172 research outputs found
Electrostatic interaction between colloidal particles trapped at an electrolyte interface
The electrostatic interaction between colloidal particles trapped at the
interface between two immiscible electrolyte solutions is studied in the limit
of small inter-particle distances. Within an appropriate model exact analytic
expressions for the electrostatic potential as well as for the surface and line
interaction energies are obtained. They demonstrate that the widely used
superposition approximation, which is commonly applied to large distances
between the colloidal particles, fails qualitatively at small distances and is
quantitatively unreliable even at large distances. Our results contribute to an
improved description of the interaction between colloidal particles trapped at
fluid interfaces.Comment: Submitte
Poisson-Boltzmann study of the effective electrostatic interaction between colloids at an electrolyte interface
The effective electrostatic interaction between a pair of colloids, both of
them located close to each other at an electrolyte interface, is studied by
employing the full, nonlinear Poisson-Boltzmann (PB) theory within classical
density functional theory. Using a simplified yet appropriate model, all
contributions to the effective interaction are obtained exactly, albeit
numerically. The comparison between our results and those obtained within
linearized PB theory reveals that the latter overestimates these contributions
significantly at short inter-particle separations. Whereas the surface
contributions to the linear and the nonlinear PB results differ only
quantitatively, the line contributions show qualitative differences at short
separations. Moreover, a dependence of the line contribution on the solvation
properties of the two adjacent fluids is found, which is absent within the
linear theory. Our results are expected to enrich the understanding of
effective interfacial interactions between colloids
Brоnsted Acidic Ionic Liquid-Catalyzed Tandem Reaction: an Efficient Approach Towards Regioselective Syntheses of Pyrano[3,2-c]Coumarins under Solvent-Free Conditions Bearing Lower E-Factors
Effect Of Nanoclay On The Toughness Of Epoxy And Mechanical, Impact Properties Of E-glass-epoxy Composites
Organically modified montimorillonite nanoclay was added to the epoxy and E-glass-epoxy composites. The influence of nanoclay content (varied between 0 to 5wt %) on the relative crosslink density and the fracture toughness of the epoxy matrix was studied. Differential scanning calorimetry (DSC) indicated that the amino functional groups present on the nanoclay react with the epoxy matrix to increase the crosslink density of about 13 and 18% at 3 and 5wt% addition, respectively. The toughness of the epoxy composites increased by 25% at 3wt% addition of nanoclay, whereas, it decreases at 5wt%. Flexural strength and tensile strength of the E-glass-epoxy composites were found to increase by 12% and 11% respectively at 3wt% addition of nanoclay, while at 5wt% addition these properties decreased due to the matrix embrittlement. Interestingly matrix embrittlement is found to be beneficial in increasing the impact resistance due to spallation of embrittled matrix that ensures the dissipation of the impact energy. 5wt% nanoclay addition increases the impact strength by 29% and reduces the back face bulge of composite by 31%. These results may lead to the design and realization of glass-epoxy composites with better impact strength
A Mild and Efficient Method for the Syntheses and Regioselective Ring-Opening of Aziridines
We have developed a new synthetic method for the synthesis of aziridines using Chloramine-T as an effective reagent in the presence of NH2OH center dot HCl and NaIO4. We found that the same combination of NH2OH center dot HCl and NaIO4 is also very effective for nucleophilic ring opening of aziridines.This research was funded by the Russian Science Foundation, grant number 18-19-00090
Effect of argon ion energy on the performance of silicon nitridemultilayer permeation barriers grown by hot-wire CVD on polymers
One of the authors (S.M.) acknowledges Direction des Relations Extérieures of Ecole Polytechnique for financial support.Permeation barriers for organic electronic devices on polymer flexible substrates were realized by combining stacked silicon nitride (SiNx) single layers (50 nm thick) deposited by hot-wire chemical vapor deposition process at low-temperature (~100°C) with a specific argon plasma treatment between two successive layers.
Several plasma parameters (RF power density, pressure, treatment duration) as well as the number of single layers have been explored in order to improve the quality of permeation barriers deposited on polyethylene terephthalate. In this work, maximumion energy was highlighted as the crucial parameter making it possible to minimize water vapor transmission rate (WVTR), as determined by the electrical calcium test method, all the other parameters being kept fixed. Thus fixing the plasma treatment duration at 8 min for a stack of two SiNx single layers, a minimum WVTR of 5 × 10−4 g/(m2 day), measured at room temperature, was found for a maximum ion energy of ~30 eV. This minimum WVTR value was reduced to 7 × 10−5 g/(m2 day) for a stack of five SiNx single layers. The reduction in the permeability is interpreted as due to the rearrangement of atoms at the interfaces when average transferred ion energy to target atoms exceeds threshold displacement energy.The authors are grateful to Dr. R. Cortes (PMC, Ecole Polytechnique) for XRR analysis, to Dr. P. Chapon (HORIBA Jobin Yvon) for GD-OES analysis and Dr. J. Leroy (CEA Saclay) for XPS analysis. This work was partly supported by the PICS (FrenchPortuguese) project No. 5336. One of the authors (S.M.) acknowledges Direction des Relations Extérieures of Ecole Polytechnique for financial support
Synthesis of (Hetero)Macrocycles under Environmentally Friendly Conditions
This work was supported in part by the Russian Science Foundation (References Nos. 18-13-00365 and 18-73-00301)
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