PDDA/PSS分子沉积膜的摩擦学行为研究

以聚对苯乙烯磺酸钠为聚阴离子,聚二烯丙基二甲基胺盐酸盐为聚阳离子在基底上交替沉积制备分子沉积膜。用紫外-可见吸收光谱仪、接触角测量仪、原子力显微镜对所制备的有序薄膜进行了表征。用UMT-2摩擦仪考察了超薄膜的摩擦学行为,结果表明,所制备的超薄膜具有良好的减摩抗磨性能,薄膜的表面电荷及亲水、疏水性对其摩擦学行为有较大影响,负电荷表面、亲水性强的表面在较高湿度下,耐磨寿命较长。     

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。     

C60自组装单分子膜的制备及其磨擦特性

利用胺基与C60分子的加成反应,在3-胺基丙基-三乙氧基硅烷(APS)的自组装单分子膜(SAMs)表面上成功的制备了与基底化学键结合的C60-SAMs.其表面水接触角约为76°,膜厚约为1.15 nm,AFM形貌像显示其表面光滑、均匀,基本不含缺陷.摩擦学结果表明,APS自组装单分子膜由于其分子链短,膜的有序性差,表面颗粒聚集物及"针孔"等缺陷多,而不具有润滑作用.当在其上形成C60单分子层膜后,表现出优异的摩擦学性能,摩擦系数约为0.09～0.13,在给定实验条件下抗磨损寿命大于10 000次,有望作为微型机械的边界润滑材料使用.     

纳米二氧化铈与蛇纹石混合物作为润滑油添加剂的摩擦学性能研究

采用表面活性剂将蛇纹石、纳米二氧化铈以及他们的混合物稳定分散于PAO4基础油中,利用摩擦磨损试验机分别考察蛇纹石、纳米二氧化铈以及蛇纹石与二氧化铈混合物作为润滑油添加剂的摩擦学性能,借助金相显微镜观察磨损表面形貌并测量磨斑直径,并采用能量色散谱仪(EDS)分析磨损表面的元素组成。结果表明:蛇纹石、纳米CeO_2和蛇纹石/CeO_2复合颗粒都可以显著改善润滑油的减摩抗磨性能,而添加蛇纹石/CeO_2复合添加剂的润滑油的摩擦学性能更佳,其中添加质量分数0.25%纳米二氧化铈与0.25%蛇纹石混合物的润滑油的摩擦学性能最佳。蛇纹石/CeO_2复合颗粒优异的摩擦学性能归因于其在磨损表面形成了吸附膜和Fe_2O_3、SiO_2化学反应膜,其中Ce元素可能起到了催化剂的作用。     

两亲性纳米微球的制备及水润滑性能

水溶性纳米微球作为润滑添加剂成为润滑领域的重要发展方向。通过简单的无皂乳液聚合制备聚(苯乙烯-甲基丙烯酸3-磺酸丙酯钾盐)[P(St-co-SPMA)]两亲性纳米微球，通过改变聚合单体、微球浓度以及载荷，利用摩擦磨损试验机考察聚苯乙烯(PSt)和P(St-co-SPMA)2种纳米微球作为水润滑添加剂的摩擦学性能。结果表明：具有复合结构的两亲性纳米微球作为水润滑添加剂起到了非常优异的减摩抗磨性能，这是由于亲水单体的加入在微球表面形成水化层，避免了摩擦副之间的直接接触且保护了摩擦表面，有效改善了界面摩擦性能；2种纳米微球在高载荷下有着更为优异的减摩与抗磨性能，证明了纳米微球优异的承载能力。该研究为设计高效水润滑添加剂提供了新的思路，在生物润滑领域有着广阔的应用前景。     

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。     

制备条件对磷脂酰胆碱单分子膜相变行为的影响

目的全面探讨制备条件对LB膜相变行为的影响可获得试验室特定设备及条件下制备磷脂LB膜的最佳条件.方法用热力学相变理论类比描述了单分子膜的相变过程理论,并通过该理论,以π-A 曲线和相变过程为主要分析点,系统地研究了磷脂铺展量、铺展浓度、铺展溶剂、铺展时间、压膜速度、亚相温度、亚相pH值等七大因素对成膜质量的影响.结果磷脂铺展量、亚相的温度和pH值对磷脂单分子膜的质量影响最大,铺展浓度、铺展溶剂、铺展时间的影响要小得多,而在一定范围内压膜速度的大小基本上不影响膜的质量.结论50μL,0.67mmol/ml的磷脂/乙醚溶液在pH6.8的亚相上铺展20min并以5mm/min的速度挤压单分子膜可获得完整的π-A曲线.     

