Surface Modified TiO2 Nanoparticles-an Effective Anti-wear and Anti-friction Additive for Lubricating Grease

The surface modified TiO_2 nanoparticles were prepared by using 12-hydroxystearic acid chemically modified on the TiO_2 surface. The average size of the TiO_2 particles is about 30 nm. The optimum ratio of tetrabutyl titanate to 12-hydroxystearic acid was 1/0.5. The bonding form between 12-hydroxystearic acid and TiO_2 nucleus was investigated by FTIR, DSC, TGA and XRD techniques. The lubricating grease containing the surface modified TiO_2 nanoparticles possesses excellent anti-wear and anti-friction properties. Compared with the grease without TiO_2, the PB value can be increased by 52% as the best performance of the grease containing surface modified TiO_2 nanoparticles, while the friction coefficient can be reduced by 33% with the addition of a small amount of TiO_2 nanoparticles, and meanwhile the wear scar diameter decreases by 25%.

Study on application of CeO_2 and CaCO_3 nanoparticles in lubricating oils

The ceria （CeO2） nanoparticles and calcium carbonate （CaCO3） nanoparticles were chosen as additives of anti-wear and extreme pressure for lubricating oils, and the morphology and sizes of nanoparticles were examined using Transmission Electron Microscope （TEM）. The tribological performance of lubricating oils containing combined nanoparticles were determined by four-ball friction and wear tester, and the chemical composition of steel ball with worn surface were analyzed by X-ray Photoelectron Spectrurn（XPS）. The results showed that the lubricating oils containing combined nanoparticles had good anti-wear and friction reducing effects, and the tribological properties were optimal when WCeO2＋CaCO3=0.6%, WCeO2：WCaCO3=1：1. The extreme pressure value increased by 40.25%, the wear spot diameter reduced by 33.5%, and friction coefficient reduced by 32% compared with 40CD oil. The coordinated action of big and small particles made anti-wear and friction reducing effective. Tribological chemical reactions resulting from the friction surface formed metal calcium, metal cerium and oxides film, and they could fill up the concave surface and protect the worn surface.

In-situ formation of nitrogen doped microporous carbon nanospheres derived from polystyrene as lubricant additives for anti-wear and friction reduction

This study presents a nitrogen-doped microporous carbon nanospheres(N@MCNs)prepared by a facile polymerization–carbonization process using low-cost styrene.The N element in situ introduces polystyrene(PS)nanospheres via emulsion polymerization of styrene with cyanuric chloride as crosslinking agent,and then carbonization obtains N@MCNs.The as-prepared carbon nanospheres possess the complete spherical structure and adjustable nitrogen amount by controlling the relative proportion of tetrachloromethane and cyanuric chloride.The friction performance of N@MCNs as lubricating oil additives was surveyed utilizing the friction experiment of ball-disc structure.The results showed that N@MCNs exhibit superb reduction performance of friction and wear.When the addition of N@MCNs was 0.06 wt%,the friction coefficient of PAO-10 decreased from 0.188 to 0.105,and the wear volume reduced by 94.4%.The width and depth of wear marks of N@MCNs decreased by 49.2% and 94.5%,respectively.The carrying capacity of load was rocketed from 100 to 400 N concurrently.Through the analysis of the lubrication mechanism,the result manifested that the prepared N@MCNs enter clearance of the friction pair,transform the sliding friction into the mixed friction of sliding and rolling,and repair the contact surface through the repair effect.Furthermore,the tribochemical reaction between nanoparticles and friction pairs forms a protective film containing nitride and metal oxides,which can avert direct contact with the matrix and improve the tribological properties.This experiment showed that nitrogen-doped polystyrene-based carbon nanospheres prepared by in-situ doping are the promising materials for wear resistance and reducing friction.This preparing method can be ulteriorly expanded to multi-element co-permeable materials.Nitrogen and boron co-doped carbon nanospheres(B,N@MCNs)were prepared by mixed carbonization of N-enriched PS and boric acid,and exhibited high load carrying capacity and good tribological properties.

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.

