Now showing items 21-40 of 1112

    • Nerve Network-Inspired Solid Polymer Electrolytes (NN-SPE) for Fast and Single-Ion Lithium Conduction

      Li, Zhen; Guo, Dong; Li, Fan; Hou, Guangjin; Liu, Xiaowei; Li, Chunyang; Cao, Li; Wei, Ruicong; Zhou, Zongyao; Lai, Zhiping (Energy Storage Materials, Elsevier BV, 2022-05-04) [Article]
      The low lithium-ion conductivity is current the bottleneck in developing solid-state electrolytes (SSEs) that are expected to be a key component in the next generation of lithium batteries. Inspired by the high connectivity of the biological nerve network, we designed a mimic architecture inside a polymer electrolyte to provide fast lithium-ion pathways. Detailed experimental and simulation studies revealed that the mimic nerve network could efficiently form the bi-continuous structure at very low percolation threshold, and rendered an unprecedentedly non-linear increment by order of magnitudes in the lithium-ion conductivity, with a superior lithium-ion conductivity up to 0.12 mS•cm−1, transference number up to 0.974 and robust mechanical strength of 10.3 MPa. When applied in lithium metal batteries, good rate and cycling performance were achieved at both room and elevated temperatures.
    • In situ conductive spacers for early pore wetting detection in membrane distillation

      Alpatova, Alla; Qamar, Adnan; Alhaddad, Mohammed; Kerdi, Sarah; Soo Son, Hyuk; Amin, Najat A.; Ghaffour, NorEddine (Separation and Purification Technology, Elsevier BV, 2022-04-30) [Article]
      Membrane distillation (MD) suffers from pore wetting which deteriorates membrane separation properties and causes water protrusion to permeate side. The early detection of pore wetting is a challenge which needs to be addressed to achieve stable MD performance. In this study, electrically-conductive Pt-coated spacers placed inside the feed and coolant channels with a dual purpose of maximizing permeate flux and instantaneous wetting detection once first membrane pores are compromised are proposed. Upon wetting, permeate salt concentration increases thereby initiating redox reactions at two spacer electrodes under the applied electrical potential. As a result, electrical current is produced and measured. The competence of the proposed wetting detection method was explored in MD process in the presence of organic substances with high wetting propensity. An increase in generated electrical current upon wetting development and substantial signal amplification with the voltage increase was demonstrated. The new wetting detection method achieved a faster response comparing to conventional conductivity measurements. Moreover, this method allows to define the wetting onset which can serve as an indication of early membrane impairment. Different spacer geometries and observed no adverse effect of spacer coating on MD performance were further compared. Experimental and numerical simulations accentuated an importance of spacer design by providing specific permeate flux gain for a 1-helical spacer comparing to a spacer with a smooth cylindrical filament. This effect became more evident at higher feed water temperature, condition that favors greater temperature polarization.
    • Accurate thermochemistry prediction of extensive Polycyclic aromatic hydrocarbons (PAHs) and relevant radicals

      Li, Yang; Wang, Tairan; Yalamanchi, Kiran K.; Kukkadapu, Goutham; Sarathy, Mani (Combustion and Flame, Elsevier BV, 2022-04-26) [Article]
      Polycyclic aromatic hydrocarbons (PAHs) are important intermediates to soot formation in combustion. A reliable database of their thermochemistry is required for the development of chemical kinetic models describing the gas-phase chemistry of hydrocarbon fuels. In this study, temperature-dependent thermodynamic properties are consistently determined using high-accuracy quantum chemistry calculations for an extensive set of PAH compounds. The developed database comprehensively consists of 125 C6-C18 PAH molecules and radicals, which are important and commonly included in chemical mechanisms studies. At the M06-2X/6-311++G(d,p) level of theory, geometry optimizations, vibrational frequency calculations, and dihedral angle scans are performed for all PAH species. The G3 method, together with the atomization reaction approach, is selected to derive the average atomization formation enthalpy. This method produces the most accurate thermochemistry quantities for PAHs, as demonstrated in a previous study. The entropy and heat capacity values are calculated using statistical thermodynamics in MultiWell. These results exhibit good agreement with the databases in literature. To examine the application of the group additivity (GA) method for PAHs, the Bland−Altman plot, a statistical analysis approach, is employed to visualize the agreement between the results from the quantum chemical calculations and GA methods. Two GA methods are examined and significant differences are found, which indicates that GA values of relevant groups need to be further updated. The database of thermodynamic quantities developed in this study are of particular value in modeling studies and important for exploring mechanisms of the PAH growth.
    • Plasmonic Titanium Nitride Tubes Decorated with Ru Nanoparticles as Photo-Thermal Catalyst for CO2 Methanation

