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Recent Submissions

Access status: Embargo ,
DRINKING WATER TREATMENT ADAPTATION FOR LEAD CORROSION CONTROL UNDER CLIMATE-DRIVEN WATER QUALITY CHANGE
(2026-04-30) Hood, Kalli; Not Applicable; Doctor of Philosophy; Department of Civil and Resource Engineering; Not Applicable; Dr. Kelsey Pieper; Yes; Dr. Heather Murphy; Dr. Amina Stoddart; Dr. Graham Gagnon
Lead in drinking water remains a public health concern worth mitigating. Drinking water treatment and distributed water chemistry are key determinants of lead release. Gradual and acute climate-driven changes in source water quality, treatment technology and regulatory targets create new challenges for corrosion control related to natural organic matter, coagulant selection, inorganic compounds, and excess product in wastewater. The goal of this work was to investigate how drinking water treatment adaptation influences lead corrosion control with an emphasis on organic matter and treatment strategies for enhanced removal, orthophosphate-based corrosion inhibitors, trade-offs with sequestration, and the feasibility of zinc-reduction. Pilot- and bench-scale studies in combination with time-series modelling and screening-level exposure projections were used to evaluate lead response to environmental events and experimental treatments. Following an extreme precipitation event, natural organic matter increased in source water and was associated with a prolonged elevation in total lead in a model distribution system and projected increases to short-term exposure risk. Enhanced organic matter removal via granular activated carbon improved lead control in a bench-scale reactor of galvanic lead solder. Equivalent total organic carbon removal was achieved at lower product doses of a chloride-based (polyaluminum chloride) coagulant relative to sulfate- based (alum), but was linked with increased galvanic lead corrosion. Orthophosphate- silicate may be an alternative to blended phosphate for systems needing to manage discolouration due to high iron/manganese, though risks of increased dissolved lead must be considered. In low-alkalinity water, reducing zinc in orthophosphate inhibitors may be feasible without compromising lead or cement corrosion, but may result in small increases in copper. These reductions could offer a more sustainable option with lower burden for wastewater treatment. This work demonstrated shifts in source water quality and treatment processes like coagulation, filtration, corrosion inhibitors and sequestrants can be protective or destabilizing for lead control and infrastructure maintenance. Utilities should consider whole-system trade-offs in lead control, treatment performance, and downstream sustainability during process adaptation or redesign.
Access status: Open Access ,
Microfluidic Systems for Long-Term and High Spatiotemporal In Situ Total Alkalinity Measurement in Marine Environments
(2026-04-30) Motahari, Shahrooz; Yes; Doctor of Philosophy; Department of Electrical & Computer Engineering; Not Applicable; Dr. Adrian M. Nightingale; Yes; Dr. Michael Freund; Dr. Ghada Koleilat; Dr. Vincent Sieben
Atmospheric carbon dioxide (CO₂) levels continue to rise, altering the global carbon cycle and driving ocean acidification. The ocean absorbs a large fraction of emitted CO₂, making accurate measurement of marine carbonate chemistry essential. Total alkalinity (TA) is a key parameter of the carbonate system because it controls seawater buffering capacity, playing a critical role in carbon uptake and air–sea CO₂ exchange. However, most TA measurements are still performed in laboratories using discrete water samples, limiting sampling frequency and spatial coverage in dynamic marine environments. This thesis presents the first field deployment of a microfluidic Lab-on-Chip (LoC) TA analyzer during an Ocean Alkalinity Enhancement trial in Halifax Harbour. The system performed closed-cell, multi-point spectrophotometric titrations in a stop-flow configuration using integrated syringe pumps, solenoid valves, and on-chip optical absorbance cells. Over 40 days, the analyzer completed 314 TA measurements and 52 onboard certified reference material (CRM) measurements, generating approximately 3,300 optical readings. This autonomous in situ platform demonstrated high-resolution monitoring of alkalinity variability that is difficult to achieve with traditional bottle sampling. To improve performance for long-term autonomous deployment, two design advancements were developed. First, a compact Dean-flow micromixer was designed and experimentally validated to enhance mixing while reducing channel length and internal volume relative to the original ~300 µL stop-flow mixer. The design was modeled using COMSOL Multiphysics and validated through bench-top TA measurements of certified reference materials. Second, the first reported droplet-based LoC TA sensor was developed. The system performs multi-point spectrophotometric titrations in segmented flow, where each droplet represents a titration point. Superhydrophobic surface modification of PMMA channels enabled stable droplet formation. This droplet architecture significantly reduces sample and reagent consumption while increasing sampling frequency, making it well suited for long-term, high-spatiotemporal-resolution carbonate monitoring in marine environments. Overall, this work demonstrates that microfluidic Lab-on-Chip systems provide an efficient and practical solution for autonomous, high spatiotemporal, total alkalinity monitoring in marine environments.
