The research conducted can be split into three major regions; pigment material, a simulation program called QuadFit and mesoporous oxides. There has also been some extra work conducted on a catalyst for partial hydrogenation of vegetable oils. Various techniques have been used on the different systems including XPS, STEM and 77Se, 17O, 93Nb, 15N, 119Sn, 27Al, 115In and 63,65Cu static and MAS NMR. The pigment materials consist of a series of materials which are grouped under the F-Colours project. The pigments consist of sulphur doped tin niobates, copper indium sulphur selenide doped zinc selenides, sulphur doped tin tungstates and colloidal gold and silver enamels. The sulphur doped tin niobate study shows a conversion from foordite to pyrochlore and also where the sulphur sits in the structure. The copper indium sulphur selenide doped zinc selenide study shows the indium and copper moving into the zinc selenide as copper indium pairs. However, how the pairs sit in the structure remains undetermined. The sulphur doped tin tungstate study shows that the sulphur acts as a promoter for the beta phase rather than the desired alpha phase. The enamels based on gold and silver show that the tin site does not determine the colour of the enamel and the silver-gold association is likely to be the dominant factor. Mesoporous oxides show a link between the amount of mesoporous structure and their temperature stability. The nitrogen spectra of the template in the material shows that in the mesoporous silicate (which has the largest surface area) there is a breakdown of the amine into NH groups which does not appear in the other mesoporous materials. This could lead to a method of increasing the surface area of the other mesoporous oxides. QuadFit has the ability to simulate quadrupolar and CSA interactions with distributions of interactions whilst static and the quadrupolar interaction with distributions under MAS. The program is written in Java so will run on most platforms and also has near perfect stability.

In the past decades, the study of nanotechnology has brought in tremendous progress to the development of polymer electrolyte fuel cells (PEFC) and many advanced catalyst approaches have been developed. However, many of these still remain at ‘test-tube’ level and have not been implemented in practical fuel cells. The concerns about the gap between the pure material research and fuel cells are increasing, and a study focusing on the electrode structures is required to help address this issue. In this thesis, the in-situ growing process of one-dimensional (1D) Pt-based nanostructures on gas diffusion layers (GDLs) was systematically studied to help understand the structure-property relationship of the gas diffusion electrodes (GDEs). The crystal nucleation and growth, coupled with the distribution of the produced nanostructures were investigated based on the corresponding GDE performance in PEFCs. The influence of the in-situ growing temperature, the hybridizing Pd metal and the structures of the GDL itself were comprehensively investigated for a further understanding of the in-situ nanowire growing process. This work demonstrates that besides the intrinsic catalytic activities of the catalysts themselves, their optimal implementation in electrodes, i.e. the electrode structure, play an important role in the power performance of PEFCs than we initially expected.

Abrasion of polymer surface films or coatings in an everyday occurrence, whether in the home, work or industry. As a result a wide variety of polymer films can be found on surfaces. Despite the numerous applications, three body thin film abrasion appears a niche area of study and as a result under-researched. This investigation focuses on identifying, characterising and quantifying the abrasive wear of a baked dehydrated castor oil deposit formed on stainless steel. The primary aim of this project is to understand how the fundamental properties of the liquid abrasive cleaning system contribute to the material removal. Investigations have primarily been carried out using a reciprocating linear tribometer for the cleaning and a profilometer to measure the wear. The wear of the baked oil film was found to largely follow the established Archard wear equation of sliding distance and load, despite the fact it was derived to describe two body and not three body wear. However the wear rate was not inversely proportional to hardness and there were significant effects when parameters not in the Archard equation are considered. IN particular changing the speed, viscosity, particle size and distribution all had an impact on the wear.

In this thesis, a fully Lagrangian approach called the Discrete Multi-Physics is adopted and applied to biomechanics. The Discrete Multi-Physics combines the Smoothed Particle Hydrodynamics, the Mass and Spring Model and the Discrete Element Method in a common particle-based framework. In the Discrete Multi-Physics, high deformations and contact of solid structures (e.g. valve’s leaflets during closing phase or colloid contact) can be easily modelled. In biological valve simulations, for instance, we were able to account for repeated opening-closing cycles and to introduce an agglomeration algorithm to model clotting. Besides cardiovascular and venous flows, we also applied the Discrete Multi-Physics to respiratory tracts for modelling (i) cilia motion and drug diffusion in the periciliary layer (ciliated epithelium) and (ii) the release of active ingredients in powder inhalers for drug delivery in the lungs.

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No description available.