      Mateo, Diego; Navarro, Juan Carlos; Khan, Il Son; Ruiz-Martinez, Javier; Gascon, Jorge (Molecules, MDPI AG, 2022-04-22) [Article]
      Photo-thermal catalysis has recently emerged as a viable strategy to produce solar fuels or chemicals using sunlight. In particular, nanostructures featuring localized surface plasmon resonance (LSPR) hold great promise as photo-thermal catalysts given their ability to convert light into heat. In this regard, traditional plasmonic materials include gold (Au) or silver (Ag), but in the last years, transition metal nitrides have been proposed as a cost-efficient alternative. Herein, we demonstrate that titanium nitride (TiN) tubes derived from the nitridation of TiO2 precursor display excellent light absorption properties thanks to their intense LSPR band in the visible–IR regions. Upon deposition of Ru nanoparticles (NPs), Ru-TiN tubes exhibit high activity towards the photo-thermal CO2 reduction reaction, achieving remarkable methane (CH4) production rates up to 1200 mmol g−1 h−1. Mechanistic studies suggest that the reaction pathway is dominated by thermal effects thanks to the effective light-to-heat conversion of Ru-TiN tubes. This work will serve as a basis for future research on new plasmonic structures for photo-thermal applications in catalysis.
    • Ionic covalent organic nanosheet (iCON)–quaternized polybenzimidazole nanocomposite anion-exchange membranes to enhance the performance of membrane capacitive deionization

      McNair, Robert; Kumar, Sushil; Wonanke, A. D.Dinga; Addicoat, Matthew A.; Dryfe, Robert A.W.; Szekely, Gyorgy (Desalination, Elsevier BV, 2022-04-19) [Article]
      Membrane capacitive deionization (MCDI) is a promising technique to achieve desalination of low-salinity water resources. The primary requirements for developing and designing materials for MCDI applications are large surface area, high wettability to water, high conductivity, and efficient ion-transport pathways. Herein, we synthesized ionic covalent organic nanosheets (iCONs) containing guanidinium units that carry a positive charge. A series of quaternized polybenzimidazole (QPBI)/iCON (iCON@QPBI) nanocomposite membranes was fabricated using solution casting. The surface, thermal, wettability, and electrochemical properties of the iCON@QPBI nanocomposite membranes were evaluated. The iCON@QPBI anion-exchange membranes achieved a salt adsorption capacity as high as 15.6 mg g−1 and charge efficiency of up to 90%, which are 50% and 20% higher than those of the pristine QPBI membrane, respectively. The performance improvement was attributed to the increased ion-exchange capacity (2.4 mmol g−1), reduced area resistance (5.4 Ω cm2), and enhanced hydrophilicity (water uptake = 32%) of the iCON@QPBI nanocomposite membranes. This was due to the additional quaternary ammonium groups and conductive ion transport networks donated by the iCON materials. The excellent desalination performance of the iCON@polymer nanocomposite membranes demonstrated their potential for use in MCDI applications and alternative electromembrane processes.
    • Understanding Zeolite Desilication by NMR Spectroscopy

