Friction Properties of Fluorinated Carbon Nanodiscs and Nanocones

The tribologic properties of carbon nanodiscs and nanocones and their fluorinated derivatives are investigated and correlated to their structure and chemical composition (atomic fluorine/carbon ratio). Two families of products are studied obtained by fluorination of ill ordered and highly graphitized carbon nanodiscs and nanocones. The studies clearly point out that friction properties of the nanoparticles are strongly dependent on the structure of the initial carbonaceous compounds. Better tribologic behaviour is obtained when the initial nanoparticles structure is highly ordered (graphitized particles). In that case, an optimum of fluorination rate is put in evidence.     

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.     

含氟润滑油脂减摩性能及摩擦机制分析

研究分析了聚四氟乙烯润滑油脂的减摩性能,得出了聚四氟乙烯润滑油脂摩擦因数与转速、温度和载荷变化关系。利用SEM和EDS对3种润滑剂摩擦膜进行形貌和能谱分析,认为聚四氟乙烯润滑油脂减摩是表面物理吸附膜和化学迁移膜共同作用的结果。     

不同刹车压力下C/C复合材料的摩擦性能与摩擦面研究

采用MM-1000型摩擦磨损试验机对以光滑层、粗糙层为基体炭的2种C/C复合材料在不同刹车压力下的摩擦磨损性能进行了测试。借助微区拉曼光谱和扫描电镜对其摩擦表面的石墨化度与形貌进行了分析。结果表明：以粗糙层为基体炭的C/C复合材料比以光滑层为基体炭的C/C复合材料有更优异的摩擦压力或温度特性。微区拉曼光谱检测证实在摩擦面上粗糙层基体炭相对光滑层基体炭更易变形,所以以粗糙层为基体炭的C/C复合材料的摩擦面在刹车压力达到0.59 MPa时便能形成较厚的摩擦膜,故其摩擦因数能在较高刹车压力下（1.05-1.82 MPa）保持较高的稳定值（0.31）,且磨损适当;而光滑层基体炭C/C复合材料需在刹车压力超过0.82 MPa时摩擦面才能形成较薄的摩擦膜,并且由于其导热系数低,高压刹车时摩擦表面氧化严重,所以高压刹车时其摩擦因数衰减大,线性磨损率大,尤其是质量损失急剧升高。     

改性碳纤维增强纸基摩擦材料摩擦磨损性能

采用双-[γ-(三乙氧基硅基)丙基]四硫化物(Si69)和乙烯基三乙氧基硅烷(A151)对PAN基碳纤维(CF)进行表面改性处理,利用SEM、FTIR、EDX对改性前后的CF进行表征,测量接触角和表面能、力学性能和界面性能;通过湿法成形技术,制备不同改性CF增强聚酰亚胺纸基摩擦材料,并测试其孔隙率和摩擦学性能。结果表明:与未改性CF相比,Si69和A151能够有效地增加CF表面粗糙度,且新基团的引入使接触角变小,提高了CF表面活性,改善了纤维与树脂之间的结合力,使得A151-CF表面能增加了37.3%,Si69-CF表面能增加了109.4%,A151-CF/聚酰亚胺复合材料界面性能增加了19.1%,Si69-CF/聚酰亚胺复合材料界面性能提高了45.3%;相比未改性CF,Si69改性CF使纸基摩擦材料孔隙率下降了20.2%,A151改性CF使纸基摩擦材料孔隙率下降了8.8%;表面改性CF能够提高纸基摩擦材料的摩擦学性能,其中Si69改性CF增强纸基摩擦材料摩擦学性能优于A151改性CF增强纸基摩擦材料。     

类金刚石表面改性C/C复合材料的摩擦磨损性能

采用等离子体增强化学气相沉积法在C/C复合材料基底表面制备了不同厚度的类金刚石（DLC）表面改性膜;用球-盘对磨的方式测试了C/C复合材料基底和DLC膜在干态下的摩擦磨损性能。结果表明:制备的表面改性膜具有典型的DLC结构特征,均匀致密;随着沉积时间的延长,DLC膜厚度逐渐增大,膜基结合强度依次减小;C/C复合材料基底的平均摩擦因数为0.285 8,磨损率约为1.6×10^-4mm³·N^-1·m^-1,表面改性膜的摩擦因数较基底有较大程度的降低,在0.08～0.27之间,磨损率也降低了1～2个数量级,且沉积时间越长其摩擦因数越小、磨损率越低。     

Friction Properties of Carbon Nano-Onions from Experiment and Computer Simulations

The carbon nano-onion can be considered as a new kind of interesting lubricating nanoparticle. Used as lubricant additives, carbon nano-onions lead to a strong reduction of both friction and wear, even at low temperature. To better elucidate the mechanisms by which these processes occur, coupled experimental and computational investigations are carried out. In addition, it is found that lubricious iron oxide nanoparticles are generated in the core of the steel contact through mechanisms that are not yet known. The molecular dynamics simulations of carbon onions placed between sliding diamond-like carbon surfaces at high contact pressure indicate that the lubrication mechanism of the onions is based on a coupled process of rolling and sliding inside the contact area. We conclude that most of carbon onions seem to remain intact under friction processes and do not generate graphitic planes, which is in contrast to the previously determined behavior of MoS₂ fullerenes that are mainly exfoliated inside the contact area and liberate lubricating lamellar sheets of h-MoS₂.     

