Slow Reaction Research Articles

Rational design of Er2O3/ZnS as highly competent electrocatalyst for OER application

The fabrication of an extremely productive, inexpensive and prominent electrocatalyst is required to improve the slow oxygen evolution reaction (OER). Here, a hydrothermal approach was utilized to fabricate Er2O3/ZnS composite as a competent electrode material for the purpose of efficient water splitting. The various analytical tools were used to evaluate morphology, crystallinity, functionality, surface area, and thermal stability of the reported materials. The large surface area of the Er2O3/ZnS composite (61.06 m2 g−1), makes it a suitable candidate for carrying out the OER process. Moreover, the electrochemical study for Er2O3/ZnS composite was conducted on nickel foam (NF) as a substrate to determine the electrolytic nature. The electrochemical study showed that the synthesized composite responds to an impressive overpotential (260 mV) and low Tafel value (40 mV dec−1) at an ideal current density (j) of 10 mA cm−2. The Er2O3/ZnS composite exhibits a reduced onset potential of approximately 1.31 V and exceptional durability of about 30 h. The electrochemical observation suggests that incorporating Er2O3 into ZnS resulted in an enlarged surface area and enhanced active regions which reduce the resistance and promote the rapid binding of electrolyte ions. The composite (Er2O3/ZnS) developed by this approach can be utilized in various energy conversion and storage applications.

Electrical-Modulated Flexible Acoustic Metamaterial: Enhancing Low-Frequency Absorption via an Ionic Electroactive Polymer.

The growing concern over low-frequency noise pollution resulting from global industrialization has posed substantial challenges in noise attenuation. However, conventional acoustic metamaterials, with fixed geometries, offer limited flexibility in the frequency range adjustment once constructed. This research unveiled the promising potential of ionic electroactive polymers, particularly ionic polymer-metal composites (IPMCs), as a superior candidate to design tunable acoustic metamaterial due to its bidirectional energy conversion capabilities. The previously perceived limitations of the IPMC, including slow reaction and high energy expenditure, owning to its inherent sluggish intermediary ionic mass transport process, were astutely leveraged to expedite the attenuation of low-frequency sound energy. Both our experimental and simulation results elucidated that the IPMC can generate voltage potentials in response to acoustic pressure at frequencies significantly higher than those previously established. In addition, the peak absorption frequency can be effectively shifted by up to 45.7% with the application of a 4 V voltage. By further integration with a microperforated panel (MPP) structure, the developed metamaterial absorbers can achieve complete sound absorption, which was continuously tunable under minimal voltage stimulation across a wide frequency spectrum. In addition, a microslit structure IPMC metamaterial absorber was designed to realize modulation of the perforation rate, and the absorption peak can be shifted by up to 79.2%. These findings signify a pioneering application of ionic intelligent materials and may pave the way for further innovations of tunable low-frequency acoustic structures, ultimately advancing the pragmatic deployment of both soft intelligent materials and acoustic metamaterials.

Manipulating Orbital Hybridization of CoSe2 by S Doping for the Highly Active Catalytic Effect of Lithium-Sulfur Batteries.

In recent years, various transition metal compounds have been extensively studied to deal with the problems of slow reaction kinetics and the shuttle effect of lithium-sulfur (Li-S) batteries. Nevertheless, their catalytic performance still needs to be further improved by enhancing intrinsic catalytic activity and enriching active sites. Doping is an effective means to boost the catalytic performance through adjusting the electron structure of the catalysts. Herein, the electron structure of CoSe2 is adjusted by doping P, S with different p electron numbers and electronegativity. After S doping (S-CoSe2), the content of Co2+ increases, and charge is redistributed. Furthermore, more electrons are transferred between Li2S4/Li2S and S-CoSe2, and optimal Co-S bonds are formed between them with optimized d-p orbital hybridization, making the bonds of Li2S4/Li2S the longest and easy to break and decompose. Consequently, the Li-S batteries with the S-CoSe2-modified separator achieve improved rate performance and cycling performance, benefiting from the better bidirectional catalytic activity. This work will provide reference for the selection of the anion doping element to enhance the catalytic effect of transition metal compounds.

