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“Cocatalyzing Pt/PtO phase-junction nanodots on hierarchically porous TiO2 for highly enhanced photocatalytic hydrogen production”. Ren X-N, Hu Z-Y, Jin J, Wu L, Wang C, Liu J, Liu F, Wu M, Li Y, Van Tendeloo G, Su B-L, ACS applied materials and interfaces 9, 29687 (2017). http://doi.org/10.1021/ACSAMI.7B07226
Abstract: Phase-junctions. between a cocatalyst and its semiconductor host are quite effective to enhance the photo catalytic activity and are widely studied, while reports on the phase-juncted cocatalyst are still rare. In this work, we report the deposition of the Pt/PtO phase-juncted nanodots as cocatalyst via NaOH modification of an interconnected meso-macroporous TiO2 network with high surface area and inner-particle mesopores to enhance the performance of photocatalytic H-2 production. Our results show that NaOH modification can largely influence Pt/PtO phase-juncted nanodot formation and dispersity. Compared to the TiO2 nano particles, the hierarchically meso-macroporous TiO2 network containing 0.18 wt % Pt/PtO phase-juneted cocatalyst demonstrates a highest photocatalytic H-2 rate of 13 mmol g(-1) h(-1) under simulated solar light, and possesses a stable cycling activity without obvious decrease after five cycles. Such high H-2 production performance can be attributed to both the phase-juncted Pt/PtO providing more active sites while PtO suppresses the undesirable hydrogen back reaction, and the special hierarchically porous TiO2 network with inner-particle mesopores presenting short diffusion path lengths for photogenerated electrons and enhanced light harvesting efficiency. This work suggests that Pt/PtO phase-juncted cocatalyst on hierarchically porous TiO2 nanostructures is a promising strategy for advanced photocatalytic H-2 production.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 7.504
Times cited: 18
DOI: 10.1021/ACSAMI.7B07226
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“Single-walled carbon nanotube reactor for redox transformation of mercury dichloride”. Fedoseeva YV, Orekhov AS, Chekhova GN, Koroteev VO, Kanygin MA, Seovskiy BV, Chuvilin A, Pontiroli D, Ricco M, Bulusheva LG, Okotrub AV, ACS nano 11, 8643 (2017). http://doi.org/10.1021/ACSNANO.7B04361
Abstract: <script type='text/javascript'>document.write(unpmarked('Single-walled carbon nanotubes (SWCNTs) possessing a confined inner space protected by chemically resistant shells are promising for delivery, storage, and desorption of various compounds, as well as carrying out specific reactions. Here, we show that SWCNTs interact with molten mercury dichloride (HgCl2) and guide its transformation into dimercury dichloride (Hg2Cl2) in the cavity. The chemical state of host SWCNTs remains almost unchanged except for a small p-doping from the guest Hg2Cl2 nanocrystals. The density functional theory calculations reveal that the encapsulated HgCl2 molecules become negatively charged and start interacting via chlorine bridges when local concentration increases. This reduces the bonding strength in HgCl2, which facilitates removal of chlorine, finally leading to formation of Hg2Cl2 species. The present work demonstrates that SWCNTs not only serve as a template for growing nanocrystals but also behave as an electron-transfer catalyst in the spatially confined redox reaction by donation of electron density for temporary use by the guests.'));
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 13.942
Times cited: 11
DOI: 10.1021/ACSNANO.7B04361
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“Evidence of tetragonal distortion as the origin of the ferromagnetic ground state in gamma-Fe nanoparticles”. Augustyns V, van Stiphout K, Joly V, Lima TAL, Lippertz G, Trekels M, Menendez E, Kremer F, Wahl U, Costa ARG, Correia JG, Banerjee D, Gunnlaugsson HP, von Bardeleben J, Vickridge I, Van Bael MJ, Hadermann J, Araujo JP, Temst K, Vantomme A, Pereira LMC, Physical review B 96, 174410 (2017). http://doi.org/10.1103/PHYSREVB.96.174410
Abstract: <script type='text/javascript'>document.write(unpmarked('gamma-Fe and related alloys are model systems of the coupling between structure and magnetism in solids. Since different electronic states (with different volumes and magnetic ordering states) are closely spaced in energy, small perturbations can alter which one is the actual ground state. Here, we demonstrate that the ferromagnetic state of gamma-Fe nanoparticles is associated with a tetragonal distortion of the fcc structure. Combining a wide range of complementary experimental techniques, including low-temperature Mossbauer spectroscopy, advanced transmission electron microscopy, and synchrotron radiation techniques, we unambiguously identify the tetragonally distorted ferromagnetic ground state, with lattice parameters a = 3.76(2) angstrom and c = 3.50(2) angstrom, and a magnetic moment of 2.45(5) mu(B) per Fe atom. Our findings indicate that the ferromagnetic order in nanostructured gamma-Fe is generally associated with a tetragonal distortion. This observation motivates a theoretical reassessment of the electronic structure of gamma-Fe taking tetragonal distortion into account.'));
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.836
Times cited: 1
DOI: 10.1103/PHYSREVB.96.174410
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“Highly selective gas separation membrane using in situ amorphised metal-organic frameworks”. Kertik A, Wee LH, Pfannmöller M, Bals S, Martens JA, Vankelecom IFJ, Energy &, environmental science 10, 2342 (2017). http://doi.org/10.1039/C7EE01872J
