Fire safety of long-span cable-supported bridges has attracted increasing attention due to the growing risk of vehicle fires. This study experimentally investigates the thermal response of bridge cables subjected to vehicle fires using a 1:4 scaled fire-test platform developed from the Shiziyang Bridge. Gasoline and polyethylene (PE) pool fires were employed to simulate tanker-truck and cargo-truck fire scenarios under varying crosswind conditions. The results indicate that gasoline fires produce rapid and intense heating, with cable temperatures approaching 1000 °C, whereas PE fires exhibit slower temperature growth but longer thermal exposure, with peak temperatures around 650 °C. Severe vehicle fires generated extensive high-temperature regions along the cable height, indicating substantial fire exposure to the lower cable zones. A three-zone cable heating mechanism considering radiation, convection, and air entrainment effects was proposed and validated using Fire Dynamics Simulator (FDS) simulations. Furthermore, a unified temperature-distribution model accounting for wind speed and fire location was established to predict the temperature decay characteristics along the cable height. The findings provide quantitative guidance for determining fire-protection coverage, insulation temperature limits, and zoned fire-resistant design strategies for cable-supported bridges.

Microstructure manipulation represents a fundamental strategy for enhancing material properties. Herein, a new-type flame-resistant material with core-shell architecture (APP@PEI@SiO2@MXene) is prepared by iterative deposition of self-assembled monolayers, enabling microstructural control of ammonium polyphosphate (APP) via sequential coating with polyethyleneimine (PEI), SiO2, and MXene. Then the flame retardants were incorporated into thermoplastic polyurethane (TPU) at a loading of 15 wt.%, this meticulously designed microstructure enables the composite to exhibit significantly improved fire safety. The composite exhibits a markedly increased high-temperature char residue under both air and nitrogen atmospheres, indicating improved thermal resilience and char formation capacity. Thermal stability analysis of the material reveals that the coated APP enables TPU composites to engender a carbonaceous stratum of heightened tenacity. Cone calorimetry tests indicate that, compared with pure TPU, TPU/APP-1BL composites exhibit sharp declines of 87.90% in total heat release (THR) and 76.79% in the peak heat release rate (pHRR), with concurrent effective control of smoke/toxic gas emissions. Moreover, the flame-retardant effects of multi-layer coated APP are notably better than those of single-layer coated APP. Mechanistic studies reveal that the flame-retardant performance chiefly originates from the synergistic interplay of solid and vapor-stage pathways. This work highlights the critical role of microstructure design in the creation of high-performance fire-resistant polymers.

Sub-atmospheric pressure environments and curved tunnel spaces significantly influence fire behavior and heat transfer mechanisms, thereby posing challenges for fire prevention in tunnels and underground space infrastructure. This study investigates the near field flow dynamic and heat transfer characteristics of fire-induced curved ceiling jet under sub-atmospheric pressures through experimental and simulation methodology. Experiments employed a downscaled model with varied atmospheric pressures (100 kPa similar to 45 kPa), fire source-ceiling heights (0.25 m similar to 0.35 m), and fire heat release rates (7.1 kW similar to 24.0 kW) to analyze flame morphology, flow field characteristics, and ceiling heat flux distribution. Results show significantly increased flame extension length and distinct vortex formation at the flame tip under sub-atmospheric pressure. And numerical simulations visualized vortex generation and evolution within the pulsation cycle. Pressure reduction causes ceiling heat flux to decrease near the fire source. Based on theoretical analysis, a relationship between the ceiling heat flux at the stagnation point and environmental pressures has been revealed. Furthermore, by analyzing the heat transfer mechanisms within the curved ceiling and horizontal ceiling, a unified predictive model for both transverse and longitudinal heat flux under different pressures was established. This study can provide a theoretical basis for fire risk assessment and emergency rescue strategies for tunnel fires under reduced pressures.

