Matching Items (56)
Description
The project aims at utilization of hydrothermal liquefaction (HTL) byproducts like biochar to grow microalgae. HTL is a promising method to convert wet algal biomasses into biofuels. The initial microalgae liquefaction at a temperature of 300 °C for 30 minute, converted 31.22 % of the Galdieria sulphuraria and 41.00 % of the Kirchneriella cornutum into biocrude. Upon changing the reactor from a 100 ml to a 250 ml reactor, the yield in biocrude increased to 31.48 % for G. sulphuraria and dropped to 38.05 % for K. cornutum. Further, energy recoveries based on calorific values of HTL products were seen to drop by about 5 % of the 100 ml calculated values in the larger reactor.
Biochar from HTL of G. sulphuraria at 300 °C showed 15.98 and 5.27 % of phosphorous and nitrogen, respectively. HTL products from the biomass were analyzed for major elements through ICP-OES and CHNS/O. N and P are macronutrients that can be utilized in growing microalgae. This could reduce the operational demands in growing algae like, phosphorous mined to meet annual national demand for aviation fuel. Acidic leaching of these elements as phosphates and ammoniacal nitrogen was studied. Improved leaching of 49.49 % phosphorous and 95.71 % nitrogen was observed at 40 °C and pH 2.5 over a period of 7 days into the growth media. These conditions being ideal for growth of G. sulphuraria, leaching can be done in-situ to reduce overhead cost.
Growth potential of G. sulphuraria in leached media was compared to a standard cyanidium media produced from inorganic chemicals. Initial inhibition studies were done in the leached media at 40 °C and 2-3 vol. % CO2 to observe a positive growth rate of 0.273 g L-1 day-1. Further, growth was compared to standard media with similar composition in a 96 well plate 50 μL microplate assay for 5 days. The growth rates in both media were comparable. Additionally, growth was confirmed in a 240 times larger tubular reactor in a Tissue Culture Roller drum apparatus. A better growth was observed in the leached cyanidium media as compared to the standard variant.
Biochar from HTL of G. sulphuraria at 300 °C showed 15.98 and 5.27 % of phosphorous and nitrogen, respectively. HTL products from the biomass were analyzed for major elements through ICP-OES and CHNS/O. N and P are macronutrients that can be utilized in growing microalgae. This could reduce the operational demands in growing algae like, phosphorous mined to meet annual national demand for aviation fuel. Acidic leaching of these elements as phosphates and ammoniacal nitrogen was studied. Improved leaching of 49.49 % phosphorous and 95.71 % nitrogen was observed at 40 °C and pH 2.5 over a period of 7 days into the growth media. These conditions being ideal for growth of G. sulphuraria, leaching can be done in-situ to reduce overhead cost.
Growth potential of G. sulphuraria in leached media was compared to a standard cyanidium media produced from inorganic chemicals. Initial inhibition studies were done in the leached media at 40 °C and 2-3 vol. % CO2 to observe a positive growth rate of 0.273 g L-1 day-1. Further, growth was compared to standard media with similar composition in a 96 well plate 50 μL microplate assay for 5 days. The growth rates in both media were comparable. Additionally, growth was confirmed in a 240 times larger tubular reactor in a Tissue Culture Roller drum apparatus. A better growth was observed in the leached cyanidium media as compared to the standard variant.
ContributorsMathew, Melvin (Author) / Deng, Shuguang (Thesis advisor) / Lammers, Peter J. (Committee member) / Nielsen, David R (Committee member) / Arizona State University (Publisher)
Created2017
Description
Hydrothermal Liquefaction of Algae represents one of many pathways for the sustainable replacement of fossil fuels in transportation. When processing and researching algal biofuel, determination of the higher heating value (HHV) is paramount. Bomb calorimetry represents to current method for direct determination of HHV. When determining HHV’s indirectly, the industry standard is using one of many linear correlations relating elemental composition to HHV. Most of these correlations were developed from coal industry data, meaning that they do not necessarily fit algal product data well. In this study bomb calorimetry data and CHNS/O elemental composition data were collected for Chlorella, Micract, GS 5587.1, Kirchnella, and Gal 87.1 MM8 algae species. This data was added to CHNS/O and HHV values for other algal products in literature, and utilized to test the accuracy of the Dulong, Gumz, Vandralek and Boie correlations for algae products. Several preliminary algae specific correlations were proposed through a linear regression model of the data. Of the 5 samples tested, Kirchnella exhibited the highest HHV (23.2405 ± 0.0216 MJ/kg) and Chlorella exhibited the lowest (20.2055 ± 0.0484 MJ/kg). For both the experimental, and literature CHNS/O vs HHV data, the Vandralek and Boie correlations provided the best approximations in this study. For the totality of the data collected and researched in this study, 6 of 8 proposed correlations outperformed the Vandralek equation for HHV approximation. The most promising proposed correlations incorporated multiple linear regressions for elemental fractions of CHS, CHSO and CHNSO. Being that only 20 distinct algal product samples were regressed to create the proposed correlations, more data should be incorporated before publication of a final correlation. This study should serve as a starting point for the compilation of an exhaustive database for algal product assay and HHV data.
ContributorsCopp, Connor Joseph (Author) / Deng, Shuguang (Thesis director) / Muppaneni, Tapaswy (Committee member) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2017-05
Description
Layered double hydroxides (LDHs), also known as hydrotalcite-like materials, are extensively used as precursors for the preparation of (photo-)catalysts, electrodes, magnetic materials, sorbents, etc. The synthesis typically involves the transformation to the corresponding mixed metal oxide via calcination, resulting in atomically dispersed mixed metal oxides (MMOs). This process alters the porosity of the materials, with crucial implications for the performance in many applications. Yet, the mechanisms of pore formation and collapse are poorly understood. Combining an integrated in situ and ex situ characterization approach, here we follow the evolution of porosity changes during the thermal decomposition of LDHs integrating different divalent (Mg, Ni) and trivalent (Al, Ga) metals. Variations in porous properties determined by high-resolution argon sorption are linked to the morphological and compositional changes in the samples by in situ transmission electron microscopy coupled with energy dispersive X-ray spectroscopy, which is facilitated by the synthesis of well crystallized LDHs of large crystal size. The observations are correlated with the phase changes identified by X-ray diffraction, the mass losses evidenced by thermogravimetric analysis, the structural changes determined by infrared and nuclear magnetic resonance spectroscopy, and the pore connectivity analyzed by positron annihilation spectroscopy. The findings show that the multimetallic nature of the LDH governs the size and distribution (geometry, location, and connectivity) of the mesopores developed, which is controlled by the crystallization of the MMO phase, providing key insights for the improved design of porous mixed metal oxides.
ContributorsMurty, Rohan Aditya (Author) / Deng, Shuguang (Thesis director) / Nielsen, David R. (Committee member) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2017-05
Description
Excessive weight gain during pregnancy is a significant public health concern and has been the recent focus of novel, control systems-based interventions. Healthy Mom Zone (HMZ) is an intervention study that aims to develop and validate an individually tailored and intensively adaptive intervention to manage weight gain for overweight or obese pregnant women using control engineering approaches. Motivated by the needs of the HMZ, this dissertation presents how to use system identification and state estimation techniques to assist in dynamical systems modeling and further enhance the performance of the closed-loop control system for interventions.
Underreporting of energy intake (EI) has been found to be an important consideration that interferes with accurate weight control assessment and the effective use of energy balance (EB) models in an intervention setting. To better understand underreporting, a variety of estimation approaches are developed; these include back-calculating energy intake from a closed-form of the EB model, a Kalman-filter based algorithm for recursive estimation from randomly intermittent measurements in real time, and two semi-physical identification approaches that can parameterize the extent of systematic underreporting with global/local modeling techniques. Each approach is analyzed with intervention participant data and demonstrates potential of promoting the success of weight control.
In addition, substantial efforts have been devoted to develop participant-validated models and incorporate into the Hybrid Model Predictive Control (HMPC) framework for closed-loop interventions. System identification analyses from Phase I led to modifications of the measurement protocols for Phase II, from which longer and more informative data sets were collected. Participant-validated models obtained from Phase II data significantly increase predictive ability for individual behaviors and provide reliable open-loop dynamic information for HMPC implementation. The HMPC algorithm that assigns optimized dosages in response to participant real time intervention outcomes relies on a Mixed Logical Dynamical framework which can address the categorical nature of dosage components, and translates sequential decision rules and other clinical considerations into mixed-integer linear constraints. The performance of the HMPC decision algorithm was tested with participant-validated models, with the results indicating that HMPC is superior to "IF-THEN" decision rules.
Underreporting of energy intake (EI) has been found to be an important consideration that interferes with accurate weight control assessment and the effective use of energy balance (EB) models in an intervention setting. To better understand underreporting, a variety of estimation approaches are developed; these include back-calculating energy intake from a closed-form of the EB model, a Kalman-filter based algorithm for recursive estimation from randomly intermittent measurements in real time, and two semi-physical identification approaches that can parameterize the extent of systematic underreporting with global/local modeling techniques. Each approach is analyzed with intervention participant data and demonstrates potential of promoting the success of weight control.
In addition, substantial efforts have been devoted to develop participant-validated models and incorporate into the Hybrid Model Predictive Control (HMPC) framework for closed-loop interventions. System identification analyses from Phase I led to modifications of the measurement protocols for Phase II, from which longer and more informative data sets were collected. Participant-validated models obtained from Phase II data significantly increase predictive ability for individual behaviors and provide reliable open-loop dynamic information for HMPC implementation. The HMPC algorithm that assigns optimized dosages in response to participant real time intervention outcomes relies on a Mixed Logical Dynamical framework which can address the categorical nature of dosage components, and translates sequential decision rules and other clinical considerations into mixed-integer linear constraints. The performance of the HMPC decision algorithm was tested with participant-validated models, with the results indicating that HMPC is superior to "IF-THEN" decision rules.
ContributorsGuo, Penghong (Author) / Rivera, Daniel E. (Thesis advisor) / Peet, Matthew M. (Committee member) / Forzani, Erica (Committee member) / Deng, Shuguang (Committee member) / Pavlic, Theodore P. (Committee member) / Arizona State University (Publisher)
Created2018
Description
Separation of carbon dioxide and methane for the upgrade of natural gas through use of pressure swing adsorption could potentially save large amounts of energy from the current, costly process of cryogenic distillation and provides greater cost effectiveness for carbon dioxide capture, and provide larger product flowrates than membrane permeation separation. The purpose of this study is to analyze the effects of varying initial conditions of a MatLab simulation, courtesy of Mai Xu, a graduate student at ASU, designed to use Langmuir isotherms, mass transfer equations, and adsorbent and gas properties to simulate a pressure swing adsorption process with a mixture of methane and carbon dioxide gas feed. The effects that will be varied are the adsorption/desorption time, pressurization/depressurization time, adsorption feed composition, desorption purge composition, adsorption pressure, desorption pressure, adsorption flow rate, and desorption flow rate. The study found that the trends in methane purity and production generally follow the trends predicted by literature and relevant equations, with pressure boundaries being the largest impacting factor. In addition there was a markedly inverse correlation between purity of methane product and the productivity of the system. This trend was only violated in one instance, at very low vacuum pressure during desorption, which could indicate an area that requires further study. Overall, the main areas of improvement in pressure swing adsorption for this system would be improving the selectivity of adsorption of carbon dioxide over methane, which requires improvement and change of the adsorbent, and more extreme vacuum pressures during desorption, both of which will increase methane yield and reduce operating costs.
