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“Revealing pH-Dependent Activities and Surface Instabilities for Ni-Based Electrocatalysts during the Oxygen Evolution Reaction”. Yang C, Batuk M, Jacquet Q, Rousse G, Yin W, Zhang L, Hadermann J, Abakumov AM, Cibin G, Chadwick A, Tarascon J-M, Grimaud A, ACS energy letters , 2884 (2018). http://doi.org/10.1021/acsenergylett.8b01818
Abstract: Multiple electrochemical processes are involved at the catalyst/ electrolyte interface during the oxygen evolution reaction (OER). With the purpose of elucidating the complexity of surface dynamics upon OER, we systematically studied two Ni-based crystalline oxides (LaNiO3−δ and La2Li0.5Ni0.5O4) and compared them with the state-of-the-art Ni−Fe (oxy)- hydroxide amorphous catalyst. Electrochemical measurements such as rotating ring disk electrode (RRDE) and electrochemical quartz microbalance microscopy (EQCM) coupled with a series of physical characterizations including transmission electron microscopy (TEM) and X-ray absorption spectroscopy (XAS) were conducted to unravel the exact pH effect on both the OER activity and the catalyst stability. We demonstrate that for Ni-based crystalline catalysts the rate for surface degradation depends on the pH and is greater than the rate for surface reconstruction. This behavior is unlike that for the amorphous Ni oxyhydroxide catalyst, which is found to be more stable and pH-independent.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
DOI: 10.1021/acsenergylett.8b01818
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“Recent Advances in Transmission Electron Microscopy for Materials Science at the EMAT Lab of the University of Antwerp”. Guzzinati G, Altantzis T, Batuk M, De Backer A, Lumbeeck G, Samaee V, Batuk D, Idrissi H, Hadermann J, Van Aert S, Schryvers D, Verbeeck J, Bals S, Materials 11, 1304 (2018). http://doi.org/10.3390/ma11081304
Abstract: The rapid progress in materials science that enables the design of materials down to the nanoscale also demands characterization techniques able to analyze the materials down to the same scale, such as transmission electron microscopy. As Belgium’s foremost electron microscopy group, among the largest in the world, EMAT is continuously contributing to the development of TEM techniques, such as high-resolution imaging, diffraction, electron tomography, and spectroscopies, with an emphasis on quantification and reproducibility, as well as employing TEM methodology at the highest level to solve real-world materials science problems. The lab’s recent contributions are presented here together with specific case studies in order to highlight the usefulness of TEM to the advancement of materials science.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.654
Times cited: 15
DOI: 10.3390/ma11081304
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“In Situ Electron Diffraction Tomography Using a Liquid-Electrochemical Transmission Electron Microscopy Cell for Crystal Structure Determination of Cathode Materials for Li-Ion batteries”. Karakulina OM, Demortière A, Dachraoui W, Abakumov AM, Hadermann J, Nano letters 18, 6286 (2018). http://doi.org/10.1021/acs.nanolett.8b02436
Abstract: We demonstrate that changes in the unit cell structure of lithium battery cathode materials during electrochemical cycling in liquid electrolyte can be determined for particles of just a few hundred nanometers in size using in situ transmission electron microscopy (TEM). The atomic coordinates, site occupancies (including lithium occupancy), and cell parameters of the materials can all be reliably quantified. This was achieved using electron diffraction tomography (EDT) in a sealed electrochemical cell with conventional liquid electrolyte (LP30) and LiFePO4 crystals, which have a well-documented charged structure to use as reference. In situ EDT in a liquid environment cell provides a viable alternative to in situ X-ray and neutron diffraction experiments due to the more local character of TEM, allowing for single crystal diffraction data to be obtained from multiphased powder samples and from submicrometer- to nanometer-sized particles. EDT is the first in situ TEM technique to provide information at the unit cell level in the liquid environment of a commercial TEM electrochemical cell. Its application to a wide range of electrochemical experiments in liquid environment cells and diverse types of crystalline materials can be envisaged.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 12.712
Times cited: 12
DOI: 10.1021/acs.nanolett.8b02436
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“Enhanced electrochemical performance of Li-rich cathode materials through microstructural control”. Serrano-Sevillano J, Reynaud M, Saracibar A, Altantzis T, Bals S, van Tendeloo G, Casas-Cabanas M, Physical chemistry, chemical physics 20, 23112 (2018). http://doi.org/10.1039/C8CP04181D
Abstract: The microstructural complexity of Li-rich cathode materials has so far hampered understanding the critical link between size, morphology and structural defects with both capacity and voltage fadings that this family of materials exhibits. Li2MnO3 is used here as a model material to extract reliable structure–property
