Oxidation induced strain and defects in magnetite crystals

Abstract

Oxidation of magnetite (Fe3O4) has broad implications in geochemistry, environmental science and materials science. Spatially resolving strain fields and defect evolution during oxidation of magnetite provides further insight into its reaction mechanisms. Here we show that the morphology and internal strain distributions within individual nano-sized (~400 nm) magnetite crystals can be visualized using Bragg coherent diffractive imaging (BCDI). Oxidative dissolution in acidic solutions leads to increases in the magnitude and heterogeneity of internal strains. This heterogeneous strain likely results from lattice distortion caused by Fe(II) diffusion that leads to the observed domains of increasing compressive and tensile strains. In contrast, strain evolution is less pronounced during magnetite oxidation at elevated temperature in air. These results demonstrate that oxidative dissolution of magnetite can induce a rich array of strain and defect structures, which could be an important factor that contributes to the high reactivity observed on magnetite particles in aqueous environment.

Characterization and identification of Au pathfinder minerals from an artisanal mine site using X-ray diffraction

“…Au associated with Fe 3 O 4 is mostly formed in skarns of granular magnetite usually found in contact with metamorphosed areas with magma intrusion into carbonate or silico-carbonate rocks that also [45]. The same color of Fe 2 O 3 in comparison with black Fe 3 O 4 makes it difficult to distinguish between the two in branded iron formations and standing water [44,46]. It is likely that during the formation of Fe-oxides in the alluvial regime at the Dunkwa-Kubi geological site, Au is internally captured within structures associated with Fe 2 O 3 (hematite) that acts as crusts in saprolite and laterite environments.…”

“…consist of garnet and silicate minerals, among others. The residual black sand together with other dense minerals is considered to be ore that is left over during Au refinement and washing at riverbanks when recovering its Au content[44]. This shows that two of the three most common iron ore minerals; Fe 3 O 4 and Fe 2 O 3 are widely spread within the mining site and contribute to the Au host minerals alongside SiO 2 .…”

Endogenous Nanoparticles Strain Perovskite Host Lattice Providing Oxygen Capacity and Driving Oxygen Exchange and CH4 Conversion to Syngas

“…A way to further increase strain would be to take advantage of the different redox expansion of the perovskite phase and the embedded Ni phase [39] . That is, upon oxidation, the Ni lattice expands by about 15% due to oxygen incorporation.…”

Annealing of focused ion beam damage in gold microcrystals: an in situ Bragg coherent X-ray diffraction imaging study

“…Previously, BCDI has been used to investigate annealing of 3C-SiC nanoparticles (Hruszkewycz et al, 2018), diamond nanoparticles (Hruszkewycz et al, 2017), magnetite crystals (Yuan et al, 2019) and metallic glass (Chen et al, 2020). Furthermore, BCDI has been extensively used to study Au subject to iron diffusion (Estandarte et al, 2018), copper diffusion (Xiong et al, 2015) and catalytic oxidation (Suzana et al, 2019).…”