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The oxidative coupling (OCM) and the partial catalytic oxidation (POM) of methane as well as the homogeneous oxidation of methane (HOM) differ only in the ratio CH4/O2 used and of course in the use of a catalyst. It can therefore be considered that their overall reaction mechanism should be the same with elementary reactions of varying importance depending on the type of oxidation reaction studied. We have therefore tried to represent the results obtained during the experimental study of OCM and POM over La2O3 and that of the oxidation of methane in gas phase from a single mechanism. At high temperature, OCM and POM are catalytic reactions but their reaction mechanisms are very complex because the surface reactions are coupled to reactions in gas phase by the intermediary of radicals, so both homogeneous and heterogeneous mechanisms occur at the same time. In this work, the development and the validation of a hetero-homogeneous mechanism is proposed for the three reactions. This mechanism is based on elementary steps at the catalyst surface and elementary steps in gas phase for a large range of temperature (973 K–1173 K) and residence time (0.7 s–5.5 s).

A kinetic experimental study of the catalytic partial oxidation of propane was performed in an isothermal “catalytic jet stirred reactor” which has the ability to modify the ratio of the catalyst surface to the gas volume. The main goal of this study was to elucidate the detailed heterogeneous-homogeneous mechanism of this reaction and explore the capacity to produce H2. The catalyst used in this study was pellets of cerium oxide CeO2. Various operating parameters were considered: temperature, residence time, contact time and amount of catalyst. A hetero-homogeneous mechanism, composed of 71 elementary steps at the catalyst surface and 937 homogeneous gas phase reactions is proposed and validated by comparison between experimental results and simulated results over a large range of temperatures (200

Al2O3 films have been deposited at 85 °C by atomic layer deposition onto single 100 nm thick tris-(8-hydroxyquinoline) aluminium (AlQ3) films made onto silicon wafers. It has been found that a thick ALD-deposited Al2O3 layer (> 11 nm) greatly prevents the photo-oxidation of AlQ3 films when exposed to continuous UV irradiation (350 mW/cm2). Thin Al2O3 thicknesses (< 11 nm) on the contrary yield lower barrier performances. Defects in the Al2O3 layer have been easily observed as non-fluorescent AlQ3 singularities, or black spots, under UV light on the system Si/AlQ3/Al2O3 stored into laboratory conditions (22 °C/50% Relative Humidity (RH)) for long time scale (~ 2000 h). Accelerated aging conditions in a climatic chamber (85 °C/85% RH) also allow faster visualization of the same defects (168 h). The black spot density grows upon time and the black spot density occurrence rates have been calculated to be 0.024 h− 1·cm− 2 and 0.243 h− 1·cm− 2 respectively for the two testing conditions. A detailed investigation of these defects did show that they cannot be ascribed to the presence of a detectable particle. In that sense they are presumably the consequence of the existence of nanometre-scaled defects which cannot be detected onto fresh samples. Interestingly, an additional overcoating of ebeam-deposited SiO2 onto the Si/AlQ3/Al2O3 sample helps to decrease drastically the black spot density occurrence rates down to 0.004 h− 1·cm− 2 and 0.04 h− 1·cm− 2 respectively for 22 °C/50% RH and 85 °C/85% RH testing conditions. These observations highlight the moisture sensitivity of low temperature ALD-deposited Al2O3 films and confirm the general idea that a single Al2O3 ALD film performs as an ultra-high barrier but needs to be overprotected from water condensation by an additional moisture-stable layer.

100 nm thick 8‐AlQ 3 films deposited onto silicon wafers have been encapsulated by mean of low temperature atomic layer deposition of Al 2 O 3 (20 nm). Investigation of the film evolution under storage test as harsh as 65 °C/85% RH has been investigated up to ~ 1000 h and no severe degradation could be noticed. The results have been compared to raw AlQ 3 films which deteriorate far faster in the same conditions. For that purpose, fluorescence measurements and atomic force microscopy have been used to monitor the film evolution while transmission electron microscopy has been used to image the interface between AlQ 3 and Al 2 O 3 . This concept of bilayer AlQ 3 /Al 2 O 3 barrier films has finally been tested as an encapsulation barrier onto an organic light-emitting diode.

In the first part of this research, a detailed experimental study was conducted for the partial oxidation of methane (POM) over La2O3. It was shown that the interactions between gas-phase and surface reactions should be considered and that the POM is a homogeneous−heterogeneous reaction. In this second part of the study, a detailed mechanism is proposed that involves 450 elementary homogeneous reaction steps and 33 heterogeneous reactions. From this mechanism, simulations were performed using Chemkin software packages. Computed values are consistent with experimental results over a large range of temperatures (650−850 °C), residence times (0.7−6 s), and catalyst amounts (0.45−3.6 g).

A complete kinetic study of the partial oxidation of methane has been performed in a “catalytic jet-stirred reactor”. The main goal of this study was to elucidate the interactions between gas-phase reactions and surface reactions and to propose a detailed heterogeneous−homogeneous mechanism. The catalyst used in this study was lanthanum oxide (La2O3). Various kinetic parameters were considered, including the temperature, the residence time, the contact time, and the amount of catalyst. The results revealed a complex behavior. In this first part of the study, the experimental results are given and discussed.

