Polyethylene thin crystals, structure

Polyethylene was deposited on a single crystalline mica substrate. Larger area moire fringes can appear in the TEM image, caused by interference from the two crystalline thin films, i.e., the crystalline PE thin film and the crystalline mica. Figure 7 shows a TEM micrograph and an electron diffraction pattern. The crystal structure of the mica is monoclinic. The relation of the distances between crystal planes is as follows ... 

The synthesis of Pt metal nanowires and nanotubes electrochemically deposited through nanoporous membranes was reported by Ichikawa (2000). Palladium deposits with high specific surface areas, up to 50 m g", have been synthesized by Tsirlina et al. (2002) from palladium chloride solutions with additions of polyethylene glycol and polyvinyl pyrrolidone. Details of the globular structine of the deposits depend on the polymer additives. A comparison with electrochemically determined true surface areas demonstrates the coalescence of nanoparticles. Wang et al. (2003) electrochemically synthesized thin films composed of ordered arrays of palladium nanowires using silica mesoporous channels. Mesoporous channels were deposited on a conductive glass substrate. In this method, nanowires with face-centered cubic crystal structure are continuously deposited from the conductive substrate upward until the mesoporous channels are filled. 

Finally, the left curves of Fig. 2.45 show that above about 260 K, melting of small, metastable crystals causes abnormal, nonlinear deviations in the heat capacity versus crystallinity plots. The measured data are indicated by the heavy lines in the figure. The thin lines indicate the continued additivity. The points for the amorphous polyethylene at the left ordinate represent the extrapolation of the measured heat capacities from the melt. All heat capacity contributions above the thin lines must thus be assigned to latent heats. Details of these apparent heat capacities yield information on the defect structure of semicrystalline polymers as is discussed in Chaps. 4-7. 

Fig. 3. Differential thermal analysis of linear low density polyethylene on cooling (continuous lines), followed by heating (broken lines), showing a high content of reversing crystallization and melting. Standard DSC thin lines TMDSC thick lines. The overall supercooling contrasts the partially reversible crystallization and melting after an overall metastable, semicrystalline structure has been set up on the initial cooling. The modulation amplitude on TMDSC is given by the letter A, and the modulation period by p.

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