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“Multiscale modeling of radiation damage and annealing in Si samples implanted with 57-Mn radioactive ions”. Abreu Y, Cruz CM, van Espen P, Piñera I, Leyva A, Cabal AE, IEEE conference record
T2 –, IEEE Nuclear Science Symposium/Medical Imaging Conference (NSS/MIC)/18th, International Workshop on Room-Temperature Semiconductor X-Ray and, Gamma-Ray Detectors, OCT 23-29, 2011, Valencia, SPAIN , 1754 (2011)
Abstract: The radiation damage created in silicon materials by Mn-57 -> Fe-57 ion implantation has been studied and characterized by Mossbauer spectroscopy showing four main lines, assigned to: substitutional, interstitial and damaged configuration sites of the implanted ions. Nevertheless, the Mossbauer spectrum of Fe-57 in this materials remains with some ambiguous identification regarding the implantation configurations before and after annealing, specially the damaged configurations and its evolution. In the present work some possible implantation configurations are suggested and evaluated using a multiscale approach by Monte Carlo ion transport and electronic structure calculations within DFT. The proposed implantation environments were evaluated in terms of stability and the Fe-57 hyperfine parameters were calculated to establish the connections with the experimental observations. Good agreement was found between the experimental and the calculated hyperfine parameters for some configurations; suggesting which ones could be the implantation environments before and after sample annealing.
Keywords: P1 Proceeding; Engineering sciences. Technology; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
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“Radiation damage evaluation on LYSO and LuYAP materials through Dpa calculation assisted by Monte Carlo method”. Piñera I, Abreu Y, van Espen P, Diaz A, Leyva A, Cruz CM, IEEE conference record
T2 –, IEEE Nuclear Science Symposium/Medical Imaging Conference (NSS/MIC)/18th, International Workshop on Room-Temperature Semiconductor X-Ray and, Gamma-Ray Detectors, OCT 23-29, 2011, Valencia, SPAIN , 1609 (2011)
Abstract: The aim of the present work is to study the radiation damage induced in LYSO and LuYAP crystals by the gamma radiation and the secondary electrons/positrons generated. The displacements per atom (dpa) distributions inside each material were calculated following the Monte Carlo assisted Classical Method (MCCM) introduced by the authors. As gamma sources were used Sc-44, Na-22 and V-48. Also the energy of gammas from the annihilation processes (511 keV) was included in the study. This procedure allowed studying the in-depth dpa distributions inside each crystal for all four sources. It was also possible to obtain the separate contribution from each atom to the total dpa. The LYSO crystals were found to receive more damage, mainly provoked by the displacements of silicon and oxygen atoms.
Keywords: P1 Proceeding; Engineering sciences. Technology; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
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“Cation ordering within the perovskite block of a six-layer Ruddlesden-Popper oxide from layer-by-layer growth artificial interfaces in complex unit cells”. Yan L, Niu HJ, Duong GV, Suchomel MR, Bacsa J, Chalker PR, Hadermann J, Van Tendeloo G, Rosseinsky MJ, Chemical science 2, 261 (2011). http://doi.org/10.1039/c0sc00482k
Abstract: The (AO)(ABO3)n Ruddlesden-Popper structure is an archetypal complex oxide consisting of two distinct structural units, an (AO) rock salt layer separating an n-octahedra thick perovskite block. Conventional high-temperature oxide synthesis methods cannot access members with n > 3, but low-temperature layer-by-layer thin film methods allow the preparation of materials with thicker perovskite blocks, exploiting high surface mobility and lattice matching with the substrate. This paper describes the growth of an n = 6 member CaO[(CSMO)2(LCMO)2 (CSMO)2] in which the six unit cell perovskite block is sub-divided into two central La0.67Ca0.33MnO3 (LCMO) and two terminal Ca0.85Sm0.15MnO3 (CSMO) layers to allow stabilization of the rock salt layer and variation of the transition metal charge.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 8.668
Times cited: 16
DOI: 10.1039/c0sc00482k
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“High resolution mapping of surface reduction in ceria nanoparticles”. Turner S, Lazar S, Freitag B, Egoavil R, Verbeeck J, Put S, Strauven Y, Van Tendeloo G, Nanoscale 3, 3385 (2011). http://doi.org/10.1039/c1nr10510h
