Titanium (Ti) alloys show excellent fatigue and corrosion resistance, high strength to weight ratio, and no toxicity; however, poor osseointegration ability of Ti may lead to implant loosening . Plasma spraying of hydroxyapatite [HA, Ca (PO) (OH)] coating on Ti surfaces is commercially used to enhance osseointegration and the long-term stability of these implants. The biological properties of HA can be improved with the addition of both cationic and anionic dopants, such as zinc ions (Zn) and fluoride (F). However, the hygroscopic nature of fluoride restricts its utilization in the radiofrequency (RF) plasma spray process. In addition, the amount of doping needs to be optimized to ensure cytocompatibility. We have fabricated zinc and fluoride doped HA-coated Ti6Al4V (Ti64) to mitigate these challenges using compositional and parametric optimizations. The RF induction plasma spraying method is utilized to prepare the coatings. Multiple parametric optimizations with amplitude and frequency during the processing result in coating thicknesses between 80 and 145 μm. No adverse effects on the adhesion properties of the coating are noticed because of doping. The antibacterial efficacy of each composition is tested against for 24, 48, and 72 h, and showed that the addition of zinc oxide and calcium fluoride to HA leads to nearly 70 % higher antibacterial efficacy than pure HA-coated samples. The addition of osteogenic Znand F leads to 1.5 times higher osteoblast viability for the doped samples than pure HA-coated samples after 7-days of cell culture. Zn and F doped HA-coated Ti64 with simultaneous improvements in anti-bacterial efficacy and biocompatibility can find application in load-bearing implants, particularly in revision surgeries and immune-compromised patients.

Electrolytic plasma processing (EPP) was used to create hydrophilic surface profiles on titanium. The wettability, surface morphology characteristics and chemical composition of the treated samples were studied as a function of EPP processing parameters. The EPP profiled surfaces comprised of a characteristic "hills and valleys" morphology because of continuous surface melting and freezing cycles. A bimodal surface profile was produced with 2-3 μm height hills and valleys with nano-roughness (≤200 nm). The produced profile resulted in a significant contact angle decrease (from 38.7° to 5.4°). Ratios of actual surface area to projection area () and fraction of solid surface remaining dry () were obtained from profilometry. The surface characteristics and large values produced by EPP were able to induce . Hence, EPP produced superhydrophilic surfaces on Ti. The bioactivity of EPP treated Ti was evaluated using cell free and MC3T3 cells studies. The treated Ti surface significantly increased the bioactivity and formed stoichiometric hydroxyapatite after immersion in a bone cell culture medium for 21 days. Cells' attachment and proliferation studies indicated that EPP treated surface significantly enhances the cells' adhesion and growth after 24 and 48 h compared to the untreated surface. The results show that Ti surface profiling by EPP constitutes a promising method to potentially improve bone implant bonding.

The widespread of viral airborne diseases is becoming a critical problem for human health and safety, not only for the common cold and flu, but also considering more serious infection as the current pandemic COVID-19. Even if the current heating, ventilating and air conditioning (HVAC) systems limit the disease transmission by air, the air filters are susceptible to microbial colonization. In addition, viruses spread via droplets (aerosol) produced by direct or indirect contact with infected people. In this context, the necessity of an efficient HVAC system, able to capture and inactivate viruses- and bacteria-rich aerosols, thus preserving a safe indoor air environment and protecting people, is of enormous importance. The aim of this work is the assessment of the antiviral properties of a silver nanoclusters/silica composite coating deposited via co-sputtering technique on glass, on metallic fibre-based air filters as well as on cotton textiles. The selected human respiratory viruses are: (RSV), the human (HRV) and the virus type A (FluVA). The coated air filters show that the nanostructured coating develops a strong virucidal activity against RSV and FluVA, but not against the HRV.

