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In this work, tantalum-doped tungsten boride ceramic coatings were deposited from a single sputtering target with the radio frequency (RF) and high-power impulse magnetron sputtering (HiPIMS) methods. Two-inch torus targets were synthesised from pure elements with the spark plasma sintering (SPS) method with a stoichiometric composition of W1-xTaxB2.5 (x = 0, 0.08, 0.16, 0.24). Films were deposited with RF and HiPIMS power suppliers at process temperatures from RT to 600 °C. The substrate heating and the energy of the ionised material impacting the substrate increase the surface diffusivity of adatoms and are crucial in the deposition process. The results of SEM and XRD investigations clearly show that the addition of tantalum also changes the microstructure of the deposited films. The coatings without tantalum possess a finer microstructure than those with 24% of tantalum. The structure of films is homogeneous along the film thickness and composed mainly of columns with a (0001) preferred orientation. Deposited coatings are composed mainly of P6/mmm α-WB2 structures. The analysis of nanoindentation results allowed us to determine that ceramic coatings obtained with the HiPIMS method possess hardness above 41 GPa and a ratio of hardness to reduced Young modulus above 0.1. The thickness of HiPIMS-deposited films is relatively small: only around 60% of the RF magnetron sputtered coatings even when the average power input was two times higher. However, it has been shown that the RF coatings require heating the substrate above 400 °C to obtain a crystalline structure, while the HiPIMS method allows for a reduction of the substrate temperature to 300 °C. [ABSTRACT FROM AUTHOR]

In this study, for the first time, the optimization of applied pressure for achieving the one of the best tribological properties of diamond-like carbon (DLC) coating on graphite surface using plasma-enhanced chemical vapor deposition (PECVD) method was investigated. Raman spectroscopy and microscopy methods were used to characterize the applied coating. Additionally, the mechanical properties of the coating were investigated through nanoindentation testing. The wear resistance of coating has been tested as functional test. The results indicated that with increasing gas pressure, the sp3 hybridization percentage decreases, while the ID/IG ratio increases. The average roughness values for the uncoated sample and the coated samples at working pressures of 25, 30, and 35 mTorr were obtained as 1.6, 5.1, 3, and 2.4 nm, respectively. The results of hardness and wear tests showed that these properties were optimized by reducing the applied gas pressure. The highest hardness was 11.59 GPa, and the best sample in terms of the mechanical properties of the coating was the sample applied at a gas pressure of 25 mTorr. Results show that the optimal sample in tribological performance is the one applied at a working pressure of 25 mTorr. Because this sample demonstrates the lowest coefficient of friction, and wear depth. [ABSTRACT FROM AUTHOR]

The quest for lowering energy consumption during thin film growth, as by magnetron sputtering, becomes of particular importance in view of sustainable development goals. A recently proposed solution combining high power impulse and direct current magnetron sputtering (HiPIMS/DCMS) relies on the use of heavy metal-ion irradiation, instead of conventionally employed resistive heating, to provide sufficient adatom mobility, in order to obtain high-quality dense films. The major fraction of process energy is used at the sputtering sources rather than for heating the entire vacuum vessel. The present study aims to investigate the W+ densification effects as a function of increasing Al content in (Ti1-yAly)1-xWxN films covering the entire range up to the practical solubility limits (y ~ 0.67). Layers with high Al content are attractive to industrial applications as the high temperature oxidation resistance increases with increasing Al concentration. The challenge is, however, to avoid precipitation of the hexagonal wurtzite AlN phase, which is softer. We report here that (Ti1-yAly)1-xWxN layers with y = 0.66 and x = 0.05 grown by a combination of W-HiPIMS and TiAl-DCMS with the substrate bias Vs synchronized to the W+-rich fluxes (to provide mobility in the absence of substrate heating) possess single-phase NaCl-structure, as confirmed by XRD and SAED patterns. The evidence provided by XTEM images and the residual oxygen content obtained from ERDA analyses reveals that the alloy films are dense without discernable porosity. The nanoindentation hardness is comparable to that of TiAlN films grown at 400–500 °C, while the residual stresses are very low. We established that the adatom mobility due to the heavy ion W+ irradiation (in place of resistive heating) enables the growth of high-quality coatings at substrate temperatures not exceeding 130 °C provided that the W+ momentum transfer per deposited metal atom is sufficiently high. The benefit of this novel film growth approach is not only the reduction of the process energy consumption by 83%, but also the possibility to coat temperature-sensitive substrates. [ABSTRACT FROM AUTHOR]

