Thesis defence

PhD Defence | Pebax-based Composite Membranes for Carbon Capture, by Silu Chen

Linda Sherwood — Tue, 10 Dec 2019 15:45:15 +0000

PhD Defence | Pebax-based Composite Membranes for Carbon Capture, by Silu Chen Linda Sherwood Tue, 12/10/2019 - 10:45

You are welcome to attend Silu Chen's PhD defense, when they will discuss the use of pebax-based composite membranes for carbon capture.

Abstract

A great amount of anthropogenic CO2 emissions has caused the greenhouse effect which impacts the living environment of creatures on the planet.

Effective carbon capture technologies need to be developed to reduce CO2 emissions. Membrane separation technology can be applied in carbon capture due to its advantages in energy conservation and pollution prevention.

Poly(ether block amide)-based (PEBAX 1657) composite membranes were developed for carbon capture in separating CO2/N2, CO2/CH4, and CO2/H2 mixtures in this study.

Polyvinylamine/PEBAX (PVAm/PEBAX) blend membranes were prepared for carbon capture by a solution casting method. The presence of PVAm enhanced membrane hydrophilicity and gas solubility. To further increase CO2 permeability in the membranes, PEBAX/PVAm/diethanolamine (PEBAX/PVAm/DEA) composite membranes were fabricated on polysulfone substrate membranes. The structures of the composite membranes not only improved gas permeance due to reducing the thickness of the permselective layer but also provided great mechanical strength. DEA can increase membrane hydrophilicity. Water-swollen membranes showed great gas permeability, but the gas selectivity still needs to be improved. NH4F/PEBAX membranes were developed by a solution casting method.

The introduction of F- affected the permeabilities of N2, CH4, and H2 in the membranes more significantly than CO2 permeability due to the salting-out effect, resulting in an increase in gas selectivity. Mixed matrix membranes were fabricated by embedding amino-modified multi-walled carbon nanotubes

(MWCNTs) as a dispersed phase in a PEBAX polymer matrix. After acid treatment, MWCNTs were modified by polydopamine (PDA) through self-polymerization of dopamine (DA). The catechol groups can react with amine groups on branched polyethylenimine (PEI) by the Michael addition reaction and Schiff base reaction. The addition of MWCNT-PDA-PEI can facilitate CO2 transport and adjust membrane structures. The prepared PEBAX/MWCNT-PDA-PEI membrane showed higher gas permeability and selectivity than the pristine PEBAX membrane.

Supervisor: Professor Feng

PhD Defense | Developing Models Using Game Theory for Analyzing the Interaction of Various Stakeholders in Energy Systems, by Ehsan Haghi

Linda Sherwood — Wed, 27 Nov 2019 18:56:56 +0000

PhD Defense | Developing Models Using Game Theory for Analyzing the Interaction of Various Stakeholders in Energy Systems, by Ehsan Haghi Linda Sherwood Wed, 11/27/2019 - 13:56

You are invited to attend Ehsan Haghi's PhD defense, where he will discuss his research on the the use of game theory to analyze energy systems.

Abstract

The focus of this thesis is on investigating two areas: 1. The role of energy storage systems in Ontario and how they can be used to reduce GHG emissions in the province, and 2. Analyzing the interaction of the heat and electricity supply systems in Great Britain.

Supervisor: Professor Mike Fowler

MASc Oral Exam | Functionalized Vanadium Oxide as the Cathode Material for Rechargeable Aqueous Zinc-ion Batteries, by Mei Han

Linda Sherwood — Wed, 27 Nov 2019 18:42:29 +0000

MASc Oral Exam | Functionalized Vanadium Oxide as the Cathode Material for Rechargeable Aqueous Zinc-ion Batteries, by Mei Han Linda Sherwood Wed, 11/27/2019 - 13:42

You are invited to attend Mei Han's MASc oral exam, where they will discuss their research into strategies to improve the electrochemical performance of vanadium-based electrodes in rechargeable aqueous zinc-ion batteries.

