The tribological behavior of carbon-based nanomaterials is fundamentally dictated by their interfacial interactions with the contact surface. Hence, a systematic investigation of their interface adsorption properties, film-forming capabilities, and tribo-induced nanostructure evolution is crucial for achieving efficient lubrication. In this work, a series of fluorinated graphene (FG-S) additives with tunable interlayer spacing were prepared via fluorination-induced surface reconstruction of graphene oxide (GO). Among them, FG-8 exhibited exceptional dispersion stability and tribological properties in the base oil. Specifically, the addition of 0.01 wt% FG-8 to the base oil reduced the average friction coefficient and wear scar diameter by 41.0% and 46.1%, respectively. Interfacial analysis confirmed that the improvement could be attributed to the high dispersion of FG-8, which readily entered the frictional contact zone and preferentially adsorbed onto the sliding interface, thereby forming a composite protective film composed of solid adsorption film and tribochemical reaction film, capable of withstanding higher contact pressure. Its unique feature lies in the fact that tribo-induced FG-8 undergoes electrostatic self-assembly at the steel/steel interface, generating friction products with both interlayer shear and rolling bearing-like effects, thereby achieving in-situ reconstruction of the tribofilm and dynamic repair of the worn surface.

Hydrogen peroxide (H2O2) plays a critical role in surface oxidation and corrosion during the chemical mechanical polishing (CMP) of silicon carbide (SiC). A systematic density functional theory (DFT) study was conducted to investigate the adsorption and dissociation behaviors of H2O2 on SiC surfaces. Through geometric optimization, transition state analysis, and electronic structure characterization, the detailed reaction mechanisms of H2O2 and its process-derived intermediates (such as OH, OOH, and O2) on different SiC surfaces were elucidated. The results indicate that H2O2 undergoes strong dissociative adsorption on SiC surfaces due to its high reactivity. Compared to the C-terminated surface, intermediates including OH, OOH, and O2 exhibit consistently higher adsorption energies on the Si-terminated surface, suggesting stronger reactivity of the Si-face. Furthermore, two distinct reaction pathways were identified for the initial dissociation of H2O2 on the SiC (0001) Si-face. The surface reconstruction induced by the initial dissociation step significantly influences the activation energy of subsequent reactions. These computational insights provide an atomic-scale understanding of the oxidation mechanism of H2O2 on SiC surfaces, offering theoretical guidance for the design of CMP slurries.

Understanding the mechanism of action of graphene oxide (GO)-based lubrication materials is of great significance to effectively suppress the surface damage accumulation of bearing steel during service. However, GO typically exhibits weak interfacial adsorption and poor dispersion stability, severely limiting its ability to form a dynamic tribofilm during friction. In this study, we synthesized an efficient lubricant, oleylamine-grafted chlorinated graphene (OA/Cl-GO), using GO as the carrier and introducing lipophilic terminal groups through chlorination and interfacial covalent modification. The lubrication performance of GO and OA/Cl-GO in steel/steel friction pairs was evaluated under sliding wear conditions, and the effects of the additive concentration, chemical composition, and microstructure on the OA/Cl-GO interfacial lubrication behavior were systematically investigated. The results showed that the lubricating performance of OA/Cl-GO was significantly better than that of the GO at an optimal concentration of 0.15 wt %, which could reduce the coefficient of friction and wear scar diameter of the base oil by 30.1 and 22.7%, respectively. During the sliding wear process, the synergistic effects of charge adsorption, protective adsorption films, and tribochemical reaction films effectively induced the formation of a "sliding-rolling" cooperative load-bearing behavior of OA/Cl-GO nanosheets at the interface. As a result, a dynamic repair mechanism was developed on the friction surface, which effectively suppressed the damage progression of the bearing steel. This study provides a theoretical foundation and technical guidance for developing nanolubricants with high compatibility with bearing steel interfaces.

