Thermal Hazard Research Articles

Passivation of black phosphorus by triazine-based silica coating: Hierarchical BP@SiO2-N@Co(OH)2 structure for enhanced fire safety and toughness of unsaturated polyester resins

The fire and toxic smoke hazards of polymer combustion and the weak oxidation resistance of pure black phosphorus nanosheets (BPNSs) are hot and difficult issues. Here, triazinylsilane and Co(OH)2 nanoflowers are sequentially encapsulated on the surface of BPNSs to generate a novel multifunctional flame retardant (BP@SiO2-N@Co(OH)2), and incorporated into the unsaturated polyester resin (UPR). Specifically, with the addition of 2 wt% BP@SiO2-N@Co(OH)2, the nanocomposite exhibits superior thermal hazard suppression efficiency relative to previous related work. In particular, BP@SiO2-N@Co(OH)2 exhibits a superior ability to suppress toxic smoke than BPNSs, with a 42.3 % reduction in total smoke production (TSP) at 2 wt% flame retardant content. In addition, UPR with 0.5 wt% BP@SiO2@-N@Co(OH)2 achieves 76.5 % increases in impact strength, revealing excellent mechanical properties. Therefore, a novel multifunctional nano flame retardant is successfully synthesized and provided an innovative strategy for the preparation of multifunctional UPR nanocomposites.

Flame-retardant and thermal-protective polyimide-hydroxyapatite aerogel fiber-based composite textile for firefighting clothing

Firefighting protective clothing is an essential equipment for firefighters that can provide protection from all kinds of thermal hazards and prevent burn injuries. However, it is still a challenge to develop lightweight firefighting clothing without compromising their excellent fire-resistant and thermal-protective performance. In this study, we report a novel polyimide aerogel fiber-based double-layer smart textile comprising of flame-retardant outer layer (ambient-side) with excellent fire resistance and phase-changeable inner layer (next to skin side) with thermal-regulating function, achieving comprehensive flame-retardant and thermal-protective function. The polyimide-hydroxyapatite-reduced graphene oxide (PI-HAP-rGO) aerogel fabric (outer layer) acquires 54.7% and 70.0% reduction of peak heat release rate compared with that of pure PI aerogel fabric and commercial aramid fabric, respectively, exhibiting excellent fire resistance. The phase-changeable polyimide-hydroxyapatite/eicosane (PI-HAP/C20) fabric (inner layer) with high melting enthalpy of 193.2 J g−1 can delay the temperature rise by thermal buffering effects during the phase change process, endowing cool somatosensory temperature for firefighters. Consequently, the double-layer smart textile can extend the time (280.0 s) to pain threshold of human skin, much longer than that of the commercial aramid fabric (101.0 s) and glass fiber fabric (56.5 s), which exhibits huge potential for next-generation firefighting clothing.

Process optimization and thermal hazard analysis of the preparation of diphenyl sulfoxide using hydrogen peroxide as oxidant

In this study, diphenyl sulfoxide was prepared by oxidizing diphenyl sulfide with hydrogen peroxide using phosphotungstic acid as catalyst in semi-batch mode. In order to optimize the synthesis process, a four-factor three-level Box-Behnken design was adopted. The result showed that under the optimal condition, namely catalyst concentration 0.19 mmol/mol, oxygen-sulfur ratio 1.08, reaction temperature 30 ºC, and dosing time 15 min, the yield of diphenyl sulfoxide could reach up to 79.05%. In addition, the thermal behavior of synthesis process was systematically investigated using a reaction calorimeter (EasyMax 102) equipped with a situ FTIR monitoring. The receivable mechanism is that H2O2 is activated by the catalyst and subsequently reacts with diphenyl sulfide to produce oxidized product. H2O2 was relatively stable when PTA was used as catalyst. Thermal risk index was used to assess the thermal hazard of H2O2 & PTA. Furthermore, risk matrix method as well as Stoessel criticality diagram was used to assess the thermal risk of the process and an unacceptable risk was obtained. One of the main hidden dangers was the potential chemical splatter caused by decomposition of H2O2. It should be equipped with a pre-set quench or sufficient emergency discharge to avoid further loss. The results of this work proposed a solid foundation for the safe operation of this process and can be further used for scale-up.

