Search Results (2,577)

Vulcanized NR-SBR is widely used in vehicle components; however, its irreversible crosslinking limits recyclability and contributes to the large number of tires discarded annually worldwide, and in this context, this work presents an experimental comparative assessment of the tribological behavior of conventional tire rubber and silicone VMQ, motivated by a wheel concept based on a detachable tread aimed at improving durability and sustainability rather than proposing an immediate material substitution. Wear and friction behavior were investigated under abrasive and self-friction conditions using pin-on-disk testing with an abrasive counterpart representative of asphalt, supported by optical and scanning electron microscopy. The results show that NR-SBR undergoes severe abrasive and erosive wear, characterized by deep and irregular wear tracks, pronounced fluctuations in the dynamic friction coefficient, and strong sensitivity to load and sliding speed, particularly during the initial stages of track formation. In contrast, VMQ exhibits mild abrasive wear dominated by viscoelastic deformation, leading to shallow and stable wear tracks, lower friction coefficients, and significantly reduced material loss once the contact track is fully developed. These differences are attributed to the distinct mechanical responses of the elastomers, as the higher hardness and limited strain capacity of rubber promote micro-tearing and unstable material removal, while the high elasticity of silicone enables stress redistribution and stable contact conditions under abrasive loading. UV aging increases stiffness of rubber, resulting in reduced wear and friction, while silicone remains largely unaffected after 750 h due to the stability of its Si–O–Si backbone. Self-friction tests further indicate that smooth silicone sliding against rubber yields the lowest friction values, highlighting a favorable material pairing for detachable tread concepts. Factorial design analysis confirms material type as the dominant factor influencing both wear and friction. Overall, for the specific materials and operating conditions investigated, VMQ demonstrates higher durability, greater tribological stability, and improved aging resistance compared to NR-SBR, providing experimental evidence that supports its potential for long-life, more sustainable detachable tread applications. Full article

Niobium nitride (δ-NbN) coatings were deposited on AISI 316L austenitic steel using reactive DC magnetron sputtering. This study investigates the effects of air oxidation on the surface morphology, topography, roughness, nanohardness, adhesion, and wear resistance of NbN coatings. Their microstructure and thickness were analyzed by scanning electron microscopy (SEM), while surface morphology and roughness were assessed using atomic force microscopy (AFM), and surface topography was assessed by an optical profilometer. Nanohardness was measured using a Berkovich indenter. Adhesion was evaluated via progressive-load scratch testing and Rockwell indentation (VDI 3198 standard). Wear resistance was assessed using the “ball-on-disk” method. Both as-deposited and oxidized NbN coatings improved the mechanical performance of the substrate surface. Air oxidation led to the formation of an orthorhombic Nb₂O₅ surface layer, which increased surface roughness and reduced hardness. However, the brittle oxide also contributed to a lower coefficient of friction. Despite reduced adhesion and increased surface development, the oxidized coating exhibited a significantly lower wear rate than the uncoated steel, though several times higher than that of the non-oxidized NbN. Considering its good wear and corrosion performance, along with the bioactivity confirmed in earlier research, the oxidized NbN coating can be considered a promising candidate for biomedical applications. Full article

Diamond coring bits exhibit stable rock-breaking and coring processes as well as a long service life. However, when drilling in complex and challenging formations are characterized by high hardness, strong plasticity, and high abrasiveness, issues such as low rock-breaking efficiency, rapid failure, and shortened service life frequently occur. To prevent premature bit failure and enhance rock-breaking efficiency, this study investigated the effects of drilling pressure and rotational speed on rock-breaking performance through bench-scale experiments using typical rock samples. A total of 15 experimental groups were included in this study, with one independent trial performed for each group. ROP is calculated as the ratio of effective drilling depth to time consumed, and MSE is derived based on axial force, torque, and rock-breaking volume. The experimental results indicated that (1) sandstone is more sensitive to rotational speed, whereas limestone and dolomite are more sensitive to drilling pressure; (2) the minimum mechanical specific energy (MSE) of sandstone was achieved at a drilling pressure of 15 kN and rotational speed of 50 r/min; (3) limestone exhibited the lowest MSE at 10 kN drilling pressure and 50 r/min rotational speed; and (4) dolomite showed the minimum energy consumption at 10 kN drilling pressure and 25 r/min rotational speed. On this basis, this paper establishes a cutting mechanics model for single-crystal diamond and a working load calculation model for the entire bit, respectively. The cutting mechanics model for single-crystal diamond is re-established based on Hertzian contact theory and elastic-plastic deformation theory. The findings of this study are expected to provide a working load calculation method for diamond coring bits in typical complex and challenging drilling formations and offer technical support for the design of coring bit cutting structures and the development of customized new products. It should be noted that the conclusions of this study are limited to the experimental parameter range (drilling pressure: 5–15 kN; rotational speed: 25–80 r/min), and their applicability under higher load conditions requires further verification. Full article

