Search Results (671)

Aluminum matrix composites provide an ideal solution for lightweight brake disks, but conventional casting processes are prone to crack initiation due to inhomogeneous reinforcement dispersion, gas porosity, and inadequate toughness. To break the conventional trade-off between high wear resistance and low toughness of brake disks, this study fabricated a bimetallic structure of SiC_p/Al–Fe–V–Si aluminum matrix composite and cast ZL101 alloy using friction stir lap welding (FSLW). Then, the microstructural evolution, mechanical properties, and tribological behavior of the FSLW joints were studied by XRD, SEM, TEM, tensile testing, and tribological tests. The results showed that the FSLW process homogenized the distribution of SiC particle reinforcements in the SiC_p/Al–Fe–V–Si composites. The Al₁₂(Fe,V)₃Si heat-resistant phase was not decomposed or coarsened, and the mechanical properties were maintained. The FSLW process refined the grains of the ZL101 aluminum alloy through recrystallization and fragmented eutectic silicon, improving elongation to 22%. A metallurgical bond formed at the joint interface. Tensile fracture occurred within the ZL101 matrix, demonstrating that the interfacial bond strength exceeded the alloy’s load-bearing capacity. In addition, the composites exhibited significantly enhanced wear resistance after FSLW, with their wear rate reduced by approximately 40% compared to the as-received materials, which was attributed to the homogenized SiC particle distribution and the activation of an oxidative wear mechanism. Full article

Chronic lung infection is the main predictor of morbidity and mortality in cystic fibrosis (CF), and current pharmacological alternatives are ineffective against Pseudomonas aeruginosa infections. We developed ciprofloxacin (CIP) for inhalation, aiming at improving its solubility through the formation of an amorphous solid dispersion (ASD) using gelatin (GA). CIP and GA were dissolved in varying ratios and then spray-dried, obtaining CIP-GA microspheres in a single step. The dissolution rate, size distribution, morphology, and aerodynamic properties of CIP-GA microspheres were studied, as well as their antimicrobial activity on P. aeruginosa biofilms. Microspheres formulated with a higher GA ratio increased the dissolution of CIP ten-fold at 6 h compared to gelatin-free CIP. Formulations with 75% GA or more could form ASDs and improve CIP’s dissolution rate. CIP-GA microspheres outperformed CIP in eradicating P. aeruginosa biofilm at 24 h. The spray-drying process produced CIP-GA microspheres with good aerodynamic properties, as indicated by a fine particle fraction (FPF) of 67%, a D₅₀ of 3.52 μm, and encapsulation efficiencies above 70%. Overall, this study demonstrates the potential of gelatin to enhance the solubility of poorly soluble drugs by forming ASDs. As an FDA-approved excipient for lung delivery, these findings are valuable for particle engineering and facilitating the rapid translation of technologies to the market. Full article

This study investigates the hydrogen permeability of injection-molded polyamide 6 (PA6) nanocomposites reinforced with organo-modified montmorillonite (OMMT) at varying concentrations (1, 2.5, 5, and 10 wt. %) for potential use as Type IV composite-overwrapped pressure vessel (COPV) liners. While previous work examined their mechanical properties, this study focuses on their crystallinity, morphology, and gas barrier performance. The precise inorganic content was determined using thermal gravimetry analysis (TGA), while differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), and scanning electron microscopy (SEM) were used to characterize the structural and morphological changes induced by varying filler content. The results showed that generally higher OMMT concentrations promoted γ-phase formation but also led to increased agglomeration and reduced crystallinity. The PA6/OMMT-1 wt. % sample stood out with higher crystallinity, well-dispersed clay, and low hydrogen permeability. In contrast, the PA6/OMMT-2.5 and -5 wt. % samples showed increased permeability, which corresponded to WAXD and SEM evidence of agglomeration and DSC results indicating a lower degree of crystallinity. PA6/OMMT-10 wt. % showed the most-reduced hydrogen permeability compared to all other samples. This improvement, however, is attributed to a tortuous path effect created by the high filler loading rather than optimal crystallinity or dispersion. SEM images revealed significant OMMT agglomeration, and DSC analysis confirmed reduced crystallinity, indicating that despite the excellent barrier performance, the compromised microstructure may negatively impact mechanical reliability, showing PA6/OMMT-1 wt. % to be the most balanced candidate combining both mechanical integrity and hydrogen impermeability for Type IV COPV liners. Full article

