Browsing by Author "Harsh Jain"

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Nanostructuring of AlSiCrMnFeNiCu High-Entropy Alloy via Cryomilling: Exploring Structural, Magnetic, and Thermoelectric Properties
(John Wiley and Sons Inc, 2024) Yagnesh Shadangi; Pema Chida Sherpa; Harsh Jain; S. Varalakshmi; Sandip Chatterji; Labanya Ghosh; Nilay Krishna Mukhopadhyay; Ajay Tripathi; Archana Tiwari
Efforts are made to understand the influence of milling intensity on structure, morphology, magnetic and thermoelectric properties of nonequiatomic nanostructured AlSiCrMnFeNiCu high-entropy alloy (HEA) powders prepared by cryomilling. These powders are cryomilled with different ball-to-powder ratios (BPR) and present a dual-phase structure containing a major B2-type and a minor Cr5Si3-type phase. An increase in BPR enhances the refinement of crystallite size, grain size, and particle size accompanied by a decrease in the phase fraction of the minor Cr5Si3-type phase. Magnetic measurements revealed that at room temperature, sufficient increase in BPR leads to a transition from multi-domain behavior to single-domain behavior which leads to enhancement in soft magnetic properties. Thermal measurements show the presence of different magnetic phase transitions which vary with an increase in BPR. A change of charge carrier type from p to n-type was observed as the grain size is reduced. The figure of merit decreases with the decrease in grain size from 2 × 10–5 for as-cast powders and is lowest for the smallest grain-sized sample due to a decrease in electrical conductivity. This study shows the possibility of exploring nonequiatomic low-density HEAs whose functional properties can be tailored, offering flexibility in material design for specific applications. © 2024 Wiley-VCH GmbH.
Phase evolution and morphological transformation of high-entropy alloy FeMnNiAlSiC nanoparticles via sequential picosecond laser ablation and nanosecond laser annealing
(Royal Society of Chemistry, 2025) Bibek Kumar Singh; Yagnesh Shadangi; Harsh Jain; R. Sai Prasad Goud; Nilay Krishna Mukhopadhyay; Anand Prakash Pathak; Venugopal Rao Soma; Archana Tiwari; Ajay Tripathi
This study investigates the morphological evolution and enhanced crystallinity of FeMnNiAlSiC high-entropy alloy (HEA) nanoparticles (NPs) synthesized using a picosecond laser operating in burst mode and subsequently processed with a nanosecond laser in deionized water (DW). The initial synthesis via pulsed laser ablation in liquid (PLAL) revealed distinct phases, like B2, γ-brass, Fe5Si3, and body-centered cubic (BCC), as confirmed by high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), and X-ray diffraction (XRD) data. Elemental mapping indicated enrichment of B2-type phases (Al-Fe and Al-Ni) in the larger NPs, while smaller NPs exhibited γ-brass and Fe5Si3-type phases. Following nanosecond laser processing, the NPs displayed significant morphological transformations, including the emergence of hollow structures, as well as enhanced crystallinity. Post-processing analysis demonstrated the evolution of B2 and Fe5Si3-type phases, driven by a laser-induced annealing effect, which resembles the traditional furnace annealing. This dual-stage laser approach effectively combines the rapid synthesis of NPs with structural refinement, offering a versatile pathway for tailoring material properties. These findings underscore the potential of laser-based techniques in the controlled synthesis and structural modulation of HEA NPs, paving the way for applications in catalysis, energy conversion, and advanced functional materials. © 2025 The Royal Society of Chemistry.
Phase Evolution, Stability and Magnetic Behavior of Lightweight Al–Fe Aluminide-Based Nanocomposites Processed by Mechanical Alloying, Cryomilling, and Annealing
(John Wiley and Sons Inc, 2025) Ganne Ketan Balaji; Harsh Jain; Pema Chida Sherpa; Ritik Roshan Tripathy; Yagnesh Shadangi; Vikas Shivam; Ajay Tripathi; Archana Tiwari; Nilay Krishna Mukhopadhyay
Attempts are made to synthesize Al5Fe2 aluminide-based composites by mechanical alloying (MA) and cryomilling (CM). The XRD and TEM results of the milled samples confirm the formation of a major B2-AlFe phase (0.2887 ± 0.0003 nm; cP2) along with the minor amount of Al5Fe2 phase. Nanocrystalline grains of ≈16 nm and an average particle size of 4.0 ± 0.36 μm are evident. A significant refinement in the crystallite size (≈10 nm) and average particle size (1.0 ± 0.03 μm) is achieved after 10 h CM of 60 h MAed powder. CM enhances the phase fraction of the Al5Fe2 phase. The DSC thermogram discerns three exothermic heating events due to phase transformation. These can be corroborated by the structural transformation of the B2-AlFe phase to the orthorhombic Al5Fe2 phase. The phase obtained as a result of 60 h of MA transforms to orthorhombic Al5Fe2 along with a minor amount of pre-existing B2-AlFe structure after annealing at 600 °C. It becomes more stable after annealing at 900 °C. Further, the 60 h milled sample displays soft ferromagnetic properties. The saturation magnetization decreases on CM and annealing due to phase transition from B2-AlFe to Al5Fe2 phase. Coercivity is reduced when the MA sample is annealed due to an increase in crystallite size and a reduction in lattice strain. © 2024 Wiley-VCH GmbH.
Phase Evolution, Stability and Magnetic Behavior of Lightweight Al–Fe Aluminide-Based Nanocomposites Processed by Mechanical Alloying, Cryomilling, and Annealing
(John Wiley and Sons Inc, 2024) Ganne Ketan Balaji; Harsh Jain; Pema Chida Sherpa; Ritik Roshan Tripathy; Yagnesh Shadangi; Vikas Shivam; Ajay Tripathi; Archana Tiwari; Nilay Krishna Mukhopadhyay
Attempts are made to synthesize Al5Fe2 aluminide-based composites by mechanical alloying (MA) and cryomilling (CM). The XRD and TEM results of the milled samples confirm the formation of a major B2-AlFe phase (0.2887 ± 0.0003 nm; cP2) along with the minor amount of Al5Fe2 phase. Nanocrystalline grains of ≈16 nm and an average particle size of 4.0 ± 0.36 μm are evident. A significant refinement in the crystallite size (≈10 nm) and average particle size (1.0 ± 0.03 μm) is achieved after 10 h CM of 60 h MAed powder. CM enhances the phase fraction of the Al5Fe2 phase. The DSC thermogram discerns three exothermic heating events due to phase transformation. These can be corroborated by the structural transformation of the B2-AlFe phase to the orthorhombic Al5Fe2 phase. The phase obtained as a result of 60 h of MA transforms to orthorhombic Al5Fe2 along with a minor amount of pre-existing B2-AlFe structure after annealing at 600 °C. It becomes more stable after annealing at 900 °C. Further, the 60 h milled sample displays soft ferromagnetic properties. The saturation magnetization decreases on CM and annealing due to phase transition from B2-AlFe to Al5Fe2 phase. Coercivity is reduced when the MA sample is annealed due to an increase in crystallite size and a reduction in lattice strain. © 2024 Wiley-VCH GmbH.