In the context of the fifth-generation (5G) smart era, the demand for electromagnetic wave (EMW)-absorbing materials has become increasingly prominent, so it is necessary to explore promising candidate materials. This work focuses on the exploration of the material absorbing properties of a MoAlB MAB (MAB represents a promising group of alternatives, where M stands for a transition metal, A typically denotes Al, and B is boron) phase system. First, the first-principles calculations were performed to reveal the unique crystal and layered structure of the MoAlB ceramics and to predict their potential for use as an EMW absorption material. Subsequently, a series of MoAlB ceramics were synthesized at temperatures ranging from 800 to 1300 °C, and the influence of temperature on the phase compositions and microstructures of the obtained MoAlB ceramics was characterized and analyzed. Finally, the practical EMW absorption performance of the prepared MoAlB ceramics was evaluated via a combination of experiments and radar cross-sectional calculations. The MoAlB sample synthesized at 900 °C exhibits superior EMW absorption performance, achieving an impressive minimum reflection loss (RL) of −50.33 dB. The unique layered structure and good electrical conductivity of the MoAlB samples are the main reasons for their enhanced wave absorption performance, which provides interfacial polarization and multiple dielectric loss mechanisms. Therefore, this study not only contributes to the understanding of the preparation of MoAlB materials but also provides potential guidance for their utilization in the realm of electromagnetic wave absorption.

Perovskite materials (ABO₃) possess a wealth of elements selectable and exhibit a diverse range of octahedral transformations. The emergence of high-entropy perovskite ceramics provides a fresh perspective for advancing the field of wave-absorbing materials. In this study, we concentrate on the wet chemical synthesis of a high-entropy perovskite oxide, Sr(Cr_0.2Mn_0.2Fe_0.2Co_0.2Ni_0.2)O₃, and investigate its crystal structure, microstructure, chemical composition, magnetic properties, and microwave absorbing capabilities. The results indicate that when sintered at a temperature of 1,350 ℃, the sample achieves a minimum reflection loss of −54.0 dB at a frequency of 9.68 GHz, accompanied by a maximum effective absorption bandwidth (EAB) of 7.44 GHz at the thickness of 1.8 mm. The high-entropy design of the B-site induces distortions of oxygen vacancy and octahedral structure of the perovskite material. This leads to the fine tuning of its dielectric and magnetic properties, thereby endowing perovskite with excellent electromagnetic wave absorption capabilities. Consequently, perovskite emerges as a promising new electromagnetic wave absorption material with significant potential.

Due to chemical inertness of nickel and boron, the preparation of nickel borides and corresponding layered ternary transition metal borides Ni₃ZnB₂ (MAB phase) has always required high-temperature and/or high-pressure conditions. Yet, an innovative and efficient approach to preparing Ni₃ZnB₂ at only 600 ℃ and without applied pressure is presented in this study. It is discovered that by simply adjusting the temperature, a phase transition from Ni₃ZnB₂ to Ni₄B₃ with a layered structure could be induced. This transition between the binary-component and the ternary-component brings about significant variation in electromagnetic wave (EMW) shielding/absorption performance of prepared borides. For instance, Ni₂B has good EMW shielding performance (42.54 dB in X band) and Ni₃ZnB₂ is of weak EMW shielding (13.43 dB in X band); Ni₃ZnB₂ has poor EMW absorption performance (−5 dB) while Ni₄B₃ has excellent EMW absorption performance (−45.19 dB) at a thickness of 2.7 mm with effective absorption bandwidth (10.4 GHz).

