Tailoring microstructure and phase segregation for low friction carbon-based nanocomposite coatings

Friction has a direct relation with the energy efficiency and environmental cleanliness in all moving mechanical systems. To develop low friction coatings is extremely beneficial for preserving not only our limited energy resources but also the earth’s environment. This study proposes a new design for low friction carbon-based nanocomposite coatings by tailoring the microstructure and phase segregation,and thereby it contributes to better controlling the mechanical and tribological properties. Experimental findings and theoretical calculations reveal that high-hardness (18.2 GPa), high-adhesion strength (28 N) as well as low-internal stress (-0.8 GPa) can be achieved by a nanocrystallite/amorphous microstructure architecture for the nc-WC/a-C(Al) carbon-based nanocomposite coating;in particular low friction (~0.05) can be acquired by creating a strong thermodynamic driving force to promote phase segregation of graphitic carbon from the a-C structure so as to form a low shear strength graphitic tribo-layer on the friction contact surfaces. This design concept is general and has been successfully employed to fabricate a wide class of low friction carbon-based nanocomposite coating

Effects of constituent layers and interfaces on the mechanical and tribological properties of metal (Cr, Zr)/ceramic (CrN, ZrN) multilayer systems

Effects of constituent layers and interfaces on the mechanical and tribological properties of metal (Cr, Zr)/ceramic (CrN, ZrN) multilayer system

Super-hydrophilic properties of TiO2-DLC nanocomposite films fabricated by the simple electrochemical process

Anatase TiO2 nanoparticles incorporated DLC films were successfully deposited on single crystalline silicon substrates by the electrolysis of TiO2-methanol solution under ambient atmospheric pressure and low temperature. Anatase TiO2 nanoparticles were embedded into amorphous carbon matrix, forming the typical nanocrystalline/ amorphous nanocomposite films, confirmed by transmission electron microscopy (TEM). TiO2 incorporation effectively increased the sp 3-hybridized carbon concentration in the composite film, and further regulated the microstructure and surface morphology. Furthermore, the static contact testing completely displayed, TiO2 incorporation got the composite films super-hydrophilic, which fundamentally improved the wetting ability of DLC film

Electrochemical deposition of sulfur doped DLC nanocomposite film at atmospheric pressure

Sulfur doped DLC nanocomposite film was fabricated on n-type silicon substrates by the electrochemical method using the mixture of methanol and thiofuran as the precursor. The synthesis and microstructure of the composite film was investigated. Compared with pure carbon film, sulfur doping effectively enhanced carbon film graphitization, and reduced the surface roughness, confirmed by XPS, Raman and AFM. In particular, XPS analysis revealed sulfur atoms among amorphous carbon matrix was in the form of organosulfur compounds. Furthermore, a novel but feasible growth mechanism was proposed following the synergism of thermochemistry, plasma chemistry and electrochemistry processes

Investigation of microstructure and photo-magnetic properties of sulfur-doped DLC nanocomposite films by electrochemical method

Sulfur-doped DLC nanocomposite films have been successfully deposited by the electrochemical method using the mixture of methanol and thiofuran as the precursor at ambient atmospheric pressure. In contrast to DLC film, the effects of sulfur incorporation on the microstructural transformation and properties of sulfur-doped DLC nanocomposite films were investigated in detail in terms of atomic force microscopy, X-ray photoelectron spectroscopy, Raman spectrum and photoluminescence and magnetic tests. The experimental results showed that the unexpected organic molecular structure was formed like sulfone or thiols in sulfur-doped DLC nanocomposite films, and the concentration of sulfur in films was readily manipulated by the volume ratio of thiofuran to methanol. Meanwhile, the sp3-hybridized carbon content gradually decreased in films as the volume of thiofuran increased. Furthermore, sulfurdoped DLC nanocomposite films showed the monochromatic photoluminescence performance with a wide band centered at 510 nm, which could be attributed to carrier localization within an increasing sp2 clusters and the defects along with the sulfur doping. Particularly, ferro-like magnetic performance of sulfur-doped DLC nanocomposite film might originate from the magnetic moment of localized sp2 clusters with different charged carriers near the Fermi level after sulfur incorporation

The tunable wettability in multistimuli-responsive smart graphene surfaces

The tunable wettability of smart graphene films onto stainless steel substrates with a multi-response to different environmental stimuli has been investigated including light irradiation, pH, electric field, and annealing temperature. Conductive graphene film exhibited the controllable transition from water-repellent to water-loving characteristic in response to different environment fields, which primarily resulted from the morpho-chemically synergistic effect as well as the restoration of electronic stucture. Based on the fundamental theories of wettability, mechanisms in switching from hydrophobicity to hydrophilicity for smart graphene surface including thermal chemistry, electrostatic, photo-induced surface chemistry, solvent, and pH methods were presented