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Neumann S, Kuger L, Arlt CR, Franzreb M, Rafaja D. Influence of the hierarchical architecture of multi-core iron oxide nanoflowers on their magnetic properties. Sci Rep 2023; 13:5673. [PMID: 37029132 PMCID: PMC10082203 DOI: 10.1038/s41598-023-31294-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2023] [Accepted: 03/09/2023] [Indexed: 04/09/2023] Open
Abstract
Magnetic properties of superparamagnetic iron oxide nanoparticles are controlled mainly by their particle size and by their particle size distribution. Magnetic properties of multi-core iron oxide nanoparticles, often called iron oxide nanoflowers (IONFs), are additionally affected by the interaction of magnetic moments between neighboring cores. The knowledge about the hierarchical structure of IONFs is therefore essential for understanding the magnetic properties of IONFs. In this contribution, the architecture of multi-core IONFs was investigated using correlative multiscale transmission electron microscopy (TEM), X-ray diffraction and dynamic light scattering. The multiscale TEM measurements comprised low-resolution and high-resolution imaging as well as geometric phase analysis. The IONFs contained maghemite with the average chemical composition [Formula: see text]-Fe[Formula: see text]O[Formula: see text]. The metallic vacancies located on the octahedral lattice sites of the spinel ferrite structure were partially ordered. Individual IONFs consisted of several cores showing frequently a specific crystallographic orientation relationship between direct neighbors. This oriented attachment may facilitate the magnetic alignment within the cores. Individual cores were composed of partially coherent nanocrystals having almost the same crystallographic orientation. The sizes of individual constituents revealed by the microstructure analysis were correlated with the magnetic particle sizes that were obtained from fitting the measured magnetization curve by the Langevin function.
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Affiliation(s)
- Stefan Neumann
- Institute of Materials Science, TU Bergakademie Freiberg, 09599, Freiberg, Germany.
| | - Laura Kuger
- Institute of Functional Interfaces, Karlsruhe Institute of Technology, 76344, Eggenstein-Leopoldshafen, Germany
| | - Carsten-Rene Arlt
- Institute of Functional Interfaces, Karlsruhe Institute of Technology, 76344, Eggenstein-Leopoldshafen, Germany
| | - Matthias Franzreb
- Institute of Functional Interfaces, Karlsruhe Institute of Technology, 76344, Eggenstein-Leopoldshafen, Germany
| | - David Rafaja
- Institute of Materials Science, TU Bergakademie Freiberg, 09599, Freiberg, Germany
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Simple model of the electrophoretic migration of spherical and rod-shaped Au nanoparticles in gels with varied mesh sizes. Colloids Surf A Physicochem Eng Asp 2022. [DOI: 10.1016/j.colsurfa.2022.129716] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Winkler M, Rhein F, Nirschl H, Gleiss M. Real-Time Modeling of Volume and Form Dependent Nanoparticle Fractionation in Tubular Centrifuges. NANOMATERIALS (BASEL, SWITZERLAND) 2022; 12:3161. [PMID: 36144949 PMCID: PMC9500975 DOI: 10.3390/nano12183161] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/20/2022] [Revised: 08/11/2022] [Accepted: 09/06/2022] [Indexed: 06/16/2023]
Abstract
A dynamic process model for the simulation of nanoparticle fractionation in tubular centrifuges is presented. Established state-of-the-art methods are further developed to incorporate multi-dimensional particle properties (traits). The separation outcome is quantified based on a discrete distribution of particle volume, elongation and flatness. The simulation algorithm solves a mass balance between interconnected compartments which represent the separation zone. Grade efficiencies are calculated by a short-cut model involving material functions and higher dimensional particle trait distributions. For the one dimensional classification of fumed silica nanoparticles, the numerical solution is validated experimentally. A creation and characterization of a virtual particle system provides an additional three dimensional input dataset. Following a three dimensional fractionation case study, the tubular centrifuge model underlines the fact that a precise fractionation according to particle form is extremely difficult. In light of this, the paper discusses particle elongation and flatness as impacting traits during fractionation in tubular centrifuges. Furthermore, communications on separation performance and outcome are possible and facilitated by the three dimensional visualization of grade efficiency data. Future research in nanoparticle characterization will further enhance the models use in real-time separation process simulation.
