Coatings, Volume 9, Issue 12 (December 2019) – 98 articles

We have investigated new and retrieved cementless hip endoprostheses that prematurely failed due to (i) aseptic loosening, (ii) infection and (iii) latent infection. The aim was to better understand the physico-chemical phenomena on the surfaces and sub-surfaces of the Ti6Al7Nb alloy implant. The results of our studies should enable us to distinguish the causes of premature failure, optimize the surface modification, achieve optimal osseointegration and extend the useful lifetime of the implants. The surface properties of the Ti6Al7Nb alloys of the hip-stem endoprostheses (30 retrieved and 2 new) were determined by contact-angle measurements and the average surface roughness. The surface chemistry and microstructure were analysed by scanning electron microscopy (SEM) for morphology, energy-dispersive X-ray spectroscopy (EDS) for the chemistry, and electron back-scatter diffraction (EBSD) for the phase analysis; Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) for the surface chemistry; and electrochemical measurements for the corrosion. The improved wettability of the grit-blasted surface of the Ti6Al7Nb stems after autoclaving was measured, as was the super wettability after oxygen-plasma sterilization. The secondary-electron images showed that the morphology and microstructure of the new and retrieved stems (prematurely failed due to aseptic loosening, infection and latent infection) differ slightly, while the EDS analysis revealed corundum contamination of the grit-blasted surface. We found corundum-contaminated Ti6Al7Nb stem surfaces and sub-surfaces for all the investigated new and retrieved implants. These residues are a potential problem, i.e., third-body wear particles, and probably induce the osteolysis and aseptic loosening. Full article

In the present work, a coating was prepared on an Al alloy substrate by plasma electrolytic oxidation (PEO). To seal the micro defects in the oxide scale, a siloxane layer was prepared on the PEO coating by sol gel method. The polymer sealant was synthesized from Tetraethoxy silane (TEOS) and methacryloxy propyl trimethoxyl silane (MPTES). The chemical structure of the polymer was studied by Fourier transform infrared spectroscopy (FTIR). The morphologies and microstructure of the PEO coating and siloxane coating were investigated by scanning electron microscopy (SEM). The results showed that siloxane formed a continuous layer on the surface and effectively sealed the micro defects. The corrosion behavior of the coatings in three different corrosion solutions (NaCl, HCl, and NaOH) was examined by electrochemical impedance spectroscopy and potentiodynamic polarization. The corrosion resistance of the sealed coatings was superior to that of the PEO coating because it prevented the penetration of corrosive solutions. The corrosion resistance of the sealed coatings was found to decrease with increasing electrolyte concentration. The work demonstrated that siloxane sealing may greatly enhance the corrosion resistance of Al-based PEO coating in acidic, neutral, and alkaline environments. Full article

This work reviewed innovative wood surface treatments based on nanotechnology. It is well documented in the literature that the cell walls of wood present significant porosity; this porosity is on a molecular scale. The main reason for the use of nanotechnology in wood science and technology is the unique characteristic of nano-based materials to effectively penetrate deeply into wood substrates, which, in turns, results in the alteration of their surface chemistry. This subsequently causes an improvement in wood properties. Any potential change in the wood properties due to treatment with nanomaterials is based on the higher interfacial area which is developed due to the treatment. This occurs because the number of particles is significantly reduced to the nanoscale. The nanomaterials improve the properties of wood as a raw material and alter its original features to a limited extent. However, their potential impact on both health and the environment should be addressed by applying tools such as life-cycle assessments. This will avoid mistakes being made in which new technologies are released on the market prior to an impact assessment having been carried out. Full article

In this study, a new approach for producing phosphorescent aluminum coatings was studied. Using the plasma electrolytic oxidation (PEO) process, a porous oxide coating was produced on the Al6082 aluminum alloy substrate. Afterwards, activated strontium aluminate (SrAl₂O₄: Eu²⁺, Dy³⁺) powder was filled into the cavities and pores of the PEO coating, which resulted in a surface that exhibits long-lasting luminescence. The structural and optical properties were studied using XRD, SEM, and photoluminescence measurements. It was found that the treatment time affects the morphology of the coating, which influences the amount of strontium aluminate powder that can be incorporated into the coating and the resulting afterglow intensity. Full article

