六方氮化硼的同步剥离和阻燃官能化及其三维导热与阻燃网络的构筑

The development of high-performance micro/nano-fillers and the design of internal microstructure in composites are the keys to the preparation of high-performance polymer-based thermally conductive composites (PTC). In this project, both the above-mentioned two points are employed to prepare high thermal conductive and flame retardant PTC materials. In terms of the development of high-performance micro/nano-fillers, ball-milling technology will be used to achieve both the exfoliation of hexagonal boron nitride (hBN) and its doping of flame retardant groups at the same time, then obtaining the flame-retardant functionalized boron nitride nanosheets (P/N-BNNS) with high thermal conductivity and flame retardant characteristics. In this section, realizing simultaneous exfoliation and flame retardant functionalization for hBN and exploring their mechanisms are the research focuses. With respect to the micro-structure design of composites, three dimensional interconnected P/N-BNNS network supported by gel cellulose nanofibers (CNF) is constructed, so as to form continuous thermal conduction paths and flame retardant network in epoxy resin matrix at the same time. The relationship between interfacial interaction of CNF and P/N-BNNS and the structure and internal thermal resistance of BNNS network, the flame retardant mechanism of three-dimensional BNNS in composites, and the mathematical relationship between internal microstructure and properties of composites are mainly discussed in this aspect. This project is expected to provide a feasible technical route and theoretical guidance for the simultaneous exfoliation and functionalization for BNNS and the preparation of high-performance PTC materials.

高性能微/纳米填料的开发和复合材料内部微结构的设计是制备高性能聚合物基热传导复合材料（PTC）的关键。为此，本项目将从上述两方面制备兼具高导热和阻燃特性的PTC材料。高性能微/纳米填料开发方面，利用球磨手段以期同时实现hBN的剥离和其边缘阻燃基团掺杂，得到兼具导热和阻燃功效的氮化硼纳米片（P/N-BNNS）；其中实现hBN的同步剥离和阻燃功能化以及探明其中机理是该方面研究的重点。复合材料微结构设计方面，采用纤维素（CNF）辅助构筑三维P/N-BNNS网络，以期在环氧树脂基复合材料内部同时形成连续导热通路和阻燃网络结构；该方面，重点探讨CNF与P/N-BNNS间相互作用与BNNS网络结构、内部界面热阻的关系，探明三维BNNS网络在复合材料内所起到的阻燃作用，建立结构与性能之间的数理关系。本项目有望为BNNS的高效剥离和同步官能化，以及高性能PTC材料的制备提供一条可行技术路线和理论指导。

电子器件的集成化和微型化导致其单位密度上的能量耗散呈几何倍数增加，对相应的热管理封装材料在导热、阻燃、柔性、轻量化等多方面提出了更高的要求。本项目主要针对高性能环氧树脂封装材料导热性和阻燃性难以满足实际应用要求的问题，通过高性能纳米填料（BNNS）的开发和控制填料在基体内的有序分布，制备兼具高导热、高阻燃、电绝缘特性的聚合物基热传导复合材料（PTC）。具体包括：①揭示了Ni(OH)2改性的石墨烯和hBN在导热和阻燃过程中的多重协同机理，实现复合材料导热系数（2.01 W/mK）和阻燃性能（PHRR降低33.5%、THR降低33.8%）的有效提升；②以小分子磷酸铵、离子液体、硼酸、聚磷酸铵、芳纶纤维等为剥离辅助剂和阻燃改性剂，通过干法和湿法球磨方式剥离制备氮磷掺杂BNNS，实现惰性BNNS表面和边缘阻燃官能化修饰，提高了其在溶剂和基体内的分散性和相容性；③研究了阻燃改性BNNS及其在复合材料内部的分布结构（随机分布、取向分布、网络分布等）对环氧树脂导热性能的影响规律，不仅有效提升复合材料的导热系数（最高面内导热系数8.3 W/mK），而且实现了热量传递的方向控制；④揭示了表面阻燃基团、BNNS分布结构对复合材料阻燃性能的作用规律，其中离子液体剥离改性BNNS结合层状取向结构可实现阻燃参数PHRR、THR最高降幅达72.9%和75.7%，结合残渣结构和组分分析，解释了复合材料的阻燃机理。本研究为高性能PTC材料的设计和制备提供了有效的技术路线和理论基础，在商用环氧基电子封装领域有不错的应用前景。基于本项目研究内容，所获研究成果在国际权威期刊共发表SCI论文30篇，其中高被引论文7篇，热点论文1篇；申请发明专利6项，其中已授权3项。本项目研究过程中，累计培养青年骨干教师1名，博士生2名，硕士生5名。