Submonolayer coatings of noble-metal nanoparticle liquids (NPLs) are shown to provide replenishable surfaces with robust asperities and metallic conductivity that extends the durability of electrical relays by 10 to 100 times (depending on the current driven through the contact) as compared to alternative approaches. NPLs are single-component materials consisting of a metal nanoparticle core (5-20 nm Au or Pt nanoparticles) surrounded by a covalently tethered ionic-liquid corona of 1.5 to 2 nm. Common relay failure modes, such as stiction, surface distortion, and contact shorting, are suppressed with the addition of a submonolayer of NPLs to the contact surfaces. This distribution of NPLs results in a force profile for a contact-retraction cycle that is distinct from bare Au contacts and thicker, multilayer coatings of NPLs. Postmortem examination reveals a substantial decrease in topological change of the electrode surface relative to bare contacts, as well as an indication of lateral migration of the nanoparticles from the periphery towards the contact. A general extension of this concept to dynamic physical interfaces experiencing impact, sliding, or rolling affords alternatives to increase reliability and reduced losses for transmittance of electrical and mechanical energy.

MoS 2 -Sb 2 O 3 -C composite films exhibit adaptive behavior, where surface chemistry changes with environment to maintain the good friction and wear characteristics. In previous work on nanocomposite coatings grown by PVD, this type of material was called a ''chameleon'' coating. Coatings used in this report were applied by burnishing mixed powders of MoS 2 , Sb 2 O 3 and graphite. The solid lubricant MoS 2 and graphite were selected to lubricate over a wide and complementary range including vacuum, dry air and humid air. Sb 2 O 3 was used as a dopant because it acts synergistically with MoS 2 , improving friction and wear properties. The MoS 2 -Sb 2 O 3 -C composite films showed lower friction and longer wear life than either single component MoS 2 or C film in humid air. Very or even super low friction and long wear-life were observed in dry nitrogen and vacuum. The excellent tribological performance was verified and repeated in cycles between humid air and dry nitrogen. The formation of tribo-films at rubbing contacts was studied to identify the lubricating chemistry and microstructure, which varied with environmental conditions. Micro-Raman spectroscopy and Auger electron spectroscopy (AES) were used to determine surface chemistry, while scanning electron microscopy and transmission electron microscopy were used for microstructural analysis. The tribological improvement and lubrication mechanism of MoS 2 -Sb 2 O 3 -C composite films were caused by enrichment of the active lubricant at the contact surface, alignment of the crystal orientation of the lubricant grains, and enrichment of the non lubricant materials below the surface. Sb 2 O 3 , which is not lubricious, was covered by the active lubricants (MoS 2 -dry, C -humid air). Clearly, the dynamics of friction during environmental cycling cleaned some Sb 2 O 3 particles of one lubricant and coated it with the active lubricant for the specific environment. Mechanisms of lubrication and the role of the different materials will be discussed.

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Nanoscale dispersion of only a few weight percentage of layered silicate (montmorillonite) in nylon 6 and epoxy results in the formation of a uniform passivating and self-healing inorganic surface region upon exposure to oxygen plasma. The enrichment of inorganic is compositionally graded with respect to the surface and is due to the preferential oxidation of the polymer from the nanocomposite and the corresponding enhancement of the nanoscale layered silicate on the surface. The structure of the inorganic region is turbostratic, with an average distance between layered silicates of 1−4 nm. This ceramic-like silicate layer provides an overcoat to the nanocomposite and can significantly retard the penetration of oxygen plasma. Thus, layered silicate containing nanocomposites may enhance the survivability of polymeric materials in aggressive oxidative environments, such as atomic oxygen in low earth orbit (LEO). The formed inorganic region was characterized chemically and morphologically by X-ray photoelectron spectroscopy (XPS), attenuated total reflection infrared (ATR), transmission electron microscopy (TEM), and X-ray scattering.