Construction of Super-Hydrophobic Lignocellulosic Nanofibrils Aerogels as Speedy Oil Absorbents.

Lignocellulosic nanofibrils (LCNF) aerogels have a three-dimensional structure, with large specific surface area, low density, which is promising to be developed into a new type of adsorbent with high absorption capacity. However, LCNF aerogels have the problem of simultaneous oil and water adsorption. This high hydrophilicity directly leads to low adsorption efficiency in oil-water systems. This paper suggests a facile and economical method for the synthesis of biocompatible CE-LCNF aerogels using LCNF and Castor oil triglycidyl ether (CE) was successfully established. The use of LCNF enabled aerogels to possess remarkably uniform pore size and structural integrity, while the introduction of hydrophobic silica produced stable superhydrophobicity for more than 50 days at room temperature. These aerogels presented desirable hydrophobicity (131.6°), excellent oil adsorption capacity (62.5 g/g) and excellent selective sorption property, making them ideal absorbents for oil spill cleaning. The effects of ratios of LCNF to CE composition, temperatures and oil viscosity on the oil adsorption performance of aerogels were estimated. The results displayed that the aerogels had the maximum adsorption capacity at 25 °C. The pseudo-secondary model had higher validity in oil adsorption kinetic theories compared to the pseudo-first-order model. The CE-LCNF aerogels were excellent super-absorbents for oil removal. Moreover, the LCNF was renewable and nontoxic, which has the potential to promote environmental applications.

Modified approaches to prepare nano-magnesium silicates with hierarchical pore structure and their performance towards adsorption of Cd2.

A series of flower-like magnesium silicate samples with hierarchical pore were prepared by the solvothermal method under template-free conditions using sodium dodecyl sulfate as the modifier and ethanol-water as the solvent. These samples were characterized by various methods and were evaluated for the adsorption of heavy metal Cd2+. The results showed that the adding modifier did not change the crystal structure of the magnesium silicate samples. In the range of 2~80 nm, they still showed hierarchical pore distribution mainly composed of mesopores and macropores, which facilitates the rapid transport of adsorbent within the pore channel. Therefore, the adsorption of Cd2+ was greatly accelerated. Meanwhile, the larger specific surface area (as high as 553 m2/g) of these samples significantly increased the theoretical maximum adsorption amount of Cd2+ up to 295.3 mg/g due to more available adsorption sites. The adsorption dynamic behavior of the samples on Cd2+ was in accordance with the pseudo-second-order adsorption model, and their thermodynamic behavior follows the Langmuir adsorption model. The adsorption mechanism of the sample was proposed as electrostatic adsorption and exchange of metal ions and acidic groups on its surface with ions in solution. The obtained magnesium silicate materials are expected to remove heavy metals from wastewater.

The Synthesis and Polymer-Reinforced Mechanical Properties of SiO2 Aerogels: A Review.

Silica aerogels are considered as the distinguished materials of the future due to their extremely low thermal conductivity, low density, and high surface area. They are widely used in construction engineering, aeronautical domains, environmental protection, heat storage, etc. However, their fragile mechanical properties are the bottleneck restricting the engineering application of silica aerogels. This review briefly introduces the synthesis of silica aerogels, including the processes of sol-gel chemistry, aging, and drying. The effects of different silicon sources on the mechanical properties of silica aerogels are summarized. Moreover, the reaction mechanism of the three stages is also described. Then, five types of polymers that are commonly used to enhance the mechanical properties of silica aerogels are listed, and the current research progress is introduced. Finally, the outlook and prospects of the silica aerogels are proposed, and this paper further summarizes the methods of different polymers to enhance silica aerogels.

The Cytotoxicity of Tungsten Ions Derived from Nanoparticles Correlates with Pulmonary Toxicity.

Tungsten carbide nanoparticles (nano-WC) are prevalent in composite materials, and are attributed to their physical and chemical properties. Due to their small size, nano-WC particles can readily infiltrate biological organisms via the respiratory tract, thereby posing potential health hazards. Despite this, the studies addressing the cytotoxicity of nano-WC remain notably limited. To this purpose, the BEAS-2B and U937 cells were cultured in the presence of nano-WC. The significant cytotoxicity of nano-WC suspension was evaluated using a cellular LDH assay. To investigate the cytotoxic impact of tungsten ions (W6+) on cells, the ion chelator (EDTA-2Na) was used to adsorb W6+ from nano-WC suspension. Subsequent to this treatment, the modified nano-WC suspension was subjected to flow cytometry analysis to evaluate the rates of cellular apoptosis. According to the results, a decrease in W6+ could mitigate the cellular damage and enhance cell viability, which indicated that W6+ indeed exerted a significant cytotoxic influence on the cells. Overall, the present study provides valuable insight into the toxicological mechanisms underlying the exposure of lung cells to nano-WC, thereby reducing the environmental toxicant risk to human health.