Thermal hazard characteristics and essential mechanism study of 1-hydroxybenzotriazole: Thermodynamic study combined DFT simulation

1-Hydroxybenzotriazole (HOBT) as an important fine chemical has been used as reactants, reagents or catalysts in over 6 million chemical synthesis reactions. The thermal decomposition characteristics of HOBT in non-isothermal, isothermal and adiabatic conditions were investigated through differential scanning calorimetry, thermogravimetric analyzer, and accelerating rate calorimeter. The apparent activation energy, thermal safety parameters, and the decomposition reaction pattern of HOBT pyrolysis were obtained based on adiabatic accelerating calorimeter experimental data. HOBT pyrolysis is a rapid exothermic process with large amounts of gas produced, and HOBT can decompose at a temperature substantially lower than the onset temperature. The severity and probability of HOBT runaway reaction were assessed. The pyrolysis mechanism paths of HOBT were explored by using TG-MS and TG-FTIR experiments couple with density functional theory calculations. The main decomposition products of HOBT were N2, NO, C2H2, C6H6, CO, HCN, and CO2 gases. This study provides guidance for safe production and application of HOBT, and formulating emergency plans for related hazards.

Experimental and numerical study on heat emission characteristics of ventilated air annular in tunneling roadway

With the increase in mining depth, thermal hazard becomes a prominent problem. Reducing heat dissipation of the surrounding rocks on the basis of artificial refrigeration can be an important thermal hazard-control technique. There are several researches on spray and surrounding rock-filling insulations, but only a few researches were conducted on air jacket heat insulation performance. To enrich the research content of air jacket heat insulation, a similar experiment platform was designed. Based on the analysis of the test data, the friction factor for the turbulent flow in the interlayer of air annular is obtained and a modified equation for calculating the friction factor is proposed based on the Blasius equation model. The average Nusselt number of the inner and outer wall surfaces in the annular air of roadway is calculated under turbulent state, and the Gnielinski equation is modified based on the experimental results. Based on the finite volume method, the unsteady mathematical model of the heat dissipation structure of ventilated air annular with surrounding rock was established. A computer program was developed, and the accuracy of the mathematical model was verified using experimental results. The numerical calculation results were used to analyze the variations of heat absorption of airflow in the main roadway and heat exhaust of the ventilated air annular at different wind speeds and annular diameters. The results show that the heat insulation effect of interlayer of ventilated air is the best when the air flow in the annular is at the turning point of laminar flow turbulence. The heat insulation effect of ventilated air interlayer is the best in the early ventilation stage, and the heat insulation rate will decrease with the increase of ventilation time, but the heat insulation rate can reach more than 69.7% in 10 years.

Mitigation of Thermal Stability Concerns in FinFET Devices

Here, we developed a procedure for mitigating thermal hazards in packaged FinFET devices. A monitoring system was installed into devices, based on self-heating impact analysis in the system and device levels, to allow for the observation and alerting of chip temperature and reliability risks. A novel algorithm for reducing measurement noise by means of temperature fluctuation compensation and the filtering of invalid data is presented and demonstrated on packaged devices. The results presented in this work show that the proposed techniques make exceptional improvements to sensory accuracy. Using this methodology enables the mitigation of thermal concerns in systems, including large data servers, and accelerates development of smart resource allocation formations.

Interplay of Lithium Plating Quantification on Thermal Safety Characteristics of Lithium-Ion Batteries

Adverse lithium plating is a significant side reaction during the fast charging of lithium-ion (Li-ion) batteries when the Li-ion flux exceeds the intercalation or diffusion limits of graphite electrodes. Accurate quantification of lithium plating has always been a tough challenge given the severe defects of online detection methods such as coulombic efficiency and voltage relaxation plateau, making the mathematical correlation between cell-level thermal safety hazards and quantitative lithium plating events still a bottleneck problem. In this study, we apply a three-electrode (3E) Li-ion cell configuration and the accelerating rate calorimeter (ARC) to comprehensively investigate the interplay of unfavorable lithium plating on thermal runaway characteristics of Li-ion batteries. Lithium plating is introduced by cycling 3E Li-ion cells at low temperatures and quantified by analyzing potential-based plating energy, coulombic inefficiency, internal resistance, and voltage relaxation plateau. Surface microscopic characterization is carried out on graphite electrodes to reveal the morphologies and chemical states of lithium deposition. ARC experiments are implemented at full-cell and partial-cell scales to fundamentally understand the effects and contributions of thermally unstable lithium plating to the overall safety performance of Li-ion cell chemistries.

