Exothermic Research Articles

Role of submerged friction stir welding in reducing intermetallic growth and enhancing microstructure in dissimilar Al-Ti joints.

The integrity of dissimilar Al-Ti welds during conventional friction stir welding (CFSW) is compromised by excessive material mixing, leading to thick intermetallic layers. Underwater friction stir welding (UWFSW) mitigates these effects by inhibiting material mixing due to lower thermal conditions. Scanning electron microscopy revealed substantial Ti particles, appearing as blocks and strips, within the stir zone during CFSW. Static recrystallization, driven by exothermic reactions between Ti blocks and the Al matrix, resulted in over 93% recrystallized grains along stir zone, 10.7% higher than in UWFSW. In contrast, UWFSW resulted in a finer dispersion of Ti particles with reduced density due to lower frictional heat. The average grain size at the Ti interface of CFSW was 1.0μm, compared to 2.6μm in UWFSW. The inhomogeneous distribution of Ti particles in CFSW led to uneven dislocation distribution and increased stress concentrations, while finer Ti particles in UWFSW promoted a uniform grain structure, enhancing joint strength to 267MPa, 13.4% higher than CFSW. Additionally, the γ-fibre and basal fibre texture in UWFSW increased joint ductility. The study highlights UWFSW's effectiveness in joining dissimilar metals, offering significant advantages for industries such as aerospace and automotive.

Synthesis of ZrW2O8–ZrC composite powders by solid‐state exothermic oxidation reaction of ZrC and WO3 powders

AbstractIn this work, ZrW2O8‐coated ZrC composite powders are synthesized by solid‐state reaction method using ZrC and WO3 powders. Thermodynamic analysis shows that when the molar ratio of ZrC to WO3 is larger than 5:4, ZrW2O8 cannot be synthesized by solid reaction of ZrC and WO3. The favorable molar ratio of ZrC to WO3 for solid reaction synthesis ZrW2O8 is 1:2. After reacted below 800°C for 8 hours, only ZrC in the ZrC and WO3 mixture powders partially reacts with oxygen to form ZrO2. And there is no detectable reaction between WO3 and the formed ZrO2 to produce ZrW2O8. ZrC and WO3 can synthesize ZrW2O8 at 900°C. ZrW2O8‐coated ZrC composite powders can be synthesized using powder mixtures with molar ratio of ZrC:WO3 = 1:1.7 and ZrC:WO3 = 1:1.9 after heat treatment at 1000°C for 4 hours. The synthesized ZrW2O8‐coated ZrC particles show cubic shape with obvious particles growth. The exothermic oxidation reaction of ZrC leads to a significant increase in local temperature, which is believed to trigger partial reaction between ZrO2 and WO3 to form ZrW2O8.

Advances in Catalytic Hydrogenation of Liquid Organic Hydrogen Carriers (LOHCs) Using High‐Purity and Low‐Purity Hydrogen

AbstractLiquid organic hydrogen carriers (LOHCs) are emerging as a promising solution for global hydrogen logistics. The LOHC process involves two primary chemical reactions: hydrogenation for hydrogen storage and dehydrogenation for hydrogen reconversion. In the exothermic hydrogenation reaction, hydrogen‐lean compounds are converted to hydrogen‐rich compounds, storing hydrogen from various sources such as water electrolysis, fossil fuel reforming, biomass processing, and industrial by‐products. Conversely, hydrogen is extracted from hydrogen‐rich compounds through an endothermic dehydrogenation reaction and supplied to several hydrogenation utilization offtakers. This review article discusses the development trends in catalytic hydrogenation processes for various LOHC materials, including benzene, toluene, naphthalene, biphenyl‐diphenylmethane, benzyltoluene, dibenzyltoluene, and N‐ethylcarbazole. It introduces references for catalytic hydrogenation processes utilizing both high‐purity and low‐purity (alternatively, mixed) hydrogen feedstocks, with particular emphasis on low‐purity hydrogen applications. The direct storage of hydrogen with minimal purification, using by‐product hydrogen and mixed hydrogen from hydrocarbon and biomass reforming, is crucial for the economic viability of this hydrogen carrier system.

