Papers by Author: Loic Boulanger

Abstract: Reactive high energy ball-milling has known a growing interest from both fundamental and applied point of view. We focus here on the specific system Fe-Y₂O₃ metal-oxide nanocomposite because of its potential application to the synthesis of oxide dispersion strengthened steels, which are promising materials for nuclear applications. YFe₃ and Fe₂O₃ were ball-milled during different milling durations in the stoichiometric proportions defined by the chemical reaction 2 YFe₃ + Fe₂O₃ → 8 Fe + Y₂O₃. The obtained milled powder was characterized by XRD, SEM, TEM and their thermal behaviour was investigated by DTA. Through those characterizations, a Mechanically induced Self-propagating Reaction (MSR) was observed and several steps in the ball-milling process were identified: mixing of reactants, chemical reaction propagation, amorphization and refinement of the microstructure. The role of the milling intensity was also examined.

Abstract: Laser pyrolysis is a very suitable gas-phase process for the synthesis of a wide range of nanoparticles at laboratory scale. The principle of the method is based on the decomposition of gaseous or liquid reactants by a high power CO2 laser followed by a quenching effect. The literature reports the possibility to produce carbides, nitrides, oxides, metals and composites nanoparticles by this process. This paper reports a study of the effect of the laser intensity (using an innovative optical system) and of the gas flow rates on the characteristics (size and structure) of silicon carbide (SiC) nanoparticles produced at pilot scale (up to 1.13 kg/h) by using a mixture of silane (SiH4) and acetylene (C2H2). It has been shown that the decrease of the gas flow rate favors the increase of the mean grain size of the particles and that the increase of the laser intensity seems to provoke an increase of the mean crystal size and/or crystal number.