bluuebunny/crossref_metadata_2025 huggingface dataset:
Atomic Migration as a Mechanism of Superstructure Formation in Intermetallic Compounds
Authors: Abdank-Kozubski Rafał Leszek , Kozłowski Mirosław , Czekaj S. , Pierron-Bohnes Veronique , Pfeiler Wolfgang
Published: March 2009

“Order-order” relaxations driven by atomic migration in superstructures proceed in nonsteady- state of a system, which relaxes to the equilibrium atomic configuration. Hence, the corresponding studies are complementary to standard steady-state diffusion investigations. Two time scales operating in “order-order” relaxations in L12-ordered (Ni3Al) and L10-ordered (FePd, FePt) binary intermetallics were experimentally observed. On the other hand, in B2-ordered
NiAl – known of a giant vacancy concentration, “order-order” relaxations appeared surprisingly slow. Definite relationships between the activation energies for diffusion ( ) D A E and “order-order” relaxations ( ) O O A E − were revealed: ( ) D A E < ( ) O O A E − in L12-type superstructure; ( ) D A E ³ ( ) O O A E − in L10- and in B2-type superstructures. Corresponding simulation studies elucidated the specific atomistic mechanism of the processes. It has been shown that different time scales active in “order-order” relaxations in L12 and L10-ordered systems follow from specific atomic-jump correlations, which result from non-steady-state conditions and particular superlattice geometries: the availability of easy diffusion channels. A model of “order-order” kinetics in NiAl as controlled by a triple-defect mechanism is proposed.
Diffusion-Controlled Liquid Bismuth Induced Intergranular Embrittlement of Copper
Authors: Laporte V. , Wolski Krzysztof , Berger Pascal , Terlain A. , Santarini Gerard
Published: March 2009

The consequences of the contact between liquid bismuth and a copper bicrystal are
investigated at 500°C. Atoms of bismuth are shown to penetrate and embritlle the copper grain boundary. Grain boundary concentration profiles of bismuth are obtained on fracture surfaces by both Auger electron spectroscopy and He4+ Rutherford backscattering spectroscopy. The maximum bismuth intergranular concentration is calculated from experimental data to be about 1.7 monolayers (near the liquid bismuth / solid copper interface). The overall profiles are significantly different from typical erfc profiles and an interpretation is proposed, based on the coupling effect between grain boundary diffusion and non-linear segregation. These results allow us to conclude on the absence of grain boundary wetting for the Cu / Bi system at 500°C.
Diffusion of Silver in Silicate Glass and Clustering in Hydrogen Atmosphere
Authors: Kaganovsky Yuri S. , Mogilko E. , Ofir A. , Lipovskii A.A. , Rosenbluh M.
Published: March 2009

Annealing in a hydrogen atmosphere of silicate glass plates doped by Ag+ ions
leads to the reduction of silver to a metallic state (Ag0) and to the formation of silver nanoclusters. The kinetics of clustering during hydrogen diffusion into the glass and diffusion of Ag0 atoms in the glass matrix have been studied in a temperature ranging from 160 to 200oC by SEM, AFM and optical spectrometry. The absorption spectra have a peak near 410 nm corresponding to the surface
plasmon resonance in Ag clusters. The position of the peak moves as the clusters grow. A theoretical analysis of the absorption spectra allowed us to estimate the cluster size as a function of time, as well as the thickness of the layer filled by clusters, which also changes with time. From AFM data we could measure the kinetics of cluster growth on the surface. We have theoretically analyzed the kinetics of cluster growth during reactive hydrogen diffusion, the kinetics of bulk
cluster growth, surface cluster growth, and thickening of the layer filled by clusters.
Phase Formation under Pulse Loading
Authors: Gertzricken D.S. , Mazanko V.F. , Zaporozhets T.V. , Gusak Andriy
Published: March 2009

Pulse loading of diffusion couples leads to the formation of the broad metastable solid
solutions. Under higher temperatures, combined with high deformation rates, intermetallics also can form. Possible mechanisms of this phenomenon are discussed. Formation of nanostructure under uniaxial compression/decompression (observed in MD simulations) seems to be one of the possibilities.
Atomistic Monte Carlo Simulations of Homogeneous and Heterogeneous Precipitation on Grain Boundaries of NbC in Steels
Authors: Hin Céline , Soisson Frederic , Maugis Philippe
Published: March 2009

The precipitation of niobium carbides in industrial steels is commonly used to control
the recrystallization process or the amount of interstitial atoms in solid solution. It is then important to understand the precipitation kinetics and especially the competition between homogeneous and heterogeneous precipitation, since both of them have been observed experimentally, depending on the alloy composition, microstructure and thermal treatments. We propose Monte Carlo simulations of NbC precipitation in α-iron, based on a simple atomic description of the main parameters which control the kinetic pathway : - realistic diffusion properties, with a rapid diffusion of C atoms by interstitial jumps and a slower diffusion of Fe and Nb atoms by vacancy jumps
- a simple model of grain boundaries which reproduces the equilibrium segregation
properties of Nb and C - a point defect source which drives the vacancy concentration towards its equilibrium value. Depending on the precipitation conditions, MC simulations predict different kinetic behaviours, including homogeneous and heterogeneous NbC precipitation, early segregation of C atoms and its importance as a first stage for NbC precipitation, wetting phenomena on grain boundaries and transient precipitation of metastable carbides.
Role of Diffusion in Superplasticity and Brittleness of Fine-Grained Binary Eutectics
Authors: Muktepavela Faina , Zaporina N.
Published: March 2009