Hybrid materials based on porous organic polymers (POPs) and metal–organic frameworks (MOFs) are increasing attention for advanced separation processes due to the possibility to combine their properties. POPs provide high surface areas, chemical stability, and tunable porosity, while MOFs contribute a high variety of defined crystalline structures and enhanced separation characteristics. The combination (or hybridization) with PIMs gives rise to mixed-matrix membranes (MMMs) with improved permeability, selectivity, and long-term stability. However, interfacial compatibility remains a key limitation, often addressed through polymer functionalization or controlled dispersion of the MOF phase. MOF/COF hybrids are more used as biochemical sensors with elevated sensitivity, catalytic applications, and wastewater remediation. They are also very well known in the gas sorption and separation field, due to their tunable porosity and high electrical conductivity, which also makes them feasible for energy storage applications. Last but not less important, hybrids with other POPs, such as hyper-crosslinked polymers (HCPs), covalent triazine frameworks (CTFs), or conjugated microporous polymers (CMPs), offer enhanced functionality. MOF/HCP hybrids combine ease of synthesis and chemical robustness with tunable porosity. MOF/CTF hybrids provide superior thermal and chemical stability under harsh conditions, while MOF/CMP hybrids introduce π-conjugation for enhanced conductivity and photocatalytic activity. These and other findings confirm the potential of MOF-POP hybrids as next-generation materials for gas separation and carbon capture applications. Full article

Fluid dispersion directly influences the transport, mixing, and efficiency of hydrogen storage in depleted gas reservoirs. Pore structure parameters, such as pore size, throat geometry, and connectivity, influence the complexity of flow pathways and the interplay between advective and diffusive transport mechanisms. Hence, these factors are critical for predicting and controlling flow behavior in the reservoirs. Despite its importance, the relationship between pore structure and dispersion remains poorly quantified, particularly under elevated flow conditions. To address this gap, this study employs pore network modeling (PNM) to investigate the influence of sandstone and carbonate structures on fluid flow properties at the micro-scale. Eleven rock samples, comprising seven sandstone and four carbonate, were analyzed. Pore network extraction from CT images was used to obtain detailed pore structure parameters and their statistical measures. Pore-scale simulations were conducted across 60 scenarios with varying average interstitial velocities and water as the injected fluid. Effluent hydrogen concentrations were measured to generate elution curves as a function of injected pore volumes (PV). This approach enables the assessment of the relationship between the dispersion coefficient and pore structure parameters across all rock samples at consistent average interstitial velocities. Additionally, dispersivity and n-exponent values were calculated and correlated with pore structure parameters. Full article

Accurate gas prediction is crucial for identifying gas-bearing zones in tight sandstone reservoirs. Traditional seismic techniques, primarily grounded in elastic theory, often overlook inelastic dispersion effects inherent to such formations. To overcome this limitation, we introduce a gas prediction approach utilizing a dispersion attribute derived from frequency-dependent inversion based on an AVO equation parameterized by a gas indicator and related properties. Rock physics modeling, based on multi-scale fracture theory, reveals the frequency-dependent gas indicator is highly responsive to variations in porosity and gas saturation. Seismic AVO simulations exhibit distinguishable signatures corresponding to these variations, supporting the potential to estimate reservoir properties from pre-stack seismic data. Synthetic data tests confirm that the values of the proposed dispersion attribute increase with increasing porosity and gas saturation. Additionally, the calculated dispersion attribute exhibits a strong positive correlation with gas content, validating its effectiveness for gas evaluation. Field application results further demonstrate that the proposed dispersion attribute shows prominent anomalies in sandstone reservoirs with high gas content. Compared to the conventional P-wave dispersion attribute, the proposed dispersion attribute exhibits superior reliability in detecting gas-rich zones. These results demonstrate the utility of the method in predicting gas-bearing regions in tight sandstone reservoirs. Full article