Abstract: Conventional carbon dioxide (CO2) separation in the petrochemical industry via cryogenic distillation is energy intensive and environmentally unfriendly. Alternatively, polymer membrane-based separations are of significant interest owing to low production cost, low-energy consumption and ease of upscaling. However, the implementation of commercial polymeric membranes is limited by their permeability and selectivity trade-off and the insufficient thermal and chemical stability. Herein, a novel type of amorphous mixed matrix membrane (MMM) able to separate CO2/CH4 mixtures with the highest selectivities ever reported for MOF based MMMs is presented. The MMM consists of an amorphised metal-organic framework (MOF) dispersed in an oxidatively cross-linked matrix achieved by fine tuning of the thermal treatment temperature in air up to 350 degrees C which drastically boosts the separation properties of the MMM. Thanks to the protection of the surrounding polymer, full oxidation of this MOF (i.e. ZIF-8) is prevented, and amorphisation of the MOF is realized instead, thus in situ creating a molecular sieve network. In addition, the treatment also improves the filler-polymer adhesion and induces an oxidative cross-linking of the polyimide matrix, resulting in MMMs with increased stability or plasticization resistance at high pressure up to 40 bar, marking a new milestone as new molecular sieve MOF MMMs for challenging natural gas purification applications. A new field for the use of amorphised MOFs and a variety of separation opportunities for such MMMs are thus opened.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 29.518
Times cited: 122
DOI: 10.1039/C7EE01872J
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“New solid electrolyte Na9Al(MoO4)6 : structure and Na+ ion conductivity”. Savina AA, Morozov VA, Buzlukov AL, Arapova IY, Stefanovich SY, Baklanova YV, Denisova TA, Medvedeva NI, Bardet M, Hadermann J, Lazoryak BI, Khaikina EG, Chemistry of materials 29, 8901 (2017). http://doi.org/10.1021/ACS.CHEMMATER.7B03989
Abstract: <script type='text/javascript'>document.write(unpmarked('Solid electrolytes are important materials with a wide range of technological applications. This work reports the crystal structure and electrical properties of a new solid electrolyte Na9Al(MoO4)(6). The monoclinic Na9Al(MoO4)(6) consists of isolated polyhedral, [Al(MoO4)(6)](9-) clusters composed of a central AlO6 octahedron sharing vertices with six MoO4 tetrahedra to form a three-dimensional framework. The AlO6 octahedron also shares edges with one NalO(6) octahedron and two Na2O(6) octahedra. Na3-Na5 atoms are located in the framework cavities. The structure is related to that of sodium ion conductor II-Na3Fe2(AsO4)(3). High-temperature conductivity measurements revealed that the conductivity (sigma) of Na9Al(MoO4)(6) at 803 K equals 1.63 X 10(-2) S cm(-1). The temperature behavior of the Na-23 and Al-27 nuclear magnetic resonance spectra and the spin-lattice relaxation rates of the Na-23 nuclei indicate the presence of fast Na+ ion diffusion in the studied compound. At T\u003C490 K, diffusion occurs by means of Na+ ion jumps exclusively through the sublattice of Na3-Na5 positions, whereas Na1 and Na2 become involved in the diffusion processes (through chemical exchange with the Na3-Na5 sublattice) only at higher temperatures.'));
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 13
DOI: 10.1021/ACS.CHEMMATER.7B03989
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“From precursor powders to CsPbX3 perovskite nanowires : one-pot synthesis, growth mechanism, and oriented self-assembly”. Tong Y, Bohn BJ, Bladt E, Wang K, Mueller-Buschbaum P, Bals S, Urban AS, Polavarapu L, Feldmann J, Angewandte Chemie: international edition in English 56, 13887 (2017). http://doi.org/10.1002/ANIE.201707224
Abstract: <script type='text/javascript'>document.write(unpmarked('The colloidal synthesis and assembly of semiconductor nanowires continues to attract a great deal of interest. Herein, we describe the single-step ligand-mediated synthesis of single-crystalline CsPbBr3 perovskite nanowires (NWs) directly from the precursor powders. Studies of the reaction process and the morphological evolution revealed that the initially formed CsPbBr3 nanocubes are transformed into NWs through an oriented-attachment mechanism. The optical properties of the NWs can be tuned across the entire visible range by varying the halide (Cl, Br, and I) composition through subsequent halide ion exchange. Single-particle studies showed that these NWs exhibit strongly polarized emission with a polarization anisotropy of 0.36. More importantly, the NWs can self-assemble in a quasi-oriented fashion at an air/liquid interface. This process should also be easily applicable to perovskite nanocrystals of different morphologies for their integration into nanoscale optoelectronic devices.'));
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 11.994
Times cited: 223
DOI: 10.1002/ANIE.201707224
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“Frozen lattice and absorptive model for high angle annular dark field scanning transmission electron microscopy : a comparison study in terms of integrated intensity and atomic column position measurement”. Alania M, Lobato Hoyos IP, Van Aert S, Ultramicroscopy 184, 188 (2018). http://doi.org/10.1016/J.ULTRAMIC.2017.08.021
Abstract: <script type='text/javascript'>document.write(unpmarked('In this paper, both the frozen lattice (FL) and the absorptive potential (AP) approximation models are compared in terms of the integrated intensity and the precision with which atomic columns can be located from an image acquired using high angle annular dark field (HAADF) scanning transmission electron microscopy (STEM). The comparison is made for atoms of Cu, Ag, and Au. The integrated intensity is computed for both an isolated atomic column and an atomic column inside an FCC structure. The precision has been computed using the so-called Cramer-Rao Lower Bound (CRLB), which provides a theoretical lower bound on the variance with which parameters can be estimated. It is shown that the AP model results into accurate measurements for the integrated intensity only for small detector ranges under relatively low angles and for small thicknesses. In terms of the attainable precision, both methods show similar results indicating picometer range precision under realistic experimental conditions. (C) 2017 Elsevier B.V. All rights reserved.'));
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.843
