bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical Prediction of the Effective Thermal Conductivity of Open- and Closed-Cell Foam Structures
Authors: Hossein Hosseini Seyed Mohammad , Öchsner Andreas , Fiedler Thomas
Published: April 2010

This paper investigates the thermal properties of metallic open-cell and closed-cell foam structures in space filling and non-space filling configurations. In both, i.e. open-cell and closed-cell structures, a linear trend depending on the relative density has been reported. However the closed-cell structures compared to open-cell ones have a higher thermal conductivity for the same relative density.
Parametric Analysis of the Classification of Harrison Kinetics Regimes in Grain Boundary Diffusion
Authors: Belova Irina V. , Murch Graeme E. , Fiedler Thomas
Published: April 2010

Recently, the transition point between the Harrison Type-A and Type-B kinetics regimes as well as the emerging intermediate AB transition regime have been analysed in detail by making use of Lattice Monte Carlo (LMC) simulations of tracer depth concentration profiles as a function of diffusion time and distance between grain boundaries e.g. [1-3]. In the present study, we analyse Harrison Type-B to Type-C kinetics regimes in the transient grain boundary diffusion problem using the parallel slabs model and LMC numerical simulation. The transition point where the Harrison Type-B kinetics regime last occurs (transition point between the Harrison Type-B kinetics and the Type-BC kinetics) is estimated at  (= 0.5δ(Dlt)-1/2) = 0.1. The Harrison Type-C grain boundary diffusion kinetics regime is also analysed using LMC simulated concentration depth profiles. The transition point where the Harrison Type-C kinetics regime first occurs (transition point between the Type-BC kinetics and the Harrison Type-C kinetics) is estimated at  = 5.0. Therefore an intermediate Type-BC regime can be expected to occur between 0.1 <  < 5.0. Preliminary results for the cubic grain model show that the interval for the intermediate Type-BC regime is somewhat narrower for this model and occurs at 0.5 <  < 5.0.
A Mathematical Model to Predict Moisture Uptake of Dry Products Packaged Individually in Flexible Films
Authors: Delgado João M.P.Q. , Vázquez da Silva M.
Published: April 2010

This work present a model for prediction of moisture gain over storage time for individually packaged, which considered both the moisture transfer through the polymeric film to the headspace and from the headspace to the product. The transport of moisture between the headspace and each product was assumed to be controlled by external resistance. No interaction between the packaged components was considered. Moisture content within the product was assumed to be uniform for a given time and to relate to the headspace humidity by the GAB sorption isotherm. The isotherm parameters were determined by equilibrating samples at different relative humidity. The transient period of these experiments was used to estimate the mass transfer coefficients. The model was validated by monitoring the moisture take up by breakfast cereal and chocolate powder packed individually in different materials, oriented polypropylene (OPP) and low density polythelene (LDPE), during storage at 25°C and 75% RH (relative humidity). The model provided very good fits for the products packaged individually (with r2 above 0.99).
Modelling Moisture Uptake by Binary Mixtures of Products Packaged in Polymeric Films
Authors: Delgado João M.P.Q. , Vázquez da Silva M.
Published: April 2010

In this paper a mathematical model for prediction of moisture gain over storage time for binary mixtures of moisture sensitive products was developed, which considered both the moisture transfer through the polymeric film to the headspace and from the headspace to the product.
Moisture content within the product was assumed to be uniform for a given time and to relate to the headspace humidity by the GAB sorption isotherm. The transient period of these experiments was used to estimate the mass transfer coefficients. The model was validated by monitoring the moisture take up by breakfast cereal and chocolate powder mixture in different materials, oriented polypropylene (OPP) and low density polythelene (LDPE), during storage at 25°C and 75% relative humidity (RH). The model showed that for mixes some bias was clear, particularly for the cereal, probably owing to interactions between the products. If the resistance of the product to moisture uptake were not taken into consideration, the model would over-predict the experimental results by up to 20%.
Effect of Annealing on Nanocrystalline Structure of Nb3Sn Diffusion Layers in Composites with Internal Tin Sources
Authors: Popova E.N. , Popov Vladimir V. , Romanov E.P. , Sudareva S.V. , Elohina L.V. , Vorobyova A.E. , Shikov A.K. , Pantsyrny V.I. , Sudiev S.V.
Published: April 2010

Multifilamentary Nb3Sn-based superconducting composites manufactured by an internal-tin method have been studied by transmission (TEM) and scanning (SEM) electron microscopy. The main goal of this study is to reveal the effect of diffusion annealing regimes as well as the external diameter of the wires on the structure of nanocrystalline Nb3Sn layers (average grain size, grain size distribution, layer thickness, amount of Sn, etc.). It is demonstrated that multistep diffusion annealing results in quite a complete transformation of Nb filaments into Nb3Sn though some amount of the residual Nb remains in the filaments center. With an external diameter decrease the superconducting layers structure has been found to refine and get somewhat more uniform. An additional high-temperature annealing results in marked growth of Nb3Sn grain sizes and their scattering in sizes, which may negatively affect the current-carrying capacity of a wire.
Diffusion at Short Circuits: State of the Art
Authors: Bokstein Boris S.
Published: April 2010

