Metastable d-Fe During Reduction of Ferric Oxide and its Magnetic Properties
Journal Article - Open Access
NAVAL RESEARCH LAB WASHINGTON DC WASHINGTON United States
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Metallic iron exhibits three distinct crystallographic phases, -bcc, -fcc, and -bcc, under variable temperature. In this paper, we show that iron oxide, in the hematite composition, Fe2O3, was reduced to its pure metallic form, using carbon obtained from the nut shells of pistachios or walnuts, at temperatures exceeding 1400 degrees C, annealed in argon gas atmosphere. In addition to -, -, and -phases of Fe, x-ray diffraction analysis shows the presence of carbon nanotubes CNTs and amorphous carbon. There was no residual ferric oxide present as long as the appropriate ratios of nut shell powder to Fe2O3 were selected. The quantity of each of the three Fe phases was a function of the temperature and the time of processing. Transmission electron microcopy revealed the presence of large quantities of CNTs formed during annealing. Magnetic data suggested the average magnetic moment was consistent with -Fe, but reduced moment for both the -Fe and -Fe. This is the first observation of producing -Fe stable at room temperature along with CNTs. This has potential industrial applications as composites. Although both - and -ferrites are body-centered cubic, -ferrite is a more compact structure indicative of higher specific density and hence improved mechanical properties. In addition, the magnetic and structural properties of the metastable Fe provide insights in understanding the novel properties of artificial structures on the nanometer scale made using advanced thin film techniques.
- Electricity and Magnetism
- Refractory Fibers