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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]

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]

A new method for studying the two-dimensional spreading properties and sealing characteristics of surfactant solution on oil surface was provided. The actual spreading situation of the C4-Br/oil systems in axisymmetric geometry was observed directly using HD camera for the first time and the results showed that the aqueous film expanded outwards in a circle with the guiding device as the center. Meanwhile, the relation between spreading radius and time was investigated and evaluated using the model for surface-tension-viscous regime. The root-mean-square deviation (RMSD) values obtained from the correlation for all of the systems we studied below 1.64, indicating a good agreement between the experimental and theoretical values. The results of sealing experiments showed that the aqueous film could absolutely seal the oil surface for 27–65 s and the sealing effect would be lost after 216–742 s for different systems. The stronger the volatility was, the shorter the sealing time was. Additionally, the volume percentage of oil vapor with film was always lower than that without film even when the evaporation was saturated. These findings were of great significance to guide the preparation of efficient AFFF. [ABSTRACT FROM AUTHOR]

A novel short fluorocarbon chain cationic surfactant has been synthesized to reduce the bioaccumulation of traditional fluorocarbon surfactants and maintain excellent surface properties simultaneously. The structure, surface activity, and micelle formation of surfactants have been investigated by surface tension, conductivity, dynamic light scattering, steady‐state fluorescence, Fourier transform infrared spectroscopy, and Nuclear magnetic resonance. The novel surfactant (yield more than 81%) exhibited good surface activity, the critical micelle concentration and surface tension were below 2.35 mmol L−1 and 20.54 mN m−1 in the range of temperature from 288 to 303 K, respectively. The surface tension decreased to 17.45 mN m−1 with an increase in temperature. The thermodynamic parameters (ΔGm0, ΔHm0 and ΔSm0) of micellization for surfactants were evaluated, which implying the micellization process was contributed primarily by the entropy driving. In addition, the aggregation behavior of surfactants was also studied in detail, which demonstrated a small micelle aggregation number of 9.40 and large size distribution of 164–342 nm. [ABSTRACT FROM AUTHOR]

Spilled fuel that comes in contact with hot surfaces can cause a fire, and to mitigate this type of fire, we researched the evaporation patterns and heat transfer mechanisms of fuel droplets on such surfaces. Glass heating substrates were used to experimentally investigate the evaporation behavior of acetic acid, ethanol, acetone, ethyl acetate, n-heptane, and cyclohexane. Infrared imaging technology and volume estimation method were used for the experimental analysis. The study revealed various thermal patterns on the surfaces of different droplets. Hydrothermal waves (HTWs), Bénard-Marangoni (B-M) cells, cyclic thermal patterns, and double-vortex thermal patterns were observed on different types of fuel droplet surfaces. The energy absorption and breakage of intermolecular hydrogen bonds are related to the formation of HTWs and B-M cells. As the height of the droplets decreased, the rate at which the six fuel droplets evaporated was observed to decrease initially and then increase. The results of this experiment indicate that the evaporation rate of droplets is largely determined by the saturation vapor pressure. • Hydrogen bonds were related to the formation of the Marangoni flow. • Surface tension gradient of acetone produce a double-vortex thermal pattern. • The evaporation rate is largely determined by the saturation vapor pressure. [ABSTRACT FROM AUTHOR]

Oxygen-enriched indoor in the high plateau can validly address the plateau reaction, but increases the probability of fire and the hazards after it occurs. The intention of this article was to estimate the influence of oxygen enrichment in low-pressure environment on the combustion behavior of characteristic combustibles based on indoor corrugated cartons, which is believed to be profitable for high plateau indoor fire safety. The ignition time, mass loss, flue gas properties, heat flux and axial temperature were investigated in comparative trials performed in a hypobaric chamber to emulation the particular environment. A new correlations to predict the burning rate of solid materials under varying pressures and oxygen concentrations was proposed and fitted by experimental data showing a good agreement. The results show that inhibition of solid combustion by low pressure can be significantly weaken by oxygen enrichment. As oxygen concentration increases, flame shape had a thin high type into a wide low type, the color had a blue-yellow gradually turned into a bright color. Moreover, at high oxygen concentration, pressure is weakly correlated with ignition time, mass loss and heat production. The fire performance index and thermal release index indicators show a significant raise in fire hazard of oxygen-enriched atmosphere. [ABSTRACT FROM AUTHOR]

