23 results on '"Peddis, Davide"'
Search Results
2. Advancements in polyol synthesis: expanding chemical horizons and Néel temperature tuning of CoO nanoparticles.
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Baričić, Miran, Nuñez, Jorge M., Aguirre, Myriam H., Hrabovsky, David, Seydou, Mahamadou, Meneghini, Carlo, Peddis, Davide, and Ammar, Souad
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CHEMICAL synthesis ,TEMPERATURE control ,NANOPARTICLES ,MAGNETIC properties ,DIETHYLENE glycol ,HAWKING radiation - Abstract
The polyol synthesis of CoO nanoparticles (NPs) is typically conducted by dissolving and heating cobalt acetate tetrahydrate and water in diethylene glycol (DEG). This process yields aggregates of approximately 100 nm made of partially aligned primary crystals. However, the synthesis demands careful temperature control to allow the nucleation of CoO while simultaneously preventing reduction, caused by the activity of DEG. This restriction hinders the flexibility to freely adjust synthesis conditions, impeding the ability to obtain particles with varied morpho-structural properties, which, in turn, directly impact chemical and physical attributes. In this context, the growth of CoO NPs in polyol was studied focusing on the effect of the polyol chain length and the synthesis temperature at two different water/cations ratios. During this investigation, we found that longer polyol chains remove the previous limits of the method, allowing the tuning of aggregate size (20–150 nm), shape (spherical-octahedral), and crystalline length (8–35 nm). Regarding the characterization, our focus revolved around investigating the magnetic properties inherent in the synthesized products. From this point of view, two pivotal findings emerged. Firstly, we identified small quantities of a layered hydroxide ferromagnetic intermediate, which acted as interference in our measurements. This intermediate exhibited magnetic properties consistent with features observed in other publications on CoO produced in systems compatible with the intermediate formation. Optimal synthetic conditions that prevent the impurity from forming were found. This resolution clarifies several ambiguities existing in literature about CoO low-temperature magnetic behavior. Secondly, a regular relationship of the NPs' T
N with their crystallite size was found, allowing us to regulate TN over ~ 80 K. For the first time, a branching was found in this structure-dependent magnetic feature, with samples of spheroidal morphology consistently having lower magnetic temperatures, when compared to samples with faceted/octahedral shape, providing compelling evidence for a novel physical parameter influencing the TN of a material. These two findings contribute to the understanding of the fundamental properties of CoO and antiferromagnetic materials. [ABSTRACT FROM AUTHOR]- Published
- 2024
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3. Iron Oxide Nanoparticle-Assisted Delamination of Ti 3 C 2 T x MXenes: A New Approach to Produce Magnetic MXene-Based Composites.
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Sobolev, Kirill, Omelyanchik, Alexander, Shilov, Nikolai, Gorshenkov, Mikhail, Andreev, Nikolai, Comite, Antonio, Slimani, Sawssen, Peddis, Davide, Ovchenkov, Yevgeniy, Vasiliev, Alexander, Magomedov, Kurban E., and Rodionova, Valeria
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FERRIC oxide ,IRON oxide nanoparticles ,IRON oxides ,MAGNETIC nanoparticles ,MAGNETIC materials ,MAGNETIC properties - Abstract
Ti
3 C2 Tx MXene is one of the most comprehensively studied 2D materials in terms of its adsorptive, transport, and catalytic properties, cytotoxic performance, etc. Still, conventional MXene synthesis approaches provide low single-flake MXene yield and frequently uncontrollable properties, demanding further post-processing. The MXene family also lacks magnetism, which is helpful for producing effective nanoadsorbents as their magnetic decantation is the cheapest and most convenient way to remove the spent adsorbent from water. Composite materials consisting of magnetic nanoparticles grown on top of MXene flakes are commonly used to provide magnetic properties to the resulting nanocomposite. In this paper, we study the possibility to delaminate multilayer Ti3 C2 Tx MXene sheets directly by growing iron oxide magnetic nanoparticles inside their interlayer spacing. We find out that, with a mass fraction of particles comparable or exceeding that of MXenes, their growth is accompanied by an effective enhancement of single-layer MXene yield and suitable magnetic properties of the resulting composite. The developed approach can be further used for simplifying synthesis protocols to obtain magnetic MXene-based nanoadsorbents with tunable properties. [ABSTRACT FROM AUTHOR]- Published
- 2024
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4. The Boundary Between Volume and Surface-Driven Magnetic Properties in Spinel Iron Oxide Nanoparticles.
