Browsing by Author "Wei, Xiaoliang"
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Item Experimental and Modeling Study of Gas Adsorption in Metal-Organic Framework Coated on 3D Printed Plastics(2020-05) Dube, Tejesh C.; Zhang, Jing; Tovar, Andres; Wei, XiaoliangMetal-organic frameworks (MOFs) are a class of compounds consisting of metal ions or clusters coordinated to organic ligands in porous structure forms. MOFs have been proposed in use for gas adsorption, purification, and separation applications. This work combines MOFs with 3D printing technologies, in which 3D printed plastics serve as a mechanical structural support for MOFs powder, in order to realize a component design for gas adsorption. The objective of the thesis is to understand the gas adsorption behavior of MIL-101 (Cr) MOF coated on 3D printed PETG, a glycol modified version of polyethylene terephthalate, through a combined experimental and modeling study. The specific goals are: (1) synthesis of MIL-101 (Cr) MOFs; (2) nitrogen gas adsorption measurements and microstructure and phase characterization of the MOFs; (3) design and 3D printing of porous PETG substrate structures; (4) deposition of MOFs coating on the PETG substrates; and (5) Monte Carlo (MC) modeling of sorption isotherms of nitrogen and carbon dioxide in the MOFs. The results show that pure MIL-101 (Cr) MOFs were successfully synthesized, as confirmed by the scanning electron microscopy (SEM) images and X-ray diffraction (XRD), which are consistent with literature data. The Brunauer-Emmett-Teller (BET) surface area measurement shows that the MOFs samples have a high cover- age of nitrogen. The specific surface area of a typical MIL-101 (Cr) MOFs sample is 2716.83 m2/g. MIL-101 (Cr) also shows good uptake at low pressures in experimental tests for nitrogen adsorption. For the PETG substrate, disk-shape plastic samples with a controlled pore morphology were designed and fabricated using the fused deposition modeling (FDM) process. MOFs were coated on the PETG substrates using a layer-by-layer (LbL) assembly approach, up to 30 layers. The MOFs coating layer thicknesses increase with the number of deposition layers. The computational model illustrates that the MOFs show increased outputs in adsorption of nitrogen as pressure increases, similar to the trend observed in the adsorption experiment. The model also shows promising results for carbon dioxide uptake at low pressures, and hence the developed MOFs based components would serve as a viable candidate in gas adsorption applications.Item Fatigue Analysis of 3D Printed 15-5 PH Stainless Steel - A Combined Numerical and Experimental Study(2019-08) Padmanabhan, Anudeep; Zhang, Jing; Wei, Xiaoliang; Tovar, AndresAdditive manufacturing (AM) or 3D printing has gained significant advancement in recent years. However the potential of 3D printed metals still has not been fully explored. A main reason is the lack of accurate knowledge of the load capacity of 3D printed metals, such as fatigue behavior under cyclic load conditions, which is still poorly understood as compared with the conventional wrought counterpart. The goal of the thesis is to advance the knowledge of fatigue behavior of 15-5 PH stainless steel manufactured through laser powder bed fusion process. To achieve the goal, a combined numerical and experimental study is carried out. First, using a rotary fatigue testing experiment, the fatigue life of the 15-5 PH stainless steel is measured. The strain life curve shows that the numbers of the reversals to failure increase from 13,403 to 46,760 as the applied strain magnitudes decrease from 0.214\% from 0.132\%, respectively. The micro-structure analysis shows that predominantly brittle fracture is presented on the fractured surface. Second, a finite element model based on cyclic plasticity including the damage model is developed to predict the fatigue life. The model is calibrated with two cases: one is the fatigue life of 3D printed 17-4 stainless steel under constant amplitude strain load using the direct cyclic method, and the other one is the cyclic behavior of Alloy 617 under multi-amplitude strain loads using the static analysis method. Both validation models show a good correlation with the literature experimental data. Finally, after the validation, the finite element model is applied to the 15-5 PH stainless steel. Using the direct cyclic method, the model predicts the fatigue life of 15-5 PH stainless steel under constant amplitude strain. The extension