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Byline: Feliksas Ivanauskas (1,2), Aivaras Kareiva (3), Bogdanas Lapcun (2) Keywords: yttrium aluminium garnet; reaction--diffusion model; finite difference schemes Abstract: There is a model of yttrium aluminium garnet (YAG) synthesis presented in this article. The developed model is based on nonlinear reaction--diffusion partial differential equations. The solution was carried out numerically using finite difference techniques. We got dependability curves for diffusion and reaction rates and offered possible method to localize values of diffusion and reaction rate constants precisely enough. Author Affiliation: (1) Institute of Mathematics and Informatics, Akademijos str. 4, Vilnius, 08663, Lithuania (2) Department of Mathematics and Informatics, Vilnius University, Naugarduko str. 24, Vilnius, 2006, Lithuania (3) Department of Chemistry, Vilnius University, Naugarduko str. 24, Vilnius, 2006, Lithuania Article History: Registration Date: 03/12/2004 Received Date: 24/09/2004 Article note: AMS subject classification: 35K57, 65M06

Over the past few years, much effort has been devoted to studying the melting curve of elements at high pressure. This information is relevant to applications such as nuclear fission [...]

The diffusional cross-talk of reversible redox species with different diffusion coeffecients are investigated theoretically at paired microband electrodes operating under generator-collector mode within a thin film coating. Results show that several regimes of diffusion ocur according to the diffusion length of the species.

Research describes the synthesis of the zinc containing binucleating ligands that are employed in the stabilization of dinuclear metal complexes. Data show that the zinc binucleating ligands such as those containing one nitrous oxide and one oxygen as bridging atoms are suitable to create polynuclear compounds.

Research shows that the metal-metal bonding in the transition metal chalcogenides is facilitated by the crystallization of these compounds in the Fe(sub)2P structure type called Zr(sub)6CoAl(sub)2. Results demonstrate that the chalcogenides containing metal substituents exhibit structural and electronic flexibility and the metal-metal bonding is one dimensional in character.

The exchange bias field of the NiFe/FeMn system was found to increase from 30-35 Oe up to 75 Oe by annealing a three layer film structure of NiFe(300 angstroms)/FeMn/M (M = Au, Rh, Pt, Cr, Cu etc.) at elevated temperature. Auger electron spectroscopy showed that interdiffusion occurred in the multilayer structure between the FeMn and the metal layer. The increase in exchange bias field is attributed to the altered interface of NiFe/FeMn due to the interdiffusion.

Byline: Kyozo Arimoto, Fumiaki Ikuta, Shigeru Yamanaka, Kiyoshi Funatani By the use of computational simulation techniques for nitriding processes, diffusion and nitride precipitation phenomena in compound layers and diffusion zones have been predicted in low alloy steels, Fe-Cr alloys, and so on. They have been also applied to examining formations of the expanded austenite in nitrided austenitic stainless steels. However, the application of the simulation approach was so far limited to the one-dimensional problems along the depth direction in simple shape specimens, since it is built on the finite difference method. In order to innovate the simulation, the software tool based on the finite element method has been expanded for studying on arbitrary-shaped parts by using the latest models for nitriding. The tool, having the function to analyse stress and strain, contributes not only to resolving various practical problems but also to explaining the unsettled mechanisms of distortion and residual stress generations caused by nitriding. Furthermore, the models are also expected to be enhanced by considering stress and strain effects precisely. In this paper, some verification examples on distortions and residual stresses relating to the expanded austenite formation in nitrided austenite stainless steels are described after clarifying the theory and implementation of the expanded simulation tool.

Byline: Romain Quey, Fabrice Barbe, Ha Hoang, Lakhdar Taleb The γ → α diffusive phase transformations of steels can lead to transformation plasticity (TRIP) if accompanied of an external loading stress or a pre-hardening of the parent phase. The most current approaches of its modelling are based on the Greenwood-Johnson mechanism; they call upon hypotheses (about microstructure morphology, constitutive laws...) which are at the origin of discrepancies between predictions and experimental observations in particular loading cases. Some of these restricting hypotheses can be eliminated with a micromechanical finite elements approach, where the elastoplastic interactions between phases are determined at the micro-scale of a volume element containing hundreds of growing particles (Barbe et al., 2005, 2008). This paper deals with the effect of the spatial distribution of product phase nuclei on the global kinetics and transformation-induced plasticity (TRIP) in the volume element. Two distributions are considered: uniform random and at preferential nucleation sites of a Voronoi tesselation mimicking austenite microstructure.

