Different from the requirements of liquid lubricants for normal conditions, space applications require liquid lubricants to have good performance over extreme temperature variations and low temperature fluidity while maintaining adequate viscosity. However, the liquid lubricants used in the past can not meet the high demands.

Recently, new progress in this area was achieved by the research group headed by Prof. Bai Mingwu of the State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, CAS, and their research results were published in Tribology Letter (Tribol. Lett. (2009) 36:191–198). In order to develop additives with good miscibility with MACs and outstanding lubrication performance for space application, they have prepared oil-soluble ZrO₂ nanoparticles in nonhydrolytic organic solvent using surface-modified method and evaluated the tribological properties of ZrO₂ nanoparticles as additive to MACs. The results indicate that the synthetic MACs have excellent viscosity, high decomposition temperature, and very low vapor loss, which are equivalent to a commercial multiply alkylated cyclopentanes base fluid.The as-prepared ZrO₂ nanoparticles consist of inorganic ZrO₂ nanocores capped by trioctylphosphine oxide (TOPO) and are highly soluble in non-polar organic solvents such as hexane, toluene, liquid paraffin, MACs, etc. ZrO₂ nanoparticles as additives to MACs base oil significantly improve its wear performance and loadcarrying capacity, and have slight effect on its friction property.