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Publication - Dr Rachael Miles

    Effect of crystallization kinetics on the properties of spray dried microparticles


    Baldelli, A, Power, RM, Miles, REH, Reid, JP & Vehring, R, 2016, ‘Effect of crystallization kinetics on the properties of spray dried microparticles’. Aerosol Science and Technology, vol 50., pp. 693-704


    A droplet chain technique was used to study the influence of the
    crystallization process on the morphology of spray dried microparticles.
    A piezoceramic dispenser produced a chain of monodisperse solution
    droplets with an initial diameter in the range of 60–80 µm. Aqueous
    solutions of sodium nitrate were prepared in concentrations ranging from
    5 mg/ml to 5⋅10−5 mg/ml. The solution droplets were injected
    into a laminar flow with gas temperatures varying from 25 to 150°C,
    affecting the droplet temperature and the evaporation rate, accordingly.
    Dried particles with diameters between 0.3 and 18 µm were collected.
    The properties of the collected microparticles were studied and
    correlated with a particle formation model which predicted the onset of
    saturation and crystallization. The model accounted for the dependence
    of the diffusion coefficient of sodium nitrate in water on droplet
    viscosity. The viscosity trend for sodium nitrate solutions was
    determined by studying the relaxation time observed during coalescence
    of two aqueous sodium nitrate droplets levitated in optical tweezers.
    The combination of theoretical derivations and experimental results
    showed that longer time available for crystallization correlates with
    larger crystal size and higher degrees of crystallinity in the final

    Full details in the University publications repository