The reaction of the partial oxidation of methane was investigated over Ni/La2O3 catalysts prepared by impregnation. Two different reactors were used, a perfectly jet-stirred reactor and a fixed-bed reactor. The influences of nickel content, calcination temperature, reaction temperature, residence time, and contact time were investigated. Mechanistic information was derived from the comparison of the results obtained in both reactors. Characterization techniques such as X-ray diffraction, temperature-programmed oxidation, temperature-programmed reduction, and transmission electron microscopy were used to assess the state of the catalyst prior to and after the reaction.

The reduction of automotive emissions and the reformulation of gasoline composition require a better understanding of the combustion mechanism, in particular aiming at the determination of the influential reactions which are responsible for the onset of knock in spark ignition engines. We have studied the oxidation mechanism of two hydrocarbons of different research octane number: n-pentane (62) and cyclopentane (100). This work follows a previous study on the oxidation of n-heptane and isooctane. The experimental study was performed at 873 K in a jet-stirred flow reaction vessel. The reaction mechanisms of n-pentane and cyclopentane were analysed on a purely kinetic basis, derived from our experimental results, and were finally modelled by using a programme of simulation of reaction mechanisms. The different behaviour of these two hydrocarbons with respect to autoignition phenomena is mainly dependent on the relative concentration of resonance-stabilized radicals in the reaction medium. Keywords: oxidation reaction, n-pentane, cyclopentane, modelling, autoignition.

The oxidation mechanisms of two alkanes that have quite different octane numbers: n-heptane (0) and isooctane (100), were investigated to obtain a better understanding of the chemical mechanism of autoignition phenomena and to improve the compatibility of the available fuels with the engines. The experimental study was performed at 923 K in a setup equipped with a jet-stirred reactor. The oxidation mechanisms of n-heptane and isooctane were simplified first by a purely kinetic analysis based on the product formation and then by using a software of simulation of reaction mechanisms. The very different behaviour of these two hydrocarbons was explained by the presence, in the products of isooctane oxidation, of alkenes, which would have an antiknock effect due to the formation of resonance-stabilized radicals. Key words: oxidation reaction, n-heptane, isooctane, autoignition, modelling.

The human knee is one of the most frequently injured joints. More than half of these injuries are related to a failure of the anterior cruciate ligament. Current treatments (allogeneic and autologous) bear several disadvantages which can be overcome through the use of synthetic structures. Within the scope of this paper the potential of tubular woven fabrics for the use as artificial ligaments has been evaluated. Twelve fabrics made of polyethylene terephthalate and polytetrafluoroethylene were produced using shuttle weaving technology. Mechanical and biological properties of the fabrics were assessed using static tensile testing and cytotoxicity assays. The results obtained within this study show that woven tubular fabrics can be potentially used as artificial ligament structures as they can provide the desired medical and mechanical properties for cruciate ligament replacements. Through the choice of material and weaving parameters the fabrics’ tensile properties can imitate the stress–strain characteristic of the human cruciate ligament. Further assessments in terms of cyclic loading behavior and abrasion resistance of the material are needed to evaluate the success in long term implantation.

International audience; A kinetic study of the partial oxidation of propane was performed in a jet stirred reactor. The main goal of this study was to establish a detailed homogeneous mechanism of this reaction and explore the capability to produce H2 and olefins. Various operating parameters are modified: temperature, residence time, and O2/C3H8 ratio. The mechanism was validated by comparing experimental and simulated results. A different behavior was observed depending on the temperature. At 600 °C, the mechanism contains both an oxidation and a pyrolytic path. The main products are H2, C2H4, CH4, CO, and O2. At 800 °C, the mechanism mostly contains a pyrolytic path. The main products are H2 and CO.

The mechanism of the partial oxidation of methane over lanthanum oxide La 2 O 3 catalyst was investigated using a perfectly jet-stirred reactor. The proposed mechanism satisfactorily reproduces experimental findings over a large range of experimental parameters. The catalyst favors the production of methyl radicals. These radicals can follow the pyrolysis pathway leading to the C 2 compounds or they can follow the oxidative pathway leading to the formation of formaldehyde, carbon monoxide and carbon dioxide. Both routes involve gas phase reactions and surface reactions. The mechanism shows that both routes are interconnected and that their relative importance depends on the operating conditions, that is temperature, residence time and catalyst amount. The mechanism is detailed step by step on the basis of flux and sensitivity analyses.

A bibliographical study of the thermal decomposition of the ethyl radical shows that the kinetic parameters for the upper and lower limits of the pressure are rather scattered. This observation explains why we have carried out a new study of this elementary process in the pyrolysis of ethane, around 800 K, in a closed vessel and at pressures of the hydrocarbon varying from 1 to 300 Torr. The experimental results have been treated according to three theoretical approaches: the RRKM theory and two methods proposed by Troe. In each case, an excellent fit of the theoretical curves with the experimental data is obtained, as well as Arrhenius expressions for the reaction rate constants at high and low pressures. A detailed critical analysis of our results as well as those found in the literature shows that as yet there is no good agreement between recent studies on this subject. However, it is possible to present two Arrhenius expressions for the reaction rate constants at high and low pressures; these expressions represent a good compromise for the results obtained by various authors:[Formula: see text][Journal translation]