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“Oxide phase determination in silicon using infrared spectroscopy and transmission electron microscopy techniques”. Gryse OD, Clauws P, van Landuyt J, Lebedev O, Claeys C, Simoen E, Vanhellemont J, Journal of applied physics 91, 2493 (2002). http://doi.org/10.1063/1.1429800
Abstract: Infrared absorption spectra of polyhedral and platelet oxygen precipitates in silicon are analyzed using a modified Day-Thorpe approach [J. Phys.: Condens. Matter 11, 2551 (1999)]. The aspect ratio of the precipitates is determined by transmission electron microscopy analysis. The reduced spectral function and the stoichiometry of the precipitate are extracted from the absorption spectra and the amount of precipitated interstitial oxygen. The experimental absorption spectra can be divided in a set with a Frohlich frequency of around 1100 cm(-1) and in a set with a Frohlich frequency between 1110 and 1120 cm(-1). It is shown that the shift in the Frohlich frequency is not due to a differing stoichiometry, but to the detailed structure of the reduced spectral function. Inverse modeling of the spectra suggests that the oxide precipitates consist of substoichiometric SiOgamma with gamma=1.17+/-0.14. (C) 2002 American Institute of Physics.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.068
Times cited: 27
DOI: 10.1063/1.1429800
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“Oxidation state and chemical shift investigation in transition metal oxides by EELS”. Tan H, Verbeeck J, Abakumov A, Van Tendeloo G, Ultramicroscopy 116, 24 (2012). http://doi.org/10.1016/j.ultramic.2012.03.002
Abstract: Transition metal L2,3 electron energy-loss spectra for a wide range of V-, Mn- and Fe-based oxides were recorded and carefully analyzed for their correlation with the formal oxidation states of the transition metal ions. Special attention is paid to obtain an accurate energy scale which provides absolute energy positions for all core-loss edges. The white-line ratio method, chemical shift method, ELNES fitting method, two-parameter method and other methods are compared and their validity is discussed. Both the ELNES fitting method and the chemical shift method have the advantage of a wide application range and good consistency but require special attention to accurately measure the core-loss edge position. The obtained conclusions are of fundamental importance, e.g., for obtaining atomic resolution oxidation state information in modern experiments.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.843
Times cited: 413
DOI: 10.1016/j.ultramic.2012.03.002
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“Oxidation processes at the metal/oxide interface in CoFe2/CoFe2O4 bilayers deposited by pulsed laser deposition”. Viart N, Sayed Hassan R, Ulhaq-Bouillet C, Meny C, Panissod P, Loison JL, Versini G, Huber F, Pourroy G, Verbeeck J, Van Tendeloo G, Acta materialia 54, 191 (2006). http://doi.org/10.1016/j.actamat.2005.08.041
Abstract: CoFe2/CoFe2O4 bilayers were made by pulsed laser ablation of a CoFe2 target on Si(I 0 0) substrates. The metallic layer was deposited first, in vacuum. The oxide was then deposited in an oxidizing O-2:N-2 (20:80) atmosphere. Two different procedures were used for the introduction of the oxidizing atmosphere in the deposition chamber: the laser ablation of the target was either stopped (discontinuous deposition process) or maintained (continuous deposition process) during the 20 min necessary for the establishment of the desired O-2:N-2 pressure. In both cases, the different electronegativities of Fe and Co cause an important modification of the Fe/Co ratio at the metal/oxide interface, with a depletion of Fe in the metal region and of Co in the oxide region. In the continuous procedure, the combination of the kinetic energy given by the ablation process to the Fe and Co adatoms with the one they get from their different affinity towards oxidation allows the formation of a low roughness metal/oxide interface with a high (111) preferred orientation of the CoFe2O4 layer, an induced re-crystallisation of the metal layer underneath and an unusual antiferromagnetic metal/oxide magnetic coupling. (c) 2005 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 5.301
Times cited: 5
DOI: 10.1016/j.actamat.2005.08.041
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“Oxidation potential in the Earth's lower mantle as recorded by ferropericlase inclusions in diamond”. Kaminsky FV, Ryabchikov ID, McCammon CA, Longo M, Abakumov AM, Turner S, Heidari H, Earth and planetary science letters 417, 49 (2015). http://doi.org/10.1016/j.epsl.2015.02.029
Abstract: Ferropericlase (fPer) inclusions from kimberlitic lower-mantle diamonds recovered in the Juina area, Mato Grosso State, Brazil were analyzed with transmission electron microscopy, electron energy-loss spectroscopy and the flank method. The presence of exsolved non-stoichiometric Fe3+-enriched clusters, varying in size from 1-2 nm to 10-15 nm and comprising similar to 3.64 vol.% of fPer was established. The oxidation conditions necessary for fPer formation within the uppermost lower mantle (P = 25 GPa, T = 1960 K) vary over a wide range: Delta log f(o2) (IW) from 1.58 to 7.76 (Delta = 6.2), reaching the fayalite-magnetite-quartz (FMQ) oxygen buffer position. This agrees with the identification of carbonates and free silica among inclusions within lower-mantle Juina diamonds. On the other hand, at the base of the lower mantle Delta log f(o2) values may lie at and below the iron-wustite (IW) oxygen buffer. Hence, the variations of Delta log f(o2) values within the entire sequence of the lower mantle may reach ten logarithmic units, varying from the IW buffer to the FMQ buffer values. The similarity between lower- and upper-mantle redox conditions supports whole mantle convection, as already suggested on the basis of nitrogen and carbon isotopic compositions in lower- and upper-mantle diamonds. The mechanisms responsible for redox differentiation in the lower mantle may include subduction of oxidized crustal material, mechanical separation of metallic phase(s) and silicate-oxide mineral assemblages enriched in ferric iron, as well as transfer of fused silicate-oxide material presumably also enriched in ferric iron through the mantle. (C) 2015 Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 4.409
