Browsing by Author "Shimizu, George"

Now showing 1 - 18 of 18
  • Thumbnail Image
    ItemEmbargo
    Aqueous Batteries for Large-Scale Energy Storage and Carbon Removal Applications
    (2024-08-08) Iyapazham Vaigunda Suba, Prathap; Thangadurai, Venkataraman; Karan, Kunal; Shi, Yujun; Shimizu, George; Roberts, Edward (Ted) PL; Kuss, Christian
    Aqueous batteries are safe and environmentally friendly energy storage devices, suitable for intermittent renewable energy sources and carbon removal applications. However, these batteries are hindered by the low operating potential which leads to limitation in energy density. In this thesis, aqueous battery chemistry concept is applied for two different applications such as: a redox-flow battery transformation to an all-gel battery and a seawater-battery for carbon removal application. Flexible, scalable, and low-cost energy storage solutions are required for the widespread use of renewable energy and the mitigation of climate change. In this regard, redox flow batteries are scalable due to their ability to decouple power and energy; however, the commercial applications of these batteries are limited by expensive ion-selective membranes. An auxiliary electrode (AE) mediated membrane-free redox battery concept was demonstrated and different AE materials were screened for their application in vanadium based redox battery. In an AE mediated membrane-free vanadium redox battery, the Coulombic efficiency of the system was limited to 36%. The low Coulombic efficiency observed in AE based battery was mitigated by using a gel-battery design approach in which Bi/BiOCl and V4+/V5+ redox couples were utilized in a gel-based architecture. The Bi/BiOCl conversion reaction based redox couple was demonstrated to work reversibly against traditional vanadium-based redox pair in an aqueous electrolyte. Redox active materials in this cell design are in the gel form, and a traditional membrane or a separator is not required. This proof-of-concept all-gel battery delivered 0.9 V with a volumetric energy density of 22.14 Wh L-1. For carbon removal applications, an aqueous battery with seawater electrolyte was studied. In this battery, iron phosphate (FePO4) electrode was utilized to manipulate ions in different seawater aliquots to generate sodium hydroxide, a base to use in ocean alkalinity enhancement. Electrochemical analysis, Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS) revealed that Na+ ions can be reversibly intercalated in FePO4. The alkalinity titration was used to determine the increase in alkalinity of seawater. The results indicated that a 16% increase in alkalinity was achieved in 15 ml of synthetic seawater over a period of 3.5 hours (one cycle) using the FePO4 electrode coupled with Pt electrode. A seawater electrolyte based battery with Ni(OH)2/NiOOH redox reaction in place of Pt electrode coupled with FePO4 electrode was studied. The battery delivered a potential of 0.6 V and the galvanostatic cycling experiments revealed that the battery can operate in seawater electrolyte for 50 cycles with 94% Coulombic efficiency.
  • Thumbnail Image
    ItemEmbargo
    Aqueous Chemical Solution Deposition of Epitaxial Lead-Free Ferroelectric Sodium Potassium Niobate (KNN) thin films
    (2023-05-12) Mohammed, Ahmed Zaher; Dolgos, Michelle; Birss, Viola Ingrid; Shi, Yujun; Roberts, Edward; Shimizu, George
    Potassium Sodium Niobate (KxNa1-xNbO3, KNN) thin films were fabricated on SrTiO3 (STO) substrates using an environmentally friendly aqueous Chemical Solution Deposition (CSD) approach, employing water-soluble Na, K, and Nb polyoxometalate precursors. This green route for KNN thin film fabrication offers reduced environmental impact and potential industrial scalability. The annealing recipe was optimized through a detailed investigation, finding that a one-minute annealing at 700°C after each deposition yielded the best structural properties. The impact of varying the K+/Na+ stoichiometry on the films' structural properties was systematically examined. The investigation demonstrated a trend between the K+/Na+ molar ratio in the precursor solution and the strain-state and lattice parameters of the resulting films, suggesting adding 50% excess potassium in the precursor solution is promising for optimal ferroelectric performance. Leveraging the versatility of the aqueous synthesis, lithium was incorporated as a dopant in the precursor solution. Different Li concentrations were investigated, and it was determined that a 6% Li concentration improved the films' structure compared to undoped samples. This demonstrates the potential of aqueous deposition for incorporating dopants to enhance material properties. The study further highlighted the potential for strain engineering and additional dopant incorporation using the aqueous CSD method, opening up avenues for further exploration and optimization of KNN thin films' properties.
