The estimation of the active surface area (ASA) of various macrocrystalline graphitic materials is industrially valuable but the microstructures of these materials are still contestable. This in turn has led to difficulties in the unambiguous interpretation of crystallographic measurements with powder X-ray diffraction (pXRD) and Raman spectroscopy as well as their relationship to the ASA. To resolve this issue a systematic approach is required. As a starting point two widely accepted pXRD and Raman methodologies were utilized. Purified, oxidized, natural graphite flakes were extensively examined to elucidate the essential microstructural features. Based on this an illustrative model was formulated as grounds for interpreting the measured crystallite domain sizes. Only one of the crystallographic parameters could be linked to the observed microstructure. For macrocrystalline graphite both techniques are subject to instrumental limitations and should not be used. Due to the non-linearity of the correlations they are prone to measurement uncertainty and should not be used above acceptable limits. In addition, the current inability to distinguish between different defect types leads to ambiguous results. Despite being a single, interrelated 2 crystal the composite nature of the flakes will make it difficult to relate even an ideal, accurate domain size measurement to the ASA.

Thermal analysis and other techniques were employed to characterize two expandable graphite samples. The expansion onset temperatures of the expandable graphite's were ca.220°C and 300°C respectively. The key finding is that the commercial products are not just pure graphite intercalation compounds with sulfuric acid species intercalated as guest ions and molecules in between intact graphene layers. A more realistic model is proposed where graphite oxide-like layers are also randomly interstratified in the graphite flakes. These graphite oxide-like layers comprise highly oxidized graphene sheets which contain many different oxygen-containing functional groups. This model explains the high oxygen to sulfur atomic ratios found in both elemental analysis of the neat materials and in the gas generated during the main exfoliation event.

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Graphite foams were prepared from a coal tar pitch that was partially converted into mesophase. Expandable graphite was used instead of an inert gas to "foam" the pitch.

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The oxidation, in a neat oxygen atmosphere, of high-purity and highly crystalline natural graphite and synthetic Kish graphite was investigated. The physico-geometric model function of the kinetic rate equation was experimentally determined by isothermal thermogravimetric analysis at 650 °C. Analytic solutions for basic flake shapes indicate that this function strictly decreases with conversion. However, for both samples the experimental data trend was a rapid initial increase followed by the expected decrease to zero. High resolution field emission scanning electron microscopy (FEGSEM), of partially oxidized flakes, provided plausible explanations for this discrepancy. Rapid development of macroscopic surface roughness during the initial stages of oxidation was evident and could be attributed to the presence of catalytic impurities. Large fissures along the planes of the natural graphite and the initiation, growth and coalescence of internal cavities in the Kish graphite were observed.Flake models incorporating the latter two features are difficult to analyse analytically.However, a facile probabilistic approach showed that reasonably good agreement with experimental data was possible.

Two unidentified powdered graphite samples, from a natural and a synthetic origin respectively, were examined. These materials are intended for use in nuclear applications, but have an unknown treatment history since they are considered proprietary. In order to establish a baseline for comparison, the samples were compared to two commercial flake natural graphite samples with varying impurity levels. The samples were characterized by conventional techniques such as powder X-ray diffraction, Raman spectroscopy and X-ray fluorescence. The results indicated that all four samples were very similar, with low impurity levels and good crystallinity, yet they exhibit remarkably different oxidation behaviours. The oxidized microstructures of the materials were examined using high-resolution scanning electron microscopy at low acceleration voltages.The relative influence of each factor affecting the oxidation was established, enabling a structured comparison of the different oxidative behaviours. Based on this analysis, it was possible to account for the measured differences in oxidative reactivity. The material with the lowest reactivity was a flake natural graphite which was characterized as having highly visible crystalline perfection, large particles with a high aspect ratio and no traces of catalytic activity. The second sample, which had an identical inherent microstructure, was found to have an increased reactivity due to the presence of small catalytic impurities. This material also exhibited a more gradual reduction in the 2 oxidation rate at higher conversion, caused by the accumulation of particles which impede the oxidation.The sample with the highest reactivity was found to be a milled, natural graphite material, despite its evident crystallinity. The increased reactivity was attributable to a smaller particle size, the presence of catalytic impurities and extensive damage to the particle structure caused by jet milling. Despite displaying the lowest levels of crystalline perfection, the synthetic graphite had an intermediate reactivity, comparable to that of the highly crystalline but contaminated sample. The absence of catalytic impurities and the needle coke-derived particle structure were found to account for this behaviour.This work illustrates that the single most important factor when comparing unknown graphite materials from different origins is an assessment of the oxidized microstructure.This approach has the added benefit of identifying further potential processing steps and limitations for material customization.

Graphite foams of varying composition and density were prepared using a low cost, local pitch material and expandable graphite for use in solar energy capture. The foams have a high degree of graphitization but exhibit a fine mosaic texture. A small oxidative treatment (6% mass loss) was necessary to fully open the foam pores. As the density is reduced a large decrease in the foam surface area was observed. Despite this, an increase in solar energy capture efficiency was measured due to increased circulation through the foam. By varying foam geometry and the concentration ratio it was demonstrated that the receiver size can be reduced by 75% at the same efficiency.The foam with the lowest density was used to test the thermal performance of a simultaneous energy capture and storage concept using a phase change material. The melting time of the phase change material is reduced by 46% whilst only reducing the energy storage density by 18%. In addition it was found that the foam composite resulted in more ideal phase transition behaviour due to the elimination of incongruent melting. The composite can effectively capture, store and discharge thermal energy, at a constant temperature, without any additional requirements.