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In this thesis the theoretical and experimental concentration and temperature dependent band gap narrowing in uncompensated n-type silicon is studied. Electron-electron and electron-impurity interaction energies are used to calculate the theoretical band gap narrowing in the plasmon-pole approximation. These reveal an increase of 14 meV in the band gap narrowing at 300 K for a donor concentration of 3.10(^19) cm(^-3) above the zero temperature value of 95 meV. For higher concentrations the degeneracy deepens and the zero and finite temperature band gap narrowing curves converge. Localized states in the band gap resulting from local fluctuations in the electron-impurity interaction, a result of the random position of the impurities, are also considered. When the analysis includes the effect on the host band of the electron-impurity interactions calculated above the resulting density of states in the band tail of uncompensated silicon is found to be ten times smaller than is usually imagined. Using published values for the minority carrier mobility both the band gap narrowing and the minority carrier lifetime are experimentally determined in the buried n-type layer of an Integrated Injection Logic transistor. The transport factor in the base of a parasitic pnp transistor formed by the p-type substrate, buried layer and p-type Integrated Injection Logic transistors base region is calculated by monitoring the substrate current density and minority carrier injection into the buried layer. A range of temperatures from 200 K to 400 K are used to determine the temperature dependence of the minority carrier mobility in the buried layer (T(^0)). A band gap narrowing of (100 ± 15) meV) and minority carrier lifetime of (30 ± 10) ns are measured for the buried layer (2.4.10(^19) cm(^-3)).

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Studies have been made of the effects of thermo-mechanical treatment variables on the recrystallization of austenite, the transformation of austenite and precipitation strengthening in C-Hn steel containing niobium, niobium plus vanadium, vanadium and vanadium plus nitrogen. The amounts of niobium and vanadium were varied across the stoichiometric ratio of H:C and H:N in order to investigate the effect of stoichiometric ratio on the precipitation strengthening.

Most of the early studies using peroxycarbamates concerned their synthesis, decomposition and use as initiators in vinyl or diene polymerisation. The only attempt to use one as a crosslinking agent was reported in 1960 for a plastic. The author's research work is an attempt to prepare new bisperoxycarbamates and to evaluate them as crosslinking agents in natural rubber (DPNR) and polyisoprene rubber (Cariflex IR 305).

The strength and failure behaviour of nylon 6 reinforced with short E-glass fibres has been studied. The fibres were treated with different sizing compounds in order to modify the interface between the glass and polymer. The principal objective of the work was to assess, by means of mechanical testing and microscopy, the role of the interfacial bond in controlling the properties of these materials. It has been shown that the mechanical behaviour of glass reinforced nylon 6 is controlled mainly by the fibre concentration, length, and orientation and that stiffness enhancement can be adequately predicted by a modified rule of mixtures expression. The behaviour is also strongly influenced by the type of sizing compound employed on the fibres. The results clearly demonstrate the beneficial effects of silane coupling agents. In the 'dry' condition some composites exhibited a 30% strength reduction on omission of the silane, but in others this caused little variation. In the wet state however, silane treatments produced far superior properties in all cases. In addition, the size apparently exerts considerable control over the properties, indirectly, by effecting the fibre dispersion and breakage during compounding and moulding. The failure mechanism as assessed by optical and scanning electron microscopy and by acoustic emission analysis, was shown to be of a dual nature. Failure was initiated by fibre-matrix debonding in the core region of the mouldings, the debonded areas interlinked and became visible on a macroscopic scale as strain bands across the samples. The strain banding phenomenon in turn initiated a catastrophic brittle failure sequence, the resulting fracture surfaces exhibiting the characteristics of both weak and strongly bonded systems.