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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.


TEM and HRTEM images of the precursor sample S0 (a–d) and as-deoxidized samples S1 (e–h), S2 (i–j), S3 (m–p) and S4 (q–t).
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f3: TEM and HRTEM images of the precursor sample S0 (a–d) and as-deoxidized samples S1 (e–h), S2 (i–j), S3 (m–p) and S4 (q–t).

Mentions: TEM analysis was carried out to further explore the microstructures of S0-S4. Firstly, Fig. 3(a,e,i,m,q) describe the typical high-magnification TEM images of the random individuals of all samples. These closer TEM examinations powerfully certify the ribbon-like structures of S0-S3 and the chain-like structure of S4. Owing to the continued particle growth during the second annealing in H2, NPs of the deoxidized S1-S4 are bigger than that of their precursor nanoribbons S0. For S1-S4, the particle size increase gradually with the deoxidization temperature increasing. Secondly, Fig. 3(b–d,f–h,j–l,n–p,r–t) respectively display the corresponding HRTEM images. In Fig. 3(b–d), the lattice fringes scanned from the selected NPs of S0 are measured to be about 0.209, 0.249 and 0.250 nm, which are indexed well to (400), (311) and (311) planes of NiFe2O4 (JCPDS card no. 54-0964). In Fig. 3(f–h), the measured distances of about 0.177, 0.200 and 0.240 nm of S1 are approximately equivalent to the interlayer distances of (200), (110) and (222) planes of the fcc Fe-Ni alloy, bcc Fe-Ni alloy and spinel NiFe2O4, respectively. Thus it proves that the chemical phase of S0 nanoribbons is pure NiFe2O4 and the S1 nanoribbons are assembled by the fcc Fe-Ni, bcc Fe-Ni and spinel NiFe2O4 NPs. In other words, it further demonstrates that NiFe2O4 of S0 transforms to the complex of fcc Fe-Ni alloys, bcc Fe-Ni alloys and spinel NiFe2O4 ferrite after annealing in H2 at 300 °C for S1. Similarly, from Fig. 3(j–l,n–p,r–t), it also notifies that the nanoribbons S2 are constructed by the fcc and bcc Fe-Ni NPs, the nanoribbons S3 and nanochains S4 are both purely constructed by the fcc Fe-Ni NPs, respectively.


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

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

f3: TEM and HRTEM images of the precursor sample S0 (a–d) and as-deoxidized samples S1 (e–h), S2 (i–j), S3 (m–p) and S4 (q–t).
Mentions: TEM analysis was carried out to further explore the microstructures of S0-S4. Firstly, Fig. 3(a,e,i,m,q) describe the typical high-magnification TEM images of the random individuals of all samples. These closer TEM examinations powerfully certify the ribbon-like structures of S0-S3 and the chain-like structure of S4. Owing to the continued particle growth during the second annealing in H2, NPs of the deoxidized S1-S4 are bigger than that of their precursor nanoribbons S0. For S1-S4, the particle size increase gradually with the deoxidization temperature increasing. Secondly, Fig. 3(b–d,f–h,j–l,n–p,r–t) respectively display the corresponding HRTEM images. In Fig. 3(b–d), the lattice fringes scanned from the selected NPs of S0 are measured to be about 0.209, 0.249 and 0.250 nm, which are indexed well to (400), (311) and (311) planes of NiFe2O4 (JCPDS card no. 54-0964). In Fig. 3(f–h), the measured distances of about 0.177, 0.200 and 0.240 nm of S1 are approximately equivalent to the interlayer distances of (200), (110) and (222) planes of the fcc Fe-Ni alloy, bcc Fe-Ni alloy and spinel NiFe2O4, respectively. Thus it proves that the chemical phase of S0 nanoribbons is pure NiFe2O4 and the S1 nanoribbons are assembled by the fcc Fe-Ni, bcc Fe-Ni and spinel NiFe2O4 NPs. In other words, it further demonstrates that NiFe2O4 of S0 transforms to the complex of fcc Fe-Ni alloys, bcc Fe-Ni alloys and spinel NiFe2O4 ferrite after annealing in H2 at 300 °C for S1. Similarly, from Fig. 3(j–l,n–p,r–t), it also notifies that the nanoribbons S2 are constructed by the fcc and bcc Fe-Ni NPs, the nanoribbons S3 and nanochains S4 are both purely constructed by the fcc Fe-Ni NPs, respectively.

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.