Faculty Publications
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Item Chalcones: Possible new materials for third-order nonlinear optics(Nova Science Publishers, Inc., 2011) Kiran, A.J.; Chandrasekharan, K.; Kalluraya, B.; Shashikala, H.D.'Search for potential materials' for third-order nonlinear optics has been of continuing interest in recent years. In this context, organic molecules are increasingly being recognized as the materials of the future because their molecular nature combined with the versatility of synthetic chemistry can be used to alter and optimize molecular structure to maximize third order nonlinear response. Chalcones have received considerable interest as materials for second-order nonlinear optical applications due to their ability to crystallize in noncentrosymmetric structure and their blue light transmittance. Being charge transfer compounds, chalcones can also possess large thirdorder nonlinearities due to their π-conjugated structure. In this article, we discuss the structure-nonlinear response relationship among a few chalcones and the possibility of using them for third-order applications. A meager or no work, to our knowledge, has been done so far on these molecules in this regard. Z-scan and degenerate four-wave mixing techniques were employed to investigate third-order optical nonlinearities of chalcone derivatives. Some of these molecules possess large χ (3) of magnitude as high as 10-12 esu and exhibit strong optical limiting properties. Possible mechanisms that are responsible for optical limiting property of these molecules have been discussed. . © 2011 by Nova Science Publishers, Inc. All rights reserved.Item Influence of BaO Addition on Density and Refractive Index of 50P2O5- xB2O3-(50-X) BaO Glasses(Springer, 2024) Rashmi, I.; Shashikala, H.D.The borophosphate glasses of composition 50P2O5- xB2O3- (50-x)BaO (x = 5,10,15,20, 25 mol %) were prepared using the melt-quenching technique. The Archimedes principle was used to measure the density of glasses. The density has been observed to increase with the rise in BaO concentration. Molar volume (Vm) and oxygen packing density (OPD) were computed as a function of BaO using measured density to analyze the structural changes in the glass matrix. The amorphous phase of the glass was confirmed using XRD. The refractive index and UV–visible spectroscopy of prepared glasses were measured. The dielectric constant (ɛ), molar refraction (Rm), electronic polarizability (αm), anion polarizability (αO2-), reflection loss (R), metallization factor (M), and indirect bandgap which are useful in the explanation of physical and optical properties of these glasses were evaluated. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024.Item Density and Refractive Index Variation of CaF2 Added Borosilicate Glasses(Springer, 2024) Raghuvanshi, V.; Shashikala, H.D.The borosilicate glass series with general formula 30SiO2-35B2O3-(35-X) Na2O-XCaF2 (X = 0, 10, 15, and 20 mol%) were prepared using the conventional melt-quenching technique. This paper focuses on the change in physical properties of borosilicate glass with an increase in CaF2 concentration. X-ray diffraction confirmed the amorphous nature of the prepared glass samples. Density was measured using Archimedes principle, and other physical parameters like molar volume and oxygen packing density were calculated with measured density. The density increased with an increase in the concentration of CaF2. The refractive index and UV-Vis spectroscopy of the glass samples were studied. Parameters like dielectric constant, molar refraction, reflection loss, electronic polarizability, metallization factor, and other UV parameters were also calculated using this data. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024.Item Microhardness of laser ablated alumina coating on Ti-6A1-4V(2008) Sujaya, C.; Shashikala, H.D.; Umesh, G.; Prabhu, K.N.; Hegde, S.Alumina coated on Titanium alloys find wide tribological applications due to the improvement in hardness of substrate. This paper presents the effect of deposition of alumina by pulsed laser ablation on Vickers hardness of Ti-6A1-4V substrate. Nd: YAG laser of wavelength 1064nm is used with sintered alumina disc as target for ablation. The variation of Vickers microhardness with load in Ti-6A1-4V shows indentation size effect. Proportional Specimen Resistance (P.S.R) model is applied to separate load -independent hardness from the load - dependent hardness. Composite hardness of Alumina coated Ti-6A1-4V is measured for different laser processing conditions. The film hardness has been separated from the composite hardness of the film-substrate system by the use of an approach based on the law of area of mixtures model taking into an account of ISE, due to proportional specimen resistance of the material to indentation. Film hardness of different films produced by varying the target - substrate distance is presented. As the film thickness increases its hardness decreases as compared to bulk hardness. These studies will be useful in the selection of appropriate coating thickness and substrate hardness to achieve a required composite hardness in the design and production of wear-resistant parts of engineering devices.Item Synthesis and studies on microhardness of alkali zinc borate glasses(American Institute of Physics Inc. subs@aip.org, 2014) Subhashini, u.; Bhattacharya, S.; Shashikala, H.D.; Udayashankar, N.K.The mixed alkali effect on zinc borate glasses have been reported. The glass systems of nominal composition 10Zn+xLi2O+yNa2O+80B2O3 (x = y = 0, 5, 10, 15 mol%) were prepared using standard melt quenching method. The structural, physical and mechanical