“Three-dimensional valency mapping in ceria nanocrystals”. Goris B, Turner S, Bals S, Van Tendeloo G, ACS nano 8, 10878 (2014). http://doi.org/10.1021/nn5047053
Abstract: Using electron tomography combined with electron energy loss spectroscopy (EELS), we are able to map the valency of the Ce ions in CeO2-x nanocrystals in three dimensions. Our results show a clear facet-dependent reduction shell at the surface of ceria nanoparticles; {111} surface facets show a low surface reduction, whereas at {001} surface facets, the cerium ions are more likely to be reduced over a larger surface shell. Our generic tomographic technique allows a full 3D data cube to be reconstructed, containing an EELS spectrum in each voxel. This possibility enables a three-dimensional investigation of a plethora of material-specific physical properties such as valency, chemical composition, oxygen coordination, or bond lengths, triggering the synthesis of nanomaterials with improved properties.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 13.942
Times cited: 85
DOI: 10.1021/nn5047053
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“Multiscale investigation of quasi-brittle fracture characteristics in a 9Cr–1Mo ferritic–martensitic steel embrittled by liquid lead–bismuth under low cycle fatigue”. Gong X, Marmy P, Volodin A, Amin-Ahmadi B, Qin L, Schryvers D, Gavrilov S, Stergar E, Verlinden B, Wevers M, Seefeldt M, Corrosion science 102, 137 (2016). http://doi.org/10.1016/j.corsci.2015.10.003
Abstract: Liquid metal embrittlement (LME) induced quasi-brittle fracture characteristics of a 9Cr–1Mo ferritic–martensitic steel (T91) after fatigue cracking in lead–bismuth eutectic (LBE) have been investigated at various length scales. The results show that the LME fracture morphology is primarily characterized by quasi-brittle translath flat regions partially covered by nanodimples, shallow secondary cracks propagating along the martensitic lath boundaries as well as tear ridges covered by micro dimples. These diverse LME fracture features likely indicate a LME mechanism involving multiple physical processes, such as weakening induced interatomic decohesion at the crack tip and plastic shearing induced nano/micro voiding in the plastic zone.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Times cited: 16
DOI: 10.1016/j.corsci.2015.10.003
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“Tomasch effect in nanoscale superconductors”. Zhang L-F, Covaci L, Peeters FM, Physical review : B : condensed matter and materials physics 91, 024508 (2015). http://doi.org/10.1103/PhysRevB.91.024508
Abstract: The Tomasch effect (TE) is due to quasiparticle interference (QPI) as induced by a nonuniform superconducting order parameter, which results in oscillations in the density of states (DOS) at energies above the superconducting gap. Quantum confinement in nanoscale superconductors leads to an inhomogenerous distribution of the Cooperpair condensate, which, as we found, triggers the manifestation of a new TE. We investigate the electronic structure of nanoscale superconductors by solving the Bogoliubov-de Gennes (BdG) equations self-consistently and describe the TE determined by two types of processes, involving two-or three-subband QPIs. Both types of QPIs result in additional BCS-like Bogoliubov-quasiparticles and BCS-like energy gaps leading to oscillations in the DOS and modulated wave patterns in the local density of states. These effects are strongly related to the symmetries of the system. A reduced 4 x 4 inter-subband BdG Hamiltonian is established in order to describe analytically the TE of two-subband QPIs. Our study is relevant to nanoscale superconductors, either nanowires or thin films, Bose-Einsten condensates, and confined systems such as two-dimensional electron gas interface superconductivity.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 6
DOI: 10.1103/PhysRevB.91.024508
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“Topological analysis of paraxially scattered electron vortex beams”. Lubk A, Clark L, Guzzinati G, Verbeeck J, Physical review : A : atomic, molecular and optical physics 87, 033834 (2013). http://doi.org/10.1103/PhysRevA.87.033834
Abstract: We investigate topological aspects of subnanometer electron vortex beams upon elastic propagation through atomic scattering potentials. Two main aspects can be distinguished: (i) significantly reduced delocalization compared to a similar nonvortex beam if the beam centers on an atomic column and (ii) site symmetry dependent splitting of higher-order vortex beams. Furthermore, the results provide insight into the complex vortex line fabric within the elastically scattered wave containing characteristic vortex loops predominantly attached to atomic columns and characteristic twists of vortex lines around atomic columns. DOI: 10.1103/PhysRevA.87.033834
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.925
Times cited: 26
DOI: 10.1103/PhysRevA.87.033834
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“Toward deep blue nano hope diamonds : heavily boron-doped diamond nanoparticles”. Heyer S, Janssen W, Turner S, Lu Y-G, Yeap WS, Verbeeck J, Haenen K, Krueger A, ACS nano 8, 5757 (2014). http://doi.org/10.1021/nn500573x