N, S, Se-Codoped dual carbon encapsulation and Se substitution in pyrite-type FeS2 for high-rate and long-life sodium-ion batteries

The use of metal sulfides as anodes in sodium-ion batteries (SIBs) faces significant challenges due to slow reaction kinetics and extensive shuttling of sodium polysulfides (NaPSs). In response, a selenium-substituted iron disulfide encapsulated in a nitrogen-sulfur-selenium-codoped dual carbon framework (Se-FeS2@NSSC) has been engineered for high-performance SIBs. Selenium substitution within the FeS2 lattice improves electrical conductivity, facilitates favorable redox kinetics that reducing the possibility of NaPSs generation. Moreover, the dual NSSC encapsulation promotes Na+/electron transport and efficiently manages volume expansion during electrochemical processes. Strong interfacial interaction (Fe-S-C bonding) between Se-FeS2 and NSSC further suppress NaPSs shuttling, significantly alleviating the cell failure and thus prolonging its lifespan. Consequently, Se-FeS2@NSSC demonstrates a top-notch performance, achieving a notable capacity of 725 mAh g-1 at 0.5 A g-1, unparalleled rate capability (355.1 mAh g-1 at 30 A g-1), and sustained cyclic stability (89.6 % capacity is retained after 1250 cycles). Theoretical analyses underscore the critical role of selenium in diminishing bulk stress–strain energies, lowering energy barriers for Na+ diffusion, and decreasing Gibbs free energy for conversion reactions, thereby markedly bolstering electrochemical kinetics and overall performance of Se-FeS2@NSSC. The insights gleaned from this research foster advancements in developing next-generation anodes with high capacity and durability, representing a promising response to the existing hurdles in SIBs technology.

Effect of thermochemical treatment of sewage sludge on its phosphorus leaching efficiency: Insights into leaching behavior and mechanism

Thermochemical conversion, including hydrothermal processing, pyrolysis and incineration, has become a promising technology for sewage sludge (SS) treatment and disposal. Furthermore, acid leaching is considered as an effective method to recover phosphorus (P) from SS and its thermochemical treatment products. This study has investigated the potential of P reclamation from SS and its thermochemical derivatives, including hydrochar (HC), biochar (BC), and SS incinerated ash (SA). Comparative analyses of physicochemical properties of these derivatives revealed a decrease in hydroxyl and aromatic groups and an increase in aliphatic and oxygen-containing functional groups in HC and BC. Leaching experiments using 1 M sulfuric acid (H2SO4) and 1 M oxalic acid (C2H2O4) suggested that H2SO4 slightly outperformed C2H2O4 in terms of P leaching efficiency. HC achieved 79.1 % optimal leaching efficiency in 60 min using H2SO4, while BC, SS, and SA required 360 min to achieve comparable efficiency. SS and BC reached optimal leaching efficiency at 74.1 % and 76.2 % in H2SO4, while SA achieved 80.9 % in C2H2O4. Importantly, HC and SA are more favorable for P extraction using acid leaching, whereas BC tends to be a potential P carrier. Time-dependent kinetics revealed a two-stage leaching process, i.e., fast and slow reaction stages. Shrinking core model indicates product layer diffusion as the primary rate-limiting step in both stages. Overall, these fundamental insights play an important role in practical P recovery through acid leaching of SS derived residues after thermochemical treatment.

