Porosity effects Surface resistivity

Hence, the increasing nucleation density is also due to the decreasing zero nucleation zone radii. This effect leads to an increased coverage of the foreign substrate by the same quantity of deposited metal and to a decreased porosity, a surface resistance and an increased density of a deposit. Also, it can be expected that increase in compactness of a deposit is associated with a decrease in internal stresses and increased ductility and hardness of metal deposits [7]. 

A gas-solid reaction usually involves heat and mass transfer processes and chemical kinetics. One important factor which complicates the analysis of these processes is the variations in the pore structure of the solid during the reaction. Increase or decrease of porosity during the reaction and variations in pore sizes would effect the diffusion resistance and also change the active surface area. These facts indicate that the real mechanism of gas-solid noncatalytic reactions can be understood better by following the variations in pore structure during the reaction. 

The two-stage process was licensed by Mitsui Mining Company (MMC) in Japan in 1982, and by 1993 a modified form of the process was installed in four commercial plants in Japan and Germany [58]. The granular carbon or activated coke used in this process has a surface area of initially 150 to 250 mVg, which is much lower than that of commercial activated carbons. It is produced from a bituminous coal and a pitch binder. Low surface area carbons have been found to be the most effective in this process they are cheaper than high surface area activated carbons, they retain their SO2 adsorption capacity more efficiently on repeated cycling, and their relatively low porosity contributes to strength and abrasion resistance. 

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