References of "Gommes, Cédric"
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See detailKrypton adsorption as a suitable tool for surface characterization of multi-walled CNTs
Zilli, Dario; Bonelli, P.; Gommes, Cédric ULg et al

in Carbon (2011), 49

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See detailSAXS analysis in terms of density fluctuations within random observation window
Gommes, Cédric ULg

Conference (2010, December)

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See detailSynthesis and characterization of highly loaded Pt/carbon xerogel catalysts prepared by Strong Electrostatic Adsorption method
Job, Nathalie ULg; Maillard, F.; Chatenet, M. et al

Conference (2010, July 11)

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See detailRelationship between BET specific surface area, DR- and t-plot pore volume
Scherdel, C.; Reichenauer, G.; Wiener, M. et al

Poster (2010, May 23)

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See detailA more thorough analysis of water rockets: Moist adiabats, transient flows, and inertial forces in a soda bottle
Gommes, Cédric ULg

in American Journal of Physics (2010), 78(3), 236-243

Although water rockets are widely used to illustrate first year physics principles, accurate measurements show that they outperform the usual textbook analysis at the beginning of the thrust phase. This ... [more ▼]

Although water rockets are widely used to illustrate first year physics principles, accurate measurements show that they outperform the usual textbook analysis at the beginning of the thrust phase. This paper gives a more thorough analysis of this problem. It is shown that the air expansion in the rocket is accompanied by water vapor condensation, which provides an extra thrust; the downward acceleration of water within the rocket also contributes to the thrust, an effect that is negligible in other types of rockets; the apparent gravity resulting from the acceleration of the rocket contributes as much to water ejection as does the pressure difference between the inside and outside of the rocket; and the water flow is transient, which precludes the use of Bernoulli’s equation. Although none of these effects is negligible, they mostly cancel each other, and the overall accuracy of the analysis is only marginally improved. There remains a difference between theory and experiment with water rockets. [less ▲]

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See detail2-Point correlation function of nanostructured materials via the grey-tone correlation function of electron tomograms: A three-dimensional structural analysis of ordered mesoporous silica
Gommes, Cédric ULg; Friedrich, Heiner; De Jongh, Petra E et al

in Acta Materialia (2010), 58

Electron tomography is a unique technique for imaging the microstructure of materials with a nanometer resolution. The signal to noise ratio of electron tomograms is, however, often too low for a reliable ... [more ▼]

Electron tomography is a unique technique for imaging the microstructure of materials with a nanometer resolution. The signal to noise ratio of electron tomograms is, however, often too low for a reliable segmentation-based image analysis. We derive a general relation between the grey-tone correlation function of the tomograms and the 2-point correlation function of the morphology, which enables to analyze quantitatively the grey-tone correlation function with a morphological model of the material. The methodology is applied to SBA-15 ordered mesoporous silica. The three-dimensional grey-tone correlation function obtained from electron tomography is analyzed in terms of a hexagonal array of Gaussian independent pores. The model enables to relate the morphology obtained from the 2-point correlation function to macroscopic characterization data of the material, notably small-angle X-ray scattering and nitrogen adsorption. [less ▲]

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See detailImage analysis of pearlite spheroidization based on the morphological characterization of cementite particles
Nutal, Nicolas; Gommes, Cédric ULg; Blacher, Silvia ULg et al

in Image Analysis and Stereology (2010), 29

Pearlite spheroidization is a metallurgical process in steels by which cementite lamellaer decompose into spheroids, a process accompanied by a decrease of the Vickers hardness of the samples. In thi ... [more ▼]

Pearlite spheroidization is a metallurgical process in steels by which cementite lamellaer decompose into spheroids, a process accompanied by a decrease of the Vickers hardness of the samples. In thi study, different methods are compared for measuring cementite particles length and width from scanning electron micrographs. Based on a test-image, a so-called ribbon-like method is proposed for measuring particles length and width, and for discriminating lamellae from spheroids. Differently heat-treated samples are prepared and characterized. The results of analysis are used to rationalize the evolution of the microstructure of the samples. Compared to teh calssical DeHoff shape factor, it is shown that new insight into the spheroidization process is gained by analysing the lamellar length and widh distributions. [less ▲]

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See detailModeling the morphology and mechanical behavior of shape memory polyurethanes based on solid-state NMR and synchrotron SAXS/WAXD
D'Hollander, Stijn; Gommes, Cédric ULg; Mens, Raoul et al

in Journal of Materials Chemistry (2010), 20

A combination of solid-state proton Wide-line Nuclear Magnetic Resonance (NMR) relaxometry and synchrotron Small-angle (SAXS) and Wide-angle (WAXD) X-ray scattering was used to elucidate the microphase ... [more ▼]

A combination of solid-state proton Wide-line Nuclear Magnetic Resonance (NMR) relaxometry and synchrotron Small-angle (SAXS) and Wide-angle (WAXD) X-ray scattering was used to elucidate the microphase morphology of shape memory thermoplastic multi-block polyurethanes based on poly(3-caprolactone), as switching segment and polyurethane based permanent or hard segments (HS). The polyurethanes are produced from the condensation of 1,4-butanediol (BDO) with hexamethylenediisocyanate (HDI). The morphology – induced by the hard-segment crystallization – converts from dispersed randomly placed hard-segment domains into progressively more periodic, but interconnected HS nanophases with increasing HS content. Irrespective of the actual morphology, the SAXS data could be described satisfactorily by using a clipped Gaussian random field (GRF) model. The NMR data demonstrate that the HS domain fraction corresponds to the chemical feed, pointing at a complete phase separation. The material mechanical behavior during repeated deformation cycles can be explained on morphological grounds and involves a spatially heterogeneous plastic deformation of the hard domains. [less ▲]

