Search

The tribological properties of the graphitic carbon nitride (g-C 3 N 4) nanosheets are far better than morphologically similar reduced graphene oxide. Further improvement of the tribological behavior of g-C 3 N 4 nanosheet was intended by introducing lanthanum orthovanadate nanoparticles in the monoclinic phase (m-LaVO 4). The HR-SEM and TEM/HR-TEM of the binary nanocomposite (g-C 3 N 4 /m-LaVO 4) displayed dispersed m-LaVO 4 nanoparticles throughout g-C 3 N 4 nanosheets. The synthesized nano additives, nanosheets (g-C 3 N 4), nanoparticles (m-LaVO 4), and nanocomposite (g-C 3 N 4 /m-LaVO 4) could be characterized using p-XRD and FT-IR. XPS analysis of the nanocomposite helped to determine the chemical states of elements. Tribological tests were carried out on a four-ball tester using ASTM D4172 and ASTM D5183 test conditions at 0.05 % w/v optimized concentration of the additives in paraffin oil (PO), which is 4–5 times lower than the available literature reports regarding nanocomposites of g-C 3 N 4 nanosheets. The results revealed a significant decrease in friction/wear and a remarkable improvement in the load-bearing capacity of the nanocomposite as compared to g-C 3 N 4 nanosheets and m-LaVO 4 nanoparticles. The morphological examination of the worn steel surface through AFM and SEM supported the observed tribological data. EDX analysis of the tribofilm verified the elemental composition, whereas the XPS yielded the chemical states of the constituent elements. The highly advanced tribological activity of the nanocomposite has been ascribed to the synergy between noncovalently interacting nanoparticles (m-LaVO 4) and nanosheets (g-C 3 N 4). The possible lubrication mechanism has also been depicted. [Display omitted] • The g-C 3 N 4 , m-LaVO 4 , and g-C 3 N 4 /m-LaVO 4 were synthesized and characterized by XRD, FT-IR, FE-SEM, EDX, TEM, HR-TEM, XPS. • The tribological parameters for the additives were obtained from ASTM D4172 and ASTM D5183 tests. • The SEM and AFM of the worn surface lubricated with nano additives in paraffin oil corroborated the experimental data. • The in situ formed tribochemical film that indeed bears the load, was characterized by XPS studies. • The m-LaVO 4 nanoparticles and g-C 3 N 4 nanosheets are bonded in the nanocomposite by weak physical interactions. [ABSTRACT FROM AUTHOR]

Vanadium pentoxide (V 2 O 5) nanosheets were prepared and tested as an additive to improve the wear/friction-reducing and load-carrying properties of the base lube, paraffin oil. For further advancement of these properties, in situ intercalation of polyaniline (PANI) was achieved hydrothermally using the starting materials as V 2 O 5 powder and aniline. During the process, V 2 O 5 powder was exfoliated into nanosheets, and aniline was oxidatively polymerized under acidic conditions producing polyaniline, which intercalated between the nanosheets to yield the composite PANI-V 2 O 5.nH 2 O (PVO). Separately synthesized PANI, exfoliated V 2 O 5 nanosheets, and the in situ synthesized composite were characterized by p-XRD, HR-SEM, TEM, FTIR, and XPS. Intercalated PANI prevented restacking of nanosheets and reduced their agglomerating tendencies. A significant increase of interplanar spacing corresponding to the (001) plane of V 2 O 5 in the nanocomposite confirms considerable interaction between the nanosheets and PANI. Although there is no chemical interaction, the non-covalent interactions like hydrogen bonding between the organic and the inorganic components through NH(PANI)...... O-V(V 2 O 5) and van der Waals forces hold the structure firmly. Tribological tests performed on a four-ball tester following ASTM D4172 and ASTM D5183 standards in paraffin oil revealed significant enhancement in friction/wear-reducing and load-carrying properties of the composite compared to V 2 O 5 nanosheets and PANI. The advanced activity of the nanocomposite validates synergy between PANI and V 2 O 5 nanosheets. The morphological studies of the worn surface by SEM and AFM studies endorsed the observed results. The EDX and XPS studies of the tribofilm confirmed the elemental composition and chemical states of all the elements, respectively. A possible mechanism of lubrication has been presented. [Display omitted] [ABSTRACT FROM AUTHOR]

As the 2D materials were found to produce excellent performance in tribology, we have demonstrated here the use of manganese-based ultrathin metal-organic framework nanosheets [Mn-MOF (U)] as the antiwear and antifriction agent. A facile method has been developed for the synthesis of Mn-MOF (U) by hindering the 3D growth of the MOF in the presence of a strong sigma donor ligand (triethylamine) along with the bridging ligand. The atomic-level thickness (9 nm) of the Mn-MOF (U) was established by microscopic studies as well as by the Tyndall effect. The tribological parameters such as mean wear scar diameter (MWD), the average coefficient of friction (COF), and load-carrying ability of the ultrathin Mn-MOF (U) were compared with the bulk material, Mn-MOF (B). Due to atomic level thickness and 2D morphology, the performance of Mn-MOF (U) was found to be much better than the bulk material. Atomic force microscopic and scanning electron microscopic studies of the wear track indicated the exalted smoothening of the surface in the case of Mn-MOF (U), corroborating the tribological results. The upgraded activity of Mn-MOF (U) has been plausibly explained by the easy sliding of the 2D sheets compared to the bulk materials. [ABSTRACT FROM AUTHOR]

• Tribological testing of pyranopyrazoles (PPz) with fused ring system studied by four-ball tester. • Best activity of PPz at a very low concentration (0.25%w/v) while that of ZDDP (standard) at 1%w/v. • Quantum chemical calculations based on Density Functional Theory(DFT) supported very well the observed tribological data. • The order of adsorption energies and radial distribution functions(from MD simulations) validated the experimental results. • A Boron-Nitrogen synergy was confirmed by XPS of the tribofilm. The tribological properties of fused heterocyclic ring systems have been scarcely studied. Generally, increased heteroatoms in such molecules should make them better additives. Accordingly, antiwear behavior of substituted pyranopyrazoles (PPz-R, where R=H, methyl and methoxy), compounds with fused heterocyclic rings, have been investigated in the present research. These compounds were characterized by FTIR and NMR (1H and13C) spectroscopy. Their tribological activity followed the order PPz-OMe > PPz-Me > PPz-H > ZDDP (standard). Atomic force microscopy (AFM) and scanning electron micrographs (SEM) of wear scar lubricated with pyranopyrazoles exhibited surface smoothness according to tribological results. The energy-dispersive X-ray (EDX) spectroscopy analysis revealed the heteroatoms nitrogen and oxygen of additive on the surface. XPS analysis showed that interaction of the best additive, PPz-OMe with a borate ester (Van lube 289), increased the efficiency synergistically. Results of DFT calculations on the interaction between adsorbent and substituted pyranopyrazoles are in agreement with the experimental data. The order of adsorption energies found using molecular dynamics (MD) simulations, correlated very well with the additive activity order. Furthermore, MD studies gave the conformation of the additive molecules on the adsorbing surface, paving the way to an understanding of the mechanism of adsorption and triboactivity. [ABSTRACT FROM AUTHOR]