Byline: Wladyslaw K. Wlosinski The paper gives the results of work on the technological process of the diffusion bonding of Ti with Al.SUB.2O.SUB.3, using Ti and TiH.SUB.2 powder interfaces. These interfaces were applied in the form of powders with a varying percentage content of Ti in relation to TiH.SUB.2. Conditions are described under which the process of bonding was taking place, as well as the effect of these conditions on the interface sintering kinetics. The Al.SUB.2O.SUB.3 to Ti bonds had no cracks and they featured shear-strength higher than 150 MPa. Results are also given of testing the micro-hardness and microstructure of the joints obtained.

Phosphorus diffusion and activation related phenomena in germanium is described and both conventional thermal processing and laser annealing is used by pulsed nanosecond Nd:YAG laser. A combined laser thermal treatment above the melting threshold prior to conventional annealing has allowed the elimination of the implantation damage in order to understand the impact of defects on both transient dopant diffusion and outdiffusion.

Glancing angle deposition (GLAD) experiments have shown that the nanorod morphology has displayed a chaotic instability with increasing surface diffusion and the measured rod width versus growth temperature has converged onto a single curve for all metals. The GLAD data has indicated that the effective mass transport on a curved surface is described by a single normalized activation energy that can be applied to all elemental metals.

M[Cs.sub.2.sup.+] secondary ion mass spectrometry method is used for examining the Ge-Si interdiffusion using Ge(:B) solid sources for Ge concentrations between 0 and 100 at. %. The effect of in situ B doping, which has induced a retardation of the Ge-Si interdiffusion, is analyzed.

Stress evolution, microstructural development and phase formation during interdiffusion of Cu-Pd thin-film diffusion couples are examined by using Auger-electron spectroscopy and transmission electron microscopy. The results have shown that interdiffusion is accompanied with the formation of new phases and is associated with stress changes.

The effect of the carbon co-implantation on boron activation and diffusion in germanium preamorphized silicon after the millisecond laser spike annealing (LSA) scheme as well as with an additional post-LSA treatment is examined. The amount of deactivation upon rapid thermal annealing (RTA) has become independent of LSA temperature for the carbon-implanted samples, largely due to boron clusters becoming limited by the small concentration of free silicon interstitials present instead of the LSA temperatures.

The interdiffusion dynamics in self-assembled InAs/InP(001) quantum dots (QDs) subjected to rapid thermal annealing is examined. The diffusion coefficients and active energies associated with both P interstitial diffusion in InP and P-As substitution processes are determined.

The selected-area electron diffraction patters for the ZnO/Si heterostructures annealed at 900 degree centigrade has showed that orthorhombic ZnSi[O.sub.3] nanoparticles are formed in the amorphous layer between the ZnO film and the Si substrate, which has resulted from the interdiffusion between the ZnO film and the Si substrate due to thermal treatment. The formation mechanism is described for the orthorhombic ZnSi[O.sub.3] nanoparticles embedded in the amorphous [Zn.sub.2x][Si.sub.1-x][O.sub.2] layer.

The effect of the deposition temperature and the wavelength of the periodicity on the effective interdiffusivity, microstructure and magnetic properties of annealed [[Fe/Pt].sub.n] multilayer films (MLs) is examined. The results have shown that nonequilibrium reaction kinetics is desirable for the reduced temperature formation of the [L1.sub.0] FePt phase.

The phase transformations and microstructural changes of NiPtSi/polysilicon fuses programmed with three different current densities, such as under, optimal and over programming, are studied. The conduction paths created by the unremoved silicide in fuse link have caused the postprogramming resistance of the overprogrammed fuse to be low.

