TransForum Vol. 8, No. 1

Ali Erdemir uses a ring-on-liner test machine to test the performance of lubricants as a function of temperature.

Argonne and Partners Develop Advanced Nanolubrication Systems Using MoS₂

Ali Erdemir, Argonne senior scientist, has spent nearly two decades looking for ways to reduce friction between sliding surfaces. During that time, Erdemir and his colleagues have produced two remarkable inventions: near-frictionless carbon coatings and motor oil additives based on extremely small nanoparticles of boric acid. The latter innovation gave Erdemir the inspiration to look into other nano particulate materials, such as molybdenum disulfide (MoS₂), a molecule with a structure very similar to that of boric acid.

In 2007, the U.S. Department of Energy (DOE) awarded funding for MoS₂ research. The federal funds are supporting research into the use of very small particles of MoS₂ as a lubricant additive for motor oils. Scientists from the University of Arkansas, Caterpillar and nanoMech LLC are working together with Argonne to develop and test this new additive. To the naked eye, MoS₂ is a greasy black solid that looks and feels very much like graphite. The root of its slick texture, however, lies in its molecular structure, in which molybdenum atoms form sheets sandwiched by layers of sulfur atoms. The weak bonding between the planes of sulfur atoms allows them to slide over one another easily, resulting in extremely low coefficients of friction.

A MoS₂ additive might prove especially valuable for the types of industrial and agricultural equipment that represent many of Caterpillar’s products, Erdemir said. “Dust can make its way into the crank case and cause abrasive wear, so with this kind of additive the severity of that wear will be reduced,” he said. The additive may also result in increased fuel economy and reduced emissions in vehicles.

Experiments on the additive are now underway at Argonne and preliminary results show that MoS₂ is indeed a promising new low-friction additive. These preliminary results will be presented at the annual meeting of the Society of Tribologists and Lubrication Engineers in May 2008. Erdemir and his collaborators are hopeful that presenting these positive initial findings will lead to more industry interest resulting in new funding opportunities and collaboration. In addition, a scientific journal article about the MoS2 additive preliminary findings is in the draft stage.

The MoS₂ additive project appealed to DOE because it represents an ideal collaboration scenario, with a university, a laboratory and two industrial companies all working together to develop a product that meets a real-world need. Professor Ajay Malshe and others at the University of Arkansas engineered the particle size, which they then licensed to nanoMech LLC for manufacturing and distribution. Argonne’s role in the project involves testing the performance of the MoS₂ additive. The University of Arkansas approached Argonne because of the Laboratory’s positive reputation in the area of nanolubrication.

This two-year project began in late 2007. Year One work involves bench-top experimentation and optimization of the nanoparticle composition. Year Two work will involve component testing and performance validation by Caterpillar.

May 2008