bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of 4H <000-1> Silicon Carbide Films Grown by Solvent-Laser Heated Floating Zone
Authors: Woodworth Andrew A. , Sayir Ali , Neudeck Philip G. , Raghothamachar Balaji , Dudley Michael 
Published: November 2012

ABSTRACTCommercially available bulk silicon carbide (SiC) has a high number (>2000/cm2) of screw dislocations (SD) that have been linked to degradation of high-field power device electrical performance properties. Researchers at the NASA Glenn Research Center have proposed a method to mass-produce significantly higher quality bulk SiC. In order for this bulk growth method to become reality, growth of long single crystal SiC fibers must first be achieved. Therefore, a new growth method, Solvent-Laser Heated Floating Zone (Solvent-LHFZ), has been implemented. While some of the initial Solvent-LHFZ results have recently been reported, this paper focuses on further characterization of grown crystals and their growth fronts. To this end, secondary ion mass spectroscopy (SIMS) depth profiles, cross section analysis by focused ion beam (FIB) milling and mechanical polishing, and orientation and structural characterization by X-ray transmission Laue diffraction patterns and X-ray topography were used. Results paint a picture of a chaotic growth front, with Fe incorporation dependant on C concentration.
A Biocompatible SiC RF Antenna for In-Vivo Sensing Applications
Authors: Afroz Shamima , Thomas Sylvia W , Mumcu Gokhan , Locke Christopher W. , Saddow Stephen E 
Published: November 2012

ABSTRACTIn this study, we present a small-size implantable RF antenna (biosensor) which is made of fully biocompatible material, cubic silicon carbide. Silicon Carbide is one of the few semiconducting materials that combine biocompatibility and sensing potentiality. The hypothesis of a SiC based antenna, to be used for glucose monitoring, is that the changes in the medium surrounding the antenna affect the antenna properties such as input impedance and resonance frequency, and these changes can be used to estimate the patient’s plasma glucose level. An all-SiC patch antenna has been designed, simulated and fabricated with a target frequency of operation of 10 GHz. A Cu patch antenna was fabricated on SiC to serve as a reference antenna. The all-SiC antenna was realized by growing a poly-crystalline 3C-SiC film using CVD on a thick oxide layer that had been coated with poly-Si to serve as a growth template. A semi-insulating 4H-SiC substrate was used to minimize RF losses during operation.
Silicon Nanowire Integrated Electrolyte-Insulator-Semiconductor Sensor with an Above-Nernstian Sensitivity for Bio-Sensing Applications
Authors: Oh Jin Yong , Jang Hyun-June , Cho Won-Ju , Pala Nezih , Islam M. Saif 
Published: November 2012

ABSTRACTHighly sensitive electrolyte-insulator-semiconductor (EIS) sensors were realized by the integration of Si nanowires (NWs), which were fabricated by using a simple and economic electroless wet etching technique. EIS sensors with NWs longer than 1 μm were observed to have considerably increased capacitance and high pH sensitivity. The pH sensitivity of the EIS sensor with 3.8 μm long NWs was 60.2 mV/pH, which is higher than the theoretical Nernstian of 59 mV/pH. The EIS sensors with NWs exhibited slightly worse pH hysteresis and drift properties than that of the conventional planar type EIS sensor. The increases in pH sensitivity, hysteresis and drift are attributable to the extended surface area of the EIS sensors enabled by the NWs.
ZnO Nanostructured Diodes: The Influence of Synthesis Conditions and p-type Material on Device Performance
Authors: Hatch S.M. , Dunn S. 
Published: November 2012

ABSTRACTWe produce four distinct ZnO nanorod diode structures that are based on ZnO nanorods produced at pH 6 and pH 11 and have the p-type material PEDOT:PSS (hybrid device) or CuSCN (all inorganic device). After testing the performance of the diodes we show a rectification of 1050 at ±1V in the dark for the inorganic device. The device also exhibits good UV photodetection showing a rapid ca0.1ms turn on and off to a source of illumination. The hybrid devices performed as previously reported with a rectification of 25 at ±1V in both dark and under illumination. We ascribe the performance of the devices to the differences in morphology in the ZnO brought about by the processing conditions and the way in which the p-type layer coats the nanostructure.
Synthesis of Icosahedral Boron Arsenide Nanowires for Betavoltaic Applications
Authors: Frye Clint D. , Edgar J.H. , Zhang Yi , Cooper Kevin , Nyakiti Luke O. , Gaskill D.K. 
Published: November 2012

