Abstract
We report the first characterization of the internal structural features within rhombohedral nanocrystals of hematite (α-Fe2O3), specifically nanoscale pores (nanopores) within these crystals observed by high-angle annular dark-field scanning transmission electron microscopy tomography. Threedimensional observations of the internal structure of hematite nanocrystals suggest that the nanopores are formed due to a large reduction in solid volume during the transformation of a poorly crystalline precursor [aggregates of ferrihydrite: Fe8.2O8.5(OH)7.4·3H2O], which results in the formation of pores between grain boundaries. This formation mechanism is different from those previously reported, such as hollow cores originating from screw dislocations. We also discuss dissolution experiments of the hematite nanocrystals in ascorbic acid solution, in which we demonstrated that the nanopores are reactive sites for dissolution and enlarged by preferential etching. Our findings are of fundamental importance to understanding how certain crystal morphologies, internal structures, defects, and reactive sites occur in nanocrystals formed from a poorly crystalline precursor.
© 2015 by Walter de Gruyter Berlin/Boston
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Articles in the same Issue
- H/D isotope effects in brucite at low temperatures
- Coupled H and Nb, Cr, and V trace element behavior in synthetic rutile at 600 °C, 400 MPa and possible geological application
- Dissolution-reprecipitation vs. solid-state diffusion: Mechanism of mineral transformations in sylvanite, (AuAg)2Te4, under hydrothermal conditions
- Compression and structure of brucite to 31 GPa from synchrotron X-ray diffraction and infrared spectroscopy studies
- Full analysis of feldspar texture and crystal structure by combining X-ray and electron techniques
- Correlating planar microstructures in shocked zircon from the Vredefort Dome at multiple scales: Crystallographic modeling, external and internal imaging, and EBSD structural analysis
- A spectroscopic and carbon-isotope study of mixed-habit diamonds: Impurity characteristics and growth environment
- Thermal infrared and Raman microspectroscopy of moganite-bearing rocks
- Mineralogical characterization and formation of Fe-Si oxyhydroxide deposits from modern seafloor hydrothermal vents
- Cathodoluminescence properties of quartz eyes from porphyry-type deposits: Implications for the origin of quartz
- Microbeam X-ray analysis of Ce3+/Ce4+ in Ti-rich minerals: A case study with titanite (sphene) with implications for multivalent trace element substitution in minerals
- Aluminum ordering and clustering in Al-rich synthetic phlogopite: The influence of fluorine investigated by {19F/1H} 29Si CPMAS NMR spectroscopy
- DFT+U investigation of the catalytic properties of ferruginous clay
- A thermodynamic model for silica and aluminum in alkaline solutions with high ionic strength at elevated temperatures up to 100 °C: Applications to zeolites
- Nanopores in hematite (α-Fe2O3) nanocrystals observed by electron tomography
- Berthierine-like mineral formation and stability during the interaction of kaolinite with metallic iron at 90 °C under anoxic and oxic conditions
- An X-ray diffraction study of the pressure-induced hydration in cordierite at 4–5 GPa
- Natural occurrence of keatite precipitates in UHP clinopyroxene from the Kokchetav Massif: A TEM investigation
- High-pressure Raman spectroscopy, vibrational mode calculation, and heat capacity calculation of calcium ferrite-type MgAl2O4 and CaAl2O4
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- Zircon growth and recrystallization during progressive metamorphism, Barrovian zones, Scotland
- Saltonseaite, K3NaMn2+Cl6, the Mn analogue of rinneite from the Salton Sea, California
- Rongibbsite, Pb2(Si4Al)O11(OH), a new zeolitic aluminosilicate mineral with an interrupted framework from Maricopa County, Arizona, U.S.A.
- Quadratite, AgCdAsS3: Chemical composition, crystal structure, and OD character
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