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Montiel FN (2024) Voltage against illicit drug trafficking : capabilities of electrochemical fingerprinting to detect illicit drugs. 256 p
Keywords: Doctoral thesis; Pharmacology. Therapy; Engineering sciences. Technology; Antwerp Electrochemical and Analytical Sciences Lab (A-Sense Lab)
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“Shuffling atomic layer deposition gas sequences to modulate bimetallic thin films and nanoparticle properties”. Filez M, Feng J-Y, Minjauw MM, Solano E, Poonkottil N, Van Daele M, Ramachandran RK, Li C, Bals S, Poelman H, Detavernier C, Dendooven J, Filez M, Minjauw M, Solano E, Poonkottil N, Li C, Bals S, Dendooven J, Chemistry of materials (2022). http://doi.org/10.1021/acs.chemmater.2c01304
Abstract: Atomic layer deposition (ALD) typically employs metal precursors and co-reactant pulses to deposit thin films in a layer-by-layer fashion. While conventional ABAB-type ALD sequences implement only two functionalities, namely, a metal source and ligand exchange agent, additional functionalities have emerged, including etching and reduction agents. Herein, we construct gas-phase sequences-coined as ALD+-with complex-ities reaching beyond the classic ABAB-type ALD by freely combining multiple functionalities within irregular pulse schemes, e.g., ABCADC. The possibilities of such combinations are explored as a smart strategy to tailor bimetallic thin films and nanoparticle (NP) properties. By doing so, we demonstrate that bimetallic thin films can be tailored with target thickness and through the full compositional range, while the morphology can be flexibly modulated from thin films to NPs by shuI 1ing the pulse sequence. These complex pulse schemes are expected to be broadly applicable but are here explored for Pd-Ru bimetallic thin films and NPs.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Times cited: 2
DOI: 10.1021/acs.chemmater.2c01304
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“Characterization of complex silver halide photographic systems by means of analytical electron microscopy”. Oleshko V, Gijbels R, Jacob W, Alfimov M, Microbeam analysis 4, 1 (1995)
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Times cited: 9
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“Characterization of double structure tabular microcrystals of silver halide emulsions by means of electron energy-loss spectroscopy, zero-loss electron spectroscopic imaging and energy dispersive X-ray microanalysis”. Oleshko V, Gijbels R, Jacob W, Lakiere F, van Daele A, Silaev E, Kaplun L, Microscopy, microanalysis, microstructures 6, 79 (1995). http://doi.org/10.1051/mmm:1995108
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Times cited: 7
DOI: 10.1051/mmm:1995108
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“Corrélations chimiques-géothermométriques des paramètres microchimiques des hydrothermes profonds”. Pentcheva E, Van 't dack L, Veldeman E, Gijbels R, Comptes rendus de l'Académie bulgare des sciences 49, 61 (1996)
Keywords: A3 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
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“Substrate-induced proximity effect in superconducting niobium nanofilms”. Rezvani SJ, Perali A, Fretto M, De Leo N, Flammia L, Milošević, M, Nannarone S, Pinto N, Condensed Matter 4, 4 (2018). http://doi.org/10.3390/CONDMAT4010004
Abstract: Structural and superconducting properties of high-quality niobium nanofilms with different thicknesses are investigated on silicon oxide (SiO2) and sapphire substrates. The role played by the different substrates and the superconducting properties of the Nb films are discussed based on the defectivity of the films and on the presence of an interfacial oxide layer between the Nb film and the substrate. The X-ray absorption spectroscopy is employed to uncover the structure of the interfacial layer. We show that this interfacial layer leads to a strong proximity effect, especially in films deposited on a SiO2 substrate, altering the superconducting properties of the Nb films. Our results establish that the critical temperature is determined by an interplay between quantum-size effects, due to the reduction of the Nb film thicknesses, and proximity effects. The detailed investigation here provides reference characterizations and has direct and important implications for the fabrication of superconducting devices based on Nb nanofilms.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Times cited: 3
