• H V Keer

      Articles written in Bulletin of Materials Science

    • Thermodynamic analysis of the metal-insulator transitions in V2O3 alloy systems

      J M Honig H V Keer G M Joshi S A Shivashankar

      More Details Abstract Fulltext PDF

      An overview is presented concerning the entropies (ΔS) and enthalpies (ΔH) associated with metal-insulator transitions in the (V1−xMx)2O3 M=Al, Cr, Ti systems, 0⩽x⩽0·12 and in non-stoichiometric V2(1 −y)O3, 0⩽y⩽0·01. The recent literature and new data are analyzed with respect to gradiations in ΔH and ΔS withx ory, and their implications concerning the mechanism of the transitions. A revised phase diagram is presented.

    • Preparation and characterisation of γ-Fe2O3 as tape recording material

      K Seshan M R Anantharaman Venkatesh Rao A L Shashimohan H V Keer D K Chakrabarty

      More Details Abstract Fulltext PDF

      Optimum conditions for the preparation of tape recording quality γ-Fe2O3 by the thermal decomposition of ferrous oxalate dihydrate have been established. Formation of the intermediate Fe3O4 which is most important in forming γ-Fe2O3 takes place only in the presence of water vapour. Various stages of decomposition have been characterised by DTA, TG, DTG, and x-ray powder diffraction. The method for the preparation of acicular γ-Fe2O3 that matches very well with the commercial tape recording material has been developed.

    • Synthesis and characterization of γ-Fe2O3 — a magnetic tape material

      M R Anantharaman K Seshan D K Chakrabarty H V Keer

      More Details Abstract Fulltext PDF

      Acicular FeC2O4 · 2H2O was precipitated from glycerol and starch media. Thermal decomposition of this oxalate in dry and moist nitrogen yielded primarily FeO and Fe3O4 respectively. Characterization was attempted through DTA, TG, x-ray diffraction, TEM and magnetization studies. It was found that the oxalate can be completely decomposed to Fe3O4 in moist nitrogen (PH2O ∼ 35 torr) at 775 K and then oxidised by dry air to acicular γ-Fe2O3 at 575 K. The resulting material has saturation magnetization (∼ 70 emu/g), coercive field (∼ 300 Oe) and squareness ratio (∼ 0·60–0·65), which values art comparable with those of the commercial samples.

    • Development of pure and doped gamma ferric oxide

      M R Anantharaman K Seshan S N Shringi H V Keer

      More Details Abstract Fulltext PDF

      Optimum conditions and experimental details for the formation of γ-Fe2O3 from goethite have been worked out. In another method, a cheap complexing medium of starch was employed for precipitating acicular ferrous oxalate, which on decomposition in nitrogen and subsequent oxidation yielded acicular γ-Fe2O3. On the basis of thermal decomposition in dry and moist nitrogen,dta, xrd, gc and thermodynamic arguments, the mechanism of decomposition was elucidated. New materials obtained by doping γ-Fe2O3 with 1–16 atomic percent magnesiu, cobalt, nickel and copper, were synthesised and characterized.

    • A new inexpensive method for the preparation of acicular precursors for magnetic recording media

      M R Anantharaman K V Joseph H V Keer

      More Details Abstract Fulltext PDF

      Magnetic materials meant for audio/video recording applications necessitate that polycrystalline materials be in acicular shape. So preparation of acicular precursors for magnetic storage materials assumes significance. The employment of aqueous solutions do not produce needle shape crystallites. Glycerol is one of the complexing media used for the precipitation of ferrous oxalate dihydrate. An inexpensive method using starch for preparation of acicular particles is described. The influence of an additive namely Gd on acicularity is also investigated.

  • Bulletin of Materials Science | News

    • 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

    • Editorial Note on Continuous Article Publication

      Posted on July 25, 2019

      Click here for Editorial Note on CAP Mode

© 2017-2019 Indian Academy of Sciences, Bengaluru.