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51.
Aji P. Mathew Gabriel Groeninckx G. H. Michler H. J. Radusch Sabu Thomas 《Journal of Polymer Science.Polymer Physics》2003,41(14):1680-1696
The effects of the blend ratio and initiating system on the viscoelastic properties of nanostructured natural rubber/polystyrene‐based interpenetrating polymer networks (IPNs) were investigated in the temperature range of ?80 to 150 °C. The studies were carried out at different frequencies (100, 50, 10, 1, and 0.1 Hz), and their effects on the damping and storage and loss moduli were analyzed. In all cases, tan δ and the storage and loss moduli showed two distinct transitions corresponding to natural rubber and polystyrene phases, which indicated that the system was not miscible on the molecular level. However, a slight inward shift was observed in the IPNs, with respect to the glass‐transition temperatures (Tg's) of the virgin polymers, showing a certain degree of miscibility or intermixing between the two phases. When the frequency increased from 0.1 to 100 Hz, the Tg values showed a positive shift in all cases. In a comparison of the three initiating systems (dicumyl peroxide, benzoyl peroxide, and azobisisobutyronitrile), the dicumyl peroxide system showed the highest modulus. The morphology of the IPNs was analyzed with transmission electron microscopy. The micrographs indicated that the system was nanostructured. An attempt was made to relate the viscoelastic behavior to the morphology of the IPNs. Various models, such as the series, parallel, Halpin–Tsai, Kerner, Coran, Takayanagi, and Davies models, were used to model the viscoelastic data. The area under the linear loss modulus curve was larger than that obtained by group contribution analysis; this showed that the damping was influenced by the phase morphology, dual‐phase continuity, and crosslinking of the phases. Finally, the homogeneity of the system was further evaluated with Cole–Cole analysis. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1680–1696, 2003 相似文献
52.
用激光溅射 分子束技术研究了气相中Ni的等离子体与甲醇分子团簇的反应 .观察到Ni+ (CH3 OH) n、NiO+ (CH3 OH) n、H+ (CH3 OH) n、H3 O+ (CH3 OH) n 四个种类的团簇正离子和CH3 O-(CH3 OH) n(n≤ 2 5 )一种团簇负离子 .详细考察了激光烧蚀等离子体作用于脉冲分子束的不同位置时 ,对团簇产物种类和团簇尺寸大小的影响 .发现NiO+ (CH3 OH) n 是由Ni+ (CH3 OH) n 团簇内的脱甲烷反应生成的 ,而H+ (CH3 OH) n、H3 O+ (CH3 OH) n主要是激光等离子体中的电子与甲醇团簇碰撞电离产生的 相似文献
53.
A simple procedure for the synthesis of an important standard, isotopically enriched methylmercury, which is not commercially available, has been established successfully. The isotopically enriched standard synthesized is utilized in conventional isotope dilution mass spectrometry (IDMS), as well as in speciated IDMS (SIDMS), for determination of the true concentration of methylmercury in environmental samples. The CH3201Hg+ standard has been synthesized from commercially available 201HgO and tetramethyltin. The synthesis time required is 1 h at 60°C. The product is highly pure, yielding more than 90% as 201Hg in CH3201Hg+. Hazardous dimethylmercury does not occur during this synthesis procedure. The product synthesized was analyzed using high‐performance liquid chromatography coupled with inductively coupled plasma mass spectrometry (ICP‐MS) and ICP‐MS alone in order to determine its concentration, isotopic composition and purity. The stability of the product was also evaluated for over 6 months and found to be stable at 4°C in the dark. The isotopically enriched methylmercury synthesized can be used in SIDMS and IDMS analyses as a standard. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
54.
