References of "Cloots, Rudi"
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See detailExperimental Design applied to spin coating of 2D colloidal crystal masks : a relevant method?
Colson, Pierre ULg; Cloots, Rudi ULg; Henrist, Catherine ULg

in Langmuir (2011), 27(21), 12800-12806

Monolayers of colloidal spheres are used as masks in nanosphere lithography (NSL) for the selective deposition of nanostructured layers. Several methods exist for the formation of the self-organized ... [more ▼]

Monolayers of colloidal spheres are used as masks in nanosphere lithography (NSL) for the selective deposition of nanostructured layers. Several methods exist for the formation of the self-organized particles monolayers, among which spin coating appears to be very promising. However, a spin coating process is defined by several parameters like several ramps, rotation speeds and durations. All parameters influence the spreading and drying of the droplet containing the particles. Moreover, scientists are confronted to the formation of numerous defects in spin coated layers, limiting well-ordered areas to a few µm2. So far, empiricism mainly ruled the world of nanoparticles self-organization by spin coating and much of the literature is experimentally based. Therefore, the development of experimental protocols to control the ordering of particles is a major goal for further progress in NSL. We applied experimental design to spin coating, to evaluate the efficiency of this method to extract and model the relationships between the experimental parameters and the degree of ordering in the particles monolayers. A set of experiments was generated by the MODDE software and applied to the spin coating of latex suspension (diam. 490 nm). We calculated the ordering by a homemade image analysis tool. The results of Partial Least Squares (PLS) modeling show that the proposed mathematical model only fits data from strictly monolayers but is not predictive for new sets of parameters. We submitted the data to Principal Component Analysis (PCA) that was able to explain 91% of the results when based on strictly monolayers samples. PCA shows that the ordering was positively correlated to the ramp time and negatively correlated to the first rotation speed. We obtain large defect-free domains with the best set of parameters tested in this study. This protocol leads to areas of 200 µm2, which has never been reported so far. [less ▲]

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See detailPreparation of Spherical Submicronic Barium Zirconate particles in Highly Basic Solution below 100°C
Boschini, Frédéric ULg; Cloots, Rudi ULg; Vertruyen, Bénédicte ULg

in IOP Conference Series: Materials Science and Engineering (2011)

In this study, a new method has been developed to produce pure crystalline BaZrO3 powders from Ba+Zr solution or weakly soluble reactants by using precipitation route in highly basic aqueous solution. The ... [more ▼]

In this study, a new method has been developed to produce pure crystalline BaZrO3 powders from Ba+Zr solution or weakly soluble reactants by using precipitation route in highly basic aqueous solution. The influence of several synthesis parameters is studied. At high OH- concentration ([NaOH] = 20 mol/l), it is possible to obtain the well-crystallized stoichiometric perovskite phase at relatively low temperature (~80°C), after a short reaction time (15 minutes) and without requiring any precaution to avoid the presence of CO2. This synthesis method yields spherical particles, whose size can be controlled by changing the concentration of the Ba+Zr solution. No calcination treatment is necessary since the precipitate is crystalline. Suitable choice of the synthesis parameters ([NaOH] = 20 mol/l, [Ba+Zr] = 1 mol/l, reaction time = 15 minutes) yields a sub-micron precipitate. [less ▲]

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See detailNbVO5 Mesoporous Thin Films by Evaporation Induced Micelles Packing: Pore Size Dependence of the Mechanical Stability upon Thermal Treatment and Li Insertion/Extraction
Krins, Natacha ULg; Bass, John D; Grosso, David et al

in Chemistry Of Materials (2011), 23(18), 4124-4131

Mesoporous thin films (MTFs) appear as an interesting architecture for positive electrodes in Li-ion energy storage systems because they offer high specific area and interconnected porosity presenting ... [more ▼]