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Muscas, Giuseppe, Congiu, Francesco, Concas, Giorgio, Cannas, Carla, Mameli, Valentina, Yaacoub, Nader, Hassan, Rodaina Sayed, Fiorani, Dino, Slimani, Sawssen, and Peddis, Davide
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MAGNETIC properties ,IRON oxide nanoparticles ,MAGNETIC structure ,MAGNETIC anisotropy ,SPINEL ,MAGNETIC control ,IRON oxides ,SPINEL group - Abstract
Despite modern preparation techniques offer the opportunity to tailor the composition, size, and shape of magnetic nanoparticles, understanding and hence controlling the magnetic properties of such entities remains a challenging task, due to the complex interplay between the volume-related properties and the phenomena occurring at the particle's surface. The present work investigates spinel iron oxide nanoparticles as a model system to quantitatively analyze the crossover between the bulk and the surface-dominated magnetic regimes. The magnetic properties of ensembles of nanoparticles with an average size in the range of 5–13 nm are compared. The role of surface anisotropy and the effect of oleic acid, one of the most common and versatile organic coatings, are discussed. The structural and morphological properties are investigated by X-ray diffraction and transmission electron microscopy. The size dependence of the surface contribution to the effective particle anisotropy and the magnetic structure are analyzed by magnetization measurements and in-field Mössbauer spectrometry. The structural data combined with magnetometry and Mössbauer spectrometry analysis are used to shed light on this complex scenario revealing a crossover between volume and surface-driven properties in the range of 5–7 nm. [ABSTRACT FROM AUTHOR]
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- 2022
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5. Magnetic Properties of Bi-Magnetic Core/Shell Nanoparticles: The Case of Thin Shells.
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Omelyanchik, Alexander, Villa, Silvia, Singh, Gurvinder, Rodionova, Valeria, Laureti, Sara, Canepa, Fabio, and Peddis, Davide
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MAGNETIC properties ,MAGNETIC cores ,ELECTRON microscopy ,MAGNETIC nanoparticles ,DECOMPOSITION method - Abstract
Bi-magnetic core/shell nanoparticles were synthesized by a two-step high-temperature decomposition method of metal acetylacetonate salts. Transmission electron microscopy confirmed the formation of an ultrathin shell (~0.6 nm) of NiO and NiFe
2 O4 around the magnetically hard 8 nm CoFe2O4 core nanoparticle. Magnetization measurements showed an increase in the coercivity of the single-phase CoFe2 O4 seed nanoparticles from ~1.2 T to ~1.5 T and to ~2.0 T for CoFe2 O4 /NiFe2 O4 and CoFe2O4/NiO, respectively. The NiFe2 O4 shell also increases the magnetic volume of particles and the dipolar interparticle interactions. In contrast, the NiO shell prevents such interactions and keeps the magnetic volume almost unchanged. [ABSTRACT FROM AUTHOR]- Published
- 2021
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6. Optimizing the magnetic properties of hard and soft materials for producing exchange spring permanent magnets.
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Petrecca, Michele, Muzzi, Beatrice, Oliveri, Stefano Maria, Albino, Martin, Yaacoub, Nader, Peddis, Davide, de Julián Fernández, César, Innocenti, Claudia, and Sangregorio, Claudio
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MAGNETIC properties ,HARD materials ,PERMANENT magnets ,ZINC ferrites ,SOFT magnetic materials ,COMMODITY exchanges ,MAGNETS - Abstract
The exploitation of the exchange coupling between hard and soft magnetic materials has been proposed for enhancing the magnetic performances of rare-earth free permanent magnets, with the aim of extending their use to all applications where moderate energy product (35–100 kJ m
−3 ) is required. Strontium hexaferrite (SFO)/spinel ferrite composites seem particularly promising to achieve this target, although the conditions to maximize the effect while using techniques easily scalable to industrial production have not yet been identified. Within this framework, the optimization of the structural, chemical, and magnetic properties of the two moieties before the coupling procedure is crucial to enhance the energy product of the final composite. Here we report the syntheses of both nanometric SFO with high coercivity (ca. 525 kA m−1 ) and quasi-bulk saturation magnetization (68 Am2 kg−1 ) and a series of nanosized zinc-doped ferrite (Znx Fe3−x O4 , 0.0 ⩽ x ⩽ 0.4) through cheap, easily scalable and eco-friendly approaches. The structural and chemical stability of the two magnetic phases as a function of temperature were investigated up to 1100 °C, with the aim of finding the best compromise between preservation of the nanometric scale and magnetic properties. A very high-magnetization (106 Am2 kg−1 ) ferrite was obtained by annealing Zn0.3 Fe2.7 O4 nanopowder at the highest investigated temperature. A preliminary attempt at coupling the two phases, starting from a mixture of the nanopowders, was performed through a classic annealing process in the temperature range 500 °C–1100 °C. The adopted procedure allowed for obtaining an exchange coupled composite at 1100 °C where the two phases are intimately and homogeneously mixed, with micrometric (0.3–5 μm) and nanometric (up to 50 nm) spinel ferrite particles. Despite these promising results, no enhancement of the energy product was found, highlighting the need for further experimental efforts to improve the coupling procedure. [ABSTRACT FROM AUTHOR]- Published
- 2021
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7. Towards bi-magnetic nanocomposites as permanent magnets through the optimization of the synthesis and magnetic properties of SrFe12O19 nanocrystallites.
