• Ramesh Chandra

      Articles written in Pramana – Journal of Physics

    • Performance of 2-hole YBCO rf SQUID in flux-locked-loop mode at 77 K

      S K Arora A K Gupta Neeraj Khare Ramesh Chandra V S Tomar

      More Details Abstract Fulltext PDF

      A 2-hole rf SQUID has been fabricated using naturally present grain boundary Josephson weaklinks in a microbridge of bulk Y-Ba-Cu-O superconductor. Periodic oscillations in voltage-flux characteristics have been observed up to 80.5 K. The spectral density of flux noise of the SQUID is 8 × 10−4 Φ0/√Hz at 100 Hz and 77 K for open-loop mode. The SQUID has been successfully operated in flux-locked-loop mode at 77 K, demonstrating the feasiblity of the device for practical applications. In the flux-locked-loop mode the stability as well as flux noise of the SQUID has been found to improve considerably as compared to that in the open-loop mode. Various SQUID parameters have also been estimated and reported here.

    • Electroless Ni—P—ferrite composite coatings for microwave applications

      Ramesh Chandra Agarwala

      More Details Abstract Fulltext PDF

      Electroless, EL coating technique is one of the elegant ways of coating by controlling the temperature and pH of the coating bath in which there is no usage of electric current. It is estimated that the market for this chemistry will increase at a rate of about 15% per year. Use of microwave energy for synthesis of material with novel microstructures is an exciting new field in material science with enormous application.

      In this investigation, nanograined BaZn2−yCoyFe16O27y = 0.0, 0.4, 0.8, 1.2, 1.6 and 2.0) powders have been synthesized by citrate precursor method followed by heat treatment at various specified temperatures like 650, 750 and 850° C for 3 h in the furnace. In addition heat treatments are also carried out in the microwave oven of the power rating of 760 W. The powders thus produced have been characterized by SEM, EPMA, VSM, XRD and thermal analysis techniques.

      As a forward step towards EL nano-composite coatings, Ni-P-X (X = BaZn2−y CoyFe16O27) coatings with thickness less than ∼0.1 mm thick has been produced. Such coating exhibits absorption of microwave in the range of 12–18 GHz up to about 20 db depending upon the volume fraction of the ferrite particles embedded in the Ni-P matrix

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