Search results for "Microstructure"
showing 10 items of 707 documents
A numerical-analytical model for the characterization of composites reinforced by carbon nanotubes
2010
A mixed model, numerical-analytical, is presented that allows one to predict the elastic properties of carbon nanotube (CNT)/polymer composites containing a random distribution of CNTs, while taking account of the curvature that they show when immersed in the polymer. This hybrid approach is a significant advance over micromechanical modeling and can be applied to all nanostructured composites.
Selective localization of organoclay and effects on the morphology and mechanical properties of LDPE/PA11 blends with distributed and co-continuous m…
2010
A study was made on the effect of small amounts of organically modified clay on the morphology and mechanical properties of blends of low-density polyethylene and polyamide 11 at different compositions. The influence of the filler on the blend morphology was investigated using wide angle X-ray diffractometry, scanning and transmission electron microscopy and selective extraction experiments. The filler was found to locate predominantly in the more hydrophilic polyamide phase. Although such uneven distribution does not have a significant effect on the onset of phase co-continuity of the polymer components, it brings about a drastic refinement of the microstructure for the blends both with dr…
Atmospheric aging and surface degradation in As2S3 fibers in relation with suspended-core profile
2015
Abstract Microstructured optical fibers (MOF) can be seen as next generation fiber of significance in advancing the compact optics because of its excellent compatibility in integrated optics. However, the degradation of their physicochemical properties limits their efficiency and lifetime. Atmospheric moisture is responsible for the degradation of amorphous systems especially chalcogenide glasses. In the light of previously reported studies, in order to clarify the aging process continuously evolving in sulfide microstructured optical fiber over time, a detailed investigation of this phenomenon has been conducted. The time-dependent transmission and glass chemical deterioration have been st…
Chalcogenide Fibers for Mid-IR Light Generation: Potentialities and Drawbacks of the Microstructured Design in Sulfide Waveguides
2014
We study optical and structural aging in As2S3 microstructured optical fibers, submitted to room atmosphere that may have, among others, an impact on mid-infrared supercontinuum generation.
Surface plasmon near-field imaging of very thin microstructured polymer layers.
2004
We report on the near-field imaging of microstructured polymer layers deposited on an homogeneous metal thin film on which a surface plasmon mode is excited. The microstructures in the polymer layers are designed by electron beam lithography, and the near-field imaging is performed with a photon scanning tunneling microscope (PSTM). We show that, despite their very small height, the microstructures can be conveniently imaged with a PSTM thanks to the field enhancement at the surface of the metal thin film supporting the surface plasmon. The influence of the illumination conditions on the contrast of the PSTM images is discussed. In particular, we show that both the field enhancement and the…
Microstructure analysis of biocompatible phosphoester copolymers
2013
Copolymers with varying compositions of 2-ethoxy-2-oxo-1,3,2-dioxaphospholane (EEP) and 2-ethoxy-4-methyl-2-oxo-1,3,2-dioxaphospholane (EMEP) have been synthesized via 1,5,7-triazabicyclo[4.4.0]dec-5-ene-catalyzed anionic ring-opening polymerization. The molecular weights and comonomer ratios were well controlled and polymers with reasonable molecular weight distributions (<1.5) were obtained in all cases. The copolymers were investigated by 1H and 31P NMR spectroscopies to determine the underlying microstructure via detailed dyad analysis. The copolymers were found to be nontoxic to HeLa cells. Furthermore, the obtained copolymers of EEP and EMEP show thermoresponsive properties, i.e., exh…
Synthesis and characterization of water-swellable?,?-polyasparthydrazide derivatives
1995
α, β-polyasparthydrazide (PAHy) was crosslinked by glutaraldehyde to form water-swellable materials possessing a three-dimensional molecular network. Different crosslinking degrees were prepared varying glutaraldehyde/PAHy ratio and samples containing 5-fluorouracil were obtained by incorporating the drug into the polymer networks during the crosslinking reaction. All samples were characterized by swelling tests, thermal, x-ray and SEM analysis. Their microstructure was observed through scanning electron microscopy. Furthermore, for samples containing the anticancer drug,in vitro release studies were performed in pH 7.4 buffer solution.
PBI-based composite membranes for polymer fuel cells
2010
Abstract In the present study poly(2,2-(2,6-pyridin)-5,5-bibenzimidazole) was used for the preparation of novel MEAs for high-temperature polymer fuel cells (HT-PEMFCs). We prepared hybrid materials with two types of silica fillers in order to increase the MEA performances using this polymer. The membranes were characterized in terms of their microstructure and thermal stability. Cell operation tests and Electrochemical Impedance Spectroscopy were used for the characterization of the MEAs. A maximum power density of about 80 mW cm−2 was obtained at 300 mA cm−2 by using an imidazole-modified silica filler. The EIS technique showed that the fillers chiefly help to reduce the charge transfer r…
Structural properties of concave cylindrical brushes interacting with free chains
2011
We present a self-consistent field theoretical study of the microstructure of concave cylindrical brushes as a function of the cylinder radius, grafting density, grafted chain length, and the solvent quality. We show that the results for the radial monomer density profile and the distribution of the free ends are in good agreement with the corresponding molecular dynamics results. Part of the investigation is focused on the conformational behavior of a free macromolecule in a cylindrical brush. A central result is the observed non-monotonous variation of the size of a free chain in a brush-coated tube when the tube radius is systematically changed. An interpretation of this behavior which d…