Friction最新文献

{"title":"Lipophilic carbon quantum dots enable fluorescence-traceable lubricant release and tribofilm formation in self-lubricating fabric composites","authors":"Chuntao Qin,Yaoxuan Chen,Jingyu Kang,Ming Jiang,Sergey Chizhik,Xuqing Liu,Lingcai Huang,Weimin Liu","doi":"10.26599/frict.2026.9441319","DOIUrl":"https://doi.org/10.26599/frict.2026.9441319","url":null,"abstract":"Abstract Lubricant delivery and transfer-film formation govern friction and wear in enclosed sliding contacts, yet these buried interfacial processes are difficult to monitor. Oil-loaded microcapsules can supply lubricants to self-lubricating fabric composite liners, but their release behavior is usually optically silent. Here, we report an optically self-reporting microcapsule strategy for AF/PTFE fabric composites, in which dodecyl-chain-modified carbon quantum dots (CQDs-C12) were dispersed in PAO4 and encapsulated in SiO2 microcapsules as fluorescent lubricant reservoirs. During ball-on-disk sliding, local contact stresses triggered the release of CQDs-C12/PAO4 into the wear track. The normalized integrated fluorescence area provided a semi-quantitative optical indication of the cumulative release and accumulation of the fluorescent lubricant phase. The optimized CD–MCs /Fabric achieved a friction coefficient of 0.085 and a wear volume of 1.03 × 10-10 m3, which were 61.7% and 44.5% lower than those of Pure Fabric, respectively. SEM/EDS, Raman, XPS and cross-sectional FIB-TEM analyses confirmed the formation of a continuous multi-component tribofilm on the steel counterpart, which reduced direct fabric/steel contact and interfacial shear. This work couples optical release reporting with tribofilm-mediated lubrication, providing a route toward observable self-lubricating fabric composites for enclosed sliding contacts.","PeriodicalId":12442,"journal":{"name":"Friction","volume":"59 1","pages":""},"PeriodicalIF":6.8,"publicationDate":"2026-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149150791","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Sliding across veins becomes slipperier: Counterintuitive directional friction on nepenthes inner walls","authors":"Yatong Zhang,Jingwen Xu,Shaochen Wang,Fenghe Xu,Hanfei Lei,Dingru Yang,Zhiguang Guo","doi":"10.26599/frict.2026.9441320","DOIUrl":"https://doi.org/10.26599/frict.2026.9441320","url":null,"abstract":"Abstract Directional friction on soft interfaces combining wetting heterogeneity with compliant contact remains unclear under ultralow normal loads, where lubrication and contact geometry may interact strongly. We probed the inner wall of Nepenthes pitchers, which is naturally divided into a hydrophobic waxy zone and a hydrophilic digestive zone, by sliding a compliant sphere parallel and perpendicular to the venation under dry contact, water lubrication, and oil lubrication. Both zones consistently exhibited a counterintuitive frictional anisotropy, with higher average friction during venation-parallel sliding than during venation-perpendicular sliding. The waxy and digestive zones encoded this anisotropy primarily through directional roughness and wettability, respectively, supporting a groove–wetting–hydrodynamic framework for direction-dependent liquid-film load sharing and interfacial shear.","PeriodicalId":12442,"journal":{"name":"Friction","volume":"10 1","pages":""},"PeriodicalIF":6.8,"publicationDate":"2026-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149150793","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Interactions of pollen-stigma interface in fruit trees: A multiscale analysis of adhesion mechanisms","authors":"Junyu Sun,Yanjun Fang,Liyu Chen,Zhihao Zhang,Yanfei Liu,Fuxi Shi","doi":"10.26599/frict.2026.9441322","DOIUrl":"https://doi.org/10.26599/frict.2026.9441322","url":null,"abstract":"Abstract Inspired by sophisticated adhesion strategies in nature, physicochemical properties of pollen from three widely distributed fruit species (apple, pear, and kiwifruit) are investigated, and an novel adhesion mechanism for fruit tree pollination is proposed. Through simulation and measurement of natural pollination process, adhesion force between pollen and stigma is quantified, with its constituent components deduced theoretically. Herein, composition and hygroscopic capacity of pollenkitt from three species reveal that while van der Waals forces dominate the adhesion between two biological interfaces, the presence of pollenkitt confers an increased binding strength as relative humidity rises. At the microscale, pollen surfaces are characterized, and biological model between pollen surface microstructure and stigma papillae is investigated to reproduce the natural pollination adhesion system. Following the discovery of strikingly similar ridge structures in two Rosaceae pollen species and dense microprotuberances on kiwifruit pollen, various mechanical models of these microstructures with papillae as well as artificial substrates are established. Furthermore, based on electrostatic properties of pollen, the electrostatically enhanced adhesion effect is explored through theoretical analysis and experimental validation. Collectively, this research elucidates a bioadhesion mechanism underlying fruit tree pollination, providing application potential