Search results for "Porous medium"
showing 10 items of 164 documents
Porous Materials Based on 3-Dimensional Td-Directing Functionalized Adamantane Scaffolds and Applied as Recyclable Catalysts
2018
Porous materials have been of high scientific and technological interest owing to their unique performances in many topical applications related to multiphasic functional systems: gas separation and storage, heterogeneous catalysis, energy conversion, etc. We review herein the synthetic strategies applied for using functionalized adamantane derivatives as polyhedral (mainly tetrahedral, Td-directing) building units of three-dimensional (3-D) porous supramolecular structures and nanomaterials, either purely organic or within metal hybrid frameworks. The resulting materials are currently used in varied heterogeneous (or supported) transition metal catalysis and organocatalysis, including rece…
De novo synthesis of mesoporous photoactive titanium(IV)-organic frameworks with MIL-100 topology
2019
[EN] Most developments in the chemistry and applications of metal-organic frameworks (MOFs) have been made possible thanks to the value of reticular chemistry in guiding the unlimited combination of organic connectors and secondary building units (SBUs) into targeted architectures. However, the development of new titanium-frameworks still remains limited by the difficulties in controlling the formation of persistent Ti-SBUs with predetermined directionality amenable to the isoreticular approach. Here we report the synthesis of a mesoporous Ti-MOF displaying a MIL-100 topology. MIL-100(Ti) combines excellent chemical stability and mesoporosity, intrinsic to this archetypical family of porous…
Fracture flow due to hydrothermally induced quartz growth
2017
Abstract Mineral precipitations are a common feature and limitation of initially open, permeable rock fractures by forming sealing structures or secondary roughness in open voids. Hence, the objective of this numerical study is the evaluation of hydraulic properties of fractures sealed by hydrothermally induced needle and compact quartz growth. Phase-field models of progressive syntaxial and idiomorphic quartz growth are implemented into a fluid flow simulation solving the Navier–Stokes equation. Flow simulations for both quartz types indicate an obvious correlation between changes in permeability, fracture properties (e.g. aperture, relative roughness and porosity) and crystal growth behav…
Acoustics of porous materials with partially opened porosity
2013
International audience; A theoretical and experimental study of the acoustic properties of porous materials containing dead-end (or partially opened) porosity was recently proposed by Dupont et al. The present article provides a description of partially opened porosity systems and their numerous potential applications in the general context of the study of porous materials, the classical models describing them, and the characterization techniques. It is shown that the dead-end pore effect can be treated independently and that the description of this effect can be associated with any acoustic model of porous media. Different theoretical developments describing the dead-end porosity effect ar…
Simulation of liquid penetration in paper
2006
Capillary penetration of a wetting liquid in a microtomographic image of paper board, whose linear dimension was close to the average length of wood fibers, was simulated by the lattice-Boltzmann method. In spite of the size of the system not being large with respect to the size of structural inhomogeneities in the sample, for unidirectional penetration the simulated behavior was described well by that of the Lucas-Washburn equation, while for radial penetration a radial capillary equation described the behavior. In both cases the average penetration depth of the liquid front as a function of time followed a power law over many orders of magnitude. Capillary penetration of small droplets of…
Characterization of the Pore Structure of Monolithic Silicas
2011
One-pot synthesis of graphene quantum dots and simultaneous nanostructured self-assembly via a novel microwave-assisted method: impact on triazine re…
2018
One-step methods for fabricating green materials endowed with diverse functions is a challenge to be overcome in terms of reducing environmental risk and cost. We report a fast and easy synthesis of multifunctional materials composed of only fluorescent dots with structural flexibility and high sorption capability. The synthesis consists of a one-pot microwave-assisted reaction for the simultaneous formation of graphene quantum dots (GQDs) from organic precursors and their spontaneous self-assembly forming porous architectures. The GQD-assemblies are robust and no signs of degradation were observed with most organic solvents. The ensuing GQDs and their porous solids were fully characterized…
Metal-organic framework-activated carbon composite materials for the removal of ammonia from contaminated airstreams
2019
L.N.M and R.E.M wish to acknowledge the financial support from the EPSRC industrial CASE award (grant EP/N50936X/1). A.T and G.B would like to thank the financial support from the Fondo per il finanziamento delle attività base di ricerca (grant PJ-RIC-FFABR_2017). Metal-organic frameworks (MOFs) are a class of porous materials that show promise in the removal of Toxic Industrial Chemicals (TICs) from contaminated airstreams, though their development for this application has so far been hindered by issues of water stability and the wide availability and low cost of traditionally used activated carbons. Here a series of three MOF-activated carbon composite materials with different MOF to carb…
Origin of the Chemiresistive Response of Ultrathin Films of Conductive Metal–Organic Frameworks
2018
Conductive metal-organic frameworks are opening new perspectives for the use of these porous materials for applications traditionally limited to more classical inorganic materials, such as their integration into electronic devices. This has enabled the development of chemiresistive sensors capable of transducing the presence of specific guests into an electrical response with good selectivity and sensitivity. By combining experimental data with computational modelling, a possible origin for the underlying mechanism of this phenomenon in ultrathin films (ca. 30 nm) of Cu-CAT-1 is described. ispartof: ANGEWANDTE CHEMIE-INTERNATIONAL EDITION vol:57 issue:46 pages:15086-15090 ispartof: location…
Temperature dependence of magnetization reversal in Co and Fe3O4 nanowire arrays
2005
Abstract In this paper, we investigate the magnetization reversal of cobalt and magnetite nanowires, 4 nm in diameter, synthesized within the pores of mesoporous silica thin films. A SQUID magnetometer was used to study the magnetic properties of the nanowire arrays over a broad temperature interval, T= 1.8–300 K. The magnetization reversal process was found to be strongly temperature dependent. While a coherent rotation may occur at room temperature, a process involving the formation of domain structures takes place as the temperature decreases down to 1.8 K.