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1.	Acke, Filip, et al. (författare) Study of the reduction and reoxidation of a CaO surface 1997 Ingår i: J Phys Chem B. - 1520-5207 .- 1520-6106. ; 101:33, s. 6484- Tidskriftsartikel (refereegranskat)abstract The reduction of NO with CO and H2 is shown to comprise two basic reactions: a surface oxygen abstraction by the reducing agent and a reoxidation of the surface by NO. The former reaction step has been demonstrated by transient CO2 formation during CO exposure of oxidized CaO surfaces, while the latter was demonstrated by N2 and/or N2O transient formation during NO exposure of a prereduced CaO surface. It was shown that at low temperatures (between room temperature and 500 °C) both N2 and N2O were formed, but at temperatures above 500 °C only N2 was observed. The activation energies of the respective steps have been determined using temperature-programmed reaction experiments. The activation energy of the surface oxygen abstraction was determined to be 25 kcal/mol and is similar to the apparent activation energy of the overall reaction. The activation energy of the NO bond breakage was determined to be maximum 10 kcal/mol as measured by N2O formation. The importance of an N2O2- or N2O22- intermediate in the formation of N2O will be discussed, and the importance of N2O decomposition in forming N2 at temperatures above 500 °C will be compared with a N surface diffusion mechanism.
2.	Chiragwandi, Zackary, 1968, et al. (författare) Vortex rings in pure water under static external electric field 2005 Ingår i: APPLIED PHYSICS LETTERS 87 (15): Art. No. 153109. - : AIP Publishing. ; 87(15):15, s. 1-3 Tidskriftsartikel (refereegranskat)abstract The reproducible development of vortex rings in pure water under the action of a static external electric field is demonstrated. The phenomenon results from the electrochemical decomposition of water. Given the low conductivity of water in the absence of electrolyte, the field-driven buildup of hydroxide ions at the anode becomes essential to the proton release, which in turn is the result of the molecular O-2(g) evolution. Water recombination processes, which have protons flowing in a hydroxide background, as a key ingredient produce the phenomenon. (C) 2005 American Institute of Physics.
3.	Snis, Anders, et al. (författare) Abstraction of preadsorbed oxygen from CaO(100) by carbon monoxide 1994 Ingår i: Surf Sci Lett. - 0039-6028. ; 310:1-3 Tidskriftsartikel (refereegranskat)abstract The mechanism for abstraction of preadsorbed oxygen from CaO(100) by CO(g) to form CO2(g) is investigated by electronic structure calculations. The reaction mechanism is assumed to be the reverse of the one obtained for the decomposition of N2O(g) at CaO(100) [Surf. Sci 292 (1993) 317]. A 32 kcal/mol barrier for reaction is calculated. Adsorbed oxygen, Oads, to surface vibration frequencies in the range 840–930 cm−1 are calculated. These values are in qualitative agreement with experiment.
4.	Snis, Anders, et al. (författare) N2O adsorption and decomposition at a CaO (100) surface studied by means of theory 1993 Ingår i: Surf Sci. - 0039-6028. ; 292:3, s. 317-324 Tidskriftsartikel (refereegranskat)abstract The adsorption and decomposition of an N2O molecule at different sites on a CaO(s) surface are investigated by means of ab initio quantum chemistry. The calcium, Ca2+, and oxygen, Os2−, sites at a perfect (100) surface and at a corner position, Oc2−, are considered. Adsorption energies at different sites are calculated and the largest value, 6 kcal/mol, is obtained for a corner site. The barrier for dissociation is calculated to 26 and 27 kcal/mol at the Oc2− and Os2− sites, respectively. These values are some 10 kcal/mol lower than the experimental estimate, and the discrepancy is understood from methodological difficulties to describe the free N2O molecule. A mechanism for the dissociation over an O2− site is proposed, whereby the transfer of the O atom goes via a linear N-N … O … O2− transition state.
5.	Acke, Filip, et al. (författare) Activation energy of calcination by means of a temperature programmed reaction technique 1998 Ingår i: Thermochimica Acta. - 0040-6031. ; 306:1-2, s. 73-76 Tidskriftsartikel (refereegranskat)abstract Calcination of limestone is considered to demonstrate the performance of a temperature programmed reaction technique to determine apparent activation energies for decomposition in the solid state. Influences of sample weight, particle size and sweep gas (He and Ar) are discussed, and connections are made to thermogravimetry studies in the literature.
6.	Acke, Filip, et al. (författare) Effects of O-2 on the reduction of NO over prereduced CaO surfaces: A mechanistic understanding 1999 Ingår i: Journal of Physical Chemistry B Materials. - 1089-5647. ; 110:12, s. 2195-2201 Tidskriftsartikel (refereegranskat)abstract The effect of O-2 on the reduction of NO over prereduced CaO surfaces is investigated. The experimental results suggest the existence of at least three different reaction channels, of which two are related to the high-temperature reduction of the CaO surfaces and involve the use of extra electrons in breaking the NO bond. The third reaction channel does not employ extra electrons for bond breaking, but the activity is affected by the amount of adsorbed surface oxygens. The difference between the former two reaction channels is found in the temperature needed for an observable activity. The reaction channel which is already active at low temperatures is described by a model based on F-centers, whereas the one which needs elevated temperatures involves a hole transport through the bulk. The activation energy for this transport is determined experimentally using a temperature-programmed reaction technique as well as theoretically by means of ab initio quantum chemistry calculations. Room-temperature exposure to O-2 is suggested to result in a poisoning of the F-centers, but has only a minor effect on the reaction channel proposed for high temperatures. Effects on the reduction of NO of time as well as temperature for the O-2 exposure step are also investigated and found to be consistent with an understanding based on the coexistence of different reaction channels.
7.	Acke, Filip, et al. (författare) Kinetic study of heterogeneous oxygen-exchange reactions and bulk self-diffusion of oxygen 1998 Ingår i: Journal of Physical Chemistry B Materials. - 1089-5647. ; 102:26, s. 5158-5164 Tidskriftsartikel (refereegranskat)abstract Apparent activation energies are determined for oxygen-isotope exchange reactions between O2, CO, or NO and preoxidized or prereduced CaO surfaces. Oxygen exchange between N16O or C16O and isotope labeled Ca18O surfaces produced an apparent activation energy of 2 kcal/mol. Similar values are obtained for single- isotope-exchange between 18O18O and prereduced Ca16O surfaces. Apparent activation energies of 15−18 kcal/mol are found for single and double exchange between 18O18O and preoxidized Ca16O surfaces, as well as for double exchange between 18O18O and prereduced Ca16O surfaces. The low apparent activation energies are believed to result from adsorbed intermediates, whereas the high values may involve the formation of a singlet O2 transient. It is shown that eventually the self-diffusion of oxygen ions in the bulk becomes the rate-determining step in the isotope-exchange reaction. Apparent activation energies are determined, and the values are found to depend on surface treatment, (i.e., 44 kcal/mol under reducing and 78 kcal/mol under oxidizing conditions). The involvement of oxygen vacancies under reducing conditions is discussed.
