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“Preparation and study of 2-D semiconductors with Dirac type bands due to the honeycomb nanogeometry”. Kalesaki E, Boneschanscher MP, Geuchies JJ, Delerue C, Morais Smith C, Evers WH, Allan G, Altantzis T, Bals S, Vanmaekelbergh D, Proceedings of the Society of Photo-optical Instrumentation Engineers
T2 –, Proceedings of SPIE 8981, 898107 (2014). http://doi.org/10.1117/12.2042882
Abstract: The interest in 2-dimensional systems with a honeycomb lattice and related Dirac-type electronic bands has exceeded the prototype graphene1. Currently, 2-dimensional atomic2,3 and nanoscale4-8 systems are extensively investigated in the search for materials with novel electronic properties that can be tailored by geometry. The immediate question that arises is how to fabricate 2-D semiconductors that have a honeycomb nanogeometry, and as a consequence of that, display a Dirac-type band structure? Here, we show that atomically coherent honeycomb superlattices of rocksalt (PbSe, PbTe) and zincblende (CdSe, CdTe) semiconductors can be obtained by nanocrystal self-assembly and facet-to-facet atomic bonding, and subsequent cation exchange. We present a extended structural analysis of atomically coherent 2-D honeycomb structures that were recently obtained with self-assembly and facet-to-facet bonding9. We show that this process may in principle lead to three different types of honeycomb structures, one with a graphene type-, and two others with a silicene-type structure. Using TEM, electron diffraction, STM and GISAXS it is convincingly shown that the structures are from the silicene-type. In the second part of this work, we describe the electronic structure of graphene-type and silicene type honeycomb semiconductors. We present the results of advanced electronic structure calculations using the sp3d5s* atomistic tight-binding method10. For simplicity, we focus on semiconductors with a simple and single conduction band for the native bulk semiconductor. When the 3-D geometry is changed into 2-D honeycomb, a conduction band structure transformation to two types of Dirac cones, one for S- and one for P-orbitals, is observed. The width of the bands depends on the honeycomb period and the coupling between the nanocrystals. Furthermore, there is a dispersionless P-orbital band, which also forms a landmark of the honeycomb structure. The effects of considerable intrinsic spin-orbit coupling are briefly considered. For heavy-element compounds such as CdTe, strong intrinsic spin-‐orbit coupling opens a non-trivial gap at the P-orbital Dirac point, leading to a quantum Spin Hall effect10-12. Our work shows that well known semiconductor crystals, known for centuries, can lead to systems with entirely new electronic properties, by the simple action of nanogeometry. It can be foreseen that such structures will play a key role in future opto-electronic applications, provided that they can be fabricated in a straightforward way.
Keywords: P1 Proceeding; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Times cited: 2
DOI: 10.1117/12.2042882
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“Tangible versus intangible in e-learning on cultural heritage : from online learning to on-site study of historic sites”. Lobovikov-Katz A, Moropoulou A, Konstanti A, Ortiz Calderon P, Van Grieken R, Worth S, Cassar JA, De Angelis R, Biscontin G, Izzo FC, Lecture notes in computer science
T2 –, 5th EuroMed International Conference, NOV 03-08, 2014, Amathus, CYPRUS 8740, 819 (2014). http://doi.org/10.1007/978-3-319-13695-0_84
Abstract: The revolutionary development in digital theory and technology calls for non-trivial decisions in bridging between the virtual and real worlds. The field of conservation of cultural heritage thus provides various challenges, especially with regards to learning, study and investigation of tangible heritage through applications of intangible ICT technologies. This paper examines the interaction between e-learning, and the actual on-site learning and study of historic buildings and sites, with an emphasis on their visual characteristics. In this context, the paper presents some aspects of application of a methodology which allows basic documentation, monitoring and primary analysis of data on cultural (built) heritage sites by general public through educational process enabled by an e-learning platform.