Organ distribution of Nano-WC particles after repeated intratracheal instillation into the lungs of SD rats and subsequent organ injury.

Nano-tungsten carbide (nano-WC) is widely used in composite materials due to its special physical and chemical properties. Owing to their small size, nano-WC nanoparticles easily enter organisms through the respiratory tract, which may cause health hazards. However, only a few studies have reported the toxicity of nano-WC. In this study, a 10 mg/kg nano-WC suspension and 0.9% normal saline were quantitatively perfused into the lungs of two groups of healthy male SD rats by tracheal instillation, and the in vivo pulmonary toxic effects were systematically evaluated. Additionally, as multiple organs and tissues are involved, systemic effects were observed throughout the body and mainly manifested as inflammatory damage. The concentrations of tungsten ions in various organs and alveolar lavage fluid were measured by ICP-MS, and the results showed that the lung was the target organ, as it had the highest concentration of ions. In addition, the abnormal increases in the tungsten ion concentrations in the liver and kidney may be closely related to the immune damage we observed. This study provides a theoretical basis and data support for the systematic evaluation of the health hazards of nano-WC and a reference for the safe use of nanomaterials.

Study on the effect of nanoparticles combined with silicone surfactant and cationic surfactant on foam and fire extinguishing performance.

Aqueous film-forming foam (AFFF) in firefighting foam can effectively extinguish oil fire. However, AFFF will be phased out due to the presence of persistent organic pollutants such as perfluorooctane sulfonates. It is necessary to explore environment-friendly foam extinguishing agent. Silicone surfactant is a kind of environmentally friendly surfactants with high surface activity, which can be used as a substitute for fluorocarbon surfactant. In this study, silicone surfactant and cationic surfactant were combined to adsorb nanosilica particles to form a multiphase system. The foaming property and foam stability of the multiphase system were tested by stirring method. The foam suppression effect on fuel vapor, fire extinguishing, and burn-back performance was tested by self-designed foam suppression device and foam generating device of porous glass with recyclable liquid supply. The experimental results show that foam stability is enhanced and the foaming property is slightly decreased after the addition of nanoparticles. When the component of three-phase foam reaches the optimum, its suppression effect on fuel vapor is better than that of two-phase foam. The results of fire extinguishing and burn-back performance test showed that the fire extinguishing effect of three-phase foam was slightly worse than that of AFFF, but it has extremely strong burn-back performance.

Preparation and study of the flame retardant properties of C60/PMMA microspheres.

In this paper, highly flame retardant C60/PMMA composites were prepared using an in situ polymerization method by introducing fullerene (C60) into polymethyl methacrylate (PMMA) to improve its combustion characteristics. The apparent morphologies of PMMA and C60/PMMA microspheres were observed by scanning electron microscopy (SEM), and the structure was characterized by infrared spectroscopy (FT-IR). The thermal stability and flame retardancy were characterized using a synchronous thermal analyzer, a cone calorimeter and an oxygen index tester. The results show that the maximum initial decomposition temperature of C60/PMMA-2 (prepared using C60 with a concentration of 2 mg mL-1) is 234.89 °C, which is about 59.89 °C higher than that of PMMA, and the thermal stability is the best. The limiting oxygen index of the C60/PMMA-2 composite is 21.8, which is 28.2% higher than that of pure PMMA. In addition, the peak heat release rate (PHRR) of C60/PMMA is reduced by 630.4 kW m-2 when compared with pure PMMA, which means that the flame retardant property is improved. Meanwhile, the mechanical properties of the PMMA are also improved by adding C60.

Safety Criteria for Solid-Liquid Heterogeneous Systems in Semibatch Reactors.

An exothermic reaction in a semibatch reactor can potentially cause thermal runaway due to evolved energy accumulation or a secondary reaction. This research aims to propose safety criteria for solid-liquid reactions in semibatch reactors. Simulation modeling was carried out to build thermal runaway criteria for solid-liquid reactions in semibatch reactors. A new model for the energy and mass balance of solid-liquid reactions was successfully established. Criteria for the safety boundary diagram and the temperature diagram were ameliorated for solid-liquid reactions. The results showed that the dissolution heat has a great influence on the thermal behavior of the reaction. Experiments to neutralize citric acid and sodium hydroxide were carried out to determine the critical parameters for the neutralization reaction using the temperature diagram criterion. The proposed criteria would be reasonably expected to provide some guidance for chemical process optimization and safety design for engineering.

