Thesis (Ph.D.(Chemistry))--University of Pretoria, 2003. / Includes bibliographical references.

Thesis (MScEng)--Stellenbosch University, 2004. / ENGLISH ABSTRACT: During the production of pure Ti02 for the pigment industry, ilmenite, containing 35 - 60 % Ti02, is reduced to high titania slag, containing 85 - 95 % Ti02 and pig iron. These ilmenite smelters are operated in very tight operating windows. Over reducing the slag may lead to the formation of TiC and reducing much of the Ti02 to Th03. According to Namakwa Sands furnace operators, this does not only affect the grade of the product, but it can cause slag foaming and furnace eruptions. In under reducing conditions, the liquid slag is fluxed by the FeO and may corrode the furnace lining and consequently lead to run-outs. The reducing conditions in the furnace are not only controlled by carbon addition, but also by temperature. Standard practise in industrial ilmenite smelters is to operate the furnace with a slag freeze lining to protect the refractory lining from chemical and physical attack by the slag. It is therefore clear that it is of great importance to be able to predict the slag liquidus temperature at different compositions. This can help the operator to avoid dangerous operating conditions. Over the past few decades, a number of solution models have been developed to describe non-ideal solutions. With the rapid increase in computer power, these models became more valuable and practical to use in advanced control and decisionsupport. In this study, some of the better-known models are discussed and evaluated for the Ti02 - Th03 - FeO system, based on a critical review of properties and measurements published in literature. Two of these models, the "modified quasi-chemical" model and the "cell" model were chosen to be applied to the high-titania slag system. Both these models are based on statistical thermodynamics with some differences in the initial assumptions. In this study, the model parameters for the cell model were regressed from experimental data. The high-titania slag produced, consists mainly of titanium in different oxidation states and FeO, placing its composition inside the Ti02 - Th03 - FeO ternary system. Reliable experimental data for this system are very limited. All three binary systems contained in the Ti02 - ThO) - FeO system were considered, namely FeO - Ti02, Ti02 - ThO) and FeO - ThO). Only liquidus data for these three binaries were used to regress the model parameters. Accuracy of the models was determined by calculating the root mean square (RMS) error between the experimental data point and the value calculated using the model and the newly determined model parameters. These errors corresponded weil with the reported experimental error of the datasets for both the models and all the binary systems. Due to the fact that this study focussed on the liquidus surface of the system, the results were also plotted in the form of binary phase diagrams and ternary liquidus isotherms. The cell model uses only binary interaction parameters to describe the ternary system. These parameters are not expanded to higher order polynomials, which makes this model more robust, but also less accurate than other models such as the modified quasi-chemical model. / AFRIKAANSE OPSOMMING: Tydens die produksie van suiwer Ti02 vir die pigmentbedryf, word ilmeniet, wat 35 tot 60 % Ti02 bevat, gereduseer tot 'n hoë titaan slak, met 'n Ti02 inhoud van 85 tot 95 % Ti02, en potyster. Hierdie ilmeniet smeltoonde word binne baie nou bedryfskondisies beheer. Oor-redusering van die slak kan lei tot the formasie van TiC en die redusering van Ti02 tot Th03. Dit affekteer nie net die produk se kwaliteit nie, maar kan volgens Namakwa Sands oond operateurs ook slak skuiming en ontploffings tot gevolg hê. Gedurende onder-reduserende omstandighede in die oond, word die vloeibaarheid van die slak verhoog deur die hoër FeO inhoud in die slak. Dit maak die slak meer korrosief en kan lei tot faling van die vuurvaste stene. Die mate van redusering in die oond word nie net bepaal deur die toevoeging van koolstof nie, maar ook deur die temperatuur van die slak. Dit is 'n standaard praktyk van die industrie om die oond te bedryf met 'n gevriesde slak laag om sodoende die vuurvaste stene te beskerm teen chemiese en fisiese aanval van die slak. Dit is dus duidelik dat dit baie belangrik is om die slak se smeltpunt by verskillende samestellings te kan voorspel. Dit kan die operateur help om die oond binne veilige bedryfskondisies te hou. 'n Hele aantaloplossingsmodelle is oor die afgelope paar dekades ontwikkel vir die beskrywing van nie-ideale oplossings. Hierdie modelle het oor die afgelope paar jaar baie toegeneem in praktiese waarde as gevolg van die snelle toename in rekenaarkapasiteit en -spoed. Dit het veral groot waarde in gevorderde beheerstelsels en besluitneming steun. Sommige van die meer bekende modelle word in hierdie studie bespreek en ge-evalueer vir die Ti02 - Th03 - FeO stelsel, gebaseer op 'n kritiese evaluasie van eienskappe en eksperimentele data gepubliseer in die literatuur. Twee van hierdie modelle, die "gemodifiseerde kwasi-chemiese" model en die "sel" model, is gebruik om die hoë titaan slak stelsel te beskryf. Beide hierdie modelle is gebaseer op statistiese termodinamika en het klein verskille m.b.t. die aanvanklike aannames. Die model veranderlikes vir die sel model is in hierdie studie afgelei vanaf die eksperimentele data. Die hoë titaan slak wat tydens hierdie proses geproduseer word, bestaan hoofsaaklik uit FeO en titaan in sy verskillende oksidasie toestande. Dit plaas die samestelling van die slak reg binne die Ti02 - Th03 - FeO temêre stelsel. Betroubare eksperimentele data vir hierdie stelsel is baie beperk. In hierdie studie word daar gekyk al drie binêre stelsels binne die Ti02 - Th03 - FeO temêre stelsel, naamlik: FeO - Ti02, Ti02 - Th03 en FeO - Th03. Slegs die smeltpunt temperatuur data vir hierdie twee binêre is gebruik in die afskatting van die model veranderlikes. Die akkuraatheid van die modelle is bepaal deur die wortel van die gemiddelde kwadraat van die fout tussen die eksperimentele waardes en die berekende waardes te bepaal. Albei die modelle het 'n relatiewe klein fout in vergelyking met die geraporteerde eksprimentele fout gehad vir al die binêre stelsels. Hierdie studie het gefokus op die smeltpunt temperatuur van die slak en die resultate is daarom ook in die vorm van binêre fasediagramme en isoterme projeksies op die temêre fasediagramme gestip. Die "sel" model gebruik slegs binêre interaksie parameters om die temêre stelsel te beskryf Hierdie parameters word vir die "sel" model nie uitgebrei tot hoër order polinome en dit maak die "sel" model meer robuust, maar minder akkuraat as ander modelle soos byvoorbeeld die "kwasi-chemiese" model.

