bluuebunny/crossref_metadata_2025 huggingface dataset:
The Analysis of the Selective Oxidation of Multicomponent Alloy
Authors: Wierzba Bartłomiej , Danielewski Marek
Published: March 2009

The model of the heterogeneous reaction between the alloy and oxidant is shown. The
alloy reacts with oxidant and forms oxide scale. The reaction rate is controlled by the interdiffusion
in alloy and the chemical diffusion through the compact scale. In this work we extend the Wagner
model by introducing i) the variable instantaneous rate constant, ii) the composition dependent
diffusivities of the alloy components and iii) the finite geometry of the oxidized alloy. The model
allows us to predict the life time of the alloy and the evolution of the components concentration.
The comparison of Wagner’s results and our extended analysis is shown.
Size-Induced Freezing Effect in Monte-Carlo Simulations of Phase Separation Kinetics in Nanoparticles
Authors: Shirinyan A.S. , Lubyanskyy D.V.
Published: March 2009

The separation kinetics in a binary nanoparticle is studied by means of two-dimensional
Monte-Carlo sampling and Ising-type model, where the species exchange positions due to vacancy
mechanism. The model is developed in case of a free nanoparticle with a coating shell. The kinetics
is shown to depend on the size of a nanosystem. We demonstrate a distinct size-induced freezing
effect on kinetics of separation.
Generalization of Fisher Model for Periodically Non-Uniform Grain Boundary
Authors: Gapontsev V.L. , Koloskov Valerie M. , Gapontseva M.G.
Published: March 2009

The problem of grain boundary diffusion for a case of boundary grain with periodic
heterogeneity diffusion properties is considered. Dependence of Laplace transform images of
impurity concentration on various diffusion conductivity places is built. The dimensionless
parameters, forming the system of grain boundary diffusion regimes are determined. The space
(ln x,lnt,1/T) is divided into areas in which the ratio
ln ln ~ ln ln ( / ) ln eff o C r x−k t− Q RT − A is maintained, when the parameters of diffusion
regime are constant. The values of parameters , , , eff o r k Q A fully specify the diffusion regimes. On
this base the new concept for the definition of grain boundary diffusion regimes is carried out and
the method for construction of simplified tracer concentration profile is proposed.
Silicide Formation Reactions in a-Si/Co Multilayered Samples
Authors: Balogh Z. , Cserháti Csaba , Erdélyi Z. , Csik A. , Langer G.A. , Zizak I. , Darowski N. , Dudzik E. , Feyerherm R. , Beke Dezső L.
Published: March 2009

Solid state reactions between amorpous Si and crystalline Co have been investigated by
synchrotron radiation at Bessy (Berlin, Germany). The multilayered samples (with 10 periods of
a-Si(15 nm)/Co(15 nm) layers) were produced by magnetron sputtering and isothermally heat
treated at temperatures between 523 and 593 K. From the time evolution of the XRD spectra first
the growth rate of the CoSi phase as well as the decay rate of the Co layer we determined (at 523
and 543 K). The kinetics were described by a power law; tk, and for the growth of CoSi k=0.65
while for the loss of the Co the k=0.77 was obtained, respectively. At higher temperatures (at 573
and 593 K) the formation and growth of the Co2Si layer, at the expense of the Co and already
existing CoSi layers, was observed with exponents of about 1 for all the above kinetics. These
results, together with the results of resistance kinetics measurements, in similar multilayered as well
as bi-layered samples at similar temperatures, providing similar exponents will be presented.
Possibility of the interface reaction control and/or the effect of the diffusion asymmetry (which was
recently published for the interpretation of solid state reactions with non-parabolic kinetics on the
nanoscale) will be discussed.
Cluster Dynamics Simulation of Reactor Pressure Vessel Steels under Irradiation
Authors: Gokhman Aleksandr R. , Bergner F. , Ulbricht Andreas , Birkenheuer Uwe
Published: March 2009

The coupling between copper rich precipitates (CRP) and point defects in neutron
irradiated iron alloys and VVER steels was investigated by means of cluster dynamics (CD)
simulations. The consideration of the strain energy effect on CRP kinetics as well as the application
of the regular solution model for the case of different fixed copper contents of CRP provides a good
agreement between the simulation results and experimental data for complex iron based alloys with
small (0.015 wt%) and high (0.42 wt%) copper content. It was found that the CD simulation is
applicable to irradiated VVER steel with 0.07 wt% of copper.
The Ageing of Beryllium Bronze in the Pulse Magnetic Field
Authors: Osinskaya J.V. , Pokoev A.V.
Published: March 2009

Kinetics of changes of microstructure of beryllium bronze BrB-2 in d decomposition
process of supersaturated solid solution in the pulse magnetic field with 0 – 7 Hz frequency with
pulse intensity amplitude 318.4 кA/m (4 kOe) and magnetic field constant component 238.8 кA/m
(3 kOe) under the temperature 350 °С and ageing duration 1 hour was investigated by
microhardness measurements and X-ray diffraction. Frequency dependences of microhardness,
lattice parameter, beryllium concentration in a residual matrix, size of coherent scattering blocks,
dislocations density and the value of relative microdeformation of the matrix blocks under ageing in
the pulse magnetic field and without it have been investigated. Experiment results show that the
pulse magnetic field essentially influences the parameters of the fine structure and also physical and
mechanical properties of bronze.
The Influence of Ti and Zr on the Diffusion of Isotope 63Ni in the Iron Surface Layer at Electric-Spark Alloying in Carbon Containing Environment
Authors: Sidorenko Sergey I. , Ivashchenko E.V. , Lobachova G.G. , Mazanko V.F.
Published: March 2009

