Biodegradable Lubrication Coatings and Materials

In the area of environment-friendly and biodegradable lubrication several ideas have been suggested:

Water strider walking on the water

1. The use of natural (e.g., vegetable-oil based or animal-fat based) biodegradable lubricants. This involves oils that are used for engines, hydraulic applications, and metal cutting applications. In particular, corn, soybean, coconut oils have been used so far (the latter is of particular interest in tropical countries such as India). These lubricants are potentially biodegradable, although in some cases chemical modification or additives for best performance are required. Vegetable oils can have excellent lubricity, far superior than that of mineral oil. In addition, they have a very high viscosity index and high flash/fire points. However, natural oils often lack sufficient oxidative stability, which means that the oil will oxidize rather quickly during use, becoming thick and polymerizing to a plastic-like consistency. Chemical modification of vegetable oils and/or the use of antioxidants can address this problem [47].

2. Ionic liquids for green molecular lubrication. Common industrial lubricants include natural and synthetic hydrocarbons and perfluoropolyethers (PFPEs), where the latter is widely used in commercial applications requiring extreme operating conditions due to their high temperature stability and extremely low vapor pressure. However, PFPEs exhibit low electrical conductivity, making them undesirable in some nanotechnology applications. Ionic liquids (ILs) have been explored as lubricants for various device applications due to their excellent electrical conductivity as well as good thermal conductivity, where the latter allows fictional heating dissipation [60]. Since they do not emit volatile organic compounds, they are regarded as ''green'' lubricants.

3. Powder lubricants and,in particular, boric acid lubricants. In general, these tend to be much more ecologically friendly than the traditional liquid lubricants [41]. Boric acid and MoS2 powder can also be used as an additive to the natural oil. Friction and wear experiments show that the nanoscale (20 nm) particle boric acid additive lubricants significantly outperformed all of the other lubricants with respect to frictional and wear performance. In fact, the nano-scale boric acid powder based lubricants exhibited a wear rate more than an order of magnitude lower than the MoS2 and larger sized boric acid additive-based lubricants [46].

4. Self-replenishing lubrication that uses oil-free environmentally benign powders for lubrication of critical components such as bearings used in fuel cell compressors and expanders [76].

5. Water lubrication of bearings and other tribological components. Recently, a lot of attention has been paid to water lubrication which is considered an eco-friendly method.

6. New eco-friendly coating materials for tribological applications.

7. Environmental effect of wear particles. It has been suggested that environmental aspects should become an integral part of brake design [77]. Preliminary data obtained with animal experiments revealed that the inhaled metallic particles remain deposited in the lungs of rats 6 month after the exposure. The presence of inhaled particles had a negative impact on health and led to emphysema (destroyed alveoli), inflammatory response, and morphological changes of the lung tissue.

Renewable Energy Eco Friendly

Renewable Energy Eco Friendly

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable.

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