Colloidal Microwave Absorber based on Magnetic Fluid of Iron Oxide Nanoparticles

Magnetic nanofluid was prepared by dispersing iron oxide nanoparticles in aqueous medium. Water dispersible iron oxide nanoparticles were synthesized by solvothermal decomposition of iron (III) acetylacetonate [Fe(AcAc)3] in Polyethylene Glycol 400 [PEG] and Polyacrylic Acid (PAA). Crystal structure was investigated using X-ray Diffraction (XRD) and magnetic properties were measured by using Vibrating Sample Magnetometer (VSM). Further, the XRD and VSM data were successfully used to retrieve the crystallite size and size distribution from powder samples. Particle size and size distribution extracted from magnetization curve have been found to be consistent with XRD and AFM. Microwave absorption of magnetic nanofluid can be controlled through changes in volume fraction of nanoparticle in dielectric aqueous fluid. Microwave absorbing properties of iron oxide nanoparticles are evaluated and presented here. Reported approach is a first step toward the development of switchable absorbers to operate reversibly between different states (absorption in presence of magnetic fluid or transmission in absence of magnetic fluid) by movement of magnetic fluid under external magnetic field in air or in non-dispersive carrier liquid.