• S Kannan

      Articles written in Bulletin of Materials Science

    • Thermal decomposition of Co–Al layered double hydroxide: Identification of precursor to oxide with spinel structure

      A V Radha Grace S Thomas P Vishnu Kamath Churchil A Antonyraj S Kannan

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      The layered double hydroxide (LDH) of Co with Al decomposes to yield an oxide residue with the spinel structure below 250°C. The decomposition reaction is preceded by the formation of an intermediate hydroxide in which the metal hydroxide layers are regularly stacked about the 𝑐-crystallographic axis, but the layers themselves are aperiodic. Aperiodicity is modeled by locating randomly chosen Co2+ ions in tetrahedral sites in the interlayer region. This phase is characterized by a single strong basal reflection in its powder diffraction pattern. All other reflections are extinguished on account of

      turbostratic disorder which destroys all ℎ𝑘𝑙 reflections and

      layer aperiodicity, which destroys all two dimensional ℎ𝑘 reflections.

      Given its topochemical relationship with the spinel structure, such an intermediate is a necessary precursor to spinel formation.

    • Synthesis of selenium nanorods with assistance of biomolecule

      S Kannan K Mohanraj K Prabhu S Barathan G Sivakumar

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      Nanorods of one-dimensional (1D) trigonal selenium (t-Se) are synthesized using biomolecule substances for five different aging times (1 h, 2 h, 3 h, 1 day and 4 days) by precipitation method. XRD analysis indicates a shift of the (1 0 1) plane towards higher diffraction angle for 1 day aging time. It is observed that the crystallite size decreases with increase in aging time except for an aging period of 4 days. FTIR analysis confirmed that the presence of stretching and bending vibrations of Se–O in both synthesized and commercial selenium samples at 465, 668 and 1118 cm-1. The FESEM micrographs are evident for the changes of rod size as a function of aging time. It is observed that the optical band gap energy is increased with aging time up to 1 day, whereas it decreases in 4 days aging time.

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