By the method of radio isotopes (method of depleting) the redistribution of 63Ni was
investigated in the surface layer of iron after the Electric-spark alloying by titanium and zirconium
in a carbon containing atmosphere and in air. It is proved that the Electric-spark alloying results in
diffusive penetration of 63Ni both in the alloyed layer and in material of basis. The depth of
isotope’s penetration depends on the nature of an anode material. Alloying by titanium results in
penetration of nickel on the depth of 10 μm, that is almost 2 times more than the depth of its
penetration if a zirconium anode is used. In particular, a microhardness, microstructure and phase
composition of alloyed layers are examined. It is assumed that alloying of iron by zirconium results
in the hardness increase. The alloyed layer equals to 10 GPa (at treatment in kerosene) and to 8,6
GPa (at treatment in propane-butane) that exceeds the microhardness values at alloying by titanium.
Lateral Diffusion Spreading of Two Competitive Intermetallic Phases over Free Surface
Authors: Kaganovsky Yuri S. , Paritskaya Lyudmila N. , Bogdanov V.V.
Published: March 2009

The kinetics of growth and lateral spreading of intermetallic layers during surface
interdiffusion in Cu – Sn system has been studied in a temperature range 160 – 200oC by the
methods of optical microscopy, SEM provided with X-ray microprobe, and AFM. Lateral phase
spreading over the surface is characterized by competition between two phases: Cu6Sn5 and Cu3Sn.
A steady state solution for concentration distribution on the surface of growing intermetallic
phases, as well as kinetic equations of lateral spreading of growing phase layers have been
obtained. By comparison of experimental data on intermetallic growth kinetics with the proposed
theory, the dynamic surface diffusion coefficients have been calculated.
Effect of an Impulse Loading on Localization of Diffusing Atoms in Metals
Authors: Gertsriken D.S.
Published: March 2009

Distribution and mobility of own and impurity atoms in metals subjected to different
loadings: quasi-static plastic strains; quasi-static deformations in combination with impulse; sluggish
and fast elastic deformations, including alternating, impulse plastic strains are investigated by methods
of an autoradiography, layer-by-layer radiometric analysis and secondary ionic mass spectrometry. The
common regularities of migration of atoms at deformation of metals are found, and threshold values of
a strain rate, corresponding to change of the diffusion mechanism and localization of penetrating atoms
in metal, are determined. The conclusion about the bulk mechanism of substance transfer is made at
pulse actions irrespective of temperature of processing.
The Lattice Monte Carlo Method for Solving Phenomenological Mass and Thermal Diffusion Problems
Authors: Belova Irina V. , Murch Graeme E. , Fiedler Thomas , Öchsner Andreas
Published: March 2009

In this overview, we introduce the recently developed Lattice Monte Carlo method
for addressing and solving phenomenologically-based mass and thermal diffusion problems
especially for composite and porous materials. With examples, we describe the application of this
numerical method to calculate effective mass diffusivities and concentration profiles. Next, we
describe the application of this method to the calculation of effective thermal conductivities/thermal
diffusivities and temperature profiles.
Thermodynamic Diffusion Coefficients
Authors: Kale G.B.
Published: March 2009

A new form of diffusion coefficient termed as thermodynamic diffusion coefficient is
introduced in this paper. Conventionally, diffusion coefficients are evaluated using concentration
gradient as driving force. But truly, chemical potential gradient is the actual driving force that
determines the material flow in any part of the system. Thermodynamic diffusion coefficients are
based on chemical potential gradient as driving force. The relation between thermodynamic
diffusion coefficients and phenomenological coefficients has been established. The advantages of
thermodynamic diffusion coefficients have been underlined, especially, in the cases of line
compounds where concentration difference across the phase is zero or in case of intermetallic
compounds with narrow homogeneity range. The intrinsic thermodynamic diffusion coefficients are
equal to tracer diffusion coefficients. This helps in estimating tracer diffusivities in cases where
tracers are not easily available. The advantages of thermodynamic diffusion coefficients are shown
in binary and ternary systems by illustrating them in Ni-Al and Fe-Ni-Cr systems.
Effect of Thermal Aging on the Transformation Temperatures and Specific Heat Characteristics of 9Cr-1Mo Ferritic Steel
Authors: Jeya Ganesh B. , Raju S. , Mohandas E. , Vijayalakshmi M.
Published: March 2009

The effect of thermal ageing on the heat capacity and transformation behaviour of
behaviour of 9Cr-1Mo-0.1C (wt.%) ferritic / martensitic steel has been studied using differential
scanning calorimetry (DSC) in the temperature range 473 to 1273 K. It is found that a-ferrite +
carbide ® g-austenite phase transformation temperature is only mildly sensitive to microstructural
details; but the enthalpy change associated with this phase transformation and especially, the change
in specific heat around the transformation regime are found to be dependent on the starting
microstructure generated by thermal ageing treatment. Prolonged ageing for about 500 to 5000
hours in the temperature range 823 to 923 K contributed to a decrease in heat capacity, as compared
to the normalised and tempered sample. The martensite microstructure is found to possess the
lowest room temperature CP among different microstructures.
Effect of Cerium Addition on the Microstructure and Mechanical Properties of Al-Zn-Mg-Cu Alloy
Authors: Chaubey Anil K. , Mohapatra S. , Bhoi B. , Gumaste J.L. , Mishra Barada Kanta , Mukherjee P.S.
Published: March 2009