DOI: 10.3390/CONDMAT4010004
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“3D extension of the Monte Carlo code MCSHAPE for photon-matter interactions in the heterogeneous media”. Scot V, Fernandez JE, Vincze L, Janssens K, Nuclear instruments &, methods in physics research section B-Beam interactions with materiala and atoms 263, 204 (2007). http://doi.org/10.1016/J.NIMB.2007.04.205
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Times cited: 15
DOI: 10.1016/J.NIMB.2007.04.205
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“AXIL-PC, software for the analysis of complex-x-ray spectra”. van Espen P, Janssens K, Nobels J, Chemometrics and intelligent laboratory systems 1, 109 (1986). http://doi.org/10.1016/0169-7439(86)80031-4
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation); Chemometrics (Mitac 3)
DOI: 10.1016/0169-7439(86)80031-4
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“Combined Micro- and Macro scale X-ray powder diffraction mapping of degraded Orpiment paint in a 17th century still life painting by Martinus Nellius”. Simoen J, De Meyer S, Vanmeert F, De Keyser N, Avranovich E, van der Snickt G, Van Loon A, Keune K, Janssens K, Heritage science 7, 83 (2019). http://doi.org/10.1186/S40494-019-0324-4
Abstract: The spontaneous chemical alteration of artists' pigment materials may be caused by several degradation processes. Some of these are well known while others are still in need of more detailed investigation and documentation. These changes often become apparent as color modifications, either caused by a change in the oxidation state in the original material or the formation of degradation products or salts, via simple or more complex, multistep reactions. Arsenic-based pigments such as orpiment (As2S3) or realgar (alpha-As4S4) are prone to such alterations and are often described as easily oxidizing upon exposure to light. Macroscopic X-ray powder diffraction (MA-XRPD) imaging on a sub area of a still life painting by the 17th century Dutch painter Martinus Nellius was employed in combination with microscopic (mu-) XRPD imaging of a paint cross section taken in the area imaged by MA-XRPD. In this way, the in situ formation of secondary metal arsenate and sulfate species and their migration through the paint layer stack they originate from could be visualized. In the areas originally painted with orpiment, it could be shown that several secondary minerals such as schultenite (PbHAsO4), mimetite (Pb-5(AsO4)(3)Cl), palmierite (K2Pb(SO4)(2)) and syngenite (K2Ca(SO4)(2)center dot H2O) have formed. Closer inspection of the cross-sectioned paint layer stack with mu-XRPD illustrates that the arsenate minerals schultenite and mimetite have precipitated at the interface between the orpiment layer and the layer below that is rich in lead white, i.e. close to the depth of formation of the arsenate ions. The sulfate palmierite has mostly precipitated at the surface and upper layers of the painting.
Keywords: A1 Journal article; Art; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation); Antwerp Cultural Heritage Sciences (ARCHES)
Times cited: 2
DOI: 10.1186/S40494-019-0324-4
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“High resolution micro-XRF maps of iron oxides inside sensory dendrites of putative avian magnetoreceptors”. Falkenberg G, Fleissner GE, Fleissner GUE, Schuchardt K, Kühbacher M, Chalmin E, Janssens K, Journal of physics : conference series 186, 012084 (2009). http://doi.org/10.1088/1742-6596/186/1/012084
Abstract: Iron mineral containing sensory dendrites in the inner lining of the upper beak of homing pigeons [1] and various bird species [2] are the first candidate structures for an avian magnetic field receptor. A new concept of magnetoreception [3, 4] is based on detailed ultra-structural optical and electron microscopy analyses in combination with synchrotron radiation microscopic X-ray fluorescence analysis (micro-XRF) and microscopic X-ray absorption near edge structures (micro-XANES). Several behavioral experiments [5, 6] and first mathematical simulations [6] affirm our avian magnetoreceptor model. The iron minerals inside the dendrites are housed in three different subcellular compartments (bullets, platelets, vesicles), which could be clearly resolved and identified by electron microscopy on ultrathin sections [1, 3]. Micro-XRF and micro-XANES data obtained at HASYLAB beamline L added information about the elemental distribution and Fe speciation [3], but are averaged over the complete dendrite due to limited spatial resolution. Here we present recently performed micro-XRF maps with sub-micrometer resolution (ESRF ID21), which reveal for the first time subcellular structural information from almost bulk-like dendrite sample material. Due to the thickness of 30 μm the microarchitecture of the dendrites can be considered as undisturbed and artefacts introduced by sectioning might be widely reduced.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Times cited: 2
DOI: 10.1088/1742-6596/186/1/012084
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“Imaging secondary reaction products at the surface of Vermeer's Girl with the Pearl Earring by means of macroscopic X-ray powder diffraction scanning”. De Meyer S, Vanmeert F, Vertongen R, van Loon A, Gonzalez V, van der Snickt G, Vandivere A, Janssens K, Heritage science 7, 67 (2019). http://doi.org/10.1186/S40494-019-0309-3
Abstract: The use of non-invasive macroscopic imaging techniques is becoming more prevalent in the field of cultural heritage, especially to avoid invasive procedures that damage valuable artworks. For this purpose, an X-ray powder diffraction scanner (MA-XRPD) capable of visualising crystalline compounds in a highly specific manner was recently developed. Many inorganic pigments present in paintings fall into this category of materials. In this study, the 17th century oil painting Girl with a Pearl Earring (c. 1665) by Johannes Vermeer was analysed with a combination of transmission and reflection mode MA-XRPD. By employing this scanner in reflection mode, the relative sensitivity for compounds that are present at the paint surface could be increased, establishing it as a highly relevant technique for investigating the degradation processes that are ongoing at paint surfaces. Many of the original pigments employed by Vermeer could be identified, along with four secondary alteration products: gypsum (CaSO4 center dot 2H(2)O), anglesite (PbSO4), palmierite (K2Pb(SO4)(2)) and weddellite (CaC2O4 center dot 2H(2)O). The formation of gypsum was linked to the presence of chalk in the upper glaze layer while the formation of palmierite and weddellite is driven by the presence of lake pigments (and their substrates). In this manner, MA-XRPD can also be used to pinpoint locations relevant for sampling and synchrotron mu-XRPD analysis, which provides information on the microscopic make-up of the paint. A paint cross-section taken from an area rich in palmierite was analysed with synchrotron mu-XRPD, which confirmed the presence of this secondary compound at the interface of the upper paint layer with the ground layer as well as the presence of anglesite in the ground layer. The capacity of MA-XRPD to identify and chart secondary alteration products in a non-invasive manner has only very recently been demonstrated and makes it a highly relevant technique for the assessment of the chemical condition of works of art.
Keywords: A1 Journal article; Art; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation); Antwerp Cultural Heritage Sciences (ARCHES)
Times cited: 5
DOI: 10.1186/S40494-019-0309-3
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“Label-free impedance aptasensor for major peanut allergen Ara h 1”. Trashin S, De Jong M, Breugelmans T, Pilehvar S, De Wael K, Electroanalysis 27, 32 (2015). http://doi.org/10.1002/ELAN.201400365
Abstract: The peanut allergen Ara h 1 belonging to the vicilin family of seed storage proteins is known to be a suitable marker for peanut detection in foods. In the present work, we suggest an electrochemical detection of Ara h 1 using a recently selected 80-base DNA aptamer. The detection strategy relies on insulation effect of a bulky protein captured by an immobilized aptamer. The electrodes were modified by the aptamer and characterized using electrochemical impedance spectroscopy (EIS). The aptamer surface density and analytical parameters of the calibration curves for Ara h 1 were compared with the system prepared with thrombin binding aptamer (TBA) and operated in the same conditions.
