Magnetorheology and sedimentation behavior of an aqueous suspension of surface modified carbonyl iron particlesAn original procedure and device used for the estimation of a sedimentation constant of magnetorheological fluids have been developed. Experiments that vary the volume concentration and particle size of the dispersed phase, as well as the viscosity of the dispersion medium, show the flexibility of the proposed procedure. A procedure for using this device to estimate the yield stress of these fluids is also described. The results given by our device are shown to be in good agreement with flow curves generated by a commercial rheometer.

In this study, the mechanical and thermophysical properties of carbon fiber-reinforced polyethersulfone are investigated. To enhance the interfacial interaction between carbon fibers and the polymer matrix, the surface modification of carbon fibers by thermal oxidation is conducted. By means of AFM and X-ray spectroscopy, it is determined that surface modification changes the morphology and chemical composition of carbon fibers. It is shown that surface modification dramatically increases the mechanical properties of the composites. Thus, flexural strength and the E-modulus of the composites reinforced with modified fibers reached approximately 962 MPa and 60 GPa, respectively, compared with approximately 600 MPa and 50 GPa for the composites reinforced with the initial ones. The heat deflection temperatures of the composites reinforced with the initial and modified fibers were measured. It is shown that composites reinforced with modified fibers lose their stability at temperatures of about 211 °C, which correlates with the glass transition temperature of the PES matrix. The thermal conductivity of the composites with different fiber content is investigated in two directions: in-plane and transverse to layers of carbon fibers. The obtained composites had a relatively high realization of the thermal conductive properties of carbon fibers, up to 55–60%.

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