8.	Acke, Filip, et al. (författare) Promoting effects of Na and Fe impurities on the catalytic activity of CaO in the reduction of NO by CO and H-2 1998 Ingår i: Journal of Physical Chemistry B Materials. - 1089-5647. ; 102:26, s. 5127-5134 Tidskriftsartikel (refereegranskat)abstract The heterogeneous reduction of NO by H-2 and CO over different CaO materials is investigated. The dependence of the specific NO reduction rate on the impurity content is demonstrated for both reducing species. The roles of two specific impurities, i.e., Na and Fe, as well as their combined effect are investigated. The apparent activation energies for the NO + CO and NO + Hz reactions are determined for three different calcium oxides. Values between 26 and 28 kcal/mol are obtained. The influence of impurity content is found in the preexponential factor of the Arrhenius equation. A reaction mechanism based on a rate-determining surface-oxygen-abstraction step is suggested. This mechanistic understanding is explored to compare the activities of other alkaline-earth oxides. Particularly, a linear correlation between the apparent activation energy and the lattice parameter is observed.
9.	Andrews, L, et al. (författare) Infrared spectra of cis and trans-(NO)(2)(-) anions in solid argon 1998 Ingår i: Journal of Chemical Physics. - 1089-7690 .- 0021-9606. ; 109:1, s. 177-185 Tidskriftsartikel (refereegranskat)abstract Laser-ablation of over 20 different metal targets with concurrent 10 K codeposition of Ar/NO mixtures produces metal independent infrared bands at 1589.3 cm−1 due to (NO)2+, a new absorption at 1221.0 cm−1, and a band set at 1300.3, 1222.7, 884.4 cm−1. The latter bands decrease more on annealing than the 1221.0 cm−1 band. Isotopic substitution (14NO,15NO, 15N18O, and mixtures) shows that these new vibrations involve two equivalent N–O oscillators, which identifies two new (NO)2 species. The excellent agreement with frequencies, intensities, and isotopic frequency ratios from density functional theory calculations substantiates assignment of the 1221.0 cm−1 band to trans-(NO)2− and the three band set to cis-(NO)2−. The observation of a weak combination band at 2492.0 cm−1 further substantiates assignment of the two N–O stretching modes in cis-(NO)2−
10.	Antonsson, H, et al. (författare) VIBRATIONAL MOTION AND GEOMETRICAL STRUCTURE IN ADSORBED CO STUDIED BY CORE LEVEL PHOTOELECTRON-SPECTROSCOPY 1990 Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - 0368-2048. ; 54, s. 601-613 Tidskriftsartikel (refereegranskat)abstract High resolution core level spectra from CO adsorbed on clean and hydrogen precovered Ni(100) and CO adsorbed on Cu(100) are presented. The core level binding energy is shown to be sensitive to the adsorption site. Cluster calculations reproduce the general trend of the binding energy shifts between the on top and hollow sites of CO/Ni(100). In the coadsorption system CO/H/Ni(100) three different adsorption sites have been observed with a maximum binding energy shift of 2.6 eV for the Ols level. The temperature dependence of the Cls and Ols line profiles in CO/Ni(100) has been carefully investigated. The temperature dependent broadening is due to thermal excitations of frustrated translations parallel to the surface. The spectra from CO on Cu(100) show no temperature dependence below 200K.
11.	Babic, Vedad, 1990, et al. (författare) Fates of Hydrogen During Alumina Growth Below Yttria Nodules in FeCrAl(RE) at Low Partial Pressures of Water 2017 Ingår i: Electrocatalysis. - : Springer Science and Business Media LLC. - 1868-5994 .- 1868-2529. ; 8:6, s. 565-576 Tidskriftsartikel (refereegranskat)abstract Oxidation of FeCrAl(Re), when exposed to similar to 35 ppm of water as sole supply of oxygen in predominantly nitrogen atmosphere, has two characteristic signatures. One is the internal nitridation owing to chromia nodules acting windows toward nitrogen permeation locally short-circuiting the protective alpha-Al2O3 scale. The second remarkable feature is the growth of thick, apparently defect-rich alumina scale under yttria-rich nodules. Hence, one part of the present study comprises exploratory DFT calculations to discriminate between the impacts of chromia and yttria viz. nitrogen permeation. The second part concerns boundary conditions for apparent rapid growth of alumina under yttria nodules. Yttria-associated surface energy stabilization of defect-rich alumina in presence of water was argued to involve hydrolysis-driven hydroxylation of said interface. Subsequent inward growth of the alumina scale was associated with outward diffusion of oxygen vacancies to be accommodated by the remaining proton producing a hydride ion upon surfacing at yttria-decorated alumina interfaces. The latter comprises the cathode process in a quasi-Wagnerian context. Two fates were discussed for this surface ion. One has H--H+ recombination to form H-2 at the interface in conjunction with OH- accommodation upon hydration, while the second allows hydrogen to be incorporated at V-O sites in hydroxylated grain boundaries of the growing alumina scale. The latter was taken to explain the experimentally observed rapid oxide growth under yttria-rich nodules. Space charge due to proton reduction was proposed to cause transient inward cationic drag.
12.	Babic, Vedad, 1990, et al. (författare) On Water Induced Sensitization of Ni (Fe,Cr) alloys towards Stress Corrosion Cracking in LWR Piping from 1st Principles Modelling 2021 Rapport (övrigt vetenskapligt/konstnärligt)abstract In Swedish Light Water Reactors (LWR), stress corrosion cracking of reactor components and welds occurs from time to time. As the nuclear power plants are ageing, it is essential to study and further understand the mechanism for environmentally induced sensitization. Natural cracking is a phenomenon that is difcult to predict and very hard to study since it occurs suddenly and often unexpectedly. In order to study the crack initiation and growth, the crack is traditionally experimentally provoked and it is not known to what degree these experimental cracks correspond to those that occur naturally. The environment in an LWR contributes to material ageing through chemical reactions with the environment. An in-depth examination has shown that the microstructures of oxide flms changes along the crack path and the oxide flm in the crack tip is signifcantly diferent from what one detects at the crack opening. In this study, 1st principles modelling is used to articulate an environment induced sensitization mechanism for stress corrosion cracking of Ni(Fe,Cr) alloys in LWR conditions.
13.	Babic, Vedad, 1990, et al. (författare) Reactive Element Effects in High-Temperature Alloys Disentangled 2020 Ingår i: Oxidation of Metals. - : Springer Science and Business Media LLC. - 1573-4889 .- 0030-770X. ; 93:1-2, s. 229-245 Tidskriftsartikel (refereegranskat)abstract Reactive elements—REs—are decisive for the longevity of high-temperature alloys. This work joins several previous efforts to disentangle various RE effects in order to explain apparently contradicting experimental observations in alumina forming alloys. At 800–1000 °C, “messy” aluminum oxy-hydroxy-hydride transients initially formed due to oxidation by H2O which in turn undergo secondary oxidation by O2. The formation of the transient oxide becomes supported by dispersed RE oxide particles acting as water equivalents. At higher temperatures, electron conductivity in impurity states owing to oxygen vacancies in grain boundaries (GBs) becomes increasingly relevant. These channels are subsequently closed by REs pinning the said vacancies. The universality of the emerging understanding is supported by a comparative first-principles study by means of density functional theory addressing RE(III): Sc2O3, Y2O3, and La2O3, and RE(IV): TiO2, ZrO2, and HfO2, that upon reaction with water, co-decorate a generic GB model by hydroxide and RE ions. At 100% RE coverage, the GB model becomes relevant at both temperature regimes. Based on reaction enthalpy ΔHr considerations, “messy” aluminum oxy-hydroxy-hydride transients are accessed in both classes. Larger variations in ΔHr are found for RE(III)-decorated alumina GBs as compared to RE(IV). For RE(III), correlation with GB width is found, increasing with increased ionic radius. Similarly, upon varying RE(IV), minor changes in stability correlate with minor structural variations. GB decorations by Ce(III) and Ce(IV) further consolidate the emerging understanding. The findings are used to discuss experimental observations that include impact of co-doping by RE(III) and RE(IV).
