During coal mining operations, large amounts of ultra-low concentration methane are vented directly into the atmosphere because they cannot be efficiently utilized, resulting not only in a waste of resources but also in an exacerbation of the greenhouse effect. Co-firing highly diluted methane alongside coal refuse in a fluidized bed offers a viable “waste-treating-waste” solution; however, it still faces challenges like sluggish reaction kinetics and elevated CO emissions under standard atmospheric conditions. Building on previous research, this study introduces oxygen-enriched combustion technology into this fluidized-bed system. By integrating a self-developed fluidized-bed thermal oxidation experimental platform with the Chemkin Pro chemical kinetics model, the study systematically investigates how an oxygen-enhanced environment influences the combustion behavior and reaction pathways when co-firing highly diluted methane with coal refuse. The results show that an oxygen-enriched atmosphere significantly lowers the critical conversion temperature of methane and significantly reduces CO emissions. Furthermore, combustion efficiency increases with rising oxygen concentration, whereas the discharge of contaminants like SO2 and NOx initially intensifies before stabilizing alongside further oxygen enrichment. Kinetic simulations confirm that an oxygen-enriched atmosphere increases the concentrations of O and OH radicals, accelerates chain oxidation reactions, and promotes the conversion of CO to CO2. However, the accelerated NO conversion pathway contributes to NOx formation to some extent. When the oxygen concentration exceeds 35 %, the NOx formation rate tends to stabilize, consistent with experimental results. By combining experimental investigation with chemical kinetic simulations, this study clarifies the self-sustaining combustion mechanism and energy conversion behavior of a gas–solid coupled system under complex oxygen-enriched atmospheres. The findings provide a theoretical basis for the efficient utilization of ultra-low concentration methane and the development of oxygen-enriched thermal conversion technologies for coal-derived solid waste. These findings have important implications for greenhouse gas mitigation and the achievement of carbon neutrality targets.

Thermal Hall effect is a critical probe for investigating carrier transport mechanisms in functional materials. However, conventional thermal Hall effect measurements are usually limited to thermal Hall conductivity, which prevents the determination of other performance parameters. This paper presents a thermal Hall effect measurement method based on suspended devices to address these limitations. In addition to thermal Hall conductivity, this method has the distinct advantage of enabling the simultaneous measurement of longitudinal thermal conductivity, electrical conductivity, and the Seebeck coefficient. An experimental system based on this methodology was established to facilitate multiphysics synergistic characterization under extreme conditions of low temperatures and high magnetic fields. The system was validated using a platinum wire with a diameter of 20 μm as a standard sample. The thermoelectric parameters measured within the 220–270 K temperature range exhibited excellent agreement with standard data. Furthermore, the thermal Hall conductivity of a strontium titanate (SrTiO3) single crystal was characterized at 9 T and 55–65 K. Following magnetic field normalization, the experimental data showed strong consistency with literature values. These results demonstrate that the proposed method enables the comprehensive measurement of multiple magneto-thermoelectric parameters, providing a precise experimental foundation for clarifying magneto-thermoelectric coupling transport mechanisms.

Narrow-bandgap semiconductors such as InSb combine high carrier mobility with favorable band topology, yet large lattice thermal conductivity and bipolar conduction at elevated temperatures have long capped their thermoelectric figure of merit. Here, we show that introducing reactive Co2O3 nanoprecursors into an optimized In1.01Sb matrix triggers a spontaneous solid-state reaction that simultaneously reconstructs the microstructure and modulates the electronic band structure. The reaction yields a CoSbx@In2O3@CoSb3 core-shell heterostructure that is coherent with the surrounding matrix and thermodynamically stable under operating conditions. The acoustic-impedance contrasts across the multilayered interfaces curtail the mean free path of low-to-mid-frequency acoustic phonons, which are inaccessible to point-defect scattering alone, and thereby suppress lattice thermal conductivity across the full acoustic spectrum. Co incorporation concurrently shifts the Fermi level toward the heavier secondary conduction valleys, raising the density-of-states effective mass and limiting bipolar excitation at high temperatures. Together, these effects yield a peak zT of similar to 0.7 at 733 K and a projected single-leg conversion efficiency of similar to 5%. The approach provides an effective means of addressing these transport bottlenecks in other narrow-gap thermoelectric systems.

