Faculty Publications
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Item Synthesis of high hardness IR optical coating using diamond-like carbon by PECVD at room temperature(Elsevier Ltd, 2017) Krishna, K.; Varade, A.; Niranjan Reddy, K.; Dhan, S.; Chellamalai, M.; Balashanmugam, N.; Krishna, P.Diamond-like Carbon (DLC) for IR antireflective properties is currently being used in the coating of germanium based IR optics. These DLC coatings offer better wear resistance as compared to traditional anti-reflective (AR) coatings. The current work emphasizes the development of IR optics using germanium substrate coated with DLC which typically covers IR transmission in wavelength regions like 3–7 ?m and 9–15 ?m. In order to study IR transmission, an optimum film thickness of DLC was calculated and coated on a double sided polished germanium substrate. DLC was coated on a single side of a germanium substrate, as well as on both sides of germanium. DLC has been deposited using Radio Frequency Plasma Enhanced Chemical Vapour Deposition (RF-PECVD) at room temperature without the use of any intermediary buffer layers required for adhesion and high hardness values were achieved at room temperature as compared to existing literature. The transmission of IR through DLC coated germanium windows was measured using Fourier Transform Infra-Red (FTIR) spectroscopy. A comparison between transmission through a single side and double sided DLC coating on germanium has been demonstrated. The hardness of the film was measured using nanoindentation. Scratch test was also performed using nanoindentation. Adhesion and salt spray tests were performed as per MIL standards. With double sided DLC coating, a peak transmission value of 93% is achieved in 3–7 ?m and the average hardness of DLC is measured to be 32.74 GPa. © 2017 Elsevier B.V.Item Synthesis of high hardness, low COF diamond-like carbon using RF-PECVD at room temperature and evaluating its structure using electron microscopy(Elsevier Ltd, 2017) Krishna, K.; Varade, A.; Reddy, N.; Dhan, S.; Chellamalai, M.; Krishna, P.; Balashanmugam, N.Diamond-like carbon (DLC) coatings have been deposited on Silicon wafers using a Radio Frequency based Plasma Enhanced Chemical Vapor Deposition (RF-PECVD) at room temperature. Experiments were carried out using a flow rate of 100 sccm and 300 sccm of acetylene (C2H2) gas and the bias voltage was varied from 300 to 450 V for DLC deposition. Scanning electron microscope (SEM) and transmission electron microscope (TEM) has been used to study the structure and morphology of the DLC coating. TEM results of DLC coatings deposited at 100 sccm C2H2 flow suggest that some crystalline features of diamond are present in the disordered matrix of DLC. Mechanical properties of DLC coatings were studied using a nanoindenter. The results indicate that the hardest DLC film is obtained at 100 sccm flow rate of C2H2 deposited at 450 V bias voltage of about 32.25 GPa. The results also indicate that the lowest coefficient of friction (COF) of about 0.04 in DLC film is obtained at 300 sccm flow rate of C2H2 deposited at 400 V bias voltage. COF is found to be lower in high C2H2 flow rate, wherever relatively softer DLC was deposited. © 2017 Elsevier B.V.Item Tribological behaviour of monolayer and multilayer Ti-based thin solid films deposited on alloy steel(Institute of Physics Publishing helen.craven@iop.org, 2019) V Badiger, P.V.; Desai, V.; Ramesh, M.R.; Joladarashi, S.; Gourkar, H.The fretting wear and adhesive wear resistance of Ti-based thin solid films deposited on MDN121 steel substrate are evaluated. Plasma-assisted cathodic arc evaporation technique is used to develop the TiC-C monolayer coating and Ti/TiN/TiCN/TiN/TiCN multilayer coatings used in the study. FESEM-EDS, nanoindentation, Raman spectroscopy, optical profiler, and confocal microscope are used to characterise the coatings and wear tracks. Diamond-like carbon is observed in the microstructure of both the coatings. During the fretting analysis, the coefficient of friction (COF) is reduced by 68.49% in the case of the TiC-C monolayer coating and 42.46% in the Ti multilayer coatings as compared to the substrate. The volumetric wear loss of the TiC-C monolayer coating is lower than the multilayer coating. The wear surface morphology reveals the abrasive form of the fretting wear mechanism in both the monolayer and multilayer coatings whereas the galling failure in the substrate. During adhesive wear, the COF is reduced by 71.73% in the monolayer coating and 59.33% in the multilayer coatings compared to the substrate. The monolayer coating exhibits low friction and low wear rate as compared to the multilayer coating. © 2018 IOP Publishing Ltd.