Synthesis Carbon And Silicon Materials By Laser Ablation

Nowadays plasma synthesis by laser ablation plays a very importantrole among the researches about synthesis and production of clusters andnanomaterials. Many salient progresses in this area were realized by laserplasma synthesis. For example, the discovery of C60 and the family offullerenes, the production of carbon nanotubes and many kinds of othernanomaterials. So we hope to build a new efficient method of preparingmaterials by laser ablation, and to study the formation conditions anddisciplines. We hope not only to obtain macroscopic products, but also toexplain the formation mechanism by study the intermadiate products.The thesis is devoted to the study of plasma synthesis by laserablation. Various carbon clusters, silicon clusters and siliconnanomaterials were prepared by laser plasma reaction in a reaction systemincluding solid, liquid and gaseous reactants. The synthetic products wereseparated and characterized by various means. The formation mechanismof fullerenes and the growth mechanism of carbon clusters catalyzing bynickel, cobalt or iron respectively were discussed.The results can be summarized as follows:(1) By laser ablating a heterogeneous reaction system which wasconsisted of solid graphite, liquid and gaseous chloroform, a series ofperchlorinated fragments of fullerenes were synthesized. The productswere separated and characterized by high performance liquidchromatography coupled with both mass spectra and ultravioletabsorption spectroscopy. Most of the products could vest in two series, i.e.decachloro and octachloro ones. They were C12Cl10, C14Cl10, C16Cl10,C18Cl10, C20Cl10, C22Cl10 and C10Cl8, C12Cl8, C14Cl8, C16Cl8, C18Cl8,C20Cl8, C22Cl8, C24Cl8, C26Cl8, C28Cl8, C34Cl8. Among them,hexachlorobenzene (C6Cl6), octachloronaphthalene (C10Cl8),octachloroacenaphthylene (C12Cl8), decachlorobiphenyl (C12Cl10),decachloroanthracene (C14Cl10), decachlorophenanthrene (C14Cl10),decachloropyrene (C16Cl10), decachlorofluoranthene (C16Cl10) wereidentified. The results in this work indicated that laser ablation as aphysical method was combined with conditions of chemical building-upreactions, it can be used as a kind of macroscopic quantities'synthesismeans obtainning various clusters. (2) Various carbon clusters were synthesized by laser ablation nickel,cobalt or iron respectively in chloroform vapor. The products were separatedand characterized by high performance liquid chromatography coupled withmass spectra. The two sets of products preparing under catalysis of nickel orcobalt were similar, most of them were carbon-chlorine-hydrogen clustersand carbon –hydrogen clusters. The number of carbon atoms of the clustersgrew from several to tens. Most of carbon-chlorine-hydrogen clusterscontained 1～4 chlorine atoms. Otherwise, the products preparing undercatalysis of iron were quite different. The carbon-chlorine-hydrogen clusterswere smaller, but the numbers of chlorine atoms in them were almost above5, reached 12. And many kinds of carbon-chlorine clusters were included.The results indicated that nickel, cobalt and iron could catalyzed thegrowth of carbon clusters in different extent of capability. The catalysismechanisms of nickel and cobalt should be similar, but the catalysismechanism of iron was quite different. The catalyzing capability of nickeland cobalt were stronger than that of iron. The reaction of metal catalysts tocarbon clusters should begin from the period when the cluster consisted ofonly a few carbon atoms. The production of carbon-chlorine-hydrogenclusters and carbon –hydrogen clusters was because of the exist of metalcatalysts, and the chlorine atoms binded at the open edge of carbon clustersbaffled the catalysis to the growth of carbon clusters. (3) A special synthetic reaction has been developed, in which vaporof the reactant interacts with the high temperature plasma generated bylaser ablating a graphite target. By selecting chained methylsilicone asreactant, a series of methylsilsesquioxanes products with various structuralconfigurations have been obtained. Among them, two products, which wereseparated by sublimation in high vacuum and recrystalization, werecharacterized by X-ray crystal diffraction as (CH3SiO1.5)n (n=8,10). Both ofthem are found to have three-dimensional cage structure. In addition, otherproducts with double ring structure were detected by GC-MS analysis. Theresults demonstrate the potential application of the synthetic reaction. Inthe reaction described in this article, resulting from the collision andenergy-transfer of the laser plasma, chain structure of the reactantdissociated and recombined to give the cage and ring structure of theproducts. (4) By laser ablating silicon dioxide in the vapor of...