Low friction at high temperature remains a challenge for traditional solid lubricant due to high temperature oxidation and degradation. In this work, we develop a novel silicate glass lubricant to realize low friction (below 0.1) from 750 to 850 °C, representing a 79% reduction compared to dry sliding condition. Interfacial evolution analysis revealed a novel “reaction-induced self-anchoring” mechanism for enhanced lubrication performance: chemical reactions between Ca2 + in the glass phase and TiO2 in the substrate oxide layer induced in-situ precipitation of CaTiO3 micro-protrusion crystals at the interface. These crystals function as “anchors”, significantly enhancing wettability and interfacial bonding strength. This effectively inhibits the dewetting and delamination of the lubricating film under high shear stress. Furthermore, the formation of a "ceramic-glass" composite structure at the interface synergistically improves high-temperature load-bearing capacity. This unique interfacial architecture ensures structural integrity of the lubricating layer and elevates its high-temperature lubrication performance, providing a novel strategy for designing high-performance lubricants under extreme conditions.

Metal additive manufacturing (AM) is well known for its unprecedented geometric freedom through near-net-shape production. Here, we show that the AM route is not limited to fabricating bulk alloys, but can also be used to tune the microstructure and properties of the surface through melting an additional metal atop, which interdiffuses with the base AM block to achieve intimate alloying. As a model demonstration, we demonstrate surface cladding using laser powder-bed-fusion (LPBF) as a supplementary step to complement AM, implemented by melting V powders to metallurgically react with and strengthen the AM-printed Ti-Nb base alloy. The resultant surface cladding is extraordinarily strong with no flaws nor weak interface. The cladding/matrix composite exhibits enhanced yield strength without compromising the tensile ductility of the base alloy. The cladding also offers significantly enhanced hardness and wear resistance. This finding adds an innovative twist for AM in the realm of high-performance alloy fabrication.

As an organic-inorganic hybrid material, metal-organic frameworks (MOFs) are regarded as promising oil additives to reduce friction and wear due to their tunable composition and size, large specific surface area, and excellent nanomechanical properties. However, the poor compatibility of MOFs with base oils has limited wear repair and long-term lubrication in practical applications. Herein, we demonstrated that University of Oslo-67 nanoparticles (UiO-67 NPs) modified with octadecylphosphonic acid (OPA) via coordination interactions can serve as effective oil additives, achieving excellent friction and wear reduction. The UiO-67 NPs were synthesized via solvothermal method, and OPA molecules were assembled on surface with ligand-unsaturated metal sites. The OPA modification significantly enhanced the dispersibility and stability of UiO-67 NPs in polar solvents. Compared with the base oil, UiO-67@OPA with the amount of 0.2 wt% addition reduced the coefficient of friction and wear volume by 40.67% and 96.41%, respectively. The load-bearing capacity of base oil enhanced significantly, from 100 N to 350 N, upon incorporating UiO-67@OPA NPs. Under challenging conditions, like a large frequency (65 Hz) and a high temperature (120 degrees C), the UiO-67@OPA additives retained remarkable tribological properties and demonstrated high tolerance to extreme conditions. This study develops a unique MOFs@OPA NPs as oil additives to improve the lubrication performance of lubricants, providing valuable insights into the synthesis of high-performance friction- and wear-reducing lubricants suitable for severe environments.

Developing high corrosion resistant alloy used in liquid lead-bismuth eutectic (LBE) is essential for the application of lead-cooled fast reactor. In this work, two laser powder bed fusion (LPBF) fabricated FeCrAl alloys and one hot-rolled FeCrAl alloy were developed, and their corrosion behavior in LBE at 500 degrees C up to 1000 h was systematically examined. The results demonstrate that high-density grain boundaries and dislocations, along with the strong <00 1> textured structure, significantly enhance the corrosion resistance of the LPBF-fabricated alloys. Moreover, adding Y(2)O(3 )nanoparticles (ODS-FeCrAl) promotes the nucleation of intragranular oxides and accelerates intragranular diffusion by pinning dislocations and low-angle grain boundaries. Analysis suggest that such microstructural optimization facilitate a balance between intergranular and intragranular oxidation, and thus the protective oxide layer achieves strengthened integrity and continuity. This research establishes a theoretical foundation for designing nano-oxide incorporated alloys used in nuclear reactor via additive manufacturing.

