Versatile Warrior: MXene/CNT Janus Films for Electromagnetic & Infrared Shielding/Detection in Harsh Environments

The demand for multifunctional, flexible, and high-strength ultra-thin films is rapidly increasing to meet the continuous advancements in electronic technology, thermal management, and aerospace technology. Traditional metals such as copper and aluminum possess excellent electromagnetic interference (EMI) and infrared (IR) shielding capabilities. However, their high density, processing complexity, and susceptibility to corrosion limit their large-scale application. In contrast, MXenes have garnered attention due to their excellent metallic conductivity, low infrared emissivity, tunable surface chemistry, and superior solution processability. To enhance the mechanical strength and durability of MXene-based materials in harsh environments, extensive research has been conducted on MXene-based polymer composites and hybrid materials. However, the non-conductive nature of polymers compromises the EMI and IR shielding capabilities of MXenes.

Considering the good electrical conductivity of carbon materials, combining MXenes with carbon-based materials (such as carbon nanotubes and graphene) can result in mechanical properties and EMI shielding capabilities superior to those of MXene-polymer composites. Nevertheless, this combination strategy significantly weakens the IR shielding capability of MXenes. Therefore, further research is needed to optimize the composite structure, fully leveraging the high conductivity, low infrared emissivity, and strong EMI shielding capabilities of MXenes, along with the mechanical robustness of carbon materials.

To address this issue, the team led by Professor Chong Min Koo at Sungkyunkwan University has proposed a multifunctional Janus film that combines highly crystalline Ti₃C₂T_x MXene and high-strength carbon nanotube (CNT) films through strong hydrogen bonding. Janus structures have recently garnered attention because they can achieve tunable mechanical properties and multifunctional synergy without sacrificing their inherent characteristics. This Janus film not only boasts high electrical conductivity (4250 S cm^-1) but also demonstrates robust mechanical strength and durability in both extremely low and high-temperature environments, as well as excellent thermal shock resistance. The MC11-Janus film retains significant electromagnetic shielding capability even after 300 bending cycles and 30 thermal shock cycles with a temperature difference of Δ396°C. These exceptional electromagnetic shielding properties and thermal shock retention capabilities are attributed to the outstanding oxidation stability of Al-Ti₃C₂T_x MXene, the high-strength flexibility of the CNT film, and the strong interfacial interaction between Al- Ti₃C₂T_x MXene and the CNT film.

All materials emit thermal radiation in the infrared spectrum when their temperature exceeds absolute zero (0K). The lower the material's infrared emissivity, the higher the reduction in radiation temperature, enhancing the thermal camouflage performance of the sample. Chong Min Koo's team evaluated the infrared shielding capability and high-temperature thermal camouflage performance of the MC11-M film. With an average emissivity of 0.09 (minimum of 0.02), it exhibits strong infrared absorption capabilities. Additionally, the film demonstrates excellent thermal camouflage performance over a wide temperature range (-1 to 300°C), with a significant reduction in radiation temperature by 243°C at a background temperature of 300°C. This reduction is comparable to that of Cu metal films. Such exceptionally high conductivity and significantly low infrared emissivity make it an ideal candidate for infrared shielding applications.

Chong Min Koo's team constructed a system to evaluate the infrared detection capability of the MC11-C film by placing a 15μm thick MC11-C film between two Cu electrodes as an infrared radiation detector. When exposed to 250W of infrared radiation, the resistance increased by 44%. The direct correlation between temperature increases and resistance reveals the light intensity-dependent behavior of temperature and resistance changes. This MXene/CNT-Janus film provides a feasible solution for multifunctional electromagnetic shielding and infrared shielding/detection in harsh environments.