bluuebunny/crossref_metadata_2025 huggingface dataset:
Static and Dynamic Heterogeneities in Supercooled SiO2
Authors: Hoang Vo Van
Published: March 2009

Static and Dynamic heterogeneities in supercooled SiO2 have been investigated in the models containing 3000 particles obtained by cooling from the melt with the pair interatomic potentials, which have the Morse type part for the short-range interaction. The evolution of structure of the system upon cooling was presented and analyzed in details through the changes in the partial radial distribution functions (PRDFs), coordination number distributions, bond-angle distributions and structural defects. Calculation presented that the temperature dependence of diffusion constant D of components in the system shows an Arrhenius law at low temperatures and it shows a power law, γ ) ( C T T D − ∝ , at high temperatures. The critical temperature Tc is equal to 4200 K and the exponent γ is close to 0.50. In order to study the dynamical heterogeneities in the system, we evaluated the non- Gaussian parameter for the self-part of the van Hove correlation function and luster-size distributions of most mobile or immobile particles in the model. We compared the PRDFs for the 10% most mobile or immobile particles with the corresponding mean ones. We have found that the most mobile and immobile particles form clusters and mean cluster size grows with decreasing temperature.
On the Interaction of Dislocations with Impurities in Silicon
Authors: Cavalcoli Daniela , Cavallini Anna
Published: March 2009

Dislocations and impurities in silicon have been widely investigated since many years,
nevertheless many questions on this subject remain still unsolved. As an example, theory, models
and experimental phenomena provide evidence of the existence of shallow bands in silicon induced
by the dislocation strain field. Nevertheless, only deep bands, likely associated with contamination
at dislocations, have been detected up to now by junction spectroscopy. The present contribution
reviews several results, obtained by the authors, on dislocation impurity interactions and their
effects on the electronic properties of defect states in silicon. Point and extended defects introduced
in p-type Cz Si by oxygen precipitation and plastic deformation have been investigated with
electrical methods. Different materials (oxygen precipitated and deformed Cz Si and Fz Si) were
examined in order to separate the role of oxygen precipitation, plastic deformation and metallic
contamination on non-radiative electronic transitions at defect centers. A deep hole trap, named T1,
has been associated to dislocation-related impurity centers, while additional deep traps have been
related to contamination by grown-in transition metals and to clusters involving oxygen atoms.
Moreover, experimental results obtained by junction spectroscopy assessed the existence of
dislocation related shallow states. These were found to be located at 70 and 60 meV from the
valence and conduction band edge, respectively.
DFT Analysis of the Indium-Antimony-Vacancy Cluster in Silicon
Authors: Souza M.M. De , Goss Jonathan P.
Published: March 2009

A cluster comprising of indium, antimony and a vacancy in silicon is analysed using the planewave pseudopotential technique. This cluster has a strong binding energy that inhibits indium diffusion after high temperature anneal cycles. Difficulties associated with the simulation of a vacancy using the supercell approach are initially highlighted. In comparison, the indium-antimony-vacancy cluster reveals stronger distortions and reduction in relaxation volume. The indium atom in the relaxed cluster shows nearly six-fold coordination whereas the antimony atom acquires four neighbours. Due to the low symmetry of the centre, in constrast to the isolated vacancy there is no propensity for a Jahn-Teller effect. It gives rise to two defect levels in the bandgap.
Role of Diffusion in the Shaping of the High-Absorption State in a Resonatorless Exciton Bistable System
Authors: Gudyma Yuriy V. , Kruglenko Ivanna V.
Published: March 2009

We present a unified approach to description of all the stages of shaping of a highabsorption state in a resonatorless exciton bistable system, as a nonequilibrium first-order transition. The velocity of switching wave front and thickness of interface between phases are determined within the quick switching wave approximation. The size distribution functions of subcritical and supercritical nuclei and asymptotic expression for nucleus radius were obtained.
Tracer Diffusion in Nonstoichiometric Intermetallic Compounds with Random Mixing on Each Sublattice
Authors: Sandhu I.S. , Chaturvedi D.K. , Belova Irina V. , Murch Graeme E.
Published: March 2009

Tracer di f fusion by way of vacancies is invest igated in B2 intermetal l ics
AB by means of a kinet ic equat ion approach. The model used is one wi th four inter
sub-lat t ice frequencies where each sub-lat t ice is t reated as a random al loy.
Coupl ing is achieved between the two types of cycles, i .e. , wi th the vacancy
start ing on one sub- lat t ice and finishing on ei ther sub-lat t ice and wi th a vacancy
start ing on the other sub-lat t ice and finishing on ei ther sub-lat t ice. An expression
for the t racer cor relat ion factor is derived in terms of atom vacancy exchange
frequencies and atomic concentrat ions. Resul ts from this expression are compared
wi th Monte Car lo calculat ions and also resul ts f rom a previous Manning-type
random al loy approach to the problem.
Atomic Diffusion Features in Au/Al & Al/Ni Bonding Interface
Authors: Li Jun Hui , Min Si Zong , Duan Ji An , Han Lei , Zhong Jue
Published: March 2009

Vertical section features in bonding point were produced by ion-sputter thinning, and
were tested by using TEM-F30. Lift-off characteristics at the interface of Ultrasonic bond are
observed by using SEM (JSM-6360LV). Results show that thickness of Au/Al atomic diffusion
interface was about 500 Nanometer under ultrasonic and thermal energy. Ultrasonic vibration
activates dislocations at metal crystal lattice. Fracture morphology of lift-off interface was dimples.
Tensile fracture appeared by pull-test not in bonded interface but in basis material, and bonded
strength at interface was enhanced by diffused atom from the other side.
Dopant Diffusion in Si1-xGex Thin Films: Effect of Epitaxial Stress
Authors: Portavoce Alain , Berbezier Isabelle , Ronda Antoine , Gas Patrick , Christensen J.S. , Kuznetsov Andrej Yu. , Svensson Bengt Gunnar
Published: March 2009

