Lightweight and efficient microwave absorbing materials based on walnut shell-derived nano-porous carbon
Xu Qiu1, Lixi Wang, Hongli Zhu
1College of Materials Science and Engineering, Nanjing Tech University, Nanjing 210009, China. wanglixi_njut@163.com wanglixi@njtech.edu.cn.
Nanoscale
|May 26, 2017
Summary
Researchers developed lightweight microwave absorbers from nano-porous biomass carbon derived from walnut shells. Potassium hydroxide activation significantly enhanced their microwave absorption performance, showing potential for advanced material applications.
Area of Science:
- Materials Science
- Nanotechnology
- Chemical Engineering
Background:
- Lightweight microwave absorbing materials are crucial for electromagnetic interference shielding and stealth technologies.
- Biomass-derived carbon materials offer a sustainable and cost-effective alternative to traditional absorbers.
- Developing efficient porous structures is key to enhancing microwave absorption capabilities.
Purpose of the Study:
- To synthesize and characterize nano-porous biomass carbon from walnut shells for microwave absorption.
- To investigate the effect of potassium hydroxide (KOH) activation on the material's structure and microwave absorption properties.
- To elucidate the mechanisms behind the enhanced microwave absorption performance.
Main Methods:
- Walnut shells were carbonized and subsequently activated using potassium hydroxide (KOH) at varying temperatures.
- The morphology, specific surface area, and porosity of the carbon materials were analyzed.
- Microwave absorption properties, including reflection loss and effective absorption bandwidth, were measured.
Main Results:
- The KOH-activated sample at 600 °C exhibited a high specific surface area (736.2 m²/g) with abundant micropores and nanopores.
- This optimized sample achieved a maximum reflection loss of -42.4 dB and an effective absorption bandwidth of 1.76 GHz at 2 mm thickness.
- An effective absorption bandwidth of 2.24 GHz was observed at a 1.5 mm thickness.
- The enhanced performance was attributed to the 3D porous architecture, interfacial polarization, and dipolar relaxation losses.
Conclusions:
- Nano-porous biomass carbon derived from walnut shells, particularly when activated with KOH, demonstrates excellent lightweight microwave absorbing properties.
- The development of micropores and nanopores through activation is critical for improving dielectric loss and microwave absorption.
- Porous biomass carbon presents a promising material for future lightweight microwave absorber applications.
