Diamond films were applied onto zirconia substrates, to potentially enhance the wear resistance of zirconia bearings under harsh working conditions, such as vacuum and/or no lubrication. To mitigate the mismatch between the zirconia substrates and the diamond films, a tungsten-molybdenum alloy transition layer was first deposited on the zirconia substrate using magnetron sputtering technology (MS), followed by the deposition of a diamond film through hot filament chemical vapor deposition (HFCVD). Orthogonal experimental methods were employed to explore the influence of transition layer composition, substrate temperature, methane concentration, and substrate roughness on the wear resistance. The results indicated that diamond films prepared on a tungsten-molybdenum alloy transition layer with W:Mo = 1:1 exhibited the highest quality. Furthermore, the substrate temperature, methane concentration, and substrate roughness significantly affected the quality of the diamond films. Specifically, the lowest friction coefficient and wear rate were observed when the substrate temperature was set at 850 °C during HFCVD, methane concentration at 4.5

Single and gradient multilayered diamond coatings, deposited on silicon nitride (Si 3 N 4 ), were prepared by hot filament chemical vapour deposition. The tribological properties were evaluated in a wide temperature range (26 °C–300 °C), against Si 3 N 4 ceramic balls, as the friction counterpart. The results showed that with the increase of temperature from 26 °C to 300 °C, the wear rate of NCD (nanocrystalline diamond) and GCD (gradient diamond) coatings rapidly increases. When the temperature reaches 300 °C, obvious cracks and detachment appear on the surface of the NCD coatings. Due to the special interlayer, the wear rate of the GCD coatings is lower than that of the NCD coatings. In the range of 26 °C to 100 °C, GCD exhibits excellent wear resistance and low friction coefficient due to its special gradient structure. When the temperature increases to 200 °C, NCD films with smaller grain sizes exhibit higher wear rates. From the wear morphology, it can be seen that cracks are generated in the NCD film, and as the temperature increases, the cracks continue to expand until the film spalling. GCD shows relatively good wear resistance at high temperatures. This study found that gradient multilayered diamond coatings exhibited superior wear resistance at high temperatures, compared with single-layer coatings tested in identical conditions.

Monolayer and multilayer diamond films are deposited on WC‐Co cemented carbide by hot‐filament chemical vapor deposition. The growth characteristics of diamond coatings are analyzed. Cutting performance characteristics such as tool life and the stability of machining process in the machining of presintered ZrO 2 are compared based on the variation of cutting speed and resultant cutting force, and workpiece surface roughness. For the monolayer diamond coatings, as the concentration of CH 4 increases from 1% to 5%, the diamond crystal is transformed from micron columnar crystal to nanocluster crystal. The multilayer diamond coatings combine the advantages of micron‐ and nanocrystalline structures. The multilayer diamond‐coated tool exhibits longer service life and better machining quality. Because of the appearance of the brittle–plastic conversion mechanism, the surface integrity of ZrO 2 processed by multilayer diamond‐coated tool is relatively high. As for the uncoated tool, the workpiece is mainly machined by brittle spalling. The interfacial stratified fracture system between the interlayers is proposed to be the toughening mechanism of the multilayer structure.

This work was devoted to the first multi-parametric unitary comparative analysis of a selection of sintered piezoceramic materials synthesised by solid-state reactions, aiming to delineate the most promising biocompatible piezoelectric material, to be further implemented into macro-porous ceramic scaffolds fabricated by 3D printing technologies. The piezoceramics under scrutiny were: KNbO3, LiNbO3, LiTaO3, BaTiO3, Zr-doped BaTiO3, and the (Ba0.85Ca0.15)(Ti0.9Zr0.1)O3 solid solution (BCTZ). The XRD analysis revealed the high crystallinity of all sintered ceramics, while the best densification was achieved for the BaTiO3-based materials via conventional sintering. Conjunctively, BCTZ yielded the best combination of functional properties—piezoelectric response (in terms of longitudinal piezoelectric constant and planar electromechanical coupling factor) and mechanical and in vitro osteoblast cell compatibility. The selected piezoceramic was further used as a base material for the robocasting fabrication of 3D macro-porous scaffolds (porosity of ~50%), which yielded a promising compressive strength of ~20 MPa (higher than that of trabecular bone), excellent cell colonization capability, and noteworthy cytocompatibility in osteoblast cell cultures, analogous to the biological control. Thereby, good prospects for the possible development of a new generation of synthetic bone graft substitutes endowed with the piezoelectric effect as a stimulus for the enhancement of osteogenic capacity were settled.

