ABSTRACT A scaling method is proposed to speed up the numerical calculations of energetic materials subject to slow cookoff where the applied heating rate is typically of a few degrees per hour. To speed up the thermal-chemical-mechanical simulation, it is proposed that the thermal parameters and heating rate be scaled up by a large constant factor. The method was applied to simulate the Scaled Thermal Explosion Experiment (STEX) in LSDYNA using user-defined subroutines that determine the dynamics of the energetic material. A total of four valid scaling factors were tested with all the results in perfect agreement with one another in the temperature, pressure and reacted mass fraction time profiles. A fifth scale factor served as a control to demonstrate that the method is feasible if the resulting enhanced thermal velocity is below the sound speed. The computed ignition time also agreed well with the results from literature. Immediately after the cook-off was initiated, the scale factor was gradually downsized to unity with the maximum temperature and pressure attained in the ignited region computed.

The rapid expansion of electric vehicles (EVs) has led to a significant increase in the collection and transport of end-of-life (EoL) batteries. These batteries exhibit state-dependent hazard characteristics—such as electrochemical degradation, cell imbalance, uncertain residual voltage, and prior mechanical damage—that substantially elevate the likelihood of thermal runaway, fire, or explosion during road transport. However, in Korea, EoL batteries fall into a regulatory gap: they are neither classified as “waste” under the Waste Management Act nor included in the material-based classification system of the Act on the Safety Control of Hazardous Substances. As a result, no coherent legal framework governs their safe transport. To address this gap, this study proposes classifying EoL EV batteries as a new intermediate hazard group, termed Quasi-Hazardous Goods, positioned between existing hazardous substances and general cargo. An analysis of the UN Model Regulations and ADR shows that international systems differentiate normal, damaged, and waste/recycling batteries and apply tiered requirements based on state-based hazards. This supports the need for a classification approach that reflects the variable risk profiles of EoL batteries. By adopting the quasi-hazardous goods concept, Korea could utilize the established life-cycle management structure of its hazardous materials regulatory framework while incorporating safety measures specific to the characteristics of EoL batteries. Accordingly, this study presents foundational directions for future technical standards, including pre-transport condition assessment, performance-based packaging and loading requirements, transport-environment management, and emergency response procedures. The findings provide a conceptual basis for establishing safe road transport standards for EoL EV batteries in Korea.

Preparation of Porous Ni-Mg Intermetallic Compounds as Highly Efficient Catalysts for the Hydrogen Evolution Reaction by One-Step Thermal Explosion Reaction

The theory of numerical growth of living organisms in nature is proposed, in which "active components" transform "neutral components" into new "active centers" as a result of branched, chain processes, according to the autocatalytic equation, and their numerical growth is described by logistic functions. These components and the conditions of their interaction form an "autocatalytic set" that is universal for many processes of numerical growth of various living organisms in nature. Our theory follows from the "theory of chain reactions" and the "mathematical theory of epidemics and pandemics based on the laws of chain and thermal explosions" and can be used to describe the spread of infections among animals and will be useful for describing many processes of growth of wildlife. The theory is likely to make it possible to study many processes of the spread of various "viral ideas" among people, which may be of considerable practical interest in the analysis of social phenomena.

ABSTRACT In order to evaluate the thermal hazard of one-step synthesis of 1-methyl-3,4,5-trinitropyrazole (MTNP), the thermal decomposition behavior of MTNP was determined by differential scanning calorimetry (DSC) during the dynamic heating process, and the thermal decomposition kinetic parameters of MTNP were obtained, which enabled the subsequent calculation of the critical temperature for thermal explosion (T b). The thermal stability of MTNP, reaction solution, and main raw material N-methylpyrazole (N-MP) under adiabatic conditions was studied by adiabatic accelerated calorimetry (ARC), and T D24 in adiabatic state of reaction solution was obtained; At the same time, the exothermic characteristics of MTNP one-step nitrification synthesis process were monitored by Easymax HFCal, and the thermal parameters such as adiabatic temperature rise (ΔT ad) and maximum temperature of synthesis reaction (MTSR) were calculated. Based on the comprehensive test data, the thermal risk of MTNP synthesis process is analyzed, which provides theoretical basis and guidance for the safe use, storage, and production of MTNP.

