• A Venkateswara Rao

      Articles written in Bulletin of Materials Science

    • Crystal growth in gel media

      A R Patel A Venkateswara Rao

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      An attempt has been made in this review to cover the existing information on the growth of single crystals in gels. Preparation of various types of gels, in which crystals can be grown, has been briefly described. The growth of single crystals from gels is reviewed using the following classifications: (i) Crystal growth by reaction. (ii) Crystallization by complex dilution method. (iii) Crystal growth by reduction of solubility. A compact list of some important crystals grown in gels is given. Growth mechanism and nucleation problems are discussed. Morphologies of various gel-grown crystals are described. Researches on gel-grown single crystals are also briefly described.

    • Growth of larger and more perfect single crystals of KClO4 in silica gel

      A Venkateswara Rao

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      As part of a continuing effort on crystal growth in gels, this paper describes the growth of large transparent single crystals of KClO4 by the improved design. The effect of various anionic and cationic components on nucleation, growth and quality of these crystals has been studied. It has been found that a combination of KNO3 and HClO4 as the reactants resulted in the best crystals in terms of crystal size, quality and inter-crystalline separation. The effect of various impurities on nucleation, growth and quality of these crystals has been studied. It has been found that the impurities which enhance the solubility of KClO4 have a positive effect on the size and quality of the crystals. A new etchant, consisting of concentrated HCl and H2SO4 in the volume ratio 2:3 has been found to reveal as-grown as well as freshly introduced dislocations.

    • Microstructures of CaSO3 0·5 H2O single crystals grown in silica gel

      S N Patil A Venkateswara Rao

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      This paper deals with the study of surface structures of silica gel grown crystals of CaSO3 0·5 H2O. Various growth features such as growth layers, overgrowths and oriented and random liquid inclusions have been observed using optical and scanning electron microscopy techniques.

    • Nucleation and growth of CdC2O4·3H2O single crystals in silica gels

      M R Shedam A Venkateswara Rao

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      As part of our work on growth of cadmium oxalate single crystals in gels, we describe here variation of nucleation density and growth of these crystals as a function of concentration of feed solution, gel ageing, gel density, gel pH and intermediate neutral gel column. While high density and high pH gels have been found to produce opaque crystals, good quality transparent single crystals have been obtained in low density and low pH gels. It was observed that the intermediate neutral gel column and gel ageing considerably reduced the number of nucleation sites and increased the size of the crystals without affecting their quality. By concentration programming the size of the crystals increased.

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