Arc discharge synthesis and morphology control of early transition metal carbide nanopaticles.

摘要

This work is directed to the understanding of the synthesis and morphology control of early transition metal carbides. Chapter 1 gives an introduction to fcc structure nanoparticle synthesis and the parameters controlling nanoparticle morphology. Also the importance of early transition metal carbides is discussed. The experimental methods are described in Chapter 2 including a detailed description of the fabricated arc discharge apparatus employed in this study. In Chapter 3, the results of the synthesis of titanium carbide nanoparticles with different methane concentrations are presented. Titanium carbide nanoparticles prefer a cubic morphology when synthesized with low methane concentrations and cuboctahedron morphology with high methane concentrations. Chapter 4 discusses the synthesis of niobium carbide nanoparticles and how the nanoparticle morphology changes with different reactant gases. Niobium carbide nanoparticles distribution prefer a cubic morphology when synthesized with methane, a mixture of cubic and octahedron morphology when synthesized with ethylene, and a cubic morphology when synthesized with acetylene. Studies of the synthesis of zirconium carbide nanoparticles are given in Chapter 5. The zirconium carbide nanoparticles prefer cuboctahedron morphology when synthesized with methane. The change in nanoparticle morphology for the different early transition metal carbides is attributed to the stabilization of the {111} facet. The stabilization of the {111} facet under different conditions leads to changes in the relative growth rate ratio between the {111} facet and the {100} fact. The change in the growth rate ratio ultimately leads to changes in the nanoparticle morphology.