      Tsereshko, Nina (2022-04-17) [Thesis]
      Advisor: Ruiz-Martinez, Javier
      Committee members: Gascon, Jorge; Han, Yu
      Today, zeolites play a considerable role in many industrial fields, especially in heterogeneous catalysis. Well-defined microporous structure combined with acidity provides exceptional size and shape selectivity, making zeolites indispensable in petrochemistry. However, the micropores can cause diffusion limitations and, in turn, a drop in reaction rate and selectivity. Hence, the development of modification methodologies on zeolite textural properties is one of the attention-grabbing research topics nowadays. For example, to overcome transport limitations in zeolites, the particle size can be reduced, or a system of larger auxiliary pores can be introduced [1]. One of the most promising methods for introducing secondary pores on a large scale is desilication since it is low-cost, versatile, and easy [2]. Despite its simplicity, the desilication mechanism is still a matter of discussion. In detail, it is not well-understood: 1. The influence of different species on mesopore formation kinetics 2. How aluminum is assembled back into the zeolite 3. Which types of aluminum species form throughout the treatment. The present study tries to answer these questions by relating ex-situ and in-situ NMR. The proposed ex-situ 29Si MAS NMR approach allows monitoring the development of mesoporosity and silicon extraction by analyzing Q3 and Q4 changes. The combination of ex-situ with in-situ 29Si MAS NMR study showed that the limiting step of Si extraction is the transformation of Q3 into Q2. 27Al MAS NMR combined with MQMAS showed the formation of new aluminum species after desilication. It was shown that some of the Al framework T-sites might dissolve during alkaline treatment. In-situ 27Al NMR indicates redistribution of dissolved aluminum upon desilication.
    • Insight into the role of reduced graphene oxide in enhancing photocatalytic hydrogen evolution in disordered carbon nitride.

      Rahman, Mohammad Ziaur; Maity, Partha; Mohammed, Omar F.; Gascon, Jorge (Royal Society of Chemistry (RSC), 2022-04-12) [Article]
      Compared to crystalline carbon nitride, the performance of disordered carbon nitride (d-CN) as a hydrogen production photocatalyst is extremely poor. Owing to its disordered atomic orientation, it is prone to numerous defect states. These energy states are potential sites for trapping and recombination of photogenerated charge carriers. As a result, rapid recombination of photogenerated charge carriers places a fundamental photophysical challenge in charge separation and transport, which inhibits its photocatalytic activity. In the presence of reduced graphene oxide (rGO), d-CN shows enhanced photocatalytic production of hydrogen. However, photophysical insight into the tacit role of rGO is not well understood which limits the rational design of d-CN as a photocatalyst. Particularly, understanding of the early time-scale (in fs to ps) recombination mechanism and the charge transport kinetics has not yet been achieved. With the help of ultrafast transient absorption spectroscopy, femtosecond time-resolved photoluminescence spectroscopy and transient photocurrent measurements, this article deciphers the ultrafast dynamics of the separation and transport of photogenerated charge carriers in d-CN facilitated by rGO. It is found that rGO substantially suppresses the bimolecular and trap-assisted recombination and enables a faster separation of charge carriers. As a result, it increases the lifetime of the charge carriers to be transported to the surface catalytic sites, and therefore, augments the rate of hydrogen production almost by an order of magnitude. Our findings therefore offer a proof-of-concept for overcoming the trap-mediated recombination problems in disordered carbon nitride.
    • Catalytic arene-norbornene annulation (CANAL) ladder polymer derived carbon membranes with unparalleled hydrogen/carbon dioxide size-sieving capability

      Hazazi, Khalid; Wang, Yingge; Bettahalli Narasimha, Murthy Srivatsa; Ma, Xiaohua; Xia, Yan; Pinnau, Ingo (Journal of Membrane Science, Elsevier BV, 2022-04-08) [Article]
      Hydrogen is an emerging energy source with a wide range of applications in transportation, electricity generation, and manufacturing of important chemicals such as ammonia and methanol. Hydrogen is commonly coproduced with CO2 using steam reforming of methane and its purification is typically achieved using energy-intensive processes such as pressure swing adsorption (PSA) and cryogenic distillation. Membrane technology with potentially lower energy consumption and lower carbon footprint could play an important role in developing a more sustainable hydrogen economy. In this study, we prepared carbon molecular sieve (CMS) membranes by the pyrolysis of a highly aromatic catalytic arene-norbornene annulation (CANAL)-Tröger's base ladder polymer of intrinsic microporosity precursor — CANAL-TB-1. CMS membranes obtained by pyrolysis between 600 and 900 °C displayed excellent gas separation performance for hydrogen/carbon dioxide separation and related applications. The CANAL-CMS-800 °C membrane showed a pure-gas hydrogen permeability of 41 Barrer with H2/CO2, H2/N2, and H2/CH4 selectivity values of 39, 1952, and >8200 at 35 °C. Increasing the pyrolysis temperature to 850 and 900 °C further boosted the selectivity. For example, the CANAL-CMS-900 °C exhibited a stable long-term mixed-gas performance over a period of 38 days with an unprecedented H2/CO2 selectivity of 174 and H2 permeability of 8.2 Barrer at 10 bar total feed pressure and 100 °C, which significantly exceeded the performance of previously reported polymers and related CMS membrane materials.
    • Gas separation performance and physical aging of tubular thin-film composite carbon molecular sieve membranes based on a polyimide of intrinsic microporosity precursor