Abstract: Surface reduction of ceria nano octahedra with predominant {111} and {100} type surfaces is studied using a combination of aberration-corrected Transmission Electron Microscopy (TEM) and spatially resolved electron energy-loss spectroscopy (EELS) at high energy resolution and atomic spatial resolution. The valency of cerium ions at the surface of the nanoparticles is mapped using the fine structure of the Ce M4,5 edge as a fingerprint. The valency of the surface cerium ions is found to change from 4+ to 3+ owing to oxygen deficiency (vacancies) close to the surface. The thickness of this Ce3+ shell is measured using atomic-resolution Scanning Transmission Electron Microscopy (STEM)-EELS mapping over a {111} surface (the predominant facet for this ceria morphology), {111} type surface island steps and {100} terminating planes. For the {111} facets and for {111} surface islands, the reduction shell is found to extend over a single fully reduced surface plane and 12 underlying mixed valency planes. For the {100} facets the reduction shell extends over a larger area of 56 oxygen vacancy-rich planes. This finding provides a plausible explanation for the higher catalytic activity of the {100} surface facets in ceria.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 7.367
Times cited: 127
DOI: 10.1039/c1nr10510h
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“On the concept of a supervisory, fuzzy set logic based, advanced filtration control in membrane bioreactors”. Brauns E, van Hoof E, Huyskens C, de Wever H, Desalination and water treatment 29, 119 (2011). http://doi.org/10.5004/DWT.2011.2258
Abstract: The filtration process within a membrane bioreactor (MBR) is mostly controlled in a classic way through typical set-points such as aeration flow rate, filtration duration, backwash frequency or relaxation duration. The values of these filtration set-points result from experience and remain often unchanged during the installations operational lifetime. Filtration is dictated considerably by membrane fouling phenomena. The fouling potential of the mixed liquor however can significantly fluctuate, even daily, from changing influent characteristics. Fixed set-point values thus may represent sub-optimal filtration conditions. Consequently, a supervising advanced control system, being able to continuously adapt the set-points values would be beneficial regarding the MBR filtration process optimization. Such optimization could reduce the corresponding MBR energy consumption, e.g. linked to the filtration related membrane aeration. An Advanced Control System (ACS) based on Fuzzy Set Logic (FSL) is introduced here, enabling to supervise an existing classic membrane filtration control system. Such ACS is able to daily (or even more frequent) optimize the set-points of the underlying classic control system, from the input of various sensor and process parameter values. The theoretical background and practical implementation of the FSL based ACS concept is explained.
Keywords: A1 Journal article; Engineering sciences. Technology; Sustainable Energy, Air and Water Technology (DuEL)
DOI: 10.5004/DWT.2011.2258
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“Identification of substitutional nitrogen and surface paramagnetic centers in nanodiamond of dynamic synthesis by electron paramagnetic resonance”. Orlinskii SB, Bogomolov RS, Kiyamova AM, Yavkin BV, Mamin GM, Turner S, Van Tendeloo G, Shiryaev AA, Vlasov II, Shenderova O, Nanoscience and nanotechnology letters 3, 63 (2011). http://doi.org/10.1166/nnl.2011.1121
Abstract: Production of nanodiamond particles containing substitutional nitrogen is important for a wide variety of advanced applications. In the current work nanodiamond particles synthesized from a mixture of graphite and hexogen were analyzed to determine the presence of substitutional nitrogen using pulsed electron paramagnetic resonance (EPR) spectroscopy. Nitrogen paramagnetic centers in the amount of 1.2 ppm have been identified. The spin relaxation characteristics for both nitrogen and surface defects are also reported. A new approach for efficient depletion of the strong non-nitrogen EPR signal in nanodiamond material by immersing nanodiamond particles into ice matrix is suggested. This approach allows an essential decrease of the spin relaxation time of the dominant non-nitrogen defects, while preserving the substitutional nitrogen spin relaxation time.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 1.889
Times cited: 14
DOI: 10.1166/nnl.2011.1121
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“From single to multiple Ag-layer modification of Au nanocavity substrates : a tunable probe of the chemical surface-enhanced Raman scattering mechanism”. Tognalii NG, Cortés E, Hernández-Nieves AD, Carro P, Usaj G, Balseiro CA, Vela ME, Salvarezza RC, Fainstein A, ACS nano 5, 5433 (2011). http://doi.org/10.1021/nn200567m
Abstract: We present experimental and computational results that enlighten the mechanisms underlying the chemical contribution to surface-enhanced Raman scattering (SERS). Gold void metallic arrays electrochemically covered either by a Ag monolayer or 10100 Ag layers were modified with a self-assembled monolayer of 4-mercaptopyridine as a molecular Raman probe displaying a rich and unexpected Raman response. A resonant increase of the Raman intensity in the red part of the spectrum is observed that cannot be related to plasmon excitations of the cavity-array. Notably, we find an additional 1020 time increase of the SERS amplification upon deposition of a single Ag layer on the Au substrate, which is, however, almost quenched upon deposition of 10 atomic layers. Further deposition of 100 atomic Ag layers results in a new increase of the SERS signal, consistent with the improved plasmonic efficiency