We have investigated the lattice diffusion of B and Sb by means of molecular beam
epitaxy in Si1−xGex (x < 0.2) layers grown on Si(001) substrate. Using Si1−xGex relaxed buffers we were able to differentiate the chemical effect (change in the Ge composition) as opposite to the biaxial stress effect (due to the epitaxy on Si) on dopant diffusion. B diffusion follows a behavior opposite to Sb diffusion versus Ge composition and biaxial stress. These results are explained in
view of the difference of diffusion mechanism between B (interstitials) and Sb (vacancies). We also show that dopant diffusion follows contrasting behaviors under biaxial pressure and hydrostatic pressure, and that the activation volume of dopant diffusion is of opposite sign for biaxial pressure and for hydrostatic pressure. This is explained using a formalism based on the extra work done by
the system for diffusion under pressure, concluding that for biaxial stress the activation volume depends mainly on the relaxation volume linked to the defect formation.
Diffusion in the Interface Region of Ti/TiAl-Nb Bonding
Authors: Kommel Lembit A.
Published: March 2009

Diffusion in the interface regions of lightweight heatproof quality titanium and titanium/aluminum alloys was investigated. We studied the diffusion of aluminum from intermetallide to titanium alloy. The concentration of other chemical elements and microhardness has been measured in diffusion region formed in the solid titanium alloy. The interface region includes a transition zone from the initially solid Ti-alloy and the molten TiAl-Nb intermetallic substrate. The width of the interface region after diffusion bonding is 45-60 µm. The titanium content decreases and aluminum content increases starting from surface up to 120-150 µm in depth in solid titanium alloy. As a result of diffusion, the intermetallic Ti3Al thin layer was formed in the transition zone in the Ti-alloy substrate. The microporosity was also formed in the interface region.
Effect of Grain Boundary/Interface Network on Cavity Growth due to Atom Migration Induced by Stress and Electric Current in Polycrystalline LSI Conductor
Authors: Shibutani Tadahiro , Kitamura Takayuki , Shiratori Masaki
Published: March 2009

The cavity growth behavior in a polycrystalline LSI conductor is investigated on the basis of diffusion along grain boundary (GB) and interface (IF) induced by stress and electric current. The of GB and IF, which strongly affects the characteristics of the atom migration. Numerical analysis is conducted for a polycrystalline conductor with GB/IF network after a discussion on a specialized FEM for the diffusion. Results obtained are as follows. (i) In a
conductor, the atom migration is eminently activated near a cavity along GBs while there is little flow without the defect. (ii) IF diffusion between the conductor and the surrounded passivation activates the atom migration along GBs inside of a conductor. This implies that the cavity grows under the interaction between GB diffusion and IF one. (iii) Under an external stress, the cavity growth is fast in
the early stage while it is decelerated by the constraint of the triple junction ahead of the cavity. (iv) The complex branches of the atom migration due to electric current (EM) amplifies the stress evolution and the stress-induced atom migration (SM) takes place. The cavity grows under the interaction between EM and SM, which stems from the GB/IF network.
Phase Transitions and Ion Conductivity in NASICON-Type Compounds Li1±XZr2-XMX(PO4)3, M = Ta, Nb, Y, Sc, In
Authors: Stenina I.A. , Kislitsyn M.N. , Pinus I.Yu. , Haile S.M. , Yaroslavtsev Andrew B.
Published: March 2009

Ionic conductivity and phase transitions of lithium-zirconium phosphates, Li1±XZr2- XMX(PO4)3 (M = Ta, Nb, Y, Sc, In), with NASICON structure were studied using X-ray powder diffraction, calorimetry, 31P and 7Li NMR and impedance spectroscopy. Triclinic-rhombohedral phase transition in these materials occurs in a wide temperature range at coexistence of both phases. Unusual change of LiZr2(PO4)3 lattice parameters with temperature increase was found. During heating of this compound parameter “a” significantly decreases.
Effect of Mechanoactivation on Interfacial Interaction in Metal/Oxide Systems
Authors: Muktepavela Faina , Bakradze Georgy , Stolyarova Sara
Published: March 2009

Properties of interfaces in solid state metal/oxide joints (Al/SiO2, Al/MgO, Al/glass,
Mg/MgO, Mg/SiO2, In/glass etc.) are reported. The interfaces were formed by plastic deformation of metal on the oxide surface at room temperature. Their structure, chemical composition, and micromechanical properties were studied by the AFM, XRD, SIMS, optical microscopy, and precision microindentation techniques. A noticeable adhesion was observed for metals with high
affinity for oxygen and only in the regions of the maximum shear stress. Formation of an interfacial reaction zone with an oxygen concentration gradient is detected. In this zone metals are nanostructured and noticeably hardened. The effect of mechanoactivation is considered as a result of physical and chemical interaction and formation of nanostructures in deformed metal/oxide systems.
Consequences of Silicon Segregation on the Dielectric Properties of Sintered Alumina
Authors: Zarbout Kamel , Moya Gérard , Bernardini Jean , Moya-Siesse Denise , Si Ahmed A. , Kansy Jerzy , Gœuriot Dominique
Published: March 2009