Al–8.6Zn–2.6Mg-2.4Cu–xCe(x = 0–0.4 wt. %) alloys were prepared by metal mould
casting method, the effects of Ce on the microstructure and mechanical properties of the alloys were
investigated. The results showed that the dendrite as well as grain size were refined by the addition
of Ce, and the best refinement was obtained in 0.25 wt % Ce containing alloy. The main phases in
the as-cast alloys were α-Al, Mg-Zn32, Mg32 (Al, Zn)49, and Al4Ce phase was found in the alloys
containing more than 0.1%Ce. The addition of Ce improved the mechanical properties of the
alloys. The strengthening mechanism was attributed to grain refinement and compound reinforced
Formation of Point Defects in Dilute FCC Alloys
Authors: Ghorai Amitava
Published: March 2009

Using pseudopotential approach, vacancy formation energy , different non-split interstitial formation energies and binding energy for the vacancy-impurity pair and that for interstitial impurity over host have been calculated in some cubic fcc metal systems, viz. copper, silver, gold and lead using Ashcroft's potential and Taylor's exchange and correlation function with standard (AT) and fitted to (ATF) and also Heine-Abarenkov’s model potential and same exchange and correlations (HAT). It is difficult to have a universal value for all types of atomic property calculations. The results show that ATF and HAT combinations are better in comparison to AT. Also, the substitutional impurity adjacent to a vacancy is found to be more loosely bound than the interstitial impurity in fcc metals.
Studies of the Spin Hamiltonian Parameters for NiX2 and CdX2:Ni2+ (X=Cl, Br)
Authors: Zhang Zhi Hong , Wu Shao Yi , Wang Xue Feng , Hu Yue Xia
Published: March 2009

The spin Hamiltonian parameters (zero-field splitting D and the g factors) for NiX2 and CdX2:Ni2+ (X=Cl, Br) are quantitatively investigated from the perturbation formulas of these parameters for a 3d8 ion in trigonally distorted octahedra based on the cluster approach. In the calculations, the trigonal field parameters  and ′ are determined from the superposition model and the local structures of Ni2+ in the halides. The theoretical g factors show reasonable agreement with the observed values, and the experimental D for CdX2:Ni2+ are also interpreted by considering suitable lattice distortions (angular decreases) in the impurity-ligand bond angles related to the C3 axis due to the size mismatching substitution. The contributions from the ligand orbital and spin-orbit coupling interactions are important and should be taken into account.
Stick-Slip Behaviour of Bonded Planes - Phase Transitions in Dislocation Fields
Authors: Eib Wilhelm
Published: March 2009

The transition from elastic behaviour to plastic ow of technical materials under the
inuence of increasing mechanical load is obviously of major technical importance. Nevertheless
it is a challenge to formalize this transition in terms of consistent eld theories. We adopt here
the beautiful theoretical work of Kröner [1], Bilby [2], and Kunin [3], who have shown how this
formalization can be done. We shall go beyond their results by assuming energy dissipation
if dislocations are moved through surfaces as suggested earlier [4] due to the energy density
contribution from inner curved surfaces.
Sometimes the mutual movement of adhering planes is described in terms of a stick-slip movement,
meaning that the solid switches between elastic and plastic, possibly (and in fact in most
experimental cases) showing a hysteresis between the two. Earthquake shear waves, e.g., are
a dramatic example. Classical eld theories can hardly account for this eect. We shall try to
describe the solid deformations as dislocations in two dierent phases, allowing for transitions
between these phases. The tool is the Ginzburg-Landau-formalism in the form Haken [5] used
for selforganizing quantized systems. We are aware of the fact that this procedure is consequent
only after the above mentioned classical eld theories have been quantized, a still open task for
theoretical physicists, but we feel that the practical benet is worth the cavalier assumptions.
Evaluation of the Diffusion Coefficient of N in γ' Iron Nitride: Influence of the Nitriding Potential
Authors: Keddam Mourad , Bouarour B. , Kouba R. , Chegroune Redoune
Published: March 2009

This work deals with a study of the nitriding potential effect on development of the compound layer during the gas nitriding of Armco Fe samples. The gas nitriding experiments were performed in an atmosphere of partially dissociated gas ammonia (NH3) at 520 °C under a nitriding potential varying from 0.25 to 3.5 atm-0.5 during 2 h. Through this experimental work including XRD analysis, optical and SEM observations of the cross-sections of the treated samples, it is shown that the microstructural nature of the compound layer depends upon the nitriding potential value. By use of the inverse problem based on a diffusion model previously published, it was possible to estimate the diffusion coefficient of N in ' iron nitride as a function of the applied nitriding potential. XRD analysis has shown that the compound layer was composed of iron nitride. A linear semi-logarithmic relationship relating the nitriding potential to the diffusion coefficient of nitrogen in iron nitride was also derived.
The Influence of External Load and Air Pressure on Air Slide Table Performance of Ultra Precision Machines in Nano Machining
Authors: Vahdati Mehrdad , Shokuhfar Ali , Bagheri Meysam
Published: March 2009

