bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Implications of Fossil Fuel Combustion for Climate Change
Authors: Ross Kristy Eileen , Piketh Stuart J. 
Published: April 2011

ABSTRACTEmissions from fossil fuel combustion alter the composition of the atmosphere and have been touted as a major cause of climate change. The amount of carbon dioxide in the atmosphere, for example, has increased by more than 30% since pre-industrial times. Average global surface temperature has increased by approximately 0.6 ± 0.2°C since the late 19th Century, and surface temperature records indicate that the 1990s are likely to have been the warmest decade of the last millennium. The anthropogenically-induced warming is superimposed on natural climatic variability. Proxy records show a regular oscillation, on a roughly 100,000-year cycle, between glacials and interglacials. Superimposed on these long-term oscillations are shorter scale variations. It is thought that changes in the seasonality and location of radiation from the Sun trigger the onset or end of glaciation, and the change is then amplified by feedbacks in the earth-atmosphere system. A firm link between atmospheric composition and temperature has been established from ice core records spanning the last 420,000 years, which show that changes in time of global temperature and atmospheric concentrations of carbon dioxide and methane are tightly coupled. Global average surface temperature is projected to increase by between 1.4 and 5.8°C by 2100, with the warming being greatest over land and polar regions. Precipitation is predicted to increase in the tropical, mid- and high-latitude regions, but to decrease in the subtropical regions. Alternative energy technologies such as hydrogen fuel cell vehicles will lower greenhouse gas emissions and reduce climate problems and costs.
Ion Irradiation Effects of Yttria-stabilized Zirconia Conductivity
Authors: Cheng Jeremy , Crabb Kevin , Pornprasertsuk Rojana , Huang Hong , Saito Yuji , Prinz Fritz B 
Published: April 2011

ABSTRACTThe performance of solid oxide fuel cells is limited largely by ion transport in the electrolyte. Thin film electrolytes of yttria-stabilized zirconia were deposited by pulsed laser deposition. The electrolyte material was subjected to heavy ion irradiation and heat treatment and the effects on conductivity were measured using electrical impedance spectroscopy. Following irradiation there is a drop in conductivity by a factor of 3-4. After heat treatment at 800°C, the conductivity recovers to the as-deposited value.
Core-Shell Nanorods for Efficient Photoelectrochemical Hydrogen Production
Authors: Yu Z. G. , Pryor C. E. , Lau W. H. , Berding M. A. , MacQueen D. B. 
Published: April 2011

ABSTRACTWe propose core-shell InP-CdS and InP-ZnTe nanorods as photoelectrodes in the efficient photoelectrochemical hydrogen production. Based on our systematic study using strain-dependent k.p theory, we find that in these heterostructures both energies and wave-function distributions of electrons and holes can be favorably tailored to a considerable extent by exploiting the interplay between quantum confinement and strain. Consequently, these core-shell nanorods with proper dimensions (height, core radius, and shell thickness) can simultaneously satisfy all criteria for effective photoelectrodes in solar-based hydrogen production.
Large Area Depositions of Si/SiC Quantum Well Films for Thermoelectric Generator Applications
Authors: Yu Tianhua , Efstathiadis Harry , Matyi Richard , Haldar Pradeep , Ghamaty Saeid , Elsner Norbert 
Published: April 2011

ABSTRACTRecent development in thermoelectric conversion, especially in the area of quantum well (QW) thin film materials, have demonstrated the potential to achieve the high efficiency and power density to fabricate future power supplies. In this study, we develop the large area QW films of N-type Si/SiC integrated with P-type B4C/B9C, which can be used as thermoelectric devices for waste heat recovery. The approach is to fabricate thick large area film stacks (up to 11 μm) deposited by sputter deposition technique on 6” n-type (100) silicon substrates, which might be proven to be a suitable method for potentially manufacturing large area thermoelectric devices in a cost effective manner. These more basic studies are being carried out to better understand variables such as film thickness, deposition rate and other important parameters of these ∼10 nm films. The resulting as deposited and annealed multilayer stacks were characterized in terms of thin film uniformity, thickness, growth rate, composition, and thermoelectric performance, by Spectroreflectometry, atomic force microscopy (AFM), Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), X-ray reflectivity (XRR), and electrical measurements. Issues, which could cause film stack degradation, such as interface layer formation, film delamination, and crack formation lowering the device performance will be presented and correlated to device efficiency.
Energy-specific equilibrium in nanowires for efficient thermoelectric power generation
Authors: Linke Heiner , Humphrey Tammy , O'Dwyer Mark 
Published: April 2011

