Thesis (M. Phil.)--University of Hong Kong, 1999. / Includes bibliographical references (leaves 87-94).

Thesis (Ph. D.)--University of Hong Kong, 2000. / Includes bibliographical references (leaves 136-145).

Thesis (M.S.)--Youngstown State University, 2008. / Includes bibliographical references (leaves 66-71). Also available via the World Wide Web in PDF format.

Thesis (M.S.)--University of Missouri-Columbia, 2004. / Typescript. Includes bibliographical references (leaves 65-67). Also available on the Internet.

Thesis (M.S. in environmental engineering)--Washington State University, May 2006. / Includes bibliographical references (p. 12-13).

Thesis (M.S.)--University of Missouri-Columbia, 2004. / Typescript. Includes bibliographical references (leaves 65-67). Also available on the Internet.

[From Introduction]. The thermal decomposition of solids is characterized by the formation and growth of nuclei at sites on the surface of the solid or within the crystal lattice. Such nuclear formation is favoured by disorganisation of the crystal either by mechanical damage, or by the presence of impurities. Disorganisation results in positions which have a high thermodynamic instability. The nuclei are likely to be formed initially at the corners and the edges of the crystal since these are more prone to damage. Careful handling and storage in vacuo often leads to a large reduction in their number, while deliberate scratching of the surface facilitates their production. The number of potential sites for nuclear formation is also increased by pre-irradiation with ultra-violet light, though there are indications that a different type of nucleus may be produced. Nucleation can be facilitated by pre-irradiation with electrons, neutrons, X-rays, gamma-rays and atomic particles. The nature of the nuclei is not always clearly defined, but it is generally accepted that they are composed of solid reaction products e.g. in the decomposition of barium azide and silver oxalate, nuclei of metallic barium and silver, respectively, are formed.

The isothermal, endothermic, stepwise decomposition of ammonium metavanadate (AMV) in inert (argon or nitrogen), oxidising (air or oxygen) and reducing (ammonia) atmospheres as well as under high vacuum (pressure < IOn bar) conditions has been investigated. The reverse reaction, the isothermal recombination of V₂ 0₅ with ammonia and water vapour has also been investigated. The decomposition and recombination reactions were followed by continuously recording the mass loss of the sample with time using a Cahn R.G. Automatic Electrobalance. This enabled small samples ( ~ lOmg) to be used and consequently any self cooling of the sample during the decomposition was minimized. The intermediates and final products formed have been characterized by chemical analysis, X-ray powder diffraction studies, infrared spectroscopy and the mass loss involved in their formation. The changes in the physical properties of the samples during decomposition and recombination have been investigated by surface area measurements (using the BET method and krypton adsorption) and eIectron microscopy. Values for the enthalpy changes involved in the decomposition have been obtained by differential scanning calorimetry. The stoichiometry of the isothermal decomposition of ammonium metavanadate, under the various conditions of surrounding atmosphere has been discussed. Except for the later stages of the decomposition in ammonia, the results correspond well to the gradual reduction of the ratio of "(NH₄)₂ 0" to "V₂0₅" units from the original 1:1 ratio in ammonium metavanadate to pure "V₂0₅" with ammonia and water being evolved throughout the decomposition in the mole ratio of 2:1. The final product of the decomposition in vacuum, argon and air is "V₂0₅" and in ammonia, below 360°, V0₂. The kinetic parameters for each of the stages of the decomposition of AMV in each of the atmospheres studied have been determined. The mechanism of the first stage of the decomposition under the different conditions of surrounding atmosphere has been discussed from both the kinetic and the thermodynamic points of view. The absolute reaction rate theory has been applied to the decomposition in inert atmospheres enabling the formulae of the activated complexes formed during each stage to be calculated. It has also been shown that the detailed atomic movements occurring during the first stage of the decomposition in ammonia can be predicted from a knowledge of the stoichiometry of the reaction and of the detailed crystal structures of the starting and product materials. The kinetics and mechanism of the recombination of "V₂0₅" with ammonia and water vapour to form AMV have also been discussed in detail.

