Yujuan Zhang

Tribological properties of oleic acid-modified zinc oxide nanoparticles as the lubricant additive in poly-alpha olefin and diisooctyl sebacate base oils

Oleic acid (OA) modified ZnO nanoparticles with an average size of 4.04 nm were prepared via a facile in situ one-step route. The as-prepared ZnO nanoparticles were characterized by X-ray diffraction, transmission electron microscopy, and Fourier transform infrared spectroscopy. The light-absorbing performance and thermal stability of the as-prepared ZnO nanoparticles were evaluated by ultraviolet-visible light spectrophotometry and thermogravimetric analysis, and their tribological behaviour as the lubricant additive in poly-alpha olefin (PAO) and diisooctyl sebacate (DIOS) base oils was evaluated with a four-ball machine. The surface morphology of the wear scar was observed with a scanning electron microscope and a three-dimensional optical profiler, and the element composition of the wear scar was determined by energy dispersive spectrometry. It was found that the surface-capping of ZnO nanoparticles by OA helps to greatly increase their dispersibility and thermal stability. In the meantime, OA-modified ZnO nanoparticles can effectively improve the antiwear and friction-reducing abilities as well as the load-carrying capacity of the base oils, which is due to the formation of a tribofilm in association with the tribo-sintering and/or adsorption of the additives on the rubbed steel surfaces. Furthermore, the friction-reducing and antiwear performances of the as-prepared ZnO nanoparticles as lubricating oil additives seem to be closely related to the polarity of the base oils. Namely, the OA-modified ZnO additive exhibits better tribological behaviour in apolar PAO than in polar DIOS.

Large scale preparation of silver nanowires with different diameters by a one-pot method and their application in transparent conducting films

Silver nanowires (AgNWs) with varied diameters were synthesized by a facile and efficient one-pot polyol method. The effects of reaction conditions on the morphology of the as-prepared AgNWs as well as the transmittance and optoelectronic performance of the transparent conducting films made of AgNWs were investigated. Findings indicate that each run of the reaction of the established synthesis protocol can provide more than 10 g of AgNWs, and the dynamic balance between the reduction of Ag+ (yielding Ag0) and the formation of AgCl nanocubes has an important effect on the yield and morphology of AgNWs. Based on an appropriate adjustment of the reaction conditions, the average diameter of AgNWs can be adjusted in the range of 40–110 nm while the yield of one-dimensional nanostructures in the products is as much as 95%. Furthermore, the as-synthesized AgNWs can be easily spin-coated onto polyethylene glycol terephthalate substrate to afford transparent conducting films with a transmittance as high as 87% and a sheet resistivity below 70 Ω sq−1, which demonstrates that the present synthesis strategy could be of special significance for the commercial preparation and application of silver nanowires as an alternative to commercial indium tin oxide film.

Synthesis and tribological properties of oil-soluble copper nanoparticles as environmentally friendly lubricating oil additives

Purpose – The purpose of this paper is to synthesize oil-soluble copper (Cu) nanoparticles modified with free phosphorus and sulfur modifier and investigate its tribological properties as environment-friendly lubricating oil additives. Design/methodology/approach – To improve the anti-oxidation properties of these nanoparticles, two kinds of surface modifiers, oleic acid and oleylamine were used simultaneously. The morphology, composition, structure and thermal properties of as-synthesized Cu nanoparticles were investigated by means of transmission electron microscopy, X-ray powder diffraction, Fourier transform infrared spectrometry and differential thermal and thermogravimetric analysis. The tribological properties of as-synthesized Cu nanoparticles as an additive in liquid paraffin were evaluated with a four-ball friction and wear tester. Findings – It has been found that an as-synthesized Cu nanoparticle has a size of 2-5 nm and can be well dispersed in organic solvents. Tribological properties evalua...

Preparation and evaluation of tribological properties of oil-soluble rice-like CuO nanoparticles

Purpose – The purpose of this paper is synthesis of oil-soluble non-spherical nanoparticles modified with free phosphorus and sulphur modifier and investigation of their tribological properties as environment-friendly lubricating oil additives. Design/methodology/approach – To study the effect of morphology of nanoparticles on their tribological properties, rice-like CuO nanoparticles were synthesized. To improve the solubility of CuO nanoparticles in organic media, the in-situ surface modification method was used to synthesize these products. The morphology, composition and structure of as-synthesized CuO nanoparticles were investigated by means of transmission electron microscopy, X-ray powder diffraction, thermogravimetric analysis and Fourier transform infrared spectrometry. The tribological properties of as-synthesized CuO nanoparticles as an additive in liquid paraffin (LP) were evaluated with a four-ball tribometer. The morphology and elemental composition of worn steel ball surfaces were analysed ...