of Ag bulk-like structures. The SERS response as a function of the Ag layer thickness is analyzed in terms of ab initio calculations and a microscopic model for the SERS chemical mechanism based on a resonant charge transfer process between the molecular HOMO state and the Fermi level in the metal surface. We find that a rearrangement of the electronic charge density related to the presence of the Ag monolayer in the Au/Ag/molecule complex causes an increase in the distance between the HOMO center of charge and the metallic image plane that is responsible for the variation of Raman enhancement between the studied substrates. Our results provide a general platform for studying the chemical contribution to SERS, and for enhancing the Raman efficiency of tailored Au-SERS templates through electrochemical modification with Ag films.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 13.942
Times cited: 26
DOI: 10.1021/nn200567m
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“Atomic oxygen functionalization of vertically aligned carbon nanotubes”. Bittencourt C, Navio C, Nicolay A, Ruelle B, Godfroid T, Snyders R, Colomer J-F, Lagos MJ, Ke X, Van Tendeloo G, Suarez-Martinez I, Ewels CP, The journal of physical chemistry: C : nanomaterials and interfaces 115, 20412 (2011). http://doi.org/10.1021/jp2057699
Abstract: Vertically aligned multiwalled carbon nanotubes (v-MWCNTs) are functionalized using atomic oxygen generated in a microwave plasma. X-ray photoelectron spectroscopy depth profile analysis shows that the plasma treatment effectively grafts oxygen exclusively at the v-MWCNT tips. Electron microscopy shows that neither the vertical alignment nor the structure of v-MWCNTs were affected by the plasma treatment. Density functional calculations suggest assignment of XPS C 1s peaks at 286.6 and 287.5 eV, to epoxy and carbonyl functional groups, respectively.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 4.536
Times cited: 31
DOI: 10.1021/jp2057699
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“Can we control the thickness of ultrathin silica layers by hyperthermal silicon oxidation at room temperature?”.Khalilov U, Neyts EC, Pourtois G, van Duin ACT, The journal of physical chemistry: C : nanomaterials and interfaces 115, 24839 (2011). http://doi.org/10.1021/jp2082566
Abstract: Using reactive molecular dynamics simulations by means of the ReaxFF potential, we studied the growth mechanism of ultrathin silica (SiO2) layers during hyperthermal oxidation at room temperature. Oxidation of Si(100){2 × 1} surfaces by both atomic and molecular oxygen was investigated in the energy range 15 eV. The oxidation mechanism, which differs from thermal oxidation, is discussed. In the case of oxidation by molecular O2, silica is quickly formed and the thickness of the formed layers remains limited compared to oxidation by atomic oxygen. The Si/SiO2 interfaces are analyzed in terms of partial charges and angle distributions. The obtained structures of the ultrathin SiO2 films are amorphous, including some intrinsic defects. This study is important for the fabrication of silica-based devices in the micro- and nanoelectronics industry, and more specifically for the fabrication of metal oxide semiconductor devices.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 4.536
Times cited: 36
DOI: 10.1021/jp2082566
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“Hyperthermal oxygen interacting with silicon surfaces : adsorption, implantation, and damage creation”. Neyts EC, Khalilov U, Pourtois G, van Duin ACT, The journal of physical chemistry: C : nanomaterials and interfaces 115, 4818 (2011). http://doi.org/10.1021/jp112068z
Abstract: Using reactive molecular dynamics simulations, we have investigated the effect of single-impact, low-energy (thermal-100 eV) bombardment of a Si(100){2 × 1} surface by atomic and molecular oxygen. Penetration probability distributions, as well as defect formation distributions, are presented as a function of the impact energy for both species. It is found that at low impact energy, defects are created chemically due to the chemisorption process in the top layers of the surface, while at high impact energy, additional defects are created by a knock-on displacement of Si. These results are of particular importance for understanding device performances of silica-based microelectronic and photovoltaic devices.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 4.536
Times cited: 28
DOI: 10.1021/jp112068z
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“Mechanisms for the trimethylaluminum reaction in aluminum oxide atomic layer deposition on sulfur passivated germanium”. Delabie A, Sioncke S, Rip J, van Elshocht S, Caymax M, Pourtois G, Pierloot K, The journal of physical chemistry: C : nanomaterials and interfaces 115, 17523 (2011). http://doi.org/10.1021/jp206070y
