Whisker morphology

The morphology of the product derived from the vapor phase (Table III) depends on concentration and diffusion factors [27], the particular phase transformation and in turn on the melting point of the metal catalyst being used, and on the liquidus temperature of the growth substrate. 

The highest internal order, that of a single crystal, is obtained when the tip temperature is above the liquidus of the substrate, yields a liquid tip, and proceeds by a vapor-liquid-solid phase transformation. The lowest internal order, that of an amorphous structure, is obtained when the tip temperature is below the glass transition temperature of the substrate. A solid tip yields a vapor solid phase transformation. Between the liquidus and the glass transition temperature of a substrate, intermediate internal order is that of a polycrystalline fiber. In this case, whisker growth is either governed by a VLS and/or by a VS phase transformation. 

Fiber tip and metal Diffusion Supersaturation Fiber tip Most likely phase Most likely 

Liquid melt Vapor-liquid-solid Soft solid VLSA S( ) 

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Fig. 6 A,B. SEM micrograph of the whisker morphology of A the copoly(ester-imide) 17c B the homopoly(ester-imide) 15b...

FIGURE 9. SEM micrograph showing the whisker morphology of SisN -BAS composite(Reprinted with permission of The American Ceramic Society, www.ceramics.org. Copyright [2001]. All rights reserved.)... 

Whisker Morphology Consisting of Hierarchically Self-assembled Polymer Helices... 

In the previous section, we reported PMP derivatives bearing chiral side chains having a helicene-like helical structure through intrachain 7r-electron overlap interactions, which lead to a self-assembled whisker morphology due to interchain van der Waals interactions. However, each whisker of the PMP derivative is still randomly oriented, even if it has a self-assembled structure. It is therefore desirable to align the PMP derivative to construct a higher-ordered hierarchical structure and also to evolve an anisotropic nature in its potentially profound op-toelectrical properties. 

Fig. 3 Tin whisker morphologies, (a) A fluted whisker on the Sn-Cu finish surface, (b) Many other whiskers are bent at a sharp angle.

Because the morphology of the outer surface of the CAA oxide is strongly dependent on the process steps used just prior to the CAA treatment, the type of pretreatment can be chosen to enhance the bonding. Samples that are FPL-etched and then anodized have a typical FPL shallow cell-and-whisker morphology. Surfaces that are PAA treated before the CAA anodization have a deeper cell structure, typical of PAA. Finally, surfaces that have a smooth tartaric acid-anodized (TAA) oxide before CAA treatment retain a smooth surface which is typical of the TAA treatment. 

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