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hslining木虫 (正式写手)
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【原创】Opportunity for post-doctoral grant in Engineering of Materials
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The thematic project “Properties of amorphous, metastable and nano-structured metallic alloys”, supported by FAPESP (State of São Paulo Research Foundation;http://www.fapesp.br/english/) has a post doc position at the Department of Materials Engineering, Federal University of São Carlos, SP, Brazil. The project to be developed (“Analytical electron microscopy of Cu-based and Mg-based nano-composites”) involves the use of advanced techniques for structural and analytical characterization of amorphous, metastable and nano-structured metallic alloys. Interested researchers must send CV indicating experience with the electron microscopy techniques (desirable) and a list of publication in the last 2 years. Documents, in pdf format, must be sent to Prof. Walter José Botta Filho (wjbotta@ufscar.br). The value of FAPESP post-doctoral grant is R$ 4.508,10 and the period is 24 months. The summary of the thematic project is given below. Summary Properties of amorphous, metastable and nano-structured metallic alloys Metallic alloys with microstructures containing amorphous, metastable and nano-structured phases represent a new class of materials with surprising properties, which result both from intrinsic characteristics of the structure and from the presence and combination of phases produced by the compositions and by the different types of non-equilibrium processing techniques. The amorphous metallic alloys present excellent values of mechanical properties, however, acceptable ductility levels are observed only in alloys containing a small volume fraction of nanometric crystalline and/or metastable phases. In the nano-structured alloys, the mechanical properties are determined by the dimensions of the nanometric phases and by the presence of metastable phases, for example, quasicrystalline phases. Non-equilibrium processing of conventional alloys, such as very high cooling rates from the melt or high energy ball milling of solid phases, may result in the suppression of undesirable phases substituted by less-deleterious metastable phases. In particulate nano-composites the large area fraction of interfaces can modify completely the kinetics of reactions and/or transformations, with important consequences in several physical and chemical properties. In this context, the objective of this project is the detailed evaluation and optimization of mechanical properties of metallic alloys containing amorphous, metastable and nanostructured phases as a function of the microstructural characteristics of each system, and the properties of hydrogen absorption/desorption in nano-structured composites as a function of the presence of different catalysts. The amorphous metallic alloys of interest in our project are the bulk alloys, that is, with large glass forming ability, of several systems such as Cu-based, CuZr-based, Fe-based, Ni-based, NiNb-based and Ti-based and the main objective is the development and control of the micro-(nano)-structures that result in alloys with high mechanical strength and ductility. The nano-structured metallic alloys are Al-based containing several types of nano-dispersions, including the nano-quasicrystalline phases and we will be focusing on the optimization of the nano-structures to improve the thermal stability and mechanical properties. The conventional alloys of our interest are also Al-based, mainly Al-Si, which are important recycling alloys, and we will evaluate the processing conditions for selected suppression of deleterious fragile phases. The nanocomposites for hydrogen storage are based in Mg, Mg-Ni and Ti-Cr-V and we have as specific objective understanding the effect of catalysts and surface protecting layers on the decreasing temperature and increasing kinetics of hydrogen absorption/desorption of selected hydrides. Processing techniques for the production of non-equilibrium microstructures include rapid solidification, via melt-spinning, cooled metal mould casting, centrifuge casting, atomization (in this case, followed by warm-extrusion) or spray forming, and conventional and reactive high energy ball milling. The calorimetric and microstructural characterization are important aspects of this project since the mechanical properties and the properties of hydrogen absorption/desorption depend fundamentally on the presence, distribution and stability of the metastable and nanometric phases. As scientific result of our project we must contribute to the understanding of: (i) the ductilisation conditions of the amorphous metallic alloys containing dispersion of nanometric phases, (ii) the thermodynamic conditions for the control and/or suppression of certain phases in the nano-structured alloys and (iii) the fundamental mechanisms for the catalyses by the presence of nano- articles in nanocomposites for hydrogen storage. Finally, with our focus in the detailed study of properties, our project must also contribute to a careful evaluation of possible applications for the metallic alloys containing amorphous, metastable and nano-structured phases. [ Last edited by hslining on 2009-9-10 at 13:36 ] |
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