Factors Affecting Grain Size in a Compact Deposit

Factors Affecting Grain Size in a Compact Deposit 

As the deposit becomes free of the influence of the substrate structure upon thickening, instead of acquiring a randomly oriented grain structure, it often develops a preferred crystal orientation, which gives a definite texture to its cross section. Texture can be expressed in terms of degree of orientation 

In most deposits, one-dimensional texture can be observed using electron diffraction. X-ray diffraction, or electron micrography. Two types prevail the lateral growth ( substrate-oriented deposit ), in which the most densely populated crystal plane is parallel to the substrate surface, and the outward growth ( field-oriented deposit ) in which most densely packed arrays of atoms extend perpendicularly to the surface. However, other orientations are also found. Thus, cobalt, hexagonal nickel, and hexagonal silver tend to have the (1010) plane parallel to the surface. 

Two factors seem to be dominant in determining texture the base metal and the electrolyte (its composition, pH, temperature, and the presence of surface-active substances and colloidal additives). However, in the deposition of one and the same metal, different overpotentials can lead to different orientations. 

Several theories have been put forward for interpreting the appearance of texture. Early work ascribed texture to the action of internal stress causing plastic deformation of the grains. This, however, does not seem to be substantiated by changes in other physical properties (e.g., hardness) which should be a normal consequence of such a situation. 

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B.2. Factors Affecting Grain Size in a Compact Deposit... 

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