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Through an activation reaction sintering method, porous (Mo2/3Y1/3)2AlC ceramics were prepared by Mo, Y, Al, and graphite powders as raw materials. The phase composition, microstructure, element distribution, and pore structure characteristics were comprehensively studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), Archimedes method, and bubble point method. A detailed investigation was conducted on the influence of sintering temperature on the phase composition. Possible routes of phase transition and pore formation mechanisms during the sintering process were provided. The experimental results reveal that at 650–850 °C, transition metals react with aluminum, forming aluminum-containing intermetallics and a small amount of carbides. At 850–1250 °C, transition metals collaborate with graphite, producing transition metal carbides. Then, at 1250–1450 °C, these aluminum intermetallics interact with transition metal carbides and remaining unreacted Y, Al, and C, yielding the final product (Mo2/3Y1/3) 2AlC. Simultaneously, the pore structure alters correspondingly with the solid-phase reaction at different reaction temperatures. [ABSTRACT FROM AUTHOR]

The practical application of carbon dots (CDs) as lubricant additives was tremendously restrained by their complex and time-consuming preparation, separation, purification, and modification procedures. Here, the CD-based nanofluid was in situ prepared by pyrolyzing a deep eutectic solvent for 6 h under 180 °C and directly applied as a versatile lubricant additive of polyethylene glycol (PEG200) and polyalphaolefin (PAO4). At an optimum loading concentration of 3 wt %, the nanofluid distinctly improved the friction-reducing and antiwear properties of base oils. The tribological performance of the nanofluid as an additive was not only much better than that of DES but also far beyond that of the industrial additive of zinc dialkyldithiophosphate. The wear scar surface analyses illustrated that the ester compounds and CDs in nanofluid corporately induced the formation of thick tribofilms on the rubbing surfaces lubricated by PEG200 with nanofluid. These tribofilms composed of iron oxides, CDs, and carbon oxides protected the surface asperities of frictional interfaces from direct contacts, accounting for the distinguished tribological performance of the nanofluid. Considering the prominent tribological performance, S/P free merit, and possibility of preparation on a large scale, the CD-based nanofluid can be a promising lubricant additive in the field of mechanical lubrication. [ABSTRACT FROM AUTHOR]

C44H42N4O15P4Cd2Si, triclinic, P1̄ (no. 2), a = 13.4778(9) Å, b = 14.2036(9) Å, c = 15.2206(10) Å, α = 69.637(1)°, β = 72.355(1)°, γ = 64.861(1)°, V = 2431.1(3) Å3, Z = 2, Rgt(F) = 0.0428, wRref(F2) = 0.0987, T = 120(2) K.

The biggest bottleneck restricting the application of two-dimensional (2D) g-C3N4 material in water lubrication is the large-scale acquisition of g-C3N4 nanosheets with satisfactory water dispersibility. In this work, a gel-like g-C3N4 nanosheet hybrid with g-C3N4 nanosheet cores and organic shells was constructed from the bulk g-C3N4 by three procedures of Hummer's exfoliation, sulfonation, and acid–base neutralization. The hybrid in water exhibited nice water dispersibility and superior tribological performance. Adding 8 wt % of g-C3N4 nanosheet hybrid made the friction coefficient and wear volume of water reduce by 73.7 and 72.3%, respectively. Moreover, its load-carrying capacity under high load and durability under a long-term test were also impressive. The worn surface analyses reflected that a thick protective lubrication film (>150 nm) was distinctly formed on the surface lubricated by the hybrid aqueous dispersion. This film was actually a tribofilm composed of amorphous tribochemical reaction products (FexOy, FexSy, and Fex(SO4)y) embedded with FexOy and g-C3N4 nanocrystals, which not only remarkably reduced the friction and wear but also effectively restrained the oxidation and corrosion of the friction pair. Given the possibility of large-scale construction and the prominent tribological performance, the g-C3N4 nanosheet hybrid is a promising candidate to be developed as a particularly promising water-based additive. [ABSTRACT FROM AUTHOR]