“Economic performance of pyrolysis of mixed plastic waste: Open-loop versus closed-loop recycling”. Larrain M, Van Passel S, Thomassen G, Kresovic U, Alderweireldt N, Moerman E, Billen P, Journal Of Cleaner Production , 122442 (2020). http://doi.org/10.1016/j.jclepro.2020.122442
Abstract: In recent decades new recycling technologies for mixed plastic waste have emerged. In pyrolysis, the polymer chains are thermally broken (pyrolyzed) to obtain hydrocarbon materials of different molecular weights such as naphtha, oil or waxes, whose yields can be controlled by varying the reaction parameters. Naphtha represents a closed-loop recycling process as it is a feedstock for (poly)olefins; while the co-production of waxes, having several applications in e.g. the construction industry, exemplifies an open-loop recycling process. This paper compares the economic performance of the pyrolysis of mixed polyolefin waste in a closed-loop and open-loop scheme, including a probabilistic approach to the most important variables. From an economic perspective, open-loop pyrolysis as presented outperforms closed-loop recycling, due to the high prices of wax. However, the results present a high dispersion caused by the volatility of the prices of crude oil and its derivates. Considering the current oil price projections, our case study analysis showed that for open-loop recycling there is a future probability of almost a 98 % of observing positive results and around 57 % of probability in the case of closed-loop recycling, under the assumptions made. Yet, in a future scenario where decarbonized electricity would decrease oil prices, the probability of a positive outcome reduces to 57 % for the open-loop case and to less than 8 % in the case of closed-loop recycling. To make these pathways attractive to investors, the nameplate capacity should be at least 70 kt/year for open-loop recycling and 115 kt/year for closed-loop recycling. A 120 kt/year plant should operate minimally at 80 % of its capacity for open-loop recycling, while closed-loop recycling would demand running close to maximum capacity. Security of feedstock supply therefore is required.
Keywords: A1 Journal Article; Engineering Management (ENM) ;
Impact Factor: 11.1
DOI: 10.1016/j.jclepro.2020.122442
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“Economic performance of pyrolysis of mixed plastic waste: Open-loop versus closed-loop recycling”. Larrain M, Van Passel S, Thomassen G, Kresovic U, Alderweireldt N, Moerman E, Billen P, Journal Of Cleaner Production , 122442 (2020). http://doi.org/10.1016/j.jclepro.2020.122442
Abstract: In recent decades new recycling technologies for mixed plastic waste have emerged. In pyrolysis, the polymer chains are thermally broken (pyrolyzed) to obtain hydrocarbon materials of different molecular weights such as naphtha, oil or waxes, whose yields can be controlled by varying the reaction parameters. Naphtha represents a closed-loop recycling process as it is a feedstock for (poly)olefins; while the co-production of waxes, having several applications in e.g. the construction industry, exemplifies an open-loop recycling process. This paper compares the economic performance of the pyrolysis of mixed polyolefin waste in a closed-loop and open-loop scheme, including a probabilistic approach to the most important variables. From an economic perspective, open-loop pyrolysis as presented outperforms closed-loop recycling, due to the high prices of wax. However, the results present a high dispersion caused by the volatility of the prices of crude oil and its derivates. Considering the current oil price projections, our case study analysis showed that for open-loop recycling there is a future probability of almost a 98 % of observing positive results and around 57 % of probability in the case of closed-loop recycling, under the assumptions made. Yet, in a future scenario where decarbonized electricity would decrease oil prices, the probability of a positive outcome reduces to 57 % for the open-loop case and to less than 8 % in the case of closed-loop recycling. To make these pathways attractive to investors, the nameplate capacity should be at least 70 kt/year for open-loop recycling and 115 kt/year for closed-loop recycling. A 120 kt/year plant should operate minimally at 80 % of its capacity for open-loop recycling, while closed-loop recycling would demand running close to maximum capacity. Security of feedstock supply therefore is required.
Keywords: A1 Journal Article; Engineering Management (ENM) ;
Impact Factor: 11.1
DOI: 10.1016/j.jclepro.2020.122442
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“Cluster analysis of IR thermography data for differentiating glass types in historical leaded-glass windows”. Hillen M, Legrand S, Dirkx Y, Janssens K, van der Snickt G, Caen J, Steenackers G, Applied Sciences-Basel 10, 4255 (2020). http://doi.org/10.3390/APP10124255
Abstract: Infrared thermography is a fast, non-destructive and contactless testing technique which is increasingly used in heritage science. The aim of this study was to assess the ability of infrared thermography, in combination with a data clustering approach, to differentiate between the different types of historical glass that were included in a colorless leaded-glass windows during previous restoration interventions. Inspection of the thermograms and the application of two data mining techniques on the thermal data, i.e., k-means clustering and hierarchical clustering, allowed identifying different groups of window panes that show a different thermal behavior. Both clustering approaches arrive at similar groupings of the glass with a clear separation of three types. However, the lead cames that hold the glass panes appear to have a substantial impact on the thermal behavior of the surrounding glass, thus preventing classification of the smallest glass panes. For the larger panes, this was not a critical issue as the center of the glass remained unaffected. Subtle visual color differences between panes, implying a variation in coloring metal ions, was not always distinguished by IRT. Nevertheless, data clustering assisted infrared thermography shows potential as an efficient and swift method for documenting the material intervention history of leaded-glass windows during or in preparation of conservation treatments.