      Ogieglo, Wojciech; Puspasari, Tiara; Alabdulaaly, Abdullah; Nga Nguyen, Thi Phuong; Lai, Zhiping; Pinnau, Ingo (Journal of Membrane Science, Elsevier BV, 2022-04-07) [Article]
      We present a study on the fabrication of tubular thin-film composite CMS membranes based on an intrinsically microporous polyimide of intrinsic microporosity (PIM-PI), PIM-6FDA-OH. Besides the inherent structural similarity between the PIM-PI and CMS membranes (i.e. microporosity with pores <20 Å), the unique feature of the chosen precursor is its ability to undergo a thermal rearrangement (TR) reaction which constitutes an additional mechanism of microporosity evolution in addition to the pyrolysis process. By using Raman spectroscopy and in-situ thermal spectroscopic ellipsometry we tracked the structural TR- and pyrolysis-related evolution in CMS films as thin as 100 nm. Our study revealed a pronounced acceleration of the microstructure collapse (densification) due to physical aging that occurred in ultra-thin films. These, and our previous findings, suggest that excessive reductions in selective layer thickness in microporous amorphous materials, such as PIMs or CMS, may not be beneficial to obtaining highly efficient membranes. Instead, we have shown that excellent and stable separation properties could be achieved by PIM-PI-derived CMS membranes with thicker, ∼3 μm, selective layers (e.g. CO2, H2 permeances of >200 GPU, with CO2/CH4, CO2/N2, and O2/N2 selectivities of 43.0, 41.0, and 7.5, respectively) even after 3 months of aging.
    • Large-Scale Thermochemistry Calculations for Combustion Models

      Yalamanchi, Kiran; Li, Yang; Wang, Tairan; Monge Palacios, Manuel; Sarathy, Mani (Elsevier BV, 2022-04-05) [Preprint]
      Accurate thermochemical properties for chemical species are of vital importance in combustion research. Empirical group additivity approaches are extensively used to generate thermochemistry data used in chemical kinetic models, but the accuracy is limited. In this work, we performed electronic structure calculations to determine reliable thermochemistry data for an extensive set of molecules that were taken from a large and well-established chemical kinetic model. The developed database consists of 1340 species that contain up to 18 and 5 carbon and oxygen atoms, respectively. The M06-2X/aug-cc-pVTZ level of theory was used for the geometry optimizations, vibrational frequency calculations, and dihedral angle scans. The potential energy of the different species was further refined with different composite methods, and the G3 method, together with the atomization reaction approach, was selected to calculate the enthalpy of formation at 0 K. This information was then used in statistical thermodynamics to calculate standard enthalpies of formation and entropy, as well as heat capacities at different temperatures. Our thermochemistry data exhibit good agreement with existing values in the literature, verifying the accuracy of our approach. The group additivity (GA) method is also examined based on the calculated values and significant differences are found, which indicates that GA values of relevant functional groups need to be updated. The database of thermochemistry quantities developed in this study is of particular interest not only for the update of GA values, but also to develop machine learning models for predicting the data of new species, which can assist in the development of combustion models. The impact of the developed dataset is illustrated by examining the variation in ignition delay times with the updated thermochemistry values.
    • Electrospun Nanofibrous Mats Obtained from Green Resources

