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Kis VK, Kovács Z, Czigány Z. Improved Method for Electron Powder Diffraction-Based Rietveld Analysis of Nanomaterials. NANOMATERIALS (BASEL, SWITZERLAND) 2024; 14:444. [PMID: 38470774 DOI: 10.3390/nano14050444] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2024] [Revised: 02/26/2024] [Accepted: 02/27/2024] [Indexed: 03/14/2024]
Abstract
Multiphase nanomaterials are of increasing importance in material science. Providing reliable and statistically meaningful information on their average nanostructure is essential for synthesis control and applications. In this paper, we propose a novel procedure that simplifies and makes more effective the electron powder diffraction-based Rietveld analysis of nanomaterials. Our single step in-TEM method allows to obtain the instrumental broadening function of the TEM directly from a single measurement without the need for an additional X-ray diffraction measurement. Using a multilayer graphene calibration standard and applying properly controlled acquisition conditions on a spherical aberration-corrected microscope, we achieved the instrumental broadening of ±0.01 Å in terms of interplanar spacing. The shape of the diffraction peaks is modeled as a function of the scattering angle using the Caglioti relation, and the obtained parameters for instrumental broadening can be directly applied in the Rietveld analysis of electron diffraction data of the analyzed specimen. During peak shape analysis, the instrumental broadening parameters of the TEM are controlled separately from nanostructure-related peak broadening effects, which contribute to the higher reliability of nanostructure information extracted from electron diffraction patterns. The potential of the proposed procedure is demonstrated through the Rietveld analysis of hematite nanopowder and two-component Cu-Ni nanocrystalline thin film specimens.
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Affiliation(s)
- Viktória K Kis
- HUN-REN Centre for Energy Research, Institute of Technical Physics and Materials Science, Konkoly-Thege Miklós út 29-33, H-1121 Budapest, Hungary
- Department of Mineralogy, Eötvös Loránd University, Pázmány Péter sétány 1/c, H-1117 Budapest, Hungary
| | - Zsolt Kovács
- Department of Materials Physics, Eötvös Loránd University, Pázmány Péter sétány 1/a, H-1117 Budapest, Hungary
| | - Zsolt Czigány
- HUN-REN Centre for Energy Research, Institute of Technical Physics and Materials Science, Konkoly-Thege Miklós út 29-33, H-1121 Budapest, Hungary
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Abdullah JAA, Díaz-García Á, Law JY, Romero A, Franco V, Guerrero A. Quantifying the Structure and Properties of Nanomagnetic Iron Oxide Particles for Enhanced Functionality through Chemical Synthesis. NANOMATERIALS (BASEL, SWITZERLAND) 2023; 13:2242. [PMID: 37570560 PMCID: PMC10421292 DOI: 10.3390/nano13152242] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/2023] [Revised: 07/21/2023] [Accepted: 08/01/2023] [Indexed: 08/13/2023]
Abstract
This comprehensive study investigates the properties of chemical nanomagnetic iron oxide particles (CNMIOPs) synthesized through a chemical method. The primary objective is to examine how pH levels and washing solvents affect the magnetism properties of these nanoparticles. Three different pH levels (1.2, 7.5, and 12.5) using NaOH and two washing solvents (ethanol and water) are employed. The characterization techniques include FTIR, SEM, TEM, XRD, ZSP, and VSM. Furthermore, the study incorporates two specific pH- and solvent-dependent CNMIOPs into PCL electrospun materials to analyze their performance in a targeted application. The results show that pH and the washing process significantly affect the CNMIOPs' properties. Higher pH levels result in smaller particles with higher crystallinity and reduce crystalline anisotropy. SEM and TEM analysis confirm different morphologies, including cubic, spherical, and elongated shapes. Ethanol-washed CNMIOPs exhibit superior magnetic behavior, with the highest magnetization saturation at pH 12.5 (Ms = 58.3 emu/g). The stability of the CNMIOPs ranges from -14.7 to -23.8 mV, and higher pH levels exhibit promising antioxidant activity. Furthermore, the study explores the effects of pH and washing solvents on CNMIOP-infused nanofiber membranes, with better dispersion observed with ethanol washing. Overall, this research provides valuable insights into the properties and behavior of CNMIOPs under varying pH and washing conditions.
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Affiliation(s)
- Johar Amin Ahmed Abdullah
- Departamento de Ingeniería Química, Escuela Politécnica Superior, Universidad de Sevilla, 41011 Sevilla, Spain
| | - Álvaro Díaz-García
- Departamento de Física de Materia Condensada, ICMS-CSIC, Universidad de Sevilla, 41012 Sevilla, Spain; (Á.D.-G.); (J.Y.L.); (V.F.)
| | - Jia Yan Law
- Departamento de Física de Materia Condensada, ICMS-CSIC, Universidad de Sevilla, 41012 Sevilla, Spain; (Á.D.-G.); (J.Y.L.); (V.F.)
| | - Alberto Romero
- Departamento de Ingeniería Química, Facultad de Química, Universidad de Sevilla, 41012 Sevilla, Spain;
| | - Victorino Franco
- Departamento de Física de Materia Condensada, ICMS-CSIC, Universidad de Sevilla, 41012 Sevilla, Spain; (Á.D.-G.); (J.Y.L.); (V.F.)
| | - Antonio Guerrero
- Departamento de Ingeniería Química, Escuela Politécnica Superior, Universidad de Sevilla, 41011 Sevilla, Spain
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Swathilakshmi S, Devi R, Sai Gautam G. Performance of the r 2SCAN Functional in Transition Metal Oxides. J Chem Theory Comput 2023. [PMID: 37329316 DOI: 10.1021/acs.jctc.3c00030] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
We assess the accuracy and computational efficiency of the recently developed meta-generalized gradient approximation (metaGGA) functional, restored regularized strongly constrained and appropriately normed (r2SCAN), in transition metal oxide (TMO) systems and compare its performance against SCAN. Specifically, we benchmark the r2SCAN-calculated oxidation enthalpies, lattice parameters, on-site magnetic moments, and band gaps of binary 3d TMOs against the SCAN-calculated and experimental values. Additionally, we evaluate the optimal Hubbard U correction required for each transition metal (TM) to improve the accuracy of the r2SCAN functional, based on experimental oxidation enthalpies, and verify the transferability of the U values by comparing against experimental properties on other TM-containing oxides. Notably, including the U-correction with r2SCAN increases the lattice parameters, on-site magnetic moments, and band gaps of TMOs, apart from an improved description of the ground state electronic state in narrow band gap TMOs. The r2SCAN and r2SCAN+U calculated oxidation enthalpies follow the qualitative trends of SCAN and SCAN+U, with r2SCAN and r2SCAN+U predicting marginally larger lattice parameters, smaller magnetic moments, and lower band gaps compared to SCAN and SCAN+U, respectively. We observe the overall computational time (i.e., for all ionic+electronic steps) required for r2SCAN(+U) to be lower than SCAN(+U). Thus, the r2SCAN(+U) framework can offer a reasonably accurate description of the ground state properties of TMOs with better computational efficiency than SCAN(+U).
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Affiliation(s)
- S Swathilakshmi
- Department of Materials Engineering, Indian Institute of Science, Bengaluru 560012, India
| | - Reshma Devi
- Department of Materials Engineering, Indian Institute of Science, Bengaluru 560012, India
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Ichibha T, Saritas K, Krogel JT, Luo Y, Kent PRC, Reboredo FA. Existence of La-site antisite defects in [Formula: see text] ([Formula: see text], Fe, and Co) predicted with many-body diffusion quantum Monte Carlo. Sci Rep 2023; 13:6703. [PMID: 37185382 PMCID: PMC10130183 DOI: 10.1038/s41598-023-33578-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2022] [Accepted: 04/14/2023] [Indexed: 05/17/2023] Open
Abstract
The properties of [Formula: see text] (M: 3d transition metal) perovskite crystals are significantly dependent on point defects, whether introduced accidentally or intentionally. The most studied defects in La-based perovskites are the oxygen vacancies and doping impurities on the La and M sites. Here, we identify that intrinsic antisite defects, the replacement of La by the transition metal, M, can be formed under M-rich and O-poor growth conditions, based on results of an accurate many-body ab initio approach. Our fixed-node diffusion Monte Carlo (FNDMC) calculations of [Formula: see text] ([Formula: see text], Fe, and Co) find that such antisite defects can have low formation energies and are magnetized. Complementary density functional theory (DFT)-based calculations show that Mn antisite defects in [Formula: see text] may cause the p-type electronic conductivity. These features could affect spintronics, redox catalysis, and other broad applications. Our bulk validation studies establish that FNDMC reproduces the antiferromagnetic state of [Formula: see text], whereas DFT with PBE (Perdew-Burke-Ernzerhof), SCAN (strongly constrained and appropriately normed), and the LDA+U (local density approximation with Coulomb U) functionals all favor ferromagnetic states, at variance with experiment.
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Affiliation(s)
- Tom Ichibha
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
- School of Information Science, Japan Advanced Institute of Science and Technology, Asahidai 1-1, Nomi, Ishikawa 923-1292 Japan
| | - Kayahan Saritas
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
| | - Jaron T. Krogel
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
| | - Ye Luo
- Computational Sciences Division, Argonne National Laboratory, Argonne, IL 60439 USA
| | - Paul R. C. Kent
- Computational Sciences and Engineering Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
| | - Fernando A. Reboredo
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
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Olsen R, Kvamme B. Impact of ethylene glycol on ions influencing corrosion in pores between iron oxide and calcium carbonate. MOLECULAR SIMULATION 2023. [DOI: 10.1080/08927022.2023.2184298] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/11/2023]
Affiliation(s)
- Richard Olsen
- Department of Physics and Technology, University of Bergen, Bergen, Norway
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Abdullah JAA, Jiménez-Rosado M, Guerrero A, Romero A. Effect of Calcination Temperature and Time on the Synthesis of Iron Oxide Nanoparticles: Green vs. Chemical Method. MATERIALS (BASEL, SWITZERLAND) 2023; 16:1798. [PMID: 36902916 PMCID: PMC10003769 DOI: 10.3390/ma16051798] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Revised: 02/19/2023] [Accepted: 02/20/2023] [Indexed: 06/18/2023]
Abstract
Nowadays, antioxidants and antibacterial activity play an increasingly vital role in biosystems due to the biochemical and biological reactions that involve free radicals and pathogen growth, which occur in many systems. For this purpose, continuous efforts are being made to minimize these reactions, including the use of nanomaterials as antioxidants and bactericidal agents. Despite such advances, iron oxide nanoparticles still lack knowledge regarding their antioxidant and bactericidal capacities. This includes the investigation of biochemical reactions and their effects on nanoparticle functionality. In green synthesis, active phytochemicals give nanoparticles their maximum functional capacity and should not be destroyed during synthesis. Therefore, research is required to establish a correlation between the synthesis process and the nanoparticle properties. In this sense, the main objective of this work was to evaluate the most influential process stage: calcination. Thus, different calcination temperatures (200, 300, and 500 °C) and times (2, 4, and 5 h) were studied in the synthesis of iron oxide nanoparticles using either Phoenix dactylifera L. (PDL) extract (green method) or sodium hydroxide (chemical method) as the reducing agent. The results show that calcination temperatures and times had a significant influence on the degradation of the active substance (polyphenols) and the final structure of iron oxide nanoparticles. It was found that, at low calcination temperatures and times, the nanoparticles exhibited small sizes, fewer polycrystalline structures, and better antioxidant activities. In conclusion, this work highlights the importance of green synthesis of iron oxide nanoparticles due to their excellent antioxidant and antimicrobial activities.
