ANUJ UPADHYAY
Articles written in Bulletin of Materials Science
Volume 38 Issue 3 June 2015 pp 599-606
Effect of isochronal annealing on phase transformation studies of iron oxide nanoparticles
Anjali J Deotale R V Nandedkar A K Sinha Anuj Upadhyay Puspen Mondal A K Srivastava S K Deb
The effect of isochronal annealing on the phase transformation in iron oxide nanoparticles is reported in this work. Iron oxide nanoparticles were successfully synthesized using an ash supported technique followed by annealing for 2 h at various temperatures between 300 and 700° C. It was observed using X-ray diffraction (XRD) and transmission electron microscopy (TEM) that as-grown samples have mixed phases of crystalline haematite (α-Fe2O3) and a minor phase of either maghemite (𝛾-Fe2O3) or magnetite (Fe3O4). On annealing, the minor phase transforms gradually to haematite. The phase transformation is complete at annealing temperature of 442° C as confirmed by differential scanning calorimetric (DSC) analysis. The unresolved phases in XRD were further analysed and confirmed to be maghemite from the X-ray absorption near edge structure (XANES) studies. The magnetic measurements showed that at room temperature nano-𝛼-Fe2O3 is weak ferromagnetic, and its magnetization is larger than the bulk value. The mixed phase sample shows higher value of magnetization because of the presence of ferromagnetic 𝛾-Fe2O3 phase.
Volume 45 All articles Published: 27 September 2022 Article ID 0190
Pressure-induced variations of medium-range order in B$_2$O$_3$ glasses
SOUMEE CHAKRABORTY V SIVASUBRAMANIAN MANVENDRA NARAYAN SINGH ANUJ UPADHYAY ANIL K SINHA T R RAVINDRAN
Lead-borate glasses manifest unique structure with lead oxide composition owing to their dual role of modifier and former. The medium-range signature from the first sharp diffraction peak (FSDP) in lead-borates exhibits substantial correlations due to the presence of superstructural units. Pressure plays an important role in altering bonding characteristics and hence structure in materials. To understand pressure-induced changes in the medium-range order (MRO) in lead-borate glasses, we have carried out high pressure X-ray diffraction studies in the FSDP region of these glasses up to 25 GPa. Two clear peaks, $q_0$ and $q_1$ are observed in all the modified glasses, below and above the position of the FSDP in pure B$_2$O$_3$ glass. This shows that lead oxide alters the FSDP and causes changes in the network structure at the MRO. $q_1$ exhibits an increase under compression, resulting in a reduction in correlation lengths for all glass compositions.The initial steep decrease is accompanied by a lower rate of reduction at higher pressures. This shows that correlations arising from structural voids in the boron matrix exhibit similar decrease for various lead oxide compositions.
Volume 45 All articles Published: 26 October 2022 Article ID 0215
Compressibility studies of RE$_6$UO$_{12}$ at extreme conditions of pressure
BALMUKUND SHUKLA N R SANJAY KUMAR HRUDANANDA JENA ANUJ UPADHYAY N V CHANDRA SHEKAR
Rare-earth uranates-RE$_6$UO$_{12}$ are synthesized by heating mixture of uranium oxide and rare-earth oxides in 1:6 ratio
above 1273 K. These compounds stabilize in rhombohedral structure at ambient. High-pressure (HP) X-ray diffraction studies reveal that the compounds are
stable at lower pressures, beyond which disorder is seen to originate and compound has a tendency to amporphize at very HPs. The
Volume 46, 2023
All articles
Continuous Article Publishing mode
Prof. Subi Jacob George — Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bengaluru
Chemical Sciences 2020
Prof. Surajit Dhara — School of Physics, University of Hyderabad, Hyderabad
Physical Sciences 2020
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