Synthesis And Characterization Of Carbon Nitride And Silicon Nitride Nanomaterials

This paper concentrates on the synthesis and characterization of carbon nitride and silicon nitride nanostructures. Graphite-like carbon nitride nanowire bundles with diameters of 200-500 nm were synthesized from the solid state thermolysis of melamine at relatively low temperature (400℃). Hexagonal carbon nitride tubes with diameters of 500-800 nm and flake arrays were prepared by heating the nanowire bundles at 550℃in argon atmosphere. The products were characterized in detail and the forming process of tubes and transformation of the molecular structures from s-triazine rings to tri-s-triazine units was analyzed. The blue and yellow-green emission photoluminescent (PL) properties of the products were investigated in detail, and the reasons for the differences of PL properties between the bundles and tubes were discussed.Starting from ferro-silicone alloy brezee and ammonium chloride,α-Si₃N₄ nanowires bundles have been obtained at 600℃. The nanowires have about 8 nm in diameter, up to 800 nm in length. The influence of reaction time and temperature on the products was investigated. As ferro-silicone alloy was substituted with silicon and metallic iron,α-Si₃N₄ olivary nanoparticles with a diameter of about 100-200 nm at the middle and a length of 500-1000 nm have been obtained at 650℃. When silicon and metallic aluminium were used to react with ammonium chloride,α-Si₃N₄ nanowire bundles can be also obtained at 600℃. Since all of the starting materials used are relatively cheap, the methods will have potential prospect in industrial application.Orthogonal strategy was performed for preparing nano-crystalline Si₃N₄ in 200-350℃using NaN₃, SiCl₄ and Mg powder as the starting materials to find the optimized reaction condition. The conversion ratio was 54.04 % calculated from the amount of limited reactant NaN₃. Magnified experiments were carried out in a 1000 mL autoclave. The conversion ratio was about 50 % calculated which indicated that it was a promising process in industrial application. XRD analysis showed that the products were the mixtures ofα- andβ-Si₃N₄. TEM observation presented that the products were nanorods (over 50%) together with nanoparticles.