Carbonized Silk Fiber Mat: a Flexible and Broadband Microwave Absorber, and the Length Effect
Yi Hou, Jing Quan, Xinran Su, Chaoran Deng, Yong Yang, Boo Cheong Khoo
Abstract
Sustainable manufacture of renewable materials without compromising performance remains a challenge to material scientists. Biomass material is acknowledged as a cost-effective approach to alleviate the situation. In this work, carbonized silk fiber (average 5 μm diameter) mats were derived from silkworms through degumming and subsequent one-step carbonization process at high temperature. It is demonstrated that the resultant mats are able to show great flexibility and high-efficiency microwave attenuation performance by optimizing the annealing process. At the optical carbonization temperature of 650 °C, the carbonized silk fiber mat/silicone composite could exhibit a minimal reflection loss (RL) value of −70 dB at 17.6 GHz and 2.5 mm thickness. At 3.2 mm thickness, an effective absorption bandwidth (EAB, RL < −10 dB) as wide as 8.7 GHz (9.3–18 GHz) is achieved. Such a broad bandwidth is mainly attributed to the long fiber length and well-connected conductive network in the mat, which leads to promoted permittivity at a low filling ratio (5 wt %). Combining the great flexibility, broad bandwidth, lightweight, and low cost with a simple fabrication process, the established carbonized silk fiber mat could be an environmentally friendly alternative to currently existing traditional absorber materials for microwave attenuation in electromagnetic compatibility applications.