bluuebunny/crossref_metadata_2025_split huggingface dataset:
Charge Storage Properties of Nickel Silicide Nanocrystal Layer Embedded in Silicon Dioxide
Authors: Jang Yoo-Sung , Yoon Jong-Hwan 
Published: June 2009

AbstractMemory properties of nickel silicide nanocrystal monolayers embedded in silicon dioxide have been investigated. The nanocrystal layers were produced by thermal annealing of a sandwich structure comprised of ultrathin Ni film (0.2 nm) sandwiched between two silicon-rich oxide (SiO1.57) layers. Average diameter and areal density is about 2.9 nm and 1.3×1012 cm-2, respectively. Capacitance-voltage (C-V) measurements are shown to have C-V characteristics suitable for nonvolatile memory applications, including large memory window (∼ 10 V), long retention time ( > 107 s), and excellent endurance ( > 106 program/erase cycles).
Photonic Thermal Conductance in Multi-layer Photonic Crystals
Authors: Lau Wah Tung , Shen Jung-Tsung , Fan Shanhui 
Published: June 2009

AbstractPhotonic thermal conductance of a multi-layer photonic crystal, when normalized with the corresponding thermal conductance of vacuum at each temperature, can be significantly below unity. The minimum of this normalized thermal conductance occurs at the high-temperature limit, and the conductance value at this limit is independent of the layer thicknesses. We give an analytic theory to explain such independence, and show that it is related to the ergodic nature of the distribution of photonic bands in frequency space.
Effects of CuIn0,5Ga0,5Se2 growth by isothermal and bithermal Cu-Poor/Rich/Poor sequence on solar cells properties
Authors: Marko Hakim , Hultqvist Adam , Platzer-Björkman Charlotte , Noël Sébastien , Kessler John 
Published: June 2009

AbstractCo-evaporated CuIn0,5Ga0,5Se2 thin film solar cells were grown using a sequential Cu-Poor/Rich/Poor process (CUPRO). During the growth process, the substrate temperature was either kept constant at 570 °C (iso-CUPRO) or decreased during the first step to either 360 or 430 or 500 °C (bi-CUPRO). According to atomic force microscopy (AFM) measurements, the lower the temperature is in the first step the smoother the final CIGS surface becomes. By decreasing the first step temperature, cross-section scanning electron microscopy (SEM) and θ-2θ x-ray diffraction (XRD) do not reveal clearly any important changes of morphology and crystallographic preferred orientation. SLG/Mo/CIGS/Buffer layer/i-ZnO/ZnO:Al/grid(Ni/Al/Ni) solar cells with either a chemical bath deposited CdS or an atomic layer deposited Zn(O,S) buffer layer were fabricated. For both buffer layers, the bi-CUPRO processes lead to higher efficiencies. Besides, using Zn(O,S), the electronic collection was improved for the infrared spectrum as well as for the ultraviolet spectrum. This resulted in efficiencies close to 14,5% for the Zn(O,S) cells.
Mechanical Properties and Adhesion of CdTe/CdS Thin Film Solar Cells Deposited on Flexible Foil Substrates
Authors: Hodges Deidra Ranel , Palekis Vasilios , Bhandaru Shweta , Singh Kartikay , Morel Don L , Stefanakos Lee 
Published: June 2009

AbstractCadmium telluride (CdTe) is a leading thin film photovoltaic (PV) material due to its near ideal band gap of 1.45 eV, its high optical absorption coefficient and availability of various device fabrication methods. Superstrate CdTe solar cells fabricated on glass have to-date exhibited efficiencies of 16.5%. Work on substrate devices has been limited due to difficulties associated with the formation of an ohmic contact with CdTe. Foil substrate curvature, flaking, delamination and adhesion as a result of compressive strain due to the coefficient of thermal expansion (CTE) mismatch between the flexible foil substrate and the solar cell films has been studied. Thin films have been characterized by AFM, XRD, SEM, ASTM D3359-08 tape test, and solar cells have been characterized using J-V and spectral measurements. Adhesion improves by minimizing the mismatch of the CTE . A CdCl2 treatment is important for high efficiency solar cells. The treatment influences the microstructure and interface properties of the layers. The effect of the current CdCl2 chemical treatment increases flaking and has to be optimized for the CdTe substrate cell on foil. We have also fabricated solar cells on tantalum, molybdenum and tungsten foils, all with lower CTEs than SS430. We are currently producing solar cells with a VOC of 630mV, a 50% fill factor and over 6.0% efficiency.
Improvement in the FF over 0.700 by Controlling the Interface Quality
Authors: Kushiya Katsumi , Tanaka Y. , Hakuma H. , Kijima S. , Aramoto T. , Fujiwara Y. , Chiba Y. , Sugimoto H. , Kawaguchi Y. , Kakegawa K. 
Published: June 2009

