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“Phonon hydrodynamics, thermal conductivity, and second sound in two-dimensional crystals”. Scuracchio P, Michel KH, Peeters FM, Physical review B 99, 144303 (2019). http://doi.org/10.1103/PHYSREVB.99.144303
Abstract: Starting from our previous work in which we obtained a system of coupled integrodifferential equations for acoustic sound waves and phonon density fluctuations in two-dimensional (2D) crystals, we derive here the corresponding hydrodynamic equations, and we study their consequences as a function of temperature and frequency. These phenomena encompass propagation and damping of acoustic sound waves, diffusive heat conduction, second sound, and Poiseuille heat flow, all of which are characterized by specific transport coefficients. We calculate these coefficients by means of correlation functions without using the concept of relaxation time. Numerical calculations are performed as well in order to show the temperature dependence of the transport coefficients and of the thermal conductivity. As a consequence of thermal tension, mechanical and thermal phenomena are coupled. We calculate the dynamic susceptibilities for displacement and temperature fluctuations and study their resonances. Due to the thermomechanical coupling, the thermal resonances such as the Landau-Placzek peak and the second-sound doublet appear in the displacement susceptibility, and conversely the acoustic sound wave doublet appears in the temperature susceptibility, Our analytical results not only apply to graphene, but they are also valid for arbitrary 2D crystals with hexagonal symmetry, such as 2D hexagonal boron nitride, 2H-transition-metal dichalcogenides, and oxides.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 16
DOI: 10.1103/PHYSREVB.99.144303
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“Convergence of quasiparticle band structures of Si and Ge nanowires in the GW approximation and the validity of scissor shifts”. Peelaers H, Partoens B, Giantomassi M, Rangel T, Goossens E, Rignanese G-M, Gonze X, Peeters FM, Physical review : B : condensed matter and materials physics 83, 045306 (2011). http://doi.org/10.1103/PhysRevB.83.045306
Abstract: Starting from fully converged density-functional theory calculations, the quasiparticle corrections are calculated for different sized Si and Ge nanowires using the GW approximation. The effectiveness of recently developed techniques in speeding up the convergence of the quasiparticle calculations is demonstrated. The complete quasiparticle band structures are also obtained using an interpolation technique based on maximallylocalized Wannier functions. From the quasiparticle results, we assess the correctness of the commonly applied scissor-shift correction. Dispersion changes are observed, which are also reflected in changes in the effective band masses calculated taking into account quasiparticle corrections.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 18
DOI: 10.1103/PhysRevB.83.045306
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“Evolution of multigap superconductivity in the atomically thin limit : strain-enhanced three-gap superconductivity in monolayer MgB2”. Bekaert J, Aperis A, Partoens B, Oppeneer PM, Milošević, MV, Physical review B 96, 094510 (2017). http://doi.org/10.1103/PHYSREVB.96.094510
Abstract: Starting from first principles, we show the formation and evolution of superconducting gaps in MgB2 at its ultrathin limit. Atomically thin MgB2 is distinctly different from bulk MgB2 in that surface states become comparable in electronic density to the bulklike sigma and pi bands. Combining the ab initio electron-phonon coupling with the anisotropic Eliashberg equations, we showthat monolayer MgB2 develops three distinct superconducting gaps, on completely separate parts of the Fermi surface due to the emergent surface contribution. These gaps hybridize nontrivially with every extra monolayer added to the film owing to the opening of additional coupling channels. Furthermore, we reveal that the three-gap superconductivity in monolayer MgB2 is robust over the entire temperature range that stretches up to a considerably high critical temperature of 20 K. The latter can be boosted to >50K under biaxial tensile strain of similar to 4%, which is an enhancement that is stronger than in any other graphene-related superconductor known to date.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 56
DOI: 10.1103/PHYSREVB.96.094510
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“Sound waves and flexural mode dynamics in two-dimensional crystals”. Michel KH, Scuracchio P, Peeters FM, Physical review B 96, 094302 (2017). http://doi.org/10.1103/PHYSREVB.96.094302
Abstract: Starting from a Hamiltonian with anharmonic coupling between in-plane acoustic displacements and outof-plane (flexural) modes, we derived coupled equations of motion for in-plane displacements correlations and flexural mode density fluctuations. Linear response theory and time-dependent thermal Green's functions techniques are applied in order to obtain different response functions. As external perturbations we allow for stresses and thermal heat sources. The displacement correlations are described by a Dyson equation where the flexural density distribution enters as an additional perturbation. The flexural density distribution satisfies a kinetic equation where the in-plane lattice displacements act as a perturbation. In the hydrodynamic limit this system of coupled equations is at the basis of a unified description of elastic and thermal phenomena, such as isothermal versus adiabatic sound motion and thermal conductivity versus second sound. The general theory is formulated in view of application to graphene, two-dimensional h-BN, and 2H-transition metal dichalcogenides and oxides.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 6
DOI: 10.1103/PHYSREVB.96.094302
