Investigation on tribological performance of CuO vegetable-oil based nanofluids for grinding operations

With ball-bearing and tribofilm lubrication effects, CuO vegetable oil-based nanofluids have exhibited excellent anti-wear and friction reduction properties. In this study, CuO nanofluids were synthesized by a one-step electro discharge process in distilled water containing polysorbate-20 and vegetable oil as a nanoparticle stabilizer and source of fatty-acid molecules in the base fluid, respectively. Pin-on-disk tribotests were conducted to evaluate the lubrication performance of synthesized CuO nanofluids between brass/steel contact pairs under various loadings. Surface grinding experiments under minimum lubrication conditions were also performed to evaluate the effectiveness of the synthesized nanofluids in improving the machining characteristics and surface quality of machined parts. The results of pin-on-disk tests revealed that adding nanofluids containing 0.5% and 1% (mass fraction) CuO nanoparticles to the base fluid reduced the wear rate by 66.7% and 71.2%, respectively, compared with pure lubricant. The lubricating action of 1% (mass fraction) CuO nanofluid reduced the ground surface roughness by up to 30% compared with grinding using lubricant without nano-additives. These effects were attributed to the formation of a lubrication film between the contact pairs, providing the rolling and healing functions of CuO nanoparticles to the sliding surfaces. The micrography of ground surfaces using a scanning electron microscope confirmed the tribological observations.The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-020-00314-1     

Reactively sputtered TiN coatings for tribological applications

The results of tribological studies carried out on TiN sputter-coated ferrous and non-ferrous materials are presented. A disc magnetron system was used to sputter TiN reactively onto samples suitable for standard friction and wear tests. The tests carried out show that thin films of reactively sputtered TiN, typically 5 microm thick, provide good wear protection for ferrous and non-ferrous surfaces subjected to sliding and rolling contacts. Cutting tests with coated cermet tool inserts show that reactive sputtering is also useful for improving the performance of cutting tool inserts. The results obtained suggest that magnetron reactive sputtering can be useful to enhance the wear resistance of finished precision components.     

High performance nanocomposites for tribological applications: Preparation and characterization

High performance nanocomposites were prepared by incorporating 0–12 vol.% nano-sized (39 nm) Al₂O₃ particles into PEEK matrix using compression molding. The microhardness and dynamic mechanical properties of the nanocomposites increase with increasing Al₂O₃ content. The wear resistance of the nanocomposites evaluated at a sliding speed of 1.0 m/s and nominal pressure from 0.5 MPa to 1.25 MPa under dry sliding conditions was improved more than threefold at 0.8 vol.% Al₂O₃ content. However, the wear resistance of the nanocomposites containing above 1.67 vol.% Al₂O₃ was deteriorated, despite their higher hardness and stiffness as compared to that of nanocomposites containing lower Al₂O₃ content. The surface roughness of the wear track formed over the countersurface increases with increasing Al₂O₃ content. The coefficient of friction of nanocomposites was higher than that of pure PEEK. SEM and optical microscopy have shown that wear of pure PEEK occurs by the mechanism of adhesion mainly, whereas of nanocomposites by microploughing and abrasion. Energy dispersive spectrometry (EDS) shows that Fe and alloying elements of countersurface transfer to the wear debris at higher Al₂O₃ content.     

Graphene-based materials: synthesis, characterization, properties, and applications

Graphene, a two-dimensional, single-layer sheet of sp(2) hybridized carbon atoms, has attracted tremendous attention and research interest, owing to its exceptional physical properties, such as high electronic conductivity, good thermal stability, and excellent mechanical strength. Other forms of graphene-related materials, including graphene oxide, reduced graphene oxide, and exfoliated graphite, have been reliably produced in large scale. The promising properties together with the ease of processibility and functionalization make graphene-based materials ideal candidates for incorporation into a variety of functional materials. Importantly, graphene and its derivatives have been explored in a wide range of applications, such as electronic and photonic devices, clean energy, and sensors. In this review, after a general introduction to graphene and its derivatives, the synthesis, characterization, properties, and applications of graphene-based materials are discussed.     