Lubricants are vital for reducing forming force and improving workpiece quality during the precision forming of metallic components. However, it is still challenging to obtain low friction above 1000 degrees C. In this study, we prepared TiB2-borosilicate glass composite lubricants and systematically investigated their wetting behavior and tribological properties in the temperature range of 900-1100 degrees C. The results indicate that the moderate TiB2 (5 wt%) in glass improves the wettability of glass on the Inconel 718 alloy surface and achieves low friction coefficients of 0.048 and 0.053 at 1000 degrees C and 1100 degrees C, corresponding to reductions of 76.2% and 63.2% compared with the TiB2-free lubricant. The enhancement in tribological performance is attributed to the appropriate amount of TiB2 (5 wt%), which optimizes the network strength and load-bearing capacity of the molten glass, whereas excessive TiB2 causes the depolymerization of the borosilicate network. Our research reveals that TiB2 is beneficial to stabilize the glass tribofilm by modifying the internal glass structure, which provides a feasible strategy to optimize the high temperature lubrication performance of glass lubricants.

Metal-organic frameworks (MOFs) demonstrate considerable potential for biomedical applications. Due to their high porosity and photoactive porphyrin ligands, PCN-224 is considered an ideal drug delivery nanocarrier. However, the synthesis strategy for tailoring the application of PCN-224 in complex pathological diseases remains unclear. In this study, we investigated the structure-activity relationship of PCN-224 nanoparticles as bifunctional nanocarriers for osteoarthritis (OA) treatment under a precisely controlled temperature gradient. By tuning the temperatures, a series of PCN-224 nanoparticles with adjustable sizes were synthesized and their morphologies transitioned from a spindle-shaped to a spherical-shaped structure. The photoluminescence intensity of PCN-224 nanoparticles decreased as the synthesis temperatures increased. Using PCN-224 nanoparticles as aqueous lubricating additives, both the friction coefficient and wear volume were significantly reduced. Among the MOFs, PCN-224 (synthesized at 105 degrees C) exhibited excellent antifriction performances and acid-responsive drug release properties, demonstrating their promise as bifunctional OA treatment nanocarriers. Our work enhanced the understanding of the relationships between PCN-224 synthesis conditions and its physicochemical properties relationships, expanding their potential for multifunctional biomedical applications.

Understanding how the friction and wear of MoS2 coatings on alloy surfaces vary with operating conditions remains limited, and predicting the coefficient of friction (COF) is challenging due to nonlinear parameter coupling. Here, we propose a cross-scale framework that couples molecular dynamics (MD) simulations with machine learning (ML) to interpret and predict the tribological response of MoS2 coatings under load. MD results identify coating thickness as a primary control parameter: trilayer MoS2 yields the most stable sliding and achieves a COF of ~0.15. Penetration depth governs the transition from stable lubrication at shallow indentation (5Å) to coating failure at deep indentation (10Å). Temperature influences friction mainly through structural evolution; above ~900K, partial decomposition reduces load-bearing capacity and shifts the dominant friction mechanism. ML models capture nonlinear interactions and enable accurate COF prediction across the explored parameter space, with gradient-boosted decision trees and random forests achieving R2 > 0.98. The integrated MD-ML workflow offers a practical route to optimize layered solid-lubricant designs and guide operating-window selection for engineering applications.

Abstract Supramolecular gels hold great potential in engineering applications as lubricants. However, the pure organic network of the gel limits its rheological and lubrication performance. Here, we report a nanoporous material-functionalized supramolecular composite gel lubricant by incorporating polymer brush-grafted metal-organic framework (MOF) nanoparticles (NPs) as nanoadditives. The composite gel was produced by encapsulating poly(lauryl methacrylate) (PLMA) polymer brush-functionalized UiO-67 (UiO-67@PLMA) NPs in 500 SN base oil of a three-dimensional (3D) network formed by 12-hydroxystearic acid (12-HSA) through hydrogen bonding and van der Waals (vdW) interactions. The addition of UiO-67@PLMA NPs largely improved the thermal and rheological properties of the 12-HSA/500 SN gel, and the storage modulus and loss modulus increased significantly. Tribological tests showed that incorporating 0.40 wt% UiO-67@PLMA NPs into the composite gel reduced the coefficient of friction and wear volume by 45.68% and 86.85%, respectively. Furthermore, the UiO-67@PLMA gel demonstrated remarkable tribological performance under challenging conditions, such as 400 N, 65 Hz, and 160 °C. The outstanding lubrication performance of the supramolecular composite gel arises from the shear-triggered release of base oil and nanoadditives, which act as nanobearings and promote protective film formation.