Keywords: A1 Journal article; Engineering sciences. Technology; Antwerp Cultural Heritage Sciences (ARCHES); AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 2.7
DOI: 10.3390/APP10124255
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Milagres de Oliveira T (2020) Three-dimensional characterisation of nanomaterials : from model-like systems to real nanostructures. 230 p
Keywords: Doctoral thesis; Electron microscopy for materials research (EMAT)
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“Mainstream partial nitritation/anammox with integrated fixed-film activated sludge : combined aeration and floc retention time control strategies limit nitrate production”. Seuntjens D, Carvajal Arroyo JM, Van Tendeloo M, Chatzigiannidou I, Molina J, Nop S, Boon N, Vlaeminck SE, Bioresource Technology 314, 123711 (2020). http://doi.org/10.1016/J.BIORTECH.2020.123711
Abstract: Implementation of mainstream partial nitritation/anammox (PN/A) can lead to more sustainable and cost-effective sewage treatment. For mainstream PN/A reactor, an integrated fixed-film activated sludge (IFAS) was operated (26 °C). The effects of floccular aerobic sludge retention time (AerSRT_floc), a novel aeration strategy, and N-loading rate were tested to optimize the operational strategy. The best performance was observed with a low, but sufficient AerSRTfloc (~7d) and continuous aeration with two alternating dissolved oxygen setpoints: 10 min at 0.07–0.13 mg O2 L−1 and 5 min at 0.27–0.43 mg O2 L−1. Nitrogen removal rates were 122 ± 23 mg N L−1 d−1, and removal efficiencies 73 ± 13%. These conditions enabled flocs to act as nitrite sources while the carriers were nitrite sinks, with low abundance of nitrite oxidizing bacteria. The operational strategies in the source-sink framework can serve as a guideline for successful operation of mainstream PN/A reactors.
Keywords: A1 Journal article; Engineering sciences. Technology; Sustainable Energy, Air and Water Technology (DuEL)
Impact Factor: 11.4
Times cited: 3
DOI: 10.1016/J.BIORTECH.2020.123711
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“Integrated techno-economic assessment of a biorefinery process: The high-end valorization of the lignocellulosic fraction in wood streams”. Tschulkow M, Compernolle T, Van den Bosch S, Van Aelst J, Storms I, Van Dael M, Van den Bossche G, Sels B, Van Passel S, Journal Of Cleaner Production 266, 122022 (2020). http://doi.org/10.1016/j.jclepro.2020.122022
Abstract: A new lignin-first biorefinery with a reductive catalytic fractionation process, which targets the valorization of the lignin and the carbohydrate fraction into higher value end-products, is currently being designed. To identify the various R&D drivers for projects with a low technology readiness level (TRL), we developed an integrated techno-economic assessment (TEA) that directly integrates the results of lab studies with economic costs and benefits. Furthermore, different linkages are made to upstream wood availability and downstream demand to understand its fit into existing wood value chains. By making the relations across the wood value chain explicit within the integrated TEA, we find that the scale of the plant, the feedstock-specific output quantities, and output prices highly determine the economic feasibility. Furthermore, this detailed analysis reveals the importance of assessing different types of feedstock. If only virgin wood is available as feedstock, minimum capacity levels between 190 and 234 kilotons per year are needed for the investment to be profitable. Waste wood proves to be the most profitable feedstock with an NPV of M€ 59 and an IRR of 26%. Using only waste wood as feedstock makes the investment profitable at a lower capacity level of 80 kilotons per year and economic shocks can be absorbed. Based on these results we show that an integrated and detailed TEA is indispensable to define future development paths for early-stage, innovative technologies.
Keywords: A1 Journal Article; Engineering Management (ENM) ;
Impact Factor: 11.1
DOI: 10.1016/j.jclepro.2020.122022
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“Drought risk assessment: Towards drought early warning system and sustainable environment in western Iran”. Sharafi L, Zarafshani K, Keshavarz M, Azadi H, Van Passel S, Ecological Indicators 114, 106276 (2020). http://doi.org/10.1016/j.ecolind.2020.106276
Abstract: Prolonged drought is considered as a creeping natural hazard, which has created a financial burden and unsustainable environment in Iran. Moreover, the effect of drought phenomenon in rural areas is more extensive, causing significant challenges to the rural economy in general and agricultural production in particular. A common strategy to manage drought is based on crisis management (ex-ante). However, for effective drought management, risk management seems to be more in line with drought early warning systems. This quantitative study used risk assessment, which is the function of two elements such as hazard (SPI and SDI indices) and vulnerability (exposure, sensitivity, and adaptive capacity). This study aims to build the foundations for drought early warning systems in limited resource areas such as Kermanshah Township in the northwestern part of Iran. The population of this study comprised of wheat farmers in which 293 farmers were selected using multistage cluster sampling method. In the next step, the drought risk map for Kermanshah Township was developed, which revealed that the majority of villages are at intense environmental risk. The result of this study has implications for drought management practitioners. For example, the results can aid policymakers in the design of an early warning system in order to reduce risk and thus empower farmers toward resilient farming.
Keywords: A1 Journal Article; Drought; Early warning system; Risk management; Vulnerability; Environmental risk; Resilient farming; Engineering Management (ENM) ;
DOI: 10.1016/j.ecolind.2020.106276
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“Conflict, fraud, and distrust in Ethiopian agricultural cooperatives”. Sebhatu KT, Gezahegn TW, Berhanu T, Maertens M, Van Passel S, D’Haese M, Journal of Co-operative Organization and Management 8, 100106 (2020). http://doi.org/10.1016/j.jcom.2020.100106
Abstract: Agricultural cooperatives are seen as an efficient way for smallholder farmers to create bargaining power in order to achieve poverty reduction and food security. However, the success of these cooperatives depends on their ability to maintain their social capital, which is at the core of collective action. A few studies have addressed issues of member participation, commitment, and trust, yet less is known about rural cooperatives in developing countries as a social organization. It is also unclear whether a relationship exists between cooperative size and the incidence of conflict, fraud, and distrust. Using unique data collected from 511 agricultural cooperatives in 12 districts of Tigray region in northern Ethiopia, this paper examines the effects of cooperative size on conflict, fraud, and distrust. We used instrumental variables (IV) probit estimation techniques, accounting for endogeneity of membership size, to confirm that cooperative size does affect the occurrence of conflict, fraud, and trust. The results also indicate that other influencing factors include: cooperative age, number of employees, payment of dividends based on transaction volume, and heterogeneity of member goals.