碳纤维含量对摩擦材料性能的影响

用D-MS摩擦试验机研究了摩擦材料中碳纤维含量对其摩擦磨损性能的影响。结果表明，碳纤维含量对摩擦材料的摩擦磨损性能影响显著，其摩擦系数和磨损率都随碳纤维含量的增加而减小，推荐碳纤维的含量≤5％。SEM分析表明，其摩擦磨损机理亦与碳纤维含量密切相关。     

硬碳填充PTFE复合材料摩擦磨损性能研究

以硬碳为填料制备了PTFE基复合材料,并研究了该复合材料在干摩擦条件下与不锈钢对摩时的摩擦磨损行为,并探讨其磨损机制.实验结果表明:硬碳能提高FIFE硬度,硬碳/PTFE复合材料的耐磨性能明显优于纯PTFE.其摩擦因数随着硬碳含量的增加而减小.复合材料的摩擦表面SEM观察发现:纯PTFE摩擦表面分布着较明显的犁削和粘着磨损的痕迹,硬碳/PTFE的磨痕较浅,表明硬碳作为填料可有效地抑制FTFE的磨损.     

双壁碳纳米管轴承移动摩擦特性的论研究

基于分子动力学方法对双壁碳纳米管轴承的移动摩擦特性进行了理论研究.针对双壁碳纳米管轴承的结构和物理模型,使用经验势函数分析了双壁碳纳米管轴承的管间交互作用势和交互作用力.建立碳纳米管轴承移动动力学模型,采用数值模拟方法,研究不同长度、半径和内外纳米管质心相对位移对纳米管轴承移动阻尼系数的影响,并给出双壁碳纳米管轴承移动阻尼系数与长度、半径和质心相对位移的定量关系.     

双壁碳纳米管轴承移动摩擦特性的理论研究

基于分子动力学方法对双壁碳纳米管轴承的移动摩擦特性进行了理论研究。针对双壁碳纳米管轴承的结构和物理模型,使用经验势函数分析了双壁碳纳米管轴承的管间交互作用势和交互作用力。建立碳纳米管轴承移动动力学模型,采用数值模拟方法,研究不同长度、半径和内外纳米管质心相对位移对纳米管轴承移动阻尼系数的影响,并给出双壁碳纳米管轴承移动阻尼系数与长度、半径和质心相对位移的定量关系。     

碳材料填充 PTFE 复合材料摩擦磨损性能

利用 MM-200 型磨损试验机考察了石墨、碳纤维、硬碳和软碳填充 PTFE 复合材料的摩擦磨损性能,采用扫描电子显微镜观察分析磨损表面形貌及磨损机制.结果表明,碳材料可以不同程度地提高 PTFE 的耐磨性,它们对PT-FE 耐磨性的提高程度各不相同,其中以硬碳填充 PTFE 复合材料的磨损质量损失最小,石墨填充 PTFE 复合材料的磨损质量损失较大;不同填充材料对 PTFE 摩擦因数的影响各不相同,其中石墨填充 PTFE 的摩擦因数较小.石墨、软碳填允复合材料磨损机制以粘着磨损为主,硬碳、碳纤维复合材料,则表现为粘着磨损和磨粒磨损.     

表面粗糙度对碳/铜载流摩擦副摩擦磨损性能的影响

通过环-块式摩擦磨损试验研究了表面粗糙度对碳/铜载流摩擦副摩擦磨损性能的影响,并分析了磨损形貌及机制。结果表明:其摩擦因数与电弧行为密切相关,无电弧时摩擦因数曲线平滑;对磨环的表面粗糙度越大越容易产生电弧,电弧的烧蚀导致块试样的磨损加剧;不同表面粗糙度下均存在临界起弧法向压力,且随着表面粗糙度的增大而增大;载流摩擦副的磨损机制主要为磨粒磨损、粘着磨损、电弧烧蚀及材料转移。     

软碳填充PTFE复合材料摩擦磨损性能研究

以不同含量的软碳为填料制备了PTFE基复合材料,测量了其机械性能,在M-2000型摩擦磨损试验机上研究其摩擦磨损行为,并探讨了其磨损机制.结果表明:软碳能提高PTFE复合材料的硬度,软碳/PTFE复合材料的耐磨性能优于纯PTFE,当软碳质量分数为7%时其耐磨性能最好.复合材料的摩擦因数随着软碳含量的增加而增加.摩擦表面的SEM观察发现:纯PTFE的摩擦表面分布着较明显的犁削和黏着磨损的痕迹,复合材料的摩擦表面均出现犁削,随着软碳含量的增加,犁削现象减轻,这表明以软碳作为填料可有效地抑制PTFE的磨损.     

