References of "Cloots, Rudi"
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See detailNa2FePO4F/multi-walled carbon nanotubes for lithium-ion batteries: Operando Mössbauer study of spray-dried composites
Brisbois, Magali; Caes, Sébastien ULg; Sougrati, M.T. et al

in Solar Energy Materials & Solar Cells (in press)

In order to favor electronic conductivity in sodium iron fluorophosphate electrodes for lithium- or sodium-ion batteries, composites of Na2FePO4F with multi-walled carbon nanotubes (CNTs) were prepared by ... [more ▼]

In order to favor electronic conductivity in sodium iron fluorophosphate electrodes for lithium- or sodium-ion batteries, composites of Na2FePO4F with multi-walled carbon nanotubes (CNTs) were prepared by pilot-scale spray drying. Addition of multi-walled CNTs in the solution results in an excellent dispersion of the CNTs within the volume of Na2FePO4F and not only at the surface of the particles. Following a heat treatment at 600°C in argon in order to reach crystallization, X-ray diffraction and ex situ Mössbauer spectroscopy revealed the presence of significant amounts of Fe(III) and maghemite (γ-Fe2O3) in the powder. However, Na2FePO4F/CNTs composites exhibit good electrochemical performance when cycling against lithium, with a discharge capacity of 104mAhg-1 at C/10 rate and 90mAhg-1 at 1C rate. Therefore, operando 57Fe transmission Mössbauer spectroscopy analyses were carried out in order to investigate the evolution of the iron oxidation state during cycling. During the first discharge, all the Fe(III) is reduced to Fe(II), explaining the good electrochemical performance. [less ▲]

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See detailSurfactant-assisted ultrasonic spray pyrolysis of hematite mesoporous thin films
Henrist, Catherine ULg; Toussaint, Caroline ULg; De Vroede, Jordan et al

in Microporous and Mesoporous Materials (2016), 221

Mesoporous crystalline hematite is a material difficult to prepare by soft-templating with conventional techniques, because of its high crystallization temperature associated to the crystal-to-crystal ... [more ▼]

Mesoporous crystalline hematite is a material difficult to prepare by soft-templating with conventional techniques, because of its high crystallization temperature associated to the crystal-to-crystal goethiteto-hematite phase transition. In a previous work, it has been reported that with very careful calcination steps, it is possible to prepare mesoporous hematite films with the spin-coating technique. However, with less conventional techniques such as surfactant-assisted ultrasonic spray pyrolysis, the deposition usually leads to non-porous oxide films or to films with interstitial porosity. In this work, we demonstrate for the first time the proof-of-concept of block-copolymer templating of hematite thin films by the ultrasonic spray pyrolysis technique. Despite the fast thermal decomposition during spray deposition, a regular, monodisperse packing of spherical pores is observed after deposition on pre-heated substrates (250 C) and after a careful post-annealing step at 470 C. Moreover, with the use of a silica scaffold, we successfully preserved porosity up to a temperature as high as 800 C. These films are highly crystalline and they are composed by randomly oriented nanocrystallites with sizes as small as 25 nm. Furthermore, we show that the crystallization evolution with temperature is influenced by the presence of the templating agent and also by the preparation technique. [less ▲]

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See detailInnovative semiconducting oxide materials reducing the energy footprint of buildings
Dewalque, Jennifer ULg; Maho, Anthony ULg; Spronck, Gilles ULg et al

Conference (2015, October 26)

In the current energy context, many efforts are devoted to the reduction of the energy footprint of buildings. To meet this challenge, the LCIS-GREENMAT laboratory developes a front edge research in the ... [more ▼]

