“Identification of a Robust and Durable FeN4CxCatalyst for ORR in PEM Fuel Cells and the Role of the Fifth Ligand”. Nematollahi P, Barbiellini B, Bansil A, Lamoen D, Qingying J, Mukerjee S, Neyts EC, ACS catalysis , 7541 (2022). http://doi.org/10.1021/acscatal.2c01294
Abstract: Although recent studies have advanced the understanding of pyrolyzed
Fe−N−C materials as oxygen reduction reaction (ORR) catalysts, the atomic and
electronic structures of the active sites and their detailed reaction mechanisms still remain unknown. Here, based on first-principles density functional theory (DFT) computations, we discuss the electronic structures of three FeN4 catalytic centers with different local topologies of the surrounding C atoms with a focus on unraveling the mechanism of their ORR activity in acidic electrolytes. Our study brings back a forgotten, synthesized pyridinic Fe−N coordinate to the community’s attention, demonstrating that this catalyst can exhibit excellent activity for promoting direct four-electron ORR through the addition of a fifth ligand such as −NH2, −OH, and −SO4. We also identify sites with good stability properties through the combined use of our DFT calculations and Mössbauer spectroscopy data.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 12.9
DOI: 10.1021/acscatal.2c01294
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“Thermal Activation of Gold Atom Diffusion in Au@Pt Nanorods”. Pedrazo-Tardajos A, Arslan Irmak E, Kumar V, Sánchez-Iglesias A, Chen Q, Wirix M, Freitag B, Albrecht W, Van Aert S, Liz-Marzán LM, Bals S, ACS nano (2022). http://doi.org/10.1021/acsnano.2c02889
Abstract: Understanding the thermal stability of bimetallic nanoparticles is of vital importance to preserve their functionalities during their use in a variety of applications. In contrast to well-studied bimetallic systems such as Au@Ag, heat-induced morphological and compositional changes in Au@Pt nanoparticles are insufficiently understood, even though Au@Pt is an important material for catalysis. To investigate the thermal instability of Au@Pt nanorods at temperatures below their bulk melting point, we combined in situ heating with two- and three-dimensional electron microscopy techniques, including three-dimensional energy-dispersive X-ray spectroscopy. The experimental results were used as input for molecular dynamics simulations, to unravel the mechanisms behind the morphological transformation of Au@Pt core–shell nanorods. We conclude that thermal stability is influenced not only by the degree of coverage of Pt on Au but also by structural details of the Pt shell.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 17.1
Times cited: 8
DOI: 10.1021/acsnano.2c02889
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“Atomic-scale detection of individual lead clusters confined in Linde Type A zeolites”. Fatermans J, Romolini G, Altantzis T, Hofkens J, Roeffaers MBJ, Bals S, Van Aert S, Nanoscale (2022). http://doi.org/10.1039/D2NR01819E
Abstract: Structural analysis of metal clusters confined in nanoporous materials is typically performed by X-ray-driven techniques. Although X-ray analysis has proved its strength in the characterization of metal clusters, it provides averaged structural information. Therefore, we here present an alternative workflow for bringing the characterization of confined metal clusters towards the local scale. This workflow is based on the combination of aberration-corrected transmission electron microscopy (TEM), TEM image simulations, and powder X-ray diffraction (XRD) with advanced statistical techniques. In this manner, we were able to characterize the clustering of Pb atoms in Linde Type A (LTA) zeolites with Pb loadings as low as 5 wt%. Moreover, individual Pb clusters could be directly detected. The proposed methodology thus enables a local-scale characterization of confined metal clusters in zeolites. This is important for further elucidation of the connection between the structure and the physicochemical properties of such systems.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT); Applied Electrochemistry & Catalysis (ELCAT)
Impact Factor: 6.7
Times cited: 2
DOI: 10.1039/D2NR01819E
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“Catalyst-free single-step plasma reforming of CH4 and CO2 to higher value oxygenates under ambient conditions”. Wang Y, Chen Y, Harding J, He H, Bogaerts A, Tu X, Chemical Engineering Journal 450, 137860 (2022). http://doi.org/10.1016/j.cej.2022.137860
Abstract: Direct conversion of CH4 and CO2 to liquid fuels and chemicals under mild conditions is appealing for biogas conversion and utilization but challenging due to the inert nature of both gases. Herein, we report a promising plasma process for the catalyst-free single-step conversion of CH4 and CO2 into higher value oxygenates (i.e., methanol, acetic acid, ethanol, and acetone) at ambient pressure and room temperature using a water-cooled dielectric barrier discharge (DBD) reactor, with methanol being the main liquid product. The distribution of liquid products could be tailored by tuning the discharge power, reaction temperature and residence time. Lower discharge powers (10–15 W) and reaction temperatures (5–20 ◦ C) were favourable for the production of liquid products, achieving the highest methanol selectivity of 43% at 5 ◦ C and 15 W. A higher discharge power and reaction temperature, on the other hand, produced more gaseous products, particularly H2 (up to 26% selectivity) and CO (up to 33% selectivity). In addition, varying these process parameters (discharge power, reaction temperature and residence time) resulted in a simultaneous change in key discharge properties, such as mean electron energy (Ee), electron density (ne) and specific energy input (SEI), all of which are essential determiners of plasma chemical reactions. According to the results of artificial neural network (ANN) models, the relative importance of these process parameters and key discharge indicators on reaction performance follows the order: discharge power > reaction temperature > residence time, and SEI > ne > Ee, respectively. This work provides new insights into the contributions and tuning mechanism of multiple parameters for optimizing the reaction performance (e.g., liquid production) in the plasma gas conversion process.
