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There is significant concern about the accumulation of potentially toxic elements (PTEs) in soils because of both direct and indirect impacts on human and ecosystem health. Knowledge of the fate and distribution of such contamination can lead to an effective assessment of the hazards to soil biota and the need for protective or mitigation activities. This is a particular challenge due to the heterogeneity of the soil matrix and complexity of the processes that determine PTE availability to soil biota. While whole-cell bacterial biosensors have been proposed as tools in enabling greater confidence in addressing such biological and chemical interfaces their genuine value remains to be realised. The underpinning objective of this work was to link the response of microbial biosensors to detailed chemical analysis and to relate the dose response sensitivity to other biological measurements. To better understand the phenomena of PTE bioavailability, the study considered changes in toxicity within the context of ion competition in both freshly amended and historically impacted soils. The interaction of test bacteria with both free (soil pore water) and sorbed (solid phase) fractions of the target analytes (copper, nickel and zinc) has enabled a better estimation of bioavailability/toxicity of PTEs in soils. In comparison to other assays, the responses of the microbial sensor to Cu, Ni and Zn highlighted its relative sensitivity to PTE contamination. The use of luminescence marked microbial sensors complements the performance of rigorous analytical soil chemistry approaches. Their value in soil pollution should be considered a technique that should be interpreted alongside chemical analysis rather than an alternative as their performance in complex environmental matrixes is yet to be validated.

Friction Stir Processing (FSP), a hot working materials processing technology, and various analytical and computational models for it are reviewed. A simulation is used to develop a new predictive relationship for power dissipated during FSP of Ni-Al bronze according to tool traversing velocity and rotational velocity. The model is then applied to empirical data and found to fit very well. Correlations between the cooling rate and material properties are examined. A relationship between cooling rate and ductility is found, and a predictive model is developed.

We propose a new formula for the mineral nickelskutterudite, based on our observation that either (or both) Co or Fe3+ are essential structure constituents. The crystal structure of nickelskutterudite, (Ni,Co,Fe) As-3, cubic, Im (3) over bar, Z = 8: a = 8.2653(6) angstrom, V = 564.65(7) angstrom, has been refined to R-1 = 1.4% for 225 unique reflections I > 2 sigma(1) collected on a Bruker X8 four-circle diffractometer equipped with fine-focus, sealed tube MoKa radiation and an APEX-II CCD detector. This is the first report of the crystal structure of nickelskutterudite. Nickelskutterudite, a member of the skutterudite group of isostructural minerals, adopts a distorted perovskite structure with notably tilted octahedra and an unoccupied to partially occupied icosahedral metal site. In the structure of nickelskutterudite, there is one metal (B) site occupied by Ni, Co, or Fe in octahedral coordination with six As atoms. Procrystal electron density analysis shows each As anion is bonded to two cations and two As anions, resulting in a four-membered ring of bonded As with edges 2.547 and 2.475 angstrom. The extreme tilting of BAs6 octahedra is likely a consequence of the As-As bonding. The nickelskutterudite structure differs from the ideal perovskite structure (A(4)B(4)X(12)) in that As4 anion rings occupy three of the four icosahedral cages centered on the A sites. There are reported synthetic phases isomorphous with skutterudite with the other A site completely occupied by a cation (AB(4)X(12)). Electron microprobe analyses of nickelskutterudite gave an empirical chemical formula of (Ni0.62Co0.28Fe0.12)(Sigma 1.02)(AS(2.95)S(0.05))(Sigma 3.00) normalized to three anions. Pure NiAs3 nickelskutterudite, natural or synthesized, has not been reported. In nature, nickelskutterudite is always observed with significant Co and Fe, reportedly because all non-bonded valence electrons must be spin-paired. This suggests that nickelskutterudite must contain Co3+ and Fe2+, consistent with previous models since Ni4+ cannot spin-pair its seven non-bonded electrons, Co3+ and Fe2+, which can spin-pair all non-bonded electrons, are required to stabilize the structure. No anion deficiencies were found in the course of this study so, including the structurally necessary Co and Fe, the chemical formula of nickelskutterudite (currently given as NiAs3-x, by the IMA) should be considered (Ni,Co,Fe)As-3.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

