Theses, Dissertations, and other Required Graduate Degree Essays

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This collection contains digitized SFU theses except for those theses submitted within the last 12 months. If you cannot find the thesis you are looking for please search Recently Submitted Theses as it may be a recently submitted thesis and thus not yet available in Summit.

Covalent surface modification of silicon oxides

Date created: 
2017-08-30
Abstract: 

Microwave radiation was utilized as a tool to modify surface properties of silicon oxides. Covalent surface modification of silicon oxides has been widely pursued in the areas of material science, electronics, microfluidics, biology, and separation science. Chemical surface modifications are often achieved through the formation of organic monolayers, often referred to as self-assembled monolayers (SAMs). While these organic monolayers have been proposed as an effective surface modification strategy, the defects in these organic monolayers compromise the effectiveness on their ability to alter surface properties. For example, in the case of passivation of microscale electronic devices, the surfaces that are not covered by the organic monolayers are susceptible to environmental stress or corrosion, which can cause detrimental failures of the devices. Traditional methods of formation of monolayers often cause many defects including formation of multilayers or micelles, physically adsorbed organic film, and/or voids. In this thesis, microwave radiation is utilized as a tool to accelerate the formation of uniform monolayers. In particular, the formation of silane based monolayers and alcohol based monolayers on silicon oxide surfaces have been extensively studied. Microwave heating, unlike the traditional heating methods, delivers the thermal energy to the substrate surfaces. It can effectively accelerate the formation of both silane and alcohol based monolayers. Alcohol based reagents, in particular, is proposed as an alternative building blocks for their widespread availability and minimal reactivity with moisture. Tuning of surface chemistry of silicon oxides have been achieved with alcohol based regents with different functional groups. Furthermore, the formation of mixed monolayers has been proposed as means of controlling oleophobicity of the silicon oxide surfaces. Finally, the film thickness of the alcohol based monolayers has been characterized with angle-resolved X-ray photoelectron spectroscopy (ARXPS). The film thickness can be precisely tuned by choosing the alcohol based reactants with particular lengths of alkyl chains. A variety of surface chemistry can be designed towards many practical applications requiring surface functionalized silicon oxides using the research presented herein.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Byron D. Gates
Department: 
Science: Department of Chemistry
Thesis type: 
(Thesis) Ph.D.

Design and Synthesis of Novel, Lead-reduced Piezo-/Ferroelectric Materials

Author: 
Date created: 
2017-08-24
Abstract: 

Relaxor-based piezo-/ferroelectric materials of complex perovskite structure, represented by (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT), have demonstrated excellent piezoelectric performance. However, they also exhibit some inherent drawbacks, such as a low Curie temperature, an even lower de-poling temperature due to the presence of a morphotropic phase boundary (MPB) region, a weak coercive field and a high content of lead, which make them unsuitable for high-temperature and high-field (power) applications and raise environmental concerns. Bismuth-based complex perovskites, such as Bi(Zn1/2Ti1/2)O3 (BZT) seem to be an interesting candidate for the replacement of lead-based compounds because, like Pb2+ ion, Bi3+ also contains the 6s2 lone electron pair which is considered to be essential for the high piezo-/ferroelectric performance in lead-based perovskite. In addition, the solid solution between BZT and PT indeed exhibits larger structural distortion resulting in a higher Curie temperature than PT. However, its coercive field is too large for the material to be poled in order to make its potentially high piezo-/ferroelectric properties useful. Faced with those issues and challenges, outcomes of this thesis are two-fold: Firstly, addition of a non-stereochemically active ion and related complex compound, namely La(Zn1/2Ti1/2)O3 (LZT), as an end-member "softens" the structures, chemical bonding and electric properties of "hard" ferroelectric materials, to achieve improved electric properties, such as giant dielectric constant, smaller coercive field and switching polarization and excellent piezoelectricity and ferroelectricity.Secondly, addition of BZT as the third component "hardens" the structures, chemical bonding and electric properties of PMN-PT binary system in order to increase its coercive field and to improve its piezo-/ferroelectricity. In particular, special efforts have been made to grow the single crystals of the PMN-PT-BZT ternary system. The studies of the single crystals provide invaluable information on the phase symmetry, domain structures, phase transitions and electric properties and allow to gain a better understanding of the relationship between crystal formation, chemical composition, phase symmetry and macroscopic properties.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Zuo-Guang Ye
Department: 
Science: Department of Chemistry
Thesis type: 
(Thesis) Ph.D.

