Membrane microstructure resulting from deposition of polydisperse particles

Abstract

The membrane microstructure resulting from deposition of polydisperse circular particles is investigated with a combined off-lattice deposition model. The model takes into account particle movement resulting from both deterministic and non-deterministic forces. The size distribution of depositing particles considered includes uniform, normal, and log-normal distributions. The resulting membrane microstructure is studied in terms of porosity/mean height, surface roughness, mean coordination number, mean pore radius, normalized standard deviation of pore radii, and specific perimeter, subject to variation in deposition conditions including transition parameter ( κ), incident angle ( φ), and number of post-contact rolling ( N r) of the deposition. It is found that porosity/mean height, surface roughness, and mean pore radius increase with increasing κ and φ, but decrease sharply with increasing N r, while specific perimeter decreases with increasing κ and φ, and increases sharply with increasing N r. Mean coordination number is almost invariant with respect to variation in depositing particle size distribution, and acquires a value of 2 for cases without post-contact restructuring and a value of 4 for cases with post-contact restructuring. On the basis of equal deposition particle area, surface roughness, mean pore radius, and normalized standard deviation of pore radii are the largest for the log-normal case, and the smallest for the uniform case, while the trend is the opposite for specific perimeter. Porosity/mean height and mean coordination number are found to be almost invariant to size distribution. The extent of deposit restructuring as quantified by N r is found to play the most decisive role in determining membrane microstructure.