Flame spheroidisation of dense and porous Ca2Fe2O5 microspheres†
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.