Times cited: 23
DOI: 10.1016/j.epsl.2015.02.029
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“Oxidation of Innate Immune Checkpoint CD47 on Cancer Cells with Non-Thermal Plasma”. Lin A, Razzokov J, Verswyvel H, Privat-Maldonado A, De Backer J, Yusupov M, Cardenas De La Hoz E, Ponsaerts P, Smits E, Bogaerts A, Cancers 13, 579 (2021). http://doi.org/10.3390/cancers13030579
Abstract: Non-thermal plasma (NTP) therapy has been emerging as a promising cancer treatment strategy, and recently, its ability to locally induce immunogenic cancer cell death is being unraveled. We hypothesized that the chemical species produced by NTP reduce immunosuppressive surface proteins and checkpoints that are overexpressed on cancerous cells. Here, 3D in vitro tumor models, an in vivo mouse model, and molecular dynamics simulations are used to investigate the effect of NTP on CD47, a key innate immune checkpoint. CD47 is immediately modulated after NTP treatment and simulations reveal the potential oxidized salt-bridges responsible for conformational changes. Umbrella sampling simulations of CD47 with its receptor, signal-regulatory protein alpha (SIRPα), demonstrate that the induced-conformational changes reduce its binding affinity. Taken together, this work provides new insight into fundamental, chemical NTP-cancer cell interaction mechanisms and a previously overlooked advantage of present NTP cancer therapy: reducing immunosuppressive signals on the surface of cancer cells.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT); Laboratory for Experimental Hematology (LEH); Center for Oncological Research (CORE)
DOI: 10.3390/cancers13030579
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“Oxidation barrier of Cu and Fe powder by Atomic Layer Deposition”. Cremers V, Rampelberg G, Barhoum A, Walters P, Claes N, Oliveira TM de, Assche GV, Bals S, Dendooven J, Detavernier C, Surface and coatings technology 349, 1032 (2018). http://doi.org/10.1016/j.surfcoat.2018.06.048
Abstract: Atomic layer deposition (ALD) is a vapor based technique which allows to deposit uniform, conformal films with a thickness control at the atomic scale. In this research, Al 2 O 3 coatings were deposited on micrometer-sized Fe and Cu powder (particles) using the thermal trimethylaluminum (TMA)/ water (H 2 O) process in a rotary pump-type ALD reactor. Rotation of the powder during deposition was required to obtain a pinhole-free ALD coating. The protective nature of the coating was evaluated by quantifying its effectiveness in protecting the metal particles during oxidative annealing treatments. The Al 2 O 3 coated powders were annealed in ambient air while in-situ thermogravimetric analysis (TGA) and in-situ x-ray diffraction (XRD) data were acquired. The thermal stability of a series of Cu and Fe powder with different Al 2 O 3 thicknesses were determined with TGA. In both samples a clear shift in oxidation temperature is visible. For Cu and Fe powder coated with 25 nm Al 2 O 3 , we observed an increase of the oxidation temperature with 300-400°C. For the Cu powder a thin film of only 8 nm is required to obtain an initial increase in oxidation temperature of 200°C. In contrast, for Fe powder a thicker coating of 25 nm is required. In both cases, the oxidation temperature increases with increasing thickness of the Al 2 O 3 coating. These results illustrate that the Al 2 O 3 thin film, deposited by the thermal ALD process (TMA/H 2 O) can be an efficient and pinhole-free barrier layer for micrometer-sized powder particles, provided that the powder is properly agitated during the process to ensure sufficient vapour-solid interaction.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.589
Times cited: 10
DOI: 10.1016/j.surfcoat.2018.06.048
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“Oxidation and degradation of native wheat starch by acidic bromate in water at room temperature”. Komulainen S, Verlackt C, Pursiainen J, Lajunen M, Carbohydrate Polymers 93, 73 (2013). http://doi.org/10.1016/j.carbpol.2012.06.001
Abstract: Native wheat starch was oxidized by benign acidic bromate in water at room temperature. HPLC-ELSD study indicated that starch degraded in the course of oxidation but it still had a polymeric structure characterized by H-1, C-13, HSQC and HMBC NMR measurements. Products were generally water-soluble fragments but the use of a short reaction time and dilute reaction mixture yielded water-insoluble products. Titration of the products showed, that the increase of the starch content and reaction time increased the content of carbonyl and carboxyl groups in the range of 0.5-2.5% and 1.7-17.2%, respectively, in the product fragments. A mechanism for the oxidation reaction was proposed. (C) 2012 Elsevier Ltd. All rights reserved.
