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991.
The thermodynamic properties, such as free energy of mixing, heat of mixing, activity and structural properties, such as concentration fluctuation in long wavelength limit, short-range order parameter of Pb–Hg liquid alloy at 600 K have been calculated using theoretical modelling. It has then been correlated with modified Butler model to compute the surface tension of the alloys at different temperatures. The Pb–Hg system at 600 K is found to be ordering at higher concentration of Pb. 相似文献
992.
993.
The improvement of miscibility between toughened Polyamide-6 (PA6) and Styrene-Butadiene Rubber (SBR) was carried out using grafted Glycidyl Methacrylate (SBR-g-GMA). At first, the compatibilizers were prepared using different comonomers, Styrene, and N-vinyl pyrrolidone. Central composited design (CCD) was distinctly applied to study the influence of Glycidyl Methacrylate (GMA) content and comonomer/GMA on the process of compatibilizer preparation. Four models were developed for Gel content and Degree of grafting for both comonomers using Design-expert software. The models were used to calculate the optimum operating conditions and according to the Flory-Huggins parameter and obtained results, SBR-co-NVP-g-GMA was chosen as an effective compatibilizer. Afterward, another CCD was employed to scrutinize the effect of various amounts and grafting degree of compatibilizer on morphology and mechanical properties of PA6/SBR. The Interparticle distance and polydispersity were studied using a Scanning electron microscope (SEM) and also the Izod impact test inspected in order to evaluate the mechanical properties. Finally, modulus and impact strength were optimized to minimize the former and maximize the latter. Also, the most practical terms in the fitted model are statistically specified using F-value. The root causes for the improvement of blend properties were attributed to a chemical reaction between epoxy groups in SBR-g-GMA and both the carboxylic and amine groups in PA6. Impact strength (539.8 J/m) and modulus (2017.2 N/mm2) of the optimum blend indicate an excellent agreement with the amounts predicted by the models. 相似文献
994.
Juan M. Venegas Zisheng Zhang Theodore O. Agbi William P. McDermott Anastassia Alexandrova Ive Hermans 《Angewandte Chemie (International ed. in English)》2020,59(38):16527-16535
Boron‐containing materials, and in particular boron nitride, have recently been identified as highly selective catalysts for the oxidative dehydrogenation of alkanes such as propane. To date, no mechanism exists that can explain both the unprecedented selectivity, the observed surface oxyfunctionalization, and the peculiar kinetic features of this reaction. We combine catalytic activity measurements with quantum chemical calculations to put forward a bold new hypothesis. We argue that the remarkable product distribution can be rationalized by a combination of surface‐mediated formation of radicals over metastable sites, and their sequential propagation in the gas phase. Based on known radical propagation steps, we quantitatively describe the oxygen pressure‐dependent relative formation of the main product propylene and by‐product ethylene. Free radical intermediates most likely differentiate this catalytic system from less selective vanadium‐based catalysts. 相似文献
995.
AbstractEffective extraction of phyto-biomolecules insures retaining maximum functionality along with higher recovery. In this study, ultrasound-solvent assisted extraction (USAE) was employed for optimal extraction of phyto-biomolecules from Sesamum indicum (sesame) leaves using the approach of Response Surface Methodology (RSM). The optimized condition of 200?W power, 59% methanol concentration with 1:14?g/mL solid–liquid ratio and 15?min of extraction time yielded 367.39?±?1.85?mg GAE/100?g of total phenolic content, 96.72?±?3.27% of free radical scavenging activity and 81.20?±?2.87% of iron chelating activity respectively. The extract consist of essential phytocomponents like gallic acid, chlorogenic acid, and quercetin with lipid peroxidation activities of >50% over incubation time of 48?h. Also, showed antimicrobial activity against various Gram’s negative and positive food borne pathogens. The results of this study implied the importance of USAE for effective and optimum recovery of phyto-biomolecules from Sesame leaves with retained functional properties. 相似文献
996.