AbstractIn this study, the pn hetero-interface between Zn(O,S,OH)x buffer and Cu(InGa)(SSe)2 (CIGSS) surface layers is discussed in order to achieve the fill factor (FF) over 0.73 and the circuit efficiency of 16 % on aperture area of over 800 cm2. Two resistances, i.e. shunt resistance (Rsh) and series resistance (Rs), in the circuits are employed as a yardstick to evaluate the interface quality. Since there are no realistic yardsticks on the Rs, the difference between Voc and optimum-power voltage (Vop) (i.e. Voc-Vop [V/cell]) is applied as a simple tool to evaluate the Rs. It is emphasized that it is important to reduce the Rs mainly correlated to the buffer deposition process and, as a result, the interface quality. We consider the Rs is dependent on the remaining Zn(OH)2 concentration in the Zn(O,S,OH)x buffer deposited by a chemical-bath deposition (CBD) technique. As an approach to make the Rs minimize and the Rsh maximize simultaneously, adjusting the thickness of a CBD-Zn(O,S,OH)x buffer layer and a non-doped ZnO layer deposited by a metal-organic chemical vapor deposition (MOCVD) technique has been effective to reduce the remaining Zn(OH)2 concentration. Determining the optimized deposition procedure to achieve the FF over 0.700 consistently, the circuit efficiency of 15.3 % with aperture area of 856 cm2 and the FF of 0.717 has been achieved.
Suitability of Atmospheric-pressure MOCVD CdTe Solar Cells for Inline Production Scale
Authors: Barrioz Vincent , Lamb Dan A , Jones Eurig W. , Irvine Stuart 
Published: June 2009

AbstractCdTe, with a direct band gap of 1.45 eV is well suited to the terrestrial AM1.5 solar irradiance and currently makes up half of the thin film (TF) photovoltaic (PV) market. There are 4 main factors that determine final cost of PV modules: the conversion efficiency, materials amount per unit area of module, production yield, and the economy of scale. It is therefore valuable to investigate alternative and/or innovative deposition techniques and processes which have the potential to impact on these factors. Metal organic chemical vapour deposition (MOCVD) is a powerful technique offering increased process repeatability, achieving a high level of control of materials characteristics. Recent improvements in CdTe devices using atmospheric–pressure (AP) MOCVD have led to efficiencies of 13.3 % using 2 μm absorber layers and 11 % with a 1 μm absorber layer [11, 12]. These results were achieved: by extending the optical band gap of the window layer, using a ternary alloy (Cd0.9Zn0.1S), with intentional p-type doping of the CdTe layers with As, and the use of an in situ (dry) deposited CdCl2 layer and anneal. All layers, except the front and back contact, are grown by a sequential MOCVD process. Furthermore this is a dry process without the need for any etch treatment. The inherent design of the horizontal MOCVD laboratory chambers do not lend themselves well to large scale production. However, the CSER group has designed and built an experimental inline reaction chamber to evaluate AP-MOCVD as an inline production process. Discussion is made based on kinetically limited growth and molar supply models to assess the suitability of the MOCVD process to deposit fast enough for an inline process. The AP-MOCVD inline reactor uses a showerhead to deliver the precursors onto a moving 5 × 7.5 cm2 substrate and preliminary results for deposited layers are given. From these preliminary results it has been extrapolated that a 1 μm thick CdTe layer can be deposited on substrates moving at 60 cm/min.
Enhancement of the Thermoelectric Figure of Merit in Gated Bismuth Telluride Nanowires
Authors: Bejenari Igor , Kantser Valeriu , Balandin Alexander 
Published: June 2009