The diffusion of implanted [super 7]Be in [Si.sub.1-x][Ge.sub.x] (x = 0.20, 0.65, 1.00) systems is analyzed under intrinsic conditions by the modified radiotracer method. It is shown that Be diffusion in [Si.sub.1-x][Ge.sub.x] systems are dissociative mechanism dominated for germanium rich materials and the kick-out mechanism has dominated in silicon rich materials.

The capacity of 3 keV ion beams, formed from the common noble gases, He, Ne, Ar, Kr, and Xe, to controllable 'sculpt' nanometer scale pores in silicon nitride films is demonstrated. The experimental results reveal surface atomic transport phenomena and parameters that can be extracted for an adatom diffusion model in a quantitative ways.

Bicrystalline nanowires of hematite are successfully synthesized by the oxidation of pure iron. It is found that most of the bicrystalline nanowires are nanotwins with ellipsoidal heads and the growth mechanism of such unique nanostructures is considered to be a solid-phase growth via surface and internal diffusions of molecules from base to tip.

A study is carried out on the effect of thin film morphology on energy transfer and migration in host-guest systems involving a phenylene-ethynylene oligomer matrix doped with collodially prepared CdSe quantum dots. The findings show that annealing the film produces continuous domain structures that enhance excitation migration by extending the excitation diffusion length.

A realistic 1D model of a bistable two-variable chemical system with a stable focus (SF) surrounded by a stable limit cycle (SLC) is investigated. The wave source generates an infinite number of impulses both in finite system and in infinite ones.

The secondary ion mass spectrometry (SIMS) depth profiles of high-dosage implanted Cr and V ions in Si as a function of annealing temperature and implant dose are studied. The combination of SIMS and cross-sectional transmission electron microscopy (XTEM) analyses of Cr and V implanted silicon provide a clear picture of the diffusion characteristics of these two elements.

The mechanism of abnormal grain growth (AGG) with solid state wetting in Fe-3%Si steel based on the microstructure evolution at the growth front of grain undergoing abnormal growth is investigated. The microstructure evidence for solid-state wetting at the growth of Goss grain is presented.

The mechanism involved in the Tm (super 3+) (3f4)-> HO (super 3+) (5I (super 7)) energy transfer and Tm (super 3+) (3H4, 3H6)-> Tm (super 3+) (3F4, 3F4) cross relaxation as a function of the donor and acceptor concentration in Tm-Ho codoped fluorozirconate glass is investigated. The energy transfers rates for different combination of doner and acceptor using diffusion model is highlighted.

The results of a systematic study regarding the morphological, structural, compositional and spectral changes involved in the reaction between silver nanostructures and an aqueous HAuCl4 solution on the nanoscale are presented. Through processes such as alloying and Ostwald ripening, the diffusion of Ag and Au atoms at low temperatures, prevents the nanostructures from smoothening their surfaces.

Byline: Oleksandr I. Raychenko, Oleksandr V. Derev|yanko, Victor P. Popov A novel approach was developed for the problem of mass transfer from a solid inclusion surrounded by the liquid current-carrying metal. The primary mechanism of this process is diffusion under electric current action. The named phenomenon provides more effective diffusion for the alloying process under some conditions than the usual atomic diffusion. Computer calculations and experimental investigations that show this are presented. The systems investigated were the CusolAlliq and NisolAlliq compositions. The relations between the conductivity of the solid inclusion and the surrounding liquid metal are opposite in the two systems named. Knowledge of the phenomena analysed might be useful for the improvement of alloying technologies.

A study is conducted to demonstrate that a fluorous phase can screen two otherwise miscible heavier and lighter organic phases in the bromination of alkenes and the dealkylation of aromatic ethers by boron tribromide. The conclusion states that the fluorous phase acts as a liquid membrane regulating the exchange between the two organic phases by passive diffusion.

The mechanism for the activation of the sigma bonds, the O-H of water, C-H of CH4, and the H-H of hydrogen, and the pi bonds, the triple bond of C of C2H2, C=C of C2H4 and the C=O of HCHO, at the Pd=X (x=Sn, Si, C) bonds of the model complexes (H2PC2H4PH2) Pd=XH2 has been detailed. The activation of the)-H bond with the lone pair electron is heterolytic at the Pd=X (X=Sn, Si) bonds, while it is homolytic at the Pd=C bond.