bluuebunny/crossref_metadata_2025_split huggingface dataset:
Single-Walled Carbon Nanotube Growth with Narrow Diameter Distribution from Pt Catalysts by Alcohol Gas Source Method
Authors: Kondo Hiroki , Ghosh Ranajit , Naritsuka Shigeya , Maruyama Takahiro , Iijima Sumio 
Published: June 2019

ABSTRACTSingle-walled carbon nanotube (SWCNT) growth were carried out on SiO2/Si substrates using Pt catalysts at different temperatures, from 400°C to 700°C, under various ethanol pressures by an alcohol gas source method, a type of cold-wall chemical vapor deposition (CVD). Raman measurements showed that the optimal ethanol pressure decreased as the growth temperature was reduced, and that SWCNTs grew even at 400°C by optimizing the ethanol pressure to 1×10-5 Pa in a high vacuum system. Compared to the SWCNTs grown from Co catalysts, the diameters of SWCNTs grown from Pt were smaller, irrespective of the growth temperature. In addition, both the SWCNT diameter and the distribution became narrower by reducing the growth temperature and we obtained small-diameter SWCNTs of which the diameters were less than 1 nm using Pt catalysts.
Investigating Charge Dynamics in Halide Perovskite Sensitized Mesostructured Solar Cells
Authors: Listorti Andrea , Roiati Vittoria , Colella Silvia , Mosconi Edoardo , Lerario Giovanni , De Marco Luisa , Rizzo Aurora , De Angelis Filippo , Gigli Giuseppe 
Published: June 2019

ABSTRACTCharge generation and transport in CH3NH3PbI3-xClx based mesostructured solar cells are investigated. Time correlated single photon counting analysis proves highly efficient charge generation and provides insights on the structural properties of perovskite films. Photoinduced absorption and transient photovoltage analyses depict a double charge recombination dynamics suggesting the existence of two complementary paths for electron transport, involving either TiO2 and perovskite matrixes. Stark spectroscopy, a powerful tool allowing interface-sensitive analysis, is employed to prove the existence of oriented permanent dipoles, consistent with the hypothesis of an ordered perovskite layer close to the oxide surface. This evidence is also confirmed by first principle DFT calculations. The existence of a structural order, promoted by specific local interactions, could be one of the decisive reasons for highly efficient carriers transport within perovskite films.
Electrospun photonics topography for organic photovoltaics
Authors: Khanum Khadija Kanwal , Ramamurthy Praveen C. 
Published: June 2019

ABSTRACTA Photonics device requires uniform periodic structural arrangement. Various techniques have been used to fabricate these types of structures, which employs several steps of fabrication. This work proposes single step hierarchical array of equal submicron size porous structure fabricated through tuning electrospinning processing parameters. The dictating parameters were high voltage, tip to collector distance and solvent used on the evolving structure. Morphological and optical investigations suggested the uniform periodic topography and enhancement in light absorption, which is assumed due to internal reflection of light. This structure was evaluated for better light harvesting as active layer in organic photovoltaic devices using poly (3 hexyl thiophene) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM) blend, and further studying enhancement in photoelectrical characteristics.
Imidazole-Based Solvents and Membranes for CO2 Capture Applications
Authors: Bara Jason E. , Shannon Matthew S. , Jeffrey Horne W. , Whitley John W. , Liu Haining , Wallace David A. , Turner Heath , Verevkin Sergey P. , Brown Nathan , Staab Greg , Kupfer Rene 
Published: June 2019

ABSTRACTImidazoles present a tunable, versatile and economical platform for the development of novel liquid solvents and polymer membranes for CO2 capture. An overview of our studies in this area is presented, with emphasis on characterization of structure-property relationships in imidazole-based materials through both experimental and computational studies. To this end, a growing library of systematically varied imidazole compounds has been synthesized using only commercial available starting materials and straightforward reactions. Using this library of compounds, we have sought to understand and develop predictive models for thermophysical properties relating to process design, including: density, viscosity, vapor pressure, pKa and CO2 absorption capacity. Furthermore, we have discovered that imidazoles are stable in the presence of SO2 and can form reversible 1:1 adducts, which can be beneficial as SO2 is typically present at ppm levels alongside CO2 in flue gas from coal-fired power plants.
Characteristics of N-doped Sb2Te3 Films by X-ray Diffraction and Resistance Measurement for Phase-change Memory
Authors: Yin You , Higano Naoya , Ohta Kazuhiro , Miyachi Akihira , Asai Masahiro , Niida Daisuke , Sone Hayato , Hosaka Sumio 
Published: June 2019