Crystal chemistry and properties of bismuth-modified complex oxide perovskites

Date created: 
2017-08-23
Abstract: 

There is a great interest in developing new high-performance piezo-/ferroelectric materials that are lead-reduced or lead-free. This work focuses on using bismuth as a lead alternative, and studies solid solutions based on the end-member Bi(Zn2/3Nb1/3)O3 (BZN). First, ceramics of the (1-x)PbTiO3-xBi(Zn2/3Nb1/3)O3 [(1-x)PT-xBZN] solid solution were synthesized. The tetragonality (c/a ratio) and A-site displacement increase with increasing BZN content, as revealed by X-ray diffraction analysis. Dielectric measurements show that the Curie temperature TC increases with increasing BZN up to a maximum of 520 °C for the composition of x = 0.20. These results indicate the structural origin of the enhanced tetragonality and properties that arise from the increased anisotropy in the Bi-bonding environment with the increased substitution of Bi3+, with its 6s2 stereochemically active lone electron pair. Synchrotron X-ray pair distribution functions (PDFs) reveal that the tetragonal distortions are preserved down to the local scale, suggesting that studies of the average structure provide reasonable insight into the structure-property relationships in this system. These results provide guidance for designing new materials with high TC. Single crystals of (1-x)PT-xBZN were then successfully grown using the high-temperature solution growth (HTSG) method. The dielectric measurements indicate the ferroelectric-paraelectric phase transition at an average TC of 436 °C. Polarized light microscopy reveals the domain structure of tetragonal symmetry, with domain walls oriented along the <100>cub directions, and birefringence measurements as a function of temperature confirmed the first order phase transition. HTSG allows for a higher BZN content to be incorporated into the crystals in comparison to their ceramic counterpart. Moving toward lead-free materials, ceramics of a novel solid solution, (1−x)BaTiO3 xBi(Zn2/3Nb1/3)O3 (BT-BZN) were synthesized. With increasing BZN content, the materials show a decrease in tetragonality and undergo a transition to pseudocubic symmetry, which is accompanied by a crossover from normal ferroelectric to relaxor behaviour. This crossover is explained by increased cationic disorder that disrupts the ferroelectric order. Synchrotron X-ray PDF analysis reveals that all the compositions show local tetragonal distortions that decrease at larger scales to reach the average structure, demonstrating the striking difference between the local and long-range structures.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Zuo-Guang Ye
Department: 
Science: Department of Chemistry
Thesis type: 
(Thesis) Ph.D.

Development of a microfluidic platform for size-based enrichment and immunomagnetic isolation of circulating tumour cells

Date created: 
2017-08-16
Abstract: 

Cancer is a leading cause of death worldwide. Efforts to improve the longevity and quality of life of cancer patients are hindered by delays in diagnosis of tumours and treatment deficiency, as well as inaccurate prognosis that leads to unnecessary or inefficient treatments. More accurate biomarkers may address these issues and could facilitate the selection of effective treatment courses and development of new therapeutic regimens. Circulating tumour cells (CTCs), which are cancer cells that are shed from tumours and enter the vasculature, hold such a promise. Therefore, there is much interest in the isolation of CTCs from the blood. However, this is not a trivial task given the extreme scarcity of CTCs in the circulation. In this thesis, the development of a microfluidic immunomagnetic approach for isolation of CTCs is presented. First, the design, microfabrication, and experimental evaluation of a novel integrated microfluidic magnetic chip for sensitive and selective isolation of immunomagnetically labelled cancer cells from blood samples is reported. In general, to ensure the efficient immunomagnetic labelling of target cancer cells in a blood sample, an excessive number of magnetic beads should be added to the sample. When an immunomagnetically labelled sample is processed through the chip, not only cancer cells but also free magnetic beads that are not bonded to any target cells would be captured. The accumulation of these beads could disrupt the capture and visual detection of target cells. This is an inherent drawback associated with immunomagnetic cell separation systems and has rarely been addressed in the past. Therefore, the design, microfabrication, and characterization of a microfluidic filter for continuous size-based removal of free magnetic beads from immunomagnetically labelled blood samples is presented next. Connected in tandem, the two chips developed in this work form a microfluidic platform for size-based enrichment and immunomagnetic isolation of CTCs. Preclinical studies showed that the proposed approach can capture up to 75% of blood-borne prostate cancer cells at clinically-relevant low concentrations (as low as 5 cells/mL) at an acceptable throughput (200 μL/min). The retrieval and successful propagation of captured prostate cancer cells is also investigated and discussed in this thesis.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Dr. Edward J. Park
Dr. Timothy V. Beischlag
Department: 
Applied Sciences: School of Mechatronic Systems Engineering
Thesis type: 
(Thesis) Ph.D.

