Search results

Nanoparticles as the grease additives play an important role in anti-wear and friction-reducing property during the mechanical operation. To improve the lubrication action of grease, the tribological behavior of lithium-based greases with single (nanometer Al₂O₃ or nanometer ZnO) and composite additives (Al₂O₃–ZnO nanoparticles) were investigated in this paper.

The morphology and microstructure of nanoparticles were characterized by means of transmission electron microscope and X-ray diffraction. Tribological properties of different nanoparticles as additives in lithium-based greases were evaluated using a universal friction and wear testing machine. In addition, the friction coefficient (COF) and wear scar diameter were analyzed. The surface morphology and element overlay of the worn steel surface were analyzed by scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS), respectively.

The results show that the greases with nanometer Al₂O₃ or nanometer ZnO and the composite nanoparticles additives both exhibit lower COFs and wear scar diameters than those of base grease. And the grease with Al₂O₃–ZnO composite nanoparticles possesses much lower COF and shows much better wear resistance than greases with single additives. When the additives contents are 0.4 Wt.% Al₂O₃ and 0.6 Wt.% ZnO, the composite nanoparticles-based grease exhibits the lowest mean COF (0.04) and wear scar diameter (0.65 mm), which is about 160% and 28% lower than those of base grease, respectively.

The main innovative thought of this work lies in dealing with the grease using single or composite nanoparticles. And through a serial contrast experiments, the anti-wear and friction-reducing property with different nanoparticles additives in lithium grease are evaluated.

The purpose of this paper is to study the influences of test conditions to the tribological behavior of LaF₃ nanoparticles as an additive to a polyalphaolefin (PAO).

An Optimol‐SRV4 oscillating friction and wear tester (SRV) were used to investigate the tribological properties of LaF₃ nanoparticles as an additive in a polyalphaolefin (PAO). The 3‐D morphologies and wear loss volume of the worn scar were measured using a surface profilometer. The chemical state and the intensity of La and F elements on worn surface after friction test was investigated with X‐ray photoelectron spectroscopy to interpret the possible mechanisms of friction‐reduction and anti‐wear with LaF₃ nanoparticles.

The experimental results show that LaF₃ nanoparticles added to PAO exhibit excellent load‐carrying capacity, anti‐wear and friction‐reduction properties. LaF₃ nanoparticles deposited on the worn surface under lower test temperature during the friction test, and higher applied load, higher test frequency and longer test duration are propitious to the deposition of LaF₃ nanoparticles accumulated on the rubbing surface. Under higher temperature, a complicated tribo‐chemical reaction occurred during the friction process, the tribo‐chemical reaction product of La₂O₃ deposit on worn surface, which also exhibits good lubricating performance.

This paper investigates the tribological properties of LaF₃ nanoparticles as green oil additive in poly‐alpha‐olefin (PAO) under variable temperature, applied load, sliding speed and sliding duration. The results could be very helpful for the further applications of LaF₃ nanoparticles additives in industry.

The purpose of this paper is to investigate the tribological properties of liquid paraffin with SiO₂ nanoparticles additive made by a sol‐gel method.

The tribological properties of the SiO₂ nanoparticles as an additive in liquid paraffin are measured using a ball‐on‐ring wear tester to determine the optimal additive concentration. The mechanism that wear and friction are reduced is studied using scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), and atomic force microscope (AFM).

Experimental results indicate that the sizes of the synthesized SiO₂ nanoparticles are distributed uniformly and that the optimal concentrations of SiO₂ nanoparticles in liquid paraffin is associated with better tribological properties than pure paraffin oil, and an anti‐wear (AW) ability that depends on the particle size.

It is shown in the paper that by reducing friction and AW, the lubricant prepared by the methods described can prolong operating hours of machinery.

The purpose of this paper is to study the dispersion and tribological properties of liquid paraffin with aluminum nanoparticles as additive, which are prepared by the surface‐modification method using oleic acid (OA).

The dispersion stability of aluminum nanoparticles in liquid paraffin is measured by spectrophotometry, which can be optimization by Taguchi method. The tribological properties are evaluated by using a ball‐on‐ring wear tester.