Thermodynamics and kinetics of cation partitioning between plagioclase and trachybasaltic melt in static and dynamic systems: A reassessment of the lattice strain and electrostatic energies of substitution

Most of the solidification history of magmas beneath active volcanoes takes place in chemically and physically perturbed plumbing systems where the growth of crystals is collectively governed by a range of kinetic processes related to the dynamics of crustal reservoirs and eruptive conduits. In this context, we have experimentally investigated the partitioning of major, minor, and trace cations between plagioclase and trachybasaltic melt under conventional static (no physical perturbation) and dynamic (melt stirring) crystallization regimes. Slow interface reaction kinetics are established between the advancing crystal surface and the adjacent melt, as the result of the combined control of a small degree of effective undercooling, prolonged diffusive relaxation, and convective homogenization. The kinetic aspects of plagioclase growth influence the partitioning of trace cations during transport of structural units across the crystal-melt interface, with consequent departure from macroscopic equilibrium in the system. The type and number of charge–balanced and −imbalanced configurations produced by the accommodation of trace cations into the coordination polyhedron can be thermodynamically rationalized in terms of lattice strain and electrostatic partitioning energetics. However, the overall solution energy accompanying trace cation kinetic substitutions cannot be entirely deconvoluted from major component activities in both melt and plagioclase phases. The emerging view that slow interface kinetic processes may lead to strong compositional dependence for the partition coefficient in dynamic subvolcanic environments contrasts markedly with the conventional idea that the energetics of cation partitioning are dominantly controlled by the effect of isothermal changes in the bulk system.

Efficient photocatalytic H2O2 production and green oxidation of glycerol over a SrCoO3-incorporated catalyst

Photocatalysis for H2O2 production suffers from low carrier utilization and slow reaction kinetics. Herein, a photocatalytic system supported by a SrCoO3-MoS2 (SCOS) heterojunction, which possessed a unique S-O electron transport channel, was proposed to facilitate H2O2 production under condition where glycerol served as a sacrificial agent. The SCOS heterojunction achieved a remarkable yield of 15.90 mmol g−1 h−1 H2O2 production, 3.7 times higher than the base component SCO. The construction of the heterojunction enriched the oxygen vacancies on the catalyst surface, facilitated photogenerated charge separation, and promoted the adsorption of O2, reducing the oxygen reduction reaction (ORR) energy barrier. Besides, glycerol served as a unique proton donor, efficiently captured holes to enhance H2O2 production, and generated valuable by-products including glyceric acid and dihydroxyacetone. Furthermore, SCOS exhibited excellent stability over repeated cycles with consistent H2O2 yields. This study offers an efficient photocatalytic system and demonstrates glycerol’s potential in green oxidation processes.

Programming Fast DNA Amplifier Circuits with Versatile Toehold Exchange Pathway.

DNA amplifier circuits establish powerful tools to dynamically control molecular assembly for computation, sensing, and biological applications. However, the slow reaction speed remains a major barrier to their practical utility. Here, diverse fast DNA amplifier circuits termed toehold exchange polymerization (TEP) and toehold exchange catalysis (TEC) using toehold exchange-mediated assembly as a fundamental mechanism are built. Both TEP and TEC with a duplex and a hairpin can respond within minutes to diverse nucleic acid inputs with high fidelity. In addition, the circuits can amplify live-cell signals for fluorescence imaging target RNA dynamics and discriminating different cell lines. Compared with existing DNA circuits that involve time scales of hours for transducing small signals, TEP and TEC exhibit much faster dynamics, simpler design, and comparable sensitivity. These features make TEP and TEC promising platforms to develop programmable nucleic acid tools and devices and to create fast sensing and processing systems, amenable to wide practical applications.

