| 摘要 |
Spherical particles having sizes below 1 mu m, or at maximum of 3.04 mu m, a narrow size size distribution consisting, or consisting essentially, of TiO2 coated by a uniform layer having a thickness up to 400 ANGSTROM consisting essentially alpha -, or gamma -Fe2O3, or magnetite, or mixtures thereof, said particles being prepared by a process consisting, or consisting essentially, in the precipitation of the oxide from Fe (III) salt solutions on the surface of solid pre-formed TiO2 particles having a narrow size distribution and a number average diameter below 1 mu m or </=3 mu m, the Fe (III) concentration being </=40% by weight calculated on TiO2, the pH of the suspension ranging from 1.0 to 2.8, extremes excluded, by heating the suspensions to temperatures of from 80 DEG to 100 DEG C., and by aging them under such conditions for at least 30 minutes. |
