Catalytic Effect of CaF ₂ Nanoparticles on Sintering Behavior of Kaolin‐Based Materials

The present work represents preliminary results concerning the effect of nanometric CaF 2 particles on the sintering behavior of kaolin. The nanoparticles were synthesized using aqueous solutions of CaCl 2 dissolved with an organic dispersant and HF. The morphology and particle size of the obtained nanoparticles were square‐like, having a mean length of 25 nm. Kaolin was mixed with different amounts of nanometric CaF 2 (from 0.625 to 5.0 wt%) and the mixtures were milled, pressed, and sintered. From sintering experiments, it was observed that additions of CaF 2 nanoparticles in kaolin clay could shift the phase transition temperatures to lower values. Specifically, the densification temperature could be reduced by almost 150°C when 2.5 wt% of CaF 2 was incorporated. Besides, adding 1.25% of nanometric CaF 2 can achieve that compressive strength augments from 125 to 185 MPa in kaolin samples sintered at 1200°C, meaning an improvement of 40% in the properties of the final material.