Ti Multilayer Films Research Articles

Structure, mechanical properties and tribological behavior of sp2-C:Ti/sp3-C:Ti multilayer films deposited by magnetron sputtering

Amorphous carbon (a-C), one of the most studied carbon-based films, has been widely applied in the filed of artificial joints due to its excellent mechanical and tribological properties and high corrosion resistance. However, low adhesive strength and poor fatigue resistance are fatal shortcomings of this kind of films. In this study, carbon (sp2-C:Ti/sp3-C:Ti) nano-multilayer films (MFs) with sequential sp3-rich and sp2-rich layers were deposited on Ti6Al4V and c-Si substrate by DC magnetron sputtering. X-ray diffraction, scanning electron microscopy, the X-ray photoelectron spectroscopy and the transmission electron microscopy were used to characterize the composition, structure and morphologies of the MFs. In the sp2-C:Ti/sp3-C:Ti MFs, the sp3-C rich layer and the sp2-C rich layer exhibit amorphous features and onion-like structure, respectively. Moreover, the layered structure is continuous in a relatively clear region but with a rough layer interface. The mechanical and the scratch behaviors were elaborately characterized by nanoindentation and scratch tests. The results revealed that the sp2-C:Ti/sp3-C:Ti MFs possess hardness of 21.9 GPa and excellent scratch behavior at sputtering bias voltage −220 V, which are significantly better than single-layer films. Furthermore, the adhesion and tribological behaviors of the sp2-C:Ti/sp3-C:Ti MFs were obtained by Rockwell and ball-on-disk tribometer tests. It was found that the sp2-C:Ti/sp3-C:Ti MFs synthesized under a sputtering bias of −220 V not only exhibit relatively low coefficient of friction (only 0.11) in humid air, but also present lower coefficient of friction (0.085) and wear rate (7.5 × 10−17m3N−1 m−1) of Si3N4 balls in Fetal bovine serum (FBS) solution. In conclusion, the critical loads and wear resistance of the sp2-C:Ti/sp3-C:Ti-MFs were effected by the sputtering bias and the mechanical properties of the MFs. And when sputtering bias is −220 V, the sp2-C:Ti/sp3-C:Ti MFs exhibited the improved mechanical properties, the lowest coefficient of friction (CoF) and the highest wear resistance.

Effect of the thickness of the individual layers in Al2O3/Pt/Al2O3 solar absorber films on the photo-thermal conversion efficiency for rapid industrial production

The optical properties and the photo-thermal conversion efficiency (PTCE) of solar absorber films are very much dependent on the thicknesses of the various layers. In order to achieve rapid industrial production (RIP), it is necessary to examine the relationship between the film thickness and optical reflectance. Given the permissible PTCE, Contour maps (CM) of the PTCE are examined to find allowable changes in layer thickness. It is found that the PTCE is strongly dependent on the thickness of each layer in the Al2O3/Pt/Al2O3 multilayer films. The allowable changes in layer thickness, are ±10 nm, ±1 nm and ±10 nm, permitting PTCE values of more than 90.5%. Using the RIP process, two Al2O3/Pt/Al2O3/Ti multilayer films with the thicknesses of 70.7/7.3/75.8/152 nm are fabricated. The test results agree well with the simulation results. The area defined in the contour maps has a PTCE value of more than 91%. And their performances are examined.

Mechanical and wear characteristics of a-C:H/Cr/AlN/Ti multilayer films deposited by PVD/PACVD

In the present work, the feasibility from the mechanical behavior point of view of embedding piezoelectric AlN/Ti interlayer sensors between wear resistant a:C-H coatings and steel substrates was evaluated. The wear sensor composed by a bottom electrode of Ti and a piezoelectric AlN layer, along with the adhesion/top electrode Cr interlayer were deposited by magnetron sputtering (MS), while plasma assisted chemical vapor deposition (PACVD) was used to build up the wear resistant diamond-like carbon coating.The effects of the AlN/Ti interlayer on the properties of this system of coatings were investigated by several means. X-Ray photoelectron spectroscopy was used in order to assess the type of chemical bonds present in the coatings. The surface and section morphologies were observed by scanning electron microscopy, while the mechanical characteristics (hardness, adherence to the substrate and wear behavior) were analyzed by nanoindentation, scratch tests and ball-on-disc friction tests. The results showed that the presence of AlN/Ti interlayers is reducing the carbon sp3 content and is increasing the bonded oxygen at the surface of the coatings, which, in turn, leads to an increased chemical activity, giving rise to abrasive wear and a higher friction coefficient. The adhesion to the steel substrate of these multilayer coatings, compared to an a:C-H/Cr coating, used as reference, was greatly improved. However, the hardness was gradually degraded, compared to the same a:C-H/Cr film. This indicates that the AlN/Ti interlayers might decrease the mechanical strength of the top DLC films, but can bring benefits in terms of adhesion to the steel substrate. The mechanical and wear characteristics of the a:C-H/Cr/AlN/Ti/steel system are dependent on, and can be varied due to the deposition process parameters.

