Ti-doped Diamond-like Carbon Films Research Articles

Improvement of corrosion resistance and biocompatibility of 316L stainless steel for joint replacement application by Ti-doped and Ti-interlayered DLC films

Titanium was incorporated and interlayered into diamond-like carbon (DLC) films deposited on 316L stainless steel using a filtered cathodic vacuum arc. The local bonding structure, corrosion, and biocompatibility of non-doped DLC (ta-C), Ti-interlayered (ta-C/Ti), Ti-doped (ta-C:Ti), and Ti-doped and Ti-interlayered (ta-C:Ti/Ti) DLC films were thoroughly investigated. ta-C:Ti/Ti (0.55 at.%Ti) exhibited not only the highest corrosion resistance performance, including the lowest corrosion rate (7.34 × 10 −8 mm yr −1 ), the highest pitting potential (1672.97 mV), and the highest polarization resistance (5.97 MΩ cm 2 ), owing to the formation of TiO 2 on its surface, as confirmed by X-ray photoelectron spectroscopy and near-edge X-ray absorption fine structure spectroscopy, but also the highest amount of hydroxyapatite , an indicator for biocompatibility, on its surface as determined with Fourier transform infrared spectroscopy and scanning electron microscopy. Two barrier layers, namely, outer and inner layers, were observed in ta-C/Ti and ta-C:Ti/Ti, while only one barrier layer was in ta-C and ta-C:Ti, as demonstrated by electrochemical impedance spectroscopy . Therefore, ta-C:Ti/Ti is an alternative promising DLC film for joint replacement biomaterials . • ta-C:Ti and ta-C:Ti/Ti notably increased sp 2 bonding fractions. • All DLC films notably improved 316L corrosion resistance in PBS + 1 g L −1 of HA. • Ti interlayer enhanced pitting corrosion resistance while Ti dopant increased R p . • ta-C:Ti/Ti exhibited the most corrosion resistance and biocompatibility due to TiO 2 . • TiO 2 manifested as a barrier layer and a preferred site for HAp formation.

Synthesis and electrochemical properties of Ti-doped DLC films by a hybrid PVD/PECVD process

Low electrical conductivity and poor adhesion to metallic substrates are the main drawbacks of diamond-like carbon (DLC) films when used in electrode applications. In this study, Ti-doped DLC films with various Ti contents were synthesized on metal Ti substrates by a hybrid PVD/PECVD process, where PECVD was used for deposition of DLC films and PVD was used for Ti doping. The effects of the Ti doping ratio on the microstructure, adhesion strength, and electrical and electrochemical properties of the DLC films were systematically investigated. An increase in the Ti content led to increased surface roughness and a higher sp2/sp3 ratio of the Ti-DLC films. Ti atoms existed as amorphous-phase Ti carbide when the Ti doping ratio was less than 2.8 at.%, while the nanocrystalline TiC phase was formed in DLC films when the Ti doping ratio was exceeded 4.0 at.%. The adhesion strength, electrical resistivity, electrochemical activity and reversibility of the DLC films were greatly improved by Ti doping. The influence of Ti doping ratio on the electrical and electrochemical properties of the DLC films were also investigated and the best performance was obtained at a Ti content of 2.8 at.%.

Effect of microstructural evolution on mechanical and tribological properties of Ti-doped DLC films: How was an ultralow friction obtained?

This paper examined the evolution of microstructure and its effect on the mechanical and tribological properties of ultralow friction Ti-doped diamondlike carbon (DLC) films, by adjusting the CH4/Ar ratio under constant radio frequency discharge power and bias. The Raman, high resolution transmission electron microscopy, atomic force microscope and nanoindentation measurements consistently reveal or indicate the formation of curved graphene sheets or fullerenelike nanostructures with increasing CH4/Ar ratio. The superior frictional performance (0.008–0.01) of Ti-DLC films can be attributed to the special microstructure related to the development of embedded fullerenelike nanostructures as a result of incorporation of TiO2 clusters. The contributing factors include high hardness and cohesion, excellent toughness, high load-bearing capacity, as well as the ultralow shear resistance transform layer and the excellent antioxidation stability brought by the doped Ti.

Performance of CoCrMo Alloy with Me-Doped DLC Coatings Prepared by a Magnetron Sputtering Method

Abstract To enhance the wear resistance of CoCrMo alloy used as hip joints for longer service time, the W-DLC (W doped-diamond like carbon) films and Ti-DLC (Ti doped-diamond like carbon) films were prepared by a DC magnetron sputtering method combined with ion source technique. The thickness of the as-prepared films was 1.89 μm. Results show that the coated CoCrMo alloy exhibits higher wear resistance in comparison with uncoated CoCrMo one, and the friction properties of W-DLC coated CoCrMo alloy are better than those of Ti-DLC coated CoCrMo alloy. The wear rates of uncoated CoCrMo, Ti-DLC coated CoCrMo and W-DLC coated CoCrMo are 15.25×10 −6 , 0.76×10 −6 , and 0.19×10 −6 mm 3 m −1 N −1 , respectively. Raman spectrum analysis shows that the excellent wear resistance of coated CoCrMo alloys is attributed to the graphitization of the top layer of DLC films during rubbing.