      Gulyas Oldal , Diana (2022-04) [Thesis]
      Advisor: Szekely, Gyorgy
      Committee members: Nunes, Suzana Pereira; Castaño, Pedro
      The fabrication of electrospun nanofibers has sparked great interest in both academia and industry owing to their unique properties, such as a high surface area to volume ratio, porosity, interconnected porous structure, or controllable fiber morphology. They are highly desired in numerous application areas such as filtration, biotechnology, and energy storage. Cellulose acetate is an ester of cellulose, one of the most abundant natural polymers, that is biodegradable, non-toxic, and has good stability. Electrospinning of cellulose acetate has received significant interest in a broad spectrum of applications, including membranes and air filters, drug-delivery systems, scaffolds for tissue engineering, sensors, and batteries. The electrospinning of cellulose acetate predominantly suffers from the use of toxic and hazardous solvents, which makes the final products less suitable for application in biosystems. In this work, the sustainable electrospinning of cellulose acetate has been shown using renewable-based green solvents, dimethyl carbonate, and cyclopentanone. A binary system consisting of these solvents has been applied. The addition of green salts and biosurfactants substantially improved the spinnability of the cellulose-based solutions. Altering the composition of the solvents allowed tuning of the fiber texture from highly porous to smooth fiber morphology. The thermal analysis revealed that the polymer’s thermal behavior had not been influenced by the salt in nanofibers. Incorporating additives into the polymer matrix resulted in enhanced mechanical properties of nanofibers. Uniform cellulose acetate-based porous nanofibers from green solvents and additives could be successfully fabricated, which has not been reported yet. Based on the reported advantageous properties of electrospun CA nanofibers, it may serve as a possible green and biodegradable porous support layer in thin-film composite membranes replacing the conventional fossil-derived polymeric membrane supports.
    • Thickness-dependent physical aging of a triptycene-based Tröger’s base ladder polymer of intrinsic microporosity (PIM-Trip-TB)

      Albuwaydi, Ahmed Y (2022-04) [Thesis]
      Advisor: Pinnau, Ingo
      Committee members: Lai, Zhiping; Yavuz, Cafer T.
      Gas separation membranes are proving to be a sustainable method to mitigate climate change given the rising energy demand. Polymers of intrinsic microporosity (PIMs) have emerged as a novel material class for such application. Physical aging is a major concern for the growth and commercialization of these glassy polymers. Several factors play an important role in determining the effects of physical aging for a PIM film; one important parameter is its thickness. Gas transport properties of PIM-Trip-TB films of thicknesses between 20-150 µm were monitored over 150 days for physical aging and its dependence on film thickness. Over this period, thicker films had generally higher permeability, and thinner films aged faster. Although fresh films showed higher selectivity during the initial tests, no correlation was found between film thickness and selectivity after aging. In addition, physical aging was more severe and independent of film thickness for larger-sized gases. Film storing environment affected the physical aging of multiply tested samples significantly, whereas films which were not tested periodically showed very minimal aging. A more systematic approach is required to fully analyze and comprehend factors yielding this phenomenon.
    • Intrinsically Microporous Ladder Polymer-based Carbon Molecular Sieve Membranes for Gas Separation Applications

      Hazazi, Khalid (2022-04) [Dissertation]
      Advisor: Pinnau, Ingo
      Committee members: Han, Yu; Koros, William J.; Lai, Zhiping
      Industrial separations – primarily dominated by thermally driven distillation-based processes – consume 10-15% of the global energy production and emit more than 100 million tonnes of CO2 annually. Membrane technology, a 90% thermodynamically more energy-efficient than distillation processes, could be a desirable alternative with potentially lower energy consumption and lower carbon footprint. Industrial implementation of membrane technology, particularly for olefin/paraffin separations and hydrogen purification from syngas, remains challenging due to the substantially low mixed-gas selectivity of the currently available polymeric materials. Carbon molecular sieve (CMS) membranes – formed by high-temperature pyrolysis of solution-processable polymeric-based precursors at an oxygen-free atmosphere – have shown superior gas separation performance far beyond the polymeric upper bounds for many gas-pairs (e.g., CO2/CH4, N2/CH4). The ultimate goal of the research reported in this dissertation was to develop highly performing CMS membranes for industrially important but challenging gas separation applications (e.g., C2H4/C2H6, H2/CO2, etc.). This work successfully introduced a promising approach to fine-tune the pore size distribution of CMS membranes through a systematic modification of the contortion sites of highly aromatic ladder polymer of intrinsic microporosity (PIM) precursors. CMS membranes derived from Trip(Me2)-TB – a precursor with large and thermally stable triptycene units – demonstrated unprecedented pure- and-mixed C2H4/C2H6 selectivities of 96 and 57, respectively, with relatively higher ethylene permeability than other CMS membranes. Similarly, CMS membranes derived from an alternative ladder PIM-based precursor, EA(Me2)-TB, also showed an outstanding performance for C2H4/C2H6 with a pure-gas selectivity up to 77 but with, however, low ethylene permeability of 0.35 barrer. Furthermore, CMS membranes derived from ladder CANAL-TB-1 – a precursor with the smallest contortion site – exhibited superior pure- and-mixed H2/CO2 selectivities of 248 and 174, respectively, due to their tightly packed structure enabled by the lack of any shape-persistence unit such as triptycene. CMS membranes fabricated in this work also showed promising gas separation performance for many other important energy-intensive industrial applications, including CO2/CH4, O2/N2, N2/CH4, H2/CH4, etc. In summary, this dissertation frameworks a facile and effective approach to obtain CMS membranes with exceptional gas separation performance by rational design of the contortion sites of intrinsically microporous ladder polymer-based precursors.
    • Highly efficient size-sieving-based removal of arsenic(III) via defect-free interfacially-polymerized polyamide thin-film composite membranes