  • Thumbnail Image
    ItemOpen Access
    Customizing Nanoparticles for Environmental Applications - Wastewater Treatment and Valuable Metals Extraction
    (2020-10-06) Nafie, Ghada Hamdy; Pereira-Almao, Pedro; Maini, Brij; Moore, Robert Gorden; De Visscher, Alex; Shimizu, George; De Lasa, Hugo
    This thesis focuses on two related objectives: the remediation of the environmental footprint of oil sands mining and increasing the efficiency of new energy technologies. Both aim to design and develop nanoparticles for energy and environment applications in order to ensure the sustainability of the global energy resources. Canada produces large volumes of wastewater as a result of mining and other industrial operations. This water contains significant amounts of oil and fines consisting of silt and clays that form a stable colloidal suspension, which presents a challenge to settling. Classical flocculants were proven to be ineffective or costly in the treatment of this water. Tailor-made grafted acrylamide monomer pyroxene nanoparticles (GAM) were prepared and characterized using FTIR, TGA, BET, XRD and SEM. The prepared nanoparticles were then employed as efficient environmentally friendly flocculants for enhanced particle settling. After settling, the turbidity of the supernatant and the capillary suction time of the subnatent were measured. GAM was compared to the commonly used flocculants and were found to enhance particle settling and solid dewaterability. Thus, presenting one material that serves as a practical wastewater treatment solution.The second part of this thesis focuses on the selective recovery of metals present in water sources. Advances in lithium extraction technologies are creating alternative energy possibilities with the goal to exploit the various natural resources, while lowering the carbon and other environmental footprints. However, efficiency and effective extraction remains an ongoing challenge. A lithium titanate nanomaterial was designed and prepared to recover lithium from water sources. Lithium titanate was prepared in the nano range using a hydrothermal method followed by thermal treatment. The material was characterized using XRD, TGA and BET. Experiments were conducted to test the ability of lithium to exit the prepared selective nanostructure. After exposing the nanomaterial to acids for ionic exchange, the supernatant was recovered and tested using an inductively coupled plasma-atomic spectroscopy (ICP). The solids were dried and tested using the XRD to confirm their crystalline structure. This research presents promising applications for the past and future energy market that ensures the sustainability of our natural resources while reducing environmental impacts.
  • Thumbnail Image
    ItemOpen Access
    Designing Electrolytes and Electrode-electrolyte Interfaces for Next-Generation Lithium Metal Batteries
    (2021-08-26) Zhou, Chengtian; Thangadurai, Venkataraman; Shimizu, George; Yujun, Shi
    State-of-the-art lithium-ion batteries (LIBs) are approaching their energy density limits and thus may not be the answer to the ever-increasing demand for higher specific energy density in today’s energy storage and power applications. Li metal is considered the ultimate anode material due to its ultra-high specific capacity 3860 mAh g-1, more than 10 times higher than lithiated graphite. Solid-state electrolytes (SSEs) provide a potential solution to advance the performance of Li metal batteries (LMBs). However, the device integration of SSEs, especially Li-stuffed garnet, is exceptionally challenging. Another critical aspect for LMBs is to limit excess Li metal at the anode. In this thesis, the interface between Li metal anode and Li-stuffed garnet Li6.5La2.9Ba0.1Zr0.4Ta1.6O12 is investigated. Poor contact between Li and garnet is identified as the reason for high interfacial resistance. A viable surfactant-assisted wet chemical method to deposit ZnO layer on Li-stuffed garnet is reported to reduce the interfacial resistance to as low as 10 Ω cm2. A composite polymer-ceramic electrolyte (CPE) for room temperature solid-state Li-S battery (SSLSB) is demonstrated. The CPE has low interfacial resistance against both Li metal anode and sulfur cathode. An engineered sulfur-Ketjen black(S@KB) composite cathode is coupled with CPE to demonstrate a SSLSB with a pronounced specific capacity of 1108 mAh g−1 and areal capacity of 1.77 mAh cm−2. As CPE is prepared by a solution casting method, lean solvent confinement affects the morphological structure and ionic conductivity of CPE. A higher amount of solvent retention leads to higher ionic conductivity but at the cost of membranes’ mechanical properties. In order to study anode-free Li-metal batteries (AFLMBs), a special coin cell configuration is designed with high compression. The high pressure leads to more stable cycling performance, providing a more accurate assessment of AFLMBs. A carbonate-glyme hybrid electrolyte for AFLMB is demonstrated with capacity retention of 73% for 50 cycles. The hybrid electrolyte possesses a unique solvation structure, where diglyme solvates both Li-ions and film-forming additive, while carbonates dilute the mixture, enabling facile ion migrations.
