bluuebunny/crossref_metadata_2025 huggingface dataset:
Two-Way Memory Effect in NiTi Shape Memory Alloys
Authors: Wada Kiyohide , Liu Yong
Published: March 2009

In general, the development mechanisms of TWME have long been understood as the
nucleation and growth of preferentially oriented martensite guided by the internal stress. This work
extends the study by investigating the effects of martensite deformation, constrained stress and
retained martensite via partial reverse transformation through thermal arrest during heating on the
stress-assisted two-way memory effect (SATWME) and TWME. It was observed that the generation
of maximum SATWME was caused by the development of optimum internal stress. The increase of
internal stress was accompanied by the increase of martensitic strain resulting from constrained
cooling. When the martensitic strain exceeded the initial pre-strain, it directly influenced on the
magnitudes of SATWME and TWME. The accommodation process of stress-assisted and detwinned
martensite variants as a result of partial reverse transformation caused the formation of internal
forward and back stresses. TWME was promoted by the dominant internal forward stress formation,
while the dominance of internal back stress decreased the TWME by decreasing the martensitic
strain.
PVDF Nanoweb Touch Sensors Prepared Using Electro-Spinning Process for Smart Apparels Applications
Authors: Yoon Sun , Prabu Arun Anand , Ramasundaram S. , Kim Kap Jin
Published: March 2009

Polyvinylidene fluoride (PVDF) based electrospun nanoweb fibers with outstanding
piezo-, pyro- and ferroelectric behavior are being intensely studied by many researchers, especially
for touch-sensor applications. In order to further improve the advantageous characteristics of PVDF
nanoweb fibers, we focused our attention on studying the effect of filling PVDF solution with
calculated amount of calcium chloride (CaCl2) or multi-walled carbon nanotube (MWCNT), and
their electrospun nanoweb fibers were analyzed for the changes in β-crystalline phase, and its
associated piezoelectric characteristics using a custom-made sensor set-up developed in our lab.
FT-IR spectroscopy was used to confirm the changes in the β-crystalline content with varying content
of CaCl2 and MWCNT. SEM data revealed the reducing fiber diameter with increasing CaCl2 content.
PVDF nanoweb subjected to pressure showed changes in touch sensing property as analyzed using an
oscilloscope integrated with Labview program. Overall, the PVDF nanoweb containing the additives
used in our study exhibited greater sensitivity-in-touch for use in smart apparel applications
compared to unmodified PVDF nanoweb, and the results are reported in detail here.
Variable-Stiffness–Mode Dielectric Elastomer Devices
Authors: Pelrine Ron , Kornbluh Roy
Published: March 2009

Dielectric elastomers, or more precisely dielectric polymers, are a relatively new class of
materials for variable-stiffness and variable-damping devices. Dielectric elastomers offer significant
potential advantages compared with previous variable stiffness smart materials. Advantages include
simplicity, broad dynamic range, ability to reach zero stiffness, low cost, minimal mass, shock
tolerance, simple drive circuitry, and design flexibility.
Dielectric elastomer devices in the variable-stiffness mode convert electrical and mechanical energy
back and forth to change mechanical impedance. This type of electromechanical transduction
distinguishes the variable stiffness mode from simply using a dielectric elastomer actuator to alter
the geometry, and hence the stiffness, of the device. Stiffness using a variable-stiffness mode
depends heavily on the electrical loading of the dielectric elastomer. Analysis shows that a constant
voltage loading reduces stiffness, down to zero in some cases, while a constant charge loading
increases stiffness.
Many applications can be considered for dielectric elastomer variable-stiffness mode such as
vibration control, suspensions, and tuning consumer devices for user comfort or preference. As with
dielectric elastomer actuators and generators, silicones and acrylics are the most promising
materials for variable-stiffness-mode devices.
Enhancing the Electro-Mechanical Response of Maxwell Stress Actuators
Authors: Gallone Giuseppe , Carpi Federico , Galantini Fabia , De Rossi Danilo , Levita Giovanni
Published: March 2009

The need for high electric fields to drive dielectric elastomers is still retaining their
diffusion as actuators in some areas of potential application, as in the case of biomedical
disciplines. The development of new materials offering superior electromechanical properties is
thus an essential requirement in order to effectively reduce the driving fields. In this light, the
present work is aimed to enhance the electromechanical properties of two silicone and polyurethane
based dielectric elastomers, both by making particulate composites with high-permittivity ceramic
fillers, and by blending with a highly polarisable polymeric phase. Due to a consequent worsening
of the mechanical properties, pure composite architectures yielded only limited results on the
overall electromechanical response. With the blend approach, instead, both an increase of the
dielectric permittivity and an unexpected reduction of the tensile elastic modulus were observed,
leading to an overall increase of the electromechanical response. In any case, a key role appears to
be played by the nature and intensity of polarisation phenomena arising at interfaces between
different phases.
Synthesis and Characterization of IPNs for Electrochemical Actuators
Authors: Vidal Frederic , Plesse Cedric , Palaprat Guillaume , Juger Jonathan , Citerin Johann , Kheddar Abderrahmane , Chevrot Claude , Teyssié Dominique
Published: March 2009

