Water-based Lubricant Additives Research Articles

Tribological properties of carbon nanotube/SiO2 combinations as water-based lubricant additives for magnesium alloy

The major objective of this work was to evaluate the tribological properties of the carbon nanotube/spherical SiO2 nanoparticles combinations as lubricant additives in deionized water. The tribological experiments were carried out on a linear reciprocating ball-on-plate tribometer at magnesium alloy/steel interfaces. The results demonstrate that dispersion of CNT/SiO2 combinations in deionized water exhibited superior tribological properties as well as the load-bearing capacity and lubrication film stability than individual CNT or SiO2 nanofluids. It especially emphasizes the outstanding tribological properties of the CNT/SiO2 combinations with a mass ratio of 0.2:0.3. The friction coefficient is decreased by 30.6% and the wear volume is decreased by 52.5%, when compared to the 0.5 wt % CNT nanofluids. The enhanced performances are most likely driven by the sliding-induced tribofilm of CNT and the possible ball bearings effect of nano-SiO2. These findings could provide new insights into the understanding and application of carbon nanomaterials-based combinations as water based lubricant additive and help to develop specific lubricants for magnesium alloy forming.

Assessment of Tribological Properties of Ti3C2 as a Water-Based Lubricant Additive.

Water-based lubrication has attracted remarkable interest due to its environmental and economic advantages. However, practical applications of water-based lubrication are often limited, mainly because of low viscosity and corrosivity. The use of additives has been proposed to overcome these limitations. In this work, the tribological characteristics of titanium carbide (Ti3C2) MXenes, as additives for water-based lubrication, were systematically investigated for contact sliding between stainless steel under various normal forces and Ti3C2 concentrations. Both friction and wear were found to decrease with increasing Ti3C2 concentration up to 5 wt%, and then increased when the concentration was larger than 5 wt%. The results suggest that Ti3C2 flakes hindered direct contact, particularly at the edges of the contact interfaces. It was further shown that the agglomeration of Ti3C2 flakes may have reduced the hindering when an excessive amount of Ti3C2 (e.g., 7 wt%) was applied. The decreases in the friction coefficient and wear rate with 5 wt% of Ti3C2 concentration w approximately 20% and 48%, respectively. The outcomes of this work may be helpful in gaining a better understanding of the tribological properties of Ti3C2 as a feasible water-based lubrication additive.

Ionic Liquids as Additives in Water-Based Lubricants: From Surface Adsorption to Tribofilm Formation

Ionic liquids (ILs) are potential lubricant additives that can potentially perform simultaneously as friction modifiers and anti-wear agents. In addition, they possess good thermal stability, they are non-flammable, they have high polarity with negligible volatility, etc. These characteristics make them also ideal for polar lubricants, like water-based fluids. In this work, the friction and wear mechanisms of stainless steel 316L tested in water-based lubricants containing three different ionic liquids, i.e. Tributylmethylphosphonium dimethylphosphate, (2-hydroxyethyl) trimethylammonium dimethylphosphate and 1-butyl-1-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate, have been investigated and compared with a reference water-based lubricant containing dodecanoic acid (Lauric acid, C12) as a well-known organic friction modifier. All lubricants formulated with the three ionic liquids showed frictional values lower than the water-based lubricant alone, but higher than the lubricant formulated with C12. A detailed surface adsorption study using Quartz Crystal Microbalance with Impedance measurements (QCM-I) revealed differences in the adsorption kinetics, strength of the adsorption bonds to the metallic surface and also different viscoelastic properties of the adsorbed layers for all the different additives. In the case of one of the ionic liquids (1-butyl-1-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate), a tribofilm is formed after some sliding cycles and a significant friction to values lower than that of C12 is observed. A detailed surface and sub-surface investigation of the structure and the chemistry of the wear tracks using SEM/FIB, S(T)EM, and XPS showed that an oxide-rich tribolayer built in the wear track was the cause for the decrease in both wear rate and coefficient of friction. The other ionic liquids were not able to create a tribofilm on the surface of the steel and therefore friction and wear values were higher.

