Molybdenum disulfide (MoS2) is a black, slippery solid lubricant found in molybdenite. Its hexagonal crystal structure results in low friction and good adhesion to metals, making it suitable for use in space and heavy load applications. Commercial grade MoS2 is obtained by mining and processing molybdenite ore, with proprietary methods used to increase purity. Non-lubricating applications include catalysis and as a semiconductor material.
The combination of a metallic molybdenum atom with two sulfur atoms produces a molybdenum disulfide (MoS2) molecule. In nature, this substance is found in the important mineral molybdenite. With its black appearance and slippery feel, MoS2 is used as a solid lubricant. It takes the form of interconnected trigonal prisms, with layers of molecules loosely associated through van der Waal forces. The favorable distribution of electrons can increase the distance between the layers, increasing the lubricity.
The hexagonal crystal structure of molybdenum disulfide results in extremely low friction, but good adhesion to metals. MoS2 forms quality blued or sprayed films on surfaces such as pistons, threads, bearings and valves. It is best suited for low oxygen applications, such as in space. There, it is used in connection with spacecraft, antenna systems, satellites and solar panels. In some cases, the disulfide is combined with resins such as acrylics, phenolics, urethanes and polyimides to form sprayable coatings.
Molybdenum disulfide can also be used in slightly unfavorable environments, such as moderately high temperatures in the presence of oxygen. Although the disulfide oxidises slowly to the trioxide, the result is still non-abrasive, with an acceptable level of lubricity lingering. Furthermore, by increasing the particle size of molybdenum disulfide, its susceptibility to degradation decreases significantly. Sometimes, such as with heavy loads, molybdenum disulfide is the lubricant of choice. Applications can involve more than 250,000 pounds per square inch (17,580 kg per square cm) in some cases.
Molybdenite ore must be obtained and processed to produce commercial grade molybdenum disulfide. The ore is first mined using the open pit method or block caving technique, whereby material is extracted from beneath the ore which then collapses under its own weight. Processing of ore includes its being ground or milled; follows flotation and involves foaming with air, sometimes under the influence of additives for best results. Interestingly, the useful ore rises as the waste rock settles. If necessary, acid leaching is used to remove metal contaminants.
At this point in the process, the purity may already exceed 92 percent. Proprietary methods can then be employed to further increase the purity. The final machined molybdenum sulfide particles often range from a few microns down to sub-micron size. Typical online suppliers quote molybdenum disulfide purities ranging from 98 to 99 percent. Non-lubricating applications include catalysis in the petroleum industry for desulfurization and as a p-type semiconductor material for the electronics industry.
Protect your devices with Threat Protection by NordVPN