ABSTRACTThere is great scientific, economic and environmental interest in the development of thermoelectric materials capable of direct thermal-to-electric energy conversion with high efficiency. Recent theory predicts that in materials with a fine-tuned electronic density of states, electrons can be placed in energy-specific equilibrium, and the efficiency of thermoelectric power generation can approach the fundamental Carnot limit. Here we review the relevant theory of energy-specific equilibrium. We describe a concept for a proof-of principle demonstration of near-Carnot efficient power conversion involving a single, ballistic nanowire at low temperatures, and we discuss the potential for room-temperature applications in diffusive materials.
Substitutions in the Homologous Family CsPbmBi3Te5+m and Preliminary Thermoelectric Results
Authors: Guéguen Aurélie , Quarez Eric , Kanatzidis Mercouri G. 
Published: April 2011

ABSTRACTWe report analogs of the homologous family CsPbmBi3Te5+m, namely Cs0.74K0.76Bi3.5Te6, CsNa0.98Bi4.01Te7, Cs0.69Ca0.65Bi3.34Te6, Rb0.82Pb0.82Bi3.18Te6, Rb0.19K1.31Bi3.50Te6, RbSnBi3Te6, Rb0.94Ca0.94Bi3.06Te6 and RbYbBi3Te6. They all crystallize in the orthorhombic space group Cmcm and are isostructural to CsPbBi3Te6 the first member of the family except for CsNa0.98Bi4.01Te7 which is isostructural to CsPb2Bi3Te7, the second member of the family. Preliminary thermoelectric measurements on Cs0.76K0.74Bi3.5Te6 show electrical conductivity values in the range of 600-1000 S/cm. The thermopower shows n-type charge transport with room temperature values of ∼ -35 µV/K. By comparison, the electrical conductivity at room temperature of Rb0.82Pb0.82Bi3.18Te6 was ∼1400S/cm, while the thermopower was ∼ -20 µV/K.
Transport Properties of Type II Sodium-Silicon Clathrates
Authors: Beekman Matt , Grkyo Jan , Nolas George S. 
Published: April 2011

ABSTRACTWe have synthesized the type II silicon clathrates Na1Si136 and Na8Si136, and report on the electrical and thermal transport in these materials. The crystal structure consists of a covalently bonded silicon framework in which sodium guest atoms are encapsulated inside the silicon host framework. Differential scanning calorimetry measurements show the compounds decompose above 600°C to diamond-structure silicon. Temperature dependant electrical resistivity measurements show the specimens to have an insulating character, with magnitudes that decrease with increasing sodium content. For the first time, thermal conductivity measurements on type II sodium-silicon clathrates are presented. The thermal conductivity is very low for both specimens, and for Na8Si136 exhibits a clear dip in the range from 50 to 70 K. These data suggest that the “rattling” behavior observed in type I clathrates may also be present in type II clathrates.
Thermoelectric properties of polycrystalline Si1-xGex grown by die-casting vertical Bridgman growth technique
Authors: Baba Takashi , Iida Tsutomu , Hirahara Hisashi , Itoh Takashi , Akasaka Masayasu , Takanashi Yoshifumi 
Published: April 2011

ABSTRACTThe die-casting growth process combined with an advanced version of the Bridgman method was employed for manufacturing the multicrystalline bulk crystal of Si1−xGex. This process provides a form of phase transformation which is completely different from that predicted by the Si-Ge phase diagram. By combining this growth with subsequent heat treatment of the precipitated sample, the variation in the germanium content obtained was within ± 4 % for Si0.65Ge0.35 sample with a carrier concentration in the mid-1018 cm−3. The power factor obtained exhibited a quite flat characteristic over the temperature range of room temperature to 800 K. However, there was a drop in the Seebeck coefficient at about 800 K, which corresponded to a rise in the electrical conductivity. The value of the thermal conductivity was about 0.04 W/cmK at temperatures ranging from 600 to 900 K. The maximum value of the figure of merit obtained for the grown Si0.65Ge0.35 sample was 0.19 at 773 K.
400 element ErAs:InGaAs/InGaAlAs superlattice power generator
Authors: Zeng Gehong , Bahk Je-Hyeong , Bowers John E. , Zide Joshua M. O. , Gossard Arthur C. , Zhang Yan , Singh Rajeev , Bian Zhixi , Shakouri Ali , Kim Woochul , Singer Suzanne , Majumdar Arun 
Published: April 2011

