Search Results (378)

The development of sustainable electrocatalysts for clean energy by modifying biomass-derived activated carbon with nitrogen and transition metals is presented. Activated carbon (AWC) material was obtained using alder wood char as a precursor, while nitrogen and cobalt or copper nanoparticles were incorporated with the aim of creating efficient materials for hydrazine oxidation (HzOR) and direct hydrazine–hydrogen peroxide fuel cells (DHHPFC, N₂H₄–H₂O₂). The composition, structure, and surface morphology of the created materials were examined using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), and inductively coupled plasma optical emission spectroscopy (ICP-OES). The activity of the AWC, AWC–Co–N, and AWC–Cu–N catalysts for HzOR was investigated using cyclic voltammetry (CV) and linear sweep voltammetry (LSV). N₂H₄–H₂O₂ fuel-cell tests were performed by applying the catalysts as both the anode and cathode. It was found that all materials retained a hierarchical porous carbon framework, while metal incorporation altered surface compactness. Cobalt doping produced well-dispersed Co nanoparticles and abundant Co–N–C coordination sites, whereas Cu introduction resulted in moderately compact structures with uniformly distributed Cu-based nanoparticles. Electrochemical measurements demonstrated that both metal dopants enhanced HzOR activity, with the catalytic performance following the order of AWC–Co–N > AWC–Cu–N > AWC. Fuel-cell testing further confirmed this trend: AWC–Co–N achieved the highest maximum power density (30.4 mW cm⁻²), outperforming AWC–Cu–N (17.7 mW cm⁻²). These results identify AWC–Co–N as a highly effective bifunctional electrocatalyst for DHHPFCs. Full article

Wood’s inherent flammability, arising from its cellular organic composition, demands effective protective strategies. This study aimed to develop a multifunctional bio-based wood coating simultaneously integrating flame retardancy, optical transparency, moisture-triggered self-healing, and surface hydrophobicity within a single formulation. An intumescent flame retardant (PAGHR) was synthesized via ionic assembly of a phytic acid–phosphorylated polyethylene glycol conjugate (PgP) with a piperazine–etidronic acid salt (HEPHR), subsequently blended with gelatin (G) and surface-finished with fluorosilane. The optimized coating (G/PAGHR-4) achieved a limiting oxygen index (LOI) of 37.2% and passed the UL-94 V-0 rating. Cone calorimetry demonstrated reductions of 75.1% in peak heat release rate (pHRR) and 50.0% in total heat release (THR) relative to the neat gelatin control. Char yield at 700 °C increased substantially from 17.8 wt% to 41.0 wt%, confirming effective condensed-phase char promotion. Beyond fire performance, the coating maintained high visible-light transmittance, preserved natural wood aesthetics, and achieved macroscopic scratch healing within 40 min upon ambient water contact. Fluorosilane finishing elevated the water contact angle to 122°. These results establish a scalable, environmentally friendly strategy for multifunctional bio-based protective coatings applicable to wood, textiles, and polymer substrates. Full article

