Zirconia and 10%, 20%, and 30% cerium-doped zirconia nanoparticles (ZCO), ZCO-1, ZCO-2, and ZCO-3, respectively, were prepared using auto-combustion method. Binary nanohybrids, ZrO
@rGO and ZCO-2@rGO ...(rGO = reduced graphene oxide), and ternary nanohybrids, ZrO
@rGO@MoS
and ZCO-2@rGO@MoS
have been prepared with an anticipation of a fruitful synergic effect of rGO, MoS
, and cerium-doped zirconia on the tribo-activity. Tribo-activity of these additives in paraffin oil (PO) has been assessed by a four-ball lubricant tester at the optimized concentration, 0.125% w/v. The tribo-performance follows the order: ZCO-2@rGO@MoS
> ZrO
@rGO@MoS
> ZCO-2@rGO > ZrO
@rGO > MoS
> ZrO
> rGO > PO. The nanoparticles acting as spacers control restacking of the nanosheets provided structural augmentation while nanosheets, in turn, prevent agglomeration of the nanoparticles. Doped nanoparticles upgraded the activity by forming defects. Thus, the results acknowledge the synergic effect of cerium-doped zirconia and lamellar nanosheets of rGO and MoS
. There is noncovalent interaction among all the individuals. Analysis of the morphological features of wear-track carried out by scanning electron microscopy (SEM) and atomic force microscopy (AFM) in PO and its formulations with various additives is consistent with the above sequence. The energy dispersive X-ray (EDX) spectrum of ZCO-2@rGO@MoS
indicates the existence of zirconium, cerium, molybdenum, and sulfur on the wear-track, confirming, thereby, the active role played by these elements during tribofilm formation. The X-ray photoelectron spectroscopy (XPS) studies of worn surface reveal that the tribofilm is made up of rGO, zirconia, ceria, and MoS
along with Fe
O
, MoO
, and SO
as the outcome of the tribo-chemical reaction.
Vanadium pentoxide (V2O5) 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 V2O5 powder and aniline. During the process, V2O5 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-V2O5.nH2O (PVO). Separately synthesized PANI, exfoliated V2O5 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 V2O5 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(V2O5) 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 V2O5 nanosheets and PANI. The advanced activity of the nanocomposite validates synergy between PANI and V2O5 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.
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The tribological properties of the graphitic carbon nitride (g-C3N4) nanosheets are far better than morphologically similar reduced graphene oxide. Further improvement of the tribological behavior of ...g-C3N4 nanosheet was intended by introducing lanthanum orthovanadate nanoparticles in the monoclinic phase (m-LaVO4). The HR-SEM and TEM/HR-TEM of the binary nanocomposite (g-C3N4/m-LaVO4) displayed dispersed m-LaVO4 nanoparticles throughout g-C3N4 nanosheets. The synthesized nano additives, nanosheets (g-C3N4), nanoparticles (m-LaVO4), and nanocomposite (g-C3N4/m-LaVO4) 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-C3N4 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-C3N4 nanosheets and m-LaVO4 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-LaVO4) and nanosheets (g-C3N4). The possible lubrication mechanism has also been depicted.
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•The g-C3N4, m-LaVO4, and g-C3N4/m-LaVO4 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-LaVO4 nanoparticles and g-C3N4 nanosheets are bonded in the nanocomposite by weak physical interactions.
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•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.
The tribological activity of the synthesized nanosheets of a polymeric graphitic carbon nitride, g-C3N4, was upgraded by introducing hydrothermally synthesized N-doped zinc oxide nanorods. The ...high-resolution scanning electron microscopy, TEM, and HR-TEM studies of the hybrid (N–ZnO/g-C3N4) reveal that N-doped ZnO nanorods were spread over g-C3N4 nanosheets. The tribological activity of well-characterized nanomaterials was graded in paraffin oil (PO) at an optimized concentration, 0.20% w/v, on a four-ball tester conducting ASTM D4172 and ASTM D5183 tests. According to the observed tribological data, mean wear scar diameter, friction coefficient (COF), and seizure load, nanorods performed much better than the nanosheets. The hybrid exhibited highly advanced activity because of the synergy between noncovalently interacting nanorods and nanosheets. The SEM and AFM analyses of the wear pathway corroborated the tribological results. The energy-dispersive X-ray and X-ray photoelectron spectroscopy studies of the tribofilm confirmed the elemental composition and chemical states of all the elements, respectively. A possible mechanism of lubrication has been presented.
