Frictional Behavior of Carbon Film Embedded with Controlling-Sized Graphene Nanocrystallites

Graphene nanocrystallites embedded in amorphous carbon matrix can bring excellent tribological, electrical and magnetical properties to the carbon films. But too large size of graphene nanocrystallite would lead to degradation of the tribological performance. So it is necessary to clarify the dependence of frictional behavior of the carbon film on graphene nanocrystallite size. In order to control the size, different electron irradiation densities were introduced during film growth in the electron cyclotron resonance plasma sputtering process. Frictional tests on the films were carried out with a Pin-on-Disk tribometer. The evolution of graphene nanocrystallite size along with electron irradiation density was examined by transmission electron microscopy and Raman spectroscopy. The results showed that the graphene nanocrystallite size increased with increasing of the electron irradiation density. The film with a graphene nanocrystallite size of 1.09 nm exhibited a low friction coefficient of 0.03 and a long wear life. When nanocrystallite size increased, the friction coefficient increased and the wear life decreased. Observation on transfer film revealed that the nanocrystallite in transfer film grew larger when initial size was 1.09 nm, and changed smaller when initial size was 1.67 nm. The results suggested that embedded graphene nanocrystallite played an important role in the formation of transfer film, the initial size of graphene nanocrystallite strongly affected the frictional behavior of the film, and the graphene nanocrystallite needed to be controlled under a certain size in order to keep the good tribological performance.     

Fabrication and Tribological Investigation of a Novel Hydrophobic Polydopamine/Graphene Oxide Multilayer Film

Polydopamine (PDA)/graphene oxide (GO) multilayer was successfully constructed on the surface of silicon substrate by a layer-by-layer self assembling process. In order to further obtain hydrophobic outer surface, low energy molecules of 1H, 1H, 2H, 2H-perfluorodecyltrichlorosilane (PFDTS) were grafted thereon and the sample was coded as PDA/GO-PFDTS. The microstructures, chemical compositions, and morphologies of PDA/GO-PFDTS were characterized by the water contact angle (WCA) measurements, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). In particular, the tribological performances were investigated by AFM and ball-on-plate tribometer. Experimental results showed that PDA/GO-PFDTS could lower the stiction and friction greatly as compared with the bare substrate and control samples. It was indicated that the as-fabricated film of PDA/GO-PFDTS was a very promising candidate for solving the tribological problems in micro/nano devices.     

Tribological Behavior of UHMWPE Reinforced with Graphene Oxide Nanosheets

In this article, a series of graphene oxide (GO)/ultrahigh molecular weight polyethylene (UHMWPE) composites are successfully fabricated through an optimized toluene-assisted mixing followed by hot-pressing. The mechanical and tribological properties of pure UHMWPE and the GO/UHMWPE composites are investigated using a micro-hardness tester and a high speed reciprocating friction testing machine. Also, the wear surfaces of GO/UHMWPE composites are observed by a scanning electron microscope (SEM), to analyze the tribological behavior of the GO/UHMWPE composites. The results show that, when the content of GO nanosheets is up to 1.0 wt%, both the hardness and wear resistance of the composites are improved significantly, while the friction coefficient increases lightly. After adding GO, the tribological behavior of the GO/UHMWPE composites transforms from fatigue wear to abrasive wear associated with the generation of a transfer layer on the contact surface, which efficiently reduced the wear rate of the GO/UHMWPE composites.     

Tribological Characteristics of Aqueous Graphene Oxide,Graphitic Carbon Nitride,and Their Mixed Suspensions

The tribological performance of graphene oxide (GO), graphitic carbon nitride (g-C₃N₄), and their mixed (g-C₃N₄/GO) aqueous suspensions was investigated. The 0.06 wt% GO, 0.06 wt% g-C₃N₄, and 0.06 wt% 1:1 g-C₃N₄/GO suspensions reduced the coefficient of friction (COF) by 37, 26 and 37% and wear mark radius by 19.1, 16.0 and 19.6%, respectively, in comparison with water. Pure g-C₃N₄ and GO suspensions showed unstable lubrication in the tests with relatively high loads and speeds, while the g-C₃N₄/GO mixed suspension had superior tribological performance in all tested conditions. This is because in the mixed suspension g-C₃N₄ agglomerates became smaller, and GO nanosheets exhibited fewer wrinkles and less stacking, which enabled the formation of a layer of tribo-composite film. As a result, the friction, wear and tribo-corrosion were reduced during sliding.     

