MoS2 nanoparticle/activated carbon composite as a dual-band material for absorbing microwaves

Preparation of rGO/MoSe2 nanocomposites for enhanced microwave absorption of whole X and Ku bands

rGO-MoSe2 nanocomposites were prepared via a one-pot hydrothermal method in which MoSe2 microspheres (MS) were decorated on rGO sheets. Three nanocomposites named F1, F2, and F3 were prepared using different weight ratios of MoSe2 MS to rGO: (3 : 1), (4 : 1), and (5 : 1), respectively. FESEM images showed a flower-like porous morphology of the MoSe2 microspheres. All the rGO-MoSe2 nanocomposites exhibited remarkable microwave absorption properties as demonstrated by strong reflection loss (-58 dB to -99 dB) and an ultrabroad effective absorption bandwidth (equivalent to 90% attenuation), which covers whole X and Ku frequency bands at matching thicknesses of 2.8-3.2 mm. The minimum reflection loss reached -98, -99, and -75 dB for F1, F2 and F3, respectively. The excellent absorption properties of the rGO-MoSe2 nanocomposites is related to the unique morphology and micro size of MoSe2 in which incident waves are attenuated by multiple reflections and scattering.

Controllable preparation of 2D carbon paper modified with flower-like WS2 for efficient microwave absorption

In the practical application of microwave absorbing materials, traditional powder materials need to be mixed with the matrix to fabricate composite coatings. However, the complex preparation process of composite coatings and the uneven dispersion of powders in the matrix limit their application. To solve these problems, two-dimensional (2D) F-WS₂/CP composite films were prepared by using carbon paper (CP) as a dispersion matrix and loading flower-like WS₂ on its surface through a simple hydrothermal method. The morphology and microwave absorption (MA) performance of the composite films are easily regulated by adjusting the amount of reaction precursors. The combination of WS₂ and CP facilitates impedance matching and improves the electromagnetic wave attenuation performance based on the synergistic effect of different loss mechanisms including multiple reflections and scattering, interfacial polarization, dipolar polarization, and conduction loss. At a low filler content (5 wt%), the maximum reflection loss (RL) of the composite film is up to -50 dB (99.999% energy absorption) at 12.5 GHz with 2.8 mm thickness. Moreover, at a relatively thin 1.8 mm thickness, its maximum RL remains -35 dB (>99.9% energy absorption). The as-prepared composite film shows excellent MA properties at a thinner thickness and lower filling content, providing inspiration for the preparation of light weight and efficient 2D thin-film microwave absorbers in the future.

Constructing MoSe2/MoS2 and MoS2/MoSe2 inner and outer-interchangeable flower-like heterojunctions: A combined strategy of interface polarization and morphology configuration to optimize microwave absorption performance

Interfacial polarization and geometrical morphology play a significant role in the attenuation of electromagnetic (EM) wave. Herein, the two-dimensional (2D)/2D heterojunction with flower-like geometrical morphology is proposed and produced, which may simultaneously provide a large contact area for achieving strong interfacial polarization and activates more sites for the possible multiple EM wave reflection and scattering. By adopting a simple two-step hydrothermal method, MoSe₂/MoS₂and MoS₂/MoSe₂ inner and outer-interchangeable heterojunctions consisting of 2D MoSe₂ and MoS₂ nanosheets with flower-like geometrical morphology were successfully synthesized. The results revealed that the hydrothermal temperatures significantly impacted the flower-like geometrical morphology and MoS₂ content. By optimizing the microstructures, the designed MoSe₂/MoS₂ and MoS₂/MoSe₂ heterojunctions presented enhanced comprehensive EM wave absorption properties (EMWAPs), possessing strong absorption capability, wide absorption bandwidth and thin matching thicknesses. Generally, this work demonstrates that the optimized EMWAPs of designed heterojunctions mainly originate from the special interfaces and morphology configuration, which also paves a new way for the designing and synthesis of transition metal dichalcogenides-based heterojunction as a novel and desirable candidate for high-performance microwave absorbers.