Preparation And Application Of Inorganic/organic Magnetic Suspensions

In this paper, Fe₃O₄/ethiodized-oil suspensions, strontium hexaferrite/polyurethane suspensions and microwave absorption magnetic suspensions were prepared and the properties of the obtained suspensions were systematically studied.(1) Fe₃O₄ nanoparticles (NPs) were prepared by co-precipitation, and were modified by four different surfactants. The modified Fe₃O₄ NPs were characterized by FT-IR, XRD, TEM, VSM and TGA. Thereafter, the modified nanoparticles were dispersed in ethiodized-oil by mechanical agitation and ultrasonic to gain stable Fe₃O₄/ethiodized-oil magnetic suspensions (MSs). The magnetic properties and stability of the MSs were characterized using a Gouy magnetic balance. The rheological properties of the Fe₃O₄/ethiodized-oil MSs were measured using a rotational rheometer. Furthermore, the inductive heating property of the MSs in an alternating current (AC) magnetic field was investigated and the results indicated that the heating effect of oleic acid stabilized Fe₃O₄/ethiodized-oil MSs was remarkable. It has a potential application in arterial embolization hyperthermia.(2) Strontium hexaferrite NPs were prepared by co-precipitation of strontium and ferric ions in the sodium hydroxide solution. The as-prepared NPs were determined to have perfect crystal structure, nanometer-scale size, high saturation magnetization and coercivity. Strontium hexaferrite/polyester-polyurethane magnetic suspensions (MSs) were prepared using a method of high-speed sand milling. The rheological behavior, magnetic properties and stability of magnetic suspensions (MSs) with different magnetic powder content have been studied. The MSs were spread to form wet films using an automatic coating machine. Then the cured magnetic coatings (MCs) were obtained after evaporation of the solvents under 50oC. The properties of MCs were investigated, such as surface tension, mechanical and thermodynamic properties. The experimental results indicated that the optimal content of magnetic powder is about 50g.(3) Fe₃O₄@dextran@SnO₂ multilayer magnetic microspheres were successfully synthesized by solvothermal and hydrothermal reactions. The synthesized magnetic microspheres were characterized by XRD, FT-IR, SEM, EDXA and VSM. Experimental results indicated that the microspheres were about 500 nm in size and well-defined in shape, and shown superparamagnetic property. The magnetic fluorocarbon suspensions were prepared by mechanical milling method using magnetic microspheres as the dispersed phase and fluorocarbon resin as the film-former. The basic properties, mechanical properties, morphology of the cured films were studied. The complex permittivity and permeability of the cured films were measured by vector network analysis from 2 GHz to 18 GHz. The maximum reflection loss of cured films can reach 20.26 dB at 4.72 GHz, and the bandwidth with a reflection loss less than -10 dB is 4.86 GHz with 4mm in thickness. The excellent microwave absorption properties of the films are attributed to the special multilayer structures of Fe₃O₄@dextran@SnO₂ magnetic microspheres and the effective complementarity between dielectric loss and magnetic loss.