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Xu et al. Soft Sci. 2025, 5, 43 https://dx.doi.org/10.20517/ss.2025.63 Page 3 of 16

the X-band at a low Ti C T content of 0.74 vol.%. However, the large specific surface area and high number
3 2 X
of surface functional groups make MXenes highly susceptible to oxidation in air. The poor compressive
ability and insufficient mechanical properties of MXene aerogels are greatly limited by their inherent
brittleness, 2D lamellar structure, and lack of a protective layer. The researchers found that the oxidation of
MXenes could be effectively prevented, and their stability improved through compositing with other
materials and structural design. Wu et al. reported on an MXene/MoS composite coated with carbon to
2
protect its structure . This carbon layer reduces oxidation by external oxygen and the formation of
[44]
oxygen-containing groups during annealing at high temperatures. Zhao et al. reported that an MXene/GO-
based aerogel possesses structural diversity and an outstanding electromagnetic interference (EMI)
shielding effectiveness of > -50 dB . All of the abovementioned second-phase materials are highly
[43]
[45]
conductive . The introduction of these materials affects the dielectric properties of the substrate, making it
difficult to regulate these properties. This increases the reflection of electromagnetic waves on the surface of
the material, thereby reducing its absorption efficiency. In contrast, introducing electromagnetic wave
transparent materials with lower dielectric constants does not affect the dielectric properties of the substrate
material but can improve its stability to a certain extent. Si N is characterized by its low density (3.18-3.44
4
3
g/cm ), excellent microwave transparent dielectric properties , and good mechanical and chemical
3
[46]
stabilities [47,48] . Therefore, it can maintain structural integrity in extremely harsh environments and is not
easily deformed or damaged. Its low dielectric loss helps reduce the reflection of electromagnetic waves on
the material surface [49-51] , allowing the electromagnetic waves to pass through effectively and reach deep
inside the material. Amorphous Si N prepared by Chemical Vapor Infiltration (CVI) has several unique
4
3
advantages [52,53] , including (1) Structural homogeneity: Amorphous Si N has no long-range ordering and
4
3
does not have structural defects such as grain boundaries, twins, and dislocations; (2) Excellent mechanical
properties: amorphous Si N are stronger and harder than crystalline Si N , making them suitable for high-
3
3
4
4
strength and high-toughness applications; (3) Chemical stability: amorphous Si N is chemically stable and
3
4
has good antioxidant properties, enabling it to remain stable in high-temperature and oxidative
environments. Therefore, depositing amorphous Si N on the surface of MXene using the CVI process
3
4
results in a uniformly distributed Si N layer, forming a unique Si N -MXene-Si N sandwich structure .
[54]
3
4
3
4
4
3
This effectively improved the mechanical properties and chemical stability of the aerogel. Overall, a Si N -
4
3
MXene composite aerogel with a layered porous structure is expected to enhance both the mechanical and
electromagnetic wave absorbing properties simultaneously; however, there are currently few related studies.
Here, we provide new ideas for nanomaterials in the field of electromagnetic wave absorption by
introducing insulating electromagnetic wave transparent materials in combination with MXene’s properties.
In this study, MXene aerogel with lamellar structure was fabricated via a bidirectional freeze-drying
method. Then we deposited amorphous Si N onto the surface of MXene nanosheets of Ti CT aerogels
2
3
X
4
[55]
using the CVI technique . The resulting Ti CT /Si N composites retained the pristine lamellar structure of
3
4
2
X
MXene aerogel. The layered porous structure of the Ti CT /Si N aerogel promotes multiple reflections and
3
4
2
X
scattering of electromagnetic waves within the material, which significantly increases the propagation path
of electromagnetic waves, thereby improving the opportunity for absorption. In addition, the combination
of the high electrical conductive MXenes and the low dielectric Si N produces interfacial polarization, the
3
4
abundance of functional groups on the surface of MXene brings sufficient dipole polarization, the high
electrical conductivity of MXene given conductive loss, the synergistic effect of the multiple reflections and
scattering, interfacial polarization, dipole polarization, and conductive loss results in an efficient
electromagnetic wave absorption system . With a Ti CT content of only 0.21 wt.%, the composites have
[56]
2
X
an effective absorption bandwidth (EAB) that covers the entire X-band (8.2-12.4 GHz). The lowest
reflection loss of −53 dB was achieved at a sample thickness of 5 mm. Therefore, this study proposes the
design and fabrication of biomimetic porous Ti CT /Si N composites with a laminated structure to
4
3
X
2
effectively absorb and dissipate electromagnetic radiation.