Surface properties of three fluorocarbon surfactants with different carbon chain lengths were studied at low pressures of 94.6, 74.1 and 61.0 kPa, respectively. The results showed that the saturation adsorption capacity and the critical micelle concentration (CMC) decreased, while the average molecular area (AS) and the surface tension at CMC (γCMC) of fluorocarbon surfactants increased with decreasing pressure. The surface tension (γ) decreased with the decrease of pressure when the concentration of fluorocarbon surfactants was low. However, γ tended to be stable and increased with the drop of pressure when the concentration of surfactants was close or reach to CMC. In addition, the foaming and spreading performance of fluorocarbon surfactants decrease with the decrease of pressure, and the combination of fluorocarbon and hydrocarbon surfactants is beneficial to the improvement of performance (mixed systems: foam expansion E>6, 25% drainage time t25%>241 s, 1/2 defoaming time t1/2>851 s, spreading amount Vs>223 μL, spreading time ts<2 s). Further fire extinguishing experiment found that the influence of low pressure environment on fuel combustion characteristics is the key factor to determine fire extinguishing performance, while the influence of aqueous film‐forming foam (AFFF) performance is small. And AFFF based on the environmental‐friendly surfactant C4F9SO2NH(CH2)2N+(CH3)2CH2BrCH2OH (FC‐4) is an effective fire extinguishing agent under low pressure. [ABSTRACT FROM AUTHOR]

A new type of turn-on fluorescent probe CF-AC for the detection of Cys was firstly reported. The probe exhibited an excellent response to Cys with high selectively and sensitivity. In the presence of Cys, two fluorescence emission peaks at 525 nm and 650 nm appeared accompanied by the fluorescence color change from blue to red. Morever, the probe had good biocompatibility and could be successfully used for fluorescence imaging of Cys in MCF-7 cells. [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]

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]

Aqueous film-forming foam (AFFF) is a very important extinguishing agent for hydrocarbon fuel fires. The spreading performance of AFFF is one of the key factors to decide its extinguishing efficiency. There are many parameters that affect the spreading performance of AFFF, but few studies have been done on its spreading mechanism. A method for studying the spreading performance of surfactant solution on different oil surfaces was provided in this work. Additionally, the kinetics of C4-Br/CH 3 (CH 2) 5 NaO 3 S, C6-Br/CH 3 (CH 2) 5 NaO 3 S and C8-Br/CH 3 (CH 2) 5 NaO 3 S equimolar system spread on the surfaces of cyclohexane, n -heptane, aviation kerosene, solvent naphtha and diesel oil 0# were investigated. Meanwhile, the relationship between spreading length and time at 25℃ were obtained and the experimental data were evaluated using the model for surface-tension-viscous regime. The root-mean-square deviation (RMSD) values obtained from the correlation using surface-tension-viscous regime model for all of the systems we studied below 3.41, indicating a good agreement between the experimental and theoretical values. It meant that the surface-tension-viscous regime model could be used to predict the process of the aqueous film formed by surfactant solution spread on the hydrocarbon oils. Furthermore, the theoretical spreading rate (R) and average spreading rate (R ¯) from 0 to 50 s of C4-Br/oil, C6-Br/oil and C8-Br/oil systems were also investigated. The results showed that the R decreased with increasing time and the rate of decline slowed down gradually. The R ¯ increased with the increase of fluorocarbon chains. In particular, the effect of fuel kinematic viscosity on spreading rate was also very obvious. The greater the kinematic viscosity of fuel, the smaller influence of the surfactant tail length on spreading rate. [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]

