Narrow Results

The single-phase nanostructure forsterite powder was successfully synthesized by mechanical activation of talc and magnesium carbonate powder mixture followed by annealing in the presence and absence of ammonium chloride. Mechanical activation was used as an efficient method for the optimization of powder properties by means of combination and uttermost homogenization of the powder mass. Besides, the presence of chlorine ion affected the forsterite formation rate via producing smaller particle size during subsequent annealing which is very important in the case of diffusion-controlled reactions. The single-phase nanostructure forsterite powder with crystallite size of about 36 nm was successfully synthesized by 10 h mechanical activation with subsequent annealing at 1000°C for 1 h. While in the presence of chlorine ion, the single-phase nanostructure forsterite powder with crystallite size of about 20 nm could be obtained by 5 h of mechanical activation with subsequent annealing at 1000°C for 2 min.

Combustion synthesis has emerged as a facile and economically viable technique for the preparation of advanced ceramics, catalysts and nanomaterials. This paper is the report of the investigations carried out on the synthesis of titania–rare-earth mixed oxide pigments: TiCe_1-xPr_xO_4-δ by the solution combustion method and their characterization by X-ray powder diffraction, transmission electron microscopy, reflectance spectral data, thermal analysis and surface area measurements. The synthesized nanopigments exhibit yellow to brick red color with the increase of praseodymium content. The dominant reflectance of these pigments lies above a wavelength of 600 nm. These pigments are found to be promising candidates as ecological pigments because of their high reflectance, lightness and intense coloration.

The tetragonal Ca₉Nd₂W₄O₂₄ (CNW) ceramic was prepared by the conventional solid state ceramic route and their dielectric properties were investigated in the radio and microwave frequencies. The CNW ceramics sintered at 1450 °C for 4 h showed a densification 92 % with ε_r = 16 and tanδ = 0.004 at 15.1 GHz. The thermal conductivity of ceramic at room temperature was found to be 1.6 W m⁻¹K⁻¹ and coefficent of thermal expansion of CNW ceramics was 4.2 ppm/°C measured in the range of 25 to 600 °C. The dielectric and thermal properties of CNW ceramic are reported for the first time.

Aluminium phosphate (AlPO₄)-Magnesium fluoride (MgF₂) composite has been prepared through solid state ceramic route. The formation of composite has been confirmed by X-ray diffraction studies. The variation in ε_r and tanδ of the composite with frequency in the range (1K Hz – 3 MHz) has been studied. The AlPO₄-MgF₂ has a small temperature dependence of ε_r. The composite shows low relative permittivity of 3 and low dielectric loss (tanδ = 7×10⁻³) at 5.85 GHz.

The binary glassy systems 60V₂O₅-(40-x)P₂O₅ –xB₂O₃ were prepared by melt quenching technique. The mole of B₂O₃ was varies from 5 to 20 mol % with constant mol % of V₂O₅ during preparation of glass samples. The dc electrical conductivity of samples was measured in temperature range 303-473 K and found to be higher for sample 60 V₂O₅-20P₂O₅ –20B₂O₃. Using the Arrhenius equation of conductivity, the activation energy of conduction is estimated. The conduction in these glasses is takes place by phonon-assisted hopping between the localized states.