Theses and Dissertations
This collection includes both ASU Theses and Dissertations, submitted by graduate students, and the Barrett, Honors College theses submitted by undergraduate students.
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- Creators: Yu, Hongyu
- Creators: Navrotsky, Alexandra
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 instrumentational measurement of seismic motion is important for a wide range of research fields and applications, such as seismology, geology, physics, civil engineering and harsh environment exploration. This report presents series approaches to develop Micro-Electro-Mechanical System (MEMS) enhanced inertial motion sensors including accelerometers, seismometers and inclinometers based on Molecular Electronic Transducers (MET) techniques.
Seismometers based on MET technology are attractive for planetary applications due to their high sensitivity, low noise floor, small size, absence of fragile mechanical moving parts and independence on the direction of sensitivity axis. By using MEMS techniques, a micro MET seismometer is developed with inter-electrode spacing close to 5 μm. The employment of MEMS improves the sensitivity of fabricated device to above 2500 V/(m/s2) under operating bias of 300 mV and input velocity of 8.4μm/s from 0.08Hz to 80Hz. The lowered hydrodynamic resistance by increasing the number of channels improves the self-noise to -135 dB equivalent to 18nG/√Hz (G=9.8m/s2) around 1.2 Hz.
Inspired by the advantages of combining MET and MEMS technologies on the development of seismometer, a feasibility study of development of a low frequency accelerometer utilizing MET technology with post-CMOS-compatible fabrication processes is performed. In the fabricated accelerometer, the complicated fabrication of mass-spring system in solid-state MEMS accelerometer is replaced with a much simpler post-CMOS-compatible process containing only deposition of a four-electrode MET structure on a planar substrate, and a liquid inertia mass of an electrolyte droplet. With a specific design of 3D printing based package and replace water based iodide solution by room temperature ionic liquid based electrolyte, the sensitivity relative to the ground motion can reach 103.69V/g, with the resolution of 5.25μG/√Hz at 1Hz.
By combining MET techniques and Zn-Cu electrochemical cell (Galvanic cell), this letter demonstrates a passive motion sensor powered by self-electrochemistry energy, named “Battery Accelerometer”. The experimental results indicated the peak sensitivity of battery accelerometer at its resonant frequency 18Hz is 10.4V/G with the resolution of 1.71μG without power consumption.
Seismometers based on MET technology are attractive for planetary applications due to their high sensitivity, low noise floor, small size, absence of fragile mechanical moving parts and independence on the direction of sensitivity axis. By using MEMS techniques, a micro MET seismometer is developed with inter-electrode spacing close to 5 μm. The employment of MEMS improves the sensitivity of fabricated device to above 2500 V/(m/s2) under operating bias of 300 mV and input velocity of 8.4μm/s from 0.08Hz to 80Hz. The lowered hydrodynamic resistance by increasing the number of channels improves the self-noise to -135 dB equivalent to 18nG/√Hz (G=9.8m/s2) around 1.2 Hz.
Inspired by the advantages of combining MET and MEMS technologies on the development of seismometer, a feasibility study of development of a low frequency accelerometer utilizing MET technology with post-CMOS-compatible fabrication processes is performed. In the fabricated accelerometer, the complicated fabrication of mass-spring system in solid-state MEMS accelerometer is replaced with a much simpler post-CMOS-compatible process containing only deposition of a four-electrode MET structure on a planar substrate, and a liquid inertia mass of an electrolyte droplet. With a specific design of 3D printing based package and replace water based iodide solution by room temperature ionic liquid based electrolyte, the sensitivity relative to the ground motion can reach 103.69V/g, with the resolution of 5.25μG/√Hz at 1Hz.
By combining MET techniques and Zn-Cu electrochemical cell (Galvanic cell), this letter demonstrates a passive motion sensor powered by self-electrochemistry energy, named “Battery Accelerometer”. The experimental results indicated the peak sensitivity of battery accelerometer at its resonant frequency 18Hz is 10.4V/G with the resolution of 1.71μG without power consumption.
ContributorsLiang, Mengbing (Author) / Yu, Hongyu (Thesis advisor) / Dai, Lenore (Committee member) / Kozicki, Michael (Committee member) / Jiang, Hanqing (Committee member) / Arizona State University (Publisher)
Created2016
Description
This thesis presents approaches to develop micro seismometers and accelerometers based on molecular electronic transducers (MET) technology using MicroElectroMechanical Systems (MEMS) techniques. MET is a technology applied in seismic instrumentation that proves highly beneficial to planetary seismology. It consists of an electrochemical cell that senses the movement of liquid electrolyte between electrodes by converting it to the output current. MET seismometers have advantages of high sensitivity, low noise floor, small size, absence of fragile mechanical moving parts and independence on the direction of sensitivity axis. By using MEMS techniques, a micro MET seismometer is developed with inter-electrode spacing close to 1μm, which improves the sensitivity of fabricated device to above 3000 V/(m/s^2) under operating bias of 600 mV and input acceleration of 400 μG (G=9.81m/s^2) at 0.32 Hz. The lowered hydrodynamic resistance by increasing the number of channels improves the self-noise to -127 dB equivalent to 44 nG/√Hz at 1 Hz. An alternative approach to build the sensing element of MEMS MET seismometer using SOI process is also presented in this thesis. The significantly increased number of channels is expected to improve the noise performance. Inspired by the advantages of combining MET and MEMS technologies on the development of seismometer, a low frequency accelerometer utilizing MET technology with post-CMOS-compatible fabrication processes is developed. In the fabricated accelerometer, the complicated fabrication of mass-spring system in solid-state MEMS accelerometer is replaced with a much simpler post-CMOS-compatible process containing only deposition of a four-electrode MET structure on a planar substrate, and a liquid inertia mass of an electrolyte droplet encapsulated by oil film. The fabrication process does not involve focused ion beam milling which is used in the micro MET seismometer fabrication, thus the cost is lowered. Furthermore, the planar structure and the novel idea of using an oil film as the sealing diaphragm eliminate the complicated three-dimensional packaging of the seismometer. The fabricated device achieves 10.8 V/G sensitivity at 20 Hz with nearly flat response over the frequency range from 1 Hz to 50 Hz, and a low noise floor of 75 μG/√Hz at 20 Hz.
ContributorsHuang, Hai (Author) / Yu, Hongyu (Thesis advisor) / Jiang, Hanqing (Committee member) / Dai, Lenore (Committee member) / Si, Jennie (Committee member) / Arizona State University (Publisher)
Created2014