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Description
Nanomaterials that exhibit enzyme-like catalytic activity or nanozymes have many advantages compared to biological enzymes such as low cost of production and high stability. There is a substantial interest in studying two-dimensional materials due to their exceptional properties. Hafnium diboride is a type of two-dimensional material and belongs to the

Nanomaterials that exhibit enzyme-like catalytic activity or nanozymes have many advantages compared to biological enzymes such as low cost of production and high stability. There is a substantial interest in studying two-dimensional materials due to their exceptional properties. Hafnium diboride is a type of two-dimensional material and belongs to the metal diborides family made of hexagonal layers of boron atoms separated by metal layers. In this work, the peroxidase-like activity of hafnium diboride nanoflakes dispersed in the block copolymer F77 was discovered for the first time. The kinetics, mechanisms and catalytic performance towards the oxidation of the chromogenic substrate 3,3,5,5-tetramethylbenzidine (TMB) in the presence of hydrogen peroxide are presented in this work. Kinetic parameters were determined by steady-state kinetics and a comparison with other nanozymes is given. Results show that the HfB2/F77 nanozyme possesses a unique combination of unusual high affinity towards hydrogen peroxide and high activity per cost. These findings are important for applications that involve reactions with hydrogen peroxide.
ContributorsMatar Abed, Mahmoud (Author) / Wang, Qing Hua (Thesis advisor) / Green, Alexander (Thesis advisor) / Jiao, Yang (Committee member) / Arizona State University (Publisher)
Created2019
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Description
As the microelectronics industry continues to decrease the size of solder joints, each joint will have to carry a greater current density, making atom diffusion due to current flow, electromigration (EM), a problem of ever-increasing severity. The rate of EM damage depends on current density, operating temperature, and the original

As the microelectronics industry continues to decrease the size of solder joints, each joint will have to carry a greater current density, making atom diffusion due to current flow, electromigration (EM), a problem of ever-increasing severity. The rate of EM damage depends on current density, operating temperature, and the original microstructure of the solder joint, including void volume, grain orientation, and grain size. While numerous studies have investigated the post-mortem effects of EM and have tested a range of current densities and temperatures, none have been able to analyze how the same joint evolves from its initial to final microstructure. This thesis focuses on the study of EM, thermal aging, and thermal cycling in Sn-rich solder joints. Solder joints were either of controlled microstructure and orientation or had trace alloying element additions. Sn grain orientation has been linked to a solder joints’ susceptibility to EM damage, but the precise relationship between orientation and intermetallic (IMC) and void growth has not been deduced. In this research x-ray microtomography was used to nondestructively scan samples and generate 3D reconstructions of both surface and internal features such as interfaces, IMC particles, and voids within a solder joint. Combined with controlled fabrication techniques to create comparable samples and electron backscatter diffraction (EBSD) and energy-dispersive spectroscopy (EDS) analysis for grain orientation and composition analysis, this work shows how grain structure plays a critical role in EM damage and how it differs from damage accrued from thermal effects that occur simultaneously. Unique IMC growth and voiding behaviors are characterized and explained in relation to the solder microstructures that cause their formation and the possible IMC-suppression effects of trace alloying element addition are discussed.
ContributorsBranch Kelly, Marion (Author) / Chawla, Nikhilesh (Thesis advisor) / Ankit, Kumar (Committee member) / Antoniswamy, Aravindha (Committee member) / Arizona State University (Publisher)
Created2019
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Description
Corrosion fatigue has been of prime concern in railways, aerospace, construction industries and so on. Even in the case of many medical equipment, corrosion fatigue is considered to be a major challenge. The fact that even high strength materials have lower resistance to corrosion fatigue makes it an interesting

