Production of nanomaterials using highly concentrated solar radiations

Abstract
Oxide nanomaterials have been prepared by two processes using solar furnaces (specially usefull when the melting point of the material is high) : the vaporization-condensation in solar reactors leading to nanophases and the splat-cooling from the melt leading to nanostructured materials. The first method is efficient when the vapor pressure of the material is high. Oxide nanophases have been prepared by this way and characterized by X-ray diffraction and High Resolution Electron Microscopy. Some examples are shown (ZnO, γ-Fe₂O₃, yttria dopi zirconia). The second method is called "splat cooling" ; it leads to nanomaterials (stripes or rough powders depending on the viscosity of the melt) which can be amorphous or nanostructured (depending on the composition). Nanosize powders can be obtained from that by ball-milling. Bulk nanomaterials can be prepared by sintering the powders. This method is specially well adapted to prepare yttria-doped zirconia/alumina nanocomposites but it has also been applied to prepare (Nd or La)_1-xSr_xMnO_3±δ nanomaterials.