Magnetic properties of nanocrystalline Fe–10%Ni alloy obtained by planetary ball mills (original) (raw)
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Fe–10 wt.% Ni and Fe–20 wt.% Ni alloys were prepared, using a planetary ball mill. The bcc Fe(Ni) phase formation is identified by X-ray diffraction after 36 h of milling. The higher the shock power, the larger the bcc lattice parameter and the lower the grain size. In the friction mode, the lower the crystallite size (11.1 ± 1.5 nm for Fe–10% Ni and 10.9 ± 1.5 nm for Fe–20% Ni), the lower the lattice strain (0.42 ± 0.05% for Fe–10% Ni and 0.43 ± 0.05% for Fe–20% Ni) for the following milling conditions: (Ω = 300 rpm/ω = 400 rpm) (Ω and ω being the disc and the vial rotation speeds, respectively). In the shock mode (corresponding roughly to the lowest values), the lower the crystallite size (10.2 ± 1.5 nm for Fe–10% Ni and 10.0 ± 1.5 nm), the higher the lattice strain (0.60 ± 0.05% for Fe–10% Ni and 0.67 ± 0.05% for Fe–20% Ni) for the following milling condition (424 rpm/100 rpm). The highest values of the coercivity have been found in the shock mode. Such highest values, have been found to be equal to 1600 A/m and 1420 A/m for Fe–10% Ni and Fe–20% Ni, respectively. The milling performed in the friction mode has been found to lead to the formation of alloys exhibiting a soft magnetic behavior for both Fe–10 wt.% Ni and Fe–20 wt.% Ni alloys.
The so called “vario mill” (P4 Fritsch) planetary ball mill has been used to prepare nanocrystalline Fe-10 wt% Ni and Fe-20 wt% Ni alloys from powder mixtures. For both studied alloys, a disordered body cubic centered (BCC) solid solution has been formed after 36 h of milling. The higher the shock power, the larger the lattice parameter of the investigated systems. It has been found that in friction mode process (FMP), the lower the crystallite size, the lower the lattice strain of the prepared alloy. In shock mode process (SMP), the lower the crystallite size, the higher the lattice strain. FMP has been found to induce a soft magnetic behavior for Fe-10% Ni and F-20% Ni alloys. The highest values of coercivity have been found in materials prepared by SMP.
Journal of Superconductivity and Novel Magnetism, 2020
We investigate the structural and magnetic properties of nancrystalline Fe50Co25Ni15X10 (X=Bamorphous, Bcrystalline and Si) alloy powders prepared by mechanical alloying process. Morphological, microstructural and structural characterizations of the powders milled several times were investigated by scanning electron microscopy and X-ray diffraction. The final metallurgical state strongly depends on the chemical composition and the grinding time; it can be single-phase or two-phase. The crystallite size reduction down the nanometer scale is accompanied by the introduction of high level of lattice strains. The dissolution of Co, Ni, B (amorphous and crystalline) and Si into the α-Fe lattice leads to the formation of highly disordered Fe-based solid solutions. Coercivity (Hc) and the saturation magnetization (Ms) of alloyed powders were measured at room temperature by a vibration sample magnetization. The magnetic measurements show a contrasting Ms and (Hc) in all alloy compositions. Conclusively, soft magnetic properties of nanocrystalline alloys are related to various factors such as metalloids addition, formed phases and chemical compositions.
Alloys of Fe–Si–B with varying compositions of Mn were prepared using high energy planetary ball mill for maximum duration of 120 h. X-ray diffraction (XRD) analysis suggests that Si gets mostly dissolved into Fe after 80 h of milling for all compositions. The residual Si was found to form an intermetallic Fe3Si. The dissolution was further confirmed from the field emission scanning electron microscopy/energy dispersive X-ray analysis (FE-SEM/EDX). With increased milling time, the lattice parameter and lattice strain are found to increase. However, the crystallite size decreases from micrometer (75–95 μm) to nanometer (10–20 nm). Mössbauer spectra analysis suggests the presence of essentially ferromagnetic phases with small percentage of super paramagnetic phase in the system. The saturation magnetization (Ms), remanance (Mr) and coercivity (Hc) values for Fe–0Mn sample after 120 h of milling were 96⋅4 Am2/kg, 11⋅5 Am2/kg and 12⋅42 k Am–1, respectively. However, for Fe–10Mn–5Cu sample the Ms, Hc and Mr values were found to be 101⋅9 Am2/kg, 10⋅98 kA/m and 12⋅4 Am2/kg, respectively. The higher value of magnetization could be attributed to the favourable coupling between Mn and Cu.
Analysis of structure and magnetic properties of nanocrystalline milled alloys
Fe–20% Ni alloys were prepared using a planetary ball mill P4 vario ball mill from Fritsch (with different milling conditions (Ω/ω), Ω and ω being the disc and the vial rotation speeds, respectively). An artificial neural network (ANN) methodology was applied to rely the powder milling process parameters (Ω/ω) to the structure and magnetic properties of the Fe–20% alloys. An optimization procedure based on ANN training and testing steps was developed to predict structure and magnetic properties over a large range of process parameters. The following features have been anticipated: (i) In the friction mode process (FMP), the lower the crystallite size, the lower the lattice strain. (ii) In the shock mode process (SMP), the lower the crystallite size, the higher the lattice strain. (iii) FMP lead to the formation of alloys exhibiting a soft magnetic behavior (Hc between 380 A/m and 750 A/m) for Fe–20% Ni alloys. (iv) SMP lead to the formation of alloys exhibiting a memory and hard magnetic behavior (Hc = 900–1500 A/m) for Fe–20% Ni alloys.
