<p>Two species of emergent macrophytes, Typha latifolia (common cattail) and Phalaris arundinacea (reed canary grass) were evaluated as substrates for biogas production. The specific methane yield for each plant was obtained by batch wise anaerobic digestion in 300-mL bottles. Three different pretreatments were evaluated for increased biogas production; mechanical milling, alkaline treatment with lime and fungal degradation with Pleurotus ostreatus (oyseter mushroom).The methane yield for Typha latifolia and Phalaris arundinacea was determined to 300 and 323mL methane per g VS, respectively. There was no statistical difference in methane yield between the two species. Milling pretreatment increased the biogas yield with 16 % by average compared to untreated plant. Alkaline pretreatment with lime increased the biogas yield with 27 % at roomtemp. and 22 % at 55 °C. The fungal pretreatment decreased the biogas production by 20 % and is probably not suitable for this kind of substrate.The results showed that emergent macrophytes have a biogas yield similar to other plants already tested (grasses) and commonly used (pasture crops) in large scale reactors. However, emergent macrophytes and grasses cause mechanical problems in a reactor due to their structure. Probably some kind of milling must be done to decrease the fiber length of the emergent macrophytes. The costs for harvest, transport, handling and possible pretreatment of the emergent macrophytes have to be estimated and included in the overall cost calculations. This can tell if emergent macrophytes should be used as a substrate for biogas production.</p>

The environmentally friendly n-type Mg2(Si, Sn) thermoelectric solid solutions have a strong potential of commercial utilization in thermoelectric (TE) energy conversion due to their availability, low density (~3.02 g/cm3), and high stability at middle temperature range (400-600 ▫C) that are typically observed from waste heat dissipating systems. The bulk materials were prepared from element powders via slow cooking under vacuum condition and current-assisted hot-press sintering. Temperature vs time curves have been researched in this thesis for fully reacted magnesium-silicide & magnesium-stannide green ingots with doping materials i.e. antimony, bismuth by different doping ratios. These ingots were ground by a high energy ball miller, uniaxial cold pressed into half inch pallets and then sintered by Direct Current-assisted hot pressing. Different synthesis conditions such as ball milling, sintering time, pressure, have been compared by SEM images and XRD tests analysis to figure out optimized process parameters. Several samples’ thermal conductivities (κ) were plotted as a function of temperature to study different synthesis strategies and doping materials’ effects on phonon scattering inside bulk thermoelectric materials.

Mechanical Alloying is a manufacturing process that produces alloys by cold welding of powders. Usually, a vial containing both the powder and steel balls is agitated. Due to impact between the balls and balls and the vial, the powder is mechanically deformed, crushed, and mixed at nano-scales. In this thesis, a numerical model is developed to simulate the dynamics of the vial and the grinding balls of the SPEX 8000 ball milling device, a standardized equipment in both industrial and academic investigations of ball milling. The numerical model is based on the Event Driven Method, typically used to model granular flows. The method implemented is more efficient than the discrete element method used previously to study ball milling dynamics. The numerical tool obtained is useful for scale-up and optimization of mechanical alloying of various materials. An optimization study is presented for the SPEX 8000.

Previous studies on fishes exposed to effluent from the Key Lake uranium mill in northern Saskatchewan have demonstrated elevated lipids in young-of-the-year pike (Esox lucius), deformities in larval pike and decreased survival of fathead minnows (Pimephales promelas). The objectives of this thesis were to evaluate possible factors that could be contributing to altered bioenergetics of juvenile northern pike inhabiting lakes receiving effluent from the Key Lake operation and to examine the effects of effluent exposure on biomarkers of oxidative stress and histopathology of target organs. Although glycogen and triglycerides stores were significantly greater in pike from exposure lakes compared to the reference, triglycerides stores of juvenile pike prey items showed no overall differences among lakes. Measures of parasitism, however, were negatively correlated with pike bioenergetics thereby reflecting a possible energetic cost of parasitism on reference lake fish. The degree of infection by intestinal parasites and gill monogeneans was greatest in reference pike and intermediate in low exposure pike, whereas high exposure pike harboured no parasites. <p>Arsenic, nickel and selenium are elevated in lakes downstream of the Key Lake mill and have been shown to be associated with increased reactive oxygen species (ROS) in biological systems causing oxidative stress. The potential for oxidative stress was assessed in pike liver and kidney using several biomarkers. Overall, the concentrations of total, reduced and oxidized glutathione and the ratio of oxidized to reduced glutathione did not differ significantly among exposure and reference pike. The activity of glutathione peroxidase was greater in high exposure than reference liver whereas, contrary to predictions, lipid peroxidation was greater in reference than exposure pike tissues. <p>Histopathological evaluations revealed greater kidney and gill pathology in reference lake pike, whereas for liver, hepatocyte morphology differed among lakes without any clear signs of pathology. Trace metal analyses of muscle showed that eight elements (arsenic, cobalt, copper, iron, molybdenum, selenium, thallium, uranium) were significantly elevated in exposure pike. These results provide only limited evidence of oxidative stress in exposure pike tissues and no evidence of histopathology despite indications that metals are bioaccumulating in tissue. Overall, the results from this thesis suggest that the health and condition of juvenile northern pike living downstream of the Key Lake uranium mill may not be compromised by effluent exposure.