Mechanical properties of interphase boundaries (IB), stability of defects and
microstructure in heavily deformed binary eutectics (Al-Sn, Zn-Sn, Pb-Sn, Cd-Sn, Bi-Sn) have been investigated at room temperature. Experiments were carried out on atomically clean surfaces of alloys and on bimetallic joints with clean interface. It has been shown that after severe deformation the phases are strengthened and relaxation processes occur mainly on the boundaries in all eutectics. For superplastic eutectics with low interphase boundary energy the intensive development of the diffusion – controlled processes of self- healing, sintering, segregation and enveloping were observed. These diffusion processes, directed to restoration of a contact, are the reason of softening of interphase boundaries and superplastic viscous flow. It has been shown that for the eutectics with high IB energy (Al−Sn, Zn−Sn) the interphase boundary sliding leads to the formation of narrow IB cracks with sharp angles. Diffusion healing of micropores and cracks on these IB does not develop at room temperature and deformation defects are stable. Such deformed structure of IB defines low temperature brittleness of Zn-Sn, Al-Sn
eutectics and hydrogen brittleness of Al-Sn.
Ageing Kinetics of Al.-4.7 % Cu Alloy. Dilatometric and DTA Studies
Authors: Wierszyłłowski Ignacy , Wieczorek Sebastian
Published: March 2009

Studies of transformation kinetics during ageing of Al-4.7 % Cu were performed
with use of dilatometric and DTA methods. The dilatometric method was used for studies of isothermal ageing, DTA for studies of ageing during isochronal heating. In order to determine isothermal transformation kinetics the JMA (Johnson – Mehl – Avrami) equation was applied, for isochronal heating transformation kinetics Kissinger method was used. Ageing of Al- Cu alloys consist of precipitation processes and dissolution processes that overlap each other. These processes, during isothermal ageing were distinguished with help of the time exponent n of JMA equation that is very sensitive to change of the transformation mechanism. During isochronal ageing, precipitation processes produce heat, dissolution processes
consume heat. That helps to distinguish them. Results obtained during isothermal studies were in agreement with isochronal heating studies. Activation energies for precipitation processes 324-530 K temperature range varied from about 50 kJ/mol to about 100 kJ/mole and complied with the values obtained before. For precipitation processes at 650- 735 K temperature range, activation energies varied from 226 to 300 kJ/mole. The results obtained were discussed with literature data.
Reaction Diffusion in Mo-Si System above the Melting Point of Silicon
Authors: Galstyan Gegham S. , Chatilyan Hakob A. , Kirakosyan Artavazd G. , Kharatyan Suren L. , Mukasyan Alexander S. , Varma Arvind
Published: March 2009

The results of direct kinetic measurements and SEM observations on formation of silicide phases in Mo-Si system at temperatures 1400-1700о
С are presented in the work. It was shown, that the formation of MoSi2 proceeds by two different mechanisms and accordingly, two types of microstructures are formed: (i) a compact layer (usually with expressed columnar structure) by the
reaction diffusion mechanism; and (ii) separated fine grains by crystallization in the volume of saturated Me-Si melt. A model of product formation is offered which allows to calculate the relative contributions of the two mechanisms of disilicide phase formation at various stages of interaction and to estimate the role each of them in the total process.
Annealing of Fe-15at.%Cr Alloy in N2-H2 Gas Mixtures: Effect of Hydrogen
Authors: Park Eungyeul , Hüning Boris , Grabke Hans Jürgen , Spiegel Michael
Published: March 2009

The effect of hydrogen during annealing of Fe-15.at%Cr alloy on the diffusion profile was investigated concerning the enrichment of chromium and the selective oxidation. Samples were exposed to an annealing gas mixture with different hydrogen contents in an infrared heating furnace and heated to 800oC, kept for 60 seconds and then cooled down to room temperature. After the experiments, field emission scanning electron microscopy (FE-SEM) equipped with electron back-scattering diffraction (EBSD) and x-ray photoelectron spectroscopy (XPS) were employed to characterize the morphology, elemental depth profiles and the chemical states of the elements. The annealing increased the Cr content at the surface in all atmospheres. The increase of hydrogen content in the atmosphere further increased the Cr to Fe ratio in near-surface, and the thickness of the layer
affected by the heat treatment. The selective oxidation of chromium occurred as internal Cr2O3 formation, as a function of the Cr content, rather than the oxygen partial pressure. Hydrogen facilitated the diffusion of chromium probably by cleaning of fast diffusion paths.
Modelling of Oxidation of Fe-Ni-Cr Alloys
Authors: Danielewski Marek , Filipek Robert , Pawełkiewicz M. , Klassek Dominika , Kurzydlowski Krzysztof Jan
Published: March 2009

