Browsing by Author "Banerjee, R."

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    Composition-dependent apparent activation-energy and sluggish grain-growth in high entropy alloys
    (Taylor & Francis, 2019) Gwalani, B.; Salloom, R.; Alam, T.; Valentin, S. G.; Zhou, X.; Thompson, G.; Srinivasan, S. G.; Banerjee, R.; University of North Texas System; University of North Texas Denton; University of Alabama Tuscaloosa; United States Department of Energy (DOE); Pacific Northwest National Laboratory
    Experimental results reveal that the apparent activation-energy for grain-growth in an fcc-based AlxCoCrFeNi high entropy alloy (HEA) system increases from 179 to 486kJ/mol when the Al content increases from x=0.1 to 0.3. These unexpectedly high apparent activation-energy values can be potentially attributed to solute clustering within the fcc solid-solution phase that develops with increasing Al content in this HEA. Detailed microstructural analysis using atom-probe tomography and density functional theory (DFT) calculations strongly indicate the presence of such nanoscale clusters. This phenomenon can change grain-growth from a classical solute-drag regime to a much more sluggish cluster-drag based mechanism in these HEAs. [GRAPHICS] IMPACT STATEMENTFirst report on a composition dependent change in apparent activation-energy for grain-growth in high entropy alloys. A novel cluster drag effect inhibiting grain-growth kinetics is suggested.
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    Lattice Expansion in Nanocrystalline Niobium Thin Films
    (2003-04-09) Banerjee, R.; Sperling, E. A.; Thompson, G. B.; Fraser, H. L.; Bose, S.; Ayyub, P.; University of Alabama Tuscaloosa
    High-purity nanocrystalline niobium (Nb) thin films have been deposited using high-pressure magnetron sputter deposition. Increasing the pressure of the sputtering gas during deposition has systematically led to reduced crystallite sizes in these films. Based on x-ray and electron diffraction results, it is observed that the nanocrystalline Nb films exhibit a significantly large lattice expansion with reduction in crystallite size. There is however, no change in the bcc crystal structure on reduction in crystallite size to below 5 nm. The lattice expansion in nanocrystalline Nb has been simulated by employing a recently proposed model based on linear elasticity and by appropriately modifying it to incorporate a crystallite-size-dependent width of the grain boundary.