Browsing by Author "Zhou, MF"

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    Determination of niobium diffusion in titania and zirconia using secondary ion mass spectrometry
    (Taylor & Francis (Informa UK), 2007-01-01) Sheppard, LR; Zhou, MF; Atanacio, AJ; Bak, T; Nowotny, J; Prince, KE
    This paper provides an outline for the use of secondary ion mass spectrometry (SIMS) in the determination of diffusion data in metal oxides. The focus is on the determination of Nb bulk and grain boundary diffusion coefficients in TiO2 and zirconia. Specifically, the diffusion of Nb in TiO2 and yttria doped (10 mol.-%) ZrO2 (10YSZ) has been assessed. The following bulk diffusion coefficients D 93Nb were obtained D 93Nb =(1·03±0·051) × 10−18 m2 s−1 10YSZ(1273K) D 93Nb =(1·91±0·096) × 10−16 m2 s−1 TiO2(1273K) The grain boundary diffusion parameter for Nb grain boundary diffusion in 10YSZ was also determined D 93Nb δα =(7·48 ± 0·37) × 10−25 m2 s−1 10YSZ(1273K) The Nb grain boundary diffusion coefficient D′93Nb was determined to be D′93Nb =(3·99 ± 0·20) × 10−16 m2 s−1 10YSZ(1273K) © 2007 Informa UK Limited
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    Effective gel for gold nanoparticle formation, support and metal oxide templating
    (Royal Society of Chemistry, 2007-08-07) Wang, XD; Egan, CE; Zhou, MF; Prince, KE; Mitchell, DRG; Caruso, RA
    Gold nanoparticles were synthesized using agarose as a reducing agent, which gelled to support the gold nanoparticles, then readily functioned as a template to produce a porous, evenly-distributed Au/TiO2 nano-hybrid. © 2007, Royal Society of Chemistry
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    Electrical conductivity and defect disorder of tantalum‐doped TiO2
    (John Wiley & Sons, 2017-05-02) Alim, MA; Bak, T; Atanacio, AJ; Du Plessis, J; Zhou, MF; Davis, J; Nowotny, J
    The present work reports the electrical properties of polycrystalline Ta‐doped TiO2 (0.39 at.% Ta) determined in situ at elevated temperatures (1173‐1323 K) in the gas phase of controlled oxygen activity (10−12 Pa to 105 Pa). The effect of oxygen activity on the electrical conductivity and thermoelectric power of TiO2 is discussed in terms of defect disorder, including (1) the intrinsic electronic disorder that is governed by electronic compensation in the strongly reducing regime, (2) the extrinsic electronic disorder that is governed by electronic charge compensation in the reducing regime, and (3) the extrinsic ionic disorder that is governed by ionic compensation in the oxidizing regime. It is shown that tantalum ions are incorporated into the titanium sublattice of TiO2 leading to the formation of donor‐type energy levels. The Arrhenius‐type plot of the electrical conductivity data leads to the determination of the formation enthalpy terms. The obtained results are considered in terms of the effect of tantalum and oxygen activity on the defect disorder and the associated key performance‐related properties in the light‐induced partial water oxidation. © 2017 The American Ceramic Society
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    Photocatalytic properties of Ta-doped TiO2
    (Springer Nature, 2017-06-10) Alim, MA; Bak, T; Atanacio, AJ; Ionescu, M; Kennedy, BJ; Price, WS; Du Plessis, J; Pourmahdavi, M; Zhou, MF; Torres, AM; Nowotny, J
    This work reports the effect of tantalum (0.1–1 at.% Ta) on the photocatalytic performance of TiO2 annealed at 1373 and 1673 K in air. It was shown that addition of tantalum resulted in an increase of photocatalytic activity of TiO2 for the specimens annealed at 1373 K. However, the activity of the Ta-doped TiO2 specimens annealed at 1673 K was reduced. The effect of tantalum on the photocatalytic performance at 1373 K was rationalised in terms of an increased concentration of titanium vacancies acting as the active surface sites, and increased charge transport. In this work, it was also shown that the band gap reduction due to tantalum incorporation had little effect on photocatalytic performance. The effect of annealing at 1673 K on photocatalytic activity was explained in terms of reduced surface segregation of tantalum. © 2017 Springer Nature Switzerland AG.