Keywords: P1 Proceeding; Documentation and information; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
DOI: 10.1007/978-3-319-13695-0_84
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“Pd5InSe and Pd8In2Se : new metal-rich homological selenides with 2D palladium-indium fragments : synthesis, structure and bonding”. Zakharova EY, Kazakov SM, Isaeva AA, Abakumov AM, Van Tendeloo G, Kuznetsov AN, Journal of alloys and compounds 589, 48 (2014). http://doi.org/10.1016/j.jallcom.2013.11.172
Abstract: Two new metal-rich palladium-indium selenides, Pd5InSe and Pd8In2Se, were synthesized using a high-temperature ampoule technique. Their crystal structures were determined from Rietveld analysis of powder diffraction data, supported by energy-dispersive X-ray spectroscopy and selected area electron diffraction. Both compounds crystallize in tetragonal system with P4/mmm space group (Pd5InSe: a = 4.0290(3) angstrom, c = 6.9858(5) angstrom, Z = 1; Pd8In2Se: a = 4.0045(4) angstrom, c = 10.952(1) angstrom, Z = 1). The first compound belongs to the Pd5TlAs structure type, while the second one – to a new structure type. Main structural units in both selenides are indium-centered [Pd12In] cuboctahedra of the tetragonally distorted Cu3Au type, single-and double-stacked along the c axis in Pd5InSe and Pd8In2Se, respectively, alternating with [Pd8Se] rectangular prisms. DFT electronic structure calculations predict both compounds to be 3D metallic conductors and Pauli-like paramagnets. According to the bonding analysis based on the electron localization function topology, both compounds feature multi-centered palladium-indium interactions in their heterometallic fragments. (C) 2013 Elsevier B. V. All rights reserved.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 3.133
Times cited: 12
DOI: 10.1016/j.jallcom.2013.11.172
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“Formation and diffusion characteristics of Pt clusters on Graphene, 1H-MoS2 and 1T-TaS2”. Ozaydin HD, Sahin H, Senger RT, Peeters FM, Annalen der Physik 526, 423 (2014). http://doi.org/10.1002/andp.201400079
Abstract: Many experiments have revealed that the surfaces of graphene and graphene-like structures can play an active role as a host surface for clusterization of transition metal atoms. Motivated by these observations, we investigate theoretically the adsorption, diffusion and magnetic properties of Pt clusters on three different two-dimensional atomic crystals using first principles density functional theory. We found that monolayers of graphene, molybdenum disulfide (1H-MoS2) and tantalum disulfide (1T-TaS2) provide different nucleation characteristics for Pt cluster formation. At low temperatures, while the bridge site is the most favorable site where the growth of a Pt cluster starts on graphene, top-Mo and top-Ta sites are preferred on 1H-MoS2 and 1T-TaS2, respectively. Ground state structures and magnetic properties of Pt-n clusters (n= 2,3,4) on three different monolayer crystal structures are obtained. We found that the formation of Pt-2 dimer and a triangle-shaped Pt-3 cluster perpendicular to the surface are favored over the three different surfaces. While bent rhombus shaped Pt-4 is formed on graphene, the formation of tetrahedral shaped clusters are more favorable on 1H-MoS2 and 1T-TaS2. Our study of the formation of Pt-n clusters on three different monolayers provides a gateway for further exploration of nanocluster formations on various surfaces.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.039
Times cited: 10
DOI: 10.1002/andp.201400079
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“A qualitative model structure sensitivity analysis method to support model selection”. Van Hoey S, Seuntjens P, van der Kwast J, Nopens I, Journal of hydrology 519, 3426 (2014). http://doi.org/10.1016/J.JHYDROL.2014.09.052
Abstract: The selection and identification of a suitable hydrological model structure is a more challenging task than fitting parameters of a fixed model structure to reproduce a measured hydrograph. The suitable model structure is highly dependent on various criteria, i.e. the modeling objective, the characteristics and the scale of the system under investigation and the available data. Flexible environments for model building are available, but need to be assisted by proper diagnostic tools for model structure selection. This paper introduces a qualitative method for model component sensitivity analysis. Traditionally, model sensitivity is evaluated for model parameters. In this paper, the concept is translated into an evaluation of model structure sensitivity. Similarly to the one-factor-at-a-time (OAT) methods for parameter sensitivity, this method varies the model structure components one at a time and evaluates the change in sensitivity towards the output variables. As such, the effect of model component variations can be evaluated towards different objective functions or output variables. The methodology is presented for a simple lumped hydrological model environment, introducing different possible model building variations. By comparing the effect of changes in model structure for different model objectives, model selection can be better evaluated. Based on the presented component sensitivity analysis of a case study, some suggestions with regard to model selection are formulated for the system under study: (1) a non-linear storage component is recommended, since it ensures more sensitive (identifiable) parameters for this component and less parameter interaction; (2) interflow is mainly important for the low flow criteria; (3) excess infiltration process is most influencing when focussing on the lower flows; (4) a more simple routing component is advisable; and (5) baseflow parameters have in general low sensitivity values, except for the low flow criteria. (C) 2014 Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; Sustainable Energy, Air and Water Technology (DuEL)
DOI: 10.1016/J.JHYDROL.2014.09.052
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“Accurate description of the van der Waals interaction of an electron-positron pair with the surface of a topological insulator”. Saniz R, Vercauteren S, Lamoen D, Partoens B, Barbiellini B, Journal of physics : conference series 505, 012002 (2014). http://doi.org/10.1088/1742-6596/505/1/012002
Abstract: Positrons can be trapped in localized states at the surface of a material, and thus quite selectively interact with core or valence surface electrons. Hence, advanced surface positron spectroscopy techniques can present the ideal tools to study a topological insulator, where surface states play a fundamental role. We analyze the problem of a positron at a TI surface, assuming that it is a weakly physisorbed positronium (Ps) atom. To determine if the surface of interest in a material can sustain such a physisorption, an accurate description of the underlying van der Waals (vdW) interaction is essential. We have developed a first-principles parameterfree method, based on the density functional theory, to extract key parameters determining the vdW interaction potential between a Ps atom and the surface of a given material. The method has been successfully applied to quartz and preliminary results on Bi2Te2Se indicate the existence of a positron surface state. We discuss the robustness of our predictions versus the most relevant approximations involved in our approach.