Access status: Open Access ,
Understanding Optimism: Winston Churchill and the Evolution of British Strategic Bombing Warfare Against Germany, 1914-1941
(2026-04-30) Wang, Yufan; Not Applicable; Master of Arts; Department of History; Not Applicable; na; Not Applicable; Paul Doerr; Gregory Hanlon; Denis Kozlov
This thesis examines the origins, evolution and early effectiveness of British strategic bombing warfare against Germany from 1914 to 1941. It traces the intellectual and institutional foundations of air power, from the creation of the Royal Air Force, which included the Independent Force and later Bomber Command. The treatise situates British air policy within the broader framework of interwar grand strategy, highlighting the expectations that bombers could deter enemies and deliver decisive results. Particular emphasis is placed on Winston Churchill, whose support for strategic bombing reflected both strategic calculation and personal inclination towards offensive actions. The work evaluates the limited effectiveness of strategic bombing from both British and German perspectives. Although early results fell short of expectations, British optimism and continued investment were not irrational given contemporary theorical and technological constraints. Ultimately, effective inter-service cooperation is more important than over reliance on single magic weapon in winning a war.
Access status: Embargo ,
CHEMICAL MODIFICATION APPROACHES IN ORGANOMETAL HALIDE PEROVSKITE MATERIALS AND SOLAR CELLS
(2026-04-30) Abdelmageed, Ghada; Yes; Doctor of Philosophy; Department of Process Engineering and Applied Science; Not Applicable; Dr Bryan Koivisto; Yes; Dr Suzanne Budge; Dr Mita Dasog; Dr Ghada Koleilat
Metal halide perovskites are promising for future photovoltaics due to their optical absorption, carrier diffusion, and tunable bandgaps. Despite efficiency gains, instability and defects remain barriers. This thesis explores chemical modifications, additive engineering, and surface passivation to improve their optoelectronic properties and stability. First, the study examined how film formation and surface chemistry affect passivation by linking deposition techniques to the results. Oleic acid was used as a hydrophobic ligand for the surface passivation of MAPbI3 films prepared by different deposition techniques. Our findings showed that the success of surface treatments depends heavily on film morphology, and that customized passivation strategies notably improve resistance to humidity and stability. Next, we explored additive engineering through sulfur-based molecular engineering with thiazoline to boost crystallization, passivate halide vacancies, and enhance interfacial charge extraction. Strong Pb–S bonds lowered trap densities, increased carrier lifetimes, and led to high-performance devices with over 22% efficiency and better stability under humid and illuminated conditions. Finally, we synergistically combined additive engineering and surface passivation techniques by using carbamide-based additives to improve crystallization and reduce defect density in the bulk and 2D capping layer, passivating surface defects. These treatments resulted in significant improvements in charge-carrier lifetimes and recombination dynamics, emphasizing the importance of controlling defect formation during film growth. Overall, this research shows that incorporating specific chemical modifications into both the bulk and interfaces of perovskite films is an effective strategy to reduce recombination losses and improve environmental stability. By elucidating the connections between molecular design, film formation, and device physics, this thesis provides a detailed framework for creating high-efficiency, durable perovskite solar cells and supporting their development toward scalable, practical use.
