Diamond formation from C60 crystals heated under high pressure

X-ray Diffraction (XRD) and Raman Microspectroscopy showed that diamond is detected when solid C60 crystals are heated above 1600°C, in the 9-15 GP range. These samples are here studied by High Resolution Transmission Electron Microscopy (HRTEM) in order to allow the structural characteristics of more or less organised co-existing carbon phases

Promotion effect of rare earth elements (Ce, Nd, Pr) on physicochemical properties of M-Al mixed oxides (M = Cu, Ni, Co) and their catalytic activity in N2O decomposition

A series of M-AlOx mixed oxides (M = Cu, Co, Ni) with the addition of high loadings of rare earth elements (REE, R = Ce, Nd, Pr; R0.5M0.8Al0.2, molar ratio) were investigated in N2O decomposition. The precursors were prepared by coprecipitation and subsequent calcination at 600\ua0\ub0C. The obtained mixed metal oxides were characterized by X-ray diffraction with Rietveld analysis, N2 sorption, and H2 temperature-programmed reduction. Depending on the nature of REE and the initial M-Al system, R cations could be separately segregated in oxide form or coordinated with the transition metal cations and form mixed structures. The addition of Ce3+ consistently led to nanocrystalline CeO2 mixed with the divalent oxides, whereas the addition of Nd3+ or Pr3+ resulted in the formation of their respective oxide phases as well as perovskites/Ruddlesden–Popper phases. The presence of REE modified the textural and redox properties of the calcined materials. The rare earth element-induced formation of low-temperature reducible MOx species that systematically improved the N2O decomposition on the modified catalysts compared to the pristine M-Al materials by the order of Co > Ni > Cu. The Ce0.5Co0.8Al0.2 catalyst revealed the highest activity and remained stable (approximately 90% of N2O conversion) for 50\ua0h during time-on-stream in 1000\ua0ppm N2O, 200\ua0ppm NO, 20 000\ua0ppm O2, 2500\ua0ppm H2O/N2 balance at WHSV = 16 L g−1\ua0h−1

Pseudomorphic synthesis of mesoporous zeolite Y crystals

International audienceA simple method for the conception of mesoporous zeolite Y crystals with a narrow intracrystalline mesopore size distribution is reported. It involves the pseudomorphic transformation of parent zeolite crystals by recrystallisation in the presence of surfactants, and leads to two interconnected pore systems in the zeolite crystals

Thermosensitive and drug-loaded ordered mesoporous silica: a direct and effective synthesis using PEO-b-PNIPAM block copolymers

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Tunable hierarchical porosity from self-assembled chitin-silica nano-composites

International audienceWe studied new mesoporous materials with original properties and obtained from self-assembled chitin-silica nano-composites. Our novel synthesis allows the controlled colloidal assembly of a-chitin nanorods (bundles of elongated chitin monocrystals) and siloxane oligomers. Calcination of nanocomposites results in mesoporous silica materials. Their pore volume fraction fPOR (0-0.52) is strongly correlated to the initial chitin content. Using N2 sorption and TEM data, we identify and characterize primary and secondary textural units related to the imprints of chitin monocrystals (2.5 nm wide) and nanorods (20-30 nm wide) respectively. Primary textural units are preserved over a wide fPOR range (linear relationship between pore volume and specific surface area). The coating of monocrystals by siloxane oligomers leads to a siloxane network of fractal nature as deduced from complementary SAXS data. Beyond a critical value fPOR 0 estimated near 0.2, the coating is partial, and the porosity becomes more open and connected. At larger scales, the arrangements of secondary textural units result in complex textures and long-range ordering, showing similarities with textural features found in natural materials. We discuss the competition between entropy-driven transitions typical of anisotropic particles and kinetic arrest due to colloidal gelation and inorganic condensation. Finally, a schematic model for texture formation is given

Spray-dried solid dispersions of nifedipine and vinylcaprolactam/vinylacetate/PEG6000 for compacted oral formulations

International audienceThe aim of this work was to investigate an alternative processing technology for a new polymeric solubilizer used mainly in hot melt extrusion. Poorly soluble nifedipine was co-processed through spray-drying with poly(vinyl caprolactam-co-vinyl acetate-co-ethylene glycol) (PVCVAEG) in different ratios. The resulting spray-dried powders were formulated and compacted into tablets forms. Spray drying produced reduced smooth spherical particles with PVCVAEG and more rough surfaces without PVCVAEG. Crystallinity of the co-processed nifedipine with the polymeric solubilizer was reduced. Plasticization of the polymeric solubilizer was observed with increasing drug content. Diffraction patterns in the small angle region as well as transmission electron microscopy showed results supporting phase separation throughout the spray dried particles of high drug content. Compaction with PVCVAEG improved cohesiveness of spray-dried compacts. Heckel modeling showed that deformation of PVCVAEG containing powders was more plastic compared than brittle nifedipine powders. Dissolution kinetics of all spray-dried samples was improved compared to original nifedipine crystals. Co-processed nifedipine with PVCVAEG did not show improved dissolution rate when compared to spray drying nifedipine alone. All though PVCVAEG is more commonly co-processed with drugs by hot melt extrusion to produce solid dispersions, the results show that it also can be processed by spray drying to produce solid dispersions. PVCVAEG improved compactibility of formulated spray dried powders

Spray-dried porous silica microspheres functionalised by phosphonic acid groups

International audiencePorous silica-based microspheres with pore surfaces functionalized by phosphonic acids are obtained for the first time from a direct co-condensation route using two alkoxide precursors (Si(OEt)4 and Si(OEt)3(CH2)2P(O)(OEt)2), surfactant self-assembly and spray-drying methods. The synthesis employs octadecyltrimethylammonium bromide as template agent. The post-treatment of the microspheres in boiling concentrated hydrochloric acid insures the hydrolysis of the ethoxy groups initially bound to phosphorus in the organophosphonate-siloxane precursor, without destroying the morphological and textural properties. Final porous materials have the chemical structure [SiO1.81(OZ)0.38]0.91[SiO1.35(OZ)0.29 (CH2)2P(O)(OH)2]0.09 (with Z @ H or Et), and posses interesting textural properties: SBET = 747 m2 g-1, and dp = 2.3 nm

Epoxy-functionalized large-pore SBA-15 and KIT-6 as affinity chromatography supports

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Chitosan templated synthesis of porous metal oxide microspheres with filamentary nanostructures

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