References of "Vanderbemden, Philippe"
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See detailAn experimental approach for synthesis of Fe-Al-O multiferroic fibrous material
Starbov, N; Starbova, K; Vanderbemden, Philippe ULg et al

in Journal of Physics: Conference Series (2012), 398

Basic principles of the electro-hydrodynamics are applied for synthesis of solid state Fe-Al-O multi-ferroic fibrous material. For that purpose stable blend spinning solutions comprised of a high ... [more ▼]

Basic principles of the electro-hydrodynamics are applied for synthesis of solid state Fe-Al-O multi-ferroic fibrous material. For that purpose stable blend spinning solutions comprised of a high molecular assisting organic polymer and salts of iron and aluminum are developed. These solutions are tested under electrospinning conditions and synthesis of homogeneous as spun non-woven mats characterized by fibre mean diameters in the microand nano-size range is successfully demonstrated. Multi-step thermal procedure is applied for the consecutive solvent evaporation, polymer pyrolisis and final fibre calcination. Electronoptical imaging technique and XRD are applied for revealing the sample morphology and the phase composition correspondingly. The results obtained outline the wide possibilities for fabrication of multi-ferroics fibrous nano-materials on the basis of Fe-Al-O. [less ▲]

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See detailMagnetic shielding properties of a superconducting hollow cylinder containing slits: Modelling and experiment
Fagnard, Jean-François ULg; Elschner, S.; Hobl, A. et al

in Superconductor Science and Technology (2012), 25(10), 104006

This paper deals with the magnetic properties of bulk high temperature superconducting cylinders used as magnetic shields. We investigate, both numerically and experimentally, the magnetic properties of a ... [more ▼]

This paper deals with the magnetic properties of bulk high temperature superconducting cylinders used as magnetic shields. We investigate, both numerically and experimentally, the magnetic properties of a hollow cylinder with two axial slits which cut the cylinder in equal halves. Finite element method modelling has been used with a three-dimensional geometry to help us in understanding how the superconducting currents flow in such a cut cylinder and therefore how the magnetic shielding properties are affected, depending on the magnetic field orientation. Modelling results show that the slits block the shielding current flow and act as an entrance channel for the magnetic flux lines. The contribution of the slits to the total flux density that enters the cylinder is studied through the angle formed between the applied field and the internal field. The modelled data agree nicely with magnetic shielding properties measured on a bulk Bi-2212 hollow cylinder at 77K. The results demonstrate that the magnetic flux penetration in such a geometry can be modelled successfully using only two parameters of the superconductor (constant J c and n value), which were determined from magnetic measurements on the plain cylinder. © 2012 IOP Publishing Ltd. [less ▲]

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See detailMagnetocaloric and transport study of poly- and nanocrystalline composite manganites La0.7Ca0.3MnO3/La0.8Sr0.2MnO3
Pekala, M; Pekala, K; Drozd, V et al

in Journal of Applied Physics (2012), 112

Magnetocaloric and transport properties are reported for novel poly- and nanocrystalline double composite manganites, La0.8Sr0.2MnO3/La0.7Ca0.3MnO3, prepared by the sol-gel method. Magnetic field ... [more ▼]

Magnetocaloric and transport properties are reported for novel poly- and nanocrystalline double composite manganites, La0.8Sr0.2MnO3/La0.7Ca0.3MnO3, prepared by the sol-gel method. Magnetic field dependence of magnetic entropy change is found to be stronger for the nano- than the polycrystalline composite. The remarkable broadening of the temperature interval, where the magnetocaloric effect occurs in poly- and nanocrystalline composites, causes the relative cooling power (RCP(S)) of the nanocrystalline composite to be reduced by only 10% compared to the Sr based polycrystalline phase. The RCP(S) of the polycrystalline composite becomes remarkably enhanced. The low temperature magnetoresistance is enhanced by 5% for the nanostructured composite. © 2012 American Institute of Physics [less ▲]

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See detailMagnetic Shielding with Bulk High Temperature Superconductors: Factors Influencing the Magnetic Field Penetration in Hollow Cylinders
Fagnard, Jean-François ULg; Vanderheyden, Benoît ULg; Vanderbemden, Philippe ULg

in Muralidhar, Miryala (Ed.) Superconductivity: Recent Developments and New Production Technologies (2012)

