Electromagnetic Materials Research Articles

Hollow N doped carbon/SiCN hierarchical structures for thermostable electromagnetic absorptions

Electromagnetic absorption materials present widespread application prospects. The thermal oxidative aging issues for electromagnetic absorption materials have received little attention. In this paper, N-doped carbon tubes, and the SiCN ceramics are combined to realize thermostable electromagnetic absorptions. The hierarchical structures show significantly enhanced broadband electromagnetic absorption with an optimal RL of -53.61 dB at 14 GHz under a thickness of 2 mm. The effective electromagnetic absorption bandwidth reaches 5.53 GHz, and the coverage range is 11.88–17.41 GHz. More importantly, after 1 h calcination at 300 °C, the optimum RL of NCT/SiCN-1 h is still -45.67 dB under the thickness of 2.5 mm. The effective electromagnetic absorption bandwidth increases to 5.95 GHz, and the coverage range is 10.69–16.64 GHz. Our work proves the possibility for improving the thermostable electromagnetic absorptions of carbon materials, and provides referencing ways for the design of thermostable electromagnetic absorption materials.

Efficient Nanofibrous Electromagnetic Wave Absorber Inspired by Spider Silk Hunting.

With the rapid advancements in wireless communication and radar detection technologies, there has been a significant uptick in the utilization frequency of electromagnetic waves across both civilian and military sectors, consequently generating substantial electromagnetic radiation and interference. These electromagnetic pollutants present a considerable threat to public health and information security. Consequently, materials capable of absorbing and mitigating electromagnetic pollution have garnered significant attention.The nanomaterials with multiple components and various heterogeneous interfaces have been considered as preferred efficient electromagnetic wave (EMW) absorbers. In this work, carbon nanofibers doped with magnetic metal oxide particles (Co/Ni-CNFs) are prepared by electrospinning and heat treatment. In these samples, the minimum reflection loss can reach -40.13dB at 4.6mm, and the widest effective absorption bandwidth is 4.4GHz. The excellent microwave absorption is attributed to the appropriate impedance matching. The electromagnetic parameters of Co/Ni-CNFs are balanced by adjusting the concentration of magnetic metal-organic framework material (MOFs) in the precursor solution. It is believed that this work can provide a reference for developing lightweight, flexible, and robust electromagnetic wave-absorbing materials.

Prediction of Broadband and Highly-Efficient Electromagnetic Wave-Absorbing SiC@SiO2 Nanowire Aerogel by Genetic Algorithm.

Searching for lightweight and high-temperature stable electromagnetic wave-absorbing materials with broad absorbing bandwidth and high efficiency is of significance for applications in daily life and industry. Optimizing the dielectric properties of SiC nanowire aerogel by both compositional and structural designs is an efficient way to obtain simultaneous efficient wave-dissipation ability and good impendence matching and thus the desired properties. However, due to the complex effects of dielectric parameters on the wave-absorbing properties, rational design of high-performance electromagnetic wave-absorbing materials remains challenging. Herein, we propose a genetic algorithm-based approach to predict broadband and highly efficient electromagnetic wave-absorbing materials in a SiC@SiO2 nanowire aerogel-based system. The obtained SiC@SiO2 nanowire aerogels exhibit a gradient multilayered structure with a low dielectric outer layer, a medium layer with alternatively distributed electromagnetic wave transparent and attenuation layers, and an inner high attenuation layer, giving it a broadband electromagnetic wave-absorbing performance covering almost all the 2-18 GHz bandwidth and simultaneous high efficiency. The results show that the genetic algorithm-based approach is efficient in predicting high-performance electromagnetic wave-absorbing ceramic aerogels.