Mathematical model of selective and competitive oxidation of multi-component non
ideal alloys is used for modelling oxidation of Fe-Cr-Ni alloys. The model is based on: a) the Danielewski-Holly model of interdiffusion, b) the Wagner model of the Ni-Pt alloy oxidation, c) the postulate that the values of fluxes in reacting alloy are limited (the kinetic constraint) and d) the thermodynamics of the Fe-Ni-Cr system. In this paper for the first time modelling of oxidation of a ternary non-ideal alloy based on Danielewski-Holly model is presented. The model is used to predict the evolution of component distributions in the reacting ternary Fe-Cr-Ni alloy. The results of the modelling of oxidation of the 316L stainless steel at 1173 K are presented. We compute the chromium depletion during the long term oxidation. The results allows to conclude that the oxidation reaction is limited by interdiffusion in reacting alloy. The computations demonstrate that the chromium depletion is the key factor affecting the scale stability during the long time exposition.
Prediction of the Depletion Zone due to Selective Oxidation of P91 Steel
Authors: Danielewski Marek , Filipek Robert , Kucharska Barbara
Published: March 2009

Experimental measurements do not allow for a unique determination of the concentration profiles, e.g., in case of multi-layer systems. The measured concentration of the elements at the alloy/scale interface is an average concentration in an alloy and in a scale near the spot of the beam [1]. The knowledge of the concentration of the elements at the boundary is necessary for the
understanding corrosion of alloys. This essential obstacle of experimental techniques can be overcome by computer modelling. Namely, by combining the different methods (non-unique measurement with unique modelling). The Danielewski-Holly model of interdiffusion has a unique solution. This model enables to predict the evolution of component distributions in the reacting alloy. The model is valid for time dependent boundary conditions and consequently can be used for
modelling the more complex reactions, eg., the formation of complex oxides. To avoid the nonphysical values of fluxes in reacting alloy the kinetic constraint on all fluxes was introduced, i.e., the flux limitation method. The results of the selective oxidation of the P91 steel (0,1 wt.% C, 8,6 wt.% Cr, 0,25 wt.% Ni) are presented. Calculated concentration profiles are compared with the experimental data. We
show the evolution of chromium distribution in oxidizing steel up to 3 000 hours. The computations demonstrate that chromium depletion is the key factor determining the scale composition.
Investigation of the Scale Growth Mechanism on FeCrAl Thin Foil in SO2 Using Tracer Method
Authors: Żurek Zbigniew , Jedlinski Jerzy , Gilewicz-Wolter Jolanta , Homa Martah , Bernasik Andrzej
Published: March 2009

The results of the study of the scale growth mechanism on the 50 µm thick foil of
Fe18Cr5Al are reported. The experiments were carried out at 1093 K using a two-stage-oxidation approach. In the first stage, the samples were exposed to the SO2 + 1 vol. % O2 mixture for 1.5 h and 24 h in order to produce the primary scale. Subsequently, the samples were cooled down to the room temperature and moved to the furnace where they were exposed to the atmosphere rich in 18O2. The duration of the second stage was 0.5 h and 4.5 h for samples previously oxidized for 1.5 h, 8 h and 72 h, for the samples oxidized previously for 24 h. The elemental distributions were determined using high resolution SIMS, while the scale
morphology was observed by means of SEM. In addition the radioisotopic studies using 35SO2 were carried out in order to assess whether sulfide phases developed at the initial stage of oxidation. All the results were interpreted in terms of the transport processes in the oxide scale.
Comparison of Two Methods of Calculation of Activation Energy for some Chosen Industrial Steels after its Oxidation at High-Temperatures in Air
Authors: Adamaszek Krzysztof , Jurasz Zbigniew
Published: March 2009

In this work it will be presented the results of calculation of energy activation Q
of selected industrial steels (e.g. grade 55 - carbon steel, LH15 – bearing steel, H10S2M, 4H14N14W2M and 50H21G9N4 valve steels) according to Polish Norm by two methods. In the first method the calculations of Q are based on the dependence of value of parabolic growth rate constants kp in function of reciprocal temperature. The second method is based on the calculated parameters, which allow to determine the value of Q for examined steels by using value of Q for pure iron, taken from literature data, and the particular values of mass concentrations of elements in oxidised steels. The growth kinetics of layers were almost according to parabolic law. The values of parabolic rate constant kp were calculated on the basis of measurements of thickness of oxide layers. To the experiment the cylindrical specimens were used. The isothermal process of oxidation was conducted in chamber furnace at 1100, 1060, 1020, 980 and 940°C in the air. Time of oxidation
various from 3 till 1303.5 hrs. The comparison of obtained results of activation energy Q for mentioned methods of each individual examined steels gives a good agreement.
Germanium in Czochralski Silicon
Authors: Yang De Ren , Chen Jiahe
Published: March 2009

The behaviors of isovalent impurities doped in Czochralski (CZ) silicon crystal have attracted considerable attention in recent years. In this article, a review concerning recent processes in the study about germanium in CZ silicon is presented. The disturbance of silicon crystal lattice in and the influence on the mechanical strength due to germanium doping is described. Oxygen related donors, oxygen precipitation and voids defects in germanium doped Czochralski (GCZ) silicon has been demonstrated in detail. In addition, the denuded zone formation and the internal gettering technology of GCZ silicon is also discussed.
Synthesis and Characterization of Lithium Ion Conductors, Li3InBr6 and their Substituted Compounds
Authors: Tomita Yasumasa , Matsushita Hideyoshi , Maeda Yasuhisa , Kobayashi Kenkichiro , Yamada Koji
Published: March 2009