The integration of thermal insulation, transient thermal buffering, and fire safety in lightweight sustainable materials is highly desirable but remains challenging. Herein, a multifunctional phase-change cellulose aerogel (PCMA) was developed by incorporating a flame-retardant PWUiO-66 phase into a cellulose nanofiber framework via hydrothermal-assisted freeze-drying. The resulting aerogel exhibits a hierarchically porous structure with confined functional domains, enabling simultaneous suppression of heat transfer and enhanced fire resistance. Relative to pristine CNF, PCMA exhibits reduced thermal conductivity (0.710 m-1·K-1 and 0.164 m-1·K-1) and thermal diffusivity (0.700 (mm)2/s, 0.700 (mm)2/s), together with improved resistance to transient thermal shock. The confined phase-change domains provide heat-buffering capability by absorbing thermal energy during heating, while cone calorimetry reveals a substantial reduction in peak heat release rate from 69.4 to 30.8 kW·m-2. Structural characterization shows that the incorporation of PWUiO-66 transforms the smooth fibrillar CNF network into a roughened and interconnected porous architecture, which improves thermal insulation and promotes the formation of a stable char barrier during combustion. These results indicate that the multifunctional performance of PCMA arises from the synergistic combination of hierarchical porous insulation, phase-change-assisted thermal buffering, and MOF-mediated flame-retardant stabilization. This work offers an effective strategy for designing cellulose-based aerogels for advanced thermal protection and fire-safe insulation applications.

To investigate the influence of tunnel slope on the longitudinal ceiling temperature distribution under lowpressure conditions, and to evaluate the effectiveness of neural network models in predicting fire heat release rates, tunnel models with varying ambient pressures and inclination angles were developed using the FDS. Using the temperature distribution dataset along the tunnel ceiling, three neural network models-RNN, LSTM, and GRU-were trained and evaluated. The results indicated that: (i) At a heat release rate of 5 MW, increasing pressure leads to greater variation and a general decrease in peak ceiling temperature. In contrast, at 10 MW and 15 MW, the variation in peak temperature is smaller, and overall temperature trends increase steadily. (ii) As the slope increases, the peak temperature position shifts progressively downstream, the peak value tends to decrease. (iii) Among the models, the RNN achieved the highest prediction accuracy, with a minimum relative error of 10 % under the current dataset scale. The LSTM and GRU models demonstrated comparable performance, each with a maximum relative error of 20 %. (iiii) Under the present simulation framework, deploying multiple measurement points starting at 25 m downstream yielded the best overall performance, whereas single-point setups exhibited relative errors of up to 15 %. These findings provide a theoretical foundation and technical guidance for tunnel design, fire behavior analysis, and the development of intelligent fire monitoring systems.

Presently, hydrogen-blended natural gas pipeline transportation is the most efficient and economical mode of transportation. However, process pipelines in the hydrogen-blended natural gas station are susceptible to micro-leakage during operation due to factors such as hydrogen embrittlement, corrosion, and geological changes. The utilization of infrared imaging in the early warning of hydrogen-blended natural gas stations offers several advantages, including non-contact nature, ability to detect over long distances, and high degree of accuracy. However, challenges persist, including the limited adaptability of intelligent monitoring and recognition algorithms, the paucity of infrared image datasets, and the inability to implement hierarchical monitoring and early warning systems. This paper proposes an infrared imaging-based early warning method for pipeline micro-leakage risks in hydrogen-blended natural gas station, aiming to address the aforementioned core problems. Firstly, an experimental platform for hydrogen-blended natural gas process pipelines is designed and constructed. The infrared image dataset (MultiGasVid) of pipeline micro-leakage with multiple working conditions is established by the experiments. Secondly, the YOLOv11 target detection model is employed as the monitoring algorithm. The attention mechanism is incorporated, leading to the development of GAS-YOLO model, which is a real-time hierarchical quantitative monitoring algorithm for pipeline micro-leakage. Finally, the MultiGasVid dataset is trained and tested, and the GAS-YOLO model proposed in this paper outperforms the original YOLOv11 object detection model in terms of performance.

