Molten Salt Synthesis Of Sheet Iron Oxide Powders

Flaky iron oxide, as one of the special species of iron oxide, has lots of excellent properties and is widely used in inorganic anticorrosive industry. In this paper, the flaky iron oxide was prepared by molten salt synthesis method on the basis of the theory of crystal growth and molten salt chemistry in detail.The iron oxide samples obtained were characterized by means of microscope, X-ray diffraction, scanning electron microscope and color measurement apparatus in order to investigate the factors in the process of preparation. It was found that the varieties and dosage of molten salt and additives, sintering temperature and time were the most important factors. Using FeSO₄(NH₄)₂SO₄.7H₂O as iron resource, it was seen that only in sulfate molten salt system, could the flaky iron oxide be obtained; while chloride was used, iron oxide powder was not flaky, but granular; and a-iron oxide could not be synthesized in nitrate and carbonate system. When the mole ratio of α-Fe₂O₃ to mixture sulfate salts (Na₂SO₄ : K₂SO₄ = 81: 19) was 1 :6, and sintering temperature and time were 1100℃ and 6 hours, the flaky α-Fe₂O₃ powder could be obtained with 20⁵0μm in diameter, 1-5μm in thickness and 10²0 in aspect ratio. In the investigation for the effect of some oxide adulterants, it was found that when TiO₂ was adulterated to the iron oxide, the sample's thickness was increased and black congeries were formed on the surface; while using 6.61%(w/w) of A1₂O₃ instead of TiO₂, the flaky α-Fe₂O₃ obtained had vivid red color with thin thickness.On the other hand, the study of flaky iron oxide coated by TiO₂ was caught through according to the theory of Ti⁴+ hydrolysis. The effect of TiO₂ coating was measured by color measurement apparatus. It was seen that flaky iron oxide was turned to purple from red color with some nacreous effect when the percentage of TiO₂ was 15%.