Abstract: Germanium combined with high-κ dielectrics is investigated for the next generations of CMOS devices. Therefore, we study reaction mechanisms for Al2O3 atomic layer deposition on sulfur passivated Ge using calculations based on density functional theory and total reflection X-ray fluorescence (TXRF). TXRF indicates 6 S/nm2 and 4 Al/nm2 after the first TMA/H2O reaction cycle, and growth inhibition from the second reaction cycle on. Calculations are performed on molecular clusters representing −GeSH surface sites. The calculations confirm that the TMA reaction does not affect the S content. On fully SH-terminated Ge, TMA favorably reacts with up to three −GeSH sites, resulting in a near tetrahedral Al coordination. Electron deficient structures with a GeS site shared between two Al atoms are proposed. The impact of the cluster size on the structures and reaction energetics is systematically investigated.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 4.536
Times cited: 9
DOI: 10.1021/jp206070y
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“Nitrogen control in nanodiamond produced by detonation shock-wave-assisted synthesis”. Shenderova OA, Vlasov II, Turner S, Van Tendeloo G, Orlinskii SB, Shiryaev AA, Khomich AA, Sulyanov SN, Jelezko F, Wrachtrup J, The journal of physical chemistry: C : nanomaterials and interfaces 115, 14014 (2011). http://doi.org/10.1021/jp202057q
Abstract: Development of efficient production methods of nanodiamond (ND) particles containing substitutional nitrogen and nitrogen-vacancy (NV) complexes remains an important goal in the nanodiamond community. ND synthesized from explosives is generally not among the preferred candidates for imaging applications owing to lack of optically active particles containing NV centers. In this paper, we have systematically studied representative classes of NDs produced by detonation shock wave conversion of different carbon precursor materials, namely, graphite and a graphite/hexogen mixture into ND, as well as ND produced from different combinations of explosives using different cooling methods (wet or dry cooling). We demonstrate that (i) the N content in nanodiamond particles can be controlled through a correct selection of the carbon precursor material (addition of graphite, explosives composition); (ii) particles larger than approximately 20 nm may contain in situ produced optically active NV centers, and (iii) in ND produced from explosives, NV centers are detected only in ND produced by wet synthesis. ND synthesized from a mixture of graphite/explosive contains the largest amount of NV centers formed during synthesis and thus deserves special attention.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 4.536
Times cited: 54
DOI: 10.1021/jp202057q
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“Single layer vs bilayer graphene : a comparative study of the effects of oxygen plasma treatment on their electronic and optical properties”. Nourbakhsh A, Cantoro M, Klekachev AV, Pourtois G, Vosch T, Hofkens J, van der Veen MH, Heyns MM, de Gendt S, Sels BF, The journal of physical chemistry: C : nanomaterials and interfaces 115, 16619 (2011). http://doi.org/10.1021/jp203010z
Abstract: This contribution presents the effects of a mild O2 plasma treatment on the structural, optical, and electrical properties of single-layer (SLG) and bilayer graphene (BLG). Unexpectedly, we observe only photoluminescence in the SLG parts of a graphene flake composed of regions of various thickness upon O2 plasma treatment, whereas the BLG and few-layer graphene (FLG) parts remain optically unchanged. Confirmed with X-ray photoelectron spectroscopy (XPS) that O2 plasma induces epoxide and hydroxyl-like groups in graphene, density functional theory (DFT) calculations are carried out on representative epoxidized and hydroxylated SLG and BLG models to predict density of states (DOS) and band structures. Sufficiently oxidized SLG shows a bandgap and thus loss of semimetallic behavior, while oxidized BLG maintains its semimetallic behavior even at high oxygen density in agreement with the results of the photoluminescence spectroscopy (PL) experiments. DFT calculations confirm that the Fermi velocity in epoxidized BLG is remarkably comparable with that of pristine SLG, pointing to a similarity of electronic band structure. The similarity is also experimentally demonstrated by the electrical characterization of a plasma-treated BLG-FET. As expected from the electronegative oxygen adatoms in the graphene, epoxidized BLG presents conductive features typical of hole doping. Moreover, the electrical characteristics suggest band structures closely related to that of epoxidized graphene while deviating from that of hydroxylated graphene. Finally, upon O2 plasma treatment of BLG, the four-component 2D peak around 2700 cm1 in the Raman spectrum evolves into a single Lorentzian line, very like the 2D peak of pristine SLG. Summarizing, the data in this contribution recommend that a controlled O2 plasma treatment, which is compatible with CMOS process flow in contrast to wet chemical oxidation methods, provides an efficient and valuable technique to exploit the transport properties of the bottom layer of BLG.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 4.536
Times cited: 46
DOI: 10.1021/jp203010z
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“Surface chemistry and properties of ozone-purified detonation nanodiamonds”. Shenderova O, Koscheev A, Zaripov N, Petrov I, Skryabin Y, Detkov P, Turner S, Van Tendeloo G, The journal of physical chemistry: C : nanomaterials and interfaces 115, 9827 (2011). http://doi.org/10.1021/jp1102466