ABSTRACT Flame‐retardant polymer composites are widely used in engineering products, but their safety evaluation remains challenging because an improved result in a small‐scale flammability test does not necessarily indicate a lower overall fire hazard. This review clarifies the relationship between fire‐test methods, evaluation indicators, and application scenarios for flame‐retardant polymer composites. Screening tests, bench‐scale calorimetry, smoke and toxic‐effluent measurements, and intermediate‐ or large‐scale tests are compared according to the evidence they provide for ignition/early flaming, fire growth, smoke obscuration, toxic exposure, and assembly‐level behavior. The limitations of single‐parameter metrics, including UL‐94 classification and limiting oxygen index, are emphasized. The review further discusses how multi‐scale test outputs can be translated into an integrated scenario‐aware evidence framework, supported by multi‐criteria decision analysis and data‐driven tools when the boundary conditions are clearly defined. Future work should connect standardized fire testing, product‐specific requirements, toxicity assessment, and practical implementation so that flame‐retardant materials can be evaluated in terms of realistic fire safety rather than isolated flammability improvement.

The increasing integration of energy systems into urban structures has led to a corresponding rise in fire risks. Metro tunnels, serving as critical underground transportation corridors, are characterized by their narrow, enclosed design and dense energy-related infrastructure. Meanwhile, rail transit systems are accelerating their transition toward clean energy, with energy-powered trains-driven by batteries, supercapacitors, or hydrogen fuel cells-being deployed on an expanding scale. This study experimentally and numerically investigates spilled fire behaviors in a narrow carriage under longitudinal ventilation. The evolution of flame overflow with ventilation velocity is divided into three stages within the intermittent spillage regime: Stage I: internal combustion without ventilation; Stage II: flame shifts toward the opening and is easily blown out under moderate ventilation; Stage III: flame is pressed back into the compartment and becomes unstable at higher velocities. The spilled flame height decreases with increasing ventilation velocity, and the decay rate gradually slows with larger opening width. The flame horizontal extension length increases gradually with increasing wind speed, and the growth is more rapid at low wind speeds. The flame depth increases first and then decreases with ventilation velocity, and is smaller than that in still air when the opening width is relatively small. Based on dimensional analysis, two impact factors-"Excessive Fuel Spillage" and "Absence of Facade"-are proposed to quantify flame geometry. Predictive models for flame height, horizontal extension length and depth, incorporating opening size, ventilation velocity, and heat release rate, are established to well describe flame geometric parameters.

High loading of flame retardants typically impairs the mechanical and thermal insulation properties of polypropylene foam (PPF). Herein, a silicone resin-based (poly-DDPM) coating containing expandable graphite (EG) and montmorillonite (MMT) was applied to PPF via brush painting, aiming to enhance flame retardancy while preserving intrinsic performance. At an ultra-low coating loading of similar to 5 mg/cm(2), flammability evaluations revealed significant improvements. The limiting oxygen index (LOI) increased to 31% from 21% for pure PPF, UL 94 rating reached V-0, and peak heat release rate and peak smoke production rate decreased by 35.8% and 31.3%, respectively. Additionally, the compressive strength was improved by 14.3% with retained thermal insulation property, resolving the traditional fire safety-performance trade-off. When PP matrix suffered burning, poly-DDPM formed a continuous "Si-O"/"Si-C" network that suppressed melt dripping, creating a stable base for EG to expand into a "worm-like" char layer. This porous structure was further reinforced by MMT, which intercalated into the char to increase pore density, reduce pore size, and enhance phonon scattering during heat penetration. Collectively, these components built a robust barrier that blocked heat, oxygen, and fuel transfer. This coated PPF composite shows strong commercial potential in structural insulation and aerospace applications.

Cellulose-based aerogels are promising sustainable thermal-insulation materials, but their practical application is often limited by insufficient mechanical robustness and intrinsic flammability. Herein, a multiscale network-engineering strategy is proposed to fabricate a cellulose-based composite aerogel integrating structural stability, thermal insulation, and fire safety. By synergistically introducing in situ generated aluminum trihydroxide (ATH) and microencapsulated APP@ATH-MEL into the cellulose scaffold, the flame-retardant components function not only as active fire-safety agents but also as structural regulators that promote the formation of a highly interconnected hierarchical framework. This regulated architecture enhances interfacial interactions, improves load-transfer efficiency, suppresses structural collapse during freeze-drying, and introduces tortuous pathways and abundant interfaces for heat-transfer regulation. As a result, the optimized composite aerogel exhibits a low thermal conductivity of 35 mW·m-1·K-1 together with improved compression resistance. Thermal analysis reveals a reduced mass-loss rate and increased char yield, while cone calorimetry confirms suppressed heat release, reduced gaseous emissions, and improved residue stability. The enhanced fire safety is attributed to a synergistic multi-phase mechanism involving endothermic shielding, gas-phase dilution, condensed-phase char formation, and inorganic-residue reinforcement, which collectively inhibit heat and mass transfer during combustion. This work provides an effective strategy for the design of lightweight, mechanically robust, and fire-safe cellulose-based composite aerogels for advanced thermal-insulation applications.

