Faculty Publications
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Item Statistical optimization of melt-quenching process parameters for multiple properties of ternary barium phosphate glasses(Elsevier Ltd, 2015) Narayanan, M.K.; Shashikala, H.D.; Manjaiah, M.In the present work simultaneous optimization of density, refractive index and hardness (multiple performance characteristics) of ternary barium phosphate glasses has been carried out using Taguchi based grey relational analysis. Effect of the parameters such as CaF2 content, melting temperature and melting time on the response parameters of (50 - X)BaO-XCaF2-50P2O5 (X = 0, 10, 20 mol%) glasses prepared according to the experimental layout of Taguchi's standard orthogonal array has been studied. Highest grey relational grade is the performance criteria used in this study to indicate the optimum level of process parameters needed for the best multiple performance characteristics. Analysis of variance (ANOVA) conducted on grey relational grade shows that under 95% confidence level, CaF2 content is the only parameter significantly affecting multiple performance characteristics. Experimental values of response parameters obtained by conducting the confirmatory experiment at optimum level of process parameters are closer to the optimal set of predicted values. © 2014 Elsevier B.V. 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.