bluuebunny/crossref_metadata_2025_split huggingface dataset:
Changes in Surface Mechanical Properties Through Electrochemical Modifications
Authors: McCann Martha M. , Corcoran Sean G. 
Published: April 2011

AbstractThe mechanical response of materials can be dramatically altered by the presence of absorbed species on the surface. An electrochemical environment enables discrete control of the surface, keeping it clean (comparable to ultra-high vacuum) and inducing stable stress states. Applying a potential to the surface alters surface charge, which changes the surface free energy. Oxides are easily added or removed. Utilizing the phenomenon of underpotential deposition (UPD), one monolayer of metal can be added to a surface. The degree of lattice mismatch between the metal and the deposited monolayer will also vary the stress state of the surface. The changes in the mechanical properties of these highly controlled surfaces are measured by in-situ nanoindentation at various potentials. Nanoindentation of single crystals with very low dislocation densities allows careful observation of dislocation behavior with applied load. This enables the identification of dislocation mechanisms by quantifying the changes in mechanical properties under specific environments. Au has been extensively studied in electrochemistry literature; it is well behaved and well characterized. It is a model system that has demonstrated variation in mechanical properties in different electrochemical states. Lessons learned on Gold have also been applied to Zn and Ni systems.
Functionally Graded CVD Mullite Coatings
Authors: Basu Soumendra N. , Sarin Vinod K. 
Published: April 2011

AbstractFunctionally graded mullite (3Al2O3.2SiO2) coatings were deposited on SiC substrates by Chemical Vapor Deposition (CVD) using the AlCl3-SiCl4-CO2-H2 system. It was found that due to preferential adsorption, coatings on SiC started off being Si-rich, while coatings on alumina substrates started out being Al-rich. In either case, if the coating composition was not close to stoichiometric mullite, the microstructure consisted ofg-Al2O3 nanocrystallites imbedded in a vitreous SiO2-rich matrix (nanocrystalline microstructure). On grading the composition, mullite grains nucleated when the composition of the growing nanocrystalline coatings reached a narrow surface composition range of Al/Si molar ratio of 2.9-3.4. Once nucleated, columnar mullite grains could be graded to highly nonstoichiometric Al-rich compositions. However, if the nucleated mullite grains were graded to be Si-rich, the mullite structure could not be sustained, and the coating reverted back to the nanocrystalline microstructure. This phenomenon is explained on the basis of the linkage of coordination polyhedra in the atomic structure of mullite.
Relationships between the structural, chemical, and mechanical properties of Si-aC:H thin films
Authors: Evans Ryan D. , Doll Gary L. , Morrison Philip W. , Bentley James , More Karren L. , Glass Jeffrey T. 
Published: April 2011

AbstractSilicon-incorporated amorphous hydrocarbon (Si-aC:H) films with varying Si contents were deposited onto a Ti interlayer on Si and steel substrates by reactive sputtering in an unbalanced magnetron sputtering system. The objective of this study was to measure and relate the structural, chemical, and mechanical properties of these Si-aC:H films. Transmission electron microscopy revealed that the Si-aC:H phase is amorphous and TiC exists at the Si-aC:H/Ti phase boundary for all compositions. Mechanical properties such as hardness, indentation modulus, and intrinsic stress decreased with increasing Si and H content in the films, for Si/C ≥ 0.04. XPS measurements suggested that this is most likely due to the decreasing presence of a C-C sp3 interlinked network, accompanied by an increase in C-H and Si-H bonds. This conclusion was supported by radial distribution functions obtained using extended electron energy-loss fine structure analysis (EXELFS).
The Structures of Copper-Doped Carbon Aerogels Prepared by an Ion Exchange Method
Authors: Yoshizawa Noriko , Fu Ruowen , Dresselhaus Mildred S. , Dresselhaus Gene , Satcher Joe , Baumann Ted 
Published: April 2011

AbstractAbstract -- The copper-doped carbon aerogels were fabricated by ion exchange method. Their structures were investigated by surface area detection, TEM, SEM and XPS. The experimental results showed that the copper-doped carbon aerogels produced have low mass density, a high density of nano-pores and high surface areas. Many copper nano-particles were produced after carbonization of copper-doped carbon aerogels. Before carbonization, part of the copper atoms were reduced into low valence compounds, such as Cu2O.
Nanoscale Electrochemical Deposition of Metals on FIB Sensitized p-Type Silicon
Authors: Spiegel Adrian , Döbeli M. , Schmuki Patrik 
Published: April 2011