Bio-nanocomposites based on poly (vinyl alcohol) (PVA) and cellulosic nanostructures are favorable for active food packaging applications. The current study systematically investigates the mechanical properties, gas permeation, and swelling parameters of PVA composites with cellulose nanocrystals (CNC) or nano lignocellulose (NLC) fibers. Alterations in these macroscopic properties, which are critical for food packaging applications, are correlated with structural information at the molecular level. Strong interactions between the fillers and polymer host matrix were observed, while the PVA crystallinity exhibited a maximum at ~1% loading. Finally, the orientation of the PVA nanocrystals in the uniaxially stretched samples was found to depend non-monotonically on the CNC loading and draw ratio. Concerning the macroscopic properties of the composites, the swelling properties were reduced for the D1 food simulant, while for water, a considerable decrease was observed only when high NLC loadings were involved. Furthermore, although the water vapor transmission rates are roughly similar for all samples, the CO₂, N₂, and O₂ gas permeabilities are low, exhibiting further decrease in the 1% and 1–5% loading for CNC and NLC composites, respectively. The mechanical properties were considerably altered as a consequence of the good dispersion of the filler, increased crystallinity of the polymer matrix, and morphology of the filler. Thus, up to ~50%/~170% enhancement of the Young’s modulus and up to ~20%/~50% enhancement of the tensile strength are observed for the CNC/NLC composites. Interestingly, the elongation at break is also increased by ~20% for CNC composites, while it is reduced by ~40% for the NLC composites, signifying the favorable/unfavorable interactions of cellulose/lignin with the matrix. Full article

Propylene production through the CO₂-assisted oxidative dehydrogenation of propane (CO₂-ODP) is an effective route able to address the ever-increasing demand for propylene and simultaneously utilize CO₂. In this study, a series of alumina-supported gallium oxide catalysts of variable Ga₂O₃ loading was synthesized, characterized, and evaluated with respect to their activity for the CO₂-ODP reaction. It was found that both the catalysts’ physicochemical characteristics and performance were strongly affected by the amount of Ga₂O₃ dispersed on Al₂O₃. Surface basicity was maximized for the sample containing 20 wt.% Ga₂O₃, whereas surface acidity was monotonically increased with increasing Ga₂O₃ loading. A volcano-type correlation was found between catalytic performance and acid/base properties, according to which propane conversion and propylene yield exhibited optimum values for intermediate surface basicity and acidity, which both correspond to the sample containing 30 wt.% Ga₂O₃. The dispersion of a suitable amount of Ga₂O₃ on the Al₂O₃ surface not only enhances the conversion of propane to propylene but also suppresses the formation of side products (C₂H₄, CH₄, and C₂H₆) at temperatures of practical interest. The 30%Ga₂O₃-Al₂O₃ catalyst exhibited very good stability at 550 °C, where byproduct formation and carbon deposition were limited. Mechanistic studies indicated that the reaction proceeds through a two-step oxidative route with the participation of CO₂ in the abstraction of H₂, originating from propane dehydrogenation, through the reverse water–gas reaction (RWGS) reaction, shifting the thermodynamic equilibrium towards propylene generation. Full article

Superparamagnetic magnetite nanoparticles (Fe₃O₄) have garnered considerable interest due to their unique magnetic properties and potential for integration into multifunctional biomaterials. In particular, their incorporation into bacterial cellulose (BC) matrices offers a promising route for developing sustainable and high-performance magnetic composites. Numerous studies have explored BC-magnetite systems; however, innovations combining ex situ coprecipitation synthesis within BC matrices, tailored reagent molar ratios, stirring protocols, and purification processes remain limited. This study aimed to optimize the ex situ coprecipitation method for synthesizing superparamagnetic magnetite nanoparticles embedded in BC membranes, focusing on enhancing particle stability and crystallinity. BC membranes containing varying concentrations of magnetite (40%, 50%, 60%, and 70%) were characterized using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and vibrating sample magnetometry (VSM). The resulting magnetic BC membranes demonstrated homogenous dispersion of nanoparticles, improved crystallite size (6.96 nm), and enhanced magnetic saturation (Ms) (50.4 emu/g), compared to previously reported methods. The adoption and synergistic optimization of synthesis parameters—unique to this study—conferred greater control over the physicochemical and magnetic properties of the composites. These findings position the optimized BC-magnetite nanocomposites as highly promising candidates for advanced applications, including electromagnetic interference (EMI) shielding, electronic devices, gas sensors, MRI contrast agents, and targeted drug delivery systems. Full article