Corrosion fatigue has been of prime concern in railways, aerospace, construction industries and so on. Even in the case of many medical equipment, corrosion fatigue is considered to be a major challenge. The fact that even high strength materials have lower resistance to corrosion fatigue makes it an interesting area for research. The analysis of propagation of fatigue crack growth under environmental interaction and the life prediction is significant to reduce the maintenance costs and assure structural integrity. Without proper investigation of the crack extension under corrosion fatigue, the scenario can lead to catastrophic disasters due to premature failure of a structure. An attempt has been made in this study to predict the corrosion fatigue crack growth with reasonable accuracy. Models that have been developed so far predict the crack propagation for constant amplitude loading (CAL). However, most of the industrial applications encounter random loading. Hence there is a need to develop models based on time scale. An existing time scale model that can predict the fatigue crack growth for constant and variable amplitude loading (VAL) in the Paris region is initially modified to extend the prediction to near threshold and unstable crack growth region. Extensive data collection was carried out to calibrate the model for corrosion fatigue crack growth (CFCG) based on the experimental data. The time scale model is improved to incorporate the effect of corrosive environments such as NaCl and dry hydrogen in the fatigue crack growth (FCG) by investigation of the trend in change of the crack growth. The time scale model gives the advantage of coupling the time phenomenon stress corrosion cracking which is suggested as a future work in this paper.
ContributorsKurian, Bianca (Author) / Liu, Yongming (Thesis advisor) / Nian, Qiong (Committee member) / Zhuang, Houlong (Committee member) / Arizona State University (Publisher)
Created2019
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Description
Global warming resulted from greenhouse gases emission has received widespread attention. Meanwhile, it is required to explore renewable and environmentally friendly energy sources due to the severe pollution of the environment caused by fossil fuel combustion. In order to realize a substantial adsorption process to resolve the environmental issues, the

Global warming resulted from greenhouse gases emission has received widespread attention. Meanwhile, it is required to explore renewable and environmentally friendly energy sources due to the severe pollution of the environment caused by fossil fuel combustion. In order to realize a substantial adsorption process to resolve the environmental issues, the development of new adsorbents with improved properties has become the most critical issue. This dissertation presents the work of four individual but related studies on systematic characterization and process simulations of novel adsorbents with superior adsorption properties.

A perovskite oxide material, La0.1Sr0.9Co0.9Fe0.1O3-δ (LSCF1991), was investigated first for high-temperature air separation. The oxygen sorption/desorption behavior of LSCF1991 was studied by thermogravimetric analysis (TGA) and fixed-bed breakthrough experiments. A parametric study was performed to design and optimize the operating parameters of the high-temperature air separation process by pressure swing adsorption (PSA). The results have shown great potential for applying LSCF1991 to the high-temperature air separation due to its excellent separation performance and low energy requirement.

Research on using nanostructured zeolite NaX (NZ) as adsorbents for CO2 capture was subsequently conducted. The CO2/N2 adsorption characterizations indicated that the NZ samples lead to enhanced adsorption properties compared with the commercial zeolites (MZ). From the two-bed six-step PSA simulation, NZ saved around 30% energy over MZ for CO2 capture and recovery while achieving a higher CO2 purity and productivity.

A unique screening method was developed for efficient evaluation of adsorbents for PSA processes. In the case study, 47 novel adsorbents have been screened for coal bed methane (CBM) recovery. The adsorbents went through scoring-based prescreening, PSA simulation, and optimization. The process performance indicators were correlated with the adsorption selectivity and capacities, which provides new insights for predicting the PSA performance.

A new medium-temperature oxygen sorbent, YBaCo4O7+δ (YBC114), was investigated as an oxygen pumping material to facilitate solar thermochemical fuel production. The oxygen uptake and release attributes of YBC114 were studied by both TGA and a small-scale evacuation test. The study proved that the particle size has a significant effect on the oxygen pumping behavior of YBC114, especially for the uptake kinetics.
ContributorsXu, Mai (Author) / Deng, Shuguang (Thesis advisor) / Lind, Marylaura (Committee member) / Lin, Jerry Y.S. (Committee member) / Green, Matthew D. (Committee member) / Seo, Dong-Kyun (Committee member) / Arizona State University (Publisher)
Created2020
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Description
This dissertation describes the synthesis and study of porous nanocarbon and further treatment by introducing nitrogen and oxygen groups on nanocarbon, which can be used as electrodes for energy storage (supercapacitor). Electron microscopy is used to make nanoscale characterization. ZnO nanowires are used as the template of the porous nanocarbon,

This dissertation describes the synthesis and study of porous nanocarbon and further treatment by introducing nitrogen and oxygen groups on nanocarbon, which can be used as electrodes for energy storage (supercapacitor). Electron microscopy is used to make nanoscale characterization. ZnO nanowires are used as the template of the porous nanocarbon, and nitrogen doping and oxidation treatment can help further increase the capacitive performance of the nanocarbon.

The first part of this thesis focuses on the synthesis of ZnO nanowires. Uniform ZnO nanowires with ~30 nm in width are produced at 1100℃ in a tube furnace with flowing gases (N2: 500 sccm; O2: 15 sccm). The temperature control is one of the most important parameters for making thin and ultra-long ZnO nanowires.