The nickel-based superalloys have been a key enabler to the development of modern gas turbine engines. Since their introduction the chemical complexity of these alloys has increased significantly, with current generation nickel-based superalloys usually containing over 10 different elements. It is this combination of alloying additions that is responsible for the superior high temperature properties these alloys exhibit. Traditionally, alloy design has invoked considerable use of trial-and-error based approaches involving costly and exhaustive processing backed up by empirical property testing. In this work a computational materials design approach is developed. This method links physically-faithful composition-dependent models with thermodynamic calculations to understand material behaviour. By doing this it is possible to consider large compositional design spaces and isolate alloys expected to have optimal performance for specific applications. The scope of this research has been to apply the computational model to the design of a polycrystalline nickel-based superalloy for turbine disc applications in next generation jet engines. The design trade-offs encountered when developing the new alloy are highlighted. Alloy compositions which are predicted to be optimal for turbine disc applications are isolated. These alloys have been manufactured using a scaled down version of the commercial production method. The newly manufactured alloys have been characterised using microstructural evaluation, mechanical testing and corrosion testing. The experimental results have been compared with modelling predictions in order to determine the capability of the computational approach.

Ph.D. (Chemistry) / Compounds 3-ferrocenylpyrazole (L1) 3-ferrocenyl-5-methylpyrazole (L2) and 4- ferrocenyl-1-methyl diketone (L7) were synthesized according to literature procedure, while compounds 3-ferrocenylpyrazolyl-methylenepyridine (L3), 3-ferrocenyl-5- methylpyrazolyl-methylenepyridine (L4), 3-ferrocenylpyrazolyl-ethyl amine (L5) and 3- ferrocenyl-5-methylpyrazolyl-ethylamine (L6) were prepared by phase transfer alkylation of the 2,6-bis(bromomethyl)pyridine or 2-bromoethylamine with the appropriate ferrocenylpyrazole L1 or L2 in a 1:1 ratio. These compounds L3-L6 show structural isomers labelled a and b. The isomers were in a ratio of 4:1 for L3 and L4 while for L5 and L6 the isomers were 2:1 ratio...

One of the environmental concerns associated with mining waste is the contamination of soil. This study addresses the decontamination of soil, particularly of Co and Ni using Berkheya coddii (B. coddii). B. coddii is a hyperaccumulater plant that is able to decontaminate Co and Ni from the contaminated land. The use of B. coddii to decontaminate soil or waste must be based on a cognizance of the complicated, integrated effects of pollutant sources and soil-plant variables. Phytoextraction pot trials using B. coddii were carried out under green house condition, with controlled watering. A contaminated metallurgical waste residue known as Rustenburg Base Mine Refineries waste (RBMR waste soil) collected from Rustenburg while a serpentine (native) soil (N soil) where B. coddii grows naturally was collected from Mpumalanga. The experiment involved the addition of sulfur doses to both soils in order to test whether acidification and higher sulfur availability could enhance the uptake of both Co and Ni by B. coddii. The results indicate that the addition of sulfur from 2.0 to 8.0 g per kilogram decreased pH in both substrates. RBMR waste soil pH was found to have decreased from 7.8 to 7.4 while the N soil pH was found to have decreased from 6.4 to 4.7. The reduction oxidation potential (redox potential) in both substrates was observed to have decreased along with the increase in sulfur dosage. The mean redox potential for RBMR waste soil was found to be 350 mV and 506 mV for the N soil after the addition of sulfur. Conductivity increased along with the increase in sulfur dosage in both substrates. The mean conductivity for the N soil was found to be 961 μS/cm while that of the RBMR waste soil was found to be 1453 μS/cm after the addition of sulfur. The decrease in soil pH was significant (p = 0.00115) in the N soil than RBMR waste soil. Despite the increase in sulfur dosage and decrease in soil pH in both substrates, B. coddii observed growing. Although it was evident that B. coddii is able to grow in the RBMR waste soil, it was observed that the RBMR waste soil limits the root depth of the B. coddii, reducing chances for the roots to penetrate into the ground especially when dry. The RBMR waste soil becomes more compacted than the N soil when dry. It is therefore crucial to ensure that there is enough moisture to allow for the B. coddii being able to survive effectively in the RBMR waste soil. B. coddii plant height in the RBMR waste soil after four months was observed to be in the range of 190 to 200 mm tall. This was found to be less than the height observed for the B. coddii planted in the N soil, which was in the range of 350 to 400 mm. Nonetheless, plants grown in both substrates were able to absorb Ni and Co into their tissues. More Co and Ni were found to have accumulated into the leaf tissues than in other parts of the plant. This could be an advantage since one would harvest only the leaf part or the canopy (shoots) and allow B. coddii to resprout in order to continue taking up more Co and Ni from the same waste substrate to remediation levels that could be stipulated by Government as desirable for the ecosystem and the protection of human health. Although the accumulated Ni and Co can be recovered from biomass, this alone might not provide sufficient economic justification for phytoextraction due to the low concentrations that could be recovered. B. coddii was found to absorb higher concentrations of Co and Ni from the N soil than from the RBMR waste soil. However, the results found in this study may not be conclusive. This could be due to many variables that could control metal uptake which were not investigated. These include mycorrhizal fungi and metal forms in the soil. Moreover, this study was performed in a green house and not in the outdoor environment. Ni is generally toxic to most plants, hyperaccumulators (i.e. B.coddii) contain elements that nullify the toxic effect of nickel, and in this case the accumulated nickel is bound to malate to form a harmless nickel complex which could be absorbed by the plants as nutrients.