AbstractIn this paper, characterizations of sputtered undoped and nitrogen-doped Sb2Te3 (ST and STN) films by X-ray diffraction (XRD) and resistance measurements are described and their application of lateral phase-change memory (PCM) is presented. Nitrogen concentration of the films was controlled by changing the flow rate ratio of N2/Ar during sputtering. Resitivity of STN films drops by 3-4 orders of magnitude due to crystallization. Resistivity increase of the STN film (N2/Ar=0.15) at above 270°C results from phase precipitation of SbN. Experimental results reveal that the temperature of crystallization to face-centered cubic (fcc) significantly increases from below 100°C to 160–220°C with increasing the ratio of N2/Ar (in the range of 0–0.15) and crystal structure further transforms from fcc to hexagonal. At high flow rate ratio of N2/Ar (>0.15), hexagonal Te phase firstly appears at 160°C and then orthorhombic SbN appears at 290°C.
Microstructural Study of Aggregate/Hydrated Paste Interface in Very High Strength River Gravel Concretes
Authors: Sarkar Shondeep L. , Diatta Yaya , Aïtcin Pierre-Claude 
Published: June 2019

ABSTRACTThe aggregate/hydrated paste interface represents the weakest link in very high strength river gravel concrete, due to the surface smoothness of these aggregates.Microstructural examination of the aggregate/hydrated paste interface in four different (very low W/C ratio) very high strength concretes with and without silica fume shows major differences in the nature of the transition zone at the interface level. In the non-silica fume concretes, hydrated lime and ettringite are found quite exclusively at the interface, while in silica fume concretes, only C-S-H is observed.The modulus of elasticity can be correlated to the compressive strength by the equation, , with a low correlation index (78%) for non-silica fume concrete, whereas in silica fume concrete it becomes MPa, with excellent correlation in ex of 95%.These results can be explained by the nature of the aggregate/hydrated paste interface, which is stronger in silica fume concrete.
Interaction Between Naphthalene Sulfonate and Silica Fume in Portland Cement Pastes
Authors: Diamond Sidney , Struble Leslie J. 
Published: June 2019

ABSTRACTPortland cement pastes were mixed with predissolved naphthalene sulfonate superplasticizer at normal water:cement ratios. Solutions were separated from the fresh pastes at intervals and the residual concentration of the superplasticizer determined by UV spectrophotometry. At low dosage levels essentially all of the superplasticizer was found to be removed from solution within a few minutes; at high dosage levels a substantial concentration was maintained in solution at least to approximately the time of set. In pastes in which silica fume replaced 10% by weight of the cement, it was found that the incorporation of silica fume significantly increased the uptake of superplasticizer. In separate trials it was found that the silica fume by itself adsorbed little superplasticizer, even from high pH solution simulating that of cement paste.
Bond Strength Of Deformed Bars and Steel Fibers in High Strength Concrete
Authors: Wecluat Methi , Chimamphant Schboon 
Published: June 2019

ABSTRACTIn recent years, the means of making high strength concrete are simple by adding microsilica, fly ash, or other types of additives. As the use of high strength concrete increases, the need to clearly understand its prcperties is essentially a necessity for engineering design. While much of the basic properties of high strength concrete such as compressive strength (fc), modulus of elasticity (Ec), and modulus of rupture (fr), etc., has been investigated and reported recently, many remain unavailable. This paper presents the bond strength characteristics of deformed bar, steel fibers, and normal aggregate in high strength concrete matrix. The compressive strength of concrete used in this study is 75–80 MPa (11,000-12,000 psi). Bond slip relationships of deformed bars of three different bar diameters were obtained from the pull-cut test. Two types of steel fiber reinforced high strength cemented composites were tested in a directtension, tapered specimen to observe the pulled-out behavior of steel fibers. Fiber reinforced concretes with fiber volume fraction of 0.5, 1.0, 1.5, and 2.0 % were compared to the unreinforced matrix. A direct-tension, dog boned specimen was used to study the bond between aggregate-matrix interface. The results from this study indicate that high strength concrete is generally more brittle, and in essence, allows less microcracking, less slippage, and less pulled-out deformation. This general trend is observed in both the deformed bar and fiber pulled-out as well as in aggregate-matrix interfacial debonding. The maximum slip of deformed bars in high strength concrete is about 0.15 mm.(0.006 in.) which is only one-tenth of that reported for normal concrete as 1.5 to 2.0 mm.(0.06–0.08 in.). A normalized pull-out stress-displacement relationship of high strength fiber reinforced concrete exhibits a unique behavior similar to those reported for normal fiber reinforced matrix.
The Effect of the Cement Paste-Steel Interfacial Zone on the Electrochemical Properties of Reinforcing Rods
Authors: Yuan Chen Zhi , Zhi Wang Nian 
Published: June 2019