Abstract: The production of boron-doped diamond nanoparticles enables the application of this material for a broad range of fields, such as electrochemistry, thermal management, and fundamental superconductivity research. Here we present the production of highly boron-doped diamond nanoparticles using boron-doped CVD diamond films as a starting material. In a multistep milling process followed by purification and surface oxidation we obtained diamond nanoparticles of 1060 nm with a boron content of approximately 2.3 × 1021 cm3. Aberration-corrected HRTEM reveals the presence of defects within individual diamond grains, as well as a very thin nondiamond carbon layer at the particle surface. The boron K-edge electron energy-loss near-edge fine structure demonstrates that the B atoms are tetrahedrally embedded into the diamond lattice. The boron-doped diamond nanoparticles have been used to nucleate growth of a boron-doped diamond film by CVD that does not contain an insulating seeding layer.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 13.942
Times cited: 71
DOI: 10.1021/nn500573x
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“Towards quantitative EDX results in 3 dimensions”. Goris B, Freitag B, Zanaga D, Bladt E, Altantzis T, Ringnalda J, Bals S, Microscopy and microanalysis 20, 766 (2014). http://doi.org/10.1017/S1431927614005558
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 1.891
DOI: 10.1017/S1431927614005558
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“Transport of intensity phase retrieval of arbitrary wave fields including vortices”. Lubk A, Guzzinati G, Börrnert F, Verbeeck J, Physical review letters 111, 173902 (2013). http://doi.org/10.1103/PhysRevLett.111.173902
Abstract: The phase problem can be considered as one of the cornerstones of quantum mechanics intimately connected to the detection process and the uncertainty relation. The latter impose fundamental limits on the manifold phase reconstruction schemes invented to date, in particular, at small magnitudes of the quantum wave. Here, we show that a rigorous solution of the transport of intensity reconstruction (TIE) scheme in terms of a linear elliptic partial differential equation for the phase provides reconstructions even in the presence of wave zeros if particular boundary conditions are given. We furthermore discuss how partial coherence hampers phase reconstruction and show that a modified version of the TIE reconstructs the curl-free current density at arbitrary (in)coherence. Our results open the way for TIE-based phase retrieval of arbitrary wave fields, eventually containing zeros such as phase vortices.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 8.462
Times cited: 40
DOI: 10.1103/PhysRevLett.111.173902
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“Type of phase transitions in a mesoscopic superconducting disc”. Deo PS, Schweigert VA, Peeters FM, Geim AK, Physica: E 1, 297 (1997). http://doi.org/10.1016/S1386-9477(97)00063-5
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.221
DOI: 10.1016/S1386-9477(97)00063-5
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“Ultra-high resolution electron tomography for materials science : a roadmap”. Batenburg KJ, Bals S, Van Aert S, Roelandts T, Sijbers J, Microscopy and microanalysis 17, 934 (2011). http://doi.org/10.1017/S143192761100554X
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Vision lab
Impact Factor: 1.891
DOI: 10.1017/S143192761100554X
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“Emergent phenomena in multicomponent superconductivity: an introduction to the focus issue”. Milošević, MV, Perali A, Superconductor Science &, Technology 28, 060201 (2015). http://doi.org/10.1088/0953-2048/28/6/060201
Keywords: A1 Journal article; CMT
Impact Factor: 2.878
Times cited: 41
DOI: 10.1088/0953-2048/28/6/060201
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“The uptake and elimination of ZnO and CuO nanoparticles in Daphnia magna under chronic exposure scenarios”. Adam N, Leroux F, Knapen D, Bals S, Blust R, Water research 68, 249 (2015). http://doi.org/10.1016/j.watres.2014.10.001
Abstract: In this study, the uptake and elimination of ZnO and CuO nanoparticles in Daphnia magna was tested. Daphnids were exposed during 10 days to sublethal concentrations of ZnO and CuO nanoparticles and corresponding metal salts (ZnCl2 and CuCl2.2H2O), after which they were transferred to unexposed medium for another 10 days. At different times during the exposure and none-exposure, the total and internal zinc or copper concentration of the daphnids was determined and the nanoparticles were localized in the organism using electron microscopy. The exposure concentrations were characterized by measuring the dissolved, nanoparticle and aggregated fraction in the medium. The results showed that the ZnO nanoparticles quickly dissolved after addition to the medium. Contrarily, only a small fraction (corresponding to the dissolved metal salt) of the CuO nanoparticles dissolved, while most of these nanoparticles formed large aggregates. Despite an initial increase in zinc and copper concentration during the first 48 hour to 5 day exposure, the body concentration reached a plateau level that was comparable for the ZnO nanoparticles and ZnCl2, but much higher for the CuO nanoparticles (with visible aggregates accumulating in the gut) than CuCl2.2H2O. During the remaining exposure and subsequent none-exposure phase, the zinc and copper concentration decreased fast to concentrations comparable with the unexposed daphnids. The results indicate that D. magna can regulate its internal zinc and copper concentration after exposure to ZnO and CuO nanoparticles, similar as after exposure to metal salts. The combined dissolution, accumulation and toxicity results confirm that the toxicity of ZnO and CuO nanoparticles is caused by the dissolved fraction. Keywords nano; zinc; copper; dissolution; aggregation; electron microscopy
