Preparation and characterization of a novel MR fluid with MWCNTs/GO composites coated ferromagnetic particles

Magnetorheological (MR) fluid is a typical intelligent material which is widely adopted in the mitigation of civil engineering structures, and it is normally composed of nano-sized or micro-sized iron particles, carrier fluids and additives. In the study, ferromagnetic particles coated with multi-walled carbon nanotubes (MWCNTs) and graphene oxide (GO) composites were prepared with grafting technology and the influence concerning ratio of MWCNTs, GO, grafting agent as well as carbonyl iron (CI) particles was studied to select the composite ferromagnetic particles which have the best effects of coating through surface topography analysis. In addition, the MWCNTs/GO composites coated CI particles and surfactants-modified CI particles were combined together to prepare a series of MR fluids with different ratio of the two compound ferromagnetic particles, volume fraction of total ferromagnetic particles and additives by the control variable method and the influence of the factors on the performances of MR fluids was investigated through sedimentation stability, re-dispersion, zero field viscosity and shear yield stress tests. The test results presented that the introduction of MWCNTs/GO composites coated CI particles was beneficial to the improvement of stability with sedimentation rate lower than 6%.