Background: Autologous platelet concentrates, including platelet-rich fibrin (PRF) matrices, have been proposed as biologically active scaffolds for vital pulp therapy. Evidence on the clinical use of different solid PRF matrices for direct pulp capping remains limited. Objective: The aim of this study is to describe and monitor two clinical cases of reversible pulpitis treated with direct pulp capping using two PRF membranes prepared by different centrifugation approaches, namely advanced platelet-rich fibrin plus (A-PRF+) and horizontal platelet-rich fibrin plus (H-PRF). Methods: In Case 1, A-PRF+ was prepared using a fixed-angle centrifugation protocol; in Case 2, H-PRF was prepared using a horizontal centrifugation protocol. In both cases, deep carious lesions with small carious pulp exposures (<1.5 mm) were managed by caries removal, ozone-assisted dentin disinfection, and direct pulp capping with the respective PRF membrane, followed by temporary calcium-silicate cement definitive coronal restoration. Clinical and radiographic follow-up, including cone-beam computed tomography, was performed for up to 12 months. Results: In Case 1 (A-PRF+), reparative dentin bridge formation was confirmed at 90 days, with a thickness of 0.2 mm. In Case 2 (H-PRF), reparative dentin was observed within 46 days, with a thickness of 0.28 mm. In both cases, pulp vitality was maintained, and no clinical symptoms or periapical changes were detected during the 12-month follow-up. Conclusions: These two cases suggest that direct pulp capping using PRF membranes (A-PRF+ or H-PRF), combined with ozone-assisted dentin disinfection and adequate coronal sealing, may be associated with maintained pulp vitality and hard-tissue repair after carious pulp exposure diagnosed as reversible pulpitis. Due to the descriptive two-case design and major confounding factors (including age and lesion characteristics), no comparative conclusions can be drawn. Prospective controlled clinical studies with standardized protocols are warranted. Full article

Carbon capture, utilization, and storage (CCUS) play an increasingly important role in climate mitigation strategies by addressing industrial emissions and enabling pathways toward net-negative emissions. A key challenge lies in determining the pathway of captured CO₂, whether through permanent geological storage or conversion into value-added products to enhance system viability. As hard-to-abate sectors and the power industry remain major sources of emissions, a comprehensive assessment of the technical, environmental, and economic performance of CCUS pathways is essential. This study evaluates bioenergy with carbon capture and storage/utilization (BECCUS) in the context of the Polish energy sector. Techno-environmental performance was assessed across three pathways: CO₂ storage in saline formations, CO₂ mineralization, and methanol synthesis. The results show levelized costs of 59.9 EUR/tCO_2,in for storage, 109.7 EUR/tCO_2,in for mineralization, and 631.1 EUR/tCO_2,in for methanol production. Corresponding carbon footprints (including full chain emissions) were −936.4 kgCO_2-eq/tCO_2,in for storage, −460.6 kgCO_2-eq/tCO_2,in in for mineralization, and 3963.4 kgCO_2-eq/tCO_2,in for methanol synthesis. These values highlight the trade-offs between economic viability and climate performance across utilization and storage options. The analysis underscores the potential of BECCS to deliver net-negative emissions and supports strategic planning for CCUS deployment in Poland. Full article

