【作者】 徐磊华；

【导师】 江利；

【作者基本信息】 中国矿业大学 ， 矿物材料工程， 2011， 博士

【摘要】 在科学技术高速发展的时代,许多电子机械器件逐渐向微型化、多功能集成化、质量轻、智能化的方向发展,促使微电子机械系统(mircroelectromechanical system, MEMS)和纳电子机械系统(Nanoelectromechanical system, NEMS)的出现,并且受到各方的广泛关注。微电子机械系统尺寸微型化后,器件之间的间隙非常小,通常处于纳米级范围内,相对滑移表面之间的摩擦及磨损行为对微电子机械系统的稳定性和可靠性产生很大的影响。降低器件表面的粘附力,减小摩擦,改善抗磨损性能是确保微电子机械系统高速稳定运转的关键问题。材料表面改性被认为是解决这一关键问题的有效途径,其中近二三十年发展起来的分子自组装技术为解决这一难题提供了新的思路目前,由于单晶硅在MEMS中普遍应用,有机硅烷在单晶硅基片上的自组装膜的摩擦磨损性能研究得到广泛关注。研究结果表明:有机硅烷自组装膜能够有效降低单晶硅表面的粘附力,起到减摩降磨的效果,但其抗磨损性能不尽如人意。为此,我们将自润滑性能良好的无机纳米粒子组装到具有活性官能团的有机分子自组装膜表面,形成有机-无机复合自组装膜,以期提高自组装膜的抗磨损性能。采用湿化学还原法制备得到尺寸均一的Au溶胶,然后利用巯基(-SH)与Au之间能够形成共价键的作用,将Au纳米粒子组装到3-巯基丙基三乙氧基硅烷(MPTS)组装膜表面,形成MPTS/Au复合自组装膜。用X射线光电子能谱仪测定薄膜的化学成分;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,并分析了自组装膜摩擦学性能与表面形貌、表面性质之间的关系。水在MPTS薄膜上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MPTS分子在单晶硅基片上的自组装是逐层进行的,当MPTS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。Au纳米粒子在MPTS薄膜上组装后,使得水在薄膜表面的接触角增大,自由能降低,表面粗糙度有所下降,摩擦系数减小,耐磨性能得到极大的改善。我们还从化学热力学角度分析了Au纳米粒子在MPTS薄膜表面组装的可能性,并根据接触角随组装时间的变化,从化学动力学角度分析了Au纳米粒子在MPTS薄膜表面自组装的可行性。此外,我们还试验将十八烷基三甲氧基硅烷(OTS)分别与3-胺基丙基三乙氧基硅烷(APTES)和3-巯基丙基三甲氧基硅烷(MPTS)组合,在羟基化单晶硅基片上制备得到分子碳链不同、端基不同的双组分有机自组装膜,比较了双组分有机硅烷自组装膜与单组分自组装膜的不同,考察了双组分有机硅烷自组装膜的摩擦学性能随载荷、滑移速度的变化情况。APTES、MPTS、OTS及OTS/APTES, OTS/MPTS都能有效地减小基片的摩擦。在法向载荷为20g,滑移速率为2mm/s的测试条件下,单晶硅基片的摩擦系数是0.76,APTES薄膜的摩擦系数是0.25,MPTS薄膜是0.2,OTS薄膜为0.06,OTS/APTES双组分薄膜为0.06,OTS/MPTS双组分膜为0.06。APTES与MPTS薄膜的耐磨损性能较差,很快被磨穿。OTS薄膜及其复合膜的减摩降磨效果都很好,试验周期内其摩擦系数都保持不变,尤其复合膜的摩擦系数波动很小,稳定性比OTS单组分膜更佳。该论文有图51幅,表8个,参考文献172篇更多还原

【Abstract】 As the rapid development of science and technology, many electronic component are gradually microminiaturizing, multifunction integrating, intelligentizing and having ligter weight. These development precipitate emerge of micro/nanoelectro mechanical systems(MEMs/NEMs). As the dimension of the systems decrease sharply, the interfacial clearance between the components are always a few of nanometers. Therefore tribological limitations such as stiction, friction and wear are the major problems that limited the efficiency, power output, steady-state motion, and reliability of MEMS/NMES devices. Therefore controlling the surface force as adhesion and friction acting in devices on the molecular level is of critical importance to successful operation of MEMS systems. Surface modification is regarded the effective approach to reducing the adhesion and friction in MEMS device. Attempt to deposit the organosilane films on the hydroxylated silicon substrate have been employed to reduce the adhesion between the contacting surfaces.MEMS components are routinely made from Si, which is a poor triblologycial material. The tribological properties of organosilane SAMs deposited on monocrystalline silicon were studed entensively. The results indicated that the organsilane SAMs possess excellent lubrication and adhesive-resistant ability. However, the SAMs could be worn easily. In order to improve anti-wear ability of SAMs, some kinds of inorganic nanoparticle with fine self-lubricating ability were bonded to surface modificated with function group by chemical force.Gold colloids were prepared via chemical reduction of HAuCl4 using sodium citrate as reductant. The Au nanoparicles were covalently bonded to silicon wafers surface modified with sulfhydryl group through Au-S bonds and form MPTS/Au composite film.The chemical composite of films were characterized by X-ray photoelectron spectroscopy (XPS); the contact angles of ultra-pure water on the MPTS films were determined with JC2000PC contact angle meter. Atomic force microscope (AFM) has been employed to study the morphology of the prepared films. The tribological properties of as-prepared films were tested on tribometer in a ball-on-plate contact configuration. It was investigated that the influence of surface topography and surface property on the tribological behavior.Some properties of films deposited on silicon wafers changed after Au nanoparticles convalently bonded to MPTS films, for example, contact angle increased and surface Gibbs free energy decreased. The change of surface properties improved the tribological behavior of films. The contact angle of MPTS/Au dual-layers film is greater than that of MPTS film; the surface roughness of the dual-layers is lower than the MPTS, so the friction coefficient is lower than that of the MPTS films. Furthermore, the feasibility of Au colloids chemisorbed on the thiol modified silicon wafer surface were analysed from angle of thermodynamics. According to the variation of contact angle with assembly time, we studied the practicability of the reaction between the Au and sulfhydryl group.In addition, the dual-components films with different chain length and functional group were prepared by self-assembling technology and the tribological properties of as-prepared films were evaluated on a friction and wear tester. It was found that the friction coefficients of MPTS and APTES film were higher than that of the OTS/MPTS and OTS/APTES dial-component films. Moreover, the results indicated that APTES and MPTS films have poor anti-wear ability, whereas the OTS/MPTS and OTS/APTES have fine anti-wear ability and stable friction coefficient.In this paper, there are 52 figures, 8 tables and 172 reference articles.更多还原