bluuebunny/crossref_metadata_2025_split huggingface dataset:
Microstructural and Mechanical Characterization of a TRIP-800 Steel Welded By Laser-CO2 Process
Authors: Perez-Medina G. Y. , Zambrano P. , López H. F. , Reyes-Valdés F. A. , López-Cortés V. H. 
Published: April 2011

AbstractThis paper presents results on the impact of Laser CO2 process variables on the weldability, phase transformations and tensile properties of a TRIP800 Steel. The microstructure of this steel is comprised of ferrite, bainite and retained austenite phases. This is obtained by controlled cooling from the intercritical annealing temperature to the isothermal bainitic holding temperature. These steels have been increasingly used in the last 10 years in the automotive industry and for these materials to be used effectively; the influence of material and the CO2 laser welding process condition must be clearly understood. Hence, in this work the effect of the welding process on the resultant microstructures and on the exhibited mechanical properties is investigated. It is found that the tensile strength of welded specimens falls below 800 MPa and that the elongation becomes 15 % or lower. In turn, this clearly indicates that the implemented laser welding process leads to a reduction in the TRIP800 steel toughness.
Evolution of microstructure of 304 stainless steel joined by brazing process
Authors: García-Vázquez F. , Guzmán-Flores I. , Garza A. , Acevedo J. 
Published: April 2011

AbstractBrazing is a unique method to permanently join a wide range of materials without oxidation. It has wide commercial application in fabricating components. This paper discusses results regarding the brazing process of 304 stainless steel. The experimental brazing is carried out using a nickel-based (Ni-11Cr-3.5Si-2.25B-3.5Fe) filler alloy. In this process, boron and silicon are incorporated to reduce the melting point, however they form hard and brittle intermetallic compounds with nickel (eutectic phases) which are detrimental to the mechanical properties of brazed joints. This investigation deals with the effects of holding time and brazing temperature on the microstructure of joint and base metal, intermetallic phases formation within the brazed joint as well as measurement of the tensile strength. The results show that a maximum tensile strength of 464 MPa is obtained at 1120°C and 4 h holding time. The shortest holding times will make boron diffuse insufficiently and generate a great deal of brittle boride components.
Strengthening phases in the production of Al2024-CNTs composites by a milling process
Authors: Pérez-Bustamante R. , Pérez-Bustamante F. , Herrera-Ramíreza J. M. , Estrada-Guel I. , Amézaga-Madrid P. , Miki-Yoshida M. , Martínez-Sánchez R. 
Published: April 2011

AbstractCarbon nanotubes (CNTs) synthesized by a chemical vapor deposition (CVD) method and the 2024 aluminum alloy (Al2024) are used in the production of Al2024-CNTs composites. An homogeneous dispersion of the CNTs into the aluminum matrix is achieved by a mechanical milling processing. CNTs keet their morphology after milling and sintering processes. Formation of aluminum carbide as a function of CNTs contents is observed. Formation of equilibrium phases during sintering is observed by electron microscopy. CNTs and aluminum carbide in the composites are characterized by transmission electron microscopy. Hardness results of sintered products show an increment of up to 285% over the unreinforced alloy prepared by the same route.
Mathematical Modeling of Impingement of an Air Jet in a Liquid Bath
Authors: Solórzano-López J. , Zenit R. , Ramírez-Argáez M. A. 
Published: April 2011

AbstractPhysical and mathematical modeling of jet-bath interactions in electric arc furnaces represent valuable tools to obtain a better fundamental understanding of oxygen gas injection into the furnace. In this work, a 3D mathematical model is developed based on the two phase approach called Volume of Fluid (VOF), which is able to predict free surface deformations and it is coded in the commercial fluid dynamics software FLUENTTM. Validation of the mathematical model is achieved by measurements on a transparent water physical model. Measurements of free surface depressions through a high velocity camera and velocity patterns are recorded through a Particle Image Velocimetry (PIV) Technique. Flow patterns and depression geometry are identified and characterized as function of process parameters like distance from nozzle to bath, gas flow rate and impingement angle of the gas jet into the bath. A reasonable agreement is found between simulated and experimental results.
Magnetic properties of bulk composite FeBSiM (M=Cr,Zr) alloys with high microhardness
Authors: Báez S. , Betancourt I. , Hernandez-Rojas M. E. , Figueroa I. A. 
Published: April 2011