Past monitoring has noted benthic macroinvertebrate community impairment downstream of both the Key Lake and Rabbit Lake uranium operations in northern Saskatchewan, Canada. The objective of this research was to try to identify the cause(s) of these impacts using a weight-of-evidence approach. Given that sediments generally accumulate contaminants that are related to metal mining activities (such as metals and radionuclides), the initial hypothesis for this research was that contaminated sediments were the primary cause of benthic community impairment at both operations.<p>In 2003 and 2004 a Sediment Quality Triad (SQT) approach confirmed the presence of an effect on benthic community structure, in addition to significant differences in surface-water, pore-water and whole-sediment chemistry at the immediate down-stream exposure sites at both uranium operations. However, no significant adverse effects were noted in 10-d whole-sediment bioassays with <i>Hyalella azteca</i>, although this lack of response could be partially due to sediment pore-water dilution resulting from the automated clean overlying water renewal process employed. Potential causes of benthic community impairment identified through the 2003 and 2004 SQTs for Key Lake include physical sediment composition, surface water pH and total ammonia, in addition to pore-water total ammonia and arsenic. Potential stressors identified at Rabbit Lake included high surface water manganese and uranium concentrations, and increases in pore-water total ammonia, manganese, iron, arsenic, and uranium levels.<p>In the summer of 2004, 4-d in-situ bioassays using <i>H. azteca</i> were conducted along with the SQTs to investigate the role both contaminated surface water and sediment played in benthic community impairment in-situ. Results from the Key Lake in-situ bioassay demonstrated that surface-water was the primary cause of acute toxicity to <i>H. azteca</i>. Results from the Rabbit Lake in-situ study also demonstrated that surface water as the primary cause of acute toxicity to <i>H. azteca</i>, although the relationship was not as strong. The cause of in-situ toxicity at Key Lake could not be correlated with any of the variables measured within the in-situ study, including trace metals, total ammonia, and pH. Of the measured constituents at Rabbit Lake, only concentrations of uranium in both surface water and pore-water were suspected of causing the observed in-situ mortality. Two data sets from two methods of surface water and pore-water collection supported these conclusions.<p>Due to time constraints and stronger cause-effect relationships, efforts were focused on the in-situ toxicity observed at Key Lake. Surface water collected in 2004 at the time of the related in-situ study was also found to be acutely toxic to <i>H. azteca</i> in separate laboratory surface water bioassays, thus verifying that contaminated surface water, not sediment, was the primary cause of the observed in-situ <i>H. azteca</i> mortality. Further information revealed that organic mill-process chemicals, which have been previously linked with sporadic effluent toxicity, were released at the Key Lake operation during the time of the in-situ experiment and associated surface water collection. Additional surface water samples collected in June and August, 2005, were not acutely toxic to <i>H. azteca</i>. Furthermore, a second bioassay with archived surface waters from the initial 2004 collection demonstrated that the water was no longer acutely toxic (i.e., acute toxicity disappeared after one-year storage). Chemistry comparisons of the toxic and non-toxic surface water samples, verified that trace metals, ammonia, pH, and major ions, including sulphate, were not the cause of toxicity, leaving only organic mill-process chemicals as a possible cause. Subsequent 4-d laboratory toxicity tests demonstrated that these process chemicals (kerosene, amine, and isodecanol) are toxic to H. azteca at the levels released in 2004, and are therefore believed to be the cause of the <i>H. azteca</i> mortality seen in the earlier in-situ experiment.<p>In short, this weight-of-evidence research provided new information on the possible causes of benthic macroinvertebrate community impairment downstream of both the Key Lake and Rabbit Lake uranium operations.

