bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mechanism of Grain Growth During Annealing of Si-Al Electrical Steel Strips Deformed in Tension
Authors: B J. Salinas , R A. Salinas 
Published: April 2011

AbstractThe mechanism of recrystallization as a result of annealing during 600–7200 seconds at 700 °C of a Si-Al, low C electrical steel strip is investigated in samples deformed in tension. The evolution of grain size during annealing is evaluated by optical microscopy and electron backscatter diffraction in the scanning electron microscope. It is found that grain growth starts after an incubation time of 600 s with no apparent evidence of primary recrystallization. After that, the grain size-time relationship exhibits two different stages. Initially, the grain size increases linearly with time up to about 3600 s. During this time, some selected grains grow until they consume the deformed microstructure. In the second stage, the rate of growth decreases significantly and a final grain size of about 150 m is reached after 7200 seconds of annealing. Grain orientation spread maps obtained from EBSD data of deformed and partially recrystallized samples during the stage of linear growth reveals that the growing grains exhibit lower misorientation and therefore smaller stored energy than the non-recrystallized matrix grains. Analysis of image quality maps reveal that the IQ values for {100}<uvw>orientations are higher than those observed for {111}<uvw>orientations thus suggesting that the {100}<uvw>orientations grow at the expense of {111}<uvw>orientations by a mechanism of strain-induced boundary migration.
Performance of Cement Systems with Nano-SiO2 Particles Produced Using Sol-gel Method
Authors: Sobolev Konstantin , Flores Ismael , Torres Leticia M. , Cuellar Enrique L. , Valdez Pedro L. , Zarazua Elvira 
Published: April 2011

AbstractThe reported research examines the effect of 5–70 nm SiO2 nanoparticles on the mechani-cal properties of nanocement materials. The strength development of portland cement with nano-SiO2 and superplasticizing admixture is investigated. Experimental results demonstrate an in-crease in the compressive strength of mortars with SiO2nanoparticles. The distribution of nano-SiO2 particles within the cement paste plays an essential role and governs the overall perfor-mance of these products. Therefore, the addition of a superplasticizer is proposed to facilitate the distribution of nano-SiO2 particles. The application of effective superplasticizer and high-speed dispergation are found to be very effective dispersion techniques that improve the strength of su-perplasticized portland cement mortars, reaching up to 63.9 MPa and 95.9 MPa after aging dur-ing 1 and 28 days, respectively. These values compare favorably with the observed compressive strengths of reference portland cement mortars of 53.3 MPa and 86.1 MPa. It is concluded that the effective dispersion of nanoparticles is essential to obtain the composite materials with im-proved performance.
Development of an Algorithm for Random Packing of Multi-Sized Spherical Particles
Authors: de la Garza-Gutiérrez H. , Plascencia-Barrera G. , de la Torre S. D. 
Published: April 2011

AbstractA new computational algorithm is introduced for packing simulation of spherical elements/particles into an imaginary container with three main possible geometries, cubic, cylindrical and spherical. The performance of the algorithm depends directly on the strategy or logic considered to solve the problem and the quality of its computational implementation. The combination of these two factors let the packing algorithm here presented and named as Octant Packing Random Algorithm (OPRA) to reduce the computation time between 2 and 127 times, when compared with the simplest or classical Packing Algorithm. OPRA is designed to reduce the number of comparisons needed to accept or reject a new position for an element/particle to be allocated into the virtual container. OPRA considers the container as if it were divided into 8 equal cells or octants limiting the overlap detection for a new position.
Stress Ratio Effect on Fatigue Behavior of Aircraft Aluminum Alloy 2024 T351
Authors: Benachour M. , Hadjoui A. , Benguediab M. , Benachour N. 
Published: April 2011

AbstractAluminum alloy series 2xxx, 6xxx, 7xxxx and 8xxx enjoy the widest use in aircraft structural applications. Among these materials, aluminum alloy 2024 remains the most commonly used and especially in T351 temper situation. The fatigue crack propagation behaviour of aluminum alloy 2024 T351 has been investigated using V-notch specimen in four bending test. A series of stress ratios from 0.10 to 0.50 was investigated in order to observe the influence of stress ratio on the fatigue life and fatigue crack growth rate (FCGR). The increase in FCGR, which occurs as the stress ratio is increased from 0.10 to 0.50, is generally attributed to an extrinsic crack opening effect. In T-S orientation and at low stress intensity factor, the increasing of stress ratio increase the FCG. Experimental results are presented by Paris law when coefficients C and m are affected by stress ratio. Contrary, at high stress intensity factor, the effect of stress ratio is reversed. We notice a decreasing of fatigue crack growth rate with an increasing of stress ratio. This effect may be explained by microstructure effect in (T-S) crack growth. The analysis of stress ratio effect by Elber model, shown that this model gives bad interpolation in this situation and the parameter characterized the crack closure factor will be adjusted.
Effect of Hot Band Annealing on the Microstructure and Mechanical Properties of Low Carbon Electrical Steels
Authors: Gutiérrez-Castañeda E. , Salinas-Rodríguez A. 
Published: April 2011

