Tribological properties of crown‐type phosphate ionic liquids as lubricating additives in rapeseed oils

The friction and wear properties of rapeseed oils with different concentrations and crown‐type phosphate ionic liquids were studied by an Optimol SRV oscillating friction and wear tester. Crown‐type phosphate ionic liquids have better solubility than conventional ionic liquids in rapeseed oils. The tribological test results showed that the crown‐type phosphate ionic liquids as lubricating additives in rapeseed oil exhibited better tribological performance than the base oil for steel/steel friction pair under various loads. It is noted that the friction pair showed the least friction coefficient and wear volume when the concentration of ionic liquids was 1 wt.%. The better tribological properties of friction pair should be attributed to the effective boundary films formed in the worn surface, on various tribochemical products, organometallic products and iron oxides. Copyright © 2012 John Wiley & Sons, Ltd.     

Tribologic behaviour and suspension stability of iron and copper nanoparticles in rapeseed and mineral oils

Abstract

Metal particles, suspended as wear debris or as additives, have a major influence on lubrication technology. They are known mostly for negative roles, but even iron nanoparticles, which are likely to pass through most filters, have not yet been quantitatively evaluated for their effects on friction and wear. In this study iron and copper nanoparticle suspensions were formulated in high sulphur paraffinic mineral oils and food grade rapeseed oil. The suspension stabilisation mechanism based on steric repulsion appeared more effective than ionic repulsion principle. Iron nanoparticle suspensions were investigated using four ball antiwear tribotester. Iron nanoparticles did not show statistically significant effects on wear or friction in mineral oil suspension. However, addition of surfactants improved the tribological performance. Wear, friction and sample temperature data along with microscopy evaluation suggested that formation of protective films in the friction zone was the most likely reason for reduction of wear, average friction and the duration of break-in regime.     

纳米ZnS粒子作为润滑油添加剂摩擦学性能研究

采用均匀沉淀法制备了硬脂酸修饰的纳米ZnS粒子,用四球摩擦磨损试验机考察了其作为润滑油添加剂的摩擦学性能,并用扫描电子显微镜和X射线光电子能谱仪对磨斑进行了表面分析.结果表明:在一定添加量范围内,硬脂酸修饰的纳米ZnS粒子可明显改善基础油的摩擦学性能;在摩擦过程中,纳米ZnS粒子在摩擦表面的沉积和通过摩擦化学反应生成的化学反应膜,显著提高了基础油的抗磨减摩性能.     

烷基咪唑-螯合硼酸离子液体摩擦学性能

以1,3-二癸基咪唑为阳离子,双水杨酸螯合硼酸为阴离子开发一类新型的环境友好螯合硼酸酯-烷基咪唑离子液体n-DICB/i-DICB,采用四球试验机考察2种添加剂在三羟甲基丙烷三油酸酯(PETO)基础中的摩擦学性能,采用SEM、EDX和XANES分析磨损表面的形态和摩擦中形成的摩擦膜的化学成分。结果表明：n-DICB/i-DICB具有优异的综合摩擦学性能,可显著提高可生物降解基础油的减摩、抗磨和极压性能;i-DICB的减摩性能和极压性能优于n-DICB,质量分数2.5%的i-DICB可使PETO的摩擦因数和磨斑直径分别降低33.0%和22.1%,最大无卡咬负荷提高66.6%。摩擦过程中,n-DICB/i-DICB形成了由B₂O₃、Na₂B₄O₇、NaBO₃和BN等混合物组成的致密摩擦膜,这是离子液体具有优异的摩擦性能根本原因。     

Tribological Performance and Mechanism of Phosphate Ionic Liquids as Additives in Three Base Oils for Steel-on-aluminum Contact

Butylammonium dibutylphosphate and tetrabutylammonium dibutylphosphate ionic liquids (ILs) were evaluated as antiwear additives for steel-on-aluminum contact in three different base oils, a polyalphaolefin, an ester oil and an IL 1-methy-3-hexylimidazolium hexafluorophosphate, respectively, with similar viscosity and different polarities. The friction experiments were carried out on an Optimal SRV-IV oscillating reciprocating friction and wear tester at room temperature. Results indicate phosphate ILs can effectively improve the tribological properties of the base oil, especially the antiwear property, as additives for steel/aluminum contacts. For the base oils PAO10 and PAO40 with different viscosities, the higher viscosity of PAO40 can be beneficial to reducing the friction coefficient. The worn surface morphologies and chemical compositions of wear scars were analyzed by a JSM-5600LV scanning electron microscope and PHI-5702 multifunctional X-ray photoelectron spectrometer (XPS). The XPS analysis results illustrate that the phosphate IL additives in the base oils with different polarities exhibit the same tribological mechanism. A synergy exists between the adsorbed layers and boundary-lubricating films generated from the tribochemical reaction of IL and the substrate surface, which may reduce the friction coefficient and wear volume of the friction pairs.     