ContributorsCook, Alexander Charles (Author) / Deng, Shuguang (Thesis director) / Mu, Bin (Committee member) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2018-05
Description
Carbon capture is an essential way to reduce greenhouse gas emissions. One way to decrease the emissions is through the use of adsorbents such as zeolites. Dr. Dong-Kyun Seo’s group (School of Molecular Sciences, Arizona State University) synthesized the nanostructured faujasite (NaX). The zeolite was characterized using Scanning Electron Microscopy (SEM) and the physisorption properties were determined using ASAP 2020. ASAP 2020 tests of the nano-zeolite pellets at 77K in a liquid N2 bath determined the BET surface area of 547.1 m2/mol, T-plot micropore volume of 0.2257 cm3/g, and an adsorption average pore width of 5.9 Å. The adsorption isotherm (equilibrium) of CH4, N2, and CO2 were measured at 25ºC. Adsorption isotherm experiments concluded that the linear isotherm was the best fit for N2, and CH4 and the Sips isotherm was a better fit than the Langmuir and Freundlich isotherm for CO2. At 25ºC and 1 atm the zeolite capacity for CO2 is 4.3339 mmol/g, 0.1948 mmol/g for CH4, and 0.3534 mmol/g for N2. The zeolite has a higher CO2 capacity than the conventional NaX zeolite. Breakthrough experiments were performed in a fixed bed 22in, 0.5 in packing height and width at 1 atm and 298 K with nano-zeolite pellets. The gas chromatographer tested and recorded the data every two minutes with a flow rate of 10 cm3/min for N2 and 10 cm3/min CO2. Breakthrough simulations of the zeolite in a fixed bed adsorber column were conducted on MATLAB utilizing varying pressures, flow rates, and fed ratios of various CO2, N2 and CH4. Simulations using ideal adsorbed solution theory (IAST) calculations determined that the selectivity of CO2 in flue gas (15% CO2 + 85% N2) is 571.79 at 1 MPa, significantly higher than commercial zeolites and literature. The nanostructured faujasite zeolite appears to be a very promising adsorbent for CO2/N2 capture from flue gas and the separation of CO2/N2.
ContributorsClark, Krysta D. (Author) / Deng, Shuguang (Thesis director) / Green, Matthew (Committee member) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2018-05
Description
Granulation is a process within particle technology where a liquid binding agent is added to a powder bed to create larger granules to modify bulk properties for easier processing. Three sets of experiments were conducted to screen for which factors had the greatest effect on granule formation, size distribution, and morphological properties when wet granulating microcrystalline cellulose and water. Previous experiments had identified the different growth regimes within wet granulation, as well as the granule formation mechanisms in single-drop granulation experiments, but little research has been conducted to determine how results extracted from single drop experiments could be used to better understand the first principles that drive high shear granulation. The experiment found that under a liquid solid ratio of 110%, the granule growth rate was linear as opposed to the induction growth regime experienced at higher liquid solid ratios. L/S ratios less than 100% led to a bimodal distribution comprised of large distributions of ungranulated powder and large irregular granules. Insufficient water hampered the growth of granules due to lack of enough water bridges to connect the granules and powder, while the large molecules continued to agglomerate with particles as they rotated around the mixer. The nozzle end was augmented so that drop size as well as drop height could be adjusted and compared to single-drop granulation experiments in proceeding investigations. As individual factors, neither augmentation had significant contributions to granule size, but preliminary screens identified that interaction between increasing L/S ratio and decreasing drop size could lead to narrower distributions of particles as well as greater circularity. Preliminary screening also identified that decreasing the drop height of the nozzle could increase the rate of particle growth during the 110% L/S trials without changing the growth mechanisms, indicating a way to alter the rate of steady-state particle growth. This paper screens for which factors are most pertinent to associating single-drop and wet granulation in order to develop granulation models that can ascertain information from single-drop granulations and predict the shape and size distribution of any wet granulation, without the need to run costly wet granulation experiments.
ContributorsLay, Michael (Author) / Emady, Heather (Thesis advisor) / Muhich, Christopher (Committee member) / Holloway, Julianne (Committee member) / Arizona State University (Publisher)
Created2019
Description
Rotary drums are commonly used for their high heat and mass transfer rates in the manufacture of cement, pharmaceuticals, food, and other particulate products. These processes are difficult to model because the particulate behavior is governed by the process conditions such as particle size, particle size distribution, shape, composition, and operating parameters, such as fill level and rotation rate. More research on heat transfer in rotary drums will increase operating efficiency, leading to significant energy savings on a global scale.
This research utilizes infrared imaging to investigate the effects of fill level and rotation rate on the particle bed hydrodynamics and the average wall-particle heat transfer coefficient. 3 mm silica beads and a stainless steel rotary drum with a diameter of 6 in and a length of 3 in were used at fill levels of 10 %, 17.5 %, and 25 %, and rotation rates of 2 rpm, 6 rpm, and 10 rpm. Two full factorial designs of experiments were completed to understand the effects of these factors in the presence of conduction only (Case 1) and conduction with forced convection (Case 2). Particle-particle friction caused the particle bed to stagnate at elevated temperatures in Case 1, while the inlet air velocity in Case 2 dominated the particle friction effects to maintain the flow profile. The maximum heat transfer coefficient was achieved at a high rotation rate and low fill level in Case 1, and at a high rotation rate and high fill level in Case 2. Heat losses from the system were dominated by natural convection between the hot air in the drum and the external surroundings.
This research utilizes infrared imaging to investigate the effects of fill level and rotation rate on the particle bed hydrodynamics and the average wall-particle heat transfer coefficient. 3 mm silica beads and a stainless steel rotary drum with a diameter of 6 in and a length of 3 in were used at fill levels of 10 %, 17.5 %, and 25 %, and rotation rates of 2 rpm, 6 rpm, and 10 rpm. Two full factorial designs of experiments were completed to understand the effects of these factors in the presence of conduction only (Case 1) and conduction with forced convection (Case 2). Particle-particle friction caused the particle bed to stagnate at elevated temperatures in Case 1, while the inlet air velocity in Case 2 dominated the particle friction effects to maintain the flow profile. The maximum heat transfer coefficient was achieved at a high rotation rate and low fill level in Case 1, and at a high rotation rate and high fill level in Case 2. Heat losses from the system were dominated by natural convection between the hot air in the drum and the external surroundings.
ContributorsBoepple, Brandon (Author) / Emady, Heather (Thesis advisor) / Muhich, Christopher (Committee member) / Holloway, Julianne (Committee member) / Arizona State University (Publisher)
Created2019
Description
Zwitterionic polymers, due to their supurior capability of electrostatically induced hydration, have been considered as effective functionalities to alleviate bio-fouling of reverse osmosis (RO) membranes. Bulk modification of polysulfone-based matrices to improve hydrophilicity, on the other hand, is favored due to the high membrane performance, processibility, and intrinsic chlorine resistance. Here a novel synthetic method was demonstrated to prepare zwitterionic poly(arylene ether sulfone) (PAES) copolymers, which was blended with native polysulfone (PSf) to fabricate free-standing asymmetric membranes via non-solvent induced phase separation process. Both the porosity of the support layer and surface hydrophilicity increased drastically due to the incorporation of zwitterion functionalities in the rigid polysulfone matrix. The water permeance and antifouling ability of the blend membranes were both remarkably improved to 2.5 Lm−2 h−1 bar−1 and 94% of flux recovery ratio, respectively, while salt rejection remained at a high level (98%) even under the high exposure to chlorine (8,000 ppm•h). Besides the preliminary blended membrane design, for the future membrane property enhancement, this dissertation also focused on polymer structure optimizations via elucidating the fundamentals from two perspectives: 1). Synthetic reaction kinetics and mechanisms on polycondensation of PAES. Interestingly, in combination of experiments and the computational calculations by density functional theory (DFT) methods in this work, only the aryl chlorides (ArCl) monomer follows the classical second-order reaction kinetics of aromatic nucleophilic substitution (SNAr) mechanism, while the kinetics of the aryl fluorides (ArF) reaction fit a third-order rate law. The third order reaction behavior of the ArF monomer is attributed to the activation of the carbon-fluorine bond by two potassium cations (at least one bounded to phenolate), which associate as a strong three-body complex. This complex acts as the predominant reactant during the attack by the nucleophile. 2). Optimized copolymer structures were developed for controlled high molecular weight (Mw ~ 65 kDa) and zwitterionic charge content (0~100 mol%), via off-set stoichiometry during polycondensations, following with thiol-ene click reaction and ring-opening of sultone to introduce the sulfobetaine functional groups. The structure-property-morphology relationships were elucidated for better understanding atomic-level features in the charged polymers for future high-performance desalination applications.
ContributorsYang, Yi, Ph.D (Author) / Green, Matthew D (Thesis advisor) / Lin, Jerry Y.S. (Committee member) / Lind, Marylaura (Committee member) / Perreault, Francois (Committee member) / Deng, Shuguang (Committee member) / Arizona State University (Publisher)
Created2019
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 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.
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
Description
This thesis investigated the effects of differing diameters and varying moisture content on the flowability properties of granular glass beads through use of a Freeman FT4 Powder Rheometer. These parameters were tested in order to construct an empirical model to predict flowability properties of glass beads at differing size ranges and moisture contents. The final empirical model outputted an average error of 8.73% across all tested diameters and moisture ranges.
Mohr's circles were constructed from experimentally-obtained shear stress values to quantitatively describe flowability of tested materials in terms of a flow function parameter. A high flow function value (>10) was indicative of a good flow.
By testing 120-180 µm, 120-350 µm, 180-250 µm, 250-350 µm, 430-600 µm, and 600-850 µm glass bead diameter ranges, an increase in size was seen to result in higher flow function values. The limitations of testing using the FT4 became apparent as inconsistent flow function values were obtained at 0% moisture with size ranges above 120-180 µm, or at flow function values of >21. Bead sizes larger than 430 µm showed significant standard deviation over all tested trials--when excluding size ranges above that value, the empirical model showed an average error of only 6.45%.
Wet material testing occurred at all tested glass bead size ranges using a deionized water content of 0%, 1%, 5%, 15%, and 20% by weight. The results of such testing showed a decrease in the resulting flow function parameter as more water content was added. However, this trend changed as 20% moisture content was achieved; the wet material became supersaturated, and an increase in flow function values was observed. The empirical model constructed, therefore, neglected the 20% moisture content regime.
Mohr's circles were constructed from experimentally-obtained shear stress values to quantitatively describe flowability of tested materials in terms of a flow function parameter. A high flow function value (>10) was indicative of a good flow.
By testing 120-180 µm, 120-350 µm, 180-250 µm, 250-350 µm, 430-600 µm, and 600-850 µm glass bead diameter ranges, an increase in size was seen to result in higher flow function values. The limitations of testing using the FT4 became apparent as inconsistent flow function values were obtained at 0% moisture with size ranges above 120-180 µm, or at flow function values of >21. Bead sizes larger than 430 µm showed significant standard deviation over all tested trials--when excluding size ranges above that value, the empirical model showed an average error of only 6.45%.
Wet material testing occurred at all tested glass bead size ranges using a deionized water content of 0%, 1%, 5%, 15%, and 20% by weight. The results of such testing showed a decrease in the resulting flow function parameter as more water content was added. However, this trend changed as 20% moisture content was achieved; the wet material became supersaturated, and an increase in flow function values was observed. The empirical model constructed, therefore, neglected the 20% moisture content regime.
ContributorsKleppe, Cameron (Author) / Emady, Heather (Thesis advisor) / Marvi, Hamidreza (Committee member) / Deng, Shuguang (Committee member) / Arizona State University (Publisher)
Created2019
Description
In Nepal, a viable solution for environmental management, food and water security is the production of biochar, a carbon material made of plants burned in low oxygen conditions. Currently, the biochar is manufactured into charcoal briquettes and sold on the market for energy usage, however this may not provide the best value for community members who make less than a dollar a day and sell the biochar for as little as 16 cents per kilogram. This thesis seeks to improve the price of biochar and help their livelihoods as well as explore innovative solutions. One way to improve biochar while addressing water security problems is to create activated carbon, which uses its heightened porosity to adsorb contaminants from water or air. Activated carbon is also worth 100x the price of biochar. This thesis evaluates the mass content of biochar produced in Nepal, comparing it to literature values, and performed gravimetric and thermogravimetric analysis, comparing it to Activated Charcoal. Analysis of the biochar system used in Nepal reveals that the byproduct of biochar, biofuels, is highly underutilized. The higher heating value of biochar is 17.95 MJ/kg, which is much lower than other charcoals which burn around 30 MJ/kg. Low volatile content, less than 5% in biochar, provides a smokeless briquette, which is favorable on the market, however low heating value and misutilizations of biofuels in the solution indicate that creating a briquette is not the best use for biochar. Ash content is really high in this biochar, averaging around 12% and it may be due to the feedstock, a composite between Mikania and Lantana, which have 5.23% and 10.77% ash content respectively. This does not necessarily indicate a poor quality biochar, since ash values can vary widely between charcoals. Producing activated charcoal from this biochar is a favored solution; it will increase the price of the biochar, provide water security solutions, and be an appropriate process for this biochar, where heating value and underutilization of biofuel byproducts pose a problem.
