We report the sequential polyol synthesis of Co3O4@ZnO nanocomposite. Firstly, Co3O4 was synthesized and ZnO was produced on the surface of the as synthesized Co3O4 NPs in the same pot. The nanoparticles have been investigated by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscope (TEM), and physical properties measurement system (PPMS) of Quantum Design. The weight percentage of phases were found as 26.3 % for ZnO and 73.5 % Co3O4 (crystal thickness ratio \(D_{\mathrm{Co}_{3}\mathrm{O}_{4}}/ D_{\mathrm{ZnO}}= 1.38\)) by using the generalized reference intensity ratios (RIRs) method. Superparamagnetism in Co3O4@ZnO nanocomposite at room temperature was first detected with high Ms value of 10 emu/g, and the non-hysteric curve with nearly saturated nature at high fields. This non-hysteric and nearly saturated nature at 15 kOe is the nature of superparamagnetic structures.

Nano-sized single-phase Mn3O4@ZnO core–shell nanocomposite was prepared via a simple one-pot sequential polyol using triethylene glycol as a high boiling point solvent as well as a reducing agent. The presence of both Mn3O4 and ZnO was confirmed with X-ray diffractometry. Infrared measurements proved the presence of triethylene glycol on the surface of Mn3O4@ZnO core–shell. The average particle size is between 8 and 13 nm. Reference intensity ratios method calculations showed that the weight percentage of phases were found as 54.7 % ZnO and 45.3 % Mn3O4. The lower Tc maybe explained by interface effects and dominant ZnO shell in magnetic properties of core–shell nanocomposite.

We present, for the first time, on a facile route for the fabrication of highly crystalline Co3O4 nanoparticles using trietanolamine (TEA) assisted hydrothermal synthesis route and single precursor. Synthesized material has been evaluated for its structural, morphological and magnetic properties using x-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and vibrating sample magnetometry (VSM) techniques. The material has been identified as highly crystalline Co3O4, with superparamagnetic character due to size confinement. Estimated particle size from SEM is about 10 nm, which is close to the magnetic domain size (estimated from VSM as 8.4 ± 1.7 nm) and the crystallite size (estimated from XRD as 11 pm 4 nm), which reveal nearly single crystalline character of Co3O4 nanoparticles. The suggested route is facile, which provides a good size control over the nanoparticles, and can be used for the fabrication of other ceramic materials.

In this study, the effect of temperature on the hydrothermal synthesis of single-phase SrFe12O19 hexaferrite (SrM) was investigated. For this synthesis, annealing or calcination process was applied. The Fe/Ba molar ratio was taken as 8:1. In this study, single-phase SrM NPs were synthesized via hydrothermal method. XRD patterns showed the presence of the hard (SrM) phase in the samples treated at 200 and 220 ∘C. Besides, formation of hexagonal plate-like samples was observed in SEM micrographs. Despite the low magnetization and coercive field values, the presence of the SrM phase was also shown in magnetization measurements. A reduced magnetization was explained by the existence of SrCO3 and Fe2O3 phases, and a high shape anisotropy is probably the reason of low coercivity.

Manganese ferrite (MnFe2O4)-polyvinyl alcohol (PVA) nanocomposite was prepared by a PVA assisted sot-gel auto-combustion method. The magnetic core of the carriers was manganese ferrite (MnFe2O4), with average crystallite size of 9.1 +/- 2.1 nm. The PVA-MnFe2O4 nanocomposite exhibited superparamagnetic behavior at room temperature and ferromagnetic behavior at low temperatures. Zero-field-cooled and field-cooled measurements further confirm the superparamagnetic behavior with a blocking temperature of 160 K. The lower reduced remanent magnetization values than theoretical value of 0.5 indicate that the PVA/MnFe2O4 nanocomposite used in this study has uniaxial anisotropy rather than the expected cubic anisotropy according to the Stoner-Wohlfarth model. The calculated magnetic anisotropy constant of the sample is similar to 1.45 x 10(6) erg/cm(3) which is significantly higher than that of the bulk MnFe2O4 due to the strong magnetic coupling between magnetic core and surface spins. (c) 2013 Elsevier Ltd. All rights reserved.

Polyaniline (PANI)–MnFe2O4 nanocomposite was successfully synthesized by using 1-butyl-3-methyl-imidazolium bromide as ionic liquid and cetyl trimethylammonium bromide as surfactant via in situ polymerization. Structural, morphological, spectral and magnetic investigation of the product were done by X-ray powder diffractometry, fourier transform infrared spectroscopy, thermal gravimetric analyzer, transmission electron microscopy, vibrating sample magnetometry respectively. Electrical properties of PANI–MnFe2O4–CTAB nanocomposite was characterized with a measurement of an impedance spectroscopy, which was evaluated at frequency range varying from 1 Hz to 3 MHz for temperature range of 20–120 °C. In general ac conductivity remained almost unchanged until it reaches up to 160 kHz, and then reduced slightly almost for all temperatures except for some slight fluctuation somehow.