Abstract
Porous magnetite (Fe3O4) nanospheres are successfully prepared through a one‐pot solvothermal method with a gas‐bubble‐assisted Ostwald ripening process. The formation mechanism is explored by studying the reaction parameters, including the concentration of the precipitating agent, capping agent, and urea gas source for a fixed reaction temperature and time. The authors’ results show that the Fe3O4 nanospheres are composed of many primary nanocrystals, the sizes of which are well regulated by urea concentration. As such, the size of the spherical primary nanocrystal determines the porosity of Fe3O4 nanospheres. Strong reflection loss of −49.2 dB is observed at 11.9 GHz for highly porous Fe3O4 nanospheres with a thickness of 2.7 mm due to multiple scatterings in void spaces and increased dielectric loss caused by higher interfacial polarization relaxation loss in the porous structure. The authors believe that the prepared porous Fe3O4 nanospheres are good candidates for electromagnetic absorption applications.
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