Ultra precision machine tools are used in nano machining technology. Two main assemblies creating rotational and linear motion, called air spindle and linear air table are used in these machines. The linear air table has been simulated experimentally like a linear air bearing. This bearing moves in the main direction, X, while it has straightness error motions in Y and Z directions. The error values vary due to different parameters. This investigation deals with the influential parameters and their proportion in the error value.
As far as the two mating surfaces are separated by a thin layer of pressurized air, the air pressure, location and amount of external load, are some of the parameters which have been studied. Results show that the more air pressure, the more stability and stiffer table. There will be less error motions as well. The error amount is not the same in X and Y directions. Finally, in order to have linear stiffness, the optimum air pressure, external load, and load location have been decided.
Evaluation of Concentration Dependent Diffusivities of Manganese in the Diffusion Joint Fe/FeMn-Steel by Means of Mathematical-Analytical Methods
Authors: Kubíček Petr , Drápala Jaromír , Wostrý P.
Published: March 2009

When developing new types of materials with special properties for the automotive industry, steels with high content of manganese (up to 25 wt. % Mn) were studied. These steels embody increased failure resistance, high level of deformation hardening, plastic response and high value of energy absorption in crash situations [1,2]. The aim of our work was to study an interaction of a FeMn alloy with pure iron from the view of diffusion processes. For that purpose, diffusion joints Fe/FeMn-steel were created and long-term heated at the temperatures of 800, 900 and 1050 °C. Dependences of diffusivities of Mn on its concentration were calculated from concentration profiles of manganese after diffusion heating applying three analytical methods. In the first method, constant values of diffusivities Di, i = 1,2 for both Fe and steel were taken into account. In the second case a modified Matano-Boltzmann method utilizing polynomials was applied, which simplifies solution in numerous cases. The third method performs the solution of the non-linear equation of diffusion on the assumption of a linear dependence of diffusivity on concentration applying a procedure based on perturbation calculus. The results of the solution will be graphically documented in details together with the description of experiments.
Hydrogen Diffusion Coefficient during Hydrogen Permeation through Nb-Based Hydrogen Permeable Membranes
Authors: Yukawa Hiroshi , Zhang G.X. , Watanabe N. , Morinaga Masahiko , Nambu T. , Matsumoto Yoshihisa
Published: March 2009

The hydrogen diffusion coefficients are investigated during the hydrogen permeation through Nb-based hydrogen permeable membranes at high temperature. It is found that the hydrogen diffusion coefficient for pure niobium under practical conditions is much lower than the reported values measured for dilute hydrogen solid solutions. Surprisingly, the hydrogen diffusion is found to be faster in Pd-Ag alloy with fcc crystal structure than in pure niobium with bcc crystal structure at 773K during the hydrogen permeation. It is also found that the addition of Ru or W into niobium increases the hydrogen diffusion coefficient under the practical conditions.
Dynamics of Hydrogen in the Hexagonal (C14) Laves Phase Compounds TiCr1.8-xMnx
Authors: Mazzolai Giovanni
Published: March 2009

The diffusion of hydrogen has been investigated in the AB2 Laves phase Compounds TiCr1.78 and TiCr1.4Mn0.4, by absorption techniques. It has been found that H at temperatures higher than 700 K diffuses through the classical over-barrier mechanism, while at low temperature (around 100 K) the diffusion is governed by phonon-assisted tunnelling. The activation energy for classical hopping is rather high and increases with the substitution of Mn for Cr. In the range of H contents nH investigated (nH=H/Me0.03) the chemical diffusion coefficient does not depend on the H concentration.
The Diffusion of Gallium into Copper-Tin Alloy Particles
Authors: Shubin A.B. , Shunyaev K. Y. , Yamshchikov L.F.
Published: March 2009

Properties of diffusive-hardening pastes based on liquid gallium have been investigated. The optimal conditions were found for producing the paste (solder) with best technological characteristics. The liquid-solid ratio, powder alloy composition and dispersity, dust fractions percentage, exposition time and temperature are the main factors which determine the rheological properties of the gallium paste.
Numerical Simulation of a Ceramic Furnace Burner - Capacity of Turbulent and Radiation Models
Authors: Souid Anouar , Kriaa Wassim , Mhiri Hatem , Le Palec Georges , Bournot Philippe
Published: March 2009

We intend in this work to model an industrial burner replica of the ceramic tunnel furnace of the Ceramics Modern Society (SOMOCER, TUNISIA). This study aims to evaluate the ability of turbulence and radiation models to predict the dynamics and heat transfer fields. The study is conducted by means of numerical simulations in presence of a reactive flow using the commercial code FLUENT. The 3D Navier-Stokes equations and four species transport equations are solved with the eddy-dissipation (ED) combustion model. We use three turbulence models (k- standard, k- RNG, and RSM) and two radiation models (DTRM and DO). The obtained results demonstrate that the k- standard turbulence model is unable to predict the flow characteristics whereas; the k- RNG and RSM models give a satisfying agreement with the experiments. Suitable results are provided by the DTRM radiation model; whereas, those given by the DO model can be improved.
Synthesis and Characterization of Ag Doped Hydroxylapatite as an Antibacterial Scaffolds Material
Authors: Bahadir Abdurrahman , Ergun Celaletdin , Baydogan Murat
Published: March 2009

Not many studies have been found in the literature on the effect of Ag ions on the structure and phase stability of hydroxylapatite which may be recognized as important information in the scaffold fabrication. The objective of the current study is to develop a better understanding on the structure and behavior of the antibacterial Ag incorporated hydroxylapatite. In order to do this, Ag doped hydroxylapatite was made by a precipitation method, and sintered in air at 1300oC. The materials were characterized by X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FTIR), density measurements and scanning electron microscopy (SEM).
Numerical Three-Dimensional Double Diffusion Poiseuille-Rayleigh-Benard Flows in Rectangular Channels
Authors: Rahli Omar , Bouhadef K. , Bennacer Rachid , Ameziani Djamel Eddine
Published: March 2009