In the global context of climate change and carbon neutrality, this work proposes a strategy to improve the light absorption of photocatalytic water-splitting materials into the visible spectrum by anion doping. In this framework, reactive high power impulse magnetron sputtering (HiPIMS) of a pure Zr target in Ar/N 2 /O 2 gas mixture was used for the deposition of crystalline zirconium oxynitride (ZrO 2-x N x ) thin films with variable nitrogen doping concentration and energy band-gap. The nitrogen content into these films was controlled by the discharge pulsing frequency, which controls the target surface poisoning and peak discharge current. The role of the nitrogen doping on the optical, structural, and photocatalytic properties of ZrO 2-x N x films was investigated. UV-Vis-NIR spectroscopy was employed to investigate the optical properties and to assess the energy band-gap. Surface chemical analysis was performed using X-ray photoelectron spectroscopy, while structural analysis was carried out by X-ray diffraction. The increase in the pulse repetition frequency determined a build-up in the nitrogen content of the deposited ZrO 2-x N x thin films from ∼10 to ∼25 at.%. This leads to a narrowing of the optical band-gap energy from 3.43 to 2.20 eV and endorses efficient absorption of visible light. Owing to its narrow bandgap, ZrO 2-x N x thin films obtained by reactive HiPIMS can be used as visible light-driven photocatalyst. For the selected processing conditions (pulsing configuration and gas composition), it was found that reactive HiPIMS can suppress the hysteresis effect for a wide range of frequencies, leading to a stable deposition process with a smooth transition from compound to metal-sputtering mode.

The paper studies the UV exposure influence on the mechanical properties, crystalline, interface and morphology of the optimised (previously water immersed) composites with wastes of rubber, PET, HDPE, wood and inorganic filler (CaO and fly ash). The mechanical strength, photo-degradation, crystalline structure and surface morphologies changes of the composites are evaluated after their exposure under simulated UV light and compared to unexposed ones. Experimental results showed UV exposure lead to the increase of Young moduli, compressive strength and tensile for high content PET samples. Significant mechanical strength even after water immersion and UV exposure were recorded for the rubber–PET–HDPE–wood–fly ash with a compression strength of about 70 MPa and for the 40 wt% PET composites with Young moduli of about 15 MPa. Therefore short term UV treatment could be used to enhance de composite’interface strength aiming at their outdoor applications.

This study presents a novel laser processing technique in a liquid media to enhance the surface mechanical properties of a material, by thermal impact and micro-alloying at the subsurface level. An aqueous solution of nickel acetate (15% wt.) was used as liquid media for laser processing of C45E steel. A pulsed laser TRUMPH Truepulse 556 coupled to a PRECITEC 200 mm focal length optical system, manipulated by a robotic arm, was employed for the under-liquid micro-processing. The study's novelty lies in the diffusion of nickel in the C45E steel samples, resulting from the addition of nickel acetate to the liquid media. Micro-alloying and phase transformation were achieved up to a 30 µm depth from the surface. The laser micro-processed surface morphology was analysed using optical and scanning electron microscopy. Energy dispersive spectroscopy and X-ray diffraction were used to determine the chemical composition and structural development, respectively. The microstructure refinement was observed, along with the development of nickel-rich compounds at the subsurface level, contributing to an improvement of the micro and nanoscale hardness and elastic modulus (230 GPa). The laser-treated surface exhibited an enhancement of microhardness from 250 to 660 HV0.03 and an improvement of more than 50% in corrosion rate.

