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Repository of the University of Hasselt containing publications in the fields of statistics, computer science, information strategies and material from the Institute for behavioural sciences.

Research Institutes - Institute for Materials Research (IMO)

Mostrando recursos 1 - 20 de 1.372

  1. Biodesulphurized low rank coal: Maritza east lignite and its "humus-like" byproduct

    Gonsalvesh, L.; Marinov, S. P.; Stefanova, M.; Carleer, R.; Yperman, J.
    Bulgarian coal sample from "Maritza East'' lignite deposit, with a significant impact in the total energy supply for the country, is biodesulphurized on laboratory scale. In order to improve the desulphurization effect, sample under study is preliminary chemically treated, i.e. demineralized, depyritized and oxidized. For microbial treatment the microorganism Pseudomonas putida is applied. Maximum total (71.0%), pyritic (90.6%) and organic (49.4%) sulphur desulphurization effects are achieved as a result of combined action of chemical and microbial attacks. The protocol of Maritsa East lignite biotreatment by P. putida bacterial strain persisted on copious washing of the coal. During it, a high...

  2. Current-induced nanogap formation and graphitization in boron-doped diamond films

    Seshan, V.; Arroyo, C.R.; Castellanos-Gomez, A.; Prins, F.; Perrin, M. L.; Janssens, S. D.; HAENEN, Ken; NESLADEK, Milos; Sudhoelter, E. J. R.; de Smet, L. C. P. M.; van der Zant, H. S. J.; Dulic, D.
    A high-current annealing technique is used to fabricate nanogaps and hybrid diamond/graphite structures in boron-doped nanocrystalline diamond films. Nanometer-sized gaps down to similar to 1 nm are produced using a feedback-controlled current annealing procedure. The nanogaps are characterized using scanning electron microscopy and electronic transport measurements. The structural changes produced by the elevated temperature, achieved by Joule heating during current annealing, are characterized using Raman spectroscopy. The formation of hybridized diamond/graphite structure is observed at the point of maximum heat accumulation. (C) 2012 American Institute of Physics. []

  3. Solution derived ZnO:Al films with low resistivity

    SCHELLENS, Kevin; Capon, B.; DE DOBBELAERE, Christopher; Detavernier, C.; HARDY, An; VAN BAEL, Marlies
    ZnO:Al thin films were prepared via chemical solution deposition, using 2-butoxyethanol as an alternative for 2-methoxyethanol, which is more commonly used, but acutely toxic. The precursor solutions can be readily spin coated. The phase, morphology, electrical and optical properties of the deposited films are investigated, by XRD (X-ray diffraction), scanning electron microscopy, a two-point contact measurement and UV-vis spectrophotometry respectively. This way, the effect of this solvent is investigated. The films are deposited on borosilicate glass substrates and were found to be continuous and smooth. XRD measurements show a highly preferential c-axis orientation. The effects of the thermal treatment profile...

  4. Mesoscopic modelling of masonry using weak and strong discontinuities

    Vandoren, Bram; De Proft, Kurt; Simone, Angelo; Sluys, Lambertus Johannes
    A mesocopic masonry model is presented in which joints are modelled by weak and strong discontinuities through the partition of unity property of finite element shape functions. A Drucker-Prager damage model describes joint degradation whereas the bricks remain linear elastic throughout the simulations. Analogies and differences amongst strong and weak discontinuity models are discussed, with special emphasis on kinematic description and implementation. Mesh sensitivity and performance of the presented models are illustrated by two-brick, three-point bending and shear wall tests.

  5. Solvent-Dependent Deprotonation of meso-Pyrimidinylcorroles: Absorption and Fluorescence Studies

    Kruk, Mikalai; Ngo, Thien H.; Savva, Vadim; Starukhin, Aleksander; Dehaen, Wim; MAES, Wouter
    The absorption spectra of 10-(4,6-dichloropyrimidin-5-yl)-5,15-dimesitylcorrole have been studied in 15 solvents. The formation of deprotonated corrole species was found to account for the dramatic changes in the absorption spectra in several solvents. Careful analysis of the relationship between the formation of deprotonated species and solvent properties results in the conclusion that there is no single solvent parameter correlation, and either multiparameter correlations or specific solute-solvent interactions (preferential solvation of the most acidic NH tautomer or perturbation of intramolecular hydrogen bonding in the macrocycle core) should be considered. The fluorescence properties of the deprotonated pyrimidinylcorrole are also reported for the first...