The second part of the thesis is about the synthesis of nanocarbons. Ultrapure ethanol is used as the carbon source to make carbonaceous deposition on ZnO nanowires. The thickness of the nanocarbons can be controlled by reaction temperature and reaction time. When the reaction time was controlled around 1h, the carbonaceous materials coating the ZnO nanowires become very thin. Then by flowing (1000 sccm) hydrogen at 750℃ through the reaction tube the ZnO nanowires are removed due to reduction and evaporation. Electrochemical evaluation of the produced nanocarbons shows that the nanocarbons possess very high specific surface area (>1400 m2/g) and a capacitance as high as 180 F/g at 10A/g in 6M KOH).

The third part of the thesis is the treatment of the as-synthesized nanocarbons to further increase capacitance. NH3 was used as the nitrogen source to react with nanocarbons at 700℃ to incorporate nitrogen group. Nitric acid (HNO3) is used as the oxidant to introduce oxygen groups. After proper nitrogen doping, the nitrogen doped nanocarbons can show high specific capacitance of 260 F/g at 1A/g in 6M KOH. After further oxidation treatment, the capacitance of the oxidized N-doped nanocarbons increased to 320 F/g at 1A/g in 6M KOH.
ContributorsZhang, Yizhi (Author) / Liu, Jingyue (Thesis advisor) / Wang, Qinghua (Committee member) / Deng, Shuguang (Committee member) / Arizona State University (Publisher)
Created2020
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Description
Programmable Metallization Cell (PMC) devices are, in essence, redox-based

solid-state resistive switching devices that rely on ion transport through a solid electrolyte (SE) layer from anode to cathode. Analysis and modeling of the effect of different fabrication and processing parameter/conditions on PMC devices are crucial for future electronics. Furthermore, this work

Programmable Metallization Cell (PMC) devices are, in essence, redox-based

solid-state resistive switching devices that rely on ion transport through a solid electrolyte (SE) layer from anode to cathode. Analysis and modeling of the effect of different fabrication and processing parameter/conditions on PMC devices are crucial for future electronics. Furthermore, this work is even more significant for devices utilizing back-end- of-line (BEOL) compatible materials such as Cu, W, their oxides and SiOx as these devices offer cost effectiveness thanks to their inherent foundry-ready nature. In this dissertation, effect of annealing conditions and cathode material on the performance of Cu-SiOx vertical devices is investigated which shows that W-based devices have much lower forming voltage and initial resistance values. Also, higher annealing temperatures first lead to an increase in forming voltage from 400 °C to 500 °C, then a drastic decrease at 550 °C due to Cu island formation at the Cu/SiOx interface. Next, the characterization and modeling of the bilayer Cu2O/Cu-WO3 obtained by annealing the deposited Cu/WO3 stacks in air at BEOL-compatible temperatures is presented that display unique characteristics for lateral PMC devices. First, thin film oxidation kinetics of Cu is studied which show a parabolic relationship with annealing time and an activation energy of 0.70 eV. Grown Cu2O shows a cauliflower-like morphology where feature size on the surface increase with annealing time and temperature. Then, diffusion kinetics of Cu in WO3 is examined where the activation energy of diffusion of Cu into WO3 is calculated to be 0.74 eV. Cu was found to form clusters in the WO3 host which was revealed by imaging. Moreover, using the oxidation and diffusion analyses, a Matlab model is established for modeling the bilayer for process and annealing-condition optimization. The model is built to produce the resulting Cu2O thickness and Cu concentration in Cu-WO3. Additionally, material characterization, preliminary electrical results along with modeling of lateral PMC devices utilizing the bilayer is also demonstrated. By tuning the process parameters such as deposited Cu thickness and annealing conditions, a low-resistive Cu2O layer was achieved which dramatically enhanced the electrodeposition growth rate for lateral PMC devices.
ContributorsBalaban, Mehmet Bugra (Author) / Kozicki, Michael N (Thesis advisor) / Barnaby, Hugh J (Committee member) / Goryll, Michael (Committee member, Committee member) / Arizona State University (Publisher)
Created2020
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Description
III-V-bismide semiconductor alloys are a class of materials with applications in the mid and long wave infrared spectrum. The quaternary alloy InAsSbBi is attractive because it can be grown lattice-matched to commercially available GaSb substrates, and the adjustment of the Bi and Sb mole fractions enables both lattice constant

III-V-bismide semiconductor alloys are a class of materials with applications in the mid and long wave infrared spectrum. The quaternary alloy InAsSbBi is attractive because it can be grown lattice-matched to commercially available GaSb substrates, and the adjustment of the Bi and Sb mole fractions enables both lattice constant and bandgap to be tuned independently. This dissertation provides a comprehensive study of the surface morphology and the structural and chemical properties of InAsSbBi alloys grown by molecular beam epitaxy.