ABSTRACTWith a wide band gap of greater than 3.0 eV and the ability to self-heal from radiation damage, icosahedral boron arsenide (B12As2) is an apt candidate for use in next-generation betavoltaics. By capturing and converting high energy electrons from radioisotopes into usable electricity, “nuclear batteries” made from B12As2 could potentially power devices for decades. Compared to bulk crystals or epitaxial films, B12As2 nanowires may have lower defect densities or may even be defect-free, leading to better electrical properties and device performance. In our study, B12As2 nanowires were synthesized via vapor-liquid-solid (VLS) growth using platinum powder and nickel powder on silicon carbide and 20 nm thick nickel film on silicon substrates from 700 °C to 1200 °C. Platinum yielded the highest quality nanowires from 900 °C to 950 °C, resulting in platinum particles densely covered with wires formed by straight segments connected by sharp angular kinks. At these growth temperatures, diameters ranged from less than 30 nm to about 300 nm as determined by scanning electron microscopy and transmission electron microscopy. Growth temperatures of 850 °C or less produced curled wires 200-1000 nm in diameter. Transmission electron microscopy and selected area electron diffraction revealed excellent crystallinity in wires grown above 850 °C, while wires grown at or below 850 °C were partially amorphous. Wires grown from the 20 nm nickel film displayed similar morphologies at temperatures up to 850 °C; from 900 °C to 950 °C, straight, isolated wires were grown with diameters of 200-400 nm. Nickel powder only produced wires larger than 1 μm in diameter. The comparative quality and growth of B12As2nanowires will be discussed.
Effect of c-Si1-xGex Thickness Grown by LPCVD on the Performance of Thin-Film a-Si/c-Si1-xGex/c-Si Heterojunction Solar Cells
Authors: Hadi Sabina Abdul , Hashemi Pouya , DiLello Nicole , Nayfeh Ammar , Hoyt Judy L. 
Published: November 2012

ABSTRACTIn this paper the effect of Si1-xGex absorber layer thickness on thin film a-Si:H/crystalline-Si1-xGex/c-Si heterojunction solar cells (HIT cells) is studied by simulation and experiment. Cells with 1, 2 and 4 μm-thick epitaxial cap layers of p-type Si0.59Ge0.41 on top of 5 μm Si1-xGex graded buffer layers are fabricated and compared to study the effect of the absorber layer thickness. The results show no change in Voc (0.41V) and that Jsc increases from 17.2 to 18.1 mA/cm2 when the Si0.59Ge0.41 absorber layer thickness is increased from 1 to 4 μm. The effect of thickness on Jsc is also observed for 2 and 4 μm-thick Si and Si0.75Ge0.25 absorber layers. Experiments and simulations show that larger Ge fractions result in a higher magnitude and smaller thickness dependence of Jsc, due to the larger absorption coefficient that increases optical carrier generation in the near surface region for larger Ge contents.
Optimization of Graded CIGS Solar Cells Using TCAD Simulations
Authors: Lee Mankoo , Pramanik Dipankar , Liang Haifan , Korczynski Ed , van Duren Jeroen 
Published: November 2012

