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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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53.
Paul Podsiadlo Galyna V. Krylova Arnaud Demortière Elena V. Shevchenko 《Journal of nanoparticle research》2011,13(1):15-32
In this article, we review the state-of-the-art in the preparation and characterization of multicomponent self-assembled superlattices
of colloidal nanoparticles with core sizes in the range of 2–20 nm and interparticle spacing less than 2 nm down to intimate
contact stemming from sintering. Several aspects of the field are discussed, including: structural organization, the role
of particle size distribution, key interparticle forces at play, and methods of investigation of the structures. Contrary
to the extensively studied colloidal crystals composed of microscale particles, the nanoparticles possess unique size-dependent
properties, such as electronic, optical, or magnetic, which when combined into periodic structures can potentially lead to
new collective states stemming from precise positioning of the nanocolloids. As such, we examine a number of emerging applications
of this new class of metamaterials. Finally, we speculate on the potential impact of these materials, the new directions,
and the challenges for the researchers. 相似文献
54.
The tetxaacetylation of isobutene has been perfomed in AlCl3/AcCl. Treatment of the crude reaction medium with liquid ammonia yields the title compound. 相似文献
55.
Magrez A Seo JW Mikó C Hernadi K Forró L 《The journal of physical chemistry. B》2005,109(20):10087-10091
Multiwalled carbon nanotubes (MWCNTs) were grown by chemical vapor deposition by applying C(2)H(2) fluxed over Fe(1)(-x)Co(x) catalyst supported by alkaline earth carbonate. Detailed investigations of the chemical process occurring prior and during the growth allowed us a significant improvement of the nanotube production rate and quality. We observed a strong influence of the catalyst stoichiometry on the carbon deposition rate and the nanotube characteristics. We also found evidence for the active role of the support in the growth process, which is explained by the decomposition of the carbonate at the growth temperature. Using the optimized parameters obtained from our study performed in a fixed bed furnace, we could improve the production rate to about 500 g/day of purified MWCNTs in our large-scale rotary tube furnace. 相似文献
56.
Porras MA Dubietis A Kucinskas E Bragheri F Degiorgio V Couairon A Faccio D Di Trapani P 《Optics letters》2005,30(24):3398-3400
We show that the angle-wavelength spectra of light filaments excited by ultrashort pulses experience a transition from X- to O-like structures when their carrier wavelengths are switched from normal to anomalous dispersion. Calculations confirm that the O-shaped conical emission follows the elliptic geometry of the nonlinear Schr?dinger equation with anomalous dispersion. 相似文献
57.
Arbouet A Christofilos D Del Fatti N Vallée F Huntzinger JR Arnaud L Billaud P Broyer M 《Physical review letters》2004,93(12):127401
The absorption of a single isolated metal cluster is directly measured using a novel far-field optical technique based on modulation of its position. Single gold nanoparticles with average diameters down to 5 nm, dispersed on a transparent substrate, are optically detected and their absolute absorption cross section determined. 相似文献
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Femtosecond laser direct writing is employed for the fabrication of buried tubular waveguides in bulk poly(methyl methacrylate). A novel technique using selective chemical etching is presented to resolve the two-dimensional refractive-index profile of the fabrication structures. End-to-end coupling in the waveguides reveals a near-field intensity distribution that results from the superimposition of several propagating modes with different azimuthal symmetries. Mode analysis of the tubular waveguides is performed using the finite-difference method, and the possible propagating mode profiles are compared with the experimental data. 相似文献
60.
Henry-dit-Quesnel A Toupet L Pommelet JC Lequeux T 《Organic & biomolecular chemistry》2003,1(14):2486-2491
The synthesis of difluoromethylphosphonates is becoming difficult due to environmental protective laws restricting the use of HCFCs and CFCs as starting chemicals. To circumvent this limitation, we report the preparation of a thioether as a new source of the lithiodifluoromethylphosphonate. This methodology avoiding the use of HCFCs involves a selective fluorination of sulfide followed by a thiaphilic addition of an organometallic reagent, which offers an alternative route to obtain phosphonodifluoromethyl carbanion. A contrasted reactivity, due to a medium effect, was also noted which allows addition of a wide range of electrophiles including nitroalkenes and DMF to thioethers. 相似文献