Elucidating the crystal-chemistry of Jbel Rhassoul stevensite (Morocco) by advanced analytical techniques

The composition of Rhassoul clay is controversial regarding the nature of the puremineral clay fraction which is claimed to be stevensite rather than saponite. In this study, the raw and mineral fractions were characterized using various techniques including Fourier transform infrared spectroscopy and magic angle spinning nuclear magnetic resonance (MAS NMR). The isolated fine clay mineral fraction contained a larger amount of Al (>1 wt.%) than that reported for other stevensite occurrences. The 27Al MAS NMR technique confirmed that the mineral is stevensite in which the Al is equally split between the tetrahedral and octahedral coordination sites. The 29Si NMR spectrum showed a single unresolved resonance indicating little or no short-range ordering of silicon. The chemical composition of the stevensite from Jbel Rhassoul was determined to be ((Na0.25K0.20 (Mg5.04Al0.37Fe0.20&0.21)5.61(Si7.76Al0.24)8O20(OH)4). This formula differs from previous compositions described from this locality and shows it to be an Al-bearing lacustrine clay mineral

Zigzag-shaped nickel nanowires via organometallic template-free route

In this manuscript, the formation of nickel nanowires (average size: several tens to hundreds of μm long and 1.0-1.5 μm wide) at low temperature is found to be driven by dewetting of liquid organometallic precursors during spin coating process and by self-assembly of Ni clusters. Elaboration of metallic thin films by low temperature deposition technique makes the preparation process compatible with most of the substrates. The use of iron and cobalt precursor shows that the process could be extended to other metallic systems. In this work, AFM and SEM are used to follow the assembly of Ni clusters into straight or zigzag lines. The formation of zigzag structure is specific to the Ni precursor at appropriate preparation parameters. This template free process allows a control of anisotropic structures with homogeneous sizes and angles on standard Si/SiO2 surface

Deposition of tin oxide, iridium and iridium oxide films by metal-organic chemical vapor deposition for electrochemical wastewater treatment

In this research, the specific electrodes were prepared by metal-organic chemical vapor deposition (MOCVD) in a hot-wall CVD reactor with the presence of O2 under reduced pressure. The Ir protective layer was deposited by using (Methylcyclopentadienyl) (1,5-cyclooctadiene) iridium (I), (MeCp)Ir(COD), as precursor. Tetraethyltin (TET) was used as precursor for the deposition of SnO2 active layer. The optimum condition for Ir film deposition was at 300 °C, 125 of O2/(MeCp)Ir(COD) molar ratio and 12 Torr of total pressure. While that of SnO2 active layer was at 380 °C, 1200 of O2/TET molar ratio and 15 Torr of total pressure. The prepared SnO2/Ir/Ti electrodes were tested for anodic oxidation of organic pollutant in a simple three-electrode electrochemical reactor using oxalic acid as model solution. The electrochemical experiments indicate that more than 80% of organic pollutant was removed after 2.1 Ah/L of charge has been applied. The kinetic investigation gives a two-step process for organic pollutant degradation, the kinetic was zero-order and first-order with respect to TOC of model solution for high and low TOC concentrations, respectively

Homogeneous 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

Seven 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

Low-temperature MOCVD of molybdenum sulfide on silicon and 100Cr6 steel substrates

Thin films of molybdenum sulfides, MoSx (1<x<2), have been grown on silicon and 100Cr6 steel substrates, in the 130°C-180°C temperature range, using Mo(CO)6and H2S as precursors. Influences of molar fraction, temperature and total pressure on growth rate and chemical and structural features of the layers were investigated. The films are homogeneous and amorphous. The S/Mo ratio depends upon the molar fraction ratio [χH2S/χMo(CO)6], as well as on total pressure and growth temperature. The highest S/Mo ratios were obtained for T = 130°C, P = 3330 Pa and [χH2S/χMo(CO)6] = 150. Friction tests have been carried out at different loads and humidity ratios. The results show that friction coefficient decreases when humidity level decreases : in dry conditions (<5% humidity) the friction coefficient is lower than 0.05. There is also an inverse dependence on the load. In addition, friction tests also show that the films grown by MOCVD have the same hardness and exhibit the same behaviour as films grown by PVD

Antipeptide antibodies recognizing plasmin sensitive sites in bovine beta-casein sequence

International audienc

Antipeptide antibodies recognizing plasmin sensitive sites in bovine beta-casein sequence

International audienc

Chemisorption on nickel nanoparticles of various shapes: Influence on magnetism

International audienc

An experimental and computational analysis of a MOCVD process for the growth of Al films using DMEAA

The 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

MOCVD of Ni and Ni3C films from Ni(dmen)(2)(tfa)(2)

In this study results are reported on the transport and decomposition behavior of a trifluoroacetato complex of formula Ni(dmen)(2)(tfa)(2), in view of its use as a precursor for the MOCVD of Ni. It is shown that Ni(dmen)(2)(tfa)(2) can be sublimed up to 190 degrees C without decomposition with, however, a relatively low partial pressure. MOCVD of Ni films from this precursor on silicon and on silica are also reported, performed at temperatures varying between 275 degrees C and 350 degrees C. It was found that the process is kinetically controlled. Films are crystalline, present a granular morphology and, depending on operating conditions, are composed of Ni, of metastable nickel carbide Ni(3)C or of mixtures thereof. The carbon content decreases with decreasing deposition temperature and with increasing hydrogen flow rate. It is also higher in the first deposited layers, revealing a different decomposition mechanism of the precursor on an inert relatively to a metallic surface. Although processing conditions have not been optimized, MOCVD of Ni films from this family of complexes appears promising. However, modifications of the structure of Ni(dmen)(2)(tfa)(2) are necessary to increase its volatility and consequently the growth rate of the films.open111sciescopu