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Affiliation(s)
- Johar Amin Ahmed Abdullah
- Departamento de Ingeniería Química, Escuela Politécnica Superior, Universidad de Sevilla, 41011 Sevilla, Spain
| | - Mercedes Jiménez-Rosado
- Departamento de Ingeniería Química, Escuela Politécnica Superior, Universidad de Sevilla, 41011 Sevilla, Spain
| | - Antonio Guerrero
- Departamento de Ingeniería Química, Escuela Politécnica Superior, Universidad de Sevilla, 41011 Sevilla, Spain
| | - Alberto Romero
- Departamento de Ingeniería Química, Facultad de Química, Universidad de Sevilla, 41012 Sevilla, Spain
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Jäker P, Aegerter D, Kyburz T, Städler R, Fonjallaz R, Detlefs B, Koziej D. Flow cell for operando X-ray photon-in-photon-out studies on photo-electrochemical thin film devices. OPEN RESEARCH EUROPE 2022; 2:74. [PMID: 37645301 PMCID: PMC10446061 DOI: 10.12688/openreseurope.14433.2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 12/01/2022] [Indexed: 08/31/2023]
Abstract
Background: Photo-electro-chemical (PEC) water splitting represents a promising technology towards an artificial photosynthetic device but many fundamental electronic processes, which govern long-term stability and energetics, are not yet fully understood. X-ray absorption spectroscopy (XAS), and particularly its high energy resolution fluorescence-detected (HERFD) mode, emerges as a powerful tool to study photo-excited charge carrier behavior under operating conditions. The established thin film device architecture of PEC cells provides a well-defined measurement geometry, but it puts many constraints on conducting operando XAS experiments. It remains a challenge to establish a standardized thin film exchange procedure and concurrently record high-quality photoelectrochemical and X‑ray absorption spectroscopy data that is unperturbed by bubble formation. Here we address and overcome these instrumental limitations for photoelectrochemical operando HERFD-XAS. Methods: We constructed a novel operando photo-electro-chemical cell by computer numerical control milling, guided by the materials' X‑ray and visible light absorption properties to optimize signal detection. To test the cell's functionality, semiconducting thin film photoelectrodes have been fabricated via solution deposition and their photoelectrochemical responses under simulated solar light were studied using a commercial potentiostat in a three-electrode configuration during HERFD-XAS experiments at a synchrotron. Results: We demonstrate the cell's capabilities to measure and control potentiostatically and in open‑circuit, to detect X‑ray signals unperturbed by bubbles and to fluently exchange different thin film samples by collecting high-resolution Fe K-edge spectra of hematite ( α -Fe 2O 3) and ferrite thin film ( MFe 2O 4, M= Zn, Ni) photoelectrodes during water oxidation. Conclusions: Our cell establishes a measurement routine that will provide experimental access of photo-electro-chemical operando HERFD-XAS experiments to a broader scientific community, particularly due to the ease of sample exchange. We believe to enable a broad range of experiments which acquired fundamental insights will spur further photoelectrochemical research and commercialization of water splitting technologies.
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Affiliation(s)
- Philipp Jäker
- Department of Materials, Laboratory for Multifunctional Materials, ETH Zürich, Zurich, Vladimir-Prelog-Weg 5, 8093, Switzerland
- Institutes of Nanostructure and Solid State Physics, Center for Hybrid Nanostructures, University of Hamburg, Hamburg, Luruper Chaussee 149, 22607, Germany
| | - Dino Aegerter
- Department of Materials, Laboratory for Multifunctional Materials, ETH Zürich, Zurich, Vladimir-Prelog-Weg 5, 8093, Switzerland
| | - Till Kyburz
- Department of Materials, Laboratory for Multifunctional Materials, ETH Zürich, Zurich, Vladimir-Prelog-Weg 5, 8093, Switzerland
| | - Roman Städler
- Department of Materials, Laboratory for Multifunctional Materials, ETH Zürich, Zurich, Vladimir-Prelog-Weg 5, 8093, Switzerland
| | - Rea Fonjallaz
- Department of Materials, Laboratory for Multifunctional Materials, ETH Zürich, Zurich, Vladimir-Prelog-Weg 5, 8093, Switzerland
| | - Blanka Detlefs
- European Synchrotron Radiation Facility, Grenoble, 71 avenue des Martyrs, CS 40220, 38043, France
| | - Dorota Koziej
- Department of Materials, Laboratory for Multifunctional Materials, ETH Zürich, Zurich, Vladimir-Prelog-Weg 5, 8093, Switzerland
- Institutes of Nanostructure and Solid State Physics, Center for Hybrid Nanostructures, University of Hamburg, Hamburg, Luruper Chaussee 149, 22607, Germany
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Kou X, Jin J, Wang Y, Li Y, Hou F. Understanding the effect of calcium containing compounds on ash deposition during boiler operation: experiment study and dynamics calculation. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2022; 29:72126-72139. [PMID: 34981373 DOI: 10.1007/s11356-021-17572-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2021] [Accepted: 11/12/2021] [Indexed: 06/14/2023]
Abstract
During the operation of the boiler, the ash deposition phenomenon in the furnace will cause abnormal operation of the boiler system. This will lead to an increase the pollutant emission. To relieve the pollutant emission during the abnormal operation of the boiler, the mechanism of ash deposition was investigated from the perspective of reducing the phenomenon for ash deposition in this paper. Calcium-containing compounds play an important role in ash deposition burning coal. Therefore, the influence of calcium-containing compounds on ash deposition was investigated with Zhundong coal in a horizontal tube furnace in this paper. Furthermore, the binding and diffusion properties of calcium-containing compounds on the oxide film's surface were characterized under different temperatures by molecular dynamics simulations. The growth process of surface crystals was also researched by kinetic Monte Carlo method. The results indicated the precipitation rate of calcium gradually increases with the increase of combustion temperature. CaO, CaSO4, and CaSiO3 can play an important role in ash deposition burning Zhundong coal. CaSO4 is more easily to react with α-Fe2O3 (110) than CaO or CaSiO3. The diffusion coefficient of CaSO4, CaO, or CaSiO3 increases gradually with the increase of temperature. Furthermore, the system composed of CaSO4 and oxide film is more affected by temperature than that of CaO or CaSiO3 and oxide film. Moreover, under the whole temperature, the content of CaSO4 on the surface of the oxide film is the most. Finally, three calcium-containing minerals can promote each other during the deposition process and accelerate the formation of ash deposits.
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Affiliation(s)
- Xuesen Kou
- School of Energy and Power Engineering, University of Shanghai for Science and Technology, Shanghai, 200093, China
| | - Jing Jin
- School of Energy and Power Engineering, University of Shanghai for Science and Technology, Shanghai, 200093, China.
| | - Yongzhen Wang
- School of Civil Engineering and Architecture, Linyi University, Shangdong, 276000, China.
| | - Yanhui Li
- Key Laboratory of Thermo-Fluid Science and Engineering of MOE, School of Energy and Power Engineering, Xi'an Jiaotong University, Xi'an, 710049, Shanxi, China
| | - Fengxiao Hou
- School of Energy and Power Engineering, North University of China, Taiyuan, 030051, China
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Ilton ES, Collins RN, Ciobanu CL, Cook NJ, Verdugo-Ihl M, Slattery AD, Paterson DJ, Mergelsberg ST, Bylaska EJ, Ehrig K. Pentavalent Uranium Incorporated in the Structure of Proterozoic Hematite. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2022; 56:11857-11864. [PMID: 35876701 DOI: 10.1021/acs.est.2c02113] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Characterizing the chemical state and physical disposition of uranium that has persisted over geologic time scales is key for modeling the long-term geologic sequestration of nuclear waste, accurate uranium-lead dating, and the use of uranium isotopes as paleo redox proxies. X-ray absorption spectroscopy coupled with molecular dynamics modeling demonstrated that pentavalent uranium is incorporated in the structure of 1.6 billion year old hematite (α-Fe2O3), attesting to the robustness of Fe oxides as waste forms and revealing the reason for the great success in using hematite for petrogenic dating. The extreme antiquity of this specimen suggests that the pentavalent state of uranium, considered a transient, is stable when incorporated into hematite, a ubiquitous phase that spans the crustal continuum. Thus, it would appear overly simplistic to assume that only the tetravalent and hexavalent states are relevant when interpreting the uranium isotopic record from ancient crust and contained ore systems.
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Affiliation(s)
- Eugene S Ilton
- Pacific Northwest National Laboratory, Richland, Washington 99353, United States
| | - Richard N Collins
- University of New South Wales, Sydney New South Wales 2052, Australia
| | - Cristiana L Ciobanu
- School of Chemical Engineering and Advanced Materials, The University of Adelaide, Adelaide, South Australia, 5005, Australia
| | - Nigel J Cook
- School of Civil, Environmental, and Mining Engineering, The University of Adelaide, Adelaide, South Australia, 5005, Australia
| | - Max Verdugo-Ihl
- School of Chemical Engineering and Advanced Materials, The University of Adelaide, Adelaide, South Australia, 5005, Australia
| | - Ashley D Slattery
- Adelaide Microscopy, The University of Adelaide, Adelaide, South Australia, 5005, Australia
| | - David J Paterson
- Australian Synchrotron, 800 Blackburn Road, Clayton Victoria 3168, Australia
| | | | - Eric J Bylaska
- Pacific Northwest National Laboratory, Richland, Washington 99353, United States
| | - Kathy Ehrig
- BHP Olympic Dam, 10 Franklin Street, Adelaide, South Australia 5000, Australia
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Electronic Structure Calculation of Cr3+ and Fe3+ in Phosphor Host Materials Based on Relaxed Structures by Molecular Dynamics Simulation. TECHNOLOGIES 2022. [DOI: 10.3390/technologies10030056] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The electronic structures of the luminescent center ions Cr3+ and Fe3+ in the deep red phosphors LiAl5O8:Cr3+, α-Al2O3:Cr3+, and γ-LiAlO2:Fe3+ were calculated by the DV-Xα method, in which the local distortion induced by the replacement of Al3+ sites in the host crystals by the luminescent center ions was reproduced by classical molecular dynamics (MD) simulation. The MD simulations based on classical dynamics allowed for the handling of more than 1000 atoms for the lattice relaxation calculations, which was advantageous to simulate situations in which a small number of foreign atoms (ions) were dispersed in the host lattice as in phosphors, even when typical periodic boundary conditions were applied. The relaxed lattices obtained after MD indicated that the coordination polyhedra around Cr3+ and Fe3+ expanded in accordance with the size difference between the luminescent center ions and Al3+ in the host crystals. The overall profiles of the partial density of states (p-DOSs) of the isolated Cr3+ and Fe3+ 3d orbitals were not significantly affected by the lattice relaxation, whereas the widths of the energy splitting of the 3d orbitals were reduced. The electronic structure calculations for Fe–Fe pairs in γ-LiAlO2 showed that the antiferromagnetic interactions with antiparallel electron spins between the Fe3+ ions were preferred, especially when the Fe–Fe pair was on the first-nearest neighboring cation sites.