AbstractThe synthesis, mechanical and magnetic properties of bulk composite Fe72B19.2Si4.8M4 (M=Cr, Zr) alloys obtained by a copper mould injection casting technique under a protective helium atmosphere are reported and discussed. The resultant microstructure of the composite alloys consists of crystalline Fe92Si8 and Fe2B phases embedded in a glassy matrix. The values of microhardness (Hv) show maxima for the alloy containing Cr with 10.24±0.95 GPa. The maximum value of saturation magnetization average (μ0Ms) is 1.25±0.02 T for Cr-containing alloy. The Curie temperatures (Tc) of amorphous phases are higher than 390 K for both alloys. However, the bulk composite alloys presents values for crystallization temperature (Tx) of 1289±10 K and 1140±10 K for Cr and Zr-containing alloys, respectively. These results are interpreted on the basis of the interplay between the crystalline and amorphous phases.
Stress concentration on artificial pitting holes and fatigue life for aluminum alloy 6061-T6, undergoing rotating bending fatigue tests
Authors: Lemus Víctor H. M. , Almaraz Gonzalo M. D. , V. Lopez J. Jesús 
Published: April 2011

AbstractThis work deals with rotating bending fatigue tests on aluminum alloy 6061-T6, under loading condition close to the elastic limit of the material. Results have been obtained for three types of specimens: without artificial pitting, specimens with one artificial pitting hole and specimens with two neighboring artificial pitting holes. Results show that fatigue endurance is reduced in the case of one pitting hole and considerably for two neighboring pitting holes. In order to explain this behavior, numerical analysis by FE are carried out to determine the stress concentrations for the three types of specimens. It is found that the stress concentration for two neighboring pitting holes is an exponential function of the separation between the two holes, under uniaxial loading. The probability to find two or more neighboring pitting holes in real industrial materials, such as cast iron, corroded or pitting metallic alloys is high; then, the stress concentration for two or more neighboring pitting holes needs to be considered for the fatigue prediction life under fatigue loading and corrosion attack applications.
Effect of the deposition rate on thin films of CuZnAl obtained by thermal evaporation
Authors: López-Pavón L. , López-Cuellar E. , Torres-Castro A. , Ballesteros C. , de Araújo C. José 
Published: April 2011

AbstractThermal evaporation is used to deposit thin films of CuZnAl on silicon substrates. For this purpose, a CuZnAl shape memory alloy is used as evaporation source. The chemical composition and the phases present in the films are evaluated at two different deposition rates: 7 and 0.2 Å/s. The thin films are heat treated to promote the diffusion of the elements and characterized by X-ray Diffraction, Energy Dispersive X-ray Spectroscopy and Scanning Transmission Electron Microscopy (STEM). It is shown that the chemical composition of the thin films is significantly different to that of the CuZnAl alloy used as evaporation source. Moreover, the films produced at 7 Å/s show a significant loss of Zn, contrary to the results obtained using a deposition rate of 0.2 Å/s. It is also observed that the composition varies across the thickness of the film, suggesting that the various alloying elements are evaporated at different rates during the deposition process. Finally the predominant phases present in the films belong to the AlxCuy family.
Development of a New Nickel-base Superalloy for High Temperature Applications
Authors: Covarrubias Octavio 
Published: April 2011

AbstractSince their appearance during in the 1940 decade, nickel-base alloys are appreciated for their superior mechanical properties and microstructural stability at elevated temperatures and high stresses. They are typically used in jet-engines and land-based turbines for energy generation. Such materials, known as superalloys are in constant evolution as designers are encouraged to propose more efficient and powerful systems of propulsion and energy generation. This evolution leads to conceive and manufacture new superalloys capable to fulfill higher requirements. Alloy 718Plus® is emerging as an alternative material for the design and construction of components to be used in jet-engines and land-based turbines for energy generation. 718Plus® is a precipitation hardened nickel-base alloy designed to have the stability of superalloys similar to Waspaloy and the good processing characteristics of other materials as the 718 alloy. Since the early 2000 decade, ATI Allvac has lead a complete program in order to validate capabilities and properties of the 718Plus® alloy. Objectives for this effort include a characterization and its introduction as a viable material for the design and manufacture of components to be installed technologically. As part of this project, contoured rings made of 718Plus® are rolled considering industrial conditions. Several heat treatments, involving solution and precipitation processes are performed on segments extracted from involved contoured rings. Effects of such hot-working conditions and heat treatment procedures on properties as forgeability, tensile, hardness and stress-rupture characteristics are evaluated. Optical and electron microscopy are performed to evaluate microstructural properties as grain size and promotion of precipitates, in order to complement reported results.
Application of clay as a means of support to biomaterial with anti-inflammatory agents
Authors: Domínguez-Patiño M.L. , Chávez-Castillo M , Rodríguez-Martínez A. , Alemán R.M. Melgoza , Jiménez-Ferrer E , Herrera-Ruíz M. 
Published: April 2011

