In the present study, a nickel-zinc (Ni–Zn) alloy coating has been selected as the foundational coating, and the formation of a composite Ni–Zn-titanium dioxide (Ni–Zn–TiO2) coating, along with the ...factors influencing its development, has been thoroughly examined. The influential factors explored in this research encompass applying ultrasonic waves, current density, and incorporating varying concentrations of TiO2 nanoparticles (NPs). X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), energy-dispersive X-ray (EDX) spectroscopy, and a wear test apparatus were utilized to assess the characteristics of these coatings. The findings indicate that the concentration of TiO₂ NPs in the plating bath profoundly impacts the morphology and coating properties. An increased TiO₂ concentration in the plating bath led to a finer morphology. Applying ultrasonic waves during the plating process enhanced the dispersion and finer distribution of NPs within the coating, resulting in improved wear resistance due to the confinement of irregularities. Applying ultrasonic waves up to 60 W improved the properties; however, a reduction in elemental levels was observed when the ultrasonic waves were increased to 120 W. This decrease in elemental levels can be attributed to the high-intensity ultrasonic waves, resulting in diminished wear resistance.
•Investigated Ni–Zn–TiO2 coating properties under varying conditions.•XRD patterns showed limited TiO2 NPs, impacting crystal size.•Higher TiO2 NPs concentrations enhanced wear resistance.•Ultrasonic waves improved grain boundaries and coating compaction.•40 W ultrasonic waves led to agglomerates, influenced by power levels.
Superlubricity between MoS2 Monolayers Li, He; Wang, Jinhuan; Gao, Song ...
Advanced materials (Weinheim),
July 19, 2017, Volume:
29, Issue:
27
Journal Article
Peer reviewed
The ultralow friction between atomic layers of hexagonal MoS2, an important solid lubricant and additive of lubricating oil, is thought to be responsible for its excellent lubricating performances. ...However, the quantitative frictional properties between MoS2 atomic layers have not been directly tested in experiments due to the lack of conventional tools to characterize the frictional properties between 2D atomic layers. Herein, a versatile method for studying the frictional properties between atomic‐layered materials is developed by combining the in situ scanning electron microscope technique with a Si nanowire force sensor, and the friction tests on the sliding between atomic‐layered materials down to monolayers are reported. The friction tests on the sliding between incommensurate MoS2 monolayers give a friction coefficient of ≈10−4 in the regime of superlubricity. The results provide the first direct experimental evidence for superlubricity between MoS2 atomic layers and open a new route to investigate frictional properties of broad 2D materials.
A method for friction tests between atomic layers of 2D materials is developed based on the in situ scanning electron microscopy technique. Friction tests on the sliding between MoS2 monolayers give an ultralow friction coefficient of ≈10−4, providing the first direct experimental evidence for the superlubricity between atomic layers of hexagonal MoS2.
The anisotropic friction properties of biomimetic Cf/ZrB2-SiC ceramic composites with fibers disposed along Bouligand structures are analyzed. First, the friction properties parallel to and vertical ...to the hot-pressing surfaces are analyzed for the Cf/ZrB2-SiC ceramic composites with different carbon fiber contents. The anisotropy of friction properties of the biomimetic Cf/ZrB2-SiC ceramic composites with Bouligand structures is analyzed based on the microstructures of wear surfaces. Second, the anisotropic friction properties of biomimetic Cf/ZrB2-SiC ceramic composites with Bouligand structures under high speed and wet conditions are also explored. Under various working environments, the wear mechanisms including abrasive wear, adhesive wear, oxidation wear, and fatigue wear are analyzed in detail based on the microstructures of the wear surfaces. This paper provides a good reference for analyzing the anisotropic friction properties of ceramic composites with Bouligand structures.