Keywords: A1 Journal article; Engineering sciences. Technology; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation); Applied Electrochemistry & Catalysis (ELCAT)
Times cited: 10
DOI: 10.1002/ELAN.201400365
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“The preparation and preliminary characterisation of eight geological MPI-DING reference glasses for in-site microanalysis”. Jochum KP, Dingwell DB, Rocholl A, Janssens K, Vincze L, et al, Geostandards newsletter 24, 87 (2000). http://doi.org/10.1111/J.1751-908X.2000.TB00590.X
Abstract: Eight silicate glasses were prepared by directly fusing and stirring 50-100 g each of basalt, andesite, komatiite, peridotite, rhyolite, and quartz-diorite. These are referred to as MPI-DING glasses and were made for the purpose of providing reference materials for geochemical, in-situ microanalytical work. Results from various analytical techniques indicate that individual glass fragments are well homogenised with respect to major and trace elements at the mu m to mm scale. Heterogeneities due to quench crystallisation of olivine have been observed in small and limited areas of the two komatiitic glasses. In order to obtain concentration values for as many elements as possible, the glasses were analysed by a variety of bulk and microanalytical methods in a number of laboratories. From the analytical data, preliminary reference values for more than sixty elements were calculated. The analytical uncertainties of most elements are estimated to be between 1% and 10%.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
DOI: 10.1111/J.1751-908X.2000.TB00590.X
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“The hidden youth of Dirck Jacobsz leeuw : a portrait by Govert Flinck revealed”. Van Hommes ME, Lambour R, Du Mortier BM, De Winkel M, Tauber G, Alfeld M, Janssens K, Dik J, The Rijksmuseum bulletin 64, 4 (2016)
Keywords: A1 Journal article; Art; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
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“Water quality assessment in Pangani river basin, Tanzania : natural and anthropogenic influences on concentrations of nutrients and inorganic ions”. Hellar-Kihampa H, De Wael K, Lugwisha E, Van Grieken R, International journal of river basin management 11, 55 (2013). http://doi.org/10.1080/15715124.2012.759119
Abstract: The ongoing rapid expansions of human activities and population dynamics have potential impact on the environmental quality of the Pangani river basin, one of the largest water resources in Tanzania, including possible loadings of different kinds of micro-contaminants. However, specific extents of the impacts are rather not well investigated. In this work, we assessed the environmental quality of the basin, based on seasonal characterisation of physicochemical water and sediments parameters, dissolved inorganic ions and nutrient loads. The contributions of geochemical processes and land-use practices were evaluated by multivariate correlations and principal component analysis (PCA). Hierarchical cluster analysis was used to classify similar water quality stations and identify the most and least enriched ones. Surface waters were slightly alkaline, characterised by low total dissolved solids (48652 mg/L). Extremely low oxygen concentration (2.0 mg/L) was also a cause of concern at one station. The Na+ and HCO3 − ions provided the dominant cation and anion, respectively. PCA identified weathering of carbonate and Na+ bearing rocks, gypsum dissolution and atmospheric deposition of sea-salt as the major factors controlling the ionic composition, contributing more than 60% of the spatial variance. Concentration profiles of the chemical species showed a generally low level of anthropogenic inputs, except at a few locations where nitrate and nitrite were significantly enriched above the limits of safe exposure, with patterns indicating influences of farming and livestock keeping. A seasonal difference was observed, with lower ion concentrations during the rainy season, likely due to the dilution effect of increased water discharge. The study provides new insights into the environmental quality of the basin, and indicates the need for continuous monitoring and assessment of the chemical species in the area.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
DOI: 10.1080/15715124.2012.759119
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“X-Ray Fluorescence as an analytical tool for studying the copper matrices in the collection of the Museum Plantin-Moretus”. Storme P, Fransen E, De Wael K, Caen J, De gulden passer 95, 7 (2017)