  • Thumbnail Image
    ItemOpen Access
    Designing Proton Conductivity in a Metal-Organic Framework from a Molecular Scale
    (2014-06-23) Kim, SiRim; Shimizu, George
    Two design strategies were investigated to enhance proton conductivity of a proton conducting MOF named β-PCMOF2. First design strategy was isomorphous ligand replacement where an entire C3-symmetric trisulfonate ligand was substituted with a C3-symmetric tris(hydrogen phosphonate) ligand to yield PCMOF2½, which had its proton conductivity raised 1.5 orders of magnitude, to 2.1 × 10-2 S cm-1 at 85 °C and 90% relative humidity compared to the parent material, while maintaining the parent MOF structure. To further enhance the proton conductivity of PCMOF2½, isomorphous ligand replacement was paired with heterocycle doping. Seven new PCMOFs were synthesized and investigated. One resulting material, PCMOF2½(Pyrazole), had its proton conductivity raised 1.9 orders of magnitude compared to the parent material, to 1.1 × 10-1 S cm-1 at 85 °C and 90% relative humidity, while maintaining the parent MOF structure. In addition, the exact mechanism of isomorphous ligand replacement synthesis was elucidated to be a thermodynamically driven solid state reaction.
  • Thumbnail Image
    ItemOpen Access
    Developing Porous Water Stable Metal Phosphonates for CO2 Capture Applications
    (2016) Mah, Roger K; Shimizu, George; Marriott, Robert; Thangadurai, Venkataraman; Maeda, Kazuyuki
    Porous solid sorbents have emerged as a promising class of materials for CO2 capture applications. A subclass of solid sorbents, metal-organic frameworks (MOFs), has been thoroughly investigated towards implementation into CO2 capture systems, owing to high tailorability from an inherently modular nature. The crux of conventional carboxylate-based MOFs has been stability against hydrolytic cleavage in the presence of elevated temperature and humidity. This thesis investigated the development of water stable phosphonate MOFs using the trigonal 1,3,5-tris(phosphonophenyl)benzene (H6L1) as the ligand coordinated to trivalent and tetravalent metals. The first metal investigated was Sn4+, which required significant efforts towards enhancing crystallinity. An ordered material for SnH2L1 (CALF-28) was achieved through solvothermal reaction followed a humidity exposure step. After the harsh humidity treatment, CALF-28 remained porous albeit with a decreased surface area. The second framework investigated utilized La3+ producing single crystals of LaH3L1 (CALF-29). Upon exposure to mild humidity treatment, CALF-29 decomposed resulting in significant loss of surface area revealing CALF-29 had no stability against hydrolytic cleavage. The final metal investigated with L1 was Zr4+ to produce ZrH2L1 (CALF-31). After repeated exposures to harsh humidity, CALF-31 remained porous with only a minor surface area drop. CALF-28 and CALF-31 were evaluated as potential CO2 capture sorbents and revealed the strengths of solid sorbents against the traditional monoethanolamine benchmark using calculations developed during this work. Finally, coordination of 1,3,5-tris(phosphonobiphenyl)benzene (H6L2) with Zr4+ provided insights into the effect of extending the L1 ligand. From the preliminary results, the potential advantages of H6L2, namely increased functionalization sites to accommodate polarizing groups, were discussed in the context of enhancing the CO2 capture potential of frameworks formed using trigonal trisphosphonates.
