Iranian Journal of Materials Science and Engineering

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Abstract:

materials can be fabricated by sintering of W-Cu composite powders. In this research W-20%wt Cu composite powders

was synthesized via a co-precipitation method. Precipitate obtained from a mixture of copper nitrate and ammonium

paratungstate (APT) in distilled water contained W-Cu compounds. This precipitate was washed, dried and calcined

at 550

of dried precipitate powder was determined by thermogravimetry (TG), differential thermal analysis (DTA) and X-ray

diffraction (XRD). The sintering of the reduced powders was investigated as a function of temperature. Relative density

of more than 98% obtained for the powders sintered at 1200

close to theoretical calculations. The hardness of the sintered powders was 320 Vickers.

W-Cu composites are widely used as contacts, heat sinks and electro discharge electrodes. These kinds of°C in air and then reduced in H2 atmosphere in order to convert to W-Cu powders. The calcination temperature°C . The corresponding electrical conductivity was too

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Mn doped ZnO nanocrystals were prepared by co-precipitation route sintered at 450 °C temperature. XRD results indicate that the samples having hexagonal (wurtzite) structure. From X-ray data it is found that the lattice parameters increase with increasing Mn concentration. The X-ray density decreases with increasing Mn concentration of Zn 1-x Mnx O nanocrystals. It indicates that the Mn ions go into the Zn site in the ZnO lattice structure. TEM results reveal that the pure and Mn substituted ZnO samples are spherical in shape with average particle size about 20-60 nm. The crystalline size and lattice strain were evaluated by Williamson-Hall (W-H) analysis using X-ray peak broadening data. All other relevant physical parameters such as strain, stress and energy density were calculated by the different models Viz, uniform deformation model (UDM), uniform deformation stress model (UDSM) and Uniform deformation energy density model (UDEDM) considering the Williamson-Hall analysis. These models reveal different strain values it may be due to the anisotropic nature of the material. It is found that the mean particle size of Zn 1-x MnxO nanoparticles was estimated from TEM analysis, Scherrer’s formula & W-H analysis is highly comparable

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The synthesis of micro-sized, uniformly distributed Al₂O₃-15Vol% Ni powders were studied through three step co-precipitation of hydroxides mixtures from proper solution, calcination at air atmosphere and final step of calcined powders in a carbon bed. Al and Ni hydroxide and amorphous phase were first obtained from their salt’s solutions through chemical co-precipitation method by adjusting pH. The precipitated powders were then calcined to obtain a mixture of their oxides as NiO and NiAl₂O₄ which were reduced in a carbon bed at various temperatures up to 1300. Proper temperature for calcination in air was determined through TG analysis; 900. SEM observation of powders after reduction, revealed micro-sized Ni particles, along with fin distribution of Ni and Al₂O₃ elements. XRD analysis of the calcined sample showed the presence of NiAl₂O₄ and NiO and the same analysis for the reduced sample confirmed the formation of Al₂O₃ and Ni.    

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In present work Ni_0.7Cd_0.3Nd_xFe_2-xO₄ ferrite samples (0≤x≤0.03) were prepared by using oxalate co-precipitation technique. The different characterization techniques were achieved using X-ray diffraction (XRD), FT-infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), DC electrical resistivity and dielectric measurements. The crystallographic parameters such as crystal structure, crystallite size, lattice constant, unit cell volume and theoretical density have been systematically analysed. The XRD and FT-IR measurements confirmed the formation of single phase spinel ferrite structure. The cation distribution among the octahedral and tetrahedral sites has been proposed on the basis of analysis of XRD patterns by employing Rietveld refinement analysis. The samples exist as a mixed type spinel with cubic structure. The DC electrical resistivity confirms the semiconducting behaviour and the Curie temperature decreases with increase in Nd³⁺ content. The dielectric constant and loss tangent decreases with frequency and higher frequencies remain constant, which shows the usual dielectric dispersion due to space charge polarization. The AC conductivity reveals that the small type polarons responsible for conduction process.