ContributorsCayer, Joelle Marie Caroline (Author) / Chhetri, Netra (Thesis director) / Henderson, Mark (Committee member) / Deng, Shuguang (Committee member) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2019-05
Description
This honors thesis is focused on two separate catalysis projects conducted under the mentorship of Dr. Javier Pérez-Ramírez at ETH Zürich. The first project explored ethylene oxychlorination over supported europium oxychloride catalysts. The second project investigated alkyne semihydrogenation over nickel phosphide catalysts. This work is the subject of a publication of which I am a co-author, as cited below.
Project 1 Abstract: Ethylene Oxychlorination
The current two-step process for the industrial process of vinyl chloride production involves CuCl2 catalyzed ethylene oxychlorination to ethylene dichloride followed by thermal cracking of the latter to vinyl chloride. To date, no industrial application of a one-step process is available. To close this gap, this work evaluates a wide range of self-prepared supported CeO2 and EuOCl catalysts for one-step production of vinyl chloride from ethylene in a fixed-bed reactor at 623 773 K and 1 bar using feed ratios of C2H4:HCl:O2:Ar:He = 3:3 6:1.5 6:3:82 89.5. Among all studied systems, CeO2/ZrO2 and CeO2/Zeolite MS show the highest activity but suffer from severe combustion of ethylene, forming COx, while 20 wt.% EuOCl/γ-Al2O3 leads to the best vinyl chloride selectivity of 87% at 15.6% C2H4 conversion with complete suppression of CO2 formation and only 4% selectivity to CO conversion for over 100 h on stream. Characterization by XRD and EDX mapping reveals that much of the Eu is present in non-active phases such as Al2Eu or EuAl4, indicating that alternative synthesis methods could be employed to better utilize the metal. A linear relationship between conversion and metal loading is found for this catalyst, indicating that always part of the used Eu is available as EuOCl, while the rest forms inactive europium aluminate species. Zeolite-supported EuOCl slightly outperforms EuOCl/γ Al2O3 in terms of total yield, but is prone to significant coking and is unstable. Even though a lot of Eu seems locked in inactive species on EuOCl/γ Al2O3, these results indicate possible savings of nearly 16,000 USD per kg of catalyst compared to a bulk EuOCl catalyst. These very promising findings constitute a crucial step for process intensification of polyvinyl chloride production and exploring the potential of supported EuOCl catalysts in industrially-relevant reactions.
Project 2 Abstract: Alkyne Semihydrogenation
Despite strongly suffering from poor noble metal utilization and a highly toxic selectivity modifier (Pb), the archetypal catalyst applied for the three-phase alkyne semihydrogenation, the Pb-doped Pd/CaCO3 (Lindlar catalyst), is still being utilized at industrial level. Inspired by the very recent strategies involving the modification of Pd with p-block elements (i.e., S), this work extrapolates the concept by preparing crystalline metal phosphides with controlled stoichiometry. To develop an affordable and environmentally-friendly alternative to traditional hydrogenation catalysts, nickel, a metal belonging to the same group as Pd and capable of splitting molecular hydrogen has been selected. Herein, a simple two-step synthesis procedure involving nontoxic precursors was used to synthesize bulk nickel phosphides with different stoichiometries (Ni2P, Ni5P4, and Ni12P5) by controlling the P:Ni ratios. To uncover structural and surface features, this catalyst family is characterized with an array of methods including X-ray diffraction (XRD), 31P magic-angle nuclear magnetic resonance (MAS-NMR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). Bulk-sensitive techniques prove the successful preparation of pure phases while XPS analysis unravels the facile passivation occurring at the NixPy surface that persists even after reductive treatment. To assess the characteristic surface fingerprints of these materials, Ar sputtering was carried out at different penetration depths, reveling the presence of Ni+ and P-species. Continuous-flow three-phase hydrogenations of short-chain acetylenic compounds display that the oxidized layer covering the surface is reduced under reaction conditions, as evidenced by the induction period before reaching the steady state performance. To assess the impact of the phosphidation treatment on catalytic performance, the catalysts were benchmarked against a commercial Ni/SiO2-Al2O3 sample. While Ni/SiO2-Al2O3 presents very low selectivity to the alkene (the selectivity is about 10% at full conversion) attributed to the well-known tendency of naked nickel nanoparticles to form hydrides, the performance of nickel phosphides is highly selective and independent of P:Ni ratio. In line with previous findings on PdxS, kinetic tests indicate the occurrence of a dual-site mechanism where the alkyne and hydrogen do not compete for the same site.
This work is the subject of a publication of which I am a co-author, as cited below.
D. Albani; K. Karajovic; B. Tata; Q. Li; S. Mitchell; N. López; J. Pérez-Ramírez. Ensemble Design in Nickel Phosphide Catalysts for Alkyne Semi-Hydrogenation. ChemCatChem 2019. doi.org/10.1002/cctc.201801430
Project 1 Abstract: Ethylene Oxychlorination
The current two-step process for the industrial process of vinyl chloride production involves CuCl2 catalyzed ethylene oxychlorination to ethylene dichloride followed by thermal cracking of the latter to vinyl chloride. To date, no industrial application of a one-step process is available. To close this gap, this work evaluates a wide range of self-prepared supported CeO2 and EuOCl catalysts for one-step production of vinyl chloride from ethylene in a fixed-bed reactor at 623 773 K and 1 bar using feed ratios of C2H4:HCl:O2:Ar:He = 3:3 6:1.5 6:3:82 89.5. Among all studied systems, CeO2/ZrO2 and CeO2/Zeolite MS show the highest activity but suffer from severe combustion of ethylene, forming COx, while 20 wt.% EuOCl/γ-Al2O3 leads to the best vinyl chloride selectivity of 87% at 15.6% C2H4 conversion with complete suppression of CO2 formation and only 4% selectivity to CO conversion for over 100 h on stream. Characterization by XRD and EDX mapping reveals that much of the Eu is present in non-active phases such as Al2Eu or EuAl4, indicating that alternative synthesis methods could be employed to better utilize the metal. A linear relationship between conversion and metal loading is found for this catalyst, indicating that always part of the used Eu is available as EuOCl, while the rest forms inactive europium aluminate species. Zeolite-supported EuOCl slightly outperforms EuOCl/γ Al2O3 in terms of total yield, but is prone to significant coking and is unstable. Even though a lot of Eu seems locked in inactive species on EuOCl/γ Al2O3, these results indicate possible savings of nearly 16,000 USD per kg of catalyst compared to a bulk EuOCl catalyst. These very promising findings constitute a crucial step for process intensification of polyvinyl chloride production and exploring the potential of supported EuOCl catalysts in industrially-relevant reactions.
Project 2 Abstract: Alkyne Semihydrogenation
Despite strongly suffering from poor noble metal utilization and a highly toxic selectivity modifier (Pb), the archetypal catalyst applied for the three-phase alkyne semihydrogenation, the Pb-doped Pd/CaCO3 (Lindlar catalyst), is still being utilized at industrial level. Inspired by the very recent strategies involving the modification of Pd with p-block elements (i.e., S), this work extrapolates the concept by preparing crystalline metal phosphides with controlled stoichiometry. To develop an affordable and environmentally-friendly alternative to traditional hydrogenation catalysts, nickel, a metal belonging to the same group as Pd and capable of splitting molecular hydrogen has been selected. Herein, a simple two-step synthesis procedure involving nontoxic precursors was used to synthesize bulk nickel phosphides with different stoichiometries (Ni2P, Ni5P4, and Ni12P5) by controlling the P:Ni ratios. To uncover structural and surface features, this catalyst family is characterized with an array of methods including X-ray diffraction (XRD), 31P magic-angle nuclear magnetic resonance (MAS-NMR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). Bulk-sensitive techniques prove the successful preparation of pure phases while XPS analysis unravels the facile passivation occurring at the NixPy surface that persists even after reductive treatment. To assess the characteristic surface fingerprints of these materials, Ar sputtering was carried out at different penetration depths, reveling the presence of Ni+ and P-species. Continuous-flow three-phase hydrogenations of short-chain acetylenic compounds display that the oxidized layer covering the surface is reduced under reaction conditions, as evidenced by the induction period before reaching the steady state performance. To assess the impact of the phosphidation treatment on catalytic performance, the catalysts were benchmarked against a commercial Ni/SiO2-Al2O3 sample. While Ni/SiO2-Al2O3 presents very low selectivity to the alkene (the selectivity is about 10% at full conversion) attributed to the well-known tendency of naked nickel nanoparticles to form hydrides, the performance of nickel phosphides is highly selective and independent of P:Ni ratio. In line with previous findings on PdxS, kinetic tests indicate the occurrence of a dual-site mechanism where the alkyne and hydrogen do not compete for the same site.
This work is the subject of a publication of which I am a co-author, as cited below.
D. Albani; K. Karajovic; B. Tata; Q. Li; S. Mitchell; N. López; J. Pérez-Ramírez. Ensemble Design in Nickel Phosphide Catalysts for Alkyne Semi-Hydrogenation. ChemCatChem 2019. doi.org/10.1002/cctc.201801430
ContributorsTata, Bharath (Author) / Deng, Shuguang (Thesis director) / Muhich, Christopher (Committee member) / Chemical Engineering Program (Contributor, Contributor) / School of Sustainability (Contributor) / Barrett, The Honors College (Contributor)
Created2019-05
Description
Fossil fuels have been the primary source of energy in the world for many decades. However, they are among the top contributors of the greenhouse gas emissions in the atmosphere. The objective of this research was to produce a more environmentally friendly biofuel from Algae-Helix and Salicornia biomasses. Experiments were conducted using a hydrothermal liquefaction (HTL) technique in the HTL reactor to produce biofuel that can potentially replace fossil fuel usage. Hydrothermal Liquefaction is a method used to convert the biomass into the biofuels. HTL experiments on Algae-Helix and Salicornia at 200°C-350°C and 430psi were performed to investigate the effect of temperature on the biocrude yield of the respective biomass used. The effect of the biomass mixture (co-liquefaction) of Salicornia and algae on the amount of biocrude produced was also explored. The biocrude and biochar (by-product) obtained from the hydrothermal liquefaction process were also analyzed using thermogravimetric analyzer (TGA). The maximum biocrude yield for the algae-helix biomass and for the Salicornia biomass were both obtained at 300°C which were 34.63% and 7.65% respectively. The co-liquefaction of the two biomasses by 50:50 provided a maximum yield of 17.26% at 250°C. The co-liquefaction of different ratios explored at 250°C and 300°C concluded that Salicornia to algae-helix ratio of 20:80 produced the highest yields of 22.70% and 31.97%. These results showed that co-liquefaction of biomass if paired well with the optimizing temperature can produce a high biocrude yield. The TGA profiles investigated have shown that salicornia has higher levels of ash content in comparison with the algae-helix. It was then recommended that for a mixture of algae and Salicornia, large-scale biofuel production should be conducted at 250℃ in a 20:80 salicornia to algae biocrude ratio, since it lowers energy needs. The high biochar content left can be recycled to optimize biomass, and prevent wastage.
ContributorsLaideson, Maymary Everrest (Co-author) / Luboowa, Kato (Co-author) / Deng, Shuguang (Thesis director) / Nielsen, David (Committee member) / Chemical Engineering Program (Contributor) / Economics Program in CLAS (Contributor) / Barrett, The Honors College (Contributor)
Created2019-05
Description
Fossil fuels have been the primary source of energy in the world for many decades. However, they are among the top contributors of the greenhouse gas emissions in the atmosphere. The objective of this research was to produce a more environmentally friendly biofuel from Algae-Helix and Salicornia biomasses. Experiments were conducted using a hydrothermal liquefaction (HTL) technique in the HTL reactor to produce biofuel that can potentially replace fossil fuel usage. Hydrothermal Liquefaction is a method used to convert the biomass into the biofuels. HTL experiments on Algae-Helix and Salicornia at 200°C-350°C and 430psi were performed to investigate the effect of temperature on the biocrude yield of the respective biomass used. The effect of the biomass mixture (co-liquefaction) of Salicornia and algae on the amount of biocrude produced was also explored. The biocrude and biochar (by-product) obtained from the hydrothermal liquefaction process were also analyzed using thermogravimetric analyzer (TGA). The maximum biocrude yield for the algae-helix biomass and for the Salicornia biomass were both obtained at 300°C which were 34.63% and 7.65% respectively. The co-liquefaction of the two biomasses by 50:50 provided a maximum yield of 17.26% at 250°C. The co-liquefaction of different ratios explored at 250°C and 300°C concluded that Salicornia to algae-helix ratio of 20:80 produced the highest yields of 22.70% and 31.97%. These results showed that co-liquefaction of biomass if paired well with the optimizing temperature can produce a high biocrude yield. The TGA profiles investigated have shown that salicornia has higher levels of ash content in comparison with the algae-helix. It was then recommended that for a mixture of algae and Salicornia, large-scale biofuel production should be conducted at 250℃ in a 20:80 salicornia to algae biocrude ratio, since it lowers energy needs. The high biochar content left can be recycled to optimize biomass, and prevent wastage.