The results show that few concentrations of aluminum nanoparticles as additives in liquid paraffin have better antiwear and antifriction properties than the pure paraffin oil. Scanning electron microscopy and energy dispersive spectrometer analyses can show that the thin films on the rubbing surfaces can be formed by these aluminum nanoparticles, which not only bear the load but also separate the both interfaces, thus the wear and friction can be reduced.

Machine components and mechanism pairs rely on high‐quality lubricants to withstand high temperature and extreme pressure. Extreme pressure and antiwear additives are typically adopted to improve the tribological performance of a fluid lubricant in reducing friction and surface damage under severe conditions.

The purpose of this paper is to improve the properties of metal nanoparticles which are easy to agglomerate and hard to disperse evenly, thus limiting the application of metal nanoparticles in grease. A novel technology was proposed for modifying metal oxide to improve the dispersibility of nanoparticles.

SA-TiO2 nanoparticles were synthesized using an in-situ esterification method followed by surface modification with stearic acid. The microstructure of the nanoparticles was characterized by scanning electron microscope, transmission electron microscope and Fourier transform infrared spectroscopy and their thermal stability was evaluated by thermogravimetric analyzer. The tribological properties of the SA-TiO2 nanoparticles as additives in lithium grease were evaluated with a four-ball tester and TE77 reciprocating friction tester. The worn surfaces of the steel balls were investigated by EDS and XPS.

The prepared nanoparticles can be well dispersed in the lithium grease and possess much better tribological properties compared to traditional nanoparticles. The results indicated that the excellent tribological performance of SA-TiO2 was attributed to the chemical reaction film composing of Fe2O3, iron oxide and other organic compounds.

This paper provides a method to prevent the agglomeration of nano-TiO2 by surface modification with stearic acid. And the prepared nanoparticles can effectively improve the tribology performance of lithium grease.

The purpose of this work is to investigate the effect of temperature on the extreme-pressure (EP) properties of CuO and TiO₂ nanoparticle-filled polymeric lubricants for metal-forming processes.

This paper studies the effect of nanoparticle additives of CuO and TiO₂ on the load-carrying capacity of a metal-forming polymer lubricant used for deep-drawing at varying temperatures. EP measurements are performed with a four-ball tribotester according to the ITeE-PIB Polish method for testing lubricants under scuffing conditions. Tests are run at 25, 40, 60 and 75°C to further decrease the lubricant film thickness and determine the effect on the load-carrying capacity and the tribological mechanisms of nanoparticles. The tribological mechanisms of nanoparticles is studied using energy dispersive spectrometry (EDS).

Results indicate that nanoparticle additives increase the load-carrying capacity of the polymeric lubricant at all concentrations up to 60°C attributed to a mending effect and a reduction in the area of contact of moving surfaces; at 75°C, the improvement is lowered due to nanoparticle re-agglomeration. The best results are found with TiO₂ nanoparticles due to their smaller size compared to CuO.

Nanoparticles of CuO and TiO₂ are potential EP additives for metal-forming lubricants, providing protection to working components and extending tool life.

These results show the effectiveness and the tribological mechanisms of nanoparticle additives under EP conditions and increasing temperatures found in metal-forming processes.

The purpose of this paper is to discuss the dispersion capacity and tribological behavior of liquid paraffin added by diamond nanoparticles.

The structure of the modified diamond nanoparticles which are prepared by oleic acid (OA) is observed by scanning electron microscopy (SEM) and infrared spectroscopy (IR). The dispersivity of these nanoparticles in liquid paraffin is measured by nanoparticle analyzer. The tribological behavior of adding diamond nanoparticles in liquid paraffin is evaluated by using a ball‐on‐ring wear tester.

The measurement results reveal the dispersion capability of OA modified diamond nanoparticles and indicate the dispersing stability in liquid paraffin of the OA which is bonded to the surface of diamond nanoparticles through esterification. It is found from wear testing results that the diamond nanoparticle as additive in liquid paraffin at proper concentration shows better tribological properties for anti‐wear (AW) and antifriction than the pure paraffin oil and different AW ability depending on the particle size.

It is shown in the paper that by reducing friction and AW, the lubricant prepared by the methods described can prolong operating hours of machinery.