Epoxy protective coatings have garnered significant attention due to their cost-effectiveness, ease of application, and tunable properties for protecting diverse substrates. However, their broader application and long-term performance are limited by inherent brittleness and suboptimal tribological properties of epoxy resins. In this study, we addressed these challenges by developing a composite coating through strategic incorporation of polycaprolactone (PCL) into epoxy resin followed by controlled thermal treatment. The crystallinity of PCL was regulated by systematically optimizing thermal treatment parameters, including temperature, holding duration, and cooling rate. The flexible PCL molecular chains enhance toughness through energy dissipation via chain slippage, while the crystalline domains increase surface hardness and reduce adhesive wear. Specifically, at the optimal thermal treatment temperature of 140 degrees C, the PCL/EP coating achieved an ideal mechanical property, demonstrating a reduced coefficient of friction of 0.11 (83.1 % reduction) and an extremely low wear rate of 1.17 x 10-5 mm3 center dot N- 1 center dot m- 1 (99.6 % reduction). This work presents a strategy for improving the tribological performance of epoxy coatings using PCL. The superior tribological performance of the self-lubricating coating makes it suitable for a wide range of engineering applications, with the potential for extended durability.

In the complex and harsh operating environments of critical moving components in aerospace, it is still a challenge for current lubricating coatings that survive in various environment. Herein, we prepared phosphate bonded lubricating coatings containing MoS2/Cr2O3 composite nanoparticles, graphene and mullite whiskers, which performed well in various conditions (friction coefficient below 0.3), including wide temperature range (- 120-500 degrees C), nitrogen, water vapor (30-90% RH), and salt spray (3.5 wt.% NaCl) environments. The lubricating phase and various fillers were filled into the reticulated crosslinked structure of the phosphate binder, which improved the bonding strength and hardness of the coating. Stable low friction was achieved by the aluminum phosphate amorphous passivation film formed on the friction interface and the synergetic layered lubrication of graphene and MoS2. H+ and OH-groups dissociated from water molecules reacted with the high-activity hanging bonds at graphene edges in humidity environment, maintaining its lubricating characteristic. At elevated temperature, the P-C bond formed by the reaction of P in phosphate binder with high-energy hanging covalent bonds at the graphene boundaries reduced intergranular adhesion and oxidation. The results provide an effective strategy for improving the environmental adaptability of solid lubricating coatings and expanding the application scope.

This study experimentally investigates the mechanical behavior and failure mechanisms of externally prestressed concrete continuous beams using Carbon Fiber Reinforced Polymer (CFRP) tendons subjected to static and fatigue loading. Five specimens were tested, comprising two specimens subjected to monotonic, static loading and three subjected to constant-amplitude sinusoidal fatigue loading. The results show that the static failure mode is characterized by crushing of the concrete in the compression zone. Compared with specimen SB-1 tested under sustained loading on one span and static loading on the other, specimen SB-2 subjected to simultaneous static loading on both spans exhibited a 11.4% increase in loading capacity and more pronounced moment redistribution. It should be noted that this difference in load-carrying capacity is influenced not only by the number of loaded spans but also by the distinct loading protocols and the locations of the critical failure section. The fatigue life of the beams followed an approximately linear trend with the applied load level on a double-logarithmic scale. Deflection, CFRP tendon stress, steel stress, and crack width evolved through three distinct stages: rapid growth, stable growth, and sudden escalation prior to failure. Notably, non-uniform stiffness degradation caused significant fatigue-induced internal-force redistribution, characterized by a progressive decrease in bending moment at the critical section of the fatigue-loaded span and a corresponding increase at the intermediate support. These findings provide critical insights into fatigue performance and predicting the service life of concrete continuous beams externally prestressed with CFRP tendons, offering guidance for improving the performance and safety of dynamically-loaded infrastructure such as railway bridges.

Monitoring the axial force of anchor bolts is critical for ensuring the safety of geotechnical engineering structures. This paper proposes a novel method based on piezoelectric active sensing to accurately assess anchor bolt axial force. The method exploits variations in signal energy dissipation at the contact interface within the anchoring system under load, addressing the limitations of traditional piezoelectric techniques in monitoring stability and zero-point quantification. The contact interface characteristics of the anchor bolt system were analyzed, and a unidirectional energy dissipation path was designed to ensure stable signal acquisition. Key indicators were extracted using the Welch power spectral density estimation method, and a mathematical model relating axial force to these indicators was established. The model’s reliability was validated through multiple independent experiments along three test paths. Results demonstrate a strong linear correlation under various conditions, with an average monitoring error within 10%, enabling precise identification of absolute axial force. The proposed method features real-time performance, high accuracy, and robust anti-interference capability, providing a reliable technical approach for anchor bolt axial force monitoring in geotechnical engineering applications.