Interpenetrating polymer networks (IPNs) have been developed for many years leading to
materials with controlled properties. When an electronic conducting polymer (ECP) is incorporated
into an IPN, this one becomes a conducting IPN (CIPN). The synthetic pathway ensures a non
homogeneous dispersion of the ECP through the IPN thickness of the material. The system is thus
similar to a layered one with the advantage that the intimate combination of the three polymers
needs no adhesive interface. The last step in making the CIPN into an actuator is to ensure the ionic
conductivity by incorporation of an ionic salt. The highest ionic conductivity through the IPN matrix
is necessary in order to ensure the best actuation. The chosen salt is an ionic liquid, i.e. 1-ethyl-3-
methylimidazolium bis(trifluoromethylsulfonyl)imide (EMImTFSI). Based on IPN architectures
electrochemical actuators have been designed and actuation in open air has been characterized.
Crystal Growth and Characterization of Rare-Earth Gallates
Authors: Sasaura M. , Miyazawa S.
Published: March 2009

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Role of Cation Vacancy-Related Defects in Self-Assembling of CdSe Quantum Dots
Authors: Borkovska L.V. , Beyer R. , Hoffmann M. , Holzhey A. , Korsunska N. , Sadofyev Yu.G. , Weber Joerg
Published: March 2009

In this chapter we present the results of the photoluminescent and optical investigations of the influence of cation vacancy-related defects on CdSe/ZnSe quantum dot organization. Selfassembling growth was achieved under molecular beam epitaxy with subsequent annealing step. Number of cation vacancies was controlled by the intensity of the emission band connected with complex that includes cation vacancy and shallow donor. For the first time it is shown that increase of number of cation vacancy related defects results in the reduction of potential fluctuations in the QD layer. In this case a relatively uniform dense array of QDs with shallow localization potential is organized. It is proposed that generation of cation vacancies during the growth suppresses both Cd segregation and Cd surface diffusion as well as facilitates Cd/Zn interdiffusion. Interdiffusion process is proved by the changes in the photoluminescence and optical reflection spectra of ZnSe layers. It is showned that Cd/Zn interdiffusion can play an important role in CdSe/ZnSe intermixing during the QD formation at least under such growth conditions which can stimulate generation of cation vacancies.
Analytical Solution of Fick's Equations in the Case of Foreign Atom Diffusion in a Metallic Sample
Authors: Benmakhlouf A.
Published: March 2009

In this work we develop an analytical method for resolution of the reaction-diffusion
equations which govern impurity diffusion by the dissociative mechanism in a finite-thickness sample and from a deposit of solute atoms on the surface. This method is based upon the perturbation of basic solutions corresponding to limiting cases and the choice of suitable small parameters. The solutions obtained and their comparison to those of numerical studies are also presented in this paper.
Metal Lattice Atomic Structure Characterization Using Mirage Effect Technique
Authors: Boubaker Karem
Published: March 2009

This study develops a theoretical and experimental method for atomic structure characterization. The mirage technique has been performed to prospect unknown material structures in order to diagnose eventual treatment or defect. The use of Gaussian Laser beam made photothermal deflection signal more appropriate to build-up a simple algorithm in order to investigate metal structure frequential response to a modulated heating excitation and thus identify its more probable structure. Some applications on steel quenched or annealed samples yielded interesting results such as delimitation of martensitic structure . Method is actually to be tested on differently treated material.
The Kirkendall Plane in Binary Interdiffusion Systems
Authors: Kodentsov A.A. , Paul A. , van Loo F.J.J.
Published: March 2009

There is now a considerable body of experimental evidence to indicate that in a volumediffusion controlled interaction the Kirkendall plane need not be unique. The Kirkendall plane can microstructurally be stable as well as unstable (it does not exist!). Under predictable circumstances, it can also bifurcate and even trifurcate. This can be rationalised in terms of Kirkendall velocity construction as well as from a purely chemical point of view considering diffusion-controlled interactions at the interphase interfaces. The physico-chemical approach is also used to explain significance of the Kirkendall effect in the morphogenesis of interdiffusion systems.
An Ab Initio Study of the Effects and Stability of Vacancies, Antisites and Small Radius Atoms (B, C, N and O) in the B2-FeAl Structure
Authors: Kellou A. , Grosdidier Thierry , Aourag H.
Published: March 2009

Atomistic modeling based on Density Functional Theory (DFT) within the framework of the Generalized Gradient Approximation (GGA) is used to show the effects of defects such as vacancy, boron, carbon, nitrogen and oxygen substituting Fe or Al atoms in the B2-FeAl structure. The site preference of each type of defect is determined from a comparison of total energycalculations using a supercell structure, consisting of 16-atoms, within which each the various defects are introduced. The changes in lattice parameter and bulk modulus associated to the presence of the defects in the FeAl matrix are also studied.
First Principles Suggestions of Targeted Diffusion Experiments on SiO2
Authors: Roma Guido , Limoge Yves
Published: March 2009

In this paper we propose a couple of experimental lines in order to probe specific
features of oxygen and silicon diffusion in -quartz and SiO2 in general. We start from the results of atomistic first principles calculations and from their predictions concerning point defects formation free enthalpies; we suggest that measurements with variable oxygen partial pressure could confirm that, in well defined regimes, oxygen diffusion is controlled by doubly negative oxygen interstitials. Along similar lines, for silicon diffusion, one should check the real equilibrium conditions of samples, with gaseous oxygen or bulk silicon, or closed conditions. We discuss our predictions for silicon diffusion, that could clarify some discrepancies between
experimental results. Another possible probe would be to perform measurements under hydrostatic pressure, in order to measure the formation volume of the migrating species and to compare it to the theoretical values.
Diffusion in Intermetallic Compounds Studied Using Nuclear Quadrupole Relaxation
Authors: Collins Gary Scott , Favrot A. , Kang L. , Solodovnikov D. , Zacate Matthew O.
Published: March 2009