14.	Babic, Vedad, 1990, et al. (författare) Towards in silico mining for superconductors – Cutting the Gordian knot 2023 Ingår i: Physica C: Superconductivity and its Applications. - : Elsevier BV. - 0921-4534. ; 604 Tidskriftsartikel (refereegranskat)abstract Utilizing the random forest model, feasibility of training machine learning regressor models to predict critical temperatures of superconductivity from Density Functional Theory (DFT) based electronic band structures is explored. This complementarity between experiment and theory draws inspiration from the merging of Kohn-Sham and Bogoliubov-De Gennes equations [W. Kohn, W, EKU Gross, and LN Oliveira, Int. J. of Quant. Chem., 36(23), 611–615 (1989)]. Features in the Kohn-Sham Density Functional Theory band structure away from EF becoming decisive for the superconducting gap demonstrates this divide-and-conquer physical understanding. Not committing to any microscopic mechanism for the SC at this stage, it implies that in different classes of materials, different electronic features are responsible for the superconductivity. However, training on known members of a class, the performance of new members may be predicted. The method is validated for the A15 materials, including both binary A3X and ternary A6XY intermetallics, A = V, Nb, demonstrating that the two do indeed belong to the same class of superconductors.
15.	Babic, Vedad, 1990, et al. (författare) Transition metal attenuated mechanism for protective alumina formation from first principles 2018 Ingår i: RSC Advances. - 2046-2069. ; 8:72, s. 41255-41269 Tidskriftsartikel (refereegranskat)abstract A mechanistic perspective on the growth of protective oxides on high temperature alloys at elevated temperatures is provided. Early, defect rich transient alumina is understood to form by outwards diffusion of oxygen vacancies and electrons. The impact of transition metal (TM) ions (Sc, Ti, V, Cr, Mn, Fe, Co, Ni) on the oxygen vacancy diffusion and electron transport in α-alumina was studied by employing density functional theory. Activation energies for electron transfer EA(ET) between oxygen vacancies in pure as well as TM doped α-alumina were subject to analysis, and similarly so for the TM and charge dependent activation energy for oxygen vacancy diffusion EA(VO). EAQ(ET) were found to be ∼0.5 eV while 2 eV < EAQ(VO) < 5 eV was obtained. The higher and lower EAQ(VO) values correspond to uncharged and doubly charged VO sites, respectively. Redox processes among VO sites, addressed by a bipolaron approach, were understood to enhance VO mobility and thus to facilitate oxide growth. TM adatoms induced asymmetry in the potential energy surface for oxygen vacancy diffusion was subject to analysis. Competition for electrons between all-Al3+surrounded oxygen vacancies and vacancies adjacent to the late 3d adatoms comes out in favor of the latter. A novel take on the 3rd element effect in FeCrAl emerges from analysis of the ternary TM-TM*-Al system.
16.	Bauschlicher, C.W., et al. (författare) A further study of the products of scandium and dioxygen reactions 1999 Ingår i: Journal of Physical Chemistry A. - 1089-5639 .- 1520-5215. ; 103:28, s. 5463-5467 Tidskriftsartikel (refereegranskat)abstract The products of the reaction of Sc and dioxygen have been reinvestigated. By adding the electron-trapping molecule CCl4 additional information about the IR spectra has been obtained, as well as the observation of new bands. New ab initio calculations are also performed on possible products of the Sc plus O-2 reaction. The previously observed band at 722.5 cm(-1) is assigned as the b(2) mode of ScO2-. Bands arising from ScO+, Sc(O-2)(+), and(O-2)ScO are also assigned. We are still unable to assign any bands to OScO. The problems associated with the computational study of ScO2 are discussed.
17.	Bawa, Fathi, et al. (författare) Competing pathways for MgO, CaO, SrO, and BaO nanocluster growth 2002 Ingår i: Physical Chemistry Chemical Physics. - 1463-9084 .- 1463-9076. ; 4:103-108, s. 3042-3047 Tidskriftsartikel (refereegranskat)abstract A comparative structure and stability study is performed on a sequence of (MgO)n , (CaO)n , (SrO)n and (BaO)nclusters, 44n412. The B3LYP functional is employed to seek preferred cluster growth pathways. Similarstabilities are found for two growth strategies, one producing rock-salt-like structures, and a second whichemploys stacks of hexagonal (MO)3 rings. Structures based on hexagonal rings are slightly preferred in the caseof MgO and BaO, while for CaO and SrO the rock salt structural analogue prevails. The shift in isomer stabilityorder is discussed in terms of packing of spheres. The small magnitude of the atomic size difference for oxygenand the corresponding metal atoms in the cluster implies preference for the rock salt structure. Larger jDRAjresult in a preference for hexagonal ring-based structures.
18.	Bawa, Fathi, et al. (författare) Limiting properties of (MgO)(n) and (CaO)(n) clusters 2001 Ingår i: Physical Chemistry Chemical Physics. - 1463-9084 .- 1463-9076. ; 3:15, s. 3042-3047 Tidskriftsartikel (refereegranskat)abstract The limiting behaviours of bond distances and binding energies are studied for small alkaline earth oxide clusters, employing the B3LYP density functional. Validation of the applicability of density functional theory is made on selected clusters by MP4 calculations. Basis set effects on cluster structures and binding energies are determined, and comparisons between (MgO)1–16 and (CaO)1–12 are made. For CaO, the need to include at least two d-polarisation functions for a proper description of the cluster binding energy is emphasised. Consistency in limiting binding energies for monolayers of MgO and CaO, determined here to be 8.3 eV and 9.2 eV respectively, in conjunction with MP4 calculations on (MgO)4, is employed to critically reassess claimed converged bulk binding energies for small cube-like MgO clusters.
19.	Björnström, Joakim, et al. (författare) Accelerating effects of collodial nano-silica for benificial calcium-silicate-hydrate formation in cement 2004 Ingår i: Chem. Phys. lett.. ; 392, s. 242- Tidskriftsartikel (refereegranskat)
20.	Björnström, Joakim, 1976, et al. (författare) Antagonistic effect of superplasticizer and colloidal nano-silica in the hydration of Alite and Belite pastes 2007 Ingår i: Journal of Materials Science. - : Springer Science and Business Media LLC. - 0022-2461 .- 1573-4803. ; 42:11, s. 3901-3907 Tidskriftsartikel (refereegranskat)abstract The dependence on the hydration rate for Alite and Belite clinker phases in the presence of a polycarboxylate superplasticizer PC SP upon addition of colloidal nano-silica CNS were monitored by means of Diffuse Reflectance Infrared spectroscopy DR-FTIR. Spectral signatures of clinker dissolution and product formation were acquired for both materials. The rates for the build-up of product vibrational band intensities were found to depend sensitively on addition of CNS. The hydration product was proposed to be calcium-silicate-hydrate C-S-H. Details in the spectral signatures were found to differ. Quantum chemical calculations were employed and found to be consistent with the interpretation that small clusters dominate the Alite C-S-H spectrum, whereas the Belite C-S-H spectrum results from extended polymers.