AbstractWe theoretically studied how the electric filed effect can modify thermoelectric properties of intrinsic bismuth telluride nanowires, which are grown along [110] direction. The electronic structure and wave functions were calculated by solving the self-consistent system of the Schrodinger and Poisson equations by means of both the Thomas-Fermi approximation and the spectral element method. The thermoelectric parameters were determined using a constant relaxation-time approximation. The external electric field can increase the Seebeck coefficient of a nanowire with 7 - 15 nm lateral dimensions by nearly a factor of two, and enhance the figure of merit by an order of magnitude.
Melt-Textured Growth of Grain Aligned Bulk Oxide Thermoelectrics
Authors: Selvamanickam Venkat , Zhang Bo 
Published: June 2009

AbstractA new process, based on melt processing has been investigated with oxide thermoelectrics to achieve long-range grain alignment for low resistivity as well as to embed secondary phase precipitates and associated crystal defects for low thermal conductivity. Melt-processing of Bi2Sr2Co2Ox and CaMnO3 has been studied. A high degree of (00l) grain alignment has been achieved by melt processing. Good values of Seebeck coefficient of nearly -250 μV/K were measured in the melt-processed CaMnO3. Secondary phases of Ca4Mn3O10 and CaMn2O4 are found to be trapped between the aligned grains which led to high electrical resistivity values and limited the figure of merit in our initial samples.
Expanded 3D Electrode Architecture for Low Temperature Direct Liquid Fuel Cells
Authors: Urian Richard Craig 
Published: June 2009

AbstractThe US Navy continues to pursue electrochemical power sources with high energy density for low rate, long endurance undersea applications. The direct electro-oxidation and electro-reduction of sodium borohydride and hydrogen peroxide are being investigated to meet these goals. In an effort to minimize polarization losses and increase power density, a novel carbon microfiber array (CMA) electrode is being investigated.The CMA is composed of 750 micron long, 10 micron diameter graphite fibers that protrude from a current collector like blades of grass. The CMA was developed for the direct reaction of peroxide in the Mg-H2O2 semi fuel cell. [1] There, the high surface area of the microfiber cathode reduces peroxide concentration polarization, resulting in increased power and energy density. For this work the CMA architecture was adapted into a novel membrane electrode assembly and evaluated in the direct BH4- / H2O2 fuel cell. The unique feature of this architecture vs. traditional membrane electrode assemblies (MEAs) is how all three components of the triple boundary interface are optimized: electrical connectivity, ionic connectivity and mass transport. The current iteration of this electrode architecture utilizes a carbon cloth that has been hot pressed into N115 membrane. This component is then placed over the CMFA electrode. The carbon microfibers of the CMFA protrude up into the carbon cloth matrix forming a 3-dimewnsional, interdigitated electrode architecture. The result of this modification is improved electrolyte flow through the CMFA and improved utilization of the surface area afforded by the carbon microfibers that was not observed in the non modified CMFA.
Half cell polarization measurements were obtained simultaneously with the fuel cell polarization. Initial results using this modified CMFA electrode architecture show that the polarization losses observed for both the reduction of hydrogen peroxide and for the oxidation of borohydride were 5.2 times lower than for the non-modified CMAs electrode (0.014 ohms vs. 0.074 ohms). Comparing these results to those calculated from the literature [2, 3], where traditional membrane electrode assemblies were used for borohydride oxidation, 5 and 2.6 time improvements were obtained (0.07 ohms and 0.037 ohms were the effective resistive losses seen in the anode half cell polarizations).
Design of 3-dimensional Textured Organic Solar Cells
Authors: Nalwa Kanwar Singh , Chaudhary Sumit 
Published: June 2009

