Papers by Author: C. Rossignol

Abstract: This work deals with the study of a new aluminum brazing process, called Galluminium. This technique, consisting in using gallium as a solder, is advantageous since it enables to braze at ambient air without flux. Indeed if the gallium coating is done mechanically, it descales the alumina layer and acts as a barrier against further reoxidation. Nevertheless, liquid gallium causes a severe aluminum embrittlement since it penetrates into the aluminum grain boundaries. We will show in this paper that this phenomenon has only a little impact on the mechanical resistance of the brazed joints since the amount of deposited gallium is enough low to avoid a severe embrittlement and the heat treatment (from 200°C to 600°C during several minutes) during brazing process dissolves gallium in the bulk.

Abstract: During the past few years, a pilot-scale spray pyrolysis set-up able to produce large quantities of submicronic powders (1kg/day) has been assembled in our laboratory. During the process, droplets of a precursor solution are dried and decomposed to the required compound. The presence of an additional soluble flux in the precursor solution permits to obtain agglomerate - free nanoparticles after washing the product. Therefore, pure zinc oxide nanoparticles have been successfully synthesized by adding lithium or sodium nitrates to the initial zinc nitrate solution. The nanoparticles have been characterized by X-ray diffraction, field-emission scanning electron microscopy, laser scattering size analyzer. The influence of the precursor solution composition and of the operating parameters on the morphology and the average size of ZnO nanoparticles is discussed.