Percolation in Models of Thin Film Depositions

We have studied the percolation behaviour of deposits for different (2+1)-dimensional models of surface layer formation. The mixed model of deposition was used, where particles were deposited selectively according to the random (RD) and ballistic (BD) deposition rules. In the mixed one-component models with deposition of only conducting particles, the mean height of the percolation layer (measured in monolayers) grows continuously from 0.89832 for the pure RD model to 2.605 for the pure RD model, but the percolation transition belong to the same universality class, as in the 2- dimensional random percolation problem. In two- component models with deposition of conducting and isolating particles, the percolation layer height approaches infinity as concentration of the isolating particles becomes higher than some critical value. The crossover from 2d to 3d percolation was observed with increase of the percolation layer height.Comment: 4 pages, 5 figure

Adlayers of palladium particles and their aggregates on porous polypropylene hollow fiber membranes as hydrogenization contractors/reactors

Principal approaches for the preparation of catalytic membrane reactors based on polymer membranes containing palladium nanoparticles and for the description of their characteristics are presented. The method for the development of adlayers composed of palladium nanoparticles and their aggregates on the surface of hydrophobic polypropylene porous hollow fiber membranes is proposed, and their comprehensive study is performed. Various regimes of the deposition of palladium on individual fibers and on membrane surface inside membrane modulus are considered. The sizes of primary Pd particles range from 10 to 500 nm, and dimensions of their aggregates vary from 200 nm to tens of microns. The sizes of primary particles in a free state and in their aggregates are estimated by the methods of X-ray analysis and scanning electron microscopy. The proposed approach is used for the preparation of catalytic membrane contactors/reactors for the removal of dissolved oxygen from water. In the systems under study, the limiting stage of dissolved oxygen removal is concerned with diffusion-controlled delivery of oxygen to the surface of catalytic particles. © 2010 Elsevier B.V. All rights reserved