The jump frequency of Cd tracer atoms was measured as a function of temperature in seven rare-earth tri-indide intermetallic compounds having the L12, or Cu3Au, structure. The frequency, proportional to the diffusivity, was detected by relaxation of nuclear quadrupole interaction at Cd nuclei caused by reorientation of the electric field gradient in each diffusive jump. Measurements were made using perturbed angular correlation of gamma rays, sensitive to jump frequencies in the range 1-1000 MHz. Results are as follows. (1) Jump frequencies measured in LaIn3 and CeIn3 were observed to be 10-100 times greater at the more In-rich boundary composition than the less In-rich boundary composition, even though the phases appear as line compounds in phase diagrams. (2) Arrhenius plots of the jump frequency were fitted to activation enthalpies that increase from 0.535 to 1.80 eV across the series of phases LaIn3, CeIn3, PrIn3, and NdIn3.
Stress Development and Relaxation during Reaction of a Cobalt Film with a Silicon Substrate
Authors: Rivero Christian , Gergaud Patrice , Gailhanou Marc , Boivin Philippe , Fornara Pascal , Niel Stephan , Thomas Olivier
Published: March 2009

Thin metal films react with silicon substrates to form various metal silicides. The
sequence and kinetics of phase formation are still an area of intense research. Comparatively much less work has been done on the issue of stress development caused by the appearance of these new phases. A detailed review of the subject has been done ten years ago. We present here recent results obtained on Pd-Si, Co-Si, Ni-Si and discuss them in the light of what is known today on the elastic
and plastic properties of thin films. A simple model published by S. - L. Zhang and F. M. d’Heurle takes into account the simultaneous stress formation due to the reaction and the relaxation of these stresses. It provides a qualitatively satisfying picture of stress evolution at least for the first phase which forms. The model relies on two basic elements: 1) stress formation due to the formation of a new phase, and 2) the stress relaxation mechanism at work in the growing silicide film. The sign of the stress can be understood from the variation in volume that occurs at the growing interface(s). The stress relaxation mechanisms at work in a growing film are complex. They are highly dependent on the microstructure (as we have shown when comparing Pd/Si(001) and Pd/Si (111)) but should be also highly size dependent (e.g. dislocation glide is more difficult in small scale structures). Inhomogeneous plastic relaxation in polycrystalline silicide films may be an important
issue.
Formation of Nanostructure during High-Pressure Torsion of Al-Zn, Al-Mg and Al-Zn-Mg Alloys
Authors: Mazilkin A.A. , Kogtenkova Olga A. , Straumal Boris B. , Valiev Ruslan , Baretzky B.
Published: March 2009

Structure and phase composition of binary Al–Zn, Al–Mg and ternary Al–Zn–Mg alloys were studied before and after high pressure torsion (HPT) with shear strain 300. The size of (Al) grains and crystals of reinforcing second phases decreases drastically after HPT reaching nanometer range. As a result of HPT, the Zn-rich (Al) supersaturated solid solution decomposes completely and reaches the equilibrium state corresponding to room temperature. The decomposition is less
pronounced for Al–Mg and Al–Zn–Mg alloys. We conclude that the severe plastic deformation of supersaturated solid solutions can be considered as a balance between deformation-induced disordering and deformation-accelerated diffusion towards the equilibrium state.
Defect-Diffusion-Stress Relationships in Modeling the Oxidation and Degradation Processes of Alumina Formers: A Brief Survey
Authors: Jedlinski Jerzy
Published: March 2009

In the modeling of the oxidation and degradation processes of the superior metallic materials in terms of the high temperature oxidation resistance, being the so-called alumina formers, the matter transport only via grain boundaries of α-Al2O3 is usually taken into account. This paper indicates that such an approach needs to be re-visited. It is pointed out that the following factors should be taken into account (i) diffusion via point defects in the unstable alumina polymorphs (γ, δ, θ) which
grow during the early oxidation stages; (ii) dislocation-related processes; (iii) formation of the oxide in three-dimensional defects, being the cracks in the oxide layer; (iv) outward oxide growth resulting from the formation of the new oxide within the existing layer. The mentioned above effects as well as the other ones, related to the interfacial and stress-induced processes are illustrated and discussed. It is pointed out that alumina formers constitute a wide group of materials and several categories should be distinguished among them with respect to their
composition and production route on one hand, and the oxidation and degradation mechanisms, on the other hand. It is shown that the comprehensive approach enables better and self-consistent modeling of the oxidation and degradation mechanisms of alumina formers.
The Effect of Grain-Boundary Diffusion on the Oxidation of Low-Chromium Steels
Authors: Krupp Ulrich , Trindade V.B. , Schmidt Peter , Christ Hans-Jürgen , Buschmann U. , Wiechert W.
Published: March 2009

