bluuebunny/crossref_metadata_2025 huggingface dataset:
Orthogonal Experiment Study on the Hydrogen Desorption Properties of NaAlH4 and LiAlH4
Authors: van Ek J. , Lodder A.
Published: March 2009

Orthogonal experiment design and variance analysis were adopted to investigate the hydrogen desorption properties of NaAlH4and LiAlH4, which consisted of three stages, ball-milled under argon. Optimum milling condition was very important for the performance of NaAlH4and LiAlH4, which was obtained from the orthogonal experiments. The orthogonal experiment design considered three experimental factors, i.e. weight ratio of ball to power, weight ratio of ɸ8 ball to ɸ4 ball and milling time, which varied on three different levels, respectively. According to the range analysis and variance analysis from the orthogonal experiments, the weight ratio of ball to powder and ɸ8 ball to ɸ4 ball had more impacts on the hydrogen desorption time of NaAlH4,while the most sensitive influencing factor of LiAlH4was milling time. NaAlH4had the optimum performance when the weight ratio of ball to power was 30:1, the weight ratio of ɸ8 ball to ɸ4 ball was 0.5:1 and milling time was 0.5h. LiAlH4had the optimum performance when the weight ratio of ball to power was 40:1, the weight ratio of ɸ8 ball to ɸ4 ball was 0.5:1 and milling time was 2h.
Anisotropy of Strain Relaxation in III-V Semiconductor Heterostructures
Authors: Yastrubchak O. , Wosiński T. , Domagała J.Z. , Łusakowska E.
Published: March 2009

Partially relaxed III–V heterostructures: GaAs/InGaAs and InP/InAlAs/InGaAs, with a small lattice mismatch, grown using molecular beam epitaxy under compressive or tensile misfit stress at the (001) interface, have been investigated by means of high-resolution X-ray diffractometry, atomic force microscopy and generalized ellipsometry. Additionally, transmission electron microscopy and electron-beam induced current in a scanning electron microscope have been employed to reveal misfit dislocations at the heterostructure interface. Chemical etching was used to determine polarity of the crystals and threading dislocation densities in the epitaxial layers. Our findings are interpreted in terms of the dependent on growth conditions, material’s composition and doping glide velocities of two types of misfit dislocations: α and β, differing in their core structure and lying along two orthogonal 〈110〉 crystallographic directions at the (001) interface.
The "C" Factor in LeClaire's Theory of Solute Impurity Diffusion
Authors: Cahoon J.R.
Published: March 2009

The "C" factor for the calculation of the relative activation energy for solute impurity
diffusion using LeClaire's theory as modified by Burachynsky and Cahoon has been determined for the diffusion of several solutes in FCC Cu , FCC Fe and BCC Fe. Inclusion of the "C" factor results in good agreement between the calculated and experimental values of relative activation energy for impurity diffusion inn the solvents considered. For positive values of relative valence, Z, the value of C is given by C » 20 Z. For negative values of Z, C » 0.
p+-CdB2 - n-CdF2 and p+-Si - p-CdB2 - n-CdF2 Diffusion Heterostructures
Authors: Bagraev Nikolai T. , Klyachkin L.E. , Malyarenko A.M. , Shcheulin A.S. , Ryskin Alexandr I.
Published: March 2009

The ionic semiconductor CdF2 that is of extraordinary interest for the modern optics and optoelectronics because of the largest band-gap value, 7.8 eV, from all wide-gap semiconductors and of the n-type conductivity caused by doping with the III group elements and subsequent thermal colouring is used to prepare the ultra-shallow p+- n junctions and p+-Si - n-CdF2 heterostructures by the short-time diffusion of boron from the gas phase. The forward branches of the I-V characteristics of the quantum-size p+-n junctions and heterostructures are shown to reveal not only the CdF2 gap value, but also the CdF2 valence band structure as well thereby identifying the ballistic character of the transport of holes. The studies of the I-V characteristics under the voltage applied along the p+-n junction plane demonstrate the metal conductivity of the two-dimensional hole gas, which seems to be evidence of the formation of the p-CdB2 compounds on the n-CdF2 surface in the
process of doping with boron.
In Situ TEM Investigation of Diffusion of Nano-Scale Liquid Pb Inclusions on Dislocations and in Bulk Aluminum
Authors: Prokofjev S.I. , Zhilin V.M. , Johnson Erik , Levinsen M. , Dahmen U.
Published: March 2009

Diffusion of nano-sized liquid Pb inclusions in thin aluminum foils is investigated using
in-situ transmission electron microscopy (TEM). Free diffusion of the inclusions in the bulk and diffusion constrained by dislocations trapping is studied. The motion of trapped Pb inclusions is spatially confined in close proximity to the dislocations. The diffusion coefficients of free motion of the inclusions are determined using Einstein's equation. The diffusion coefficients of trapped inclusions were obtained using an equation based on Smoluchowski's analysis of the Brownian motion of particle in a harmonic potential. The agreement of the diffusion coefficients of free and trapped inclusions indicates the same underlying microscopic mechanism, and no strong influence from dislocations. The microscopic mechanism controlling the mobility is discussed.
Nitrogen-Induced Formation of Nano-Structured Precipitations in the Ti-W-C-N System
Authors: Eder Alexander , Königshofer Rudolf , Lengauer Walter
Published: March 2009