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Valášková M, Leštinský P, Matějová L, Klemencová K, Ritz M, Schimpf C, Motylenko M, Rafaja D, Bělík J. Hematites Precipitated in Alkaline Precursors: Comparison of Structural and Textural Properties for Methane Oxidation. Int J Mol Sci 2022; 23:ijms23158163. [PMID: 35897740 PMCID: PMC9332227 DOI: 10.3390/ijms23158163] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Revised: 07/21/2022] [Accepted: 07/22/2022] [Indexed: 12/10/2022] Open
Abstract
Hematite (α-Fe2O3) catalysts prepared using the precipitation methods was found to be highly effective, and therefore, it was studied with methane (CH4), showing an excellent stable performance below 500 °C. This study investigates hematite nanoparticles (NPs) obtained by precipitation in water from the precursor of ferric chloride hexahydrate using precipitating agents NaOH or NH4OH at maintained pH 11 and calcined up to 500 °C for the catalytic oxidation of low concentrations of CH4 (5% by volume in air) at 500 °C to compare their structural state in a CH4 reducing environment. The conversion (%) of CH4 values decreasing with time was discussed according to the course of different transformation of goethite and hydrohematites NPs precursors to magnetite and the structural state of the calcined hydrohematites. The phase composition, the size and morphology of nanocrystallites, thermal transformation of precipitates and the specific surface area of the NPs were characterized in detail by X-ray powder diffraction, transmission electron microscopy, infrared spectroscopy, thermal TG/DTA analysis and nitrogen physisorption measurements. The results support the finding that after goethite dehydration, transformation to hydrohematite due to structurally incorporated water and vacancies is different from hydrohematite α-Fe2O3. The surface area SBET of Fe2O3_NH-70 precipitate composed of protohematite was larger by about 53 m2/g in comparison with Fe2O3_Na-70 precipitate composed of goethite. The oxidation of methane was positively influenced by the hydrohematites of the smaller particle size and the largest lattice volume containing structurally incorporated water and vacancies.
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Affiliation(s)
- Marta Valášková
- Institute of Environmental Technology, CEET, VSB-Technical University of Ostrava, 17. listopadu 15/2172, 708 00 Ostrava, Czech Republic; (P.L.); (L.M.); (K.K.)
- Correspondence: ; Tel.: +420-597-327-308
| | - Pavel Leštinský
- Institute of Environmental Technology, CEET, VSB-Technical University of Ostrava, 17. listopadu 15/2172, 708 00 Ostrava, Czech Republic; (P.L.); (L.M.); (K.K.)
| | - Lenka Matějová
- Institute of Environmental Technology, CEET, VSB-Technical University of Ostrava, 17. listopadu 15/2172, 708 00 Ostrava, Czech Republic; (P.L.); (L.M.); (K.K.)
| | - Kateřina Klemencová
- Institute of Environmental Technology, CEET, VSB-Technical University of Ostrava, 17. listopadu 15/2172, 708 00 Ostrava, Czech Republic; (P.L.); (L.M.); (K.K.)
| | - Michal Ritz
- Department of Chemistry and Physico-Chemical Processes, Faculty of Material Science and Technology, VSB-Technical University of Ostrava, 17. listopadu 15/2172, 708 00 Ostrava, Czech Republic;
| | - Christian Schimpf
- Institute of Materials Science, Technical University Bergakademie Freiberg, Gustav Zeuner Street 5, D-09599 Freiberg, Germany; (C.S.); (M.M.); (D.R.)
| | - Mykhailo Motylenko
- Institute of Materials Science, Technical University Bergakademie Freiberg, Gustav Zeuner Street 5, D-09599 Freiberg, Germany; (C.S.); (M.M.); (D.R.)
| | - David Rafaja
- Institute of Materials Science, Technical University Bergakademie Freiberg, Gustav Zeuner Street 5, D-09599 Freiberg, Germany; (C.S.); (M.M.); (D.R.)
| | - Jakub Bělík
- RPG Recycling, s.r.o., Member of REC Group, Vazová 2143, 688 01 Uhersky Brod, Czech Republic;
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