Even though the oxidation behavior of steels is generally considered as to be widely
understood, a closer look reveals some open questions, e.g. regarding the influence of the substrate grain size on the overall oxidation kinetics. At temperatures below 570°C the main constituent of the oxide scale formed on top of low alloy steels is magnetite. As shown by gold marker experiments it grows outward and inward at the same time, the latter exhibiting a gradual transition to the more stable spinel compound FeCr2O4. As indicated by intergranular-oxidation attack below the superficial scale, inward oxide growth seems to be driven by oxygen transport along the grain boundaries serving as fast diffusion paths. This is supported by thermogravimetric oxidation tests in air on low-Cr steels with varying grain size: The
smaller the grains the higher the oxidation rate. Recently, a numerical model for the diffusive transport processes based on the finite-difference approach has been developed, which distinguishes between fast grain-boundary diffusion and bulk
diffusion. Qualitatively, it is capable to predict the relationship between substrate grain size and inward oxide growth kinetics. Together with the thermodynamic tool ChemApp and in combination with a data set for the Fe-Cr-O system the mechanism-based simulation of the overall oxidation process of low-Cr steels is possible.
Growth and Characterization of Boron-Doped Si1-x-yGexCy Layers Grown by Reduced Pressure Chemical Vapor Deposition
Authors: Radamson H.H. , Hållstedt J.
Published: March 2009

In this paper, the following issues: epitaxial growth, boron incorporation and electrical properties of Si1-x-yGexCy layers grown by reduced pressure chemical vapor deposition (RPCVD) are presented. Furthermore, diffusion of carbon and boron in silicon-based material is also discussed.
The Magneto-Plastic Effect at Beryllium Bronze after Aging in the Constant Magnetic Field
Authors: Osinskaya J.V. , Pokoev A.V. , Perov Nikolai S.
Published: March 2009

In this research, the process of artificial aging of beryllium bronze as diffusioncontrollable process was studied at the temperatures of 250–500 0C, at aging time intervals of 0.17 till 2 hours, in the constant magnetic field and without it by microhardness and residual magnetization methods.
Hardness of Nanostructured Al-Zn, Al-Mg and Al-Zn-Mg Alloys Obtained by High-Pressure Torsion
Authors: Mazilkin A.A. , Baretzky B. , Enders S. , Kogtenkova Olga A. , Straumal Boris B. , Rabkin Eugen , Valiev Ruslan
Published: March 2009

Microstructure and hardness of ternary Al–Zn–Mg alloys were studied both in as cast state and after high pressure torsion (HPT) with 5 torsions (shear strain about 6). The size of (Al) grains and of reinforcing second phase precipitates decreases drastically after HPT reaching nanometer range. During HPT, the Zn- and Mg-rich supersaturated (Al) solid solution decomposes and reaches the equilibrium state corresponding to the room temperature. In the as cast state the hardness of the supersaturated solid solutions increases with increasing Zn and Mg content due to the solid-solution hardening. However, after HPT the work hardening and Hall-Petch hardening due to the decreasing grain size competes with softening due to the decomposition of a supersaturated solid solution. In the net effect, the severe plastic deformation results in softening of ternary Al–Zn– Mg alloys.
Sum-Rule Relations among Phenomenological Coefficients: Application to Segregation and Chemical Diffusion in Multicomponent Alloys and Mixed Ceramic Oxides
Authors: Belova Irina V. , Murch Graeme E.
Published: March 2009

In this overview, we discuss the sum-rule relating phenomenological coefficients in randomly mixed systems and consider several applications to collective diffusion problems. These applications include intrinsic diffusion multicomponent alloys, chemical diffusion in strongly ionic mixed cation crystals and demixing of cations in randomly mixed quaternary transition metal oxides. In each case a substantial simplification is possible as a result of the sum-rule.
Role of Diffusion as a Control Stage of a Grain Boundary Liquid Grooving
Authors: Dolgopolov Nikolai , Petelin A. , Rakov S.
Published: March 2009

The interaction of liquid metals with solid polycrystalline metal leads to the appearance of liquid grooves at grain boundaries. The shapes of these grooves may be of a very wide variety. In this paper the typical features of different liquid grooves are presented, classified and analyzed on the base of our experimental data. The developed models confirm the dominant role of diffusion mechanisms.
Grain Boundary Wetting in Zn Bicrystals by a Sn-Based Melt
Authors: Murashov Vladimir , Straumal Boris B. , Protsenko Pavel
Published: March 2009

The kinetics and morphology of the grain boundary grooving of Zn bicrystals with 16°
<1010> tilt GB by Sn(Zn) melt has been studied at 325°C in equilibrium conditions in vacuum. It is shown that grooving process is interface controlled at least on the first stage. Groove walls mobility is evaluated. Changing of GB grove shape from “faceted walls” corner for annealing time < 78 h to concave “Mullins type” groove for annealing time > 78 h at the same experimental temperature was
observed for the first time.
Structure and Phase Transformations upon Carburisation of High-Speed Steel
Authors: Chaus Alexander S.
Published: March 2009

Diffusion effects of alloying elements on the structure and phase transformation during thermo-chemical treatment in AISI M2 high-speed steel additionally alloyed with vanadium, titanium and niobium have been investigated. The results of metallographic, X-ray diffraction, and electron microprobe analyses of the steels after casting, annealing, hot plastic deformation, carburising, quenching and tempering are discussed. The redistribution of alloying elements between the metallic matrix and carbide phases upon high-temperature treatment due to diffusion was shown to result in the structure and phase transformations in the steels studied.
Calculation of Phenomenological Coefficients by Monte Carlo Computer Simulation Methods
Authors: Belova Irina V. , Brown M.J. , Murch Graeme E.
Published: March 2009

In this paper we first review the principal indirect and direct Monte Carlo methods for calculating the Onsager phenomenological transport coefficients in solid state diffusion. We propose a new Monte Carlo method that makes use of a steady state calculation of a flux of atoms that is driven by a difference in chemical potential of the atoms between a source and a sink plane. The method is demonstrated for the simple cubic one component lattice gas with nearest neighbour interactions. The new method gives results in good agreement with a Monte Carlo method based on Einsteinian expressions for the phenomenological coefficients.
Calculation of Atom Configuration and Characteristic of Vacancy in bcc Lattice of α-Fe
Authors: Valikova Irina , Nazarov Andrei V. , Mikheev Alexandr A.
Published: March 2009