Synthesis of in situ grown CNTs on MOF-derived Ni@CNT with tailorable microstructures toward regulation of electromagnetic wave absorption performance

Metal-Organic framework (MOF) derivatives have been applied as electromagnetic wave absorption (EMA) materials in recent years. Carbon nanotubes (CNTs) can achieve in situ growth on the surface of MOF derivatives. However, there is limited research on the EMA performance by regulating the morphology of the in situ grown CNTs. In this work, we prepared MOF-derived Ni@carbon nanotubes (Ni@CNT) with controllable length of CNTs by solvothermal and simple one-step pyrolysis method and revealed the CNT growth mechanism. We further investigated the effect of in situ grown CNT morphology on electromagnetic parameters and EMA performance. In situ grown CNTs of similar length on the surface of MOF derivatives lead to similar electromagnetic parameters. When the length of CNTs is short, the relaxation strength (Δε=εs−ε∞) is high, leading to excellent microwave absorption performance. For Ni@CNT-600, the reflection loss of −44.4 dB can be achieved at merely 1.72 mm. Finite element (FE) simulation was used to evaluate the EMA mechanism of different samples by calculating electric field and polarization strength. This work has explored the electromagnetic wave absorption performance from the perspective of microstructural tailoring, helpful for understanding the unique role of the in situ grown CNTs on the surface of MOF derivatives and investigating the ultra-thin electromagnetic wave absorption materials.

Research on Efficient Electromagnetic Shielding Performance and Modulation Mechanism of Aero/Organo/Hydrogels with Gravity-Induced Asymmetric Gradient Structure.

To eliminate electromagnetic pollution, it is a challenging task to develop highly efficient electromagnetic shielding materials that integrate microwave absorption (MA) performance with high shielding capability and achieve tunability in shielding performance. Asymmetrically structured aero/organo/hydrogels with a progressively changing concentration gradient of liquid metal nanoparticles (LMNPs), induced by gravity, are prepared by integrating the conductive fillers Ti3C2Tx MXene and LMNPs into a dual-network structure composed of polyvinyl alcohol and cellulose nanofibers. Benefiting from the unique structure, which facilitates the absorption-reflection-reabsorption process of electromagnetic waves along with conductive fillers and the porous structure, three types of gels demonstrate efficient shielding performance. HPCML achieves a total shielding effectiveness (SET) of up to 86.9dB and a reflection shielding effectiveness (SER) of as low as 2.85dB. Especially, APCML, with an ultra-low reflection coefficient (R) of 6.4%, achieves compatibility between shielding performance and MA properties. The relationship between dispersing media (air, water, and glycerol/water) and the shielding performance of aero/organo/hydrogels is explored, thereby achieving modulation of the shielding performance of the gel system. The work has paved a clear path for integrating absorption and shielding capabilities into a composite material, thereby providing a prototype of a highly efficient shielding material with MA performance.

Zr4+ and Al3+ coordinated cross-linked conductive collagen fibers/solvent-free polyurethane foam with ultra-low reflective electromagnetic shielding properties

In recent years, electromagnetic shielding materials with low reflectance have developed rapidly. However, high material cost, poor bonding fastness, weak mechanical properties and other problems seriously limit its effect in practical use. In this work, flexible conductive collagen fibers (CLF-Zr4+/Al3+-CNTs) were prepared using chromium tanned waste leather as ingredient, carbon nanotubes (CNTs) as conductive filler and transition metal ions as coordination crosslinking agents, and their molecular dynamics were investigated by quantum chemical simulation software. On this basis, a flexible conductive foam with the double layer and double core-clad structure containing carbon nanotubes was constructed using the solvent-free polyurethane (SFPU) chemical foaming technology, and their electromagnetic shielding properties and reflectance were studied. The experiment results showed that when the ratio of CLF-Zr4+/Al3+-CNTs to SFPU polyol is 1:9 and the impregnation times of CNTs are 2, the loading capacity of CNTs in conductive foam is 0.14 mg/cm3, the electrical conductivity is 57.8 S/m, and the thermal conductivity is 0.061 W/(m·K). Meanwhile, when the thickness is 3 cm, the electromagnetic shielding performance is 42.09 dB, and the reflection efficiency is 0.66 %, the lowest reflection efficiency reaches 0.16 % in the experiment. The mechanism of electromagnetic shielding in conductive foams with the double layer and double core-clad structure has been further explored. The experiment results proved that the flexible conductive foam has excellent mechanical properties, stability, heat insulation and flame retardant properties, and has excellent electromagnetic shielding and low reflection characteristics due to its abundant holes, functional group, interface and hierarchical structure.

