bluuebunny/crossref_metadata_2025 huggingface dataset:
The Enhanced Kinetics of Precipitation Effects in Ultra Fine Grained Mg Alloys Prepared by High Pressure Torsion
Authors: Čížek Jakub , Procházka Ivan , Smola Bohumil , Stulíková Ivana , Očenášek Vladivoj , Islamgaliev Rinat K. , Kulyasova Olya B.
Published: March 2009

Precipitation effects in ultra fine grained (UFG) lightweight Mg-based alloys were
studied in the present work by means of positron lifetime spectroscopy, transmission electron
microscopy, and microhardness. The UFG samples with grain size around 100 nm were fabricated
by high pressure torsion (HPT). The UFG structure contains a significant volume fraction of grain
boundaries and exhibits a high number of lattice defects (mainly dislocations) introduced by severe
plastic deformation during the HPT processing. A high dislocation density and volume fraction of
grain boundaries enhance the long range diffusion of solute elements. Moreover, dislocations and
grain boundaries act as nucleation centers for precipitates. As a consequence, the precipitation
effects are facilitated in the UFG alloys compared to the conventional coarse-grained samples. This
phenomenon was examined in this work by comparison of the precipitation sequence in Mg alloys
with UFG structure and solution treated coarse-grained alloys.
Reduction of Solids in Leachate Streams by Membrane Bioreactors: Mass Transfer Topics and Fouling Problems
Authors: Castelo-Grande Teresa , Augusto Paulo A. , Monteiro P. , Barbosa Domingos
Published: March 2009

In this work the use of Membrane Bioreactors to treat leachate effluents is discussed. The
problem of membrane fouling is addressed, and some of the efforts being done to overcome this
problem presented. The process optimization requires the reduction of other parameters, some
directly related to mass transfer, such as the total amount of solids, the total dissolved solids and the
total suspended solids. The preliminary results obtained show the high potential of this technique
for the treatment of leachates, mainly for the reduction of solids in leachate streams.
Comparison between Maxwell-Stefan and Nernst-Planck Equations to Describe Ion Exchange in Microporous Materials
Authors: Lito Patricia F. , Silva Carlos Manuel
Published: March 2009

Two models comprising external and intraparticle mass transfer resistances developed to
describe ion exchange in microporous materials are compared. Maxwell-Stefan and Nernst-Planck
equations account for both concentration and electric potential gradients. However, under certain
conditions, Maxwell-Stefan approach can be more advantageous particularly due to taking into
account ion-ion and ion-solid interactions separately. The models were tested and compared with
data available in the literature, namely batch experiments on cadmium (II) removal from aqueous
solution using ETS-4 microporous titanosilicate. Calculated results reveal both models provide
good and similar representations as well as fine predictive capability. Therefore, under the
conditions investigated, both models can be successfully applied to describe intraparticle ionic
transport.
Liquid Chromatographic Method for Quantifying Atrazine Extracted by Supercritical Extraction
Authors: Castelo-Grande Teresa , Augusto Paulo A. , Barbosa Domingos
Published: March 2009

An analytical method, using High Performance Liquid Chromatography, was developed
for quantification of atrazine in extracts obtained by supercritical extraction of contaminated soils.
The method shows good linearity, for concentrations ranging from 0.1 mg/L to 200 mg/L, and
reproducibility, giving deviations lower than 2%. The recovery of atrazine by SCE was in the range
of 96 to 98%.
Heat and Mass Transfer Porous Medium Saturated with Compressible Fluid with Boundary Domain Integral Method
Authors: Kramer Janja , Jecl Renata , Škerget Leo
Published: March 2009

A numerical approach to solve a problem of combined heat and mass transfer in porous
medium saturated with compressible fluid is presented. Transport phenomena in porous media is
described using the modified Navier-Stokes equations, where for the governing momentum
equation the Brinkman extended Darcy formulation is used. Governing equations are solved with
the Boundary Domain Integral Method, which is an extension of classical Boundary Element
Method.
Modeling of Transport Phenomena in a Fuel Cell Anode
Authors: Coutelieris Frank A.
Published: March 2009

A mathematical model for the simulation of the transport phenomena occurred in the
anode of a typical fuel cell is presented here. The model initially considers a simple onedimensional
geometry where the mass transport equation is combined with a Tafel-type description
for the current density. By assuming isothermal conditions, the numerical solution of the differential
equations was achieved with the use of a non-linear shooting scheme in conjunction with the
multidimensional Newton algorithm. The space was discretized through a constant-step mesh while
the resulting nonlinear system of ordinary differential equations was solved by using the 4th order
Runge-Kutta method. The whole algorithm was implemented by developing a new FORTRAN
code. In addition, a planar two-dimensional geometry is also considered, where the mass transport is
described by the convection-diffusion equation within the catalyst layer together with the Navier-
Stokes equation for laminar flow conditions and the electrochemical effects, while the convective
heat transfer within the developed diffusion layer is also taken into account. This approach has been
numerically implemented and solved by using the finite volume method being applicable through
the CFD-RC© commercial package. For the sake of simplicity, the feedstream of the fuel cell was
assumed to be a hydrogen-rich mixture (H2 >90%) for all cases. Both SOFC and PEM type fuel
cells were considered in this study, while the results are presented in terms of fuel concentration,
produced current density and overpotential.
Co Anomalous Growth Kinetics of the CoSi Reaction Layer in a Si/System
Authors: Cserháti Csaba , Glodán Györgyi , Csik A. , Langer G.A. , Erdélyi Z. , Balogh Z. , Beke Dezső L.
Published: March 2009

