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1.
Bulk superconducting samples of type Tl0.5Pb0.5Sr1.6Ba0.4CaCu2−x
Ru
x
O7−δ, (Tl, Pb)/Sr-1212, with 0.0 ≤ x ≤ 0.525 were prepared by the conventional one-step solid-state reaction technique. The prepared samples were investigated
using X-ray powder diffraction, electrical resistivity and electron paramagnetic resonance (EPR) measurements. Enhancement
of the phase formation, superconducting transition temperature T
c and hole carriers concentration P was observed up to x = 0.075. For x > 0.075, a reverse trend was observed. EPR spectra were measured at different temperatures (120–290 K) for all prepared samples.
The number of spins N participating in the resonance and the paramagnetic susceptibility χ were calculated as a function of both Ru-content and
temperature. N and χ increased as the Ru-content increased. A linear relationship between logN and 1/T was established, from which the activation energy E
a was calculated as a function of the Ru-content. The temperature dependence of χ was fitted according to Curie–Weiss type
of magnetic behavior. Curie constant C, Curie temperature θ, the effective magnetic moment μ and the electronic specific heat γ were estimated as a function of the Ru-content. 相似文献
2.
The static system decomposition kinetics of disilane (\documentclass{article}\pagestyle{empty}\begin{document}${\rm Si}_{\rm 2} {\rm H}_{\rm 6} \mathop {\longrightarrow}\limits^1 {\rm SiH}_{\rm 2} + {\rm SiH}_{\rm 4}$\end{document}, 538–587 K and 10–500 Torr), are reported. Reaction rate constants are weakly pressure dependent, and best fits of the data are realized with RRKM fall-off calculations using logA1,∞ = 15.75 and E1,∞ = 52,200 cal. These parameters yield AHf0(SiH2)298 = (63.5 ? Eb, c) kcal mol,?1 where Eb, c is the activation energy for the back reaction at 550 K, M = 1 std state. Five other silylene heat-of-formation values (ranging from 63.9 – Eb, c to 66.0 - Eb, c kcal mol?1) are deduced from the reported decomposition kinetics of trisilane and methyldisilane, and from the reported absolute and relative rate constants for silylene insertions into H2 and SiH4. Assuming Eb, c = 0, an average value of ΔHf0(SiH2) = 64.3 ± 0.3 kcal mol?1 is obtained. Also, a recalculation of the activation energy for silylene insertion into H2, based in part on the new disilane decomposition Arrhenius parameters, gives (0.6 + Eb, c) kcal mol?1, in good agreement with theoretical calculations. 相似文献
3.
4.
The homogeneous gas-phase decomposition kinetics of methylsilane and methylsilane-d3 have been investigated by the comparative-rate-single-pulse shock-tube technique at total pressures of 4700 torr in the 1125–1250 K temperature range. Three primary processes occur: CH3SiH3 → CH3SiH + H2 (1), CH3SiH3 → CH4 + SiH2 (2), and CH3SiH3 → CH2 = SiH2 + H2 (3). The high-pressure rate constants for the primary processes in CH3SiH3 obtained by RRKM calculations are log (k1 + k3) (s?1) = 15.2 - 64,780 Cal/θ and log k2 (s?) = 14.50 - 67,600 → 2800 Cal/θ. For CH3SiD3 these same rate constants are log k1 (s?) = 14.99 - 64,700 cal/θ log k2 (s?) = 14.68 – 66,700 → 2000 cal/θ, and log k3 (s?) = 14.3 ? 64,700 cal/θ. 相似文献
5.
The kinetics and mechanism of the thermal decomposition of n-propylsilane have been studied by the single pulse shock tube-comparative rate technique at pressures around 4700 torr between 1095–1240 K. The primary dissociation processes are 1,1 and 1,2 H2 elimination with ø1,1 ? 0.75 and ø1,2 ? 0.25, respectively. Subsequent decompositions of the primary process product, n-propylsilylene, to propylene and ethylene is complete even in the presence of excess butadiene. Possible mechanistic paths for these decompositions are discussed and an activation energy range of 30 ± 4 kcal is established for both processes. Induced decomposition via silylene chains accounts for 36–46% of the overall reaction in the uninhibited decomposition of n-propylsilane. The silylene chains are quenched in excess butadiene, and studies under maximum inhibition give overall decomposition kinetics of, log k(nPrSiD3, s?1) = 15.26–65,300 ± 1950 cal/2.303. Computer modeling results of the overall reaction both in the absence and presence of butadiene are also presented and shown to be in acceptable agreement with the experimental observations. 相似文献
6.
The shock-induced thermal decompositions of vinylsilane and vinylsilane-d3 (0.2% on argon) have been studied in the temperature range of 1085–1275 K, and at total pressures of about 3100 torr. In systems without silylene traps, some induced decomposition occurs which is attributed to the silylene chain sequence VSiH → C2H2 + SiH2, S?iH2 + VSiH3 ? VSiH2SiH3 → VSiH2S?iH + H2, VSiH2S?iH → VSiH + S?iH2. In the presence of silylene traps (butadiene and acetylene), the overall decomposition kinetics are log k(VSiH3, s?1) = 14.95 ? 63,268 cal/2.303RT and log k(VSiD3, s?1) = 15.14 ? 64,815 cal/2.303RT. Three primary processes contribute to the decomposition: 1,1-H2 elimination, 1,2-H2 elimination, and ethylene elimination. Two mechanisms are proposed, one for exclusive primary process formation of C2H4, and the other for both primary and secondary formation routes. Modeling studies are reported which show that both mechanisms can be made compatible with the rate and product yield data within experimental errors. 相似文献
7.
8.
ABSTRACTBayfol (PC-PBT blend ?lm) is a class of polymeric solid-state nuclear track detector which has a lot of applications in several radiation detection ?elds. It is a bisphenol-A polycarbonate PC blended with polybutylene terephthalate PBT. Bayfol/Palladium (PC-PBT/Pd) nanocomposite films have been deposited using the molding technique. It is worth mentioning that this report is almost the first one dealing with the topic of the changes of physical properties of Bayfol/Pd nanocomposite due to laser exposure. Samples from PC-PBT/Pd (5?wt%) nanocomposite were exposed to IR-pulsed laser of 5-W power, capable of producing 2000 pulses per second with pulse duration of 200?ns at 904?nm. The laser fluences were in the range 2–25?J/cm2. The resultant modi?cations in the exposed nanocomposite samples have been studied as a function of fluence using different characterization techniques such as X-ray diffraction (XRD), UV spectroscopy and color difference studies. The results indicate the proper dispersion of Pd nanoparticles in the PC-PBT matrix that causes a strong intermolecular interaction between Pd and PC-PBT, resulted in an increase in refractive index and the amorphous phase. Also, it is found that the laser exposure reduces the optical energy gap that could be attributed to the increase in structural disorder of the exposed PC-PBT/Pd nanocomposites due to crosslinking. Further, the color intensity ΔE, which is the color difference between the exposed samples and the non-exposed one, was increased with increasing the laser fluence, convoyed by a significant increase in the green and yellow color components. 相似文献
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10.