Abstract
In present study, aligned α-Fe2O3 nanowires were synthesized successfully by using of α-Fe2O3 commercial powder. And 1-D α-Fe2O3 nanostructures were also selectively grown on Si wafer. According to experiment results, composition of substrate, temperature, gas flow, and relative position were the factors could cause various morphologies of α-Fe2O3 nanomaterials. TEM and EELS analysis indicated that there were axial long-range ordered oxygen vacancies inside the nanowire. The defects were considered as the channels for internal diffusion of iron atoms during growth. In addition, significant magnetocrystalline anisotropy was obtained by SQUID measurement. The field-emission of α-Fe2O3 nanowires was following F-N behavior with β value of 560 at low electrical field and of 1500 at high electrical field.Fe3O4 nanowires were synthesized by reduction of α-Fe2O3 nanowires with gas mixed of H2 and Ar. The reduction mechanism was based on modifying the stacking sequence of oxygen ions along the close packed direction. It was found that Fe3O4 nanowires were unstable at higher temperature, which would owing to the isotropic cubic structure of Fe3O4. About the magnetic properties, Fe3O4 nanowires displayed significant shape anisotropy.Introducing of gaseous Si or Ge during reduction process, the Fe3O4/oxide core-shell nanowires could be synthesized. And the oxidization of shell was due to the release of oxygen from inner nanowire during reduction.According to the observation from in-situ TEM, reduction of α-Fe2O3 to Fe3O4 at higher temperature in environment without oxygen was evidenced. Furthermore, the result demonstrated that the Fe3O4 naowires was unstable at high temperature.