Catalytic Effect of CaF₂ Nanoparticles on Sintering Behavior of Kaolin‐Based Materials

Abstract

The present work represents preliminary results concerning the effect of nanometric CaF2 particles on the sintering behavior of kaolin. The nanoparticles were synthesized using aqueous solutions of CaCl2 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 CaF2 (from 0.625 to 5.0 wt%) and the mixtures were milled, pressed, and sintered. From sintering experiments, it was observed that additions of CaF2 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 CaF2 was incorporated. Besides, adding 1.25% of nanometric CaF2 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.