Mechanical and Energy Engineering Works
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Item Electricity Demand Time Series Forecasting Based on Empirical Mode Decomposition and Long Short-Term Memory(Tech Science Press, 2021) Taheri, Saman; Talebjedi, Behnam; Laukkanen, Timo; Mechanical and Energy Engineering, Purdue School of Engineering and TechnologyLoad forecasting is critical for a variety of applications in modern energy systems. Nonetheless, forecasting is a difficult task because electricity load profiles are tied with uncertain, non-linear, and non-stationary signals. To address these issues, long short-term memory (LSTM), a machine learning algorithm capable of learning temporal dependencies, has been extensively integrated into load forecasting in recent years. To further increase the effectiveness of using LSTM for demand forecasting, this paper proposes a hybrid prediction model that incorporates LSTM with empirical mode decomposition (EMD). EMD algorithm breaks down a load time-series data into several sub-series called intrinsic mode functions (IMFs). For each of the derived IMFs, a different LSTM model is trained. Finally, the outputs of all the individual LSTM learners are fed to a meta-learner to provide an aggregated output for the energy demand prediction. The suggested methodology is applied to the California ISO dataset to demonstrate its applicability. Additionally, we compare the output of the proposed algorithm to a single LSTM and two state-of-the-art data-driven models, specifically XGBoost, and logistic regression (LR). The proposed hybrid model outperforms single LSTM, LR, and XGBoost by, 35.19%, 54%, and 49.25% for short-term, and 36.3%, 34.04%, 32% for long-term prediction in mean absolute percentage error, respectively.Item Effects of Ink Formulation on the Structure and Performance of PGM-Free Catalyst Layer in PEMFCs(IOP, 2021) Li, Chenzhao; Liu, Shengwen; Zeng, Yachao; Liu, Yadong; Wu, Gang; Cullen, David A.; Xie, Jian; Mechanical and Energy Engineering, Purdue School of Engineering and TechnologyPlatinum group metal (PGM) catalysts are the major electrocatalysts for oxygen reduction reaction (ORR) in the polymer electrolyte membrane fuel cells (PEMFCs). The cost becomes unaffordable if the PEMFC is in massive application. The PGM-Free catalyst shows very promising activity in rotation disk electrode (RDE) testing. The half-wave potential could reach 0.91 V versus standard hydrogen electrode (SHE). However, in a membrane electrode assembly (MEA), the performance of PGM-Free catalysts is not good enough to replace the PGM catalysts. Since the PGM-free catalysts are so different from the PGM catalysts in terms of catalytic activity, stability, surface conditions, particle size, etc., the fabrication of PGM-Free catalyst MEA cannot simply copy the method of making PGM MEA. We proposed a novel method of fabricating PGM-Free catalyst MEA, so that the intrinsic catalyst activity from RDE can be translated into MEA performance. The method is based on the catalyst coated membrane (CCM) method using optimized ionomer to carbon (I/C) ratio and solvent mixture of catalyst ink. Using this method, the PGM-free catalyst MEA achieved the current density 44.9 mA cm-2 at 0.9 V iR-free in H2/O2 and 150 mA cm-2 at 0.8 V in H2/air, which surpassed the performance targets of US Department of Energy (DOE)for PGM-Free catalyst MEA. The property (solvent composition, dispersion of catalyst and ionomer in an ink), structure (pore structure) and the MEA performance have been characterized using, mercury intrusion porosimetry (MIP), MEA testing. A property-structure-performance relationship has been established.Item Treatment of carbon electrodes with Ti3C2Tx MXene coating and thermal method for vanadium redox flow batteries: a comparative study(Royal Society of Chemistry, 2024-04-19) Teenakul, Kavin; Ahmad Alem, Sayed Ali; Gond, Ritambhara; Thakur, Anupma; Anasori, Babak; Khataee, Amirreza; Mechanical and Energy Engineering, Purdue School of Engineering and TechnologyOne of the significant challenges of vanadium redox flow batteries is connected to the negative electrode where the main reaction of V(ii)/V(iii) and the side reaction of hydrogen evolution compete. To address this