Plasma and gaseous nitrocarburizing of C60W steel for tribological applications

A comparison has been made between plasma and gas nitrocarburizing processes for C60W steel in terms of structural features of the layers and the tribological properties of the specimens. Gaseous treatments were performed in a sealed quench industrial furnace in optimized process cycles. A semi - industrial size unit was operated at a range of process parameters for plasma nitrocarburizing. Experimental results indicate that increasing the treatment time increases the thickness of the compound layer but lowers the wear resistance. Plasma treatment produced a more effective case depth compared with gaseous process, providing a better uniformity. Analysis of X-ray diffraction patterns indicated that the compound layer in gas nitrocarburizing and plasma nitrocarburizing consisted of both ? and γ′ phases.     

Diamond-like carbon coatings for orthopaedic applications: an evaluation of tribological performance

A detailed investigation of the tribological behaviour of vacuum arc diamond-like carbon coated Ti–6Al–4V against a medical grade ultra-high molecular weight polyethylene is conducted in this work in order to investigate the potential use of diamond-like carbon coatings for orthopaedic appplications. Lubricated and non-lubricated wear experiments are performed using a standard pin-on-disc wear tester. The coefficient of friction is monitored continuously during testing and wear rate calculations are performed using surface profilometry measurements of worn disc surfaces. Sliding wear tests show the existence of two distinct friction and wear regimes distinguished by physically different mechanisms. In the first stages of wear, adhesion and abrasion are the dominant mechanisms of wear while fatigue processes are activated later in the tests. The effects of diamond-like carbon coating structure, surface roughness and lubrication on tribological behaviour are presented. Optimal process–structure–property design for vacuum arc plasma deposition is utilized in order to obtain strong adhesion to the titanium alloy substrate. Diamond-like carbon coatings significantly improve the friction and wear performance of the orthopaedic bearing pair and show exceptional promise for biomedical applications. © 1999 Kluwer Academic Publishers     

发动机机油冷却器性能试验系统的研制

为了满足不同发动机冷却系统的匹配性能试验要求,研制了一种自动化程度较高的机油冷却器性能试验系统,能够实时测量与控制机油和冷却水的温度、流量、压力等参数,实现对冷却器性能参数的分析、显示,并具有数据库存储与查询功能.还详细介绍了系统的设计方案及关键参数的精确测量与控制方法.试验结果表明,系统测控精度与试验效率较高,并可辅助完成其他整机及部件的性能试验.     

Experimental study on heat transfer and rheological characteristics of hybrid nanofluids for cooling applications

The enhancement of heat transfer and rheological behaviour of hybrid nanofluids (HyNF) flowing through the tubular heat exchanger system were experimentally analysed. In this study, the effects of Nusselt number, Peclet number, Reynolds number, heat transfer coefficient and pressure drop were investigated for various volume concentrations of copper-titania hybrid nanocomposite (HyNC). The experiments were performed for various HyNC volume concentrations in the base fluid (cold water) ranging from 0.1% to 1.0%. The experimental results showed that the convective heat transfer coefficient of the HyNF increased by 59.3% for the particular volume concentration of 0.7% of HyNC. The friction factor and pressure drop of HyNF for 1.0% volume concentration were expected to be 0.8% and 5.4%, respectively. This implies for experiencing penalty in the pumping capacity. The experimental measurements, on the other hand, were validated using a newly developed correlation. For all the volume concentrations of HyNF, the deviation obtained for the experimental data and the prediction was observed to be +8% and ?8%, respectively. The present correlation has been found to be in good agreement with the experimental data, which can be helpful in predicting the heat transfer characteristics of the HyNF.     

An automotive engine oil viscosity sensor

For the evaluation of the condition of automotive engine oil, the oil's viscosity is one of the most important parameters. Using microacoustic viscosity sensors, an oil-viscosity measurement can be performed on-board. In this contribution, we discuss the behavior of the viscosity of engine oil, its temperature dependence, and the resulting representation in terms of output signals of microacoustic viscosity sensors. These considerations are illustrated by means of measurement results obtained for used oil samples, which have been obtained from test cars and fresh oil samples out of different viscosity classes. Finally, the detection of the viscosity increase due to soot contamination is demonstrated.     

Nanostructured polymers for detecting chemical changes during engine oil degradation

Organic and inorganic polymers nanostructured by molecular imprinting yield functional materials for detecting engine oil degradation. Using both fresh and waste oils as templates, respectively, allows us to selectively tune the polymer to incorporate either fresh or used lubricant. FT-IR studies on polymer pellets prove bulk incorporation of the analyte. By the same strategy sensitive materials can be designed for selectively determining fuel in the engine oil. Waste oil selective sensor layers yield signals that are clearly correlated both to the oil age (known from test stand measurements) and standard oil parameters, such as the total base number (TBN). TBN and sensors additionally show the same time behavior.     

