bluuebunny/crossref_metadata_2025_split huggingface dataset:
Profiling of Anode Surface Cycled in LiBOB-based Electrolyte of Li Ion Batteries
Authors: Lee Unchul , Xu Kang , Zhang Sheng S. , Richard T. 
Published: April 2011

AbstractAs the youngest battery chemistry, Li ion technology was made possible by the formation of stable electrode/electrolyte interfaces. The correlation between the electrochemistry and the surface profile of the graphitic anode was studied in this work with a new salt lithium bis (oxalate) borate (LiBOB).In an attempt to depict a dynamic picture of the formation of graphite/electrolyte interface during the initial forming cycle, we employed X-ray photoelectron spectroscopy in combination with the “pre-formation” technique to establish the dependence of the surface chemistry on the forming potential of the anode. A progressive transition in the 1s electron binding energies of the major elements was observed as the lithiation proceeds; however, the surface chemical species as well as their abundances seemed to stabilize around 0.55 V and remained constant during the subsequent delithiation process, indicating that a stable solid electrolyte interface (SEI) exists thereafter. Integrating the information revealed by different analyses, we believe that the reductive decomposition of BOB−-anion starts at ca. 1.00 V, while the effective protection of graphene surface by SEI is available after the anode is lithiated below the potential of 0.55 V.
Anode Hosts for Lithium Batteries: Revisiting Tin and Aluminum
Authors: Fan Quan , Zavalij Peter , Stanley Whittingham M. 
Published: April 2011

ABSTRACTPure tin reacts readily with four lithium atoms, and so is a prime candidate as the host for the anode of lithium batteries. Tin foil and an expanded tin grid (microporous tin) have a capacity of >600 mAh/g over more than 10 deep reaction cycles, indicating the inherent reversibility of tin anode. The microporous tin showed superior chemical capacity retention. Different phases are observed during the intercalation of lithium. Capacity loss was observed after 10 cycles though, consistent with the significant increase of the cell impedance. For comparison aluminum expanded grids were also examined as hosts, where LiAl is formed. Capacities approaching 1 Ah/g were obtained. LiBOB (lithium bis(oxalato)borate) was also studied as the electrolyte salt for comparison with the reactive and high cost LiPF6 salt.
Density-Functional Theoretical Study on the Intercalation Properties of Layered LiMO2 (M = Zr, Nb, Rh, Mo, and Ru)
Authors: Singh S. P. , Tomar M. , Ishikawa Yasuyuki , Majumder S. B. , Katiyar R. S. 
Published: April 2011

AbstractAverage Li intercalation potentials were calculated for lithium-4d-transition-metal-oxides. The effect on the intercalation voltage of metal substitution was systematically studied by altering the 4d transitional metals M (M= Mo, Nb, Rh, Zr, Ru) in LiMO2 in the α-NaFeO2 structure. Lattice parameters in the layered α-NaFeO2 structure computed in the GGA approximation are in reasonable agreement with experiment. The intercalation potentials and relative formation energies of the fully lithiated LiNi1/3Mn1/3Mo1/3O2, fully delithiated Ni1/3Mn1/3Mo1/3O2 and the intermediate phases, Li1/3Ni1/3Mn1/3Mo1/3O2 and Li2/3Ni1/3Mn1/3Mo1/3O2, were computed by employing a generalized alloy theory. A minute substitution of cationic Mo in LiNiMnO2 was experimentally investigated to examine the effect of the Mo substitution on the electrochemical properties.
Nanostructured PEFC Electrode Catalysts Prepared via In-situ Colloidal Impregnation
Authors: Sasaki Kazunari , Shinya Kenji , Tanaka Shuhei , Kawazoe Yuudai , Kuroki Takashi , Takata Kouhei , Kusaba Hajime , Teraoka Yasutake 
Published: April 2011

ABSTRACTNanostructured Platinum-based electrode catalysts were prepared via in-situ colloidal impregnation for polymer electrolyte fuel cells. Crystallite size, grain size, and distribution of Pt nanoparticles on carbon support materials were characterized by XRD, TEM, high-resolution FESEM, and STEM. Effective surface area and kinetically-controlled current density of Pt electrode catalysts were analyzed by cyclic and hydrodynamic voltammetry using rotating disk electrodes. PEFCs with these electrode catalysts were also prepared and their I-V characteristics were examined at 80°C.We have succeeded to develop Pt electrode catalysts with a diameter of a few nm, supported on carbon nanofibers with different structures (including herringbone-type fibers, platelet-type fibers, and highly-conductive vapor-grown fibers), carbon nanotubes, as well as carbon black. The dependencies of nanostructure and electrochemical properties on crystallographic structure of carbon support materials and preparation conditions of electrode catalysts are analyzed and discussed. Nanostructural design of PEFC electrode catalyst layers using carbon nanofibers as catalyst supports and electrode fillers is also discussed.
Investigation of Imidazole-Based Lithium Conducting Materials
Authors: Czardybon A. R. , Sivasubramaniam K. , Goward G.R. 
Published: April 2011