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Veterinary physiology and biochemistry
Impact Factor: 6.942
Times cited: 51
DOI: 10.1016/j.watres.2014.10.001
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“Using electron vortex beams to determine chirality of crystals in transmission electron microscopy”. Juchtmans R, Béché, A, Abakumov A, Batuk M, Verbeeck J, Physical review : B : condensed matter and materials physics 91, 094112 (2015). http://doi.org/10.1103/PhysRevB.91.094112
Abstract: We investigate electron vortex beams elastically scattered on chiral crystals. After deriving a general expression for the scattering amplitude of a vortex electron, we study its diffraction on point scatterers arranged on a helix. We derive a relation between the handedness of the helix and the topological charge of the electron vortex on one hand and the symmetry of the higher-order Laue zones in the diffraction pattern on the other for kinematically and dynamically scattered electrons. We then extend this to atoms arranged on a helix as found in crystals which belong to chiral space groups and propose a method to determine the handedness of such crystals by looking at the symmetry of the diffraction pattern. In contrast to alternative methods, our technique does not require multiple scattering, which makes it possible to also investigate extremely thin samples in which multiple scattering is suppressed. In order to verify the model, elastic scattering simulations are performed, and an experimental demonstration on Mn2Sb2O7 is given in which we find the sample to belong to the right-handed variant of its enantiomorphic pair. This demonstrates the usefulness of electron vortex beams to reveal the chirality of crystals in a transmission electron microscope and provides the required theoretical basis for further developments in this field.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.836
Times cited: 54
DOI: 10.1103/PhysRevB.91.094112
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“Using the macroscopic scale to predict the nano-scale behavior of YSZ thin films”. Lamas JS, Leroy WP, Lu Y-G, Verbeeck J, Van Tendeloo G, Depla D, Surface and coatings technology 238, 45 (2014). http://doi.org/10.1016/j.surfcoat.2013.10.034
Abstract: In this work, Yttria-stabilized zirconia (YSZ) thin films were deposited using dual reactive magnetron sputtering. By varying the deposition conditions, the film morphology and texture of the thin films are tuned and biaxial alignment is obtained. Studying the crystallographic and microstructural properties of the YSZ thin films, a tilted columnar growth was identified. This tilt is shown to be dependent on the compositional gradient of the sample. The variation of composition within a single YSZ column measured via STEM-EDX is demonstrated to be equal to the macroscopic variation on a full YSZ sample when deposited under the same deposition parameters. A simple stress model was developed to predict the tilt of the growing columns. The results indicate that this model not only determines the column bending of the growing film but also confirms that a macroscopic approach is sufficient to determine the compositional gradient in a single column of the YSZ thin films. (C) 2013 Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.589
Times cited: 8
DOI: 10.1016/j.surfcoat.2013.10.034
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“Atomically flat superconducting nanofilms: multiband properties and mean-field theory”. Shanenko AA, Aguiar JA, Vagov A, Croitoru MD, Milošević, MV, Superconductor science and technology 28, 054001 (2015). http://doi.org/10.1088/0953-2048/28/5/054001
Abstract: Recent progress in materials synthesis enabled fabrication of superconducting atomically flat single-crystalline metallic nanofilms with thicknesses down to a few monolayers. Interest in such nano-thin systems is attracted by the dimensional 3D-2D crossover in their coherent properties which occurs with decreasing the film thickness. The first fundamental aspect of this crossover is dictated by the Mermin-Wagner-Hohenberg theorem and concerns frustration of the long-range order due to superconductive fluctuations and the possibility to track its impact with an unprecedented level of control. The second important aspect is related to the Fabri-Perot modes of the electronic motion strongly bound in the direction perpendicular to the nanofilm. The formation of such modes results in a pronounced multiband structure that changes with the nanofilm thickness and affects both the mean-field behavior and superconductive fluctuations. Though the subject is very rich in physics, it is scarcely investigated to date. The main obstacle is that there are no manageable models to study a complex magnetic response in this case. Full microscopic consideration is rather time consuming, if practicable at all, while the standard Ginzburg-Landau theory is not applicable. In the present work we review the main achievements in the subject to date, and construct and justify an efficient multiband mean-field formalism which allows for numerical and even analytical treatment of nano-thin superconductors in applied magnetic fields.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.878
