The closed shell structures of certain all-carbon fragments originally observed in mass spectroscopy experiments leads to the enhanced stability of these species, known as fullerenes, which have excited sufficient interest amongst chemists and physicists over the last decade to warrant the award of the 1996 Nobel Prize for Chemistry to their discoverers. ¶ Studies of the stability, symmetry, and consequent remarkable properties of fullerenes began in earnest in 1991 with the development of a technique enabling the production and purification of macroscopic quantities of material. The best known and most widely studied fullerene is the truncated icosahedral C[subscript 60] molecule, which forms the basis of the present work. ¶ One important property of C[subscript 60] is that it forms salts with sufficiently electropositive species, such as the alkali metals. The resulting salts contain C[subscript 60] anions and are known as fullerides. Certain of these salts display metallic behaviour, and some superconduct at temperatures as high as 33 K. ¶ Three aspects of fulleride research are addressed in this work. These are: i) the preparation, crystal structure determination and superconductivity characterization of several new fullerides, particularly those including ammonia as an additional intercalant; ii) the electronic structure of the C[superscript n-, subscript 60] (n = 1 - 6) anions, as probed by solution-phase near infrared absorption spectroscopy; and iii) the molecular dynamics of a number of fullerides, superconducting and non-superconducting, by inelastic neutron scattering. ¶ This work has grown out of an Honours project also concerning C[subscript 60], the combined duration of the two studies covering essentially the entire history of this widely and competitively studied field.

<p>The goal of this work has been to evaluate the different experimental techniques used for quantitative analysis of multi-phase materials systems. </p><p>Powder based specimens containing two-phases, austenite and ferrite , were fabricated and quantified. The volume fraction of ferrite varied from 2 Vol% to 50 Vol%. </p><p>X ray powder diffraction (XRD) measurements were based on two peak analysis. Computer based software Topas was used for quantitative analysis, which is believed to be the most advanced in this field. XRD results were found within the absolute limit of +/- 4% of given ferrite volume fraction. Volume fraction as low as 2 Vol% was successfully detected and quantified using XRD. However, high statistical error was observed in case of low volume fraction, such as 2 Vol% and 5 Vol% ferrite volume fraction. </p><p>Magnetic balance (MB) measurements were performed to determine the volume fraction of magnetic phase, ferrite. MB results were found in good agreement with given volume fractions. As low as 2 Vol% volume fraction was detected and quantified with MB. MB results were within the absolute limit of +/- 4% of given ferrite volume fraction. </p><p>Image analysis (IA) was performed after proper sample preparation as required by electron backscatter diffraction (EBSD) mode of Scanning electron microscopy (SEM). IM results were found within the absolute limit of +/- 2 % of given ferrite volume fraction. However, high statistical error was observed in case of 2 Vol% volume fraction.</p>

The goal of this work has been to evaluate the different experimental techniques used for quantitative analysis of multi-phase materials systems. Powder based specimens containing two-phases, austenite and ferrite , were fabricated and quantified. The volume fraction of ferrite varied from 2 Vol% to 50 Vol%. X ray powder diffraction (XRD) measurements were based on two peak analysis. Computer based software Topas was used for quantitative analysis, which is believed to be the most advanced in this field. XRD results were found within the absolute limit of +/- 4% of given ferrite volume fraction. Volume fraction as low as 2 Vol% was successfully detected and quantified using XRD. However, high statistical error was observed in case of low volume fraction, such as 2 Vol% and 5 Vol% ferrite volume fraction. Magnetic balance (MB) measurements were performed to determine the volume fraction of magnetic phase, ferrite. MB results were found in good agreement with given volume fractions. As low as 2 Vol% volume fraction was detected and quantified with MB. MB results were within the absolute limit of +/- 4% of given ferrite volume fraction. Image analysis (IA) was performed after proper sample preparation as required by electron backscatter diffraction (EBSD) mode of Scanning electron microscopy (SEM). IM results were found within the absolute limit of +/- 2 % of given ferrite volume fraction. However, high statistical error was observed in case of 2 Vol% volume fraction.

The hydrothermal and solid state methods were used in the synthesis of some aluminoborophosphate compounds. The products were investigated by using XRD, IR, DTA, DSC, ICP and SEM methods. The solid state reactions have been studied in the range 700 &ndash / 1200&amp / #61616 / C. Using several hydrothermal methods a novel aluminum phosphate compound Al3-xBxP3O12 was synthesized. The crystal system was found to be tetragonal with a=17.1629 and c = 12.6084A&deg / unit cell parameters and space group is P4212 (No:90). In anorthite mineral (CaAl2Si2O8) by replacing two silicon with boron and phosphorus, a boron containing anorthite with the formula of CaAl2BPO8 was prepared. The indexed data was reported for the first time in this thesis. Its crystal system was found to be monoclinic with the following unit cell parameters and &amp / #946 / angle / a=10.0440&Aring / , b = 12.6587 &Aring / , c = 14.4332 &Aring / and &amp / #946 / = 91.55&deg / . In this study, AlPO4.xH2O was also obtained by a hydrothermal method while trying to synthesize AlBP4O13. All the prepared compounds have been investigated by IR spectroscopy and the assignment of the functional B-O and P-O groups were done.