The dielectric breakdown strengths of two series of sintered alumina samples of low and high impurity content (where Si is the dominant element with, respectively, 90 and 1500 ppm) and impurity level (25 ppm of Si and 12 ppm of Ti) are compared with positron lifetime measurements. The dielectric breakdown strength of sintered alumina is found higher than that of single crystal. This improvement is stronger when silicon is the only major foreign element. If, in addition to SiO2, MgO and CaO are present in substantial amounts, the improvement is lessened. This is attributed to the enhanced bulk solubility of Si. These results are discussed by calling for the potential traps for positrons and electrons that are located at grain boundaries. It is deduced that the improvement of the dielectric breakdown strength stems from the consequences of Si segregation at grain boundaries via electron trapping in shallow traps, which are likely the x '' Al • Al ) V : (3Si clusters.
Ad- and Desorption of Oxygen at Metal-Oxide Interfaces: Numerical Approach for Non-Homogeneous Oxide Distribution
Authors: Öchsner Andreas , Stasiek Michael , Grácio José
Published: March 2009

A numerical approach for the segregation of atomic oxygen at Ag/MgO interfaces is presented. A general segregation kinetics is considered and the coupled system of partial differential equations is solved due to a one-dimensional finite difference scheme. Based on a model oxide distribution, the influence of the oxide distribution is numerically investigated and compared with the solution for equidistant arrangements. The numerical approach allows for the consideration of general boundary conditions, specimen sizes and time-dependent material and process parameters. Furthermore, a numerical procedure to convert two-dimensional microstructures into representative one-dimensional distributions is described.
Some Thoughts and/or Questions about Activation Energy and Pre-Exponential Factor
Authors: Philibert Jean
Published: March 2009

The first part of this paper presents a brief historical account of the Arrhenius law, starting from the seminal paper by Arrhenius (1889) up to theoretical developments mainly based on the rate theory. The second part describes the so called compensation rule (Meyer-Neldel rule), a correlation between activation enthalpy and entropy (or between pre-exponential factor and activation energy) , and discusses whether this correlation is trivial or bears some physical meaning.
The Effect of Defect Disorder on the Electronic Structure of Rutile TiO2-x
Authors: Hossain Faruque M. , Murch Graeme E. , Sheppard L. , Nowotny Janusz
Published: March 2009

The purpose of this work is to study the effect of bulk point defects on the electronic
structure of rutile TiO2. The paper is focused on the effect of oxygen nonstoichiometry in the form
of oxygen vacancies, Ti interstitials and Ti vacancies and related defect disorder on the band gap
width and on the local energy levels inside the band gap. Ab initio density functional theory is used
to calculate the formation energies of such intrinsic defects and to detect the positions of these
defect induced energy levels in order to visualize the tendency of forming local mid-gap bands.
Apart from the formation energy of the Ti vacancies (where experimental data do not exist) our
calculated results of the defect formation energies are in fair agreement with the experimental
results and the defect energy levels consistently support the experimental observations. The
calculated results indicate that the exact position of defect energy levels depends on the estimated
band gap and also the charge state of the point defects of TiO2.
Effect of γ-Irradiation on the Mechanical Properties of Al-Cu Alloy
Authors: Abo-Elsoud M. , Ismail H.
Published: March 2009

SEM observations and Vickers-hardness tests were performed to identify the irradiation effects. γ- irradiation effect during the aging hardening process can be explained depending on the composition of the alloy and is used to derive quantitative information on the kinetics of the transformation precipitates. Increasing the Cu content of an Al-Cu alloy can improve the aging hardness. The present results of hardness behavior with SEM observations of surveillance specimens at different doses suggest that the radiation-induced defects are probably complex valance-solute clusters. These clusters act as nuclei for the precipitation of θ-Al2Cu type. This can be effectively utilized to study the systematic of nucleation of precipitates at vacancy-type defects. γ-irradiation probably play the key role in defects responsible for material strengthening and embrittlement.
Phenomenological Model for Creep Behaviour in Cu-8.5at%Al Alloy
Authors: Abo-Elsoud M.
Published: March 2009

Creep experiments were conducted on Cu-8.5at.% Al alloy in the intermediate temperature range from 673 to 873K, corresponding to 0.46-0.72 Tm where Tm is the absolute melting temperature. The present analysis reveals the presence of two distinct deformation regions (climb and viscous glide) in the plot of log ε vs. log σ. The implications of these results on the transition from powerlaw to exponential creep regime are examined. The results indicated that the rate controlling mechanism for creep is the obstacle-controlled dislocation glide. A phenomenological model is proposed which assumes that cell boundaries with sub-grains act as sources and obstacles to gliding dislocations.
Interphase Diffusion with Curved Phase Boundaries
Authors: Eib Wilhelm
Published: March 2009

The liquid phase of adhesives is most readily described by the theory of solutions.
Adhesives act on phase boundaries. Yet right there, the fact that an adhesive is a solution
does not fully describe its special performance. Some of the outstanding properties of adhesives
are designed by the use non- soluble components, like Nanofillers, fibre reinforcements, color
pigments, additives for the improvement of electrical and heat conductivity, etc. We would like
to compare near phase boundary properties inside adhesives and outside near the substrates.
We expect a relation between rheology and thermodynamical parameters of adhesion.
Solutions are characterized by their chemical potential. We expect the above relationship to
manifest itself by a change of the chemical potential near a phase boundary.
Formation of Diffusion Potential Barrier for Oxygen Ions in Nio1-δ Crystal
Authors: Bannikov V.V. , Fishman Anatoly Yakovlevich , Leontiev Leopold , Mitrofanov Valentin Yakovlevich
Published: March 2009

