| 초록 |
Processing of particle dispersion is frequently encountered in many areas such as paints, composite materials, ceramics, electronic industry, polymers and so on. Generally, the flow of particle dispersions shows highly non-Newtonian behaviors even though they are suspended in Newtonian medium [1, 2]. Moreover, the deviation from the Newtonian flow behaviors becomes pronounced at high volume fractions and under strong flow field. When the particle volume fraction is very low, the suspension behaves like a Newtonian fluid as the medium solvent. However, as the solid concentration increases, non-Newtonian behaviors are observed at high shear rates. Semi-dilute or moderately concentrated suspension displays shear thinning and high-shear-rate limiting viscosity. When the particles are highly concentrated, the suspension undergoes shear thickening in a continuous or discontinuous fashion by formation of three dimensional particle clustering. When the imposed flow becomes strong, a semi-dilute or moderately concentrated suspension displays shear thinning behavior and the high shear-rate limiting viscosity through the alignment to flow direction [3]. Meanwhile, shear thickening occurs in concentrated suspensions at high shear rates under which the ordered layered or string structure transforms into a disordered network structure by forming particle cluster [4, 5]. These phenomena were monitored by advanced experimental techniques such as small angle neutron scattering (SANS) [6] and dichroism [4, 5, 7]. However, the microstructure evolutions and related rheological behavior of the particle suspension have not been successfully explained yet especially in terms of the effects of stabilization of the particle dispersion, which is of practical significance. In the present work, the rheological behavior and phase stability were investigated for the silica suspensions stabilized by steric repulsive layer or elecrostatic repulsive force. |
