Fly Ash/Rare Earth Oxide Coatings by EPD: Processing and Characterization

Novel materials that can be used as thermal barrier coatings in high temperature applications were obtained by homogenization, mechanical milling and thermal treatment. Samarium oxide was investigated as an alternative to react with the free silica from fly ash and to form new silicate compounds. The main phases found in fly ash-Sm2O3 mixtures were mullite and samarium silicate Sm4.66O(SiO4)(3). Electrophoretically deposited coatings from these materials were obtained at 50 V and 3 minutes deposition time. The surface microstructure of the coatings was characterized by scanning electron microscopy (SEM-EDXS). The coatings were homogeneous and showed no crack formation. Additionally, thermal conductivity of the bulk samples at room temperature was determined. The thermal conductivity values of the new materials were below 1 W/mK which makes them suitable for thermal and environmental barrier applications.