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See detailLa0.7Ca0.3MnO3 / Mn3O4 composites: does an insulating secondary phase always enhance the low field magnetoresistance of manganites?
Bhame, Shekhar ULg; Fagnard, Jean-François ULg; Pekala, Marek et al

in Journal of Applied Physics (2012), 111

Composites of magnetoresistive La0.7Ca0.3MnO3 (LCMO) with insulating Mn3O4 are useful as a model system because no foreign cation is introduced in the LCMO phase by interdiffusion during the heat ... [more ▼]

Composites of magnetoresistive La0.7Ca0.3MnO3 (LCMO) with insulating Mn3O4 are useful as a model system because no foreign cation is introduced in the LCMO phase by interdiffusion during the heat treatment. Here we report the magnetotransport properties as a function of sintering temperature Tsinter for a fixed LCMO/Mn3O4 ratio. Decreasing Tsinter from 1250°C to 800°C causes an increase in low field magnetoresistance (LFMR) that correlates with the decrease in crystallite size (CS) of the LCMO phase. When plotting LFMR at (77 K, 0.5 T) vs. 1/CS, we find that the data for the LCMO/Mn3O4 composites sintered between 800°C and 1250°C follow the same trend line as data from the literature for pure LCMO samples with crystallite size > ~25 nm. This differs from the LFMR enhancement observed by many authors in the "usual" manganite composites, i.e., composites where the insulating phase contains cations other than La, Ca or Mn. This difference suggests that diffusion of foreign cations into the grain boundary region is a necessary ingredient for the enhanced LFMR. [less ▲]

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See detailStudy of Conduction Mechanisms in Antistatic Felts at the Mesoscopic Scale
Boutaayamou, Mohamed ULg; Léonard, Angélique ULg; Vanderheyden, Benoît ULg et al

in International Symposium on New Frontiers in Fiber Materials Science; Conference Proceedings (2011, October 11)

This work is part of a project that deals with the optimization of the quantity and the nature of conductive fibers in antistatic felts used for filtering and sieving powders. Our research concerns the ... [more ▼]

This work is part of a project that deals with the optimization of the quantity and the nature of conductive fibers in antistatic felts used for filtering and sieving powders. Our research concerns the electrical properties at the mesoscopic scale. It aims at determining the conduction mechanisms and the distribution of the electric potential at the scale of the distance between the conductive fibers. In this paper, current-voltage (I-V) measurement results are presented and discussed. X-ray microtomography is used to obtain the geometry of the conductive fibers inside the felts before and after these I-V tests. The studied textile material is based on polyester fibers and stainless steel conductive fibers. [less ▲]

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See detailSpray drying: An alternative synthesis method for polycationic oxide compounds
Rivas-Murias, B.; Fagnard, Jean-François ULg; Vanderbemden, Philippe ULg et al

in Journal Of Physics And Chemistry Of Solids (2011), 72(3), 158-163

Synthesis of polycationic compounds by the spray-drying technique is an interesting alternative in the domain of aqueous precursor synthesis methods. Spray drying yields high quality samples with good ... [more ▼]

Synthesis of polycationic compounds by the spray-drying technique is an interesting alternative in the domain of aqueous precursor synthesis methods. Spray drying yields high quality samples with good reproducibility. The possibility of scaling up for production of large quantities with fast processing time is well established by the commercial availability of powders of various compositions. In this paper, we have discussed the advantages and limitations of this method and demonstrated its interest by synthesizing a few polycationic compounds selected for their attractive properties of thermoelectricity [Bi1.68Ca2Co1.69O8, La(0.95)A(0.05)CoO(3) (A = Ca, Sr, Ba)] or magnetoresistance [La(0.70)A(0.30)MnO(3) (A=Sr, Ba)]. We have confirmed the quality of these samples by reporting their structure, magnetic and transport properties. (C) 2010 Elsevier Ltd. All rights reserved. [less ▲]

