cobalt ferrite
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2022 ◽  
Author(s):  
Hamid Hosseinzadeh ◽  
Hamidreza Oveisi

Abstract In the present study, CoFe2O4 and CoFe2-xGdxO4 nanoparticles were synthesized by the hydrothermal process. The CoFe2O4 nanoparticles were synthesized at different temperatures (70oC, 100oC, 150oC, and 200oC), molar ratio of CoCl2/ FeCl3 (0/2, 0.75/2, 1/2, 1.5/2, and 2/2). Gadolinium-doped cobalt ferrite (CoFe2-xGdxO4) nanoparticles have also been synthesized with Gd/Fe molar ratios of 0.18 and 0.53. The XRD patterns indicate that cobalt ferrite and Gadolinium-doped cobalt ferrite nanoparticles have been successfully synthesized without impurities with a medium degree of crystallinity. The XRD patterns show that by increasing the synthesis temperature from 70oC to 200oC, the size of the nanoparticles decreased from 50.49nm to 32.45nm while the morphology of the nanoparticles also changed from a shapeless and agglomerated state to a spherical shape. The XPS curve illustrated several peaks corresponding to Fe+3, Co+2, and O 1s. The binding energies for Co and Fe were consistent with Fe 2p and Co 2p binding energies for cobalt ferrite nanoparticles. The magnetic saturation value (Ms) increased from 17.253 emu/g to 54.438 emu/g with a rise in the synthesis temperature. The effects of FeCl3/CoCl2 molar ratio on the magnetic properties showed the highest value of Ms (54.438 emu/g) and the coercivity (HC) of 744.56 Oe for a 2/1 molar ratio. The addition of gadolinium to the composition resulted in a reducing of the magnetic properties of nanoparticles; accordingly, the amount of saturated magnetization was reduced to 22.469 emu/g. Another effect of gadolinium dopant in the composition was a change in nanoparticle morphology from spherical to rod shape. The final aim of this study was to investigate the possible utilization of CoFe2O4 and CoFe2-xGdxO4 nanoparticles in medical treatment in the near future.


Author(s):  
F. A. Revoredo ◽  
Von Ivison ◽  
M. E. Silva-Junior ◽  
J. Neves-Araujo ◽  
E. Padrón-Hernández

2022 ◽  
Vol 275 ◽  
pp. 125300
Author(s):  
V. Mowlika ◽  
C.S. Naveen ◽  
A.R. Phani ◽  
A. Sivakumar ◽  
S.A. Martin Britto Dhas ◽  
...  

2022 ◽  
Author(s):  
Manfred Wuttig ◽  
Abdellah Lisfi ◽  
Lourdes Salamanca-Riba ◽  
Sabin Pokharel
Keyword(s):  

Ceramist ◽  
2021 ◽  
Vol 24 (4) ◽  
pp. 399-410
Author(s):  
Junghum Park ◽  
Hojae Lee ◽  
Yonghyun Lim ◽  
Jisung Yoon ◽  
Miju Ku ◽  
...  

The high temperature(900oC~) thermal sintering process is necessary to fabricate the Solid oxide fuel cells(SOFCs). However, the chemical reaction has occurred between solid oxide material components, electrode and electrolyte. In the case of lanthanum strontium cobalt ferrite (La0.6Sr0.4Co0.2Fe0.8O3-δ, LSCF) electrode, the SrZrO3(SZO) secondary phase is produced at the electrolyte interface even when using the gadolinium doped ceria(GDC) buffer layer for blocking the strontium and zirconium diffusion. The SZO layer hinders the oxygen ion transfer and deteriorates fuel cell performance. By using a novel flash light sintering(FLS) method, we have successfully solved the problem of secondary phase formation in the conventional high temperature thermal sintering process. The microstructure and thickness of the LSCF electrode are analyzed using a field emission scanning electron microscope(FE-SEM). The strontium diffusion and secondary phase are confirmed by X-ray diffraction (XRD), energy dispersive spectrometer method of SEM, TEM (SEM-, TEM-EDS). The NiO-YSZ anode supported LSCF cathode cells are adopted for electro chemical analysis which is measured at 750oC. The maximum power density of the thermal sintered LSCF cathode at 1050oC is 699.6mW/cm2, while that of the flash light sintered LSCF cathode is 711.6mW/cm2. This result proves that the electrode was successfully sintered without a secondary phase using flash light sintering.


Author(s):  
A. S. Kamzin ◽  
I. M. Obaidat ◽  
V. S. Kozlov ◽  
E. V. Voronina ◽  
V. Narayanaswamy ◽  
...  

Catalysts ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 21
Author(s):  
Julian Kubisztal ◽  
Marian Kubisztal

In this paper, two novel procedures based on powder sedimentation, thermal treatment, and galvanostatic deposition were proposed for the preparation of porous cobalt ferrite (CoFe2O4) coatings with a metallic and organic binder for use as catalysts in the oxygen evolution reaction (OER). The electrochemical properties of the obtained electrode materials were determined as well, using both dc and ac methods. It was found that cobalt ferrite coatings show excellent electrocatalytic properties towards the oxygen evolution reaction (OER) with overpotential measured at a current density of 10 mAcm−2 from 287 to 295 mV and a Tafel slope of 35–45 mVdec−1. It was shown that the increase in the apparent activity of the CoFe2O4 coatings with an organic binder results mainly from a large electrochemically active area. Incorporation of the nickel binder between the CoFe2O4 particles causes an increase in both the conductivity and the electrochemically active area. The Tafel slopes indicate that the same rate-determining step controls the OER for all obtained coatings. Furthermore, it was shown that the CoFe2O4 electrodes exhibit no significant activity decrease after 28 h of oxygen evolution. The proposed coating preparation procedures open a new path to develop high-performance OER electrocatalysts.


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