Covalent surface modification of silicon oxides

Date created: 
2017-08-30
Abstract: 

Microwave radiation was utilized as a tool to modify surface properties of silicon oxides. Covalent surface modification of silicon oxides has been widely pursued in the areas of material science, electronics, microfluidics, biology, and separation science. Chemical surface modifications are often achieved through the formation of organic monolayers, often referred to as self-assembled monolayers (SAMs). While these organic monolayers have been proposed as an effective surface modification strategy, the defects in these organic monolayers compromise the effectiveness on their ability to alter surface properties. For example, in the case of passivation of microscale electronic devices, the surfaces that are not covered by the organic monolayers are susceptible to environmental stress or corrosion, which can cause detrimental failures of the devices. Traditional methods of formation of monolayers often cause many defects including formation of multilayers or micelles, physically adsorbed organic film, and/or voids. In this thesis, microwave radiation is utilized as a tool to accelerate the formation of uniform monolayers. In particular, the formation of silane based monolayers and alcohol based monolayers on silicon oxide surfaces have been extensively studied. Microwave heating, unlike the traditional heating methods, delivers the thermal energy to the substrate surfaces. It can effectively accelerate the formation of both silane and alcohol based monolayers. Alcohol based reagents, in particular, is proposed as an alternative building blocks for their widespread availability and minimal reactivity with moisture. Tuning of surface chemistry of silicon oxides have been achieved with alcohol based regents with different functional groups. Furthermore, the formation of mixed monolayers has been proposed as means of controlling oleophobicity of the silicon oxide surfaces. Finally, the film thickness of the alcohol based monolayers has been characterized with angle-resolved X-ray photoelectron spectroscopy (ARXPS). The film thickness can be precisely tuned by choosing the alcohol based reactants with particular lengths of alkyl chains. A variety of surface chemistry can be designed towards many practical applications requiring surface functionalized silicon oxides using the research presented herein.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Byron D. Gates
Department: 
Science: Department of Chemistry
Thesis type: 
(Thesis) Ph.D.

Design and Synthesis of Novel, Lead-reduced Piezo-/Ferroelectric Materials

Author: 
Date created: 
2017-08-24
Abstract: 

Relaxor-based piezo-/ferroelectric materials of complex perovskite structure, represented by (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT), have demonstrated excellent piezoelectric performance. However, they also exhibit some inherent drawbacks, such as a low Curie temperature, an even lower de-poling temperature due to the presence of a morphotropic phase boundary (MPB) region, a weak coercive field and a high content of lead, which make them unsuitable for high-temperature and high-field (power) applications and raise environmental concerns. Bismuth-based complex perovskites, such as Bi(Zn1/2Ti1/2)O3 (BZT) seem to be an interesting candidate for the replacement of lead-based compounds because, like Pb2+ ion, Bi3+ also contains the 6s2 lone electron pair which is considered to be essential for the high piezo-/ferroelectric performance in lead-based perovskite. In addition, the solid solution between BZT and PT indeed exhibits larger structural distortion resulting in a higher Curie temperature than PT. However, its coercive field is too large for the material to be poled in order to make its potentially high piezo-/ferroelectric properties useful. Faced with those issues and challenges, outcomes of this thesis are two-fold: Firstly, addition of a non-stereochemically active ion and related complex compound, namely La(Zn1/2Ti1/2)O3 (LZT), as an end-member "softens" the structures, chemical bonding and electric properties of "hard" ferroelectric materials, to achieve improved electric properties, such as giant dielectric constant, smaller coercive field and switching polarization and excellent piezoelectricity and ferroelectricity.Secondly, addition of BZT as the third component "hardens" the structures, chemical bonding and electric properties of PMN-PT binary system in order to increase its coercive field and to improve its piezo-/ferroelectricity. In particular, special efforts have been made to grow the single crystals of the PMN-PT-BZT ternary system. The studies of the single crystals provide invaluable information on the phase symmetry, domain structures, phase transitions and electric properties and allow to gain a better understanding of the relationship between crystal formation, chemical composition, phase symmetry and macroscopic properties.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Zuo-Guang Ye
Department: 
Science: Department of Chemistry
Thesis type: 
(Thesis) Ph.D.

