Microwave Absorption Properties of Fe-Doped Ordered Mesoporous Carbon (CMK-3)/Silica Matrix Nanocomposites with Magnetic Multi-Resonance Mechanisms

NANO ◽  
2015 ◽  
Vol 10 (08) ◽  
pp. 1550110 ◽  
Author(s):  
Yanyan Ren ◽  
Le Yang ◽  
Liuding Wang ◽  
Hui Xing ◽  
Hongjing Wu
Keyword(s):  
Electron Microscope ◽  
Mesoporous Carbon ◽  
Magnetic Loss ◽  
Silica Matrix ◽  
Ordered Mesoporous Carbon ◽  
Metal Species ◽  
Silica Nanocomposites ◽  
Transmission Electron ◽  
Ordered Mesoporous ◽  
Cole Model

Low-density Fe-doped ordered mesoporous carbon (CMK-3)-silica (SBA-15) nanocomposites with different Fe contents have been prepared by a catalytic carbonization procedure followed by high-temperature calcination in N2. From field emission-scanning electron microscope (FE-SEM) and high resolution-transmission electron microscope (HR-TEM) images, it can be concluded that CMK-3 particles are dispersed homogeneously into a silica matrix and form a novel, special and interesting composite nanostructure. The metal species ([Formula: see text]18[Formula: see text]nm) are dispersed on the surface of frameworks during the catalytic carbonization procedure and endow a magnetic property to the carbon–silica nanocomposites. The optimal reflection loss (RL) calculated from the measured permittivity and permeability is [Formula: see text]19[Formula: see text]dB at 17.2[Formula: see text]GHz for an absorber thickness of 2.00[Formula: see text]mm. Moreover, the electromagnetic (EM) wave absorption less than [Formula: see text]10[Formula: see text]dB is found to exceed 5.76[Formula: see text]GHz as the layer thickness is 2.37 mm. The permittivity dispersion behaviors have been explained based on the Cole–Cole model and the conductivity contribution model. A new simple empirical model was also supposed to find the fitted curves of the multi-resonance imaginary permeability spectra of the composites. The EM wave can hardly be reflected on the absorber surface because of a better match between dielectric loss and magnetic loss, which originates from the combination of dielectric carbon–silica and magnetic Fe species.

Facile Fabrication of Magnetic Nanocomposites of Ordered Mesoporous Carbon Decorated with Nickel Nanoparticles

2007 ◽  
Vol 7 (2) ◽  
pp. 504-509 ◽  
Author(s):  
Yulin Cao ◽  
Jieming Cao ◽  
Mingbo Zheng ◽  
Jinsong Liu ◽  
Guangbin Ji ◽  
...  
Keyword(s):  
Mesoporous Carbon ◽  
Nickel Nanoparticles ◽  
Hysteresis Loops ◽  
Ordered Mesoporous Carbon ◽  
Cubic Phase ◽  
X Ray Diffraction ◽  
Transmission Electron ◽  
Ordered Mesoporous ◽  
Special Surface ◽  
Facile Fabrication

A magnetic nanocomposite of ordered mesoporous carbon (CMK-3) decorated with nickel nanoparticles was synthesized successfully by a simple chemistry method. Nickel nanoparticles were prepared and uniformly supported on ordered mesoporous carbon CMK-3 by reduction route with CMK-3 as a reducing agent at 673 K. The Ni/CMK-3 composite materials were characterized by powder X-ray diffraction, nitrogen sorption, and transmission electron microscopy. As-prepared nickel nanoparticles supported on CMK-3 were crystalline with a face-center-cubic phase and a size distribution ranging from 10 to 60 nm. The BET special surface area and pore volume of Ni/CMK-3 were as high as 797 m2 g−1 and 0.72 cm3 g−1, respectively. The formation mechanism of the nickel nanoparticles outside the surface of CMK-3 was preliminarily discussed. The hysteresis loops of the CMK-3 decorated with nickel nanoparticles were measured by vibrating sample magnetometer (VSM), and the results showed that the composite was ferromagnetism with the saturated magnetization of 15 emu/g, and the coercivity value of 214 Oe. Furthermore, the application of Ni/CMK-3 as magnetically separable adsorbent for vitamin B2 was primarily examined in this study.

Enhanced Microwave Absorption by Incorporating Fe3O4 Nanoparticles into Ordered Mesoporous Carbon

2013 ◽  
Vol 634-638 ◽  
pp. 2193-2197
Author(s):  
Hu Zhou ◽  
Jian Dong Zhuang ◽  
Qian Liu
Keyword(s):  
Microwave Absorption ◽  
Mesoporous Carbon ◽  
Magnetic Loss ◽  
Nitrate Solution ◽  
Ordered Mesoporous Carbon ◽  
Impedance Match ◽  
Ferric Nitrate ◽  
Composite Powders ◽  
Ordered Mesoporous ◽  
Microwave Absorbing

Novel Fe3O4/ordered mesoporous carbon (OMC) composite powders have been prepared by impregnation and reduction methods for the microwave absorbing application purpose. The Fe3O4nanoparticles were encapsulated in the mesopores of OMCs, and Fe3O4contents in the composite could be easily controlled by changing the concentration of ferric nitrate solution during the preparation. The Fe3O4/OMC composites show very excellent microwave absorbing properties with respect to pure OMC samples, in a frequency ranging of 8.2-12.4 GHz. A minimum reflection loss (RL) value of -32 dB at 11.35 GHz and a broader absorption band with the RL values under -10 dB are obtained when the thickness of samples is 1.6 mm. The enhanced microwave absorption of the Fe3O4/OMC nanocomposites is contributed to the better impedance match between dielectric loss and magnetic loss, which originates from the incorporation of magnetic species into OMC.

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