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Ahart CS, Rosso KM, Blumberger J. Electron and Hole Mobilities in Bulk Hematite from Spin-Constrained Density Functional Theory. J Am Chem Soc 2022; 144:4623-4632. [PMID: 35239359 PMCID: PMC9097473 DOI: 10.1021/jacs.1c13507] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Transition metal oxide materials have attracted much attention for photoelectrochemical water splitting, but problems remain, e.g. the sluggish transport of excess charge carriers in these materials, which is not well understood. Here we use periodic, spin-constrained and gap-optimized hybrid density functional theory to uncover the nature and transport mechanism of holes and excess electrons in a widely used water splitting material, bulk-hematite (α-Fe2O3). We find that upon ionization the hole relaxes from a delocalized band state to a polaron localized on a single iron atom with localization induced by tetragonal distortion of the six surrounding iron-oxygen bonds. This distortion is responsible for sluggish hopping transport in the Fe-bilayer, characterized by an activation energy of 70 meV and a hole mobility of 0.031 cm2/(V s). By contrast, the excess electron induces a smaller distortion of the iron-oxygen bonds resulting in delocalization over two neighboring Fe units. We find that 2-site delocalization is advantageous for charge transport due to the larger spatial displacements per transfer step. As a result, the electron mobility is predicted to be a factor of 3 higher than the hole mobility, 0.098 cm2/(V s), in qualitative agreement with experimental observations. This work provides new fundamental insight into charge carrier transport in hematite with implications for its photocatalytic activity.
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Affiliation(s)
- Christian S Ahart
- Department of Physics and Astronomy, University College London, London WC1E 6BT, U.K
| | - Kevin M Rosso
- Pacific Northwest National Laboratory, Richland, Washington 99354, United States
| | - Jochen Blumberger
- Department of Physics and Astronomy, University College London, London WC1E 6BT, U.K
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12
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Dong J, Li Q, Xia W, Lv B, Jing G, Shen H, Yuan CS. Improvement of water resistance by Fe 2O 3/TiO 2 photoelectrocatalysts for formaldehyde removal: experimental and theoretical investigation. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2022; 29:13805-13821. [PMID: 34599445 DOI: 10.1007/s11356-021-16459-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Accepted: 09/06/2021] [Indexed: 06/13/2023]
Abstract
TiO2-based photocatalysts are a potential technology for removing indoor formaldehyde (CHOH) owing to their strong photooxidation ability. However, their photooxidation performance is generally weakened when suffering from the competitive adsorption of H2O. In a method inspired by the oxygen evolution reaction (OER) to generate intermediates with hydroxyl radicals on the anode electrode catalysts, an electric field was employed in this research and applied to the photooxidation of CHOH to prevent the competitive adsorption of H2O. Additionally, 0.5-5% Fe2O3 decorated TiO2 was employed to improve the photoelectrocatalytic activity. The influence of an electric field on hydroxyl-radical production was investigated by both density functional theory (DFT) with direct-imposed dipole momentum and photoelectrocatalytic experimental tests. The surface characterization of the photocatalysts, including transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and electron paramagnetic resonance (EPR), was conducted. DFT results show that a positive electric field with a strength of 0.05 Å/V was more favorable to produce hydroxyl on Fe2O3/TiO2(010) than was a negative electric field. Fe2O3 decoration can significantly boost hydroxyl formation, resulting from a decrease in the binding energy between the Fe of Fe2O3 and the oxygen and hydrogen atoms of H2O. The dissociated hydrogen atom of the H2O preferentially remained on the catalysts' surface rather than being released into the gas flow. The experimental results demonstrated that applying 150 V could not directly enhance the photooxidation of CHOH by either TiO2 or Fe2O3/TiO2 but that it could relieve the H2O inhibitory effect by more than 10% on the Fe2O3/TiO2.
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Affiliation(s)
- Jing Dong
- College of Chemical Engineering, Huaqiao University, Xiamen, Fujian, People's Republic of China
| | - Qing Li
- College of Chemical Engineering, Huaqiao University, Xiamen, Fujian, People's Republic of China
| | - Wenjie Xia
- Department of Civil and Environmental Engineering, North Dakota State University, Fargo, ND, USA
| | - Bihong Lv
- College of Chemical Engineering, Huaqiao University, Xiamen, Fujian, People's Republic of China
| | - Guohua Jing
- College of Chemical Engineering, Huaqiao University, Xiamen, Fujian, People's Republic of China
| | - Huazhen Shen
- College of Chemical Engineering, Huaqiao University, Xiamen, Fujian, People's Republic of China.
| | - Chung-Shin Yuan
- Institute of Environmental Engineering, National Sun Yat-sen University, No. 70, Lian-Hai Road, Kaohsiung, 804, Taiwan
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Peng MW, Qi J, Yan P, Guan Y, Liu YY, Sun ZH, Zhang LJ, Weng X, Shen Y, Fang F, Guo JS, Chen YP. Insight into the structure and metabolic function of iron-rich nanoparticles in anammox bacteria. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 806:150879. [PMID: 34627893 DOI: 10.1016/j.scitotenv.2021.150879] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2021] [Revised: 10/03/2021] [Accepted: 10/04/2021] [Indexed: 06/13/2023]
Abstract
Anaerobic ammonium-oxidizing (anammox) bacteria are iron abundant and depend heavily on iron-binding proteins. The iron demand of anammox bacteria is relatively large. However, it still remains some doubts where these large quantities of available iron come from and how they are regulated in anammox bacteria. Herein, iron-rich nanoparticles in anammoxosomes were detected by synchrotron soft X-ray tomography coupled with scanning transmission X-ray microscopy (STXM). The iron-rich nanoparticles were identified as ferric oxide (α-Fe2O3) mineral cores, and the local atomic structure of iron-rich nanoparticles was obtained by X-ray absorption fine-structure (XAFS) spectra. The bacterioferritin of Q1Q315 and Q1Q5F8 were detected by proteomics analysis. On this basis, the metabolic pathway centered on iron-rich nanoparticles was proposed.
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Affiliation(s)
- Meng-Wen Peng
- Key Laboratory of the Three Gorges Reservoir Region's Eco-Environments of MOE, Chongqing University, Chongqing 400045, China; China Three Gorges Corporation, Beijing 100038, China
| | - Jing Qi
- Key Laboratory of the Three Gorges Reservoir Region's Eco-Environments of MOE, Chongqing University, Chongqing 400045, China
| | - Peng Yan
- Key Laboratory of the Three Gorges Reservoir Region's Eco-Environments of MOE, Chongqing University, Chongqing 400045, China
| | - Yong Guan
- National Synchrotron Radiation Laboratory, University of Science & Technology of China, Hefei 230026, China
| | - Ying-Ying Liu
- Department of Earth and Environmental Sciences, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
| | - Zhi-Hu Sun
- National Synchrotron Radiation Laboratory, University of Science & Technology of China, Hefei 230026, China
| | - Li-Juan Zhang
- Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China
| | - Xun Weng
- Key Laboratory of the Three Gorges Reservoir Region's Eco-Environments of MOE, Chongqing University, Chongqing 400045, China
| | - Yu Shen
- National Base of International Science and Technology Cooperation for Intelligent Manufacturing Service, Chongqing Technology and Business University, Chongqing 400067, China
| | - Fang Fang
- Key Laboratory of the Three Gorges Reservoir Region's Eco-Environments of MOE, Chongqing University, Chongqing 400045, China
| | - Jin-Song Guo
- Key Laboratory of the Three Gorges Reservoir Region's Eco-Environments of MOE, Chongqing University, Chongqing 400045, China
| | - You-Peng Chen
- Key Laboratory of the Three Gorges Reservoir Region's Eco-Environments of MOE, Chongqing University, Chongqing 400045, China.
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14
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Kuklin MS, Eklund K, Linnera J, Ropponen A, Tolvanen N, Karttunen AJ. Structural Properties and Magnetic Ground States of 100 Binary d-Metal Oxides Studied by Hybrid Density Functional Methods. Molecules 2022; 27:molecules27030874. [PMID: 35164135 PMCID: PMC8838575 DOI: 10.3390/molecules27030874] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2021] [Revised: 01/23/2022] [Accepted: 01/24/2022] [Indexed: 02/04/2023] Open
Abstract
d-metal oxides play a crucial role in numerous technological applications and show a great variety of magnetic properties. We have systematically investigated the structural properties, magnetic ground states, and fundamental electronic properties of 100 binary d-metal oxides using hybrid density functional methods and localized basis sets composed of Gaussian-type functions. The calculated properties are compared with experimental information in all cases where experimental data are available. The used PBE0 hybrid density functional method describes the structural properties of the studied d-metal oxides well, except in the case of molecular oxides with weak intermolecular forces between the molecular units. Empirical D3 dispersion correction does not improve the structural description of the molecular oxides. We provide a database of optimized geometries and magnetic ground states to facilitate future studies on the more complex properties of the binary d-metal oxides.
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15
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Sakr NI, Kizilkaya O, Carlson SF, Chan S, Oumnov RA, Catano J, Kurtz RL, Hall RW, Poliakoff ED, Sprunger PT. Formation of Environmentally Persistent Free Radicals (EPFRs) on the Phenol-Dosed α-Fe 2O 3(0001) Surface. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2021; 125:21882-21890. [PMID: 34992708 PMCID: PMC8725784 DOI: 10.1021/acs.jpcc.1c04298] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Environmentally persistent free radicals (EPFRs) are a class of toxic air pollutants that are found to form by the chemisorption of substituted aromatic molecules on the surface of metal oxides. In this study, we employ X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS) to perform a temperature-dependent study of phenol adsorption on α-Fe2O3(0001) to probe the radical formation mechanism by monitoring changes in the electronic structure of both the adsorbed phenol and metal oxide substrate. Upon dosing at room temperature, new phenol-derived electronic states have been clearly observed in the UPS spectrum at saturation coverage. However, upon dosing at high temperature (>200 °C), both photoemission techniques have shown distinctive features that strongly suggest electron transfer from adsorbed phenol to Fe2O3 surface atoms and consequent formation of a surface radical. Consistent with the experiment, DFT calculations show that phenoxyl adsorption on the iron oxide surface at RT leads to a minor charge transfer to the adsorbed molecule. The experimental findings at high temperatures agree well with the EPFRs' proposed formation mechanism and can guide future experimental and computational studies.