  • Thumbnail Image
    ItemOpen Access
    Developing Structure-Property Relationships for N-Annulated Perylene Diimides
    (2021-05-12) Cann, Jonathan Robert; Welch, Gregory; Trudel, Simon; Derksen, Darren; Maly, Kenneth; Shimizu, George
    This thesis presents structure-property relationships of a series of functionalized N-annulated perylene diimide chromophores. Chapter one introduces the perylene diimide (PDI) chromophore and covers functionalization through bay annulation. Chapter two of this thesis explores the impact of electron deficient nitro groups on N-annulated PDI (NPDI) and further evaluates the impact of varied alkyl substituents (M2-M4). Chapter three explores a set of NPDI dimers and the importance of the dihedral angle between the two fragments (M5-M7). Chapter four explores the modified the optical and electronic properties of M7 by incorporating small organic chromophores between the two halves of the NPDI dimer (M8-M10). Chapter five explores derivatives of the NPDI where small electron rich aryl groups have been appended to the periphery (M11-M15). Finally, in chapter six a pair of highly related NPDI tetramers (M17, M17) are examined and found to have unusually disparate properties. Each of these derivatives was characterized by 1H NMR, CV, UV-Vis absorption and emission as well as X-Ray crystallography and spectroelectrochemistry as needed.
  • Thumbnail Image
    ItemOpen Access
    Development of Phosphonate Monoester-Based Coordination Frameworks
    (2018-04-26) Gelfand, Benjamin; Shimizu, George; Roesler, Roland; Marriott, Robert; Mahinpey, Nader; Li, Qiaowei
    This thesis emphasizes the development and gas sorption properties of metal-phosphonate monoester compounds. The first chapter discusses hydrolytic stability in metal-organic frameworks, with a focus on the types of hydrolytic exposure and assessing stability. The next four chapters focus on the synthesis and characterization of seven new coordination compounds. The first three compounds (2-4) are compared and contrasted to a pillared-layered material consisting of barium and a linear diphosphonate (1); 2 is based on a planar triphosphonate analogue, 3 is based on a linear diphosphonate bis(monoester), and 4 is based on a planar triphosphonate tris(monoester). Though none of these materials have any function, comparisons of 1-4 has allowed several structural trends to be determined, notably that both the change from diphosphonate to triphosphonate and from phosphonate to phosphonate monoester result in the building units in 1 being truncated. 5 is based on the same linear ditopic phosphonate monoester as 3 but with copper(II) and is insoluble and stable in water, a feature not often seen with similar building units. 6 was synthesized based on the stability and building unit found in 5 but with the planar tritopic phosphonate monoester used in 4. 6 is a permanently porous material with a surface area exceeding 300 m^2/g. Though the same level of stability is not found in 6 as in 5, 6 was found to retain its crystallinity and porosity even in steam-like conditions. In an attempt to increase the porosity of 6, a longer linker was synthesized and used to make 7 and 8. 8 was found to be highly porous (>1000 m^2/g) and it was also discovered that one of the esters in 8 can be systematically hydrolyzed in situ in order to increase the materials affinity for CO2. Furthermore, experimental results and simulations for 8 conclude that the removal of these esters is randomly distributed in the framework, rather than being clustered. Though 7 is non-porous and no function has been found, it is made from nearly identical building units to 8, allowing for potential synthetic factors to be considered and discussed.
  • Thumbnail Image
    ItemOpen Access
    Greenhouse Gas Detection Using Metal Oxides: Experiments and Challenges
    (2016) Mulmi, Suresh; Thangadurai, Venkataraman; Etsell, Thomas; Birss, Viola; Shimizu, George; Almao, Pedro
    The primary goal of this study has been to develop the mixed ion-electron conductors (MIECs) to illustrate their potential applications for real-time detection of CO2 and SO2 in ppm level. For this purpose, B-site substituted ordered perovskite-type MIECs Ba2(Ca0.66Nb1.34-xFex)O6-δ (x = 0, 0.34, 0.66, 1) (BCNF) and B-site disordered MIECs Ba(Mg0.33Nb0.67-xFex)O3-δ (x = 0, 0.17, 0.33, 0.50) (BMNF) were successfully synthesized by conventional solid state method in air at 1400 °C. Fe-substitution in BCNFs and BMNFs increased the total conductivity, while in-situ high temperature (25–800 °C) PXRD results under CO2 exhibited excellent chemical stability. The resistance of the MIEC ceramics significantly decreased upon exposure to CO2 gas in synthetic air. Response time (t90) of 4 min at 700 °C was obtained with higher Fe-content samples with thickness of 2 mm and diameter of 10 mm. To develop a fundamental understanding of the sensing mechanism, Fe-doped BCNFs were investigated. Firstly, p-type bulk semiconducting nature of BCNF was explored using AC impedance spectroscope and DC measurements using different p(CO2) and p(O2). Secondly, BCNFs were further studied using SEM coupled with EDX, 57Fe Mössbauer spectroscopy, Raman spectroscopy, TPO-MS. Upon CO2 exposure, CO2 was found to be catalytically reduced to C and can be explained using oxidation of Fe3+ to Fe4+/ Fe5+. Thus, the increase in total conductivity upon CO2 exposure is interpreted by the deposition of conducting graphitic C, which was confirmed using Raman spectra and TPO-MS. Furthermore; SEM/EDX results displayed the deposited C due to the reduction of CO2. For SO2 sensors, SnO2-TiO2 (S-T) composites with different molar ratios were also prepared at 700 °C in air to selectively monitor ppm level of SO2 in air. For S-T composites, the chemical stability were tested using PXRD, SEM and EDX, while the sensing performance was measured at different temperatures using various concentrations of SO2 (10-100 ppm). The highest sensitivity was obtained from a mixture of 25 mol.% of SnO2 and 75 mol.% ofTiO2 at 450 °C with t90 of ~5 mins. S-T composite sensors behave as a resistive-type SO2 sensor and sensing mechanism has been explained through the band structure model.
