Flame spheroidisation of dense and porous Ca2Fe2O5 microspheres

Abstract

Compositionally uniform magnetic Ca₂Fe₂O₅ (srebrodolskite) microspheres created via a rapid, single-stage flame spheroidisation (FS) process using magnetite and carbonate based porogen (1 : 1 Fe₃O₄ : CaCO₃) feedstock powders, are described. Two types of Ca₂Fe₂O₅ microsphere are produced: dense (35–80 μm), and porous (125–180 μm). Scanning electron microscopy (SEM) based techniques are used to image and quantify these. Complementary high-temperature X-ray diffraction (HT-XRD) measurements and thermogravimetric analysis (TGA) provide insights into the initial process of porogen feedstock decomposition, prior to the coalescence of molten droplets and spheroidisation, driven by surface tension. Evolution of CO₂ gas (from porogen decomposition) is attributed to the development of interconnected porosity within the porous microspheres. This occurs during Ca₂Fe₂O₅ rapid cooling and solidification. The facile FS-processing route provides a method for the rapid production of both dense and porous magnetic microspheres, with high levels of compositional uniformity and excellent opportunity for size control. The controllability of these factors make the FS production method useful for a range of healthcare, energy and environmental remediation applications.