Combustion-assisted low-temperature ZrO2/SnO2 films for high-performance flexible thin film transistors

We developed high-performance flexible oxide thin-film transistors (TFTs) using SnO2 semiconductor and high-k ZrO2 dielectric, both formed through combustion-assisted sol-gel processes. This method involves the exothermic reaction of fuels and oxidizers to produce high-quality oxide films without extensive external heating. The combustion ZrO2 films were revealed to have an amorphous structure with a higher proportion of oxygen corresponding to the oxide network, which contributes to the low leakage current and frequency-independent dielectric properties. The ZrO2/SnO2 TFTs fabricated on flexible substrates using combustion synthesis exhibited excellent electrical characteristics, including a field-effect mobility of 26.16 cm2/Vs, a subthreshold swing of 0.125 V/dec, and an on/off current ratio of 1.13 × 106 at a low operating voltage of 3 V. Furthermore, we demonstrated flexible ZrO2/SnO2 TFTs with robust mechanical stability, capable of withstanding 5000 cycles of bending tests at a bending radius of 2.5 mm, achieved by scaling down the device dimensions.

Adsorptive behavior of Rhodamine B dye over hierarchical N-doped carbons from hexamine-based complexes: Equilibrium and kinetics

Pollution from water-soluble dyes is a common issue due to high toxicity and diffiulty in degradation, and its effectively removal is critical for human health and sustainability. In this work, N-doped hierarchical carbons were derived by facile pyrolysis of Co-including hexamine-based complex using glucose as a cross-linker, showing high removal ability using Rhodamine B (RhB) as a model dye. Porous architecture and N-coordination can be easily altered by pyrolysis temperature, where the GNC-900 sample obtained at 900 °C exhibits the best removal ability even outperforming several classical carbons under equal conditions, owing to synergistic effects from large surface areas, high ratio of pyrrolic-N, enhanced interaction between RhB molecules and pore walls, and possible Co-Nx active sites. Adsorptive behaviour is better fitted by pseudo-second-order kinetic model, and the maximum RhB capacity over GNC-900 determined by Langmuir model is highly up to 400.1 mg/g, following mechanisms of pore filling, π-π conjugation, electrostatic, surface complexation and H-bonding. Thermodynamics indicate that RhB removal is exothermic and spontaneous process. Moreover, GNC-900 can be readily regenerated using ethanol and reused at least six times without notable loss in capacity. This novel method facilitates synthesis of N-doped carbons from metal-based complexes, exhibiting high efficiency as adsorbents for water remediation.

Thermodynamic and Kinetic Studies on the Pyrophoricity of Uranium Flakes

The objective of this work was to arrive at quantitative estimates of pyrophoricity of uranium in different geometries. The major source of heat generation was identified to be exothermic chemical reactions of uranium with moist air. Time evolution of temperature was studied for uranium considering 3D conduction and convection heat loss routes using Finite Element Analysis. Auto ignition temperature for uranium flakes was quantified using heat balance equation and was found to be around 500 K. Excess heat generation rates needed to cause auto ignition of uranium flakes at room temperature were also estimated. The major sources of excess heat leading to its ambient ignition could be attributed to friction and other exothermic chemical reactions of process impurities in uranium.

Highly Efficient and Selective Electrocatalytic Semihydrogenation of Acetylene to Ethylene via Continuous Proton Feeding and Accelerated Transfer on Cu NP/FeNC Composite