  • Thumbnail Image
    ItemOpen Access
    Investigation of electrical properties of perovskite-type metal oxides
    (2024-05-14) Selvakumar, Bhavadharini; Thangadurai, Venkataraman; Dolgos, Michelle; Shimizu, George; Sutherland, Todd
    Materials development has led to the growth of several technologies to reduce carbon footprints and to develop a sustainable environment. These strategies have led to the advancement of several renewable energy storage and conversion systems like fuel cells, batteries, solar cells, and capacitors that have been beneficial and environmentally benign. Moving towards clean energy includes using renewable energy sources and safe and sustainable materials for energy applications. However, the existing issues with materials development are the use of expensive and scarcely available raw materials, complex and multiple steps in material processing, and not exploring new family of materials. This thesis addresses the use of studying the electrical properties of a family of materials known as perovskite-type oxides. The thesis focuses on the solid-state synthesis of transition metal doped double perovskite-type Ba2Ca0.67Nb1.33-xCuxO6-δ (x = 0, 0.05, 0.13 and 0.26) Ba2Ca0.67-xCuxNb1.33O6-δ (x = 0 and 0.13) and BaY0.5Nb0.5O3 (BYN). The study includes the morphology of these materials, investigation of the electrical and dielectric properties of the above materials in different atmospheres, and their chemical stability in CO2 and moisture containing environments. Among the compositions studied, Ba2Ca0.67Nb1.2Cu0.13O6-δ shows the highest conductivity of 4.6 × 10-4 Scm-1 in dry air at 600 ˚C. The dielectric studies were also conducted among the investigated samples, the highest dielectric constant exhibited by Ba2Ca0.67Nb1.2Cu0.13O6-δ (x = 0.13) was 587 and dielectric loss of 2 at 106 Hz at 500 ˚C in air. In general, Ba2Ca0.67Nb1.2Cu0.13O6-δ (x = 0.13) shows highest dielectric constant values in the range of ~100 – 600 and lowest dielectric loss exhibited by Ba2Ca0.67Nb1.28Cu0.05O6-δ (x = 0.05) was ~0.3 – 0.6 at 500 ˚C in various atmospheres. The second part of the thesis focuses on the synthesis of multi-element doped BaY0.5Nb0.5O3 (BYN) perovskite oxides, where alkaline earth and rare earth elements were doped in the A- and B-site of BYN. Synthesis and structural optimizations were also carried out to come up with pure single-phase materials. Out of all the compositions synthesized, (Ba1-xA’x)(Y1/2Nb1/2-y-zM’yM”z)O3-δ (A’ = Sr, Ca; M’ = Mg and M” = Ni) (x = 0, 0.5; y = 0, 0.1; z = 0, 0.05, 0.1), the PXRD pattern reveals the crystallization of only BaY0.5Nb0.5O3 and Ba0.5Sr0.5Y0.5Nb0.4Mg0.1O3-δ in a cubic crystal system with Pm3̅m space group. Although, the crystal formation was successful for these compositions, several attempts were made to modify and optimize the synthesis and sintering conditions. The surface morphology of the pellet samples shows BaY0.5Nb0.5O3 containing more pores and grain boundaries than that of Ba0.5Sr0.5Y0.5Nb0.4Mg0.1O3-δ, emphasizing better particles formed in doped BYN. The chemical stability of these compositions in CO2- and moisture-containing environment shows their potential to be used in devices for energy applications that are present in such operating conditions.