氧化石墨烯和纳米SiO2增强PTFE复合材料的摩擦磨损行为

为研究具有层状结构和球状结构的纳米填料之间的相互作用对聚四氟乙烯（PTFE）复合材料摩擦磨损行为的影响,采用冷冻干燥超声共混-冷压-热烧结法制备纳米二氧化硅（nano-SiO2）和氧化石墨烯（GO）填充改性PTFE复合材料。利用LSM-2R往复式摩擦磨损试验机测试干摩擦条件下nano-SiO2和GO复配改性PTFE复合材料的摩擦学性能,采用MicroXAM-800非接触式三维表面轮廓仪、扫描电子显微镜(SEM)和能谱仪(EDS)分析表征转移膜形貌、元素分布和磨痕表面三维形貌,从微观层面揭示nano-SiO2和GO的减摩机制。结果表明：单独填充nano-SiO2与GO均可改善PTFE复合材料的摩擦学特性,其中在较低添加量下,GO在提高PTFE耐磨性方面明显优于nano-SiO2;GO和nano-SiO2复配填充时存在协同效应,与单一填充相比进一步改善了复合材料的摩擦学性能;相比于纯PTFE,3%nano-SiO2/0.5%GO/PTFE复合材料的磨损率降低60.36%。机制分析表明,协同作用和均匀连续转移膜的形成是nano-SiO2和GO增强PTFE复合材料性能优异的主要原因。     

磷型极压抗磨剂对双酯摩擦学性能的影响

采用四球摩擦试验机研究磷酸三甲酚酯（T306）和硫代磷酸铵盐（T307）2种磷型极压抗磨添加剂在双酯中的摩擦学性能;采用扫描电子显微镜（SEM）分析钢球磨损表面的微观形貌,采用X射线光电子能谱仪（XPS）分析摩擦表面典型元素的化学状态,进而对摩擦机制进行探讨。结果表明,在所考察的添加剂添加量和载荷范围内,2种添加剂均可不同程度地改善双酯的摩擦学性能,其中,T307在双酯中展现出更为优异的减摩抗磨以及极压性能,其综合性能优于T306。SEM和XPS分析表明,添加剂分子在摩擦副表面发生了复杂的摩擦化学反应,在摩擦表面上形成了复杂的含有S、P、N等元素的边界润滑膜,从而起到一定的降低摩擦磨损的作用。     

二氧化硅微米球与纳米粒子膜间的摩擦研究

通过旋涂法制备表面粗糙度为(57±1.7)nm的SiO2纳米粒子膜来模拟纳米器件的基底。采用原子力显微镜胶体探针,分别对有无正辛基三氯硅烷修饰时,该体系的纳米摩擦学性能进行评价。结果表明:二氧化硅胶体探针与SiO2纳米粒子膜之间的黏着力和摩擦力均随着法向载荷增加而增大,而经正辛基三氯硅烷修饰后,该自组装膜能显著改善SiO2表面间的摩擦学性能,起到明显减摩擦抗黏的效果。     

Developing of N‐(4‐methylpyrimidine‐2‐yl)methacrylamide Langmuir–Blodgett thin film chemical sensor via quartz crystal microbalance technique

In the present work, the characterization and gas sensing properties of newly synthesized N‐(4‐methylpyrimidine‐2‐yl)methacrylamide ( N‐MPMA ) monomer Langmuir–Blodgett (LB) thin films were investigated. The UV–visible spectroscopy, quartz crystal microbalance (QCM), and atomic force microscopy were utilized to characterize N‐MPMA LB thin films. The surface behavior of N‐MPMA monolayer was stable and allowed an effective transfer at a surface pressure of 14 mN/m. The mass change/unit area value of the N‐MPMA LB thin film deposited quartz crystal surfaces was investigated. The amount of N‐MPMA LB thin film deposited on the substrate for bilayer was calculated as 228.72 ng (86.31 ng/mm²) and 12.5 Hz frequency shift was observed for each layer of the N‐MPMA film. The kinetic responses of N‐MPMA LB film against chloroform, dichloromethane, benzene, and toluene were measured via QCM system at room temperature. N‐MPMA QCM sensor results displayed that chloroform has the largest frequency shifts compared with the other vapors used in the present work and these results can be illuminating in terms of physical properties of organic vapors.     