Numeric Study on Skin Friction Reduction of Engine Oil-WS2 Nanofluid by MRT Lattice Boltzman Method

New lubricants use nanoparticles like WS2 to improve lubrication performance.The aim of the present study is to determine numerically the skin friction of nanofluid on moving surfaces in a lubricating system.The base fluid is 5W-30 engine oil and the nano-additive is WS2 nanoparticles.This numerical study is based on the multiple-relaxation-time Lattice Boltzmann method(MRT-LBM).The two-dimensional nine-velocity(D2Q9)model is adopted to simulate the nanofluid flow confined by two moving surfaces.The parameters considered are the nanoparticle concentration􀟮and the flow Reynolds number Re.The results obtained show a reduction of skin friction factor when we increase the nanoparticle concentration.

Lubrication of dry sliding metallic contacts by chemically prepared functionalized graphitic nanoparticles

Understanding the mechanism of precision sliding contacts with thin, adherent solid nano lubricating particle films is important to improve friction and wear behavior and ensure mechanical devices have long service lifetimes. Herein, a facile and multistep approach for the preparation of graphene oxide (GO) is presented. Subsequently, surface modification of as-synthesized GO with octadecyl amine (ODA) is performed to prepare hydrophobic GO-ODA and with 6-amino-4-hydroxy-2-naphthalenesulfonic acid (ANS) to prepare amphoteric GO-ANS through a nucleophilic addition reaction. X-ray diffraction and ultraviolet-visible, Fourier transform infrared, and Raman spectroscopy provide significant information about the reduction of oxygen functionalities on GO and the introduction of new functionalities in GO-ODA and GO-ANS. The effects of particle functionalization for the improved control of particle adhesion to the tribocontact have been studied. Wettability and thermal stability were determined using the water contact angle, and atomic force microscopy and differential scanning calorimetry (DSC) were used to characterize particle adhesion to the tribocontact. The tribological performances of the particles have been investigated using macro- and micro-tribometry using pin/ball-on-disc contact geometries. The influence of particle functionalization on the contact pressure and sliding velocity was also studied under rotating and reciprocating tribo-contact in ambient conditions. With an increase in the contact pressure, the functionalized particles are pushed down into the contact, and they adhere to the substrate to form a continuous film that eventually reduces friction. Amphoteric GO-ANS provides the lowest and most steady coefficient of friction (COF) under all tested conditions along with low wear depth and minimal plastic deformation. This is because particles with superior wetting and thermal properties can have better adherence to and stability on the surface. GO-ANS has a superior ability to adhere on the track to form a thicker and more continuous film at the interface, which is investigated by field emission scanning electron microscopy, energy dispersive spectroscopy, and Raman analysis.

Nanotribological studies using nanoparticle manipulation: Principles and application to structural lubricity

The term“structural lubricity”denotes a fundamental concept where the friction between two atomically flat surfaces is reduced due to lattice mismatch at the interface.Under favorable circumstances,its effect may cause a contact to experience ultra-low friction,which is why it is also referred to as“superlubricity”.While the basic principle is intriguingly simple,the experimental analysis of structural lubricity has been challenging.One of the main reasons for this predicament is that the tool most frequently used in nanotribology,the friction force microscope,is not well suited to analyse the friction of extended nanocontacts.To overcome this deficiency,substantial efforts have been directed in recent years towards establishing nanoparticle manipulation techniques,where the friction of nanoparticles sliding on a substrate is measured,as an alternative approach to nanotribological research.By choosing appropriate nanoparticles and substrates,interfaces exhibiting the characteristics needed for the occurrence of structural lubricity can be created.As a consequence,nanoparticle manipulation experiments such as in this review represent a unique opportunity to study the physical conditions and processes necessary to establish structural lubricity,thereby opening a path to exploit this effect in technological applications.

Study on Tribology Performance of Different Lubricant Additives under Atmospheric Pressure and High Vacuum Conditions

By using PAO-10 as the base oil, the tribological behavior of 11 additives under high vacuum condition was evaluated. By adopting some surface analytical instruments, such as scanning electron microscopy(SEM), energy dispersive spectroscopy(EDS) and X-ray photoelectron spectroscopy(XPS), the tribological mechanisms of these additives were studied. In air, O_2 can react with metal to form metal oxide that can protect the surfaces of rubbing pair during the tribological tests. According to the theory of the competitive adsorption, the function of some active elements is weakened. In a vacuum environment, the additives contributed more to the lubrication performance. The sulfur-containing additives could react with Fe to produce Fe Sx and "M—C" bonds("M" represents metal). They both had contributions to the lubrication. As for the phosphorus-containing additives, they only generated the phosphates during the tests. When the sulfur and phosphorus-containing additives were applied, the generated phosphates and Fe Sx had the primary contribution to the lubrication performance during the tests.