The contribution of this work is to characterize the travelling wave’s appearance and to generalize the behavior of Poiseuille-Rayleigh-Benard (PRB) systems for a broad range of dimensionless parameters, which control the double diffusive mixed convection. The numerical results consist to analyzing the flow regimes of the steady longitudinal thermoconvectives rolls for the case of purely thermal mixed convection and for both thermal and mass diffusion. The passage from an opposed volume forces to cooperating one at fixed Rayleigh (Ra), Reynolds (Re) and Lewis (Le) numbers, affects considerably the birth and the development of the longitudinal rolls R//. The distribution of the heat and mass transfer, presented by the average Nusselt and Sherwood numbers, is also examined.
Diffusion of Interstitial Elements in Ti Alloys Used as Biomaterials
Authors: Grandini Carlos Roberto , de Almeida Luciano Henrique , Nogueira Renata Abdallah , Niemeyer Terlize Cristina
Published: March 2009

Titanium alloys are excellent implant materials for orthopedic applications due to their desirable properties, such as good corrosion resistance, low elasticity modulus, and excellent biocompatibility. The presence of interstitial elements (such as oxygen and nitrogen) causes strong changes in the material’s mechanical properties, mainly in its elastic properties. Study of the interaction among interstitial elements present in metals began with Snoek’s postulate, that a stress-induced ordering of interstitials gives rise to a peak in the mechanical relaxation (internal friction) spectra. In the mechanical relaxation spectra, each species of interstitial solute atom gives rise to a distinct Snoek’s peak, whose temperature and position depend on the measurement frequency. This effect is very interesting because its peculiar parameters are directly related to the diffusion coefficient (D) for the interstitial solute. This paper presents a study of diffusion of heavy interstitial elements in Ti-35Nb-7Zr-5Ta alloys using mechanical spectroscopy. Pre-exponential factors and activation energies are calculated for oxygen and nitrogen in theses alloys.
Evaluation of Environmentally Friendly Zr Based Nano Structured Conversion Coating for HRS (Hot Rolled Steel) in Powder Coating
Authors: Tepe Bulent , Gunay Banihan
Published: March 2009

Metals, despite their deterioration in a corrosive atmosphere, continue to dominate the automotive, agricultural, furniture, process and appliance industries and HRS (Hot Rolled Steel) plays a significant role in those areas. Powder coating on HRS is widely employed for protective and aesthetic purposes. Prior to powder coating, phosphating conversion coating is often used to increase effectiveness of protection. However, due to tightening environmental legislations, phosphating process is now problems for industry. Therefore, newly developed environmentally friendly conversion coats are introduced to industry. In this study a new environmentally friendly zirconium fluoro-based (H2ZrF6) generation of conversion coating has been introduced to replace the conventional phosphating conversion coatings process. It is deposited on the surface with a thin nanometre range, therefore shortening the process, which also has advantages such as being free of heavy metal and operating in low or ambient temperature. The present work closely examines Zr based nano structured conversion coatings for HRS. Extensive corrosion and adhesion studies are carried out on differently prepared HRS test panels, pre-treated with Zr based conversion coating in various conditions, such as different composition ratio, temperature and contact time.
Numerical Model for Multilayer Thin Films Irradiated by a Moving Laser Source
Authors: Bianco Nicola , Manca Oronzio , Ricci Daniele
Published: March 2009

A two-dimensional transient analysis of the conjugate optical-thermal fields induced in a multilayer thin film structure on a glass substrate by a moving Gaussian laser source is carried out numerically. The workpiece is considered semi-infinite along the motion direction and its optical and thermophysical properties are assumed temperature dependent. The COMSOL Multiphysics 3.3 code has been used to solve the combined thermal and electromagnetic problem. 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 starting point of the heat source with respect to the workpiece boundary along the motion direction.
Synthesis and Characterization of Single Crystals Y3Fe5O12 and Bi3Fe5O12 Prepared via Sol Gel Technique
Authors: Yahya Noorhana , Koziol Krzysztof , Bin Mansor Mohd Kamarulzaman
Published: March 2009

Magnetic properties of nano-crystalline yttrium iron garnet, Y3Fe5O12 and bismuth iron garnet, Bi3Fe5O12 were studied. The samples were synthesized by using sol gel route. The gel were prepared using nitrates of yttrium and iron for the yttium iron garnet (YIG) and nitrates of bismuth and iron for the bismuth iron garnet (BIG). The raw materials were mixed and dissolved in citric acid and were stirred for 3 months in room temperature until the gel was observed. The X-ray diffraction pattern reveals the cubic structure of YIG and BIG samples at 7000C and 5000C respectively. From the M-H diagrams it was found that the YIG and BIG samples have saturation magnetization, Ms of 27.2 Gs with rectangular hysteresis loop and 24.4 Gs with S hysteresis loop, respectively. It is evident from the FESEM micrographs that the rectangular loop shape (YIG) arises from the homogeneous and rounded microstructure as compared to the inhomogenous and random orientation microstructure (BIG) of the samples. From the Electron diffraction done on Transmission Electron Microscope, both of the samples were shown to be single crystals.
Microstructural Evolution and Resulting Mechanical Properties of Weld Joints upon Flux Cored Arc Welding and Post-Weld Heat Treatment
Authors: Yu Hui , Shin Kee Sam , Dong Ji Ling , Yoo Dae Hwang , Lee Woong , Im Hee Dae , Kil Woong , Jung Won Jung
Published: March 2009