Journal of Magnetism and Magnetic Materials, 2000
Fe 60 Mn 10 Al 20 Nb 10 , (Fe 60 Mn 10 Al 30 ) 95 Nb 5 and (Fe 60 Mn 10 Al 30 ) 90 Nb 10 ball milled powdered alloys were investigated using X-ray diffraction, Mössbauer spectrometry, thermomagnetic (TGM) and magnetization measurements. We studied the influence of Nb content and of different milling times on the structural and magnetic properties. Two main features can be concluded: (1) the FeAlMn induces a BCC phase whatever the Nb content is, and (2) as both increasing Nb content and milling time give rise to an highly disordered state in conjunction with a decrease of the ferromagnetic behavior.
Structure, magnetic and M¨ossbauer studies of mechanically alloyed Fe–20 wt.% Ni powders
Fe–20 wt.% Ni alloys were prepared using a planetary ball mill PM 400 from Retsch (with different milling times for Ω= 400 rpm, ω = 800 rpm) and P4 vario ball mill from Fritsch (with different milling conditions (Ω/ω), Ω and ω being the disc and the vial rotation speeds, respectively). The bcc-Fe(Ni) phase formation is identified by X-ray diffraction. The higher the shock power and the higher milling time are, the larger the bcc lattice parameter and the lower the grain size. The highest value of the coercive field is 1420 A/m for Fe–20 wt.% Ni (with shock mode (424 rpm/100 rpm) after 36 h of milling), while the lowest value is 110 A/m for (400 rpm/800 rpm) after 96 h of milling. The milling performed in the friction mode favors the formation of alloys exhibiting a soft magnetic behavior for Fe–20 wt.% Ni alloys. The M¨ossbauer spectra of the alloys recorded at 77 and at 300K differ according to the milling conditions and give relevant information on the local structure environment in relation with the nature of the mode used (friction or shock mode).
Structure and magnetic properties of nanocrystalline Co–Ni and Co–Fe mechanically alloyed
Our previous studies relating to the effect of ball milling (BM) parameters on the microstructure and, consequently, on the magnetic properties have shown that the combination of low values of the plateau rotation X and the high vial velocities x can enhance the cubic phase formation and consequently the coercivity. However, the most relevant parameter remained the ball milling time. Indeed, coercivity and crystallite size exhibit both a regular and similar decrease when mechanical alloying time is increasing. In the case of Co–Ni alloy, a slight increase occurred after 72 h milling. The soft magnetic properties of the alloys (low values of both the squareness ratio Mr/Ms and the coercivity) indicate that small magnetic particles are typically single domain.
Structural and magnetic study of mechanically alloyed Fe-Ni
Nanostructured Materials, 1999
The Fe x Ni 100-x (x ϭ 50, 65 and 80) alloys were synthesized in a conventional horizontal low energy ball mill. The X-ray diffraction was used to identify and characterise various phases during the milling process of the Fe 80 Ni 20 alloy exhibiting a bcc structure whereas for x ϭ 65 and 50 the fcc structures are found. The steady state grain size is about 10 nm. Magnetisation measurements after various milling periods allow to monitor a rate at which Ni atoms dissolve in the iron lattice. The room temperature values of the effective magnetic moment raise with the increasing milling period. All the alloys studied exhibit the ferromagnetic ordering. The magnitude of the magnetic interactions is moderately suppressed at prolonged milling as revealed by the Curie temperatures reduced down to 950 K. Such variations are caused by the deviations in the interatomic arrangements of atoms especially in the intergrain regions. The Moessbauer spectroscopy confirmed the ferromagnetic ordering and was used to calculate the distribution of hyperfine magnetic fields. The mean hyperfine fields are 33.8 T for Fe 80 Ni 20 and correspond to the one to two Ni atoms in nearest neighbourhood. In the remaining alloys, at most, five Ni atoms are located in a neighbourhood of the Fe atom.
Magnetic Properties of Nanocrystalline Fe x Cu 1-x Alloys Prepared by Ball Milling
Hyperfine Interactions, 2000
X-ray diffraction, Mössbauer and magnetization measurements were used to study Fe x Cu 1−x alloys prepared by ball-milling. The X-ray data show the formation of a nanocrystalline Fe-Cu solid solution. The samples with x 0.8 and x 0.5 exhibit bcc or fcc phase, respectively. Both the bcc and fcc phases are principally ferromagnetic for x 0.2, but the sample with x = 0.1 remains paramagnetic down to 78 K. The influence of the local environment on the hyperfine parameters and the local magnetic moment are discussed using calculations based on the discrete-variational method in the local density approximation.