Due to the growing environmental concern, an initiative to switch toward ecofriendly options for engineering problems has been observed lately. Tribology is one such domain in which a lot of scope exists for employing ecosustainable solutions. This chapter discusses the tribological materials from an ecosustainable viewpoint. Various surface finishing methods and bio-friendly lubricants have been deliberated. Besides, suitable biomimetic techniques have also been presented. Finally, some aspects touching the economics and ecosustainable philosophies relevant to the subject have been discussed.
Rice husk and rice bran are the main byproducts of grain production and are considered solid biomass resources. The comprehensive utilization of biomass resources has received increasing attention as a solution to current serious environment pollution, resource and energy crises. Bio-based ceramic particles and their composites are important to the comprehensive utilization of rice waste. This study clarified the preparation process of bio-based ceramic particles and summarized their physical and chemical properties. The morphology, composition and structure of bio-based ceramic particles varied at different carbonization temperatures. Adhesives (phenolic resin) can strengthen the hardness of bio-based ceramic particles at optimum temperatures (900-1,000 °C). Bio-based ceramic particles and their composites can be used as functional additives in polymer- or metal-based composites. Bio-based ceramic particles can enhance the mechanical properties, such as hardness and compression strength of composites and reduce stress concentration. The tribological performance of bio-based ceramic particles and composites was studied under different test conditions. The friction reduction and wear resistance of composites were ascribed to the enhancement of composite hardness and the formation of a transfer film on the counter rubbing pair. The detailed wear map was also described under different test conditions. These results are helpful to understand how the development of bio-based ceramic particles and composites is a simple and effective method of comprehensive utilization of rice waste.
Because of the merits of saving energy and environmentally friendly, lubrication system using low viscosity fluids (e. g., water and short-chain alcohols) is expected to meet the requirement of green tribology. In this connection, the tribological behavior of tribomaterials (alloy, ceramic and composite) in low-viscosity fluids has been investigated in recent years. Ti3SiC2, which has combined merits of metal and ceramic including machinability, tolerance to damage and many others, shows good tribological property in alcohols. This suggests that Ti3SiC2 and its composites are a promising tribomaterial in alcohols. In the laboratory-based evaluation, however; the tribological behavior of Ti3SiC2 in water is poor, that is, high friction coefficient, high wear rate and rough worn surface. In a grinding and polishing process of Ti3SiC2, when water acts as a lubricant and a coolant, the surface quality of Ti3SiC2 surface is unexpectedly good. In this chapter, the tribological behavior of Ti3SiC2 in water and alcohols is reviewed. Because water and alcohols are reactive fluids, especially in sliding as well as grinding and polishing, the tribochemistry of Ti3SiC2 is also included in this chapter.
Synthetic lubricants with nano-additives have seen greater improvements in recent times. However, the information about the performance peculiarities of nano-based biolubricants in actual machines is scarce. Oil-film pressure is one of the crucial parameters when developing a new lubricant that describes the operating conditions in hydrodynamic lubrication regimes. To fill this gap, a response surface methodology (RSM) based on D-optimal design was employed to model and analyse the oil-film pressure of a hydrodynamic journal bearing, lubricated by nano-based biolubricants and a synthetic lubricant (SAE 20W40). The analysis was executed by selecting the bearing load and speed as numerical factor and synthetic/nano-based biolubricants as the categorical factor, to evaluate the lubricant’s oil-film pressure. The results showed that RSM based on D-optimal design was influential in the selection of suitable lubricant for a typical system, especially for the hydrodynamic journal bearing used in internal combustion engines. A bearing load of 2 kN, a speed of 1,000 rpm and a bronze bearing material lubricated with chemically modified rapeseed oil (CMRO) as the biolubricant dispersed with nano-CuO had the lowest oil-film pressure. Furthermore, the scanning electron microscopy analysis of the tested bearing surfaces lubricated with CMRO containing nano-CuO showed smoother than with a synthetic lubricant and other nano-based biolubricants.
The current work is an attempt to study the tribological characteristics of oil palm seed fibre-reinforced polyester (OpSeFRP) composite aged in brake fluid solutions. Two different brake fluid solutions were used with different kinematic viscosities: DOT3 and DOT4 solutions. The ageing period was set as 3 years. A linear tribomachine was used to study the tribological performance of the composite at different fibre loadings; 2.5-3.5 wt %. The tribological test was performed using different applied loads (5-20 N) and different sliding speeds (0.05-0.25 m/s) sliding on a stainless steel counterface at 0.45 km of sliding distance. The outcome of the work showed that the aged samples demonstrated better tribological properties as compared to the unaged samples. For fibre loading of 3.0 wt %, specific wear rate of the OpSeFRP composite was lowered by 28.6 % and 36.7 %, while friction coefficient was reduced by 2.2 % and 11.7 % for DOT3 and DOT4 ageing solutions as compared to the nonaged samples for the same fibre loading conditions. On microscopic analysis of the worn samples, low thermal deformation was evidenced on the aged samples when compared with the unaged samples. For the aged samples, the fibres at the rubbing zone had served as a “coolant” since they had absorbed a certain amount of brake fluid solution. The roughness average of the composite and counterface after the test was high for the unaged samples since the samples experienced high deformation rate.