Search results for "porous material"
showing 10 items of 361 documents
Generalised syntheses of ordered mesoporous oxides: the atrane route
2000
Abstract A new simple and versatile technique to obtain mesoporous oxides is presented. While implying surfactant-assisted formation of mesostructured intermediates, the original chemical contribution of this approach lies in the use of atrane complexes as precursors. Without prejudice to their inherent unstability in aqueous solution, the atranes show a marked inertness towards hydrolysis. Bringing kinetic factors into play, it becomes possible to control the processes involved in the formation of the surfactant–inorganic phase composite micelles, which constitute the elemental building blocks of the mesostructures. Independent of the starting compositional complexity, both the mesostructu…
Expanding the atrane route: Generalized surfactant-free synthesis of mesoporous nanoparticulated xerogels
2008
Abstract A diversity of silica-based and non-silica nanoparticulated mesoporous xerogels have been synthesized from aqueous solution using a surfactant-free strategy, and starting from molecular atrane complexes as precursors. This approach constitutes an extension of the “atrane route” previously described for the surfactant-assisted synthesis of mesoporous materials, and allows us to unify the multiplicity of protocols described for the preparation of conventional xerogels. In fact, we have used exactly the same preparative conditions for obtaining all the compositions reported here. The xerogels synthesized in this way include pure silica (UVM-11), aluminosilicates and titanosilicates (M…
Novel pathways for the preparation of mesoporous MCM-41 materials: control of porosity and morphology
1999
Two novel synthesis routes for the preparation of mesoporous MCM-41 materials are introduced. Both methods use tetra-n-alkoxysilanes such as tetraethoxysilane (TEOS) or tetra-n-propoxysilane (TPS) as a silica source which are added to an aqueous solution of a cationic surfactant in the presence of ammonia as catalyst. In this study, n-alkyltrimethylammonium bromides and n-alkylpyridinium chlorides were employed as templates. The addition of an alcohol (e.g. ethanol or isopropanol) leads to a homogeneous system which allows the formation of spherical MCM-41 particles. The main advantages of these methods are short reaction times, excellent reproducibility and easy preparation of large batche…
Consolidation and protection by nanolime: recent advances for the conservation of the graffiti, Carceri dello Steri Palermo and of the 18th century l…
2014
Abstract Nanolime dispersed in 2-propanol was extensively used for the consolidation of wall paintings. The knowledge of the advances of this methodology dealing with all the possible effects associated with the nanolime new material in conservation is fundamental to assess and improve the technique. In this paper, four different dispersions of Ca(OH) 2 nanoparticles were characterised by Small Angle X-rays Scattering technique (SAXS) and Transmission Electron Microscopy (TEM) in order to achieve information on size, shape, polydispersity, agglomeration, and crystal structure (by SAED patterns) of the particles. Once characterised, the dispersions were tested in two different case studies, …
Sorption of argon and nitrogen on network types of zeolites and aluminophosphates
1991
Abstract Synthetic zeolites and aluminophosphates comprising 10- and 12- membered ring openings, unidimensional and network type of pore systems (MFI, MEL, ERI, LTA, AEL, AFI and FAU) were used as model adsorbents to examine the impact of micropore structure on the sorption properties. Argon and nitrogen were employed as adsorptives. Adsorption measurements were carried out on gravimetric and volumetric sorption devices and also monitored by microcalorimetry. From the low coverage regime of the isotherm Henry's constants and isosteric heats of adsorption were derived. Both quantities allowed the discrimination between 10- and 12- membered ring systems. Unidimensional 10- and 12- membered ri…
High-resolution sorption studies of argon and nitrogen on large crystals of microporous zeolite ZSM-5
1989
High resolution adsorption (HRADS) with argon and nitrogen at 77 K were performed on large crystals of zeolite ZSM-5 using a novel volumetric device. Multi-step isotherms for both adsorptives could be observed for the first time. The micropore filling was followed by low temperature microcalorimetry. Exothermic heats of adsorption were found to be correlated with steps in the adsorption isotherms. Based on results from atom-atom potential energy calculations (AAP) as well as from independent model building it is shown that 24 kinetic adsorbate molecules can be situated in a ZSM-5 unit cell. Localized adsorption is presented as possible filling mechanisms. Experimental results are reasonably…
Confident methods for the evaluation of the hydrogen content in nanoporous carbon microfibers
2012
Abstract Nanoporous carbon microfibers were grown by chemical vapor deposition in the vapor-liquid solid mode using different fluid hydrocarbons as precursors in different proportions. The as-grown samples were further treated in argon and hydrogen atmospheres at different pressure conditions and annealed at several temperatures in order to deduce the best conditions for the incorporation and re-incorporation of hydrogen into the microfibers through the nanopores. Since there are some discrepancies in the results on the hydrogen content obtained under vacuum conditions, in this work, we have measured the hydrogen content in the microfibers using several analytical methods in ambient conditi…
Fluorogenic detection of Tetryl and TNT explosives using nanoscopic-capped mesoporous hybrid materials
2013
[EN] A hybrid capped mesoporous material, which was selectively opened in the presence of Tetryl and TNT, has been synthesised and used for the fluorogenic recognition of these nitroaromatic explosives.
Effect of linker distribution in the photocatalytic activity of multivariate mesoporous crystals
2021
The use of Metal-Organic Frameworks as crystalline matrices for the synthesis of multiple component or multivariate solids by the combination of different linkers into a single material has emerged as a versatile route to tailor the properties of single-component phases or even access new functions. This approach is particularly relevant for Zr6-MOFs due to the synthetic flexibility of this inorganic node. However, the majority of materials are isolated as polycrystalline solids, which are not ideal to decipher the spatial arrangement of parent and exchanged linkers for the formation of homogeneous structures or heterogeneous domains across the solid. Here we use high-throughput methodologi…
Insights into the production of upgraded biofuels using Mg-loaded mesoporous ZSM-5 zeolites
2020
9 figures, 6 tables.-- Supplementary information available.-- https://authorservices.wiley.com/author-resources/Journal-Authors/licensing/self-archiving.html