A theoretical investigation of peculiarities in the formation of diffusion potential barrier
for oxygen atoms in NiO1-δ crystal is performed. The approximation of pair interionic potentials set
in analytical expressions is used for the evaluation of the potential barrier for the diffusing oxygen
atom. It is shown that the potential energy of diffusing oxygen atom originates first of all from
compensation between positive contribution of short-range interaction and negative contributions of
the long-range Coulomb interaction. It is also influenced by effects of degenerate term splitting due
to the low-symmetry crystal fields, created by the diffusing atom and vacancy, lattice relaxation and
redistribution of excess charges in the vicinity of diffusing oxygen atom.
Reaction Diffusion Behaviour in Bronze Route Cu-Nb-Sn Superconducting Wires
Authors: Hopkins Simon C. , Tan K.S. , Pong I. , Glowacki Bartek A.
Published: March 2009

The bronze process is a mature technology for the production of Nb3Sn superconducting
wires exploiting reaction diffusion behaviour in the Cu-Nb-Sn system. However, the
superconducting properties depend strongly on the applied heat treatment, and optimisation of the
heat treatment is still largely by trial and improvement. Modelling of the reaction-diffusion
behaviour would allow improved heat treatments to be designed; combination of this with a nondestructive
in situ characterisation technique would also permit improved superconducting wires to
be produced. A finite difference reaction diffusion model has been designed to permit rapid
calculation of the bronze matrix composition and Nb3Sn layer thickness profiles across the wire
cross-section as a function of time for any applied heat treatment. The model has also been designed
to calculate the electrical resistivity of the wire, which has previously been demonstrated as a
suitable in situ characterisation technique. This model has been applied to isothermal and more
complex heat treatments and compared with experimental results. Good qualitative agreement has
been found, and plans for further improvement of the model are described in detail.
Self- and Impurity Diffusion in γ-TiAl Single Crystals
Authors: Nakajima Hideo , Nose Y. , Ikeda Teruyuki
Published: March 2009

The diffusion coefficients of 44Ti, 63Ni and 59Fe in γ-TiAl single crystals have been
measured by ion-beam sputter-sectioning technique, while those of In have been measured using ion
implantation technique and secondary ion mass spectroscopy (SIMS) in order to clarify the diffusion
anisotropy: the diffusion perpendicular and parallel to the [001] axis. The diffusion of Ti and In
perpendicular to the [001] axis is faster than that parallel to the [001] axis. However, the diffusion
anisotropies of Fe and Ni show opposite trend to those of Ti and In, namely the diffusion parallel to
the [001] axis is faster than that perpendicular to the axis. The predominant process of diffusion
perpendicular to the [001] axis has been discussed from a viewpoint of activation energy using the
expression of the diffusion coefficients in L10-ordered alloys.
Numerical Model to Describe the Growth of the Internal Oxidation Layer in Binary Alloys
Authors: Plascencia Gabriel , Utigard Torstein A. , Gutiérrez Juliana , Jaramillo David , Martínez Fernando
Published: March 2009

Several analytical models have been developed through the years to describe the
formation and growth of the internal oxidation layer in binary alloys. Such models are often
complex and their validity strongly rely on precise measurements of molar fluxes of the
different species involved in the oxidation process. The main disadvantage of such
measurements is that they are difficult to made and present a high degree of uncertainties,
thus some assumptions are needed to ease understanding and the applicability of them. In this
paper we set up a numerical scheme (finite differences) to describe the growth of the internal
oxidation layer in binary Cu-Al alloys oxidized in air at different temperatures. There is good
agreement between the experimental results and the values calculated with the aid of our
numerical approach.
Diffusion Coefficients of Aqueous Solutions of Carbohydrates as Seen by Taylor Dispersion Technique at Physiological Temperature (37 °C)
Authors: Ribeiro Ana C.F. , Santos Cecilia Isabel A.V , Lobo Victor M.M. , Valente Artur J.M. , Prazeres Pedro M.R.A. , Burrows Hugh D.
Published: March 2009

Binary mutual diffusion coefficients have been measured for aqueous solutions of some
carbohydrates (glucose, fructose, lactose, sucrose, α-cyclodextrin and β- cyclodextrin) at
concentrations from 0.002 mol dm-3 to 0.010 mol dm-3. The concentration dependence of the
diffusion coefficients at physiological temperature, 37 °C, is discussed on the basis of their
structures.
Thermal Conductivity in Nanoscale Lennard-Jones Systems: Size Effects in the Fluid and Solid Phases
Authors: Botelho D.F. , Branício Paulo S. , Rino José Pedro
Published: March 2009

We simulate fluid and solid Lennard-Jones argon systems via non-equilibrium molecular
dynamics and study how the system behaves under an imposed temperature gradient until it reaches
the stationary state, from where the thermal conductivity is calculated. We show that transient
pressure waves propagate in the system giving rise to a density oscillation pattern. Based on the
damping of this pattern we estimate the time needed to reach the stationary state. We also show that
thermal conductivity is size independent in the fluid phase, while it increases until the Casimir limit
in the solid phase.
Thermal Expansion and Oxidation of Calcium Oxysulfides by Diffusion
Authors: Selivanov Evgeny N. , Gulyaeva R.I. , Chumarev V.M. , Selmenskikh N.I.
Published: March 2009