AbstractElectrocatalytic hydrogenation of acetylene to ethylene in aqueous electrolytes under ambient conditions faces efficiency and selectivity limitation due to the competitive formation of 1,3‐butadiene and hydrogen. In this study, the development of a copper nanoparticle/FeNC composite catalyst is reported through a simple mechanical grinding approach that demonstrates remarkable performance, achieving a highest ethylene Faradaic efficiency of 97.7% at 180 mA cm−2 and selectivity of 92.6% at 200 mA cm−2. Experimental investigations reveal that Cu atoms serve as the active sites, and the integration of FeNC improves the specific surface area through its 2D nanosheet morphology. Further analysis utilizing in situ Raman measurements coupled with theoretical calculations confirms that FeNC accelerates water dissociation to provide abundant protons and improving their transfer, thereby suppressing 1,3‐butadiene formation and elevating acetylene selectivity. Notably, the integration of FeNC also transforms the desorption of *C2H4 into an exothermic process, further facilitating ethylene production. Overall, this study introduces a simple and innovative preparation approach of composite catalysts for selective ethylene synthesis, expanding the application scope of Cu‐based FeNC materials in various electrocatalytic hydrogenation reactions.

Synthesis and thermal behavior of acrylonitrile/guanidine crotonate copolymer for carbon fiber precursor

AbstractThe thermal oxidation stabilization of polyacrylonitrile (PAN) copolymer is a highly exothermic process. It significantly impacts the quality of the finished PAN‐based carbon fiber, which is often addressed by adding appropriate comonomers. This paper synthesized guanidine crotonate (GCA) as a comonomer and copolymerized with acrylonitrile (AN) to prepare P(AN‐GCA). DSC analysis revealed that when compared to PAN and P(AN‐CA) copolymers, the initial exothermic temperature, maximum exothermic heat flux, and heat flux of P(AN‐GCA) copolymer were greatly reduced. FT‐IR spectroscopy showed that the degree of pre‐oxidation increased with the increasing comonomer GCA content, indicating that the addition of comonomer GCA could promote PAN pre‐oxidation cyclization and improve the copolymer's degree of pre‐oxidation. The activation energies of PAN and P(AN‐GCA) were 160 and 126 KJ/mol, respectively. It was shown that the addition of GCA could effectively reduce the activation energy of the cyclization reaction of the polymer while simultaneously promoting it. TGA analysis shows that the introduction of GCA improves the copolymer's thermal stability, and the yield at 800°C is more than 54%, which is at least 19% higher than PAN homopolymer. P(AN‐GCA) has the potential to be carbon fiber precursor.

Rapid Thermal Shutdown of Deep-Eutectic-Polymer Electrolyte Enabling Overheating Self-Protection of Lithium Metal Batteries.

Safety concerns and uncontrollable dendrite growths have severely impeded the advancement of lithium-metal batteries. Herein, a safe deep-eutectic-polymer electrolyte with built-in thermal shutdown capability is proposed by utilizing hydrophobic association of methylcellulose within a novel deep-eutectic-solvent. Specifically, at elevated temperatures, methylcellulose chains aggregate to form dense polymer networks due to hydrophobic association and break the solvation structure equilibrium inside the deep-eutectic system through encapsulating Li+ in polymer matrix, leading to quick solidification of the electrolyte. The solidified electrolyte obstructs Li+ transports and terminates electrochemical processes, protecting LMBs from unstoppable exothermic chain reactions. The accelerating rate calorimeter tests of 1 Ah pouch cells demonstrate that the as-prepared electrolyte significantly improves the onset self-heating temperature from 73°C for conventional electrolytes to 172°Cand prolongs the thermal runaway waiting time more than 20 hours. More impressively, benefiting from its favorable electrochemical performance, this polymer electrolyte enables LiNi0.8Mn0.1Co0.1O2||Li batteries to retain 92% capacity over 200 cycles and LiFePO4||Li batteries to maintain 90% capacity after 500 cycles. This research paves a promising avenue for enhancing both the safety and electrochemical performance of high-energy-density LMBs.