The quest for lowering energy consumption during thin film growth, as by magnetron sputtering, becomes of particular importance in view of sustainable development goals. A recently proposed solution combining high power impulse and direct current magnetron sputtering (HiPIMS/DCMS) relies on the use of heavy metal-ion irradiation, instead of conventionally employed resistive heating, to provide sufficient adatom mobility, in order to obtain high-quality dense films. The major fraction of process energy is used at the sputtering sources rather than for heating the entire vacuum vessel. The present study aims to investigate the W+ densification effects as a function of increasing Al content in (Ti1-yAly)1-xWxN films covering the entire range up to the practical solubility limits (y ~ 0.67). Layers with high Al content are attractive to industrial applications as the high temperature oxidation resistance increases with increasing Al concentration. The challenge is, however, to avoid precipitation of the hexagonal wurtzite AlN phase, which is softer. We report here that (Ti1-yAly)1-xWxN layers with y = 0.66 and x = 0.05 grown by a combination of W-HiPIMS and TiAl-DCMS with the substrate bias Vs synchronized to the W+-rich fluxes (to provide mobility in the absence of substrate heating) possess single-phase NaCl-structure, as confirmed by XRD and SAED patterns. The evidence provided by XTEM images and the residual oxygen content obtained from ERDA analyses reveals that the alloy films are dense without discernable porosity. The nanoindentation hardness is comparable to that of TiAlN films grown at 400–500 °C, while the residual stresses are very low. We established that the adatom mobility due to the heavy ion W+ irradiation (in place of resistive heating) enables the growth of high-quality coatings at substrate temperatures not exceeding 130 °C provided that the W+ momentum transfer per deposited metal atom is sufficiently high. The benefit of this novel film growth approach is not only the reduction of the process energy consumption by 83%, but also the possibility to coat temperature-sensitive substrates. [ABSTRACT FROM AUTHOR]

Nanoindentation hardness and compressive stress in amorphous carbon nitride thin films prepared by unbalanced magnetron sputter-deposition were studied. The coating hardness and compressive stress were found to be strongly dependent on processing parameters such as substrate bias and nitrogen partial pressure. Under optimized deposition conditions, carbon nitride thin films with nanoindentation hardness about 25 GPa have been coated onto Si wafers and M2 steels. A strong correlation between coating hardness and compressive stress in the coating was observed. [ABSTRACT FROM AUTHOR]

Nickel-titanium shape memory alloys have attracted notable interest for biomedical applications due to their unique properties. However, there are still some concerns on the potential release of nickel ions causing adverse reactions in-vivo at high concentrations. In this work, samples were coated with a polyvinyl alcohol/gelatin hydrogel. Coating stability, corrosion resistance and biocompatibility were investigated. Coated samples exhibited similar shape memory response to that of the uncoated substrates in wire form. Additionally, the hydrogel coating led to a decrease in the surface temperature and significantly improved the corrosion resistance of the shape memory substrate. The presence of the hydrogel layer does not affect the biocompatibility of the alloy while providing a semi-degradable, hydrophilic surface that forms a cushion at the tissue-implant interfaces. [ABSTRACT FROM AUTHOR]

In this paper, the incorporation of auxiliary grids/electrodes into the design of the sputtering method is scrutinized by studying the impact of factors such as grid size, grid position, grid bias voltage, electrode sheath design, substrate bias voltage, reactive gas partial pressure, and magnetic trap configuration on the discharge condition and thin-film growth. In this regard, utilizing the updated Berg model for reactive sputtering, the authors obtained a formulation for the reactive grid-assisted sputtering. By the newly-developed formulation, the sputtering rate and the reactive gas partial pressure were simulated as a function of the reactive gas flow rate for various grid-to-target distances, argon partial pressures (0.67, 1.6, and 3.6 Pa), and discharge current densities (0.01, 0.015, and 0.02 A/cm2). According to the computation results, with a grid being utilized, the width of the hysteresis loops can be modified in a broader range by changing either the grid-to-target distance, the argon partial pressure, or the discharge current, resulting in better control over the deposition process. Moreover, the novel configuration of anode-spot-assisted sputtering was proposed to significantly ionize sputtered/neutral atoms near the substrate and to simultaneously deposit sputtered species and products produced as the direct result of introducing dust into the dense plasma. Finally, diverse configurations of the grid-assisted co-sputtering method were introduced for two prime purposes: deposition of composite films in any desired ratios of constituents without significantly changing the other co-sputtering parameters, and favorable alternation of a hysteresis loop for one of the guns at shared gas flow rates. [ABSTRACT FROM AUTHOR]

Hydrogenized carbon films 0.5–7.0 μm thick doped with silicon (11.9 ± 0.4 at %) and oxygen (1.7 ± 0.1 at %) have been grown on VT-6 titanium and silicon substrates in an externally heated arc discharge plasma. The hardness, internal stresses, surface morphology, wettability, and surface potential of the films against their thickness have been studied. It has been found that as the film gets thicker, the allowable load on the material and its hardness grow. It has been shown that the films have low internal stresses (below 600 MPa) and the water contact angle is 75°–80°. It have turned out that an increase in film thickness raises the negative surface potential from 50 to 670 mV. [ABSTRACT FROM AUTHOR]