Biomass aerogels are promising sustainable materials for thermal insulation and fire-safe applications, but their practical use is limited by poor flame retardancy, insufficient structural stability, and high wettability. In this work, a flame-retardant biomass composite aerogel was fabricated through the co-assembly of cellulose, lignin, and chitosan, followed by incorporation of the hybrid flame retardant APP@SiO2-MEL. The introduction of lignin and chitosan generated a more integrated biomass framework, while APP@SiO2-MEL further regulated the pore architecture and interfacial structure of the aerogel. Compared with the pristine cellulose aerogel, the optimized BA/APP@SiO2-MEL sample exhibited a more complex porous morphology, increased specific surface area, improved water resistance, and enhanced structural stability. Thermal analysis showed reduced decomposition rate and increased char yield, while TG-FTIR and Raman results indicated the formation of a more stable carbonaceous residue during pyrolysis. Cone calorimetry and direct flame tests confirmed significantly improved fire safety, including reduced heat release, suppressed volatile evolution, delayed combustion, and enhanced residue integrity. This work provides an effective strategy for developing biomass-derived aerogels with improved flame retardancy and structural stability.

Achieving high safety in energy storage systems is paramount but hindered by the catastrophic risks of thermal runaway propagation (TRP). This study develops a gradient-laminated ceramifiable silicone foam composite to resolve the inherent trade-off between thermal insulation and dynamic impact toughness. By integrating a polydimethylsiloxane foam matrix with a load-bearing glass fiber fabric skeleton, the material utilizes silane coupling agents for robust interfacial adhesion, while multiscale fillers promote synergistic ceramicization. Characterization reveals robust mechanical durability, maintaining stable elasticity across a wide temperature range (− 40 to 300 °C) and retaining 93

Cellulose aerogels exhibit exceptional thermal insulation properties but face deficiencies in flame resistance, mechanical properties, and compression resistance. This study synthesized an inexpensive, flame-resistant cellulose aerogel by incorporating aluminum oxide and magnesium hydroxide as flame retardants. The resulting material demonstrates enhanced thermal insulation capabilities alongside improved compressive mechanical properties. Through in situ reactions, the metal ions (Al3+, Mg2+) interact with the cellulosic matrix, strengthening the composite structure and increasing its spatial stability. Upon heating, the surface expands significantly through the involvement of aluminum trihydroxide and magnesium hydroxide, forming an insulating barrier that prevents oxygen penetration and creates a porous carbon layer. This modification provides enhanced thermal insulation at high temperatures (200 degrees C) while also achieving effective smoke suppression and flame retardancy. Experimental trials revealed sustained thermal insulation for 2 h under 200 degrees C conditions, with the rear surface maintaining a stable temperature of 60 degrees C, indicating excellent insulation performance. Furthermore, the incorporation of these metal ions not only improved flame resistance but also enhanced mechanical stability, potentially expanding the industrial applications of cellulose-based aerogels.

The rational design of organic-inorganic hybrid architecture enables the creation of functional additives with tailored properties, enabling precise optimization of polymer composite material performance. Through molecular engineering, multi-site nucleophilic substitution between hexachlorocyclotriphosphazene (HCCP) and adenine to generate a P/N-rich hybrid ligand (AH ligand), then non-directional coordination self-assembly with transition metal ions (Co2+) to form multidirectionally crosslinked organic-inorganic coordination complex (AHcomplex). The molecular-scale multidirectionally crosslinked and micro-scale porous floral architecture of AHcomplex enables extensive interfacial interactions with the epoxy (EP) matrix, enabling homogeneous dispersion. At 2 wt% loading, the EP/AH-complex composites exhibit remarkable mechanical enhancement, with 94.4 % and 72.7 % improvements in tensile strength and elongation at break, respectively. The EP/AH-complex 2.0 composites also demonstrate superior thermal stability and flame retardancy, exhibiting a 30.7 % reduction in maximum thermal degradation. On the other hand, significant decreases of 41.0 %, 36.4 % and 51.4 % in peak heat release rate (PHRR), total smoke production (TSP), and peak CO production (P CO) for EP/AH-complex 2.0 composites were observed, respectively. The superior flame retardancy originates from the maximized catalytic sites and matrix contact mediated by high-surface-area AH-complex, which simultaneously accelerates the formation of a dense, thermally stable char layer, adsorbs combustible fragments, enhances radical scavenging, and dilutes flammable gaseous products, collectively achieving exceptional flame suppression.