This study aims to accurately predict the compression stress–strain curves of medium Mn steel under high-temperature conditions. The Arrhenius constitutive equation with Zener–Hollomon, machine learning (ML), and genetic programming-based symbolic regression (GP-SR) was used to construct a prediction model for the high-temperature compression properties of medium manganese steel. The prediction performance of the three models was fairly compared by using the leave-one-out cross-validation dataset partitioning method. The average R2 value of the Arrhenius constitutive equation on the training set is 0.855, and the average RMSE value is 12.14MPa. The ML dataset was constructed using the equidistant point method, and a new feature “strain level” was introduced. Combining support vector regression (SVR) with eXtreme gradient boosting (XGBoost) improved model performance, increasing R2 from 0.824 to 0.907 and reducing RMSE from 10.70 to 8.28 MPa. The GP-SR method, combined with optimized hyperparameters and multiple iterations, produced a highly effective predictive formula with an average R2 of 0.942 and an average RMSE of 7.87 MPa, and it demonstrated significant advantages. Compared with the ML models, this formula has excellent interpretability. Therefore, the formula obtained using the GP-SR method achieves higher accuracy compared to traditional equations and models. It provides an accurate reference for predicting stress–strain curves and selecting hot working parameters in the hot working process of medium Mn steel.

In this study, density functional theory (DFT) methods were employed to systematically investigate the adsorption, dissociation, and subsequent reaction pathways of methanol molecules (CH3OH) on the C-terminated surface and Si-terminated face of silicon carbide (SiC) cluster models. By optimizing geometric structures, tracing reaction pathways and transition states, analyzing electronic density of states, strong and weak interactions, and bond orders, the detailed reaction mechanisms of methanol molecules on different surfaces of SiC were revealed. The research found that methanol molecules undergo dissociative adsorption on both the Si-terminated surface and C-terminated surface of SiC, with two dissociative pathways existing due to variations in adsorption sites or external conditions. The Si-terminated surface is more reactive compared to the C-terminated surface. These findings provide atomistic insights into surface reactivity, guiding the design of non-aqueous slurries for efficient SiC chemical mechanical polishing (CMP).

Abnormal wear has always been a common concern in engineering lubrication, which sometimes depends on the lubrication. The present work aimed to elucidate the formation mechanism of abnormal non-circular wear scar of GCr15 ball-ball contact in the presence of dibutyl phosphite (DBPI). A detailed characterization of morphology, composition, and structure was performed. The results show that the abnormal wear depended on the chemical reactivity of DBPI, structure and size of wear products. Importantly, wear products exhibited a flocculent structure at the macroscale and had a capsule structure with metal debris encapsulated into an amorphous shell at the microscale. The redeposition of wear products formed a multilayered tribofilm, containing a metal-debris-dominated layer and multiple organic-dominated amorphous layers. The total thickness of tribofilm can be up to 268 nm. Fe3(POx)2, FePOx, Fe[DBPI]2, and Fe[DBPI]3 were the principal composition of tribofilm. The present work elucidates the molecule-dependent abnormal wear of ball-ball contact, which will have wide potential for the additives design and the corresponding lubrication mechanism research.

This study innovatively utilized nanolattice defect engineering to design a series of medium Mn steels (MMS) with ultrahigh strength and plasticity through the simple two-stage warm rolling process. The composition of this steel is 0.31 % C-8.1 % Mn-2.6 % Al-0.4 %V (wt%),successfully breaking the trade-off between strength and elongation. The high-density stacking fault networks, Lomer-Cottrell locks (L-C locks), nano precipitates, nano phase transition layers, and nano twins are introduced into the microstructure, allowing the materials to achieve the ultra-high yield strength (1.39-1.46GPa), sufficient strain-hardening ability, excellent elongation (32 % similar to 38 %) and ultra-high tensile strength (1.41-1.65GPa). The results illustrate that the rolling temperature of second stage has a significant impact on the characteristics of nanolattice defects and the related work-hardening behavior. When the rolling temperature increase from 330 degrees C to 380 degrees C, the contents of stacking fault networks, L-C locks, and nano epsilon- or alpha'- martensite layers remain unchanged, but the increase of element segregation at the stacking-fault networks and L-C locks and the generation of nano twins induce a significant improvement of work-hardening ability. The gradual increase of nano twins effectively guaranteed the yield strength as the temperature increased to 430 degrees C and 480 degrees C. However, they cannot compensate for the significant decrease in work-hardening ability caused by the absence of stacking fault networks and L-C locks. The abnormal enhancement of work-hardening ability during tensile deformation mainly come from the dynamic refinement of the C-segregated nanoscale stacking fault networks, which effectively improves the resistance to the movement of dislocation. In addition, the contributions of stacking faults and nano twins were specifically highlighted to the calculation of yield strength of austenite. Therefore, this study innovatively proposes a new strategy to break the contradiction between strength and plasticity of MMS through the lattice defect engineering. These results have important guiding significances for the development of a new generation MMS with ultrahigh strength and excellent plasticity.

