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In this study, QUV accelerated weathering of polyvinyl chloride (PVC) composites with different amounts of titanium dioxide (TiO2) particle was conducted to investigate the effect of TiO2 particle on the surface morphology and the mechanical properties. The results indicate that the surface morphology of PVC without TiO2 particle did not exhibit changes up to 960 h, but exhibited a rough and brittle surface after 1920 h of QUV accelerated weathering. In addition, the tan δ intensity, the elongation at break, and the mean failure energy (MFE) decreased significantly with increasing exposure time due to embrittlement. In contrast, for TiO2 particle-loaded PVCs, no significant influence on the tan δ intensity and the mechanical properties after accelerated weathering were observed, despite the appreciable degradation that occurred in the surface layer. The weatherability, as determined by the mechanical performance, was improved with increasing loading of TiO2 particle in the PVC composites. Although the TiO2 particle in the PVC matrix acts as a photocatalyst to enhance the surface degradation, it is also an effective radiation screener that inhibits embrittlement and retards the decrease in mechanical properties caused by the accelerated weathering process. POLYM. COMPOS., 37:3391–3397, 2016. © 2015 Society of Plastics Engineers

In order to prepare high purity lead iodide (PbI2) single crystals, the starting material-iodine (I) has been purified by the sublimation method, and the PbI2 polycrystalline by the normal freezing method. The purification effect of these methods has been confirmed by evaluating the impurity concentration in ingot by glow discharge mass spectrometry (GDMS) analysis. By comparing the purity of three different starting materials, non-purified iodine+6N-Pb, purified iodine+6N-Pb and commercial 6N-PbI2, PbI2 synthesized by purified iodine in the present experiment has the highest purity. This indicates that these purification methods are suitable. The present research results are expected to prepare high-resistivity PbI2 used in radiation detector. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The bonding between the atoms in the II-VI compound semiconductors has always been a subject of rigorous research because of their tremendous applications in a variety of fields. The bonding and ionic character in CdTe at 300 and 200 K have been determined quantitatively as well as qualitatively using single crystal X-ray data sets and MEM (Maximum Entropy Method) as the tool for the reconstruction of the electron densities distributed within the unit cell. The ab-initio band calculation of the total and valence charge densities have been carried out theoretically by means of the local density approximation (LDA) method in support of the experimentally derived MEM maps. The difference density maps show fewer errors between the theoretical and experimental charge density and thus gives credence to the results accordingly. Along the bonding direction [111], the mid-bond electron densities are found to be 0.233 e/A3 and 0.284 e/A3 at 300 K and 200 K at distances 1.4026 A and 1.4036 A respectively. The densities along [100] and [110] show an increase in the charge concentration at the bond at lower temperatures. © 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

In order to grow β-FeSi2 single crystals by the chemical vapor transport (CVT) method, the growth conditions, including density of iodine transport agent and growth duration, were examined. An iodine density of 8.9 mg cm–3 was thought to be optimum in the present experiment. It was found that the growth duration should be over 4 weeks for growing β-FeSi2 single crystals. X-ray structural analysis revealed that the growth direction of the β-FeSi2 crystals was The growth rate along the directions with lower Miller indexes was slower than that along the directions with higher Miller indexes. The measured lattice constants were a = 0.986 nm, b = 0.780 nm, and c = 0.781 nm. These values are consistent with the previously reported values. Hall measurements showed that the electron mobility was over 350 cm2 V–1 s–1 at 10 K. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

In order to prepare p-type ZnSe, bismuth (Bi) as an acceptor dopant was doped into ZnSe single crystal by vertical Bridgman method. Photoluminescence (PL) spectra measured at 4.2 K on as-grown crystal showed the strong shallow donor–acceptor pair (DsAP) emission, deep donor–acceptor pair (DdAP) emission and weak I1Bi emission line. To enhance the activation ratio of Bi in ZnSe single crystals, ZnSe:Bi was annealed in saturated zinc and selenium atmosphere at different temperatures. In the case of annealing in the range of 700–800 °C, DdAP emission disappeared and the intensities of DsAP and I1Bi emission relatively increased. From the dependence of PL spectra on excitation light intensity and the temperature, the acceptor activation energy and deep donor level were estimated about 103 meV and 34 meV, respectively. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

A ZnSe epitaxial layer doped with nitrogen (N) has been grown on ZnSe substrate at optimized conditions by a low-pressure metalorganic chemical vapor deposition (MOCVD) system using hydrogen as a carrier gas and ammonia as a dopant source. In order to enhance the activation ratio of nitrogen in ZnSe epitaxial layer, ZnSe:N/ZnSe was annealed in atmosphere with zinc-saturated vapor pressure. Photoluminescence spectra measured at 4.2K from annealed ZnSe : N epilayers showed the stronger I 1 N emission. C-V measurement showed that the ZnSe:N epitaxial layer is of p-type conductivity and the highest net acceptor concentration reaches as high as 6.7 x 10 1 7 cm - 3 . This is the highest value for the ZnSe homosystem epitaxial layers grown by the MOCVD method at present. Furthermore, the ionization energy of nitrogen in ZnSe was estimated to be 109 meV by examining the dependence of DAP emission on the measuring temperature.

In order to grow high-quality ZnTe epilayers on (100) GaAs substrates by improved hot wall epitaxy (HWE), the optimum growth condition including the reservoir temperature has been determined by the full-width at half-maximum (FWHM) of the four-crystal rocking curve and the low temperature photoluminescence (PL). Under the determined optimum growth condition, ZnTe epilayers with thickness of 0.7-24.8 μm were grown for studying the effect of the thickness on the crystalline quality. The PL and FWHM values indicated that the quality of ZnTe epilayers was significantly improved when increasing their thickness up to 6 μm. The narrowest FWHM value of 66 arcsec was obtained on an epilayer with 13 μm thickness. Meanwhile, the typical PL spectrum showed the strongly split free exciton emissions and very weak deep band emissions. These results show that the ZnTe epilayers are of high quality.