Studies of calciomagnetite phase by means of thermal analysis

Abstract

Iron oxides doped with calcium occur in such natural metallurgical materials as sinters and lumps for the blast furnace process. In this work the Ca-doped magnetite phase Fe3 _yCayO4 with 0 < y <~ 0.55 was produced and studied as a pattern phase for investigation of the magnetit0 phase in sinters.The synthesis process was studied by means of simultaneous thermal analysis, while the synthesized products were studied by diffraction analysis, scannipg and optical microscopy, and spectral analysis in microareas.The solubility limits for Ca in magnetite were estimated, and an explanation of the shapes of the thermal curves was given.A precise identification of the oxide phases in blast furnace sinters is very difficult, due to the complex and inhomogeneous chemical composition of the phases.A possible modification of the blast furnace technology could be reached only if the properties of all the phase components of the sinter are known. Therefore, in this study we first synthesized a sinter with chemical composition close to that of the blast furnace sinter and determined its physico-chemical properties. This enabled us to find a proper investigation techniquewhich could be applied to study some blast furnace sinters.The magnetite phase doped ~vith calcium was produced and then studied as a pattern phase for the subsequent investigations of the magnetite phase in the blast furnace sinter.

Application of thermal analysis for the investigation of calcium ferrites

“…The most stable and the least reducible is Ca2Fe205 [8], which forms at higher temperatures than CaFe204. Both ferrites appear in the intergranular space of calciomagnetites and calciowustites obtained by reduction or synthesis [9,10]. The parallel thermal analyses demonstrate the complexity of both above-mentioned processes.…”

Signatures in magnetites formed by (Ca,Mg,Fe)CO3 thermal decomposition: Terrestrial and extraterrestrial implications

“…Vidyasagar et al (1984) demonstrated that a variety of complex metal oxides, including calcium ferrite (CaFe 2 O 4 ) and brownmillerite (Ca 2 Fe 2 O 5 ), can be produced by the thermal decomposition of CaCO 3 -FeCO 3 solid solutions under air or oxygen at >400°C. Calcium magnetite has been synthesized at high temperature from CaO-or calcite-hematite melts (Hrynkiewicz et al, 1971;Orewczyk and Jasienska, 1987;Orewczyk et al, 1995;Orewczyk, 2000), and low-temperature Ca-magnetite is documented in the remediation of acid mine drainage waters (Wang et al, 1996;Morgan et al, 2003).…”