Dr. Ryohei Yasukuni Prof. Nordin Félidj Dr. Leïla Boubekeur-Lecaque Stéphanie Lau-Truong Prof. Jean Aubard 《Chemphyschem》2020,21(22):2614-2619
Localized surface plasmon resonance (LSPR) excitation on the photochromic reaction of a diarylethene derivative (DE) was studied by surface enhanced Raman scattering (SERS). UV and visible light irradiations transform reversibly DE between open-form (OF) and closed-form (CF) isomers, respectively. A mixture of PMMA and DE (either OF or CF isomer) was spin-coated onto gold nanorods (GNRs) arrays, designed by electron beam lithography, with two localized surface plasmon resonances (LSPR) at distinct wavelengths, due to their anisotropy. The photochromic reaction rates from CF to OF isomers, under LSPR excitation, were monitored from SERS spectral changes under different polarizations, on the same GNR substrate to compare the effect of LSPR field strength. It appears that the photoisomerization rate was faster when LSPR was excited with the polarization parallel to the GNR long axis. The present results highlight a potential genuine mechanism, from near field LSPR excitation, involved in the photochromic enhancement of diarylethene photochromes. 相似文献
997.
Y. Lin H. Yasuda M. Miyama T. Yasuda 《Journal of polymer science. Part A, Polymer chemistry》1996,34(10):1843-1851
Perfluorocarbon monomers such as C2F4, C2F6, C4F10, and mixtures thereof with H2, were subjected to plasma polymerization and deposited onto low-density polyethylene (LDPE) substrates. The effect of plasma conditions, surface characteristics, and surface dynamics of plasma polymers on their ability to improve the resistance to water vapor permeation was investigated. An optimum discharge energy density was found for a monomer which provided the greatest reduction water vapor permeability. Although all of the plasma polymers show higher hydrophobicity than polyethylene, the reduction in water vapor permeability is not uniquely related to water contact angle. The surface-dynamic stability of a plasma polymer surface was found to be the key factor in determining the barrier performance of the plasma polymer. The extent of change of surface-configuration after water immersion strongly correlated with the improvement in the water vapor permeation resistance. Plasma polymers with the higher surface-dynamic stability provided the better water barrier coating applied on LDPE films. © 1996 John Wiley & Sons, Inc. 相似文献
998.
999.
Thierry Boxus Michle Deldime-Rubbens Patrick Mougenot Yves-Jacques Schneider Jacqueline Marchand-Brynaert 《先进技术聚合物》1996,7(7):589-598
Poly(ethylene terephthalate) (PET) films and track-etched microporous membranes naturally display, on their surfaces, reactive chain-ends, i.e. carboxyl and hydroxyl functions. These were assayed by suitable activation (reaction with carbodiimide and tosyl chloride, respectively), followed by coupling with 3H-lysine and liquid scintillation counting of the sample-associated radioactivity. Values ranging between 5 and 30 pmol/cm2 (open surface) of labeled end-groups were obtained, depending on the physico-chemical nature of the samples. Basic hydrolysis enriched the PET films with both types of endings (15–25 pmol/cm2). Reduction of films with the NaBH4-catechol complex in tetrahydrofuran enriched their surfaces with hydroxyl groups. However, this procedure was not readily applicable to the surface modification of membranes; we observed an erosion effect that was confirmed by scanning electron microscope analyses. In contrast with the reduction process, the oxidation with KMnO4 in 1.2N H2SO4 could be easily applied to the modification of either films or membranes; their surfaces were significantly enriched with carboxyl groups (15–50 pmol/cm2). This surface modification strategy has been used for the covalent coupling of adhesive proteins on PET membranes developed as supports for cell cultivation. 相似文献
1000.
The stabilizing structure of cationic surfactant-protected platinum clusters in water and tertiary amine-protected rhodium clusters in chloroform, prepared by photo- and hydrogen-reduction, respectively, was investigated. These nanoscopic noble metal clusters present a narrow size distribution and are stable. The structural information of protective organic molecules on the surface of metal clusters was studied by transmission electron microscopy and hydrodynamic radius measurements according to the Taylor dispersion method. The size of the entire cluster with the protective layer surrounding the metal surface, obtained as Stokes' radii by the Taylor dispersion method, is considered to be fairly consistent with the sum of the naked particle size, obtained by transmission electron micrographs, and the size of the adsorbed protective layer, supporting the conformational information. 相似文献