Magnetic Interaction Effects in MXene Frameworks: Enhanced Heat Generation for EMI Shielding

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Research abstract

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With the prosperity and development of communication and electronic devices, electromagnetic functional materials have been widely used. However, high-frequency electronics can generate undesirable electromagnetic interference (EMI) that is released into the environment, which not only causes data/system issues, but also increases health risks for the associated workers. Therefore, there is an urgent need for EMI shielding materials to play an important role in mitigating/eliminating electromagnetic radiation pollution. MXenes are a new family of two-dimensional transition metal carbides, nitrides, and carbonitrides (Mn+1XnTx, where n=1, 2, or 3, M is an early transition metal, X stands for C/n, and TX stands for end group. ), first reported in 2011 by selective etching of MAX. They have the advantages of large specific surface area, good electrical conductivity, and high structural stability, and have received extensive attention in various fields. Despite its enormous capacity, the metallic nature of dense MXene films results in almost complete reflection of incident electromagnetic waves. Good progress has been made in tuning the EMI reflection and absorption contributions of MXene and MXene-based composites. In order to effectively reduce electromagnetic pollution, traditional metal materials are used as electromagnetic shielding functional materials due to their easy corrosion, heavy weight, and vulnerability to damage. Compared with traditional metal materials, carbon-based materials (graphene or carbon nanotubes) have the advantages of light weight, good flexibility, superior electrical properties, and excellent performance after being assembled into macroscopic films or structures, and have broad applications in the field of electromagnetic interference shielding. application prospects. Combining carbon materials with MXene endows composites with properties such as low density, transparency, and mechanical properties. However, previous researches on fabricating high-efficiency electromagnetic shielding materials have mainly focused on improving the electrical conductivity while ignoring the absorption efficiency, which can generate severe reflections and adverse secondary electromagnetic pollution. Therefore, it is very urgent to design next-generation EMI shielding materials with various requirements, such as excellent feature shielding efficiency, light weight, high electrical conductivity, and low secondary pollution.

Introduction

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Recently, the team of Prof. Che Renchao from Fudan University prepared a new type of electromagnetic interference shielding material Ti3C2Tx-MXene/MWCNTs/SrFe12O19 by a simple filtering method based on conductive Ti3C2Tx-MXene. Two-dimensional hexagonal SrFe12O19 flakes with intrinsic magnetic loss and anisotropy were introduced into Ti3C2Tx-MXene/MWCNT substrates for enhanced energy absorption. One-dimensional multi-walled carbon nanotubes (MWCNTs) act as isolation to isolate the Ti3C2Tx MXene sheets, so that the SrFe12O19 sheets can be pre-uniformly distributed without magnetic agglomeration. By using Ti3C2Tx-MXene flakes, one-dimensional multi-walled carbon nanotubes, and hexagonal SrFe12O19 flakes, Ti3C2Tx-MXene/MWCNTs/SrFe12O19 thin films (MCSF) exhibit high electrical conductivity up to 438 S cm at a thickness of only 40 μm, and the optimized average The electromagnetic shielding efficiency is 62.9 dB. Taking advantage of the interfacial polarization and magnetic responsiveness of the film, the introduction of SrFe12O19 can improve the absorption capacity and overall shielding ability, thereby improving the EMI shielding ability without increasing the reflection. More importantly, the electron holography images strongly verify the magnetic dissipation mechanism in hexagonal SrFe12O19 flakes, which are found to be related to magnetic coupling and domain wall migration. This strategy will pave the way for the manufacture of flexible EMI shielding films to meet current market demands.

The result was published online in the top international journal Small (impact factor 13.281) with the title: Magnetic Interacted Interaction Effect in MXene Skeleton: Enhanced Thermal-Generation for Electromagnetic Interference Shielding.

Huang Mengqiu is the first author of this article.

Graphical guide



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Figure 1. Schematic diagram of the preparation process of Ti3C2Tx-MXene/MWCNTs/SrFe12O19 thin films.



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Figure 2. Structural characterization. a, d) MCF-1, b, e) MSF-1 and c, f) Cross-sectional SEM images of MCSF-10 showing hexagonal SrFe12O19 sheets and multi-walled carbon nanotubes inserted into the Ti3C2Tx layer. g) Elemental mapping and h) photographs of MCSF showing the flexibility and magnetic properties of the laminated film.



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Figure 3. Electromagnetic shielding performance. a-c) Comparison of EMI SE, SET, SEA, and SER, and the electrical conductivity of MF-2, MSF-2, MCF-2, MCSF-10 with the same thickness of 40 μm. d, i) EMI SE, e) conductivity, f) image, h) comparison of SET, SEA and SER of MCSF-5, MCSF-10, MCSF-15, MCSF-20, MCSF-25, MCSF-30. j) Compare the characteristic EMI shielding effectiveness as a function of thickness.



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Figure 4. EMI shielding mechanism analysis. a-c) The real part εof the complex permittivity, b) The imaginary part ε″, c) The dielectric loss tangent of MCSF-5, MCSF-10, MCSF-15, MCSF-20, MCSF-25, MCSF-30 tanδe. d) The related electromagnetic mechanism of Ti3C2Tx-MXene/MWCNTs/SrFe12O19 thin films. e) Reconstructed phase images of the MCSF-10 composite and corresponding charge density distribution line profiles and f, g) reconstructed stray magnetic field distributions.





Summarize

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In this paper, ultrathin and flexible Ti3C2Tx-MXene/MWCNTs/SrFe12O19 thin films with a layered structure were prepared by a simple vacuum filtration method and used as a novel electromagnetic interference shielding material. At a thickness of only 40 μm, the composite exhibits excellent conductivity in the X-band (438 S cm−1) and an average electromagnetic shielding efficiency value (62.9 dB). The insertion of magnetically anisotropic flakes SrFe12O19 leads to an effective enhancement of the absorption efficiency of the magnetized MXene-based films. Through an unprecedented magnetic dissipative absorption mechanism, the overall shielding efficiency is simultaneously increased. Hexagonal SrFe12O19 sheets can efficiently convert electromagnetic wave energy into thermal energy through domain wall migration, ferromagnetic resonance, and expansion of magnetic coupling space. Meanwhile, the layered structure also yields excellent EMI shielding effectiveness, providing substantial reflection and dielectric interface dissipation for MXene-MXene, MXene-MWCNTs, and MXene-SrFe12O19. Off-axis electron holography confirmed the magnetically dominant absorption mechanism. The synthesized MXene/MWCNTs/SrFe12O19 films have great potential for application in microwave energy conversion and EMI shielding.


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Literature link

https://doi.org/10.1002/smll.202201587

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