Membrane microstructure resulting from deposition of polydisperse particles

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 (Nr) 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 Nr, while specific perimeter decreases with increasing κ and φ, and increases sharply with increasing Nr. 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 Nr is found to play the most decisive role in determining membrane microstructure.