Mechanical Alloying is a manufacturing process that produces alloys by cold welding of powders. Usually, a vial containing both the powder and steel balls is agitated. Due to impact between the balls and balls and the vial, the powder is mechanically deformed, crushed, and mixed at nano-scales. In this thesis, a numerical model is developed to simulate the dynamics of the vial and the grinding balls of the SPEX 8000 ball milling device, a standardized equipment in both industrial and academic investigations of ball milling. The numerical model is based on the Event Driven Method, typically used to model granular flows. The method implemented is more efficient than the discrete element method used previously to study ball milling dynamics. The numerical tool obtained is useful for scale-up and optimization of mechanical alloying of various materials. An optimization study is presented for the SPEX 8000.

An experimental ball-milling study was performed to compare the deagglomeration behavior and the evolution of the particle size distribution with increasing milling time of two relatively coarse WC powders used for the production of cemented carbide cutting tools. The WC-powders were found to have distinctly different particle size distributions and particle morphologies prior to milling. Lab-scale WC samples were made using a range of different process parameters and milling times. These were then analysed by means of microscopy, laser light scattering, gas adsorption BET analysis and X-ray powder diffraction, XRD, to attain particle size distribution, specific surface area and a mean crystal size, respectively. The results suggested a linear relation between log(particle size) and log(milling time) between 10 and 80 hours milling. The viscosity was shown to have a minor effect on the milling efficiency. Both the number of collisions of milling balls per unit time as well as the kinetic energy of the milling ball affected the size reduction; more collisions or higher energy resulted in a higher milling efficiency. The evaluation of the effect of the process parameters on milling efficiency was facilitated by the use of simple scaling factors. For example, all milling curves for samples with different WC amounts coincided when rescaling the milling time using a scaling factor based on the weight of the WC and milling balls. The same scaling factor could be used with success for rescaling the results from different trials obtained with laser light scattering, gas adsorption and XRD. The results of this work are useful for future work on modeling of the milling process which should lead to more accurate predictions of the outcome of milling unit operations.

Past monitoring has noted benthic macroinvertebrate community impairment downstream of both the Key Lake and Rabbit Lake uranium operations in northern Saskatchewan, Canada. The objective of this research was to try to identify the cause(s) of these impacts using a weight-of-evidence approach. Given that sediments generally accumulate contaminants that are related to metal mining activities (such as metals and radionuclides), the initial hypothesis for this research was that contaminated sediments were the primary cause of benthic community impairment at both operations.<p>In 2003 and 2004 a Sediment Quality Triad (SQT) approach confirmed the presence of an effect on benthic community structure, in addition to significant differences in surface-water, pore-water and whole-sediment chemistry at the immediate down-stream exposure sites at both uranium operations. However, no significant adverse effects were noted in 10-d whole-sediment bioassays with <i>Hyalella azteca</i>, although this lack of response could be partially due to sediment pore-water dilution resulting from the automated clean overlying water renewal process employed. Potential causes of benthic community impairment identified through the 2003 and 2004 SQTs for Key Lake include physical sediment composition, surface water pH and total ammonia, in addition to pore-water total ammonia and arsenic. Potential stressors identified at Rabbit Lake included high surface water manganese and uranium concentrations, and increases in pore-water total ammonia, manganese, iron, arsenic, and uranium levels.<p>In the summer of 2004, 4-d in-situ bioassays using <i>H. azteca</i> were conducted along with the SQTs to investigate the role both contaminated surface water and sediment played in benthic community impairment in-situ. Results from the Key Lake in-situ bioassay demonstrated that surface-water was the primary cause of acute toxicity to <i>H. azteca</i>. Results from the Rabbit Lake in-situ study also demonstrated that surface water as the primary cause of acute toxicity to <i>H. azteca</i>, although the relationship was not as strong. The cause of in-situ toxicity at Key Lake could not be correlated with any of the variables measured within the in-situ study, including trace metals, total ammonia, and pH. Of the measured constituents at Rabbit Lake, only concentrations of uranium in both surface water and pore-water were suspected of causing the observed in-situ mortality. Two data sets from two methods of surface water and pore-water collection supported these conclusions.<p>Due to time constraints and stronger cause-effect relationships, efforts were focused on the in-situ toxicity observed at Key Lake. Surface water collected in 2004 at the time of the related in-situ study was also found to be acutely toxic to <i>H. azteca</i> in separate laboratory surface water bioassays, thus verifying that contaminated surface water, not sediment, was the primary cause of the observed in-situ <i>H. azteca</i> mortality. Further information revealed that organic mill-process chemicals, which have been previously linked with sporadic effluent toxicity, were released at the Key Lake operation during the time of the in-situ experiment and associated surface water collection. Additional surface water samples collected in June and August, 2005, were not acutely toxic to <i>H. azteca</i>. Furthermore, a second bioassay with archived surface waters from the initial 2004 collection demonstrated that the water was no longer acutely toxic (i.e., acute toxicity disappeared after one-year storage). Chemistry comparisons of the toxic and non-toxic surface water samples, verified that trace metals, ammonia, pH, and major ions, including sulphate, were not the cause of toxicity, leaving only organic mill-process chemicals as a possible cause. Subsequent 4-d laboratory toxicity tests demonstrated that these process chemicals (kerosene, amine, and isodecanol) are toxic to H. azteca at the levels released in 2004, and are therefore believed to be the cause of the <i>H. azteca</i> mortality seen in the earlier in-situ experiment.<p>In short, this weight-of-evidence research provided new information on the possible causes of benthic macroinvertebrate community impairment downstream of both the Key Lake and Rabbit Lake uranium operations.

