The Experts below are selected from a list of 117 Experts worldwide ranked by ideXlab platform
K L Narayanan - One of the best experts on this subject based on the ideXlab platform.
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evidence for Excess Vacancy defects in the pd si system positron annihilation x ray diffraction and auger electron spectroscopy study
Journal of Physics: Condensed Matter, 2003Co-Authors: S Abhaya, G Amarendra, G L N Reddy, R Rajaraman, K L NarayananAbstract:The transformation of Pd/Si to Pd2Si/Si is investigated using depth-resolved positron annihilation, x-ray diffraction and Auger electron spectroscopy studies. The observed defect-sensitive positron S-parameter value of 1.022–1.054 indicates the existence of divacancies across the silicide/silicon interface and Si substrate region. Our experimental observation of Vacancy defects is consistent with the model proposed for Excess Vacancy generation across the interface consequent to Si diffusion.
Ernst Kozeschnik - One of the best experts on this subject based on the ideXlab platform.
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Process-controlled suppression of natural aging in an Al-Mg-Si alloy
Scripta Materialia, 2014Co-Authors: Stefan Pogatscher, Ernst Kozeschnik, Helmut Antrekowitsch, Marion Werinos, Stephan S.a. Gerstl, Jörg F. Löffler, Peter J. UggowitzerAbstract:In this study natural aging of an Al–Mg–Si alloy was investigated using various quenching processes. Atom probe tomography and electrical resistivity measurements reveal that solute clustering during natural aging can be suppressed by interrupting quenching for 120 s at 160 °C. This phenomenon is elucidated by simulating the Excess Vacancy annihilation. Reduced frozen-in Excess Vacancy concentration after the interrupted quenching can explain this experimentally observed suppression of natural aging.
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Precipitation in Al-Alloy 6016 – The Role of Excess Vacancies
Materials Science Forum, 2012Co-Authors: Ahmad Falahati, Peter Lang, Ernst KozeschnikAbstract:6xxx Al alloys owe their superior mechanical properties to the precipitation of finely dispersed metastable β´´ precipitates. These particles are formed in the course of optimized heat treatments, where the desired microstructure is generated in a sequence of precipitation processes going from MgSi co-clusters and GP zones to β´´ and β´ precipitates and finally to the stable β and Si diamond phases. The entire precipitation sequence occurs at relatively low temperatures (RT to approx. 200 °C) and is mainly controlled by the Excess amount of quenched-in vacancies, which drive the diffusional processes at these low temperatures. Very recently a novel model for the prediction of the Excess Vacancy evolution controlled by the annihilation and generation of vacancies at dislocation jogs, grain boundaries and Frank loops was developed and implemented in the thermo-kinetic software MatCalc. In the present work, we explore the basic features of this model in the simulation of the Excess Vacancy evolution during technological heat treatments. The focus of this article lies on the effect of Vacancy supersaturation during different heat treatment steps, such as quenching, heating, natural and artificial aging.
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modeling of Excess Vacancy annihilation at different types of sinks
Acta Materialia, 2011Co-Authors: F D Fischer, Jiři Svoboda, Fritz Appel, Ernst KozeschnikAbstract:The equilibrium site fraction of vacancies increases with temperature and, thus, annealing and rapid quenching may lead to states with a significant Vacancy supersaturation. Excess vacancies can then gradually annihilate at available sinks represented by jogs at dislocations, by grain boundaries or free surfaces. Significant supersaturation by vacancies may also lead to the nucleation and growth of Frank loops acting as additional sinks. Three models corresponding to three different annihilation mechanisms are developed in this paper. They refer to annihilation of Excess vacancies at jogs at dislocation with a constant density, at homogeneously distributed Frank loops with a constant density and at grain boundaries. The simulations based on the models are performed for individual annihilation mechanisms under isothermal and non-isothermal conditions as well as for simultaneous annihilation of vacancies at Frank loops and dislocation jogs and grain boundaries using different cooling conditions.
Yu A Kuznetsov - One of the best experts on this subject based on the ideXlab platform.
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Excess Vacancy generation in silicon during surface silicide formation
Applied Surface Science, 1993Co-Authors: A G Italyantsev, Yu A KuznetsovAbstract:Abstract A model for Vacancy injection into a silicon wafer during surface silicide formation is proposed. It was found theoretically, that for the typical silicide growth rates, and temperatures of 600–700°C, the Excess over the equilibrium concentration C∗v can reach values of (106–107) C∗v, which in turn was confirmed experimentally using data on Sb redistribution in silicon underlying a vanadium-silicide contact.
S Abhaya - One of the best experts on this subject based on the ideXlab platform.
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evidence for Excess Vacancy defects in the pd si system positron annihilation x ray diffraction and auger electron spectroscopy study
Journal of Physics: Condensed Matter, 2003Co-Authors: S Abhaya, G Amarendra, G L N Reddy, R Rajaraman, K L NarayananAbstract:The transformation of Pd/Si to Pd2Si/Si is investigated using depth-resolved positron annihilation, x-ray diffraction and Auger electron spectroscopy studies. The observed defect-sensitive positron S-parameter value of 1.022–1.054 indicates the existence of divacancies across the silicide/silicon interface and Si substrate region. Our experimental observation of Vacancy defects is consistent with the model proposed for Excess Vacancy generation across the interface consequent to Si diffusion.
C S Pande - One of the best experts on this subject based on the ideXlab platform.
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diffusion and Excess Vacancy production in cu ni laminates
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2003Co-Authors: R A Masumura, B B Rath, C S PandeAbstract:Abstract The Excess Vacancy concentration in a periodic laminate structure is examined by modifying Darken's equations for a finite sized binary diffusion couple. These equations are solved numerically for the Excess or supersaturated Vacancy concentration in a Cu–Ni laminate structure. A measure of potential pore condensation is also examined and compared with experimental results.
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analysis of cu ni diffusion in a spherical geometry for Excess Vacancy production
Acta Materialia, 2002Co-Authors: R A Masumura, B B Rath, C S PandeAbstract:Abstract Darken’s equations are formulated for a spherical geometry and used to examine Excess Vacancy formation for a Cu–Ni binary system. A subsequent numerical analysis is performed to solve for the Excess (above the local thermodynamic equilibrium) vacancies. The results indicate a propensity for pore formation due to the presence of supersaturated vacancies.
