Mohsen Ahmadipour

Formation of nanoscale Mg (x) Fe (1-x) O (x = 0.1, 0.2, 0.4) structure by solution combustion: effect of fuel to oxidizer ratio

Mg(x)Fe(1-x)O (magnesiowustite) nanopowder samples synthesized by solution-combustion method and fuel to oxidizer ratio (Ψ = 1, 1.25) are used as a control parameter to investigate how particle size and morphology vary with Ψ. The method is inexpensive and efficient for synthesis of oxide nanoparticles. The average crystallite size of Mg(x)Fe(1-x)O nanoparticles was estimated from the full-width-half maximum of the X-ray diffraction peaks of powders using Debye-Scherrers formula; the average crystallite size varies from 16 nm to 51 nm. From X-ray diffraction analysis, it was observed that Mg(x)Fe(1-x)O nanoparticles have cubic structure. The particle size measured by particle size analyzer ranges from 37.7 nm to 73 nm which is in the order of XRD results. Thermal analysis was done by thermal gravimetric-differential thermal analyzer. The particle size and morphology of the synthesized powder were examined by transmission electron microscope and scanning electron microscope. The crystal size and particle size were compared with some of the most recently published research works by XRD and TEM. FTIR conforms formation of the Mg(x)Fe(1-x)O.

Dielectric Properties of CaCu3Ti4O12/Al2O3 Composites

In this work, (1-x)CaCu3Ti4O12/xAl2O3 (x = 0, 0.01, 0.03, 0.05 and 0.1) composite samples were prepared by the conventional solid-state reaction method. The dielectric properties of the samples were investigated at frequency range of 20 – 106 Hz. X-ray diffractogram results show that the samples with Al2O3 sintered at 1040 °C/10 h are mixed phase and consist of CaCu3Ti4O12, CuAl2O4, TiO2 and Al2O3. The average grain size of the samples increased greatly for x = 0.01, then abruptly depressed for x ≥ 0.03. Al2O3-added (x = 0.01) has been shown to increase the dielectric permittivity (ε’) up to ~5000 over frequency range of 102 – 105 Hz, while retaining the dielectric loss (tan δ ~ 0.15) at 1 kHz. With further increase of Al2O3 content, the ε’ and tan δ values of the samples are decreased monotonically in all frequency ranges. The improvement of dielectric properties in the composite sample was attributed to the enhanced grain boundary resistance.