Search Results (2,511)

The development of resin-regolith composites represents a promising In Situ Resource Utilization (ISRU) strategy for future lunar missions. While unsuitable for primary habitat construction due to the payload cost of transporting polymers from Earth, these composites offer a highly efficient solution for manufacturing non-structural, everyday items (e.g., containers, tools, and plant cultivation pots) directly on the Moon via mold–casting. This approach significantly reduces the volume and mass of pre-formed plastic payloads. In this work, the influence of the particle size distribution of a lunar highland simulant (LHS-1E) on the mechanical properties of epoxy-based composites was systematically investigated for such applications. First, the regolith-to-resin ratio was optimized for castability, establishing a maximum regolith content of 60 wt.%. Then, four different size fractions of the simulant were prepared by sieving (>200 µm, 200–100 µm, 100–50 µm, and <50 µm), and composite samples were cast maintaining this optimal ratio. X-ray microtomography revealed that using larger particles (>200 µm) increased composite porosity, whereas smaller fractions promoted more compact structures. Three-point bending tests showed that intermediate particle sizes (200–100 µm and 100–50 µm) led to enhanced flexural strength, while the smallest particles (<50 µm) decreased mechanical performance, likely due to a lower basalt content in this finer fraction. Finally, ball-on-disk tribological analyses highlighted that composites made with larger particles (>200 µm) exhibited superior wear resistance, whereas particle size had negligible effects on the coefficient of friction. Overall, the results demonstrate that both particle size and mineralogical composition significantly influence the performance of regolith–epoxy composites, providing essential guidelines for the in situ manufacturing of functional, non-structural objects for lunar outposts. Full article

Wire laser cladding (WLC) of bronze on stainless steel offers a promising approach for combining the structural strength of steel with the superior tribological and corrosion properties of copper alloys. In this study, the influence of key process parameters, including wire preheating current, deposition speed, laser power, and wire feed speed on melt pool temperature and clad geometry was investigated using response surface methodology (RSM). Experiments were performed using a robot-assisted coaxial wire feeding laser cladding system, and real-time thermal monitoring was conducted using an infrared camera. The results showed that defect-free bronze clads with good metallurgical bonding and limited dilution were achieved across the investigated parameter range. Statistical analysis revealed that melt pool temperature is primarily governed by laser power and deposition speed, with a significant interaction between these parameters. Clad height was mainly influenced by wire feed speed and deposition speed, whereas clad width was controlled by laser power and deposition speed. The side angle was affected by deposition speed, laser power, and wire feed speed, reflecting the balance between vertical buildup and lateral spreading. Overall, the study demonstrates that stable and high-quality clads can be achieved by properly balancing energy input and material supply. The developed models provide valuable insight for optimizing process parameters in wire laser cladding of bronze on stainless steel. Full article

Ice accumulation on critical infrastructure surfaces threatens operational safety in aviation, power transmission, and transportation systems. Conventional anti-icing and deicing strategies, such as chemical deicers and energy-intensive active heating, have inherent drawbacks. These include environmental pollution, high energy consumption, and low efficiency. In recent years, photothermal-responsive extremely water-repellent surfaces have attracted widespread attention. They can harvest renewable solar energy and achieve efficient anti-icing and deicing through tailored interfacial wetting properties. This review summarizes photothermal extremely water-repellent surfaces based on the “water as a lubricating layer” strategy. This strategy reduces ice adhesion strength and enables low-energy deicing. It works by forming a continuous lubricating film via photothermally induced interfacial meltwater. We discuss photothermal conversion mechanisms and strategies to enhance performance for stable lubricating film formation. We also analyze the stagewise physics of anti-icing and deicing, focusing on the interfacial tribological behavior of the water film. Key engineering challenges are addressed, including mechanical durability and all-weather applicability. Finally, we clarify future research directions for industrial translation. This review aims to provide theoretical insights and technical pathways for developing next-generation anti-icing and deicing surfaces that are efficient, eco-friendly, and sustainable. Full article