Artificial weathering can significantly reduce the testing time needed for proving coating durability, nevertheless its reliability is still not thoroughly proven. In this study, eight different transparent and pigmented coating systems, namely oil, acrylate, alkyd and urethane alkyd were evaluated through natural and artificial weathering tests on oak samples by measuring colour, gloss and surface wettability and by macroscopic and microscopic evaluation. The oil coatings performed well in wood colour stability evaluations, while the best gloss and wettability change results were noted for acrylate coatings. Pigmented coatings were characterized by significantly lower colour changes than transparent ones. The gloss and wettability changes were more sensitive to coating disruption than to total colour changes of coated wood associated with chemical changes in wood. The findings in this work showed that values of gloss changes and surface wettability for all types of coatings exposed to artificial and natural weathering resulted in significant differences from each other. The data obtained by artificial weathering method provide basic results of coatings durability and, ideally, natural weathering should be performed at the same time to support the results from laboratory tests by exposing wood under real conditions. Full article

In this work, titanium nitride (TiN) nanorod arrays were fabricated using glancing angle deposition in a magnetron sputtering system. The deposition parameters, including the bias on the substrate and the flow rate of nitrogen, were varied to deposit various TiN nanorod arrays. Before glancing angle deposition was conducted, uniform TiN films were deposited and their permittivity spectra, for various deposition parameters, were obtained. The effect of the deposition parameters on the morphology of the nanorods is analyzed here. The polarization-dependent extinctance spectra of TiN nanorod arrays were measured and compared. Extinction, which corresponds to the longitudinal mode of localized surface plasmon resonance, can be significantly changed by tuning the N₂ flow rate and substrate bias voltage during deposition. Full article

In this work, nanochitosan (NC) was prepared through ionic gelation using low molecular weight chitosan and maleic acid (MA). The synthesized NC was characterized by atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). During preparation, the particle size of the material depended on parameters such as concentration of chitosan and pH of the aqueous solution. After controlling the mentioned parameters, NC smaller than 100 nm was prepared. The chitosan and prepared NC were employed for the adsorption of Pb(II) from an aqueous solution in the form of a batch system. Among the sorption parameters, pH showed the strongest effect on the sorption process and removal of the maximum number of Pb(II) ions was obtained at pH value of 6. Pseudo-first-order and pseudo-second-order models were used to track the kinetics of the adsorption process. Langmuir and Freundlich’s isotherms were subjected to the absorption data to evaluate absorption capacity. NC proved to be an excellent adsorbent with a remarkable capacity to eliminate Pb(II) ions from aqueous solutions at multiple concentrations. The NC also showed better performance with a comparatively easier preparation process than in other reported work. Full article

In order to solve the problem of dust accumulation on the fin surface of a mine air cooler, a method of preparing super-hydrophobic polyurethane (SPU) coating based on waste cooking oil (WCO) was proposed. Firstly, the polyurethane prepolymer was synthesized with WCO as a raw material, and then the polyurethane prepolymer was modified with amino-terminated polydimethylsiloxane (ATP) to obtain SPU emulsion. The chemical structure and thermal stability of SPU were characterized by infrared spectrum and thermogravimetric analysis. A series of nanocomposites were prepared by combining modified silicon carbide (APT-SiC) particles and SPU emulsions. According to the parameters of pull-off strength, contact angle, sliding angle and thermal conductivity, the filler ratio of nanocomposites was optimized. The test results show that when the content of APT-SiC particles is 20 wt %, super-hydrophobic polyurethane coating can be obtained. The coating has good pull- off strength and thermal conductivity, and the contact angle and sliding angle are 161° and 3°, respectively. In addition, the practical application of the super-hydrophobic polyurethane coating was tested by related experiments. The experimental results show that the coating has good self-cleaning, wear resistance and anti-corrosion performance, can meet the requirements of air coolers in special environments, and has great application prospects. Full article

The current study pertains to the self-cleaning nanoscale coating of graphene/polymer nanohybrid system for the separation of oil–water mixture. Using a single nanohybrid system, we have developed a two-stage process for the selective removal of the hydrocarbons. Total petroleum hydrocarbons (TPHs) and separation efficiency are determined by gas chromatography-flame ionization detector (GC-FID). Analysis of the polycyclic aromatic hydrocarbons (PAHs) in the two stage samples is carried out by using gas chromatography coupled to mass spectrometry (GC-MS). The analysis shows the reduction in TPHs from 290 ppm to less than 1 ppm and more than 99.5% separation efficiency (oil removal from oil–water mixture) is achieved. No polycyclic aromatic hydrocarbons (PAHs) were detected in the treated water. Full article

