PREPARATION OF CERAMIC NANOPARTICLES BY CO2 LASER VAPORISATION

Functional ceramic nanopowders are prepared by means of CO2 laser vaporisation (LAVA) starting from coarse ceramic powders. Vaporisation proceeds in a continuously flowing process gas at normal pressure. The nanoparticles (NP) are formed as a result of rapid gas phase condensation. Selected LAVA nanopowders are presented as promising candidates for future applications, e.g. drug targeting and magnetic resonance imaging, load-bearing ceramic implants, and biological fluorescence labelling, respectively. Starting from a haematite powder, ferrimagnetic Fe2O3 nanopowders were prepared. It was found that, in an oxygen-free process gas, maghemite (gamma-Fe2O3) NP were formed. Applying oxygen as the process gas leads to the formation of gamma- and epsilon-Fe2O3 NP. Superparamagnetic composite NP were prepared from mixtures of haematite powder and quartz sand (SiO2). NP comprising an intraparticular dispersion of alumina and tetragonal zirconia (t-ZrO2) were obtained by vaporising a powder mixture of corundum (alpha-Al2O3) as the main component and t-ZrO2. Europium-doped strontium aluminate (SrAl2O4) NP were prepared from a mixture of strontia (SrO), corundum, and Eu2O3. The as-prepared amorphous NP reveal a red photoluminescence emission under excitation with UV radiation. Annealing in a reducing atmosphere yields a crystalline Eu2+:SrAl2O4 nanopowder showing an intense green emission.