Tunable dielectric properties of mesoporous carbon hollow microspheres via textural properties

Abstract

In this study, mesoporous carbon hollow microspheres (PCHMs) with tunable textural properties have been prepared through a facile hard template etching method. The PCHMs were characterized by scanning electron microscopy, transmission electron microscopy, x-ray diffraction, Raman spectra, and nitrogen adsorption and desorption systems. Uniform PCHMs with shell thickness ranging from 23 nm to 55 nm are realized. PCHMs with different textural properties can regulate dielectric and electromagnetic (EM) wave absorption effectively. The composite of paraffin wax mixed with 10 wt% PCHMs (the shell thickness of PCHMs is 35 nm) exhibits a minimum coefficient value of -53.8 dB at 8.8 GHz, with a thickness of 3.4 mm. Besides, it is remarkable that the effective absorption bandwidth covers all the X band with as low as a 10 wt% filler ratio, compared with other spherical EM wave absorbers. The excellent EM wave absorption capability of PCHMs can be ascribed to the better impendence matching and strong EM wave attenuation constant based on tunable textural properties. Our results provide a facile strategy to tune dielectric properties of spherical carbon absorbers based on textural properties, and can be extended to other spherical absorbers.

Achieving Sustainable Ultralight Electromagnetic Absorber from Flour by Turning Surface Morphology of Nanoporous Carbon

“…When the EM wave propagates on these nanopore structures, the enhanced space charge polarization would occur because of the accumulation of charge on the carbon−air boundary. 12 The visible relaxation peaks of ε″ and the multiple Cole−Cole hemicycles (Figure 4c−e) could better demonstrated this. 32 Also, the surface areas of the three samples increase with prolonged heat treated time.…”

“…The former BET results confirm that all samples possess high porosity in the nanoscale. When the EM wave propagates on these nanopore structures, the enhanced space charge polarization would occur because of the accumulation of charge on the carbon–air boundary . The visible relaxation peaks of ε″ and the multiple Cole–Cole hemicycles (Figure c–e) could better demonstrated this .…”

“…Specifically, nanoporous carbon has been regarded as one of the most promising candidates for lightweight and high-efficiency EM wave absorption applications owing to its large surface area and pore volume. − Recently, vast progress in EM wave loss theory and processing technology has demonstrated that tailoring the morphology and modifying the surface is an effective strategy to improve the final loss ability for EM waves. Hence, many nanoporous carbon materials with diverse surface morphologies have been reported as EM absorbers.…”

Protein-Derived Hybrid Carbon Nanospheres with Tunable Microwave Absorbing Performance in the X-Band

“…57 According to Debye theory, the dielectric loss of carbon materials can be divided into the conductive loss corresponding to conductivity and the polarization loss, which often originate from dipoles, defects, and heterogeneous interfaces. 51,58 Based on the previous analysis, the increase of the carbonization temperature plays an important role in the composition and microstructure of the carbon absorbent. First, a higher temperature leads to a higher degree of crystallization, which contributed to the elevated conductivity 59 (the surface conductivities of GCNs-T-20% samples were measured by a four point probe device and shown in Figure S5) as well as conductive loss.…”

Biomass-Derived Porous Carbon-Based Nanostructures for Microwave Absorption

“…When the extra EM wave radiates on these boundaries, plenty of charges would accumulate at the carbon–air interfaces, inducing the strong space charge polarization. This can boost the EM wave attenuation capacity of material [ 48 ].…”