issue, we used titanium carbide (Ti3C2Tx) MXene coating via drop-casting to introduce oxygen functional groups and metals on the carbon electrode surface. Characterization through scanning electron microscopy and X-ray photoelectron spectroscopy confirmed the even distribution of Ti3C2Tx MXene on the electrodes and the presence of titanium and termination groups (-O, -Cl, and -F). The cyclic voltammetry analysis of MXene-coated electrodes showed more sharp electrochemical peaks for the V(ii)/V(iii) reaction than thermal-treated electrodes, even at relatively high scan rates. Notably, a relatively high reaction rate of 5.61 × 10-4 cm s-1 was achieved for the V(ii)/V(iii) reaction on MXene-coated electrodes, which shows the competitiveness of the method compared to thermal treatment (4.17 × 10-4 cm s-1). The flow battery tests, at a current density of 130 mA cm-2, using MXene-coated electrodes showed pretty stable discharge capacity for over 100 cycles. In addition, the voltage and energy efficiency were significantly higher than those of the system using untreated electrodes. Overall, this work highlights the potential application of MXene coating in carbon electrode treatment for vanadium redox flow batteries due to remarkable electrocatalytic activity and battery performance, providing a competitive method for thermal treatment.Item Multiple Metal-Nitrogen Bonds Synergistically Boosting the Activity and Durability of High-Entropy Alloy Electrocatalysts(American Chemical Society, 2024) Zhao, Xueru; Cheng, Hao; Chen, Xiaobo; Zhang, Qi; Li, Chenzhao; Xie, Jian; Marinkovic, Nebojsa; Ma, Lu; Zheng, Jin-Cheng; Sasaki, Kotaro; Mechanical and Energy Engineering, Purdue School of Engineering and TechnologyThe development of Pt-based catalysts for use in fuel cells that meet performance targets of high activity, maximized stability, and low cost remains a huge challenge. Herein, we report a nitrogen (N)-doped high-entropy alloy (HEA) electrocatalyst that consists of a Pt-rich shell and a N-doped PtCoFeNiCu core on a carbon support (denoted as N-Pt/HEA/C). The N-Pt/HEA/C catalyst showed a high mass activity of 1.34 A mgPt-1 at 0.9 V for the oxygen reduction reaction (ORR) in rotating disk electrode (RDE) testing, which substantially outperformed commercial Pt/C and most of the other binary/ternary Pt-based catalysts. The N-Pt/HEA/C catalyst also demonstrated excellent stability in both RDE and membrane electrode assembly (MEA) testing. Using operando X-ray absorption spectroscopy (XAS) measurements and theoretical calculations, we revealed that the enhanced ORR activity of N-Pt/HEA/C originated from the optimized adsorption energy of intermediates, resulting in the tailored electronic structure formed upon N-doping. Furthermore, we showed that the multiple metal-nitrogen bonds formed synergistically improved the corrosion resistance of the 3d transition metals and enhanced the ORR durability.Item Perspectives of 2D MXene Tribology(Wiley, 2023) Rosenkranz, Andreas; Righi, Maria Clelia; Sumant, Anirudha V.; Anasori, Babak; Mochalin, Vadym N.; Mechanical and Energy Engineering, Purdue School of Engineering and TechnologyThe large and rapidly growing family of two-dimensional early transition metal carbides, nitrides, and carbonitrides (MXenes) raises significant interest in the materials science and chemistry of materials communities. Discovered a little more than a decade ago, MXenes have already demonstrated outstanding potential in various applications ranging from energy storage to biology and medicine. The past two years have witnessed increased experimental and theoretical efforts toward studying MXenes’ mechanical and tribological properties when used as lubricant additives, reinforcement phases in composites, or solid lubricant coatings. Although research on the understanding of the friction and wear performance of MXenes under dry and lubricated conditions is still in its early stages, it has experienced rapid growth due to the excellent mechanical properties and chemical reactivities offered by MXenes that make them adaptable to being combined with other materials, thus boosting their tribological performance. In this perspective, we summarize the most promising results in the area of MXene tribology, outline