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This paper focuses on the understanding of the main mechanisms that participate in the growth process of an SiO2‐like film in an atmospheric pressure Townsend discharge in N2 with small ad‐mixtures of HMDSO and N2O. The approach consists of analyzing the influence of operating parameters on the growth rate profile through a fluid dynamics model. The suggested chemical mechanism is constituted by one volume reaction and one surface reaction. This simple model enables us to assume which phenomena control the film growth process among the following mechanisms: HMDSO dissociation by N2(A3Σ) in Si‐containing radicals, radicals transport to the surface, and surface activation process by plasma.magnified image

Atmospheric pressure plasma deposition of nano-crystalline graphite films on titanium substrates from a predominantly ethanolic liquid phase was carried out under varying applied voltage. A thorough study of the plasma electrolytic deposition mechanisms has been performed. The investigation of the composition, structural properties, and the morphology of these graphite coatings have been performed by visible and ultraviolet Raman spectroscopy, X-ray Photoelectron Spectroscopy, Scanning Electron Microscopy and X-ray elemental microanalysis. The experimental evidence of the reduction of the work function and the enhancement of the plasma intensity with the presence of the carbon film has been reported. These properties make such nano-crystalline graphite coatings very attractive for the production of inexpensive cold cathodes for electronics and plasma devices.

International audienceA space-used filled silicone rubber (silica and iron oxide fillers) and its polysiloxane isolated matrix were exposed to high energy electrons in order to determine their ageing mechanisms from a structural point of view. Physicochemical analysis evidenced that both filled and unfilled materials predominantly crosslink under such irradiation. Solid-state 29Si NMR spectroscopy allowed the identification of T-type SiO3 units as the main new crosslinks formed in the polymer network. It also revealed an increase in Qtype SiO4 units in the irradiated filled sample. Thanks to the combination of NMR spectroscopy and ammonia-modified swelling tests, these Q-type units were associated with new crosslinks formed at the silica fillers-matrix interface. While the main interaction between the polysiloxane network and the fillers was shown to proceed mainly through hydrogen bonding in the pristine filled samples, it was suggested that the hydrogen bonds were progressively replaced with SiO4 chemical bonds. These additional chemical crosslinks induced evolutions of the shear modulus on the rubber plateau and crosslink density that were significantly more pronounced in the filled material than in the neat one