The growing demand for fire-safe, sustainable materials has driven extensive research into advanced flame retardants particularly polystyrene (PS), a widely utilized yet inherently flammable polymer. Graphene-derived materials are considered effective flame retardants owing to their higher thermal stability, char-formation, and gas barrier properties. However, despite these advantages, challenges such as agglomeration, high thermal conductivity, poor interfacial compatibility, and processing limitations hinder their full-scale adoption in building insulation and other applications. This review presents an in-depth analysis of recent progress in graphene-enhanced flame-retardant systems for polystyrene applications, focusing on synthesis methods, flame-retardant mechanisms, and material performance. It also discusses strategies to address these challenges, such as surface functionalization, hybrid flame-retardant formulations, optimized graphene loading, and improved dispersion techniques. Furthermore, future research directions are proposed to enhance the effectiveness and commercial viability of graphene-based flame-retardant polystyrene composites. Overcoming these challenges is essential for high-performance, eco-friendly, flame-retardant materials on a larger scale. Full article

Catalytic methane decomposition offers an attractive and sustainable pathway for producing CO_x-free hydrogen and valuable carbon nanotubes. This work investigates the innovative use of liquid metals, particularly gallium and indium, as promoters for iron catalysts based on a titanium dioxide and alumina composite to improve this process even more. In a fixed-bed reactor operating at 800 °C and atmospheric pressure, all catalyst activities for methane decomposition were thoroughly assessed while keeping the gas hourly space velocity at 6 L/g h. Surface area and porosity, H₂-temperature programmed reduction/oxidation, X-ray diffraction, Raman spectroscopy, scanning transmission electron microscopy, and thermogravimetry analysis were utilized to investigate the physicochemical properties of the catalyst. The result showed that iron supported on a titanium-alumina catalyst exhibited higher activity, stability, and reproducibility with a methane conversion of 90% and hydrogen production of 81% after three cycles, with 240 min for each cycle and stability for 480 min. In contrast, the liquid metal-promoted catalysts improved the metal-support interaction and textural properties, such as surface area, pore volume, and particle dispersion of the catalysts. Still, the catalytic efficiency significantly improved. However, the gallium-promoted catalyst displayed excellent reusability. The characterization of the spent catalyst proved that both the iron supported on a titanium-alumina and its gallium-promoted derivative produced graphitic carbon; on the contrary, the indium-promoted catalyst produced amorphous carbon. These results demonstrate how liquid metal promoters can be used to adjust the characteristics of catalysts, providing opportunities for improved reusability and regulated production of carbon byproducts during methane decomposition. Full article

Ammonia is emerging as a promising zero-carbon marine fuel due to its high hydrogen density, low storage pressure, and long-term stability, making it well-suited for supporting sustainable maritime energy systems. However, its adoption introduces serious safety challenges, as its toxic, flammable, and corrosive properties pose greater risks than many other alternative fuels, necessitating rigorous risk assessment and safety management. This study presents a comprehensive investigation of potential ammonia leakage scenarios that may arise during the fuel gas supply process within confined compartments of marine vessels, such as the fuel preparation room and engine room. The simulations were conducted using FLACS-CFD V22.2, a validated computational fluid dynamics tool specialized for flammable gas dispersion and explosion risk analysis in complex geometries. The model enables detailed assessment of gas concentration evolution, toxic exposure zones, and overpressure development under various leakage conditions, providing valuable insights for emergency planning, ventilation design, and structural safety reinforcement in ammonia-fueled ship systems. Prolonged ammonia exposure is driven by three key factors: leakage occurring opposite the main ventilation flow, equipment layout obstructing airflow and causing gas accumulation, and delayed sensor response due to recirculating flow patterns. Simulation results revealed that within 1.675 s of ammonia leakage and ignition, critical impact zones capable of causing fatal injuries or severe structural damage were largely contained within a 10 m radius of the explosion source. However, lower overpressure zones extended much further, with slight damage reaching up to 14.51 m and minor injury risks encompassing the entire fuel preparation room, highlighting a wider threat to crew safety beyond the immediate blast zone. Overall, the study highlights the importance of targeted emergency planning and structural reinforcement to mitigate explosion risks in ammonia-fueled environments. Full article