CNTs/AZ91复合材料的摩擦磨损性能

采用粉末冶金法和热挤压工艺制备了碳纳米管增强AZ91镁合金(CNTs/AZ91)复合材料,研究了复合材料在干滑动条件下的摩擦磨损性能、磨损形貌及磨损机制,并与AZ91镁合金基体的进行了对比。结果表明:由于CNTs的自润滑和增强作用,复合材料的摩擦磨损性能明显优于基体合金的;随着载荷和CNTs质量分数增加,复合材料的摩擦因数逐渐降低;随着载荷增加,复合材料的磨损量增大;在相同的载荷下,复合材料的磨损量随CNTs质量分数的增大而减小;AZ91镁合金的磨损机制为疲劳磨损和磨粒磨损,复合材料的磨损机制以轻微的粘着磨损和磨粒磨损为主。     

聚丙烯、炭黑和碳纤维共混填充超高分子量聚乙烯复合材料的力学和摩擦磨损性能

采用模压成型的方式制备超高分子量聚乙烯(UHMWPE)复合材料,通过AG-1型电子万能实验机和MM-200型摩擦磨损试验机分别研究填料对复合材料力学性能和摩擦磨损性能的影响,采用光学显微镜分析复合材料磨损表面的形貌。结果表明:聚丙烯(PP)和无机填料炭黑(CB)或CB与碳纤维(CF)混杂填料的加入使UHMWPE复合材料的拉伸强度降低,弯曲模量和硬度增加,其中UHMWPE/PP/CB/CF复合材料的弯曲模量和硬度增幅大于UHM-WPE/PP/CB复合材料。填料的加入可改善UHMWPE复合材料的摩擦磨损性能,当填料的质量分数为5%时,UHMWPE复合材料的摩擦磨损性能最好,且UHMWPE/PP/CB/CF复合材料的耐磨性能优于UHMWPE/PP/CB复合材料。与UHM-WPE相比,UHMWPE/PP/CB/CF复合材料的摩擦因数和磨痕宽度分别下降了10%和44%,UHMWPE/PP/CB复合材料则分别下降了12%和42%。光学显微镜观察表明填料的加入大大改善了UHMWPE的磨粒磨损,复合材料表面以较浅的犁沟磨损为主要特征。     

碳黑填充PTFE复合材料干摩擦磨损性能分析

以碳黑为填料制备了PTFE基复合材料,并研究了该复合材料在干摩擦条件下与不锈钢对摩时的摩擦磨损行为,并探讨其磨损机制。实验结果表明,碳黑/PTFE复合材料的摩擦因数随着碳黑含量的增加呈增加的趋势,其耐磨性能明显优于纯PTFE。当碳黑的质量分数为5%时,其抗磨性能最好。SEM观察发现纯PTFE的断面上分布着大量的带状结构,而填充了碳黑后,则未观察到这种带状结构,这说明碳黑有效地抑制了PTFE结构的破坏。对PTFE和碳黑/PTFE复合材料的摩擦表面的SEM观察发现,前者的摩擦表面分布着较明显的犁削和粘着磨损的痕迹,而后者的摩擦表面则平整光滑,这表明以碳黑作为填料可有效地抑制PTFE的磨损。     

Superlow Friction of Diamond-Like Carbon Films: A Relation to Viscoplastic Properties

Composition, structure, electrical, optical, mechanical properties and tribological behavior of diamond-like carbon films (DLC) are strongly dependent on the deposition system. Some hydrogenated amorphous carbon films (a-C:H) may exhibit superlow friction properties in ultra-high vacuum (UHV). The present paper compares tribological and mechanical properties of several DLC films prepared under different conditions. Friction coefficients were measured in an analytical ultra-high vacuum tribometer. The mechanical properties were evaluated from force-displacement curves using a nanoindentation instrument. Making use of continuous stiffness mode, Young's modulus and hardness were determined as a function of indentation depth. The measurements were performed at constant strain rates by special control of the load during indentation. We were, thus, able to determine the dependence of hardness on strain rate, characterizing a viscoplastic behavior. Many of the hydrogenated amorphous carbon films studied were significantly viscoplastic. The aim of this paper is to highlight the correlation between superlow friction and viscoplastic behavior.     

不锈钢纤维/碳纤维混杂增强聚醚醚酮基摩擦材料的制备与性能

研究了不锈钢纤维/碳纤维混杂增强聚醚醚酮(PEEK)树脂基半金属摩擦材料的配比、成型工艺对其摩擦磨损性能的影响,对其摩擦磨损机理进行了初步分析.结果表明:制备摩擦材料的优化工艺条件是热压温度320 ℃、压力35 MPa、保温时间3 min/mm,固化处理工艺为80 ℃×30 min 150 ℃×30 min 270 ℃×30 min 320 ℃×180 min;最佳配方为19.63%的PEEK、7.57%的不锈钢纤维、10.97%的碳纤维、6.51%的腰果壳油粉及55.33%的填料.经优化工艺制备的摩擦材料的摩擦因数稳定,磨损率低,摩擦材料的磨损在低温区主要属于磨粒磨损,在较高温度时属于粘着磨损和磨粒磨损的共同作用.