R. P. Viswanath

Bio: R. P. Viswanath is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Thermomechanical analysis & Iron oxide. The author has an hindex of 2, co-authored 2 publications receiving 18 citations.

Hydrogen spillover effects in the reduction of iron oxide

Abstract: Freshly formed metal accelerates the rate of reduction of ferric oxide in the presence of water vapour. This effect is explained on the basis of the spillover of hydrogen from the metal sites to the oxide phase through “portholes” of water.

Hydrothermal phase transformation of hematite to magnetite

Abstract: Different phases of iron oxide were obtained by hydrothermal treatment of ferric solution at 200°C with the addition of either KOH, ethylenediamine (EDA), or KOH and EDA into the reaction system. As usually observed, the α-Fe2O3 hexagonal plates and hexagonal bipyramids were obtained for reaction with KOH and EDA, respectively. When both KOH and EDA were added into the reaction system, we observed an interesting phase transformation from α-Fe2O3 to Fe3O4 at low-temperature hydrothermal conditions. The phase transformation involves the formation of α-Fe2O3 hexagonal plates, the dissolution of the α-Fe2O3 hexagonal plates, the reduction of Fe3+ to Fe2+, and the nucleation and growth of new Fe3O4 polyhedral particles.

Temperature selectivity for single phase hydrothermal synthesis of PEG-400 coated magnetite nanoparticles

Abstract: Herein, we have presented a detailed investigation of the temperature effect on hydrothermal synthesis of Fe3O4 magnetic nanoparticles (MNPs). The appearance of single-phase cubic spinel Fe3O4 at and above critical temperature provides a clear indication that temperature plays a crucial role in the single-phase synthesis of the Fe3O4 MNPs. A detailed investigation of the structural, magnetic and spin dynamic properties of PEG-400 coated Fe3O4 MNPs synthesized by a facile hydrothermal method at different temperatures (120 °C, 140 °C, 160 °C and 180 °C for 16 hours) has been presented. The single-phase cubic magnetite structure with high crystallinity was found in the samples synthesized at 160 and 180 °C and confirmed from XRD results, whereas samples prepared at 120 and 140 °C are of mixed phase (α-Fe2O3 and Fe3O4). The magnetic hysteresis curves reveal that saturation magnetization and coercivity of MNPs enhanced systematically with the increase in the reaction temperature from 120 °C to 180 °C. Maximum saturation magnetization (88.98 emu g−1) and coercivity (134.16 Oe) were found for the sample synthesized at 180 °C. Furthermore, ferromagnetic resonance (FMR) spectra obtained for samples synthesised at higher temperatures indicate a lower value of the line width due to the high magnetic ordering in the samples. Also, the resonance field decreased, and the g-value increased due to enhancement in magnetization for the single-phase samples synthesized at higher reaction temperatures. The spin resonance properties obtained from fitting the FMR data clearly indicate that a large spin–orbit coupling was observed for the single phase Fe3O4 MNPs and excellent magnetic properties were obtained from the static magnetic measurements.