properties of the samples have been studied using X-ray diffraction(XRD), density measurement and Vickers hardness measurement, respectively. A consistent increase in the density was observed, which explains the role of the modifiers (Li2O and Na2O) in the network modification of borate structure. The molar volume is decreasing linearly with the alkali concentration, which is attributed to the conversion of tetrahedral boron (BO4/2)- into (BO3/2)-. The microhardness studies reveals the anisotropy nature of the material. It further confirms that the samples belong to hard glass category. © 2014 AIP Publishing LLC.Item Effect of CaF2 addition on optical properties of barium phosphate glasses(American Institute of Physics Inc. subs@aip.org, 2014) Narayanan, N.M.; Venkateswara Rao, G.; Akhila, B.E.; Shashikala, H.D.Ternary barium phosphate glasses, (50-X)BaO-XCaF2-50P2O5 have been prepared by adding 0-10 mol% of CaF2 to binary barium phosphate glasses. The amorphous nature of the prepared glasses was confirmed by X-ray diffraction technique. The UV-Visible absorption spectra have been recorded, optical band gap energy Eopt and Urbach energy Etail were determined. Shift in Eopt and Etail with increase in concentration of CaF2 is noted. FTIR analysis was carried out to investigate the short and intermediate-range orders in glasses. Shift of (P-O-P) band to higher wave number with the substitution of BaO with CaF2 shows the shortening of the phosphate chains. Hardness and density of glass samples were measured and correlated with the composition of glasses. © 2014 AIP Publishing LLC.Item Optical absorption and TEM studies of silver nanoparticle embedded BaO-CaF2-P2O5 glasses(American Institute of Physics Inc. subs@aip.org, 2016) Narayanan, M.K.; Shashikala, H.D.Silver nanoparticle embedded 30BaO-20CaF2-50P2O5-4Ag2O-4SnO glasses were prepared by melt-quenching and subsequent heat treatment process. Silver-doped glasses were heat treated at temperatures 500 °C, 525°C and 550 °C for a fixed duration of 10 hours to incorporate metal nanoparticles into the glass matrix. Appearance and shift in peak positions of the surface plasmon resonance (SPR) bands in the optical absorption spectra of heat treated glass samples indicated that both formation and growth of nanoparticle depended on heat treatment temperature. Glass sample heat treated at 525 °C showed a SPR peak around 3 eV, which indicated that spherical nanoparticles smaller than 20 nm were formed inside the glass matrix. Whereas sample heat treated at 550 °C showed a size dependent red shift in SPR peak due to the presence of silver nanoparticles of size larger than 20 nm. Size of the nanoparticles calculated using full-width at half-maximum (FWHM) of absorption band showed a good agreement with the particle size obtained from transmission electron microscopy (TEM) analysis. © 2016 Author(s).Item Effective role of P2O5 on in-vitro bioactivity of soda lime phosphosilicate glasses(Elsevier Ltd, 2017) Kiran, P.; Udayashankar, N.K.; Shashikala, H.D.In-vitro bio active properties have been studied on Sol-gel derived 58SiO2-33CaO-(5-X) Na2O-(4+X) P2O5 (where X=0, 5) bio glass samples soaked for seven days in a simulated body fluid (SBF) solution. X-ray diffraction studies indicated the presence of Hydroxyl Apatite (HA) crystalline phase in the synthesized samples. The spherical shaped hydroxyl carbonated apatite (HCA) nuclei were observed under scanning electron microscope. The Fourier transform infrared (FTIR) and Raman spectroscopic analysis confirmed the presence of carbonates in the glass matrix. In particular, larger concentration of P2O5 in the bioglass resulted in superior bioactivity compared to low concentration of P2O5. © 2017 Elsevier Ltd.Item Optical and electrical studies of sputter-deposited transparent and conducting ITO/Ag/ITO multilayer on Kapton® substrate for transparent flexible electronic applications(Elsevier Ltd, 2018) Sibin, K.P.; Srinivas, G.; Shashikala, H.D.; Dey, A.; Sridhara, N.; Sharma, A.K.; Barshilia, H.C.Transparent and conducting thin films on flexible substrates have enormous applications in the areas of space, solar, displays, etc. We hereby report the sputter deposition of transparent and conducting ITO/Ag/ITO (IAI) thin films on commercially available flexible Kapton® substrate at a lower substrate temperature. IAI multilayer has been deposited by magnetron sputtering system using an alloy In:Sn (90% :10%) and Ag targets at room temperature without breaking the vacuum. The optimized IAI coating shows high transmittance (∼81.3 % at γ= 650 nm) along with very low resistance (8.36 ω/). Optical haze value of IAI on Kapton was measured and found to be <7%. The figure of merit of IAI coating on Kapton® has been calculated using the Haacke's formula Ï€ = r10/Rs. At γ= 650 nm Ï€ = 15 × 10 ω was observed. Our findings give worthful insight into the sputter deposition of transparent conducting IAI coating on flexible Kapton® substrate for flexible electronics applications. © 2017 Elsevier Ltd. All rights reserved.Item Effect of Calcination Temperature and Time on Synthesis of BaO-CaO-Al2O3-SiO2 Glass(Elsevier Ltd, 2018) Bhattacharya, S.; Shashikala, H.D.Alkaline-borosilicate glass of a particular composition was prepared. 30mol%BaO-15CaO-05Al2O3-40SiO2-10B2O3 glass system mix was calcined at different temperatures, from 300°C to 400°C for varying number of hours from 0 to 7 hrs. X Ray Diffraction (XRD) and Thermo Gravimetric Analysis (TGA) studies were conducted on non calcined and calcined powders. Conversion of H3BO3to B2O3 was observed from XRD studies and increase in thermal stability was confirmed from thermal analysis study. © 2017 Elsevier Ltd.