Solid state reactions between amorphous Si and crystalline Co have been investigated by
4W electrical resistance and TEM. Multilayered (with 10 periods of 5nm a-Si/5nm Co and 10 nma-
Si/10nm Co layers) as well as tri-layered samples (20nm a-Si/3nmCoSi/6nm Co) were produced by
magnetron sputtering and isothermally heat treated at different temperatures between 473 and 523K.
From the time evolution of the normalized resistance the kinetics of the process were determined by
fitting a power law, tk, and k was between 0.8 and 1. Possibility of the interface reaction control
and/or the effect of the diffusion asymmetry (which was recently published for the non-parabolic
interface shifts on the nanoscale) will be discussed.
Surface Diffusion in Coadsorbed Layers with Different Mobilities of Adsorbates: (Li +Dy) on Mo(112) and (Li+Sr) on W(112)
Authors: Loburets A.T. , Senenko N.B. , Mukhtarov M.A. , Vedula Yu.S. , Naumovets A.G.
Published: March 2009

With the aim to study the regularities of surface diffusion in coadsorbed layers, we
investigated diffusion of lithium on the (112) surfaces of Mo and W precovered with
submonolayers of dysprosium and strontium, which have substantially lower mobilities than
lithium. Experiments were carried out using scanning contact-potential microscopy, and Li
diffusion parameters were extracted from diffusional evolution of coverage profiles. Dy and Sr
preadsorbed in amounts of ∼10–1 of a monolayer were found to reduce the diffusion rate of Li by
orders of magnitude. The strong impact of coadsorbates with low mobility on Li diffusion can be
caused by important role of collective mechanisms in surface diffusion, which entails pronounced
pinning effects, as well as by the possibility of formation of surface alloys and surface vitrification.
Modeling of Diffusion Saturation of (α + β) Titanium Alloys by Nitrogen in the Rarefied Medium
Authors: Matychak Ya. , Fedirko V. , Pohreljuk I. , Yaskiv O. , Tkachuk O.
Published: March 2009

The diffusion saturation of (α + β) titanium alloy by nitrogen under rarefied medium
taking into account the peculiarities of interaction both at the interface and in the metal core is
modeled. The corresponding diffusion problem using the diffusion equations in the medium
consisting two families of diffusion paths and non-stationary boundary condition at interface is
analytically solved. The effect of the temperature and time parameters, volumetric quantity of β-
phase on the kinetics of nitriding is estimated. It is established that with the increase of isothermal
exposure temperature and quantity of β-phase the surface saturation by nitrogen decreases. It is
caused by more intensive nitrogen penetration into bulk and formation of a deeper diffusion zone.
Studies on the Local Structure and the Spin Hamiltonian Parameters for Co2+ in CaTiO3
Authors: Lu Guang Duo , Wu Shao Yi , Zhang Hua Ming , Wei Li Hua
Published: March 2009

The local structure and the spin Hamiltonian parameters g factors gi (i =x, y and z) and
the hyperfine structure constants Ai for Co2+ in orthorhombic CaTiO3 are theoretically investigated
from diagonalization of 6 × 6 energy matrix within the 4T1 ground state for a 3d7 ion in
orthorhombic symmetry. In the calculations, the contributions from the admixtures of various J
states (J=1/2, 3/2, 5/2), the ligand orbitals and spin-orbit coupling and the fourth-order orthorhombic
field parameter, which were usually neglected in the previous works, are taken into account. The
crystal-field parameters are determined from the superposition model in consideration of the
suitable lattice distortion due to the charge and size mismatching substitution of Ti4+ by Co2+. Based
on the studies, the bond lengths R1 and R2 in the xy plane are estimated to suffer the relative
alternation R ≈ 5.4%, yielding more significant orthorhombic distortion in the impurity center as
compared with that for the host Ti4+ site in pure crystal. The calculation results based on the above
local lattice distortion show reasonable agreement with the observed values. The various
contributions to the spin Hamiltonian parameters are discussed. Present studies may theoretically
verify that the impurity Co2+ occupies the 6-fold coordinated Ti4+ site rather than the 12-fold
coordinated Ca2+ site, associated with the enhanced orthorhombic distortion due to the mismatching
substitution.
Calorimetric Studies of Dissolution Kinetics of Ni2(Cr,Mo) Phase in Ni-Cr-Mo Alloys Using Non-Isothermal Approach
Authors: Pai H.C. , Maji Bikas C. , Biswas A. , Krishnan Madangopal , Sundararaman M.
Published: March 2009

The kinetics of dissolution of ordered phase with Pt2Mo structure has been studied in two
nickel chromium alloys – one without molybdenum and another with molybdenum - using
differential scanning calorimetry. The activation energy for dissolution, determined using three nonisothermal
approaches was found to be ~ 418 kJ /mole for both the alloys. This value agreed very
well with the activation energy for coarsening of g″ precipitates in Ni-Cr-Mo matrix and is close to
activation energy for mobility of chromium and molybdenum in complex nickel alloy matrix.
Diffusion and Melting
Authors: Tiwari G.P. , Mehrotra R.S.
Published: March 2009