Li3-2xMxInBr6 (M=Mg, Ca, Sr and Ba) and Li3In1-xMxBr6 was synthesized, and thier substitution effect was investigated by means of 7Li and 115In NMR, X-ray diffraction and AC conductivity measurements. Phase transition was observed at 314 K in Li3InBr6 and fast Li+ diffusion was observed in the high temperature phase. Li3InBr6 has high Li+ ion conductivity and showed a little difference in X-ray diffraction patterns between the low-temperature phase and the high-temperature phase. These indicate that the sub-lattice for Li+ ions changed largely at the phase transition point and this change makes Li+ diffusion easily. In the high temperature phase of substituted compounds, the conductivity decreased with the amounts of substitution. and defects produced by the substitution with divalent cation did not contribute to the Li+ ion conduction. In the LT phase for Mg compound, the ionic conductivity increases up to x = 0.4 due to the introduction of the extrinsic vacancies.
Review: Stress-Induced Diffusion and Cation Defect Chemistry Studies of Perovskites
Authors: Salama K. , Majkic G. , Balachandran U.(Balu)
Published: March 2009

In this paper we review a number of studies of stress-induced diffusional matter transport in perovskites, with an emphasis on creep studies used as a means of studying defect chemistry on the cation sublattices. Studies of diffusional creep in air or fixed atmospheres are reviewed first, and the common characteristics among these perovskites are identified. Creep studies of several perovskiterelated or perovskite-like structures are reviewed next, and the similarities/dissimilarities to perovskites are outlined. The diffusional creep studies in controlled atmosphere are reviewed next, with the emphasis on defect chemistry modeling from creep data. The paper presents a detailed review of two creep studies in oxygen controlled atmosphere that show particularly interesting and remarkedly different behavior from that predicted by standard defect chemistry models. Defect chemistry modeling from creep data is presented for these two cases. The potential and limitations of using creep experiments for studying diffusional matter transport and cation defect chemistry are discussed.
Analysis of the Effect of the Oxide Ion Vacancy on the Crystal Structure of La1-xCaxCrO3-δ by High-Temperature X-Ray Diffraction under Various Oxygen Partial Pressures
Authors: Ohba Norifumi , Oikawa Eri , Hashimoto Takuya
Published: March 2009

In order to evaluate potential of La1-xCaxCrO3-δ as a material for interconnector of solid oxide fuel cells, reduction expansion was measured by using high temperature X-ray diffraction under various P(O2). Obtained reduction expansion increased with increasing temperature and Ca content. With combination of obtained lattice constants and oxygen nonstoichiometry data, the effect of oxide ion vacancy on crystal lattice and their thermodynamic behavior have been deduced. It was proposed that expansion behavior by δ of La0.9Ca0.1CrO3-δ can be explained assuming ideal solution model on oxide ion vacancies, however, deviation from ideal solution model was observed in reduction expansion behavior of La0.8Ca0.2CrO3-δ and La0.7Ca0.3CrO3-δ with δ region larger than 0.03 and 0.05, respectively. It was revealed that the crystal system approached to cubic with increase of δ in the region where the deviation from ideal solution model was observed.
Determination of Copper Self-Diffusion Coefficients on the Base of High-Temperature Creep Data
Authors: Vaganov Danil V. , Zhevnenko Sergei
Published: March 2009

Indirect method is used for determination of copper self-diffusion coefficient on the base of high-temperature creep data. These data are obtained by the use of the new measuring device and assuming that Nabarro-Herring mechanism acts.
Diffusion of Cr in Nanostructured Fe and Low Carbon Steel Produced by Means of Surface Mechanical Attrition Treatment
Authors: Wang Z.B. , Tao N.R. , Tong W.P. , Lu Jian , Lu K.
Published: March 2009

By means of surface mechanical attrition treatment (SMAT), nanostructured (NS) surface layers were fabricated on a pure iron plate and a low carbon steel plate. Cr diffusion behaviors in the NS Fe phase and the SMAT low carbon steel were investigated. Experimental results showed the activation energy of Cr diffusion in the NS Fe is comparable to that of the GB diffusion, but the pre-exponential factor is much higher. A much thicker Cr-diffusion surface layer was obtained in the SMAT low carbon steel plate than in the coarse-grained one after the same chromizing treatment. The much enhanced diffusivities of Cr in the SMAT samples can be attributed to numerous GBs and triple junctions with a high excess stored energy in the NS surface layer.
Experimental Evidence of Iron Segregation in Copper Grain Boundaries as Deduced from Type B Diffusion Measurements
Authors: Bernardini Jean , Girardeaux Christophe , Rolland Andree
Published: March 2009

Grain-boundary heterodiffusion of iron in pure copper and self diffusion of iron in copper–0.091at% iron were measured by the serial sectioning technique in the Harrison B-regime. The penetration profiles corresponding to iron heterodiffusion in pure copper show a strong positive curvature far beyond the (Dvt)1/2 depth . This peculiar shape, which does not exist for self diffusion in the solid solution, proves the presence of a strong non linear grain-boundary segregation of iron in copper in spite of the respective surface energies of these metals. This segregation is linked to the size effect which is, as predicted by numerical simulation, the main driving force for grainboundary segregation.
Diffusion Parameters Determination by a Non-Destructive Technique with an Assumption of Mass Exchange on the Surface
Authors: Bodnar O.B. , Aristova I.M. , Mazilkin A.A. , Chaika A.N. , Popov P.Yu
Published: March 2009