ContributorsLuboowa, Kato Muhammed (Co-author) / Laideson, Maymary (Co-author) / Deng, Shuguang (Thesis director) / Nielsen, David (Committee member) / Chemical Engineering Program (Contributor) / School of Sustainability (Contributor) / Barrett, The Honors College (Contributor)
Created2019-05
Description
A Study of the gasification of municipal solid waste (MSW) for hydrogen production was completed through research and statistical design of experiment. The study was done for general syngas production with conditions of high temperature and pressure. Waste samples from kitchen waste including rice, avocado, and egg shells were used. Dry orange blossom tree leaves were included and a very minimal fraction of used paper and Styrofoam. One of the components of the syngas predicted was hydrogen, but this study does not discuss techniques for the separation of the hydrogen from the syngas. A few suggestions, however, such as the use of gas chromatography and membranes are made for the study of the syngas and separation of the hydrogen from the syngas. A three level, three factors-half factorial design was used to analyze the impact of pressure, residence time and temperature on the gasification of MSW through a hydrothermal gasification approach. A series 4590 micro stirred reactor of 100mL was used to gasify MSW, but first, it was established through a TGA approach that the waste was about 5% moisture content and 55% organic content (OC). The TGA device used was the TG 209 F1 Libra. Results of the gasification indicated that the most important factor in the gasification of MSW is temperature, followed by residence time and that the syngas yield increases with a decreasing pressure of the system. A thermodynamic model relating the three factors and the syngas yield was developed.
ContributorsBuyinza, Allan Smith (Author) / Deng, Shuguang (Thesis director) / Nannenga, Brent (Committee member) / Chemical Engineering Program (Contributor) / School of Sustainability (Contributor) / Barrett, The Honors College (Contributor)
Created2019-05
Description
In this study, the viability of doped ceria for SOFC electrolyte application is investigated through calculation of the oxygen anion diffusion through undoped, Zr-doped, Pr-doped, and Gd-doped ceria. DFT calculations are performed to determine the oxygen vacancy formation and activation energy to vacancy migration barriers for each material. All dopants were found to increase the activation energy to vacancy migration and decrease the oxygen vacancy formation energy. These energy barriers are then integrated into a kinetic Monte Carlo simulation that models the oxygen vacancy diffusion over time. From the simulation results, the diffusivity of oxygen anion through each material is calculated as a function of dopant concentration and temperature. It was discovered that diffusivity increased with temperature and decreased with dopant concentration in all dopant cases. Gd-doped ceria exhibited the highest overall oxygen diffusion rates, making it the most effective choice for SOFC electrolyte application, while Zr-doped ceria would be the least effective choice with the lowest diffusion rates.
ContributorsMandal, Bennett (Author) / Muhich, Christopher (Thesis director) / Milcarek, Ryan (Committee member) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2019-12
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 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.
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
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, 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.
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
Description
Transition metal di- and tri-halides (TMH) have recently gathered research attention owing to their intrinsic magnetism all the way down to their two-dimensional limit. 2D magnets, despite being a crucial component for realizing van der Waals heterostructures and devices with various functionalities, were not experimentally proven until very recently in 2017. The findings opened up enormous possibilities for studying new quantum states of matter that can enable potential to design spintronic, magnetic memory, data storage, sensing, and topological devices. However, practical applications in modern technologies demand materials with various physical and chemical properties such as electronic, optical, structural, catalytic, magnetic etc., which cannot be found within single material systems. Considering that compositional modifications in 2D systems lead to significant changes in properties due to the high anisotropy inherent to their crystallographic structure, this work focuses on alloying of TMH compounds to explore the potentials for tuning their properties. In this thesis, the ternary cation alloys of Co(1-x)Ni(x)Cl(2) and Mo(1-x)Cr(x)Cl(3) were synthesized via chemical vapor transport at a various stoichiometry. Their compositional, structural, and magnetic properties were studied using Energy Dispersive Spectroscopy, Raman Spectroscopy, X-Ray Diffraction, and Vibrating Sample Magnetometry. It was found that completely miscible ternary alloys of Co(1-x)Ni(x)Cl(2) show an increasing Néel temperature with nickel concentration. The Mo(1-x)Cr(x)Cl(3) alloy shows potential magnetic phase changes induced by the incorporation of molybdenum species within the host CrCl3 lattice. Magnetic measurements give insight into potential antiferromagnetic to ferromagnetic transition with molybdenum incorporation, accompanied by a shift in the magnetic easy-axis from parallel to perpendicular. Phase separation was found in the Fe(1-x)Cr(x)Cl(3) ternary alloy indicating that crystallographic structure compatibility plays an essential role in determining the miscibility of two parent compounds. Alloying across two similar (TMH) compounds appears to yield predictable results in properties as in the case of Co(1-x)Ni(x)Cl(2), while more exotic transitions, as in the case of Mo(1-x)Cr(x)Cl(3), can emerge by alloying dissimilar compounds. When dissimilarity reaches a certain limit, as with Fe(1-x)Cr(x)Cl(3), phase separation becomes more favorable. Future studies focusing on magnetic and structural phase transitions will reveal more insight into the effect of alloying in these TMH systems.
ContributorsKolari, Pranvera (Author) / Tongay, Sefaattin (Thesis advisor) / Jiao, Yang (Committee member) / Muhich, Christopher (Committee member) / Arizona State University (Publisher)
Created2020
Description
Losses in commercial microwave dielectrics arise from spin excitations in paramagnetic transition metal dopants, at least at reduced temperatures. The magnitude of the loss tangent can be altered by orders of magnitude through the application of an external magnetic field. The goal of this thesis is to produce “smart” dielectrics that can be switched “on” or “off” at small magnetic fields while investigating the influence of transition metal dopants on the dielectric, magnetic, and structural properties.
A proof of principle demonstration of a resonator that can switch from a high-Q “on state” to a low-Q “off state” at reduced temperatures is demonstrated in (Al1-xFex)2O3 and La(Al1-xFex)O3. The Fe3+ ions are in a high spin state (S=5/2) and undergo electron paramagnetic resonance absorption transitions that increase the microwave loss of the system. Transitions occur between mJ states with a corresponding change in the angular momentum, J, by ±ħ (i.e., ΔmJ=±1) at small magnetic fields. The paramagnetic ions also have an influence on the dielectric and magnetic properties, which I explore in these systems along with another low loss complex perovskite material, Ca[(Al1-xFex)1/2Nb1/2]O3. I describe what constitutes an optimal microwave loss switchable material induced from EPR transitions and the mechanisms associated with the key properties.
As a first step to modeling the properties of high-performance microwave host lattices and ultimately their performance at microwave frequencies, a first-principles approach is used to determine the structural phase stability of various complex perovskites with a range of tolerance factors at 0 K and finite temperatures. By understanding the correct structural phases of these complex perovskites, the temperature coefficient of resonant frequency can be better predicted.
A strong understanding of these parameters is expected to open the possibility to produce new types of high-performance switchable filters, time domain MIMO’s, multiplexers, and demultiplexers.
A proof of principle demonstration of a resonator that can switch from a high-Q “on state” to a low-Q “off state” at reduced temperatures is demonstrated in (Al1-xFex)2O3 and La(Al1-xFex)O3. The Fe3+ ions are in a high spin state (S=5/2) and undergo electron paramagnetic resonance absorption transitions that increase the microwave loss of the system. Transitions occur between mJ states with a corresponding change in the angular momentum, J, by ±ħ (i.e., ΔmJ=±1) at small magnetic fields. The paramagnetic ions also have an influence on the dielectric and magnetic properties, which I explore in these systems along with another low loss complex perovskite material, Ca[(Al1-xFex)1/2Nb1/2]O3. I describe what constitutes an optimal microwave loss switchable material induced from EPR transitions and the mechanisms associated with the key properties.
As a first step to modeling the properties of high-performance microwave host lattices and ultimately their performance at microwave frequencies, a first-principles approach is used to determine the structural phase stability of various complex perovskites with a range of tolerance factors at 0 K and finite temperatures. By understanding the correct structural phases of these complex perovskites, the temperature coefficient of resonant frequency can be better predicted.
A strong understanding of these parameters is expected to open the possibility to produce new types of high-performance switchable filters, time domain MIMO’s, multiplexers, and demultiplexers.
ContributorsGonzales, Justin Michael (Author) / Newman, Nathan (Thesis advisor) / Muhich, Christopher (Committee member) / Tongay, Sefaattin (Committee member) / Arizona State University (Publisher)
Created2020
Description
Polyurea is a highly versatile material used in coatings and armor systems to protect against extreme conditions such as ballistic impact, cavitation erosion, and blast loading. However, the relationships between microstructurally-dependent deformation mechanisms and the mechanical properties of polyurea are not yet fully understood, especially under extreme conditions. In this work, multi-scale coarse-grained models are developed to probe molecular dynamics across the wide range of time and length scales that these fundamental deformation mechanisms operate. In the first of these models, a high-resolution coarse-grained model of polyurea is developed, where similar to united-atom models, hydrogen atoms are modeled implicitly. This model was trained using a modified iterative Boltzmann inversion method that dramatically reduces the number of iterations required. Coarse-grained simulations using this model demonstrate that multiblock systems evolve to form a more interconnected hard phase, compared to the more interrupted hard phase composed of distinct ribbon-shaped domains found in diblock systems. Next, a reactive coarse-grained model is developed to simulate the influence of the difference in time scales for step-growth polymerization and phase segregation in polyurea. Analysis of the simulated cured polyurea systems reveals that more rapid reaction rates produce a smaller diameter ligaments in the gyroidal hard phase as well as increased covalent bonding connecting the hard domain ligaments as evidenced by a larger fraction of bridging segments and larger mean radius of gyration of the copolymer chains. The effect that these processing-induced structural variations have on the mechanical properties of the polymer was tested by simulating uniaxial compression, which revealed that the higher degree of hard domain connectivity leads to a 20% increase in the flow stress. A hierarchical multiresolution framework is proposed to fully link coarse-grained molecular simulations across a broader range of time scales, in which a family of coarse-grained models are developed. The models are connected using an incremental reverse–mapping scheme allowing for long time scale dynamics simulated at a highly coarsened resolution to be passed all the way to an atomistic representation.
ContributorsLiu, Minghao (Author) / Oswald, Jay (Thesis advisor) / Muhich, Christopher (Committee member) / Jiang, Hanqing (Committee member) / Peralta, Pedro (Committee member) / Jiao, Yang (Committee member) / Arizona State University (Publisher)
Created2020
Description
The continued reliance on fossil fuel for energy resources has proven to be unsustainable, leading to depletion of world reserves and emission of greenhouse gases during their combustion. Therefore, research initiatives to develop potentially carbon-neutral biofuels were given the highest importance. Hydrothermal liquefaction (HTL, a thermochemical conversion process) of microalgae is recognized as a favorable and efficient technique to produce liquid biofuels from wet feedstocks. In this work, three different microalgae (Kirchneriella sp., Galdieria sulphuraria, Micractinium sp.) grown and harvested at Arizona State University were hydrothermally liquefied to optimize their process conditions under different temperatures (200-375 °C), residence times (15-60 min), solids loadings (10-20 wt.%), and process pressures (9-24 MPa). A one-factor-at-a-time approach was employed, and comprehensive experiments were conducted at 10 % solid loadings and a residence time of 30 min. Co-liquefaction of Salicornia bigelovii Torr. (SL), Swine manure (SM) with Cyanidioschyzon merolae (CM) was tested for the presence of synergy. A positive synergistic effect was observed during the co-liquefaction of biomasses, where the experimental yield (32.95 wt.%) of biocrude oil was higher than the expected value (29.23 wt.% ). Co-liquefaction also led to an increase in the energy content of the co-liquefied biocrude oil and a higher energy recovery rate ( 88.55 %). The HTL biocrude was measured for energy content, elemental, and chemical composition using GC-MS. HTL aqueous phase was analyzed for potential co-products by spectrophotometric techniques and is rich in soluble carbohydrates, dissolved ammoniacal nitrogen, and phosphates. HTL biochar was studied for its nutrient content (nitrogen and phosphorous) and viability of its recovery to cultivate algae without any inhibition using the nutrient leaching. HTL biochar was also studied to produce hydrogen via pyrolysis using a membrane reactor at 500 °C, 1 atm, for 24 h to produce 5.93 wt.% gas. The gaseous product contains 45.7 mol % H2, 44.05 ml % CH4, and 10.25 mol % of CO. The versatile applications of HTL biochar were proposed from a detailed physicochemical characterization. The metal impurities in the algae, bio-oil, and biochar were quantified by ICP-OES where algae and biochar contain a large proportion of phosphorous and magnesium.