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“Enamels in stained glass windows: preparation, chemical composition, microstructure and causes of deterioration”. Schalm O, van der Linden V, Frederickx P, Luyten S, van der Snickt G, Caen J, Schryvers D, Janssens K, Cornelis E, van Dyck D, Schreiner M, Spectrochimica acta: part B : atomic spectroscopy 64, 812 (2009). http://doi.org/10.1016/j.sab.2009.06.005
Abstract: Stained glass windows incorporating dark blue and purple enamel paint layers are in some cases subject to severe degradation while others from the same period survived the ravages of time. A series of dark blue, greenblue and purple enamel glass paints from the same region (Northwestern Europe) and from the same period (16early 20th centuries) has been studied by means of a combination of microscopic X-ray fluorescence analysis, electron probe micro analysis and transmission electron microscopy with the aim of better understanding the causes of the degradation. The chemical composition of the enamels diverges from the average chemical composition of window glass. Some of the compositions appear to be unstable, for example those with a high concentration of K2O and a low content of CaO and PbO. In other cases, the deterioration of the paint layers was caused by the less than optimal vitrification of the enamel during the firing process. Recipes and chemical compositions indicate that glassmakers of the 1617th century had full control over the color of the enamel glass paints they made. They mainly used three types of coloring agents, based on Co (dark blue), Mn (purple) and Cu (light-blue or greenblue) as coloring elements. Bluepurple enamel paints were obtained by mixing two different coloring agents. The coloring agent for redpurple enamel, introduced during the 19th century, was colloidal gold embedded in grains of lead glass.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation); Vision lab
Impact Factor: 3.241
Times cited: 28
DOI: 10.1016/j.sab.2009.06.005
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“Giant magnetic anisotropy in doped single layer molybdenum disulfide and fluorographene”. Sivek J, Sahin H, Partoens B, Peeters FM, Journal of physics : condensed matter 28, 195301 (2016). http://doi.org/10.1088/0953-8984/28/19/195301
Abstract: Stable monolayer materials based on existing, well known and stable two-dimensional crystal fluorographene and molybdenum disulfide are predicted to exhibit a huge magnetocrystalline anisotropy when functionalized with adsorbed transition metal atoms at vacant sides. Ab initio calculations within the density-functional theory formalism were performed to investigate the adsorption of the transitional metals in a single S (or F) vacancy of monolayer molybdenum disulfide (or fluorographene). We found strong bonding of the transitional metal atoms to the vacant sites with binding energies ranging from 2.5 to 5.2 eV. Our calculations revealed that these systems with adsorbed metal atoms exhibit a magnetic anisotropy, specifically the structures including Os and Ir show a giant magnetocrystalline anisotropy energy of 31-101 meV. Our results demonstrate the possibility of obtaining stable monolayer materials with huge magnetocrystalline anisotropy based on preexisting, well known and stable two-dimensional crystals: fluorographene and molybdenum disulfide. We believe that the results obtained here are useful not only for deeper understanding of the origin of magnetocrystalline anisotropy but also for the design of monolayer optoelectronic devices with novel functionalities.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.649
Times cited: 7
DOI: 10.1088/0953-8984/28/19/195301
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“Optical encoding of luminescent carbon nanodots in confined spaces”. Bartholomeeusen E, De Cremer G, Kennes K, Hammond C, Hermans I, Lu J-B, Schryvers D, Jacobs PA, Roeffaers MBJ, Hofkens J, Sels BF, Coutino-Gonzalez E, Chemical Communications 57, 11952 (2021). http://doi.org/10.1039/D1CC04777A
Abstract: Stable emissive carbon nanodots were generated in zeolite crystals using near infrared photon irradiation gradually converting the occluded organic template, originally used to synthesize the zeolite crystals, into discrete luminescent species consisting of nano-sized carbogenic fluorophores, as ascertained using Raman microscopy, and steady-state and time-resolved spectroscopic techniques. Photoactivation in a confocal laser fluorescence microscope allows 3D resolved writing of luminescent carbon nanodot patterns inside zeolites providing a cost-effective and non-toxic alternative to previously reported metal-based nanoclusters confined in zeolites, and opens up opportunities in bio-labelling and sensing applications.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 6.319
DOI: 10.1039/D1CC04777A
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“Synthesis, structure, and electrochemical properties of k-based sulfates K2M2(SO4)3) with M = Fe and Cu”. Lander L, Rousse G, Batuk D, Colin CV, Dalla Corte DA, Tarascon J-M, Inorganic chemistry 56, 2013 (2017). http://doi.org/10.1021/ACS.INORGCHEM.6B02526
Abstract: Stabilizing new host structures through potassium extraction from K-based polyanionic materials has been proven to be an interesting approach to develop new Li+/Na+ insertion materials. Pursuing the same trend, we here report the feasibility of preparing langbeinite “Fe-2(SO4)(3)” via electrochemical and chemical oxidation of K2Fe2(SO4)(3). Additionally, we succeeded in stabilizing a new K2Cu2(SO4)(3) phase via a solid-state synthesis approach. This novel compound crystallizes in a complex orthorhombic structure that differs from that of langbeinite as deduced from synchrotron X-ray and neutron powder diffraction. Electrochemically, the performance of this new phase is limited, which we explain in terms of sluggish diffusion kinetics. We further show that K2Cu2(SO4)(3) decomposes into K2Cu3O(SO4)(3) on heating, and we report for the first time the synthesis of fedotovite K2Cu3O(SO4)(3). Finally, the fundamental attractiveness of these S = 1/2 systems for physicists is examined by neutron magnetic diffraction, which reveals the absence of a long-range ordering of Cu2+ magnetic moments down to 1.5 K.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 4.857