Experimental and kinetic study of thermal runaway gas explosion characteristics under different safety vent bursting pressures of 18650 battery

With the development of society and increasing changes in energy demands, safety issues concerning lithium-ion batteries in applications such as electric aircraft have garnered significant attention. To investigate the influence of aviation propulsion lithium-ion battery system design on safety performance, this research introduces the concept of the Thermal Runaway Explosion Index and applies it to the quantitative assessment of lithium-ion battery system safety design. Through experimental and theoretical analyses, utilizing self-built modules for lithium-ion battery thermal runaway, gas explosion characteristics testing, and thermal runaway containment testing, a quantitative assessment was conducted on the inherent safety, operational safety, and protective safety of the lithium-ion battery system. The results demonstrate that protective design plays a critical role in reducing the thermal runaway explosion index. Specifically, the protective effect achieved by applying a fireproof coating is superior to that obtained by increasing the thickness of the top plate. Moreover, the E85S15B3 coating exhibits the optimal performance in reducing both temperature and weight. Following correction with 1mm thick E85S15B3 coating protection, the thermal runaway explosion index is 0.0942. Compared to the scenario without a protective top plate, the maximum temperature drops by 55.80%, and the weight of the battery top plate can be reduced by 36.59% under equivalent volume conditions. The conclusion of this research provides a theoretical basis and practical guidance for the hazard assessment and system safety design of aviation lithium-ion battery systems.

ABSTRACT Metal hydrides are ideal additives for solid propellants, which can improve the energy level and load capacity of solid propellants. However, the safety and interaction mechanisms between metal hydrides and energetic materials remain unclear, which limits their broader application in propellants. In this study, RDX/ZrH2/F2602 energetic composite particles with varying ZrH2 contents were prepared using the molding powder method and subsequently characterized in terms of their performance. The experimental results demonstrate that the energetic composite particles display a regular morphology and dense structure, with no changes observed in their chemical and crystal structures. As the ZrH2 content increases, the thermal stability and thermal explosion critical temperature of the composite particles decrease. In comparison to the raw material RDX, the energetic composite particles with 10% and 15% ZrH2 contents exhibit better mechanical sensitivity, with critical impact values increasing by 6 J and 5.5 J, respectively, and critical friction values increasing by 84 N and 60 N, respectively. Combustion experiments reveal that energetic composite particles containing 15% ZrH2 demonstrate superior comprehensive performance in terms of safety and combustion, outperforming those with other ZrH2 contents. The oxidative combustion mechanism of RDX/ZrH2/F2602 energetic composite Particles is discussed, offering insights into the interaction between metal hydrides and the combustion of energetic materials. This research establishes a theoretical framework to support the design and improvement of solid propellant formulations.

To prevent thermal explosions in octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) crystals during diamond turning, it is essential to manage the energy dissipation process at cutting hotspots located at the tip of the diamond tool. In this study, a comprehensive model is developed to analyze the friction-induced thermal safety of HMX crystals during diamond turning, incorporating both heat conduction and entropy generation mechanisms. The temperature distribution and the entropy generation at the hotspots are further validated through equivalent heat conduction experiments. The underlying cause of the friction hazard is identified from both temporal and spatial perspectives. The results demonstrate that there is an intrinsic relationship between entropy generation and hazardous energy: an increase in entropy generation generally corresponds to a decrease in the quality (i.e., chaos level) of the hazardous energy during the diamond turning process. Compared to temperature distribution, entropy generation offers a more effective and reliable indicator for safety evaluation in both time and space domains. Therefore, the integrated use of temperature distribution and entropy generation as safety criteria is of great significance in elucidating the ignition mechanism of friction hotspots in HMX crystal machining.

