Vinay Jaiswal

Tribological studies of stearic acid-modified CaCu2.9Zn0.1Ti4O12 nanoparticles as effective zero SAPS antiwear lubricant additives in paraffin oil

Stearic acid modified ceramic nanoparticles SCCZTO-6 h, SCCZTO-8 h and SCCZTO-12 h of average sizes 60, 80 and 90 nm were prepared from CCZTO-6 h, CCZTO-8 h and CCZTO-12 h respectively (where CCZTO represents CaCu2.9Zn0.1Ti4O12; 6 h, 8 h and 12 h are the sintering times). The SCCZTO nanoparticles have been characterized by Fourier transform infrared spectroscopy (FT-IR) and transmission electron microscopy (TEM). Tribological behavior of these nanoparticles in liquid paraffin oil has been evaluated using a four-ball lubricant tester and compared with conventional high SAPS containing zinc dialkyldithiophosphates (ZDDP). All antiwear tests have been performed using an optimized concentration of the SCCZTO nanoparticles (1% w/v) by varying the load for a 30 min test duration and by varying the test durations at 392 N load. Various tribological parameters such as mean wear scar diameter (MWD), friction coefficient (μ), mean wear volume (MWV), running-in, steady-state and overall wear rates show that all the SCCZTO nanoparticles act as efficient antiwear additives and possess a high load carrying capacity. The best tribological behavior is shown by SCCZTO-6 h, followed by SCCZTO-8 h and then SCCZTO-12 h. The surface morphology and roughness of the wear scar have been studied by Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) respectively. AFM and SEM micrographs of the wear scar in the presence of SCCZTO-6 h and SCCZTO-8 h at 392 N applied load for a 90 min test duration show a drastic decrease in surface roughness. Energy-Dispersive X-ray (EDX) analysis of the worn surface under similar experimental conditions in the presence of SCCZTO-6 h nanoparticles exhibits the presence of calcium, copper, zinc, titanium and oxygen on the worn steel surface indicating tribosinterization and/or adsorption of the additive on the rubbing surface resulting in the formation of a strong tribofilm. X-ray Photoelectron Spectroscopy (XPS) of the tribofilm shows the presence of CaO, CuO, Cu2O, TiO2, Fe2O3 and adsorbed carbon in the form of –C–C– and –C(O)O– moieties.

Synthesis, Characterization, and Tribological Evaluation of TiO2-Reinforced Boron and Nitrogen co-Doped Reduced Graphene Oxide Based Hybrid Nanomaterials as Efficient Antiwear Lubricant Additives

The microwave-synthesized reduced graphene oxide (MRG), boron-doped reduced graphene oxide (B-MRG), nitrogen-doped reduced graphene oxide (N-MRG), boron-nitrogen-co-doped reduced graphene oxide (B-N-MRG), and TiO2-reinforced B-N-MRG (TiO2-B-N-MRG) nanomaterials have been synthesized and characterized by various state-of-the-art techniques, like Raman spectroscopy, powder X-ray diffraction, scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy. Furthermore, the tribological properties of prepared nanomaterials as antiwear additives in neutral paraffin oil have been evaluated using a four-ball machine at an optimized additive concentration (0.15% w/v). The tribological parameters, like mean wear scar diameter, coefficient of friction, and wear rates, revealed that these nanomaterials have potential to be developed as environmentally friendly sulfated-ash-, phosphorus-, and sulfur-free antiwear lubricant additives. The friction- and wear-reducing behavior of MRG increased upon successive doping of nitrogen, boron, and both nitrogen and boron. Among these additives, B-N-co-doped MRG shows superior tribological behavior in paraffin base oil. Besides this, the load-carrying properties of B-N-co-doped MRG have significantly improved after its reinforcement with TiO2 nanoparticles. A comparative study of the surface morphology of a lubricated track in the presence of various additives has been assessed by SEM and contact-mode atomic force microscopy. The X-ray photoelectron spectroscopy studies have proved that the excellent lubrication properties of TiO2-B-N-MRG are due to the in situ formation of a tribofilm composed of boron nitride, adsorbed graphene layers, and tribosintered TiO2 nanoparticles during the tribocontact. Being sulfur-, halogen-, and phosphorus-free, these graphene-based nanomaterials act as green antiwear additives, protecting interacting surfaces significantly from wear and tear.