Keywords: A1 Journal Article; Agricultural cooperatives; Cooperative size; Conflict; Fraud; Distrust; Ethiopia; Engineering Management (ENM) ;
DOI: 10.1016/j.jcom.2020.100106
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“Climate-Smart Agriculture in the Northeast of Brazil: An Integrated Assessment of the Aquaponics Technology”. Finizola e Silva M, Van Passel S, Sustainability 12, 3734 (2020). http://doi.org/10.3390/su12093734
Abstract: The purpose of this study is to determine if aquaponic systems can reduce food insecurity in the semi-arid regions of Brazil and generate income for the beneficiaries. Aquaponics is a potentially sustainable way to produce food based on gardening, hydroponics and aquaculture. A case study, based on a project called Aquaponova, was developed. The aquaponic systems currently used in the project are non-commercial and designed for households with limited resources. The data based on six existing systems within this project were used to compare the costs and the benefits. The cost–benefit analysis covers four scenarios and three financing options. The results show that aquaponic systems have a large potential and can reduce food insecurity in semi-arid regions while generating income for the beneficiaries. Even if the system only produces 40% of the total estimated production, the system will still be feasible. However, the low opportunity cost of labour is an essential factor for obtaining these positive results. Moreover, the social benefits, such as a community spirit and the health benefits of the system, should not be underestimated.
Keywords: A1 Journal Article; aquaponics; Aquaponova; Brazil; semi-arid region; food insecurity; cost–benefit analysis; socio-economic approach; climate-smart agriculture; Engineering Management (ENM) ;
Impact Factor: 3.9
DOI: 10.3390/su12093734
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“A review on learning effects in prospective technology assessment”. Thomassen G, Van Passel S, Dewulf J, Renewable &, Sustainable Energy Reviews 130, 109937 (2020). http://doi.org/10.1016/j.rser.2020.109937
Abstract: Global environmental problems have urged the need for developing sustainable technologies. However, new technologies that enter the market have often higher economic costs and potentially higher environmental impacts than conventional technologies. This can be explained by learning effects: a production process that is performed for the first time runs less smooth than a production process that has been in operation for years. To obtain a fair estimation of the potential of a new technology, learning effects need to be included. A review on the current literature on learning effects was conducted in order to provide guidelines on how to include learning effects in prospective technology assessment. Based on the results of this review, five recommendations have been formulated and an integration of learning effects in the structure of prospective technology assessment has been proposed. These five recommendations include the combined use of learning effects on the component level and on the end product level; the combined use of learning effects on the technical, economic and environmental level; the combined use of extrapolated values and expert estimates; the combined use of learning-by-doing and learning-by-searching effects and; a tier-based method, including quality criteria, to calculate the learning effect. These five complementary strategies could lead to a clearer perspective on the environmental impact and cost structure of the new technology and a fairer comparison base with conventional technologies, potentially resulting in a faster adoption and a shorter time-to-market for sustainable technologies.
Keywords: A1 journal article; Learning effects; Life cycle assessment; Techno-economic assessment; Prospective technology assessment; Learning-by-doing; Learning curve; Progress rate; Experience curve; Engineering Management (ENM) ;
Impact Factor: 15.9
DOI: 10.1016/j.rser.2020.109937
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“Plasma Technology for CO2 Conversion: A Personal Perspective on Prospects and Gaps”. Bogaerts A, Centi G, Frontiers in energy research 8 (2020). http://doi.org/10.3389/fenrg.2020.00111
Abstract: There is increasing interest in plasma technology for CO2 conversion because it can operate at mild conditions and it can store fluctuating renewable electricity into
value-added compounds and renewable fuels. This perspective paper aims to provide a view on the future for non-specialists who want to understand the role of plasma
technology in the new scenario for sustainable and low-carbon energy and chemistry. Thus, it is prepared to give a personal view on future opportunities and challenges. First, we introduce the current state-of-the-art and the potential of plasma-based CO2 conversion. Subsequently, we discuss the challenges to overcome the current limitations and to apply plasma technology on a large scale. The final section discusses the general context and the potential benefits of plasma-based CO2 conversion for our life and the impact on climate change. It also includes a brief analysis on the future scenario for energy and chemical production, and how plasma technology may realize new paths for CO2 utilization.
