In this paper, Al-20Si-5Fe-2Ni composites reinforced with varying contents of Mo2BC and Cu-coated Mo2BC were fabricated via vacuum hot-press sintering. The influence of Cu-coated Mo2BC content on the mechanical and tribological properties of the composites was systematically examined. Results revealed that the Cu coating on Mo2BC ceramic particles reacted with the aluminum alloy matrix during sintering, leading to the formation of Al2Cu interfacial bridges. The incorporation of Cu-coated Mo2BC significantly enhanced the overall mechanical properties of the composites, which was attributed to the synergistic effects of interfacial bridging strengthening and the pinning effect provided by the Mo2BC ceramic particles. Moreover, the tribological performance of the Al-20Si-5Fe-2Ni composites was markedly improved. When sliding against GCr15 bearing steel, the primary wear mechanisms of the unreinforced alloy included adhesive, fatigue, and abrasive wear. With the addition of up to 20 wt.% Cu-coated Mo2BC, a smooth and continuous oxide film formed on the worn surface, which exerted a lubricating effect and reduced wear. However, as the content of Cu-coated Mo2BC further increased to 30 wt.%, agglomeration of Mo2BC particles became evident. Under applied shear stresses during sliding, these agglomerated particles were prone to fracture and disperse within the wear track, ultimately resulting in an increased friction coefficient and higher wear rate.

The current-carrying frictional pair is the core channel for current transmission and energy conversion between moving components. The current-carrying frictional pair for electromagnetic launch consists of the Al armature and Cu rails. At variable working conditions with a peak velocity exceeding 103 m/s and a peak current surpassing 105 A, the current-carrying tribological damage of Cu rail pairs were investigated. Under the same discharge voltage of 3800 V, the armature final velocity of Al armature decreased from 1515.6 m/s for the first launch to 1233.4 m/s for the 20th launch. The peak current dropped from 347 kA to 241 kA, and the final contact resistance increased from 35.7 mS2 to 176.4 mS2. The damage at the initial position of the rail is dominated by melting and oxidation, a porous transfer film formed on the surface. While the damage at the terminal position is dominated by high-velocity sliding current-carrying damage such as adhesion, oxidation, and abrasive wear, which has lower roughness and less oxidation. The transition of the damage mechanism is related to the change of the Al-Cu contact state from solid-liquid-solid to solid-solid, and the contact states for damage transition is contact load = 13.1 kN, velocity= 1000 m/s, and current = 160 kA. This finding is valuable for understanding current-carrying wear and material protection under extreme conditions.

To enhance the tribological properties of CuNiAl, a textured composite surface was fabricated by filling WS2 solid lubricant (silane coupling method) into micro-dimples with varying area densities (40%, 45%, and 50%). The tribological behaviors of original (No MT), microtextured (MT), and WS2-filled microtextured (MT-WS2)—were evaluated under dry and oil-lubricated conditions. With a density of 45%, the MT-WS2 sample demonstrated the best tribological performance. Under dry conditions, its average friction coefficient (AFC) and wear rate (WR) decreased by 27.87% and 76.9%, respectively, compared to the No MT sample, and by 49.16% and 87.1%, respectively, compared to the MT sample. Under oil lubrication, the reductions in AFC and WR were 2.96% and 64.8% relative to the No MT sample, and 2.81% and 61.33% relative to the MT sample. The improvement mechanism involves WS2 forming a solid lubricating film during dry friction, while in oil, it synergizes with lubricant to create a composite film that significantly enhances wear resistance.