21.	Björnström, Joakim, et al. (författare) Signatures of a drying SiO2(H2O)x gell from Raman spectroscopy and quantum chemistry 2003 Ingår i: Chemical Physics Letters. ; 380, s. 165-172 Tidskriftsartikel (refereegranskat)
22.	Blomberg, Margareta, et al. (författare) Accurate Studies on the Structures and Reactivities of Transition Metal Complexes and Clusters 1986 Ingår i: NATO Science Series C. - 9789027722379 ; 176, s. 1-14 Konferensbidrag (refereegranskat)abstract Three different applications of CASSCF and Ci methods on transition metal systems are described. The first application is concerned with the accuracy of calculated binding energies. For NiH+ ad NiO+ comparison is made to molecular beam experiments. For NiCO+ and NiCO comparisons are made to measurements of appearance potential in fragmentation experiments. In the second application, comparisons are made to matrix isolation experiments for Ni(H2O), Cu(H2O), and Ni(C2H4)n with n=1,2. The final application is concerned with the modeling of chemical reactions of transition metal surfaces. A strategy for choosing a proper effective core potential for the metal atoms is outlined. Preliminary results for O2 dissociation on nickel clusters are presented.
23.	Boll, Torben, 1979, et al. (författare) On aliovalent cations control of α-alumina growth on doped and undoped NiAl 2021 Ingår i: Acta Materialia. - : Elsevier BV. - 1359-6454. ; 210 Tidskriftsartikel (refereegranskat)abstract Alumina forming Ni-base superalloys are essential due to their oxidation resistance at elevated temperatures. A two-step procedure allows to assess the outward growth of the oxide scale from the resulting oxide ridges that form at 1100°C and cap the alumina grain boundaries. Employing undoped 50Ni50Al (at%) as reference, the impact of reactive elements on the diffusion processes, here Zr and Hf, is quantified using atom probe tomography. Unexpectedly, we find that up to one monolayer of Ni may co-decorate the alumina grain boundaries. Additionally, a decrease in Al-, and Ni-diffusivity of two orders of magnitude is observed owing to the reactive element effect. We employ density functional theory calculations to better understand the role of aliovalent cations, here Ni(II), Zr(IV), and Hf(IV) in the α−alumina scale. The calculations show that Ni may not only decorate the alumina grain boundaries but also facilitates transport of electrons as well as oxygen vacancies. Thereby oxide scale growth becomes enhanced. In turn, the dual impact of reactive elements, i.e. to annihilate oxygen vacancies and to remove impurity states in the band gap, explains the reduced scale growth rate.
24.	Broqvist, Peter, 1975, et al. (författare) A DFT Study on CO Oxidation over Co3O4 2002 Ingår i: Journal of Catalysis. - : Elsevier BV. - 0021-9517 .- 1090-2694. ; 210:1, s. 198-206 Tidskriftsartikel (refereegranskat)abstract A pilot investigation regarding the CO oxidation mechanism at the Co3O4(110) surface is performed by means of first-principles calculations based on density functional theory. Preferred adsorption of CO is found to occur at a surface Co3+ site. A possible mechanism for CO2(g) formation of the Mars–van Krevelen type is also looked into via the monitoring of two inequivalent oxygen abstraction routes. Experimental observations regarding partial surface deactivation are discussed based on surface intermediates. The oxidative property of the Co3O4 substrate, i.e., Co3++e−→Co2+, is found to be crucial for the O abstraction step. This implies that CoAl2O4 is inactive in CO oxidation, in agreement with experiment.
25.	Broqvist, Peter, 1975, et al. (författare) Characterization of NOx species adsorbed on BaO: Experiment and theory 2004 Ingår i: Journal of Physical Chemistry B. - 1520-5207 .- 1520-6106. ; 108:11, s. 3523-3530 Tidskriftsartikel (refereegranskat)abstract Charged NO, species (x = 1,2,3) formed upon adsorption of NO2 on BaO are characterized by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy and theoretical vibrational analysis using the density functional theory (DFT). Experiments at 30degreesC reveal nitrite formation. At T > 250degreesC, shifts associated with formation of nitrates are observed, indicating an interconversion of oxygen atoms among adsorbates. The theoretical study includes single and pairwise NO2 adsorption on (BaO)(9) clusters. As has been reported previously [Broqvist, P.; Panas, I.; Fridell, E.; Persson, H. J. Phys. Chem. B 2002, 106, 137], an additional energy gain is calculated for the second adsorbed NO2. A vibrational analysis of the investigated adsorption configurations supports the interpretation of nitrite to nitrate interconversion on the BaO surface. Moreover, the calculations demonstrate the sensitivity in the NO2 vibrational band splitting with respect to adsorption configuration.
26.	Broqvist, Peter, 1975, et al. (författare) NOx storage on BaO(100) surface from first principles: a two channel scenario 2002 Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-5207 .- 1520-6106. ; 106:1, s. 137-145 Tidskriftsartikel (refereegranskat)abstract NO2 adsorption at a BaO(100) surface is investigated by means of spin polarized GGA density functional theory. A periodic supercell procedure is employed, and two redox reaction channels are mapped out, involving two chemisorbed NO2 molecules per supercell. The chemisorption is studied in two subsequent steps. The reaction paths are initiated by NO2 adsorption in the form of a nitrite over a Ba2+ site. This generates an electron hole among the surrounding surface oxygen atoms. A reaction path branching occurs as the second NO2 either (a) acts as surface oxidant, forming a surface nitrite−peroxide pair by releasing NO(g), or (b) binds to an O-surf site to form a formal surface nitrate. A redox reaction involving surface nitrite−nitrate interconversion is also addressed. The computed results are employed to interpret experimental observations of surface nitrites, peroxides, NO(g) desorption, and surface Ba(NO3)2 formation. The understandings are discussed in the context of the NOx storage concept of lean-burn catalysis.
27.	Broqvist, Peter, 1975, et al. (författare) NOx storage on BaO: theory and experiment 2004 Ingår i: Catalysis Today. - : Elsevier BV. - 0920-5861. ; 96:1-2, s. 71-78 Tidskriftsartikel (refereegranskat)abstract We review our understanding of the NO2 interaction with BaO. The presented picture has evolved from calculations using the density functional theory, reactor measurements and vibrational spectroscopy of surface species during NO2 storage on a BaO/Al2O3 catalyst and BaO powder. The DFT calculations predict nitrite formation on the BaO(1 0 0) surface upon NO2 adsorption. A particular stable adsorption configuration is a nitrate-nitrite pair geometry, with the nitrate bonded to a barium cation and the nitrite involving a surface oxygen anion. This configuration is supported by vibrational spectroscopy. Only nitrite formation is observed for NO exposure to BaO powder at low temperatures, whereas signatures at similar to250degreesC reveal the formation of surface nitrates. Continuous NO2 adsorption at this temperature results in surface Ba(NO3)(2), as well as bulk Ba(NO3)(2), formation.
