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Artificial oxygenation facilities are installed in the high altitude airport living areas, and the fire behaviors of solid materials will change significantly under low-pressure with oxygen-enriched. The influence law of pressure and oxygen concentration on solid combustion rate was deduced from the perspective of heat and mass transfer. Carton fire experiments were carried out in the self-designed low-pressure oxygen-enriched chamber to measure parameters such as mass combustion rate, flame morphology and flame temperature during the combustion process, with a view to providing some basis for indoor fire safety in high plateau airports. The results showed that the relationship between the rate of combustion of carton and the pressure and oxygen concentration is , and the empirical formula is obtained through experimental results. At 60 kPa, as the oxygen concentration increased from 21% to 33%, the heat release rate grew by 63.56%, the total heat production increased by 8%, and the maximum flame temperature increased by 19%. Furthermore, flame shape had a thin high type into a wide low type, the color had a blue-yellow gradually turned into a bright color. The inhibition of carton combustion by low pressure can be significantly weakened by oxygen enrichment and the fire hazard increases. In addition, pressure was weakly correlated with mass loss and heat production at high oxygen concentration.

Nanofluidic osmotic energy, which can be directly converted into electricity, is considered a clean and sustainable energy that effectively utilizes salinity gradients. The rational construction of nanochannel is of great significance to ion transport and osmotic energy conversion, but there is currently little attention paid to naturally formed rough and irregular channels. In this study, a model that considers the effects of nanochannel cone angle and waveform surface on interface reaction coupling was established for osmotic energy conversion. The results indicate that cone angle and waveform have a significant effect on osmotic energy conversion. It is found that the reduction of cone angle and the addition of waveform will improve ion selectivity and increase energy conversion efficiency, and ion rectification effect of corrugated cylindrical channel is the most obvious. Meanwhile, enlarging waveform dimensions leads to a significant overlap of electric double layer, resulting in a growth in cation transference number and selectivity, thereby enhancing the system's energy conversion efficiency, which can reach 49.62%. At low concentration ratios, the waveform dimensions are inversely proportional to the maximum output power, whereas at high concentration ratios, increasing the waveform dimensions and applying the waveform at channel entrance can efficiently improve the maximum output power. [ABSTRACT FROM AUTHOR]

Oxygen enrichment at high altitudes indoors can be effective in meeting demand. However, the high oxygen environment inevitably brings about additional fire hazards, and the specific changes are still unclear. As pine wood is a common material in construction, this paper provides data support for fire protection for buildings in highland areas by studying the combustion characteristics of pine wood at different oxygen concentration (21.0%, 23.0%, 30.0%, 27.0%, 33.0%) under different atmospheric pressures (50.0 kPa, 60.0 kPa, 70.0 kPa). The results show the relations of mass loss rate and the oxygen concentration with different pressures: m ∝ P Y O 2 , ∞ 2 1.84 (m is the mass loss rate; P is the pressure; and Y o 2 is the oxygen concentration). The relation of flame spread rate and the oxygen concentration with different pressures is also shown: V f ∝ P Y O 2 4.5 1.2 ( V f is the flame spread rate). It was observed that the increase in pressure and oxygen concentration made the combustion reaction more complete, for burning time, flame area, flame propagation rate, MLR, flame temperature, and CO2 production increase, but CO shows an opposite trend. Oxygen enrichment will significantly increase the fire risk of pine wood within a low-pressure environment. [ABSTRACT FROM AUTHOR]

Short‐chain fluorocarbon surfactants grafted with alcohol, carboxyl and ester functional groups were prepared by quaternization with short‐chain perfluorobutyl sulfonyl fluoride as raw material. The structures of surfactants were characterized by infrared spectroscopy, nuclear magnetic resonance and mass spectrum. The surface activity, micelle formation process and micelle aggregation behavior of surfactants were studied by surface tensiometer, dynamic light scattering particle size analyzer and fluorescent spectrophotometer. The results show that the critical micelle concentration (CMC) of surfactants are 19.3, 7.8 and 2.2 mmol L−1, and the surface tension of the surfactant solution at CMC are as low as 17.3, 19.2 and 18.5 mN m−1, respectively. The standard Gibbs free energy (ΔGm0 ${\Delta G_{\rm{m}}^0 }$) values of surfactants are negative, and the absolute values of ΔGm0 ${\Delta G_{\rm{m}}^0 }$ are less than the standard Gibbs adsorption energy (ΔGa0 ${\Delta G_{\rm{a}}^{\rm{0}} }$), illustrating that the adsorption process is easier than the micelle formation process. In addition, the size distribution of the aggregates is much larger than that of spherical micelles, showing that the surfactant self‐assembled into larger aggregates in solution. The grafted hydrophilic functional groups show a significant effect on the performance of surfactants. The ester‐based surfactant has a lower CMC value, which has the advantages of small dosage, good economy and excellent application value. [ABSTRACT FROM AUTHOR]