催化剂对蛇纹石粉体减摩抗磨性能的影响

采用UMT 3摩擦磨损试验机,在高接触压力下考察蛇纹石粉体及其与催化剂组合作为润滑油添加剂对45#钢的减摩抗磨作用.结果表明:在高接触压力下,润滑油中添加蛇纹石粉体后摩擦因数和磨损量都变大;相对于蛇纹石粉体,以蛇纹石和某种催化剂组合作为润滑油添加剂,可有效地降低摩擦因数和磨损量,并提高摩擦因数的稳定性.     

油酸修饰PbS纳米粒子的摩擦学性能剖析

合成了基础油中分散性良好的油酸（OA）修饰PbS纳米粒子，并用四球摩擦磨损试验机考察了其作为润滑油添加剂的摩擦学行为，结果表明，OA修饰PbS纳米粒子在较低的添加浓度下就具有良好的减摩和抗磨效果，未修饰PbS纳米粒子作为润滑油添加剂时有一定的减磨作用，而修饰剂油酸则具有一定的抗磨性能。     

Enhancement of Lubrication Properties of Nano-oil by Controlling the Amount of Fullerene Nanoparticle Additives

In this article, the tribological properties of fullerene nanoparticles-added mineral oil were investigated as a function of volume concentration of fullerene nanoparticle additives (e.g., 0.01, 0.05, 0.1, and 0.5 vol.%). The lubrication tests were performed at the disk-on-disk type tester under the various normal forces and fullerene volume concentrations. Tribological properties were evaluated by measuring the friction surface temperature and friction coefficient, and then interpreted in terms of Stribeck curves. At the same time the friction surfaces tested were evaluated by observing their SEM images, surface roughness, and AFM images. The results showed that the nano-oil containing the higher volume concentration of fullerene nanoparticles resulted in the lower friction coefficient and less wear in the fixed plate, indicating that the increase of fullerene nanoparticle additives improved the lubrication properties of regular mineral oil.     

油溶性CuO纳米颗粒的抗磨性能研究

利用四球摩擦磨损实验机考察了油酸铜修饰CuO纳米颗粒作为润滑油添加剂的抗磨性能,并用扫描电子显微镜（SEM）和X-射线光电子能谱（XPS）等对钢球磨损表面进行了分析。摩擦磨损试验结果表明,当添加质量分数仅为0.025%时,油酸铜修饰CuO纳米颗粒作为润滑油添加剂即能够明显提高基础油的抗磨能力。SEM及XPS分析结果表明,油酸铜修饰CuO纳米颗粒作为润滑油添加剂在摩擦过程中形成了一层富含Cu2O和Fe2O3的化学反应膜,正是这层膜的存在使得其表现出良好的抗磨性能。     

离子液体对WS2纳米润滑油摩擦学性能的影响

纳米二硫化钨的润滑性能优异,但由于其在润滑油中易团聚沉降,影响了其在润滑油中抗磨减摩性能的发挥。为改善纳米WS2的抗磨减摩性能,将一种磷酸盐离子液体添加到WS2纳米润滑油中,通过四球摩擦试验机对其摩擦学性能进行测试,采用XPS、EDS和电子显微镜等表征方法对钢球磨损表面进行表征。结果表明：虽然添加离子液体后纳米润滑油的摩擦因数略微上升,但相对基础油,离子液体仍可使其摩擦因数最大降低28%,同时能显著地减小磨斑直径,最大降幅达到了44%。离子液体在摩擦过程中与WS2反应生成PW,该物质作为催化剂加速了摩擦过程中的氧化反应,生成的化合物作为化学摩擦膜减少磨损,提升润滑油抗磨减摩性能。     

Correlation Studies of WS 2 Fullerene-Like Nanoparticles Enhanced Tribofilms: A Scanning Electron Microscopy Analysis

