Granular Crystallites Research Articles

Structural studies on polymer whiskers by transmission electron microscopy: I. Morphological and high‐resolution observations

The structures of poly(p-hydroxybenzoic acid) (PHBA) whisker crystals and crystalline fine fibrils of copolymer prepared from p-hydroxybenzoic acid (HBA) and 2-hydroxy-6-naphthoic acid (HNA), namely poly(HBA/HNA) (monomer molar ratio: 97/3), were investigated by transmission electron microscopy (TEM). As for a PHBA whisker, microfibril-like bright regions were recognized in the 210 dark-field image. In the high-resolution TEM image of another PHBA whisker, however, lattice fringes were continuous through the whisker, showing that the whisker is highly crystalline and almost perfect. On the other hand, in the high-resolution images of poly(HBA/HNA) fine fibrils, granular crystallites (20– 40 nm in lateral dimension) were observed. The lattice fringes in the crystallites were not successfully indexed with the orthorhombic unit cells of the homopolymer crystal, suggesting the coexistence of another different structure as a minor component. Microsc. Res. Tech. 46:325–333, 1999. © 1999 Wiley-Liss, Inc.

Structural studies on polymer whiskers by transmission electron microscopy: I. Morphological and high-resolution observations.

The structures of poly(p-hydroxybenzoic acid) (PHBA) whisker crystals and crystalline fine fibrils of copolymer prepared from p-hydroxybenzoic acid (HBA) and 2-hydroxy-6-naphthoic acid (HNA), namely poly(HBA/HNA) (monomer molar ratio: 97/3), were investigated by transmission electron microscopy (TEM). As for a PHBA whisker, microfibril-like bright regions were recognized in the 210 dark-field image. In the high-resolution TEM image of another PHBA whisker, however, lattice fringes were continuous through the whisker, showing that the whisker is highly crystalline and almost perfect. On the other hand, in the high-resolution images of poly(HBA/HNA) fine fibrils, granular crystallites (20-40 nm in lateral dimension) were observed. The lattice fringes in the crystallites were not successfully indexed with the orthorhombic unit cells of the homopolymer crystal, suggesting the coexistence of another different structure as a minor component.

Dielectric Properties of the Fast‐Ion Conductor Na3Sc2P3O12

AbstractDielectric properties of granular crystallites of the fast‐ion conductor Na3Sc2P3O12 are measured in the frequency range 0.05 to 26 MHz and the temperature range − 70 to + 125 °C. Plots of the loss tangent, at fixed frequency, vs. temperature show a very sharp change in tan δ accompanying a structural phase change at about 63 °C. These plots show two loss maxima in the low temperature phase which indicate the occurrence of two relaxation processes with activation energies of 0.49 and 0.77 eV. These relaxation processes are probably distinct from the process of fast‐ion conduction which occurs at temperatures above the phase change at 63 °C. The existence of the structural phase change is substantiated by heat capacity measurements.

An electron microscope study on the calcification of the exoskeleton in a shore crab.

The early phase of calcification of the endocuticle newly formed after molting in the shore crab, Gaetice depressus, was studied by electron microscopy. In endocuticle matrix near the outer surface of the epidermal cell in which the calcification has begun, a number of small or large granular crystallites, 2-150 mμ in diameter, were found to be deposited in the fibrils. The fibrils, about 30-80mμ thick, are dispersed randomly in the ground substance. In each elliptical border of the pore canals situated between the fibrils, the small granular crystallites, 2-26 mμ in diameter, are often deposited in minute spaces. With the advancement of calcification, small or large granular crystallites deposited in the fibrils begin to join with one another and gradually form the band-shaped clusters of crystallites. On the other hand, the small granular crystallites deposited in each border of the pore canals do not form any crystallite clusters even with the advancement of calcification.