The coating/substrate interface and oxide layers of the Inconel 625 film may have significant impacts on its material properties, especially the corrosion behavior of the film. However, since the interface and oxide layer can be very thin and experimental toolbox to characterize them is limited, the detailed vertical structure of Inconel 625 coatings remains poorly understood. In this study, a multi-layer structure in Inconel 625 film prepared by magnetron sputtering is revealed using X-ray reflectometry (XRR) and neutron reflectometry (NR) techniques. Thickness and major composition of each layer are obtained. The results indicate that there exists a ~2 nm-thick Cr-rich Inconel sublayer underneath the main Inconel 625 film. An oxide layer mainly consisting of NiO with thickness of ~2 nm is found on the surface of the main Inconel 625 film. In addition, we identified a ~2 Å contamination layer between sapphire substrate and Inconel film even after argon ion sputtering cleaning. We also found that the thickness of the main Inconel 625 film grows linearly with the deposition time, with thicknesses of other layers remaining constant. Our findings provide insight into the multi-layered structures of Inconel 625 coatings with atomic-scale spatial resolution and give directions for future study to improve the corrosion resistance of Inconel 625 coatings.

Recently, medical applications for 3D printing are expanding rapidly and are expected to revolutionize health care, specifically, manufacturing surgical guides and protective face mask against coronavirus (COVID-19). These instruments come in contact with the human tissues, being necessary 3D printed materials free of pathogenic microbes or other contaminants. Therefore, they must be sterilized to avoid that bacteria can attach to the surface and produce biofilm. With the aim of avoiding bacterial biofilm formation and minimize the health risks, acrylic acid (AcAc) coatings applied by plasma-polymerization have been deposited on 3D printed polylactic acid (PLA) Petri dishes. Six antimicrobial-resistant clinical and two susceptible control strains of and species were analyzed. AcAc coatings provide the surface with greater hydrophilicity and, consequently, the formation of a hydration layer, whose thickness is related to the surface roughness. This hydration layer could explain the reduction of bacterial attachment and, consequently, the biofilm formation. Antibiofilm coatings are more successful against strains than against ones; due to some coatings presents a smaller topography scale than the length, reducting the contact area between the bacteria and the coating, and causing a potential rupture of the cellular membrane. AcAc coatings with less number of plasma passes were more effective, and showed up to a 50% relative biofilm reduction (in six of the eight strains studied) compared with the untreated plates.

Plasma-sprayed hydroxyapatite (HAp) coated titanium (Ti) implants are being extensively used in orthopedic surgeries and post-tumor resection to repair load-bearing segmental bone defects. In this study, vitamin C, an abundantly available natural biomolecule, is loaded onto plasma-sprayed HAp-coated commercially pure titanium (cpTi) surface to evaluate its chemopreventive and osteogenic properties, suggesting its clinical significance as an alternative or adjunct therapy in the treatment for osteosarcoma bone resection. Controlled release of vitamin C from HAp coated cpTi implant is assessed by drug release study, where Korsmeyer-Peppas model was applied to understand the release kinetics. After 21 days, the implants loaded with 400 and 800 μg of vitamin C showed a cumulative release of 62.7 and 74.1% in acidic microenvironment, whereas, 50.9% and 53.1% of total vitamin C release were observed by the implants loaded with 400 and 800 μg of vitamin C in physiological pH, respectively. To observe the effects of vitamin C release on osteosarcoma and osteoblast cellular activity, MG-63 (human osteosarcoma) and hFOB (human fetal osteoblast) cells were cultured on the surface of the implant and MTT cell viability assay and FESEM were carried out at 3 and 7 days of culture. Presence of high dosages 25 mM vitamin C shows a statistically significant (p≤0.05) decrease in osteosarcoma cell viability after 3 days, while both 5 mM and 25mM vitamin C reduced cellular viability by 2.5 folds (p≤0.05) compared to the control after 7 days. Interestingly, the presence of vitamin C showed no obvious signs of cytotoxicity towards osteoblast cell-line at day 3 and day 7, as confirmed by the MTT assay. Additionally, the FESEM images depict layers of hFOB cellular morphology on the surface of the implants, suggesting excellent cytocompatibility towards the osteoblast cells. These results suggest that vitamin C loaded HAp coated cpTi implant with improved osteogenic and chemopreventive properties can be considered as a promising reconstructive option to repair the post-tumor resection defects in osteosarcoma.