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Maltoni, Pierfrancesco, Sarkar, Tapati, Varvaro, Gaspare, Barucca, Gianni, Ivanov, Sergey A, Peddis, Davide, and Mathieu, Roland
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MAGNETIC properties ,MAGNETIC anisotropy ,MAGNETIC measurements ,X-ray powder diffraction ,NANOCOMPOSITE materials ,MAGNETS ,PERMANENT magnets - Abstract
Sol–gel synthesis was used in order to obtain nanocrystallites of the SrFe
12 O19 (SFO) hexaferrite in an efficient and reliable way. By optimizing the initial synthetic conditions, we were able to control the size of the nanoparticles (NPs), at lower annealing temperature. The x-ray powder diffraction, transmission electron microscopy (TEM), and magnetic measurements have demonstrated a significant relation between the morphology, size, and magnetic properties of the nanoscale SFO, revealing a definite dependence on the crystallite size along the c-axis. The obtained NPs appear almost isotropic, in the form of platelets and exhibit similar magnetic performance, in terms of the energy product (BH)MAX , thus, demonstrating the suitability of reducing the annealing temperature without any deterioration in the magnetic properties. Additionally, this work illustrates the feasibility of the sol–gel bottom-up approach to employ magnetic NPs as building-blocks for designing hard/soft exchange-coupled bi-magnetic nanocomposites, combining the high coercivity of a hard phase (SFO) and the high saturation magnetization of a soft phase (CoFe2 O4 ); in this regard, we discuss the tunability of the magnetic anisotropy by symbiotically restricting the growth of both phases. [ABSTRACT FROM AUTHOR]- Published
- 2021
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8. High Magnetic Coercivity in Nanostructured Mn3O4 Thin Films Obtained by Chemical Vapor Deposition.
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Bigiani, Lorenzo, Hassan, Mariam, Peddis, Davide, Maccato, Chiara, Varvaro, Gaspare, Sada, Cinzia, Bontempi, Elza, Martí-Sánchez, Sara, Arbiol, Jordi, and Barreca, Davide
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- 2019
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9. Efficiency in Ofloxacin Antibiotic Water Remediation by Magnetic Zeolites Formed Combining Pure Sources and Wastes.
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Belviso, Claudia, Guerra, Giulia, Abdolrahimi, Maryam, Peddis, Davide, Maraschi, Federica, Cavalcante, Francesco, Ferretti, Maurizio, Martucci, Annalisa, and Sturini, Michela
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FLY ash ,IRON oxide nanoparticles ,SODALITE ,ANTIBIOTICS ,WASTE products ,SYNTHETIC products ,FERULIC acid - Abstract
In this work, red mud (RM) and spinel iron oxide nanoparticles (SPIONs) were added to pure silica/alumina sources (SAs) and fly ash (FA) with the aim of synthesizing and investigating the magnetic behavior of different zeolites. SAs were used to synthesize zeolite with LTA topology (zeolite A) with the addition of both red mud and spinel iron oxide nanoparticles. FA and RM were mixed to synthesize sodalite whereas only FA with the addition of SPIONs was used to form zeolite with FAU-topology (zeolite X). All the synthetic products showed magnetic properties. However, zeolites with spinel iron oxide nanoparticles (zeolites A and X) showed ferromagnetic-like behavior. Sodalite was characterized by a reduction in saturation magnetization, whereas zeolite A with red mud displayed antiferromagnetic behavior. For the first time, all the synthetic products were tested for polluted water remediation by a persistent emerging contaminant, ofloxacin (OFL) antibiotic. The four zeolite types showed good adsorption affinity towards OFL under actual conditions (tap water, natural pH). All materials were also tested for OFL removal in real waters spiked with OFL 10 µg L
−1 . Satisfactory recoveries (90–92% in tap water, 83–87% in river water) were obtained for the two zeolites synthesized from industrial waste materials. [ABSTRACT FROM AUTHOR]- Published
- 2021
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10. Magnetism of Nanoparticles: Effect of the Organic Coating.
