Water-based Lubricant Additives Research Articles

Methylcellulose-Functionalized Gallium-Based Liquid-Metal Nanoparticles as Water-based Lubricant Additives

Ga-based liquid metal nanoparticles (GLM-NPs) are a novel high-performance additive for lubricants and this work novelty prepared a novel type of heterogeneous nanoparticles modified with a cost-effective and available methylcellulose (GLM-NPs/MC). It displays a clear core-shell structure with a particle size of about 270nm, and as a water-based lubricant additive, it exhibits good tribology properties, reducing the friction coefficient and wear rate of the 304 steel discs by about 59% and 40% respectively. The high dispersion and good stability of GLM-NPs/MC make them slowly enter into the worn surface to form a Ga-rich tribo-film. In addition, the influence of GLM-NPs/MC content on the lubrication performance of the water was also studied and the optimization additive content is 0.6wt. %. This study provides insights into the design of nano-composite materials based on gallium-based liquid metal for lubrication applications.

Correlation between preparation techniques and frictional properties of cellulose nanocrystals as additives in water-based lubricants

To explore the tribological characteristics of cellulose nanocrystals derived through various preparation techniques when utilized as additives in water-based lubricants, two types of cellulose nanocrystals (S-CNC and C-CNC) were chosen. These were produced via sulfuric acid hydrolysis and oxidation methods. The morphology and structural features were assessed through techniques such as Fourier-transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), laser confocal Raman spectroscopy, elemental analysis, scanning electron microscopy (SEM), and laser particle size analysis. According to thermogravimetric analysis (TGA), the thermal stability of S-CNC is slightly superior to that of C-CNC. S-CNC exhibits liquid crystallinity when the concentration exceeds 0.5 %, whereas C-CNC does not display liquid crystallinity at any concentration tested. Further investigation was conducted on the frictional properties of the two types of CNCs using a UMT reciprocating friction tester. The results indicate that both types of CNC exhibit significant friction reduction properties at various additive concentrations, provided the addition does not exceed w=1 %. When below their respective liquid crystalline phase concentrations, the friction reduction performance of S-CNC is slightly inferior to that of C-CNC; however, when above the liquid crystalline phase concentration, the friction reduction performance of S-CNC surpasses that of C-CNC. The addition of w=0.5 % S-CNC leads to a relative reduction of 63.4 % in the friction coefficient compared to the base system. Analysis of the steel plate surface contact angle and post-wear surface suggests that the lubrication mechanism of CNC involves the adsorption of polar functional groups such as hydroxyl or carboxyl groups from the CNC structure onto the friction pair surface, forming a lubricating protective film to varying degrees. Additionally, the liquid crystalline structure of S-CNC facilitates the formation of an ordered lubricating film, further enhancing the frictional properties. These findings provide valuable insights into the application of nanocellulose crystals as lubricant additives.

Tribological and Anticorrosion Properties of N-Heterocyclic-Organophosphonic Acid Ionic Liquids as Water-Based Lubricant Additives

Four ionic liquids (ILs) were synthesized by a simple neutralization reaction using 1,8-diazabicyclo[5.4.0]undecane-7-ene as the cation and organophosphonic acids with different carbon chain lengths as the anion. The obtained ILs had an excellent water-soluble property and the tribological performance was studied by a four-ball friction tester. The results showed that the longer carbon chains, the better tribological properties of the ILs. Compared with the blank, only 0.05 wt% of ILs addition resulted in the decrease of friction coefficient and wear volume about 30% and 60%, respectively. The adsorption state of the ionic liquid on the steel surface was also investigated by molecular dynamics simulation. It is believed that the good tribological performance and corrosion inhibition was attributed to the effective physical adsorption due to the polarity of the organophosphonate, which can form an effective adsorption film and prevent the steel surface from corrosion.

In-situ surface modified water-soluble Cu nanoparticles as lubrication additives in water-based cutting fluids

Water-based lubricants are essential in the field of tribology, and the application of nanoparticles as additives in water-based lubricants shows promise and significant practical importance. In this study, water-soluble Cu nanoparticles modified with methoxypolyethyleneglycol xanthate long-chain polymers were fabricated by a in-situ surface modification method. The tribological behavior of the Cu nanoparticles synthesized as additives in a water-PEG system was evaluated using a universal micro-tribotester. It was found that the synthesized nanoparticles could be stably dispersed in the water-PEG system and could enhance the tribological properties and load-carrying capacity of the system significantly. For example, the coefficient of friction could be reduced to 0.052, and the PB value increased to 588 N when the Cu nanoparticles were added at a mass fraction of 1.5 %. This was mainly attributed to the formation of a boundary lubrication film consisting of Cu, Fe2O3, Fe2(SO4)3, and FeS throughout the entire friction process. The boundary film effectively prevents direct contact between the friction surfaces, thereby improving the tribological properties. The incorporation of Cu nanoparticles as additives into commercial cutting fluids resulted in a lower coefficient of friction and significantly enhanced the extreme pressure performance of the cutting fluids, demonstrating promising application prospects.