Two-dimensional(2D)nanomaterials have always been regarded as having great development potential in the field of oil-based lubrication due to their designable structures,functional groups,and abundant active sites.However,understanding the structure-performance relationship between the chemical struc-ture of 2D nanomaterials and their lubrication performance from a comprehensive perspective is crucial for guiding their future development.This review provides a timely and comprehensive overview of the applications of 2D nanomaterials in oil-based lubrication.First,the bottlenecks and mechanisms of ac-tion of 2D nanomaterials are outlined,including adsorption protective films,charge adsorption effects,tribochemical reaction films,interlayer slip,and synergistic effects.On this basis,the review summarizes recent structural regulation strategies for 2D nanomaterials,including doping engineering,surface mod-ification,structural optimization,and interfacial mixing engineering.Then,the focus was on analyzing the structure-performance relationship between the chemical structure of 2D nanomaterials and their lubrication performance.The effects of thickness,number of layers,sheet diameter,interlayer spacing,Moiré patterns,wettability,functional groups,concentration,as well as interfacial compatibility and dis-persion behavior of 2D nanomaterials were systematically investigated in oil-based lubrication,with the intrinsic correlations resolved through computational simulations.Finally,the review offers a preliminary summary of the significant challenges and future directions for 2D nanomaterials in oil-based lubrica-tion.This review aims to provide valuable insights and development strategies for the rational design of high-performance oil-based lubrication materials.

Water-based lubricants have attractive properties compared to flammable oily lubricants but in high-temperature environments remain a tricky challenge due to the Leidenfrost effect-induced poor wettability once contacting sufficiently hot surfaces. Herein, a surfactant-modified Laponite nanoclay (LNC), as a prototype water-based lubricant with considerable lubricity, exhibits spontaneous high-temperature wettability by which the Leidenfrost point (LFP) can be improved above approximate to 350 degrees C on crude stainless steels, increasing by approximate to 140 degrees C compared to pure water. The inter-particle attractions between LNC nanoplates increase the liquid viscosity, causing viscous force of bulk water near the substrate, allowing in situ deposition of LNC layers on the hot surface to trigger three-phase contact line (TCL) pinning. As a basis, wettable lubricants are further optimized on their lubricity by intercalating zwitterionic surfactants between LNC nanoplates, thereby reducing friction coefficient to approximate to 0.1. The LNC lubricants have been demonstrated in a four-ball tribometer to simulate hot rolling lubrication, providing insights for high-temperature metal processing, and potential applications in mechanical engineering and the aerospace field. A new paradigm is developed to suppress the Leidenfrost effect of water droplets on crude stainless steel above approximate to 350 degrees C via tuning the fluid characteristics. A surfactant-modified Laponite nanoclay (LNC) water-based lubricant is fabricated, exhibiting spontaneous high-temperature wettability while preserving considerable lubricity. image