Grain boundary engineering (GBE) provides an effective approach for tailoring the properties of metallic materials by optimizing the grain boundary character distribution (GBCD). Using electron backscatter diffraction analysis and uniaxial tensile testing at room temperature, this study systematically investigated the impact of GBE-type thermomechanical processing (TMP) on the ductility of an Incoloy 925 nickel-based superalloy (Alloy 925). The results showed that at 5 % strain, increasing the annealing temperature results in larger twin-related domains through strain-induced boundary migration. The GBE-type TMP can significantly enhance the ductility of Alloy 925, namely, the elongation increases from 64.22 % to 95.86 % as the annealing temperature increases from 1050 °C to 1100 °C. The evolved GBCD introduces more coherent twin boundaries with lower average residual Burgers vectors, enabling efficient dislocation transmission. In addition, extensive twinning can widely generate some soft orientations and simultaneously reduce the average Taylor factor within the twin clusters, leading to easy dislocation activation during plastic deformation. The synergistic effect of the optimized grain boundary network and twin cluster anisotropy promotes uniform plastic flow and effective strain accommodation, thereby enhancing the ductility of Alloy 925. Overall, this work provides novel and valuable insights into ductility optimization through GBE in a nickel-based superalloy. [ABSTRACT FROM AUTHOR]

Cryogenic deformation was introduced in thermomechanical processing to restrict dislocation mobility and tailor the initial dislocation distribution at the deformation stage, subsequently followed by annealing treatment to alter the grain boundary characteristic distribution with a view to the feasibility of grain boundary engineering in Incoloy 925. The microstructural evolution deformed at cryogenic (77 K) and room temperature (298 K) under various rolling reductions and annealing conditions was systematically studied to optimize the grain boundary network, which is evaluated using multi-source quantitative statistics of the twin related domains. The results showed that cryogenic deformation can adjust the dislocation accumulation mode and plastic deformation mechanism. Geometrically dislocation distributions, reconstructed by HR-EBSD device, with fishbone-like, ribbon-like or lamellar characteristics can be observed for the deformed specimens. During the subsequent annealing, the samples with 5% and 15% pre-strain are incapable of producing the ideal twin related domains, while the sample annealed at 1075°C with 10% pre-strain show the optimization of GBCD with the highest Σ3 n (n = 1, 2, and 3) boundary fraction being 69.67%. Compared with the room temperature pre-deformation, cryogenic deformation can effectively reduce the critical temperature of GBE, and also leads to the Σ3 n grain boundaries proportion increasing from 31.47% to 67.46% in 10%/1050°C sample. Meanwhile, with the appropriate strain, cryogenic deformation is more conducive to optimizing the GBCD than room-temperature deformation. • Cryogenic deformation was applied in TMP to tailor dislocation accumulation and GBCD. • GNDs with fishbone-like, ribbon-like, and lamellar are observed after cryogenic deformation. • Modified GBCD is realized by cryogenic deformation under appropriate strain. [ABSTRACT FROM AUTHOR]

In order to purify phosphoric acid, the suspension melt crystallization process was studied. The suspension crystallization experiments were carried out with 80, 84 and 88 wt% phosphoric acid melt at the cooling rates of 0.05, 0.1 and 0.2 K/min, respectively. Sweating experiments were executed for various crystals obtained in suspension crystallization step. The purification effects of the sweating parameters including sweating time, initial inclusion amount and initial impurity content were studied. The inclusion fraction increases with the increase in cooling rate. The inclusion fraction of the crystals which were formed with feed concentration of 84 wt% phosphoric acid melt is lowest among the three feed concentrations. Different impurities have different purification performances during sweating. High inclusion amount and low impurity concentration favor the purification of H3PO4·0.5H2O crystals during sweating. [ABSTRACT FROM AUTHOR]