Boron–Nitrogen Codoped Carbon Nanosheets as Oil-Based Lubricant Additives for Antioxidation, Antiwear, and Friction Reduction

Abstract

Leveraging the advantages of shape retention and atomic reconstruction during the carbonizing of crystalline precursors, we demonstrated an efficient strategy to manufacture boron–nitrogen codoped carbon nanosheets (B,N@PCNS) by virtue of pyrolysis combining metal–organic framework (MOF) precursors and B-dopants. Through the regulation of the ratio between reactants, we implemented an ultrahigh-surface heteroatomic doping rate of N at 10.44 atom % and B at 5.60 atom % with homogeneous distribution, which significantly enhanced the compatibility between carbon nanosheets and the lubricant oil PAO10, resulting in outstanding dispersion stability. Expectedly, the hybrid oil with 2.0 wt % B,N@PCNS displayed fascinating tribological performances in multiple aspects: it lowered the mean coefficient of friction to 0.088, promoted the load-carrying ability from 100 to 400 N, and diminished the wear loss by 91.3%. What is most laudable was the dramatic antioxidation property brought about by B doping; the unique radical scavenging effect of B atoms can restrain the decomposition of oil molecules, consequently prolonging the oxidative induction time from 15.7 min of PAO10 to exceeding 90 min with B,N@PCNS and promoting the onset oxidative temperature by 31.4 °C. With the aid of Raman mapping and XPS sputtering analysis, we verified that a complex tribochemical reaction occurred between B,N@PCNS and the steel substrate and induced the formation of a robust protective tribofilm composed of iron oxides, boron oxides, iron borides, and an amorphous carbonaceous compound. Among these, the rigid boron oxides and iron borides pervaded the whole tribofilm and strengthened it as a reinforcing phase, accounting for the tremendous boost in load-carrying and antiwear performances. This work not only puts forward a novel path in the synthesis of multidoped carbon nanosheets with tailored properties but also broadens the cognition of the tribochemical reaction via intuitive characterization.

Silica-Coated N-Doped Porous Carbon Nanospheres as Antiwear and Friction-Reduction Lubricant Additives

“…The antiwear performance of the as-obtained additives in base oil was mainly evaluated by the wear volume of friction pairs (Figure ). In Figure a–e, the worn area of the disk lubricated by SiO 2 @N-MCNs is smaller and shallower than that of other samples, ,, and the cross-sectional profile of the worn surface (Figure f) also confirms this phenomenon more visually (as shown in Figure S16, it is consistent with the situation of steel ball grinding). As shown in Figure g, the wear volume of the lower disk lubricated by 500SN is 17.6 × 10 4 μm 3 .…”

Fabrication of Zwitterionic Polymer-Functionalized Onion-like Carbon Nanoparticles as Aqueous Lubricant Additives

“…The successful grafting of PEIS is demonstrated by the appearance of signals of N and S elements, and the elemental content of typical samples is shown in Table S1. Concretely, the signal peaks of C 1s (Figure d) can be fitted to three components of C–C/CC at 284.8 eV, C–O/N at 286.5 eV, and CO/N at 289.0 eV, , while the N 1s fine spectrum shown in Figure e is divided into two peaks with the binding energies of 399.7 and 401.8 eV, related to C–N/N–H and C–N + bonds of PEIS, respectively. , Besides, the signal peaks appearing at 164.0 and 168.1 eV in the S 2p spectrum (Figure f) are recognizable as the C–S and SO 3 – structures …”

Sulfur-Containing Carbon Nanospheres as Lubricant Additives for Antiwear and Friction Reduction

“…Nanoparticles are thought to be thermally stable at elevated temperatures compared to other organic additives, which makes them advantageous lubricant additives. – In addition, the high surface–volume ratio allows them to fully react with the environment, including atmosphere, base oil, and friction pair surfaces, thereby improving the tribological properties of oils in different forms. The nanoparticles mainly exhibit four behaviors in antiwear and friction reduction when they are used as friction modifiers: the rolling effect of nanobearing, the tribo-film effect formed by friction physical and chemical reaction, the mending effect due to minimum size, and the polishing effect. , …”