Zinc gallate (ZnGa₂O₄) thin films were grown on sapphire (0001) substrate using radio frequency (RF) magnetron sputtering. After the thin film deposition process, the grown ZnGa₂O₄ was annealed at a temperature ranging from 500 to 900 °C at atmospheric conditions. The average crystallite size of the grown ZnGa₂O₄ thin films increased from 11.94 to 27.05 nm as the annealing temperature rose from 500 to 900 °C. Excess Ga released from ZnGa₂O₄ during thermal annealing treatment resulted in the appearance of a Ga₂O₃ phase. High-resolution transmission electron microscope image analysis revealed that the preferential crystallographic orientation of the well-arranged, quasi-single-crystalline ZnGa₂O₄ (111) plane lattice fringes were formed after the thermal annealing process. The effect of crystallite sizes and lattice strain on the width of the X-ray diffraction peak of the annealed ZnGa₂O₄ thin films were investigated using Williamson-Hall analysis. The results indicate that the crystalline quality of the deposited ZnGa₂O₄ thin film improved at higher annealing temperatures. Full article

Fe-based amorphous/nanocrystalline coatings with smooth, compact interior structure and low porosity were fabricated via supersonic plasma spraying (SPS). The coatings showed outstanding corrosion resistance in a 3.5% NaCl solution at room temperature. In order to analyze the effect of annealing treatment on the microstructure, corrosion resistance and microhardness, the as-sprayed coating was annealed for 1 h under different temperatures such as 350, 450, 550 and 650 °C, respectively. The results showed that the number of oxides and cracks in the coatings presented an obvious increase with increasing annealing temperature, and the corrosion resistance of the coatings showed an obvious reduction. However, the microhardness of coatings showed an important increase. The microhardness of the coating could reach 1018 HV when the heat treatment temperature reached 650 °C. The X-ray diffraction (XRD) results showed that there appeared a number of crystalline phases in the coating when the heat treatment temperature was at 650 °C. The crystalline phases led to the increase of the microhardness. Full article

The technology of applying a colloidal single-layer coating of transparent polystyrene (PS) Ø 1 μm spheres at the tip face of a quartz fiber has been proposed and tested. Such a coating plays, in a light absorbing liquid, the role of a converter of pulsed laser radiation into acoustic radiation. The generation of ultrasound in water using a converter based on a quartz fiber 1 mm in diameter with a 2D colloidal crystalline coating consisted of polystyrene spheres with a diameter of ~1 μm at the fiber end was investigated. When excited by laser radiation (λ = 1.064 µm), coating of polystyrene spheres created in the liquid a laser thermal microstructure with a characteristic size of fractions of ~λ and a maximum temperature up to 10⁻² degree at an energy in a short laser pulse of ~0.005 J. This short-lived thermal microstructure generated sound pulses in the liquid in the approximately 0.2–4 MHz range. The results of the experimental study of this effect are reported. The proposed laser radiation converter with colloidal coating of the optical fiber distal tip by a single layer of transparent spheres can be used for the development of new laser microtools for studying, processing of various objects in microsurgery, microstructuring of the surface, spot cleaning and restoration of objects of art and history. Full article

The hard and corrosion resistant coatings of Mo₂NiB₂ cermet were prepared by the laser cladding technique. The influences of the Mo:B ratio and the laser scanning speed on the microstructure and property of the Mo₂NiB₂ cermet coatings were investigated. The results showed that the laser scanning speed of 1.5 mm/s and the Mo:B ratio of 1 were more beneficial to the formation of Mo₂NiB₂ cermet than 2.0 mm/s and 0.8, 1.2, respectively. The amount of the Mo₂NiB₂ ceramic phases were decreased from the top layer to the bottom layer of the coating. The changes of microstructure and composition led to the changes of hardness and corrosion resistance of the Mo₂NiB₂ cermet coatings. The coating prepared at the Mo:B ratio of 1 and the scanning speed of 1.5 mm/s possessed the highest hardness, and the hardness gradually decreased from the top layer to the bottom layer of the coating. The formation of Mo₂NiB₂ and {FeM} phases led to the enhanced corrosion resistance of the Mo₂NiB₂ cermet coatings, and the coating prepared at the Mo:B ratio of 0.8 possessed the best corrosion resistance and the minimum corrosion current. Full article