Polyether ether ketone (PEEK) rods were coated via ion beam asssited deposition (IBAD) at room temperature. The coating consists of a two-layer design of yttria-stabilized zirconia (YSZ) as a heat-protection layer, and hydroxyapatite (HA) as a top layer to increase bioactivity. A rotating substrate holder was designed to deposit an even coating on the cylindrical surface of PEEK rods; the uniformity is verified by cross-sectional measurements using scanning electron microscopy (SEM). Deposition is followed by heat treatment of the coating using microwave annealing and autoclaving. Transmission electron microscopy (TEM) showed a dense, uniform columnar grain structure in the YSZ layer that is well bonded to the PEEK substrate, while the calcium phosphate layer was amorphous and pore-free in its as-deposited state. Subsequent heat treatment via microwave energy introduced HA crystallization in the calcium phosphate layer and additional autoclaving further expanded the crystallization of the HA layer. Chemical composition evaluation of the coating indicated the Ca/P ratios of the HA layer to be near that of stoichiometric HA, with minor variations through the HA layer thickness. The adhesion strength of as-deposited HA/YSZ coatings on smooth, polished PEEK surfaces was mostly unaffected by microwave heat treatment, but decreased with additional autoclave treatment. Increasing surface roughness showed improvement of bond strength.

Ultrananocrystalline diamond (UNCD), an extremely smooth, low cost diamond coating was successfully developed herein for antithrombogenic application which requires high biocompatibility, low wear, low friction, and chemical inertness. The substrate materials utilized in the Jarvik 2000 ventricular assist device (VAD), silicon carbide and titanium alloy, provide an excellent substrate match for UNCD integration. The paper addresses the development of medical-quality UNCD films to significantly improve the knowledge base regarding the defect mechanisms of UNCD films, to reduce or eliminate known wear-inducing imperfections in the film, and to thoroughly characterize and test the films as well as assembled UNCD-coated VADs. After the defect reduction and seeding experiments to improve film adhesion and coating quality, the best candidate deposition method has been down-selected for coating and assembly of VAD parts from Jarvik Heart. The coated and assembled devices have been tested with mechanical and blood-simulating fluid hydrodynamic testing at Jarvik Heart for full verification of the new coating technology. UNCD interface takes advantage of combining unmatched durability and antithrombogenicity.

While it is well-known that supersaturated cubic-structured Ti Al N can be prepared by physical vapor deposition, the impact of point defects on formation process and cubic to wurtzite transition is largely unexplored. Irrespective of point defects, ab initio calculations correctly predict the Al concentration of the cubic to wurtzite transition. By means of density functional theory we show that vacancies on metal and/or non-metal sites only slightly affect the cubic to wurtzite transition region, whereas they clearly affect the physical properties.

The energy distribution functions of ions in the cathodic arc plasma using composite AlCr cathodes were measured as a function of the background gas pressure in the range 0.5 to 3.5 Pa for different cathode compositions and gas atmospheres. The most abundant aluminium ions were Al regardless of the background gas species, whereas Cr ions were dominating in Ar and N and Cr in O atmospheres. The energy distributions of the aluminium and chromium ions typically consisted of a high-energy fraction due to acceleration in the expanding plasma plume from the cathode spot and thermalised ions that were subjected to collisions in the plasma cloud. The fraction of the latter increased with increasing background gas pressure. Atomic nitrogen and oxygen ions showed similar energy distributions as the aluminium and chromium ions, whereas the argon and molecular nitrogen and oxygen ions were formed at greater distance from the cathode spot and thus less subject to accelerating gradients. In addition to the positively charged metal and gas ions, negatively charged oxygen and oxygen-containing ions were observed in O atmosphere. The obtained results are intended to provide a comprehensive overview of the ion energies and charge states in the arc plasma of AlCr composite cathodes in different gas atmospheres as such plasmas are frequently used to deposit thin films and coatings.

