Study of Grain Size Distribution in Nanocrystalline Iron Oxides Synthesized by Hydrothermal Method (original) (raw)
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A simple, rapid, one-step synthesis way of pure iron oxide nanoparticles: magnetite (Fe 3 O 4), maghemite (c-Fe 2 O 3) and hematite (a-Fe 2 O 3) was investigated. Nano-particles were prepared by microwave synthesis, from eth-anol/water solutions of chloride salts of iron (FeCl 2 and FeCl 3) in the presence of sodium hydroxide NaOH. X-ray powder diffraction (XRD), Transmission Electron Micros-copy (TEM), Fourier transform infrared (FTIR) spectros-copy and X-ray photoelectron spectroscopy (XPS) were used to characterize these nanoparticles.
Nanostructured Iron Oxide Powders by Microwave Assisted Synthesis
Journal of Science and Arts, 2021
A range of nanostructured oxides with excellent properties is used in technology and science for applications in several fields: catalysis, gas detection, biomedical applications. The most studied forms of oxides are hematite, maghemite and magnetite. In this study, microwave-assisted hydrolytic synthesis and microwave-assisted coprecipitation synthesis are described for the preparation of undoped and doped iron oxide powders using iron (III) chloride (FeCl3), potassium chloride (KCl) as precursors and sodium hydroxide (NaOH) solution as a hydrolysis agent. Microwave-assisted hydrolysis was performed at different concentrations of FeCl3 precursor: 0.1 M, 0.4 M, 0.7 M to which a constant concentration of hydrolysis agent was added, and the synthesis to obtain potassium-doped powders consisted of co-precipitation of 0.1M FeCl3 and 0.025M KCl precursor solutions in the presence of 2M NaOH hydrolysis agent. The developed powders were characterized by X-ray diffraction (XRD), scanning el...
Microwave hydrothermal preparation of submicron-sized spherical magnetite (Fe3O4) powders
Materials Letters, 2002
Submicron-sized (0.15 -0.2 Am) spherical agglomerates of magnetite (Fe 3 O 4 ) powders have been prepared successfully by microwave hydrothermal (MH) reaction of ferrous sulphate and sodium hydroxide in the temperature range of 90 -200 jC. Xray powder diffraction patterns of all these powders indicated that the product is single-phase magnetite with cubic spinel structure having lattice parameter, a 0 = 8.392 Å . The Mössbauer spectra of these powders indicated that stoichiometric Fe 3 O 4 particles are obtained only when molar ratio of Fe/NaOH z 0.133 is maintained in the solution. It is observed that Fe/NaOH ratio is an important parameter for the controlled oxidation of ferrous salts in alkaline media under MH condition to produce stoichiometric Fe 3 O 4 . Further, the kinetics of MH synthesis is one order faster than the reported conventional hydrothermal (CH) synthesis. The value of saturation magnetization M = 70 emu/g is obtained in case of stoichiometric Fe 3 O 4 . However, when ferric salt is treated in alkaline medium single-phase a-Fe 2 O 3 is obtained under the MH conditions of 200 jC (194 psi). D
Nanocrystalline/Nanosized Fe3O4 Powder Obtained by Mechanosynthesis
Advanced Engineering Forum, 2015
Nanocrystalline/nanosized magnetite - Fe3O4 powder was obtained by mechanical milling of well crystallized magnetite obtained by ceramic method starting from stoichiometric mixture of commercial hematite - Fe2O3 and iron - Fe powders. The mean crystallites size of the magnetite is decreasing upon increasing the milling time down to 6 nm after 240 minutes of milling. After 30 minutes of milling an undesired hematite phase is formed in the material. The amount of this phase increases upon increasing the milling time. In the early stage of milling (up to 30 minutes) the existence of nanometric particles (mean size below 100 nm) is noticed. The d50 median diameter decreases first (up to 5 minutes of milling) and after that, an increase follows for milling times up to 120 minutes. Saturation magnetization decreases upon increasing the milling time and is more difficult to saturate. X-ray diffraction, laser particle size analysis and magnetic measurements have been used for powder charact...
Hyperfine Interactions, 2007
Microwave–hydrothermal (MH) route was employed to synthesize various iron oxide phases in ultra-fine crystalline powders by using ferrous sulphate and sodium hydroxide as starting chemicals. All chemical reactions were carried out under identical MH conditions, namely, at 190C, 154 psi, 30 min, by varying the molar ratio (MR) of FeSO4/NaOH in the aqueous solutions. The variation of MR has a dramatic effect on the crystallization behavior of various phases of iron oxides under MH processing conditions. For example, spherical agglomerates of Fe3O4 powder were obtained if MR equal to 0.133 (pH > 10 sample A). On the other hand non-stoichiometric Fe3O4 powders (Sample B) were obtained for all higher MR of FeSO4/NaOH between 0.133 and 4.00 (6.6 < pH < 10). However, when MR was equal to 4.0 (pH ≅ 6.6) a varied distribution of shapes and sizes of agglomerates of -Fe2O3 powders (sample C) were produced. Fe57 Mssbauer spectra were recorded for all the three sets of samples at room temperature. In the case of sample B, temperature dependent Mssbauer spectra were recorded in the range of 77–300 K to understand the non-stoichiometric nature of Fe3O4 powders. All these results are discussed in the present paper.