This work is devoted to the simulation of atom configurations in bcc metals near the point defect using the molecular static method. The values of migration and formation volumes are very sensitive to the atomic structure in the vicinity of a defect, which makes it necessary to consider a large number of atoms in the computation cell and to take into account an elastic matrix around the cell. We have developed the new model taking into consideration these factors. It allows defining the “fine structure” of displacement atoms near the point defect. The atoms of third zone were
embedded in an elastic continuum. The displacement of each atom embedded in an elastic continuum was defined as the first and the second terms in solution of elastic equation. In the framework of this model we calculated the formation and migration energies and volumes of defect. Also we take into consideration that the energy of system (in particular the system with defect) depends on the external pressure. This dependence gives an addition to the values of migration and
formation volumes.
Einstein's Theory of Brownian Motion
Authors: Shvindlerman Lasar S.
Published: March 2009

The story of the creation of Einstein’s theory of Brownian motion is considered to the background of Einstein private life and understanding of science at the end of the 19th and the very beginning of the 20th century.
Influence of Liquid-Glass Transition on Diffusion and Nucleation in Computer-Simulated Iron
Authors: Evteev Alexander V. , Kosilov A.T. , Levchenko Elena V. , Logachev O.B.
Published: March 2009

A molecular dynamic model for instantaneously undercooled iron melt has been applied to model the isothermal annealing of the stable percolation clusters. They contain mutual penetrating and contacting icosahedra with atoms at the vertices and centers. Such stable clusters form only below the critical temperature Tg ~1180 K. We identify Tg as the glass transition temperature. It is established that the time when a homogeneous nucleation starts is minimal for Tg. The stable icosahedral
percolation clusters do not form above Tg. The proposed quantitative model describes the atomic mobility in metal glasses, where root-mean-square atomic displacement is the sum of contributions from both linear (Einsteinian) and logarithmic terms, associated to irreversible structure relaxation.
The activation parameters of the model change abruptly at the icosahedral percolation transition.
Deep Trap Concentrations from Three-Dimensional Carrier Concentration Profiles in Hydride Vapor Pressure Epitaxially-Grown GaN
Authors: Halder N.C. , Martin J. , Sisler Jr. D.
Published: March 2009

We have investigated deep trap concentrations in hydride vapor pressure epitaxy (HVPE) - grown
GaN by measuring three-dimensional carrier concentration profiles and ionization energies.
Schottky contacts were fabricated on 28-68μm thick films using Ni/Au contacts. Extensive
capacitance-voltage measurements were made in the temperature range 100-350K at reverse bias
voltages in the range 0 to –5V. Effective carrier concentrations and ionization energies were
determined from three-dimensional plots of concentration-temperature-depth. Carrier concentration
versus temperature plots show slowly changing three-step behavior. During the first step, all the
plots rise linearly up to about 200K reaching respective plateaus before reversing courses
downwards again linearly. Ionization energy plots, on the other hand, are almost linear all the way
up to 350 K showing some tendency of upward bending. Trap concentrations were determined from
carrier concentrations and previously measured deep level transient spectroscopy (DLTS) plots as
function of reverse bias voltages. In almost every case, trap concentrations also rise linearly with
increasing depth in the samples.
Slow Positron Studies of Defects in Si-Doped GaAs
Authors: Godbole B. , Badera N. , Shrivastava S.B. , Joshi K.P.
Published: March 2009

The mechanism of slow positron annihilation in Si-doped GaAs has been discussed in terms of the diffusion trapping model (DTM). The trapping of positrons has been considered in SiAs acceptors i.e. shallow defects and in VGa-SiGa vacancy complexes. The model has been used to obtain the Doppler broadening line shape parameter (S-parameter) and average positron lifetime in Si-doped GaAs, for a temperature range 20K to 290K and for different doping concentrations. Observations are made regarding the effect of doping on the nature and concentration of point defects. The change in point defect concentration due to Si- doping has been found to be proportional to the doping concentration. The effect of detrapping from the shallow defects has been found to be important at higher temperatures.
Defect Densities Using the Positron Annihilation Doppler Broadening Technique in Wrought Alloys 3003 and 3005
Authors: Abdel-Rahman M.A. , Kamel N.A. , Abdel-Rahman M. , Abo-Elsoud M. , Lotfy Yahia A. , Badawi Emad A.
Published: March 2009

Positron Annihilation Doppler Broadening Spectroscopy (PADPS) is one of the nuclear techniques used in material science. PADPS measurements are used to study the behavior of defect concentration and dislocation density in a set of 3003 and 3005 wrought aluminum alloy. It has been shown that positrons can become trapped at imperfect locations in solids. The S-parameter can be influenced by changes in the concentration of such defects. There is no observed change in the Sparameter values after the saturation of defect concentration. The S-parameter and trapping rates for the samples deformed up to 10 percent were studied. The concentration of defect range varies from 1017 to 1018 cm-3 and from 1016 to 1017 cm-3 for 3003 and 3005 wrought Al alloy respectively. While trapping rate range varies from 1 x1010 to 1.2x1011 s-1 for 3003 and from 1 x109 to 1.2x1010 s-1 for 3005 wrought Al alloy.
The Influence of Defects on Proton Diffusion in Perovskites АIIВIV11-xRIIIxO3-δ: Monte Carlo Study
Authors: Tsidilkovski V.I. , Uritsky M.Z. , Varaksin A.N. , Fishman Anatoly Yakovlevich
Published: March 2009