The paper reviews the correlation between the processes of diffusion and melting. It is
shown that the entropy of fusion and the melting temperature have a governing influence on the
self-diffusion rates in solids. The relationship between self-diffusion coefficient (D) in solids and
the melting parameters can be expressed as follows:
D = fa2ν exp (κSm / R) exp (– κSmTm / RT) ,
where f is the correlation factor, a the lattice parameter, ν the vibration frequency, Sm the entropy of
fusion, Tm the melting temperature in degree K, κ a constant and R, T have their usual meaning. The
above equation has been derived on the basis that the free energy of activation for diffusion is
directly proportional to the free energy of liquid phase. The well known relationships of the
activation energy for self-diffusion with the melting point and enthalpy of fusion can be derived on
the basis of this assumption. The constant κ is a group constant for any class or group of solids
having identical physical and chemical properties. The validity of the above equation is
demonstrated by the fact that when the self-diffusion coefficients are plotted as a function of
homologous temperature, they scale inversely with the magnitude of the entropy of fusion. The
hierarchy of self-diffusion rates within any group of solids is governed by the magnitude of the
entropy of fusion and the melting temperature.
The paper also discusses some interesting fall out of the close relationship between the
diffusion and the melting parameters concerning (a) the diffusion in elemental anisotropic lattices,
(b) anomalous diffusion behavior in bcc transition metals, lanthanides and actinides and (c)
congruently melting compounds.
Structural Characterisation of Diffusion-Bonded Hollow Sphere Structures
Authors: Veyhl Christoph , Winkler Rolf , Merkel Markus , Öchsner Andreas
Published: March 2009

This paper investigates the structural properties of sintered hollow sphere struc-
tures. First of all, the packing density is analysed using three different methods: namely, liquid
infiltration, Archimedes' principle, and image processing of micrographs. In addition, the pore
fraction in the metallic sphere shells is characterised based on micrographs and the density of the
structure and the base material is determined. In the final part, the geometrical characteristics
of the sphere structure and the material composition of the base material are analysed.
Boundary Line of Microcrystallites in Amorphous and Crystalline Structures of Metallic Glasses
Authors: Habib Khaled , Al-Arbeed A.
Published: March 2009

In a recent study conducted by the author, microcrystallites were observed to exist in amorphous, short range ordered, structures of several metallic glasses. The observation is based on X-Ray Diffraction (XRD) and Electron Diffraction (ED) and Transmission Electron Microscopy (TEM). The data from the X-ray diffraction shows that the metallic glasses have typical amorphous structures. However, the data from the Electron Diffraction indicates that the metallic glasses possess polycrystalline structures. This discrepancy between the XRD and ED data can be interpreted and explained by diffraction theory [1,2] with the aid of Transmission Electron Microscopy. In fact results in the recent work show that with a mathematical relationship originally derived by Sherrer [1], one can determine the boundary line between microcrystallites in amorphous, short range ordered, structures and crystalline, long range ordered, structures. The boundary line of microcrystallites is defined with the aid of Transmission Electron Microscopy in which the size of subgrains, of the metallic glasses was determined from the mathematical relationship.
Potassium Self-Diffusion in Potassium Bismuth/Rare Earth Molybdate Crystals
Authors: Trnovcová Viera , Palcut Marian , Furár Ivan , Schultze Dietrich
Published: March 2009

The anisotropy of self-diffusion of K+ ions, ionic conductivity, and static permittivity in stoichiometric disordered K5Bi1-xRx(MoO4)4 (R = Nd, Gd; x = 0, 0.92, 1) single crystals is studied. A high value of the 2-D diffusion and ionic conductivity by K+ ions is detected. The fast ionic transport is parallel to the double layers formed by MoO4 tetrahedrons.
Carbon Diffusion in Cementite: A Molecular Dynamics Study
Authors: Levchenko Elena V. , Evteev Alexander V. , Belova Irina V. , Murch Graeme E.
Published: March 2009

. In this paper, carbon diffusion in cementite is studied by molecular dynamics simulation. An assumption that carbon-carbon interaction occurs only indirectly via neighbouring iron atoms is used. An interstitial mechanism of carbon diffusion in cementite is revealed. The principal tracer diffusion coefficients and activation parameters of carbon diffusion in cementite are calculated for the temperature range 1223-1373 K and compared with the available published experimental data.
Axial Fission Gas Transport in Nuclear Fuel Rods
Authors: del Barrio M.T. , Herranz Luisen E.
Published: March 2009

Fission of fissile uranium or plutonium nucleus in nuclear fuel results in fission products. A small fraction of them are volatile and can migrate under the effect of concentration gradients to the grain boundaries of the fuel pellet. Eventually, some fission gases are released to the rod void volumes by a thermally activated process. Local transients of power generation could distort even further the already non-uniform axial power and fission gas concentration profiles in fuel rods. Most of the current fuel rod performance codes neglects these gradients and the resulting axial fission gas transport (i.e., gas mixing is considered instantaneous). Experimental evidences, however, highlight axial gas mixing as a real time-dependent process. The thermal feedback between fission gas release, gap composition and fuel temperature, make the “prompt mixing assumption” in fuel performance codes a key point to investigate due to its potential safety implications. This paper discusses the possible scenarios where axial transport can become significant. Once the scenarios are well characterized, the available database is explored and the reported models are reviewed to highlight their major advantages and shortcomings. The convection-diffusion approach is adopted to simulate the axial transport by decoupling both motion mechanisms (i.e., convection transport assumed to be instantaneous) and a stand-alone code has been developed. By using this code together with FRAPCON-3, a prospective calculation of the potential impact of axial mixing is conducted. The results show that under specific but feasible conditions, the assumption of “prompt axial mixing” could result in temperature underestimates for long periods of time. Given the coupling between fuel rod thermal state and fission gas release to the gap, fuel performance codes predictions could deviate non-conservatively. This work is framed within the CSN-CIEMAT agreement on “Thermo-Mechanical Behaviour of the Nuclear Fuel at High Burnup”.
Synthesis of B4C/SiC Composite from Sugar Based Precursor
Authors: Cihangir S. , Ergun Celaletdin , Yılmaz Suat , Şahin Filiz Çinar
Published: March 2009