Evidence for solid-state diffusion (the second half of the 19th century). The first measurements of solid state diffusion (W. Roberts-Austen, 1896–1922). The first tracer experiments to determine the solid-state diffusion (G. von Hevesy, 1913–1923). The first evidence of accelerated diffusion in polycrystalline materials (1924–1935). Autoradiographic studies of grain boundary diffusion (50s of 20th century). The first quantitative experimental and theoretical studies of the “short circuiting” diffusion (beginning from 1949, D. Turnbull and R. Hoffman – General Electric Research Lab.): radiotracer serial sectioning method, the Fisher model (1951) for grain boundary diffusion, exact solutions and developments of the Fisher model (1954–1963). The progress in the experimental methods for determination of grain boundary diffusion data and results of measurements for different metallic systems (up to date). The measurements of grain boundary diffusion parameters in the B and C regimes. Grain boundary diffusion and grain boundary segregation. Nonlinear segregation effects. Structural effects of grain boundary diffusion. Diffusion in bicrystals. Diffusion in nanocrystals. Computer simulation of grain boundary diffusion. Mechanisms of grain boundary diffusion.
Isotope Exchange of Gaseous Oxygen with Oxide LaMno3+δ Nanograins Boundary
Authors: Fishman Anatoly Yakovlevich , Kurennykh Tatiana Eugenievna , Vykhodets Vladimir Borisovich , Vykhodets V.B.
Published: April 2010

Isotope exchange of oxygen 18О2 with the boundary of nanograins of oxide LaMnO3+ obtained by the method of shock-wave loading was investigated in the temperature range of 400 – 500 °C. It was established that the temperature dependence of the isotope exchange rate is described by the Arrhenius expression, the activation energy and the pre-exponential factor being 1.67 eV and 1.8∙102 cm/s, respectively. Comparison with literature data has shown that for oxide LaMnO3+, a significant difference in activation energies and pre-exponential factors is observed for the isotope exchange rate with a ‘defect-free’ surface and the nanograin boundary. In case of the boundary, these parameters were higher: the activation energy about two times, and the pre-exponential factor, by almost 7 orders of magnitude.
Hydrogen-Induced Enhancement of Atomic Diffusion in Metals
Authors: Fukai Yuh
Published: April 2010

Atomic diffusion in metals is invariably enhanced by dissolution of hydrogen, in some cases by many orders of magnitude. This is a consequence of the formation of superabundant vacancies (SAVs), one of the general properties of M-H systems. Some examples of H-induced enhancement of interdiffusion in alloys and a detailed investigation of self-diffusion in Nb hydride, NbHx, are described, together with accelerated atomic migration observed in electrodeposited metals, also a consequence of SAV formation in the electrodeposition process.
Effects of Combined Surface Modification on Adhesion Strength of CrN Coatings for STS420
Authors: Jeong G.C. , Choi H.J. , Sohn Yong Ho , Kwun S.I.
Published: April 2010

In order to improve the durability and performance of molds and tools, diverse methods of surface modification are used where the adhesion strength between a substrate and coating plays an important role. To improve adhesion strength, a combined surface modification method is often utilized. In this study, adhesion strength and microstructure of various combined surface modifications (i.e., ion-nitriding, Cr intermediate layer, CrN layer and nitrogen ion- implantation) were examined on STS420. Phase constituents, microstructure, adhesion strength and hardness of coating-substrate system with combined surface modification were examined by using optical microscopy, X-ray diffraction, transmission electron microscopy, scratch test, and nano-indentation. The highest adhesion strength was observed when CrN coating was formed by nitrogen implantation on ion-nitrided substrate with a Cr-intermediate layer. Influence of processing sequence and combination is related to microstructural observations and adhesion strength.
Composition and Pressure Dependence of the Diffusion Coefficients in Binary Liquid Alloys
Authors: Beke Dezső L.
Published: April 2010

There are a number of well-known empirical relations for diffusion in solids. For example the proportionality between the self-diffusion activation energy and melting point or between the entropy of the diffusion and the ratio of activation energy and the melting point (Zener rule) are perhaps the best known ‘rules of thumb’. We have shown earlier in our Laboratory, that these relations are direct consequences of the similarity of interatomic potentials seen by ions in solids. On the basis of this, similar relations were extended for impurity and self diffusion in binary solid alloys. In this paper, results for binary liquid mixtures will be reviewed. First a minimum derivation of the temperature dependence of the self-diffusion coefficient, D, is presented (minimum derivation in the sense that it states only that the reduced (dimensionless) D should be a universal function of the reduced temperature), using the similarity of interatomic potentials and dimensional analysis. Then the extension of this relation for determination of the pressure and composition dependence of the self-diffusion coefficients is described using pressure and composition dependent scaling parameters (melting point, atomic volume and mass). The obtained universal form (valid for binary liquid alloys) is very useful for the estimation of the temperature, composition and pressure dependence of the self-diffusion coefficients. Finally, the relation for the ratio of the impurity and self-diffusion coefficients is derived.
Diffusion in Binary Silicides of Iron and Molybdenum
Authors: Mehrer Helmut
Published: April 2010