Times cited: 13
DOI: 10.1021/ACS.INORGCHEM.6B02526
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“Magnetic and structural studies of the multifunctional material SrFe0.75Mo0.25O3-\text{\textgreek{d}}”. Retuerto M, Li MR, Go YB, Ignatov A, Croft M, Ramanujachary KV, Hadermann J, Hodges JP, Herber RH, Nowik I, Greenblatt M;, Inorganic chemistry 51, 12273 (2012). http://doi.org/10.1021/ic301550m
Abstract: SrFe0.75Mo0.25O3-delta has been recently discovered as an extremely efficient electrode for intermediate temperature solid oxide fuel cells (IT-SOFCs). We have performed structural and magnetic studies to fully characterize this multifunctional material. We have observed by powder neutron diffraction (PND) and transmission electron microscopy (TEM) that its crystal symmetry is better explained with a tetragonal symmetry (I4/mcm space group) than with the previously reported orthorhombic symmetry (Pnma space group). The temperature dependent magnetic properties indicate an exceptionally high magnetic ordering temperature (T-N similar to 750 K), well above room temperature. The ordered magnetic structure at low temperature was determined by PND to be an antiferromagnetic coupling of the Fe cations. Mossbauer spectroscopy corroborated the PND results. A detailed study, with X-ray absorption spectroscopy (XAS), in agreement with the Mossbauer results, confirmed the formal oxidation states of the cations to be mixed valence Fe3+/4+ and Mo6+.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 4.857
Times cited: 12
DOI: 10.1021/ic301550m
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“Impact of anionic ordering on the iron site distribution and valence states in oxyfluoride Sr2FeO3+xF1-x(x=0.08, 0.2) with a layered Perovskite network”. Gamon J, Bassat J-M, Villesuzanne A, Duttine M, Batuk M, Vandemeulebroucke D, Hadermann J, Alassani F, Weill F, Durand E, Demourgues A, Inorganic chemistry 62, 10822 (2023). http://doi.org/10.1021/ACS.INORGCHEM.3C01455
Abstract: Sr2FeO3+x F1-x (x = 0.08, 0.2), an n = 1 Ruddlesden-Popperphase, was synthesized from the oxidationof Sr2FeO3F in air at high temperature followinga fluorine for oxygen substitution and Fe3+ to Fe4+ oxidation. A structural investigation of both compounds was performedusing complementary and high-resolution techniques (Synchrotron X-rayand electron diffraction, Mo''ssbauer spectroscopy, HR-STEM)coupled to DFT calculation. This study reveals that oxidation leadsto a high degree of apical anion disorder coupled to antiphase boundaries. Sr2FeO3F, an oxyfluoride compoundwith an n = 1 Ruddlesden-Popper structure,was identifiedas a potential interesting mixed ionic and electronic conductor (MIEC).The phase can be synthesized under a range of different pO(2) atmospheres, leading to various degrees of fluorinefor oxygen substitution and Fe4+ content. A structuralinvestigation and thorough comparison of both argon- and air-synthesizedcompounds were performed by combining high-resolution X-ray and electrondiffraction, high-resolution scanning transmission electron microscopy,Mo''ssbauer spectroscopy, and DFT calculations. While the argon-synthesizedphase shows a well-behaved O/F ordered structure, this study revealedthat oxidation leads to averaged large-scale anionic disorder on theapical site. In the more oxidized Sr2FeO3.2F0.8 oxyfluoride, containing 20% of Fe4+, two differentFe positions can be identified with a 32%/68% occupancy (P4/nmm space group). This originates due to the presenceof antiphase boundaries between ordered domains within the grains.Relations between site distortion and valence states as well as stabilityof apical anionic sites (O vs F) are discussed. This study paves theway for further studies on both ionic and electronic transport propertiesof Sr2FeO3.2F0.8 and its use in MIEC-baseddevices, such as solid oxide fuel cells.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 4.6
DOI: 10.1021/ACS.INORGCHEM.3C01455
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“Magnetic Ordering in the Layered Cr(II) Oxide Arsenides Sr2CrO2Cr2As2and Ba2CrO2Cr2As2”. Xu X, Jones MA, Cassidy SJ, Manuel P, Orlandi F, Batuk M, Hadermann J, Clarke SJ, Inorganic Chemistry 59, 15898 (2020). http://doi.org/10.1021/acs.inorgchem.0c02415
Abstract: Sr2CrO2Cr2As2 and Ba2CrO2Cr2As2 with Cr2+ ions in CrO2 sheets and in CrAs layers crystallize with the Sr2Mn3Sb2O2 structure (space group I4/mmm, Z = 2) and lattice parameters a = 4.00800(2) Å, c = 18.8214(1) Å (Sr2CrO2Cr2As2) and a = 4.05506(2) Å, c = 20.5637(1) Å (Ba2CrO2Cr2As2) at room temperature. Powder neutron diffraction reveals checkerboard-type antiferromagnetic ordering of the Cr2+ ions in the arsenide layers below TN1Sr, of 600(10) K (Sr2CrO2Cr2As2) and TN1Ba 465(5) K (Ba2CrO2Cr2As2) with the moments initially directed perpendicular to the layers in both compounds. Checkerboard-type antiferromagnetic ordering of the Cr2+ ions in the oxide layer below 230(5) K for Ba2CrO2Cr2As2 occurs with these moments also perpendicular to the layers, consistent with the orientation preferences of d4 moments in the two layers. In contrast, below 330(5) K in Sr2CrO2Cr2As2, the oxide layer Cr2+ moments are initially oriented in the CrO2 plane; but on further cooling, these moments rotate to become perpendicular to the CrO2 planes, while the moments in the arsenide layers rotate by 90° with the moments on the two sublattices remaining orthogonal throughout [behavior recently reported independently by Liu et al. [Liu et al. Phys. Rev. B 2018, 98, 134416]]. In Sr2CrO2Cr2As2, electron diffraction and high resolution powder X-ray diffraction data show no evidence for a structural distortion that would allow the two Cr2+ sublattices to couple, but high resolution neutron powder diffraction data suggest a small incommensurability between the magnetic structure and the crystal structure, which may account for the coupling of the two sublattices and the observed spin reorientation. The saturation values of the Cr2+ moments in the CrO2 layers (3.34(1) μB (for Sr2CrO2Cr2As2) and 3.30(1) μB (for Ba2CrO2Cr2As2)) are larger than those in the CrAs layers (2.68(1) μB for Sr2CrO2Cr2As2 and 2.298(8) μB for Ba2CrO2Cr2As2) reflecting greater covalency in the arsenide layers.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 4.6