The tracer diffusion coefficient D* and the mobility of protons in proton-conducting
oxides of the АIIВIV
1-xRIII
xO3-δ family have been calculated using the Monte Carlo method as
functions of temperature and concentration x of the acceptor impurity RIII. The effect of protondopant
interactions (proton trapping) and the effect of protonic sites blocking caused by protonproton
and proton - oxygen vacancy interactions, are analyzed. It is shown that the proton
diffusivity depends significantly on the dopant content and is considerably reduced already at small
x. The D* value weakly depends on the concentration of oxygen vacancies at fixed, not too large
values of x. The conductivity dependence on the doping concentration σ(x) can have a maximum
due to the proton-defect and proton-proton interactions. The Haven ratio deviates slightly from
unity at the expected intensity of interparticle correlations. The calculated values of both the
diffusivity activation energy increase (with x), and the location of the σ(x) maxima agree with the
experimental data for a number of proton-conducting oxides.
Anelastic Relaxation due to Interstitial Solutes Diffusion in Nb and Nb-1 wt% Zr
Authors: Florêncio Odila , Silva Paulo Sergio , Grandini Carlos Roberto
Published: March 2009

Metals and alloys containing solute atoms dissolved interstitially often show anelastic
behavior due to a process know as stress-induced ordering. The application of mechanical
spectroscopy measurements to diffusion studies in body-centered cubic metals has been extensively
used in the last decades. However the kind of preferential occupation of interstitial solutes in bodycentered
cubic metals is still controversial. The anelastic properties of the Nb and Nb-1 wt% Zr
polycrystalline alloys were determined by internal friction and oscillation frequency measurements
using a torsion pendulum inverted performed between 300K and 650K, operating in a frequency
oscillation in the hertz bandwidth. The interstitial diffusion coefficients of oxygen and nitrogen in
Nb and Nb-1 wt% Zr samples were determined at two distinct conditions: (a) for low concentration
of oxygen and (b) for high concentration of oxygen.
The Influence of Increased Cr Content and Austenite Grain Size on the Kinetics of Phase Transformations when Cooling Hypo-Eutectoid Steel
Authors: Wierszyłłowski Ignacy
Published: March 2009

The paper presents the influence of the grain size and a little higher Cr content on
the kinetics of austenite phase transformations during continuous cooling of hypo-eutectoid
steel. The kinetics of austenite phase transformations during continuous cooling were
determined by means of analysis of the dilatometric curves and structure investigations. The
influence of the austenite grain size and the higher Cr content was analysed in two hypoeutectoid
steels containing about 0.4% C. One of them had, Cr content higher, by about 1%.
In both steels, the austenite grain size was changing insignificantly up to the austenitising
temperature of about 950fl. Above that temperature, the austenite grain size in carbon steel
grew much quicker than that in the steel with Cr addition. The austenite grain in the Cr
enriched steel was smaller than that in carbon steel and, in spite of that, the duration of cooled
austenite transformations were several times longer. This means that the phase
transformations are much more strongly influenced by the addition of chromium slowing
down carbon diffusion in austenite, than by the austenite grain size. For each phase
transformation in the examined steels, the activation energy of the transformation has been
determined. The activation energy of all the phase transformations varied slightly with the
increase of austenitising temperature. On the basis of the obtained results, curves of true
isothermal transformations have been developed for the beginning of the phase
transformations in both steels, related to infinitely quick cooling down to the transformation
temperature.
Thermodynamic Properties of Liquid Binary Transition-Metal Alloys in the Bretonnet-Silbert Model
Authors: Dubinin N.E. , Son L.D. , Vatolin N.A.
Published: March 2009

In the present study, we apply the Bretonnet-Silbert local model pseudopotential, which
takes into account the s-d hybridization in interacting between ion and s-electron to calculate the
thermodynamic properties of binary transition-metal liquid alloys. The Wills-Harrison approach is
used to take into account the d-electron terms in the free energy. We use the simplest variant of the
variational method of the thermodynamic perturbation theory (with the hard-sphere reference
system), the Vashishta-Singwi exchange-correlation function, and the Lorenz form of the density of
d-electron states. The free energy of mixing, internal energy of mixing, and excess entropy of
mixing are calculated for a Fe-Co liquid alloy at different compositions near the melting
temperature. The agreement with the experimental data is quite satisfactory.
Diffusion of Carbon and Manganese in Fe-C-Mn
Authors: Král Lubomir , Million B. , Čermák Jiří
Published: March 2009

In this paper, the results of measurements of chemical diffusion of C in weldments of Fe-
C-Mn alloys with content of 0-15 % Mn, are reported. Alloys were cast in induction furnace under
protective Ar atmosphere. They were hot-forged to rods of diameter 15 mm, machined down to
diameter 12 mm, and cut into pieces of 4 mm thickness. These cylindrical samples were
metallographically polished. Diffusion couples, welded by electrical impulse, were sealed together
with Ti-chips, into evacuated silica ampoules. After that, they were annealed at 1073-1373 K for
96-1.5 hours, respectively. Measurement of C redistribution was done in a normal direction to
welding interface using electron-scanning microscope Philips SEM-505WDS equipped with
Microspec WDX-2A. Diffusion coefficients of C were obtained and the relations between
manganese and carbon were found.
Microstructural Stability of Dissimilar Weld Joint of Creep-Resistant Steels with Increased Nitrogen Content at 500 – 900 °C
Authors: Zlámal Bronislav , Foret Rudolf , Buršík Jiří , Svoboda Milan
Published: March 2009