relationships that can be further exploited for the development of high-performing and long-lasting Li-rich oxides. A series of samples with microstructural variability have been prepared and thoroughly characterized using the FAULTS software, which allows quantification of planar defects and extraction of
average crystallite sizes. Together with transmission electron microscopy (TEM) and density functional theory (DFT) results, the successful application of FAULTS analysis to Li2MnO3 has allowed rationalizing the synthesis conditions and identifying the individual impact of concurrent microstructural features on
both voltage and capacity fadings, a necessary step for the development of high-capacity Li-ion cathode materials with enhanced cycle life.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 4.123
Times cited: 36
DOI: 10.1039/C8CP04181D
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“Enhancement of toughness of Al-to-steel Friction Melt Bonded welds via metallic interlayers”. Jimenez-Mena N, Jacques PJ, Ding L, Gauquelin N, Schryvers D, Idrissi H, Delannay F, Simar A, Materials science and engineering: part A: structural materials: properties, microstructure and processing 740-741, 274 (2019). http://doi.org/10.1016/j.msea.2018.10.101
Abstract: The toughness of Al-to-steel welds decreases with increasing thickness of the intermetallic (IM) layer formed at the interface. Co plating has been added as interlayer in Al-to-steel Friction Melt Bonded (FMB) welds to control the nature and thickness of the IM layer. In comparison to a weld without interlayer, Co plating brings about a reduction of the thickness of the IM layer by 70%. The critical energy release rate of the crack propagating in the weld is used as an indicator of toughness. It is evaluated via an adapted crack propagation test using an energy conservation criterion. For a weld without interlayer, critical energy release rate is found to increase when the thickness of the intermetallic layer decreases. When the intermetallic layer is thick, the crack propagates in a brittle manner through the intermetallic whereas, at low layer thickness, the crack deviates and partially propagates through the Al plate, which causes an increase of toughness. The use of a Co interlayer brings about an increase of toughness by causing full deviation of the crack towards the Al plate.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 3.094
Times cited: 4
DOI: 10.1016/j.msea.2018.10.101
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“Characterization of (Ti,Mo,Cr)C nanoprecipitates in an austenitic stainless steel on the atomic scale”. Cautaerts N, Delville R, Stergar E, Schryvers D, Verwerft M, Acta materialia 164, 90 (2019). http://doi.org/10.1016/j.actamat.2018.10.018
Abstract: Nanometer sized (Ti,Mo,Cr)C (MX-type) precipitates that grew in a 24% cold worked Ti-stabilized austenitic stainless steel (grade DIN 1.4970, member of the 15-15Ti austenitic stainless steels) after heat treatment were fully characterized with transmission electron microscopy (TEM), probe corrected high angle annular dark field scanning transmission electron microscopy (HR-HAADF STEM), and atom probe tomography (APT). The precipitates shared the cube-on-cube orientation with the matrix and were facetted on {111} planes, yielding octahedral and elongated octahedral shapes. The misfit dislocations were believed to have Burgers vectors a/6<112> which was verified by geometrical phase analysis (GPA) strain mapping of a matrix-precipitate interface. The dislocations were spaced five to seven atomic
planes apart, on average slightly wider than expected for the lattice parameters of steel and TiC. Quantitative atom probe tomography analysis of the precipitates showed that precipitates were significantly enriched in Mo, Cr and V, and that they were hypostoichiometric with respect to C. These findings were consistent with a reduced lattice parameter. The precipitates were found primarily on Shockley
partial dislocations originating from the original perfect dislocation network. These novel findings could contribute to the understanding of how TiC nanoprecipitates interact with point defects and matrix dislocations. This is essential for the application of these Ti-stabilized steels in high temperature environments or fast spectrum nuclear fission reactors.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 5.301
Times cited: 2
DOI: 10.1016/j.actamat.2018.10.018
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“Metal–insulator-transition engineering by modulation tilt-control in perovskite nickelates for room temperature optical switching”. Liao Z, Gauquelin N, Green RJ, Müller-Caspary K, Lobato I, Li L, Van Aert S, Verbeeck J, Huijben M, Grisolia MN, Rouco V, El Hage R, Villegas JE, Mercy A, Bibes M, Ghosez P, Sawatzky GA, Rijnders G, Koster G, America 115, 9515 (2018). http://doi.org/10.1073/pnas.1807457115