Cerium-doped construction of oxygen vacancies in IrO2 to promote acidic OER reaction

Proton exchange membrane electrolysis of water is currently recognized in the world as an up-and-coming method for the preparation of green hydrogen energy. Due to its sustainability and low pollution, it has attracted much attention from practitioners recently. The most advanced iridium oxide (IrO2) is the most promising catalyst.However, developing a highly efficient and stable IrO2 catalyst that can adapt to industrial conditions remains a terrific challenge. One of the main problems to be solved is that the slow oxygen evolution reaction(OER) at the anode limits the production of hydrogen. We propose a straightforward method for synthesizing Ce metal-doped IrO2 with a high oxygen vacancy concentration while simultaneously improving the IrO2 catalytic activity and stability.The Ce-doped IrO2 (Ce-IrO2) exhibits a microscopic nanoparticle morphology and a high density of oxygen vacancies, enabling a rapid oxygen evolution reaction (OER) process with a low overpotential of 240 mV at 10 mA·cm-2 and a remarkable stability of over 50 h under acidic conditions.A growing body of research shows a synergistic effect of oxygen vacancies and mental dopants on the adsorption and evolution of active intermediates in the active center so that the oxygen evolution reaction activity of the Ir-based catalyst can be improved. We hope that ourwork will provide a sample method for acquiring catalysts capable of adapting to a wide range of conditions via metal doping.

Efficient Co-ZrO2 electrocatalyst achieves high-performance solid-state lithium-sulfur batteries

Abstract Li-S batteries are recognized as a promising secondary battery system because of their high energy density, low cost, and environmental friendliness. However, the development of Li-S batteries is mainly limited by issues such as electrode volume expansion, lithium polysulfide (LiPSs) shuttle, and slow redox reaction kinetics of sulfur. Here, a kind of solid-state Li-S battery with in situ solidified solid-state electrolytes (SSEs) is reported, which dramatically reduces the electrode/electrolyte interfacial impedance. In addition, electrospinning is used to fabricate a macroporous carbon nanofibers film (MP-CNFs) loaded with dispersed Co-ZrO2 nanodot electrocatalyst as the cathode host. The in-situ gel electrolyte can be easily infiltrated into the porous carbon nanofibers and contact the Co-ZrO2 catalyst, thus fully exerting its catalytic and conversion effects on LiPSs. The results indicate that solid-state Li-S batteries exhibit a high initial capacity of 795.5 mA h·g−1 and a capacity retention rate of ∼100% after 200 cycles at 1 C.

ZIF-67 기반의 산소 환원 반응用 촉매 합성을 통한 Zinc-Air Primary Battery의 효율 개선에 관한 연구

Zinc-air batteries are attracting attention nowadays due to their environment-friendliness, stability, and high efficiency. However new catalyst development is necessary for commercialization with a slow reaction rate of ORR (Oxygen Reduction Reaction) occurring in the cathode and low efficiency compared to the price of Pt/C catalysts. This study produced a catalyst based on the ZIF-67 (Zeolic Imidazolate Framework-67) to compensate for this, and the effects of PVP addition, carbonization, and sulfidation on the catalyst efficiency were confirmed in the ZIF-67 synthesis process. As a result of the analysis, when 0.52 mmol of PVP was added and carbonization and sulfidation processes were performed, high efficiency, high driving force, stability, and life comparable to Pt/C catalyst were shown. Therefore, the ZIF-67-based oxygen reduction reaction catalyst is expected to contribute to the commercialization of Zinc-air batteries by replacing the existing Pt/C catalyst.

Preparation of MoS2 nanosheets/nitrogen-doped carbon nanotubes/MoS2 nanoparticles and their electrochemical energy storage properties