Keywords: A1 Journal article; Engineering sciences. Technology; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 15.1
DOI: 10.1016/j.cej.2022.137860
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“Cytoglobin inhibits non-thermal plasma-induced apoptosis in melanoma cells through regulation of the NRF2-mediated antioxidant response”. De Backer J, Lin A, Berghe WV, Bogaerts A, Hoogewijs D, Redox Biology 55, 102399 (2022). http://doi.org/10.1016/j.redox.2022.102399
Abstract: Melanoma arises from pigment-producing cells called melanocytes located in the basal layers of the epidermis of the skin. Cytoglobin (CYGB) is a ubiquitously expressed hexacoordinated globin that is highly enriched in melanocytes and frequently downregulated during melanomagenesis. Previously, we showed that non-thermal plasma (NTP)-produced reactive oxygen and nitrogen species (RONS) lead to the formation of an intra molecular disulfide bridge that would allow CYGB to function as a redox-sensitive protein. Here, we investigate the cytotoxic effect of indirect NTP treatment in two melanoma cell lines with divergent endogenous CYGB expression levels, and we explore the role of CYGB in determining treatment outcome. Our findings are consistent with previous studies supporting that NTP cytotoxicity is mediated through the production of RONS and leads to apoptotic cell death in melanoma cells. Furthermore, we show that NTP-treated solutions elicit an antioxidant response through the activation of nuclear factor erythroid 2–related factor 2 (NRF2). The knock down and overexpression of CYGB respectively sensitizes and protects melanoma cells from RONS-induced apoptotic cell death. The presence of CYGB enhances heme-oxygenase 1 (HO-1) and NRF2 protein expression levels, whereas the absence impairs their expression. Moreover, analysis of the CYGB-dependent transcriptome demonstrates the tumor suppressor long non-coding RNA maternally expressed 3 (MEG3) as a hitherto unde scribed link between CYGB and NRF2. Thus, the presence of CYGB, at least in melanoma cells, seems to play a central role in determining the therapeutic outcome of RONS-inducing anticancer therapies, like NTP-treated solutions, possessing both tumor-suppressive and oncogenic features. Hence, CYGB expression could be of in terest either as a biomarker or as a candidate for future targeted therapies in melanoma.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT); Proteinscience, proteomics and epigenetic signaling (PPES)
Impact Factor: 11.4
DOI: 10.1016/j.redox.2022.102399
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“Sustainability analysis of methane-to-hydrogen-to-ammonia conversion by integration of high-temperature plasma and non-thermal plasma processes”. Osorio-Tejada J, van't Veer K, Long NVD, Tran NN, Fulcheri L, Patil BS, Bogaerts A, Hessel V, Energy Conversion And Management 269, 116095 (2022). http://doi.org/10.1016/j.enconman.2022.116095
Abstract: The Covid era has made us aware of the need for resilient, self-sufficient, and local production. We are likely willing to pay an extra price for that quality. Ammonia (NH3) synthesis accounts for 2 % of global energy production and is an important point of attention for the development of green energy technologies. Therefore, we propose a thermally integrated process for H2 production and NH3 synthesis using plasma technology, and we evaluate its techno-economic performance and CO2 footprint by life cycle assessment (LCA). The key is to integrate energy-wise a high-temperature plasma (HTP) process, with a (low-temperature) non-thermal plasma (NTP) process and to envision their joint economic potential. This particularly means raising the temperature of the NTP process, which is typically below 100 ◦ C, taking advantage of the heat released from the HTP process. For that purpose, we proposed the integrated process and conducted chemical kinetics simulations in the NTP section to determine the thermodynamically feasible operating window of this novel combined plasma process. The results suggest that an NH3 yield of 2.2 mol% can be attained at 302 ◦ C at an energy yield of 1.1 g NH3/kWh. Cost calculations show that the economic performance is far from commercial, mainly because of the too low energy yield of the NTP process. However, when we base our costs on the best literature value and plausible future scenarios for the NTP energy yield, we reach a cost prediction below 452 $/tonne NH3, which is competitive with conventional small-scale Haber-Bosch NH3 synthesis for distributed production. In addition, we demonstrate that biogas can be used as feed, thus allowing the proposed integrated reactor concept to be part of a biogas-to-ammonia circular concept. Moreover, by LCA we demonstrate the environmental benefits of the proposed plant, which could cut by half the carbon emissions when supplied by photovoltaic electricity, and even invert the carbon balance when supplied by wind power due to the avoided emissions of the carbon black credits.