Keywords: P1 Proceeding; Electron microscopy for materials research (EMAT); Condensed Matter Theory (CMT)
Times cited: 2
DOI: 10.1088/1742-6596/505/1/012002
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“Coherent dynamics of confinement-induced multiband superconductors”. Croitoru MD, Zachmann M, Vagov A, Axt VM, Shanenko AA, Kettmann P, Papenkort T, Kuhn T, Physica: C : superconductivity 503, 183 (2014). http://doi.org/10.1016/j.physc.2014.04.014
Abstract: We study the coherent dynamics of pairing in a nanoscale superconductor, that is intrinsically multiband, after an external perturbation in the non-adiabatic regime. The description of the dynamics of the pairing order is within the density-matrix approach based on the BCS model and the Bogoliubov-de Gennes equations. We find that for certain resonant wire widths the superconducting order parameter exhibits two oscillatory frequencies which are determined by the long-time asymptotic values of the subgaps. This in turn leads to a pronounced beating phenomenon. (C) 2014 Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 1.404
Times cited: 1
DOI: 10.1016/j.physc.2014.04.014
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“Optimizing mesoscopic two-band superconductors for observation of fractional vortex states”. Piña JC, de Souza Silva CC, Milošević, MV, Physica: C : superconductivity 503, 48 (2014). http://doi.org/10.1016/j.physc.2014.04.017
Abstract: Using the two-component Ginzburg-Landau model, we investigate the effect of sample size and magnitude and homogeneity of external magnetic field on the stability of fractional vortex states in a mesoscopic two-band superconducting disk. We found that each fractional state has a preferable sample size, for which the range of applied field in which the state is stable is pronouncedly large. Vice versa, there exists an optimal magnitude of applied field for which a large range of possible sample radii will support the considered fractional state. Finally, we show that the stability of fractional states can be enhanced even further by magnetic nanostructuring of the sample, i.e. by suitably chosen geometrical parameters and magnetic moment of a ferromagnetic dot placed on top of the superconducting disk. (C) 2014 Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 1.404
Times cited: 5
DOI: 10.1016/j.physc.2014.04.017
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“The option to abandon : stimulating innovative groundwater remediation technologies characterized by technological uncertainty”. Compernolle T, Van Passel S, Huisman K, Kort P, Science Of The Total Environment 496, 63 (2014). http://doi.org/10.1016/J.SCITOTENV.2014.07.019
Abstract: Many studies on technology adoption demonstrate that uncertainty leads to a postponement of investments by integrating a wait option in the economic analysis. The aim of this study however is to demonstrate how the investment in new technologies can be stimulated by integrating an option to abandon. Furthermore, this real option analysis not only considers the ex ante decision analysis of the investment in a new technology under uncertainty, but also allows for an ex post evaluation of the investment. Based on a case study regarding the adoption of an innovative groundwater remediation strategy, it is demonstrated that when the option to abandon the innovative technology is taken into account, the decision maker decides to invest in this technology, while at the same time it determines an optimal timing to abandon the technology if its operation proves to be inefficient. To reduce uncertainty about the effectiveness of groundwater remediation technologies, samples are taken. Our analysis shows that when the initial belief in an effective innovative technology is low, it is important that these samples provide correct information in order to justify the adoption of the innovative technology. (C) 2014 Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; Economics
Impact Factor: 4.9
Times cited: 4
DOI: 10.1016/J.SCITOTENV.2014.07.019
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“Composition of PM2.5 and PM1 on high and low pollution event days and its relation to indoor air quality in a home for the elderly”. Buczyńska AJ, Krata A, Van Grieken R, Brown A, Polezer G, De Wael K, Potgieter-Vermaak S, The science of the total environment 490, 134 (2014). http://doi.org/10.1016/J.SCITOTENV.2014.04.102
Abstract: Many studies probing the link between air quality and health have pointed towards associations between particulate matter (PM) exposure and decreased lung function, aggravation of respiratory diseases like asthma, premature death and increased hospitalisation admissions for the elderly and individuals with cardiopulmonary diseases. Of recent, it is believed that the chemical composition and physical properties of PM may contribute significantly to these adverse health effects. As part of a Belgian Science Policy project (Health effects of particulate matter in relation to physicalchemical characteristics and meteorology), the chemical composition (elemental and ionic compositions) and physical properties (PM mass concentrations) of PM were investigated, indoors and outdoors of old age homes in Antwerp. The case reported here specifically relates to high versus normal/low pollution event periods. PM mass concentrations for PM1 and PM2.5 fractions were determined gravimetrically after collection via impaction. These same samples were hence analysed by EDXRF spectrometry and IC for their elemental and ionic compositions, respectively. During high pollution event days, PM mass concentrations inside the old age home reached 53 μg m− 3 and 32 μg m− 3 whilst outside concentrations were 101 μg m− 3 and 46 μg m− 3 for PM2.5 and PM1, respectively. The sum of nss-sulphate, nitrate and ammonium, dominate the composition of PM, and contribute the most towards an increase in the PM during the episode days constituting 64% of ambient PM2.5 (52 μg m− 3) compared to 39% on non-episode days (10 μg m− 3). Other PM components, such as mineral dust, sea salt or heavy metals were found to be considerably higher during PM episodes but relatively less important. Amongst heavy metals Zn and Pb were found at the highest concentrations in both PM2.5 and PM1. Acidbase ionic balance equations were calculated and point to acidic aerosols during event days and acidic to alkaline aerosols during non-event days. No significant sources of indoor pollutants could be identified inside the old-age home as high correlations were found between outdoor and indoor PM, confirming mainly the outdoor origin of indoor air.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 4.9