Application of microencapsulated phase change materials for controlling exothermic reactions

Abstract Thermal runaway is a frequent source of process safety issues, and the uncontrolled release of chemical energy puts reactors at risk. The design of the exothermic reactor faces challenges due to the selective sensitivity of the product to high temperatures and the need to increase the lifetime of the catalyst, optimize the product distribution, and improve the thermodynamic properties. Phase change material (PCM) encapsulation is recommended to reduce leakage, phase separation, and volume change problems. This work introduces encapsulated PCMs to improve reactor temperature control and minimize thermal runaway in exothermic processes. The warning temperature value setting effectively inhibits fugitive exothermic reactions and enhances heat transfer. When a sufficient quantity of encapsulated PCMs is input, the response speed will automatically accelerate. Spontaneous acceleration of the reaction rate due to thermal runaway of the reaction may be completely avoided by adding a sufficient amount of encapsulated PCM. Microencapsulation is used to control volume changes and inhibit thermal reactions. Preventive strategies include cooling, depressurization, safety release, emergency resources, and reaction containment. Encapsulated PCMs improve mechanical and thermal properties, surface-to-volume ratio, heat transfer surface, thermal capacity, and efficiency.

On‐Purpose Production of Light Olefins Through Oxidative Dehydrogenation: An Overview of Recent Developments

AbstractProducts made from light olefins play an important role in our daily lives. Traditional light olefins production based on steam cracking and fluid catalytic cracking suffer from high energy consumption and CO2 emissions. Thereby, the continually increasing demand for light olefins needs to be met through more environmentally sustainable procedures. On‐purpose production routes are preferred choice among petrochemicals manufacturers, being energy efficient and having lower carbon footprint. Among them, oxidative dehydrogenation (ODH) of light paraffins is a thermodynamically favourable exothermic process as compared to non‐oxidative routes. They can be operated at lower temperatures and have propensity of low coke deposition on catalyst, thereby resisting rapid catalyst deactivation. Herein, we have analysed various catalytic systems utilised in the oxidative dehydrogenation process. We have reviewed role of support, chemical composition of catalyst, presence of dopant, oxidation state of active metal, controlled surface modification by oxidative and reductive pretreatments, and reaction factors for each system. The performance of various catalytic systems for ODH of ethane, propane and butane in the presence of O2, CO2, N2O and special oxidants have been reviewed. A short critical overview on emerging on‐purpose routes for the production of renewable 1,3 butadiene has also been discussed.

Investigation of Microhardness, Microstructural, Tribological, and Thermal Properties of Al7075/TiO2/Kaoline Hybrid Metal Matrix Composites Produced by Powder Metallurgy Process

The shift from traditional, single‐component metals and alloys continues, and researchers are currently investigating alternative materials. This evolution has led to the creation of innovative materials, including hybrid metal‐matrix composites. The present study aims to investigate the microstructural, surface morphological, and thermal properties of a novel Al7075/TiO2/Kaoline hybrid metal‐matrix composite prepared using high‐energy ball milling and sintering methods. In this study, phases related to the composite components are formed depending on the milling time, no undesirable phase is formed, but the peak intensities decreas as the milling time increases. Particle size increases from 63 to 215 μm with increasing milling time. Increasing the kaoline reinforcement ratio and sintering temperature increases the microhardness from 62.27 ± 2 to 75.83 ± 2 HV, and reduces the friction coefficient from 0.82 ± 0.01 to 0.62 ± 0.01. The wear rate of the composite without kaoline addition is 2.1 (mm3 m−1) × 10−3, while with 6 wt% kaoline addition, it decreases to 1.5 (mm3 m−1) × 10−3. There are no cracks in the composite other than plastic deformation due to sintering and wear. Peaks indicating endothermic and exothermic reactions during continuous heating occurr in the 635–750 °C temperature range.

Preparation of adsorbent from coal gasification slag for the treatment of waste water from lanchar and its adsorption mechanism

ABSTRACT Solid waste coal gasification slag has certain hardness, porosity, pore structure and specific surface area, etc. which can be utilized in environmental protection materials and other areas of high value. Yulin City, high-quality coal resources derived from the excellent quality of charcoal products, but its processing will produce a large number of high chemical oxygen demand (COD), high volatile phenol, high ammonia nitrogen ‘three high’ wastewater, the ecological environment is very harmful. The results of the modification of the refined coal gasification fine residue showed that the removal rates of the three were enhanced to 91%, 89% and 83%, respectively, after adsorption at a pH of 9.5, an injection ratio of 1:5 and 25 ℃ for 25 min. The reason is that the modification treatment significantly increased the specific surface area of the adsorbent from 103 m2/g to 606 m2/g, which effectively increased the adsorption active sites for the pollutant molecules. The adsorption process of COD from modified refining coal gasification slag for the treatment of charcoal wastewater was thermodynamically investigated. The thermodynamic study shows that the adsorption process of modified refining coal gasification slag on pollutants in the charcoal wastewater is an exothermic and spontaneous process.