ABSTRACTThe interfacial zone between cement paste and embedded steel is a porous one, to which the rust can easily diffuse and where it can be deposited. Strengthening the zone makes the passive oxide film more complete, and harder to rupture; the rate of corrosion decreases, the initiation stage of pitting corrosion is delayed, the effect of self-catalysis is weakened, and the acceleration of corrosion is greatly decreased. Therefore, a strengthened interfacial zone can improve the anti-corrosion properties greatly, with less cost than other methods of inhibiting corrosion.
Bonding in Aluminum Phosphate Ceramics Prepared At Low Temperatures
Authors: Silsbee Michael R. , Roy D. M. 
Published: June 2019

ABSTRACTPhosphates have a long history of use as binding agents in ceramic systems. In particular the phosphate bonded alumina refractories and dental cements that employ the chemical reaction between a complex alumino-silicate glass and a buffered phosphoric acid to produce binding are among the most well known.The work described here has been undertaken in an effort to achieve a more complete understanding of the nature of the chemical binding in these materials.The results of a series of characterization studies on materials from the Al2O3-P2O5-H2O and SiO2-Al2O3-P2O5-H2O systems will be discussed with particular emphasis on the nature of the binding produced in these materials.
Microstructure and Chemical Variation in Class F Fly Ash Glass
Authors: Qian J. C. , Lachowski E. E. , Glasser F. P. 
Published: June 2019

ABSTRACTFly ash consists of mixtures of crystalline substances in a glassy matrix. This matrix is itself inhomogeneous. The combustion process gives rise to compositional fluctuations typically on a micrometer scale; these fluctuations are preserved in the glass and are gradational. However, high-resolution transmission electron microscopy of Class F ash also reveals the existence of interfaces on a nanometer scale. These arise as a consequence of phase separation. Textures and interfaces typical of spinodal decomposition and possibility also suggestive of classical immiscibility have been observed. It is believed that the occurrence of phase separation resulting in nanometer-scale inhomogeneities will be a feature common to most Class F glasses. The consequences of this complex microstructure to reactivity are not as yet known, but some speculations are presented.
Is the Available Alkalitest a Good Durability Predictor for Fly Ash Concrete Incorporating Reactive Aggregate?
Authors: Smith Robert L. 
Published: June 2019

ABSTRACTThe available alkali test has been used for years as a method for preventing the use of a high-alkali fly ash in concrete containing reactive aggregate. This report presents data on fifteen good-quality Western ashes, both Class C and Class F, that are currently used in readymixed concrete. All fifteen ashes were effective in reducing the expansion due to the alkaliaggregate reaction. The reduction in mortar bar expansion (ASTM C 441) varied from 16% to 81%. Correlation of the percent reduction was made with available alkalies as Na2O, silica content, lime content, sulfur content, and the sum of silica, alumina and iron oxide. Surprisingly, the best correlation to percent reduction was with sulfur and the least was with available alkalies. This data indicates that most, if not all, fly ashes are effective in reducing the alkali aggregate reaction and that the available alkali test is not the best method for predicting the effectiveness of a fly ash in controlling this reaction.
The Permeability of Chloride Ions in Fly Ash-Cement Pastes, Mortars and Concrete
Authors: Malek R. I. A. , Roy D. M. 
Published: June 2019