In this paper, the influence of decreasing Zr content (0.0110 wt%, 0.0044 wt%) on the microstructure, MnS inclusion characteristics, and mechanical properties of medium carbon ferrite-pearlite steel was studied. The results show that the volume fraction of intragranular ferrite (IGF) in steel increases with a reduction in Zr content. The ductility of the steel is reduced by 1.83%, the impact toughness is increased by 2.5 times, and the yield strength is almost unchanged. Compound MnS inclusions are the main inclusions that induce IGF formation. The proportion of heterogeneous nucleation of MnS inclusions using oxides as nucleation sites is increased, which is the main reason for the increase in the volume fraction of IGF. Furthermore, MnS inclusions change from type III to type I and II, and their distribution is gradually uniform. Thermodynamic analysis reveals that the underlying cause for the morphological transformation of MnS inclusions is the rapid surge in the supersaturation of S element in molten steel. The presence of liquid-phase low-melting inclusions (MnS-Al2O3) promotes the formation of type I MnS inclusions. The volume fraction and the dimension perpendicular to the fracture surface of the MnS inclusions are increased by at least 33% and 111%, while their aspect ratio is reduced by a maximum of up to 19%. The change in the volume fraction of MnS inclusions is the primary factor contributing to the decrease of tensile plasticity. The toughness of steel is mainly affected by the aspect ratio and the dimension perpendicular to the fracture surface of MnS inclusions.

Micro-alloyed medium-carbon steel is increasingly used as a cost-effective alternative to quenched and tempered steel in the production of half-shaft components. Current research emphasizes controlling the microstructure during thermomechanical processing to achieve the desired structural properties after cooling. This study investigated the effect of continuous cooling transformation on the microstructure and mechanical properties of micro-alloyed medium-carbon steel. At a cooling rate of 0.5 degrees C s-1, only pearlite transformation occurred. At rates between 1 degrees C s-1 and 8 degrees C s-1, both bainite and martensite transformations were observed, while only martensite formed at rates exceeding 12 degrees C s-1. Subsequently, a four-factor, three-level orthogonal experiment was designed based on the actual production process for half shafts. The optimal forging parameters were identified as a heating temperature of 1000 degrees C, a deformation temperature of 920 degrees C, a deformation extent of 15%, and a cooling rate of 0.5 degrees C s-1. The study offered solutions to enhance microstructural uniformity and effectively manage abnormal bainite and martensite formations, thereby establishing a foundation for the high-quality application of micro-alloyed medium-carbon steel in half-shaft components.

Cold rolling emulsion contains a variety of functional additives, which often exhibit complex interactions with each other. Sodium alkane sulfonate (SAS) is a common corrosion inhibitor used in cold rolling emulsions for temporary rust prevention. In this study, it was found that SAS would deteriorate the tribological properties of the emulsion. Emulsions containing SAS and different friction modifiers were prepared. Tribology tests were carried out on a four-ball friction and wear tester. White light interferometer was used to investigate the 3D morphology of the friction surface and wear volume. Microscopic morphology of friction surfaces was observed using a scanning electron microscope (SEM). The chemical activity and electrostatic potential of the molecules were calculated based on density functional theory (DFT). The adsorption energies of additives on metal surfaces were calculated via molecular dynamics (MD) simulation. The results indicate that the strong electrostatic force gives SAS an advantage in competitive adsorption with ester friction modifiers due to the positive charge on the metal surface. This results in the friction modifier not functioning properly and the tribological properties of the emulsion being significantly reduced.

通过合金成分分析、显微组织定量表征、断口形貌观察及力学性能测定,对中碳微合金非调质钢 36MnVS4 连杆断口掉渣和断口不齐缺陷进行分析.在VW 50030 标准和TCCMI 13.1-2021 标准下进行比较,结果表明:4 支连杆组织为珠光体+铁素体,均无异常组织,晶粒度均为 5.5～6.0 级,不符合标准要求;缺陷连杆的抗拉强度、屈服强度、断后伸长率符合标准,但断面收缩率为26.5%～27.4%,明显低于合格连杆的32.8%～33.5%的断面收缩率,未达到要求.断口不齐的主要原因为断口附近的Ca、Si氧化物夹杂物,在断口侧面发现激光切槽的位置较深,不仅改变胀断轨迹,还降低断面收缩率;掉渣的主要原因为断口附近出现微孔型断裂韧窝,改变了断口表面状态.最后提出采用控锻控冷技术精确控制组织性能是解决问题的关键.

