Surface redeposition

The morphology of surface redeposition shows a pattern of uniform current density when the electrode is injected with 30 p,C/cm, well within its charge-injection limit. However, at 2 mC/cm, increased current density is observed at sharp convex edges, indicating a dissolution-dominated mode of charge injection at the higher current level (Fig. 21). 

As might be expected, large differences in the removabiUty of soHd particulate soil are due to differences in the chemical nature of the particle surface. Thus, kon oxides, lampblacks, and clays, all of the same particle size, differ greatly in thek redeposition behavior and the manner in which they are removed. 

Removal of deposits and corrosion products from internal surfaces revealed irregular metal loss. Additionally, surfaces in wasted areas showed patches of elemental copper (later confirmed by energy-dispersive spectroscopy) (Fig. 13.12). These denickelified areas were confined to regions showing metal loss. Microscopic analysis confirmed that dealloying, not just redeposition of copper onto the cupronickel from the acid bath used during deposit removal, had occurred. 

The most arresting development is the use of an STM tip, manipulated to move both laterally and vertically, to shepherd individual atoms across a crystal surface to generate features of predeterminate shapes an atom can be contacted, lifted, transported and redeposited under visual control. This was first demonstrated at... 

Efflorescence usually takes place when groundwater penetrates within porous solids, where it leaches (dissolves) soluble salts from the solids. When the water with the leached solids eventually evaporates, the solution migrates toward the surface if the water continues to evaporate, the dissolved salts are redeposited, forming small crystals just below and on the surface of the objects. The forces generated by the crystallization of the efflorescent salts below the surface (in the bulk of the solid), as well as... 

Coalescence of dyes during cooling is characteristic of their existence in a viscous state at elevated temperatures [53]. Surfactants minimise the redeposition of insolubilised dye onto the surface of the fibres from the cooling bath. 

For most design purposes, it may be assumed that the rate of drying is proportional to the transfer coefficient multiplied by (Ps — P, ). Chakravorty(10) has shown that, if the temperature of the surface is greater than that of the air stream, then Pw may easily reach a value corresponding to saturation of the air. Under these conditions, the capacity of the air to take up moisture is zero, while the force causing evaporation is (Ps — Pw). As a result, a mist will form and water may be redeposited on the surface. In all drying equipment, care must therefore be taken to ensure that the air or gas used does not become saturated with moisture at any stage. 

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