A FEA-based methodology was developed in order to predict the wear status of an osteotome (surgical instrument) during its use in a lateral nasal bone osteotomy considering its fatigue strength. The latter parameter was determined by appropriate FEM-evaluation of the perpendicular impact test results. For the simulation of the surgical procedure, two scenarios were examined: (i) when utilizing a brand new osteotome and (ii) when utilizing an already used osteotome characterized by decreased fatigue strength. The actual nasal bone geometry used in the FEA model was obtained from a high-resolution, maxillofacial, computed tomography (CT) scan of a single patient. In both cases examined, depiction of fracture patterns for the osteotome and the nasal bone were obtained. The wear of a new osteotome and an already used osteotome was also calculated and compared. The developed von Mises stresses in both the osteotome and nasal bone were depicted. The proposed methodology allowed an accurate prediction of the critical number of impacts that the osteotome can receive during the lateral nasal osteotomy which is followed in all rhinoplasties. Based on the developed methodology, a preventive replacement of the osteotome before its extensive fracture can be determined, thereby minimizing the risk of postoperative complications. Full article

The formation of an ordered surface texture with micro and nanometer features on Ti/Zr multilayers is studied for better understanding and improvement of cell integration. Nanocomposite in form 30×(Ti/Zr)/Si thin films was deposited by ion sputtering on Si substrate for biocompatibility investigation. Surface texturing by femtosecond laser processing made it possible to form the laser-induced periodic surface structure (LIPSS) in each laser-written line. At fluence slightly above the ablation threshold, beside the formation of low spatial frequency-LIPSS (LSFL) oriented perpendicular to the direction of the laser polarization, the laser-induced surface oxidation was achieved on the irradiated area. Intermixing between the Ti and Zr layers with the formation of alloy in the sub-surface region was attained during the laser processing. The surface of the Ti/Zr multilayer system with changed composition and topography was used to observe the effect of topography on the survival, adhesion and proliferation of the murine mesenchymal stem cells (MSCs). Confocal and SEM microscopy images showed that cell adhesion and their growth improve on these modified surfaces, with tendency of the cell orientation along of LIPSS in laser-written lines. Full article

Burr is an undesirable phenomenon occurring in drilling operation which is one of the essential operations in the machining industry since it is directly influencing the operating costs. Exit burr height (EBH) values as the function of drilling time during drilling the specific holes of the forging brass workpieces used for producing the water-valve components with the uncoated- tungsten carbide (WC) and the AlCrN coated-WC drills were discussed. The data sets of drilling time, corresponding to EBH values at the appropriate criterion were used to develop the tool life models in terms of cutting speed and feed rate using Taylor’s equation. Monte Carlo simulation was adopted to study the uncertainty of cutting speed and feed rate on tool life predictions for sensitivity analysis. The results showed that drilling with a low feed rate decreased the averages of EBH. The predicted tool life values of the AlCrN coated-WC drills were higher than those of the uncoated-WC ones based on the results of tool life predictions. The appropriate operating condition of the cutting speed of 60 m/min and the feed rate of 0.2 mm/rev was recommended for manufacturers in the drilling of the forging brass workpieces using the AlCrN coated-WC drills. Moreover, the predicted tool life values for the uncoated-WC and the AlCrN coated-WC drills were about 600 and 800 min, respectively. This indicated that the AlCrN coated-WC drill increased tool life by 30%. Full article

Electrochemical noise (EN) is expected to be an in-situ evaluation method for coating performance in the real deep-ocean environment. The asymmetric factors of working electrodes (WEs) in EN configuration, including coating area, coating thickness, and coating impedance, were considered under marine alternating hydrostatic pressure (AHP) condition. The effect of WE asymmetry was discussed mainly by EN time records, wavelet analysis and shot noise method. The results indicated that coating impedance is the most important factor, and the coating with higher impedance contributes more to current noise in a pair of electrodes. The reason of asymmetry influence on EN measurements is mainly by the variation of average charge of current sources but not the current source frequency during the initial period of coating failure process. When the obvious corrosion of metal substrate happens, the corresponding EN proportion relationship between coating/metal WEs may be not exist. Full article

