Controllable Preparation of Fe3O4@RF and Its Evolution to Yolk–Shell-Structured Fe@C Composite Microspheres with High Microwave Absorbing Performance

Fe3O4@RF microspheres with different phenolic (RF) layer thicknesses are prepared by adjusting the polymerization time. With the prepared Fe3O4@RF as the precursor, Fe@C composite microspheres with rattle-like morphology are obtained through one-step controlled carbonization. This method simplifies the preparation of rattle-shaped microspheres from sandwich microspheres. Fe@C microspheres exhibit excellent microwave absorbing properties. The morphology and composition of the product are investigated depending on the effects of carbonization temperature, time and thickness of the RF layer. When the carbonization temperature is 700 °C, the carbonization time is 12 h and the polymer shell thickness is 62 nm, the inner hollow Fe3O4 is completely reduced to Fe. The absorption properties of the materials are compared before and after the reduction of Fe3O4. Both Fe@C-12 and Fe3O4@C-700 show excellent absorbing properties. When the filler content is 50%, the maximum reflection loss (RLmax) of the rattle-shaped Fe@C microspheres is −50.15 dB, and the corresponding matching thickness is 3.5 mm. At a thickness of 1.7 mm, the RLmax of Fe3O4@C-700 is −44.42 dB, which is slightly worse than that of Fe@C-12. Both dielectric loss and magnetic loss play a vital role in electromagnetic wave absorption. This work prepares rattle-shaped absorbing materials in a simple way, which has significance for guiding the construction of rattle-shaped materials.

Controllable preparation and electrocatalytic hydrogen evolution characteristics of Fe3S4 nanocrystals

In order to obtain better electrocatalytic hydrogen evolution performance, Fe3S4 with different morphologies was synthesized by controlling the reaction conditions. During that progress, the ferric oleate as an iron source, and the sulfur powder dissolved in oleylamine as a sulfur source. Fe3S4 with particle morphology proved to have the best electrochemical catalytic activity after adding 40% carbon black. In dehydrogenation, the overpotential was 234 mV and the Tafel slope was 213 mV/dec at a current density of 10 mA/cm2. Meanwhile, Fe3S4 with a particle morphology exhibited superior electrochemical stability. Therefore, the controllably fabricated Fe3S4 with a particle morphology is a promising electrocatalyst for dehydrogenation.

Controllable Preparation and Rapid Photoelectric Response of Homogeneous ZnTe Microspheres

With the use of ethylene glycol as a solvent, polyvinylpyrrolidone as a surfactant and hydrazine hydrate as a reducing agent, uniform spherical ZnTe microstructure was synthesized in a homogeneous reactor...

Theoretical study on the controllable preparation of superhard BC2N under high pressure

High-density B-C-N ternary compounds have attracted considerable attention due to their potential and excellent properties combined with diamond and cubic boron nitride (c-BN). However, the development of B-C-N is restricted...

Adsorption performances and electrochemical characteristics of methyl blue onto magnesium-zinc ferrites

A novel and facile rapid combustion approach was developed for the controllable preparation of small size and easy recovery magnesium-zinc ferrites for methyl blue (MB) removal in dye solution. The effects of prepared criteria of x value, calcination temperature, and the amount of ethanol on the average grain sizes and magnetic property were reviewed. The characterization results displayed that Mg0.5Zn0.5Fe2O4 nanoparticles met the expectations of the experiment at the calcination temperature of 400℃ with absolute ethanol volume of 20 mL, and they were selected to remove MB. The adsorption process belonged to chemical adsorption on the basis of the pseudo-second-order model. The electrochemical characteristics of MB onto the prepared nanoparticles were analyzed by cyclic voltammetry (CV). The influences of pH and cycle times on the removal efficiency were investigated. When the pH went beyond 3, the removal efficiency of MB onto the magnetic Mg0.5Zn0.5Fe2O4 nanoparticles maintained above 99%，the maximum adsorption capacity was 318.18 mg/g. After seven cycles, the relative removal rate of MB remained 96% of the first one.