Lattice orientation within stirring-induced crystals of polyethylene

Micro-shish-kebab stirring-induced polyethylene crystals, as defined and described in the preceding paper, are flat, ribbon-shaped fibers. Selected area electron-diffraction techniques were used to determine the orientation of the crystal axes with respect to the external fiber shape. It has been shown that in addition to the crystal-lographic c-axis laying along the fiber direction, the normal to the ribbon plane is parallel to the crystallographic a-axis.     

Characterization of BGO glass–ceramic materials

Glass–ceramics of the compositions Bi₄Ge₃O₁₂ (BGO) and Bi₂O₃–GeO₂ have been obtained by pouring molten materials onto graphite plates heated below and above the glass transition temperatures. Glass transitions temperatures have been measured by DSC. T_g is lower in the case of BGO than with the Bi₂O₃–GeO₂ glass ceramics material. Crystallization is evaluated by X-ray diffraction and microscopic observations. The XRD measurements confirm the amorphous structure of the samples cast below T_g. The Hruby factor, which measures the stability of the glass–ceramics, is about 0.21 in the case of BGO glass ceramics suggesting a rather stable glass. The fluorescence under U.V. excitation is larger by one order of magnitude in the case of BGO glass–ceramics by comparison to the Bi₂O₃–GeO₂ glasses, suggesting it is a good candidate for scintillation materials. The images obtained under U.V. excitation shows structured luminescent centers in the case of BGO glass–ceramics.     

Synthesis of Nb2O5·nH2O nanoparticles by water-in-oil microemulsion

Hydrous niobium oxide (Nb₂O₅·nH₂O) nanoparticles had been successfully prepared by water-in-oil microemulsion. They were characterized by X-ray diffraction (XRD), thermal analysis (TG/DTG), Fourier transform infrared spectroscopy (FTIR), BET surface area measurement, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The results showed that the nanoparticle was exactly Nb₂O₅·nH₂O with spherical shape. Their BET surface area was 60 m² g⁻¹. XRD results showed that Nb₂O₅·nH₂O nanoparticles with crystallite size in nanometer scale were formed. The crystallinity and crystallity size increased with increasing annealing temperature. TT-phase of Nb₂O₅ was obtained when the sample is annealed at 550 °C.     

Effect of microcrystallinity on the mechanical performance of polycarbonate

Samples of polycarbonate (PC) before and after remelting and isothermal solidification treatment were characterized by wide-angle X-ray scattering (WAXS) and small-angle X-ray scattering (SAXS), microhardness, and stretching calorimetry techniques. Both PC samples could be regarded as structurally identical (X-ray amorphous); however, the isothermally solidified sample exhibited higher microhardness and Young's modulus, as well as a lower linear expansion coefficient and greatly reduced breaking strain. These results are attributed to the overlap of a network of ultramicrocrystals on the original entanglement network in the reference (untreated) PC sample.