ABSTRACTWe report the fabrication and characterization of thin film power generators composed 400 p- and n-type ErAs:InGaAs/InGaAlAs superlattice thermoelectric elements. The thermoelectric elements incorporate erbium arsenide metallic nanoparticles into the semiconductor superlattice structure to provide charge carriers and create scattering centers for phonons. 10 µm p- and n-type InGaAs/InGaAlAs superlattices with embedded ErAs nano-particles were grown on InP substrates using molecular beam epitaxy. Thermal conductivity values were measured using the 3ω method and cross-plane Seebeck coefficients were determined using Seebeck device test patterns. 400 element ErAs:InGaAs/InGaAlAs thin film power generators were fabricated from superlattice elements 10 µm thick and 200 µm × 200 µm in area. The output power was 4.7 milliwatts for an external electrical load resistor of 150 Ω at about 80 K temperature difference drop across the generator. We discuss the limitations to the generator's performance and provide suggestions for further improvement.
Surface Segregation in Multicomponent Clusters
Authors: Dowben Peter A. , Wu Ning , Palina Natalie , Modrow Hartwig , Müller Robert , Hormes Josef , Losovyj Yaroslav B. 
Published: April 2011

ABSTRACTNanostructured materials are not immune from surface segregation, as can be shown for solid samples made from nanosized BaFe12−2xCoxTixO19 barium ferrite particles and a variety of free clusters. Both theory and experiment provide ample demonstration that very limited dimensions of very small clusters does not necessarily impart stability against surface and grain boundary segregation. In fact, with the larger surface to volume ratio in small clusters and lower average atomic coordination, we anticipate that compositional instabilities in small clusters will readily occur.
Photo-oxidation of Multiwalled Carbon Nanotubes
Authors: Parekh B. , Debies Thomas , Knight Pam , Santhanam K. S. V. , Takacs Gerald A. 
Published: April 2011

ABSTRACTMWNTs were photo-oxidized in quartz boats using low-pressure Hg lamps and emission downstream from Ar microwave plasmas which are primarily atomic line sources of 253.7 and 184.9 nm UV, and 106.7 and 104.8 nm vacuum UV (VUV) radiation, respectively. X-ray photoelectron spectroscopy (XPS) showed rapid oxidation during the first hour of UV treatment and then an increase that was directly proportional to the time of treatment up to 4 h where the oxygen concentration was 7.5 at%. VUV photo-oxidation resulted in an oxygen concentration up to 9.5 at% with exposure time for the initial 2 h of treatment. Beyond 2 h, the oxygen concentration decreased with VUV exposure due to a larger rate of de-oxidation than oxidation at the surface. Curve fitting of the XPS C1s spectra revealed mainly the C-O-C functional group with the presence of C=O, O-C=O and O=C-O-C=O moieties. SEM micrographs showed no apparent effect on the structure or appearance of the MWNTs as expected for surface modification.
Degradation Phenomenon in Semiconductive Nanoamorphous Structures from Molybdenum Oxide
Authors: Markosyan A. , Kamanchadgyan Sergo , Malkhasyan Razmik 
Published: April 2011

ABSTRACTThe condition of degradation of electrical properties of samples prepared from powder of nanoamorphous semiconductive oxide in the course of time is discovered and studied when investigating electro-physical properties of the given materials for the first time synthesized at Scientific Production Enterprise “ATOM”. It has been shown that degradation phenomenon is also present in amorphous materials, which relies on the configuration of the pores of the sample.The resistance of sample in the open air changes over a period of several months. However, it decreases and is comparatively fast stabilized when placed in vacuum. The absorption and de-absorption of different gases have diffusion nature and highly depend on environment temperature. Water steam in atmosphere has been determined to be the main cause of degradation.
Superconductors in confined geometries
Authors: Xiao Zhili , Hor Yew-San , Welp Ulrich , Ito Yasuo , Patel Umesh , Hua Jiong , Mitchell John , Kwok Wai-Kwong , Crabtree George W. 
Published: April 2011