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Abdolrahimi, Maryam, Vasilakaki, Marianna, Slimani, Sawssen, Ntallis, Nikolaos, Varvaro, Gaspare, Laureti, Sara, Meneghini, Carlo, Trohidou, Kalliopi N., Fiorani, Dino, and Peddis, Davide
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ORGANIC coatings ,MAGNETISM ,MAGNETIC nanoparticles ,SURFACE structure ,MAGNETIC properties - Abstract
The design of novel multifunctional materials based on nanoparticles requires tuning of their magnetic properties, which are strongly dependent on the surface structure. The organic coating represents a unique tool to significantly modify the surface structure trough the bonds between the ligands of the organic molecule and the surface metal atoms. This work presents a critical overview of the effects of the organic coating on the magnetic properties of nanoparticles trough a selection of papers focused on different approaches to control the surface structure and the morphology of nanoparticles' assemblies. [ABSTRACT FROM AUTHOR]
- Published
- 2021
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11. Green Synthesis of Co-Zn Spinel Ferrite Nanoparticles: Magnetic and Intrinsic Antimicrobial Properties.
- Author
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Omelyanchik, Alexander, Levada, Kateryna, Pshenichnikov, Stanislav, Abdolrahim, Maryam, Baricic, Miran, Kapitunova, Anastasiya, Galieva, Alima, Sukhikh, Stanislav, Astakhova, Lidiia, Antipov, Sergey, Fabiano, Bruno, Peddis, Davide, and Rodionova, Valeria
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MAGNETIC nanoparticles ,MAGNETIC structure ,FERRITES ,MAGNETIC properties ,ZINC ferrites ,SPINEL ,NANOPARTICLES - Abstract
Spinel ferrite magnetic nanoparticles have attracted considerable attention because of their high and flexible magnetic properties and biocompatibility. In this work, a set of magnetic nanoparticles of cobalt ferrite doped with zinc was synthesized via the eco-friendly sol-gel auto-combustion method. Obtained particles displayed a room-temperature ferromagnetic behavior with tuned by chemical composition values of saturation magnetization and coercivity. The maximal values of saturation magnetization ~74 Am
2 /kg were found in cobalt ferrite nanoparticles with a 15–35% molar fraction of cobalt replaced by zinc ions. At the same time, the coercivity exhibited a gradually diminishing trend from ~140 to ~5 mT whereas the concentration of zinc was increased from 0 to 100%. Consequently, nanoparticles produced by the proposed method possess highly adjustable magnetic properties to satisfy the requirement of a wide range of possible applications. Further prepared nanoparticles were tested with bacterial culture to display the influence of chemical composition and magnetic structure on nanoparticles-bacterial cell interaction. [ABSTRACT FROM AUTHOR]- Published
- 2020
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12. Obsidian as a Raw Material for Eco-Friendly Synthesis of Magnetic Zeolites.
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Belviso, Claudia, Peddis, Davide, Varvaro, Gaspare, Abdolrahimi, Maryam, Reverberi, Andrea Pietro, and Cavalcante, Francesco
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OBSIDIAN , *RAW materials , *ZEOLITES , *MAGNETIC separation , *SCANNING electron microscopy , *MAGNETIC properties , *SONICATION - Abstract
A sample of rhyolitic obsidian (OS) was used as raw material for zeolite synthesis by long (4 days) and fast (2 h)-aging hydrothermal processes. Zeolite synthesis was also performed by a fast (2 h) sonication method. The products were analysed by X-ray diffraction (XRD) and scanning electron microscopy (SEM) both immediately after and 3 years after their formation in order to determine the stability of synthetic materials according to the method used. The results confirm zeolitization of obsidian both by long-aging conventional hydrothermal heating and fast hydrothermal process. However, the data highlight the efficiency of direct ultrasound energy in achieving more stable zeolite crystals over time. These results carried out using a natural source, follow those already obtained using wastes and pure sources as raw materials thus providing a definitive validation of the different mechanisms controlling zeolite formation according to the process used. Moreover, the results confirm the effectiveness of ultrasonic energy in the formation of zeolites that are more stable over time. Due to the chemical composition of the obsidian precursor, all synthetic zeolites show good magnetic properties (i.e., saturation magnetization), in view to potential magnetic separation. [ABSTRACT FROM AUTHOR]
- Published
- 2020
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13. Magnetocrystalline and Surface Anisotropy in CoFe2O4 Nanoparticles.