ABSTRACTThis study aims to develop novel polyelectrolytes including lithiated imidazole heterocycles for use in lithium ion rechargeable batteries. Lithium ion local mobility in these materials is characterized by 6, 7Li solid-state NMR. By comparing these results with macroscopic ionic conductivity, measured by impedance spectroscopy, we will be able to develop a picture of the ionic conductivity at the microscopic level. Multinuclear solid state NMR provides information on microscopic interactions including ionic mobility and ring reorientations which govern the efficiency of conductivity. Our research includes 6, 7Li variable MAS NMR studies at intermediate spinning speeds, relaxation investigations to determine spin-lattice relaxation times (T1) of lithium ion hopping, and 2D exchange spectroscopy to determine possible chemical exchange processes. A very long T1 (135 s at ambient temperature) and an activation energy Ea = 17.2 kJ/mol suggests rigid molecule structure and the absence of the ring reorientation of the model compound, lithium imidazolium (LiIm). We compare this to the behavior of LiIm doped with lithium methanesulfonate, which we show to form a new ionic complex with lower T1 and corresponding lower activation energy. With the goal of creating new polyelectrolytes, we have synthesized electrolytes incorporating lithiated imidazole rings, where lithium transport may be independent of polymer-backbone flexibility, and thus polymers with high Tg may be viable. Such materials are highly desirable for secondary lithium polymer battery applications.
Amphiphilic Dye for Solid-State Dye-Sensitized Solar Cells
Authors: Schmidt-Mende Lukas , Zakeeruddin Shaik M. , Grätzel Michael 
Published: April 2011

ABSTRACTWe report a solid-state dye-sensitized solar cell with a record efficiency of 4% under simulated sunlight (AM1.5global, 100mW/cm2). This was made possible by using a new amphiphilic dye with hydrophobic spacers in combination with spiro-OMeTAD. We attribute the significant improvement in the device performance to the self-assembly of the dye to form a compact layer on the TiO2 surface and to the hydrophobic chains working as blocking layer between spiro-OMeTAD and TiO2 to reduce the back electron transfer. In addition, we studied the influence of nanoporous TiO2 film thickness on the performance of the device. These results demonstrate the high potential for solid state dye sensitized solar cells to compete with amorphous silicon cells as low cost alternative.
Plasticized conjugated polymers: a possible route to higher voltage solar cells
Authors: Wentzel Paul , Pasquier Aurelien Du 
Published: April 2011

ABSTRACTThe introduction of propylene carbonate (PC) into the poly (3-alkyl)thiophenes (P3AT) poly(octyl)thiophene (P3OT) and poly(hexyl)thiophene) (P3HT) is studied. In both cases, we observe a diminution of their melting temperature, which demonstrates a plasticizing effect. We also observe an increase of photovoltage and photocurrent in sandwich devices M//P3AT+PC//ITO-PET where M=Al, Mg and ITO-PET is Indium thin oxide coated on polyester. We attribute this effect to the introduction of oxygen from the PC. When mixed with an electron acceptor PCBM, the photocurrents only slightly increase and the photovoltages are similar. In this case, the presence of oxygen is detrimental to the system.
Star-shaped heptamers of discotic dyes as new materials for photovoltaic devices
Authors: Holger Eichhorn S. , Fox Nicholas , Bornais Bryan 
Published: April 2011

AbstractPotentially n-type and p-type semi-conducting discotic liquid crystal dyes are linked together to star-shaped heptamers, which might self-organize into super-columns of separated p-type and n-type columnar stacks. Their synthesis, mesomorphism, and electronic properties will be discussed along with their potential use in photovoltaic devices.
Structural studies of chloride-treated RF sputtered Cd1-xMnxTe films
Authors: Wang S. L. , Lee S. H. , Gupta A. , Compaan A. D. 
Published: April 2011

