@article{islam_liu_boyd_zhong_nahid_henry_taussig_ko_nguyen_myers_et al._2020, title={Enhanced mid-wavelength infrared refractive index of organically modified chalcogenide (ORMOCHALC) polymer nanocomposites with thermomechanical stability}, volume={108}, ISSN={["1873-1252"]}, url={http://dx.doi.org/10.1016/j.optmat.2020.110197}, DOI={10.1016/j.optmat.2020.110197}, abstractNote={Abstract Organically modified chalcogenide (ORMOCHALC) polymers have proven to be alternatives to the conventional inorganic materials for mid-wavelength infrared (MWIR, λ = 3–5 μm) optical components. While the refractive index of ORMOCHALC can be reinforced by the content of chalcogenides such as sulfur (S) and selenium (Se), the increased portion of the S or Se deteriorate the thermomechanical stabilities. As a remedy, this study utilizes ZnS nanoparticles to reinforce both optical and thermomechanical properties of the sulfur-based ORMOCHALC polymer, poly(S-random-1,3-diisopropenylbenzene). The refractive index n and extinction coefficient k of the nanocomposites were characterized by Infrared Variable Angle Spectroscopic Ellipsometry (IR-VASE). The results show a significant increment in the refractive index of Δn = 6.58% at the wavelength of 4 μm by adding 20 wt% ZnS (or 7.29 vol%) in the ORMOCHALC polymer. The low extinction coefficient of the nanocomposites (}, journal={OPTICAL MATERIALS}, author={Islam, Md Didarul and Liu, Sipan and Boyd, Darryl A. and Zhong, Yaxu and Nahid, Masrur Morshed and Henry, Reece and Taussig, Laine and Ko, Yeongun and Nguyen, Vinh Q. and Myers, Jason D. and et al.}, year={2020}, month={Oct} }
 @article{chromik_baker_voevodin_wahl_2007, title={In situ tribometry of solid lubricant nanocomposite coatings}, volume={262}, ISSN={["1873-2577"]}, DOI={10.1016/j.wear.2007.01.001}, abstractNote={The friction and wear behavior of nanocomposite coatings comprised of yttria stabilized zirconia (YSZ), Au, carbon and MoS2 were studied by in situ tribometry in both dry nitrogen (3–5% RH) and humid air (35–45% RH). Transfer film formation and interfacial dynamics were evaluated by direct observation of the sliding contact through a sapphire hemisphere. Four different third-body velocity accommodation modes (VAMs) were identified: (1) interfacial sliding, (2) interfacial sliding combined with transfer film shearing, (3) plowing and (4) local plowing and transfer film extrusion. The first two VAMs were associated with low, stable friction in dry and humid environments. The second two VAMs were associated with high friction in dry conditions and increased wear. Tribological performance and VAMs were also correlated with coating composition and mechanical properties. Friction spiking occurred for coatings with greater YSZ content. Harder coatings exhibited high friction run-in that was more pronounced for coatings with high carbon content. In situ experiments demonstrated that friction and wear performance was controlled by stable transfer film formation and VAMs associated with a lubricating condition (interfacial sliding or transfer film shearing).}, number={9-10}, journal={WEAR}, author={Chromik, Richard R. and Baker, Colin C. and Voevodin, Andrey A. and Wahl, Kathryn J.}, year={2007}, month={Apr}, pages={1239–1252} }
 @article{baker_chromik_wahl_hu_voevodin_2007, title={Preparation of chameleon coatings for space and ambient environments}, volume={515}, ISSN={["0040-6090"]}, DOI={10.1016/j.tsf.2007.02.005}, abstractNote={Tribological coatings of yttria-stabilized zirconia (YSZ), Au, diamond like carbon (DLC) and MoS2 were synthesized using magnetron assisted pulsed laser deposition. The coatings were synthesized in four-component and three-component combinations that included YSZ/Au/DLC/MoS2, YSZ/Au/MoS2, and YSZ/Au/DLC. A range of coating compositions was studied to explore coating optimization for low friction in varying environments (dry, humid and high temperature). For four-component YSZ/Au/DLC/MoS2 coatings, the optimal compositions for friction adaptation between dry nitrogen and humid air included relatively high concentrations of the soft phase, Au (> 20 at.%), and low amounts of the hard phases, DLC and YSZ. Ex situ Raman spectroscopy analysis indicates that friction adaptation involves a combination of both lubricating species, MoS2 and carbon, where transitions of DLC to graphitic-carbon and amorphous MoS2 to its hexagonal phase occur after cycling between both room temperature humid air and dry nitrogen. In large carbon concentrations (> 30 at.%), the DLC component was found to be detrimental for friction in dry nitrogen and humid air, but promoted a longer coating wear life at 500 °C. The three-component coating of YSZ/Au/MoS2 performed well in both dry nitrogen and humid air, suggesting a synergism between Au and MoS2, where carbon was not necessary for lubrication in humid air.}, number={17}, journal={THIN SOLID FILMS}, author={Baker, C. C. and Chromik, R. R. and Wahl, K. J. and Hu, J. J. and Voevodin, A. A.}, year={2007}, month={Jun}, pages={6737–6743} }
 @article{baker_hu_voevodin_2006, title={Preparation of Al2O3/DLC/Au/MoS2 chameleon coatings for space and ambient environments}, volume={201}, ISSN={["0257-8972"]}, DOI={10.1016/j.surfcoat.2006.08.067}, abstractNote={We have investigated the tribological properties of nanocomposite “chameleon” coatings, which adapt their low friction behavior with the surrounding environmental humidity and temperature. The material system of interest included alumina (Al2O3) in an Au matrix with diamond-like carbon (DLC) and MoS2 nanoparticle inclusions. The coating design included formation of nanocrystalline hard oxide particles for wear resistance, embedding them into an amorphous matrix for toughness enhancement, and inclusion of nanocrystalline and/or amorphous solid lubricants for friction adaptation to different environments. Chemical analysis was used to ascertain a correlation between chemical bonding of species and frictional properties. Friction measurements were studied in cycling between humid air and dry nitrogen conditions at room temperature and during heating in air to 500 °C. It was observed that both graphitic carbon and MoS2 worked together to give low friction in variable humidity environment, while Au was valuable for a low friction at elevated temperatures. Friction coefficients were found to be 0.02–0.03 in dry nitrogen, 0.1–0.15 in humid air, and 0.1 in air at 500 °C. Thus the tribological property results have shown that the system provides “chameleon” type adaptation behavior in different environments relevant for aerospace systems.}, number={7}, journal={SURFACE & COATINGS TECHNOLOGY}, author={Baker, C. C. and Hu, J. J. and Voevodin, A. A.}, year={2006}, month={Dec}, pages={4224–4229} }