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41.
N. Narasimha Rao I.V. Kityk V. Ravi Kumar P. Raghava Rao B.V. Raghavaiah P. Czaja P. Rakus N. Veeraiah 《Journal of Non》2012,358(3):702-710
Piezoelectric coefficients d33 as well as ultrasonic velocities and elastic coefficients of ZnF2–PbO–TeO2 glasses crystallized with different concentrations of TiO2 (0.5 to 2.0 wt.%) were measured. The contribution to the piezoelectric coefficients is attributed to presence of Pb5Ti3F19, PbTiO3 and PbTeO3 ferroelectric crystal phases. The piezoelectric coefficients show substantial sensitivity to presence of TiO2. The ultrasonic velocities and the related elastic coefficients in these glass ceramics as a functions of concentration of nucleating agent TiO2 exhibited minimal effect at 1.0 wt.%. This is ascribed to the larger presence of titanium ions in Ti3+ states which act as modifiers and finally de-polymerize glass ceramic network. The results have been further discussed quantitatively within a framework of different oxidation states of titanium ions and the nature of the crystal phases ingrained in the glass ceramic. 相似文献
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Wójcik Kamil Czaja Tomasz Szostak Roman Grzeszczuk Maria 《Journal of Solid State Electrochemistry》2018,22(12):3933-3945
Journal of Solid State Electrochemistry - Silver(I) halide particles embodied in polypyrrole matrices are synthesized and further processed electrochemically to get nanoparticles of silver with... 相似文献
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Two broad luminescence bands in weakly hydrogenated (glow discharge) undoped amorphous silicon have been observed using time resolved spectroscopy on a nanosecond timescale. Whereas the luminescence decay of the low energy band has been found to be sample independent, the peak position of the luminescence does show a sample dependence. We propose an intrinsic origin of this luminescence. 相似文献
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Agata Krasuska Marzena Białek Krystyna Czaja 《Journal of polymer science. Part A, Polymer chemistry》2011,49(7):1644-1654
A series of bis(phenoxy‐imine) vanadium and zirconium complexes with different types of R3 substituents at the nitrogen atom, where R3 = phenyl, naphthyl, or anthryl, was synthesized and investigated in ethylene polymerization. Moreover, the catalytic performance was verified for three supported catalysts, which had been obtained by immobilization of bis[N‐(salicylidene)‐1‐naphthylaminato]M(IV) dichloride complexes (M = V, Zr, or Ti) on the magnesium carrier MgCl2(THF)2/Et2AlCl. Catalytic performance of both supported and homogeneous catalysts was verified in conjunction with methylaluminoxane (MAO) or with alkylaluminium compounds (EtnAlCl3?n, n = 1–3). The activity of FI vanadium and zirconium complexes was observed to decline for the growing size of R3, whereas the average molecular weight (MW) of the polymers was growing for larger substituent. Moreover, vanadium complexes exhibited the highest activity with EtAlCl2, whereas zirconium ones showed the best activity with MAO. All immobilized systems were most active in conjunction with MAO, and their activities were higher than those for their homogeneous counterparts, and they gave polymers with higher average MWs. That effect was in particular evident for the titanium catalyst. The vanadium complex 3 was also a good precursor for ethylene/1‐octene copolymerization; however, its immobilization reduced its potential for incorporation of a comonomer into a polyethylene chain. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献
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Krystyna Czaja Marzena Biaek Alicja Utrata 《Journal of polymer science. Part A, Polymer chemistry》2004,42(10):2512-2519
The study of ethylene/1‐hexene copolymerization with the zirconocene catalyst, bis(cyclopentadienyl)zirconium dichloride (Cp2ZrCl2)/methylaluminoxane (MAO), anchored on a MgCl2(THF)2 support was carried out. The influence of 1‐hexene concentration in the feed on catalyst productivity and comonomer reactivity as well as other properties was investigated. Additionally, the effect of support modification by the organoaluminum compounds [(MAO, trimethlaluminum (AlMe3), or diethylaluminum chloride (Et2AlCl)] on the behavior of the MgCl2(THF)2/Cp2ZrCl2/MAO catalyst in the copolymerization process and on the properties of the copolymers was explored. Immobilization of the Cp2ZrCl2 compound on the complex magnesium support MgCl2(THF)2 resulted in an effective system for the copolymerization of ethylene with 1‐hexene. The modification of the support as well as the kind of organoaluminum compound used as a modifier influenced the activity of the examined catalyst system. Additionally, the profitable influence of immobilization of the homogeneous catalyst as well as modification of the support applied on the molecular weight and molecular weight distribution of the copolymers was established. Finally, with the successive self‐nucleation/annealing procedure, the copolymers obtained over both homogeneous and heterogeneous metallocene catalysts were heterogeneous with respect to their chemical composition. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2512–2519, 2004 相似文献
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Marzena Białek Krystyna Czaja 《Journal of polymer science. Part A, Polymer chemistry》2008,46(20):6940-6949
Vanadium complexes with tetradentate salen‐type ligands were first time explored in ethylene polymerizations. The effects of the vanadium complex structure, the alkyl aluminum cocatalysts type (EtAlCl2, Et2AlCl, Et3Al, and MAO), and the polymerization conditions (Al/V molar ratio, temperature) on polyethylene yield were explored. It was found that EtAlCl2 in conjunction with investigated vanadium complexes produced the most efficient catalytic systems. It was shown, moreover, that the structural changes of the tetradentate salen ligand (type of bridge which bond donor nitrogen atoms and type of substituent on aryl rings) affected activity of the catalytic system. The complexes containing ligands with cyclohexylene bridges were more active than those with ethylene bridges. Furthermore, the presence of electron‐withdrawing groups at the para position and electron‐donating substituents at the ortho position on the aryl rings of the ligands resulted in improved activity in relation to the systems with no substituents (with the exception of bulky t‐Bu group). The results presented also revealed that all vanadium complexes activated by common organoaluminum compounds gave linear polyethylenes with high melting points (134.8–137.6 °C), high molecular weights, and broad molecular weight distribution. The polymer produced in the presence of MAO possesses clearly lower melting point (131.4 °C) and some side groups (around 9/1000 C). © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6940–6949, 2008 相似文献
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