Mesoporous thin films (MTFs) appear as an interesting architecture for positive electrodes in Li-ion energy storage systems because they offer high specific area and interconnected porosity presenting homogeneous pore size and wall thickness. However, it must be ascertained that the mesostructure survives template removal or/and crystallization and is retained on electrochemical cycling. In order to investigate the potentialities and limits of the soft-templating approach in the case of complex transition metal oxide networks, we deliberately selected a "difficult" compound: NbVO5 was chosen because it combines a challenging synthesis with reported severe structural distortions during the first lithium insertion in the bulk material. In this work, NbVO5 MTFs with different pore sizes were synthesized using the evaporation induced micelles packing (EIMP) method. PS-b-PEO diblock copolymers of different molar weights were used as structure directing agent in order to obtain wormlike porous networks with pore size and wall thickness ranging from 15 to 100 nm. Thermal ellipsometry analysis, used to track surfactant removal and crystallization of the layer, reveals that partial crystallization is possible while retaining the mesoporous architecture. Electron tomography complements result from environmental ellipsometric porosimetry, atomic force microscopy, and transmission electron microscopy to provide a comprehensive description of the structure. A multilayer process is also proposed to build crack-free thick mesoporous films. The mechanical stability of MTFs presenting three different pore sizes is tested by inserting Li(+) in amorphous NbVO5 MTFs using cyclic voltammetry. Capacity retention data show that the mechanical stresses associated with Li+ insertion are better accommodated by MTFs compared to nonporous films, and this ability is enhanced as the pore size decreases. [less ▲]

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See detailWell Shaped Mn(3)O(4) Nano-octahedra with Anomalous Magnetic Behavior and Enhanced Photodecomposition Properties
Li, Yu; Tan, Haiyan; Yang, Xiao-Yu et al

in Small : Nano Micro (2011), 7(4), 475-483

Very uniform and well shaped Mn(3)O(4) nano-octahedra are synthesized using a simple hydrothermal method under the help of polyethylene glycol (PEG200) as a reductant and shape-directing agent. The nano ... [more ▼]

Very uniform and well shaped Mn(3)O(4) nano-octahedra are synthesized using a simple hydrothermal method under the help of polyethylene glycol (PEG200) as a reductant and shape-directing agent. The nano-octahedra formation mechanism is monitored. The shape and crystal orientation of the nanoparticles is reconstructed by scanning electron microscopy and electron tomography, which reveals that the nano-octahedra only selectively expose {101} facets at the external surfaces. The magnetic testing demonstrates that the Mn(3)O(4) nano-octahedra exhibit anomalous magnetic properties: the Mn(3)O(4) nano-octahedra around 150 nm show a similar Curie temperature and blocking temperature to Mn(3)O(4) nanoparticles with 10 nm size because of the vertical axis of [001] plane and the exposed {101} facets. With these Mn(3)O(4) nano-octahedra as a catalyst, the photodecomposition of rhodamine B is evaluated and it is found that the photodecomposition activity of Mn(3)O(4) nano-octahedra is much superior to that of commercial Mn(3)O(4) powders. The anomalous magnetic properties and high superior photodecomposition activity of well shaped Mn(3)O(4) nano-octahedra should be related to the special shape of the nanoparticles and the abundantly exposed {101} facets at the external surfaces. Therefore, the shape preference can largely broaden the application of the Mn(3)O(4) nano-octahedra. [less ▲]

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See detailThermoelectric properties of n-type Ca1-xDyxMn1-yNbyO3-delta compounds (x=0, 0.02, 0.1 and y=0, 0.02) prepared by spray-drying method
Muguerra, Hervé; Rivas-Murias, Beatriz; Traianidis, Maria et al

in Journal Of Alloys And Compounds (2011), 509(29), 7710-7716

We report the high temperature thermoelectric properties of Ca1-xDyxMn1-yNbyO3-delta (x = 0, 0.02, 0.1 and y = 0, 0.02) synthesized by spray-drying method. A maximum power factor (PF) value of 2.65 mu WK ... [more ▼]

We report the high temperature thermoelectric properties of Ca1-xDyxMn1-yNbyO3-delta (x = 0, 0.02, 0.1 and y = 0, 0.02) synthesized by spray-drying method. A maximum power factor (PF) value of 2.65 mu WK-2 cm(-1) is obtained at 1100 K for CaMn0.98Nb0.02O3-delta. This represents an improvement of about 75% with respect to undoped CaMnO3-delta sample at the same temperature. We also provide a complete structural characterization of the samples. (C) 2011 Elsevier B.V. All rights reserved. [less ▲]