MoCoB ceramic shows promising potential for tribological applications, due to their exceptional oxidation resistance and mechanical strength. Therefore, to evaluate its tribological suitability in high-temperature environments, the tribological behaviors of single-phase MoCoB coupling against SiC counterpart from room temperature (RT) to 800 degrees C are systematically investigated. The results revealed that MoCoB could exhibit outstanding wear resistance across the entire temperature range. However, it showed good lubricity only at RT and 800 degrees C, where the coefficients of friction (COFs) were as low as 0.39 and 0.38, respectively. The favorable lubrication at RT was attributed to the formation of SiO2 tribo-film on the MoCoB surface, which was derived from tribo-oxidation reaction of SiC counterpart. At 200 degrees C, the SiO2 film became discontinuous and failed to provide lubrication, resulting in a high COF (0.74). As the temperature climbed up to 400 degrees C, the tribo-oxidation product, MoO3-x, could be detected as well. Nevertheless, the limited amount of MoO3-x can only provide moderate lubrication, and the COF at 400 degrees C still remains relatively high (0.62). At 600 degrees C and 800 degrees C, the primary tribo-oxidation products consisted of CoMoO4 and MoO2. However, the CoMoO4-MoO2 tribo-film could only provide lubrication at 800 degrees C. The dominant wear mechanisms at 600 degrees C were adhesion and tribo-oxidation wear.

Investigating tribological mechanisms in human locomotion aids the early detection of musculoskeletal and neurological disorders. A comparative study involving abnormal and normal gait group revealed that abnormal gait was associated with increased Fx forces at peak, reduced Fy and Fz forces at peak in contact forces, and lower required coefficient of friction (RCOF). The reduction of the vertical contact force leads to an insufficient coefficient of dynamic friction, resulting in a compensatory balance. Male patients exhibited higher asymmetry in contact forces, while female required elevated RCOF. Contact forces and RCOF analysis under varied walking conditions identified 23 distinguishing features between PD patients and 12 gender-specific features among patients. These findings may facilitate to improve balance and gait dysfunction in individuals with abnormal gait.

Adsorption is one of the effective strategies to treat organic pollution in wastewater. Herein, a novel hollow nanorod of C-Na2Ti3O7 (CNTO) were fabricated from the MAX phase Ti2AlC by a facile method. The CNTO nanorods own a unique hollow structure and abundant-OH and Ti-O groups. Particularly, the as-prepared CNTO sample possesses a large specific surface area of 238.49 m2/g, which is 100 times larger than that of bulk Ti2AlC (2.11 m2/g). In MB removal, CNTO nanorods perform an excellent property with 97 % removal efficiency in 5 min and a maximal adsorption capacity of 159.1 mg/g. This ultrafast removal ability can attribute to the large specific surface area, negative zeta potential and hollow nanorod structure of CNTO samples. Kinetic experiments implied that the adsorption process conforms to the pseudo second-order kinetic model, and the adsorption form on CNTO is consistent with the Langmuir adsorption model. The mechanism studies revealed that CNTO samples adsorbed MB mainly by electrostatic adsorption and hydrogen bond adsorption. Furthermore, CNTO samples possess high structural stabilities and excellent recycling capacities in MB adsorption. This research highlights the great prospect of MAX phase derived CNTO nanorods for treating wastewater and pollutants.

Photoelectrocatalytic (PEC) reduction of carbon dioxide (CO2) into high-value-added chemicals can not only address environmental issues but also alleviate energy problems. Nevertheless, achieving high selectivity of C2+ products remains a significant challenge due to the complexities of CO2 reduction. Herein, a Cu-coated Cu2O/ TiO2/Ti3C2 with cooperative p-n heterojunction and Schottky junction composites were designed and employed as the photocathode in a three-electrode system of Cu@Cu2O/TCO||SCE||BiVO4. The Cu@Cu2O/TCO electrodes exhibited excellent photoelectrochemical properties and stabilities, which demonstrate a high current density of 6 mA/cm2 and no apparent decrease during 6 h under light irradiation. In PEC CO2 reduction experiments, C2H5OH and CH3OH are the main products, with high formation rates of 960.5 mu Mg-1h-1 and 1276.2 mu Mg-1h-1, respectively. Surprisingly, a high selectivity of C2H5OH was gained, which is up to 60 %. The key generation intermediates of C2H5OH including *CO, *CHO, and *COOH were detected by in-situ ATR-FTIR spectroscopy. Additionally, in-situ ATR-FTIR spectroscopy revealed that the Cu/Cu2O interface facilitates the direct C--C dimerization of two adjacent *CO intermediates at the catalyst's active center, forming *COCOH intermediates. The research results indicate that it can effectively enhance the selectivity of C2H5OH through the double heterojunction synergistic effect of TiO2/Cu2O and Cu/Cu2O, and the double heterojunctions channel possesses a good advantage in PEC CO2 reduction.