Studies of tracer diffusion in silicides of iron and molybdenum mainly from our laboratory are reviewed. For three compositions of the DO3-structured Fe3Si tracer diffusion data of Fe and Ge are available. Fe diffusion is relatively fast and increases with Si content. Ge diffusion, which mimics Si self-diffusion, is fairly slow and almost independent of composition. A Mössbauer study of Fe diffusion revealed nearest-neighbour jumps. Positron annihilation and high pressure diffusion data indicate that, in addition to isolated vacancies, vacancy pairs also contribute to Fe diffusion. Ge and Si diffusion is presumably restricted to the Si sublattice. Tracer diffusion of Fe and Ge has been studied for B20-structured FeSi with the conventional tracer technique. Tracer diffusion studies after implantation of 31Si (half-life 2.6 hours) performed at the IGISOL facility in Jyväskylä, Finland, show that Ge and Si diffusion have similar diffusivities. Fe diffusion rates are considerably slower than those of Si and Ge. Tracer data of Mo, Ge and Si diffusion are available for both principal directions of the tetragonal C11b-structured molybdenum disilicide (MoSi2). For all three kinds of atoms diffusion perpendicular to the tetragonal axis is faster than parallel to it. Mo diffusion in both principal directions is by orders of magnitude slower than Si and Ge diffusion. The huge asymmetry between Mo and Si or Ge suggests that diffusion of both constituents is restricted to their own sublattice. Positron annihilation studies show formation of thermal vacancies on the Si sublattice. This suggests that Si and Ge diffusion proceed by a vacancy mechanism in the Si sublattice of MoSi2. The anisotropy ratio of Si self-diffusion is attributed to a high mobility of vacancies in the Si double layers perpendicular to the tetragonal axis.
Numerical Investigation on Transient Conjugate Optical-Thermal Fields in Thin Films Irradiated by Moving Sources for Front Treatments
Authors: Bianco Nicola , Manca Oronzio , Ricci Daniele
Published: April 2010

In this paper a numerical analysis on two-dimensional transient of the combined optical-thermal fields caused by a moving Gaussian laser source in a multilayer thin film structure on a glass substrate is carried out. The workpiece is considered semi-infinite along the motion direction and its optical and thermophysical properties are assumed temperature dependent. The COMSOL Multiphysics 3.4 code has been used to solve the combined thermal and electromagnetic problem. In this way, the optical field is considered locally one-dimensional and Maxwell equations are solved in order to evaluate the absorption in thin film. Results, in terms of transient temperature profiles and fields, are presented for different Peclet numbers and thin film thicknesses.
Bi-Velocity Method and Linear Nonreversible Thermodynamics, Interdiffusion in R2
Authors: Danielewski Marek , Wierzba Bartek
Published: April 2010

Kirkendall and Darken findings of the drift velocity since 1948 have stimulated progress in transport phenomenological models. The convection velocity (the Darken drift in solids), , and velocity of diffusion, , require definition and the method how the diffusion displacement is defined, computed and measured. The equation of volume continuity allowed the extension of the Darken method and avoids the rigid assumption of the constant molar concentration. In this work, we use the bi-velocity approach, i.e., the generalized Darken method, to model interdiffusion in two-dimensional diffusion multiple. We show the convergence of one- and two-dimensional models in the case of the process at the constant volume and perfect agreement between R1 and R2 simulations. We impose modifications in the foundations of mechanics of solids namely, the Navier-Lamé-Fourier equations. We show that the method can be used in the mechano-chemistry of solids and is self-consistent with linear irreversible thermodynamics.
The Effect of Alloying Elements on the Stability of Centerline Segregation
Authors: Réger Mihály , Verő Balázs , Kardos Ibolya , Varga Péter
Published: April 2010

The paper deals with the stability of centerline inhomogenity of continuously cast slabs and hot rolled products. The centerline segregation is a disadvantageous failure of slabs which can affect the quality properties of the final products. During hot rolling of slabs the centerline segregation pattern will become thin and stretch and it can also be detected in the middle part of heavy plates and coils. It is a common experience that the centerline segregation of heavy plates can not be easily decreased by post heat treatment. The pattern of the centerline segregation was modeled physically by preparing a sandwich structure of steel plates with different levels of carbon and alloying elements. Homogenization experiments were performed and the samples were examined metallographically. Diffusional calculations proved the governing role of carbon activity which is influenced by the distribution of alloying elements.
Anomalous Diffusion Coefficients for W(IV) Ion Diffusion in NaCl-KCl Melt at 700-750°C
Authors: Lugovskoy Alex , Unger Z. , Zinigrad Michael , Aurbach D.
Published: April 2010

The electrodepostion of bi-valent iron, zinc and tungsten (IV) on tungsten electrodes in equimolar NaCl-KCl melt at 700-750oC was studied by Cyclic Voltammetry and Chronoamperometry. While iron (II) and zinc (II) ions demonstrate regular values of diffusion coefficients, which are all in the range of 10-6-10-5 cm2/sec, tungsten (IV) ions diffuse considerably slower. Plausible process mechanisms were proposed, according to which the tungsten (IV) ions form polynuclear ions and these massive species diffuse at considerably more moderate rates.
Overview and Functional Characterization of Pb–Free Solders
Authors: Chin L.T. , Hing Peter , Tan K.S. , Olofinjana A.O.
Published: April 2010