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See detailYBa2Cu3O7−x dispersion in iodine acetone for electrophoretic deposition: Surface charging mechanism in a halogenated organic media
Dusoulier, Laurent; Cloots, Rudi ULg; Vertruyen, Bénédicte ULg et al

in Journal of the European Ceramic Society (2011), 31

Electrophoretic deposition (EPD) performance strongly depends on the particles surface chemistry and the ability to manipulate surface–liquid interfaces. In this study an extensive investigation of YBCO ... [more ▼]

Electrophoretic deposition (EPD) performance strongly depends on the particles surface chemistry and the ability to manipulate surface–liquid interfaces. In this study an extensive investigation of YBCO suspension in dry acetone, acetone–water mixtures and acetone–iodine is reported. Chemical instability of YBCO particles determines their colloidal behaviour. Charging mechanism of particles has therefore had to be deeply investigated for complete dispersion understanding. In order to determine the conditions of the YBCO suspension stability, measurements of pH, conductivity, zeta-potential, settling tests, modelling of the particle networks and electrophoretic deposition were done. The influence of the water and iodine concentration, and their role as stabilizers was evaluated. Based on experimental results, pair particle potentials were calculated and then different charging mechanisms of YBCO surfaces in acetone were proposed. [less ▲]

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See detailPolymer micelles decorated by gadolinium complexes as MRI blood contrast agents: design, synthesis and properties
Grogna, Mathurin ULg; Cloots, Rudi ULg; Luxen, André ULg et al

in Polymer Chemistry (2010), 1

New micellar macrocontrast agents with improved contrast at high frequencies were designed by grafting a gadolinium based contrast agent onto functional stealth micelles formed by poly(ethylene oxide)-b ... [more ▼]

New micellar macrocontrast agents with improved contrast at high frequencies were designed by grafting a gadolinium based contrast agent onto functional stealth micelles formed by poly(ethylene oxide)-b-poly(ε-caprolactone) (PEO-b-PCL) in water. As evidenced by relaxometry measurements and the hemolytic CH50 test, the new contrast agents are of interest as MRI blood pool agents. [less ▲]

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See detailTiO2 thin films (1 µm) with ordered porosity used as high performance photoelectrode in DSSC
Dewalque, Jennifer ULg; Cloots, Rudi ULg; Dubreuil, Olivier et al

Poster (2010, July 06)

Mesoporous anatase thin films are very promising materials to act as electrode in dye-sensitized solar cells. Randomly oriented nanocrystalline TiO2 particles are usually used to prepare photoelectrodes ... [more ▼]

Mesoporous anatase thin films are very promising materials to act as electrode in dye-sensitized solar cells. Randomly oriented nanocrystalline TiO2 particles are usually used to prepare photoelectrodes with a thickness of 10-15 µm. Templated-assisted dip-coating techniques are used to obtain thin films with ordered porosity. The use of different templates influences the film porosity in terms of long-range order, percentage of porosity, pore size and pores connectivity. The photovoltaic performances of the samples have been evaluated. Such mesostructured films are compared in terms of photovoltaic performance with TiO2 nanoparticles films, generally used in DSSC. [less ▲]

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See detailRepeated thermal treatments applied to ordered TiO2 mesoporous thin film: Effect on the film crystallization and surface area
Henrist, Catherine ULg; Dubreuil, Olivier; Krins, Natacha ULg et al

Conference (2010, July 06)

Ordered, mesoporous films are prepared by template-assisted sol-gel techniques such as dip-coating from a precursors solution. However, monolayer films are only a few hundred nanometers thick and present ... [more ▼]

