The effect of hydrogen incorporation in the nanocrystalline iron particles on their magnetic properties (original) (raw)
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Structural, microstructural and hyperfine properties of nanocrystalline iron particles
Journal of Magnetism and Magnetic Materials, 2010
Nanocrystalline Fe particles were successfully prepared by the mechanical milling process using a highenergy planetary ball mill. The physical properties of the samples were investigated as a function of the milling time, t (in the 0-54 h range) by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) and Mössbauer spectroscopy. After 54 h of milling, the lattice parameter increases from 0.28620 (3) nm for the starting Fe powder to 0.28667 (3) nm, the grain size decreases from 110 to 13 nm, while the strain increases from 0.09% to 0.7%. The powder particle morphology was observed by SEM at different stages of milling. For t less than 24 h, the Mössbauer spectra are characterized by one sextet corresponding to the crystalline bcc Fe phase, while for t greater than 24 h, the iron particles exhibit a two-component Mössbauer spectrum due to the presence of two phases: the crystallites bcc Fe phase and the grain-boundary region. The appearance and the increase in intensity of the second sextet with t may indicate that the interfacial region effect increases with milling time due to the grain size reduction and a probable disordered state of the grain boundaries.
Powder Technology, 1995
In this paper, we report a detailed morphological study and analysis performed on finely powdered magnetic alloy based on rare earthtransition metals, produced by hydrogen absorption--desorption cycles. We have analyzed the morphology of these particles by computing all the required morphological descriptors. The size of these particles ranges from 5 to 40/zm. The values of the morphological descriptors lie very close to those corresponding to adipic acid powders produced by comminution which are reported in the literature. The main advantage of the hydrogen absorption-desorption process over the conventional powder production route (ball milling) is that the particles do not undergo oxidation.
Study of Grain Size Distribution in Nanocrystalline Iron Oxides Synthesized by Hydrothermal Method
Solid State Phenomena, 2003
A novel microwave reactor was used to hydrothermally synthesize nanopowders of iron oxides under a pressure of up to 10 MPa and temperatures of up to 250 0 C. At reactions time as short as 5 minutes it was possible to synthesize powders with grain size in the range 10 -100 nm. Proper selections of the substrates and their concentration enabled the grain size and phase composition to be controlled to some extent. Pure hematite, maghemite and magnetite were obtained. The grain size and distribution were determined by image analysis of the powders.
Hydrogen Behavior in an Ultrafine-Grained Electrodeposited Pure Iron
ISIJ International, 2011
The behavior of hydrogen in an ultrafine-grained electrodeposited pure iron with Lankford (r) value larger than 7.0 was studied by small angle neutron scattering (SANS) and thermal desorption spectroscopy (TDS). Nano-sized inhomogeneity consisting of hydrogen bubble exists in the deposited specimen. The bubble size increases a little by 673 K annealing and then all the bubbles disappear after 973 K annealing. With rolling at room temperature (RT), the bubble size and number density are found to decrease, which must be caused by the change in the status of hydrogen location during plastic deformation. Crystal rotation and grain coalescence are revealed to occur after rolling deformation from electron backscattered diffraction (EBSD) results. KEY WORDS: electrodeposited pure iron; small angle neutron scattering; hydrogen; annealing; cold rolling.
Magnetic behaviour of iron nanoparticles passivated by oxidation
Physica Status Solidi (c), 2006
This study is to understand the effect of oxidation, especially magnetically, on iron nanoparticles. According to generation of the oxidated iron nanoparticles, mechanical alloying technique was used and nanosized magnetite (Fe3O4), maghemite (-Fe2O3) and hematite (-Fe2O3) particles were obtained as the resultant samples. The reactance to the thermal treatment was determined by differential thermal analysis and thermogravimetric (DTA-TG) measurements. X-ray powder diffractions (XRD) helped to exhibit the structure of the sample by ICDD cards and to determine the size of nanoparticles by using the Scherrer formula. On the other hand, VSM (vibrating sample magnetometer) measurements were determined to understand the magnetic behaviour. Through the transformation of Fe3O4 to other iron-oxides, two exothermic peaks were observed at around 169.11 °C and 562.61 °C by DTA analysis. Beside of this, the experimental results demonstrate the effects of mechanical milling parameters, atmosphere and lubricant, to the structure and to the size of the resultant particles and the change of magnetic behavior of the iron-oxide and iron nanoparticles when they approach to superparamagnetic region, especially in single domain region.
