Coatings continued discontinuities

In terms of the process time control, CVD can be divided into three categories, namely continuous, discontinuous and pulsed CVD (P-CVD). Discontinuous CVD is used in most CVD processes, whereas continuous CVD is extensively used for fibre coating and high-volume production of semiconductor devices. In order to improve the coating thickness uniformity and its microstructure, P-CVD is commonly used. 

Treated surfaces involve fine-scale alternation of the surface finish or coating (continuous or discontinuous). They are used for boiling and condensing the roughness height is below that which affects single-phase heat transfer. 

At) This statement should not necessarily discourage the use of the contact metal as a coating for the metal considered , provided that continuity is good under abrasive conditions, however, even a good coating may become discontinuous. 

Almost all new metallic surfaces exposed to the environment are sooner or later coated with a layer of corrosion products metal oxides, sulfides, and carbonates, for example, are common corrosion products formed when a metal or alloy interacts with contaminants in the environment. If the layer is continuous and stable, as in uniform corrosion, it may conceal the underlying metal from further exposure and protect it from additional corrosion if it is discontinuous, or chemically unstable, however, the metal surface below the initial layer of corrosion products remains in contact with the environment. Exposed to humidity and pollutants, the corrosion process continues, penetrating deeper into the metallic bulk and eventually resulting in its total destruction. 

Effects of Flooding and Redox Conditions onfs. I know of no published data on this. Bnt it is likely that the natnre of particle surfaces in intermittently flooded soils wonld restrict snrface mobility. For ions to diffuse freely on the surface there must be a continuous pathway of water molecules over the surface and uniform cation adsorption sites. But in intermittently flooded soils the surface typically contains discontinuous coatings of amorphous iron oxides on other clay minerals, and on flooding reduced iron is to a large extent re-precipitated as amorphons hydroxides and carbonates as discussed above, resulting in much microheterogeneity with adsorption sites with disparate cation affinities. 

FIGURE 31 (a) Tablet coated with HPMC smooth film, medium discontinuity between film and core. (b) Tablet coated with SEPIFILM 752 white clear edge perfectly coated, good adhesion of film to core and continuity between film and core. 

---