Synthesis of α-Fe2O3 and Fe-Mn Oxide Foams with Highly Tunable Magnetic Properties by the Replication Method from Polyurethane Templates

Abstract

Open cell foams consisting of Fe and Fe-Mn oxides are prepared from metallic Fe and Mn powder precursors by the replication method using porous polyurethane (PU) templates. First, reticulated PU templates are coated by slurry impregnation. The templates are then thermally removed at 260 °C and the debinded powders are sintered at 1000 °C under N2 atmosphere. The morphology, structure, and magnetic properties are studied by scanning electron microscopy, X-ray diffraction and vibrating sample magnetometry, respectively. The obtained Fe and Fe-Mn oxide foams possess both high surface area and homogeneous open-cell structure. Hematite (α-Fe2O3) foams are obtained from the metallic iron slurry independently of the N2 flow. In contrast, the microstructure of the FeMn-based oxide foams can be tailored by adjusting the N2 flow. While the main phases for a N2 flow rate of 180 L/h are α-Fe2O3 and FeMnO3, the predominant phase for high N2 flow rates (e.g., 650 L/h) is Fe2MnO4. Accordingly, a linear magnetization versus field behavior is observed for the hematite foams, while clear hysteresis loops are obtained for the Fe2MnO4 foams. Actually, the saturation magnetization of the foams containing Mn increases from 5 emu/g to 52 emu/g when the N2 flow rate (i.e., the amount of Fe2MnO4) is increased. The obtained foams are appealing for a wide range of applications, such as electromagnetic absorbers, catalysts supports, thermal and acoustic insulation systems or wirelessly magnetically-guided porous objects in fluids.

Biodegradation behaviour of Fe-based alloys in Hanks’ Balanced Salt Solutions: Part II. The evolution of local pH and dissolved oxygen concentration at metal interface

“…Powder processing has consistently been a popular processing technique for the preparation of biodegradable implant materials. Its applicability has been exploited for the preparation of cardiovascular stents [ 6 , 31 ] and porous scaffold structures using more flexible methods like the space-holder technique [ 23 ], the replication method [ 12 , 32 , 33 ] and recent novel techniques involving pressureless microwave sintering [ 34 ] and extrusion-based 3D printing [ 35 ]. The fundamental difference in powder-processing microstructures and microstructures prepared using melt processing, is the resultant porosity in the former.…”

Effects of annealing on the structural and magnetic properties of flame spray pyrolyzed MnFe2O4 nanoparticles

“…This reduction is due to the decomposition of MnFe 2 O 4 into γ‐Fe 2 O 3 and FeMnO 3 phases as observed from the XRD results. In the literature, the FeMnO 3 phase is known to exhibit the weak ferrimagnetic behavior 55 . When the sample is annealed at 500°C, the M s significantly diminishes, and the value of M s for the sample is found to be 5.30 emu/g.…”

“…In the literature, the FeMnO 3 phase is known to exhibit the weak ferrimagnetic behavior. 55 When the sample is annealed at 500 • C, the M s significantly diminishes, and the value of M s for the sample is found to be 5.30 emu/g. This phenomenon is hypothesized to be caused by a decrease in the substantial quantity of the phase ratio of ferrimagnetic γ-Fe 2 O 3 .…”

Preparation of Local Raw Material for α-Fe₂O₃ Nanoparticles Powder from Mineral Extraction of Iron Sand

“…Several methods used in the synthesis of hematite α-Fe2O3 material nanoparticles include microwave method [1], green synthesis [2], precipitation [3], Pechini sol-gel [4][5][6], hydrothermal process [7,8], sol -gel autocombution [9,10] and replication method from polyurethane templates [11]. From the several methods, particle size varies from 10-81 nm using SEM or TEM.…”