Black phosphorus quantum dots: A new-type of water-based high-efficiency lubricant additive

Black phosphorus quantum dots (BPQDs), obtained via a typical solution-based top-down method, were used as water-based lubricant additives. BPQDs exhibited remarkable friction reduction and anti-wear properties even at the ultra-low concentration of 0.005 wt%, which reduced the friction coefficient and wear volume of the base liquid by 32.3% and 56.4%, respectively. In addition, the load-supporting capacity of the base liquid increased from 120 N to over 300 N. BPQDs-based additives exhibited a relatively long lifetime at a relatively high load of 80 N. The performance of BPQDs considerably exceeded that of the BP; this may be attributed to their small and uniform particle size, good dispersion stability in water, and high reactivity at the frictional surfaces. The results of the surface wear resistance analysis demonstrated that a robust tribochemical film with a thickness of approximately 90 nm was formed on the rubbing surface lubricated with 0.005 wt% of BPQDs dispersion. Moreover, the film served as a direct evidence of the excellent tribological performance of BPQDs.

Controllable synthesis of different morphologies of CuO nanostructures for tribological evaluation as water-based lubricant additives

In this study, water soluble CuO nanostructures having nanobelt, nanorod, or spindle morphologies were synthesized using aqueous solutions of Cu(NO3)2·3H2O and NaOH by adjusting the type of surface modifier and reaction temperature. The effect of morphologies of these various CuO nanostructures as water-based lubricant additives on tribological properties was evaluated on a UMT-2 micro-friction tester, and the mechanisms underlying these properties are discussed. The three different morphologies of CuO nanostructures exhibited excellent friction-reducing and anti-wear properties. Tribological mechanisms differed in the initial stage of frictional interactions, but in the stable stage, a tribochemical reaction film and adsorbed lubricious film on the rubbing surfaces played important roles in hindering direct contact between friction pairs, leading to improved tribological properties.

Facile Preparation and Tribological Properties of Water-Based Naphthalene Dicarboxylate Ionic Liquid Lubricating Additives

Taking 1,4-naphthalene dicarboxylic acid (1,4-ND), 2,3-naphthalene dicarboxylic acid (2,3-ND) and tetrabutyl ammonium hydroxide (N4444OH), tetrabutyl phosphonium hydroxide (P4444OH) as raw materials, water-based lubricant additives tetrabutyl ammonium 1,4-naphthalene dicarboxylate (1,4-NDN4444), tetrabutyl phosphonium 1,4-naphthalene dicarboxylate (1,4-NDP4444), tetrabutyl ammonium 2,3-naphthalene dicarboxylate (2,3-NDN4444), and tetrabutyl phosphonium 2,3-naphthalene dicarboxylate (2,3-NDP4444) were prepared in aqueous solution. The additives are not only simple to prepare, but also have good solubility in water. More importantly, they can significantly improve the friction reducing and anti-wear performances of water. On account of the mechanism analysis, it is estimated that the introduction of aromatic ring and more carboxyl groups to the additives play an important role for them to form stable lubrication protective films during the friction process and then to achieve excellent lubrication performance on steel/steel, copper/steel, and aluminum/steel friction pairs. Remarkably, the performances of 2,3-NDN4444 and 2,3-NDP4444 are superior to those of 1,4-NDN4444 and 1,4-NDP4444, which is ascribed to their stronger adsorption on the metal surfaces contributed by the two adsorption targets (two –COO− groups). For 1,4-NDN4444 and 1,4-NDP4444, there is only one –COO− group that can be simultaneously adsorbed on the metal surfaces from the perspective of space configuration. It weakens the adsorption and decreases the effectiveness of the lubrication protective films resulting in the reduced friction reducing and anti-wear properties of 1,4-NDN4444 and 1,4-NDP4444. Water-based lubricant additives tetrabutyl ammonium 1,4-naphthalene dicarboxylate (1,4-NDN4444), tetrabutyl phosphonium 1,4-naphthalene dicarboxylate (1,4-NDP4444), tetrabutyl ammonium 2,3-naphthalene dicarboxylate (2,3-NDN4444) and tetrabutyl phosphonium 2,3-naphthalene dicarboxylate (2,3-NDP4444) were prepared in aqueous solution. The additives are not only simple to prepare, but also have good solubility in water. More importantly, they can significantly improve the friction reducing and anti-wear performances of water. Evolution of the friction coefficients (a) and wear volume losses (b) for different samples on steel/steel friction pairs.

Analysis and comparison of tribological performance of fatty acid-based lubricant additives with phosphorus and sulfur

Two environmentally friendly, water-based lubricant additives (phosphorus-containing ricinoleic acid (PRA) and sulfur-containing ricinoleic acid (SRA)) were prepared. The lubrication performance of the additives in a water-based lubricant was tested using a four-ball tribotester. The stainless steel surface was analyzed by using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The additives reduced the coefficient of friction (COF) value, wear scar diameter (WSD) and improved the extreme pressure (PB) value. Water-based fluids containing the PRA exhibited lower COF, WSD, and PB values than the SRA. The good tribological performances of the PRA and SRA were attributed to the synergistic action of long aliphatic chains and highly active phosphorus and sulfur elements.