In the current energy context, many efforts are devoted to the reduction of the energy footprint of buildings. To meet this challenge, the LCIS-GREENMAT laboratory developes a front edge research in the field of advanced materials associated to energy and environment, including structured materials for dye-sensitized solar cells (DSSCs) and electrochromic coatings. DSSCs have been reported by O’Regan and Grätzel in the early nineties as a very promising alternative to conventional photovoltaic silicon devices. Main benefits of these cells are their low cost as well as their mild manufacturing process. In most of the specific literature, DSSCs are made of TiO2 films prepared by doctor-blade or screen-printing of anatase nanoparticles paste. However, due to the random organization of the nanoparticles, pore accessibility by the dye and electrolyte could be incomplete. Moreover, some anatase crystallites could suffer from a lack of connectivity, leading to electron transfer issues. The strategy adopted by our group to improve photovoltaic efficiencies involves a templating-assisted process to prepare highly porous layers with well-ordered and accessible pores as well as improved crystallites connectivity. This talk especially focuses on the templating-assisted synthesis of TiO2 and ZnO semiconducting layers used as photoelectrode in DSSCs. Due to the surface area improvement as well as the perfect control of the pore organization and the pore size, the templating strategy is an effective solution to maximize the adsorption of active dye and the electrolyte infiltration inside the porous network. Besides, in the last few years, there has been increasing interest in electrochromic glazing due to its potential use as an energy-efficient component for buildings, as it could reduce considerably their CO2 emission by decreasing their energy consumption up to 30%. The crucial issues of such devices are the durability, the coloration efficiency and the reversibility upon coloration and bleaching of the electrochromic layers. In order to improve the performances of those electrochromic films, we have investigated a surfactant-assisted deposition process for WO3 layer and the insertion of lithium in the NiO layer. All films have been deposited on FTO glass substrates by ultrasonic spray pyrolysis (USP), which is a low-cost alternative to industrial vacuum processes for manufacturing high quality thin films. The presence of lithium ions in nickel oxide films has shown improved coloration efficiency compared to the undoped films. The higher active surface of surfactant-assisted tungsten oxide films has led to higher reversibility and coloration contrast. [less ▲]

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See detailLi4Ti5O12 powders by spray-drying: influence of the solution concentration and particle size on the electrochemical properties
Jamin, Claire; Brisbois, Magali; Caes, Sébastien ULg et al

Conference (2015, June 23)

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See detailRheological behavior of β-Ti and NiTi powders produced by atomization for SLM production of open porous orthopedic implants
Yablokova, G.; Speirs, M.; Van Humbeeck, J. et al

in Powder Technology (2015)

The growing interest for Selective Laser Melting (SLM) in orthopedic implant manufacturing is accompanied by the introduction of novel Ti alloys, in particular β-Ti for their excellent corrosion ... [more ▼]

The growing interest for Selective Laser Melting (SLM) in orthopedic implant manufacturing is accompanied by the introduction of novel Ti alloys, in particular β-Ti for their excellent corrosion resistance as well as favorable combination of high mechanical strength, fatigue resistance and relatively low elastic modulus. As part of the SLM process for producing quality β-Ti parts powder flowability is essential to achieve uniform thickness of powder layers. In this work the flowability of different gas atomized β-Ti, including NiTi, powders has been studied. Their rheological properties were compared to those of commercially available plasma-atomized Ti–6Al–4V powder using a newly developed semi-automatic experimental set-up. Not only the particle size, shape and size distribution of the powders display a large influence on the powder flowability but also particle surface properties such as roughness, chemical composition and the presence of liquid on the surface of the particles. It was found that plasma or gas atomization production techniques for SLM powder have a considerable effect on the particle topography. Among the powders studied regarding SLM applicability only rheological properties of the fine size fraction (25–45 μm) of Ti–45Nb didn't conform to SLM processing requirements. To improve flowability of the Ti–45Nb powder itwas annealed both in air and argon atmosphere at 600 °C during 1 h, resulting in an improved rheological behavior suitable for SLM processing. [less ▲]

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See detailTiO2 templated films used as photoelectrode for solid-state DSSC applications: Study of the solid electrolyte infiltration by Rutherford Backscattering Spectrometry
Dewalque, Jennifer ULg; Colson, Pierre ULg; Mathis, François et al

