Spherical shape Ni-Co alloy powders directly prepared by spray pyrolysis

Spherical shape Ni-Co alloy powders were directly prepared by spray pyrolysis in reduction atmosphere. The alloy powders prepared at temperatures of 1000 and 1200 °C had hollow structures and large sizes. On the other hand, the alloy powders prepared at a temperature of 1400 °C had dense structure and fine size. The mean size and geometric standard deviation of the powders prepared at a temperature of 1400 °C were 0.69 μm and 1.5. The BET surface area of the alloy powders prepared at a temperature of 1400 °C was 1.6 m²/g. The composition ratio of Ni and Co components were well coincided with that of the spray solution. The alloy powders had similar saturation magnetization (M_s) values irrespective of the preparation temperatures. However, the coercive force (H_c) values of the alloy powders decreased with increasing the preparation temperatures.