future important problems to be pursued further, and provide methodological recommendations that we believe could be useful for experts, as well as newcomers to MXenes research, in particular, to the emerging area of MXene tribology.Item Self-assembly and in-situ characterization of Ti3C2Tx in Al: A step toward additive manufacturing of MXene-metal composites(Elsevier, 2022) Wyatt, Brian C.; Anasori, Babak; Mechanical and Energy Engineering, Purdue School of Engineering and TechnologyTwo-dimensional (2D) transition metal carbides, known as MXenes, have grown in research interest since 2011 partly due to their impressive high electrical conductivity, stiff mechanical properties, and abundant chemically-active surface groups. These key features of MXenes make them attractive candidates for uniform coverage of metal powders for additive manufacturing of multi-functional metal composites. In this study, we report on a tunable self-assembly process of nanometer-thick 2D MXene flakes on micron-size Al particles using 1–10 wt% of single-to-few and multi-layer Ti3C2Tx MXene. In addition, we discuss the characterization of these composites using 2D x-ray diffraction (XRD2) for identification of the characteristic Ti3C2Tx diffraction peaks. Lastly, we use in-situ XRD2 paired with Vickers hardness and scanning electron microscopy/energy dispersive x-ray spectroscopy methods to understand the effect of sintering on the Ti3C2Tx morphology and the resultant mechanical properties of the bulk composite. This study aims to assist future advances in additive manufacturing of MXene-metal composites for an array of multi-functional applications.Item Computation of conductive thermal distribution using non-homogenous graph theory for real-time applications in metal PBF process(Elsevier, 2022-09) Malekipour, Ehsan; El-Mounayri, Hazim; Mechanical and Energy Engineering, Purdue School of Engineering and TechnologyThe Powder Bed Fusion (PBF) process is inherently a thermal process with complex thermal interactions between different printed zones as well as different layers. There exist only a few methods such as finite element analysis (FEA), finite element differences (FDM), graph theory (GT), Goldak’s FEA, and Rosenthal equation, which are able to predict thermal temperature distribution throughout a printed layer (2D) or part (3D). All these approaches suffer from inherent limitations including the applied boundary conditions and computational time. A rapid and reliable method to compute thermal distribution throughout a printed part is pivotal to supporting real-time closed-loop monitoring and control, enabling thermal simulation software with rapid and precise prediction, and advancing current research on thermal-related abnormalities such as residual stress and distortion. The literature shows that the conventional graph theory is the fastest approach that generates relatively precise results in a fraction of the computational time of other techniques; however, the lack of a solution to the non-homogeneous governing thermal equation through GT has hampered this method in terms of thermal load resolution, accuracy in highly rapid process such as PBF, and scope of application. In this paper, we describe the characteristics that make GT a superior approach for real-time computation of thermal field compared to other similar approaches such as FDM. Also, we develop a solution to the non-homogeneous term of the thermal conduction equation by using GT. This solution represents a breakthrough for the development of precise real-time closed-loop monitoring and control systems by providing a precise numerical solution to the thermal conduction equation in a fraction of time compared with previous traditional methods such as FEA and FDM. Ongoing work includes the development of an intelligent monitoring and control system that leverages this solution in order to optimize scan strategy real-time in metal PBF.Item Predictive Optimal Control of Mild Hybrid Trucks(MDPI, 2022) Pramanik, Sourav; Anwar, Sohel; Mechanical and Energy Engineering, Purdue School of Engineering and TechnologyNumerous per- and polyfluoroalkyl substances (PFASs) occur in consumer food packaging due to intentional and unintentional addition, despite