Cell-to-Cell Variation in Thermal Runaway Behavior

As one of the most promising energy storage mediums, Lithium-ion batteries (LIBs) have attracted extensive research interest. A major challenge associated with LIB application is thermal runaway, which can be triggered during overheating, overcharging, collision, and other abused conditions, leading to a direct threat to lives and properties. Here, we select Li-ion batteries with lithium cobalt oxide cathode and graphite anode (18650, Samsung), which are relatively simple and extensively investigated, to revisit thermal runaway. The experiment is conducted using an accelerating rate calorimeter (EV+ ARC, Thermal Hazard Technology) following the standard heat-wait-seek strategy, and is repeated for 9 similar new cells with 100% state of charge (SOC). Key features such as onset temperature of self-heating, the onset temperature of thermal runaway, maximum heat release rate, thermal runawaydelay time, and maximum temperature are measured experimentally. Although the cells are all brand new and have been initiated similarly, obvious cell-to-cell variability has been observed during thermal runaway. Major differences exhibit in the measured exothermic onset temperature, delay time, and mass losses; however, each cell nevertheless shows highly consistent activation energy processed from the heat release rate. Additionally, thermal runaway models are established in COMSOL to simulate the experimental conditions, with and without the effect of reactant consumption during the heating stage. It is shown that the widely used four-step thermal runway model cannot quantitatively capture the activation energy from the heat release rate. To improve the kinetic modeling and accommodate the cell-to-cell variability, statistical analysis is conducted to process the experimental results. Meanand standard deviation of the frequency factor and activation energy has been acquired to determine the lower and upper bound of the kinetic modeling using a one-step global chemistry. The measured and simulated thermal runaway delay time has reached a reasonable agreement, with the uncertainty of the kinetic model considered. The identified cell-to-cell variability is most likely due to manufacturing inconsistencies, which should not only be considered for cell-level safety evaluation but also the design and evaluation of battery modules and packs.

Experimental investigation of environmental pressure effects on thermal runaway properties of 21700 lithium-ion batteries with high energy density

As lithium-ion batteries (LIBs) with higher energy density are becoming more widely applied, especially in aviation field, understanding the potential thermal hazards of which at low pressure is beneficial to evaluate the safety during storage, transport and use. In this paper, thermal runaway (TR) behaviors of 21700 cylindrical LIBs with high energy density under various pressures were investigated, and characteristic parameters at low pressure such as surface temperature of LIBs and mass loss were analyzed. The results showed that combustion behaviors of LIBs could be weaker as the pressure decreased. Besides, T mean was used to characterize the temperature variation of the TR. Several critical parameters such as T open , T tr , T max , and t interval during the TR of LIBs were analyzed, respectively. The results indicated that T tr followed an upward trend as the environmental pressure decreased from 101 to 30 kPa. The t interval reduced from 48 s to 22 s when the pressure declined from 101 to 30 kPa. A heat transfer model under external heating could be used to explain the trend in TR influence at low pressure, and the temperature change rate ( d T d t ) was related to the internal and external pressure of the battery. In addition, the relationship between the mass loss rate (MLR) and the pressure was analyzed, which indicated that environmental pressure had a little significance on mass loss for 21700 LIBs. Moreover, for given test conditions, the phenomenon of flame lift-off was not observed at different pressures, and the jet flame height reached the maximum at 50 kPa, which was 0.28 m. To quantify the maximum jet flame height, an approximate power law dependence between flame height and pressure could be deduced. This study might be helpful to further understand the fire risk of the LIB jet fires under low pressure.

Evaluating combustion characteristics and combustion kinetics of corn stover-derived hydrochars by cone calorimeter

This study investigated the combustion properties of corn stover-derived hydrochars using cone calorimeter. Hydrochars were prepared by hydrothermal carbonization (HTC) at 200, 230, and 260 °C for 30 min. Six different heat fluxes (5–50 kW/m2) were applied to hydrochars to determine critical heat flux (CHF), ignition temperature, thermal response, peak heat release rate (pHRR), thermal hazard risk, and combustion efficiency. Results show that increasing the HTC temperature decreased the CHF and ignition temperature but increased the thermal resistivity. Increasing the heat flux decreased the thermal resistivity and ignition time of all the hydrochars. Thermal hazard analysis indicated that the hydrochars posed lower thermal risk than raw corn stover. Finally, combustion kinetics were proposed using two parallel first order reactions for volatile matters and fixed carbon. The reaction rate of volatile matter was significantly higher than the reaction rate of fixed carbon. HTC increased the fixed carbon activation energies to as high as 24.0 MJ/mol. Overall, HTC forms hydrochars which are less flammable, more stable, and a lower thermally risk material for piloted ignition than raw corn stover.

