• K Chandra Sekhar

      Articles written in Bulletin of Materials Science

    • Spectrophotometric determination of Ce(IV) usingo-phenylenediamine in steels

      Archana Agrawal K Chandra Sekhar L P Pandey

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      A simple and sensitive spectrophotometric method for the determination of cerium(IV) was developed. Witho-phenylenediamine cerium(IV) gives an orange-red colour with an absorption maximum at 470 nm. The system obeys Beer’s law in the range 7 ppm to 500 ppm with a molar absorptivity of 2·4 × 103l mol−1 cm−1 and Sandell sensitivity of 0·5 ppm. Interference by various ions was studied. This method was used for the determination of cerium in low-alloy steels and the results are in good agreement with the certified values.

    • Physical, optical and structural studies of copper-doped lead oxychloro borate glasses

      K CHANDRA SEKHAR ABDUL HAMEED VASANT G SATHE M NARASIMHA CHARY MD SHAREEFUDDIN

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      Bluish coloured glasses are obtained from the composition PbCl$_2$–PbO–B$_2$O$_3$ doped with Cu$^{2+}$ ions. Basic physical properties and spectroscopic studies (optical absorption, electron paramagnetic resonance, Fourier transform infrared and Raman spectroscopies) were carried out on these samples. The increase in PbCl2 content resulted in the decrease in density and increase in molar volume. At optical frequencies, band gaps and Urbach energies were evaluated and their variation is explained. Spin-Hamiltonian parameters (SHP) obtained from the EPR spectra suggest that the ligand environmentaround Cu$^{2+}$ is tetragonally distorted octahedral sites and the orbital $d_{x^2−y^2}$ is the ground state. The characteristics broad bands in the optical absorption spectra are assigned to the ${}^2B_{1g} \to {}^2B_{2g}$ transition. The bonding coefficient values were evaluated using optical data and SHP. FTIR studies suggested that the glass structure is built up of BO$_3$ and BO$_4$ units. The presence of diborate, pyroborate, pentaborate groups, etc. in the glass network was confirmed from Raman spectra.

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    • Dr Shanti Swarup Bhatnagar for Science and Technology

      Posted on October 12, 2020

      Prof. Subi Jacob George — Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bengaluru
      Chemical Sciences 2020

      Prof. Surajit Dhara — School of Physics, University of Hyderabad, Hyderabad
      Physical Sciences 2020

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      Posted on July 25, 2019

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