• Shivani Agarwal

      Articles written in Bulletin of Materials Science

    • Structural, electrical and thermodynamical aspects of hydrogenated La–Ni–Si alloy

      Ankur Jain R K Jain Shivani Agarwal I P Jain

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      The structural, electrical and thermodynamic properties of a La–Ni–Si [La = 28.9%, Ni = 67.5%, Si = 3.6%] alloy have been investigated. Powder XRD results show that the lattice constants and unit cell volume of the alloy increase after hydrogen storage. It was also found that the resistance of the alloy increased with dissolved hydrogen concentration. Hydrogen absorption pressure composition isotherms have also been investigated which show the presence of two single 𝛼 and 𝛽 regions and one mixed (𝛼 + 𝛽) phase. The thermodynamic parameters viz. the relative partial molar enthalpy (𝛥 𝐻) and relative partial molar entropy (𝛥 𝑆) of dissolved hydrogen, are found to be in the range 8–18 kJ (mol H)-1 and 25–63 JK-1 (mol H)-1. From the dependence of 𝛥 𝐻 on the hydrogen concentration, 𝑋, the different phases [𝛼, 𝛼+ 𝛽, 𝛽] and phase boundaries of the alloy-𝐻 system are identified. Thermal conductivity and diffusivity of La–Ni–Si and its hydride have been measured at room temperature by using TPS technique. Thermal conductivity was found to decrease due to absorbed hydrogen in the alloy.

    • Structural and electrical properties of swift heavy ion beam irradiated Co/Si interface

      Garima Agarwal Ankur Jain Shivani Agarwal D Kabiraj I P Jain

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      Synthesis of swift heavy ion induced metal silicide is a new advancement in materials science research. We have investigated the mixing at Co/Si interface by swift heavy ion beam induced irradiation in the electronic stopping power regime. Irradiations were undertaken at room temperature using 120 MeV Au ions at the Co/Si interface for investigation of ion beam mixing at various doses: 8 × 1012, 5 × 1013 and 1 × 1014 cm-2. Formation of different phases of cobalt silicide is identified by the grazing incidence X-ray diffraction (GIXRD) technique, which shows enhancement of intermixing and silicide formation as a result of irradiation. 𝐼–𝑉 characteristics at Co/Si interface were undertaken to understand the irradiation effect on conduction mechanism at the interface.

    • Effect of annealing on magnetic properties and silicide formation at Co/Si interface

      Shivani Agarwal V Ganesan A K Tyagi I P Jain

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      The interaction of Co (30 nm) thin films on Si (100) substrate in UHV using solid state mixing technique has been studied. Cobalt was deposited on silicon substrate using electron beam evaporation at a vacuum of 4 × 10-8 Torr having a deposition rate of about 0.1 Å/s. Reactivity at Co/Si interface is important for the understanding of silicide formation in thin film system. In the present paper, cobalt silicide films were characterized by atomic force microscopy (AFM) and secondary ion mass spectroscopy (SIMS) in terms of the surface and interface morphologies and depth profile, respectively. The roughness of the samples was found to increase up to temperature, 300°C and then decreased with further rise in temperature, which was due to the formation of crystalline CoSi2 phase. The effect of mixing on magnetic properties such as coercivity, remanence etc at interface has been studied using magneto optic Kerr effect (MOKE) techniques at different temperatures. The value of coercivity of pristine sample and 300°C annealed sample was found to be 66 Oe and 40 Oe, respectively, while at high temperature i.e. 748°C, the hysteresis disappears which indicates the formation of CoSi2 compound.

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