Alpha iron (III) oxide crystals and derivatives
AssigneeThe Dow Chemical Company
InventorHenry Nelson Beck
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Abstract
Elongated, polycrystalline particles of alpha iron oxide, characterized by an open, porous structure and consisting of hematite microcrystallites containing from 2 to 4 percent of sulfate are prepared by the reaction of lithium hydroxide and ferric sulfate in weakly acidic to neutral aqueous solution under at least autogenous pressures at temperatures in the range of 150.degree.-350.degree. C. The particles are readily converted to gamma iron oxide of good magnetic properites and also have utility as pigments and catalysts.
Claims5
Porous, elongated, polycrystalline, hematite particles having lengths of from about 0.05 to about 5 microns, effective diameters of from about 0.02 to about 0.9 microns and aspect ratios of from about 1.2 to about 6,
- said particles being physically composed of elongate microcrystallites, loosely adhered together in the form of a generally cylindrical bundle with their long axes generally parallel to the long axis of the bundle,
- said microcrystallites having effective diameters of from about 80A up to about one half the effective diameter of said bundle, and
- said particles being chemically composed of alpha iron oxide containing from about 2 to about 4 weight percent of chemically bound sulfate and from about 0.003 to about 0.02 weight percent of chemically bound lithium.
Dependencies are inferred from the claim text.