Keywords: A1 Journal article; Engineering sciences. Technology; History; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation); Antwerp Cultural Heritage Sciences (ARCHES)
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“Diatom silica-titania materials for photocatalytic air purification”. Van Eynde E, Tytgat T, Smits M, Verbruggen S, Hauchecorne B, Blust R, Lenaerts S, Communications in agricultural and applied biological sciences 1, 141 (2013)
Keywords: A2 Journal article; Engineering sciences. Technology; Sustainable Energy, Air and Water Technology (DuEL)
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“Exhaust composition of a small diesel engine”. Smits M, Vanpachtenbeke F, Hauchecorne B, van Langenhove H, Demeestere K, Lenaerts S, Communications in agricultural and applied biological sciences 77, 85 (2012)
Keywords: A2 Journal article; Engineering sciences. Technology; Sustainable Energy, Air and Water Technology (DuEL)
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“Integration of a photocatalytic coating in a corona discharge unit for plasma assisted catalysis”. Van Wesenbeeck K, Hauchecorne B, Lenaerts S, Journal of environmental solutions 2, 16 (2013)
Abstract: The combination of a non-thermal plasma with catalysis is considered as a sustainable indoor air purification technology to achieve complete oxidation at reduced energy cost with a longer electrode lifetime. An optimal window of operation for plasma assisted catalysis is found by varying the polarity, the applied voltage, the relative humidity of the gas phase and the configuration of the plasma reactor. The results show that, in general, negative corona discharge can obtain higher nitric oxide (NO) conversion efficiencies compared to positive corona. It is also clear that at higher applied voltages, higher conversion efficiency can be reached. The effect of relative humidity, however, is not found to be significant in the range (0 20.3 %) tested in this work. Additionally, the configuration of the plasma reactor is changed by varying the amount of pins that are attached at the collector electrode. The results show that there is an optimum at 10 pairs of pins to obtain a high conversion efficiency of NO. By applying a coating on the collector electrode of the plasma reactor, it is possible to see the influence of the coating on the performance of the plasma system, which was operating in the previously found optimal window. It stands clear that the use of a plasma assisted catalysis system has high potential as an integrated and sustainable indoor air purification technology.
Keywords: A1 Journal article; Engineering sciences. Technology; Sustainable Energy, Air and Water Technology (DuEL)
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“Study of a TiO2 photocatalytic coating for use in plasma catalysis”. Van Wesenbeeck K, Hauchecorne B, Lenaerts S, Communications in agricultural and applied biological sciences 78, 227 (2013)
Keywords: A2 Journal article; Engineering sciences. Technology; Sustainable Energy, Air and Water Technology (DuEL)
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“The idea of weak sustainability is illegitimate”. Biely K, Maes D, Van Passel S, Environment, development and sustainability 20, 223 (2018). http://doi.org/10.1007/S10668-016-9878-4
Abstract: Since the introduction of the sustainability challenge, scientists disagree over the interpretation of the term sustainability. Weak and strong sustainability are the two main interpretations of sustainability, which are opposing each other. Some researchers stated that the interpretation of the term depends on the context; others disagree pointing out that it always implies the meaning of continuation. The term sustainability can be used as attribute, which adds a certain characteristic to the noun. If something can be attributed as being sustainable, it can also be unsustainable. The sustainability challenge consists of shifting from the current unsustainable towards a sustainable system. This paper outlines that the weak sustainability term is illegitimate, as it leads to a contradiction with the acknowledged assumption that the current state is unsustainable. This contradiction is revealed through an analysis of the occurrence of decoupling in agriculture: Agricultural land use could be decoupled from agricultural production, but only with the trade-off of massive increases in fertilizer, pesticide, energy and water usage. This paper outlines an inherent inconsistency within the ongoing discussion about the interpretation of sustainability. Through identifying the invalidity of the weak sustainability interpretation the focus can be shifted form the discourse to the sustainability challenge itself.
