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Dependence of phase configurations, microstructures and magnetic properties of iron-nickel (Fe-Ni) alloy nanoribbons on deoxidization temperature in hydrogen

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ABSTRACT

Iron-nickel (Fe-Ni) alloy nanoribbons were reported for the first time by deoxidizing NiFe2O4 nanoribbons, which were synthesized through a handy route of electrospinning followed by air-annealing at 450 °C, in hydrogen (H2) at different temperatures. It was demonstrated that the phase configurations, microstructures and magnetic properties of the as-deoxidized samples closely depended upon the deoxidization temperature. The spinel NiFe2O4 ferrite of the precursor nanoribbons were firstly deoxidized into the body-centered cubic (bcc) Fe-Ni alloy and then transformed into the face-centered cubic (fcc) Fe-Ni alloy of the deoxidized samples with the temperature increasing. When the deoxidization temperature was in the range of 300 ~ 500 °C, although each sample possessed its respective morphology feature, all of them completely reserved the ribbon-like structures. When it was further increased to 600 °C, the nanoribbons were evolved completely into the fcc Fe-Ni alloy nanochains. Additionally, all samples exhibited typical ferromagnetism. The saturation magnetization (Ms) firstly increased, then decreased, and finally increased with increasing the deoxidization temperature, while the coercivity (Hc) decreased monotonously firstly and then basically stayed unchanged. The largest Ms (~145.7 emu·g−1) and the moderate Hc (~132 Oe) were obtained for the Fe-Ni alloy nanoribbons with a mixed configuration of bcc and fcc phases.

No MeSH data available.


FESEM images of the precursor sample S0 (a–c) and as-deoxidized samples S1 (d–f), S2 (g–i), S3 (j,l) and S4 (m–o).
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f2: FESEM images of the precursor sample S0 (a–c) and as-deoxidized samples S1 (d–f), S2 (g–i), S3 (j,l) and S4 (m–o).

Mentions: The morphology features of all samples S0-S4 with the defined phase configurations are examined by FESEM firstly. As presented in Fig. 2(a–c), a large number of continuously ribbon-like structures with random direction are found for sample S0 (NiFe2O4). The ribbon-width is ranged from 269 nm to 512 nm and the average width is about 348.4 nm. Each of nanoribbon is quite uniform in width along the length direction and is constructed by small nanoparticles (NPs). When the NiFe2O4 nanoribbons are deoxidized at 300 to 600 °C, some changes are also occurred on the microstructures beyond on the phase configurations of the resultant products, which are shown in Fig. 2(d–o). Firstly, in Fig. 2(d–f), when the deoxidization temperature is 300 °C, the obtained composite nanoribbons S1 of NiFe2O4 + fcc Fe-Ni + bcc Fe-Ni well keep the continuous structures of the NiFe2O4 nanoribbons. Secondly, when the temperature is risen up to 400 and 500 °C, the NPs contained within the composite nanoribbons S2 of fcc Fe-Ni + bcc Fe-Ni (Fig. 2(g–i)) and pure nanoribbons S3 of fcc Fe-Ni (Fig. 2(j–l)) increase sharply and fuse together. And the nanoribbons S3 become uneven and bent. Compared to S0, however, the average ribbon-widths of S1, S2 and S3 don’t change much and they are about 347.9, 345.1 and 345.4 nm respectively. Thirdly, when the deoxidization temperature is further increased to 600 °C, basically no nanoribbons except for NP-chain (or nanochains) are found in the final fcc Fe-Ni sample (S4) (Fig. 2(m–o)). Due to the excessive growth and fusion together of their NPs, the nanochains S4 are constructed by the NP-clusters as one-by-one and the average diameter is about 241 nm. Moreover, unlike the nanoribbons of S0-S3, the nanochains of S4 connect with each other by lots of junctions, which were marked by the red circles. Hence the whole sample S4 looks more like a three-dimensional network of the nanochains.