AbstractMagnetic properties of grain non-oriented low-C electrical steels are improved when the hot rolled strip is annealed (HBA) prior to cold rolling and final annealing treatments. This improvement results from development of a {100}<uvw> texture in the large grained ferrite microstructure produced during final annealing. HBA at 800–850 °C results in rapid decarburization and elimination of carbide particles which have caused concerns about the suitability of the mechanical properties in the final product. In this work, samples taken from a hot rolled electrical steel coil are subjected to HBA during 150 minutes at 850 °C, cold rolled and finally annealed three minutes at temperatures between 700 and 1000 °C. The resulting tensile properties are compared with those of samples subjected to a similar processing route but without the HBA treatment and samples of industrially semi-processed grain non-oriented electrical steel decarburized 16 hours at 750 °C. It is shown that the yield strength of samples with and without HBA depends on the final grain size according to the Hall-Petch relationship; the final grain size depends strongly on annealing temperature. However, the HBA treatment causes the strength to decrease by a factor of about 2.5 and the ductility to increase by a factor of about 1.5. It is observed that the microstructure and tensile properties of the semi-processed electrical steel subjected to a final decarburization annealing are identical to those observed in material subjected to HBA in the present work. These results indicate that the HBA treatment not only improves the magnetic properties but also leads to a significant reduction of production time for grain non-oriented electrical steels.
Grinding Admixture for Portland Cement Obtained from The Acetic Fermentation of Molasses
Authors: Jiménez-Alvarez Francisco J. , Téllez-Jurado Lucía 
Published: April 2011

AbstractThe acetic acid is used for the manufacture of grinding admixtures in the cement industry. The most admixtures used by commercial milling are mixtures of amine acetates, glycols and sugars. The commercial formulations contain 10% acetic acid as amine acetate. In this work the amine acetate was synthesized using the product from fermentation of molasses. In this paper amine acetate was synthesized using the product from acetic fermentation of molasses and it was followed by fermentation of molasses through FT-IR and pH measurement. The fermented product was neutralized with tertiary amine, and finally were adding glycols into the grinding admixture. This admixture was compared with a commercial admixture, having a similar size distribution in both cases.
Ultrasound Influence on Kinetics of Phenol Sulphoxidation in Water Solutions in the Presence of Cobalt Complexes Immobilized on Polyacrylic Acid
Authors: T. V. C.c.s. Shakieva 
Published: April 2011

AbstractThe influence of hypersonic on phenol sulfoxidation kinetics in the presence of cobalt complexes fixed on polyacrylic acid (PAA) is investigated in the soft conditions (313-333K). Products arep- ando-phenolsulfonic acids. Phenol conversion under the investigated conditions reaches 98-100 %. The ultrasonic sound in the interval from 0 to 60 kHz leads to aggrandizement of trivalent cobalt concentration in a solution, as a result, increasing the reaction activity. The enlargement of ultrasound influence (USI) modulation frequency and the exposure time results in destruction of a binuclear complex, which may be responsible for enhanced catalytic activity. KEDWORDS: ultrasound influence; polyacrylic acid; immobilized cobalt complexes; kinetics
NO Reduction by CO Catalyzed with Au/TiO2 in Oxygen-rich Condition
Authors: Wang J. A. , Toledo J. A. , Angeles C. , Moran-Pineda M. , García-Ruiz A. 
Published: April 2011