Keywords: A1 Journal article; Economics; Engineering sciences. Technology; Engineering Management (ENM)
Times cited: 1
DOI: 10.1007/S10668-016-9878-4
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“Economic and environmental multi-objective optimization to evaluate the impact of Belgian policy on solar power and electric vehicles”. De Schepper E, Van Passel S, Lizin S, Vincent T, Martin B, Gandibleux X, Journal of environmental economics and policy 5, 1 (2016). http://doi.org/10.1080/21606544.2015.1019569
Abstract: This research uses multi-objective optimisation to determine the optimal mixture of energy and transportation technologies, while optimising economic and environmental impacts. We demonstrate the added value of using multi-objective mixed integer linear programming (MOMILP) considering economies of scale versus using continuous multi-objective linear programming assuming average cost intervals. This paper uses an improved version to solve MOMILPs exactly. To differentiate optimal solutions with and without subsidies, the impact of policy on the Pareto frontier is assessed. We distinguish between minimising economic life cycle costs (complete rationality) and required investments (bounded rationality). The approach is illustrated using a Belgian company with demands for electricity and transport. Electricity technologies are solar photovoltaics and the grid; transportation includes internal combustion engine vehicles, grid powered battery electric vehicles (BEVs), and solar-powered BEVs. The impact of grid powered BEVs to reduce GHG emissions is limited, yet they are less costly than solar panels to decrease emissions. Current policy measures are found to be properly targeting rational investors who consider life cycle costs, while private (potentially bounded rational) investors often focus on required investments only.
Keywords: A1 Journal article; Economics; Engineering Management (ENM)
DOI: 10.1080/21606544.2015.1019569
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“Determinants of internal governance quality : evidence from corporations in Ethiopia”. Adane YG, Engida TG, Asfaw YA, Azadi H, Van Passel S, Cogent economics &, finance 6, 1537051 (2018). http://doi.org/10.1080/23322039.2018.1537051
Abstract: The study analysed the factors that affect the internal governance quality of corporations in Ethiopia. It performed an ordered logistic regression analysis on a randomly selected sample of 76 corporations to analyse the effect of the ownership structure, form of ownership (private or government), leverage, corporate size, and sales growth on the internal governance quality score (IGQS). The governance quality score was measured using 20 indices categorized into four perspectives: disclosure, board characteristics, ethics, and shareholder rights. In this study, a significant positive effect of the corporate size and sales growth on the IGQS was found. In addition, government-owned corporations were found to perform better than privately owned corporations. It is recommended that appropriate authorities and officials should encourage the use of the corporate governance system in privately owned corporations and the convergence of internal governance quality of the two groups of corporations to the highest level.
Keywords: A1 Journal article; Economics; Engineering Management (ENM)
DOI: 10.1080/23322039.2018.1537051
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“Bandgap engineering of two-dimensional semiconductor materials”. Chaves A, Azadani JG, Alsalman H, da Costa DR, Frisenda R, Chaves AJ, Song SH, Kim YD, He D, Zhou J, Castellanos-Gomez A, Peeters FM, Liu Z, Hinkle CL, Oh S-H, Ye PD, Koester SJ, Lee YH, Avouris P, Wang X, Low T, npj 2D Materials and Applications 4, 29 (2020). http://doi.org/10.1038/S41699-020-00162-4
Abstract: Semiconductors are the basis of many vital technologies such as electronics, computing, communications, optoelectronics, and sensing. Modern semiconductor technology can trace its origins to the invention of the point contact transistor in 1947. This demonstration paved the way for the development of discrete and integrated semiconductor devices and circuits that has helped to build a modern society where semiconductors are ubiquitous components of everyday life. A key property that determines the semiconductor electrical and optical properties is the bandgap. Beyond graphene, recently discovered two-dimensional (2D) materials possess semiconducting bandgaps ranging from the terahertz and mid-infrared in bilayer graphene and black phosphorus, visible in transition metal dichalcogenides, to the ultraviolet in hexagonal boron nitride. In particular, these 2D materials were demonstrated to exhibit highly tunable bandgaps, achieved via the control of layers number, heterostructuring, strain engineering, chemical doping, alloying, intercalation, substrate engineering, as well as an external electric field. We provide a review of the basic physical principles of these various techniques on the engineering of quasi-particle and optical bandgaps, their bandgap tunability, potentials and limitations in practical realization in future 2D device technologies.