Cross-laminated timber (CLT) is increasingly used in multi-story timber construction, but its combustible nature requires reliable fire protection, particularly in layered wall assemblies with concealed cavities. This study compares two medium-scale cross-laminated timber (CLT) sandwich wall assemblies exposed to radiant heat flux of 20 kW/m² for 90 min: an uncoated reference assembly and an assembly with PROMADUR^® intumescent coating applied to the CLT surfaces. Both specimens consisted of a 90 mm three-ply CLT panel encapsulated with 12.5 mm gypsum-fiber boards fixed to a wooden stud frame forming a 40 mm installation cavity. Fire-test observations were supplemented by simultaneous thermal analysis (STA), i.e., thermogravimetry (TG)/differential thermogravimetry (DTG)/differential scanning calorimetry (DSC), of uncoated and coated CLT specimens under oxidative conditions. During the applied medium-scale radiant exposure, the unexposed-face temperatures of both assemblies remained below the insulation temperature-rise limits defined in STN EN 1363-1; however, these limits were used only as a comparative benchmark and the test does not represent a formal fire-resistance classification. The coated assembly showed improved thermal protection during the early and intermediate stages of exposure, delaying a critical thermal event near the wooden stud by approximately 35 min. However, flaming combustion of the stud occurred at about 75 min and led to degradation of the intumescent char within the cavity. In contrast, the uncoated assembly reached higher early CLT surface temperatures but showed no flaming combustion during the test. STA results supported the fire-test interpretation: the coated specimen showed a 37% reduction in peak DTG rate, a higher residual mass at the end of the test, and substantially greater mass loss in the 150–280 °C range, consistent with intumescent activation and volatile release. The results indicate that, under the tested medium-scale exposure, the intumescent coating improved early and intermediate thermal protection of the CLT surface, but did not prevent late-stage cavity flaming involving the wooden stud. Therefore, the behavior of intumescent-coated CLT in partially enclosed cavities with combustible framing should be validated under replicated, standardized and larger-scale fire exposure. Full article

Point-supported connections are an innovative modern connection design that can benefit from the 2-way structural action of cross-laminated timber (CLT) slabs, which is typically not considered in traditional timber design. It also allows for flatter ceiling surfaces where no beams are needed to support the mass timber floor slabs. In an attempt to better understand the structural behaviour of this type of connection in fire conditions, preliminary unloaded fire tests were conducted to evaluate their thermal performance. The test results indicated that, for these tested configurations, the presence of steel connection components does not inherently increase charring rates within adjacent mass timber elements. While the outcomes provided valuable insights on the thermal performance of such assemblies, their actual mechanical behaviour under structural loading in fire conditions remains unknown. This paper presents the results of two structural fire-resistance tests under load: Test 1 had the gap fully exposed to fire, and Test 2 had the gap protected by a firestop. Neither assembly reached failure during the 2 h of standard fire exposure, while the target load could not be fully maintained to the end of the tests. Test 1 experienced charring at the CLT-steel plate interface, while Test 2 did not. Their mechanical behaviours were also similar. Lastly, a preliminary design approach is being proposed, although it requires further validation. Full article

Background/Objectives: Methods of smoking have evolved over the years, including heated tobacco products. The impact of exposure to traditional tobacco smoke and heated/electronic tobacco products (IQOS) on biofilm formation has not been previously compared in vitro. Aims and objectives: The present study aimed to evaluate the impact of tobacco and electronic smoking on microbial biofilm formation on dental hard tissues. Materials and Methods: Thirty premolars were randomly assigned to six groups (n = 10 per group) according to tissue type and smoking exposure: Six experimental groups were defined: Group 1, non-exposed enamel; Group 2, enamel subjected to conventional cigarette smoke (CS); Group 3, enamel subjected to heated tobacco (HT); Group 4, non-exposed cementum; Group 5, cementum subjected to conventional cigarette smoke; and Group 6, cementum exposed to heated tobacco. Enamel and root discs were then immersed in 2 mL of an adjusted, standardized bacterial suspension of Streptococcus mutans (S. mutans) to allow bacterial biofilm adhesion after incubation for 48 h at 37 °C. The mean colony-forming unit (CFU) count was calculated, and the surface topography and roughness were assessed using scanning electron microscopy and ImageJ software with the SurfCharJ plugin, respectively. Results: Conventional cigarette smoking showed significantly higher S. mutans adhesion on the enamel and root discs compared with IQOS and control groups. Both IQOS and cigarette smoking increased roughness on enamel and root versus the control group, and cigarette smoking produced significantly higher roughness on the enamel surface when compared to IQOS; however, there were no significant differences in the roughness between the two smoking methods on the root surface. SEM analysis showed the most extensive enamel and root microtopography change in IQOS smoking. Conclusions: Aerosols from heated tobacco products (IQOS) alter the surface topography and roughness of enamel and root, while traditional cigarette smoking significantly increases bacterial colonization. Further in vivo studies are warranted to simulate the dynamic nature of the oral cavity. Full article