AbstractGold nanoparticles supported on titania catalysts with different Au loadings were prepared and evaluated in the reaction of NO reduction by CO in an oxygen rich condition. The crystalline structures of the Au/TiO2 materials were refined with Rietveld method. TiO2 support chiefly contains anatase phase, having a crystalline size ranged from 5 to 15 nm. Au particles have an average crystal size approximately 2-5 nm as Au concentration less 3 wt %. In the reaction of NO + CO + O2, the Au/TiO2catalysts show a selectivity to 100 % N2, neither NO2 nor N2O was yielded in the reaction temperature between 25 and 400 °C, which strongly indicates that Au/TiO2catalysts are much superior to the other catalysts like Pt/TiO2 catalysts on which N2O was usually produced in the reaction temperature below 200 °C and NO2 was produced in the reaction temperature above 300 °C under a similar reaction condition.
Hydrogen Production via Methane Decomposition Using Ni and Ni-Cu Catalysts Supported on MgO, Al2O3and MgAl2O4
Authors: Pola José F. , Valenzuela Miguel A. , Córdova Iván A. , Wang J. A. 
Published: April 2011

AbstractNi (10%) and Ni-Cu (50 and 25%, respectively) catalysts supported on alumina, magnesia and magnesium aluminate were synthesized. The characterization was carried out by X-ray diffraction, nitrogen physisorption, temperature programmed-reduction, Raman spectroscopy and SEM. The catalysts were tested in the methane decomposition reaction using a tubular fixed bed reactor operated in the range of 500-580°C under atmospheric pressure. A higher activity was observed with the bimetallic catalysts supported on alumina and magnesium aluminate. These results were explained in terms of Ni-Cu alloy formation and weak metal-support interaction. In the case of monometallic catalysts, a strong metal-support interaction was detected, which revealed the lowest activity and stability compared with the bimetallic catalysts. The formed carbon was a combination of amorphous and graphite.
Production of Di-isopropyl ether (DIPE) over 12-Molybdophosphoric Acid Supported on ZrO2. An Alternative Octane Enhancer for Lead-free Petrol
Authors: Hernández-Cortez J. G. , López-Salinas E. , Manríquez Ma. , Picquart M. 
Published: April 2011

AbstractSolid acid catalysts of 12-Molybdophosphoric acid (MoP) supported on hydrous zirconia have been synthesized using impregnation method. Structural transformations due to thermal effects have been studied by different techniques including X-Ray diffraction, thermogravimetric analysis (TGA), infrared absorption (DRIFT), Raman spectroscopy and31P MAS NMR. These techniques showed that the heteropolyacid present undegradedKegginstructure. The transformation of heteropoly anion of pure HPMo to MoO3begins at a temperature lower than that for its ZrO2-supported counterpart. The activity of ZrO2-supported (MoP-Z) catalysts in the 2-propanol decomposition presents a high selectivity to the formation of DIPE and propene, this selectivity is related with acid sites determined by thermodesorption (TPD) of NH3.
The Study of Charge Transport in Nanoscale DNA Structures
Authors: Bart G. , Singh M. R. , Zinke-Allamang M. 
Published: April 2011

AbstractWe have studied the variable range hopping (VRH) mechanism for polarons in DNA structures using an exponential density of states. Due to the electron-phonon interaction localized polarons are formed in the DNA helix. The unwinding of DNA increases molecular orbital overlap between bases while decreasing the base-to-base distance. These types of vibrations create phonons. We consider that DNA has a band tail which has an exponential density of states and we have calculated the temperature- and the electric field dependence of the conductivity. We compare our model with the experiments of the electrical conductivity of samples of double-stranded H5N1 genes of avian Influenza virus DNA. Our theory is able to explain their data.
Low Resistance Ohmic Contacts to n-Hg1−xCdxTe Using a HgTe Cap Layer
Authors: Leech Patrick W. , Reeves Geoffrey K. 
Published: April 2011

AbstractNon-alloyed ohmic contacts of HgTe on Hg1−xCdxTe (x = 0.60) with metallisations of Ti, In and Au have been investigated. Layers of HgTe with thickness in the range from 0.1 μm to 1.0 μm were grown by organometallic epitaxy either as an abrubt or a graded junction, depending on the in-situ annealing conditions. The layer thickness and the extent of interdiffusion with the Hg1−CdxTe were determined using Rutherford backscattering spectrometry (RBS). The results have shown that an abrupt rather than a graded structure was essential in order to achieve the minimum value of specific contact resistance, ρc, of ≈5 × 10−5 Ωcm2. In addition, a critical thickness of HgTe (≥0.2 μm) was required in order to obtain a substantial reduction in ρc. For these metal/HgTe/Hg1−xCdxTe contacts, the metal Ti has produced the lowest values of ρc and greatest adhesion to the HgTe. Both of these properties have been attributed to the strong interfacial reaction of the overlayer of Ti with HgTe.
Quality of Bulk CdTe Substrates and its Relation to Intrinsic Defects
Authors: Meyer B. K. , Hofmann D. M. , Stadler W. , Emanuelsson P. , Omling P. , Weigel E. , Müller-Vogt G. , Wienecke F. , Schenk M. 
Published: April 2011