A Series of Novel Flame Retardants Produced with Nanosilica, Melamine, and Aluminum Diethylphosphinate to Improve the Flame Retardancy of Phenolic Resin.

To facilitate the flame retardancy of phenolic resin (PF), a series of novel flame retardants with nano-SiO2, melamine, and aluminum diethylphosphinate (ADP) were freshly prepared and tested. A thermogravimetric analysis, cone calorimeter, and scanning electron microscopy were employed to determine the thermal decomposition, flame retardancy, combustion properties, and structure of the carbon residue layer of PF. The pyrolysis kinetic parameters of modified PF were then computed, and the pyrolysis process was appraised. The results indicated that when 1.5 wt % of nano-SiO2, 3 wt % of melamine, and 15 wt % of ADP were added to PF, the limiting oxygen index value reached 39.6%, and UL-94 passed the V-0 level. A substantial synergistic effect was also observed. The thermogravimetric analysis revealed that the char residue at 800 °C reached 59.93 wt %. Furthermore, in the cone calorimeter test, the total thermal release and thermal release rate decreased to 30.7 MJ/m2 and 105.7 kW/m2, respectively.

Effects of passenger blockage on smoke flow properties in subway station fires.

This study investigates the effects of the passenger blockage on the smoke flow properties in the subway station fires. A series of numerical simulations was conducted in a full-scale subway station model under different smoke exhaust volumes (24-96 m3/s) and passenger blockage scenarios. The parameter uncertainty and the model uncertainty were fully analyzed. Results demonstrate that the optimal smoke exhaust volume is 96 m3/s when there is no passenger blockage. When the passenger blockage exists, its effects on the smoke exhaust efficiency, the smoke layer height, and the temperature profile beneath the ceiling are significant. The optimal smoke exhaust volume can only guarantee the passenger's safe evacuation in the blockage scenarios with the low passenger blockage level. For the high passenger blockage level, some measures should be taken to reduce the harm to the passengers near the fire source.

Thermodynamic properties, decomposition kinetics of 2-(5-amino-2H-tetrazol-1-yl)-4-amine-3,5-dinitropyridine.

A novel energetic material 2-(5-amino-2H-tetrazol-1-yl)-4-amine-3,5-dinitropyridine (ATDP) was synthesized and characterized by 1H NMR, 13C NMR, mass spectroscopy, and elemental analysis. The research by differential scanning calorimetry (DSC) shows that ATDP decomposed about 290 °C. The calculating results of kinetic parameters using Ozawa method, Kissinger method, and Starink method were quite consistent. Self-accelerated decomposition temperature (TSADT), thermal ignition temperature (TTIT), and critical temperature of thermal explosion (Tb) were 272.55 °C, 121.71 °C, and 137.67 °C, respectively. Geometric optimization, heat of formation, detonation velocity (D), detonation pressure (P), bond dissociation energy (BDE), and electrostatic potential (ESP) were explored using Gaussian 16. The results show that ATDP has a much larger ΔHf,gas value than HMX(272.6 kJ mol-1). The D and P are predicted with the value of 7.50 km s-1 and 24.47 GPa, respectively. The relatively high BDE value (270.77 kJ mol-1) indicates that ATDP has moderate thermal stability.

Experimental Study of the Thermal Decomposition Properties of Binary Imidazole Ionic Liquid Mixtures.

Ionic liquids (ILs) have a wide range of applications, owing to their negligible vapor pressure, high electrical conductivity, and low melting point. However, the thermal hazards of ILs and their mixtures are also non-negligible. In this study, the thermal hazards of various binary imidazolium ionic liquids (BIIL) mixtures were investigated. The effects of parent salt components and molar ratios on the thermal decomposition temperature (Td) and flashpoint temperature (Tf) are investigated. It is found that both Td and Tf increase as the proportion of highly thermally stable components in BIIL mixtures increases. Furthermore, the decomposition process of BIIL mixtures can be divided into two stages. For most molar ratios, the Tf of the BIIL mixtures is in the first stage of thermal decomposition. When the proportion of highly thermally stable components is relatively high, Tf is in the second stage of thermal decomposition. The flammability is attributed to the produced combustible gases during the thermal decomposition process. This work would be reasonably expected to provide some guidance for the safety design and application of IL mixtures for engineering.