There are now new legislations emerging or being contemplated to restrict the use of Pb in electronic devices. This development has provided the impetus for the development of Pb- free solder alloys and efforts are now geared towards characterizing their operational and functional properties. The most common alloys being recommended and investigated are those primarily based on the Sn-Ag-Cu (SAC) system. These SAC alloys generally have higher melting points than conventional Pb-Sn alloy. Additionally they are susceptible to microstructural evolution of inter-metallic compounds that have been implicated in thermal fatigue life, mechanical strength and fracture toughness of the soldered joints. We have studied the Sn rich corner of the Sn-Ag-Cu system with minor additions aimed at minimizing detrimental microstructural development and improving the solderability and the mechanical strength of soldered joints. Some of the SAC alloys with minor additions showed some interesting properties. Their shear strength measured ranged from 30 – 60 MPa. The combined properties of strength and conductivity recorded compared favorably with that of traditional Pb-Sn solders.
Diffusion in Materials by Atomic-Scale Modeling: Exploiting the Predictive Power of Classical and First-Principles Molecular Dynamics
Authors: Bulou Hervé , Goyhenex Christine , Massobrio Carlo
Published: April 2010

This paper highlights the role played by diffusion processes to achieve a better characterization of structure and dynamics in atomic-scale studies of materials. Two classes of examples are presented. In the first, we take advantage of diffusion coefficients to assess the performances of different exchange-correlation functionals employed within the framework of density functional theory. By calculating the diffusion coefficients one is able to make a choice on the functional best suited to describe a prototypical disordered system, liquid GeSe2. In the second class of examples, we rely on classical molecular dynamics to describe diffusion mechanism on nanostructured substrates. The migration of a Co adatom on a stepped Pt(111) surface is analyzed in detail and correlated to the value of the different diffusion barriers. The diffusion behavior of Au adatoms on the reconstructed Au(111) substrate is described in terms of diffusion isotropy and anisotropy, by comparison with the case of Co/Au(111). Taken altogether, these studies exemplify the close link between diffusion properties, a realistic description of materials and the current level of performances of atomic-scale simulations methods.
Metallographic and Numerical Studies of the Role of Catalyst Particles of MgH2-Mg System
Authors: Celino Massimo , Montone Amelia , Cleri Fabrizio , Aurora Annalisa , Mirabile Gattia Daniele , Giusepponi Simone , Vittori Antisari Marco
Published: April 2010

Magnesium is one of the most promising materials for hydrogen storage due to its high capacity and low cost. Unfortunately, practical applications are for the moment limited by the slow kinetics and the high operating temperature. Nanostructuring magnesium hydride MgH2, generally by ball milling, introduces plastic deformations and catalysts that highly enhances the H2 absorption and desorption. However a fundamental understanding of the role played by catalysts and interfaces in MgH2 is still lacking. Microscopic characterization of MgH2-Mg system with and without heavy metal catalysts, is achieved by combining accurate SEM observations of samples after partial desorption process and atomic level ab-initio molecular dynamics simulations of MgH2-Mg interfaces. The experimental method is based on low voltage SEM observations of cross sectional powder samples, prepared by a new specific metallographic process. Identification of nucleation sites of the sorption reaction and their correlation with the presence of catalyst particles is achieved by suitable experimental conditions. Moreover ab-initio molecular dynamics clarifies the interplay of interfaces and the deformations induced during desorption by the presence of catalysts that are able to lower binding energies and free hydrogen atoms toward interfaces. Both approaches confirm and characterize the nucleation step in the catalysts driven phase transformation.
A Coupled Model of Two-Phase Diffusion and Flow through Deforming Porous Cosserat Media
Authors: Adhikary Deepak P. , Guo Hua
Published: April 2010

Simulation of mining induced rock deformation, rock fracture enhanced permeability and fluid and gas diffusion and flow process is a complex task.
A new three dimensional coupled mechanical two-phase double porosity desorption and diffusion finite element code called COSFLOW has been recently developed by CSIRO Exploration and Mining to service the mining industry’s need. A unique feature of COSFLOW is the incorporation of Cosserat continuum theory in its formulation. In the Cosserat model, inter-layer interfaces (joints, bedding planes) are considered to be smeared across the mass, i.e. the effects of interfaces are incorporated implicitly in the choice of stress-strain model formulation. An important feature of the Cosserat model is that it incorporates bending rigidity of individual layers in its formulation and this makes it different from other conventional implicit models.
The Cosserat continuum formulation has a major advantage over conventional continuum models in that it can efficiently simulate rock breakage and slip as well as separation along the bedding planes. Any opening/closure along a bedding plane may introduce a strong anisotropy in fluid flow properties of the porous medium. This, in turn, will impact on the fluid/gas flow behaviour of the porous medium.
This paper will briefly describe the Cosserat continuum theory, the treatment of permeability changes with rock deformation and the coupling of the two-phase dual porosity fluid diffusion- flow model and present a number of examples highlighting the capability of the developed code in simulating the mining induced rock deformation, permeability changes and fluid diffusion and flow will be presented.
Diffusion in Electrodes Used for Resistance Spot Welding of Galvannealed Steel
Authors: de la Garza Maribel , del C. Zambrano Patricia , Guerrero-Mata Martha Patrizia , Réti Tamás , Réger Mihály , Felde Imre , Colás Rafael
Published: April 2010

