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Solvothermal synthesis, characterization, and magnetorheological study of zinc ferrite nanocrystal clusters

In this study, zinc ferrite (ZnFe2O4) nanocrystal clusters were synthesized successfully with a surfactant-assistant solvothermal method and investigated as a potential magnetorheological material. The morphology, structure, and magnetic properties of the obtained ZnFe2O4 nanocrystal clusters were investigated in detail using a scanning electron microscope, transmission electron microscope, X-ray diffraction, and superconducting quantum interference device. It was found that the ZnFe2O4 nanocrystal clusters showed well-defined shape and homogeneous dispersion with narrow size distribution of 276 nm in diameter. The field-dependent magnetization curve indicated superparamagnetic properties of as-prepared ZnFe2O4 nanocrystal clusters with saturation magnetization (Ms) of 86.6 emu/g at room temperature. The magnetorheological fluid with 25% particle mass fraction was prepared by ZnFe2O4 nanocrystal clusters, and the corresponding magnetorheological properties were also tested using a Physica MCR301 rheometer fitted with a magnetorheological module. The prepared magnetorheological fluid changed from a liquid-like to a solid-like state under an external magnetic field, suggesting typical Bingham plastic behavior. Compared with conventional carbonyl iron particles, ZnFe2O4 nanocrystal clusters–based magnetorheological fluid showed enhanced sedimentation stability. The obtained ZnFe2O4 nanocrystal clusters are considered as an ideal candidate for magnetorheological fluid with typical magnetorheological effect as well as improved sedimentation stability.