of the prediction curve matches well with the previously measured experimental results, following the combined Coffin-Manson Basquin Law. Under multi-amplitude strain, the kinematic hardening evolution parameter is incorporated into the model. The model is capable to capture the stresses at varied strain amplitudes. Higher stresses are predicted when strain amplitudes are increased. The model presented in the work can be used to design reliable 3D printed metals under cyclic loading conditions.Item Fluorination Enables Simultaneous Improvements of a Dialkoxybenzene-Based Redoxmer for Nonaqueous Redox Flow Batteries(American Chemical Society, 2022) Bheemireddy, Sambasiva R.; Li, Zhiguang; Zhang, Jingjing; Agarwal, Garvit; Robertson, Lily A.; Shkrob, Ilya A.; Assary, Rajeev S.; Zhang, Zhengcheng; Wei, Xiaoliang; Cheng, Lei; Zhang, Lu; Mechanical and Energy Engineering, Purdue School of Engineering and TechnologyRedoxmers or redox-active organic materials, are one critical component for nonaqueous redox flow batteries (RFBs), which hold high promise in enabling the time domain of the grid. While tuning redox potentials of redoxmers is a very effective way to enhance energy densities of NRFBs, those improvements often accompany accelerated kinetics of the charged species, undermining stability and cycling performance. Herein, a strategy for designing redoxmers with simultaneous improvements in redox potential and stability is proposed. Specifically, the redoxmer 1,4-di-tert-butyl-2,5-bis(2,2,2-trifluoroethoxy)benzene (ANL-C46) is developed by incorporating fluorinated substitutions into the dialkoxybenzene-based platform. Compared to the non-fluorinated analogue, ANL-C46 demonstrates not only an increased (∼0.41 V) redox potential but also much enhanced stability (1.6 times) and cyclability (4 times) evidenced by electron paramagnetic resonance kinetic study, H-cell and flow cell cycling. In fact, the cycling performance of ANL-C46 is among the best of high potential (>1.0 V vs Ag/Ag+) redoxmers ever reported. Density functional theory calculations suggest that while the introduced fluorine substitutions elevate the redox potentials, they also help to depress the decomposition reactions of the charged redoxmers, affording excellent stability. The findings represent an interesting strategy for simultaneously improving energy density and stability, which could further prompt the development of high-performance redoxmers.Item Fundamental Investigation of Direct Recycling Using Chemically Delithiated Cathode(2022-12) Bhuyan, Md Sajibul Alam; Shin, Hosop; Zhu, Likun; Wei, XiaoliangRecycling valuable cathode material from end-of-life (EOL) Li-ion batteries (LIBs) is essential to preserve raw material depletion and environmental sustainability. Direct recycling reclaims the cathode material without jeopardizing its original functional structures and maximizing return values from spent LIBs compared to other regeneration processes. This work employed two chemically delithiated lithium cobalt oxide (LCO) cathodes at different states of health (SOH), which are analogous to the spent cathodes but free of any impurities, to investigate the effectiveness of cathode regeneration. The material and electrochemical properties of both delithiated SOHs were systematically examined and compared to pristine LCO cathode. Further, those model materials were regenerated by a hydrothermal-based approach. The direct cathode regeneration of both low and high SOH cathode samples restored their reversible capacity and cycle performance comparable to pristine LCO cathode. However, the inferior performance observed in higher current density (2C) rate was not comparable to pristine LCO. In addition, the higher resistance of regenerated cathodes is attributed to lower high-rate performance, which was pointed out as the key challenge of the cathode recycling process. This study provides valuable knowledge about the effectiveness of cathode regeneration by investigating how the disordered, lithium-deficient cathode at different SOH from spent EOL batteries are rejuvenated without changing any material and electrochemical functional properties.Item Lithium Storage Mechanisms and Electrochemical Behavior of Molybdenum Disulfide(2024-05) Li, Xintong; Zhu, Likun; Hosop, Shin; Wei, XiaoliangThis study investigates the electrochemical behavior of molybdenum disulfide (MoS2) when utilized as an anode material in Li-ion batteries, particularly focusing on the intriguing phenomenon of extra