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2 Open Chemistry

2 2010

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Sonochemical synthesis and chracterization of Mn3O4 nanoparticles

100%

Baykal A. , Kavas H. , Durmuş Z. , Demir M. , Kazan S. , Topkaya R. , Toprak M.

Open Chemistry

2010

tom 8

nr 3

633-638

We report on the synthesis of Mn3O4 nanoparticles (NPs) using a novel sonochemical method without requiring any pH adjustment. Synthesized material was identified as tetragonal hausmannite crystal structure model of Mn3O4 from XRD analysis. Crystallite size was estimated from x-ray line profile fitting to be 17±5 nm. FTIR analysis revealed stretching vibrations of metal ions in tetrahedral and octahedral coordination confirming the crystal structure. TEM analysis revealed a dominantly cubic morphology of NPs with an average size of ∼20 nm. Magnetic evaluation revealed a blocking temperature, T B of 40 K above which the material behaves paramagnetic. Asymmetric coercive field is attributed to the interaction between ferromagnetic Mn3O4 and antiferromagnetic Mn oxide at the surface of nanoparticles. [...]

Composition-induced phase transition in a [Ag2HgI4:0.2AgI] mixed composite system doped with CuI

100%

Noorussaba , Ahmad A.

Open Chemistry

2010

tom 8

nr 6

1227-1235

A novel composite superionic system, [Ag2HgI4:0.2AgI]:xCuI, (x = 0.2, 0.4, 0.6 mol. wt.%), was prepared and [Ag2HgI4:0.2AgI] mixed system was used as the host. Electrical conductivity was measured to study the transition behavior at frequencies of 100 Hz, 120 Hz, 1 kHz, and 10 kHz in the temperature range 90°–170°C by a Gen Rad 1659 RLC Digibridge. Sharp increase in conductivity was observed for β-α phase transitions. As a result of increase in the dopant-to-host ratio, the conductivity of the system exhibited Arrhenius (thermally activated)-type behavior. X-ray powder diffraction, differential scanning calorimetry (DSC), differential thermal analysis (DTA) and thermo-gravimetric analysis (TGA) studies confirmed the doping effect on the transition in the host, the phase transition temperature increased with an increase in the dopant concentration. Activation energies for the system in eV both for the pretransition and post-transition phase transformations are reported. The addition of CuI to [Ag2HgI4:0.2AgI] shifted the phase transition of the host [Ag2HgI4:0.2AgI], due to an interaction between [Ag2HgI4:0.2AgI] and CuI.