Search Results (363)

In this study, carbon quantum dots (CQDs) were synthesized from various lignocellulosic and hemicellulosic biomass precursors via a semi-hydrothermal torrefaction process, and their structural, optical, colloidal, and photocatalytic properties were systematically investigated. Biomass sources including Oriental thuja cone (Thuja orientalis), sawdust, tea waste, apricot kernel shell, walnut shell, sugar beet pulp, hazelnut residue, soybean residue, and chitosan were used to evaluate the effect of precursor composition on CQDs characteristics. UV–Vis spectroscopy confirmed the formation of CQDs in all samples, exhibiting characteristic π–π* and n–π* transitions, while significant variations in absorption intensity and spectral behavior were observed depending on biomass type. Dynamic light scattering and zeta potential analyses revealed that most CQDs exhibited aggregation tendencies, with limited systems showing improved colloidal stability due to electrostatic and/or steric stabilization. The synthesized CQDs were combined with TiO₂ and their influence on the photocatalytic degradation of Reactive Black 5 under UV irradiation was investigated. Although high decolorization efficiencies (85–98%) were achieved, total organic carbon removal remained lower (2.6–41.4%), indicating incomplete mineralization. The highest mineralization efficiencies were observed for TiO₂ systems modified with sawdust- and thuja-derived CQDs. Overall, the results demonstrate that the photocatalytic performance of CQDs-modified TiO₂ systems is governed not only by optical properties but also by surface functionalization, colloidal stability, and charge carrier dynamics. The findings highlight the critical role of biomass composition in determining CQD properties and provide a comparative framework for designing sustainable nanomaterials for environmental applications. Full article

In this study, a new approach to improving the fire resistance of flexible polyurethane (PUR) foams is presented, based on the incorporation of cotton chemically modified with boron compounds into the polyurethane matrix. The developed system was additionally modified with melamine polyphosphate (MPP). The effects of the applied modifications on the morphology and chemical structure of the PUR composites were investigated using scanning electron microscopy and infrared spectroscopy. Thermal stability was evaluated by thermogravimetric analysis, whereas fire hazard was assessed using cone calorimetry and a smoke optical density chamber. The toxicometric index (WLC_50SM) was determined using a coupled TG-Omega 5 gas analyzer system. The results provide insight into the mechanism responsible for reducing flammability and limiting the emission of toxic combustion and thermal decomposition products through the modification of PUR foams with chemically modified cotton in combination with MPP. It was observed that, during the combustion of the developed PUR composites, the addition of cotton promotes the formation of a three-dimensional spatial network, which substantially limits heat release and the emission of toxic combustion products. Consequently, the composites exhibited a reduction in heat release of up to 67% in terms of HRR_MAX, together with decreased production of HCN and CO. Nevertheless, the formation of a protective carbon layer contributed to an increase in smoke optical density, which was associated with increased CO₂ emission. Overall, this work demonstrates the development of a new synergistic system capable of reducing both the flammability and toxicity of flexible PUR foams. Full article

The valorization of secondary biomass streams is an important step toward more resource-efficient biorefinery concepts and reduced dependence on fossil-based materials. In this study, agricultural and forest residues, namely Atlas cedar cones, mixed conifer cones, hazelnut shells, walnut shells, coffee silverskin, and cocoa shells, were investigated as feedstocks for producing colloidal lignin particles. Lignin-rich extracts were obtained by Organosolv pretreatment using 60 wt% aqueous ethanol, followed by particle formation through solvent shifting and purification by ultrafiltration. A particular novelty of this work is that highly different feedstocks were processed under identical Organosolv and solvent-shifting conditions, enabling a direct comparison of their suitability for colloidal lignin particle production within one consistent process route. The feedstocks differed markedly in extractive content and chemical profile, as shown by sequential Soxhlet extraction and qualitative GC-MS screening. Despite these differences in extract composition, solvent shifting yielded colloidal lignin particles with largely similar properties. Dynamic light scattering showed hydrodynamic diameters of 65–88 nm immediately after precipitation for all samples except cocoa shell, which formed strong agglomerates. The ultrafiltration step further introduced an industry-relevant downstream purification stage by removing most water-soluble low-molecular-weight compounds before product evaluation. After purification and redispersion, particle sizes ranged from 121 to 389 nm, indicating partial aggregation but overall successful recovery of stable colloidal dispersions. All purified particle suspensions exhibited comparable antioxidant activity in the FRAP (ferric reducing antioxidant power) assay, ranging from 12.3 to 18.4 mg lignin per mg ascorbic acid equivalents. These results demonstrate that even chemically diverse biomass side streams can be converted into purified colloidal lignin suspensions with similar colloidal behavior and functional performance. The findings highlight the potential of low-value agricultural and forest residues as promising raw materials for lignin-based antioxidant and material applications. Full article