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Omelyanchik, Alexander, Salvador, María, D'Orazio, Franco, Mameli, Valentina, Cannas, Carla, Fiorani, Dino, Musinu, Anna, Rivas, Montserrat, Rodionova, Valeria, Varvaro, Gaspare, and Peddis, Davide
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MAGNETIC anisotropy ,MAGNETIC properties ,FERRITES ,NANOPARTICLES ,SILICA ,MAGNETIZATION ,ANNEALING of metals - Abstract
The effect of the annealing temperature T
ann on the magnetic properties of cobalt ferrite nanoparticles embedded in an amorphous silica matrix (CoFe2 O4 /SiO2 ), synthesized by a sol-gel auto-combustion method, was investigated by magnetization and AC susceptibility measurements. For samples with 15% w/w nanoparticle concentration, the particle size increases from ~2.5 to ~7 nm, increasing Tann from 700 to 900 °C. The effective magnetic anisotropy constant (Keff ) increases with decreasing Tann , due to the increase in the surface contribution. For a 5% w/w sample annealed at 900 °C, Keff is much larger (1.7 × 106 J/m3 ) than that of the 15% w/w sample (7.5 × 105 J/m3 ) annealed at 700 °C and showing comparable particle size. This indicates that the effect of the annealing temperature on the anisotropy is not only the control of the particle size but also on the core structure (i.e., cation distribution between the two spinel sublattices and degree of spin canting), strongly affecting the magnetocrystalline anisotropy. The results provide evidence that the magnetic anisotropy comes from a complex balance between core and surface contributions that can be controlled by thermal treatments. [ABSTRACT FROM AUTHOR]- Published
- 2020
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14. Magnetic Interactions: a Tool to Modify the Magnetic Properties of Materials Based on Nanoparticles.
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Peddis, Davide, Joensson, Petra F., Laureti, Sara, and Varvaro, Gaspare
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MAGNETIC properties , *NANOPARTICLES - Abstract
Review: 190 refs. [ABSTRACT FROM AUTHOR]
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- 2015
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15. Magnetic properties of ε iron(III) oxide nanorod arrays functionalized with gold and copper(II) oxide.
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Maccato, Chiara, Carraro, Giorgio, Peddis, Davide, Varvaro, Gaspare, and Barreca, Davide
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IRON oxide nanoparticles , *CHEMICAL vapor deposition , *RADIO frequency , *COPPER oxide , *GOLD oxide - Abstract
A sequential Chemical Vapor Deposition (CVD) – Radio Frequency (RF)-sputtering approach was adopted to fabricate supported nanocomposites based on the scarcely investigated ε-iron(III) oxide polymorph. In particular, ε-Fe 2 O 3 nanorod arrays were obtained by CVD, and their subsequent functionalization with Au and CuO nanoparticles (NPs) was carried out by RF-sputtering under mild operational conditions. Beside a multi-technique characterization of material structure, morphology and chemical composition, particular efforts were dedicated to the investigation of their magnetic properties. The pertaining experimental data, discussed in relation to the system chemico-physical characteristics, are directly dependent on the actual chemical composition, as well as on the spatial distribution of Au and CuO nanoparticles. The approach adopted herein can be further implemented to control and tailor different morphologies and phase compositions of iron oxide-based nanomaterials, meeting thus the open requests of a variety of technological utilizations. [ABSTRACT FROM AUTHOR]
- Published
- 2018
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16. Magnetic properties of bauxites and pre-fused hydrothermal product (zeolite).
