No description available.

No description available.

A series of tri-substituted iron and cobalt complexes of the form [M(A)3]n+ were synthesized, and were characterised by UV/Visible absorption and 1H-NMR spectroscopy. The complexes [Co(phen)2(en)]3+ and [Co(bipy)2(en)]3+ have been reported in the literature but 1H-NMR spectroscopy showed that the material produced in both syntheses is [Co(en)3]3+. Spectroscopy further showed that these species cannot be prepared by the literature methods. The complexes were tested in the oxidation of adamantane in the solvents, acetic acid and trifluoroacetic acid and they all oxidised adamantane to a mixture of 1-adamantanol, 1-adamantanol and 2-adamantanone both in the presence and the absence of the oxidant, O2. In all the reactions, however, the yield of conversion was very low. The mechanism for this oxidation was different depending on the presence or absence of O2. In the presence of O2 a catalytic cycle was produced for the oxidation of adamantine. In the oxidation in the presence and absence of O2 there was little variation in activity between the tri-substituted iron and cobalt complexes of 1,10-phenanthroline when compared with the analgous 2,2’-bipyridine complexes. However, the substitution of an ethylenediamine ligand into the co-ordination sphere of cobalt produced significant increase in the activity, although the change was not constant. / Master of Science (Hons)

This research project focused on moderately thermophilic acidophilic microorganisms and their role in the oxidation of pyrite. A major objective of the work was to assess the relative efficiencies of defined combinations of moderate thermophiles in oxidising pyrite under defined conditions. In addition, various aspects of the physiology and phylogeny of moderately thermophilic acidophiles were investigated. Moderately thermophilic acidophiles, including novel acidophiles (a thermotolerant Leptospirillum and a Ferroplasma sp. ), were isolated from a commercial stirred-tank pilot plant. Pyrite oxidation by mixed cultures of different combinations of moderate thermophiles, including the novel isolates, was assessed in preliminary shake flask experiments. Data from these experiments were used to select microbial consortia in later experiments in temperature- and pH-controlled bioreactors. These involved monitoring rates of mineral oxidation, and relative numbers of the different microorganisms included in the original inoculum, using a plating technique in conjunction with a molecular approach (FISH). The results from the pyrite oxidation studies indicated that mixed populations of acidophiles may accentuate or diminish the rates and extent of pyrite oxidation, relative to pure cultures. The thermotolerant Leptospirillum isolate was found to be unable to oxidise a pyrite concentrate when grown in pure culture, though this inhibition was overcome when the iron-oxidiser was grown in mixed cultures with various Grampositive acidophiles. Investigation of the effects of fifteen individual and mixtures of flotation chemicals on moderately thermophilic acidophiles revealed different degrees of toxicities of the different reagents and sensitivities of the microorganisms, with the Leptospirillum isolate generally being the most sensitive of those tested. The phenomenon of pH-related ferric iron toxicity to moderately thermophilic and mesophilic Gram-positive bacteria was also investigated. ARDREA (Amplified Ribosomal DNA Restriction Enzyme Analysis) using the 16S rRNA gene sequences of known acidophilic bacteria, was refined and developed, and applied successfully to identify moderate thermophiles isolated from environmental samples.

No description available.

No description available.

This study presents findings on the effect of domestic laundry detergents on the fastness to light of selected fibre reactive dyes applied to cotton. The study was carried out to elucidate the reasons for the accelerated colour loss of cotton garments washed under Australian domestic laundering conditions. Cotton fabric dyed with commonly used reactive dyes were laundered with water only, several domestic detergents and a laboratory formulated neutral detergent, and then exposed to light for two hours in the wet state. Quantities of detergent used were in accordance with the manufacturers recommendations. Exposures were repeated fifteen times equivalent to 30 hours exposure. Colour loss and colour difference were measured after 5, 10 and 15 wash cycles and 10, 20 and 30 hours exposure. When the fabric was exposed wet the colour faded more rapidly than when exposed dry to light. Detergents increased the colour loss even when the fabric was not exposed to light. The presence of an oxidizing bleach (sodium perborate) in the detergent increased colour loss during washing and wet exposure to light. Ultraviolet radiation from the light source, heat, moisture, alkali and oxidising bleach during exposure resulted in hydrolysis of the dye-fibre bond causing dye desorption during washing and rinsing. Water alone increased the fading of the dyes most likely due to presence of dissolved oxygen held within the fibre. The combination of ultraviolet radiation and oxidizing bleaches altered the chemistry of the dye and hence its shade. This was particularly evident on the black dye and one of the navy blue dyes.

No description available.