Aiming at the problems of insufficiently tight sealing of all-metal dissolvable frac plugs and the poor fracturing effect in the extraction of shale gas, the effects of structural parameters on the performance of metal dissolvable ball seat sealing rings was analyzed using numerical simulation and an experimental method. The key structural factors affecting performance were identified. The problem of stress concentration at the contact position between the sealing ring and the slip of the existing structure was discovered. To solve the above problems, a combination structure sealing ring was designed. Then the performance comparison analysis of the two structures and optimal structural parameters were carried out. Under the same sealing force, the combination structure sealing ring can be smoothly sealed, and the stress distribution of the upper sealing ring is uniform. This indicates that the performance of the combination structure sealing ring is superior, and the optimal cone angle and thickness obtained are 9° and 17 mm, respectively. Based on the optimized structural parameters, experiments were conducted. After being pressurized at room temperature to 51 MPa and stabilized for 15 min, the pressure gradually decreased to 47.4 MPa, indicating a secondary setting. After unloading, the lower end face of the dissolvable ball seat has no liquid leakage. Under high temperature, a pressure of 51 Mpa was applied; the pressure inside the wellbore remained basically unchanged. During the process of applying pressures of 60 MPa and 70 MPa, there was also a decrease in pressure, indicating the presence of secondary sealing. The above results indicate that the optimized combined metal sealing ring has strict sealing and good pressure-bearing performance. At the same time, the reliability of the simulation results was verified. The designed sealing ring was applied to the shale gas horizontal well deployed in Changning block, China. The application results show that when the displacement remains unchanged, the casing pressure increases from 51 MPa to 60 MPa, and continues to maintain the displacement. The pressure did not fall back to 51 MPa, proving that the formation pressure is released. The successful on-site application once again verifies the safe and reliable performance of the all-metal sealing ring. Full article

In biomass pellet combustion, the formation of ash layers on particle surfaces severely hinders combustion reactions and heat transfer, while the key parameters governing particle motion behavior and ash pre-separation in rotating cone burners remain insufficiently understood. To address these challenges and to optimize particle mixing and ash separation performance, this study adopts a combined numerical approach. The discrete element method (DEM) coupled with the Hertz–Mindlin (no-slip) contact model is employed to simulate particle motion and mixing dynamics, while a separate cold-state computational fluid dynamics (CFD) model based on the Realizable k-ε turbulence model and the discrete phase model (DPM) with Rosin–Rammler particle size distribution is established to investigate ash separation mechanisms. The Lacey mixing index is used to quantify mixing uniformity, and grid independence verification is performed to ensure numerical reliability. Key findings reveal that the rolling regime (rotational speed: 1.7–11 r/min), a uniform particle size of 25 mm, and a cone inclination angle of 45° collectively optimize particle mixing. Rotational speed is identified as the dominant factor affecting mixing effectiveness. Furthermore, an optimal secondary-to-primary air ratio of approximately 7:3 (within the tested range) balances enhanced centrifugal separation with flow field stability by mitigating backflow and excessive turbulence. This work not only fills the knowledge gap regarding the coupled effects of operational and structural parameters on particle behavior in rotating cone burners but also provides novel, quantitative guidance for the rational design and parameter tuning of such burners to improve combustion efficiency and operational stability. Full article