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See detailCzochralski crystal growth, thermal conductivity, and magnetic properties of Pr(x)La(1- x)AlO3, where x = 1, 0.75, 0.55, 0.40, 0
Turczynski, S.; Orlinski, K.; Pawlak, D. A. et al

in Crystal Growth & Design (2011), 11(4), 1091-1097

Crystals of Pr(x)La(1-x)AlO3 solid solution have been grown by the Czochralski method for the first time, to the best of our knowledge. Crystals with high praseodymium concentration tend to grow spirally ... [more ▼]

Crystals of Pr(x)La(1-x)AlO3 solid solution have been grown by the Czochralski method for the first time, to the best of our knowledge. Crystals with high praseodymium concentration tend to grow spirally. The color of the crystals changes with chemical composition. X-ray diffraction shows an increase of the lattice constants with an increase in lanthanum ion concentration. The thermal conductivity has been investigated in the temperature range from 5 to 300 K. Completely different behavior of thermal conductivity is observed at low temperatures for the investigated crystals, whereas it remains roughly constant at high temperatures. The values of magnetic susceptibility lie within the expected range that could be expected for a paramagnetic material. (Figure Presented) © 2011 American Chemical Society. [less ▲]

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See detailAC Magnetic Measurements on Superconductors: Design of a Device for Magneto-Thermal Measurements
Laurent, Philippe ULg; Fagnard, Jean-François ULg; Vanderbemden, Philippe ULg

in International Journal of Measurement Technologies and Instrumentation Engineering (2011), 1

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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 detailMagnetic properties of drilled bulk high-temperature superconductors filled with a ferromagnetic powder
Lousberg, Grégory; Fagnard, Jean-François ULg; Chaud, Xavier et al

in Superconductor Science and Technology (2011), 24

It is shown that filling the holes of a drilled bulk high-temperature superconductor (HTS) with a soft ferromagnetic powder enhances its trapping properties. The magnetic properties of the trapped field ... [more ▼]

It is shown that filling the holes of a drilled bulk high-temperature superconductor (HTS) with a soft ferromagnetic powder enhances its trapping properties. The magnetic properties of the trapped field magnet are characterized by Hall probe mapping and magnetization measurements. This analysis is completed by a numerical model based on a 3D finite-element method where the conductivity of the superconducting material is described by a power law while the permeability of the ferromagnetic material is fixed to a given value and is considered uniform. Numerical results support the experimental observations. In particular, they confirm the increase of trapped flux that is observed with Hall probe mapping after impregnation. [less ▲]

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See detailBulk melt-processed (RE)BCO superconductors subjected to AC fields in “parallel” and “crossed” direction, experiment and modelling
Vanderbemden, Philippe ULg; Fagnard, Jean-François ULg; Babu, N. H. et al

Conference (2010, November)

When bulk melt-processed (RE)BCO samples are used as permanent magnets in various engineering applications (e.g. rotating machines, magnetic bearings), they may experience transient or periodic variations ... [more ▼]

When bulk melt-processed (RE)BCO samples are used as permanent magnets in various engineering applications (e.g. rotating machines, magnetic bearings), they may experience transient or periodic variations of the applied magnetic field. In such a situation, the remnant magnetization of the sample is found to decrease in running operation, which is particularly inconvenient for the long-term reliability of the system. There are several possible causes for such a phenomenon. The first is the temperature increase resulting from the losses caused by the variable applied field, and may arise when the field is parallel to the main direction of the trapped flux. The second is caused by the component of the magnetic field perpendicular to the main direction of the trapped flux (“crossed field” configuration). In the present talk we review the relevant parameters which have a detrimental impact on the remnant magnetization in both cases. Modelling results are compared to experimental data obtained on bulk YBCO samples subjected to field oscillations of large amplitude. [less ▲]

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See detailClosing address for the session "Bullks and Characterization"
Vanderbemden, Philippe ULg

Conference (2010, November)

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See detailNumerical Study of the Shielding properties of Macroscopic Hybrid Ferromagnetic/Superconductor Hollow Cylinders
Lousberg, Grégory ULg; Fagnard, Jean-François ULg; Ausloos, Marcel ULg et al

in IEEE Transactions on Applied Superconductivity (2010), 20(1), 33

We study the magnetic shielding properties of hybrid ferromagnetic/superconductor (F/S) structures consisting of two coaxial cylinders, with one of each material.We use an axisymmetric finite-element ... [more ▼]

