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Description
This work systematically investigates structure-stability relations in various polymer derived ceramic (PDC) systems and metal organic frameworks (MOFs), both of which are hybrid materials. The investigation of silicon carbides (SiC) confirms thermodynamic stabilization of PDCs with increasing mixed bonding (Si bonded to both C, O and/or N). The study of more complex silicon oxycarbide (SiOC) structures shows stabilization of SiOCs with increasing pyrolysis temperature (between 1200 and1500 oC), and points to dissimilarities in the stabilizing effect of different mixed bonding environments (SiO3C, SiO2C2, or SiOC3) and their relative amounts. Analyses of quaternary silicon oxycarbonitride (SiC(N)(O)) materials suggests increased stabilization with increasing N content, and superior stabilization due to SiNxC4-x compared to SiOxC4-x mixed bonds. Investigation of the energetics of metal filler (Nb, Hf, Ta) incorporation in SiOCs shows that choice of metal filler influences the composition, structural evolution, and thermodynamic stability in PDCs. Ta fillers can stabilize otherwise unstable SiO3C mixed bonds. Independent of metal incorporation or lack thereof, in SiOC systems, higher pyrolysis temperature (1200-1500 oC) forms more stable ceramics. The stabilizing effect of order/disorder of the free carbon phase is system-dependent. The work on (MOFs) highlights stabilization trends obtained from the investigation of zeolitic imidazolate frameworks (ZIFs) and boron imidazolate frameworks (BIFs) based on azolate linkers. Study of the energetics of metal (Co(II), Cu (II), and Zn (II) ) substitution in isostructural ZIFs shows that in MOFs the stabilizing effect of metal is dependent on both framework topology (diamondoid (dia) > sodalite (SOD)) and dimensionality (2D > 3D). Thermodynamic analyses of metal substitution (Ag(I), Cu(I), and Li (I)) in isostructural ii SOD and dia BIF systems confirm increase in density as a general descriptor for increased stabilization in MOFs. The study of energetics of guest-host interactions during CO2 incorporation in azolate frameworks (i.e., ZIF-8) shows strong dependence of energetics of adsorption on choice of linker and metal. Additionally, several energetically favorable reaction pathways for the formation of CO3-ZIF-8 have been identified. Both PDCs and MOFs show a complex energetic landscape, with identifiable system dependent and general structural descriptors for increased thermodynamic stabilization and tunability of the energetics of guest-host interactions.
ContributorsLeonel, Gerson J (Author) / Navrotsky, Alexandra (Thesis advisor) / Dai, Lenore (Committee member) / Thomas, Mary (Committee member) / Singh, Gurpreet (Committee member) / Friščić, Tomislav (Committee member) / Arizona State University (Publisher)
Created2023
Description
The management of underground utilities is a complex and challenging task due to the uncertainty regarding the location of existing infrastructure. The lack of accurate information often leads to excavation-related damages, which pose a threat to public safety. In recent years, advanced underground utilities management systems have been developed to improve the safety and efficiency of excavation work. This dissertation aims to explore the potential applications of blockchain technology in the management of underground utilities and reduction of excavation-related damage. The literature review provides an overview of the current systems for managing underground infrastructure, including Underground Infrastructure Management (UIM) and 811, and highlights the benefits of advanced underground utilities management systems in enhancing safety and efficiency on construction sites. The review also examines the limitations and challenges of the existing systems and identifies the opportunities for integrating blockchain technology to improve their performance. The proposed application involves the creation of a shared database of information about the location and condition of pipes, cables, and other underground infrastructure, which can be updated in real time by authorized users such as utility companies and government agencies. The use of blockchain technology can provide an additional layer of security and transparency to the system, ensuring the reliability and accuracy of the information. Contractors and excavation companies can access this information before commencing work, reducing the risk of accidental damage to underground utilities.