Extreme pressure and anti-wear properties of polycarboxylate superplasticizer modified 3D porous graphene/SiO2 as water-based lubricant additives

Lubricants can effectively solve the large amount of energy loss and environmental pollution caused by frictional wear. Graphene-based materials water-based lubricants have attracted attention due to their excellent various properties. But their application is still hindered by many obstacles. In this paper, a novel polycarboxylate superplasticizer modified 3D porous graphene/SiO2 (PG/SiO2) nanomaterial was prepared as water-based lubrication additives. The base fluid with good cooling properties was obtained by adding Kunlun full synthetic grinding/cutting fluid to deionized water and diluting it to 5% by weight. It is found that PG/SiO2 had a good synergistic effect, which could effectively improve the extreme pressure performance (PB/PD), with the maximum improvement rates of 39.7% and 86.3%, respectively. Meanwhile, significantly enhance the friction reduction (35%) and anti-wear (72.2%) properties of the base fluid. The enhancement mechanism was revealed by experimental and characterization analysis. Due to the excellent mechanical properties of graphene itself and synergistic effects including the rolling bearing effect of PG/SiO2 and the buffering effect of SiO2 in its intercalation, the PG/SiO2 nanomaterials can significantly improve the extreme pressure performance of the base fluid. Further, theoretical calculations revealed the enhancement effects of the long chains of the polycarboxylate superplasticizer on the dispersibility and surface adsorption of graphene, and the modified graphene on the diffusive movement of water molecules.

Tribological properties of Sargassum carbon dots as additives in water-based lubricants

This study evaluated the tribological characteristics of a novel eco-friendly water-based lubricant containing carbon dots (CDs) obtained from Sargassum as additives. The mean friction coefficient of a lubricant containing 5 mg/ml CD contents was 78 % lower than that of pure water. Furthermore, a correlation between wear rate, contact shape, and kinetic vertical ball displacement was also established.

A Tribological and Electrochemical Study of Protic Ionic Liquid and Bentonite Particles Used as Lubricating Additives in Water-Based Lubricants

A Tribological and Electrochemical Study of Protic Ionic Liquid and Bentonite Particles Used as Lubricating Additives in Water-Based Lubricants

Novel concept of nano-additive design: PTFE@silica Janus nanoparticles for water lubrication

Polytetrafluoroethylene (PTFE) has been widely used as a lubrication additive for reducing friction and wear; however, the hydrophobic nature of PTFE restricts its application in eco-friendly water-based lubrication systems. In this study, for the first time, we designed novel PTFE@silica Janus nanoparticles (JNs) to meet the requirement for additives in water-based lubricants, which have excellent dispersion stability in water attributed to the unique amphiphilic structure. By introducing the lubrication of the aqueous dispersion of the JNs with a concentration of 0.5 wt%, the coefficient of friction (COF) and wear volume were reduced by 63.8% and 94.2%, respectively, comparing to those with the lubrication of pure water. Meanwhile, the JNs suspension also exhibits better lubrication and wear-resistance performances comparing to commercial silica and PTFE suspensions. The excellent tribological behaviors of PTFE@silica JNs as nano-additives could be attributed to the synergetic effect of the two components, where the PTFE provided lubrication through the formed tribofilms on the friction pairs, and the rigid silica further enhanced the wear-resistance performance. Most importantly, the unique structure of JNs makes it possible to use PTFE as an additive in water-lubrication systems. Our study shed light on the design and application of novel JNs nanomaterials as additives to meet the requirements of future industrial applications.

