References of "Gommes, Cédric"
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See detailMesoporosity of Zeolite Y – 3D Quantitative Study by Image Analysis of Electron Tomograms
Zecevic, Jovana; Gommes, Cédric ULg; friedrich, Heiner et al

in Angewandte Chemie International Edition (2012), 51

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See detailThe number of structures compatible with any given correlation function
Gommes, Cédric ULg

Scientific conference (2012)

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See detailMicrostructural degeneracy associated with a two-point correlation function and its information content
Gommes, Cédric ULg; Jiao, Yang; Torquato, Salvatore

in Physical Review. E : Statistical, Nonlinear, and Soft Matter Physics (2012), 85

A two-point correlation function provides a crucial yet an incomplete characterization of a microstructure because distinctly differentmicrostructures may have the same correlation function. In an earlier ... [more ▼]

A two-point correlation function provides a crucial yet an incomplete characterization of a microstructure because distinctly differentmicrostructures may have the same correlation function. In an earlier Letter [Gommes, Jiao, and Torquato, Phys. Rev. Lett. 108, 080601 (2012)], we addressed the microstructural degeneracy question: What is the number of microstructures compatible with a specified correlation function? We computed this degeneracy, i.e., configurational entropy, in the framework of reconstruction methods, which enabled us to map the problem to the determination of ground-state degeneracies. Here, we provide a more comprehensive presentation of the methodology and analyses, as well as additional results. Since the configuration space of a reconstruction problem is a hypercube on which a Hamming distance is defined, we can calculate analytically the energy profile of any reconstruction problem, corresponding to the average energy of allmicrostructures at a given Hamming distance from a ground state. The steepness of the energy profile is a measure of the roughness of the energy landscape associated with the reconstruction problem, which can be used as a proxy for the ground-state degeneracy. The relationship between this roughness metric and the ground-state degeneracy is calibrated using a Monte Carlo algorithm for determining the ground-state degeneracy of a variety of microstructures, including realizations of hard disks and Poisson point processes at various densities as well as thosewith known degeneracies (e.g., single disks of various sizes and a particular crystalline microstructure). We show that our results can be expressed in terms of the information content of the two-point correlation functions. From this perspective, the a priori condition for a reconstruction to be accurate is that the information content, expressed in bits, should be comparable to the number of pixels in the unknown microstructure. We provide a formula to calculate the information content of any two-point correlation function, which makes our results broadly applicable to any field in which correlation functions are employed. [less ▲]

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See detailMolecular and Morphological Aspects of Annealing-Induced Stabilization of Starch Crystallites
Gomand, Sara; Lamberts, Lieve; Gommes, Cédric ULg et al

in Biomacromolecules (2012), 13

A unique series of potato (mutant) starches with highly different amylopectin/amylose (AP/AM) ratios was annealed in excess water at stepwise increasing temperatures to increase the starch melting (or ... [more ▼]

A unique series of potato (mutant) starches with highly different amylopectin/amylose (AP/AM) ratios was annealed in excess water at stepwise increasing temperatures to increase the starch melting (or gelatinization) temperatures in aqueous suspensions. Small-angle X-ray scattering (SAXS) experiments revealed that the lamellar starch crystals gain stability upon annealing via thickening for high-AM starch, whereas the crystal surface energy decreases for AM-free starch. In starches with intermediate AP/AM ratio, both mechanisms occur, but the surface energy reduction mechanism prevails. Crystal thickening seems to be associated with the cocrystallization of AM with AP, leading to very disordered nanomorphologies for which a new SAXS data interpretation scheme needed to be developed. Annealing affects neither the crystal internal structure nor the spherulitic morphology on a micrometer length scale. [less ▲]

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See detailDensity of states for a specified correlation function and the energy landscape
Gommes, Cédric ULg; Jiao, Yang; Torquato, Salvatore

in Physical Review Letters (2012)

The degeneracy of two-phase disordered microstructures consistent with a specified correlation function is analyzed by mapping it to a ground-state degeneracy. We determine for the first time the ... [more ▼]

The degeneracy of two-phase disordered microstructures consistent with a specified correlation function is analyzed by mapping it to a ground-state degeneracy. We determine for the first time the associated density of states via a Monte Carlo algorithm. Our results are described in terms of the roughness of the energy landscape, defined on a hypercubic configuration space. The use of a Hamming distance in this space enables us to define a roughness metric, which is calculated from the correlation function alone and related quantitatively to the structural degeneracy. This relation is validated for a wide variety of disordered systems. [less ▲]

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See detailBridging the gap between cellulose chemistry and heterogeneous catalysis
Van de Vyver, S; Geboers, J; Peng, Li et al

in WIT Transactions on Ecology and the Environment (2011), 154

Although cellulosic biomass offers a promising alternative as an abundant renewable resource in the production of biofuels and platform chemicals, so far only a few studies have reported its aqueous-phase ... [more ▼]

Although cellulosic biomass offers a promising alternative as an abundant renewable resource in the production of biofuels and platform chemicals, so far only a few studies have reported its aqueous-phase conversion into glucose or sugar alcohols using solid chemocatalysts. The principal reason is that these polymeric biomolecules with semi-crystalline structure cannot penetrate the pores of conventional heterogeneous chemocatalysts. New advances in the conversion of cellulose thus require the design of efficient multifunctional catalytic systems with sterically accessible acid and metal sites. [less ▲]

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See detailIn situ SAXS under shear unveils the gelation of aqueous starch suspensions and the impact of added amylose-lipid complexes
Putseys, Joke; Gommes, Cédric ULg; Van Puyvelde, P. et al

in Carbohydrate Polymers (2011), 84

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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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