• Login
    JavaScript is disabled for your browser. Some features of this site may not work without it.
    Continuous hydrothermal flow synthesis of nanoceramics for photocatalytic and microwave dielectric applications 
    •   QMRO Home
    • Queen Mary University of London Theses
    • Theses
    • Continuous hydrothermal flow synthesis of nanoceramics for photocatalytic and microwave dielectric applications
    •   QMRO Home
    • Queen Mary University of London Theses
    • Theses
    • Continuous hydrothermal flow synthesis of nanoceramics for photocatalytic and microwave dielectric applications
    ‌
    ‌

    Browse

    All of QMROCommunities & CollectionsBy Issue DateAuthorsTitlesSubjectsThis CollectionBy Issue DateAuthorsTitlesSubjects
    ‌
    ‌

    Administrators only

    Login
    ‌
    ‌

    Statistics

    Most Popular ItemsStatistics by CountryMost Popular Authors

    Continuous hydrothermal flow synthesis of nanoceramics for photocatalytic and microwave dielectric applications

    View/Open
    ZHANGContinuousHydrothermal2009.pdf (5.268Mb)
    Publisher
    Queen Mary University of London
    Metadata
    Show full item record
    Abstract
    TiO2 is widely considered as a promising photocatalyst to degrade various organic pollutants in water, and to harvest sunlight renewable energy application. However, the efficiency of the photocatalytic reaction using TiO2 is not high due to its wide band-gap (3.22 eV, corresponding to the wavelength of 385 nm), which corresponds to the lower end of the wavelengths of solar light. The aim of this project is to use a continuous hydrothermal flow synthesis (CHFS) technique and other post-treatment methods to synthesize and tailor nano-TiO2 and TiO2-related photocatalysts for improved photoactivity. It was demonstrated that the rapid crystallising environment in a CHFS system resulted in the anatase phase of TiO2 (ca. 5 nm) with a high surface area and a high crystallinity. The CHFS system provides a flexible route of doping TiO2 at the atomic level (lattice doping) either to decrease the band-gap or to introduce intra-band gap states, which allow activation by visible-light. The structures of the resulting nanocatalysts were investigated using powder X-ray diffraction (XRD) and Raman spectroscopy. The quantity and chemical nature of the catalyst surface were determined by X-ray photoelectron spectroscopy (XPS). Morphologies of the products were characterized by Transmission Electron Spectroscopy (TEM) and Scanning Electron Spectroscopy (SEM). Band-gap energy was determined by UV-Vis spectrophotometry. A TiO2-CeO2 composite catalyst was successfully synthesized by CHFS. A stable solid-solution was indentified, which leads to a totally different optical property (i.e. with a narrow band-gap) when mixed with a methylene blue (MB) dye solution. All the composites materials show improved photodecolourisation rates. Novel 2D sodium titanate nano-sheets (ca. 400×500 nm) were developed with a high concentration of NaOH into the reactor. This material exhibits the highest photocatalytic efficiency amongst all materials being tested in this project. Several post-treatment methods were also adopted to further modify the CHFS-prepared nano-TiO2 samples. By heat-treating nano-TiO2 powder in air, the crystallinity of the sample was increased. By exposing the nano-TiO2 to ammonia atmosphere at a range of temperatures, products ranging from N-doped anatase TiO2 to phase-pure titanium nitride (TiN) were successfully obtained. N-doped TiO2 materials showed significant red-shift in band-gap. Surface modification of TiO2 in vanadium salt leads to a high surface absorbability and photo-oxidising power. Among all the modified samples, some of them indeed exhibited improved photocatalytic activity over the unmodified nano-TiO2. Moreover, the microwave dielectric properties of selected TiO2 samples (metal ion lattice doped) were also examined using sintered TiO2 discs. The results suggest that a useful dielectric resonator material can be achieved by introduction of certain dopants in combination with a spark plasma sintering (SPS) method.
    Authors
    Zhang, Zhice
    URI
    https://qmro.qmul.ac.uk/xmlui/handle/123456789/359
    Collections
    • Theses [3930]
    Copyright statements
    The copyright of this thesis rests with the author and no quotation from it or information derived from it may be published without the prior written consent of the author
    Twitter iconFollow QMUL on Twitter
    Twitter iconFollow QM Research
    Online on twitter
    Facebook iconLike us on Facebook
    • Site Map
    • Privacy and cookies
    • Disclaimer
    • Accessibility
    • Contacts
    • Intranet
    • Current students

    Modern Slavery Statement

    Queen Mary University of London
    Mile End Road
    London E1 4NS
    Tel: +44 (0)20 7882 5555

    © Queen Mary University of London.