Poster (2015, May 10)

Liquid-state dye-sensitized solar cells can suffer from electrolyte evaporation and leakage. Therefore solid-state hole transporting materials are investigated as alternative electrolyte materials ... [more ▼]

Liquid-state dye-sensitized solar cells can suffer from electrolyte evaporation and leakage. Therefore solid-state hole transporting materials are investigated as alternative electrolyte materials. However, in solid-state dye-sensitized solar cells, optimal TiO2 films thickness is limited to a few microns allowing the adsorption of only a low quantity of photoactive dye and thus leading to poor light harvesting and low conversion efficiency. In order to overcome this limitation, high surface area templated films are investigated as alternative to nanocrystalline films prepared by doctor-blade or screen-printing. Moreover, templating is expected to improve the pore accessibility what would promote the solid electrolyte penetration inside the porous network, making possible efficient charge transfers. In this study, films prepared from different structuring agents are discussed in terms of microstructural properties (porosity, crystallinity) as well as effect on the dye loading and Spiro-OMeTAD (2,2',7,7'-tetrakis-(N,N-di-p-methoxyphenylamine)9,9'-spirobifluorene) solid electrolyte filling. Different techniques such as transmission electron microscopy (TEM), atmospheric poroellipsometry (AEP) and UV-visible absorption spectroscopy (UV-vis.) have been used to describe the microstructural features of the films. Besides, we have implemented Rutherford backscattering spectrometry (RBS) as an innovative non-destructive tool to characterize the hole transporting materials infiltration. Templated films show dye loading more than two times higher than nanocrystalline films prepared by doctor-blade or screen-printing and solid electrolyte infiltration up to 88%. [less ▲]

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See detailSpray-drying synthesis of Na3V2(PO4)2F3 as cathode material for Li/Na ion batteries
Eshraghi, Nicolas ULg; Caes, Sébastien ULg; Cloots, Rudi ULg et al

Poster (2015, May 08)

In this communication, Na3V2(PO4)2F3 (NVPF) powder with a NASICON-type structure is synthesized for the first time by spray-drying method. The effects of molar ratio of precursors, inlet temperature and ... [more ▼]

In this communication, Na3V2(PO4)2F3 (NVPF) powder with a NASICON-type structure is synthesized for the first time by spray-drying method. The effects of molar ratio of precursors, inlet temperature and heat treatment temperature on the powder purity and particle morphology were investigated. Structural and microstructural characterizations were carried out by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Best electrochemical properties, from specific capacities of 94 mAh .g-1 at C/15 to 80 mAh.g-1 at 1C in li-ion batteries, were obtained for powders dried at 180°C and fired at 600°C. These preliminary results show that spray-drying technique is suitable for obtaining complex powders with a very good homogeneity leading to very good electrochemical properties. [less ▲]

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See detailSurface treatments for electrochromic glazing: toward reduced costs and optimal performances through ultrasonic spray pyrolysis
Maho, Anthony ULg; Denayer, Jessica; Bister, Geoffroy et al

Conference (2015, May)

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See detailDeposition of electrochromic oxide films by surfactant-assisted ultrasonic spray pyrolysis
Maho, Anthony ULg; Denayer, Jessica; Bister, Geoffroy et al

Conference (2015, May)

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See detailUn assemblage épitaxique… d’hématite sur rutile.
Warin; Robert, A; Hatert, Frédéric ULg et al

in Le Règne Minéral (2015), 124

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See detailElucidating the opto-electrical properties of solid and hollow titania scattering layers for improvement of dye-sensitized solar cells
Thalluri, Venkata Visveswara Gopala Kris; Henrist, Catherine ULg; Spronck, Gilles ULg et al

in Thin Solid Films (2015)

The light scattering method has been adapted in dye-sensitized solar cells (DSCs) for optical absorption enhancement. In DSC's, particle-size of TiO2 should be inline with the scattering wavelength range ... [more ▼]