  • Thumbnail Image
    ItemOpen Access
    MOFs as proton conductors - challenges and opportunities
    (2014-08-21) Shimizu, George; Ramaswamy, P; Wong, N
  • Thumbnail Image
    ItemEmbargo
    Molecular Imprinting of Metal-Organic frameworks (MOFs) for Selective Separations
    (2022-04) Evans, David; Shimizu, George; Ling, Chang-Chun; Jalilehvand, Farideh
    This thesis explores the idea of using chromium(III) ions and an orthogonal polyaromatic phosphonate linker to produce a stable metal-organic framework (MOF) for the separation of xylene isomers. This began by creating a charge-assisted hydrogen-bonded metal-organic framework (HMOF) that uses weaker interactions to hold the framework together. The orthogonalized phosphonate creates pores due to its bulky nature that prevents efficient ligand packing. In tandem, this allows for the inclusion of guest molecules within the HMOF structure. Once the guest-incorporated structure is formed, heating can remove water molecules from the HMOF to form coordination bonds between the chromium and the phosphonate ligand. This dehydration locks the template in place as it converts to a coordinated metal-organic framework (MOF). The template for this technique is of great importance since you can imprint the pore to a specific molecule. For this study, the xylene isomers ortho, meta, and para, were looked at for separation. The separation of xylenes is of great importance since the different isomers are used in a variety of different applications, such as para-xylene for terephthalic acid (TPA) to manufacture polyethylene terephthalate (PET). The problem with separating xylenes is how expensive the separation is. Since the xylene isomers have very similar boiling points and sizes, either cryogenic distillation or recrystallization has to be performed to acquire a pure product. On this note, three different chromium phosphonate HMOFs were developed. The first structure incorporated a para-xylene template (HCALF 50αP) while the second structure incorporated ortho-xylene as the template (HCALF 50α)). The final structure used meta-xylene as a template (HCALF 50M). These HMOFs were dehydrated into the corresponding MOF structures and used to test selective xylene separation. Initial studies using a static separation and nuclear magnetic resonance (NMR) spectroscopy were conducted followed by a flow-through separation using high-pressure liquid chromatography (HPLC) and a MOF-packed column. The findings were intriguing showing selectivity towards para-xylene for some of the materials. Most notable is that HCALF 50βM showed anti-selectivity towards para-xylene allowing it to flow freely through and making it easier to collect.
  • Thumbnail Image
    ItemOpen Access
    Multiple-scale wettability and imbibition in engineered and natural nanoporous media
    (2021-06) Pan, Bin; Clarkson, Christopher; Birss, Viola; Bryant, Steven; Marriott, Robert; Shimizu, George; Kovscek, Anthony
    Wettability is an important parameter influencing imbibition into nanoporous media, and therefore, affects many processes in the fields of engineering and science. However, there are many challenges in quantifying wettability and imbibition in natural and heterogeneous nanoporous media. In order to provide fundamental understanding of wettability and imbibition in nanoporous media, in this dissertation, an engineered nanoporous carbon scaffold (NCS) with controllable wettability and pore geometry was used to investigate multi-scale wettability and imbibition (including spontaneous and electrocapillary) dynamics. The learnings obtained from studying this engineered material were subsequently applied to the evaluation of multi-scale wettability and spontaneous imbibition in unconventional hydrocarbon reservoirs. For spontaneous imbibition of nanoliter droplets in NCS and tight rocks, it was found that 1) spontaneous imbibition can take place in hydrophobic nanoporous media; 2) contact line remains pinned during the entire droplet lifetime; and 3) the estimated pore- contact angle (from new theoretical models) is larger than the measured macro- and micro- contact angles. For spontaneous imbibition of bulk liquid in NCS and shale/tight rocks, the following results were obtained: 1) a larger pore size leads to faster imbibition; 2) imbibition volume is linear with square root of time until front breakthrough; 3) a small amount of evaporation causes a deviation from this linear relationship; and 4) pore- contact angle is required for upscaling spontaneous imbibition data from laboratory to reservoir scales. Further, two theoretical models were developed to characterize these dynamics in the presence and absence of evaporation, respectively. Additionally, two new methods were developed to examine impacts of osmotic pressure and surfactant on fracturing fluid loss, respectively, which mitigated the effects of capillary pressure and rock heterogeneity. For electrocapillary imbibition of 1 M KCl electrolyte in hydrophobic NCS, two phenomena were observed: a dependence of electrocapillary imbibition on voltage polarity, and an appearance of electro-dewetting at negative voltages. Fundamentally, this dissertation advances the understanding of multi-scale wettability and imbibition physics in nanoporous media, and fracturing fluid loss mechanisms in unconventional reservoirs. Practically, this thesis provides useful guidance on fracturing fluid loss control and prediction in unconventional reservoirs, and on fluid manipulation at nanoscales.