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Affiliation(s)
- N I Sakr
- Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - Orhan Kizilkaya
- Center for Advanced Microstructures and Devices, Louisiana State University, Baton Rouge, Louisiana 70806, United States
| | - Sierra F Carlson
- Department of Natural Sciences and Mathematics, Dominican University of California, San Rafael, California 94901, United States
| | - Simon Chan
- Department of Natural Sciences and Mathematics, Dominican University of California, San Rafael, California 94901, United States
| | - Reuben A Oumnov
- Department of Natural Sciences and Mathematics, Dominican University of California, San Rafael, California 94901, United States
| | - Jaqueline Catano
- Department of Natural Sciences and Mathematics, Dominican University of California, San Rafael, California 94901, United States
| | - Richard L Kurtz
- Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, United States; Center for Advanced Microstructures and Devices, Louisiana State University, Baton Rouge, Louisiana 70806, United States
| | - Randall W Hall
- Department of Natural Sciences and Mathematics, Dominican University of California, San Rafael, California 94901, United States; Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - E D Poliakoff
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - Phillip T Sprunger
- Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, United States; Center for Advanced Microstructures and Devices, Louisiana State University, Baton Rouge, Louisiana 70806, United States
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16
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Adsorption of Strontium onto Synthetic Iron(III) Oxide up to High Ionic Strength Systems. MINERALS 2021. [DOI: 10.3390/min11101093] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
In this work, the adsorption behavior of Sr onto a synthetic iron(III) oxide (hematite with traces of goethite) has been studied. This solid, which might be considered a representative of Fe3+ solid phases (iron corrosion products), was characterized by X-Ray Diffraction (XRD) and X-Ray Photoelectron Spectroscopy (XPS), and its specific surface area was determined. Both XRD and XPS data are consistent with a mixed solid containing more than 90% hematite and 10% goethite. The solid was further characterized by fast acid-base titrations at different NaCl concentrations (from 0.1 to 5 M). Subsequently, for each background NaCl concentration used for the acid-base titrations, Sr-uptake experiments were carried out involving two different levels of Sr concentration (1 × 10−5 and 5 × 10−5 M, respectively) at constant solid concentration (7.3 g/L) as a function of −log([H+]/M). A Surface Complexation Model (SCM) was fitted to the experimental data, following a coupled Pitzer/surface complexation approach. The Pitzer model was applied to aqueous species. A Basic Stern Model was used for interfacial electrostatics of the system, which includes ion-specific effects via ion-specific pair-formation constants, whereas the Pitzer-approach involves ion-interaction parameters that enter the model through activity coefficients for aqueous species. A simple 1-pK model was applied (generic surface species, denoted as >XOH−1/2). Parameter fitting was carried out using the general parameter estimation software UCODE, coupled to a modified version of FITEQL2. The combined approach describes the full set of data reasonably well and involves two Sr-surface complexes, one of them including chloride. Monodentate and bidentate models were tested and were found to perform equally well. The SCM is particularly able to account for the incomplete uptake of Sr at higher salt levels, supporting the idea that adsorption models conventionally used in salt concentrations below 1 M are applicable to high salt concentrations if the correct activity corrections for the aqueous species are applied. This generates a self-consistent model framework involving a practical approach for semi-mechanistic SCMs. The model framework of coupling conventional electrostatic double layer models for the surface with a Pitzer approach for the bulk solution earlier tested with strongly adsorbing solutes is here shown to be successful for more weakly adsorbing solutes.
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17
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Schaefer MV, Abernathy MJ, Nguyen D, Cornell T, Ying SC. Firing Increases Arsenic Leaching from Ceramic Water Filters via Arsenic and Iron Phase Transformations. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2021; 55:9826-9835. [PMID: 34232034 PMCID: PMC8761037 DOI: 10.1021/acs.est.1c00169] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Ceramic water filters (CWFs) are produced globally using local clay sources and can effectively remove bacterial pathogens during point-of-use water treatment. The ceramic production process involves firing clay mixed with burnout material at temperatures of 800-1100 °C, which induces mineralogical changes leading to increased arsenic (As) leaching from CWF material compared to source clay. Unfired clay and fired CWFs from Cambodia, Canada, and Mexico, CWF from Laos, and test-fired clay from the United States were analyzed to determine the extent of As leaching from CWFs that range in As (<1 to 16 mg kg-1) and iron (Fe) (0.6 to 5%) content. Deionized water, NaOH, HCl, and oxalate extractions showed that firing increased As solubility and decreased Fe solubility compared to unfired clay, with up to 8 mg kg-1 of water-soluble As in Cambodian CWFs. X-ray absorption spectra of the Cambodian clay and CWF showed a decrease in the Fe-O distance from 2.01 to 1.91 Å and decreased Fe coordination number from 6.3 to 4.6 after firing, indicating a decrease in Fe-O coordination. Arsenic(V) was the dominant species in Cambodia clay and CWF, existing primarily as a surface complex with average As-Fe distance of 3.28 Å in clay while in CWF As was either an outer-sphere As(V) phase or a discrete arsenate phase with no significant As-Fe scattering contribution within the resolution of the data. Improved understanding of molecular-scale processes that cause increased As leaching from CWFs provides a basis for assessing As leaching potential prior to CWF factory capital investment as well as engineered solutions (e.g., modified firing temperature, material amendments, and leaching prior to distribution) to mitigate As exposure from CWFs.
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Affiliation(s)
- Michael V Schaefer
- Department of Earth and Environmental Science, New Mexico Institute of Mining and Technology, Socorro, New Mexico 87801, United States
| | - Macon J Abernathy
- Environmental Toxicology Graduate Program, University of California, Riverside, California 92521, United States
| | - Dominique Nguyen
- Department of Environmental Sciences, University of California, Riverside, California 92521, United States
| | - Thida Cornell
- Department of Environmental Sciences, University of California, Riverside, California 92521, United States
| | - Samantha C Ying
- Environmental Toxicology Graduate Program, University of California, Riverside, California 92521, United States
- Department of Environmental Sciences, University of California, Riverside, California 92521, United States
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18
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Pawlędzio S, Malinska M, Woińska M, Wojciechowski J, Andrade Malaspina L, Kleemiss F, Grabowsky S, Woźniak K. Relativistic Hirshfeld atom refinement of an organo-gold(I) compound. IUCRJ 2021; 8:608-620. [PMID: 34258009 PMCID: PMC8256711 DOI: 10.1107/s2052252521004541] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/02/2021] [Accepted: 04/28/2021] [Indexed: 06/13/2023]
Abstract
The main goal of this study is the validation of relativistic Hirshfeld atom refinement (HAR) as implemented in Tonto for high-resolution X-ray diffraction datasets of an organo-gold(I) compound. The influence of the relativistic effects on statistical parameters, geometries and electron density properties was analyzed and compared with the influence of electron correlation and anharmonic atomic motions. Recent work in this field has indicated the importance of relativistic effects in the static electron density distribution of organo-mercury compounds. This study confirms that differences in electron density due to relativistic effects are also of significant magnitude for organo-gold compounds. Relativistic effects dominate not only the core region of the gold atom, but also influence the electron density in the valence and bonding region, which has measurable consequences for the HAR refinement model parameters. To study the effects of anharmonic motion on the electron density distribution, dynamic electron density difference maps were constructed. Unlike relativistic and electron correlation effects, the effects of anharmonic nuclear motion are mostly observed in the core area of the gold atom.
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Affiliation(s)
- Sylwia Pawlędzio
- Biological and Chemical Research Centre, Department of Chemistry, University of Warsaw, Żwirki i Wigury 101, Warszawa 02-089, Poland
| | - Maura Malinska
- Biological and Chemical Research Centre, Department of Chemistry, University of Warsaw, Żwirki i Wigury 101, Warszawa 02-089, Poland
| | - Magdalena Woińska
- Biological and Chemical Research Centre, Department of Chemistry, University of Warsaw, Żwirki i Wigury 101, Warszawa 02-089, Poland
| | | | - Lorraine Andrade Malaspina
- Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Freiestrasse 3, Bern 3012, Switzerland
| | - Florian Kleemiss
- Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Freiestrasse 3, Bern 3012, Switzerland
| | - Simon Grabowsky
- Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Freiestrasse 3, Bern 3012, Switzerland
| | - Krzysztof Woźniak
- Biological and Chemical Research Centre, Department of Chemistry, University of Warsaw, Żwirki i Wigury 101, Warszawa 02-089, Poland
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19
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Wielinski J, Voegelin A, Grobéty B, Müller CR, Morgenroth E, Kaegi R. Transformation of TiO 2 (nano)particles during sewage sludge incineration. JOURNAL OF HAZARDOUS MATERIALS 2021; 411:124932. [PMID: 33858078 DOI: 10.1016/j.jhazmat.2020.124932] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/22/2020] [Revised: 12/18/2020] [Accepted: 12/19/2020] [Indexed: 06/12/2023]
Abstract
Titanium dioxide (TiO2) (nano)particles are produced in large quantities and their potential impacts on ecosystems warrants investigations into their fate after disposal. TiO2 particles released into wastewater are retained by wastewater treatment plants and accumulate in digested sludge, which is increasingly incinerated in industrialized countries. Therefore, we investigated the changes of the Ti-speciation during incineration of as-received sludge and of sludge spiked with anatase (d=20-50 nm) or rutile (d=200-400 nm) using X-ray absorption spectroscopy (XAS) and transmission electron microscopy (TEM). In the as-received sludge, rutile and anatase were the dominant Ti bearing minerals and both remained unaffected by the anaerobic treatment. During incineration, Ti reacts with hematite to members of the hematite-ilmenite solid solution series (Hem-Ilm). Up to 80% of the Ti spiked as anatase transformed into Hem-Ilm, a distorted 6-fold coordinated Ti (Ti(IV)sulfate) and rutile during incineration. Up to 30% and 60% of rutile transformed into Hem-Ilm and Ti(IV)sulfate represented phases in fly and bottom ash, respectively. Fe and Ti were spatially correlated in ash derived from as-received and anatase spiked sludge, whereas only a thin layer of the spiked rutile reacted with Fe, in line with XAS data. This study highlights the transient nature of nano-Ti species during sewage sludge incineration.
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Affiliation(s)
- Jonas Wielinski
- Eawag, Swiss Federal Institute of Aquatic Science and Technology, 8600 Dübendorf, Switzerland; ETH Zürich, Institute of Environmental Engineering, 8093 Zürich, Switzerland
| | - Andreas Voegelin
- Eawag, Swiss Federal Institute of Aquatic Science and Technology, 8600 Dübendorf, Switzerland
| | - Bernard Grobéty
- University of Fribourg, Department of Geosciences, 1700 Fribourg, Switzerland
| | - Christoph R Müller
- ETH Zürich, Department of Mechanical and Process Engineering, 8092 Zürich, Switzerland
| | - Eberhard Morgenroth
- Eawag, Swiss Federal Institute of Aquatic Science and Technology, 8600 Dübendorf, Switzerland; ETH Zürich, Institute of Environmental Engineering, 8093 Zürich, Switzerland
| | - Ralf Kaegi
- Eawag, Swiss Federal Institute of Aquatic Science and Technology, 8600 Dübendorf, Switzerland.
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20
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Yu H, Wei B, Wang J, Zhao H, Zeng S, Xue C, Zhu J, Zhang Y, Xu P. Facile synthesis, characterization, mechanism and enhanced visible-light photocatalytic activity of SiW 12/α-Fe 2O 3 nanocomposites. NEW J CHEM 2021. [DOI: 10.1039/d1nj00021g] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The photocatalytic mechanism of the SiW12/α-Fe2O3 nanohybrid.