The objective of this study is to determine the mechanism of the dramatic increase of impact toughness at low temperatures after post-weld heat treatment on weld joints. In this study, weld joints using two semi-automatic welding consumables were fabricated by flux cored arc welding with subsequent PWHT at 660°C for 65 min and 195 min, respectively. Tests of the tensile and yield strength, microhardness and impact toughness, were carried out. The microstructure was inspected by optical, scanning electron, and transmission electron microscopy in addition to compositional analysis using energy dispersive spectrometry. PWHT was observed to result in grain coarsening, sub-grain structure formation and decrease of the dislocation density. The increase of impact toughness is attributed to the relieved thermal stress, the inclusions and precipitations, softening of the structure, dislocation recovery and sub-grain structure.
Electron Microscopic Characterization of the Microstructural Evolution of 9-12% Cr Steels upon Aging
Authors: Dong Ji Ling , Huynh Quoc Bao , Yoo Dae Hwang , Yu Hui , Kim Min Soo , Kang Sung Tae , Shin Kee Sam
Published: March 2009

In this study, the microstructural behavior of two kinds of 9-12% Cr steels (specimen A and B) used for power plants with and without W, Co, B which were subjected to aging during various time and temperature were investigated by electron microscope and related analytical techniques. The results indicate that there are four kinds of precipitates in these materials, i.e., M23C6, Nb-rich and V-rich MX, W-rich and Mo-rich Laves phase, and Z-phase. Upon aging, the area fraction of M23C6 increased whereas that of Laves phases decreased despite an increase in size. The area fraction of W-rich Laves phase was much higher than that of Mo-rich Laves phase, indicating that W addition compared to that of Mo addition is more powerful in the formation of Laves phase precipitation (specimen A). Specimen A aged at 700°C exhibited the formation of Z-phase. The formation of Z-phase is known to have a tendency of dissolving MX precipitates in similar alloys. The high activity of Cr at 700°C is believed to be the cause of Z-phase formation.
An Indirect Approach for Correlation of Permeability and Diffusion Coefficients
Authors: Al-Tarawneh Khaled K. , Buzzi Olivier , Krabbenhoft Kristian , Lyamin Andrei V. , Sloan Scott William
Published: March 2009

Diffusion tests in porous media are quite sensitive and long lasting procedures compared to permeability tests, which are usually more reliable and of shorter duration. Both diffusion and advection phenomena are dependent on the tortuosity of the material tested. A relevant question is to know whether it is possible to correlate permeability tortuosity p and diffusion tortuosity d. Several diffusion and permeability tests have been performed on non-uniform sand specimens having different grain size distribution. For each specimen, both the permeability and diffusion coefficients have been measured and two tortuosity factors (permeability and diffusion) have been back calculated. A theoretical model has been proposed to estimate d from p for a non-uniform granular material. The maximum particle diameter dmax is used to determine the maximum hydraulic diameter dh-max using the Hydraulic Radius Theory (HRT) for a 3D arrangement of spheres of same diameter dmax. Then, a filling factor  is applied to dh-max in order to capture the fact that smaller grains tend to fill the voids present in between the bigger particles. The filling factor is based on the coefficient of uniformity Cu. Relatively good results are obtained so that this model allows estimating the diffusion properties from a simple permeability test rapidly and at a fraction of the diffusion test cost.
Numerical Modelling of Mass Transfer Problems in Combined Domains with Non-Linear Imperfect Transmission Conditions
Authors: Wrobel Michal , Mishuris Gennady
Published: March 2009

This work deals with a nonlinear mass transfer problem in an infinite combined domain, consisting of half-space matched to a bounded part via a thin intermediate layer. The latter exhibits high contrast material properties, whereas its thickness is assumed to be negligible in comparison with the dimensions of the bounded subdomain. The corresponding problem is reduced to an auxiliary one, defined only in the bounded region with a non-local boundary condition on the transmission surface, which is solved numerically by means of FEM. To introduce the boundary condition, a special iterative subroutine based on the classic Robin type boundary condition is constructed. The accuracy of the procedure and the range of its applicability are investigated for an analytical benchmark. Numerical results for an axisymmetrical stationary mass transfer problem are presented.
Extraction of Antioxidant Compounds from Grape Stalk Dried at Different Conditions
Authors: García-Pérez J.V. , Cárcel J.A. , Benedito J. , Blasco M. , Mulet A.
Published: March 2009

Grape stalk constitutes a by-product of wineries with low economic value. The extraction of compounds with antioxidant capacity may be considered as an alternative to increasing its value. Prior to extraction there must be a drying process, which may affect not only the product structure but also the antioxidant activity of extracts. The aim of this work was to address the influence of grape stalk drying conditions on the subsequent extraction of antioxidant compounds.
Prior to the extraction experiments, grape stalk was dried under different conditions: freeze dried and hot air dried at different temperatures (40, 70 and 100 °C). The extraction experiments were carried out at 60 °C using ethanol-water (80 % v/v) as solvent. Extracts were taken after 5, 10, 15, 30, 60, 120, 180, 240 and 1380 min. Antioxidant concentration in the solvent was evaluated by measuring the total antioxidant activity using the FRAP method. Extraction kinetic was modelled from the evolution of antioxidant concentration in the solvent using a diffusion model.
Extracts obtained from freeze dried samples presented the highest antioxidant concentration, almost double that from hot air dried samples. Among these, the highest antioxidant concentration was found for samples dried at 100 and 40 °C. The freeze dried samples also showed the highest kinetic parameters: effective antioxidant diffusivity and mass transfer coefficient.
Anodic Polarisation Characterisation of Absorbed Hydrogen in Modified Mm(B5)x Alloys
Authors: Santos Diogo M.F. , Chen Yun , Sequeira César A.C.
Published: March 2009