A Novel Tribometer Designed to Evaluate Geological Sliding Contacts Lubricated by Drilling Muds

Abstract Great interest in improving lubricity, or reducing friction, of drilling muds used for horizontal oil well drilling is motivated by increasing the horizontal reach that can be attained by a single drilling site. However, there are a limited number of commercially available devices that can be used to evaluate novel drilling mud solutions under sliding conditions that accurately replicate those encountered in the field, and those that are available are often prohibitively expensive. Here, the design of a low-cost lubricity meter, or tribometer, is documented. The purpose-built tribometer is capable of varying rotating speeds, applied normal loads, temperature, and counter surface materials. In particular, the counter surface of the tribometer can be either a steel surface, as is often used in the industrial lubricity meters available in corporate laboratories, or a geological core specimen taken from the drill site. The novel instrument was then used to evaluate four commercially available water-based drilling fluid lubricant additives, dissolved in distilled water, for both a steel-on-steel contact and a steel-on-rock contact. The steel-on-steel contact shows that the tribometer replicates the results of tests typically conducted in drilling fluid labs, thus verifying the performance of the newly developed tribometer. Additional results show that the friction and performance of the lubricant depend significantly on the materials used: steel-on-steel contacts show much lower friction than steel-on-sandstone contact. Finally, a weak dependence on the applied load is shown for a number of lubricant additives examined.

Role of nanoparticle materials as water-based lubricant additives for ceramics

Abstract The long running-in time and high wear of water-lubricated ceramics restrict their utility in the tribological field. Aqueous lubricant additives have been added to improve the tribological performance, but the effect of additive materials on the lubrication behavior is still unclear. In this study, nanoparticles of different materials were synthesized and tested for their tribological properties. The wear surfaces were systematically analyzed. The compatibility between the ceramic surface and the nanoparticles is indicated to be one of the key factors for good lubrication behavior. SiO2 nanoparticles performed cooperatively with the ceramic surface and significantly reduced the friction and wear, while ZnO and TiO2 could not form a homogenous protective film, leading to poor tribological performance.

Simultaneous production and functionalization of hexagonal boron nitride nanosheets by solvent-free mechanical exfoliation for superlubricant water-based lubricant additives

Hexagonal boron nitride nanosheets (h-BNNSs), with a crystal lattice structure similar to graphene by over 98%, exhibit good lubrication properties as lubricant additives. However, the poor dispersibility in solvents has limited their wide practical applications as lubricant additives. In the present report, water dispersible Pebax functionalized h-BNNSs (Pebax-BNNSs) have been prepared through a one-step solvent-free mechanical exfoliation process which relies on a simple exfoliation of h-BN layers by shearing force in molten Pebax at 200 °C. In this process, Pebax molecules can synchronously react with the dangling bonds formed during the exfoliation process to achieve in situ functionalization of h-BNNSs. The reciprocating friction tests demonstrate that the as-obtained Pebax-BNNSs possess excellent antifriction and antiwear performance as water-based lubricant additive with a low concentration of 0.3 mg/mL under atmospheric condition. The friction coefficients can be <0.01, achieving superlubrication. Further systematical investigations on the wear traces, wear debris, and counter balls propose a “dispersion-compensation-filling repairment” friction mechanism. All these results demonstrate that h-BNNSs can achieve superlubrication as water-based lubricant additives via facile surface modification, making them very promising candidates as lubricant additives in practical applications.

A Simple Preparation of HDA-CuS Nanoparticles and Their Tribological Properties as a Water-Based Lubrication Additive

In this paper, water-soluble CuS nanoparticles as water-based lubricant additives were synthesized by a simple surface modification method. Bis (2-hydroxyethyl) dithiocarbamic acid (HDA) was used as a modifier to ensure water solubility of nanoparticles, also acted as a reactant to offer sulfur source in this synthesis reaction of CuS. The tribological properties and thermal conductivity of as-prepared CuS nanoparticles modified by HDA (HDA-CuS) in distilled water were studied using UMT-2 micro friction tester and thermal conductivity meter. The results show that the as-prepared HDA-CuS nanoparticles can effectively improve the tribological behaviors and coefficient of thermal conductivity of distilled water. When the additive concentration is 0.8 wt%, the friction coefficient and wear rate are reduced by 78.3% and 93.7%, respectively, and the coefficient of thermal conductivity can be increased by 3%. The three-dimensional surface profiler, scanning electron microscope, and X-ray photoelectron spectroscopy were used to analyze the worn surface. It was found that a complex lubricating film was generated on the surface of the friction pairs during the friction process.

