Preparation and characterization of solvent-free Fe ₃O ₄ nanofluids

The surfactant was used to functionalize the nanoparticles to prepare solvent-free nanofluids. To prevent Fe ₃O ₄ nanoparticles from agglomerating and improve the dispersion of Fe ₃O ₄ nanoparticles, the solvent-free Fe ₃O ₄ nanofluids were synthesized through surface modification. Magnetic Fe ₃O ₄ nanoparticles were firstly prepared by chemical co-precipitation method. Then graft the quaternary ammonium salt (CH ₃O) ₃Si(CH ₂) ₃ N ⁺ (CH ₃) ₂(C ₁₈H ₃₇) Cl ^-, which has silanol groups, on Fe ₃O ₄ nanoparticles with hydroxyl groups. Finally, the chloridion was replaced with the anion C ₉H ₁₉-C ₆H ₄ (OCH ₂CH ₂) ₂₀O (CH ₂) ₃ SO ₃ through an ion-exchang process. An organic layer was formed on the surface of Fe ₃O ₄ nanoparticles, and made the Fe ₃O ₄ nanoparticles from black powder to brown fluid(at room temperature). The solvent-free Fe ₃O ₄ [KG*3]nanofluids were characterized by X-ray diffraction, Fourier transform infrared spectrum, differential scanning calorimetry, thermogravimetric analysis, transmission electron microscopy and rheometer. The Fe ₃O ₄ nanoparticles were monodispersed in solvent-free nanofluids, and the content of Fe ₃O ₄ nanoparticles in the nanofluids proved to be about 12%. The loss shear modulus G″ was higher than the storage shear modulus G'.