As energy exploration and development continue to advance into deep and ultradeep formations, systematic studies of rock mechanical properties face significant challenges due to high core acquisition costs and sample damage under extreme conditions. To overcome these challenges, high-precision, minimally invasive, or non-destructive testing methods are urgently needed. This study systematically characterizes the microstructural features and mechanical heterogeneity of deep carbonate rocks from the Shunbei area by integrating XRD, SEM-EDS, and nanoindentation techniques. The results show that these rocks are primarily composed of a continuous calcite phase, with quartz as the secondary phase occurring in regional aggregates embedded within the calcite matrix. The two phases commonly exhibit an intergrown texture, and mineral distribution displays notable spatial heterogeneity and sample-to-sample variation. Nanoindentation tests reveal that the quartz phase exhibits excellent mechanical stability, with elastic moduli ranging from 70.6 to 101.8 GPa and hardness values between 10.8 and 13.5 GPa. The data are tightly clustered, indicating structural homogeneity and strong resistance to deformation. In contrast, the calcite phase shows lower and more scattered mechanical parameters, with elastic moduli of 27.4~76.0 GPa and hardnesses of 0.7~2.3 GPa, reflecting pronounced microscale heterogeneity. Furthermore, a strong negative correlation exists between hardness and maximum indentation depth, further confirming the dominant influence of mineral composition on local mechanical response. Notably, despite similar mineralogical compositions among samples A13, A15, and A18, their micromechanical performance follows the order A15 > A18 > A13, indicating that subtle differences in diagenetic history, crystal development, and local stress conditions can significantly affect rock mechanical behavior. Full article

The development of lithium-ion batteries necessitates cathode materials that possess excellent mechanical and thermal properties in addition to electrochemical performance. As a prominent functional ceramic, the properties of spinel LiMn₂O₄ are governed by its atomic-level structure. This study systematically investigates the impact of Ni doping concentration on the mechanical and thermal properties of spinel LiNi_xMn_2−xO₄ via first-principles calculations combined with the bond valence model. The results suggest that when x = 0.25, the LiNi_xMn_2−xO₄ shows excellent mechanical properties, including a high bulk modulus and hardness, due to the favorable ratio of bond valence to bonds length in octahedra. Furthermore, this optimized composition shows a lower thermal expansion coefficient. Additionally, Ni doping concentration has a very minimal influence on the maximum tolerable temperature of the cathode material during rapid heating. Therefore, from the perspective of mechanical and thermal properties, this composition could be beneficial for improving the cycling life of the battery, since comparatively inferior mechanical properties and a higher thermal expansion coefficient make it prone to microcrack formation during charge–discharge cycles. Full article

Toughening modification of epoxy resin (EP) matrices is important for advancing high-performance fiber-reinforced composites. A promising strategy involves the use of multi-component additive systems. However, synergistic effects in such additive systems are difficult to achieve for multidimensional performance optimization due to insufficient interfacial interactions and competing toughening mechanisms. Herein, a “hard–soft” biphasic synergistic toughening system was engineered for epoxy resin, composed of furan-ring-grafted polyhedral oligomeric silsesquioxane (FPOSS) and liquid polysulfide rubber. The hybrid toughening agent significantly enhanced the integrated performance of the epoxy system: Young’s modulus, tensile strength, and elongation at break increased by 13%, 56%, and 101%, respectively. These improvements are attributed to the formation of enriched molecular chain entanglement sites and optimized dispersion, facilitated by nucleophilic addition reactions between flexible rubber segments and rigid FPOSS units with the epoxy matrix. The marked enhancement in toughness primarily stems from the synergistic toughening mechanism involving “crazing pinning” and “crazing-shear band”. Concurrently, FPOSS incorporation effectively modulated the curing reaction kinetics, rendering the process more gradual while substantially elevating the glass transition temperature (T_g) of the cured system by 16.82 °C and endowing it with superior thermal degradation stability. This work provides a simple and unique strategy to leverage multi-scale mechanisms for the construction of epoxy-based composites with good toughness and strength, and enhanced heat resistance. Full article

In this work, samples of 30KhGS steel coated by thermal spray were investigated. The coating procedure consisted of two stages. At the first stage, a powder mixture of Cu + Al (mass ratio 4:1) was deposited. At the second stage, under the same process parameters, TiC powder was applied. After each spraying stage, the structure, elemental composition and stress state of the coatings were examined. Following the second deposition, hardness and wear resistance of the sample were measured. The results showed that the hardness and wear resistance of the test specimen increased on average by 40% compared to the corresponding properties of 30KhGS steel subjected to quenching and tempering. The residual stress level in the first (lower) coating was higher than in the upper layer; this difference is related to the distinct mechanisms of layer formation. The lower layer forms through melting and subsequent solidification, whereas the top layer forms by liquid-phase sintering. The obtained results demonstrate the effectiveness of the two-layer coating for increasing the hardness and wear resistance of 30KhGS steel, which broadens the possibilities for surface restoration and repair of parts. Full article