ABSTRACTTo understand paths towards higher efficiency (η) for copper-indium-gallium-(sulfur)-selenide [CIG(S)Se] solar cells, we investigated a variety of absorber composition grading schemes for various back-side gallium (Ga), front-side sulfur (S), and double-graded Ga composition depth profiles in TCAD 1D/2D simulations. We fitted experimental results of a Back-Side Graded (BSG) solar cell with our TCAD models, prior to investigating other grading and interface schemes. The BSG solar cell was fabricated on a High Productivity Combinatorial (HPC™) platform based on sputtering Cu(In,Ga) followed by selenization. Our TCAD simulation methodology for optimizing CIG(S)Se solar cells started with a sensitivity analysis using 1D Solar-cell CAPacitance Simulator (SCAPS) [1] by selecting a typical range of key model parameters and analyzing the impact on η. We then used a 2D commercially-available Sentaurus simulation tool [2] to incorporate wavelength-dependent optical characteristics. As a result, we provide insight in the impact of grading schemes on efficiency for a fixed ‘material quality’ equal to an in-house BSG solar cell. We also quantify the effects of interface layers like MoSe2 at the Mo/CIG(S)Se interface, and an inverted surface layer at the CIG(S)Se/CdS interface.
Addressing Bottlenecks in Dye-sensitized Solar Cell Manufacture Using Rapid Near-infrared Heat Treatments
Authors: Watson Trystan , Charbonneau Cecile , Carnie Matthew , Mabbett Ian , Cherrington Martyn , Worsley David 
Published: November 2012

ABSTRACTA primary challenge to the industrial uptake of dye-sensitized solar cells (DSC) is the ability to improve manufacturing efficiency. New thinking is required in terms of lowering cost, improving the process steps and increasing throughput. The typical manufacture of a DSC contains a number of long process steps; the sintering and dyeing of the TiO2 are prime examples. The current solution is to batch process on rigid substrates or use long energy intensive convection ovens for flexible metal substrates. Here we present a method for reducing some of the bottlenecks in the manufacturing process using near infra red radiation to speed up the thermal treatment of TiO2 and silver inks reducing their processing times to 12 and 2 seconds from normal process times of 30 and 10 minutes respectively.
Does Thermal Annealing Affect the Mechanical Properties of Silkworm (Bombyx mori) Cocoon Silk?
Authors: Reed Emily J. , Viney Christopher 
Published: November 2012

ABSTRACTIt has been reported [1] that microwave radiation can enhance many of the mechanical properties of Bombyx mori silkworm cocoon silk, as measured in constant strain rate tensile tests to failure and in stress relaxation tests. The consequences of microwave radiation will affect decisions about the use of silk in settings subjected to significant microwave exposure – for example, as a reinforcing fiber in an epoxy matrix composite that may be microwave cured, or as a component in aircraft radomes.There are two possible mechanisms by which microwave radiation may affect a material [2]: (i) the radiation may enable chemical and/or microstructural changes – and therefore property changes – in the same way that conventional heating would, or (ii) the high heating rates that are achievable by microwaving may selectively favor changes that would be masked under conventional conditions, where heating rates are low enough to give preference to changes that have a lower activation energy. Here we explore the former possibility for silk.We characterized several mechanical properties of degummed and subsequently annealed B. mori silk, and compared them to the corresponding properties of degummed B. mori silk that was not annealed. The annealing treatment was carried out at 140 °C for 7 hours (conditions that optimally increased crystal size in an unrelated study of B. mori silk [3]), and then the fibers were allowed to cool gradually to room temperature over the course of an hour. Comparison of mechanical properties revealed no differences between the materials that we tested. Thus, for annealed silk, we do not observe the enhancements that can be achieved by microwaving. We conclude that in cases where microwaving affects the properties of silk, those changes are not a simple consequence of annealing by the microwaves.
Ab initio studies of the crystal structure of cellulose triacetate I
Authors: Kobayashi Takanori , Hayakawa Daichi , Khishigjargal Tegshjargal , Ueda Kazuyoshi 
Published: November 2012

ABSTRACTWe have investigated crystal structure of cellulose triacetate I (CTA I) by using first principal density functional theory (DFT) calculation. The results are in good agreement with the experimentally obtained crystal structure when we used the cutoff energy higher than 70 Ry. However, the cell parameters calculated without dispersion correction are overestimated the results compared to the experimental value. Contrary, with the inclusion of dispersion correction, the cell parameters were calculated slightly smaller than the experimental one. The smaller cell parameter can be considered to be reasonable because the effect of the thermal expansion is not included in the density functional calculation. That is, inclusion of the dispersion term is important in the calculation of this crystal structure of CTA I.
Molecular Dynamics Based Study on Ductility Enhancement Effect of Nano-scale Void in Fine-grained Metallic Materials
Authors: Taniguchi Shin , Kameda Toshihiro , Fujita Toshiyuki 
Published: November 2012