Anodic polarisation curves of Mm(Ni3.6Co0.7Mn0.4Al0.3)x (Mm = mischmetal, 0.85  x  1.15) electrodes were measured under the conditions of various initial concentrations of absorbed hydrogen (H/M), potential sweeping rates (v), temperatures (T), and amounts of reducing agent (y = [NaBH4]) in alkaline solution. Anodic peak current (Ip) at the Mm(B5)x electrodes increased with an increase in T, x and y values. In addition, the Ip value depended linearly on initial hydrogen concentration and square root of potential sweeping rate, irrespective of T, x and y values. Furthermore, the activation energy for hydrogen diffusion decreased with an increase in x and y values. From these results, it is considered that the surface reduction treatment of the Mm(B5)x alloys, performed in alkaline solution with sodium borohydride, the nonstoichiometry and the initial concentration of absorbed hydrogen, are important factors for improving the charge-discharge performance of negative electrodes for metal-hydrogen energy systems.
Hydrogen Absorption in Ion Beam Sputtered Titanium Thin Films
Authors: Tal-Gutelmacher Ervin , Gemma Ryota , Pundt Astrid , Kirchheim Reiner
Published: March 2009

Titanium films were prepared on sapphire substrates in an UHV chamber, by means of ion beam sputter deposition under Ar-atmosphere at the pressure of 1.5ּ10-4 mbar, with a deposition rate of 2,1 nm/min. The crystal structure was investigated by means of X-Ray diffraction using a Phillips X-Pert diffractometer with a Co-Kα radiation. For electrochemical hydrogen loading, the films were covered by a 30 nm thick layer of Pd in order to prevent oxidation and facilitate hydrogen absorption. The samples were step-by-step loaded with hydrogen by electrochemical charging, which was carried out in a mixed electrolyte of phosphoric acid and glycerine (1:2 in volume). An Ag/AgCl (sat.) and Pt wires were used as the reference and the counter electrode, respectively. XRD measurements were performed before and after hydrogenation in order to investigate the effect of hydrogen loading on the microstructure. The main characteristics of hydrogen's absorption behaviour, as well as the thermodynamics and phase boundaries of titanium-hydrogen thin films are discussed in detail with specific emphasis on the comparison to titanium-hydrogen bulk system.
Modelling and Quantification of Gas Flux through an Artificial Epidermis
Authors: Habib A. , Habib Khaled
Published: March 2009

A general model of transport of gases in an artificial epidermal layer (membrane) was
established. The model was developed based on Dusty Gas Model (DGM), solution diffusion and
surface diffusion. As a result, solutions of the model for different transport conditions were derived.
In this investigation, parameters of oxygen and carbon dioxide gases through an artificial
“epidermal” membrane of varying porosity were used to calculate semi-empirical solutions of the
general model. In other words, the solutions of the general model were analytically obtained for
different transport conditions, using experimentally obtained parameters of oxygen and carbon
dioxide gases through the artificial “epidermal” membrane of varying porosity. The obtained
solutions of the general model were for the oxygen and carbon dioxide gases through the artificial
“epidermal” membrane of the varying porosity.
Effect of Grain Size on the Luminescent Properties of Nano-Scale Gd2O3:Eu
Authors: Liu Qing Feng , Liu Qian
Published: March 2009

Nano-scale Gd2O3:Eu phosphor powders were synthesized by combustion method. In this process, the grain sizes of nano-scale Gd2O3:Eu were controlled by changing the amount of citric acid. Compared with micro-scale powders obtained from co-precipitation process, XRD revealed that the lattice parameter of nano-scale powders Gd2O3:Eu decreased. Further detailed study show that the luminescent properties were related to the grain size of nano Gd2O3:Eu powders under UV excitation.
Development of High Permeability Nanocrystalline Ferromagnetic Materials by Pulse Plating
Authors: Li Xiao Ping , Seet H.L. , Zhao Z.J. , Kong Y.K.
Published: March 2009

For the purpose of developing a composite micro sensor for weak magnetic field, fabrication of high permeability ferromagnetic material is needed. The magnetic properties of the pulse-plated samples depend greatly on the chemical composition and nanocrystalline grain size of the ferromagnetic layer. In this study, the effect of the pulse plating parameter: duty cycle on the chemical composition and grain size of the deposited layer was investigated. A layer of soft ferromagnetic material Ni-Fe was deposited onto copper wires of 20µm diameter by means of pulse and dc plating and tested under XRD for grain size measurement. It was found that
variations in duty cycle do not affect the thickness of the plated layer, but affect significantly the chemical composition. There is an optimum duty cycle for getting the minimum grain size of plated layer in pulse plating with saccharin. The results from the magnetic measurement showed that the permeability of the plated material increased greatly as the grain size decreased in the range of 10 – 55 nm.
Microwave-Assisted Synthesis of Platinum Nanoparticles
Authors: Ling Xing Yi , Liu Zhaolin , Lee Jim Yang
Published: March 2009

