Structure, Thermal and Magnetic Properties of Nanocrystalline Materials

A special issue of Crystals (ISSN 2073-4352). This special issue belongs to the section "Inorganic Crystalline Materials".

Deadline for manuscript submissions: 30 May 2024 | Viewed by 2524

Special Issue Editors


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Guest Editor
Laboratory of Magnetism and Spectroscopy of Solids, Department of Physics, Badji Mokhtar Annaba University, B.P. 12, Annaba 23000, Algeria
Interests: nanocrystalline materials; mechanical alloying; self laser melting; electrodeposition; magnetocaloric effect; XRD; rietveld refinement; magnetic properties; thermal analysis; Mössbauer spectrometry

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Guest Editor
Department of Physics, University of Girona, Campus Montilivi s/n, 17003 Girona, Spain
Interests: powder metallurgy; structural analysis; thermal analysis; mechanical alloying; nanocrystalline
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Special Issue Information

Dear Colleagues,

Nanocrystalline (NC) materials have attracted great attention during the last decades owing to their superior physical, mechanical, magnetic, and electrochemical properties compared to their coarse-grained counterparts due to their small crystallite size and the presence of a large amount of atoms residing in grain boundaries and interfaces. Since the volume fraction of interfaces can reach as much as 50% for 5 nm grains, surfaces and interfaces play a crucial role in controlling the process kinetics at the nanoscale level in many applications in the interdisciplinary fields of energy storage, sensors, drug delivery, functionalization of nanostructures, electrochemistry, etc. NC materials can be prepared by different methods such as mechanical alloying (MA), rapid solidification, sol gel, hydrothermal, spray pyrolysis, electrodeposition, chemical vapour deposition (CVD), physical vapour deposition (PVD), inert gas condensation, spin coating, chemical bath deposition (CBD), etc. Besides, the applications of NC materials are strongly linked to the preparation conditions and methods which have an influence on their atomic arrangements and microscopic characteristics that affects not only the product’s overall attributes, but also their performance and future uses. Hence, to achieve high performance characterization, altering the structure of the materials has an impact on the material’s overall properties. Also, the modification of the morphological and microscopic characteristics of materials leads to noticeable changes in their properties and behaviours. Therefore, it is important to be able to control the structure, microstructure, thermal, mechanical, and magnetic properties of materials.   

This Special Issue deals with structural, microstructural, thermal stability, mechanical, and magnetic characterization of NC. Both reviews and original papers are welcomed for submission.

Prof. Dr. Safia Alleg
Prof. Dr. Joan-Josep Suñol
Guest Editors

Manuscript Submission Information

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Keywords

  • Nanocrystalline materials;
  • Powder alloys;
  • Thin films;
  • Ribbons alloys;
  • Structure;
  • Microstructure;
  • Magnetic properties;
  • Thermal behavior.

Published Papers (3 papers)