Experimental study on thermal runaway and its propagation of large format prismatic lithium-ion batteries

Lithium-ion batteries (LIBs) are one of the most promising technologies in electric vehicles and electric energy storage systems. However, safety accidents related to TR (thermal runaway) often occur. At present, large-format prismatic batteries have been put into use as part of the energy storage system. In practice, batteries often appear in the form of modules, which also increases the risk of TR control. The phenomenon of TR propagation of prismatic lithium-ion battery in modules is rarely studied. In this study, the TR behaviors of the single battery and module were investigated through overheating experiments. The results showed that the highest spontaneous-heating power of batteries with 0 %, 50 % and 100 % SOC (State of charge) are 67 W, 1336 W and 2308 W, respectively. Experiments also performed TR propagation experiments between monolayer and bilayer cell modules, which showed that TR is transmitted in the monolayer module, but not in different layer modules. In addition, compared with the single battery, the TR of the battery module in the propagation process is more intense, and the TR is most likely to fail in the propagation process of the second and the third battery. To gain a comprehensive understanding of the TR propagation of the prismatic LIB modules, a method to determine whether the TR will spread is achieved based on the spontaneous thermal power. This study further reveals the propagation behavior of heat abuse of prismatic lithium batteries, and its results provide guidance for the safety design and thermal hazard prevention of battery storage systems.

Thermal stability evaluation of tert-butyl peroxybenzoate mixed with impurities

In this article, the thermal stability of tert-butyl perbenzoate (TBPB) mixed with different concentrations of toluene and p-tert-butylcatechol (TBC) was investigated. The exothermic onset temperature (T 0), the heat of decomposition (ΔH), and the adiabatic temperature rise (ΔTad ) of the samples were obtained by differential scanning calorimetry (DSC) and Phi-TEC II adiabatic calorimetry. The apparent activation energy (Ea ) and the maximum reaction rate arrival time under adiabatic conditions were obtained by adiabatic kinetic calculations for 8 h (TD8 ) and 24 h (TD24 ). Based on Semenov’s theory, the self-accelerated decomposition temperature was calculated as a support for safe storage and transport. The results of DSC and Phi-TEC II showed that toluene was effective in reducing the thermal hazard during the decomposition of TBPB. The addition of TBC caused side reactions. The moderate addition of toluene and TBC improves the thermal stability of TBPB and can improve the safety of TBPB in industrial applications.

Thermal Hazard and Smoke Toxicity Assessment of Building Polymers Incorporating TGA and FTIR—Integrated Cone Calorimeter Arrangement

Building polymers are highly flammable and produce a vast amount of toxic chemical compounds in the event of a fire which can lead to potential incapacitation and death. To gain an in-depth understanding of this issue, smoke toxicity and thermal characteristics of seven commonly used building polymers were analysed through a systematic fire performance evaluation system using a Thermogravimetric Analyzer and a Cone Calorimeter coupled with an FTIR arrangement. Four Fractional Effective Dose (FED) expressions were compared to assess the smoke toxicity of the fire effluents based on different assumptions. It was found that FEDN2, calculated using Purser’s equation, reported the highest values of FED with the following order of potential smoke toxicity at 50 kW/m2 radiative heat flux: LDPU > HDPU > PE > HDEPS > XPS > EVA > LDEPS. Furthermore, fire performance evaluation of the polymers was carried out by considering three key fire risk parameters, i.e., flashover propensity, total heat released, and toxic hazard. At 50 kW/m2 radiative heat flux, HDPU exhibited 11.7 times flashover propensity compared to the least flammable polymer (HDEPS), EVA exhibited 5 times total heat release compared to the polymer with the lowest total heat release (LDEPS) and, LDPU exhibited 6.7 potential times toxic hazard compared to the least toxic polymer (EVA).

