The ignition of flowing gases by a hot surface is considered briefly in relation to the potentially hazardous environments associated with supersonic aircraft. A theoretical model is proposed as a basis for investigating pre—ignition conditions in the neighbourhood of a heated surface exposed to a combustible gas stream. By assuming a series of quasi—steady states prior to ignition onset, critical heat release rates are determined, which, it is suggested, may be used to establish safe conditions for any system in which the distributions of temperature and velocity are specified. The development of suitable experimental systems is described, along with the application of various optical methods to the study of conditions preceding ignition in the systems concerned. Interferometry is found to be ideally suited for this purpose, under the experimental conditions considered, and a detailed account is given of the relevant optics and analysis involved. A discussion of the results obtained from a thermal analysis for an ethylene—air mixture includes the deduction of potentially useful kinetic data. It is concluded that the method described in this research could be profitably extended and suggestions are given for developing the present work further.

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No description available.

No description available.

No description available.

X-ray Photoelectron Spectroscopy (XPS) has been used to probe the influence of cation structure on fundamental interactions within Ionic Liquid (IL) systems. A series of tetraalkylammonium-based ILs and their phosphonium analogues have been investigated. A robust C 1s peak fitting model has been developed and described for the tetraalkylphosphonium and tetraalkylammonium families of ionic liquid, with comparisons made between the two series. Cation-anion interactions have been investigated to determine the impact of changing the cationic core from nitrogen to phosphorus on the electronic environment of the anion. Comparisons between long and short chain cationic systems, and the effect of cation conformational restriction, are also described. Additionally, a high-energy Ag Lα’ X-ray source has been utilised to probe the structure of the IL/vacuum interface using Energy-resolved XPS (ERXPS) for tetraalkylammonium- and tetraalkylphosphonium-based ILs, with comparison made to data obtained with Angle-resolved XPS (ARXPS) experiments using a standard Al Kα X-ray source. The capability of the Ag Lα’ source for IL analysis is confirmed, alongside the characterisation of previously undetected high energy core level photoelectron emissions. The effect of cation functionalisation is also studied by XPS, with a view to establish fine-tuning of charge transfer from anion to cation using electron-withdrawing substituents embedded within the alkyl side chain of the cation. Binding energy analysis indicated cation functionalisation had minimal influence on the electronic environment of the ionic head groups with respect to the non-functionalised analogues. The performance of ILs, with respect to cation functionalisation, as solvents in the Suzuki reaction is also reported in this Thesis, whereby evidence is provided for changing the nature of catalysis via cation functionalisation.

This thesis presents work undertaken in the design, build, characterisation and first results of a new instrument for the optical characterisation of wide band gap materials by their luminescence. Optical spectroscopy is a promising method for investigating material properties due to its non-destructive nature and high sensitivity. The ability to relate to a material's optical properties to its structure and composition is highly desirable in Materials Physics applications. Spatial information is lost when measuring heterogeneous samples due to the convolution of spectral information from different regions within the sample. Though the combination of imaging and spectroscopy spatially resolved data can be a. In this work the spectro-radiometrically calibrated instrument HeLIOS (Hyperspectral Imaging for Optical Spectroscopy) is introduced. This instrument has allowed the collection of spatially resolved radiometrically calibrated photoluminescence investigations on a number of wide band gap materials.

This thesis is initially concerned with the determination of trace amounts of a number of metals in aluminium salts, Various continuous sources are then examined and finally multi-element electrodeless discharge tubes are investigated as excitation sources in atomic-fluorescence spectroscopy. The determination of trace amounts of calcium and magnesium in solutions containing large concentrations of aluminium salts may be accomplished by co-precipitating their hydroxides on iron(III) hydroxide, dissolving the precipitate, and extracting the 8-hydroxyquinolates of calcium and magnesium into methyl isobutyl ketone at about pH 110 The extract may be sprayed into the air-propane flame and atomic-absorption measurements made. Iron and nickel may be co-precipitated on hydrated manganese(IV) oxide and their 8-hydroxyquinolates extracted at pH 4.5. Chromium may be extracted directly into methyl isobutyl ketone. A number of continuous sources are investigated and compared with line sources for the atomic-absorption of silver. 3 The atomic-fluorescence of selenium, tellurium, bismuth and mercury; cadmium and zinc; and indium and gallium is examined using multi-element electrodeless discharge tubes of these metals.

The utilisation of the area enclosed between the absorbance spectrum of a substance and the zero absorbance line, and between two fixed wavelength limits, as a calibration measurement for spectroscopic techniques has been investigated, with special reference to solution absorption spectrophotometry, and is shown to be comparable with the conventional measurement technique which utilises a narrow band. A spectrophotometric method for the determination of microgram amounts of Tantalum utilising ternary complexation with hydrofluoric acid and a dyestuff, Victoria Blue B, is presented. The method has a molar absorptivity of 83,000 at 635 mγ and is used to determine Tantalum in a series of synthetic samples with Tantalum content in the range 0.4 to 1.6 γg/ml. A similar ternary system for the estimation of gold is also investigated. The development of a differential spectrophotometric technique for the estimation of Magnesium in the 200 ppm. concentration range is presented, and an investigation has been carried out into the possibility of developing differential atomic absorption spectrophotometry methods parallel in nature to differential solution spectrophotometry methods; this possibility is shown to be completely practical. A method for the estimation of Caesium has been developed in which an inorganic complex, ammonium rhodanilate, NH4Cr(NCS)4 (H2NC6H5), is used as a reagent for the extraction of Caesium in the presence of other alkali metals. In the final chapter the work presented in this thesis is summarised and some suggestions are offered as to the channels into which future research efforts might be fruitfully directed.

An examination was made of the recently described Bromo-pyrogallol red (BPR) method for determination of niobium in aqueous solution (εPH6/610mγ = 60,000). This approach was made to examine the efficiency of the method in general and its amine-containing amyl acetate extraction system in particular (εpH6/610 mγ = 21,000). Experiments were also conducted to enhance the sensitivity and selectivity of the method. In aqueous medium, the Nb-BPR colour complex was stabilised and considerably enhanced in intensity by the presence of gelatin. As a result of the present study, 1,10-phenanthroline was found capable of producing the same effect as gelatin. In this case, 20 mg of Fe (III) interfered extensively in the determination of 9 ɲg Nb, using the solvent extraction procedure. This interference.was eliminated completely by achieving a quantitative reduction of Fe(III) to Fe(II) by means of ascorbic acid, since extraction of Fe(II) by high molecular weight amines is reported to be negligible.