Graphitic carbon nitride quantum dots as novel and efficient friction-reduction and anti-wear additives for water-based lubrication

Undeniably, advances in water-based nano-additives play a considerable role in energy conservation and pollution reduction accompanied by the resurgence of water-based lubricants. Graphitic carbon nitride quantum dots (g-CNQDs) have attracted remarkable attention in water-based lubricant additives owing to their strong designability, favorable mechanical property, and unique self-lubricating effect. Therefore, a series of different-sized g-CNQDs with good water dispersibility were expediently synthesized via a hydrothermal strategy and directly used as water-based lubricant additives. Tribological tests indicated that the tribological behaviors of the g-CNQDs-based additives displayed an obvious phenomenon of performance-dependent physical dimensions. With the introduction of g-CNQDs-based additives (1.0 wt%) into the water-based lubrication system, which friction-reduction, anti-wear, and load-supporting performances can be maximally increased by 45.5%, 94.0%, and 233.3%, respectively. Meanwhile, the long-term operating performance of the lubrication system can be promoted under high-load conditions. The formed tribo-film caused by tribo-chemical reaction integrated with the nano-lubrication effect of g-CNQDs collectively contributed to their good tribological performances.

Influence of the molecular structure on the tribological properties of choline-based ionic liquids as water-based additives under current-carrying lubrication

In this work, four types of choline/fatty acid ionic liquids were synthesised and used as water-based lubricant additives in an ethylene glycol system, and the tribological behaviours of the mixtures were investigated under the control of an applied electric field. Under current-carrying lubrication, the friction and wear resistances of the steel friction pair lubricated with the ionic liquid-added lubricant became more pronounced. As the number of double bonds in the fatty acid structure increases, the molecular compactness decreases, and the friction-reduction performance is affected. Mechanistic analyses indicated that the [Ch][SA] ionic liquid can strongly adsorb to the metal surface and form a tribochemical reaction film during the friction process, leading to excellent tribological properties.

Mechanochemical preparation of zwitterionic polymer functionalized covalent organic frameworks as water-based lubricant additives

In this paper, we report the successful synthesis of the zwitterionic polymer PEIS functionalized covalent organic frameworks (COFs), abbreviated as LZU1-PEIS, via two mechanochemical means, namely tribochemical reaction and ball milling, denoted as LZU1-PEIS-TC and LZU1-PEIS-BM, respectively. The LZU1-PEIS can be derived when a mechanochemical-driven Schiff base reaction occurs between the aldehyde-terminated COFs and the rich amino-terminated zwitterionic polymers. On account of their two-dimensional nanoscale structure, easiness to shear, and superior hydration capability, the as-prepared LZU1-PEIS manifested remarkable tribological properties as water lubricant additives. The average friction coefficients were reduced from 0.67 to 0.31 (LZU1-PEIS-TC) and 0.23 (LZU1-PEIS-BM), respectively. Furthermore, the formation of a physical protective film fabricated via deposition of the nano-additives and tribochemical reaction is instrumental in curtailing friction and wear. Our research focuses on the preparation of functionalized COFs as lubrication additives, and offers a credible experience and promising design contemplation toward lubricating materials.

Ultra-dispersive sulfonated graphene as water-based lubricant additives for enhancing tribological performance

The weak dispersion stability of graphene in water restricts its practical application as water-based lubricant additives. Herein, sulfonated graphene (SGO) with ultra-dispersive and superior lubrication performance was synthesized by means of sulfonating graphene oxide (GO). It was found that SGO was well dispersed in water. Besides, viscosity of water was enhanced by 25.8 % after adding 0.2 wt. % of SGO, which might be favorable to enhance film thickness between tribo-pairs. Furthermore, SGO lubrication contributed to significant reduction in friction coefficient (CoF) and wear scar diameter (WSD) by 74 % and 15.7 %, respectively. SGO exhibited the better lubricity in comparison to GO, which could be ascribed to that adsorption ability of -SO3H groups was stronger than that of -OH and -COOH groups.

Tribological behavior of graphene oxide-Fe3O4 nanocomposites for additives in water-based lubricants

Graphene oxide-Fe3O4 (GO-Fe3O4) nanocomposites were synthesized via the solvothermal method and used as lubricant additives. The tribological tests and a series of characterization techniques were conducted to understand the lubrication mechanism of GO-Fe3O4 nanocomposite. The GO-Fe3O4 nanocomposites exhibited excellent tribological properties due to high dispersion stability in water. Friction results indicated that the GO-Fe3O4 can significantly improve the tribological properties and the friction coefficient and wear scar diameter had been reduced by 33.6% and 32.3% compared with base fluid, respectively. Raman results showed that the GO nanosheets formed a protective film on the contact interfaces, which facilitated shear, reduced the wear and inhibited the tribo-corrosion. The lubrication mechanism was attributed to the synergistic lubrication effect between the Fe3O4 nanospheres and the GO nanosheets.

