References of "Cloots, Rudi"
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See detailSynthesis and characterization of new inorganic polymeric composites based on kaolin or white clay and on ground-granulated blast furnace slag
Lecomte, I.; Liégeois, Monique ULg; Rulmont, André ULg et al

in Journal of Materials Research (2003), 18(11), 2571-2579

Alkali activation of dehydroxylated kaolin or clay yielded high-strength polymeric materials, so-called geopolymers. They were synthesized by mixing the aluminosilicate with solutions of sodium ... [more ▼]

Alkali activation of dehydroxylated kaolin or clay yielded high-strength polymeric materials, so-called geopolymers. They were synthesized by mixing the aluminosilicate with solutions of sodium metasilicate and KOH followed by adding 45 wt.% of ground-granulated blast furnace slag. The influence of the aluminosilicate source, its activation temperature, and the order of mixing raw materials were studied on the workability of the blending paste, the microstructure, and the Vickers hardness of the geopolymer samples. The polymeric material is completely amorphous according to x-ray diffraction. Solid-state 27Al and 29Si magic-angle-spinning nuclear magnetic resonance showed that the geopolymer consists of AlO 4 and SiO 4 tetrahedra linked together through a polymeric network constituted by branched entities SiQ 4(4Al) and SiQ 4(3Al), but also by less-polymerized silicates SiQ 1 and SiQ 2. Scanning electron microscopy showed a homogeneous polymeric gel matrix containing unreacted slag (and quartz) grains; thermogravimetric analysis and differential scanning calorimetry exhibited a high content of water and an elevated melting point (1260 °C). Vickers hardness values are in the range of 200 MPa. [less ▲]

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See detailPhosphate mineral formation in Lake Baïkal sediments and implications for paleoclimate
Fagel, Nathalie ULg; Alleman, L. Y.; André, Luc et al

Poster (2003)

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See detailPhosphate mineral occurrences in Lake Baïkal sediments : Paleo-environment or diagenesis record ?
Fagel, Nathalie ULg; Alleman, L. Y.; André, Luc et al

Poster (2003)

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See detailMagneto-transport study of nb-doped Bi/Pb2223 superconductor
Pekala, Marek; Mucha, Jan ULg; Cloots, Rudi ULg et al

in Physica C: Superconductivity (2003), 387(1-2), 191-197

The magneto-transport properties of Bi1.5Pb0.4Nb0.1Sr2Ca2Cu3O10-x polycrystalline, superconducting ceramic are reported. The material was found to be chemically homogeneous and partially textured. The ... [more ▼]

The magneto-transport properties of Bi1.5Pb0.4Nb0.1Sr2Ca2Cu3O10-x polycrystalline, superconducting ceramic are reported. The material was found to be chemically homogeneous and partially textured. The mixed state properties were investigated by measuring the electrical resistivity, longitudinal and transverse (Nernst effect) thermoelectric power, and thermal conductivity. The magnetization and AC susceptibility measurements were also performed. The variation of these characteristics for magnetic fields up to 5 T are discussed and compared to those of the zero field case. The transport entropy and thermal Hall angle are extracted and quantitatively compared to previously reported data of closely related systems. (C) 2003 Elsevier Science B.V. All rights reserved. [less ▲]

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See detailMagnetotransport study of MgB2 superconductor
Mucha, Jan ULg; Pekala, Marek; Szydlowska, Jadwiga et al

in Superconductor Science and Technology (2003), 16(10), 1167-1172

Precise magnetotransport studies of heat and charge carriers in polycrystalline MgB2 show that magnetic fields up to 8 T remarkably influence electrical resistivity, thermoelectric power and thermal ... [more ▼]

Precise magnetotransport studies of heat and charge carriers in polycrystalline MgB2 show that magnetic fields up to 8 T remarkably influence electrical resistivity, thermoelectric power and thermal conductivity. The superconducting transition temperature shifts from 39 K to 19 K at 8 T as observed on electric signals. The temperature transition width is weakly broadened. Electron and phonon contributions to the thermal conductivity are separated and discussed. The Debye temperature calculated from a phonon drag thermoelectric power component is inconsistent with values derived through other effects. [less ▲]

