Cobalt@-coated needle-like berthollide iron oxide pigments - used for magnetic recording purposes in audio tapes and having high saturation magnetisation

摘要

Co-coated needle-like berthollide Fe oxide pigments contain an Fe oxide core of compsn. (Fex(2+),Fe2(3+))03+x (where x = 0.3-0.75). The amt. of Co is 0.1-1.5 wt.%. The pigments are produced by coating a magnetic berthollide iron oxide core of compsn. (Fex(2+),Fe2(3+))O3+x (where x = 0.3-0.75) with a berthollide cpd. of corresponding compsn. with addn. of a Zn-cpd. in an amt. of 0.1-2 (pref. 0.5-1.2) wt.%, and then coating with a Co-cpd., pref. using CaSO4 in alkaline medium. USE/ADVANTAGE - For magnetic recording in audio tapes. They have high saturation magnetisation