• P K Rohatgi

      Articles written in Bulletin of Materials Science

    • Potential new solidification experiments in space environment

      P K Rohatgi M R Madhava M K Surappa

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      The paper discusses the potential effects of space environment on solidification; reviews the previous solidification experiments in space and suggests new-experiments. The proposed experiments in space include (a) breakdown of planar interfaces in transparent systems, (b) thermal perturbations ahead of interfaces, (c) dendrite spacings, (d) fragmentation of dendrites and their transport, (e) solute concentration profiles in castings, (f) maximum undercoolings in alloy melts under containerless conditions; ultrafine structures produced on freezing of highly under-cooled melts, (g) preparation of wires and ribbons from alloys; solidification in ultrathin films and (h) dendritic shrinkage.

    • Potential new experiments on fabrication of cast particulate composites in space

      P K Rohatgi M K Surappa M R Madhava

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      Recent developments in fabrication of cast metal ceramic particle composites by liquid metallurgy techniques are outlined. Difficulties encountered in preparing cast composites in the ground environment (including non-uniform distribution and agglomeration of dispersed particles and relatively poor bonding between dispersoids and matrix) and how these can be overcome in a microgravity environment have been discussed. This paper also reviews experiments performed by various space agencies including NASA and ESA on fabrication of composites in space. Some new experiments concerning fabrication of cast composites like dispersion of submicron ceramic particles in molten metals, preparation of cermets with very large volume fractions of ceramic particles and dispersion of flake-type ceramic particles to achieve grain refinement have been proposed.

    • Nature and reactivity of silica available in rice husk and its ashes

      G Rama Rao A R K Sastry P K Rohatgi

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      Scanning electron microscopy, reactivity and surface area measurements of rice husk and its ashes reveal the gradual formation of amorphous silica during ashing. The reactivity of the silica thus formed is found to be at its maximum for ashing temperatures between 400 and 600°C and hold-time from 6 to 12 h. The reactivity of the ash is found to decrease with increasing temperature (⩾ 600°C) and hold-time.

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