DOI: 10.1021/acs.inorgchem.0c02415
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“Spin transport in a Mn-doped ZnSe asymmetric tunnel structure”. Papp G, Borza S, Peeters FM, Journal of applied physics 97, 113901 (2005). http://doi.org/10.1063/1.1861520
Abstract: Spin-dependent tunneling of electrons in a diluted magnetic semiconductor ZnSe/Zn1-xMnxSe/Zn1-yMnySe/ZnSe/Zn1-xMnxSe/ZnSe heterostructure is investigated theoretically in the presence of parallel magnetic and electric fields, but our modeling is appropriate for any dilute magnetic II-VI semiconductor system. In the studied asymmetric system the transmission of electrons and the degree of spin polarization depend on the strength of the magnetic and electric fields and on the direction of the applied bias. For suitable magnetic fields, the output current of the system exhibits a nearly 100% spin polarization and the device can be used as a spin filter. (C) 2005 American Institute of Physics.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.068
Times cited: 26
DOI: 10.1063/1.1861520
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“Driven spin transitions in fluorinated single- and bilayer-graphene quantum dots”. Zebrowski DP, Peeters FM, Szafran B, Semiconductor science and technology 32, 065016 (2017). http://doi.org/10.1088/1361-6641/AA6DF4
Abstract: Spin transitions driven by a periodically varying electric potential in dilute fluorinated graphene quantum dots are investigated. Flakes of monolayer graphene as well as electrostatic electron traps induced in bilayer graphene are considered. The stationary states obtained within the tight-binding approach are used as the basis for description of the system dynamics. The dilute fluorination of the top layer lifts the valley degeneracy of the confined states and attenuates the orbital magnetic dipole moments due to current circulation within the flake. The spin-orbit coupling introduced by the surface deformation of the top layer induced by the adatoms allows the spin flips to be driven by the AC electric field. For the bilayer quantum dots the spin flip times is substantially shorter than the spin relaxation. Dynamical effects including many-photon and multilevel transitions are also discussed.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.305
DOI: 10.1088/1361-6641/AA6DF4
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“Spin-dependent on-site electron correlations and localization in itinerant f erromagnets”. Gotter R, Fratesi G, Bartynski RA, da Pieve F, Offi F, Ruocco A, Ugenti S, Trioni MI, Brivio GP, Stefani G, Physical review letters 109, 126401 (2012). http://doi.org/10.1103/PhysRevLett.109.126401
Abstract: Spin selectivity in angle-resolved Auger photoelectron coincidence spectroscopy (AR-APECS) is used to probe electron correlation in ferromagnetic thin films. In particular, exploiting the AR-APECS capability to discriminate Auger electron emission events characterized by valence hole pairs created either in the high or in the low total spin state, a strong correlation effect in the Fe M2,3VV Auger line shape (measured in coincidence with the Fe 3p photoelectrons) of Fe/Cu(001) thin films is detected and ascribed to interactions within the majority spin subband. Such an assignment follows from a close comparison of the experimental AR-APECS line shapes with the predictions of a model based on spin polarized density functional theory and the Cini-Sawatzky approach.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 8.462
Times cited: 9
DOI: 10.1103/PhysRevLett.109.126401
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“Resonant harmonic generation and collective spin rotations in electrically driven quantum dots”. Nowak MP, Szafran B, Peeters FM, Physical review : B : condensed matter and materials physics 86, 125428 (2012). http://doi.org/10.1103/PhysRevB.86.125428
Abstract: Spin rotations induced by an ac electric field in a two-electron double quantum dot are studied by an exact numerical solution of the time-dependent Schrodinger equation in the context of recent electric-dipole spin resonance experiments on gated nanowires. We demonstrate that the splitting of the main resonance line by the spin exchange coupling is accompanied by the appearance of fractional resonances and that both these effects are triggered by interdot tunnel coupling. We find that the ac-driven system generates residual but distinct harmonics of the driving frequency, which are amplified when tuned to the main transition frequency. The mechanism is universal for electron systems in electrically driven potentials and works also in the absence of electron-electron interaction or spin-orbit coupling.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 29
DOI: 10.1103/PhysRevB.86.125428
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“Spatially resolved micro-X-ray fluorescence and micro-X-ray absorption fine structure study of a fractured granite bore core following a radiotracer experiment”. Denecke MA, Brendebach B, de Nolf W, Falkenberg G, Janssens K, Simon R, Spectrochimica acta: part B : atomic spectroscopy 64, 791 (2009). http://doi.org/10.1016/J.SAB.2009.05.025