Potential energy-assisted coupling of phase change materials with triboelectric nanogenerator enabling a thermally triggered, smart, and self-powered IoT thermal and fire hazard sensor: Design, fabrication, and applications

Thermal and Fire hazards result in numerous damage to human life and property. The early detection and instant communication of potential hazards using environmentally sustainable sensors before they occur would significantly reduce the negative impact on the environment while saving lives and property from destruction. Here-in, for the first time, a self-powered thermal and fire hazard sensor was designed by coupling gravitational potential energy to the triboelectric effect to generate electric signals. Harnessing the mechanical integrity and phase change property of the paraffin rod, it is employed as mechanical load support and thermal receptor in the sensor. Furthermore, the sensor was integrated with several communication interfaces such as liquid crystal display (LCD), Wi-Fi emitter, light-emitting diode (LED) light, IoT network, and mobile phone. The sensor exhibited an instant response (∼0 s response time) at temperature ranges between 80 and 89 °C.

Experiments and modeling of the temperature profile of turbulent diffusion flames with large ullage heights

In the last decades, several major fire accidents involving storage tanks occurred, particularly for the tanks with a low fuel level (large ullage height). In case of a tank fire, the axial temperature profile is affected by the ullage because of the restriction in air entrainment by the tank sidewall. This work is aimed at examining the temperature profile of turbulent diffusion flames with large ullage heights. A series of experiments were conducted with different ullage heights (h = 16–42 cm) and fuel supply rates. The temperature profiles both inside and outside the fuel tray were measured and analyzed. Five regions were identified based on flame intermittencies: namely 1) fuel vapor, 2) down-reaching intermittent flame, 3) continuous flame (down-reaching and upper flame), 4) upper intermittent flame and 5) buoyant plume. It was found that for a given fuel supply rate the length of the fuel vapor region increases linearly with the ullage height. The lengths of the fuel vapor and continuous flame regions both increase with the fuel supply rate, whereas that of the down-reaching intermittent flame region shows an opposite trend. Based on the experimental data and dimensionless analysis, new correlations for the virtual origin were proposed, which were then incorporated in the predictions of the temperature profiles in both upper and down-reaching flames. The present results could not only contribute to the understanding the effects of the ullage height on the axial temperature profile in storage fuel tank fires with large ullage heights but are also of practical importance in the thermal hazard assessment of fire accidents involving tank liquid fuels.

Thermal Safety and Structure-Related Reactivity Investigation of Five-Membered Cyclic Sulfamidates

Five-membered cyclic sulfamidates are very valuable electrophiles in organic synthesis and readily used on a multikilogram scale. However, their thermal degradation is underreported and might lead to unforeseen and undesirable safety events. In addition, ring or nitrogen substitution can have a tremendous influence on cyclic sulfamidate reactivity toward bases and therefore impact the overall safety assessment of a process. An understanding of such behavior is therefore of high importance in the industry while designing a synthetic route, as a change of, e.g., a protecting group can increase the thermal safety of a step on scale. We report herein the thermal degradation investigation as well as the structure-related reactivity exploration of cyclic sulfamidates, including their use in combination with strong bases. The design of a predictive model to rapidly assess the thermal hazard based on collected data and selected molecular descriptors is also presented.

Development and Validation of a Tunable Diode Laser Absorption Spectroscopy System for Hot Gas Flow and Small-Scale Flame Measurement.

TDLAS (tunable diode laser absorption spectroscopy) is an important gas analysis method that can be employed to obtain characteristic parameters non-invasively by the infrared absorption spectra of tracer molecules such as CH4, H2O and O2. In this study, a portable H2O-based TDLAS system with a dual optical path was developed with the aim of assessing the combustion characteristics of flammable gases. Firstly, a calculation method of gas characteristics including temperature and velocity combining absorption spectra and a HITRAN database was provided. Secondly, to calibrate and validate this TDLAS system precisely, a pressure vessel and a shock tube were introduced innovatively to generate static or steady flow fields with preset constant temperatures, pressures, or velocities. Static tests within environment pressures up to 2 MPa and steady flow field tests with temperatures up to 1600 K and flow velocities up to 950 m/s were performed for verification. It was proved that this system can provide an accurate values for high temperature and velocity gas flows. Finally, an experimental investigation of CH4/air flames was conducted to test the effectiveness of the system when applied to small diffusion flames. This TDLAS system gave satisfactory flame temperature and velocity data owing to the dual optical path design and high frequency scanning, which compensated for scale effects and pulsation of the flame. This work demonstrates a valuable new approach to thermal hazard analysis in specific environments.

