Synthesis Of Nanocomposites Via Millisecond Pulsed Laser Ablating Binary Metal Targets

Laser ablation can provide an extreme and non-equilibrium environment with high temperature and pressure. After being ablated by laser, a metal target can be heated and cooled very rapidly, and then nanomaterials with various structures can be obtained. As for a binary metal composite target being ablated by laser with enough energy, the two constituent metals will be melted or vaporized to form a mixed vapor. And various nanocomposites with novel structures can be got during the cooling process. In this thesis, millisecond pulsed laser was used to ablate binary metal composite target in gas or liquid to prepare diverse composite nanomaterials, the mechanisms of millisecond pulsed laser ablating binary metal target were also studied.We obtained phase-separated nanocomposites by millisecond pulsed laser ablation of Pb-Zn alloy target in inert medium. At the same time, we studied the effects of the composition of alloy targets, laser energy, liquid media on the final products, and we found that the size differences between the two phases in the nanoparticles are relevant to the composition of composite target. Meanwhile, we found that laser energy and liquid media played important roles in the formation of the composite nanoparticles. At last, on the basis of the Pb-Zn phase diagram, we proposed the mechanism for the formation of phase-separated nanocomposites by laser ablation of Pb-Zn binary alloy target.We obtained one-dimensional composite nanostructures by millisecond pulsed laser ablation of Pb-Zn alloy target in different reactive media. ZnS nanorod/PbS nanoparticle heterostructures were obtained in dodecyl mercaptan, ZnO nanowire/Pb nanoparticle heterostructures in air and argon gas mixture and ZnO nanorod/PbO dumbbell heterostructures in air. We analyzed the growth mechanism of these heterostructures, and drew a conclusion that the millisecond pulsed laser with long pulse width can provide a high-temperature environment which was necessary for the growth of naowires, and Pb nanodroplets could be served as catalyst for Zn atoms adsorbing constantly, precipitating and reacting with surrounding S/O precursor to form nanowire by a gas-liquid-solid (VLS) growth mechanism.We also obtained several novel composite nanostructures such as hemisphere and dendritic structures, stings binary metals nanospheres and core-shell nanostructures, by millisecond pulsed laser ablating binary metal targets (Zn-Al, Zn-Fe, Pb-Sn) in ethanol. Therefore, millisecond pulsed laser ablation is a promising synthesis method for the composite nanomaterials.