Crystal chemistry and properties of bismuth-modified complex oxide perovskites

Date created: 
2017-08-23
Abstract: 

There is a great interest in developing new high-performance piezo-/ferroelectric materials that are lead-reduced or lead-free. This work focuses on using bismuth as a lead alternative, and studies solid solutions based on the end-member Bi(Zn2/3Nb1/3)O3 (BZN). First, ceramics of the (1-x)PbTiO3-xBi(Zn2/3Nb1/3)O3 [(1-x)PT-xBZN] solid solution were synthesized. The tetragonality (c/a ratio) and A-site displacement increase with increasing BZN content, as revealed by X-ray diffraction analysis. Dielectric measurements show that the Curie temperature TC increases with increasing BZN up to a maximum of 520 °C for the composition of x = 0.20. These results indicate the structural origin of the enhanced tetragonality and properties that arise from the increased anisotropy in the Bi-bonding environment with the increased substitution of Bi3+, with its 6s2 stereochemically active lone electron pair. Synchrotron X-ray pair distribution functions (PDFs) reveal that the tetragonal distortions are preserved down to the local scale, suggesting that studies of the average structure provide reasonable insight into the structure-property relationships in this system. These results provide guidance for designing new materials with high TC. Single crystals of (1-x)PT-xBZN were then successfully grown using the high-temperature solution growth (HTSG) method. The dielectric measurements indicate the ferroelectric-paraelectric phase transition at an average TC of 436 °C. Polarized light microscopy reveals the domain structure of tetragonal symmetry, with domain walls oriented along the <100>cub directions, and birefringence measurements as a function of temperature confirmed the first order phase transition. HTSG allows for a higher BZN content to be incorporated into the crystals in comparison to their ceramic counterpart. Moving toward lead-free materials, ceramics of a novel solid solution, (1−x)BaTiO3 xBi(Zn2/3Nb1/3)O3 (BT-BZN) were synthesized. With increasing BZN content, the materials show a decrease in tetragonality and undergo a transition to pseudocubic symmetry, which is accompanied by a crossover from normal ferroelectric to relaxor behaviour. This crossover is explained by increased cationic disorder that disrupts the ferroelectric order. Synchrotron X-ray PDF analysis reveals that all the compositions show local tetragonal distortions that decrease at larger scales to reach the average structure, demonstrating the striking difference between the local and long-range structures.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Zuo-Guang Ye
Department: 
Science: Department of Chemistry
Thesis type: 
(Thesis) Ph.D.

Development of a microfluidic platform for size-based enrichment and immunomagnetic isolation of circulating tumour cells

Date created: 
2017-08-16
Abstract: 

Cancer is a leading cause of death worldwide. Efforts to improve the longevity and quality of life of cancer patients are hindered by delays in diagnosis of tumours and treatment deficiency, as well as inaccurate prognosis that leads to unnecessary or inefficient treatments. More accurate biomarkers may address these issues and could facilitate the selection of effective treatment courses and development of new therapeutic regimens. Circulating tumour cells (CTCs), which are cancer cells that are shed from tumours and enter the vasculature, hold such a promise. Therefore, there is much interest in the isolation of CTCs from the blood. However, this is not a trivial task given the extreme scarcity of CTCs in the circulation. In this thesis, the development of a microfluidic immunomagnetic approach for isolation of CTCs is presented. First, the design, microfabrication, and experimental evaluation of a novel integrated microfluidic magnetic chip for sensitive and selective isolation of immunomagnetically labelled cancer cells from blood samples is reported. In general, to ensure the efficient immunomagnetic labelling of target cancer cells in a blood sample, an excessive number of magnetic beads should be added to the sample. When an immunomagnetically labelled sample is processed through the chip, not only cancer cells but also free magnetic beads that are not bonded to any target cells would be captured. The accumulation of these beads could disrupt the capture and visual detection of target cells. This is an inherent drawback associated with immunomagnetic cell separation systems and has rarely been addressed in the past. Therefore, the design, microfabrication, and characterization of a microfluidic filter for continuous size-based removal of free magnetic beads from immunomagnetically labelled blood samples is presented next. Connected in tandem, the two chips developed in this work form a microfluidic platform for size-based enrichment and immunomagnetic isolation of CTCs. Preclinical studies showed that the proposed approach can capture up to 75% of blood-borne prostate cancer cells at clinically-relevant low concentrations (as low as 5 cells/mL) at an acceptable throughput (200 μL/min). The retrieval and successful propagation of captured prostate cancer cells is also investigated and discussed in this thesis.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Dr. Edward J. Park
Dr. Timothy V. Beischlag
Department: 
Applied Sciences: School of Mechatronic Systems Engineering
Thesis type: 
(Thesis) Ph.D.