The beneficiary effects of tungsten disulphide (WS₂) inorganic fullerene-like nanoparticles (IFLNPs) in the lubrication industry were shown in recent years. However, their successful incorporation into lubricants (oils, greases) is not straightforward. In practice, the lubricant contains several components for different purposes, e.g. reducing the oxidization of the oil (antioxidant), minimizing the wear rate (anti-wear additive), dispersants, etc. These additives can contain chemically active compounds, which under the lubrication process (where locally extreme conditions can develop: high pressure and flash temperatures) can change the chemistry in the contact zone and block the beneficial effects of the inorganic nanoparticles. In this investigation, poly-alpha-olefin (PAO) is being used as base oil in which the WS₂ nanoparticles and different additives are mixed. A ball-on-disc sliding test revealed that certain additives inhibit the nanoparticles to reduce friction (less than 5 % decrease in friction coefficient), while in other cases, the friction reduction was above 50 %. The comparison is being made between PAO + additive and PAO + additive + IFLNPs. Scanning electron microscope and energy dispersive X-ray spectroscopy were used to investigate the elemental composition of the tribofilms formed on the wear marks. Further analysis was made in order to reveal correlations between elemental compositions of the tribofilms and external parameters such as the friction coefficient and wear rate. For instance, a strong correlation between tungsten content of the tribofilm and the friction coefficient was found.     

苦参碱-6、左旋肉碱-柠檬酸离子液体的制备及润滑特性研究

制备苦参碱-6和左旋肉碱-柠檬酸2种离子液体,分析其结构和热稳定性。研究Si_3N_4球与316不锈钢、Al、Cu、Ti 4种金属基体对摩时,2种离子液体作为润滑剂的润滑性能,并与美孚一号润滑油的润滑性能进行比较。结果表明:2种离子液体在不同基体上具有不同的润滑效果,其中左旋肉碱-柠檬酸具有较低的摩擦因数和较高的热稳定性,其润滑下基体表面磨痕较均匀光整且磨损体积小;左旋肉碱-柠檬酸润滑效果较美孚一号润滑油更好,这是因为其在摩擦过程中形成了有效的物理吸附保护膜和摩擦化学反应膜,并生成了更加复杂的含铁化合物润滑涂层,二者共同作用提高了润滑效果。     

胆甾醇润滑添加剂的摩擦噪声与胶合分析

在N15机械油中添加胆甾醇,用标准的立式万能摩擦磨损试验台实验分析了N15机械油、N15油机械 胆甾醇的摩擦磨损性能。针对磨合阶段、稳定磨损阶段、胶合失效与摩擦噪声进行分析。结果表明,在磨合阶段摩擦因数有较大变化,随后的稳定磨损阶段中摩擦因数变化减小;在摩擦副出现胶合失效前,摩擦副的摩擦因数急剧上升;N15机械油 1.7%胆甾醇的抗胶合性能较好,但N15机械油 0.106%胆甾醇的摩擦噪声特性较好;胆甾醇添加剂可以显著改善N15号机械油的抗胶合能力。     

薄膜油润滑中电粘度效应影响研究

利用组合滑块油润滑试验考察了双电层的电粘度效应对薄膜润滑性能的影响，采用施加外加电场和添加添加剂两种方法以改变润滑剂中离子浓度进行试验研究。结果表明：双电层引起的电粘度效应对摩擦因数有明显影响，摩擦因数随着外加电场的增强而变大，当外电场增大到一定程度时摩擦因数开始减小；在离子浓度较小时，摩擦因数随着离子浓度的增加而增大，当离子浓度增大到一定程度时摩擦因数开始减小。     

Improvement in the tribological properties of imidazolium‐derived ionic liquids by additive technology

Molecular design of wear‐preventing and friction‐reducing additives for ionic liquids is described. The tribological properties of carboxylic acid‐derived additives were evaluated by a ball‐on‐flat type tribotest under reciprocating motion. Tetraalkylammonium and tetraalkylphosphonium salts of N‐benzyl‐protected aspartic acid were dissolved in 1‐alkyl‐3‐methylimidazolium‐derived ionic liquids. They prevented wear remarkably and reduced friction fairly. Influences of alkyl group in imidazolium molecule on additive response were observed. In tetraalkylammonium‐derived ionic liquids, the additive reduced wear but did not reduce friction under these conditions. The salt of N‐acetyl‐protected glutamic acid prevented wear, but did not reduce friction. Copyright © 2008 John Wiley & Sons, Ltd.     