for research in agricultural science and technology, biomedicine, and ecological environment.","PeriodicalId":12442,"journal":{"name":"Friction","volume":"22 1","pages":""},"PeriodicalIF":6.8,"publicationDate":"2026-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149150795","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Analytical solution of ball-disc oil film capacitance for various lubrication conditions","authors":"Zhiyao He,Ziqiang Zhao,Su Yan,Haibo Zhang,Xiangyu Ge,He Liang,Wenzhong Wang","doi":"10.26599/frict.2026.9441323","DOIUrl":"https://doi.org/10.26599/frict.2026.9441323","url":null,"abstract":"Abstract Accurately solving the electrical impedance in various conditions is fundamental in monitoring the lubrication conditions of rolling bearings with electrical impedance method. In the present study, an analytical solution using Legendre polynomials for the capacitance of ball-disc contact is proposed, accounting for the clearance, oil reservoir angle, oil-solid contact angle, Hertz deformation, air capacitance, and extending to dynamic oil reservoir. The analytical results show good agreement with the numerical simulation results from finite element model and ball-disc experiment with specific oil reservoirs and dynamic conditions. Parametric studies reveal that the oil reservoir angle, indicating the oil supply condition, should be considered, especially for larger film thickness and fully-flooded lubrication. The capacitance contributed by air should be involved because the dielectric constants of oil and air are generally close, while the effect of contact angle is negligible for common practical conditions.","PeriodicalId":12442,"journal":{"name":"Friction","volume":"466 1","pages":""},"PeriodicalIF":6.8,"publicationDate":"2026-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149150797","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Efficient one-pot synthesis of molybdenum dialkyl dithiocarbamate and investigation on evolution mechanism of tribofilms in ester-based lubricants","authors":"Yunhan Zhang,Yifan Liu,Xianjuan Pang,Haocheng Xu,Guangbin Yang,Yujuan Zhang,Shengmao Zhang,Pingyu Zhang","doi":"10.26599/frict.2026.9441321","DOIUrl":"https://doi.org/10.26599/frict.2026.9441321","url":null,"abstract":"Abstract Base oil polarity critically governs additive solubility, interfacial adsorption, and tribochemical reactions, which collectively determine friction, wear, and component service life. In this study, molybdenum dialkyldithiocarbamate (MoDTC) was synthesized via a facile one-pot route. Its dispersion stability and tribological properties were compared in two base oils with distinct polarities: polar diisooctyl sebacate (DIOS) and nonpolar polyalphaolefin (PAO6). The tribological behavior of the MoDTC/DIOS blend was further evaluated under variable applied loads and temperatures. The results reveal that MoDTC delivers superior friction-reducing and anti-wear performance in nonpolar PAO6, attributed to stable adsorption on friction surfaces and tribochemical decomposition into protective tribofilms. In contrast, polar DIOS enables the MoDTC/DIOS blend to reach a steady friction coefficient (COF) much faster, with a drastically shortened running-in stage. Cross-sectional characterizations demonstrate that the polar DIOS environment accelerates MoDTC decomposition and rapid formation of an amorphous Mo- and S-containing tribofilm, accounting for the sharp COF decline. Nevertheless, this amorphous tribofilm exhibits low load-bearing capacity and cannot effectively suppress interfacial wear, resulting in a larger wear scar diameter (WSD) than the MoDTC/PAO6 blend. At 25 °C, MoDTC achieves optimal lubrication, reducing the COF and WSD of neat DIOS by 50.0% and 23.3%, respectively. At 75 °C, COF reduction reaches 61.5%; at 125 °C, despite severe fluctuations in the friction curve, the WSD remains smaller than that of neat DIOS, indicating sustained anti‑wear capability. Combined with multiple modern characterizations, the underlying lubrication mechanisms is clarified: at low‑to‑medium temperatures, MoDTC preferentially generates a dense tribofilm dominated by layered MoS2; at elevated temperatures, the tribofilm transforms into a composite of MoO3 and MoSxOy. Despite increasing the COF, this composite tribofilms retain excellent load‑bearing and anti‑adhesion properties to mitigate severe wear. This study provides guidance for optimizing MoDTC synthesis, polarity matching, and tribofilm regulation, facilitating its wide application in lubrication systems.","PeriodicalId":12442,"journal":{"name":"Friction","volume":"29 1","pages":""},"PeriodicalIF":6.8,"publicationDate":"2026-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149150792","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"LubZero: An active molecular generation framework for multiobjective properties of lubricant molecules","authors":"Luyao Bao,Rui Zhou,Xiangmeng Jia,Feng Zhou,Meirong Cai,Weimin Liu","doi":"10.26599/frict.2026.9441293","DOIUrl":"https://doi.org/10.26599/frict.2026.9441293","url":null,"abstract":"Abstract The screening of lubricant candidates with tailored multiproperty profiles is a foundational challenge in tribology, driven by increasing demands for energy efficiency and operational