Keywords: A1 Journal article; Engineering sciences. Technology; Condensed Matter Theory (CMT)
Times cited: 604
DOI: 10.1038/S41699-020-00162-4
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“Direct visualization of irreducible ferrielectricity in crystals”. Du K, Guo L, Peng J, Chen X, Zhou Z-N, Zhang Y, Zheng T, Liang Y-P, Lu J-P, Ni Z-H, Wang S-S, Van Tendeloo G, Zhang Z, Dong S, Tian H, npj Quantum Materials 5, 49 (2020). http://doi.org/10.1038/S41535-020-00252-Y
Abstract: In solids, charge polarity can one-to-one correspond to spin polarity phenomenologically, e.g., ferroelectricity/ferromagnetism, antiferroelectricity/antiferromagnetism, and even dipole-vortex/magnetic-vortex, but ferrielectricity/ferrimagnetism kept telling a disparate story in microscopic level. Since the definition of a charge dipole involves more than one ion, there may be multiple choices for a dipole unit, which makes most ferrielectric orders equivalent to ferroelectric ones, i.e., this ferrielectricity is not necessary to be a real independent branch of polarity. In this work, by using the spherical aberration-corrected scanning transmission electron microscope, we visualize a nontrivial ferrielectric structural evolution in BaFe2Se3, in which the development of two polar sub-lattices is out-of-sync, for which we term it as irreducible ferrielectricity. Such irreducible ferrielectricity leads to a non-monotonic behavior for the temperature-dependent polarization, and even a compensation point in the ordered state. Our finding unambiguously distinguishes ferrielectrics from ferroelectrics in solids.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
DOI: 10.1038/S41535-020-00252-Y
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“Nanoscale photovoltage mapping in CZTSe/CuxSe heterostructure by using kelvin probe force microscopy”. Vishwakarma M, Varandani D, Hendrickx M, Hadermann J, Mehta BR, Materials Research Express 7, 016418 (2020). http://doi.org/10.1088/2053-1591/AB65E6
Abstract: In the present work, kelvin probe force microscopy (KPFM) technique has been used to study the CZTSe/CuxSe bilayer interface prepared by multi-step deposition and selenization process of metal precursors. Transmission electron microscopy (TEM) confirmed the bilayer configuration of the CZTSe/CuxSe sample. Two configuration modes (surface mode and junction mode) in KPFM have been employed in order to measure the junction voltage under illumination conditions. The results show that CZTSe/CuxSe has small junction voltage of similar to 21 mV and the presence of CuxSe secondary phase in the CZTSe grain boundaries changes the workfunction of the local grain boundaries region. The negligible photovoltage difference between grain and grain boundaries in photovoltage image indicates that CuxSe phase deteriorates the higher photovoltage at grain boundaries normally observed in CZTSe based device. These results can be important for understanding the role of secondary phases in CZTSe based junction devices.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
DOI: 10.1088/2053-1591/AB65E6
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“A note on spirals and curvature”. Gielis J, Caratelli D, Shi P, Ricci PE, Growth and form 1, 1 (2020). http://doi.org/10.2991/GAF.K.200124.001
Abstract: Starting from logarithmic, sinusoidal and power spirals, it is shown how these spirals are connected directly with Chebyshev polynomials, Lamé curves, with allometry and Antonelli-metrics in Finsler geometry. Curvature is a crucial concept in geometry both for closed curves and equiangular spirals, and allowed Dillen to give a general definition of spirals. Many natural shapes can be described as a combination of one of two basic shapes in nature—circle and spiral—with Gielis transformations. Using this idea, shape description itself is used to develop a novel approach to anisotropic curvature in nature. Various examples are discussed, including fusion in flowers and its connection to the recently described pseudo-Chebyshev functions.
