Preparation and magnetic properties of Al2O3-coated acicular α-Fe particles

Abstract Al-modified acicular α -Fe particles were produced using the chemical precipitation method by adding Al ion on the surface of α -FeOOH. This was followed by air oxidation, dehydration, and hydrogen reduction processes. Various dehydration, reduction temperatures and times were also studied. The addition of Al ion impeded the interparticle sintering, spherization, and grain growth processes which were found to occur during dehydration and reduction. Consequently, i H c increased with the addition of Al ion, reached a maximum at 3 wt.% Al and later decreased again. The addition of Al ion always decreased the gs value of α -Fe particles. The addition of Al ion prevented the α -Fe particles from deteriorating. At room temperature, 3 and 1.5 wt.% of Al ions would be required, respectively, for stabilizing the σ and i H c values of α -Fe particles. At elevated temperature, i H c would deteriorate faster than the σ value.