      Aljubran, Murtadha A.; Ali, Zain; Wang, Yingge; Alonso, Emmanuel; Puspasari, Tiara; Cherviakouski, Klimentsi; Pinnau, Ingo (Journal of Membrane Science, Elsevier BV, 2022-03-30) [Article]
      Serious health problems have been linked to the consumption and exposure of arsenic-contaminated groundwater. In comparison to As(V), As(III) is smaller and predominantly present in its neutral form in groundwater, which hinders its efficient removal by conventional nanofiltration and reverse osmosis membranes. In this study, the removal of As(III) was investigated at different pH conditions using three defect-free interfacially polymerized thin-film composite (TFC) membranes made by an optimized in-house developed interfacial polymerization process (KRO). The membranes were fabricated from aromatic para-phenylenediamine (PPD) or meta-phenylenediamine (MPD) and cycloaliphatic piperazine (PIP) by reaction with trimesoyl chloride (TMC). The PPD-KRO, MPD-KRO, and PIP-KRO polyamide membranes were tested with a feed containing 5 ± 1 mg L−1 (ppm) As(III). Two commercial TFC membranes, a seawater (Sepro RO4) and a nanofiltration (DOW NF270) membrane, were also evaluated for comparison. At natural conditions (pH 6–8), the defect-free fully aromatic TFC membranes demonstrated unprecedented size-sieving performance for As(III) removal with a rejection of ∼99.5 and > 99.8% for PPD-KRO and MPD-KRO, respectively, in comparison to ∼95% for the commercial Sepro RO4 seawater membrane tested under the same conditions. In contrast, As(III) rejection of semi-aromatic piperazine-based TFCs, PIP-KRO and NF270, showed a strong dependence on the charge-exclusion mechanism with maximum As(III) rejections of 69.5 and 46.3% at pH 10, respectively. Most notably, we demonstrated that the MPD-KRO membrane achieved an As(III) concentration ∼5 μg L−1 in the permeate (less than the WHO permissible arsenic standard level of 10 μg L−1), whereas PPD-KRO achieved a slightly higher value of ∼14 μg L−1. Our results are very promising considering the arsenic standard level in highly As(III) contaminated groundwater in Bangladesh and India is set at 50 μg L−1.
    • Development of a Reduced TPRF-E (Heptane/Isooctane/Toluene/Ethanol) Gasoline Surrogate Model for Computational Fluid Dynamic Applications in Engine Combustion and Sprays