AbstractSub-micrometer copper nanostructures were deposited on p-type silicon (p-Si) by means of a selective electrochemical reaction. Ga+-ions from a focused ion beam (FIB) were used to 'write' damage patterns on p-Si; in a subsequent electrochemical reaction Cu was deposited selectively at these defect sites. So far we have been able to obtain Cu structures with a lateral resolution of 300nm, which is also the limit of the FIB currently used.The process may offer advantages over traditional lithographic methods for producing nanometer sized metal structure on Si as no masking steps are required. Also, structures with a lateral resolution in the sub- 100nm region seem possible; so far the process has only been limited by the FIB's lateral resolution.
Effects of Mask Materials on Near Field Optical Nanolithography
Authors: McNab Sharee J. , Blaikie Richard J. 
Published: April 2011

AbstractSimulations have been performed to study the effects of different masking materials (Cr, Au, W and Si) on near field optical contact lithography. For near field amplitude masks it is found that Cr is an excellent material at blue/UV wavelengths, due to its small skin depth. Au is too transmissive to be considered. W has a small skin depth like Cr, although its dielectric behaviour at blue/UV wavelengths leads to image reversal phenomena that may be undesirable. Image reversal is even more pronounced for Si. For Evanescent Interferometric Lithography (EIL) - a technique that relies on surface-plasmon-induced resonant enhancement of the evanescent fields beneath a grating - Cr and W are again superior to Au, and significant intensity enhancements are predicted beyond the grating cutoff. For Si the resonant enhancements can be very large and narrow band, which may be of great advantage. For example, near field exposure intensity approximately 100 times the incident intensity is predicted for a 270 nm period silicon grating illuminated at a wavelength less than 10 percent higher than cutoff.
Design, Synthesis and Electrospinning of a Novel Fluorescent Polymer for Optical Sensor Applications
Authors: Lee Soo-Hyoung , Ku Bon-Cheol , Wang X. , Samuelson L.A. , Kumar J. 
Published: April 2011

ABSTRACTThis work describes the synthesis and electrospinning of new fluorescent polymers and their use for the fabrication of optical chemical sensors. A new fluorescent monomer was first synthesized by coupling reactions between methacryloyl chloride and a pyrene derivative, 1-pyrene butanol. Fluorescent polymers containing pyrene molecules were then obtained by the copolymerization of this monomer with methylmethacrylate using 2,2'-azobisisobutyronitrile as the initiator. These polymers show distinct and well-defined fluorescence that is characteristic of the pyrene chromophores. Electrospinning was used to process these polymers into high surface area nanofibrous membranes for optical sensing. The resulting membranes show a high sensitivity to 2,4-dinitro toluene based on the fluorescence quenching of the pyrene chromophores. Fluorescence intensities decreased with increasing concentration of the 2,4-dinitro toluene. The quenching behavior follows Stern-Volmer bimolecular quenching kinetics. The synthesis, characterization, electrospinning fabrication, and sensing capability of these polymers will be discussed.
Reductive photopatterning of phenylene-vinylene-based polymers
Authors: Kavc T. , Langer G. , Kern W. , Ruplitsch A. , Mahler K. , Stelzer F. , Hayn G. , Saf R. , List E.J.W. , Zojer E. , Ahmed M. T. , Pogantsch A. , Iskra K.F. , Neger T. , Hörhold H.-H. , Tillmann H. , Kranzelbinder G. , Toussaere E. , Jakopic G. 
Published: April 2011

ABSTRACTPhotochemical methods were developed to obtain a variation of the refractive index in aromatic polymer surfaces and a change in the photoluminescence characteristics of phenylenevinylene-based polymers. Films of aromatic polymers, among them polystyrene (PS), poly(2-vinylnaphthalene) (PVN) and derivatives of poly(p-phenylene-vinylene) (PPV) were UV irradiated in the presence of gaseous hydrazine (N2H4). The photoreaction led to a strong reduction of the refractive index of the polymers due to a hydrogenation of the aromatic units. In the case of PPV, we observed reductive photobleaching. This new technique was employed to produce photogenerated patterns in PPV. The results are compared to oxidative bleaching.
Singlet and Triplet Energy Transfer in Phosphorescent Dye Doped Polymer Light Emitting Devices
Authors: Noh Yong-Young , Lee Chang-Lyoul , Lee Hae Won , Cho Hyun-Nam , Kim Jang-Joo 
Published: April 2011