Magnesium hydroxide is attracting growing interest as a versatile, halogen-free flame retardant, and this review surveys its production routes, structure–property relationships and use in polymer systems from commodity polyolefins to advanced bio-based materials. Industrial Mg(OH)₂ is still predominantly obtained from mining or hydration of MgO, but increasing attention is being devoted to recovery from seawater and saltwork brines, where precipitation from Mg²⁺-rich streams followed by controlled rehydration or direct precipitation yields fine, high-purity powders suitable for flame retardant use and simultaneously valorizes saline wastes. In parallel, hydrothermal synthesis has been extensively explored to tailor particle size and morphology by adjusting the precursor, solvent, temperature and time, enabling high-surface-area Mg(OH)₂ or MgO with narrow size distributions that are attractive for high-performance composites also evaluated via ball milling, crushing and refining. More recently, process intensification strategies such as microwaves and ultrasounds have been proposed to shorten reaction times, lower temperatures and better control nucleation and growth, opening paths toward energy efficient production of structured Mg(OH)₂ from both conventional and brine-derived precursors. The second part of the review analyzes how the intrinsic endothermic decomposition and basic character of Mg(OH)₂ can be utilized across a broad range of polymer matrices and how surface functionalization strategies extend its applicability. In addition to “as received” powders, stearic acid and other fatty acids, metal soaps and various organic coupling agents are widely used to render the surface more hydrophobic, enhance dispersion and interfacial adhesion, and in some cases introduce additional char-forming or barrier functionality. In terms of the application, the review methodically synthesizes and contrasts fire and mechanical data for Mg(OH)₂-containing polyolefins (HDPE, LLDPE, PP and EVA) utilized in cables and building products, expandable polymers and foams, biopolymers (PLA and PBS), and elastomers. The review places particular emphasis on the balance between loading level, processability, flame performance and mechanical integrity. This review aims to provide a comprehensive framework for designing next-generation Mg(OH)₂-based flame-retardant systems for both conventional and emerging polymer technologies. To this end, it integrates advances in sustainable feedstocks, controlled synthesis and surface engineering with the rapidly expanding application space. Full article

The impending wave of retired wind turbines has brought the issue of blade recycling to the forefront, presenting a major test for global sustainable resource management. Among the recycling methods, pyrolysis can be regarded as the most effective treatment approach, which can recycle the glass fibers that account for about 80% of the total weight of the blade. However, the pyrolytic char remaining on the fiber surface and the damage to the fiber structure caused by the excessively high pyrolysis temperature can both have a negative impact on fiber recycling. In this paper, a pyrolysis and in situ oxidation process with low treatment temperature is proposed for the recycling of glass fibers from the thermosetting epoxy resin–glass fiber composite material in the blades. Pyrolysis is performed at 450 °C, yielding a residual char content of 3.56%. Subsequently, in situ oxidation is conducted at the same temperature by switching the atmosphere to air, while the char content is reduced to below 0.01%, meeting the industrial recycling standard and achieving a glass fiber yield of 74%. Characterization reveals that the fiber structure and properties are well maintained. Additionally, through a series of characterization and density functional theory (DFT) calculations, the pyrolysis pathway from the resin repeating unit to various liquid phase products is supposed, and the corresponding pyrolysis mechanism is concluded. This paper provided a practical and feasible process scheme and theoretical basis for the efficient and clean resource recovery of retired wind turbine blades. Full article