DOI: 10.1016/J.ULTRAMIC.2017.08.021
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“Observation of hidden atomic order at the interface between Fe and topological insulator Bi2Te3”. Sanchez-Barriga J, Ogorodnikov II, Kuznetsov MV, Volykhov AA, Matsui F, Callaert C, Hadermann J, Verbitskiy NI, Koch RJ, Varykhalov A, Rader O, Yashina LV, Physical chemistry, chemical physics 19, 30520 (2017). http://doi.org/10.1039/C7CP04875K
Abstract: <script type='text/javascript'>document.write(unpmarked('To realize spintronic devices based on topological insulators (TIs), well-defined interfaces between magnetic metals and TIs are required. Here, we characterize atomically precisely the interface between the 3d transition metal Fe and the TI Bi2Te3 at different stages of its formation. Using photoelectron diffraction and holography, we show that after deposition of up to 3 monolayers Fe on Bi2Te3 at room temperature, the Fe atoms are ordered at the interface despite the surface disorder revealed by our scanning-tunneling microscopy images. We find that Fe occupies two different sites: a hollow adatom deeply relaxed into the Bi2Te3 quintuple layers and an interstitial atom between the third (Te) and fourth (Bi) atomic layers. For both sites, our core-level photoemission spectra and density-functional theory calculations demonstrate simultaneous chemical bonding of Fe to both Te and Bi atoms. We further show that upon deposition of Fe up to a thickness of 20 nm, the Fe atoms penetrate deeper into the bulk forming a 2-5 nm interface layer containing FeTe. In addition, excessive Bi is pushed down into the bulk of Bi2Te3 leading to the formation of septuple layers of Bi3Te4 within a distance of similar to 25 nm from the interface. Controlling the magnetic properties of the complex interface structures revealed by our work will be of critical importance when optimizing the efficiency of spin injection in TI-based devices.'));
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 4.123
Times cited: 4
DOI: 10.1039/C7CP04875K
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“Improving the redox response stability of ceria-zirconia nanocatalysts under harsh temperature conditions”. Arias-Duque C, Bladt E, Munoz MA, Hernandez-Garrido JC, Cauqui MA, Rodriguez-Izquierdo JM, Blanco G, Bals S, Calvino JJ, Perez-Omil JA, Yeste MP, Chemistry of materials 29, 9340 (2017). http://doi.org/10.1021/ACS.CHEMMATER.7B03336
Abstract: <script type='text/javascript'>document.write(unpmarked('By depositing ceria on the surface of yttrium stabilized zirconia (YSZ) nanocrystals and further activation under high-temperature reducing conditions, a 13% mol. CeO2/YSZ catalyst structured as subnanometer thick, pyrochlore-type, ceria-zirconia islands has been prepared. This nanostructured catalyst depicts not only high oxygen storage capacity (OSC) values but, more importantly, an outstandingly stable redox response upon oxidation and reduction treatments at very high temperatures, above 1000 degrees C. This behavior largely improves that observed on conventional ceria-zirconia solid solutions, not only of the same composition but also of those with much higher molar cerium contents. Advanced scanning transmission electron microscopy (STEM-XEDS) studies have revealed as key not only to detect the actual state of the lanthanide in this novel nanocatalyst but also to rationalize its unusual resistance to redox deactivation at very high temperatures. In particular, high-resolution X-ray dispersive energy studies have revealed the presence of unique bilayer ceria islands on top of the surface of YSZ nanocrystals, which remain at surface positions upon oxidation and reduction treatments up to 1000 degrees C. Diffusion of ceria into the bulk of these crystallites upon oxidation at 1100 degrees C irreversibly deteriorates both the reducibility and OSC of this nanostructured catalyst.'));
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 20
DOI: 10.1021/ACS.CHEMMATER.7B03336
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“The influence of acids on tuning the pore size of mesoporous TiO2 templated by non-ionic block copolymers”. Loreto S, Vanrompay H, Mertens M, Bals S, Meynen V, European journal of inorganic chemistry 2018, 62 (2018). http://doi.org/10.1002/EJIC.201701266
Abstract: <script type='text/javascript'>document.write(unpmarked('We show the possibility to tune the pore size of mesoporous TiO2 templated by non-ionic block copolymers by adding different inorganic acids at well-chosen concentration. The effect of the inorganic anions on both the TiO2 cluster formation and the non-ionic block copolymers micelles is investigated to explain the experimental results.'));
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Laboratory of adsorption and catalysis (LADCA)
Impact Factor: 2.444
Times cited: 6
DOI: 10.1002/EJIC.201701266
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van den Bos KHW (2017) Quantitative atomic resolution transmission electron microscopy for heterogeneous nanomaterials. Antwerpen
Keywords: Doctoral thesis; Electron microscopy for materials research (EMAT)
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“Epitaxial stress-free growth of high crystallinity ferroelectric PbZr0.52Ti0.48O3 on GaN/AlGaN/Si(111) substrate”. Li L, Liao Z, Gauquelin N, Minh Duc Nguyen, Hueting RJE, Gravesteijn DJ, Lobato I, Houwman EP, Lazar S, Verbeeck J, Koster G, Rijnders G, Advanced Materials Interfaces 5, 1700921 (2018). http://doi.org/10.1002/ADMI.201700921
Abstract: <script type='text/javascript'>document.write(unpmarked('Due to its physical properties gallium-nitride (GaN) is gaining a lot of attention as an emerging semiconductor material in the field of high-power and high-frequency electronics applications. Therefore, the improvement in the performance and/or perhaps even extension in functionality of GaN based devices would be highly desirable. The integration of ferroelectric materials such as lead-zirconate-titanate (PbZrxTi1-xO3) with GaN has a strong potential to offer such an improvement. However, the large lattice mismatch between PZT and GaN makes the epitaxial growth of Pb(Zr1-xTix)O-3 on GaN a formidable challenge. This work discusses a novel strain relaxation mechanism observed when MgO is used as a buffer layer, with thicknesses down to a single unit cell, inducing epitaxial growth of high crystallinity Pb(Zr0.52Ti0.48)O-3 (PZT) thin films. The epitaxial PZT films exhibit good ferroelectric properties, showing great promise for future GaN device applications.'));