ABSTRACTEffect of host polymers on energy transfer in phosphorescent dye doped polymer light emitting devices has been investigated. Poly (N-vinylcarbazol) [PVK] and poly (9,9'-di-n-hexyl-2,7-fluorene-alt-1,4(2,5dinhexyloxy) phenylene) [PFHP] were examined as the host materials for the phosphorescent dyes fac tris(2-phenypyridine) irdium(III) [Ir(ppy)3] and 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrin platinum(II) [PtOEP]. The host and guest materials have the large spectrum overlap between the emission of the hosts and absorption of the guests. When the guests were doped in PVK, the singlet-singlet and triplet-triplet energy transfer took place efficiently. On the contrary, the energy transfer did not take place from φ-conjugated polymer PFHP to the guests, even though common requirements for Förster and Dexter energy transfer were fulfilled. Host aggregation in PFHP based phosphorescent dye doped light emitting devices can play an undesired role obstructing efficient energy transfer.
Optoelectronic Junction Devices Based on Organic/Inorganic Hetero-paired Semiconductors
Authors: Schroeder R. , Ullrich B. 
Published: April 2011

ABSTRACTThe use of hybrid devices consisting of organic and inorganic semiconductors provides many advantages for optoelectronic applications, such as combining the high charge carrier mobilities in inorganic polycrystalline thin films and high photosensitivity, intense photoluminescence, and ease of deposition of conjugated molecules. In this paper, thin film hybrid structures based on organic conjugated molecules and II-VI inorganic semiconductors were fabricated using spin-coating, evaporation and pulsed-laser deposition (PLD), respectively. A promising hetero-pairing is CdS and DQP, a diisoquinoline perrylene derivate, with the potential to form sensitive photodiodes and effective solar cells. Varying the deposition techniques alters the quality of the interface between CdS and DQP and results in different efficiencies of charge collection and recombination in the device.
Rational Design of Organic Electro-Optic Materials
Authors: Jen Alex , Neilsen Robert , Robinson Bruce , Steier William H. , Dalton Larry 
Published: April 2011

ABSTRACTA number of material properties must be optimized before organic electro-optic materials can be used for practical device applications. These include electro-optic activity, optical transparency, and stability including both thermal and photochemical stability. Exploiting an improved understanding of the structure/function relationships, we have recently prepared materials exhibiting electro-optic coefficients of greater than 50 pm/V and optical loss values of less than 0.7 dB/cm at the telecommunication wavelengths of 1.3 and 1.55 microns. When oxygen is excluded to a reasonable extent, long-term photostability to optical power levels of 20 mW has been observed. Photostability is further improved by addition of scavengers and by lattice hardening. Long-term (greater than 1000 hours) thermal stability of poling-induced electro-optic activity is also observed at elevated temperatures (greater than 80°C) when appropriate lattice hardening is used. The successful improvement of organic electro-optic materials rests upon (1) attention to the design of chromophore structure including design to inhibit unwanted intermolecular electrostatic interactions and to improve chromophore instability and (2) attention to processing conditions including those involved in spin casting, electric field poling, and lattice hardening. A particularly attractive new direction has been the exploitation of dendrimer structures and particularly of multi-chromophore containing dendrimer structures. This approach has permitted the simultaneous improvement of all material properties. Development of new materials has facilitated the fabrication of a number of prototype devices and most recently has permitted investigation of the incorporation of electro-optic materials into photonic bandgap and microresonator structures. The latter are relevant to active wavelength division multiplexing (WDM). Significant quality factors (greater than 10,000) have been realized for such devices permitting wavelength discrimination at telecommunication wavelengths of 0.01 nm.
Low-loss Polymer Optical Waveguides with High Thermal Stability
Authors: Kang Jae-Wook , Kim Jae-Pil , Lee Won-Young , Kim Joon-Sung , Lee Jae-Suk , Kim Jang-Joo 
Published: April 2011