Architectural Design of a Multichannel Porous Carbon Fiber for Efficient Electromagnetic Microwave Absorption.

An ingenious microstructure of electromagnetic microwave absorption materials is crucial to achieve strong absorption and a broad bandwidth. Herein, one-dimensional (1D) carbon fibers with implantation of zero-dimensional (0D) ZIF-8-derived carbon frameworks and construction of a three-dimensional (3D) microcosmic multichannel porous structure are fabricated by electro-blown spinning, solvent-thermal reaction, and high-temperature pyrolysis techniques. The 1D carbon fiber skeleton with a multichannel structure provides a direct axial conductive pathway for charge transport, which plays an important role in dielectric loss. The 0D surface carbon frameworks offer plenty of heterogeneous interfaces to trigger intensive interfacial polarization loss and act as dihedral angles for microwave scattering. The 3D microcosmic multichannel pores can not only generate multiple reflections as much as possible to dissipate electromagnetic microwave energy but also supply huge interior cavities to improve impedance matching. Thanks to the synergistic effect of a strong electrically conductive pathway for enhancing the conductive loss, a plenteous heterogeneous interface for triggering intensive interfacial polarization loss, microcosmic multichannel pores for generating multiple reflections and improving impedance matching, and N and O atom doping for inducing dipole polarization, the optimal sample with an ingenious microstructure delivers an excellent absorption performance of a minimum reflection loss of -35.5 dB at a thickness of 5.0 mm and an effective absorption bandwidth of 6.72 GHz (10.96-17.68 GHz) at a thickness of 2.0 mm. Such a well-designed multichannel porous carbon fiber may pave the way for the exploitation of high-performance microwave absorbing materials.

Preparation of broad-bandwidth porous carbon electromagnetic wave absorption materials from agricultural waste corncob

Developing advanced electromagnetic wave-absorbing materials tend to focus on the characteristics of low cost, renewability, environmental friendliness, strong absorption, wide bandwidth, and lightweight. This paper described the preparation of porous carbon electromagnetic wave-absorbing materials with strong absorption, broad bandwidth and thin thickness by one-step charring of corncob, an agricultural waste. The corncob porous carbon (CPC) materials were prepared when the charring temperature was 600 °C, the charring time was 3 h and the activator ratio was 0.25:1. The obtained CPC exhibited porous microstructure with average pore size of approximately 1 μm. Its specific surface area was 713.971 m2·g−1, with pore volume of 0.289 mL·g−1 and high degree graphitization. CPC showed excellent electromagnetic wave absorption performance with minimum reflection loss (RL min) of −38.21 dB and effective absorption bandwidth (EAB) of 5.6 GHz at a relatively thin thickness of 2.0 mm. CPC was capable of absorbing 99.9 % of electromagnetic wave (EMW).

New System for Green EMI shielding: Organohydrogel with Multi-band Green Electromagnetic Shielding, Sensing, and Infrared-Stealth Capacity

Current research on green EMI shielding materials is often based on the misconception that absorption-dominated shielding is achieved when reflection loss (SER) exceeds absorption loss (SEA). Although this misconception has been corrected by a large body of literature, few studies have actually achieved absorbed power (A) greater than reflected power (R). In this study, PVA, glycerol and MXene were combined to form an organohydrogel (PMG) with oriented pores. The gel displays remarkable flexibility and strength, attributed to its robust network of hydrogen bond cross-links (the hysteresis return line remains stable under 1000 compression cycles). The PMG20-3 organohydrogel (0.78 wt% MXene) demonstrates a shielding performance of 42.34 dB (A/R=1.38) in the X-band and absorbs 99.9% of power in the terahertz band. This performance exceeds that of most previously reported systems and represents a new system for green electromagnetic shielding materials. Additionally, the PMG organohydrogel has flexible sensing and infrared stealth capabilities. These findings hold great promise for the development of green electromagnetic shielding multifunctional devices.