210 nm thick InAsSbBi layers grown at temperatures from 280 °C to 430 °C on (100) on-axis, (100) offcut 1° to (011), and (100) offcut 4° to (111)A GaSb substrates are investigated using Rutherford back scattering, X-ray diffraction, transmission electron microscopy, Nomarski optical microscopy, atomic force microscopy, and photoluminescence spectroscopy. The results indicate that the layers are coherently strained and contain dilute Bi mole fractions.

Large surface droplets with diameters and densities on the order of 3 µm and 106 cm-2 are observed when the growth is performed with As overpressures around 1%. Preferential orientation of the droplets occurs along the [011 ̅] step edges offcut (100) 1° to (011) substrate. The surface droplets are not observed when the As overpressure is increased to 4%. Small crystalline droplets with diameters and densities on the order of 70 nm and 1010 cm-2 are observed between the large droplets for the growth at 430°C. Analysis of one of the small droplets indicates a misoriented zinc blende structure composed of In, Sb, and Bi, with a 6.543 ± 0.038 Å lattice constant.

Lateral variation in the Bi mole fraction is observed in InAsSbBi grown at high temperature (400 °C, 420 °C) on (100) on-axis and (100) offcut 4° to (111)A substrates, but is not observed for growth at 280 °C or on (100) substrates that are offcut 1° to (011). Improved crystal and optical quality is observed in the high temperature grown InAsSbBi and CuPtB type atomic ordering on the {111}B planes is observed in the low temperature grown InAsSbBi. Strain induced tilt is observed in coherently strained InAsSbBi grown on offcut substrates.
ContributorsKosireddy, Rajeev Reddy (Author) / Johnson, Shane R (Thesis advisor) / Smith, David J. (Committee member) / Alford, Terry L. (Committee member) / Soignard, Emmanuel (Committee member) / Arizona State University (Publisher)
Created2020
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Description
Shock loading produces a compressive stress pulse with steep gradients in density, temperature, and pressure that are also often modeled as discontinuities. When a material is subject to these dynamic (shock) loading conditions, fracture and deformation patterns due to spall damage can arise. Spallation is a dynamic material failure that

Shock loading produces a compressive stress pulse with steep gradients in density, temperature, and pressure that are also often modeled as discontinuities. When a material is subject to these dynamic (shock) loading conditions, fracture and deformation patterns due to spall damage can arise. Spallation is a dynamic material failure that is caused by the nucleation, growth, and coalescence of voids, with possible ejection of the surface of the material. Intrinsic defects, such as grain boundaries are the preferred initiation sites of spall damage in high purity materials. The focus of this research is to study the phenomena that cause void nucleation and growth at a particular grain boundary (GB), chosen to maximize spall damage localization.

Bicrystal samples were shock loaded using flyer-plates via light gas gun and direct laser ablation. Stress, pulse duration, and crystal orientation along the shock direction were varied for a fixed boundary misorientation to determine thresholds for void nucleation and coalescence as functions of these parameters. Pressures for gas gun experiments ranged from 2 to 5 GPa, while pressures for laser ablation experiments varied from 17 to 25 GPa. Samples were soft recovered to perform damage characterization using electron backscattering diffraction (EBSD) and Scanning Electron Microscopy (SEM). Results showed a 14% difference in the thresholds for void nucleation and coalescence between samples with different orientations along the shock direction, which were affected by pulse duration and stress level. Fractography on boundaries with strong damage localization showed many small voids, indicating they experience rapid nucleation, causing early coalescence. Composition analysis was also performed to determine the effect of impurities on damage evolution. Results showed that higher levels of impurities led to more damage. ABAQUS/Explicit models were developed to simulate flyer-plate impact and void growth with the same crystal orientations and experimental conditions. Results are able to match the damage seen in each grain of the target experimentally. The Taylor Factor mismatch at the boundary can also be observed in the model with the higher Taylor Factor grain exhibiting more damage.
ContributorsFortin, Elizabeth Victoria (Author) / Peralta, Pedro (Thesis advisor) / Mignolet, Marc (Committee member) / Loomis, Eric (Committee member) / Oswald, Jay (Committee member) / Solanki, Kiran (Committee member) / Arizona State University (Publisher)
Created2020
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Description
Soft materials are matters that can easily deform from their original shapes and structures under thermal or mechanical stresses, and they range across various groups of materials including liquids, foams, gels, colloids, polymers, and biological substances. Although soft materials already have numerous applications with each of their unique characteristics, integrating