Keywords: A1 Journal article; Electron Microscopy for Materials Science (EMAT);
Impact Factor: 4.811
Times cited: 32
DOI: 10.1016/j.carbpol.2012.06.001
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“Overcoming Crystallinity Limitations of Aluminium Metal-Organic Frameworks by Oxalic Acid Modulated Synthesis”. Canossa S, Gonzalez-Nelson A, Shupletsov L, Carmen Martin M, Van der Veen MA, Chemistry-A European Journal 26, 3564 (2020). http://doi.org/10.1002/chem.201904798
Abstract: A modulated synthesis approach based on the chelating properties of oxalic acid (H2C2O4) is presented as a robust and versatile method to achieve highly crystalline Al‐based metal‐organic frameworks. A comparative study on this method and the already established modulation by hydrofluoric acid was conducted using MIL‐53 as test system. The superior performance of oxalic acid modulation in terms of crystallinity and absence of undesired impurities is explained by assessing the coordination modes of the two modulators and the structural features of the product. The validity of our approach was confirmed for a diverse set of Al‐MOFs, namely X‐MIL‐53 (X=OH, CH3O, Br, NO2), CAU‐10, MIL‐69, and Al(OH)ndc (ndc=1,4‐naphtalenedicarboxylate), highlighting the potential benefits of extending the use of this modulator to other coordination materials.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 4.3
DOI: 10.1002/chem.201904798
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“Overcoming contrast reversals in focused probe ptychography of thick materials: An optimal pipeline for efficiently determining local atomic structure in materials science”. Gao C, Hofer C, Jannis D, Béché, A, Verbeeck J, Pennycook TJ, Applied physics letters 121, 081906 (2022). http://doi.org/10.1063/5.0101895
Abstract: Ptychography provides highly efficient imaging in scanning transmission electron microscopy (STEM), but questions have remained over its applicability to strongly scattering samples such as those most commonly seen in materials science. Although contrast reversals can appear in ptychographic phase images as the projected potentials of the sample increase, we show here how these can be easily overcome by a small amount of defocus. The amount of defocus is small enough that it not only can exist naturally when focusing using the annular dark field (ADF) signal but can also be adjusted post acquisition. The ptychographic images of strongly scattering materials are clearer at finite doses than other STEM techniques and can better reveal light atomic columns within heavy lattices. In addition, data for ptychography can now be collected simultaneously with the fastest of ADF scans. This combination of sensitivity and interpretability presents an ideal workflow for materials science.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 4
Times cited: 9
DOI: 10.1063/5.0101895
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“Oscillations of the superconducting temperature induced by quantum well states in thin metallic films: numerical solution of the Bogoliubov-de Gennes equations”. Shanenko AA, Croitoru MD, Peeters FM, Physical review : B : condensed matter and materials physics 75, 014519 (2007). http://doi.org/10.1103/PhysRevB.75.014519
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 85
DOI: 10.1103/PhysRevB.75.014519
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“Oscillating sliding wear of mono- and multilayer ceramic coatings in air”. Huq MZ, Celis JP, Meneve J, Stals L, Schryvers D, Surface and coatings technology 113, 242 (1999). http://doi.org/10.1016/S0257-8972(99)00009-2
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.589
Times cited: 10
DOI: 10.1016/S0257-8972(99)00009-2
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“Orthorhombic vs. hexagonal epitaxial SrIrO3 thin films : structural stability and related electrical transport properties”. Bhat SG, Gauquelin N, Sebastian NK, Sil A, Béché, A, Verbeeck J, Samal D, Kumar PSA, Europhysics letters 122, 28003 (2018). http://doi.org/10.1209/0295-5075/122/28003
Abstract: Metastable orthorhombic SrIrO3 (SIO) is an arch-type spin-orbit coupled material. We demonstrate here a controlled growth of relatively thick (200 nm) SIO films that transform from bulk “6H-type” structure with monoclinic distortion to an orthorhombic lattice by controlling growth temperature. Extensive studies based on high-resolution X-ray diffraction and transmission electron microscopy infer a two distinct structural phases of SIO. Electrical transport reveals a weak temperature-dependent semi-metallic character for both phases. However, the temperature-dependent Hall-coefficient for the orthorhombic SIO exhibits a prominent sign change, suggesting a multiband character in the vicinity of E-F. Our findings thus unravel the subtle structure-property relation in SIO epitaxial thin films. Copyright (C) EPLA, 2018