In this work, a masking technique was used to improve the thickness uniformity of a Mo/Si multilayer deposited on a curved spherical mirror by direct current (DC) magnetron sputtering with planetary rotation stages. The clear aperture of the mirror was 125 mm with a radius of curvature equal to 143.82 mm. Two different shadow masks were prepared; one was flat and the other was oblique. When using the flat mask, the non-uniformity considerably increased owing to the relatively large gap between the mask and substrate. The deviation between the designed and measured layer thickness and non-uniformity gradually reduced with a smaller gap. The second mask was designed with an oblique profile. Using the oblique mask, the deviation from multilayer thickness uniformity was substantially reduced to a magnitude below 0.8% on the curved spherical substrate over the clear aperture of 125 mm. Multilayers still achieved a smooth growth when deposited with obliquely incident particles. The facile masking technique proposed in this study can be used for depositing uniform coatings on curved spherical substrates with large numerical apertures for high-resolution microscopes, telescopes, and other related optical systems. Full article

A facile periodical secondary growth method, based on conventional secondary growth, is proposed to prepare bilayer TS-1 membranes. The novel periodical secondary growth consists of two or several periods, which involve three steps: the temperature is programmed to a desired crystallization temperature as the first stage, followed by holding for a certain duration, and finally cooling to room temperature. This periodical crystallization model enables a bilayer TS-1 membrane to be produced, while the conventional secondary growth method produces a monolayer TS-1 membrane. The bilayer TS-1 membrane exhibits a superior defect-free structure and hydrophobic properties, as illustrated by SEM, gas permeance, pore size distribution analysis, and water contact angle measurement. It displays an earlier desalination separation factor compared to the monolayer TS-1 membrane. This work demonstrates that the periodical secondary growth is an advanced approach for preparing a bilayer zeolite membrane with excellent properties. Full article

The present research examines the impact of second-order slip with thermal and solutal stratification coatings on three-dimensional (3D) Williamson nanofluid flow past a bidirectional stretched surface and envisages it analytically. The novelty of the analysis is strengthened by Cattaneo–Christov (CC) heat flux accompanying varying thermal conductivity. The appropriate set of transformations is implemented to get a differential equation system with high nonlinearity. The structure is addressed via the homotopy analysis technique. The authenticity of the presented model is verified by creating a comparison with the limited published results and finding harmony between the two. The impacts of miscellaneous arising parameters are deliberated through graphical structures. Some useful tabulated values of arising parameters versus physical quantities are also discussed here. It is observed that velocity components exhibit an opposite trend with respect to the stretching ratio parameter. Moreover, the Brownian motion parameter shows the opposite behavior versus temperature and concentration distributions. Full article

Curvature effects are typically present in the process of additive manufacturing (AM), particularly for wire arc additive manufacturing. In this paper, stainless-steel wire was adopted to deposit thin-walled samples with different curvatures. Optical microscopy, SEM, EDS and micro-hardness was used to analyse the microstructure, composition and properties of the samples. The result shows that the bottom region of the thin-walled sample had a mainly planar and cellular crystal microstructure. For the middle region, the microstructure revealed mainly dendrites, and the top layer has equiaxed dendrite morphology. The microhardness value of the bottom was greater than that of the middle, and the microhardness value of the middle was greater than that of the top. Moreover, the grain size of the inner part (direct to curvature radius) was larger than that of the outer part, and the micro-hardness value exhibited an increasing tendency from the inner to the outer side. With enlarging curvature, the degree of grain size differences and micro-hardness variants decreased. Finally, an investigation with a low carbon steel wire showed that it had a similar curvature effect for its AM specimen. Full article

The development of erosion-resistant functional materials usable as plasma facing first wall components (PFC) is crucial for increasing the lifetime of future fusion reactors. Generally, PFCs have to be quality checked and characterized regarding their composition, before integrating them into the fusion reactor vessel. Enhanced X-ray fluorescence (XRF) methods represent an effective alternative to conventional analysis methods for the characterization of refractive metallic coatings on large areas of fusion materials. We have developed and applied XRF methods as fast and robust methods for the characterization of the thickness and composition uniformity of complex functional coatings. These coatings consist of tungsten included in multilayer configuration and deposited on low or high Z substrates. We have further developed customized calibration protocols for quantifying the element composition and layer thickness of each investigated sample. The calibration protocols are based on a combination of standard samples measurements, Monte Carlo simulations, and fundamental parameter theoretical calculations. The calibrated results are discussed considering a selection of relevant PFC samples. The deposition uniformity was successfully investigated for different PFC-relevant tiles and lamella shaped samples with W layers below and over the W L-line saturation thickness. Also, the 2D thickness mapping capability of the XRF method was demonstrated by studying the plasma post-erosion pattern. Full article