Severe drill string vibrations, particularly stick–slip, significantly compromise drilling efficiency and tool longevity in deep hard formations. Compound percussive drilling (CPD) has emerged as a promising technique to mitigate these vibrations and enhance the rate of penetration (ROP). However, the complex coupling mechanisms between impact loads and bit dynamics remain insufficiently understood. This study aims to elucidate the axial–torsional vibration characteristics of the drill bit and the underlying vibration reduction mechanisms under CPD conditions. A multi-degree-of-freedom (MDOF) dynamic model was first established, integrating both the dynamics of the CPD tool and the regenerative cutting effects inherent in bit–rock interactions. The governing equations were then solved numerically using the fourth-order Runge–Kutta method, followed by a systematic parametric sensitivity analysis to quantify the influence of impact parameters on vibration mitigation. The results show that while CPD induces detrimental axial–torsional vibrations in soft rock formations, it effectively suppresses stick–slip and enhances ROP in hard rock formations. Notably, coupled axial–torsional impact loading exhibits superior vibration suppression capabilities compared to singular axial or torsional impacts. A critical proportional relationship for parameter optimization was identified; specifically, maximizing vibration mitigation requires scaling the axial impact load proportionally with the torsional impact load. For example, when the axial impact load amplitudes are 5 kN and 10 kN, the corresponding optimal torsional impact load amplitudes are approximately 500 N·m and 1000 N·m, respectively. Furthermore, maintaining the impact frequency within the range of 10–30 Hz yields optimal vibration reduction effects. The benefits of CPD become increasingly pronounced with higher rock strength and longer drill strings. These findings confirm the suitability of CPD technology for deep hard rock environments and provide theoretical guidelines for the optimal selection of impact parameters in engineering applications. Full article

Inconel 718 is widely utilized in critical engineering sectors, particularly aerospace, owing to its exceptional creep resistance, corrosion resistance, and retention of mechanical strength at elevated temperatures. However, its high hardness, low thermal conductivity, and strong work-hardening tendency make it extremely difficult to machine using conventional techniques. Ultrasonic Vibration-Assisted Machining (UVAM) has emerged as an effective strategy to overcome these limitations by superimposing high-frequency, low-amplitude vibrations onto the cutting process. Depending on the vibration direction, UVAM can significantly change chip formation, tool–workpiece interaction, and surface integrity. In this study, the influence of three UVAM modes—longitudinal (Z-UVAM), feed-directional (X-UVAM), and multi-axial (XZ-UVAM)—on the machining behavior of Inconel 718 was systematically investigated. The findings reveal that XZ-UVAM provides the most advantageous outcomes, primarily due to its intermittent cutting mechanism. Compared with Conventional Machining (CM), XZ-UVAM reduced cutting forces by up to 43% and areal surface roughness by 37%, while generating surfaces with more uniform topographies and smaller peak-to-valley variations. Furthermore, UVAM enhanced subsurface microhardness as a result of the surface hammering effect, which may improve fatigue performance. XZ-UVAM also effectively minimized burr formation, demonstrating its potential for high-quality, sustainable, and efficient machining of Inconel 718. Full article

The interfacial behavior between lattice reinforcement and aluminum matrix plays an important role in determining the mechanical and tribological properties of lattice-reinforced aluminum matrix composites. In this study, 316L lattices with different aspect ratios were prepared by laser powder bed elting (LPBF) technology, and LY12 aluminum alloy was infiltrated under vacuum conditions. The effects of lattice aspect ratio on the interfacial reaction, microstructure, hardness, compressive strength, and wear resistance of the composites were systematically studied. First-principles calculations show that FeAl₂ and FeAl₃ intermetallic compounds are preferentially formed at the interface, showing good thermodynamic stability and mechanical properties. The microstructure analysis shows that the increase in aspect ratio promotes the formation of coarse FeAl₃ phase and network AlCu, while a too-large aspect ratio leads to the instability of microstructure and the generation of microcracks. When the lattice constant is 10 mm and the diameter of the support is 1 mm (BCC-10-1), the composite material has the best wear resistance, and the specific wear rate is 3.07 × 10⁻⁴ mm³/(N·m). These findings provide valuable insights into the design of high-performance lattice-reinforced aluminum matrix composites with customized interface properties. Full article