Abstract: Nanodiamond from ozone purification (NDO) demonstrates very distinctive properties within the class of detonation nanodiamonds, namely very high acidity and high colloidal stability in a broad pH range. To understand the origin of these unusual properties of NDO, the nature of the surface functional groups formed during detonation soot oxidation by ozone needs to be revealed. In this work, thermal desorption mass spectrometry (TDMS) and IR spectroscopy were used for the identification of surface groups and it was concluded that carboxylic anhydride groups prevail on the NDO surface. On the basis of the temperature profiles of the desorbed volatile products and their mass balance, it is hypothesized that decomposition of carboxylic anhydride groups from NDO during heating proceeds by two different mechanisms. Other distinctive features of NDO in comparison with air-treated nanodiamond are also reported.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 4.536
Times cited: 105
DOI: 10.1021/jp1102466
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“Dynamic shear localization in Ti6Al4V”. Peirs J, Verleysen P, Tirry W, Rabet L, Schryvers D, Degrieck J, Procedia Engineering
T2 –, 11th International Conference on the Mechanical Behavior of Materials, (ICM), 2011, Como, ITALY (ICM11) , 1 (2011). http://doi.org/10.1016/j.proeng.2011.04.386
Abstract: The alloy Ti6Al4V is known to be prone to the formation of adiabatic shear bands when dynamically loaded in shear. This causes a catastrophic decrease of the load carrying capacity and is usually followed by fracture. Although, the main mechanism is recognized to be the competition between strain hardening and thermal softening, a detailed understanding of the role of microstructural plasticity mechanisms and macroscopic loading conditions does not exist yet. To study strain localization and shear fracture, different high strain rate shear tests have been carried out: compression of hat-shaped specimens, torsion of thin walled tubular specimens and in-plane shear tests. The value of the three techniques in studying shear localization is evaluated. Post-mortem analysis of the fracture surface and the materials' microstructure is performed with optical and electron microscopy. In all cases a ductile fracture is observed. SEM and TEM techniques are used to study the local microstructure and composition in the shear band and as such the driving mechanism for the ASB formation. (C) 2011 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of ICM11
Keywords: P1 Proceeding; Electron microscopy for materials research (EMAT)
Times cited: 4
DOI: 10.1016/j.proeng.2011.04.386
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“Superconducting nanowires : new type of BCS-BEC crossover driven by quantum-size effects”. Shanenko AA, Croitoru MD, Vagov A, Peeters FM, , 119 (2011). http://doi.org/10.1007/978-94-007-0044-4_9
Abstract: We show that a superconducting quantum nanowire undergoes a new type of BCS-BEC crossover each time when an electron subband approaches the Fermi surface. In this case the longitudinal Cooper-pair size drops by two-three orders of magnitude down to a few nanometers. This unconventional BCS-BEC crossover is driven by quantum-size effects rather than by tuning the fermion-fermion interaction.
Keywords: P1 Proceeding; Condensed Matter Theory (CMT)
DOI: 10.1007/978-94-007-0044-4_9
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“Nickel/carbon composite materials based on expanded graphite”. Afanasov IM, Lebedev OI, Kolozhvary BA, Smirnov AV, Van Tendeloo G, New carbon materials 26, 335 (2011). http://doi.org/10.1016/S1872-5805(11)60085-1
Abstract: Monolithic nickel/carbon (Ni/C) composites were prepared from coal tar pitch-impregnated compressed expanded graphite pre-decorated with NiO particles (EGNiO) by pyrolysis at 550 °C and subsequent steam activation at 800 °C. The microstructural arrangement of the Ni-comprising nanoparticles in the composites was investigated using transmission electron microscopy. The specific surface area and porosity of the composites were analyzed by nitrogen adsorption. The catalytic activity of the composites was compared with the material obtained by the conventional H2 treatment of EGNiO using hydrocracking of 2,2,3-trimethylpentane as a model reaction.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Times cited: 7
DOI: 10.1016/S1872-5805(11)60085-1
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“Characterization of indoor and outdoor atmospheric pollutants impacting architectural monuments : the case of San Jerónimo Monastery (Granada, Spain)”. Kontozova-Deutsch V, Cardell carolina, Urosevic M, Ruiz-Agudo E, Deutsch F, Van Grieken R, Environmental earth sciences 63, 1433 (2011). http://doi.org/10.1007/S12665-010-0657-5
