分子自组装膜与摩擦学

1 有序分子膜技术有效地进行润滑是摩擦学工作者孜孜以求的目的。随着技术的进步,特别是微型机械的发展,这一目标又面临着新的挑战。有序分子膜技术的发展为解决有效润滑问题提供了新的机遇。     

La纳米自组装膜的制备及摩擦学性能研究

采用乙二胺四乙酸(EDTA)分子自组装技术在硅基材料表面制备了稀土La复合纳米膜,利用浓缩体系全功能稳定性分析仪研究了自组装改性剂制备温度对氢氧化镧胶粒稳定性的影响,通过X-射线荧光光谱仪(XRF)研究了自组装改性剂溶液pH值对复合纳米膜中引入La量的影响,利用AFM研究了EDTA/La摩尔比及组装时间对复合纳米膜形貌的影响,利用AFM研究了在硅基材料表面自组装复合稀土纳米润滑膜前后的摩擦磨损性能.结果表明,在玻璃基片表面成功地组装上了稀土La纳米薄膜;相对于原构件,La纳米膜表面粘附力较小,摩擦因数亦较低,呈现出良好的润滑效果;其摩擦稳定性和耐磨性都有很大程度上的提高.     

磁头表面含氟硅烷自组装膜的制备和摩擦学性能

利用分子自组装技术,在磁头表面制备1H,1H,2H,2H-全氟葵烷基三乙氧基硅烷(FTE)自组装膜。应用时间飞行二次离子质谱仪(TOF-SIMS)、原子力显微镜(AFM)和接触角测量仪对FTE自组装膜进行表征。通过O lympus磁头磁盘界面可靠性测试系统对FTE自组装膜的摩擦学性能进行研究。实验结果表明磁头表面可制备膜厚1.2 nm、接触角值110.6°、表面粗糙度0.198 nm的FTE单层自组装膜。FTE单层自组装膜能够降低磁头起停过程的粘着力、增强磁头的摩擦性能,具有良好的耐磨性能。     

纳米润滑材料的摩擦学研究

随着纳米材料和纳米摩擦学的发展,近来许多材料工作者注意到了纳米材料的摩擦学性能,并开展了一些积极的研究工作。综述了纳米颗粒作为增强材料、润滑油添加剂以及超薄纳米膜的摩擦学性能,并对纳米润滑材料今后的发展提出了一些建议。     

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.     

基于高子尺度的摩擦学研究——纳米摩擦学

在评述摩擦学发展趋势的基础上，从现代纳米科学技术的需要出发，阐述纳米摩擦学兴起的背景及其在理论和应用上的意义，提出纳米摩擦学的研究特征和学科基础，以及加速其发展的有效途径，论述基于原子尺度的微观研究在固体表面接触与粘着行为，界面分子膜与边界润滑特性，微观摩擦，纳米刻划与微磨损机理等领域取得主要进展，并提出以发展微型机械－电子系统和实现超滑和零磨损的为目标的研究方向，包括微观表面工程和有序分子膜润膜     

铜表面硅烷自组装膜的制备及其摩擦学特性的研究

利用分子自组装技术在纯铜表面制备十七氟葵基硅烷单分子膜,用X射线光电子能谱对薄膜的表面结构进行表征,分析自组装膜的成膜机制,并利用UMT-3摩擦磨损试验机评价薄膜的摩擦磨损性能。接触角测试表明,该薄膜具有疏水性,其对水的接触角达117°。摩擦磨损实验结果表明,铜片表面沉积硅烷单分子膜可以大幅度降低铜基片的摩擦因数,使铜基片表面的摩擦因数由无膜时的0.8降至0.23,且在低负荷下具有很好的耐磨性。     

PAH/PAA(TiO2)分子沉积膜及其纳米摩擦学行为的研究

用分子沉积技术制备了PAH／PAA(TiO2)多层聚合物复合纳米粒子薄膜，为了增大薄膜自身的结合强度，采用加热的方式使其成膜动力发生转变。用紫外光谱及原子力显微镜(AFM)研究了薄膜的微观结构及其纳米摩擦学性能。结果表明，加热后薄膜中纳米粒子的长大导致薄膜表面粗糙度降低，同时提高了表面硬度，降低了薄膜表面摩擦力。     

