| TECHNOLOGY |
Tiny aluminum or iron oxide flakes measuring approximately 20 microns (20 thousandths of a millimeter) which reflect incidental light form the core of RTM pigments. The flakes are coated in a layer of silicon dioxide 200 to 600 nm thick (200 to 600 millionths of a millimeter). This layer is responsible for the change in color depending on the angle of vision. At a layer thickness of approximately 370 nm a head-on view reveals a reddish purple hue which changes to gold when viewed from an oblique angle. The third layer composed of iron oxide enhances the brilliance of the colors and superimposes its absorption color on the interference color. Layering in two stages The chemical synthesis route is made up of two stages. In the first step, the substrates are coated in silicon dioxide by base-catalyzed hydrolysis in a suspension of alcohol by a sol-gel process. After washing and drying, a second, outer coat is applied in a fluidized bed reactor by chemical deposition from the gas phase. In this process, gaseous iron pentacarbonyl [Fe(CO)5] is oxidized at an elevated temperature and precipitated onto the pigments as an a-Fe2O3 film of exact thickness. |
| USES | used in car paints, decorative and industrial coatings and for adding color to plastics and decorative cosmetic preparations |
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