Abstract
Spinel NiFe2O4 nanocrystals have been obtained by means of a novel composite-hydroxide-salt-mediated approach, which is based on a reaction between metallic salt and metallic oxide in the solution of composite-hydroxide-salt eutectic at ~225 ºC and normal atmosphere without any organic dispersant or capping agent. The obtained products are characterized by an X-ray diffraction (XRD), a transmission electron microscopy (TEM) and an alternating gradient magnetometer (AGM). The formation process of NiFe2O4 nanosheet is proposed to begin with a ‘‘dissolution-recrystallization’’ which is followed by an ‘‘Ostwald ripening’’ mechanism. The NiFe2O4 nano-octahedrons can be obtained through adjusting the reaction water content in the hydroxide melts at constant temperature. At 300 K, magnetic hysteresis loops at an applied field of 15 kOe show zero coercivity, indicating the superparamagnetic behavior of the as-prepared NiFe2O4 nanocrystals.
Highlights
Nanocrystalline spinel ferrites with the general formula MFe2O4 (M = divalent metal ions, e.g. Ni, Co, Cu, Zn, Mg, Mn, Cd, etc.) are attractive for their interesting magnetic, magnetoresistive, and magneto-optical properties
We report a novel one-step, simple method to directly synthesize uniform, mass-production nanostructured NiFe O by the composite-hydroxide‐salt‐mediated (CHSM)
Our experiments have revealed that the morphology can be controlled through adjusting the reaction water content in the hydroxide melts with constant temperature
Summary
Nanocrystalline spinel ferrites with the general formula MFe2O4 (M = divalent metal ions, e.g. Ni, Co, Cu, Zn, Mg, Mn, Cd, etc.) are attractive for their interesting magnetic, magnetoresistive, and magneto-optical properties. As a kind of important spinel ferrite, NiFe2O4 has attracted much interest because of its fascinating magnetic and electromagnetic properties[1]. Nanoscale NiFe O ferrites have been successfully synthesized by various methods including sol-gel[11,14,15,16], solid-state reaction[6,17,18], co‐precipitation[7,12,19,20], mechanochemical[21], rheological phase reaction method[22], pulsed wire discharge[23], arc plasma assisted gas phase synthesis method[24], combustion[25], surfactant-assisted refluxing method[26], micromulsion[27], electrospinning[28], thermolysis of mixed metal-oleate complexes[29], sonochemical[30] and hydrothermal[31,32,33,34,35].
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