Keywords: A1 Journal article; Engineering sciences. Technology; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 10.4
DOI: 10.1016/j.enconman.2022.116095
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“Element Specific Atom Counting at the Atomic Scale by Combining High Angle Annular Dark Field Scanning Transmission Electron Microscopy and Energy Dispersive X‐ray Spectroscopy”. De Backer A, Zhang Z, van den Bos KHW, Bladt E, Sánchez‐Iglesias A, Liz‐Marzán LM, Nellist PD, Bals S, Van Aert S, Small methods , 2200875 (2022). http://doi.org/10.1002/smtd.202200875
Abstract: A new methodology is presented to count the number of atoms in multimetallic nanocrystals by combining energy dispersive X-ray spectroscopy (EDX) and high angle annular dark field scanning transmission electron microscopy (HAADF STEM). For this purpose, the existence of a linear relationship between the incoherent HAADF STEM and EDX images is exploited. Next to the number of atoms for each element in the atomic columns, the method also allows quantification of the error in the obtained number of atoms, which is of importance given the noisy nature of the acquired EDX signals. Using experimental images of an Au@Ag core–shell nanorod, it is demonstrated that 3D structural information can be extracted at the atomic scale. Furthermore, simulated data of an Au@Pt core–shell nanorod show the prospect to characterize heterogeneous nanostructures with adjacent atomic numbers.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 12.4
Times cited: 5
DOI: 10.1002/smtd.202200875
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“Enhancing CO2 conversion with plasma reactors in series and O2 removal”. Vertongen R, Trenchev G, Van Loenhout R, Bogaerts A, Journal Of Co2 Utilization 66, 102252 (2022). http://doi.org/10.1016/j.jcou.2022.102252
Abstract: In this work, we take a crucial step towards the industrial readiness of plasma-based CO2 conversion. We present a stepwise method to study plasma reactors in series as a first approach to a recycle flow. By means of this procedure, the CO2 conversion is enhanced by a factor of 3, demonstrating that a single-pass plasma treatment performs far below the optimal capacity of the reactor. Furthermore, we explore the effect of O2 in the mixture with our flexible procedure. Addition of O2 in the mixture has a clear detrimental effect on the conversion, in agreement with other experiments in atmospheric pressure plasmas. O2 removal is however highly beneficial, demonstrating a conversion per pass that is 1.6 times higher than the standard procedure. Indeed, extracting one of the products prevents recombination reactions. Based on these insights, we discuss opportunities for further improvements, especially in the field of specialised separation techniques.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 7.7
DOI: 10.1016/j.jcou.2022.102252
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“The pro- and anti-tumoral properties of gap junctions in cancer and their role in therapeutic strategies”. Oliveira MC, Verswyvel H, Smits E, Cordeiro RM, Bogaerts A, Lin A, Redox Biology 57, 102503 (2022). http://doi.org/10.1016/j.redox.2022.102503
Abstract: Gap junctions (GJs), essential structures for cell-cell communication, are made of two hemichannels (commonly called connexons), one on each adjacent cell. Found in almost all cells, GJs play a pivotal role in many physiological and cellular processes, and have even been linked to the progression of diseases, such as cancer. Modulation of GJs is under investigation as a therapeutic strategy to kill tumor cells. Furthermore, GJs have also been studied for their key role in activating anti-cancer immunity and propagating radiation- and oxidative stress-induced cell death to neighboring cells, a process known as the bystander effect. While, gap junction (GJ)based therapeutic strategies are being developed, one major challenge has been the paradoxical role of GJs in both tumor progression and suppression, based on GJ composition, cancer factors, and tumoral context. Therefore, understanding the mechanisms of action, regulation, and the dual characteristics of GJs in cancer is critical for developing effective therapeutics. In this review, we provide an overview of the current under standing of GJs structure, function, and paradoxical pro- and anti-tumoral role in cancer. We also discuss the treatment strategies to target these GJs properties for anti-cancer responses, via modulation of GJ function.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT); Center for Oncological Research (CORE)
Impact Factor: 11.4
DOI: 10.1016/j.redox.2022.102503
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“Molecular understanding of the possible mechanisms of oligosaccharide oxidation by cold plasma”. Yusupov M, Dewaele D, Attri P, Khalilov U, Sobott F, Bogaerts A, Plasma processes and polymers (2022). http://doi.org/10.1002/ppap.202200137
Abstract: Cold atmospheric plasma (CAP) is a promising technology for several medical applications, including the removal of biofilms from surfaces. However, the molecular mechanisms of CAP treatment are still poorly understood. Here we unravel the possible mechanisms of CAP‐induced oxidation of oligosaccharides, employing reactive molecular dynamics simulations based on the density functional‐tight binding potential. Specifically, we find that the interaction of oxygen atoms (used as CAP‐generated reactive species) with cellotriose (a model system for the oligosaccharides) can break structurally important glycosidic bonds, which subsequently leads to the disruption of the oligosaccharide molecule. The overall results help to shed light on our experimental evidence for cellotriose CAP. This oxidation by study provides atomic‐level insight into the onset of plasma‐induced removal of biofilms, as oligosaccharides are one of the main components of biofilm.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 3.5
DOI: 10.1002/ppap.202200137
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“Chiral Seeded Growth of Gold Nanorods Into 4‐Fold Twisted Nanoparticles with Plasmonic Optical Activity”. Ni B, Mychinko M, Gómez‐Graña S, Morales‐Vidal J, Obelleiro‐Liz M, Heyvaert W, Vila‐Liarte D, Zhuo X, Albrecht W, Zheng G, González‐Rubio G, Taboada JM, Obelleiro F, López N, Pérez‐Juste J, Pastoriza‐Santos I, Cölfen H, Bals S, Liz‐Marzán LM, Advanced materials , 2208299 (2022). http://doi.org/10.1002/adma.202208299