A general trend in the field of hardmetals is to achieve a refinement of the microstructures, usually by using sub-micron powders as raw materials. In this study, an alternative route to produce fine structures within the fcc hard phase (W,Ti)(C,N) is investigated: nitrogen indiffusion into (W,Ti)C leads to precipitation of tungsten-rich phases. The mechanism of precipitation (lamella- and labyrinth-like structures with a size of 100-400nm) is thought do be discontinuous segregation on the one hand and spinodal decomposition on the other hand. Hot-pressed (W,Ti)(C,N) samples of different compositions were annealed at different temperatures and C activities in high-pressure N2 atmosphere. The composition and resulting structures of the precipitates were correlated with composition of the (W,Ti)(C,N) phase as well as with annealing conditions. An outlook of a possible application of the observed phenomena to powder particles is given to achieve micron-sized particles of this hard phase with nanometer-sized structures as a raw material for fine-grained hardmetals.
Modeling of Phase Competition and Diffusion Zone Morphology Evolution at Initial Stages of Reaction Diffusion
Authors: Pasichnyy Mykola , Gusak Andriy
Published: March 2009

The initial stages of reactive diffusion have been studied by Monte-Carlo simulations.
New MC-scheme describing the competition of two ordered intermediate phases is proposed. Main peculiarity of presented MC-model is a strong dependence of interatomic interaction energies on the local atomic surrounding, enabling us to distinguish new phases more distinctly.
Diffusion Measurements in Chromium-Manganese Steels by Means of Multiple Radiotracer Test
Authors: Dudała Joanna , Gilewicz-Wolter Jolanta , Stęgowski Zdzisław
Published: March 2009

The paper presents the application of multitracer method of diffusion measurement in
Cr-Mn steels. Two austenitic steels were investigated: Cr13Mn18SiCa and Cr17Mn17 as well as austenitic-ferritic one: Cr15Mn19. The serial sectioning technique was used for simultaneous evaluation of diffusion coefficients of radioisotopes of chromium 51Cr, manganese 54Mn and iron 59Fe at 1073K and 1173 K. Diffusion coefficients of radiotracers at 1173 K were calculated on the
basis of both: activity of removed layer (differential method) and residual activity of the sample (integral method). The evaluated diffusion coefficients of metals in austenitic steels are higher than those in austenitic-ferritic one; their values are about 10-12 ÷ 10-11 cm2s-1. Moreover it was found that at 1173 K the diffusion rate of manganese is higher than that for iron and chromium while at 1073 K diffusion rates of chromium and manganese are comparable and higher than that for iron.
Furthermore the experimental results point out that at 1173 K the volume diffusion is the dominant mechanism of metals’ transport while at 1073 K the high diffusivity paths diffusion prevails.
Phase Transformations during the Heating of Fe-Si-B Amorphous Alloys
Authors: Hryhoryeva O. , Belous M. , Sidorenko Sergey I.
Published: March 2009

Phase transformations during the heating of amorphous Fe-Si-B alloys were investigated. The differential thermomagnetic analysis and X-ray method are used for the studies. The intervals of phase transformations are revealed, and the magnetic properties of phases are determined. The method of calculation of magnetic effects during the phase transformations, registered by differential technique is suggested.
Interaction of Phase Transformation and Deformation Process during Hot Deformation of 0.16%C Steel
Authors: Błaż Ludwik , Nowotnik Andrzej , Siwecki Tadeusz
Published: March 2009

The effect of hot deformation process on the structure within the temperature range corresponding to the g→a+P transformation was tested for commercial carbon steel containing of 0.158% C. Hot compression tests were performed at computer controlled constant cooling rate. Before testing CCT diagrams were carefully determined in order to fit hot deformation conditions to the g→a+P phase
transformation range. The material microstructure was examined by means of optical and electron transmission microscopy. It was found that ferrite, pearlite or bainite were typical microstructural components observed at hot deformed samples. Localized distribution of pearlite or bainite that resulted from flow localization was observed rarely. Precipitation of carbides on ferrite grain boundaries is the most typical microstructural effect of the hot deformation/precipitation interaction that was noted for the most of hot deformed samples.
Calculating of Diffusion Paths in Ternary Systems Using Effective Interdiffusion Coefficients of Components
Authors: Priimets J. , Ainsaar A. , Ugaste Ü.
Published: March 2009

The peculiarities of practical application of effective interdiffusion coefficients of
components for calculating diffusion paths in ternary systems are analysed. It is shown that infinite values of the interdiffusion coefficients at zero concentration gradient’s points do not remarkably affect the accuracy of calculation in the case of a correct choice of variables. At zero-flux planes where the respective effective interdiffusion coefficient is equal to zero, no calculation problems arise, as evidently zero-flux planes can occur simultaneously only for one of the components. The
results of calculation of diffusion paths for diffusion couples in the ternary systems Cu-Fe-Ni and Co-Fe-Ni using respective effective interdiffusion coefficients are presented. These results demonstrate a good accuracy of such kind of calculations even in the case of very strong deviation from linearity of the diffusion path.
Simulation of Interstitial Atom Diffusion in FCC Metals with Point Defects
Authors: Selezneva Liudmila V. , Nazarov Andrei V.
Published: March 2009

This work is devoted to simulation of interstitial atom diffusion in fcc metals with point
defects. We used the molecular static and the Monte Carlo methods. An activation barrier set for different configurations of the carbon–vacancy complexes is simulated by the method of the molecular static (MS). Then we calculate atom jump rates for these configurations. The simulation of the carbon and vacancy migration in an fcc metal is realized on the basis of obtained atom jump rates by using the Monte-Carlo (MC) method. In particular, the calculations were made for the system of the nickel-carbon. In the result of that interstitial atom diffusion coefficient has been obtained at different temperatures.
Structural and Transport Properties of La1-xSrxCo1- y-zFeyNizO3-δ Perovskites
Authors: Świerczek K. , Marzec J. , Ojczyk W. , Molenda J.
Published: March 2009