ContributorsDandamudi, Kodanda Phani Raj (Author) / Deng, Shuguang (Thesis advisor) / Lammers, Peter J. (Committee member) / Fini, Elham H. (Committee member) / Lind Thomas, MaryLaura (Committee member) / Varman, Arul M. (Committee member) / Arizona State University (Publisher)
Created2020
Description
Granular material can be found in many industries and undergo process steps like drying, transportation, coating, chemical, and physical conversions. Understanding and optimizing such processes can save energy as well as material costs, leading to improved products. Silica beads are one such granular material encountered in many industries as a catalyst support material. The present research aims to obtain a fundamental understanding of the hydrodynamics and heat transfer mechanisms in silica beads. Studies are carried out using a hopper discharge bin and a rotary drum, which are some of the most common process equipment found in various industries. Two types of micro-glass beads with distinct size distributions are used to fill the hopper in two possible packing arrangements with varying mass ratios. For the well-mixed configuration, the fine particles clustered at the hopper bottom towards the end of the discharge. For the layered configuration, the coarse particles packed at the hopper bottom discharge first, opening a channel for the fine particles on the top. Also, parameters such as wall roughness (WR) and particle roughness (PR) are studied by etching the particles. The discharge rate is found to increase with WR, and found to be proportional to (Root mean square of PR)^(-0.58). Furthermore, the drum is used to study the conduction and convection heat transfer behavior of the particle bed with varying process conditions. A new non-invasive temperature measurement technique is developed using infrared thermography, which replaced the traditional thermocouples, to record the temperatures of the particles and the drum wall. This setup is used to understand the flow regimes of the particle bed inside the drum and the heat transfer mechanisms with varying process conditions. The conduction heat transfer rate is found to increase with decreasing particle size, decreasing fill level, and increasing rotation speed. The convection heat transfer rate increased with increasing fill level and decreasing particle size, and rotation speed had no significant effect. Due to the complexities in these systems, it is not always possible to conduct experiments, therefore, heat transfer models in Discrete Element Method codes (MFIX-DEM: open-source code, and EDEM: commercial code) are adopted, validated, and the effects of model parameters are studied using these codes.
ContributorsAdepu, Manogna (Author) / Emady, Heather (Thesis advisor) / Jiao, Yang (Committee member) / Green, Matthew (Committee member) / Thomas, Marylaura (Committee member) / Muhich, Christopher (Committee member) / Arizona State University (Publisher)
Created2020
Description
Bio-modification of asphalt binder brings significant benefits in terms of increasing sustainable and environmental practices, stabilizing prices, and decreasing costs. However, bio-modified asphalt binders have shown varying performance regarding susceptibility to moisture damage; some bio-oil modifiers significantly increase asphalt binder's susceptibility to moisture damage. This variability in performance is largely due to the large number of bio-masses available for use as sources of bio-oil, as well as the type of processing procedure followed in converting the bio-mass into a bio-oil for modifying asphalt binder. Therefore, there is a need for a method of properly evaluating the potential impact of a bio-oil modifier for asphalt binder on the overall performance of asphalt pavement, in order to properly distinguish whether a particular bio-oil modifier increases or decreases the moisture susceptibility of asphalt binder. Therefore, the goal of this study is a multi-scale investigation of bio-oils with known chemical compositions to determine if there is a correlation between a fundamental property of a bio-oil and the resulting increase or decrease in moisture susceptibility of a binder when it is modified with the bio-oil. For instance, it was found that polarizability of asphalt constituents can be a promising indicator of moisture susceptibility of bitumen. This study will also evaluate the linkage of the fundamental property to newly developed binder-level test methods. It was found that moisture-induced shear thinning of bitumen containing glass beads can differentiate moisture susceptible bitumen samples. Based on the knowledge determined, alternative methods of reducing the moisture susceptibility of asphalt pavement will also be evaluated. It was shown that accumulation of acidic compounds at the interface of bitumen and aggregate could promote moisture damage. It was further found that detracting acidic compounds from the interface could be done by either of neutralizing active site of stone aggregate to reduce affinity for acids or by arresting acidic compounds using active mineral filler. The study results showed there is a strong relation between composition of bitumen and its susceptibility to moisture. This in turn emphasize the importance of integrating knowledge of surface chemistry and bitumen composition into the pavement design and evaluation.
ContributorsOldham, Daniel Joshua (Author) / Fini, Elham F (Thesis advisor) / Kaloush, Kamil (Committee member) / Deng, Shuguang (Committee member) / Mallick, Rajib B (Committee member) / Louie, Stacey M (Committee member) / Parast, Mahour M (Committee member) / Arizona State University (Publisher)
Created2020
Description
The current research is based on the principles of three-dimensional discrete element method (3D – DEM) through simulations, by using heat transfer models in EDEM, to investigate the effects of fill level, rotation rate and particle size on the steady-state conduction heat transfer in rotary drums. The high heat and mass transfer rates obtained through rotary drums make them very useful for powder mixing and heating processes in metallurgical, cement, mining, pharmaceutical, detergent and other particulate processing applications. However, these complex processes are difficult to model and operate since the particles can have a wide range of properties, and there is currently no way to predict the optimal operating conditions for a given material.
Steady-state heat transfer by conduction forms the basis for understanding other steady-state and unsteady-state heat transfer in a rotary drum – conduction, convection and radiation. Statistical analysis is carried out to determine the effects of these process parameters and find optimal operating conditions, which will thereby improve the heat transfer efficiency in rotary drums. A stainless-steel drum with a diameter of 6 inches and a length of 3 inches was modeled in EDEM with silica beads of sizes 2 mm, 3 mm and 4 mm at fill levels of 10%, 17.5% and 25%, and at rotation rates of 2 rpm, 5 rpm and 10 rpm. It was found that the heating uniformity increased with decreasing particle size, decreasing fill level and increasing rotation rate. This research is the first step towards studying the other heat transfer modes and various other process parameters. Better understanding of the various heat transfer modes, when used in combination for heating the particles, will be beneficial in improving the operating efficiency, reducing material costs and leading to significant energy conservation on a global scale.
Steady-state heat transfer by conduction forms the basis for understanding other steady-state and unsteady-state heat transfer in a rotary drum – conduction, convection and radiation. Statistical analysis is carried out to determine the effects of these process parameters and find optimal operating conditions, which will thereby improve the heat transfer efficiency in rotary drums. A stainless-steel drum with a diameter of 6 inches and a length of 3 inches was modeled in EDEM with silica beads of sizes 2 mm, 3 mm and 4 mm at fill levels of 10%, 17.5% and 25%, and at rotation rates of 2 rpm, 5 rpm and 10 rpm. It was found that the heating uniformity increased with decreasing particle size, decreasing fill level and increasing rotation rate. This research is the first step towards studying the other heat transfer modes and various other process parameters. Better understanding of the various heat transfer modes, when used in combination for heating the particles, will be beneficial in improving the operating efficiency, reducing material costs and leading to significant energy conservation on a global scale.
ContributorsBheda, Bhaumik (Author) / Emady, Heather (Thesis advisor) / Muhich, Christopher (Committee member) / Nielsen, David (Committee member) / Arizona State University (Publisher)
Created2020
Description
Mixed-ionic electronic conducting (MIEC) oxides have drawn much attention from researchers because of their potential in high temperature separation processes. Among many materials available, perovskite type and fluorite type oxides are the most studied for their excellent oxygen ion transport property. These oxides not only can be oxygen adsorbent or O2-permeable membranes themselves, but also can be incorporated with molten carbonate to form dual-phase membranes for CO2 separation.
Oxygen sorption/desorption properties of perovskite oxides with and without oxygen vacancy were investigated first by thermogravimetric analysis (TGA) and fixed-bed experiments. The oxide with unique disorder-order phase transition during desorption exhibited an enhanced oxygen desorption rate during the TGA measurement but not in fixed-bed demonstrations. The difference in oxygen desorption rate is due to much higher oxygen partial pressure surrounding the sorbent during the fixed-bed oxygen desorption process, as revealed by X-ray diffraction (XRD) patterns of rapidly quenched samples.
Research on using perovskite oxides as CO2-permeable dual-phase membranes was subsequently conducted. Two CO2-resistant MIEC perovskite ceramics, Pr0.6Sr0.4Co0.2Fe0.8 O3-δ (PSCF) and SrFe0.9Ta0.1O3-δ (SFT) were chosen as support materials for membrane synthesis. PSCF-molten carbonate (MC) and SFT-MC membranes were prepared for CO2-O2 counter-permeation. The geometric factors for the carbonate phase and ceramic phase were used to calculate the effective carbonate and oxygen ionic conductivity in the carbonate and ceramic phase. When tested in CO2-O2 counter-permeation set-up, CO2 flux showed negligible change, but O2 flux decreased by 10-32% compared with single-component permeation. With CO2 counter-permeation, the total oxygen permeation flux is higher than that without counter-permeation.
A new concept of CO2-permselective membrane reactor for hydrogen production via steam reforming of methane (SRM) was demonstrated. The results of SRM in the membrane reactor confirm that in-situ CO2 removal effectively promotes water-gas shift conversion and thus enhances hydrogen yield. A modeling study was also conducted to assess the performance of the membrane reactor in high-pressure feed/vacuum sweep conditions, which were not carried out due to limitations in current membrane testing set-up. When 5 atm feed pressure and 10-3 atm sweep pressure were applied, the membrane reactor can produce over 99% hydrogen stream in simulation.
Oxygen sorption/desorption properties of perovskite oxides with and without oxygen vacancy were investigated first by thermogravimetric analysis (TGA) and fixed-bed experiments. The oxide with unique disorder-order phase transition during desorption exhibited an enhanced oxygen desorption rate during the TGA measurement but not in fixed-bed demonstrations. The difference in oxygen desorption rate is due to much higher oxygen partial pressure surrounding the sorbent during the fixed-bed oxygen desorption process, as revealed by X-ray diffraction (XRD) patterns of rapidly quenched samples.
Research on using perovskite oxides as CO2-permeable dual-phase membranes was subsequently conducted. Two CO2-resistant MIEC perovskite ceramics, Pr0.6Sr0.4Co0.2Fe0.8 O3-δ (PSCF) and SrFe0.9Ta0.1O3-δ (SFT) were chosen as support materials for membrane synthesis. PSCF-molten carbonate (MC) and SFT-MC membranes were prepared for CO2-O2 counter-permeation. The geometric factors for the carbonate phase and ceramic phase were used to calculate the effective carbonate and oxygen ionic conductivity in the carbonate and ceramic phase. When tested in CO2-O2 counter-permeation set-up, CO2 flux showed negligible change, but O2 flux decreased by 10-32% compared with single-component permeation. With CO2 counter-permeation, the total oxygen permeation flux is higher than that without counter-permeation.
A new concept of CO2-permselective membrane reactor for hydrogen production via steam reforming of methane (SRM) was demonstrated. The results of SRM in the membrane reactor confirm that in-situ CO2 removal effectively promotes water-gas shift conversion and thus enhances hydrogen yield. A modeling study was also conducted to assess the performance of the membrane reactor in high-pressure feed/vacuum sweep conditions, which were not carried out due to limitations in current membrane testing set-up. When 5 atm feed pressure and 10-3 atm sweep pressure were applied, the membrane reactor can produce over 99% hydrogen stream in simulation.