Ce travail porte sur l’étude du comportement d’un acier inoxydable (matériau passivable) en situation de tribocorrosion. L’accent a été mis sur l’effet de synergie existant entre la sollicitation mécanique et l’électrochimie du milieu, conduisant à une usure significative. Dans un premier temps, une méthodologie a été mise en place, sur une microstructure ferritique, pour quantifier cette synergie et ses deux composantes que sont l’électrochimie accélérée par l’usure (E.A.U.) et l’usure accélérée par l’électrochimie (U.A.E.). La première représente la dissolution du matériau consécutive à l’action mécanique du pion sur la surface. La seconde rend compte des modifications des propriétés mécaniques de la surface induites par l’électrochimie. Les paramètres de la sollicitation mécanique étant tout d’abord fixés, l’évolution des composantes de l’effet de synergie a été étudiée en fonction du caractère oxydant d’un milieu acide, modifié à l’aide d’un potentiostat. Un minimum d’usure, déterminé sous polarisation cathodique est considéré comme l’usure mécanique de référence. Dans le domaine passif, pour des potentiels passifs croissants, l’U.A.E. diminue suite à un épaississement de la partie oxyde du film passif, renforçant les propriétés mécaniques de la surface. A l’inverse, l’augmentation de l’E.A.U. s’explique par une intensité supérieure des réactions d’oxydation sur la surface mise à nu au cours du frottement. Ceci conduit à une usure maximale pour un potentiel passif intermédiaire. L’évolution des composantes de l’effet de synergie a ensuite été investiguée en potentiel libre sous les influences croisées de l’acidité du milieu et du temps de latence. L’E.A.U. augmente avec l’acidité en lien avec une dissolution plus prononcée mais diminue pour un temps de latence plus court suite à la diminution du couplage galvanique entre la trace d’usure partiellement repassivée et la zone cathodique. La diminution du temps de latence limite la maturation du film passif. En milieu acide, l’U.A.E. ne diminue pas car le film passif, majoritairement constitué d’oxyde, conserve son caractère abrasif. A l’inverse en milieu neutre, la proportion d’hydroxyde étant alors majoritaire, l’U.A.E. diminue. Dans un second temps, l’influence de la microstructure sur le comportement à la tribocorrosion a été mise en évidence en fonction des paramètres étudiés précédemment. Après traitement thermique, l’acier inoxydable présente une microstructure ferrito martensitique. En considérant l’usure totale, l’effet de la microstructure apparait négligeable sur la tenue à la tribocorrosion en potentiel libre, dans les conditions étudiées. Le biphasage est par contre bénéfique lorsque le frottement se déroule sous potentiels cathodiques ou passifs grâce à un transfert d’effort de la martensite à la ferrite sous-jacente. De même, l’effet délétère du film passif sur les propriétés mécaniques de la surface est réduit lorsque la microstructure comporte une phase dure (U.A.E.). / This study deals with the behaviour of a stainless steel (passive material) undergoing tribocorrosion. Focus has been put on the synergistic effect existing between mechanical action and medium electrochemistry, leading to significant wear. In a first step, a methodology has been set up, on a ferritic microstructure, to quantify this synergy as well as its two compounds that are the wear-accelerated electrochemistry (W.A.E.) electrochemistry-accelerated wear (E.A.W.). The former stands for the material dissolution following the mechanical action of the pin on the surface. The latter accounts for the modifications of the surface mechanical properties induced by electrochemistry. The parameters of the mechanical action being set, the evolution of the synergistic effect compounds has been studied as a function of the oxidizing feature of an acidic medium, modified by using a potentiostat. A minimum of wear, determined under cathodic polarisation is considered as the reference mechanical wear. In the passive domain, for higher passive potentials, E.A.W. decreases due to the thickening of the oxide part of the passive film, enhancing the mechanical properties of the surface. On the contrary, the W.A.E. increase is explained by more intense oxidising reactions occurring on the bare material revealed to the electrolyte by sliding. This leads to a maximum wear obtained at an intermediate passive potential. The evolution of the synergistic effect compounds has then been investigated under free potential condition with crossed influences of the medium acidity and the latency period. The more acidic the medium, the greater the W.A.E. because dissolution is enhanced. However, it decreases with a shorter latency period because of a weaker galvanic coupling between the partially repassivated wear track and the cathodic surface. The latency period decrease limits the passive film maturation. In acidic medium, E.A.W. does not decrease because the passive film, mainly composed of oxide, keeps its abrasive feature. To the opposite, in neutral medium, the hydroxide proportion being majority, E.A.W. decreases. In a second step, the microstructure influence on the tribocorrosion behaviour has been evidenced as a function of the previously studied parameters. After a thermal treatment, the stainless steel shows a ferrite-martensite microstructure. Considering global wear, the microstructure effect appears to be negligible on the tribocorrosion resistance in free potential situation, under the studied conditions. On the contrary, a two-phase microstructure is beneficial when sliding is performed under cathodic or passive potentials thanks to a mechanical transfer occurring from the martensite to the underlying ferrite. Moreover, the detrimental effect of the passive film on the surface mechanical properties is reduced when the microstructure involves an hard phase (E.A.W.).