In the last fifteen years, there have been significant changes in the production of medicines, mainly in the addition of new components to the formulation of solid dosage forms. The current trend of “back to nature” to lead to a healthier life has led those who are engaged in the pharmaceutical field to develop new formulations that allow the use of natural products of plant originFor example, excipient ingredients, used as carriers for a drug's active ingredients, are now being used. These are incorporated into a drug in order to facilitate the drug's preparation, maintenance, or administration. The excipient is beneficial to the patient because it allows the drug to be easily administered and absorbed by the human body [3]There is evidence that the clays have great potential for both absorption and adsorption due to its tiny particles. In addition, it has been reported that some clays have an effective antiseptic and healing ability [5–8]In the present work, a clay called bentonite was tested as a support vehicle of an inflammatory agent derived from a Mexican native plant called Distictis buccinatoria, commonly named “Tonacaxóchitl”. Studies carried out by Rojas et al. have shown that the organic extract of this plant has important antibacterial, antifungal, cytotoxic and anti-inflammatory properties [9]
Thermoluminescence Properties of Novel La2O3 Phosphor Obtained by Solution Combustion Synthesis
Authors: Orante-Barrón V. R. , Cruz-Vázquez C. , Bernal R. , Denis G. , Yukihara E. G. 
Published: April 2011

AbstractThermoluminescence (TL) of La2O3 is reported for the first time. Novel La2O3 phosphor was obtained by solution combustion synthesis (SCS) in which a redox combustion process between lanthanum nitrate and urea at 500 °C is accomplished. The powder samples obtained were annealed at 900 °C during 2 h in air. X-Ray Diffraction (XRD) results showed the hexagonal phase of La2O3 for annealed powder samples. The TL glow curve obtained after exposure to beta radiation of these samples, displayed two maxima located at ˜ 101 °C and ˜ 200 °C, and a shoulder at ˜ 247 °C. Results from experiments such as dose response and fading showed that annealed La2O3 powder obtained by SCS is a promising material for radiation dosimetry applications.
Hydrogen Production by Catalytic Steam Reforming of Model Compounds of Biomass Fast Pyrolysis Oil
Authors: Lan P. , Xu Q. L. , Lan L. H. , Yan Y. J. , Wang J. A. 
Published: April 2011

AbstractA Ni/MgO-La2O3-Al2O3 catalyst with Ni as active component, Al2O3 as support, MgO and La2O3 as additives was prepared and its catalytic activity was evaluated in the process of hydrogen production from catalytic steam reforming of bio-oil. In the catalytic evaluation, some typical components present in bio-oil such as acetic acid, butanol, furfural, cyclopentanone and m-cresol were mixed following a certain proportion as model compounds. Reaction parameters like temperature, steam to carbon molar ratio and liquid hourly space velocity were studied with hydrogen yield as index. The optimal reaction conditions were obtained as follows: temperature 750-850 °C, steam to carbon molar ratio 5-9, liquid hourly space velocity 1.5-2.5 h-1. The maximum hydrogen yield was 88.14%. The carbon deposits were formed on the catalyst surface but its content decreased as reaction temperature increased in the bio-oil steam reforming process.
A Comparative Study on the Sorption of BTEX and Cr (VI) in Drinking Water by Anionic and Cationic Sorbents
Authors: Flores-Valle S. O , Carrera S. P. Paredes , Valenzuela-Zapata M. A. 
Published: April 2011