  • Thumbnail Image
    ItemOpen Access
    Parameterizing and grading hydrolytic stability in metal-organic frameworks
    (Dalton Transactions, 2016) Shimizu, George; Gelfand, Ben
    Metal–organic frameworks (MOFs) are a class of porous solid, which have a variety of potential applications. Unfortunately, MOFs often lack hydrolytic stability, which hinders their use as viable materials for large scale applications. Though there have been an increasing number of reports proving water stability, this aspect is often ignored and negative results often remain unpublished. As a result, this report has been produced to offer common benchmarks for stability of MOFs to moisture. This will be done by discussing what water stability means – both with regards to the exposure methods and the means of assessing the MOF after exposure. Based on these two criteria, definitions are proposed in order to allow MOFs to be discussed more consistently. The purpose of this report is not to rank existing MOFs based on water stability or for potential application but to promote and facilitate discussion about hydrolytic stability of MOFs.
  • Thumbnail Image
    ItemOpen Access
    Proton Conduction with Metal-Organic Frameworks
    (2013-07-26) Shimizu, George; Taylor, JM; Kim, S
  • Thumbnail Image
    ItemEmbargo
    Supramolecular Coordination Compounds as Recyclable Templates for Mesoporous Silica
    (2024-09-03) Lin, Giselle; Shimizu, George; Marriott, Robert; Ling, Chang-Chun; Clarkson, Christopher
    Porous solid sorbents have emerged as a promising class of materials for capture and storage of guests. One of the most common sorbents is porous silica, which is used in capture and separations, biomedical and research purposes. Porous silica is templated with organic surfactant groups which yield high porosity materials and a specific pore size. However, the templated organics are usually removed by calcination, which generates emissions and does not allow the template to be recycled. Additionally, inducing pores in the size regime of 1-3 nm is often challenging due to the lack of suitable templates. This thesis proposes an alternative strategy that yields pores in this range and a template that can be regenerated. This thesis involves the development of two supramolecular coordination compounds that were used as templates in the synthesis of mesoporous silica. The lanthanum-based coordination compounds (La(CSA)3 and La(TBSA)3) exhibited reversible shifting of peaks in their PXRD patterns with the addition or removal of different solvents. Porous silicas were synthesized upon crosslinking within a silica network, and the template was removed by washing the samples. Changing concentrations and solvents were found to affect the packing of the templates, which affected the porosity of the templated silica. Pore size distribution models applied to the samples calculated that the smallest micropore size was approximately the same size as the width of a single template molecule, showing the ability of these templates to act as porogens for the 1-3nm size range. However, much larger pores were induced by aggregation of the templates and more work is needed to enhance the consistency of the pore size distributions.