In the present study, a method based on sulfuric acid dehydration of sugar was developed to synthesize a precursor material, which can yield B4C/SiC composites at much lower temperatures compared to traditional carbothermal methods. The precursor material for pure B4C was heat treated at the temperatures between 400 and 1600oC under inert atmosphere. The precursor material for B4C /SiC composites was heat treated only at 1600oC under an inert atmosphere. Then the samples were characterized by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The results showed that B-C bonds formed as low as 400oC. On the other hand, crystallized B4C and B4C / SiC composites can be obtained at the heat treatment temperatures between 1400 and 1600oC.
Simulation of a Liquid Droplet Impinging on a Horizontal Solid Substrate Using Lattice Boltzmann Moment Model
Authors: Guo Ya Li , Bennacer Rachid , Shen Sheng Qiang , Li Wei Zhong
Published: March 2009

The shape and surface texture of a liquid droplet were studied in two-dimension when a droplet impinges on a solid substrate under isothermal condition. The lattice Boltzmann moment model was applied to simulate the fluid dynamics considering the adhesive interaction between fluid particles and surfaces. The results show the influence of wetting on the process and the drop shape. For the hydrophobic surface, the process after impinging may be divided into two stages: the spreading process driven by inertial forces and the subsequent oscillation (recoiling process) driven by surface tension forces. While for the hydrophilic surface, the droplet will only deposits on the surface and there is no the recoiling stage. In addition, the effects of the impinging speed on the shape and texture of the droplet were studied. The spreading speed and the maximum diameter of the spreading droplet increase with the rise of the impinging speed.
Exhaust Thermal Energy Use and Optimization in Remote Areas
Authors: Benzaoui Ahmed , El Gharbi Najla
Published: March 2009

In these recent thirty years, several investigations have been encouraged and done about the environment improve and the enhancement of the energy efficiency. In some arid areas, an important agrarian activity is developed because the fecundity of the soil and the presence of an important underground reservoir of water. The fruits production is important and must be stored for few months before its delivery to consumers. In order to protect the production some cold rooms have been constructed for more than 30 years. They need to be renewed. The extracted water is hot and must be cooled for its use in irrigation. This work is concerned by these two topics; renewing the cold rooms as recommended in Kyoto protocol and use of heat recovered from that released by the hot water. Fur this purpose an absorption refrigeration process is adopted using a not prohibited refrigerant and waste heat recovered as energy source. A reduced cold room is designed for theoretical simulation and experimental tests. Calculations and results are presented and discussed.
Study of Macrosegregation Defects Formation Caused by Double Diffusive Convective Flow during Solidification of a Binary Alloy
Authors: Mechighel Farid , Kadja Mahfoud , El Ganaoui Mohammed , Pateyron Bernard
Published: March 2009

Numerical study of both the solidification of the binary alloy Al-4.1%wtCu and macrosegregation defects formation have been carried out. The mixture continuum model was used in the development of the mathematical model representing the solidification phenomena. This model included the conservative equations (mass, momentum, energy and species); these equations were numerically solved by using a finite volume approach.
Experimental and Numeric Study of Flow Around a Parallelepiped Obstacle Issued from a Bent Chimney
Authors: Bhouri Baouab Inès , Mahjoub Said Nejla , Mhiri Hatem , Le Palec Georges , Bournot Philippe
Published: March 2009

Our work consisted in carrying out an experimental investigation in order to study the structure of the flow field issuing from a bent chimney and deviated when meeting a parallelepiped obstacle. For the matter we used: the Particle Image Velocimetry (PIV). A parallel numeric simulation of the problem was also elaborated and compared with the above mentioned experimental results. A three-dimensional numerical model based on the RMS turbulence closure model was used. The adopted grid is not uniform, particularly refined near the chimney and around the obstacle. A good level of agreement was achieved between the experimental data and numerical calculations. Once the model validated, we studied the effects of the distance separating the chimney and the obstacle. The tested values are Dch-obs= 10 cm and Dch-obs= 20 cm.
Transient Heat Conduction in Solids Irradiated by a Moving Heat Source
Authors: Bianco Nicola , Manca Oronzio , Nardini Sergio , Tamburino Salvatore
Published: March 2009

Transient three-dimensional temperature distribution in a solid irradiated by a moving Gaussian laser beam was investigated numerically by means of COMSOL Multiphysics 3.3. The investigated work-piece are simply brick-type solids. A laser source is considered moving with constant velocity along the motion direction. The solid dimension along the motion direction is assumed as semi-infinite while width and thickness are considered finite. Several different grid distributions are tested to ensure that the calculated results are grid independent. Typical parameters involved in the processes for any particular application should be evaluated, in order to optimize the material processing and forecast the solid behavior. The results are presented in terms of temperature profiles and thermal fields are given for some Biot and Peclet numbers.
Hydrogen Trap on the Microstructure of Cr-Mo Type Steels
Authors: Lemus L.F. , Rodrigues Janyne H. , Santos D.S. , Almeida L.H.
Published: March 2009