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See detailPreparation of nanosized barium zirconate powder by thermal decomposition of urea in an aqueous solution containing barium and zirconium, and by calcination of the precipitate
Boschini, Frédéric ULg; Robertz, B.; Rulmont, André ULg et al

in Journal of the European Ceramic Society (2003), 23(16), 3035-3042

The synthesis of barium zirconate was initiated by urea induced homogeneous precipitation followed by a "low temperature" thermal treatment. The kinetic of the reaction and the optimum urea/cation ratio ... [more ▼]

The synthesis of barium zirconate was initiated by urea induced homogeneous precipitation followed by a "low temperature" thermal treatment. The kinetic of the reaction and the optimum urea/cation ratio have been determined by means of X-ray diffraction and Inductive Coupled Plasma analyses. It has been demonstrated that an amorphous zirconium hydrated oxide starts to precipitate followed by the precipitation of barium carbonate. A calcination at 1200 degreesC during 2 h gives rise to the formation of a pure barium zirconate phase. Microstructural characterisations have been performed in order to evaluate the sintering behaviour. Dilatometric measurements, coupled with scanning electron microscopy analyses clearly indicate that barium carbonate decomposition process leads to the formation of internal porosity which severely limits the density of the material, even if a sintering was performed at 1500 degreesC. A careful control of the heating profile seems to be necessary in order to produce dense materials. (C) 2003 Elsevier Ltd. All rights reserved. [less ▲]

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See detailSynthesis of CMR manganate compounds: the consequences of the choice of a precursor method
Vertruyen, Bénédicte ULg; Rulmont, André ULg; Cloots, Rudi ULg et al

in Materials Letters (2002), 57(3), 598-603

We have studied the electrical transport properties of manganate samples synthesized by different precursor methods. Differences in the synthesis process of the materials can result in samples with ... [more ▼]

We have studied the electrical transport properties of manganate samples synthesized by different precursor methods. Differences in the synthesis process of the materials can result in samples with similar grain size but very different physical properties, contrary to what happens in samples prepared by the same method. (C) 2002 Elsevier Science B.V. All rights reserved. [less ▲]

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See detailMagnon-polaron and spin-polaron signatures in the specific heat and electrical resistivity of La0.6Y0.1Ca0.3MnO3 in zero magnetic field and the effect of Mn - O - Mn bond environment
Ausloos, Marcel ULg; Hubert, L.; Dorbolo, Stéphane ULg et al

in Physical Review B (2002), 66(17),

La0.6Y0.1Ca0.3MnO3, an ABO(3) perovskite manganite oxide, exhibits a nontrivial behavior in the vicinity of the sharp peak found in the resistivity rho as a function of temperature T in zero magnetic ... [more ▼]

La0.6Y0.1Ca0.3MnO3, an ABO(3) perovskite manganite oxide, exhibits a nontrivial behavior in the vicinity of the sharp peak found in the resistivity rho as a function of temperature T in zero magnetic field. The various features seen on drho/dT are discussed in terms of competing phase transitions. They are related to the Mn-O-Mn bond environment depending on the content of the A crystallographic site. A Ginzburg-Landau type theory is presented for incorporating concurrent phase transitions. The specific heat C of such a compound is also examined from 50 to 200 K. A log-log analysis indicates different regimes. In the low temperature conducting ferromagnetic phase, a collective magnon signature (Csimilar or equal toT(3/2)) is found as for what are called magnon-polaron excitations. A Csimilar or equal toT(2/3) law is found at high temperature and discussed in terms of the fractal dimension of the conducting network of the weakly conducting (so-called insulating) phase and an Orbach estimate of the excitation spectral behaviors. The need of considering both independent spin scattering and collective spin scattering is thus emphasized. The report indicates a remarkable agreement for the Fisher-Langer formula, i.e., Csimilar todrho/dT at second order phase transitions. Within the Attfield model, we find an inverse square root relationship between the critical temperature(s) and the total local Mn-O-Mn strain. [less ▲]

