Browsing by Author "Libor, Zsuzsanna"

Now showing 1 - 6 of 6
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    Chemical synthesis of nanoparticles and electrohydrodynamic manipulation of nanoparticulate suspensions
    (Cranfield University, 2009-09) Libor, Zsuzsanna; Wilson, Stephen A.; Zhang, Qi
    This research concerns the study of nanoparticle synthesis methods and the influence that nanoparticles can have on the physical and electrical properties of non-polar fluids. In this study it is demonstrated that a very small volume fraction of nanoparticles can have a very large effect on the macroscopic properties of fluids. Characterization of nanoparticles and nanofluids has led to the creation of new techniques for controlled deployment of nanoparticles within larger structures. A new dielectrophoretic technique can be used for (1) uniformly sized droplet generation and manipulation with controllable droplet size, (2) oil-in-water emulsion creation in unique way, (3) recycling nanoparticles from nanoparticulate suspensions and (4) creation of core-shell structures. Different types, sizes and morphologies of nanoparticles have been made successfully by chemical synthesis and new synthesis routes have been created. A new wet chemical route has been devised to synthesise nickel nanoparticles with controllable size and different morphology including new shapes such as micro-flower and nano-stars. PZT nanoparticles have been synthesized hydrothermally with controllable size and new morphologies created such as nearly spherical nanoparticles and pellets. A novel wet chemical synthesis method was developed to produce core-shell structures of Ni- and also Fe3O4 - coated SiO2, BT, and PZT particles. The characterization of non-polar fluid-based nanofluids included a sedimentation study, studies of the fluidic properties (viscosity and surface tension) and electrical properties such as DC conductivity and dielectric permittivity. The results clearly show that the macroscopic properties of base fluids (silicone oil and perfluorinated oil) were changed even with a very low concentration (< 0.6 vol %) of nanoparticles added. The properties of nanofluids are found to depend on the properties of the base fluid and also on the properties of the dispersed nanoparticles. Importantly, the properties are demonstrated to depend on the fluid-particle interaction.
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    DBT degradation enhancement by decorating Rhodococcus erythropolis IGST8 with magnetic Fe3O4 nanoparticles
    (Wiley-Blackwell, 2009-04) Ansari, Farahnaz; Grigoriev, P.; Libor, Zsuzsanna; Tothill, Ibtisam E.; Ramsden, Jeremy J.
    Biodesulfurization (BDS) of dibenzothiophene (DBT) was carried out by Rhodococcus erythropolis IGST8 decorated with magnetic Fe3O4 nanoparticles, synthesized in-house by a chemical method, with an average size of 45-50 nm, in order to facilitate the post-reaction separation of the bacteria from the reaction mixture. Scanning electron microscopy (SEM) showed that the magnetic nanoparticles substantially coated the surfaces of the bacteria. It was found that the decorated cells had a 56% higher DBT desulfurization activity in basic salt medium (BSM) compared to the nondecorated cells. We propose that this is due to permeabilization of the bacterial membrane, facilitating the entry and exit of reactant and product, respectively. Model experiments with black lipid membranes (BLM) demonstrated that the nanoparticles indeed enhance membrane permeability.
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    Enhanced DC conductivity of low volume-fraction nano-particulate suspensions in silicone and perfluorinated oils.
    (Iop Publishing Ltd, 2009-03-01T00:00:00Z) Wilson, Stephen A.; Libor, Zsuzsanna; Skordos, Alexandros A.; Zhang, Qi
    The contrasting DC conductivities of several different types of nanoparticles (nickel, barium titanate and magnetite) suspended in both silicone and perfluorinated oils have been measured and compared. Enhanced DC conductivity through interaction between the particles and the fluid has been demonstrated even at quite moderate fields and different types of nanoparticles have been shown to exhibit different behavioural trends. Whilst the DC enhancement is partly related to the concentration (or spatial arrangement) of the particles as expected, there is clear evidence that energy-activated (electric-field activated) processes also play a major role. It can be said that effective medium theories based solely on the electrical properties and volume fractions of the component materials have limited applicability when assessing the DC conductivity of these nanoparticle-fluid combinations at low volume fractions.
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    Nanocoatings on micro- or nano-particles
    (Maney Publishing, 2009-11) Libor, Zsuzsanna; Zhang, Qi; Israel, C.; Mathur, N. D.
    In recent years, coating processes with nanoparticles have been investigated for the development of nanostructured materials. In this work we report the core-shell structures of micro-composites of SiO2/Ni, SiO2/Fe3O4, and nano-composites of BaTiO3/Fe3O4 and PZT/Fe3O4. These composites were prepared by an aqueous chemical synthesis method and characterised by scanning electron microscopy (SEM), X-ray diffraction (XRD), Energy Dispersive X-Ray (EDX) analysis and Vibrating Sample Magnetometry (VSM) before and after incorporation into the core-shell structure. The composite core-shell structures were formed by the control of the surface charges of particles in aqueous solutions. A specific composite (SiO2/Ni, SiO2/Fe3O4 and BaTiO3/Fe3O4 and PZT/Fe3O4 nano-composites) can be produced by controlling the pH and the molar ratio of components. These magnetic composites can be potentially applied in wide range of fields such as micro-reactors, delivery vehicle systems, drug delivery systems and multiferroics.
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    Rheological properties of magnetic and electro-active nanoparticles in non-polar liquids
    (Springer Science Business Media, 2011-08-31T00:00:00Z) Libor, Zsuzsanna; Wilson, Stephen A.; Zhang, Qi
    The rheological properties of two non-polar liquids [silicone oil or perfluorinated oil (FC70)] containing various types of particles, barium titanate, nickel and iron oxide, were investigated as functions of solid loading, particle size and shear rate. All the particles were synthesised in- house. The viscosities of either silicone oil or FC70 containing different solid loadings (10, 20 and 30 g/L) were measured over the shear rate range of 0.10-10 s(-1). All the nanofluids showed shear-thinning behaviour within this range and the viscosities increased with the increase of concentrations of nanoparticle and with the decrease of particle size. The highest increase of viscosity was found to be caused by nickel particles in silicone oil due to the formation of Ni network.
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    The synthesis of nickel nanoparticles with controlled morphology and SiO2/Ni core-shell structures
    (Elsevier Science B.V., Amsterdam., 2009-04-30T00:00:00Z) Libor, Zsuzsanna; Zhang, Qi
    The magnetic nanopowders can be potentially applied in wide range of fields such as magnetic storage, magnetic fluid, medical diagnosis, conducting paints, rechargeable batteries, optoelectronics, magnetic recording media, drug delivery system and catalysis. They have attracted interest in the past decade and have also been studied extensively because of their size- and shape-dependent physical-chemical and magnetic properties for applications in various useful technologies. In this work, we present our experimental results on the preparation of nanosized Ni nanoparticles with different shapes by using a wet chemical solution route. Ni nanoparticles were prepared by reducing a Ni-complex formed between nickel-acetate and hydrazine solution under basic condition. Then through the control of reaction temperature and ageing time, nanosized Ni particles with different morphologies could be formed. The morphology and sizes of synthesised nanostructures were studied by scanning electron microscopy (SEM). Structural properties of nanoparticles were examined by X-ray diffraction. We also report the core-shell structures of micro-composites of silica-nickel (SiO2/Ni). The composite core-shell structures were formed by the control of the surface charges of particles in aqueous solutions. A specific composite (SiO2/Ni) can be produced by controlling the surface charge, the pH and the molar ratio of the components. Core-shell structures are stable at room temperature.