Times cited: 27
DOI: 10.1016/J.SCITOTENV.2014.04.102
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“Sustainability appraisal tools for soil and groundwater remediation : how is the choice of remediation alternative influenced by different sets of sustainability indicators and tool structures?”.Beames A, Broekx S, Lookman R, Touchant K, Seuntjens P, The science of the total environment 470, 954 (2014). http://doi.org/10.1016/J.SCITOTENV.2013.10.044
Abstract: The state-of-the-science in sustainability assessment of soil and groundwater remediation is evaluated with the application of four decision support systems (DSSs) to a large-scale brownfield revitalization case study. The DSSs were used to perform sustainability appraisals of four technically feasible remediation alternatives proposed for the site. The first stage of the review compares the scope of each tool's sustainability indicators, how these indicators are measured and how the tools differ in terms of standardization and weighting procedures. The second stage of the review compares the outputs from the tools and determines the key factors that result in differing results between tools. The evaluation of indicator sets and tool structures explains why the tools generate differing results. Not all crucial impact areas, as identified by sustainable remediation forums, are thoroughly considered by the tools, particularly with regard to the social and economic aspects of sustainability. Variations in boundary conditions defined between technologies, produce distorted environmental impact results, especially when in-situ and ex-situ technologies are compared. The review draws attention to the need for end users to be aware of which aspects of sustainability are considered, how the aspects are measured and how all aspects are ultimately balanced in the evaluation of potential remediation strategies. Existing tools can be improved by considering different technologies within the same boundary conditions and by expanding indicator sets to include indicators deemed to be relevant by remediation forums. (C) 2013 Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; Sustainable Energy, Air and Water Technology (DuEL)
DOI: 10.1016/J.SCITOTENV.2013.10.044
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“Ag nanoparticles on mixed Al2O3-Ga2O3 supports as catalysts for the N-alkylation of amines with alcohols”. Geukens I, Vermoortele F, Meledina M, Turner S, Van Tendeloo G, De Vos DE, Applied catalysis : A : general 469, 373 (2014). http://doi.org/10.1016/j.apcata.2013.09.044
Abstract: The combination of AgNO3 with NaH results in Ag nanoparticles that can selectively perform alcohol aminations under mild reaction conditions (110 °C). NaH not only serves as a reducing agent for the Ag salt, but also activates the alcohol for dehydrogenation to the corresponding ketone/aldehyde. The stability of the particles can be improved by immobilizing them onto mixed Al2O3Ga2O3 supports; the combination of Ga and Al provides materials with stronger Lewis acidic sites compared to pure alumina or gallium oxide supports. This leads to catalysts with enhanced activities, without the necessity of adding external Lewis acids. Detailed TEM characterization also reveals a close interaction between the Ag NPs and the gallium oxide phase. The obtained catalysts are recyclable and show activity for the alcohol amination using a variety of aliphatic and aromatic amines under mild conditions.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 4.339
Times cited: 24
DOI: 10.1016/j.apcata.2013.09.044
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“Nanofilms as effectively multiband superconductors: Intraband-pairing approximation and Ginzburg-Landau theory”. Shanenko AA, Vagov A, Peeters FM, Aguiar JA, Physica: B : condensed matter 455, 3 (2014). http://doi.org/10.1016/j.physb.2014.06.032
Abstract: It is well-known that the Ginzburg-Landau (GL) theory is a reliable and powerful theoretical tool to investigate the magnetic response of a superconducting state. However, in its standard form, this approach is not applicable to atomically uniform nano-thin superconducting films which are effective multiband superconductors. Here we discuss a relevant generalization of the GL theory, focusing on the underlying intraband-pairing approximation. (C) 2014 Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 1.386
Times cited: 1
DOI: 10.1016/j.physb.2014.06.032
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“Preface”. Aguiar JA, Roa-Rojas J, Parra Vargas CA, Landinez Tellez DA, Corredor Bohorquez LT, Shanenko A, Jardim RF, Peeters F, Physica: B : condensed matter 455, 1 (2014). http://doi.org/10.1016/j.physb.2014.05.013
Keywords: Editorial; Condensed Matter Theory (CMT)
Impact Factor: 1.386
DOI: 10.1016/j.physb.2014.05.013
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“Stability of CH3 molecules trapped on hydrogenated sites of graphene”. Berdiyorov GR, Milošević, MV, Peeters FM, van Duin AT, Physica: B : condensed matter 455, 60 (2014). http://doi.org/10.1016/j.physb.2014.07.046
Abstract: We study the effect of a hydrogen atom on the thermal stability of a trapped CH3 molecule on graphene using ReaxFF molecular dynamics simulations. Due to the hydrogen-molecule interaction, enhanced pinning of the CH3 molecule is observed when it is positioned adjacent to the graphene site with the hydrogen atom. We discuss the formation process of such a stable configuration, which originates from different adhesion and migration energies of the hydrogen atom and the CH3 molecule. We also studied the effect of the CH3-H configuration on the electronic transport properties of graphene nanoribbons using first principles density-functional calculations. We found that the formation of the CH3-H structure results in extra features in the transmission spectrum due to the formation of strongly localized states, which are absent when the CH3 molecule is trapped on pristine graphene. Our findings will be useful in exploiting gas sensing properties of graphene, especially for selective detection of individual molecules. (C) 2014 Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 1.386
