Continuous Hydrothermal Synthesis of Fe₂O₃ Nanoparticles Using a Central Collision-Type Micromixer for Rapid and Homogeneous Nucleation at 673 K and 30 MPa

Abstract

Continuous hydrothermal synthesis of Fe 2 O 3 nanoparticles was carried out at 673 K and 30 MPa. Two types of mixers, a conventional T-type micromixer and a central collision-type micromixer (CCM), were used for the synthesis. CCM was newly fabricated on the basis of the concept for preventing heterogeneous nucleation induced on the inner wall of the mixer. Residence time and Fe(NO 3 ) 3 molality of the starting solution varied from 0.1 to 1.0 s and 0.05 to 0.50 mol/kg, respectively. Effects of the mixer structure, the residence time, and the Fe(NO 3 ) 3 molality on crystal structure, Fe 3+ conversion, average particle size, and size distribution were discussed. CCM effectively worked for producing smaller Fe 2 O 3 nanoparticles with narrow and monomodal distribution.

Hydrothermal synthesis of nanostructured Cr-doped hematite with enhanced photoelectrochemical activity

“…These data are compared with the Cr-doped hematite obtained from the hydrothermal method described in this work. To dope α-Fe2O3, diverse methods have been attempted, using a range of synthesizing methods including sol-gel [25,26,27], hydrothermal [28,29], magnetron sputtering [30,31], atomic layer deposition [32], spray pyrolysis [8,33,34,35], atmospheric pressure chemical vapor deposition (APCVD) [11,36,37], and electrodeposition [38,39,40,41]. These dopants influence the conductivity of the hematite as well as band gap width, the Fermi level, and charge-transfer-processes.…”

Crystalline iron oxide nanotube arrays with high aspect ratio as binder free anode for Li-ion batteries

“…Various synthesis techniques such as hydrothermal routes , template replication , co‐precipitation , thermal decomposition , and electrochemical anodization have been reported for the synthesis of iron oxide nanostructures. Among these methods, anodization is particularly attractive for its low cost, excellent structure control, and great convenience in obtaining self‐ordered nanotubes (NTs) over a large surface area.…”

Neutron radiography and numerical simulation of mixing behavior in a reactor for supercritical hydrothermal synthesis

“…Recently, tomographic x‐ray methods have been applied to image the formation of CeO 2 nanoparticles in the interior of a hydrothermal synthesis reactor . Numerical simulations have also been carried out to study the flow dynamics of supercritical water in flow reactors, and the relationship between the mixing behavior determined from numerical simulations and the size and shape of the nanoparticles determined from experiments was investigated under various conditions including reactor configuration . Although such previous experimental and numerical works provided various types of valuable information, there remain several problems, including difficulties in experimentally reproducing the real reactor configuration used for the actual production of nanoparticles and in verifying the numerical results of the complicated flow behavior near the critical point of water.…”