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Plasma treatment is often used to modify the surface properties of polymer films, since it offers numerous advantages over the conventional surface modification techniques. In this paper, a polypropylene (PP) film is plasma-treated using a dielectric barrier discharge (DBD) operating in air at medium pressure (5.0 kPa). The modified polymer films are characterized using contact angle measurements, XPS-analysis and attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy. Results show that plasma treatment leads to a remarkable decrease in contact angle owing to the implantation of oxygen-containing functional groups. Using XPS and ATR-FTIR, these oxygen-containing groups can be identified as C-O, C O and O-C O. In this paper, it is also shown that XPS is well-suited to provide quantitative chemical analysis of the PP films, while ATR-FTIR can only give qualitative information. To perform quantitative ATR-FTIR measurements, chemical derivatization will be explored in the near future.

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Retaining large surface areas in alumina powders during high-temperature annealing is a major challenge in applications as catalyst supports and ceramic precursors. This is because the alumina surface area drastically decreases with transformation from the γ modification (defect spinel structure) into the α modification (corundum structure). The objective of this work is to show the thermodynamic basis of using additives, such as Zr and Mg, to control the γ-Al2O3 surface and bulk energetics and to manipulate the transformation temperature and surface area. These additives are observed to change the pattern of phase transformation and densification. Direct measurements of heats of solution in a lead borate melt of pure and doped alumina as a function of surface area enabled us to experimentally derive trends in the surface energies of hydroxylated surfaces. Accounting for heats of water adsorption measured on pure and doped alumina surfaces allowed us to delineate the thermodynamic effects of hydration on surface energies. Zr-doped γ-alumina showed a higher energy of the hydroxylated surface than did pure γ-alumina but showed a lower energy of the anhydrous surface. Mg addition does not change surface energies significantly but decreases the energetic instability of the bulk γ phase.

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Abstract-We present the results ofirradiation experiments aimed at understanding the structural and chemical evolution ofsilicate grains in the interstellar medium. A series of'Het irradiation experiments have been performed on ultra-thin olivine, (Mg,FehSi0 4 samples having a high surface/volume (S/V) ratio, comparable to the expected S/V ratio of interstellar dust. The energies and fluences of the helium ions used in this study have been chosen to simulate the irradiation of interstellar dust grains in supernovae shock waves. The samples were mainly studied using analytical transmission electron microscopy. Our results show that olivine is amorphized by low-energy ion irradiation. Changes in composition are also observed. In particular, irradiation leads to a decrease ofthe atomic ratios O/Si and Mg/Si as determined by x-ray photoelectron spectroscopy and by x-ray energy dispersive spectroscopy. This chemical evolution is due to the differential sputtering of atoms near the surfaces. We also observe a reduction process resulting in the formation ofmetallic iron. The use of very thin samples emphasizes the role of surface/volume ratio and thus the importance of the particle size in the irradiation-induced effects. These results allow us to account qualitatively for the observed properties of interstellar grains in different environments, that is, at different stages oftheir evolution: chemical and structural evolution in the interstellar medium, from olivine to pyroxenetype and from crystalline to amorphous silicates, porosity of cometary grains as well as the formation of metallic inclusions in silicates.

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