Abstract: Spatially resolved X-ray absorption and fluorescence investigation with a micrometer-scale resolution on actinide-containing samples provide information necessary for safety assessment of nuclear waste disposal. In this paper one example of such an experiment is presented. This example entails neptunium speciation in a fractured granite bore core from the Swedish Äspö Hard Rock Laboratory following a radiotracer experiment using µ-XAFS and µ-XRF. In order to probe micro-volumes below the surface in the granite samples and thereby avoid potential changes in the Np speciation during cutting of the bore core, a confocal irradiationdetection geometry is employed. µ-XAFS results for a selected granite bore core cross section with ~ 3 nmol Np/g reveal that Np, originally introduced as Np(V) in the tracer cocktail, is present in the granite in its reduced Np(IV) form. The Np(IV) is often present as particles, tens of µm in size. Elemental distribution maps show the tracer Np to be located in fissures and permeable channels not larger than 100 µm. The Np distribution appears often correlated with Zn also present in some fissures. We observe small granite fissures containing Fe (presumably Fe(II)), where we do not detect any Np. It is feasible that inflowing Np(V) has a shorter residence time in large fractures, while in the smaller fissures migration is slower, leading to longer residence times, i.e., reaction times, where it is reduced to less soluble Np(IV) and becomes thereby immobilized.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 3.241
Times cited: 21
DOI: 10.1016/J.SAB.2009.05.025
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“Spin-engineered quantum dots”. Fleurov V, Ivanov VA, Peeters FM, Vagner ID, Physica. E: Low-dimensional systems and nanostructures 14, 361 (2002). http://doi.org/10.1016/S1386-9477(01)00487-8
Abstract: Spatially nonhomogeneously spin polarized nuclei are proposed as a new mechanism to monitor electron states in a nanostructure, or as a means to create and, if necessary, reshape such nanostructures in the course of the experiment. We found that a polarization of nuclear spins may lift the spin polarization of the electron states in a nanostructure and, if sufficiently strong, leads to a polarization of the electron spins. Polarized nuclear spins may form an energy landscape capable of binding electrons with energy up to several meV and the localization radius > 100 Angstrom. (C) 2002 Elsevier Science B.V. All rights reserved.
Keywords: A1 Journal article; Engineering sciences. Technology; Condensed Matter Theory (CMT)
Impact Factor: 2.221
Times cited: 12
DOI: 10.1016/S1386-9477(01)00487-8
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“Effect of process parameters on the photocatalytic soot degradation on self-cleaning cementitious materials”. Smits M, Huygh D, Craeye B, Lenaerts S, Catalysis today 230, 250 (2014). http://doi.org/10.1016/J.CATTOD.2013.10.001
Abstract: Soot deposition has the negative ability to devalue the aesthetic appearance of buildings. Titanium dioxide applied on the building material is one way to counteract this problem as it provides air-purifying and self-cleaning properties due to its photocatalytic activity. In literature, photocatalytic soot oxidation was described, but until now, little information was available about the influence of process parameters on the photocatalytic degradation efficiency. The influence of three process parameters was tested in this study, namely TiO2 concentration, soot concentration and water-to-cement ratio (WIC-ratio) of the mortar substrates. The results revealed 50 mu gTiO(2) cm(-2) is better to use on the cementitious materials than 250 mu gTiO(2) cm(-2). The soot concentrations occurring in real-world situations will not inhibit the photocatalyst to be activated by light. Furthermore, the photonic efficiency increases slightly for lower WIC-ratios. This can be of interest for structural building applications, since a lower WIC-ratio results in a lower porosity of the samples and consequently in an increase in mortar strength. (C) 2013 Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; Sustainable Energy, Air and Water Technology (DuEL); Energy and Materials in Infrastructure and Buildings (EMIB)
Impact Factor: 4.636
Times cited: 14
DOI: 10.1016/J.CATTOD.2013.10.001
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“Influence of surface defects on the vortex transitions in mesoscopic superconductors”. Baelus BJ, Kadowaki K, Peeters FM, AIP conference proceedings 850, 745 (2006)
Abstract: Solving the nonlinear Ginzburg-Landau equations self-consistently, we investigate the influence of a triangular surface defect (i.e. pacman shaped sample) on the vortex transitions in mesoscopic superconducting disks. Depending on the size of the defect, vortices may enter/leave one by one or in pairs.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
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“Time evolution studies of dithieno[3,2-b:2 ',3 '-d] pyrrole-based A-D-A oligothiophene bulk heterojunctions during solvent vapor annealing towards optimization of photocurrent generation”. Ben Dkhil S, Pfannmöller M, Ata I, Duche D, Gaceur M, Koganezawa T, Yoshimoto N, Simon J-J, Escoubas L, Videlot-Ackermann C, Margeat O, Bals S, Bauerle P, Ackermann J, Journal of materials chemistry A : materials for energy and sustainability 5, 1005 (2017). http://doi.org/10.1039/C6TA08175D