Electromagnetic wave absorption performance of rapid emergency magnesium phosphate cement (MPC) canvas

This study leverages the rapid emergency protection advantages of magnesium phosphate cement (MPC) canvas to develop a novel electromagnetic wave-absorbing material based on MPC canvas. The composite is composed of an MPC matrix with magnetite and iron powder as absorbers, arranged in a gradient structure. The research investigates the effects of absorbers and gradient contents on the electromagnetic wave absorption performance (EWAP) of MPC canvas. Experimental results show a maximum RL of −37.2 dB in the 2–18 GHz range, with a 6.3 GHz absorption bandwidth below −10 dB. Simulations further confirm that the gradient MPC canvas exhibits excellent EWAP across different frequency bands. The gradient design effectively adjusts the electromagnetic parameters through multiple reflection, scattering, and interference attenuation effects within the multilayer structure, enabling broadband absorption of electromagnetic waves.

Opportunities to Enhance sCO2 Power Cycle Turbomachinery with Bearingless Motor/Generators

Thermal power cycles using sCO2 as a working fluid place extreme demands on their turbomachinery components and their electric motors/generators. In this paper, new system topologies for sCO2 turbomachinery are proposed which take advantage of “bearingless” electric machine technology to improve performance. Bearingless motors/generators are a new type of electric machine which integrate the functionality of active magnetic bearings into the existing hardware of an electric motor/generator. The existing electromagnetic surfaces and materials are reused to enable controllable production of radial forces on the machine shaft. This is envisioned to improve hermetic direct-drive turbomachinery systems by either augmenting existing bearings (i.e., bearing assist) or replacing existing bearings (i.e., bearing removal). The state-of-the-art technologies for several bearing types (gas foil bearings, externally pressurized porous (EPP) gas bearings, and active magnetic bearings) and electric machines are reviewed to motivate the introduction of bearingless technology. Two system designs using bearingless machines are proposed and compared against existing commercial solutions in terms of maximum shaft weight, number of passthroughs into the hermetic environment, cost, and complexity. A case-study bearingless motor/generator is assessed via simulations and a hardware prototype to investigate practical considerations for using bearingless technology in sCO2 turbomachinery. The proposed bearingless solutions have potential to enable a new generation of sCO2 turbomachinery with improved reliability, reduced complexity, and lower cost. This paper shows that by transforming the motor/generator already present in turbomachinery into a bearingless motor/generator, the technical challenges involved with sCO2 can be overcome without adding significant cost.

Valorization of Ricinus communis outer shell biomass to biochar: Impact of thermal decomposition temperature on physicochemical properties and EMI shielding performance

The rising awareness of electromagnetic pollution has increased interest in renewable and ecologically sustainable materials for shielding electromagnetic waves. Research on carbon-based electromagnetic wave absorption materials derived from agro waste is widely explored due to their advantageous characteristics, including low density and consistent physicochemical properties. The research aims to produce biochar with maximum carbon content from Ricinus communis outer shell (RCOS) and to examine the characteristics of biochar/epoxy composites for their application in electromagnetic (EM) shielding. In this study, the composite made from RCOS-based biochar was effectively developed using slow pyrolysis at 400 °C–700 °C. The characterisations of enhanced properties of biochar were conducted by using yield analysis and proximate analysis, elemental analysis, field emission scanning electron microscope (FE-SEM), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction analysis (XRD), thermogravimetric analysis (TGA), electrical conductivity. The biochar pyrolysis results revealed that the biochar yield, fixed carbon and maximum carbon content were 30 wt%, 50.49 wt% and 79.2 wt%, respectively, at 700 °C. Fourier transform infrared (FTIR) spectroscopy revealed that for the biochar at 700 °C, C=C and C-H functional groups were present, and the others were eliminated as volatile gases during biochar production. TG analysis demonstrated higher biochar stability with residues of 75 % for 700 °C. The biochar produced at 700 °C possesses the maximum electrical conductivity of 95 S/m due to the presence of graphitic carbon. The vector network analyser (VNA) measured a maximum shielding efficiency of 26.5 dB in the X-band frequency when adding 40 wt% biochar prepared at 700 °C to the epoxy matrix. The results suggest that the RCOS biochar/epoxy composites have promise as a novel type of absorbent materials because of their low density, lightweight structure, and extensive absorption capacities. These biochar-based lightweight composites can be used as a shielding material for electronic enclosures, telecommunication equipment, and aerospace applications.