Times cited: 23
DOI: 10.1088/0953-2048/28/5/054001
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“Vortex states in axially symmetric superconductors in applied magnetic field”. Ludu A, Milošević, MV, Peeters FM, Sn –, 0378-4754 82, 1258 (2012). http://doi.org/10.1016/j.matcom.2012.02.001
Abstract: We solve analytically the linearized Ginzburg-Landau (GL) equation in the presence of an uniform magnetic field with cylindrical boundary conditions. The solution of the non-linear GL equation is provided as an expansion in the basis of linearized solutions. We present examples of the resulting vortex structure for a solid and perforated superconducting cylinder. (C) 2012 IMACS. Published by Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 1.218
Times cited: 1
DOI: 10.1016/j.matcom.2012.02.001
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“Vortex states in nanoscale superconducting squares : the influence of quantum confinement”. Zhang L-F, Covaci L, Milošević, MV, Berdiyorov GR, Peeters FM, Physical review : B : condensed matter and materials physics 88, 144501 (2013). http://doi.org/10.1103/PhysRevB.88.144501
Abstract: Bogoliubov-de Gennes theory is used to investigate the effect of the size of a superconducting square on the vortex states in the quantum confinement regime. When the superconducting coherence length is comparable to the Fermi wavelength, the shape resonances of the superconducting order parameter have strong influence on the vortex configuration. Several unconventional vortex states, including asymmetric ones, giant-multivortex combinations, and states comprising giant antivortices, were found as ground states and their stability was found to be very sensitive on the value of k(F)xi(0), the size of the sample W, and the magnetic flux Phi. By increasing the temperature and/or enlarging the size of the sample, quantum confinement is suppressed and the conventional mesoscopic vortex states as predicted by the Ginzburg-Laudau (GL) theory are recovered. However, contrary to the GL results we found that the states containing symmetry-induced vortex-antivortex pairs are stable over the whole temperature range. It turns out that the inhomogeneous order parameter induced by quantum confinement favors vortex-antivortex molecules, as well as giant vortices with a rich structure in the vortex core-unattainable in the GL domain.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 19
DOI: 10.1103/PhysRevB.88.144501
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“Wet-STEM tomography : principles, potentialities and limitations”. Masenelli-Varlot K, Malchere A, Ferreira J, Heidari Mezerji H, Bals S, Messaoudi C, Garrido SM, Microscopy and microanalysis 20, 366 (2014). http://doi.org/10.1017/S1431927614000105
Abstract: The characterization of biological and inorganic materials by determining their three-dimensional structure in conditions closer to their native state is a major challenge of technological research. Environmental scanning electron microscopy (ESEM) provides access to the observation of hydrated samples in water environments. Here, we present a specific device for ESEM in the scanning transmission electron microscopy mode, allowing the acquisition of tilt-series suitable for tomographic reconstructions. The resolution which can be obtained with this device is first determined. Then, we demonstrate the feasibility of tomography on wet materials. The example studied here is hydrophilic mesoporous silica (MCM-41). Finally, the minimum thickness of water which can be detected is calculated from Monte Carlo simulations and compared with the resolution expected in the tomograms.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 1.891
Times cited: 9
DOI: 10.1017/S1431927614000105
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“Application of the weighted-density approximation to the accurate description of electron-positron correlation effects in materials”. Callewaert V, Saniz R, Barbiellini B, Bansil A, Partoens B, Physical review B 96, 085135 (2017). http://doi.org/10.1103/PhysRevB.96.085135
