| LI Dongxin,WANG Jingjing,MI Baosen,MA Xun,CHEN Tianju,LIU Ping,LI Wei.Effect of Ta Doping Content on Mechanical Properties and Biocompatibility of Diamond-like Carbon Thin Films[J],53(20):208-222 |
| Effect of Ta Doping Content on Mechanical Properties and Biocompatibility of Diamond-like Carbon Thin Films |
| Received:November 02, 2023 Revised:February 01, 2024 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2024.20.019 |
| KeyWord:diamond-like carbon film magnetron sputtering Ta-doped friction and wear property biocompatibility |
| Author | Institution |
| LI Dongxin |
School of Materials and Chemistry, University of Shanghai for Science and Technology, Shanghai , China |
| WANG Jingjing |
School of Materials and Chemistry, University of Shanghai for Science and Technology, Shanghai , China |
| MI Baosen |
School of Materials and Chemistry, University of Shanghai for Science and Technology, Shanghai , China |
| MA Xun |
School of Materials and Chemistry, University of Shanghai for Science and Technology, Shanghai , China |
| CHEN Tianju |
School of Materials and Chemistry, University of Shanghai for Science and Technology, Shanghai , China |
| LIU Ping |
School of Materials and Chemistry, University of Shanghai for Science and Technology, Shanghai , China |
| LI Wei |
School of Materials and Chemistry, University of Shanghai for Science and Technology, Shanghai , China |
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| Abstract: |
| Moderate doping of heterogeneous elements can effectively solve the problem of insufficient adhesion between diamond-like carbon (DLC) thin films and substrates, leading to film detachment. In recent years, tantalum (Ta) has been introduced as a new metal dopant in carbon-based thin films, which can significantly improve the mechanical and tribological properties of the films. As a biocompatible metal with high melting point, wear resistance, corrosion resistance, high ductility, and excellent biocompatibility, tantalum exhibits structure and mechanical properties similar to human bones, promoting the proliferation and osteogenesis of human osteoblast cells. However, there is still limited research on tantalum-doped DLC films, especially regarding their biocompatibility. This study aims to explore the structural transformation of tantalum-doped DLC films and enhance their mechanical properties, tribological performance, and biocompatibility. The non-equilibrium magnetron sputtering technique was employed to deposit the films, and the tantalum doping level was controlled by adjusting the power of the tantalum target. DLC films with different Ta doping levels were prepared at power levels ranging from 0 to 0.5 kW. The films were characterized in terms of microstructure, chemical composition, friction performance, mechanical properties, and biocompatibility. The relationship between tantalum doping level and film performance was investigated to identify the optimal tantalum doping ratio and obtain DLC films with excellent performance, laying a foundation for their widespread applications in surface modification of artificial joints and other fields. The results showed that the inclusion of tantalum increased the carbon deposition rate, leading to an increase in film thickness. The sp3-C content in the films initially increased and then decreased with the increase of the Ta doping level. TaC crystals and Ta—Ta nanoclusters were observed in the DLC films doped with Ta at 0.2 kW and above, which resulted in an initial increase and subsequent decrease in surface roughness. Compared with undoped DLC films, Ta-doped DLC films exhibited several improvements. The film-based bonding force increased from 10 N to 25 N, leading to enhanced adhesion between the film and the substrate. The fracture toughness also improved from 0.6 MPa.m1/2 to a value of 1.6 MPa.m1/2 or higher. This indicated that the Ta-doped DLC films were more resistant to crack propagation, making them more mechanically robust. In terms of friction properties, the dry friction coefficient decreased from 0.45 to a range of 0.1 to 0.15. This meant that the Ta-doped DLC films experience reduced friction when in contact with dry surfaces. Similarly, the wet friction coefficient decreased from 0.35 to around 0.1, indicating improved lubrication and reduced friction under wet conditions. Moreover, the wear rate associated with dry friction diminished significantly from 4 500×10−6 mm3/(N.m) to 7×10−6 mm3/(N.m) or lower. The wet friction wear rate also decreased to 1×10−6 mm3/(N.m). This suggested that Ta-doped DLC films exhibited superior wear resistance, making them more durable in both dry and wet environments. However, there were slight compromises in other aspects. The elastic modulus of Ta-doped DLC films experienced a slight decrease, indicating a slight reduction in their stiffness. Additionally, the wettability of the films also underwent a slight decrease. In addition, by simulating body fluid immersion, Ta doped thin films exhibited good capability in inducing hydroxyapatite formation, with a calcium-to-phosphorus (Ca/P) ratio ranging from 1.4 to 1.65, close to the Ca/P ratio in the human body. No cytotoxicity was observed for either doped or undoped films. In summary, the doping of Ta significantly improves the tribological and mechanical properties of DLC films, as well as the capability to induce hydroxyapatite formation. Therefore, these films have the potential to be used as a bio-protective layer on the surface of implants. The Ta-DLC film exhibits the best overall performance at Ta-0.4 kW. |
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