Fabrication and magnetorheology of bidisperse magnetic microspheres coated with gelatin and multi-walled carbon nanotubes

Abstract

To improve the magnetorheological (MR) properties and dispersion stability of the carbonyl iron (CI) particles, bidisperse magnetorheological (BMR) fluids consisting of magnetic micron-sized CI and nanoparticles dual-coated with gelatin and multi-walled carbon nanotubes (MWCNTs) were synthesized for the first time. Gelatin was used as a grafting agent to improve the stability of bidisperse magnetic particles and restrict the oxidation of nanoparticles (Fe3O4). And a dense network composed of MWCNTs on the surface of gelatin-coated bidisperse particles was fabricated based on the self-assembly of MWCNTs to produce considerably rough surfaces. The influence of functional dual-coated layer on rheological performance such as shear stress and yield stress behavior was investigated by a rotational rheometer upon various magnetic field applications. Additionally, the dispersion stability was measured through sedimentation tests. The results showed that CI–Fe3O4-Gelatin-MWCNTs (CI–Fe3O4–G–NT) magnetic microspheres possessed enhanced MR properties compared with those from CI–Fe3O4-Gelatin (CI–Fe3O4–G) microspheres, while the dispersion stability of CI–Fe3O4–G–NT microspheres was still maintained.