THE NATURE OF THE ELECTRORHEOLOGICAL AND ELECTROPHORETIC EFFECTS OF DETONATION NANODIAMONDS SUSPENSIONS IN MINERAL OIL

Qualitative differences in the nature of the electrorheological response of a detonation nanodiamonds suspensions in mineral oil depending on the type of particle surface functionaliza-tion were established from a number of rotational and oscillation tests. The type of modification and the chemical composition of the surface for particles of hydrogenated and carboxylated nanodiamonds were studied by infrared spectroscopy. Particles morphology and their structural organization in a mineral oil medium were studied by small-angle X-ray scattering method. It was found that suspensions of hydrogenated and carboxylated particles under an electric field exhibit an electrorheological and electrophoretic effects, respectively. The reasons for the electrophoretic motion of carboxylated nanodiamonds in a mineral oil medium were analyzed in comparison with the previously observed effect in the medium of weakly amphiphilic polydimethylsiloxane (silicon oil). The water content on the surface of both hydrogenated and carboxylated nanodiamond par-ticles was determined by Karl Fischer titration of suspensions. The correlation between the elec-trophoretic effect and the adsorbed water content on the surface of the particles was suggested. The method of rotational viscometry revealed the dependences of the static yield stress for sus-pensions filled with hydrogenated and carboxylated nanodiamonds at various electric field strength. The flow curves of the fluid filled with hydrogenated particles without and under an electric field were fitted by Bingham and Cho-Choi-Jhon rheological models. An analysis of the used models matching to practical results was performed. Based on the dependences of the stor-age and loss moduli on the deformation amplitude, a linear range of the viscoelastic properties of the fluid was revealed. An increase in the values of the storage and loss moduli, as well as a narrow-ing of the linear viscoelasticity range with an increase in the electric field strength was detected.