Abstract: Indoor and outdoor concentrations of atmospheric gaseous pollutants as well as composition, size, and morphology of particulate matter have been investigated at the monastery of San Jerónimo in Granada (Southern Spain). Complementary micro- and nano-analytical techniques were applied; elemental and mineralogical composition and morphological characteristics of particulate matter were investigated combining electron probe microanalysis at the single particle level, and bulk aerosol samples were analyzed using energy-dispersive X-ray fluorescence, X-ray diffraction, scanning electron microscopy with energy-dispersive X-ray analyzer and transmission electron microscopy (TEM). Microclimatic conditions at the monastery were monitored, and gas concentrations were assessed by means of diffusion tubes subsequently analyzed with ion chromatography. Results revealed high abundances of soil dust particles (aluminosilicates, calcite, dolomite, quartz), salt aerosols (chlorides, sulfates and ammonium-rich salts), and NO2 and SO2 both outdoors and indoors. Amorphous black carbon particles had surprisingly high abundances for Granada, a non-industrialized city. The composition of indoor particles corresponds to severe weathering affecting the construction materials and artworks inside the church; moreover their composition promotes a feedback process that intensifies the deterioration. Chemical reactions between chloride-rich salts and pigments from paintings were confirmed by TEM analyses. Indoors, blackening of surface decorative materials is fostered by particle re-suspension due to cleaning habits in the monastery (i.e. dusting). This is the first air quality study performed in a monument in the city of Granada with the aim of developing a strategy for preventive conservation.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
DOI: 10.1007/S12665-010-0657-5
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“Design of Ru-zeolites for hydrogen-free production of conjugated linoleic acid”. Philippaerts A, Goossens S, Vermandel W, Tromp M, Turner S, Geboers J, Van Tendeloo G, Jacobs PA, Sels BF, Chemsuschem 4, 757 (2011). http://doi.org/10.1002/cssc.201100015
Abstract: While conjugated vegetable oils are currently used as additives in the drying agents of oils and paints, they are also attractive molecules for making bio-plastics. Moreover, conjugated oils will soon be accepted as nutritional additives for functional food products. While current manufacture of conjugated vegetable oils or conjugated linoleic acids (CLAs) uses a homogeneous base as isomerisation catalyst, a heterogeneous alternative is not available today. This contribution presents the direct production of CLAs over Ru supported on different zeolites, varying in topology (ZSM-5, BETA, Y), Si/Al ratio and countercation (H+, Na+, Cs+). Ru/Cs-USY, with a Si/Al ratio of 40, was identified as the most active and selective catalyst for isomerisation of methyl linoleate (cis-9,cis-12 (C18:2)) to CLA at 165 °C. Interestingly, no hydrogen pre-treatment of the catalyst or addition of hydrogen donors is required to achieve industrially relevant isomerisation productivities, namely, 0.7 g of CLA per litre of solvent per minute. Moreover, the biologically most active CLA isomers, namely, cis-9,trans-11, trans-10,cis-12 and trans-9,trans-11, were the main products, especially at low catalyst concentrations. Ex situ physicochemical characterisation with CO chemisorption, extended X-ray absorption fine structure measurements, transmission electron microscopy analysis, and temperature-programmed oxidation reveals the presence of highly dispersed RuO2 species in Ru/Cs-USY(40).
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 7.226
Times cited: 24
DOI: 10.1002/cssc.201100015
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“Multimodal zeolite-beta-based catalysts with a hierarchical, three-level pore structure”. Chen L-H, Li X-Y, Tian G, Li Y, Tan H-Y, Van Tendeloo G, Zhu G-S, Qiu S-L, Yang X-Y, Su B-L, Chemsuschem 4, 1452 (2011). http://doi.org/10.1002/cssc.201100181
Abstract: Hole diggers: The hierarchically structured porous solid-acid catalyst described in this report possess a remarkable pore system, encompassing well-defined macrochannels, interconnected mesopores, intracrystalline mesopores, and tunable zeolite micropores. Importantly, the catalyst exhibits very strong acidity and superior catalytic activity for esterification reactions.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 7.226
Times cited: 33
DOI: 10.1002/cssc.201100181
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“A non-aqueous synthesis of TiO2SiO2 composites in supercritical CO2 for the photodegradation of pollutants”. Jammaer J, Aprile C, Verbruggen SW, Lenaerts S, Pescarmona PP, Martens JA, Chemsuschem 4, 1457 (2011). http://doi.org/10.1002/CSSC.201100059
Abstract: Titania/silica composites with different Ti/Si ratios are synthesized via a nonconventional synthesis route. The synthesis involves non-aqueous reaction of metal alkoxides and formic acid at 75 °C in supercritical carbon dioxide. The as-prepared composite materials contain nanometer-sized anatase crystallites and amorphous silica. Large specific surface areas are obtained. The composites are evaluated in the photocatalytic degradation of phenol in aqueous medium, and in the elimination of acetaldehyde from air. The highest photocatalytic activity in both processes is achieved with a composite containing 40 wt % TiO2.