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Research

20 pages, 8645 KiB  
Article
Structural, Dielectric, Electrical, and Magnetic Characteristics of Bi0.8Ba0.1Er0.1Fe0.96Cr0.02Mn0.02O3 Nanoparticles
by A. Bougoffa, E. M. Benali, A. Benali, A. Tozri, E. Dhahri, M. P. Graça, M. A. Valente and B. F. O. Costa
Crystals 2024, 14(5), 445; https://doi.org/10.3390/cryst14050445 - 7 May 2024
Viewed by 347
Abstract
Bi0.8Ba0.1Er0.1Fe0.96Cr0.02Mn0.02O3 (BBEFCMO) multiferroic ceramic was synthesized through the sol-gel route. The impact of incorporating various dopants into both A and B sites of the BiFeO3 was investigated, and structural, [...] Read more.
Bi0.8Ba0.1Er0.1Fe0.96Cr0.02Mn0.02O3 (BBEFCMO) multiferroic ceramic was synthesized through the sol-gel route. The impact of incorporating various dopants into both A and B sites of the BiFeO3 was investigated, and structural, Raman, dielectric, electric, and magnetic properties were studied. X-ray diffraction analysis and Raman spectroscopy revealed a rhombohedral structure with the R3c space group for the doped material (BBEFCMO). Dielectric properties were examined across a frequency range of 102–106 Hz. The present multiferroic material exhibits a colossal dielectric constant and minimal dielectric loss tangent, making it suitable for applications in energy storage. Furthermore, the Cole-Cole type of relaxation was deduced from the imaginary part of the modulus for both grain and boundary-grain contributions. Overall, this study indicates that substituting ions in both A and B sites of BiFeO3 significantly enhances its multiferroic properties, as evidenced by dielectric and magnetic measurements. Full article
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14 pages, 3001 KiB  
Article
Nanocrystalline Iron Oxides with Various Average Crystallite Size Investigated Using Magnetic Resonance Method
by Rafał Pelka, Urszula Nowosielecka, Kamila Klimza, Izabela Moszyńska, Konstantinos Aidinis, Grzegorz Żołnierkiewicz, Aleksander Guskos and Nikos Guskos
Crystals 2024, 14(4), 363; https://doi.org/10.3390/cryst14040363 - 11 Apr 2024
Viewed by 581
Abstract
A series of nanocrystalline iron oxide samples (M1–M5) which differ from each other in average crystallite size (from 26 to 37 nm) was studied. The raw material was nanocrystalline iron with an average crystallite size equal to 21 nm promoted with hardly reducible [...] Read more.
A series of nanocrystalline iron oxide samples (M1–M5) which differ from each other in average crystallite size (from 26 to 37 nm) was studied. The raw material was nanocrystalline iron with an average crystallite size equal to 21 nm promoted with hardly reducible oxides: Al2O3, CaO, K2O (in total, max. 10 wt%). Nanocrystalline iron was subjected to oxidation with water vapor to achieve different oxidation degrees (α = 0.16–1.00). Metallic iron remaining in the samples after the oxidizing step was removed by etching. Magnetic resonance spectra of all samples were obtained at room temperature. All resonance lines were asymmetric and intense. These spectra were fitted by Lorentzian and Gaussian functions. All spectral parameters depend on the preparation method of the nanoparticles. We suppose that the Lorentz fit gives us a spectrum from larger agglomerated sizes whereas the Gaussian fit comes from much smaller magnetic centers. For the nanocrystalline samples with the largest size of iron oxide nanocrystallites, the highest value of total integrated intensity was obtained, indicating that at smaller sizes, they are more mobile in reorientation processes resulting in more settings of anti-parallel magnetic moments. The magnetic anisotropy should also increase with the increase in size of nanocrystallites. Full article
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17 pages, 5105 KiB  
Article
Effect of Aluminum Addition on the Microstructure, Magnetic, and Mechanical Properties of FeCrCoNiMn High-Entropy Alloy
by Safia Alleg, Ahlem Bekhouche, Hacene Hachache and Joan Jose Sunol
Crystals 2023, 13(10), 1483; https://doi.org/10.3390/cryst13101483 - 12 Oct 2023
Cited by 4 | Viewed by 1098
Abstract
High-entropy FeCoCrNiMn (C1) and FeCoCrNiMn10Al10 (C2) alloys (HEAs) were mechanically alloyed for 24 h and heated to 900 °C (C1_900 °C and C2_900 °C). The powders were also compacted into pellets (C1_pellet and C2_pellet) and sintered at 500 °C for [...] Read more.
High-entropy FeCoCrNiMn (C1) and FeCoCrNiMn10Al10 (C2) alloys (HEAs) were mechanically alloyed for 24 h and heated to 900 °C (C1_900 °C and C2_900 °C). The powders were also compacted into pellets (C1_pellet and C2_pellet) and sintered at 500 °C for 1 h. Crystal structure, microstructure, magnetic, and mechanical properties were investigated by X-ray diffraction, scanning electron microscopy, vibrating sample magnetometry, and microindentation. During the milling process, a mixture of body-centered-cubic (BCC) and face-centered-cubic (FCC) phases with a crystallite size in the range of 9–13 nm was formed in the C1 HEA alloy. The dual FCC + BCC solid solutions remain for the C1_pellet and transform to a single FCC for the C1_900 °C powders. Al addition stabilizes the BCC structure in the FeCoCrNiMn10Al10 HEA alloy, as revealed by the structural refinement. The structure exhibits a mixture of BCC + FCC solid solutions for the C2 powders and BCC + FCC + CrCo sigma phase for the C2_pellet and C2_900 °C powders. The crystallite sizes are in the range of 6-93 nm for all the samples. The saturation magnetization (Ms), coercivity (Hc), and squareness ratio (Mr/Ms) are estimated to be 24.2 emu/g, 153.62 Oe, and 0.165, respectively, for C1 and 28.45 emu/g, 188.48 Oe, and 0.172 for C2. The C1_900 °C and C2_900 °C powders exhibit, respectively, paramagnetic and soft magnetic behaviors and an exchange bias at room temperature. The C1_pellet and C2_pellet HEAs show high hardness values of 584.85 Hv and 522.52 Hv, respectively. Full article
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Title: Investigations on structural, Magnetic, and dielectric properties of the multiferroic Bi0.8Er0.1Ba0.1Fe0.96Cr0.02Mn0.02O3 nanoparticles.

Authors: Benali, E.M. Benali, A. Bougoffa, M.A. Valente, M.P.F. Graça, B.F.O. Costa.

Abstract:

In the present work, efforts have been made to synthesize the Bi0.8Er0.1Ba0.1Fe0.96Cr0.02Mn0.02O3 nanoparticles via Sol-gel route and were denoted as successful. The structural analysis confirms the distorted rhombohedral structure (the R3C space group) along with some impurities (Bi4O7 and Ba2FeO4). Nanosize criteria of the synthesized material was confirmed through Williamson-Hall formalism and TEM analyses. The alterations in the vibration modes observed in Raman spectra (expansion, reduced intensity, merge, and shift) strongly confirmed the substitution effect on structure. Investigation of magnetic properties reveals that the BEBFCM sample possess high magnetic saturation which was assigned to the Ferromagnetic interactions as result of substitutions. Mössbauer spectroscopy revealed two Fe cations differently coordinated confirming that magnetization results from a coexistence of Ferromagnetic and Antiferromagnetic contributions. Further, the BEBFCM nanoparticles were found to exhibit an important value of maximum energy product (BH)max, which makes them good candidate for permanent magnet applications. Additionally, the BEBFCM sample with giant dielectric constant and low dielectric loss tangent could be an effective candidate for capacitors and dynamic random-access memory applications.

Keywords: multiferroics; magnetism; Mössbauer spectroscopy, dielectric relaxation.

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