ContributorsAlnahari, Mohammed S (Author) / Ariaratnam, Samuel T (Thesis advisor) / El Asmar, Mounir (Committee member) / Czerniawski, Thomas (Committee member) / Arizona State University (Publisher)
Created2023
Description
The first part of this dissertation focuses on quantum structures with type-II band alignment, which are designed for applications in infrared photodetection and optical nonlinearity. A short- and mid-wavelength infrared dual-band optically-addressed photodetector structure has been designed and fabricated by molecular beam epitaxy, which is used to demonstrate the operational principles of optical address for extended tri-band detection. High-resolution x-ray diffraction and photoluminescence measurement were used to characterize the samples and revealed excellent crystalline quality and optical properties. An analytical model has been developed to address the effects of luminescence coupling and light leakage effects in optically-addressed tri-band photodetectors in terms of the absorber thicknesses and photoluminescence quantum efficiencies.Beyond superlattices, asymmetric quantum wells with type-II band alignment find application in optical nonlinearity enhancement which is the result of increased wavefunction overlap and larger electric dipole moments of the interband transitions compared to the conventional structures with type-I band edge alignment. The novel type-II AQW structure exhibits interband second-order susceptibility tensor elements ranging between 20 pm/V to 1.60×103 pm/V for nearly-resonant optical rectification and difference frequency generation applications at near-infrared and terahertz wavelengths, an improvement of nearly one order of magnitude over the type-I structures and one to three orders of magnitude over natural crystals such as LiNbO3, KTP, or GaAs. A factor of 2-3 further enhancement of the tensor elements is achieved by optimizing the well widths and band offsets of the type-II asymmetric quantum wells.
The second part of the dissertation reports the study of CdSe thin films with mixed zincblende and wurtzite phases grown on lattice-matched InAs(100) substrate using molecular beam epitaxy. These CdSe thin films reveal single-phase zincblende (ZB) structure with high crystalline quality with low defect density. In contrast, CdSe layers grown on lattice-matched InAs(111)B (As-terminated) substrates under different growth temperatures and Cd/Se flux ratios all have their demonstrated mixed ZB and wurtzite phases in coexistence confirmed by high-resolution x-ray diffraction, transmission electron microscopy and photoluminescence measurements. The reason for these properties is due to the small formation energy difference between the ZB and WZ phases of CdSe, which has been confirmed by density functional theory simulations.
ContributorsJu, Zheng (Author) / Zhang, Yong-Hang YHZ (Thesis advisor) / Smith, David DJS (Committee member) / Johnson, Shane SRJ (Committee member) / Ponce, Fernando FAP (Committee member) / Arizona State University (Publisher)
Created2023
Description
Air conditioning is a significant energy consumer in buildings, especially in humid regions where a substantial portion of energy is used to remove moisture rather than cool the air. Traditional dehumidification methods, which cool air to its dew point to condense water vapor, are energy intensive. This process unnecessarily overcools the air, only to reheat it to the desired temperature.This research introduces thermoresponsive materials as efficient desiccants to reduce energy demand for dehumidification. A system using lower critical solution temperature (LCST) type ionic liquids (ILs) as dehumidifiers is presented. Through the Flory-Huggins theory of mixtures, interactions between ionic liquids and water are analyzed. LCST ionic liquids demonstrate superior performance, with a coefficient of performance (COP) four times higher than non-thermoresponsive desiccants under similar conditions. The efficacy of ionic liquids as dehumidifiers is assessed based on properties like LCST temperature and enthalpic interaction parameter.
The research also delves into thermoresponsive solid desiccants, particularly polymers, using the Vrentas-Vrentas model. This model offers a more accurate depiction of their behaviors compared to the Flory-Huggins theory by considering elastic energy stored in the polymers. Moisture absorption in thin film polymers is studied under diverse conditions, producing absorption isotherms for various temperatures and humidities. Using temperature-dependent interaction parameters, the behavior of the widely-used thermoresponsive polymer (TRP) PNIPAAm and hypothetical TRPs is investigated. The parameters from the model are used as input to do a finite element analysis of a thermoresponsive dehumidifier. This model demonstrates the complete absorption-desorption cycle under varied conditions such as polymer absorption temperature, relative humidity, and air speed. Results indicate that a TRP with enhanced absorption capacity and an LCST of 50℃ achieves a peak moisture removal efficiency (MRE) of 0.9 at 75% relative humidity which is comparable to other existing thermoresponsive dehumidification systems. But other TRPs with even greater absorption capacity can produce MRE as high as 3.6. This system also uniquely recovers water in liquid form.
