Shanenkov Ivan, Sivkov Alexander, Ivashutenko Alexander, Zhuravlev Viktor, Guo Qing, Li Liping, Li Guangshe, Wei GuoDong, Han Wei
Jilin Supercapacitor Engineering Laboratory, College of Physics, Jilin University, Changchun City 130012, P. R. China.
Phys Chem Chem Phys. 2017 Aug 2;19(30):19975-19983. doi: 10.1039/c7cp03292g.
High-performance magnetite-based hollow spheres with the advantages of low density and low loading content are promising as an ideal lightweight electromagnetic (EM) wave absorption candidate. However, the effective preparation methods for these hollow spheres are still limited, and as a result, materials design and practical applications based on their size-dependent EM microwave attenuation properties are poorly accessible. In this study, high quality magnetite hollow spheres were successfully prepared by a simple, fast, one-step, and scalable plasma dynamic method with sole use of inexpensive precursors (oxygen and mild steel). The experimental results reveal that the as-prepared products are hollowed multiple-component magnetite spheres and have a very wide size distribution with a diameter of several tens of nanometers to hundreds of micrometers, which can be further separated into three fractions with different particle size distributions (0-30 μm, 30-100 μm, and >100 μm) by a simple magnetic separation method. The EM wave absorption results demonstrate that the hollow microspheres can exhibit excellent absorption ability with an effective absorption bandwidth (reflection loss ≤-10 dB) of 11.9 GHz from 3.7 to 15.6 GHz for an only 2 mm thick test absorber (50 wt% filler) and a maximum RL value of -36 dB at ∼8.2 GHz. Moreover, the positions of these resonant absorption peaks strongly depend on the sphere sizes and can be regulated at the L + C band, X band, and Ku band. Strikingly, differing from the nearly negligible microwave absorption for the ground powders, the dominating absorption mechanism for the hollow microspheres could be ascribed to the enhanced magnetic loss and multiple scattering due to the novel hollow magnetic structures, which are beneficial for the attenuation ability and improvements to their permeability and impedance matching.
具有低密度和低负载量优势的高性能磁铁矿基空心球有望成为理想的轻质电磁（EM）波吸收候选材料。然而，这些空心球的有效制备方法仍然有限，因此，基于其尺寸依赖性EM微波衰减特性的材料设计和实际应用难以实现。在本研究中，通过一种简单、快速、一步且可扩展的等离子体动力学方法，仅使用廉价的前驱体（氧气和低碳钢）成功制备了高质量的磁铁矿空心球。实验结果表明，所制备的产品是空心的多组分磁铁矿球，尺寸分布非常宽，直径从几十纳米到几百微米不等，通过简单的磁选方法可进一步分离成具有不同粒径分布的三个部分（0 - 30μm、30 - 100μm和>100μm）。EM波吸收结果表明，对于仅2mm厚的测试吸收体（50wt%填料），空心微球在3.7至15.6GHz范围内可表现出优异的吸收能力，有效吸收带宽（反射损耗≤ - 10dB）为11.9GHz，在约8.2GHz时最大RL值为 - 36dB。此外，这些共振吸收峰的位置强烈依赖于球体尺寸，并且可以在L + C波段、X波段和Ku波段进行调节。引人注目的是，与研磨后的粉末几乎可忽略不计的微波吸收不同，空心微球的主要吸收机制可归因于新型空心磁性结构导致的增强磁损耗和多重散射，这有利于提高其衰减能力以及改善其磁导率和阻抗匹配。