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Affiliation(s)
- Haihui Yu
- School of Chemical Engineering
- Northeast Electric Power University
- Jilin 132000
- P. R. China
| | - Bing Wei
- School of Chemical Engineering
- Northeast Electric Power University
- Jilin 132000
- P. R. China
| | - Junping Wang
- School of Chemical Engineering
- Northeast Electric Power University
- Jilin 132000
- P. R. China
| | - Haiqi Zhao
- School of Chemical Engineering
- Northeast Electric Power University
- Jilin 132000
- P. R. China
| | - Sai Zeng
- School of Chemical Engineering
- Northeast Electric Power University
- Jilin 132000
- P. R. China
| | - Chaobo Xue
- School of Chemical Engineering
- Northeast Electric Power University
- Jilin 132000
- P. R. China
| | - Jiayu Zhu
- School of Chemical Engineering
- Northeast Electric Power University
- Jilin 132000
- P. R. China
| | - Yanlin Zhang
- School of Chemical Engineering
- Northeast Electric Power University
- Jilin 132000
- P. R. China
| | - Peng Xu
- CoInnovation Center for Efficient Processing and Utilization of Forest Products
- College of Chemical Engineering
- Nanjing Forestry University
- Nanjing 210037
- P. R. China
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21
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Snegirev NI, Lyubutin IS, Kulikov AG, Yagupov SV, Seleznyova KA, Mogilenec YA, Strugatsky MB. Transformations of Crystalline Phases in Fe1 – xGaxBO3 Single Crystals at Annealing. CRYSTALLOGR REP+ 2020. [DOI: 10.1134/s1063774520040197] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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22
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Davidson AL, Webb PB, Silverwood IP, Lennon D. The Application of Quasi-Elastic Neutron Scattering to Investigate Hydrogen Diffusion in an Iron-Based Fischer–Tropsch Synthesis Catalyst. Top Catal 2020. [DOI: 10.1007/s11244-020-01259-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
AbstractIron-based Fischer–Tropsch synthesis (FTS) catalysts evolve in situ on exposure to synthesis gas (CO & H2) forming a mixture of iron oxides, iron carbides and carbonaceous deposits. Recently, the application of inelastic neutron scattering has shown the progressive formation of a hydrocarbonaceous overlayer during this catalyst conditioning period. The evolving nature of the catalyst alters the proportion of phases present within the catalyst, which may influence the transport of hydrogen within the reaction system. Preliminary quasi-elastic neutron scattering (QENS) measurements are used to investigate hydrogen diffusion within an un-promoted iron FTS catalyst that has experienced varying levels of time-on-stream (0, 12 and 24 h) of ambient pressure CO hydrogenation at 623 K. Measurements on the catalyst samples in the absence of hydrogen show the unreacted sample (t = 0 h) to exhibit little increase in motion over the temperature range studied, whereas the t = 12 and 24 h samples exhibit a pronounced change in motion with temperature. The contrast is attributed to the presence of the afore-mentioned hydrocarbonaceous overlayer. Measurements on the samples in the presence of liquid hydrogen show hydrogen diffusional characteristics to be modified as a function of the catalyst conditioning process but, due to the complexity of the evolving catalyst matrix, the hydrogen motion cannot be attributed to a particular phase or component of the catalyst. Problems in the use of hydrogen as a probe molecule in this instance are briefly considered. Coincident neutron diffraction studies undertaken alongside the QENS measurements confirm the transition from hematite pre-catalyst to that of Hägg carbide during the course of extended times-on-stream.
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23
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Merte LR, Olsson PAT, Shipilin M, Gustafson J, Bertram F, Zhang C, Grönbeck H, Lundgren E. Structure of two-dimensional Fe 3O 4. J Chem Phys 2020; 152:114705. [PMID: 32199440 DOI: 10.1063/1.5142558] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
We have investigated the structure of an ultrathin iron oxide phase grown on Ag(100) using surface x-ray diffraction in combination with Hubbard-corrected density functional theory (DFT+U) calculations. The film exhibits a novel structure composed of one close-packed layer of octahedrally coordinated Fe2+ sandwiched between two close-packed layers of tetrahedrally coordinated Fe3+ and an overall stoichiometry of Fe3O4. As the structure is distinct from bulk iron oxide phases and the coupling with the silver substrate is weak, we propose that the phase should be classified as a metastable two-dimensional oxide. The chemical and physical properties are potentially interesting, thanks to the predicted charge ordering between atomic layers, and analogy with bulk ferrite spinels suggests the possibility of synthesis of a whole class of two-dimensional ternary oxides with varying electronic, optical, and chemical properties.
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Affiliation(s)
- Lindsay R Merte
- Materials Science and Applied Mathematics, Malmö University, 20506 Malmö, Sweden
| | - Pär A T Olsson
- Materials Science and Applied Mathematics, Malmö University, 20506 Malmö, Sweden
| | - Mikhail Shipilin
- Department of Physics, Stockholm University, AlbaNova University Center, 10691 Stockholm, Sweden
| | - Johan Gustafson
- Division of Synchrotron Radiation Research, Lund University, 22100 Lund, Sweden
| | | | - Chu Zhang
- Division of Synchrotron Radiation Research, Lund University, 22100 Lund, Sweden
| | - Henrik Grönbeck
- Department of Physics and Competence Centre for Catalysis, Chalmers University of Technology, 41296 Göteborg, Sweden
| | - Edvin Lundgren
- Division of Synchrotron Radiation Research, Lund University, 22100 Lund, Sweden
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24
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Ahart CS, Blumberger J, Rosso KM. Polaronic structure of excess electrons and holes for a series of bulk iron oxides. Phys Chem Chem Phys 2020; 22:10699-10709. [DOI: 10.1039/c9cp06482f] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
With the use of a gap-optimized hybrid functional and large supercells, it is found that while the electron hole polaron generally localises onto a single iron site, the electron polaron localises across two iron sites of the same spin layer.
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Affiliation(s)
- Christian S. Ahart
- Department of Physics and Astronomy
- University College London
- London WC1E 6BT
- UK
| | - Jochen Blumberger
- Department of Physics and Astronomy
- University College London
- London WC1E 6BT
- UK
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25
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Surface Properties and Floatability Comparison of Aegirite and Specularite by Density Functional Theory Study and Experiment. MINERALS 2019. [DOI: 10.3390/min9120782] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Understanding the differences in surface properties between aegirite and specularite is of great significance to study their separation. In this work, the surface properties of aegirite and specularite, as well as their relationships to floatability, have been explored by first principle calculation, flotation, and Zeta potential measurement. The surface relaxation indicated that the specularite (001) surface appeared to show more surface reconstruction. The unsatisfied bond properties, Mulliken bond population, and surface charge showed that the floatability of specularite was superior to that of aegirite. The flotation results showed that the hydrophobicity of specularite was higher than that of aegirite with dodecylamine (DDA) as the collector. It is infeasible to separate specularite from aegirite by flotation using starch as the depressant, and research of effective reagents with high affinity to the element Si is the subclinical breakthrough point of specularite/aegirite separation.
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26
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Bylaska EJ, Catalano JG, Mergelsberg ST, Saslow SA, Qafoku O, Prange MP, Ilton ES. Association of Defects and Zinc in Hematite. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2019; 53:13687-13694. [PMID: 31689102 DOI: 10.1021/acs.est.9b04323] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Zn is an essential micronutrient that is often limited in tropical, lateritic soils in part because it is sequestered in nominally refractory iron oxide phases. Stable phases such as goethite and hematite, however, can undergo reductive recrystallization without a phase change under circumneutral pH conditions and release metal impurities such as Zn into aqueous solutions. Further, the process appears to be driven by Fe vacancies. In this contribution, we used ab initio molecular dynamics informed extended X-ray absorption fine structure spectra to show that Zn incorporated in the structure of hematite is associated with coupled O-Fe and protonated Fe vacancies, providing a potential link between crystal chemistry and the bioavailability of Zn.
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Affiliation(s)
- Eric J Bylaska
- Pacific Northwest National Laboratory , Richland Washington 99352 , United States
| | - Jeffrey G Catalano
- Department of Earth and Planetary Sciences , Washington University , St. Louis , Missouri 63130 , United States
| | | | - Sarah A Saslow
- Pacific Northwest National Laboratory , Richland Washington 99352 , United States
| | - Odeta Qafoku
- Pacific Northwest National Laboratory , Richland Washington 99352 , United States
| | - Micah P Prange
- Pacific Northwest National Laboratory , Richland Washington 99352 , United States
| | - Eugene S Ilton
- Pacific Northwest National Laboratory , Richland Washington 99352 , United States
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27
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Olsen R, Leirvik KN, Kvamme B. Adsorption characteristics of glycols on calcite and hematite. AIChE J 2019. [DOI: 10.1002/aic.16728] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Richard Olsen
- Department of Physics and Technology University of Bergen Bergen Norway
| | - Kim N. Leirvik
- Department of Physics and Technology University of Bergen Bergen Norway
| | - Bjørn Kvamme
- Department of Physics and Technology University of Bergen Bergen Norway
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Copper-Arsenic Nanoparticles in Hematite: Fingerprinting Fluid-Mineral Interaction. MINERALS 2019. [DOI: 10.3390/min9070388] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Metal nanoparticles (NP) in minerals are an emerging field of research. Development of advanced analytical techniques such as Z-contrast imaging and mapping using high-angle annular dark field scanning transmission electron microscopy (HAADF STEM) allows unparalleled insights at the nanoscale. Moreover, the technique provides a link between micron-scale textures and chemical patterns if the sample is extracted in situ from a location of petrogenetic interest. Here we use HAADF STEM imaging and energy-dispersive X-ray spectrometry (EDX) mapping/spot analysis on focused ion beam prepared foils to characterise atypical Cu-As-zoned and weave-twinned hematite from the Olympic Dam deposit, South Australia. We aim to determine the role of solid-solution versus the presence of discrete included NPs in the observed zoning and to understand Cu-As-enrichment processes. Relative to the grain surface, the Cu-As bands extend in depth as (sub)vertical trails of opposite orientation, with Si-bearing hematite NP inclusions on one side and coarser cavities (up to hundreds of nm) on the other. The latter host Cu and Cu-As NPs, contain mappable K, Cl, and C, and display internal voids with rounded morphologies. Aside from STEM-EDX mapping, the agglomeration of native copper NPs was also assessed by high-resolution imaging. Collectively, such characteristics, corroborated with the geometrical outlines and negative crystal shapes of the cavities, infer that these are opened fluid inclusions with NPs attached to inclusion walls. Hematite along the trails features distinct nanoscale domains with lattice defects (twins, 2-fold superstructuring) relative to hematite outside the trails, indicating this is a nanoprecipitate formed during replacement processes, i.e., coupled dissolution and reprecipitation reactions (CDRR). Transient porosity intrinsically developed during CDRR can trap fluids and metals. Needle-shaped and platelet Cu-As NPs are also observed along (sub)horizontal bands along which Si, Al and K is traceable along the margins. The same signature is depicted along nm-wide planes crosscutting at 60° and offsetting (012)-twins in weave-twinned hematite. High-resolution imaging shows linear and planar defects, kink deformation along the twin planes, misorientation and lattice dilation around duplexes of Si-Al-K-planes. Such defects are evidence of strain, induced during fluid percolation along channels that become wider and host sericite platelets, as well as Cl-K-bearing inclusions, comparable with those from the Cu-As-zoned hematite, although without metal NPs. The Cu-As-bands mapped in hematite correspond to discrete NPs formed during interaction with fluids that changed in composition from alkali-silicic to Cl- and metal-bearing brines, and to fluid rates that evolved from slow infiltration to erratic inflow controlled by fault-valve mechanism pumping. This explains the presence of Cu-As NPs hosted either along Si-Al-K-planes (fluid supersaturation), or in fluid inclusions (phase separation during depressurisation) as well as the common signatures observed in hematite with variable degrees of fluid-mineral interaction. The invoked fluids are typical of hydrolytic alteration and the fluid pumping mechanism is feasible via fault (re)activation. Using a nanoscale approach, we show that fluid-mineral interaction can be fingerprinted at the (atomic) scale at which element exchange occurs.
