“Determination of size, morphology, and nitrogen impurity location in treated detonation nanodiamond by transmission electron microscopy”. Turner S, Lebedev OI, Shenderova O, Vlasov II, Verbeeck J, Van Tendeloo G, Advanced functional materials 19, 2116 (2009). http://doi.org/10.1002/adfm.200801872
Abstract: Size, morphology, and nitrogen impurity location, all of which are all thought to be related to the luminescent properties of detonation nanodiamonds, are determined in several detonation nanodiamond samples using a combination of transmission electron microscopy techniques. Results obtained from annealed and cleaned detonation nanodiamond samples are compared to results from conventionally purified detonation nanodiamond. Detailed electron energy loss spectroscopy combined with model-based quantification provides direct evidence for the sp3 like embedding of nitrogen impurities into the diamond cores of all the studied nanodiamond samples. Simultaneously, the structure and morphology of the cleaned detonation nanodiamond particles are studied using high resolution transmission electron microscopy. The results show that the size and morphology of detonation nanodiamonds can be modified by temperature treatment and that by applying a special cleaning procedure after temperature treatment, nanodiamond particles with clean facets almost free from sp2 carbon can be prepared. These clean facets are clear evidence that nanodiamond cores are not necessarily in coexistence with a graphitic shell of non-diamond carbon.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 12.124
Times cited: 100
DOI: 10.1002/adfm.200801872
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“Study on the impregnation of archaeological waterlogged wood with consolidation treatments using synchrotron radiation microtomography”. Bugani S, Modugno F, Lucejko JJ, Giachi G, Cagno S, Cloetens P, Janssens K, Morselli L, Analytical and bioanalytical chemistry 395, 1977 (2009). http://doi.org/10.1007/S00216-009-3101-5
Abstract: In favourable conditions of low temperature and low oxygen concentration, archaeological waterlogged wooden artefacts, such as shipwrecks, can survive with a good state of preservation. Nevertheless, anaerobic bacteria can considerably degrade waterlogged wooden objects with a significant loss in polysaccharidic components. Due to these decay processes, wood porosity and water content increase under ageing. In such conditions, the conservation treatments of archaeological wooden artefacts often involve the replacement of water with substances which fill the cavities and help to prevent collapse and stress during drying. The treatments are very often expensive and technically difficult, and their effectiveness very much depends on the chemical and physical characteristics of the substances used for impregnation. Also important are the degree of cavity-filling, penetration depth and distribution in the structure of the wood. In this study, the distribution in wood cavities of some mixtures based on polyethylene glycols and colophony, used for the conservation of waterlogged archaeological wood, was investigated using synchrotron radiation X-ray computed microtomography (SR-A mu CT). This non-destructive imaging technique was useful for the study of the degraded waterlogged wood and enabled us to visualise the morphology of the wood and the distribution of the materials used in the wood treatments. The study has shown how deposition is strictly related to the dimension of the wooden cavities. The work is currently proceeding with the comparison of synchrotron observations with the data of the solutions viscosity and with those of the properties imparted to the wood by the treatments.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 3.431
Times cited: 30
DOI: 10.1007/S00216-009-3101-5
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“High resolution micro-XRF maps of iron oxides inside sensory dendrites of putative avian magnetoreceptors”. Falkenberg G, Fleissner GE, Fleissner GUE, Schuchardt K, Kühbacher M, Chalmin E, Janssens K, Journal of physics : conference series 186, 012084 (2009). http://doi.org/10.1088/1742-6596/186/1/012084
Abstract: Iron mineral containing sensory dendrites in the inner lining of the upper beak of homing pigeons [1] and various bird species [2] are the first candidate structures for an avian magnetic field receptor. A new concept of magnetoreception [3, 4] is based on detailed ultra-structural optical and electron microscopy analyses in combination with synchrotron radiation microscopic X-ray fluorescence analysis (micro-XRF) and microscopic X-ray absorption near edge structures (micro-XANES). Several behavioral experiments [5, 6] and first mathematical simulations [6] affirm our avian magnetoreceptor model. The iron minerals inside the dendrites are housed in three different subcellular compartments (bullets, platelets, vesicles), which could be clearly resolved and identified by electron microscopy on ultrathin sections [1, 3]. Micro-XRF and micro-XANES data obtained at HASYLAB beamline L added information about the elemental distribution and Fe speciation [3], but are averaged over the complete dendrite due to limited spatial resolution. Here we present recently performed micro-XRF maps with sub-micrometer resolution (ESRF ID21), which reveal for the first time subcellular structural information from almost bulk-like dendrite sample material. Due to the thickness of 30 μm the microarchitecture of the dendrites can be considered as undisturbed and artefacts introduced by sectioning might be widely reduced.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Times cited: 2