Keywords: A1 Journal article; Engineering sciences. Technology; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 3.4
DOI: 10.3389/fenrg.2020.00111
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“Micelle-directed chiral seeded growth on anisotropic gold nanocrystals”. González-Rubio G, Mosquera J, Kumar V, Pedrazo-Tardajos A, Llombart P, Solís DM, Lobato I, Noya EG, Guerrero-Martínez A, Taboada JM, Obelleiro F, MacDowell LG, Bals S, Liz-Marzán LM, Science 368, 1472 (2020). http://doi.org/10.1126/science.aba0980
Abstract: Surfactant-assisted seeded growth of metal nanoparticles (NPs) can be engineered to produce anisotropic gold nanocrystals with high chiroptical activity through the templating effect of chiral micelles formed in the presence of dissymmetric cosurfactants. Mixed micelles adsorb on gold nanorods, forming quasihelical patterns that direct seeded growth into NPs with pronounced morphological and optical handedness. Sharp chiral wrinkles lead to chiral plasmon modes with high dissymmetry factors (~0.20). Through variation of the dimensions of chiral wrinkles, the chiroptical properties can be tuned within the visible and near-infrared electromagnetic spectrum. The micelle-directed mechanism allows extension to other systems, such as the seeded growth of chiral platinum shells on gold nanorods. This approach provides a reproducible, simple, and scalable method toward the fabrication of NPs with high chiral optical activity.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 56.9
Times cited: 187
DOI: 10.1126/science.aba0980
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“Plasma-Based N2Fixation into NOx: Insights from Modeling toward Optimum Yields and Energy Costs in a Gliding Arc Plasmatron”. Vervloessem E, Aghaei M, Jardali F, Hafezkhiabani N, Bogaerts A, Acs Sustainable Chemistry &, Engineering 8, 9711 (2020). http://doi.org/10.1021/acssuschemeng.0c01815
Abstract: Plasma technology provides a sustainable, fossil-free method for N2 fixation, i.e., the conversion of inert atmospheric N2 into valuable substances, such as NOx or ammonia. In this work, we present a novel gliding arc plasmatron at atmospheric pressure for NOx production at different N2/O2 gas feed ratios, offering a promising NOx yield of 1.5% with an energy cost of 3.6 MJ/mol NOx produced. To explain the underlying mechanisms, we present a chemical kinetics model, validated by experiments, which provides insight into the NOx formation pathways and into the ambivalent role of the vibrational kinetics. This allows us to pinpoint the factors limiting the yield and energy cost, which can help to further improve the process.
Keywords: A1 Journal article; Engineering sciences. Technology; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 8.4
DOI: 10.1021/acssuschemeng.0c01815
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“Crystal structure, vibrational, electrical, optical and DFT study of C₂H₁0N₂(IO₃)₂.HIO₃”. Ben Abdallah MA, Bacchi A, Parisini A, Canossa S, Bergamonti L, Balestri D, Kamoun S, Journal Of Molecular Structure 1215, 128254 (2020). http://doi.org/10.1016/J.MOLSTRUC.2020.128254
Abstract: The reinvestigation of the EDA-HIO3-H2O system using a different stoichiometric ratio gives rise to a new iodate salt C2H10N2(IO3)(2 center dot)HIO3 denoted as EBIMIA. In this study, we reported the structural properties of ethylenediammonium bis iodate mono iodic acid using X-ray powder and single crystal diffraction at room temperature. The Hirshfeld and the potential energy surface analysis reveal that I center dot center dot center dot O and N-H center dot center dot center dot O are the most noticeable interactions that took place inside the crystal and contribute to the cohesion and stability of the synthesized compound. The DSC measurement shows that this iodate salt undergoes two structural phase transitions, the first occurs at T = 290 K while the second occurs at T = 363 K. However, the dielectric analysis confirms only the second transition because it lies in the studied temperature domain 338-413K. Besides, the impedance data obey a circuit model consisting of a parallel combination of a bulk resistance and CPE. The frequency dispersion of the conductivity follows Jonscher's law and the charge carrier transport may be interpreted using the correlation barrier hopping mechanism (CBH). Finally, the electronic properties and the vibrational analysis of this novel iodate salt are studied using DFT and compared to the experimental data given by the FT-IR, Raman and UV-visible spectroscopies. (C) 2020 Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.8
DOI: 10.1016/J.MOLSTRUC.2020.128254
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“Tight-binding studio : a technical software package to find the parameters of tight-binding Hamiltonian”. Nakhaee M, Ketabi SA, Peeters FM, Computer Physics Communications 254, 107379 (2020). http://doi.org/10.1016/J.CPC.2020.107379
Abstract: We present the Tight-Binding Studio (TB Studio) software package that calculates the different parameters of a tight-binding Hamiltonian from a set of Bloch energy bands obtained from first principle theories such as density functional theory, Hartree-Fock calculations or semi-empirical band-structure theory. This will be helpful for scientists who are interested in studying electronic and optical properties of structures using Green's function theory within the tight-binding approximation. TB Studio is a cross-platform application written in C++ with a graphical user interface design that is user-friendly and easy to work with. This software is powered by Linear Algebra Package C interface library for solving the eigenvalue problems and the standard high performance OpenGL graphic library for real time plotting. TB Studio and its examples together with the tutorials are available for download from tight-binding.com. Program summary Program Title: Tight-Binding Studio Program Files doi:http://dx.doi.org/10.17632/j6x5mwzm2d.1 Licensing provisions: LGPL Programming language: C++ External routines: BLAS, LAPACK, LAPACKE, wxWidgets, OpenGL, MathGL Nature of problem: Obtaining Tight-Binding Hamiltonian from a set of Bloch energy bands obtained from first-principles calculations. Solution method: Starting from the simplified LCAO method, a tight-binding model in the two-center approximation is constructed. The Slater and Koster (SK) approach is used to calculate the parameters of the TB Hamiltonian. By using non-linear fitting approaches the optimal values of the SK parameters are obtained such that the TB energy eigenvalues are as close as possible to those from first-principles calculations. We obtain the expression for the Hamiltonian and the overlap matrix elements between the different orbitals of the different atoms in an orthogonal or non-orthogonal basis set. (C) 2020 Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 6.3
Times cited: 27
DOI: 10.1016/J.CPC.2020.107379
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“Estimating the urban soil information gap using exhaustive land cover data: The example of Flanders, Belgium”. Van De Vijver E, Delbecque N, Verdoodt A, Seuntjens P, Geoderma 372, 114371 (2020). http://doi.org/10.1016/J.GEODERMA.2020.114371
Abstract: Human activities related to urbanization and industrialization have established a vast territory of urban soil worldwide. On traditional soil maps, urban and industrial areas usually appear as blind spots as they were beyond the interest of national soil survey campaigns. Furthermore, these soil maps are likely already outdated with respect to urban soil due to rapid urban expansion in recent decades. This research aims to evaluate the use of land cover data to estimate the urban soil information gap considering the highly urbanized region of Flanders, Belgium, as a case study. The current extent and spatial distribution of anthropogenic urban soil (1) was estimated through reclassification of recently acquired (2012) exhaustive land cover data, discriminating three qualitative likelihood levels (high-intermediate-low) of anthropogenic influence by urbanization, and (2) compared with its occurrence as represented by the 'Technosols/Not Surveyed area' in the legacy soil map of Belgium, as this map unit best matches with the likelihood for anthropogenic urban soil at the time of the National Soil Survey conducted between end 1940s and mid 1970s. The proposed reclassification of the land cover map resulted in 16.3% and 16.7% of Flanders' total area that corresponds with a high and intermediate likelihood for anthropogenic urban soil, which highlights the underestimation of the anthropogenic urban soil extent as represented by the 'Technosol/Not Surveyed' unit in the legacy soil map (only 13.7%). Moreover, a more realistic spatial pattern of anthropogenic urban soil occurrence was obtained, providing an improved basis for urban soil spatial analysis studies. The produced anthropogenic urban soil likelihood map therefore presents a useful supporting tool for coordinating future soil surveys in urban environments.
