【作者】 杨广彬；

【导师】 张平余；

【作者基本信息】 河南大学 ， 凝聚态物理， 2012， 博士

【摘要】 本文分别采用不同的制备方法合成出Cu纳米微粒,研究了其摩擦学行为,揭示了其在摩擦副表面减摩、抗磨和修复的作用机理。(1)借助聚电解质多层膜(PEMs)中的“纳米反应器”,通过一系列Cu2+离子的吸附和NaBH4溶液的还原组成的反应循环,在聚电解质多层膜内原位生成了Cu纳米微粒,合成出的纳米微粒粒径分布在3～20nm。并且随反应循环次数的增加,Cu纳米微粒的粒径和密度增加。研究了反应循环数对Cu纳米颗粒聚电解质多层复合膜的摩擦学行为的影响,研究表明适量的Cu纳米微粒既能使薄膜内部的Cu纳米微粒发挥出支撑强度和增加硬度的作用,也能保证外部的聚合物分子链有一定的柔韧性和灵活性,从而使复合膜具有优异的摩擦学性能。在Cu纳米颗粒聚电解质多层复合膜的表面修饰氟硅烷,构成疏水的铜纳米微粒聚电解质多层复合膜。反应循环数和聚电解质多层复合膜的双层数对疏水铜纳米微粒聚电解质多层复合膜的润湿性和摩擦学行为有很大的影响；研究了在水润滑和干态下疏水铜纳米微粒聚电解质多层复合膜的摩擦学行为。结果表明,表面疏水性越强,其耐磨寿命越长。使用表面修饰带有氨基的SiO2与聚烯丙胺盐酸盐(PAH)和聚丙烯酸(PAA)以旋涂辅助的方法引入到聚电解质多层膜中,形成(PAH/PAA)3(SiO2/PAA)3(PAH/PAA)3和(SiO2/PAA)9不同结构的薄膜。然后加热处理,使组分间的氨基与羧基发生酰胺化反应,使层间结合力由静电力转化为共价键。考察加热后薄膜结构对摩擦学行为的影响。结果表明,具有“三明治”结构的(PAH/PAA)3(SiO2/PAA)3(PAH/PAA)3薄膜有助于提高复合膜的摩擦学性能。因为复合膜中的最外层(PAH/PAA)3能够消除中间层产生的缺陷,又允许中间层(SiO2/PAA)3的纳米微粒提高其强度和硬度,同时又使暴露在外表面的有机分子保持柔韧性和灵活性。最内层(PAH/PAA)3的既要锚固在Si基底上,又对SiO2纳米微粒起着重要的“床”的作用,供它居住于其中,结果固定在薄膜中的纳米微粒起到了承载能力和“微轴承”效应,使薄膜具有良好的摩擦学性能。(2)分别以低S或无S、P的二辛基二硫代氨基甲酸、硫醇、烷基羟肟酸为修饰剂,水合肼为还原剂,采用水/油两相萃取法,合成原位表面修饰的Cu纳米微粒。分别采用红外光谱、X射线衍射仪、透射电子显微镜对纳米颗粒的尺寸、形貌和结构进行表征。研究了不同修饰剂与Cu纳米微粒的作用规律。这几种修饰剂分别以不同结构形式的化学键结合在Cu纳米微粒的表面。深入系统地研究了表面修饰Cu纳米微粒作为润滑油添加剂的摩擦学行为,表面修饰Cu纳米微粒作为润滑油添加剂具有优异的抗磨性能,这可能是由于铜的熔点低,易于沉积到摩擦副表面形成保护膜；另外,表面修饰Cu纳米微粒能填充摩擦副表面的微坑,发挥出自修复作用。(3)根据摩擦化学中润滑油添加剂分子设计的理念,设计并合成出新型的无S、P的直链型和杂环型硼酸酯润滑油添加剂。评价了其在液体石蜡中的摩擦学性能。采用SEM, XPS或EDS对磨斑进行了分析,结果表明：硼酸酯提高了基础油液体石蜡的承载能力和抗磨性能,磨斑直径明显减小。这是由于硼酸酯添加剂在摩擦副表面形成了氧化硼、氧化铁、含N化合物和其它无机盐等组成的保护膜。在摩擦过程中发生了化学反应,生成的化学反应膜和吸附膜,改善了基础油的摩擦学性能。更多还原