The structural changes taking place in the dissimilar laboratory welds of 6CrMoV 8-3-2
(T25), being under development, and modified X12CrMoVNb 10-1 (P91) nitrided steels annealed
at temperatures of 500 – 900 °C have been subject of study. Carbon and nitrogen redistribution
measurement by the EPMA method was complemented with detailed structural analysis aimed at
the phase profiles and chemical composition of coexisting carbides and carbonitrides in particular
regions of the weld joint. Results of experimental work were compared with thermodynamic and
kinetic modeling using the DICTRA software. A very good agreement between the modeling and
the experiments was observed.
Collective and Tracer Diffusion via a Defect Cluster in LSGM
Authors: Belova Irina V. , Murch Graeme E. , Samuelis D. , Martin Manfred
Published: March 2009

It was recently shown by Schulz and co-workers that in doped lanthanum gallate: La(1-x)
SrxGa(1-y)MgyO(3-(x+y)/2) (LSGM) the three cations: La, Sr and Mg have tracer diffusivities that are
nearly identical. To explain these findings, a bound defect cluster mechanism containing a cation
vacancy from both the A- and the B- sublattices and an anion vacancy was proposed as the principal
vehicle for cation diffusion in LSGM. In this paper, implications of this mechanism are considered
for the first time. Sum-rule expressions for the collective correlation factors are derived and found
to be in excellent agreement with Monte Carlo calculations. Expressions are also developed for the
tracer correlation factors of lanthanum and gallium for diffusion via the cluster mechanism and
tested by Monte Carlo computer simulation. Good agreement was found. The ratio of the tracer
diffusivities of lanthanum and gallium are shown to be consistent with the cluster mechanism.
Raman Investigation of Stress for Shallow Trench
Authors: Sang Sheng Bo , Xue Chen Yang , Zahng Wen Dong , Xiong Ji Jun
Published: March 2009

A trench is used as a storage capacitor in dynamic memory (DRAM) technologies (deep storage
trenches), or as an isolation structure in CMOS, bipolar and BiCMOS technologies. But a shallow
trench structure has also been shown to be a major factor in substrate defect generation during
processing. Such defect generation is directly related to mechanical stresses existing around the
trench. This stress can be monitored, using Raman spectroscopy, to a stress resolution of 10MPa
and a spatial resolution of 0.2μm. In this paper, a trench structure is designed and fabricated, and
the test results for local stresses within the trench are shown to be in good correspondence with
theory.
Effect of Nature Aging on Positron Lifetime Spectroscopy in Casting and Wrought Al-alloys
Authors: Abdel-Rahman M.A. , Abdel-Rahman M. , Kamel N.A. , Abdallah M.S. , Badawi Emad A.
Published: March 2009

Positron annihilation has been performed in order to study the isochronal annealing of wrought (2024, 7075) and cast (AlSi11.35Mg0.23, AlSi10.9Mg0.17Sr0.06) aluminum alloys, at temperatures ranging from RT to 773K, after having been deformed at RT to 25% deformation. Two annealing stages of the microstructures were distinguished, which were attributed to recovery in (2024, AlSi11.35Mg0.23, AlSi10.9Mg0.17Sr0.06) due to point defects and dislocations, respectively, and only one (due to dislocations) in (7075). Also, natural aging for up to more than 650 days was studied as a function of mean lifetime.
Non-Random Interaction of Vacancies with Atoms during Interdiffusion and Ionic Conductivity in Materials
Authors: Belova Irina V. , Murch Graeme E.
Published: March 2009

The non-random interaction of vacancies with atoms during interdiffusion and ionic conductivity is referred to as the vacancy-wind effect. This effect, first discovered by the late Dr John Manning, is a subtle phenomenon arising from the non-random distribution of vacancies with respect to a given moving atom within a net flux of vacancies. Recently, a good deal of progress has been made in determining accurate expressions for vacancy-wind factors in binary and ternary alloys, and in mixed cation ionic systems. The present paper provides an overview of these recent findings and puts them into a broader and historical context.
Dynamic and Equilibrium Swelling of Biodegradable Starch-Based Superabsorbent Polymers
Authors: Nasser R.O. , Vázquez da Silva M. , Delgado João M.P.Q. , Gonçalves Maria P. , Andrade C.T.
Published: March 2009

A series of biodegradable superabsorbent polymers (SAP’s) based on starch grafted with
acrylic acid (AA) and crosslinked with N,N’-methylenebisacrylamide (MBIS) were obtained. The
parameters that define SAP’s properties, such as starch type, amount of initiator, acrylic acid and
crosslinker concentrations, and degree of neutralization were varied.
The dynamic swelling was interpreted in terms of both a simple power of time equation and a
more detailed model based on a coupled diffusion–relaxation mechanism. The diffusivity
coefficients calculated from diffusion–relaxation model were compared with the microimages
obtained by optical microscopic.
Thermal Conductivity Enhancement of Compact Heat Sinks Using Cellular Metals
Authors: Fiedler Thomas , Öchsner Andreas , Belova Irina V. , Murch Graeme E.
Published: March 2009