ContributorsWu, Han-Chun (Author) / Lin, Jerry Y.S. (Thesis advisor) / Deng, Shuguang (Committee member) / Jiao, Yang (Committee member) / Emady, Heather (Committee member) / Muhich, Christopherq (Committee member) / Arizona State University (Publisher)
Created2020
Description
Fossil fuels are currently the main source of energy in the world’s transportation sector. They are also the primary contributor to carbon emissions in the atmosphere, leading to adverse climate effects. The objective of the following research is to increase the yield and efficiency of algal biofuel in order to establish algal-derived fuel as a competitive alternative to predominantly used fossil fuels. Using biofuel commercially will reduce the cost of production and ultimately decrease additional carbon emissions. Experiments were performed using hydrothermal liquefaction (HTL) to determine which catalyst would enhance the algal biocrude oil and result in the highest quality biofuel product, as well as to find the optimal combination of processing temperature and manure co-liquefaction of biomass ratio. For the catalytic upgrading experiments, Micractenium Immerum algae was used in conjunction with pure H2, Pt/C, MO2C, and HZSM-5 catalysts at 350℃ and 400℃, 430 psi, and a 30-minute residence time to investigate the effects of catalyst choice and temperature on the crude oil yield. While all catalysts increased the carbon content of the crude oil, it was found that using HZSM-5 at 350℃ resulted in the greatest overall yield of about 75%. However, the Pt/C catalyst increased the HHV from 34.26 MJ/kg to 43.26 MJ/kg. Cyanidioschyzon merolae (CM) algae and swine manure were utilized in the co-liquefaction experiments, in ratios (algae to swine) of 80:20, 50:50, and 20:80 at temperatures of 300℃ and 330℃. It was found that a ratio of 80:20 at 330℃ produced the highest biocrude oil yield of 29.3%. Although the 80:20 experiments had the greatest biomass conversion and best supported the deacidification of the oil product, the biocrude oil had a HHV of 33.58 MJ/kg, the lowest between the three different ratios. However, all calorific values were relatively close to each other, suggesting that both catalytic upgrading and co-liquefaction can increase the efficiency and economic viability of algal biofuel.
ContributorsMurdock, Tessa A (Author) / Deng, Shuguang (Thesis director) / Varman, Arul (Committee member) / Chemical Engineering Program (Contributor, Contributor) / Barrett, The Honors College (Contributor)
Created2020-05
Description
With renewable energy on the rise, researchers have turned their funding and their focus towards new solar cell technologies, and perovskites are a major source of interest. This class of materials is particularly interesting due to their quick, simple synthesis as well as their physical and electrical superiority when compared to current silicon-based solar cells. Through this thesis, we will explore the synthesis of various types of perovskites and their subsequent characterization, which includes optical microscopy, photoluminescence spectroscopy, Raman microscopy, and X-ray diffraction. Analyzing two different perovskites both before and after a two-week period of storage revealed that while synthesis is indeed experiment-friendly, these materials have a concerning lack of stability even in ideal conditions.
ContributorsBuzas, Benjamin Joseph (Author) / Tongay, Sefaattin (Thesis director) / Muhich, Christopher (Committee member) / Materials Science and Engineering Program (Contributor, Contributor) / Barrett, The Honors College (Contributor)
Created2020-05
Description
The paper analyzes the growing desire to use waste-to-energy strategies on municipal solid waste (MSW) to generate power. The two waste-to-energy technologies that will be explored are incineration and gasification. The background of these two technologies will be explained because incineration, which has been the pioneering technology for the past century, has come to be rivaled by gasification with its unique purification feature. Following this section, gasification and incineration power generation are studied to conclude which technology is sounder. This study will be conducted via an analysis to find the thermal and exergetic efficiencies and emissions of each. After analyzing the two technologies, both utilizing a vapor cogeneration power system, their efficiencies were found. For the gasification process, the thermal efficiency was 26% and the exergetic efficiency was 59%. The incineration process had a thermal efficiency of 25% and an exergetic efficiency of 55%. Lastly, the emission from the power generation of each method was explored to see which system had a greater impact on the environment. It was found that the primary emissions of these technologies were carbon dioxide and water.
ContributorsJackson, Cole Alan (Author) / Deng, Shuguang (Thesis director) / Milcarek, Ryan (Committee member) / Mechanical and Aerospace Engineering Program (Contributor, Contributor) / Barrett, The Honors College (Contributor)
Created2020-05
Description
Past experiments have revealed several unusual properties about interstitial hydrogen atoms in niobium. Absorption isotherms showed that niobium absorbs a large amount of hydrogen without changing its crystal structure. These isotherms also revealed that the interactions between hydrogen atoms in niobium are a combination of long-range attraction and short-range repulsion and exhibit many-body characteristics. Other experiments reported the facile thermal diffusion of hydrogen and deuterium in niobium. Contrary to the classical theory of diffusion, these experiments revealed a break in the activation energy of hydrogen diffusion at low temperatures, but no such break was reported for deuterium. Finally, experiments report a phenomenon called electromigration, where hydrogen atoms inside niobium respond to weak electric fields as if they had a positive effective charge. These experimental results date back to when tools like density functional theory (DFT) and modern high-performance computing abilities did not exist. Therefore, the current understanding of these properties is primarily based on inferences from experimental results. Understanding these properties at a deeper level, besides being scientifically important, can profoundly affect various applications involving hydrogen separation and transport. The high-level goal of this work is to use first-principles methods to explain the discussed properties of interstitial hydrogen in niobium. DFT calculations were used to study hydrogen atoms' site preference in niobium and its effect on the cell shape and volume of the host cell. The nature and origin of the interactions between hydrogen atoms were studied through interaction energy, structural, partial charge, and electronic densities of state analysis. A phenomenological model with fewer parameters than traditional models was developed and fit to the experimental absorption data. Thermodynamic quantities such as the enthalpy and entropy of hydrogen dissolution in niobium were derived from this model. The enthalpy of hydrogen dissolution in niobium was also calculated using DFT by sampling different geometric configurations and performing an ensemble-based averaging. Further work is required to explain the observed isotope effects for hydrogen diffusion in niobium and the electromigration phenomena. Applications of the niobium-hydrogen system require studying hydrogen's behavior on niobium's surface.
ContributorsRamcahandran, Arvind (Author) / Lackner, Klaus S. (Thesis advisor) / Zhuang, Houlong (Thesis advisor) / Muhich, Christopher (Committee member) / Singh, Arunima (Committee member) / Arizona State University (Publisher)
Created2021
Description
Lithium-ion and lithium-metal batteries are deemed to be the choice of energy storage media for the future. However, they are not entirely safe and their performance in terms of cycle life and charging rates is sub-optimal. A majority of these issues arise from the currently used flammable polyolefinic separators and carbonate solvent based electrolytes. This work utilizes in-house developed and specific property tuned electrode-coated inorganic separators in combination with a fire-proof electrolyte to resolve the above stated concerns.Firstly, to improve the safety of the lithium-ion cell with a commercial polypropylene separator a thermally stable in-house developed electrode coated quartz silica separator is utilized. The silica separator due to its better electrolyte wettability, electrolyte uptake and lower resistance also offers better capacity retention (~ 15 %) at high rates of discharge. Subsequently, research on developing a completely safe lithium-ion battery was conducted by replacing the traditional carbonate solvent based electrolyte with a fire-proof lithium bis-fluoro sulphonyl-imide salt/tri-methyl phosphate solvent electrolyte. However, this electrolyte has a high viscosity and low separator wetting rate.
A microporous in house synthesized silicalite electrode-coated separator due to its high surface energy functionalizes the viscous fire-proof electrolyte and together they are tested in a full-cell. The intra-particle pores of the silicalite separator result in a thinner and more robust solid electrolyte interface on graphite. This results in about 20 % higher capacity retention during long term cycling when compared to the polypropylene separator used in the same full-cell.
To enable stable and fast charging lithium-metal batteries free from dendrite propagation related failure, plate shaped γ-alumina and silicalite electrode-coated separators with high tortuosity are developed and used in a lithium-metal full-cell battery, with the former separator having no intra-particle pores and the latter having them. The γ-alumina separators show improvements in dendrite propagation prevention up to 3 C-rate of charge/discharge but a loss in active lithium is seen beyond the 75th cycle. However, microporous plate-shaped silicalite separators did not show any loss in active lithium even at 3 C-rate for 100 cycles due to the homogenized lithium-ion flux at the anode, while also preventing dendrite propagation.
ContributorsRafiz, Kishen (Author) / Lin, Jerry Y.S (Thesis advisor) / Muhich, Christopher (Committee member) / Kannan, Arunachala (Committee member) / Deng, Shuguang (Committee member) / Green, Matthew (Committee member) / Arizona State University (Publisher)
Created2021
Description
Desorption processes are an important part of all processes which involve utilization of solid adsorbents such as adsorption cooling, sorption thermal energy storage, and drying and dehumidification processes and are inherently energy-intensive. Here, how those energy requirements can be reduced through the application of ultrasound for three widely used adsorbents namely zeolite 13X, activated alumina and silica gel is investigated. To determine and justify the effectiveness of incorporating ultrasound from an energy-savings point of view, an approach of constant overall input power of 20 and 25 W was adopted. To measure the extent of the effectiveness of using ultrasound, the ultrasonic-power-to-total power ratios of 0.2, 0.25, 0.4 and 0.5 were investigated and the results compared with those of no-ultrasound (heat only) at the same total power. Duplicate experiments were performed at three nominal frequencies of 28, 40 and 80 kHz to observe the influence of frequency on regeneration dynamics. Regarding moisture removal, application of ultrasound results in higher desorption rate compared to a non-ultrasound process. A nonlinear inverse proportionality was observed between the effectiveness of ultrasound and the frequency at which it is applied. Based on the variation of desorption dynamics with ultrasonic power and frequency, three mechanisms of reduced adsorbate adsorption potential, increased adsorbate surface energy and enhanced mass diffusion are proposed. Two analytical models that describe the desorption process were developed based on the experimental data from which novel efficiency metrics were proposed, which can be employed to justify incorporating ultrasound in regeneration and drying processes.
ContributorsDaghooghi Mobarakeh, Hooman (Author) / Phelan, Patrick (Thesis advisor) / Wang, Liping (Committee member) / Wang, Robert (Committee member) / Calhoun, Ronald (Committee member) / Deng, Shuguang (Committee member) / Arizona State University (Publisher)
Created2021
Description
Functional materials can be characterized as materials that have tunable properties and are attractive solutions to the improvement and optimization of processes that require specific physiochemical characteristics. Through tailoring and altering these materials, their characteristics can be fine-tuned for specific applications. Computational modeling proves to be a crucial methodology in the design and optimization of such materials. This dissertation encompasses the utilization of molecular dynamics simulations and quantum calculations in two fields of functional materials: electrolytes and semiconductors. Molecular dynamics (MD) simulations were performed on ionic liquid-based electrolyte systems to identify molecular interactions, structural changes, and transport properties that are often reflected in experimental results. The simulations aid in the development process of the electrolyte systems in terms of concentrations of the constituents and can be invoked as a complementary or predictive tool to laboratory experiments. The theme of this study stretches further to include computational studies of the reactivity of atomic layer deposition (ALD) precursors. Selected aminosilane-based precursors were chosen to undergo density functional theory (DFT) calculations to determine surface reactivity and viability in an industrial setting. The calculations were expanded to include the testing of a semi-empirical tight binding program to predict growth per cycle and precursor reactivity with a high surface coverage model. Overall, the implementation of computational methodologies and techniques within these applications improves materials design and process efficiency while streamlining the development of new functional materials.