The purpose of this study is to investigate the tribological performance (anti-friction and anti-wear properties) of commercial Mobil grade lubricants used in a journal bearing system in a power plant.

Three grades of Mobil lubricants (DTE 24, DTE 25 and DTE 26) are considered during the study. Titanium dioxide nanoparticles (TiO₂, 0.5 Wt.%) of size 40 nm are used as a lubricant additive to examine the performance of the lubricants. The viscosity of the lubricant is computed using modified Krieger–Dougherty viscosity model. The morphology of TiO₂ nanoparticles is studied with the help of scanning electron microscopy, ultra violet spectrophotometer and X-ray diffraction. The study of antifriction and antiwear properties for lubricants is carried out on four-ball tribo-tester for operating conditions specified by ASTM standards.

The tribochemical reaction film is formed between ball surfaces during the experiments on four-ball tester that minimizes the asperity contact due to addition of TiO₂ nanoparticles in the lubricant. The viscosity of the lubricant is enhanced due to the addition of TiO₂ nanoparticles. The frictional coefficient and wear scar diameters of balls in the lubricants are reduced in the range of 6-26 and 2-7 per cent, respectively.

The tribological properties of TiO₂ as a lubricant additive in three commercial Mobil grade lubricants are investigated in this paper. The results obtained in this paper are expected to be helpful to bearing designers, researchers and academicians concerned with the relevant study.

Nanoparticles are not well dispersed in non‐polar organic solvents due to their hydrophilic property which limits their applications in lubricant oils. To improve the oil‐solubility of nanoparticles, a novel technology was used to prepare a kind of lubricant containing calcium borate nanoparticles.

The microstructures of the prepared nanoparticles were characterized by transmission electron microscope (TEM) and infrared spectra (IR). Tribological properties of calcium borate nanoparticles used as additive in base oil were evaluated using four‐ball tribotester and SRV tribotester, and the worn surface of the steel ball was investigated by Polarized microscope (PM) and X‐ray photoelectron spectroscopy (XPS). In addition, the dispersing stability and antioxidation property of lubricant containing nanoparticles were also studied.

The results indicate that the average size of the prepared nanoparticles is in the range of 50‐100 nm, and the surface of the nanoparticles was altered from hydrophilicity to hydrophobicity. At the same time, the nanoparticles can be well dispersed in the base oil totally under novel process which has no significantly negative effect on the antioxidation property. The results of tribological tests show that calcium borate nanoparticles under the novel process (CBNN) show better antiwear property and friction‐reducing property in base oil compared to calcium borate nanoparticles under tradition process (CBNT). Based on the results of PM and XPS, it can be deduced that a continuous resistance film containing depositions and the tribochemical reaction products such as B₂O₃, FeB, Fe₂O₃ and CaO formed during the sliding process.

The main innovative thought of this work lies in dealing with the oil‐solubility problem through the combination effect of surface modification and special blend process of lubricating oil, and this method was first used to prepare lubricant containing calcium borate nanoparticles. It should be helpful for the borate nanoparticles used as additives in engine oil, gear oil and other industrial lubricants.

Wear on internal combustion engines is a loss of material that occurs with the rubbing of the materials in contact with each other and significantly reduces the economic life of the engine. Even the smallest precaution that can be taken to prevent friction and wear in the engines can provide economical savings in very large quantities. Internal combustion engines are widely utilized in modem automobiles. Around 10 per cent of the total fuel energy is dissipated to heat due to mechanical friction, among which 20 per cent is caused by the contact between the cylinder liner and the piston rings.

In this study, real piston ring-cylinder specimens were tested with reciprocating tribometer by using five different nanoparticles added to engine oil to investigate their wear and friction behavior.

With regard to the experiments, it has been found that the best results were determined by TiO₂ and single-walled carbon nanotubes according to boron nitride, multi-walled carbon nanotubes and graphene nanoparticles added to the engine oil, respectively. At the end of the tests, different wear mechanisms have been determined after the surface analyses on the piston ring and cylinder liner surface, and abrasive wear has been observed as the main wear mechanism.

This paper has an originality with regard to adding different nanoparticles into the commercial engine oil.