Abstract: In transition metal perovskites ABO3 the physical properties are largely driven by the rotations of the BO6 octahedra, which can be tuned in thin films through strain and dimensionality control. However, both approaches have fundamental and practical limitations due to discrete and indirect variations in bond angles, bond lengths and film symmetry by using commercially available substrates. Here, we introduce modulation tilt control as a new approach to tune the ground state of perovskite oxide thin films by acting explicitly on the oxygen octahedra rotation modes, i.e. directly on the bond angles. By intercalating the prototype SmNiO3 target material with a tilt-control layer, we cause the system to change the natural amplitude of a given rotation mode without affecting the interactions. In contrast to strain and dimensionality engineering, our method enables a continuous fine-tuning of the materials properties. This is achieved through two independent adjustable parameters: the nature of the tilt-control material (through its symmetry, elastic constants and oxygen rotation angles) and the relative thicknesses of the target and tilt-control materials. As a result, a magnetic and electronic phase diagram can be obtained, normally only accessible by A-site element substitution, within the single SmNiO3 compound. With this unique approach, we successfully adjusted the metal-insulator transition (MIT) to room temperature to fulfill the desired conditions for optical switching applications.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 9.661
Times cited: 50
DOI: 10.1073/pnas.1807457115
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“Spectral field mapping in plasmonic nanostructures with nanometer resolution”. Krehl J, Guzzinati G, Schultz J, Potapov P, Pohl D, Martin J, Verbeeck J, Fery A, Büchner B, Lubk A, Nature communications 9, 4207 (2018). http://doi.org/10.1038/s41467-018-06572-9
Abstract: Plasmonic nanostructures and -devices are rapidly transforming light manipulation technology by allowing to modify and enhance optical fields on sub-wavelength scales. Advances in this field rely heavily on the development of new characterization methods for the fundamental nanoscale interactions. However, the direct and quantitative mapping of transient electric and magnetic fields characterizing the plasmonic coupling has been proven elusive to date. Here we demonstrate how to directly measure the inelastic momentum transfer of surface plasmon modes via the energy-loss filtered deflection of a focused electron beam in a transmission electron microscope. By scanning the beam over the sample we obtain a spatially and spectrally resolved deflection map and we further show how this deflection is related quantitatively to the spectral component of the induced electric and magnetic fields pertaining to the mode. In some regards this technique is an extension to the established differential phase contrast into the dynamic regime.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 12.124
Times cited: 15
DOI: 10.1038/s41467-018-06572-9
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“Nanoscale investigation by TEM and STEM-EELS of the laser induced yellowing”. Godet M, Vergès-Belmin V, Gauquelin N, Saheb M, Monnier J, Leroy E, Bourgon J, Verbeeck J, Andraud C, Micron 115, 25 (2018). http://doi.org/10.1016/j.micron.2018.08.006
Abstract: Nd-YAG QS laser cleaning of soiled stone at 1064 nm can sometimes result in a more yellow appearance compared to other cleaning techniques. Especially in France, this yellowing effect is still considered as a major aesthetic issue by the architects and conservators. One explanation states that the yellowing is linked to the formation of iron-rich nanophase(s) through the laser beam interaction with black crusts that would re-deposit on the cleaned substrate after irradiation. To characterize these nanophases, a model crust containing hematite was elaborated and laser irradiated using a Nd-YAG QS laser. The color of the sample shifted instantaneously from red to a bright yellow and numerous particles were ablated in a visible smoke. Transmission electron microscopy (TEM) was used to examine the morphology and the crystallinity of the neo-formed compounds, both on the surface of the samples and in the ablated materials. In addition, an investigation of the chemical and structural properties of the nanophases was conducted by X-ray dispersive energy (EDX) and electron energy loss (EELS) spectroscopies. It was found that both the surface of the sample and the ablated materials are covered by crystallized nano-spheres and nano-residues, all containing iron and oxygen, sometimes along with calcium and sulfur. In particular an interfacial area containing the four elements was evidenced between some nanostructures and the substrate. Magnetite Fe3O4 was also identified at the nanoscale. This study demonstrates that the laser yellowing of a model crust is linked to the presence of iron-rich nanophases including CaxFeySzOδ nanostructures and magnetite Fe3O4 at the surface after irradiation.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 1.98
Times cited: 9
DOI: 10.1016/j.micron.2018.08.006
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“Electron microscopy study of twinning in the Ni5Al3 bainitic phase”. Schryvers D, Ma Y, Toth L, Tanner L, TMS (1994)
Abstract: This contribution describes conventional and high resolution electron microscopy results on the different twinning arrangements in NisAl3 precipitates grown inside the B2 austenite phase. Short annealings introduce self-accommodating three-pointed star shaped precipitates consisting of twin related parts of different variants of the NisAl3 structure. Longer annealings result in plates growing separately from these wings and developing microtwinning in order to accommodate stress built-up at the interfaces with the surrounding matrix.
