Dynamic modulation of permittivity properties via compression of carbon nanotube-impregnated cotton for wide epsilon-near-zero bandwidth

• Published in: Advanced composites and hybrid materials Vol. 7; no. 3
• Main Authors: Li, Guangshen, Sun, Zhihao, Guo, Zihao, Wang, Peng, Du, Benli, Tian, Shaoyao, Ding, Han, Qiu, Yu, Bi, Jingyu, Qian, Lei
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01.06.2024
• Subjects: Ceramics; Chemistry and Materials Science; Composites; Glass; Materials Engineering; Materials Science; Natural Materials; Polymer Sciences; Negative permittivity; Metacomposites; Epsilon near zero; Compressed thickness; Epsilon-near-zero bandwidth
• ISSN: 2522-0128; 2522-0136
• DOI: 10.1007/s42114-024-00895-6

Here, carbon nanotube (CNT)-impregnated cotton was produced by impregnation and drying treatment. Negative permittivity was observed from the CNT loading above 14 wt% for air-dried CNT-impregnated cotton (AD-CNTs@cotton) and 2 wt% for freeze-dried CNT-impregnated cotton (FD-CNTs@cotton), respectively. The CNT loading of FD-CNTs@cotton with negative permittivity decreased significantly resulting from the “semi-coated” state of CNTs on cotton. Through regulating the compression, negative permittivity especially epsilon-near-zero (ENZ) was easily achieved. When the thickness was compressed to 0.1 mm, the ENZ bandwidth was up to around 950 kHz at 14%AD-CNTs@cotton. Drude and parallel model were used to explain the negative permittivity. Besides, through thin spline interpolation, this work firstly utilized fitting to predict the thickness achieving ENZ property (ENZ thickness). The curved surface graphs were fitted, and the intersection line graph showed that the ENZ thickness increased with the CNT loading. It was expected that the widest ENZ bandwidth was from 10 kHz to 1 MHz on 14%AD-CNTs@cotton at thickness of 0.24 mm. However, the ENZ bandwidth (from 322 to 376 kHz) of FD-CNTs@cotton was obviously narrow. This work provides a dynamic modulation and numerical prediction strategy to realize the wide ENZ bandwidth via compression.