A study was carried out on Zr-Cr bearing copper electrodes used for resistance spot welding of galvannealed steel strips. One electrode exhibited a series of well-defined layers in which Zn diffused to form β- and γ-brasses; an external layer containing iron was detected in this electrode. Another electrode that exhibited a high degree of damage did not exhibited continuous Zn-diffusion layers in all places, moreover, the Fe-containing layer was either removed, or had it grown to a high extent in some places; the occurrence of Cu-rich particles embedded within the Fe containing layer was observed. Multiple cracks were observed within the γ brass layer in both electrodes. The difference in the observed behaviour of the electrodes can be attributed to a difference in the characteristics of the galvannealed coating of the strips, as the first electrode was used to weld strips in which the layer corresponding to the  phase was well developed, whereas the second electrode was used to weld strips with only an incipient layer. It can be concluded that growth of the  phase changes the thermophysical properties of the zinc coating, affecting the temperature profile during spot welding.
Kinetic Monte Carlo (KMC) Simulation of GaAs (001) β2 (2x4) Reconstructed Surface and Characterization
Authors: Khachab Hamid , Abdelkafi Yamani , Belghachi Abderrahmane
Published: April 2010

Several methods have been introduced to study and simulate homoepitaxial growth of III-V materials. GaAs (001) surface has widely been used in the last three decades due both to its importance as substrate and for characterization of epitaxial growth.
In this paper, we firstly study the initial stage of homoepitaxial growth on a GaAs (001) β2(2x4) reconstructed surface using As2 . The simulation was carried out with Kinetic Monte Carlo simulations including the zinc blend structure β2 (2x4) reconstruction of GaAs surface.
Then we discus results of the homoepitaxy GaAs on GaAs particularly morphological evolution of the two dimensional islands and observations were made in real-time at the growth temperature using reﬂection high energy electron diffraction (RHEED) and roughness morphology.
Thermal Properties and Crystallization Behavior of Co67Fe4Cr7Si8B14 Amorphous Alloy
Authors: Haddad-Sabzevar M. , Sahebian S. , Jamili Z. , Hasheminejad S.A.
Published: April 2010

In order to investigate the crystallization behavior of the Co67Fe4Cr7Si8B14 amorphous metallic alloy, ribbons of this alloy were prepared by planar flow melt spinning process (PFMS). Differential scanning calorimetery (DSC) and differential thermal analyzer (DTA) were used to analyze the thermal properties and crystallization behavior of the samples at three heating rates of 10, 20 and 30º C/min. The experimental data were fitted to the Avrami model to determine the crystallization behavior. The results showed that the crystallization exotherm became wider and shifted toward a higher temperature range as the heating rate increased. The Avrami analysis also showed that n is about 1, which is related to the same transformation mechanism at different heating rates. The Kissinger method was used to determine the activation energy for the first crystallization peaks. The measured value is approximately 332.67 kJ/g.
The Consideration of Splendid Increasing Trend of Green Fuel H2 Production with the Help of Nanofine Materials
Authors: Fakhroueian Zahra , Afroukhteh Langroudi N. , Esmaeilzadeh Pouriya , Varmazyar H. , Ahmadirad M. , Shafiekhani A. , Yousefi M. , Karami M.
Published: April 2010

Processes to transform natural gas into hydrogen or synthesis of gas (H2+CO) have been extensively studied in recent decades. H2 can be used in fuel cells as a power source and syngas may be converted into hydrocarbons via the Fischer-Tropsch synthesis. An attractive alternative process for syngas production is the partial oxidation of methane (POM). The objective of this study is to find effective conditions in using of nanofine particles for producing high activity and novel nanocatalysts to syngas, especially selectivity green fuel H2 gas as a power source. Therefore, we could produce 98.6% methane conversion, and 97.1% H2 selectivity with the help of unique stable and new nanofine materials: Eco-friendly x%Ni / SiO2, Co /Ce/ZrO2, Ru / Ce / ZrO2, and highly active Co-Ru and Ni-Ru bimetallic over Ce-ZrO2 nanosized mixed oxide support catalysts. Recently, we prepared new and interesting nanostructures by Cu and Ni sputtering on the nanosized Ce-ZrO2 solid solution support in the first time. Several surfactants, dispersants and mixture of alcohol solvents were applied in synthesis of nanostructures and nanofluids as remarkable templates.
Analysis of the Recrystallization of Cold-Rolled Copper after Isothermal Annealing Using Electron Backscattered Diffraction Patterns
Authors: Matsushita M. , Ohfuji Hiroaki
Published: April 2010

Recrystallization processing of cold-rolled copper after isothermal annealing was investigated using high-resolution electron backscattered diffraction pattern analysis. The fiber texture is obtained by cold rolling with the rolled direction oriented along {111}, and the transverse and nominal directions have a random orientation. An isothermal recrystallization process at 150°C was investigated. Initially, rotations of the orientations occur from {111} to {100} and then small misfit angle boundaries decreased. Accompanying this change, the fiber-shaped grains change to a round shape grain and their sizes decrease. Considering these tendencies, we determined that rotation at subgrain boundaries is activated by isothermal annealing and subboundaries grow the boundary misfit angle >15 º. With further annealing, those grains surrounded by grain boundaries greater than 15º expanded. The rolling, transverse, and nominal orientations rotate {100}. Subsequently, a twin boundary appeared, and the fraction of twin boundaries increased.
Magnetic Assisted Abrasion, a New Method for Nano Level Surface Finishing
Authors: Vahdati Mehrdad , Sadeghinia E. , Shokuhfar Ali
Published: April 2010