DOI: 10.1088/1742-6596/186/1/012084
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“Determination of chemical composition of individual airborne particles by SEM/EDX and micro-Raman spectrometry : a review”. Stefaniak EA, Buczyńska A, Novakovic V, Kuduk R, Van Grieken R, Journal of physics : conference series 162, 012019 (2009). http://doi.org/10.1088/1742-6596/162/1/012019
Abstract: The strategies for sampling and analysis by SEM/EDX and micro-Raman spectrometry for individual airborne particles analysis as applied at the University of Antwerp (Belgium) by the MITAC group have been reviewed. Microbeam techniques provide detailed information concerning the origin, formation, transport, reactivity, transformation reactions and environmental impact of particulate matter. Moreover, some particles of certain chemical properties have been recognized as a threat for human health and cultural heritage objects. However, the small sizes of particles result in specific problems with respect to single particle analysis. Development of equipment and software for improvement of analysis and quantification are reported.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
DOI: 10.1088/1742-6596/162/1/012019
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“Geometry-guided flux behaviour in superconducting Pb microcrystals”. Engbarth M, Milošević, MV, Bending SJ, Nasirpouri F, Journal of physics : conference series 150, 052048 (2009). http://doi.org/10.1088/1742-6596/150/5/052048
Abstract: Electrochemistry offers highly flexible routes to fabrication of a wide variety of mesostructures, including three-dimensional (3D) crystallites, thin films and nanowires. Using this method we have grown various 3D superconducting Pb mesostructures with vastly different morphologies. We present here results on a truncated(half)-icosahedron with a hexagonal base and a tripod structure with a triangular base. Using Hall probe magnetometry we have obtained magnetisation curves for these structures at several temperatures and see evidence of geometry-driven flux entry and exit as well as flux trapping caused by specific sample geometries. We also observe behaviour that we interpret in terms of the formation of giant vortices, bearing in mind that bulk Pb is a type-I superconducting material.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Times cited: 1
DOI: 10.1088/1742-6596/150/5/052048
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“Vortex-antivortex 'molecular crystals' in hybrid ferromagnet/superconductor structures”. Bending SJ, Neal JS, Milošević, MV, Potenza A, san Emeterio L, Marrows CH, Journal of physics : conference series 150, 052019 (2009). http://doi.org/10.1088/1742-6596/150/5/052019
Abstract: We have used high resolution Hall probe microscopy to image vortex-antivortex (V-AV) 'molecules' induced in superconducting Pb films by the stray fields from square arrays of ferromagnetic Co/Pt dots. We have directly observed spontaneous V-AV pairs and studied how they interact with added 'free' (anti)fluxons in an applied magnetic field. We observe a rich variety of subtle phenomena arising from competing symmetries in our system which can either drive added antivortices to join AV shells around nanomagnets or stabilise the translationally symmetric AV lattice between the dots. Added vortices annihilate AV shells, leading eventually to a stable 'nulling' state with no free fluxons, which should exhibit a strongly (field-)enhanced critical current. At higher densities we actually observe vortex shells around the magnets, stabilised by the asymmetric anti-pinning potential. Our experimental findings are in good agreement with Ginzburg-Landau calculations.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
DOI: 10.1088/1742-6596/150/5/052019
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“Vortex 'puddles' and magic vortex numbers in mesoscopic superconducting disks”. Connolly MR, Milošević, MV, Bending SJ, Clem JR, Tamegai T, Journal of physics : conference series 150, 052039 (2009). http://doi.org/10.1088/1742-6596/150/5/052039
Abstract: The magnetic properties of a superconducting disk change dramatically when its dimensions become mesoscopic. Unlike large disks, where the screening currents induced by an applied magnetic field are strong enough to force vortices to accumulate in a 'puddle' at the centre, in a mesoscopic disk the interaction between one of these vortices and the edge currents can be comparable to the intervortex repulsion, resulting in a destruction of the ordered triangular vortex lattice structure at the centre. Vortices instead form clusters which adopt polygonal and shell-like structures which exhibit magic number states similar to those of charged particles in a confining potential, and electrons in artificial atoms. We have fabricated mesoscopic high temperature superconducting Bi2Sr2CaCu2O8+δ disks and investigated their magnetic properties using magneto-optical imaging (MOI) and high resolution scanning Hall probe microscopy (SHPM). The temperature dependence of the vortex penetration field measured using MOI is in excellent agreement with models of the thermal excitation of pancake vortices over edge barriers. The growth of the central vortex puddle has been directly imaged using SHPM and magic vortex numbers showing higher stability have been correlated with abrupt jumps in the measured local magnetisation curves.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