In this paper, the increase of the effective thermal conductivity of paraffin based heat
sinks is investigated by making use of cellular metallic matrixes with open cells which are
introduced in the thermal low conductive paraffin wax. Lattice Monte Carlo analyses are conducted
on different model geometries of such composites composed of a cellular matrixes and paraffin
wax. The dependence of the effective thermal conductivity on the cell geometry and the metal foam
matrix material is analysed. Furthermore, a diamond coating is simulated in order to estimate its
influence on the effective thermal conductivity.
A Model of Single Molecule Magnet Behavior of the [CuIILTbIII(hfac)2]2 Cluster
Authors: Ostrovsky S. , Reu O. , Palii A. , Fishman Anatoly Yakovlevich , Mitrofanov Valentin Yakovlevich , Tregenna-Piggott P. , Moskvin A.S. , Klokishner S.
Published: March 2009

We report a model for the explanation of the single molecule magnet behavior of the
[CuIILTbIII(hfac)2]2 cluster. The model takes into account the crystal field acting on the TbIII –ion
and the exchange interaction between the TbIII and CuII ions. The energies of the low-lying levels
are shown to increase with the decrease of the mean value of the z-projection of the total angular
momentum of the cluster, thus forming a barrier for magnetization reversal that is in accordance
with the experimental evidence.
Oxygen Isotope Exchange between Gaseous Phase Enriched with 18O Isotope and Nanocrystal Oxides LaMnO3+δ Obtained by Severe Plastic Deformation
Authors: Gizhevskii Boris A. , Fishman Anatoly Yakovlevich , Kozlov E.A. , Kurennykh Tatiana Eugenievna , Petrova S.A. , Trakhtenberg I.Sh. , Vykhodets Vladimir Borisovich , Vykhodets V.B. , Zakharov Robert Grigorievich
Published: March 2009

The kinetics of the isotope exchange between gaseous oxygen enriched with the 18O
isotope and two LaMnO3+δ oxide samples – a nanopowder and a bulk nanocrystal – has been
studied. The 18O isotope concentration has been measured by the acceleration nuclear microanalysis
method. The coefficients of the volume and the nanograin boundary self-diffusion of oxygen have
been evaluated at 500 °C. They are equal to 3.5·10
−20 and 1.5·10
−13 cm2/s, respectively.
Effects of Mg Additions on Surface Morphology and Corrosion Resistance of Hot-Dipped Zn Coatings
Authors: Suarez Lucia , Leysen Frans , Masquelier C. , Warichet D. , Houbaert Yvan
Published: March 2009

Steel is still the main construction material for automobiles, general equipment and
industrial machinery. Hot dipping has been proven to be an excellent method of corrosion protection
of steels for a wide range of applications worldwide. Coatings of Zn-Al alloys on steel sheet have
high corrosion resistance due to the corrosion prevention ability from Zn and the passivation of Al
Bath composition, immersion velocity/time and substrate composition are the hot dipping
parameters that more influence on the thickness and corrosion resistance of the deposited coating. In
order to study their influence small amounts of magnesium were added.
Experiments were performed in a hot dipping simulator using different substrates, bath
compositions and hot dipping parameters. Surface layers were characterised by: Scanning Electron
Microscopy (SEM) and Energy dispersive X-Ray spectroscopy (EDX or EDS). Cyclic corrosion
tests were performed in order to observe the corrosion resistance for different Zn-Al-Mg coatings.
Results show that the microstructure and composition of the substrate strongly affect the desired
coating properties. Nevertheless, the influence of the magnesium on coating thickness is relevant,
increasing when added in small quantities in a molten bath of Zn-5wt %Al. The quality and
microstructure of the coating is affected by the amount of Mg in the bath. Cyclic corrosion tests
results show that the quality of the coating is affected by the amount of Mg in the bath.
Determination of Concentration Dependent Diffusion Coefficients of Carbon in Expanded Austenite
Authors: Hummelshøj Thomas S. , Christiansen Thomas L. , Somers Marcel A.J.
Published: March 2009

In the present paper various experimental procedures to experimentally determine the
concentration dependent diffusion coefficient of carbon in expanded austenite are evaluated. To this
end thermogravimetric carburization was simulated for various experimental conditions and the
evaluated composition dependent diffusivity of carbon derived from the simulated experiments was
compared with the input data. The most promising procedure for an accurate determination is
shown to be stepwise gaseous carburizing of thin foils in a gaseous atmosphere; the finer the
stepsize, the more accurate the approximation of the diffusivity. Thermogravimetry was applied to
continuously monitor the weight change of thin foils of AISI 316 during carburizing in CO-H2 gas
mixtures for one of the simulated experimental procedures.
Prediction of Martensite Formation Start Temperature in Steels Using Artificial Neural Networks
Authors: Arjomandi M. , Khorsand H. , Sadati S.H. , Abdoos H.
Published: March 2009

Martensite phase and its formation are quite attractive and important in industrial steels
for reasons of having good properties such as high strength and high hardness. As such, determining
the martensite formation start temperature in steel heat treatment operations is extremely important.
Some parameters including chemical composition and grain size are effective factors on this
temperature. In this investigation, we have made an attempt to determine this temperature with
regard to chemical composition of steels. To reach this goal, we have explored the use of
feedforward Artificial Neural Network (ANN) with the Back Propagation (BP) learning algorithm.
A comparison is made between the Ms temperatures predicted with this model and those from the
empirical equation as well as the experimental values obtained from costly and time-consuming
tests in scientific and industrial centers for various steels. This comparison indicates that a better
agreement exists between the ANN-predicted results and experimental values than the results from
the empirical equation and experimental values.