Pengwan Chen

Abstract:

Shock wave action of high temperature, high pressure and high strain rate lasting for very short time (~10-6 s) will cause a series of catastrophic changes of material chemical and physical properties, and herein both detonation-driven high velocity flyer impact loading and electrical explosion technique were employed to induce shock wave for the synthesis of high-quality graphene materials. Using solid CO2 (dry ice) as the carbon source, few layer graphene nanosheets were successful synthesized by reduction of CO2 with calcium hydride through detonation-driven flyer impact. Furthermore, by adding ammonium nitrate to the reaction system, nitrogen-doped graphene materials were formed in this one-step shock-wave treatment. Similarly few layer graphene and nitrogen-doped graphene materials were also prepared through the reaction of calcium carbonate and magnesium, and the shock pressure and temperature are two important factors affecting the synthesis of few layer graphene nanosheets. Besides that, graphite nanosheets, few-layer graphene, and especially, mono-layer graphene with good crystallinity were also produced by electrical explosion of high-purity graphite sticks in distilled water at room temperature. Delicate control of energy injection is critical for graphene nanosheets formation, whereas mono-layer graphene was produced under the charging voltage of 22.5-23.5 kV. The recovered samples were characterized using various techniques such as transmission electron microscopy, scanning electron microscopy, Raman spectroscopy, atomic force microscope and X-ray photoelectron spectroscopy, and therein the nitrogen-doped graphene was demonstrated to act as a metal-free electrode with an efficient electrocatalytic activity toward oxygen reduction reaction in alkaline solution. This work provides a simple but innovative route for producing graphene nanosheets.