28.	Broqvist, Peter, 1975, et al. (författare) Surface properties of alkaline earth metal oxides 2004 Ingår i: Surface Science. - : Elsevier BV. - 0039-6028. ; 554:2-3, s. 262-271 Tidskriftsartikel (refereegranskat)abstract Structural and energetic surface properties of the alkaline earth metal oxides MgO, CaO, SrO, and BaO are investigated within the density functional theory. In particular, structural distortions (relaxation and rumpling) and surface energies are studied for the (100) and (110) surfaces. A different sign of the rumpling is calculated for MgO compared to the other oxides. This difference is carefully examined and discussed in terms of differences in electronic properties, as well as nearest and next-nearest neighbor interactions. The stability of the results is investigated with respect to model approximations, such as the finite number of atomic layers used to describe semi-infinite surfaces, and choice of exchange-correlation energy functional.
29.	Broqvist, Peter, 1975, et al. (författare) The nature of NOx species on BaO(100): An ab initio molecular dynamics study 2005 Ingår i: Journal of Physical Chemistry B. - 1520-5207 .- 1520-6106. ; B109, s. 15410-15416 Tidskriftsartikel (refereegranskat)abstract The dynamics of NO., species adsorbed on BaO(100) have been investigated with ab initio molecular dynamics simulations at a temperature of 300 degrees C. Nitrites are found to continuously interconvert between different adsorption configurations. For both nitrites and nitrates, diffusion events between anion sites are observed. These findings support the use of spillover mechanisms often postulated in mechanistic models of catalysts based on the NO, storage and reduction concept. The large number of possible adsorption configurations are reflected in broad calculated vibrational signatures. These results explain the corresponding property observed in experimental infrared measurements of NO, species on BaO. The dynamic response of the BaO(100) surface is found to strongly depend on the nature of the surface- adsorbate interaction. The largest distortions are predicted for nitrite adsorption
30.	Broqvist, Peter, 1975, et al. (författare) Toward a Realistic Description of NOxStorage in BaO: The Aspect of BaCO3 2005 Ingår i: Journal of Physical Chemistry B. ; 109, s. 9613-9621 Tidskriftsartikel (refereegranskat)abstract NOx storage over hexagonal BaCO3(110) is investigated using first-principles calculations. Special focus is put on the importance of surface decarbonation. Upon decarbonation, supported BaO quasi-molecules are formed and a small drive toward (BaO)(n) cluster formation is predicted. Introduction of NO2 makes the decarbonation energetically relevant, while forming NO2-BaO-NO2 units, on the decarbonated surface. With this configuration, it is possible to replace all surface carbonates with nitrites and nitrates, forming a BaCO3 supported BaNO3NO2 overlayer. Thermodynamic considerations are employed to elaborate on the thermal stability of the formed NOx overlayers.
31.	Brülls, Steffen, 1991, et al. (författare) Bonding between π-Conjugated Polycations and Monolayer Graphene: Decisive Role of Anions 2023 Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 127:4, s. 1917-28 Tidskriftsartikel (refereegranskat)abstract Functionalization and precise modulation of the electronic properties of graphene are key processes in the development of new applications of this promising material. This study examines the potential of using organic polycations as p-dopants and/or anchoring motifs for non-covalent functionalization. A library of hybrid materials was prepared through wet-chemical non-covalent functionalization. Both chemical vapor deposition graphene and reduced graphene oxide were functionalized with a series of neutral and polycationic benzimidazole-based systems. We report on how both the number of anions and the size, shape, and magnitude of the positive charge of the benzimidazole-based systems cooperatively affect the redox properties as well as the affinity for and the nature of bonding to graphene. The redox properties of the benzimidazole-based systems were studied by cyclic voltammetry. The functionalized graphene materials were characterized by Raman spectroscopy, X-ray photoelectron spectroscopy, and time-of-flight secondary ion mass spectrometry. Density functional theory calculations were performed to make contact between the experimental results obtained for molecular samples and hybrid materials. No universal dependence of the binding affinity on a single parameter, such as the amount of positive charge or the size of the system, was found. Instead, the cooperative effect of the three-dimensional structure of the benzimidazole-based systems and the number of anions was found to play a pivotal role. Together, these parameters determine the degree of partial electron sharing and magnitude of dispersion forces involved in the binding of members of this family of benzimidazole-based systems to graphene.
32.	Brülls, Steffen, 1991, et al. (författare) Evidence for Electron Transfer between Graphene and Non-Covalently Bound pi-Systems 2020 Ingår i: Chemistry - A European Journal. - : Wiley. - 1521-3765 .- 0947-6539. ; 26:29, s. 6694-6702 Tidskriftsartikel (refereegranskat)abstract Hybridizing graphene and molecules possess a high potential for developing materials for new applications. However, new methods to characterize such hybrids must be developed. Herein, the wet-chemical non-covalent functionalization of graphene with cationic pi-systems is presented and the interaction between graphene and the molecules is characterized in detail. A series of tricationic benzimidazolium salts with various steric demand and counterions was synthesized, characterized and used for the fabrication of graphene hybrids. Subsequently, the doping effects were studied. The molecules are adsorbed onto graphene and studied by Raman spectroscopy, XPS as well as ToF-SIMS. The charged pi-systems show a p-doping effect on the underlying graphene. Consequently, the tricationic molecules are reduced through a partial electron transfer process from graphene, a process which is accompanied by the loss of counterions. DFT calculations support this hypothesis and the strong p-doping could be confirmed in fabricated monolayer graphene/hybrid FET devices. The results are the basis to develop sensor applications, which are based on analyte/molecule interactions and effects on doping.
33.	Busch, Michael, 1983, et al. (författare) Activation Energies in Computational Chemistry - A case study 2011 Ingår i: Rate Constant Calculation of Thermal Reactions: Methods and Applications, Herbert DaCosta (Ed.), John Wiley & Sons. - Hoboken, NJ, USA : John Wiley & Sons, Inc.. - 9780470582305 Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract A straight-forward way to learn how different complementary properties of a catalyst control a resulting activation energy is proposed within the frame work of Density Functional Theory. It is argued that in special cases the activation energy can be approximated from the crossing of the two vibrational modes’ harmonic oscillator potentials corresponding to the reactant and the product, respectively. The procedure is argued to be applicable in cases were traditional transition state search algorithms such as the synchronous transit or the nudged elastic band methods are of limited use. The constraints of the present approach include accessibility of reactant and product structures as well as availability of normal modes pointing towards the transition state. The usefulness of the proposed procedure is demonstrated for the O-O bond formation step in the water oxidation reaction (OER). A comparative study of the activation energy for said reaction is understaken, employing (i) a molecular manganese dimer, (ii) an embedded manganese dimer, and (iii) an embedded cobalt dimer. In case of the two latter, an MgOx(OH)y is used as support. It is shown how the activation barrier for said reaction step is influenced by mainly two factors, (a) the flexibility of a catalyst and (b) the equilibrium O—O distance of the dioxo- species. It is demonstrated how in case of a flexible molecular catalyst, the influence of the O—O distance is negliable, while it is decisive to the activation energy in case of a more stiff embedded catalyst.