Keywords: A3 Journal Article; Electron Microscopy for Materials Science (EMAT) ;
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“Electron microscopy study of twin sequences and branching in NissAl34 3R martensite”. Schryvers D, Van Landuyt J, ICOMAT (1992)
Abstract: Microtwin sequences in Ni66Al34 martensite plates of different size were investigated by electron microscopy. Although mostly irregular sequences were observed an average twin width w can be determined which increases with twin length L following the expected relation w ~ sqrt(L). High resolution electron microscopy was used to study the twin branching close to the plate boundaries and an atomic model for the branching of a microtwin and the changes in twin thickness is suggested
Keywords: A3 Journal Article; Electron Microscopy for Materials Science (EMAT) ;
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“Firsto order phase transformation in the Ni-Al system”. Tanner LE, Shapiro SM, Krumhansl JA, Schryvers D, Noda Y, Yamada Y, Barsch GR, Gooding R, Moss SC, Metallurgy and Ceramics (1992)
Abstract: First-order displacive phase transformations in alloys and compounds are of high technological importance. We have studied this class of phase transformation in the high-temperature-stable Ni-Al f32(B2) phase as a function of composition, temperature, and stress using transmission electron microscopy and neutron scattering. The results show in detail the direct relationship between the unusually low energies of the transformation-related phonon modes and the development of pre-transformation microstructures (strain-embryos, etc.) via anharmonic coupling processes that ultimately lead to the nucleation and growth of the low-temperature martensitic phases. With these results, it is now possible to develop effective models for nonclassical heterogeneous nucleation of martensite transformations in bulk materials. This tills a critical gap and sets the stage for us to proceed in developing a more global understanding of condensed matter transformations including the coupling of displacive with replacive mechanisms.
Keywords: A3 Journal Article; Electron Microscopy for Materials Science (EMAT) ;
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“On the phase-like nature of the 7M structure in Ni-Al”. Schryvers D, Tanner LE, Ecomaterials , 849 (1994). http://doi.org/10.1016/B978-1-4832-8381-4.50198-0
Abstract: The existence of the (52) stacking of the 7M martensite structure in Ni-Al is discussed in view of different experimental observations relating this structure to the premartensitic anomalies. It is concluded that the extreme fineness of the twinning is inherited from the wavelength of the premartensitic anomalies, while, given this dimension, the actual stacking tries to comply with stress free habit plane conditions by choosing the specific (52) stacking.
Keywords: A3 Journal Article; Electron Microscopy for Materials Science (EMAT) ;
DOI: 10.1016/B978-1-4832-8381-4.50198-0
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“Tailoring the Ti-C nanoprecipitate population and microstructure of titanium stabilized austenitic steels”. Cautaerts N, Delville R, Stergar E, Schryvers D, Verwerft M, Journal of nuclear materials 507, 177 (2018). http://doi.org/10.1016/J.JNUCMAT.2018.04.041
Abstract: The present work reports on the microstructural evolution of a new heat of 24% cold worked austenitic DIN 1.4970 (15-15Ti) nuclear cladding steel subjected to ageing heat treatments of varying duration between 500 and 800 degrees C (by steps of 100 degrees C). The primary aim was studying the finely dispersed Ti-C nanoprecipitate population, which are thought to be beneficial for creep and swelling resistance during service. Their size distribution and number density were estimated through dark field imaging and bright field Moire imaging techniques in the transmission electron microscope. Nanoprecipitates formed at and above 600 degrees C, which is a lower temperature than previously reported. The observed nucleation, growth and coarsening behavior of the nanoprecipitates were consistent with simple diffusion arguments. The formation of nanoprecipitates coincided with significant dissociation of dislocations as evidenced by weak beam dark field imaging. Possible mechanisms, including Silcock's stacking fault growth model and Suzuki segregation, are discussed. Recrystallization observed after extended ageing at 800 degrees C caused the redissolution of nanoprecipitates. Large primary Ti(C,N) and (Ti,Mo)C precipitates that occur in the as-received material, and M23C6 precipitates that nucleate on grain boundaries at low temperatures were also characterized by a selective dissolution procedure involving filtration, X-ray diffraction and quantitative Rietveld refinement. The partitioning of key elements between the different phases was derived by combining these findings and was consistent with thermodynamic considerations and the processing history of the steel. (C) 2018 Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 2.048
Times cited: 1
DOI: 10.1016/J.JNUCMAT.2018.04.041
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“Subtissue plasmonic heating monitored with CaF2:Nd3+,Y3+ nanothermometers in the second biological window”. Quintanilla M, Zhang Y, Liz-Marzan LM, Chemistry of materials 30, 2819 (2018). http://doi.org/10.1021/ACS.CHEMMATER.8B00806
