| 摘要 |
<p>A pigment of irregular-shaped particles is described which comprises crystallites of the empirical formula AxByCz wherein A and B are different; A is cobalt, nickel, copper, zinc, cadmium, iron, manganese or any combination thereof; B is aluminum, chromium, molybdenum, iron, vanadium, manganese or any combination thereof; C is oxygen, selenium, tellurium or sulfur; x is 1, 2 or 3; y is 2 or 3; and z is greater than 3; the crystallites have an average size of from about 75 to about 600 Angstroms; and the surface area of the pigment particles is greater than zero up to about 20 m<2>/g. In one embodiment, when the pigment contains a mixture of copper oxide, iron oxide, manganese oxide and no chromium, the pigment contains no more than 10% of manganese, and when the pigment contains copper oxide, chromium oxide, and manganese oxide, the pigment contains up to about 5% of manganese oxide, the mole ratio of chromium to copper is no greater than about 1.3 to 1. A process for preparing such pigments also is described which comprises the steps of (1) reacting a soluble salt of A and a soluble acid or acid salt of B with a soluble base in water to form a precipitate, provided that when C is Se, Te or S, the reaction is conducted in the presence of a soluble Se, Te or S compound, (2) recovering the precipitate, (3) calcining the precipitate at a temperature of from about 500 to about 1200 DEG C, and (4) comminuting the calcined precipitate in a fluid-energy mill wherein the particles are reduced in size by particle- to-particle contact. n</p> |