ABSTRACTCd1-xMnxTe alloy films with band gaps of 1.6 ∼ 1.8 eV have been deposited by RF magnetron sputtering for solar-cell applications. The films have been treated by chloride vapors to improve the photovoltaic performance. These as-deposited and chloride-treated CdMnTe films have been investigated by Raman spectroscopy, x-ray diffraction (XRD) and scanning electron microscopy (SEM). Raman results indicate that Te and/or TeO2 exists in the annealed samples depending on anneal conditions.
Crystal growth of photovoltaic polycrystalline Si1-xGex by die-casting growth
Authors: Hirahara H. , Iida T. , Sugiyama Y. , Baba T. , Takanashi Y. , Sakuragi S. 
Published: April 2011

ABSTRACTCoin-shaped multicrystalline Si1-xGex crystals were grown using a Brigdman method combined with die-casting growth. Si1-xGex alloy is known as a candidate material for producing Auger generation, which creates more than one electron/hole pair per absorbed photon. Since Si1-xGex alloy shows a complete series of solid solutions, precipitating crystals with a certain composition of silicon or germanium by conventional selective growth methods is burdensome. Using die-casting combined with Bridgman growth brought about Si1-xGex precipitation in a form completely different from that predicted by the Si-Ge phase diagram. By combining this growth with subsequent heat treatment of the precipitated Si1-xGex sample, Si1-xGex (x= 0.5 ± 3 %) could be obtained. Indirect band-gap energy was estimated by measuring room-temperature optical absorption coefficient of the grown samples.
Characterization of polycrystalline Si silicon sheet grown by die casting combined with the Bridgman technique
Authors: Saito K. , Iida T. , Akimoto D. , Nose A. , Takanashi Y. , Sakuragi S. , Nanba H. , Sakuragi G. , Shimazaki T. 
Published: April 2011

ABSTRACTDie-casting growth was used for manufacturing the multicrystalline silicon sheet with a size of 100 × 120 × 0.5 mm. During the growth, incorporation of contaminants such as iron, cobalt, nickel and chromium was well suppressed. The average etch-pit density values ranged from 1×104 cm-2 to 4x106 cm-2 for growth rates of 5 to 60 mm/h, respectively. Measurement of minority-carrier lifetime bye microwave-photoconductivity-decay (μ-PCD) method was 0.5 μs for as-grown specimens, suggesting that defects and residual strain exist in the grown sheet. Moreover, post heat treatment at 1473 K reduced the etch-pit density and improved carrier lifetime up to 2.2 μs.
Mid-10 cm−2 threading dislocation density in optimized high-Ge content relaxed graded SiGe on Si for III-V solar on Si
Authors: Isaacson David M. , Dohrman Carl L. , Pitera Arthur J. , Gupta Saurabh , Fitzgerald Eugene A. 
Published: April 2011

ABSTRACTWe present a framework for obtaining high quality relaxed graded SiGe buffers on Si for III-V integration. By avoiding dislocation nucleation in Si1−xGex layers of x>0.96, we have achieved a relaxed Si0.04Ge0.96 platform on Si(001) offcut 2° that has a threading dislocation density of 7.4×105 cm−2. This 2° offcut orientation was determined to be the minimum necessary for APB-free growth of GaAs. Furthermore, we found that we could compositionally grade the Ge content in the high-Ge portion of the buffer at up to 17 %Ge μm−1 with no penalty to the dislocation density. The reduction in both threading dislocation density and buffer thickness exhibited by our method is an especially significant development for relatively thick minority-carrier devices which use III-V materials such as multi-junction solar cells.
Cabon Nanofibrous Materials Prepared from Electrospun Polyacrylonitrile Nanofibers for Hydrogen Storage
Authors: Park S. H. , Kim B. C. , Jo S. M. , Kim D. Y. , Lee W. S. 
Published: April 2011

ABSTRACTElectrospun PAN nanofibers were carbonized with or without iron(III) acetylacetonate to induce catalytic graphitization within the range of 900–1500°C, resulting in ultrafine carbon fibers with the diameter of about 90–300 nm. The structural properties and morphologies of the resulting carbon nanofibers were investigated using XRD, Raman IR, SEM, TEM, and surface area/pore analysis. The PAN-based carbon nanofibers carbonized without a catalyst had amorphous structures, with d002 = 0.37 nm, and smooth surfaces with very low surface areas of 22–31 m2/g. The carbonization of PAN-based nanofibers in the presence of the catalyst produced the graphite nanofibers (GNF) with d002 = 0.341 nm, indicating turbostrate structures. The graphite structures were grown by increasing the catalyst contents and the carbonization temperature. The hydrogen storage capacities of the aforementioned carbon nanofiber materials were evaluated through the gravimetric method using Magnetic Suspension Balance (MSB) at room temperature and at 100 bars. The storage data were obtained after the buoyancy correction. The CNFs showed hydrogen storage capacities of 0.16–0.50 wt.%, increasing with the increase of carbonization temperature, but that of the CNF at 1500°C was lowest. The hydrogen storage capacities of the GNFs with low surface areas of 100–250m2/g were 0.14–1.01 wt%.
The Role of Metal Catalyst in Near Ambient Hydrogen Adsorption on Multi-walled Carbon Nanotubes
Authors: Lee Yong-Won , Deshpande Rohit , Dillon Anne C. , Hebe Michael J. , Dai Hongjie , Clemens Bruce M. 
Published: April 2011

