Properties Of ta-C Research Articles

Deposition processes of superhard diamond-like carbon films co-adjusted by ion energy and ion flux in arc discharges

As a kind of protective material, Diamond-Like Carbon (DLC) film can effectively improve the mechanical and tribological properties of the substrate surface. In DLC family, tetrahedral amorphous carbon (ta-C) with ultra-high hardness and excellent protective properties has been widely concerned in the field of hard protective materials. It is well known that the structure and properties of ta-C are strongly dependent on carbon plasma characteristics in the plasma environment. Therefore, it is extremely crucial to obtain the optimal process window of ta-C described by plasma micro-parameters with general significance. This paper proposed the Langmuir probe was used to diagnose the carbon plasma of the afterglow generated by arc evaporation, aiming to investigate the characteristics of carbon plasma and sheath. The effect of ion energy and ion flux adjusted by the pulse bias voltage and arc current on the sp3 hybrid bonds and hardness of DLC films was studied, aiming to find out which conditions satisfied the formation of ta-C. The results showed the microstructure and properties of DLC films were co-adjusted by ion energy and ion flux. When the carbon ions met the appropriate ion energy range (50–300 eV) and low ion flux (<8.99 × 1010 cm−2 s−1), the films tended to form ta-C structures with high sp3 bonds. However, under the condition of high ion energy and high ion flux, the structure of the films changed from sp3 bonds to sp2 bonds, resulting in the graphitization and formation of DLC films with high sp2 bonds. This work will provide new solutions to guide the design and acquisition of high-performance DLC films.

Structure and Properties of TaC&lt;sub&gt;x&lt;/sub&gt; Coating on Biomedical 316L Stainless Steel by RF Magnetron Sputtering

In this paper, the TaCx coating with thickness around 1.2 μm was prepared by radio frequency magnetron sputtering technique on the 316L stainless steel substrate to improve its hemocompatibility. The structure and morphology of the coating were characterized by XRD and SEM. The XRD results indicated that TaCx, as a new species, appeared on the surface of the 316L stainless steel substrate. SEM images showed that the surface morphology of the TaCx coating was uniform and dense. The mechanical characteristics of the coating were measured by nanoindentation, giving a nanohardness of 13 GPa and a Young’s modulus of 210 GPa. The adhesion strength of the TaCx coating to 316L stainless steel depended on the sputtering bias voltages and increased for a higher bias voltage. The hemocompatibility of the TaCx coating, as evaluated by platelet adhesion tests, was compared to that of the bare 316L stainless steel. The results indicated that the hemocompatibility of 316L stainless steel with TaCx coating was significantly improved as compared to the original one.

Influence of substrate bias on the mechanical properties of ta-C:Co films prepared by filtered cathodic vacuum arc technique

Cobalt-containing tetrahedral amorphous carbon (ta-C:Co) films were deposited by an off-plane double-bend filtered cathodic vacuum arc (FCVA) technique on silicon wafers at room temperature. The mechanical properties of the ta-C:Co films were systematically studied. Such metal composite coatings exhibit reduced stress, thus enabling the deposition of relatively thick coatings whilst retaining acceptable hardness.

Properties of Ion Beam Deposited Tetrahedral Fluorinated Amorphous Carbon Films (ta-C:F)

ABSTRACTWe have studied the growth and the properties of ta-C:F films prepared by the deposition of mass separated 12C+ and 19F+ ions as a function of the F concentration CF. The films are always strongly F-deficient due to the formation of volatile CFx, molecules during the deposition process. CF ≈ 25 at.% is obtained for an ion charge ratio of C+:F+ = 1:1. The mass density strongly decreases from 2.9 g/cm3 for ta-C to 1.1 g/cm3 for films with CF ≈ 23 at.%, whereas the electron density related plasmon energy only varies slightly between 31.8 eV and 29 eV. Therefore, films with small CF have both a high mass and high electron density resulting in diamond-like properties. The discrepancy between low mass density and high electron density for films with large cF can be explained by voids. The thickness and composition of films with CF below 20 at.% remains unchanged for vacuum annealing to temperatures of 600 °C for 10 minutes. Loss of F was observed for films with cF above 20 at.%. The compressive film stress decreases with increasing CF, and is further reduced by annealing.

Temperature dependence of the formation of highly tetrahedral a-C:H

Deposition from a low pressure plasma beam source creates a highly tetrahedral form of hydrogenated amorphous carbon (ta-C:H)) which is analogous to the ta-C formed by deposition from a filtered cathodic arc or mass-selected ion beam. The properties of ta-C:H have been studied as a function of the substrate deposition temperatureTs and ion energy using electron energy loss spectroscopy, X-ray diffraction and atomic force microscopy. The density decreases suddenly for deposition temperatures above a threshold value, which is found to decrease with increasing ion energy. The films above the threshold are mainly sp2 bonded, with graphitic layering and high roughness. The variation of the film density with the ion energy andTs is consistent with deposition occurring by subplantation.