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Item Antibacterial MXenes: An emerging non-antibiotic paradigm for surface engineering of orthopedic and dental implants(KeAi Communications Co., 2025) Gnanasekar, S.; He, X.; Nagay, B.E.; Xu, K.; Rao, X.; Duan, S.; Murugesan, S.; Barão, V.A.R.; Kang, E.-T.; Xu, L.The colonization of planktonic bacteria onto implant surfaces is a serious concern in the medical field due to increasing infection-related mortality and fiscal difficulties worldwide. Various static, dynamic, and active coating techniques were established to tackle implant-associated infections (IAIs). However, the existing implant coating methods often confront issues with poor universality for different substrates, adaptability, stability, and the emergence of multi-drug resistance (MDR). The miraculous two-dimensional (2D) MXenes with outstanding multimodal bactericidal effects have been spotted as promising non-antibiotic implant surface coating additives for superior antibiofilm and osseointegration properties. This review systematically assesses the recent progress of antibacterial MXenes and their revolutionary usage to prevent peri-implantitis. We specifically sought to disclose the various forms of MXenes, such as composites, heterojunctions (HJs), and functional biomaterials used in combatting MDR and non-MDR bacterial pathogens by adopting therapeutic ventures such as photothermal therapy (PTT), photodynamic therapy (PDT), chemodynamic therapy (CDT), and sonodynamic therapy (SDT). In addition, we outlined the extension of MXene antibacterial systems for orthopedic and dental implant surface engineering to improve their longevity and safety. A thorough understanding of antibacterial MXenes synthesis, surface modification strategies, and biocompatible functional properties was deliberated to facilitate the construction of innovative coatings. Lastly, some viewpoints on the current limitations and key considerations for the future concept design of MXenes-coated implants were contemplated constructively to promote clinical outcomes. © 2025 The AuthorsItem Item The microstructure of a solidifying lead free Sn-3.5Ag solder alloy is found to be highly sensitive to the surface condition of the copper substrate. A transition from lamellar to fine fibrous eutectic structure is observed as the surface condition of the substrate is altered by increasing the surface roughness and application of flux. This is attributed to lowering of interfacial tension and improved wetting of the solidifying solder on the substrate material leading to a better contact at the metal/substrate interface. The results also indicated the importance of surface texture of the substrate and the application of the flux to the quality of the solder/substrate joint. © 2003 Elsevier Ltd. All rights reserved.(Elsevier Ltd, Effect of substrate surface texture and flux coating on the evolution of microstructure during solidification of lead free Sn-3.5Ag solder alloy) Prabhu, K.; Bali, R.; Ranjan, R.2004Item Thermal stability and high-temperature wear of Ti-TiN and TiN-CrN nanomultilayer coatings under self-mated conditions(Elsevier Ltd, 2007) Srinivasan, D.; Kulkarni, Trupti.G.; Anand, K.Ti-TiN and TiN-CrN nanomultilayers were thermally stable retaining uniform and sharp layer interfaces up to 24 h at 773 K, without any oxidation or phase transformation accompanying each individual layer. Decreasing the multilayer spacing resulted in an increase in the hardness in both cases. The coating hardness was found to be independent of the substrate type, when applied on HS718, Ti64 and HCHCr substrates. In scratch testing, the multilayers displayed a better resistance to the onset of failure, as compared to the monolayer TiN. The substrate plasticity played an important role in determining the coating failure mode. Self-mated wear tests revealed the CrN-TiN system to exhibit the best wear behaviour, both at room temperature and at 773 K. The Ti-TiN coatings are more accommodative with all three substrates, as compared to TiN-CrN and TiN. © 2006 Elsevier Ltd. All rights reserved.Item Corrosion behavior of composition modulated multilayer Zn-Co electrodeposits produced using a single-bath technique(2009) Thangaraj, V.; Eliaz, N.; Hegde, A.Composition modulated alloy (CMA) electrodeposits of Zn-Co were produced from acid chloride baths by the single-bath technique. Their corrosion behavior was evaluated as a function of the switched cathode current densities and the number of layers. The process was optimized with respect to the