Browsing by Author "Rajesh K. Mishra"

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Enhanced hydrogenation characteristics of Li-Mg-N-H system catalyzed with TiO2 nanoparticles; a mechanistic approach
(Elsevier Ltd, 2017) Rohit R. Shahi; Rajesh K. Mishra; Vivek Shukla; Ashish Bhatnagar; O.N. Srivastava
The report describes the effect of TiO2 nano particles on the hydrogenation characteristics of promising Li-Mg-N-H hydrogen storage system. The effect of different particle size of TiO2 (200, 25 and 7 nm) on de/re-hydrogenation characteristics of Mg(NH2)2/LiH mixture has been investigated. Desorption kinetics of Li-Mg-N-H system with 25 nm TiO2 gets enhanced upto ∼25% as compared to the pristine material kinetics at 453 K (180 °C). The report also deals mechanistic approach for hydrogen release from Li-Mg-N-H system in the presence of TiO2 nanoparticles through XPS analysis of catalyzed sample at various stages of reaction. The XPS analysis confirms that during dehydrogenation nitrogen atom present in Li-Mg-N-H system share their lone pair electrons to Ti (present in TiO2) and provides an alternate decomposition path which has lower activation energy for dehydrogenation. © 2017 Hydrogen Energy Publications LLC
Investigations on phase formation and magnetic properties of promisingCo35Cr5Fe10Ni30Ti20 high entropy alloysynthesized through radio frequency induction melting
(Elsevier Ltd, 2023) Priyanka Kumari; Abhishek Kumar; Rajesh K. Mishra; M.A. Shaz; T.P. Yadav; Rohit R. Shahi
Previously, we designed and developed a promising excellent soft magnetic Co35Cr5Fe10Ni30Ti20High Entropy Alloy (HEA) through mechanical alloying (MA) followed by annealing at 790 ̊C. Densification of the powder sample synthesized through MA is critical for industrial a pplications, particularly as amagnetic material. Therefore, in the present study,optimizedCo35Cr5Fe10Ni30Ti20 HEA is synthesized again through the radio frequency (RF) induction melting.The X-ray diffraction (XRD) analysis of the RF induction melted HEA revealed the formation of mixture of fcc and ordered B2 phase. The phase stability of synthesized HEA has also been investigated through annealing at 790 °C for 2 h. Thesynthesized HEA maintained its phase identity after annealing. The synthesized and annealed Co35Cr5Fe10Ni30Ti20HEAs showed ferromagnetic behavior with high saturation magnetization (Ms) and low coercivity (Hc). For as-synthesized Co35Cr5Fe10Ni30Ti20 HEA, the value of Ms and Hcis found to be 80.22 emu/g and 4.63 Oe, respectively. However, after annealing, the value of Hcis increased to 7.89 Oe, while Ms remained same to as synthesized HEA.Vickers hardness test was also performed on the synthesized and annealed HEAs. The results displayed that hardness increased after annealing upto 512.50 Hv. The present studynot only investigates phase formation and magnetic properties of RF induction melted HEA but it also emphasizes the effect of the processing route on the structural, magnetic, and mechanical properties of the most promising magnetic Co35Cr5Fe10Ni30Ti20 HEA. The found value of hardness for the RF- melted Co35Cr5Fe10Ni30Ti20 HEA is excellent as compared to the conventional soft magnetic materials such as polycrystalline Fe (100–150 Hv), Fe50Ni50 (120 Hv) etc. The present investigation is also important for the industrial development of the magnetic Co35Cr5Fe10Ni30Ti20 HEA. © 2023 Elsevier B.V.