Low-temperature pyrolysis around 250 °C represents a mild carbonization that differs from conventional high-temperature biochar production, and the role of pyrolysis duration under mild thermal conditions remains insufficiently understood. In this study, plant residues, including rice straw, sorghum leaves and stems, barley straw, and mixed woodchips, were converted into charred materials under low-temperature pyrolysis at 250 °C (4 h, 12 h) and compared with those produced at 500 °C (4 h). Pyrolysis at 250 °C (4 h) resulted in higher solid yields (51.9–72.8%) and higher recovery of carbon and nitrogen, whereas yields declined to 27.2–31.6% at 500 °C. Materials produced at 250 °C preserved abundant oxygen-containing functional groups, exhibited lower pH, and showed significantly higher cation exchange capacity (up to 93.68–119.91 cmol_c/kg at 12 h). Prolonged treatment at 250 °C enhanced humification, increasing the carbon extracted from humic acid by 25.3–237.9%, whereas humic substances were largely decomposed at 500 °C. Structural analyses indicated that low-temperature chars maintained reactive surface chemistry, while high-temperature chars showed greater aromaticity and porosity, particularly for wood-derived materials (378.5 m²/g). Overall, low-temperature pyrolysis produces functionally active carbon materials suitable for saline-sodic soil amendment and nutrient management, whereas 500 °C pyrolysis generates more aromatic and porous materials better suited for long-term carbon stability and physical soil conditioning. Full article

Here, the degradation of a β-blocker drug (Nadolol (NAD)) and real pharmaceutical wastewater was achieved using magnetized cow bone waste-derived char (MCBWC)–alginate hydrogel beads via a periodate (PI) activation system in a continuous-flow fluidized-bed photoreactor. The removal of NAD by PI-based degradation systems has not been previously reported, and the degradation of real industrial wastewater in continuous-flow photoreactors remains underexplored. The fabricated beads exhibited a high surface area of 78.58 m² g⁻¹, a total pore volume of 0.19 cm³ g⁻¹, and an effective integration of all composite components. The MCBWC–alginate hydrogel beads/PI/light degradation system degraded 71.47% of NAD, which was higher than that of the sole photocatalysis and PI activation systems. Further, the optimal operating condition could achieve a NAD degradation efficiency of 97.1% and a total organic carbon (TOC) removal efficiency of 82.78%. Furthermore, the degradation system demonstrated the non-formation of toxic iodinated byproducts. The hydrogel beads demonstrated high stability, where the NAD degradation efficiency slightly decreased by only 2.85% across five successive experiments. Singlet oxygen and iodine-based radicals contributed to NAD degradation more than other reactive species. Bicarbonate showed the highest suppressive effect on the degradation performance, while adding 10 mg L⁻¹ of humic acid decreased the degradation efficiency to 85.58%. The degradation system could further degrade other pharmaceuticals (e.g., ibuprofen, paracetamol, carbamazepine, tetracycline) and real pharmaceutical wastewater, attaining 78.37% degradation efficiency of NAD and 44.25% TOC mineralization. This study presents a stable, effective, and continuous degradation system that can be employed in real-world industrial wastewater treatment applications. Full article

Coal gasification fine ash (CGFA) is a carbon–mineral composite solid waste whose valorization is severely hindered by poor interfacial compatibility with organic media due to its highly polar surface. Here, we report a surface alkylation strategy using haloalkanes with variable chain lengths to systematically tune the surface chemistry and thermo-oxidative behavior of CGFA. Comprehensive spectroscopic characterizations (XPS, FTIR, and ¹³C NMR) confirm successful grafting of alkyl chains, which increases aliphatic C-H content from 24.8% to 43.9% while reducing polar carboxyl groups from 7.9% to 1.6%, with the mineral framework remaining intact. Thermogravimetric analysis reveals that alkylation lowers the onset decomposition temperature from 358 °C to 295 °C and enhances the maximum mass-loss rate. Kinetic analysis shows that grafted alkyl chains act as low-energy initiation sites, reducing the initial activation energy to 95 kJ/mol, while the later-stage oxidation becomes diffusion-limited. Notably, long straight-chain alkylation achieves the best performance, whereas branched chains are less effective due to steric hindrance and pore blockage. This work establishes a clear chain-length-dependent structure–thermal response relationship, positioning alkylated CGFA as a designable precursor for functional carbon materials, intelligent char-forming agents, and tunable components for energy or responsive material systems. Full article

