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Knowledge of their bulk physical properties often guides selection of appropriate tribological coating materials. However, these properties as well as the microstructure evolve dramatically under the extreme conditions imposed during mechanical wear. The dynamic response ultimately governs the material’s wear performance; thus, understanding the dynamic evolution of the system is critical. This work characterizes the change in mechanical properties and microstructure as a function of wear cycles in model MoS2 films using a combination of nanowear testing, transmission electron microscopy, and site-specific nanopillar compression. Notably, mechanical wear enhances the mechanical properties of the MoS2 while simultaneously evolving a microstructure that reduces the coefficient of friction and wear rate. We hypothesize that this self-optimizing behavior underpins the exceptional lubricity and antiwear performance of MoS2.

An aerosol-assisted chemical vapor method leading to iron sulfide scales of varying phases and morphologies by reaction of pipeline steels with sulfur compounds has been developed. This chemical vapor reaction methodology is useful for generating model iron sulfide scales pertinent to the interaction of sour crude oil with piplelines used in the oil and gas industry.

Direct observations on nanopillars composed of molybdenum disulfide (MoS2) and chromium-doped MoS2 and their response to compressive stress have been made. Time-resolved transmission electron microscopy (TEM) during compression of the submicrometer diameter pillars of MoS2- and Cr-doped MoS2 (Cr: 0, 10, and 50 at %) allow the deformation process of the material to be observed and can be directly correlated with mechanical response to applied load. The addition of chromium to the MoS2 changed the failure mode from plastic deformation to catastrophic brittle fracture, an effect that was more pronounced as chromium content increased.

A combined single-source precursor approach has been developed for the deposition of thin films of Cr-doped molybdenum disulfide (MoS2) by aerosol-assisted chemical vapor deposition (AACVD). Tris(diethyldithiocarbamato)chromium(III) can also be used for the deposition of chromium sulfide (CrS). Films have been analyzed by a range of techniques including scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy, Raman spectroscopy, and powder X-ray diffraction (pXRD) to elucidate film morphology, composition, and crystallinity. The presence of Cr in the MoS2 films produces a number of striking morphological, crystallographic, and nanomechanical changes to the deposited films. The chromium dopant appears to be uniform throughout the MoS2 from the scanning transmission electron microscopy (STEM) EDX spectrum imaging of nanosheets produced by liquid-phase exfoliation of the thin films in N-methyl-2-pyrollidone.

Compressed and stretched polyacrylamide hydrogels previously have been shown to offer a robust method for aligning proteins. A simple, funnel-like apparatus is described for generating uniformly stretched hydrogels. For prolate-shaped proteins, gels stretched in the direction of the magnetic field yield two-fold larger alignment than gels compressed to the same aspect ratio in this direction. Empirically, protein alignment is found to be proportional to (c−2.3) 2 [(do/dN) 3 -1], where do and dN are the diameters of the cylindrical gels before and after stretching, respectively, and c is the polyacrylamide weight fraction in percent. Low gel densities, in the 4–7% range, are found to have minimal effects on macromolecular rotational correlation times, τc, and no effect of the compression ratio on τc could be discerned over the range studied (do/dN ≤ 1.4). Application is demonstrated for a sample containing the first Ig-binding domain of protein G, and for a detergent-solubilized peptide.