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Structural Chemistry of Akdalaite, Al10O14(OH)2, the Isostructural Aluminum Analogue of Ferrihydrite. CRYSTALS 2019. [DOI: 10.3390/cryst9050246] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
As part of an effort to characterize clusters and intermediate phases likely to be encountered along solution reaction pathways that produce iron and aluminum oxide-hydroxides from Fe and Al precursors, the complete structure of Al10O14(OH)2 (akdalaite) was determined from a combination of single-crystal X-ray diffraction (SC-XRD) data collected at 100 K to define the Al and O positions, and solid-state nuclear magnetic resonance (NMR) and neutron powder diffraction (NPD) data collected at room temperature (~300 K) to precisely determine the nature of hydrogen in the structure. Two different synthesis routes produced different crystal morphologies. Using an aluminum oxyhydroxide floc made from mixing AlCl3 and 0.48 M NaOH, the product had uniform needle morphology, while using nanocrystalline boehmite (Vista Chemical Company Catapal D alumina) as the starting material produced hexagonal plates. Akdalaite crystallizes in the space group P63mc with lattice parameters of a = 5.6244(3) Å and c = 8.8417(3) Å (SC-XRD) and a = 5.57610(2) Å and c = 8.77247(6) Å (NPD). The crystal structure features Al13O40 Keggin clusters. The structural chemistry of akdalaite is nonideal but broadly conforms to that of ferrihydrite, the nanomineral with which it is isostructural.
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30
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Yokosawa T, Prestat E, Polly R, Bouby M, Dardenne K, Finck N, Haigh SJ, Denecke MA, Geckeis H. Fate of Lu(III) sorbed on 2-line ferrihydrite at pH 5.7 and aged for 12 years at room temperature. II: insights from STEM-EDXS and DFT calculations. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2019; 26:5282-5293. [PMID: 29667060 DOI: 10.1007/s11356-018-1904-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2017] [Accepted: 03/28/2018] [Indexed: 06/08/2023]
Abstract
Transformation products of two-line ferrihydrite associated with Lu(III) were studied after 12 years of aging using aberration-corrected high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM), high-efficiency energy-dispersive X-ray spectroscopy (EDXS), and density functional theory (DFT). The transformation products consisted of hematite nanoparticles with overgrown goethite needles. High-efficiency STEM-EDXS revealed that Lu is only associated with goethite needles, and atomic-resolution HAADF-STEM reveals structural incorporation of Lu within goethite, partially replacing structural Fe sites. This finding corroborates those recently obtained by AsFlFFF and EXAFS spectroscopy on the same sample (Finck et al. 2018). DFT calculations indicate that Lu incorporation within goethite or hematite are almost equally likely, suggesting that experimental parameters such as temperature and reaction time which affect reaction kinetics, play important roles in determining the Lu uptake. It seems likely that these results may be transferable to predict the behavior of chemically homologous trivalent actinides.
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Affiliation(s)
- Tadahiro Yokosawa
- Institute for Nuclear Waste Disposal, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344, Eggenstein-Leopoldshafen, Germany.
- Institute of Micro- and Nanostructure Research, Friedrich-Alexander-Universität Erlangen-Nürnberg, Cauerstraße 6, 91058, Erlangen, Germany.
| | - Eric Prestat
- School of Materials, University of Manchester, M13 9PL, Manchester, UK
| | - Robert Polly
- Institute for Nuclear Waste Disposal, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344, Eggenstein-Leopoldshafen, Germany
| | - Muriel Bouby
- Institute for Nuclear Waste Disposal, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344, Eggenstein-Leopoldshafen, Germany.
| | - Kathy Dardenne
- Institute for Nuclear Waste Disposal, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344, Eggenstein-Leopoldshafen, Germany
| | - Nicolas Finck
- Institute for Nuclear Waste Disposal, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344, Eggenstein-Leopoldshafen, Germany
| | - Sarah J Haigh
- School of Materials, University of Manchester, M13 9PL, Manchester, UK
| | - Melissa A Denecke
- Dalton Nuclear Institute, University of Manchester, M13 9PL, Manchester, UK
| | - Horst Geckeis
- Institute for Nuclear Waste Disposal, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344, Eggenstein-Leopoldshafen, Germany
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31
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Finck N, Bouby M, Dardenne K. Fate of Lu(III) sorbed on 2-line ferrihydrite at pH 5.7 and aged for 12 years at room temperature. I: insights from ICP-OES, XRD, ESEM, AsFlFFF/ICP-MS, and EXAFS spectroscopy. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2019; 26:5238-5250. [PMID: 29388155 DOI: 10.1007/s11356-018-1314-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/2017] [Accepted: 01/15/2018] [Indexed: 06/07/2023]
Abstract
Two-line ferrihydrite (2LFh) was aged for 12 years under ambient conditions and sheltered from light in the presence of Lu(III) used as surrogate for trivalent actinides. 2LFh aging produced hematite rhombohedra with overgrown acicular goethite particles. Analysis of the homogeneous suspension by asymmetrical flow field-flow fractionation (AsFlFFF) coupled to ICP-MS indicated that particles have a mean hydrodynamic diameter of about 140 nm and the strong correlation of the Fe and Lu fractograms hinted at a structural association of the lanthanide with the solid phase(s). Unfortunately, recoveries were low and thus results cannot be considered representative of the whole sample. The suspension was centrifuged and X-ray absorption spectroscopy (XAS) at the Lu L3-edge on the settled particles indicated that Lu(III) is sixfold coordinated by oxygen atoms, pointing to a retention by structural incorporation within particles. This result is consistent with AsFlFFF results on the same suspension without centrifugation. The detection of next nearest Fe and O atoms were consistent with the structure of goethite, ruling out incorporation within hematite. After centrifugation of the suspension, only nanoparticulate needle-like particles, very likely goethite, could be detected in the supernatant by ESEM. AsFlFFF data of the supernatant were comparable to that obtained for the homogeneous suspension, whereas XAS indicated that Lu(III) is predominantly present as dissolved species in the supernatant. Results from both techniques can be interpreted as a major fraction of Lu present as aqueous ions and a minor fraction as structurally incorporated. Findings from this study are corroborated by STEM-HAADF data and results from DFT calculations in a companion paper.
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Affiliation(s)
- Nicolas Finck
- Institute for Nuclear Waste Disposal (INE), Karlsruhe Institute of Technology (KIT), P.O. Box 3640, 76021, Karlsruhe, Germany.
| | - Muriel Bouby
- Institute for Nuclear Waste Disposal (INE), Karlsruhe Institute of Technology (KIT), P.O. Box 3640, 76021, Karlsruhe, Germany.
| | - Kathy Dardenne
- Institute for Nuclear Waste Disposal (INE), Karlsruhe Institute of Technology (KIT), P.O. Box 3640, 76021, Karlsruhe, Germany
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32
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Kuklin MS, Karttunen AJ. Crystal Structure Prediction of Magnetic Transition-Metal Oxides by Using Evolutionary Algorithm and Hybrid DFT Methods. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2018; 122:24949-24957. [PMID: 30416641 PMCID: PMC6221369 DOI: 10.1021/acs.jpcc.8b08238] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/24/2018] [Revised: 10/10/2018] [Indexed: 06/09/2023]
Abstract
Although numerous crystal structures have been successfully predicted by using currently available computational techniques, prediction of strongly correlated systems such as transition-metal oxides remains a challenge. To overcome this problem, we have interfaced evolutionary algorithm-based USPEX method with the CRYSTAL code, enabling the use of Gaussian-type localized atomic basis sets and hybrid density functional (DFT) methods for the prediction of crystal structures. We report successful crystal structure predictions of several transition-metal oxides (NiO, CoO, α-Fe2O3, V2O3, and CuO) with correct atomic magnetic moments, spin configurations, and structures by using the USPEX method in combination with the CRYSTAL code and Perdew-Burke-Ernzerhof (PBE0) hybrid functional. Our benchmarking results demonstrate that USPEX + hybrid DFT is a suitable combination to reliably predict the magnetic structures of strongly correlated materials.
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Affiliation(s)
- Mikhail S. Kuklin
- Department of Chemistry and
Materials Science, Aalto University, P.O. Box 16100, FI-00076 Aalto, Finland
| | - Antti J. Karttunen
- Department of Chemistry and
Materials Science, Aalto University, P.O. Box 16100, FI-00076 Aalto, Finland
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33
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Tang Y, Hunter EC, Battle PD, Hendrickx M, Hadermann J, Cadogan JM. Ferrimagnetism as a Consequence of Unusual Cation Ordering in the Perovskite SrLa 2FeCoSbO 9. Inorg Chem 2018; 57:7438-7445. [PMID: 29808998 DOI: 10.1021/acs.inorgchem.8b01012] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A polycrystalline sample of SrLa2FeCoSbO9 has been prepared in a solid-state reaction and studied by a combination of electron microscopy, magnetometry, Mössbauer spectroscopy, X-ray diffraction, and neutron diffraction. The compound adopts a monoclinic (space group P21/ n; a = 5.6218(6), b = 5.6221(6), c = 7.9440(8) Å, β = 90.050(7)° at 300 K) perovskite-like crystal structure with two crystallographically distinct six-coordinate sites. One of these sites is occupied by 2/3 Co2+, 1/3 Fe3+ and the other by 2/3 Sb5+, 1/3 Fe3+. This pattern of cation ordering results in a transition to a ferrimagnetic phase at 215 K. The magnetic moments on nearest-neighbor, six-coordinate cations align in an antiparallel manner, and the presence of diamagnetic Sb5+ on only one of the two sites results in a nonzero remanent magnetization of ∼1 μB per formula unit at 5 K.
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Affiliation(s)
- Yawei Tang
- Inorganic Chemistry Laboratory , University of Oxford , South Parks Road , Oxford OX1 3QR , U.K
| | - Emily C Hunter
- Inorganic Chemistry Laboratory , University of Oxford , South Parks Road , Oxford OX1 3QR , U.K
| | - Peter D Battle
- Inorganic Chemistry Laboratory , University of Oxford , South Parks Road , Oxford OX1 3QR , U.K
| | - Mylène Hendrickx
- EMAT , University of Antwerp , Groenenborgerlaan 171 , 2020 Antwerp , Belgium
| | - Joke Hadermann
- EMAT , University of Antwerp , Groenenborgerlaan 171 , 2020 Antwerp , Belgium
| | - J M Cadogan
- School of Physical, Environmental and Mathematical Sciences , UNSW Canberra at the Australian Defence Force Academy , Canberra , BC 2610 , Australia
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Abstract
Abstract
A significant number of non-molecular crystal structures can be described as derivative structures of sphere packings, with variable degrees of distortion. The undistorted sphere packing model with all the cavities completely occupied is the aristotype, from which an idealized model of the real structure can be obtained as a substitution, undistorted hettotype. The real structure can then be seen as a distorted derivative of the substitution hettotype. In this article we revive the symbolism introduced by Zoltai and Stout to describe the substitution hettotypes and compare these with the corresponding real structures. In most cases, the distortions are small or even negligible. For some structures, a significant departure from the substitution hettotype is observed, which however does not prevent to adopt the same description as a unifying scheme.