The iron and zinc calcium oxysulfides Ca3Fe4S3O6, CaFeSO and CaZnSO are
synthesized by reacting mixtures of CaO and FeS or of CaO and ZnS in an inert atmosphere. Their
elemental compositions and lattice parameters are determined by X-ray microanalysis and X-ray
diffraction. From the temperature-dependent lattice parameters of oxysulfides (measured up to
1170K) their thermal expansion coefficients are evaluated. Oxidation Ca3Fe4S3O6 and CaZnSO are
studied by thermogravimetric analysis when air heated. Oxidation speed temperature coefficients
showing that process limiting stage is diffusion are determined.
Electrocatalytic Studies of Oxygen Reduction by Lanthanum Barium Manganate
Authors: Santos Diogo M.F. , Sequeira César A.C.
Published: March 2009

The electrocatalysis of the oxygen reduction reaction by Lanthanum Barium Manganate,
(La0.5Ba0.5MnO3) (LBM) has been studied by cyclic voltammetry using the rotating ring-disc
electrode technique (RRDE) in alkaline medium. From the ring-disc data and other kinetic
parameters it has been assumed that the oxygen reduction occurs by dissociative chemisorption at
low overpotentials. At higher overpotentials, the formation of hydrogen peroxide (HO2
- in this case)
has been observed on this electrocatalyst. The apparent exchange current density value for oxygen
reduction on LBM has been found to be 4 x 10-8 Acm-2, while the corresponding Tafel slope is
0.115 V per decade. The possible reaction mechanism for electroreduction of oxygen on this oxide
catalyst has been discussed.
Reconstruction of Brass for Tongues and Shallots from Baroque Organs
Authors: Baretzky B. , Friesel M. , Petelin A. , Shotanov A.E. , Straumal Boris B.
Published: March 2009

The composition and microstructure of historic tongues and shallots from reed pipes of
various Baroque organs have been studied. They contain Cu–Zn solid solution (α-brass with 23-29
wt. % Zn) and lead particles. Grain size in brass scatters from 10 to 200 μm. Around 50% of all
GBs in brass are Σ=3 twin GBs. The high-indexed coincidence site lattice facets were observed in
twin GBs. The increase of number of various facets roughly correlates with decreasing grain size. It
may indicate the variation in annealing temperature used by organbuilders in Baroque Era. New
brass with 25 wt. % Zn and 2 wt. % Pb has been prepared for reconstruction of historic tongues and
shallots by restoration of reed pipes in Baroque organs. The morphology of lead inclusions and twin
GBs has been investigated in temperature interval from 400 to 700°C and compared with that of
historic alloys. The annealing temperature has been estimated.
Isothermes of Grain Boundary Tension and Grain Boundary Adsorption in Cu-Sn System
Authors: Vaganov Danil V. , Zhevnenko Sergei
Published: March 2009

Grain boundary surface tension and surface tension of free surface for pure copper and
copper-tin alloys are measured. On the base of these data isothermes of grain boundary tension, free
surface tension and isothermes of adsorption are constructed in assumption of a dilute solution.
Experimental Investigation of the Effect of the Ambient Gas on Evaporating Sessile Drops
Authors: David S. , Sefiane Khellil , Tadrist Lounes
Published: March 2009

This paper presents the results of an experimental study of evaporating sessile drops in a
controlled environment. The experimental setup allowed the investigation of the evaporation rate of
sessile drops under reduced pressure (40 to 1000 mbar) and various ambient gases. Sessile drops of
initial volume 2.5μL are deposited on substrates and left to evaporate in a controlled atmosphere.
The effect of reducing pressure on the evaporation rate as well as changing the ambient gas is
studied. Three different gases are used; namely Helium, Nitrogen and Carbon Dioxide. The role of
vapour diffusion as a limiting mechanism for evaporation is studied. It is found that in all cases the
evaporation rate is limited by the mass diffusion in the ambient gas provided that interfacial
conditions are properly accounted for. This includes important evaporative cooling observed at
higher evaporation rates and lower substrate thermal conductivity.
Diffusion and Segregation in Bulk Nanomaterials and Thin Layers
Authors: Bokstein Boris S. , Petrova O.N.
Published: March 2009

The data are presented for Ni selfdiffusion and Au heterodiffusion in nanocrystalline Ni.
Volume diffusion coefficients are much greater than those for a coarse – grained polycrystals
extrapolated from high temperatures. Interface diffusion parameters were calculated based on the
assumption that B – kinetic regime is realized at temperature range more than 448 K, while C –
kinetic regime is realised at temperatures less than 423 K. The consistency of obtained results with
the proposed cluster diffusion model is discussed.
Diffusion in Au – Cu thin films (from several tens to several hundreds nanometers) was studied
with the use of the Rutherford Back Scattering, RBS, under the kinetic regime B (448 – 523 K). The
RBS spectra were transformed in the concentration depth profiles for both volume and grain
boundary (GB) diffusion. The triple products Pn = snδDn (sn is the enrichment coefficient, while δ is
the nanograin boundary width) were calculated using Whipple model. As a result of this analysis the
s – value for Cu – Au system was determined to be of the order of unity.
The paper is focused on a difference between GB diffusion parameters in nano – and coarse
grained materials.
The Grain Boundary Wetting in the Sn– 25 at% In Alloys
Authors: Yeh C.H. , Chang L.S. , Straumal Boris B.
Published: March 2009