Structure and Magnetic Properties Of Fe/Si Nanoparticles Prepared by High Energy Milling Process
INDONESIAN JOURNAL OF APPLIED PHYSICS
The structure and magnetic properties of Fe/Si nanoparticle prepared by high energy milling process have been examined, focusing on the phase transition. Fe/Si nanoparticles were processed by high energy milling (HEM) for 10 hours to 50 hours with a weight per cent ratio of 9:1. Based on the X-ray diffraction (XRD) pattern, transmission electron microscope (TEM) observations, and vibrating sample magnetometer (VSM) analysis, the phase transition induced by HEM, were evidenced. The effect of structural state and the particle size on the magnetic properties such as magnetization was also studied. It was found that iron and iron oxides (-Fe2O3/ Fe3O4) phase were exhibited on all milled samples. The magnetization value of Fe/Si nanoparticles increased up to 20 hours with 142 emu/gr saturated magnetization and then decreased linearly with increasing milling time. Referring to the XRD result, this decline was initially caused by the iron oxide formation and magnetic interaction between i...
Impact of thermal oxidation on chemical composition and magnetic properties of iron nanoparticles
Journal of Magnetism and Magnetic Materials, 2018
The main objective of this work is to study the influence of thermal oxidation on the chemical composition and magnetic properties of iron nanoparticles which were manufactured in a simple chemical reduction of Fe 3+ ions coming from iron salt with sodium borohydride. The annealing processing was performed in an argon atmosphere containing the traces of oxygen to avoid spontaneous oxidation of iron at temperatures ranging from 200 °C to 800 °C. The chemical composition and magnetic properties of as-prepared and thermally-treated nanoparticles were determined by means of X-ray diffractometry, Raman spectroscopy, Mössbauer spectroscopy and vibrating sample magnetometry. Due to the magnetic interactions, the investigated iron nanoparticles tended to create the dense aggregates which were difficult to split even at low temperatures. This causes that there was no empty space between them, which led to their partial sintering at elevated temperatures. These features hindered their precise morphological observations using the electron microscopy techniques. The obtained results show that the annealing process up to 800 °C resulted in a progressive change in the chemical composition of as-prepared iron nanoparticles which was associated with their oxidation. As a consequence, their magnetic properties also depended on the annealing temperature. For instance, considering the values of saturation magnetization, its highest value was recorded for the as-prepared nanoparticles at 1 T and it equals 149 emu/g, while the saturation point for nanoparticles treated at 600 °C and higher temperatures was not reached even at the magnetic field of about 5 T. Moreover, a significant enhancement of coercivity was observed for the iron nanoparticles annealed over 600 °C.
Science of Sintering, 2016
The hydrogenation of a crystalline Ni-Fe (80 wt.% Ni, 20 wt.% Fe) powder mixture leads to the formation of a mixture of Face Centered Cubic (FCC)-Ni and FCC-Fe phase nanocrystals embedded in an amorphous matrix. The magnetic susceptibility of the nanostructured powder is 2.1 times higher than that of the as-produced crystalline mixture. Heating in the temperature range 420-590 K causes structural relaxation in the hydrogenated powder, resulting in an increase of the magnetic susceptibility and a decrease of the electrical resistivity. During the heating procedure, the reorientation of magnetic domains in nickel and iron takes place in the temperature range 580-650 K and 790-850 K, respectively. In the pressed sample from the powder mixture, the crystallization of the amorphous phase of nickel and its FCC lattice crystalline grain growth occurs in the temperature range 620-873 K causing a decrease in the magnetic susceptibility of the nickel FCC phase and a sudden drop in the electri...
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...
Journal of the American Ceramic Society, 2006
This paper reports on the surfactant-assisted synthesis of nanotubes and nanorods of b-FeOOH and hence a-Fe 2 O 3 (hematite) with remarkable stability against temperature under different reaction conditions. Characterization and a comprehensive study of their nanosized properties are carried out by powder X-ray diffraction, thermal analysis, transmission electron microscope, and vibrating sample magnetometer. Upon calcination at 3001C, b-FeOOH nanostructures transform to a-Fe 2 O 3 with some change in morphology. The samples convert to layered rod-like structures and further into some sort of a disc resembling stacked structures upon heat treatment. Even for magnetic fields up to 10 000 G, the magnetization curves for the nanotubes/nanorods of hematite do not attain the saturation magnetization. All the materials exhibit a very low coercivity even at room temperature and hence are potential materials for magnetic applications.