The complex electromagnetic environment in national defense requires tailored microwave-absorbing materials for different scenarios. In aerospace, lightweight and multifunctional materials are especially important. While aerogels offer low density, they must be further modified to become effective microwave absorbers. Traditional fillers like carbon nanotubes often cause problems such as impedance mismatch, particle aggregation, and poor chemical reactivity, limiting their performance in aerogel systems. To overcome these issues, we used an electrostatic self-assembly strategy to deposit a FeCo-based metal-organic framework (MOF) onto black phosphorus nanosheets (BPNSs). The resulting BPNS@MOF was then integrated into a chitosan-derived aerogel through Schiff base reactions between the amino groups of the MOF and the aldehyde groups of glutaraldehyde. After freeze-drying and high-temperature pyrolysis, we obtained a lightweight, multifunctional carbon/BPNS@MOF aerogel (CS-2). CS-2 exhibits excellent electromagnetic properties, with a minimum reflection loss of -72.13 dB and an effective absorption bandwidth of 5.88 GHz. Radar cross-section simulations confirm its stealth potential. In addition, CS-2 shows ultralow thermal conductivity (0.05 W (m K)-1), superior fire resistance, and outstanding sound absorption performance (a 5.0 mm-thick sample achieves a sound absorption coefficient of above 0.95). These features demonstrate its strong potential for multifunctional aerospace and defense applications.

This study, grounded in sustainable development strategies, developed a shell-core flame retardant by coating ammonium polyphosphate (APP) with multiple layers of polyelectrolytes composed of chitosan (CS) and silicon dioxide (SiO2) through electrostatic interactions. The entire preparation process did not involve any organic solvents. The resulting APP@CS@SiO2-nBL (where "BL" denotes a bilayer structure of CS and SiO2, and "n" indicates the number of bilayers, ranging from 1 to 4) significantly enhanced the flame-resistant property of thermoplastic polyurethane (TPU). The TPU composite encompassing 20 wt% APP@CS@SiO2-4BL exhibited excellent thermal stability, where the maximum thermal decomposition rate declined by 21 % and the char residue elevated to 33.37 wt%. Additionally, this composite demonstrated superior performance in heat suppression and smoke reduction: the peak heat release rate, total heat release, peak smoke production rate, and total smoke release decreased 65 %, 86 %, 84 %, and 91 %, respectively, versus pure TPU. These enhanced properties relied on the multiple synergistic effects among APP, CS, and SiO2.

This study is dedicated to an in−depth analysis of the combustion characteristics of extruded polystyrene (XPS) as a building insulation material with the aim of accurately assessing its fire risk in the built environment. Innovatively, this research employed a cone calorimeter equipped with a self−designed insulating sample holder to conduct a systematic experimental study. Additionally, it performed a comprehensive analysis of the ignition characteristics, heat release rate, fire hazard, smoke release, and toxic gas emission of XPS materials. The experimental results revealed that the combustion behavior of XPS is influenced by multiple factors, including the content of flame retardants and external heat flux, which significantly affect the fire hazard of XPS. When the thermal radiation intensity escalates from 25 kW/m2 to 55 kW/m2, the peak heat release rate of XPS−B1 rises from 428 kW/m2 to 535 kW/m2, marking an increase of 25.00%. Conversely, the peak heat release rate of XPS−B2 surges from 348 kW/m2 to 579 kW/m2, reflecting a substantial increase of 66.38%. This research not only provides a solid theoretical foundation and detailed experimental data for the fire behavior of XPS materials but also holds significant practical importance for enhancing the fire safety of buildings. Overall, this research contributes to the scientific understanding of XPS insulation materials and supports the development of more effective fire prevention measures in construction.

