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[en] Low-density polyethylene/plasticized starch blends (LDPE/PLST) at various compositions were prepared by melt extrusion and molding in the form of sheets under hot press. The rheology properties during mixing were studied in terms of torque and melting temperature against mixing time. The effect of different compatibilizers and electron beam irradiation on the miscibility of these blends was investigated by IR spectroscopy, mechanical testing and scanning electron microscopy (SEM). The rheology studies showed that the polyethylene graft copolymer with maleic anhydride (PEMA) as a compatibilizing agent during mixing has a pronounced effect than ethylene-vinyl copolymer (EVA) as seen from the higher torque values and melting temperatures. The IR spectroscopy suggests that the compatibilization by EVA and PEMA compounds proceeds through the formation of hydrogen bonding during mixing and this compatibility was improved after electron beam irradiation. The stress- strain curves of pure LDPE and its blends with PLST showed the behaviour of tough polymers with yielding properties. The SEM micrographs of the fracture surfaces give supports to the effect of EVA and PEMA as compatibilizers and electron beam irradiation.
[en] Studies of two-beam coherent induced optical anisotropy has been performed for the cadmium sulphide nanocrystallites (NC) embedded within the different polymer matrices. The NC were fabricated by the modified electrolytical method and have been embedded into different polymer matrices: PC, PMMA, PVA. The phototreatement was performed by two space split coherent beams generated by 120 fs laser with pulse energy 23 nJ. The phototreatment has been durated several minutes until the clear diffraction grating has been observed. The monitoring of the laser induced gratings and of the anisotropy was performed using the cw 1150 nm continuous wave He–Ne laser with power about 30 mW. Varying the polarization of the laser coherent femtosecond beams we have found that the optimal gratings has been achieved for 45° polarizations between the beams. The control of the maximal laser induced gratings has been done using optically polarized method. The effect is not completely reversible and there remain some changes after switching off of the phototreatment. The anisotropy has been monitored by Senarmont method. The role of different polymers on the output photo stimulated birefringence was explored. This method may be promising for the design and engineering of optical triggers in the femtosecond laser pulse duration.
[en] It is shown that narrow band gap semiconductors Tl_1_−_xIn_1_−_xGe_xSe_2 are able effectively to vary the values of the energy gap. DFT simulations of the principal bands during the cationic substitutions is done. Changes of carrier transport features is explored. Relation with the changes of the near the surface states is explored . Comparison on a common energy scale of the x-ray emission Se Kβ _2 bands, representing energy distribution of the Se 4p states, indicates that these states contribute preliminary to the top of the valence band. The temperature dependence of electrical conductivity and spectral dependence photoconductivity for the Tl_1_−_xIn_1_−_xGe_xSe_2 and Tl_1_−_xIn_1_−_xSi_xSe_2 single crystals were explored and compared with previously reported Tl_1_−_xIn_1_−_xSn_xSe_2. Based on our investigations, a model of centre re-charging is proposed. Contrary to other investigated crystals in Tl_1_−_xIn_1_−_xGe_xSe_2 single crystals for x = 0.1 we observe extraordinarily enormous photoresponse, which exceed more than nine times the dark current. X-ray photoelectron core-level and valence-band spectra for pristine and Ar"+-ion irradiated surfaces of Tl_1_−_xIn_1_−_xGe_xSe_2 (x = 0.1 and 0.2) single crystals have been studied. These results indicate that the relatively low hygroscopicity of the studied single crystals is typical for the Tl_1_−_xIn_1_−_xGe_xSe_2 crystals, a property that is very important for handling these quaternary selenides as infrared materials operating at ambient conditions. (paper)