Abstract: Solvent vapor annealing (SVA) is one of the main techniques to improve the morphology of bulk heterojunction solar cells using oligomeric donors. In this report, we study time evolution of nanoscale morphological changes in bulk heterojunctions based on a well-studied dithienopyrrole-based A-D-A oligothiophene (dithieno[3,2-b: 2',3'-d] pyrrole named here 1) blended with [6,6]-phenyl-C-71-butyric acid methyl ester (PC71BM) to increase photocurrent density by combining scanning transmission electron microscopy and low-energy-loss spectroscopy. Our results show that SVA transforms the morphology of 1 : PC71BM blends by a three-stage mechanism: highly intermixed phases evolve into nanostructured bilayers that correspond to an optimal blend morphology. Additional SVA leads to completely phaseseparated micrometer-sized domains. Optical spacers were used to increase light absorption inside optimized 1 : PC71BM blends leading to solar cells of 7.74% efficiency but a moderate photocurrent density of 12.3 mA cm (-2). Quantum efficiency analyses reveal that photocurrent density is mainly limited by losses inside the donor phase. Indeed, optimized 1 : PC71BM blends consist of large donor-enriched domains not optimal for exciton to photocurrent conversion. Shorter SVA times lead to smaller domains; however they are embedded in large mixed phases suggesting that introduction of stronger molecular packing may help us to better balance phase separation and domain size enabling more efficient bulk heterojunction solar cells.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 8.867
Times cited: 19
DOI: 10.1039/C6TA08175D
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“Optical enhancement of a printed organic tandem solar cell using diffractive nanostructures”. Mayer JA, Offermans T, Chrapa M, Pfannmöller M, Bals S, Ferrini R, Nisato G, Optics express 26, A240 (2018). http://doi.org/10.1364/OE.26.00A240
Abstract: Solution processable organic tandem solar cells offer a promising approach to achieve cost-effective, lightweight and flexible photovoltaics. In order to further enhance the efficiency of optimized organic tandem cells, diffractive light-management nanostructures were designed for an optimal redistribution of the light as function of both wavelength and propagation angles in both sub-cells. As the fabrication of these optical structures is compatible with roll-to-roll production techniques such as hot-embossing or UV NIL imprinting, they present an optimal cost-effective solution for printed photovoltaics. Tandem cells with power conversion efficiencies of 8-10% were fabricated in the ambient atmosphere by doctor blade coating, selected to approximate the conditions during roll-to-roll manufacturing. Application of the light management structure onto an 8.7% efficient encapsulated tandem cell boosted the conversion efficiency of the cell to 9.5%. (C) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.307
Times cited: 9
DOI: 10.1364/OE.26.00A240
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“Understanding superionic conductivity in lithium and sodium salts of weakly coordinating closo-hexahalocarbaborate anions”. Jorgensen M, Shea PT, Tomich AW, Varley JB, Bercx M, Lovera S, Cerny R, Zhou W, Udovic TJ, Lavallo V, Jensen TR, Wood BC, Stavila V, Chemistry of materials 32, 1475 (2020). http://doi.org/10.1021/ACS.CHEMMATER.9B04383
Abstract: Solid-state ion conductors based on closo-polyborate anions combine high ionic conductivity with a rich array of tunable properties. Cation mobility in these systems is intimately related to the strength of the interaction with the neighboring anionic network and the energy for reorganizing the coordination polyhedra. Here, we explore such factors in solid electrolytes with two anions of the weakest coordinating ability, [HCB11H5Cl6](-) and [HCB11H5Br6](-), and a total of 11 polymorphs are identified for their lithium and sodium salts. Our approach combines ab initio molecular dynamics, synchrotron X-ray powder diffraction, differential scanning calorimetry, and AC impedance measurements to investigate their structures, phase-transition behavior, anion orientational mobilities, and ionic conductivities. We find that M(HCB11H5X6) (M = Li, Na, X = Cl, Br) compounds exhibit order-disorder polymorphic transitions between 203 and 305 degrees C and display Li and Na superionic conductivity in the disordered state. Through detailed analysis, we illustrate how cation disordering in these compounds originates from a competitive interplay among the lattice symmetry, the anion reorientational mobility, the geometric and electronic asymmetry of the anion, and the polarizability of the halogen atoms. These factors are compared to other closo-polyborate-based ion conductors to suggest guidelines for optimizing the cation-anion interaction for fast ion mobility. This study expands the known solid-state poly(carba)borate-based materials capable of liquid-like ionic conductivities, unravels the mechanisms responsible for fast ion transport, and provides insights into the development of practical superionic solid electrolytes.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Times cited: 5
DOI: 10.1021/ACS.CHEMMATER.9B04383
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“The influence of the 6s², configuration of Bi³+ on the structures of A ' BiNb₂O₇, (A ' = Rb, Na, Li) layered perovskite oxides”. Mallick S, Khalsa G, Kaaret JZ, Zhang W, Batuk M, Gibbs AS, Hadermann J, Halasyamani PS, Benedek NA, Hayward MA, Journal of the Chemical Society : Dalton transactions 50, 15359 (2021). http://doi.org/10.1039/D1DT02974F
