• Cyriac Joseph

      Articles written in Bulletin of Materials Science

    • Some structural aspects of neodymium praseodymium oxalate single crystals grown in hydro silica gels

      Cyriac Joseph M A Ittyachen K S Raju

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      The mixed crystals of neodymium praseodymium oxalate are grown by the diffusion of a mixture of aqueous solutions of neodymium nitrate and praseodymium nitrate (as an upper reactant) into the set gel embedded with oxalic acid. By varying the concentration (by volume) of rare earth nitrates in the upper reactant, the incorporation of Nd and Pr in the mixed crystals has been studied. Tabular crystals with the well defined hexagonal basal planes are observed in the mixed crystals of varying concentrations. X-ray diffraction patterns of these powdered samples reveal that these mixed crystals are ‘isostructural’, while IR and FTIR spectra establish the presence of oxalate groups. TGA and DSC analyses show the correctness of the chemical formula for the mixed crystals, by the release of water molecules (endothermic) and of CO and CO2 (exothermic), with the rare earth oxides as the stable residue. X-ray fluorescence (XRF) and energy dispersive X-ray analyses (EDAX) establish the presence of heavy rare earth elements qualitatively and to a good extent quantitatively. X-ray photoelectron spectroscopic (XPS) studies confirm the presence of rare earth elements (Nd and Pr) as their respective oxides. The findings of these techniques of characterization are in excellent agreement with the proposed empirical structure for the mixed rare earth oxalates. The implications are discussed.

    • Microhardness study of (1-x-y)(B2O3)-x(Li2O)-y(MCI2), (M=Cd, Zn) glasses

      P S Vijoy M Abdul Khadar Cyriac Joseph

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      Results of microhardness measurements on (1-x-y)(B2O3)-x(Li2O)-y(MCI2), (M=Cd, Zn) glasses, in the applied load range 25–500 g, are presented. The microhardness was found to decrease with increase in load up to 50 g, then it increased and finally attained a practically constant value with increase in load. The effects of composition of the glasses on microhardness are discussed.

    • Growth and micro-topographical studies of gel grown cholesterol crystals

      Anit Elizabeth Cyriac Joseph M A Ittyachen

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      Cholesterol (C27H46O) is the most abundant and best-known steroid in the animal kingdom. The in vitro crystallization of this important biomaterial has been attempted by few researchers. Here we are reporting crystallization of pure cholesterol monohydrate crystals in gel medium. It is found that the morphology of the crystals depends on various parameters. The effect of solvent has been studied in detail. The different morphologies observed are fibrous, needle, platelet, dendrite etc. Micro topographical studies have been made and it is found that the crystals grow, at least in the last stage, by spreading of layers. However, at initial stage microcrystals formed and developed into dendrite or needle forms. These one-dimensional crystals developed into platelets and finally thickened. Further studies reveal that micro impurities play a vital role in the development of these crystals as seen by dissolution figures on the crystals. These crystals are characterized by using the XRD and IR spectroscopic methods.

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