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91.
Amauri J. Paula Rodrigo Parra Maria A. Zaghete Jos A. Varela 《Solid State Communications》2009,149(39-40):1587-1590
Because of the environmental concerns, the manufacture of ceramics based on lead titanate zirconate [Pb(Zr1−xTix)O3−PZT] has been condemned because of the lead toxicity. In this context, the electromechanical properties of sodium, potassium and lithium niobate [(Na0.5−x/2K0.5−x/2Lix)NbO3−NKLN] at the morphotropic phase boundary granted these materials the position of most suitable candidate to replace PZT. However, the production of these ceramics is rather critical mainly because of a natural tendency of forming secondary phases. To help with the studies of the synthesis of this lead-free piezoceramic, this work presents an evaluation of the crystallization of the (Na0.47K0.47Li0.06)NbO3 phase by solid-state reactions. TG-DTA, XRD, dilatometric and ferroelectric hysteresis analyses indicated that a secondary phase (K3Li2Nb5O15) crystallizes at temperatures above 850 C and also during the sintering of the powders compacts at 1080 C. To prevent the formation of this phase, the addition of Na2Nb2O6.nH2O microfibers obtained through a microwave hydrothermal synthesis was performed in the sintering process. After to this addition, the suppression of the K3Li2Nb5O15 phase occurred and an increase of the NKLN electrical properties was then obtained. 相似文献
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Sandra Medel Jos Manuel García Leoncio Garrido Isabel Quijada‐Garrido Rodrigo París 《Journal of polymer science. Part A, Polymer chemistry》2011,49(3):690-700
A series of gradient and block copolymers, based on 2‐(2‐methoxyethoxy)ethyl methacrylate (MEO2MA) and tert‐butyl acrylate (tBA), were synthesized by atom transfer radical polymerization (ATRP) in a first step. The MEO2MA monomer leads to the production of thermosensitive polymers, exhibiting lower critical solution temperature (LCST) at around room temperature, which could be adjusted by changing the proportion of tBA in the copolymer. In a second step, the tert‐butyl groups of tBA were hydrolyzed with trifluoroacetic acid to form the corresponding block and gradient copolymers of MEO2MA and acrylic acid (AA), which exhibited both temperature and pH‐responsive behavior. These copolymers showed LCST values strongly dependent on the pH. At acid pH, a slightly decrease of LCST with an increase of AA in the copolymer was observed. However, at neutral or basic conditions, ionization of acid groups increases the hydrophilic balance considerably raising the LCST values, which even become not observable over the temperature range under study. In the last step, these carboxylic functionalized copolymers were covalently bound to biocompatible and biodegradable films of poly(3‐hydroxybutyrate‐co‐3‐hydroxyhexanoate) [P(HB‐co‐HHx)] obtained by casting and, previously treated with ethylenediamine (ED) to render their surfaces with amino groups. Thereby, thermosensitive surfaces of modified P(HB‐co‐HHx) could be obtained. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献
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Bailly J. L. Caso C. Chiba Y. Dibon H. Epp B. Ferrando A. Fontanelli F. Ganguli S. N. Gémesy T. Gurtu A. Hamatsu R. Hidas P. Hirose T. Hrubec J. Ivanyshenkov Yu. Kageya T. Khalatyan N. Kistenev E. Kita I. Kitamura S. Kubik V. MacNaughton J. Malhotra P. K. Matsumoto S. Mittra I. S. Montanet L. Neuhofer G. Pinter G. Porth P. Raghavan R. Rodrigo T. Singh J. Squarcia S. Takahashi K. Tanaka R. Tikhonova L. A. Trevisan U. Yamagata T. Zholobov G. Zotkin S. A. 《Zeitschrift fur Physik C Particles and Fields》1989,43(3):341-348
Zeitschrift für Physik C Particles and Fields - Correlations among identically charged pions were measured for pions produced inp p collisions at 360 GeV/c using the EHS spectrometer. The... 相似文献
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Juan C. Castillo Rodrigo Abonía Michael B. Hursthouse Justo Cobo Christopher Glidewell 《Acta Crystallographica. Section C, Structural Chemistry》2009,65(10):o495-o497
In the title compound, C23H22N4O, there is evidence for some bond fixation in the aryl component of the quinolinone unit. Pairs of molecules related by inversion are linked into R22(8) dimers by almost linear N—H...O hydrogen bonds, and dimers related by inversion are linked into chains by a single aromatic π–π stacking interaction. 相似文献