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Effect of Spark Plasma Sintering Pressure on the Microstructure of Carbon Nanofibers

Carbon naonfibers (CNFs) were heat-treated in a spark plasma sintering (SPS) system with vacuum condition at 1500°C with various uniaxial pressures. The microstructural evolutions of CNFs under both high temperature and additional pressure were investigated by scanning electron microscopy, transmission electron microscopy and Raman spectroscopy. It is proposed that the high temperature is contributing to the formation of high ordered and large crystalline graphitic layers, while applied pressure is in favor of cutting down the CNFs to shorter ones and coalescing them to form micro-sized graphitic sheets. Our results propose that the SPS is an efficient route to explore the materials’ structural conversions at high pressure and high temperature.