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[Display omitted] • Basalt coated by NiO is synthesized by water bath method followed by sintering process. • The enhanced microwave absorption for basalt@NiO heterostructure has been achieved when sintered at 300 °C. • An amount of vacancies defects and large heterogeneous interface in basalt@NiO-300 °C improve the dielectric loss. • Basalt@NiO heterostructure also has low density, high temperature resistance and excellent anticorrosion. The heterostructure has attracted widespread attention in improving microwave absorption due to the unique composition and structure. Herein, a novel two-dimensional (2D) plate@shell basalt@NiO heterostructure is synthesized through a sequential process of water bath method followed by a sintered operation. The sintering temperature helps regulate the microwave absorption performance by controlling the heterogeneous interface and vacancy defects of basalt@NiO to optimize the dielectric loss. The RL of the prepared basalt@NiO with the sintering temperature of 300 °C reaches up to −15.93 dB at 16.13 GHz, which is attributed to the polarization loss enhanced by vacancy defects (O, Ni vacancies) introduced by low-temperature sintering and large heterogeneous contacts constructed by basalt and NiO. Meanwhile, the high concentration of vacancy defects also leads to a large electrical conductivity that positively contributes to dielectric loss. Furthermore, the basalt@NiO composite possesses relatively low density, high thermal stability and anticorrosion. This finding provides a way for designing the light microwave absorption materials with excellent environmental stability. [ABSTRACT FROM AUTHOR]

The introduction of selenium vacancies modulates the local charge density and enhances the dipole polarization loss. In addition, the presence of selenium vacancies enhances the conductivity loss of CoSe 2. The minimum reflection loss of CoSe 2 -600 reaches −30.73 dB and the effective absorption bandwidth reaches 4.00 GHz at 1.8 mm. [Display omitted] • Re-annealing strategy successfully introduces selenium vacancies. • Selenium vacancies successfully regulate the local charge density of CoSe 2. • The RL min of CoSe 2 is −30.73 dB, and EAB covers 4.00 GHz at 1.8 mm. The weak electromagnetic loss capability of the single semiconductor material is difficult to meet the complicated electromagnetic environment nowadays, so vacancy engineering is employed to optimize the dielectric loss capability of CoSe 2. Selenium vacancies are introduced into CoSe 2 by re-annealing treatment, and the test results show that the selenium vacancies concentration enlarged with annealing temperature. The formation of selenium vacancies introduces a localized state in CoSe 2 , which enhances the capability of CoSe 2 to trap charge carriers, and the increased conductivity contributes to the enhancement of the dielectric loss capability. Density Functional Theory (DFT) calculations demonstrate that the selenium vacancies disrupt the original charge equilibrium distribution of the CoSe 2 , and the non-recombined positive and negative charge centers induce a strong electric dipole polarization loss. Benefiting from the optimization of CoSe 2 dielectric loss by the selenium vacancies engineering, RL min of CoSe 2 -600 reaches −30.73 dB and the effective absorption bandwidth reaches 4.00 GHz at 1.8 mm. This study provides a simple and effective solution to optimize the microwave absorption performance of single-component microwave absorption materials. [ABSTRACT FROM AUTHOR]

The earliest microwave absorbing materials (MAMs) are fabricated in the early 20th century for military purpose to inhibit radar detection. Currently, the application of MAMs has been existing in every part of human's life to prevent radiation and interference. The microwave absorbant and microwave absorbing coatings classified by composition including alloys, metal oxides, conductive polymers, carbon materials, ceramic materials both in traditional and innovative forms are introduced in this work. Considering the harsh and complex application environment, MAMs with high temperature resistance and infrared-compatible stealth performance are involved. Metamaterials, showing excellent electromagnetic properties which are far beyond that of the materials can achieve, including perfect absorber, digitally coded control metamaterials, bionic structural materials, and adjustable smart metamaterials, are also introduced specifically in this work. In addition, to investigate electromagnetic response of absorbant, the first-principles calculations works are overviewed. The electromagnetic properties, loss mechanisms, structure, fabrication method, regulation approaches, designing principles, current applications, and future prospects of MAMs are involved in this work. This work gives a comprehensively overview over the MAMs for their theoretical and experimental advances in recent years including the military radar (frequency range of 2–18 GHz) stealth materials, relevant infrared compatible (infrared-visible, infrared-radar, infrared-laser) stealth materials, and other stealth materials with multifrequency adaptability. [ABSTRACT FROM AUTHOR]