• Arun Pratap

      Articles written in Bulletin of Materials Science

    • Nucleation and growth of a multicomponent metallic glass

      Arun Pratap K G Raval Ajay Gupta S K Kulkarni

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      The metallic glass samples of Fe67Co18B14Si1 (2605CO), prepared by the melt spinning technique were procured from the Allied Corporation. The kinetics of crystallization of this multicomponent glassy alloy is studied using differential scanning calorimetry (DSC). The crystallization data have been examined in terms of modified Kissinger and Matusita equations for the nonisothermal crystallization. The results show enhanced bulk nucleation in general. At high heating rates added to it is surface induced abnormal grain growth resulting in fractal dimensionality.

    • Studies on poly (hydroxy alkanoates)/(ethylcellulose) blends

      Vaishali Suthar Arun Pratap Heta Raval

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      Biodegradable polymers represent one of the most significant area of research today. Among these polymers, poly (β-hydroxy butyrate co β′-hydroxy valerate) i.e. PHBV have received special attention because of their unique combination of properties. They are perfectly biocompatible, biodegradable polymers and can be processed by any conventional technique. In the present study an attempt has been made to develop the biodegradable blends of PHBV by blending them with ethyl cellulose (EC). Ethyl cellulose has been selected to monitor the biodegradation rate of PHBV and also for making the blends cost effective. The blends are thoroughly characterized for their compatibility, by the measurement of viscosity of blends and through FT-IR. Various applications of PHBV/EC blend in agriculture and pharmaceutical industries are being explored.

    • Kinetics of crystallization of a Fe-based multicomponent amorphous alloy

      Arun Pratap T Lilly Shanker Rao Kinnary Patel Mukesh Chawda

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      The Fe-based multicomponent amorphous alloys (also referred to as metallic glasses) are known to exhibit soft magnetic properties and, it makes them important for many technological applications. However, metallic glasses are in a thermodynamically metastable state and in case of high temperature operating conditions, the thermally activated crystallization would be detrimental to their magnetic properties. The study of crystallization kinetics of metallic glasses gives useful insight about its thermal stability. In the present work, crystallization study of Fe67Co18B14Si1 (2605CO) metallic glass has been carried out using differential scanning calorimetry (DSC) technique. Mössbauer study has also been undertaken to know the phases formed during the crystallization process. The alloy shows two-stage crystallization. The activation energy has been derived using the Kissinger method. It is found to be equal to 220 kJ/mol and 349 kJ/mol for the first and second crystallization peaks, respectively. The Mössbauer study indicates the formation of 𝛼-(Fe, Co) and (Fe, Co)3B phases in the alloy.

    • A thermodynamic approach towards glass-forming ability of amorphous metallic alloys

      Sonal R Prajapati Supriya Kasyap Arun Pratap

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      A quantitative measure of the stability of a glass as compared to its corresponding crystalline state can be obtained by calculating the thermodynamic parameters, such as the Gibbs free energy difference (𝛥𝐺), entropy difference (𝛥𝑆) and the enthalpy difference (𝛥𝐻) between the super-cooled liquid and the corresponding crystalline phase. 𝛥𝐺 is known as the driving force of crystallization. The driving force of crystallization (𝛥𝐺) provides very important information about the glass-forming ability (GFA) of metallic glasses (MGs). Lesser the driving force of crystallization more is the GFA. The 𝛥𝐺 varies linearly with the critical size (𝑑𝑐). According to Battezzati and Garonne the parameter 𝛾 ( = (1−(𝛥𝐻𝑥/𝛥𝐻𝑚))/(1−(𝑇 𝑥/𝑇 𝑚))) in the expression for 𝛥𝐺 should be a constant (i.e., 0.8), but its uniqueness is not observed for all MGs. The thermal stability of various alloy compositions is studied by their undercooled liquid region (𝛥𝑇 = 𝑇 𝑥 − 𝑇 𝑔). Large 𝛥𝑇 𝑥 implies greater stability against crystallization of the amorphous structure. Other GFA parameters are also calculated and correlated with critical size (𝑑𝑐).

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