The preparation of derivatives using metal-organic framework (MOF) as template is often accompanied by the loss of pore structure. Inspired by the distribution of strawberry achenes on skin, restriction sites based on biopolymers were introduced to reduce the loss of mesoporous structure. Hexachlorocyclotriphosphazene (HCCP) and melamine (MEL) are used as monomers to synthesize dodecahedral polyphosphazene (PZS) on ZIF67 (named as ZIF@PZM). The micropore structure of PZM allows hydrogen ions of alginic acid (AA) to pass through, thus etching the internal ZIF-67. The released cobalt ions are complexed to form cobalt alginate (CoA) biopolymer. At the same time, hydrogen-bonded supramolecular assembly of CoA with N-H of MEL occurs in PZM skeleton. Tessellation of CoA in PZM as a limiting site reduces the loss of mesoporous structure. As a result, a novel hollow dodecahedron flame retardant composed of two polymers is obtained (CoA/PZM). With the addition of 2.0 wt%, the total heat release (THR) and total smoke production (TSP) of EP/CoA/PZM composites decreased by 55.3% and 50.8%, respectively. The component of PZM significantly improved the UV resistance with a 98.3 % reduction in UV transmittance. CoA improved the compatibility between filler and EP matrix, enhancing mechanical properties. This work takes MOF as sacrificial templates, constructing multifunctional flame retardants with multiple elements and special nanostructures through the supramolecular assembly of biopolymers and PZM.

In this study, the authors conducted a series of one-dimensional spill fire experiments in a sealed model-scale ship cabin with different leakage rates to reveal the combustion characteristics. The results showed that a stable combustion stage with a consistent combustion area and flame height appears around the cut-off of the fuel, where the consumption of oxygen increases when the leakage rate increases. And the CO2 concentration increases more rapidly and the upward trend is found to appear earlier. Compared with the film thickness in the open space, that of the spill fire in the sealed ship cabin is slightly thinner because of the ventilation control effect. Using the "oxygen-consumption" method, the eta of this stage was calculated and verified with the "mass loss rate" method. With these two methods, the HRR of spill fie when burning steadily is calculated. This work also improved the predicting model for the flame height of rectangular pool fire and developed a predicting model for the flame height of a steadily burning spill fire. The error is 14.35 %. Additionally, a predictive model of thermal radiation risk in ship spill fire is developed, and the death risk and unacceptable risk areas are delimited.

Metal–organic frameworks (MOFs), an emerging class of crystalline microporous functional fillers, have garnered significant attention in materials science owing to their tunable pore architecture and abundant coordinatively unsaturated sites. However, MOF materials encounter substantial challenges in practical applications, including poor spatial dispersion, severe agglomeration, and insufficient interfacial compatibility with polymer matrix, which substantially impede their incorporation into polymer composite materials. Building upon the foundational research of our group in MOF surface modification and nanocomposite engineering, this work systematically investigates the hierarchical integration strategies of MOFs with dimensionally controlled nanomaterials (encompassing 0D nanoparticles, 1D nanofibers/nanotubes, 2D nanosheets, and 3D interconnected networks). Through precise modulation of interfacial chemistry and architectural design, we have successfully addressed the dispersion limitations of MOFs and significantly enhanced the synergistic effects within the composite matrix. Experimental results demonstrate that this novel integration approach effectively mitigates nanofiller aggregation and substantially enhances the flame retardancy, mechanical strength, and electrical conductivity of the resultant composites. A detailed examination has been conducted exploring how MOF-based nanocomposites integrate within the polymer matrix, encompassing fabrication approaches, physical and chemical properties, and prospective uses. Our investigation addresses existing obstacles while evaluating future directions within this expanding research domain. By offering both fundamental scientific understanding and concrete recommendations, this work aims to facilitate advances in developing advanced functional materials incorporating MOF-based nanomaterials. The findings presented serve as a foundation for researchers working toward innovative composite systems with enhanced capabilities and performance metrics.