from 28 June 2015 to 3 July 2015 (Africa/Johannesburg)
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SAIP2015 Proceeding published on 17 July 2016
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Structural and magnetic properties of NiFe2O4/NiFe bi-magnet and NiFe nano-alloy synthesized from thermal reduction of NiFe2O4

Presented by Mr. ITEGBEYOGENE EZEKIEL on 30 Jun 2015 from 11:50 to 12:10
Type: Oral Presentation
Session: DPCMM
Track: Track A - Division for Physics of Condensed Matter and Materials

Abstract

Bi-magnetic NiFe<sub>2</sub>O<sub>4</sub>/NiFe nanocomposites and NiFe nano-alloy were synthesized by reduction of NiFe<sub>2</sub>O<sub>4</sub> nano-ferrite with activated charcoal (<i>n</i><i>c</i>) in flowing high purity Ar gas atmosphere at 900 °C for 3 hours. The parent NiFe<sub>2</sub>O<sub>4</sub> nano-ferrite was synthesized by a glycol-thermal method at 200 °C. Partial and complete reduction yielded NiFe<sub>2</sub>O<sub>4</sub>/NiFe nanocomposites and NiFe nano-alloy respectively. NiFe was formed at an optimum amount of <i>n</i><i>c</i> = 5. Phase identification, morphology and magnetic properties of the samples were performed by XRD, HRSEM, HRTEM, <sup>57</sup>Fe Mössbauer spectroscope and a mini cryogenic-free system. The parent sample has an average crystallite size of about 10 nm, an XRD density of about 5.3 g/cm<sup>3</sup> and an average lattice parameter of (<i>a</i>) = 8·362±0·007Å. The NiFe nano-alloy exhibited the martensite bcc (α-Fe) and austenite fcc (γ-Fe) phases in coexistence. Fitted Mössbauer analysis for <i>n</i><i>c</i> = 5 and 6 show high hyperfine magnetic fields associated with the bcc phase while the lower field component is associated with the fcc phase of NiFe nano-alloy. The saturation magnetization increased significantly from 57 emu/g to 141 emu/g at room temperature. The saturation magnetization is enhanced at low temperatures with a maximum of 161 emu/g at ≥ 30 K. However, the coercivity showed no significant increase at low temperatures. Keywords: Nano-ferrite; Nano-alloy; Nanocomposites; Activated charcoal; martensite; austenite; Reduction reaction

Award

YES

Level

PhD

Supervisor

Dr Moyo, Moyo@ukznac.za, University of KwaZulu-Natal, Westville Campus, Durban

Paper

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Permission

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