Keywords: A1 Journal article; Sustainable Energy, Air and Water Technology (DuEL)
Impact Factor: 6.1
Times cited: 2
DOI: 10.1016/J.GEODERMA.2020.114371
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“Characterization of radioactive particles from the Dounreay nuclear reprocessing facility”. Byrnes I, Lind OC, Hansen EL, Janssens K, Salbu B, Science Of The Total Environment 727, 138488 (2020). http://doi.org/10.1016/J.SCITOTENV.2020.138488
Abstract: Radioactive particles originating from nuclear fuel reprocessing at the United Kingdom Atomic Energy Authority's Dounreay Facility were inadvertently released to the environment in the late 1950s to 1970s and have subsequently been found on site grounds and local beaches. Previous assessments of risk associated with encountering a particle have been based on conservative assumptions related to particle composition and speciation. To reduce uncertainties associated with environmental impact assessments from Dounreay particles, further characterization is relevant. Results of particles available for this study showed variation between Dounreay Fast Reactor (DFR) and Materials Test Reactor (MTR) particles, reflecting differences in fuel design, release scenarios, and subsequent environmental influence. Analyses of DFR particles showed they are small (100-300 mu m) and contain spatially correlated U and Nb. Molybdenum, part of the DFR fuel, was identified at atomic concentrations below 1%. Based on SR-based micrometer-scale X-ray Absorption Near Edge Structure spectroscopy (mu-XANES), U may be present as U (IV), and, based on a measured Nb/U atom ratio of similar to 2, stoichiometric considerations are commensurable with the presence of UNb2O7. The MTR particles were larger (740-2000 mu m) and contained U and Al inhomogeneously distributed. Neodymium (Nd) was identified in atomic concentrations of around 1-2%, suggesting it was part of the fuel design. The presence of U(IV) in MTR particles, as indicated by mu-XANES analysis, may be related to oxidation of particle surfaces, as could be expected due to corrosion of UAlx fuel particles in air. High U-235/U-238 atom ratios in individual DFR (3.2 +/- 0.8) and MTR (2.6 +/- 0.4) particles reflected the presence of highly enriched uranium. The DFR particles featured lower Cs-137 activity levels (2.00-9.58 kBq/particle) than the MTR (43.2-641 kBq Cs-137/particle) particles. The activities of the dose contributing radionuclides Sr-90/Y-90 were proportional to Cs-137 (Sr-90/Cs-137 activity ratio approximate to 0.8) and particle activities were roughly proportional to the size. Based on direct beta measurements, gamma spectrometry, and the VARSKIN6 model, contact dose rates were calculated to be approximately 74 mGy/h for the highest activity MTR particle, in agreement with previously published estimates. (C) 2020 The Authors. Published by Elsevier B.V.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 9.8
Times cited: 1
DOI: 10.1016/J.SCITOTENV.2020.138488
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“Compatibility of Zr₂AlC MAX phase-based ceramics with oxygen-poor, static liquid lead-bismuth eutectic”. Tunca B, Lapauw T, Callaert C, Hadermann J, Delville R, Caspi E'ad N, Dahlqvist M, Rosen J, Marshal A, Pradeep KG, Schneider JM, Vleugels J, Lambrinou K, Corrosion Science 171, 108704 (2020). http://doi.org/10.1016/J.CORSCI.2020.108704
Abstract: This work investigates the compatibility of Zr2AlC MAX phase-based ceramics with liquid LBE, and proposes a mechanism to explain the observed local Zr2AlC/LBE interaction. The ceramics were exposed to oxygen-poor (C-O <= 2.2 x 10(-10) mass%), static liquid LBE at 500 degrees C for 1000 h. A new Zr-2(Al,Bi,Pb)C MAX phase solid solution formed in-situ in the LBE-affected Zr2AlC grains. Out-of-plane ordering was favorable in the new solid solution, whereby A-layers with high and low-Bi/Pb contents alternated in the crystal structure, in agreement with first-principles calculations. Bulk Zr-2(Al,Bi,Pb)C was synthesized by reactive hot pressing to study the crystal structure of the solid solution by neutron diffraction.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 8.3
Times cited: 3
DOI: 10.1016/J.CORSCI.2020.108704
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“Spin textures in chiral magnetic monolayers with suppressed nearest-neighbor exchange”. Menezes RM, de Souza Silva CC, Milošević, MV, Physical Review B 101, 214429 (2020). http://doi.org/10.1103/PHYSREVB.101.214429
Abstract: High tunability of two-dimensional magnetic materials (by strain, gating, heterostructuring, or otherwise) provides unique conditions for studying versatile magnetic properties and controlling emergent magnetic phases. Expanding the scope of achievable magnetic phenomena in such materials is important for both fundamental and technological advances. Here we perform atomistic spin-dynamics simulations to explore the (chiral) magnetic phases of atomic monolayers in the limit of suppressed first-neighbors exchange interaction. We report the rich phase diagram of exotic magnetic configurations, obtained for both square and honeycomb lattice symmetries, comprising coexistence of ferromagnetic and antiferromagnetic spin cycloids, as well as multiple types of magnetic skyrmions. We perform a minimum-energy path analysis for the skyrmion collapse to evaluate the stability of such topological objects and reveal that magnetic monolayers could be good candidates to host the antiferromagnetic skyrmions that are experimentally evasive to date.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.7
Times cited: 1
DOI: 10.1103/PHYSREVB.101.214429
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“Tuning the intrinsic anisotropy with disorder in the CaKFE₄As₄, superconductor”. Torsello D, Ummarino GA, Bekaert J, Gozzelino L, Gerbaldo R, Tanatar MA, Canfield PC, Prozorov R, Ghigo G, Physical Review Applied 13, 064046 (2020). http://doi.org/10.1103/PHYSREVAPPLIED.13.064046