Broad lateral size and thickness distributions impede the application of hexagonal boron nitride nanosheets (BNNSs) as friction modifiers in base oil, although they possess remarkable potential for lubrication performance promotion. In this work, a cascade centrifugation-assisted liquid-phase exfoliation approach was presented to prepare BNNSs from hexagonal boron nitride (h-BN) efficiently and scalably. Subsequently, they were ultrasonically dispersed into gas-to-liquid (GTL) base oil, and their lubrication performance promotion was evaluated by a four-ball tribotester. Tribological tests demonstrated that BNNS possesses excellent friction-reducing and anti-wear properties in GTL. Furthermore, the findings indicate that at a BNNS content of 0.8 wt.%, the system displayed the lowest COF and WSD. Particularly, with an addition of 0.8 wt.% BNNS into GTL, the AFC and WSD are reduced significantly by 40.1% and 35.4% compared to pure base oil, respectively, and the surface roughness, wear depth, and wear volume were effectively reduced by 91.0%, 68.5%, and 76.8% compared to GTL base oil, respectively. Raman, SEM-EDS, and XPS results proved that the outstanding friction-reducing and anti-wear properties of BNNS can mainly be ascribed to the presence of physical adsorption film and tribo-chemical film, which were composed of FeOOH, FeO, Fe₃O₄, and B₂O₃. Full article

The demand for a “green” approach to the synthesis of nanomaterials is becoming increasingly pressing. In response to this need, we present, for the first time, the use of spark ablation as an environmentally friendly deposition technique to obtain nanoparticles of copper nitride, a material that is gaining increasing attention in the field of photovoltaic advanced technologies. This method involves the ablation of pure copper electrodes in nitrogen atmosphere while a spark current is tuned. The overall result is the co-presence of nitride and oxide nanoparticle agglomerates with different sizes according to the spark current, as confirmed by X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy and energy-dispersive spectroscopy techniques. Scanning probe microscopy and scanning electron microscopy show an increase in the number and size of nanoparticle agglomerates with an increasing current, while the nanoparticle size is always about sub-10 nm. The findings of this work promote spark ablation as a simple, versatile, cost-effective, environmentally friendly deposition method to obtain nitride-based nanoparticles. Furthermore, it is compatible with many types of materials and substrates, increasing the possible combinations of metals/semiconductors and carrier gas types to obtain completely innovative materials with unique compositions and properties. Full article

Recent measurements of the band properties of AlN and GaN by fluorescence yield absorption and soft X-ray emission spectroscopies revealed that their valence band (VB) is composed of two separate subbands. The upper VB subband of GaN is composed of gallium sp and nitrogen p orbitals; the lower subband consists of metal d and nitrogen s orbitals. These findings were confirmed by extensive ab initio simulations. These results are not consistent with the standard tetrahedrally coordinated semiconductors, which are bonded by sp³-hybridized orbitals of metal and nonmetal atoms. The new analysis techniques and ab initio simulations create a new picture, allowing the calculation of overlap integrals to determine the bond order in these crystals. According to these results, bonding occurs between resonant p-states of nitrogen and sp³-hybridized metal orbitals in tetrahedral nitrides, allowing tetrahedral symmetry to be maintained. A similar resonant bonding mechanism is observed in hexagonal BN, where the p orbitals of nitrogen create three resonant states necessary for maintaining the planar symmetry of the lattice. In addition, nonresonant $\pi$-type bonds in BN are created by the overlap of $p_z$ orbitals of boron and nitrogen. BN bonding differs from that in graphene, where carbon states are fully sp²-hybridized. Additionally, $\pi$-type bonds in graphene have no ionic contributions, which leads to the formation of Dirac states with linear dispersion close to the K point, closing the band gap. Full article