Catalisadores de Ni suportado em La2O3, SiO2 e La2O3-SiO2 (com teores mássicos de La2O30 de 10%, 30% e 50%) tiveram seu desempenho avaliado frente a reação de reforma a vapor de glicerol. O efeito do suporte sobre a atividade, estabilidade e seletividade do catalisador foi avaliado, assim como diferentes métodos de preparo, teores de Ni e temperaturas de reação. Os catalisadores foram preparados pelos métodos da impregnação úmida seqüencial, impregnação úmida simultânea, impregnação sobre o suporte precipitado e co-precipitação, utilizando teores mássicos de 5%, 10% e 15% de Ni. Foram utilizadas as seguintes técnicas de caracterização: espectroscopia de energia dispersiva de raios X, fisissorção de nitrogênio, difratometria de raios X, redução a temperatura programada e difração de raios X in situ. Os catalisadores foram testados por um período de 5h, a fim de verificar a atividade e seletividade para a reação de reforma a vapor de glicerol a 500°C, 600°C e 700°C, e as propriedades dos catalisadores foram correlacionadas com os resultados obtidos dos ensaios catalíticos. Após as reações, os catalisadores foram submetidos as seguintes análises: análise elementar, difratometria de raios X e microscopia eletrônica de varredura. Foi observado que o Ni interage de forma variada com os diferentes suportes, que o método de preparação utilizado influencia propriedades dos catalisadores e que, dependendo do teor mássico de Ni suportado, o catalisador pode ser mais ou menos ativo para a reação de reforma a vapor de glicerol. Observou-se também que a temperatura influencia no desempenho da reação, sendo que os melhores resultados foram obtidos a 600°C com o catalisador 15Ni30LaSi preparado por impregnação úmida simultânea, que foi testado também por 20h para que fosse analisada sua estabilidade em um maior intervalo de tempo. / Ni catalysts supported on La2O3, SiO2 and La2O3-SiO2 (with 10%, 30% and 50%wt.La2O3) were evaluated in the glycerol steam reforming reaction. The effect of the supports was analyzed on the catalysts activity; stability and selectivity as well as different methods of preparation, Ni contents and reaction temperatures. Catalysts were prepared by the sequential wet impregnation, simultaneous wet impregnation, impregnation of Ni on support precipitate and co-precipitation methods using 5%, 10% and 15%wt.Ni. The catalysts were characterized by energy dispersive X-ray spectroscopy, nitrogen physisorption, X-ray diffraction, temperature programmed reduction and X-ray diffraction in situ. The catalytic tests were performed during 5 hours in order to verify the activity and selectivity for the glycerol steam reforming at 500°C, 600°C and 700°C, and identify the relationship between the catalysts properties and the results obtained with the catalytic tests. After the reactions, the catalysts were characterized by elemental analysis, X-ray diffraction and scanning electron microscopy. It was observed that the Ni interacted variously with different supports; the preparation method used influenced on the catalysts properties and, depending on the Ni content, the catalyst was more or less active for the glycerol steam reforming. It was also observed that the temperature of reaction influenced on the reaction performance, and the best results were obtained at 600°C with the 15Ni30LaSi catalyst, prepared by simultaneous wet impregnation, which was also tested for 20 hours to analyze its stability in a longer period.