The La1-xSrxCo0.2Fe0.6Ni0.2O3-d, La1-xSrxCo0.4Fe0.4Ni0.2O3-d and
La1-xSrxCo0.2Fe0.4Ni0.4O3-d perovskites were synthesized with Sr contents 0.1 ≤ x ≤ 0.3 using precursors obtained by citric acid method and their structural and transport properties were measured. All obtained samples crystallize in hexagonal R-3c perovskite structure. The thermal stability was found to decrease with increasing Ni and Sr amounts, what leads to appearance of La2NiO4 like secondary phases with spinel structure and even NiO for higher Ni concentration. The DC electrical conductivity and thermoelectric power measurements at low temperatures (77 – 300K) suggest an appearance of variable hopping mechanism in this
temperature range. The transport properties were found to improve with both Sr and Ni concentration increases. The moessbauer spectroscopy studies of La1-xSrxCo0.2Fe0.6Ni0.2O3-d samples revealed presence of two valence states of iron (Fe2+, Fe3+). The measured high temperature (870 – 1070K) DC electrical conductivity is relatively high for samples with high Sr and Ni amounts, what makes them good candidates for a possible application as cathode materials for Intermediate Temperature Solid Oxide Fuel Cells and points to further studies of
perovskites from the (La, Sr)(Co, Fe, Ni)O3 system.
Approximate Solutions of Grain Boundary Diffusion in Thin Films in the B2 Regime
Authors: Fielitz P. , Borchardt Günter
Published: March 2009

Exact mathematical solutions of the grain boundary diffusion equation in thin films have generally a complicated form, which is too cumbersome for the evaluation of experimental average concentration depth profiles obtained by sectioning techniques. On the other hand the accuracy of the exact solutions is not necessary for practical purposes so that it is useful to derive sufficiently accurate approximate solutions. We propose a method to derive such solutions for a thin film if the grain boundary diffusion is in the B2 regime. These solutions are derived for different diffusion sources.
Influence of Platinum and Palladium on Diffusion in β-NiAl Phase
Authors: Bouchet Régis , Mévrel Rémy
Published: March 2009

A new inverse method is applied for the determination of interdiffusion coefficients in b- NiAl(Pt) and b-NiAl(Pd). The results show that substitution of Pt or Pd to b-NiAl accelerates the diffusion of aluminium. Within the studied composition range and for Al-poor aluminides, the cross coefficients are negligible except for high Pd contents
Measurement of the Impurity Diffusivity of Cu in Fe by Laser Induced Breakdown Spectrometry
Authors: Lee Chan Gyu , Lee Jung Han , Lee Byeong Seon , Lee Yong Ill , Shimozaki Toshitada , Okino Takahisa
Published: March 2009

The impurity diffusion coefficients of Cu in Fe have been determined in the temperature range of 1073 - 1163 K by means of Laser Induced Breakdown Spectrometry (LIBS). The volume diffusion coefficients for Cu impurity diffusion in a-iron found in this work are in good agreement with the previously published result. The grain boundary diffusion coefficient gb D s d was also calculated using the volume diffusivity and processing the tails of the measured profiles. The values of the activation energy for volume and grain boundary diffusion were approximately 280 and 161 kJmol-1, respectively. This indicates the possibility of a monovacancy diffusion mechanism in case of volume diffusion. The results for the diffusion coefficients are Dv= 2.2 ×10-2exp(-280 kJmol-1/RT) m2s-1 and gb D s d = 2.6 ×10-11exp(-161 kJmol-1/RT) m3s-1.
Defects and Diffusion in d-AlNiCo-Quasicrystals - Application of Mechanical Spectroscopy
Authors: Weller M. , Damson B. , Feuerbacher Michael
Published: March 2009

Mechanical loss (internal friction) measurements were applied to polycrystalline d-
AlNiCo quasicrystals for compositions ranging from Al72.8Ni7.5Co19.7 to Al71.1Ni18Co10.9 and to an Al71.3Ni13.4Co15.3 mono-quasicrystal The measurements were carried out in the temperature range from 290 K up to 1220 K for measuring frequencies between 0.1Hz and 10 kHz. A loss maximum of Debye type is observed at ≈ 700 K (2Hz) for both the I-phase and the bCo-phase, which is attributed to local rearrangement of point defects. The activation enthalpy of the peak of H = 1.9 - 2.4 eV is in the range of values obtained from tracer diffusion experiments. This indicates that local defect rearrangement and self diffusion are governed by the same atomic diffusion process.. A high temperature viscoelastic damping background is only observed in polycrystalline samples with H = 2.4 – 3 eV. The background is assigned to viscolealastic relaxation based on intergranular diffusion.
Diffusion of Hydrogen in Titanium-Vanadium Alloys
Authors: Christ Hans-Jürgen , Schroers S. , dos Santos F.H.S.
Published: March 2009

β–titanium alloys are very attractive materials for many applications because they
combine low density, high strength and excellent corrosion resistance. The available data indicate a much higher hydrogen diffusion coefficient in β–titanium alloys as compared to α and α + β alloys. In order to predict the range of applicability of β–titanium alloys in environments, which release hydrogen, the hydrogen diffusion coefficient (DH) needs to be known quantitatively. In the framework of this study the value of DH was determinated on samples, which were electrochemically hydrogen charged. Long thin rods were used as samples and
charged in such a way that high hydrogen concentrations were obtained in one half of the length of the specimens, while the other half was kept virtually unaffected. After charging, the rods were annealed enabling hydrogen to diffuse. Hydrogen concentration profiles were experimentally determined and evaluated on the basis of the Matano technique, in order to reveal any effect of concentration on DH. The experiments were carried out on β–titanium alloys of the binary Ti–V system. The concentration range of vanadium in the alloys studied was selected in such a way that it represents the compositions commonly found in commercial alloys. The results show that the effect of hydrogen concentration on DH is negligible and that
DH increases with the vanadium concentration.
Diffusion of Nb in Nb-H Alloys
Authors: Yamazaki Yoshihiro , Iida Takahiro , Iijima Yoshiaki , Fukai Yuh
Published: March 2009

