Electronic Thesis and Dissertation Repository

Degree

Doctor of Philosophy

Program

Mechanical and Materials Engineering

Supervisor

Xueliang Sun

Abstract

Nanomaterials have attracted extensive interest due to their unique structure and excellent properties compared with their bulk counterparts. To obtain nanodevices with controlled properties, it is prerequisite to synthesize nanostructured materials with designed architecture.

In this work, low (one- and two-) dimensional nanomaterials with controlled structures have been synthesized and characterized based on chemical vapour deposition strategy. Our research targets cover one-dimensinoal hollow, solid, and solid @ hollow heterostructural nanomaterials including carbon nanotubes (CNTs), nitrogen-doped carbon nanotubes (NCNTs), SnO2 nanowires, Mo doped-SnO2 nanowires, Sn nanowires encapsulated in CNTs (Sn@CNTs), and two-dimensional Mo2S3 nanopetals. Dependence of product morphology, composition and phase structure on the synthesis conditions has been systematically investigated by changing temperature, growth time, gas flow, external atom doping, catalyst and employed substrate, to get insight into the correlation between the structure control and growth conditions of the products and their growth mechanism as well.

High quality CNTs and NCNTs with uniform size were synthesized on carbon paper and Si wafer by introducing thin iron sputtering film as catalyst. High nitrogen content up to 10.4 at% was reached in the NCNTs.

Controlled growth of SnO2 and Mo-doped SnO2 nanowires was obtained on different substrates including carbon paper, stainless steel and Cu to meet substrate requirements for practical applications. It was found that Mo doping could significantly improve the corrosion resistance of the SnO2 nanowires.

Core-shell heterostructures of Sn nanowires @ CNTs were produced on carbon microfibers, stainless steel and Cu substrates. Rational control on the thickness and nature of the carbon shell of the heterostructures on carbon microfibers was realized by modulating growth parameters and introducing extra catalyst. Multi-generation Sn@CNTs were obtained by exploring SnO and SnO2 as starting materials. On the metallic substrates, Sn-alloy@CNT nanostructures were obtained. In another way, SnCo alloy nanowires @ CNTs with readily controlled Co content were achieved by introducing cobalt-contained precursor.

Non-catalytic and catalytic growth of two-dimensional Mo2S3 nanopetals was investigated on carbon microfibers. Without catalyst, the nanopetals with high density were only obtained in a narrow range of the precursor concentration. With Au catalyst, uniform nanopetals with steady high density could be achieved in a wide range of the precursor concentration.

Morphology, composition and phase structure of the nanostructures were characterized and analyzed by electron microscopy, X-ray diffraction, energy-dispersed spectroscopy and Raman spectroscopy.

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