Abstract: We discuss positron-annihilation lifetimes for a set of illustrative bulk materials within the framework of the weighted-density approximation (WDA). The WDA can correctly describe electron-positron correlations in strongly inhomogeneous systems, such as surfaces, where the applicability of (semi-)local approximations is limited. We analyze the WDA in detail and show that the electrons which cannot screen external charges efficiently, such as the core electrons, cannot be treated accurately via the pair correlation of the homogeneous electron gas. We discuss how this problem can be addressed by reducing the screening in the homogeneous electron gas by adding terms depending on the gradient of the electron density. Further improvements are obtained when core electrons are treated within the LDA and the valence electron using the WDA. Finally, we discuss a semiempirical WDA-based approach in which a sum rule is imposed to reproduce the experimental lifetimes.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 6
DOI: 10.1103/PhysRevB.96.085135
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“Zinc and copper oxides functionalized with metal nanoparticles : an insight into their nano-organization”. Maccato C, Simon Q, Carraro G, Barreca D, Gasparotto A, Lebedev OI, Turner S, Van Tendeloo G, Journal of advanced microscopy research 7, 84 (2012). http://doi.org/10.1166/jamr.2012.1101
Abstract: Ag/ZnO and Au/CuxO (x = 1, 2) nanocomposites supported on Si(100) and polycrystalline Al2O3 were synthesised by hybrid approaches, combining chemical vapor deposition (either thermal or plasma-assisted) of host oxide matrices and subsequent radio frequency-sputtering of guest metal particles. The influence of the adopted synthetic parameters on the nanocomposite morphological and compositional features was investigated by field emission-scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. Results confirm the synthesis of ZnO and CuxO nanoarchitectures, characterized by a tailored morphology and an intimate metal/oxide contact. A careful control of the processing conditions enabled a fine tuning of the mutual constituent distribution, opening thus attractive perspectives for the engineering of advanced nanomaterials.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
DOI: 10.1166/jamr.2012.1101
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“Atomic and electronic structures of BaHfO3-doped TFA-MOD-derived YBa2Cu3O7−δthin films”. Molina-Luna L, Duerrschnabel M, Turner S, Erbe M, Martinez GT, Van Aert S, Holzapfel B, Van Tendeloo G, Superconductor science and technology 28, 115009 (2015). http://doi.org/10.1088/0953-2048/28/11/115009
Abstract: Tailoring the properties of oxide-based nanocomposites is of great importance for a wide range of materials relevant for energy technology. YBa2Cu3O7−δ (YBCO) superconducting thin films containing nanosized BaHfO3 (BHO) particles yield a significant improvement of the magnetic flux pinning properties and a reduced anisotropy of the critical current density. These films were prepared by chemical solution deposition (CSD) on (100) SrTiO3 (STO) substrates yielding critical current densities up to 3.6 MA cm−2 at 77 K and self-field. Transport in-field J c measurements demonstrated a high pinning force maximum of around 6 GN/m3 for a sample annealed at T = 760 °C that has a doping of 12 mol% of BHO. This sample was investigated by scanning transmission electron microscopy (STEM) in combination with electron energy-loss spectroscopy (EELS) yielding strain and spectral maps. Spherical BHO nanoparticles of 15 nm in size were found in the matrix, whereas the particles at the interface were flat. A 2 nm diffusion layer containing Ti was found at the YBCO (BHO)/STO interface. Local lattice deformation mapping at the atomic scale revealed crystal defects induced by the presence of both sorts of BHO nanoparticles, which can act as pinning centers for magnetic flux lines. Two types of local lattice defects were identified and imaged: (i) misfit edge dislocations and (ii) Ba-Cu-Cu-Ba stacking faults (Y-248 intergrowths). The local electronic structure and charge transfer were probed by high energy resolution monochromated electron energy-loss spectroscopy. This technique made it possible to distinguish superconducting from non-superconducting areas in nanocomposite samples with atomic resolution in real space, allowing the identification of local pinning sites on the order of the coherence length of YBCO (~1.5 nm) and the determination of 0.25 nm dislocation cores.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.878
Times cited: 4
DOI: 10.1088/0953-2048/28/11/115009
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“BaHfO3artificial pinning centres in TFA-MOD-derived YBCO and GdBCO thin films”. Erbe M, Hänisch J, Hühne R, Freudenberg T, Kirchner A, Molina-Luna L, Damm C, Van Tendeloo G, Kaskel S, Schultz L, Holzapfel B, Superconductor science and technology 28, 114002 (2015). http://doi.org/10.1088/0953-2048/28/11/114002
