Magnetic properties of CoFe2O4 nanoparticles prepared by thermal treatment of ball-milled precursors

2011 ◽  
Vol 11 (3) ◽  
pp. 476-481 ◽  
Author(s):  
M. Eshraghi ◽  
P. Kameli
2020 ◽  
Vol 65 (10) ◽  
pp. 904
Author(s):  
V. O. Zamorskyi ◽  
Ya. M. Lytvynenko ◽  
A. M. Pogorily ◽  
A. I. Tovstolytkin ◽  
S. O. Solopan ◽  
...  

Magnetic properties of the sets of Fe3O4(core)/CoFe2O4(shell) composite nanoparticles with a core diameter of about 6.3 nm and various shell thicknesses (0, 1.0, and 2.5 nm), as well as the mixtures of Fe3O4 and CoFe2O4 nanoparticles taken in the ratios corresponding to the core/shell material contents in the former case, have been studied. The results of magnetic research showed that the coating of magnetic nanoparticles with a shell gives rise to the appearance of two simultaneous effects: the modification of the core/shell interface parameters and the parameter change in both the nanoparticle’s core and shell themselves. As a result, the core/shell particles acquire new characteristics that are inherent neither to Fe3O4 nor to CoFe2O4. The obtained results open the way to the optimization and adaptation of the parameters of the core/shell spinel-ferrite-based nanoparticles for their application in various technological and biomedical domains.


ACS Omega ◽  
2020 ◽  
Vol 5 (31) ◽  
pp. 19315-19330 ◽  
Author(s):  
Sumayya M. Ansari ◽  
Kartik C. Ghosh ◽  
Rupesh S. Devan ◽  
Debasis Sen ◽  
Pulya U. Sastry ◽  
...  

2021 ◽  
pp. 104112
Author(s):  
Sitchai Hunpratub ◽  
Sumalin Phokha ◽  
Pinit Kidkhunthod ◽  
Narong Chanlek ◽  
Prinya Chindaprasirt

Nanomaterials ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 1231
Author(s):  
Venkatesha Narayanaswamy ◽  
Imaddin A. Al-Omari ◽  
Aleksandr S. Kamzin ◽  
Bashar Issa ◽  
Huseyin O. Tekin ◽  
...  

Mixed ferrite nanoparticles with compositions CoxMn1-xFe2O4 (x = 0, 0.2, 0.4, 0.6, 0.8, and 1.0) were synthesized by a simple chemical co-precipitation method. The structure and morphology of the nanoparticles were obtained by X-ray diffraction (XRD), transmission electron microscope (TEM), Raman spectroscopy, and Mössbauer spectroscopy. The average crystallite sizes decreased with increasing x, starting with 34.9 ± 0.6 nm for MnFe2O4 (x = 0) and ending with 15.0 ± 0.3 nm for CoFe2O4 (x = 1.0). TEM images show an edge morphology with the majority of the particles having cubic geometry and wide size distributions. The mixed ferrite and CoFe2O4 nanoparticles have an inverse spinel structure indicated by the splitting of A1g peak at around 620 cm−1 in Raman spectra. The intensity ratios of the A1g(1) and A1g(2) peaks indicate significant redistribution of Co2+ and Fe3+ cations among tetrahedral and octahedral sites in the mixed ferrite nanoparticles. Magnetic hysterics loops show that all the particles possess significant remnant magnetization and coercivity at room temperature. The mass-normalized saturation magnetization is highest for the composition with x = 0.8 (67.63 emu/g), while CoFe2O4 has a value of 65.19 emu/g. The nanoparticles were PEG (poly ethylene glycol) coated and examined for the magneto thermic heating ability using alternating magnetic field. Heating profiles with frequencies of 333.45, 349.20, 390.15, 491.10, 634.45, and 765.95 kHz and 200, 250, 300, and 350 G field amplitudes were obtained. The composition with x = 0.2 (Co0.2Mn0.8Fe2O4) with saturation magnetization 57.41 emu/g shows the highest specific absorption rate (SAR) value of 190.61 W/g for 10 mg/mL water dispersions at a frequency of 765.95 kHz and 350 G field strength. The SAR values for the mixed ferrite and CoFe2O4 nanoparticles increase with increasing concentration of particle dispersions, whereas for MnFe2O4, nanoparticles decrease with increasing the concentration of particle dispersions. SARs obtained for Co0.2Mn0.8Fe2O4 and CoFe2O4 nanoparticles fixed in agar ferrogel dispersions at frequency of 765.95 kHz and 350 G field strength are 140.35 and 67.60 W/g, respectively. This study shows the importance of optimizing the occupancy of Co2+ among tetrahedral and octahedral sites of the spinel system, concentration of the magnetic nanoparticle dispersions, and viscosity of the surrounding medium on the magnetic properties and heating efficiencies.