ABSTRACTIn fine-grained metallic materials, the dominant grain boundary (GB) process, such as dislocation emission, dislocation absorption, and dislocation pile-up, causes non-uniform deformation, which results in high yield stress and low ductility. When a nano-scale void is introduced, the dislocation activity enhancement around the void could inhibit GB fracture and enhance ductility. In this study, by considering nanocrystalline Cu models, the influence of an intragranular nano-scale void on the fracture process has been investigated through molecular dynamics simulation. The dependence of ductility enhancement on the grain size and void size has especially been discussed at low and room temperatures. Sufficient dislocation activity enhancement accompanied by optimal void growth causes a fracture mode transition from GB fracture to transgranular fracture. While the ductility enhancement strongly depends on the void size at low temperature, it depends on the grain size at room temperature. The strong dependence of ductility enhancement on the temperature is found in the case of relatively small grains.
Collaborative Preparation of K-12 Teachers and Graduate Students in Nanoscience Research and Education.
Authors: Williams Myron N.V. , Kohlhorst Drew , Reed James L. , Khan Ishrat , Marsteller Pat , Rose Jordan 
Published: November 2012

ABSTRACTA 2010 Report to the President from the Council of Advisors on Science and Technology calls for “research and development to create “well-designed and validated examples of comprehensive, integrated instructional materials” for K-12 education. The Center for Functional Nanoscale Materials (CFNM) at Clark Atlanta University (CAU) and the Center for Science Education at Emory University have partnered in a program that provides a collaborative experience between CAU graduate students and Atlanta area high school and middle school teachers. The partnership expands Emory’s PRISM (Problems and Research to Integrate Science and Mathematics) program, a NSF Graduate Teaching Fellows in K-12 Education (GK-12) program. We believe that personal and experiential collaboration between these stakeholders in materials education provides even more substantial and tangible benefits.PRISM aims to stimulate reflection, by providing teachers and graduate students (PRISM Fellows) with an opportunity to lead in producing knowledge about pedagogical practice in STEM areas. By direct linkage with pedagogic theory, teaching practice can be subjected to continuous improvement, and it is anticipated that participants will catalyze change in both the educational and research communities.CFNM/PRISM Program ensures that both categories of Fellows participate in professional development activities designed to propagate active learning pedagogies and reflective practice during an annual Summer Institute. Teachers are immersed in a content-rich nano- and materials science research environment, while the graduate fellows have the opportunity during the subsequent academic year to assist with instruction in local schools. Thirteen graduate students and seventeen teachers have participated in the CFNM/PRISM Program over the course of five years. Teams were formed that comprised a teacher, a CAU faculty researcher and a graduate student. Each team tackled a nanoscience research problem during a summer project, developed problem-based learning (PBL) and investigative case-based learning strategies that integrate grade-appropriate science and math content, and implemented the cases in middle school and high school classrooms.The program has been preliminarily evaluated using online written attitudinal surveys and interviews with participants. Most striking among our observations is that teachers report an enhancement of their science process skills, including an increased ability to design and implement experiments for their students. Correspondingly, graduate students report a better understanding of the importance and practice of mentoring, as well as improved ability to articulate complex scientific concepts to lay audiences. Finally, since the student body at CAU and in these Atlanta area school systems is predominantly of African American heritage, the project also contributes to diversification of the Nation’s scientific enterprise.
Development of an Integrated Research, Curricular, Historically-Informed and Extracurricular Learning Environment
Authors: Cross William M. , Kellar Jon J. , Crawford Grant A. , Howard Stanley M. , Medlin Dana J. , West Michael K. 
Published: November 2012

