Fibers crystalline, growth

In contrast to chrysotile fibers, the atomic crystal stmcture of amphiboles does not inherentiy lead to fiber formation. The formation of asbestiform amphiboles must result from multiple nucleation and specific growth conditions. Also, whereas the difference between asbestiform and massive amphibole minerals is obvious on the macroscopic scale, the crystalline stmctures of the two varieties do not exhibit substantial differences. Nonfibrous amphiboles also exhibit preferential cleavage directions, yielding fiber-shaped fragments. 

Alternatively, a fiber can be one member of a group or aggregate, as a fibril is one part of a fiber. Spherulites (Fig. 1. IH), fan-shaped fibrous crusts or rosettes, and the veins depicted in Fig. 1.1A are examples of aggregates created when many crystalline fibers grow in close proximity. During fibrous growth, lateral interference may produce planar but irregular bound-... 

The fiberlike crystalline structures (shish) are highly stable to the point that they can be superheated [31]. Therefore, it is believed that the core of the shish is formed by crystallization of completely stretched polymer chains. The kebabs are believed to be folded-chain lamellar structures. The direction of growth of the kebabs is normal to the shish. The chain ahgnment in the kebabs is believed to be parallel to the shish. Similar structures are obtained by crystalhzation in polymer melt films exposed to orientational deformation [32,33]. These two-dimensional shish-kebabs also consist of a central fiber, shish, and periodically attached linear kebabs, with growth direction normal to the shish. 

Diffuse X-Ray Scattering. Polymers yield only a few diffuse X-ray peaks and streaks, which give an idea of the relative "crystallinity" of the polymer and of its growth axis. The structure of deoxyribonucleic acid (DNA) was inferred in 1953 by Watson166 and Crick167 [66] from the fiber-axis X-ray photographs of DNA salts by Franklin,168 one of which is Fig. 11.75. 

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