Self-diffusion coefficient of 95Nb in NbHx alloys (x=0.05,0.25 and 0.3) has been determined in the temperature range from 823 to 1323 K by using a serial sputter-microsectioning technique. The self-diffusion coefficient of Nb in the NbHx alloys are larger than that in Nb, suggesting that vacancies are formed by hydrogen dissolution, that is, the formation of hydrogen-induced vacancies. The value of the pre-exponential factor for the Nb diffusion in the NbH0.05 alloy is five times larger
than that in Nb, while the difference in the activation energies between the NbH0.05 alloy and pure Nb is small. The self-diffusion enhancement in the NbH0.05 alloy is mainly caused by lowering in vibrational frequencies of atoms in the immediate neighborhood of hydrogen-induced vacancies.
Self-Diffusion in Nickel-Manganese Alloys
Authors: Mehrer Helmut , Peteline S. , Huang M.L. , Chang Y.A.
Published: March 2009

Self-diffusion of nickel and manganese has been investigated by the radiotracer
technique in Ni50Mn50 alloys over a wide temperature range. Experiments were performed on disordered fcc, B2 and L10 structure phases present in the equiatomic alloy at high, intermediate, and low temperatures, respectively.
The diffusivity of manganese was found to be significantly faster (factor 3 to 5) than that of nickel in the fcc and B2 phases. More than one order of magnitude diffusivity increase was observed upon the transition from the higher temperature fcc to the intermediate temperature B2 phase. The activation enthalpy from nickel self-diffusion in the disordered fcc phase is significantly higher than the corresponding value for manganese. In the B2 phase there is only a slight difference
between the activation enthalpies of the components, which indicates a coupled diffusion mechanism of the two components. A comparison of the present tracer self-diffusion data with literature data on interdiffusion in the Ni-Mn system permits to estimate thermodynamic factors by using the Darken-Manning equation. The thermodynamic factor varies from 3 to 5 depending on the structure.
Tracer Diffusion of Fe and Pd in FePt and FePt3
Authors: Nosé Y. , Ikeda Teruyuki , Nakajima Hideo , Numakura Hiroshi
Published: March 2009

The tracer diffusion coefficients of Fe and Pd have been measured in FePt and FePt3 by standard radiotracer experiments. In FePt3 the diffusion coefficients are lower than extrapolations of those in the high-temperature disordered state, exhibiting curved Arrhenius plots below the transformation temperature. The diffusion of Pd is faster than that of Fe, and noticeable dependence on composition is found for the latter. In the L10 ordered FePt, the diffusion of Fe has been verified
to be slower in the direction of the tetragonal axis, but the case of Pd appears more complex. The diffusion coefficients of Fe and Pd are similar in magnitude in the L10 ordered state.
'Up-Hill' Interdiffusion and Accompanying Effects in Ternary Cu-Ni-5 at. % Sn(In) Systems
Authors: Kornienko Semen , Paritskaya Lyudmila N. , Bogdanov V.V.
Published: March 2009

Kinetics of phase growth in multiphase Cu-Sn and Ni-Sn systems and effect of third
substitutive component (Ni or Cu respectively) were studied experimentally in temperature range 160-220oC and analyzed theoretically. Kinetic equations for calculation of diffusion coefficients in growing competitive phases were obtained. It was found that the substitutive components accelerated phase growth lowering the values of diffusion activation energy and pre-exponential factor. As a result the growth rates of competitive phases Cu6Sn5 and Cu3Sn in Cu-Sn system changed with substitutive Ni so, that only one (CuNi)6Sn5 phase survived whereas (CuNi)3Sn phase was suppressed. Obtained results are discussed in terms of higher disordering caused by substitutive components in ternary phases as compared with binary ones.
The Role of Intrinsic Defects for the Diffusion of Ag and Cu in CdTe
Authors: Wolf Herbert , Wagner F. , Wichert Th.
Published: March 2009

Ag and Cu diffused into CdTe exhibit unusual shapes of their concentration profiles,
especially if the diffusion was performed under Cd vapor pressure. The shapes of the concentration profiles at low concentrations of Ag or Cu are well described by a model based on the interaction with intrinsic defects. In that model the characteristic features of the profiles can be independently reproduced by appropriate parameters. It turns out that the resulting profiles are determined by the diffusion of interstitial Cd atoms and reflect the actual distribution of the intrinsic defects in the
crystal, i.e. the deviation from stoichiometry.
Solute Segregation Studied by Grain Boundary Diffusion
Authors: Divinski Sergiy V. , Herzig Christian
Published: March 2009

