Search Results (9)

This work characterises the structure and mechanical properties, such as adhesion, of two different chemical vapour deposition (CVD) coatings deposited onto silicon aluminium oxynitride (Si₃N₄ + Al₂O₃ + Y₂O₃) round (RNGN) milling cutter tooling inserts. These inserts are often known by the trade abbreviation “SiAlON”. Wear was produced on the inserts using unidirectional sliding (pin-on-disc type) and scratch testing. Two coatings were investigated: a multilayer CVD coating (Coating A) with a composition of TiN + TiCN + Al₂O₃ and a bilayer coating (Coating B) with a composition of Al₂O₃ + TiN. Microstructural analysis was conducted after wear testing and Coating B demonstrated high stability when subjected to high alternating shear and tensile stresses, high abrasion resistance and very high adhesion to the SiAlON ceramic insert substrate when compared to Coating A. Coating A demonstrated a low capacity to distribute alternating shear and tensile stresses during the pin-on-disc and scratch testing, which led to failure. The scratch and pin-on-disc results from this study correlate highly with completed machining insert wear analysis that has used Coating A and Coating B SiAlON inserts to machine aged Inconel 718. Full article

Silica, titania, and mixed silica–titania powders have been used as supports for loading 5 wt% Cu, 5 wt% Ag, and 2.5 wt% Cu-2.5 wt% Ag with the aim of providing a series of nanomaterials with antifouling properties. All the solids were easily prepared by the wetness-impregnation method from commercially available chemical precursors. The resulting materials were characterized by several techniques such as X-ray diffraction analysis, X-ray photoelectron spectroscopy, N₂ physisorption, and temperature-programmed reduction measurements. Four selected Cu and Ag SiO₂- and TiO₂-supported powders were tested as fillers for the preparation of marine antifouling coatings and complex viscosity measurements. Titania-based coatings showed better adhesion than silica-based coatings and the commercial topcoat. The addition of fillers enhances the resin viscosity, suggesting better workability of titania-based coatings than silica-based ones. The ecotoxicological performance of the powders was evaluated by Microtox luminescence tests, using the marine luminescent bacterium Vibrio fisheri. Further investigations of the microbiological activity of such materials were carried out focusing on the bacterial growth of Pseudoalteromonas sp., Alteromonas sp., and Pseudomonas sp. through measurements of optical density at 600 nm (OD_600nm). Full article

Optimization of the composition of a new generation of bi-nano-multilayered TiAlCrSiN/TiAlCrN-based coatings is outlined in this study for the machining of direct aged (DA) Inconel 718 alloy. Three types of TiAlCrSiN/TiAlCrN-based bi-nano-multi-layer coatings with varying chemical compositions were investigated: (1) a previous state-of-the-art Ti_0.2Al_0.55Cr_0.2Si_0.03Y_0.02N/Ti_0.25Al_0.65Cr_0.1N (coating A); (2) Ti_0.2Al_0.52Cr_0.2Si_0.08N/Ti_0.25Al_0.65Cr_0.1N with increased amount of Si (up to 8 at.%; coating B); (3) a new Ti_0.18Al_0.55Cr_0.17Si_0.05Y_0.05N/Ti_0.25Al_0.65Cr_0.1N coating (coating C) with an increased amount of both Si and Y (up to 5 at.% each). The structure of each coating was evaluated by XRD analysis. Micro-mechanical characteristics were investigated using a MicroMaterials NanoTest system and an Anton Paar-RST3 tester. The wear performance of nano-multilayered TiAlCrSiN/TiAlCrN-based coatings was evaluated during the finish turning of direct aged (DA) Inconel 718 alloy. The wear patterns were assessed using optical microscopy imaging. The tribological performance was evaluated through (a) a detailed chip characteristic study and (b) XPS studies of the worn surface of the coated cutting tool. The difference in tribological performance was found to correspond with the type and amount of tribo-films formed on the friction surface under operation. Simultaneous formation of various thermal barrier tribo-films, such as sapphire, mullite, and garnet, was observed. The overall amount of beneficial tribo-films was found to be greater in the new Ti_0.18Al_0.55Cr_0.17Si _0.05Y_0.05N/Ti_0.25Al_0.65Cr_0.1N nano-bi-multilayer coating (coating C) than in the previous state-of-the-art coatings (A and B). This resulted in over two-fold improvement of this coating’s tool life compared with those of the commercial benchmark AlTiN coating and coating B, as well as a 40% improvement of the tool life of the previous state-of-the-art coating A. Multi-scale self-organization processes were observed: nano-scale tribo-film formation on the cutting tool surface combined with micro-scale generation of strain-induced martensite zones as a result of intensive metal flow during chip formation. Both of these processes are strongly enhanced in the newly developed coating C. Full article

The use of nano-enabled products (NEPs) can release engineered nanomaterials (ENMs) into water resources, and the increasing commercialisation of NEPs raises the environmental exposure potential. The current study investigated the release of ENMs and their characteristics from six commercial products (sunscreens, body creams, sanitiser, and socks) containing nTiO₂, nAg, and nZnO. ENMs were released in aqueous media from all investigated NEPs and were associated with ions (Ag⁺ and Zn²⁺) and coating agents (Si and Al). NEPs generally released elongated (7–9 × 66–70 nm) and angular (21–80 × 25–79 nm) nTiO₂, near-spherical (12–49 nm) and angular nAg (21–76 × 29–77 nm), and angular nZnO (32–36 × 32–40 nm). NEPs released varying ENMs’ total concentrations (ca 0.4–95%) of total Ti, Ag, Ag⁺, Zn, and Zn²⁺ relative to the initial amount of ENMs added in NEPs, influenced by the nature of the product and recipient water quality. The findings confirmed the use of the examined NEPs as sources of nanopollution in water resources, and the physicochemical properties of the nanopollutants were determined. Exposure assessment data from real-life sources are highly valuable for enriching the robust environmental risk assessment of nanotechnology. Full article