Synthesis and characterization of porous Cu-30 at. %Al intermetallic compounds via thermal explosion: Effect of porosity on the microstructure and thermal properties

Experimental thermal explosion risk assessment of high-concentration hydrogen peroxide

During transmission line faults, the pre-insertion resistors in circuit breakers accumulate heat and lead to thermal explosion during repeated closing. The risk of thermal explosion can be reduced if the pre-insertion resistor temperature can be accurately predicted. This study proposes a method for predicting the pre-insertion resistor temperature to optimize the cooling time. The overfitting problem is more serious for models using traditional loss functions. To solve this problem, deep learning models based on a new loss function, the rational smoothing loss, are used to predict the temperature of pre-insertion resistors. The rational smoothing loss, inspired by the kernel function, dynamically adjusts the error versus gradient and incorporates constraints for regularization. The coati optimization algorithm with Ornstein–Uhlenbeck mutation optimizes the rational smoothing loss parameters. The results demonstrate that models using rational smoothing loss significantly outperform those with traditional loss functions, showing reductions of 77.97% in mean absolute error and 93.72% in mean square error, reducing the mean absolute error to 0.29 K. Additionally, the prediction curves exhibit remarkable smoothness, indicating the rational smoothing loss’s robustness against overfitting. The accurate prediction of pre-insertion resistor temperature is crucial for safely operating circuit breakers and technically supporting cooling time optimization.

Abstract The temperature has a significant impact on the efficiency, dependability and cycle life of Li-ion batteries. Proper thermal management is essential for optimizing battery performance and ensuring safety. Various cooling techniques have been developed to manage battery temperature, but one promising approach involves the use of nanofluids. Compared to traditional coolants, nanofluids suspended in base-fluid offer better heat dissipation and thermal conductive properties. In this study, we explore the use of different nanofluids—precisely Al2O₃, Al, Cu, CuO and graphene nanoparticles dispersed in water at different volume concentrations of 1, 2, and 3%. These nanofluids will be circulated between battery cells with designed spacing of 5mm between each cell at different mass flow rates like 0.05, 0.10 and 0.15 kg/s to enhance cooling efficiency. This approach aims to maintain cell temperatures within safe limits, thereby mitigating risks associated with thermal runaway and potential thermal explosions. To assess the effectiveness of these nanofluids, a series of tests are conducted to evaluate their heat dissipation capabilities. ANSYS Fluent was employed to model and analyze the thermal behaviour of the nanofluids and the simulation results were utilized to rank the nanofluids based on their heat dissipation performance and overall effectiveness. This research highlights the potential of nanofluids in enhancing battery thermal management and improving the overall performance of Li-ion batteries. By leveraging advanced simulation techniques and detailed stability analysis, this paper aims to identify the most effective nanofluids for battery cooling applications.

Polymer-bonded explosives (PBX), as a classical representativeof energetic composite materials, have poor mechanical propertiesdue to weak interface interaction, which limits their wide application.Inspired by the strong adhesion of mussels, coating polydopamine (PDA)on the surface of energetic materials is considered an effective methodto enhance the interaction. In this study, the self-polymerizationof dopamine was accelerated by the addition of potassium permanganate,which was successfully coated on the surface of dihydroxylammonium5,5′-bistetrazole-1,1′-diolate (TKX-50), a high-energyand insensitive energetic material. After PDA coating, TKX-50 hadexcellent thermal stability and mechanical properties. The spontaneousdecomposition temperature and thermal explosion critical temperatureof TKX-50 after PDA coating increased from 204.300 and 217.604 °Cto 210.700 and 223.839 °C, respectively, and the compressivestrength increased from 6.38 to 7.65 MPa. This novel method improvesthe thermal stability and mechanical properties of energetic materialsto ensure their large-scale industrial production and application.