ABSTRACTThe synthesis of nanoscale superconductors with controlled geometries is extremely challenging. In this paper we present results on synthesis and characterization of one-dimensional (1D) NbSe2 superconducting nanowires/nanoribbons. Our synthesis approach includes the synthesis of 1D NbSe3 nanostructure precursors followed by nondestructive and controlled adjustment of the Se composition to formulate NbSe2. The morphology, composition and crystallinity of the synthesized 1D NbSe2 nanostructures were analyzed with scanning electron microscopy, x-ray diffraction and transmission electron microscopy. Transport measurements were carried out to explore the electronic properties of these confined superconducting nanostructures.
Simulation of Nanostructure Formation in Thin Polymer Films
Authors: Kim Dongchoul , Lu Wei 
Published: April 2011

ABSTRACTA thin polymer film subjected to an electrostatic field may lose stability at the polymer-air interface, leading to uniform self-organized pillars emerging out of the film surface. This paper presents a three dimensional dynamic model to account for the behavior. The coupled diffusion, viscous flow, and dielectric effect are incorporated into a phase field framework. Numerical simulations reveal rich dynamics of the pattern formation process and the substrate effect. The pillar size is insensitive to the film thickness, but the distance between pillars and the growth rate are significantly affected. The study suggests an approach to control structural formation in thin films with a designed electric field.
Modification on Hydrophilic property for Harsh Environment
Authors: Tsai Hsin-Chang , Chang Yu-Ru , Shing Tai-Kang 
Published: April 2011

ABSTRACTIn this research, a 1∼2 um NiCo film coated by electroplating technique as protection film in high temperature environment was studied. The improvements of hydrophilic property and high temperature stability by coating NiCo film upon pure Cu plate have been characterized through experiments. In thermal stability characterization, the specimens were put into a temperature-controlled oven and applied a thermal load at 100°C, 200°C and 300°C for annealing. After thermal annealing, the hydrophilic property was characterized to confirm that NiCo film was stable in high temperature environment. The hydrophilic property was represented by the contact angle between the DI water and the surface of NiCo film. The outgasing effect of contaminated polymer was also study. The electroplated NiCo film has advantages of good hydrophilic property, high temperature stability and easy fabrication. Therefore, the NiCo film could help the development of thermal related products.
Anti–scatter coating on slab laser head for preventing evanescent wave by photo–oxidation of silicone oil
Authors: Funatsu Takayuki , Sato Nobuhiro , Sato Yuji , Okamoto Takayuki , Murahara Masataka 
Published: April 2011

ABSTRACTA low refractive index, hard SiO2 film was photochemically coated on the surface of slab laser head at room temperature by using silicone oil and a Xe2 excimer lamp. Nd+:glass slab laser produces high power laser because the light is amplified with a repeated total reflection in the laser medium. However, an evanescent wave arises on the total reflection interface, which causes a loss of the light energy. A low refractive index film 2 μm thick is, therefore, needed to prevent this problem. The vacuum vapor deposition method as a dry process and the spin-coating method as a wet process are generally used for making optical thin films. The former method can laminate a hard thin film, but requires temperatures above 500°C, and the thermal denaturation of the optical substrate is unavoidable. On the other hand, the latter method can form a low refractive index thin film, but the produced thin film has a poor adhesiveness and a low hardness. Besides, all these films are inferior in water resistance. We, therefore, formed a water-resistant, hard, and low refractive index protective coating directly on the laser glass surface at room temperature with photochemical reaction by the Xe2 excimer lamp.
An Analysis of Surface Temperature Rise at Small Scale Sliding Contacts
Authors: Ray Sudipto , Chowdhury S. K. Roy 
Published: April 2011

ABSTRACTA great deal of work has been carried out in recent years on temperature rise at the contact between sliding bodies with engineering scale roughness. However, as surfaces become smoother and loading decreases, in applications such as MEMS and NEMS devices, the analysis of surface temperature rise must consider the small-scale asperity height distributions and the surface forces that may be operating at small separations. The paper attempts to predict surface temperature rise at sliding contacts with small-scale roughness considering the influence of relevant parameters. The important observation here is that in addition to the dependence on load, speed and material parameters the contact temperature steadily increases with surface adhesion.
Electrical Conduction in Thermally Sprayed Thin Metallic Coatings
Authors: Sharma Atin , Gambino Richard J. , Sampath Sanjay 
Published: April 2011