In this study, copper composite foams reinforced with Al2O3 decorated graphene oxide (AG) were prepared via chemical plating and electrodeposition. Subsequently, copper powders were filled into the ...pores of the composite foams and then spark plasma sintering (SPS) was employed to fabricate the 3D skeleton-reinforced composites. The tensile strength reached 365 MPa for AG/Cuf®Cu composites, which was 47.1%, 33.7%, and 13% higher compared with the pure copper, Cuf®Cu, and GO/Cuf®Cu composites, respectively. Additionally, improved friction properties with obviously decreased friction coefficient and wear rate were shown in the AG/Cuf®Cu composite. The structure study and strengthening mechanism analysis indicated that the decoration of Al2O3 on the graphene oxide resulted in enhanced interface bonding, higher load transfer efficiency for the mechanical and friction properties improvement.
•Copper composite foams reinforced with Al2O3 decorated graphene oxide (AG) were prepared.•Copper composites reinforced by AG/Cu composite foams were designed and prepared.•Enhanced mechanical and friction properties were shown in the composites.
Mesocarbon microbead-silicon carbide (MCMB-SiC) composites are promising candidates for mechanical seals of nuclear reactor main pumps due to their adaptability to severe environments. However, the ...weak bonding strength between MCMB and SiC matrix causes an unstable dry friction coefficient, which limits its further development. Herein, the interface-modified MCMB-SiC composites were prepared by hot-pressing sintering using liquid vinyl hydrido polycarbosilane (VHPCS) coated raw material powder for the first time. The pyrolytic VHPCS was loaded on the surface of MCMB particles. The effects of VHPCS content on the microstructure, mechanical properties, and dry tribological properties of MCMB-SiC composites were systematically studied. The results show that the MCMB-SiC composites with 1 wt% VHPCS (MS-P1) had good comprehensive mechanical properties. Meanwhile, compared to MCMB-SiC composites without VHPCS (MS-P0), MS-P1 exhibited improved dry friction properties, with a dry friction coefficient (μ) reduced by ∼25% (0.18) and a wear rate (WR) reduced by ∼35% (7.69 ×10−7 mm3·N−1·m−1). It was considered to be due to the nano-SiC grains generated by VHPCS after sintering improved the interface strength between MCMB and SiC matrix, which inhibited the detachment of hard SiC particles during the friction process. In addition, sufficient C-Si-O lubricating film can fill the pits, which acts as a self-healing effect. This study provides an effective route to improve the tribological properties of MCMB-SiC self-lubricating composites with high carbon content.
•A new ultrasonic vibration-assisted machining process for SiCp/Al composites is proposed.•The friction characteristics between tool-workpiece-chip during multidimensional ultrasonic vibratory ...machining are analyzed.•The coefficient of friction during three-dimensional ultrasonic vibration-assisted milling was experimentally investigated.•The effect of friction coefficient on milling force and surface roughness was investigated.
Silicon carbide particle reinforced aluminum matrix composites (SiCp/Al) have excellent mechanical and physical properties and are widely used in the defense and military industry, aerospace, and so on. However, when machining SiCp/Al, due to the large difference in cutting properties between the particles and the base material, the compression and friction on the tool may cause fluctuations in the cutting force, resulting in poor machined surface quality. Therefore, the study of friction characteristics during machining is necessary and of great significance to improve the machining quality of SiCp/Al. A three-dimensional milling processing method with the help of ultrasonic vibration is proposed in this study. The friction-reducing effect of the processing method is then demonstrated by analyzing the friction characteristics of the tool-workpiece and the friction forms of the aluminum matrix and particles when extruded on each cutter surface. Also, four different volume fractions of SiCp/Al, namely 15, 25, 45 and 60%, were machined by milling to investigate the effect of different ultrasonic amplitudes on the friction coefficient, as well as to study the effect of friction coefficient on the milling force and the machined surface. The results show that the larger the volume fraction, the larger the friction coefficient and milling force. Moreover, an increase in amplitude leads to an increase and then a decrease in the friction coefficient. The friction coefficient is reduced by up to 83% compared to conventional milling, and an increase or decrease in the friction coefficient leads to an increase or decrease in the milling force and the roughness of the machined surface.