Abstract: We report on the anisotropy of the London penetration depth of CaKFe4As4, discussing how it relates to its electronic structure and how it modifies under introduction of disorder, both chemically induced (by Ni substitution) and irradiation induced (by 3.5-MeV protons). Indeed, CaKFe4As4 is particularly suitable for the study of fundamental superconducting properties due to its stoichiometric composition, exhibiting clean-limit behavior in the pristine samples and having a fairly high critical temperature, T-c approximate to 35 K. The London penetration depth lambda(L) is measured with a microwave-coplanar-resonator technique that allows us to deconvolve the anisotropic contributions lambda(L,ab) and lambda(L,c) and obtain the anisotropy parameter gamma(lambda) = lambda(L,c)/lambda(L,ab). The gamma(lambda) (T) found for the undoped pristine sample is in good agreement with previous literature and is here compared to ab initio density-functional-theory and Eliashberg calculations. The dependence of gamma(lambda) (T) on both chemical and irradiation-induced disorder is discussed to highlight which method is more suitable to decrease the direction dependence of the electromagnetic properties while maintaining a high critical temperature. Lastly, the relevance of an intrinsic anisotropy such as gamma(lambda) on application-related anisotropic parameters (critical current, pinning) is discussed in light of the recent employment of CaKFe4As4 in the production of wires.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 4.6
Times cited: 4
DOI: 10.1103/PHYSREVAPPLIED.13.064046
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“Functionalization of single-layer TaS₂, and formation of ultrathin Janus structures”. Kahraman Z, Yagmurcukardes M, Sahin H, Journal Of Materials Research 35, 1397 (2020). http://doi.org/10.1557/JMR.2020.64
Abstract: Ab initio calculations are performed to investigate the structural, vibrational, electronic, and piezoelectric properties of functionalized single layers of TaS2. We find that single-layer TaS2 is a suitable host material for functionalization via fluorination and hydrogenation. The one-side fluorinated (FTaS2) and hydrogenated (HTaS2) single layers display indirect gap semiconducting behavior in contrast to bare metallic TaS2. On the other hand, it is shown that as both surfaces of TaS2 are saturated anti-symmetrically, the formed Janus structure is a dynamically stable metallic single layer. In addition, it is revealed that out-of-plane piezoelectricity is created in all anti-symmetric structures. Furthermore, the Janus-type single-layer has the highest specific heat capacity to which longitudinal and transverse acoustical phonon modes have contribution at low temperatures. Our findings indicate that single-layer TaS2 is suitable for functionalization via H and F atoms that the formed, anti-symmetric structures display distinctive electronic, vibrational, and piezoelectric properties.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.7
Times cited: 1
DOI: 10.1557/JMR.2020.64
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“Doping-dependent switch from one- to two-component superfluidity in coupled electron-hole van der Waals heterostructures”. Conti S, Van der Donck M, Perali A, Peeters FM, Neilson D, Physical Review B 101, 220504 (2020). http://doi.org/10.1103/PHYSREVB.101.220504
Abstract: The hunt for high-temperature superfluidity has received new impetus from the discovery of atomically thin stable materials. Electron-hole superfluidity in coupled MoSe2-WSe2 monolayers is investigated using a mean-field multiband model that includes band splitting caused by strong spin-orbit coupling. This splitting leads to a large energy misalignment of the electron and hole bands which is strongly modified by interchanging the doping of the monolayers. The choice of doping determines if the superfluidity is tunable from one to two components.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.7
Times cited: 12
DOI: 10.1103/PHYSREVB.101.220504
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“Terahertz optical Hall effect in monolayer MoS₂, in the presence of proximity-induced interactions”. Zhao XN, Xu W, Xiao YM, Liu J, Van Duppen B, Peeters FM, Physical Review B 101, 245412 (2020). http://doi.org/10.1103/PHYSREVB.101.245412
Abstract: The effect of proximity-induced interactions such as Rashba spin-orbit coupling (SOC) and exchange interaction on the electronic and optical properties of n-type monolayer (ML) MoS2 is investigated. We predict and demonstrate that the Rashba SOC can induce an in-plane spin splitting with terahertz (THz) energy, while the exchange interaction lifts the energy degeneracy in different valleys. Thus, spin polarization can be achieved in an n-type ML MoS2 and valley Hall or optical Hall effect can be observed using linearly polarized THz radiation. In such a case, the transverse optical conductivity sigma(xy) (omega) results from spin-flip transition within spin-split conduction bands and from the fact that contributions from electrons with different spin orientations in different valleys can no longer be canceled out. Interestingly, we find that for fixed effective Zeeman field (or exchange interaction) the lowest spin-split conduction band in ML MoS2 can be tuned from one in the K valley to another one in the K' valley by varying the Rashba parameter lambda(R). Therefore, by changing lambda(R) we can turn the sign of the spin polarization and Im sigma(xy) (omega) from positive to negative. Moreover, we find that the dominant contribution of the selection rules to sigma(xx)(omega) is from electrons in the K valley and to sigma(xy) (omega) is from electrons in the K' valley. These important and interesting theoretical findings can be helpful to experimental observation of the optical Hall effect in valleytronic systems using linearly polarized THz radiation fields.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.7