DOI: 10.1088/1742-6596/150/5/052039
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“Time dependent transport in 1D micro- and nanostructures: solving the Boltzmann and Wigner-Boltzmann equations”. Magnus W, Brosens F, Sorée B, Journal of physics : conference series 193, 012004 (2009). http://doi.org/10.1088/1742-6596/193/1/012004
Abstract: For many decades the Boltzmann distribution function has been used to calculate the non-equilibrium properties of mobile particles undergoing the combined action of various scattering mechanisms and externally applied force fields. When the latter give rise to the occurrence of inhomogeneous potential profiles across the region through which the particles are moving, the numerical solution of the Boltzmann equation becomes a highly complicated task. In this work we highlight a particular algorithm that can be used to solve the time dependent Boltzmann equation as well as its quantum mechanical extension, the WignerBoltzmann equation. As an illustration, we show the calculated distribution function describing electrons propagating under the action of both a uniform and a pronouncedly non-uniform electric field.
Keywords: A1 Journal article; Condensed Matter Theory (CMT); Theory of quantum systems and complex systems
Times cited: 2
DOI: 10.1088/1742-6596/193/1/012004
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“Fabrication and characterization of functionally graded Ni-Ti multilayer thin films”. Tian H, Schryvers D, Mohanchandra KP, Carman GP, van Humbeeck J, Functional materials letters 2, 61 (2009). http://doi.org/10.1142/S1793604709000570
Abstract: A functionally graded multilayer NiTi thin film was deposited on a SiO2/Si substrate by d.c. sputtering using a ramped heated NiTi alloy target. The stand-alone films were crystallized at 500°C in vacuum better than 10-7 Torr. Transmission electron microscopy micrographs taken along the film cross section show two distinct regions, thin and thick, with weak R and B2 phases, respectively. The film compositions along the thickness were measured and quantified using the standard-less EELSMODEL method. The film deposited during the initial thermal ramp (thin regions) displays an average of 54 at.% Ni while the film deposited at a more elevated target temperature (thick regions) shows about 51 at.% Ni.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 1.234
Times cited: 9
DOI: 10.1142/S1793604709000570
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“Microstructure and functional property changes in thin Ni-Ti wires heat teated by electric current: high energy X-ray and TEM investigations”. Malard B, Pilch J, Sittner P, Gartnerova V, Delville R, Schryvers D, Curfs C, Functional materials letters 2, 45 (2009). http://doi.org/10.1142/S1793604709000557
Abstract: High energy synchrotron X-ray diffraction, transmission electron microscopy and mechanical testing were employed to investigate the evolution of microstructure, texture and functional superelastic properties of 0.1 mm thin as drawn NiTi wires subjected to a nonconventional heat treatment by controlled electric current (FTMT-EC method). As drawn NiTi wires were prestrained in tension and exposed to a sequence of short DC power pulses in the millisecond range. The annealing time in the FTMT-EC processing can be very short but the temperature and force could be very high compared to the conventional heat treatment of SMAs. It is shown that the heavily strained, partially amorphous microstructure of the as drawn NiTi wire transforms under the effect of the DC pulse and tensile stress into a wide range of annealed nanosized microstructures depending on the pulse time. The functional superelastic properties and microstructures of the FTMT-EC treated NiTi wire are comparable to those observed in straight annealed wires.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 1.234
Times cited: 21
DOI: 10.1142/S1793604709000557
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“Composition of pigments on human bones found in excavations in Argentina studied with micro-Raman spectrometry and scanning electron microscopy”. Darchuk L, Stefaniak EA, Vázquez C, Palacios OM, Worobiec A, Van Grieken R, e-Preservation Science 6, 112 (2009)