A great deal of attention in manufacturing engineering has been focused on finishing operations of hard and brittle materials in recent years. This paper reports an experimental work on the analysis of surface roughness and material removal using design of experiment (DOE) method in magnetic abrasive finishing, (MAF) of flat surfaces. Change in surface roughness and material removal were found to increase with an increase in weight percentage of abrasive particles in magnetic abrasive brush, lubricant volume and decrease in working gap. Also, any decrease in the relative size of the abrasive particles vis-à-vis the iron particles would result into an increase of the surface roughness and decrease in material removal. It was observed that the work piece hardness had no considerable effect on the process results. The optimum parameter levels which lead into the best surface finish and highest material removal were also derived from these experimentations.
Optimum levels included weight percentage of abrasive particles of 40%, Lubricant volume of 1 ml, working gap of 3 mm, relative size of abrasive particles vis-à-vis the iron particles of 0.22, and work piece hardness of 82-87 HBN.
Disk type test pieces were selected from Al 7075 and their two side surfaces were under experiments. Experiments were made using a milling machine spindle as magnetic pole holder, and its table as fixture holder for work pieces.
Water Vapor Permeability of Clay Nanocomposites Based on Amorphous PET
Authors: Greco Antonio , Corcione Carola , Maffezzoli Alfonso
Published: April 2010

In this work nanocomposites based on amorphous poly(ethylene terephthalate) (PETg) were developed using melt intercalation. X-ray analysis performed on the PETg nanocomposites showed that intercalation and exfoliation took place during static mixing. The water vapor permeability of PETg nanocomposites was correlated to the volume fraction of the impermeable inorganic part of the omMMT.
Optical and Mechanical Properties of Aluminum Film Deposited on Glass Substrate
Authors: Her Shiuh Chuan , Wang Yi Hsia
Published: April 2010

The aluminum film with high reflectivity and low absorption in the visible wavelength region has been widely used in optical applications. In this investigation, aluminum films were prepared on glass substrates by electron-beam vapor deposition. The reflectivity of the Al thin film was measured by a Perkin-Elmer Lambda spectrophotometer in the wavelength region of 450-680 nm. The experimental measurements of reflectivity were validated with the numerical results using the Essential Macleod software. The surface topology and microstructure of the film were examined by means of atomic force microscope (AFM). The effects of the temperature and humidity on the reflectivity of the Al film were examined by the environmental test. Nanoindentation tests were employed to determine the hardness and Young’s modulus of the film. The measured hardness of the Al thin films were found to depend on the penetration depth.
Interdiffusion Studies in the Co- Mo System
Authors: Divya V.D. , Ramamurty U. , Paul Aloke
Published: April 2010

Study of interdiffusion in the Co-Mo system is important to understand the performance of turbine blades in jet engine applications. Mo is added to superalloys to increase the solid solution strengthening and the creep resistance. In this study, the interdiffusion coefficient in the Co(Mo) solid solution and impurity diffusion coefficient of Mo in Co are determined. Further, the activation energy and pre-exponential factors are calculated, which provide an idea about the atomic mechanism of diffusion.
Fe Ions Diffusion and Oxygen Complexes Evolution during Thermodonors Annealing in B-Doped Czochralsky Silicon Crystal
Authors: Skidanov Vladimir
Published: April 2010

The great enhancement of the minority carrier recombination rate after optical activation of FeB pairs was used for investigation of interstitial Fe ions diffusion in p-type Czochralsky silicon by Surface Photo-Voltage Technique (SPV). Highly reproducible profiles of the Fe ions distribution were obtained after one-time thermodonors annealing process (650 °C, 30 min.) with Fe film evaporated on one side of silicon slab and successive layer by layer silicon slab etching. Evolution of Fe concentration distribution between both sides of initially inhomogeneously contaminated silicon slab in durable annealing processes was investigated. Gradual Fe concentration reduction near preliminary contaminated slab surface and Fe concentration increase near opposite surface were observed. Fe concentrations near both surfaces become equal after approximately 10-times annealing in agreement with diffusion rate obtained by the first method. Chaotic release and hiding of latent Fe were observed after 5-7 hours of annealing process. Two-exponential increase of other than Fe recombination centers concentration was observed during 650 °C annealing. Both exponential factors are found to be functions of interstitial oxygen concentration in the silicon ingot.
Computer Simulation Model for First-Order Phase Transition Fluctuation Stage
Authors: Bondareva Anna , Levchenko Tatiana , Zmievskaya Galina I.
Published: April 2010

Ion irradiation of surfaces leads to blistering (vacancy-gaseous bubbles formation into crystal lattice) and/or nano-scale islands of thin cover formation. Stochastic model of first order phase transition at fluctuation stage is presented by superposition of Wiener processes of nuclei clustering and it’s Brownian motion. Solution of Ito-Stratonovich stochastic differential equations allows studying the evolution of distribution functions versus clusters sizes and relative lattice locations of nuclei.
Investigation of Optical and Thermo-Electrical Properties of SnSb2S4 Thin Layers Using the Photothermal Deflection Technique
Authors: Gaied Imen , Gassoumi Abdelaziz , Kanzari Mounir , Yacoubi Noureddine
Published: April 2010