Times cited: 5
DOI: 10.1016/j.physb.2014.07.046
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“Hyperfine electric parameters calculation in Si samples implanted with 57Mn\rightarrow57Fe”. Abreu Y, Cruz CM, Pinera I, Leyva A, Cabal AE, van Espen P, Van Remortel N, Physica: B : condensed matter 445, 1 (2014). http://doi.org/10.1016/J.PHYSB.2014.03.028
Abstract: Nowadays the electronic structure calculations allow the study of complex systems determining the hyperfine parameters measured at a probe atom, including the presence of crystalline defects. The hyperfine electric parameters have been measured by Mossbauer spectroscopy in silicon materials implanted with Mn-57 ->,Fe-57 ions, observing four main contributions to the spectra. Nevertheless, some ambiguities still remain in the Fe-57 Mossbauer spectra interpretation in this case, regarding the damage configurations and its evolution with annealing. In the present work several implantation environments are evaluated and the Fe-57 hyperfine parameters are calculated. The observed correlation among the studied local environments and the experimental observations is presented, and a tentative microscopic description of the behavior and thermal evolution of the characteristic defects local environments of the probe atoms concerning the location of vacancies and interstitial Si in the neighborhood of Fe-57 ions in substitutional and interstitial sites is proposed. (C) 2014 Elsevier B.V. All rights reserved
Keywords: A1 Journal article; Particle Physics Group; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
DOI: 10.1016/J.PHYSB.2014.03.028
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“Ferrihydrite precipitation in groundwater-fed river systems (Nete and Demer river basins, Belgium) : insights from a combined Fe-Zn-Sr-Nd-Pb-isotope study”. Dekov VM, Vanlierde E, Billström K, Gatto Rotondo G, van Meel K, Darchuk L, Van Grieken R, et al, Chemical geology 386, 1 (2014). http://doi.org/10.1016/J.CHEMGEO.2014.07.023
Abstract: Two groundwater-fed river systems (Nete and Demer, Belgium) carry red suspended material that settles on the river bed forming red sediments. The local aquifer that feeds these river systems is a glauconite-rich sand, which provides most of the dissolved Fe to the rivers. The solid component of these systems, i.e., the red suspended material and sediments, has a simple mineralogy (predominantly ferrihydrite), but shows a complex geochemistry pointing out the different processes contributing to the river chemistry: (1) the red sediments have higher transition metal (excluding Cu) and detrital element (e.g., Si, Al, K, Rb, etc.) concentrations than the red suspended matter because of their longer residence time in the river and higher contribution of the background (aquifer) component, respectively; (2) the red suspended material and sediments have inherited their rare earth element (REE) patterns from the aquifer; (3) the origin of Sr present in the red suspended matter and red sediments is predominantly marine (i.e., Quaternary calcareous rocks), but a small amount is geogenic (i.e., from detrital rocks); (4) Pb in both solids originates mostly from anthropogenic and geogenic sources; (5) all of the anthropogenic Pb in the red suspended material and sediments is hosted by the ferrihydrite; (6) Nd budget of the red riverine samples is controlled by the geogenic source and shows little anthropogenic component; (7) the significant Fe- and Zn-isotope fractionations are in line with the previous studies. Their fractionation patterns do not correlate, suggesting that the processes controlling the isotope geochemistry of Fe and Zn are different: oxidation/reduction most likely governs the Fe-isotope fractionation, whereas adsorption/desorption or admixing of anthropogenic sources controls the isotope fractionation of Zn.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
DOI: 10.1016/J.CHEMGEO.2014.07.023
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“Influence of amorphous phase separation on the crystallization behavior of glass-ceramics in the BaO-TiO2-SiO2 system”. Boulay E, Ragoen C, Idrissi H, Schryvers D, Godet S, Journal of non-crystalline solids 384, 61 (2014). http://doi.org/10.1016/j.jnoncrysol.2013.06.023
Abstract: The possible role of a prior amorphous phase separation on the subsequent crystallization has been the topic of vigorous debates over the last decades and has not yet been clarified, especially regarding the role of the interfaces created by the phase separation. This study proposes to focus on the interplay between a prior amorphous phase separation and the crystallization of fresnoite in the BaO-TiO2-SiO2 system. The crystallization behavior of a non-stoichiometric composition inside the miscibility gap (called APS) is compared with the stoichiometric composition (called FRES) and a non-stoichiometric composition outside the miscibility gap (called NoAPS). The crystallization mechanisms are compared using differential thermal analysis (DTA) by calculating the Avrami parameters and the activation energies as a function of the particle size. The DTA study shows that the two non-stoichiometric compositions exhibit a pronounced surface crystallization behavior whereas FRES undergoes bulk nucleation. This is supported by a multi-scale microstructure characterization. Furthermore, this study demonstrates that the amorphous phase separation and the associated interfaces do not play any significant role in the nucleation step. Moreover, transmission electron microscope (TEM) and local orientation measurements show that the growth of the dendrites is not hindered by the SiO2-rich droplets. The final stage of crystallization of APS is tentatively explained by two composition effects that must be further investigated: the viscosity effect and the formation of a eutectic. (C) 2013 Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.124
Times cited: 10
DOI: 10.1016/j.jnoncrysol.2013.06.023