Abstract: Results on analysis of prehistoric pigments from excavations and pigments on coloured child bones from North Patagonia, Argentina, are reported. To analyze their composition we used two micro-analytical techniques: micro- Raman spectrometry (MRS) and scanning electron microscopy coupled with X-ray micro-analysis (SEM/EDX). Most investigated excavated pigments show red or yellow ochres consistent with reddish or yellow minerals, such as á- and ã-goethite, haematite, erdite, haapalaite and jarosite. Raman spectra show also evidence of calcium oxalate monohydrate and calcite indicating lichen activity. Pigments covering human bones were identified as hematite and magnetite. This study allows us to infer that pigments found in excavation were employed for burial ceremonies, even though distances between excavated pigment archaeological site and buried remains are quite far, more than 50 km in a straight line.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation); Laboratory Experimental Medicine and Pediatrics (LEMP)
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“Scheme for coherently quenching resonant current in a three-level quantum dot energy level mixer”. Austing DG, Payette C, Nair SV, Yu G, Gupta JA, Partoens B, Amaha S, Tarucha S, Physica status solidi: C: conferences and critical reviews 6, 940 (2009). http://doi.org/10.1002/pssc.200880584
Abstract: We outline a scheme to create a dark state by three-level mixing that is potentially a useful tool for quantum coherent transport. Magnetic-field-induced intra-dot level mixing can lead to rich quantum superposition phenomena between three approaching single-particle states in a quantum dot when probed by the ground state of an adjacent weakly coupled quantum dot in the single-electron resonant tunnelling regime. The mixing relies on non-negligible anharmonicity and anisotropy in confining potentials of realistic quantum dots. Anti-crossing and transfer of strengths between resonances can be understood with a simple coherent level mixing model. Superposition can lead to the formation of a dark state by complete cancellation of an otherwise strong resonance. This is an all-electrical analogue of coherent population trapping seen in three-level-systems from quantum and atom optics.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
DOI: 10.1002/pssc.200880584
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“Tuning the superconducting properties of nanomaterials”. Croitoru MD, Shanenko AA, Peeters FM Springer, Dordrecht, page 1 (2009).
Abstract: Electron continement and its effect on the superconducting-to-normal phase transition driven by a magentic field and/or a current is studied in nanowires. Our investigation is based on a self-consistent numerical solution of the Bogoliubov-de Gennes equations. We find that in a parallel magneitc field and/or in the presence of a supercurrent the transition from the superconducting to the normal phase occurs as a cascade of discontinuous jumps in the superconducting order parameter for diameters D < 10 divided by 15 nm at T = 0. The critical magentic field exhibits quantum-size oscillations with pronounced resonant enhancements as a function of the wire radius.
Keywords: H1 Book chapter; Condensed Matter Theory (CMT); Electron microscopy for materials research (EMAT)
DOI: 10.1007/978-90-481-3120-4_1
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“Numerical study of the size-dependent melting mechanisms of nickel nanoclusters”. Neyts EC, Bogaerts A, The journal of physical chemistry: C : nanomaterials and interfaces 113, 2771 (2009)
Abstract: Molecular dynamics simulations were used to investigate the size-dependent melting mechanism of nickel nanoclusters of various sizes. The melting process was monitored by the caloric curve, the overall cluster Lindemann index, and the atomic Lindemann index. Size-dependent melting temperatures were determined, and the correct linear dependence on inverse diameter was recovered. We found that the melting mechanism gradually changes from dynamic coexistence melting to surface melting with increasing cluster size. These findings are of importance in better understanding carbon nanotube growth by catalytic chemical vapor deposition as the phase state of the catalyst nanoparticle codetermines the growth mechanism.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 4.536
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“Numerical study of the sputtering in a dc magnetron”. Kolev I, Bogaerts A, Journal of vacuum science and technology: A: vacuum surfaces and films 27, 20 (2009). http://doi.org/10.1021/jp8058992
Abstract: Molecular dynamics simulations were used to investigate the size-dependent melting mechanism of nickel nanoclusters of various sizes. The melting process was monitored by the caloric curve, the overall cluster Lindemann index, and the atomic Lindemann index. Size-dependent melting temperatures were determined, and the correct linear dependence on inverse diameter was recovered. We found that the melting mechanism gradually changes from dynamic coexistence melting to surface melting with increasing cluster size. These findings are of importance in better understanding carbon nanotube growth by catalytic chemical vapor deposition as the phase state of the catalyst nanoparticle codetermines the growth mechanism.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 4.536
Times cited: 66
DOI: 10.1021/jp8058992
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“Study of the variability in upper and lower airway morphology in Sprague-Dawley rats using modern micro-CT scan-based segmentation techniques”. de Backer JW, Vos WG, Burnell P, Verhulst SL, Salmon P, de Clerck N, de Backer W, The anatomical record: advances in integrative anatomy and evolutionary biology 292, 720 (2009). http://doi.org/10.1002/ar.20877