Preparation and Study on the Flame-Retardant Properties of CNTs/PMMA Microspheres.

In this paper, carbon nanotubes (CNTs)/poly(methyl methacrylate) (PMMA) composites with excellent thermal stability and flame retardancy were prepared by in situ polymerization. The morphology, structure, transmittance, thermal stability, flame retardancy, and mechanical properties of the materials were characterized with scanning electron microscopy (SEM), thermogravimetric analysis (TGA), cone calorimetry, etc. According to the results, the initial decomposition temperature of CNTs/PMMA prepared using carbon nanotubes with a concentration of 2 mg/mL increases from 175 to 187 °C when compared with pure PMMA, and the weight loss ratio decreases significantly at the same time. In addition, the maximum limiting oxygen index (LOI) value of CNTs/PMMA composites is 22.17, which is 26.9% higher than that of PMMA. SEM images of residues after LOI tests demonstrate that when CNTs/PMMA is heated, a dense and stable interconnected network structure (i.e., carbon layer) is formed, which can effectively inhibit the combustion of pyrolysis products, prevent the transfer of heat and combustible gas, and finally interrupt the combustion of composite materials. However, a 25% decrease in the transmittance of CNTs/PMMA composites is observed in the Ultraviolet-visible (UV-vis) spectra. Although the addition of CNTs reduces the transparency of PMMA, its tensile and impact strength are all improved, which illustrates that CNT is a competitive flame retardant for PMMA.

Prediction and Construction of Energetic Materials Based on Machine Learning Methods.

Energetic materials (EMs) are the core materials of weapons and equipment. Achieving precise molecular design and efficient green synthesis of EMs has long been one of the primary concerns of researchers around the world. Traditionally, advanced materials were discovered through a trial-and-error processes, which required long research and development (R&D) cycles and high costs. In recent years, the machine learning (ML) method has matured into a tool that compliments and aids experimental studies for predicting and designing advanced EMs. This paper reviews the critical process of ML methods to discover and predict EMs, including data preparation, feature extraction, model construction, and model performance evaluation. The main ideas and basic steps of applying ML methods are analyzed and outlined. The state-of-the-art research about ML applications in property prediction and inverse material design of EMs is further summarized. Finally, the existing challenges and the strategies for coping with challenges in the further applications of the ML methods are proposed.

Thermal hazard evaluation on spontaneous combustion characteristics of nitrocellulose solution under different atmospheric conditions.

Nitrocellulose (NC) is widely used in both military and civilian fields. Because of its high chemical sensitivity and low decomposition temperature, NC is prone to spontaneous combustion. Due to the dangerous properties of NC, it is often dissolved in other organic solvents, then stored and transported in the form of a solution. Therefore, this paper took NC solutions (NC-S) with different concentrations as research objects. Under different atmospheric conditions, a series of thermal analysis experiments and different reaction kinetic methods investigated the influence of solution concentration and oxygen concentration on NC-S's thermal stability. The variation rules of NC-S's thermodynamic parameters with solution and oxygen concentrations were explored. On this basis, the spontaneous combustion characteristics of NC-S under actual industrial conditions were summarized to put forward the theoretical guidance for the spontaneous combustion treatment together with the safety in production, transportation, and storage.

Physical model experiment on the influence of water depth on the underwater pipeline surface impacted by landslide surge.

A physical model experiment of flume block landslide was used to study the influence of landslide surge impact on underwater pipeline surface under different water depths. The influence of surge impact pressure on pipelines with different water depths and the impact pressure of surge at different angles of underwater pipelines wall were analyzed. And the relationship between the maximum impact pressure of underwater pipelines and the depth of water was obtained. The results indicated that with the decrease of the water depths, the maximum impact pressure at the wall of the underwater pipeline increases approximately linearly, and the slider is easier to form higher first wave height. The maximum impact pressure of the upper surface of the pipeline wall is greater than that of the lower surface of the pipeline wall under the same working conditions. It is also found that the smaller the depth of water, the larger the maximum pressure and average pressure at the measuring point would be and the greater the pressure fluctuation becomes when slider volume and landslide water inlet angle and speed remain the same.

Synergistic Flame Retardancy of Microcapsules Based on Ammonium Polyphosphate and Aluminum Hydroxide for Lithium-Ion Batteries.