Enhanced hydrogen storage properties of Pd/Ti/Mg/Ti multilayer films using the catalytic effects of Pd

Here, we report the microstructural and hydrogen storage properties of a 40-layer film of Pd (x nm)/Ti (40 nm)/Mg (360 nm)/Ti (40 nm) (x = 0, 5, 10, and 20) fabricated using an ultra-high vacuum DC magnetron sputtering system. The superior hydrogen uptake of the Pd/Ti/Mg/Ti films was 6.42 wt. % for x = 10 at 150 °C. The hydrogen absorption time is strongly dependent on the Pd film thickness (0–40 nm). As a result, the Pd/Ti/Mg/Ti multilayer film with the Pd interlayer can be attributed to offer the further diffusion channels and the controlled growth rate of hydride formation at the Pd/Ti/Mg interfaces, which provides an overall enhancement of the hydrogen storage properties.

Influence of duty cycle on microstructure, tribological and corrosion behaviors of a-C/a-C:Ti multilayer films

a-C/a-C:Ti multilayer films were deposited on medical Ti6Al4V alloy using a closed field unbalanced magnetron sputtering system with various substrate bias duty cycle. The tribological and corrosion behaviors of the multilayer films in Hank's solution were evaluated by a ball-on-disk tribometer and an electrochemical workshop. The duty cycle has a significant effect on the bonding structure, and mechanical and tribological properties of the films. The polarization resistance of the films on Ti alloy is approximately ten times more than that of Ti6Al4V which indicates that higher corrosion resistance can be achieved in Hank's solution at 37°C. However, the polarization resistance and corrosion current do not change so much with the variation of duty cycle, implying that its influence on corrosion behavior of these a-C/a-C:Ti multilayer films is not so obvious.

Mechanical and tribological properties of a-C/a-C:Ti multilayer films with various bilayer periods

Thick a-C/a-C:Ti multilayer films with bilayer periods of 12–70nm were deposited on Ti6Al4V alloy substrate by means of closed field unbalance magnetron sputtering. The morphology and microstructure of the multilayer films were investigated by scanning electron microscopy, high resolution transmission electron microscopy and X-ray photoelectron spectroscopy. Nanocrystalline TiC was distributed in the a-C:Ti layer and at the interface between the two adjacent layers. The mechanical and tribological properties were evaluated by Rockwell and scratch tests, a nanoindentor and a ball-on-disk tribometer. The multilayer film with a bilayer period of 12nm showed the highest adhesion strength, hardness (26GPa) and elastic modulus (232GPa); it also had the lowest average coefficient of friction (0.09) and a wear rate of 8.06×10−17m3N−1m−1.

Synthesis of Mn-Substituted Titania Nanosheets and Ferromagnetic Thin Films with Controlled Doping

We report the synthesis of Mn-substituted titania nanosheets and the preparation of room-temperature ferromagnetic thin films via layer-by-layer assembly of these nanosheets. Ti(5.2−2x)/6Mnx/2O2 (x = 0.0−0.4) nanosheets were synthesized by delaminating layered titanates [K0.8Ti(5.2−2x)/3Li(0.8−x)/3MnxO4], in which the Mn content was systematically controlled by Li+ doping. We found that Mn content in the host layers was preserved upon exfoliation, and controlled Mn doping was achieved in exfoliated Ti(5.2−2x)/6Mnx/2O2 (x = 0.0−0.4) nanosheets, where Li+ ions were completely extracted by acid-exchange reaction in the exfoliation process. The multilayer films of Ti(5.2−2x)/6Mnx/2O2 (x = 0.0−0.4) nanosheets exhibit a clear magnetic hysteresis loop at room-temperature in similar to what observed in ferromagnetic Ti1−xCoxO2 nanosheets. Electronic absorption, magnetic circular dichroism, and hard X-ray photoelectron spectroscopy were used to identify Mn-derived states, and analyze the properties of these states...

Deposition and characterization of Ti–B–N monolithic and multilayer coatings

Abstract Monolithic and multilayer films of Ti–B–N on various substrates were prepared using the DC-magnetron sputtering technique. The structure and properties of the films were affected by several reactive sputtering process variables such as substrate bias voltage and total pressure. The hardness of TiB2 films correlates with film crystallinity and stress. Well-crystallized TiB2 films with strong (001) texture and with hardness up to 44 GPa were produced. Small amount of nitrogen doping into TiB2 films enhanced their crystallinity, but an excessive amount of nitrogen rendered amorphous films of lower hardness. Ti–B–N/TiN coatings with bilayer thickness of 2.6–14 nm were prepared and their structure, hardness and toughness were affected greatly by the bilayer thickness.