Dependence of phase configurations, microstructures and magnetic properties of iron-nickel (Fe-Ni) alloy nanoribbons on deoxidization temperature in hydrogen
FESEM images of the precursor sample S0 (a–c) and as-deoxidized samples S1 (d–f), S2 (g–i), S3 (j,l) and S4 (m–o).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5120276&req=5

f2: FESEM images of the precursor sample S0 (a–c) and as-deoxidized samples S1 (d–f), S2 (g–i), S3 (j,l) and S4 (m–o).
Mentions: The morphology features of all samples S0-S4 with the defined phase configurations are examined by FESEM firstly. As presented in Fig. 2(a–c), a large number of continuously ribbon-like structures with random direction are found for sample S0 (NiFe2O4). The ribbon-width is ranged from 269 nm to 512 nm and the average width is about 348.4 nm. Each of nanoribbon is quite uniform in width along the length direction and is constructed by small nanoparticles (NPs). When the NiFe2O4 nanoribbons are deoxidized at 300 to 600 °C, some changes are also occurred on the microstructures beyond on the phase configurations of the resultant products, which are shown in Fig. 2(d–o). Firstly, in Fig. 2(d–f), when the deoxidization temperature is 300 °C, the obtained composite nanoribbons S1 of NiFe2O4 + fcc Fe-Ni + bcc Fe-Ni well keep the continuous structures of the NiFe2O4 nanoribbons. Secondly, when the temperature is risen up to 400 and 500 °C, the NPs contained within the composite nanoribbons S2 of fcc Fe-Ni + bcc Fe-Ni (Fig. 2(g–i)) and pure nanoribbons S3 of fcc Fe-Ni (Fig. 2(j–l)) increase sharply and fuse together. And the nanoribbons S3 become uneven and bent. Compared to S0, however, the average ribbon-widths of S1, S2 and S3 don’t change much and they are about 347.9, 345.1 and 345.4 nm respectively. Thirdly, when the deoxidization temperature is further increased to 600 °C, basically no nanoribbons except for NP-chain (or nanochains) are found in the final fcc Fe-Ni sample (S4) (Fig. 2(m–o)). Due to the excessive growth and fusion together of their NPs, the nanochains S4 are constructed by the NP-clusters as one-by-one and the average diameter is about 241 nm. Moreover, unlike the nanoribbons of S0-S3, the nanochains of S4 connect with each other by lots of junctions, which were marked by the red circles. Hence the whole sample S4 looks more like a three-dimensional network of the nanochains.

View Article: PubMed Central - PubMed

ABSTRACT

Iron-nickel (Fe-Ni) alloy nanoribbons were reported for the first time by deoxidizing NiFe2O4 nanoribbons, which were synthesized through a handy route of electrospinning followed by air-annealing at 450 °C, in hydrogen (H2) at different temperatures. It was demonstrated that the phase configurations, microstructures and magnetic properties of the as-deoxidized samples closely depended upon the deoxidization temperature. The spinel NiFe2O4 ferrite of the precursor nanoribbons were firstly deoxidized into the body-centered cubic (bcc) Fe-Ni alloy and then transformed into the face-centered cubic (fcc) Fe-Ni alloy of the deoxidized samples with the temperature increasing. When the deoxidization temperature was in the range of 300 ~ 500 °C, although each sample possessed its respective morphology feature, all of them completely reserved the ribbon-like structures. When it was further increased to 600 °C, the nanoribbons were evolved completely into the fcc Fe-Ni alloy nanochains. Additionally, all samples exhibited typical ferromagnetism. The saturation magnetization (Ms) firstly increased, then decreased, and finally increased with increasing the deoxidization temperature, while the coercivity (Hc) decreased monotonously firstly and then basically stayed unchanged. The largest Ms (~145.7 emu·g−1) and the moderate Hc (~132 Oe) were obtained for the Fe-Ni alloy nanoribbons with a mixed configuration of bcc and fcc phases.

No MeSH data available.