Abstract: Measuring temperature in biological environments is an ambitious goal toward supporting medical treatment and diagnosis. Minimally invasive techniques based on optical probes require very specific properties that are difficult to combine within a single material. These include high chemical stability in aqueous environments, optical signal stability, low toxicity, high emission intensity, and, essential, working at wavelengths within the biological transparency windows so as to minimize invasiveness while maximizing penetration depth. We propose CaF2:Nd3+,Y3+ as a candidate for thermometry based on an intraband ratiometric approach, fully working within the biological windows (excitation at 808 nm; emission around 1050 nm). We optimized the thermal probes through the addition of Y3+ as a dopant to improve both emission intensity and thermal sensitivity. To define the conditions under which the proposed technique can be applied, gold nanorods were used to optically generate subtissue hot areas, while the resulting temperature variation was monitored with the new nanothermometers.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 28
DOI: 10.1021/ACS.CHEMMATER.8B00806
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“Strain analysis from nano-beam electron diffraction : influence of specimen tilt and beam convergence”. Grieb T, Krause FF, Schowalter M, Zillmann D, Sellin R, Müller-Caspary K, Mahr C, Mehrtens T, Bimberg D, Rosenauer A, Ultramicroscopy 190, 45 (2018). http://doi.org/10.1016/J.ULTRAMIC.2018.03.013
Abstract: Strain analyses from experimental series of nano-beam electron diffraction (NBED) patterns in scanning transmission electron microscopy are performed for different specimen tilts. Simulations of NBED series are presented for which strain analysis gives results that are in accordance with experiment. This consequently allows to study the relation between measured strain and actual underlying strain. A two-tilt method which can be seen as lowest-order electron beam precession is suggested and experimentally implemented. Strain determination from NBED series with increasing beam convergence is performed in combination with the experimental realization of a probe-forming aperture with a cross inside. It is shown that using standard evaluation techniques, the influence of beam convergence on spatial resolution is lower than the influence of sharp rings around the diffraction disc which occur at interfaces and which are caused by the tails of the intensity distribution of the electron probe. (C) 2018 Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.843
Times cited: 1
DOI: 10.1016/J.ULTRAMIC.2018.03.013
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Karakulina O (2018) Quantitative electron diffraction tomography for structure characterization of cathode materials for Li-ion batteries. Antwerpen
Keywords: Doctoral thesis; Electron microscopy for materials research (EMAT)
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“Pushing the limits of applicability of REBCO coated conductor films through fine chemical tuning and nanoengineering of inclusions”. Rizzo F, Augieri A, Kursumovic A, Bianchetti M, Opherden L, Sieger M, Huehne R, Haenisch J, Meledin A, Van Tendeloo G, MacManus-Driscoll JL, Celentano G, Nanoscale 10, 8187 (2018). http://doi.org/10.1039/C7NR09428K
Abstract: An outstanding current carrying performance (namely critical current density, J(c)) over a broad temperature range of 10-77 K for magnetic fields up to 12 T is reported for films of YBa2Cu3O7-x with Ba2Y(Nb,Ta)O-6 inclusion pinning centres (YBCO-BYNTO) and thicknesses in the range of 220-500 nm. J(c) values of 10 MA cm(-2) were measured at 30 K – 5 T and 10 K – 9 T with a corresponding maximum of the pinning force density at 10 K close to 1 TN m(-3). The system is very flexible regarding properties and microstructure tuning, and the growth window for achieving a particular microstructure is wide, which is very important for industrial processing. Hence, the dependence of J(c) on the magnetic field angle was readily controlled by fine tuning the pinning microstructure. Transmission electron microscopy (TEM) analysis highlighted that higher growth rates induce more splayed and denser BYNTO nanocolumns with a matching field as high as 5.2 T. Correspondingly, a strong peak at the B||c-axis is noticed when the density of vortices is lower than the nanocolumn density. YBCO-BYNTO is a very robust and reproducible composite system for high-current coated conductors over an extended range of magnetic fields and temperatures.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 7.367
Times cited: 9
DOI: 10.1039/C7NR09428K
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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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“Martensite crystallography and chemistry in dual phase and fully martensitic steels”. Du C, Hoefnagels JPM, Kolling S, Geers MGD, Sietsma J, Petrov R, Bliznuk V, Koenraad PM, Schryvers D, Amin-Ahmadi B, Materials characterization 139, 411 (2018). http://doi.org/10.1016/j.matchar.2018.03.011