The effect of ultraviolet radiation on the surface deterioration of scrimber composites with different densities and levels of resin content was investigated for this paper. The surface color, gloss, roughness, and wettability of the samples were investigated to determine the extent of surface changes due to accelerated ageing. The results indicated that all scrimber composites exhibited variation in the color of their surfaces during artificial xenon light exposure. After artificial accelerated ageing, the surface contact angle and roughness were found to increase, whereas the surface gloss and surface free energy decreased. Furthermore, it was observed that the density and resin content of the scrimber composites contributed to reductions in their color variation, wettability, and roughness during weathering, which suggested that the density and resin content played important roles in determining their surface photodegradation properties. Artificial ageing resulted in the degradation of lignin and hemicellulose, thus causing severe surface characteristics. Full article

The article presents selected properties of a titanium metallization coating deposited on aluminum nitride (AlN) ceramics surface by means of the friction surfacing method. Its mechanism is based on the formation of a joint between the surface of an AlN ceramics substrate and a thin Ti coating, involving a kinetic energy of friction, which is directly converted into heat and delivered in a precisely defined quantity to the resulting joint. The largest effects on the final properties of the obtained coating include the high affinity of titanium for oxygen and nitrogen and a relatively high temperature for the deposition process. The titanium metallization coating was characterized in terms of surface stereometric structure, thickness, surface morphology, metallographic microstructural properties, and phase structure. The titanium coating has a thickness ranging from 3 to 7 μm. The phase structure of the coating surface (XPS investigated) is dominated by TiN_xO_y with the presence of TiO_x, TiN, metallic Ti, and AlN. The phase structure deeper below the surface (XRD investigated) is dominated by metallic Ti with additional AlN particles originating from the ceramic substrate due to friction by titanium tools. Full article

In this paper, hyperbranched polyether functionalized graphene oxide (EHBPE-GO) was prepared by a facile one-step method. Fourier transform infrared spectroscopy (FTIR), X-ray diffractometry (XRD), thermogravimetric analyzer (TGA), and trans-mission electron microscopy (TEM) results confirmed the formation of EHBPE-GO. Then, EHBPE-GO was cured with phenolic amides at room temperature to prepare epoxy coatings. The corrosion resistance of epoxy coatings was investigated systematically by using electrochemical and traditional immersion methods. Results show that a small amount of EHBPE-GO (8 wt % of Diglycidyl ether of bisphenol A (DGEBA)) in epoxy coating achieves 50% higher improvement in acid-resistance than unmodified neat DGEBA resin. For the nanocomposite epoxy coating, the superior acid-resistance is attributed to the increased crosslink density and the impermeable 2D structure of EHBPE-GO. This work provides a facile strategy to develop the effective improved corrosion resistance nanofiller for epoxy coating. Full article

The overall energy efficiency of machine elements and engine components could be improved by using new technologies such as surface modifications. In the literature, surface engineering approaches like micro-texturing and the application of diamond-like carbon (DLC) coatings were frequently studied separately, with focus on a specific model contact and lubrication conditions. The contribution of the current study is to elucidate and compare the underlying friction reduction mechanisms of the aforementioned surface modifications in an application-orientated manner. The study applied the operating conditions of the thermo-elastohydrodynamically lubricated (TEHL) cam/tappet-contact of the valve train. Therefore, tribological cam/bucket tappet component Stribeck tests were used to determine the friction behavior of ultrashort pulse laser fabricated microtextures and PVD/PECVD deposited silicon-doped amorphous carbon coatings. Moreover, advanced surface characterization methods, as well as numerical TEHL tribo-simulations, were utilized to explore the mechanisms responsible for the observed tribological effects. The results showed that the DLC-coating could reduce the solid and fluid friction force in a wide range of lubrication regimes. Conversely, micro-texturing may reduce solid friction while increasing the fraction of fluid friction. Full article