Abstract: Solid state compounds which exhibit non-centrosymmetric crystal structures are of great interest due to the physical properties they can exhibit. The 'hybrid improper' mechanism – in which two non-polar distortion modes couple to, and stabilize, a further polar distortion mode, yielding an acentric crystal structure – offers opportunities to prepare a range of novel non-centrosymmetric solids, but examples of compounds exhibiting acentric crystal structures stabilized by this mechanism are still relatively rare. Here we describe a series of bismuth-containing layered perovskite oxide phases, RbBiNb2O7, LiBiNb2O7 and NaBiNb2O7, which have structural frameworks compatible with hybrid-improper ferroelectricity, but also contain Bi3+ cations which are often observed to stabilize acentric crystal structures due to their 6s(2) electronic configurations. Neutron powder diffraction analysis reveals that RbBiNb2O7 and LiBiNb2O7 adopt polar crystal structures (space groups I2cm and B2cm respectively), compatible with stabilization by a trilinear coupling of non-polar and polar modes. The Bi3+ cations present are observed to enhance the magnitude of the polar distortions of these phases, but are not the primary driver for the acentric structure, as evidenced by the observation that replacing the Bi3+ cations with Nd3+ cations does not change the structural symmetry of the compounds. In contrast the non-centrosymmetric, but non-polar structure of NaBiNb2O7 (space group P2(1)2(1)2(1)) differs significantly from the centrosymmetric structure of NaNdNb2O7, which is attributed to a second-order Jahn-Teller distortion associated with the presence of the Bi3+ cations.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
DOI: 10.1039/D1DT02974F
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“Article Structure and magnetic properties of BiFe0.75Mn0.25O3 perovskite prepared at ambient and high pressure”. Belik AA, Abakumov AM, Tsirlin AA, Hadermann J, Kim J, Van Tendeloo G, Takayama-Muromachi E, Chemistry of materials 23, 4505 (2011). http://doi.org/10.1021/cm201774y
Abstract: Solid solutions of BiFe1xMnxO3 (0.0 ≤ x ≤ 0.4) were prepared at ambient pressure and at 6 GPa. The ambient-pressure (AP) phases crystallize in space group R3c similarly to BiFeO3. The high-pressure (HP) phases crystallize in space group R3c for x = 0.05 and in space group Pnma for 0.15 ≤ x ≤ 0.4. The structure of HP-BiFe0.75Mn0.25O3 was investigated using synchrotron X-ray powder diffraction, electron diffraction, and transmission electron microscopy. HP-BiFe0.75Mn0.25O3 has a PbZrO3-related √2ap × 4ap × 2√2ap (ap is the parameter of the cubic perovskite subcell) superstructure with a = 5.60125(9) Å, b = 15.6610(2) Å, and c = 11.2515(2) Å similar to that of Bi0.82La0.18FeO3. A remarkable feature of this structure is the unconventional octahedral tilt system, with the primary ab0a tilt superimposed on pairwise clockwise and counterclockwise rotations around the b-axis according to the oioi sequence (o stands for out-of-phase tilt, and i stands for in-phase tilt). The (FeMn)O6 octahedra are distorted, with one longer metaloxygen bond (2.222.23 Å) that can be attributed to a compensation for covalent BiO bonding. Such bonding results in the localization of the lone electron pair on Bi3+ cations, as confirmed by electron localization function analysis. The relationship between HP-BiFe0.75Mn0.25O3 and antiferroelectric structures of PbZrO3 and NaNbO3 is discussed. On heating in air, HP-BiFe0.75Mn0.25O3 irreversibly transforms to AP-BiFe0.75Mn0.25O3 starting from about 600 K. Both AP and HP phases undergo an antiferromagnetic ordering at TN ≈ 485 and 520 K, respectively, and develop a weak net magnetic moment at low temperatures. Additionally, ceramic samples of AP-BiFe0.75Mn0.25O3 show a peculiar phenomenon of magnetization reversal.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 57
DOI: 10.1021/cm201774y
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“Unity quantum yield of photogenerated charges and band-like transport in quantum-dot solids”. Talgorn E, Gao Y, Aerts M, Kunneman LT, Schins JM, Savenije TJ, van Huis MA, van der Zant HSJ, Houtepen AJ, Siebbeles LDA, Nature nanotechnology 6, 733 (2011). http://doi.org/10.1038/NNANO.2011.159
Abstract: Solid films of colloidal quantum dots show promise in the manufacture of photodetectors and solar cells. These devices require high yields of photogenerated charges and high carrier mobilities, which are difficult to achieve in quantum-dot films owing to a strong electronhole interaction and quantum confinement. Here, we show that the quantum yield of photogenerated charges in strongly coupled PbSe quantum-dot films is unity over a large temperature range. At high photoexcitation density, a transition takes place from hopping between localized states to band-like transport. These strongly coupled quantum-dot films have electrical properties that approach those of crystalline bulk semiconductors, while retaining the size tunability and cheap processing properties of colloidal quantum dots.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 38.986
Times cited: 129
DOI: 10.1038/NNANO.2011.159
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“Avoiding solid carbon deposition in plasma-based dry reforming of methane”. Biondo O, van Deursen CFAM, Hughes A, van de Steeg A, Bongers W, van de Sanden MCM, van Rooij G, Bogaerts A, Green Chemistry 25, 10485 (2023). http://doi.org/10.1039/D3GC03595F
Abstract: Solid carbon deposition is a persistent challenge in dry reforming of methane (DRM), affecting both classical and plasma-based processes. In this work, we use a microwave plasma in reverse vortex flow configuration to overcome this issue in CO<sub>2</sub>/CH<sub>4</sub>plasmas. Indeed, this configuration efficiently mitigates carbon deposition, enabling operation even with pure CH<sub>4</sub>feed gas, in contrast to other configurations. At the same time, high reactor performance is achieved, with CO<sub>2</sub>and CH<sub>4</sub>conversions reaching 33% and 44% respectively, at an energy cost of 14 kJ L<sup>−1</sup>for a CO<sub>2</sub> : CH<sub>4</sub>ratio of 1 : 1. Laser scattering and optical emission imaging demonstrate that the shorter residence time in reverse vortex flow lowers the gas temperature in the discharge, facilitating a shift from full to partial CH<sub>4</sub>pyrolysis. This underscores the pivotal role of flow configuration in directing process selectivity, a crucial factor in complex chemistries like CO<sub>2</sub>/CH<sub>4</sub>mixtures and very important for industrial applications.