34.	Busch, Michael, 1983, et al. (författare) Electrocatalytic Oxygen Evolution from Water on a Mn(III-V) Dimer Model Catalyst - A DFT Perspective 2011 Ingår i: Physical Chemistry Chemical Physics. - 1463-9076 .- 1463-9084. ; 13, s. 15069-15076 Tidskriftsartikel (refereegranskat)abstract A complete water oxidation and oxygen evolution reaction (OER) cycle is monitored by means of Density Functional Theory (DFT). A biomimetic model catalyst is employed, comprising a m-OH bridged Mn(III-V) dimer truncated by acetylacetonate ligand analogs and hydroxides. The reaction cycle is divided into four electrochemical hydrogen abstraction steps followed by a series of chemical steps. The former employ the Tyrosine/Tyrosyl radical acting as electron and proton sink thus determining the reference potential. Stripping hydrogen from water leads to the formation of two highly unstable Mn(V)=O/Mn(IV)-O· moieties, which subsequently combine to form a peroxy O-O bond. O2 evolution results from subsequent consecutive replacement of remaining Mn-O bonds by water. Conditions for the validities of GGA DFT and self-interaction error corrected hybrid DFT predictions despite the presence of a manifold of near-degenerate spin states, are discussed in some detail. The applicability of the former is extended to include the rate limiting steps in the OER.
35.	Busch, Michael, 1983, et al. (författare) Hydroxide Oxidation and Peroxide Formation at Embedded Binuclear Transition Metal Sites; TM=Cr, Mn, Fe, Co 2011 Ingår i: Physical Chemistry Chemical Physics. - 1463-9076 .- 1463-9084. ; 13, s. 15062-15068 Tidskriftsartikel (refereegranskat)abstract Key steps in electro-catalytic water oxidation on binuclear Transition Metal (TM) sites are addressed. These comprise (a) two one-electron oxidation steps of TM-OH moieties to form the corresponding two TM=O oxy-groups, and (b) a chemical step whereby the two oxy-species form a TM-O-O-TM peroxy-bridge. A test rig representing a generic low crystal field oxide support is described and employed. The energetics for said reactions are compared for homo-nuclear Cr(IIIV), Mn(III-V), Fe(II-IV) and Co(II-IV) sites. The uniqueness of the TyrO/TyrOH reference potential for driving said oxidation steps is demonstrated. Hydroxide oxidation on binuclear Mn and Co candidates require an overpotential of approximately 0.5 V relative to the chosen reference potential. Correspondingly, the subsequent O-O bond formation becomes strongly exothermic of the order of 1 eV. Hydroxide oxidation on binuclear CrCr and FeFe systems are exothermic by 0.2-0.4 eV relative to the TyrO/TyrOH reference potential. Consequently, the chemical step for transforming the TM=O moieties to the peroxo species is found to be endothermic on the order of 0.7 eV. These findings suggest that hetero-binuclear sites containing one TM from each class would be optimal. The validity of this concept is demonstrated for the FeCo binuclear site. The results are discussed in the context of experimental observations, which display preference for mixed oxide systems.
36.	Busch, Michael, 1983, et al. (författare) Validation of binuclear descriptor for mixed transition metal oxide supported electrocatalytic water oxidation 2013 Ingår i: Catalysis Today. - : Elsevier BV. - 0920-5861 .- 1873-4308. ; 202:1, s. 114-119 Tidskriftsartikel (refereegranskat)abstract The energy profiles of the di-hydroxo – di-oxo – peroxo pathway are discussed for a set of 3d transition metal oxides comprising V(III–V), Cr(III–V), Mn(II–IV, Mn(III–V), Fe(II–IV), Co(II–IV) and Ni(II–IV) using density functional theory (DFT). Two classes of oxides were identified. The first class, comprising V(III–V), Cr(III–V) and Fe(II–IV), displays exothermicity for the oxidation of di-hydroxo to di-oxo versus the tyrosine/tyrosyl-radical (TyrOH/TyrO) couple and endothermicity for the subsequent O-O bond formation ([−/+] class), while the second class, comprising Mn(III–V), Co(II–IV) and Ni(II–IV), shows endothermicity with respect to the oxidation step and exothermicity for the O-O bond formation ([+/−] class). The energetics of the endothermicity (exothermicity) for the oxidation step is reflected in the exothermicity (endothermicity) of the subsequent O-O bond formation step. Mn(II–IV) is not part of any of the two classes. Instead it shows zero exothermicity with respect to TyrOH/TyrO for the oxidation step and a small endothermicity for the O-O bond formation step. Despite the promising energy profile Mn(II–IV) is argued to be inactive due to a large activation barrier. A set of improved hetero-nuclear candidate catalysts is predicted by mixing [−/+] with [+/−] transition metal oxides. A simple and efficient method to estimate the energy profile of mixed transition metal oxides from the homo-nuclear systems is demonstrated. The validity of this procedure is checked and agreement with the explicitly calculated values is found. All considered heteronuclear candidate catalysts display enhanced performance compared to the pure homonuclear systems.
37.	Busch, Michael, 1983, et al. (författare) Water Oxidation on MnOx and IrOx: Why Similar Performance? 2013 Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 117:1, s. 288-292 Tidskriftsartikel (refereegranskat)abstract The critical steps in water oxidation at a binuclear Mn(II–IV) oxide site are revisited. Ideal stabilities of intermediates are confirmed by comparing to results for a binuclear Ir(III–V) system. The latter in turn is known to be an excellent water oxidation catalyst. The inefficiency of the binuclear Mn(II–IV) site is owing to the high activation energy for the chemical step whereby MnIV═O double bonds on adjacent sites are broken prior to forming the MnIII—O—O—MnIII peroxy moiety. A rationale for Mn(II–IV)—Mn(III–V) mixed oxidation state for water oxidation catalysis, analogous to mixed transition metal oxide systems, is offered. Possible virtues of the kinetic stability of the binuclear MnIV═O moiety are discussed, utilizing its oxidizing power by sidestepping oxygen evolution.
38.	Bäcktorp, Carina, 1964, et al. (författare) Theoretical investigation of linalool oxidation. 2006 Ingår i: The journal of physical chemistry. A. - : American Chemical Society (ACS). - 1089-5639 .- 1520-5215. ; 110:44, s. 12204-12 Tidskriftsartikel (refereegranskat)abstract This study concerns the autoxidation of one of the most used fragrances in daily life, linalool (3,7-dimethyl-1,6-octadien-3-ol). It reacts with O2 to form hydroperoxides, which are known to be important contact allergens. Pathways for hydroperoxide formation are investigated by means of quantum mechanical electronic structure calculations. Optimized molecular geometries and harmonic vibrational frequencies are determined using density functional theory (DFT). Insight into how the addition of O2 to linalool occurs is obtained by establishing a theoretical framework and systematically investigating three smaller systems: propene, 2-methyl-2-butene, and 2-methyl-2-pentene. 2-Methyl-2-pentene was chosen as a model system and used to compare with linalool. This theoretical study characterizes the linalool-O2 biradical intermediate state, which constitutes a branching point for the further oxidation reactions pathways. Thus, the observed linalool oxidation product spectrum is discussed in terms of a direct reaction path, the ene-type mechanism, and the radical mechanism. The major hydroperoxide found in experiments is 7-hydroperoxy-3,7-dimethyl-octa-1,5-diene-3-ol, and the calculated results support this finding.