Abstract: A robust and reproducible methodology to prepare stable inorganic nanoparticles with chiral morphology might hold the key to the practical utilization of these materials. We describe herein an optimized chiral growth method to prepare 4-fold twisted gold nanorods, where the amino acid cysteine is used as a dissymmetry inducer. Four tilted ridges were found to develop on the surface of single-crystal nanorods upon repeated reduction of HAuCl4, in the presence of cysteine as the chiral inducer and ascorbic acid as a reducing agent. From detailed electron microscopy analysis of the crystallographic structures, we propose that dissymmetry results from the development of chiral facets in the form of protrusions (tilted ridges) on the initial nanorods, eventually leading to a twisted shape. The role of cysteine is attributed to assisting enantioselective facet evolution, which is supported by density functional theory simulations of the surface energies, modified upon adsorption of the chiral molecule. The development of R-type and S-type chiral structures (small facets, terraces, or kinks) would thus be non-equal, removing the mirror symmetry of the Au NR and in turn resulting in a markedly chiral morphology with high plasmonic optical activity.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 29.4
Times cited: 35
DOI: 10.1002/adma.202208299
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“Morphological and Optical Transitions during Micelle-Seeded Chiral Growth on Gold Nanorods”. Zhuo X, Mychinko M, Heyvaert W, Larios D, Obelleiro-Liz M, Taboada JM, Bals S, Liz-Marzán LM, ACS nano (2022). http://doi.org/10.1021/acsnano.2c08668
Abstract: Chiral plasmonics is a rapidly developing field where breakthroughs and unsolved problems coexist. We have recently reported binary surfactant-assisted seeded growth of chiral gold nanorods (Au NRs) with high chiroptical activity. Such a seeded-growth process involves the use of a chiral cosurfactant that induces micellar helicity, in turn driving the transition from achiral to chiral Au NRs, from both the morphological and the optical points of view. We report herein a detailed study on both transitions, which reveals intermediate states that were hidden so far. The correlation between structure and optical response is carefully analyzed, including the (linear and CD) spectral evolution over time, electron tomography, the impact of NR dimensions on their optical response, the variation of the absorption-to-scattering ratio during the evolution from achiral to chiral Au NRs, and the near-field enhancement related to chiral plasmon modes. Our findings provide further understanding of the growth process of chiral Au NRs and the associated optical changes, which will facilitate further study and applications of chiral nanomaterials.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 17.1
Times cited: 17
DOI: 10.1021/acsnano.2c08668
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“Three Approaches for Representing the Statistical Uncertainty on Atom-Counting Results in Quantitative ADF STEM”. De wael A, De Backer A, Yu C-P, Sentürk DG, Lobato I, Faes C, Van Aert S, Microscopy and microanalysis , 1 (2022). http://doi.org/10.1017/S1431927622012284
Abstract: A decade ago, a statistics-based method was introduced to count the number of atoms from annular dark-field scanning transmission electron microscopy (ADF STEM) images. In the past years, this method was successfully applied to nanocrystals of arbitrary shape, size, and composition (and its high accuracy and precision has been demonstrated). However, the counting results obtained from this statistical framework are so far presented without a visualization of the actual uncertainty about this estimate. In this paper, we present three approaches that can be used to represent counting results together with their statistical error, and discuss which approach is most suited for further use based on simulations and an experimental ADF STEM image.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.8
DOI: 10.1017/S1431927622012284
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“Optimal experiment design for element specific atom counting using multiple annular dark field scanning transmission electron microscopy detectors”. Sentürk DG, De Backer A, Friedrich T, Van Aert S, Ultramicroscopy 242, 113626 (2022). http://doi.org/10.1016/j.ultramic.2022.113626
Abstract: This paper investigates the possible benefits for counting atoms of different chemical nature when analysing multiple 2D scanning transmission electron microscopy (STEM) images resulting from independent annular dark field (ADF) detector regimes. To reach this goal, the principles of statistical detection theory are used to quantify the probability of error when determining the number of atoms in atomic columns consisting of multiple types of elements. In order to apply this theory, atom-counting is formulated as a statistical hypothesis test, where each hypothesis corresponds to a specific number of atoms of each atom type in an atomic column. The probability of error, which is limited by the unavoidable presence of electron counting noise, can then be computed from scattering-cross sections extracted from multiple ADF STEM images. Minimisation of the probability of error as a function of the inner and outer angles of a specified number of independent ADF collection regimes results in optimal experimental designs. Based on simulations of spherical Au@Ag and Au@Pt core–shell nanoparticles, we investigate how the combination of two non-overlapping detector regimes helps to improve the probability of error when unscrambling two types of atoms. In particular, the combination of a narrow low angle ADF detector with a detector formed by the remaining annular collection regime is found to be optimal. The benefit is more significant if the atomic number Z difference becomes larger. In
addition, we show the benefit of subdividing the detector regime into three collection areas for heterogeneous nanostructures based on a structure consisting of three types of elements, e.g., a mixture of Au, Ag and Al atoms. Finally, these results are compared with the probability of error resulting when one would ultimately use a pixelated 4D STEM detector and how this could help to further reduce the incident electron dose.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.2
DOI: 10.1016/j.ultramic.2022.113626
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“Can a programmable phase plate serve as an aberration corrector in the transmission electron microscope (TEM)?”.Vega Ibañez F, Béché, A, Verbeeck J, Microscopy and microanalysis , Pii S1431927622012260 (2022). http://doi.org/10.1017/S1431927622012260
Abstract: Current progress in programmable electrostatic phase plates raises questions about their usefulness for specific applications. Here, we explore different designs for such phase plates with the specific goal of correcting spherical aberration in the transmission electron microscope (TEM). We numerically investigate whether a phase plate could provide down to 1 angstrom ngstrom spatial resolution on a conventional uncorrected TEM. Different design aspects (fill factor, pixel pattern, symmetry) were evaluated to understand their effect on the electron probe size and current density. Some proposed designs show a probe size () down to 0.66 angstrom, proving that it should be possible to correct spherical aberration well past the 1 angstrom limit using a programmable phase plate consisting of an array of electrostatic phase-shifting elements.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.8