Abstract: Chemical solution deposition (CSD) is a promising way to realize REBa2Cu3O7−x (REBCO;RE = rare earth (here Y, Gd))-coated conductors with high performance in applied magnetic fields. However, the preparation process contains numerous parameters which need to be tuned to achieve high-quality films. Therefore, we investigated the growth of REBCO thin films containing nanometre-scale BaHfO3 (BHO) particles as pinning centres for magnetic flux lines, with emphasis on the influence of crystallization temperature and substrate on the microstructure and superconductivity. Conductivity, microscopy and x-ray investigations show an enhanced performance of BHO nano-composites in comparison to pristine REBCO. Further, those measurements reveal the superiority of GdBCO to YBCO—e.g. by inductive critical current densities, Jc, at self-field and 77 K. YBCO is outperformed by more than 1 MA cm−2 with Jc values of up to 5.0 MA cm−2 for 265 nm thick layers of GdBCO(BHO) on lanthanum aluminate. Transport in-field Jc measurements demonstrate high pinning force maxima of around 4 GN m−3 for YBCO(BHO) and GdBCO(BHO). However, the irreversibility fields are appreciably higher for GdBCO. The critical temperature was not significantly reduced upon BHO addition to both YBCO and GdBCO, indicating a low tendency for Hf diffusion into the REBCO matrix. Angular-dependent Jc measurements show a reduction of the anisotropy in the same order of magnitude for both REBCO compounds. Theoretical models suggest that more than one sort of pinning centre is active in all CSD films.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.878
Times cited: 36
DOI: 10.1088/0953-2048/28/11/114002
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“Collective Plasmonic Properties in Few-Layer Gold Nanorod Supercrystals”. Hamon C, Novikov SM, Scarabelli L, Solís DM, Altantzis T, Bals S, Taboada JM, Obelleiro F, Liz-Marzán LM, ACS Photonics 2, 1482 (2015). http://doi.org/10.1021/acsphotonics.5b00369
Abstract: Gold nanorod supercrystals have been widely employed for the detection of relevant bioanalytes with detection limits ranging from nano- to picomolar levels,
confirming the promising nature of these structures for biosensing. Even though a relationship between the height of the supercrystal (i.e., the number of stacked nanorod layers)and the enhancement factor has been proposed, no systematic
study has been reported. In order to tackle this problem, we prepared gold nanorod supercrystals with varying numbers of stacked layers and analyzed them extensively by atomic force microscopy, electron microscopy and surface enhanced Raman scattering. The experimental results were compared to numerical
simulations performed on real-size supercrystals composed of thousands of nanorod building blocks. Analysis of the hot spot distribution in the simulated supercrystals showed the presence of standing waves that were distributed at different depths, depending on the number of layers in each supercrystal. On the basis of these theoretical results, we interpreted the experimental
data in terms of analyte penetration into the topmost layer only, which indicates that diffusion to the interior of the supercrystals would be crucial if the complete field enhancement produced by the stacked nanorods is to be exploited. We propose that our conclusions will be of high relevance in the design of next generation plasmonic devices.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 6.756
Times cited: 70
DOI: 10.1021/acsphotonics.5b00369
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“Onset, evolution, and magnetic braking of vortex lattice instabilities in nanostructured superconducting films”. Adami O-A, Jelić, ŽL, Xue C, Abdel-Hafiez M, Hackens B, Moshchalkov VV, Milošević, MV, Van de Vondel J, Silhanek AV, Physical review: B: condensed matter and materials physics 92, 134506 (2015). http://doi.org/10.1103/PhysRevB.92.134506
Abstract: In 1976, Larkin and Ovchinnikov [Zh. Eksp. Teor. Fiz. 68, 1915 (1975) [Sov. Phys.–JETP 41, 960 (1976)]] predicted that vortex matter in superconductors driven by an electrical current can undergo an abrupt dynamic transition from a flux-flow regime to a more dissipative state at sufficiently high vortex velocities. Typically, this transition manifests itself as a large voltage jump at a particular current density, so-called instability current density J∗, which is smaller than the depairing current. By tuning the effective pinning strength in Al films, using an artificial periodic pinning array of triangular holes, we show that a unique and well-defined instability current density exists if the pinning is strong, whereas a series of multiple voltage transitions appear in the relatively weaker pinning regime. This behavior is consistent with time-dependent Ginzburg-Landau simulations, where the multiple-step transition can be unambiguously attributed to the progressive development of vortex chains and subsequently phase-slip lines. In addition, we explore experimentally the magnetic braking effects, caused by a thick Cu layer deposited on top of the superconductor, on the instabilities and the vortex ratchet effect.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 21
DOI: 10.1103/PhysRevB.92.134506
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“Fluid modelling of a packed bed dielectric barrier discharge plasma reactor”. Van Laer K, Bogaerts A, Plasma sources science and technology 25, 015002 (2016). http://doi.org/10.1088/0963-0252/25/1/015002
