Abstract: The potential for release of soluble chromium (VI) ions in the production or processing of certain pigments is reduced by use of certain additives. The additives include aluminum metaphosphate, aluminum fluoride, tungsten oxide, tungstic acid, and mono-ammonium phosphate. The pigments are those which contain chromium and have a corundum crystal structure.

Abstract: A method for continuously calcinating product to form mixed metal oxide powders comprising providing a continuously operated indirectly heated rotary furnace having a heating cavity, introducing raw feedstock including product to be calcined into the heating cavity of the furnace while the heating cavity is maintained at temperature, and maintaining a controlled atmosphere in the heating cavity during the heating of the feedstock, and discharging and recovering the mixed metal oxide powders.

Abstract: The present invention provides new solid solutions having a corundum-hematite crystalline structure which are useful as inorganic color pigments. Solid solutions according to the present invention include a host component having a corundum-hematite crystalline structure which contains as guest components one or more elements from the group consisting of aluminum, antimony, bismuth, boron, chrome, cobalt, gallium, indium, iron, lanthanum, lithium, magnesium, manganese, molybdenum, neodymium, nickel, niobium, silicon, tin, titanium, vanadium, and zinc. Solid solutions according to the present invention are formed by thoroughly mixing compounds, usually metal oxides or precursors thereof, which contain the host and guest components and then calcining the compounds to form the solid solutions having the corundum-hematite crystalline structure. Some of the new solid solutions according to the present invention exhibit relatively low Y CIE tri-stimulus values and relatively high near infrared reflectance.

Abstract: A method for continuously calcinating product to form mixed metal oxide powders comprising providing a continuously operated indirectly heated rotary furnace having a heating cavity, introducing raw feedstock including product to be calcined into the heating cavity of the furnace while the heating cavity is maintained at temperature, and maintaining a controlled atmosphere in the heating cavity during the heating of the feedstock, and discharging and recovering the mixed metal oxide powders.

Abstract: The present invention provides new solid solutions having a corundum-hematite crystalline structure which are useful as inorganic color pigments. Solid solutions according to the present invention include a host component having a corundum-hematite crystalline structure which contains as guest components one or more elements from the group consisting of aluminum, antimony, bismuth, boron, chrome, cobalt, gallium, indium, iron, lanthanum, lithium, magnesium, manganese, molybdenum, neodymium, nickel, niobium, silicon, tin, titanium, vanadium, and zinc. Solid solutions according to the present invention are formed by thoroughly mixing compounds, usually metal oxides or precursors thereof, which contain the host and guest components and then calcining the compounds to form the solid solutions having the corundum-hematite crystalline structure. Some of the new solid solutions according to the present invention exhibit relatively low Y CIE tri-stimulus values and relatively high near infrared reflectance.

Abstract: The present invention provides new solid solutions having a corundum-hematite crystalline structure which are useful as inorganic color pigments. Solid solutions according to the present invention include a host component having a corundum-hematite crystalline structure which contains as guest components one or more elements from the group consisting of aluminum, antimony, bismuth, boron, chrome, cobalt, gallium, indium, iron, lanthanum, lithium, magnesium, manganese, molybdenum, neodymium, nickel, niobium, silicon, tin, titanium, vanadium, and zinc. Solid solutions according to the present invention are formed by thoroughly mixing compounds, usually metal oxides or precursors thereof, which contain the host and guest components and then calcining the compounds to form the solid solutions having the corundum-hematite crystalline structure. Some of the new solid solutions according to the present invention exhibit relatively low Y CIE tri-stimulus values and relatively high near infrared reflectance.

Abstract: A method for the synthesis of mixed metal oxide crystalline powders comprises the steps of preparing a raw material mixture containing at least two different metal cations; adding a template material to the mixture and blending it therewith; initiating formation of a mixed metal oxide by calcination of the mixture and the template material, whereby particles of the mixed metal oxides are formed; and thereafter recovering the mixed metal oxide particles. Mixed metal oxide crystalline powders comprise a template material; and metal oxides which form pigment classes of material containing the template material, the pigment classes being selected from the group consisting of borate, garnet, olivine, phenacite, phosphate, priderite, pyrochlore, sphene, spinel and zircon, as well as perovskite crystal classes of material containing the template, all of which have a uniform particle morphology and particle size ranging between about 0.2 to 100.mu. with minimal comminution.