Times cited: 3
DOI: 10.1017/S1431927622012260
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“On the formation mechanisms of intragranular shear bands in olivine by stress-induced amorphization”. Idrissi H, Béché, A, Gauquelin N, Ul-Haq I, Bollinger C, Demouchy S, Verbeeck J, Pardoen T, Schryvers D, Cordier P, Acta materialia 239, 118247 (2022). http://doi.org/10.1016/J.ACTAMAT.2022.118247
Abstract: Intragranular amorphization shear lamellae are found in deformed olivine aggregates. The detailed trans-mission electron microscopy analysis of intragranular lamella arrested in the core of a grain provides novel information on the amorphization mechanism. The deformation field is complex and heteroge-neous, corresponding to a shear crack type instability involving mode I, II and III loading components. The formation and propagation of the amorphous lamella is accompanied by the formation of crystal defects ahead of the tip. These defects are geometrically necessary [001] dislocations, characteristics of high-stress deformation in olivine, and rotational nanodomains which are tentatively interpreted as disclinations. We show that these defects play an important role in dictating the path followed by the amorphous lamella. Stress-induced amorphization in olivine would thus result from a direct crystal-to -amorphous transformation associated with a shear instability and not from a mechanical destabilization due to the accumulation of high number of defects from an intense preliminary deformation. The pref-erential alignment of some lamellae along (010) is a proof of the lower ultimate mechanical strength of these planes.(c) 2022 The Authors. Published by Elsevier Ltd on behalf of Acta Materialia Inc. This is an open access article under the CC BY license ( http://creativecommons.org/licenses/by/4.0/ )
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 9.4
Times cited: 5
DOI: 10.1016/J.ACTAMAT.2022.118247
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“Topotactic redox cycling in SrFeO2.5+&delta, explored by 3D electron diffraction in different gas atmospheres”. Batuk M, Vandemeulebroucke D, Ceretti M, Paulus W, Hadermann J, Journal of materials chemistry A : materials for energy and sustainability (2022). http://doi.org/10.1039/D2TA03247C
Abstract: For oxygen conducting materials applied in solid oxide fuel cells and chemical-looping processes, the understanding of the oxygen diffusion mechanism and the materials’ crystal structure at different stages of the redox reactions is a key parameter to control their performance. In this paper we report the first ever in situ 3D ED experiment in a gas environment and with it uncover the structure evolution of SrFeO2.5 as notably different from that reported from in situ X-ray and in situ neutron powder diffraction studies in gas environments. Using in situ 3D ED on submicron sized single crystals obtained from a high quality monodomain SrFeO2.5 single crystal , we observe the transformation under O2 flow of SrFeO2.5 with an intra- and interlayer ordering of the left and right twisted (FeO4) tetrahedral chains (space group Pcmb) into consecutively SrFeO2.75 with space group Cmmm (at 350°C, 33% O2) and SrFeO3-δ with space group Pm3 ̅m (at 400°C, 100% O2). Upon reduction in H2 flow, the crystals return to the brownmillerite structure with intralayer order, but without regaining the interlayer order of the pristine crystals. Therefore, redox cycling of SrFeO2.5 crystals in O2 and H2 introduces stacking faults into the structure, resulting in an I2/m(0βγ)0s symmetry with variable β.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 11.9
DOI: 10.1039/D2TA03247C
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“Modifying the Stöber Process: Is the Organic Solvent Indispensable?”.Wang J, Zhang K, Kavak S, Bals S, Meynen V, Chemistry-A European Journal (2022). http://doi.org/10.1002/chem.202202670
Abstract: The Stöber method is one of the most important and fundamental processes for the synthesis of inorganic (nano)materials but has the drawback of using a large amount of organic solvent. Herein, ethanol was used as an example to explore if the organic solvent in a typical Stöber method can be omitted. It was found that ethanol increases the particle size of the obtained silica spheres and aids the formation of uniform silica particles rather than forming a gel. Nevertheless, the results indicated that an organic solvent in the initial synthesis mixture is not indispensable. An initially immiscible synthesis method was discovered, which can replace the organic solvent-based Stöber method to successfully synthesize silica particles with the same size ranges as the original Stöber process without addition of organic solvents. Moreover, this process can be of further value for the extension to synthesis processes of other materials based on the Stöber process.
Keywords: A1 Journal Article; Electron Microscopy for Materials Science (EMAT) ;
Impact Factor: 4.3
Times cited: 3
DOI: 10.1002/chem.202202670
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“How an incineration tax changes waste management practices among firms”. De Weerdt L, De Jaeger S, Compernolle T, Van Passel S, Resources Conservation And Recycling 180, 106172 (2022). http://doi.org/10.1016/j.resconrec.2022.106172
Abstract: Sustainable management of industrial plastic waste is crucial in the transition to a circular economy. Today, most industrial plastic waste is incinerated, whereas it could be recycled. As a consequence, governments increasingly make use of incineration taxes to improve current waste management practices. This paper presents an econometric panel analysis that studies the effects of an incineration tax on industrial plastic waste in Flanders (Belgium). Not only is this study the first econometric analysis on industrial plastic waste management in which firm heterogeneity is explicitly taken into account by including firm-specific characteristics, but this study also provides policymakers with insights into the effectiveness of an incineration tax to change current waste management practices. Empirical estimates imply that heterogeneous firms generate industrial plastic waste in different ways and that heterogeneous firms reduce their waste generation in different ways after the incineration tax rate increases. The estimates also show that the unique decrease of the incineration tax in 2007, did not change waste management practices. These estimates show that firms do not disinvest or indicate that loss aversion theory, i.e. a preference for avoiding losses over acquiring equivalent gains, might apply to firms that are faced with environmental taxation in a waste management context.