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 1.957
Times cited: 4
DOI: 10.1209/0295-5075/122/28003
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“Ortho-II structure in ABa2Cu3O7-\delta compounds (A=Er, Nd, Pr, Sm, Yb)”. Krekels T, Zou H, Van Tendeloo G, Wagener D, Buchgeister M, Hosseini SM, Herzog P, Physica: C : superconductivity 196, 363 (1992). http://doi.org/10.1016/0921-4534(92)90458-O
Abstract: Oxygen ordering has been investigated in superconducting ABa2Cu3O7-delta ceramic materials with A = Er, Nd, Sm and Yb, as well as in samples of this type with the rate earth A partially substituted by Pr. The critical temperature T(c) was determined as a function of the oxygen deficiency-delta of the compound and the corresponding microstructures were investigated by electron diffraction and electron microscopy. A distinct relationship exists between the width of the 60 K plateau and the ortho II ordering. Our results show that the ortho II ordered phase is the superconducting phase with a characteristic T(c) of 60 K.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 0.942
Times cited: 52
DOI: 10.1016/0921-4534(92)90458-O
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“Ortho II structure in ABa2Cu307-d compounds (A=Er, Nd, Pr, Sm, Yb), pp”. Krekels T, Zou H, Van Tendeloo G, Wagner D, Buchgeister M, Hosseini SM, Herzog P, Physica: C : superconductivity 196, 363 (1992)
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 0.942
Times cited: 52
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“Original close-packed structure and magnetic properties of the Pb4Mn9O20 manganite”. Abakumov AM, Hadermann J, Tsirlin AA, Tan H, Verbeeck J, Zhang H, Dikarev EV, Shpanchenko RV, Antipov EV, Journal of solid state chemistry 182, 2231 (2009). http://doi.org/10.1016/j.jssc.2009.06.003
Abstract: The crystal structure of the Pb4Mn9O20 compound (previously known as Pb0.43MnO2.18) was solved from powder X-ray diffraction, electron diffraction, and high resolution electron microscopy data (S.G. Pnma, a=13.8888(2) Å, b=11.2665(2) Å, c=9.9867(1) Å, RI=0.016, RP=0.047). The structure is based on a 6H (cch)2 close packing of pure oxygen h-type (O16) layers alternating with mixed c-type (Pb4O12) layers. The Mn atoms occupy octahedral interstices formed by the oxygen atoms of the close-packed layers. The MnO6 octahedra share edges within the layers, whereas the octahedra in neighboring layers are linked through corner sharing. The relationship with the closely related Pb3Mn7O15 structure is discussed. Magnetization measurements reveal a peculiar magnetic behavior with a phase transition at 52 K, a small net magnetization below the transition temperature, and a tendency towards spin freezing.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.299
Times cited: 5
DOI: 10.1016/j.jssc.2009.06.003
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“Origin of voltage decay in high-capacity layered oxide electrodes”. Sathiya M, Abakumov AM, Foix D, Rousse G, Ramesha K, Saubanère M, Doublet M , Vezin H, Laisa CP, Prakash AS, Gonbeau D, Van Tendeloo G, Tarascon JM, Nature materials 14, 230 (2015). http://doi.org/10.1038/nmat4137
Abstract: Although Li-rich layered oxides (Li1+xNiyCozMn1−x−y−zO2 > 250 mAh g−1) are attractive electrode materials providing energy densities more than 15% higher than todays commercial Li-ion cells, they suffer from voltage decay on cycling. To elucidate the origin of this phenomenon, we employ chemical substitution in structurally related Li2RuO3 compounds. Li-rich layered Li2Ru1−yTiyO3 phases with capacities of ~240 mAh g−1 exhibit the characteristic voltage decay on cycling. A combination of transmission electron microscopy and X-ray photoelectron spectroscopy studies reveals that the migration of cations between metal layers and Li layers is an intrinsic feature of the chargedischarge process that increases the trapping of metal ions in interstitial tetrahedral sites. A correlation between these trapped ions and the voltage decay is established by expanding the study to both Li2Ru1−ySnyO3 and Li2RuO3; the slowest decay occurs for the cations with the largest ionic radii. This effect is robust, and the finding provides insights into new chemistry to be explored for developing high-capacity layered electrodes that evade voltage decay.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 39.737
Times cited: 395
DOI: 10.1038/nmat4137