氧化石墨烯/碳纳米管复合薄膜制备及表征

将氧化石墨烯(GO)和COOH官能基多壁碳纳米管MWCNT-COOH在去离子水中混合。用超声探针对GO/MWCNT-COOH水溶液进行超音波处理。表面活性剂Triton X-100能使GO和MWCNT-COOH在水中更好地分散。使用真空泵,使悬浮液通过PTFE膜过滤,GO和MWCNT-COOH混合水溶液沉积在PTFE过滤膜上形成复合薄膜。用扫描电子显微镜对薄膜进行表征。用纳米压痕仪检测薄膜的力学性能,通过霍尔效应检测薄膜的导电性能。结果表明,复合薄膜随着GO含量的增加杨氏模量和硬度不断提高,还原前复合薄膜随着GO含量的增加导电率不断降低,热处理还原后复合薄膜随着GO含量的增加导电率迅速增大。     

碳纳米管及石墨烯协同增强尼龙6摩擦学性能的分子动力学模拟

为研究碳纳米管（CNT）和石墨烯片(GNS)协同增强尼龙6（PA6）复合材料摩擦学及力学性能的微观机制,利用分子动力学方法模拟PA6及其复合材料的拉伸过程及摩擦学行为,分析CNT、GNS对PA6复合材料力学及摩擦学性能的影响。建立Fe原子与纯PA6和PA6/ CNT、PA6/GNS、PA6/GNS/CNT复合材料组成的摩擦学模型,并对模型进行几何优化、退火及动力学平衡,通过对Fe原子施加0.2 GPa应力及0.01 nm/ps速度进行摩擦模拟。研究结果发现,PA6/GNS/CNT复合材料摩擦因数在所有材料中最低为0.252;相比其他3种材料,PA6/GNS/CNT复合材料的抗剪切性能最好,且弹性模量及剪切模量均有提高。通过对比分析4种材料的径向分布函数、摩擦界面温度、材料总势能揭示了CNT和GNS协同增强PA6摩擦学及力学性能的作用机制,指出加入的CNT/GNS通过范德华及静电力作用降低了PA6与Fe原子摩擦副之间的相互作用,此外一维CNT与二维GNS通过π-π堆叠杂化作用形成了3D杂交堆叠体系,协同增强了PA6的摩擦学性能。     

含石墨烯润滑油多孔聚酰亚胺摩擦学行为研究

多孔聚酰亚胺（PI）可以在孔隙中储存润滑油,当多孔PI作为摩擦壁面时孔隙内的润滑油会渗出实现润滑。为实现更优异的润滑效果,将石墨烯润滑油渗入多孔PI中,制备含石墨烯润滑油多孔PI。以氮化硅（Si3N4）为摩擦副,基于分子动力学原理建立Si3N4-多孔PI-Si3N4层结构以及多孔含油聚酰亚胺（PI/C）-润滑油膜-Si3N4层结构,模拟多孔PI与Si3N4之间的范德华能、剪切应力、相对浓度分布以及温度分布,分析石墨烯润滑油渗入后形成的含石墨烯润滑油多孔PI结构(PI/CG)对多孔PI润滑性能的影响,并通过试验验证了仿真结果。研究发现：在PI孔隙中浸入石墨烯润滑油后,PI材料的吸附能力变强、剪切应力减小、摩擦副间温度降低以及耐磨性提高;PI/CG可明显改善润滑效果,在摩擦磨损试验过程中的摩擦学性能优于PI/C。     

Tribological Behaviour of Plasma-Functionalized Graphene as Low-Viscosity Oil Additive