To investigate the thermal damage characteristics of and its regulatory on seepage performance, this article reconstructed the 3D geometric structure of coal and quantitatively analyzed the variation of structure parameters including pore, throat, and permeability. The results show that with the increase of temperature, the pore structures extend from internal pore-enriched areas toward the surface of coal. Below 200 degrees C, pores mainly develop in the originally enriched areas, while above 200 degrees C, the distribution of internal pore becomes more uniform, and pores at different locations shows approximately synchronous development. The average coordination number of pores and the number of throats increase, and the equivalent radius of throats expands while the tortuosity decreases. At temperatures below 200 degrees C, the increase of permeability is primarily due to the rise in the number of pathways. Above 200 degrees C, the size of throats becomes the dominant factor. Within 350 degrees C to 400 degrees C, intense pyrolysis of coal led to the fluctuations in pore structures and seepage parameters. The findings clarify the temperature response of pore structures and seepage performances of coal, providing theoretical guidance for the heat transfer and mass migration mechanism of high-temperature coal in the fire zone.

Eu3+-doped LaP3O9 is a promising red phosphor, yet its luminescent efficiency is often limited by particle agglomeration during synthesis. To address this, we developed a CDPVA-assisted co-precipitation method to fabricate LaP3O9: Eu3+ phosphors. Comprehensive characterization (XRD, FT-IR, SEM, TG/DTG, PL, UV-Vis) reveals that the introduction of CDPVA not only preserves the host crystal structure but also effectively inhibits particle agglomeration, yielding a uniform morphology with enhanced thermal stability. Spectroscopically, CDPVA addition induces a new emission band at 639 nm (D-5(0) -> F-7(1)) and remarkably intensifies the dominant red emission at similar to 670 nm (D-5(0) -> F-7(2)), indicating improved energy transfer. Through systematic optimization, an optimal combination of a 6 % Eu3+ doping concentration and a 700 degrees C calcination temperature was identified, which synergistically maximizes the luminescent performance. This work demonstrates a facile and effective strategy for engineering high performance LaP3O9 based phosphors by concurrently controlling composition, morphology, and interfacial interactions.

Excessive carbon emissions from energy consumption intensify the greenhouse effect and increase the frequency of extreme heat events, posing health risks to individuals engaged in daytime outdoor activities. Consequently, energy-free personal thermal management technologies have attracted growing attention. Passive daytime radiative cooling (PDRC) is a cooling method that provides high solar reflectance during the day and utilizes an object's intrinsic thermal radiation to emit its own energy into outer space (similar to 3 K) without consuming any external energy. In recent years, significant advances in PDRC have been reported in applications including buildings, electronic devices, and personal thermal management. However, systematic reviews focusing on PDRC textiles remain limited, and many laboratory-developed systems still fall short of practical cooling requirements. Herein, we introduce the fundamental principles of PDRC and summarize recent progress in wearable PDRC textiles from the perspective of fiber fabrication techniques, with particular emphasis on material selection and structural design strategies. Furthermore, key challenges in textile applications are discussed, and thermal drawing is highlighted as a promising strategy for constructing micro/nanostructures, offering a scalable route toward sustainable and multifunctional radiative cooling fibers.

Underground heat hazards in deep coal mines require compact air coolers capable of providing both cooling and dehumidification under confined hot humid conditions. This study numerically compares helical tube air coolers with parallel-bundle and wound-bundle arrangements under the same heat transfer area to clarify the influence of tube-bundle arrangement on shell-side heat and mass transfer. The air cooler performance was evaluated in terms of heat and mass transfer coefficients, pressure drop, total cooling power, net volumetric cooling power density, and air-side temperature effectiveness. The results show that the wound-bundle configuration enhances shell-side heat and mass transfer, increasing the heat and mass transfer coefficients by 23-29% and 8-20%, respectively, over an air supply rate of 0.089-0.801 m(3).s(-1) . Although the pressure loss penalty increases, the wound-bundle cooler provides 14.9-19.0% higher total cooling power and 21% higher temperature effectiveness in average than the parallel-bundle design. When pumping power and device volume are considered, the woundbundle configuration achieves an average of 14.9% higher net volumetric cooling power density within the recommended operating range. Parametric analysis further shows that, among the investigated wound-bundle cases, a 150 mm center cylinder and a 9 mm interlayer spacing yield the highest net volumetric cooling power density, whereas increasing the interlayer spacing broadens the recommended flow rate range for positive net cooling gain and reducing the tube diameter further increases the net volumetric cooling power density. These results provide guidance for the structural and operational design of compact mine air coolers for heat hazard management in deep underground coal mines.