      Angikath Shamsudheen, Fabiyan; Li, Yang; Voice, Alexander; Yoo, Kwang Hee; Zhao, Le; Pei, Yuanjiang; Badra, Jihad; Boehman, Andre; Sarathy, Mani (SAE International, 2022-03-29) [Conference Paper]
      Investigating combustion characteristics of oxygenated gasoline and gasoline blended ethanol is a subject of recent interest. The non-linearity in the interaction of fuel components in the oxygenated gasoline can be studied by developing chemical kinetics of relevant surrogate of fewer components. This work proposes a new reduced four-component (isooctane, heptane, toluene, and ethanol) oxygenated gasoline surrogate mechanism consisting of 67 species and 325 reactions, applicable for dynamic CFD applications in engine combustion and sprays. The model introduces the addition of eight C1-C3 species into the previous model (Li et al; 2019) followed by extensive tuning of reaction rate constants of C7 - C8 chemistry. The current mechanism delivers excellent prediction capabilities in comprehensive combustion applications with an improved performance in lean conditions. The mechanism has been applied to validate the measured data across a wide range of temperature, pressure, equivalence ratio (f), and RON ranges. In addition to Ignition delay times (IDT) and Flame speed (FS), the model is used to validate species concentration analysis in the premixed flames and flow reactor as well as on coupling with CFD. The model is also used to validate HCCI combustion of PRF and TPRF mixtures in CFR engine and the reactive spray simulations for n-heptane and PRF's in constant volume chamber Spray A simulations according to ECN recommendations.
    • Hydrocarbon ladder polymers with ultrahigh permselectivity for membrane gas separations

      Lai, Holden W. H.; Benedetti, Francesco M.; Ahn, Jun Myun; Robinson, Ashley M.; Wang, Yingge; Pinnau, Ingo; Smith, Zachary P.; Xia, Yan (Science, American Association for the Advancement of Science (AAAS), 2022-03-25) [Article]
      Membranes have the potential to substantially reduce energy consumption of industrial chemical separations, but their implementation has been limited owing to a performance upper bound—the trade-off between permeability and selectivity. Although recent developments of highly permeable polymer membranes have advanced the upper bounds for various gas pairs, these polymers typically exhibit limited selectivity. We report a class of hydrocarbon ladder polymers that can achieve both high selectivity and high permeability in membrane separations for many industrially relevant gas mixtures. Additionally, their corresponding films exhibit desirable mechanical and thermal properties. Tuning of the ladder polymer backbone configuration was found to have a profound effect on separation performance and aging behavior.
    • Foldable Solid-state Batteries Enabled by Electrolyte Mediation in Covalent Organic Frameworks

      Guo, Dong; Shinde, Digambar; Shin, Woochul; Abou-Hamad, Edy; Emwas, Abdul-Hamid; Lai, Zhiping; Manthiram, Arumugam (Advanced Materials, Wiley, 2022-03-25) [Article]
      Solid-state electrolytes with high Li<sup>+</sup> conductivity, flexibility, durability, and stability offer an attractive solution to enhance safety and energy density. However, meeting these stringent requirements poses challenges to the existing solid polymeric or ceramic electrolytes. Here, we present an electrolyte-mediated single-Li<sup>+</sup> conductive covalent organic framework (COF) that represents a new category of quality solid-state Li<sup>+</sup> conductors. In situ solidification of a tailored liquid electrolyte boosts the charge-carrier concentration in the COF channels, decouples Li<sup>+</sup> cations from both COF walls and molecular chains, and eliminates defects by crystal soldering. Such an altered micro-environment activates the motion of Li<sup>+</sup> ions in a directional manner, which leads to an increase in Li<sup>+</sup> conductivity by 100 times with a transference number of 0.85 achieved at room temperature. Moreover, the electrolyte conversion cements the ultrathin COF membrane with fortified mechanical toughness. With the COF membrane, foldable solid-state pouch cells are demonstrated
    • Pure silica-supported transition metal catalysts for the non-oxidative dehydrogenation of ethane: confinement effects on the stability

