Room temperature ionic liquid 1-ethyl-3-hexylimidazolium-bis(trifluoromethylsulfonyl)-imide as lubricant for steel–steel contact

The ionic liquid 1-ethyl-3-hexylimidazolium-bis(trifluoromethylsulfonyl)-imide was synthesized and evaluated as lubricant for the contact of steel/steel. The tribological properties of the ionic liquid as lubricant were investigated on an Optimol SRV oscillating friction and wear tester in ambient condition. The synthetic ionic liquid shows excellent tribological performance and is superior to the ionic liquid of alkylimidazolium tetrafluoroborate and the conventional high temperature lubricants X-1P and PFPE in terms of antiwear performance and load-carrying capacity. The elemental composition and chemical nature of the boundary film generated on the steel surface were analyzed on a scanning electron microscope with a Kevex energy dispersive X-ray analyzer attachment (SEM/EDS) and X-ray photoelectron spectrometer (XPS), and the XPS results indicate the occurrence of a complicated tribochemical reaction of ionic liquid with iron on the rubbing surface during the sliding process, with the formation of FeS, organic fluoride, inorganic fluoride, etc.     

Tribophysical and tribochemical effects of a thermoplastic polyimide

The sliding friction and wear characteristics of a thermoplastic polyimide (PI) were investigated under different PV conditions using a pin-on-disc wear tester. The tribological characteristics of the PI were divided into three wear regions on the basis of the wear degree (slight wear, medium wear and severe wear). The friction coefficient of the PI in slight wear was stable. In the medium wear and severe regions, the friction coefficients of the Pl varied over a wide range, and was unstable. The reason for the variations of friction and wear in the different wear regions was attributed to the rising of PI surface temperature, which led to the variations of the physical state of PI friction surface layer. XPS analysis indicated that carbonation occurred on the friction surface during sliding. It was proved that the reaction product may reduce the friction coefficient.     

NH3 and HCl sensing characteristics of polyaniline nanofibers deposited on commercial ceramic substrates using interfacial polymerization

This paper reports the use of the interfacial polymerization method in a simple route for fabricating low-cost, highly sensitive NH₃ and HCl gas sensors made of polyaniline (PANI) nanofiber coatings on commercially available ceramic substrates. The PANI coatings consisted of uniform nanofibers and formed emeraldine salt. NH₃ gas-sensing properties of as-synthesized PANI nanofibers were also investigated in detail. The influence of PANI nanofiber acidification treatment at different HCl solutions (pH = 0, 1, 2, and 3) on NH₃-sensing properties was discussed as well. As-synthesized PANI nanofibers exhibited very low detection limit (1 ppm) and high sensing response (response S) was above 2 when the sensor was exposed to 50 ppm NH₃ gas, though a limited drift of the response appeared in the reproducibility test. For acid-treated PANI sensors, the response time increased and response S decreased with increasing pH value of HCl solutions. Response S, especially after acid-treatment, increased as testing proceeded. This is possibly due to the creation of reaction sites on the surface and/or the bulk of the sensors. When PANI was used to detect gaseous HCl, an irreversible process occurred and response S became saturated when the concentration of gaseous HCl reached 200 ppm.     

汽油芳烃对发动机沉积物的影响

采用实验室模拟手段以及Ford2-3 L标准发动机台架试验研究了汽油芳烃对发动机进气阀以及燃烧室沉积物的影响。结果表明,随着芳烃含量的增加,进气阀和燃烧室沉积物质量增大,并且不同结构的二甲苯对沉积物的影响不同,其中对二甲苯形成沉积物的趋势最大;相对于烯烃,芳烃含量对进气阀以及燃烧室的沉积物形成影响较大。     

Controlling friction and wear of nc-WC/a-C(Al) nanocomposite coating by lubricant/additive synergies

Owing to increasing demands for reductions in emissions and improvements in fuel economy in the automotive industry, there is an urgent need to improve tribological performances of components. In the current paper, an nc-WC/a-C(Al) carbon-based nanocomposite coating was fabricated successfully via the magnetron sputtering process. The microstructure and mechanical properties of the as-fabricated nanocomposite coating were investigated. In particular, its friction and wear behaviors under poly-alpha-olefin oil lubricant added with anti-wear (AW), extreme-pressure (EP), or molybdenum dialkyldithiocarbamate (MoDTC) additive were systemically evaluated. Results show that the nc-WC/a-C(Al) nanocomposite coating has a typical nanocrystallite/amorphous microstructure and good mechanical properties. The significant improvement in the tribological performance of the boundary-lubricated nc-WC/a-C(Al) coating is mainly attributed to the WS₂ or MoS₂ + WS₂-containing tribofilm when S-based EP or MoDTC additive was used. Superior tribological performance of nc-WC/a-C(Al) nanocomposite coating was achieved by lubricant/additive synergies, indicating its potential application as a protective coating for automotive tribo-components.     