highest corrosion resistance. Enhanced corrosion resistance was obtained when the outer layer was slightly richer with cobalt. At the optimum switched current densities 40/55 mA cm-2, a coating with 600 layers showed ~6 times higher corrosion resistance than monolithic Zn-Co electrodeposit having the same thickness. The CMA coating exhibited red rust only after 1,130 h in a salt-spray test. The increased corrosion resistance of the multilayer alloys was related to their inherent barrier properties, as revealed by Electrochemical Impedance Spectroscopy. The corrosion resistance was explained in terms of n-type semiconductor films at the interface as supported by Mott-Schottky plots. © 2008 Springer Science+Business Media B.V.Item Comparative analysis of steady state heat transfer in a TBC and functionally graded air cooled gas turbine blade(2010) Coomar, N.; Kadoli, R.Internal cooling passages and thermal barrier coatings (TBCs) are presently used to control metal temperatures in gas turbine blades. Functionally graded materials (FGMs), which are typically mixtures of ceramic and metal, have been proposed for use in turbine blades because they possess smooth property gradients thereby rendering them more durable under thermal loads. In the present work, a functionally graded model of an air-cooled turbine blade with airfoil geometry conforming to the NACA0012 is developed which is then used in a finite element algorithm to obtain a non-linear steady state solution to the heat equation for the blade under convection and radiation boundary conditions. The effects of external gas temperature, coolant temperature, surface emissivity changes and different average ceramic/metal content of the blade on the temperature distributions are examined. Simulations are also carried out to compare cooling effectiveness of functionally graded blades with that of blades having TBC. The results highlight the effect of including radiation in the simulation and also indicate that external gas temperature influences the blade heat transfer more strongly. It is also seen that graded blades with about 70% ceramic content can deliver better cooling effectiveness than conventional blades with TBC. © 2010 Indian Academy of Sciences.Item Electrolytic preparation of cyclic multilayer Zn-Ni alloy coating using switching cathode current densities(2010) Venkatakrishna, K.; Hegde, A.C.Cyclic multilayer alloy (CMA) coating of Zn-Ni was developed on mild steel using single bath technique, by proper manipulation of cathode current densities. The thickness and composition of the individual layers were altered precisely and conveniently by cyclic modulation of cathode current densities. Multilayer coatings, having sharp change in compositions were developed using square current pulses. Gelatin and sulphanilic acid (SA) acid were used as additives. Laminar deposits with different configurations were produced, and their corrosion behaviors were studied, in 5% NaCl solution by electrochemical methods. It was observed that the corrosion resistance of CMA coating increased progressively with number of layers (up to certain optimal numbers) and then decreased. Cyclic voltammetry study demonstrated the role of gelatin and SA in multilayer coating. The coating configuration has been optimized for the peak performance against corrosion. The substantial decrease of corrosion rate, in the case of multilayer coatings was attributed to the changed intrinsic electric properties, evidenced by Electrochemical Impedance Spectroscopy (EIS) study. The surface morphology and its roughness were examined by Atomic Force Microscopy (AFM). The surface and cross-sectional view of coatings were examined, using Scanning Electron Microscopy (SEM). X-ray photoelectron spectrum (XPS) study was carried out for surface analysis. The relative performance of pure Zn, monolithic and CMA coatings were compared and discussed. © 2010 Springer Science+Business Media B.V.Item Electrodeposition of high performance multilayer coatings of Zn-Co using triangular current pulses(2010) Yogesha, S.; Hegde, A.C.Compositionally modulated alloy (CMA) coatings of Zn-Co were electrodeposited on to mild steel from an acid chloride bath containing thiamine hydrochloride, as an additive. Electroplating was carried out galvanostatically from a single bath containing Zn2+ and Co2+ ions. Gradual change in composition in each layer was effected by triangular current pulses, cycling between two cathode current densities. Compositionally modulated alloy coatings were developed under different