Abstract: Lath martensite is important in industry because it is the key strengthening component in many advanced high strength steels. The study of crystallography and chemistry of lath martensite is extensive in the literature, however, mostly based on fully martensitic steels. In this work, lath martensite in dual phase steels is investigated with a focus on the substructure identification of the martensite islands and microstructural bands using electron backscattered diffraction, and on the influence of the accompanied tempering process during industrial coating process on the distribution of alloying elements using atom probe tomography. Unlike findings for the fully martensitic steels, no martensite islands with all 24 Kurdjumov-Sachs variants have been observed. Almost all martensite islands contain only one main packet with all six variants and minor variants from the remaining three packets of the same prior austenite grain. Similarly, the martensite bands are typically composed of connected domains originating from prior austenite grains, each containing one main packets (mostly with all variants) and few separate variants. The effect of tempering at similar to 450 degrees C (due to the industrial zinc coating process) has also been investigated. The results show a strong carbon partitioning to lath boundaries and Cottrell atmospheres at dislocation core regions due to the thermal process of coating. In contrast, auto-tempering contributes to the carbon redistribution only in a limited manner. The substitutional elements are all homogenously distributed. The phase transformation process has two effects on the material: mechanically, the earlier-formed laths are larger and softer and therefore more ductile (as revealed by nanoindentation); chemically, due to the higher dislocation density inside the later-formed laths, which are generally smaller, carbon Cottrell atmospheres are predominantly observed.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 2.714
DOI: 10.1016/j.matchar.2018.03.011
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“Local probing of the enhanced field electron emission of vertically aligned nitrogen-doped diamond nanorods and their plasma illumination properties”. Deshmukh S, Sankaran KJ, Srinivasu K, Korneychuk S, Banerjee D, Barman A, Bhattacharya G, Phase DM, Gupta M, Verbeeck J, Leou KC, Lin IN, Haenen K, Roy SS, Diamond and related materials 83, 118 (2018). http://doi.org/10.1016/J.DIAMOND.2018.02.005
Abstract: A detailed conductive atomic force microscopic investigation is carried out to directly image the electron emission behavior for nitrogen-doped diamond nanorods (N-DNRs). Localized emission measurements illustrate uniform distribution of high-density electron emission sites from N-DNRs. Emission sites coupled to nano graphitic phases at the grain boundaries facilitate electron transport and thereby enhance field electron emission from N-DNRs, resulting in a device operation at low turn-on fields of 6.23 V/mu m, a high current density of 1.94 mA/cm(2) (at an applied field of 11.8 V/mu m) and a large field enhancement factor of 3320 with a long lifetime stability of 980 min. Moreover, using N-DNRs as cathodes, a microplasma device that can ignite a plasma at a low threshold field of 390 V/mm achieving a high plasma illumination current density of 3.95 mA/cm2 at an applied voltage of 550 V and a plasma life-time stability for a duration of 433 min was demonstrated.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.561
Times cited: 9
DOI: 10.1016/J.DIAMOND.2018.02.005
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“Exploring possibilities of band gap measurement with off-axis EELS in TEM”. Korneychuk S, Partoens B, Guzzinati G, Ramaneti R, Derluyn J, Haenen K, Verbeeck J, Ultramicroscopy 189, 76 (2018). http://doi.org/10.1016/J.ULTRAMIC.2018.03.021
Abstract: A technique to measure the band gap of dielectric materials with high refractive index by means of energy electron loss spectroscopy (EELS) is presented. The technique relies on the use of a circular (Bessel) aperture and suppresses Cherenkov losses and surface-guided light modes by enforcing a momentum transfer selection. The technique also strongly suppresses the elastic zero loss peak, making the acquisition, interpretation and signal to noise ratio of low loss spectra considerably better, especially for excitations in the first few eV of the EELS spectrum. Simulations of the low loss inelastic electron scattering probabilities demonstrate the beneficial influence of the Bessel aperture in this setup even for high accelerating voltages. The importance of selecting the optimal experimental convergence and collection angles is highlighted. The effect of the created off-axis acquisition conditions on the selection of the transitions from valence to conduction bands is discussed in detail on a simplified isotropic two band model. This opens the opportunity for deliberately selecting certain transitions by carefully tuning the microscope parameters. The suggested approach is experimentally demonstrated and provides good signal to noise ratio and interpretable band gap signals on reference samples of diamond, GaN and AlN while offering spatial resolution in the nm range. (C) 2018 Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Condensed Matter Theory (CMT)
Impact Factor: 2.843
Times cited: 7
DOI: 10.1016/J.ULTRAMIC.2018.03.021
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“Control of the interfacial wettability to synthesize highly dispersed PtPd nanocrystals for efficient oxygen reduction reaction”. Wei H, Hu Z-Y, Xiao Y-X, Tian G, Ying J, Van Tendeloo G, Janiak C, Yang X-Y, Su B-L, Chemistry: an Asian journal 13, 1119 (2018). http://doi.org/10.1002/ASIA.201800191