Coalmine mixed dust possesses a complex composition, and its fundamental characteristics vary accordingly. To investigate the wettability of mixed coal-rock dust, this study employed both experimental testing and molecular dynamics (MD) simulations. The effects of the coal-rock ratio on dust wettability were examined, along with the dust suppression efficacy of two surfactants and binders. The proportion of rock dust was found to be the most influential factor on the wettability of the mixed dust. When pure water was applied, the contact angle for all mixed dust samples fell within the range of 50- 70 degrees. The addition of surfactants AEO-9 and SDBS to the water improved the dust settling rate, wind erosion resistance, and water retention across all samples tested. The optimal dust suppressant formulation was identified as 0.04 wt% polyacrylamide + 0.50 wt% AEO-9. MD simulations revealed that the adsorption width of water molecules on rock surfaces was approximately 4.5 times greater than that on coal surfaces. For pure coal dust, AEO-9 yielded a larger adsorption width and a steeper mean squared displacement curve slope compared with SDBS. These values were 18.17 and 3.17 & Aring; higher, respectively, than those in the pure water system. Although the adsorption widths of SDBS and AEO-9 on rock dust were similar, the overall findings confirm that AEO-9 performed best for both pure coal dust and coal-rock mixed dust. This research contributes to the control of mixed dust hazards and to the evaluation of the environmental effectiveness of dust suppressants.

Pyrolysis semi-coke plays a significant role during the spread of subsurface coal fires and the reignition of extinguished fire areas. In order to explore the combustive properties of pyrolysis semi-coke from non-stick coal, its combustion process was experimentally investigated. The kinetic characteristics of raw coal and semi-coke, along with the effect of semi-coke pyrolysis temperature, were analyzed. Meanwhile, the correlation analysis between reaction kinetic parameters and main microscopic functional groups was conducted to identify the transformation of critical functional groups during semi-coke combustion. The primary findings are summarized as follows: As the pyrolysis temperature increases, the oxygen-absorption mass-gain stage gradually expands, and the thermal decomposition/combustion mass-loss stage presents a shortening trend. The quantity of heat release increases initially and then decreases, reaching its maximum in the 400-500 °C range. The apparent activation energy (E) during semi-coke decomposition/combustion at high-temperature decreases progressively with the increase of conversion rate. The average value of E for semi-coke initially decreases and subsequently increases with rising pyrolysis temperature. It reaches the minimum at 500 °C. The reaction mechanisms of raw coal and semi-cokes pyrolyzed at 300 and 400 °C respectively correspond to spherically symmetrical phase boundary reactions, spherically symmetrical three-dimensional diffusion, and reaction orders. The semi-coke pyrolyzed at 500 and 600 °C belongs to the random nucleation and subsequent growth. From the microscopic perspective, as semi-coke pyrolysis temperature increases, the critical functional groups affecting the decomposition/combustion reaction transform from aliphatic hydrocarbons to oxygen-containing functional groups and then to aromatic hydrocarbons. These results offer theoretical groundwork for in-depth comprehension of the dynamic process associated with underground coal fire spread and the reignition characteristics in extinguished fire zones.