1999 ◽  
Vol 577 ◽  
Author(s):  
Q. Chen ◽  
B. M. Ma ◽  
B. Lu ◽  
M. Q. Huang ◽  
D. E. Laughlin

ABSTRACTThe phase transformation and the exchange coupling in (Ndo095Lao005)9.5FebaICOsNb 2BI05 have been investigated. Nanocomposites were obtained by treating amorphous precursors at temperatures ranging from 650TC to 9500C for 10 minutes. The magnetic properties were characterized via the vibrating sample magnetometer (VSM). X-ray diffraction (XRD), thermomagnetic analysis (TMA), and transmission electron microscopy (TEM) were used to perform phase identification, measure grain size, and analyze phase distribution. The strength of the exchange coupling between the magnetically hard and soft phases in the corresponding nanocomposite was analyzed via the AM-versus-H plot. It was found that the remanence (Br), coercivity (Hci), and maximum energy product (BHmax) obtained were affected by the magnetic phases present as well as the grain size of constituent phases and their distribution. The optimal magnetic performance, BHm, occurred between 700°C to 750°C, where the crystallization has completed without excessive grain growth. TMA and TEM indicated that the system was composed of three phases at this point, Nd2(Fe Co) 14B, ca-Fe, and Fe3B. The exchange coupling interaction among these phases was consistently described via the AM-versus-H plot up to 750°C. The Br, Hci, and BHmax degraded severely when the thermal treatment temperature increased from 750°C. This degradation may be attributed to the grain growth of the main phases, from 45 to 68nm, and the development of precipitates, which grew from 5nm at 750°C to 12nm at 850°C. Moreover, the amount of the precipitates was found to increase with the thermal treatment temperatures. The precipitates, presumably borides, may cause a decrease in the amount of the a-Fe and Fe 3B and result in a redistribution of the Co in the nanocomposites. The increase of the Co content in the Nd 2(Fe Co) 14B may explain the increase of its Curie temperature with the thermal treatment temperatures. In this paper, we examine the impacts of these factors on the magnetic properties of (Ndo 95Lao 05)9 5FebaICosNb2B10.5 nanocomposite.


2019 ◽  
Vol 55 (1) ◽  
pp. 85-93 ◽  
Author(s):  
M.M. Vasic ◽  
A.S. Kalezic-Glisovic ◽  
R. Milincic ◽  
Lj. Radovic ◽  
D.M. Minic ◽  
...  

The mechanical activation of the Ni85.8Fe10.6Cu2.2W1.4 powder mixture in the time intervals of 30-210 min in combination with thermal treatment at 393-873 K resulted in microstructural changes, forming the nanostructured mixture of the same composition but improved magnetic properties. The best result were achieved for mechanical activation during 120 min and thermal treatment at temperatures close to the Curie temperature (693K), enhancing the mass magnetization of the starting powder mixture by about 57%. The microstructural changes, which include the structural relaxation, decrease in free volume, density of dislocation and microstrain, improve structural characteristics of material, enabling better mobility of walls of magnetic domains and their better orientation in applied magnetic field and consequently enabling better mass magnetization of the material. With longer time of milling, the growing stress introduced in the sample undergoes easier relief, relocating stress-relieving processes toward lower temperatures.


Sign in / Sign up

Export Citation Format

Share Document