Effect of the CoFe₂O₄ initial particle size when sintered by microwave on the microstructural, dielectric, and magnetic properties

Abstract

The particle size of CoFe2O4 powders (average particle size of 350 nm) was reduced to 50 nm by high‐energy milling. In this paper, special attention was given for analyzing the densification and grain growth of both particle sizes (350 and 50 nm) subject to ultrafast sintering assays using microwave sintering and their effect on the magnetic and electric properties. The results indicated that the grain growth was 10 times higher for the nanoparticle system, reaching similar sizes of ~1 μm in both cases after sintering. The relative density values were higher (95%) in the nanoparticle system due to the wide distribution of particle sizes generated in the grinding process. Qualitatively inferred microscopy analysis showed high sinterability of fine particles with a narrow distribution of grain size when subjected to ultrafast firing processes. Magnetization measurements at room temperature clearly show the reduction of Hc with increasing grain size. Electric resistivity, dielectric constant (ε′), and dielectric loss tangent (tan δ) were measured as a function of frequency at room temperature. The low values of dielectric constant (ε′) and dielectric loss (tan δ) in the low frequency range, shown for all samples sintered by microwave, prove the excellent uniformity in the microstructure.

Synthesis of CoFe2O4 Nanomaterials via Sol–Gel Auto‐Combustion Method using Different Chelating Agent, and Its Effects on Magnetic and Dielectric Properties

“…The frequency versus temperature-dependent ε r and tanδ of CFO nanomaterial obtained from different chelating agents at selected temperatures (27, 40, 60, 80, 100, 120, 140, 160, 180, and 200 °C) were depicted in Figures 5 and 6, respectively. However, temperature-depended ε r plots of CFO nanomaterial obtained from different chelating agents at few selected frequency ( 10 dielectric constant is higher than that of earlier reported CFO [50] and other spinel ferrites, [51][52][53] and this may be due to the changes of synthesis route. [54,55] For instance, measured at same frequency of dielectric constant was observed different for Mn 0.4 Zn 0.6 Fe 2 O 4 nanomaterial prepared by the coprecipitation (%450) route and combustion route (%190).…”

Biodegradation of Oxide Nanoparticles in Apoferritin Protein Media: A Systematic Electrochemical Approach

“…[17][18][19] Among them, spinel ferrites as cobalt ferrite (CoFe 2 O 4 , CFO) nanoparticles have gained particular scientific and technological interest and are extensively utilized in several branches of engineering and medicine due to their magnetic and catalytic properties, mechanical hardness, and chemical stability, among others. [20][21][22][23] Furthermore, by compositing the CFO or creating core-shell nanoparticles by covering it with multiferroic materials such as bismuth ferrite (BiFeO 3 , BFO) into CFO-BFO, we can achieve novel multifunctionalities including magnetoelectric, magnetooptic, and photocatalytic properties. [24,25] Although there have been many efforts to enhance their biocompatibility, control drug targeting, and efficiently release therapeutics by modifying the surfaces or compositions of magnetic nanoparticles, [26,27] studies on their other important aspects, such as biodegradation, metal ion release, and remediation mechanisms in contact with different proteins, cells, or macrophages are still lacking.…”

“…[ 17–19 ] Among them, spinel ferrites as cobalt ferrite (CoFe 2 O 4 , CFO) nanoparticles have gained particular scientific and technological interest and are extensively utilized in several branches of engineering and medicine due to their magnetic and catalytic properties, mechanical hardness, and chemical stability, among others. [ 20–23 ] Furthermore, by compositing the CFO or creating core‐shell nanoparticles by covering it with multiferroic materials such as bismuth ferrite (BiFeO 3 , BFO) into CFO‐BFO, we can achieve novel multifunctionalities including magnetoelectric, magnetooptic, and photocatalytic properties. [ 24,25 ]…”