Browsing by Author "Cele, Hastings Mthobisi"

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    Synthesis of VO2 Nanostructures for Infrared Modulation Applications
    (2009) Cele, Hastings Mthobisi; Maaza, M.; Ndwandwe, O.M.
    Vanadium pentoxide (V2O5) is a thermochromic material, meaning it can change is colour upon heating. It has potential application in the fields of lithium-ion batteries, actuators, catalysis (mostly in organic reactions and a precursor for the other vanadium salts) and sensors. In this project, the V2O5 sol-gel is used as a precursor of producing thermochromic vanadium dioxide (VO2) thin films. The consolidated nano- and microcrystal materials based on vanadium (IV) oxide have attracted various fundamental and applied interest due to its unique optical properties related to the Mott’s type 1st order transition exhibited at about 68°C. The most interesting property of VO2 coatings is to transmit in the visible light region as well as infrared region. This makes the good coating for smart windows such as windscreens of the cars, windows of the dwellings as well as infrared shutter in laser laboratories. In synthesis of the film, ultrasonically cleaned normal glass and silicon (111) substrates were used for the deposition of V2O5 film. The low cost method used in synthesis of the film is soft chemistry, which is well-known as valence reduction method. The reduction of V2O5 was done using three techniques: reduction using 10 % H2 mixed with 90 % of Ar, reduction using 50 % of CO mixed with 50 % with CO2 and reduction using laser ablation. During valence reduction, V2O5 was reduced into different vanadium oxides before VO2: V2O5; V3O7; V4O9; V6O13; VO2. The produced V2O5 films were studied under atomic force microscope (AFM) and scanning electron microscope (SEM) techniques to see the surface morphology and compare roughness, the changes of the pure V2O5 crystals with VO2 crystals. There are some other characterization techniques used in this project including: EDX, XRD, RBS, ERDA, FTIR, UV-Visible, and Raman. The main aim of producing VO2 films was to study them for FTIR modulation applications.