We study the magnetic shielding properties of hybrid ferromagnetic/superconductor (F/S) structures consisting of two coaxial cylinders, with one of each material.We use an axisymmetric finite-element model in which the electrical properties of the superconducting tube are modeled by a nonlinear E-J power law with a magnetic-field-dependent critical current density whereas the magnetic properties of the ferromagnetic material take saturation into account. We study and compare the penetration of a uniform axial magnetic field in two cases: 1) a ferromagnetic tube placed inside a larger superconducting tube (Ferro-In configuration) and 2) a ferromagnetic tube placed outside the superconducting one (Ferro-Out configuration). In both cases, we assess how the ferromagnetic tube improves the shielding properties of the sole superconducting tube. The influence of the geometrical parameters of the ferromagnetic tube is also studied: It is shown that, upon an optimal choice of the geometrical parameters, the range of magnetic fields that are efficiently shielded by the hightemperature superconductor tube alone can be increased by a factor of up to 7 (2) in a Ferro-Out (Ferro-In) configuration. The optimal configuration uses a 1020 carbon steel with a thickness of 2 mm and a height that is half that of the superconducting cylinder (80 mm). [less ▲]

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See detailMeasurement of dielectric properties at low temperatures: application to the study of magnetoresistive manganite/ insulating oxide bulk composites
Vanderbemden, Philippe ULg; Rivas-Murias, Beatriz; Lovchinov, Vassil et al

in Journal of Physics: Conference Series (2010), 253

In this paper, we report low temperature dielectric measurements of bulk composite electroceramic samples containing a colossal magnetoresistive (CMR) manganite phase (La0.7Ca0.3MnO3 [abbreviated LCMO ... [more ▼]

In this paper, we report low temperature dielectric measurements of bulk composite electroceramic samples containing a colossal magnetoresistive (CMR) manganite phase (La0.7Ca0.3MnO3 [abbreviated LCMO]) and an insulating phase (Mn3O4). Details of the experimental system are given and possible experimental artefacts due to moisture are outlined. For a LCMO volume fraction of ~ 16%, the permittivity of the LCMO/ Mn3O4 composite at T = 50 K is found to be much higher than that of pure Mn3O4 and magnetic field dependent. This effect is related to an extrinsic space charge polarization mechanism between the insulating phase (Mn3O4) and the conducting magnetoresistive phase (LCMO). [less ▲]

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See detailModification of the trapped field in bulk HTS as a result of the drilling of a pattern of artificial holes
Lousberg, G. P.; Fagnard, Jean-François ULg; Ausloos, Marcel ULg et al

in Journal of Physics: Conference Series (2010), 234

The trapped magnetic field is examined in bulk high-temperature superconductors that are artificially drilled along their c-axis. The influence of the hole pattern on the magnetization is studied and ... [more ▼]

The trapped magnetic field is examined in bulk high-temperature superconductors that are artificially drilled along their c-axis. The influence of the hole pattern on the magnetization is studied and compared by means of numerical models and Hall probe mapping techniques. To this aim, we consider two bulk YBCO samples with a rectangular cross-section that are drilled each by six holes arranged either on a rectangular lattice (sample I) or on a centered rectangular lattice (sample II). For the numerical analysis, three different models are considered for calculating the trapped flux: (i), a two-dimensional (2D) Bean model neglecting demagnetizing effects and flux creep, (ii), a 2D finite-element model neglecting demagnetizing effects but incorporating magnetic relaxation in the form of an E – J power law, and, (iii), a 3D finite element analysis that takes into account both the finite height of the sample and flux creep effects. For the experimental analysis, the trapped magnetic flux density is measured above the sample surface by Hall probe mapping performed before and after the drilling process. The maximum trapped flux density in the drilled samples is found to be smaller than that in the plain samples. The smallest magnetization drop is found for sample II, with the centered rectangular lattice. This result is confirmed by the numerical models. In each sample, the relative drops that are calculated independently with the three different models are in good agreement. As observed experimentally, the magnetization drop calculated in the sample II is the smallest one and its relative value is comparable to the measured one. By contrast, the measured magnetization drop in sample (1) is much larger than that predicted by the simulations, most likely because of a change of the microstructure during the drilling process. [less ▲]

