Papers by Author: Philippe Vermaut

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Authors: A. Béré, Philippe Vermaut, A. Hairie, E. Paumier, Piere Ruterana, Gerard Nouet
Authors: Frédéric Prima, Philippe Vermaut, I. Thibon, D. Ansel, Jean Debuigne, Thierry Gloriant
Authors: Richard Portier, Philippe Vermaut, Patrick Ochin, Tomasz Goryczka, Jorge Malarría
Abstract: The thermoelastic martensitic transformation which gives remarkable functional properties to Shape Memory Alloys (SMA) is very sensitive to the chemistry of the alloys and to its microstructure. In many cases, especially for alloys with high transformation temperatures, applications are limited by the poor ductility. To overcome the brittleness of SMA, one approach can be effective : the development of non conventional production technologies which enable to obtain materials in forms close to requirements: strips of SMA have been prepared by Twin Roll Casting (TRC). The formation of a solid sheet with plane surface is only possible for a limited combination of the different machine parameters and they will be discussed. For comprehension of the process parameters effect, the attention will be focused on TiNi. Microstructures and functional properties will be examined in relation with the microstructures induced by the technique or after specific thermal treatment.
Authors: Victor I. Kolomytsev, M. Babanly, Alexandre Pasko, A.P. Shpak, Tetjana Sych, P. Ochin, Philippe Vermaut, Richard Portier, Eduard Cesari, D. Rafaja
Abstract: A series of multielementary AB-type shape memory alloys, quaternary (Ti,Hf)50(Ni,Cu)50 and quinary (Ti,Zr,Hf)50(Ni,Cu)50, have been produced by means of the melt-spinning (ribbons), twin-roll casting (strips) and injection casting (bars) techniques. The glass forming ability (GFA) has been investigated by means of calorimetric studies (DSC, DTA), microscopic observations (TEM/SAD, SEM, XRD, optical microscopy) and deformation tests (bending, tension). The glass transition (Tg) and crystallization (Tx) temperatures with the corresponding supercooled liquid window ΔT = Tx – Tg have been determined for the mentioned rapid solidification techniques. GFA is found to be strongly dependent on specific ratio between the constituent alloying elements, with effective element A containing mixture of the early transition elements A = (Ti,Zr,Hf) and effective element B containing mixture of the late transition elements B = (Ni,Cu), respectively. We report a choice of the alloy composition, which is amorphous after fast cooling while recovers a reversible B2 ↔ B19 ↔ B19' martensitic transformation sequence and demonstrates shape memory and superelastic properties (up to MS ~ 400 K, AF ~ 450 K in the bulk material versus MS ~ 250 K, AF ~ 350 K in the ribbon and strip states) after an adequate thermal treatment.
Authors: Gerard Nouet, Philippe Vermaut, V. Potin, Piere Ruterana, A. Salvador, Hadis Morkoç
Authors: Philippe Vermaut, Patrick Ochin, A. Dezellus, Ph. Plaindoux, F. Dalle, Ph. Muguerra, Richard Portier
Authors: Aurelie Bessière, Fabienne Pellé, Claire Mathieu, Bruno Viana, Philippe Vermaut
Abstract: Y2O3:19%Yb,1%Er nanoparticles were synthesized with the aim of imaging the luminescent cell. Coprecipitation and combustion synthesis were used to obtain particulate sizes ranging from 25 up to 140 nm. The powders showed predominant red upconversion and the emission efficiency is controlled by the particle size. A colloidal route was also followed and 2-5 nm-large agglomerated nanoparticles were obtained. In that case, the luminescence of Er3+ was only observed by direct excitation and no upconversion light has been detected on these very small particles.
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