A method combining liquid-liquid phase separation and the pyrolysis process has been developed to fabricate the wormhole-like porous carbon/magnetic nanoparticles composite with a pore size of about 80 nm (WPC/MNPs-80). In this work, the porous structure was designed to enhance interaction between the electromagnetic (EM) wave and the absorber, while the magnetic nanoparticles were used to bring about magnetic loss ability. The structure, morphology, porosity and magnetic properties of WPC/MNPs-80 were investigated in detail. To evaluate its EM wave attenuation performance, the EM parameters of the absorber and wax composite were measured at 2-18 GHz. WPC/MNPs-80 has an excellent EM wave absorbency with a wide absorption band at a relatively low loading and thin absorber thickness. At the absorber thickness of 1.5 and 2.0 mm, minimum RL values of -29.2 and -47.9 dB were achieved with the RL below -10 dB in 12.8-18 and 9.2-13.3 GHz, respectively. The Co and Fe nanoparticles derived from the chemical reduction of Co0.2Fe2.8O4 can enhance the graphitization process of carbon and thus improve dielectric loss ability. Polarizations in the nanocomposite absorber also play an important role in EM wave absorption. Thus, EM waves can be effectively attenuated by dielectric loss and magnetic loss through multiple reflections and absorption in the porous structure. WPC/MNPs-80 could be an excellent absorber for EM wave attenuation; and the design strategy could be extended as a general method to synthesize other high-performance absorbers.
For RHPC/Fe, RL of −21.8 dB can be achieved with the absorption bandwidth (RL ≤ −10 dB, ABW) of 5.6 GHz at a thickness of 1.4 mm, while for RHPC/Co, RL of −40.1 dB can be achieved with ABW of 2.7 GHz at a thickness of 1.8 mm.
A novel transparent Co0.2Fe2.8O4@SiO2-polyetheretherketone hybrid material is prepared for electromagnetic interference shielding via in situ sol-gel process. 20% amino-functionalized polyetheretherketone (AFPEEK), containing trifluoromethyl units with excellent solubility is designed and synthesized to improve the stability and mechanical properties of Co0.2Fe2.8O4@SiO2 nanoparticles. The hydrophilic nanoparticles and hydrophobic polymer matrix are covalently connected after the effective interface modification with 3-isocyanatopropyltriethoxysilane. SEM and TEM images demonstrate that the strong interaction between inorganic-organic phases results in great improvement of dispersion and compatibility at even 40 wt% nanoparticles contents. The functional integration of organic polymer and inorganic nanoparticles leads to excellent comprehensive performances such as high transparency, thermal stability and mechanical properties of the hybrid material, as well as the high adhesion with substrate, which benefits its application as coating materials. This high performance material exhibits good superparamagnetic behaviour and microwave electromagnetic properties (RLmax ∼ -13 dB), which can be utilized as a promising electromagnetic interference shielding material.
We report a simple and effective method for preparing novel ternary-hybrid membranes comprising Fe 3 O 4 @polyaniline nanocomposites and polyazomethine/polyetheretherketone matrix via a sol-gel process. Polyetheretherketone as a superior engineering thermoplastics matrix can significantly enhance the thermal stability of the hybrid membranes with high glass transition temperature (T g > 160 C) and thermal decomposition temperature (T d-5% > 300 C). Meanwhile, the conductive-polymer/magnetic nanocomposites can effectively improve the microwave-absorbing property of the membranes. Their electromagnetic and microwave-absorbing properties are studied in detail. The hybrid materials with 40 wt% nanocomposites content exhibits significant microwave-absorbing properties with a maximum reflection loss about À18 dB at 14 GHz. Moreover, the crosslinked hybrid materials exhibit excellent solvent resistance. This hybrid technique provides a novel route for the designing and preparation of light-weight, stable and high performance microwave-absorbing materials.
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