PROCESS FOR COATING FINELY DIVIDED MATERIAL WITH TITANIA ANDMOISTURE INSENSITIVE ZINC SULFIDE LUMINESCENT MATERIALS MADE THEREFROM

摘要

A method for coating finely divided material with titania is disclosed. The method involves the fluidization of the finely divided material in an inert carrier gas containing vaporized titanium isopropoxide. The isothermal fluidized bed is kept at a temperature equal to or below approximately 300.degree.C. The vaporized titanium isopropoxide reacts to form a coating of titania on the surfaces of the particles within the fluidized bed. The greatest coating efficiency occurs when the fluidized bed is kept at approximately 300.degree.C for approximately the first 10 minutes of the reaction and thereafter at approximated 250.degree.C. The titania coating process is particularly useful for electroluminescent phosphors such as copper doped zinc sulfide phosphor. The titania coated electroluminescent phosphors are relatively insensitive to moisture. Lamps made from the coated electroluminescent phosphor are also relatively insensitive to moisture.