High-performance and rapid response
electrical heaters with ultraflexibility, superior heat resistance,
and mechanical properties are highly desirable for the development
of wearable devices, artificial intelligence, and high-performance
heating systems in areas such as aerospace and the military. Herein,
a facile and efficient two-step vacuum-assisted filtration followed
by hot-pressing approach is presented to fabricate versatile electrical
heaters based on the high-performance aramid nanofibers (ANFs) and
highly conductive Ag nanowires (AgNWs). The resultant ANF/AgNW nanocomposite
papers present ultraflexibility, extremely low sheet resistance (minimum R
s of 0.12 Ω/sq), and outstanding heat
resistance (thermal degradation temperature above 500 °C) and
mechanical properties (tensile strength of 285.7 MPa, tensile modulus
of 6.51 GPa with a AgNW area fraction of 0.4 g/m2), benefiting
from the partial embedding of AgNWs into the ANF substrate and the
extensive hydrogen-bonding interactions. Moreover, the ANF/AgNW nanocomposite
paper-based electrical heaters exhibit satisfyingly high heating temperatures
(up to ∼200 °C) with rapid response time (10–30
s) at low AgNW area fractions and supplied voltages (0.5–5
V) and possess sufficient heating reliability, stability, and repeatability
during the long-term and repeated heating and cooling cycles. Fully
functional applications of the ANF/AgNW nanocomposite paper-based
electrical heaters are demonstrated, indicating their excellent potential
for emerging electronic applications such as wearable devices, artificial
intelligence, and high-performance heating systems.
In order to ensure the operational reliability and information security of sophisticated electronic components and to protect human health, efficient electromagnetic interference (EMI) shielding materials are required to attenuate electromagnetic wave energy. In this work, the cellulose solution is obtained by dissolving cotton through hydrogen bond driving self-assembly using sodium hydroxide (NaOH)/urea solution, and cellulose aerogels (CA) are prepared by gelation and freeze-drying. Then, the cellulose carbon aerogel@reduced graphene oxide aerogels (CCA@rGO) are prepared by vacuum impregnation, freeze-drying followed by thermal annealing, and finally, the CCA@rGO/polydimethylsiloxane (PDMS) EMI shielding composites are prepared by backfilling with PDMS. Owing to skin-core structure of CCA@rGO, the complete three-dimensional (3D) double-layer conductive network can be successfully constructed. When the loading of CCA@rGO is 3.05 wt%, CCA@rGO/PDMS EMI shielding composites have an excellent EMI shielding effectiveness (EMI SE) of 51 dB, which is 3.9 times higher than that of the co-blended CCA/rGO/PDMS EMI shielding composites (13 dB) with the same loading of fillers. At this time, the CCA@rGO/PDMS EMI shielding composites have excellent thermal stability (THRI of 178.3 °C) and good thermal conductivity coefficient (λ of 0.65 W m-1 K-1). Excellent comprehensive performance makes CCA@rGO/PDMS EMI shielding composites great prospect for applications in lightweight, flexible EMI shielding composites.
Graphic abstract
Flexible electromagnetic
interference (EMI) shielding materials with excellent thermal conductivities
and Joule heating performances are of urgent demand in the communication
industry, artificial intelligence, and wearable electronics. In this
work, highly conductive silver nanowires (AgNWs) were prepared using
the polyol method. Cellulose sheets were then prepared by dissolving
natural cotton in a green and efficient NaOH/urea aqueous solution.
Finally, multifunctional flexible EMI shielding AgNWs/cellulose films
were fabricated based on vacuum-assisted filtration and hot-pressing.
AgNWs are evenly embedded in the inner cellulose matrix and overlap
with each other to form a 3D network. AgNWs/cellulose films, with
a thickness of 44.5 μm, obtain the superior EMI shielding effectiveness
of 101 dB, which is the highest value ever reported for shielding
materials with the same thickness. In addition, AgNWs/cellulose films
present excellent tensile strength (60.7 MPa) and tensile modulus
(3.35 GPa), ultrahigh electrical conductivity (σ, 5571 S/cm),
and excellent in-plane thermal conductivity coefficient (λ∥, 10.55 W/mK), which can effectively dissipate the
heat accumulation. Interestingly, AgNWs/cellulose films also show
outstanding Joule heating performances, good stability, and sensitive
temperature response at driving voltages, absolutely safe for the
human body. Therefore, our fabricated multifunctional flexible AgNWs/cellulose
films have broad prospects in the fields of EMI shielding and protection
of outdoor large-scale power transformers and wearable electronics.
With the widespread application of electronic communication technology, the resulting electromagnetic radiation pollution has been significantly increased. Metal matrix electromagnetic interference (EMI) shielding materials have disadvantages such as high density, easy corrosion, difficult processing and high price, etc. Polymer matrix EMI shielding composites possess light weight, corrosion resistance and easy processing. However, the current polymer matrix composites present relatively low electrical conductivity and poor EMI shielding performance. This review firstly discusses the key concept, loss mechanism and test method of EMI shielding. Then the current development status of EMI shielding materials is summarized, and the research progress of polymer matrix EMI shielding composites with different structures is illustrated, especially for their preparation methods and evaluation. Finally, the corresponding key scientific and technical problems are proposed, and their development trend is also prospected. "Image missing"
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.