The use of activated carbon (AC) in environmental applications, particularly for water and air purification, is highly valued due to its excellent microstructural and adsorption properties. However, its powdered form presents significant challenges in industrial applications, such as difficulty in handling and potential environmental risks due to its tendency to disperse easily. To overcome these issues, converting activated carbon into a more industrially viable form, such as pellets, is crucial. In this study, pelletizing AC within a crosslinked polyvinyl alcohol–diglycidyl ether of bisphenol A (PVA–DGEBA) matrix enabled the production of structurally stable cylindrical pellets through the formation of a robust three-dimensional polymeric network. This approach required minimal binder usage and facilitated processing at relatively low temperatures, effectively overcoming common disintegration issues associated with traditional pelletization methods reliant on linear polymer binders and compression-based techniques. The resulting pellets exhibited methylene blue (MB) adsorption (q max ~14.8 mg/g of pellet), which is about 50% of the initial AC’s adsorption capability, and retained structural integrity across multiple aqueous cycles. They also remained stable in methanol, ethanol and acetone by showing no observable disintegration, which highlights their excellent stability. Comprehensive characterizations, including hardness tests, swelling behavior, and various structural evaluations, revealed a mechanical strength of 3.37 ± 0.46 MPa and an adsorption volume of ~250 cm³/g through Brunauer–Emmett–Teller analysis, confirming effective crosslinking and the adsorption capabilities of the pellets. This eco-friendly and stable pelletization strategy demonstrated great potential for low-temperature pelletizing of AC, ensuring advanced applications in wastewater treatment even under pressurized conditions, presenting a significant improvement over the traditional method. Full article

Active screen plasma nitriding (ASPN) of additively manufactured nickel-based superalloys represents an understudied surface enhancement pathway. This study presents the first systematic investigation of ASPN applied to additively manufactured Inconel 939 (IN 939), evaluating four distinct post-processing routes combining heat treatment atmospheres (argon versus air cooling), vibratory finishing, and lapping under identical nitriding parameters (450 °C, 8 h, 25% N₂ + 75% H₂, 3 hPa). Contrasting nitriding behaviours emerged as a function of the post-processing route: the air-cooled thermal treatment (HT-air-vibr-lap) promotes formation of a thick Al/Cr-rich oxide layer (10–15 µm) that substantially inhibits nitrogen diffusion, resulting in thin and discontinuous nitrided layers. Conversely, the inert atmosphere route (HT-Ar-vibr-lap) circumvents oxide formation, enabling continuous S-phase (expanded austenite, γN) layer development of a 6.4 ± 0.3 µm thickness with exceptional surface hardness (~1200 HV, representing 3–4× enhancement relative to base material). X-ray diffraction confirmed S-phase formation with refined lattice parameter (3.609 Å) and secondary nitride phases (CrN-type and NbN/TaN-type precipitates). The post-processing sequence—particularly heat treatment atmosphere and mechanical finishing methodology—emerged as a critical controlling parameter for S-phase formation efficiency and mechanical properties of nitrided layers in additively manufactured nickel-based superalloys. This work addresses a knowledge gap distinct from the existing literature on conventional Inconel systems, establishing that controlled surface modification through post-processing can achieve the required properties. Full article

Spinel-based glass-ceramics face challenges such as a narrow crystallization window for the target phase and the difficulty in suppressing the competitive Li_xAl_xSi_1−xO₂ crystals. This study proposes a method to regulate the phase formation in ZnO-MgO-Al₂O₃-SiO₂ glass by precisely controlling the heat treatment temperature. The microstructural evolution was analyzed by DSC, XRD, Raman spectroscopy, SEM, TEM, and XPS. The results indicate that the heat treatment at a nucleation temperature of 780 °C for 2 h and a crystallization temperature of 880 °C for 2 h effectively inhibits the precipitation of the Li_xAl_xSi_1−xO₂ secondary phase, yielding a glass-ceramic with nano-sized MgAl₂O₄, ZnAl₂O₄ spinel as the primary crystalline phase. The obtained glass-ceramic exhibits excellent mechanical properties, including a Vickers hardness of 922.6 HV, a flexural strength of 384 MPa, and an elastic modulus of 113 GPa, while maintaining a high visible light transmittance of 84.3%. This work provides a clear processing window and theoretical basis for fabricating high-performance, highly transparent spinel-based glass-ceramics through tailored heat treatment. Full article