| 摘要 |
PROBLEM TO BE SOLVED: To obtain an environmentally safe carrier material for electrophotographic development by calcining a composition consisting of specified proportions of manganese oxide, iron (III) oxide and a titanium dioxide to form a spinel structure. SOLUTION: Titanium dioxide is added to a mixture of 10-50 mol% manganese oxide and 90-50 mol% iron (III) oxide by 0.5-10 wt.% of the mount of the mixture and the mixture is calcined by heating at 700-1,200 deg.C for 30 min to 2 hr to obtain a mixture of particles having a spinel structure containing manganese oxide and iron (III) oxide. A slurry prepared by wet-comminuting the mixture is spray-dried to form spherical dry beads. After classification, the beads are sintered in a kiln having <2% oxygen content. Since titanium dioxide is substituted for iron in crystals by the sintering, the mixture has enhanced property of iron (II) and the magnetic moment of the resulting material is reduced while retaining the electric conductivity. The material is suitable for use as a carrier for a color copying machine because the magnetic moment can be controlled to <6,320 Am2/g. |