Synthesis of carbon spheres and their composite Ag@C was accomplished by the hydrothermal method. The composite Ag@C was stabilized by the ionic liquid, 1-decyl 3-methyl imidazolium boron ...tetrafluoride (DMIM BF4) to yield (IL-Ag@C). The Fourier Transform Infrared(FT-IR) spectra approved the formation of composites. The powder XRD patterns of the composites matched with JCPDS files. Examination of morphological characteristics of Ag@C by scanning electron microscopy/high-resolution scanning electron microscopy(SEM/HR-SEM), transmission electron microscopy/high-resolution transmission electron microscopy(TEM/HR-TEM) revealed spherical nanoparticles of about 30–40 nm size embedded on carbon spheres of 1.2–1.6 μm. Upon addition of ionic liquid, the composite appears to be wrapped in it. Energy-dispersive X-ray(EDX) analysis associated with SEM exhibited the presence of additional elements of ionic liquid, fluorine and nitrogen, besides silver and carbon in IL-Ag@C confirming its formation. The binding energy data obtained from X-ray photoelectron spectroscopy (XPS) corroborated the formation of IL-Ag@C. Triboactivity of the carbon nanospheres and the composites were assessed in base lube PEG-200 at 0.5% w/v concentration on a four-ball tester under ASTM D4172 and ASTM D5183 conditions. Based on tribological data namely coefficient of friction(COF), mean wear scar diameter(MWD), load-carrying capacity and loss of frictional power, the relative order of activity of different additives could be established as:IL−Ag@C>Ag@C>IL>Cspheres>PEG−200
The above order was authenticated by morphological studies of the wear scar by SEM and AFM(Atomic Force Microscopy) techniques. The EDX analysis of the wear scar surface lubricated with IL-Ag@C showed iron also in addition to the constituent elements of the composite. Thus, active participation of the adsorbed additive towards tribofilm formation is validated. The XPS studies of the same surface, further confirm the presence of boron nitride, boron carbide along with iron oxide. These boron compounds have, indeed, enriched the tribofilm for improved triboactivity.
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•Synthesis of carbon spheres, Ag@C and IL-Ag@C composite by hydrothermal method•Characterization of the synthesized additives by FT-IR, TGA, XRD, FE-SEM, TEM, Raman and XPS•Evaluation of triboactivity of the synthesized additives at the optimized concentration 0.5% w/v•Morphological studies of the worn surface by SEM/EDX and AFM•Characterization of tribofilm by XPS
Magnetic zero valent iron – silica nanocomposite (Fe/SiO2) was synthesized using sol – gel technique followed by in-situ hydrogen reduction. The prepared nanocomposite was characterized by ...Nitrogen-Brunner–Emmett–Teller (N2-BET) isotherm studies, X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Vibrating Sample Magnetometer (VSM) techniques. The Fe/SiO2 nanocomposite demonstrated great adsorption potential against different explosives viz. 2,4-Dinitrotoluene (DNT) and 2,4,6-Trinitrotoluene (TNT) with maximum adsorption capacity of 12.32 and 13.56 mg/g, respectively. Both Langmuir and Freundlich isotherm model fitted well with the experimental data indicating a heterogenous adsorption of these explosives by the nanocomposite. The magnetic Fe/SiO2 nanocomposite could be easily separated after adsorption process with the help of a magnet. A plausible reduction pathway of both the explosives using nanocomposite has also been discussed.
Nanoporous zinc borate (ZB) and 10% lanthanum-doped porous zinc borate (LZB) were synthesized to explore the role of porosity and doping in zinc borate during lubrication. HR-SEM, TEM, and HR-TEM ...authenticated nanoporous structures. The tribological properties of their blends with paraffin oil (PO) were compared by employing ASTM D4172 and ASTM D5183 norms on a four-ball tester. Vanadium selenide nanosheets (VSe
2
) were used to reinforce the structure of LZB for further advancement of the tribological properties. The superiority of the LZB/VSe
2
over LZB and VSe
2
nanosheets could be adjudged by tribological data. The porosity and lanthanum doping have yielded commendable tribological activity. The VSe
2
nanosheets have strengthened the LZB matrix. The other constituent oxides of tribofilm from the LZB matrix, based on EDX analysis and XPS studies of the worn surface, ZnO, B
2
O
3
, La
2
O
3
, and V
2
O
5
, have abetted lubrication. The AFM and SEM investigations of wear track corroborated the tribological results.
Successful reinforcement of nanoporous lanthanum-doped zinc borate by vanadium selenide nanosheets and their utilization in Tribology has been described.
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