Beside machining condition and parameters, coating properties is one of the main factors affecting tool performance and wear pattern. These properties include coating hardness and elastic modulus, adhesion to substrate, roughness, defects, and most importantly residual stress. In general, the properties of a physical vapor deposition (PVD) coating can be controlled by adjusting deposition parameters such as substrate bias voltage and nitrogen pressure. Therefore, a coating can be tailored to withstand a specific wear mode which is dominant in machining the workpiece material. In this work a strategy is suggested to decrease adhesion wear and formation of built-up edge during machining of compacted graphite iron (CGI). This strategy involves deposition of thick TiAlN coating with low residual stress in order to promote cohesive failure within the coating. For this purpose, monolayer Ti40Al60N PVD coatings with high thickness (5–10 μm) were deposited under various deposition parameters. A comprehensive coating characterization was done using scanning electron microscope (SEM), X-ray diffraction (XRD), nanoindentation, and scratch test. Tool life of selected coatings were then tested under dry finishing of compacted graphite iron, and wear pattern was investigated with optical and scanning electron microscope. The results showed that coating under low compressive residual stress is successful in reducing sticking and built-up edge formation. This phenomenon happens with gradual cohesive failure of the coating under adhesion wear, resulting in a higher tool life under adhesive wear. [ABSTRACT FROM AUTHOR]

Undulating compositional step-graded AlGaInAs buffers are applied to transit the lattice mismatch of 3.8% between InP cap layer and GaAs substrates with misorientation of 2°, 7° and 15° toward (111)A by metal organic chemical vapor deposition (MOCVD). The surface morphology and strain relaxation are strongly dependent on the substrate misorientation. The sample grown on 15° GaAs substrate showed a substantial improvement of surface roughness and reduction of dislocation pile-up densities compared with that on the 2° and 7° substrate. The experiment results showed that the substrate with 15° misorientation can maintain a smooth epitaxial film surface by increasing the possibility of atoms incorporating into the lattice and ease the imbalance of the misfit strain stress distributed between different slip systems to make dislocations distributed more uniformly, which can reduce the strain field to exaggerate the channel width for dislocation gliding along the interface and decrease the threading dislocation densities. Overall, this work provides a promising way to obtain virtual substrates for the achievement of desired metamorphic devices. [ABSTRACT FROM AUTHOR]

A bilayer film deposition process for synthesizing ultrathin amorphous carbon (a-C) films with structure and properties dominated by those of the sp3-rich bulk layer was developed in this study. This was accomplished by incorporating in conventional filtered cathodic vacuum arc (FCVA) deposition a low-ion-energy pre-deposition step (no substrate biasing) leading to the formation of an ultrathin (<1 nm) carbon layer and a post-deposition step of high-energy Ar+ ion sputtering resulting in film thinning. The thickness and cross-sectional structure of hydrogen-free a-C ultrathin films synthesized by this multistep FCVA process under optimum substrate bias conditions (−100 V pulsed bias voltage) were examined by high-resolution transmission electron microscopy and electron energy loss spectroscopy. The bilayer a-C films synthesized under these conditions exhibit slightly higher sp3 fractions and interface and bulk layers significantly thinner and thicker, respectively, compared with single-layer a-C films of similar thickness deposited under the same FCVA conditions. [ABSTRACT FROM PUBLISHER]

Objectives: Biomaterial surfaces are at high risk for initial microbial colonization, persistence, and concomitant infection. The rationale of this study was to assess the initial adhesion on novel implant surfaces of Enterococcus faecalis, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Candida albicans upon incubation. Materials and methods: The tested samples were 3 mol% yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP) samples with nitrogen-doped hydrogenated amorphous carbon (a-C:H:N) coating (A) and 3Y-TZP samples coated with ceria-stabilized zirconia-based (Ce-TZP) composite and a-C:H:N (B). Uncoated 3Y-TZP samples (C) and bovine enamel slabs (BES) served as controls. Once the surface was characterized, the adherent microorganisms were quantified by estimating the colony-forming units (CFUs). Microbial vitality was assessed by live/dead staining, and microbial-biomaterial surface topography was visualized by scanning electron microscopy (SEM). Results: Overall, A and B presented the lowest CFU values for all microorganisms, while C sheltered significantly less E. faecalis, P. aeruginosa, and C. albicans than BES. Compared to the controls, B demonstrated the lowest vitality values for E. coli (54.12 %) and C. albicans (67.99 %). Interestingly, A (29.24 %) exhibited higher eradication rates for S. aureus than B (13.95 %). Conclusions: Within the limitations of this study, a-C:H:N-coated 3Y-TZP surfaces tended to harbor less initially adherent microorganisms and selectively interfered with their vitality. Clinical relevance: This could enable further investigation of the new multi-functional zirconia surfaces to confirm their favorable antimicrobial properties in vivo. [ABSTRACT FROM AUTHOR]