Microstructure influence on hydrogen trapping in a Cr-Mo type steels −2.25Cr 1Mo and 2.25Cr 1Mo 0.25V− was studied by means of electrochemical permeation test, thermal desorption spectrometry, scanning and transmission electron microscopy analysis. Both steels, used in hydrogenation reactors, in as received and artificial aged conditions exhibit a bainitic microstructure with CrxMoy and CrxMoyVz carbides finely dispersed. The hydrogen diffusivity for the 2.25Cr-1Mo-0.25V is lower than 2.25Cr-1Mo due to its higher carbide precipitation. At aged conditions TDS on samples cathodically charged with hydrogen showed an increase on the hydrogen trapping capacity for 2.25Cr-1Mo and a reduction for the vanadium modified steel, compared with the as-received state.
Heat Transfer during Hot Distortion Test of Ceramic Porous Material Bonded by Various Resins
Authors: Ignaszak Zenon , Popielarski Paweł
Published: March 2009

The problems of thermomechanical phenomena, which occur in low stability – porous ceramic material (LS-PCM) submitted to thermal shock, are discussed. The authors tried to answer the question concerning the usefulness of Hot Distortion tests (HD) for estimation of parameters necessary in data base of simulation codes, which permit to simulate the phenomena in casting-mould system. These parameters should be accessible as temperature function, especially in high temperature range of LS-PCM used as mold heating using poured casting. The new methodology and equipment, based on British Cast Iron Association (BCIRA) method, allowed to study LS-PCM specimen feature called Hot Distortion method. In this paper the modified HD methodology, are shown. The modified apparatus DMA includes two thermal sources (electric and gaseous) used to 114 x 25 x 6 mm and 120 x 22 x 22 mm sample heating were tested and analyzed. The measurement and recording of chosen parameters, i.e. deformation (distortion) during heating and variability of surface temperature fields in heated sample, by use of pyrometer and thermal camera are presented. The virtual volume temperature field in heating sample was simulated. The comparative analysis of both, experimental and virtual results are realized. This permitted also to estimate the substitute thermo-physical coefficients using inverse solution by try & error method for predefined boundary conditions on bottom and upper specimen surfaces.
Microstructure and Phase Identification of Tertiary Oxide Scale on Steel by EBSD
Authors: Suarez Lucia , Rodriguez-Calvillo Pablo , Colás Rafael , Houbaert Yvan
Published: March 2009

Oxide scales growing during hot rolling of steel represent an industrial and environmental problem. Tertiary oxide, which starts to form before entering the finishing stands, remains on the steel surface until the end of the process, affecting the final surface quality and the response to downstream processing. Characterizing scale layers and the scale/steel interface in terms of phase morphology, texture, grain structure and chemical composition is fundamental for a better understanding of their behaviour and the effect of thermomechanical cycles on the material response to further processing.
Thin tertiary scale layers have been grown on ULC steel under controlled conditions in a laboratory device adequately positioned in a compression-testing machine, immediately before plane strain deformation. After heating under a protective atmosphere (nitrogen), the samples have been oxidized in air at 1050°C for a short oxidation time. Immediately after this controlled oxidation, some of the samples were subjected to plane strain compression (PSC) inside the experimental device, in order to simulate the finishing hot rolling process.
Direct observations of oxide scale layers are impossible. The EBSD technique has been identified as a powerful tool that can be used to reveal the microstructure within the oxide scale and to distinguish between its constitutive phases, based on their distinct crystal lattices. The texture of the deformed oxide scales, originally grown on ULC steel, was determined in a SEM using the EBSD technique. This will help to achieve a better understanding of their complex deformation behaviour. Because the substrate deformation affects the oxide layer, orientation relationships between scale layer and substrate were measured and the crystallographic orientation between undeformed and deformed areas was determined. Strongly textured wustite grains with a clearly pronounced columnar structure were observed after oxidation at 1050°C. The detailed EBSD study reveals that the oxide layer is able to accommodate a significant amount of deformation.
Influence of Strain Rate and Strain on the Surface Properties in Superplastically Boronized Duplex Stainless Steel (DSS)
Authors: Abd Aziz N.H. , Jauhari Iswadi , Yusof H.A. Mohd , Ahamad Nor Wahida
Published: March 2009

It was reported that superplastic boronizing process (SPB) provides a much faster boronizing rate than the conventional boronizing process (CB). This process was conducted on duplex stainless steel (DSS) which exhibit superplasticity. The study concentrated on the effect of strain rate and compression strain on SPB. The process was conducted under four different strain rates and three diferent strains condition. Boronizing was successfully conducted with the best result obtained under the high strain rate range of 5 x 10-5 s-1 to 1 x 10-3 s-1 which is associated with the superplastic region. Through SPB, movement of atoms into the specimen was highly accelerated by the grain boundary sliding process leading to a formation of thick and hard boronized layer in extraordinarily short period of time.
Selective Oxidation of Low Alloyed Ferritic Steels
Authors: Giorgi Marie Laurence , Ollivier Amelie , Guillot Jean Bernard , Goodwin F.
Published: March 2009

