Structural and morphological study of Mn, Zn and Zr freeze-dried transition metal acetates

Abstract

Manganese (II) acetates tetrahydrate, zinc dihydrate and anhydrous zirconium, processed by freeze-drying, were heat-treated in free atmosphere at different temperatures and times, generating the main oxides of these metals. These acetates were structurally characterized by scanning electron microscopy (SEM), thermogravimetry (TG), differential scanning calorimetry (DSC) and, along with all the oxides generated, by X-ray diffraction (XRD). Calculations obtained from TG data showed that manganese acetate lost two waters after freeze-drying, also confirmed by X-ray data and that the same phenomenon may be occurring for zinc acetate. The results indicate that exothermic events occurred at lower temperatures for freeze-dried acetates, which may be related to the high surface area of the material, and consequent greater reactivity. The total decomposition temperatures of the acetates in the ZnO and ZrO2 semiconducting oxides and the manganese oxides Mn2O3 and Me3O4, with excellent crystallization, were obtained.