The influence of plasma functionalization of multilayer graphene (MG) as an additive for low-viscosity polyolester (POE) oil in terms of dispersion stability and tribological behaviour was investigated. Pure MG and MG functionalized via N2 and NH3 plasma were analysed. The plasma functionalization significantly improved the substrate wettability and the dispersion stability of the nanofluids. The tribological behaviour of the nanofluids was investigated using a reciprocating cylinder on plane configuration. 0.05 wt% of the functionalized nanoparticles dramatically increased the scuffing resistance and significantly improved the anti-wear properties of the POE oil (over 60% wear reduction). Optical microscopy, white light interferometry, scanning electron microscopy and micro-Raman spectroscopy were used to identify the wear mechanisms. The functionalization provides a well-dispersed suspension, which contributes to the formation of a continuous and homogeneous anti-wear tribofilm. Once between the sliding surfaces, the MG improves the load-carrying capacity of the oil, avoiding the seizure of the tribolayer.     

柴油机活塞环表面类金刚石薄膜在模拟工况下摩擦学性能

大缸径、长冲程的大功率柴油机的活塞环-缸套摩擦副易发生异常磨损,使柴油机动力性能丧失,甚至发生拉缸等重大事故,通过先进的表面处理技术可显著改善活塞环-缸套摩擦副的润滑条件,提高活塞环-缸套摩擦副的摩擦学性能。采用阴极电弧离子镀技术在铬-陶瓷复合镀(CKS)活塞环表面制备厚度为7 μm的DLC薄膜,研究CKS活塞环表面的DLC薄膜在柴油机模拟工况下的摩擦学性能。结果表明：在干摩擦、室温贫油和高温贫油的工况下,CKS活塞环表面的DLC薄膜可以显著减小活塞环-缸套摩擦副对摩的摩擦因数,降低缸套的磨损;摩擦过程中DLC薄膜与润滑油的协同润滑作用以及DLC薄膜的石墨化是改善活塞环-缸套摩擦副摩擦学性能的主要原因。     

Tribological Properties of Fluorinated Carbon Nanofibres

This work is concerned with the study of the tribological properties of fluorinated carbon nanofibres with various fluorination rates. The tribological tests, carried out in the presence of pentane and in air after liquid’s evaporation demonstrate good friction properties for all the compounds (the friction coefficients ranging between 0.04 and 0.06 in the presence of pentane and between 0.07 and 0.09 in air). Raman analyses reveal that the friction process induces a partial deterioration of the carbon fibres and SEM studies show that the tribofilm is composed of individual fibres embedded in a more disordered carbonaceous matrix. The fibrous nature of the tribofilm and the experimental relationship between friction coefficient and fluorination rate strongly support that friction properties of fluorinated carbon nanofibres are governed by surface fibres interaction. The modification of the nanofibres surface tension by action of pentane or optimum fluorination rate leads to a lowering of interfibres interactions resulting in an improvement of the friction properties.     

Theoretical Study of Superlow Friction Between Two Single-Side Hydrogenated Graphene Sheets

First-principles calculations within density functional theory were performed to predict the friction properties between two single-side hydrogenated graphene sheets at the atomic scale. In this study, the coefficients of the friction along two sliding paths were calculated under normal loads ranging from 1 to 9?nN. The calculated results show a general increase of the coefficient of friction with increasing normal load, and the coefficients of friction for this system exhibit an isotropic feature. Coefficients of friction in the range of 0.01?C0.05 were predicted. Compared with clean graphene, the coefficients of friction decreased greatly due to electrons accumulating between the carbon and attached hydrogen atoms, leading to a significant decrease in the potential energy of the single-side hydrogenated graphene. This study suggests that atomic-scale friction may be controlled by adjusting the electronic structure.     