A study of structure and properties of Ti-doped DLC film by reactive magnetron sputtering with ion implantation

Ti-doped diamond-like carbon (DLC) films were prepared on Ti alloys by reactive magnetron sputtering combined with PSII technology. The structure and properties of unmodified and Ti-doped DLC films were analyzed in a systematic way by different testing, such as TEM, XPS, frictional wear testing, contact angle measurement and so on. The results showed that Ti-doped DLC was a typical a-C:H film containing TiC nanometer grains, whose mechanical properties were obviously improved, such as hardness, wear resistance and cohesive strength, still kept good wear resistance at the ambient temperature of 450°C, and held a rather large mean water contact angle of 104.2±1°.

A Study on Metal-Doped Diamond-Like Carbon Film Synthesized by Ion Source and Sputtering Technique

DLC (diamond-like carbon) has many excellent properties similar to diamond, which make it an attractive film in industrial applications. However, the large residual stress of DLC films limits the maximum film thickness because it reduces the adhesion of the DLC film to substrate causing delamination and cracking of the film. Metal-doped DLC (Me-DLC) has been studied extensively to avoid these disadvantages. Both large area Ti-doped and W-doped DLC films have been synthesized by a hybrid of ion source technique and unbalanced magnetron sputtering. The microstructure and mechanical properties have been analyzed by SEM, Raman, and XPS. A wear tester was used to evaluate the tribiological behavior of Me-DLC. Experimental results demonstrated that a smooth large area DLC film with good mechanical properties could be prepared by this hybrid technology, thick Me-DLC could be deposited with good adhesion and excellent wear resistance.

The effect of applied negative bias voltage on the structure of Ti-doped a-C:H films deposited by FCVA

Ti-doped hydrogenated diamond-like carbon (DLC) films were deposited on Si(100) substrates by a filtered cathodic vacuum arc (FCVA) method using Ar and CH4 as the feedstock. The composition and microstructure of the films were investigated by Raman spectroscopy, X-ray photoelectron spectroscopy and IR spectroscopy. The internal stress was determined by the radius of curvature technique. The influence of the bias voltage on the microstructure of the as-deposited films was investigated. It was found that the graphite-like bonds was dominated in the Ti-doped DLC film deposited at 0V bias voltage. When bias voltage was increased to −150V, more diamond-like bond were produced and the sp3 content in film reached the maximum value, after which it decreased and more graphite-like bonds feature produced with further increase of the negative bias voltage. The compressive internal in the Ti-doped DLC films also exhibited a maximum value at −150V bias voltage. IR results indicated that CH bonded intensity reduced, and H atoms bonded with C atoms were substituted for the Ti atoms as the negative bias voltage increasing. All the composition and microstructure change can be explained by considering the plasma conditions and the effect of negative bias voltage applied to the substrate.

The study of doped DLC films by Ti ion implantation

Diamond-like carbon (DLC) films were prepared by unbalanced magnetron sputtering. Ti-doped DLC films were obtained by Ti ion implanted into the achieved DLC films using metal vapor vacuum arc (MEVVA). The effects of Ti+ ion implantation on the surface morphology, structure, and tribological properties of the DLC films were investigated by means of atomic force microscopy (AFM), Raman spectroscopy, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and friction measurement. The smooth and uniform Ti-doped film with the surface roughness of 0.595 nm was obtained. Raman result revealed that the formation of DLC films and sp2 bonds content increase by Ti+ ion implantation. TEM showed that the nanocrystalline phases of TiC were formed in the films. Ti+ was implanted into the interface between C and substrate, detecting the sputtering depth profiles of the film by XPS; thus, the interface was widened due to reserve diffusion. Tribological test experiment indicated that friction coefficient of the films decreased to approximately 0.15 by Ti+ ion implantation.

Characterization of hydrogen-free diamond-like carbon films deposited by pulsed plasma technology

Diamond-like carbon (DLC) films demonstrated significant advantages in cutting and forming non-ferrous materials. The ultra-low friction coefficient and high surface hardness make DLC one of the most promising surface modification technologies available for processing advanced structural materials. In this study, Ti-doped and hydrogen-free DLC films (a-C:Ti) were synthesized by unbalanced magnetron sputtering of Ti and graphite targets. The high residual stress of the DLC thin films was dissipated through a compound interface consisting of a series of Ti, TiN, and TiCxNy graded interlayers. The target poisoning problem was resolved with a 2 kHz medium-frequency DC power supply. In addition, a 20–100 kHz variable-frequency DC power supply was used for both arc suppressing and substrate biasing. The effects of deposition parameters on film qualities were investigated by SEM/EDS, XRD, EELS and wear tests. Results demonstrated an improved DLC thin film with superior microhardness and adhesion strength compared with the conventional DLC deposited by PVD or PECVD processes.