Access status: Open Access ,
Extreme Water Level Predictions on the Nova Scotian Coastline using a Bayesian Hierarchical Model
(2026-04-29) Sarhan, Fatma; Not Applicable; Master of Science; Department of Mathematics & Statistics - Statistics Division; Not Applicable; n/a; Not Applicable; Dr. Bruce Smith; Dr. Edward Susko; Dr. Orla Murphy; Dr. Jonathan Jalbert
The modelling of extreme coastal water levels is crucial when it comes to flood risk preparations, management, and defense design in Nova Scotia. Given the increasing frequency of flooding events in this region, it is essential to estimate their potential magnitude to mitigate their potentially devastating consequences. In extreme value analysis, return levels are quantifications of risk and represent the level that is expected to be exceeded once on average in a given time period. The challenge is that these extreme events are rare, and the data are limited and often incomplete. To address this challenge, a Bayesian hierarchical extreme value model is developed where information on extreme events is shared spatially across locations. By incorporating atmospheric covariates as physical drivers of extreme water levels, this research aims to establish a well informed Bayesian Hierarchical Model that enhances estimation precision and enables return level predictions for ungauged locations across the Nova Scotian coastline.
Access status: Open Access ,
Improving Lifetime of Lithium-Ion Cells with Electrolyte Additives
(2026-04-30) Azam, Saad; Not Applicable; Doctor of Philosophy; Department of Chemistry; Not Applicable; Betar Gallant; Not Applicable; Michael Metzger; Alex Speed; Michael Freund; Jeff Dahn
Lithium-ion batteries are the dominant technology for electric vehicles and grid energy storage, yet improvements in lifetime across wide voltage and temperature ranges remain essential for next-generation applications. Electrolyte additives improve cell lifetime by modifying the electrode–electrolyte interphases, which govern degradation processes including lithium inventory loss, transition metal dissolution, impedance growth, and electrolyte decomposition. In this work, nearly 25 novel additives and more than 100 additive combinations were evaluated in lithium-ion pouch cells containing layered oxide cathodes (LiNixMnyCozO2 or NMC) and olivine cathodes (LiFePO4 or LFP). Cells were tested under demanding conditions including high voltage operation up to 4.4 V and elevated temperatures up to 70 °C. For LFP/graphite cells cycled at 70 °C, 4% vinylene carbonate (VC) emerged as an effective additive formulation. The improved performance is attributed to residual VC in the electrolyte, which suppresses the formation of lithium alkoxide species that promote Fe dissolution from the LFP positive electrode and accelerate solid electrolyte interphase growth and lithium inventory loss. While cells containing 4% VC achieved about 1500 cycles at 70 °C, they failed at room temperature due to the formation of a highly resistive negative electrode surface impedance. To overcome this limitation, a novel additive, bis(1,3,2-dioxathiolane-2,2-dioxide) (bis-DTD), was synthesized by the author and investigated as a co-additive with lower VC concentrations. In LFP/graphite cells, the combination of 2% VC + 2% bis-DTD delivered a lifetime at 70 °C comparable to that obtained with 4% VC, while maintaining stable cycling at room temperature due to lower charge transfer resistance. This formulation enables LFP/graphite cells to operate over a wider temperature range. Bis-DTD also dramatically improved lifetime of LiNi0.65Mn0.3Co0.05O2/graphite pouch cells cycled to 4.4 V, where electrolytes containing 2% bis-DTD retained more than 80% capacity after over 2500 cycles at 40 °C and over 5000 cycles at 20 °C. In sodium-ion cells using layered oxide cathodes paired with hard carbon, bis-DTD improved capacity retention to more than 92% after about 1100 cycles at 40 °C. This single electrolyte additive has demonstrated significant lifetime improvements across diverse lithium-ion and sodium-ion chemistries, highlighting the potential of rational electrolyte additive design for next-generation energy storage systems.