ContributorsRana, Ashish (Author) / Wang, Robert RW (Thesis advisor) / Green, Matthew MG (Committee member) / Milcarek, Ryan RM (Committee member) / Wang, Liping LW (Committee member) / Phelan, Patrick PP (Committee member) / Arizona State University (Publisher)
Created2023
Description
Enzyme induced carbonate precipitation (EICP) treatment is a stabilization method of dust mitigation that applies a spray-on treatment to form a soil crust and increase the wind erosion resistance of a disturbed soil surface. The purpose of this work was to evaluate the EICP treatment with multiple field and laboratory test methods for measuring the wind erosion resistance of EICP treated soil. The threshold friction velocity (TFV) is defined as the minimum wind speed required to initiate continuous particle movement and represents the wind erosion resistance of a soil surface. Tested soil type and textures included a clean fine sand to a loamy sandy soil that contained a significant amount of fines. Dry untreated soil and disturbed field soil surfaces were compared to a chloride salt solution treatment and an EICP treatment solution in both laboratory and field testing to evaluate the wind erosion resistance of the treatments.
ContributorsWoolley, Miriam Arna (Author) / Kavazajian, Edward (Thesis advisor) / van Paassen, Leon (Committee member) / Khodadaditirkolaei, Hamed (Committee member) / Hamdan, Nasser (Committee member) / Arizona State University (Publisher)
Created2023
Description
Some subterranean animals, such as mole-rats, can burrow underground, sense the environment around them, and communicate with each other. Inspired by the mole-rats, this dissertation is dedicated to developing an active wireless underground sensor network (WUSN) for active underground exploration. Special attention is paid to two key functions: wireless underground data transmission, and underground self-burrowing. In this study, a wireless underground communication system based on seismic waves was developed. The system includes a bio-inspired vibrational source, an accelerometer as the receiver, and a set of algorithms for encoding and decoding information. With the current design, a maximum transmission bit rate of 16–17 bits per second and a transmission distance of 80 cm is achieved. The transmission range is limited by the size of container used in the laboratory experiments. The bit error ratio is as low as 0.1%, demonstrating the robustness of the algorithms. The performance of the developed system shows that seismic waves produced by vibration can be used as an information carrier and can potentially be implemented in the active WUSNs. A minimalistic horizontal self-burrowing robot was designed. The robot mainly consists of a tip (flat, cone, or auger), and a pair of cylindrical parts. The robot can achieve extension-contraction with the utilization of a linear actuator and have options for tip rotation with an embedded gear motor. Using a combined numerical simulation and laboratory testing approach, symmetry-breaking is validated to be the key to underground burrowing. The resistance-displacement curves during the extension-contraction cycles of the robot can be used to quantify the overall effect of asymmetries and estimate the burrowing behavior of the robots. Findings from this research shed light on the future development of self-burrowing robots and active WUSNs.