  6. Selective Desulfurization of Model Diesel Fuel by Carbon Nanoparticles as Adsorbent

    NAVIRI FALLAH, Rahimeh; Azizian, Saeid; REGGERS, Guy; SCHREURS, Sonja; CARLEER, Robert; YPERMAN, Jan
    This work examines the effect of aromatic compounds (naphthalene and 1-methylnaphthalene) on the adsorption of sulfur thiophenic compounds (including benzothiophene, dibenzothiophene, and dimethyldibenzothiophene) from simulated diesel fuel by dispersed carbon nanoparticles (CNPs) in aqueous solution. To evaluate the equilibrium and kinetics of adsorptive desulfurization by synthesized CNPs, two model diesel fuels with 300 ppmw total concentration of sulfur compounds were used in a batch reactor at ambient conditions. The solid CNPs were characterized using FTIR, thermal analysis, elemental analysis, TEM, and surface pH. The equilibrium experimental data were fitted to Langmuir, Freundlich, and Langmuir-Freundlich models to estimate the adsorption parameters....

  7. Corrole NH Tautomers: Spectral Features and Individual Protonation

    Ivanova, Yulia B.; Savva, Vadim A.; Mamardashvili, Nugzar Z.; Starukhin, Aleksander S.; Ngo, Thien H.; Dehaen, Wim; MAES, Wouter; Kruk, Mikalai M.
    Protonation of a free-base meso-pyrimidinyl-substituted AB(2)-corrole (H(3)AB(2)) in ethanol solution by stepwise addition of sulfuric acid has been studied in the temperature range from 293 to 333 K. The formation rate of protonated species was found to depend profoundly on the temperature at which the titration was undertaken. Two steps in the titration curve were identified at temperatures around 293-298 K, whereas one-step formation of protonated species was found to occur at temperatures above 308 K. The protonation product was the same in both cases, i.e., H(4)AB(2)(+) corrole, protonated at the macrocycle core nitrogen atoms. The two steps in the...

  8. Unraveling the Fluorescence Features of Individual Corrole NH Tautomers

    Kruk, Mikalai; Ngo, Thien H.; VERSTAPPEN, Pieter; Starukhin, Aleksander; Hofkens, Johan; Dehaen, Wim; MAES, Wouter
    The fluorescence spectra of 10-(4,6-dichloropyrimidin-5-yl)-5,15-dimesitylcorrole have been studied in the temperature range from 4.2 to 332 K. For the first time, the individual fluorescence profiles of the two corrole NH tautomers have been assigned over the whole temperature range. The pronounced temperature dependence of the fluorescence spectra of the meso-pyrimidinylcorrole under study was found to originate from switching between the fluorescence emissions of the two tautomers due to a reduced NH tautomerization rate with decreasing temperature. As a result, the long wavelength tautomer dominates the total emission spectrum at room temperature, whereas at low temperatures, the majority of the emission...

  9. Mesoscopic modelling of masonry using weak discontinuities: the choice of the enrichment functions

    Vandoren, Bram
    This report gives an overview of the two different approaches used in the developed mesoscopic masonry models. Implementation aspects are discussed and comparative results are given. This document also addresses the potential implementation errors of the previous masonry model.

  10. Mesoscopic modelling of masonry using GFEM: a comparison of strong and weak discontinuity models

    Vandoren, Bram; De Proft, Kurt
    Masonry structures are characterised by their low material cost and relatively simple way of constructing. The computational modelling of these structures remains, however, a great challenge. Two major modelling groups exist: macroscale and mesoscale models. The former approach homogenises the masonry constituents, i.e. the bricks and joints, to one orthotropic material whereas the latter approach models the constituents as separate entities. In this contribution, two mesoscopic masonry models are presented and compared: a model in which the joints are represented as strong discontinuities and a model in which weak discontinuities are used to model the joints. The bricks remain linear elastic...