Flame retardants have important theoretical research and applied value for lithium-ion battery safety. Microcapsule flame retardants based on ammonium polyphosphate (APP) and aluminum hydroxide (ATH) were synthesized for application in lithium-ion batteries. First, the ATH-APP was prepared by coating a layer of ATH on the surface of the core APP. Then, the ATH-APP was encapsulated by poly(urea-formaldehyde) (PUF) to obtain en-ATH-APP. The structure and flame-retardant property of en-ATH-APP, the influence of en-ATH-APP on the thermal stability of the electrode, and the electrochemical performance of the battery were studied. The results of Fourier transform infrared and scanning electron microscope experiments indicated that APP was coated with ATH and PUF in turn. The results of differential scanning calorimetry and the fire extinguishing test for electrodes manifested that en-ATH-APP had better flame-retardant property than APP because of the synergistic effect between APP and ATH. Moreover, the flame-retardant efficiency of en-ATH-APP was comparable to that of ATH-APP, indicating that the presence of PUF had almost no effect on the flame-retardant property. The results of electrochemical experiments indicated that en-ATH-APP had the best electrochemical compatibility for the battery compared with APP and ATH-APP. The research lights the way to improve inherent safety of lithium-ion batteries by adding en-ATH-APP to the cathode.

Geographical discrimination of ethanol based on stable isotope ratio analysis coupled with statistical methods: The Chinese case study.

The demand for the effective traceability of hazardous chemicals is crucial for preventing and controlling chemical spills and other accidents involving hazardous chemicals. The aim of the study was to investigate the correlation between the geographical location of ethanol-producing industrial sites and the carbon, hydrogen, and oxygen stable isotope ratios of the Chinese-manufactured ethanol using statistical classification analysis to enable the traceability of the ethanol. The isotopic data of 54 ethanol samples obtained from 18 different ethanol manufacturing plants in China between 2019 and 2020. The results of the statistical analysis demonstrated that the δ18O values of the ethanol positively correlated with latitudes of the production plants but negatively correlated with the δ13C values of the ethanol. A small number of samples derived from sites that were geographically close to each other could not be visually distinguished by PCA and HCA. However, by applying and comparing the results of classification by LDA, K-NN and Ensemble, an optimal classification model was obtained. Upon application of these models, 96.3% of the ethanol samples were correctly classified based on their geographical origin, indicating that the combination of isotopic ratios and latitude data is practical and effective for measuring the traceability of ethanol.

Theoretical studies of novel high energy density materials based on oxadiazoles.

In this study, 32 energetic compounds were designed using oxadiazoles (1,2,5-oxadiazole, 1,3,4-oxadiazole) as the parent by inserting different groups as well as changing the bridge between the parent. These compounds had high density and excellent detonation properties. The electrostatic potentials of the designed compounds were analyzed using density functional theory (DFT). The structure, heat of formation (HOF), density, detonation performances (detonation pressure P, detonation velocity D, detonation heat Q), and thermal stability of each compound were systematically studied based on molecular dynamics. The results showed that the -N3 group has the greatest improvement in HOF. For the detonation performances, the directly linked -N=N- and -NH-NH- were beneficial when used as a bridge between 1,2,5-oxadiazole and 1,3,4-oxadiazole, and it can also be found that bridge changing had little effect on the trend of detonation performance, while energetic groups changing influenced differently. In general, the introduction of nitro groups contributes to the improvement of the detonation performance of the compounds. In this study, the compounds containing the highest amount of nitro groups were found to have better detonation performance than their counterparts and were not significantly different from RDX and HMX.

Thermal Effect and Mechanism Analysis of Flame-Retardant Modified Polymer Electrolyte for Lithium-Ion Battery.

In recent years, the prosperous electric vehicle industry has contributed to the rapid development of lithium-ion batteries. However, the increase in the energy density of lithium-ion batteries has also created more pressing safety concerns. The emergence of a new flame-retardant material with the additive ethoxy (pentafluoro) cyclotriphosphazene can ameliorate the performance of lithium-ion batteries while ensuring their safety. The present study proposes a new polymer composite flame-retardant electrolyte and adopts differential scanning calorimetry (DSC) and accelerating rate calorimetry to investigate its thermal effect. The study found that the heating rate is positively correlated with the onset temperature, peak temperature, and endset temperature of the endothermic peak. The flame-retardant modified polymer electrolyte for new lithium-ion batteries has better thermal stability than traditional lithium-ion battery electrolytes. Three non-isothermal methods (Kissinger; Kissinger-Akahira-Sunose; and Flynn-Wall-Ozawa) were also used to calculate the kinetic parameters based on the DSC experimental data. The apparent activation energy results of the three non-isothermal methods were averaged as 54.16 kJ/mol. The research results can provide valuable references for the selection and preparation of flame-retardant additives in lithium-ion batteries.