Keywords: A1 Journal Article; Engineering Management (ENM) ;
Impact Factor: 13.2
DOI: 10.1016/j.resconrec.2022.106172
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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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“Prospective material and substance flow analysis of the end-of-life phase of crystalline silicon-based PV modules”. Thomassen G, Dewulf J, Van Passel S, Resources Conservation And Recycling 176, 105917 (2022). http://doi.org/10.1016/J.RESCONREC.2021.105917
Abstract: The approaching end-of life phase of early installed PV modules gave rise to a variety of potential end-of-life strategies, ranging from basic generic waste management strategies to advanced case-specific recycling options. However, no comprehensive assessment on the full range of technological possibilities is available and only limited attention was given to the material recovery rates of these different technologies in light of circular economy. In addition, current material recovery rates are indifferent towards the material value and the value of their secondary applications. Based on an extensive literature review, ten end-of-life scenarios with potential learning effects are identified and their material flows are quantified using a combined material and substance flow analysis. Subsequently, material recovery rates from a mass, economic value and embodied energy perspective are calculated, incorporating the differences in secondary applications. The differences in the mass-based recovery rates of the seven end-of-life scenarios that did not have landfill or municipal waste incineration as the main destination were minimal, as 73-79% of the mass was recovered for the best-case learning scenario. For the economic value recovery rate (9-66%) and the embodied energy recovery rate (18-45%), more profound differences were found. The collection rate was identified as most crucial parameter for all end-of-life scenarios, learning scenarios and recycling indicators. The mass-based recovery rate might favor end-of-life scenarios that lead to dissipation of valuable materials in non-functional secondary applications. Additional targets are required to avoid cascading of valuable materials and to avoid the economic cost and environmental burden of virgin materials.
Keywords: A1 Journal article; Engineering Management (ENM)
Impact Factor: 13.2
DOI: 10.1016/J.RESCONREC.2021.105917
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“Ferroelectric engineering : enhanced thermoelectric performance by local structural heterogeneity”. Meng X, Chen S, Peng H, Bai H, Zhang S, Su X, Tan G, Van Tendeloo G, Sun Z, Zhang Q, Tang X, Wu J, Science China : materials (2022). http://doi.org/10.1007/S40843-021-1927-9
Abstract: Although traditional ferroelectric materials are usually dielectric and nonconductive, GeTe is a typical ferroelectric semiconductor, possessing both ferroelectric and semiconducting properties. GeTe is also a widely studied thermoelectric material, whose performance has been optimized by doping with various elements. However, the impact of the ferroelectric domains on the thermoelectric properties remains unclear due to the difficulty to directly observe the ferroelectric domains and their evolutions under actual working conditions where the material is exposed to high temperatures and electric currents. Herein, based on in-situ investigations of the ferroelectric domains and domain walls in both pure and Sb-doped GeTe crystals, we have been able to analyze the dynamic evolution of the ferroelectric domains and domain walls, exposed to an electric field and temperature. Local structural heterogeneities and nano-sized ferroelectric domains are generated due to the interplay of the Sb3+ dopant and the Ge-vacancies, leading to the increased number of charged domain walls and a much improved thermoelectric performance. This work reveals the fundamental mechanism of ferroelectric thermoelectrics and provides insights into the decoupling of previously interdependent properties such as thermo-power and electrical conductivity.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 8.1
DOI: 10.1007/S40843-021-1927-9
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“In situ atomistic insight into magnetic metal diffusion across Bi0.5Sb1.5Te3 quintuple layers”. Lu W, Cui W, Zhao W, Lin W, Liu C, Van Tendeloo G, Sang X, Zhao W, Zhang Q, Advanced Materials Interfaces , 2102161 (2022). http://doi.org/10.1002/ADMI.202102161
Abstract: Diffusion and occupancy of magnetic atoms in van der Waals (VDW) layered materials have significant impact on applications such as energy storage, thermoelectrics, catalysis, and topological phenomena. However, due to the weak VDW bonding, most research focus on in-plane diffusion within the VDW gap, while out-of-plane diffusion has rarely been reported. Here, to investigate out-of-plane diffusion in VDW-layered Bi2Te3-based alloys, a Ni/Bi0.5Sb1.5Te3 heterointerface is synthesized by depositing magnetic Ni metal on a mechanically exfoliated Bi0.5Sb1.5Te3 (0001) substrate. Diffusion of Ni atoms across the Bi0.5Sb1.5Te3 quintuple layers is directly observed at elevated temperatures using spherical-aberration-corrected scanning transmission electron microscopy (STEM). Density functional theory calculations demonstrate that the diffusion energy barrier of Ni atoms is only 0.31-0.45 eV when they diffuse through Te-3(Bi, Sb)(3) octahedron chains. Atomic-resolution in situ STEM reveals that the distortion of the Te-3(Bi, Sb)(3) octahedron, induced by the Ni occupancy, drives the formation of coherent NiM (M = Bi, Sb, Te) at the heterointerfaces. This work can lead to new strategies to design novel thermoelectric and topological materials by introducing magnetic dopants to VDW-layered materials.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 5.4
DOI: 10.1002/ADMI.202102161