Covalent surface modification of silicon oxides

Date created: 
2017-08-30
Abstract: 

Microwave radiation was utilized as a tool to modify surface properties of silicon oxides. Covalent surface modification of silicon oxides has been widely pursued in the areas of material science, electronics, microfluidics, biology, and separation science. Chemical surface modifications are often achieved through the formation of organic monolayers, often referred to as self-assembled monolayers (SAMs). While these organic monolayers have been proposed as an effective surface modification strategy, the defects in these organic monolayers compromise the effectiveness on their ability to alter surface properties. For example, in the case of passivation of microscale electronic devices, the surfaces that are not covered by the organic monolayers are susceptible to environmental stress or corrosion, which can cause detrimental failures of the devices. Traditional methods of formation of monolayers often cause many defects including formation of multilayers or micelles, physically adsorbed organic film, and/or voids. In this thesis, microwave radiation is utilized as a tool to accelerate the formation of uniform monolayers. In particular, the formation of silane based monolayers and alcohol based monolayers on silicon oxide surfaces have been extensively studied. Microwave heating, unlike the traditional heating methods, delivers the thermal energy to the substrate surfaces. It can effectively accelerate the formation of both silane and alcohol based monolayers. Alcohol based reagents, in particular, is proposed as an alternative building blocks for their widespread availability and minimal reactivity with moisture. Tuning of surface chemistry of silicon oxides have been achieved with alcohol based regents with different functional groups. Furthermore, the formation of mixed monolayers has been proposed as means of controlling oleophobicity of the silicon oxide surfaces. Finally, the film thickness of the alcohol based monolayers has been characterized with angle-resolved X-ray photoelectron spectroscopy (ARXPS). The film thickness can be precisely tuned by choosing the alcohol based reactants with particular lengths of alkyl chains. A variety of surface chemistry can be designed towards many practical applications requiring surface functionalized silicon oxides using the research presented herein.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Byron D. Gates
Department: 
Science: Department of Chemistry
Thesis type: 
(Thesis) Ph.D.

Design and Synthesis of Novel, Lead-reduced Piezo-/Ferroelectric Materials

Author: 
Date created: 
2017-08-24
Abstract: 

Relaxor-based piezo-/ferroelectric materials of complex perovskite structure, represented by (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT), have demonstrated excellent piezoelectric performance. However, they also exhibit some inherent drawbacks, such as a low Curie temperature, an even lower de-poling temperature due to the presence of a morphotropic phase boundary (MPB) region, a weak coercive field and a high content of lead, which make them unsuitable for high-temperature and high-field (power) applications and raise environmental concerns. Bismuth-based complex perovskites, such as Bi(Zn1/2Ti1/2)O3 (BZT) seem to be an interesting candidate for the replacement of lead-based compounds because, like Pb2+ ion, Bi3+ also contains the 6s2 lone electron pair which is considered to be essential for the high piezo-/ferroelectric performance in lead-based perovskite. In addition, the solid solution between BZT and PT indeed exhibits larger structural distortion resulting in a higher Curie temperature than PT. However, its coercive field is too large for the material to be poled in order to make its potentially high piezo-/ferroelectric properties useful. Faced with those issues and challenges, outcomes of this thesis are two-fold: Firstly, addition of a non-stereochemically active ion and related complex compound, namely La(Zn1/2Ti1/2)O3 (LZT), as an end-member "softens" the structures, chemical bonding and electric properties of "hard" ferroelectric materials, to achieve improved electric properties, such as giant dielectric constant, smaller coercive field and switching polarization and excellent piezoelectricity and ferroelectricity.Secondly, addition of BZT as the third component "hardens" the structures, chemical bonding and electric properties of PMN-PT binary system in order to increase its coercive field and to improve its piezo-/ferroelectricity. In particular, special efforts have been made to grow the single crystals of the PMN-PT-BZT ternary system. The studies of the single crystals provide invaluable information on the phase symmetry, domain structures, phase transitions and electric properties and allow to gain a better understanding of the relationship between crystal formation, chemical composition, phase symmetry and macroscopic properties.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Zuo-Guang Ye
Department: 
Science: Department of Chemistry
Thesis type: 
(Thesis) Ph.D.