ABSTRACTThe in-plane electrical conductivity and the apparent density of air plasma sprayed (APS) molybdenum coatings having thicknesses in the range 30 um to 450 um were measured as a function of coating thickness. Both conductivity and the apparent density were found to increase with thickness until a saturation density (∼ 80% of the bulk density of molybdenum metal) was achieved. Attributing this increase in the apparent density to the increased volume fraction of the metallic component (or decreased porosity volume) in the coatings allows for the treatment of the problem in a framework of percolation theories. In order to eliminate the contribution of surface roughness the results were further analyzed using a two-layer parallel resistor model of the coating. In this model the top layer, which was composed of coating roughness, was assumed to have fixed thickness and conductivity whereas the conductivity of the bottom layer was assumed to vary with thickness (density). A fit to the data obtained from the above model showed that the conductivity of the bottom layer obeys a power law relationship of the type σ α (V –Vc)n throughout the composition range (with n=1.72 and Vc=0.09). These results show that that the coatings behave as a three-dimensional percolation system [1] and also indicate the asymmetric shape of the metallic and insulator regions in the coatings [2].
Tunneling Injection Quantum-Dot Lasers
Authors: Chuang Shun Lien , Kim Jungho , Kondratko Peter K. , Walter Gabriel , Holonyak Nick , Heller Richard B. , Zhang Xuebing B. , Dupuis Russell D. 
Published: April 2011

ABSTRACTWe investigate a tunneling injection InP quantum-dot (QD) laser theoretically and experimentally. The device consists of a single compressively strained InP QD layer coupled closely to two tensile strained InGaP quantum wells (QWs). While most tensile strained QW lasers in this wavelength (red) range lase in the transverse-magnetic (TM) polarization, our QD laser lases in the transverse-electric (TE) polarization from the first excited state of the compressively strained QDs, which is coupled to the ground state of the tensile-strained InGaP QWs. When we measure TE and TM modal gain spectra, a typical QW gain evolution behavior is observed at low injection currents, which can be theoretically explained by the quasi-equilibrium of carrier distribution. When the injection current is increased near threshold, a TE gain narrowing and a simultaneous TM gain pinning are observed in the measured modal gain spectra, which cannot be explained via the quasi-equilibrium model. We propose a polarization-dependent photon-mediated carrier re-distribution in the QD-coupled-QW structure to explain this TE and TM gain evolution behavior. When the injection current is just below threshold, the strong carrier depletion via stimulated emission due to coupling between the InP QD and InGaP QW states plays an important role in carrier re-distribution, which depends on the optical transition energy and polarization. This polarization-dependent photon-mediated carrier re-distribution explains the TE gain narrowing and TM gain pinning behavior. To quantitatively demonstrate the photon-mediated carrier re-distribution near the threshold current, a set of coupled rate equations are solved taking into account the polarization-dependent stimulated emission processes. The calculated polarization power ratio based on the coupled rate equations explains the experimental observations.
Structure, Composition and Optoelectronic Properties of Small Pyramidal Semiconductor Quantum Dots of Ga and In Atoms With As
Authors: Pozhar Liudmila A. , Yeates Alan T. , Szmulowicz Frank , Mitchel William C. 
Published: April 2011

ABSTRACTElectronic properties of small pyramidal clusters of Ga, In and As atoms are investigated using a multi-configuration self-consistent field approximation (MCSCF). The structure and composition of some of these (pre-designed) clusters have been derived from those of the symmetry elements of the corresponding bulk fcc lattices, to reflect the cluster formation in confinement or on surfaces. The counterpart (vacuum) clusters obtained without any spatial constraints applied to the atomic positions have also being synthesized computationally. It has been shown that manipulations with the cluster structure, composition and spatial constraints permit to engineer virtual (i.e., fundamental theory-based, computational) clusters with pre-designed electronic properties that can serve as prototypes for nanoscale heterostructure (NHS) units. Computational data so obtained are in agreement with existing experimental evidence concerning such pyramidal clusters.