Theoretical and Experimental Study on the Preparation of High-Viscosity Magnetic Nanofluid by Combined Surfactants

In this study, the mechanism by which combined surfactants affect the dispersion stability of magnetic nanofluids (MNFs) was improved. Two stable lubricating oil-based magnetic nanofluids with high viscosity and one with low viscosity were prepared by chemical coprecipitation. Erucic acid and octanoic acid were used as the combined surfactants to modify the Fe₃O₄ nanoparticles (MNPs). The size and morphology of the particles were observed using TEM. The rheological properties were tested with a rotational rheometer. The magnetization of the lubricating oil-based magnetic nanofluids was characterized by VSM. The results indicated that the prepared magnetic nanofluids had high viscosity, high magnetism, and good stability. This study provided ideas for the preparation of a high-viscosity magnetic nanofluid. By using combined surfactants, sufficient steric repulsion energy can be provided to counteract the attraction energy of sterically protected nanoparticles, thus achieving a balance of the dispersion stability of MNF.