화학공학소재연구정보센터
Journal of Colloid and Interface Science, Vol.260, No.1, 36-48, 2003
Multiscale simulation of irreversible deposition in presence of double layer interactions
Sequential lattice Monte Carlo simulations, in which the transition probabilities are derived from the discrete form of the continuum-level mass conservation law, are used to predict the morphology of colloidal deposits. The simulations account for particle-surface (P-S) and particle-particle (P-P) electrostatic and van der Waals interactions. Simulation results for maximum coverage for monolayer deposition are in quantitative agreement with the hard-sphere RSA jamming limit. Moreover, as reported in earlier studies, monolayer simulations in the absence of P-S interactions qualitatively predict the monotonic increases in fractional coverage with increasing ionic strength, characterized by the Debye screening length (Ka). Monolayer simulations with P-S interactions show that the dependence of fractional coverage on Ka is strongly influenced by the ratio of particle to surface potentials (psi(p)/psi(s)). P-S and P-P forces achieve their respective maximum at different values Of Ka leading to a nonmonotonic trend in surface coverage as a function Of Ka. These results indicate that the incorporation of P-S interactions into colloidal deposition studies allows more accurate interpretation of the experimental data. In multilayer deposition simulations, balance between long-ranged weak interactions and short-ranged strong interactions between P-P and P-S, coupled with physical screening effects, resulted in widely varying coverages with height of the deposit, ionic strength, and psi(p)/psi(s). Moreover, fractal dimension of the deposit ranged from approximate to 1 (Ka much less than 1) to 1.7 (Ka much greater than 1). Qualitative kinetic analysis showed widely varying deposition rates in different layers depending on psi(p)/psi(s) and ionic strength. The multilayer system approached the monolayer system in the limit ka --> infinity and psi(p)/psi(s) --> infinity. (C) 2003 Elsevier Science (USA). All rights reserved.