The conditions of the surface treatment of alumina, titania and talc with isopropyltriisostearoyltitanate, cetanol and octadecyltriethoxysilane and their surface properties were investigated from the results of their carbon contents, surface areas, dispersibility, infrared absorption spectra and pyrolysis. The followings were found : (1) all reagents used for the treatment reacted effectively with alumina, titania and talc though the reactivity of the reagents varied and (2) hydroxyl group on the surface was replaced with alcoxy-, octadecyldihydroxysilyl- and triisostearoyltitanyl- group in the surface treatment.
Well-dispersed α-FeOOH prismatic particles with short axis length of 0.1 μm and axial ratio of 3 were obtained by a hydrothermal treatment of Fe2O3·2 H2O which had been precipitated by the reaction between FeCl3 and NaOH in water at 10°C. These seed particles were air-oxidized to hrow in an FeSO4 aqueous solution with immersed Fe metal, in which the short axis length grew preferably compared with long axis length, retaining crystal morphology. After the crystal growth of 100 hours, uniform crystalline α-FeOOH particles with short axis length of 0.3 μm and axial ratio of 2 were obtained by a hydrothermal treatment at 200°C for 1 hour in a 1 mol/l of NaOH aqueous solution. Hiding power and brightness of the particles were improved by twice compared with those of the seed particles.