bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nano and micro- structural self-organization of implant surface from nitinol, fabricated by laser control SHS
Authors: Shishkovsky Igor V. , Morozov Yuri G. 
Published: June 2019

ABSTRACTTopology of the surface micro- and nano- structures induced by the synthesis of NiTi intermetallic phases under Selective Laser Sintering is studied by Scanning Electron Microscopy. According previously developed us method, those data were analysed by image processing software for identification and discussion of common features and peculiarities of the phase and structural transformations. It was shown, that fine substructures have self- ordering nature. Geometric similarity of synthesizing structures expects their fractal nature. The dependence between the fractal dimension -D of low-dimensional nanostructures and laser energy input -A was found. The change of the fractal dimension of low dimensional structures clearly correlates with the change of roughness, while the increase of the laser energy input influences the fractal dimension - D in different ways. Shown that particularities of phase structural transformations at the intermetallic synthesis in the Ni-Ti system have been defined an appearance of nano sized and self-ordering substructures of cellular, dendrite or mosaic types. A sharp variation of the D orientation indicates about of change of the phase-formation mechanism.
Simulation of Particle Synthesis by Premixed Laminar Stagnation Flames
Authors: Modak Abhijit , Puduppakkam Karthik , Naik Chitralkumar , Meeks Ellen 
Published: June 2019

ABSTRACTA sectional method for determining particle size distributions has been implemented within the particle tracking module included with CHEMKIN-PRO. The module is available for use with many types of reactor models, ranging from 0-D batch reactors to laminar flame simulations. Coupled with the Burner-stabilized Stagnation Flame (BSSF) Model, the sectional model offers a high-fidelity, robust, and efficient computational framework for simulating flame synthesis of particles in a laminar, premixed stagnation flame environment. The CHEMKIN-PRO coupling allows inclusion of detailed gas-phase chemistry that determines key particle-formation precursors, along with physical processes such as nucleation and coagulation of particles. These capabilities are demonstrated for two flame-particle systems of practical importance, viz. nanocrystalline titania synthesis and soot formation. The results are compared with experimental data obtained at the University of Southern California (USC) flame facility. Computed particle size distributions show good agreement with experimental data. Simulations have led to exploration of the parameter space for particle production and particle-size influences.
Valence Band Offset at Amorphous Boron Carbide / Silicon Interfaces
Authors: King Sean W. , French Marc , Jaehnig Milt , Kuhn Markus 
Published: June 2019

ABSTRACTIn order to understand the fundamental charge transport in a-B4-5C:H/Si heterostructure devices, we have utilized x-ray photoelectron spectroscopy to determine the valence band offset at interfaces formed by Plasma Enhanced Chemical Vapor Deposition of a-B4-5C:H on (100) Si. For such interfaces, we observed relatively small valence band offset values of ± 0.25 eV.
The Viability of Nanotechnology-based InGaN Solar Photovoltaic Devices for Sustainable Energy Generation
Authors: Pearce Joshua M. , Zhang Chenlong , Rozario Joseph , Gwamuri Jephias 
Published: June 2019

ABSTRACTThe unrestrained combustion of fossil fuels has resulted in vast pollution at the local scale throughout the world, while contributing to global warming at a rate that seriously threatens the stability of many of the world's ecosystems. Solar photovoltaic (PV) technology is a clean, sustainable and renewable energy conversion technology that can help meet the energy demands of the world’s growing population. Although PV technology is mature with commercial modules obtaining over 20% conversion efficiency there remains considerable opportunities to improve performance. The nearly global access to the solar resource coupled to nanotechnology innovation-driven decreases in the costs of PV, provides a path for a renewable energy source to significantly reduce the adverse anthropogenic impacts of energy use by replacing fossil fuels. This study explores several approaches to improving indium gallium nitride-based PV efficiency with nanotechnology: optical enhancement, microstructural optimization for electronic material quality and increasing the spectral response via bandgap engineering. The results showing multibandgap engineering with InGaN and impediments to widespread deployment and commercialization are discussed including technical viability, intellectual property laws and licensing, material resource scarcities, and economics. Future work is outlined and conclusions are drawn to overcome these limitations and improve PV device performance using methods that can scale to the necessary terawatt level.
Crystallinity and Mechanical Properties of Polypropylene-based Graphene Nanocomposites Studied with Atomic Force Microscopy and Raman Spectroscopy
Authors: Gronski Kjerstin , Flaig Robinson , Camacho Jorge , Wu Yan , Hamilton James P. 
Published: June 2019

