Introduction to achievements
Since biomass carbon materials have rich microstructures, in order to study the synergistic effect of the microstructure and macrostructure of structural absorption materials. this article, Hunan University Zou Yanhong and other researchers published a paper titled "Controlling the microstructure of biomass-derived porous carbon to assemble structural absorber for broadening bandwidth" in the journal Carbon . The study chose almond shells as raw materials because With its unique layered porous structure, porous carbon materials with different microstructures are prepared through a simple chemical activation process. Experiments show that the EAB of porous carbon materials can be effectively expanded by changing the microstructure of the porous carbon materials. Subsequently, these porous carbon materials were used individually to assemble structural absorbers. Coincidentally, the EAB of structural absorbers can also be expanded by changing the microstructure of porous carbon materials.
Based on the above experiments, the authors proposed a structural absorber (SA) made of two porous carbon materials with different microstructures. At the microscopic scale, the two porous carbon materials have different dielectric losses and impedance matching, as well as different EM wave dissipation mechanisms. At the macro scale, the macro structure of SA will fully contact the EM wave with the porous carbon material, thereby enhancing the impedance matching of SA. Therefore, the EAB of SA can be effectively enhanced by combining the microwave absorption mechanism and macrostructure enhancement of porous carbon materials. Finally, compared with pure porous carbon materials, the EAB of SA extends from 9.04-14.56 GHz to 4.2-18 GHz. Research on controlling the microstructure of biomass-derived porous carbon materials to optimize the absorption performance of structural absorbing materials will provide a reference for the preparation of advanced broadband absorbing materials.
Graphic introduction
Figure 1. Preparation process and characterization of almond shell-derived porous carbon
Figure 2. (a) XRD pattern and (b) Raman spectra of samples prepared with different conditions.
Figure 3. Reflection loss of samples: (a) and (b) PC-700; (c) and (d) PC-800; (e) and (f) CP-800; (g) and (h) PC-900.
Figure 4. Computed impedance spectra of SA, SA(PC-800), SA(CP-800) and plate structures
Figure 5. Distribution of electric field, magnetic field and power loss of SA at different frequencies: (a) 5.9 GHz, (b) 6.4 GHz, (c) 12 GHz, (d) 16.6 GHz.
Figure 6. (a) SA fabricated specimen with mold. (b) Experimental and simulated reflectance of SA .
Summary
In summary, this work designed a low-cost broadband structure microwave absorber by preparing porous carbon materials with different microstructures. Based on chemical activation and 3D printing techniques, the structure of SA can be tuned and designed at both micro and macro scales. The synergistic effect of microstructure and macrostructure can improve the impedance matching of SA and preserve the high dielectric loss of carbon materials. Therefore, SA can provide ultra-wideband absorption in the 4.2-18 GHz range. Furthermore, for both TE and TM polarization, broadband absorption can remain stable over a wide range of incidence angles. Furthermore, the agreement between experimental and simulation results suggests that the EAB of structured microwave absorbers can be broadened by controlling the microstructure of the biomass-derived porous carbon materials from which the metastructure is built. The research in this work provides options for broadening the bandwidth of structural microwave absorbers and for the recovery and reuse of waste biomass materials.
Literature:
https://doi.org/10.1016/j.carbon.2022.06.074