High-entropy ceramic coatings exhibit excellent mechanical properties and show great potential for aerospace wear-resistant coating applications. However, their tribological performance strongly depends on counterpart selection, while the underlying wear mechanisms remain insufficiently understood. This study investigates the dry sliding tribological behavior of the AlCrZrNbVC coating against various ceramic (SiC, Al2O3, WC and Si3N4) and metallic (316L) counterparts. The tribological properties of the AlCrZrNbVC coating is strongly governed by the elastic modulus, hardness, and interfacial lubricating ability of the counterpart materials. The results show that the AlCrZrNbVC/SiC tribo-pair exhibits a significantly lower friction coefficient (0.30) and wear rate (1.14 × 10−5 mm3 N−1 m−1) than the other four tribo-pairs. This superior tribological performance is mainly attributed to the favorable interfacial compatibility between SiC and the coating. The friction process promotes the transformation of free carbon into a graphite-like structure, resulting in the formation of a continuous and compact carbon-based lubricating film that effectively reduces friction and wear. In contrast, ceramic counterparts with higher hardness and elastic modulus, such as Al2O3 and Si3N4 are chemically inert and difficult to form lubricating phases. The contact stress is directly transmitted into the coating, leading to brittle fracture and predominant abrasive wear. Among the investigated tribo-pairs, the AlCrZrNbVC/WC exhibits the highest wear rate due to its extremely high contact stiffness. This study elucidates the wear mechanisms of the AlCrZrNbVC coating and provides insights into rational counterpart selection strategies for high-entropy ceramic coatings in wear-resistant applications.

ABSTRACT Ceramics are widely regarded as ideal candidate materials for extreme high‐temperature applications (>900°C) due to their excellent high‐temperature strength and chemical stability. However, their inherent insufficient lubrication performance at high temperatures has long restricted their use in advanced tribological systems. Existing improvement strategies primarily rely on incorporating solid lubricants, but this often leads to a sharp decline in material strength, making it difficult to balance lubricity and wear resistance. This study proposes a breakthrough approach, which is that of in situ constructing a high‐temperature liquid lubricating layer at the friction interface. We found a novel high‐hardness, high boron‐fraction AlMgB 14 ceramic exhibits, for the first time, ultra‐low friction (with a friction coefficient as low as 0.09) and near‐zero wear in both air and vacuum environments at extremely high‐temperature over 900°C. This remarkable performance originates from a co‐evolved double‐layer structure formed during the friction process: a low‐shear liquid lubrication layer (partial oxidized under limited vacuum conditions) that enables very low friction, and a high‐hardness load‐bearing layer that maintains interface stability. This research provides new strategies and a theoretical basis for designing high‐performance ceramic materials for extreme environments.

Molybdenum disulfide (MoS2) serves as an outstanding solid lubricant applied in harsh service conditions. However, enhancing its lubricating, antioxidative and anti-wear capabilities over a broader temperature range stills a formidable challenge, owing to its susceptibility to oxidation at high-temperature. In this work, we achieved superior wide-temperature lubrication from room temperature (RT) to 800 degrees C via the design of core-shell structure, with the introduction of Bi2O3 nanoparticles and encapsulation of SiO2 shell, and phosphate as binder. At RT and 200 degrees C, stable low friction was realized through the synergistic interlayer sliding of MoS2 and in-situ formed Bi2S3 with low shear strength. At 400 degrees C, the protective SiO2 shell inhibited the oxidation of the core lubricating phase, thus enabling MoS2 and Bi2S3 to retain their lubricating functionality. When the temperature exceeded 600 degrees C, the remarkable enhancement in lubricating property (with a coefficient of friction of 0.13-0.16) was attributed to the synergy of phosphate molten-phase lubrication and low-shear lubricating phases (Bi2S3 and Bi2MoO6). An amorphous phosphate molten layer formed at high temperatures and constructed a readily shearable lubricating interface. Low-shear lamellar-chain structure Bi2S3, weak interlayer van der Waals forces reduced the sliding resistance. The distorted MoO6 octahedral structure of Bi2MoO6 induced an enlarged interlayer distance and weakened interionic coupling, which enhanced shear capability and excellent high-temperature lubrication performance. This work provides some reference for improving wide-temperature-range lubricating capabilities of solid lubricating materials.