Abstract: Animal models are being used extensively in pre-clinical and safety assessment studies to assess the effectiveness and safety of new chemical entities and delivery systems. Although never entirely replacing the need for animal testing, the use of computer simulations could eventually reduce the amount of animals needed for research purposes and refine the data acquired from the animal studies. Computational fluid dynamics is a powerful tool that makes it possible to simulate flow and particle behavior in animal or patient-specific respiratory models, for purposes of inhaled delivery. This tool requires an accurate representation of the respiratory system, respiration and dose delivery attributes. The aim of this study is to develop a representative airway model of the Sprague-Dawley rat using static and dynamic micro-CT scans. The entire respiratory tract was modeled, from the snout and nares down to the central airways at the point where no distinction could be made between intraluminal air and the surrounding tissue. For the selection of the representative model, variables such as upper airway movement, segmentation length, airway volume and size are taken into account. Dynamic scans of the nostril region were used to illustrate the characteristic morphology of this region in anaesthetized animals. It could be concluded from this study that it was possible to construct a highly detailed representative model of a Sprague-Dawley rat based on imaging modalities such as micro-CT scans
Keywords: A1 Journal article; Condensed Matter Theory (CMT); Laboratory Experimental Medicine and Pediatrics (LEMP)
Impact Factor: 1.431
Times cited: 16
DOI: 10.1002/ar.20877
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“Multi-functional copper oxide nanosystems for H2 sustainable production and sensing”. Gasparotto A, Barreca D, Fornasiero P, Gombac V, Lebedev O, Maccato C, Montini T, Tondello E, Van Tendeloo G, Comini E, Sberveglieri G, ECS transactions 25, 1169 (2009)
Abstract: This work focuses on the use of tailored copper oxide nanoarchitectures as multi-functional materials for the sustainable production of hydrogen and its on-line detection. An innovative copper(II) precursor, Cu(hfa)2TMEDA, was adopted in the CVD of CuxO (x=1,2) nanosystems under both O2 and O2+H2O atmospheres on Si(100) and Al2O3 substrates. A multi-technique characterization indicates that both the phase composition (from Cu2O to CuO) and morphology (from continuous films to entangled quasi-1D nanosystems) can be tailored by varying the growth temperature and reaction atmosphere. The obtained CuxO nanodeposits are active in the photocatalytic H2 production from aqueous solutions under UV-Vis irradiation and display interesting gas sensing performances towards hydrogen detection even at moderate temperatures.
Keywords: A2 Journal article; Electron microscopy for materials research (EMAT)
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“Characterization of nano-crystalline diamond films grown under continuous DC bias during plasma enhanced chemical vapor deposition”. Mortet V, Zhang L, Echert M, Soltani A, d' Haen J, Douheret O, Moreau M, Osswald S, Neyts E, Troadec D, Wagner P, Bogaerts A, Van Tendeloo G, Haenen K, Materials Research Society symposium proceedings (2009). http://doi.org/10.1557/PROC-1203-J05-03
Abstract: Nanocrystalline diamond films have generated much interested due to their diamond-like properties and low surface roughness. Several techniques have been used to obtain a high re-nucleation rate, such as hydrogen poor or high methane concentration plasmas. In this work, the properties of nano-diamond films grown on silicon substrates using a continuous DC bias voltage during the complete duration of growth are studied. Subsequently, the layers were characterised by several morphological, structural and optical techniques. Besides a thorough investigation of the surface structure, using SEM and AFM, special attention was paid to the bulk structure of the films. The application of FTIR, XRD, multi wavelength Raman spectroscopy, TEM and EELS yielded a detailed insight in important properties such as the amount of crystallinity, the hydrogen content and grain size. Although these films are smooth, they are under a considerable compressive stress. FTIR spectroscopy points to a high hydrogen content in the films, while Raman and EELS indicate a high concentration of sp2 carbon. TEM and EELS show that these films consist of diamond nano-grains mixed with an amorphous sp2 bonded carbon, these results are consistent with the XRD and UV Raman spectroscopy data.
Keywords: A3 Journal article; Electron microscopy for materials research (EMAT); Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
DOI: 10.1557/PROC-1203-J05-03
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Caen J, Schalm O, Janssens K (2009) 15th century stained-glass windows in the former County of Flanders : a historical and chemical study related to recent conservation campaigns. 459–466
Keywords: P2 Proceeding; Engineering sciences. Technology; History; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
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