This article presents preliminary research on the development of a cast iron–ceramic composite for modern braking systems, such as brake discs. The composite matrix is gray cast iron with flake graphite (EN-GJL-150). The reinforcing phase is a porous ceramic composed of SiC and Al₂O₃ particles introduced separately (10% each) and together (70% SiC + 30% Al₂O₃). These particles were applied as a suspension onto polyurethane foam, yielding a ceramic structure with a pore density of up to 10 ppi. The resulting insert was placed in a mold cavity, and cast iron was poured into it. The resulting samples were treated as brake disc material, with a pad made of the commercial friction material P50094 serving as the countersample. Tribological tests showed that the lowest sample wear (average 2.23 mg/5000 m) was achieved for the composite reinforced with SiC + Al₂O₃ particles. This is probably due to the synergy between the antifriction properties of these particles and the lower friction coefficient (µ = 0.180–0.22). Similar mass loss values and the smallest difference between the tested samples were observed for composites with SiC particles (3.01 mg/5000 m) and Al₂O₃ (3.30 mg/5000 m). The second part consisted of microstructural studies. Microstructural analysis of the EN-GJL-150 + SiC + Al₂O₃ composite revealed a previously unobserved nucleation phenomenon at the cast iron–ceramic interface. This confirmed the general assumptions of Riposan’s theory regarding the involvement of oxide microinclusions and complex manganese sulfides of the (Mn, X)S type in the nucleation and crystallization of graphite precipitates. It was also found that, in the case of “in situ” GJL-150 + SiC + Al₂O₃ composites, this theory should account for the beneficial role of ceramic particles in promoting the uniform distribution of type A graphite flakes, which nucleate on their surfaces in the transition zone. Thus, the nucleating role of oxide microinclusions (the first stage of Riposan’s theory) could be taken over by SiC and Al₂O₃ particles, constituting a substrate for the heterogeneous nucleation of (Mn, X)S sulfides. Full article

HfC, TaC, and HfTaC composite coatings were successfully fabricated on SiC-coated carbon/carbon (C/C) composites using the double glow plasma alloying (DGPA) technique. The microstructure, mechanical properties, and tribological behaviors of the coatings were systematically investigated. The HfTaC coating exhibited a dense and uniform structure with good interfacial integrity and a compositionally graded transition layer, effectively relieving thermal stress. The hardness of HfTaC and HfC coatings (approximately 12 GPa) was higher than that of the TaC coating. Moreover, the higher K value (1.02) and H/E ratio (H/E = 0.09, H³/E² = 0.085 GPa) indicate that the HfTaC coating exhibits good load-bearing capacity and toughness. Under both 5 N and 15 N loads in the reciprocating friction, the HfTaC coating maintained the lowest and most stable friction coefficient (~0.18). Under the 15 N load, it exhibited the smallest specific wear rate. Observation of the wear scars revealed that the HfC and TaC coatings suffered from pore formation and flake-like spallation, while the HfTaC coating retained structural integrity with only minor cracks. In high-temperature ball-on-disc friction tests up to 500 °C, the wear mechanism of the HfTaC coating gradually transitioned from mild abrasive wear to severe oxidative and adhesive wear, yet the HfTaC coating still provided effective protection. These findings demonstrate that the DGPA-fabricated HfTaC coating is a promising candidate for enhancing the wear resistance and service durability of C/C composites. Full article

Titanium alloy is difficult to cut, with tools prone to adhesion and diffusion wear that reduces life and surface quality. Traditional coatings fail to meet precision machining demands. Based on TiAlN, Ce-doped coatings were prepared via magnetron sputtering at varying powers to investigate mechanical and tribological properties. The results show that with the increase in Ce doping amount, the hardness, elastic modulus, H/E, and H³/E² ratios of the coating increase first and then decrease, and the friction coefficient decreases first and then increases. The performance is optimal at 50 W, the friction coefficient is 0.676, and the film-based adhesion is 113.8 N. Compared with the TiAlN coating, the hardness increased by 12%, the wear loss decreased by 24%, and the H/E and H³/E² increased by 31% and 95%, respectively. The mechanism analysis shows that the appropriate amount of Ce doping can improve the toughness of the coating by grain refinement and solid solution strengthening and significantly inhibit adhesive wear and oxidative wear. Ce-modified tools were further prepared for titanium alloy turning experiments. Compared with uncoated and traditional TiAlN-coated tools, Ce doping can effectively reduce tool wear and improve the surface quality of the workpiece and has significant advantages under high-speed and large cutting depth conditions. This study systematically reveals the adaptive lubrication mechanism of Ce-doped TiAlN coating in the cutting process of titanium alloy and provides theoretical support and engineering guidance for the preparation of special tool coatings for difficult-to-machine materials. Full article