AbstractA comparative study of different sorbent materials was performed in order to propose an integrated system to eliminate both, anionic and cationic contaminant ions in drinking water, such as Cr (VI) and BTEX (benzene, toluene, ethylbenzene and xylenes). The adsorption process was studied using several adsorbents: activated carbon, cationic clays (bentonite) and natural zeolite as well as anionic clays (Al-Mg/Nitrate hydrotalcites). The activated carbon and natural zeolites were commercial samples, while hydrotalcite-like compounds were synthesized by an ultrasound-assisted method. It was found that although activated carbon showed a good performance in the cationic sorption, the calcined hydrotalcites presented the highest sorption capacity of chromates compared with activated carbon which had a good performance only up to 100 ppm. For higher concentrations (>100 ppm) activated carbon is saturated rapidly and its sorptive capacity is practically null.
Variable Temperature Study of Au and Au-Pt Nanoparticles on Selected Oxide Supports
Authors: Barrett D. , Franklyn P. , Scurrell M. 
Published: April 2011

AbstractWe report on the size relationship of Au and Au-Pt nanoparticles that were synthesised on silica and anatase phase titania supports. Deposition-precipitation (DP) of metal chlorides with the addition of urea and ammonium hydroxide was used to produce the nanoparticles. The relative particle size relationship of the Au and Au-Pt nano particles (NP's) was investigated, relating the Pt concentration and the support polymorph over a temperature range. It was found, with the use of in-situ variable temperature powder X-ray diffraction (VT-PXRD) and transmission electron microscopy (TEM), that the addition of Pt to the Au system corresponded to a reduction in particle size over a broad temperature range.
Photocatalytic Deposition of Nickel Nanoparticles on Titanium Dioxide
Authors: Rodríguez Julia L. , Pola Francisco , Valenzuela Miguel A. , Poznyak Tatiana 
Published: April 2011

AbstractMetallic nanoparticles may be tailored to obtain specific size and morphology. In this work we present the synthesis of Ni/TiO2 catalysts by a photodeposition method. Our investigation included the photochemical and photocatalytic reduction of the nickel organometallic precursor (Ni (II) acetylacetonate) over titania (Degussa P-25) support. The photo-reduction kinetics was followed by UV-Vis and the catalysts were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). According to the results, the photochemical reduction of the Ni precursor was only 30% at λ= 254 nm, whereas, the photocatalytic route was approximately 90 % (λ= 365 nm) yielding Ni nanoparticles with diameter ranging from 10 to 40 nm.
Characterization of Growth Defects in ZnTe Single Crystals
Authors: Zhou W. , Wu J. , Dudley M. , Su C.H. , Volz M.P. , Gillies D.C. , Szofran F.R. , Lehoczky S.L. 
Published: April 2011

Abstract(111) wafers sliced from a boule of ZnTe grown by horizontal physical vapor transport (PVT) have been characterized using synchrotron white beam X-ray topography. The growth axis was about 6° off [311]. The presence of dislocation slip bands, subgrain structures and [111] axis 180° rotational twins were revealed. The slip bands were observed to break up the ordered dislocation cell structures comprising the subgrain boundaries. The initiation of slip at regions of stress concentration at the junctions of subgrain boundaries and twin boundaries was observed. The asymmetric distribution of slip bands either side of the twinned region of crystal suggests that twin boundaries can act as barriers for slip. Several types of detailed twin boundary configuration were determined from the topographs. Using a combination of white beam X-ray topography and Nomarski interference microscopy, the three dimensional shapes of the twin boundaries were determined. Approximate atomic structures at these boundaries are presented.
InAs/InxGa1-xSb Type II Strained Layer Superlattices for Long Wavelength Infrared Detection Applications
Authors: Talwar D. N. , Loehr John P. , Jogai B. 
Published: April 2011

AbstractShort period InAs/InxGa1−xSb superlattices (SLs) may allow strong optical transitions in the long wavelength infrared (> 10 μm) spectral region. Absorption calculations can be difficult, however, because of the strongly type - II interface and because of the large lattice mismatch. We propose that a long wavelength response can be achieved for substantially thinner layers of SLs if the In composition in InxGa1−xSb is properly chosen. This will misalign the bands through strain effects and further reduce the superlattice bandgap. Band structure calculations are reported for InAs/InxGa1−xSb type - II SLs grown on GaSb substrate by using an empirical tight-binding model (ETBM). All of the structures considered here are assumed to be well within the critical strain thickness. Particular care is taken to incorporate the strain effects accurately in the ETBM formalism by modifying the overlap integrals according to the bond lengths and bond angles. We compute the band structure and the cutoff wavelengths of InAs/InxGa1−xSb (001) SLs and compare the results with the existing magnetooptical and photo conductivity data. In addition, we compare the ETBM with the k.p and effective bond orbital models.
Effects of the Substrate on the Response of P(VDF-TrFE) Pyroelectric Detector
Authors: Mahrane A. , Djafari-Rouhani M. , Najmi A. , Esteve D. 
Published: April 2011

