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.

Ta Doping Enhanced Room‐Temperature Ferromagnetism in 2D Semiconducting MoTe2 Nanosheets

“…Among the TMDCs family, molybdenum ditelluride (MoTe 2 ) with semiconducting polymorphism (2H‐phase) have drawn particular attention for potential electronics and spintronics due to its exceptional properties such as small band gap and strong spin−orbit coupling recently . In addition, the most recent investigations have indicated that ferromagnetism can be introduced into TMDCs like MoS 2 , WS 2 , and WSe 2 via doping of 3d transition metal atoms (Ti, V, Cr, Mn, Fe, Co, and Ni) . Liu et al have revealed the dopants of Ti, V, Mn, Fe, Co, and Ni atoms can induce magnetic moments in MoTe 2 monolayer based on first‐principles calculations within the density functional theory, which mainly originated from the localizing unpaired TM‐ 3d electrons .…”

Paramecium‐Like Iron Oxide Nanotubes as a Cost‐Efficient Catalyst for Nonaqueous Lithium‐Oxygen Batteries

“…Ramans pectra of FNTs and FNPs samples in the range of ñ = 100-1000 cm À1 are presented in Figure 1b.T he spectra of both samples are similar, and six peaks located at 226, 248, 291, 411, 499, and 613 cm À1 are observed.T he peaks at 226 and4 99 cm À1 are attributed to the A 1g mode, and the other four peaks located at 248, 291, 411, and 613 cm À1 correspond to the E g mode. [53,54] There are no other peaks observed for impurities,w hichf urther indicates that pure FNTsand FNPs were obtained.…”

Optimization of Chemi‐adsorption, EDLC, and Redox Capacitance Through Electro‐precipitation Synthesis of Fe3O4/NiO@rGO/h‐BN for the Development of Hybrid Supercapacitor

“…Due to the formation of intermediate phase of rGO and h‐BN, the G peak intensity was relatively smaller in BNG ,. Two additional intense peaks at 604 and 1119 cm −1 , corresponding to the Fe 3 O 4 and NiO is shown for BNG_IN2 ,,. However, these two peaks disappeared in BNG_IN2 and BNG_IN3 due to the lesser deposition of metal cations on the rGO/h‐BN surface of BNG_IN2 and BNG_IN3.…”

“…[9,19] Two additional intense peaks at 604 and 1119 cm À 1 , corresponding to the Fe 3 O 4 and NiO is shown for BNG_IN2. [3,36,37] However, these two peaks disappeared in BNG_IN2 and BNG_IN3 due to the lesser deposition of metal cations on the rGO/h-BN surface of BNG_IN2 and BNG_IN3. Figure S2 of supporting information shows the XRD pattern of BNG, BNG_IN1, BNG_IN2 and BNG_IN3, respectively.…”