Influence of particle perfection on properties of γ-Fe2O3

In this paper, two parameters ΔSSA and OAPM are suggested to describe quantitatively the particle perfection which has strong influence on the magnetic and rheological properties of magnetic powder. ΔSSA is the difference between the value determined by BET method and that calculated by the following equation: SSA = 2/dl (2R+1), where d, l and R are density, particle length and acicularity ratio of particles respectively. OAPM is the oil absorption per unit specific surface area of γ-Fe2O3. The technical data of products provided by two famous manufacturers are analysed. The relations among ΔSSA, OAPM, coercivity, squareness, orientation ratio and SFD etc. are discussed.