  11. Mesoscopic modelling of masonry using embedded weak discontinuities based on partitions of unity

    Vandoren, Bram; De Proft, Kurt
    The modelling of masonry has been a popular topic within computational mechanics for some years now. Two major groups of modelling approaches exist: macroscopic and mesoscopic models. The macroscopic approach homogenises the mortar joints and bricks creating one orthotropic material, whereas the mesoscopic approach models the joints and bricks as separate entities. In this contribution a two dimensional mesoscopic model will be developed, where mortar joints are modelled by embedded discontinuities using the partition of unity property of the finite element shape functions. Unlike classical mesoscopic models, where joints are modelled using strong discontinuities (i.e. jumps in the displacement field),...

  12. Charge transfer in the weak driving force limit in blends of MDMO-PPV and dithienylthiazolo[5,4-d]thiazoles towards organic photovoltaics with high V-OC

    Nevil, Nissy; Ling, Yun; Van Mierloo, Sarah; Kesters, Jurgen; Piersimoni, Fortunato; Adriaensens, Peter; Lutsen, Laurence; Vanderzande, Dirk; Manca, Jean; Maes, Wouter; Van Doorslaer, Sabine; Goovaerts, Etienne
    A series of three 5'-aryl-2,5-dithienylthiazolo[5,4-d]thiazole (DTTzTz) semiconducting molecules with different aryl substituents has been investigated as alternative acceptor materials in combination with the donor polymer poly[2-methoxy-5-(3',7'-dimethyloctyloxy)-1,4-phenylene vinylene] (MDMO-PPV) in order to evaluate the photoinduced charge transfer (CT) efficiency in the resulting blends, designed towards possible application in organic photovoltaics. Photoluminescence quenching together with polaron detection by electron paramagnetic resonance and photoinduced absorption (PIA) demonstrate an increasing charge transfer efficiency when the DTTzTz substituents are varied from thien-2-yl to 4-trifluoromethylphenyl and 4-cyanophenyl groups, correlating well with the increasing acceptor strength in this series of molecules. In line with this observation, there...

  13. Mesoscopic modelling of masonry using weak discontinuities in the partition of unity framework

    Vandoren, Bram; Heyens, Koen; De Proft, Kurt
    Modelling of masonry has been a popular topic within computational mechanics for some years now. Three major groups of modelling approaches exist: macroscopic, mesoscopic and microscopic. In this contribution a two dimensional mesoscopic model will be developed, in which mortar joints are modelled by embedded discontinuities using the partition of unity property of the finite element shape functions. Unlike classical mesoscopic models, where joints are modelled using strong discontinuities (i.e. jumps in the displacement field), the model developed in this PhD research uses weak discontinuities. A weak discontinuity introduces a jump in the strain field, allowing for failure to localise...

  14. Time-dependent mesoscopic modelling of masonry using embedded weak discontinuities

    Vandoren, Bram; Heyens, Koen; De Proft, Kurt
    The modelling of masonry has been a popular topic within computational mechanics for some years now. Two major groups of modelling approaches exist: macroscopic and mesoscopic models. In this contribution a two dimensional mesoscopic model (i.e. joints and bricks are modelled as separate entities) will be developed that incorporates time-dependent behaviour. Since in masonry structures the cracks often follow the joints, the potential crack paths are known in advance. Unlike classical mesoscopic models, where joints are modelled using strong discontinuities (i.e. jumps in the displacement field), the model developed in this paper uses embedded weak discontinuities. A weak discontinuity introduces...

  15. Thickness dependent residual stress in sputtered AlN thin films

    Pobedinskas, Paulius; Bolsee, Jean-Christophe; Dexters, Wim; Ruttens, Bart; Mortet, Vincent; D'Haen, Jan; Manca, Jean V.; Haenen, Ken
    Thin aluminium nitride (AIN) films of different thickness are deposited by DC-pulsed magnetron sputtering under identical conditions on sapphire (0001) and silicon (100) substrates. An investigation of the residual stress, morphology and structural properties is carried out. The thickness of the films covers the range from 17 nm to 3.9 μm. A higher compressive residual stress is measured for the thinner films and the presence of a stress gradient is proven. X-ray diffraction (XRD) studies show that all AIN films are achieved with perfect c-axis orientation perpendicular to the film surface and that the films are biaxially strained. XRD rocking...