The rapid synthesis of platinum nanoparticles using ethylene glycol and microwave
dielectric heating is reported here. The Pt nanoparticles after synthesis were transferred to a toluene solution of dodecanethiol (DDT) to form DDT-encapsulated Pt nanoparticles. The TEM examinations showed nearly spherical platinum nanoparticles. The particles were in the size range of 2~8 nm and exhibited narrow size distribution. They were stable in the toluene solution for at least 10 months. Larger particles were formed with longer microwave heating time, higher metal precursor salt concentrations, and lower pH values. XPS measurements revealed >80% of Pt was in the zero valent state and the S 2p signal showed strong adsorption of sulfur species on the surface of platinum nanoparticles. FTIR
spectroscopy also confirmed the interactions of thiol groups and the platinum surface.
Monte Carlo Simulation of Surface Segregation in Nanoparticles
Authors: Jayaganthan Rengaswamy , Chow Gan Moog
Published: March 2009

An analysis of surface segregation of Au-Ti alloy nanoparticle (atomic ratio 1:1) is carried out using Monte Carlo simulation with the energetics described by Bozzolo-Ferrante-Smith method. The surface compositions of Au in Au-Ti nanoparticles are calculated based on the simulation that takes into account the size effect. The segregated surface compositions of Au in the Au-Ti binary alloy single-crystal nanoparticles (with particle diameter of 10-100 nm) are observed to be larger than
that of the corresponding bulk single crystal (with the particle diameter > 100 nm). The details of Monte Carlo simulation and the calculated surface compositions due to segregation are discussed.
Near-Amorphous Alloy Thin Films by Co-Sputtering Deposition
Authors: Hsieh J.H. , Li Can Hua , Wang C.M. , Liu Y.C. , Tang Z.Z.
Published: March 2009

Four alloy thin films were deposited on Si(100) by co-sputtering of various metals to investigate the formation of near-amorphous structure which may lead to featureless surface morphology and boundary-free structure. These thin films, Nb-Cr, Ta-Cr, Ti-Nb, and Zr-Cr, were examined using XRD SEM, and TEM. It is found that the forming ranges of near-amorphous thin films by co-sputtering are related to the difference in atomic size of the paired metals as well as their heat of mixing. Accordingly, Zr-Cr has the widest concentration range to form the near-amorphous
structure. The addition of nitrogen during deposition can further enhance amorphization and reduce the surface roughness, until nitride phases are formed.
The Preparation of Spinel Ferrite Nanoparticles Using Precipitation in Water-in-Oil Microemulsions
Authors: Košak Aljoša , Makovec Darko , Drofenik Miha
Published: March 2009

MnZn-ferrite nanoparticles with a narrow size distribution were prepared in situ in water-CTAB-hexanol microemulsions using a two-step process: the precipitation of the corresponding hydroxides, followed by the oxidation of the Fe2+. The influence of the temperature and the time of the precipitation step was systematically studied.
The Quasi Static Fracture Behavior of a Bulk Al-Cr-Fe Alloy Made by Consolidating Micron- and Nano-Sized Powders
Authors: Srivatsan T.S. , Givens S. , Al-Hajri Meslet , Petraroli M. , Radhakrishnan R. , Sudarshan Tangali S.
Published: March 2009

Micron-sized powders of an Al-7Cr-1Fe alloy were prepared by the technique of Gas Atomization Reaction Synthesis (GARS) at the Ames Laboratory (Ames, Iowa, USA). A pre-alloyed stock of the aluminum alloy was melted and atomized in an inert environment. A mixture of micron-sized and nano-sized powder particles was consolidated in a vacuum environment using the technique of plasma pressure compaction (P2CTM). The powders were initially pulsed at 150oC for 10 minutes and subsequently consolidated at 550oC under a pressure of 40 MPa for 10 minutes. In this paper, the tensile deformation and fracture characteristics of the aluminum alloy are highlighted at two different test temperatures. An attempt is made to elucidate the microscopic mechanisms governing tensile response and fracture in light of the competing and mutually interactive influences of intrinsic microstructural features, deformation characteristics of the constituents of the material, and test temperature.
Chemical Treatment Enhanced Gas Sensitivity Properties of Carbon Nanotubes
Authors: Wang W.L. , Liao K.J. , Cai C. , Wan B.Y. , Hu C.G.
Published: March 2009

The gas sensitivity properties of carbon nanotubes were investigated. The carbon nanotubes in this study were fabricated by hot filament chemical vapor deposition using Ni/Fe catalyst. The sensor samples were treated by chemical etching using H2SO4/HNO3. The experimental results have shown that the electrical resistance of carbon nanotubes was sensitively changed on exposure to gaseous ambient containing ethanol and water vapor. It was found that the gas sensitivity of carbon nanotubes was greatly enhanced after chemical treatment. It was also shown that the response time of nanotube sensor was faster than that of usual sensors.
Growth and Characterization of Misostructural Zinc Oxide Tubes
Authors: Sun X.W. , Xu C.X. , Chen B.J. , Yang Y.
Published: March 2009

Zinc oxide (ZnO) microtube has been fabricated by heating the mixture of ZnO and graphite powders in the atmosphere. The ZnO microtubes showed perfect hexagonal profiles with bell-mouth or normal hexagonal tops. Both X-ray diffraction (XRD) and high-resolution transmission electron microscopy (TEM) demonstrated that the product was composed of ZnO with typical hexagonal structure grown predominantly along (002) direction. The growth process was interpreted by means of vaporliquid-solid mechanism combining with the evaporation of metallic zinc.