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 (Ms) values irrespective of the preparation temperatures. However, the coercive force (Hc) values of the alloy powders decreased with increasing the preparation temperatures.