Aqueous suspensions of cellulose nanocrystals as water-based lubricants

The tribological tests were performed on a pin on cylinder tribometer, in order to investigate the application of cellulose nanocrystals (CNC) as additives in water-based lubricants. The coefficient of friction and wear between a stainless steel shaft and chrome steel ball were measured in the presence of CNC lubricant with different concentrations. The effect of the normal force, the rotational speed and the shaft diameter on the coefficient of friction and wear were studied as well. It was found that adding 2 wt% of CNC in water improved lubrication and provided a very low friction coefficient of approximately 0.09. The wear depth and width were reduced by more than 50%. The improvement of the coefficient of friction and wear was mainly due to the high strength and alignment of CNC rods.

Synthesis of polyethylene glycol modified carbon dots as a kind of excellent water-based lubricant additives

The polyethylene glycol (PEG) modified carbon dots (CDs-PEG) were facile synthesized by one-pot pyrolysis of the mixture of gluconic acid and PEG. When the average molecular weight of PEG was 200, 600, 1000 and 4000 g/mol, the CDs-PEG were denoted as CDs-PEG200-4000, respectively. As the water-based lubricant additives, the tribological properties of CDs-PEG200 under four-ball mode and steel/steel contact were far superior to PEG200, CDs derived from gluconic acid only, and CDs-PEG600-4000, reflecting the carbon cores and surface groups of CDs-PEG200 should play a synergetic lubrication effect. Specifically, at load of 40 N, adding 0.20 wt% of CDs-PEG200 into base liquid resulted in the largest friction coefficient and wear volume reductions up to 83.5% and 90.9%. Meanwhile, the load carrying capacity of base liquid increased from 50 N to at least 200 N. Amazingly, the lubrication ability of base liquid containing 0.20 wt% of CDs-PEG200 sometimes was even comparable to some lubricant oils. The results of worn surface analyses revealed that the distinguished friction-reducing and antiwear performance of CDs-PEG200 as additives could be attributed to the formed composite lubrication film composed of CDs-PEG200 and Fe3O4 on the rubbing surfaces.

Tribological performances of SiO2/graphene combinations as water-based lubricant additives for magnesium alloy rolling

The tribological performances and rolling lubrication properties of SiO2/graphene combinations as water-based lubricant additives were evaluated using a reciprocating ball-on-plate tribometer and two-high rolling mill. The results obtained therein revealed that dispersion of the SiO2/graphene combinations in water is conducive to the reduction of the friction coefficient and wear volume and the increase in the load-bearing capacity, which were superior to the results obtained for the graphene nanofluids or SiO2 nanofluids separately. In the best case, the addition of 0.1 wt% nano-SiO2 mixed with 0.4 wt% graphene in water reduced the friction coefficient by 48.5% and the wear volume by 79% compared with the addition of 0.5 wt% graphene. Transmission electron microscopy images of the SiO2/graphene combinations additives after friction testing showed that nano-SiO2 supports the graphene layers as pillars and prevent assembly between the graphene layers. The synergistic effect of the components considerably enhanced the SiO2/graphene combination. Additionally, the preliminary application of the SiO2/graphene combination nanofluids in magnesium alloy rolling effectively decreased the rolling force and improved the surface quality of sheets.

Urea modified fluorinated carbon nanotubes: unique self-dispersed characteristic in water and high tribological performance as water-based lubricant additives

UF-CNTs retaining a long-term dispersion stability in aqueous environments exhibit excellent tribological properties.

Lubricating performances of graphene oxide and onion-like carbon as water-based lubricant additives for smooth and sand-blasted steel discs

Graphene oxide (GO) nanosheets and onion-like carbon (OLC) nanoparticles were synthesized from natural graphite powder and candle soot, respectively, and characterized by transmission electron microscopy and Raman spectroscopy. The lubricating performances of GO and OLC as lubricant additives in water were comparatively evaluated using a ball-on-disc tribometer. The effects of sand blasting of a steel disc on its morphology and tribological property were evaluated. The results show that the two nanomaterials, GO and OLC, when used as lubricant additives in water effectively reduce the friction and wear of the sliding discs, which is independent of the disc surface treatment. On applying heavy loads, it is observed that GO exhibits superior friction-reducing and anti-wear abilities compared to those of OLC—a trace amount of GO can achieve a lubricating ability equivalent to that of an abundant amount of OLC. Furthermore, it is observed that sand blasting cannot improve the wear resistance of the treated steel disc, even though the hardness of the disc increased after the treatment. The possible anti-wear and friction-reducing mechanisms of the GO and OLC as lubricant additives in water are discussed based on results for the wear surfaces obtained by scanning electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy

Carbon quantum dots: An innovative additive for water lubrication

Water soluble carbon quantum dots (CQDs) were prepared and used as lubricant additives in deionized (DI) water. The impacts of CQDs on the tribological properties of water were evaluated for both Si3N4-on-steel and Si3N4-on-Si3N4 contacts. Experimental results show that the coefficient of friction (COF) reduced in the two types of tribopairs after the addition of CQDs. Maximum reductions in COF were found to be 30% and 14% for the Si3N4-steel and Si3N4-Si3N4 contacts, respectively. In terms of wear behaviors, the CQDs notably improved tribofilm formation on the Si3N4 disk surface for the Si3N4-Si3N4 contacts, confirming that the nanoparticles increase friction while providing better protection from wear. This research will help to expand the application of CQDs as promising additives in water-based lubricants.

In situ preparation of multifunctional additives in water

Abstract An in situ preparation of multifunctional additives in water was firstly developed in this paper. The additives can be conveniently obtained by stirring anionic raw materials benzotriazole (BTAH) and cationic materials tetrabutyl ammonium hydroxide (N4444OH) or tetrabutyl phosphonium hydroxide (P4444OH) in water. The physicochemical and tribological properties of the obtained additives benzotriazole tetrabutylammonium (N4444BTA) and benzotriazole tetrabutylphosphonium (P4444BTA) were systematically studied. Compared with traditional water-based lubricant additives, they are simple to prepare, have excellent tribological properties and good solubilities in water. In addition to their excellent tribological properties, these additives also show significant corrosion resistant abilities, which make them multifunctional additives for water based lubricants.

Tribological properties of oxidized wood-derived nanocarbons with same surface chemical composition as graphene oxide for additives in water-based lubricants

The tribological properties of oxidized wood-derived nanocarbons (oWNCs), which have the same surface chemical composition as graphene oxide (GO), were investigated as additives in water-based lubricants using a sintered tungsten carbide ball and a stainless steel flat plate with a reciprocating sliding configuration. WNCs were synthesized from four kinds of Japanese wood powder by metal-catalyzed carbonization, and were strongly oxidized by a modified Hummer's method. The four oWNCs have aggregated chain-like nanostructures and maintain graphitic layers. In addition, the four oWNCs were well-dispersed in water due to their high level of oxidation. The four oWNC aqueous dispersions improved lubrication. In particular, the aqueous dispersion of the oWNC derived from Japanese cedar (J. Cedar) wood powder showed a very low friction coefficient and formed a thick tribofilm on the plate surface. The most distinctive properties of the J. Cedar oWNC, compared to the other oWNCs, were the small primary and secondary particle sizes, which were much smaller than those of the other oWNCs. The small-sized J. Cedar oWNC may possibly enter the frictional interface, preventing direct contact between the ball and plate surfaces and forming a tribofilm.

Facile pyrolysis synthesis of ionic liquid capped carbon dots and subsequent application as the water-based lubricant additives

Carbon dots (CDs) were facilely synthesized by one-pot pyrolyzing a lactic acid-ionic liquid (IL) gel with a relatively high yield of 34.9 wt%. The CDs, with a mean particle size of 4.4 nm and high thermal stability, were almost amorphous and capped by IL groups. The CDs-IL in water exhibited an obvious excitation-, concentration-, pH-dependent and high salt-tolerant photoluminescence property. Specifically, the CDs-IL emitted the strongest blue fluorescence at 454 nm under 365 nm excitation with a quantum yield of 16%. In addition, the CDs-IL, as a kind of water-based lubricant additives, greatly improved the tribological properties of base liquid. The loading capability of base liquid for steel–steel pair increased from 50 N to at least 80 N when only 0.015 wt% of CDs-IL was added. Meanwhile, the mean friction coefficient and wear volume of base liquid reduced by 57.5% and 64% at the load of 40 N, respectively. In addition, the friction-reducing and antiwear performance of CDs-IL was far superior to the CDs and IL, reflecting a synergetic lubrication effect between the IL groups and carbon cores. Based on the worn surface analyses, the CDs were prone to be squeezed out of the rubbing surfaces during the boundary shear friction process, while the CDs-IL were prone to quickly form ordered absorption layers on rubbing surfaces by electrostatic interaction between the IL groups and steel surface, which is of key importance for the formation of effective lubrication film to largely reduce friction and wear.