This study evaluates β-cyclodextrin (β-CD) and malonic acid functionalized pine sawdust biochar for organic pollutant removal, benchmarking efficacy against commercial Norit GSX activated carbon for sustainable water treatment. Characterization revealed that β-CD modification successfully developed porous structures, with Sawdust Activated Carbon (SDAC) and Norit GSX Activated Carbon (GSXAC) achieving Brunauer–Emmett–Teller (BET) surface areas of 438.36 m²/g and 1223.79 m²/g, respectively. Adsorption kinetics and isotherm studies demonstrated the superiority of β-CD-modified materials over traditional acid-functionalized variants. The adsorption kinetics were exceptionally well-described by the Pseudo-Second-Order model R² > 0.99, indicating that the process is governed by chemical interactions rather than simple physical attachment. In contrast, the Pseudo-First-Order and Elovich models provided poor descriptions of the system (R² = 0.54 and 0.11, respectively). An isotherm analysis further confirmed the heterogeneous nature of the SDAC surface, with the Freundlich model exhibiting an excellent fit (R² > 0.99) and an n value of 0.79. For GSXAC, the Freundlich model also outperformed the Langmuir model, yielding a K_F of 441.72 mg/g and n = 0.77, reflecting high adsorption intensity on a heterogeneous surface. The comparative advantage of β-CD is in line with its unique truncated cone structure, which is consistent with guest–host inclusion complex formation, multi-modal hydrogen bonding, and enhanced pH resilience. These findings validate β-CD-modified sawdust-derived adsorbents as potential, sustainable, high-capacity alternatives to industrial-grade carbons. Full article

The interaction between crossflows from sprinkler nozzles and airflow is crucial for engineering applications, particularly affecting the efficiency of sprayed areas. This study investigates the deformation of a continuously injected conical water spray subjected to horizontal airflow, using a planar laser imaging method as a visualisation technique. Experiments were conducted in a wind tunnel at a constant water pressure of 0.2 MPa and four airflow rates (0.1, 0.2, 0.4, and 0.6 m³·s⁻¹) to systematically vary the air-to-water momentum ratio. A grayscale-based analysis method was developed using a per-pixel Look-Up Table (LUT), enabling indirect assessment of droplet concentrations and spray structure. This approach allowed for a detailed examination of changes in the spray cone shape under flowing air. By assessing the water spray across three vertical planes intersecting the spray cone, it became possible to calculate lateral area and cone volume at different air-to-water mass flow ratios. The spray formation region exposed to airflow exhibited larger cone volumes than those with minimal airflow. The changes in apparent spray angles for the tested nozzles were determined to characterize the cone shape. The apparent spray angle varies systematically with the air-to-water mass flow ratio, confirming the dominant role of aerodynamic forces. These findings improve the understanding of spray behavior under crossflow and provide a basis for validating numerical models of air–water interactions. Full article

This study investigates the stress–strain state of rocks subjected to the impact of penetrators with diverse configurations, employing numerical simulations in the ANSYS Workbench Static Structural module. The research focuses on the interaction between roller cone drill bit teeth and rock formations during blast hole drilling. Through finite element modeling using a linear elastic constitutive model, the influence of penetrator geometry, position relative to borehole walls, angle of attack, and distance to open surfaces on rock fracture parameters is analyzed. Key quantitative findings include: the relative breaking force near the borehole wall reaches 2.8 for soft rocks (siltstones) with a 10 mm tooth diameter, and decreases to approximately 1.0 at a distance of 1.5d from the wall; the optimal angle of attack ranges from 60° to 90° depending on rock hardness; and the proximity to a free surface reduces fracture resistance to as low as 0.23 of the baseline value. Six sets of parabolic regression equations (R² > 0.95) are derived for relative breaking forces across three rock hardness groups and two tooth diameters. Optimal parameters for tooth placement, borehole bottom shapes, and operational conditions are proposed. Implementation of the recommended parameters is estimated to increase drilling efficiency by 10–20% and extend tool service life by 15–30%. The findings provide a scientific foundation for designing advanced roller cone drill bits suitable for rocks with Protodyakonov hardness indices ranging from f = 5 to f = 18. Full article