Keywords: A1 Journal article; Engineering sciences. Technology; Sustainable Energy, Air and Water Technology (DuEL)
Impact Factor: 7.226
Times cited: 15
DOI: 10.1002/CSSC.201100059
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“Study on the giant positive magnetoresistance and Hall effect in ultrathin graphite flakes”. Vansweevelt R, Mortet V, D' Haen J, Ruttens bart, van Haesendonck C, Partoens B, Peeters FM, Wagner P, Physica status solidi : A : applications and materials science 208, 1252 (2011). http://doi.org/10.1002/pssa.201001206
Abstract: In this paper, we report on the electronic transport properties of mesoscopic, ultrathin graphite flakes with a thickness corresponding to a stack of 150 graphene layers. The graphite flakes show an unexpectedly strong positive magnetoresistance (PMR) already at room temperature, which scales in good approximation with the square of the magnetic field. Furthermore, we show that the resistivity is unaffected by magnetic fields oriented in plane with the graphene layers. Hall effect measurements indicate that the charge carriers are p-type and their concentration increases with increasing temperature while the mobility is decreasing. The Hall voltage is non-linear in higher magnetic fields. Possible origins of the observed effects are discussed. Ball and stick model of the two topmost carbon layers of the hexagonal graphite structure.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 1.775
Times cited: 8
DOI: 10.1002/pssa.201001206
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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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“Synthesis and characterisation of lanthanide-based dioxide”. Esquivel MR, Zelaya E, Advances in applied ceramics 110, 219 (2011). http://doi.org/10.1179/1743676110Y.0000000021
Abstract: In the present work, the microstructure and structure of La(0.25)Ce(0.52)Nd(0.17)Pr(0.06)(OH)(3) and La(0.25)Ce(0.52)Nd(0.17)Pr(0.06)O(2) is obtained from transmission electron microscopy and X-ray diffraction measurements. Space group P6(3)/m is assigned to the structure of La(0.25)Ce(0.52)Nd(0.17)Pr(0.06)(OH)(3). Lanthanides are assigned to Wyckoff positions 2c. Cell parameters are a=6.375(5) angstrom and c=3.753(5) angstrom. The thermal decomposition of this compound was studied by differential scanning calorimetry. The process is exothermal with an enthalpy change Delta H degrees value of -254 +/- 10 kJ mol(-1). The decomposition kinetics is complex and two global processes with E(a) values of 98 +/- 4 and 61 +/- 2 kJ mol 21 were observed. The product is a lanthanide dioxide. Space group Fm3m is assigned to the La(0.25)Ce(0.52)Nd(0.17)Pr(0.06)O(2). Lanthanides are distributed in Wyckoff positions 4a. The cell parameter is a=5.479(5) angstrom. Nanopores in the oxide surface are obtained using this method and characterised by STEM measurements.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 1.325
Times cited: 3
DOI: 10.1179/1743676110Y.0000000021
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“Stability of Ni in nitinol oxide surfaces”. Tian H, Schryvers D, Liu D, Jiang Q, van Humbeeck J, Acta biomaterialia 7, 892 (2011). http://doi.org/10.1016/j.actbio.2010.09.009
Abstract: The stability of Ni in titanium oxide surface layers on nitinol wires known to release certain amounts of Ni was investigated by first principles density functional theory and transmission electron microscopy. The oxides were identified as a combination of TiO and TiO2 depending on the thickness of the layer. The calculations indicate that free Ni atoms can exist in TiO at ambient temperature while Ni particles form in TiO2, which was confirmed by the transmission electron microscopy observations. The results are discussed with respect to surface stability and Ni release due to free Ni atoms and Ni particles.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 6.319
Times cited: 39
DOI: 10.1016/j.actbio.2010.09.009
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“Plasma chemistry modeling for an inductively coupled plasma used for the growth of carbon nanotubes”. Mao M, Bogaerts A, Journal of physics : conference series 275, 012021 (2011). http://doi.org/10.1088/1742-6596/275/1/012021
Abstract: A hybrid model, called the hybrid plasma equipment model (HPEM), is used to describe the plasma chemistry in an inductively coupled plasma, operating in a gas mixture of C2H2 with either H2 or NH3, as typically used for carbon nanotube (CNT) growth. Two-dimensional profiles of power density, electron temperature and density, gas temperature, and densities of some plasma species are plotted and analyzed. Besides, the fluxes of the various plasma species towards the substrate (where the CNTs can be grown), as well as the decomposition rates of the feedstock gases (C2H2, NH3 and H2), are calculated as a function of the C2H2 fraction in both gas mixtures.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
DOI: 10.1088/1742-6596/275/1/012021
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“Advanced TEM and SEM methods applied to 3D nano- and microstructural investigations of Ni4Ti3 precipitates in Ni-Ti (SMA)”. Schryvers D, Tirry W, Cao S, Diffusion and defect data : solid state data : part B : solid state phenomena 172/174, 229 (2011). http://doi.org/10.4028/www.scientific.net/SSP.172-174.229