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“First-principles investigation of structural, Raman and electronic characteristics of single layer Ge3N4”. Yayak YO, Sozen Y, Tan F, Gungen D, Gao Q, Kang J, Yagmurcukardes M, Sahin H, Applied surface science 572, 151361 (2022). http://doi.org/10.1016/J.APSUSC.2021.151361
Abstract: By means of density functional theory-based first-principle calculations, the structural, vibrational and electronic properties of single-layer Ge3N4 are investigated. Structural optimizations and phonon band dispersions reveal that single-layer ultrathin form of Ge3N4 possesses a dynamically stable buckled structure with large hexagonal holes. Predicted Raman spectrum of single-layer Ge3N4 indicates that the buckled holey structure of the material exhibits distinctive vibrational features. Electronic band dispersion calculations indicate the indirect band gap semiconducting nature of single-layer Ge3N4. It is also proposed that single-layer Ge3N4 forms type-II vertical heterostructures with various planar and puckered 2D materials except for single-layer GeSe which gives rise to a type-I band alignment. Moreover, the electronic properties of single-layer Ge3N4 are investigated under applied external in-plane strain. It is shown that while the indirect gap behavior of Ge3N4 is unchanged by the applied strain, the energy band gap increases (decreases) with tensile (compressive) strain.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 6.7
DOI: 10.1016/J.APSUSC.2021.151361
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Arslan Irmak E (2022) Modelling three-dimensional nanoparticle transformations based on quantitative transmission electron microscopy. 169 p
Abstract: Nanomaterials are materials that have at least one dimension in the nanometer length scale, which corresponds to a billionth of a meter. When three dimensions are confined to the nanometer scale, these materials are referred to as nanoparticles. These materials are of great interest since they exhibit unique physical and chemical properties that cannot be observed for bulk systems. Due to their unique and often superior properties, nanomaterials have become central in the field of electronics, catalysis, and medicine. Moreover, they are expected to be one of the most promising systems to tackle many challenges that our society is facing, such as reducing the emission of greenhouse gases and finding effective treatments for cancer. The unique properties of nanomaterials are linked to their size, shape, structure, and composition. If one is able to measure the positions of the atoms, their chemical nature, and the bonding between them, it becomes possible to predict the physicochemical properties of nanomaterials. In this manner, the development of novel nanostructures can be triggered. However, the morphology and structure of nanomaterials are highly sensitive to the conditions for relevant applications, such as elevated temperatures or intense light illumination. Furthermore, any small change in the local structure at higher temperatures or pressures may significantly modify their performance. Hence, three-dimensional (3D) characterization of nanomaterials under application-relevant conditions is important in designing them with desired functional properties for specific applications. Among different structural characterization approaches, transmission electron microscopy (TEM) is one of the most efficient and versatile tools to investigate the structure and composition of nanomaterials since it can provide atomically resolved images, which are sensitive to the local 3D structure of the investigated sample. However, TEM only provides two-dimensional (2D) images of the 3D nanoparticle, which may lead to an incomplete understanding of their structure-property relationship. The most known and powerful technique for the 3D characterization of nanomaterials is electron tomography, where the images of a nanostructured material taken from different directions are mathematically combined to retrieve its 3D structure. Although these experiments are already state-of-the-art, 3D characterization by TEM is typically performed under ultra-high vacuum conditions and at room temperature. Such conditions are unfortunately not sufficient to understand transformations during synthesis or applications of nanomaterials. This limitation can be overcome by in situ TEM where external stimuli, such as heat, gas, and liquids, can be controllably introduced inside the TEM using specialized holders. However, there are some technical limitations to successful perform 3D in situ electron tomography experiments. For example, the long acquisition time required to collect a tilt series limits this technique when one wants to observe 3D dynamic changes with atomic resolution. A solution for this problem is the estimation of the 3D structure of nanomaterials from 2D projection images acquired along a single viewing direction. For this purpose, annular dark field scanning TEM (ADF STEM) imaging mode provides a valuable tool for quantitative structural investigation of nanomaterials from single 2D images due to its thickness and mass sensitivity. For quantitative analysis, an ADF STEM image is considered as a 2D array of pixels where relative variation of pixel intensity values is proportional to the total number of atoms and the atomic number of the elements in the sample. By applying advanced statistical approaches to these images, structural information, such as the number or types of atoms, can be retrieved with high accuracy and precision. The outcome can then be used to build a 3D starting model for energy minimization by atomistic simulations, for example, molecular dynamics simulations or the Monte Carlo method. However, this methodology needs to be further evaluated for in situ experiments. This thesis is devoted to presenting robust approaches to accurately define the 3D atomic structure of nanoparticles under application-relevant conditions and understand the mechanism behind the atomic-scale dynamics in nanoparticles in response to environmental stimuli.