Preparing fluorocarbon surfactant for aqueous film-forming foam is a complex process. Overcoming steric hindrance when introducing imidazolium to the fluorocarbon chain is a key challenge. In this significant work, we proposed a simple one-step route to prepare imidazolium-contained fluorocarbon surfactant under mild conditions. The FT-IR, 1H NMR, 13C NMR, MS, and TG technologies characterized the imidazolium-contained fluorocarbon surfactant by analyzing functional groups, molecular weight, and thermal stability. An equimolar mixture of imidazolium-contained fluorocarbon surfactant and C6H13NaO3S demonstrated high surface activity, enabling the foam to spread effectively on commercial fuels. The spreading coefficient of foam on n-cyclohexane met the US Military Specification. Coordinatively, the foam drained in time to maintain the stability and completeness of the aqueous layer, with a moderate 25% drainage time of 317 s and a proper foam expansion ratio of 10.5. In extinguishing experiments, the imidazolium-contained fluorocarbon surfactant/C6H13NaO3 mixture extinguished test fires in 65 s, suggesting an essential potential in the aqueous film-forming foam formula. [ABSTRACT FROM AUTHOR]

Aqueous film‐forming foams (AFFFs) are an important for fire extinguishing, and their key ingredient is fluorinated surfactant. In recent years, traditional long‐chain fluorinated surfactants have been banned by most countries because of their persistence, bio‐accumulation and toxicity. Therefore, increased attention has been paid to the research and development of short‐chain fluorinated surfactants. As is well known, the introduction of hydrophilic or hydrophobic groups in a surfactant affects its surface activity, and therefore, the fire extinguishing performance of AFFFs. In this work, a series of short‐chain fluorosurfactant‐based AFFFs with different hydrophobic chain lengths were prepared. The physicochemical performance of mixed systems (fluorinated surfactant plus sodium hexanesulfonate), including surface activity, spreading ability, foam expansion, drainage time, and the fire extinguishing and burn‐back performance of AFFFs were studied. The results show that the critical micelle concentration (CMC) and the surface tension (γCMC) at the CMC of mixed systems at 25°C are lower than 7.68 mmol/L and 16.51 mN/m, respectively. For mixed systems, the average spreading rate is more than 1.09 cm/s, the foam expansion is over 7.1, and the drainage time is greater than 3.28 min. The fire extinguishing time of AFFFs on fuels is less than 51 s while the burn‐back time is more than 15.18 min. The results imply a potential application prospect of the short‐chain fluorinated surfactants in AFFFs. [ABSTRACT FROM AUTHOR]

Liquid–liquid equilibrium and tie line data forthe nitricacid/phosphoric acid/water/tri-n-octylamine (TOA)system have been determined at 298.15 K for HNO3mass fractionsof 0.028 to 0.26 and H3PO4mass fractions of0.00 to 0.19. The distribution coefficients of nitric acid (D1) and water (D3) were studied, and the separation factors β(HNO3/H3PO4) was also investigated. The resultsshow that TOA is very selective, since only small quantities of waterand phosphoric acid are present in the organic phase, which indicatesthe good ability of TOA to extract nitric acid from nitric acid/phosphoricacid mixtures. The experimental tie line data were correlated usingthe nonrandom two-liquid (NRTL) model. TOA can be used as an effectiveextractant to separate nitric acid from the HNO3/H3PO4/H2O system. [ABSTRACT FROM AUTHOR]

The key components of aqueous film foaming foam extinguishing agents are fluorocarbon surfactants. Due to their toxicity and bioaccumulation, long-chain fluorocarbon surfactants have limited application prospects. Therefore, it is of great significance to study short-chain fluorocarbon surfactants as substitutes. In this work, three short-chain fluorocarbon surfactants with various hydrophilic groups and corresponding fire extinguishing agents were prepared. The physical and chemical properties of a single system and mixed system of fluorocarbon surfactants, including surface activity, spreading property, foaming property, 25% drainage time, and AFFF fire extinguishing property, were studied. For the results of the mixed systems, it was found that the critical micelle concentrations did not exceed 3.97 mmol/L and the minimum surface tension did not exceed 17.21 mN/m. Fluorocarbon surfactant solutions spread effectively on the surface of all fuels. The foam expansion is greater than 7.2, and the shortest of all 25% drainage times is 3.31 min. The extinguishing time of AFFFs on several fuel fires does not exceed 55 s, and the shortest burn-back time is 15.08 min. Anyways, these results indicate that the grafted hydrophilic short-chain fluorocarbon surfactants have significant application prospects in AFFFs., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)