大面积石墨烯强流发射冷阴极的构建基础及应用研究

Intense current emission cathodes are the core component of high-energy devices, and graphene has excellent electron emission properties for its special structure and properties, which can be selected as intense current emission cold cathodes. In this study, large-area graphene cold cathodes will be fabricated and applied in high power vacuum electronic devices as intense electron beam sources. Controllable and macroscopic quantity preparation methods of graphene will be established and developed, large-quantity and low-cost preparation techniques of graphene will be obtained. Large-area, high-quality substrate-based and self-supporting graphene films will be fabricated respectively. The preparation method will be improved to achieve the morphology,thickness and uniformity controlling of graphene films. The effective compound of graphene and other nanomaterials will be obtained, and the electron emission properties of the nanocomposites will be improved by utilizing the unique advantages of graphene nanocomposites. The emission properties of large-area graphene and nanocomposite cold cathodes under high voltage pulse electric field will be investigated. The relationship between the size effect, edge states and defect states of graphene and emission properties will be revealed. The effect of the thickness, morphology and composite synthesis technics of graphene films on the cathode emission properties will be studied, and related effective rules will be presented. The emission properties of cathodes will be improved by modification of substrates, depositing CsI and plasma treatments on graphene surface, and the cathode life will be prolonged. The study on the practical application of graphene cold cathodes used as intense-current electron beam sources in high power devices, such as linear induction accelerators (LIAs) will be carried out. The intense current electron beam emission process of graphene cathodes under the pulse electric field will be studied, and the intense electron beam emission mechanism of graphene based cold cathodes will be clarified.

强流发射冷阴极是高能器件的核心部件，石墨烯以其独特的结构性能，具有优异的电子发射性能，可作强流发射冷阴极。本研究拟制备大面积石墨烯冷阴极作为强流电子束源应用于高能电子器件。建立和发展石墨烯可控的低成本宏量制备方法，分别制备基于基底和自支撑的高质量大面积石墨烯薄膜，完善制备方法，实现对薄膜形貌、厚度和均匀性的控制。实现石墨烯与其他纳米材料的有效复合，两者优势互补，提高电子发射性能。系统研究大面积石墨烯及其复合材料冷阴极在高压脉冲电场中的发射性能，揭示石墨烯的尺寸效应、边缘态和缺陷态与发射性能的理论关系；确定石墨烯薄膜形貌、厚度和复合工艺对阴极发射性能的影响规律。通过基片预处理、石墨烯表面沉积CsI和等离子体处理等提高阴极的发射性能，延长阴极寿命。开展大面积石墨烯冷阴极在加速器等高能器件上的实际应用研究。分析石墨烯阴极在脉冲电场中的强流电子束发射过程，阐明石墨烯冷阴极的强流电子束发射机理。

强流发射冷阴极是高能真空电子器件的核心部件，石墨烯具有独特的结构和电学特性，是一种优异的电子发射材料，可用于构建强流发射冷阴极。本项目主要围绕石墨烯强流发射冷阴极的研制和实现其在国防武器装备上的应用开展研究。在实现石墨烯可控低成本宏量制备的基础上，采用手术刀法、超声雾化喷涂法和电泳沉积法成功制备了大面积石墨烯冷阴极，实现对石墨烯薄膜形貌、厚度和均匀性的控制。将石墨烯与其他纳米材料进行复合，成功制备了3D石墨烯/氧化锌纳米棒阵列和石墨烯/层状二硫化钼两种复合结构场发射冷阴极。研究了石墨烯冷阴极在直流及脉冲两种电场下的电子发射性能。在直流电场下，当石墨烯薄膜厚度为130μm，场强为5V/μm时的阴极发射电流密度达到30mA/cm2。阴极电子发射的荧光发光均匀、发射电流稳定性好。通过退火处理使石墨烯阴极的开启电场由2.03 V/μm降到1.99 V/μm。在1.89MV脉冲电场下，石墨烯冷阴极的最高发射电流密度达到70A/cm2，远高于在直流电场下的发射电流密度。对两种石墨烯复合结构材料阴极的电子发射性能进行了研究，通过材料形貌和结构调控优化了阴极发射性能，显著降低了阴极的发射开启电场和阈值电场。3D石墨烯/氧化锌和石墨烯/层状二硫化钼复合结构冷阴极的场增强因子分别达到3087和6081。构建的石墨烯冷阴极在高压脉冲电场中获得了强流电子束发射，Ni/3D graphene/ZnO NRAs结构阴极的脉冲发射电流密度达到91.42 A/cm2。在石墨烯冷阴极的强流发射过程中发现了等离子体产生，证实了阴极发射过程中的气体释放和石墨烯氧化现象，石墨烯分解氧化生成了CO2，建立了石墨烯冷阴极的场致等离子体强流电子束发射机理。发展了石墨烯的高性能功能器件，研制的大面积石墨烯冷阴极实现了在直线感应加速器上记录武器爆轰过程的实际应用。研究成果对推动我国新型国防武器装备的研发具有重要作用。