DLC Films Research Articles

A Study about Deposition Process and Improvement of Friction Properties on Chlorine-Containing DLC Films

A Study about Deposition Process and Improvement of Friction Properties on Chlorine-Containing DLC Films

Probing the Low Friction Mechanism of Hydrogen-Free Dlc Film in Oxygen and Nitrogen Environments by First-Principles Calculations and Molecular Dynamics Simulation

Probing the Low Friction Mechanism of Hydrogen-Free Dlc Film in Oxygen and Nitrogen Environments by First-Principles Calculations and Molecular Dynamics Simulation

The influence of Ti plasma etching pre‐treatment on mechanical properties of DLC film on cemented carbide

The pre‐treatment of substrate surface had been a key part of DLC film preparation to improve mechanical and tribological properties. Ti plasma etching pre‐treatment was investigated in this paper as a new effective surface pre‐treatment method to substitute transition layer. This pre‐treatment used high‐energy Ti plasma to impact substrate surface. Ti plasma etched the substrate to a depth of 407 nm and increased the roughness from 1.36 to 40.39 nm. A trace layer of substrate, together with cobalt, oxides, and other impurities, was removed. Ti plasma broke some top WC crystals and combined with the free carbon ions separating from the substrate. A DLC film was deposited on the etched surface. Compared with DLC films deposited on the untreated substrate and Ti transition layer, the DLC film on the Ti plasma etched substrate had best adhesion strength of 34.14 N. The three DLC films had the same sp3 bonding carbon content, but Ti plasma etching treatment could promote the formation of sp3 bonds on the interface of substrate and DLC film. This DLC film had low friction coefficient of 0.12 and low wear rate of 5.11 × 10−7 mm3/m·N. In summary, Ti plasma etching pre‐treatment could significantly improve the adhesion of DLC film and keep its excellent tribological properties.

Si and N incorporated hydrogenated diamond like carbon film with excellent performance for marine corrosion resistance

Under the background of the development of marine resources, marine corrosion has become a focus problem. A series of Si and N incorporated hydrogenated diamond like carbon (SiN-HDLC) film with excellent corrosion resistance performance was deposited by plasma enhanced chemical vapor deposition. Results suggest that the sp3/sp2 ratio of SiN-HDLC films presents a trend of increasing first and then decreasing with the improvement of the N2/SiH4 ratio. The adhesion between the as-deposited HDLC film and the substrate is tight (no microcracks) and the film surface is uniform and compact. The potentiodynamic polarization and electrochemical impedance spectroscopy results indicate that the SiN-HDLC film possesses better corrosion resistance in artificial seawater than that of Si-HDLC and N-HDLC film, and is much better than 304SS substrate. Besides, the SiN-HDLC film with the N2/SiH4 of 1/1 shows the best corrosion resistance. The as-deposited SiN-HDLC film possesses more excellent corrosion resistance in the artificial seawater environment compared with the reported DLC films and this study provides a promising protective material for marine corrosion resistance.

The tribological performance of W-DLC in solid–liquid lubrication system addivated with Cu nanoparticles

Judicious selection of additives having chemical and physical compatibility with the DLC films may help improving the triboligical properties and durability life of DLC-oil composite lubrication systems. In this study, Cu nanoparticles were added to PAO6 base oil to compose a solid-liquid composite lubrication system with W-DLC film. The effects of nanoparticle concentration, test temperature and applied load on tribological performance were systematically studied by a ball-on-disk friction test system. The tribological results illustrated that Cu nanoparticles could lower the coefficient of friction (COF) and dramatically reduce the wear rates of W-DLC films. The optimal tribological behavior was achieved for the 0.1 wt% concentration under 30 °C and the applied load of 100 N. The test temperature and applied load were vital influencing factors of the solid–liquid lubrication system. The bearing effect and soft colloidal abrasive film of spherical Cu nanoparticle contributed to the excellent tribological performance of the composite lubrication system under mild test conditions, meanwhile, the local delamination of W-DLC film and oxidation were the main causes of the friction failure under harsh test conditions. With test temperature and applied loads increase the degree of graphitization of the W-DLC film increased. In conclusion, there are several pivotal factors affecting the tribological performance of solid–liquid lubrication systems, including the number of nanoparticles between rubbing contact area, graphitization of the worn W-DLC films, tribofilms on the worn ball specimens and oxidation formed in friction test, and the dominant factor is determined by the testing condition.