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Belviso, Claudia, Abdolrahimi, Maryam, Lettino, Antonio, Cavalcante, Francesco, and Peddis, Davide
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MAGNETIC properties , *BAUXITE , *ALUMINUM ores , *SYNTHETIC products , *WEATHERING , *ZEOLITES , *IRON oxides - Abstract
Bauxites are deposits rich in aluminium and iron oxides/hydroxides, formed by the weathering of aluminosilicates rocks under warm and humid conditions. Due to their mineralogical composition, bauxites represent the primary source for aluminum and, subordinately, iron production. However, these sediments rich in Si and Al can be also used as raw material for the synthesis of zeolite with magnetic properties thanks to the high availability of Fe. In this work, three bauxite samples collected from Upper Cretaceous deposits of southern Italy were characterized for their magnetic parameters and used for the synthesis of zeolite with LTA topology (zeolite A). The results indicate differences in antiferromagnetic behaviour among the three raw materials. All the synthetic products, instead, display the same antiferromagnetic behaviour thus suggesting that the method used for the zeolite crystallization neutralizes the parameters responsible for raw bauxite magnetic differences. [Display omitted] • Bauxites are deposits rich in aluminium and iron oxides/hydroxides; • Three bauxite samples were used as sources for magnetic LTA zeolite synthesis; • The three raw materials showed differences in antiferromagnetic behaviour; • The synthetic products displayed the same antiferromagnetic behaviour; • Pre-fused NaOH treatment neutralizes raw materials compositional differences. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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17. Surfactant-assisted route to fabricate CoFe2O4 individual nanoparticles and spherical assemblies
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Cannas, Carla, Ardu, Andrea, Peddis, Davide, Sangregorio, Claudio, Piccaluga, Giorgio, and Musinu, Anna
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SURFACE active agents , *MICROFABRICATION , *COBALT compounds , *FERRITES , *NANOCRYSTALS , *SURFACE area , *POROUS materials , *TRANSMISSION electron microscopy - Abstract
Abstract: A surfactant-assisted route in aqueous media has been shown to be suitable to prepare either individual primary CoFe2O4 nanocrystals or secondary spherical nanoporous assemblies with a high surface area. The formation of primary nanoparticles or of spherical assemblies is found to be dependent on the presence of the surfactant and on the particle size, but is shown that the nanoparticle–surfactant interface plays a dominant role. The size of the primary CoFe2O4 particles is controlled by the type of salt, the synthesis temperature and the concentration of the precursors. A detailed characterization evidences the shape and size of the primary particles, the way in which the primary particles assemble and their features in terms of morphological, textural and magnetic properties. [Copyright &y& Elsevier]
- Published
- 2010
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18. High magnetic coercivity in nanostructured Mn3O4 thin films obtained by chemical vapor deposition
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Sara Martí-Sánchez, Elza Bontempi, Chiara Maccato, Gaspare Varvaro, Cinzia Sada, Mariam Hassan, Jordi Arbiol, Davide Peddis, Davide Barreca, Lorenzo Bigiani, Università degli Studi di Padova, Agencia Estatal de Investigación (España), Ministerio de Ciencia, Innovación y Universidades (España), Generalitat de Catalunya, Bigiani, Lorenzo [0000-0003-4283-1489], Hassan, Marian [0000-0002-8592-5672], Peddis, Davide [0000-0003-0810-8860], Maccato, Chiara [0000-0001-6368-5754], Varvaro, Gaspare [0000-0001-7313-7268], Sada, Cinzia [0000-0002-7607-0481], Bontempi, Elza [0000-0003-1656-7506], Martí-Sànchez, Sara [0000-0003-4283-1489], Arbiol, Jordi [0000-0002-0695-1726], Barreca, Davide [0000-0002-8779-3386], Bigiani, Lorenzo, Hassan, Marian, Peddis, Davide, Maccato, Chiara, Varvaro, Gaspare, Sada, Cinzia, Bontempi, Elza, Martí-Sànchez, Sara, Arbiol, Jordi, and Barreca, Davide
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Chemical vapour deposition ,Materials science ,Thin films ,Chemical vapor deposition ,Coercivity ,Mn ,chemical vapor deposition ,Mn3O4 ,Chemical engineering ,thin films ,Magnetic properties ,General Materials Science ,magnetic properties ,coercivity ,Thin film ,3 ,O ,4 - Abstract
Nanostructured α-Mn3O4 (haussmannite) thin films consisting of evenly interconnected nanoaggregates were prepared on Si(100) substrates by chemical vapor deposition from a Mn(II) diketonate-diamine precursor under different reaction atmospheres (dry vs wet O2) and total operating pressures. The combination of chemico-physical results obtained by the joint use of complementary techniques enabled us to demonstrate the obtainment of high-purity Mn3O4 materials free from other manganese oxide phases, characterized by controllable structural and morphological characteristics as a function of the adopted processing conditions. Magnetic properties were investigated by analyzing temperature dependence (i.e., field-cooled and zero-field-cooled measurements) and field-dependence of the magnetization behavior. The obtained films show bulk-like magnetic properties, together with extraordinarily high low-temperature in-plane coercivities (up to ∼1 T). The possibility to tailor these values by varying the content of microstructural defects may foster the implementation of the obtained films in eventual technological applications., The authors thank Padova University DOR 2016–2018 and P-DiSC #03BIRD2016-UNIPD projects. Funding from Generalitat de Catalunya 2017 SGR 327, the Spanish MINECO ENE2017-85087-C3-3-R, and Severo Ochoa Program SEV-2017-0706, as well as CERCA Programme/Generalitat de Catalunya is also acknowledged.