Phosphorous free antiwear formulations: Zinc thiosemicarbazones–borate ester mixtures

Antiwear properties of zinc(II) complexes of salicylaldehyde N(4)-phenyl-p-substituted thiosemicarbazones and their synergic action with Vanlube 289 additive were evaluated in paraffin oil on four ball tester using steel balls of 12.7 mm diameter and the results were compared with those of zinc dibutyl dithiophosphate. On the basis of mean wear scar diameter, mean wear volume, friction coefficient, running-in and steady-state wear rate under optimum conditions, the following order of efficiency emerged: Zinc(II) thiosemicarbazones + Vanlube 289 > Vanlube 289 > ZDDP > Zinc(II) thiosemicarbazones. Among the zinc(II) complexes alone or their synergic formulations, salicylaldehyde N(4)-p-methoxyphenylthiosemicarbazones [Zn(HSTC-p-OMePh)2] exhibits best antiwear properties followed by salicylaldehyde N(4)-p-chlorophenylthiosemicarbazone [Zn(HSTC-p-ClPh)2], salicylaldehyde N(4)-p-methylphenylthiosemicarbazone [Zn(HSTC-p-MePh)2] and salicylaldehyde N(4)-p-phenyl thiosemicarbazones [Zn(HSTC-Ph)2] derivatives. The topography of the wear scar studied by atomic force microscopy and scanning electron microscopy in absence and presence of the additives indicated reduced roughness of the surface in presence of the additives. The admixtures containing zinc(II) complexes and their synergic formulations with Vanlube 289 showed presence of sulfur, nitrogen, oxygen and zinc in the energy-dispersive X-ray analysis of the wear scar.

Quantum chemical calculation studies for interactions of antiwear lubricant additives with metal surfaces

Theoretical calculations based on density functional theory (DFT) have been performed to correlate experimentally observed antiwear properties of Schiff base lubricant additives derived from condensation of salicylaldehyde with N-phenylthiosemicarbazide, [(E)-1-(2-hydroxybenzylidene)-4-phenylthiosemicarbazide; H2STC-Ph], N-p-tolylthiosemicarbazide [(E)-1-(2-hydroxybenzylidene)-4-p-tolylthiosemicarbazide; H2STC-p-MePh] and N-(4-chlorophenyl)thiosemicarbazide, [(E)-1-(2-hydroxybenzylidene)-4-(4-chlorophenyl)thiosemicarbazide; H2STC-p-ClPh] with their chemical structure. antiwear properties have been discussed on the basis of the interactions between the additive molecules and the metal surface. In order to compare the antiwear behavior of different additives, various parameters such as frontier molecular orbital energy EHOMO (Energy of Highest Occupied Molecular Orbital), ELUMO (Energy of Lowest Unoccupied Molecular Orbital), the energy gap (ΔE), mutual orbitals’ interactions between additive molecules and metal surface (ΔE1 & ΔE2), global properties (hardness and softness) and the dipole moment have been calculated and correlated with the respective energies of the metal surface. The quantum chemical calculations (QCC) have shown that the wear-reducing behavior of Schiff bases increases with an increase in EHOMO, decrease in ELUMO, decrease in the energy gap between ELUMO and EHOMO and increase in the dipole moment of the additives. The results obtained by quantum chemical calculations are in good agreement with the experimental results.

Zero SAPs and Ash Free Antiwear Additives: Schiff Bases of Salicylaldehyde with 1,2-Phenylenediamine, 1,4-Phenylenediamine, and 4,4′-Diaminodiphenylenemethane and Their Synergistic Interactions with Borate Ester

Schiff bases of salicylaldehyde with 1,2-phenylenediamine (H2Saloph), 1,4-phenylenediamine (H2Salpph), and 4,4′-diaminodiphenylmethane (H2Saldphm) have been synthesized for their application as ecofriendly, zero sulfated ash, phosphorous, and sulfur (SAPs) and ash-free antiwear additives. Testing of the compounds was carried out in paraffin oil on a four-ball testing machine using steel balls and zinc dibutyl dithiophosphate (ZDDP) as a reference additive. Their synergistic behavior with borate ester was also studied. Testing of the compounds (1% w/v) was performed at various loads for 30-min test duration and for different times at 392 N load. On the basis of various tribological parameters, the following order is given for the activity of the compounds: When the mixtures of Schiff bases and borate ester were tested, they showed a high amount of synergy. Schiff bases follow the above order in their mixtures, too. The efficiencies of the synergistic formulations were far better than that of the standard ZDDP. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) were used to study the topography of the wear scar. In the presence of synthesized additives, a tribofilm was formed on the rubbing surface, reducing its roughness. Energy-dispersive X-ray (EDX) analysis showed chemisorption of the additive resulting in the formation of a tribofilm that bore the load. The surface roughness was diminished appreciably when borate ester was added to the additives, which may be due to the formation of a wear-resistant tribofilm.