Abstract

The battery offers a viable solution for storing intermittent energy supplies associated with renewable energy production. Although lithium-ion batteries take up the most battery market, they are still limited by lithium metal resources, high cost and safety concerns. With this regard, aqueous batteries with mildly acidic electrolytes hold a promise for large-scale energy storage. In particular, zinc, as an attractive alternative to lithium metal, has been employed in aqueous rechargeable batteries due to its low-cost, high safety and environmental friendliness. Layered vanadium oxide (V2O5) as cathode material has gained enhanced interests in the studies of rechargeable aqueous zinc-ion batteries (RAZBs) due to its relatively high capacity.

However, commercial V2O5 shows poor stability during cycling since the zinc ion intercalation causes degradation of the cathode and battery components.

Therefore, in this project, two strategies involving surface coating and metal-ion doping are proposed and utilized to improve the electrochemical performance of vanadium-based electrodes in RAZBs.

First, we introduce a coating method to fabricate polymer-modified cathode materials for aqueous zinc-ion batteries, which display improved electrochemical performances under both ambient and elevated temperature conditions. A polymer-coated cathode is demonstrated and the assembled battery delivers a high capacity of 195.7 mAh·g-1 (at a current density of 1 A·g-1), with only 9.5% capacity decay at room temperature after 200 cycles. Even at an elevated temperature (60°C), the polymer-coated battery still shows outstanding capacity retention, of 80% vs. 25% for bare V2O5 cathode after 150 cycles.

Second, two kinds of metal ions (Zn2+ and Na+) are doped simultaneously into the V2O5 interlayer by a molar ratio of Zn:Na = 2:1 to form a metal-ion doped cathode material Zn0.38Na0.19V2O5 (ZNVO). Besides, in order to prevent the extraction of Na ions from the positive electrode, an additional 2M sodium salt is added to the 2M ZnSO4 aqueous solution to prepare a dual-ion electrolyte. This dual-ion system (containing dual ion-doped positive electrode and dual ion electrolyte) offers a long-term cycle life, ~ 89% capacity retention after 4000 cycles, and a relatively high discharge capacity of 190 mAh·g-1 at 1 A·g-1 during fast charge / discharge process.

More importantly, this dual-ion electrolyte effectively suppresses zinc dendrite formation on the anode surface because of the electrostatic shield mechanism, where creating a positively charged shield around the sharp zinc protuberances. Thus, this dual-ion system provides the excellent electrochemical performance of Zn // ZNVO batteries and holds a promise for realizing practical applications of zinc-ion batteries.

Supervisor: Professor P Chen

PhD Defence | Application of Cellulose Nanomaterials in Water Treatment Processes, by Nathan Grishkewich

Linda Sherwood — Tue, 19 Nov 2019 16:16:37 +0000

PhD Defence | Application of Cellulose Nanomaterials in Water Treatment Processes, by Nathan Grishkewich Linda Sherwood Tue, 11/19/2019 - 11:16

You are welcome to join the department as Nathan Grishkewich defends his PhD thesis, which explores the synthesis of new cellulose nanomaterials nanocomposites tailored towards advanced water treatment operations, and the construction and evaluation of continuous water treatment processes utilizing cellulose nanomaterials nanocomposites.

Abstract

Many advanced water treatment processes have been designed and implemented to purify water, such as adsorption, photocatalysis, and membrane filtration processes. All these processes have the potential to be enhanced through the use of nanotechnology, however, it is paramount that we use materials that are both functional and sustainable.

The most abundant resource on the planet, cellulose, fits the above criteria, as it is the source of cellulose nanomaterials (CNs). CNs encompass both cellulose nanocrystals (CNCs) and cellulose nanofibres (CNFs), and they possess many excellent properties, such as high specific strength, enormous surface area, high dispersibility in water, and immense potential for modification via the surface hydroxyl groups. Their ease of modification and abundance make them excellent candidates for water treatment applications, both in pristine form and as nanocomposites. They can be easily incorporated into both aerogel and hydrogel structures for adsorbing contaminants, coated with semiconducting metal oxides as supports for photocatalysts, and embedded in membranes to enhance strength and functionality in membrane filtration processes.

This thesis will explore (1) the synthesis of new CN nanocomposites tailored towards advanced water treatment operations, and (2) the construction and evaluation of continuous water treatment processes utilizing CN nanocomposites.