  16. No additional reduction of mortality or heart failure events with intrathoracic impedance measurements in a context of telemonitoring with structural biofeedback

    GRIETEN, Lars; VERBRUGGE, Frederik; STORMS, Valerie; Verhaert, D.; Rivero-Ayerza, M.; De Vusser, P.; Van Herendael, H.; Vercammen, J.; Jacobs, L.; Rondelez, K.; MULLENS, Wilfried; VANDERVOORT, Pieter
    Our aim was to test if intra-thoracic impedance (ITI) measurements would improve short-term clinical outcome (i.e. all-cause mortality and heart failure hospitalizations) in patients with cardiac resynchronization therapy (CRT) who were followed in a telemonitoring program with structural biofeedback. Methods: CRT patients (n=200; age= 70 +/-14y) were included in a telemonitoring program at Ziekenhuis Oost-Limburg Genk, which comprised daily transmissions through a wireless system installed at their homes. All patients were followed for potential lead/device problems, episodes of anti-tachycardia pacing, device shocks, occurrence of arrhytmias, a decline in biventricular pacing percentage and/or a sudden drop in physical activity. Patients with...

  17. Single-pulse pulsed laser polymerization-electron paramagnetic resonance investigations into the termination kinetics of n-butyl acrylate macromonomers

    Barth, Johannes; Buback, Michael; Barner-Kowollik, Christopher; Junkers, Thomas; Russell, Gregory T.
    The termination of model mid-chain radicals (MCRs), which mimic radicals that occur in acrylate polymerization over a broad range of reaction conditions, has been studied by single-pulse pulsed laser polymerization (SP-PLP) in conjunction with electron paramagnetic resonance spectroscopy. The model radicals were generated by initiator-fragment addition to acrylic macromonomers that were preformed prior to the kinetic experiments, thus enabling separation of termination from the propagation reaction, for these model radicals propagate sparingly, if at all, on the timescale of SP-PLP experiments. Termination rate coefficients of the MCRs were determined in the temperature range of 060 degrees C in acetonitrile and...

  18. Activated carbon by co-pyrolysis and steam activation from particle board and melamine formaldehyde resin

    Vanreppelen, Kenny; Schreurs, Sonja; Carleer, Robert; Yperman, Jan

  19. Poly(3-alkylthiophene) nanofibers for photovoltaic energy conversion

    Bertho, Sabine; Oosterbaan, Wibren D.; Vrindts, Veerle; Bolsee, Jean-Christophe; Piersimoni, Fortunato; Spoltore, Donato; D'Haen, Jan; Lutsen, Laurence; Vanderzande, Dirk; Manca, Jean V.
    The use of nanostructured non-conventional semiconductors such as conjugated polymers and metal oxides (e.g. TiO2), opens promising perspectives towards a new generation of solar cells based on the concept of donor:acceptor bulk heterojunctions. In this concept donor material and acceptor material form interpenetrating networks allowing light absorption, charge transfer and charge transport throughout the entire bulk of the thin film. Since nanomorphology is of crucial importance for this type of solar cells, in this contribution the use of nanofibers in bulk heterojunction solar cells is explored in order to obtain highways for charge transport. We investigate in particular the use...

  20. Characterization of Modification of 193-nm Photoresist by HBr Plasma

    Vereecke, G.; CLAES, Monica; Le, Q. T.; KESTERS, Els; Struyf, H.; CARLEER, Robert; ADRIAENSENS, Peter
    HBr plasma treatments are used to decrease surface line edge roughness (LER) of patterned photoresist (PR). In this work the modification of two 193-nm photoresists by an HBr plasma treatment was characterized by Fourier Transform Infrared (FTIR) spectroscopy, H-1-NMR (Nuclear Magnetic Resonance) and gel permeation chromatography (GPC). PR modification was shown to follow similar schemes as the degradation of poly(methyl methacrylate) (PMMA) by UV light. Beside the cleavage of ester side-groups, this study showed extensive scission of PR chains, which will contribute to LER reduction by increasing PR chains mobility. However chain scission was accompanied by cross-linking, which may put...

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