Die strukturelle Vielfalt von Metallphosphonaten macht sie zu vielversprechenden Kandidaten für vielzählige Anwendungen, erschwert aber zugleich eine planmäßige Synthese. Die Untersuchung der Bildungsmechanismen kristalliner Übergangs-metallphosphonate stellt Zusammenhänge zwischen Synthesebedingungen und resultierender Struktur her. In dieser Arbeit wurden unterschiedliche Phosphonsäuren mit divalenten Metallionen umgesetzt und so verschiedene Metallphosphonate mit diversen Strukturen erhalten. Die Kristallstrukturen neuer Verbindungen wurden mittels Röntgenpulver-diffraktometrie aufgeklärt. Systematische Untersuchungen zeigten einen direkten Zusammenhang zwischen bestimmten Strukturmotiven und Eigenschaften der Verbindungen. Das Bestreben nach umweltfreundlichen und wirtschaftlichen Synthesemethoden wird durch die Mechanochemie erfüllt. Die zugrundeliegenden Reaktions-mechanismen liegen im Dunkeln, sodass Mechanochemie größtenteils als „trial and error“-Methode funktioniert. In situ Untersuchungen mechanochemischer Reaktionen erlauben die Aufklärung der Reaktionswege und weitere Optimierung der Prozesse. Nach der Optimierung des experimentellen Aufbaus wurde in dieser Arbeit eine Kombination der Methoden Röntgenpulverdiffraktometrie und Thermographie zur Aufklärung der Bildungmechanismen von Metallphosphonaten eingesetzt. Die Ergebnisse der in situ Untersuchungen zeigen die Bildung von Metallphosphonaten als dreistufigen Prozess, der über einen nicht-kristallinen Zustand verläuft. / The structural diversity of metal phosphonates makes them promising candidates for numerous applications, but at the same time makes planned synthesis difficult. The study of the formation mechanisms of crystalline transition metal phosphonates establishes correlations between synthesis conditions and resulting structure. In this work, different phosphonic acids were reacted with divalent metal ions to obtain various metal phosphonates with diverse structures. The crystal structures of new compounds were solved by X-ray powder diffraction. Systematic studies showed a direct correlation between certain structural motifs and properties of the compounds. The search for environmentally friendly and economical synthesis methods is met by mechanochemistry. The underlying reaction mechanisms are unclear, so mechanochemistry functions largely as a "trial and error" method. In situ studies of mechanochemical reactions allow the elucidation of reaction pathways and further optimization of processes. After optimizing the experimental setup, a combination of X-ray powder diffraction and thermography methods was used in this work to elucidate the formation mechanisms of metal phosphonates. The results of the in situ investigations show the formation of metal phosphonates as a three-step process proceeding via a non-crystalline state.

No description available.

A range of small molecules of interest for use in organic semiconductor devices were studied computationally. Trends in geometry, absorption spectra, molecular orbitals, electrostatic potentials, reorganisation energies were studied. Results suggest that, as with acenes, the performance of non-linear cata-condensed polyaromatic hydrocarbons improves as number of fused benzene rings increases. The torsion in these molecules did not appear to have a large impact on the conjugation across the core and little effect on the absorption spectra, although it did affect the reorganisation energies on which charge mobilities depend. Computational studies of mobilities of anthradithiophene molecules were broadly able to reproduce trends seen experimentally and emphasised the importance of crystal morphology. Experimental work was also carried out to search for cocrystals between anthradithiophene derivatives. Many examples were found with some mixtures forming different cocrystals at different mixture ratios. These results were rationalised by a computational study that showed molecules which had a similar binding energy were more likely to be able to form cocrystals. Cocrystal devices were fabricated and 3 out of 7 showed a larger mobility than devices made out of its constituent materials alone. The best of these had a mobility 65% higher than a device made out of the constituent material with the largest mobility. An energy decomposition analysis was carried out on a novel thallophilic system, a complex of thallium with a neutral β-triketimine ligand which was found to form dimers with close Tl-Tl interactions. Calculations show the electrostatic interaction to be repulsive for the dimer with no counter ions, but attractive when 3,5-bistrifluoromethylphenyl borate counter ions are included. This suggests the metallophilic interaction is counter ion-mediated, requiring the anions to provide favourable electrostatics, even in the case of spatially diffuse and distant counter ions such used here. To enable the studies described here software was written for simulating absorption spectra. An implementation into the Gaussian Suite of programs of an energy decomposition scheme and its extension to include an empirical dispersion correction was also carried out.