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 4.279
Times cited: 15
DOI: 10.1002/ADMI.201700921
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“Quantitative HAADF STEM of SiGe in presence of amorphous surface layers from FIB preparation”. Grieb T, Tewes M, Schowalter M, Müller-Caspary K, Krause FF, Mehrtens T, Hartmann J-M, Rosenauer A, Ultramicroscopy 184, 29 (2018). http://doi.org/10.1016/J.ULTRAMIC.2017.09.012
Abstract: <script type='text/javascript'>document.write(unpmarked('The chemical composition of four Si1-xGex layers grown on silicon was determined from quantitative scanning transmission electron microscopy (STEM). The chemical analysis was performed by a comparison of the high-angle annular dark field (HAADF) intensity with multislice simulations. It could be shown that amorphous surface layers originating from the preparation process by focused-ion beam (FIB) at 30 kV have a strong influence on the quantification: the local specimen thickness is overestimated by approximately a factor of two, and the germanium concentration is substantially underestimated. By means of simulations, the effect of amorphous surface layers on the HAADF intensity of crystalline silicon and germanium is investigated. Based on these simulations, a method is developed to analyze the experimental HAADF-STEM images by taking the influence of the amorphous layers into account which is done by a reduction of the intensities by multiplication with a constant factor. This suggested modified HAADF analysis gives germanium concentrations which are in agreement with the nominal values. The same TEM lamella was treated with low-voltage ion milling which removed the amorphous surface layers completely. The results from subsequent quantitative HAADF analyses are in agreement with the nominal concentrations which validates the applicability of the used frozen-lattice based multislice simulations to describe the HAADF scattering of Si1-xGex in STEM. (C) 2017 Elsevier B.V. All rights reserved.'));
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.843
Times cited: 7
DOI: 10.1016/J.ULTRAMIC.2017.09.012
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“Automatic correction of nonlinear damping effects in HAADF-STEM tomography for nanomaterials of discrete compositions”. Zhong Z, Aveyard R, Rieger B, Bals S, Palenstijn WJ, Batenburg KJ, Ultramicroscopy 184, 57 (2018). http://doi.org/10.1016/J.ULTRAMIC.2017.10.013
Abstract: <script type='text/javascript'>document.write(unpmarked('HAADF-STEM tomography is a common technique for characterizing the three-dimensional morphology of nanomaterials. In conventional tomographic reconstruction algorithms, the image intensity is assumed to be a linear projection of a physical property of the specimen. However, this assumption of linearity is not completely valid due to the nonlinear damping of signal intensities. The nonlinear damping effects increase w.r.t the specimen thickness and lead to so-called \u0022cupping artifacts\u0022, due to a mismatch with the linear model used in the reconstruction algorithm. Moreover, nonlinear damping effects can strongly limit the applicability of advanced reconstruction approaches such as Total Variation Minimization and discrete tomography. In this paper, we propose an algorithm for automatically correcting the nonlinear effects and the subsequent cupping artifacts. It is applicable to samples in which chemical compositions can be segmented based on image gray levels. The correction is realized by iteratively estimating the nonlinear relationship between projection intensity and sample thickness, based on which the projections are linearized. The correction and reconstruction algorithms are tested on simulated and experimental data. (C) 2017 Elsevier B.V. All rights reserved.'));
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.843
Times cited: 8
DOI: 10.1016/J.ULTRAMIC.2017.10.013
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“Interplay of morphology, composition, and optical properties of InP-based quantum dots emitting at the 1.55 \mum telecom wavelength”. Carmesin C, Schowalter M, Lorke M, Mourad D, Grieb T, Müller-Caspary K, Yacob M, Reithmaier JP, Benyoucef M, Rosenauer A, Jahnke F, Physical review B 96, 235309 (2017). http://doi.org/10.1103/PHYSREVB.96.235309
Abstract: <script type='text/javascript'>document.write(unpmarked('Results for the development and detailed analysis of self-organized InAs/InAlGaAs/InP quantum dots suitable for single-photon emission at the 1.55 mu m telecom wavelength are reported. The structural and compositional properties of the system are obtained from high-resolution scanning transmission electron microscopy of individual quantum dots. The system is composed of almost pure InAs quantum dots embedded in quaternary InAlGaAs barrier material, which is lattice matched to the InP substrate. When using the measured results for a representative quantum-dot geometry as well as experimentally reconstructed alloy concentrations, a combination of strain-field and electronic-state calculations is able to reproduce the quantum-dot emission wavelength in agreement with the experimentally determined photoluminescence spectrum. The inhomogeneous broadening of the latter can be related to calculated variations of the emission wavelength for the experimentally deduced In-concentration fluctuations and size variations.'));
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.836
Times cited: 3
DOI: 10.1103/PHYSREVB.96.235309