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“Correlation between the nanocrystalline Sm(Fe,Mo)12 and its out of equilibrium phase Sm(Fe,Mo)10”. Khazzan S, Bessais L, Van Tendeloo G, Mliki N, Journal of magnetism and magnetic materials 363, 125 (2014). http://doi.org/10.1016/j.jmmm.2014.03.030
Abstract: Nanostructured Sm-Fe-Mo semi-hard magnetic material exhibiting enhanced magnetic properties can be produced by ball milling followed by recrystallization. Milled samples were annealed for 30 min in a vacuum at different temperatures (T-A) between 700 and 1190 degrees C. The effects of heat treatment and Mo content on structural and magnetic property changes have been investigated by means of X-ray diffraction using the Rietvekl method, transmission electron microscopy and magnetic measurements. For samples annealed at T-A > 900 degrees C the tetragonal ThMn12-type structure is identified, while for 700 < T-A < 900 degrees C a new out of equilibrium P6/mmm type structure was found as the major phase. This novel nanocrystalline phase has never been synthesized before. The correspondent stoichiometry is determined on the basis of the vacancy model. The Rietveld analysis gives a stoichiometry ratio equal to 1:10, for the out of equilibrium hexagonal phase, which is described with three crystallographic transition metal sites: 3g is fully occupied, 61 occupation is limited to hexagons surrounding the Fe dumbbell pairs 2e. We have performed a magnetic and structural study of nanocrystalline metastable P6/mrnm Sm(Fe1-xMo)(10), correlated with structural transformation towards its equilibrium derivative 14/mrnm Sm(Fe1-xMo)(12). A maximum of the coercive field H-C (H-C > 5 kOe) has been observed for the new hexagonal P6/rnmm phase suggesting that nanocrystalline Sm(Fe,Mo)(10), is a semi hard material, and is potential candidate for magnetic recording. (C) 2014 Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.63
Times cited: 6
DOI: 10.1016/j.jmmm.2014.03.030
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“Ferromagnetism in stacked bilayers of Pd/C60”. Ghosh S, Tongay S, Hebard AF, Sahin H, Peeters FM, Journal of magnetism and magnetic materials 349, 128 (2014). http://doi.org/10.1016/j.jmmm.2013.07.024
Abstract: We provide experimental evidence for the existence of ferromagnetism in bilayers of Pd/C-60 which is supported by theoretical calculations based on density functional theory (DFT). The observed ferromagnetism is surprising as C-60 and Pd films are both non-ferromagnetic in the non-interacting limit. Magnetization (M) versus applied field (H) data acquired at different temperatures (T) show magnetic hysteresis with typical coercive fields (H-c) on the order of 50 Oe. From the temperature-dependent magnetization M(T) we extract a Curie temperature (T-c >= 550 K) using Bloch-like power law extrapolations to high temperatures. Using DFT calculations we investigated all plausible scenarios for the interaction between the C-60 molecules and the Pd slabs, Pd single atoms and Pd clusters. DFT shows that while the C-60 molecules are nonmagnetic, Pd films have a degenerate ground state that subject to a weak perturbation, can become ferromagnetic. Calculations also show that the interaction of C-60 molecules with excess Pd atoms and with sharp edges of a Pd slab is the most likely configuration that render the system ferromagnetic Interestingly, the calculated charge transfer (0.016 e per surface Pd atom, 0.064 e per Pd for intimate contact region) between C-60 and Pd does not appear to play an important role. (C) 2013 Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.63
Times cited: 8
DOI: 10.1016/j.jmmm.2013.07.024
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“Long-range orientation and atomic attachment of nanocrystals in 2D honeycomb superlattices”. Boneschanscher MP, Evers WH, Geuchies JJ, Altantzis T, Goris B, Rabouw FT, van Rossum SAP, van der Zant HSJ, Siebbeles LDA, Van Tendeloo G, Swart I, Hilhorst J, Petukhov AV, Bals S, Vanmaekelbergh D;, Science 344, 1377 (2014). http://doi.org/10.1126/science.1252642
Abstract: Oriented attachment of synthetic semiconductor nanocrystals is emerging as a route for obtaining new semiconductors that can have Dirac-type electronic bands like graphene, but also strong spin-orbit coupling. The two-dimensional assembly geometry will require both atomic coherence and long-range periodicity of the superlattices. We show how the interfacial self-assembly and oriented attachment of nanocrystals results in two-dimensional (2D) metal chalcogenide semiconductors with a honeycomb superlattice. We present an extensive atomic and nanoscale characterization of these systems using direct imaging and wave scattering methods. The honeycomb superlattices are atomically coherent, and have an octahedral symmetry that is buckled; the nanocrystals occupy two parallel planes. Considerable necking and large-scale atomic motion occurred during the attachment process.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 37.205
Times cited: 304
DOI: 10.1126/science.1252642
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“Improved calculation of displacements per atom cross section in solids by gamma and electron irradiation”. Pinera I, Cruz CM, Leyva A, Abreu Y, Cabal AE, van Espen P, Van Remortel N, Interactions With Materials And Atoms 339, 1 (2014). http://doi.org/10.1016/J.NIMB.2014.08.020
Abstract: Several authors had estimated the displacements per atom cross sections under different approximations and models, including most of the main gamma- and electron-material interaction processes. These previous works used numerical approximation formulas which are applicable for limited energy ranges. We proposed the Monte Carlo assisted Classical Method (MCCM), which relates the established theories about atom displacements to the electron and positron secondary fluence distributions calculated from the Monte Carlo simulation. In this study the MCCM procedure is adapted in order to estimate the displacements per atom cross sections for gamma and electron irradiation. The results obtained through this procedure are compared with previous theoretical calculations. An improvement in about 10-90% for the gamma irradiation induced dpa cross section is observed in our results on regard to the previous evaluations for the studied incident energies. On the other hand, the dpa cross section values produced by irradiation with electrons are improved by our calculations in about 5-50% when compared with the theoretical approximations. When thin samples are irradiated with electrons, more precise results are obtained through the MCCM (in about 20-70%) with respect to the previous studies. (C) 2014 Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; Engineering sciences. Technology; Particle Physics Group; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