Thickness-controlled HsGDY/N-doped double-shell hollow carbon tubes for broadband high-performance microwave absorption

With the increasing deterioration of the electromagnetic environment, it is important to develop new and efficient electromagnetic wave-absorbing materials. In this work, bilayer hollow HsGDY/NC nanotubes with controllable thickness are constructed by introducing high conductivity polydopamine (PDA) and hydrogen-substituted graphdiyne (HsGDY) followed by the etching and carbonization. Subsequently, the effects of the composition, coating order, and structural characteristics of nanotubes on the electromagnetic parameters are thoroughly investigated, thereby analyzing the microwave absorption mechanism. The impedance matching of HsGDY/NC is optimized by changing the thickness of NC layer, while utilizing unique multi-heterogeneous interfaces and hierarchical conductive structures that enhance the interface polarization and conductive loss. As a result, HsGDY@NC-3 displays the optimal absorbing performance with an effective absorption bandwidth (EAB) of 7.8 GHz (10.1–17.9 GHz) and a minimum reflection loss (RLmin) of −47.18 dB at the filler content of only 11 %. This work broadens the application scopes of HsGDY and provides a novel insight into the design of lightweight, high-efficiency, and wide-frequency microwave absorbers, which is expected to be a potentially effective microwave-absorbing material.

A Hybrid Perovskite-Based Electromagnetic Wave Absorber with Enhanced Conduction Loss and Interfacial Polarization through Carbon Sphere Embedding.

Electronic equipment brings great convenience to daily life but also causes a lot of electromagnetic radiation pollution. Therefore, there is an urgent demand for electromagnetic wave-absorbing materials with a low thickness, wide bandwidth, and strong absorption. This work obtained a high-performance electromagnetic wave absorption system by adding conductive carbon spheres (CSs) to the CH3NH3PbI3 (MAPbI3) absorber. In this system, MAPbI3, with strong dipole and relaxation polarization, acts dominant to the wave absorber. The carbon spheres provide a free electron transport channel between MAPbI3 lattices and constructs interfacial polarization loss in MAPbI3/CS. By regulating the content of CSs, we speculate that this increased effective absorption bandwidth and reflection loss intensity are attributed to the conductive channel of the carbon sphere and the interfacial polarization. As a result, when the mass ratio of the carbon sphere is 7.7%, the reflection loss intensity of MAPbI3/CS reaches -54 dB at 12 GHz, the corresponding effective absorption bandwidth is 4 GHz (10.24-14.24 GHz), and the absorber thickness is 2.96 mm. This work proves that enhancing conduction loss and interfacial polarization loss is an effective strategy for regulating the properties of dielectric loss-type absorbing materials. It also indicates that organic-inorganic hybrid perovskites have great potential in the field of electromagnetic wave absorption.