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Affiliation(s)
- Akihiro Umayahara
- Graduate School of Science and Technology , Kumamoto University , Kumamoto 860-8555 , Japan
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35
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Lukens WW, Saslow SA. Facile incorporation of technetium into magnetite, magnesioferrite, and hematite by formation of ferrous nitrate in situ: precursors to iron oxide nuclear waste forms. Dalton Trans 2018; 47:10229-10239. [DOI: 10.1039/c8dt01356j] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The fission product, 99Tc, presents significant challenges to the long-term disposal of nuclear waste due to its long half-life, high fission yield, and to the environmental mobility of pertechnetate (TcO4−), the stable Tc species in aerobic environments.
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Affiliation(s)
- Wayne W. Lukens
- Chemical Sciences Division
- Lawrence Berkeley National Laboratory
- Berkeley
- USA
| | - Sarah A. Saslow
- Geosciences Division
- Pacific Northwest National Laboratory
- Richland
- USA
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36
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Sassi M, Pearce CI, Bagus PS, Arenholz E, Rosso KM. First-Principles Fe L 2,3-Edge and O K-Edge XANES and XMCD Spectra for Iron Oxides. J Phys Chem A 2017; 121:7613-7618. [PMID: 28933158 DOI: 10.1021/acs.jpca.7b08392] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
X-ray absorption near-edge structure (XANES) and X-ray magnetic circular dichroism (XMCD) spectroscopies are tools in widespread use for providing detailed local atomic structure, oxidation state, and magnetic structure information for materials and organometallic complexes. The analysis of these spectra for transition-metal L-edges is routinely performed on the basis of ligand-field multiplet theory because one- and two-particle mean-field ab initio methods typically cannot describe the multiplet structure. Here we show that multireference configuration interaction (MRCI) calculations can satisfactorily reproduce measured XANES spectra for a range of complex iron oxide materials including hematite and magnetite. MRCI Fe L2,3-edge XANES and XMCD spectra of Fe(II)O6, Fe(III)O6, and Fe(III)O4 in magnetite are found to be in very good qualitative agreement with experiment and multiplet calculations. Point-charge embedding and small distortions of the first-shell oxygen ligands have only small effects. Oxygen K-edge XANES/XMCD spectra for magnetite investigated by a real-space Green's function approach complete the very good qualitative agreement with experiment. Material-specific differences in local coordination and site symmetry are well reproduced, making the approach useful for assigning spectral features to specific oxidation states and coordination environments.
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Affiliation(s)
- Michel Sassi
- Pacific Northwest National Laboratory , Richland, Washington 99352, United States
| | - Carolyn I Pearce
- Pacific Northwest National Laboratory , Richland, Washington 99352, United States
| | - Paul S Bagus
- Department of Chemistry, University of North Texas , Denton, Texas 76203, United States
| | - Elke Arenholz
- Advanced Light Source, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States
| | - Kevin M Rosso
- Pacific Northwest National Laboratory , Richland, Washington 99352, United States
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37
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Shim HM, Lim GE, Kim JK, Kim HS, Koo KK. Preparation of the spherical nano-Fe2O3/NH4ClO4 composites by reactive crystallization and their characterization. J IND ENG CHEM 2017. [DOI: 10.1016/j.jiec.2017.06.024] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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38
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Samed AJ, Yamamoto Y, Hidaka M, Hinokuma S, Machida M. An attempt to stabilize supported Ru catalysts against oxidative volatilization. CATAL COMMUN 2017. [DOI: 10.1016/j.catcom.2016.11.023] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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39
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Severin J, Jund P. Thermal conductivity calculation in anisotropic crystals by molecular dynamics: Application to α-Fe 2O 3. J Chem Phys 2017; 146:054505. [PMID: 28178828 DOI: 10.1063/1.4974933] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
In this work, we aim to study the thermal properties of materials using classical molecular dynamics simulations and specialized numerical methods. We focus primarily on the thermal conductivity κ using non-equilibrium molecular dynamics (NEMD) to study the response of a crystalline solid, namely hematite (α-Fe2O3), to an imposed heat flux as is the case in real life applications. We present a methodology for the calculation of κ as well as an adapted potential for hematite. Taking into account the size of the simulation box, we show that not only the longitudinal size (in the direction of the heat flux) but also the transverse size plays a role in the determination of κ and should be converged properly in order to have reliable results. Moreover we propose a comparison of thermal conductivity calculations in two different crystallographic directions to highlight the spatial anisotropy and we investigate the non-linear temperature behavior typically observed in NEMD methods.
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Affiliation(s)
- Jonathan Severin
- UMR 5253 CNRS-UM-ENSCM, Institut Charles Gerhardt Montpellier, Place E. Bataillon CC1506, 34095 Montpellier, France
| | - Philippe Jund
- UMR 5253 CNRS-UM-ENSCM, Institut Charles Gerhardt Montpellier, Place E. Bataillon CC1506, 34095 Montpellier, France
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40
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Han H, Riboni F, Karlicky F, Kment S, Goswami A, Sudhagar P, Yoo J, Wang L, Tomanec O, Petr M, Haderka O, Terashima C, Fujishima A, Schmuki P, Zboril R. α-Fe 2O 3/TiO 2 3D hierarchical nanostructures for enhanced photoelectrochemical water splitting. NANOSCALE 2017; 9:134-142. [PMID: 27874124 DOI: 10.1039/c6nr06908h] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
We report the fabrication of 3D hierarchical hetero-nanostructures composed of thin α-Fe2O3 nanoflakes branched on TiO2 nanotubes. The novel α-Fe2O3/TiO2 hierarchical nanostructures, synthesized on FTO through a multi-step hydrothermal process, exhibit enhanced performances in photo-electrochemical water splitting and in the photocatalytic degradation of an organic dye, with respect to pure TiO2 nanotubes. An enhanced separation of photogenerated charge carriers is here proposed as the main factor for the observed photo-activities: electrons photogenerated in TiO2 are efficiently collected at FTO, while holes are transferred to the α-Fe2O3 nanobranches that serve as charge mediators to the electrolyte. The morphology of α-Fe2O3 that varies from ultrathin nanoflakes to nanorod/nanofiber structures depending on the Fe precursor concentration was shown to have a significant impact on the photo-induced activity of the α-Fe2O3/TiO2 composites. In particular, it is shown that for an optimized photo-electrochemical structure, a combination of critical factors should be achieved such as (i) TiO2 light absorption and photo-activation vs.α-Fe2O3-induced shadowing effect and (ii) the availability of free TiO2 surface vs.α-Fe2O3-coated surface. Finally, theoretical analysis, based on DFT calculations, confirmed the optical properties experimentally determined for the α-Fe2O3/TiO2 hierarchical nanostructures. We anticipate that this new multi-step hydrothermal process can be a blueprint for the design and development of other hierarchical heterogeneous metal oxide electrodes suitable for photo-electrochemical applications.
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Affiliation(s)
- Hyungkyu Han
- Regional Centre of Advanced Technologies and Materials, Department of Physical Chemistry, Faculty of Science, Palacky University, Slechtitelu 11, 783 71 Olomouc, Czech Republic.
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41
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Gualtieri AF, Gandolfi NB, Pollastri S, Pollok K, Langenhorst F. Where is iron in erionite? A multidisciplinary study on fibrous erionite-Na from Jersey (Nevada, USA). Sci Rep 2016; 6:37981. [PMID: 27892512 PMCID: PMC5125093 DOI: 10.1038/srep37981] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2016] [Accepted: 10/31/2016] [Indexed: 01/21/2023] Open
Abstract
Fibrous erionite is a mineral fibre of great concern but to date mechanisms by which it induces cyto- and geno-toxic damage, and especially the role of iron associated to this zeolite species, remain poorly understood. One of the reasons is that we still don't know exactly where iron is in natural erionite. This work is focused on fibrous erionite-Na from Jersey (Nevada, USA) and attempts to draw a general model of occurrence of iron in erionite and relationship with toxicity mechanisms. It was found that iron is present as 6-fold coordinated Fe3+ not part of the zeolite structure. The heterogeneous nature of the sample was revealed as receptacle of different iron-bearing impurities (amorphous iron-rich nanoparticles, micro-particles of iron oxides/hydroxides, and flakes of nontronite). If iron is not part of the structure, its role should be considered irrelevant for erionite toxicity, and other factors like biopersistence should be invoked. An alternative perspective to the proposed model is that iron rich nano-particles and nontronite dissolve in the intracellular acidic environment, leaving a residue of iron atoms at specific surface sites anchored to the windows of the zeolite channels. These sites may be active later as low nuclearity groups.
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Affiliation(s)
- Alessandro F Gualtieri
- Chemistry and Earth Sciences Department, The University of Modena and Reggio Emilia, Via Campi 103, I-41125 Modena (Italy)
| | - Nicola Bursi Gandolfi
- Chemistry and Earth Sciences Department, The University of Modena and Reggio Emilia, Via Campi 103, I-41125 Modena (Italy)
| | - Simone Pollastri
- Chemistry and Earth Sciences Department, The University of Modena and Reggio Emilia, Via Campi 103, I-41125 Modena (Italy)
| | - Kilian Pollok
- Institut für Geowissenschaften Mineralogie, Friedrich-Schiller-Universität Jena, Carl-Zeiss-Promenade 10, D-07745 Jena (Germany)
| | - Falko Langenhorst
- Institut für Geowissenschaften Mineralogie, Friedrich-Schiller-Universität Jena, Carl-Zeiss-Promenade 10, D-07745 Jena (Germany)
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Schoch R, Bauer M. Pollution Control Meets Sustainability: Structure-Activity Studies on New Iron Oxide-Based CO Oxidation Catalysts. CHEMSUSCHEM 2016; 9:1996-2004. [PMID: 27440425 DOI: 10.1002/cssc.201600508] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2016] [Indexed: 06/06/2023]
Abstract
A new class of catalysts for the oxidation of CO based on iron oxide as a biocompatible, earth-abundant and non-toxic metal is presented. The catalytic activities achieved with these catalysts provide promising milestones towards the substitution of noble metals in CO oxidation catalysts. The catalysts can be obtained by using iron core-shell nanoparticle precursors. The metal used for the shell material determines whether the iron core is integrated in or isolated from the support. The active iron site is effectively integrated into the γ-Al2 O3 support if an aluminum shell is present in the core-shell precursor. When the metal used for the shell is different from the support, an isolated structure is formed. Using this directed synthesis approach, different iron oxide species can be obtained and their structural differences are linked to distinct catalytic activities, as demonstrated by combined in-depth analytical studies using XRD, X-ray absorption spectroscopy (XAS), UV/Vis, and Brunauer-Emmett-Teller (BET) analysis. The key species responsible for high catalytic activity is identified as isolated tetrahedrally coordinated Fe(III) centers, whereas aggregation leads to a reduction in activity.