<p>There are today clear indications that the Li-ion battery of the type currently used worldwide in mobile-phones and lap-tops is also destined to soon become the battery of choice in more energy-demanding concepts such as electric and electric hybrid vehicles (EVs and EHVs). Since the currently used cathode materials (typically of the Li(Ni,Co)O₂-type) are too expensive in large-scale applications, these new batteries will have to exploit some much cheaper transition-metal. Ideally, this should be the very cheapest - iron(Fe) - in combination with a graphite(C)-based anode. In this context, the obvious Fe-based active cathode of choice appears to be LiFePO₄. A second and in some ways even more attractive material - Li₂FeSiO₄ - has emerged during the course of this work.</p><p>An effort has here been made to understand the Li extraction/insertion mechanism on electrochemical cycling of Li₂FeSiO₄. A fascinating picture has emerged (following a complex combination of Mössbauer, X-ray diffraction and electrochemical studies) in which the material is seen to cycle between Li₂FeSiO₄ and LiFeSiO₄, but with the structure of the original Li₂FeSiO₄ transforming from a metastable short-range ordered solid-solution into a more stable long-range ordered structure during the first cycle. Density Functional Theory calculations on Li₂FeSiO₄ and the delithiated on LiFeSiO₄ structure provide an interesting insight into the experimental result.</p><p>Photoelectron spectroscopy was used to study the surface chemistry of both carbon-treated LiFePO₄ and Li₂FeSiO₄ after electrochemical cycling. The surface-layer on both materials was concluded to be very thin and with incomplete coverage, giving the promise of good long-term cycling.</p><p>LiFePO₄ and Li₂FeSiO₄ should both be seen as highly promising candidates as positive-electrode materials for large-scale Li-ion battery applications.</p>

There are today clear indications that the Li-ion battery of the type currently used worldwide in mobile-phones and lap-tops is also destined to soon become the battery of choice in more energy-demanding concepts such as electric and electric hybrid vehicles (EVs and EHVs). Since the currently used cathode materials (typically of the Li(Ni,Co)O2-type) are too expensive in large-scale applications, these new batteries will have to exploit some much cheaper transition-metal. Ideally, this should be the very cheapest - iron(Fe) - in combination with a graphite(C)-based anode. In this context, the obvious Fe-based active cathode of choice appears to be LiFePO4. A second and in some ways even more attractive material - Li2FeSiO4 - has emerged during the course of this work. An effort has here been made to understand the Li extraction/insertion mechanism on electrochemical cycling of Li2FeSiO4. A fascinating picture has emerged (following a complex combination of Mössbauer, X-ray diffraction and electrochemical studies) in which the material is seen to cycle between Li2FeSiO4 and LiFeSiO4, but with the structure of the original Li2FeSiO4 transforming from a metastable short-range ordered solid-solution into a more stable long-range ordered structure during the first cycle. Density Functional Theory calculations on Li2FeSiO4 and the delithiated on LiFeSiO4 structure provide an interesting insight into the experimental result. Photoelectron spectroscopy was used to study the surface chemistry of both carbon-treated LiFePO4 and Li2FeSiO4 after electrochemical cycling. The surface-layer on both materials was concluded to be very thin and with incomplete coverage, giving the promise of good long-term cycling. LiFePO4 and Li2FeSiO4 should both be seen as highly promising candidates as positive-electrode materials for large-scale Li-ion battery applications.

Demands for new, energy-efficient appliances have greatly increased in response to our growing need for a more environmentally friendly society. Magnetic refrigeration is a technique that utilizes the magnetocaloric effect, with possible energy savings of up to 30% compared to commercial gas compression refrigerators. A material appropriate for commercial magnetocaloric devices should be both cheap and non-toxic; it should also exhibit a first-order magnetic transitions close to room temperature. The magnetic properties of Fe2P-related materials can be relevant in this context, since their magnetic properties can be finely tuned through the substitution of Fe by Mn and P by Si, As, Ge or B to meet the general requirements for a magnetocaloric device. An in-depth study has therefore here been made of the structural and magnetic properties of the (Fe,Mn)2(P,Si)-system. The phase diagram of the FeMnP1-xSix-system has been carefully re-examined. It is found to contain two single-phase regions: an orthorhombic Co2P-type structure (x &lt; 0.15) and a hexagonal Fe2P-type structure (0.24 ≤ x &lt; 0.50). Selected compounds within the Fe2P-type region of the phase diagram have been shown to exhibit potential for use in magnetic refrigeration applications. Neutron powder diffraction has here been used to determine the magnetic structures of selected crystalline compositions within the FeMnP1-xSix-system to gain a better understanding of its magnetic properties. The Fe2P-type region is mainly ferromagnetic, but an incommensurate antiferromagnetic structure has also been identified close to the Co2P/Fe2P-type phase border for x ≈ 0.25. The so-called ''virgin effect'' in the Fe2P-type region of the FeMn(P,Si) phase diagram is found to be accompanied by an irreversible structural phase transition induced by magnetostriction. This new phase is found to be preserved during successive cooling-heating cycles. Furthermore, the magnetic properties of the substituted Fe2P-type structure changes significantly for metal:non-metal ratios away from 2:1. Such deviations could well explain the apparently conflicting structure-property relationships described in earlier literature for the FeMnP1-xSix-system.