ABSTRACTAtomic force microscopy (AFM) and Raman spectroscopy were used to characterize the morphology and the local mechanical properties of polypropylene-based graphene nanocomposites. Amplitude Modulated AFM was used to perform phase angle measurements to estimate the loss tangent, along with the local elastic modulus of the nanocomposite’s surface as a function of graphene content. We have observed an increasing trend in phase angle as the graphene content increased. We also identified wrinkled graphene flakes embedded in the polymer matrix. The graphene corrugation and mismatched strain between polymer and graphene sheets show a variation in the phase angle that is corroborated with Raman measurements. Mechanically exfoliated graphene on SiO2 was characterized as a baseline to understand the effect of graphene wrinkles compared to graphene surfaces on phase angle. The Raman results revealed that there are changes in the crystalline morphology of the polymer with the addition of graphene.
Lithium-containing semiconductor crystals for radiation detection
Authors: Stowe Ashley C. , Cochran Joe , Bhattacharya Pijush , Tupitsyn Eugene , Wiggins Brenden , Groza Michael , Burger Arnold 
Published: June 2019

ABSTRACTSemiconductor materials have shown promise as ionizing radiation detection devices; however, to be used as a neutron detector, these materials require the addition of a nucleus with a large neutron absorption cross section (such as 10B or 6Li) to capture thermal neutrons and convert them into directly detectable particles. A semiconducting material that contains the neutron absorber within its regular stoichiometry has the potential to be more efficient than a layered or heterogeneous device at transferring the kinetic energy of the charged particle into the semiconducting material. One class of materials that has shown promise is Li-containing AIBIIIXVI2 compounds such as LiGaTe2, LiGaSe2, and LiInSe2. These materials have band gaps (2-3.5 eV) appropriate for room-temperature detection of thermal neutrons and would be the first detection material that is simultaneously, exquisitely sensitive to thermal neutrons; is insensitive to gammas; and acts as a direct conversion device. A vacuum distillation process provided high-purity lithium metal for AIBIIIXVI2 synthesis. Single crystals of sufficient bulk resistivity (grown for LiGaSe2 and LiInSe2LiInSe2) showed a distinct photo response as well as a clear response to alpha particles. Additional radiation measurements indicated that a 6 mm x 7 mm x 1.33 mm crystal of LiInSe2 detected gamma rays, and despite being composed of natural abundance lithium, responded to thermal neutrons as well.
Microwave Reflection From The Microwave Photo-Excited High Mobility GaAs/AlGaAs Two-Dimensional Electron System
Authors: Ye Tianyu , Mani R. G. , Wegscheider W. 
Published: June 2019

ABSTRACTWe examine the microwave reflection from the high mobility GaAs/AlGaAs two-dimensional electron system (2DES). Strong correlations have been observed between the microwave induced magnetoresistance oscillations and the microwave reflection oscillations in a concurrent measurement of the microwave illuminated magnetoresistance and the microwave reflection from the 2DES. The correlations were followed as a function of the microwave frequency and the microwave power dependent. Different existing theories are considered to explain the results.
Microstructural evolution during mechanical treatment of ZnO and black NiO powder mixture
Authors: Kakazey M. , Vlasova M. , Vorobiev Y. , Leon I. , Gonzalez M. Cabecera , Urbiola E.A. Chávez 
Published: June 2019

ABSTRACTKinetics of the microstructural evolution in ZnO and NiO black powder mixture during prolonged mechanical processing (MP) was investigated by Scanning electron microscopy (SEM), Laser Particle Sizer (LPS), X-ray diffraction, electron paramagnetic resonance (EPR), infrared absorption (FTIR) and UV-Visible diffuse reflection methods.
A new mild synthesis and optical properties of colloidal ZnO nanocrystals in dimethylformamide/ethanol solutions
Authors: Panasyuk Yaroslav V. , Rayevska Oleskandra E. , Stroyuk Oleksandr L. , Kuchmiy Stepan Ya. 
Published: June 2019