The light scattering method has been adapted in dye-sensitized solar cells (DSCs) for optical absorption enhancement. In DSC's, particle-size of TiO2 should be inline with the scattering wavelength range. Scattering particles can be used either by forming a bilayer structure with TiO2 nanocrystalline film or into the bulk of TiO2 nanocrystalline film. For improving the DSCs performances these scattering layers aim to refract/reflect the incident light by extending the traveling distance of UV-Visible/near-IR light within the dye-sensitized TiO2 nanocrystalline film. In this work, the scattering layers with two different particle-sizes (~200 nm-solid and ~400 nm-hollow) were deposited as an additional layer on the top of dye-sensitized TiO2 nanocrystalline film and the morphological properties were studied. By using various opto-electrical characterization techniques, the influence of these scattering layers for two different classes of DSCs prepared from N3 (UV-Vis) and SQ2 (near-IR) dyes were investigated. [less ▲]

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See detailComparison of structural features of spin-coated and USP-deposited templated α-Fe2O3films
Toussaint, Caroline ULg; Chatzikyriakou, Daphne; Cloots, Rudi ULg et al

Poster (2015)

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See detailAtmospheric Pressure Plasma as an Activation Step for Improving Protein Adsorption on Hydroxyapatite Powder
Ozhukil Kollath, Vinayaraj ULg; Put, Sofie; Mullens, Steven et al

in Plasma Processes and Polymers (2015)

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See detailCombining mesoporosity and Ti-doping in hematite films for water splitting
Toussaint, Caroline ULg; Tran, Hoang Son ULg; Colson, Pierre ULg et al

in Journal of Physical Chemistry C (2015), 119(4), 1642-1650

(Graph Presented). In this study, we report the synthesis of Ti-doped mesoporous hematite films by soft-templating for application as photoanodes in the photoelectrolysis of water (water splitting ... [more ▼]

(Graph Presented). In this study, we report the synthesis of Ti-doped mesoporous hematite films by soft-templating for application as photoanodes in the photoelectrolysis of water (water splitting). Because the activation of the dopant requires a heat treatment at high temperature (≥800°C), it usually results in the collapse of the mesostructure. We have overcome this obstacle by using a temporary SiO2 scaffold to hinder crystallite growth and thereby maintain the mesoporosity. The beneficial effect of the activated dopant has been confirmed by comparing the photocurrent of doped and undoped films treated at different temperatures. The role of the mesostructure was investigated by comparing dense, collapsed, and mesoporous films heated at different temperatures and characterized under front and back illumination. It turns out that the preservation of the mesotructure enables a better penetration of the electrolyte into the film and therefore reduces the distance that the photogenerated holes have to travel to reach the electrolyte. As a result, we found that mesoporous films with dopant activation at 850°C perform better than comparable dense and collapsed films. [less ▲]

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See detailMagnetic shielding performances of YBa2Cu3O7−δ -coated silver tubes obtained by electrophoretic deposition
Devendra Kumar, N; Closset, Raphaël ULg; Wera, Laurent ULg et al

in Superconductor Science and Technology (2015), 28

We report a complete procedure to achieve multilayer YBCO thick films by electrophoretic deposition on silver tubes using a suspension of YBCO powder in butanol. With the aim to optimize the magnetic ... [more ▼]

We report a complete procedure to achieve multilayer YBCO thick films by electrophoretic deposition on silver tubes using a suspension of YBCO powder in butanol. With the aim to optimize the magnetic shielding performances of the coatings, we have carried out an extensive investigation of the influence of the deposition parameters, the multilayer deposition sequence and the intermediate/final heat treatments on the coating microstructure. Using the optimized conditions, a 24-layer YBCO coating has been successfully prepared on an 80 mm long Ag tube: the melt growth processed multilayered YBCO thick film thus obtained can shield an applied magnetic field of 1.9 mT at 77 K, the highest value per thickness unit reported so far in the literature for these materials. [less ▲]

