• A P Moon

      Articles written in Bulletin of Materials Science

    • Electrochemical passivation behaviour of nanocrystalline Fe80Si20 coating in borate buffer solution

      G Gupta A P Moon K Mondal

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      Passivation behaviour of nanocrystalline coating (Fe80Si20) obtained by in situ mechanical alloying route is studied and compared with that of the commercial pure iron and cast Fe80Si20 in sodium borate buffer solution at two different pH values (7.7 and 8.4). The coating reveals single passivation at a pH of 7.7 and double stage passivity at a pH of 8.4. The first passive layer is due to the dissolution mechanism and second passivity is related to stable passivation. The cast sample shows single stage passivity in the solution of pH 8.4. The difference in the passivation behaviour for the cast alloy (Fe80Si20) and the coating is related to the presence of highly iron-enriched localized regions, formed during the processing stage of coating.

    • Nanoporous Ag template from partially sintered Ag–Zn compact by dezincification

      M Mandal A P Moon S Sangal K Mondal

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      A novel approach is followed to successfully fabricate nanoporous thin Ag template using partial sintering of elemental Ag and Zn (both have 99.9% purity) and subsequent dezincification. The starting materials for dezincification are partially sintered Ag–Zn aggregates (2.5, 5 and 10 wt% Zn). Partial sintering is done in order to achieve only interfacial bonding with the aim to maintain maximum potential difference between Ag and Zn particles during dezincification process in 1 N HCl and 3.5 wt% NaCl solutions. Two different dissolution methods, namely, simple immersion for 45 days and electrochemical way (holding the sample at critical potential), are employed. Electrochemical polarization tests are carried out to determine the critical potential for subsequent chrono-amperometry. X-ray diffraction, optical microscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy are carried out to examine microstructural evolution, size, distribution and nature of pores in sintered aggregate as well as in template.

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