TiSiN-Ag composite coatings with different Si doping contents were prepared by multi-arc ion plating technology on 316L, TC4, and H65 copper substrates, respectively. The microstructure of the prepared coatings was characterized by X-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy, respectively. The mechanical properties, electrochemical properties, and tribological properties were characterized by a micro-hardness tester, electrochemical workstation, scratch tester, and friction and wear tester, respectively. Results showed that the coatings with 8 wt.% Si doping content had a smaller average grain size, denser structure, excellent mechanical properties, and better anti-tribocorrosion performance than those with 5 wt.% Si doping content. The coating on the TC4 substrate with 8 wt.% Si doping content presented the best combination of properties and is a candidate for an anti-tribocorrosion material in seawater. Full article

In this study, we compare the tribological performance of a multilayer TiSiN/Ti(Ag)N coating with a TiSiN/TiN coating with a similar Si content in order to demonstrate the effect of the solid lubricant phase, silver. For Al₂O₃ balls, the hardness and reduced modulus determine the tribological performance of the coatings for tests conducted at room temperature (RT) against Al₂O₃ balls. At 550 °C, the TiSiN/TiN coating failed, whereas the Ag-containing coating performed better due to the presence of Ag in the contact, which decreased the shear stress and, consequently, the friction. For tests against TiAl6V4 balls, the Ag-containing coating was always better than the TiSiN/TiN one. At 550 °C, Ag in the wear track prevented the adhesion of the oxidized Ti-alloy wear debris in the contact, favoring the adhesion of wear debris from the coating to both the coating and counterpart surfaces. No wear could be measured for the 700 °C tests for both coatings due to different reasons: (i) the presence of oxidized adhered material from the ball to the reference TiSiN/TiN coating surface protected from wear and (ii) the presence of Ag-agglomerated particles decreased the friction and minimized the adhesion wear of the counterpart for the TiSiN/TiN(Ag) coating. Full article

The surface modification of NiTi shape memory alloys is a method for increasing their multi-functionalities. In our solution, hydroxyapatite powder was mixed with a chemically synthesized silicon dioxide/silver (nSiO₂/Ag) nanocomposite in a different weight ratio between components (1:1, 5:1, and 10:1) and then electrophoretically deposited on the surface of the NiTi alloy, under various time and voltage conditions. Subsequently, uniform layers were subjected to heat treatment at 700 °C for 2 h in an argon atmosphere to improve the strength of their adhesion to the NiTi substrate. A change in linear dimensions of the co-deposited materials during the sintering process was also analyzed. After the heat treatment, XRD, Raman, and Scanning Electron Microscopy (SEM) + Energy Dispersive Spectrometer (EDS) studies revealed the formation of completely new composite coatings, which consisted of rutile and TiO₂-SiO₂ glass with silver oxide and HAp particles that were embedded into such coatings. It was found that spalling characterized the 1:1 ratio coating, while the others were crack-free, well-adhered, and capable of deformation to 3.5%. Coatings with a higher concentration of nanocomposite were rougher. Electrochemical impedance spectroscopy (EIS) tests in Ringer’s solution revealed the capacitive behavior of the material with high corrosion resistance. The kinetics and susceptibility to pitting corrosion was the highest for the NiTi electrode that was coated with a 5:1 ratio HAp/nSiO₂/Ag hybrid coating. Full article

Magnetron sputtering has been employed for several decades to produce protective and multi-functional coatings, thanks to its versatility and ability to achieve homogeneous layers. Moreover, it is suitable for depositing coatings with very high melting points and that are thermodynamical unstable, which is difficult to accomplish by other techniques. Among these types of coating, transition metal (Me) carbides/nitrides (MeC/N) and amorphous carbon (a-C) films are particularly interesting because of the possibility of tailoring their properties by selecting the correct amount of phase fractions, varying from pure MeN, MeC, MeCN to pure a-C phases. This complex phase mixture can be even enhanced by adding a fourth element such Ag, Pt, W, Ti, Si, etc., allowing the production of materials with a large diversity of properties. The mixture of phases, resulting from the immiscibility of phases, allows increasing the number of applications, since each phase can contribute with a specific property such as hardness, self-lubrication, antibacterial ability, to create a multifunctional material. However, the existence of different phases, their fractions variation, the type of transition metal and/or alloying element, can drastically alter the global electrochemical behaviour of these films, with a strong impact on their stability. Consequently, it is imperative to understand how the main features intrinsic to the production process, as well as induced by Me and/or the alloying element, influence the characteristics and properties of the coatings and how these affect their electrochemical behaviour. Therefore, this review will focus on the fundamental aspects of the electrochemical behaviour of magnetron-sputtered films as well as of the substrate/film assembly. Special emphasis will be given to the influence of simulated body fluids on the electrochemical behaviour of coatings. Full article

In this work, we introduce a totally vacuum-free cost-efficient crystalline silicon solar cells. Solar cells were fabricated based on low-cost techniques including spin coating, spray pyrolysis, and screen-printing. A best efficiency of 17.51% was achieved by non-vacuum process with a basic structure of <AI/p+/p−Si/n+/SiO₂/TiO₂/Ag> CZ-Si p-type solar cells. Short circuit current density (J_SC) and open circuit voltage (V_OC) of the best cell were measured as 38.1 mA·cm⁻² and 596.2 mV, respectively with fill factor (FF) of 77.1%. Suns-Voc measurements were carried out and the detrimental effect of the series resistance on the performance was revealed. It is concluded that higher efficiencies are achievable by the improvements of the contacts and by utilizing good quality starting wafers. Full article