Multifunctional 3D pristine graphene with tunable electromagnetic properties via self-assembly strategy

Nowadays, there is an urgent demand for multifunctional materials with tunable properties to meet the requirements of intricate environments with alternating temperatures and electromagnetic conditions. Pristine graphene is a highly promising electromagnetic material owing to its intrinsic advantages. However, issues related to aggregation and weak gelation capability would hinder the fabrication and advancement of multifunctional pristine graphene. Herein, multifunction properties are first integrated into one 3D structured pristine graphene via a self-assembly method. By regulating the microstructures, 3D structured pristine graphene can exhibit a range of electromagnetic properties, including wave transmission (wave transmittance of 88 %-93 %), electromagnetic wave (EMW) absorption (reflection loss of −50.70 dB), and electromagnetic interference (EMI) shielding (shielding effectiveness (SE) of ∼37.90 dB), which are not available in existing graphene materials. Furthermore, the 3D structured pristine graphene exhibits mechanical stability and thermal performances to guarantee a stable and durable electromagnetic response for complex environmental applications. The outstanding multifunction can be attributed to the low defects and controllable microstructures of pristine graphene. This work supplies an inspiration for the development of multifunctional graphene materials as well as the microstructure design of 3D pristine graphene.

Multi-dimensional, multi-interface Fe3C/carbon sheets/carbon tubes nanoarchitecture towards high-performance microwave absorption

The serious problem of electromagnetic (EM) interference brings growing demand for developing high-performance electromagnetic shielding materials. In this study, three-dimensional (3D) Fe3C/carbon/carbon tubes (Fe3C/C/CT) absorber with multi-heterointerface was prepared by a facile self-propagating followed by chemical vapor deposition (CVD) strategy. Initially, Fe3O4 nanoparticles were anchored onto carbon nanosheets through the self-propagating process. After different etching times with diluted acid, CTs with diverse dimensions and quantities were catalyzed by the modified Fe3O4 catalysts during the CVD approach and grown from the carbon sheets. Such a special nanoarchitecture, which consists of carbon sheets and carbon tubes, acts as the source of dielectric loss. Meanwhile, Fe3C nanoparticles provide magnetic loss, and the abundant interfaces facilitate synergistic electromagnetic loss. Moreover, large numbers of heterointerfaces from the unique multidimensional nanoarchitecture significantly enhance the impedance matching and produce abundant dipole polarization. Ultimately, with etching time of 30 min, the Fe3C/C/CT-30 achieves excellent electromagnetic wave (EMW) absorption property with a minimum reflection loss of −46.4 dB at 10.56 GHz with a thickness of 3.0 mm. When the thickness is 3.57 mm, the effective absorption bandwidth (EAB) can extend up to 4.48 GHz. Moreover, the practical application of the absorbers was evaluated using radar cross-section (RCS) simulation, indicating that Fe3C/C/CT-30 achieves a maximum RCS reduction value of 58 dBm2. The multi-dimensional and multi-heterointerface absorber presented in this work might offer valuable insights for optimizing electromagnetic absorbers.

Improved Electromagnetic Interference Shielding Efficiency of PVDF/rGO/AgNW Composites via Low-Pressure Compression Molding and AgNW-Backfilling Strategy.

Silver nanowires (AgNWs) have excellent electrical conductivity and nano-sized effects and have been widely used as a high-performance electromagnetic shielding material. However, silver nanowires have poor mechanical properties and are prone to fracture during the preparation of composite materials. In this study, PVDF/rGO/AgNW composites with a segregated structure were prepared using low-pressure compression molding and the AgNW-backfilling process. The low-pressure compression of the composite significantly improves its electromagnetic shielding performance because the low-pressure process can maintain the AgNWs' integrity. The backfilled AgNWs played a vital role in increasing the path of electromagnetic wave propagation and the absorption of electromagnetic waves. The backfilled amount of AgNWs was only 1 wt%, which increased the composite material's conductivity by one order of magnitude. The total electromagnetic interference shielding (SET) of the composite materials increased by 23.3% from 24.88 dB to 30.67 dB. The absorption contribution (SEA/SET) increased from 84.2% to 92.8%, significantly improving the electromagnetic interference shielding and the absorption contribution of the AgNWs in the composites. This was attributed to the backfilling of the porous structure by the AgNWs, which promoted multiple reflections and enhanced the absorption contribution.