Inferior electrical conductivity, huge volume swell, shuttle effect and slow redox reactions in Li-S batteries restrict their practical applications. In this study, molybdenum disulfide nanosheets anchored on nitrogen-doped carbon nanotubes encapsulating molybdenum disulfide nanoparticles (MoS2/NC/MoS2 NTs) were prepared by heat treatment, ammonia etching, high-temperature sulfurization, and solvent-thermal in-situ growth using polypyrrole-coated molybdenum trioxide nanorods (MoO3 NRs) as templates. The hollow structure of nitrogen-doped carbon nanotubes and the high specific surface area are conducive to increasing sulfur loading, increasing the contact area of electrolyte, accelerating the electron transport, and shortening the lithium ion transport route. The MoS2 nanosheets on the outer layer of the nitrogen-doped carbon tubes and the MoS2 particles wrapped inside can anchor polysulfides by chemisorption, slowing down the shuttle effect and enhancing the energy storage performance of lithium-sulfur batteries. The MoS2/NC/MoS2/S nanotubes (MoS2/NC/MoS2/S NTs) maintain a capacity of 498.9 mAh g−1 over 500 cycles at 1.0 A g−1, with an average single-cycle capacity decay rate of 0.061 %. The density functional theory calculations, the adsorption experiments, and the X-ray photoelectron spectroscopy results all confirm that the MoS2/NC/MoS2 NTs are able to anchor lithium polysulfides through strong adsorption, thus effectively mitigating the shuttle effect of polysulfides. The synthesis of MoS2/NC/MoS2/S NTs in this study is of important significance for the development of advanced lithium-sulfur batteries.

Constructing p-n heterojunction in CoO@TiO2 photocatalytic material to enhance the performance of catalytic degradation of Rhodamine B

Traditional Fenton reactions suffer from slow reaction rates and energy wastage degrade dye contaminant. By constructing a heterojunction interface between quantum dots and titanium dioxide, a CoO@TiO2 photocatalyst is prepared to extend the photoresponse range to longer wavelengths. Under infrared light irradiation, RhB is degraded by over 97 % after 120 min. CoO@TiO2 possesses a large surface area, loaded with a substantial amount of quantum dots, forming a p-n heterojunction, significantly enhancing the photocatalytic rate. This study provides a new approach for the efficient preparation of photocatalysts for the degradation of organic dye pollutants.

Progresses and Perspectives of Carbon-Free Metal Compounds-Modified Separators for High-Performance Lithium-Sulfur Batteries.

Lithium-sulfur batteries (LSBs) have the advantages of high theoretical specific capacity, excellent energy density, abundant elemental sulfur reserves. However, the LSBs is mainly limited by shuttling of lithium polysulfides (LiPSs), slow reaction kinetics of sulfur cathode. For solving the above problems, by developing high-performance battery separators, the reversible capacity, Coulombic efficiency (CE) and cycle life of LSBs can be effectively enhanced. Carbon-free based metal compounds are expected to be highly efficient separator modifiers for a new generation of high-performance LSBs by virtue of superior chemical adsorption capacity, strong catalytic properties and excellent lithophilicity to a certain extent. They can give play to the synergistic effect of their "adsorption-catalysis" sites to accelerate the redox kinetics of LiPSs, and their good lithophilicity can accelerate the Li+ transport kinetics, thus showing more remarkable electrochemical performances. However, a comprehensive summary of carbon-free metal compounds-modified separators for LSBs is still lacking. Here, this review systematically summarizes the researching progresses and performance characteristics of carbon-free-based metal compounds modified materials for separators of LSBs, and summarizes the corresponding mechanisms of using carbon-based separators to enhance the performance of LSBs. Finally, the review also looks forward to the prospects of LSBs using carbon-free metal compounds separators.

Hydrogen-bonded organic framework-sulfur composite for high performance lithium–sulfur batteries

