Carbon-based materials have been recognized as a promising
method
to eliminate electromagnetic interference (EMI) shielding and electromagnetic
(EM) wave absorption. However, developing lightweight, ultrathin,
and efficient EM wave-shielding and wave-absorbing materials remains
a challenge. Herein, a series of magnetic porous carbon composite
films with a hierarchical network structure were fabricated via pyrolysis
of porous polyimide (PI) films containing magnetic metallic salts
of Fe(acac)3 and Ni(acac)2. After pyrolysis,
the obtained uniform porous carbon films (CFs) possess a favorable
EMI-shielding efficiency (SE) of 46 dB in the X-band with a thickness
of ∼0.3 mm. In addition, a higher EMI SE of 58 dB can be achieved
by increasing the thickness of the porous CF-20Ni to 0.53 mm. Moreover,
the CF-20Ni composites also present effective EM wave-absorbing performance
of RLmin = – 30.2 dB with a loading amount of 20
wt % at 13.0 GHz owing to the hierarchically conductive carbon skeleton,
magnetic Ni nanoparticles, and dielectric interlaced carbon nanotube
cluster within the micropores. These novel lightweight and ultrathin
porous CFs are expected to be attractive candidates for efficient
EM wave absorption and EMI shielding.
High-performance and light-weight polymer foams with
ultralow dielectric
constant, good thermal stability, and high mechanical strength are
greatly needed in aviation and aerospace fields. In this work, cross-linked
and rigid polyimide (PI) composite foams were fabricated based on
norbornene terminated polyamide ester oligomer precursor powders via
thermal foaming method. The obtained PI composite foams exhibit outstanding
characteristics of light weight (90–130 kg·m–3) and high mechanical strength. When the glass fiber (GF) loading
was 10 wt %, the compressive strength and modulus of PI/GF composite
foams reached 1.7 and 49.6 MPa, respectively. Moreover, the PI foams
exhibit remarkable thermal stability and fire-resistant property (LOI
> 42%). The thermal conductivity of the prepared PI foams was measured
to be in the range of 0.039–0.052 W·m–1·K–1 at room temperature. In addition, the
PI composite foams present ultralow dielectric characteristic (tan
δ = 0.006–0.008 at 10 GHz) and prominent wave-transparent
performance (>95%) in the X band (8.2–12.4 GHz). These beneficial
integrated properties enable the resultant PI composite foams to be
attractive candidates for applications in aviation and aerospace fields.
With the rapid development of 5G communication technologies, the high-performance electromagnetic interference (EMI) shielding materials with less secondary reflection for electronic devices have become an urgent demand in recent years. In this study, flexible opencell polyimide (PI) foams containing graphene nanoplatelets (GN)/Fe 3 O 4 coatings for absorption-dominated EMI shielding were fabricated. The result shows that the EMI shielding efficient (EMI SE) of composite foam PI/GN/ Fe 3 O 4 (PF/GN/Fe 3 O 4 ) can achieve 60.6 dB with a thickness of 6.0 mm along with an absorption coefficient (A) of 0.4−0.6, indicating excellent EMI shielding and a low reflection property. Furthermore, the optimal reflection loss (R L ) of PF/GN/Fe 3 O 4 with a low GN loading can be up to −35 dB at 5.0 mm and less than or equal to −10 dB in the whole X-band with a thickness of ≥4.5 mm. In addition, the prepared composite foam PI/GN (PF/GN) exhibits good electrical conductivity of 2.5 × 10 3 S/m and sensing stability. Notably, this research systematically studied the application performance of the composite foam in EMI shielding, electromagnetic wave (EW) absorption, and sensing monitoring. The prepared composite foam can be applied as "Green" EMI shielding materials for flexible electronic devices due to the remarkable EW absorption properties.
Electromagnetic interference (EMI) -shielding and microwave-absorbing
materials are of great significance in the fields of microelectronics
and telecommunication to achieve electromagnetic protection and compatibility.
However, it still remains a challenge to design and fabricate materials
integrating both microwave absorbing and shielding properties. In
this study, we prepared fluffy and porous EMI shielding materials
via facile vapor deposition of pyrrole (Py) on commercial polyamide
fibrous mats (FMs). The uniform polypyrrole (PPy) coating on the fiber
surface endows the FM with a favorable three-dimensional (3D) conductive
network. By the combination of a highly porous microstructure, the
fabricated polyamide fibrous mat@polypyrrole (FM@PPy) presents excellent
microwave-absorbing and EMI-shielding properties. The EMI shielding
efficiency (EMI SE) of FM@PPy can reach 40 dB with a high absorption
coefficient (A) of 0.8, showing extremely low reflection
with “green” EMI shielding characteristics in the whole
X-band (8.2–12.4 GHz). Meanwhile, the reflection loss (RL)
of FM@PPy is less than −10 dB in the X-band. Moreover, FM@PPy
also exhibits favorable stability and reliability as a wearable sensor.
The FM@PPy demonstrates promising potential for “green”
EMI shielding, broadband microwaves absorbing and highly stable intelligent
sensor.
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