SIMULATION AND SANS STUDIES OF GELATION UNDER SHEAR

Computer simulations of a two-dimensional Lennard-Jones fluid undergoi ng spinodal decomposition are reported for the system subjected to pla nar Couette Bow. Key results are the images of the atomic structure an d plots of the corresponding pair correlation functions. A companion s mall-angle neutron scattering (SANS) study of shear-influenced gelatio n in colloidal silica suspensions at volume fractions phi = 0.1, 0.12, 0.18, and 0.24 is discussed. It is found that the scattered intensity -wave vector curves from the unsheared gels obey a power law for phi < 0.24. At higher volume fractions, the power law does not seem to be f ollowed, Shear, however, induces an apparent fractal structure in the gel at phi = 0.24. Results from the computer and the SANS experiments indicate that the spinodal decomposition process and the gelation mech anism have features in common.