The possibility to tune the elemental composition and structure of binary Me oxynitride-type compounds (Me1Me2ON) could lead to attractive properties for several applications. For this work, tantalum-titanium oxynitride (TaTiON) thin films were deposited by DC reactive magnetron co-sputtering, with a –50 V bias voltage applied to the substrate holder and a constant substrate temperature of 100 °C. To increase or to decrease in a controlled manner, the Ti and Ta content in the co-sputtered films, the Ti and Ta target currents were varied between 0.00 and 1.00 A, in 0.25 A steps, while keeping the sum of the currents applied to the two targets at 1.00 A. The reactive gases flow, consisting of a nitrogen and oxygen gas mixture with a constant N2/O2 ratio (85%/15%), was also kept constant. The single-metal oxynitrides (TaON and TiON) showed a low degree of crystallinity, while all the other co-sputtered films revealed themselves to be essentially amorphous. These two films also exhibited higher adhesion to the metallic substrate. The TaON film showed the highest hardness value (14.8 GPa) and the TiON film a much lower one (8.8 GPa), while the co-sputtered coatings exhibited intermediary values. One of the most interesting findings was the significant increase in the O content when the Ti concentration surpassed the Ta one. This significantly influenced the optical characteristic of the films, but also their electrical properties. The sheet resistivity of the co-sputtered films is strongly dependent on the O/(Ta + Ti) atomic ratio.

Direct current magnetron co-sputtered titanium and tantalum based oxynitride coatings (TaTiON) were analyzed in terms of their chemistry, surface morphology, surface energy, photocatalytic activity, and corrosion resistance. The variable parameter for the deposition was the applied current on each target, changing between 0.75A and 0.25A for the Ta target, and from 0.25A to 0.75 A for the Ti target, to obtain a total current of 1A. Reference single-sputtered samples (TaON and TiON) were deposited under identical conditions. It was observed that a higher degree of oxidation occurred in the samples deposited with higher current on the Ti target, while nitriding and oxynitriding processes occurred only on the surfaces of the films containing Ta. In terms of surface roughness, the co-sputtered coatings exhibited significantly smaller values, compared to the single-sputtered coatings. The highest photodegradation efficiency was registered for the co-sputtered sample which contains the highest N concentration. The corrosion rate, obtained from electrochemical tests, varies in a rather large domain, as function of the chemical species in the coatings.

HFCVD method was used to prepare and characterize single and gradient multi-layered diamond coatings on tungsten carbide. The wear behaviour was evaluated in ambient air, against Si3N4 ceramic balls. The results demonstrated that with the increase of carbon-source concentration from 1% to 5%, the diamond surface grains gradually refined and formed crystal clusters, and the roughness (Ra) of diamond surface decreased from 62.3 to 32.54 nm. Concerning the 100, 300, and 600 nm gradient of multilayer diamond coatings, the roughness Ra was 31.3, 35.6, and 40.5 nm, respectively. The diamond film obtained with 1% CH4 concentration exhibited poor wear resistance. For higher CH4 concentration, the abrasion resistance increased gradually. The average friction coefficient of multilayer diamond coatings decreased from 0.052 to 0.023 as the modulated layer thickness increased from 100 to 600 nm. The gradient multilayer structure significantly improved the tribological behaviour.

Due to an attractive combination of chemical and physical properties, silicon carbide (SiC) thin films are excellent candidates for coatings to be used in harsh environment applications or as protective coatings in heat exchanger applications. This work reports the deposition of near-stoichiometric and nanocrystalline SiC thin films, at room temperature, on silicon (100) substrates using a DCMS/HiPIMS co-sputtering technique (DCMS-direct current magnetron sputtering; HiPIMS-high-power impulse magnetron sputtering). Their structural and mechanical properties were analyzed as a function of the process gas pressure. The correlation between the films' microstructure and their mechanical properties was thoroughly investigated. The microstructure and morphology of these films were examined by appropriate microscopic and spectroscopic methods: atomic force microscopy (AFM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and Raman spectroscopy, while their mechanical and tribological properties were evaluated by instrumented indentation and micro-scratch techniques. The lowest value of the working gas pressure resulted in SiC films of high crystallinity, as well as in an improvement in their mechanical performances. Both hardness (H) and Young's modulus (E) values were observed to be significantly influenced by the sputtering gas pressure. Decreasing the gas pressure from 2.0 to 0.5 Pa led to an increase in H and E values from 8.2 to 20.7 GPa and from 106.3 to 240.0 GPa, respectively. Both the H/E ratio and critical adhesion load values follow the same trend and increase from 0.077 to 0.086 and from 1.55 to 3.85 N, respectively.