ABSTRACTFly ash-cement pastes are known to develop fine pore structures that may retard the transport of ionic species. The rapid chloride permeability technique for studying the Cl− ion diffusion in hydrated fly ash/cement pastes, mortars and concrete was used. The technique applies an electrical potential across a cylindrical sample and measures the charge passed in a certain period of time. The results obtained on pastes and mortars cured for 28 days were reported previously and contrasted with those of neat cement pastes and mortars. The present paper reports more extensive studies made to examine the chloride permeabilities of pastes and mortars cured for up to 90 days. In addition, the effect of variable fly ash contents was examined. Concrete samples were included in the test scheme and the data were compared with pastes and mortars. Two important factors controlling the test results are discussed: first the mix design and curing conditions; second the experimental conditions during Cl− permeability measurements. In the second factor, the amount and rate of heat build up and the chloride ion concentrations are compared with the current passed. In addition, measuring current versus resistivity are critically discussed in terms of the voltage-current varistic characteristics of cement matrices.
Modification of the Interfacial Zone Between Aggregate and Cement Paste
Authors: Xueqan Wu , Dongxu Li , Xiun Wu , Minshu Tang 
Published: June 2019

ABSTRACTIn order to improve the properties of concrete, the composition and structure of the interfacial zone must be modified. This may be done by pretreating the inert aggregate with special reagents to form a reactive surface, which will then react with the cement paste, resulting in an enhancement of the bond strength between cement paste and aggregate through the combination of the physical, chemical and mechanical interlocking effects. A cylindrical hole was drilled in a limestone cake and the surface of the hole coated with special solutions; cement slurry was then poured into the hole and the specimens were cured in a fog room. The shearing strength was determined to evaluate the effect of the aggregate pretreatment on the bond strength. The mechanical strength, porosity, electric conductivity of the concrete, orientation degree of the Ca(OH)2 and morphology in the interfacial zone were also examined. It was found that the compressive and flexural strengths increased, and the bond strength between aggregate and cement paste also increased; the porosity, average pore size, number of large harmful pores, electric conductivity and the orientation index of the Ca(OH)2 decreased.
Effect of Bond Strength Between Aggregate and Cement Paste on the Mechanical Behaviour of Concrete
Authors: Yuan Chen Zhi , Guo Wang Jian 
Published: June 2019

ABSTRACTConcrete is a composite material, consisting of hardened cement paste (HCP), aggregate and pores. The interfacial bond between HCP and aggregate is very important in determining some of the properties of concrete, such as the mechanical behaviour and durability. Recently, the microstructure of the transition zones between different aggregates and HCP has been studied and a mechanism for the formation of the transitional zone has been proposed by Maso. The objective of the present work has been to study the relationship between interfacial bond and mechanical behaviour of concrete in the light of both theoretical and experimental research on the microstructure of the interfacial zone.
A Stludy of the Interfacial Region Between Cement Paste and Aggregate in Concrete
Authors: Scrivener Karen L. , Crumbie Alison K. , Pratt P. L. 
Published: June 2019

ABSTRACTThe application of quantitative image analysis to the measurenent of microstructural gradients in the interfacial zone in concrete is described. Some preliminary results are presented and discussed.
The Mechanisms of Reactive Ion Etching Of SiOx (x≤2) with Electron Cyclotron Resonance and Kaufman Ion Sources
Authors: Kant R. A. , Eddy C. R. , Sartwell B. D. 
Published: June 2019

ABSTRACTThe dominant factors governing reactive ion etching of Si, SiO, and SiO2 thin films during bombardment with energetic Ar ions in a Cl atmosphere were investigated. Etch rates were determined in-situ by measuring weight loss as a function of ion fluence for films deposited on a quartz micro-balance. Measurements were made as a function of ion energy and Cl pressure using a Kaufman gun for ion energies from 300 to 1500 eV and an electron cyclotron resonance microwave ion source for ion energies from 50 to 600 eV and for Cl pressures ranging from 0.006 to 0.05 Pa. Results were compared to sputtering in Ar alone. The results indicated that the presence of the C1 enhanced the etch rate for all three materials, with the degree of enhancement being inversely proportional to the oxygen content of the film. It was also discovered that there was an optimum pressure for enhancement of the etching and that at the highest pressures, the etching could actually be suppressed. These results are discussed in terms of physisorbed gas layers, the thickness of which depends on the balance between the flux of energetic particles and the gas flux.
Thin Film Growth of High Tc Superconductors by Microwave Plasma Assisted Reactive Evaporation
Authors: Tukamoto Akira , Hiratani Masahiko , Aida Toshiyuki , Tarutani Yoshinobu , Takagi Kazumasa 
Published: June 2019

