| Double metal oxides such as silver vanadate, as well as silver, copper, and zinc tungstates were synthesized at room temperature by a simple wet chemical route, and their tribological behavior was investigated at high temperature using a pin on disk tribotester against silicon nitride balls. In this chemical method, the resultant precipitates obtained during the sudden mixing of the various reactants were washed with deionized water and absolute alcohol to remove the impurities. The structural and microstructural characterization of the products; using X-ray diffraction (XRD) and scanning electron microscopy (SEM); revealed different structures such as nanorods and nanoparticles of vanadates and tungstates. Silver vanadate nanorods had a length of 0.5-4 mum, width of 100-300 nm and thickness of 50-100 nm, while silver tungstate nanorods had a length of 0.25-3 mum, width of 300-500 nm and thickness of 75-100 nm. The SEM characterization of zinc tungstate revealed the formation of nanoparticles of diameter 30-75 nm. This synthesis process required no surfactants, high temperatures, or long reaction times. All of the synthesized nanomaterials were further tested for their tribological behavior at 25°C and 700°C. Silver vanadate (1:2 molar ratio) and zinc tungstate showed good lubrication behavior at 700°C with a coefficient of friction (CoF) in the range of 0.11-0.27. Silver tungstate was found to be lubricious over a broad range of temperatures. The CoF for silver tungstate at 25°C was ∼0.18, and at HT was in the range of 0.01-0.15. Therefore silver tungstate may prove to be an excellent lubricant material for a wide range of temperature applications. The low CoFs at high temperatures may be due to their layered atomic structure with weak interplanar bonds. |
