(260az) Effect of Washing and Drying Process on Particle Growth of Cerium Oxide Nanoparticles

Cerium oxide nanomaterials have been used widely in many applications including catalyst, fuel cell electrolyte, chemical polishing, anti-oxidant due to their property of oxygen vacancy which is occurred by reversible redox reaction between Ce³⁺ and Ce⁴⁺. Because this chemical activity of cerium oxide arises from surface of particles, studies regarding surface properties of cerium oxide particles have been carried out up to this day. Particularly, many researchers have studied about synthesis of smaller cerium oxide nanoparticles to extend surface area per unit mass, or particle morphology control using additives and surfactant to expose more catalytic active crystal plane.

However, there are not enough studies how washing and drying processes affects growth of synthesized nanoparticles. This study has focused on washing and drying processes of cerium oxide nanoparticles, which are inevitable procedures for synthesized nanoparticles to be used in industry. Firstly, synthesis of surface modified cerium oxide nanoparticles was carried out using decanoic acid as surfactant and water as solvent under supercritical condition. And then synthesized nanoparticles were treated to wash out residual surfactant and solvent and to dry in the three different following manners; i) Evaporative drying after residual surfactant and solvent washing, ii) Freeze-sublimation drying after residual surfactant and solvent washing, iii) Supercritical CO₂ washing and drying. Samples obtained from different methods were analyzed by Cs-TEM(Spherical aberration corrected Transmission Electron Microscope) to observe particle size and shape. Particle morphology was also characterized by electron diffraction pattern of nanoparticles depending on three post-treatment methods. In result, it was concluded that nanoparticles growth could occur during washing and drying process and kind of post-treatment method also could affect degree of particle growth. Therefore, it is considered that washing and drying processes are also as important to control particle size and morphology as particle synthesis procedure.