The present work is focused on the micro-structural, antibacterial potential and corrosion resistance of silver (Ag) doped diamond-like carbon (DLC) coatings deposited by Thermionic Vacuum Arc on ...titanium substrates. The Ag-DLC coatings have spherical nanoparticulates in the film, with a size of either ≈50 nm or ≈20 nm, depending on the deposition time. The incorporation of Ag in the DLC coatings was clearly evident, as observed in both energy dispersive X-ray spectroscopy and in structural analysis (X-ray diffraction), while X-ray photoelectron spectroscopy confirmed their composition as well as the presence of Ag and diamond-like carbon. Such coatings show an increase in the wettability, which can be related to the increase in the surface free energy. Comparing their corrosion resistance to bare (uncoated) titanium, an increased electrochemical stability is observed. Subsequently, the silver release profiles in phosphate buffer saline, for a 10 days period, were investigated; the release is initially fast in the first 12 h followed by saturation at 66 h. These coatings were further investigated for antibacterial efficacy against Staphylococcus aureus (model Gram positive bacteria) which confirms that the silver doped DLC coatings exhibit an excellent antibacterial activity.
•Ag doped diamond-like carbon coatings were deposited by thermionic vacuum arc.•Characterization confirmed the structure of the Ag doped coatings.•Wettability was evaluated by contact angles and computation of the surface free energy.•Electrochemical tests for coatings and bare Ti were performed in Hank solution.•A range of corrosion resistance and antibacterial activity was established.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Low friction between DLC coating and Ti6Al4V alloy was investigated under fretting conditions on a fretting-wear testing machine. The results indicated that, during the beginning period, the Ti6Al4V ...surface was damaged as a consequence of adhesion (and abrasion), leading to high friction coefficients of around 0.5. With the test ongoing, a tribofilm was formed on the rubbed Ti6Al4V surface. This tribofilm was derived from the wear product of Ti6Al4V alloy with oxidization. Its nano-hardness and reduced elastic modulus were greater than the Ti6Al4V matrix. Meanwhile, structural transformation occurred on the rubbed DLC surface. The tribofilm and transformed carbonaceous layer prevented the Ti6Al4V alloy and the DLC surface from direct contact and led to low friction coefficients (below 0.2).
•Friction of DLC coating/Ti6Al4V contact declined from 0.5 to 0.2 during running-in.•Evolution of DLC coating and Ti6Al4V rubbed surfaces was investigated.•Tribofilm and carbonaceous layer formed on Ti6Al4V surface led to low friction.•The rougher surface led to more severe damage to Ti6Al4V and the coating.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Here, N-doped hydrogenated diamond-like carbon (a-C:H:N) coatings were deposited onto 316 L stainless steel and silicon wafer substrates by applying plasma-enhanced chemical vapor deposition at ...different bias voltages (Vb). The coatings were annealed at 25–590 °C for 4 h. The structure and chemical bonding of the coatings were characterized using scanning electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. The residual stress, surface hardness, and tribological performance were investigated by using the Stoney method, a nanoindenter, and sliding against alumina. The fraction of the constituent bonds in the coating was controlled depending on Vb. The evolution of these bonds during annealing determined the thermal and mechanical performance of the a-C:H:N coatings, particularly the CHn group, sp2C bonds, and CO bonds (CO and CO). As Vb increased, the fraction of CHn groups, CO bonds, and CN bonds decreased, whereas that of sp2C increased. When annealed at above 430 °C, the breakage of the CHn groups and CN bonds accelerated the sp3 → sp2 transformation. The coating prepared at −500 V exhibited the highest hardness of 22.5 GPa and low residual stress of −0.57 GPa; after annealing at 590 °C for 4 h, a hardness of 15 GPa was maintained. The wear resistance was positively related to the surface hardness of the coatings, whereas the coefficient of friction was responsible for the fraction of sp3CHn, CO bonds, and sp2C bonds. The wear resistance of the coating deposited at −500 V was double that of the coating deposited at −740 V.
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•Bias voltage (Vb) can tune the N content and constituent bonds in the a-C:H:N coating.•Vb influences the evolution of hybrid C and bonds and the residual stress during annealing.•Surface O content enhances the friction shear resistance when sliding against Al2O3.•a-C:H:N deposited at −500 Vb had a low residual stress, high hardness, and wear resistance.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The aim of this study was to compare E1-Irrisonic (Helse Ultrasonics, Ocoee, FL) and Irri Black (Helse Ultrasonics), a novel ultrasonic tip with diamondlike carbon treatment, regarding their design, ...metallurgy, microhardness, bending resistance, and time to fracture under the oscillatory fatigue test.
A total of 17 E1-Irrisonic and 17 Irri Black new ultrasonic tips were selected. The tip geometry and surface finishing were assessed using scanning electron microscopy. The elemental composition was defined by energy-dispersive X-ray spectroscopy. Hardness Knoop was calculated using a microhardness tester. The maximum load required to displace the instrument in 45° was recorded in gram/force, oscillatory fatigue was measured in seconds at the moment of instrument fracture, and the size of the separate fragments was determined in millimeters. The Student t test was used for statistical comparison (α = 5%).
Scanning electron microscopic analyses revealed that E1-Irrisonic had a flat end tip, whereas a noncutting rounded tip was observed in Irri Black. The surface of E1-Irrisonic was smoother than Irri Black, which was irregular. Energy-dispersive X-ray spectroscopic analyses showed that the elemental compositions of the E1-Irrisonic and Irri Black tips were consistent with stainless steel and titanium-aluminum alloys, respectively. Irri Black showed significantly higher bending load resistance, time to fracture under oscillatory motion, and hardness Knoop than the E1-Irrisonic tip (P < .05), whereas the length of fragments was similar (P > .05).