To alleviate the agglomeration and deposition of MoS2 nanofluid, MoS2 nanosheets were modified using self-made surface modifier. The self-made surface modifier was synthesized using triethanolamine (TEA) and stearic-acid (SA). Both total weight and mass ratio of TEA and SA were researched to gain modified MoS2 nanosheets with better dispersion stability. The modified MoS2 nanosheets prepared using surface modifier with optimal mass ratio and total weight were characterized by FT-IR and TEM. An organics solvation layer with a thickness of 15-17 nm was found adsorbed on MoS2 nanosheets, which prevented their agglomeration and improved their dispersion stability. Both four-ball tribotester and Molecular Dynamics simulation method were conducted to learn the effects of surface modification on the tribological properties of modified MoS2 nanofluid. The diffusion rate, interlayer distance, interlayer adsorption energy and shear stress of modified and unmodified MoS2 nanosheets were calculated. Due to interaction between MoS2 nanosheets and surface modifier, the interlayer distance of modified MoS2 nanosheets was increased. And the interlayer adsorption energy and interlayer shear stress were decreased, especially when the normal pressure was applied. The modified MoS2 nanosheets had not only better dispersion stability, but also excellent tribological properties.

It was discovered the application of Al2O3 nanofluid as lubricant for steel hot rolling could synchronously achieve oxidation protection of strips surface. The underlying mechanism was investigated through hot rolling tests and molecular dynamics (MD) simulations. The employment of Al2O3 nanoparticles contributed to significant enhancement in the lubrication performance of lubricant. The rolled strip exhibited the best surface topography that the roughness reached lowest with the sparsest surface defects. Besides, the oxide scale generated on steel surface was also thinner, and the ratio of Fe2O3 among various iron oxides became lower. It was revealed the above oxidation protection effect of Al2O3 nanofluid was attributed to the deposition of nanoparticles on metal surface during hot rolling. A protective layer in the thickness of about 193 nm was formed to prevent the direct contact between steel matrix and atmosphere, which was mainly composed of Al2O3 and sintered organic molecules. MD simulations confirmed the diffusion of O-2 and H2O could be blocked by the Al2O3 layer through physical absorption and penetration barrier effect.

LiFePO4 powders with different sizes and shapes were successfully synthesized in water, ethylene glycol, and mixed water/ethylene glycol solvents. The morphological evolution of LiFePO4 crystals from micrometer-sized bulky particles to nanorods was easily achieved by varying the water-to-ethylene glycol volume ratio. The morphological evolution process and formation mechanism were investigated. Electrochemical measurements showed that the charge transport and the diffusion rate of Li ions significantly improved with the structural evolution. The initial discharge capacity at 0.1 C was increased from 61 mAh center dot g-1 for micrometer-sized bulky particles to 164 mAh center dot g-1 for nanorods. Furthermore, the LiFePO4 nanorods exhibited a discharge capacity of about 120 mAh center dot g-1 at 20 celcius and an excellent rate capability at high discharge rates.

A novel nanomaterial reduced graphene oxide-Al2O3 nanocomposite (rGO-Al2O3) was synthesized through the hydrothermal method. The nanofluid containing rGO-Al2O3 nanocomposite was prepared as lubricant and exhibited superior dispersion stability. To clarify the lubrication mechanism of rGO-Al2O3 nanofluid, tribological tests and cold rolling lubrication experiments were conducted using the four-ball tribometer and two-high rolling mill. The results indicated that excellent anti-wear and friction-reducing properties as well as desired strip surface topography could be obtained under the lubrication of 0.20 wt% rGO-Al2O3 nanofluid. Induced by the interfacial tribochemical reaction, a bilayer lubrication film composed of adsorption film and reaction layer was formed at the friction interface. Through theoretical calculation and experimental characterizations, the thickness of lubrication film was about 25 nm. The adsorption film, dominated by nano-Al2O3 and graphene oxide fragments, played a vital role in synergistic lubrication. Meanwhile the reaction layer contained iron oxides (primarily Fe2O3 and FeO) with high mechanical properties. This bilayer structure ensured the denseness and continuity of the lubrication film, thus achieving significant lubrication performance.