Amorphous hydrogenated carbon films for tribological applications I. Development of moisture insensitive films having reduced compressive stress

Although earlier investigations on the tribological behaviour of amcrphous hydrogenated carbon (AHC) films in sliding contact with steel showed encouraging results, four open issues were identified. They were: (a) dependence of friction and wear on humidity (i.e., the friction coefficient and the wear increased with humidity), (b) limitations on film thickness (i.e., films greater than 2 μm thick delaminated due to large compressive stress), (c) deposition of films on substrates other than silicon and (d) lubricant compatibility (i.e., formation of lubricant-derived antiwear films on AHC film surfaces). Steps were taken to address some of these open issues by incorporating silicon in AHC films. Friction and wear tests were conducted on AHC films containing various amounts of silicon. Incorporation of silicon in AHC films rendered the friction coefficients and the wear of a steel counterface insensitive to moisture. Silicon incorporation in AHC films also significantly reduced compressive stress. This allowed deposition of 10 μm thick films. These effects were achieved without any compromise with the friction coefficient and the film wear if the amount of silicon in the film was kept within a certain concentration range. In addition, silicon-containing AHC films were thermally more stable than silicon-free films. Experiments conducted with two lubricants resulted in significantly lower wear of the silicon-free AHC films than that obtained for unlubricated sliding. Similar friction coefficients were obtained for AHC film/steel and steel/steel combinations in lubricated sliding.     

Investigation of the Tribological Behaviors of Polymer Molecular Deposition Films by Tribometer Based on Interferometer

The polymer molecular deposition films including polyelectrolyte molecular deposition (PEMD) film and nanoparticles composite molecular deposition (NPs/MD) film have been prepared using the molecular deposition method and the in situ synthesize method. The polymer molecular deposition films were characterized by atomic force microscope (AFM) and X-ray photoelectron spectroscopy (XPS). The tribological behaviors of the substrate and polymer molecular deposition films were investigated by a tribometer based on interferometer. It is found that the NPs/MD film has a lower friction force and a better anti-wear property than the PEMD film under the dry friction. The poly alpha olefin (PAO2) and water films confined between samples and steel ball surfaces have been investigated using thin film interferometry. The friction force of substrate was lower than the polymer molecular deposition films under PAO2 lubrication. The friction forces alteration of PEMD film and NPs/MD film were similar and consistent, and lower than that for substrate under water lubrication.     

The tribological behaviors of ordered system ultrathin films

The tribological behaviors of various long chain organic molecule LB films, organic molecule modified inorganic nanoparticle LB films, and the C₆₀-LB films were systematically investigated. The correlation between the structure and tribological behavior of the LB films has been explored, while the structural changes of the LB films during friction process were analyzed with Fourier transform infrared (FTIR) microscope. Three kinds of C₆₀-LB films were prepared; its micro-frictional behaviors were investigated by AFM. As the results, the tribological behavior of long chain organic molecule LB films is highly dependent on the molecular chain length and the characteristics of the polar end groups. The optimal tribological behavior is reached at a balanced stiffness and toughness of the molecular chain, which is also related to the bonding strength of the LB film to the substrate. The LB films of nanoparticles modified with organic molecules are superior to long chain organic molecule ones in terms of resisting wear. This is attributed to the enhanced load-carrying capacity of the inorganic nanocores in the LB films of nanoparticles modified with organic molecules. The tribochemical changes including ordering and partial decomposition of the organic modifier have been observed in the sliding of the LB films of inorganic nanoparticles modified with organic molecules against steel. C₆₀-LB film shows excellent tribological behavior, which is highly dependent on the interaction between the C₆₀ nanocluster and the organic long chain molecules.     

Tribological Properties of Langmuir–Blodgett Films on Silicon Surface in Microscale Sliding Contact

Microtribological properties of Langmuir–Blodgett (LB) films transferred from behenic acid (BehA), 2,4-heneicosanedione (HD) and its copper complex ((HD)₂Cu) onto silicon surface were examined. To better understand the wear resistance performance of these LB monolayers, a comparison was made with a chemically grafted octadecyltrichlorosilane (OTS) monolayer. Auger electron spectroscopy (AES) was used for identification of the chemical composition of the monolayers, worn areas and counterpart surfaces. We observed that the studied LB films in microscale sliding contact exhibited stable friction properties comparable to OTS, and better wear performance than OTS at high contact pressure. The tribological properties of these LB monolayers were explained in terms of molecular packing density and molecular transfer to the counterpart surface. The relationship between the wear resistance of the studied LB films and the degree of molecular packing of the surfactants indicated that the wear properties of the LB films are strongly associated with the degree of molecular packing. We suggest that the steady low friction and high wear resistance of the BehA monolayer may partly be attributed to the transfer of the amphiphilic molecules to the counterpart surface in the contact region.     

