Thermal behavior of samarium oxide – Ball clay mixtures for high macroscopic neutron capture cross section ceramic materials

Abstract The effect of the addition of samarium oxide (Sm2O3) in the thermal behavior of (66%) kaolinitic ball clay was studied and compared with the pure clay. The incorporation of Sm2O3 is of technological interest for the design of smart traceable ceramic proppants used for unconventional gas and oil well stimulation. These high macroscopic neutron capture cross section proppants are used to obtain relevant information, such as the location and height of the created hydraulic fractures, through a neutron based detection technology. The study comprised a set of thermal analysis up to 1400 °C and the sintering behavior of the clay, up to 5% of addition. The developed texture and microstructure was also assessed. A simple mechanical characterization was performed as well. No important effects in kaolinite dehydration temperature (500–600 °C); and mullites formation (primary and secondary) were observed (990 and ≈1200 °C). The sintering range of the studied clay is 1080–1360 °C; the 5% wt. addition resulted in 80 °C decrease of the final sintering temperature, due to the more active flux nature of the added oxide. Mixtures fired at 1250 and 1400 °C resulted in dense ceramic materials with mullite as principal crystalline phase accompanied by quartz and cristobalite; imbibed in a viscous glassy phase which was proportionally increased by the added oxide. The mullite content and cell parameters were not affected. No samarium containing binary or ternary crystalline phases were detected, inferring that the rare earth is dissolved by the active viscous glassy phase thermally formed from the clay crystalline phases. No significant effect was observed in the spherical diametral compression test. Low concentration addition of the oxide did not affect the porosity or water absorption of the developed ceramics. Only the 5% wt. addition resulted in a noticeably higher de-sinterization with the appearance of macro-porosity if fired at 1400 °C.