AbstractOrganic materials are attractive for photovoltaics primarily because of the prospect of high throughput solution-processible manufacturing using roll-to-roll or spray deposition. In the formation of polymer based photovoltaic devices, the aspect that limits the power conversion efficiency is the bottleneck between short diffusion lengths of the excited states (excitons) in polymers, in the range of 10-20 nm. Optical absorption length, which is in the range of 50-200 nm and much larger than the exciton diffusion length, poses the limit on charge generation and collection. It is important to achieve complete optical absorption in active layers much thinner than optical absorption length to minimize losses due to recombination of charge carriers. Previously, light trapping techniques have been coupled with organic solar cell but without significant success. In this paper, three-dimensional sub micron grating structure is analyzed using finite element method (FEM) simulations for finding the optical absorption in different layers of solar cell to optimize the photonic concentrator effect of the grating structure. The energy dissipation of electromagnetic field in the active layer is studied as a function of active layer thickness, grating pitch and height. The superiority of grating structure in terms of light trapping feature as compared to planar geometry is clearly demonstrated by simulation results.
Deformation Mapping in Micro- and Nanoscale Fibers
Authors: Garman Christina , Bindert Natalie , Sunkara Adhira , Paliulis Leocadia , Ebenstein Donna M 
Published: June 2009

AbstractSmall-scale natural fibers are among the biological materials being studied by researchers seeking innovative methods to create new high performance materials. For example, spider dragline silk fibers are being studied because of their unique combination of high strength-to-weight ratio and high extensibility, which leads to a tough and lightweight fiber. Biomimetic fibers based on spider silk have been a focus of research for the past decade. However, there are still many unanswered questions about the mechanisms by which silk achieves its unique mechanical properties, as well as challenges in mechanical testing of biomimetic silk fibers (which is often hindered by both small diameters and limited material availability). A method to characterize local mechanical behavior in small diameter fibers was developed to both improve understanding of structure-property relationships in natural fibers and provide a method for comparing mechanical behavior in natural and biomimetic fibers. The deformation mapping technique described in this paper, which utilizes a piezoelectric micromanipulator with pulled glass tips, an inverted microscope with attached camera, and an image processing MATLAB program, is also applicable to the characterization of other micro- and nanoscale fibers where local deformation mechanisms may be of interest (e.g., for mechanical characterization of electrospun fibers).
Nano-meter scale plasticity in KBr studied by nanoindenter and force microscopy
Authors: Manimunda Praveena , Filleter Tobin , Egberts Philip , Jayaram Vikram , Biswas Sanjay Kumar , Bennewitz Roland 
Published: June 2009

AbstractThe early stages of plasticity in KBr single crystals have been studied by means of nanometer-scale indentation in complementary experiments using both a nanoindenter and an atomic force microscope. Nanoindentation experiments precisely correlate indentation depth and forces, while force microscopy provides high-resolution force measurements and images of the surface revealing dislocation activity. The two methods provide very similar results for the onset of plasticity in KBr. Upon loading we observe yield of the surface in atomic layer units which we attribute to the nucleation of single dislocations. Unloading is accompanied by plastic recovery as evident from a non-linear force distance unloading curve and delayed discrete plasticity events.
Nacre Evolution : A Proteomic Approach
Authors: Marie Benjamin , Le Roy Nathalie , Marie Arul , Dubost Lionel , Milet Christian , Bedouet Laurent , Becchi Michel , Zanella-Cléon Isabelle , Jackson Daniel , Degnan Bernard , Luquet Gilles , Marin Frederic 
Published: June 2009

AbstractFrom an evolutionary viewpoint, the molluscan nacre constitutes a fascinating object. This microstructure appeared early, in the Lower Cambrian period, about 530 million years ago, and since then, has been kept unchanged until today. Nacre is restricted to the conchiferan mollusks, where it occurs in t least three main classes, bivalves, gastropods and cephalopods. The aim of the present study is to investigate whether all nacres are built from the same “macromolecular tools”, proteins of the nacre matrix. To this end, we studied three new nacre models, the freshwater bivalveUnio pictorum, the cephalopodNautilus macromphalus, and the gastropodHaliotis asinina, to which we applied a combined biochemical and proteomic characterization of their respective nacre matrices. The results of our approach, that can be defined as “shellomics” (proteomics applied to shell proteins) shed a new light on the macroevolution of nacre matrix proteins and on the in vitro design of nacre-like biomaterials.
Circumferential Arc-Shaped Microcracks in Haversian Bone: Lead-Uranyl Acetate Staining for Micro-CT Imaging
Authors: Ebacher Vincent , Wang Rizhi 
Published: June 2009