In this study, the surface chemistry and morphology and the photocatalytic and antibacterial potential of pure and chlorine (Cl)-doped indium sulfide (In 2 S 3 ) thin films, produced by spray pyrolysis, were analyzed. The root-mean-square roughness seemed not to be affected significantly by the chlorine concentration in three of the doped films (around 12 nm). The roughness seemed not to affect the characteristics of the films analyzed in this study. The samples presented a photocatalytic efficiency higher than 80%, but no correlation with the chlorine concentration was found. The antibacterial potential of the films was assessed against the multidrug-resistant bacteria Pseudomonas aeruginosa, responsible for serious infections, which are extremely difficult to treat in hospitals. The obtained results evidence an increase in antibacterial activity with the increase in chlorine concentration. These results encourage further studies to support the potential of this material to be used in biomedical applications.

Micro-diamond film, nano-diamond film and diamond-graphite composite film were deposited on silicon carbide substrate by hot filament chemical vapor deposition. The surface morphology and phase of the grown diamond films were analyzed using scanning electron microscope, atomic force microscope and Raman spectrometer. The friction coefficient and the wear rate of diamond films were measured by friction experiments. The friction and wear properties of diamond films were studied by comparing the experimental results. The results show that the diamond-graphite composite film has better friction and wear properties, the surface roughness of which is 53.8 nm. The friction coefficient (0.040) is similar to that of the nano-diamond film (0.037), while the wear rate is the lowest, 2.07×10−7 mm3·N−1·m−1. Compared with those of SiC substrate, the wear rate (9.89×10−5 mm3·N−1·m−1) and the friction coefficient (0.580) of the diamond films have been greatly improved, which indicates that depositing diamond on the surface of SiC substrate significantly improves the performance of the silicon carbide in the field of friction.

Starting from solid-solutions (SS) of AlCoCrFeNix high-entropy alloys (HEAs) that have been produced with high purity constituent elements by vacuum arc remelting (VAR) method varying the nickel molar ratio x from 0.2 to 2.0, we investigated the synthesis of protective thin films of HEAs and high-entropy nitrides (HENs) with the aid of the pulsed laser deposition (PLD) system. The structure of all ten available bulk targets have been examined by means of X-Ray Diffraction (XRD), as well as their elemental composition by means of energy dispersion X-ray spectroscopy (EDS). Three targets with nickel molar composition x = 0.4, 1.2 and 2.0 corresponding to BCC, mixed BCC and FCC, and finally FCC structures were used for thin film depositions using a KrF excimer laser. The depositions were performed in residual low vacuum (10−7 mbar) and under N2 (10−4 mbar) at room temperature (RT~25 °C) on Si and glass substrates. The deposited films’ structure was investigated using grazing incidence XRD, their surface morphology, thickness and elemental composition by scanning electron microscopy (SEM), EDS and X-ray photoelectron spectroscopy (XPS), respectively. A homemade four-point probe (4PP) set-up was applied to determine layers electrical resistance. Besides, a Nanoindentation (NI) was employed to test films’ mechanical properties. XRD results showed that all deposited films, regardless of the initial structure of targets, were a mixture of FCC and BCC structures. Additionally, the quantitative and qualitative EDS and XPS results showed that the elemental composition of films was rather close to that of the targets. The depositions under an N2 atmosphere resulted in the inclusion of several percentage nitrogen atoms in a metallic nitride type compound into films, which may explain their higher electrical resistivity. The Young’s modulus, nanohardness and friction coefficient values showed that the deposited films present good mechanical properties and could be used as protective coatings to prevent damage in harsh environments.