Ionic Liquid Additives in Water-Based Lubricants for Bearing Steel – Effect of Electrical Conductivity and pH on Surface Chemistry, Friction and Wear

Water-based lubricants have the potential to become the largest environmentally friendly lubricants in applications such as electric vehicles and the newly emerging green technologies of the future due to their inherent low viscosity and cooling properties. In order to be environmentally acceptable (EAL), both base lubricants and additives should comply with biodegradability, non-toxicity, and non-bioaccumulation requirements. Additives for water-based lubricants should ideally be polar and soluble in water and, at the same time, should not increase the electrical conductivity to critical levels for corrosion. However, most additives used in synthetic or mineral oils are non-polar. Ionic liquids have recently gained attention as lubricant additives due to their high polarity, making them highly surface-active (i.e. high tendency to adsorb on metal surfaces). However, they are seen as highly corrosive for many metal alloys. In this work, a water-glycol lubricant containing two different ionic liquids has been investigated as a potential green lubricant for a bearing steel AISI 52100 with accurate control on electrical conductivity and pH. The selected ionic liquids were tributylmethylphosphonium dimethylphosphate (PP) and 1-butyl-1-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate (BMP). The tribological behaviour of the ionic liquids was compared with a well-known organic friction modifier, dodecanoic acid (C12). The ionic liquids showed lower friction and wear rate than the water-based lubricant alone. However, they showed higher friction than the lubricant formulated with C12, in which PP gave lower friction than BMP due to low pH. A detailed subsurface analysis of the wear track using scanning-transmission electron microscopy (STEM) showed that a thick oxide tribofilm was built on the wear track for both lubricants formulated with ionic liquids due to high electrical conductivity. This tribofilm gave beneficial effect on wear. Although PP and BMP gave thicker tribofilms than C12, it was not durable, resulting in cracking and detachment.

Triboelectrochemical friction control of W- and Ag-doped DLC coatings in water-glycol with ionic liquids as lubricant additives.

In the last years, diamond like carbon (DLC) coatings doped with both carbide forming and non-carbide forming metallic elements have attracted great interest as novel self-lubricating coatings. Due to the inherent properties of DLC, the doping process can provide adsorption sites for lubricant additives depending on the chemical and electrochemical state of the surface. Ionic liquids (ILs) are potential lubricant additives with good thermal stability, non-flammability, high polarity, and negligible volatility. These characteristics make them also ideal for polar fluids, like water-based lubricants. In this work, three different DLC coatings (DLC, W- and Ag-doped DLC) were deposited on stainless steel substrates and their friction in dry and lubricated conditions in water-based lubricants was studied. Three ILs, tributylmethylphosphonium dimethylphosphate (PP), 1,3-dimethylimidazolium dimethylphosphate (IM) and 1-butyl-1-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate (BMP) were used as additives and compared with a well-known organic friction modifier (dodecanoic acid). The results showed better mechanical integrity, toughness and adhesion of the doped coatings compared to the undoped DLC. The Ag-doped DLC coating had the best mechanical properties of all the coatings. W formed tungsten carbide precipitates in the DLC coating. Two different additive-adsorption mechanisms controlled friction: a triboelectrochemical activation mechanism for Ag-DLC, and an electron-transfer mechanism for W-DLC resulting in the largest reduction in friction.

Study of Tribological Properties of Fullerenol and Nanodiamonds as Additives in Water-Based Lubricants for Amorphous Carbon (a-C) Coatings.

The tribological performances of fullerenol and nanodiamonds (NDs) as additives in water-based lubricants for amorphous carbon (a-C) coatings are investigated to avoid disadvantage factors, such as chemical reactions and deformation of particles. The effects of size and additive amount on tribological properties of nanoparticles are studied by rigid nanoparticles within the dot size range. The results show that owing to its small particle size (1–2 nm), fullerenol cannot prevent direct contact of the friction pair at low concentration conditions. Only when the quantity of fullerenol increased to support the asperity contact loads in sufficient concentration did nano-bearings perform well in anti-friction and anti-wear effects. Unlike fullerenol, nanodiamond particles with a diameter of about 5–10 nm show friction-reducing effect based on the nano-bearing effects at ultra-low concentration (0.01 wt.%), whereas particles at higher concentration block the rolling movement, hence increasing the coefficient of friction (COF) and wear. As a result of the effect of difference in size, fullerenol provides a better overall lubrication, but it is hard to reach a friction coefficient as low as NDs even under the optimal conditions.

