Oxidation Protection of Mo Sealing Foils Using Fused Silica Coatings

摘要

Thin molybdenum (Mo) foils of lenticular cross section are used extensively as electrical feed-throughs in quartz HID and tungsten-halogen lamps that employ pinch and shrink seals to fused silica envelopes. Mo foils are typically welded to Mo lead-in wires, and in lamps without outer jackets, the exposed foil ends and weld junctions are highly susceptible to air oxidation and failure at temperatures above ~350°C. Previous approaches to oxidation protection include protective films of chromium [1], low melting glasses [2] and silicide, aluminide and phosphide compounds [3]. This paper describes a new approach in which a thin film of silica derived from a colloid of nano-particles of silica in an aqueous or organic suspension is fused at high temperatures onto the Mo foil surface [4], These fused coatings are shown to provide oxidation protection of molybdenum foils.