Properties Of Graphite-like Carbon Films Research Articles

Effect of graphite target power density on tribological properties of graphite-like carbon films

In order to improve the tribological performance, a series of graphite-like carbon (GLC) films with different graphite target power densities were prepared by magnetron sputtering. The valence bond and microstructure of films were characterized by AFM, TEM, XPS and Raman spectra. The variation of mechanical and tribological properties with graphite target power density was analyzed. The results showed that with the increase of graphite target power density, the deposition rate and the ratio of sp2 bond increased obviously. The hardness firstly increased and then decreased with the increase of graphite target power density, whilst the friction coefficient and the specific wear rate increased slightly after a decrease with the increasing graphite target power density. The friction coefficient and the specific wear rate were the lowest when the graphite target power density was 23.3 W/cm2.

Structure and properties of GLC films deposited by PEMS

In this paper, an unbalanced plasma enhanced magnetron sputtering system was adopted to deposit four types of the graphite-like carbon (GLC) films under different currents of ion source. The results show that a moderate Ar+ bombardment effectively adjusts the content of sp3 hybrid structure, and significantly improves the film’s compactness. With the increase of ion source current, the hardness, H/E and H3/E2 ratios of the film present a change rule of increasing first and decreasing subsequently, and all achieve their maximum values under the ion source current of 10 A. Moreover, the average values of the studied GLC films are all below 0.05 with slight fluctuation, while the wear rate of the film presents a significant difference with the increase of ion source current. Especially, when the ion source current is 10 A, the friction coefficient and the wear rate of the GLC films are 0.01 and 1.7 × 10−16 m3 N−1 m−1, respectively, presenting excellent tribological properties.

Study on Microstructure and Tribological Properties of Graphite-Like Carbon Films

Graphite-like carbon films were deposited on DC53 steel substrate by unbalanced magnetron sputtering. The microstructures of the resultant films were investigated by Raman spectroscopy, scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and X-ray diffractometer (XRD), respectively. Ball-on-disc tribometer was employed to analyze the tribological properties of the film. The results show that the films were dominated by sp2 sites. The surfaces are uniform and dense, the sectional morphology of the films present dense columnar crystal. The films have superior tribological properties under different loads, including low friction coefficient (0.18-0.33) and low wear rate (2.53×10-17m3/(Nm)- 8.47×10-17m3/(Nm)).

Friction and Wear Properties of Graphite-Like Carbon Films Deposited on Different Substrates with a Different Interlayer Under High Hertzian Contact Stress

Four types of graphite-like carbon (GLC) films were deposited on different substrates (Ti6Al4V, WC-27CrNi) with a different interlayer (TiC/Ti, TiC/Ti/TiN) using an unbalanced magnetron sputtering system. The effect of substrate and interlayer on the microstructure and properties of the studied GLC films was then investigated using different characterization techniques. The results show that both the substrate and interlayer had an obvious influence on the tribological properties of the studied GLC films even though there was no significant structural difference between these films. Specifically, a substrate with a high hardness was propitious to achieving superior tribological behaviors for carbon film even with a different interlayer. However, the interlayer had a distinct influence on the tribological properties of the carbon film deposited on different substrates, and this effect varied with the hardness property of the substrate. For a hard substrate, the wear rate and wear life were similar irrespective of the interlayer. For a soft substrate, the addition of a TiN interlayer improved the wear life sevenfold compared to the film with only a TiC/Ti interlayer, but the wear rate for a film with and without a TiN interlayer was approximately the same. The obvious discrepancy between wear life and wear rate for a carbon film deposited on soft substrate was closely related with the film adhesion strength and plastic deformation of the substrate materials. Based on these results, it can be concluded that the wear life is a better parameter than wear rate in terms of characterization of the wear resistance of carbon film once the applied load causes the plastic deformation of the substrate.

Study on the microstructure and properties of graphite-like carbon films deposited by unbalanced magnetron sputtering

A series of graphite-like amorphous carbon films were deposited by unbalanced magnetron sputtering system with different sputtering currents. The microstructure, morphology, contact angle, and tribological properties of the resultant carbon films were subsequently investigated by means of different characterization techniques. Raman analysis shows that the resultant amorphous carbon films are dominated by sp2 sites, and the intensity ratio of the D and G peaks increases gradually from ∼4.1 to ∼5.4 with decrease in the sputtering current from 16 to 4 A, which is one order of magnitude larger than that of diamond-like carbon films with high sp3 content, indicating a more graphite-like structure. The surface of the resulting carbon films is composed of granular structure with different diameters and heights, and the root mean square roughness of the studied films monotonically increases from 3.5 nm at a sputtering current of 4 A to 8.2 nm at 16 A. The contact angle of graphite-like carbon films with water changes from 43.4° to 89.5° with decrease in the sputtering current. Besides, these graphite-like carbon films demonstrate superior tribological properties with high load-bearing capacity and low friction coefficient in humid atmosphere. The superior tribological behaviors of this graphite-like carbon film are promising for a wide range of applications such as gears, cutting tools, automobile parts, etc.

Preparation and properties of graphite-like carbon films fabricated by unbalanced magnetron sputtering

A series of graphite-like carbon films is fabricated by the middle frequency magnetron sputtering technique. The microstructures and the morphologies of the resulting films are investigated by Raman spectroscopy, high resolution transmission electron microscopy and atomic force microscopy, respectively. The mechanical and the tribological properties of the films are studied by nanoindentation and CSM tribometer. The results show that the deposited carbon film is dominated by sp2 sites, and has an amorphous structure, a moderate hardness, low internal stress, high surface roughness and superior tribological properties. With the increase of the duty ratio, the intensity ratio between D and G peaks first decreases and then increases, while the film hardness first increases and then decreases. Tribological testing in humid atmosphere demonstrates that the present carbon film has a superior wear resistance (～10-11 cm3/N-1.m-1) and high load bearing capacity (～2.5 GPa). Although the duty ratio has no obvious influence on friction coefficient, the wear rate decreases obviously and then increases slightly with the increase of duty ratio. The superior tribological properties of the graphite-like carbon film are attributed mainly to its unique structure, low internal stress and high structure stability.

The effect of microtopography and deposition regime on the field emission properties of graphitelike carbon films

Technological factors controlling the formation of the microtopography of the surface of graphitelike carbon films deposited from the plasma of a microwave gas discharge in ethanol vapor are established. Parameters of the deposition regime and the surface roughness influence the electric conductivity and the field emission properties of the films obtained by this method. Using graphitelike carbon films, an emission current density of up to 0.3 A/cm2 was obtained at an electric field strength in the gap of about 7 V/μm.

Optical properties of graphite-like carbon films

A model of the electronic structure of graphite-like carbon films, describing the semiconductor properties of this material, is presented. Spectra of optical constants of microcrystalline carbon films in the region λ = 0.4–8.0 μm were studied by the spectral ellipsometry and IR reflection methods. A number of distinctive features of the spectra, associated with both the appearance of CC- and CHn-type bonds and direct energy gaps, were found. Analysis of the optical data using the proposed model makes possible a common interpretation of our results and literature data. Values of a parameter Θ, which is an averaged qualitative parameter of structural distortions within carbon microcrystallites as compared with crystalline graphite, are determined from comparison of theoretical results and experimental data.