Synthesis of nanostructured materials with potential renewable energy generation applications

Gallagher, Jamie Brian (2015) Synthesis of nanostructured materials with potential renewable energy generation applications. PhD thesis, University of Glasgow.

Abstract

The work in this thesis is concerned with growth of low dimensional materials in a variety of morphologies which have potential renewable energy generation applications. The work described within demonstrates synthesis methods for the production of materials with thermoelectric applications and materials for photovoltaic purposes. Products are characterised using a range of techniques including: scanning and transmission electron microscopy; energy dispersive X-ray spectroscopy and powder X-ray diffraction. Presented here is an investigation into the growth of bismuth telluride on silicon surfaces via chemical vapour deposition (CVD). Resultant particle morphology is reported in relation to experimental conditions such as surface conditions (silicon, gold/palladium on silicon and disordered silicon surfaces), temperature and reagent concentration. Successful synthesis of Bi2Te3 plates is presented starting from elemental precursors via a closed vessel CVD process. Plates with sub-micron thickness (but up to 40 μm diameter) are produced template free on a silicon surface and without the need for transport gases or expensive precursors. Using modification of silicon surfaces the growth of 2-4 μm tetragonal pyramids of Bi2Te3 are demonstrated. CVD is also used to produce bismuth rich nanowires up to 40 μm but <100 nm in diameter, these were produced by increasing the bismuth concentration in comparison to other methods. This thesis also details an investigation into the suitability of a range of substrates for CVD. Alumina is demonstrated to be a suitable surface for Bi2Te3 CVD with nanostructured Bi2Te3 spheres of 5-20 μm diameter presented. Additionally vertically aligned arrays of copper telluride are presented using a single step CVD process. Arrays consist of hexagonal plates <500 nm in thickness but up to 25 μm in diameter. Due to preferential reaction with tellurium GaAs is demonstrated to be a poor facilitator for Bi2Te3 growth as is cobalt. The production of nanostructured sphere of TiO2 is also presented. Spheres with tuneable diameter are produced in <60 s in multi-mode microwave reactors using a hydrothermal process. The spheres are comprised of radially aligned nanorods producing spheres of 1-3 μm. Spheres are demonstrated to be a single rutile TiO2 phase. Spheres are characterised with phase, band gap and morphology presented and influence of experimental parameters such as time and reagent concentration is discussed. 2 Finally this work investigates the doping and conversion of TiO2 structures to TiN and TiO2-xNx structures. Using ammonolysis TiO2 is converted to a TiN structure while retaining its original its original spherical morphology. Using the same ammonolysis process TiO2 is doped and the demonstrational shift in band gap to the visible region is presented.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Keywords: Thermoelectric, bismuth telluride, Bi2Te3, nanoscale, morphology, energy materials, titanium dioxide, TiO2, chemical vapour deposition
• Subjects: Q Science > QD Chemistry; T Technology > TK Electrical engineering. Electronics Nuclear engineering
• Colleges/Schools: College of Science and Engineering > School of Chemistry
• Supervisor's Name: Gregory, Professor Duncan, Paul, Professor Douglas and Knox, Professor Andrew
• Date of Award: 2015
• Depositing User: Mr Jamie Gallagher
• Unique ID: glathesis:2015-7040
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 19 Jan 2016 15:22
• Last Modified: 03 Feb 2016 08:58
• URI: https://theses.gla.ac.uk/id/eprint/7040