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See detailLes biomatéraux.
Grandfils, Christian ULg; Cloots, Rudi ULg; Maquet, V

Conference (2002, March 07)

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See detailYBa2Cu3O7 tapes prepared by sol-gel deposition techniques: microstructure and structural characterizations
Marguillier, David ULg; Cloots, Rudi ULg; Rulmont, André ULg et al

in Physica C: Superconductivity (2002), 372(Part 2), 715-718

We report on the preparation conditions of YBa2Cu3O7 polycrystalline superconducting tapes by a sol-gel deposition technique. We present some discussion on the compatibility between the nature of the ... [more ▼]

We report on the preparation conditions of YBa2Cu3O7 polycrystalline superconducting tapes by a sol-gel deposition technique. We present some discussion on the compatibility between the nature of the substrate, the use of a buffer layer, and the conditions used to prepare appropriate superconducting YBa2Cu3O7,, materials. We report also on the microstructural characterizations performed in order to evaluate the crystallites size, degree of orientation and connectivity. (C) 2002 Elsevier Science B.V. All rights reserved. [less ▲]

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See detailCu doping as a tool for understanding CMR
Vertruyen, Bénédicte ULg; Cloots, Rudi ULg; Rulmont, André ULg et al

in Key Engineering Materials [=KEM] (2002), 206-2

Doping at the Mn-site in CMR manganate-based perovskites has been shown to affect strongly the physical properties of those compounds. We study here the effect of copper substitution in the low doping ... [more ▼]

Doping at the Mn-site in CMR manganate-based perovskites has been shown to affect strongly the physical properties of those compounds. We study here the effect of copper substitution in the low doping range on the electrical transport properties of La0.7Ca0.3MnO3. It turns out that the transition temperature decrease observed in doped samples can be drastically reduced by addition of silicon dioxide SiO2. It is shown that copper is trapped in a secondary phase composed of La,Ca,Si,Cu and O. The resultant Mn-site vacancies appear to be less detrimental to the electronic conduction than the likely antiferromagnetic clusters induced by the copper ions in the Mn-O network. [less ▲]

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See detailIntragranular and intergranular behaviour of multifilamentary Bi-2223/Ag tapes
Fagnard, Jean-François ULg; Vanderbemden, Philippe ULg; Crate, David et al

in Physica C: Superconductivity (2002), 372(Part 2), 970-973

This communication aims at reporting the superconducting properties of Bi-2223/Ag tapes determined by using various measuring techniques. First. the original samples have been characterized by electrical ... [more ▼]

This communication aims at reporting the superconducting properties of Bi-2223/Ag tapes determined by using various measuring techniques. First. the original samples have been characterized by electrical resistance, AC susceptibility. and DC magnetization. The transport (intergranular) critical Current vs. magnetic field was also determined at T = 77 K using pulsed currents up to 40 A. Next. the same combination of experiments as performed oil bent tapes in order to bring out relevant information concerning the strength of the intergranular coupling. The results show that intergranular and intragranular currents differ by at least one order of magnitude, Finally, additional magnetic measurements were carried out in order to determine the anisotropy ratio Jc(ab)/Jc(c), which was found to lie around 30. (C) 2002 Elsevier Science B.V. All rights reserved. [less ▲]

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See detailMagnetic and transport measurements on melt-textured DyBCO single domains
Vanderbemden, Philippe ULg; Misson, Vincent; Ausloos, Marcel ULg et al

in Physica C: Superconductivity (2002), 372(Part 2), 1225-1228

In this communication we report critical current measurements of melt processed DyBa2Cu3O7-x samples determined by several measuring techniques. First the material was characterized by AC susceptibility ... [more ▼]

In this communication we report critical current measurements of melt processed DyBa2Cu3O7-x samples determined by several measuring techniques. First the material was characterized by AC susceptibility and DC magnetization. The results are characteristic of good quality melt-processed (RE)BCO material with T-c = 89 K and Jc(77 K, 1 T) = 10^4 A/cm^2. Next, pulsed currents were used in order to determine both I-V curves and transport critical currents. The origin of the discrepancy between transport and magnetic data has been discussed. The results point out significant local variations of the critical current density throughout the single domain. (C) 2002 Elsevier Science B.V. All rights reserved. [less ▲]