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“Origin of the extra capacity in nitrogen-doped porous carbon nanofibers for high-performance potassium ion batteries”. Liu F, Meng J, Xia F, Liu Z, Peng H, Sun C, Xu L, Van Tendeloo G, Mai L, Wu J, Journal Of Materials Chemistry A 8, 18079 (2020). http://doi.org/10.1039/D0TA05626J
Abstract: While graphite has limited capacity as an anode material for potassium-ion batteries, nitrogen-doped carbon materials are more promising as extra capacity can usually be produced. However, the mechanism behind the origin of the extra capacity remains largely unclear. Here, the potassium storage mechanisms have been systematically studied in freestanding and porous N-doped carbon nanofibers with an additional similar to 100 mA h g(-1)discharge capacity at 0.1 A g(-1). The extra capacity is generated in the whole voltage window range from 0.01 to 2 V, which corresponds to both surface/interface K-ion absorptions due to the pyridinic N and pyrrolic N induced atomic vacancies and layer-by-layer intercalation due to the effects of graphitic N. As revealed by transmission electron microscopy, the N-doped samples have a clear and enhanced K-intercalation reaction. Theoretical calculations confirmed that the micropores with pyridinic N and pyrrolic N provide extra sites to form bonds with K, resulting in the extra capacity at high voltage. The chemical absorption of K-ions occurring inside the defective graphitic layer will prompt fast diffusion of K-ions and full realization of the intercalation capacity at low voltage. The approach of preparing N-doped carbon-based materials and the mechanism revealed by this work provide directions for the development of advanced materials for efficient energy storage.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 11.9
Times cited: 2
DOI: 10.1039/D0TA05626J
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“Origin of predominance of cementite among iron carbides in steel at elevated temperature”. Fang CM, Sluiter MHF, van Huis M, Ande CK, Zandbergen HW, Physical review letters 105, 4 (2010). http://doi.org/10.1103/PhysRevLett.105.055503
Abstract: A long-standing challenge in physics is to understand why cementite is the predominant carbide in steel. Here we show that the prevalent formation of cementite can be explained only by considering its stability at elevated temperature. A systematic highly accurate quantum mechanical study was conducted on the stability of binary iron carbides. The calculations show that all the iron carbides are unstable relative to the elemental solids, -Fe and graphite. Apart from a cubic Fe23C6 phase, the energetically most favorable carbides exhibit hexagonal close-packed Fe sublattices. Finite-temperature analysis showed that contributions from lattice vibration and anomalous Curie-Weis magnetic ordering, rather than from the conventional lattice mismatch with the matrix, are the origin of the predominance of cementite during steel fabrication processes.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 8.462
Times cited: 65
DOI: 10.1103/PhysRevLett.105.055503
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“Origin of magnetism and quasiparticles properties in Cr-doped TiO2”. da Pieve F, Di Matteo S, Rangel T, Giantomassi M, Lamoen D, Rignanese G-M, Gonze X, Physical review letters 110, 136402 (2013). http://doi.org/10.1103/PhysRevLett.110.136402
Abstract: Combining the local spin density approximation (LSDA)+U and an analysis of superexchange interactions beyond density functional theory, we describe the magnetic ground state of Cr-doped TiO2, an intensively studied and debated dilute magnetic oxide. In parallel, we correct our LSDA+U (+ superexchange) ground state through GW corrections (GW@LSDA+U) that reproduce the position of the impurity states and the band gaps in satisfying agreement with experiments. Because of the different topological coordinations of Cr-Cr bonds in the ground states of rutile and anatase, superexchange interactions induce either ferromagnetic or antiferromagnetic couplings of Cr ions. In Cr-doped anatase, this interaction leads to a new mechanism which stabilizes a (nonrobust) ferromagnetic ground state, in keeping with experimental evidence, without the need to invoke F-center exchange. The interplay between structural defects and vacancies in contributing to the superexchange is also unveiled.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 8.462
Times cited: 15
DOI: 10.1103/PhysRevLett.110.136402