微型机械的摩擦学特性及其表面润滑技术的研究

综述了微型机械的摩擦学特性,阐述了微型机械中摩擦学问题研究的重要性,分析了影响微摩擦力的关键因素。基于目前国内外对微型机械表面润滑问题的研究现状,探讨了LB膜、自组装膜和分子沉积膜各自的特点及其在微型机械表面润滑领域的应用进展,对它们性能的优缺点进行了比较,并提出降低微型机械的表面能是减轻微摩擦磨损的有效措施。     

原子力显微镜在分子自组装研究中的应用

原子力显微镜(AFM)以其分辨率高、样品无需特殊制备、实验可在大气环境中进行等优点被广泛应用于分子自组装这种自下而上的微细加工技术的研究中。近年来,随着对自组装行为研究的深入,其应用已由对自组装分子表面几何形貌的观测发展到制备纳米级结构和表征表面其它性能的研究领域。文中在简单介绍AFM及分子自组装优势的基础上,总结了AFM在自组装研究方面的若干新应用,并对其应用前景作出展望。     

氨基表面自组装膜成膜及摩擦性能研究

运用原子力显微镜与接触角测量仪研究了3-氨丙基三乙氧基硅烷(APTES)自组装膜不同成膜时间的表面形貌平均粗糙度、接触角,并进行了XPS(X射线光电子能谱)元素分析,表明APTES自组装膜以“岛”状生长,随着反应的时间的延长,岛的数量急剧增加,形成平整光滑的膜,进一步延长成膜时间,可能形成多层膜,从而平均粗糙度先增大再减小然后再增大,表面性质一直变化不大。微摩擦磨损实验研究表明,APTES自组装膜大大降低镀Cr钢球与硅片之间的摩擦因数,摩擦因数从0.71左右降低到0.16左右,在分子级润滑中有广阔的应用前景。     

Tribological Properties of Self-Assembled Monolayers and Their Substrates Under Various Humid Environments

Using friction force microscopy (FFM) under controlled environments, we have systematically investigated the humidity effect on the frictional properties of two important classes of self-assembled monolayers (SAMs), i.e., N-octadecyltrimethoxysilane (OTE, CH₃(CH₂)₁₇Si(OCH₃)₃) on SiO₂(OTE/SiO₂), and N-alkanethiols on Au(111), together with their respective substrates. Experimental results show that both OTE and alkylthiol SAMs can decrease the friction force between a Si₃N₄ atomic force microscope (AFM) tip and substrates. The nearly humidity-independent friction of the two kinds of SAMs indicates that these SAMs are ideal lubricants in applications of micro-electro-mechanical systems (MEMS) under different environments. The humidity dependence—as the humidity increases, the friction first increases and then decreases—of the two substrates, SiO₂ and Au(111), can be explained by the adsorption of water. The decrease in the friction at high humidity is attributed to the low viscosity in the multilayers of water, while the increase in the friction at low humidity can be explained by the high viscosity between the water monolayer and the surfaces (AFM tip and sample), possibly due to the confinement effects. The effect of modification of the AFM tip with alkanethiol molecules on the humidity dependence of Au(111) friction has also been investigated.     

Nanotribological Studies of Chromium Thin Films

Systematic nanotribological studies of Cr thin films using nanoscratch and AFM techniques are presented. Constant and ramped loading scratches were made using a Nano Indenter II system at various loads (1mN, 2.5mN and 5mN). Extensive AFM studies of the scratch wear tracks have been performed after scratching. The dependence of the displacement, residual wear depth, percent elastic recovery, and friction coefficient on load in constant load and ramped load tests is compared. Under the same (maximum) load, constant load tests exhibit higher displacements, residual depths and friction coefficients but lower percent elastic recoveries. Detailed AFM observations of the wear tracks indicate that significant differences in lateral deformation accompany the observed displacement differences.     