Preparation of Composites Derived from Modified Loess/Chitosan and Its Adsorption Performance for Methyl Orange

A modified loess/chitosan composite (ML@CS) was prepared via solution. The microstructure and physicochemical properties of ML@CS were characterised via scanning electron microscope (SEM), Zeta potential, X-ray diffraction (XRD), Fourier transform infrared spectrum (FT-IR), and thermogravimetric analysis (TGA). An aqueous solution of methyl orange (MO) was used as simulated wastewater from which the influence of the initial concentration and pH of MO, the dosage amount and regeneration performance of ML@CS, adsorption temperature, and time on the adsorption effect of MO were systematically investigated. The adsorption kinetics, isothermal adsorption, and adsorption mechanism were also analysed. The results indicate that ML@CS had a good adsorption effect on MO. When the initial concentration of MO was 200 mg/L, pH was 5.0, and ML@CS dosage was 1.0 g/L, the adsorption equilibrium could be reached within 180 min at room temperature, and the equilibrium adsorption capacity and removal rate reached 199.52 mg/g and 99.75%, respectively. After five adsorption–desorption cycles, the MO removal rate remained above 82%. The adsorption behaviour of ML@CS for MO conforms to the pseudo–second–order kinetic model and the Langmuir isotherm adsorption model. The spontaneous exothermic process was mainly controlled by monolayer chemical adsorption and the physical adsorption only played an auxiliary role. ML@CS efficiently adsorbed MO in water and can be used as a high-efficiency, low-cost adsorbent for printing and dyeing wastewater treatment.

Arabic gum-grafted-polyaniline@MnFe2O4/UIO66-NH2 bionanocomposite as adsorbent for quercetin antioxidant: Efficiency, kinetics, thermodynamics and isotherm modelling

Quercetin is one of the most powerful antioxidants in nature and a major dietary flavonoid, so its efficient recovery by nanoadsorbents can be valuable for human health. In this study, the nanocomposite Arabic gum-grafted-polyaniline@MnFe2O4/UIO66-NH2 (AG-g-PANI@MnFe2O4/UIO66-NH2) was synthesized by in situ copolymerization. The physicochemical and structural properties of the AG-g-PANI@MnFe2O4/UIO66-NH2 nanocomposite were examined using various methods, including XRD, FE-SEM, FT-IR, EDX, VSM, TGA, and BET. The adsorption capacity of natural nanoadsorbent was evaluated for the adsorption of quercetin antioxidant from an ethanol-water solution (50 % v/v) in a batch system. The influence of controlling factors such as solution pH, adsorbent dose, contact time, initial quercetin concentration and temperature on the adsorption process was investigated. The highest adsorption capacity (9.1157 mg.g−1) was achieved at a pH of 8, with 0.025 g of adsorbent, a quercetin solution concentration of 20 mg.L−1, a 300 min contact time and at the temperature 298.15 K. In addition, the data from adsorption experiments were analyzed using different isotherm and kinetic models. The findings demonstrated that the Temkin isotherm and the pseudo-second-order kinetic model are the most suitable for representing the adsorption behavior. In addition, from analysis of the temperature effect was found that the adsorption of quercetin on AG-g-PANI@MnFe2O4/UIO66-NH2 is a spontaneous (∆G° < 0) and exothermic (ΔH° < 0) process. Finally, the reusability of nanoadsorbent and desorption kinetics of quercetin were investigated and it was specified that AG-g-PANI@MnFe2O4/UIO66-NH2 can be effectively renewed and recycled, maintaining its adsorption efficacy without significant reduction after five repeated cycles.

Mechanism for Site-Selective Hydroboration of C70 Fullerene with Borane by DFT-D3 Study.