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“Origin of different deactivation of Pd/SnO2 and Pd/GeO2 catalysts in methanol dehydrogenation and reforming: a comparative study”. Lorenz H, Zhao Q, Turner S, Lebedev OI, Van Tendeloo G, Kloetzer B, Rameshan C, Pfaller K, Applied catalysis : A : general 381, 242 (2010). http://doi.org/10.1016/j.apcata.2010.04.015
Abstract: Pd particles supported on SnO2 and GeO2 have been structurally investigated by X-ray diffraction, (High-Resolution) transmission and scanning electron microscopy after different reductive treatments to monitor the eventual formation of bimetallic phases and catalytically tested in methanol dehydrogenation/ reforming. For both oxides this included a thin film sample with well-defined Pd particles and a powder catalyst prepared by incipient wetness impregnation. The hexagonal and the tetragonal polymorph were studied for powder GeO2. Pd2Ge formation was observed on all GeO2-supported catalysts, strongly depending on the specific sample used. Reduction of the thin film at 573K resulted in full transformation into the bimetallic state. The partial solubility of hexagonal GeO2 in water and its thermal structural instability yielded Pd2Ge formation at 473 K, at the cost of a structurally inhomogeneous support and Ge metal formation at higher reduction temperatures. Pd on tetragonal GeO2 entered a state of strong metalsupport interaction after reduction at 573673 K, resulting in coalescing Pd2Ge particles on a sintered and re-crystallized support, apparently partially covering the bimetallic particles and decreasing the catalytic activity. Pd2Ge on amorphous thin film and hexagonal GeO2 converted methanol primarily via dehydrogenation to CO and H2. At 573 K, formation of Pd2Sn and also PdSn occurred on the Pd/SnO2 thin film. Pd3Sn2 (and to some extent Pd2Sn) were predominantly obtained on the respective powder catalyst. Strong deactivation with increasing reduction temperature was observed, likely not based on the classical strong metalsupport interaction effect, but rather on a combination of missing active structural ensembles on Sn-enriched bimetallic phases and the formation of metallic -Sn. Correlations to Pd and its bimetallics supported on ZnO, Ga2O3 and In2O3 were also discussed.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 4.339
Times cited: 14
DOI: 10.1016/j.apcata.2010.04.015
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“Orientational disorder in some molecular solids in relation to the boson peak in glasses”. Lamoen D, March NH, Physics letters : A 373, 799 (2009). http://doi.org/10.1016/j.physleta.2009.01.003
Abstract: Orientational disorder in some molecular solids is discussed in relation to the emphasis placed on transverse vibrational modes in glasses as the origin of the observed boson peak in two very recent contributions in Nature Materials. In particular, facts are here presented for (i) CH4, (ii) C60 and (iii) ethanol in their solid phases for (a) specific heat and (b) neutron scattering. The results for ethanol in particular do not fit in with the interpretation of the boson peak in terms of transverse acoustic phonons in disordered systems. Glasses will therefore have to be separated into at least two classes where the physical interpretation of the boson peak is concerned.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 1.772
Times cited: 3
DOI: 10.1016/j.physleta.2009.01.003
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“Orientation relationship of the austenite-to-ferrite transformation in austenitic stainless steels due to dissolution corrosion in contact with liquid Pb-Bi eutectic”. Charalampopoulou E, Cautaerts N, Van der Donck T, Schryvers D, Lambrinou K, Delville R, Scripta materialia 167, 66 (2019). http://doi.org/10.1016/J.SCRIPTAMAT.2019.03.035
Abstract: The orientation relationship of an austenite-to-ferrite phase transformation in 316L stainless steels induced by the loss of austenite stabilizers resulting from the steel dissolution corrosion in liquid Pb-Bi eutectic was studied by means of electron backscatter diffraction. The misorientations at the austenite/ferrite interface were compared to the prevailing orientation relationship models in steels. The Pitsch orientation relationship model was found to be predominant, which is unusual for austenite-to-ferrite bulk transformations in steels. The nature of this particular transformation, which involves loss of steel alloying elements and the presence of an interfacial liquid metal layer, is discussed to explain this finding. (C) 2019 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: 3.747
Times cited: 3
DOI: 10.1016/J.SCRIPTAMAT.2019.03.035