Diamondlike carbon treatment improved hardness Knoop and reduced the flexibility of the Irri Black ultrasonic tip, improving its time to fracture under oscillatory motion compared with the nontreated E1-Irrisonic tip.
The interfacial thermal transport (ITT) between vertically aligned carbon nanotube (VACNT) arrays and heat sink is the dominant barrier blocking the path towards practical application of VACNT arrays ...as nano-thermal interface materials (nTIMs). Although developing VACNT arrays with homogeneous heights and larger diameters could lower the thermal contact resistance between the arrays and heat sink (Rc), little effect is achieved at present stage. Here, by using Plasma Enhanced Chemical Vapor Deposition approach, we attain DLC/TiN-coated VACNT arrays, which gives up to 50 times reduction in Rc from 15 mm2 K/W to 0.3 mm2 K/W. Microscopic morphological analyses confirm that the remarkably expanded contact area brought by coatings can promote the ITT and also retain the high phonon transmission rate within individual CNTs. These novel structures are significantly in favor of fulfilling a nTIM function. It is also intriguing to note that Rc is no longer linearly dependent on CNT height variations once CNT diameters become large enough. This indicates that the contact area with heat sink is dominant in influencing Rc instead of the surface roughness. The above findings fuel future effort towards industrial realization of high-performance VACNT array-based nTIM and high-efficiency thermal management in microelectronic and nanoenergy fields.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
We fabricated Ti‐6Al‐7Nb bone scaffolds with 5 mm diameter and 20 mm length comprise of a three‐dimensional (3D) honeycomb frame structure of truncated octahedra created by selective laser sintering ...3D printing. The honeycomb frame was then coated with 0.1 μm thick diamond‐like carbon (DLC) to increase biocompatibility. A round rod of Ti‐6Al‐7Nb alloy (ASTM F1295) was as a control material. They were implanted into the femur bones of beagles to evaluate bone morphometrics and to investigate changes in the transcriptome of the new bone tissue using DNA microarray analysis and real‐time polymerase chain reaction (PCR). In the present report, the 3D honeycomb material with and without DLC film consisting of a‐C:H is referred to as 3D_a‐C:H and 3D_non, respectively. At 3 weeks after implantation, the 3D_non had more contact between the new and artificial bones compared with the control, and the 3D_a‐C:H had more contact between the new and artificial bones compared with the control and 3D_non. Furthermore, 3D_a‐C:H showed even more new bone compared with the control and 3D_non. At 8 weeks after implantation, more appeared lamellar bone with the 3D_a‐C:H implant than those with the control and 3D_non. The real‐time PCR results at 1 week of implantation revealed higher expression levels of VEGF, RANKL, and NOTCH2 expression with 3D_a‐C:H than with 3D_non and control. As a result of real‐time PCR at 2 weeks of implantation, OPN and CTSK expressions were found to be higher with 3D_a‐C:H and 3D_non than that with the control.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Thick multilayered DLC coatings were deposited on the inner surface of pipes with different draw ratios by hollow cathode plasma immersion ion processing (PIIP). By tuning the acetylene (C2H2) flow ...rate, the change of plasma density caused by different draw ratios can be compensated to fulfill the uniform deposition of thick DLC coatings along the pipes. The influence of C2H2 flow rate on the mechanical and tribological properties of the DLC coatings were investigated. With the increase of draw ratio, the deposition temperature and gas pressure declined, and the plasma density became more asymmetrical in the axial direction. Increasing the flow rate can timely replenish the plasma inside the pipe and resolve the mass depletion problem, resulting in better thickness and structure uniformity of the DLC coatings. The greatest deposition rate of 28.6 μm/h was obtained at the 250 sccm C2H2 flow with a draw ratio of 5:1. The results of Raman spectrum and XPS indicated that the content of sp2-carbon bonds decreased with the increasing draw ratio for lower impact energies of ions. The higher sp3 carbon bonds content contributed to the formation of carbonaceous transfer layers, which resulted in the lower friction coefficient and wear rate.
•Uniform deposition of thick DLC coatings inside of pipes with different aspect ratio.•The greatest deposition rate of 28.6 μm/h was obtained.•Increasing the C2H2 flow rate can improve the coating uniformity and cover the mass depletion.•The higher sp3 carbon bonds content contributed to the lower friction coefficient and wear rate.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•The coatings are distinguished by the low coefficient of friction and wear•Wear traces suggesting fretting appear on the coatings•Coating damage consists in micropullouts, abrasions and material ...buildups in places•No traces of fretting wear are noted on the CrN-a:C:H:W:Ti coating
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Abstract
Optical elements used in outer space must be designed considering the effects of such factors as space vacuum, atomic oxygen in low Earth orbit, solar and space radiation, large temperature ...drops, gas release of spacecraft materials and structural elements, space dust and debris. In order to harden and protect mirror surfaces of optical elements from external factors, it has been promisingly applied diamond-like carbon coatings on their surface. These coatings are characterized by high strength and wear-resistant properties, in particular, high hardness, low friction coefficient, high wear resistance and chemical inertness. This leads to their widespread use in various fields of science and technology, including optical instrumentation. This paper presents the results of testing an aluminum mirror with a diamondlike carbon coating under the effect of cyclic temperature changes for determining their ability to withstand a rapid cyclic ambient temperature change, and specifically, to maintain optical and mechanical properties.
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