Praperation of Fe3O4 Hexane Ferrofluid with Phase-transfer Method

A novel and facile phase-transform method has been presented for the preparation of double-coated Fe3O4 hexane ferrofluid. Firstly, the double-coated Fe3O4 nanoparticles were synthesized via chemical coprecipitation and excess sodium oleate were used as surfactant to yield a stable water-based magnetic fluid. Based on this, hydrophilic Fe3O4 nanoparticles were transformed into hydrophobic ones which were extracted to hexane by adding acetic acid. Fourier transform infrared(FTIR) spectra show that -COO- at the outer layer of Fe3O4 nanoparticles transforms into -COOH at proper pH value adjusted by acetic acid, which makes Fe3O4 nanoparticles hydrophobic and dispersive in polar or nonpolar carrier liquid. X-Ray diffractometer (XRD), vibrating sample magnetometer(VSM) and transmission electron microscope(TEM) were also used to characterize the magnetic nanopartieles and the ferrofluid. Our method ensures that Fe3O4 nanoparticles are coated compactly and mono-dispersive state without any agglomeration, which makes the thus obtained hexane ferrofluid stable and less delamination after several months. The ferrofluid with different solid content and dispersed in other oil-based carriers can be obtained through evaporating n-hexane.