Achieving ultra-broadband electromagnetic wave absorption in high-entropy transition metal carbides (HE TMCs)

Abstract

Electronic devices pervade everyday life, which has triggered severe electromagnetic (EM) wave pollution. To face this challenge, developing EM wave absorbers with ultra-broadband absorption capacity is critically required. Currently, nano-composite construction has been widely utilized to realize impedance match and broadband absorption. However, complex experimental procedures, limited thermal stability, and interior oxidation resistance are still unneglectable issues. Therefore, it is appealing to realize ultra-broadband EM wave absorption in single-phase materials with good stability. Aiming at this target, two high-entropy transition metal carbides (HE TMCs) including (Zr,Hf,Nb,Ta)C (HE TMC-2) and (Cr,Zr,Hf,Nb,Ta)C (HE TMC-3) are designed and synthesized, of which the microwave absorption performance is investigated in comparison with previously reported (Ti,Zr,Hf,Nb,Ta)C (HE TMC-1). Due to the synergistic effects of dielectric and magnetic losses, HE TMC-2 and HE TMC-3 exhibit better impedance match and wider effective absorption bandwidth (EAB). In specific, the exclusion of Ti element in HE TMC-2 endows it optimal minimum reflection loss (RLmin) and EAB of −41.7 dB (2.11 mm, 10.52 GHz) and 3.5 GHz (at 3.0 mm), respectively. Remarkably, the incorporation of Cr element in HE TMC-3 significantly improves the impedance match, thus realizing EAB of 10.5, 9.2, and 13.9 GHz at 2, 3, and 4 mm, respectively. The significance of this study lays on realizing ultra-broadband capacity in HE TMC-3 (Cr, Zr, Hf, Nb, Ta), demonstrating the effectiveness of high-entropy component design in tailoring the impedance match.

Pushing the limits of microwave absorption capability of carbon fiber in fabric design based on genetic algorithm

“…In the optimization process, the impedance matching of the PCGFs was screened aiming at different targets. Equivalent impedance (Z eff ) of the PCGFs calculated by equivalent impedance calculations (Section 2.3) is consistent with the above measured RL results [36,52,53], as shown in Fig. 4(d), in which the PCGF-1 exhibits an excellent impedance matching in the range of 7.3-40.0 GHz corresponding to the effective absorption.…”

Structural Defects in Phase‐Regulated High‐Entropy Oxides toward Superior Microwave Absorption Properties

“…[ 29a,47 ] A Z in /Z 0 value closer to 1.0 indicates a better impedance match. [ 48 ] The non‐oscillation of the real part ( µ ′) ensures the notion of modifying the dielectric constant to achieve optimal impedance matching. As shown in Figure S30 (Supporting Information), the values of Z in / Z 0 for HE‐Fe‐1200 at a thickness of 1.9–2.5 mm were ≈1.0 in a broad frequency range, indicating a balanced impedance match; however, those of others significantly deviated from 1.0.…”

Low thermal conductivity of dense (TiZrHfVNbTa)Cxhigh-entropy carbides by tailoring carbon stoichiometry

“…Although the thermal conductivity of ZrC x can be effectively reduced by tailoring the carbon stoichiometry, the large-scale application of the transition metal carbides is still restricted due to the stringent requirement for applications in an ultra-high-temperature insulation system. Recently, the emerging high-entropy carbides have evoked extensive research, possessing excellent mechanical properties [4,5], corrosion and oxidation resistance [6,7], low thermal conductivity [8][9][10], prominent electrical properties [11], and electromagnetic wave absorbing properties [12]. Therefore, adjusting the carbon stoichiometry of the high-entropy carbides is feasible to further lower the thermal conductivity and maintain moderate mechanical properties at the same time, making them promising to be candidates for thermal protection materials.…”