Spherulite


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spherulite

[′sfir·ə‚līt]
(geology)
A spherical body or coarsely crystalline aggregate having a radial internal structure arranged about one or more centers.

Spherulite

 

a small sphere consisting of an aggregate of very fine acicular crystals radiating from a central point. Spherulites are found in magmatic and sedimentary rocks and vary in mineral composition and size. In magmatic rocks, spherulites are usually interpreted as endogenic contact formations in the marginal sections of diorites. In acidic lavas, they may occur through consolidation when the primary glassy mass cools; in basic lavas (variolites), such formations are called varióles. Spherulites also form in gas bubbles of already hardened rock during secondary precipitation of zeolites, quartz, and similar minerals; in such cases they may be called pseudospherulites. Carbonate, iron-manganese phosphate, chalcedonic, and other types of spherulites are found in sedimentary rocks. They usually result from the crystallization of material in colloidal nodules, and many are close in origin to concretions.

References in periodicals archive ?
7, we notice that PPN27, with the highest spherulite dimensions among all samples and with a trans-crystalline zone near the sample surface, also has the most different gloss and color coordinates.
This comprised the spherulite size and distribution as well as the layer structure introduced through injection molding.
The material used displayed strong crystalline peaks without the addition of TCB which, in this case, only induces radial growth and the formation of large spherulites. Here, we discuss and demonstrate that similar formation of large spherulites composed of oriented nanofibers can be obtained when using conjugated polymers with smaller crystallinity such as F8BT (Figure 4(a)).
The nuclei of the spherulites consist of aggregates of isolated and small calcite crystals (around 1 [micro]m in size), which progressively become larger, more elongated and radially arranged in the direction of belemnite growth as hemispherical fans of crystals (Fig.
In situ AFM studies gave the opportunity to observe developing morphologies at a lamellar scale, from the generation of the primary stable nucleus [8] to the development of dominant lamellae, followed by the birth of branching lamellae that splay, leading to the spherulitic morphology [4, 6, 8] with, finally, impingement of adjacent spherulites [5].
Besides, the spherulite morphology of PLLA with TTAD during isothermal crystallization process was observed by POM.
SCF induces the transcrystalline texture in the adjacent regions, while the morphology far from fibers remains spherulite. The classic Kolmogorov model can be used to calculate the crystallinity evolution of spherulites, as mentioned in the Introduction section.
These results further confirm that NA can accelerate the crystallization of PLLA.The spherulite morphology of PLLA/0.8%NA was compared with that of the neat PLLA by POM analysis.
For P(3HB) and P(3HB-co-3HV), nonbanded spherulites or banded spherulites could be formed, which was determined by crystallization conditions.
Crystallinity affects optical transparency because of the scattering taking place when light passes from amorphous to crystalline regions: spherulites in i-PP are much larger than the wavelength of visible light (0.4-0.7 [micro]m), and the refractive index of crystalline regions is higher than that of amorphous regions; as light rays pass from amorphous to crystalline regions, they encounter the large spherulites, resulting in light scattering; as a result, optical transparency is lower, and haze is produced.
Assouline and coworkers utilized the [beta]-NA coated glass fibers to induce [beta]-TC in iPP matrix, and investigated the crystallization kinetics of [beta]-TC [28], The growth rates of bulk spherulites and transcrystalline layers was found to be similar, but differed in the induction time under isothermal conditions.
They added a clarifying agent such as a dibenzylidene sorbitol acetal derivative, reducing spherulite sizes, which reduces light scattering and maintains clarity.