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See detailUse of second generation coated conductors for efficient shielding of DC magnetic fields
Fagnard, Jean-Francois ULg; Dirickx, Michel; Levin, G. A. et al

in Journal of Applied Physics (2010), 108

This paper reports the results of an experimental investigation of the performance of two types of magnetic screens assembled from YBa2Cu3O7-d (YBCO) coated conductors. Since effective screening of the ... [more ▼]

This paper reports the results of an experimental investigation of the performance of two types of magnetic screens assembled from YBa2Cu3O7-d (YBCO) coated conductors. Since effective screening of the axial DC magnetic field requires the unimpeded flow of an azimuthal persistent current, we demonstrate a configuration of a screening shell made out of standard YBCO coated conductor capable to accomplish that. The screen allows the persistent current to flow in the predominantly azimuthal direction at a temperature of 77 K. The persistent screen, incorporating a single layer of superconducting film, can attenuate an external magnetic field of up to 5 mT by more than an order of magnitude. For comparison purposes, another type of screen which incorporates low critical temperature quasi-persistent joints was also built. The shielding technique we describe here appears to be especially promising for the realization of large scale high-Tc superconducting screens. [less ▲]

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See detailMagnetocaloric effect in La0.75Sr0.25MnO3 manganite
Pekala, M.; Pekala, K.; Drozd, V. et al

in Journal of Magnetism & Magnetic Materials (2010), 322(21), 3460-3463

The polycrystalline manganite La0.75Sr0.25MnO3 prepared by an alternative carbonate precipitation route reveals the rhombohedral perovskite structure. Magnetization isotherms measured up to 2 T are used ... [more ▼]

The polycrystalline manganite La0.75Sr0.25MnO3 prepared by an alternative carbonate precipitation route reveals the rhombohedral perovskite structure. Magnetization isotherms measured up to 2 T are used to determine Curie temperature of 332 K by means of Arrott plot. Maximum of magnetic entropy change is found at Curie temperature. The relative cooling power equal to 64 J/kg for 1.5 T magnetic field, is superior as compared to the manganite with the same chemical composition from the sol–gel method. [less ▲]

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See detailShielding efficiency and E(J) characteristics measured on large melt cast Bi-2212 hollow cylinders in axial magnetic fields
Fagnard, Jean-François ULg; Elschner, Steffen; Bock, Joachim et al

in Superconductor Science and Technology (2010), 23

We show that tubes of melt cast Bi-2212 used as current leads for LTS magnets can also act as efficient magnetic shields. The magnetic screening properties under an axial DC magnetic field are ... [more ▼]

We show that tubes of melt cast Bi-2212 used as current leads for LTS magnets can also act as efficient magnetic shields. The magnetic screening properties under an axial DC magnetic field are characterized at several temperatures below the liquid nitrogen temperature (77 K). Two main shielding properties are studied and compared with those of Bi-2223, a material that has been considered in the past for bulk magnetic shields. The first property is related to the maximum magnetic flux density that can be screened, Blim; it is defined as the applied magnetic flux density below which the field attenuation measured at the centre of the shield exceeds 1000. For a cylinder of Bi-2212 with a wall thickness of 5 mm and a large ratio of length over radius, Blim is evaluated to 1 T at T = 10 K. This value largely exceeds the Blim value measured at the same temperature on similar tubes of Bi-2223. The second shielding property that is characterized is the dependence of Blim with respect to variations of the sweep rate of the applied field, dBapp/dt. This dependence is interpreted in terms of the power law E = Ec(J/Jc)^n and allows us to determine the exponent n of this E(J) characteristics for Bi-2212. The characterization of the magnetic field relaxation involves very small values of the electric field. This gives us the opportunity to experimentally determine the E(J) law in an unexplored region of small electric fields. Combining these results with transport and AC shielding measurements, we construct a piecewise E(J) law that spans over 8 orders of magnitude of the electric field. [less ▲]

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