Faculty Publications
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Item Mechanical Instabilities in 2D-SiC with Defects(American Institute of Physics Inc., 2023) Madhusoodanan, M.; Narayanan, M.K.; Madam, A.K.Elasticity of material is important in understanding the elastic deformation, to flexure, to strain softening. Elastic properties provide the measure of resistance of a system to elastic deformation thus validating its structural stability. Understanding the elasticity of a material is important in understanding their response to any external perturbations. This is required for their synthesis and practical applications. Mechanical stability is determined through the knowledge of second order elastic constants (SOEC) and the higher order elastic constants are necessary to understand the non-linear, anharmonic behaviors. A material is said to be mechanically stable satisfying the Born stability criteria. Here, 2D-SiC, a silicene derivative is introduced with point and topological defects to understand its variation in mechanical properties. Defects namely, mono-, bi- and Stone-Wales types are incorporated into SiC. Computed values of elastic constants implied mechanical instability for C removed monovacancy. All other configurations implied mechanical stability satisfying Born criteria. © 2023 American Institute of Physics Inc.. All rights reserved.Item Physical, mechanical and structural properties of BaO-CaF2-P2O5 glasses(Elsevier, 2015) Narayanan, M.K.; Shashikala, H.D.Mechanical properties and structure of melt-quenched ternary barium phosphate glasses belonging to the composition (50 - X)BaO-XCaF2-50P2O5 (X = 0 to 10 mol%) were studied using Vickers indentation and vibrational spectroscopy. Elastic moduli of prepared samples were calculated using the Makishima and Mackenzie (M-M) model. Density of glasses was measured using the Archimedes method, while molar volume and atomic packing density were calculated from measured density to study structural changes in the glass matrix. Vickers hardness and brittleness increased and fracture toughness decreased with increase in CaF2 content. This can be attributed to increase in the compactness of phosphate bonds and reduction in the molar volume of glasses with partial substitution of Ba2 + with Ca2 +. Infrared and Raman spectroscopies revealed that the glass network mainly consisted of metaphosphate units arranged in chain and ring structures together with small amounts of ultraphosphate and pyrophosphate units. © 2015 Elsevier B.V. All rights reserved.Item Optical absorption, mechanical properties and FTIR studies of silver-doped barium phosphate glasses(Society of Glass Technology christine@glass.demon.co.uk, 2016) Narayanan, M.K.; Shashikala, H.D.Silver-doped barium phosphate glasses, of composition 50BaO-50P2O5-4Ag2O-4SnO, were prepared by conventional melt quenching and subsequent heat treatment. Prepared glasses were heat treated for a fixed duration of 10 h at different temperatures 400, 450 and 500°C to develop silver nanoparticles of different sizes. Formation and the size of the silver nanoparticles were evaluated using the surface plasmon resonance (SPR) band of the optical absorption spectrum, which revealed that both of them were temperature dependent. Spectral positions of the SPR peaks of the glass samples heat treated at 450 and 500°C were observed around 3.0 eV. Absence of significant size dependent shift in SPR peaks of these samples from 3.0 eV indicates the formation of spherical silver nanoparticles smaller than 20 nm inside the glass matrix, which falls in the quasi-static regime of Mie theory. The effect of heat treatment on the local network structure of the phosphate glass matrix assessed using FTIR spectra shows that formation and growth of silver nanoclusters do not affect the basic metaphosphate network structure. A slight improvement is observed in density as well as in the mechanical properties of the heat treated samples due to densification of the glass matrix by dispersed silver nanoparticles.