We studied the hydroboration of the C70 fullerene using both B3LYP-D3(BJ)/6-311G(d,p) and M06-2X-D3/6-311G(d,p) levels of theory, incorporating the empirical dispersion interaction, and Fukui index calculations. Potential energy surfaces (PESs) and Gibbs free energy surfaces (GFESs) were calculated for the pathways from four BH3 adducts (located at the AB, CC, D, and E sites) on the C70 to eight products formed by the 1,2-addition of BH3 across the four [6,6]-ring fused bonds (AB, CC, DE, and EE) and across the two [5,6]-ring fused bonds (AA and DD). These pathways are two-step consecutive reactions. We denoted the positions on the fullerene cage as A through E, from the pole to the equator, based on the D5h symmetry of the C70 fullerene. In the first step reaction, the product ratios for the four adduct intermediates should be as the primary intermediate BH3(D), the secondary intermediate BH3(AB), the tertiary intermediate BH3(CC), and the minor intermediate BH3(E), based on the Fukui indices. In addition, in the second step reaction, transition states (TSs) from four adduct intermediates to eight product isomers, namely, BH2(A)H (B) to BH2(E)H (E), were obtained using the QST2 method. The calculated reaction coordinates showed exothermic reactions for all bonds except the EE bond. We also confirmed the transition states by frequency calculations and intrinsic reaction coordinate (IRC) analyses. The PESs and GFESs suggest spontaneous processes for the four isomers, of which the primary products are BH2(A)H (B) and its isomer BH2(B)H (A), the secondary product is BH2(C)H (C), and the tertiary product is BH2(D)H (D), all formed through adduct intermediates. Therefore, through the hydroboration reaction of C70, we could predict and design the site selectivity of C70 by controlling the energy barrier of the transition state in the second step of the reaction. This implies that we could selectively synthesize mainly BH2(B)H (A) isomers across the AB-[6,6]-ring fused bond and also design BH2(D)H(D) isomers across the DD-[5,6]-ring fused bond. Also, the calculations of formation rate constants can well simulate the experimental ratio of two C70H2 isomers by the hydrolysis of BH2(A)H(B), BH2(B)H(A), and BH2(C)H(C) products at room temperature.

Preparation of Poly(allylamine Hydrochloride) Grafted Porous Boron Nitride Fibers for Efficient Cr(VI) Adsorption from Aqueous Solution.

Cr(VI) pollution poses great harm to the cyclic utilization of groundwater and surface water resources. Efficient adsorbent materials have great potential to change this situation and assist in the restoration of ecosystems. This work chooses porous boron nitride fibers (pBN) with stable physical and chemical properties as the matrix, 3-aminopropyltriethoxysilane (APTES) as the coupling agent, and uses a one-step crosslinking method to graft poly(allylamine hydrochloride) (PAH) onto pBN, forming pBN-AS@PAH with fascinating Cr(VI) adsorption capacity. PAH is uniformly covered and modified on the surface of pBN, and the composite with high specific surface area (383.33 m2/g), large pore volume (0.37 cm3/g), and abundant amino groups. Its equilibrium adsorption capacity for Cr(VI) can reach up to 123.32 mg/g, and the adsorption behavior follows the quasi second-order kinetic model and Langmuir model, indicating the chemical adsorption process of monolayer. The adsorption style belongs to a spontaneous exothermic process and has the optimal adsorption effect at a pH of ~2. Additionally, after cycling for 5 times, the decrease rate of adsorption capacity is less than 10 %, showing an excellent reusability.