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See detailConeX: a program for angular calibration and averaging of two-dimensional powder scattering patterns
Gommes, Cédric ULg; Goderis, Bart

in Journal of Applied Crystallography (2010), 43

CONEX is a Windows application for converting series of two-dimensional X-ray powder patterns measured on flat two-dimensional detectors into onedimensional scattering patterns. It is based on the ... [more ▼]

CONEX is a Windows application for converting series of two-dimensional X-ray powder patterns measured on flat two-dimensional detectors into onedimensional scattering patterns. It is based on the rigorous use of scattering patterns of calibration samples to determine the three-dimensional position of the detector, with respect to the sample and to the beam. This enables correction of the data for geometric distortions, even when the detector is highly tilted and not centred on the beam. [less ▲]

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See detailSulfonated silica/carbon nanocomposites as novel catalysts for hydrolysis of cellulose to glucose
van de Vijver, Stijn; Peng, Li; Geboers, Jan et al

in Green Chemistry (2010), 12

Sulfonated silica/carbon nanocomposites were successfully developed as reusable, solid acid catalysts for the hydrolytic degradation of cellulose into high yields of glucose.

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See detailCondensation-Induced Decrease of Small-Angle X-ray Scattering Intensity in Gelling Silica Solutions
Gommes, Cédric ULg; Pirard, Jean-Paul ULg; Goderis, Bart

in Journal of Physical Chemistry C: Nanomaterials, Interfaces, and Hard Matter (2010), 114

We propose a mathematical modeling of the total SAXS intensity in silica sol-gel processes in terms of hydrolysis and condensation reactions, as well as of microsyneresis. The results are used to ... [more ▼]

We propose a mathematical modeling of the total SAXS intensity in silica sol-gel processes in terms of hydrolysis and condensation reactions, as well as of microsyneresis. The results are used to rationalize previously published SAXS data of TEOS solutions reacting with organically modified trialkoxysilanes. We notably show that the decrease in SAXS intensity reported for these samples at the end of gelation is a consequence of condensation reactions. The water released by the latter reactions contributes to reduce the electron density difference between the silica and the solvent phases of the gels [less ▲]

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See detailSynthesis and characterization of highly loaded Pt/carbon xerogel catalysts prepared by Strong Electrostatic Adsorption method
Job, Nathalie ULg; Maillard, Frédéric; Chatenet, Marian et al

in Studies in Surface Science and Catalysis (2010), 175

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See detailMorphological models of complex ordered materials based on inhomogeneously clipped Gaussian fields
Gommes, Cédric ULg; Pirard, Jean-Paul ULg

in Physical Review. E : Statistical, Nonlinear, and Soft Matter Physics (2009), 80

Clipping a Gaussian random field at a level that is position-dependent yields statistically non-homogeneous morphologies, relevant to many ordered nanostructured materials. The 1-point and 2-point ... [more ▼]

Clipping a Gaussian random field at a level that is position-dependent yields statistically non-homogeneous morphologies, relevant to many ordered nanostructured materials. The 1-point and 2-point probability functions of the morphology are derived, as well as a general relation between the specific surface area and the gradient of the clipping function. The general results are particularized for the comprehensive analysis of small-angle x-ray scattering and nitrogen adsorption of SBA-15 ordered mesoporous silica. [less ▲]

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See detailPEM fuel cell cathodes based on Pt/carbon xerogel catalysts
Job, Nathalie ULg; Chatenet, M.; Brigaudet, M. et al

Poster (2009, October 25)

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See detailSAXS Data Analysis of Ordered and Disordered Morphologies With Gaussian Random Field Models
Gommes, Cédric ULg; Goderis, Bart

Conference (2009, September)

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See detailCharacterization of nanometer-scale roughness in SBA-15 mesoporous silica using image analysis of electron tomograms
Friedrich, Heiner; Gommes, Cédric ULg; de Jongh, Petra et al

Conference (2009, September)

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See detailPractical Methods for Measuring the Tortuosity of Porous Materials from Binary or Gray-Tone Tomographic Reconstructions
Gommes, Cédric ULg; Bons, Anton-Jan; Blacher, Silvia ULg et al

in AIChE Journal (2009), 55(8), 2000-2012

Two practical methods are proposed to measure the tortuosity of a porous or permeable material from its tomographic reconstruction. The first method is based on the direct measurement of the shortest ... [more ▼]

Two practical methods are proposed to measure the tortuosity of a porous or permeable material from its tomographic reconstruction. The first method is based on the direct measurement of the shortest distance between two points in the pores, and the second is based on the geodesic reconstruction of the pore or permeation space. Unlike the first method, the second can be directly applied to gray-tone tomograms, without the need of a segmentation step. The methods are illustrated with an electron tomogram of clay/plastic nanocomposite, an X-ray microtomogram of sandstone, and a series of model morphologies consisting of penetrable random spheres. For the latter series, the measured tortuosities compare very well with those derived independently from the theoretical effective diffusion coefficients [less ▲]

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See detail15 Minutes about SAXS and gels
Gommes, Cédric ULg; Goderis, Bart; Pirard, Jean-Paul ULg

Scientific conference (2009, May)

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