Nano-additives enabled advanced lubricants

Abstract

The presently disclosed technology relates to a nano-additives to improve the performance of lubricants, oils, and greases. More specifically, the presently disclosed technology relates to applying capped metal oxide nanoparticles, such as capped zirconia nanoparticles, in the lubricants to produce a tribofilms on the lubricating surfaces to provide wear protection to the said surfaces. Also, the interaction of the capped zirconia nanoparticles with other commonly used additives in lubricants may further optimize the performance of the resulting tribofilms.

We claim: 
     
         1 . A lubricant comprising zirconia nanoparticles, wherein the zirconia nanoparticles are capped with at least one capping agent, and wherein the lubricant has a minimum transmittance of larger than 50% when measured in a cuvette with a 10 mm path length when the dispersion contains 10% by weight nanoparticles in the lubricant. 
     
     
         2 . The lubricant of  claim 1 , wherein the lubricant comprises an oil, a grease or a synthetic, mineral or natural lubricant and/or contains at least one of synthetic hydrocarbon, an ester, a silicone or a polyglycol. 
     
     
         3 . The lubricant of  claim 1 , wherein the lubricant is a stable dispersion and exhibits less than 10% change in optical transmittance, when measured in a cuvette with 10 mm optical path, after 1 month of storage to greater than 3 years storage. 
     
     
         4 . The lubricant of  claim 1 , wherein the lubricant further comprises at least one lubricant additive selected from the group consisting of anti-wear (AW) additives, friction modifiers (FM), anti-oxidants, extreme pressure (EP) additives, anti-foaming agents, detergents, dispersants, and pour point depressants. 
     
     
         5 . The lubricant of  claim 1 , wherein the lubricant further comprises zinc dialkyldithiophosphates (ZDDP). 
     
     
         6 . The lubricant of  claim 1 , wherein the lubricant has a viscosity in the range of 2 to 1000 mPas (cP) at a temperature of 100° C. 
     
     
         7 . The lubricant of  claim 1 , wherein the lubricant is a crankcase lubricant for internal combustion engines, a lubricating oil for geared transmissions in vehicles and wind turbine drivetrains, or a lubricant for rolling bearing elements. 
     
     
         8 . The lubricant of  claim 1 , wherein the zirconia nanoparticles have a size which is 4-20 nm. 
     
     
         9 . The lubricant of  claim 1 , wherein the zirconia nanoparticles are present in an amount of 0.01 to 10 wt. %, based on total weight of the lubricant. 
     
     
         10 . The lubricant of  claim 1 , wherein the nanoparticles comprise nanocrystals. 
     
     
         11 . The lubricant of  claim 5 , wherein the zinc dialkyldithiophosphates (ZDDP) is present in an amount of 0.01 to 2 wt. %, based on total weight of the lubricant. 
     
     
         12 . The lubricant of  claim 1 , wherein the nanoparticles in use undergo selective removal of the at least one capping agent due to tribological stresses. 
     
     
         13 . A tribofilm which comprises the lubricant of  claim 1 , wherein the at least one capping agent is removed due to tribological stresses.