39.	Camerani, Caterina, et al. (författare) X-ray fluorescence tomography of individual municipal solid waste and biomass fly ash particles 2004 Ingår i: ANALYTICAL CHEMISTRY. ; 76:6, s. 1586-1595 Tidskriftsartikel (refereegranskat)abstract Information about Cd distribution inside single municipal solid waste and biomass fly ash particles is fundamental since it affects its leachability. The internal 2D distributions of the main and trace elements in such highly inhomogeneous matrixes were successfully determined by means of the combined synchrotron radiation induced micro X-ray fluorescence (mu-SRXRF) and tomography (mu-SRXRFT) techniques. Scanning mu-SRXRF measurements show Cd elemental distribution within single fly ash particles to be inhomogeneous, but no information can be obtained about its internal distribution. During mu-SRXRFT analysis, single fly ash particles are successively measured by a rotational-translational scan in a VH = 2 x 5 mum(2) microbeam. The 2D internal elemental distribution images, obtained by the modified simultaneous algebraic reconstruction technique algorithm, provide the size and the location of Cd-containing areas together with the location of other measurable elements. Results showed Cd concentration to be higher in the core of the fly ash particles analyzed rather than on the surface of the particles. Moreover, in both ashes, Ca-containing matrixes are found to be the main Cd-bearing phases. A possible mechanism for Cd adsorption on the fly ash particles is proposed based on the obtained results.
40.	Camerani, Maria Caterina, et al. (författare) Determination of the cd-bearing phases in municipal solid waste and Biomass single fly ash particles using SR-mu XRF Spectroscopy 2007 Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 79:17, s. 6496-6506 Tidskriftsartikel (refereegranskat)abstract By using an excitation energy of 27.0 keV, synchrotron radiation-induced micro-X-ray fluorescence (SR-mu XRF) is employed to extract information regarding the composition and distribution of Cd-bearing phases in municipal solid waste (MSW) and biomass fly ashes. Significance of observation is based on statistics of totally more than 100 individual MSW and biomass fly ash particles from a fluidized bed combustion (FBC) plant. Cd concentrations in the parts-per-million range are determined. In general, although previous leaching studies have indicated Cd to be predominant in the smaller-size ash particles, in the present study Cd is more evenly distributed throughout all the particle sizes. For MSW fly ashes, results indicate the presence of Cd mainly as CdBr2 hot-spots, whereas for biomass fly ashes, which exhibit lower CdX2 concentration, a thin Cd layer on/in the particles is reported. For both ashes, Ca-containing matrixes are found to be the main Cd-bearing phases. Support for this observation is found from independent first-principles periodic density functional theory calculations. The observations are condensed into a schematic mechanism for Cd adsorption on the fly ash particles.
41.	Campbell, Charles, et al. (författare) Bridging model and real catalysts: general discussion 2016 Ingår i: Faraday Discussions. - 1359-6640 .- 1364-5498. ; 188, s. 565-589 Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract Charles Campbell opened the discussion of the paper by Hans-JoachimFreund: If you have a 3D gold particle and it spreads out to be a 2D particle whenyou adsorb CO2, it must gain energy stability. Did you estimate the energy changeof the overall process to do that?
42.	Campbell, Charles, et al. (författare) Catalyst design from theory to practice: general discussion 2016 Ingår i: Faraday Discussions. - 1359-6640 .- 1364-5498. ; 188, s. 279-307 Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract Hans-Joachim Freund opened the discussion of the paper by Alberto Roldan:How is the atomic hydrogen produced on the greigite surface? In the paper (DOI:10.1039/C5FD00186B) there is no comment whether you studied dissociatehydrogen adsorption.
43.	Cantatore, Valentina, 1986, et al. (författare) Design strategy of a graphene based bio-sensor for glucose 2018 Ingår i: Carbon. - : Elsevier BV. - 0008-6223. ; 137, s. 343-348 Tidskriftsartikel (refereegranskat)abstract A novel graphene-based glucose sensor-design is formulated and explored in silico. An ad hoc host molecule is tailored to bind to glucose by multiple hydrogen bonds. A pyridinic core is chosen for this receptor in order to allow for “socket-plug” dative bonding to boron sites of boron doped graphene. The modeling employs DFT (Density Functional Theory) together with an effective aqueous environment to take into account the solvation effect. High selectivity is demonstrated for the suggested host molecule towards glucose as compared to other possible competitors in blood such as fructose, biotin and ascorbic acid. A route to achieve improved sensitivity, exploiting the hydrophilic/hydrophobic properties of the host + glucose system for enhanced selective binding to the hydrophobic boron doped graphene support is discussed.
44.	Cantatore, Valentina, 1986, et al. (författare) Enhanced Manifold of States Achieved in Heterostructures of Iron Selenide and Boron-Doped Graphene 2017 Ingår i: Condensed Matter. - : MDPI AG. - 2410-3896. ; 2:4 Tidskriftsartikel (refereegranskat)abstract Enhanced superconductivity is sought by employing heterostructures composed of boron-doped graphene and iron selenide. Build-up of a composite manifold of near-degenerate noninteracting states formed by coupling top-of-valence-band states of FeSe to bottom-of-conduction-band states of boron-doped graphene is demonstrated. Intra- and intersubsystem excitons are explored by means of density functional theory in order to articulate a normal state from which superconductivity may emerge. The results are discussed in the context of electron correlation in general and multi-band superconductivity in particular.
45.	Cantatore, Valentina, 1986, et al. (författare) Insights into the zinc effect on radio-cobalt deposition on stainless steel piping surfaces under BWR conditions from experiment guided 1st principles modelling 2020 Ingår i: Journal of Nuclear Materials. - : Elsevier BV. - 0022-3115. ; 540 Tidskriftsartikel (refereegranskat)abstract The beneficial effect of zinc to mitigate radio-cobalt uptake on stainless steel piping surfaces under BWR conditions is revisited by means of 1st principles modelling. A viable generic hydroxylated grain boundary interface (HGBI) model for magnetite, i.e., an inverse spinel, is formulated and interrogated in order to unravel how Zn may cause exclusion of Co by competing for the same sites. While Co2+ as well as Ni2+ reside preferentially in the octahedral lattice sites of the inverse spinel lattice, Zn2+ prefers to reside at the HGBI. The difference is consolidated for M(II), M being Cr, Mn, Fe, Co, Ni, Cu, or Zn. Similar affinities as well as mobilities of Co2+ and Zn2+ in the HGBI are taken to explain how, upon Fe2+ dissolution, Zn2+ may compete with Co2+ for the Fe2+ sites in the inner layer of the duplex oxide film. Impacts of Zn2+ and Ni2+ on Co2+ uptake in the outer oxide layer is also addressed. Zn2+ guided precipitation is found to be less effective than the Ni2+ guided process. Reported beneficial effects on radio-cobalt uptake upon sealing off the stainless steel acting Ni2+ source by coating with magnetite as well as hematite are discussed.
