关键词: 铁基金属有机框架, Fe/C多孔碳材料, 柔性纺织复合材料, 涂层棉织物, 吸波性能

Abstract:

Objective With the rapid development of modern society and the increase of electronic equipment, the problem of electromagnetic pollution are causing increasing attention. In order to reduce the influence of electromagnetic radiation on people's health, textiles can be functionalized to shield the electromagnetic absorption waves. In view of the above ideas, electromagnetic wave absorption materials can be mixed in the polymer solution in the fiber production, and can be coated onto the textiles as functional finishing.
Method To improve the electromagnetic wave absorption performance of coated cotton fabrics, an iron based magnetic metal-organic framework (Fe-MOF) material was prepared following the solution mixing method. Fe/C porous carbon material was prepared by a high temperature pyrolysis. Polyacrylate was used as a binder to the Fe/C porous carbon material on cotton fabrics to prepare a flexible textile composite.The phase structure, microstructure and surface elements, magnetic properties and thermodynamic properties of Fe-MOF material and Fe/C porous carbon material were characterized and evaluated by X-ray diffractometer, field emission scanning electron microscope, vibrating sample magnetometer and thermogravimetric analyzer, respectively. The Fe-MOF material and Fe/C porous carbon material have been successfully separately prepared. The electromagnetic microwave absorption properties of the Fe/C porous carbon material and coated cotton fabrics are analyzed with a vector network analyzer, respectively.
Results At frequency 4.6 GHz, the Fe/C porous carbon material has a minimum reflection loss of -60.4 dB, an effective bandwidth less than -10 dB of 1.4 GHz with thickness of 4.3 mm (Fig. 6). Synergistic effect of dielectric loss and magnetic loss enhances the electromagnetic microwave absorption properties of the Fe/C porous carbon material (Fig. 7). The Debye relaxation process and magnetic loss exist in the Fe/C porous carbon material according to the Debye theory and eddy current loss (Fig. 8), respectively. The reflection loss and impedance matching coefficient reflect the impedance matching performance of the Fe/C porous carbon material with different thickness. When the thickness is 4.3 mm, the matching coefficient is close to 1 (Fig. 9), indicating excellent impedance matching property of the Fe/C porous carbon material. Most incident waves enter the Fe/C porous carbon material, and the synergistic effect of dielectric loss and magnetic loss inside the material is optimum. The minimum reflection loss of the coated cotton fabric is -53.94 dB, the effective bandwidth less than -10 dB is the X-band, and the optimal coating thickness is 4.5 mm (Fig. 10). The thickness of the Fe/C porous carbon material-coated cotton fabric reaches more than 3.5 mm, and the coated cotton fabric has excellent electromagnetic microwave absorption properties (Fig. 10).
Conclusion The research reported in this paper not only provides a basis for the research of the microwave absorption properties of the MOF derivatives, but also provides a basis for the study of the microwave absorption properties of flexible textiles. However, there are still many aspects to be studied in the future, such as the synthesis of biomass-based carbon materials, other preparation methods of the MOF derivatives and different fabrics coated finishing. The research on the application of microwave absorption materials to textiles needs further exploration. For example, the effective absorption bandwidth less than -10 dB is 1.4 GHz, which needs further improvement. To enhance the optimal thickness corresponding to the optimal absorption intensity, the effective absorption bandwidth may be reduced by doping, changing ligands and other methods. Meanwhile, the intersection of material science and textile chemistry will be the key factor for the breakthrough of electromagnetic microwave absorption materials in the textile field.

Key words: iron based magnetic metal-organic framework, Fe/C porous carbon material, flexible textile composite, coated cotton fabric, microwave absorption property