Ionic Liquid Lubrication Effects on Ceramics in a Water Environment

Ionic liquids were studied to determine their effectiveness as boundary lubricant additives for water. The chemical and tribochemical reactions that govern their behavior were probed to understand lubrication mechanisms. Under water lubricated conditions, silicon nitride ceramics are characterized by a running-in period of high friction, during which time the surface is modified causing a dramatic decrease in friction and wear. Two mechanisms have been proposed to explain the friction and wear behavior. Si₃N₄ sliding against itself may result in tribochemical reactions that form a hydrated silicon oxide layer on the surface of the sliding contact. This film has been suggested to mediate friction and wear. Others have suggested that tribo-dissolution of SiO₂ results in an ultra smooth surface and after a running-in period of high wear, the lubrication mode becomes hydrodynamic. The goal of this study was to examine the effects that ionic liquids have on the friction and wear properties of Si₃N₄, in particular their effects on the running-in period. Tribological properties were evaluated using pin-on-disk and reciprocating tribometers. The tribological conditions of the tests were selected to produce mixed/hydrodynamic lubrication. The relative lubrication mode between mixed and hydrodynamic was controlled by the initial surface roughness. Solutions containing 2 wt% ionic liquids were produced for testing purposes. Chemical analysis of the sliding surfaces was accomplished with X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). The test specimens were 1 in diameter Si₃N₄ disks sliding against 1/4 in Si₃N₄ balls. The addition of ionic liquids to water resulted in dramatically reduced running-in periods for silicon nitride from thousands to the hundreds of cycles. Proposed mechanisms include the formation of BF_x and PF_x films on the surface and creation of an electric double layer of ionic liquid.     

FAP− Anion Ionic Liquids Used in the Lubrication of a Steel–Steel Contact

This study compares the tribological behavior of two ionic liquids ([BMP][FAP] and [(NEMM)MOE][FAP]) used as oil additive for the lubrication of a steel–steel contact. Friction and wear experiments were performed using a HFRR test machine. Friction coefficient and electrical contact resistance were measured during the tests, and the wear surface was analyzed by confocal microscopy and XPS. The tribological results showed that both ionic liquids used as additive decrease friction and wear but the [BMP][FAP] had a better performance than the [(NEMM)MOE][FAP] due to its higher reactivity with the steel.     

Ionic liquids with ammonium cations as lubricants or additives

A new class of more effective lubricants could lead to huge energy savings. Limited recent literature has suggested potential for using room-temperature ionic liquids as lubricants, however, only a few out of millions (or more) of species possible have been evaluated. In this study, a series of new protic alkylammonium ionic liquids were synthesized by neutralization and metathesis reactions, and have demonstrated promising lubricating properties as neat lubricants or lubricant additives, particularly for use with difficult-to-lubricate metals like aluminum. More than a 30% friction reduction was observed with ammonium-based ionic liquids compared to conventional hydrocarbon oils in reciprocating sliding tests of 52100 bearing steel on aluminum alloy 6061-T6511. The inherent polarity of ionic liquids is believed to provide strong adsorption to contact surfaces and can form a boundary lubricating film leading to friction and wear reductions. Other advantages of ionic liquids include (1) negligible volatility, (2) high thermal stability, (3) non-flammability, and (4) better intrinsic properties that may eliminate the need for more complex and expensive additive packages. With very flexible molecular structures, this new class of lubricants, particularly ammonium-based ionic liquids, can be tailored to fit a variety of applications.     

超声振动对不同黏度润滑油摩擦学性能的影响

研究GCr15/45#钢摩擦副在4种不同黏度的润滑油润滑时,有和无超声振动下的摩擦磨损性能,采用扫描电子显微镜分析磨痕表面形貌,探讨在不同黏度润滑油作用下,超声振动对润滑油摩擦学性能的影响机制。结果表明:超声振动对不同黏度润滑油摩擦学性能的影响是不同的;超声振动可以提高低黏度润滑油润滑的减摩抗磨性能,如在6#白油润滑时施加超声振动后,摩擦副间的摩擦因数和磨损体积分别减小了13.6%和17.5%;高黏度润滑油润滑时,超声振动会加剧摩擦副的摩擦磨损,如在150BS润滑时施加超声振动后,摩擦副间的摩擦因数和磨损体积分别增加了10.4%和50%。     

Lubrication effectiveness investigation on the friendly capped MoS2 nanoparticles

The compatibility and effectiveness of nanoparticles with the existing additives in formulated oil are still unclear. In the present study, some lubricant additives were selected to modify nanoparticles to obtain friendly capped nano‐MoS₂. Various polyisobutyleneamine succinimide (PIBS) concentrations were applied to investigate the lubrication effectiveness of capped nano‐MoS₂. The results showed that the reduction in COF and wear volume of friendly capped nanoparticles without PIBS reached about 35% and 75% in comparison with those of the base oil respectively. However, the average coefficient of friction and wear volume loss of nano oil increased with PIBS concentration in the range of 0.05%–1%. By scanning electron microscope, energy‐dispersive X‐ray spectroscopy and X‐ray photoelectron spectroscopy analysis, it is identified that (i) MoS₂ tribofilm was formed on the wear track for the oil with nano‐MoS₂ and (ii) wear scar was smooth for nano‐MoS₂ with low PIBS concentration and without PIBS, while it showed plowing wear when containing high PIBS concentration. Copyright © 2016 John Wiley & Sons, Ltd.