Additive manufacturing (AM) techniques are becoming key factors for repairing and replacing damaged bone. These techniques enable the customization of implants, which can be tailored to the specific area to be treated or healed. Additionally, the combination of absorbable and osteoconductive biomaterials with 3D printing could eliminate second surgeries to remove implants, which is particularly relevant in pediatric and geriatric patients. The capabilities of AM in this context affect not only the external shape but also the internal microarchitecture, where the arrangement of struts to develop complex infills enhances relevant properties such as specific strength, degradation rate, and vascularization. In this study, auxetic scaffold structures made of both polylactic acid (PLA) and a PLA-hydroxyapatite (PLA-HA) composite with 40 wt% of hydroxyapatite (HA) are designed and produced using Fused Filament Fabrication (FFF). Samples of PLA and PLA-HA were 3D printed in dense samples and with auxetic infills. In dense samples, the characterization is performed by X-ray diffraction (XRD), Raman spectroscopy, wettability tests, nanoindentation, and tribological assessments. Two auxetic cellular models have been tested after degradation in PBS media, and their microstructural, structural, and mechanical properties are analyzed. Results show that the addition of hydroxyapatite (HA) significantly improves the hydrophilicity of the PLA matrix, as evidenced by a decrease in water contact angle from 73.4 ± 4.4° to 52.6 ± 2.8° (≈28% reduction), while also enhancing its mechanical and tribological properties, with hardness increasing from 207 ± 30 MPa to 241 ± 28 MPa (≈15%) and Young’s modulus from 4.08 ± 0.55 GPa to 6.24 ± 0.61 GPa (≈53%). Additionally, biodegradation of PLA-HA composites reveals a significant reduction in mechanical properties after 15 days, while the auxetic re-entrant structures mostly retain their shape during compression testing. Full article

This study investigates the influence of preliminary severe plastic deformation on the efficiency of ion-plasma nitriding (IPN) and the formation of a nitrided layer in 12Kh18N10T austenitic stainless steel. Two types of surface mechanical treatment were compared: vibro-impact ball mechanical treatment (VIMT) and ultrasonic nanocrystalline surface modification (UNSM). After the preliminary treatments, the samples were subjected to ion-plasma nitriding at 500 °C for 10 h using ammonia (NH₃) as the working gas. The phase composition, microstructure, elemental distribution, surface roughness, microhardness, and scratch resistance were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS) analysis, profilometry, instrumented indentation, and progressive scratch testing. The results show that both types of preliminary treatment promote the formation of a nitrogen-enriched diffusion layer. The UNSM-treated samples exhibited more pronounced peak broadening and shifting in XRD patterns, indicating a higher level of lattice distortion and nitrogen supersaturation. The maximum nitrogen concentration in the near-surface region reached 15.56 wt.%. Microhardness increased significantly after nitriding for both treatments. Under the selected processing conditions, the UNSM + IPN samples demonstrated a thicker diffusion layer, lower surface roughness, and higher critical loads in scratch testing, indicating improved resistance to surface damage compared with VIMT + IPN samples. The obtained results highlight the important role of the defect structure formed during preliminary treatment in controlling nitrogen diffusion and the resulting mechanical and tribological properties of ion-plasma nitrided austenitic stainless steel. Full article

