Research On Detonation Synthesis Of Carbon-encapsulated Metal Nanomaterials

Since the nineties of 20 th century, CEMNPs become the another major new discovery in carbon composite materials afterwards fullerene-C60,CNTs. The new type of core-shell structural carbon/metal nanocomposites, in which graphite carbon layers arrange round spherical metal nanocrystal located in the composite center. Because that CEMNPs have excellent properties and potential broad application prospects in many areas, this kind of unique structure and physical and chemical properties of CEMNPs have aroused wide attention and research from domestic and foreign scholars in recent years. Due to the carbon shell protection, bare metal nanocrystals were prevented from aggregation and growth and provided from the oxidation resistance and environmental effect and even improved the bio-compatibility.Among these methods, detonation technique has the advantage of high efficiency, simple and lower energy consumption so that it has prepared for many nanomaterials such as nanodiamond, nano-nitride, nano-oxide, carbon nanomaterial and so on. This paper mainly explained the synthetic mechanism of CEMNPs by two ways:experiment analysis and theoretic calculation. The CEMNPs have been prepared by detonation technique and characterized by means of XRD, SEM, TEM, EDX, XRF, Raman,VSM and DSC/TG characterization methods. Finally,the synthetic mechanism of CEMNPs was presented by numerical modeling of explosive precursors.Based on a large body of evidence on detonation synthesis of nanomaterials, the OB, explosion characterization, thermal safety and composition of explosive precursors were preliminary conceived and designed, so that the carbon-encapsulated metal (Ni, Co, Fe) nanoparticles were successfully synthesized. The results showed that the explosive precursors with a certain mole ratio of nitrate and complexing agent for metallic source materials, which mixed carbon source materials such as organic matter were ignited by detonator under nitrogen in closed detonation vessel. The preliminary reaction mechanism were discussed in this part.And then Carbon-encapsulated ferronickel and ferrocobalt nanomaterials were further synthesized and characterized. The results indicated that carbon-encapsulated ferronickel or ferrocobalt nanoparticles were prepared successfully and the spherical composite nanoparticles were with a core-shell structure. The yield of synthesized composite nanoparticles was about 10-15% one time. And the compatibility of carbon and a type of metal such as copper was poor. So the another gel-precursors were prepared by mixing copper nitrate, citrate and ethylene glycol then the gel mixed with RDX for gel-explosive precursors. The gel-precursors were synthesized by detonation technique for carbon-encapsulated copper nanoparticles under argon gas in closed vessel. The explosive precursors with iron/cobalt/nickel ions or its mixtures were thermodynamically analyzed for thermal safety by DSC/TG. Base on the thermal safety analysis on characteristics of thermal decomposition of the main ingredients and their mutual effect in explosive precursors. The results showed that the best stoichiometry content of metal ions in these precursors were obtained and the DSC/TG plots method along with several thermal analysis methods were employed to determine the kinetic parameters and model of the decomposition processes for detonation synthesis of CEMNPs.Finally, Based on BKW equation of state of detonation products, and the global minimum of Gibbs free energy were applied to originally design GS-BKW programs and described chemical reacted explosive and detonation products, which realized the coupling equation of state for gas and metal or alloy products. The calculated results showed that the pressure and temperature in the range of 9-15GPa and 2000-3500K are conducive to the formation of synthesizing CEMNPs, and the growth mechanism of CEMNPs and detonation pressure and temperature were analyzed and illustrated.