No description available.

This thesis discusses the investigation of the two-dimensional S = œ Heisenberg antiferromagnet copper formate tetrahydrate (CFTH) and the layered triangular lattice material NaTi0₂ which was thought to be a candidate for the possession of a non-classical antiferromagnetic ground state due to the frustration inherent in a triangular antiferromagnet. Single crystals of CFTH are investigated using elastic, quasielastic and inelastic neutron scattering, electron spin resonance (ESR) spectroscopy and DC magnetometry. Using the appropriate theory, these measurements are used to determine values for the terms in the Hamiltonian which describes the interactions between the Cu²⁺ ions in this material. The Hamiltonian is compared with that of La₂Cu0₄, and the two are determined to be quite similar. There does not appear to be any evidence for a non-classical ground state in either material. This was proposed to exist in La₂Cu0₄ to account for the superconductivity of doped samples. The difficulties in preparing pure NaTi0₂ have been surmounted, and a technique is described for preparing powder samples with very reproducible structural and magnetic properties. The structural properties have been investigated using X-ray and neutron diffraction, the latter at temperatures between 100 K and room temperature. The magnetic properties have been probed using DC magnetometry and ESR spectroscopy. The sample dependence of the structural and magnetic properties of samples prepared in slightly different ways is discussed. The temperature dependence of the magnetic susceptibility and of the structural parameters is explained by comparison with other oxides and chlorides of trivalent Ti and V, many of which show similar behaviour. The magnetic and structural changes which occur between 200 and 250 K are assigned to changes in the Ti-Ti bonding within the layers, which leads to a transition between two metallic states with subtle differences in their band structures.