AbstractDespite much progress in recent years, the nature of microcracking in bone at the nano-meter scale is still not well understood. This is partly due to the complexity of bone's hierarchical structure, but also to the difficulty of detecting cracks at very fine scales. Bone microcracking is typically detected using fluorescent dye staining techniques followed by optical or laser microscopy examinations. However, fluorescence-based methods are limited to sub-micron resolution and do not fit three-dimensional imaging such as micro-CT or high resolution imaging such as electron microscopy. This pilot study explores the potential of a heavy metal staining technique to label nano-sized cracks in bone that could be detected by electron microscopy and, albeit at a larger scale, by micro-computed tomography. Upon further development, the method described here may lead to the nano-meter scale characterization of bone microcracking.
A New Multilayered Composite Bioceramic for Bone Graft
Authors: Arias JoséIgnacio , Neira-Carrillo Andrónico , Yazdani-Pedram Mehrdad , Fernandez Maria Soledad , Arias Jose 
Published: June 2009

AbstractBone grafts need to comply with some criteria of biocompatibility, including favoring neovascularization, new bone formation, and discourage inflammatory response and graft rejection. It is also expected that these materials should have mechanical properties similar to those of natural bone, that is, having enough pores to permit osteoprogenitor cells and vascular endothelium penetration but maintaining strength and flexibility.Here, a new resistant and flexible tridimensional multilayered bioceramic composite was obtained by using chitosan and hydroxyapatite in combination with cells and their associated growth factors from the bone marrow tissue, allowing the development of a biocompatible bone graft.This multilayered graft made out of chitosan functionalized with phosphate groups and mineralized with calcium phosphate (hydroxyapatite) was analyzed with scanning electron microscopy (SEM), X ray diffraction (XRD), energy dispersive X-ray analysis (EDX) and Fourier transform infrared spectroscopy (FTIR) to assess the degree of phosphorylation and the amount of hydroxyapatite present in the graft. The composite was further characterized by mechanical testing (Vicker's microhardness test), in vitro osteoblasts culture citotoxicity tests.The results showed that this multilayered graft has mechanical properties comparable to that of trabecular bone and it was capable to keed osteogenic cells alive.
Mechanical Properties of Sintered and Non Sintered Stainless Steel Wools: Experimental Investigation and Modelling
Authors: Masse Jean-Philippe , Bouaziz Olivier , Bréchet Yves , Salvo Luc 
Published: June 2009

AbstractEntangled fibrous materials have a common point with cellular solids: the architecture is at the millimetric scale. However, they present one extra degree of freedom which is the connectivity on the constituents: while compressing a fibrous structure, the number of contacts between fibers is variable, by contrast to cellular solids where the building lock is the cell. In this respect, fibrous entangled solids can span a whole range of mechanical behavior depending on the possibility offered to fibers to create new contacts: from the felt where they are totally free, to the fully sintered wool where their relative motion is constrained by irreversible contacts.
The purpose of this paper is to investigate the mechanical properties of this class of materials, based on micro tomography observations for the number of contacts, and on a physically based model for fiber bending and collective reorganization. The material studied is a stainless steel wool. The properties investigated are the loading curves for sintered and non sintered wools. Qualitative differences introduced by sintering motivate a modification of the classical Toll model, which will be presented together with the experimental results.
Anisotropic Clay Aerogel Composite Materials
Authors: Gawryla Matthew D , Schiraldi David A. 
Published: June 2009

AbstractClay aerogel composites have been around for over 50 years but still they represent a relatively under studied class of materials. Clay aerogel composites have been made in our labs that have low densities, 0.05-0.1g/cm3, provide good thermal insulation, k 0.02W/mK, and are created through an environmentally benign process. The mechanical properties of the composites resemble those of typical foamed polymers such as expanded polystyrene and polyurethane, with compressive moduli ranging from 0.5MPa to 40MPa depending on composition. Aqueous solutions of clay and polymer are frozen in cylindrical molds and freezedried to create these foam-like materials. Typically there is no particular orientation to the often layered structure that results, however if frozen in a unidirectional manner, anisotropic materials can be made. In this paper we will discuss the effects of molecular weight on mechanical properties of various composites as well as discussing the orientated layered structure within the anisotropic materials.