      De, Sudipta; Aguilar-Tapia, Antonio; Ould-Chikh, Samy; Zitolo, Andrea; Hazemann, Jean-Louis; Shterk, Genrikh; Ramirez, Adrian; Gascon, Jorge (Journal of Materials Chemistry A, Royal Society of Chemistry (RSC), 2022-03-25) [Article]
      Designing robust catalysts for high-temperature applications has always been a critical task for chemical industries. As an example, the non-oxidative dehydrogenation of alkanes is an important chemical process that requires thermally stable metal catalysts with high resistance to metal sintering. The main obstacle is to maintain the high dispersion of the active metal centres under reaction and regeneration conditions. In an attempt to overcome this issue, here we use all-silica zeolite as a support to make nanometric and single-site metal catalysts with enhanced stability for the non-oxidative dehydrogenation of ethane. Preliminary screening of different metal catalysts suggests that Co has the highest intrinsic activity while Cr and V are highly stable against sintering and display a moderate activity. The high stability of Cr and V could be attributed to their high Gibbs energy of reduction under reaction conditions. Operando X-ray absorption spectroscopy revealed that Cr based catalysts remain as single-site monomeric species during the reaction, making it possible to increase the loading and therefore productivity. In the case of Co, we established the optimum parameters to achieve the highest activity by evaluating the effects of support, metal loading, promoter, and synthesis process
    • Biorenewable Nanocomposite Materials in Membrane Separations

      Kumar, Sushil; Abdellah, Mohamed H.; Alammar, Abdulaziz; Szekely, Gyorgy (ACS, 2022-03-24) [Book Chapter]
      Owing to the toxic nature of petroleum-based resources as well as the waste accumulation, long degradation time, usage of harsh chemicals associated with these resources, and limited availability, there is a great demand for suitable ecofriendly alternatives. Research on the development of new composite materials using biorenewable and sustainable resources has garnered profound interest because of their low carbon footprint, ecofriendliness, biodegradability, biocompatibility, and green and sustainable nature. The academic and industrial sectors have already started exploring biorenewable materials and nanotechnology to meet the 17 sustainability goals set by the United Nations. Composite materials comprise a mixture of polymer matrices and reinforcement materials. Because of their ease of fabrication, mechanical strength, thermal stability, antifouling properties, hydrophilicity, and porosity, composite materials have been explored in the development of new techniques and materials. Nanocomposites are widely used to enhance the hydrophilicity, surface charges, and antiadhesive, antifouling, and separation performances of the nanocomposite membranes. However, the lack of a homogeneous dispersion and compatibility with the polymer matrix during synthesis appear to hinder their effective fabrication, thereby limiting the potential of nanocomposite materials in the separation performance of nanocomposite membranes. To alleviate such shortcomings, several routes have been employed for fabricating nanocomposite membranes, which are explained in this book. Furthermore, to understand the performance of nanocomposite membranes, we reviewed the related chemistry, new applications, and developments with respect to the separation performance of biorenewable nanocomposite membranes.
    • Applying Artificial Neural Networks to Engines

      Giraldo Delgado, Juan Camilo (2022-03-23) [Thesis]
      Advisor: Sarathy, Mani
      Committee members: Turner, James W. G.; Castaño, Pedro
      Internal combustion engines, used for light duty transportation, represent a major role in mobility, contributing 28.6% to CO$_2$ emissions worldwide. To mitigate environmental impact and ease the transition to clean technologies, the search for more efficient, less polluting engines has been demanded, and unique tools are necessary to meet the constantly upgraded policies. Hence, data-driven approaches that emulate current vehicles represent a valuable contribution to the improvement of engine performance. Dynamometer tests of commercial engines are open-data, and a dependable source for understanding on-road behavior of several vehicle variables. Artificial neural network (ANN) algorithms, a subset of machine learning, have received considerable attention recently given their wide number of applications and the possibility to provide accurate data-driven approximations. This work describes a methodology for applying ANN’s to predict emissions, efficiency, and fuel consumption in combustion engines using dynamometer test data, and to extrapolate its use in new technologies. The procedure is also applied to a hybrid vehicle case study. The proposed methodology accurately generates ANN’s for the prediction of brake thermal efficiency (BTE), brake specific fuel consumption (BSFC) and emissions in conventional engines with 𝑅$^2$>0.91 and mean absolute errors (MAE) of less than five percent. Using the same approach, the hybrid vehicle state of charge (SOC), and the fuel scale state, are predicted, showing good agreement 𝑅$^2$>0.96 and confirming the versatility of the proposed algorithm. Finally, an initial approach for dealing with missing data in the databases is introduced. Using various simple and iterative imputation methods, it was possible to obtain 𝑅$^2$>0.80 for predicting the BTE and BSFC with five percent of the data missing from the input values.