This Thesis describes the synthesis and characterisation of titanium imido compounds supported by pendant arm functionalised amidinate ligands. Reactivity studies of cyclopentadienyl amidinate-imido compounds with CO2 are presented. Chapter 1 introduces transition metal imido chemistry, with a particular emphasis on imido complexes of titanium. Chapter 2 describes recent developments in the chemistry of functionalised amidinate ligands. The synthesis and characterisation of new titanium imido compounds with pendant amine functionalised amidinate ligands is described. The preparation of an amidinate ligand with a pendant propyl arm is reported. Reactions of a selection of these complexes with small molecules are presented. Chapter 3 reviews recent developments in the chemistry of cyclopentadienyl amidinate-imido compounds. The preparation of cyclopentadienyl-supported titanium imido compounds bearing pendant arm amidinate ligands is described andthereactionsofthesecompoundswithCC>2arediscussed. Kineticanddensity functional theory studies of these reactions are presented. Chapter 4 describes the synthesis and characterisation of alkyl and aryloxide titanium amidinate-imido compounds. The preparation of cationic derivatives is also described and reactions of these cationic derivatives with small molecules are discussed. Chapter 5 presents full experimental procedures for all of the syntheses and reactivity studies outlined in Chapters 2 to 4. Chapter 6 contains characterising data for all of the new compounds reported. Appendices A - K contain tables of selected crystallographic data for all new crystallographically characterised complexes described in this Thesis. Appendices L - O contain kinetics data relating to work discussed in Chapter 3.

Thesis (M.S.)--West Virginia University, 2002. / Title from document title page. Document formatted into pages; contains vii, 48 p. : ill. Vita. Includes abstract. Includes bibliographical references (p. 45-47).

Thesis (Ph. D.)--University of Delaware, 2006. / Principal faculty advisor: Andrew V. Teplyakov, Dept. of Chemistry and Biochemistry. Includes bibliographical references.

No description available.

