• S K Sharma

      Articles written in Bulletin of Materials Science

    • Effect of high-energy heavy ion irradiation on the crystallization kinetics of Co-based metallic glasses

      Rohit Jain Deepika Bhandari N S Saxena S K Sharma A Tripathi

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      Differential scanning calorimeter (DSC) is employed to study the crystallization kinetics of irradiated (at three different fluences with high-energy heavy ion; Ni11+ of 150 MeV) specimens of two Co-based metallic glasses. It is found that the crystallization process in both the glasses is completed in two phases. The DSC data have been analysed in terms of kinetic parameters viz. activation energy (𝐸𝑐), Avrami exponent (𝑛), dimensionality of growth (𝑚), using two different theoretical models. The results obtained have been compared with that of virgin samples. The lower activation energy in case of second crystallization occurring at higher temperature indicates the easier nucleation of second phase. The abnormally high value of Avrami exponent in Co–Ni glass indicates very high nucleation rate during first crystallization.

    • Study of oxidation behaviour of Zr-based bulk amorphous alloy Zr65Cu17.5Ni10Al7.5 by thermogravimetric analyser

      A Dhawan K Raetzke F Faupel S K Sharma

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      The oxidation behaviour of Zr-based bulk amorphous alloy Zr65Cu17.5Ni10Al7.5 has been studied in air environment at various temperatures in the temperature range 591–684 K using a thermogravimetric analyser (TGA). The oxidation kinetics of the alloy in the amorphous phase obeys the parabolic rate law for oxidation in the temperature range 591–664 K. The values of the activation energy and pre-factor as calculated from the Arrhenius temperature dependence of the rate constants have been found to be 1.80 eV and 2.12 × 109 g cm–2.sec–1/2, respectively.

    • Corrosion behaviour of amorphous Ti48Cu52, Ti50Cu50 and Ti60Ni40 alloys investigated by potentiodynamic polarization method

      A Dhawan S Roychowdhury P K De S K Sharma

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      Potentiodynamic polarization studies were carried out on virgin specimens of amorphous alloys Ti48Cu52, Ti50Cu50 and Ti60Ni40 in 0.5 M HNO3, 0.5 M H2SO4 and 0.5 M NaOH aqueous media at room temperature. The value of the corrosion current density (𝐼corr) was maximum for Ti48Cu52 alloy in all the three aqueous media as compared to the remaining two alloys. The value of 𝐼corr for the alloy Ti48Cu52 was maximum (𝐼corr = 2.6 × 10-5 A/cm2) in 0.5 M H2SO4 and minimum (𝐼corr = 3.5 × 10-6 A/cm2) in 0.5 M NaOH aqueous solutions. In contrast, the alloy Ti60Ni40 exhibited the least corrosion current density in 0.5 M HNO3 (𝐼corr = 4.0 × 10-7 A/cm2) and in 0.5 M NaOH (𝐼corr = 5.5 × 10-7 A/cm2) aqueous media as compared to those for Ti–Cu alloys, while its value in 0.5 M H2SO4 was comparable to that for Ti50Cu50. It is suggested that the alloy Ti60Ni40 is more corrosion resistant than the alloys Ti48Cu52 and Ti50Cu50 in all the three aqueous media.

    • Optical, electrochemical and morphological investigations of poly (3,4-propylenedioxythiophene)–sultone (PProDOT–S) thin films

      S Sindhu C R Siju S K Sharma K N Rao E S R Gopal

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      In this paper, we have carried out thin film characterization of poly(3,4-propylenedioxythiophene)–sultone (PProDOT–S), a derivative of electrochromic poly(3,4-propylenedioxythiophene) (PProDOT). PProDOT–S was deposited onto transparent conducting oxide coated glass substrates by solution casting method. Single wavelength spectrophotometry is used to monitor the switching speed and contrast ratio at maximum wavelength (𝜆max). The percentage transmittance at the 𝜆max of the neutral polymer is monitored as a function of time when the polymer film is repeatedly switched. This experiment gives a quantitative measure of the speed with which a film is able to switch between the two states i.e. the coloured and the bleached states. PProDOT–S films were switched at a voltage of 1.9 V with a switching speed of 2 s at 𝜆max of 565 nm and showed a contrast of ∼37%. Cyclic voltammetry performed at different scan rates have shown the characteristic anodic and cathodic peaks. The structural investigations of PProDOT–S films by IR spectra were in good agreement with previously reported results. Raman spectra of PProDOT–S showed a strong Raman peak at 1509 cm-1 and a weak peak at 1410 cm-1 due to the C = C asymmetric and symmetric stretching vibrations of thiophene rings. The morphological investigations carried out by using scanning electron microscope (SEM) of polymer films have shown that these polymers are found to be arranged in dense packed clusters with non-uniform distribution having an average width and length of 95 nm and 160 nm, respectively.

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