Lanthanum dithiocarbamates as potential extreme pressure lubrication additives

BackgroundThe extreme pressure lubrication (EPL) properties of bipyridyl adducts of different lanthanum dithiocarbamates of the type LaL3·bipy (where LH = dimethyl dithiocarbamate (Me2DTCH), piperidine dithiocarbamate (PipDTCH), morpholine dithiocarbamate (MorphDTCH), and diphenyl dithiocarbamate (Ph2DTCH); bipy = 2,2′-bipyridyl) have been evaluated with a four-ball lubricant tester using steel balls of 12.7-mm diameter and molybdenum disulfide as a reference additive. Various tribological parameters, viz. mean wear scar diameter, friction coefficient, mean specific pressure, initial seizure load, 2.5-s seizure delay load, weld load, flash temperature parameter, mean Hertz load, pressure wear index, etc., have been determined. The surface topography of wear scar has been studied by atomic force microscopy and scanning electron microscopy. Energy-dispersive X-ray analysis has been performed to give the composition of the wear scar surface.ResultsExperimental results indicate that admixtures containing bipyridyl adducts of lanthanum dithiocarbamates in paraffin oil exhibit better EPL properties than paraffin oil alone or with a reference additive (MoS2).ConclusionsIn view of very high efficiency, the synthesized compounds can be recommended for their application as EPL additives.

Evaluation of antiwear activity of substituted benzoylhydrazones and their copper(II) complexes in paraffin oil as efficient low SAPS additives and their interactions with the metal surface using density functional theory

Sulfur, phosphorus and halogen-free benzoylhydrazones of the formula (HL) [where HL = acetophenonebenzoylhydrazone, H-Abh; and salicylaldehydebenzoylhydrazone, H-Sbh] and their copper(II) complexes (CuL2) have been synthesized and characterized by FT-IR, NMR spectroscopy and Mass spectrometry. The antiwear performance of these compounds as antiwear additives in paraffin oil has been evaluated using a four-ball tester at an optimized concentration of additives (1% w/v) by varying the load for 30 min test duration and by varying the test durations at 392 N load. Various tribological parameters such as mean wear scar diameter (MWD), mean wear volume (MWV) and wear rates show that ligands and the conventional zinc dibutyldithiophosphate (ZDDP) effectively enhance the antiwear properties of the base lube and possess high load bearing ability. The ligand H-Sbh shows much better antiwear efficiency than H-Abh. Upon complexation the efficiency has increased tremendously in the both cases following the same order as the ligands thereof. The surface topography of the wear track has been studied by Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) at various test conditions. The AFM and SEM micrographs of wear scar lubricated with copper complexes at different conditions show a drastic decrease in surface roughness in comparison to ZDDP/ligands/paraffin oil alone. The enhanced antiwear behavior of copper complexes is attributed to the in situ formation of a tribofilm under sliding contact which eventually leads to energy saving and prevents material loss. Tribochemistry of the worn surface has been investigated using X-ray photoelectron spectroscopy (XPS) which shows that the protective tribofilm/s is composed of CuO, Cu2O, nitrogen in the form of –NC/–N–C–, adsorbed carbon in the form of –C–C−/−C–H, –C–O– moieties and Fe2O3 and/or Fe3O4. Theoretical calculations based on density functional theory (DFT) for the interactions of different additives with the metal surface strongly match with the observed experimental results. Copper strip corrosion tests show non-corrosive behavior of the additives. These additives also show non-corrosive behavior towards AISI 52100 steel in paraffin oil.