Study on the tribological behaviors of copper nanoparticles in three kinds of commercially available lubricants

Purpose The purpose of this paper is to study the tribological properties of Cu nanoparticles (NPs) as lubricant additives in three kinds of commercially available lubricants. Design/methodology/approach A four-ball machine is used to estimate the tribological properties of Cu NPs as lubricant additives in three kinds of commercially available lubricants. Three-dimensional optical profiler and electrical contact resistance are evaluated to investigate the morphology of the worn surfaces and the influence of Cu NPs on tribofilms. Findings Wear tests show that the addition of Cu NPs as lubricant additives could reduce wear and increase load-carrying capacity of commercially available lubricants remarkably, indicating that Cu NPs have a good compatibility with the existing lubricant additives in commercially available lubricants. Originality/value The tribological properties of Cu NPs as lubricant additives in three kinds of commercially available lubricants were investigated in this paper. These results are reliable and can be very helpful for application of Cu NPs as lubricant additives in industry.

Structure and mechanical properties of nc-TiC/a-C:H nanocomposite films deposited by filtered cathodic arc technique

Abstractnc-TiC/a-C:H nanocomposite films were prepared by filtered cathodic arc technique. The influence of C2H2/Ar flow ratio on the composition, structure, and mechanical properties of films was investigated by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, nanoindentation, and ball-on-disc tribometry. The films show a nanocomposite structure in which TiC crystallites are embedded in the amorphous matrix of a-C:H phase. C content in films increases with the flow ratio of C2H2/Ar, simultaneously, the crystallite size of TiC decreases. Contrary to the nc-TiC/a-C:H films deposited by magnetron sputtering in which the sp3 C content increases with C2H2 flow rate, the increase of C2H2 flow rate leads to the increase of sp2 C content in films deposited by filtered cathodic arc technique. The nc-TiC/a-C:H films deposited by cathodic arc technique have a pronounced hardness maximum of 30 GPa under the C2H2/Ar flow ratio of 12. Tribological performance of films is controlled by the sp2 content in films. Higher sp2 content promotes the formation of graphite-like transfer layer during sliding, and results in lower wear rate and friction coefficient.

Preparation of Nickel-Based Nanolubricants and Investigation of their Tribological Behavior

In situ surface-modification technique is adopted in present research to fabricate a series of Ni nanoparticles as well as Cu@Ni nanoparticles with different size and morphology. The correlation among the composition, structure, size, and morphology and tribological properties of as-synthesized additives were explored, and the frictionreducing, antiwear, and worn surface self-healing mechanisms of the additives were discussed. It was found that Ni nanoparticles with a smaller size show higher surface activity and can readily deposit on the sliding surface and form a stable and continuous protective layer thereon. Compared with sphere-like and triangular rodlike Ni nanoparticles, triangular plate-like Ni nanoparticles are more liable to form protective layer. Compared to Ni-based nanolubricants, as-synthesized Cu@Ni nanolubricants exhibit better friction-reducing, antiwear, and extreme pressure properties. It is because the highly active Ni nanocores and Oand N-containing organic modifying agents can readily form boundary lubricating film on sliding steel surfaces, while Cu nanocores can easily deposit on sliding steel surface to form a protective layer (self-healing film) thereon. Ni nanoparticles as nanoadditives in solidliquid lubricating system significantly reduce the friction in all lubrication regimes: As a nanolubricant, Ni nanoparticles exhibit popular and effective friction-reducing, antiwear, and extreme pressure properties.

nc-TiC/a-C纳米复合多层薄膜的制备及其摩擦学性能的研究

采用磁过滤阴极弧等离子体沉积技术,在单晶硅片上制备了不同亚层厚度和亚层弹性模量匹配的nc-Ti C/a-C纳米复合多层薄膜,采用X射线粉末衍射仪、扫描电子显微镜和透射电子显微镜对其微观结构进行表征,利用激光扫描仪对其内部应力进行测试,采用微摩擦磨损试验机表征薄膜的摩擦磨损性能,以考察多层结构设计对于薄膜机械性能的影响.结果表明:多层薄膜相对于单层薄膜可以有效降低膜层内应力,同时薄膜的减摩抗磨性能也得到了提高.亚层厚度为40 nm和相邻亚层弹性模量差距较小的nc-Ti C/a-C纳米复合多层薄膜的抗磨性能最佳.