ContributorsZhong, Yi (Author) / Tao, Junliang (Thesis advisor) / Kavazanjian, Edward (Committee member) / Martinez, Alejandro (Committee member) / Arizona State University (Publisher)
Created2023
The Intercoupling of Thermal Transport and Mechanical Properties in Colloidal Nanocrystal Assemblies
Description
Colloidal nanocrystals (NCs) are promising candidates for a wide range of applications (electronics, optoelectronics, photovoltaics, thermoelectrics, etc.). Mechanical and thermal transport property play very important roles in all of these applications. On one hand, mechanical robustness and high thermal conductivity are desired in electronics, optoelectronics, and photovoltaics. This improves thermomechanical stability and minimizes the temperature rise during the device operation. On the other hand, low thermal conductivity is desired for higher thermoelectric figure of merit (ZT). This dissertation demonstrates that ligand structure and nanocrystal ordering are the primary determining factors for thermal transport and mechanical properties in colloidal nanocrystal assemblies. To eliminate the mechanics and thermal transport barrier, I first propose a ligand crosslinking method to improve the thermal transport across the ligand-ligand interface and thus increasing the overall thermal conductivity of NC assemblies. Young’s modulus of nanocrystal solids also increases simultaneously upon ligand crosslinking. My thermal transport measurements show that the thermal conductivity of the iron oxide NC solids increases by a factor of 2-3 upon ligand crosslinking. Further, I demonstrate that, though with same composition, long-range ordered nanocrystal superlattices possess higher mechanical and thermal transport properties than disordered nanocrystal thin films. Experimental measurements along with theoretical modeling indicate that stronger ligand-ligand interaction in NC superlattice accounts for the improved mechanics and thermal transport. This suggests that NC/ligand arranging order also plays important roles in determining mechanics and thermal transport properties of NC assemblies. Lastly, I show that inorganic ligand functionalization could lead to tremendous mechanical enhancement (a factor of ~60) in NC solids. After ligand exchange and drying, the short inorganic Sn2S64- ligands dissociate into a few atomic layers of amorphous SnS2 at room temperature and interconnects the neighboring NCs. I observe a reverse Hall-Petch relation as the size of NC decreases. Both atomistic simulations and analytical phase mixture modeling identify the grain boundaries and their activities as the mechanic bottleneck.
ContributorsWang, Zhongyong (Author) / Wang, Robert RW (Thesis advisor) / Wang, Liping LW (Committee member) / Newman, Nathan NN (Committee member) / Arizona State University (Publisher)
Created2021
Description
Over the past few years, research into the use of doped diamond in electronics has seen an exponential growth. In the course of finding ways to reduce the contact resistivity, nanocarbon materials have been an interesting focus. In this work, the transfer length method (TLM) was used to investigate Ohmic contact properties using the tri-layer stack Ti/Pt/Au on nitrogen-doped n-type conducting nano-carbon (nanoC) layers grown on (100) diamond substrates. The nanocarbon material was characterized using Secondary Ion Mass Spectrometry (SIMS), Scanning electron Microscopy (SEM) X-ray diffraction (XRD), Raman scattering and Hall effect measurements to probe the materials characteristics. Room temperature electrical measurements were taken, and samples were annealed to observe changes in electrical conductivity. Low specific contact resistivity values of 8 x 10^-5 Ωcm^2 were achieved, which was almost two orders of magnitude lower than previously reported values. The results were attributed to the increased nitrogen incorporation, and the presence of electrically active defects which leads to an increase in conduction in the nanocarbon. Further a study of light phosphorus doped layers using similar methods with Ti/Pt/Au contacts again yielded a low contact resistivity of about 9.88 x 10^-2 Ωcm^2 which is an interesting prospect among lightly doped diamond films for applications in devices such as transistors. In addition, for the first time, hafnium was substituted for Ti in the contact stack (Hf/Pt/Au) and studied on nitrogen doped nanocarbon films, which resulted in low contact resistivity values on the order of 10^-2 Ωcm^2. The implications of the results were discussed, and recommendations for improving the experimental process was outlined. Lastly, a method for the selective area growth of nanocarbon was developed and studied and the results provided an insight into how different characterizations can be used to confirm the presence of the nanocrystalline diamond material, the limitations due to the film thickness was explored and ideas for future work was proposed.
