利用竹粉制备吸波磁性炭

电磁辐射污染已成为一种除水和空气污染外的新环境污染问题,为解决这一问题,对废弃的竹粉进行回收利用,制备吸波性能较好的磁性竹炭,不仅可以提高产品附加值,同时也可解决废弃竹粉污染环境的问题。采用原位共沉淀、Fe2+/Fe3+混合液和NaOH溶液两步常压浸渍法制备磁性竹粉,并在1000℃下原位碳化,合成了α?/β?Fe/Fe3O4/Fe3C四相Fe/C复合材料(CF3)的磁性竹炭。通过扫描电子显微镜、能谱仪、X射线衍射仪、振动样品磁强计以及矢量网络分析仪等研究方法可以看出,随着热解温度的升高,生成的CF3表面出现许多微孔,有利于实现电磁波的吸收,磁性竹粉炭化前后的饱和磁化强度由2.18 emu/g显著提高到67.00 emu/g。CF3的电磁波吸收性能较好,其在5.72 GHz处具有最小反射损耗值,为-19.82 dB,匹配厚度为4.25 mm,有效响应带宽为13.76 GHz。研究表明,较好的吸波性能是由于α?/β?Fe/Fe3O4/Fe3C多相复合形成的连续网络结构可得到最佳的阻抗匹配特性,以及最大的介电损耗和磁损耗能力。3种材料中磁性竹炭表现出最高的电导率,说明磁性竹炭的导电性能最好,具有较强的电磁波衰减能力。此外,在C?Fe3C、C?Fe和C?Fe3O4界面处的界面极化对提高微波吸收性能有积极作用。

Preparation of magnetic carbon with microwave absorption property using bamboo powder

With the increasing usage of varied electronic devices,the induced electromagnetic interference(EMI)irra?diation pollution has become a novel environmental pollution besides of water and air pollutions,drawing a great of interests from the scientists to address electromagnetic wave(EMW)radiation problem via designing various EMW absorbers.The developed EMW absorbers are required to be with light weight,thin thickness,wide effective absorb?ing bandwidth and strong absorbing capacity.One kind of the most attractive absorbers is magnetic carbon composites.On the other hand,biomass is considered to be a renewable energy alternative to energy and chemical raw materials.Waste bamboo powder currently lacks reasonable and effective utilization and is prone to dust pollution,unsuitable for handling and even causing explosion or fire.Pyrolysis is one of the most commonly used methods to produce biofuels and biochar.In order to address the previously mentioned challenges,waste bamboo powder was used to prepare mag?netic bamboo charcoal with excellent wave?absorbing properties,which could improve the market value of products and solve the problem of waste bamboo powder pollution of the environment.The magnetic bamboo powder was pre?pared by the in?situ co?precipitation,Fe2+/Fe3+mixture and NaOH solution by two?step atmospheric impregnation method,and then carbonized in situ at 1000℃to successfully synthesizedα?/β?Fe/Fe3O4/Fe3C four?phase Fe/C composite material(CF3).The developed CF3 was examined by the scanning electron microscope,energy spectrome?ter,X?ray diffractometer,vibrating sample magnetometer,vector network analyzer and other research methods.The results showed that the electromagnetic wave absorption performance of CF3 was excellent.With the increase of the pyrolysis temperature,many micropores appeared on the surface of the generated CF3,which was conducive to the absorption of electromagnetic waves.The saturation magnetization before and after the carbonization of the magnetic bamboo powder was significantly increased from 2.18 emu/g to 67.00 emu/g.CF3 had the minimum reflection loss value of-19.82 dB at 5.72 GHz,a thin matching thickness of 4.25 mm and a wide response bandwidth of 13.76 GHz.This excellent absorption performance was proved to be the strongest dielectric loss and the optimal magnetic loss due to the continuous network ofα?/β?Fe plus Fe3O4 plus Fe3C hybrids,permitting optimal impedance matching.Among the three materials in this study,the magnetic bamboo charcoal exhibited the highest electrical conductivity,indicating that the magnetic bamboo charcoal had the best electrical conductivity and strong electromagnetic wave attenuation a?bility.Moreover,the interface polarizations at C?Fe3C,C?Fe and C?Fe3O4 interfaces were positive to improve the mi?crowave absorption performance.