铁磁性氟化BN包覆对纳米碳材料吸波性能的影响及其机理研究

Transition metals including Fe, Co, and Ni as well as their compounds are traditionally used as magnetic lossy media in microwave absorbing (MA) materials. However, the densities of these transition-metal based magnetic lossy materials are quite high (about 7-8 g/cm3), which severely restricts the weight reduction of MA materials. As a light-element compound, fluorinated BN (F-BN) is found magnetic in recent years. Although F-BN does not contain 3d and 4f electrons, it still exhibits strong ferromagnetism. If F-BN (with density about 2 g/cm3) can be used as magnetic lossy medium instead of traditional transition-metal based ones, the density of the MA materials will effectively reduced. Moreover, the impedance matching characteristics of the MA materials may also be improved (because BN is conventionally used as impedance matching layer in MA materials), which leads to further improvement of the microwave absorption performance. Nevertheless, the MA properties of F-BN and its composites were rarely reported. For the first time, this project will study the MA properties of F-BN, and will also investigate the influence of F-BN coating on the MA properties of nano carbon materials (carbon black, carbon nanotubes, graphene, etc.). The microwave absorption mechanism of the ferromagnetic F-BN will be revealed and compared with that of the traditional transition-metal based MA materials. The synergetic microwave loss mechanism of the F-BN coated nano carbon materials will be clarified. The successful implementation of this project will break through the bottleneck of the low-density MA materials, and will promote the developing level of MA materials, which is of strategic significance to our country.

传统吸波材料通常以Fe、Co、Ni及其化合物作为磁损耗介质，这些材料密度大(约7-8g/cm3)，严重制约了吸波材料的轻量化。氟化BN(F-BN)是近年来发现的轻元素铁磁性材料，虽然不含有3d和4f电子，仍然能产生较强的铁磁性。如果能将F-BN(密度约2g/cm3)作为吸波材料使用(代替传统高密度磁性材料)，将有效降低吸波材料的密度，同时还能提高吸波材料的阻抗匹配特性(BN常被用作阻抗匹配层)，从而进一步提高吸波性能。但目前尚没有关于F-BN及其复合材料吸波性能的报道。本项目首次研究F-BN的吸波性能及其包覆对纳米碳材料(炭黑、碳纳米管、石墨烯等)吸波性能的影响，揭示轻元素铁磁性F-BN的吸波机理与传统过渡金属磁性材料吸波机理的区别与联系，阐明F-BN包覆纳米碳材料复合吸波体对电磁波的协同损耗机制。本项目的成功实施，将突破低密度吸波材料研制的瓶颈，提升我国吸波材料的研制水平，具有战略意义。

纳米碳材料(石墨烯及碳纳米管等)具有低密度、耐腐蚀等优点，是一种潜在的电损耗型吸波材料。然而，碳材料介电常数较大，对电磁波有较强的反射作用，容易造成阻抗失配。BN是一种低密度透波材料，将BN包覆在碳材料表面能有效降低介电常数，引导电磁波进入吸波材料内部，提升阻抗匹配。将BN进行氟化，能使其带有一定磁性，从而在保持低密度的条件下引入磁损耗，从而进一步提升吸波性能。.本项目分别以石墨烯及碳纳米管为主要吸波剂，以BN和氟化BN调控其阻抗匹配，制备了BN包覆型石墨烯及碳纳米管吸波材料、氟化BN吸波材料，阐明了BN及氟化BN对碳材料的阻抗匹配调控机制，揭示了纳米复合吸波材料的电磁波损耗机理。取得的主要成果如下：(1)在碳纳米管表面包覆了BN，BN的包覆有效提升了碳纳米管的阻抗匹配特性，同时引入了界面极化损耗机制，获得了低密度(1-2g/cm3)、耐腐蚀、吸波强(-36dB)的吸波材料；(2)在石墨烯表面包覆了BN，石墨烯的阻抗匹配得到有效提高，反射损耗可达-29dB，吸波频带宽达到5GHz；(3)优化多孔BN合成工艺，并将其与碳纳米管复合，得到多孔氮化硼/碳纳米管复合材料，BN为微米多孔棒结构，能提高界面极化和多重散射。(4)以氟化氨为主要氟化原料，制备了氟化BN吸波材料，该吸波材料在X和Ku波段表现出优异的吸波性能，在16.56GHz最小反射损耗可达-43.09dB，吸波性能提升归因于氟化导致BN电子结构的重新分布。.此外，将上述研究思想进行了拓展，先后制备了SiO2包覆碳纳米管、SiO2包覆碳石墨烯、SiO2包覆羰基铁、TiO2包覆羰基铁、金属氧化物修饰石墨烯等多个体系的吸波材料，均取得了良好的效果，形成了通过透波陶瓷包覆来提升材料吸波性能的通用策略，为新型吸波材料的开发提供了很好的思路。.总之，在基金委的资助下，项目任务目标得到圆满完成。目前发表SCI学术论文21篇(均已标注)，其中高被引1篇；申报发明专利13项，其中授权5项；培养研究生13名；部分成果用于申报黑龙江省自然科学二等奖并成功获批。