Ionic liquids as boundary additives in water-based and PAO lubricants

Ionic liquids have been widely discussed as potential lubricants, however, their properties make them also very good potential candidates as lubricant additives (e.g., friction modifiers and anti-wear). In this work, the tribological study of two ionic liquids (tributylmethylphosphonium dimethylphosphate (PP), and 1-butyl-1-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate (BMP)) as lubricant additives has been performed on stainless steel (AISI 316L) exposed to polar (water-glycol) and non-polar (polyalphaolefin) based lubricants under boundary lubricating conditions. The performance of these ionic liquids as lubricant additives has been compared to a classical organic friction modifier (dodecanoic acid (C12)). The water-glycol lubricant formulated with the two ionic liquids showed friction values higher than the same base lubricant formulated with dodecanoic acid, however, opposite results were observed for polyalphaolefin (PAO). A detailed surface chemical analysis using X-ray photoelectron spectroscopy (XPS) revealed differences in the passive/tribofilm thickness and chemical composition of the stainless steel surface tested in all lubricants. In the case of the polar lubricant additivated with ionic liquids, the tribochemical reaction accompanied by a tribocorrosion process led to the formation of an unstable passive/tribofilm resulting in high friction and wear. However, in the absence of tribocorrosion process (polyalphaolefin base lubricant), the tribochemical reaction led to the formation of a stable passive/tribofilm resulting in low friction and wear. A detailed surface and subsurface investigation of the microstructure using scanning electron microscopy equipped with a focused ion beam (SEM-FIB) showed that high wear rates resulted in thicker recrystallization region under the wear track surface. Among all lubricant additives tested in this work, BMP in non-polar lubricant media showed the best tribological performance.

Alkyl glyceryl ethers as water-based lubricant additives in mixtures with xanthan gum

Water-based lubricants are greener and more environmentally friendly than comparable oil-based lubricants. However, water-based lubricants typically have a poorer performance and, thus, need to be formulated with various additives. Here, alkyl glyceryl ethers, a class of nonionic surfactants, were investigated as lubricant additives. To this purpose, aqueous solutions of newly synthesized ethers (with different alkyl chain lengths, C8, C10, C12, and C14) were formulated with xanthan gum. The lubrication performance of these formulations was then tested experimentally. Clearly, alkyl glyceryl ethers showed a significantly improved performance (higher friction reduction) with increasing the alkyl chain length. However, the ethers had to be formulated with xanthan gum, with which they formed a complex, which promoted ether dispersion and probably adsorption on the metal surface in the aqueous phase, thereby drastically reducing friction. Thus, the alkyl glyceryl ethers synthesized in this work are attractive green and highly efficient lubricant additives, which can improve the sustainability of industrial lubrication processes.

Water-Based Lubricants: Development, Properties, and Performances

Water-based lubricants (WBLs) have been at the forefront of recent research, due to the abundant availability of water at a low cost. However, in metallic tribo-systems, WBLs often exhibit poor performance compared to petroleum-based lubricants. Research and development indicate that nano-additives improve the lubrication performance of water. Some of these additives could be categorized as solid nanoparticles, ionic liquids, and bio-based oils. These additives improve the tribological properties and help to reduce friction, wear, and corrosion. This review explored different water-based lubricant additives and summarized their properties and performances. Viscosity, density, wettability, and solubility are discussed to determine the viability of using water-based nano-lubricants compared to petroleum-based lubricants for reducing friction and wear in machining. Water-based liquid lubricants also have environmental benefits over petroleum-based lubricants. Further research is needed to understand and optimize water-based lubrication for tribological systems completely.

Ultralow friction of copper by a green water-based lubricant containing phytic acid

Water can be used as an ecological lubricant base if the water-based lubricant additives are properly developed to enhance its tribological properties. Moreover, those additives should be friendly to both human and nature. Inositol hexakisphosphoric acid (IP6), known as phytic acid, is biodegradable and non-toxic and widely used in food industrial. We focus here on understanding the lubrication of copper by IP6 aqueous solution. A pin-on-disk tester is used to investigate the lubrication performance of using IP6 aqueous solution under boundary lubrication condition. Lower friction coefficient of 0.03 is obtained when 20 wt% IP6 solution is used. The tribofilms are characterized by using X-ray photoelectron spectroscopy. The results indicate that the surface hydrate tribofilms from adsorption of IP6 molecules on the copper surface provides excellent lubrication performance.