Times cited: 8
DOI: 10.1103/PHYSREVB.101.245412
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“Spinodal decomposition in alkali feldspar studied by atom probe tomography”. Petrishcheva E, Tiede L, Schweinar K, Habler G, Li C, Gault B, Abart R, Physics And Chemistry Of Minerals 47, Unsp 30 (2020). http://doi.org/10.1007/S00269-020-01097-4
Abstract: We used atom probe tomography to complement electron microscopy for the investigation of spinodal decomposition in alkali feldspar. To this end, gem-quality alkali feldspar of intermediate composition with a mole fraction of a(K) = 0.43 of the K end-member was prepared from Madagascar orthoclase by ion-exchange with (NaK)Cl molten salt. During subsequent annealing at 550 degrees C and close to ambient pressure the ion-exchanged orthoclase unmixed producing a coherent lamellar intergrowth of Na-rich and K-rich lamellae. The chemical separation was completed, and equilibrium Na-K partitioning between the different lamellae was attained within four days, which was followed by microstructural coarsening. After annealing for 4 days, the wavelength of the lamellar microstructure was approximate to 17 nm and it increased to approximate to 30 nm after annealing for 16 days. The observed equilibrium compositions of the Na-rich and K-rich lamellae are in reasonable agreement with an earlier experimental determination of the coherent solvus. The excess energy associated with compositional gradients at the lamellar interfaces was quantified from the initial wavelength of the lamellar microstructure and the lamellar compositions as obtained from atom probe tomography using the Cahn-Hilliard theory. The capability of atom probe tomography to deliver quantitative chemical compositions at nm resolution opens new perspectives for studying the early stages of exsolution. In particular, it helps to shed light on the phase relations in nm scaled coherent intergrowth.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 1.4
DOI: 10.1007/S00269-020-01097-4
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“Nanocrystals of lead chalcohalides : a series of kinetically trapped metastable nanostructures”. Toso S, Akkerman QA, Martin-Garcia B, Prato M, Zito J, Infante I, Dang Z, Moliterni A, Giannini C, Bladt E, Lobato I, Ramade J, Bals S, Buha J, Spirito D, Mugnaioli E, Gemmi M, Manna L, Journal Of The American Chemical Society 142, 10198 (2020). http://doi.org/10.1021/JACS.0C03577
Abstract: We report the colloidal synthesis of a series of surfactant-stabilized lead chalcohalide nanocrystals. Our work is mainly focused on Pb4S3Br2, a chalcohalide phase unknown to date that does not belong to the ambient-pressure PbS-PbBr2 phase diagram. The Pb4S3Br2 nanocrystals herein feature a remarkably narrow size distribution (with a size dispersion as low as 5%), a good size tunability (from 7 to similar to 30 nm), an indirect bandgap, photoconductivity (responsivity = 4 +/- 1 mA/W), and stability for months in air. A crystal structure is proposed for this new material by combining the information from 3D electron diffraction and electron tomography of a single nanocrystal, X-ray powder diffraction, and density functional theory calculations. Such a structure is closely related to that of the recently discovered high-pressure chalcohalide Pb4S3I2 phase, and indeed we were able to extend our synthesis scheme to Pb4S3I2 colloidal nanocrystals, whose structure matches the one that has been published for the bulk. Finally, we could also prepare nanocrystals of Pb3S2Cl2, which proved to be a structural analogue of the recently reported bulk Pb3Se2Br2 phase. It is remarkable that one high-pressure structure (for Pb4S3I2) and two metastable structures that had not yet been reported (for Pb4S3Br2 and Pb3S2Cl2) can be prepared on the nanoscale by wet-chemical approaches. This highlights the important role of colloidal chemistry in the discovery of new materials and motivates further exploration into metal chalcohalide nanocrystals.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 15
Times cited: 32
DOI: 10.1021/JACS.0C03577
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“Exciton g factors of van der Waals heterostructures from first-principles calculations”. Wozniak T, Faria PE Jr, Seifert G, Chaves A, Kunstmann J, Physical Review B 101, 235408 (2020). http://doi.org/10.1103/PHYSREVB.101.235408
Abstract: External fields are a powerful tool to probe optical excitations in a material. The linear energy shift of an excitation in a magnetic field is quantified by its effective g factor. Here we show how exciton g factors and their sign can be determined by converged first-principles calculations. We apply the method to monolayer excitons in semiconducting transition metal dichalcogenides and to interlayer excitons in MoSe2/WSe2 heterobilayers and obtain good agreement with recent experimental data. The precision of our method allows us to assign measured g factors of optical peaks to specific transitions in the band structure and also to specific regions of the samples. This revealed the nature of various, previously measured interlayer exciton peaks. We further show that, due to specific optical selection rules, g factors in van der Waals heterostructures are strongly spin and stacking-dependent. The calculation of orbital angular momenta requires the summation over hundreds of bands, indicating that for the considered two-dimensional materials the basis set size is a critical numerical issue. The presented approach can potentially be applied to a wide variety of semiconductors.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.7
DOI: 10.1103/PHYSREVB.101.235408
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“Boosting Monte Carlo simulations of spin glasses using autoregressive neural networks”. McNaughton B, Milošević, MV, Perali A, Pilati S, Physical Review E 101, 053312 (2020). http://doi.org/10.1103/PHYSREVE.101.053312