Abstract: A packed bed dielectric barrier discharge plasma reactor is computationally studied with a fluid model. Two different complementary axisymmetric 2D geometries are used to mimic the intrinsic 3D problem. It is found that a packing enhances the electric field strength and electron temperature at the contact points of the dielectric material due to polarization of the beads by the applied potential. As a result, these contact points prove to be of direct importance to initiate the plasma. At low applied potential, the discharge stays at the contact points, and shows the properties of a Townsend discharge. When a high enough potential is applied, the plasma will be able to travel through the gaps in between the beads from wall to wall, forming a kind of glow discharge. Therefore, the inclusion of a so-called ‘channel of voids’ is indispensable in any type of packed bed modelling.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 3.302
Times cited: 50
DOI: 10.1088/0963-0252/25/1/015002
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“Can plasma be formed in catalyst pores? A modeling investigation”. Zhang Y-R, Van Laer K, Neyts EC, Bogaerts A, Applied catalysis : B : environmental 185, 56 (2016). http://doi.org/10.1016/j.apcatb.2015.12.009
Abstract: tWe investigate microdischarge formation inside catalyst pores by a two-dimensional fluid model forvarious pore sizes in the m-range and for various applied voltages. Indeed, this is a poorly understoodphenomenon in plasma catalysis. The calculations are performed for a dielectric barrier discharge inhelium, at atmospheric pressure. The electron and ion densities, electron temperature, electric field andpotential, as well as the electron impact ionization and excitation rate and the densities of excited plasmaspecies, are examined for a better understanding of the characteristics of the plasma inside a pore. Theresults indicate that the pore size and the applied voltage are critical parameters for the formation of amicrodischarge inside a pore. At an applied voltage of 20 kV, our calculations reveal that the ionizationmainly takes place inside the pore, and the electron density shows a significant increase near and inthe pore for pore sizes larger than 200m, whereas the effect of the pore on the total ion density isevident even for 10m pores. When the pore size is fixed at 30m, the presence of the pore has nosignificant influence on the plasma properties at an applied voltage of 2 kV. Upon increasing the voltage,the ionization process is enhanced due to the strong electric field and high electron temperature, andthe ion density shows a remarkable increase near and in the pore for voltages above 10 kV. These resultsindicate that the plasma species can be formed inside pores of structured catalysts (in the m range),and they may interact with the catalyst surface, and affect the plasma catalytic process.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 9.446
Times cited: 75
DOI: 10.1016/j.apcatb.2015.12.009
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“Multi-level molecular modelling for plasma medicine”. Bogaerts A, Khosravian N, Van der Paal J, Verlackt CCW, Yusupov M, Kamaraj B, Neyts EC, Journal of physics: D: applied physics 49, 054002 (2016). http://doi.org/10.1088/0022-3727/49/5/054002
Abstract: Modelling at the molecular or atomic scale can be very useful for obtaining a better insight in plasma medicine. This paper gives an overview of different atomic/molecular scale modelling approaches that can be used to study the direct interaction of plasma species with biomolecules or the consequences of these interactions for the biomolecules on a somewhat longer time-scale. These approaches include density functional theory (DFT), density functional based tight binding (DFTB), classical reactive and non-reactive molecular dynamics (MD) and united-atom or coarse-grained MD, as well as hybrid quantum mechanics/molecular mechanics (QM/MM) methods. Specific examples will be given for three important types of biomolecules, present in human cells, i.e. proteins, DNA and phospholipids found in the cell membrane. The results show that each of these modelling approaches has its specific strengths and limitations, and is particularly useful for certain applications. A multi-level approach is therefore most suitable for obtaining a global picture of the plasma–biomolecule interactions.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 2.588
Times cited: 11
DOI: 10.1088/0022-3727/49/5/054002
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“Effect of lipid peroxidation on membrane permeability of cancer and normal cells subjected to oxidative stress”. Van der Paal J, Neyts EC, Verlackt CCW, Bogaerts A, Chemical science 7, 489 (2016). http://doi.org/10.1039/C5SC02311D
