This research reveals a catalyst development towards achieving catalysts with hierarchical porous structures with enhanced mechanical properties by using nano-structured macro-porous PolyHIPE polymer. This work can be divided into two parts: the fabrication and its characterisation of hierarchical metal structure using PHP and other fibre materials; and the fabrication and characterisation of PHP with silica particles and glass wool, further coated with silane material as templates. A catalyst system was successfully fabricated forming a 3D-interconnecting network of pore size, ranging from tens of micrometers and gradually reducing finally to nanometer scale. An electroless deposition flow through method using Ni-B bath solution was performed on the templates and was subsequently heat treated to obtain porous metallic structures, thus providing accessibility for reactants to the surface and for products away from the surface. Meanwhile, silanated templates were produced by surface treatment. This was performed by submerging templates directly into the silanes solution at room temperature (24°C) using a water-ethanol based solution of the silanes. The polymer-metal/alloy or silica functionalized based composite demonstrated a high impact strength. The results showed that not only hierarchical pore structure was formed, but it was also demonstrated that silica particles were totally and uniformly covered/coated by metal deposit and had good adhesion. When used on glass wool, silanation had greatly improved the bond strengths of metal deposits to the templates. SEM micrographs revealed that the formation of cracks were tremendously reduced and exhibited higher bond strengths due to silanated glass surface. It is expected to be more efficient and robust in the case of an enhanced surface area, and most desirable in catalyst applications.

Over the past decade, nanomaterials have been the subject of enormous interest. Notable for their extremely small feature size, they have the potential for wide-ranging industrial applications. Using such materials combined with epoxy resin to synthesise nanocomposite is proposed to enhance the corrosion protection performance of the resin.

This work focuses on the conditions under which multiple carbon nano-fibres (CNFs) can be grown radially on a single metal catalyst, known as carbon nano-octopi (CNO) structures, and expands on the evaluation for this type of growth in order to produce large surface areas at the low temperatures that are compatible with large area electronic processing. It was found that the CNF growth was promoted by the use of an adhesive tape initially utilised to fasten a carbon cloth coated with a nickel catalyst onto a silicon support. Compositional characterisation of the catalyst using electron energy loss spectroscopy (EELS), revealed copper in the bulk of the nickel catalyst and in some surface locations near the catalyst edges. An investigation of the growth mechanism was necessmy to increase the CNO yield and produce homogeneous large-area growth, and was I facilitated by the control and reduction of the number of experimental parameters in the growth runs. It was observed that CNO growth can occur under a range of temperatures and copper to nickel ratios, however, the growth resulted in a single CNF per catalyst in the absence of the polymer, the copper metal and/or in the case of a large copper to nickel ratio on the catalyst surface. Growth would not occur at all in the absence of acetylene. It was concluded that both the copper and the polymer of the adhesive played a role in the growth mechanism of the CNOs: the polymer enabled catalyst faceting, allowing for multiple carbon leg fonnation, and the active nickel regions on the surface of the cupro-nickel catalyst served to separate the growing carbon legs. Maximising the specific yield and surface area of carbon nanostructures can help to improve the efficiency of a range of devices. CNO forests with higher yields and higher specific surface areas were achieved by optimising growth parameters such as temperature, catalyst annealing time and catalyst thickness. It was found that the radial growth of thinner, longer, more numerous legged CNOs is promoted by the choice of the size of the catalysts on which they are grown. It was also found that the diameter and length of the nanofibres depend on the catalyst diameter which can be tuned by controlling the annealing time of the catalyst. The sUlface area that can be obtained from the octopus geometry was optimised at a critical catalyst size of 125 mn through growth of a large number of octopus legs. Carbon films consisting of CNOs resulted in relatively low electrical resistivity, highlighting the possibility of their use as high surface area electrical contacts.