- Published
- 2019
19. Synthesis of phase-pure highly-doped MAX-phase (Cr1-xMnx)2AlC.
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Sobolev, Kirill, Gorshenkov, Mikhail, Manfrinetti, Pietro, Peddis, Davide, Pazniak, Anna, and Rodionova, Valeria
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BULK solids , *DOPING agents (Chemistry) , *MAGNETIC properties , *ACID solutions , *MANGANESE , *HYDROFLUORIC acid , *PEROVSKITE - Abstract
Mn doped (Cr 1-x Mn x) 2 AlC compounds constitute a family of MAX-phases of great interest due to the possibility of tuning the magnetic properties they possess. Their synthesis, however, is not an easy task. Two main issues make its preparation difficult. First is the strong tendency secondary phases have to segregate when manganese is added to the parent compound and, secondly, the resulting doping level which remains relatively low due to the poor incorporation of Mn atoms into the MAX-phase hexagonal structure [Cr 2 AlC-type]. In the present work the highest dopant concentration so far reported for bulk materials of 18.3 at.% Mn has been obtained through the exploitation of the arc-melting technique. At the same time, the use of the Cr 3 C 2 , as a precursor from the initial stage of the synthesis procedure, led to the preservation of the phase content in the Mn-doped samples. Finally, chemical post-treatment in acid solutions (HF, HCl) proved to be effective and helpful to dissolve the remaining secondary intermetallic phases; the final material resulting in a pure MAX-phase powder (>99 vol%). However, the doping level reached seems to be the limit for the arc fusion technique used; additional manganese no longer dissolves into the MAX-phase structure but tends to form some new Mn-based secondary phases, such as the perovskite Mn 3 AlC and the carbide MnC 2. After the chemical etching, pure MAX-phase powders can be compacted into bulk using spark plasma sintering technique. However, while this method is useful for the non-doped Cr 2 AlC, it needs further optimization for (Cr 1-x Mn x) 2 AlC as it leads to a partial decomposition of Mn-containing MAX-phase. [ABSTRACT FROM AUTHOR]
- Published
- 2021
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20. Tunable magnetic properties of Ni-doped CoFe2O4 nanoparticles prepared by the sol–gel citrate self-combustion method.
- Author
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Omelyanchik, Alexander, Singh, Gurvinder, Volochaev, Mikhail, Sokolov, Alexey, Rodionova, Valeria, and Peddis, Davide
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COBALT , *FERRITES , *X-ray diffraction , *MAGNETIC properties , *NANOSTRUCTURED materials - Abstract
Highlights • The obtained samples show relatively high values of M S and H C without any thermal treatment. • Magnetic properties of cobalt ferrite nanoparticle were strongly affected when there are doped with nickel. • The higher value of magnetization saturation was found for the Ni 0.25 Co 0.75 Fe 2 O 4 sample. Abstract The nanostructured spinel ferrites with complex stoichiometry are an important family of the materials in a number of applications, especially in electronics through their good electrical and magnetic properties. In the framework of this study, a set of mixed cobalt and nickel ferrites was prepared with the sol–gel self-combustion route. The structural and morphological features of particles were studied with X-ray diffraction (XRD), Scanning Transmission Electron Microscopy (STEM) and Energy Dispersive X-ray analysis (EDX) techniques. The prepared particles show a crystalline nature with a monotonic distribution of the elements and particles size distribution in the range of 17–29 nm. The obtained particles demonstrate good magnetic properties with tunable saturation magnetization and magnetic anisotropy, i.e., coercivity depending on chemical composition. [ABSTRACT FROM AUTHOR]
- Published
- 2019
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21. Red mud as aluminium source for the synthesis of magnetic zeolite.
