low-temperature (below 150°C) heating. Oxygen plasma etching was applied to improve the adhesion of the sol-gel coatings on the plastic surface. Nanoindentation analysis revealed that the sol-gel coatings have a surface hardness up to 2.5±0.27 GPa, approximately an order of magnitude higher than that of the plastic surface.
Preparation and Properties of Inorganic-Organic Hybrids From Vinyland 3-Methacryloxypropyltrimethoxysilane
Authors: Takamura N. , Gunji T. , Abe Y. 
Published: April 2011

ABSTRACTThe organic-inorganic polymer hybrids consisting of carbon-carbon and siloxane chains were prepared by radical polymerization of vinyltrimethoxysilane (VTS) and 3-methacryloxypropyltrimethoxysilane (MAS) followed by hydrolytic polycondensation. Polyvinyltrimethoxysilane (PVTS) and poly(3-methacryloxypropyltrimethoxysilane) (S-PMA) with various molecular weights Mw=3900–64800 were prepared by polyaddition of VTS and MAS, respectively. PVTS and S-PMA provided transparent and flexible free-standing films and coating films. With increasing carbon-carbon chain length, the elasticity of the films increased, while the tensile strength and Young's modulus decreased. The adhesive strength of the coating films on organic substrates was particularly dependent on the solubility parameter, polarity and crystallinity of each substrate. The pencil-hardness of coating films was clearly increased with increasing degree of condensation of sila-functional group in PVTS and S-PMA.
Tear Strengths of Poly(Dimethylsiloxane) Networks Reinforced with in-Situ Precipitated Silica
Authors: Kumudinie Chandima , Mark James E. 
Published: April 2011

ABSTRACTThe tear strengths of in-situ filled poly(dimethylsiloxane) (PDMS) networks were investigated using “trouser-tear” tests. The filled PDMS networks were prepared by the simultaneous curing and in-situ precipitation technique, the silica reinforcing phase being obtained by the hydrolysis and condensation of tetraethoxysilane present in excess of that required for the chain end-linking process. Transmission electron micrographs showed well-dispersed and unagglomerated silica particles, and thermogravimetric analysis indicated that the silica particles gave some improvements in thermal stability. In the tearing tests, “stick-slip” tearing was observed at higher rates, especially for the filled networks. The tear strengths were found to increase with increase in the amount of silica incorporated, with the largest increases occurring at the low silica contents.
Mechanical Properties of Soluble Polymer/Silica Gel Hybrids
Authors: Klein L. C. , Wert J. Van , Beaudry C. L. 
Published: April 2011

ABSTRACTStrengths have been measured for silica gels prepared with poly(ethylene oxide) (PEO) and poly(vinyl acetate) (PVAc). The modulus of rupture was determined using standard three-point bending in a mechanical tester. The samples were prepared by mixing tetraethylorthosilicate with the polymers dissolved in water (PEO) or water/ethanol(PVAc). Molecular weights between 200 and 3400 were used for PEO. Substitutions of the polymer for silica represented between 5 and 25% on a weight basis. In these systems, the interactions between the polymer and the silica network are largely through hydrogen bonding, between ether oxygens in PEO and silanols and between hydroxyls in PVAc and silanols. The extent of the bonding increases with increasing aging time, as indicated by an almost linear increase in the modulus of rupture. The increase for PEO was greater than for PVAc. Among PEO samples, the strengths were higher for higher molecular weights at the same weight fraction.
Viscoelastic Responses of Inorganic-Oranic Hybrids Polymers
Authors: Lee Andre 
Published: April 2011

ABSTRACTThe properties of nano-structured plastics are determined by complex relationships between the type and size of the nano-reinforcement, the interface and chemical interaction between the nano-reinforcement and the polymeric chain, along with macroscopic processing and microstructural effects. In this paper we investigated the thermal and viscoelastic property enhancement on crosslinked epoxy using two types of nano-reinforcement, namely organoion exchange clay and polymerizable polyhedral oligomeric silsesquioxane (POSS) macromers. Glass transitions of these nano-composites were studied using differential scanning calorimetry. Small strain stress relaxation under uniaxial deformation was examined to provide insights into the timedependent viscoelastic behavior of these nano-composites. Since the size of POSS macromer is comparable to the distance between molecular junctions, hence as we increase the amount of POSS macromers, the glass transition temperature, Tg, as observed by DSC increase. However for epoxy network reinforced with clay, we did not observe any effect on the Tg due to the presence of clay reinforcements. In small strain stress relaxation experiments, both types of reinforcement provided some enhancement in creep resistance, namely the characteristic relaxation time as determined using a stretched exponential relaxation function increased with the addition of reinforcements. However, due to different reinforcement mechanisms, enhancement in the instantaneous modulus was observed for clay-reinforced epoxies, while the instantaneous modulus was not effected in POSS-epoxy nano-composites.
Synthesis-Morphology-Mechanical Properties Relationships Of Polymer-Silica Nanocomposite Hybrid Materials
Authors: Hajji P. , David L. , Gerard J. F. , Kaddami H. , Pascault J. P. , Vigier G. 
Published: April 2011

ABSTRACTTwo types of polymer-silica nanocomposites have been prepared by undergoing free radical polymerization of 2-hydroxyethyl methacrylate (HEMA) either in the presence of HEMA-functionalized SiO2 nanoparticles (Type 1) or during the simultaneous in situ growing of the silica phase through the acid-catalyzed sol-gel polymerization of tetraethoxysilane (TEOS) (Type 2). Relationships between synthesis, morphology and mechanical properties are discussed mainly on the basis of solid state 29Si nuclear magnetic resonance spectroscopy (NMR), transmission electron microscopy (TEM), small angle X-ray scattering (SAXS), and dynamic mechanical analysis (DMA).
Synthesis & Characterization of Optically-Active Lanthanide-Doped Hybrid Inorganic-Organic Systems
Authors: Taylor-Smith R.E. , Choi K. M. 
Published: April 2011

ABSTRACTThe materials chemistry of sol-gel-derived inorganic-organic molecular composites offers significant potential for molecular-level systems design. One focus in this arena is the chemical design and microstructural engineering of optically-active systems. We report the generation of rare-earth-doped inorganic-organic hybrids, based on a bridged polysilsesquioxane architecture. Derived from lanthanide precursors such as Erbium isopropoxide, which we co-condense with the requisite silsesquioxane monomer, these systems exhibit significant optical activity. In experiments on hybrids doped with Erbium, we conclusively demonstrate strong fluorescence at wavelengths in the vicinity of 1540 nm, from stimulation with 488 nm radiation. We discuss materials-driven impacts of the bridged-silsesquioxane architecture on system complexities arising from the solution sol-gel route which would affect fluorescence efficiencies and luminescence levels, such as hydroxyl impurities and clustering-effects.