Keywords: A1 Journal Article; Plasma, laser ablation and surface modeling Antwerp (PLASMANT) ;
Impact Factor: 9.8
DOI: 10.1039/D3GC03595F
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“Accelerated Discovery of Efficient Solar Cell Materials Using Quantum and Machine-Learning Methods”. Choudhary K, Bercx M, Jiang J, Pachter R, Lamoen D, Tavazza F, Chemistry of materials 31, 5900 (2019). http://doi.org/10.1021/acs.chemmater.9b02166
Abstract: Solar energy plays an important role in solving serious environmental
problems and meeting the high energy demand. However, the lack of suitable
materials hinders further progress of this technology. Here, we present the largest
inorganic solar cell material search till date using density functional theory (DFT) and
machine-learning approaches. We calculated the spectroscopic limited maximum
efficiency (SLME) using the Tran−Blaha-modified Becke−Johnson potential for 5097
nonmetallic materials and identified 1997 candidates with an SLME higher than 10%,
including 934 candidates with a suitable convex-hull stability and an effective carrier
mass. Screening for two-dimensional-layered cases, we found 58 potential materials
and performed G0W0 calculations on a subset to estimate the prediction uncertainty. As the above DFT methods are still computationally expensive, we developed a high accuracy machine-learning model to prescreen efficient materials and applied it to over a million materials. Our results provide a general framework and universal strategy for the design of high-efficiency solar
cell materials. The data and tools are publicly distributed at: https://www.ctcms.nist.gov/~knc6/JVASP.html, https://www.
ctcms.nist.gov/jarvisml/, https://jarvis.nist.gov/, and https://github.com/usnistgov/jarvis.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 6
DOI: 10.1021/acs.chemmater.9b02166
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“Identification of heavy metal origins related to chemical and morphological soil properties using several non-destructive X-ray analytical methods”. Akbulut S, Van Grieken R, Kilic MA, Čevik U, Rotondo GG, Environmental monitoring and assessment 185, 2377 (2013). http://doi.org/10.1007/S10661-012-2718-6
Abstract: Soils are complex mixtures of organic, inorganic materials, and metal compounds from anthropogenic sources. In order to identify the pollution sources, their magnitude and development, several X-ray analytical methods were applied in this study. The concentrations of 16 elements were determined in all the soil samples using energy dispersive X-ray fluorescence spectrometry. Soils of unknown origin were observed by scanning electron microscopy equipped with a Si(Li) X-ray detector using Monte Carlo simulation approach. The mineralogical analyses were carried out using X-ray diffraction spectrometry. Due to the correlations between heavy metals and oxide compounds, the samples were analyzed also by electron probe microanalyzer (EPMA) in order to have information about their oxide contents. On the other hand, soil pH and salinity levels were identified owing to their influence between heavy metal and soil-surface chemistry. Moreover, the geoaccumulation index (I geo) enables the assessment of contamination by comparing current and pre-industrial concentrations.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
DOI: 10.1007/S10661-012-2718-6
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“Insertion compounds and composites made by ball milling for advanced sodium-ion batteries”. Zhang B, Dugas R, Rousse G, Rozier P, Abakumov AM, Tarascon J-M, Nature communications 7, 10308 (2016). http://doi.org/10.1038/ncomms10308
Abstract: Sodium-ion batteries have been considered as potential candidates for stationary energy storage because of the low cost and wide availability of Na sources. However, their future commercialization depends critically on control over the solid electrolyte interface formation, as well as the degree of sodiation at the positive electrode. Here we report an easily scalable ball milling approach, which relies on the use of metallic sodium, to prepare a variety of sodium-based alloys, insertion layered oxides and polyanionic compounds having sodium in excess such as the Na4V2(PO4)(2)F-3 phase. The practical benefits of preparing sodium-enriched positive electrodes as reservoirs to compensate for sodium loss during solid electrolyte interphase formation are demonstrated by assembling full C/P'2-Na-1[Fe0.5Mn0.5]O-2 and C/'Na3+xV2(PO4)(2)F-3' sodium-ion cells that show substantial increases (>10%) in energy storage density. Our findings may offer electrode design principles for accelerating the development of the sodium-ion technology.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 12.124
Times cited: 104
DOI: 10.1038/ncomms10308
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“Competition between the Ni and Fe redox in the O3-NaNi1/3Fe1/3Mn1/3O2 cathode material for Na-ion batteries”. Shevchenko VA, Glazkova IS, Novichkov DA, Skvortsova I, V Sobolev A, Abakumov AM, Presniakov IA, Drozhzhin OA, V Antipov E, Chemistry of materials 35, 4015 (2023). http://doi.org/10.1021/ACS.CHEMMATER.3C00338
Abstract: Sodium-ion batteries are attracting great attention due to their low cost and abundance of sodium. The O3-type NaNi1/3Fe1/3Mn1/3O2 layered oxide material is a promising candidate for positive electrodes (cathodes) in Na-ion batteries. However, its stable electrochemical performance is restricted by the upper voltage limit of 4.0 V (vs Na/Na+), which allows for reversibly removing 0.5-0.55 Na+ per formula unit, corresponding to the capacity of 120-130 mAh.g(-1). Further reduction of sodium content inevitably accelerates capacity degradation, and this issue calls for a detailed study of the redox reactions that accompany the electrochemical (de)intercalation of a large amount of sodium. Here, we present operando and ex situ studies using powder X-ray diffraction and X-ray absorption spectroscopy combined with Fe-57 Mossbauer spectroscopy. Our approach reveals the sequence of the redox transitions that occur during the charge and discharge of O3-NaNi1/3Fe1/3Mn1/3O2. Our data show that in addition to nickel and iron cations oxidizing to M+4, a part of iron transforms into the “3 + delta” state owing to the fast electron exchange Fe3+ + Fe4+ <-> Fe4+ + Fe3+. This process freezes upon cooling the material to 35 K, producing Fe4+ cations, some of which occupy tetrahedral positions.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 8.6
DOI: 10.1021/ACS.CHEMMATER.3C00338
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