The Influence of Thermophysical Parameters on Thermal Runaway Characteristics for Pouch-Type Lithium-Ion Batteries

Abstract The thermal variation during the temperature rise process of batteries is closely related to multiple physical parameters. Establishing a direct relationship between these parameters and thermal runaway (TR) features under abusive conditions is challenging using theoretical equations due to complex electrochemical and thermal coupling. In this paper, a high-temperature thermal runaway model of pouch-type lithium-ion battery is established through electrical-thermal coupled approach, demonstrating a good agreement between the simulation and experimental results. The results reveal distinct trends in thermal parameters of the early temperature rise, trigger time for TR and peak temperature during TR process, for varying convective heat transfer coefficient, cell specific heat capacity, cell density and cell thermal conductivity. Across various convective heat transfer coefficients, the rates of temperature increase, moments of TR, and peak temperatures within a battery emerge as the cumulative outcomes of competing processes of the intricate exothermic secondary reactions within the battery, and the heat transfer with the surroundings. Batteries with lower heat capacity exhibit reduced thermal inertia and heightened sensitivity to temperature changes. Alterations in the thermal capacity of a battery wield a profoundly significant impact upon the moment of thermal runaway within the battery. Enhancing the thermal conductivity yields limited improvements in heat dissipation during thermal runaway primarily due to the relatively small geometrical scale of the battery. Results of this paper can provide valuable insights for size optimization design, thermal management system optimization design, thermal runaway safety warning and prevention of Lithium-ion batteries.

Effective remediation of toxic metal ions (Cd(II), Pb(II), Hg(II), and Ba(II)) using mesoporous glauconite-based iron silicate nanorods: Experimental and theoretical studies

Glauconite minerals underwent an advanced exfoliation and scrolling process, yielding novel iron silicate nanorods (GRs) with increased surface area, reactivity, and improved physicochemical properties. These structures were introduced as superior adsorbents for the highly efficient adsorption of various toxic metal ions, such as Cd(II), Pb(II), Hg(II), and Ba(II). The GRs exhibited maximum adsorption capacities of 283 mg/g for Cd(II), 247 mg/g for Pb(II), 132.3 mg/g for Hg(II), and 165.2 mg/g for Ba(II). The adsorption properties of the GRs during the adsorption of these four metal ions were elucidated through traditional (Langmuir model) and advanced (monolayer model of single energy site) isotherm analyses. Advanced isotherm modeling revealed that the GR surface was saturated with numerous effective adsorption sites, with densities of 125 mg/g for Cd(II), 68.8 mg/g for Pb(II), 40.9 mg/g for Hg(II), and 57.9 mg/g for Ba(II). Moreover, each site could accommodate approximately four ions of the studied metals, which are vertically oriented and participate in multi-ionic adsorption reactions. Energetic analyses, whether based on classical models (Gaussian energy <8 kJ/mol) or advanced models (adsorption energy <40 kJ/mol), indicated that the adsorption processes are governed by physical mechanisms, including electrostatic attractions, van der Waals forces, and hydrogen bonding. Furthermore, thermodynamic assessments confirmed that the adsorption of these ions occurs through exothermic and spontaneous reactions.

Experimental measurement and modeling of the internal pressure in cylindrical lithium-ion battery cells under abuse conditions

The internal pressure evolution of cylindrical lithium-ion battery cells under abuse tests is evaluated in this work. The pressure evolution is recorded through a cavity at the center of the inner structure of the cylindrical cell. Understanding pressure buildup due to exothermic reactions aids in designing safety features, such as improved venting mechanisms. The pressure activation for the safety mechanism depends on both the venting cap design and the different abuse test conditions. This study focuses on two important parameters: the state of charge (SOC) and the overheating ramp. The SOC significantly influences the venting pressure activation at the overheating abuse tests. The 18650 cell exhibits a similar venting behavior as the 21700 cell, with pressure safety mechanisms activating sooner for the 18650 cell. The geometric structure of the battery and safety mechanisms significantly influence vent-activation thresholds. After the Current Interruptor Device (CID) breakdown, pressure rises exponentially until venting occurs, due to gas generation from the decomposition of internal components and electrolyte vaporization. With the experimental data for the overheating abuse test, a model that predicts the evolution of the pressure has been developed. For the overcharging abuse test, the pressure evolution has been measured with different current rates (C-rates) to simulate overcharge with standard charging current and fast charging current. However, the internal pressure inside the cell activates the current interrupt device, which avoids overcharging the cell, thus preventing the thermal runaway (TR) from occurring.