Organic-inorganic hybrid membranes of nanosized SiO 2 -filled polyamide composites were prepared via film casting and their transport properties were studied. Gas permeation measurements were performed at room temperature, and the membrane exhibited an increase in membrane permeability performance. In contrast to the performance of traditional dense filled polymer systems, the permeability increased with an increased number of nanosilica particles. The nanocomposites were studied using positron annihilation lifetime spectroscopy (PALS). From the ortho-positronium (o-Ps) lifetime ( 3 ), the size of the local free volume (holes) was estimated. The increase in permeability is ascribed to the additional free volume obtained. This is created by the presence of nanoparticles that alter the PA chain packing. Furthermore, wide angle X-ray diffraction (WAXD) patterns revealed that the incorporation of silica induced the structural modification of polymer chains by modifying the degree of crystallinity in comparison with the neat polymer.
Hydrogenated diamond-like-carbon (a-C:H) and hydrogen-free amorphous carbon (a-C) coatings are known to be biocompatible and have good chemical inertness. For this reason, both of these materials are strong candidates to be used as a matrix that embeds metallic elements with antimicrobial effect. In this comparative study, we have incorporated silver into diamond-like carbon (DLC) coatings by plasma based ion implantation and deposition (PBII&D) using methane (CH 4 ) plasma and simultaneously depositing Ag from a pulsed cathodic arc source. In addition, we have grown amorphous carbon -silver composite coatings using a dualcathode pulsed filtered cathodic-arc (FCA) source. The silver atomic content of the deposited samples was analyzed using glow discharge optical spectroscopy (GDOES). In both cases, the arc pulse frequency of the silver cathode was adjusted in order to obtain samples with approximately 5 at.% of Ag. Surface hardness of the deposited films was analyzed using the nanoindentation technique. Cell viability for both a-C:H/Ag and a-C:/Ag samples deposited on 24-well tissue culture plates has been evaluated.
Para-positronium (p-Ps) and ortho-Ps (o-Ps) which are formed in the pores of materials are very sensitive probes to determine pore sizes and type of porosity in porous thin film materials. In addition to Positron Beam Analysis with Doppler Broadening a high resolution technique for measuring momentum distributions of the p-Ps is applied: 2D-ACAR combined with the intense positron beam facility present in Delft. Effusion of hot p-Ps was observed from highly porous low-k dielectric SiO 2 films. In silicon nanocavities p-Ps and even o-Ps appeared to exist, but the fractions were seen to depend strongly on the hydrogen content of the cavities. Hydrogen coverage of the cavity walls leads to effective cooling of the hot Ps. Helium in the nanocavities causes a change in the annihilation of Ps. Models for cooling of Ps and the influence of gas and internal gas coverage are discussed.
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