safety. However, the vast discrete chemical space and the sparse-reward nature of molecular design often hinder efficient optimization. In this work, we present LubZero, a graph-based molecular generation framework that adapts the AlphaZero algorithm for the de novo design of lubricant ester materials. LubZero reformulates fragment-based molecular assembly as a single-player combinatorial game, integrating a graph isomorphism network with edge features (GINE) and Monte Carlo tree search (MCTS) to enable principled forward planning. Crucially, we implement a high-throughput parallel self-play architecture that utilizes multiprocess inference on a shared GPU, significantly enhancing exploration efficiency and hardware resource utilization compared to serial implementations. This framework enables LubZero to navigate complex property trade-offs efficiently within a constrained molecular-design protocol. We applied LubZero to the multiobjective optimization of ester lubricants, specifically targeting high flash points and low pour points. The results show that LubZero identifies high-ranking surrogate-predicted screening candidates that extend the predicted flash-point/pour-point trade-off space beyond the region covered by the available experimental data. By integrating artificial intelligence planning with a scalable parallel computing strategy, LubZero offers a surrogate-guided workflow for screening and prioritizing candidate lubricant molecules under explicitly defined objective and applicability domain constraints.","PeriodicalId":12442,"journal":{"name":"Friction","volume":"26 1","pages":""},"PeriodicalIF":6.8,"publicationDate":"2026-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149150794","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Ultra-low wear of WC/bronze composite prepared by binder jet printing and infiltration via amorphous–crystalline nanocomposite tribofilm","authors":"Xinyi Liu,Yi Ren,Xibo Shao,Jiangkun Fan,Jinshan Li","doi":"10.26599/frict.2026.9441271","DOIUrl":"https://doi.org/10.26599/frict.2026.9441271","url":null,"abstract":"Abstract Anti-wear performance is vital for the lifespan of moving components. Herein, ultra-low wear, even negative wear, was obtained for the tungsten carbide/bronze composites prepared by additive manufacturing binder jet printing (BJPWC), especially when in sliding contact with SiC ceramic. Sliding interface observation reveals that the promising tribological performance of SiC/BJPWC is ascribed to the in situ formed stable tribofilm which can deliver beneficial friction reduction and anti-wear effects. The friction process between SiC balls and WC/bronze composite under varying loads induces the diffusion of Si atoms toward the sliding interface, where they form negative mixing enthalpy and network chemical bonds with other metals, promoting the amorphization of the tribolayer. An in situ formed unique nanocomposite protective layer is generated, in which Cu/WC nanocrystals are uniformly dispersed within a silicate amorphous matrix. This unique structure effectively accommodates friction-induced plastic deformation and resists damage. This work can provide some basic understanding for ultra-low-wear materials and guides the selection of sliding counterparts for future applications of additive manufactured components.","PeriodicalId":12442,"journal":{"name":"Friction","volume":"8 1","pages":""},"PeriodicalIF":6.8,"publicationDate":"2026-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149150796","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Formation of robust graphene tribofilms on hydrogen-free amorphous carbon/boron carbide periodic nanomultilayer coatings achieving low friction","authors":"Mingfeng Li,Pengyuan Wu,Boyang Shen,Jingjing Peng,Yuzhen Liu,Dae-Eun Kim,Oleksiy V. Penkov","doi":"10.26599/frict.2026.9441280","DOIUrl":"https://doi.org/10.26599/frict.2026.9441280","url":null,"abstract":"Abstract Achieving superlubricity in hydrogen-free amorphous carbon (a-C) coatings through the formation of multilayer graphene-based tribofilms via tribochemical reactions has remained a significant challenge. Here, we report the successful fabrication of H-free a-C/B4C periodic nanomultilayer coatings (PNCs) with systematically varied modulation periods (3–8.5 nm), which achieve low friction through tribochemically induced graphene tribofilm formation. The optimal coating structure, consisting of alternating 1.5 nm a-C and 2.5 nm B4C nanolayers (a-C1.5), demonstrated a remarkably low coefficient of friction of ~0.075 and exceptional wear resistance (~1.3×10−10 mm3/(N·mm)) under ambient conditions. Advanced characterization techniques, including 2D Raman mapping and high-resolution transmission electron microscopy (HRTEM), confirmed the formation of multilayer graphene structures on the counter surface and the wear track during sliding. The formation of this multilayer graphene-based tribofilm, previously reported only in hydrogenated a-C coatings, transforms asperity-dominated shearing into low-resistance interlayer sliding between graphene nanoflakes. After extending the reciprocating sliding to 60k cycles, the tribofilm persisted, even though the coating had worn out. Molecular dynamics simulations revealed that the superior tribological