Pulsed laser deposition of the protective and Anti-reflective DLC film

Protective and anti-reflective DLC film with double-layer structure was designed and prepared on the easy-corrosive silicon. The inner oxygen-doped DLC layer deposited in oxygen atmosphere by femto-second laser had high transmittance, while the outer pure DLC layer grown in high vacuum by nano-second laser had high hardness and corrosion resistance. The atomic bonds and microscopic structures of the pure and oxygen-doped DLC layers showed the inherent reason for the huge difference in their optical and mechanical properties. Tests showed that when the thickness of outer pure DLC layer reduced, the optical transmission of the double-layer DLC film could increase, however, the nano-hardness for the protective effect would decrease. Corrosion test demonstrated the pure DLC layer had good corrosion resistance against the alkaline solution, but it must be thick enough to prevent the alkaline solution effectively from soaking into the deep-seated depth to corrupt the inner oxygen-doped DLC layer.

Influences of Ti, Al and V metal doping on the structural, mechanical and tribological properties of DLC films

DLC films are widely used in different engineering products. However, some problems such as inadequate toughness, insufficient adhesion and internal stresses affect their performance. Therefore, we aimed to enhance the mechanical and tribological features of Cp-Ti by metal-free and metal-doped DLC films in this study. Cp-Ti samples were coated with un-doped and Ti, Al and V metal-doped DLC films by PVD. Their properties were investigated by Raman, XPS, XRD, SEM and wear tester. The results revealed that the incorporation of metal in DLC increased the disorder. Ti, Al and V carbides formed on DLC due to bonding of doping elements with carbon. Metal-doping improved the adhesion and decreased the internal stresses and these improvements caused metal-doped films to exhibit better tribological properties than metal-free film.

Effects of silicon doping on the chemical bonding states and properties of nitrogen-doped diamond-like carbon films by plasma-enhanced chemical vapor deposition

• The properties of Si and N doped diamond-like carbon (Si–N–DLC) have been examined. • The internal stress on Si–N–DLC was lower than that on N doped DLC. • The optical bandgap of Si–N–DLC showed an increasing trend with increasing N content. • Si–N–DLC/p-type Si junctions annealed in a vacuum showed rectifying characteristics. We have investigated the effects of silicon (Si) doping on the chemical bonding states and the electrical, optical, and mechanical properties of nitrogen-doped diamond-like carbon (N−DLC) films prepared via plasma-enhanced chemical vapor deposition using hydrogen as a dilution gas. N doping accelerated the formation of clustered sp 2 C in N−DLC films, whereas the clustering was almost suppressed in Si and N doped DLC (Si−N−DLC) films. Sp 3 C sites in the Si–N–DLC films were higher than those in the N–DLC films. For the Si−N−DLC films, sp 3 C-N bonds were preferentially formed compared with the sp 2 C=N bonds. The internal stress on the Si−N−DLC films was lower than that on the N−DLC films. The Si−N−DLC films exhibited higher optical bandgaps than the N−DLC films. As the N 2 flow ratio increased, the optical bandgap of the Si−N−DLC films showed an increasing trend, whereas that of the N−DLC films showed an opposite trend. The current−voltage characteristics of Si−N−DLC/p-type Si heterojunctions were not rectifying; however, after postdeposition annealing, the heterojunctions exhibited rectifying characteristics.

