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1.
Ana Luísa Daniel‐da‐Silva João Carlos Moura Bordado José Miguel Martín‐Martínez 《Journal of Polymer Science.Polymer Physics》2007,45(22):3034-3045
The degree of phase separation in several moisture‐cured poly(urethane urea)s (PUUs) was studied by FTIR spectroscopy, wide angle X‐ray diffraction (WAXD), and temperature‐modulated differential scanning calorimetry (TMDSC). This latter technique was shown to be particularly useful in analysing the degree of phase separation in PUU polymers. Both phase mixing and phase segregation coexisted in the PUUs and the degree of phase separation increased as the urea hard segment (HS) content in the PUU increased. The maximum solubility of urea HSs into the polyol soft segments (SSs) was achieved for 50 wt % urea HS content in diol‐based PUUs, whereas for triol‐based PUUs the highest solubility between HS and SS was reached for lower urea HS amount. Finally, the higher the urea HS content the higher the extent of phase separation in the PUU. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 3034–3045, 2007 相似文献
2.
Siripon Anantawaraskul João B. P. Soares Preechathorn Jirachaithorn Jumras Limtrakul 《Journal of Polymer Science.Polymer Physics》2006,44(19):2749-2759
Four polyethylene samples (PE) with different molecular weight distributions (MWD) were analyzed by crystallization analysis fractionation (Crystaf) at several cooling rates to investigate the effect of MWD and cooling rate on their Crystaf profiles. Using these results, we developed a mathematical model for Crystaf that considers crystallization kinetic effects, which are ignored in all previous Crystaf models. The Crystaf model we proposed can fit the experimental Crystaf profiles of the 4 polyethylene resins very well. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2749–2759, 2006 相似文献
3.
Sodium hexafluoromanganate(III) has been synthesized by heating equimolecular quantities of Na2MnF5 and NaF in argon atmosphere. The compound is monoclinic witha=5.56 (1) Å,b=5.84 (1) Å,c=8.10 (2) Å, =90.7 (2) andZ=2. It is a high spin complex with
eff
and the deformation of the octahedra is evident from its IR-spectra. Two enantiotropic transitions (at 562 and 653°C) and the melting point at 800°C have been observed.
8. Mitt.: Mh. Chem.106, 483 (1975). 相似文献
8. Mitt.: Mh. Chem.106, 483 (1975). 相似文献
4.
Jože Slivnik Mateja Žvanut Borka Sedej 《Monatshefte für Chemie / Chemical Monthly》1968,99(5):1713-1717
Zusammenfassung Die Reaktion zwischen MgCO3 und wässerigen Lösungen von Hydraziniumdifluorid und Flußsäure führt zum Hydraziniumfluoromagnesat. Diese Verbindung ist auch aus Magnesiumchlorid-und Hydraziniumdifluorid-Lösungen herstellbar. Es werden röntgenographische, IR-spektrographische und thermogravimetrische Untersuchungen dieser Verbindung angegeben.
Mit 3 Abbildungen 相似文献
Hydrazinium(+2) fluoromagnesate is formed in the reaction between MgCO3 and hydrazinium difluoride dissolved in hydrogen fluoride. The reaction of magnesium chloride and an aqueous solution of hydrazinium difluoride yields the same product. The results of X-ray diffraction studies, IR spectroscopical studies and thermogravimetrical investigation are given.
Mit 3 Abbildungen 相似文献
5.
Joó F Kovács J Bényei AC Nádasdi L Laurenczy G 《Chemistry (Weinheim an der Bergstrasse, Germany)》2001,7(1):193-199
Hydrolysis and hydrogenation of [RhCl(tppms)3] (1) and trans-[RhCl(CO)(tppms)2] (2) was studied in aqueous solutions in a wide pH range (2 < pH < 11) in the presence of excess TPPMS (3-diphenylphosphinyl-benzenesulfonic acid sodium salt). In acidic solutions hydrogenation of 1 yields a mixture of cis-mer- and cis-fac-[RhClH2(tppms)3] (3a,b) while in strongly basic solutions [RhH(H2O)(tppms)3] (4) is obtained, the midpoint of the equilibrium between these hydride species being at pH 8.2. The paper gives the first successful 1H and 31P NMR spectroscopic characterization of a water soluble rhodium(I)-monohydride (4) bearing only monodentate phosphine ligands. Hydrolysis of 2 is negligible below pH 9 and its hydrogenation results in formation of [Rh(CO)H(tppms)3] (5), which is an analogue to the well known and industrially used hydroformylation catalyst [Rh(CO)H(tppts)3] (6) (TPPTS = 3,3',3'-phosphinetriyltris(benzenesulfonic acid) trisodium salt). It was shown by pH-potentiometric measurements that formation of 5 is strongly pH dependent in the pH 5-9 range, this gives an explanation for the observed but previously unexplained pH dependence of several hydroformylation reactions. Conversely, the effect of pH on the rate of hydrogenation of maleic and fumaric acid catalyzed by 1 in the 2 < pH < 7 range can be adequately described by considering solely the changes in the ionization state of these substrates. All these results warrant the use of buffered (pH-controlled) solutions for aqueous organometallic catalysis. 相似文献
6.