ABSTRACTMultiwalled carbon nanotubes (MWNTs) were continuously synthesized by hot wire chemical vapor deposition (HWCVD) using a methane source catalyzed by metal-organic ferrocene. The microstructure of the MWNTs and the catalyst particles were subsequently characterized with transmission electron microscopy which identified three different phases, i.e., bcc α-Fe, fcc γ-Fe and orthorhombic Fe3C. The hydrogen storage capacity of MWNTs was determined with temperature-programmed desorption (TPD) technique. Hydrogen adsorption at near ambient conditions was observed only in as-synthesized MWNTs containing iron particles and was dramatically increased after hydrogen reducing treatment. Possible adsorption mechanism was also discussed.
Dehydrogenation kinetics and long term cycling behavior of Titanium doped NaAlH4
Authors: Srinivasan Sesha S. , Jensen Craig M. 
Published: April 2011

ABSTRACTThe development of light weight hydrogen storage systems with high volumetric and gravimetric hydrogen densities is indeed essential for the on-board fuel cell vehicular applications. Titanium doped NaAlH4 is right now considered as the potential hydrogen storage system, which satisfies the said criteria. The dehydrogenation of NaAlH4 consists of two consecutive steps of decomposition at 220 and 250° C with the total hydrogen release of 5.6 wt.%. However, doping a few mole concentrations of selected transition metal complexes to the host hydride reduces significantly the decomposition temperatures to 100 and 185° C (equilibrium H2 pressure ∼1 MPa) respectively. This breakthrough has been followed by a great deal of effort to develop NaAlH4 as a practical hydrogen storage material. For an ideal hydrogen storage material, the dehydrogenation kinetics and the cycling stability are important properties to be evaluated. Keeping these points to ponder, we have studied the dehydriding kinetics of the Ti-doped NaAlH4 over a number of dehydrogenation and rehydrogenation cycles. Besides, the Ti-doped NaAlH4 has been prepared from the hydrogenation of NaH and Al using the solvent mediated milling method. Comparing the initial and final cycling stages of Ti doped (NaH + Al), the synchrotron powder x-ray diffraction profiles exhibit, a growing resistance to the hydrogenation of Na3AlH6 to NaAlH4.
An in-situ X-ray Diffraction Study of the Desorption of TiCl3-doped Sodium Alanate
Authors: Speakman Scott A. , Schneibel Joachim H. , Easton Dewey S. 
Published: April 2011

ABSTRACTSodium alanate was milled with and without TiCl3. The hydrogen release and uptake was measured during temperature-programmed absorption and desorption, as well as by isothermal charging and discharging, using a Sieverts' type apparatus. These data were supplemented by in-situ X-ray diffraction studies of hydrogen desorption. Rate constants derived from XRD were slower than those derived from volumetric H2 measurements. Al formation observed in XRD exceeded that expected from the observed decomposition of NaAlH4 and Na3AlH6.
Discovering the Mechanism of H2 Adsorption on Aromatic Carbon Nanostructures to Develop Adsorbents for Vehicular Applications
Authors: Dillon A. C. , Blackburn J. L. , Parilla P. A. , Zhao Y. , Kim Y-H. , Zhang S. B. , Mahan A. H. , Alleman J. L. , Jones K. M. , Gilbert K. E. H. , Heben M. J 
Published: April 2011

ABSTRACTHydrogen adsorption has been observed with a binding energy of ∼ 50 kJ /mol on as-synthesized carbon multi-wall nanotubes (MWNTs). The MWNTs are virtually free of non-nanotube carbon impurities but contain residual iron catalyst particles. The MWNTs are also highly graphitic. No hydrogen adsorption is observed at near ambient temperatures for purified MWNTs that are free of iron particles. However, hydrogen adsorption is also not observed on bare iron particles even following reduction in the presence of hydrogen at 775 K. These results imply that a special synergy occurs when small iron particles or atoms are in intimate contact with sp2-hybridized aromatic carbon. Interestingly, reducing the as-synthesized MWNTs in H2 at 573 K results in an increased hydrogen capacity. Understanding this hydrogen storage mechanism could facilitate the economical engineering of a hydrogen storage material that meets the United States Department of Energy targets for vehicular fuel cell applications. Recent theoretical studies have shown that an iron ad atom forms a complex with a C36 fullerene and shares charge with four carbon atoms of a bent five-membered ring. Three H2 ligands then coordinate with the iron forming a stable 18-electron organometallic complex. Here the binding energy of the molecular hydrogen ligands is ∼43 kJ /mol. These theoretical results could possibly explain the unique hydrogen storage properties of MWNTs that are grown with an iron catalyst.
Force-Strain Curves Of Microcapsules With Atomic Force Microscopy
Authors: Lansey Eli , Zypman Fredy R. 
Published: April 2011