Tribological Properties of Engine Oil with Carbon Nano-horns as Nano-additives

The work illustrates the preparation of stable suspensions of single-walled carbon nano-horns (SWCNHs) in engine oil and shows their tribological behavior at different temperatures. The suspension stability was verified by dynamic light scattering, and the viscosity of suspensions was measured. Stribeck test was used to evaluate the tribological performances of nano-lubricants in the 25–80 °C temperature range. The coefficient of friction was reduced with the addition of SWCNHs at all temperatures and concentrations. In particular, at T = 25 °C, the coefficient friction was reduced up to about 12 % in boundary regime even with a very low SWCNH concentration (0.01 vol%). Wear tests were carried out to verify results obtained from Stribeck characterization. A decrease in mean wear rate was observed at each temperature, between 25 and 30 %. In particular, at 25 °C, a decrease of about 30 % in wear rate was estimated. Friction coefficient decrease was also observed during all wear tests, probably due to the ball-bearing effect played by SWCNHs spherical aggregates. Therefore, SWCNHs revealed the potential to be promising candidates as additives, to develop a new class of lubricants that are suitable and effective in different operating environments.     

稀土复合纳米材料改性树脂基制动片摩擦学性能

为提升风电偏航树脂基制动片高温下的摩擦磨损性能,采用稀土和纳米材料对树脂基制动片进行改性。采用热压成型工艺制备改性树脂基制动片,对试样进行力学性能测试和摩擦磨损试验。采用SEM、EDS、XRD对试验后试样摩擦表面进行观察和分析,探究稀土和纳米材料对树脂基复合材料的作用机制。结果表明：添加稀土和纳米材料后试样的相关力学性能和摩擦学性能均有提高,其中质量分数1%的氧化铈和氧化钇、4%的纳米二氧化硅可使复合材料350℃高温下的摩擦因数提高9.09%,磨损率下降64.28%。稀土和纳米二氧化硅通过优异的界面效应,提高了高温下试样的抗热衰退性,降低了高温下试样的磨损量,使试样磨损形式从磨粒磨损为主转变为黏着磨损为主。     

钛铝系金属间化合物薄膜的制备和摩擦性能

应用射频磁控溅射方法沉积钛铝系金属间化合物薄膜;用X射线衍射仪(XRD)、配有能谱仪(EDS)的扫描电子显微镜(SEM)和UMT-2型摩擦试验机对薄膜的相组成、形貌和摩擦性能进行了分析.结果表明:该薄膜是由TiAl、TiAl3、Al2O3和TiO2相组成;薄膜表面晶粒均匀细小;对于不同钛、铝含量的薄膜,当铝含量(原子分数)为45%时具有最低的摩擦因数;摩擦因数随着载荷、转速和摩擦时间的增加而减小.     

辛硫醇改性氧化石墨烯在润滑脂中的摩擦学性能

氧化石墨烯(GO)的结构中拥有众多含氧基团,可作为化学反应的活性位点。以辛硫醇为改性剂对GO进行修饰,得到辛硫醇-GO。使用红外光谱(FTIR)、X射线衍射(XRD)、X射线光电子能谱(XPS)、热重分析(TGA)对其进行结构表征。将GO、辛硫醇-GO作为添加剂与润滑脂复配,考察其在润滑脂中的摩擦学性能。依据ASTM D2596-15标准方法,采用四球机测定GO润滑脂的抗磨减摩性能,使用白光干涉三维表面轮廓仪测定钢球表面形貌和磨损率。结果表明:GO可略微减小润滑脂的摩擦因数和磨损率;辛硫醇-GO对润滑脂的润滑性能有较大提升,可使润滑脂的摩擦因数减小11.7%,磨损率减少31.5%。XPS磨损表面分析表明,摩擦过程中会有GO颗粒吸附到金属表面,而且改性GO润滑脂中的活性硫元素会与钢球表面反应,生成硫化铁,减少钢球表面的摩擦磨损,从而有效提升润滑脂的润滑性能。     

3-巯基丙基三乙氧基硅烷自组装膜摩擦学性质研究

利用自组装技术将3-巯基丙基三乙氧基硅烷薄膜沉积在单面抛光的单晶硅基片上.用X射线光电子能谱仪测量薄膜的化学成分;用原子力显微镜(AFM)观察薄膜表面形貌;用接触角测量仪测量薄膜的接触角;在摩擦试验机上考察薄膜的摩擦学性能与接触角之间的关系.结果表明:薄膜的接触角随着组装时间的增加先增加后减小然后再增加,表明MM分子在单晶硅基片上的自组装是逐层进行的,当MM完成一层组装时,其薄膜表面自由能较低,所表现出的接触角较大;薄膜的摩擦磨损性能与接触角成对应关系,接触角增大,摩擦因数减小,抗磨损能力提高.     