Abstract: Two different kinds of experimental approaches yielding three-dimensional structural information on metastable semi-coherent precipitates are demonstrated. By combining high-resolution images from two independent viewing directions a full description of the strain field surrounding a nano-sized Ni4Ti3 precipitate in Ni-Ti can be obtained. The principal axes and strains correlate well with the transformation strain of the observed R-phase transformation close to the precipitate. Using a slice-and-view procedure in a FIB/SEM dual-beam instrument, a three-dimensional voxel dataset is produced from which morphological and distributional information on the same precipitates can be obtained yielding new insight into the particular transformation paths of these alloys, relevant for their functional behaviour.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
DOI: 10.4028/www.scientific.net/SSP.172-174.229
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“FIB/SEM applied to quantitative 3D analysis of precipitates in Ni-Ti”. Cao S, Nishida M, Schryvers D, Diffusion and defect data : solid state data : part B : solid state phenomena 172/174, 1284 (2011). http://doi.org/10.4028/www.scientific.net/SSP.172-174.1284
Abstract: Ni4Ti3 precipitates with a heterogeneous distribution growing in a polycrystalline Ni50.8Ti49.2 alloy have been investigated in a Dual-Beam FIB/SEM system. The volume ratio, mean volume, central plane diameter, thickness, aspect ratio and sphericity of the precipitates in the grain interior as well as near to the grain boundary were measured or calculated. The morphology of the precipitates was classified according to the Zingg scheme. The multistage martensitic transformation occurring in these kinds of samples is interpreted in view of the data of this heterogeneous microstructure of matrix and precipitates.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
DOI: 10.4028/www.scientific.net/SSP.172-174.1284
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“Special microstructures and twin features in Ti50Ni50-x(Pd,Au)x at small hysteresis”. Delville R, Shi H, James RD, Schryvers D, Diffusion and defect data : solid state data : part B : solid state phenomena 172/174, 105 (2011). http://doi.org/10.4028/www.scientific.net/SSP.172-174.105
Abstract: The breaking of symmetry due to atomic displacements in the austenite-martensite phase transformation generally leads to their crystallographic incompatibility. Energy minimizing accommodation mechanisms such as martensite twinning have been recently shown to be a source of hysteresis and irreversible plastic deformation. Compatibility between the two phases can however be achieved by carefully tuning lattice parameters through composition change. A dramatic drop in hysteresis and novel microstructures such as a lowering of the amount of twin lamella are then observed. Related theoretical and simulation works also support the existence of such microstructures including peculiar self-accommodating configurations at near-compatibility. We present the transmission electron microscopy (TEM) study of these novel microstructures for the alloy systems Ti50Ni50-xPdx and Ti50Ni50-xAux where the composition was systemically tuned to approach perfect compatibility. High resolution imaging of the interface between austenite and martensite supplies evidences of compatibility at the atomic level.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Times cited: 3
DOI: 10.4028/www.scientific.net/SSP.172-174.105
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“Transmission electron microscopy study of microstructural evolution in nanograined Ni-Ti microwires heat treated by electric pulse”. Delville R, Malard B, Pilch J, Sittner P, Schryvers D, Diffusion and defect data : solid state data : part B : solid state phenomena 172/174, 682 (2011). http://doi.org/10.4028/www.scientific.net/SSP.172-174.682
Abstract: Transmission electron microscopy and mechanical testing were employed to investigate the evolution of microstructure and functional superelastic properties of 0.1mm diameter as-drawn Ni-Ti wires subjected to a non-conventional heat treatment by controlled electric pulse current. This method enables a finer control of the recovery and recrystallisation processes taking place during the heat treatment and accordingly a better control on the final microstructure. The best functional properties were obtained for heat-treated Ni-Ti wires having a nanograined microstructure (20-50 nm) partially recovered through polygonization and partially recrystallized. Such microstructure is highly resistant against dislocation slip upon cycling, while microstructures annealed for longer time and showing mostly recrystallized grains were prone to dislocation slip, particularly as the grain size exceeds 100 nm. The density of dislocation defects increased significantly with increasing grain size of the microstructure. The activity of three <100>/{011} slip systems was identified in the largest grains of 500-1200 nm. An additional mode of plastic deformation, {114} compound austenite twinning, was observed in the largest grains of fully recrystallized microstructures. It is proposed that dislocation slip (and possibly deformation twinning) occurring in superelastic cycling is coupled with the stress-induced martensitic transformation.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Times cited: 3
DOI: 10.4028/www.scientific.net/SSP.172-174.682
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