Supervisor: Professor Michael Tam

PhD Defence | Electrode Design for Durable and Energy-Dense Rechargeable Zinc-Air Batteries, by Zachary Cano

Linda Sherwood — Tue, 12 Nov 2019 19:37:57 +0000

PhD Defence | Electrode Design for Durable and Energy-Dense Rechargeable Zinc-Air Batteries, by Zachary Cano Linda Sherwood Tue, 11/12/2019 - 14:37

You are welcome to attend Zachary Cano's PhD defence, in which he will discuss his research into the viability of zinc-air batteries in electric vehicles, including the investigation of the use of nickel-based air electrodes.

Abstract

Zinc-air batteries have been proposed as a low-cost and energy-dense candidate to replace or supplement lithium-ion batteries in electric vehicles. This thesis explores the viability of zinc-air batteries in electric vehicles and experimentally investigates the use of nickel-based air electrodes. The failure mechanism of these electrodes is uncovered, and a new nickel-based air electrode, which has both an improved cycle life and a substantially lower mass and volume than previous designs, is presented.

Supervisor: Professor Mike Fowler

PhD Defence | Platinum Group Metal-Free Catalyst and Catalyst Layer Design for PEM Fuel Cells, by Pan Xu

Linda Sherwood — Wed, 30 Oct 2019 14:50:50 +0000

PhD Defence | Platinum Group Metal-Free Catalyst and Catalyst Layer Design for PEM Fuel Cells, by Pan Xu Linda Sherwood Wed, 10/30/2019 - 10:50

You are welcome to attend Pan Xu's PhD defence, in which they will discuss their research into platinum group metal-free (PGM-free) catalyst synthesis for the oxygen reduction reaction in proton exchange membrane (PEM) fuel cells.

Abstract

The thesis focuses on platinum group metal-free (PGM-free) catalyst synthesis for the oxygen reduction reaction in proton exchange membrane (PEM) fuel cells. Different methodologies have been tried to prepare the catalysts.

We've been able to successfully synthesize PGM-free catalysts with high ORR activity in half-cell testings, and remarkable performance in a PEM fuel cell. Testing parameter study and MEA optimization were conducted to get a more comprehensive understanding of the fuel cell and achieve better performance.

Supervisor: Professor Zhongwei Chen

PhD Defence | Design of Polymeric Materials: Novel Functionalized Polymers for Enhanced Oil Recovery & Gas Sorption Applications, by Alison Scott

Linda Sherwood — Tue, 15 Oct 2019 19:14:05 +0000

PhD Defence | Design of Polymeric Materials: Novel Functionalized Polymers for Enhanced Oil Recovery & Gas Sorption Applications, by Alison Scott Linda Sherwood Tue, 10/15/2019 - 15:14

You are welcome to attend Alison Scott's PhD defence, in which she will discuss her research, using two case studies to discuss a general framework for the design of polymeric materials that is limited by neither industry, nor application, nor specific type of polymeric material.

Abstract

As material requirements for particular applications become more specific and strict, using a targeted approach to design polymeric materials becomes a necessity. A general framework for the design of polymeric materials has been developed, and the specific aspects are grounded in two independent case studies. These two distinct (yet related) case studies have been selected to demonstrate that the framework is not limited to a particular industry or application, nor to a specific type of polymeric material.

In Case Study #1, water-soluble terpolymers are investigated for use in polymer flooding during enhanced oil recovery. In contrast, Case Study #2 examines a variety of polymeric materials that have the potential to be used for acetone gas sensing (for diabetic applications). Both case studies use the same general design framework in a sequential, iterative manner to move towards optimally designed materials for each target application.

Supervisor: Professor Alex Penlidis

PhD Defence | Thin Film Composite Membranes via Layer-by-Layer Assembly for Pervaporation Separations, by Elnaz Halakoo

Linda Sherwood — Mon, 26 Aug 2019 19:05:04 +0000

PhD Defence | Thin Film Composite Membranes via Layer-by-Layer Assembly for Pervaporation Separations, by Elnaz Halakoo Linda Sherwood Mon, 08/26/2019 - 15:05

You are welcome to attend Elnaz Halakoo's PhD defence, in which they will discuss their research to investigate pervaporative desalination of high-salinity water and dehydration of ethylene glycol, ethanol and isopropanol.

