Synthesis of MCM-41 nanomaterial from Algerian bentonite: influence of synthesis pH

Mesoporous materials of the MCM-41 type were synthesized from Algerian bentonite as an aluminosilicate source without the addition of pure silica and aluminum reagents. The samples were synthesized under hydrothermal condition using cetyltrimithylammonium bromide (CTAB) as surfactant. The influence of initial synthesis pH on the material properties of as-synthesis MCM-41 samples was studied at different temperatures of crystallization. The samples were characterized using several techniques e.g. X-ray diffraction (XRD), N2 adsorption-desorption and transmission electron microscope (TEM). The experimental results showed that bentonite can be used as an aluminosilicate source for the synthesis of Al-MCM-41. By decreasing the synthesis temperature of crystallization, it is necessary to decrease the synthesis pH value to form the best ordered hexagonal phase and eliminate the lamellar phase.Keywords: bentonite; alkaline fusion; pH; Al-MCM-4

Effects of Impurity Content on the Sintering Characteristics of Plasma-Sprayed Zirconia

Yttria-stabilized zirconia powders, containing different levels of SiO2 and Al2O3, have been plasma sprayed onto metallic substrates. The coatings were detached from their substrates and a dilatometer was used to monitor the dimensional changes they exhibited during prolonged heat treatments. It was found that specimens containing higher levels of silica and alumina exhibited higher rates of linear contraction, in both in-plane and through-thickness directions. The in-plane stiffness and the through-thickness thermal conductivity were also measured after different heat treatments and these were found to increase at a greater rate for specimens with higher impurity (silica and alumina) levels. Changes in the pore architecture during heat treatments were studied using Mercury Intrusion Porosimetry (MIP). Fine scale porosity (<_50 nm) was found to be sharply reduced even by relatively short heat treatments. This is correlated with improvements in inter-splat bonding and partial healing of intra-splat microcracks, which are responsible for the observed changes in stiffness and conductivity, as well as the dimensional changes

Amélioration du comportement en cyclage thermique d'un dépôt plasma métallique par compression isostatique à chaud

Afin d'améliorer les performances de revêtements métalliques FeCrAlY projetés par plasma sous pression réduite sur des substrats de type FeCrAl et compte-tenu des résultats intéressants déjà obtenus par application d'un post-traitement par compression isostatique à chaud, nous avons cherché à optimiser les conditions d'application de la CIC. Trois types de traitement ont ainsi été testés. Les différentes évolutions des depôts obtenus dans chacun des cas ont été caractérisés par diffraction des RX, microscopie, microanalyse et microdureté. Les comportements des différents échantillons ont ensuite été comparés au cours d'essais de cyclage thermique ainsi que l'évolution respective de leurs microstructures.A HIP post-treatment applied on LPPS FeCrAIY coatings improved resistance under thermal cycling (high coating densification, strong adherence to the substrate). Observation of the oxide scale using SEM, enabled us to explain such an improvement of the behaviour of post-hipped coatings when submitted to both oxidation and thermal stresses

L'évolution des propriétés catalytiques de silices mésoporeuses dopées au titane en fonction du greffage hydrophobe en surface des matériaux

Depuis la découverte des matériaux mésoporeux par la firme Mobil Oil en 1992, beaucoup d'études ont été réalisées sur la modification des propriétés physico-chimiques pour améliorer l'activité et la sélectivité catalytique de la surface de ces matériaux. Dans cette étude, on a greffé un organosilane de type triméthylchlorosilane (TMCS) sur la surface de ces matériaux mésoporeux de type MCM-41, MCM-48 et FSM-16 purement silicique et autres dopés au titane par post-synthèse. Ce traitement a permis d'améliorer le rendement des produits d'oxydation du cyclohexène en présence de H2O2. L'effet du greffage sur la structure et la texture de ces matériaux a été examiné par (DRX, BET et IR). Les produits de la réaction sont analysés par GC/MAS

β-diketone functionalized SBA-15 and SBA-16 for rapid liquid–solid extraction of copper

International audienc

Metal-loaded mesoporous MCM-41 for the catalytic wet peroxide oxidation (CWPO) of acetaminophen

MCM-41 based catalysts (molar ratio Si/Al = 40) were prepared by a hydrothermal route, modified by ionic exchange with different metals (Cu, Cr, Fe and Zn) and finally calcined at 550 °C. The catalysts were fully characterized by different techniques that confirmed the formation of oxides of the different metals on the surfaces of all materials. Low-angle X-ray diffraction (XRD) analyses showed that calcination resulted in the incorporation of metallic Zn, Fe and Cr in the framework of MCM-41, while in the case of Cu, thin layers of CuO were formed on the surface of MCM-41. The solids obtained were tested in the catalytic wet peroxide oxidation (CWPO) of acetaminophen at different temperatures (25–55 °C). The activity followed the order: Cr/MCM-41 ≥ Fe/MCM-41 > Cu/MCM-41 > Zn/MCM-41. The increase of the reaction temperature improved the performance and activity of Cr/MCM-41 and Fe/MCM-41 catalysts, which achieved complete conversion of acetaminophen in short reaction times (15 min in the case of Cr/MCM-41). Fe/MCM-41 and Cr/MCM-41 were submitted to long-term experiments, being the Fe/MCM-41 catalyst the most stable with a very low metal leaching. The leaching results were better than those previously reported in the literature, confirming the high stability of Fe/MCM-41 catalysts synthesized in this study

Synthesis of MCM-41 nanomaterial from Algerian bentonite: influence of synthesis pH

International audienceMesoporous materials of the MCM-41 type were synthesized from Algerian bentonite as an aluminosilicate source without the addition of pure silica and aluminum reagents. The samples were synthesized under hydrothermal condition using cetyltrimithylammonium bromide (CTAB) as surfactant. The influence of initial synthesis pH on the material properties of as-synthesis MCM-41 samples was studied at different temperatures of crystallization. The samples were characterized using several techniques e. g. X-ray diffraction (XRD), N-2 adsorption-desorption and transmission electron microscope (TEM). The experimental results showed that bentonite can be used as an aluminosilicate source for the synthesis of Al-MCM-41. By decreasing the synthesis temperature of crystallization, it is necessary to decrease the synthesis pH value to form the best ordered hexagonal phase and eliminate the lamellar phase

Development and characterization of a new dolomite-based catalyst: application to the photocatalytic degradation of pentachlorophenol

PMID = 3097594