Diffusion of 64Cu, 59Fe, and 63Ni radiotracers has been measured in Cu–Fe–Ni alloys of different compositions at 1271 K. The measured penetration profiles reveal grain boundary-induced part along with the volume diffusion one. Correction on grain boundary diffusion was taken into account when determining the volume diffusivities of the components. When the Cu content in the alloys increases, the diffusivities increase by order of magnitude. This behaviour correlates well with decreasing of the melting temperature of corresponding alloys, as the Cu content increases. Modelling of interdiffusion in the Cu–Fe–Ni system based on Danielewski-Holly model of interdiffusion is presented. In this model (extended Darken method for multi-component systems) a postulate that the total mass flow is a sum of the diffusion and the drift flows was applied for the description of interdiffusion in the closed system. Nernst-Planck’s flux formula assuming a
chemical potential gradient as a driving force for the mass transport was used for computing the diffusion flux in non-ideal multi-component systems. In computations of the diffusion profiles the measured tracer diffusion coefficients of Cu, Fe and Ni as well as the literature data on thermodynamic activities for the Cu–Fe–Ni system were used. The calculated interdiffusion concentration profiles (diffusion paths) reveal satisfactory agreement with the experimental results.
Grain Boundary Segregation Versus Precipitation in Grains. Effect on Diffusion
Authors: Bokstein Boris S. , Smirnov A.N.
Published: March 2009

Thermodynamic model is developed of which it follows that saturation value of solute
segregated in grain boundary, provided all available sites occupied, must be close to the solute concentration, in the nearest in composition phase in grain as it follows from phase diagram. Based on the analysis of experimental data for three binary systems (Cu –Sb, Fe – P and Fe – Sn) it is shown that the surplus concentration of the solute atoms in GB as compared with a concentration in
grain is distributed equally between two fracture surfaces but takes up more than one atomic layer. The thickness of the segregation region (with surplus concentration in grain boundary) averages usually from 3 to 6 interatomic distances. As a rule, solute distribution is symmetrical on each side of the fracture surface. It is shown that maximum of grain boundary concentration falls on the first layer on the fracture surface. The method is developed of the calculation of the first layer concentration. It is shown that this concentration is close to the solute concentration in the nearest in composition phase in grain.
Nitrogen Self-Diffusion in Polycrystalline Si3N4 Films: Isotope Heterostructures vs. Gas-Exchange
Authors: Schmidt Harald , Borchardt Günter , Rudolphi Mario , Baumann H. , Bruns Michael , Weber S. , Scherrer Hubert
Published: March 2009

The self-diffusion of nitrogen is investigated in polycrystalline thin silicon nitride films
using a gas-exchange method (14N2/Si3 15N4) in comparison to Si3 14N4/Si3
15N4/Si3 14N4 isotope heterostructures. The films are produced by reactive r. f. magnetron sputtering. Depth profile analysis is carried out with secondary ion mass spectrometry (SIMS), secondary neutral mass spectrometry (SNMS), and nuclear resonant reaction analysis (NRRA). The nitrogen diffusivities determined with the use of isotope heterostructures follow an Arrhenius law in the temperature
range between 1200 and 1700 °C with an activation enthalpy of DH = 4.9 eV and a pre-exponential factor of D0 = 1 x 10-6 m2/s, indicating a conventional diffusion mechanism via localized point defects. Using the gas-exchange method, the nitrogen diffusivities could be obtained only in the temperature range between 1600 and 1700 °C. This is due to the fact that at temperatures below 1600 °C the surface exchange process with its high activation enthalpy (about 10 eV) is rate limiting, leading to non detectable diffusion profiles. The application of the different methods of
depth profiling leads to the same diffusivities within estimated errors.
Iron Self-Diffusion in Chemically Homogeneous Multilayers
Authors: Gupta Mukul , Gupta Ajay , Chakravarty Sujoy , Gutberlet Thomas
Published: March 2009

Iron self-diffusion measurements in amorphous and nanocrystalline chemically
homogenous multilayers (CHM) of FeZr/57FeZr, (with nm range periodicity) have been studied with neutron reflectivity technique. It has been found that both the activation energy for diffusion and the pre-factor were significantly smaller as compared with bulk alloys. Effect of compressive stress on self-diffusion reveals a significant dependence on the activation energy as a function of applied stress. On the basis of the obtained results the diffusion mechanism in amorphous and nanocrystalline CHM of FeZr/57FeZr is reviewed in this paper.
Interdiffusion in Co/Ta Multilayer Thin Films
Authors: Lee Hui Myeong , Lee Byeong Seon , Lee Chan Gyu , Hayashi Yasunori , Koo Bon Heun
Published: March 2009

We will discuss the stress release phenomena, structural relaxation and interdiffusion processes during annealing. The [Co(4nm)/Ta(4nm)]38 multilayers were prepared by dc magnetron sputtering on Si substrate. The multilayers were annealed at various temperatures (523 - 673K) in vacuum
(under 10-5 torr) furnace. The effective interdiffusion coefficients were determined from the slope of the best straight line fit of the first peak intensity versus annealing time [d ln(I(t)/I(0)) /dt] by X-ray diffraction (XRD) low angle measurements. The drastic decrease of the relative intensity in the initial stage shown due to the structural relaxation was excluded in the calculation of effective interdiffusion coefficients. The temperature dependence of interdiffusion in the range of 523 - 673K is described by D = 3.2×10-19 exp(-0.51±0.11 eV/kT) m2s-1.
The Effect of Magnetic Field on Kinetics of Grain Boundary Grooving in Iron
Authors: Rabkin Eugen , Gabelev A. , Matsuzaki T. , Watanabe Tadao
Published: March 2009

It was shown that external magnetic field of 5 kOe slows down the kinetics of grain
boundary grooving in iron at 750 °C by about one order of magnitude. This observation is discussed in terms of magnetic effect in surface diffusion.
Migration of Ion Implanted Hydrogen in Amorphous and Polycrystalline Si3N4:H Films: Experiments and Numerical Simulations
Authors: Schmidt Harald , Borchardt Günter
Published: March 2009