Phosphate and tellurite glasses can be used in optics, optoelectronics, magneto-optics, and nuclear and medical fields. Two series of phosphate-tellurite glasses, (50-x)ZnO-10Al2O3-40P2O5-xTeO2 and (40-x)Li2O-10Al2O3-5TiO2-45P2O5-xTeO2 (x = 5, 10), were synthesized by a non-conventional wet-route, and the mechanical properties as key performance measures for their application in optoelectronics were investigated. X-ray Diffraction (XRD) measurements revealed the vitreous nature of the investigated materials. Instrumented indentation tests allowed the calculation of hardness (H) and Young's modulus (E) using the Oliver and Pharr model. The influence of increasing the TeO2 content, as well as the substitution of ZnO by Li2O-TiO2, on the variation of hardness, Young's modulus, penetration depth (PD), and fracture toughness (FT) was evaluated in both series. As a general trend, there is a decrease in the hardness and Young's modulus with increasing penetration depth. The addition of Li2O and TiO2 instead of ZnO leads to improved hardness and elastic modulus values. Regarding the H/E ratio, it was found that the samples with lower TeO2 content should be significantly more crack-resistant compared to the higher TeO2 content samples. The H3/E2 ratio, being lower than 0.01, revealed a poor resistance of these glasses to plastic deformation. At the same time, a decrease of the fracture toughness with increasing TeO2 content was noticed for each glass series. Based on dilatometry measurements, the thermal expansion coefficient as well as the characteristic temperatures of the glasses were measured. Field Emission Scanning Electron Microscopy-Energy Dispersive X-ray analysis (FESEM-EDX) revealed a uniform distribution of the elements in the bulk samples. The mechanical properties of these vitreous materials are important in relation to their application as magneto-optical Faraday rotators in laser cavities.

Direct current (DC) and radio frequency (RF) magnetron sputtering methods were selected for conducting the deposition of structural materials, namely ceramic and metallic co-depositions. A total of six configurations were deposited: single thin layers of oxides (Cr2O3, SiO2) and co-deposition configurations (50:50 wt.%) as structural materials (W, Be)-(Cr2O3, SiO2), all deposited on 304L stainless steel (SS). A comprehensive evaluation such as surface topology, thermal desorption outgassing, and structural/chemical state was performed. Moreover, mechanical characterization evaluating properties such as adherence, nano indentation hardness, indentation modulus, and deformation relative to yielding, was performed. Experimental results show that, contrary to SiO2 matrix, the composite layers of Cr2O3 with Be and W exhibit surface smoothing with mitigation of artifacts, thus presenting a uniform and compact state with the best microstructure. These results are relevant in order to develop future dense coatings to be used in the fusion domain.

Compact and defect-free high melting point oxide strengthened metallic matrix configurations are promising to resolve the hydrogen permeation and brittleness issues relevant to the fusion research community. Previous studies on oxide addition to metallic matrix demonstrated a mitigation in brittleness behavior, while deposition techniques and material configurations are still to be investigated. Thus, here, we report the structural, morphological, and mechanical characterization of metal-oxides thin layers co-deposited by radio frequency (RF)and direct current (DC) magnetron sputtering. A total of six configurations were deposited such as single thin layers of oxides (Al2O3, Er2O3) and co-deposition configurations as metal-oxides (W, Be)-(Al2O3, Er2O3). The study of films roughness by atomic force microscopy (AFM) method show that for Al2O3 metallic-oxides is increased to an extent that could favor gaseous trapping, while co-depositions with Be seem to promote an increased roughness and defects formation probability compared to Wco-depositions. Lower elastic modulus on metal-oxide co-depositions was observed, while the indentation hardness increased for Be and decreased for W matrix configurations. These outputs are highly relevant for choosing the proper compact and trap-free configuration that could be categorized as a permeation barrier for hydrogen and furtherly studied in laborious permeation yield campaigns.

