Yaru Wang,Ruyue Su,Jingyi Chen,Wenqing Wang,Xueqin Zhang,Hao Xu,Rujie He
With 5G and millimeter-wave technologies evolving rapidly, the high communication frequency leads to high integration and miniaturization of the Luneburg lens (LL). In this paper, a miniaturized K-band flat LL with 0.95MgTiO 3 –0.05CaTiO 3 (95MCT) ceramic was designed and successfully printed by vat-photopolymerization 3D printing . Optimal 3D printing parameters and thermal treatment processes of 95MCT ceramic were investigated. The as-prepared 95MCT ceramic showed excellent properties: a density of 3.40 g/cm 3 , a high flexural strength of 81.78 MPa, a dielectric constant of 17.7, and a remarkably low dielectric loss value of 4.56 × 10 -4 . Based on the 95MCT ceramic, a flat LL with a diameter of 40 mm and thickness of 6 mm was printed with sophisticated metastructure. While miniaturization was accomplished with a high degree of dimensional compression, the printed flat LL showed a maximum gain enhancement over 5 dBi. Thus, this study provides a novel viewpoint on the fabrication of microwave dielectric ceramic and miniaturized ceramic radio frequency (RF) devices with complex structures.
Ni 0.42-x/3 Nb x /3 Cu 0.18 Zn 0.4 Mn x Fe 1.98− x O 4− δ ( x = 0–0.1) materials, possessing a high saturation magnetization, high dielectric constant, and narrow ferromagnetic resonance linewidth, were prepared via the solid-phase reaction method. The cation distribution, as well as the dielectric and gyromagnetic properties, were studied in detail. Mn 2+ and Nb 5+ incorporated in the lattice occupy tetrahedral site, causing the redistribution of cation and the reduction of A–B superexchange interaction. This leads to an increase in saturation magnetization followed by a decrease. The introduction of appropriate amounts of Mn 2+ and Nb 5+ ions reduces the magnetocrystalline anisotropy constant | K 1 | and thus reduces the ferromagnetic resonance linewidth ( ΔH ). Furthermore, high polarisability of Mn 2+ and Nb 5+ causes the increase in the dielectric constant of the ferrites. At x = 0.08, excellent gyromagnetic and dielectric properties, including a high dielectric constant ( ε ’ = 15.4@100 MHz), high saturation magnetization (4π M s = 4577 G), and narrow ferromagnetic resonance linewidth (Δ H = 129 [email protected] GHz) for the NiCuZn ferrite, was achieved. Finally, a K-band microstrip circulator operating at 20.8 to 28 GHz was designed. The simulation showed that the isolation of the circulator in the working frequency band is greater than 20 dB, showing the potential of the prepared ferrites in microwave circulators.
Bing Zhou,Zhen Zhang,Yanli Li,Gaojie Han,Yuezhan Feng,Bo Wang,Dianbo Zhang,Jianmin Ma,Chuntai Liu
Flexible, lightweight, robust, and multifunctional characteristics are greatly desirable for next-generation wearable electromagnetic interference (EMI) shielding materials. In this work, an alternating multilayered structure with robust polymer frame layers and directly contacted conducting layers was designed to prepare high-performance EMI films. Especially, the multilayered films containing alternating cellulose nanofiber (CNF) layers and MXene layers are fabricated via a facile and efficient alternating vacuum filtration approach. Deriving from the mechanical frame effect acted by CNF layers in, which is capable of preventing the nanosized “zigzag” crack in MXene layers from growing to the whole film, the alternating multilayered film (CNF@MXene) revealed the improved mechanical strength (112.5 MPa) and toughness (2.7 MJ m–3) compared to both freestanding MXene film and homogeneous CNF/MXene film. Meanwhile, the directly contacted MXene layers resulted in the increased electrical conductivity from 2 (homogeneous CNF/MXene film) to 621–82 S m–1 (CNF@MXene films). In conjunction with the extra “reflection-absorption-zigzag reflection” mechanism among the alternating multilayers, CNF@MXene films demonstrated an exceptional EMI shielding effectiveness of ∼40 dB in the X-band and K-band and high specific shielding effectiveness up to 7029 dB cm2 g–1 at a thickness of only 0.035 mm. Besides, the excellent mechanical flexibility ensured the stable EMI shielding and electrical properties, which can withstand the folding test more than 1000 times without obvious reduction. Moreover, the excellent electrical conductivity endows the alternating multilayered film with an outstanding and steady Joule heating performance, which could reach more than 100 °C at only 6 V impressed voltage to within 10 s. As a result, our alternating multilayered film with reinforced EMI shielding and Joule heating performance is promising in the next-generation intelligent protection devices applying in cold and complex practical environments.
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