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Specific Features of Reactive Pulsed Laser Deposition of Solid Lubricating Nanocomposite Mo-S-C-H Thin-Film Coatings.

ABSTRACT: This work investigates the structure and chemical states of thin-film coatings obtained by pulsed laser codeposition of Mo and C in a reactive gas (H₂S). The coatings were analysed for their prospective use as solid lubricating coatings for friction units operating in extreme conditions. Pulsed laser ablation of molybdenum and graphite targets was accompanied by the effective interaction of the deposited Mo and C layers with the reactive gas and the chemical states of Mo- and C-containing nanophases were interdependent. This had a negative effect on the tribological properties of Mo-S-C-H nanocomposite coatings obtained at H₂S pressures of 9 and 18 Pa, which were optimal for obtaining MoS₂ and MoS₃ coatings, respectively. The best tribological properties were found for the Mo-S-C-H_5.5 coating formed at an H₂S pressure of 5.5 Pa. At this pressure, the x = S/Mo ratio in the MoS_x nanophase was slightly less than 2, and the a-C(S,H) nanophase contained ~8 at.% S and ~16 at.% H. The a-C(S,H) nanophase with this composition provided a low coefficient of friction (~0.03) at low ambient humidity and 22 °C. The nanophase composition in Mo-S-C-H_5.5 coating demonstrated fairly good antifriction properties and increased wear resistance even at -100 °C. For wet friction conditions, Mo-S-C-H nanocomposite coatings did not have significant advantages in reducing friction compared to the MoS₂ and MoS₃ coatings formed by reactive pulsed laser deposition.

SUBMITTER: Fominski V

PROVIDER: S-EPMC7764125 | biostudies-literature | 2020 Dec

REPOSITORIES: biostudies-literature

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Specific Features of Reactive Pulsed Laser Deposition of Solid Lubricating Nanocomposite Mo-S-C-H Thin-Film Coatings.

Fominski Vyacheslav V Fominski Dmitry D Romanov Roman R Gritskevich Mariya M Demin Maxim M Shvets Petr P Maksimova Ksenia K Goikhman Alexander A

Nanomaterials (Basel, Switzerland) 20201208 12

This work investigates the structure and chemical states of thin-film coatings obtained by pulsed laser codeposition of Mo and C in a reactive gas (H<sub>2</sub>S). The coatings were analysed for their prospective use as solid lubricating coatings for friction units operating in extreme conditions. Pulsed laser ablation of molybdenum and graphite targets was accompanied by the effective interaction of the deposited Mo and C layers with the reactive gas and the chemical states of Mo- and C-contai ...[more]

PMID: 33302538

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Project description:Over the years, vanadium dioxide, (VO2(M1)), has been extensively utilised to fabricate thermochromic thin films with the focus on using external stimuli, such as heat, to modulate the visible through near-infrared transmittance for energy efficiency of buildings and indoor comfort. It is thus valuable to extend the study of thermochromic materials into the mid-infrared (MIR) wavelengths for applications such as smart radiative devices. On top of this, there are numerous challenges with synthesising pure VO2 (M1) thin films, as most fabrication techniques require the post-annealing of a deposited thin film to convert amorphous VO2 into a crystalline phase. Here, we present a direct method to fabricate thicker VO2(M1) thin films onto hot silica substrates (at substrate temperatures of 400 °C and 700 °C) from vanadium pentoxide (V2O5) precursor material. A high repetition rate (10 kHz) femtosecond laser is used to deposit the V2O5 leading to the formation of VO2 (M1) without any post-annealing steps. Surface morphology, structural properties, and UV-visible optical properties, including optical band gap and complex refractive index, as a function of the substrate temperature, were studied and reported below. The transmission electron microscopic (TEM) and X-ray diffraction studies confirm that VO2 (M1) thin films deposited at 700 °C are dominated by a highly texturized polycrystalline monoclinic crystalline structure. The thermochromic characteristics in the mid-infrared (MIR) at a wavelength range of 2.5-5.0 μm are presented using temperature-dependent transmittance measurements. The first-order phase transition from metal-to-semiconductor and the hysteresis bandwidth of the transition were confirmed to be 64.4 °C and 12.6 °C respectively, for a sample fabricated at 700 °C. Thermo-optical emissivity properties indicate that these VO2 (M1) thin films fabricated with femtosecond laser deposition have strong potential for both radiative thermal management or control via active energy-saving windows for buildings, and satellites and spacecraft.

Dataset Information

Specific Features of Reactive Pulsed Laser Deposition of Solid Lubricating Nanocomposite Mo-S-C-H Thin-Film Coatings.

Publications

Specific Features of Reactive Pulsed Laser Deposition of Solid Lubricating Nanocomposite Mo-S-C-H Thin-Film Coatings.

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