41 research outputs found
Conductive Thin Films of θ-(BETS)4[Fe(CN)5NO] on Silicon Electrodes - New Perspectives on Charge Transfer Salts
No full textAl–Cu intermetallic coatings processed by sequential metalorganic chemical vapour deposition and post-deposition annealing
No full textSequential processing of aluminum and copper followed by reactive diffusion annealing is used as a paradigm for the metalorganic chemical vapour deposition (MOCVD) of coatings containing intermetallic alloys. Dimethylethylamine alane and copper N,N'-di-isopropylacetamidinate are used as aluminum and copper precursors, respectively. Deposition is performed on steel and silica substrates at 1.33 kPa and 493–513 K. Different overall compositions in the entire range of the Al–Cu phase diagram are obtained by varying the relative thickness of the two elemental layers while maintaining the overall thickness of the coating close to 1 µm. As-deposited films present a rough morphology attributed to the difficulty of copper to nucleate on aluminum. Post-deposition annealing is monitored by in situ X-ray diffraction, and allows smoothening the microstructure and identifying conditions leading to several Al–Cu phases. Our results establish a proof of principle following which MOCVD of metallic alloys is feasible, and are expected to extend the materials pool for numerous applications, with innovative thin film processing on, and surface properties of complex in shape parts
An experimental and computational analysis of a MOCVD process for the growth of Al films using DMEAA
No full textThe analysis of a metal-organic chemical vapor deposition (MOCVD) process is performed by combining computational fluid dynamics (CFD) simulations and experimental measurements. The analysis is applied to a vertical, cold-wall reactor, where aluminum coatings are grown from dimethylethylamine alane (DMEAA), under low-pressure conditions. A two-dimensional model, based on the finite-volume method, is developed to predict the thermal and hydrodynamic characteristics of the flow within the MOCVD reactor, and the simulation results are compared with experimental data. It is shown that the computational predictions of the growth rates are in fair agreement with the experimental measurements
Correlation between eletrokinetic mobility and ionic dyes adsorption of Moroccan stevensite
No full textThis study aims at establishing a correlation between the electrical charge of Moroccan stevensite particles and ionic dyes adsorption. The electrophoretic mobility, (Ue), of the stevensite particles in water, was measured at pH 2.5–12 by microelectrophoresis. At pH between 2.5 and 8, Ue remained constant (Ue = − 1.6 10− 8 m2/(V s)), as resulting from the permanent charge of the clay mineral planar surfaces. At pH > 8, the magnitude of electrophoretic mobility increased (Ue = − 2.7 10− 8 m2/(V s)) due to the deprotonation of silanol groups on the surfaces. The anionic Orange G adsorption at the clay mineral–water interface was negligible whereas the methylene blue cations were strongly adsorbed due to the electrostatic attraction
Synthesis, characterization and photocatalytic activity of TiO2 supported natural palygorskite microfibers
No full textThis study deals with the synthesis of TiO2 supported Moroccan palygorskite fibers and their use as photocatalyst for the removal of Orange G pollutant from wastewater. The TiO2-palygorskite nanocomposite synthesis was accomplished according to a colloidal route involving a cationic surfactant as template (hexadecyltrimethylammonium bromide) assuring hence organophilic environment for the formation of TiO2 nanoparticles. The clay minerals samples were characterized before and after functionalization with TiO2. Anatase crystallizes above ca. 450 °C and remarkably remains stable up to 900 °C. In contrast, pure TiO2 xerogel obtained from titanium tetraisopropoxide (TTIP) showed before calcination a nanocrystalline structure of anatase. By increasing the temperature, anatase readily transforms into rutile beyond 600 °C. The remarkable stability at high temperature of anatase particles immobilized onto palygorskite microfibers was due to the hindrance of particles growth by sintering. Homogeneous monodisperse distribution of anatase particles with an average size of 8 nm was found by TEM and XRD onto palygorskite fibers. This anatase particle size remains below the nucleus critical size (ca. 11 nm) required for anatase–rutile transition. The TiO2 supported palygorskite sample annealed in air at 600 °C for 1 h exhibits the highest photocatalytic activity towards the degradation of Orange G compared to nanocomposite samples prepared under different conditions as well as pure TiO2 powders obtained from the xerogel route or commercially available as Degussa P25
Single-phased hard coatings of the metastable Cr3(C0.8N0.2)2 ternary phase grown by low pressure MOCVD
No full textOptimization of the Vaporization of Liquid and Solid CVD Precursors: Experimental and Modeling Approaches
No full textHomogeneous catalysis in water (III). The catalytic hydrogenation of propionaldehyde with [RuCl2L2]2, RuHClL3, RuH(OAc)L3, RuH2L4, RuHIL3, RuCl2(CO)2L2, and [Ru(OAc)(CO)2L]2 (L=P(C6H4-m-SO3Na)3.3H2O). A kinetic investigation of salt effect in water
No full textSeven water-soluble ruthenium complexes (RuCl2L2)2 1, RuHClL3 2, RuH(OAc)L3 3, RuH2L4 4, RuHIL3 5, RuCl2(CO)2L2 6 and [Ru(OAc)(CO)2L]2 7 (L-P(C6H4–mSO3Na)3·3H2O) have been tested in the catalytic hydrogenation of propionaldehyde. Their catalytic performances have been compared to those of their organosoluble analogues (1′–7′, L-PPh3). The non-carbonylated complexes 1–5 exhibit comparable rates of propionaldehyde hydrogenation in water at 100 °C, as determined by their first-order rate constants. In contrast, the rates observed with 1′–4′ are different from one another and extremely solvent dependent. With 1, the reaction is first order in aldehyde, catast and hydrogen pressure, as is found for the organosoluble complex RuH(CO)Cl(PPh3)3. Starting with 1–4, various equilibria have been observed which lead to the same complex RuH2L3(H2O). These equilibria suggest that the real catalyst precursor in water is RuH2L3. Whatever the precursor (1–5) used, addition of alkaline, alkaline-earth and ammonium salt dramatically increases the activity without any loss of selectivity. The rate equation is drastically modified in the presence of salt. It has been established that the salt acts by both its cation and its anion. For a given anion, the rate increases in the order: NR4+ (R-Et, n-Bu)Na+Li+K+Mg2+Ca2+. For a given cation, the rate increases in the order: SiF62−NO3−Cl−Br−I−. In the presence of NaI, the coordination spheres of 2-4 are modified in water and lead to the same complex RuHIL3 5. The role of the cation has been verified by adding to the catalytic solution a specific sodium cryptand, which resulted in a dramatic drop in activity. A mechanism has been proposed which takes into account the kinetic equation as well as the various observations which were made on the different catalyst precursors
Homogeneous catalysis in water Part II. Synthesis and characterization of ruthenium water-soluble complexes
No full textChemInform Abstract: Low Pressure Catalytic Hydroformylation of 1‐Hexene by Carbonylhydridotris(triphenylphosphine)rhodium(I), RhH(CO)(PPH3)3, in Association with Phosphinomethylzirconium Complexes.
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