The development of high-performance flame-retardant (FR) polypropylene (PP) with high mechanical integrity remains a challenge. Herein, we demonstrate a synergistic flame retardancy system for PP achieved via partial substitution of piperazine pyrophosphate (PAPP) with 1 wt.% magnesium borate whiskers (MBW) for improved flame retardancy, and thermal and mechanical properties. The optimized PP/24PAPP/1MBW exhibits exceptional FR performance, driven by the formation of a highly ordered, continuous phosphorus–boron hybrid char in the condensed phase. Cone calorimetry test results reveal an 80% reduction in peak heat release rate, a 54% reduction in total heat release, and a 33% reduction in total smoke production compared to neat PP, while the UL-94 test confirms a V-0 rating with complete suppression of flaming drips. Morphological study of the char residue using Raman spectroscopy and SEM attributes this performance to enhanced char graphitization and structural coherence enabled by boron-mediated cross-linking. More importantly, this transformative flame retardancy performance is achieved without severe compromise to mechanical properties, retaining over 89% of the original tensile strength. This work confirms the PAPP/MBW system as a highly efficient, low-additive approach to creating advanced fire-safe polymer composites for engineering applications. 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

The Dengying Formation gas reservoir in the Penglai gas field, located in the central Sichuan Basin, exhibits substantial resource potential and promising development prospects. This reservoir is characterized by well-developed fractures and dissolution cavities, strong heterogeneity, complex gas–water relationships, and widespread edge–bottom water. During production, edge–bottom water is prone to channeling and intrusion through high-permeability pathways, which severely constrains well productivity and overall gas recovery. To address these challenges, this study takes a fractured-vuggy carbonate edge–bottom water gas reservoir as an example. By integrating large-scale physical simulation with cross-scale numerical simulation, a rational production allocation method suitable for strongly heterogeneous gas reservoirs has been developed. The research results indicate that: (1) Large-scale physical simulation experiments demonstrate that for fractured-vuggy bottom water gas reservoirs, implementing rate reduction and pressure control after water breakthrough can effectively suppress water invasion and coning, extend the stable production period, and increase the recovery factor by approximately 16%; (2) Based on the dynamic characteristics of water invasion, key similarity criteria including the Bond number, capillary number, gravity–viscous force ratio, and geometric–temporal similarity ratio were selected to establish a scientific parameter design method for cross-scale numerical simulation; (3) By considering factors such as reservoir type and aquifer energy, single-well mechanistic models were used to determine appropriate production rates for individual wells, enabling rapid optimization of production allocation plans. This provides crucial guidance for efficient gas well development and surface facility planning. Full article

Zr alloy-shaped charge liners (SCLs) offer broad application prospects due to their multiple post-penetration damage effects. However, research on these liners is still in its early stages. The mechanisms of jet formation and penetration for Zr alloys SCL remain unclear, and the specific contribution of different liner regions to the penetration process is not yet understood. This gap in knowledge has limited their structural design to a black-box correlation between global structural parameters and macroscopic penetration efficiency. To address this gap, a region-tracing Smoothed Particle Hydrodynamics (SPH) simulation was employed. Following a strategy of “wall thickness layering + axial segmentation,” the Zr alloy liner was partitioned into ten characteristic regions. This methodology facilitated the tracking of material transport from each region during jet formation and penetration into an AISI 1045 steel target. The contribution of each region to the penetration depth was then quantitatively assessed via post-processing. For the first time, the “critical region” contributing most to penetration depth was identified, and the influence of the liner’s cone angle and wall thickness on the contribution of each region was revealed. This study enhances the theoretical framework for understanding the damage effects of Zr alloy shaped charge liners. It not only advances the fundamental understanding of jet penetration mechanisms but also provides a theoretical basis for the refined design and performance optimization of these liners. Full article