This thesis describes investigations into the design and evaluation of novel ultrasonic methods for 3-dimensional ionising radiation dose verification. Pulse-echo ultrasound methods were investigated for the measurement and analysis of complex radiation therapy dose delivery. The physical properties of MAGIC (Methacrylic and Ascorbic acid in Gelatin Initiated by Copper) polymer gel dosimeters have been characterized. The variations of speed of sound, ultrasonic attenuation coefficient and density of MAGIC gel with radiation dose and temperature have been quantified. This extends work that has previously been reported for the properties of this gel to the effect of measurement temperature on the results. The facilities to perform these measurements were specified, constructed and evaluated as part of the project. The measurement of radiation dose using ultrasound back scatter from an interface between the polymer gel dosimeter and an inert reflector is demonstrated. To enable the measurement of radiation dose using pulse-echo ultrasound methods a novel inert material has been specified, manufactured and characterised. This material is matched to the acoustic impedance of MAGIC gel to produce the most dose-sensitive reflections. The reflections from the interface between the inert reflector and dose-dependent MAGIC gel have been analysed using both a single element transducer and a commercial ultrasound scanner. Both measurement systems demonstrate the same dose and temperature dependence of the ultrasonic reflection. A methodology has been developed to relate pixel values from the ultrasound scanner to the amplitude of the reflected ultrasound signal. A phantom consisting of an array of threads formed from the inert backscattering material has been designed and constructed and a method of extracting pixel data from images of the array acquired using a commercial ultrasound scanner has been developed, so that multiple imaging positions could be used to perform a 3-dimensional assessment of radiation dose distributions. It has been demonstrated that a pulse-echo technique using a commercial ultrasound scanner shows promise for radiation gel dosimetry. Further investigation and alternative polymer gel and inert reflector combinations may improve these techniques.

This thesis describes a study into the optical properties of nano-structured metallic films. Structures are produced by electrochemically depositing metal through a self-assembled template of polymer micro-spheres. This versatile technique allows nano-structured surface made from almost any metal to be produced quickly and cheaply. Geometries ranging from array of shallow dishes, to sharp metallic spikes and encapsulated spherical cavities can all be produced on the same sample. This thesis presents an in-depth study into the properties delocalised and localised surface plasmon polaritons. These plasmons can be tuned in energy by controlling the sample geometry and angle of the incident light. The coupling between these two types of plasmon is also investigated and theories are put forward to understand the observed results. These findings could prove useful in the design of plasmon guiding and computing devices. With an understanding into the plasmonic properties of the metallic nanostructures, research is undertaken to explore how the associate local electric field couples to molecules adsorbed onto a samples surface. A strong correlation between surface plasmons and enhanced Raman scattering is found, leading the observation of the beaming of the Raman scattered light. The nano-structured substrates are also shown to have excellent reproducibility as well as enhancement of the Raman signals, leading to applications such as high sensitivity molecular sensors. Finally, the interaction between organic semiconductor molecules and surface plasmons is explored. A strong interaction between the different states is found and plasmon enhanced fluorescence is also observed. These studies open the way for greater control over the exciton states, which have potential for the use in novel laser systems.

Nanoparticles are ubiquitous in nature, and the number of technological applications exploiting nano-objects, either synthesized chemically or fabricated lithographically, is in steady rise. In particular, metal nano-objects exhibit resonant modes corresponding to an enhanced coupling to electromagnetic radiation. The interaction of light with a nano-object is wholly described by its cross-sections for absorption and elastic scattering. In this thesis we present a method to measure the absolute amplitude of the cross-sections. Differently from currently available techniques, we account for the finite angular collection of the objective via an analytical model of the scattering process, thereby rendering our method accurate also for objects dominated by scattering and high numerical aperture detection. The model of scattering assumes that the nano-object is placed at a planar dielectric interface, representing the substrate, and a homogeneous optical environment is obtained as a limiting case. The accuracy of the quantitative method was tested on several model systems using two widespread experimental techniques: Micro-spectroscopy and widefield imaging, which are both implemented with a simple experimental set-up, constituted by a commercial microscope equipped with an imaging spectrometer or a camera. In order to quantitatively simulate microscopy experiments, a realistic description of the excitation must be included in numerical models. In this thesis we describe novel modelling practices which reproduce typical coherent or incoherent microscope illumination. Comparison of quantitative experimental and numerical results is used to estimate parameters describing the geometry of a nano-object, such as the diameter or the aspect ratio. In conjunction with the high-throughput capabilities of widefield image analysis, quantitative cross-section measurements and optical characterization of the geometry can provide a thorough statistical appraisal of the dispersity of the structural and optical properties of a sample. Therefore, this thesis represents a significant step towards an ‘all-optical’ characterization of nano-objects, complementing costly and time-consuming electron microscopy techniques.