Tribological studies of some SAPS-free Schiff bases derived from 4-aminoantipyrine and aromatic aldehydes and their synergistic interaction with borate ester

Tribological performance of sulfur, phosphorous and metal-free Schiff bases of 4-aminoantipyrine with benzaldehyde (AAPB), salicylaldehyde (AAPS), p-chlorobenzaldehyde (AAPC) and p-methoxybenzaldehyde (AAPM) and their synergistic formulations with borate ester (BE) in paraffin oil has been evaluated using a four-ball tester at optimized concentrations of Schiff bases (1% w/v) and their synergistic formulations with BE (0.5% w/v for each) by varying loads for 30 min duration and varying test durations at 392 N load. Synergistic formulations effectively enhance antiwear properties of oil and possess high load carrying capacity in comparison to the conventional zinc dibutyldithiophosphate (ZDDP)/BE/Schiff bases alone. The best efficiency is shown by AAPM, followed by AAPC, AAPS and then AAPB. The same order is observed in their corresponding synergistic formulations. AFM and SEM micrographs of the wear scar lubricated with synergistic formulations show a drastic decrease in surface roughness in comparison to borate ester/ZDDP alone. EDX analysis of the worn surface in the presence of AAPM + BE exhibits nitrogen, boron and oxygen indicating adsorption of the additive on the surface. XPS of the tribofilm shows B2O3, BN, Fe2O3, Fe3O4 and adsorbed carbon in the form of –C–C– and –C(O)O– moieties. Quantum chemical calculations (DFT) for interactions of Schiff bases with surfaces show good agreement with experimental results.

Tribological investigations on β-lactam cephalosporin antibiotics as efficient ashless antiwear additives with low SAPS and their theoretical studies

The antiwear behavior of β-lactam cephalosporin antibiotics such as cefixime, cefadroxil and cephalexin has been studied using the Four Ball lubricant tester in paraffin oil. The results have been compared with high sulphated ash, phosphorous and sulfur (SAPS) containing conventional zinc dibutyldithiophosphate (ZDDP). The tests have been performed using the optimized concentration of the additives (1% w/v) at various loads from 294, 392, 490, 588, 686 to 784 N for 30 min test duration and for various test durations from 15, 30, 45, 60, 75 and 90 min at 392 N load. Various tribological parameters such as mean wear scar diameter (MWD), friction coefficient (μ), mean wear volume (MWV), running-in, steady-state and overall wear rates show that all the studied antibiotics act as efficient antiwear additives. Among all the investigated antibiotics, cefixime shows excellent antiwear properties along with very high load bearing capacity. The surface topography of the worn surface has been studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Moreover, the AFM and SEM micrographs of the wear scar in the presence of cefixime at 392 N applied load for 90 min test duration show a drastic decrease in surface roughness. Energy-dispersive X-ray (EDX) analysis of the worn surface under similar experimental conditions in the presence of the cefixime exhibits the presence of sulfur, nitrogen and oxygen on the steel surface, indicating adsorption of the additive on the rubbing surface, resulting in the formation of a strong tribofilm. Further, X-ray photoelectron spectroscopy (XPS) of tribofilm shows the presence of FeSO4 and Fe2O3/Fe3O4 and adsorbed nitrogen in the form of NC– and/or an amide moiety. Quantum chemical calculations using density functional theory have been performed to investigate the structure-antiwear activity relationship of these antibiotics. The theoretical calculations explain very well the observed experimental results.

Studies on Lanthanum Complexes of 1-Aryl-2,5-Dithiohydrazodicarbonamides in Paraffin Oil as Extreme Pressure Lubrication Additives

Testing of lanthanum complexes of 1-aryl-2,5-dithiohydrazodicarbonamides of the formula LaL3 [LH=1-phenyl-2,5-dithiohydrazodicarbonamide(PhTHC), 1-methylphenyl-2,5-dithiohydrazodicarbon-amide(p-MePhTHC), 1-methoxyphenyl-2,5-dithiohydrazodicarbonamide(p-MeOPhTHC), 1-phenyl-2,5-dithiohydrazodicarbonamide(p-ClPhTHC)] for their application as extreme pressure lubrication (EPL) additives was performed on four ball tester using steel balls of 12.7 mm diameter and MoS2 as reference additive. The efficiency of the complexes has been evaluated using the tribological parameters, wear scar diameter, friction coefficient, initial seizure load, 2.5 s seizure delay load, weld load, mean Hertz load, flash temperature parameter and pressure wear index. The tested complexes behave as good extreme pressure additives; however, the best performance is shown by the p-methoxyphenyl derivative. The surface morphology of the wear scar on steel ball has been studied by atomic force microscopy and scanning electron microscopy. In presence of this complex, roughness of the worn surface is significantly reduced. The composition of wear scar has been analyzed by energy dispersive X-ray spectroscopy. The presence of lanthanum and sulfur in energy dispersive X-ray spectrum emphasizes role of additive in the tribofilm formed on the surface.