High-temperature transformations of Zr-pillared bentonite

Abstract

A Zr-modifed bentonite (B-OHZr) obtained by intercalation of OH-Zr species was obtained, and its thermal transformations at >800 °C were studied. Raw clay and B-OHZr were characterized by X-ray difraction, thermogravimetric and diferential thermal analysis, and its sintering behavior was studied by hot-stage microscopy. Two Zr-based phases—tetragonal zirconia and zircon—were observed in thermally treated B-OHZr with a sharp decrease in amorphous glassy phase in comparison with the parental clay. An increase in refractoriness was observed in B-OHZr, enabling the sintering of samples up to 1300 °C, while the parental clay bloated and deformed with thermal treatment. The Zr interlayering enhanced the refractoriness at high temperatures of the parental clay, eliminating thermal expansion (bloating) and enabling sintering at T>1000 °C. The observed features and thermochemical processes enlighten the temperature usage range of these kinds of materials. Finally these results yield promising features for potential use of these clays for the preparation of ceramic materials with zircon content.