This work investigates
the role of water and oxygen on the shear-induced
structural modifications of molybdenum disulfide (MoS
2
)
coatings for space applications and the impact on friction due to
oxidation from aging. We observed from transmission electron microscopy
(TEM) and X-ray photoelectron spectroscopy (XPS) that sliding in both
an inert environment (i.e., dry N
2
) or humid lab air forms
basally oriented (002) running films of varying thickness and structure.
Tribological testing of the basally oriented surfaces created in dry
N
2
and air showed lower initial friction than a coating
with an amorphous or nanocrystalline microstructure. Aging of coatings
with basally oriented surfaces was performed by heating samples at
250 °C for 24 h. Post aging tribological testing of the as-deposited
coating showed increased initial friction and a longer transition
from higher friction to lower friction (i.e., run-in) due to oxidation
of the surface. Tribological testing of raster patches formed in dry
N
2
and air both showed an improved resistance to oxidation
and reduced initial friction after aging. The results from this study
have implications for the use of MoS
2
-coated mechanisms
in aerospace and space applications and highlight the importance of
preflight testing. Preflight cycling of components in inert or air
environments provides an oriented surface microstructure with fewer
interaction sites for oxidation and a lower shear strength, reducing
the initial friction coefficient and oxidation due to aging or exposure
to reactive species (i.e., atomic oxygen).
Li10GeP2S12 (LGPS) is a superionic conductor that has an ionic conductivity equivalent to conventional liquid electrolytes (~10-2 S cm-1) and thus shows exceptional potential to fulfill the promise of solid-state...
The family of thio-LISICON solid-state electrolytes (SSEs) is one of the most promising material systems for the realization of fully solid state batteries due to comparable performance with liquid electrolyte-based counterparts. Among this SSE family, Li 10 GeP 2 S 12 (LGPS) is one of the most promising candidates due to its high theoretical ionic conductivity (1 × 10 −2 S cm −1 ). However, the narrow electrochemical and chemical stability windows of LGPS make it unstable in direct contact with both Li metal and conventional transition metal oxide cathode materials, leading to dramatic degradation during battery cycling and even during battery storage prior to battery operation. In this study, we employ an elastomeric artificial solid electrolyte interphase (ASEI) as a protective layer grown directly on Li metal by electrochemically polymerizing 1,3-dioxolane prior to assembling Li/LGPS/Li test cells. This ASEI serves as a Li + -conducting interlayer capable of halving the chemical degradation rate as compared to untreated pristine Li at the Li/LGPS interface, while also significantly lowering the absolute impedance and overpotential of Li/LGPS/Li symmetric cells during galvanostatic cycling at 0.1 mA h cm −2 . The elemental composition and spatial structure of this ASEI layer were investigated using X-ray photoelectron spectroscopy and scanning electron microscopy characterization techniques. Density functional theory calculations were performed to understand the impact of the elastomeric ASEI layer on chemical aging at the Li/LGPS interface.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.