Method of making fast warm up picture tube cathode cap having high heat emissivity surface on the interior thereof

摘要

Performance of fast warm up cathodes can be improved by providing a black heat radiating surface on the interior of the cathode cap. A particular material can be nichrome which is a nickel chromium alloy. The cathode cap material can be selected from any of the known cathode nickel alloys. A preferred method for accomplishing the result includes the steps of cladding a selected nickel alloy with the nichrome material and then forming the substantially cup shaped cap with the clad material on the interior thereof. The formed cathode cap is then fired for about 10 minutes or longer in wet dissociated ammonia at a temperature of about 900 DEG C to 1300 DEG C to oxidize the available chromium on the surface of the nichrome. This produces an even dark surface thereon which has much higher heat radiating capabilities than the silver looking nickel cathode alloy.