Soft materials are matters that can easily deform from their original shapes and structures under thermal or mechanical stresses, and they range across various groups of materials including liquids, foams, gels, colloids, polymers, and biological substances. Although soft materials already have numerous applications with each of their unique characteristics, integrating materials to achieve complementary functionalities is still a growing need for designing advanced applications of complex requirements. This dissertation explores a unique approach of utilizing intermolecular interactions to accomplish not only the multifunctionality from combined materials but also their tailored properties designed for specific tasks. In this work, multifunctional soft materials are explored in two particular directions, ionic liquids (ILs)-based mixtures and interpenetrating polymer network (IPN).

First, ILs-based mixtures were studied to develop liquid electrolytes for molecular electronic transducers (MET) in planetary exploration. For space missions, it is challenging to operate any liquid electrolytes in an extremely low-temperature environment. By tuning intermolecular interactions, the results demonstrated a facile method that has successfully overcome the thermal and transport barriers of ILs-based mixtures at extremely low temperatures. Incorporation of both aqueous and organic solvents in ILs-based electrolyte systems with varying types of intermolecular interactions are investigated, respectively, to yield optimized material properties supporting not only MET sensors but also other electrochemical devices with iodide/triiodide redox couple targeting low temperatures.

Second, an environmentally responsive hydrogel was synthesized via interpenetrating two crosslinked polymer networks. The intermolecular interactions facilitated by such an IPN structure enables not only an upper critical solution temperature (UCST) transition but also a mechanical enhancement of the hydrogel. The incorporation of functional units validates a positive swelling response to visible light and also further improves the mechanical properties. This studied IPN system can serve as a promising route in developing “smart” hydrogels utilizing visible light as a simple, inexpensive, and remotely controllable stimulus.

Over two directions across from ILs to polymeric networks, this work demonstrates an effective strategy of utilizing intermolecular interactions to not only develop multifunctional soft materials for advanced applications but also discover new properties beyond their original boundaries.
ContributorsXu, Yifei (Author) / Dai, Lenore L. (Thesis advisor) / Forzani, Erica (Committee member) / Holloway, Julianne (Committee member) / Jiang, Hanqing (Committee member) / Zhuang, Houlong (Committee member) / Arizona State University (Publisher)
Created2020
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Description
Two-dimensional quantum materials have garnered increasing interest in a wide

variety of applications due to their promising optical and electronic properties. These

quantum materials are highly anticipated to make transformative quantum sensors and

biosensors. Biosensors are currently considered among one of the most promising

solutions to a wide variety of biomedical and environmental problems

Two-dimensional quantum materials have garnered increasing interest in a wide

variety of applications due to their promising optical and electronic properties. These

quantum materials are highly anticipated to make transformative quantum sensors and

biosensors. Biosensors are currently considered among one of the most promising

solutions to a wide variety of biomedical and environmental problems including highly

sensitive and selective detection of difficult pathogens, toxins, and biomolecules.

However, scientists face enormous challenges in achieving these goals with current

technologies. Quantum biosensors can have detection with extraordinary sensitivity and

selectivity through manipulation of their quantum states, offering extraordinary properties

that cannot be attained with traditional materials. These quantum materials are anticipated

to make significant impact in the detection, diagnosis, and treatment of many diseases.

Despite the exciting promise of these cutting-edge technologies, it is largely

unknown what the inherent toxicity and biocompatibility of two-dimensional (2D)

materials are. Studies are greatly needed to lay the foundation for understanding the

interactions between quantum materials and biosystems. This work introduces a new

method to continuously monitor the cell proliferation and toxicity behavior of 2D

materials. The cell viability and toxicity measurements coupled with Live/Dead

fluorescence imaging suggest the biocompatibility of crystalline MoS2 and MoSSe

monolayers and the significantly-reduced cellular growth of defected MoTe2 thin films

and exfoliated MoS2 nanosheets. Results show the exciting potential of incorporating

kinetic cell viability data of 2D materials with other assay tools to further fundamental

understanding of 2D material biocompatibility.
ContributorsTran, Michael, Ph.D (Author) / Tongay, Sefaattin (Thesis advisor) / Green, Matthew (Thesis advisor) / Muhich, Christopher (Committee member) / Arizona State University (Publisher)
Created2019