Electrorheology of urea-functionalized lathlike goethite particles in silicone oil

Electrorheological fluids (ERFs) are smart materials with unique rheological properties tuned by the application of electric fields. Initially discovered in the late 1940s, ERFs have been studied for applications in various fields, including engineering and biomedicine. However, challenges such as unstable response and high production costs have hindered their widespread use. This paper explores the synthesis and characterization of ERFs based on goethite, an abundant and inexpensive iron oxyhydroxide, investigating the impact of urea functionalization on its properties. Goethite nanostructures have been successfully synthetized and dispersed in silicone oil, with subsequent characterization using techniques such as scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), and rotational electro-rheology. The experimental results indicate the successful synthesis of lath-like goethite nanostructures and the effective surface functionalization with urea. The electrorheological characterization reveals enhanced rheological properties in urea-doped ERFs, suggesting the potential for optimizing and reducing the concentration of the filler with respect to undoped materials to match the desired performances. The problem of the electrical conductivity of these systems has also been adequately taken into consideration, which must be kept as low as possible for them to be usable in practical applications. UNCLASSIFIED – Based on foreground information under EDA contract no. B.PRJ.RT.980 covering the Ad Hoc Project entitled “COMMON-LINK”. • Lath-like goethite nanoparticles have been successfully synthesized and purified to show low electrical conductivity. • Lath-like goethite nanoparticles have been functionalized with urea. • Stable dispersions of bare and urea-functionalized goethite nanoparticles in silicone oil have been obtained. • The electrorheological characterization showed enhanced rheological properties in suspensions based on urea-functionalized nanoparticles.