Contact cracking and delamination of thin solid lubricating films on deformable substrates

Effects of substrate plastic deformation on the cracking and delamination damage of thin solid lubricating films at sliding contacts were investigated. Diamond-like carbon films were evaluated by using micro-scratch tests. A three-dimensional finite element method was applied to analyze the stress-strain evolution of the film−substrate systems with consideration to the interfacial adhesion. Intense plastic deformations were generated in the softer SUS304 substrate due to the low shear strength, leading to parallel cracks along the track borders. A pile-up effect resulted in the film buckling and fragmentation ahead of the sliding stylus. However, on the harder M50 substrate, angular cracks in DLC films were generated at the trailing edge of the contact area, which led to wing-shaped spallation of the films.

Influence of the substrate pre-treatment on the mechanical and corrosion response of multilayer DLC coatings

This work evaluates the mechanical, tribological and corrosion response of single-layer and multilayer DLC films deposited on top of martensitic stainless steel, which was previously plasma nitrided. The efficiency of plasma nitriding as pre-treatment was evaluated using a control group of samples, which was only coated under the same conditions. The pre-treated samples showed a better adhesion of both single and multi-layer DLC films, showing no signs of spallation after applying up to 50 N load during the scratch test.Fretting wear tests (ball on disk) with applied loads 40‐70 N were used to evaluate the mechanical response of the different systems. The best response to fretting wear was given by the coatings deposited onto the pre-treated stainless steel substrate, showing a good mechanical stability without cracking up to 70 N load. Additionally, the corrosion resistance evaluated using step-increasing bias potentiostatic tests, turned out to be acceptable when using plasma nitriding as a pre-treatment. On the contrary, the DLC coatings on top of non- pre-treated substrates failed at a potential 400 mV lower than the 1DLC or 5DLC + N samples. Finally, it is seen that combining nitriding with DLC in the form of multilayers constituted the best protective system, since it can delay the formation of pathways between the corrosive solution and the substrate, until 2000 V bias and 3 hours duration of the experiment.

High-temperature tribological performance of the Si-gradually doped diamond-like carbon film

Silicon containing diamond-like carbon films is of value for engineering applications operating at the temperature above 200 °C. This work presents a Si-gradually doped diamond-like carbon film with increasing the Si content from outer layer to inner layer deposited by plasma-assisted reactive magnetron sputtering process. The microstructure, chemical bonding state and temperature-dependence tribological properties upto 500 °C of the film are investigated by using focused ion beam/transmission electron microscope (FIB/TEM), X-ray photoelectron spectroscopy (XPS) techniques and ball-on-disk tribometer, respectively. The results show that the as-deposited Si-gradually doped DLC film exhibit amorphous structure. The wear track tested at 500 °C are composed of carbon, SiO2 and silicon oxide. High-temperature tribological tests show that the friction coefficient values are 0.05 ± 0.01, 0.02 ± 0.004 and 0.09 ± 0.04, while the wear rates are 1.17 × 10−7 mm3/N·m, 1.65 × 10−7 mm3/N·m and 1.4 × 10−6 mm3/N·m at 300 °C, 400 °C and 500 °C, respectively. It is proposed that the improved high-temperature tribological properties of the Si-gradually doped DLC film benefit from its special composition structure that the inner layer with high Si content provides the required mechanical properties and the outer layer with low Si content reduces the friction coefficient as well as the wear rate.

Effect of substrate bias on the properties of DLC films created using a combined vacuum arc

Effect of substrate bias on the properties of DLC films created using a combined vacuum arc

Effect of the methane flow ratio on the structural and mechanical properties of high-entropy alloy co-doped DLC films

High-entropy alloy is co-doped in diamond-like carbon films by sputtering using a single (AlCrNbSiTiV) target. This study analyzed the effects of methane flow rates [Rm = CH4/(Ar + CH4) flow ratio], which varied in the range from 16 to 24%, on the morphological, phase structures, mechanical characteristics and tribological behavior of diamond-like carbon films. The diamond-like carbon film is characterized using Raman spectroscopy, nano-indentation, high-resolution transmission electron microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy and scratch testing. As a result, the element concentration in the diamond-like carbon films is quite near to the High-entropy alloy target composition, and the metal content of co-doped diamond-like carbon films decreases as the fraction of the methane reactive gas increases. For a monotonically increasing Rm flow ratio, the position of the G-peak is downshifted to a low wavenumber, a decrease in ID/IG ratio suggests a decrease in sp2/sp3 ratio, which is associated with the decrease in the fraction of graphite and the more disordered carbon structure. An increase in the Rm flow ratio results in increased hardness (H) and elastic modulus (E) and a decreased friction coefficient, wear rate, H3/E2 and H/E. Cutting tests using a tool coated in a diamond-like carbon film shows the cutter life was extended.