Nanotribological Properties of Amorphous Carbon-Fluorine Films

An investigation of the friction on the nanoscale was performed on amorphous carbon-fluorine films deposited by plasma-enhanced chemical vapor deposition. A direct correlation between friction forces, measured by lateral force microscopy in air, and the contact angles of the films was observed. The dependence of friction on the relative scanning velocity was also studied. The results show that the friction dependence on the velocity is influenced by the films' surface wettability. It is also shown that as the fluorine content in the films increases, there is an increase in the dependence of friction on the scanning velocity. These results highlight the influence of the capillary condensation of water between the moving parts on the nanoscale friction.     

Characterization of mixed self-assembled monolayers for immobilization of streptavidin using chemical force microscopy

Mixed self-assembled monolayers (SAMs) to immobilize streptavidin on a gold surface were investigated by measuring the pull-off force between an AFM tip and a biotin-modified surface using CFM. Biotin-LC-NHS was modified on SAMs prepared from a mixed solution of cystamine and MEOH. Increased pull-off forces between the AFM tip and the surface were observed with an increased cystamine mole fraction in the solution. Streptavidin was immobilized onto biotin-LC-NHS modified mixed SAMs and analyzed by tapping AFM. Also, the formation of mixed SAMs containing MUOH and MBDA was confirmed using CFM. The measured pull-off forces on the only MBDA surface were larger than those on the surface with MUOH. These results can be applied to determine an optimal mixing ratio of MUOH and MBDA SAMs that reduces non-specific streptavidin binding onto a surface.     

硅烷化单晶硅表面自组装ZrO2薄膜及其摩擦学性能研究

利用自组装成膜技术在磺酸化的MPTS自组装单层薄膜表面制备了ZrO2薄膜,应用接触角测定仪、X射线光电子能谱仪(XPS)、原子力显微镜(AFM)分析了薄膜的组成和结构。结果表明：该ZrO2薄膜比较致密、无裂缝,呈“准二维”特征,且与基底的牢固性好。摩擦磨损试验表明：ZrO2薄膜经500℃烧结处理后适于在低负荷、低滑动速度下作为减摩、抗磨保护性涂层。     

Macroscopic Tribological Testing of Alkanethiol Self-assembled Monolayers (SAMs): Pin-on-disk Tribometry with Elastomeric Sliding Contacts

We demonstrate that the frictional properties of alkanethiol self-assembled monolayers (SAMs) with various surface-chemical and structural features can be investigated on a macroscopic scale by employing an elastomer as the sliding partner in pin-on-disk tribometry. The mild contact conditions at the elastomeric tribological interface allow the SAM films to remain virtually intact despite the tribological stress. Sliding contact between SAMs and elastomers over the speed range available from an ordinary tribometer in a liquid environment induced a broad range of lubrication mechanisms, ranging from boundary to fluid-film lubrication regimes. Thus, the impact of both the chemical and structural characteristics of SAMs on the formation of fluid films and interfacial friction forces could be probed in the absence of wear processes. Given the large SAM “toolbox” that is readily available for the modification of surface-chemical characteristics, this approach provides an opportunity to investigate the influence of surface chemistry on the frictional properties of elastomeric tribological contacts.     

沉积时间对MPTS自组装膜摩擦学性质的影响

利用分子自组装技术在羟基化后的单晶硅硅片表面制备(3-巯基丙基)三甲氧基硅烷(MPTS)自组装膜,用X射线光电子能谱仪(XPS)对薄膜的表面结构进行表征,用JGW-360a型接触角测量仪测量硅片表面的接触角,用UMT-200型微观摩擦磨损实验机测量硅片的摩擦因数,探讨沉积时间对自组装膜的摩擦学性能的影响。结果表明:MPTS自组装膜具有亲水疏水性能,其对水的接触角超过60°;硅片表面沉积MPTS可以大幅度降低硅片的摩擦因数,使硅基片表面的摩擦因数由无膜时的0.6降至0.25左右,且具有很好的耐磨性;沉积时间对硅表面自组装膜的摩擦学性能影响较大,在本实验条件下,0.5 h沉积时间所制备的MPTS-SAM硅片的耐磨性最佳,1 h沉积时间制得的硅片表面最为光滑。