Before hot-dip galvanizing, the steel sheets are annealed in an atmosphere of N2 and H2, containing only traces of water (about -30°C dew point). The main purposes of this heat treatment are to recrystallize the steel substrate after cold rolling and to reduce the iron oxides in order to improve the wettability by liquid zinc. At the same time, the less-noble alloying elements (Mn, Si, P, Cr, Al, B) of the steel preferentially oxidize and segregate to the surface. The steel surface is then partly or wholly covered by oxide particles, sometimes resulting in problems of wettability by liquid zinc.
The present study focuses on the characterization of the oxide particles formed on the surface of a low alloyed ferritic steel. The steel samples are annealed by means of a laboratory furnace with a temperature profile relevant to galvanizing line practice. The parameters characteristic of the oxide particles (size, surface coverage, chemical composition, depth of oxidation) are then determined using several analysis techniques.
Numerical Study of Melting/Solidification by a Hybrid Method Coupling a Lattice Boltzmann and a Finite Volumes Approaches
Authors: Addakiri S. , Semma E. , El Ganaoui Mohammed , Pateyron Bernard
Published: March 2009

In this paper, we propose a hybrid method coupling a Lattice Boltzmann Method (LBM) and a Finite Volume Method (FVM), to study melting and solidification problems. The LBM is used to determine the dynamics field while the FVM is applied to discretize the energy equation. This model is validated by comparison to available literature results concerning a square cavity heated without phase change then for the melting of Gallium in an enclosure commonly used as benchmark test case.
Effect of SiC Particles Volume Fraction on the Mutual Diffusion of Al and Cu during Fabrication of Al-4.5wt%Cu/SiC via Mechanical Alloying
Authors: Mostaed Ehsan , Mostaed Ali , Saghafian H. , Shokuhfar Ali , Rezaie Hamid Reza
Published: March 2009

The effects of volume fraction at different milling times and impact forces, defined as the ball-to-powder weight ratio (BPR), on the elemental diffusion during mechanical alloying process of Al-4.5wt%Cu/SiC composite were evaluated and compared with the SiC free samples (Al-4.5wt%Cu alloy) in the current work. X-ray diffraction patterns of the monolithic and composite samples imply the fact that a higher level of mutual diffusion of constituents, Al and Cu, happened in the matrix in the presence of SiC particles. This effect of the reinforcing particles can be attributed to the increased densities of dislocation and vacancy caused by the presence of SiC particles within the matrix giving rise to increasing the micro-strain, lattice parameter and decreasing the crystallite size.
Kinetics of the Calcium Oxysulfides Reduction by Carbon Monoxide
Authors: Gulyaeva R.I. , Selivanov Evgeny N. , Mansurova A.N.
Published: March 2009

The chemistry and the kinetics of the reduction of calcium containing CaFeSO and Ca2FeCuSO3) oxysulfides in a mixture of flowing gases that contains (75% CO) carbon monoxide and argon have been investigated by thermogravimetric analysis and X-ray diffraction. Experiments were carried out on the synthesized samples by heating up to 1270 K with heating rates of 5-20 K/min. The Netzsch Thermokinetics program was used for the analysis of the experimental data. Kinetic parameters of reduction processes are determined.
Cold-Set Whey Protein Isolate Gels Prepared with Mg2+: Denaturing Conditions and Phase Diagram
Authors: Vázquez da Silva M. , Delgado João M.P.Q.
Published: March 2009

Cold-set gels of whey protein isolate (WPI) were produced. The cold gelation was induced through the addition of magnesium chloride whose cation is an alternative to the most common cations used in this kind of gelation.
A phase diagram for denatured WPI in magnesium was determined by varying protein and salt concentrations. In this diagram the protein and cation concentrations varied from 0.3 to 8.0 wt % and 1 to 75 mM, respectively.
The viscoelastic behaviour of the WPI was analysed, whereas gels elastic properties were measured by means of texture tests. Mathematical manipulation of the experimental data relative to the puncture tests was made in order to obtain the Young’s modulus for each cold-set gel.
Water Sorption Isotherms and Textural Properties of Biodegradable Starch-Based Superabsorbent Polymers
Authors: Delgado João M.P.Q. , Vázquez da Silva M. , Nasser R.O. , Gonçalves Maria P. , Andrade C.T.
Published: March 2009

A series of biodegradable superabsorbent polymers (SAP) based on starch grafted with acrylic acid (AA) and crosslinked with N,N’-methylenebisacrylamide (MBIS) were obtained. The parameters that define SAPs properties, such as starch type, amount of initiator, acrylic acid and crosslinker concentrations, and degree of neutralization were varied according to an experimental design. The swelling rate, the degree of swelling, the water sorption isotherms and the texture profile of the new materials were determined. A new method was used to measure the swelling rate. The water sorption results were correlated using various isothermal models as the BET (Brunauer-Emmett-Teller) and GAB (Guggenheim-Andersson-DeBoer) models.
Hydrogels obtained from regular cornstarch presented better absorption capacities than those from waxy cornstarch. Maximum swelling was observed for 70% neutralization of carboxylic acid groups. More rigid SAPs presented lower swelling rates, but not necessarily lower swelling degrees.
Heat and Mass Transport in the Unsaturated Porous Media: Application to the Soil Dry Drainage Method
Authors: Adala Meriem , Bennacer Rachid , Sammouda Habib , Guizani Amenallah
Published: March 2009

