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931.
Song C Wang D Gu G Lin Y Yang J Chen L Fu X Hu Z 《Journal of colloid and interface science》2004,272(2):340-344
Silver-coated poly(methyl acrylic acid) (PSA) core-shell colloid particles were prepared by an in situ chemical reduction method. Crystalline silver/titania composite hollow spheres were obtained by coating the as-prepared PSA/silver particles with an amorphous titania layer and subsequently calcining in Ar atmosphere. SEM and TEM investigation indicated that the size of the as-prepared PSA/silver and PSA/silver/TiO(2) core-shell particles and silver/titania composite hollow particles was fairly uniform and the wall thickness of the hollow spheres was in the range of 40-80 nm. UV-vis absorption spectra were recorded to investigate their optical properties. 相似文献
932.
Jocelyn Jalbert Roland Gilbert Pierre Tétreault Brigitte Morin Denise Lessard-Déziel 《Cellulose (London, England)》2007,14(4):295-309
In this study, headspace gas chromatography/mass spectrometry has been used to assess the volatile by-products generated by
the ageing of oil-impregnated paper insulation of power transformers. Sealed-glass ampoules were used to age under oxidative
conditions 0.5-g specimens of insulating paper in 9 mL of inhibited mineral oil in a temperature range of 60–120 °C and moisture
of 0.5, 1 and 2% (w/w). A linear relationship between one of the oil-soluble degradation by-products, i.e. methanol, and the
number of ruptured 1,4-β-glycosidic bonds of cellulose, regardless of the type of paper (ordinary Kraft or thermally-upgraded
(TU) Kraft paper), was established for the first time in this field. Ageing at 130 °C of model compounds of the Kraft paper
constituents (α-cellulose, hemicellulose and lignin) and two cellulosic breakdown by-products (D-(+)-glucose and 1,6-anhydro-β-d-glucopyranose) confirmed that the α-cellulose degradation was mostly responsible for the presence of this molecule in the
system. Furthermore, additional 130 °C-tests with six different papers and pressboard samples under a tight control of initial
moisture indicated that at least one molecule of methanol is formed for each rupture of 1,4-β-glucosidic bond of the molecular
chains. Stability tests showed that the ageing indicator is stable under the oxygen and temperature conditions of open-breathing
transformers. The presence of methanol was detected in 94% of oil samples collected from over than 900 in-service pieces of
equipment, confirming the potential for this application. Lastly, the tests have shown that oil-oxidation by-products and
TU-nitrogenous agents modify the methanol partitioning coefficients in the paper/oil/air system, which makes their study essential
over a range of field conditions encountered by power transformers. Results are presented and discussed in comparison with
2-furfuraldehyde, which is the current reference in the domain. 相似文献
933.
Muhammad Ilyas Sarwar Sonia Zulfiqar Zahoor Ahmad 《Colloid and polymer science》2007,285(15):1733-1739
Fluoro-aramid-based sol/gel-derived nanocomposites were synthesized by condensing a mixture of 4,4′-(hexafluoro-isopropylidene)dianiline
and 1,3-phenylenediamine with terephthaloylchloride (TPC) in dimethylacetamide. TPC was added in slight excess to produce
amide chains with carbonyl chloride end groups and then replaced with alkoxy groups using aminophenyltrimethoxysilane to develop
bonding with the silica network. Mechanical, dynamic mechanical thermal, water absorption and morphological measurements were
carried out on the thin hybrid films. Increase in the tensile strength and modulus was observed as compared to pristine polyamide.
The thermal decomposition temperature was found in the range of 400–500 °C. The water absorption was found to be reduced with
higher silica content. The glass transition temperature and the storage moduli increased with increasing silica concentration.
The maximum increase in the T
g value (345 °C) was observed with 20 wt% silica. Scanning electron microscopy revealed the uniform distribution of silica
in the matrix with an average particle size ranging from 8 to 50 nm. 相似文献
934.
935.
We suggest a new phenomenological potential for heavy quarkonium. The potential has a Lorentz vector term motivated by experimental leptonic widths for vector mesons and perturbative QCD at short distances and a Lorentz scalar term responsible for quark confinement at large distances. Using this potential we calculate the energy levels, leptonic decay widths, radiative transition rates and hadronic decay rates of the \(c\bar c, b\bar b\) and \(t\bar t\) systems. Most results agree well with the experiment. 相似文献
936.
937.
Mokhammad Arif G. V. Samoilenko Yu. G. Sergeev L. N. Blinov 《Russian Journal of Applied Chemistry》2005,78(9):1398-1402
The phase diagram of the system Sb2S3-AgI was constructed from data of the differential thermal and X-ray phase analyses. The physicochemical properties of glassy and crystalline alloys were studied. 相似文献
938.
A facile one-step method has been developed for the synthesis of N-protected α-amino aldehyde acetals in moderate to good yields by three-component reaction of fluoroalkanesulfonyl azides, vinyl ethers and alcohol at 0 °C within 10 min. This practical synthetic method provides a convenient and expeditious access to N-per(poly)fluoroalkanesulfonyl α-amino aldehyde acetals. 相似文献
939.
Ch. V. Subba Reddy Y. Y. Qi W. Jin Q. Y. Zhu Z. R. Deng W. Chen Sun-il Mho 《Journal of Solid State Electrochemistry》2007,11(9):1239-1243
Molybdenum trioxide (MoO3) xerogel films modified with poly(vinyl alcohol)+poly(vinyl pyrrolidone) (PVP+PVA) polyblends were obtained by ion-exchange
method with sol-gel technique. Investigations were conducted using X-ray “diffractometry”, Fourier transform infrared spectroscopy,
and cyclic voltammetry. The results show that the H atoms in polyblend are H-bonded with the O atoms in the Mo=O bonds of
MoO3 xerogel, which effectively shield the electrostatic interaction between MoO3 interlayer and Li+ ions when MoO3 xerogel is modified by the intercalation of (PVP+PVA). The reversibility of the insertion/extraction of Li+ ions is greatly improved by the modification with polyblend of MoO3 nanocomposite films. MoO3 and (PVP+PVA)
x
MoO3 (x = 0, 0.5) nanobelts were obtained by a simple hydrothermal process from MoO3 sol. The electrochemical cells with configuration Li/(LiPF6+EC+DMC)/MoO3 modified by (PVP+PVA) were fabricated and their discharge profiles studied. 相似文献
940.
Quasiclassical, direct dynamics trajectories have been used to study the reaction of formaldehyde cation with molecular hydrogen, simulating the conditions in an experimental study of H2CO+ vibrational effects on this reaction. Effects of five different H2CO+ modes were probed, and we also examined different approaches to treating zero-point energy in quasiclassical trajectories. The calculated absolute cross-sections are in excellent agreement with experiments, and the results provide insight into the reaction mechanism, product scattering behavior, and energy disposal, and how they vary with impact parameter and reactant state. The reaction is sharply orientation-dependent, even at high collision energies, and both trajectories and experiment find that H2CO+ vibration inhibits reaction. On the other hand, the trajectories do not reproduce the anomalously strong effect of nu2(+) (the CO stretch). The origin of the discrepancy and approaches for minimizing such problems in quasiclassical trajectories are discussed. 相似文献