Structural investigations and magnetic properties of sol-gel Ni0.5Zn0.5Fe2O4 thin films for microwave heating

Abstract

Nanocrystalline Ni 0.5 Zn 0.5 Fe 2 O 4 thin films have been synthesized with various grain sizes by a sol-gel method on polycrystalline silicon substrates. The morphology, magnetic, and microwave absorption properties of the films calcined in the 673-1073 K range were studied with x-ray diffraction, scanning electron microscopy, x-ray photoelectron spectroscopy, atomic force microscopy, vibrating sample magnetometry, and evanescent microwave microscopy. All films were uniform without microcracks. Increasing the calcination temperature from 873 to 1073 K and time from 1 to 3 h resulted in an increase of the grain size from 12 to 27 nm. The saturation and remnant magnetization increased with increasing the grain size, while the coercivity demonstrated a maximum near a critical grain size of 21 nm due to the transition from monodomain to multidomain behavior. The complex permittivity of the Ni-Zn ferrite films was measured in the frequency range of 2-15 GHz. The heating behavior was studied in a multimode microwave cavity at 2.4 GHz. The highest microwave heating rate in the temperature range of 315-355 K was observed in the film close to the critical grain size.

Effect of Pr3+ substitution on the microstructure, specific surface area, magnetic properties and specific heating rate of Ni0.5Zn0.5Pr Fe2−O4 nanoparticles synthesized via sol–gel method

“…The use of nanostructured magnetic materials for radiofrequency heating (RF) and magnetic separation within a chemical reactor provides a novel process intensified platform for system integration [2]. In these applications, magnetic nanoparticles embedded into composite catalytic microparticles are used as susceptors of induction or microwave heating [3,4]. RF heating provides efficient, fast and uniform heat transfer into catalyst [5,6] and flowing fluid [7][8][9][10].…”

“…NiZn polycrystalline ferrites, with an inverse spinel structure formed by a close-packed face centered cubic (FCC) lattice, can be represented with the general formula (ZnxFe1-x)[Ni1-xFe1+x]O4, where the Zn 2+ ions occupy the interstitial tetrahedral (A) sites, the Ni 2+ ions occupy the octahedral (B) sites [4], and the Fe 3+ ions are distributed between the A and B sites.…”

Effects of annealing temperature on the magnetic properties of ZnFe1.97Eu0.03O4 nanoparticles

“…People took this method to prepare Ni-Zn ferrite nanoparticles [25,26], Mn-Zn ferrite powders [27], NiCuZn ferrite films [28]. For this method, the sintering temperature generally has great influence on the structure and magnetic properties of samples.…”

Controllable synthesis of one-dimensional isolated Ni 0.5 Zn 0.5 Fe 2 O 4 microtubes for application as catalyst support in RF heated reactors

“…Combination of spinel ferrites with catalyst nanoparticles allows a novel process intensified platform for reactor system integration, in these composites, ferrites work as the susceptors of induction heating to provide efficient RF heating due to the adjustable Curie temperatures and moderate magnetic losses in the kHz range [23,24], and catalyst loaded on the ferrites can work on some fine chemicals synthesis [16,25]. RF heating provides efficient, fast and uniform heat transfer into catalytic sites and flowing fluid [26][27][28][29].…”

“…They have an inverse spinel structure formed by a nearly close packed face centered cubic (FCC) array of anions with holes partly filled with cations, can be represented with the formula (ZnxFe1-x)[Ni1-xFe1+x]O4, in which Zn 2+ ions locate in A interstitial (tetrahedral) sites, Ni 2+ ions in B (octahedral) sites [16], and Fe 3+ ions in the spinel lattice involve both tetrahedral A and octahedral B sites. The Ni-Zn ferrites have been prepared by co-precipitation, ball milling, spray pyrolysis, combustion synthesis, hydrothermal synthesis, and sol-gel methods [17][18][19][20][21][22].…”