ABSTRACTWe develop an algorithm to measure elastic properties of microcapsules with Atomic Force Microscopy (AFM). The AFM is used as an indenter and presses down on a spherical microcapsule. We study the system from an atomic point of view (considering interactions between the atoms in the system via Equivalent Crystal Theory) and calculate the force produced by the system to balance the external AFM force. We plot this force as a function of the indentation depth, and from that curve we extract the interatomic parameters of ECT that are related with elastic constants. Our calculations model measurements of force-strain curves including non-linear effects. This is relevant as classical elasticity theory breaks down in the AFM indentation regime, when atomic interactions must be considered explicitly.
Frequency Response of Microcantilevers in Viscous Fluids
Authors: Schilowitz A. M. , Yablon D. G. , Zypman F. 
Published: April 2011

ABSTRACTThis paper presents a new, general reconstruction algorithm that enables modeling of the experimental resonance spectrum of a prismatic microcantilever in a viscous fluid. A closed-form solution is obtained for the microcantilever frequency response from the equation of motion with fluid damping and internal friction terms, which allows direct calculation of the fluid damping and internal friction damping constants. In principle, the fluid damping constant has a simple relationship to viscosity thus potentially simplifying the process of obtaining viscosity from experimental data. Finally, the model is compared to experimental data.
In Situ Monitoring of Dispersion Film Formation Using Tapping-Mode Atomic Force Microscopy
Authors: Li Jing , Liang Wenbin , Chum Steve 
Published: April 2011

ABSTRACTThe coalescence process of poly (ethylene-co-vinyl acetate) (EVA) and poly (ethylene-co-octene) (EO) dispersion particles was monitored in situ using tapping-mode atomic force microscopy (TMAFM) equipped with a miniature hot stage. This work describes the effect of particle size on the film formation temperature based on direct experimental observation, clarifying further the debate about particle size effect on minimum film formation temperature (MFFT). The results suggest that semicrystalline polyolefin particles have similar deformation temperature dependence. Smaller particles tend to deform faster than larger particles, which is attributed to their smaller mass. Furthermore, morphology changes and mechanical property development associated with the film formation process are also discussed. The TMAFM technique is shown to be very useful in gaining insight into the film formation mechanism, which will provide guidance in future practical applications with polyolefin dispersions.
Novel Dynamic Scanning Microscope Probe and its Application to Local Electrical Measurement in an Ion Sensitive Field Effect Transistor
Authors: Akiyama T. , Suter K. , de Rooij N. F. , Staufer U. 
Published: April 2011

ABSTRACTA unique self-actuating and self-sensing probe, which is based on a quartz tuning fork and a microfabricated cantilever, is presented for dynamic scanning probe microscopy. The probing tip can be electrically connected to an external source or measure unit. The sensitivity of the drain-source current of an ion sensitive field effect transistor (ISFET) was investigated as a function of the probe position in order to assess the potential of the probe in device testing, where its non-optical read-out mechanism may proof to be a particular advantage.
Improve the Accuracy of Scanning Kelvin Probe Microscopy by Eliminating the Cantilever Effect
Authors: Yang Zhitao , Spencer Michael G. 
Published: April 2011

ABSTRACTScanning Kelvin probe microscopy (SKPM) is widely used to measure surface work functions and electrostatic potentials on nanoscale circuits, devices and materials. However, the accuracy of scanning Kelvin probe microscopy is reduced by a cantilever effect, which is due to a large capacitance gradient associated with the cantilever. We introduce an aperture structure to quantitatively moderate the strength of the cantilever effect. In this approach, the cantilever effect is eliminated and the true surface potential can be extracted by solving a set of linear equations. Experimental results show that this approach yields very accurate surface potentials when there is only a single potential source within the aperture. In the case of multiple potential sources, this method significantly improves accuracy as well. A mobile aperture structure mounted on a micromanipulator can make this approach more versatile.