纳米粒子改善润滑油摩擦磨损性能的研究

利用MM2 0 0型磨损试验机研究了纳米粒子作为润滑油添加剂的摩擦磨损性能。实验结果表明 :纳米粒子能明显地提高润滑油的抗磨减摩性能。并利用光学显微镜和扫描电子显微镜 (SEM)观察了磨痕形貌 ,分析了纳米粒子在磨痕表面分别以“垫片”和“轴承”形式参与润滑。

润滑油中CuS纳米粒子的摩擦学性能研究

本文用合成工艺简单、成本低廉、易于工业化生产的液相法制备了CuS纳米粒子 ,并对该粒子在润滑油中的摩擦学性能进行了研究。结果表明 ,CuS纳米粒子加入润滑油中 。

分散介质对铜纳米粒子润滑油添加剂摩擦学性能的影响

本文利用十二烷基硫酸钠/异戊醇/环已烷/水微乳液体系制备了铜纳米粒子,并将其作为添加剂分散在含有聚丁二酰亚胺(T154)、石油磺酸钙(T101)或三烷基氯化铵(Aliquat336)的500SN基础油中,用四球实验机考察了不同分散介质对铜纳米粒子添加剂摩擦学性能的影响,并用X-射线光电子能谱(XPS)分析磨斑表面的组成和价态.实验结果表明:分散介质对铜纳米粒子添加剂的摩擦学性能的影响较大.分散介质对铜纳米粒子添加剂润滑性能影响的优劣顺序为5000SN+T101+Alquat336>500SN+T101+Alquat336≈5000SN+T154+T101>500SN+T154>500SN;在磨斑表面能形成含有铜、氧化亚铜和氧化铜粒子的保护膜,且这些粒子在磨斑表面上可能起到类似“轴承”的作用,从而使铜纳米粒子添加剂表现出较好的摩擦学性能.

离子液体中二氧化硅纳米微粒的制备及其摩擦学性能

以 1-甲基-3-丁基咪唑四氟硼酸盐离子液体为溶剂, 合成了二氧化硅纳米颗粒, 并以含有二氧化硅纳米颗粒的离子液体作为基础油,对其摩擦学性能进行研究; 用透射电子显微镜对二氧化硅的形貌进行分析, 用扫描电子显微镜对钢球磨斑表面的形貌进行了分析. 结果表明, 添加二氧化硅纳米颗粒的离子液体具有较好的润滑性能.

减摩抗磨类新型润滑油添加剂的研究进展

减摩抗磨类润滑油添加剂能提高基础润滑油的摩擦学性能使其在润滑领域具有广阔的应用前景,但是商用润滑油添加剂大多含有P、S等有害元素,因此,寻找更加环保、经济的润滑油添加剂具有重要意义。本文根据润滑油添加剂结构种类和润滑机理的不同,以及国内外各种润滑油添加剂在润滑方面的相关成果,综述了近年来纳米颗粒(纳米单质及其复合颗粒、纳米氧化物、纳米硫化物、纳米氮化物)、含氮杂环化合物及其衍生物、硼酸酯及其衍生物、离子液体等添加剂的合成方法以及在减摩抗磨方面的应用,并对其发展状况和减摩抗磨机理进行了探究。指出了其润滑机理主要为吸附膜机理、摩擦反应膜机理和滚珠机理。最后对其存在的问题进行分析,提出了当前润滑领域研究的热点和方向依然是复合添加剂的制备和机理探究。

碳酸钙纳米粒子润滑油添加剂的制备及其摩擦学性能的研究

本文利用十二烷基硫酸钠/异戊醇/环已烷/水微乳液体系制备了碳酸钙纳米粒子,用透射电镜(TEM)、X—射线衍射仪(XRD)和动态光散射仪(DLS)测定其物理形态,并将其作为添加剂分散到500SN基础油中,用四球实验机考察了其摩擦学性能和用X—射线光电子能谱仪(XPS)对磨斑表面进行分析。实验结果表明:所制备的碳酸钙纳米粒子的粒径约为13nm、呈球形和六方型晶体结构,具有较好的单分散性;具有较好的摩擦学性能,少量的碳酸钙纳米粒子即可提高润滑油的抗磨减摩性能。其摩擦机理是在磨斑表面形成了含有碳酸钙和由其分解而成的氧化钙的保护膜,从而表现出较好的摩擦学性能。

