Low-temperature synthesis of zircon by soft mechano–chemical activation-assisted sol–gel method

Abstract

Zircon (i.e., ZrSiO4) was synthesized by a sol–gel route at a low temperature with assistance of soft mechano–chemical activation of derived precursors in a high-energy density stirred bead mill. The reaction of precursors pretreated by soft mechano–chemical at different time in sol–gel process was analyzed. The samples were characterized by X-ray diffraction, Fourier transfer infrared spectroscopy, nitrogen gas adsorption method (BET), thermogravimetry, scanning electron microscopy and high-resolution 29Si nuclear magnetic resonance spectroscopy. The results show that zircon powder with a high crystallinity and a small grain size can be formed via soft mechano–chemical pre-activation and sol–gel route at a lower temperature. The specific surface area of calcined powder increases and the average crystalline size and mean surface particle size decreases with increasing the soft mechano–chemical treatment time. It is indicated that the soft mechano–chemical activation can accelerate the dehydration/dehydroxylation reactions, reduce the bonding degree of Si–O bonds, and break a certain extent of [SiO4]4− tetrahedral three-dimensional network, which is formed in the sol–gel reaction, thus enhancing the reactivity of precursors and facilitating the formation of ZrSiO4 from Zr4+ ions with [SiO4]4− tetrahedra during the subsequent thermal treatment at a lower temperature (i.e., 700 °C). XRD patterns of all the ground precursors fired at 700 °C. Soft mechano–chemical activation of precursor prepared in sol–gel route could decrease the subsequent sintering temperature of ZrSiO4. Compared to the precursor unactivated, ZrSiO4 powder with a high crystallinity was formed at a lower sintering temperature (i.e., 700 °C) for the precursor activated for 6 h.