Salinity currently has the highest priority of all environmental issues nowadays. The only means of preventing the development of soil salinity was combining leaching and artificial drainage. Recently a new method of capturing and removing salt from the soil surface called a dry drainage method [1-4] has been studied (fig.1) to help arid soils prevention against such threat. This work is a numerical simulation of the simultaneous water, solute and heat transfer in an unsaturated porous media during the simultaneous evaporation and drainage of saline dry land soils. A detailed mathematical model was formulated to describe the non-isothermal transport of water in the unsaturated porous media [5]. The model consists of the coupled conservative equations of mass for liquid phase, gas phase, water vapour, species and the energy. The boundary conditions at the soil–atmosphere interface include dynamical mass flux and energy flux. Comparison of numerical simulations with analytical results demonstrated that the present model is able to describe water and energy transport dynamics.
Experimental Investigation of Pressure Drop in One Phase Flow, Particle-Liquid Two-Phase Flow, and Porous Media Consisting of the Same Particle Size
Authors: Aybar Hikmet Ş. , Sharifpur Mohsen , Vaziri Roozbeh
Published: March 2009

Many researches have performed some studies about pressure gradient in the one phase flow, particle-liquid two-phase flow and porous media. However, there is no any report about interaction among them. In this study, this interaction idea is developed by using the same particle size for particle-liquid two-phase flow and porous media. For the experimental study, an apparatus is designed, and at the first step one phase water pressure gradient is investigated, next in the further steps, little by little spherical particles are added to the cycle till accumulation of the particles did not allow any movement to the particles (i.e. porous media occur), and after that well pack porous media is investigated. The results confirm the relation between pressure gradient over mass flow rate in the one phase flow, particle-liquid two-phase flow and porous media obeys as a parabolic curve.
Ti Redistribution in Multifilamentary Nb/Cu-Sn Composites
Authors: Popova E.N. , Popov Vladimir V. , Romanov E.P. , Sudareva S.V. , Dergunova E.A. , Vorobyova A.E. , Shikov A.K. , Balaev S.M.
Published: March 2009

Multifilamentary bronze-processed Nb3Sn-based composites have been studied by the methods of TEM and SEM. Ti as a doping element required for an enhancement of superconducting characteristics, especially in high magnetic fields, was inserted either in a bronze matrix, or in Nb filaments of a composite. It has been found that Ti diffuses into the growing Nb3Sn layer in both cases, and affects positively its structure and superconducting characteristics of a composite as a whole, especially in case of the doped matrix. When Ti is added to Nb filaments, it forms fine particles of intermetallic compounds with Sn in the nanocrystalline diffusion layer. When these particles are formed, grain boundaries of the diffusion Nb3Sn layer purify from segregations, and grains in the vicinity of these particles coarsen, which negatively affects the current-carrying capacity of a composite. That’s why an optimal amount of Ti in Nb should be chosen, when Ti mainly dissolves in the Nb3Sn phase increasing its superconducting properties and not deteriorating its grain structure.
Diffusion Parameters of Carbide-Forming Elements in Fe-M-C Systems
Authors: Popov Vladimir V.
Published: March 2009

The results of interdiffusion studies in Fe-Ti-C, Fe-V-C, Fe-Cr-C, Fe-Mo-C and Fe-W-C ternary systems are summarized. Interdiffusion coefficients of substitution elements in austenite and ferrite are determined and their concentration and temperature dependencies are analyzed. Using the available literature data and the results of our own studies the analytical expressions for interdiffusion coefficients have been obtained.
Investigation of Harrison Type-A, B and Intermediate AB Kinetics Regimes in Grain Boundary Diffusion
Authors: Belova Irina V. , Murch Graeme E.
Published: March 2009

Recently, the transition point between the Harrison Type-A to 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 simulations of tracer depth concentration profiles as a function of diffusion time and distance between grain boundaries e.g. [7-9]. The principal model in this area has been the grain boundary slab model. However, depending on the diffusion time and grain size a given tracer atom can be expected to cross a number of grain boundaries in its diffusion time. This has recently been taken into account in square and cubic grain models for determining the limit of the Harrison Type-A regime [1]. In the present study, we determine the limits of the intermediate AB transition regime where we have used the Lattice Monte Carlo method to analyse the tails of tracer concentration depth profiles. The applicability of different solutions for the grain boundary diffusion analysis is numerically investigated for the 3D model. The solutions are those by Whipple-Le Claire [12,13] and Suzuoka [11], Bokstein, Magidson and Svetlov [15], Levine and MacCallum [14] for the type B kinetic regime and that by Divinski and Larikov [2] for the intermediate Type-AB regime. We also review the progress that has been made concerning the limits of the various Harrison regimes supplemented with the results of the present simulations.
An empirical factor of 1.5 should be applied when Suzuoka or Whipple-Le Clair solutions are applied to the analysis of the tracer diffusion profile, tail section, in the polycrystalline material and an empirical factor of 2.0 should be applied when Bokshtein-Magidson-Svetlov solution is applied to the analysis of the tracer diffusion problem in the polycrystalline material.
Surgical Sutures: Performance, Development and Use
Authors: Azhahia Manavalan R. , Mukhopadhyay A.
Published: March 2009