The mechanical recycling of mono-material biaxially oriented polypropylene (BOPP) packaging films produces recycled polypropylene (rPP) with degraded properties, limiting its use in higher-performance applications. This study investigates rPP reinforcement with 6–12 µm microcellulose fibres (MCFs, 2–10 pbw) and microcellulose-derived biochar (BC, 5–20 pbw), characterized by DSC, TGA/DTG, MVR/MFR, temperature-dependent rheology, mechanical testing and water contact angle (WCA) measurements. Both fillers acted as heterogeneous nucleating agents, shifting crystallization by up to 4 °C and increasing crystallinity by 2–4%. MCF introduced an additional low-temperature degradation step, whereas BC increased onset and peak degradation temperatures by up to 20 °C and increased char yield. Low MCF loadings increased MVR/MFR by 20–25% and reduced melt viscosity, while BC decreased flow indices by up to 50% and stiffened the melt. Tensile and flexural moduli increased by 15–25% with MCF and 40–50% with BC, with a stiffness–toughness trade-off at the highest BC contents. MCF reduced the water contact angle to 63.0° at 10 pbw, while BC increased it to 108.1° at 20 pbw, indicating opposite effects on surface wettability. Converting a single cellulosic feedstock into fibrous or carbonised fillers enables bio-based upgrading of rPP, in line with circular economy principles. Full article

Environmental fires pose a serious threat to energy security, ecosystems and public safety, whilst traditional halogenated flame retardants suffer from limitations such as high environmental residue risks and insufficient flame-retardant efficacy. In this study, sodium alginate (SA) was utilised as the matrix, with the incorporation of ammonium polyphosphate (APP) and phytic acid (PA), in conjunction with SiO₂-APTES surface modification, to prepare nitrogen–phosphorus synergistic bio-based flame-retardant gels. The present study systematically investigated the influence of the N/P molar ratio on the gelation kinetics, rheological behaviour, microstructure and flame-retardant performance of the gel. The study revealed a nitrogen–phosphorus coupled gas–solid two-phase synergistic flame-retardant mechanism. The results indicate that at an N/P ratio of 1/4, the gel forms a stable dual-network structure comprising ionic cross-links and Si–O–P covalent bonds. In the gas phase, the thermal decomposition of APP releases inert NH₃, which dilutes oxygen and quenches gas-phase radicals (·OH, ·H). In the condensed phase, the phosphate groups of PA-catalysed SA form Si–O–P covalent bonds with SiO₂ under the mediation of APTES, creating a dense, insulating char layer. In comparison with the control group (N/P = 0/0), the optimal gel sample (N/P = 1/4) demonstrated a 33% increase in shear stress, a 10% reduction in the peak heat release rate (HRR), a 75% decrease in total smoke production (TSP), and a 150% increase in char layer thickness after combustion, while maintaining adequate mechanical strength, thermal stability, and environmental friendliness. This work provides novel insights and strategies for the development of green, highly efficient flame-retardant materials for environmental fire prevention and control. Full article