【Abstract】 In this dissertation, surface-modified Cu nanoparticles were synthesized by different methods. The tribological behaviors were studied to explore the anti-wear and friction reducing mechanism of the Cu nanoparticles.(1) Polyelectrolyte multilayers (PEMs) fabricated by spin-assisted layer-by-layer assembly technique were used as "nanoreactors" for in situ synthesis of Cu nanoparticles, initiated by a series of reaction cycles in which Cu2+was absorbed into the polymer-coated silicon substrate and reduced in NaBH4solution, allowing generation of Cu nanoparticles polyelectrolyte multilayers. The as-prepared Cu nanoparticles were small with a size distribution ranging from3-20nm. Futhermore, the size and the density of Cu nanoparticles in PEMs increased with the number of reaction cycle increasing. And the tribological behaviors of Cu nanoparticles PEMs were also affected by the reaction cycles. PEMs reinforced with appropriate density and size of Cu nanoparticles possess considerably good tribological behavior, allowing nanoparticles therein to maintain strength and robustness while keeping soft and fluid-like exposed surface of the polymer chain at the optimum amount of Cu nanoparticles in the PEMs.Then the surface of Cu-nanoparticles PEMs was modified by fluoroalkylsilane (FAS-17) with low surface energy, generating hydrophobic Cu nanoparticles PEMs. The tribological behavior and wettability of the hydrophobic Cu nanoparticles PEMs were affected by the number of reaction cycles and the number of bilayer of PEMs. And the tribological behaviors of hydrophobic Cu nanoparticles PEMs were also studied under water lubrication than under dry-sliding. The result show that the more hydrophobic the surfaces are, the longer the antiwear life is.SiO2nanoparticles capped with y-aminopropyltrimethoxysilane were doped into polyelectrolyte multilayer films via spin-assisted layer-by-layer self-assembly. The resulting nano-SiO2-doped different composite films (SiO2/PAA)9and (PAH/PAA)3(SiO2/PAA)3(PAH/PAA)3. The amide bond (-CONH-) was formed between not only PAH and PAA but also SiO2and PAA after heating at a proper temperature to transform the adhesion from static electricity to covalent bond. The tribological behavior of the multilayer films was evaluated on a micro-tribometer. It was found that the "sandwich-like" structure (PAH/PAA)3(Si02/PAA)3(PAH/PAA)3was beneficial to contributed to increasing the wear resistance of multilayer film. Namely, the outermost strata of (PAH/PAA)3in composite multilayer film were able to eliminate defects associated with the middle strata, allowing the nanoparticles therein to maintain strength and robustness while keeping soft and fluid-like exposed surface and hence decreasing shearing stress during sliding. And the inner strata of (PAH/PAA)3well anchored to Si substrate acted as an initial "bed" for SiO2nanoparticles to be inhabited, resulting in better antiwear ability associated with good load-carrying capacity and "miniature ball bearings" effect as well of SiO2nanoparticles.(2) Cu nanoparticles surface-modified by dioctylamine dithiocarbamate, alkanethiolate and tetradecyl hydroxamic acid were synthesized with hydrazine hydrate as a reductant using a two-phase extraction route. The size, morphology and structure of resultant surface-capped Cu nanoparticles were analyzed by means of infrared spectrometry, X-ray diffraction and transmission electron microscopy. And the different modifier bond to Cu nanoparticles with different structure chemical bonds. The tribological behavior of surface-modified Cu nanoparticles as an additive in liquid paraffin was evaluated with a four-bail machine. Results show that as-synthesized surface-modified Cu nanoparticles as additive in liquid paraffin have excellent antiwear ability, This is because surface-capped Cu nanoparticles with a low melting point are able to deposit on sliding steel surface to form a good protective film thereon; also because surface-capped Cu nanoparticles can fill up micro-pits on the rubbing steel surface and exert self-repairing function.(3) From the point view of molecular design, two kinds of straight-chain and heterocyclic S-and P-free borate esters as environmental friendly lubricant additive were synthesized. The tribological properties of the borate esters as additive in liquid paraffin were investigated on a four-ball tester. The morphologies and the chemical components of the worn scars were analyzed by means of scanning electron microscopy and X-ray photoelectron spectroscopy or energy dispersive spectrometer. The results showed that the load-carrying capacity and the antiwear performance of the liquid paraffin with the additive added were improved, and wear scar diameter was decrease in comparison with the base oil. This may be closely related to the protective film consisting of boron oxide, Fe2O3, N-containing compounds and other inorganic salts formed during the friction process. And the tribochemical reaction films and physisorption films formd during the friction process play a certain role in reducing wear.更多还原