AbstractBoth the cadmium vacancy (Vcd) and the tellurium vacancy (VTe) in CdTe are identified by means of electron paramagnetic resonance (EPR). The Vcd is a double acceptor and the EPR spectrum is observed in its single negative charge state. The symmetry is found to be trigonal, which can be explained in a model in which the hole occupies a dangling bond t2 orbital and the orbital degeneracy is removed by a static Jahn-Teller distortion. The hyperfine interaction shows that the hole is localised on one of the four Te neighbours. The EPR spectrum of VTe+ reveals cubic (unperturbed) symmetry and the hyperfine structure shows that the unpaired electron is equally spread over the four Cd neighboursPhoto-EPR measurements locate the 0/+ state of VTe at Ev + 0.2 eV and the 2-/- acceptor level of VCd to be situated less than 0.47 eV above the valence band.
Defect Reduction in Cd1-xZnxTe Epilayers on GaAs Substrates
Authors: Chadda Saket , Malloy Kevin , Reno John 
Published: April 2011

AbstractCd0.91Zn0.09Te/CdTe multilayers of various period thicknesses were inserted into Cd0.955Zn0.045Te bulk alloys grown on (001) GaAs. The net strain of the multilayer on the underlying Cd0.955Zn0.045Te was designed to be zero. X-ray diffraction full width at half maximum (FWHM) was used as a means to optimize the period thickness of the multilayer. Transmission electron microscopy of the optimum period thickness samples demonstrated four orders of magnitude decrease in the threading dislocation density. Mechanism of bending by equi-strained multilayers is discussed.
An Array of CdTe Detectors for Inaging Applications
Authors: Eisen Y. , Polak E. 
Published: April 2011

AbstractThe performance characteristics of a linear array composed of several hundred miniature spectroscopy grade CdTe detectors are described. The linear array is utilized in a X-ray security imaging system. It operates either in an energy dispersive mode to highlight certain atomic elements in the luggage or in a regular mode for obtaining only the transmission image of the luggage. The array functions in the photon counting mode and tolerates count rates as high as 106 counts/sec. The array has high quantum efficiency and good spatial resolution which result in excellent image quality. The dynamic range, the electronic noise, the energy resolution, the homogeneity of response among detectors and the image quality are presented.
Performance Characteristics of N-Type SI-SI/GE Quantum well Infrared Photodetectors
Authors: Shadrin V. D. , Coon V. T. , Serzhenko F. L. 
Published: April 2011

AbstractThe theory of multiple quantum well n-type Si-SiGe IR detectors is presented. The coefficient of photoabsorption, quantum efficiency and responsivity of Si-SiGe quantum well detector are calculated taking in consideration the effects of depolarization and electron-electron exchange interaction. We show that the Si-SiGe quantum well detectors possess lower dark current and better performance characteristics compared to GaAs-AlGaAs photodetectors.
Photoconductive (PC) and Photovoltaic (PV) Dual-Mode Operation III-V Quantum well Infrared Photodetectors for 2–14 μm IR Detection
Authors: Li Sheng S. , Wang Y. H. , Chuang M. Y. , Ho P. 
Published: April 2011

AbstractWe present four new types of III-V quantum well infrared photodetectors (QWIPs) operating in photoconductive (PC) and photovoltaic (PV) modes for the wavelength range from 2 to 14 μm. These dual-mode (DM) operation QWIPs were grown by the MBE technique using GaAs/AlGaAs, AlAs/AlGaAs, and InGaAs/InAlAs material systems. Based on the bound-to-miniband (BTM) and the enhanced bound-to-continuum (BTC) intersubband transition schemes, these detectors provide the features of large absorption coefficient, low dark current, and high detectivity in the wavelength of interest, and show promising for use in large area IR focal plane array image sensor applications.
Process Optimization for the Fabrication of the Thin PtSi Schottky Barrier Diode IRCCD
Authors: Wang Wang-Nang , Ho Chia , Shiue Jee-Ming 
Published: April 2011