Reduced graphene oxide-Al2O3 (rGO-Al2O3) nanoparticle (NP) was synthesized and applied as additive in water -based lubricants. Pin-on-disk tribological experiments indicated that rGO-Al2O3 nanofluid exhibited reinforced lubricity due to the formation of a double-layer tribofilm, contributing to 34.8 % +/- 2.3 % and 78.2 % +/- 2.5 % reduction in friction coefficient and wear rate. Combined with nonequilibrium molecular dynamics (NEMD) simulation, rGO-Al2O3 NP exerted synergistic effects of interlayer sliding, rolling, polishing and self-mending to obtain higher surface quality. A new parameter (p) was proposed to determine the motion modes of Al2O3. Al2O3 NP exhibited both rolling and sliding motion. The synergy of rGO and Al2O3 NPs increased the rolling motion proportion of Al2O3 from 78 % to 91 % compared to using alone. Similarly, about 12.6 % of the friction force in friction system was shared by the interlayer sliding of rGO monolayers in the presence of Al2O3 than the system with only rGO (9.5 %). Besides, rGO-Al2O3 had higher diffusion coefficient, which was more conducive to the formation of tribofilm. rGO nanosheets with large transverse size adsorbed on the Fe surface to prevent the embedding of high hardness Al2O3 to maintain its rolling effect. Meanwhile, Al2O3 can reversely stimulate the interlaminar sliding of rGO to enhance the lubrication performance of rGO-Al2O3 nanofluid.

In this study, a novel lubricant additive nitrogen-doped carbon quantum dot (N-CQD) nanoparticle was prepared by the solvothermal method. The synthesized spherical N-CQD nanoparticles in the diameter of about 10 nm had a graphene oxide (GO)-like structure with various oxygen (O)- and nitrogen (N)-containing functional groups. Then N-CQDs were added to MoS2 nanofluid, and the tribological properties for steel/steel friction pairs were evaluated using a pin-on-disk tribometer. Non-equilibrium molecular dynamics (NEMD) simulations for the friction system with MoS2 or MoS2 + N-CQD nanoparticles were also conducted. The results showed that friction processes with MoS2 + N-CQD nanofluids were under the mixed lubrication regime. And MoS2 nanofluid containing 0.4 wt% N-CQDs could achieve 30.4% and 31.0% reduction in the friction coefficient and wear rate, respectively, compared to those without N-CQDs. By analyzing the worn surface topography and chemical compositions, the excellent lubrication performance resulted from the formation of tribochemistry-induced tribofilm. The average thickness of tribofilm was about 13.9 nm, and it was composed of amorphous substances, ultrafine crystalline nanoparticles, and self-lubricating FeSO4/Fe2(SO4)3. NEMD simulation results indicated the interaction between S atoms in MoS2 as well as these O- and N-containing functional groups in N-CQDs with steel surfaces enhanced the stability and strength of tribofilm. Thereby the metal surface was further protected from friction and wear.

综述了量子化学计算和分子动力学模拟在金属加工液个性化设计、定制与性能评测研究方面的应用.量子化学计算可以准确获取金属加工液体系中各种分子的化学反应活性、在金属表面的吸附行为等微观性质,实现对摩擦改进剂、防锈剂等添加剂的高效筛选和设计;而分子动力学模拟的优势在于能够得到金属加工液的黏度、热导率等理化性能,模拟或重现实际金属加工的摩擦润滑等过程,尤其是含纳米粒子添加剂的复杂固-液体系的宏观性能.两种方法将为金属加工液功能化、个性化配方优化以及高效性能评价提供理论指导,实现从微观尺度到宏观尺度、从分子性质到产品性能的"自下而上"设计开发.