Covalent grafting diazotized black phosphorus with ferrocene oligomer towards smoke suppression and toxicity reduction.

In comparison with the thermal hazard of polymers, noxious smoke and gas produced by the combustion of polymers make the environment self-purification a huge challenge. As a new type of a highly effective flame retardant, black phosphorus (BP) can effectively decrease the thermal hazard of polymers, but its performances in smoke suppression and toxicity reduction are unsatisfactory. In this article, a method of covalently grafting diazotized BP with a ferrocene oligomer was applied to promote the smoke suppression and toxicity reduction efficiency of BP. In our work, the BP-NH nanomaterials with a mass of amino groups on the surface were acquired by diazotizing the BP. Then, the BP-Fe was obtained by covalently grafting the ferrocene chloride salt and nitrogen-containing heterocycles on the surface of BP. The smoke production rate (SPR) and total smoke production (TSP) values of the epoxy resin (EP) decreased by 49.8% and 52.5% with the addition of 2wt% BP-Fe, respectively. In comparison with previous studies, this work was far more effective than the previous work in smoke suppression and flame retardant. The release of toxic gases (CO and HCN) and volatile organic compounds in the EP was also effectively inhibited at the same time. In addition, the storage modulus and tensile strength of nanocomposites increased by 35.1% and 27.2% with the addition of 1wt% BP-Fe. This work also provides a new idea on how to simultaneously strengthen the toxic smoke suppression, mechanical properties, and flame retardant of polymer materials.

Applying experiment and numerical simulation to evaluate the thermal hazards of Bis(1-(tert‑butylperoxy)-1-methylethyl)-benzene in the presence of metal ions or sulfuric acid

Bis(1-(tert‑butylperoxy)-1-methylethyl)-benzene (BIPB) is susceptible to thermal runaway or explosion when exposed to metal ions or acid during production. In this article, thermal decomposition of BIPB and its thermal sensitivity to metal ions and acid were firstly systematically studied by DSC and ARC. Experiments demonstrate that BIPB decomposes around 105–115 °C with ΔH¯ of 1483.78J·g−1. FeCl3 and H2SO4 have a more pronounced impact on the thermal decomposition characteristics of BIPB compared with other impurities. Furthermore, the effect became more pronounced with increasing H2SO4. The model-free and model-fitting methods were combined to determine BIPB's decomposition as a two-step consecutive n-order reaction (A→r1B→r2C), then to evaluate thermal hazard indicators. Ultimately, two sem-quantitative risk assessment methods were separately used to evaluate thermal risk of compounds and processes. It's shown that the MF of BIPB mixtures doped with FeCl3 is highest, 2, and the Borda index of the purification process in BIPB synthesis is 44 and risk rank is 2, which is an unacceptable risk.

Thermal hazard assessment of 3-nitro-1,2,4-triazole-5-one (NTO) synthesis

In order to assess thermal hazard of 3-nitro-1,2,4-triazole-5-one (NTO) synthesis, the thermal decomposition behaviors of 1,2,4-triazole-5-one (TO), nitrification liquor and NTO under the kinetic and adiabatic environments were explored by virtue of differential scanning calorimeter (DSC) and accelerating rate calorimeter (ARC). The outcomes provide key safety parameters for the safety of NTO during the reaction process, transportation and preservation. In addition, the exothermic characteristics of TO nitrification process was monitored by automatic multifunctional reaction calorimeter (EasyMax HFCal), the total heat release of nitrification reaction at different feeding temperatures were comparatively studied and the relationship between feeding rate and thermal runaway in NTO synthesis process is explored. The outcomes reveal that the thermal release rate is high at the reactive feeding phase, and the feeding rate ought to be regulated. The thermal variables such as adiabatic temperature elevation (∆Tad) and maximal temperature of the synthesis reaction (MTSR) were calculated to evaluate the thermal hazard of NTO synthesis at diverse feeding temperatures. To ensure the safety of NTO industrial production, these studies provide theoretical basis and guidance for controlling the thermal runaway risk of NTO synthesis.