Study On The Explosive Synthesis And Mechanism Of Carbon-based Nanomaterials

Research and application on carbon materials could be dated back to long time ago,but they could still catch extensive interests today. There are various forms of carbon,including graphite and diamond which have been utilized since ancient times as well asfullerene, carbon nanotubes and graphene which are found recently. Carbon and otherelements (nitrogen, metals, etc) can be combined to form a variety of compounds, whichhave important application in different fields. Explosive synthesis technology is anadvanced research topic around the world. The high temperature and high pressure causedby explosion can result in complex changes in the material properties. In this dissertation,systematic research on explosive synthesis and mechanism of carbon-based nano-materialshas been carried out.The detonation-driven high velocity and cylindrical geometry with two co-axial tubeswere developed in this paper, and can be used to synthesis of carbon-based nanomaterials.Hugoniot parameters of mixtures of porous powders were obtained by using weightedaverages based on Mie-Gruneisen eqution. Shock loading process and shock pressure werestudied by using AUTODYN. The shock loading device could be optimized and improvedby analyzing the results of experiments.Explosion shock synthesis of graphene was first achieved in this research. Dry ice andcalcium hydride were used as precursors, as well as alcium carbonate and magnesiumpowder. Ammonium nitrate and urea were used as nitrogen doping source. The precursorswere impacted by detonation driven flyer, in order to complete shock synthesis of grapheneand nitrogen-doped graphene, which has has an efficient electrocatalytic activity for oxygenreduction reaction (ORR) in an alkaline medium. Shock synthesis of graphene requires abalance between the growth rate of graphene and the formation rate of carbon during theshock loading process. Furthermore, the pressure and temperature are two important factorsin the synthesis of graphene by controlling the formation rate of carbon.Graphitic carbon nitride (g-C3N4) was prepared via benzene solvothermal route. TheHugoniot curve of g-C3N4was measured by using a light-gas gun and Displacement Interferometer System for any Reflector(DISAR). Shock velocity (D) versus particlevelocity (u) relation showed a discontinuity at22.4GPa. According to the recoveryexperiment results, the α-C3N4could be formed when the pressure is higher than22.4GPat,which means that the inflexion point indicates phase transition. Meanwhile, g-C3N4transforms to α-C3N4under shock wave loading as a kind of martensite phasetransformation, where pressure induced phase transition dominates. The quenching rateplays quite important role in synthesis of metastable phase (α-C3N4). The α-C3N4can alsobe formed in process of mixing nickel powder and Dicyandiamide under cylindrical doubletube impact loading. Catalytic property of nickel powder has enhanced effect on synthesisof α-C3N4.Carbon-encapsulated iron-based nanoparticles with a core–shell structure were producedby detonation of RDX and iron tristearate mixtures with different mass ratios. The coreswere tightly covered by graphitic shells, which can effectively protect the metal-containedcores against acid. The mass ratios of RDX to iron astearate are crucial for the formation ofcarbon encapsulated nanoparticles. With the increase of the mass ratio, the number of thegraphitic coating layers and the size of particles decrease. Meanwhile, the content of ironalso increases. The carbon encapsulated iron-based nanoparticles exhibit ferroparamagneticbehavior. The carbon-encapsulated iron-based nanoparticles have excellent microwaveabsorbing properties in range of2.8to18GHz wide-frequency.