Sulfosalt SnSb2S4 films have been deposited on glass substrates by thermal evaporation and subsequently thermally annealed in vacuum at temperatures from 100 to 250°C. Below a transition temperature of 140°C, the films are highly resistive with a dominant amorphous component, however above this temperature, the samples exhibit p+-type semiconductor behaviour with a dominant crystalline component.In this work we have studied the thermal and optical properties of these films using the photothermal deflection technique. The thermal properties are determined by comparing the experimental amplitude and phase curves variations versus square root modulation frequency of the photothermal signal to the corresponding theoretical ones. The best theoretical fitting curves are obtained for well-defined values of thermal conductivity and thermal diffusivity. The optical absorption spectrum is obtained by comparing the experimental normalized amplitude of the photothermal signal curves variations versus the wavelength to the corresponding theoretical curves variations versus the optical absorption coefficient. We have determined the energy gap by using the Tock law. From a measure of the sample’s resistance, one can deduce the electrical resistivity which may be correlated to the thermal conductivity.
The Effect of Pressure on the Phase Transition of Pd3Cu Alloy
Authors: Davoodi J. , Ahmadi M.
Published: April 2010

In this investigation, we focused on the effects of pressure on the melting of elements Cu, Pd as well as Pd3Cu order alloy. We have performed molecular dynamics based computations of the variation of the physical properties of the elements Cu, Pd and Pd3Cu alloy with pressure and temperature. The quantum Sutton-Chen many-body interatomic potentials have been used for these elements, and the standard mixing rule has been used to obtain the parameters of this potential for the alloy state. This molecular dynamics simulation was performed in the NPT ensemble. Our study enabled us to predict the thermodynamic properties such as melting temperature, isobaric heat capacity as well as the lattice thermal expansion. The temperature dependence of energy and density were calculated at high pressure. Moreover, we presented the variation of the melting temperature, heat capacity as well as the thermal expansion of the crystal with pressure. The obtained results showed that the melting temperature increase with increasing pressure and isobaric heat capacity as well as lattice thermal expansion decrease with increasing pressure. Our computed results are in reasonable agreement with the experimental data where they are available.
Evaluations of Hydrogen Permeation on TiN-20wt.%Co Membrane by Hot Press Sintering
Authors: Kim Kyeong Il , Kim Sang Hern , Kim Whan Gi , Ur Soon Chul , Hong Tae Whan
Published: April 2010

Nowadays, the most promising methods for high purity hydrogen production are membranes separation such as polymer, metal, ceramic and composites. It is well known that Pd and Pd-alloys membranes have excellent properties for hydrogen separation. However, it has hydrogen embrittlement and high cost for practical applications. Therefore, most scientists have studied new materials instead of Pd and Pd-alloys. On the other hand, TiN powders are great in resistance to acids and chemically stable under high operating temperature. In order to get specimens for hydrogen permeation, the TiN powders synthesized were consolidated together with pure Co powders by hot press sintering. During the consolidation of powders at HPS, heating rate was 10K/min and the pressure was 10MPa. It was characterized by XRD, SEM, and BET. Also, we estimated the hydrogen permeability by Sievert's type hydrogen permeation membrane equipment.
The Effect of Traveling and Rotation Speeds on Mechanical Properties during Friction Stir Welding of Dissimilar Al Alloys
Authors: Park Jae Cheul , Kim Seong Jong
Published: April 2010

Interest in Al alloys for ship construction has increased because of the advantages of high speed with lightweight, increased load capacity, and ease of recycling compared to fiber-reinforced plastic. This study determined that the optimum traveling and rotation speeds for friction stir welding of 5052-O and 6061-T6 Al alloys for shipbuilding applications are 61 mm/min and 1600 RPM, respectively.
Measurement of Mass Diffusion Coefficient of Multi-Component System in Aqueous Media by Phase Shifting Interferometer
Authors: Komiya Atsuki , Torres Juan F. , Maruyama Shigenao
Published: April 2010

This paper describes a novel technique to determine mass diffusion coefficients of multi-component system within a transparent mixture by using an optical system. The mixture is composed of sodium chloride and lysozyme as solutes. Binary and multi-component solution experiments were conducted separately under constant temperature conditions. By measuring transient diffusion fields inside the cell, as well as for mixed multi-component solutions, it was confirmed that within the concentration ranges considered in this study, the diffusion of each solute inside the cell progresses independently. This indicates the superposition principle of concentration for certain levels of sodium chloride and lysozyme within the cell. Furthermore, by using this concentration superposition principle and an inverse analysis based on the conjugate gradient method, the diffusion coefficients of each solute in the mixture were successfully obtained from several multi-component experiments. Each obtained diffusion coefficient was good agreement with the determined diffusion coefficient from binary experiment.
Diffusion Kinetics of BSA Protein in Stimuli Responsive Hydrogels
Authors: Naddaf A.A. , Bart H.J. , Tsibranska I.
Published: April 2010