Ti₃C₂T_x nanosheets have attracted significant attention for their potential in electromagnetic wave absorption (EWA). However, their inherent self-stacking and exorbitant electrical conductivity inevitably lead to serious impedance mismatch, restricting their EWA application. Therefore, the optimization of impedance matching becomes crucial. In this work, we developed polymethyl methacrylate (PMMA)@Ti₃C₂T_x@SiO₂ composites with a sandwich-like core–shell structure by coating SiO₂ on PMMA@Ti₃C₂T_x. The results demonstrate that the superiority of the SiO₂ layer in combination with PMMA@Ti₃C₂T_x, outperforming other relative graded distribution structures and meeting the requirements of EWA equipment. The resulting PMMA@Ti₃C₂T_x@SiO₂ composites achieved a minimum reflection loss of −58.08 dB with a thickness of 1.9 mm, and an effective absorption bandwidth of 2.88 GHz. Mechanism analysis revealed that the structural design of SiO₂ layer not only optimized impedance matching, but also synergistically enhanced multiple loss mechanisms such as interfacial polarization and dipolar polarization. Therefore, this work provides valuable insights for the future preparation of high-performance electromagnetic wave absorbing Ti₃C₂T_x-based composites.

Two-dimensional (2D) transition metal carbides (MXene) possess attractive conductivity and abundant surface functional groups, providing immense potential in the field of electromagnetic wave (EMW) absorption. However, high conductivity and spontaneous aggregation of MXene suffer from limited EMW response. Inspired by dielectric–magnetic synergy effect, the strategy of decorating MXene with magnetic elements is expected to solve this challenge. In this work, zigzag-like Mo₂TiC₂–MXene nanofibers (Mo-based MXene (Mo–MXene) NFs) with cross-linked networks are fabricated by hydrofluoric acid (HF) etching and potassium hydroxide (KOH) shearing processes. Subsequently, Co-metal–organic framework (MOF) and derived CoNi layered double hydroxide (LDH) ultrathin nanosheets are grown inside Mo–MXene NFs, and the N-doped carbon matrix anchored by CoNi alloy nanoparticles formed by pyrolysis is firmly embedded in the Mo–MXene NFs network. Benefiting from synergistic effect of highly dispersed small CoNi alloy nanoparticles, a three-dimensional (3D) conductive network assembled by zigzag-like Mo–MXene NFs, numerous N-doped hollow carbon vesicles, and abundant dual heterogeneous interface, the designed Mo–MXene/CoNi–NC heterostructure provides robust EMW absorption ability with a reflection loss (RL) value of −68.45 dB at the thickness (d) of 4.38 mm. The robust EMW absorption performance can be attributed to excellent dielectric loss, magnetic loss, impedance matching (Z), and multiple scattering and reflection triggered by the unique 3D network structure. This work puts up great potential in developing advanced MXene-based EMW absorption devices.

Ti₃C₂T_x MXene shows great potential in the application as microwave absorbers due to its high attenuation ability. However, excessively high permittivity and self-stacking are the main obstacles that constrain its wide range of applications. To tackle these problems, herein, the microspheres of SiO₂@Ti₃C₂T_x@CoNi with the hydrangea-like core–shell structure were designed and prepared by a combinatorial electrostatic assembly and hydrothermal reaction method. These microspheres are constructed by an outside layer of CoNi nanosheets and intermediate Ti₃C₂T_x MXene nanosheets wrapping on the core of modified SiO₂, engendering both homogenous and heterogeneous interfaces. Such trilayer SiO₂@Ti₃C₂T_x@CoNi microspheres are "magnetic microsize supercapacitors" that can not only induce dielectric loss and magnetic loss but also provide multilayer interfaces to enhance the interfacial polarization. The optimized impedance matching and core–shell structure could boost the reflection loss (RL) by electromagnetic synergy. The synthesized SiO₂@Ti₃C₂T_x@CoNi microspheres demonstrate outstanding microwave absorption (MA) performance benefited from these advantages. The obtained RL value was −63.95 dB at an ultra-thin thickness of 1.2 mm, corresponding to an effective absorption bandwidth (EAB) of 4.56 GHz. This work demonstrates that the trilayer core–shell structure designing strategy is highly efficient for tuning the MA performance of MXene-based microspheres.