This thesis focuses on the hydrothermal synthesis of different ZnO nanostructures where rational control over their morphology allows for the optimization of the · different morphologies for a range of sensing applications. ZnO nanostructures with different dimensionalities have been synthesized through low temperature hydrothermal techniques. One dimensional ZnO NW s have been synthesized with and without the assistance of a seed layer, with a higher degree of control over their structure, morphology, density and dimensions. The large scale production of two dimensional ZnO nanodisks with a high fi.-action of exposed polar mcets have also been produced through using zinc counter ions with preferential capping capabilities on defined mcets. Furthermore, using a multistage hydrothermal synthesis, a range of three dimensional hierarchical ZnO nanostructures grown from initial mono-morphological ZnO nanostlUctmes/seeds has been reported. The growth parameters, such as the nutlient concentration, quantity of polyethylenirnine, growth time, and zinc counter ions have had a substantial impact on the morphological properties of the grown structures.

This thesis is concerned with the synthesis of 1 D nanomaterials via a template-assisted route. Porous anodic aluminium oxide templates prepared electrochemically have been utilised with two intrinsically different deposition techniques, sol-gel and high power pulsed magnetron sputtering (HPPMS), to obtain ID metal and metal oxide nanowires and nanotubes. The resultant morphologies and crystal structures were examined via SEM, XPS, XRD, TEM and EELS. A number of porous template alumina structures have been grown via the anodisation of pure and sputtered aluminium. The effects of surface pre-treatments, etching treatments and anodisation conditions on the resultant morphologies were investigated. It has been found that pore growth is largely dependent on the surface roughness of the substrate as well as the anodisation conditions. The anodisation duration is critical in promoting and allowing self-ordering. Obtained templates, varied in thickness from a few hundred run to several tens of pu-m, with an average pore diameter of 70 nm, interpore distance of 100 nm and pore density of 4 x 1010 cm2. . The implementation of HPPMS led to the successful deposition of Ti inside the alumina template to depths of around 45-50 run. It was found that templates with highly parallel pores on a rigid substrate such as Si, are more suited if this deposition method is to be used. Control of the pressure and substrate biasing is critical in avoiding 'pinch-off and 'bridging' and leading to complete pore filling. The results have shown that HPPMS is a promising plasma technology for the synthesis of nanomaterials such as nanodots, nanopillars or nanowires, when used with porous alumina templates under appropriate conditions. The use of sol-gel deposition has led to the growth of a number of interesting materials and structures. Nanocrystalline Ce02 and Ce1-xZrx02 and Ce1-xSmx02 thin films and powders have been successfully obtained exhibiting novel micro- and nano-structures, likely to find useful applications in catalysis and gas sensing due to their redox properties and large surface to volume ratio. FUlihermore, the treatment of porous alumina templates via a sol-gel/hydrothermal method led to the formation of Ce-doped y-Ah03 nanowires. Hence, a simple, direct and cost effective method for producing large scale Ah03 (and doped Ah03) nanowires is repotied. Moreover, by annealing at temperatures above 600 DC, nanowires of different crystallographic forms such as 0-, e- and a-Ah03 can also be readily obtained. As the dopant Ce was successfully introduced through this method a wide range of doped-Ah03 nanowires (by other rare eatihs such as Y, La, Gd, Srn), at various concentrations (e.g. 1,3,5 at. %) can be readily obtained.

No description available.