capacity observed beyond theoretical expectations and the unique discharge curve of the first cycle. Employing a robust suite of advanced characterization methods such as in situ and ex situ X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM), the research unravels the complex structural and chemical evolution of MoS2 throughout its cycling process. A pivotal discovery of the research is the identification of a distinct lithium intercalation mechanism in MoS2, which leads to the formation of reversible LixMoS2. These phases play a crucial role in contributing to the extra capacity observed in the MoS2 electrode. Additionally, density functional theory (DFT) calculations have been utilized to explore the potential for overlithiation within MoS2, suggesting that Li5MoS2 could be the most energetically favorable phase during the lithiation-delithiation process. This study also explores the energetics of a Li-rich phase forming on the surface of Li4MoS2, indicating that this configuration is energetically advantageous and could contribute further to the extra capacity. The incorporation of reduced graphene oxide (RGO) as a conductive additive in MoS2 electrodes, demonstrating that RGO notably improves the electrochemical performance, rate capability, and durability of the electrodes. These findings are supported by experimental observations and are crucial for advancing the understanding of MoS2 as a high-capacity anode material. The implications of this research are significant, offering a pathway to optimize the design and composition of electrode materials to exceed traditional performance and longevity limits in Li-ion batteries.Item Multielectron Organic Redoxmers for Energy-Dense Redox Flow Batteries(ACS, 2022-01) Fang, Xiaoting; Li, Zhiguang; Zhao, Yuyue; Yue, Diqing; Zhang, Lu; Wei, Xiaoliang; Mechanical Engineering, School of Engineering and TechnologyRedox flow battery is a highly promising stationary energy storage method, but the limited energy density and high chemical cost are among the main barriers for commercialization. Multielectron organic redoxmers represent a family of structurally tailorable candidates that can achieve multiplied energy density with decreased materials consumption, potentially resulting in a viable solution to address these challenges. Here, the recent development of organic molecules with reversible multiredox activities in both aqueous and nonaqueous electrolytes is reviewed. The major focus is on the fundamental correlation between the chemical structures and the functional properties of reported multielectron organic molecules. Valuable insights are offered on rational structural design strategies for improving the relevant physicochemical and electrochemical properties. Finally, the current challenges are discussed to suggest future research needs along the avenue of using the multielectron approach to achieve energy-dense, stable, cost-effective redox flow batteries.Item Simulation of Mechanical, Thermodynamic, and Magnetic Properties of Magnesia with Substitutional Elements for Improved Magnetic Core Coating Applications(2019-12) Tiamiyu, Asimiyu A.; Zhang, Jing; Wei, Xiaoliang; Yang, ShengfengIn transformers used in the electrical industry, a coating, such as magnesium oxide or magnesia (MgO), is needed to coat the magnetic ferrite core, such as silicon steel. The coating is to provide electrical insulation of the layers of the ferrite core material, in order to reduce its heat dissipation loss. The coating also separate the layers of the coiled materials to prevent their sticking or welding during high temperature uses. The goal of this thesis is to perform a modeling study to understand the mechanical, thermodynamic, magnetic and thermal properties of pure and M-doped (M stands for Mn, Co, or Ni) magnesia, thus providing a theoretical understanding of the application of this group of coating materials for transformer applications. The study has the following sections. The first section is focused on the mechanical properties of pure magnesia. Using density functional theory (DFT) based calculations, the computed Young’s modulus, Poisson’s ratio, bulk modulus, and compressibility are 228.80 GPa, 0.2397, 146.52 GPa, and 0.00682, respectively, which are in good agreement with the literature data. Using molecular dynamics (MD) simulations, the computed Young’s modulus is 229 GPa. Using discrete element model (DEM) approach, the bending deformation of magnesia is simulated. Finally, using finite element model (FEM), micro-hardness indentation of magnesia is simulated, and the computed Brinell hardness is 16.1 HB, and Vickers hardness is 16 GPa. The second section is on the thermodynamic and physical properties of pure and doped magnesia. Using DFT based simulations, the temperature-dependent thermodynamic properties, such as free energy, enthalpy, entropy, heat capacity at constant volume, and Debye temperature of magnesia, are computed. The X-ray powder diffraction (XRD) spectra of M-doped magnesia are simulated, at the doping level of 1.5%, 3%, 6% and 12%, respectively. The simulated XRD data show that peaks shift to higher angles as the doping level increases. The third section is on the magnetic properties of pure and doped magnesia. Using DFT based simulations, the calculated magnetic moments increase with the doping level, with Mn as the highest, followed by Co and Ni. This is due to the fact that Mn has more unpaired electrons than Co and Ni. The fourth section is on the thermal properties of the pure magnesia. Using the Reverse Non-Equilibrium Molecular Dynamics (RNEMD) method, the computed thermal conductivity of magnesia is 34.63 W/m/K, which is in agreement with the literature data of 33.0 W/m/K at 400 K.Item Six-electron organic redoxmers for aqueous redox flow batteries(Royal Society of Chemistry, 2022-12) Fang, Xiaoting; Cavazos, Andres T.; Li, Zhiguang; Li, Chenzhao; Xie, Jian; Wassall, Stephen R.; Zhang, Lu; Wei, Xiaoliang; Physics, School of ScienceWe have developed a novel molecular design that enables six-electron redox activity in fused phenazine-based organic scaffolds. Combined electrochemical and spectroscopic tests successfully confirm the two-step 6e− redox mechanism. This work offers an opportunity for achieving energy-dense redox flow batteries, on condition that the solubility and stability issues are addressed.Item Spatially Constrained Organic Diquat Anolyte for Stable Aqueous Flow Batteries(ACS, 2018-09) Huang, Jinhua; Yang, Zheng; Murugesan, Vijayakumar; Walter, Eric; Hollas, Aaron; Pan, Baofei; Assary, Rajeev S.; Shkrob, Ilya A.; Wei, Xiaoliang; Zhang, Zhengcheng; Mechanical Engineering, School of Engineering and TechnologyRedox-active organic materials (ROMs) are becoming increasingly attractive for use in redox flow batteries as promising alternatives to traditional inorganic counterparts. However, the reported ROMs are often accompanied by challenges, including poor solubility and stability. Herein, we demonstrate that the commonly used diquat herbicides, with solubilities of >2 M in aqueous electrolytes, can be used as stable anolyte materials in organic flow batteries. When coupled with a ferrocene-derived catholyte, the flow cells with the diquat anolyte demonstrate long galvanic cycling with high capacity retention. Notably, the mechanistic underpinnings of this remarkable stability are attributed to the improved π-conjugation that originated from the near-planar molecular conformations of the spatially constrained 2,2′-bipyridyl rings, suggesting a viable structural engineering strategy for designing stable organic materials.Item Substituted thiadiazoles as energy-rich anolytes for nonaqueous redox flow cells(RSC, 2018-04) Huang, Jinhua; Duan, Wentao; Zhang, Jingjing; Shkrob, Ilya A.; Assary, Rajeev S.; Pan, Baofei; Liao, Chen; Zhang, Zhengcheng; Wei, Xiaoliang; Zhang, Lu; Mechanical Engineering and Energy, School of Engineering and TechnologyUnderstanding structure–property relationships is essential for designing energy-rich redox active organic molecules (ROMs) for all-organic redox flow batteries. Herein we examine thiadiazole ROMs for storage of negative charge in the flow cells. These versatile molecules have excellent solubility and low redox potentials, allowing high energy density to be achieved. By systematically incorporating groups with varying electron accepting/withdrawing ability, we have examined substituent effects on their properties of interest, including redox potentials, calendar lives of charged ROMs in electrolyte, and the flow cell cycling performance. While the calendar life of energized fluids can be tuned in a predictable fashion over a wide range, the improvements in the calendar life do not automatically translate into the enhanced cycling performance, indicating that in addition to the slow reactions of charged species in the solvent bulk, there are other parasitic reactions that occur only during the electrochemical cycling of the cell and can dramatically affect the cycling lifetime.