ABSTRACTThe Department of Materials and Metallurgical Engineering faculty at the South Dakota School of Mines and Technology (SDSM&T) has developed a unique undergraduate program that integrates research, extracurricular activities, and outreach experiences. A common thread throughout the program is an introduction to the artistic and historical background of metallurgical engineering. These activities use kinesthetic learning to promote student learning of metallurgical engineering, aspects often not traditionally included in engineering curricula. These programs are similar to those envisioned by the National Academy of Engineering in response to the changing needs of engineering. These are described in two visionary books published by the National Research Council.A major focus of the program integrates blacksmithing activities with curricular, extracurricular, and outreach activities. All SDSM&T students are invited to a weekly blacksmithing activity called Hammer-in. Blacksmithing-related laboratories were added to the curriculum. Additionally, students developed a portable blacksmithing laboratory with faculty supervision. The laboratory has been taken to K-12 schools, including Native American schools on reservations, to reach out to regional students, thereby promoting interest in STEM careers. The success of these activities led to their incorporation into a National Science Foundation Research Experience for Undergraduate (REU) at SDSM&T called Back to the Future that focuses on understanding new technologies through historical antecedents. The SDSM&T students who participated in this REU used this experience as part of their junior/senior design courses. This program has increased enrollment in the department and has led to better learning outcomes for the students.
Colloidal Stability in Ionic Liquids and Relevant Soft Materials
Authors: Ueno Kazuhide , Watanabe Masayoshi 
Published: November 2012

ABSTRACTIonic liquids (ILs) are receiving a great deal of attention as synthetic and dispersion media for colloidal systems, as well as alternatives to organic solvents and electrolyte solutions. Colloidal stability is an essential factor for determining the properties and performance of colloidal systems combined with ILs. The remarkable properties of ILs primarily originate from their highly ionic nature. While such high ionic strength often causes colloidal aggregation in aqueous and organic dispersions, certain colloidal particles can be well dispersed in ILs without any stabilizers. First, we will discuss the colloidal stability of bare and polymer-grafted silica nanoparticles and the surface force between silica substrates in ILs. Three different repulsions between colloidal particles—electrostatic, steric, and solvation forces—will be highlighted. A possible interpretation of the stabilization mechanism in ILs, both in the presence and in the absence of stabilizers, will be proposed. Next, we will provide an overview of our recent studies on colloidal soft materials with ILs. On the basis of dispersed states of the silica colloids, two different soft materials, colloidal gel and colloidal glass in ILs, were fabricated. Their functional properties (such as ionic transport, rheological properties, and optical properties) and the microstructure of the colloidal materials will also be presented.
Parameters of Matrix/Fracture Immiscible-Fluids Transfer Obtained by Modeling of Core Tests
Authors: Civan F.. , Rasmussen M.L.. L. 
Published: November 2012

Summary
Methodology is presented and proved for determination of the best-estimate parameter values affecting the matrix/fracture-interface fluid transfer in naturally fractured reservoirs. Fracture/surface-hindered interface transfer of immiscible fluids is considered between matrix blocks and surrounding natural fractures. Improved matrix/fracture-transfer models are applied on the basis of presumed matrix-block shapes. Analytical solutions and the limiting isotropic-matrix long-time shape factors developed for special boundary conditions are used for interpretation of typical laboratory tests conducted using rectangular- and cylindrical-shaped rock samples. Workable equations and straight-line data-plotting schemes are developed for effective analysis and interpretation of laboratory data obtained from various-shaped oil-saturated reservoir-rock samples immersed into brine. Applications concerning the water/air and water/decane systems in laboratory core tests are also presented. The present approach allows rapid determination of the characteristic parameters of the matrix/fracture-transfer models for various-shaped matrix blocks, which are essential for prediction of petroleum recovery from naturally fractured reservoirs. The methodology is verified using various experimental data, and the values of the characteristic parameters (e.g., the average diffusion-coefficient and the interface-skin-mass-transfer coefficient) are determined. The Arrhenius (1889) equation is shown to represent the temperature dependency of these parameters effectively.