The tracer diffusion of ion implanted deuterium is studied in amorphous and
polycrystalline magnetron-sputtered Si3N4:H films with secondary ion mass spectrometry (SIMS). The experimentally obtained diffusion profiles are numerically simulated by computer calculations based on the concept of trap-limited diffusion where the tracer atoms form immobile complexes with: (a) intrinsic film defects like dangling bonds and (b) extrinsic defects caused by the implantation damage. For amorphous Si3N4:H films a moderately high dissociation rate of intrinsic
complexes (dangling bonds) is present and time independent effective diffusivities are observed, which obey an Arrhenius law with an activation energy of DE = 3.4 eV and a pre-exponential factor of D0 = 4 x 10-4 m2/s. For polycrystalline Si3N4 films non-Gaussian depth profiles and strongly time dependent diffusivities are observed, which have their reason in the presence of intrinsic traps with negligible dissociation, presumably located at the grain boundaries.
Aging of Oxides under Irradiation
Authors: Limoge Yves , Barbu Alain
Published: March 2009

In this conference we try to give a survey of the main characteristics of aging of oxides under irradiation in the perspective of the recent developments of the ab-initio modeling capabilities. After a brief recall of the relevant radiation – matter interactions, we present the main aspects of materials aging under irradiation, I) defect creation either elastically or inelastically, ii) microstructure evolution due to defect elimination, iii) radiation enhanced diffusion, iv) phase changes under irradiation.
Thermo Mechanical Treatment of Nickel and Titanium Aluminides
Authors: Agarwala Vijaya , Karwan-Baczewska Joanna
Published: March 2009

Polycrystalline Ni3Al and TiAl are attractive materials for high temperature structural applications due to their stability in oxidizing and sulphidizing environment upto700 0 C. They possess significantly higher specific stiffness and similar specific strength as that of super alloys. Hence, these materials can replace super alloys for high temperature applications (~900°C). TiAl has lesser density and can be used for reducing component weight up to 50% and suitable for aerospace and automobile (high performance vehicles) sectors. The major difficulty for putting Ni3Al for
engineering applications is its extremely low ductility and inter-granular fracture at ambient temperatures. TiAl, apart from the said brittleness it also suffers from high temperature corrosion. However the brittleness of these aluminides can be reduced by micro-alloying and by subjecting them to Thermo Mechanical Treatments, TMT.
This paper deals with the recrystallization studies on nickel aluminides, deformed to different extents by rolling. The average grain size dependence with the % elongation is evaluated in the grain size range of 10-35micron. For the nickel aluminide deformed for 50% by rolling, the variation of resistivity and hardness with annealing time is determined. The homogenized TiAl samples were cold worked and annealed at 1000 0 C. Since the aluminide suffers from low ductility at room temperature, an arbitrary parameter, electrical resistivity, was chosen. Corresponding hardness values were also obtained. Finally a qualitative determination of ductility was made by studying the flow behavior of alloy around the hardness indentation. Thus a correlation was developed between resistivity, hardness and ductility values. It was then to some extent possible to investigate the TMT cycles on the microstructure and hence on the ductility of the TiAl without going for the actual tensile tests.
Effect of Self-Interstitial Diffusion Anisotropy in Electron-Irradiated Zirconium. A Cluster Dynamics Modeling
Authors: Christien Frédéric , Barbu Alain
Published: March 2009

Irradiation of metals leads to the formation of point-defects (vacancies and selfinterstitials) that usually agglomerate in the form of dislocation loops. Due to the elastic interaction between SIA (self-interstitial atoms) and dislocations, the loops absorb in most cases more SIA than vacancies. That is why the loops observed by transmission electron microscopy are almost always interstitial in nature. Nevertheless, vacancy loops have been observed in zirconium following electron or neutron irradiation (see for example [1]). Some authors proposed that this unexpected behavior could be accounted for by SIA diffusion anisotropy [2]. Following the approach proposed by Woo [2], the cluster dynamics model presented in [3] that describes point defect agglomeration was extended to the case where SIA diffusion is anisotropic. The model was then applied to the loop microstructure evolution of a zirconium thin foil irradiated with electrons in a high-voltage microscope. The main result is that, due to anisotropic SIA diffusion, the crystallographic orientation of the foil has considerable influence on the nature
(vacancy or interstitial) of the loops that form during irradiation.
Kinetics of Precipitation: Comparison between Monte Carlo Simulations, Cluster Dynamics and the Classical Laws
Authors: Maugis Philippe , Soisson Frederic , Lae Ludovic
Published: March 2009

We test the main approximations of the classical laws for nucleation, growth and
coarsening by comparison with atomistic simulations of the kinetics of precipitation. We investigate the kinetics of phase separation in dilute A-B solid solutions by precipitation of B atoms in the Arich matrix. Classically, the kinetics is represented by the time evolution of the total number of particles and their mean radius. In this work, the kinetics is predicted by three types of models: (a) an Atomic-scale Kinetic Monte Carlo (AKMC) model based on a vacancy diffusion mechanism, (b) a Cluster Dynamics model, and (c) the MultiPreci model, based on the coupling of the classical laws of nucleation, growth and coarsening. Cluster Dynamics and the Multipreci model have been parameterized such that the thermodynamic and kinetic parameters (solubility, diffusion coefficient, interface energy) be identical to that of the AKMC. Under these conditions we find that the classical laws are in good agreement with the atomistic simulations as long as the thermodynamics of the solid solution remains strictly regular. As expected, Cluster Dynamics compares better with the atomistic simulations, especially if a precise description of the energetics of the smallest clusters is applied.
Evidence for a Diffusion-Based Mechanism of Liquid Metal Intergranular Penetration: Case Study of a Ni-Bi Model System
Authors: Wolski Krzysztof , Marie N. , Laporte V. , Berger Pascal , Biscondi M.
Published: March 2009

