Synthesis and characterization of low density porous nickel zinc ferrites

Nanocrystalline Ni-Zn spinel ferrites: size-dependent physical, photocatalytic and antioxidant properties

The physical properties of nanomagnetic particles are expected to be highly dependent on their size. In this study, besides the promising applications of nanocrystalline Ni-Zn spinel ferrites in the area of photocatalysis and free radical scavenging, we present a detailed study with appropriate scientific explanations on the role of size change in modifying and tuning the microstructural, optical and magnetic properties. Three nanostructured Zn0.3Ni0.7Fe2O4 samples of different particle sizes were prepared via the chemical co-precipitation method. Crystallographic phase purity and formation of the spinel cubic phase for all the samples were tested by X-ray diffraction studies. The magnetic properties of the as-synthesized ferrite nanoparticles have been examined thoroughly at 5 K and 300 K. Emergence of superparamagnetic behavior has been observed for the sample with the smallest size ferrite nanoparticles (ZNF-1). The photocatalytic efficiency of all the nanocatalysts was tested on methylene blue (MB) dye and the smallest sized nanocatalyst (ZNF-1) was identified as the most efficient catalyst in degrading MB dye under light illumination. The degradation efficiency was found to decrease with increasing mean particle size of the prepared samples. The antioxidant properties of the prepared ferrite samples were also studied. Here, too, the ZNF-1 sample with the smallest sized nanoparticles exhibited maximum scavenging of free radicals compared to other samples. Hence, the present study clearly demonstrates that smaller-sized Ni-Zn spinel ferrites are efficient materials for tuning the physical properties as well as for use in photocatalytic and antioxidant applications.

Generation of Abundant Defects in Ferrite Carbon Magnetic Nanomaterials for Eliminating Electromagnetic Interference in Communication

A series of novel ferrite carbon nanomaterials are considered to obtain the potential advantages in elimination of the electromagnetic interference effects. Herein, the iron nanoparticles coated on amorphous carbon were prepared by facile agar-gel synthesis. Meanwhile, the synergy between carbon supporting and ferrite nanomaterials could be proved to promote the absorption properties. Among all samples, the iron nanoparticles coated on amorphous carbon show the highest microwave absorption properties, achieving the maximum reflection loss (RL) of -14.3 dB at 6 GHz (5.5-milimeter thickness), and the bandwidths over -10 dB (90% absorption) was 2.5 GHz. Combining analysis results, it is confirmed that the as-prepared iron nanoparticles have the highest surface area, homogeneous distribution, abundant defect, and well-defined pore structure, which could significantly affect the absorption properties at 6 GHz. Furthermore, the abundant defects derived from the interface were the essential reason for the improved absorption properties. Overall, it provided a new strategy to design an effective method to absorb nanomaterials for the elimination of electromagnetic interference, especially the coordination of metal species and carbon supporting.

Synthesis and Characterization of New Ferrite-Lignin Hybrids

The paper presents the synthesis and characterization of new cobalt ferrite-lignin hybrids. The hybrids were obtained through the combustion of cobalt nitrate and ferric nitrate, two kinds of lignin being used as combustion agents. The temperatures of calcination were 500 °C and 900 °C, respectively. The hybrids were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), and X-ray photoelectron spectroscopy (XPS). The magnetic properties were also assessed by vibrating sample magnetometer system (VSM). This facile synthesis method made it possible to obtain cobalt ferrite-lignin hybrids with a spinel structure. Their particle sizes and crystallite sizes have increased with an increment in the calcination temperature. A different occupancy of cations at octahedral and tetrahedral sites also occurred upon the increase in temperature. The hybrids comprising organic lignin presented the best magnetic properties.