Morphology, needle-like microstructure

Random copolymers of VF2/F3E when crystallized from the molten state above the Curie temperature show a microstructure in the form of very thin needle-like morphological units which are probably semicrystalline. Figure 5a illustrates the needle-like microstructure of the copolymer 80/20 melt crystallized in the paraelectric phase observed at 140 °C. After codling at room temperature the microstructure of the ferroelectric crystals is such that what appear in the optical microscope as radial fibers are, in fact, stacks of thin platelet-like morphological units (see Fig. 5b). 

Microstructure is also affected by water content. The 1 16 mortar contained hexagonal plates, while the 1 8 mortar had an ellipsoidal morphology. The 1 5 mortar when prepared at — 5 °C developed striking, well-formed, needle-like crystals (Figure 6.9). 

The SMC whiskers composed of Si02, MgO, and CaO have a light yellow appearance and needle-like or rod morphology with diameters ranging from 0.5 to 2 pm and an L/D ratio above l6/° Figure 3.11 shows the microstructure of SMC whiskers. 

Tin-lead and lead-free solder alloys exhibit different bulk solder nucrostructures. Tin-lead alloys exhibit distinct Sn- and Pb-rich grains the majority of tin-based lead-free solder alloys exhibit intermetallic structures within the tin-matrix. The intermetallic morphology is not in lamellae form and may be round, plate-like, blocky, and needle-like structures. Examples of the deep etched microstructure of lead-free solder alloys follow. 

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