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Microwave interferometers have been attractive devices for high-precision measurements of displacement-related physical quantities in a variety of scientific and engineering applications. However, due to the long operating wavelength, the displacement measurement resolution of microwave interferometers is limited to the micrometer scale. In this article, we propose and demonstrate a novel technology based on microwave interferometry for displacement measurements with potential picometer resolution. An open-ended (OE) transmission line resonator based on a homemade hollow coaxial cable is explored in proof-of-concept numerical and experimental investigations. The technique involves two stages of displacement sensitivity amplification: one is the open end-based phase sensitivity amplification, and the other is the destructive interference-based phase sensitivity amplification. We experimentally demonstrate a wavelength sensitivity amplification factor of 1800 through spectral interrogation where only the open end-based amplification is involved, and a phase sensitivity amplification factor of 1.4 million through phase interrogation where both the open end-based amplification and the destructive interference-based phase shift amplification are involved, i.e., two-stage phase shift amplified microwave interferometry (TPAMI). The numerical investigations and the experimental results match well. [ABSTRACT FROM AUTHOR]

[Display omitted] • Functionalized CNTs disrupt electromagnetic properties. • Amide bonds repaired the blocked electron transport pathways. • CD bridges boost electron flow, aiding electron migration and jumping in composites. • Heterogeneous charges & band gap impact polarization relaxation & conduction loss. Carbon nanotube (CNT)-based composites hold immense promise in the realm of electromagnetic (EM) wave absorption. Surface functionalization of CNTs plays a pivotal role in augmenting their surface binding energy, thereby bolstering their affinity for composites. However, the incorporation of functional groups may disrupt the electronic configuration of sp2 plus delocalized π-bonds and impede electronic transport within the CNT framework. Herein, carbon dots (CDs) were introduced onto the surface of oxidized CNTs (O-CNTs) using a one-step hydrothermal method to enhance their bonding capability and microwave absorption performance. Analysis showed that the characteristic functional groups on the surfaces of the CDs formed amide bonds between the CNTs, bridging them with π-conjugated structures and repairing the blocked electron transport pathway triggered by carboxyl groups. The bridging accelerated the electron flow between adjacent CNTs and enhanced the electron jumping and migration in the CDs-CNTs system. Additionally, a comprehensive investigation of the heterogeneous charge distribution within the CDs bridges and their tunable band gap demonstrated their significant influence on polarization relaxation and conduction loss. In short, the study presents a novel functionalization theory for CNTs that exhibit remarkable microwave-absorption performance in X-band. [ABSTRACT FROM AUTHOR]

The advancement of absorption materials and coating preparation technology is crucial to address the challenges posed by electromagnetic interference and pollution in high-temperature extreme environments. Here, by using a granulation and plasma spraying strategy, we successfully fabricated a series of La 0.8 Sr 0.2 MnO 3 /Al 2 O 3 –13%TiO 2 (LSMO/AT13) high-temperature microwave absorption coatings that have excellent dielectric properties and extremely thermal stability. The results showed that the LSMO/AT13 coatings exhibited remarkable oxidation resistance, withstanding high-temperature aerobic environments of up to 1000 °C. Based on the temperature-dependent permittivity of the coatings, the establishment process of polarization and the transformation of loss mechanism were observed and explained. With the increase of temperature, the main dielectric loss mechanism of the coatings transitions from polarization loss to conductive loss. Thanks to the coordinated effects of impedance and loss, the coatings are capable of effectively absorbing microwave over a wide temperature range. When the LSMO content was 30 wt% and the thickness was 1.9 mm, the effective bandwidth ranged from 1.7 GHz to 2.4 GHz at temperatures below 773 K. This study demonstrates the promising application of LSMO/AT13 microwave absorption coatings for ultra-high temperature environment, and provides a reference for the design and optimization of high-temperature microwave absorption coatings. [ABSTRACT FROM AUTHOR]