The paper reports about different kind of sutures, their suitability and performance. An ideal suture should possess many characteristics such as - easy to handle, bio-compatibility, minimal tissue reaction, resistance to bacterial growth, adequate tensile strength and elasticity, knot security, strength loss versus healing rate of tissues. Selection of suture is often very complex for satisfying host of physical, mechanical and biological properties, and fulfilling contradictory requirements in varied applications. The paper develops an understanding about the selection of suture depending on the varied requirement. Past research work pertaining to the development of suture as reported in this paper, provides insight about the suitability of different surgical sutures and possible direction of future research.
Characterisation of Calcium Phosphate Cement-Derived Hydroxyapatite Scaffolds with a PLGA-Bioactive Glass Composite Coating
Authors: Tan D.M.F. , Miao X. , Li J. , Xiao Yin , Crawford Ross
Published: March 2009

The limitations of autogenic, allogenic and xenogenic grafting methods have led to the development
of synthetic grafts as an alternative. The aim of this study was to manufacture highly porous and
well interconnected hydroxyapatite scaffolds and modify them with a poly(lactic-co-glycolic acid)
(PLGA)-bioactive glass composite coating to achieve mechanical properties close to those of
natural cancellous bones. In this study, hydroxyapatite scaffolds were prepared from a calcium
phosphate cement (CPC) powder and cell culture using fibroblast cells was done to examine the
cytotoxicity of the materials used for the scaffolds. The average pore size of the scaffolds was found
to be 650μm and the total porosity was about 80%. The hydroxyapatite scaffolds without the
coating had a mean compressive strength and a mean compressive modulus of 0.74 MPa and 20.46
MPa, respectively, which were in contrast to those of the scaffolds coated with the PLGA-bioacitve
glass composite material (1.36 MPa and 24.58 MPa, respectively). The fibroblast cells were
observed to proliferate well on the PLGA-bioactive glass coated scaffolds. The cells had also
penetrated into the scaffold to a depth of approximately 2mm. Thus the scaffolds fabricated in this
study exhibited a favourable porous structure and good cell response which are desirable for bone
tissue engineering.
Optical and Electron Correlation Effects in Silicon Quantum Dots
Authors: Ghoshal S.K. , Jain K.P. , Elliott R.
Published: March 2009

We study (through computer simulation) the variation of the band gap as a function of sizes and shapes of small Silicon (Si) dots using pseudo-potential approach. We have used empirical pseudo-potential Hamiltonian and a plane wave basis expansion and a basic tetrahedral structure. It is found that the gap decreases for increasing dot size. Furthermore, the band gap increases as much as
0.13eV on passivation the surface of the dot with hydrogen. So both quantum confinement and surface passivation determine the optical and electronic properties of Si quantum dots. Visible luminescence is probably due to radiative recombination of electrons and holes in the quantum confined nanostructures. The effect of passivation of the surface dangling bonds by hydrogen atoms and the role of surface states on the gap energy as well as on the HOMO-LUMO states has also been examined. We have investigated the entire energy spectrum starting from the very low lying ground state to the very high lying excited states for silicon dots having 5, 18, 17 and 18 atoms. The results for the size dependence of the HOMO-LUMO gap and the wave functions for the bonding-antibonding states are presented and the importance of the confinement and the role of hydrogen
passivation on the confinement are also discussed.
Encapsulation of Luminescent Quantum Nanodots in Polystyrene Nanocapsules by Microemulsion Polymerization
Authors: Yang Xiaotun , Huang Ning , Zhang Yong
Published: March 2009

This paper reported on the one-step synthesis of polystyrene-quantum dots (PS@QD)nanoparticles using microemulsion polymerization method. The synthesized QD and PS@QD nanoparticles were characterized by UV, fluorescence spectroscopy, transmission electron microscopy (TEM) and fluorescence microscopy. The PS@QD is highly luminescent, which have the potential to be used as fluorescent probes in biological staining and diagnostics.
Rheological Characteristics of Ethylene Vinyl Acetate (EVA)/Silane Nanocomposites
Authors: Kruenate Jittiporn , Tongpool R. , Kongrat P.
Published: March 2009

EVA/tetraethylorthosilane(silane) nanocomposites were prepared. Rheological properties were studied in both dynamic and steady modes at 150oC. The rheological properties of the nanocomposites are strongly affected by silane dispersed in EVA matrix. As silane content incresed, the polymer strength increased due to interconnections between filler clusters which can be disrupted by high shear rate (in steady mode). The degree of silane dispersion in the EVA matrix
decreased with increasing silane content, leading to a “pseudo-solid-like” behaviour. The samples showed viscous and elastic behaviour at low- and high-shear rate regions, respectively. The nanocomposite films were almost as clear as EVA film.
The Characteristics of Nickel-Electroplating on Copper Substrate in CO2 Supercritical Fluid
Authors: Hong Kyo-Min , Kim Moon Sun , Lee Yong Chul , Kim Nam Ki
Published: March 2009

In this work, a nickel electroplating was performed on the copper substrate using nonionic surfactant in supercritical carbon dioxide to improve the dispersion characteristics of nickel nano-particles. The electric resistance of emulsion decreased rapidly from 46 to 25 Ω with an increasing pressure from 8 MPa to 16 MPa and was nearly constant at 25 Ω over 14 MPa. The conductivity of emulsion solution was highest at nonionic surfactant concentration of 0.1 vol% and the dispersion of nickel nano-particles was better than at any other concentration. CO2 concentration was controlled under 0.5 vol% to reduce electric resistance in emulsion solution. Roughness (Ra) of copper substrate without plating was 0.084 ㎛, however, that of nickel film plated for 10 min was smoothed to 0.020 ㎛ and the surface of nickel film plated was smoothed with an increasing plating time. The plating properties of nickel in CO2 supercritical fluid showed better properties than in
conventional method.