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“Spin-orbit semimetal SrIrO3 in the two-dimensional limit”. Groenendijk DJ, Autieri C, Girovsky J, Martinez-Velarte MC, Manca N, Mattoni G, Monteiro AMRVL, Gauquelin N, Verbeeck J, Otte AF, Gabay M, Picozzi S, Caviglia AD, Physical review letters 119, 256403 (2017). http://doi.org/10.1103/PHYSREVLETT.119.256403
Abstract: <script type='text/javascript'>document.write(unpmarked('We investigate the thickness-dependent electronic properties of ultrathin SrIrO3 and discover a transition from a semimetallic to a correlated insulating state below 4 unit cells. Low-temperature magnetoconductance measurements show that spin fluctuations in the semimetallic state are significantly enhanced while approaching the transition point. The electronic properties are further studied by scanning tunneling spectroscopy, showing that 4 unit cell SrIrO(3)d is on the verge of a gap opening. Our density functional theory calculations reproduce the critical thickness of the transition and show that the opening of a gap in ultrathin SrIrO3 requires antiferromagnetic order.'));
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 8.462
Times cited: 79
DOI: 10.1103/PHYSREVLETT.119.256403
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“Synthesis of Li-Rich NMC : a comprehensive study”. Pimenta V, Sathiya M, Batuk D, Abakumov AM, Giaume D, Cassaignon S, Larcher D, Tarascon J-M, Chemistry of materials 29, 9923 (2017). http://doi.org/10.1021/ACS.CHEMMATER.7B03230
Abstract: <script type='text/javascript'>document.write(unpmarked('Li-rich NMC are considered nowadays as one of the most promising candidates for high energy density cathodes. One significant challenge is nested in adjusting their synthesis conditions to reach optimum electrochemical performance, but no consensus has been reached yet on the ideal synthesis protocol. Herein, we revisited the elaboration of Li-rich NMC electrodes by focusing on the science involved through each synthesis steps using carbonate Ni0.1625Mn0.675Co0.1625CO3 precursor coprecipitation combined with solid state synthesis. We demonstrated the effect of precursors concentration on the kinetics of the precipitation reaction and provided clues to obtain spherically agglomerated NMC carbonates of different sizes. Moreover, we highlighted the strong impact of the Li2CO3/NMC carbonate ratio on the morphology and particles size of Li-rich NMC and subsequently on their electrochemical performance. Ratio of 1.35 was found to reproducibly give the best performance with namely a first discharge capacity of 269 mAh g(-1) and capacity retention of 89.6% after 100 cycles. We hope that our results, which reveal how particle size, morphology, and phase composition affect the materials electrochemical performance, will help in reconciling literature data while providing valuable fundamental information for up scaling approaches.'));
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 23
DOI: 10.1021/ACS.CHEMMATER.7B03230
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“Crystal growth of the Nowotny chimney ladder phase Fe2Ge3 : exploring new Fe-based narrow-gap semiconductor with promising thermoelectric performance”. Verchenko VY, Wei Z, Tsirlin AA, Callaert C, Jesche A, Hadermann J, Dikarev EV, Shevelkov AV, Chemistry of materials 29, 9954 (2017). http://doi.org/10.1021/ACS.CHEMMATER.7B03300
Abstract: <script type='text/javascript'>document.write(unpmarked('A new synthetic approach based on chemical transport reactions has been introduced to obtain the Nowotny chimney ladder phase Fe2Ge3 in the form of single crystals and polycrystalline powders. The single crystals possess the stoichiometric composition and the commensurate chimney ladder structure of the Ru2Sn3 type in contrast to the polycrystalline samples that are characterized by a complex microstructure. In compliance with the 18-n electron counting rule formulated for T-E intermetallics, electronic structure calculations reveal a narrow-gap semiconducting behavior of Fe2Ge3 favorable for high thermoelectric performance. Measurements of transport and thermoelectric properties performed on the polycrystalline samples confirm the formation of a narrow band gap of similar to 30 meV and reveal high absolute values of the Seebeck coefficient at elevated temperatures. Low glass-like thermal conductivity is observed in a wide temperature range that might be caused by the underlying complex microstructure.'));
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 11
DOI: 10.1021/ACS.CHEMMATER.7B03300
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“Designing diameter-modulated heterostructure nanowires of PbTe/Te by controlled dewetting”. Kumar A, Kundu S, Samantaray D, Kundu P, Zanaga D, Bals S, Ravishankar N, Nano letters 17, 7226 (2017). http://doi.org/10.1021/ACS.NANOLETT.7B02442
Abstract: <script type='text/javascript'>document.write(unpmarked('Heterostructures consisting of semiconductors with controlled morphology and interfaces find applications in many fields. A range of axial, radial, and diameter-modulated nanostructures have been synthesized primarily using vapor phase methods. Here, we present a simple wet chemical routine to synthesize heterostructures of PbTe/Te using Te nanowires as templates. A morphology evolution study for the formation of these heterostructures has been performed. On the basis of these control experiments, a pathway for the formation of these nanostructures is proposed. Reduction of a Pb precursor to Pb on Te nanowire templates followed by interdiffusion of Pb/Te leads to the formation of a thin shell of PbTe on the Te wires. Controlled dewetting of the thin shell leads to the formation of cube-shaped PbTe that is periodically arranged on the Te wires. Using control experiments, we show that different reactions parameters like rate of addition of the reducing agent, concentration of Pb precursor and thickness of initial Te nanowire play a critical role in controlling the spacing between the PbTe cubes on the Te wires. Using simple surface energy arguments, we propose a mechanism for the formation of the hybrid. The principles presented are general and can be exploited for the synthesis of other nanoscale heterostructures.'));