In this Thesis I have studied the mechanisms of photo-induced processes at surfaces of nano-crystalline oxides, such as MgO and CaO. To model the photon-induced processes in MgO and CaO nano-particles, I have employed an embedded cluster approach, which combines a quantum-mechanical treatment of a site of interest with a self-consistent classical description of the remaining part of the system. The main results of this work can be summarised as follows: 1) G-tensor, absorption spectra, and formation energies of excitons, electron and hole in MgO and CaO surfaces are calculated and compared with experimental results. It is demonstrated that low coordinated sites such as corner sites are active centre for selective absorption and emission of light with sub bulk band gap energy. By calculating adiabatic energy surfaces for the ground and several excited states, mechanisms of photo induced process in corner sites are proposed. In particular, theoretical estimates of absorption spectra and luminescence energy for these sites are provided for the first time. Results are in good agreement with experiments. Adsorption of CI and F ion by MgO corners and terrace has been also studied. Results indicate that CI and F have shown similar behaviour, trapping an electron and producing an hole centre in the neighbour O ion on the MgO surface. Absorption spect5ra and g tensor estimates have been provided for experimental comparisons. 2) Recent experimental data clearly demonstrate that using both femto- and nano-second laser pulses with photon energies tuned to excite particular surface features at the MgO and CaO nano-cluster surfaces, one can achieve a very effective desorption of hyper-thermal atomic O and Mg species. Two main mechanisms are suggested: the double excitation process and trapping hole or electron and subsequent excitation. From the precursor excitation, trapped electron, or hole in corner ions, a further excitation can neutralize the charge of ion terminated corner and lead to desorption of atom. The adiabatic potential energy surfaces for this excited state is such that atom prefers to leave the surfaces with the maximum kinetic energy of several tenths on an eV. The surface site relaxes with the formation of an F+ or V- centre at the corner site previously occupied by the desorbed atom. Results are in good agreement with the experimental photon energies and kinetic energies of desorbed species. 3) Photo induced desorption processes can be iterated from the formed corner vacancies (mechanisms of secondary processes of desorption). Results of calculations show that subsequent excitations in Mg corner vacancy can lead to further desorption of O atom. To summarise, I have provided mechanisms that can explain both production of electron hole centres and photo induced desorption of species. Estimates of hyperthermal kinetic energy of desorbed species have been given.

Layered double hydroxides (LDHs) have generated a large amount of interest in recent years due to their ability to intercalate a multitude of anionic species. Atomistic simulation techniques such as molecular dynamics have provided considerable insight into the behaviour of these materials. The advent of supercomputing grids allows us to explore larger scale models with considerable ease. In this thesis we present our findings from large scale molecular dynamics simulations of Mg_2AI-LDHs intercalated with either chloride ions or a mixture of DNA and chloride ions. The system exhibits emergent properties, which are suppressed in smaller scale simulations. Undulatory modes are caused by the collective thermal motion of atoms in the LDH layers. Thermal undulations provide information about the materials properties of the system. In this way, we obtain values for elastic properties of the system including the bending modulus, Young's moduli and Poisson's ratios. The intercalation of DNA into LDHs has various applications, including drug delivery for gene therapy and origins of life studies. The nanoscale dimensions of the interlayer region make the exact conformation of the intercalated DNA difficult to elucidate experimentally. We use molecular dynamics techniques to perform simulations of double stranded, linear and plasmid DNA up to 480 base pairs in length intercalated within LDHs. Currently only limited experimental data has been reported for these systems. Our models are found to be in agreement with experimental observations, according to which hydration is a crucial factor in determining the structural stability of DNA. Phosphate backbone groups are found to align with aluminium lattice positions. At elevated temperatures and pressures, relevant to origins of life studies which maintain that the earliest life forms originated around deep ocean hydrothermal vents, the structural stability of LDH-intercalated DNA is substantially enhanced as compared to DNA in bulk water. We also discuss how the materials properties of the LDH are modified due to DNA intercalation. Recent experimental studies of LDHs have shown that these minerals can form staged intermediate structures during intercalation. However, the mechanism which produces staged structures remains undetermined. Our studies show that LDHs are flexible enough to deform around bulky intercalants such as DNA. The flexibility of layered materials has been shown to affect the pathway by which staging occurs. Even though the structures under study are all energetically very similar, overall there is greater diffusion of DNA strands in a Daumas-Hérold configuration compared to a Rüdorff model and a stage-1 structure.

No description available.

No description available.