ABSTRACTA green and mild synthesis of colloidal zinc oxide nanocrystals in ethanol/dimethylformamide mixtures was introduced which allows to produce stable crystalline ZnO particles and tailor their average size in the range of 2.8−4.5 nm by varying temperature and duration of post-synthesis ageing. An increase in dimethylformamide fraction in the mixture results in acceleration of ZnO nanocrystals ripening. Colloidal ZnO nanocrystals emit broadband photoluminescence in the range of 2−3 eV with the quantum yields of up to 12 %.
Modeling of the effect of bio-conjugation to anti-interleukin-10 antibodieson the photoluminescence of CdSe/ZnS quantum dots
Authors: Torchynska Tetyana V. , Vorobiev Yuri V. , Horley Paul P. 
Published: June 2019

ABSTRACTBio-conjugated CdSe/ZnS core/shell quantum dots (QDs) attract essential scientific interest due to their possible nano-medicine applications, including selective highlighting of affected tissues and targeted drug delivery to the certain type of cells. The paper is focused on the theoretical description of the blue shift observed in the luminescence spectra of CdSe/ZnS QDs upon their bio-conjugation with the anti-interleukin-10 antibodies. We propose a model that describes the ground state of the exciton confined in a quantum dot and explaining the bio-conjugation phenomenon by the change of the effective confinement volume.
Using First Principles Thermodynamics to Predict the Shape Surface Structure and Reactivity of Solvated Nanoparticles at High Temperatures and Pressures.
Authors: O’Brien Christopher J. , Brenner Donald W. 
Published: June 2019

ABSTRACTHydrothermal nanoparticle synthesis uses high temperature and pressure water to control the chemical processes that lead to specific compositions and structures. Analyses of the chemistry associated with this process have been mainly restricted to bulk thermodynamics in the form of quantities such as solubilities and empirical models based on experimental observations. In this paper we demonstrate for NiO and NiFe2O4 particles how effective reference chemical potentials derived from first principles calculations can be used to predict cluster shapes, nucleation barriers and surface reactivity. Implications for controlling the nanoparticle size and shape by adjusting pH and temperature will be discussed, as well as implications of these results in forming nanostructured materials by cluster condensation.
High-Temperature Dielectric Polyimide Films for Energy Storage Applications
Authors: Wang David H. , Kurish Brian A. , Treufeld Imre , Yang Lianyun , Zhu Lei , Tan Loon-Seng 
Published: June 2019

ABSTRACTTwo new diamines containing three nitriles are synthesized via a 3-step route. They are polymerized with four commercial dianhydrides (i.e. 6FDA, OPDA, BTDA and PMDA) in N,N-dimethylacetamide (DMAc) to afford poly(amic acid)s, which are thermally cured at temperatures up to 300 °C to form tough, creasable films. Most of these polyimides are soluble in common solvents. Their glass transition temperatures range from 216 to 341 °C. The polyimides are stable up to 400 °C. The dielectric constants of these OPDA-based polyimides increase from 2.9 (CP2) to 4.7 as measured by the D-E loops.
High Performance Lithium-ion Battery Electrode: Silicon Coated on Vertically Aligned Carbon Nanofibers
Authors: Klankowski Steven , Rojeski Ronald , Li Jun 
Published: June 2019

ABSTRACTThis study reports a high-performance hybrid lithium-ion anode material using coaxially coated silicon shells on vertically aligned carbon nanofiber (VACNF) cores. The robust bush-like highly conductive VACNFs effectively connect high-capacity silicon shells for lithium-ion storage. Such architecture allows the Si shells to freely expand/contract in the radial direction during lithium-ion insertion/extraction. A high specific capacity of 3000-3650 mAh(gSi)-1 was obtained at C/1 rate, comparable to the maximum value of amorphous Si, and ∼89% of the capacity was retained after 100 charge-discharge cycles. The lithium-ion storage capacity remains nearly the same from C/10 to C/0.5 rates. The ability to obtain high capacity at significantly improved power rates while maintaining the extraordinary cycle stability demonstrates the utilization of the unique properties of such hybrid architecture for lithium-ion batteries.
Role of Inter-Dopant Interactions on the Diffusion of Li and Na Atoms in Bulk Si Anodes
Authors: Tan Teck L. , Malyi Oleksandr I. , Legrain Fleur , Manzhos Sergei 
Published: June 2019