不同维度碳纳米颗粒对汽轮机油摩擦学性能的影响

为探究不同维度碳纳米颗粒对汽轮机油摩擦学性能的影响,用静置沉淀法评定汽轮机油中碳纳米颗粒分散稳定性,利用四球机和梯姆肯试验机以及扫描电子显微镜等试验装置评价3种常见维度的碳纳米颗粒(即零维的富勒烯(以C60为代表)、一维的碳纳米管(CNTs)、二维的还原氧化石墨烯(RGO))在汽轮机油中减摩抗磨效果.结果表明:RGO在...     

粘结固体润滑膜的摩擦学特性研究

采用2种不同的固体润滑粉末(石墨和二硫化钼)分别与溶剂、粘结树脂组合制得粘结固体润滑剂,涂敷于钢板表面成膜,然后对得到的粘结固体润滑膜的润滑性能、物理化学性能和耐磨性能进行了测试。结果表明:粘结固体润滑剂中的固体粉末含量越多、颗粒越细,润滑膜的润滑性能越好,但固体粉末含量的增加影响了润滑膜的干燥时间,附着力、柔韧性和耐冲击性能也变差;只有当润滑剂中加入了适量固体粉末后,得到的润滑膜的减磨效果最佳。     

Tribological Behaviors of Lubricants Modified Nanoporous Anodic Alumina Film

A uniform closely packed hexagonal array of porous anodic alumina (PAA) film with an average pore diameter of ~100 nm and a pore height of ~330 nm was obtained by anodizing in oxalic acid solution. Low surface energy molecules of perfluoropolyether (PFPE) and octadecyltrichlorosilane (OTS) were used to enhance the hydrophobicity of the PAA and aluminum (Al) surface. The tribological performances were investigated in detail. The results showed that the static friction coefficient of PAA was much lower than that of smooth Al, which could be due to the higher hardness of the PAA than that of Al. PAA modified with PFPE was characterized by lower friction coefficient and longer wear life as compared with bare Al, PAA, and PAA modified with OTS. This is caused by the combined effects of flexibility, mobility, and inherent lubricity of PFPE molecules and the nanoporous structure of PAA as a reservoir for lubricants and wear particles.     

不同石墨烯添加量下MoS2基复合涂层的摩擦磨损及耐腐蚀性能

为改善MoS2基固体润滑涂层的摩擦磨损性能和耐蚀性能,制备了不同石墨烯（GE）添加量的MoS2复合涂层,利用HSR-2M摩擦磨损试验机测试了复合涂层的摩擦磨损性能,并分析了其磨损机理,通过极化曲线、交流阻抗谱（EIS）研究了涂层在3.5%NaCl溶液中的电化学腐蚀行为。试验结果表明,0.8-GE/MoS2复合涂层的摩擦磨损和耐腐蚀性能最优,其平均摩擦因数和磨损率分别为0.232和2.379×10-13 m3/(N·m),较未添加石墨烯的MoS2涂层分别降低了49.56%和43%,腐蚀速率（1.96×10-8 A/cm2）较纯MoS2涂层（5.54×10-6 A/cm2）降低了近2个数量级。石墨烯的二维片状结构具有良好的自润滑性能,在涂层中均匀分布时能有效阻隔腐蚀介质的渗透,因此,石墨烯的添加提高了MoS2基复合涂层的摩擦学性能和耐腐蚀性能,石墨烯的最优添加量为0.8%（质量分数）。