Previous studies on fishes exposed to effluent from the Key Lake uranium mill in northern Saskatchewan have demonstrated elevated lipids in young-of-the-year pike (Esox lucius), deformities in larval pike and decreased survival of fathead minnows (Pimephales promelas). The objectives of this thesis were to evaluate possible factors that could be contributing to altered bioenergetics of juvenile northern pike inhabiting lakes receiving effluent from the Key Lake operation and to examine the effects of effluent exposure on biomarkers of oxidative stress and histopathology of target organs. Although glycogen and triglycerides stores were significantly greater in pike from exposure lakes compared to the reference, triglycerides stores of juvenile pike prey items showed no overall differences among lakes. Measures of parasitism, however, were negatively correlated with pike bioenergetics thereby reflecting a possible energetic cost of parasitism on reference lake fish. The degree of infection by intestinal parasites and gill monogeneans was greatest in reference pike and intermediate in low exposure pike, whereas high exposure pike harboured no parasites. <p>Arsenic, nickel and selenium are elevated in lakes downstream of the Key Lake mill and have been shown to be associated with increased reactive oxygen species (ROS) in biological systems causing oxidative stress. The potential for oxidative stress was assessed in pike liver and kidney using several biomarkers. Overall, the concentrations of total, reduced and oxidized glutathione and the ratio of oxidized to reduced glutathione did not differ significantly among exposure and reference pike. The activity of glutathione peroxidase was greater in high exposure than reference liver whereas, contrary to predictions, lipid peroxidation was greater in reference than exposure pike tissues. <p>Histopathological evaluations revealed greater kidney and gill pathology in reference lake pike, whereas for liver, hepatocyte morphology differed among lakes without any clear signs of pathology. Trace metal analyses of muscle showed that eight elements (arsenic, cobalt, copper, iron, molybdenum, selenium, thallium, uranium) were significantly elevated in exposure pike. These results provide only limited evidence of oxidative stress in exposure pike tissues and no evidence of histopathology despite indications that metals are bioaccumulating in tissue. Overall, the results from this thesis suggest that the health and condition of juvenile northern pike living downstream of the Key Lake uranium mill may not be compromised by effluent exposure.

Bismuth telluride based compounds is known to be the best thermoelectric materials within the low temperature regime. In this study, the P-type Bi0.5Sb1.5Te3 thermoelectric alloy was synthesized by ceramic processing method. The Bi0.5Sb1.5Te3 thermoelectric materials were prepared via the ball milling, cold pressing, and sintering processes. The effects of sintering time and temperature on the microstructures and thermoelectric properties were investigated and discussed. The X-ray diffraction patterns of Bi0.5Sb1.5Te3 reveal that the compounds have the oxides after the sintering processes and the heat treatment process causes grain growth by the increased sintering temperature and time. The results of thermoelectric properties show that the optimal Seebeck coefficient 300(£gV/K) was obtained as the sample was sintered at 350¢XC for 3h and the resistivity will reach the maximum. The figure of merit of 0.15 was obtained at room temperature as the sample was sintered at 375¢XC for 3h.