Page 14 - ESAM-1-2

Engineering Science in
Additive Manufacturing AM-CFRP structures for EMWA properties

3.3. CF-based hybrid materials composites with graded porosity minimize surface

The capacity of CF-based hybrid materials to combine the reflections and demonstrate broadband absorption. The
structural advantages of CFs with the benefits of numerous addition of supplementary fillers to the porous framework,
functional fillers has drawn much attention owing to their like graphene oxide or MXenes, improves interfacial
EMWA properties. These hybrids exploit the synergistic polarization and conductivity loss. Figure 4 presents
the fabrication procedure of hollow- and PCFs-based
effects between several loss processes, such as magnetic composite materials, each tailored for enhanced EMA
resonance, dipole polarization, and conductive networks, through distinct structural and compositional strategies.
to achieve excellent broadband absorption. A multiscale
conductive network produced by CFs hybridized with In Figure 4A, Co O /carbon composite nanofibers
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CNTs or graphene sheets improves dielectric loss is produced via electrospinning and carbonization,
across a broad frequency range by enhancing interfacial where cobalt oxide nanoparticles embedded in carbon
polarization and electron hopping. nanofibers (CNFs) introduce magnetic loss and interfacial
polarization. In contrast, Figure 4B shows the creation of
Strategic filler distribution and alignment are frequently Fe/Fe₃O₄/C hollow fibers, leveraging a sacrificial template
used in the design of CF-based hybrid materials to maximize to form a hollow core, which improves impedance matching
impedance matching and reduce reflection. These hybrids’ and reduces density while the iron-based components
spatial organization can be precisely controlled through enhance magnetic loss. In Figure 4C, hierarchical porous
additive manufacturing processes, resulting in graded or carbon nanofibers are fabricated using CaCO₃ as a
patterned structures that improve wave attenuation. There porogen, resulting in multiscale porosity that optimizes
is increasing promise for high-performance, customizable wave penetration and multiple scattering for broadband
CF-based hybrid absorbers as the development of additive absorption. In Figure 4D, silica nanoparticle templates and
manufacturing. The creation of multipurpose hybrids with selective etching are employed to produce N-doped porous
energy-absorbing or self-sensing properties creates new CFs, combining high surface area for dielectric loss with
possibilities for intelligent electromagnetic protection nitrogen doping for improved conductivity. Comparatively,
systems. These cutting-edge materials make next- Figures 4B and C demonstrate the excellent lightweight
generation EMWA systems with previously unheard-of designs and broadband performance due to their hollow and
performance characteristics possible. hierarchical porous structures, whereas Figures 4A and D

3.4. Hollow- and porous CFs-based materials depict the integration of magnetic or heteroatom-doped
functionalities. The choice of method depends on the target
The structural properties of hollow and porous CFs (PCFs) application: the methods illustrated in Figures 4A and B
have made them novel materials for EMWA properties. To are ideal for magnetic-dielectric synergy, whereas those
improve impedance matching with free space, these fibers in Figure 4C and D prioritize tunable porosity and surface
hollow cores and porous walls produce a large surface area chemistry for tailored absorption properties.
and several air-material contacts, increasing dielectric loss
and decreasing the effective permittivity. Hollow CFs packed Table 2 summarizes several electromagnetic microwave
with magnetic nanoparticles or lightweight conductive characteristics of various CF-based materials, revealings
polymers have shown remarkable absorption capabilities. several essential trends in CF-based microwave absorbers.
For instance, Tan et al. investigated CNTs/CNFs CF Firstly, absorber thickness shows a clear correlation
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construction of 3D network hierarchical structures toward with performance-thinner absorbers (1 – 2 mm) like
multiple synergistic losses. The minimum RL was achieved the SCF+TiO /paraffin system achieve remarkable
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at −66.00 dB at 1.00 mm, and the maximum effective RL of −46.3 dB, whereas thicker designs (4 – 4.5 mm)
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generally show reduced effectiveness. Second, hybrid
absorption bandwidth was 4.48 GHz at 1.29 mm. It implies systems incorporating magnetic materials with CF
a good prospect for the continuous large-scale preparation demonstrate superior bandwidth performance, with CF/
of ultrathin and efficient electromagnetic wave absorbers.
CoFe O achieving an exceptional 6.48 GHz bandwidth
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Template-assisted techniques, chemical activation, or at −10 dB threshold. Third, paraffin wax emerges as a
controlled pyrolysis of polymer precursors are commonly particularly effective matrix material, which enables the
used to manufacture hollow and PCFs. Porous CF designs, best-performing absorbers in the dataset, likely due to
including lattice or foam-like structures, may now be its favorable dielectric properties and ability to disperse
precisely designed thanks to recent developments in fillers uniformly. It is shown that nanoscale modifications
additive printing, further optimizing electromagnetic (e.g., TiO coating, MnO nanowires) consistently enhance
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wave attenuation. Through the creation of incremental absorption compared to plain CF, with all nanowire-
permittivity transitions, 3D-printed PCF-reinforced modified systems achieving RL below −28 dB. Notably,
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Volume 1 Issue 2 (2025) 8 doi: 10.36922/ESAM025160008