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ContributorsKoozer, Robin R. (Conductor) / Rittenhouse, Jacob (Conductor) / Klassen, Roy (Conductor) / Preble, Debbie (Conductor) / Graduate Chorale II (Performer) / Recital Chorale (Performer) / ASU Library. Music Library (Publisher)
Created1984-10-14
ContributorsDavis, Teena (Performer) / Williams, Heather (Performer) / Biffle, Stephanie (Performer) / Christianson, Donald (Performer) / Hugl-Mohr, Klaus (Performer) / Graduate Chorale (Performer) / Recital Chorale (Performer) / ASU Library. Music Library (Publisher)
Created1996-12-09
ContributorsDarrough, Galen P. (Performer) / Peterson, Craig C. (Performer) / Shryock, Darin W. (Performer) / Stocker, David, 1939- (Performer) / University Choir (Performer) / Vocal Jazz Choir (Performer) / ASU Library. Music Library (Publisher)
Created1988-11-20
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 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
This thesis presents a study of Boron Nitride (BN) and Copper (Cu)/BN multilayer thin films in terms of synthesis, chemical, structural, morphological, and mechanical properties characterization.
In this study, the influence of Ar/N₂ flow rate in synthesizing stoichiometric BN thin films via magnetron sputtering was investigated initially. Post magnetron sputtering, the crystalline nature and B:N stoichiometric ratio of deposited thin films were investigated by X-ray diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS) respectively. Thicknesses revealed by ellipsometry analysis for nearly stoichiometric B:N thin films and their corresponding deposition times were used for estimating BN interlayer deposition times during the deposition of Cu/BN multilayer thin films. To characterize the microstructure of the synthesized Cu/BN multilayer thin films, XRD and scanning electron microscopy (SEM) have been used. Finally, a comparison of nanoindentation measurements on pure Cu and Cu/BN multilayer thin films having different number of BN interlayers were used for studying the influence of BN interlayers on improving mechanical properties such as hardness and elastic modulus.
The results show that the stoichiometry of BN thin films is dependent on the Ar/N₂ flow rate during magnetron sputtering. An optimal Ar/N₂ flow rate of 13:5 during deposition was required to achieve an approximately 1:1 B:N stoichiometry. Grazing incidence and powder XRD analysis on these stoichiometric BN thin films deposited at room temperature did not reveal a phase match when compared to hexagonal boron nitride (h-BN) and cubic boron nitride (c-BN) reference XRD patterns. For a BN thin film deposition time of 5 hours, a thickness of approximately 40 nm was achieved, as revealed by ellipsometry. XRD and microstructure analysis using scanning electron microscopy (SEM) on pure Cu and Cu/BN thin films showed that the Cu grain size in Cu/BN thin films is much finer than pure Cu thin films. Interestingly, nanoindentation measurements on pure Cu and Cu/BN thin films having a similar overall thickness demonstrated that hardness and Young’s modulus of the films were improved significantly when BN interlayers are present.
ContributorsCaner, Sumeyye (Author) / Rajagopalan, Jagannathan (Thesis advisor) / Oswald, Jay (Committee member) / Solanki, Kiran (Committee member) / Arizona State University (Publisher)
Created2023
ContributorsChagnon, Richard (Performer) / Smith, Larry (Performer) / Biffle, Stephanie (Performer) / Hugl-Mohr, Klaus (Performer) / Recital Chorales (Performer) / ASU Library. Music Library (Publisher)
Created1997-04-24
ContributorsStocker, David, 1939- (Performer) / McEwen, Douglas R. (Performer) / Kelly, Kathy (Performer) / Cherland, Carl (Performer) / Petersen, Carol E. (Performer) / University Choir (Performer) / Concert Choir (Performer) / ASU Library. Music Library (Publisher)
Created1987-11-15
ContributorsMeredith, Steve (Performer) / Rathmell, Robert (Performer) / Fuller, Charles L. (Performer) / Women's Chorus (Performer) / Arizona Statesmen (Performer) / ASU Library. Music Library (Publisher)
Created1988-10-13