ContributorsAmonoo, Evangeline Abena (Author) / Thornton, Trevor (Thesis advisor) / Alford, Terry L (Thesis advisor) / Anwar, Shahriar (Committee member) / Theodore, David (Committee member) / Arizona State University (Publisher)
Created2023
Description
Engineering polymers are critical for contemporary high-performance applications where toughness, thermal stability, and density are at a premium. These materials often demand high-energy processing conditions or highly reactive monomers that hold negative impacts on human and environmental health. Thus, this work serves to remediate the negative impacts of engineering polymer synthesis by addressing toxicity and processing at the monomer level, while maintaining or exceeding previous thermomechanical and stimuli-responsive performance. Polyurethanes (PUs) represent a class of engineering polymers that possess highly modular properties due to the diverse monomer selection available for their synthesis. The efficient reaction between isocyanates and hydroxyls impart stellar properties and flexible processing modalities, however recent scrutiny regarding the toxicity of the isocyanate precursors has driven the search for non-isocyanate polyurethane (NIPU) pathways. The advancement of bis-carbonylimidazolide (BCI) monomers for the synthesis of NIPU thermoplastics and foams is thoroughly investigated in this work. Remarkably, a novel decarboxylation pathway for BCI monomers controlled by catalyst loading enabled in-situ CO2 generation during crosslinking with trifunctional amines, and resulted in a facile synthetic route for NIPU foams. Further explorations into catalyst considerations revealed Dabco® 33-LV as a suitable mechanism for controlling reaction times and careful selection of surfactant concentration provided control over pore size and geometry. This led to a library of flexible and rigid NIPU foams that displayed a wide range of thermomechanical properties. Furthermore, sequestration of the imidazole byproduct through an efficient Michael reaction identified maleimide and acrylate additives as a viable pathway to eliminate post-processing steps resulting in NIPU foam synthesis that is amenable to current industrial standards. This route held advantages over the isocyanate route, as condensate removal drove molecular weight increase and ultimately achieved the first reported phase separation behavior of a NIPU thermoplastic containing a poly(ethylene glycol) soft segment. Furthermore, sustainable considerations for engineering polymers were explored with the introduction of a novel cyclobutane bisimide monomer that readily installs into various polymeric systems. Direct installation of this monomer, CBDA-AP-I, into a polysulfone backbone enabled controlled photo-cleavage, while further hydroxy ethyl functionalization allowed for incorporation into PU systems for photo-cleavable high-performance adhesive applications.
ContributorsSintas, Jose Ignacio (Author) / Long, Timothy E (Thesis advisor) / Sample, Caitlin S. (Committee member) / Jin, Kailong (Committee member) / Arizona State University (Publisher)
Created2024
Description
The consequences of failures from large-diameter water pipelines can be severe. Results can include significant property damage, damage to adjacent infrastructure such as roads and bridges resulting in transportation delays or shutdowns, adjacent structural damage to buildings resulting in loss of business, service disruption to a significant number of customers, loss of water, costly emergency repairs, and even loss of life. The American Water Works Association’s (AWWA) 2020 “State of the Water Industry” report states the top issue facing the water industry since 2016 is aging infrastructure, with the second being financing for improvements. The industry must find innovative ways to extend asset life and reduce maintenance expenditures. While are many different assets comprise the drinking water industry, pipelines are a major component and often neglected because they are typically buried. Reliability Centered Maintenance (RCM) is a process used to determine the most effective maintenance strategy for an asset, with the ultimate goal being to establish the required function of the asset with the required reliability at the lowest operations and maintenance costs. The RCM philosophy considers Preventive Maintenance, Predictive Maintenance, Condition Based Monitoring, Reactive Maintenance, and Proactive Maintenance techniques in an integrated manner to increase the probability an asset will perform its designed function throughout its design life with minimal maintenance. In addition to determining maintenance tasks, the timely performance of those tasks is crucial. If performed too late an asset may fail; if performed too early, resources that may be used better elsewhere are expended. Utility agencies can save time and money by using RCM analysis for their drinking water infrastructure. This dissertation reviews industries using RCM, discusses the benefits of an RCM analysis, and goes through a case study of an RCM at a large aqueduct in the United States. The dissertation further discusses the consequence of failure of large diameter water pipelines and proposes a regression model to help agencies determine the optimum time to perform maintenance tasks on large diameter prestressed concrete pipelines using RCM analysis.
ContributorsGeisbush, James R (Author) / Ariaratnam, Samuel T (Thesis advisor) / Grau, David (Committee member) / Chong, Oswald (Committee member) / Arizona State University (Publisher)
Created2024