Harsh modern industrial working conditions require high-performance lubricants, but traditional additives are limited by single functionality and poor compatibility, driving the development of multifunctional alternatives. Two novel hindered phenolic amide–esters (MADE, DAME) were synthesized and characterized. Their thermal/storage stability, antioxidant and tribological properties in synthetic oil were evaluated, with commercial 1010 and T203 as references. DFT calculations and worn surface analysis were also employed to clarify the lubrication mechanism. The results indicate that MADE exhibits better thermal/storage stability, comprehensive antioxidation and lubricating performance than DAME, with residual mass of 85.3% and 73.2% at 300 °C, respectively. A total of 1 wt.% MADE shortens the running-in period to 200 s (vs. 300 s for base oil), reduces the average. WSD by 12.1% and wear volume by 60.2%. Mechanistically, MADE adsorbs strongly on metal surfaces and forms a protective tribofilm via tribochemical reaction, exhibiting synergistic antioxidant and anti-wear effects. This work establishes a novel and sustainable paradigm for developing next-generation, multifunctional lubricant additives with high performance. Full article

Driven by global environmental regulations that strictly limit copper content in brake pads, traditional copper-based friction materials face significant challenges due to their negative ecological impacts. Consequently, the development of sustainable, copper-free alternatives has become an inevitable trend in the braking industry. This study proposes a novel approach to developing high-performance green friction materials by utilizing a synergistic combination of agricultural wastes, specifically corn cobs, wheat straw, rice husks, and sugarcane bagasse, and carbon fibers. Research indicates that the friction coefficient of the synergistic formulation remains stable within the range of 0.35 to 0.48. Compared with the control group, this formulation achieves an average reduction in the wear rate of 19.28% and an increase in the recovery rate of 5.15%, demonstrating superior tribological performance. The synergistic interfacial regulation between carbon fibers and agricultural waste facilitates the construction of a smooth and stable friction layer, which maintains consistent performance during extended operating conditions. Among all formulations investigated, the composite reinforced by the synergy of corncob and carbon fiber exhibits the most prominent comprehensive properties, with the wear rate decreasing by 28.73% and the recovery performance improving by 4.05% relative to the specimen containing copper fibers. This work not only provides a new pathway for the sustainable development of green friction materials but also offers a theoretical basis for the high-value utilization of agricultural waste resources. Full article

Chromium nitride (CrN) can be used as a coating material deposited via physical vapour deposition (PVD), thereby improving the corrosion and wear resistance of the substrate. However, this level of corrosion protection may not be sufficient in an aggressive corrosion environment. The coatings often contain intrinsic microstructural defects, such as microcraters, which can serve as pathways for the corrosive medium to reach the substrate, thereby initiating and promoting corrosion. In this study, the influence of parameters on the formation of a TiO₂ layer using the ALD technique was investigated. In particular, the work focused on assessing the effectiveness of the TiO₂ layer as a sealing barrier for CrN coatings (PVD) applied to austenitic 316L steel. The TiO₂ ALD coatings were produced at a constant temperature of 200 °C with a varying number of cycles, ranging from 200 to 1000 cycles. Structural investigations were carried out using scanning electron microscopy SEM and atomic force microscopy. Electrochemical properties were investigated using a potentiodynamic test and electrochemical impedance spectroscopy (EIS) in a 3.5% NaCl solution. SEM observations indicate that the morphology of the hybrid coatings is strongly influenced by the number of ALD cycles. The TiO₂ layer conformally reproduces the underlying PVD topography while progressively sealing the coating by filling intrinsic defects and discontinuities. Hybrid coatings (PVD/ALD) with titanium oxide deposited at 500 ALD cycles were found to have the best corrosion resistance. The polarisation resistance for these coatings was nearly four times higher than that of both the single PVD (CrN) coating and the uncoated stainless steel 316L substrate. At the same time, the corrosion current density was several times lower than that of the reference systems. The corrosion mechanisms were investigated by observing the surfaces of the samples after corrosion testing using SEM. Abrasion resistance tests using the pin-on-disc method and adhesion tests (scratch tests) were also performed, which showed that appropriate optimisation of the layer architecture in the PVD/ALD hybrid system significantly improves its tribological durability, interlayer stability, and adhesion to the substrate. Full article

