Effect of surface state of powder particles on activity

The surface state of reduced iron powder particles is very complex. The finer the powder particles are, the more developed the outer surface is. At the same time, the defects of the powder particles are many, and the inner surface is quite large. The surface of the developed powder stores high surface energy, so the ultrafine powder is easy to spontaneously gather into secondary particles, and it is easy to oxidize and spontaneously combinate in the air.