The influence of some key parameters of hot filament chemical vapor deposition (HFCVD) on the temperature distribution during the deposition of diamond coatings on silicon nitride (Si 3 N 4 ) substrates was assessed with the help of the finite element method. Solid heat transfer, fluid heat transfer and surface radiation heat transfer mechanisms were used to calculate the substrate temperature in the steady state during the deposition process. The accuracy of the model was verified by comparing the simulation model with experimental measurements. The comparison shows that the deviation between the model and the actual substrate temperature measurements is within 3%. Furthermore, a Taguchi orthogonal experiment was designed (3 factors, 3 levels, L9). By changing the number of hot filaments, the distance between the filaments and the substrate, and the separation between two adjacent hot filaments, the influence trend of these parameters on the substrate temperature was assessed, leading to an optimal hot filament arrangement. A deposition experiment was carried out using the optimized parameters, and the results showed that the substrate surface temperature obtained by numerical simulation is highly consistent with the temperature measured by the infrared thermometer. The optimized deposition parameters contributed to a more suitable temperature range and more uniform temperature distribution on the Si 3 N 4 ceramic substrate. The deposited diamond film exhibited uniform crystal quality and grain morphology, thus verifying the validity of the simulation results.

Despite its great potential for thin films deposition and technological applications, the HiPIMS technology has its own limitations including the control of ion energy and flux towards the substrate when coping with the deposition of electrical insulating films and/or the deposition onto insulating/electrically grounded substrates. The bipolar-HiPIMS has been recently developed as a strategy to accelerate the plasma ions towards a growing film maintained at ground potential. In this work, the benefits of bipolar-HiPIMS deposition onto floating or nonconductive substrates are explored. The effect of bipolar-HIPIMS pulsing configuration, magnetic balance-unbalance degree, and substrate's condition on plasma characteristics, microstructure evolution, and mechanical properties of CrN coatings was investigated. During the deposition with a balanced magnetron configuration, a significant ion bombardment effect was detected when short negative pulses and relative long positive pulses were used. XRD analysis and AFM observations revealed significant microstructural changes by increasing the positive pulse duration, which results in an increase in hardness from 7.3 to 16.2 GPa, during deposition on grounded substrates, and from 4.9 to 9.4 GPa during the deposition on floating substrates. The discrepancies between the hardness values of the films deposited on floating substrates and those of the films deposited on grounded substrates become smaller/larger when a type I/type II unbalanced magnetron configuration is used. Their hardness ratio was found to be 0.887, in the first case, and 0.393, in the second one. Advanced application-tailored coatings can be deposited onto floating substrates by using the bipolar-HiPIMS technology if short negative pulses, relative long positive pulses together with type I unbalanced magnetron are concomitantly used.

This work presents preliminary results regarding improving the mechanical, wear and protective properties (hardness, coefficient of friction, corrosion resistance) of AISI 304 stainless steel surfaces by open atmosphere cold plasma surface treatment method. Comparative evaluations of the morphological, corrosion resistance, mechanical and tribological properties for different periods of treatment (using N2 gas for cold plasma generation in an open atmosphere) were performed. AFM surface analyses have shown significant surface morphology modifications (average roughness, FWHM, surface skewness and kurtosis coefficient) of the treated samples. An improved corrosion resistance of the N2 treated surfaces in open atmosphere cold plasma could be observed using electrochemical corrosion tests. The mechanical tests have shown that the surface hardness (obtained by instrumented indentation) is higher for the 304 stainless steel samples than it is for the un-treated surface, and it decreases gradually for higher penetration depths. The kinetic coefficient of friction (obtained by ball-on-disk wear tests) is significantly lower for the treated samples and increases gradually to the value of the un-treated surface. The low friction regime length is dependent on the surface treatment period, with a longer cold plasma nitriding process leading to a significantly better wear behavior.