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 12.712
Times cited: 11
DOI: 10.1021/ACS.NANOLETT.7B02442
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“The role of the electrode surface in Na-Air batteries : insights in electrochemical product formation and chemical growth of NaO2”. Lutz L, Corte DAD, Chen Y, Batuk D, Johnson LR, Abakumov A, Yate L, Azaceta E, Bruce PG, Tarascon J-M, Grimaud A, Advanced energy materials 8, 1701581 (2018). http://doi.org/10.1002/AENM.201701581
Abstract: The Na-air battery, because of its high energy density and low charging overpotential, is a promising candidate for low-cost energy storage, hence leading to intensive research. However, to achieve such a battery, the role of the positive electrode material in the discharge process must be understood. This issue is herein addressed by exploring the electrochemical reduction of oxygen, as well as the chemical formation and precipitation of NaO2 using different electrodes. Whereas a minor influence of the electrode surface is demonstrated on the electrochemical formation of NaO2, a strong dependence of the subsequent chemical precipitation of NaO2 is identified. In the origin, this effect stems from the surface energy and O-2/O-2(-) affinity of the electrode. The strong interaction of Au with O-2/O-2(-) increases the nucleation rate and leads to an altered growth process when compared to C surfaces. Consequently, thin (3 mu m) flakes of NaO2 are found on Au, whereas on C large cubes (10 mu m) of NaO2 are formed. This has significant impact on the cell performance and leads to four times higher capacity when C electrodes with low surface energy and O-2/O-2(-) affinity are used. It is hoped that these findings will enable the design of new positive electrode materials with optimized surfaces.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 16.721
Times cited: 13
DOI: 10.1002/AENM.201701581
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“High-temperature properties of (La,Ca)(Fe,Mg,Mo)O3-\delta perovskites as prospective electrode materials for symmetrical SOFC”. Istomin SY, Morozov AV, Abdullayev MM, Batuk M, Hadermann J, Kazakov SM, Sobolev AV, Presniakov IA, Antipov EV, Journal of solid state chemistry 258, 1 (2018). http://doi.org/10.1016/J.JSSC.2017.10.005
Abstract: La1-yCayFe0.5+x(Mg,Mo)(0.5-x)O3-delta oxides with the orthorhombic GdFeO3-type perovskite structure have been synthesized at 1573 K. Transmission electron microscopy study for selected samples shows the coexistence of domains of perovskite phases with ordered and disordered B-cations. Mossbauer spectroscopy studies performed at 300 K and 573 K show that while compositions with low Ca-content (La0.55Ca0.45Fe0.5Mg0.2625Mo0.2375O3-delta and La0.5Ca0.5Fe0.6Mg0.175Mo0.225O3-delta) are nearly oxygen stoichiometric, La0.2Ca0.8Fe0.5Mg0.2625Mo0.2375O3-delta is oxygen deficient with delta approximate to 0.15. Oxides are stable in reducing atmosphere (Ar/H-2, 8%) at 1173 K for 12 h. No additional phases have been observed at XRPD patterns of all studied perovskites and Ce1-xGdxO2-x/2 electrolyte mixtures treated at 1173-1373K, while Fe-rich compositions (x >= 0.1) react with Zr1-xYxO2-x/2 electrolyte above 1273 K. Dilatometry studies reveal that all samples show rather low thermal expansion coefficients (TECs) in air of 11.4-12.7 ppm K-1. In reducing atmosphere their TECs were found to increase up to 12.1-15.4 ppm K-1 due to chemical expansion effect. High-temperature electrical conductivity measurements in air and Ar/H-2 atmosphere show that the highest conductivity is observed for Fe- and Ca-rich compositions. Moderate values of electrical conductivity and TEC together with stability towards chemical interaction with typical SOFC electrolytes make novel Fe-containing perovskites promising electrode materials for symmetrical solid oxide fuel cell.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.299
Times cited: 5
DOI: 10.1016/J.JSSC.2017.10.005
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“Comparative study of the magnetic properties of La3Ni2B'O9 for B' = Nb, Ta or Sb”. Chin C-M, Battle PD, Blundell SJ, Hunter E, Lang F, Hendrickx M, Sena RP, Hadermann J, Journal of solid state chemistry 258, 825 (2018). http://doi.org/10.1016/J.JSSC.2017.12.018
Abstract: Polycrystalline samples of La3Ni2NbO9 and La3Ni2TaO9 have been characterised by X-ray and neutron diffraction, electron microscopy, magnetometry and muon spin relaxation (mu SR); the latter technique was also applied to La3Ni2SbO9. On the length scale of a neutron diffraction experiment, the six-coordinate sites of the monoclinic perovskite structure are occupied in a 1:1 ordered manner by Ni and a random 1/3Ni/2/3B' mixture. Electron microscopy demonstrated that this 1:1 ordering is maintained over microscopic distances, although diffuse scattering indicative of short-range ordering on the mixed site was observed. No magnetic Bragg scattering was observed in neutron diffraction patterns collected from La3Ni2B'O-9 (B' = Nb or Ta) at 5 K although in each case mu SR identified the presence of static spins below 30 K. Magnetometry showed that La3Ni2NbO9 behaves as a spin glass below 29 K but significant short-range interactions are present in La3Ni2NbO9 below 85 K. The contrasting properties of these compounds are discussed in terms of their microstructure.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.299
Times cited: 6
DOI: 10.1016/J.JSSC.2017.12.018
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“Interplay of interfacial layers and blend composition to reduce thermal degradation of polymer solar cells at high temperature”. Ben Dkhil S, Pfannmöller M, Schroeder RR, Alkarsifi R, Gaceur M, Koentges W, Heidari H, Bals S, Margeat O, Ackermann J, Videlot-Ackermann C, ACS applied materials and interfaces 10, 3874 (2018). http://doi.org/10.1021/ACSAMI.7B17021
