| 摘要 |
A catalytic combustion-type, gas sensing, resistive element and the method of making it by forming an electrical conductor, whose electrical resistance varies with temperature, into a helical coil, coating the coil with a refractory material whose coating matures at a temperature in the range of 1200 DEG C to 1400 DEG C, and heating the coated coil at that temperature range until the coating matures and shrinks into a dense, gas-tight sheath about the helical coil. The coating on the helical coil is integral between adjacent loops and there is a hollow space along the longitudinal axis of the coil. The exterior of the sheath coating may then be further coated with a catalyst, catalytic wash coating, or in some embodiments the hollow space is filled with a porous catalytic material such as platinum and the ends of the hollow space are capped with a porous refractory ceramic material. In these and other embodiments a porous refractory ceramic material may also be applied over the catalytic surface to allow combustible gases and oxygen to diffuse into the catalytic surface while protecting the catalytic surface from airborne materials which would otherwise render it inactive. A compensating element is made by the same method but is coated with a non-reactive, non-catalytic material. In the preferred embodiments the refractory material contains primarily alumina with small and equal amounts of manganese dioxide and titanium dioxide.
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