Abstract In the synthesis of colloidal carbon spheres (CCSs) from glucose by hydrothermal carbonization, agglomeration and cross-linking often occur, affecting their functions as templates. In this study, the effects of various surfactants on the dispersion and particle size of CCS were investigated. The CCS synthesized with dodecyltrimethylammonium bromide was much larger than those of other groups, and the average diameter exceeded 6.4 μm. CCS with complete spherical shape and good dispersion were obtained using sodium polyacrylate, with a diameter of approximately 450 nm CoFe2O4 hollow spheres were prepared by a simple adsorption–calcination method using CCS as the templates, and the effects of different dispersions and particle sizes on the electromagnetic parameters and microwave absorption properties of hollow spheres were studied. The results show that the absorption bandwidth corresponding to reflection loss less than −7 dB widened from 2.64 GHz to 3.44 GHz with improving dispersion of hollow sphere structure. When the size of the hollow sphere increased to the micron level, the thickness required to reach the maximum bandwidth reduced by 0.5 mm. Compared to the unoptimized hollow spheres, the microwave absorption performance of the as-prepared CCCs improved effectively. The effect of surfactants on the dispersion of CCS and the effect of the dispersion and size of CoFe2O4 hollow spheres on their electromagnetic properties are discussed in detail.

中文翻译：

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碳球模板CoFe2O4空心球的制备及其吸波性能

摘要 在葡萄糖水热碳化合成胶体碳球（CCSs）过程中，经常发生团聚和交联，影响其作为模板的功能。在这项研究中，研究了各种表面活性剂对 CCS 的分散和粒径的影响。用十二烷基三甲基溴化铵合成的 CCS 比其他组大得多，平均直径超过 6.4 μm。以聚丙烯酸钠为模板剂，通过简单的吸附-煅烧方法制备了直径约 450 nm 的 CoFe2O4 空心球，制备出球状完整、分散性良好的 CCS，并考察了不同分散体和粒径对 CoFe2O4 空心球的影响。研究了空心球的电磁参数和微波吸收特性。结果表明，随着空心球结构色散的改善，对应于小于-7 dB反射损耗的吸收带宽从2.64 GHz扩大到3.44 GHz。当空心球的尺寸增加到微米级时，达到最大带宽所需的厚度减少了 0.5 mm。与未优化的空心球相比，所制备的 CCC 的微波吸收性能有效提高。详细讨论了表面活性剂对CCS分散的影响以及CoFe2O4空心球的分散和尺寸对其电磁性能的影响。当空心球的尺寸增加到微米级时，达到最大带宽所需的厚度减少了 0.5 mm。与未优化的空心球相比，所制备的 CCC 的微波吸收性能有效提高。详细讨论了表面活性剂对CCS分散的影响以及CoFe2O4空心球的分散和尺寸对其电磁性能的影响。当空心球的尺寸增加到微米级时，达到最大带宽所需的厚度减少了 0.5 mm。与未优化的空心球相比，所制备的 CCC 的微波吸收性能有效提高。详细讨论了表面活性剂对CCS分散的影响以及CoFe2O4空心球的分散和尺寸对其电磁性能的影响。