Formation of diamond like carbon films on materials for medical application

The aim of this experimental work is to identify how the surfaces of materials that are most often used inmedical implants and prostheses, affect the properties of the deposited amorphous carbon films. The DLCfilms were formed on the stainless steel, aluminium, polyetheretherketone (PEEK) and polycaprolactone(PCL) surfaces by PECVD method using C2H2 gas plasma and their properties was compared with the filmsdeposited on silicon. The differences of the films properties were determined by a null-ellipsometry and Ramanspectroscopy. It was found that the thicknesses of the carbon coatings deposited on metallic substratesare larger than on the silicon when the deposition conditions were the same. When the films are formed athigh bias voltage the refractive index of the DLC films deposited on stainless steel are lower compared tothe coatings on silicon but the extinction coefficients are higher. Raman spectra shows that sp2 bonds concentrationis higher in this case. When the ion energy is lowest (bias voltage -400 V), Raman spectroscopyshows that D peak isn’t observed on the Si-deposited carbon coating, while the typical carbon amorphouscoating is formed on the Al substrate. The thickness of amorphous carbon coatings deposited on the polymersdepends on the bias voltage, and the optical properties depend on the type of polymer. The coatingsdeposited on PCL have a much higher refractive index than on PEEK. Key words: amorphous carbon films, steel, aluminum, polyetheretherketone, polycaprolactone, Ramanspectroscopy.

Study of DLC Formation with Ion-Beam Assisted Magnetron Sputtering Deposition

TiC-containing DLC films are deposited by magnetron sputtering by means of ion beam deposition using acetylene as carbon source. The deposition rate of the films is three times as fast as that by ion beam deposition alone. The minimum roughness is 2.2 nm and the highest hardness is 11.97 GPa for the synthesized DLC films. The effects of ion beam voltage and deposition temperature on the composition, microstructures, and surface states are studied using infrared spectroscopy, XRD, Raman spectroscopy, and AFM. Mechanical properties of the DLC films from nanoindentation tests are analyzed with the variation of H and TiC, as well as content of sp3 bonds.

High temperature nanomechanical properties of sub-5 nm nitrogen doped diamond-like carbon using nanoindentation and finite element analysis

Nitrogen doped diamond-like carbon (NDLC) is a candidate protective coating in state-of-the-art heat assisted magnetic recording (HAMR) media. To ensure the robustness of the media particularly at higher temperature applications, mechanical properties of ultra-thin sub 5-nm NDLC coatings are of great interest. Due to instrument limitations and very shallow films, it is very challenging to accurately measure sub-5 nm NDLC films and other HAMR components from experiments without substrate effects. In this study, very shallow nanoindentations were performed, and the results were fitted with finite element analysis using a modified indenter geometry to predict the elastic modulus and yield strength of NDLC films of two different thicknesses (3.5 and 4.5 nm) and other components without any substrate effect. Results showed that higher NDLC film thickness led to better elastic modulus and yield strength at 25 °C before and after heating and at 300 °C. Hardness to yield strength ratio (H/Y) for NDLC films was also determined and found within the range of 2.2–2.8, which is higher than the H/Y ratio of DLC films from earlier studies. This implied the dependence of H/Y ratio on the thickness, temperature conditions, and chemical structure of NDLC films. Results also showed that the yield strength of FeCo metal layer and glass substrate in HAMR media decreased at 300 °C, but almost fully recovered to their initial properties after removal of heat.

