J. Mater. Sci. Technol. ›› 2021, Vol. 74: 105-118.

• Research Article •

### Electromagnetic wave absorbing properties of TMCs (TM=Ti, Zr, Hf, Nb and Ta) and high entropy (Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)C

Yanchun Zhoua,*(), Biao Zhaob, Heng Chena,c, Huimin Xianga, Fu-Zi Daia, Shijiang Wud, Wei Xue

1. a Science and Technology on Advanced Functional Composite Laboratory, Aerospace Research Institute of Materials & Processing Technology, Beijing, 100076, China
b Henan Key Laboratory of Aeronautical Materials and Application Technology, School of Material Science and Engineering, Zhengzhou University of Aeronautics, Zhengzhou, 450046, China
c Key Laboratory of Advanced Ceramics and Machining Technology of Ministry of Education, School of Materials Science and Engineering, Tianjin University, Tianjin, 300072, China
d Zibo Firstar New Material Incorporated Co. Ltd., Zibo, 255000, China
e Shanghai Chenhua Science and Technology Corporation Ltd., Shanghai, 201804, China
• Received:2020-08-08 Revised:2020-09-28 Accepted:2020-10-02 Published:2021-05-30 Online:2020-10-18
• Contact: Yanchun Zhou
• About author:*E-mail address: yczhou@alum.imr.ac.cn (Y. Zhou).

Abstract:

Electromagnetic wave (EMW) absorbing materials play a vital role in modern communication and information processing technologies to inhibit information leakage and prevent possible damages to environment and human bodies. Currently, most of EMW absorbing materials are either composites of two or more phases or in the form of nanosheets, nanowires or nanofibers in order to enhance the EMW absorption performance through dielectric loss, magnetic loss and dielectric/magnetic loss coupling. However, the combination of complex shapes/multi phases and nanosizes may compound the difficulties of materials processing, composition and interfaces control as well as performance maintenance during service. Thus, searching for single phase materials with good stability and superior EMW absorbing properties is appealing. To achieve this goal, the EMW absorbing properties of transition metal carbides TMCs (TM=Ti, Zr, Hf, Nb and Ta) and high entropy (Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)C which belong to ultrahigh temperature ceramics, were investigated in this work. Due to the good electrical conductivity and splitting of d orbitals into lower energy t2g level and higher energy eg level in TMC6 octahedral arrangement, TMCs (TM=Ti, Zr, Hf, Nb and Ta) exhibit good EMW absorbing properties. Especially, HfC and TaC exhibit superior EMW absorbing properties. The minimum reflection loss (RLmin) value of HfC is -55.8 dB at 6.0 GHz with the thickness of 3.8 mm and the effective absorption bandwidth (EAB) is 6.0 GHz from 12.0 to 18.0 GHz at thickness of 1.9 mm; the RLmin value of TaC reaches -41.1 dB at 16.2 GHz with a thickness of 2.0 mm and the EAB is 6.1 GHz with a thickness of 2.2 mm. Intriguingly, the electromagnetic parameters, i.e., complex permittivity and permeability are tunable by forming single phase solid solution or high entropy (Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)C. The RLmin value of high entropy (Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)C is -38.5 dB at 9.5 GHz with the thickness of 1.9 mm, and the EAB is 2.3 GHz (from 11.3 to 13.6 GHz) at thickness of 1.5 mm. The significance of this work is that it opens a new window to design single phase high performance EMW absorbing materials by dielectric/magnetic loss coupling through tuning the conductivity and crystal field splitting energy of d orbitals of transition metals in carbides, nitrides and possibly borides.