Lihua Yu

Microstructure, mechanical and tribological properties of TaCN composite films

Tantalum and carbon nitride films, with varied power of the carbon target were synthesised by multi-target magnetron sputtering. The microstructure, mechanical and tribological properties of TaCN films were investigated by X-ray diffraction, Fourier transform infrared spectroscopy, atomic force microscopy, scanning electron microscopy, nano-indentation, nano-scratch, and a high temperature ball-on-disc tribometer. X-ray diffraction reveals that these films exhibit face centred cubic and base centred orthorhombic crystal structures, regardless of the power of the carbon target. At 50 W, the hardness, critical loads for cohesive failure (Lc1) and critical loads for adhesive failure (Lc2) of these films reach a maximum, 28·6 GPa, 4·52 N and 8·1 N, respectively, while at 80 W, the lowest average friction coefficient and wear rate of TaCN films are obtained, measured as 0·36 and 2·91×10−7 mm2 N−1, respectively.

Microstructure, mechanical, and tribological properties of niobium vanadium carbon nitride films

Composite Nb-V-C-N films with different carbon content were synthesized using reactive magnetron sputtering system, and the influence of carbon on the microstructure, mechanical, and tribological properties of niobium vanadium nitride films was investigated. The films with carbon content below 9.1 at. % exhibited a two-phase of solid solution face-centered cubic (fcc) (NbV)(CN) and hexagonal close-packed (hcp) (NbV)2(CN); increasing the carbon content further induced the formation of amorphous carbon and CNx, and the films consist of fcc-(NbV)(CN), hcp-(NbV)2(CN), amorphous carbon, and CNx. Solid solution strengthening and the heterostructure led to an increase in hardness to ∼32 GPa at 9.1 at. % carbon. A further increase in carbon content led to a gradual decrease in hardness due to the formation of soft amorphous phases of carbon and CNx. The tribological properties of the films against alumina counterpart at room temperature were significantly influenced by the carbon content. The incorporation of carbon into the films decreased the average friction coefficient (μ) from ∼0.61 at 0 at. % carbon to ∼0.25 at 21.6 at. % carbon. As the carbon content increased, the wear rate first dropped from ∼2.6 × 10−8 mm3/(N mm) at 0 at. % carbon to ∼1.2 × 10−8 mm3/(N mm) at 9.1 at. % carbon, and then rose gradually to ∼8.7 × 10−7 mm3/(N mm) at 21.6 at. % carbon.Composite Nb-V-C-N films with different carbon content were synthesized using reactive magnetron sputtering system, and the influence of carbon on the microstructure, mechanical, and tribological properties of niobium vanadium nitride films was investigated. The films with carbon content below 9.1 at. % exhibited a two-phase of solid solution face-centered cubic (fcc) (NbV)(CN) and hexagonal close-packed (hcp) (NbV)2(CN); increasing the carbon content further induced the formation of amorphous carbon and CNx, and the films consist of fcc-(NbV)(CN), hcp-(NbV)2(CN), amorphous carbon, and CNx. Solid solution strengthening and the heterostructure led to an increase in hardness to ∼32 GPa at 9.1 at. % carbon. A further increase in carbon content led to a gradual decrease in hardness due to the formation of soft amorphous phases of carbon and CNx. The tribological properties of the films against alumina counterpart at room temperature were significantly influenced by the carbon content. The incorporation of car...

Microstructure, mechanical and tribological properties of magnetron sputtered VCN films

ABSTRACT VCN films with various carbon contents were deposited by reactive magnetron sputtering. The elemental compositions, microstructure, mechanical and tribological properties were investigated by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), energy-dispersive spectrometer, scanning electron microscope (SEM), nano-indentation and friction and wear test. The results showed that the microstructure, mechanical properties and tribological properties of VCN films were influenced by the variation of the carbon content. The VCN films exhibited a face-centered cubic (fcc) structure. By increasing of carbon content of the film, the grain size of VCN films decreases gradually. The hardness of the films first increased and then decreased with increasing carbon content, after reaching the maximum values of 28.1 GPa, at 16.89 at.-% carbon. The average friction coefficient and wear rate decreased with the increasing carbon content at room temperature.

Influence of V content on properties of Ti–W–V–N films

ABSTRACT Ti–W–V–N composite films with different vanadium contents were synthesised by multi-target reactive magnetron sputtering. The microstructure, mechanical and tribological properties of Ti–W–V–N films were investigated by X-ray diffraction, scanning electron microscope, high-resolution transmission electron microscopy, nanoindentation and high-temperature ball-on-disc tribometer. The results showed that all the Ti–W–V–N composite films were face-centred cubic (fcc) structure, consisting of fcc-(Ti,W,V)N substitutional solid solution. When the V content ≥21.5 at.-%, the films consisted of fcc-(Ti,W,V)N and fcc-VN. The hardness of the films first increased and then decreased with the maximum value of 32.4 GPa, at 21.5 at.-% V. The test temperature had a significant effect on the tribological properties of Ti–W–V–N film with 21.5 at.-% V, the coefficient of friction (CoF) first increased and then decreased, with a minimum value of 0.304 at 700°C.While the wear rate increased gradually with increasing temperature.

Influence of Ag content on the microstructure, mechanical, and tribological properties of TaVN–Ag films

A series of TaVN–Ag nanocomposite films were deposited using a radio-frequency magnetron sputtering system. The microstructure, mechanical properties, and tribological performance of the films were investigated. The results showed that TaVN–Ag films were composed of face-centered cubic (fcc) TaVN and fcc-Ag. With increasing Ag content, the hardness of TaVN–Ag composite films first increased and then decreased rapidly. The maximum hardness value was 31.4 GPa. At room temperature, the coefficient of friction (COF) of TaVN–Ag films decreased from 0.76 to 0.60 with increasing Ag content from 0 to 7.93at%. For the TaVN–Ag films with 7.93at% Ag, COF first increased and then decreased rapidly from 0.60 at 25°C to 0.35 at 600°C, whereas the wear rate of the film increased continuously from 3.91 × 10−7 to 19.1 × 10−7 mm3/(N·mm). The COF of the TaVN–Ag film with 7.93at% Ag was lower than that of the TaVN film, and their wear rates showed opposite trends with increasing temperature.

Effect of Electric Field Intensity on Atom Diffusion in Cu/Ta/Si Stacks

In this letter, we present a quantitative analysis of different electric field intensity on interface atom diffusion in a Cu/Ta/Si stack at 650 °C annealing. It was found that the external electric field accelerated the Cu atom diffusion in the Ta layer. With the increment of electric field intensity, the effect of the electric field upon the atomic diffusion becomes more significant. The mechanism of accelerated effect is mainly attributed to the perturbation of the electric state of the defects in the interface and grain interior.