A method of nonaqueous capillary zone electrophoresis (CZE) has been developed to characterize block (co)polymers of poly(ethylene oxide) and poly(styrene) containing metallo bis(terpyridine) complexes as bridging units. Specific CZE separation conditions had to be applied, with barium perchlorate dissolved in N-methylformamide (NMF) as background electrolyte and OV-1701-OH deactivated capillaries. For detection UV absorption was measured at a wavelength of 316 nm. Metallo diblock polymers with molecular weights up to 30,000 Da could be analyzed by the proposed nonaqueous CZE method. Experiments performed with polymeric compounds containing Fe, Ni or Ru as central metal ions showed that their electrophoretic mobilities were independent of the type of metal ion. Therefore, the data on the size of the polymeric compounds could be obtained using just one set of calibration standards. Polydispersities of the samples calculated from the experimental results were in correlation with the polydispersities of the polymers used in the synthesis of the metallo diblock polymers. Several polymeric samples contained metallo mono(terpyridine) complexes as impurities. These by-products could be separated from the main product. With symmetrical diblock polymers only one by-product was detected, while with an asymmetric diblock polymer two types of mono-complexes were found. The amount of the mono-complexes present as impurities was dependent on the type of central metal ion (Ni > Fe >> Ru). 相似文献
55.
Leo Brewin 《General Relativity and Gravitation》2007,39(4):521-528
We show by an almost elementary calculation that the ADM mass of an asymptotically flat space can be computed as a limit involving
a rate of change of area of a closed 2-surface. The result is essentially the same as that given by David Brown and York (Phys.
Rev. D 55, 1977–1984 1997; Phys. Rev. D 47, 1407–1419 1993). We will prove this result in two ways, first by direct calculation from the original formula as given by
Arnowitt, Deser and Misner and second as a corollary of an earlier result by Brewin for the case of simplicial spaces. 相似文献
56.
C. D. Habben 《无机化学与普通化学杂志》1991,606(1):229-232
Synthesis of Boron-Sulfur(IV)-Nitrogen Heterocycles The reaction of bis(lithio.tert.-butylamino)phenylborane with tert.-butyldichlorosulfimide and bischlorodimethylsilylsulfodiimide respectively leads to four- or eight-membered heterocycles. The disulfanebridge of one dithiazadiborolidine can be replaced by the ? N?S?N-sequence to yield a Thiatriazadiborine. 1H, 11B, 13C-NMR, mass spectra, and analytical data are reported and discussed. 相似文献
57.
58.
Shayesteh S. Farjami B. Soltani M. A. Solimany 《International Journal of Infrared and Millimeter Waves》2002,23(12):1691-1697
We present and discuss infrared magnetoplasma reflectivity and surface polariton modes in Ga1–xNxAs. It assumed that the sample is characterized by a magnetoplasma dielectric tensor. Surface polariton dispersion for two component magnetoplasma was calculated from reflectivity spectra data. We detect transverse optic phonon of GaN sublattice in 470 cm-1. The origin of sharp feature in p-polarization reflectivity about 300 cm–1 as well as LO phonon frequency of GaAs sublattice is due to Brewster mode. An interesting feature of surface modes in Voigt geometry is nonreciprocalicity, which means that the frequency changes when the direction of propagation is reversed. Also, the infrared magnetoplasma reflectivity of GaNAs should be providing determination of the electrons and heavy holes effective mass and carrier's concentration. 相似文献
59.
60.
Summary Dielectric measurements on Na2B4O7(99.5%)−V2O5(0.5%) glass system, in the frequency range 10−3 to 104 Hz and temperature range 300 to 500 K, have been carried out. The normalized plots of complex capacitance have shown a single
mechanism responsible for conduction for both volume and surface measurements with their close values of activation energies
(0.67±0.03) eV and (0.64±0.03) eV, respectively. The low-frequency dispersion (LFD) behaviour has been observed to be perturbed
by the presence of more than one competing process. The impedance plots have shown a parallel combination of a capacitor (C) and a resistor (R), with some contribution of a dispersive element due to charge accumulation in the vicinity of the electrodes. The values
ofR andC were found to be of the same order of magnitude, for both surface and volume measurements. The observedR has shown a decrease with an increase in temperature due to an increase in mobility of Na+ ions, whereasC remains practicaly constant. The complex capacitance surface behaviour is dominated by volume, due to hygroscopy of this
glass system. 相似文献