ABSTRACTThe oxidizing activity of an oxygen plasma is investigated in terms of the oxygen content of HoBa2Cu3Ox. thin films. The thermodynamically stable region of HoBa2Cu3Ox. and the region where the HoBa2Cu2Ox films are formed are also determined both in molecular oxygen and in an oxygen plasma. The oxidizing activity of an oxygen plasma is equivalent to that of molecular oxygen at three orders of magnitude higher pressure. The oxygen plasma expands the thermodynamic stability limit toward higher temperatures and the oxidizing activity limit toward lower oxygen pressures. In addition, the interfacial reaction between an oxide superconductor and silicon is investigated. The oxygen ions in HoBa2Cu3O film diffuse into Si even at room temperature, probably enhanced by the strong affinity of silicon for oxygen ions.
Energy Distribution of Negative Oxygen Ions Emitted from YBaCuO and Iron Garnet Targets by dc- and rf-Magnetron Sputtering
Authors: Krumme Jens-Peter , Hack Ron A. A. , Raaijmakers Ivo J. M. M. 
Published: June 2019

ABSTRACTThe energy distribution of negative O− species sputtered from an YBaCuO and an iron-garnet target in dc- and rf-magnetron discharges has been analyzed by means of an energy-dispersive mass spectrometer in the range of noble-gas pressures from 0.05 to 4.2 Pa. Evidence is presented that energetic 0- ions originate essentially from two sources: (a) those formed directly by sputtering from the target surface and accelerated across the sheath in the full cathode-potential gradient; and (b) those created by electron attachment to neutral oxygen atoms near the sheath boundary to the plasma and accelerated in the remaining potential gradient of the sheath. On their path through the plasma these energetic O− ions are eventually annihilated by electron stripping and elastic scattering dominating in the pressure × distance regime above ∼0.1 Pa × m. The yield YO- of type-a O− ions increases with decreasing oxygen-vacancy density. Thus, doping of the noble-gas plasma with up to ∼1 vol% oxygen results in enhanced yield of 0- ions, while doping with hydrogen reduces the formation of O− species but gives rise to the creation of OH- ions. Furthermore, YO-increases with increasing ionicity of the oxides constituting the target, like BaO, exhibiting a larger difference in electronegativity between anions and cations. Thus, we find a between 1 and 2 orders of magnitude less yield of O− ions from a GdBiFeGaAl-gamet, as compared to the YBaCuO target, confirming the dissociative behavior of the BaO bond.
CH4 :H2 :Ar rf/ECR Plasma Etching of GaAs and InP
Authors: Law Victor. J. , Ingram S. G. , Jones G. A. C. , Grimwood R. C. , Royal H. 
Published: June 2019

ABSTRACTA comparative study of CH4 :H2 , and CH4 :H2 :Ar rf-plasma and microwave electron cyclotron resonance (ECR) plasma etching of GaAs and InP is presented. The study is in two parts;(i) Kinetic studies of GaAs and InP etch rates as a function of the constituent gas flow rates, applied rf and microwave powers, substrate temperature and position. The results indicate that CH4 :H2 :Ar ECR etching of GaAs is 10× more efficient in the utilisation of the CH4 precursor gas than rf-plasmas. However, the absolute etch rates are lower (70 nm min−1 for rf and 25 nm min−1 for rf biassed ECR-plasmas).The effect of etching conditions on InP morphology is also examined.(ii) The study of electrical “damage” in GaAs/AlGaAs high electron mobility transistor (HEMT) Hall bar structures, was investigated by ECR-plasma etching off the top GaAs capping layer. Results indicate that ECR-plasma etching with an rf-bias between 0V and −30V does not significantly effect the electrical characteristics of such devices at 300K, with some degredation at 1.2 K.
Chemical Precursors for GaAs Etching with low Energy ion Beams: Chlorine adsorption on GaAs(100)
Authors: Jackman Richard B. , Tyrrell Glenn C. , Marshall Duncan , French Catherine L. , Foord John S. 
Published: June 2019

ABSTRACTThis paper addresses the issue of chlorine adsorption on GaAs(100) with respect to the mechanisms of thermal and ion-enhanced etching. The use of halogenated precursors eg. dichloroethane is also discussed in regard to chemically assisted ion beam etching (CAIBE).