The grain boundary (GB) wetting was investigated in the Sn – 25 at.% In alloy. It was
found that the portion of GBs wetted by the melt depends on the annealing temperature. No GB
completely wetted by melt was observed at 140°C, while all GBs were fully wetted after annealing
at 180°C. Between 140°C and 180°C the portion of wetted GBs increases with increasing
temperature. The tie-lines of GB wetting phase transition were constructed in the Sn–In bulk phase
diagram.
Materials Science Issues for the Fabrication of Nanocrystal Memory Devices by Ultra Low Energy Ion Implantation
Authors: Claverie A. , Bonafos Caroline , Assayag G. Ben , Schamm S. , Cherkashin N. , Paillard V. , Dimitrakis P. , Kapetenakis E. , Tsoukalas Dimitris , Muller T. , Schmidt Bernd , Heinig K.H. , Perego M. , Fanciulli Marco , Mathiot D. , Carrada M. , Normand P.
Published: March 2009

Nanocrystal memories are attractive candidate for the development of non volatile
memory devices for deep submicron technologies. In a nanocrystal memory device, a 2D network of
isolated nanocrystals is buried in the gate dielectric of a MOS and replaces the classical polysilicon
layer used in floating gate (flash) memories. Recently, we have demonstrated a route to fabricate
these devices at low cost by using ultra low energy ion implantation. Obviously, all the electrical
characteristics of the device depend on the characteristics of the nanocrystal population (sizes and
densities) but also on their exact location with respect to the gate and channel of the MOS transistor.
It is the goal of this paper to report on the main materials science aspects of the fabrication of 2D
arrays of Si nanocrystals in thin SiO2 layers and at tunable distances from their SiO2/interfaces.
Effective Diffusion Coefficients during Osmotic Dehydration of Vegetables with Different Initial Porosity
Authors: Mayor Luis , Moreira Ramón , Chenlo Francisco , Sereno Alberto M.
Published: March 2009

Chesnut and pumpkin fruits were dehydrated with osmotic solutions of sucrose and NaCl
at 25°C. These food materials have different structure, composition and porosity. Water loss and
solids gain kinetics were experimentally determined and modeled using a diffusional model. In spite
of the several mass transfer mechanisms taking place along with diffusion during osmotic
dehydration, the modeling was satisfactory and involved effective coefficients of diffusion useful to
quantify the different mass transfer fluxes. Water and sucrose transfer rates during osmotic
dehydration with sucrose solutions are independent on the initial food material characteristics;
however they seem to be related with the permeability of these components to a sucrose layer
formed in the surface of the samples. In the case of osmotic dehydration with sodium chloride
solutions, the coefficients of diffusion show a dependence on food material characteristic and higher
values of these coefficients for pumpkin (more porous material) were found.
Mass Transfer and Concentration Contours around Surfaces Buried in Granular Beds and Exposed to Fluid Flow
Authors: Delgado João M.P.Q. , Alves M.A. , Carvalho J.R.F.G
Published: March 2009

This work describes the process of mass transfer which takes place when a fluid flows
past a soluble surface buried in a packed bed of small inert spherical particles of uniform voidage.
The fluid is assumed to have uniform velocity far from the buried surface and different surface
geometries are considered; namely, cylinder in cross flow and in flow aligned with the axis, flat
surface aligned with the flow and sphere.
The differential equations describing fluid flow and mass transfer by advection and diffusion in
the interstices of the bed are presented and the method for obtaining their numerical solution is
indicated. From the near surface concentration fields, given by the numerical solution, rates of mass
transfer from the surface are computed and expressed in the form of a Sherwood number (Sh). The
dependence between Sh and the Peclet number for flow past the surface is then established for each
of the flow geometries.
Finally, equations are derived for the concentration contour surfaces at a large distance from the
soluble solids, by substituting the information obtained on mass transfer rates in the equation
describing solute spreading in uniform flow past a point (or line) source.
Use of Sγ Momentums for the Modeling of Tracer Transport in Homogeneous Porous Media
Authors: Coutelieris Frank A.
Published: March 2009

Droplets transport in homogeneous porous media has been found to be an attractive
problem applicable in a lot of industrial and scientific sectors such as enhanced oil recovery, food
production, plastics etc. As applications become wider, a predictive method for the process is
warranted. To this end, it has been widely accepted that the collection of γ-order moments, Sγ, can
describe the time evolution of any spatially averaged quantity like the mean diameter of spherical
droplets, while it has been also found that Sγ satisfies the transport equations [1]. Here, the so-called
“Sγ concept” is applied in a CFD module for the modeling of the transport processes occurring in a
mixture of a continuous aqueous phase which includes a discontinuous one in the form of droplets.
This mixture flows within a homogeneous porous medium under creeping or laminar flow
conditions. The momentums of the particle size distribution are evaluated using the local flow
conditions as obtained from CFD simulations for the processes considered. To solve the transport
equations, the microstructure droplets formation/destruction has been also taken into account by
using already known analytical expressions for the source terms representing the break up and
coalescence of the droplets [2-4]. The proposed constitutive model adequately simulates the effect
of porous geometry on the droplets size distribution and could be helpful in understanding the
phenomena that take place in microscopic scale.
Diffusion of Molecules at the Interface of Water-Membrane Structures
Authors: Tourleigh Ye.V. , Shaitan K.V. , Balabaev N.K.
Published: March 2009

The distributions and transfer energies of several molecules and atomic groups between
water and a structured hydrophobic phase were calculated by the molecular dynamics method. The
coefficients of oxygen diffusion in a tetradecane membrane were estimated. The transfer energy of
charged atomic groups was found to correlate with changes in the Born solvation energy. The
contributions of atoms to the transfer energy of functional groups were shown to be non-additive.
The steered dynamics method for estimating the kinetic parameters of the penetration of molecules
through interphase boundaries was developed. Heterogeneous microviscosity of a membrane was
calculated for a hydrated l-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylcholine bilayer. Effects of
the chemical properties of penetrant molecule on its translocation through the membrane were
studied.
Positron Lifetime in Deformed AlSi10.9Mg0.17Sr0.06 Alloys
Authors: Abdel-Rahman M.A. , Abdallah M.S. , Badawi Emad A.
Published: March 2009