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See detailImportance of soft solution processing for advanced BaZrO3 materials
Robertz, B.; Boschini, Frédéric ULg; Cloots, Rudi ULg et al

in International Journal of Inorganic Materials (2001), 3(8), 1185-1187

Barium zirconate is an interesting material for refractory applications as well as a good substrate for the manufacturing of high temperature superconductors. However, its solid state synthesis requires ... [more ▼]

Barium zirconate is an interesting material for refractory applications as well as a good substrate for the manufacturing of high temperature superconductors. However, its solid state synthesis requires high temperature and provides inhomogeneous powder with a broad particle size distribution. In order to avoid these disadvantages, soft solution routes are of growing importance in the ceramic powder synthesis. Precipitation. decomposition of precursors, combustion techniques offer alternative ways to the solid state method. Advantages of these are a lower calcination temperature, production of homogeneous and fine monodisperse powders. The obtained powders have been characterised by XRD, IR, SEM and DTA/TG analysis. The influence of the synthesis conditions on the properties of BaZrO3 has been studied. (C) 2001 Elsevier Science Ltd. All rights reserved. [less ▲]

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See detailPreparation and properties of layered silicate nanocomposites based on ethylene vinyl acetate copolymers
Alexandre, Michaël ULg; Beyer, Günter; Henrist, Catherine ULg et al

in Macromolecular Rapid Communications (2001), 22(8), 643-646

(Nano)composites based on ethylene vinyl acetate copolymers (EVA) and montmorillonite modified by various alkylammonium cations were processed by mechanical kneading. Polymer intercalation and filler ... [more ▼]

(Nano)composites based on ethylene vinyl acetate copolymers (EVA) and montmorillonite modified by various alkylammonium cations were processed by mechanical kneading. Polymer intercalation and filler exfoliation were evidenced by X-ray diffraction and transmission electron microscopy, respectively. Nano-composites tensile properties showed that Young's modulus increases significantly even at very low content of the organo-modified filler while preserving high ultimate elongation and tensile stress. The matrix thermal stability in air was increased by 40°C and, interestingly, the obtained nanocomposites present flame retardant properties. TEM micrograph of the nanocomposite based on EVA3 filled with 5 wt.-% of Mont-2CN2C18. [less ▲]

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See detailMagnetic properties of melt-textured DyBCO single domains
Vanderbemden, Philippe ULg; Ausloos, Marcel ULg; Cloots, Rudi ULg

in Materials Research Society Symposium Proceedings (2001), 659

This communication aims at reporting the superconducting properties of several bulk melt-processed DyBa2Cu3O7-x samples determined by using various measuring techniques. The original single domain ... [more ▼]

This communication aims at reporting the superconducting properties of several bulk melt-processed DyBa2Cu3O7-x samples determined by using various measuring techniques. The original single domain material was first cut into 9 similar cubic samples which have been characterized by AC susceptibility, flux profiles and DC magnetization. The results indicate good quality melt-processed (RE)BCO materials with Tc = 89 K. Next, the effect of post oxygen annealing treatments on these samples was studied. The influence of the non-uniformity of the oxygen content on the magnetic property anisotropy is discussed. Finally, additional magnetic measurements were carried out by using a couple of parallel pick-up coils wound on the same sample. From the results we conclude that geometric effects have to be taken into account in order to extract the critical current density from the magnetic properties. [less ▲]

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See detailMagnetotransport properties of a single grain boundary in a bulk La-Ca-Mn-O material
Vertruyen, Bénédicte ULg; Cloots, Rudi ULg; Rulmont, André ULg et al

in Journal of Applied Physics (2001), 90(11), 5692-5697

Besides the "intrinsic" colossal magnetoresistance effect observed in single crystals, the polycrystalline manganate compounds also exhibit an "extrinsic" magnetoresistance related to the presence of ... [more ▼]