DOI: 10.1016/J.NIMB.2014.08.020
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“Infrared to terahertz absorption window in mono- and multi-layer graphene systems”. Xiao YM, Xu W, Peeters FM, Optics communications 328, 135 (2014). http://doi.org/10.1016/j.optcom.2014.04.079
Abstract: We present a theoretical study on optical properties such as optical conductance and light transmission coefficient for mono- and multi-layer graphene systems with AB- and ABC-stacking. Considering an air/graphene/dielectric-water structure, the optical coefficients for those graphene systems are examined and compared. The universal optical conductance sigma(N)(0)=N pi e(2)/(2h) for N layer graphene systems in the visible region is verified. For N 3 layer graphene, the mini-gap induced absorption edges can be observed in odd layers AB-stacked multilayer graphene, where the number and position of the absorption edges are decided by the layers number N. Meanwhile, we can observe the optical absorption windows for those graphene systems in the infrared to terahertz bandwidth (0.2-150 THz). The absorption window is induced by different transition energies required for inter- and intra-band optical absorption channels. We find that the depth and width of the absorption window can be tuned not only via varying temperature and electron density but also by changing the number of graphene layers and the stacking order. These theoretical findings demonstrate that mono- and multi-layer graphene systems can be applied as frequency tunable optoelectronic devices working in infrared to terahertz bandwidth. (C) 2014 Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 1.588
Times cited: 7
DOI: 10.1016/j.optcom.2014.04.079
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“A MoVI grafted metal organic framework : synthesis, characterization and catalytic investigations”. Leus K, Liu Y-Y, Meledina M, Turner S, Van Tendeloo G, van der Voort P, Journal of catalysis 316, 201 (2014). http://doi.org/10.1016/j.jcat.2014.05.019
Abstract: We present the post-modification of a gallium based Metal Organic Framework, COMOC-4, with a Mo-complex. The resulting Mo@COMOC-4 was characterized by means of N2 sorption, XRPD, DRIFT, TGA, XRF, XPS and TEM analysis. The results demonstrate that even at high Mo-complex loadings on the framework, no aggregation or any Mo or Mo oxide species are formed. Moreover, the Mo@COMOC-4 was evaluated as a catalyst in the epoxidation of cyclohexene, cyclooctene and cyclododecene employing TBHP in decane as oxidant. The post-modified COMOC-4 exhibits a very high selectivity toward the epoxide (up to 100%). Regenerability and stability tests have been carried out demonstrating that the catalyst can be recycled without leaching of Mo or loss of crystallinity.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 6.844
Times cited: 36
DOI: 10.1016/j.jcat.2014.05.019
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“First-principles electronic functionalization of silicene and germanene by adatom chemisorption”. van den Broek B, Houssa M, Scalise E, Pourtois G, Afanas'ev VV, Stesmans A, Applied surface science 291, 104 (2014). http://doi.org/10.1016/j.apsusc.2013.09.032
Abstract: This study presents first-principles results on the electronic functionalization of silicene and germanene monolayers by means of chemisorption of adatom species H, Li, F, Sc, Ti, V. Three general adatom-monolayer configurations are considered, each having its distinct effect on the electronic structure, yielding metallic or semiconducting dispersions depending on the adatom species and configuration. The induced bandgap is a (in)direct F gap ranging from 0.2 to 2.3 eV for both silicene and germanene. In general the alternating configuration was found to be the most energetically stable. The boatlike and chairlike conformers are degenerate with the former having anisotropic effective carrier masses. The top configuration leads to the planar monolayer and predominately to a gapped dispersion. The hollow configuration with V adatoms retains the Dirac cone, but with strong orbital planar hybridization at the Fermi level. We also observe a planar surface state the Fermi level for the latter systems. (C) 2013 Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 3.387
Times cited: 32
DOI: 10.1016/j.apsusc.2013.09.032
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“Theoretical aspects of graphene-like group IV semiconductors”. Houssa M, van den Broek B, Scalise E, Ealet B, Pourtois G, Chiappe D, Cinquanta E, Grazianetti C, Fanciulli M, Molle A, Afanas’ev VV, Stesmans A;, Applied surface science 291, 98 (2014). http://doi.org/10.1016/j.apsusc.2013.09.062
Abstract: Silicene and germanene are the silicon and germanium counterparts of graphene, respectively. Recent experimental works have reported the growth of silicene on (1 1 1)Ag surfaces with different atomic configurations, depending on the growth temperature and surface coverage. We first theoretically study the structural and electronic properties of silicene on (1 1 1) Ag surfaces, focusing on the (4 x 4) silicene/Ag structure. Due to symmetry breaking in the silicene layer (nonequivalent number of top and bottom Si atoms), the corrugated silicene layer, with the Ag substrate removed, is predicted to be semiconducting, with a computed energy bandgap of about 0.3 eV. However, the hybridization between the Si 3p orbitals and the Ag 5s orbital in the silicene/(1 1 1)Ag slab model leads to an overall metallic system, with a distribution of local electronic density of states, which is related to the slightly disordered structure of the silicene layer on the (1 1 1)Ag surface. We next study the interaction of silicene and germanene with different hexagonal non-metallic substrates, namely ZnS and ZnSe. On reconstructed (0 0 0 1)ZnS or ZnSe surfaces, which should be more energetically stable for very thin layers, silicene and germanene are found to be semiconducting. Remarkably, the nature and magnitude of their energy bandgap can be controlled by an out-of-plane electric field, an important finding for the potential use of these materials in nanoelectronic devices. (C) 2013 Elsevier B. V. All rights reserved.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 3.387