Abstract: We performed molecular dynamics simulations to investigate the effect of lipid peroxidation products on the structural and dynamic properties of the cell membrane. Our simulations predict that the lipid order in a phospholipid bilayer, as a model system for the cell membrane, decreases upon addition of lipid peroxidation products. Eventually, when all phospholipids are oxidized, pore formation can occur. This will allow reactive species, such as reactive oxygen and nitrogen species (RONS), to enter the cell and cause oxidative damage to intracellular macromolecules, such as DNA or proteins. On the other hand, upon increasing the cholesterol fraction of lipid bilayers, the cell membrane order increases, eventually reaching a certain threshold, from which cholesterol is able to protect the membrane against pore formation. This finding is crucial for cancer treatment by plasma technology, producing a large number of RONS, as well as for other cancer treatment methods that cause an increase in the concentration of extracellular RONS. Indeed, cancer cells contain less cholesterol than their healthy counterparts. Thus, they will be more vulnerable to the consequences of lipid peroxidation, eventually enabling the penetration of RONS into the interior of the cell, giving rise to oxidative stress, inducing pro-apoptotic factors. This provides, for the first time, molecular level insight why plasma can selectively treat cancer cells, while leaving their healthy counterparts undamaged, as is indeed experimentally demonstrated.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 8.668
Times cited: 106
DOI: 10.1039/C5SC02311D
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“Heterogeneous interfacial chemical nature and bonds in a W-coated diamond/Al composite”. Ji G, Tan Z, Lu Y, Schryvers D, Li Z, Zhang D, Materials characterization 112, 129 (2016). http://doi.org/10.1016/j.matchar.2015.12.013
Abstract: Heterogeneous Al/Al4C3/Al2O3/diamond{111}, Al/nanolayered Al4C3/diamond{111} and Al12W particle/Al4C3/Al2O3/diamond{111} multi-interfaces have been developed at the nanoscale in a W-coated diamond/Al composite produced by vacuum hot pressing. The formation of nanoscale Al4C3 crystals is strongly associated with local O enrichment and can be further promoted by Al12W interfacial particles. The latter effectively contributes to enhance interfacial chemical bonding reducing interfacial thermal resistance and, in turn, enhancing thermal conductivity.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 2.714
Times cited: 7
DOI: 10.1016/j.matchar.2015.12.013
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“Merging Metadynamics into Hyperdynamics: Accelerated Molecular Simulations Reaching Time Scales from Microseconds to Seconds”. Bal KM, Neyts EC, Journal of chemical theory and computation 11, 4545 (2015). http://doi.org/10.1021/acs.jctc.5b00597
Abstract: The hyperdynamics method is a powerful tool to simulate slow processes at the atomic level. However, the construction of an optimal hyperdynamics potential is a task that is far from trivial. Here, we propose a generally applicable implementation of the hyperdynamics algorithm, borrowing two concepts from metadynamics. First, the use of a collective variable (CV) to represent the accelerated dynamics gives the method a very large flexibility and simplicity. Second, a metadynamics procedure can be used to construct a suitable history-dependent bias potential on-the-fly, effectively turning the algorithm into a self-learning accelerated molecular dynamics method. This collective variable-driven hyperdynamics (CVHD) method has a modular design: both the local system properties on which the bias is based, as well as the characteristics of the biasing method itself, can be chosen to match the needs of the considered system. As a result, system-specific details are abstracted from the biasing algorithm itself, making it extremely versatile and transparent. The method is tested on three model systems: diffusion on the Cu(001) surface and nickel-catalyzed methane decomposition, as examples of reactive processes with a bond-length-based CV, and the folding of a long polymer-like chain, using a set of dihedral angles as a CV. Boost factors up to 109, corresponding to a time scale of seconds, could be obtained while still accurately reproducing correct dynamics.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 5.245
Times cited: 41
DOI: 10.1021/acs.jctc.5b00597
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“Improving the Conversion and Energy Efficiency of Carbon Dioxide Splitting in a Zirconia-Packed Dielectric Barrier Discharge Reactor”. van Laer K, Bogaerts A, Energy technology 3, 1038 (2015). http://doi.org/10.1002/ente.201500127
Abstract: The use of plasma technology for CO2 splitting is gaining increasing interest, but one of the major obstacles to date for industrial implementation is the considerable energy cost. We demonstrate that the introduction of a packing of dielectric zirconia (ZrO2) beads into a dielectric barrier discharge (DBD) plasma reactor can enhance the CO2 conversion and energy efficiency up to a factor 1.9 and 2.2, respectively, compared to that in a normal (unpacked) DBD reactor. We obtained a maximum conversion of 42 % and a maximum energy efficiency of 9.6 %. However, it is the ability of the packing to almost double both the conversion and the energy efficiency simultaneously at certain input parameters that makes it very promising. The improved conversion and energy efficiency can be explained by the higher values of the local electric field and electron energy near the contact points of the beads and the lower breakdown voltage, demonstrated by 2 D fluid modeling.
Keywords: A1 Journal article; Engineering sciences. Technology; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 2.789
Times cited: 59
DOI: 10.1002/ente.201500127
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