Keywords: Doctoral thesis; Electron microscopy for materials research (EMAT)
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“Boron structure evolution in magnetic Cr₂O₃, thin films”. Sun C, Street M, Zhang C, Van Tendeloo G, Zhao W, Zhang Q, Materials Today Physics 27, 100753 (2022). http://doi.org/10.1016/J.MTPHYS.2022.100753
Abstract: B substituting O in antiferromagnetic Cr2O3 is known to increase the Ne ' el temperature, whereas the actual B dopant site and the corresponding functionality remains unclear due to the complicated local structure. Herein, A combination of electron energy loss spectroscopy and first-principles calculations were used to unveil B local structures in B doped Cr2O3 thin films. B was found to form either magnetic active BCr4 tetrahedra or various inactive BO3 triangles in the Cr2O3 lattice, with a* and z* bonds exhibiting unique spectral features. Identification of BO3 triangles was achieved by changing the electron momentum transfer to manipulate the differential cross section for the 1s-z* and 1s-a* transitions. Modeling the experimental spectra as a linear combination of simulated B K edges reproduces the experimental z* / a* ratios for 15-42% of the B occupying the active BCr4 structure. This result is further supported by first-principles based thermodynamic calculations.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 11.5
DOI: 10.1016/J.MTPHYS.2022.100753
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“Microstructural investigation of IASCC crack tips extracted from thimble tube O-ring specimens”. Penders AG, Konstantinovic MJ, Yang T, Bosch R-w, Schryvers D, Somville F, Journal of nuclear materials 565, 153727 (2022). http://doi.org/10.1016/J.JNUCMAT.2022.153727
Abstract: The microstructural features of intergranular irradiation-assisted stress corrosion crack tips from a redeemed neutron-irradiated flux thimble tube (60 dpa) have been investigated using focused-ion beam analysis and (scanning) transmission electron microscopy. The current work presents a close examination of the deformation field and oxide assembly associated with intergranular cracking, in addition to the analysis of radiation-induced segregation at leading grain boundaries. Evidence of stress induced martensitic transformation extending from the crack tips is presented. Intergranular crack arrest is demonstrated on the account of the external tensile stress orientation, and as a consequence of MnS inclusion particles segregating close to the fractured grain boundary. Exclusive observations of grain boundary oxidation prior to the cracking are presented, which is in full-agreement with the internal oxidation model.(c) 2022 Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 3.1
DOI: 10.1016/J.JNUCMAT.2022.153727
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“On the formation of antiphase boundaries in Fe₄Al₁₃, intermetallics during a high temperature treatment”. Ding L, Sapanathan T, Schryvers D, Simar A, Idrissi H, Scripta materialia 215, 114726 (2022). http://doi.org/10.1016/J.SCRIPTAMAT.2022.114726
Abstract: In this paper, we report atomic scale observations and formation mechanisms of a high-density of antiphase boundaries (APBs) within an ultra-fine-grained Fe4Al13 intermetallic layer at an Al/steel interface after a heat treatment at 596 degrees C. The results reveal that the APBs are formed by nucleation and the glide of partial dislocations with Burgers vector of b/3[010] (b = 12.47 angstrom). The intensive activation of APBs locally transforms the Fe4Al13 structure from the quasicrystal approximant structure to a quasicrystal. Very few stacking faults and nanotwins are observed indicating that the formation of planar defects is mainly driven by this transformation. This new insight on the formation of high density of APBs could possibly lead to an improvement in toughness by increasing the strength/ductility balance of this intermetallic.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 6
DOI: 10.1016/J.SCRIPTAMAT.2022.114726
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“Shear banding-activated dynamic recrystallization and phase transformation during quasi-static loading of β-metastable Ti &ndash, 12 wt % Mo alloy”. Choisez L, Ding L, Marteleur M, Kashiwar A, Idrissi H, Jacques PJ, Acta materialia 235, 118088 (2022). http://doi.org/10.1016/J.ACTAMAT.2022.118088
Abstract: Dynamic recrystallization (DRX) within adiabatic shear bands forming during the fracture of TRIP-TWIP β−metastable Ti-12Mo (wt %) alloy was recently reported. The formation of 1-3 µm thick-adiabatic shear bands, and of dynamic recrystallization, was quite surprising as their occurrence generally requires high temperature and/or high strain rate loading while these samples were loaded in quasi-static conditions at room temperature. To better understand the fracture mechanism and associated microstructural evolution, thin foils representative of different stages of the fracture process were machined from the fracture surface by Focused Ion Beam (FIB) and analyzed by Transmission Electron Microscopy (TEM) and Automated Crystal Orientation mapping (ACOM-TEM). Complex microstructure transformations involving severe plastic deformed nano-structuration, crystalline rotation and local precipitation of the omega phase were identified. The spatial and temporal evolution of the microstructure during the propagation of the crack was explained through dynamic recovery and continuous dynamic recrystallization, and linked to the modelled distribution of temperature and strain level where TEM samples were extracted.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 9.4
DOI: 10.1016/J.ACTAMAT.2022.118088
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“A new healing strategy for metals : programmed damage and repair”. Arseenko M, Hannard F, Ding L, Zhao L, Maire E, Villanova J, Idrissi H, Simar A, Acta materialia 238, 118241 (2022). http://doi.org/10.1016/J.ACTAMAT.2022.118241
Abstract: Self-healing strategies aim at avoiding part repair or even replacement, which is time consuming, expen-sive and generates waste. However, strategies for metallic systems are still under-developed and solid-state solutions for room temperature service are limited to nano-scale damage repair. Here we propose a new healing strategy of micron-sized damage requiring only short and low temperature heating. This new strategy is based on damage localization particles, which can be healed by fast diffusing atoms of the matrix activated during heat treatment. The healing concept was successfully validated with a com-mercial aluminum alloy and manufactured by Friction Stir Processing (FSP). Damage was demonstrated to initiate on particles that were added to the matrix during material processing. In situ 2D and 3D nano -imaging confirmed healing of the damaged material and showed that heating this material for 10 min at 400 degrees C is sufficient to heal incipient damage with complete filling of 70% of all damage (and up to 90% when their initial size is below 0.2 mu m). Furthermore, strength is retained and the work of fracture of the alloy is improved by about 40% after healing. The proposed Programmed Damage and Repair healing strategy could be extended to other metal based systems presenting precipitation. (C) 2022 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 9.4
DOI: 10.1016/J.ACTAMAT.2022.118241
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