Page 89 - MSAM-3-3

Materials Science in Additive Manufacturing Wide-angle broadband MMA with CB-CIP/PLA

resistance loss (carbon black [CB], graphene, carbon MMA has a broadband absorption of 6.8 – 20.8 GHz.
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fiber, carbon nanotubes ) and magnetic loss (ferrite, 10,11 These studies achieved the best absorption performance
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metal powder 12,13 ). However, broadening the absorption by using different materials and adjusting geometric
bandwidth greatly reduces the reflection loss (RL) and parameters, but these absorbing structures still struggled
absorption performance. Metamaterial absorbers (MMA) to achieve over 90% absorption in the frequency range of
provide a solution to this problem. An MMA is an artificial 2 – 18 GHz.
structure composed of a periodic array of unit structures In comparison to the conventional preparation process,
(subwavelength scale) with adjustable electromagnetic 3D printing technology is suitable for fabricating a complex
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characteristics. Compared with the conventional wave- microwave-absorbing structure and features advantages
absorbing coating, the electromagnetic properties of MMA such as high efficiency and material utilization. 30-32
are not just dependent on the material properties, but also A variety of 3D printing processes have been used to
the unit structure. Through macroscale (structural) and prepare composite MMAs, including stereolithography,
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microscale (material) control, better impedance-matching selective laser sintering, direct ink writing, digital light
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performance can be achieved, effectively increasing the processing, and fused filament fabrication (FFF). 23,32,37
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absorption bandwidth and angle. 16 Among them, the FFF process is the most widely used
Recent designs of the MMA have been proposed to because of the low cost of materials and equipment.
improve the microwave absorption performance. 17-19 In this study, a complex composite MMA was proposed
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Chen et al. proposed a pyramidal absorber, which can to achieve excellent absorption properties and fabricated
achieve over 90% absorption in the frequency range of using FFF 3D printing technology. The MMA material
5.3 – 18 GHz due to both the material properties and the consists of CB (for resistance loss), carbonyl iron powder
synergistic effect of its geometry. Pei et al. designed and (CIP; for magnetic loss), and polylactic acid (PLA; as the
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fabricated a gradient honeycomb absorber, which has an matrix). The MMA structures were designed and optimized
excellent absorption property at 8 – 12 GHz. Feng et al. using electromagnetic simulation. The reflectivity of
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designed a truncated pyramidal metamaterial and studied printed MMA structures was experimentally measured to
the impact of geometric parameters and array period on verify the simulation results.
its absorption property. The absorption performance of the
metamaterial can be improved by changing the geometric 2. Methods
parameters of the structure while maintaining the inherent
electromagnetic characteristics of the material. The peak 2.1. Design of MMA structure and electromagnetic
RL of the optimized structure reached −22.5 dB, and the simulation
corresponding effective absorption bandwidth (EAB) was The MMA structure is composed of an array of stepped
up to 9 GHz. Yin et al. and Tian et al. designed and square hole (SSH) units as schematically presented in
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fabricated a multilayer metamaterial microwave absorption Figure 1. This design was inspired by the pyramidal
structure based on the impedance gradient change of absorber with stepped projection. The SSH unit can
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woodpile structure. The impedance matching coefficient be seen as the remaining part of a cube subjected to
varied with the pile width. The optimized bandwidth geometric Boolean operations with a pyramid structure.
was 4.5 – 40 GHz and the peak RL was −35 dB. Begaud The geometric parameters of the SSH structure include the
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et al. designed a multilayer structure that can reach maximum hole radius (R), wall thickness (W), and height
−10 dB absorption bandwidth in the frequency range (H, H , and H ). An electromagnetic model was developed
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of 3.7 – 17.5 GHz. Wang et al. proposed a wide-angle in CST Studio Suite software (Dassault Systèmes, France)
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broadband absorption based on both indium tin oxide to simulate the microwave absorption performance of
and metapyramid geometry at 8 – 12 GHz. Xu et al. the structure. Finer tetrahedral meshes were used in the
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designed a kirigami-inspired transformable metamaterial simulation to ensure convergence and data validity. The
for adaptive invisibility, which provides a new avenue electromagnetic properties of the CB-CIP/PLA composite
toward multifunctional smart devices. Xu et al. were input into the model. The parameter sweep method
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designed a triple-band absorber enhanced by a planar was used for the optimization of geometric parameters.
2D artificial metamaterial transmission line concept. The The sweep range for different parameters is listed in
absorber featured near-unity absorption for a wide range Table 1. The sweep interval is 2 mm for R, H, H and H and
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1,
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of incident angles and polarization states. Wang et al. 0.2 mm for W. The effect of geometric parameters on the
proposed a thin broadband multilayer MMA, using the RL of the MMA was compared, and the optimal geometric
concepts of multimode-assisted strategy and impedance- parameters were determined based on factors such as peak
gradient theory to widen the bandwidth. The designed value and EAB. The effect of polarization and incident
Volume 3 Issue 3 (2024) 2 doi: 10.36922/msam.4158