The influence of reactive and non-reactive sputtering on structure, mechanical properties, and thermal stability of ZrAlN thin films during annealing to 1500 °C is investigated in detail. Reactive sputtering of a ZrAl target leads to the formation of ZrAlN thin films, mainly composed of supersaturated cubic (c) ZrAlN with small fractions of (semi-)coherent wurtzite (w) AlN domains. Upon annealing, the formation of cubic Zr-rich domains and growth of the (semi-)coherent w-AlN domains indicate spinodal-like decomposition. Loss of coherency can only be observed for annealing temperatures above 1150 °C. Following these decomposition processes, the hardness remains at the as-deposited value of ~ 29 GPa with annealing up to 1100 °C. Using a ceramic (ZrN)(AlN) target and sputtering in Ar atmosphere allows preparing c-ZrAlN coatings with a well-defined crystalline single-phase cubic structure combined with higher hardnesses of ~ 31 GPa. Due to the absence of (semi-)coherent w-AlN domains in the as-deposited state, which could act as nucleation sites, the decomposition process of c-ZrAlN is retarded. Only after annealing at 1270 °C, the formation of incoherent w-AlN can be detected. Hence, their hardness remains very high with ~ 33 GPa even after annealing at 1200 °C. The study highlights the importance of controlling the deposition process to prepare well-defined coatings with high mechanical properties and thermal stability.

This paper describes synthesis of ultrathin pinhole-free insulating aluminum oxide layers for electronic device protection in corrosive liquid environments, such as phosphate buffered saline (PBS) or clinical fluids, to enable emerging biomedical applications such as biomolecular sensors. A pinhole-free 25-nm thick amorphous aluminum oxide layer has been achieved using ultra-high vacuum DC magnetron reactive sputtering of aluminum in oxygen/argon plasma followed by oxygen plasma post-processing. Deposition parameters were optimized to achieve the best corrosion protection of lithographically defined device structures. Electrochemical deposition of copper through the aluminum oxide layers was used to detect the presence (or absence) of pinholes. FTIR, XPS, and spectroscopic ellipsometry were used to characterize the material properties of the protective layers. Electrical resistance of the copper device structures protected by the aluminum oxide layers and exposed to a PBS solution was used as a metric to evaluate the long-term stability of these device structures.

In most metal matrix composites (MMCs) interfaces are decisive but hard to manipulate. Especially copper-carbon composites can exhibit excellent mechanical and thermal properties only if the Cu/C interface is modified by an optimised interlayer. Due to the excellent thermal conductivity and mechanical stability of diamond this form of carbon is preferred as reinforcement in heat sink materials (copper-diamond composite) which are often subjected to severe thermal and mechanical loads. In the present case niobium and boron interlayers of various thicknesses were deposited on diamond and vitreous carbon substrates by magnetron sputter deposition. After the coverage of all samples by a copper film, a part of the samples was subjected to heat treatment for 30 min at 800 °C under high vacuum (HV) to simulate the thermal conditions during the production of the composite material by uniaxial hot pressing. De-wetting during heat treatment leads to the formation of holes or humps in the Cu coating. This effect was investigated by scanning electron microscopy (SEM) and atomic force microscopy (AFM). A comparison of time-of-flight secondary ion mass spectroscopy (TOF SIMS) profiles of heat treated samples with those of as deposited ones showed the influence of interdiffusion during the heating process. Diffusion behaviour and chemical composition of the interface were also studied by cross sectional transmission electron microscopy (X-TEM) investigations using focused ion beam (FIB) cut samples. The thermal contact resistance (TCR) of the interface was calculated from results obtained from modulated infrared radiometry (IR). Thin interlayers suppressed de-wetting most effectively and consequently the TCR at the Cu-diamond interface was found to decrease. Therefore they are promising candidates for optimising the Cu-diamond interface.

The influence of a local thermal treatment on the properties of Ti-Al-N coatings is not understood. In the present work, a TiAlN coating on a WC-Co substrate was heated with a diode laser up to 900 °C for 30 s and radially symmetric lateral gradients of phases, residual stress and hardness were characterized - using position-resolved synchrotron X-ray diffraction, Raman spectroscopy, transmission electron microscopy and nanoindentation. The results reveal (i) a residual stress relaxation at the edge of the irradiated area and (ii) a compressive stress increase of few GPa in the irradiated area center due to the Ti-Al-N decomposition, in particular due to the formation of small wurtzite (w) AlN domains. The coating hardness increased from 35 to 47 GPa towards the center of the heated spot. In the underlying heated substrate, a residual stress change from about - 200 to 500 MPa down to a depth of 6 μm is observed. Complementary, - high-temperature X-ray diffraction analysis of stresses in a homogeneously heated TiAlN coating on a WC-Co substrate was performed in the range of 25-1003 °C. The - experiment revealed the origin of the observed thermally-activated residual stress oscillation across the laser heated spot. Finally, it is demonstrated that the coupling of laser heating to produce lateral thermal gradients and position-resolved experimental techniques opens the possibility to perform fast screening of structure-property relationships in complex materials.