Francisco Eduardo de Sousa Filho João Hermínio da Silva Antônio Álamo Feitosa Saraiva Deyvid Dennys S. Brito Bartolomeu Cruz Viana Bruno Tavares de Oliveira Abagaro Paulo de Tarso Cavalcante Freire 《Brazilian Journal of Physics》2011,41(4-6):275-280
X-ray diffraction was combined with X-ray energy-dispersion, Fourier-transform infrared, and Raman spectroscopies to study the fossilization of a Cretaceous specimen of the plant Brachyphyllum castilhoi, a fossil from the Ipubi Formation, in the Araripe Sedimentary Basin, Northeastern Brazil. Among the possible fossilization processes, which could involve pyrite, silicon oxide, calcium oxide, or other minerals, we were able to single out pyritization as the central mechanism producing the fossil, more than 100 million years ago. In addition to expanding the knowledge of the Ipubi Formation, this study shows that, when combined with other experimental techniques, Raman spectroscopy is a valuable tool at the paleontologist’s disposal. 相似文献
7.
Eliana F. C. Simões João M. M. Leitão Joaquim C. G. Esteves da Silva 《Journal of fluorescence》2014,24(2):639-648
The quantification of nitric oxide (NO) based on the quenching of the fluorescence of a nanocomposites sensor constituted by cadmium/selenium quantum dots (CdSe) stabilized by chitosan (CS) and mercaptosuccinic acid (MSA) is assessed. The optimization of the response of the CS-CdSe-MSA nanocomposites to NO was done by multivariate response surface experimental design methodologies. The highest fluorescence quenching was obtained at pH 5.5 and at room temperature. The NO quantification capability of CS-CdSe-MSA was evaluated using standard solutions and a NO donor reagent. A large linear working range from 5 to 200 μM and a limit of detection of 1.86 μM were obtained. Better quantification results were obtained using the NO donor reagent. Besides NO, the response of the fluorescence of CS-CdSe-MSA to the main reactive oxygen and nitrogen species and similar NO compounds was also assessed. 相似文献
8.
Jooung-Hyun Jo Hyun-Cheol Ko Byeong-Woo Kim Hyun Park In-won Lee Ho-Hwan Chun 《Composite Interfaces》2016,23(8):797-805
AbstractMarine fouling can be a serious problem in the shipping industry, since it increases the surface roughness of the hull and hence its frictional resistance to its movement through water. Antifouling paint can be defined as preventing the attachment of marine organisms onto surfaces. However, the most commonly used antifouling coating which is the tributyltin-based self-polishing copolymer causes the severe pollution of marine environment. Ammonium salt-based paints include tertiary amines as biocides which have effective biocidal and biodegradable properties without accumulation in the sea environment. However, ammonium salt-based coatings were too sensitive to seawater and became swollen. In this study, polyurethane-acrylic copolymers were synthesized by radical polymerization. These hybrid materials were found to form core–shell structures in aqueous media. Synthesis and properties of copolymers were investigated by Fourier transform-infrared spectrometer, proton-nuclear magnetic resonance, transmission electron microscopy, and dynamic light scattering. The polishing rate of self-polishing copolymer was determined from the reduction in dry film thickness after artificial seawater immersion under a dynamic condition. 相似文献
9.
Chun SH Chai YS Jeon BG Kim HJ Oh YS Kim I Kim H Jeon BJ Haam SY Park JY Lee SH Chung JH Park JH Kim KH 《Physical review letters》2012,108(17):177201
We find the realization of large converse magnetoelectric (ME) effects at room temperature in a magnetoelectric hexaferrite Ba0.52Sr2.48Co2Fe24O41 single crystal, in which rapid change of electric polarization in low magnetic fields (about 5 mT) is coined to a large ME susceptibility of 3200 ps/m. The modulation of magnetization then reaches up to 0.62μ(B)/f.u. in an electric field of 1.14 MV/m. We find further that four ME states induced by different ME poling exhibit unique, nonvolatile magnetization versus electric field curves, which can be approximately described by an effective free energy with a distinct set of ME coefficients. 相似文献
10.
Sangsu Park Seungjae Jung Manzar Siddik Minseok Jo Jubong Park Seonghyun Kim Wootae Lee Jungho Shin Daeseok Lee Godeuni Choi Jiyong Woo Euijun Cha Byoung Hun Lee Hyunsang Hwang 《固体物理学:研究快报》2012,6(11):454-456
We propose a selector‐less Pr0.7Ca0.3MnO3 (PCMO) based resistive‐switching RAM (RRAM) for high‐density cross‐point memory array applications. First, we investigate the inhomogeneous barrier with an effective barrier height (Φeff), i.e., self‐formed Schottky barrier. In addition, a scalable 4F2 selector‐less cross‐point 1 kb RRAM array has been successfully fabricated, demonstrating set, reset, and read operation for high cell efficiency and high‐density memory applications. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献