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“Ordering principles for tetrahedral chains in Ga- and Co-substituted YBCO intergrowths”. Milat O, Krekels T, Van Tendeloo G, Amelinckx S, Journal de physique: 1: physique générale, physique statistique, matière condensée, domaines interdisciplinaires 3, 1219 (1993)
Abstract: A model for superstructure ordering in the <<chain>> layers of Ga (Co) substituted YBCO intergrowths with general formula (REO2)NSr2MCu2O5 (M = Co, Ga; n = 1, 2, ...) is proposed. By Ga or Co substitution for Cu, the structure of the <<chain>> layer changes : instead of the CuO4 planar squares, the chains consist of MO4 tetrahedra (M = Ga, Co) running along the [110] perovskite direction. The existing model for the Ga substituted <<123>> implies that all the chains are the same. Our new model is based on the results of Electron diffraction and High-resolution electron microscopy investigations. The model reveals the occurrence of two types of chains as a consequence of <<opposite>> ordering between neighbouring tetrahedra. The comer linked tetrahedra in each chain appear as alternatingly rotated in opposite sense, and a chain itself, as being displaced with respect to the underlying structure in one of two senses ; either forth (right) or back (left) along the chain direction. The regular alternation of chains of opposite type doubles the periodicity within a layer and induces the possibility for intrinsic disorder in the chain layer stacking sequence. The planar superstructure and a staggered stacking of the tetrahedral chain layers is found irrespective of the rest of the intergrowth structure. Superstructure ordering in the case of Co substitution is more perfect than for the Ga substitution.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Times cited: 16
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“Ordering principles and defect structure of “1201”, “1212”, and “1222&rdquo, type (Hg,Pr)-Sr-(Sr,Ca,Pr)-Cu-O superconductors”. Van Tendeloo G, Hervieu M, Zhang XF, Raveau B, Journal of solid state chemistry 114, 369 (1995). http://doi.org/10.1006/jssc.1995.1057
Abstract: The new families of superconducting compounds ''1201'' (Hg0.4Pr0.6Sr2CuO4+delta), ''1212'' (Hg0.4Pr0.6Sr2(Ca1-x-ySrxPry) Cu2O6+delta), and ''1222'' (Hg0.4Pr0.6Sr2(Pr1.7Sr0.3)(2)Cu2O8+delta) all show ordering between praseodymium and mercury in the (Hg,Pr)O-delta plane, reducing the symmetry from tetragonal to orthorhombic or even to monoclinic. In the 1201 compound the ordered superstructure can be described as O-I (a(I) approximate to 2a(p), b(I), approximate to a(p), c(I) approximate to c(1201)). In the 1212 compound two distinct superstructures are identified, O-I (a(I) approximate to 2a(p), b(II) approximate to a(p), c(I) approximate to c(1212)) and O-II (a(II) approximate to 2a(p), b(II) approximate to a(p), c(II) approximate to 2c(1212)). In some compounds, such as Hg0.4Pr0.6Sr2(Ca0.4Sr0.4Pr0.2) Cu2O6+delta, the Hg-Pr ordering is only present in microdomains, but due to an ordering between Sr layers and Ca layers, the c-axis doubles and one obtains a tetragonal superstructure T-III (a(III) approximate to a(p), c(III) approximate to 2c(1212)). In the 1222 compound, ordering in the (Pr,Hg)O-delta plane is very defective; a large number of translation defects actually reduce the symmetry to triclinic. (C) 1995 Academic Press, Inc.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.133
Times cited: 11
DOI: 10.1006/jssc.1995.1057
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“Ordering of tetrahedral chains in the Sr2MnGaO5 brownmillerite”. Abakumov AM, Alekseeva AM, Rozova MG, Antipov EV, Lebedev OI, Van Tendeloo G, Journal of solid state chemistry 174, 319 (2003). http://doi.org/10.1016/S0022-4596(03)00226-3
Abstract: Tetrahedral chain ordering in the Sr2MnGaO5 structure is studied using electron diffraction (ED) and high-resolution electron microscopy. The ED patterns show the presence of satellite reflections, which indicate a commensurately modulated structure with a = 5.4056(8) Angstrom b 16.171(3) Angstrom, c = 5.5592(7) Angstrom, q – 1/2c*, superspace group Immma(00gamma,)s00. The Superstructure arises due to ordering of the two types of symmetry related tetrahedral chains (L and R) according to a ... LRLR ... sequence, where L and R chains alternate along the c-axis within the same (GaO) layer. Numerous defects at different structural levels were observed, comprising interleaving L and R chains, violation of the ... LRLR ... chain sequence within one layer, different stacking modes of the ... LRLR ... ordered layers with subsequent alternation of blocks of different width along the h-axis of the brownmillerite subcell and island fragmentation of the modulated superstructure. By in situ heating ED experiments it is found that the long-range ordering of the tetrahedral chains is stable tip to 665degreesC and is completely suppressed at 905degreesC. (C) 2003 Elsevier Inc. All rights reserved.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.299
