• T N Kim

      Articles written in Bulletin of Materials Science

    • Effect of high thermal expansion glass infiltration on mechanical properties of alumina–zirconia composite

      A Balakrishnan B B Panigrahi K P Sanosh Min-Cheol Chu T N Kim Seong-Jai Cho

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      This work studies the effect on the mechanical properties of alumina-10 wt% zirconia (3 mol% yttria stabilized) composite by infiltrating glass of a higher thermal expansion (soda lime glass) on the surface at high temperature. The glass improved the strength of composite at room temperature as well as at high temperature. This could be attributed to the drastic drop in the coefficient of thermal expansion due to the compositional change in the soda lime glass during infiltration. There was a significant improvement in the Weibull modulus after glass infiltration. Glass infiltrated samples showed better thermal shock resistance. The magnitude of strength increment was found to be in the order of the surface residual stress generated by thermo-elastic properties mismatch between the composite and the penetrated glass.

    • Preparation and characterization of nano-hydroxyapatite powder using sol–gel technique

      K P Sanosh Min-Cheol Chu A Balakrishnan T N Kim Seong-Jai Cho

      More Details Abstract Fulltext PDF

      Hydroxyapatite (HA) nano powders (20–60 nm) were synthesized using a sol–gel route with calcium nitrate and phosphoric acid as calcium and phosphorus precursors, respectively. Double distilled water was used as a diluting media for HA sol preparation and ammonia was used to adjust the pH. After aging, the HA gel was dried at 65°C and calcined to different temperatures ranging from 200–800°C. The dried and calcined powders were characterized for phase composition using X-ray diffractometry, elemental dispersive X-ray and Fourier transform infra-red spectroscopy. The particle size and morphology were studied using transmission electron microscopy. Calcination revealed HA nano powders of increased particle size and crystallinity with increase in temperature. For all calcinations temperatures, the particle size distribution analysis of HA powders showed skewed distribution plot. At temperature of 700°C and above, formation of CaO was noticed which was attributed to phosphorous volatilization. This study showed that high purity HA with varying degrees of crystallinity could be obtained using this simple technique.

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      Prof. Surajit Dhara — School of Physics, University of Hyderabad, Hyderabad
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      Posted on July 25, 2019

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