A model Ni-Bi system has been used to investigate intergranular penetration (IGP) phenomenon. All experiments have been done on Ni 26°<110> bicrystal at 700°C using bismuth vapour condensation as a source of liquid bismuth. Such a procedure results at room temperature in either partial or total Liquid Metal Induced Embrittlement (LMIE) of a unique grain boundary, depending on the duration of liquid Bi / solid Ni contact at 700°C. Auger Electron Spectrometry (AES) and Rutherford Backscattering Spectrometry (RBS) have been used to measure the Bi concentration profile between the source of liquid bismuth and the penetration front. Two zones have been clearly identified : the first one of almost constant Bi concentration called nanometrethick film which is interpreted in terms of Fowler-Guggenheim multi-layer segregation under local equilibrium conditions and the second one with a progressive decrease of Bi concentration over a distance of the order of 20-200µm. Such a long transition zone, together with parabolic diffusion
kinetics indicates diffusion-based mechanism of intergranular penetration as opposed to the direct grain boundary wetting.
Diffusion in L10-Type Single Crystal TiAl and FePt Intermetallic Compounds
Authors: Nakajima Hideo , Nosé Y. , Terashita N. , Ikeda Teruyuki , Numakura Hiroshi
Published: March 2009

The diffusion coefficient of In in TiAl has been measured using ion implantation
technique and secondary ion mass spectrometry. The diffusion coefficients of Fe and Pd in FePt have been measured at two compositions by radioactive tracer method. In order to clarify diffusion anisotropy, single crystal of each alloy was used. The In diffusion perpendicular to the [001] axis is faster than that parallel to the [001] axis. Such trend is similar to Ti diffusion previously measured in our group. The diffusion of Fe in FePt perpendicular to the [001] axis is faster than that parallel to the [001] axis at each composition, while the anisotropy of the Pd diffusion is different with composition. The predominant process of the diffusion in perpendicular to the [001] has been discussed on the basis of the expressions of the diffusion coefficients.
Calculation of Surface Self-Diffusion Coefficients from AES Data on Decay of Thin Metal Films
Authors: Beszeda I. , Beke Dezső L. , Gontier-Moya E.G. , Kaganovsky Yuri S. , Ianetz D.
Published: March 2009

We propose a simple method for calculation of surface self-diffusion coefficients using kinetic data on the decay of thin films – void growth and transformation of the island shape to the equilibrium. Calculations are made taking into account equilibrium wetting angle of the film on a substrate. The kinetic data on the decay of Pd thin films on sapphire and silica substrates were obtained using Auger electron spectroscopy. By in situ monitoring the intensity of the Auger signal from the film, three different stages of the decay could be distinguished. The surface self-diffusion
coefficients were calculated for the temperature range 583 – 823 K. The values of the surface diffusion coefficients and the activation energies are discussed compared to those obtained by other methods.
Peculiarities of Diffusion Mass Transfer in System Fe[Cr]-Pb[O]
Authors: Matychak Ya. , Yeliseyeva O. , Fedirko V. , Tsisar V.
Published: March 2009

Process of high-temperature (650°С) interaction of Cr(Si)-containing steel EP-823 with stagnant Pb melt containing oxygen (CО[Pb] » 10-5 - 10-6 mass.%) was theoretically and experimentally investigated. The structure and composition of oxide layer formed on the steel surface during exposure to Pb melt was examined. It is determined that thin (£ 1000 Å) Cr(Si) - rich oxide layer is formed on the steel surface in the early stages of oxidation. Oxide layer is being formed intensively over the grain boundaries followed by a lateral diffusion of Cr and spreading of Cr2O3 over alloy surface. Iron diffuses through the Cr(Si) - rich continuous oxide layer in the course of time. The formed oxide layer protects the steel against liquid metal penetration. Kinetics of iron diffusion dissolution in the liquid Pb is analytically described taking into account the chemical interaction between iron and oxygen. It is assumed that oxygen ions serves as a “traps” for iron ions and eliminates them from the diffusion flux. Fe−O complexes are considered as separate slowmoving components of the melt. In order to formulate the diffusion problem equations with additional parameter describing the volume reaction between Fe and O in melt and boundary conditions involved the time dependence of oxygen concentration at the interface of both melt and solid metal sides were used. Result is obtained in analytical form using the Laplace transformation. Analysis of obtained relations allow to assert that in the case of dissolution of iron in the lead melt containing “oxygen traps” the diffusion zone are less than that in the conditions of dissolution (without “traps”). However, the total concentration of iron both on surface of oxide layer and in the contact zone of melt is increased.
Anionic and Cationic Diffusion in Ionic Conducting Oxides
Authors: Petot-Ervas Georgette , Petot C. , Raulot Jean Marc , Kusinski J.
Published: March 2009

This paper concerns an analysis of the transport processes at high temperature in anionic conducting oxides subjected to a chemical potential gradient or an applied electrical field. The general equations are given. The principle of the cationic kinetic demixing under a “generalized“ thermodynamical potential gradient is reviewed. Experimental results obtained with yttria-doped zirconia are reported. An experimental procedure for the determination of the oxygen diffusion coefficient in ionic and semiconducting oxides is also described. The results obtained with yttriastabilized zirconia are compared to both self diffusion and conductivity data. This has allowed us to obtain information concerning the defect structure.
Study of Fe Diffusion in Cr2O3 by Secondary Ion Mass Spectrometry
Authors: Sabioni Antônio Claret Soares , Huntz Anne Marie , Silva F. , Jomard François
Published: March 2009