TiAlN coatings are widely used for wear resistant applications due to their excellent mechanical and thermal properties, which depend to a great extent on the Al content. Here, we concentrate on a comparative study of the effect of Al content on crystal structure, thermal stability and oxidation resistance of TiAlN coatings. In agreement to earlier studies, thermal annealing of the individual cubic (c) and wurtzite (w) structured metastable TiAlN coatings induces decomposition into their stable phases c-TiN and w-AlN. The decomposition process for c-TiAlN involves an intermediate formation of cubic Al-rich and Ti-rich domains which results in a hardness increase to 34.7 and 34.4 GPa for x = 0.52 and 0.62 when annealed at 950 and 900 °C, respectively. In general, coatings with an Al content closer to the solubility limit, exhibit an earlier decomposition process, and hence an earlier peak-hardness. During exposure of the TiAlN coatings to ambient air at elevated temperatures AlO, TiO and AlTiO are formed. The oxidation resistance of as-deposited single-phase TiAlN coatings, cubic or wurtzite structured, increases with increasing Al content. However, coatings containing Al contents at the metastable solubility limit, which result in a mixed cubic-wurtzite structure, have the worst oxidation resistance of the Al-containing coatings investigated. The single phase wurtzite structured coating w-TiAlN shows the best oxidation resistance, with only ~0.7 μm oxide scale thickness, after thermal exposure for 20 h at 850 °C in ambient air.

Protective coatings for high temperature applications, as present e.g. during cutting and milling operations, require excellent mechanical and thermal properties during work load. The Ti(1 - x)Al(x)N system is industrially well acknowledged as it covers some of these requirements, and even exhibits increasing hardness with increasing temperature in its cubic modification, known as age hardening. The thermally activated diffusion at high temperatures however enables for the formation of wurtzite AlN, which causes a rapid reduction of mechanical properties in Ti(1 - x)Al(x)N coatings. The present work investigates the possibility to increase the formation temperature of w-AlN due to Hf alloying up to 10 at.% at the metal sublattice of Ti(1 - x)Al(x)N films. Ab initio predictions on the phase stability and decomposition products of quaternary Ti(1 - x - y)Al(x)Hf(y)N alloys, as well as the ternary Ti(1 - x)Al(x)N, Hf(1 - x)Al(x)N and Ti(1 - z)Hf(z)N systems, facilitate the interpretation of the experimental findings. Vacuum annealing treatments from 600 to 1100 °C indicate that the isostructural decomposition, which is responsible for age hardening, of the Ti(1 - x - y)Al(x)Hf(y)N films starts at lower temperatures than the ternary Ti(1 - x)Al(x)N coating. However, the formation of a dual phase structure of c-Ti(1 - z)Hf(z)N (with z = y/(1 - x)) and w-AlN is shifted to ~ 200 °C higher temperatures, thus retaining a film hardness of ~ 40 GPa up to ~ 1100 °C, while the Hf free films reach the respective hardness maximum of ~ 38 GPa already at ~ 900 °C. Additional annealing experiments at 850 and 950 °C for 20 h indicate a substantial improvement of the oxidation resistance with increasing amount of Hf in Ti(1 - x - y)Al(x)Hf(y)N.

Transition metal aluminium nitride (TM-Al-N) thin films are valued for their excellent mechanical (e.g. hardness) as well as protective (e.g. oxidation resistance) properties. This paper addresses the structure and phase stability of group IVB TM-Al-N systems Ti(1-x)Al(x)N, Zr(1-x)Al(x)N, and Hf(1-x)Al(x)N. The predicted stability regions of the rock salt cubic structures are x ≤ 0.7, x ≤ 0.45, and x ≤ 0.45, respectively, while the wurtzite-type single phase field is obtained for x ≥ 0.7, x ≥ 0.68, and x ≥ 0.62 respectively. The predicted phase stability regions and the broad dual-phase transition regions in the case of Zr(1-x)Al(x)N and Hf(1-x)Al(x)N are validated by experiments. Furthermore, the phase transition from cubic to wurtzite with increasing Al content in the alloys is correlated with changes of electronic structure and bonding in the systems.