conditions of cyclic cathode current density and number of layers, and their corrosion resistances were evaluated by potentiodynamic polarisation and electrochemical impedance spectroscopy. The formation of multilayer and corrosion mechanism was analysed using scanning electron microscopy. The corrosion resistances of CMA and monolithic alloy coatings were compared with that of the base metal. Compositionally modulated alloy coating at optimal configuration, represented as (Zn-Co) 2•0/4•0/300, was found to exhibit ?80 times better corrosion resistance compared with monolithic (Zn-Co)3•0 alloy, deposited for the same length of time from the same bath. Improved corrosion resistance was attributed to the formation of n-type semiconductor film at the interface, supported by Mott-Schottky plots. Decrease in corrosion resistance at high degree of layering was found, and is due to lower relaxation time for redistribution of solutes in the diffusion double layer, during plating. © 2010 Maney Publishing.Item Electroplating and characterization of Zn-Ni, Zn-Co and Zn-Ni-Co alloys(2010) Eliaz, N.; Venkatakrishna, K.; Hegde, A.C.Zn-Ni, Zn-Co and Zn-Ni-Co coatings were electrodeposited on mild steel from an acidic chloride bath containing p-aminobenzenesulphonic acid (SA) and gelatin. These additives changed the phase content in the coatings, most likely as a result of their adsorption at the surface of the cathode. The effect of gelatin was more pronounced than that of SA. The Faradaic efficiency was higher than 90%. As the current density was increased or the bath temperature was decreased, the concentration of the nobler metal in the coating increased. Both concentrations of Ni and Co in the ternary alloy increased as the applied current density was increased. Nickel and cobalt were found to have a synergistic catalytic effect. The thickness of all coatings increased as the applied current density was increased. The hardness increased with current density to a peak value, and then decreased. The rate of Zn deposition was heavily influenced by mass-transport limitation at high applied current densities, while the rates of Ni and Co deposition were not. The anomalous codeposition was explained by the great difference between the exchange current densities of Zn and the iron-group metal. Potentiodynamic polarization scans and electrochemical impedance spectroscopy showed that the corrosion resistance of the ternary Zn-Ni-Co alloy coatings was approximately 10 times higher than that of Zn-Ni and 7 times higher than that of Zn-Co. The improved corrosion resistance of the ternary alloy was attributed to its surface chemistry, phase content, texture, and surface morphology. The ternary Zn-Ni-Co coating may thus replace the conventional Zn-Ni and Zn-Co coatings in a variety of applications. © 2010 Elsevier B.V.Item Electrodeposition of Zn-Ni, Zn-Fe and Zn-Ni-Fe alloys(2010) Hegde, A.C.; Venkatakrishna, K.; Eliaz, N.Zn-Fe, Zn-Ni and Zn-Ni-Fe coatings were electrodeposited galvanostatically on mild steel from acidic baths (pH 3.5) consisted of ZnCl2, NiCl2, FeCl2, gelatin, sulfanilic (p-aminobenzenesulfonic) acid and ascorbic acid. Cyclic voltammetry showed that the effect of gelatin was more pronounced than that of sulfanilic acid, and that the deposition of the ternary alloy behaved differently from the deposition of the binary alloys. In all three systems, the Faradaic efficiency was higher than 88%, the rate of Zn deposition was heavily influenced by mass-transport limitation at high applied current densities, and the deposition was of anomalous type. For each applied current density, the concentrations of Ni and Fe in the ternary alloy were higher than the corresponding concentrations in the binary alloys. The hardness of Zn-Ni coatings was the highest, while that of Zn-Fe coatings was the lowest. The Zn-Ni-Fe coatings were the smoothest, had distinguished surface morphology, and contained ZnO in the bulk, not just on the surface. The lowest corrosion rate in each alloy system (214, 325 and 26?m year-1 for Zn-Ni, Zn-Fe and Zn-Ni-Fe, respectively) was characteristic of coatings deposited at 30, 30 and 40mAcm-2, respectively. The higher corrosion resistance of the ternary alloy was also reflected by a higher corrosion potential, a higher impedance and a higher slope of the Mott-Schottky line. The enhanced corrosion behavior of the ternary alloy was thus attributed to its chemical composition, phase content, roughness and the synergistic effect of Ni and Fe on the n-type semiconductor surface film. © 2010 Elsevier B.V.