EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Zircon, or zirconium silicate (ZrSiO4), is a ceramic material widely known for its excellent thermal properties, such as low thermal conductivity and high resistance to thermal shock. This makes it an ideal material for obtaining coatings used as thermal barriers and other structural applications.

In this work, dense zircon complex shape parts have been obtained by means of polysaccharides gelation. For this purpose, concentrated solutions of the biopolymer agar, which is a natural biopolymer extracted from the cell walls of several species of algae and whose production involves a low environmental impact, were used. The colloidal stability study was performed for the zircon particles by means of Z-potential measurements as a function of both the pH and the concentration of a polyacrylic type anionic polyelectrolyte (PAA), which acts as a deflocculant. The rheological study of the different zircon suspensions was also carried out, varying the total solids content and the dispersant concentration, as well as the sonication mixing time. For this objective, the corresponding flow curves were measured first at room temperature and, once the conditions were optimized, the rheological study of the suspensions with the polysaccharide, which was added in solution, was performed. To conclude the rheological studies, the viscosity versus temperature curves were recorded for the zircon-agar mixtures, observing the gelation process of the material at around 35ºC. Once the green pieces were obtained, dynamic sintering (0 - 1600ºC) and static sintering (1550ºC and 1600ºC) tests were carried out, studying the shrinkage and densification of the material. Finally, the phases evolution study and the microstructural characterization of the sintered parts at different temperatures were performed using X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques.

This work has been financed by the Spanish Ministry of Science, Innovation and Universities (RTI2018-099033-B-C33, MCIU/AEI/FEDER, UE).