423 research outputs found
Qualitative assessment of the purity of multi-walled carbon nanotube samples using krypton adsorption
peer reviewedKrypton is a subcritical vapour at the nitrogen boiling temperature. As such, its adsorption on
crystalline surfaces leads to condensation steps, typical of type VI isotherms according to
IUPAC, while its adsorption on rough surfaces is BET-like. Based on this property of krypton
adsorption at 77 K, a methodology is proposed to determine the purity of carbon nanotubes
samples. The method is tested on model samples obtained by mixing mechanically purified
multi-walled carbon nanotubes with various amounts of the same catalyst as used for their
synthesis
Characterization of the porous structure of biodegradable scaffolds obtained with supercritical CO2 as foaming agent
Poly(ε-caprolactone) foams were prepared, via a batch process, by using supercritical CO2 as foaming agent. Their porous structure was characterized through mercury porosimetry, helium and mercury pycnometry, scanning electron microscopy (SEM) and X-ray microtomography observations coupled with image analysis. The pore size distributions obtained by these two latter techniques show that the pore structure is more homogeneous when the foaming process is performed under a high CO2 saturation pressure (higher than 250 bars)
Analyse d'images obtenues par microtomographie à rayons X d'un catalyseur de type xérogel Pd-Ag/SiO2 supporté sur une mousse de Al2O3
peer reviewedIn order to preshape and mechanically strengthen, Pd-Ag/SiO2 xerogel catalysts were carried out in Al2O3 foams (pore-sizes similar to40 mum). The final material consists of a Pd-Ag/SiO2 xerogel immobilized in the open cells of the alumina foam. The localization of the xerogel catalyst in alumina foams of various pore structure was studied by X-ray microtomography. The three-dimensional (3D) porous structure was reconstructed from the consecutive cross-sections obtained by this technique. Total porosity, porous density distribution, and pore-size distribution were determined by image analysis on the free and impregnated supports. Our results show that the success of the used impregnation technique depends on the pore structure of the support. (C) 2004 Elsevier B.V. All rights reserved
4MOST : the 4-metre multi-object spectroscopic telescope project in the assembly, integration, and test phase
4MOST is a new high-multiplex, wide-field spectroscopic survey facility under construction for ESO's 4m-VISTA telescope at Paranal, Chile. Its key specifications are: a large field of view of 4.4 square degrees, a high multiplex fibre positioner based on the tilting spine principle that positions 2436 science fibres in the focal surface of which 1624 fibres go to two low-resolution optical spectrographs (R = λ/Δλ ~ 6500) and 812 fibres transfer light to the high-resolution optical spectrograph (R ~ 20,000). Currently, almost all subsystems are completed and full testing in Europe will be finished in spring 2023, after which 4MOST will be shipped to Chile. An overview is given of instrument construction and capabilities, the planned science of the consortium and the recently selected community programmes, and the unique operational scheme of 4MOST
Influence of temperature for carbon nanotube synthesis by the CCVD method in a continuous inclined mobile bed reactor
Aerogel compression theoretical analysis
Several authors have empirically shown that, in aerogels, a power law exists between the mechanical moduli and the bulk density. An exponent value can be determined from mercury porosimetry curves. The shrinkage of aerogels under mercury pressure follows a buckling mechanism which links the pore size to the exerted pressure. The present study relates the exponent to the pore volume distribution which can be described by a hierarchical model valid in a large range of pore size, so a physical meaning is given to the exponent
nanostructured carbon materials by surfactant-templating of resorcinol-formaldehyde gels: towards a control of porosity for energy storage applications
Nanostructured carbon materials for energy storage applications: control of porosity of resorcinol-formaldehyde xerogels
Synthesis and characterization of porous carbon xerogels and ordered mesoporous carbons for anode materials in Li-based batteries
Contrôle de la porosité de xérogels de carbone poreux via l’ajout de tensioactifs non-ioniques
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