With the rapid development of energy storage devices, lithium–sulfur batteries are considered as one of the promising candidates due to their high energy density (2600 Wh Kg−1) and low cost of sulfur. Despite these advantages, the application of lithium–sulfur batteries is limited by many issues, such as the shuttle effect of polysulfide and slow redox reactions. In this paper, hydrogen-bonded organic frameworks (HOFs) materials are chosen for the first time to improve the performance of sulfur cathodes by exploiting their unique properties. Thanks to the abundant hydrogen bond of HOFs materials, which can interact with lithium polysulfide, this S-HOF composite can inhibit the shuttle of polysulfide and enhance the transformation of polysulfide. As a result, the HOF-S composite has a high initial capacity of 1100 mAh g−1 at 0.1 C and 530 mAh g−1 at 1 C. In this paper, hydrogen-bonded organic frameworks (HOFs) materials are chosen for the first time to improve the performance of sulfur cathodes. In the S-HOF, abundant hydrogen bond sites can interact with lithium polysulfide to inhibit the shuttle of polysulfide and accelerate the redox conversion of polysulfide. Therefore, the S-HOF composite has higher capacity and cycle stability. The initial capacity of the S-HOF composite is 1100 mAh g–1 at 0.1 C and 530 mAh g–1 at 1 C.

Interface Engineering of VOx/Ni/Ni3N Heterostructures for Electrochemical Urea-Assisted Hydrogen Production.

Electrocatalytic hydrogen generation driven by renewable energy sources is severely limited by the slow oxygen evolution reaction (OER). Urea-assisted alkaline hydrogen production offers a perspective approach. However, the construction of efficient and robust anode catalysts is still challenging. Herein, an amorphous/crystalline VOx/Ni/Ni3N-heterostructured catalyst grown on carbon cloth was synthesized and used as a bifunctional electrocatalyst for the hydrogen evolution reaction (HER) and urea electrooxidation reaction (UOR). Benefiting from the electronic modification of intercomponents and abundant active sites, VOx/Ni/Ni3N exhibits an excellent electrochemical performance toward the HER and UOR. Theoretical calculations confirmed that the crystalline/amorphous VOx/Ni/Ni3N heterostructure has a suitable water dissociation energy and H* adsorption energy, thereby promoting the HER process. When the UOR and HER are integrated into an electrolytic device, VOx/Ni/Ni3N requires a potential of 1.40 V to achieve a current density of 10 mA cm-2.

Electrospun carbon nanofibers loaded with sulfur vacancy CoS2 as separator coating to accelerate sulfur conversion in Lithium-Sulfur batteries

Lithium–sulfur batteries (LSBs) have been sought after by researchers owing to their high energy density; however, the inevitable capacity decay and slow reaction kinetics have hindered their advancement. Here, we prepare a Prussian blue analog, Co3[Co(CN)6]2 and synthesize carbon nanofibers/S vacancy CoS2−x (CNFs/CoS2−x) as electrocatalysts for separator coating via electrospinning, carbonization, sulfurization, and hydrogen reduction. CNFs/CoS2−x exhibits excellent electrocatalytic activity, wherein S vacancies induce the partial oxidation of Co2+ to Co3+ in CoS2 and CNFs provide long-range electron transport pathways. Various electrochemical tests, such as Tafel, ion diffusion coefficient, Li2S precipitation, and Li2S6 symmetric cells, further confirm the enhanced electrocatalytic activity. The LSBs with CNFs/CoS2−x modified separator delivers an initial discharge capacity of 1056.7 mAh g−1 at 0.2C, maintaining 840.8 mAh g−1 after 100 cycles at 0.2C. When S loading is increased to 4.42 mg cm−2, the battery retains a discharge capacity of 687.9 mAh g−1 (3.04 mAh cm−2) after 70 cycles at 0.1C. Our work can provide a reference for synthesizing anion-vacancy materials and designing anion-vacancy electrocatalytic composites for LSBs.

Pd-Ru pair on Pt surface for promoting hydrogen oxidation and evolution in alkaline media

Hydrogen oxidation reaction in alkaline media is critical for alkaline fuel cells and electrochemical ammonia compressors. The slow hydrogen oxidation reaction in alkaline electrolytes requires large amounts of scarce and expensive platinum catalysts. While transition metal decoration can enhance Pt catalysts’ activity, it often reduces the electrochemical active surface area, limiting the improvement in Pt mass activity. Here, we enhance Pt catalysts’ activity without losing surface-active sites by using a Pd-Ru pair. Utilizing a mildly catalytic thermal pyrolysis approach, Pd-Ru pairs are decorated on Pt, confirmed by extended X-ray absorption fine structure and high-angle annular dark-field scanning transmission electron microscopy. Density functional theory and ab-initio molecular dynamics simulations indicate preferred Pd and Ru dopant adsorption. The Pd-Ru decorated Pt catalyst exhibits a mass-based exchange current density of 1557 ± 85 A g−1metal for hydrogen oxidation reaction, demonstrating superior performance in an ammonia compressor.