performance originates from enhanced elastic recovery, optimal stress distribution across nanolayers, and boron-promoted tribochemical graphitization of amorphous carbon. This discovery demonstrates that graphene-based tribofilms can be derived from H-free a-C-based coatings, opening a novel and practical strategy for achieving low friction in carbon-based protective coatings without the limitations associated with hydrogen content or preconstructed 2D material additives.","PeriodicalId":12442,"journal":{"name":"Friction","volume":"154 1","pages":""},"PeriodicalIF":6.8,"publicationDate":"2026-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149021305","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Multilevel-structured phase-responsive solid–liquid composite lubricating coating and its tribological and anti-corrosion performance","authors":"Junhao Sang,Yunlong Li,Xinyuan Ji,Yongling Wu,Mingming Liu,Hongyu Zheng","doi":"10.26599/frict.2026.9441317","DOIUrl":"https://doi.org/10.26599/frict.2026.9441317","url":null,"abstract":"Abstract Laser-induced graphene (LIG) has attracted widespread attention owing to its excellent solid-lubricating property, chemical stability, and designable surface structure, and has shown broad application prospects in fields such as friction reduction and corrosion protection. However, its limited structural stability and lubricant-storage capability restrict its practical application. In this work, a multifunctional composite lubricating surface integrating LIG, epoxy resin, laser surface texturing, and phase-change paraffin wax (PW@LST@E-LIG) was developed. The LIG structure was firstly optimized by tuning the laser power, followed by epoxy resin infiltration to enhance structural stability. Subsequently, laser-textured micropore arrays were introduced and combined with phase-change paraffin wax to establish a thermally responsive lubrication system, thereby achieving the synergistic enhancement of tribological and anti-corrosion performance. Compared with the original LIG, the optimized sample exhibited a reduction in coefficient of friction (COF) of 45–55% (approximately 0.09) and the wear depth decreased by approximately 90% under the same load. Anti-corrosion performance tests showed that the interfacial charge-transfer resistance increased to 105 Ω cm2, while the corrosion current density decreased to 10−7 A·cm⁻2. The corrosion current density decreased by more than two orders of magnitude compared with that of the substrate, resulting in an inhibition efficiency of 99.54%. Through the coupling of structural design and phase-change materials, this study achieved the synergistic enhancement of wear resistance, lubrication, lubricant-storage capability, and anti-corrosion performance, providing a new strategy for the design of multifunctional surfaces for diverse service conditions.","PeriodicalId":12442,"journal":{"name":"Friction","volume":"27 1","pages":""},"PeriodicalIF":6.8,"publicationDate":"2026-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149021303","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Dealloying-induced surface porosity for enhancing tribological properties of Ag-DLC films under starved lubrication","authors":"Junjie Lu,Shiqi Lu,Xubing Wei,Meng Cheng,Haiyan Feng,Chengyuan Liu,Aiping Lin,Kwang-Ryeol Lee,Guangan Zhang,Xiaowei Li","doi":"10.26599/frict.2026.9441318","DOIUrl":"https://doi.org/10.26599/frict.2026.9441318","url":null,"abstract":"Abstract Surface porous architectures serving as micro-oil reservoirs offer a promising adaptive self-lubrication strategy for critical engine components under starved lubrication conditions, especially during frequent start-stop cycles. However, the controlled fabrication of such structures on DLC surfaces and their tribological behavior under representative oil-starved conditions remain insufficiently explored. Herein, we propose a novel strategy that exploits the inherent thermodynamic incompatibility and self-migration behavior of Ag in the carbon matrix as a natural advantage. A simple dealloying method was employed to construct surface porous structure on Ag-DLC films via the selective removal of Ag particles, aiming to improve tribological properties under starved lubrication. Results reveal that the size and density of porous structure is regulated by the Ag target current during deposition. Notably, the introduced porous structure significantly mitigates abnormal wear at the friction interface while maintaining a low and stable friction coefficient under starved lubrication. The porous structure acts as micro-oil reservoirs, and it effectively replenishes the boundary lubricating film via load/thermal stimuli induced oil release. Mechanisms attribute to the synergistic effects of replenished the boundary lubricating film, reduced real contact area, and graphitized transfer films. These findings provide a foundation for designing intelligent adaptive DLC-based lubrication systems capable of autonomous oil replenishment under intermittent lubrication regimes.","PeriodicalId":12442,"journal":{"name":"Friction","volume":"4 1","pages":""},"PeriodicalIF":6.8,"publicationDate":"2026-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149021304","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}