Theoretical base for non-destructive diffusion parameters determination technique in solids taking into account the dopant flux from the sample surface is presented. Diffusion of the nitrogen implanted in the tungsten single crystals was determined in temperature range 700–820°C. Surface concentration of nitrogen was obtained by Auger electron spectroscopy. Initial distribution of the nitrogen in subsurface region was measured by secondary-ion mass-spectroscopy. Two dopant atom fluxes found in subsurface region of the ion-implanted material are supposed to connect with the radiation damages and with the bulk diffusion mechanism.
On the Grain Boundary Grooving in Thin Filaments
Authors: Klinger Leonid , Rabkin Eugen
Published: March 2009

We considered a polycrystalline cylindrical wire of the initial radius R0 composed of
identical cylindrical grains of the length L0, strained uniaxially by an external stress P. At the temperatures at which some surface and grain boundary diffusion are allowed the thinning of the nanowire in the vicinity of grain boundaries occurs due to the phenomenon of grain boundary grooving. We calculated the equilibrium shapes of the nanowire achieved after long annealing times. Our calculations demonstrated that for any given L0/R0 ratio some critical value of the applied
stress exists above which the nanowire is unstable and breaks down into the string of isolated spherical particles, in full analogy with the Rayleigh instability of long cylinders. The kinetics of the shape change was calculated numerically. It was shown that the rate of thinning of unstable wires diverges as the moment of breakdown is approached. We also demonstrated that the breakdown
may occur even for nominally stable wires “on the way” to achieving their equilibrium shape. Therefore, the stability of nanowire is determined by a combination of geometric (L0/R0), thermodynamic (grain boundary energy), and kinetic (ratio of grain boundary and surface diffusivities) parameters. An application of external tensile stress accelerates the breakdown of nanowires.
Diffusion and Phase Transformations in Steels: a Tool for Experimentation and a Method for Modelling
Authors: Bréchet Yves , Hutchinson Christopher R. , Purdy Gary R. , Zurob Hatem S.
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 of Historical Brass Tongues and Shallots from Baroque Organs
Authors: Baretzky B. , Friesel M. , Petelin A. , Mazilkin A.A. , Straumal Boris B.
Published: March 2009

The composition and microstructure of historic tongues and shallots from reed pipes of various Baroque organs has been studied. They contain Cu-Zn solid solution (α-brass with 23-29 wt. % Zn) and lead particles. Lead is mainly present as spherical bulk or lens-like grain boundary (GB) inclusions. However, in two samples Pb wets the brass GBs. In this case Pb forms the branched root-like structures. 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. The annealing temperature has been estimated using the faceting phase diagram for twin GBs in Cu.
DIGM - Entropy Balance and Free Energy Release Rate
Authors: Lyashenko Yu.A. , Gusak Andriy
Published: March 2009

A model of alloying in the three-layer thin-film system at the low temperature is constructed. Solid solution formation takes place as a result of the diffusion-induced grain boundary migration (DIGM). The unknown parameters are determined from the set of the equations for: (1) grain boundary diffusion along the moving planar phase boundary; (2) the entropy balance in the region of the phase transformation moving with constant velocity; (3) the maximum rate of the free energy release. We consider the model system with complete solubility of the components. The main parameters are self-consistently determined using thermodynamic and kinetic description in the frame of the regular solution model. The model allows determining the concentration distribution along the planar moving phase boundary, its velocity, the thickness of the forming solid solution layer and the limiting average concentration in this layer.
Kinetic Features of Reactive Diffusion in Binary Systems
Authors: Kajihara M.
Published: March 2009

The temperature dependence of the kinetics of the reactive diffusion was numerically
analyzed for a hypothetical binary system composed of one compound phase (β) and two primary solid solution phases (α and γ). The growth rate of the β phase during the reactive diffusion between α and γ phases in a semi-infinite diffusion couple was expressed as a function of the interdiffusion coefficient Dθ and the solubility range of the θ phase ( θ = α, β, γ). For the reactive diffusion controlled by volume diffusion, the thickness l of the β phase is described as a function of
the annealing time t by the parabolic relationship l2 = Kt. The equations K = K0 exp(−QK/RT) and Dθ = D0 θexp(−Qθ/RT) were adopted to express K and Dθ as functions of temperature T, respectively. The relationship between the temperature dependence of K and that of Dθ was evaluated according to the following assumptions: the molar volume, the solubility range and the value of D0
θ are constant and equivalent for all the phases. When Qα or Qγ is smaller than Qβ, QK is greater than Qβ. On the other hand, QK is close to Qβ, if both Qα and Qγ are greater than Qβ. In such a case, the temperature dependence of the kinetics represents that of interdiffusion in the growing compound.
Mathematical Model of Sintering of Powder Solids
Authors: Dmitriev Andrey N. , Bulanov V.I.
Published: March 2009

Reduction and sintering are complicated processes demanding use of mathematical
modelling - consolidation of multicomponent materials. The most representative of them are
products formed during consolidation during sintering of powders. They have common physical and
chemical characteristics both from the viewpoint of initial (multicomponent) materials, and from
the viewpoint of technological parameters. Such processes simultaneously involve both the
reduction and the sintering with simultaneous consolidation of particles into materials. The sintering
of powders of crystals is a flexible and effective way of production of polycrystalline composite
materials with a given structure and properties. In this paper a mathematical model of the process of
sintering suggested by us is considered.
Interstitial Diffusion of Oxygen in Tantalum Obtained by Anelastic Relaxation Measurements
Authors: Florêncio Odila , Barbosa Geovani F. , Silva Paulo Sergio , Ishikawa Tomaz Toshimi , Rodrigues Durval
Published: March 2009

