Large-scale synthesis of high-content Fe nanotubes/nanorings with high magnetization by H2 reduction process

•Single-crystal α-Fe2O3 hollow structures are synthesized by hydrothermal method.•As-prepared α-Fe2O3 NRs and NTs are reduced at various temperatures by 5% H2/95% Ar.•We investigate the influence of reduction condition to the structure of products.•We investigate the influence of reduction condition to magnetic property of products.•The Ms increases with increasing reduction temperature.

High-content Fe hollow nanostructures from nanotubes (NTs) to nanorings (NRs) have been successfully fabricated by reduction of α-Fe2O3 hollow nanostructures at designated temperature. We investigated the influence of reduction condition on the structure and property of the products. With increasing reduction temperature, α-Fe2O3 with rhombohedral phase could be converted to cubic inverse spinel phase Fe3O4. Thereafter the phase was converted to the dominant cubic Fe preserving the same morphology. The highest Ms is 126 emu/g and 123 emu/g for 70 nm NRs and NTs reduced at 450 °C, respectively. Our results provide a general strategy of reducing single-crystalline α-Fe2O3 hollow nanostructures to get high magnetization which is required for many applications.

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