46.	Cantatore, Valentina, 1986, et al. (författare) Oxidation Driven Permeation of Iron Oxide Scales by Chloride from Experiment Guided First-Principles Modeling 2019 Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 123:42, s. 25957-25966 Tidskriftsartikel (refereegranskat)abstract In this comprehensive investigation, it is demonstrated how chloride ions may permeate a crack-free oxide scale, thus providing hitherto missing mechanistic insight as to the impacts of KCl(s) or HCl(g) exposures on the high-temperature corrosion of biomass- and waste-fired boilers. Guided by dedicated experimental analyses, mechanistic understanding is gained by means of density functional theory. Chloride ions, being accommodated in oxygen anion vacancies that are generated at the receding magnetite/alloy interface, are driven through the oxide scale by the oxidation process. Intermediate stabilities of quasi-homogeneous transient iron oxychloride species are found, employing potassium ferrite and goethite as complementary cation sinks for the KCl(s) and HCl(g) reactants, respectively. Spontaneous disproportionation of the supersaturated oxychlorides into two different types of chloride decorated magnetite grain boundaries is demonstrated. These motifs are proposed to explain loss of scale integrity as well as accelerated oxidation by offering short-circuiting transient pathways for ion diffusion.
47.	Cantatore, Valentina, 1986, et al. (författare) Possible Socket-Plug Standard Connection for Functionalized Graphene – Validation by DFT 2016 Ingår i: Carbon. - : Elsevier BV. - 0008-6223. ; 104, s. 40-46 Tidskriftsartikel (refereegranskat)abstract A possible Socket-Plug standard coupling to connect molecular moieties to graphene is proposed whereby the electronic characteristics in the vicinity of the Fermi energy become virtually independent of choice of molecular "antenna". Proof of concept is offered by means of DFT. A Lewis acid - base coupling is utilized. Thus, the socket property is obtained by boron atoms introduced in the graphene matrix, while the plug property is offered by a lone-pair of the molecular adsorbate. Standard electronic response of boron doped graphene to three different nucleophilic adsorbates is demonstrated. Moreover, conceptual connection is made to hydrogenated pristine graphene and the origins of the similarities in the electronic structures are analyzed. Boron doping introduces holes in the valence band while the dative bonding between electrophilic boron sites and nuleophilic lone-pairs effectively achieves electronic undoping of the boron doped graphene. The Lewis acid - base connection is understood to render the socket-plug functionality robust to adsorption-desorption of the "antenna" molecules. This socket-plug standard may well comprise a necessary prerequisite for making systematic progress in contemporary graphene technology.
48.	Cantatore, Valentina, 1986, et al. (författare) Towards catalytic nitric oxide reduction via oligomerization on boron doped graphene 2016 Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 1089-7690 .- 0021-9606. ; 144, s. 151102- Tidskriftsartikel (refereegranskat)abstract We use Density Functional Theory (DFT) to describe a novel way for metal free catalytic reduction of nitric oxide NO utilizing boron doped graphene. The present study is based on the observation that boron doped graphene and O-N=N-O- act as Lewis acid-base pair allowing the graphene surface to act as a catalyst. The process implies electron assisted N=N bond formation prior to N-O dissociation. Two N2 + O2 product channels, one of which favoring N2O formation, are envisaged as outcome of the catalytic process. Beside, we show also that the N2 + O2 formation pathways are contrasted by a side reaction that brings to N3O3- formation and decomposition into N2O + NO2-.
49.	Cantatore, Valentina, 1986, et al. (författare) Towards multifunctional coating in the boron-doped graphene/copper system 2017 Ingår i: Carbon. - : Elsevier BV. - 0008-6223. ; 115, s. 375-379 Tidskriftsartikel (refereegranskat)abstract A route to achieve multi-functional graphene coating is explored. Chemical bonding between copper substrate and coating results if the graphene is a priori boron doped. After pair-wise binding of boron sites to the Cu(111) surface, co-existence of pseudo-gap property in the graphene subsystem and a metallic density of states in the Cu subsystem at the common Fermi energy emerges. Apparently a paradox is that the two subsystems preserve and even recover their individual integrities upon formation of surface chemical bonds. Sensor capabilities are inferred. Employing pyridine as test molecule, conditioned ability of a nucleophile to offer competitive dative bonding, with the sub-strate, for boron sites is demonstrated. It is shown to occur for the case of half coverage and for adsorption to boron atoms originally bound to the on-top site on Cu(111). The ability of complementary boron sites to compensate for loss of binding between on-top site and boron, resulting from said bonding to the incoming nucleophile, is emphasized. Multifunctional substrate-coating system for catalysis as well as enhanced sensitization is inferred.
50.	Carmona Quiroga, Paula, et al. (författare) Protective performances of two anti-graffiti treatments towards sulfite and sulfate formation in SO2 polluted model environment 2010 Ingår i: Applied Surface Science. - : Elsevier BV. - 0169-4332. ; 257:3, s. 852-856 Tidskriftsartikel (refereegranskat)abstract Specific strategies for protection are being developed to counter both the staining and corrosive effects of polluted air in cities, as well as to allow for efficient removal of unwanted graffiti paintings. These protection strategies employ molecules with tailored functionalities, e.g. being hydrophobic, while maintaining porosity for molecular water vapour permeation.The present study employs SO2 and water to probe the behaviors of two anti-graffiti treatments, a water-base fluoroalkylsiloxane (“Protectosil Antigraffiti” marketed by Degussa) and an organically modified silicate (Ormosil) synthesized from a polymer chain (polydimethyl siloxane, PDMS) and two network forming alkoxides (Zr propoxide and methyl triethoxy silane, MTES) dissolved in n-propanol, on five building materials, comprising limestone, aged lime mortar, hydrated cement mortar, granite, and brick material.The materials were exposed to a synthetic atmosphere for 20 h in a climate chamber, 0.78 ± 0.03 ppm of SO2 and 95% RH. Diffuse reflectance Fourier transform infrared (DR-FTIR) spectra were registered before and after exposure in the climate chamber in the cases of both treated and untreated samples. DR-FTIR, scanning electron microscope (SEM) images and energy dispersive X-ray (EDX) analyses, suggest the anti-graffiti Ormosil to suppress formation of calcium sulfite hemihydrate (the primary initial product of the reaction of calcium compounds with SO2 and water) on carbonate materials (limestone and lime mortar).In case of the granite, brick and cement mortar, Ormosil has a negligible influence on the SO2 capture. While no sulfite formation was detected by DR-FTIR, gypsum is inferred to form due to metal oxides and minority compounds catalysed oxidation of sulfite to sulfate. In case of brick, this understanding finds support from SEM images as well as EDX. A priori presence of gypsum in hydrated cement mortars prevents positive identification by SEM. However, support for sulfur accumulation in hydrated cement mortar is provided by means of EDX.In case of a second anti-graffiti considered, Protectosil, no influence of the anti-graffiti treatment on the SO2 uptake of any of the building materials was observed.

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