In this article, the intention is to explore the flow of a magneto-hydrodynamic (MHD) bioconvective micro-polar Nanofluid restraining microorganism. The numerical solution of 2-D laminar bioconvective boundary layer flow of micro-polar nanofluids are presented. The phenomena of multi-slip, convective thermal and Solutal boundary conditions have been integrated. A system of non-linear partial differential equations are transformed into the system of coupled nonlinear ordinary differential equations by applying appropriate transformations, the transformed equations are then solved by applying the variational finite element method (FEM). The fascinating features of assorted velocity parameter, microrotation, temperature, microorganism compactness, solutal and nanoparticles concentration have been inspected. The rate of heat transfer, the skin friction coefficient, couple stress and Sherwood number for microorganisms have also been discussed graphically and numerically. The investigations illustrated that increase in material parameters causes a reduction in microorganism compactness, concentration and temperature. As a result of enhancement in the unsteadiness parameter, the fluid velocity, concentration of microorganisms and the temperature are observed to be declines. Energy and microorganism compactness profile affected by the improvement in the buoyancy ratio parameter. As the improvement in results of buoyancy ratio parameter effects on improvement in the energy and the microorganism compactness profile while the velocity profile is condensed. In the end, rationalized convergence of the finite element solution has been inspected; the computations are found out via depreciating the mesh size. Full article

Ti_0.92Ta_0.08N and Ti_0.41Al_0.51Ta_0.08N thin films grown on stainless-steel substrates, with no external heating, by hybrid high-power impulse and dc magnetron sputtering (HiPIMS/DCMS), were investigated for corrosion resistance. The Ta target was operated in HiPIMS mode to supply pulsed Ta-ion fluxes, while two Ti (or Ti and Al) targets were operated in DCSM mode in order to provide a high deposition rate. Corrosion resistance was investigated using potentiodynamic polarization and electrochemical impedance spectroscopy employing a 3.5% NaCl solution at room temperature. The 300-nm-thick transition-metal nitride coatings exhibited good corrosion resistance due to film densification resulting from pulsed heavy Ta-ion irradiation during film growth. Corrosion protective efficiencies were above 99.8% for both Ti_0.41Al_0.51Ta_0.08N and Ti_0.92Ta_0.08N, and pore resistance was apparently four orders of magnitude higher than for bare 304 stainless-steel substrates. Full article

In the present work Cr₃C₂-NiCr powder containing Al particles was deposited on ductile cast iron with high-velocity oxy-fuel (HVOF) thermal spray coating technique. An investigation was conducted to determine the role of Al particles in the Cr₃C₂-NiCr coating produced with HVOF technique on microstructure, mechanical and wear properties in a system Cr₂C₃-NiCr coating/ductile cast iron. The microstructure of the HVOF-sprayed Cr₃C₂-NiCr+Al coating was characterized by light microscopy, X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and energy dispersive X-ray spectroscopy (EDS). Microstructure analysis reveals the formation of coating with low porosity, good adhesion to the substrate and dense structure with irregularly shaped particles of Al arranged in strips and finely fragmented Cr₃C₂ particles embedded in a nanocrystalline Ni-Cr alloy matrix. In addition, the results were discussed in reference to examination of bending strength considering cracking and delamination in the system of (Cr₃C₂-NiCr+Al)/ductile cast iron as well as microhardness and wear resistance of the coating. It was found that the addition of Al particles significantly increased resistance to cracking and wear behaviour in the studied system. Full article

For improving the vacuum and mitigating the electron clouds in ultra-high vacuum chamber systems of high-energy accelerators, the deposition of Ti-V-Hf-Zr getter film on a laser-treated aluminum alloy substrate was proposed and exploited for the first time in this study. The laser-treated aluminum surface exhibits a low secondary electron yield (SEY), which is even lower than 1 for some selected laser parameters. Non-evaporable getter (NEG) Ti-V-Hf-Zr film coatings were prepared using the direct current (DC) sputtering method. The surface morphology, surface roughness and composition of Ti-V-Hf-Zr getter films were characterized and analyzed. The maximum SEY of unactivated Ti-V-Hf-Zr getter film on laser-treated aluminum alloy substrates ranged from 1.10 to 1.48. The X-ray photoelectron spectroscopy (XPS) spectra demonstrate that the Ti-V-Hf-Zr coated laser-treated aluminum alloy could be partially activated after being heated at 100 and 150 °C, respectively, for 1 h in a vacuum and also used as a pump. The results were demonstrated initially and the potential application should be considered in future particle accelerators. Full article