ABSTRACTWe synthesized novel cross-linkable fluorinated copoly(arylene ether sulfide)s for optical waveguide applications, which have high thermal stability, high optical transparency in the infrared communication region, and much smaller birefringence than other thermally stable fluorinated polyimides. The refractive index of the material can be easily controlled from 1.515 to 1.587 by changing the copolymer composition in the materials. The birefringence of the cured polymers were 0.0031∼0.0039 at the wavelength of 1.55 μm. This is much lower than those of fluorinated polyimides for optical waveguides. The refractive index of fluorinated poly(arylene ether sulfide) (FPAESI) after being stored at 100 °C for 1000 hr remains almost constant demonstrating the thermal stability. The propagation loss of the channel waveguides fabricated using reactive ion etching was less than 0.4 dB/cm at the wavelength of 1.55 μm.
Hybrid active polymer/silica microstructured photonic crystal optical fibers
Authors: Eggleton B. J. , Kerbage C. 
Published: April 2011

ABSTRACTWe review several applications of microstructured photonic crystal optical fibers that incorporate active materials infused into the air-holes. The tunable optical characteristics of the materials combined with the unique structure of the fiber enable a number of functionalities including reconfigurability and tunability for various fiber device applications. We describe a brief characterization of the modes and discuss the experimental results of the fibers.
XRD, SEM and TEM Study of the Gd-Doped Zirconolites
Authors: Stefanovsky Sergey V. , Troole Albert Y. , Lapina Maria I. , Nikonov Boris S. , Sivtsov Anatoliy V. , Yudintsev Sergey V. 
Published: April 2011

ABSTRACTCeramic samples with formulations Ca1-xGdxZrTi2-xAlxO7(0 ≤ x ≤1) were prepared by cold pressing in pellets at 200 MPa followed by their sintering at either 1400 or 1500 °C for 5 hours. All the samples produced were single phase with rare grains of cubic zirconia based solid solution in the samples with high Gd and Al contents (x = 0.9 and 1.0). The samples produced at 1500 °C were more homogeneous and less porous than the samples sintered at 1400 °C. From SEM/EDS data average compositions of zirconolite in the samples are very close to specified formulation (within experimental error), for example, the zirconolite formula in the ceramic with x = 1 was found to be Gd1.04Zr1.02Ti1.07Al0.85O7. XRD and TEM patterns showed monoclinic (2M) structure for zirconolites, which transforms to higher symmetry modification within 0 ≤ x ≤ 0.5 compositional range. Zirconolite with high Gd content x →1 forms two varieties with trigonal and orthorhombic structure.
Performance Assessment of Low-Level Waste Disposal Facilities Using Coupled Unsaturated Flow and Reactive Transport Simulators
Authors: Bacon Diana H. , McGrail B. Peter , Freedman Vicky L. , Ventura Giancarlo , Risoluti Piero , Krupk Kenneth M. 
Published: April 2011

ABSTRACTRecent advances in the development of reactive chemical transport simulators have made it possible to use these tools in performance assessments (PAs) for nuclear waste disposal. Reactive transport codes were used to evaluate the impacts of design modifications on the performance of two shallow subsurface disposal systems for low-level radioactive waste. The first disposal system, located at the Hanford site in Richland, Washington, is for disposal of lowlevel waste glass. Glass waste blocks will be disposed in subsurface trenches, surrounded by backfill material. Using different waste package sizes and layering had a small impact on technetium release rates to the vadose zone. The second disposal system involves a hypothetical repository for low-level waste in Italy. A model of uranium release from a grout waste form was developed using the STORM reactive transport code. Uranium is predicted to be relatively insoluble for several hundred years under the high-pH environment of the cement pore water. The effect of using different filler materials between the waste packages on uranium flux to the vadose zone proved to have a negligible impact on release rates.
Evaluating Cladding Creep during Dry Storage and Repository Emplacement
Authors: Siegmann Eric , Macheret Pierre 
Published: April 2011