ABSTRACTWe explore, via density functional theory (DFT) calculations, the effect on the barrier height for Li and Na diffusion in bulk Si of the presence of an extra Li/Na atom at the neighboring tetrahedral (T) or hexagonal (H) interstitial site. For both neighboring sites, the lowest diffusion barrier height is reduced, although the magnitude of the reduction depends on the inter-atomic distance between the 2 Li/Na atoms. We further calculate the effective interaction between the 2 atoms and show that it is a strong predictor of diffusion barrier heights for both Li-Si and Na-Si systems. Importantly, the correlation between inter-dopant interaction and barrier height may be used in future work to predict the diffusion barriers at higher concentration of inserted atoms.
Extraction and Characterization of Natural Dyes Applied to ZnO-based DSSC
Authors: Perez Hernandez G. , Pantoja Enriquez J. , Ramos-Villegas C. I. , Gonzalez-Solano M. , Oskam G. , Escobar-Morales B. , Flota-Robledo A. , Ricardez-Jiménez C. 
Published: June 2019

ABSTRACTThe dye-sensitized solar cells (DSSC) are a technological and economical alternative to conventional p-n junction solar cells. The DSSC is composed of a transparent conducting electrode (SnO2:F) coated by a porous, nanocrystalline film of n-ZnO to which dye molecules are attached, an organic electrolyte containing a reduction-oxidation couple, and finally a counter-electrode (glass/SnO2:F) coated by a thin film of platinum. The most efficient dyes for DSSCs are based on Ruthenium polypyridyl complexes, related to the high absorption coefficient in the entire visible range and the efficient injection of electrons into the conduction band of ZnO. However, the ruthenium polypyridyl complex contains a heavy metal of relatively high cost, and synthetic routes are complicated with low yields. Moreover, natural dyes in addition to their availability, are cost-effective, non-toxic and biodegradable materials, and can be extracted by simple procedures. In this paper we report the extraction of natural dyes from the stems of mangrove (D1) and tinto (D2) trees as well as from walnut (D3) shell. First, it was necessary to dehydrate the materials, after which extraction was performed using ethanol, water and sodium hydroxide solution. The dyes were characterized using UV-visible and infrared spectroscopy. The analysis of the infrared spectra shows an intense and broad band related to OH bond stretching vibration at 3393, 3442 and 3390 cm-1 for the mangrove tree, tinto tree and walnut shell, respectively. At 1051, 1123 and 1050 cm-1, there was a very strong absorption due to the stretching vibration of CO group, for the mangrove tree, tinto tree and walnut shell, respectively. These results indicate that the functional group for bonding to the ZnO is -OH for these dyes. The results of the U-Vis spectroscopy show that the strongest absorption in the visible region is provided by dyes of the tinto and mangrove trees. The current - voltage curve of a preliminary ZnO-DSSC sensitized with the natural dye of the mangrove tree bark is presented.
A Comparative Study of Quasi-solid Nanoclay Based Electrolyte and Liquid Electrolyte Dye Sensitized Solar Cells
Authors: Main Laura , Munukutla Lakshmi , Fauss Brian , Curtis Travis , Kannan Arunachalanadar M. 
Published: June 2019

ABSTRACTDye sensitized solar cells (DSSCs) are currently being explored as a cheaper alternative to the more common silicon (Si) solar cell technology with improved performance in low light conditions and less sensitivity to varying angles of incident light. One of the major challenges facing DSSCs is loss of the liquid electrolyte, through evaporation or leakage, which lowers stability and leads to increased degradation. To address this, batches of gel electrolyte cells are fabricated with 7 wt% nanoclay gel electrolyte and liquid electrolyte and were evaluated at standard test conditions over time. The gel cells achieved efficiencies as high as 9.18% compared to the 9.65% achieved by the liquid cells. Over a period of 10 days, the liquid cells degraded less than 20% of its maximum efficiency. By contrast, the gel cell's efficiency did not decrease to 20% of its maximum efficiency until 45 days. After several measurements, the liquid cells showed visible signs of leakage through the sealant, whereas the gel cells did not. This resistance to leakage likely contributed to the improved performance of the quasi-solid cells over liquid electrolyte DSSCs.
Modeling the Mechanical Behavior of P3HT/Fullerene Blends For Photovoltaic Applications
Authors: Zhao B. , Awartani O. , O’Connor B.T. , Zikry M. A. 
Published: June 2019