The thermal decompositions of a series of amide complexes of nickel(II) chloride have been studied. Thermochemical, kinetic, structure and solid-state stability correlations have been investigated. Complexes containing homologous amide ligands (L) of the form NiLCℓ₂, Ni₃L₂Cℓ₆, Ni₃LCℓ₆, NiL₂Cℓ₂(2H₂0) and ML₂Cℓ₂ (where M = Ni(II), Co(II) or Cu(II)) have been prepared. Chemical analysis, spectral and thermogravimetric measurements were used to characterize the complexes and their decomposition stoichiometries. Three sets of reactions were identified as yielding stable products in a single step: (i) NiLCℓ₂ (s) → NiCℓ₂ (s) + L (g) (ii) Ni₃LCℓ₆ (s) → 3NiCℓ₂ (s) + 2L (g) (iii) Ni₃LCℓ₆ (s) → 3NiCℓ₂ (s) + L (g) Characterization of the processes in the ML₂Cℓ₂ and NiL₂Cℓ₂(2H₂0) complexes was not straightforward. Reaction enthalpies (ΔH) were determined using DSC. The orders of the reaction onset temperatures (Tc), peak temperatures (Tmax) and ΔHL values for the NiCℓ₂ system were: N-methylacetamide < acetamide < N-methylformamide, suggesting the importance of steric hindrance of the methyl-substituent groups in the amide skeleton. In the Ni₃LCℓ₆, NiL₂Cℓ₂(2H₂0) and ML₂Cℓ₂ systems no simple orders could be deduced. The Te and Tmax sequences obtained from analogous metal(II) chloride complexes indicated that the copper(II) complexes were the least stable. The kinetics of the loss of L from NiLCℓ₂ complexes were investigated using isothermal TG, non-isothermal TG and DSC measurements. The contracting geometry models described the course of the decompositions in the most satisfactory manner. Apparent activation energies ( Ea) were estimated from Arrhenius plots of rate coefficients from: (i) an approximate zero-order relationship, (ii) the contracting-area (R2) and contracting-volume (R3) equations, (iii) a new empirical (B2) expression, (iv) the half-life ( 1/t₀.₅) and (v) the characteristic feature of the rate-time curve ( 1/tmax/2 ). The non-dependence of Ea on the rate equation used supports the reliability of the kinetic parameters. Non-isothermal experiments were analyzed by the Coats-Redfern, the modified BorchardtDaniels and the Kissinger methods. Arrhenius parameters were in keeping with results from the isothermal kinetic measurements. The values of Ea obtained for the NiLCℓ₂ system increased with an increase in basicity of the amide ligands. No straightforward correlation was found between Ea and Te, Tmax, ΔHL or spectral properties.

Ph.D, Faculty of Science, University of the Witwatersrand, 2011 / Investigations into methane conversion (both catalytic and non-catalytic) and characterization of the carbon produced for use in high efficiency DCFCs were performed. Under non-catalytic processes, a high methane conversion (> 80%) was achieved at 1200 oC at flow rates of between 10-60 ml/min. Analysis of the carbon using Raman spectroscopy showed that the carbon was highly disordered and the degree of disorder increased with increase in methane flow rate (from aD/aG = 1.54 at 10 ml to aD/aG = 2.24 at 60 ml/min). Further analysis of the carbon using thermogravimetric analysis (TGA) demonstrated that the carbon produced at higher flow rates e.g. 100 ml/min were easily oxidized (746 oC) compared with those produced at lower flow rates (10 ml/min, 846 oC). Therefore, a high temperature coupled with high flow rates (60-100 ml/min) produced carbon with desired qualities (high disorder, low crystallinity and more thermally reactive) for DCFC uses. In the catalytic decomposition of methane, Ni supported on TiO2 and a 1:1 mixture of TiO2/Al2O3 gave high and stable methane conversions of about 60% at only 600 oC compared to 1200 oC required for the non-catalytic conversion. These catalysts were found to be the best catalyst systems of the tested catalysts. Considering the thermal oxidation and crystallinity data which are some of the properties of the carbon required for direct carbon fuel cells (DCFCs), the carbon produced can potentially be used in DCFC systems.