Times cited: 34
DOI: 10.1016/S0022-4596(03)00226-3
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“Ordering of Pd2+ and Pd4+ in the mixed-valent palladate KPd2O3”. Panin RV, Khasanova NR, Bougerol C, Schnelle W, Van Tendeloo G, Antipov EV, Inorganic chemistry 49, 1295 (2010). http://doi.org/10.1021/ic902187a
Abstract: A new potassium palladate KPd2O3 was synthesized by the reaction of KO2 and PdO at elevated oxygen pressure. Its crystal structure was solved from powder X-ray diffraction data in the space group Rm (a = 6.0730(1) Å, c = 18.7770(7) Å, and Z = 6). KPd2O3 represents a new structure type, consisting of an alternating sequence of K+ and Pd2O3− layers with ordered Pd2+ and Pd4+ ions. The presence of palladium ions in di- and tetravalent low-spin states was confirmed by magnetic susceptibility measurements.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 4.857
Times cited: 9
DOI: 10.1021/ic902187a
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“Ordering and defects in BanTaxTiyO3n ternary oxides”. Nistor L, Van Tendeloo G, Amelinckx S, Shpanchenko RV, van Landuyt J, Electron Microscopy 1994, Vols 2a And 2b: Applications In Materials Sciences , 869 (1994)
Keywords: P1 Proceeding; Electron microscopy for materials research (EMAT)
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“Ordered end-member of ZSM-48 zeolite family”. Kirschhock CEA, Liang D, Van Tendeloo G, Fécant A, Hastoye G, Vanbutsele G, Bats N, Guillon E, Martens JA, Chemistry of materials 21, 371 (2009). http://doi.org/10.1021/cm802614x
Abstract: ZSM-48 and related zeolites are considered to be highly disordered structures. Different polytypes can be clearly distinguished by simulation of high-resolution electron microscopy images. Synthesis of phase-pure polytypes was attempted. One of the investigated samples crystallized via seeding designated as COK-8 consisted of nanoscopic, needlelike crystals with a very large length/width ratio, growing along the pore direction. These specimens are phase-pure polytype 6 (PT6, numbering according to Lobo and van Koningsveld). Aggregates of these nanoneedles occasionally contained a second polytype: PT1. The latter polytype occurred more abundantly in larger crystal rods in an IZM-1 sample crystallized in ethylene glycol. Here too, the isolated crystallites mainly consist of large, defect-free regions of PT6. A simulation of polytype lattice energies offers a rational explanation for the observed polytypical intergrowth formation.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 30
DOI: 10.1021/cm802614x
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“Order, disorder and structure of crystals C60/C70”. Bohr J, Gibbs D, Sinha SK, Krätschmer W, Van Tendeloo G, Larsen E, Egsgaard H, Berman LE, Europhysics letters 17, 327 (1992). http://doi.org/10.1209/0295-5075/17/4/008
Abstract: Single crystals with two different morphologies, black and brown, of C60 with about 12% C70 have been studied by synchrotron X-ray diffraction. Integrated intensities from 8 reflections show that the charge distribution of the C60 cluster is shell-like giving rise to an oscillatory behaviour in the diffracted intensities. From the intensities, the distance between diametrically opposite carbon atoms has been determined to be (7.24 +/- 0.22) angstrom. The thickness of the charge distribution of the shell can be estimated as 3.06 angstrom and the cavity within a C60 cluster to have a diameter of about 4.18 angstrom. The finite longitudinal width of the diffraction peaks from black crystals indicates a lack of long-range crystalline order. The rocking curves are about 7-degrees broad and depict an unusually smooth behaviour. This may be indicative of a glassy or hexatic phase. High-resolution electron microscopy allows small crystallites with a relatively well-defined orientation relationship to be identified. In contrast, brown crystals have long-range order.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.095
Times cited: 15
DOI: 10.1209/0295-5075/17/4/008
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“Order and twining in Sb2W0.75Mo0.25O6”. Enjalbert R, Galy J, Castro A, Lidin S, Withers R, Van Tendeloo G, Solid state sciences 5, 721 (2003). http://doi.org/10.1016/S1293-2558(03)00093-1
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 1.811
Times cited: 3
DOI: 10.1016/S1293-2558(03)00093-1
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