ABSTRACTCreep strain has been identified as the dominant failure mode for commercial spent nuclear fuel cladding during dry storage, including the vacuum drying phase. It could also be important during the early period of repository closure. A statistical analysis of creep failure during these three phases was performed. Statistical analysis is an important tool for predicting fuel behavior and the distributions can be modified for specific applications. A burnup distribution (rod average = 44 MWd/kgU, range = 2 to 75 MWd/kgU) was assumed and a distribution of rod properties, including stress was developed. The Murty creep correlation was selected after comparing six different correlations with results from five different experiments. It was then modified to better predict irradiated cladding creep data. Creep failure criteria is a Complementary Cumulative Distribution Function (CCDF) based on 52 failure tests. The fuel rods are exposed to three consecutive temperature histories that are typical of what is to be expected: 24 hours of vacuum drying, 20 years dry storage, and 1000 years of repository thermal history. Each phase has a peak temperature, treated as an independent variable, and temperature history taken from the literature. Uncertainties in the temperatures and strain rate are included. The radial temperature distribution across the waste package is also modeled. For the first phase, vacuum drying, rod failures start to occur at about 550°C and exceed 1% failure at 600°C. With a peak vacuum drying temperature of 430°C, rods begin to fail during dry storage when the peak temperature reaches 400°C and approached a 1% failure level at 450°C. With representative peak temperatures of 430°C for drying and 350°C for dry storage, rod failures start to occur during repository closure at a peak cladding temperature of 390°C. They reached 1% at about 430°C. In the current repository design, the cladding temperatures are below 210°C and rod failures from creep are not expected
FTIR Characterization Of PZT Nano Fibers Synthesized from Metallo-organic Compounds Using Electrospinning
Authors: Wang Yu , Santiago-Avilés Jorge J. 
Published: April 2011

ABSTRACTWe have synthesized Pb(Zr0.54Ti0.48)O3 fibers with diameter ranging from 500 nm to several microns using electrospinning and metallo-organics decomposition (MOD) techniques. By a refinement of our electrospinning technique, i.e. by increasing the viscosity of the precursor solution, and by adding a filter to the tip of the syringe, the diameter of synthesized PZT fibers has been reduced to the neighborhood of a hundred nanometers. The complex thermal decomposition was characterized using Fourier-transform infrared (FTIR) spectroscopy and x-ray diffraction (XRD). It was found that alcohol evaporated during electrospinning and that the organic groups had pyrolized before the intermediate pyrochlore phase was formed. There is a good correspondence between XRD and FTIR spectra. It was also found that a thin film of platinum coated on silicon substrate surface not only seems to have catalyzed the phase transformation to PZT but also favored the formation of 110 texture in the synthesized PZT fibers.
Initial Development of a Portable Acoustic Array on a Large-Scale E-Textile Substrate
Authors: Luthy K. A. , Mattos L. S. , Braly J. C. , Grant E. , Muth J. F. , Dhawan A. , Natarajan K. , Ghosh T. , Seyam A. 
Published: April 2011

ABSTRACTElectronic textiles offer possibilities for producing large-area sensors circuits on conformal substrates. To demonstrate this concept, a 5×4 element acoustic array was produced on a 3m × 1m fabric substrate. In the course of fabricating the acoustic array a variety of production issues were identified that impacted the performance of the prototype when experimental tests were carried out with this prototype acoustic array. Fabric-based acoustic array design and production, along with design issues related to scaling an acoustic array to handle larger numbers of microphones on large-area fabrics, are the focus of this paper.
Resonant photoluminescence and excitation spectroscopy of CdSe/ZnSe and CdTe/ZnTe self-assembled quantum dots
Authors: Nguyen T. A. , Mackowski S. , Rho H. , Jackson H. E. , Smith L. M. , Wrobel J. , Fronc K. , Kossut J. , Karczewski G. , Dobrowolska M. , Furdyna J. 
Published: April 2011

ABSTRACTWe show that two major carrier excitation mechanisms are present in II-VI self-assembled quantum dots. The first one is related to direct excited state – ground state transition. It manifests itself by the presence of sharp and intense lines in the excitation spectrum measured from single quantum dots. Apart from these lines, we also observe up to four much broader excitation lines. The energy spacing between these lines indicates that they are associated with absorption related to longitudinal optical phonons. By analyzing resonantly excited photoluminescence spectra, we are able to separate the contributions from these two mechanisms. In the case of CdTe dots, the excited state – ground state relaxation is important for all dots in ensemble, while phonon-assisted processes are dominant for the dots with smaller lateral size.