Thermorheological properties of nano-magnetorheological fluid in dynamic mode: experimental investigation

In this work, the field-dependent rheological properties of a nano-sized magnetic particle-based ferrofluid (NMPFF) are experimentally investigated in dynamic mode at different temperatures. This NMPFF has several inherent rheological properties such as improved shear thinning, elevated dynamic moduli, and thermo-rheological complexity. These properties come from the presence of a long chain- like structure in the NMPFF under the influence of an applied magnetic field. The proposed NMPFF is a magnetic colloidal suspension of a mixture of two different nano-sized magnetic particles, which are dispersed in a carrier liquid in an appropriate weight fraction. The structural and morphological properties of the particles are firstly investigated using small-angle neutron scattering and a transmission electron microscope, respectively. Subsequently, the temperature-dependent rheological properties of the NMPFF are measured in an oscillatory mode using the magneto-rheometer. In the amplitude sweep test, it is observed that as the temperature increases due to the thermal expansion of the carrier liquid, the structure continuously expands up to critical temperature. In the frequency sweep test, it is found that the magnitude of the storage modulus is nearly constant with increasing temperature. (technical note)