The partial nitrification (PN) was a pivotal approach for supplying NO2--N to anammox and facilitate the application of the anammox technology. However, PN-related process was mainly carried out in activated sludge in intermittent-flow mode. In this study, a continuous-flow biofilm system for PN was proposed. Hydroxylamine dosing was utilized to rapidly initiate PN in the sludge system, followed by timely immobilization of functional bacteria onto carriers. Finally, by adjusting the operation mode from intermittent-flow to continuous-flow, a nitrite accumulation ratio of 89.42% was achieved. Microbial community succession demonstrated that the excellent PN performance in continuous-flow PN biofilm system was attributed to Nitrosomonas proliferation, with Nitrospira was effectively inhibited by hydroxylamine dosing. This study provided valuable insights for the design and operation of PN-based processes in future sewage treatment plants.

Carbon fiber(CF)was modified using a PEI sizing agent and a PAMAM coupling agent to enhance the interfacial bonding strength in carbon fiber/polyetheretherketone(CF/PEEK)composites.Pure polyetheretherketone(PEEK)and CF/PEEK composites were fabricated via hot-press sintering.The study investigated the interfacial characteristics,mechanical performance,and tribological behavior of the composites both pre-and post-modification.Results indicated that the surface energy of the CF filler increased by 30.9％after PEI sizing modification and by 10.58％following treatment with the PAMAM coupling agent,relative to unmodified CF.In friction and wear tests conducted at a constant speed of 200 r/min,the friction coefficient and wear rate for PAMAM-CF/PEEK and PEI-CF/PEEK decreased by 11.63％and 72.34％,and 11.51％and 75.58％,respectively,compared to unmodified CF/PEEK.Under a fixed load of 90 N,similar reductions were observed:15.1％and 52.53％,and18.78％and 63.04％,respectively.These results demonstrate improved interfacial bonding strength and tribological performance in the modified composites.Overall,CF/PEEK composites modified with PEI sizing exhibited superior interfacial bonding strength and tribological properties compared to those treated with the PAMAM coupling agent.

In this study, the interfacial bonding between carbon fibers (CFs) and polyetheretherketone (PEEK) was enhanced via three modification strategies, namely, incorporation of multiwalled carbon nanotubes (MWCNTs) as filler, CF surface sizing with a polyethylenimine (PEI)-based agent containing MWCNTs, and CF functionalization using a polyamidoamine (PAMAM) coupling agent carrying MWCNTs. These approaches aimed at improving CF-PEEK compatibility through physical entanglement and chemical bonding. The addition of MWCNTs enhanced the mechanical interlocking, while amide bonds and pi-pi interactions in CF-PEI-MWCNTs/PEEK and CF-PAMAM-MWCNTs/PEEK systems further strengthened the interface. Designed for high-wear-resistance applications such as aerospace components and sliding bearings, the CF/PEEK composites were tested against GCr15 steel under dry friction conditions. Results showed that the CF-PEI-MWCNTs/PEEK composite exhibited superior mechanical and tribological performance compared to the MWCNTs-filled CF/PEEK system. The dominant wear mechanism was mild adhesive wear.

Carbon fiber (CF)-reinforced polyether ether ketone (PEEK) composites exhibit excellent comprehensive properties. However, the inert surface and poor wettability of CF reduce the interfacial performance in CF/PEEK composites, thereby limiting their applicability in harsh environments. To address this limitation, CF was chemically grafted using two modifiers: a polyethyleneimine (PEI) sizing agent containing carboxylated multi-walled carbon nanotubes (MWCNTs), and a polyamidoamine (PAMAM) coupling agent also containing carboxylated MWCNTs. The amino groups in PEI and PAMAM can form amide bonds with carboxylated CF. Additionally, the long-chain structure of PEI physically entangles the CF, and its pi-pi conjugation with the PEEK matrix enhances interfacial bonding. As a result, CF-PEI-MWCNTs/PEEK composites (0.3 wt.% MWCNTs) demonstrated superior interfacial properties compared to CF-PAMAM-MWCNTs/PEEK composites (0.5 wt.% MWCNTs). The wear resistance of the composite is improved, and the wear mechanism changes from plastic deformation to mild adhesive wear.