AbstractThe thermal analysis on the response of pyroelectric detector revealed that an optimal configuration structure could be found for a certain frequency range. Thus, it appeared that the pyroelectric layer should be thick at low frequencies but it should be very thin at high frequencies. The introduction of a thermal insulator is done trying to find out a trade off between sensitivity and response time. It has been found that its influence is restricted to a certain frequency range. The optimal thickness is related to the thermal diffusion length. We noticed also that it depends very little on the configuration structure.
Bulk Homogeneity of Iron Doped InP
Authors: Jimenez J. , Avella M. , Gonzalez M. A. , Martin P. , Sanz L. F. , Chafai M. 
Published: April 2011

AbstractFe- doped InP is studied by a spatially resolved photocurrent technique, probing electronic transitions related to the iron impurity levels. This scanning technique allows to get information on bulk homogeneity regarding to the electrically active iron impurity distribution. The presence of doping growth striations is revealed with a high sensitivity. Also results about the local photocurrent at the Cottrell atmospheres of the dislocations are shown. The role played by other defect levels in the photocurrent contrast is also discussed.
Modeling of MBE Growth with Interacting Fluxes
Authors: Tomich David H. , Eyink K. G. , Haas T. W. , Capano M. A. , Kaspi R. , Cooley W. T. 
Published: April 2011

AbstractTernary and quaternary III-V alloys are important for many optical device applications, and a precise control of the composition is required. Molecular beam epitaxy (MBE) is generally considered a non-equilibrium or kinetically controlled process but most of these models are too computationally intensive for real time control. We report on using a precursor state growth model 1,2 for the growth of GaAsSb to control the growth conditions and hence the film composition. The activation energies and the parameters appearing in the relationship are determined by fitting the calculated compositions to experimental ones as determined by x-ray diffraction. The effect of substrate temperature, growth rate and flux intensities on composition is discussed.
More Insight into the VHF-Glow-Discharge by Plasma Impedance Measurements
Authors: Kroll U. , Ziegler Y. , Meier J. , Keppner H. , Shah A. 
Published: April 2011

ABSTRACTWe performed plasma impedance measurements at room temperature for a hydrogen plasma using an impedance analyser. The plasma excitation frequency range spans from 40 to 70 MHz. Both the real and imaginary part of the impedance decrease monotonously with increasing frequency. These measurements are in agreement with prior experimental observations [1], that the required peak-to-peak voltage between the electrodes is reduced at higher excitation frequencies. Using a simple equivalent circuit for the plasma this effect can be mainly attributed to the increased sheath capacitance. Furthermore, by modelling the sheath with a simple parallel plate capacitor, its thickness could be estimated: it decreases from 2 MM at 40 MHz to about 1.4 MM at 70 MHz plasma excitation frequency. Finally, a possible link between the decreasing sheath thickness on the increase of deposition rate is discussed.
Characterization of Amorphous Silicon Deposited at high rate by Helium Dilution PECVD and used for Applications in Radiation Detection
Authors: Ilie A. , Pochet T. , Foulon F. , Equer B. 
Published: April 2011

ABSTRACTPECVD hydrogenated Amorphous silicon (a-Si:H) layers have been deposited at high rates using helium dilution of the reacting precursors. This allows the fabrication of very thick layers (a few tens of microns) within reasonable processing times. This technique can be applied to the fabrication of thick p-i-n detector devices to be used for direct X-ray detection. Several p-i-n devices have been processed at deposition rates as high as 15 A/sec without significant changes in the optoelectronic properties of the a-Si:H films. Capacitance-Voltage measurements have been performed in order to measure the residual space charge density in the intrinsic region of the devices. The results demonstrate a moderate increase of the N*DoS concentration with the deposition rate. DC bias photoconductivity measurements have also been performed. The experimental data have been fitted with a multiple trapping transport model for holes. The model parameters have been studied and related to the electronic properties of the films.