Anelastic relaxation measurements have been used in order to obtain information about
several aspects of the behavior of solutes in metals, for example, matrix-solute interaction,
interstitial diffusion, etc. The diffusion coefficient for interstitial solutes in body centered-cubic
metals is accurately determined by anelastic relaxation measurements. The kind of preferential
occupation of the interstitial solutes in body centered-cubic metals, such as oxygen and nitrogen in
tantalum, is still controversial. Internal friction and frequency measurements as a function of
temperature in tantalum sample were performed using a torsion pendulum operating in a frequency
oscillation in the hertz bandwidth. These results presented the following phenomenon: the intensity
of the internal friction peak decreased between the first run and the other runs. These results were
decomposed, by the successive subtraction method, in elementary Debye peaks, for determination of
characteristic anelastic relaxation parameters (relaxation strength, peak temperature, activation
energy and relaxation time). Interstitial diffusion coefficients for oxygen in tantalum were
determined, for different intensities of internal friction peaks, and when compared with literature,
these results introduced a better adjustment for the tetrahedral preferential occupation sites of
oxygen in tantalum.
Theoretical Model Development for Nanofluids Thermal Effectiveness
Authors: Kanagaraj S. , Varanda F.R. , Oliveira Monica S.A. , Simões J.A.
Published: March 2009

Heat transfer fluids play an important role in many industrial sectors. However, the
low heat transfer characteristics of conventional fluids obstruct the performance enhancement
and the high compactness of heat exchangers. In order to improve thermal characteristics of
the conventional fluids, nanofluids are prepared by adding multi walled carbon nanotubes
(CNTs) with base fluids. Though different experimental studies on nanofluids are available,
theoretical models are also needed to predict its thermal behaviour. This work intends to
address dimensional analysis using the Buckingham Pi theorem to develop an empirical
model for predicting thermal characteristics of nanofluids. The latter will be achieved through
the use of operational variables and physical properties for the identification of detrimental
factors which eventually lead to the thermal enhancement of nanofluids. It can be observed
from this analysis that volume fraction and temperature of the nanofluids are the most
influencing parameters on the nanofluids thermal conductivity. In what concerns heat transfer
coefficient, it is the velocity of the nanofluid that plays a critical role apart from the afore
mentioned two parameters. Therefore it is believed that by controlling these parameters, the
thermal effectiveness of the nanofluids can be established.
Physico-Chemical Analysis of Compound Growth in Binary Interdiffusion Systems
Authors: Kodentsov A.A. , Paul A. , van Loo F.J.J.
Published: March 2009

A diffusion-controlled growth of intermetallic phases and the role of the Kirkendall effect
in morphological evolution of the product phase layers can be described in terms of an alternative
theory considering chemical reactions at the interphase interfaces. Application of this “physicochemical”
treatment to diffusional growth of intermediate phases with fairly wide homogeneity
ranges is illustrated by the example of interaction in the Ag-Zn system. The model is purely
phenomenological, and its use is convenient, since no explicit assumption of the underlying
diffusion mechanism is required.
Structural and Parametric Optimization of an Absorption Refrigeration Machine: Inverse Rectification as Auxiliary Absorption Process
Authors: Morosuk Tatiana
Published: March 2009

This paper discusses how the result of exergetic analysis should be used for improving
efficiency of an absorption refrigeration machine. In the present work the process of inverse
rectification as auxiliary absorption process in an absorption refrigeration machine is analyzed from
the point of view of structural and parametric optimization.
Analysis of Interdiffusion and Intrinsic Diffusion in Multicomponent Alloys to Obtain Information about Diffusion Mechanisms
Authors: Belova Irina V. , Murch Graeme E.
Published: March 2009

In this paper, we present and discuss some of the theoretical procedures that have been
established recently for binary and ternary alloy systems for the purposes of analyzing chemical
diffusion data (interdiffusion and intrinsic diffusion) alone and chemical diffusion data in
combination with tracer diffusion data. Emphasis is put on extracting information about diffusion
mechanisms by way of tracer correlation factors/vacancy-wind factors. Examples are taken from the
intrinsic diffusion, interdiffusion and tracer diffusion data in the Ag-Cd and Ag-Cd-Zn, Fe-Ni-Cr
and Cu-Fe-Ni alloy systems.
Molecular Dynamics Study of Carbon Diffusion in Austenite
Authors: Evteev Alexander V. , Levchenko Elena V. , Belova Irina V. , Murch Graeme E.
Published: March 2009

The mmolecular dynamics method is applied to investigate carbon interstitial diffusion in
austenite at low carbon content. An approximation that carbon atoms can interact with each other only
indirectly (via neighbouring iron atoms) is used. Sets of Arrhenius parameters of interstitial carbon
jump frequencies identified by the four-frequency model are determined. Comparison of the
molecular dynamics results with experimental data analysis in the context of the four-frequency
model is performed. It is shown that the four-frequency model may not be adequate to describe the
carbon diffusion process. To improve the analytical model the specific role of the transition
probabilities during association and dissociation of the first nearest neighbour carbon pairs through
the second neighbour sites should be considered. The direct repulsion between the carbon first
neighbour positions should be also taken into account in molecular dynamics simulation.
Carburizing of Low Carbon Steel with Plasma Electrolysis in Aqueous Solution
Authors: Rezaei Arash , Shokuhfar Ali , Asadi M. , Hosseinzadeh M.M. , Ahmadi Shahram
Published: March 2009