Abstract: Highly dispersed PtPd bimetallic nanocrystals with enhanced catalytic activity and stability were prepared by adjusting the interfacial wettability of the reaction solution on a commercial carbon support. This approach holds great promise for the development of high-performance and low-cost catalysts for practical applications.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 4.083
Times cited: 3
DOI: 10.1002/ASIA.201800191
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“Chemical activity of the peroxide/oxide redox couple : case study of Ba5Ru2O11 in aqueous and organic solvents”. Grimaud A, Iadecola A, Batuk D, Saubanere M, Abakumov AM, Freeland JW, Cabana J, Li H, Doublet M-L, Rousse G, Tarascon J-M, Chemistry of materials 30, 3882 (2018). http://doi.org/10.1021/ACS.CHEMMATER.8B01372
Abstract: The finding that triggering the redox activity of oxygen ions within the lattice of transition metal oxides can boost the performances of materials used in energy storage and conversion devices such as Li-ion batteries or oxygen evolution electrocatalysts has recently spurred intensive and innovative research in the field of energy. While experimental and theoretical efforts have been critical in understanding the role of oxygen nonbonding states in the redox activity of oxygen ions, a clear picture of the redox chemistry of the oxygen species formed upon this oxidation process is still missing. This can be, in part, explained by the complexity in stabilizing and studying these species once electrochemically formed. In this work, we alleviate this difficulty by studying the phase Ba5Ru2O11, which contains peroxide O-2(2-) groups, as oxygen evolution reaction electrocatalyst and Li-ion battery material. Combining physical characterization and electrochemical measurements, we demonstrate that peroxide groups can easily be oxidized at relatively low potential, leading to the formation of gaseous dioxygen and to the instability of the oxide. Furthermore, we demonstrate that, owing to the stabilization at high energy of peroxide, the high-lying energy of the empty sigma* antibonding O-O states limits the reversibility of the electrochemical reactions when the O-2(2-)/O2- redox couple is used as redox center for Li-ion battery materials or as OER redox active sites. Overall, this work suggests that the formation of true peroxide O-2(2-) states are detrimental for transition metal oxides used as OER catalysts and Li-ion battery materials. Rather, oxygen species with O-O bond order lower than 1 would be preferred for these applications.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 2
DOI: 10.1021/ACS.CHEMMATER.8B01372
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“Carbon Incorporation and Anion Dynamics as Synergistic Drivers for Ultrafast Diffusion in Superionic LiCB11H12 and NaCB11H12”. Dimitrievska M, Shea P, Kweon KE, Bercx M, Varley JB, Tang WS, Skripov AV, Stavila V, Udovic TJ, Wood BC, Advanced energy materials 8, 1703422 (2018). http://doi.org/10.1002/AENM.201703422
Abstract: The disordered phases of LiCB11H12 and NaCB11H12 possess superb superionic conductivities that make them suitable as solid electrolytes. In these materials, cation diffusion correlates with high orientational mobilities of the CB11H12- anions; however, the precise relationship has yet to be demonstrated. In this work, ab initio molecular dynamics and quasielastic neutron scattering are combined to probe anion reorientations and their mechanistic connection to cation mobility over a range of timescales and temperatures. It is found that anions do not rotate freely, but rather transition rapidly between orientations defined by the cation sublattice symmetry. The symmetry-breaking carbon atom in CB11H12- also plays a critical role by perturbing the energy landscape along the instantaneous orientation of the anion dipole, which couples fluctuations in the cation probability density directly to the anion motion. Anion reorientation rates exceed 3 x 10(10) s(-1), suggesting the underlying energy landscape fluctuates dynamically on diffusion-relevant timescales. Furthermore, carbon is found to modify the orientational preferences of the anions and aid rotational mobility, creating additional symmetry incompatibilities that inhibit ordering. The results suggest that synergy between the anion reorientational dynamics and the carbon-modified cation-anion interaction accounts for the higher ionic conductivity in CB11H12- salts compared with B12H122-.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 16.721
Times cited: 20
DOI: 10.1002/AENM.201703422
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“Atomic-scale identification of novel planar defect phases in heteroepitaxial YBa2Cu3O7-\delta thin films”. Gauquelin N, Zhang H, Zhu G, Wei JYT, Botton GA, AIP advances 8, 055022 (2018). http://doi.org/10.1063/1.5011761
Abstract: We have discovered two novel types of planar defects that appear in heteroepitaxial YBa2Cu3O7-delta(YBCO123) thin films, grown by pulsed-laser deposition (PLD) either with or without a La2/3Ca1/3MnO3 (LCMO) overlayer, using the combination of highangle annular dark-field scanning transmission electron microscopy (HAADF-STEM) imaging and electron energy loss spectroscopy (EELS) mapping for unambiguous identification. These planar lattice defects are based on the intergrowth of either a BaO plane between two CuO chains or multiple Y-O layers between two CuO2 planes, resulting in non-stoichiometric layer sequences that could directly impact the high-Tc superconductivity. (C) 2018 Author(s).