Positron annihilation lifetime spectroscopy (PALS) is one of the nuclear techniques used in material science. (PALT) measurements are used to study the behaviour of the defect concentration in a set of AlSi10.9Mg0.17Sr0.06 alloys. It has been shown that positrons can become trapped at imperfect locations in solids, and that their mean lifetime can be influenced by changes in the concentration of such defects. No changes have been observed in the mean lifetime values following saturation of the defect concentration. The mean lifetime and trapping rates were studied for samples deformed up to 34.9 %. The concentrations of defects range vary from 5.194x1015 to 1.934x1018 cm-3 for thickness reductions of 2.2 to 34.9 %. The range of the dislocation density varies from 1.465x 108 to 5.454x1010 cm/cm3 over the same range of deformations.
Low Temperature Self-Diffusion of Iron in the 56Fe/57Fe Stable-Isotope Thin-Film System
Authors: Vasylyev M. , Sidorenko Sergey I. , Voloshko S.M. , Kostiuchenko V. , Kotenko I.E.
Published: March 2009

Low-temperature diffusion in thin films of the stable isotopes, 56Fe/57Fe, was studied by
applying secondary ion mass spectrometry (SIMS). Processing of the concentration profiles obtained
was done by using the Hall – Morabitto “median gradient” method. The bulk and intergrain selfdiffusion
coefficients were determined.
Diffusion and Phase Transformations in Multi-Component Systems
Authors: Inden Gerhard
Published: March 2009

The simulation of diffusion-controlled transformations in multi-component systems is
presented using the software DICTRA. It is shown that not only stable phases precipitate during
heat treatments, but also metastable phases. These phases appear in the microstructure for a certain
interim time period, which can be predicted by the simulation. Various reaction regimes are
possible: local equilibrium which is a slow reaction, local equilibrium with no partitioning which is
a fast reaction, para-equilibrium which is a regime with no diffusion at all of the substitutional
elements. The transition between the various regimes leads to the development of precipitation
stases.
The Influence of Thermodynamic Properties of Alloys on Effective Interdiffusion Coefficients in Ternary Systems
Authors: Ugaste Ü. , Laas Tony , Škled-Gorbatšova T.
Published: March 2009

To prove the validity of Dayananda’s phenomenological model of interdiffusion in
ternary systems the effective interdiffusion coefficients for a few diffusion couples in the system
Cu-Ni-Fe, annealed at 1000 oC, are calculated on the basis of this model using available tracer
diffusion and thermodynamic data. It is found that the calculated values of effective interdiffusion
coefficients are in reasonable agreement with experimental values extracted independently from
experimental concentration--penetration curves. Using the relationship between effective
interdiffusion coefficients, tracer diffusion coefficients and thermodynamic factors, it is shown that
thermodynamic properties of alloys play a significant role in interdiffusion processes in the system
Cu-Fe-Ni.
Iron-Based Nanocomposite Synthesised by Microwave Plasma Decomposition of Iron Pentacarbonyl
Authors: David B. , Pizúrová N. , Schneeweiss O. , Hoder T. , Kudrle V. , Janča J.
Published: March 2009

A nanocrystalline iron-based powder has been prepared by microwave plasma method:
Fe(CO)5 vapor was introduced into an argon discharge at ~1 kPa. A microwave 2.45 GHz generator
was operated at 430 W. The reaction took place inside a quartz tube passing through a microwave
waveguide. The microwave discharge (without and with Fe(CO)5) was characterized by optical
emission spectroscopy. The synthesized nanopowder was passivated in situ with air. The asprepared
nanopowder was characterized by TEM, XRD, Raman and Mössbauer spectroscopies. The
nanopowder included α-Fe, α-Fe2O3, and Fe3O4 phases. The core-shell nanoparticles were observed
under TEM: α-Fe cores had shells formed of Fe3O4 or carbon. The mean crystallite size of α-Fe was
36 nm (Scherrer formula). The synthesized nanopowder exhibited ferromagnetic behavior.
Surface Diffusion and Island Growth
Authors: Reitinger Rüdiger , Pfau B. , Stadler L.M. , Stankov S. , Zajac M. , Spiridis N. , Sepiol B. , Zontone F. , Korecki J.
Published: March 2009

Grazing-Incidence Small Angle X-ray Scattering (GISAXS) and X-Ray Photon
Correlation Spectroscopy (XPCS) studies of island growth in two different systems are presented:
5 ML of iron on MgO(001) and 10 ML of iron on Au(001). Due to a missing conducting surface
Fe/MgO thinner than approximately 20 ML could not be studied previously by common methods
like STM. Fe/Au(001) is interesting as atoms of gold diffuse easily through iron layers and form
precipitates. The coarsening dynamics of these precipitates is investigated by XPCS in GISAXS
geometry. Their growth depends on the crystallographic directions of the substrate and correlates
with the morphology measured by STM microscopy. Measurements were performed at the ESRF in
Grenoble.
Interfacial Interaction and Diffusion in Binary Systems
Authors: Dybkov Vasil I.
Published: March 2009