Multifunctional thin film sensors based on amorphous diamond-like carbon for use in tribological applications

Amorphous diamond-like carbon films are well known for their excellent tribological properties. In this paper, we will discuss the sensoric properties of multifunctional a-C:H films with respect to force/load/pressure and temperature measurement. It turned out that nanostructured amorphous carbon films showed an impressive piezoresistive effect.Unlike well known strain gages and piezoresistive sensors, which detect a deformation of the base substrate, this novel sensor can be used in a complete stiff arrangement without any elastic joint. For film preparation, rf-plasma CVD processes were used. Besides gas pressure, a variation of the substrate power and bias potential was performed. It turned out that the tribological parameters varied slightly (hardness: 20-30 GPa, friction coefficient: 0.10 to 0.15), whereas the electrical parameters showed remarkable differences with respect to the electrical resistivity and piezoresistivity.This paper will also present different applications of amorphous carbon thin film sensors.     

Processes of the activated reactive evaporation type and their tribological applications

Plasma-assisted deposition processes have created a breakthrough in the deposition of compounds particularly the refractory compounds such as oxides, carbides, nitrides etc. Processes such as sputtering or ion plating inherently contain a plasma in the space between the target and the substrate. Evaporation and chemical vapor deposition processes have to be modified to include a plasma. In all of these reactive deposition processes the plasma plays a vital role in providing the activation energy necessary to carry out the process or to enhance its efficiency. All types of vapor sources can be used in these processes. The original development in 1971 used a thermionic electron beam evaporation source. Subsequently, resistance- heated, arc, induction, plasma electron beam and sputtering sources have all been used. In this paper we shall discuss the processes and the influence of deposition parameters on the microstructure and properties of compounds. Specific examples of the use of these compounds in tribological applications are considered.     

PMMA/SiO2纳米杂化材料的制备及作为润滑油添加剂的摩擦学性能

用无皂乳液聚合法，一步制备了聚甲基丙烯酸甲酯，表面有机化二氧化硅（PMMA／SiO2）纳米杂化材料，采用了红外光谱（FT-IR）、透射电子显微镜（TEM）以及热分析（TGA-DSC）等仪器对材料的核一壳结构进行表征，利用四球机考察了添加剂在AN10全损耗系统用油中的摩擦学性能。结果表明，合成的PMMA／SiO，纳米杂化材料能提高润滑油的抗磨性能及承载能力，并能降低摩擦系数，其最佳用量为1．5％，同时，PMMA／SiO2纳米杂化材料能极大地提高润滑油的极压性能。     

智能包装系统用石墨烯基超级电容器的制备

目的 制备具有优异电化学性能的石墨烯/纳米纤维素/二氧化锰复合纤维水系超级电容器。方法 采用超声波分散处理制备氧化石墨烯/纳米纤维素/二氧化锰混合纺丝液;运用湿纺纺丝工艺制备氧化石墨烯/纳米纤维素/二氧化锰杂化纤维电极;通过氢碘酸还原和冷冻干燥处理构建具有多孔结构的石墨烯/纳 米纤维素/二氧化锰复合纤维电极;最后,将其组装成两电极水系超级电容器。结果 在石墨烯/纳米纤维素/二氧化锰复合纤维中,纳米纤维素的添加有效抑制了石墨烯片层的自聚集,并显著提升了复合纤维的亲水性和拉伸强度。二氧化锰的加入显著提升了纤维电极的电化学性能。得益于精心的实验设计,石墨烯/纳米纤维素/二氧化锰复合纤维的拉伸强度为338 MPa。组装后的水系超级电容器具有优异的电容性能和循环稳定性,在电流密度为0.1 mA/cm2时,面积电容为412.5 mF/cm2,循环1500次后,电容保持率为87%。结论 将切实可行的湿法纺丝策略与精心设计的电极结构相结合,制备的石墨烯/纳米纤维素/二氧化锰水系超级电容器为可穿戴便携式储能设备和智能包装能源供应系统的发展提供了良好的参考。     

纳米锑颗粒作为液压油添加剂的摩擦学性能

为了研究纳米锑颗粒作为润滑油添加剂的润滑摩擦学性能,充分发挥其减磨、抗磨效果,采用CFT-1型材料性能测试仪对比研究了不同载荷下纳米锑粒子作为液压油添加剂的摩擦学性能,通过SEM对试样摩擦表面进行了形貌分析,利用EDX进行了磨痕表面元素分析.结果表明:不同载荷下纳米锑颗粒在液压油中的最佳添加量不同,重载荷下纳米锑粒子表现出优良的抗磨减摩性能;纳米锑粒子在一定程度上可以提高液压油的抗磨减摩性能,这是由于磨痕表面形成了含锑元素的表面膜,起到良好的抗磨减摩效果.     