Abstract: The thermal stability of printed polymer solar cells at elevated temperatures needs to be improved to achieve high-throughput fabrication including annealing steps as well as long-term stability. During device processing, thermal annealing impacts both the organic photoactive layer, and the two interfacial layers make detailed studies of degradation mechanism delicate. A recently identified thermally stable poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b'-dithiopherie-2,6-diyl] [3-fluoro-2-[(2-ethylhexyl) carbonyl] thieno [3,4-b]thiophenediyl]] : [6,6]-phenyl- C-71-butyric acid methyl ester (PTB7:PC70BM) blend as photoactive layer in combination with poly(3,4-ethylenedioxythiophene) polystyrene sulfonate as hole extraction layer is used here to focus on the impact of electron extraction layer (EEL) on the thermal stability of solar cells. Solar cells processed with densely packed ZnO nanoparticle layers still show 92% of the initial efficiency after constant annealing during 1 day at 140 degrees C, whereas partially covering ZnO layers as well as an evaporated calcium layer leads to performance losses of up to 30%. This demonstrates that the nature and morphology of EELs highly influence the thermal stability of the device. We extend our study to thermally unstable PTB7:[6,6]-phenyl-C-61-butyric acid methyl ester (PC60BM) blends to highlight the impact of ZnO on the device degradation during annealing. Importantly, only 12% loss in photocurrent density is observed after annealing at 140 degrees C during 1 day when using closely packed ZnO. This is in stark contrast to literature and addressed here to the use of a stable double-sided confinement during thermal annealing. The underlying mechanism of the inhibition of photocurrent losses is revealed by electron microscopy imaging and spatially resolved spectroscopy. We found that the double-sided confinement suppresses extensive fullerene diffusion during the annealing step, but with still an increase in size and distance of the enriched donor and acceptor domains inside the photoactive layer by an average factor of 5. The later result in combination with comparably small photocurrent density losses indicates the existence of an efficient transport of minority charge carriers inside the donor and acceptor enriched phases in PTB7:PC60BM blends.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 7.504
Times cited: 9
DOI: 10.1021/ACSAMI.7B17021
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Ş,entosun K (2018) 2D and 3D characterization of plasmonic and porous nanoparticles using transmission electron microscopy. Antwerp
Keywords: Doctoral thesis; Electron microscopy for materials research (EMAT)
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“Influence of stress aging process on variants of nano-N4Ti3precipitates and martensitic transformation temperatures in NiTi shape memory alloy”. Radi A, Khalil-Allafi J, Etminanfar MR, Pourbabak S, Schryvers D, Amin-Ahmadi B, Materials &, design 262, 74 (2018). http://doi.org/10.1016/J.ELECTACTA.2018.01.024
Abstract: In this study, the effect of a stress aging process on the microstructure and martensitic phase transformation of NiTi shape memory alloy has been investigated. NiTi samples were aged at 450 degrees C for 1 h and 5 h under different levels of external tensile stress of 15, 60 and 150 MPa. Transmission electron microscopy (TEM) was used to characterize different variants and morphology of precipitates. The results show that application of all stress levels restricts the formation of precipitates variants in the microstructure after I h stress aging process. However, all variants can be detected by prolonging aging time to 5 h at 15 MPa stress level and the variants formation is again restricted by increasing the stress level. Moreover, the stress aging process resulted in changing the shape of precipitates in comparison with that of the stress-free aged samples. Coffee-bean shaped morphologies were detected for precipitates in all stress levels. According to the Differential Scanning Calorimetry (DSC) results, the martensite start temperature (M-s) on cooling shifts to higher temperatures with increasing the tensile stress during the aging process. This can be related to the change ofaustenite to martensite interface energy due to the different volume fractions and variants of precipitates. (c) 2018 Elsevier Ltd. All rights reserved.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 4.364
DOI: 10.1016/J.ELECTACTA.2018.01.024
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“Gold nanoclusters with bright near-infrared photoluminescence”. Pramanik G, Humpolickova J, Valenta J, Kundu P, Bals S, Bour P, Dracinsky M, Cigler P, Nanoscale 10, 3792 (2018). http://doi.org/10.1039/C7NR06050E
Abstract: The increase in nonradiative pathways with decreasing emission energy reduces the luminescence quantum yield (QY) of near-infrared photoluminescent (NIR PL) metal nanoclusters. Efficient surface ligand chemistry can significantly improve the luminescence QY of NIR PL metal nanoclusters. In contrast to the widely reported but modestly effective thiolate ligand-to-metal core charge transfer, we show that metal-to-ligand charge transfer (MLCT) can be used to greatly enhance the luminescence QY of NIR PL gold nanoclusters (AuNCs). We synthesized water-soluble and colloidally stable NIR PL AuNCs with unprecedentedly high QY (similar to 25%) upon introduction of triphenylphosphonium moieties into the surface capping layer. By using a combination of spectroscopic and theoretical methods, we provide evidence for gold core-to-ligand charge transfer occurring in AuNCs. We envision that this work can stimulate the development of these unusually bright AuNCs for promising optoelectronic, bioimaging, and other applications.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 7.367
Times cited: 97
DOI: 10.1039/C7NR06050E
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“Electrorheological fluids with high shear stress based on wrinkly tin titanyl oxalate”. Wu J, Zhang L, Xin X, Zhang Y, Wang H, Sun A, Cheng Y, Chen X, Xu G, ACS applied materials and interfaces 10, 6785 (2018). http://doi.org/10.1021/ACSAMI.8B00869