The manipulation of mechanical and thermal interfaces is essential for the design of modern composites. Amongst these are copper carbon composites which can exhibit excellent heat conductivities if the Cu/C interface is affected by a suitable interlayer to minimize the Thermal Contact Resistance (TCR) and to maximize the adhesion strength between Cu and C.In this paper we report on the effect of boron based interlayers on wetting, mechanical adhesion and on the TCR of Cu coatings deposited on glassy carbon substrates by magnetron sputtering. The interlayers were 5 nm thick and consisted of pure B and B with additions of the carbide forming metals Mo, Ti and Cr in the range of 5 at.% relative to B. The interlayers were deposited by RF magnetron sputtering from either a pure B target or from a composite target. The interlayer composition was checked by Auger Electron Spectroscopy and found to be homogenous within the whole film.The system C-substrate/interlayer/Cu coating was characterized in as deposited samples and samples heat treated for 30 min at 800 °C under High Vacuum (HV), which mimics typical hot pressing parameters during composite formation. Material transport during heat treatment was investigated by Secondary Ion Mass Spectroscopy (SIMS). The de-wetting and hole formation in the Cu coating upon heat treatment were studied by Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). The adhesion of the Cu coating was evaluated by mechanical pull-off testing. The TCR was assessed by infrared photothermal radiometry (PTR). A correlation between the adhesion strength and the value of the TCR which was measured by PTR was determined for as deposited as well as for heat treated samples.

This paper reports preparation of a highly crystalline nano hydroxyapatite (HA) coating on commercially pure titanium (Cp-Ti) using inductively coupled radio frequency (RF) plasma spray and their in vitro and in vivo biological response. HA coatings were prepared on Ti using normal and supersonic plasma nozzles at different plate powers and working distances. X-ray diffraction (XRD) and Fourier transformed infrared spectroscopic (FTIR) analysis show that the normal plasma nozzle lead to increased phase decomposition, high amorphous calcium phosphate (ACP) phase formation, and severe dehydroxylation of HA. In contrast, coatings prepared using supersonic nozzle retained the crystallinity and phase purity of HA due to relatively short exposure time of HA particles in the plasma. In addition, these coatings exhibited a microstructure that varied from porous and glassy structure at the coating-substrate interface to dense HA at the top surface. The microstructural analysis showed that the coating was made of multigrain HA particles of ~200 nm in size, which consisted of recrystallized HA grains in the size range of 15- 20 nm. Apart from the type of nozzle, working distance was also found to have a strong influence on the HA phase decomposition, while plate power had little influence. Depending on the plasma processing conditions, a coating thickness between 300 and 400 μm was achieved where the adhesive bond strengths were found to be between 4.8 MPa to 24 MPa. The cytotoxicity of HA coatings was examined by culturing human fetal osteoblast cells (hFOB) on coated surfaces. In vivo studies, using the cortical defect model in rat femur, evaluated the histological response of the HA coatings prepared with supersonic nozzle. After 2 weeks of implantation, osteoid formation was evident on the HA coated implant surface, which could indicate early implant- tissue integration in vivo.

Press-hardened steel (PHS), used for automotive safety-related structure parts, is sensitive to hydrogen embrittlement due to its martensitic microstructure. Hydrogen is introduced in PHS during the hot press forming (HPF) process, by an atmospheric corrosion process. In this study, the hydrogen embrittlement behavior of uncoated, aluminized, and galvanized PHSs was investigated. The Al-10%Si coating promoted the absorption of diffusible hydrogen at elevated temperature during the HPF while the reacted coating layer prevented the absorbed hydrogen from out-diffusing through the reacted coating surface layer at room temperature. Therefore, the aluminized PHS showed a greater sensitivity to both the hydrogen uptake and the resultant embrittlement, as compared to the uncoated and galvanized PHSs. Use of galvanized PHS for HPF application reduces the risk of hydrogen embrittlement, since the Zn coating effectively prevents the hydrogen uptake. The greater embrittlement resistance of the galvanized PHS is possibly due to the inhibition of the hydrogen generation reaction by the surface ZnO oxide layer and the low rate of hydrogen transport through the liquid Zn phase.