Journal of Superconductivity and Novel Magnetism, 2014
Different size of iron oxide nanoparticles were synthesized via hydrothermal process. The change of the size of nanoparticles with reaction temperatures (60, 100, 150, and 180°C) was investigated. To have further insight into the growth of nanoparticles, the different reaction times were also studied at the temperatures of 100, 150, and 180°C. The structural characterization was carried out with X-ray diffractometer and Fourier transform infrared spectroscopy. The nanoparticles were found to have high crystalline iron oxides with a mixture of magnetite and maghemite crystalline phases. With the increase of the nanoparticle size, the ratio of magnetite to maghemite phase increased and reached to a pure magnetite phase for the 123 ± 44 nm particles. When the reaction temperature increased from 100 to 180°C for 12 h, the size of the nanoparticles increased from 14.5 ± 4 to 29.9 ± 9 nm according to transmission electron microscopy analysis. At 180°C, as the reaction time increased from 1 to 48 h, the size of nanoparticles increased from 20.6 ± 6 to 123 ± 44 nm. This means that the reaction times are more effective on the growth of the nanoparticles at high temperatures. Magnetic analysis by vibrating sample magnetometer showed that the nanoparticles are ferrimagnetic. By considering all nanoparticles, the saturation magnetization increased as the size of the nanoparticle increased. And the high size of nanoparticles reached the high saturation magnetization value at low applied magnetic fields. The structural and magnetic properties of the nanoparticles are found to be depending on the nanoparticle sizes which are substantially affected by the reaction temperature and time.
Ultra Fast Hematite Preparation using a Microwave-Assisted Hydrothermal Method
Current Physical Chemistry, 2013
Nanostructured iron (III) oxide (α-Fe 2 O 3) was synthesized using Fe(NO 3) 3 , PEG and different bases (NaOH and NH 4 OH) as precursors via hydrothermal microwave method. Several experimental techniques were employed to formulate an optic-structural model. The results proved the efficient synthesis of α-Fe 2 O 3 and demonstrated that the material's behavior could be tuned using different conditions in the reaction. Ultra fast synthesis (1 min) of α-Fe 2 O 3 was obtained when NH 4 OH was used as the alkalinizing agent. Evaluating the short-and long-range order before and after microwave heating was possible. PEG and the alkalinizing agent fundamentally influenced the material morphology; three different particle shapes were observed: hexagons (NaOH with PEG), rods (NaOH without PEG) and spheres (NH 4 OH with PEG).
Synthesis and Characterisation of Iron Oxide Nanoparticles with Tunable Sizes by Hydrothermal Method
arXiv (Cornell University), 2021
The present study investigates the effect of different reaction times on the crystallinity, surface morphology and size of iron oxide nanoparticles. In this synthetic system, aqueous iron (III) nitrate (Fe(NO3)3•9H2O) nonahydrate, provided the iron source and triethylamine was the precipitant and alkaline agent. The as-synthesised iron oxide nanoparticles were characterised by X-ray diffraction (XRD), Rietveld analysis, Scanning Electron Microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). Prolonged reaction times indicated the change on nanoparticle shape from elongated nanorods to finally distorted nanocubes. Analysis on the crystallinity of the iron oxide nanoparticles suggest that the samples mainly consist of two phases, which are Goethite (α-FeOOH) and Hematite (α-Fe2O3) respectively.
Effect of precursors on chemical composition, morphology, and dimension size of Iron oxide
Iron oxides nanostructures have a wide range of applications in different fields. Properties of nanostructures depend on their size, morphology and chemical composition. The precipitation method is one of the most known and advantageous techniques for the synthesis of metal oxide nanoparticles. To investigate the effect of precursor on properties of iron oxide nanostructures, iron oxide has been synthesized using precipitation method with iron (III) acetate, iron (III) chloride and iron (III) nitrate as the iron precursor. The products were characterized by X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FTIR) and field emission scanning electron microscopy (FESEM). Hematite Nanorods were obtained using acetate precursor with uniform shape and lack of agglomeration. Chloride and nitrate precursors were led to the formation of Wuestite and magnetite phase, respectively. In the case of using chloride and nitrate precursors, nanoparticles existed with bulk structures. FTIR spectra of all samples showed strong absorption peaks of Fe-O bond vibration at 400-600 cm-1. This study provides good insights into the synthesis of engineered iron oxide nanostructure with desired properties for different applications.
2019
Magnetic iron oxide particles are used for in vitro diagnostics for nearly 40 years. Due to their unique physical, chemical, thermal and mechanical properties, as well as biocompatibility and low toxicity in the human body, iron oxide nanoparticles have been used in many biomedical applications, such as contrast agents for magnetic resonance imaging, carriers for controlled drug delivery and immunoassays, but also in magnetic hyperthermia. Our aim is to investigate the effect of pressure and temperature on the structural, thermal and magnetic properties of iron oxide nanomaterials prepared by hydrothermal synthesis. Iron oxide nanoparticles were synthesized at temperatures of 100-200°C and pressures of 20-1000 bar. It has been found that pressure influences the type of iron oxide crystalline phase. Thus, for lower pressure values (< 100 bar), iron oxide is predominantly formed as hematite, while at pressures > 100 bar, the major crystalline phase is goethite. The complex therm...