油溶性Cu纳米微粒添加剂对几种商品润滑油摩擦性能的影响

采用液相还原法制备了油溶性铜纳米微粒 ,用四球摩擦磨损试验机考察了其在SJ 5W /3 0汽油机油、CD 15W/4 0柴油机油及GL 4中负荷齿轮油中的摩擦学性能。结果表明 :油溶性纳米铜添加剂可以在一定程度上改善SJ 5W/3 0汽油机油和CD 15W/4 0柴油机油的抗磨作用 ;在较高载荷和浓度下则可以显著改善CD 15W /4 0柴油机油的抗磨作用 ;但其对基础油减摩作用的影响较小。油溶性纳米铜添加剂可望作为减摩抗磨剂直接用于SJ及CD成品油 ,但不宜用于GL

纳米粒子在润滑材料中的应用进展

介绍了纳米润滑粒子的制备方法,探讨了纳米粒子的润滑机理,包括膜作用机理、类滚珠作用机理和表面优化作用机理。着重综述了纳米粒子在润滑材料中的应用,具体包括:纳米无机粒子可作为添加剂在润滑油、聚合物基复合材料中起抗磨、减摩作用;纳米粒子应用于非聚合物基复合涂层,可形成一种根据环境自我调节的活泼纳米复合涂层,此涂层具有广泛的应用前景。

纳米铜添加剂改善钢-铝摩擦副摩擦磨损性能的研究

采用环-块摩擦磨损试验机对比考察了钢-铝摩擦副在液体石蜡与含纳米铜粒液体石蜡润滑下的摩擦磨损特性，研究了对纳米铜添加剂添加量与载荷对其按摩磨损性能的影响，通过对磨损表面粗糙度，形貌及其主要元素找 能谱分析，探讨了纳米铜颗粒作为添加剂时钢-铝摩擦副的润滑机制，结果表明：含0.25%纳米铜颗粒液体石蜡时，钢-铝摩擦副的摩擦磨损性能最优；在不同载荷下纳米铜颗粒可以改善铝的摩擦磨损性能，特别在中等载荷（50-125N）下，其抗磨减摩作用更明显；纳米铜颗粒能够在磨损表面形成一层低剪切强度的铜保护膜，有效地避免粘着磨损，同时阻止铝元素向钢表面的转移，从而显著改善钢-铝摩擦副的摩擦磨损性能。

纳米微粒作为润滑油脂添加剂的现状与发展趋势

通过对目前润滑油脂添加剂研究成果的综合分析,提出了当前研究中存在的一些问题以及今后应关注的研究方向,特别强调应重点加强特殊环境,如高温、重载、磨损表面的修复、环境友好等条件下的纳米润滑添加剂的研制,纳米微粒润滑机理与其特殊的摩擦学性能之间的关系,以及表面修饰纳米微粒的工业化研究。

纳米Sn粒子的制备及其作润滑油添加剂的摩擦学性能研究

用化学还原法制备了表面经油酸修饰的纳米Sn粒子,并在透射电镜(TEM)下观测到所制备的纳米Sn粒子呈球形、平均粒径为20 nm。在MSR-10D四球摩擦磨损试验机上考察了纳米Sn粒子作为CF-4 15W/40润滑油添加剂的摩擦学性能,并在扫描电子显微镜(SEM)和能谱分析仪(EDS)上对钢球磨斑表面进行了形貌观测和表层成分分析。试验结果表明,纳米Sn粒子作为润滑油添加剂具有一定的减摩性能和较好的抗磨性能,当所添加的体积分数仅为0.1%时,添加纳米Sn粒子润滑油的摩擦力比基础油降低了16.64%,其磨斑直径比基础油减小了38.4%。分析认为,纳米Sn粒子通过隔离摩擦表面而改善了润滑油的减摩抗磨性能。

含纳米稀土、铁复合粒子润滑油的摩擦学性能

选择了吐温(Tween)-60、司本(Span)-20、司本(Span)-80和聚醚表面活性剂,配制了纳米稀土(RE)和铁粒子的复合润滑油。采用透射电子显微镜(TEM)观察、测定了纳米稀土、铁粒子形貌和粒径。采用磨损试验机测试了含纳米稀土、铁复合粒子润滑油的摩擦学性能。结果表明:纳米稀土与纳米铁粒子比例为1∶1,总浓度为0.6%时该润滑油具有最佳的抗磨、减摩性能。并探讨了其抗磨、减摩机制。