54 Microsc. Microanal. 22 (Suppl 5), 2016 doi:10.1017/S1431927616012290 © Microscopy Society of America 2016 Real Time Evolution of the Reduction of Ilmenite in H 2 : A Correlative In Situ and Ex Situ Study Arne Janssen, Eric Prestat and M. Grace Burke Materials Performance Centre, School of Materials, The University of Manchester, Manchester, UK. In situ TEM, particularly in situ high voltage electron microscopy (HVEM) has been utilised in the past to provide a unique perspective on the reduction of oxides. Since the early 1970’s when Tighe and Swann [1] reported the first in situ observations of iron oxide reduction in a special differentially- pumped gas reaction cell in an AEI EM 7 HVEM, there have been significant advances in the ability to perform detailed nanostructural and chemical analysis of materials in a gaseous environment at elevated temperatures. In this study the reduction of ilmenite (FeTiO3) in H2 has been examined using a special environmental heating and gas cell TEM holder in the analytical electron microscope (AEM). In addition, a complementary approach exploring the production of high-grade TiO 2 via an ex situ heat treatment and acid leaching has been examined for comparison purposes. Ilmenite is essential for the production of TiO2, which is widely used in ceramics, paints, paper and plastics. The high stability of ilmenite means that a combination of extensive energy-consuming methods such as heat treatment (both oxidising and reducing), mechanical activation and acid leaching are required to produce high quality synthetic TiO2. The pre-reduction treatment converts the mineral to TiO2 and the contained Fe 3+ and Fe 2+ to Fe. The present investigation is directed at generating fundamental information about the reduction reaction mechanism as well as elucidating the structural and chemical relationships at the nanometre scale during the oxygen transfer. The ilmenite used in this study was obtained from a bulk Norwegian hard-rock ilmenite mineral specimen, which was subsequently cut and ground with ethanol. To generate the appropriate TEM samples, droplets of this suspension were deposited on the surface of the heater E-chip. The real-time evaluation of ilmenite reduction was performed at 470 °C in 950 mbar H2 using the Protochips Atmosphere In Situ Heating and Gas Reaction Cell (Protochips Inc.). Analytical TEM investigation has been carried out using a spherical aberration corrected FEI Titan G2 80-200 with Super X EDX and X- FEG operated at 200 kV and equipped with a GIF Quantum ER. Energy Electron Spectroscopy (EELS) in STEM mode have been used to map selected areas to observe chemical changes during the reduction process. Electron loss near-edge structure (ELNES) analyses have been was used to extract O bonding information [2]. The obtained results revealed that the decomposition of ilmenite to Ti and Fe resulting in restructuring of the overall morphology of the initial grains (Fig1), with a non-uniform distribution of Fe particles on the surface due to volume diffusion of Fe towards the surface, as Ti is not mobile below 900 °C [3]. We have previously reported that the formation of porosity in the residual TiO2 is due to the volume reduction of nearly 40% associated with the ilmenite reduction [4]. Our ELNES analyses of the oxygen K-pre-edge indicated that most of the iron is still covalent bonded with oxygen and not reduced to metallic iron (Fig2). However, a complete reduction of Fe oxides can be accomplished at this temperature by a disproportionation reaction of FeO to Fe 3 O 4 to Fe [5]. Our in situ observations will be compared and discussed with respect to the analyses of the ex situ processed ilmenite [6]. https://doi.org/10.1017/S1431927616012290 Downloaded from https://www.cambridge.org/core. IP address: 54.163.42.124, on 09 Jun 2020 at 05:12:38, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms.