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Eikeland AZ, Gjørup FH, Andersen HL, Christensen M. High-performance hexaferrite magnets tailored through alignment of shape-controlled nanocomposites. RSC Adv 2024; 14:10790-10798. [PMID: 38572347 PMCID: PMC10988282 DOI: 10.1039/d3ra05634a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2023] [Accepted: 03/20/2024] [Indexed: 04/05/2024] Open
Abstract
Nanoparticles of strontium hexaferrite, SrFe12O19, were prepared by two different synthesis methods: hydrothermal (autoclave) and sol-gel autocombustion (solid-salt-matrix). The two synthesis pathways yield nanoparticles with different morphologies and correspondingly different magnetic characteristics. The autoclave synthesis results in large plate-like crystallites, which spontaneously align with a preferred crystallographic orientation when applying a uniaxial pressure, but exhibit a relatively poor coercivity. Meanwhile, the solid-salt-matrix synthesis method results in smaller less anisotropic crystallites with enhanced coercivity, but with a relatively limited ability to align under a uniaxial applied pressure. The obtained nanocrystalline powders were dry or wet mixed in different ratios followed by Spark Plasma Sintering (SPS) into dense pellets. A clear correlation between mixing ratio, the level of alignment and resulting coercivity was observed for the dry mixed samples, i.e. as more solid-salt-matrix powder is added, the texture of the pellets decreases and the coercivity increases. The best performing pellet in terms of maximum energy product (BHmax = 32.1(6) kJ m-3) was obtained by dry-mixing of 75 wt% autoclave prepared powder and 25 wt% solid-salt-matrix powder. The results presented here illustrate the potential of mixing magnetic nanoparticle powders with different shape characteristics to gain improved magnetic performance.
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Affiliation(s)
- Anna Zink Eikeland
- Department of Chemistry & Interdisciplinary Nanoscience Center (iNANO), Aarhus University Langelandsgade 140, 8000 Aarhus C Denmark
| | - Frederik Holm Gjørup
- Department of Chemistry & Interdisciplinary Nanoscience Center (iNANO), Aarhus University Langelandsgade 140, 8000 Aarhus C Denmark
| | - Henrik Lyder Andersen
- Departamento de Física de Materiales, Universidad Complutense de Madrid 28040 Madrid Spain
| | - Mogens Christensen
- Department of Chemistry & Interdisciplinary Nanoscience Center (iNANO), Aarhus University Langelandsgade 140, 8000 Aarhus C Denmark
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Knudsen CG, Mørch MI, Christensen M. Texture formation in W-type hexaferrite by cold compaction of non-magnetic interacting anisotropic shaped precursor crystallites. Dalton Trans 2023; 52:281-289. [PMID: 36484381 DOI: 10.1039/d2dt02091b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Crystallites of the W-type hexaferrites, Sr(Ni1-xZnx)2Fe16O27 (x = 0, 0.5, 1) have been aligned without applying magnetic field nor hot compaction, but through a simple synthesis process taking advantage of easy alignment of non-magnetic interacting, anisotropic-shaped precursor crystallites of goethite. The goethite precursor was prepared through a simple hydrothermal synthesis route, forming lathlike crystallites with apparent dimensions of 23.3 × 40.1 × 11.0 nm3 as extracted from powder X-ray diffraction along the a-, b- and c-axis, respectively. The calcined pellets consisted of almost phase pure W-type hexaferrites with relative small impurities of spinel ferrite (≤9.02(3) wt%). The high synthesis temperature resulted in large crystallites, which in turn caused low coercivities (Hc ≤ 5.4(1) kA m-1) and a squareness ration (Mr/Ms, remanence (Mr) over saturation magnetisation (Ms)) close to zero for all samples. The vanishing coercivity makes Mr/Ms an unsatisfying measure of preferred orientation. Quantitative texture analysis of the samples was carried out based on 2D transmission synchrotron diffraction data collected at different orientations of the samples. The texture investigations revealed alignment of the crystallites with the c-axis normal to the pressing surface of the pellets. The SrNi2Fe16O27 sample showed the highest texture index of 7.5 m.r.d.2.
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Affiliation(s)
- Cecilie G Knudsen
- Department of Chemistry & iNANO, Aarhus University, Aarhus C-8000, Denmark.
| | - Mathias I Mørch
- Department of Chemistry & iNANO, Aarhus University, Aarhus C-8000, Denmark.
| | - Mogens Christensen
- Department of Chemistry & iNANO, Aarhus University, Aarhus C-8000, Denmark.
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Thomas-Hunt J, Povlsen A, Vijayan H, Knudsen CG, Gjørup FH, Christensen M. Alignment of strontium hexaferrite, by cold compaction of anisotropic non-magnetically interacting crystallites. Dalton Trans 2022; 51:3884-3893. [PMID: 35188524 DOI: 10.1039/d2dt00062h] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Cold compacted, anisotropic shaped non-magnetically interacting precursors are used to achieve aligned strontium hexaferrites. The simple process of dry mixing platy hematite and/or rod-like goethite with strontium carbonate removes the need for external magnetic fields or high temperatures during compaction to assist in alignment. The calcined strontium hexaferrite pellets all displayed preferred orientation and high levels of phase purity (>99 wt%). The mix of goethite and strontium carbonate achieved the highest degree of magnetic alignment with Mr/Ms reaching 0.83(1) obtained by vibrating sample magnetometry. The magnetic data were supported by examining crystallographic alignment using powder X-ray diffraction as well as 2D texture synchrotron analysis.
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Affiliation(s)
- Jack Thomas-Hunt
- Department of Chemistry & iNANO, Aarhus University, Aarhus C-8000, Denmark. .,School of Chemistry, Cardiff University, Park Place, Cardiff, CF10 3AT Wales, UK
| | - Amalie Povlsen
- Department of Chemistry & iNANO, Aarhus University, Aarhus C-8000, Denmark.
| | | | | | - Frederik H Gjørup
- Department of Chemistry & iNANO, Aarhus University, Aarhus C-8000, Denmark.
| | - Mogens Christensen
- Department of Chemistry & iNANO, Aarhus University, Aarhus C-8000, Denmark.
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Natali M, Tamburini S, Bertani R, Desideri D, Mozzon M, Pavarin D, Spizzo F, Del Bianco L, Zorzi F, Sgarbossa P. Novel Magnetic Inorganic Composites: Synthesis and Characterization. Polymers (Basel) 2021; 13:1284. [PMID: 33920795 PMCID: PMC8071178 DOI: 10.3390/polym13081284] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2021] [Revised: 04/11/2021] [Accepted: 04/13/2021] [Indexed: 12/24/2022] Open
Abstract
The addition of magnetic particles to inorganic matrices can produce new composites exhibiting intriguing properties for practical applications. It has been previously reported that the addition of magnetite to concrete improves its mechanical properties and durability in terms of water and chloride ions absorption. Here we describe the preparation of novel magnetic geopolymers based on two different matrices (G1 without inert aggregates and G2 with inert quartz aggregates) containing commercial SrFe12O19 particles with two weight concentrations, 6% and 11%. The composites' characterization, including chemical, structural, morphological, and mechanical determinations together with magnetic and electrical measurements, was carried out. The magnetic study revealed that, on average, the SrFe12O19 magnetic particles can be relatively well dispersed in the inorganic matrix. A substantial increase in the composite samples' remanent magnetization was obtained by embedding in the geopolymer SrFe12O19 anisotropic particles at a high concentration under the action of an external magnetic field during the solidification process. The new composites exhibit good mechanical properties (as compressive strength), higher than those reported for high weight concretes bearing a similar content of magnetite. The impedance measurements indicate that the electrical resistance is mainly controlled by the matrix's chemical composition and can be used to evaluate the geopolymerization degree.
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Affiliation(s)
- Marco Natali
- ICMATE, CNR, Corso Stati Uniti 4, 35127 Padova, Italy; (M.N.); (S.T.)
| | - Sergio Tamburini
- ICMATE, CNR, Corso Stati Uniti 4, 35127 Padova, Italy; (M.N.); (S.T.)
| | - Roberta Bertani
- Department of Industrial Engineering, University of Padova, Via Marzolo 9 (P.S., R.B., M.M.), Via Gradenigo 6/a (D.D.) and Via Venezia 1 (D.P.), 35131 Padova, Italy; (R.B.); (D.D.); (M.M.); (D.P.)
| | - Daniele Desideri
- Department of Industrial Engineering, University of Padova, Via Marzolo 9 (P.S., R.B., M.M.), Via Gradenigo 6/a (D.D.) and Via Venezia 1 (D.P.), 35131 Padova, Italy; (R.B.); (D.D.); (M.M.); (D.P.)
| | - Mirto Mozzon
- Department of Industrial Engineering, University of Padova, Via Marzolo 9 (P.S., R.B., M.M.), Via Gradenigo 6/a (D.D.) and Via Venezia 1 (D.P.), 35131 Padova, Italy; (R.B.); (D.D.); (M.M.); (D.P.)
| | - Daniele Pavarin
- Department of Industrial Engineering, University of Padova, Via Marzolo 9 (P.S., R.B., M.M.), Via Gradenigo 6/a (D.D.) and Via Venezia 1 (D.P.), 35131 Padova, Italy; (R.B.); (D.D.); (M.M.); (D.P.)
| | - Federico Spizzo
- Department of Physics and Earth Science, Polo Scientifico Tecnologico, University of Ferrara, Via G. Saragat 1, 44122 Ferrara, Italy; (F.S.); (L.D.B.)
| | - Lucia Del Bianco
- Department of Physics and Earth Science, Polo Scientifico Tecnologico, University of Ferrara, Via G. Saragat 1, 44122 Ferrara, Italy; (F.S.); (L.D.B.)
| | | | - Paolo Sgarbossa
- Department of Industrial Engineering, University of Padova, Via Marzolo 9 (P.S., R.B., M.M.), Via Gradenigo 6/a (D.D.) and Via Venezia 1 (D.P.), 35131 Padova, Italy; (R.B.); (D.D.); (M.M.); (D.P.)
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Saura-Múzquiz M, Eikeland AZ, Stingaciu M, Andersen HL, Granados-Miralles C, Avdeev M, Luzin V, Christensen M. Elucidating the relationship between nanoparticle morphology, nuclear/magnetic texture and magnetic performance of sintered SrFe 12O 19 magnets. NANOSCALE 2020; 12:9481-9494. [PMID: 32347264 DOI: 10.1039/d0nr01728k] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Several M-type SrFe12O19 nanoparticle samples with different morphologies have been synthesized by different hydrothermal and sol-gel synthesis methods. Combined Rietveld refinements of neutron and X-ray powder diffraction data with a constrained structural model reveal a clear correlation between crystallite size and long-range magnetic order, which influences the macroscopic magnetic properties of the sample. The tailor-made powder samples were compacted into dense bulk magnets (>90% of the theoretical density) by spark plasma sintering (SPS). Powder diffraction as well as X-ray and neutron pole figure measurements and analyses have been carried out on the compacted specimens in order to characterize the nuclear (structural) and magnetic alignment of the crystallites within the dense magnets. The obtained results, combined with macroscopic magnetic measurements, reveal a direct influence of the nanoparticle morphology on the self-induced texture, crystallite growth during compaction and macroscopic magnetic performance. An increasing diameter-to-thickness aspect ratio of the platelet-like nanoparticles leads to increasing degree of crystallite alignment achieved by SPS. Consequently, magnetically aligned, highly dense magnets with excellent magnetic performance (30(3) kJ m-3) are obtained solely by nanostructuring means, without application of an external magnetic field before or during compaction. The demonstrated control over nanoparticle morphology and, in turn, crystal and magnetic texture is a key step on the way to designing nanostructured hexaferrite magnets with optimized performance.
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Affiliation(s)
- Matilde Saura-Múzquiz
- Center for Materials Crystallography, Department of Chemistry and iNANO, Aarhus University, Langelandsgade 140, DK-8000 Aarhus C, Denmark. and Australian Nuclear Science and Technology Organisation (ANSTO), New Illawarra Road, Lucas Heights, NSW 2234, Australia
| | - Anna Zink Eikeland
- Center for Materials Crystallography, Department of Chemistry and iNANO, Aarhus University, Langelandsgade 140, DK-8000 Aarhus C, Denmark.
| | - Marian Stingaciu
- Center for Materials Crystallography, Department of Chemistry and iNANO, Aarhus University, Langelandsgade 140, DK-8000 Aarhus C, Denmark.
| | - Henrik Lyder Andersen
- Center for Materials Crystallography, Department of Chemistry and iNANO, Aarhus University, Langelandsgade 140, DK-8000 Aarhus C, Denmark.
| | - Cecilia Granados-Miralles
- Center for Materials Crystallography, Department of Chemistry and iNANO, Aarhus University, Langelandsgade 140, DK-8000 Aarhus C, Denmark.
| | - Maxim Avdeev
- Australian Nuclear Science and Technology Organisation (ANSTO), New Illawarra Road, Lucas Heights, NSW 2234, Australia
| | - Vladimir Luzin
- Australian Nuclear Science and Technology Organisation (ANSTO), New Illawarra Road, Lucas Heights, NSW 2234, Australia
| | - Mogens Christensen
- Center for Materials Crystallography, Department of Chemistry and iNANO, Aarhus University, Langelandsgade 140, DK-8000 Aarhus C, Denmark.
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