Modeling smothering limit of smoldering combustion: Oxygen supply, fuel density, and moisture content

Smoldering, characterized as a slow, low-temperature, and flameless reaction process, represents one of the most persistent types of combustion phenomena. While oxygen supply is one of the governing mechanisms controlling smoldering, the specific oxygen threshold or smothering limit remains inadequately investigated. Herein, we built a physics-based 1-D computational model integrating heat-and-mass transfer and 5-step heterogeneous chemistry to investigate the oxygen threshold or smothering limit of smoldering propagation in porous pine needle beds subjected to forced internal oxidizer flow. Simulation results revealed that, the required oxidizer flow velocity or oxygen supply rate increased as the oxygen concentration decreased, and the predicted limiting oxygen concentration (LOC) was about 3 %, agreeing well with the experimental observations and theoretical analysis. Moreover, the required airflow velocity was predicted to increase as the fuel density and environmental temperature decreased, or the moisture content increased, and the predicted maximum moisture content capable of supporting smoldering was about 110 %. At the smothering limit, the modeled minimum smoldering temperature and propagation rate were around 300 °C and 0.5 cm/h. This work helps deepen our understanding of the limiting conditions of smoldering combustion, thus improving the mitigation strategy of smoldering fire and the efficiency of applied smoldering systems. Novelty and significance statementsOxygen supply is one of the key mechanisms governing the smoldering propagation. In the literature, scattered studies have examined the limiting oxygen concentration (LOC) of smoldering under different conditions, leading to disparate results even for the same fuels. In our previous work, for the first time, we developed a tubular smoldering reactor capable of precisely controlling the flow of oxidizer, and successfully quantified the exact oxygen supply limit of smoldering combustion. However, no computational model was established specifically for the oxygen threshold of smoldering with forced internal oxygen supply.The novelty of this research is the establishment of the first-ever computational model to investigate the oxygen threshold or smothering limit of smoldering propagation in porous pine needle beds subjected to forced internal oxidizer flow. It is significant because (1) it contributes to a fundamental understanding of smoldering combustion; (2) it investigates the role of fuel properties and environmental conditions in smoldering dynamics and the oxygen supply limits; (3) it assists in optimizing the applied smoldering systems and enriching prevention strategies for smoldering fires.

Tough epoxy resin systems for cryogenic applications

This work presents the development of new epoxy systems that combine high fracture toughness at cryogenic temperatures (▪) with a slow curing reaction (long pot life) and a glass transition temperature between ▪ and ▪, ensuring good mechanical performance at room temperature. This was achieved by incorporating varying amounts and types of short-chain alkylamines into epoxy networks based on bisphenol A diglycidyl ether (DGEBA) crosslinked with metaphenylene diamine (MPD). This modification enhanced the cryogenic fracture toughness of the base system, DGEBA crosslinked with MPD, from 2 to ▪. It has been suggested that the significantly improved cryogenic fracture toughness in systems with flexible aliphatic chain extenders might result from nano- or micro-phase separation, but X-ray scattering and dynamic mechanical spectroscopy did not provide conclusive evidence for this hypothesis.The required slow curing reaction was achieved by using a sterically hindered alkylamine (2-heptylamine) as chain extender, which increased the pot life more than twofold, resulting in resin formulations that combine a high cryogenic fracture toughness, a low viscosity and a long processing window at room temperature.