Study On Carbon Nanotube/Carbon Black Self-assembly Reinforced Carbon Graphite Composites

With the continuous development of the electrified railroad in the direction of heavy load and high speed,the impact vibration of the arch network intensifies,off-line arcing occurs frequently,and the pantograph slide plate is abnormally worn out or even broken,leading to frequent failures.Therefore,for long time,high speed and high current operating conditions,the development of high performance,long life and low cost pantograph sliding plates is the top priority of high-speed railroad bow network system.However,as a multi-component,multi-phase,structural carbon graphite material,the carbon matrix part of the in-service pure carbon skids and dipped metal skids will inevitably undergo pyrolysis and shrinkage during heat treatment,producing internal defects such as cracks and pores,which have been proven to be the cause of composite material performance degradation.In this paper,carbon nanotubes and carbon black are used as reinforcing phases to address the basic defect problem of charcoal-graphite materials from two perspectives of inhibiting crack development and reducing defect generation.Two means,plasma modification and electrostatic self-assembly,were used to improve the interfacial bonding between carbon nanotubes and matrix and to regulate the spatial distribution and action range of carbon black in the matrix.Carbon nanotube/carbon black reinforced carbon-graphite composites were prepared and the synergistic effects of carbon nanotubes and carbon black on the fundamental performance properties of the material were investigated.It was found that carbon nanotubes/carbon black reduced the weight loss of bitumen by about 5% during heat treatment,and the porosity of the composites was reduced from 21% to 15%,carbon black promoted the interfacial bonding between carbon nanotubes and the matrix,and carbon nanotubes/carbon black/bitumen carbonization formed a carbon skeleton structure,which improved the graphitization and structural integrity of the carbon graphite materials.In order to evaluate the comprehensive performance effects of carbon nanotube/carbon black reinforced carbon graphite composites,material static characterization parameters such as compressive strength,flexural strength,and resistivity were tested.Carbon black enhanced the interfacial bonding of carbon nanotubes with the matrix,and the highest compressive strength of the composite was 143.2 MPa and the flexural strength was 29.2MPa,which was about one times higher than that before the addition of nanomaterials.Carbon nanotubes and carbon black formed a globally connected conductive network,and the composites exhibited the lowest resistivity of 44.8 μΩ·m,which was 42% lower than that before the addition of nanomaterials.The carbon nanotube/carbon black assemblies also reveal the frictional wear and anti-arc ablation mechanisms of carbon graphite materials based on dynamic performance tests such as current-carrying friction experiments and arc ablation tests.The bridging effect of carbon nanotubes retarded the friction film shedding,and the wear rate decreased by up to 26.4%.The enhanced bonding between each grouping of the composite dispersed the temperature gradient stress and reduced the amount of ablation by 20%.This study analyzed the synergistic effect of carbon nanotubes and carbon black in carbon graphite composites,and provided theoretical support and scientific guidance for the development of high-performance carbon-based pantograph slide materials.