Reflective and transmissive film interference colors were calculated for DLC films on the Si and SiO substrates. The calculated interference colors were compared with photographed colors of the prepared DLC samples. The observed film colors were found to match reasonably well with the corresponding calculated colors, indicating that DLC film colors come from interference instead of color center effects. Color charts for DLC films on the Si and SiO substrates with various optical gaps were constructed, and the relationship between interference color and film properties such as optical gap, thickness and substrate were investigated. Usefulness of the calculated color charts in estimating optical gap or thickness of DLC films were demonstrated. [ABSTRACT FROM AUTHOR]

A series of graphite-like carbon films with a titanium concentration of about 3.0 at.% were successfully deposited on silicon wafer substrates using an unbalanced magnetron sputtering system with different bias voltages. The microstructure, surface morphology, and properties of the titanium-containing graphite-like carbon films were subsequently studied using different characterization techniques. The results show that the resulting titanium-containing graphite-like carbon films are completely dominated by sp sites and that these films have moderate hardness, low internal stress, and superior tribological properties with low friction and a high load-bearing capacity. The hardness ( H), elastic modulus ( E), H/ E, H/ E, and internal stress of the titanium-containing graphite-like carbon films initially increase with increasing bias voltage, only to be followed by a decrease with further increases in the bias voltage. Tribologically, the studied carbon film shows a slight increase in friction with increasing bias voltage, while the wear rate initially decreases, followed by an obvious increase. The tribological properties of the studied titanium-containing graphite-like carbon films are greatly improved under the liquid paraffin-lubricated condition, achieving extremely low friction (~0.045) and wear (~10 mm/Nm). The effect of bias voltage on the microstructure and properties of the titanium-containing graphite-like carbon films is discussed in detail. [ABSTRACT FROM AUTHOR]

The article examines the effects of deposition conditions and counter bodies on the tribological properties of pulsed magnetron sputtered titanium nitride (TiN)-MoSx composite coating. Two counter bodies have been used to determine the tribological response of TiN-MoSx composite coatings. These are cemented carbide ball and pin made of aluminum alloy (AlSiMg). The methods use to investigate the tribological behavior of the coating against aluminum alloy are described.

Recently, great attention has been devoted to the pulsed direct current (DC) reactive magnetron sputtering technique, due to its ability to reduce arcing and target poisoning, and its capability of producing insulating thin films. In this study, chromium nitride (CrN) coatings were deposited by the bipolar symmetric pulsed DC magnetron reactive sputtering process at different pulse frequency, substrate bias voltage, and the substrate temperature. It was observed that the texture of CrN changed from (111) to (200) as substrate temperature increased to 300°C as deposited at 2 kHz without substrate bias. With increasing pulsing bias and pulse frequency of target, predominated (200) orientation of CrN film was shown due to the ion bombardment/ channeling effect to preferentially sputter those unaligned planes. For the CrN coatings deposited with pulsed biasing, the grain size decreased with increasing pulse frequency and substrate bias, whereas the surface roughness showed a reverse trend. The deposition rate of the CrN films decreased with increasing pulse frequency. It was concluded that the pulse frequency, substrate bias, and substrate temperature played important role in the texture, microstructure, and surface roughness of the CrN coatings deposited by the pulsed DC magnetron sputtering process. [ABSTRACT FROM AUTHOR]

One of the key issues for future hard disk drive technology is to design and develop ultrathin (<2 nm) overcoats with excellent wear- and corrosion protection and high thermal stability. Forming carbon overcoats (COCs) having interspersed nanostructures by the filtered cathodic vacuum arc (FCVA) process can be an effective approach to achieve the desired target. In this work, by employing a novel bi-level surface modification approach using FCVA, the formation of a high sp3 bonded ultrathin (~1.7 nm) amorphous carbon overcoat with interspersed graphene/fullerene-like nanostructures, grown on magnetic hard disk media, is reported. The in-depth spectroscopic and microscopic analyses by high resolution transmission electron microscopy, scanning tunneling microscopy, time-of-flight secondary ion mass spectrometry, and Raman spectroscopy support the observed findings. Despite a reduction of ~37 % in COC thickness, the FCVA-processed thinner COC (~1.7 nm) shows promising functional performance in terms of lower coefficient of friction (~0.25), higher wear resistance, lower surface energy, excellent hydrophobicity and similar/better oxidation corrosion resistance than current commercial COCs of thickness ~2.7 nm. The surface and tribological properties of FCVA-deposited COC was further improved after deposition of lubricant layer. [ABSTRACT FROM AUTHOR]