A biomimetic approach for effective reduction in micro-scale friction by direct replication of topography of natural water-repellent surfaces

In this paper, we report on the replication of surface topographies of natural leaves of water-repellent plants of Lotus and Colocasia onto thin polymeric films using a capillarity-directed soft lithographic technique. The replication was carried out on poly(methyl methacrylate) (PMMA) film spin coated on silicon wafer using poly(dimethyl siloxane) (PDMS) molds. The friction properties of the replicated surfaces were investigated at micro-scale in comparison with those of PMMA thin film and silicon wafer. The replicated surfaces exhibited superior friction property when compared to those of PMMA thin film and silicon wafer. The superior friction behaviour of the replicated surfaces was attributed to the reduced real area of contact projected by them.     

PECVD法硅基氮化硅薄膜的制备及其耐磨性研究

以N(111) 型的单晶硅片为基体,运用PECVD-2D等离子体化学气相淀积台在单晶硅片表面沉积氮化硅薄膜,通过薄膜颜色与厚度间的关系探讨了制备工艺参数对薄膜厚度的影响,用原位纳米力学测试系统对氮化硅薄膜的纳米硬度进行测定,在UMT-2型摩擦试验机上对不同制备工艺的硅基氮化硅薄膜进行耐磨寿命试验.结果表明:随着沉积温度的升高,薄膜厚度逐渐递减,SiH4和N2流量比越大,薄膜厚度越大;温度越高,薄膜硬度越大,耐磨寿命越长;随着SiH4和N2流量比的增加,薄膜硬度和耐磨寿命均先增加后减小.     

Lift-off patterning of thin Au films on Si surfaces with atomic force microscopy

We studied a new lift-off process of thin Au film on silicon surfaces in nanometer-scale, combining anodic oxidation patterning with AFM, deposition of Au thin film on the patterned substrate and chemical etching processes of the Si oxide underneath the Au film. For Au films of thickness of 2-5 nm, the Au films on the Si oxide patterns were left unbroken and bent down to stick to Si surface after the removal of the oxide by the chemical etching. For an Au film of 1 nm in thickness, it was possible to lift-off the Au film on oxide patterns of the lines and dots in nanometer-scale using Si oxide as a sacrificial mask.     

AZO薄膜理想表面形貌的制备与加工工艺优化

非晶硅薄膜太阳能电池主要采用掺氟氧化锡(FTO)导电玻璃作为基板,但FTO薄膜雾度较低、表面形貌无法优化,导致无法得到较优的陷光结构,从而限制了太阳能电池的转换效率。为了进一步提升太阳能电池的转换效率,探讨了替代型的掺铝氧化锌(AZO)薄膜,通过优化前段磁控溅射镀膜工艺和后段湿化学蚀刻工艺,用以平衡AZO薄膜的光电性能和雾度,从而获得具有理想表面形貌的AZO导电玻璃,使其成为理想的非晶硅薄膜太阳能电池的基板材料。实验表明,经工艺优化后制作的AZO导电玻璃可提升光电转换效率。     

Small amplitude reciprocating wear performance of diamond-like carbon films: dependence of film composition and counterface material

Small amplitude (50 μm) reciprocating wear of hydrogen-containing diamond-like carbon (DLC) films of different compositions has been examined against silicon nitride and polymethyl-methacrylate (PMMA) counter-surfaces, and compared with the performance of an uncoated steel substrate. Three films were studied: a DLC film of conventional composition, a fluorine-containing DLC film (F-DLC), and silicon-containing DLC film. The films were deposited on steel substrates from plasmas of organic precursor gases using the Plasma Immersion Ion Implantation and Deposition (PIIID) process, which allows for the non-line-of-sight deposition of films with tailored compositions. The amplitude of the resistive frictional force during the reciprocating wear experiments was monitored in situ, and the magnitude of film damage due to wear was evaluated using optical microscopy, optical profilometry, and atomic force microscopy. Wear debris was analyzed using scanning electron microscopy and energy dispersive spectroscopy. In terms of friction, the DLC and silicon-containing DLC films performed exceptionally well, showing friction coefficients less than 0.1 for both PMMA and silicon nitride counter-surfaces. DLC and silicon-containing DLC films also showed significant reductions in transfer of PMMA compared with the uncoated steel. The softer F-DLC film performed similarly well against PMMA, but against silicon nitride, friction displayed nearly periodic variations indicative of cyclic adhesion and release of worn film material during the wear process. The results demonstrate that the PIIID films achieve the well-known advantageous performance of other DLC films, and furthermore that the film performance can be significantly affected by the addition of dopants. In addition to the well-established reduction of friction and wear that DLC films generally provide, we show here that another property, low adhesiveness with PMMA, is another significant benefit in the use of DLC films.