Failure mechanisms of high-power electrical connectors operating under hot-swap conditions at currents spanning tens to hundreds of amperes (interfacial current densities spanning 10(1)-10(3) A/mm(2)) have remained elusive. To address this problem, reciprocating sliding tests were performed on comparative Cu pairs and Au-plated Cu pairs under electrical currents ranging from 0 A to 20 A (interfacial current density spanning 0-2.0 x 10(3) A/mm(2)). At low currents (0-10 A), the Au-plated layer reduced average COF from similar to 0.6 (Cu pairs) to similar to 0.2 (Au-plated Cu pairs), representing a 70 % reduction. And surface resistance was lowered from similar to 7 m Omega mm(2) in Cu pairs to similar to 0.6 m Omega mm(2) in Au-plated Cu pairs, a 90 % decrease. The wear rate of Au-plated Cu pairs (similar to 10(-5) mm(3) N-1 m(-1)) was an order of magnitude lower than that of Cu pairs (similar to 10(-4) mm(3) N-1 m(-1)), demonstrating excellent anti-wear performance. But at high currents (15-20 A), the COF and surface resistance of Au-plated Cu pairs became comparable to those of Cu pairs. This was primarily attributed to wear-induced degradation of the Au plating, where the Au content dropped below 5 %, diminishing its protective effect. Notably, at 20 A, arcing occurred in Cu pairs, but no arcing was observed in Au-plated Cu pairs. This indicates that the Au-plated layer effectively suppressed arc generation even at high currents. Interfacial temperatures generated by Joule and arc heating could explain the observed wear behaviors. These results offer valuable references for designing damage-tolerant high-power electrical connectors, where Au plating can be strategically used to enhance reliability under varying current conditions.

This study investigates the effects of ultrasonic surface rolling (USR) on the microstructure and fretting wear resistance of nickel aluminum bronze (NAB). Fretting tests were conducted using a ball-on-flat contact configuration under three distinct environments: oil, simulated seawater, and dry conditions. The worn surface morphology, wear volume, and chemical composition were systematically analyzed. The results demonstrate that USR treatment led to a 58% reduction in surface roughness, a 61.8% increase in surface hardness, and a significant increase in grain boundary density. Following USR treatment, the wear rate, dissipated energy, and average friction coefficient all showed notable reductions. The enhanced wear resistance of NAB under the three lubrication conditions is primarily attributed to the formation of a surface-hardened layer after USR treatment. Under oil lubrication, the oil film plays a critical role in reducing abrasive wear and spalling. In the case of simulated seawater lubrication, the combined effects of the Cu2O generated during processing and the surface-hardened layer contribute to a lower wear rate.

Corrugated damage to bearings is a common fault in electrical facilities such as new energy vehicles, wind power, and high-speed railways. The aim of this article is to reveal the microscopic characteristics and formation mechanism of such damages. The corrugation with alternating “light” and “dark” shape was produced on GCr15 bearing races in the experimental conditions. Compared to the light area, the dark area (in the images generated by optical microscope) has more severe electrical erosion, lower hardness, more concave morphology, and lower oxidation. As the voltage increases, the width of the corrugation, the height difference between corrugation, and surface roughness all increase. It is believed that the formation of corrugated damage requires a sufficiently high voltage to induce the periodic destruction and reconstruction of the lubrication film. When the bearing is in a metal-lubrication film–metal contact state, the high voltage causes the lubrication film to break down and induce electrical erosion. Then, the contact area is in metal–metal contact, and the surface is mainly damaged by mechanical rolling. After the reconstruction of lubrication film, the next round of electrical erosion begins. The results are helpful for a deeper understanding of the mechanism of bearing erosion in electrical application.