This study investigates the influence of surface-modified fly ash particles on the fire behavior of polyamide 6 (PA6) composites containing two types of flame retardants: melamine polyphosphate (MPP) and aluminum diethyl phosphinate (AlPi). The objective was to evaluate how interfacial modification of fly ash using amino-silane (APTES), glycidoxy-silane (GPTES), or titanate coupling agents affects dispersion, thermal stability, and combustion performance. A series of 18 formulations containing up to 25 wt% of additives was prepared by melt compounding and characterized by thermogravimetric analysis (TGA) and cone calorimetry. TGA results showed that MPP-based systems favored char formation, with residues up to 21%, whereas AlPi provided higher thermal stability (T₅₀% ≈ 445 °C). The incorporation of untreated or surface-treated fly ash improved both thermal stability and char yield, depending on the nature of the coupling agent. Cone calorimeter results confirmed a strong synergistic effect between flame retardants and fly ash. The peak heat release rate (pHRR) decreased by 65–75% compared to neat PA6, while total heat release (THR) and mass loss were also significantly reduced. Titanate-modified fly ash showed the most homogeneous dispersion and provided the highest residue and lowest pHRR values. Energy-dispersive X-ray (EDX) analyses confirmed enhanced phosphorus retention in the residues (up to 100%), evidencing the formation of stable inorganic species and protective ceramic-like structures. These results demonstrate that surface-modified fly ash can act as an efficient synergistic additive in PA6 flame-retardant formulations, simultaneously improving fire performance and promoting the valorization of industrial by-products for sustainable polymer design. Full article

Biomass, composed of natural polymers such as cellulose, hemicellulose, and lignin, can be converted into circular chemical feedstocks through thermochemical conversion processes like pyrolysis. Char conversion is the rate-limiting step in the thermochemical conversion process, and thus, char reactivity is essential for determining the overall efficiency of pellet-based thermochemical processes. Pyrolysis experiments were conducted on rice straw pellets of different sizes (i.e., 8, 10, and 12 mm) in a vertical quartz tube reactor at 700 °C, and then the chemical structure of chars sampled at different stages and locations within a 10 mm pellet was analyzed using Raman spectroscopy and Fourier transform infrared spectroscopy (FTIR). The results indicate that increasing the pellet size facilitates the growth of polycyclic aromatic structures, as evidenced by the observed variations in the abundance of typical aromatic compounds in bio-oil. This also promotes volatile–char interactions, leading to greater deposition of large aromatic structures on the char surface, thereby enhancing char aromatization. Analogous to the spatial scale effect of pellet size on char structure, the evolution of the char structure within a single pellet exhibits distinct spatial heterogeneity during the initial devolatilization and subsequent char aromatization stages due to the location-dependent coupling of heat/mass transfer limitations and aromatization reactions during pyrolysis. Furthermore, the spatiotemporal evolution of the char structure leads to differences in the specific reactivity: during the devolatilization stage at 75 s, the center exhibits the highest reactivity, whereas the outer surface becomes the most reactive in the subsequent char aromatization stage at 300 s. Full article

Accurate modeling of the burning rate of char particles in particle-laden flows is essential. However, because of the strong inhomogeneity and nonlinearity of the process, accurately resolving the surface burning rate of char particles remains challenging. In this study, an eXtreme Gradient Boosting (XGBoost)-based framework is developed to reformulate the conventional char oxidation rate model, namely the Baum&Street (B&S) model, resulting in a modified model referred to as the XGB-B&S model. In this model, a correction term ${\beta }_{\mathrm{turb}}$ is incorporated and formulated using the particle Reynolds number together with a dimensionless temperature. A turbulent mixing layer with char particle combustion is simulated by means of particle-resolved direct numerical simulation with three-dimensions, generating a high-fidelity dataset for model training and validation. To assess the predictive capability of the XGBoost model, its results are benchmarked against those obtained from an Artificial Neural Network model. The comparison indicates that XGBoost provides better overall accuracy, as reflected by a larger coefficient of determination (${\mathrm{R}}^2$) and smaller values of both the root mean square error and the mean absolute error. Finally, the XGB-B&S model is validated against the test dataset. The ${\mathrm{R}}^2$ between the XGB-B&S predictions and the PR-DNS results is significantly higher than that between the conventional B&S model and the PR-DNS results, confirming the strong predictive capability of XGBoost for modeling char particle oxidation rate. Full article