Thesis (Ph.D. (Physics)) -- University of Limpopo, 2021 / Titanium metal and its alloy components find extensive applications in various industries such as aerospace, medicine and automotive due to its light weight-strength ratio. More importantly, titanium-based components with better surface finishing are required in the titanium manufacturing industries. However, these components suffer from surface roughness and brittleness due to the formation of alpha-case layer. Recently, the etching process has been widely used for metal surface modification, but the etching mechanism and the choice of etchant are not well prescribed. On the other hand, the adsorption of halogen molecules on the metal surface has received much attention due to their technological applications and relevance for material surface processing, corrosion and etching. This is considered as a promising approach towards selecting an effective etchant for the metal surface etching process. In this study, the first-principle approach has been used to study the adsorption behaviour of halogen molecules and ions on Ti (100) and (110) surfaces. Their adsorption mechanism was deduced from the calculated adsorption energy, heats of formation, desorption energy, work function, charge density difference and density of states. In particular, to understand how different etchant can influence the properties of titanium metal surface during etching process. Firstly, the free halogen molecules (HF, HCl, HBr and HI), as well as the clean Ti (100) and (110) surfaces were investigated to deduce the reactivity and surface stability, respectively. It was established that the HF dissociate easily due to its lowest dissociation energy and higher electronegativity, which suggest stronger interaction with the Ti surfaces. The halogen molecules stability trend was found to follow the order of HF>HCl>HBr>HI consistent with the electronegativity strength. Furthermore, it was also found that Ti (110) is the most stable surface displaying the lowest surface energy as compared to Ti (100) surface. v Secondly, the adsorption of halogen molecules on Ti (100) and Ti (110) surfaces was studied to investigate the chemical interaction and their reactivity. The halogens were adsorbed on three possible adsorption sites (Top, Bridge and Hollow) and their reaction is spontaneous. Moreover, the bridge and top sites were found to be the most favourable sites on Ti (100) and Ti (110) surfaces, respectively. Our results showed that all halogen molecules dissociate spontaneously on both Ti surfaces. The findings revealed that the adsorption of halogen molecules on Ti surfaces is energetically favourable suggesting adsorption energy strength order of 𝐸𝑎𝑑𝑠𝐻𝐹>𝐸𝑎𝑑𝑠𝐻𝐶𝑙>𝐸𝑎𝑑𝑠𝐻𝐵𝑟>𝐸𝑎𝑑𝑠𝐻𝐼. This indicates that the adsorption of HF molecule on these surfaces is thermodynamically more stable than HCl, HBr and HI molecules. Also, our results revealed that the adsorption of halogen ions (F-, Cl-, Br- and I-) is more favourable than the adsorption of halogen molecules (HF, HCl, HBr and I) on the bridge site in both Ti surfaces considered. The F ion was found to be the most preferable than Cl, Br, and I ions. In addition, the interaction of halogen ions with Ti surfaces was deduced with regards to electron charge. We found that the amount of electron charge transferred depends on the adsorption energy strength. In particular, it was found that the F atom accepts more electrons than other halogen ions. Moreover, the spherical shape was observed, this suggests that the charge density distribution between Ti atom and halogen exhibit ionic bonding behaviour. We also found that the adsorption of halogen has a stronger effect on the work function of Ti surfaces depending on the halogen ion. The magnitude of the induced work function varies from the halogen ionic order of F>Cl>Br>I. Lastly, in order to describe the dependence of the surface coverage of an adsorbed molecule, F2 and Cl2 molecules were adsorbed on Ti (100) surface at different coverages. We observed the formation of etching products TixFy and TixCly species on the surface. The heats of formation (EHF) and desorption energy of volatile etch products were calculated. Our findings show that the formed volatile molecules (TixFy and TixCly) are energetically favourable (EHF<0), suggesting an vi exothermic process. We also found that the TixFy clusters is more stable with lower heats of formation than the TixCly species. Moreover, the desorption energy of the formed volatile (TiF4) species was found to be lower than TiCl4 indicating that that TiF4 species desorb easily. This demonstrates that F2 is more suitable for surface etching as compared to Cl2. / Council for Scientific and Industrial Research (CSIR) and the Department of Science and Innovation (DSI)

Yes / Herein, we report 31 new β-diketonate titanium compounds of the type [Ti(O,O)2X2], whereby O,O = asymmetric or symmetric β-diketonate ligand and X = Cl, Br, OEt or OiPr. Thirteen new crystal structures are discussed and show that these octahedral species all adopt cis geometries in the solid state. These compounds have been tested for their cytotoxicity using SRB and MTT assays, showing several of the compounds are as potent as cisplatin against a range of tumour cell lines. Results also show the [Ti(O,O)2Br2] complexes are more potent than [Ti(O,O)2Cl2], [Ti(O,O)2(OEt)2] and [Ti(O,O)2(OiPr)2]. Using a simple symmetrical heptane-3,5-dione (O,O) ligand bound to titanium, we observed more than a 50-fold increase in potency with the [Ti(O,O)2Br2] (28) when compared to [Ti(O,O)2Cl2] (27). One of the more potent compounds (6) has been added to three different sixmers of DNA, in order to analyse the potential DNA binding of the compound. NMR studies have been carried out on the compounds, in order to understand the structural properties and the species formed in solution during the in vitro cell assays.