Microwave absorption properties of titanium carbide-based MXene materials
Hällbacka, Ella (2025)
2025
Teknis-luonnontieteellinen DI-ohjelma - Master's Programme in Science and Engineering
Tekniikan ja luonnontieteiden tiedekunta - Faculty of Engineering and Natural Sciences
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Hyväksymispäivämäärä
2025-12-16
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:tuni-2025121611752
https://urn.fi/URN:NBN:fi:tuni-2025121611752
Tiivistelmä
Stealth technologies play a crucial role in modern warfare. For decades, stealth technologies have been primarily developed for aircraft, but in recent years, the growing demand for unmanned aerial vehicles (UAV) is driving an increased need for stealth capabilities in smaller platforms. Combined with the rapid advancement of RADAR technology, this has sparked significant interest in stealth materials—specifically, microwave absorbing materials (MAMs) that are lightweight, thin, broadband, and chemically and thermally stable. The development of the a new type of material is required for the RADAR application.
MXenes are a relatively new class of two-dimensional (2-D) transition metal carbides, nitrides, and carbonitrides. Their unique properties—including layered structure, abundant surface func tional groups, high electrical conductivity, large specific surface area, thermal stability, flexibility, durability, and water dispersibility, have made them a hot topic in the research field of MAMs. These properties can be tuned by modifying the synthesis method or by combining MXenes with other materials, leading to promising MA performance. However, a major challenge in the devel opment of MXene-based MA materials is impedance matching. Current research often addresses this issue through complex synthesis routes and relatively thick structures, which remain problem atic and limit practical applications.
This work aims to deepen the understanding of the impedance matching problem and develop nanometer-thick layers to investigate the MA properties of MXene. A relatively simple and repeat able synthesis route is presented, converting the MAX phase into Ti3C2Tx MXene using a mild and safe LiF/HCl etching method. Coatings are prepared using an industrially scalable spray coating technique. The chemistry and reproducibility of the synthesized material are thoroughly charac terized using X-ray photoelectron spectroscopy (XPS). To identify impedance-matched conditions, the sheet resistance of the MXene coatings is measured. Finally, the microwave absorption per formance is analyzed by measuring scattering parameters in the 6–16 GHz frequency range using a vector network analyzer (VNA) and LB40400 antennas.
The measured sheet resistance values fell within the optimal range of 20–200 Ω/□, and the re peatability varied by approximately 20 Ω/□. The final microwave absorption performance reached approximately 40% when the signal was incident from the coated side and up to 80% when in cident from the substrate side. The best impedance matching—and highest absorption—was achieved at a sheet resistance of 200 Ω/□.
MXenes are a relatively new class of two-dimensional (2-D) transition metal carbides, nitrides, and carbonitrides. Their unique properties—including layered structure, abundant surface func tional groups, high electrical conductivity, large specific surface area, thermal stability, flexibility, durability, and water dispersibility, have made them a hot topic in the research field of MAMs. These properties can be tuned by modifying the synthesis method or by combining MXenes with other materials, leading to promising MA performance. However, a major challenge in the devel opment of MXene-based MA materials is impedance matching. Current research often addresses this issue through complex synthesis routes and relatively thick structures, which remain problem atic and limit practical applications.
This work aims to deepen the understanding of the impedance matching problem and develop nanometer-thick layers to investigate the MA properties of MXene. A relatively simple and repeat able synthesis route is presented, converting the MAX phase into Ti3C2Tx MXene using a mild and safe LiF/HCl etching method. Coatings are prepared using an industrially scalable spray coating technique. The chemistry and reproducibility of the synthesized material are thoroughly charac terized using X-ray photoelectron spectroscopy (XPS). To identify impedance-matched conditions, the sheet resistance of the MXene coatings is measured. Finally, the microwave absorption per formance is analyzed by measuring scattering parameters in the 6–16 GHz frequency range using a vector network analyzer (VNA) and LB40400 antennas.
The measured sheet resistance values fell within the optimal range of 20–200 Ω/□, and the re peatability varied by approximately 20 Ω/□. The final microwave absorption performance reached approximately 40% when the signal was incident from the coated side and up to 80% when in cident from the substrate side. The best impedance matching—and highest absorption—was achieved at a sheet resistance of 200 Ω/□.