A physico-chemical consideration of the interfacial interaction and diffusion resulting in
the formation of chemical compound layers at the interface of initial substances A and B is
presented. The layer-growth kinetics is shown to be much more complicated than it follows from
conventional diffusional views neglecting interfacial reactions. In the majority of multiphase binary
systems, layer occurrence appears to be sequential rather than simultaneous. Under conditions of
diffusion control, the number of simultaneously growing compound layers at the A–B interface
cannot exceed two. Multiple layers (three and more) can only form as a result of secondary
processes connected with the rupture of a diffusion couple. In such cases, great care is necessary
when calculating diffusion coefficients to avoid obtaining their physically meaningless values.
Mechanism and Kinetics of Plasma Nitriding of the Nb-Alloyed PM Tool Steel
Authors: Novák Pavel , Vojtech Dalibor , Šerák Jan , Novák Michal , Bártová Barbora
Published: March 2009

The aim of this work was to describe the mechanism and kinetics of plasma nitriding of a
Nb-containing PM (powder metallurgy) tool steel. Material containing 2.5 wt.% C, 3.3% Si, 6.2%
Cr, 2.2% Mo, 2.6% V, 2.6% Nb and 1.0% W was prepared by nitrogen melt atomization and hot
isostatic pressing. Heat-treated steel (quenching from 1100 °C, triple tempering at 550 °C for 1h)
was plasma nitrided at temperatures ranging from 470 °C to 530 °C / 30 - 180 min. Light
microscopy, TEM, SEM and WDS were used to study the nitrided steel. It has been shown, that
nitriding at 470°C leads to the formation of thin layers composed only of a diffusion zone
containing nitrogen-rich martensite and fine nitride precipitates, no layer of nitrides is formed on
the surface. Nitriding is probably controlled by the nitrogen diffusion in martensite to the material
or by the processes in the nitriding atmosphere at this temperature. Nitriding at the temperature of
500°C and more leads to the formation of a continuous layer of nitrides and carbonitrides on the
surface that limits further nitrogen diffusion. Niobium, as a prospective element in tool steels, was
not found to play a role in the formation of the nitrided layer directly. Niobium replaces vanadium
in very thermodynamically stable primary MC carbides. This results in higher vanadium content in
others less stable carbides and in the matrix. Due to this effect, higher portion of vanadium can
precipitate as VC carbides and VN nitrides during heat treatment and nitriding, respectively.
Stress and Intermixing in Epitaxial Ni(111)/Mo(110) Superlattices
Authors: Abadias Gregory , Debelle Aurelien , Michel Anny , Jaouen Christiane
Published: March 2009

The stress state and intermixing in epitaxial Ni/Mo multilayers grown on (11 2 0)
sapphire substrates are investigated using X-ray Diffraction (XRD). Two deposition techniques
were used, namely ion beam sputtering (IBS) and magnetron sputtering (MS), to vary the energy of
the deposited species. In both cases, high-quality superlattices with a Nishiyama-Wasserman
epitaxial relationship Ni [110] (111) // Mo [001] (110) were obtained. The residual stress state
appears rather complex, resulting from two contributions: a growth-stress whose magnitude and
sign depend on growth conditions and coherency stresses of opposite signs in the two elemental
sublayers (tensile for Ni and compressive for Mo). Post-growth ion irradiation at low fluences was
used to induce structural changes in a controlled way. For the case of IBS, it resulted in partial
stress relaxation, as the growth stress could be almost fully relaxed, while the coherency stresses
remained unchanged. For the case of MS, a distinct behavior was found: a stress increase of the
tensile component of Mo-sublayers was observed, while a stress reduction of the compressive
component was noticed. We attribute this phenomenon to ion irradiation induced intermixing. For
the Ni sublayers, this intermixing leads to a stress relaxation. The modeling of the stress evolution
during ion irradiation was performed using a triaxial stress analysis which enabled us to determine
the ‘stress-free and defect-free lattice parameter’, solely linked to chemical effect.
Study of Diffusion and Reaction Diffusion in the Fe-C-Nb System
Authors: Pérez Rodolfo A. , Gas Patrick , Maugis Philippe
Published: March 2009

Experiments of niobium diffusion at infinite dilution and Nb reaction-diffusion in pure
iron and in ferrites with different amounts of carbon were performed, for comparison, in order to
understand the influence of carbon on the diffusion process in the Nb-Fe system. A proportional
decrease of the diffusion coefficient with the increasing amount of carbon was found. This effect
seems to be stronger than in the self-diffusion analyzing the literature; moreover SIMS
measurements in niobium- implanted samples show a redistribution of carbon during the first steps
of the diffusion process. For those reasons, a stronger effect of carbon-niobium interaction over the
carbon-vacancy interaction seems to be responsible for the decrease in the diffusion coefficient.
On the Local Equilibrium during Dissolution of a Thin Film
Authors: Erdélyi Z. , Taranovskyy A. , Beke Dezső L.
Published: March 2009

Thirty years ago, Lagües and Domange [1] studied surface segregation kinetics and
proposed a method by which it is possible to determine the equilibrium surface segregation
isotherm from one measurement, supposing that the local equilibrium hypothesis (LEH) is obeyed.
This method has been using widely in the literature (e.g. [2-4]) since its born. It was used e.g. to
study of dissolution of thin films into different substrates. In this case additionally it was assumed
that the kinetics can be described by the classical Fick I equation (hybrid method). In this paper,
using computer simulations, we investigate that under which conditions the LEH is obeyed during
the dissolution of a thin film. Moreover, we show that even when the LEH is fulfilled the proposed
‘hybrid’ method cannot be always applied. We make also some considerations on the effect of
stress fields developed by the redistribution of the solute elements during the segregation kinetics.