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51.
Strong,Thermally Superinsulating Biopolymer–Silica Aerogel Hybrids by Cogelation of Silicic Acid with Pectin 下载免费PDF全文
Dr. Shanyu Zhao Dr. Wim J. Malfait Dr. Arnaud Demilecamps Dr. Yucheng Zhang Dr. Samuel Brunner Lukas Huber Dr. Philippe Tingaut Dr. Arnaud Rigacci Dr. Tatiana Budtova Dr. Matthias M. Koebel 《Angewandte Chemie (International ed. in English)》2015,54(48):14282-14286
Silica aerogels are excellent thermal insulators, but their brittle nature has prevented widespread application. To overcome these mechanical limitations, silica–biopolymer hybrids are a promising alternative. A one‐pot process to monolithic, superinsulating pectin–silica hybrid aerogels is presented. Their structural and physical properties can be tuned by adjusting the gelation pH and pectin concentration. Hybrid aerogels made at pH 1.5 exhibit minimal dust release and vastly improved mechanical properties while remaining excellent thermal insulators. The change in the mechanical properties is directly linked to the observed “neck‐free” nanoscale network structure with thicker struts. Such a design is superior to “neck‐limited”, classical inorganic aerogels. This new class of materials opens up new perspectives for novel silica–biopolymer nanocomposite aerogels. 相似文献
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Flat channel asymmetrical flow field-flow fractionation with multi-angle light scattering (MALS) detection was used to study the swelling behaviour of core-shell particles with either carboxylated or hydroxylated shells as a function of pH and ionic strength. The equilibration time of the most heavily carboxylated core-shells appeared to be of the order of several hours. At low ionic strength (5 mM), the carboxylated core-shells showed a definite swelling response to a change in pH in the range from 5 to 10, ranging from a hydrodynamic radius increase of 24 to 118%, depending on the degree of carboxylation. A much milder response was found for the change of the root mean square (r.m.s.) radius as measured with MALS, indicating that the scattering plane is moving inwards during the swelling process due to a decreasing density of the shell. The hydroxylated core-shells appeared to be inert to a change in pH. Also the response of two expanded (pH 10) carboxylated core-shells on increasing ionic strength was studied. Comparison of the results of these ionic strength experiments with theoretical predictions based on Donnan equilibrium led us to the conclusion that a significant amount of counter-ion condensation may take place in the shells. 相似文献
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Sikharulidze I Dolbnya IP Fera A Madsen A Ostrovskii BI de Jeu WH 《Physical review letters》2002,88(11):115503
The dynamics of the layer-displacement fluctuations in smectic membranes have been studied by x-ray photon correlation spectroscopy (XPCS). We report transitions from an oscillatory damping regime to simple exponential decay of the fluctuations, both as a function of membrane thickness and upon changing from specular to off-specular scattering. This behavior is in agreement with recent theories. Employing avalanche photodiode detectors and the uniform filling mode of the synchrotron storage ring, the fast limits of XPCS have been explored down to 50 ns. 相似文献
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Wim Vervaat 《Stochastic Processes and their Applications》1973,1(4):317-334
Weak and strong functional limit theorems are obtained for record values and record epochs in a sequence of independent random variables with common distribution F. The emphasis is on the case in which F is concentrated on the non-negative integers. For contrast, the well-known case of continuous F is also considered. Analogues of results obtained earlier by Resnick, de Haan and the author for continuous F are presented here for F concentrated on the non-negative integers. Also is investigated under which circumstances the latter case is so close to the continuous F case that the resulting limit theorems are the same. 相似文献
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Gu R Depraetere S Kotek J Budka J Wagner-Wysiecka E Biernat JF Dehaen W 《Organic & biomolecular chemistry》2005,3(16):2921-2923
The first example of substitution reaction in the free alpha-position of N-confused calix[4]pyrroles is reported: azo-coupling with various arenediazonium salts. The obtained azocompounds were used for studies of their anion-binding properties by UV-Vis spectroscopy. 相似文献
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Bonn D Kobylko M Bohn S Meunier J Morozov A van Saarloos W 《Physical review letters》2004,93(21):214503
When a rotating rod is brought into a polymer melt or concentrated polymer solution, the meniscus climbs the rod. This spectacular rod climbing is due to the normal stresses present in the polymer fluid and is thus a purely non-Newtonian effect. A similar rod climbing of an interface between two fluids has therefore been taken as a signature that one of the fluids exhibits normal stress effects. We show here, however, that the effect can occur with simple Newtonian fluids: it occurs when a Taylor-Couette instability happens in the less viscous of the two liquids but not in the more viscous one. 相似文献