Ordered, mesoporous films are prepared by template-assisted sol-gel techniques such as dip-coating from a precursors solution. However, monolayer films are only a few hundred nanometers thick and present a limited surface area of active material resulting in poor photovoltaic performances. Therefore it is needed to increase the film thickness. A multilayer deposition process for anatase mesoporous film has been reported in the literature in 2005 by Zukalova and all. Unfortunately, later researches have shown a surface area limitation despite the increase of film thickness due to the repeated thermal treatments applied to the layers. In this study, we have investigated the microstructural evolution of a single mesoporous TiO2 layer submitted to repeated thermal treatments. The modifications are discussed in terms of film thickness, surface area, anatase crystals size and global crystallinity. Besides, we propose an alternative thermal treatment designed in an attempt to overcome the limitations induced by repeated calcinations. We have followed and compared the properties of mesoporous films submitted to both thermal treatments by X-ray diffraction (XRD), transmission electron microscopy (TEM) and environmental poroellipsometry (EEP). Those results show the importance of the tuning of thermal treatment when multilayers films are envisaged for DSSC applications. Indeed, this study quantifies the maximum perturbation encountered by the first layer during the preparation of a multilayer (up to 12) coating, which is submitted to a multistep calcination. Finally, the photovoltaic performances of assembled cells have been evaluated. [less ▲]

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See detailSynthesis of hybrid lamellar silica by liquid crystal templating and silanation
Toussaint, Gilles; Henrist, Catherine ULg; Vertruyen, Bénédicte ULg et al

in Advances in Science and Technology (2010), 68

This paper is focused on the preparation and characterization of different lamellar silica prepared by liquid crystal templating and silanisation. The initial template can be removed and replaced in the ... [more ▼]

This paper is focused on the preparation and characterization of different lamellar silica prepared by liquid crystal templating and silanisation. The initial template can be removed and replaced in the interlamellar spaces by different types of silane, being covalently grafted to the solid by reaction with the surface silanols. The lamellar stacking periodicity remains after this modification. The surfactant extraction can lead in significant grafting of isopropanol if the solid is simply refluxed in isopropanol, which have the effect of preserving the periodicity of the lamellar stacking. The surfactant extraction in an Soxhlet equipment avoid this reaction, with the effect of platelets organization collapsing. The lamellar silica studied exhibit great specific surface and combination of meso and microporosity, making them interesting materials for nanocomposite or catalysis applications. [less ▲]

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See detailVanadium oxide-based mesoporous films as positive electrode material in Li-ion batteries
Krins, Natacha ULg; Caes, Sébastien ULg; Arrebola, José-Carlos et al

Conference (2010)

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See detailStructural and magnetic properties of nanosized barium hexaferrite powders obtained by microemulsion technique
Koutzarova, Tantyana; Kolev, Svetoslav; Ausloos, Marcel ULg et al

in Diffusion and Defect Data--Solid State Data, Pt. B: Solid State Phenomena (2010), 159

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See detailImprovement of the thermoelectric properties of [Bi1.68Ca2O4-delta](RS)[CoO2](1.69) cobaltite by chimie douce methods
Muguerra, Hervé; Rivas-Murias, Beatriz; Traianidis, Maria et al

in Journal of Solid State Chemistry (2010), 183(6), 1252-1257

[Bi1 68Ca2O4 delta](RS)[CoO2](1 69) has been obtained by different chimie douce methods and uniaxially or isostatically pressed The influence of these parameters on the thermoelectric properties has been ... [more ▼]

[Bi1 68Ca2O4 delta](RS)[CoO2](1 69) has been obtained by different chimie douce methods and uniaxially or isostatically pressed The influence of these parameters on the thermoelectric properties has been investigated. Contrary to the Seebeck coefficient, which remains unchanged, the electrical conductivity is greatly modified In particular, spray-drying synthesis followed by uniaxial pressing results in an electrical conductivity two times larger than in the case of conventional solid state synthesis. Our results suggest that a narrow particle size distribution is beneficial to the thermoelectric properties of the layered compounds. The spray-drying technique seems to be promising to Improve the electrical conductivity of layered materials. Moreover, this method presents other advantages (homogeneous samples and less energetic processing) which could be interesting to the future manufacturing of thermoelectric devices (C) 2010 Elsevier Inc. All rights reserved [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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