Magnesium Doped Hercynite: Preparation and Formation Mechanism

Abstract

We investigated the formation mechanism of magnesium doped hercynite during reaction sintering process at 1400 ºC. A two-step synthesis procedure based on combining of spinel and ferrous chloride was considered here. Firstly, magnesium aluminate spinel was prepared by sol-gel method, using Al and Mg chlorides as raw materials. Then, the powder particles were dispersed in an aqueous solution of ferrous chloride in 1.5:1 molar ratio and the solution was stirred at 60 °C. After solvents removal, the thermal properties of a sample of the dried specimens were studied, using simultaneous thermal analysis (STA) method. Afterwards, the specimens were calcined at 400, 800, 1100 and 1400 ºC for 1, 3 and 6 hrs, under air atmosphere. X-ray diffraction (XRD) analysis, field emission scanning electron microscope (FESEM) and X-ray fluorescence spectroscopy (XRF) were used for characterization of the specimens. Study of the obtained results leads us to conclude that hercynite was formed thorough a diffusion-based mechanism, when heated to high enough temperatures. After heating for a prolonged period (6 hrs.) at 1400 °C, hercynite decomposes into its constituent oxides and also a new crystal phase appears. This new phase was identified as FeAlO3. The modified Scherrer, Williamson-Hall and Rietveld methods are also used to estimate the crystallite size of the as-synthesized magnesium doped hercynite.

Evidence for the Disproportionation of Iron in a Eucrite Meteorite: Implications for Impact Processes on Vesta

“…The lack of silica grains and original mesostasis in NWA 11592 implies that the melt pocket studied here is not a result of crystallization of a residual igneous melt, but instead is likely a result of shock metamorphism (Barrat et al., 2007; Takeda & Graham, 1991). The presence of hercynite in the melt pocket suggests that the temperature should exceed ∼1,310°C (Rahmani‐Boldaji et al., 2018). Although the Dawn mission observed many craters on Vesta, only a few high‐pressure minerals have been confirmed in HEDs, and for these, likely equilibrium shock‐pressure conditions were generally lower than 15 GPa.…”

Palladium doped PDA-coated hercynite as a highly efficient catalyst for mild hydrogenation of nitroareness

“…Recently, hercynite has become a good candidate to make novel magnetic catalysts due to its large surface area, high capacity for adsorption of chemicals, magnetic character, and considerable physicochemical stability 14 , 15 . Moreover, it is synthesizable in the laboratory through various methods, including reaction sintering 8 , chemical vapor deposition 12 , microwave magnetic field (H-field) irradiation 16 , combustion 17 , molten salt 18 , co-precipitation, and sol–gel methods 19 . Due to its magnetic properties, hercynite is extensively considered as the magnetic core of a catalyst 20 , and the hydroxyl groups on its surface are suitable to be modified with various catalytic species 21 .…”