In this study, diffused carbon in workpiece surface with Plasma Electrolysis Carburizing
(PEC) treatment applied to harden SAE 1015 steel is investigated. The workpiece is connected
cathodically to a high current DC power supply that applies high voltage and uses stainless steel as
the anode. After water ionization with this voltage, a hydrogen film forms around the workpiece.
This film acts as a thermal and electrical insulation layer which increases the electric resistance
around the workpiece and makes it being heated. The surface of the workpiece is transformed to
austenite and after the disconnection of the current, the workpiece is quenched in aqueous solution.
By the aid of this method, the workpiece can be hardened to 1200HV or more. In this paper, the
effect of time and solution concentration on the depth of diffused carbon was studied. The hardness
of workpiece was measured and the variation of the diffusion depth versus time and solution
concentration was investigated.
Non-Hydrostatic Pressure Induced Structural Phase Transitions of Silicon Analyzed by Raman Scattering
Authors: Pizani Paulo S. , Jasinevicius Renato G. , Zanatta Ricardo A.
Published: March 2009

In this work a study on the structural phase transitions of silicon undergone by two
different methods were performed. The samples were submitted to high non-hydrostatic pressure
applied by cyclic Vickers indentations and by the tool tip during the single point diamond turning.
The indentations were performed on virgin surface (polished as received) and on an amorphous
surface generated either by the machining process or RF sputtering. The analysis on the machined
surface, debris on the diamond tool and around of imprints were also performed using Raman micro
spectroscopy. The results indicated the formation of some phases may depend upon the initial
structural state of the surface, i.e., amorphous or crystalline.
On the Atomistic Dynamic Modelling of Simultaneous Diffusion of Dopant and Point Defect (B, V, I) in Silicon Material
Authors: Dao Khac An , Tuan Phan Ahn , Dung Vu Ba , Van Truong Nguyen
Published: March 2009

Understanding the atomic movements of simultanous diffusion of dopant (B) and point
defects (V, I) in silicon is of great importance for both experimental and theoretical diffusion
studies. This paper presents the atomistic dynamic diffusion modelling of boron (B), self-interstitial
(I) and vacancy (V) process in silicon based on simultaneous diffusion of boron dopant and point
defects based on a previous developed theory. The simulation is based on the random walk theory
with three main diffusion mechanisms: namely vacancy, interstitial and interstitialcy mechanism.
The migration frequencies of dopant and point defects have been programmed based on the
experimental diffusion data of boron, vacancy and Si self-interstitial. This simulation procedure can
be seen very clearly about the atomic movements, the interactions between dopant and point defects
via three diffusion mechanisms. The diffusion depth of B, V, I in very short time can be estimated
from the simulation picture on the screen. The simulation results reflect the simultaneous diffusion
as well as the interaction of boron and point defects via the three diffusion mechanisms. The point
defects (V, I) were generated during the dopant diffusion and they diffused further into the depth as
shown in the results of the simulation as well as in the previous published experimental findings.
Evaluation of Diffusion Coefficients from Composition Profiles - The Influence of Trapping
Authors: Christiansen Thomas L. , Somers Marcel A.J.
Published: March 2009

The applicability of the Boltzmann-Matano method for evaluation of a diffusion
coefficient and its concentration dependency by line profile analysis is tested on three different
(model) systems. All systems involve interstitial diffusion. It is shown that the occurrence of
trapping corrupts the applicability of the Boltzmann-Matano method.
Microstructural Development of Electrical Steels under Si and Al Diffusion
Authors: Barros José , Houbaert Yvan
Published: March 2009

The effect of Si and Al diffusion from a coating in the microstructure of electrical
steels have been investigated for three different processing routes. In general the final texture
is not affected by the diffusion of Si or Al from the coating whereas the grain size and mor-
phology can be affected if the silicon content of the substrate is low enough to allow phase
transformation. The gamma to alpha phase transformation caused by the diffusion of Si and
Al determines the grain size and morphology resulting in columnar grain growth. The evolu-
tion of the microstructures during the diffusion annealing for the production of high Si steels
shows some common features with the microstructure evolution during the grain growth in
conventional low silicon (Si < 3 wt.%) electrical steels.
Wetting of Stressed Grain Boundaries in Polycrystals and Rheological Behaviour of Resulting Materials
Authors: Traskine Vladimir , Skvortsova Z. , Barrallier Laurent , Volovitch Polina , Pertsov Alexandre
Published: March 2009

Orientational patterns of wetted grain boundaries (GB's) in stressed NaCl polycrystals
have been used for describing the GB penetration process on the basis of combined interfacial and
mechanical energy balance considerations. The response of the internally wetted polycrystals to
static loading has been shown to obey “pressure solution” constitutive laws involving dissolution at
stressed surfaces, diffusive transport of dissolved matter and precipitation at less stressed surfaces.
Direct experimental evidence for pressure solution mechanism is presented.
Effect of Structure on Water Diffusion in Hydrophilic Polymers
Authors: Thominette Francette , Gaudichet-Maurin Emmanuelle , Verdu Jacques
Published: March 2009

The relationships between polymer structure and water diffusivity have been investigated
in four structural series: amine-epoxyde networks (A), aromatic polysulfones (B), styrene
crosslinked polyesters or vinylesters (C) and polyethylenes containing polar groups (D). In each
family, it appears water diffusivity is almost inversely proportional to equilibrium water
concentration. This result indicates that water diffusion is considerably slowed down by its
interactions with polar sites in the polymer.
Process-Induced Diffusion Phenomena in Advanced CMOS Technologies
Authors: Pichler Peter , Burenkov Alexander , Lerch Wilfried , Lorenz Jürgen , Paul Silke , Niess Jürgen , Nényei Zsolt , Gelpey Jeffrey C. , McCoy Steve , Windl Wolfgang , Giles Luis Felipe
Published: March 2009

The continuous scaling of electron devices places strong demands on device design
and simulation. The currently prevailing bulk transistors as well as future designs based on
thin silicon layers all require a tight control of the dopant distribution. For process simulation,
especially the correct prediction of boron diffusion and activation was always a problem. The
paper describes the model developed for boron implanted into crystalline silicon and shows
applications to hot-shield annealing and flash-assisted rapid thermal processing.
Theory of Interdiffusion in Solids
Authors: Chen Y.C.
Published: March 2009

Traditional theories of interdiffusion in solids based on Fick’s first and second laws and
Darken’s equations can not describe the relationship between the diffusion fluxes and the
diffusion-induced stresses, because the subject matter of the traditional theories is the diffusing
atom or atomic flux, not the volume unit within the interdiffusion field. For this reason, it is
suggested that the concept of flow point in the interdiffusion field should be constructed to describe
the diffusion-induced stresses and the phase growth.
Oxygen and Silicon Self-Diffusion in Quartz and Silica: The Contribution of First Principles Calculations
Authors: Roma Guido , Limoge Yves , Martin-Samos Layla
Published: March 2009

Despite its importance as a material in many domains, SiO2 is still a very badly known material from the point of view of materials science. Experimentally the silicon and oxygen diffusion has been determined in silica as well as in quartz, but several discrepancies arise between different authors. From a theoretical point of view the various possible atomic defects have mostly been studied in an electronic perspective, so even the simplest ones remained quite poorly known till recently, the silicon related ones remaining completely unknown. The great similarity between silica and quartz properties is in favour of a common model. The determination of the precise formation and migration energies of the various defects is then of paramount importance for the understanding of the kinetic properties of SiO2. We will present in this paper the results of a study of the formation and mobility properties of oxygen and silicon defects in the view of determining the self-diffusion mechanism(s). Our work relies on up to date ab-initio methods: total energy calculations in a DFT-LDA approach, using either plane wave or pseudo-atomic basis for the wave functions and pseudopotentials.We shall discuss the role of the various parameters controlling the kinetic behaviour: chemical potential of the species, nature of the main impurities, cristallinity, and preparation mode of the sample.
Oxygen Self-Diffusion in Silicon Dioxide: Effect of the Si/SiO2 Interface
Authors: Uematsu Masashi , Gunji Marika , Itoh Kohei M.
Published: March 2009

The effect of the SiO2/Si interface on oxygen self-diffusion in SiO2 during thermal
oxidation was investigated using oxygen isotopes. A Si18O2 layer was first grown in 18O2 and then the
sample was reoxidized in 16O2 at 900 ~ 1100 °C. The O diffusion in SiO2 during the 16O2 oxidation
was investigated by secondary ion mass spectrometry (SIMS) measurements. Near the SiO2/Si
interface, a significant broadening of the 18O profile toward the newly grown Si16O2 was observed.
This 18O diffusion became slower with oxidation time and hence with increasing distance between
18O diffusion region and the interface. This distance-dependent 18O self-diffusion was simulated
taking into account the effect of SiO generated at the interface upon oxidation and diffusing into SiO2
to enhance O self-diffusion. The simulation fits the SIMS profiles and shows that the SiO diffusion is
greatly retarded by the oxidation with O2 from the oxygen-containing atmosphere and that the O
self-diffusion therefore becomes distance-dependent. In addition, near the SiO2 surface, 16O diffusion
profiles develop with the 16O2 oxidation time from the surface into the initially grown Si18O2. The
integrated surface 16O concentration increases with oxidation time and the SiO from the interface
affects the O self-diffusion near the surface as well.
Mass Transport Modelling in Porous Media Using Delay Differential Equations
Authors: Martins António , Laranjeira Paulo , Dias Madalena , Lopes José Carlos
Published: March 2009

In this work the application of delay differential equations to the modelling of mass
transport in porous media, where the convective transport of mass, is presented and discussed. The
differences and advantages when compared with the Dispersion Model are highlighted. Using
simplified models of the local structure of a porous media, in particular a network model made up
by combining two different types of network elements, channels and chambers, the mass transport
under transient conditions is described and related to the local geometrical characteristics. The delay
differential equations system that describe the flow, arise from the combination of the mass balance
equations for both the network elements, and after taking into account their flow characteristics. The
solution is obtained using a time marching method, and the results show that the model is capable of
describing the qualitative behaviour observed experimentally, allowing the analysis of the influence
of the local geometrical and flow field characteristics on the mass transport.