The electrical transmission between moving parts requires contact pairs such as rolling rings, sliding rings, connectors, etc. These functional contact pairs can be defined as current-carrying frictional pairs because they need to bear the transmission of current while enduring friction and wear. The rough current-carrying frictional pairs are typical contact surface withstands the load of force, heat, and electricity, resulting in the unique contact characteristics of the current-carrying pair. The research progress of current-carrying tribology has been reviewed in this paper. The correlation mechanism between tribological performance and current-carrying performance has been summarized. The composite and competitive relationship between mechanical damage and electrical damage has been discussed. Methods for evaluating the dynamic performance of current-carrying tribology has been proposed. The spatiotemporal non-uniformity of current-carrying frictional damage has been revealed. Future research trends are expected at the end.

Cu matrix composites (CMCs) are widely employed for tribological applications such as in sliding bearings and electrical contact fields. However, the Cu matrix needs to be modified to improve its mechanical and tribological properties. In this study, CMCs reinforced with Mo2BC ceramic particles (10-30 wt%) are prepared via the spark plasma sintering (SPS) route method. In comparison with the plain Cu sample, when the content of the Mo2BC particles increased to 30 wt%, the Vickers hardness, yield strength, and tensile strength of CMCs increased by 196 %, 157 %, and 588 %, respectively. Fine grain and load transfer strengthening mechanism are considered the main strengthening mechanism. Introducing the Mo2BC ceramic effectively reduces friction and wear as well as the frictional noise vibration of CMCs. Incorporating Mo2BC ceramic into the Cu matrix can elevate the loadbearing ability, inhibiting mechanical and adhesive wear. In addition, the composite exhibits superior friction and wear properties as the content of Mo2BC ceramic increases gradually up to 30 wt%, where the friction coefficient and wear rate are as low as 0.35 and 3.25 x 10-6 mm3/Nm, respectively. A layer of tribo-film containing Fe2O3 derived from the counterparts and induced by the tribo-oxidation reaction can provide a lubricating effect. Considering the superior mechanical and tribological properties, the as-prepared CMCs could be an attractive alternative material for sliding bearing fields.

This study focuses on the evolution of fluting damage in bearing outer races. Fluting damage first occurred at the loading position and then extended along outer races. This non-uniform distribution of fluting damage is related to the non-uniform load inside bearing. It is speculated that the alteration of bright and dark areas in fluting is related to the periodic destruction and reconstruction of lubricating film. The phase transition from alpha '-Fe to alpha-Fe is observed beneath erosion surface. At microscale, non-uniform damage of the fluting appears as the dark area exhibiting more severe erosion, lower oxidation, greater roughness, deeper depth, and lower hardness. The results can provide deeper understanding of the failure process and damage mechanism of bearings in electric fields.

_ The paper establishes the lumped parameter vibration mathematical model of shafting and uses the system matrix method to calculate and analyze steady-state frequency domain vibration characteristics of the shaft system in the range of diesel engine speed. Then in order to further study the transient torsional vibration of the shaft system under the resonance speed point, the state space method and finite element analysis method were used to compare and analyze the transient time domain response characteristic curve of the shaft system; finally, the test data of the real ship was compared with the theoretical calculation results, which verified the correctness of the mathematical model and the theoretical calculation method. This study has certain theoretical significance for carrying out the design of low-noise and vibration of shaft systems and improving the safety of ship navigation. Keywords shafting torsional vibration; transient time domain; finite element method; vibration test

Electrical erosion pit is a fundamental manifestation of electrical bearing damage. As the shaft voltage increased, the degree of electrical damage became more severe, and the residual compressive stress and hardness of bearing surface decreased. The transition of martensite into ferrite induced by high discharge temperature was found at the edge of the erosion pit using a transmission electron microscopy. This phenomenon has not been observed below the mechanically rolled surface under the same conditions. Electrical penetration harmed the bearing through surface erosion, lubrication deterioration and martensite decomposition. The electrical pit could be observed when current density exceeded 0.95 A/mm2. The results can help understand bearing failure in the fields of railways, wind turbines, and new-energy vehicles.