As urbanization develops, China has become the largestmarket inurban subway construction. The vibration induced by subway tunnelexcavation blasting critically threatens the structural integrityand human safety in overlying buildings. To address this, this studypioneers a comparative experimental analysis of two damping systemsunder thermal explosion loading in shallow metro tunnels. These twodamping systems are large-diameter empty-hole cutting (LDC) and single-stagewedge cutting (SWC), respectively. Crucially, our work demonstratesthat LDC reduces peak vibration velocity by 58–59% comparedto SWC, directly correlating the cavity size with vibration intensity(PPV is positive correlation with cavity volume). Furthermore, a detailedanalysis and explanation of the damping mechanism are also conductedusing numerical simulation and classical theory. These findings offera validated thought for vibration control technology for tunnel blasting.The research results provide a “revolutionizing infrastructuretechnology” for urban tunnel projects in vibration-sensitiveenvironments under China’s high-quality urban development strategy.

Thermal runaway mechanisms and explosion risk evolution of sodium-ion batteries with varying states of charge in a confined chamber

Inhibitory effect of C6F12O on thermal runaway gas explosion of lithium-ion cells in a semi-confined channel

Abstract In cylindrical storage silos, exothermic reactions carry the inherent danger of triggering a thermal explosion. Such an explosion can transpire when the rate at which heat is generated by the chemical reaction exceeds the heat dissipated through conduction and convection. Frank-Kamenetskii defined a parameter δ to indicate that the explosion occurred when its critical value was exceeded. This study aims to delve into the principles of thermal ignition, clarifying the behavior of exothermic reactions within ventilated open granular silos. The findings include a series of plots that demonstrate an increase in δ with increasing Rayleigh number, particularly when natural convection is pronounced. The study also examines the location of the hot spot, which moves from the center to the top of the vessel because of buoyancy forces. Additionally, for minimal Rayleigh values, lower Biot numbers lead to reactions occurring at lower temperatures, suggesting that a reduced Biot number indicative of poor surface ventilation heightens the risk of explosion and diminishes the stabilizing influence of natural convection. Furthermore, the findings show that the storage time has been improved from approximately 6 months to 12 months with an increase in the Biot number and at a Rayleigh value of 103. This analysis of the role of natural convection relative to that of thermal explosions provides valuable knowledge for enhancing storage safety protocols to prevent thermal explosions in such storage environments.

A model for the flow and thermal explosion of a micropolar gas is investigated, assuming the equation of state for a real gas. This model describes the dynamics of a gas mixture (fuel and oxidant) undergoing a one-step irreversible chemical reaction. The real gas model is particularly suitable in this context because it more accurately reflects reality under extreme conditions, such as high temperatures and high pressures. Micropolarity introduces local rotational dynamic effects of particles dispersed within the gas mixture. In this paper, we first derive the initial-boundary value system of partial differential equations (PDEs) under the assumption of spherical symmetry and homogeneous boundary conditions. We explain the underlying physical relationships and then construct a corresponding approximate system of ordinary differential equations (ODEs) using the Faedo–Galerkin projection. The existence of solutions for the full PDE model is established by analyzing the limit of the solutions of the ODE system using a priori estimates and compactness theory. Additionally, we propose a numerical scheme for the problem based on the same approximate system. Finally, numerical simulations are performed and discussed in both physical and mathematical contexts.

Abstract With the advancement of augmented reality (AR) and virtual reality (VR) technologies, the demand for Mini/Micro‐LED displays has surged. To address the challenges of mass transfer and backlight leakage in Mini/Micro‐LED, this study proposes a stacked color conversion layer based on a laser‐induced ring‐enclosed structure. A nanosecond pulsed laser is focused on the aluminum film to fabricate the ring‐enclosed metal hole structure by thermal explosions and shock effects. This structure integrates inorganic perovskite quantum dots (QDs) and LiF encapsulation to achieve high‐brightness, leakage‐free light‐emitting arrays. The aluminum layer with a suitable thickness (100 nm) eliminates backlight leakage while maintaining intense luminescence. Building on this structure, a tri‐color color conversion layer is developed through repeated fabrication of metal/LiF/QDs multilayers atop the initial LiF/metal/QDs configuration. The transmission differences between dissimilar metals of varying thicknesses make it feasible for this stacked structure to achieve backlight excitation. Eventually, backlight‐excited tri‐color coplanar light‐emitting arrays are successfully achieved with this composite structure.