Times cited: 20
DOI: 10.1016/j.apsusc.2013.09.062
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“Vibrational properties of epitaxial silicene layers on (111) Ag”. Scalise E, Cinquanta E, Houssa M, van den Broek B, Chiappe D, Grazianetti C, Pourtois G, Ealet B, Molle A, Fanciulli M, Afanas’ev VV, Stesmans A;, Applied surface science 291, 113 (2014). http://doi.org/10.1016/j.apsusc.2013.08.113
Abstract: The electronic and vibrational properties of three different reconstructions of silicene on Ag(1 1 1) are calculated and compared to experimental results. The 2D epitaxial silicon layers, namely the (4 x 4), (root 13 x root 13) and (2 root 3 x 2 root 3) phases, exhibit different electronic and vibrational properties. Few peaks in the experimental Raman spectrum are identified and attributed to the vibrational modes of the silicene layers. The position and behavior of the Raman peaks with respect to the excitation energy are shown to be a fundamental tool to investigate and discern different phases of silicene on Ag( 1 1 1). (C) 2013 Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 3.387
Times cited: 36
DOI: 10.1016/j.apsusc.2013.08.113
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“Corrosion rate estimations of microscale zerovalent iron particles via direct hydrogen production measurements”. Velimirovic M, Carniato L, Simons Q, Schoups G, Seuntjens P, Bastiaens L, Journal of hazardous materials 270, 18 (2014). http://doi.org/10.1016/J.JHAZMAT.2014.01.034
Abstract: In this study, the aging behavior of microscale zerovalent iron (mZVI) particles was investigated by quantifying the hydrogen gas generated by anaerobic mZVI corrosion in batch degradation experiments. Granular iron and nanoscale zerovalent iron (nZVI) particles were included in this study as controls. Firstly, experiments in liquid medium (without aquifer material) were performed and revealed that mZV1 particles have approximately a 10-30 times lower corrosion rate than nZVI particles. A good correlation was found between surface area normalized corrosion rate (R-SA) and reaction rate constants (K-SA) of PCE, TCE, cDCE and 1,1,1-TCA. Generally, particles with higher degradation rates also have faster corrosion rates, but exceptions do exists. In a second phase, the hydrogen evolution was also monitored during batch tests in the presence of aquifer material and real groundwater. A 4-9 times higher corrosion rate of mZV1 particles was observed under the natural environment in comparison with the aquifer free artificial condition, which can be attributed to the low pH of the aquifer and its buffer capacity. A corrosion model was calibrated on the batch experiments to take into account the inhibitory effects of the corrosion products (dissolved iron, hydrogen and OH-) on the iron corrosion rate. (C) 2014 Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; Sustainable Energy, Air and Water Technology (DuEL)
DOI: 10.1016/J.JHAZMAT.2014.01.034
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“Lattice deformations in quasi-dynamic strain glass visualised and quantified by aberration corrected electron microscopy”. Lu J, Martinez GT, Van Aert S, Schryvers D, Physica status solidi: B: basic research 251, 2034 (2014). http://doi.org/10.1002/pssb.201350351
Abstract: Advanced transmission electron microscopy and statistical parameter estimated quantification procedures were applied to study the room temperature quasi-dynamical strain glass state in NiTi alloys. Nanosized strain pockets are visualised and the displacements of the atom columns are quantified. A comparison is made with conventional high-resolution transmission electron microscopy images of point defect induced strains in NiAl alloys.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 1.674
Times cited: 2
DOI: 10.1002/pssb.201350351
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“Review on TEM analysis of growth twins in nanocrystalline palladium thin films : toward better understanding of twin-related mechanisms in high stacking fault energy metals”. Idrissi H, Amin-Ahmadi B, Wang B, Schryvers D, Physica status solidi: B: basic research 251, 1111 (2014). http://doi.org/10.1002/pssb.201350161
Abstract: Various modes of transmission electron microscopy including aberration corrected imaging were used in order to unravel the fundamental mechanisms controlling the formation of growth twins and the evolution of twin boundaries under mechanical and hydrogen loading modes in nanocrystalline (nc) palladium thin films. The latter were produced by electron-beam evaporation and sputter deposition and subjected to uniaxial tensile deformation as well as hydriding/dehydriding cycles. The results show that the twins form by dissociation of grain boundaries. The coherency of Σ3{111} coherent twin boundaries considerably decreases with deformation due to dislocation/twin boundary interactions while Σ3{112} incoherent twin boundaries dissociate under hydrogen cycling into two-phase boundaries bounding a new and unstable 9R phase. The effect of these elementary mechanisms on the macroscopic behavior of the palladium films is discussed and compared to recent experimental and simulation works in the literature. The results provide insightful information to guide the production of well-controlled population of growth twins in high stacking fault energy nc metallic thin films. The results also indicate directions for further enhancement of the mechanical properties of palladium films as needed for instance in palladium-based membranes in hydrogen applications.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 1.674
Times cited: 7
DOI: 10.1002/pssb.201350161
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