高强高导特高压石墨烯/CuW触头材料制备及烧蚀特性研究

Erosion spots or craters are easily formed on the surface when CuW contacts are subjected to arc breakdown, leading to premature failure, which raises a high requirement on the strength and conductivity of the materials. High strength and dispersion arc properties of CuW contacts has obtained using refine microstructure and alloying methods, however, resulting in deteriorating the electrical conductivity. So, in order to overcome CuW contacts performance’ contradictory relationship, the super-high strength and fascinating electrical properties graphene as a doping phase in this project is introduced into CuW contacts. Graphene/CuW contacts were fabricated by SPS infiltration-activation sintering technology with controllable thickness and content copper coated graphene (Cu@graphene) using thermoelectroless plating assisted with ultrasound method. By investigating the microstructure formation mechanism, mechanical and electric behavior, the interdependent relationship of the graphene size, distribution, interface state and composites strength and electrical conductivity can be clarified. And the electron transition barrier level and arc spots production, geometric structure and motion are observed by STM and high-speed video camera. And the evolution process of the arc spots on the surface of Cu@graphene/CuW contacts is clarified, and the coupling mechanism of the mechanics and electricity to the ablation performance is revealed. And then synergistically enhanced the mechanical and electrical properties and the internal regularity of arc ablation resistance on Cu@graphene/CuW contacts are further revealed. It is expected that this project will shed some light on the in-depth understanding of the new phenomena, the basic law and the corresponding physical nature of surface arc ablation behavior of new Cu@graphene/ CuW contacts. The research results will provide experimental data and the theoretical basis for microstructure optimization design and preparation of new contacts materials.

触头材料在电弧作用下易形成烧蚀斑点（坑），导致过早失效，这对材料的强度和导电性提出了高要求。细化晶粒、合金化等虽能提高强度，改善分散电弧能力，但严重损伤电性能。本申请采用室温超声化学镀铜改性石墨烯，解决与CuW润湿性，结合SPS熔渗活化烧结制备呈连续状结构的石墨烯/CuW触头，充分发挥石墨烯超高强化效应与导电性，彻底解决已往触头材料性能上此消彼长的矛盾。研究改性石墨烯/CuW触头微观组织形成机制与力学、导电行为，阐明石墨烯尺寸、分布、界面状态等与触头整体强度、导电性相互依赖关系；结合隧道扫描电镜和高速摄影等测量和观察电子跃迁势垒能级和电弧斑点产生、几何结构及运动过程，阐明石墨烯/CuW触头表面电弧烧蚀斑点演变过程，揭示力、电学对烧蚀性能的耦合作用机制，深入理解石墨烯/CuW触头表面电弧烧蚀行为的新现象、基本规律及对应的物理本质。本研究可为新型触头材料的微观设计和制备提供理论和实验参考。

触头材料在电弧作用下易形成烧蚀斑点，导致过早失效，这对材料的强度和导电性提出了高要求。细化晶粒和合金化等虽能提高强度，改善分散电弧能力，但严重损伤电性能。本项目采用室温超声化学镀铜改性石墨烯，球磨混粉和SPS制备了呈连续网状结构的Cu@rGO/CuW复合材料。研究石墨烯表面金属化制备工艺，阐明了Cu@rGO形成机制；Cu@rGO/CuW复合材料中，Cu@rGO和铜相呈网状分布在W颗粒周围，同时原位形成碳化钨。研究了Cu@rGO/CuW触头微观组织形成机制与力学、导电行为，阐明了石墨烯含量/分布、界面状态与触头整体力学性能相互依赖关系；Cu@rGO活化烧结W颗粒，促进基体致密化过程。掺杂Cu@rGO提高了CuW复合材料硬度和电性能，当Cu@rGO含量为3wt.%时，CuW复合材料的致密度、硬度和电导率分别是98.6%，245HB，35%IACS。阐明Cu@rGO/CuW表面电弧烧蚀斑点形成和演变过程。经过在15kV电弧百次击穿后，随着Cu@rGO含量升高，触头材料的平均击穿场强先降低后升高，最高击穿场强为5.8×106 V·m-1，相比CuW基体，平均击穿场强提高了~28.93%。在电弧烧蚀过程中，Cu@rGO及碳化钨延迟了起弧时间，电弧烧蚀首击穿相由铜相转移到低功函数Cu@rGO表面，同时烧蚀表面铜液飞溅小，烧蚀坑数量减少且平坦，Cu@rGO起到分散电弧的作用。电弧烧蚀性能的提高归因于：（1）Cu@rGO增加了熔融金属Cu的粘度，抑制快速流动和飞溅；（2）石墨烯和碳化钨较低的功函数抑制了电弧击穿过程中的电子发射；（3）碳化钨稳定性好，熔点高，缩短了铜液的凝固时间，延长了Cu@rGO/CuW的使用寿命。此外，Cu@rGO和碳化钨提高了复合材料在氧乙炔环境下的烧蚀性能。尤其是3wt% Cu@rGO/CuW复合材料的质量烧蚀率和线烧蚀率分别为0.015 g/s和0.0023 mm/s，分别比CuW基体烧蚀率小0.25和0.3倍。Cu和WO3的蒸发冷却、Cu@rGO的热消耗和高熔点碳化钨是获得优异烧蚀性能的主要原因。Cu@rGO/CuW复合材料在烧蚀过程中的失效机制主要是由形成的WO3、Cu2O和CuWO4产物的热化学氧化和热机械侵蚀引起的。高导电导热Cu@rGO有利于热量散失，显著改善材料的电、力、热多场耦合条件下的烧蚀性能，为CuW材料的微观设计制备提供理论和实验参考。