【作者】 刘悦；

【导师】 吴金珠；

【作者基本信息】 哈尔滨工业大学 ， 物理化学， 2021， 硕士

【摘要】 随着信息技术在民用和军用领域的迅速发展,电磁干扰与污染已经成为世界各国亟待解决的关键问题之一,因此科研人员致力于找寻“薄、轻、宽、强”的电磁波吸收材料。在众多微波吸收材料中,二维材料由于其感应电子能够沿二维分子网络转移,在交变电磁场下形成耗散电流,对电磁波有很好的响应。二硒化钼（MoSe₂）因其特殊的二维分子结构和优异的本征电导率引起了科研人员的兴趣。因此本文研究二硒化钼的微波吸收性能,探究其微波吸收机制,并将MoSe₂分别与FeSe₂和Fe₂O₃复合,增强介电损耗,引入磁损耗,改善其阻抗匹配特性,进一步提高其微波吸收性能。本文采用水热法合成了超薄MoSe₂,探究了水热温度与时间对合成材料的形貌与微波吸收性能的影响。测试结果表明超薄MoSe₂拥有卷曲的片层结构,增加了电磁波在材料中的传输路径,因而增强了微波损耗。此外,由于1T相的存在,超薄MoSe₂的电导率增大,导致材料在交变电磁场中载流子引起的电流增大,从而有利于电磁能转化成为热能。200℃、20 h合成的MoSe₂在13.36GHz处,匹配厚度为2.29 mm时,反射损耗为-52.1 d B。为了进一步提高材料的微波吸收性能,采用一步水热法,在原料中引入铁源,合成了MoSe₂-FeSe₂复合材料,提高了材料的介电损耗。通过XRD、SEM、Raman、TEM、BET等测试分析研究了形貌、相态等对材料微波吸收性能的影响。MoSe₂-FeSe₂复合材料保留了材料的片层结构,同时MoSe₂-FeSe₂之间界面的存在,也增强了介电损耗。测试结果表明Mo:Fe=1:1时合成的材料微波吸收性能最佳,在13.92 GHz处,匹配厚度为1.71 mm时,材料的反射损耗为-52.26d B,相比于复合前的MoSe₂其匹配厚度明显降低,更有实际应用价值。为了探究磁损耗对于材料性能的影响,首先通过水热合成Fe₂O₃,继而通过两步水热法合成了MoSe₂-Fe₂O₃复合材料。Fe₂O₃的引入在增强材料界面损耗的同时,又引入磁损耗,提高阻抗匹配条件,使得微波吸收性能增强。当MoSe₂:Fe₂O₃=4:1时,在12.72 GHz处,匹配厚度为1.63 mm时,材料的反射损耗为-56.14 d B,甚至在匹配厚度更低的1.2 mm时,在16.96 GHz处,反射损耗达到-52.14 d B,其有效吸收宽度达到了4 GHz。Fe₂O₃的引入使得材料在保持超薄片层结构的同时,增强了自然共振与涡流损耗对于微波吸收的贡献。更多还原

【Abstract】 With the rapid development of information technology in the civilian and military fields,electromagnetic interference and pollution have become one of the key issues that needs to be resolved urgently all over the world.Therefore,researchers are dedicated to find"thin,light,wide,and strong"electromagnetic wave absorbing materials.Among many microwave absorbing materials,two-dimensional materials have a good response to electromagnetic waves,because induced electrons can transfer along the two-dimensional molecular network to form a dissipation current under the alternating electromagnetic field.Molybdenum diselenide has attracted the interest of researchers due to its special two-dimensional molecular structure and excellent intrinsic conductivity.Therefore,this work investigates the microwave absorption performance and mechanism of molybdenum diselenide,and then prepare MoSe₂-FeSe₂ and MoSe₂-Fe₂O₃ nanocomposites,respectively,to further improve its microwave absorption performance.This work used hydrothermal method to synthesize ultra-thin MoSe₂,and explored the influence of hydrothermal temperature and time on the morphology and microwave absorption properties.The experimental fingings show that the as-prepared MoSe₂ has ultra-thin and curly lamellar structure,increasing the transmission paths of the electromagnetic wave in the material.This leads to enhanced microwave loss.In addition,the phase composition of the as-prepared MoSe₂ is different.The existence of 1T phase in the as-prepared MoSe₂ increases the conductivity,leading to an increase in the current caused by carriers in the electromagnetic field of the material,which is conducive to the conversion of electromagnetic energy into thermal energy.The reflection loss of MoSe₂ synthesized at 200℃and 20 h is-52.1 d B,when the matching thickness is 2.29mm at 13.36 GHz.In order to improve the microwave absorption performance of the material,a one-step hydrothermal method was used to prepare the MoSe₂-FeSe₂ nanocomposite by introducing an iron source.The as-prepared MoSe₂-FeSe₂ nanocomposite has a interface which contributes to enhance the dielectric loss of the material.Through XRD,SEM,Raman,TEM and BET analysis,the effects of morphology and phase on the microwave absorption properties of the material was studied.The as-prepared MoSe₂-FeSe₂ nanocomposite not only retains the lamellar structure,but also possesses interface between MoSe₂-FeSe₂,which enhances the dielectric loss.When Mo:Fe=1:1,the as-prepared MoSe₂-FeSe₂ nanocomposite has the best microwave absorption performance.At 13.92 GHz,when the matching thickness is 1.71 mm,the reflection loss of the material is-52.26 d B.Importantly,compared with ultra-thin MoSe₂,the matching thickness of the material is significantly reduced.In order to explore the influence of magnetic loss on material properties,MoSe₂-Fe₂O₃ nanocomposite was synthesized by a two-step hydrothermal method.The introduction of Fe₂O₃ not only enhances the interface loss of the material,but also introduces magnetic loss.As a result,the as-prepared MoSe₂-Fe₂O₃ nanocomposite presents the improved impedance matching condition and enhances the microwave absorption performance.When MoSe₂:Fe₂O₃=4:1,the reflection loss is-56.14 d B at 12.72 GHz when the matching thickness is 1.63 mm.Even at lower matching thickness of 1.2 mm,the reflection loss is-52.14 d B at 16.96 GHz.Therefore,the effective absorption width of the material reaches about 4 GHz.The introduction of Fe₂O₃ contributes natural resonance and eddy current loss to the microwave absorption.更多还原