Yasaman Kolvandi; Mohammad Aghagholizadeh; Saeed Sheibani
Abstract
In this paper, the possibility of production of Cu matrix nano-composite powder containing 10, 37 and 54 wt.% NiO using mechano-chemical reduction of different copper oxides (CuO and Cu2O) was studied. Structural evolutions were characterized by X-ray diffraction. Also, the microstructure was characterized ...
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In this paper, the possibility of production of Cu matrix nano-composite powder containing 10, 37 and 54 wt.% NiO using mechano-chemical reduction of different copper oxides (CuO and Cu2O) was studied. Structural evolutions were characterized by X-ray diffraction. Also, the microstructure was characterized by scanning electron microscopy and transmission electron microscopy. Particular attention has been paid to the reaction mechanism and kinetics using differential scanning calorimetry. It was found that the reactions completed gradually between 5 to 22h of milling. Formation of Cu2O and Cu(Ni) solid solution, as intermediate phases, were observed during the reaction. It was found that, the initial excess Cu delayed reduction reaction and decreased the final crystallite size up to 18nm. Microstructural results showed that relatively large nano-composite agglomerates powder composed of uniform dispersion of NiO nano-particles in nano-crystalline Cu matrix were obtained. Kinetic study revealed that CuO reduction to Cu through two-steps reaction with lower activation energies in each step had higher rate, compared to one-step reduction of Cu2O.
Aida Mohammadi; Abolghasem Ataie; Saeed Sheibani
Abstract
Barium hexaferrite (BaFe12O19) magnetic nano-powder was prepared by co-precipitation method. The effectiveness of different chemical synthesis variables such as solvent and mechanical milling on the adsorption efficiency of barium hexaferrite nano-particles to remove Cr (VI) ions from aqueous solutions ...
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Barium hexaferrite (BaFe12O19) magnetic nano-powder was prepared by co-precipitation method. The effectiveness of different chemical synthesis variables such as solvent and mechanical milling on the adsorption efficiency of barium hexaferrite nano-particles to remove Cr (VI) ions from aqueous solutions was examined. Structural, magnetic, and adsorption properties of the powders are investigated by different techniques. X-ray diffraction analysis revealed that barium hexaferrite formed at a relatively low temperature of 700?C in the sample prepared with a mixture of water/alcohol as a solvent. The FESEM and VSM studies confirmed that all samples had a plate like structure with a particle size in the range of 87-145 nm and high magnetic properties. It was demonstrated that nanometer barium hexaferrite was produced to be an operative adsorbent for removal of Cr (VI) ions from solutions. Different Cr (VI) adsorption experiments were carried out by controlling effective adsorption factors. It was revealed that the sample calcined at a temperature of 700°C and then milled for 5 h (owing themaximum surface area 13 m2/g) showed the highest removal efficiency of 99.5% at pH 3.0, amount of nano adsorbent 1.5 g, initial chromium concentration 133 mg/l, and contact time 1 h. FTIR analysis showed that due to the existence of Cr-O stretching band on the surface of nano-particles, the electrostatic reaction between Cr (VI) ions and nano-adsorbent is possible. The adsorption data were best fitted with the pseudo-second-order kinetic model. Also, the equilibrium adsorption capacity of Cr (VI) calculated from adsorption experiments was found to be 13.25 mg/g. Adsorption studies indicated that the potential use of barium hexaferrite nano-adsorbents for the removal of the other heavy metal ions without sacrificing adsorption capacity can be practical.
