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Abstract: Nuclear fusion power is the promise of clean energy generation to meet the demands of the new century. However, containing a plasma with a core temperature ten times hotter than that of the sun is no easy task. The confinement vessel must be constructed from resilient materials that can withstand both the heat and the bombardment of the plasma species. ITER is the first proof-of-concept reactor in constructed. This thesis aims to assist in ITER's goals of understanding the complex fundamental plasma-material interactions and developing materials resilient to the harsh reactor conditions in the global push for nuclear fusion energy. The first goal of the thesis aims to investigate the thermodynamic properties of helium (He) bubbles to contribute to the existing understanding and models of He PMI expected in ITER. Bulk W samples were exposed to a low-energy (25 eV) He plasma at 573 K (LT) and 1050 K (HT). After plasma exposure, these samples were subject to TDS, ERDA, SEM, and in-situ TEM annealing. Structures comprised of a network of bubbles were stable up to 998 K during in-situ TEM annealing of the LT sample. He desorption from the LT sample was inferred to stem from interstitial He rather than these bubbles. Bubbles in the HT sample were found to be thermally active up to 998 K, resulting in an increase in the average bubble size and a loss of number density. GISAXS analysis on the effects of annealing on bubble radius distribution produces results consistent with the TEM. An "Ostwald ripening-like" model was proposed to explain the differences in annealing behaviours of the LT and HT samples. In-situ TEM annealing of a HT bulk W sample at 1073 K showed a reconfiguration of lattice atoms to reduce the surface area of large voids left behind after plasma exposure. It is suggested that lattice effects also contribute to the formation of fuzz and require more investigation. The results provided a deeper understanding of the bubble formation mechanism and subsequent thermodynamics based on the plasma exposure temperature. The differences in behaviour observed from these experiments can be used to help explain temperature-dependent effects such as recrystallisation suppression and form a wide set of consistent experiments for computational models to be compared to. The second goal of the thesis is to characterise the He-PMI of three alloys for possible use as a divertor material in future fusion reactors. Four sputter-deposited materials: sputtered pure W (WS), W-5%(wt)Ta, W-3%(wt)Cr, and W-5%(wt)Ta-3%(wt)Cr were exposed to 25 eV He plasma at LT and HT. After plasma exposure, these materials were subject to TDS, ERDA, SEM and TEM. The addition of Ta to Ws and WCr has been shown to inhibit the formation of He bubbles. This may be a case of increasing the fluence threshold for fuzz rather than the complete prevention of fuzz. Additionally, the addition of Ta slows grain growth of both Ws and WCr. This property is intrinsic to Ta rather than from an emergent W-Ta interaction and could potentially be used to delay the undesired but inevitable onset of recrystallisation. The electrical resistivities of the four sputtered films were measured as a surrogate for its thermal conductivity to characterise how this property changes with alloying and He exposure. The alloying of Ta significantly increases the resistivity of W, much more than that of Cr. As expected, He plasma exposure degrades the resistivity regardless of the material. WTaCr has the largest electrical resistivity and suffers the largest increase after He plasma exposure likely due to the presence of both alloying impurities deforming the lattice and serving as trapping sites. Both effects increase probability of electron scattering. The reduction in thermal conductivity from both alloying and He plasma irradiation, especially for alloys with more elements, will have to be considered alongside its other benefits when determining its viability for fusion reactors.

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Abstract: A polysiloxane with tris-alkoxy-ended rod-like mesogenic side groups forms an unusually low-symmetry antiferrochiral liquid crystal, space group P1̅, consisting of distorted left- and right-handed double-helices containing alternating splay and twist sections. The unit cell contains two double-helical columns. On faster cooling, a closely related metastable orthorhombic structure is formed, symmetry Fddd, with 8 double helices per cell.

Open Access

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Abstract: Gyroid, double diamond and the body-centred “Plumber’s nightmare” are the three most common bicontinuous cubic phases in lyotropic liquid crystals and block copolymers. While the first two are also present in solvent-free thermotropics, the latter had never been found. Containing six-fold junctions, it was unlikely to form in the more common phases with rod-like cores normal to the network columns, where a maximum of four branches can join at a junction. The solution has therefore been sought in side-branched mesogens that lie in axial bundles joined at their ends by flexible “hinges”. But for the tightly packed double framework, geometric models predicted that the side-chains should be very short. The true Plumber’s nightmare reported here, using fluorescent dithienofluorenone rod-like mesogen, has been achieved with, indeed, no side chains at all, but with 6 flexible end-chains. Such molecules normally form columnar phases, but the key to converting a complex helical column–forming mesogen into a framework-forming one was the addition of just one methyl group to each pendant chain. A geometry-based explanation is given.

Open Access

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Abstract: The process of electrochemically assisted surfactant assembly was followed in real time by grazing incidence small angle X-ray scattering with the aim to deconvolute the formation of mesoporous silica film and unwanted porous particles. The X-ray technique proved to be useful for the characterisation of this process, as it takes place at a very dynamic, solid/liquid interface. This paper shows the electrochemically driven onset and evolution of silica/surfactant structures. Additional control experiments indicate the formation of vertically aligned structures without the use of an electric field, although it seems to be beneficial increased pore ordering.

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Abstract: The overall focus of this thesis is investigations into the preferential locations of biomolecules, including membrane proteins, in orientated self-assembled lipid nanostructured materials known as QII phases. The three QII phases, known as the QII G, QII D and QII P , consist of 3 dimensional periodic self-assembled surfaces over which a lipid bilayer is draped. The lipid bilayer in each QII phase consists of regions of flat or high curvature into which it has been hypothesised that guest biomolecules will preferentially partition. Research efforts focus on orientated QII phase domains as more information can be extracted from characteristic Small Angle Scattering (SAS) experiments than from polydomain samples. Different lipid mesophases including the QII phases, were prepared as orientated lipid films and an automated method of 2D Small Angle X-ray Scattering (SAXS) analysis for orientated samples was created. The addition of biomolecules to a QII phase was achieved by co-dissolving with the lipids in an organic solvent before formation of the orientated QII phase, or by addition to an already formed QII phase. Both methods are presented here and the incorporation of various biomolecules into a QII D phase bilayer was monitored in two separate fashions, via SAXS and Raman Spectroscopy. Finally, the addition of biomolecules to orientated QII phases was undertaken and any preferential partitioning into flat or highly curved regions of the bilayer was investigated. It was found via Grazing Incidence Small Angle Neutron Scattering (GISANS) that monopalmitin and cholesterol in a monoolein QII D phase, preferentially partition into the flatter regions of the bilayer. At several instances during my research, variable humidity control was required. Lipid films require particular humidity to maintain specific phase behaviour and for the neutron experiments, the host lipid was contrast matched to a D2O environment. To meet this requirement, two separate humidity control systems were designed and created: the first a low cost, portable, and chamber independent system, the second a fully automated system calibrated to a chamber at Diamond Light Source. A separate study into the relaxed curvature of four lipids, monoolein, monolinolein, phytantriol, and phytantetrol using inverse micelles is also detailed. The relaxed curvature was obtained by calculating the parameters of the neutral surface, or the surface whose area does not change due to bending within a lipid monolayer.