Epoxy resins (EP) are widely used in aerospace, electronics, and coatings due to their excellent mechanical and thermal properties. However, their inherent flammability and brittleness limit high-end applications. In this work, a novel reactive flame retardant epoxy monomer (EP-DVGA) containing DOPO and triazole units was designed and synthesized via a molecular engineering strategy. The chemical structure was confirmed by FTIR and NMR. A series of modified epoxy thermosets were prepared by co-curing EP-DVGA with bisphenol A epoxy resin (E51) using DDM as curing agent. The results showed that EP-DVGA significantly enhanced flame retardancy: At 16.31 wt% loading, the limiting oxygen index increased from 25.9% to 34.3% with UL-94 V-0 rating, and cone calorimetry revealed 73.2% and 69.2% reductions in peak heat release rate and total heat release, respectively. Mechanistic studies demonstrated a dual flame retardant effect involving phosphorus radical quenching in the gas phase and formation of a dense graphitized char layer in the condensed phase. Remarkably, EP-DVGA also improved mechanical properties—impact strength increased by 47% and tensile strength by 33.1% at optimal loadings—attributed to energy dissipation through reversible hydrogen bonding and π–π interactions. This molecular design successfully overcomes the traditional trade-off between flame retardancy and mechanical performance, offering a promising strategy for developing high-performance intrinsically flame retardant epoxy materials. Full article

Background/Obectives: Alveolar bone resorption after tooth extraction compromises esthetics and implant placement. Conventional alveolar ridge preservation (ARP) relies on grafting. This randomized controlled study evaluated a graft-free, lamina-based approach aimed at preserving ridge morphology by protecting the buccal cortical plate. Methods: Forty alveoli were randomly assigned to Guided Alveolar Ridge Preservation (G-ARP) with a subperiosteally positioned cortical lamina (test) or unassisted healing (control; CTRL). Cone-beam computed tomography (CBCT) was performed before extraction and after five months. Vertical and horizontal dimensional changes were statistically compared. Results: Healing was uneventful. At five months, the G-ARP group showed a vertical gain of 0.5 mm and a horizontal reduction of 0.2 mm, whereas the CTRL group exhibited a vertical loss of 1.7 mm (p < 0.01) and a horizontal loss of 2.7 mm (p < 0.001). Effect sizes were large for vertical change and very large for horizontal change (Hedges’ g = 0.95 and 2.19, respectively). Regeneration occurred through native bone formation without grafts. Conclusions: Subperiosteal placement of a cortical lamina effectively preserved ridge dimensions after extraction. This graft-free approach may offer technical and biological advantages while supporting new bone regeneration. Full article

To investigate the mechanism of texture formation during the cold rolling of Ti-3Al-2.5V tubes for aerospace hydraulic systems, this study examines the microstructure at various locations of two deformation cones with ‘Q’ ratios of 1.055 and 1.300, respectively, in a single cold-rolling pass, revealing their continuous texture evolution. The results indicate that the cold-rolling texture primarily forms during the sinking section. A higher ‘Q’ ratio leads to a stronger tendency for the c-axis of grains to align parallel to the radial direction of the tube, resulting in enhanced radial texture intensity. Beyond influencing texture through dislocation slip, a higher ‘Q’ ratio also elevates the Schmid factor for {10$\stackrel{\mathrm{-}}{1}$2} twinning. This twinning mechanism primarily forms the radial texture by altering the stress state. Consequently, this change not only facilitates twin activation but also modifies the rotation direction of grains during the twinning process. Compared to the cone with a ‘Q’ ratio of 1.055, the deformation cone with a ‘Q’ ratio of 1.300 contains a greater number of twins oriented along <0001>//RD, leading to a stronger radial texture in the tube. Full article