Abstract: The autoregressive neural networks are emerging as a powerful computational tool to solve relevant problems in classical and quantum mechanics. One of their appealing functionalities is that, after they have learned a probability distribution from a dataset, they allow exact and efficient sampling of typical system configurations. Here we employ a neural autoregressive distribution estimator (NADE) to boost Markov chain Monte Carlo (MCMC) simulations of a paradigmatic classical model of spin-glass theory, namely, the two-dimensional Edwards-Anderson Hamiltonian. We show that a NADE can be trained to accurately mimic the Boltzmann distribution using unsupervised learning from system configurations generated using standard MCMC algorithms. The trained NADE is then employed as smart proposal distribution for the Metropolis-Hastings algorithm. This allows us to perform efficient MCMC simulations, which provide unbiased results even if the expectation value corresponding to the probability distribution learned by the NADE is not exact. Notably, we implement a sequential tempering procedure, whereby a NADE trained at a higher temperature is iteratively employed as proposal distribution in a MCMC simulation run at a slightly lower temperature. This allows one to efficiently simulate the spin-glass model even in the low-temperature regime, avoiding the divergent correlation times that plague MCMC simulations driven by local-update algorithms. Furthermore, we show that the NADE-driven simulations quickly sample ground-state configurations, paving the way to their future utilization to tackle binary optimization problems.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.366
Times cited: 15
DOI: 10.1103/PHYSREVE.101.053312
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“High-voltage cycling induced thermal vulnerability in LiCoO₂, cathode : cation loss and oxygen release driven by oxygen vacancy migration”. Sun C, Liao X, Xia F, Zhao Y, Zhang L, Mu S, Shi S, Li Y, Peng H, Van Tendeloo G, Zhao K, Wu J, Acs Nano 14, 6181 (2020). http://doi.org/10.1021/ACSNANO.0C02237
Abstract: The release of the lattice oxygen due to the thermal degradation of layered lithium transition metal oxides is one of the major safety concerns in Li-ion batteries. The oxygen release is generally attributed to the phase transitions from the layered structure to spinel and rocksalt structures that contain less lattice oxygen. Here, a different degradation pathway in LiCoO2 is found, through oxygen vacancy facilitated cation migration and reduction. This process leaves undercoordinated oxygen that gives rise to oxygen release while the structure integrity of the defect-free region is mostly preserved. This oxygen release mechanism can be called surface degradation due to the kinetic control of the cation migration but has a slow surface to bulk propagation with continuous loss of the surface cation ions. It is also strongly correlated with the high-voltage cycling defects that end up with a significant local oxygen release at low temperatures. This work unveils the thermal vulnerability of high-voltage Li-ion batteries and the critical role of the surface fraction as a general mitigating approach.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 17.1
Times cited: 8
DOI: 10.1021/ACSNANO.0C02237
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“A demonstration of donor passivation through direct formation of V-As-i complexes in As-doped Ge1-XSnx”. Khanam A, Vohra A, Slotte J, Makkonen I, Loo R, Pourtois G, Vandervorst W, Journal Of Applied Physics 127, 195703 (2020). http://doi.org/10.1063/5.0003999
Abstract: Positron annihilation spectroscopy in the Doppler and coincidence Doppler mode was applied on Ge1 xSnx epitaxial layers, grown by chemical vapor deposition with different total As concentrations (1019-1021 cm3), high active As concentrations (1019 cm3), and similar Sn concentrations (5.9%-6.4%). Positron traps are identified as mono-vacancy complexes. Vacancy-As complexes, V-Asi, formed during the growth were studied to deepen the understanding of the electrical passivation of the Ge1 xSnx:As epilayers. Larger monovacancy complexes, V-Asi (i 2), are formed as the As doping increases. The total As concentration shows a significant impact on the saturation of the number of As atoms (i 1/4 4) around the vacancies in the sample epilayers. The presence of V-Asi complexes decreases the dopant activation in the Ge1 xSnx:As epilayers. Furthermore, the presence of Sn failed to hinder the formation of larger V-Asi complexes and thus failed to reduce the donor-deactivation.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 3.2
DOI: 10.1063/5.0003999
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“Substrate dependent terahertz response of monolayer WS₂”. Dong HM, Tao ZH, Li LL, Huang F, Xu W, Peeters FM, Applied Physics Letters 116, 1 (2020). http://doi.org/10.1063/5.0006617
Abstract: We investigate experimentally the terahertz (THz) optoelectronic properties of monolayer (ML) tungsten disulfide (WS2) placed on different substrates using THz time-domain spectroscopy (TDS). We find that the THz optical response of n-type ML WS2 depends sensitively on the choice of the substrate. This dependence is found to be a consequence of substrate induced charge transfer, extra scattering centers, and electronic localization. Through fitting the experimental results with the Drude-Smith formula, we can determine the key sample parameters (e.g., the electronic relaxation time, electron density, and electronic localization factor) of ML WS2 on different substrates. The temperature dependence of these parameters is examined. Our results show that the THz TDS technique is an efficient non-contact method that can be utilized to characterize and investigate the optoelectronic properties of nano-devices based on ML WS2.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 4
Times cited: 17
DOI: 10.1063/5.0006617
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