Aluminum alloy (AA5083) is widely used in the aerospace and marine industries. However, its use is sometimes limited by its low surface hardness, wear resistance, and thermal stability. The microstructural, mechanical, tribological, and dynamic behavior of AA5083 matrix composites incorporated with mono-reinforcements (hexagonal boron nitride (hBN), graphene (G), and carbon nanotubes (CNTs)) and hybrid reinforcements (hBN+CNTs, G+hBN, and CNTs+G) by friction stir processing (FSP) is thoroughly investigated. Microstructural examination demonstrated that extensive dynamic recrystallization was induced by FSP, reducing the base-metal grains (about 215 μm) to very small sizes. The hybrid hBN+CNT composite had the smallest grain size (about 4.5 μm), the mono-CNT composite had the highest microhardness (~60 HV), whereas the hybrid CNTs+G composite had the highest ultimate compressive strength (~350 MPa). This enhancement was attributed to the formation of a 3D network within the hybrid composite, which hindered graphene agglomeration and restacking. Tribological tests revealed that hybridization greatly reduced wear; in particular, hBN-containing hybrids (hBN+CNTs and hBN+G) had the lowest wear rates (~0.037 mg/bar.min), owing to hBN’s solid-lubrication effect. Moreover, dynamic mechanical analysis and free-vibration testing showed the tunability of vibrational characteristics; the mono-CNT composite had the greatest structural stiffness (storage modulus ~72.75 GPa), whereas the G+CNTs hybrid had the best damping ratio (damping ratio ~4.82%). These results demonstrate that hybrid nanoreinforcements can tailor the multifunctional characteristics of AA5083 composites. Full article

Microwave-sintered lunar regolith bricks are promising candidates for in situ construction of lunar infrastructure, where structural load-bearing capacity and multifunctional performance are simultaneously required. Currently, there remains a research gap concerning the service performance of microwave-sintered lunar soil bricks under predictable load-bearing, wave-transparent, and friction working conditions. In this study, lunar bricks were fabricated at different microwave sintering temperatures, and the effects of temperature on their microstructure and engineering properties were systematically investigated. The sample sintered at 1000 °C achieved a density of 2.96 g/cm³ and a compressive strength of 260 MPa. Combined experimental observations and numerical simulations revealed a typical brittle fracture behavior, primarily governed by residual porosity within the material. Tribological tests showed a low wear rate of 6.51 × 10⁻⁵ mm³/(N·m), indicating good wear resistance and potential applicability for lunar road paving. Dielectric measurements in the X-band (8.2–12.4 GHz) demonstrated a high electromagnetic wave transmittance ranging from 49.8% to 94.6%, suggesting suitability for communication-related or protective wall structures. These results demonstrate that microwave sintering effectively enhances the densification of lunar regolith while enabling the coordinated optimization of mechanical, tribological, and electromagnetic properties, providing practical guidance for the design of multifunctional materials for lunar infrastructure construction. Full article

The continuous research progress in materials science has enabled the development of advanced nano-materials, including carbon nano-tubes, graphene and metal oxides with specialized properties, which can fundamentally affect the mechanical, thermal and tribological properties of conventional materials when used in the reinforcing phase [...] Full article

This study focuses on China’s domestically developed K452 alloy. Using Si₃N₄ ceramic balls as the counterface material, the tribological properties of the K452 alloy were investigated after heat treatment over a wide temperature range (RT–800 °C), and the wear mechanisms were analyzed. The results show that the heat treatment process enhances the material hardness slightly by promoting the dissolution of the γ′-strengthening phase and the precipitation of the η phase. From RT to 600 °C, the wear rate of the K452 alloy remains at a relatively low level, on the order of 10⁻⁶ mm³·m⁻¹·N⁻¹. Compared with the as-cast condition, intermediate treatment exhibits a significant reduction in the wear rate. Compared with traditional processes, it reduces one step of heat treatment. This improvement is attributed to the precipitation of the uniformly fine η phase, along with the re-dissolution of the γ′-strengthening phase. When the testing temperature is raised to 800 °C, the tribological performance of the K452 alloy deteriorates significantly, with the wear rate increasing to the order of 10⁻⁵ mm³·m⁻¹·N⁻¹. Microstructural characterization confirms that the in situ formations of dense Cr₂O₃ and Al₂O₃ oxide films during friction are the primary mechanism for improved wear resistance from RT to 600 °C. But when the temperature rises to 800 °C, the dynamic equilibrium of the oxide layers is disrupted, leading to oxidative wear becoming the dominant mechanism. Full article