ContributorsGliege, Marisa Elise (Author) / Dai, Lenore (Thesis advisor) / Derecskei-Kovacs, Agnes (Thesis advisor) / Muhich, Christopher (Committee member) / Emady, Heather (Committee member) / Zhuang, Houlong (Committee member) / Arizona State University (Publisher)
Created2021
Description
The objective of this research was to develop Aluminophosphate-five (AlPO4-5, AFI) zeolite adsorbents for efficient oxygen removal from a process stream to support an on-going Department of Energy (DOE) project on solar energy storage. A molecular simulation study predicted that substituted AlPO4-5 zeolite can adsorb O2 through a weak chemical bond at ambient temperature. Substituted AlPO4-5 zeolite was successfully synthesized via hydrothermal crystallization by following carefully designed procedures to tailor the zeolite for efficient O2 adsorption. Synthesized AlPO4-5 in this work included Sn/AlPO-5, Mo/AlPO-5, Pd/AlPO-5, Si/AlPO-5, Mn/AlPO-5, Ce/AlPO-5, Fe/AlPO-5, CuCe/AlPO-5, and MnSnSi/AlPO-5. While not all zeolite samples synthesized were fully characterized, selected zeolite samples were characterized by powder x-ray diffraction (XRD) for crystal structure confirmation and phase identification, and nitrogen adsorption for their pore textural properties. The Brunauer-Emmett-Teller (BET) specific surface area and pore size distribution were between 172 m2 /g - 306 m2 /g and 6Å - 9Å, respectively, for most of the zeolites synthesized. Samples of great interest to this project such as Sn/AlPO-5, Mo/AlPO-5 and MnSnSi/AlPO-5 were also characterized using x-ray photoelectron spectroscopy (XPS) and energy-dispersive x-ray spectroscopy (EDS) for elemental analysis, scanning electron microscopy (SEM) for morphology and particle size estimation, and electron paramagnetic resonance (EPR) for nature of adsorbed oxygen. Oxygen and nitrogen adsorption experiments were carried out in a 3-Flex adsorption apparatus (Micrometrics) at various temperatures (primarily at 25℃) to determine the adsorption properties of these zeolite samples as potential adsorbents for oxygen/nitrogen separation. Experiments showed that some of the zeolite samples adsorb little-to-no oxygen and nitrogen at 25℃, while other zeolites such as Sn/AlPO-5, Mo/AlPO-5, and MnSnSi/AlPO-5 adsorb decent but inconsistent amounts of oxygen with the highest observed values of about 0.47 mmol/ g, 0.56 mmol/g, and 0.84 mmol/ g respectively. The inconsistency in adsorption is currently attributed to non-uniform doping of the zeolites, and these findings validate that some substituted AlPO4-5 zeolites are promising adsorbents. However, more investigations are needed to verify the causes of this inconsistency to develop a successful AlPO4-5 zeolite-based adsorbent for oxygen/nitrogen separation.
ContributorsBuyinza, Allan Smith (Author) / Deng, Shuguang (Thesis advisor) / Varman, Arul M (Committee member) / Jin, Kailong (Committee member) / Arizona State University (Publisher)
Created2021
Description
This research seeks to answer the question if there is a singular relationship between stishovite nucleation and the atomistic structure of the preshocked amorphous SiO$_2$. To do this a stishovite manufacturing method is developed in which 1,152 samples were produced. The majority of these samples did crystallize. The method was produced through two rounds of experiments and fine-tuning with the pressure damp, temperature damp, shock pressure using an NPHug fix, and sample origin. A new random atomic insertion method was used to generate a new and different SiO$_2$ amorphous structure not before seen within the research literature. The optimal values for shock were found to be 60~GPa for randomly atom insertion samples and 55~GPa for quartz origin samples. Temperature damp appeared to have a slight effect optimizing at 0.05~ps and the pressure damp had no visible effect, testing was done with temperature damp from 0.05 to 0.5~ps and pressure damp from 0.1 to 10.0~ps. There appeared to be significant randomness in crystallization behavior. The preshocked and postnucleated samples were transformed into Gaussian fields of crystal, mass, and charge. These fields were divided and classified using a cut-off method taking the number of crystals produced in portions of each simulation and classifying each potion as nucleated or non-nucleated. Data in which some nucleation but not a critical amount was present was removed constituting 2.6\% to 20.3\% of data in all tests. A max method was also used which takes only the maximum portions of each simulation to classify as nucleating. There are three other variables tested within this work, a sample size of 18,000 or 72,728~atoms, Gaussian variance of 1 or 4~\AA, and Convolutional neural network (CNN) architecture of a garden verity or all convolution along with the portioning classification method, sample origination, and Gaussian field type. In total 64 tests were performed to try every combination of variable. No significant classifications were made by the CNNs to nucleation or non-nucleation portions. The results clearly confirmed that the data was not abstracting to atomistic structure and was random by all classifications of the CNNs. The all convolution CNN testing did show smoother outcomes in training with less fluctuations. 59\% of all validation accuracy was held at 0.5 for a random state and 84\% was within $\pm0.02$ of 0.5. It is conclusive that prenucleation structure is not the sole predictor of nucleation behavior. It is not conclusive if prenucleation structure is a partial or non-factor within nucleation of stishovite from amorphous SiO$_2$.
ContributorsChristen, Jonathan Scorr (Author) / Oswald, Jay (Thesis advisor) / Muhich, Christopher (Committee member) / Zhuang, Houlong (Committee member) / Arizona State University (Publisher)
Created2021
Description
Temperature swing adsorption is a commonly used gas separation technique, and is being<br/>further researched as a method of carbon capture. Carbon capture is becoming increasingly<br/>important as a potential way to slow global warming. In this study, algae-derived activated<br/>carbon adsorbents were analyzed for their carbon dioxide adsorption effectiveness.<br/>Algae-derived carbon adsorbents were synthesized and then studied for their adsorption<br/>isotherms and adsorption breakthrough behavior. From the generated isotherm plots, it was<br/>determined that the carbonization temperature was not high enough and that more batches of<br/>adsorbent would have to be made to more accurately analyze the adsorptive potential of the<br/>algae-derived carbon adsorbent.
ContributorsCiha, Trevor (Author) / Deng, Shuguang (Thesis director) / Taylor, David (Committee member) / Chemical Engineering Program (Contributor, Contributor) / Barrett, The Honors College (Contributor)
Created2021-05
Description
Rotary drums are tools used extensively in various prominent industries for their utility in heating and transporting particulate products. These processes are often inefficient and studies on heat transfer in rotary drums will reduce energy consumption as operating parameters are optimized. Research on this subject has been ongoing at ASU; however, the design of the rotary drum used in these studies is restrictive and experiments using radiation heat transfer have not been possible.<br/><br/>This study focuses on recounting the steps taken to upgrade the rotary drum setup and detailing the recommended procedure for experimental tests using radiant heat transfer upon completed construction of the new setup. To develop an improved rotary drum setup, flaws in the original design were analyzed and resolved. This process resulted in a redesigned drum heating system, an altered thinner drum, and a larger drum box. The recommended procedure for radiant heat transfer tests is focused on determining how particle size, drum fill level, and drum rotation rate impact the radiant heat transfer rate.
ContributorsMiller, Erik R (Author) / Emady, Heather (Thesis director) / Muhich, Christopher (Committee member) / Chemical Engineering Program (Contributor, Contributor) / Barrett, The Honors College (Contributor)
Created2021-05
Description
Supported catalytic nanoparticles undergo rapid structural transformations faster than many transmission electron microscopes (TEMs) can track. This is the case with platinum nanoparticles supported on cerium oxide (Pt/CeO2) in a CO and O2 gaseous environment. By furthering our understanding of the structural dynamics of the Pt/CeO2 system, improved catalyst design principles may be derived to enhance the efficiency of this catalyst. Developing static models of a 2 nm Pt nanoparticle supported on CeO2 and simulating TEM images of the models was found to create similar images to those seen in experimental TEM time-resolved series of the system. Rotations of static models on a ceria support provides a way to understand the experimental samples in three dimensions, which is difficult in two dimensional TEM images. This project expands the possibilities of interpreting TEM images of catalytic systems.
ContributorsBlock, Claire (Author) / Crozier, Peter (Thesis director) / Muhich, Christopher (Committee member) / Materials Science and Engineering Program (Contributor, Contributor) / Watts College of Public Service & Community Solut (Contributor) / Barrett, The Honors College (Contributor)
Created2021-05
Description
Carbon capture has been a highly sought-after technology for decades because of its<br/>capabilities to restore atmospheric damage done by greenhouse gasses. Thanks to evolving<br/>separation techniques, carbon capture is becoming more efficient with every new discovery in<br/>the field. Currently the biggest problems that carbon capture are facing is the cost of<br/>manufacturing material to aid the process and obtaining ideal conditions for removal of carbon<br/>from air and devising solutions for removal of CO2 in ambient and flue gas conditions.<br/>This Honors Thesis is a continuation of Dr. Shuguang Deng and Dr. Mai Xu’s research<br/>initiative to manufacture and test various zeolitic CO2 removal efficiencies. The goals of this<br/>Honors Thesis are to investigate the adsorption/desorption kinetics and isothermal equilibrium<br/>CO2 capacity of a NaX nanozeolite under ambient air conditions.<br/>What was determined from the following testing was that the zeolite of interest had a<br/>higher adsorption capacity of CO2 at lower temperatures, had a maximum equilibrium quantity<br/>adsorbed of 0.203 mmol/g for CO2 and 0.367 mmol/g of N2, had a maximum breakthrough CO2<br/>capacity of 0.101 mmol of CO2 per gram of zeolite at dry conditions and 298.15K and this<br/>linearly decreased to 0.040 mmol/g at 25% relative humidity.
ContributorsBonelli, Xavier Berlage (Author) / Deng, Shuguang (Thesis director) / Xu, Mai (Committee member) / Chemical Engineering Program (Contributor, Contributor) / Barrett, The Honors College (Contributor)
Created2021-05
Description
Interfacial interactions between materials in complex heterostructures can dominate the material's response in manymodern-day energy-related devices and processes. Considerable research has been dedicated towards addressing
the profound effects of interfaces. Here, first-principles-based quantum mechanical simulations are discussed to
characterize the interfacial materials properties of two systems. First, density-functional theory (DFT) calculations
were performed for ceramic oxide grain boundaries in undoped and doped CeO2. Second, the development,
theoretical framework, and utilization of high-throughput, workflow-based, DFT calculations are presented to model
the synthesis of two-dimensional (2D) heterostructured materials. Utilizing this workflow, predictive machine learning
models were created to elucidate key interface-property relationships in 2D heterostructured materials. The DFT simulations reveal that the Σ3(111)/[101] grain boundary was energetically more stable than theΣ3(121)/[101]grain boundary due to the larger atomic coherency in the Σ3(111)/[101] grain boundary plane. The
alkaline-earth metal-doped grain boundary energies demonstrate a parabolic dependence on the size of the
solutes, interfacial strain, and packing density of the grain boundary. The grain boundary energies were stabilized
upon Ca, Sr, and Ba doping whereas Be and Mg render them energetically unstable. The electronic density of states
reveals that no defect states were present in/above the band gap. The thermodynamic trapping of oxygen
vacancies in the near grain boundary region was not significantly impacted by the presence of Ca-solute ions.
However, the migration energy barriers within the grain boundary core were dramatically reduced with high local
Ca-solute concentrations, around 0.3 eV-0.5 eV. Chapter 5 and Chapter 6 discusses the development of the open-source, high-throughput computational "synthesis"based workflow package Hetero2d and the application of Hetero2d using 52 Janus 2D materials and 19 metallic,
cubic phase, elemental substrates. The 438 Janus 2D-substrate pairs were analyzed by identifying substrate
surfaces that stabilize metastable Janus 2D materials, characterizing their effects on the post-adsorbed 2D
materials, and identifying the bonding between the 2D material and substrate. Machine learning models were
applied to predict the binding energy, z-separation, and charge transfer of the Janus 2D-substrate pairs providing
insight into the critical properties which factor into these properties.
ContributorsBoland, Tara Maria (Author) / Crozier, Peter A (Thesis advisor) / Singh, Arunima K (Thesis advisor) / Rez, Peter (Committee member) / Muhich, Christopher (Committee member) / Dholabhai, Pratik (Committee member) / Arizona State University (Publisher)
Created2022
Description
The objective of this research is to create a python program that can describe the adsorption breakthrough performance of direct air capture of CO2 by zeolite and other adsorbents. The purpose of creating this open-source code is because many commercial simulation software for adsorption process simulation can be extremely expensive and typically are yearly subscriptions which can be a costly expenditure for academic research labs and chemical engineers working on adsorption processes development and design. The simulation models are generated by solving the governing mass and energy transfer equations and validating the models with experimental data. The typical inputs for the adsorption process simulation include adsorption equilibrium of both CO2 and N2 on selected adsorbents, mass transfer coefficients information, adsorbent bed length and void fraction, and other physical and chemical properties of the adsorbent being tested. The outputs of the simulation package are the dimensionless CO2 concentration profile as a function of dimensionless time, which is usually used for evaluating the adsorbent performance for CO2 capture. The models created were compared to the commercial package gPROMs and they performed extremely well. The main variation between the models created and gPROMs was that the models tended to underpredict the breakpoint of experimental data and gPROMs tended to overpredict. This M.S. research is part of the major research efforts for developing an open-source adsorption process simulation package for carbon capture and conversion in Prof. Deng’s group at ASU. The ultimate goal of this research program is to reduce carbon emissions and develop a sustainable solution for a future carbon-free economy.