Besides the "intrinsic" colossal magnetoresistance effect observed in single crystals, the polycrystalline manganate compounds also exhibit an "extrinsic" magnetoresistance related to the presence of grain boundaries. We report electrical transport and magnetic measurements carried out on a bigrain sample extracted from a floating zone method-grown rod of calcium doped lanthanum manganate. Electrical resistance was measured both within a grain and across the grain boundary, between 20 and 300 K and from 0 to 8 T. Magnetoresistance values up to 99% are reached within the grain. The temperature dependence of the resistance across the grain boundary displays a "foot-like" feature towards the bottom of the transition. Low field and high field magnetoresistance effects are examined. We compare our results for a "bulk" grain boundary to those obtained by other authors for bicrystal thin films and bulk polycrystalline materials. (C) 2001 American Institute of Physics. [less ▲]

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See detailPoly(e-caprolactone) layered silicate nanocomposites: effect of clay surface modifiers on the melt intercalation process
Pantoustier, Nadège; Alexandre, Michaël ULg; Degée, Philippe et al

in e-Polymers (2001), (9), 1-9

Nanocomposites based on biodegradable poly(e-caprolactone) (PCL) and layered silicates (montmorillonite) modified by various alkylammonium cations were prepared by melt intercalation. Depending on whether ... [more ▼]

Nanocomposites based on biodegradable poly(e-caprolactone) (PCL) and layered silicates (montmorillonite) modified by various alkylammonium cations were prepared by melt intercalation. Depending on whether the ammonium cations contain non-functional alkyl chains or chains terminated by carboxylic acid or hydroxyl functions, microcomposites or nanocomposites were recovered as shown by X-ray diffraction and transmission electron microscopy. Mechanical and thermal properties were examined by tensile testing and thermogravimetric analysis. The layered silicate PCL nanocomposites exhibited some improvement of the mechanical properties (higher Young's modulus) and increased thermal stability as well as enhanced flame retardant characteristics as result of a charring effect. This communication aims at reporting that the formation of PCL-based nanocomposites strictly depends on the nature of the ammonium cation and its functionality, but also on the selected synthetic route, i.e. melt intercalation vs. in situ intercalative polymerization. Typically, protonated w-aminododecanoic acid exchanged montmorillonite allowed to intercalate e-caprolactone monomer and yielded nanocomposites upon in situ polymerization, whereas they exclusively formed microcomposites when blended with preformed PCL chains. In other words, it is shown that the formation of polymer layered silicate nanocomposites is not straightforward and cannot be predicted since it strongly depends on parameters such as ammonium cation type and functionality together with the production procedure, i.e., melt intercalation, solvent evaporation or in situ polymerization [less ▲]

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See detailMagnetic properties of magnetically textured Bi-2212 ceramics
Vanderbemden, Philippe ULg; Bougrine, Hassan ULg; Ausloos, Marcel ULg et al

in Physica C: Superconductivity (2001), 351(1), 67-70

This paper aims at reporting magnetic properties of bulk polycrystalline Bi2Sr2Ca0.8Dy0.2Cu2O8-y samples textured under a magnetic field. The microstructure of these materials is highly anisotropic and ... [more ▼]

This paper aims at reporting magnetic properties of bulk polycrystalline Bi2Sr2Ca0.8Dy0.2Cu2O8-y samples textured under a magnetic field. The microstructure of these materials is highly anisotropic and exhibits particular features needed to be taken into account in order to interpret their magnetic and electrical properties. First the AC magnetic susceptibility has been measured for several magnetic fields (H parallel to ab and H parallel to c) and compared to the electrical resistivity data. The structure of the chi'' peak is shown to be related to the chemical content distribution of the superconducting grains. Next, the magnetic flux profiles have been extracted from the magnetic measurements using the Campbell-Rollins procedure. The anisotropy of the flux profiles and their peculiar curvature behaviour for H parallel toc point out the role of both grain platelet structure and the presence of secondary phases. From these results, we conclude that the magnetic properties of such magnetically textured materials do not allow for a reliable extraction of the critical current density J(c) but essentially probe geometric effects. Such effects have to be taken into account for improving the manufacture of attractive high-T-c materials. (C) 2001 Elsevier Science B.V. All rights reserved. [less ▲]

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