Two-dimensional (2D) transition metal carbide MXene-based materials hold great potentials applied for new electromagnetic wave (EMW) absorbers. However, the application of MXenes in the field of electromagnetic wave absorption (EMA) is limited by the disadvantages of poor impedance matching, single loss mechanism, and easy oxidation. In this work, MoO₃/TiO₂/Mo₂TiC₂T_x hybrids were prepared by the annealing-treated Mo₂TiC₂T_x MXene and uniform MoO₃ and TiO₂ oxides in-situ grew on Mo₂TiC₂T_x layers. At the annealing temperature of 300 ℃, the minimum reflection loss (RL_min) value of MoO₃/TiO₂/Mo₂TiC₂T_x reaches −30.76 dB (2.3 mm) at 10.18 GHz with a significantly broadening effective absorption bandwidth (EAB) of 8.6 GHz (1.8 mm). The in-situ generated oxides creating numerous defects and heterogeneous interfaces enhance dipolar and interfacial polarizations and optimize the impedance matching of Mo₂TiC₂T_x. Considering the excellent overall performance, the MoO₃/TiO₂/Mo₂TiC₂T_x hybrids can be a promising candidate for EMA.

Multifunctionalization is the development direction of personal thermal energy regulation equipment in the future. However, it is still a huge challenge to effectively integrate multiple functionalities into one material. In this study, a simple thermochemical process was used to prepare a multifunctional SiC nanofiber aerogel spring (SiC NFAS), which exhibited ultralow density (9 mg/cm³), ultralow thermal conductivity (0.029 W/(m·K) at 20 ℃), excellent ablation and oxidation resistance, and a stable three-dimensional (3D) structure that composed of a large number of interlacing 3C-SiC nanofibers with diameters of 300-500 nm and lengths in tens to hundreds of microns. Furthermore, the as-prepared SiC NFAS displayed excellent mechanical properties, with a permanent deformation of only 1.3% at 20 ℃ after 1000 cycles. Remarkably, the SiC NFAS exhibited robust hyperelasticity and cyclic fatigue resistance at both low (~ -196 ℃) and high (~700 ℃) temperatures. Due to its exceptional thermal insulation performance, the SiC NFAS can be used for personal thermal energy regulation. The results of the study conclusively show that the SiC NFAS is a multifunctional material and has potential insulation applications in both low- and high-temperature environments.

In order to prevent the microwave leakage and mutual interference, more and more microwave absorbing devices are added into the design of electronic products to ensure its routine operation. In this work, we have successfully prepared MoS₂/TiO₂/Ti₃C₂T_x hierarchical composites by one-pot hydrothermal method and focused on the relationship between structures and electromagnetic absorbing properties. Supported by comprehensive characterizations, MoS₂ nanosheets were proved to be anchored on the surface and interlayer of Ti₃C₂T_x through a hydrothermal process. Additionally, TiO₂ nanoparticles were obtained in situ. Due to these hierarchical structures, the MoS₂/TiO₂/Ti₃C₂T_x composites showed greatly enhanced microwave absorbing performance. The MoS₂/TiO₂/Ti₃C₂T_x composites exhibit a maximum reflection loss value of -33.5 dB at 10.24 GHz and the effective absorption bandwidth covers 3.1 GHz (13.9-17 GHz) at the thickness of 1.0 mm, implying the features of wide frequency and light weight. This work in the hierarchical structure of MoS₂/TiO₂/Ti₃C₂T_x composites opens a promising door to the exploration of constructing extraordinary electromagnetic wave absorbents.

Ultra-large zirconia toughened alumina (ZTA, mass ratio of Al₂O₃ and ZrO₂ is 78:22) ceramics with eccentric circle shape were successfully sintered by microwave sintering with a multi-mode cavity at 2.45 GHz. The dimension of ZTA ceramics (green body) is 165 mm (outer diameter) × 25 mm (thickness). The optimized sintering temperature of microwave sintering is about 1500 ℃ for 30 min, and the total sintering time is about 4 h which is much shorter than that of conventional sintering. An auxiliary-heating insulation device was designed based on the principle of local caloric compensation to guarantee the intact sintered samples. With the increasing of sintering temperature, more and more microwave energy is absorbed within the entire sample, volumetric densification performs, and phases shift from m-ZrO₂ phase to t-ZrO₂ phase and cause Al₂O₃ grain growth.