increasing concern about their health and environmental hazards. We present a substance flow analysis framework to assess the flows of PFASs contained in plant fiber-based and plastic food packaging to the waste stream and environment. Each year between 2018 and 2020, an estimated 9000 (range 1100–25 000) and 940 (range 120–2600) tonnes per year of polymeric PFASs were used in 2% of food packaging in the U.S. and Canada, respectively. At least 11 tonnes per year of non-polymeric PFASs also moved through the food packaging life cycle. Approximately 6100 (range 690–13 000) and 700 (range 70–1600) tonnes per year of these PFASs were landfilled or entered composting facilities in the U.S. and Canada, respectively, with the potential to contaminate the environment. The results suggest that minimal food packaging contains intentionally added PFASs which, nonetheless, has the potential to contaminate the entire waste stream. Further, this indicates that PFASs are not needed for most food packaging. These results serve as a benchmark to judge the effectiveness of future industry and government initiatives to limit PFAS use in food packaging.Item 2D rare-earth metal carbides (MXenes) Mo2NdC2T2 electronic structure and magnetic properties: A DFT + U study(AIP, 2022) Yao, Shukai; Anasori, Babak; Strachan, Alejandro; Mechanical and Energy Engineering, Purdue School of Engineering and Technology2D rare-earth metal carbides (MXenes) are attractive due to their novel electronic and magnetic properties and their potential as scalable 2D magnets. In this study, we used density functional theory with the Hubbard U correction to characterize the structure, termination, and magnetism in an out-of-plane ordered rare-earth containing M3C2Tx MXene, Mo2NdC2T2 (T = O or OH). We investigated the effect of the U parameter on the stability and magnetism of two possible termination sites: the hollow sites aligned with the inner Nd atoms (Nd-hollow sites) and those aligned with the closest C atoms (C-hollow sites). We found that increasing UMo stabilized the Nd hollow sites, which minimized electrostatic repulsion between C and O atoms. Using UMo = 3.0 eV and UNd = 5.6 eV, obtained via the linear response method, we found that the energetically preferred termination site was C-hollow in Mo2NdC2O2 and Nd-hollow in Mo2NdC2(OH)2. Regardless of termination and the Hubbard U value, we found Mo2NdC2O2 and Mo2NdC2(OH)2 to be magnetic. The C-hollow termination resulted in ferromagnetic states for all Hubbard U tested with no magnetic moment in Mo. In the case of Nd-hollow, Mo became magnetic for UMo ≥ 4 eV. The difference of Mo magnetism in Nd-hollow and C-hollow was explained by crystal field splitting of the Mo d orbital caused by a distorted ligand.Item Spherical Templating of CoSe2 Nanoparticle-Decorated MXenes for Lithium-Sulfur Batteries(American Chemical Society, 2022) Lieu, Wei Ying; Fang, Daliang; Li, Yuanjian; Li, Xue Liang; Lin, Congjian; Thakur, Anupma; Wyatt, Brian C.; Sun, Shengnan; Ghosh, Tanmay; Anasori, Babak; Ng, Man-Fai; Yang, Hui Ying; Seh, Zhi Wei; Mechanical and Energy Engineering, Purdue School of Engineering and TechnologyTwo-dimensional MXenes produce competitive performances when incorporated into lithium–sulfur batteries (LSBs), solving key problems such as the poor electronic conductivity of sulfur and dissolution of its polysulfide intermediates. However, MXene nanosheets are known to easily aggregate and restack during electrode fabrication, filtration, or water removal, limiting their practical applicability. Furthermore, in complex electrocatalytic reactions like the multistep sulfur reduction process in LSBs, MXene alone is insufficient to ensure an optimal reaction pathway. In this work, we demonstrate for the first time a loose templating of sulfur spheres using Ti3C2Tx MXene nanosheets decorated with polymorphic CoSe2 nanoparticles. This work shows that the templating of sulfur spheres using nanoparticle-decorated MXene nanosheets can prevent nanosheet aggregation and exert a strong electrocatalytic effect, thereby enabling improved reaction kinetics and battery performance. The S@MXene-CoSe2 cathode demonstrated a long cycle life of 1000 cycles and a low capacity decay rate of 0.06% per cycle in LSBs.