Graphite and graphitic materials underpin a number of modern technologies such as electrodes for energy storage and conversion systems. Due to their aromatic honeycomb-type lattice and layered structure, these carbons host a rich variety of foreign elements in their interstices. Whether possessing a tubular morphology - that enables the encapsulation of inorganic compounds, or a planar texture - where anions and molecules can intercalate, the chemical analysis of graphite and graphitic materials is often confronted with the need to disintegrate the carbon matrix to quantify target elements, most often metals. However, the resilience of the sp2-hybridized carbon lattice to chemical attacks is an obstacle to its facile solubilization, a necessary step to perform some of the most common elemental analysis measurements. Over the years, a range of alternative approaches have sprung out to address this issue such as the combustion of the carbon matrix followed by the acid dissolution of its ash product. Unfortunately, none of these represents a viable method that can be applied to batteries, in great part because of the different components that make up the carbon-based electrodes. In this dissertation, a new protocol has been developed to digest graphitic materials aiming to access their elemental composition in bulk scale. The approach is based on the use of molten alkaline salts to promote the oxidation of the carbon lattice and leach out metals into a dilute acid solution. As a model sample, given the existence of standards with a matching matrix, single-walled carbon nanotubes were examined. After being subjected to the alkaline oxidation (a.k.a. fusion), they were solubilized and analyzed with Inductively Coupled Plasma-Optical Emission Spectroscopy, a widely popular tool for elemental analysis of metals. Structural analysis ensued to understand the interaction of the molten salts with the nanotubes. After evaluating the applicability of the protocol to other carbons, a more complex system was investigated, namely the carbon-based anode of an intercalation-type potassium ion battery. In this process, a direct way to quantify the mass of the alkali metal was discovered, one which makes use of complementary chemical and structural analytical tools.

Fused glass beads as a sample preparation method for X-ray Fluorescence spectroscopy (XRF) were introduced in 1957 by Claisse; it soon became the preferred method to introduce oxide samples to the spectrometer, because heterogeneity, mineralogical and particle size effects are eliminated during the fusion process. Matrix effects are largely reduced by the resulting dilution. With the recent advances in XRF spectrometers, instruments with enhanced generator and temperature stability, improved sensitivity (even for light elements), and effective matrix correction software are available. Consequently, the largest proportion of analytical error results from the sample preparation step. Sampling error will always contribute the largest overall error but that is not the topic of this discussion. After more than 50 years of fused bead use in XRF analysis, certain matrices remain problematic. Although many fusion methods for chromite-, sulphide- and cassiterite-rich materials have been published, easily reproduced, routine methods for these still elude analytical chemists. Lengthy fusions at temperatures higher than 1100ºC are often prescribed for refractory materials and ores, and until recently one of the biggest challenges was a metal-bearing sample e.g. contained in slags or certain refractory materials. This study was conducted to identify and elucidate the reactions occurring in the formation of a lithium borate glass, but also between the lithium borate and oxides during glass formation. Different analytical techniques were used to investigate the reactions occurring during the fusion process based on theoretical glass-making principles. As a starting point, Thermo Gravimetric Analysis (TGA) and Differential Thermal Analysis (DTA) were used jointly to evaluate the reactions occurring during the fusion of lithium borate glasses, and at a later stage, oxide/flux mixtures. When a different TGA instrument was used, Differential Scanning Calorimetry (DSC) was used in conjunction with the TGA. Observed reactions were modelled in a muffle furnace to produce identical material in larger quantities, and this material was then investigated using X-ray Powder Diffractometry (XRD), Raman Spectroscopy and Electron Microprobe Analysis (EPMA). The most enlightening result from the TGA/DSC results was the large mass loss above 1050 ºC. Literature often prescribes prolonged fusions at elevated temperatures for certain fusions, but it was proved beyond reasonable doubt that this practise causes volatilisation of the flux and leads to erroneous analytical results. The next analytical technique applied to the flux and flux/oxide samples was XRD. Where pre-fused fluxes were investigated, the XRD data served as confirmation of the glassy state of the pre-fused flux as a broad humpy scan indicative of an amorphous material was seen in stead of a diffractogram with sharp, well defined peaks. After heating to above the temperature of re-crystallisation, the phases present could be identified from the diffractogram. Provisional results using the in-situ, high temperature stage point towards the possibility of using this technique to great effect to investigate the presence of different phases formed at high temperatures. Flux-oxide mixtures were measured on the high temperature stage and after cooling a new phase was observed indicating that new phases formed during a fusion reaction. As the heating stage is slow-cooled, the chance of crystallisation in the glass is good, providing the possibility for investigating this formation of new phases at elevated temperatures further with a more suitable heating element that will contain the material. Raman spectroscopy was subsequently used to gain information about the bonds within the flux. Pure lithium tetraborate and lithium metaborate fluxes were analysed as well as flux oxide mixtures. The vibrations could not be predicted from first principles as band broadening occurs in glasses that makes theoretical predictions very difficult. The data obtained was compared to similar studies in literature and good agreement was found. In oxide-flux mixtures definite new bands were observed that was not part of the flux or oxide spectrum. EPMA results allowed calculation of the maximum solubilities of an oxide in a specific flux. It was done using Cr2O3 and ZrO2 and compared well with experimental values obtained from literature. The microscope images revealed some new insights into the theory of XRF fusions. It could clearly be seen that dissociation of the minerals in the sample occurred, thus proving that no mineralogical effects exist in a fused glass bead, and it could be observed that the flux oxide mixture devitrify when over saturated. / Dissertation (MSc)--University of Pretoria, 2010. / Chemistry / unrestricted