Chromia protective layers are used to prevent corrosion by oxidation of many alloys, such as the stainless steels, for instance. To check if chromia is a barrier to the outward diffusion of iron in these alloys, iron diffusion in chromia was studied in both polycrystals and oxide films formed by oxidation of Ni-30Cr alloy in the temperature range 700-1100°C at an oxygen pressure equal to 10-4 atm. An iron film of about 70 nm thick was deposited on the chromia surface, and after the
diffusing treatment, the iron depth profiles were established by secondary ion mass spectrometry (SIMS). Using a solution of the Fick’s second law for diffusion from a thick film, effective or bulk diffusion coefficients were determined in a first penetration domain. Then, Le Claire’s and Hart’s models allowed both the bulk diffusion coefficient and the grain boundary diffusion parameter (aDgbd) to be obtained in a second penetration domain. Iron bulk and grain boundary diffusion does not vary significantly according to the nature-microstructure of chromia. The activation energy of grain boundary diffusion is at least equal or even greater than the activation energy of bulk diffusion, probably on account of segregation phenomena. Iron diffusion was compared to cationic self-diffusion and related to the protective character of chromia.
MCrAlY Coatings for Gas Turbine Blades Life Time Estimation Based on the Diffusion-Controlled Processes Modelling
Authors: Krukovsky P. , Tadlya K. , Rybnikov A. , Kolarik Vladislav , Stamm W.
Published: March 2009

Calculational and experimental approach was developed for life time analysis of
MCrAlY coatings for industrial gas turbine blades. This approach based on the model that describes the main diffusion and oxidation processes within the coating-base metal system as well as the experimental data for specimens after different short time exposures at different temperatures. In comparison with existing models the proposed model describes interdiffusion zone between coating and base alloy.
The models adequacy to physical processes is provided by model parameters identification with short-time experiment data for coating – base alloy systems. The measured Al concentration profiles were used as input values for the model parameters estimation and a calculational prediction of the long term diffusion and oxidation behaviour of the coating was performed. The model, calculational and experimental approach as well as MCrAlY life time estimation results for 10000 h at 950°C are presented. These results were obtained with short time experimental data
for Al concentration profiles across the coating thickness measured after 300 and 1000 h. The predicted and measured b-phase content at coating during oxidation for coating thickness 200 micron at 900, 950 and 1000 °C are presented too. The b-phase content disappear at coating was assumed as a corrosion life time criterium.
Ag-Diffusion in the Organic Semiconductor Diindenoperylene
Authors: Scharnberg M. , Hu J. , Kanzow Jörn , Rätzke Klaus , Adelung Rainer , Faupel Franz , Pflaum J.
Published: March 2009

The metallization of organic thin films is a crucial point in the development of organic
electronic devices. There is no method established yet to detect trace amounts of metal atoms in the organic thin films after metal deposition. Radiotracer measurements are probably the most sensitive tool to study diffusion and to quantify even very small amounts of material penetrating into the bulk. So far, this has been shown for metals and polymers, but not for thin ordered molecular organic films. Here, the first application of this technique on a well-characterized organic thin film
system, diindenoperylene using thermally evaporated Ag containing 110mAg radiotracers is shown. The results show that Ag is mainly adsorbed on the surface, but indicate that already at moderate substrate temperatures small concentrations of Ag can penetrate into the organic thin films and agglomerate at the interface during metallization.
Identification of Mg Vacancy in MgO by Positron Lifetime Measurements and First-Principles Calculations
Authors: Mizuno Masataka , Araki Hideki , Shirai Yasuharu , Oba Fumiyasu , Tanaka Isao
Published: March 2009

The formation of Mg vacancy induced by ultra-dilute trivalent impurities in MgO is investigated by a combination of positron lifetime measurements and first-principles calculations. The undoped MgO yields the shortest positron lifetime of 140 ps that is shorter than that of a single crystal sample. The positron lifetime of the doped samples increases with the increase of the Al dopant concentration and is saturated at around 180 ps. This result clearly indicates that the formation of Mg vacancy is induced by Al dopant. The concentration of the other trivalent impurities can be evaluated using the result of component analysis of positron lifetimes. The experimental bulk lifetime of 130 ps, which is obtained by employing trapping model, is well reproduced by the theoretical calculation using the semiconductor model. The calculated defect lifetime is about 20 ps longer than the experimental value. This may be due to the lattice relaxation around Mg vacancy associated with the trapping of positrons.
Diffusion of Oxygen at Ceramic Interfaces for High-Temperature Solid Oxide Fuel Cells
Authors: Horita Teruhisa , Kishimoto Haruo , Yamaji Katsuhiko , Sakai Natsuko , Xiong Yue Ping , Brito Manuel E. , Yokokawa Harumi
Published: March 2009

Oxygen diffusion was measured at oxygen/cathode/electrolyte interfaces and at oxide scales/alloy interconnects in Solid Oxide Fuel Cells (SOFCs). A stable isotope oxygen exchange technique (16O/18O exchange) was adopted to label the diffusion profiles in the oxides, and secondary ion mass spectrometry (SIMS) depth profiles were examined to determine the diffusion coefficients in the oxide ceramic materials. Diffusivity of oxygen in LaMnO3 cathode was measured under polarized condition (that is, considering the electrochemical process and diffusion). Also, oxygen diffusion in the oxide scales formed on the alloy was measured to clarify the formation mechanism of oxide scale.