ContributorsBonelli, Xavier Berlage (Author) / Deng, Shuguang (Thesis advisor) / Andino, Jean (Committee member) / Seo, Don (Committee member) / Arizona State University (Publisher)
Created2022
Description
Siloxane, a common contaminant present in biogas, is known for adverse effects on cogeneration prime movers. In this work, the solid oxide fuel cell (SOFC) nickel-yttria stabilized zirconia (Ni-YSZ) anode degradation due to poisoning by siloxane was investigated. For this purpose, experiments with different fuels, different deposition substrate materials, different structure of contamination siloxane (cyclic and linear) and entire failure process are conducted in this study. The electrochemical and material characterization methods, such as Electrochemical Impedance Spectroscopy (EIS), Scanning Electron Microscope- Wavelength Dispersive Spectrometers (SEM-WDS), X-ray Photoelectron Spectroscopy (XPS), X-ray Diffraction (XRD), and Raman spectroscopy, were applied to investigate the anode degradation behavior. The electrochemical characterization results show that the SOFCs performance degradation caused by siloxane contamination is irreversible under bio-syngas condition. An equivalent circuit model (ECM) is developed based on electrochemical characterization results. Based on the Distribution of Relaxation Time (DRT) method, the detailed microstructure parameter changes are evaluated corresponding to the ECM results. The results contradict the previously proposed siloxane degradation mechanism as the experimental results show that water can inhibit anode deactivation. For anode materials, Ni is considered a major factor in siloxane deposition reactions in Ni-YSZ anode. Based on the results of XPS, XRD and WDS analysis, an initial layer of carbon deposition develops and is considered a critical process for the siloxane deposition reaction. Based on the experimental results in this study and previous studies about siloxane deposition on metal oxides, the proposed siloxane deposition process occurs in stages consisting of the siloxane adsorption, initial carbon deposition, siloxane polymerization and amorphous silicon dioxide deposition.
ContributorsTian, Jiashen (Author) / Milcarek, Ryan J. (Thesis advisor) / Muhich, Christopher (Committee member) / Wang, Liping (Committee member) / Phelan, Patrick (Committee member) / Nian, Qiong (Committee member) / Arizona State University (Publisher)
Created2022
Idiographic Models of Walking Behavior for Personalized mHealth Interventions: Some Novel Approaches
Description
This thesis presents the development of idiographic models (i.e., single subject or N = 1) of walking behavior as a means of facilitating the design of control systems to optimize mobile health (mHealth) interventions for sedentary adults. Model-on-Demand (MoD), an adaptive modeling technique, is demonstrated as an ideal method for modeling nonlinear systems with noise on a simulated continuously stirred tank reactor (CSTR). Comparing MoD to AutoRegressive with eXogenous input (ARX) estimation, MoD outperforms ARX in terms of addressing both nonlinearity and noise in the CSTR system. With the CSTR system as an initial proof of concept, MoD is then used to model individual walking behavior using intervention data from participants of HeartSteps, a walking intervention that studies the effect of within-day suggestions. Given the number of possible measured features from which to design the MoD models, as well as the number of model parameters that influence the model’s performance, optimizing MoD models through exhaustive search is infeasible.
Consequently, a discrete implementation of simultaneous perturbation stochastic approximation (DSPSA) is shown to be an efficient algorithm to find optimal models of walking behavior. Combining MoD with DSPSA, models of walking behavior were developed using participant data from Just Walk, a day-to-day walking intervention; MoD outperformed ARX models on both estimation and validation data. DSPSA was also applied to ARX modeling, highlighting the use of DSPSA to not only search over model parameters and features but also data partitioning, as DSPSA was used to evaluate models under various combinations of estimation and validation data from a single participant’s walking data. Results of this thesis point to ARX with DSPSA as a routine means for dynamic model estimation in large-scale behavioral intervention settings.
ContributorsKha, Rachael T (Author) / Rivera, Daniel E (Thesis advisor) / Deng, Shuguang (Committee member) / Muhich, Christopher (Committee member) / Arizona State University (Publisher)
Created2022
Description
Lithium-ion batteries are widely used for high energy storage systems and most of the commercially manufactured lithium-ion batteries use liquid electrolytes and
polymeric separators. However, these electrolytes and polymeric separators pose safety
issues under high temperatures and in the event of short circuit which may lead to
thermal runaway and cause fire. The application of fire-retardant high salt concentrated
electrolytes can be used to address the safety issues that arises in the use of liquid
electrolytes, but these electrolytes have high viscosity and low wettability when used on
polymeric separators which are commercially used in lithium-ion batteries. To address
this issue, zeolite powder has been synthesized and separators were prepared by coating
on the electrode using scalable blade coating method. Zeolite separators have higher
wettability and electrolyte uptake compared to polymeric separators such as
polypropylene (PP) due to their intra-particle micropores. The zeolite separators also
have higher porosity compared to PP separators resulting in higher electrolyte uptake and
better electrochemical performance of the lithium-ion batteries. Zeolite separators have
been prepared using spherical-silicalite and plate-silicalite to analyze the effect of
morphology of the particles on the electrochemical performance of the cells. The platesilicalite separators have higher capacity retention during long-term cycling at low Crates and better capacity performance at high C-rates compared to spherical-silicalite.
Therefore plate-silicalite is very promising for the development of high-performance safe
lithium-ion batteries.
ContributorsLINGAM MURALI, DHEERAJ RAM (Author) / Lin, Jerry (Thesis advisor) / Muhich, Christopher (Committee member) / Torres, Cesar (Committee member) / Arizona State University (Publisher)
Created2022
Description
Adsorption equilibrium is an important metric used to assess adsorbent performance for gas mixture separation processes. Gas adsorption processes such as carbon capture are becoming more urgent as climate change and global warming accelerate. To speed up and reduce the cost of research on adsorbent materials and adsorption processes, I developed an open-source Python code that generates mixed gas adsorption equilibrium data using pure gas adsorption isotherms based on the ideal adsorbed solution theory (IAST). The major efforts of this M.S. research were placed on adding additional components to the mixture models since most other publications focused on binary gas mixtures. Generated mixed-gas equilibrium data were compared to experimentally collected data in order to validate the multicomponent IAST model and to determine the accuracy of the computer codes developed in this work. Additional mixed-gas equilibrium data were then generated and analyzed for trends in the data for humid flue gas conditions, natural gas processing conditions, and hydrogen gas purification conditions. For humid flue gas conditions, neither the analyzed Mg-MOF-74 nor the Zeolite 13X were shown to be suitable for use. For natural gas processing conditions, the Zeolite 13X was determined to be a much better candidate for use than the MIL-101. For hydrogen gas purification conditions, the Zeolite 5A was determined to be a better adsorbent for use than CD-AC due to the Zeolite 5A’s much lower adsorption of H2.
ContributorsCiha, Trevor (Author) / Deng, Shuguang (Thesis advisor) / Machas, Michael (Committee member) / Huang, Huei-Ping (Committee member) / Arizona State University (Publisher)
Created2022
Description
Utilizing DFT calculations, various substitutions on the AlPO-5 zeolite were screened for adsorption of common air molecules. Furthermore, free energy analyses using the Helmholtz free energy equation were performed to determine candidates for selective adsorption of one specific air molecule, and their operating temperature range. Through this study, it was found that Cerium- (92-542 K), Germanium- (69-370 K), Chromium- (35-293 K), and Praseodymium- (0-420 K) substituted AlPO-5 selectively adsorbs to O2 molecules for the given temperature ranges. In addition, Palladium-substituted AlPO-5 selectively adsorbs to CO within 430-755 K.
ContributorsIrudaya Pious Suresh, Enosh (Author) / Muhich, Christopher (Thesis director) / Emady, Heather (Committee member) / Barrett, The Honors College (Contributor) / Chemical Engineering Program (Contributor)
Created2022-05
Description
This study presents an evaluation of the predicted flow behavior and the minimum outlet diameter in a computationally simulated hopper. The flow pattern in hoppers was simulated to test three size fractions, three moisture levels of microcrystalline cellulose (MCC), and two hopper wall angles in Multiphase Flow with Interphase eXchanges (MFiX). Predictions from MFiX were then compared to current literature. As expected, the smaller size fractions with lower water content were closer to ideal funnel flow than their larger counterparts. The predicted minimum outlet diameter in simulations showed good agreement with close to ideal flowability. These findings illustrate the connection between lab flowability experiments and computational simulations. Lastly, three fluidized bed simulations were also created in MFiX with zeolite 13X to analyze the pressure and velocity within the bed. The application of flowability simulations can improve the transport of solids in processing equipment used during the production of powders.
ContributorsBuchanan, Lidija (Author) / Emady, Heather (Thesis advisor) / Muhich, Christopher (Committee member) / Deng, Shuguang (Committee member) / Arizona State University (Publisher)
Created2023
Description
Anthropogenic processes have increased the concentration of toxic Se, As and N in water. Oxo-anions of these species are poisonous to aquatic and terrestrial life. Current remediation techniques have low selectivity towards their removal. Understanding the chemistry and physics which control oxo-anion adsorption on metal oxide and the catalytic nitrate reduction to inform improved remediation technologies can be done using Density functional theory (DFT) calculations. The adsorption of selenate, selenite, and arsenate was investigated on the alumina and hematite to inform sorbent design strategies. Adsorption energies were calculated as a function of surface structure, composition, binding motif, and pH within a hybrid implicit-explicit solvation strategy. Correlations between surface property descriptors including water network structure, cationic species identity, and facet and the adsorption energies of the ions show that the surface water network controls the adsorption energy more than any other, including the cationic species of the metal-oxide. Additionally, to achieve selectivity for selenate over sulphate, differences in their electronic structure must be exploited, for example by the reduction of selenate to selenite by Ti3+ cations.
Thermochemical or electrochemical reduction pathways to convert NO3- to N2 or NH3, which are benign or value-added products, respectively are examined over single-atom electrocatalysts (SAC) in Cu. The activity and selectivity for nitrate reduction are compared with the competitive hydrogen evolution reaction (HER). Cu suppresses HER but produces toxic NO2- because of a high activation barrier for cleaving the second N-O bond. SACs provide secondary sites for reaction and break traditional linear scaling relationships. Ru-SACs selectively produce NH3 because N-O bond scission is facile, and the resulting N remains isolated on SAC sites; reacting with H+ from solvating H2O to form ammonia. Conversely, Pd-SAC forms N2 because the reduced N* atoms migrate to the Cu surface, which has a low H availability, allowing N atoms to combine to N2. This relation between N* binding preference and reduction product is demonstrated across an array of SAC elements.
Hence, the solvation effects on the surface critically alter the activity of adsorption and catalysis and the removal of toxic pollutants can be improved by altering the surface water network.
ContributorsGupta, Srishti (Author) / Muhich, Christopher L (Thesis advisor) / Singh, Arunima (Committee member) / Emady, Heather (Committee member) / Westerhoff, Paul (Committee member) / Deng, Shuguang (Committee member) / Arizona State University (Publisher)
Created2023
Description
Adsorption is fundamentally known to be a non-isothermal process; in which temperature increase is largely significant, causing fairly appreciable impacts on the processkinetics. For porous adsorbent particles like metal organic frameworks (MOFs), silica
gel, and zeolite, the resultant relative heat generated is partly distributed within the
particle, and the rest is transferred to the surrounding ambient fluid (air).
For large step changes in adsorbed phase concentration and fast adsorption rates,
especially, the isothermality of adsorption (as in some studies) is an inadequate assumption and inspires rather erroneous diffusivities of porous adsorbents. Isothermal models, in consequence, are insufficient for studying adsorption in porous adsorbents. Non-isothermal models can satisfactorily and exhaustively describe adsorption
in porous adsorbents. However, in many of the analyses done using the models, the
thermal conductivity of the adsorbent is assumed to be infinite; thus, particle temperature is taken to be fairly uniform during the process—a trend not observed for
carbon dioxide (CO2) adsorption on MOFs.
A new and detailed analysis of CO2 adsorption in a single microporous MOF-5
particle, assuming a finite effective thermal conductivity along with comprehensive
parametric studies for the models, is presented herein. A significant average temperature increase of 5K was calculated using the new model, compared to the 0.7K
obtained using the Stremming model. A corresponding increase in diffusivity from
8.17 x 10-13 to 1.72 x 10-11 m2/s was observed, indicating the limitations of both
isothermal models and models that assume constant diffusivity.
ContributorsNkuutu, John (Author) / Lin, Jerry (Thesis advisor) / Emady, Heather (Committee member) / Deng, Shuguang (Committee member) / Arizona State University (Publisher)
Created2023