- Author
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Belviso, Claudia, Kharchenko, Anastasia, Agostinelli, Elisabetta, Cavalcante, Francesco, Peddis, Davide, Varvaro, Gaspare, Yaacoub, Nader, and Mintova, Svetlana
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CHEMICAL synthesis , *ZEOLITES , *ALUMINATES , *CRYSTALLIZATION , *SILICA gel , *MUD - Abstract
Zeolite synthesis typically requires batch systems (precursor mixture) in which aluminate and silicate solutions are first mixed and then subjected to hydrothermal treatment. In this study, FAU and GIS types zeolite with wool ball-like morphology were synthesized using colloidal silica and red mud as an alternative aluminium source. The addition of aluminium powder to the precursor mixture composed by colloidal silica and red mud resulted in the crystallization of pure GIS-type zeolite with a cactus-like morphology. The crystalline products (GIS and FAU zeolites) were thoroughly characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and nitrogen adsorption. In addition, the magnetic properties of the zeolites were studied since the red mud used as aluminium source is mainly containing a mixture of magnetic iron-based oxides. The magnetic zeolites will be further considered for wastewater treatment, as they can be easily separated using an external magnetic field. [ABSTRACT FROM AUTHOR]
- Published
- 2018
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22. Synthesis of magnetic zeolite at low temperature using a waste material mixture: Fly ash and red mud.
- Author
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Belviso, Claudia, Agostinelli, Elisabetta, Belviso, Sandra, Cavalcante, Francesco, Pascucci, Simone, Peddis, Davide, Varvaro, Gaspare, and Fiore, Saverio
- Subjects
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ZEOLITES , *CHEMICAL synthesis , *WASTE products , *FLY ash , *MAGNETIC nanoparticles , *MAGNETIC properties , *MAGNETIC moments , *CENTRIFUGATION , *SODALITE - Abstract
A low temperature environmentally friendly synthesis of magnetic zeolites by hydrothermal activation is reported. The novelty of the process is related to the use of a mixture of waste materials (fly ash (FA) and red mud (RM)) as precursors for the one-step synthesis (without passing through the additional synthesis of magnetic nanoparticles) of zeolites with good magnetic properties. The structural and magnetic investigation indicated that different types of zeolites were obtained for different FA/RM percentages and incubation temperatures, and all of these zeolites possess sufficiently high magnetic moments to enable their easy separation from the solution using an external magnet. Therefore, the time consuming and expensive high performance centrifugation processes, which are typically employed to recover zeolites, can be eliminated. In detail, sodalite and mixed Ti–Fe oxides formed using the 80% RM mixture, and a higher amount of A-type zeolites was observed for the 50% RM mixture. However, a mixture of A-, X- and ZK-5-type zeolites was obtained using 20% RM. The global magnetic properties of the newly formed minerals are discussed based on the magnetic properties of the precursors in which different magnetic behaviours were observed. A preliminary characterisation of the synthetic products was performed. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
23. Effect of citric acid on the morpho-structural and magnetic properties of ultrasmall iron oxide nanoparticles.
- Author
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Omelyanchik, Alexander, da Silva, Franciscarlos Gomes, Gomide, Guilherme, Kozenkov, Ivan, Depeyrot, Jerome, Aquino, Renata, Campos, Alex Fabiano Cortez, Fiorani, Dino, Peddis, Davide, Rodionova, Valeria, and Jovanović, Sonja
- Subjects
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IRON oxides , *CITRIC acid , *MAGNETIC properties , *IRON oxide nanoparticles , *NANOPARTICLE size , *IRON ions , *COOLING curves - Abstract
• Iron oxide nanoparticles with average sizes ~2, 4, 6 and 8 nm were synthesized by the co-precipitation method. • The particle size was controlled by adding citric acid during the reaction. • The effects of magnetic interaction among particles and of disordered surface in ultrasmall nanoparticles were investigated. • An exchange bias and magnetic memory effects were found in samples with average particle sizes of 2 and 4 nm. The structural and magnetic properties of iron oxide nanoparticles obtained by the precipitation of iron ions in the presence of different amounts of citric acid were studied. The citric acid acts as a capping agent and provides control of the particle size to be obtained. The size dependence of the magnetic properties was investigated by comparing the results for ~2, 4, 6, and 8 nm particles. With decreasing the particle size, a reduction of the saturation magnetization (from ~84 to 33 Am2/kg) and an increase of coercivity (from ~32 to ~100 mT) were observed, due to the increasing role of the disordered surface. The behaviour of the zero-field cooled/field cooled magnetization curves indicates a superspin-glass freezing for 2 nm and 4 nm particle samples. Memory experiments below the freezing temperature on the 2 nm particle sample provide further evidence of a glassy magnetic state. The observation of exchange bias, due to core/shell interface exchange coupling, for 2 nm and 4 nm particle samples provides evidence of a surface spin-glass type freezing, which contributes to the observed glassy properties. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
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