聚合物表面的润湿性及其应用

本文论述了真实聚合物表面的润湿性，聚合物表面张力的计算，界面张力的极性理论及酸碱理论，并对近年来材料表面的改性在聚合物中的应用进行了简要的评述。     

The tribological properties of diethylammonium lanthanide tetrakis (diethyldithiocarbamate) in lubricating oil

The synthesis of four oil-soluble rare earth complexes of diethylammonium lanthanide tetrakis(diethyldithiocarbamate) (ReDTC) is described. The tribological properties of these rare earth complexes as additives in lubricating oil have been evaluated using a four-ball machine. The results show that these novel complexes have excellent extreme-pressure properties and selective antiwear properties in lubricating oil. The action mechanism of the rare earth complexes as additives in lubricating oil was investigated using X-ray photoelectron spectroscopy (XPS).     

The performance and antiwear mechanism of S-containing organic borate as an oil additive

A sulphur-containing organic borate (BS-2) was prepared. Its friction and wear properties when added to n-tetradecane, and the effect on wear of addition of dodecyl amine to the synthesised S-containing borate oil, were measured using a Timken test machine. The results were compared with those of tridodecyl borate, and a combination of tridodecyl borate and sulphurised cotton seed oil. X-ray Photoelectron Spectroscopy (XPS) was used to examine the rubbed surfaces of the test blocks, while Scanning Electron Microscopy (SEM), Energy Dispersion Analysis of X-ray (EDAX) and X-ray Diffraction (XRD) were used to study the wear debris. It is found that S-containing organic borate exhibits a poorer antiwear property than tridodecyl borate but, with the addition of dodecyl amine to the S-containing borate, its antiwear property can be improved. XPS analyses indicate that sulphur on the rubbed surfaces exists in the forms of organic sulphide and FeSO₄, and the addition of amine reduces the adsorption and reaction of sulphur to the rubbing surfaces. SEM analyses revealed that the wear debris was in powder form, and the EDAX and XRD analyses indicated that iron sulphide, iron oxide and elemental iron were contained in the wear debris. A corrosive wear mechanism of steel test blocks lubricated by S-containing organic borate is proposed.     

Improved Tribological Behavior of DLC Films Under Water Lubrication by Surface Texturing

Textured diamond-like carbon (DLC) films with the pattern of parallel grooves were developed by depositing DLC on textured stainless substrates in a PVD system. The texturing effects on tribological performance of DLC in water-lubricated condition were investigated. Results show that introducing specific patterns into DLC film not only retains the low friction coefficients, but also dramatically extends coating lifetime through affecting the coating delamination behavior and graphitization process during friction. Besides the adherence difference induced by surface texturing which could influence the delamination, another possible mechanism, “buffer stripes”, which is characteristic of the lateral soft/hard periodical structure, was proposed by us based on the Micro-Raman spectroscopy and nanoindentation analysis. Additionally, a much lower graphitization for textured DLC during friction may also be responsible for the improved wear resistance.     

Effect of AlN Thickness on Structure and Properties of AlN/Al Dual Protective Coatings on NdFeB by DC Magnetron Sputtering

In order to improve the corrosion resistance of NdFeB,AlN/Al dual protective coatings were prepared by DC magnetron sputtering in a home-made industrial apparatus.The inner Al layer with an excellent toughness was deposited onto NdFeB substrate firstly.And then the outmost AlN layer with a higher hardness was prepared with the nitrogen/argon mixture gas of the nitrogen partial pressure at 50%of the total pressure of 0.5 Pa and depositing time of 30,50 and 70 min,respectively.The denser outmost AlN layer was formed on the inner Al crystal layer.There is an occurrence of the interfacial reaction and metallurgy bonding in the interface layer between the coatings and NdFeB substrate.It has been found that the thickness of outmost AlN layer has a significant impact on corrosion resistance.For 50 min to deposit outmost AlN layer,AlN/Al coated NdFeB has the best corrosion resistance.