A two-dimensional diffusion mathematical model with moving boundary conditions was developed to evaluate the diffusion kinetics of bovine serum albumin (BSA) through the network of poly(N-isopropylacrylamide) hydrogel (poly(NIPAAm)). These thermosensitive hydrogels were experimentally tested for their response to BSA by exposing the hydrogel disc-shaped geometry to different temperatures and varied protein concentration. The BSA release, which is coupled with hydrogel shrinking when reaching the low critical solution temperature (LCST) of poly(NIPAAm), could be satisfactory described by the model. During the early course of hydrogel shrinking, the hydrogel outermost surface layer collapses to form a dense layer in comparison to the interior bulk matrix. Due to the hydrophobic interaction between polymer chains and polymer protein, the formed layer is thick and dense enough to restrict the outward permeation of entrapped BSA molecules from the hydrogel interior, which greatly slows down the release rate. A good agreement between experimental and calculated data was achieved.
Heat Transfer in Black Holes
Authors: Corral Bustamante R. Leticia , Sáenz D. , Arana N.I. , Cárdenas D.
Published: April 2010

In a universe in indefinite expansion, undetermined amounts of dark material suspended in the space-time continuum exist. The case of ‘sufficient’ amount of material contracted throughout time due to its density can occur. Using relativistic equations, in the present work a thermodynamic system was considered whose volume of control is limited by a gigantic mass that is suspended in space in order to predict its behavior. Given the obtained results, evidence of a certain quantized dark material in process of collapse or collapsed into a black hole can be argued.
The heat transfer of the black hole was measure through entropy change with respect to the time and other forms of energy, it was determined that the hole emits particles to surroundings from its event horizon (black hole ‘shining’). The emissions are proportional to the disappearance of the hole; they are candidates to integrate the “baby universes" of Hawking with new histories that satisfy the theorem "a black hole has no hair".
Hydrogen Diffusivity and Solubility in Internally Oxidized Pd0.97Zr0.03 and Pd0.97Nb0.03 Alloys
Authors: Lagreca E.R. , Azambuja Viviane M. , dos Santos Dílson Silva
Published: April 2010

Internally oxidized (I.O.) Pd0.97Zr0.03 and Pd0.97Nb0.03 alloys were submitted to gas permeation tests with temperatures in the range of 473-873 K. The internal oxidation was kept in a conventional furnace at 1073 K for 24 hours in air contact. The formation of nano-oxides, ZrO2 and Nb2O5, dispersed in the Pd matrix was observed. SEM images showed a preferential segregation of these oxides in the grain boundaries. It was observed that the diffusion coefficient in the sample containing Nb oxide was smaller than that in the Pd-Zr oxide. The effect of hydrogen pressure was investigated in the Pd-Nb samples. It was observed that the hydrogen diffusion coefficient increases with increasing the pressure. The hydrogen solubility is bigger for the Pd-Zr internally oxidized. This effect is attributed to the Zr nanoxides, which are smaller than Pd-Nb precipitates and then offer more interface for trapping the hydrogen.
A High Order Time Advancement Scheme for Prediction of Solidification Processes
Authors: Abbasnejad A. , Maghrebi M.J. , Basirat Tabrizi H.
Published: April 2010

The aim of this study is the simulation of alloys and pure materials solidification. A third order compact Runge-Kutta method and second order scheme are used for time advancement and space derivative modeling. The results are compared with analytical and semi-analytical solutions and show very good agreement.
Performance Characteristics of Capacity Control of Industrial Water Cooler Using Pulse Modulation Valves
Authors: Choi W.J. , Kim H.W. , Baek Seung Moon , Kang H.J. , Lee Ho Saeng , Yoon Jung In
Published: April 2010

Recently, the technical trend for machine tools is focused on enhancing of speed and accuracy. For high speed and high accuracy, the thermal deformation must minimize in machine tools. To minimize the thermal influence, accurate machine tools need to be adopted to a cooling system with high precision. In this study, we suggest a high accuracy water cooling system using PMV(Pulse Modulation Valve) control. In this system, we use a compressor which is able to be driven under the condition of unloading to improve the efficiency of the PMV control. And a vapor refrigerant from the suction side of the compressor is injected back into the compressor suction side using a solenoid valve. The PMV control can be used by this method. Also, by comparing with the existing ON-OFF control method on identical operating conditions, we evaluated the efficiency and reliability of the new method. This method showed a shorter reaction time than that of the existing method. Also, the efficiency and performance improved by lower compressor work using the vapor injection without compressor stop. This study shows that the COP of this system decreased when load capacity of compressor was decreasing. In addition, the precision of this system using PMV was higher than for the ON/OFF type. This result will be used for a basis data of comparative experiment with inverter control and to manufacture of high accuracy water cooling system.
Thermal Conductivity and Thermal Expansion of Copper Matrix Composites Reinforced with High Modulus C Fibres
Authors: Beronská Naďa , Štefánik Pavol , Iždinský Karol
Published: April 2010

Copper matrix composite with pure copper matrix reinforced with high modulus carbon fibres Thornel K 1100 was prepared by gas pressure infiltration technique. As-received composite was subjected to thermal expansion and thermal conductivity measurements in longitudinal and transversal directions. Large anisotropy of properties as well as surprisingly good structural stability has been observed. The mean coefficients of thermal expansion as low as 0.8 x 10-6 K-1 in longitudinal and as high as 23.5 x 10-6 K-1 in transversal directions were determined, the thermal conductivities as high as 650 Wm-1K-1 in longitudinal direction and as low as 60.7 Wm-1K-1in transversal directions were measured.