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Szatmari A, Bortnic R, Souca G, Hirian R, Barbu-Tudoran L, Nekvapil F, Iacovita C, Burzo E, Dudric R, Tetean R. The Influence of Zn Substitution on Physical Properties of CoFe 2O 4 Nanoparticles. NANOMATERIALS (BASEL, SWITZERLAND) 2022; 13:189. [PMID: 36616099 PMCID: PMC9823853 DOI: 10.3390/nano13010189] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/28/2022] [Revised: 12/23/2022] [Accepted: 12/27/2022] [Indexed: 06/17/2023]
Abstract
Co1−xZnxFe2O4 nanoparticles (0 ≤ x ≤ 1) have been synthesized via a green sol−gel combustion method. The prepared samples were studied using X-ray diffraction measurements (XRD), transmission electron microscopy (TEM), Raman, and magnetic measurements. All samples were found to be single phases and have a cubic Fd-3m structure. EDS analysis confirmed the presence of cobalt, zinc, iron, and oxygen in all studied samples. Raman spectra clearly show that Zn ions are preferentially located in T sites for low Zn concentrations. Due to their high crystallinity, the nanoparticles show high values of the magnetization, which increases with the Zn content for x < 0.5. The magnetic properties are discussed based on Raman results. Co ferrite doped with 30% of Zn produced the largest SAR values, which increase linearly from 148 to 840 W/gMNPs as the H is increased from 20 to 60 kA/m.
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Affiliation(s)
- Adam Szatmari
- Faculty of Physics, “Babes Bolyai” University, Kogalniceanu 1, 400084 Cluj-Napoca, Romania
| | - Rares Bortnic
- Faculty of Physics, “Babes Bolyai” University, Kogalniceanu 1, 400084 Cluj-Napoca, Romania
| | - Gabriela Souca
- Faculty of Physics, “Babes Bolyai” University, Kogalniceanu 1, 400084 Cluj-Napoca, Romania
| | - Razvan Hirian
- Faculty of Physics, “Babes Bolyai” University, Kogalniceanu 1, 400084 Cluj-Napoca, Romania
| | - Lucian Barbu-Tudoran
- Electron Microscopy Center “Prof. C. Craciun”, Faculty of Biology & Geology, “Babes-Bolyai” University, 5-7 Clinicilor St., 400006 Cluj-Napoca, Romania
- Integrated Electron Microscopy Laboratory, National Institute for Research and Development of Isotopic and Molecular Technologies, 67-103 Donat St., 400293 Cluj-Napoca, Romania
| | - Fran Nekvapil
- Faculty of Physics, “Babes Bolyai” University, Kogalniceanu 1, 400084 Cluj-Napoca, Romania
- RDI Laboratory of Applied Raman Spectroscopy, RDI Institute of Applied Natural Sciences (IRDI-ANS), Babeş-Bolyai University, Fântânele 42, 400293 Cluj-Napoca, Romania
| | - Cristian Iacovita
- Department of Pharmaceutical Physics-Biophysics, Faculty of Pharmacy, Iuliu Hatieganu University of Medicine and Pharmacy, 6 Pasteur St., 400349 Cluj-Napoca, Romania
| | - Emil Burzo
- Faculty of Physics, “Babes Bolyai” University, Kogalniceanu 1, 400084 Cluj-Napoca, Romania
| | - Roxana Dudric
- Faculty of Physics, “Babes Bolyai” University, Kogalniceanu 1, 400084 Cluj-Napoca, Romania
| | - Romulus Tetean
- Faculty of Physics, “Babes Bolyai” University, Kogalniceanu 1, 400084 Cluj-Napoca, Romania
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Burzo E, Tetean R. New Insights on the Spin Glass Behavior in Ferrites Nanoparticles. NANOMATERIALS 2022; 12:nano12101782. [PMID: 35631004 PMCID: PMC9146788 DOI: 10.3390/nano12101782] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/14/2022] [Revised: 05/13/2022] [Accepted: 05/21/2022] [Indexed: 12/10/2022]
Abstract
The magnetic properties of nanocrystalline MxFe3-xO4 ferrites with M=Fe, Co, and Zn were investigated. The data support a core-shell model, where the core is ferrimagnetically ordered, and the shell shows a spin glass type behavior. The reduced magnetizations of spin glass components follow an mg = (1 - b/H-1/2) field dependence. The b values are strongly correlated with the intensities of exchange interactions. The field dependences of the magnetoresistances of Fe3O4 and ZnxFe3-xO4 nanoparticles pellets, experimentally determined, are well described if instead of the core reduced magnetization, commonly used, that of the shell is taken into account. For similar compositions of the nanoparticles, identical b values are obtained both from magnetization isotherms and magnetoresistances studies. The half-metallic behavior of spinel Fe3O4 based nanoparticles is discussed comparatively with those of double perovskites.
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Affiliation(s)
- Emil Burzo
- Correspondence: (E.B.); (R.T.); Tel.: +40-624405300 (ext. 5164) (R.T.)
| | - Romulus Tetean
- Correspondence: (E.B.); (R.T.); Tel.: +40-624405300 (ext. 5164) (R.T.)
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Unsteady Magnetohydrodynamics (MHD) Flow of Hybrid Ferrofluid Due to a Rotating Disk. MATHEMATICS 2022. [DOI: 10.3390/math10101658] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The flow of fluids over the boundaries of a rotating disc has many practical uses, including boundary-layer control and separation. Therefore, the aim of this study is to discuss the impact of unsteady magnetohydrodynamics (MHD) hybrid ferrofluid flow over a stretching/shrinking rotating disk. The time-dependent mathematical model is transformed into a set of ordinary differential equations (ODE’s) by using similarity variables. The bvp4c method in the MATLAB platform is utilised in order to solve the present model. Since the occurrence of more than one solution is presentable, an analysis of solution stabilities is conducted. Both solutions were surprisingly found to be stable. Meanwhile, the skin friction coefficient, heat transfer rate—in cooperation with velocity—and temperature profile distributions are examined for the progressing parameters. The findings reveal that the unsteadiness parameter causes the boundary layer thickness of the velocity and temperature distribution profile to decrease. A higher value of magnetic and mass flux parameter lowers the skin friction coefficient. In contrast, the addition of the unsteadiness parameter yields a supportive effect on the heat transfer rate. An increment of the magnetic parameter up to 30% reduces the skin friction coefficient by 15.98% and enhances the heat transfer rate approximately up to 1.88%, significantly. In contrast, the heat transfer is rapidly enhanced by improving the mass flux parameter by almost 20%.
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