K Govinda Rajan
Articles written in Bulletin of Materials Science
Volume 6 Issue 4 September 1984 pp 717-732
The main attribute of a solid is its resistance to deformation, or its ‘strength’. We discuss first the interpretation of the strength parameter. The current situation with regard to the central problem of providing a microscopic description of the strength parameter is briefly reviewed. Electrons in metals provide the cohesion, so that an understanding of the role played by electronic structure in the strength attribute should lead to practical hints for building stronger materials. The useful ‘aircraft alloy’ (Ti + Al + V) illustrates one such important relationship,
Volume 8 Issue 4 October 1986 pp 467-470
Low dislocation density single crystals of nickel have been grown at high ambient pressure by the Czochralski method. X-ray Laue picture shows that the crystals are strain-free. The dislocation density was determined to be <103/cm2 by the etching procedure. It was found that the necking and cone regions are very critical in the dislocation introduction in the crystals. An increase in the ambient pressure used during the growth seems to aid the crystal quality.
Volume 10 Issue 3 May 1988 pp 181-185
Boric oxide, used as an encapsulant, prevents loss of volatile components in the growth of compound semiconductors. As the material readily absorbs moisture, and as moisture content has to be kept below a certain level, preparation and handling of this material becomes an involved process. In the present paper we report the process developed for preparing boric oxide from boric acid and growth of cylindrical rods of the desired diameter. The grown boric oxide is characterized by thermal analysis. Infrared characterization is also a powerful method and the advantages of this technique as well as the problems faced in taking the IR spectrum are discussed.
Volume 11 Issue 4 December 1988 pp 269-275
Gallium phosphide is a typical III–V compound semiconductor and is also an important electronic material. The synthesis and single crystal growth of this compound by melt methods is rendered very difficult because of the large phosphorus vapour pressure. A high pressure vessel with internal heating and a quartz reactor was first developed for the direct synthesis of gallium phosphide. The crystal growth was carried out in a second high pressure chamber rated for 100 bars gas pressure and equipped with the paraphernalia for crystal growth. Single crystals of gallium phosphide were grown from the polycrystalline starting material by the vertical Bridgman method and the vapour pressure problem was overcome by encapsulating the melt in a column of molten boric oxide. Both boron nitride and silica were employed as crucibles, and with the former, single crystal rods of 8–10 mm diameter and 10–15 mm length were obtained.
Volume 11 Issue 4 December 1988 pp 277-280
Studies on the single crystal growth of YBa2Cu3O7−
Volume 45, 2022
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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
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