石墨烯纳米复合材料光驱动技术的研究进展

石墨烯纳米复合材料在光驱动中的应用引起了研究人员的关注。石墨烯具有优异的物理化学性质,尤其是它的高比表面积、热传导性和机械强度,促进了光驱动智能化、远程控制技术的发展。基于石墨烯复合材料的光驱动器为精密机械、光学等领域提供了一种前途光明的先进驱动技术。本文通过述评基于石墨烯复合材料光驱动技术研究的最新进展,展望了石墨烯复合材料的合成方法、石墨烯材料作为光驱动复合材料填料等研究热点,及其在仿生物研究、微型机器人、生物医疗等领域的应用前景。     

Graphene-based photonic devices for soft hybrid optoelectronic systems

Graphene, a two-dimensional one-atom-thick planar sheet of carbon atoms densely packed in a honeycomb crystal lattice, has attracted appreciable attention due to its extraordinary mechanical, thermal, electrical, and optical properties. One of these properties, graphene's outstanding tensile strength, allows graphene-based electronic and photonic devices to be flexible, stretchable, and foldable. In this work, we propose a novel platform technology and architecture of graphene-based flexible photonic devices for the development of high-performance flexible devices and components. We investigated the characteristics of the graphene-based plasmonic waveguide for the development of high-performance optical interconnection in flexible human-friendly optoelectronic devices. We concluded that graphene-based photonic devices have huge potential for the development of next-generation human-friendly flexible optoelectronic systems.     

Effect of oil and oil with graphite on tribological properties of glass filled PTFE polymer composites

Present work deals with the experimental investigation of tribological properties of GF-filled polymer composites considering three velocities, i.e. 0.5, 1 and 2.0 m/s and loads ranging from 15.7 N to 45.13 N keeping rest of the parameters constant. The test has been carried out for three materials, PTFE + 15% GF, PTFE + 25% GF and PTFE + 35% GF in wet (oil) and adding additive as graphite (5% wt) in oil. SAE 20W40 oil is used for the test. Friction and wear tests of PTFE composite against a counter surface of EN8 with surface finish of 0.56 μm are carried out at ambient conditions using pin-on-disc tribometre (TR-20), Ducom make, Bangalore. The results are tabulated and graphs are plotted. It has been found that load and wet conditions have significant effect on coefficient of friction and specific wear rate of the materials. Where as sliding velocity also plays little role in wear mechanism of the material. It is concluded from the experimental study that the specific wear rate in wet condition as well as by adding additives in lubricating oil with 5% (by wt.) has been declined. Also the specific wear rate decreases with normal load and sliding velocity. Wear of PTFE + GF composite decreases with increase in glass percentage. Microscopic analysis of pin and disc surface is made with optical microscope. The mathematical models has been developed by using regression analysis and found to be valid for the above tested parameters.     

Graphene-based conducting inks for direct inkjet printing of flexible conductive patterns and their applications in electric circuits and chemical sensors

A series of inkjet printing processes have been studied using graphene-based inks. Under optimized conditions, using water-soluble single-layered graphene oxide (GO) and few-layered graphene oxide (FGO), various high image quality patterns could be printed on diverse flexible substrates, including paper, poly(ethylene terephthalate) (PET) and polyimide (PI), with a simple and low-cost inkjet printing technique. The graphene-based patterns printed on plastic substrates demonstrated a high electrical conductivity after thermal reduction, and more importantly, they retained the same conductivity over severe bending cycles. Accordingly, flexible electric circuits and a hydrogen peroxide chemical sensor were fabricated and showed excellent performances, demonstrating the applications of this simple and practical inkjet printing technique using graphene inks. The results show that graphene materials-which can be easily produced on a large scale and possess outstanding electronic properties-have great potential for the convenient fabrication of flexible and low-cost graphene-based electronic devices, by using a simple inkjet printing technique.