Oxygen doping effect on wettability of diamond-like carbon films

DLC films were deposited on Ge substrates using direct ion beam deposition method, followed by investigating the influence of O2 doping on their morphological, electrical, and structural properties. The films were doped with oxygen under flow rates of 5, 10, 20, and 40 sccm (standard cubic centimeters per minute). The structure of the films was studied by Raman spectroscopy. Result showed that by increasing oxygen incorporation, sp2 content decreases, sp3 content increases, and the C-C bonding loses its order. The hydrophilicity of the layers was analyzed by the contact angle measuring experiment. The results showed that by increasing the O2 flow ratio from 5 to 40 sccm, the percentage of O2 increases from 1.1 to 3.9%. The water contact angle measurement showed that an increase in oxygen flow ratio results in a decrease in contact angle from 82.9° ± 2.1° to 50° ± 3°.

Tribo-mechanism of amorphous carbon films under corrosion solution and various mechanical loads

Diamond-like carbon films (DLC) as a prominent surface protection coating are used to enhance the tribological performance of engineering components due to their low coefficient of friction (COF), high wear resistance and excellent chemical stability. In recent years, researchers have separately studied the environment-dependent and load-dependent tribological behaviors of DLC films. However, there is few studies about the influence of corrosive media on the load-dependent tribological behaviors of DLC films. In this paper, we explained the tribo-mechanism of chromium doped DLC film (Cr-DLC) in hydrochloric acid (HCl) by combing the effect of load-dependent. For comparison, tribological behaviors of Cr-DLC films in ambient air and distilled water environment were also investigated. It is found that the coefficient of friction of Cr-DLC film complies with the Hertzian elastic contact model in HCl solution. In other words, the COF decreases with the increase of normal contact load except 2 N. The Cr-DLC film shows the highest wear resistance with wear rate of 1.79 × 10−7 mm3/Nm at 5 N. The main wear mechanism at 2 N and 5 N is governed by the formation of a graphite-like transfer film and tribochemical products on friction interfaces; Whereas the wear mechanism for 7 N and 10 N contact load is attributed to the superimposed effect of the high Hertzian contact stress and the corrosion function of chloride ion. The insights acquired from this study can be used to the design of high-performance of DLC coated tribo-systems in corrosive environment.

Properties, mechanism and applications of diamond as an antibacterial material

Antibiotic resistance in bacteria is a current threat causing an increasing number of infections of difficult clinical management. While the overuse and misuse of antibiotics are investigated to reduce them, the need for alternatives to approaches is rising. Carbon-based materials shown recent moderate to high antibacterial properties and diamond, thanks to its superior mechanical, tribological, electrical, chemical and biological quality is a choice material to investigate for safe antibacterial films, coatings and particles. Here, the antibacterial properties of diamond films, nanodiamonds, DLC films and a comprehensive list of the composites developed from them are discussed along with a summary of the bacterial strains used and the most efficient composition and/or concentration discovered. In a later stage, the mechanisms of action and the parameters that are believed to influence them are discussed and finally, an overview of the biomedical and food industry applications is given.

Effect of Soft X-ray Irradiation on Film Properties of a Hydrogenated Si-Containing DLC Film.

The effect of soft X-ray irradiation on hydrogenated silicon-containing diamond-like carbon (Si-DLC) films intended for outer space applications was investigated by using synchrotron radiation (SR). We found that the reduction in film thickness was about 60 nm after 1600 mA·h SR exposure, whereas there was little change in their elemental composition. The reduction in volume was attributable to photoetching caused by SR, unlike the desorption of hydrogen in the case of exposure of hydrogenated DLC (H-DLC) film to soft X-rays. The ratio of the sp2 hybridization carbon and sp3 hybridization carbon in the hydrogenated Si-DLC films, sp2/(sp2 + sp3) ratio, increased rapidly from ~0.2 to ~0.5 for SR doses of less than 20 mA·h. SR exposure significantly changed the local structure of carbon atoms near the surface of the hydrogenated Si-DLC film. The rate of volume reduction in the irradiated hydrogenated Si-DLC film was 80 times less than that of the H-DLC film. Doping DLC film with Si thus suppresses the volume reduction caused by exposure to soft X-rays.