Synthesis of Fe3O4@SiO2@ZnO core–shell structured microspheres and microwave absorption properties

Magnetically separable type-II semiconductor based ZnO/MoO3 photocatalyst: a proficient system for heteroarenes arylation and rhodamine B degradation under visible light

Shedding light on a magnetically retrievable ZnO/MoO3 photocatalyst that efficiently coupled diazonium substituted arenes with heteroarene substrates along with efficient degradation of toxic Rhodamine B.

Preparation of Fe3O4@SiO2–ZnO catalyst and its catalytic synthesis of rosin glycol ester

In order to solve the problems of low recovery, low availability, and high cost in the synthesis of rosin glycol ester, a series of supported ZnO magnetic catalysts were prepared with Fe3O4 as the magnetic center, and their structures and compositions were characterized by TEM, XRD, and XPS. Through screening, the results show that Fe3O4@SiO2–ZnO has the best catalytic effect, far better than other catalysts, and has good stability. At the same time, the effects of zinc source and its load and different reaction conditions on the synthesis of rosin glycol ester were also investigated. The results showed that: When zinc chloride was used as zinc source, theoretical loading of zinc source was 0.45 g, reaction temperature was 270°C, reaction time was 5 h, and catalyst dosage was 0.2 g, the esterification rate of rosin-glyceryl ester was 87.2% and acid value was 26.5 mg KOH g−1.

MOF-derived Co@C nanoparticle anchored aramid nanofiber (ANF) aerogel for superior microwave absorption capacity

High-efficiency, porous and renewable magnetic microwave absorbing (MA) materials have been enthusiastically pursued due to their suitable impedance matching, light weight, strong multiple scattering and the synergy effect of dielectric and magnetic loss. Herein, a three-dimensional (3D) Co@C/ANF aerogel, composed of magnetic MOF derivatives embedded in biomass aramid nanofiber (ANF), was prepared for the first time through a directional-freezing method followed by an annealing process. To evaluate their MA attenuation performance, the electromagnetic parameters of Co@C/ANF composites with different component ratios were measured at 2-18 GHz. Profiting from the preserved porous structure of MOF derivatives, the construction of multiple heterogeneous interfaces and suitable electromagnetic parameters, Co@C/ANF 2 : 1 exhibited a good MA performance of RL_min = -64.3 dB (indicating more than 99.99996% microwaves were absorbed) and EAB_max = 6.8 GHz. Considering the admirable overall performance, the Co@C/ANF aerogel is deemed to be a promising candidate for the next-generation of lightweight, reproducible, and high-performance MA materials.

Microwave Absorption Properties of Magnetite Particles Extracted from Nickel Slag

The utilization of nickel slag has attracted much attention due to its high-content of valuable elements. As a part of these efforts, this work focuses on whether magnetite crystals, obtained from nickel slag via molten oxidation, magnetic separation, and ball-milling can be used as a microwave absorber. The composition, morphology, microstructure, magnetic properties, and microwave absorption performance were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM), and vector network analysis (VNA). The results reveal that the magnetite crystals exhibit excellent microwave absorption properties because of the synergistic action between dielectric loss and magnetic loss. The minimum reflection loss (RL) of the particles obtained after 6 h ball-milling reaches −34.0 dB at 16.72 GHz with thickness of 5 mm. The effective frequency bandwidth (RL ≤ −10 dB) is 4.8–5.4 GHz and 15.9–17.6 GHz. Interfacial polarization of the particles could play a crucial role in improving absorbing properties because several components contained in the particles can dissipate electromagnetic wave effectively. The current study could show great potential in the preparation of magnetite crystals and utilization of nickel slag.

Tuning of Shells in Trilaminar Core@Shell Nanocomposites in Controlling Electromagnetic Interference through Switching of the Shielding Mechanism

Fe₃O₄@SiO₂@PPy core-shell nanocomposites were fabricated by the coating of SiO₂ on Fe₃O₄ through base catalyzed hydrolysis of tetraethyl orthosilicate followed by encapsulation of polypyrrole (PPy). Subsequently, these trilaminar composites have been characterized by Fourier-transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, Brunauer-Emmett-Teller, superconducting quantum interference devices, and measurement of the total shielding efficiency in the frequency range of 2-8 GHz. Our findings showed the highest total shielding efficiency (∼32 dB) of Fe₃O₄@SiO₂@PPy (Fe₃O₄@SiO₂/pyrrole wt/wt = 1:9) and followed reflection as the dominant shielding mechanism. Such performance was attributed to poor impedance matching between the PPy (conducting)/SiO₂ (insulating) and high electrical conductivity of Fe₃O₄@SiO₂@PPy. Alternatively, electromagnetic (EM) waves incident on the SiO₂@PPy interface could also account for enhancing the total shielding efficiency of Fe₃O₄@SiO₂@PPy because of multireflection/refraction. Our earlier work also showed excellent total shielding efficiency of Fe₃O₄@C@PANI nanocomposites, through absorption as the dominant shielding mechanism. These findings clearly suggest that EM interference shielding in Fe₃O₄@SiO₂@PPy and Fe₃O₄@C@PANI trilaminar core@shell nanocomposites is controlled by tuning of the shells through switching of the mechanism.

Facile synthesis of yolk–shell structured ZnFe2O4 microspheres for enhanced electrocatalytic oxygen evolution reaction

Yolk–shell structured ZnFe₂O₄ microspheres with excellent OER performance are synthesized via a facile solvothermal method and annealing treatment.

Solvothermal synthesis of flower-like CoS hollow microspheres with excellent microwave absorption properties

In this study, flower-like CoS hollow spheres (CHSs), synthesized via a facile solvothermal method in the presence of CTAB, were initially investigated as microwave absorbers.