  • Thumbnail Image
    ItemOpen Access
    Tailoring Perovskite- and Fluorite-Type Oxides for Solid Oxide Fuel Cells (SOFCs)
    (2016) Singh, Kalpana; Thangadurai, Venkataraman; Birss, Viola; Shimizu, George; Cheng, Frank; Kesler, Olivera
    A solid oxide fuel cell (SOFC) is a high temperature solid state energy conversion device that directly converts the chemical energy of fuels into electrical energy at high efficiency. The objective of thesis is to develop and tune fluorite- and perovskite-type metal oxides that serve as alternate anodes, electrolytes, and cathodes for intermediate temperature SOFCs. Here, the chemical reactivity between a fluorite-based Ce0.7RE0.2Mo0.1O2 (RE = Y, Sm) anode and 8 mol% yttria-stabilized zirconia electrolyte was evaluated at 1000 ºC. The electrical conductivity of the reaction product Ce1-x-y-zRExZrYMozO2 in air and wet H2 was found to be lower than that of Ce0.7RE0.2Mo0.1O2, due to the formation of defect associates and a decrease in concentration of charge carriers. The effect of A-and B-site co-doping on the chemical and electrical properties of potential perovskite-type Ba0.5Sr0.5Ce1-x-y-zZrxGdyYzO3-δ (0 < x < 0.5; y = 0, 0.1, 0.15; z = 0.1, 0.2) proton conducting electrolyte was evaluated. Excellent chemical stability under water vapor for 24 h at 90 ºC was observed for all compositions. The electrical conductivity measurements under dry and humid atmospheres revealed the proton conductivity in these oxides. Among the samples investigated, Ba0.5Sr0.5Ce0.6Zr0.2Gd0.1Y0.1O3-δ showed the highest proton conductivity of 10-3 S/cm at 600 ºC in humid air and H2. The effect of sintering temperature on the proton dynamics of Ba0.5Sr0.5Ce0.6Zr0.2Gd0.1Y0.1O3-δ was evaluated by establishing a correlation between the grain boundary space charge effect, electrical conductivity, and dielectric loss of the samples sintered at 1300, 1400, and 1550 ºC. The proton dynamics in local motion and long-range motion appears to be different due to the difference seen in the relaxation time and activation energy of protons in local motion and bulk conduction properties. Furthermore, the electrochemical performance of the layered perovskite-type Gd0.5Pr0.5BaCo2O5+δ and Ba0.5Sr0.5Ce0.6Zr0.2Gd0.1Y0.1O3-δ composite cathode, and Ni and Ba0.5Sr0.5Ce0.6Zr0.2Gd0.1Y0.1O3-δ composite anode for proton conducting SOFCs was evaluated through symmetrical cell studies. The symmetrical cell of Gd0.5Pr0.5BaCo2O5+δ-Ba0.5Sr0.5Ce0.6Zr0.2Gd0.1Y0.1O3-δ composite cathode showed an area specific polarization resistance of 2.4 and 1.9 Ω.cm2 at 700 ºC for oxygen reduction reaction in the air and wet air, respectively, and exhibited an activation energy of 1.2 eV in both atmospheres.
  • Thumbnail Image
    ItemOpen Access
    Tuning Proton Conduction in Metal-Organic Frameworks
    (2017) Wong, Norman; Shimizu, George; Thangadurai, Venkataraman; Trudel, Simon; Nishihara, Hirotomo; Horike, Satoshi
    Proton conductivity was explored in an organosulfonate and three organophosphonate based metal-organic frameworks (MOFs). The MOFs synthesized closely resembled a number of previously reported structures allowing for comparison between structure and property. Modifications to the MOFs resulted in significant differences in their properties relative to the reported derivatives. The first MOF discussed utilized Cs+ and 2,4,6-trihydroxy-1,3,5-benzenetrisulfonic acid to form a highly connected framework, Cs3PGS·3H2O. Owing to the large, polarizable cation and thus dynamic nature, the MOF achieved a maximum proton conductivity of 1.1x10-5 Scm-1 at 70°C, 50% relative humidity (RH). The second MOF, utilizing Cu2+ and 1,3,5-benzenetriphosphonic acid yielded Cu-BTP, a layered structure with hydrated interlayer. The robustness of Cu-BTP was explored for proton conduction and allowed hydration level, structure and proton conductivity to be explored together. Proton conductivity in CuBTP reached 7.0 x 10-5 Scm-1 at 85°C, 98% RH. The third MOF, formed by a series of trivalent lanthanides (Ce, Pr, Nd, Sm, Eu, Gd) and 1,2,4,5-tetrakisphosphonomethyl benzene, explored the lanthanide contraction effect, to which the Pr3+ derivative resulted in the maximum conductivity of 3.9x10-3 Scm-1 at 85°C, 95% RH. This high conductivity was achieved due to the contraction effect on the growth of particles. Finally, anion substitution in a Zr-phosphate-phosphonate MOF, using the ligand bis(2-phosphonoethyl)-4,4’-bipyridinium dibromide, enabled control over the proton conductivity. The substitution of HSO4- for F- anions content and conductivity were explored. In all four projects, the MOFs were crystalline and enabled structure-property relationships to be established.