Liu Yijie,Wang Xiaodong,Hou Shuaihang,Wu Zuoxu,Wang Jian,Mao Jun,Zhang Qian,Liu Zhiguo,Cao Feng
Flexible thermoelectric generators can power wearable electronics by harvesting body heat. However, existing thermoelectric materials rarely realize high flexibility and output properties simultaneously. Here we present a facile, cost-effective, and scalable two-step impregnation method for fabricating a three-dimensional thermoelectric network with excellent elasticity and superior thermoelectric performance. The reticular construction endows this material with ultra-light weight (0.28 g cm −3 ), ultra-low thermal conductivity (0.04 W m −1 K −1 ), moderate softness (0.03 MPa), and high elongation (>100%). The obtained network-based flexible thermoelectric generator achieves a pretty high output power of 4 μW cm −2 , even comparable to state-of-the-art bulk-based flexible thermoelectric generators.
Exploring N-type High-entropy materials with both high thermoelectric and mechanical properties is highly desirable for all-high-entropy thermoelectric generators (TEGs) since the thermoelectric and mechanical properties of N-type one are largely behind its P-type counterparts. Herein, a new rock-salt structure N-type high entropy thermoelectric AgBiPbSe 2 S is introduced with a bandgap of ≈0.43 eV. The atomic radii difference of each component results in a large lattice distortion of 0.246, leading to a low thermal conductivity of 0.36 W m −1 K −1 at 823 K. The figure of merit ( ZT ) reaches 0.6 for AgBiPbSe 2 S at 823 K. Moreover, Ag 2 Se precipitates are included in AgBiPbSe 2 S to filter low energy carriers for high Seebeck coefficients and to scatter phonons with nanoscale wavelength for ultralow lattice thermal conductivities. Consequently, a peak ZT of ≈1.18 at 823 K and an average ZT of 0.60 at 400–823 K are obtained for Ag 1.02 BiPbSe 2 S. More importantly, high mechanical properties are also obtained in Ag 1.02 BiPbSe 2 S, of which the Vickers hardness and flexural strength are ≈209 Hv and 32 MPa, respectively, originating from the enhanced lattice friction by chemical short-range disorder (i.e., high entropy effect) and dispersion strengthening caused by Ag 2 Se nanoprecipitates.
With the rapid development of modern information technology, high-level electromagnetic wave (EMW) absorbing materials are playing an increasingly important role in military and civilian fields. However, current EMW absorbers usually have narrow absorption bandwidths and low absorption strengths , which hinder their practical applications. Herein, lightweight aerogels with low thermal conductivity and highly efficient EMW absorption were fabricated via a sol–gel method and subsequent carbothermal reduction with a simple chemical reaction process. The as-prepared graphene/SiC-nanosheets aerogels are composed of a large number of the interconnected two-dimensional SiC nanosheets and graphene sheets with abundant micrometer-sized pores that favored impedance matching, which endows the aerogels with outstanding EMW-absorbing performance. Conductive loss and interfacial polarization further promote the EMW-absorbing of the graphene/SiC-nanosheets aerogels. In addition, the highly porous and interconnected three-dimensional graphene/SiC-nanosheets aerogel networks not only facilitate the absorption of infiltrated EM waves via multiple reflection but also effectively reduce the number of heat transmission routes in the aerogels. The as-prepared SiC/G-2 aerogel exhibites excellent EMW-absorbing property, with a RL min of −65.08 dB at a frequency of 13.20 GHz, a thickness of 3.5 mm and an EAB of 2.21 GHz. These results demonstrate that the as-prepared graphene/SiC-nanosheets aerogel is fascinating material with possible applications in high-performance EMW-absorbing and heat-insulating in the aviation and aerospace fields.
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