Abstract

In this study, thin film composite (TFC) membranes were prepared via layer-by-layer (LbL) assembly of polyethyleneimine (PEI) and graphene oxide (GO) to investigate pervaporative desalination of high-salinity water and dehydration of ethylene glycol (EG), ethanol (EtOH) and isopropanol (IPA).

Supervisor: Professor Xianshe Feng

PhD Defence | On the Prediction of Gas Hold-up in Ebullated Bed Reactors, by Amir Mowla

Linda Sherwood — Wed, 24 Jul 2019 20:32:46 +0000

PhD Defence | On the Prediction of Gas Hold-up in Ebullated Bed Reactors, by Amir Mowla Linda Sherwood Wed, 07/24/2019 - 16:32

You are welcome to attend Amir Mowla's final PhD defence, in which they will discuss their research into the hydrodynamics of commercial ebullated bed reactors through a combination of experimental investigation and CFD modelling.

Abstract

Commercial ebullated bed reactors (EBRs) are three-phase fluidized bed systems used for hydroprocessing (upgrading) of bitumen, a major Canadian resource. The objective of this thesis is to improve the understanding of the hydrodynamics of the EBRs through a combination of experimental investigation and CFD modelling. The experiments were conducted in a transparent cold-flow pilot scale reactor and were focused on the most important parameter in the design and operation of fluidized bed systems, i.e., the overall (average) gas hold-up.

Supervisor: Professor Marios Ioannidis

PhD Defence | Hydrogel Composite Adhesives Inspired by Algae and Mussels, by Aleksander Cholewinski

Linda Sherwood — Fri, 19 Jul 2019 19:15:24 +0000

PhD Defence | Hydrogel Composite Adhesives Inspired by Algae and Mussels, by Aleksander Cholewinski Linda Sherwood Fri, 07/19/2019 - 15:15

You are welcome to attend Aleksander Cholewinski's PhD defence, in which he will discuss his research to develop and fabricate underwater adhesives that take inspiration from the adhesive chemistry and processes of both marine mussels and benthic algae.

Abstract

The ocean is a vast source of a multitude of materials used in daily life, but has also provided numerous sources of inspiration for creating novel bio-inspired materials. Marine mussels are one of the best-known marine organisms that have inspired numerous underwater adhesives.

These materials have found applications in a broad variety of fields; their usage in biomedical applications is the most prevalent, due to the abundance of wet environments within the body. However, many organisms that adhere to rocks and the sea floor have their own unique strategies for achieving adhesion in wet conditions. Additionally, many synthetic bio-inspired adhesives look purely to the chemistry of mussel adhesion for inspiration, while other facets of mussel adhesive strategies (such as process control) offer their own improvements.

The objective of this dissertation is to develop and fabricate underwater adhesives that take inspiration from the adhesive chemistry and processes of both marine mussels and benthic algae.

Firstly, Algae and mussel systems were combined by covalently modifying alginate polymer chains (extracted from brown algae) with catechol functionality (inspired by mussel chemistry). After ionic crosslinking, the resulting hydrogels were adhesive to soft and organic materials, showing promise adhesion to animal tissue samples. The effects of catechol functionalization on the mechanical properties of the gels were also investigated, and differences in adhesion between soft and rigid substrates was observed.

Secondly, alginate and dopamine were combined together through noncovalent interactions; the ionic crosslinking of alginate and coordinate bonding of dopamine were exploited by using ferric ions to link the adhesive and cohesive components. By mimicking the processes of mussel and algae adhesion, a sequential application method was developed that significantly improved adhesion of the algae-mussel-inspired glue.

Finally, the stability and workability of the algae-mussel glue was improved by controlling dissolution and dispersion of the components. This was used to formulate both one-part and two-part adhesives that could be used more directly to bond together objects underwater.

Supervisor: Professor Boxin Zhao, Chemical Engineering