The pursuit of power density and integration in advanced electronic devices poses a risk of electrostatic discharge to traditional packaging materials. Albeit optimizing the insulation performance of packaging materials seems to be an effective strategy, long-term charge accumulation will seriously threaten the reliability of devices. Here, we fabricate an adaptive field grading material that can transition between insulating and conductive states, enabling the rapid dissipation of charges during electrostatic discharge events. A silicon carbide-derived nanofiber mat with a "step-by-step" double Schottky barrier was synthesized using electrospinning. The coordination between the insulating epoxy-based matrix and the oriented semiconductor fiber mat achieves desirable electric field grading performance at ultra-low content (0.3 vol%), and the switching electric field of the insulation-conductive transition can be precisely customized through the nanofiber mat content. Given the diversity between insulating polymers and metal oxides, these findings have prominent guiding significance for electrostatic protection of numerous electronic devices.

The coupled disaster of coal spontaneous combustion (CSC) and gas explosions in the goaf of high-gas mines is a critical focus for disaster prevention. This paper reviewed the current research on these mechanisms and associated risk assessments, aiming to support the development of prevention technologies in China. The review covered three areas: Gas explosion mechanisms, coal spontaneous combustion characteristics and risk assessment, and the coupling laws and risk evaluation of these disasters in goafs. Five key issues for future research are identified: The need for more detailed studies on the explosion mechanisms of multi-component gas mixtures; further exploration of coal spontaneous combustion evolution and risk determination in goafs; systematic improvement of theories on coupled coal combustion and gas explosion disasters; clarification of flame shock wave propagation in gas explosions; and the urgent development of a risk evaluation system for these coupled disasters. Continuous research in this field is of vital importance for enhancing the safety standards of coalmines, promoting the sustainable development of the coal industry, and achieving the goals of carbon peak and carbon neutrality.

Coal spontaneous combustion (CSC) poses persistent safety and environmental challenges in underground mining. In this study, a novel in-situ sealing and water-retention double-network gel (S/C/P/T) was developed. The gel forms through ionic crosslinking between controlled release of Ca2 + from calcium L-lactate (CL) and sodium alginate (SA), combined with dynamic borate ester bonds between hydrolyzed sodium tetraborate (ST) and polyvinyl alcohol (PVA). Orthogonal experiments determined the optimal formulation: 2.0 wt% SA, 3.2 wt% PVA, 2.3 wt% CL, and 1.4 wt% ST, based on gelation time and water retention. FTIR and SEM investigated the formation of ionic and dynamic borate ester crosslinking, confirming a compact, continuous three-dimensional interpenetrating network. The gel evidenced the significant shear-thinning behavior and structural stability, with a maximum compressive strength of 38.92 kPa. Under varying pressures and flow rates, it achieved an average sealing efficiency exceeding 77.5%. Compared with the single-network gel, the S/C/P/T gel significantly reduced CO generation and increased the activation energy of the coal-oxygen reaction. Additionally, it exhibited higher characteristic temperatures, raising the maximum mass loss temperature of the coal sample by 7.70 degrees C. Molecular dynamics simulations yielded that the gel can overcome hydrophobic repulsion on the coal, facilitating the wetting and penetration of water molecules into the coal. Macroscopically, the gel isolated oxygen by wetting and encapsulating the coal, thereby suppressing exothermic oxidation reactions. Consequently, CSC is inhibited, and greenhouse gas emissions are reduced. These findings provide theoretical and engineering support for the prevention and control of CSC, as well as for environmental protection.

N-type thick TE fibers remain an open question to obtain fibers with both high TE properties and flexibility for wearable applications. Moreover, traditional thermoelectric fibers rely on reducing thickness for a suppressed area moment of inertia for high flexibility, which will deteriorate the output performance. Herein, as inspired by the gradient structure in soft biological materials, we report a type of n-type composite TE fibers possessing radial gradient hierarchy through in situ growing S-doped Ag2Se nanocrystals into wet-spun porous aramid nanofibers after ultrafast sintering. The coupling of gradient architecture and interfacial interaction between Ag2Se and nanofibers imparts gradient fibers with a harmonious balance between TE performance and mechanical flexibility. We qualitatively elucidate that the role of radial gradient structure endows fibers with stress redistribution and energy absorbance toward improved flexibility. The optimal gradient fiber with tuned carrier and phonon transport exhibits a ZT of 0.42 at room temperature and a bending radius of 5 mm. Its TE fabric shows a normalized power of 82 μW m-2 K-2, enabling a high thermal resolution of 0.03 K for precise temperature sensing.