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Affiliation(s)
- Roland Schoch
- Fakultät für Naturwissenschaften, Department Chemie, Universität Paderborn, Warburger Straße 100, 33098, Paderborn, Germany
| | - Matthias Bauer
- Fakultät für Naturwissenschaften, Department Chemie, Universität Paderborn, Warburger Straße 100, 33098, Paderborn, Germany.
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Ewen JP, Gattinoni C, Thakkar FM, Morgan N, Spikes HA, Dini D. A Comparison of Classical Force-Fields for Molecular Dynamics Simulations of Lubricants. MATERIALS 2016; 9:ma9080651. [PMID: 28773773 PMCID: PMC5509262 DOI: 10.3390/ma9080651] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/22/2016] [Revised: 07/20/2016] [Accepted: 07/28/2016] [Indexed: 01/26/2023]
Abstract
For the successful development and application of lubricants, a full understanding of their complex nanoscale behavior under a wide range of external conditions is required, but this is difficult to obtain experimentally. Nonequilibrium molecular dynamics (NEMD) simulations can be used to yield unique insights into the atomic-scale structure and friction of lubricants and additives; however, the accuracy of the results depend on the chosen force-field. In this study, we demonstrate that the use of an accurate, all-atom force-field is critical in order to; (i) accurately predict important properties of long-chain, linear molecules; and (ii) reproduce experimental friction behavior of multi-component tribological systems. In particular, we focus on n-hexadecane, an important model lubricant with a wide range of industrial applications. Moreover, simulating conditions common in tribological systems, i.e., high temperatures and pressures (HTHP), allows the limits of the selected force-fields to be tested. In the first section, a large number of united-atom and all-atom force-fields are benchmarked in terms of their density and viscosity prediction accuracy of n-hexadecane using equilibrium molecular dynamics (EMD) simulations at ambient and HTHP conditions. Whilst united-atom force-fields accurately reproduce experimental density, the viscosity is significantly under-predicted compared to all-atom force-fields and experiments. Moreover, some all-atom force-fields yield elevated melting points, leading to significant overestimation of both the density and viscosity. In the second section, the most accurate united-atom and all-atom force-field are compared in confined NEMD simulations which probe the structure and friction of stearic acid adsorbed on iron oxide and separated by a thin layer of n-hexadecane. The united-atom force-field provides an accurate representation of the structure of the confined stearic acid film; however, friction coefficients are consistently under-predicted and the friction-coverage and friction-velocity behavior deviates from that observed using all-atom force-fields and experimentally. This has important implications regarding force-field selection for NEMD simulations of systems containing long-chain, linear molecules; specifically, it is recommended that accurate all-atom potentials, such as L-OPLS-AA, are employed.
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Affiliation(s)
- James P Ewen
- Department of Mechanical Engineering, Imperial College London, South Kensington Campus, Exhibition Road, London SW7 2AZ, UK.
| | - Chiara Gattinoni
- Department of Mechanical Engineering, Imperial College London, South Kensington Campus, Exhibition Road, London SW7 2AZ, UK.
| | - Foram M Thakkar
- Shell India Markets Private Limited, 8B RMZ Centennial Building, Kundanahalli Main Road, Bangalore 560048, India.
| | - Neal Morgan
- Shell Global Solutions UK Ltd., Brabazon House, Manchester M22 0RR, UK.
| | - Hugh A Spikes
- Department of Mechanical Engineering, Imperial College London, South Kensington Campus, Exhibition Road, London SW7 2AZ, UK.
| | - Daniele Dini
- Department of Mechanical Engineering, Imperial College London, South Kensington Campus, Exhibition Road, London SW7 2AZ, UK.
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Ewen JP, Gattinoni C, Morgan N, Spikes HA, Dini D. Nonequilibrium Molecular Dynamics Simulations of Organic Friction Modifiers Adsorbed on Iron Oxide Surfaces. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:4450-4463. [PMID: 27064962 DOI: 10.1021/acs.langmuir.6b00586] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
For the successful development and application of lubricants, a full understanding of the nanoscale behavior of complex tribological systems is required, but this is difficult to obtain experimentally. In this study, we use nonequilibrium molecular dynamics (NEMD) simulations to examine the atomistic structure and friction properties of commercially relevant organic friction modifier (OFM) monolayers adsorbed on iron oxide surfaces and lubricated by a thin, separating layer of hexadecane. Specifically, acid, amide, and glyceride OFMs, with saturated and Z-unsaturated hydrocarbon tail groups, are simulated at various surface coverages and sliding velocities. At low and medium coverage, the OFMs form liquidlike and amorphous monolayers, respectively, which are significantly interdigitated with the hexadecane lubricant, resulting in relatively high friction coefficients. At high coverage, solidlike monolayers are formed for all of the OFMs, which, during sliding, results in slip planes between well-defined OFM and hexadecane layers, yielding a marked reduction in the friction coefficient. When present at equal surface coverage, OFMs with saturated and Z-unsaturated tail groups are found to yield similar structure and friction behavior. OFMs with glyceride head groups yield significantly lower friction coefficients than amide and particularly carboxylic acid head groups. For all of the OFMs and coverages simulated, the friction coefficient is found to increase linearly with the logarithm of sliding velocity; however, the gradient of this increase depends on the coverage. The structure and friction details obtained from these simulations agree well with experimental results and also shed light on the relative tribological performance of these OFMs through nanoscale structural variations. This has important implications in terms of the applicability of NEMD to aid the development of new formulations to control friction.
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Affiliation(s)
- James P Ewen
- Department of Mechanical Engineering, Imperial College London , London SW7 2AZ, England
| | - Chiara Gattinoni
- Department of Mechanical Engineering, Imperial College London , London SW7 2AZ, England
| | - Neal Morgan
- Shell Global Solutions UK Ltd, Manchester M22 0RR, Lancashire, England
| | - Hugh A Spikes
- Department of Mechanical Engineering, Imperial College London , London SW7 2AZ, England
| | - Daniele Dini
- Department of Mechanical Engineering, Imperial College London , London SW7 2AZ, England
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García-Guaderrama M, Montero-Cabrera ME, Morán E, Alario-Franco MA, Fuentes-Cobas LE, Macías-Ríos E, Esparza-Ponce HE, Fuentes-Montero ME. Long- and Short-Range Structure of Ferrimagnetic Iron–Chromium Maghemites. Inorg Chem 2015; 54:11200-8. [DOI: 10.1021/acs.inorgchem.5b01624] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Marco García-Guaderrama
- Departamento
de Química Inorgánica, Facultad de Ciencias Químicas, Universidad Complutense, 28040 Madrid, Spain (EU)
- Centro de
Investigación en Materiales DIP-CUCEI, Universidad de Guadalajara, Av. Revolución 1500, Col. Olímpica, Guadalajara, México
| | - María E. Montero-Cabrera
- Centro de Investigación
en Materiales Avanzados (CIMAV), Miguel
de Cervantes 120, Complejo Industrial Chihuahua, Chihuahua 31136, Chih, México
| | - Emilio Morán
- Departamento
de Química Inorgánica, Facultad de Ciencias Químicas, Universidad Complutense, 28040 Madrid, Spain (EU)
| | - Miguel A. Alario-Franco
- Departamento
de Química Inorgánica, Facultad de Ciencias Químicas, Universidad Complutense, 28040 Madrid, Spain (EU)
| | - Luis E. Fuentes-Cobas
- Centro de Investigación
en Materiales Avanzados (CIMAV), Miguel
de Cervantes 120, Complejo Industrial Chihuahua, Chihuahua 31136, Chih, México
| | - Edgar Macías-Ríos
- Centro de Investigación
en Materiales Avanzados (CIMAV), Miguel
de Cervantes 120, Complejo Industrial Chihuahua, Chihuahua 31136, Chih, México
| | - Hilda E. Esparza-Ponce
- Centro de Investigación
en Materiales Avanzados (CIMAV), Miguel
de Cervantes 120, Complejo Industrial Chihuahua, Chihuahua 31136, Chih, México
| | - María E. Fuentes-Montero
- Facultad
de Ciencias Químicas, Universidad Autónoma de Chihuahua, Av. Escorza 900, Zona Centro, Chihuahua 31000, México
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Stȩkiel M, Przeniosło R, Duczmal M, Wardecki D, Buslaps T. Synchrotron radiation diffraction study of texture in α-Fe 2O 3powder induced by the magnetic field. CRYSTAL RESEARCH AND TECHNOLOGY 2015. [DOI: 10.1002/crat.201500065] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- M. Stȩkiel
- Institute of Experimental Physics; Faculty of Physics, University of Warsaw; Pasteura 5 02-093 Warsaw Poland
| | - R. Przeniosło
- Institute of Experimental Physics; Faculty of Physics, University of Warsaw; Pasteura 5 02-093 Warsaw Poland
| | - M. Duczmal
- Institute of Experimental Physics; Faculty of Physics, University of Warsaw; Pasteura 5 02-093 Warsaw Poland
| | - D. Wardecki
- Institute of Experimental Physics; Faculty of Physics, University of Warsaw; Pasteura 5 02-093 Warsaw Poland
| | - T. Buslaps
- European Synchrotron Radiation Facility; Grenoble France
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47
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Babay S, Mhiri T, Toumi M. Synthesis, structural and spectroscopic characterizations of maghemite γ-Fe2O3 prepared by one-step coprecipitation route. J Mol Struct 2015. [DOI: 10.1016/j.molstruc.2014.12.067] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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48
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Schoch R, Huang H, Schünemann V, Bauer M. A New Iron-Based Carbon Monoxide Oxidation Catalyst: Structure-Activity Correlation. Chemphyschem 2014; 15:3768-75. [DOI: 10.1002/cphc.201402551] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2014] [Indexed: 11/11/2022]
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49
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Sanson A, Mathon O, Pascarelli S. Local vibrational dynamics of hematite (α-Fe2O3) studied by extended x-ray absorption fine structure and molecular dynamics. J Chem Phys 2014; 140:224504. [DOI: 10.1063/1.4882282] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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50
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Vaxelaire N, Gergaud P, Vaughan GBM. Sub-micrometre depth-gradient measurements of phase, strain and texture in polycrystalline thin films: a nano-pencil beam diffraction approach. J Appl Crystallogr 2014. [DOI: 10.1107/s1600576714000557] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
A single-scan approach to evaluating chemical and structural gradients in polycrystalline thin films with a resolution of tens of nanometres is reported. Thinned samples are measured in cross section in a transmission geometry with a high-energy X-ray nano-pencil beam. Powder diffraction methods can be used because of the strongly asymmetric beam shape (i.e.the large number of diffracting grains), allowing the solution of structural phases within the film thickness. For each phase, microstructural gradients such as strain, stress, texture and grain size are deduced from two-dimensional diffraction patterns. Sample preparation (i.e.sample thinning), stress release and technique throughput are evaluated. The resolution, precision and limitations are discussed. The efficiency of this approach is demonstrated on ferritic thin films, where the phase ratio and stress gradient (in each phase) have been successfully quantified with a 150 nm depth resolution.
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