AbstractHigh quality abrupt junction PtSi thin film prepared by the MBE system with in situ precleaning and annealing was obtained. Wet etching and low energy hydrogen plasma excitation to generate H-terminated Si surface and low temperature thermal desorption were used to clean the substrate. IRCCD thus fabricated achieved the quantum efficiency 0.8%. TEM, STM/AFM, AES/ESCA, and RBS were used to monitor the fabrication processes.
Iridium Silicide Formation by Rapid Thermal Annealing
Authors: Rodriguez T. , Wolters H. , Almendra A. , Sanz-Maudes J. , Da Silva M.F. , Soares J.C. 
Published: April 2011

AbstractIridium silicides formation by rapid thermal annealing (RTA) under vacuum at several temperatures in the range of 350 to 650°C has been investigated. The substrates and the silicide films were analyzed by Rutherford backscattering spectrometry (RBS) and Auger electron spectroscopy (AES). At 350°C, no distinguishable phase was detected for 240 seconds of annealing time. At 400°C, for processing time up to 45 seconds only Ir1Si1 was formed, for longer processing time Ir1Si1.75 was formed too. At higher temperatures even for very short processing time, Ir1Si1.75 was formed. Ir, Ir1Si1 and Ir1Si1.75 were present simultaneously if the iridium film was thick enough and the processing time was long enough too. For thin iridium layers, the Ir1Si1 formed was totally converted to Ir1Si1.75, if the annealing time was long enough. Formation rates were observed to be three to five orders of magnitude faster than the reported for furnace annealing.
A Shubnikov-De Haas Study of Tilted Magnetic Field in the HgTe/CdTe Superlattice
Authors: Lo Ikai , Mitchel W. C. , Boeringer D. , Harris K.A. , Yanka R.W. , Mohnkern L.M. , Reisinger A.R. , Myers T.H. 
Published: April 2011

AbstractWe have measured the Shubnikov-de Haas (SdH) effect in a HgTe/CdTe superlattice (SL) with a tilted magnetic field in the absence of an external electric field. We found that the peaks of the SdH oscillation changed with Bcosθ, indicating the two-dimensional character of the electron gas. The carrier concentration of the two-dimensional electron gas (2DEG) is equal to 2.95×1011 cm−2. The 2DEG shows the existence of a Stark ladder, which is caused by the internal electrostatic field, near the interface between the substrate and the SL. From the temperature dependence of the SdH measurements, we also show that the 3DEG in the SL miniband contributes to the non-oscillatory magnetoresistance and that the mobility of 3DEG in the miniband is lower than that of 2DEG in the Stark ladder.
The Photoemission from Superlattices of III-V Semiconductors with Graded Interfaces Under Quantizing Magnetic Field
Authors: Ghatak Kamakhya P. , De Badal 
Published: April 2011

AbstractIn this paper we have studied the photoemission from super-lattices of III-V semiconductors under magnetic quantization by formulating a new dispersion law. It is found, taking InAs/GaSb super-lattice with graded interfaces as an example that the photoemission, increases with increasing electron concentration in an oscillatory way and increases with decreasing magnetic field in the magnetic quantum limit. Besides, the photoemission in superlattices is much greater than that of the constituent materials and the well-known results for wide-gap materials have also been obtained from our generalized analysis. In addition, the theoretical analysis is in agreement with the experimental datas as given elsewhere.
Physics of the Meyer-Neldel Rule in Amorphous Silicon
Authors: Branz Howard M. , Yelon Arthur , Movaghar Bijan 
Published: April 2011

ABSTRACTWe show that the meyer-Neldel Rule (or compensation law) arises from the entropy effect of accumulating several excitations in order to surmount an activation barrier. This explanation applies both to annealing and to conductivity phenomena in a-Si:H. We consider three consequences of this theory for a-Si:H : 1) MN processes in a-Si:H involve coupling to a bath of “optical” phonons; 2) dc conductivity involves strongly electron-phonon coupled states rather than extended electrons and a fixed density of states; and 3) time-of-flight exponents depend upon the MN temperature.
Molecular Dynamics Studies of Defect Motion in a-Si:H
Authors: Fedders P. A. 
Published: April 2011

ABSTRACTFirst principles molecular dynamics methods are used to study the motion of defects including dangling bonds and H. We study motion among H passivating dangling bonds, bond centered H, and tetrahedral H. We find that relaxation effects can reduce activation energies by up to one eV. Our studies also include the actual simulation of the time evolution of an a-Si:H system for several picosec. Here we observe the motion of a dangling bond over several hops and the motion of an H atom by means dangling bond exchange.