Papers by Keyword: DLC Film

Abstract: In this study a method to deposit a-Si:H-DLC film at room temperature has been explored by CVD. The interface structure of a-Si:H-DLC film and the compositions of DLC film were studied, the adhesion strength of DLC film deposited directly on metal substrates was very poor, there was an almost complete crack at interface between DLC film and metal substrates, the local shedding could also be observed on surface of DLC film. After inserting a-Si:H intermediate material into the interface, the adhesion strength of a-Si:H-DLC film was improved well, the a-Si:H intermediate layer with about 0.2μm thickness was formed, and was very impact. In addition the structures of DLC film mainly were graphite structure with SP2 bonding, and contain a certain amount of diamond structure with SP3 bonding. Load capacity of a-Si:H-DLC film deposited on the metal substrates was also evaluated, as the contact stress (Hertz stress) was less than 544MPa for the film with 1μm-thickness, the failure life was up to 100 million cycles or more by using “ball- on- disk” wear testing machine, therefore it could be used in practice. Changes in load had little effect on friction coefficient.

Abstract: In order to analyze the effect of proceeding on the mechanical and tribological properties of DLC films. Three DLC films samples on single silicon wafers were prepared by CVD method. The changed bias voltages were 300V, 350V, 450V separately. The structure and topography of prepared films were studied by Raman spectroscopy and atomic force microscopy (AFM), respectively. The hardness and elastic modulus together with friction coefficient of DLC films were measured by Tribolab system. According to the Raman spectra, the G and D peak shift to left with the increasing of bias voltage. Nano indent showed that the hardness (H) of the DLC films decreases from 19.63GPa to 18.12GPa with the increasing of bias voltages, and the value of elastic modulus (E) is also behaving the same trend as H from 157.95GPa to 146.95GPa. Friction coefficients of the three samples were measured by nano-scratch method under the constant normal load of 1000uN and the slide velocity of 3 um/sec, the corresponding friction coefficient is 0.0804 for DLC300, 0.0508for DLC350 and 0.0594 for DLC450 separately, which indicates that high hardness materials may not necessarily the perfect frictional material, but compound properties of hardness and elastic modulus

Abstract: A silicon interlayer was introduced between the DLC films and 202 stainless steel substrate using a medium frequency magnetron sputtering. The adhesion was evaluated by the scratch tests and wear tests together. Two main parameters in the deposition process of Si interlayers, i.e. the sputtering current and pulse bias voltage, were optimized respectively, and the action mechanisms were discussed as well. Moreover, a special treatment with the purpose of forming a complete graded intermixed Si-Fe interface was designed to improve the adhesion strength further. DLC films with good adhesion strength were deposited on 202 stainless steel substrates using a silicon interlayer.

Abstract: Diamond-Like carbon (DLC) films were prepared under different bias voltage by direct current magnetic filter cathode vacuum arc deposition (DC-MFCVAD). Bias voltages changed from 0 to -200 V. The study intends to investigate the effect on the properties of DLC films for biomedical applications. X-ray photoelectron spectrum (XPS) was used to investigate composition of the films. Nano-scratch tests were used to characterize effects of bias voltage to adhesion. Furthermore, the wettability of the DLC films was investigated by contact angle measurements using four common liquids. Finally, platelet adhesion experiments were done to evaluate the interaction of blood with DLC films. The results showed that the adhesion, wettability and hemo-compatibility of DLC films were affected by bias voltage.

Abstract: DLC and nanocrystalline diamond films were prepared by PLD process using 308 nm(XeCl) laser beam with high power(200-500 W) and high frequency(200-500 Hz). The effects of some parameters such as the laser power density, the repetition rate on the structures and characters of the DLC films under such extreme power and repetition rate conditions were studied for the first time. The results indicated that: (1) The microstructures of the films were varied from amorphous to nanocrystalline with the laser power density increased from 108 W/cm2 to 1010 W/cm2; (2) The properties of the films grew at 200 Hz and 300 Hz were better than that of the films grew at 500 Hz, with the laser power density remained constant at 1010 W/cm2.