This dissertation describes magnetization experiments on various superconducting metals and alloys. Primarily, the intent of the research was to measure and explain the effect of the surface sheath on the magnetic properties of bulk material under quasi-ideal conditions. Extensive measurements have been carried out on lead (Pb), tantalum (Ta), dilute lead-bismuth (Pb-Bi) alloys and dilute tantalum- niobium (TaNb) alloys. All the samples were monocrystalline rods with carefully prepared and examined surfaces. Some preliminary results were also obtained on polycrystalline lead-bismuth (PbBi) alloys. Surface condition is crucial to an investigation of the properties of the surface sheath. For example, it has been established that a dense layer of dislocations exists on the surface of "as grown" electron-zone-refined tantalum rods. This produces a high K (short electronic mean free path) skin thicker than the coherence length which must be removed by electropolishing before meaningful (i.e. characteristic of the bulk) measurements can be made. Similar but less-understood effects occur in lead (Pb). The formation of oxide layers on the surface of well-polished lean (Pb) crystals slightly increases the surface nucleation field presumably due to changes in the nature of the electron scattering at the metal/vacuum boundary.

The use of thin film capacitors as a component in microminiaturized electrical circuits has made it necessary to obtain a more complete understanding of the conduction mechanisms occurring in these films. Silicon oxide was chosen as the dielectric material for study and the temperature behaviour of thin film capacitors was investigated in order that films with low temperature ageing and a high stability could be prepared. D.C. and A.C. conduction processes in dielectric films have been examined with particular reference to the amorphous nature of the dielectric materials considered. The theoretical contributions to the temperature coefficient capacitance have been outlined. Apparatus was designed and constructed so that complete metal-dielectric-metal sandwiches could be prepared and measurements performed on them without breaking the vacuum. The effects of deposition conditions and post-deposition heat treatment was investigated and empirical equations were obtained for the reduction in loss and capacitance during the annealing treatment. D.C. results were similar to those obtained by previous workers. A precise interpretation of these results was not possible due to uncertainties in the spatial and energy band structure of the amorphous films. From observation of the decay of the absorption current a low frequency loss peak was predicted. The audio frequency results were influenced by this peak, particularly at high temperatures. Above the audio frequency region both the loss and permittivity were independent of frequency with a very low activation energy (< 0.1 eV) which was probably due to some form of electron hopping conduction. The temperature coefficient of capacitance was found to depend on the loss, particularly for high loss materials. The intrinsic contribution to the temperature coefficient of capacitance was probably due to the temperature dependence of the ionic polarizability.

We introduce the concept of self-assembly and describe how it can explored with a system of colloids. We introduce the lock and key colloid, and describe how it can be useful probe for exploring a specific, geometry-centric, type of colloidal self-assembly called the depletion interaction. We illustrate some of the problems with simulating the lock and key colloid, and intro duce a novel simulation method to side-step many of these problems. Using this simulation technique, and derived theoretical thermodynamic apparatus, we show a methodology for parametrising the depletion drive self-assembly of colloids. This parametrisation allows us to avoid explicitly modelling the nanoparticles that mediate depletion-driven self-assembly and thereby speeds up any subsequent simulations by an order of magnitude compared to the novel simulation technique. Using our parametrisation, we repeat some measurements of explicitly modelled lock and key simulations and find good agreement. As a small aside, we also simulate a sedimenting, lock-only system in the same spirit as a published work. In this work, the authors find an interesting decrystallisation over time from a solid to liquid-like phase. We do not observe this in our experiment but instead note that we can induce a liquid-solid phase transition by varying the depth of the lock mouth. To end, we discuss the quality of our findings and what future avenues of work they may lead to.

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A study of the preparation and fundamental properties of metal oxides is of considerable importance in the technology of the manufacture of refractory materials. One method of obtaining metal oxides, which does not, as yet, appear to have been much utilised in this field, involves the use of the corresponding oxalate as the starting material. An attempt has been made to obtain a better understanding of the preparation, crystal habit, dehydration and thermal decomposition of various metal oxalates, so as to establish what effect, if any, these variables have on the properties of the resultant oxides. The preparation of oxalates has been studied with the object of obtaining a highly-pure material; a purity of 99.999% has been attained. Investigations on the thermal decomposition of oxalates have been carried out by thermogravimetric analysis, and the composition of the end products analysed by X-ray diffraction methods. Earlier work on the thermal decomposition of oxalates has been critically surveyed, and mechanisms are proposed for the decomposition of several metal oxalates. The influence of various factors (e.g., the history of the samples, compacting pressure, sintering atmosphere, lattice imperfections, purity, rate of heating, and the temperature and duration of calcining) on the sinterability of oxide powders has been investigated. Activation energies for densification in pure oxides were calculated from the rates of increase in density. A study of the growth of grains during sintering in very pure oxides has been carried out. Discontinuous grain growth is shown to occur in magnesium oxide, whereas normal grain growth odours in nickel oxide. Sintering in the presence of various additives has been studied. It is definitely established that the addition of only 0.01% of a foreign substance can have a pronounced effect on the sintering characteristics of a material. Reported work regarding sintering in metal oxides has been critically examined, and an attempt is made to correlate the experimental results obtained with those given in the literature.

Thin films of ZnS on NaC1 were grown by evaporation in vacuum. An ultra high vacuum apparatus was developed for film growth under clean conditions. This incorporated a mechanism for cleaving the NaC1 substrates. The influence of the growth conditions on the structure of the films was studied by transmission electron microscopy. Epitaxial films of ZnS with the sphalerite structure and free of included grains were grown reproducibly at substrate temperatures as low as 230°C. when the cleanest growth conditions were used. These films, however, contained defects on fill/ planes, which gave rise to streaks in the transmission electron diffraction patterns. Contamination raised the minimum substrate temperature for epitaxy. The most important single factor in obtaining reproducible epitaxial films was the use of a focused electron beam evaporator. When conventional hot tantalum evaporators were used the films contained 0.2 wt. per cent of tantalum and epitaxial films could not be grown reproducibly. Less perfect films of ZnS contained included grains of the wurtzite structure. Contamination, high deposition rates, and evaporations from a ZnS source with an excess of either Zn or S resulted in the growth of these wurtzite grains. D.G. current-voltage characteristics were obtained from a few films by applying an electric field perpendicular to the growth plane. These characteristics usually exhibited a J ∝ V2 relationship over part of the voltage range.