ABSTRACTOrganic solar cells, comprised of P3HT-fullerene blends, have the potential for photovoltaic energy applications. However, there is limited understanding of the mechanical behavior of these devices, and how this behavior can be tailored for optimal organic solar cell performance and device reliability. Therefore, a recently developed computational approach that is based on a constitutive representation of semi-crystalline polymers and fullerenes is used to identify the dominant morphological and microstructural characteristics that would affect the mechanical behavior of the active layer. The predictions indicate that stress and dislocation-density accumulation in interfacial regions and tie molecules play a significant role on the overall behavior.
Examining the crystal growth that influences the electronic device output from vertical arrays of ZnO nanowires
Authors: Lord Alex M. , Ward Michael B. , Walton Alex S. , Evans Jonathan , Smith Nathan , Maffeis Thierry G. , Wilks Steve P. 
Published: June 2019

ABSTRACTZnO nanowire (NW) arrays were examined with Transmission Electron Microscopy (TEM) in cross-section after preparation by Focused Ion Beam (FIB) milling. This technique revealed that ZnO nanowires grown using a Au catalyzed vapor technique typically have Au particles at the NW tips, and also randomly dispersed across the base crystal growth that joins adjacent NWs. It is shown the adjacent NWs and the combined base growth is one crystal structure which can be used as a back electrical contact making fabrication of vertical array devices possible. However, the base growth displays detrimental features such as embedded Au particles and lattice defects which can affect the electrical output through depletion regions and scattering centers. In an effort to overcome these problems we investigate a growth method that is nucleated through a minor alteration of the a-plane sapphire surface roughness via a weak chemical etch. Observations of various stages of the growth show the growth nucleates as separate nanoislands that grow in c-plane alignment with Sapphire (1-210), and as growth continues these islands meet and form a polycrystalline film. Further growth initiates nanowire growth and the formation of a single crystal base layer and NW structure that can cover several square millimeter’s. This allows high quality arrays that are relatively free from defects to be formed without any metals contamination and ready for further device processing.
Multi-branched gold nanoparticles for Surface Enhanced Raman scattering characterization
Authors: Johnston Jencilin , Taylor Erik N. , Gilbert Richard J. , Webster Thomas J. 
Published: June 2019

ABSTRACTSurface enhanced Raman scattering (SERS) is a sensitive and reproducible vibrational spectroscopic technique used to detect and characterize molecules near the surface of noble metals like Au, Ag, Pt, Cu, etc. SERS enhances Raman signals through light-induced plasmonic vibrations occurring on irregular metal surfaces and localized electromagnetic augmentation. To better define nano-scale regions of the Raman signal enhancement, we generated gold nanoparticles with a unique multi-branched configuration along with surface-adsorbed fluorescent reporter molecules. The reporter molecules included a set of near-infra red active fluorescent dyes IR820 (green cyanine, photo electronic dye), DTTC (3, 3'-diethylthiatricarbocyanine iodide) and DTDC (3, 3'- diethylthiadicarbocyanine iodide). We employed a one-pot synthesis method in order to generate a stellate configuration in gold nanoparticles through the reduction of HAuCl4 with Good’s buffer, HEPES, at pH 7.4 and room temperature. A cell viability assay was performed with normal esophageal cells exposed to the multi-branched gold nanoparticles and SERS molecules to assess their toxicity. Our results demonstrate the capacity of multibranched gold nanoparticles linked to Raman reporter molecules to generate distinct signature spectra and, with the exception of the gold nanoparticles functionalized with DTTC, remain non-toxic to normal esophageal cells.
Material Matters in the Physics Classroom
Authors: Chiaverina Chris 
Published: June 2019

ABSTRACTWhat do fiber optics, superconductors, memory wire, polymers, solid state devices, ferrofluid, rare earth magnets, carbon-based electroacoustic devices, and photonic crystals have in common? They are all products of materials science research. Many of these advances play an important role in improving daily life; all are capable of enhancing the teaching of physics. This paper will address how topics from materials science can be used to ignite student interest by providing the basis for exciting hands-on activities.