High-temperature tribology is a multidisciplinary science that has evolved rapidly in response to the increasing performance demands of high-technology sectors, including aviation, aerospace, nuclear energy, power generation, and advanced metal forming industries [...]

Yttria-stabilized zirconia (YSZ) is a promising candidate for abradable seal coatings (ASC) in aero-engines, yet its inherent high coefficient of friction (COF) limits further application. This study introduced dual solid lubricant phases consisting of graphene nanoplatelets (GNPs) and silica-coated hexagonal boron nitride (h-BN@SiO2) with different mass fractions into YSZ, and their tribological performance was systematically evaluated from room temperature to 750 degrees C. The composite containing 15 wt% GNPs and 5 wt% h-BN@SiO2 exhibited low and stable COF (below 0.3) and moderate wear rates. Notably, it achieved an ultra-low COF of 0.08 at 750 degrees C. This outstanding performance originates from the formation of a low-shear graphene/BN interlaced lamellar structure, while tribochemically formed silicate phases and molten boron oxide further enhance the overall tribological performance of the composite. This work proposes an effective design approach for the development of high-performance YSZ-based ASC materials across a broad temperature range.

The tribocorrosion damage behavior of SiC particles reinforced aluminum (SiCp/Al) composites poses a direct threat to their service reliability in harsh environments such as marine settings. In this study, five SiCp/6092 Al composites with varying SiC contents (0%-21%, volume fraction) were fabricated. The composite with 17% SiC achieving the best balance of tribocorrosion and mechanical properties, it reaches a tensile strength of 235 MPa and reduces the wear rate of the 6092 Al matrix under tribocorrosion conditions by over 80%. Analysis indicates that the remarkably improved tribocorrosion resistance is ascribed to the formation of an amorphous/nanocrystalline hybrid protective layer induced during tribocorrosion. Additionally, SiC particles enhance the shear resistance of the composite, thereby slowing the initiation of cracks on the worn surface. This work provides new insights for the compositional design of high-performance aluminum alloy components with synergistic tribocorrosion and mechanical properties.

CoCrFeNi high-entropy alloys (HEAs) are promising for excellent ductility and toughness, but their low strength and poor wear resistance at room temperature limit the engineering applications as sliding components. To overcome that drawback and widen the service temperature range, in this work, the mechanical property and tribological performance at room/cryogenic temperature conditions were investigated for alloys. Compared with the as-cast alloy with FCC dendrite and BCC inter-dendrite dual phases, FCC phase transited into refined equiaxed grains and fractions of Cr-rich BCC precipitates increased within the undercooled alloy, increasing the strength and hardness to 240 MPa and 183 HV, respectively. The coefficient of friction (COF) kept stable (similar to 0.5) while the wear rate reduced to 6.49 x 10(-5) mm(3)/(Nm), where the island-shaped oxide layers appear on the wear scar and the abrasive and adhesive wear behaviors dominates. Under cryogenic condition at 153 K, the wear rates were further decreased by 86.3 % with a reduced COF of 0.2, respectively, governed by the adhesive wear mechanism. The undercooling treatment for CoCrFeNi HEA can effectively improve mechanical properties and wear resistance at different operating conditions, especially for the cryogenic atmosphere. This work provides guidance for the optimizations of tribological and mechanical performance of HEAs.

Although metal-organic frameworks (MOFs) show great potential in osteoarthritis (OA) therapy, synchronous realization of long-time lubrication and anti-inflammation remains a great challenge. Herein, we demonstrate a biomimetic surface assembling strategy to modify MOFs by partially acidified sodium hyaluronate (SHA), and integrate it as a highly aqueous lubrication and anti-inflammatory system for controlled drug release. Inspired by natural composition and function of synovial fluid, SHA is partially acidified to carboxylic acid (SHA-COOH), enhancing aqueous dispersing stability and lubricating performance. Reductions in both coefficient of friction and wear volume are achieved in water, possessing high load-carrying capacity and long-term durability. After loading anti-inflammatory drug, the system shows sustained drug release, improving the drug delivery efficiency. By co-culturing the aspirin-loaded MOFs@SHA-COOH with C-28/I2 cells, the system shows good biocompatibility and anti-inflammatory effect through tuning the expression of OA-related genes. Our work promotes biomacromolecule-functionalized MOFs as biomimetic dual-functional nanocarrier for biomedical applications.