Keywords: A1 Journal article; Sustainable Energy, Air and Water Technology (DuEL)
DOI: 10.2991/GAF.K.200124.001
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“Real-time wood behaviour : the use of strain gauges for preventive conservation applications”. Anaf W, Cabal A, Robbe M, Schalm O, Sensors 20, 305 (2020). http://doi.org/10.3390/S20010305
Abstract: Within the heritage field, the application of strain gauges on wood surfaces is a little-explored but inexpensive and effective method to analyse the environmental appropriateness of rooms for the wooden heritage collections they contain. This contribution proposes a wood sensor connected to a data logger to identify short moments with an elevated risk of harm. Two experiments were performed to obtain insights pertaining to the applicability of wood sensors to evaluate preservation conditions. (1) The representativeness of strain gauges on dummies was tested for their use in evaluating the preservation conditions of a range of wooden objects exposed to the same environment. For this, three situations were mimicked: a bare wood surface, a wood surface covered with a preparation layer, and a wood surface covered with a preparation and varnish layer. (2) The usability of strain gauges to monitor the wood behaviour in real-time measurements was tested with a monitoring campaign of almost two years in a church where a new heating system was installed. The results of both experiments are promising, and the authors encourage a broader application of strain gauges in the heritage field.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation); Antwerp Cultural Heritage Sciences (ARCHES)
DOI: 10.3390/S20010305
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“Spontaneous emergence of Josephson junctions in homogeneous rings of single-crystal Sr₂RuO₄”. Yasui Y, Lahabi K, Fernández Becerra V, Fermin R, Anwar MS, Yonezawa S, Terashima T, Milošević, MV, Aarts J, Maeno Y, npj Quantum Materials 5, 21 (2020). http://doi.org/10.1038/S41535-020-0223-7
Abstract: The chiral p-wave order parameter in Sr2RuO4 would make it a special case amongst the unconventional superconductors. A consequence of this symmetry is the possible existence of superconducting domains of opposite chirality. At the boundary of such domains, the locally suppressed condensate can produce an intrinsic Josephson junction. Here, we provide evidence of such junctions using mesoscopic rings, structured from Sr2RuO4 single crystals. Our order parameter simulations predict such rings to host stable domain walls across their arms. This is verified with transport experiments on loops, with a sharp transition at 1.5 K, which show distinct critical current oscillations with periodicity corresponding to the flux quantum. In contrast, loops with broadened transitions at around 3 K are void of such junctions and show standard Little-Parks oscillations. Our analysis demonstrates the junctions are of intrinsic origin and makes a compelling case for the existence of superconducting domains.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Times cited: 10
DOI: 10.1038/S41535-020-0223-7
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“The role of temperature and drive current in skyrmion dynamics”. Litzius K, Leliaert J, Bassirian P, Rodrigues D, Kromin S, Lemesh I, Zazvorka J, Lee K-J, Mulkers J, Kerber N, Heinze D, Keil N, Reeve RM, Weigand M, Van Waeyenberge B, Schuetz G, Everschor-Sitte K, Beach GSD, Klaeui M, Nature Electronics 3, 30 (2020). http://doi.org/10.1038/S41928-019-0359-2
Abstract: Magnetic skyrmions are topologically stabilized nanoscale spin structures that could be of use in the development of future spintronic devices. When a skyrmion is driven by an electric current it propagates at an angle relative to the flow of current-known as the skyrmion Hall angle (SkHA)-that is a function of the drive current. This drive dependence, as well as thermal effects due to Joule heating, could be used to tailor skyrmion trajectories, but are not well understood. Here we report a study of skyrmion dynamics as a function of temperature and drive amplitude. We find that the skyrmion velocity depends strongly on temperature, while the SkHA does not and instead evolves differently in the low- and high-drive regimes. In particular, the maximum skyrmion velocity in ferromagnetic devices is limited by a mechanism based on skyrmion surface tension and deformation (where the skyrmion transitions into a stripe). Our mechanism provides a complete description of the SkHA in ferromagnetic multilayers across the full range of drive strengths, illustrating that skyrmion trajectories can be engineered for device applications. An analysis of skyrmion dynamics at different temperatures and electric drive currents is used to develop a complete description of the skyrmion Hall angle in ferromagnetic multilayers from the creep to the flow regime and illustrates that skyrmion trajectories can be engineered for device applications.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Times cited: 11
DOI: 10.1038/S41928-019-0359-2
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