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 1.568
Times cited: 1
DOI: 10.1063/1.5011761
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“Mono- and Multilayer Silicene-Type Honeycomb Lattices by Oriented Attachment of PbSe Nanocrystals: Synthesis, Structural Characterization, and Analysis of the Disorder”. Peters JL, Altantzis T, Lobato I, Jazi MA, van Overbeek C, Bals S, Vanmaekelbergh D, Sinai SB, Chemistry of materials 30, 4831 (2018). http://doi.org/10.1021/acs.chemmater.8b02178
Abstract: Nanocrystal (NC) solids are commonly prepared from nonpolar organic NC suspensions. In many cases, the capping on the NC surface is preserved and forms a barrier between the NCs. More recently, superstructures with crystalline connections between the NCs, implying the removal of the capping, have been reported, too. Here, we present large-scale uniform superstructures of attached PbSe NCs with a silicene-type honeycomb geometry, resulting from solvent evaporation under nearly reversible conditions. We also prepared multilayered silicene honeycomb structures by using larger amounts of PbSe NCs. We show that the two-dimensional silicene superstructures can be seen as a crystallographic slice from a 3-D simple cubic structure. We describe the disorder in the silicene lattices in terms of the nanocrystals position and their atomic alignment. The silicene honeycomb sheets are large enough to be used in transistors and optoelectronic devices.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 33
DOI: 10.1021/acs.chemmater.8b02178
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“Understanding the Effect of Iodide Ions on the Morphology of Gold Nanorods”. Amini MN, Altantzis T, Lobato I, Grzelczak M, Sánchez-Iglesias A, Van Aert S, Liz-Marzán LM, Partoens B, Bals S, Neyts EC, Particle and particle systems characterization 35, 1800051 (2018). http://doi.org/10.1002/ppsc.201800051
Abstract: The presence of iodide ions during the growth of gold nanorods strongly affects the shape of the final products, which is proposed to be due to selective iodide adsorption on certain crystallographic facets. Therefore, a detailed structural and morphological characterization of the starting rods is crucial toward understanding this effect. Electron tomography is used to determine the crystallographic indices of the lateral facets of gold nanorods, as well as those present at the tips. Based on this information, density functional theory calculations are used to determine the surface and interface energies of the observed facets and provide insight into the relationship between the amount of iodide ions in the growth solution and the final morphology of anisotropic gold nanoparticles.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT); Condensed Matter Theory (CMT); Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 4.474
Times cited: 6
DOI: 10.1002/ppsc.201800051
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“Recent breakthroughs in scanning transmission electron microscopy of small species”. van den Bos KHW, Altantzis T, De Backer A, Van Aert S, Bals S, Advances in Physics: X 3, 1480420 (2018). http://doi.org/10.1080/23746149.2018.1480420
Abstract: Over the last decade, scanning transmission electron microscopy has become one of the most powerful tools to characterise nanomaterials at the atomic scale. Often, the ultimate goal is to retrieve the three-dimensional structure, which is very challenging since small species are typically sensitive to electron irradiation. Nevertheless, measuring individual atomic positions is crucial to understand the relation between the structure and physicochemical properties of these (nano)materials. In this review, we highlight the latest approaches that are available to reveal the 3D atomic structure of small species. Finally, we will provide an outlook and will describe future challenges where the limits of electron microscopy will be pushed even further.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Times cited: 8
DOI: 10.1080/23746149.2018.1480420
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“Single Atom Detection from Low Contrast-to-Noise Ratio Electron Microscopy Images”. Fatermans J, den Dekker A J, Müller-Caspary K, Lobato I, O’Leary C M, Nellist P D, Van Aert S, Physical review letters 121, 056101 (2018). http://doi.org/10.1103/PhysRevLett.121.056101
Abstract: Single atom detection is of key importance to solving a wide range of scientific and technological problems. The strong interaction of electrons with matter makes transmission electron microscopy one of the most promising techniques. In particular, aberration correction using scanning transmission electron microscopy has made a significant step forward toward detecting single atoms. However, to overcome radiation damage, related to the use of high-energy electrons, the incoming electron dose should be kept low enough. This results in images exhibiting a low signal-to-noise ratio and extremely weak contrast, especially for light-element nanomaterials. To overcome this problem, a combination of physics-based model fitting and the use of a model-order selection method is proposed, enabling one to detect single atoms with high reliability.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Vision lab
Impact Factor: 8.462
Times cited: 6
DOI: 10.1103/PhysRevLett.121.056101
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