Key Takeaways & Executive Findings
- •• SiC@RGO porous films were fabricated via two-step reduction (HI chemical and solid-phase microwave), achieving thickness increase from ~20 to 200 μm due to gas release during 3 s microwave irradiation. • The optimal GO/SiC mass ratio of 4:1 yielded a total shielding effectiveness (SET) of 35.6 dB with a low reflection SE (SER) of 2.8 dB, indicating absorption-dominated shielding. • SiC whiskers enhance multi-reflection, interfacial polarization, and dielectric attenuation of electromagnetic waves, critical for EMI absorption. • Multilayer films combining SiC@RGO porous films and MWCNT buckypapers achieved a high SET of 75.1 dB with SER of only 2.7 dB at ~1.5 mm thickness, suitable for packaging or lining applications.
Abstract
Developing lightweight and flexible thin films for electromagnetic interference (EMI) shielding is of great importance. Porous thin films of reduced graphene oxide containing SiC whiskers (SiC@RGO) for EMI shielding were prepared by a two-step reduction of graphene oxide (GO), in which the two steps were chemical reduction by HI and the solid phase microwave irradiation. A significant increase of the film thickness from around 20 to 200 μm was achieved due to the formation of a porous structure by gases released during the 3 s of solid phase microwave irradiation. The total shielding effectiveness (SET) and the reflective SE (SER) of the SiC@RGO porous thin films depended on the GO/SiC mass ratio. The highest SET achieved was 35.6 dB while the SER was only 2.8 dB, when the GO/SiC mass ratio was 4∶1. The addition of SiC whiskers was critical for the multi-reflection, interfacial polarization and dielectric attenuation of EM waves. A multilayer film with a gradient change of SE values was constructed using SiC@RGO porous films and multi-walled carbon nanotubes buckypapers. The highest SET of the multilayer films reached 75.1 dB with a SER of 2.7 dB for a film thickness of about 1.5 mm. These porous SiC@RGO thin films should find use in multilayer or sandwich structures for EMI absorption in packaging or lining.
1. Introduction
Carbon-based electromagnetic interference (EMI) shielding materials feature low density, diverse forms and tunable properties. Electrical conductivity of carbon materials has a wide range, depending on their crystal structures, chirality, oxidation degree, etc[1,2]. Compared to metal materials, carbon-based materials give the opportunity to construct lightweight, flexible, absorption-dominated EMI shielding materials[3].
Graphene-based thin films can be considered as a two-dimensional (2D) assembly of graphene layers which can be applied as the core layer in sandwich structure, packaging and lining materials for EMI shielding purpose[4,5]. Graphene oxide (GO) with a large number of oxygen-containing functional groups can be easily dispersed in water and aligned in thin films by liquid casting, vacuum filtration and electrodeposition. EMI shielding effects can be realized by restoring the electrical conductivity of the thin films upon reduction. However, the high electrical conductivity of reduced GO (RGO) may promote the reflection of electromagnetic (EM) radiation, resulting in reduction in absorption[4] because the reflection of EM radiations is a result of the interactions between the EM waves and free charges of carbon materials[6]. Iodine-doped RGO papers with an electrical conductivity of 103 S/cm showed an EMI shielding effectiveness (SE) of 52.2 dB and SE reflection (SER) of 18.6 dB[7], which may cause secondary EMI pollution.
RGO-based composite thin films were designed to improve the absorption of EMI. The addition of magnetic and semiconductive materials can promote EM attenuation, such as Fe3O4[8], MnO[9] and SiC[10]. SiC whiskers/MnO/RGO composites were constructed for improving EMI absorption, where SiC whiskers can dielectrically attenuate EM waves as a semiconductor[11]. Synergistic effects on EMI shielding were expected by combining SiC with an conductive phase, such as carbon nanotube-carbon fiber/SiC[12] and SiC/MXene/polymer[13] composites. Compared with 2D composite thin films with RGO layers, three-dimensional (3D) assembly of graphene or RGO layers provided graphene monoliths with high porosity and low density. The EMI SE of RGO monoliths mainly came from the direct absorption and the absorption of multiple-reflected EM radiations, which were facilitated by their high porosity and large surface area[6]. The EMI SE of RGO monoliths can also be tuned by composite design, such as infiltration of conductive polymers[6], Fe3O4, carbon nanotubes[14] and MXene[15]. Porous structure was also reported for MXene/RGO flexible thin film, whic
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LI Jing, QI Yi-quan, ZHAO Shi-xiang, QIU Han-xun, YANG Jun-he, YANG Guang-zhi (2025). Reduced graphene oxide porous films containing SiC whiskers for constructing multilayer electromagnetic shields. SinoTechIntel Verified Research. https://doi.org/10.1016/S1872-5805(NCM2024-39-06-10)
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Frequently Asked Questions
What is the main achievement of this research?
The research developed porous SiC@RGO thin films with high EMI shielding effectiveness (up to 35.6 dB for single films and 75.1 dB for multilayer structures) while maintaining low reflection, indicating absorption-dominated shielding.
How were the porous SiC@RGO films prepared?
The films were prepared by a two-step reduction of graphene oxide: first chemical reduction by HI, then solid-phase microwave irradiation for 3 seconds, which created a porous structure and increased film thickness from ~20 to 200 μm.
Why is the addition of SiC whiskers important?
SiC whiskers are critical for enhancing multi-reflection, interfacial polarization, and dielectric attenuation of electromagnetic waves, which contribute to absorption-dominated EMI shielding.
What is the significance of the multilayer film design?
By constructing multilayer films with gradient SE values using SiC@RGO porous films and MWCNT buckypapers, the total shielding effectiveness reached 75.1 dB with a very low reflection SE of 2.7 dB, making them suitable for packaging or lining applications.
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