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Electron microscopy of nanoparticles for lead-free soldering prepared by wet chemical synthesis
Buršík, Jiří ; Škoda, D. ; Vykoukal, V. ; Sopoušek, J.
The nanoparticles of pure metals and alloys exhibit the depression of the melting point compared to bulk material, hence they are able to aggregate and to from firm interlayer joints at low temperatures. Exploiting this effect in soldering industry can save energy, work and materials. Using emulsions with nanopowders might be the solution of demanding task of replacing classical Sn-Pb solders by their lead-free substitutes. In this work, Ag- and Sn-based nanopowders were prepared as potential low-toxic constituents of novel solders by a chemical wet synthesis from chemicals of high purity. Various ways of preparation and further storage of the product were examined. Resulting nanoparticles (their size distribution, morphology and tendency for clustering) were characterization by means of scanning and transmission electron microscopy.
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Simulated element redistributions in Ni-based superalloys weldments
Brož, P. ; Buršík, Jiří ; Sopoušek, J. ; Picha, R.
The diffusion and phase precipitation processes in welded joints of pure Al-Cr-Ni system and low alloyed Al-Cr-Ni-X systems (where X means Co, W, or Ti) were simulated using CALPHAD method and DICTRA software. The equilibrium calculations allowed to predict phase diagram cross-sections for the Al-Cr-Ni-X systems. The performed simulations based on local equilibrium condition in diffusion couple enabled to describe the phase transformation process and obtain redistribution of alloying species, activity profiles, and other time-distance dependences for other relevant values in diffusion-affected zone of the Al-Cr-Ni / Al-Cr-Ni-X weldments.
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