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See detailElectrografting of polythiophenes on zinc oxide nanorods for photovoltaic cells
Demarteau, Jérémy ULg; Ouhib, Farid ULg; Henrist, Catherine ULg et al

Poster (2014, May 20)

As the rarefaction of fossil energies, photovoltaic cells are certainly amongst the most important energy sources for the future. Our work concentrated on hybrid photovoltaic cells that are based on ... [more ▼]

As the rarefaction of fossil energies, photovoltaic cells are certainly amongst the most important energy sources for the future. Our work concentrated on hybrid photovoltaic cells that are based on organic (polythiophene) and inorganic components (ZnO nanorods). The technology that maximizes the contact area between the two semi-conductor n and p while maintaining two separate components is the interdigital configuration. As the inorganic part, perfectly well aligned zinc oxide (ZnO) 1D nanostructures have been synthesized by hydrothermal growth on ZnO-seeded FTO substrates. SEM, AFM and XRD characterizations evidence patterned well- aligned nanorods with high c-axis, their roughness of surface and the length of their nanostructure. Concerning the organic component, we synthetize polythiophenes based diblock copolymer with high degree of regioregularity and predetermined molecular weight using Grignard Methatis (GRIM) process. Diblock polythiophene based copolymers are of interest because of the possibility of generating multifunctional materials (by associating the specific properties of each block), including their ability for self-assembly into well-defined nanostructures (fibrils or micelles) with controllable dimensions. Poly(3-hexylthiophene) (P3HT) composes the first block and the second block is either a polythiophene bearing an acrylate group on each monomer unit (PAcET), or a polythiophene bearing both acrylate and poly(ethylene glycol) side chains (P(AcET-co-PEGET)). Typically, the acrylates are used to fixe in a covalent way the copolymer to ZnO nanorods, while the PEG grafts are necessary for the solubilisation of the copolymer in the electrografting medium. 1H NMR and DLS characterizations allow us to find the backbone and the micellar structure of the copolymer. Cathodic polarization (electrografting) of ZnO nanorods induces electropolymerization of acrylate groups, leading to an adherent organized film of poly(thiophene)-based micelles. During the illumination tests, we obtained a typical response of a photovoltaic despite the low yields. This promising synthetic route opens exciting perspectives for the production and the electrochemical functionalization of different lengths of ZnO nanowires, which seems to be promising candidate for hybrids photovoltaic cells. [less ▲]

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See detailEffect of the RE (RE = Eu, Er) doping on the structural and textural properties of mesoporous TiO2 thin films obtained by evaporation induced self-assembly method
Borlaf, Mario; Caes, Sébastien ULg; Dewalque, Jennifer ULg et al

in Thin Solid Films (2014), 558

Polymeric sol–gel route has been used for the preparation of TiO2 and RE2O3–TiO2 (RE = Eu, Er) mesoporous thin films by evaporation induced self-assembly method using Si (100) as a substrate. The ... [more ▼]

Polymeric sol–gel route has been used for the preparation of TiO2 and RE2O3–TiO2 (RE = Eu, Er) mesoporous thin films by evaporation induced self-assembly method using Si (100) as a substrate. The influence of the relative humidity (RH) on the preparation of the film has been studied being necessary to work under 40% RH in order to obtain homogeneous and transparent thin films. The films were annealed at different temperatures until 900 °C/1 h and the anatase crystallization and its crystal size evolution were followed by low angle X-ray diffraction. Neither the anatase–rutile transition nor the formation of other compounds was observed in the studied temperature range. Ellipsoporosimetry studies demonstrated that the thickness of the thin films did not change after calcination at 500 °C, the porosity was constant until 700 °C, the pore size increased and the specific surface area decreased with temperature. Moreover, the effect of the doping with Er3 + and Eu3 + was studied and a clear inhibition of the crystal growth and the sintering process was detected (by transmission electron and atomic force microscopy) when the doped films are compared with the undoped ones. Finally, Eu3 + and Er3 + f–f transitions were detected by PL measurements. [less ▲]

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