Preparation and characterization of water-based ultra-high density Fe₃O₄ magnetic fluid

Ultra-high density magnetic fluid has broad application prospects in the field of aerospace, sealing and mineral flotation. We using the method of chemical co-precipitation, prepared ultra-high density Fe₃O₄ magnetic fluid by separating redundant base solution. The samples were characterized by XRD, TEM, VSM and rotary viscometer. Results and their analysis showed preliminarily that: (1) the Fe₃O₄ nanoparticles in the Ultra-high density magnetic fluid were inverse spinel structure with average particle size of 15 nm; (2) the viscosity in the saturated magnetic condition, viscosity range and saturation magnetization of the ultra-high density magnetic fluid achieved 5.64 Pa·S, 0.82~5.64 Pa·S, and 51.2 emu·g^-1, and they are respectively 564 times, 60 times, and 7 times those of the ordinary magnetic fluid; There is a significant linear correlation between the change of saturation magnetization and the magnetic particle content; (3) when the temperature changed from 20°C to 80°C, the density of the ultra-high density magnetic fluid changed merely from 4.985 2 g·cm^-3 to 4.9827 g·cm^-3.