• R Somashekar

      Articles written in Bulletin of Materials Science

    • Synthesis and characterization of castor oil based polyurethane-polyacrylonitrile interpenetrating polymer networks

      P Mallu Siddaramaiah R Somashekar

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      A series of interpenetrating polymer networks (IPNs) of castor oil based polyurethane/polyacrylonitrile (PU/PAN: 80/20, 60/40, 50/50, 40/60 and 20/80) were synthesized by condensation reaction of castor oil with methylene diisocyanate and acrylonitrile, employing benzoyl peroxide (BPO) and ethylene glycol dimethylacrylate (EGDM) as initiator and crosslinkers respectively. The physical, chemical, optical and some of the mechanical properties of PU/PAN were studied. Phase stabilization in IPNs was investigated by wide angle X-ray (WAXS) profile analysis. Variation of crystal size distribution was studied in these polymer networks.

    • Variation of crystallite size of Al1–𝑥In𝑥N for different values of 𝑥 and band gap

      V Naik R Naik H Somashekarappa S S Mahesh R Somashekar

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      By using wide angle X-ray scattering (WAXS) technique, we have characterized the epitaxial Al1–𝑥In𝑥N films (thickness, 150 nm) with 0 < 𝑥 < 1 grown by plasma source molecular beam epitaxy on sapphire (0001) at the low substrate temperature of 375°C, by computing the crystallite size in these samples. We observe that the crystallite size decreases with increase in the concentration of indium and that the band gap in these samples has a direct correlation with the crystallite size.

    • Crystal structure and elastic constants of Dharwar cotton fibre using WAXS data

      O M Samir R Somashekar

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      Wide-angle X-ray scattering (WAXS) recordings were carried out on raw Dharwar cotton fibres available in Karnataka. Using this data and employing linked atom least squares (LALS) method, we report here the molecular and crystal structure of these cotton fibres. Employing structural data, we have computed elastic moduli tensor components of these fibres. From these investigations, it turns out that the intrinsic strains present in the fibre arise due to hydrogen bonds and not covalent bonds, which is a significant result.

    • Changes in microstructural parameters of NB4D2 silk fibres due to electron irradiation: X-ray line profile analysis

      Sangappa S Asha P Parameswara R Somashekar

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      The present study is concerned with changes of microcrystalline parameters in NB4D2 (Bombyx mori) silk fibres, due to electron irradiation. The irradiation process was performed in air at room temperature using 8 MeV electron beam at different dose rates: 0, 25, 50 and 75 kGy, respectively. X-ray recording of these irradiated samples and the line profile analysis were carried out. The crystal imperfection parameters such as crystallite size $\langle N \rangle$, lattice strain (g in %) and surface weighted crystallite size ($D_{s}$) were computed and compared with other physical parameters in order to asertain the changes that have crept into these irradiated fibres. Exponential, lognormal and Reinhold functions for the column length distributions have been used for the determination of these parameters.

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