Lightweight composites derived from carbonized taro stems for microwave energy attenuation and thermal energy storage

A novel strategy has been developed for preparing porous carbon materials derived from taro stems, aimed at enhancing electromagnetic wave (EMW) attenuation and thermal energy storage. The materials were synthesized through the carbonization of taro stems to form a porous carbon structure, subsequently enhanced with polyethylene glycol (PEG) containing carbon nanotubes (CNTs) and nickel (Ni) nanoparticles. By adjusting the carbonization temperature and the loading of CNTs and Ni, the resulting carbon materials exhibited exceptional EMW attenuation performance. Specifically, the PC-800 sample demonstrated a remarkable minimum reflection loss of −61.4 dB across the frequency range of 8.2–11 GHz, with a low density of 0.054 g/cm³. The PC-1200 sample exhibited EMI SE values of 23.6 dB axially and 21.5 dB radially in the X-band, with an ultra-low density of 0.033 g/cm³. Further enhancements were observed in the PC/CNT2 and PC/CNT2-Ni15 composites, achieving EMI SE values of 26.3 dB and 26.8 dB, respectively. Additionally, these composites exhibited effective thermal energy storage and release, as confirmed by heating experiments. This study not only introduces a method for creating absorption-dominated biomass electromagnetic shielding materials but also provides a dual-functional solution for enhancing the performance of electronic devices.

Analysis of the Impact of Self-Efficacy on Student Learning Outcomes in Electromagnetic Induction Material

This study aims to analyze the impact of self-efficacy on student learning outcomes on electromagnetic induction material. This research takes the type of descriptive quantitative research, a method that focuses on analyzing numerical data using statistical methods. It was conducted at MA Ali Maksum Yogyakarta with the research subjects of XII MIPA class students totaling 30 respondents. Data collection techniques using cognitive tests and self-efficacy questionnaires assisted by Google Form applications. The results showed that the hypothesis can be accepted, namely there is a correlation between the level of self-efficacy and the results of student learning tests even though the correlation found has a weak category because it only has a share of 8.1%. This shows that the domain of student confidence, especially in terms of solving problems is still at a low level so that there is a tendency for students to solve problems based on memorizing equations. The existence of limitations in conducting research limits it in uncovering other aspects outside of self-efficacy in obtaining learning outcomes. Through the information obtained that self-efficacy on learning outcomes, teachers can apply a varied atmosphere, model, and learning process to optimize student potential which will have an impact on student learning outcomes.

High-entropy TiVNbMoC3Tx MXene hybrid with balanced dielectric-magnetic loss for high-efficient electromagnetic wave absorption with environmental stability

With the advent of the 5G era, there is a growing demand for electromagnetic wave (EMW) absorbers that offer both efficient absorption and improved environmental stability. Transition metal carbides/carbonitrides (MXene), with their atomic-layered structures and high electrical conductivity, offer substantial potential for crafting efficient electromagnetic functional materials. Yet, enhancing the antioxidant capabilities and addressing the poor loss mechanisms of traditional MXene absorbers remain challenging tasks. In this context, a TiVNbMoC3Tx high-entropy MXene (HE-MXene) and its magnetic hybrids were synthesized for the first time. The unique multicomponent structure of high-entropy MXene reduces grain boundary formation, thereby slowing the progression of oxidation reactions. The incorporation of magnetic nanoparticles induces interface polarization loss or strong magnetic coupling, thereby enhancing EMW attenuation. These magnetic HE-MXene hybrids demonstrated a minimum reflection loss of −57.59 dB at a matching thickness of 1.46 mm and an effective absorption bandwidth (EAB) of 4.72 GHz at a thickness of 1.53 mm. Furthermore, the magnetic hybrids also exhibited outstanding oxidation and electrochemical corrosion resistance. This research provides valuable theoretical insights for the development of electromagnetic composites within high entropy (HE) systems, showcasing significant potential for long-term applications.