Abstract: Electrorheological (ER) fluids are considered as a type of smart fluids because their rheological characteristics can be altered through an electric field. The discovery of giant ER effect revived the researchers' interest in the ER technological area. However, the poor stability including the insufficient dynamic shear stress, the large leakage current density, and the sedimentation tendency still hinders their practical applications. Herein, we report a facile and scalable coprecipitation method for synthesizing surfactant-free tin titanyl oxalate (TTO) particles with tremella-like wrinkly microstructure (W-TTO). The W-TTO-based ER fluids exhibit enhanced ER activity compared to that of the pristine TTO because of the improved wettability between W-TTO and the silicone oil. In addition, the static yield stress and leakage current of W-TTO ER fluids also show a fine time stability during the 30 day tests. More importantly, the dynamic shear stress of W-TTO ER fluids can remain stable throughout the shear rate range, which is valuable for their use in engineering applications. The results in this work provided a promising strategy to solving the long-standing problem of ER fluid stability. Moreover, this convenient route of synthesis may be considered a green approach for the mass production of giant ER materials.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 7.504
Times cited: 7
DOI: 10.1021/ACSAMI.8B00869
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“Controlling the formation and stability of ultra-thin nickel silicides : an alloying strategy for preventing agglomeration”. Geenen FA, van Stiphout K, Nanakoudis A, Bals S, Vantomme A, Jordan-Sweet J, Lavoie C, Detavernier C, Journal of applied physics 123, 075303 (2018). http://doi.org/10.1063/1.5009641
Abstract: The electrical contact of the source and drain regions in state-of-the-art CMOS transistors is nowadays facilitated through NiSi, which is often alloyed with Pt in order to avoid morphological agglomeration of the silicide film. However, the solid-state reaction between as-deposited Ni and the Si substrate exhibits a peculiar change for as-deposited Ni films thinner than a critical thickness of t(c) = 5 nm. Whereas thicker films form polycrystalline NiSi upon annealing above 450 degrees C, thinner films form epitaxial NiSi2 films that exhibit a high resistance toward agglomeration. For industrial applications, it is therefore of utmost importance to assess the critical thickness with high certainty and find novel methodologies to either increase or decrease its value, depending on the aimed silicide formation. This paper investigates Ni films between 0 and 15 nm initial thickness by use of “thickness gradients,” which provide semi-continuous information on silicide formation and stability as a function of as-deposited layer thickness. The alloying of these Ni layers with 10% Al, Co, Ge, Pd, or Pt renders a significant change in the phase sequence as a function of thickness and dependent on the alloying element. The addition of these ternary impurities therefore changes the critical thickness t(c). The results are discussed in the framework of classical nucleation theory. Published by AIP Publishing.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.068
Times cited: 23
DOI: 10.1063/1.5009641
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“Inkjet printing multideposited YBCO on CGO/LMO/MgO/Y2O3/Al2O3/Hastelloy tape for 2G-coated conductors”. Roxana Vlad V, Bartolome E, Vilardell M, Calleja A, Meledin A, Obradors X, Puig T, Ricart S, Van Tendeloo G, Usoskin A, Lee S, Petrykin V, Molodyk A, IEEE transactions on applied superconductivity 28, 6601805 (2018). http://doi.org/10.1109/TASC.2018.2808403
Abstract: We present the preparation of a new architecture of coated conductor by Inkjet printing of low fluorine YBa2Cu3O7-x (YBCO) on top of SuperOx tape: CGO/LMO/IBAD-MgO/Y2O3/Al-2 O-3/Hastelloy. A five-layered multideposited, 475-nm-thick YBCO film was structurally and magnetically characterized. A good texture was achieved using this combination of buffer layers, requiring only a 30-nm-thin ion-beam-assisted deposition (IBAD)-MgO layer. The LF-YBCO CC reaches self-field critical current density values of J(c)(GB) similar to NJ 15.9 MA/cm(2) (5 K), similar to 1.23 MA/cm(2) (77 K) corresponding to an I-c (77 K) = 58.4 A/cm-width. Inkjet printing offers a flexible and cost effective method for YBCO deposition, allowing patterning of structures.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 1.288
Times cited: 2
DOI: 10.1109/TASC.2018.2808403
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“Thick secondary phase pinning-enhanced YBCO films on technical templates”. Sieger M, Pahlke P, Lao M, Meledin A, Eisterer M, Van Tendeloo G, Schultz L, Nielsch K, Huehne R, IEEE transactions on applied superconductivity 28, 8000505 (2018). http://doi.org/10.1109/TASC.2018.2799419
Abstract: The critical current I-c(B) of YBa2Cu3O7-delta (YBCO) coated conductors can be increased by growing thicker superconductor layers as well as improving the critical current density J(c)(B) by the incorporation of artificial pinning centers. We studied the properties of pulsed laser deposited BaHfO3 (BHO)-doped YBCO films with thicknesses of up to 5 mu m on buffered rolling-assisted biaxially textured Ni-5 at % W tape and alternating beam assisted deposition textured Yttrium-stabilized ZrO2 layers on stainless steel. X-Ray diffraction confirms the epitaxial growth of the superconductor on the buffered metallic template. BHO additions reduce the film porosity and lower the probability to grow misoriented grains, hence preventing the J(c) decrease observed in undoped YBCO films with thicknesses > 2 mu m. Thereby, a continuous increase in I-c at 77 K is achieved. A mixed structure of secondary phase nanorods and platelets with different orientations increases J(c)(B) in the full angular range and simultaneously lowers the J(c) anisotropy compared to pristine YBCO.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 1.288
Times cited: 1
DOI: 10.1109/TASC.2018.2799419
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